HomeMy WebLinkAboutWastewater Facility Plan Update 2024
Wastewater Collection
System Facility P lan U pdate
Final Document
December 2024
Adopted by City Commission Resolution No. 5664
Ihereby certifythatthis report was preparedby me or undermydirect supervision and
thatI am adulyRegisteredProfessionalEngineer under the laws ofthe StateofMontana.
Name: ___ZacharyE. Magdol___________________________________________________
Date:___February25, 2025_______ RegistrationNumber: ___61962_____________
WastewaterCollection System
Facility Plan Update
December 2024
Table of Contents
1.0 Executive Summary
2.0 Definition of Terms and Acronyms
3.0 Data Collection Technical Memorandum
4.0 Manhole Condition Assessment Technical Memorandum
5.0 Wastewater Flow Characterization Technical Memorandum
6.0 Feature Manipulation Engine and GIS Technical Memorandum
7.0 Hydraulic Model Development and Results Technical Memorandum
8.0 Risk Assessment Technical Memorandum
9.0 Capital Improvement Plan Technical Memorandum
10.0 Asset Management Coordinate System Technical Memorandum
11.0 Updating Model Development Loading Technical Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
1.0
Executive Summary
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
1.0 – Executive Summary
Table of Contents
Chapter 1 Introduction and Purpose...........................................................................................2
Chapter 2 How to Use this Plan ..................................................................................................4
Chapter 3 Data Collection ..........................................................................................................6
Chapter 4 Manhole Condition Assessment Program....................................................................7
Chapter 5 Wastewater Flow Characterization .............................................................................8
Chapter 6 FME and GIS Data Exchange .....................................................................................10
Chapter 7 Hydraulic Model Development and Results...............................................................11
Chapter 8 Risk Assessment.......................................................................................................12
Chapter 9 Capital Improvement Plan ........................................................................................13
Chapter 10 Asset Management Coordinate System.....................................................................15
Chapter 11 Updating Model Development Loading.....................................................................16
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Wastewater Collection System Facility Plan – 2024 Update
1.0 – Executive Summary
Chapter 1 Introduction and Purpose
The City of Bozeman (City) owns and operates a wastewater collectfon system serving its residents,
businesses, and industry. The City contfnues to experience rapid growth, with an average estfmated
annual populatfon growth of 4% over the past 15 years. This growth coupled with aging infrastructure
presents many challenges to maintaining, operatfng, and expanding the wastewater collectfon system.
The City periodically undertakes comprehensive planning efforts to help guide system improvements so
that adequate service is provided to the growing community. These planning efforts are referred to as
Facility Plans. The previous Wastewater Collectfon System Facility Plan was completed in 2015. Since the
2015 wastewater facility plan, many of the improvements identffied in the facility plan have been
completed. As development pressure contfnues to grow and existfng infrastructure ages, the wastewater
collectfon system model and reference planning documents required a comprehensive update to ensure
the City can contfnue to meet its level of service goals and accommodate growth.
In 2020, Advanced Engineering and Environmental Services (AE2S) and TD&H Engineering was selected
to complete a multf-phase update of the City’s wastewater collectfon model (Phase I) and wastewater
collectfon facility plan (Phase II). An amendment to the agreement was initfated in June 2023, during
phase II of the update, to address the introductfon of Montana Senate Bill 382, which included
conformance with land use planning act and potentfal changes to development density.
This document summarizes the planning methods, assumptfons, and outcomes for the Facility Plan
Update.
The purpose and goals of the specific phases of the Facility Plan Update are outlined below:
Phase I
• Provide recommendatfons to transitfon to a uniform coordinate system.
• Complete a comprehensive survey and data collectfon of assets.
• Develop the basis for a manhole conditfon assessment program.
• Characterize existfng and future wastewater flows.
• Establish the framework processes for future hydraulic model updates.
• Update the existfng collectfon system model, including calibratfon.
• Establish or verify hydraulic performance standards for system analysis.
• Evaluate existfng and future system performance.
• Identffy hydraulic deficiencies and mitfgatfon for optfons.
Phase II
• Complete a wastewater collectfon system risk assessment.
• Evaluate increased density infill and identffy hydraulic deficiencies.
• Develop a general process to update and track system loading.
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• Prioritfze system improvements surrounding growth, risk, and hydraulic deficiencies.
• Develop a comprehensive capital improvement plan to address near-term and long-term system
needs, while contfnuing to plan for and accommodate the City’s growth.
The culminatfon of the effort provides City staff with the resources and tools to contfnue meetfng the
City’s strategic plan by fostering a well-planned City, prioritfzing improvements for existfng and new
infrastructure, and ultfmately helping guide public funds to the right project at the right tfme.
This Facility Plan organizatfon diverges from previous versions in that it is divided into nine (9) Technical
Memoranda representfng the significant and distfnct tasks carried out to update the citywide hydraulic
model, evaluate existfng performance, develop future alternatfves, and provide recommendatfons for
the City’s Capital Improvement Program. The Facility Plan Executfve Summary provides an overview of
each Technical Memorandum (TM) digestfng and reportfng the primary findings and recommendatfons.
The nine (9) Facility Plan Technical Memoranda are as follows:
• Data Collectfon (TM 3)
• Manhole Conditfon Assessment Program (TM 4)
• Wastewater Flow Characterizatfon (TM 5)
• Feature Manipulatfon Engine (FME) and Geographic Informatfon System (GIS) Data Exchange
Routfne (TM 6)
• Hydraulic Model Development and Results (TM 7)
• Risk Assessment (TM 8)
• Capital Improvement Plan (TM 9)
• Asset Management Coordinate System (TM 10)
• Updatfng Model Development Loading (TM 11)
As the City contfnues to grow, new infrastructure is added to the collectfon system, and old
infrastructure is replaced, it is recommended that the hydraulic model be updated annually at a
minimum and the Facility Plan be updated or revisited every five years. These ongoing updates will help
ensure the City contfnues to responsibly and proactfvely plan and maintain public infrastructure.
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Chapter 2 How to Use this Plan
This is a planning document and should be referenced in that way. All recommendatfons in this Facility
Plan warrant some additfonal evaluatfon prior to implementatfon. Additfonally, the City should undergo
routfne updates to the collectfon system hydraulic model and the Facility Plan to ensure its
recommendatfons are stfll aligned with City prioritfes, development trends, and community land use
plans.
In an effort to make this Facility Plan more usable, below is a summary of the distfnct sectfons (i.e.,
Technical Memoranda) and offers a suggestfon on when and why the reader may wish to reference them
in more detail. These summaries are expanded upon in this Executfve Summary in the preceding
sectfons.
• The Data Collectfon Technical Memorandum (TM 3) provides a summary of the data used in this
Facility Plan. The reader should refer to this TM to understand the source and types of the
geographic informatfon system (GIS) data referenced in the collectfon system analysis. This
sectfon also includes informatfon about the planning GIS data (e.g., land use) and overview maps
of the existfng collectfon system.
➢The Manhole Conditfon Assessment Program Technical Memorandum (TM 4) provides a
recommended framework for the City to implement a conditfon assessment program to help
with prioritfzing collectfon system maintenance, rehabilitatfon, and replacement. This TM is
especially useful for City utflity staff and can serve as a reference to guide what type of conditfon
data to collect, how to collect it, and the recommended frequency.
➢The Wastewater Flow Characterizatfon Technical Memorandum (TM 5) provides a thorough
explanatfon of the analysis carried out to define existfng wastewater flows and project future
flows. The reader should refer to this TM to dig into the details of how this Facility Plan defined
the various components of wastewater generatfon (domestfc, base groundwater inflow, wet-
weather inflow), how future wastewater is estfmated and applied to future scenarios. This TM
will be especially useful to the development community to understand planning level
wastewater flows for various zoning categories and land use types.
• The Feature Manipulatfon Engine (FME) and Geographic Informatfon System (GIS) Data Exchange
Technical Memorandum (TM 6) provides the database and hydraulic model steps to import new
collectfon system informatfon from the City. This TM should be referenced by City staff looking to
make a system-wide model update using the City’s collectfon system GIS.
➢The Model Development and Results Technical Memorandum (TM 7) provides thorough
documentatfon on how the citywide hydraulic model was developed including the model
network and wastewater allocatfon. TM 7 describes the City’s collectfon system performance
criteria and evaluates how the existfng system performs. TM 7 also provides detail on the future
conditfon scenarios evaluated in the hydraulic model and the results. This TM will help the
reader understand the basis of the infrastructure improvement recommendatfons.
• The Risk Assessment Technical Memorandum (TM 8) details the analysis carried out to quantffy
the risk to existfng collectfon system infrastructure and help prioritfze rehabilitatfon and
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replacement (R&R) recommendatfons. This TM will be especially useful to City utflity staff and
for the public to understand why R&R is important and how the City plans those projects.
• The Capital Improvement Plan (CIP) Technical Memorandum (TM 9) provides a summary of the
recommended improvement projects, their estfmated cost, and recommended tfming for near-
term (0-5) and long-term (6-20) year improvements. In general, this provides the City with a
roadmap to address growth, risk, and maintenance related projects in a data driven logical
approach.
• The Asset Management Coordinate System Technical Memorandum (TM 10) provides a
summary of the current horizontal and vertfcal coordinate systems used throughout the
community and offers recommendatfons to standardize coordinate systems for the City to help
streamline and make consistent the process of moving from development plans > record survey
> City’s asset management system. This effort is included in this Facility Plan due to previous
significant data discrepancies in the City’s collectfon system GIS database.
➢The Updatfng Model Development Loading Technical Memorandum (TM 11) provides a step-by-
step process for incorporatfng new developments into the hydraulic model. The reader should
refer to this TM if they are seeking to make model updates based on developer’s plans.
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Chapter 3 Data Collection
The Data Collectfon Technical Memorandum (TM 3) provides details about the data used to develop the
collectfon system model and recommendatfons. There are four overarching categories of data used for
this Facility Plan:
1) Survey Data
2) Wastewater Flow Data
3) Operatfon Data
4) Geographic Informatfon System (GIS) Data
As of July 2020, there were approximately 4,800 manholes in the City’s wastewater collectfon system,
most of which included varying degrees of data. In general, most of the manhole informatfon did not
include detailed pipe invert informatfon. Approximately 1,400 manholes were field surveyed during the
summer and fall of 2020. The surveyed manholes were selected based on pipe diameter (10-inches or
greater), material of pipe (i.e., VCP prioritfzed to verify older infrastructure), and overall contributfng
area. Field survey included verifying locatfon, documentfng rim elevatfon, measuring depth to incoming
and outgoing pipes, and verifying pipe size, directfon, and material. The remaining manhole rim
elevatfons were determined using citywide LiDAR. The remaining sewer invert elevatfons were
determined by either interpolatfon between known points, from minimum pipe slope standards (DEQ 2),
or applicable record drawing informatfon.
Wastewater flow monitoring data was collected at six critfcal interceptors during spring runoff 2020
(April through June). These locatfons were chosen to enable model calibratfon of the various sewersheds
and based on discussions with City staff to understand prioritfes based on previous flow monitoring
efforts. The six interceptors monitored include the North Frontage Road, Baxter, Davis-Fowler, 27th
Ave/Cattail Creek, East Gallatfn River, and 19th Ave/11th Ave. In additfon to the 2020 monitoring data,
historical data was referenced, specifically ongoing efforts carried out by the City and a 2018 effort
conducted by Sanderson & Stewart which looked at inflow and infiltratfon (I&I) in the downtown region.
The operatfng data referenced in this Facility Plan includes lift statfon SCADA records, Water Reclamatfon
Facility (WRF) inflow, and water meter records from 2016 through July 2020. The lift statfon operatfon
data further helped with model calibratfon and validatfon. The WRF inflow data was used in model
calibratfon and in developing the various collectfon system flow components, which is discussed in detail
in the Wastewater Flow Characterizatfon Technical Memorandum (TM 5). Water meter records were
used to determine the domestfc component of wastewater generatfon, which is also detailed in TM 5.GIS
data provided by the City for this Facility Plan included:
• Wastewater collectfon system network (manholes, gravity main, force main, lift statfons)
• Water meter points
• Existfng land use
• Future land use
• Tax increment districts overlay
The land use and zoning GIS data used in this Facility Plan are from 2020. Future updates to the City’s
Growth Policy should be incorporated into future Facility Plan updates.
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Chapter 4 Manhole Condition Assessment Program
In response to aging collectfon system infrastructure and a growing need for efficient asset management,
a comprehensive approach to streamline manhole inspectfon protocols was developed. The Manhole
Conditfon Assessment Program Technical Memorandum (TM 4) summarizes the protocol.
The recommended inspectfon protocols were developed using the Natfonal Associatfon of Sewer Service
Companies Organizatfon (NASSCO) industry standards but modified to specifically address the City of
Bozeman’s needs and limitatfons. A unique inspectfon form was developed in Survey 123 that is simple
for operators to complete and integrates into the City’s asset management system (Granite XP or other
GIS databases). The inspectfon data can also be included in the City’s Risk Model which was developed
for this Facility Plan and is detailed in the Risk Assessment Technical Memorandum (TM 8). The City will
be able to more accurately prioritfze R&R improvement projects as more conditfon data is collected and
included into the Risk Model, resultfng in a more effectfve use of the limited maintenance funds.
The Conditfon Assessment Program also offers a recommended inspectfon schedule which utflizes the
existfng asset informatfon such as pipe material and age. There are approximately 1,000 manholes that
have been prioritfzed based on their estfmated low remaining useful life (RUL). These manholes
represent areas with vitrified clay and asbestos cement pipes. It is recommended that the City inspect
these 1,000 manholes over a 5-year period (200 manholes per year).
The proposed modificatfons to the manhole inspectfon procedure present a forward-looking approach to
infrastructure management. By incorporatfng immediate data entry, comprehensive risk and conditfon
assessments, and robust data storage and analysis methods, the City is poised to significantly improve its
wastewater system management. The initfatfve not only prioritfzes high-risk assets but does so in a
manner that is efficient, technologically supported, and aligned with best practfce methodologies. As the
City moves forward, these strategies will be crucial in managing its infrastructure strategically, ensuring
reliability, and optfmizing resource allocatfon within its wastewater collectfon system.
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Chapter 5 Wastewater Flow Characterization
Technical Memorandum 5 provides a comprehensive characterizatfon of the current and expected future
wastewater flows in Bozeman. This memorandum forms a foundatfonal component in guiding the
strategic planning for sustainable wastewater management, aligning with Bozeman's growth policies and
infrastructure demands, and adhering to environmental regulatfons.
The study area, primarily defined by the Growth Policy Boundary as per the Bozeman Community Plan
(Resolutfon No. 5133, November 17, 2020), encompasses a total area of approximately 45,000 acres,
with 13,400 acres within existfng City limits. This boundary has been delineated based on current
planning documentatfon, historical facility plans, geographic boundaries, and collaboratfve discussions
with City staff.
The memorandum provides a detailed wastewater flow analysis correlatfng land use and zoning
categories to wastewater productfon, which are referred to as duty factors. Duty factors, typically
referred to in gallons per acre per day, provide a streamlined method to understanding potentfal
wastewater flows from proposed development.
The key findings and recommendatfons from this analysis include:
• Citywide total annual wastewater flow is generally increasing corresponding to increasing
populatfon. It is estfmated that the average annual populatfon growth of the past decade is
approximately 4%. The average daily and peak hourly wastewater flow at the Water Reclamatfon
Facility from 2015 through 2019 was approximately 5.5 and 10.6 million gallons per day (MGD),
respectfvely. This equates to an average annual per capita flowrate of 117 gallons per capita per
day (gpcd).
• The City’s collectfon system experiences relatfvely high inflow and infiltratfon (I&I) throughout
the spring runoff season and into the early summer. This high I&I is primarily driven by
seasonally high groundwater which is prevalent throughout the City but especially within the
northwestern portfons. This Facility Plan recommends contfnuing to use the City standard 150
gallons per gross acre per day to represent a constant dry-weather base inflow. A duty factor of
550 gallons per gross acre per day was utflized for planning purposes for wet-weather periods to
account for varying conditfons.
• A rainfall derived inflow and infiltratfon (RDII) allocatfon was evaluated to simulate peak flows
and worst-case conditfons. The RDII allocatfon is based on the 25-year NOAA Atlas-2 24-hour
design storm, which has a total precipitatfon depth of approximately 2 inches. This method
provides a conservatfve estfmate of RDII but is deemed reasonable given climate change and the
age of the collectfon system leaving it susceptfble to higher I&I.
• The R3, R4, R5, B-2M, and REMU zoning categories have recently been coming into the City with
higher densitfes than previously assumed and to account for this increase, a specific sub-analysis
was carried out to determine the appropriate duty factors for denser developments. The duty
factors for these zones assume densitfes between 15-20 dwelling units per gross acre.
• Future land use categories were assigned duty factors based on allowed zoning categories
described in the 2020 Community Plan. The largest future land use category is Urban
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Neighborhood and is assumed to be approximately 9 dwelling units per gross acre with a dry-
weather duty factor of approximately 1,400 gallons per acre per day.
• An Infill Scenario was evaluated to understand the impacts from building out the current City
limits. This scenario assumes that undeveloped land within the City is developed based on its
zoning category or future land use. The Infill Scenario adds an additfonal 2.8 MGD to the system
under wet-weather conditfons.
• An Increased Density Scenario was evaluated to understand the impacts of redevelopment
occurring at denser land use than existfng conditfons. This scenario assumes that all existfng
single-family areas experience a 25% increase in wastewater loading, infill areas develop at 20
dwelling units per gross acre, and B2-M and REMU zones are increased to the R5 duty factor.
Additfonally, specific areas were adjusted to reflect City staff input on antfcipated development.
The Increased Density Scenario results in an additfonal 3.6 MGD in domestfc loading over
existfng conditfons. This scenario helps provide a general sensitfvity analysis against future
growth and helps identffy areas to monitor as the City contfnues to grow.
• This Facility Plan recommends the City contfnue to use its design standards to set the criteria for
sizing wastewater collectfon infrastructure, which are also consistent with the 2015 Facility Plan.
These standards include a domestfc wastewater loading value of 64.4 gallons per person per day
plus 150 gallons per acre per day for base inflow infiltratfon and the 10-state-standard
populatfon-based peaking factor. This method provides a ratfonal estfmate of peak wastewater
flow so that sewers can be sized to maintain adequate capacity.
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Chapter 6 FME and GIS Data Exchange
The Feature Manipulatfon Engine (FME) and GIS Data Exchange Technical Memorandum (TM 6) provides
a step-by-step process for globally updatfng the hydraulic model network (i.e., links and nodes) using the
City’s collectfon system GIS database. This process is specific to InfoSWMM, the current (as of September
2024) platiorm for the City’s collectfon system hydraulic model. When, or if, the City shifts to a different
hydraulic modeling software, this routfne will need to be revised.
TM 6 includes detailed workflows for updatfng data source files, initfalizing the model, selectfng
appropriate scenario, running the InfoSWMM GIS Exchange tool, executfng the exchange, verifying the
import, and correctfng connectfvity issues. This Technical Memorandum was developed to assist City
staff or future model users in ensuring the model is consistent with most recent City asset informatfon.
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Chapter 7 Hydraulic Model Development and Results
The Hydraulic Model Development and Results Technical Memorandum (TM 7) summarizes the methods
used and assumptfons made to develop the citywide calibrated hydraulic model. TM 7 outlines the
design criteria and standards for gravity main, force main, lift statfons and other wastewater collectfon
infrastructure. The model calibratfon was completed using the wet-weather flow monitoring informatfon
and is discussed at length in TM 7.
The primary performance criteria driving this Facility Plan include:
• The peak depth to diameter (d/D) ratfo for gravity sewer must be no greater than 0.75.
• The minimum allowable velocity in gravity mains is 2.0 feet per second.
• Gravity main shall generally be no deeper than 15 feet and no shallower than 5 feet (depth to
crown of pipe).
• Minimum and maximum force main velocitfes shall be 3 and 8 feet per second, respectfvely.
• Lift statfon pumping capacity shall be sized to meet peak flow rate under wet-weather
conditfons.
Existfng conditfons were evaluated under dry-and wet-weather conditfons. Generally, the collectfon
system meets performance standards. There are some areas that experience surcharging under existfng
conditfons, these areas are summarized in detail in TM 7. Improvements to address these deficiencies
were developed in conjunctfon with the risk assessment and future conditfon analysis so that cost-
effectfve projects are recommended.
Four future conditfon scenarios were evaluated using the hydraulic model. These scenarios include Infill,
Ultfmate Buildout (UBO), Ultfmate Buildout West (UBO West), and Increased Density. The Infill Scenario
evaluates impacts from development within the current City limits. The UBO scenario evaluates
complete buildout of the growth service area boundary and assumes all future wastewater is conveyed
to the City’s existfng Water Reclamatfon Facility. The UBO West scenario includes the same loading as the
UBO scenario but includes wastewater flow diversion to a future hypothetfcal wastewater treatment
facility assumed to be located northwest of the City limits. This scenario optfmizes gravity flow and can
eliminate the need for several existfng and future lift statfons but would require substantfal planning to
establish a new treatment facility. Finally, the Increased Density scenario evaluates increased wastewater
generatfon within City limits to simulate high densitfes of redevelopment and infill. This scenario
assumes the wastewater loading outside City limits is consistent with the UBO scenario. Collectfon
system infrastructure was sized and laid out within each scenario to maintain the City’s performance
criteria. TM 7 provides figures and detailed descriptfons of the future infrastructure.
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Chapter 8 Risk Assessment
The Risk Assessment Technical Memorandum (TM 8) summarizes the assessment performed for the
City’s collectfon system pipes. The goal of this assessment is to establish a methodical, data-driven, and
adaptable framework for evaluatfon risks of potentfal sewer system failures. The assessment process
uses data from GIS, the hydraulic model, historical stoppages, and CCTV records, along with the
InfoAsset Planner® software for modeling.
Risk is calculated using two main criteria, Consequence of Failure (COF) and Likelihood of Failure (LOF),
which are combined to assess risk levels for each asset. COF assesses the impact of failure on system
operatfons and LOF estfmates the probability of failure based on factors like pipe material, historical
issues, and hydraulic performance. COF is primarily based on pipe flow rate. LOF criteria include factors
such as pipe material, flow depth-to-diameter ratfo, NASSCO defect ratfngs, repair history, and remaining
useful life. Assets with high-risk scores were grouped with other priority assets as identffied through the
existfng and future conditfons hydraulic modeling to inform the near-term capital improvements plan.
It is recommended to update this Risk Assessment periodically with new conditfon inspectfon data, work
order logs, revised GIS, and revised hydraulic model results. This update will likely be required every
three to five years.
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Chapter 9 Capital Improvement Plan
The purpose of the Capital Improvement Plan Technical Memorandum 9 (TM 9) is to present
recommended capital improvement projects aimed at enhancing the hydraulic performance of the
existfng system, address aging and critfcal assets, and ensure capacity for future expansion. These
recommendatfons are based on evaluatfons from hydraulic modeling, risk assessments, and
consultatfons with City staff. TM 9 includes projects to address both near-term (5-year) and long-term (6-
20 year) needs, providing detailed descriptfons, cost estfmates, and implementatfon consideratfons. It
also revisits previously recommended but unconstructed projects to determine their current relevancy
and incorporates them into a comprehensive Capital Improvement Plan (CIP) to ensure efficient and
cost-effectfve allocatfon of capital resources. Table 9-1 below lists the priority near-term improvement
projects, their total project cost in 2024 dollars, and their primary drivers (i.e., existfng capacity, risk
assessment, or system expansion). TM 9 provides more detail including maps displaying project
locatfons.
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Table 9-1 – Summary of Near Term (5-year) Capital Improvement Projects
Project Total Project Cost Project Drivers
Project 1 – 19th Ave / Kagy Blvd Interceptor
Improvements $5,291,600 Infill capacity
Critical aging infrastructure
Project 2 – Durston Road and 17th Avenue
Sewer Main Replacement $959,900 Critical aging infrastructure
Project 3 – 7th Avenue to Oak Street Sewer
Main Replacement $1,276,400 Critical aging infrastructure
Project 4 – North 11th Avenue Sewer Main
Replacement $574,400 Critical aging infrastructure
Project 5 – Plum Avenue Sewer Main
Replacement $1,326,500 Critical aging infrastructure
Project 6 – 4th Avenue, Babcock Street and
Grand Avenue Sewer Main Replacement $665,000 Existing capacity concerns
Critical aging infrastructure
Project 7 – North 9th Avenue, West Villard
Street, and South 9th Avenue Sewer Main
Replacement
$2,159,300 Critical aging infrastructure
Project 8 – West Harrison Street, 10th Avenue,
and Curtiss Street Sewer Main Replacement $2,478,600 Critical aging infrastructure
Lift Station Project 1 – Valley Center Lift Station $5,962,700 System expansion
Small Pipe Project 1 – South Black Avenue 6-
inch Sewer Main Replacement $1,817,000
Existing capacity concerns
Critical aging infrastructure
Small Pipe Project 2 – South Willson Avenue 6-
inch Sewer Main Replacement $1,721,700
Small Pipe Project 3 – South Grand Avenue 6-
inch Sewer Main Replacement $1,377,600
Small Pipe Project 4 – West Olive Street 6-inch
Sewer Main Replacement $691,400
Small Pipe Project 5 – South 4th Avenue 6-inch
Sewer Main Replacement $961,100
Small Pipe Project 6 – South 3rd Avenue 6-inch
Sewer Main Replacement $971,800
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Chapter 10 Asset Management Coordinate System
The Asset Management Coordinate System Technical Memorandum (TM 10) provides recommendatfons
for transitfoning the City of Bozeman to a uniform coordinate system. The City faces challenges in
efficiently managing the substantfal data associated with rapid development and City expansion. This
memorandum emphasizes the necessity of adoptfng a consistent vertfcal and horizontal coordinate
system for all drawings and surveys to streamline workflows and enhance data management.
Currently, there is no official policy in place requiring developers to submit digital data covering newly
installed City assets. The City has adopted the North American Vertfcal Datum 1988 (NAVD 88) through
Resolutfon 5113 and Ordinance 2032 for vertfcal datum but there is no formal resolutfon establishing a
uniform horizontal coordinate system or projectfon. The lack of consistency has led to significant
inefficiencies within City departments.
A citywide horizontal coordinate system should be established. This system will align all future
engineering and surveying efforts, ensuring consistency in project executfon and data management. The
City should contfnue using NAVD 88 as the uniform vertfcal datum for all projects. This will standardize
elevatfon data, aiding in more accurate and reliable engineering practfces.
It is recommended the City conduct a preliminary engineering study to determine the cost of a GPS
survey base statfon. This base statfon facility would enhance the accuracy of geospatfal data collected
throughout the City, supportfng surveying and constructfon projects.
It is also recommended that additfonal permanent monuments be installed. Durable monuments should
be established and maintained across the City at approximately one-mile intervals. These should be
placed in safe, accessible locatfons such as City parks or rights-of-way, and away from overhead
impediments to facilitate easier use by GPS. Each monument should be well-documented, including its
date of establishment, coordinates, and a descriptfon of its locatfon, ensuring their utflity for future City
projects.
The implementatfon of these standards and recommendatfons requires coordinated efforts from City
departments and external engineering and surveying firms. Specific measures include setting a citywide
horizontal and vertfcal control network under the supervision of a Licensed Professional Land Surveyor
and documentfng each control point accurately. Ensuring that all new data submissions adhere to these
standards will optfmize the City’s project efficiency and data integrity.
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Chapter 11 Updating Model Development Loading
Technical Memorandum 11 includes a step-by-step workflow for updatfng the InfoSWMM model with
new or additfonal loading based on development plans. It should be noted that the City may shift to a
new platiorm for its Collectfon System hydraulic model – if this occurs, TM 6 and TM 11 would need to
be refreshed to provide an updated workflow specific to the new platiorm / hydraulic modeling
software.
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2.0
Definition of Terms and
Acronyms
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
2.0 – Definition of Terms and Acronyms
Definition of Terms and Acronyms
Term
acres
Average Annual Flow AAF
Defined as the total flow for a one-year period divided by t he number
of days in the year. AAF includes domestic flow, base infiltration flow,
and RDII flows.
Base Infiltration BI
A port ion of total wastewater flow defined as the portion of
Montana Department of
Environmental Quality DEQ
Domestic Flow
A port ion of the total wastewater flow defined as flow that originates
Dry We ather BI A port ion of total wastewater flow defined as ground water that enters
the system during the winter months (dry season).
Dry We ather Flow DWF
Defined as the wastewater flow in the collection system that is not
Feature Manipulation
Engine FME
Gallons per acre per day gpad
Gallons per capita per day gpcd
Gallons per day per inch-gpd/idm
Gallons per minute gpm
Geographic Information GIS
Inflow and Infiltration I&I
Inflow and infiltration refers to water that enters the wastewater
collection system originating from groundwater, rainfall, and/or
snowmelt.
Maximum 30-Day Flow
Defined by t aking the 30-day rolling average daily volume of
Maximum Daily Flow Defined as the maximum volume of wastewater over a period of one
calendar day.
Maximum Hourly Flow Defined as the maximum volume of wastewater over a period of one
Maximum Monthly Flow
Defined by t aking the volume of wastewater for each month and
averaging the flow over the number of days in the month. The
maximum value is reported as the maximum monthly flow.
Million ga llons per day MGD
Minimum Daily Flow Defined as the minimum volume of wastewater over a period of one
calendar day.
Minimum Monthly Flow
Defined by t aking the volume of wastewater for each month and
2.0 – Definition of Terms and Acronyms Page 1
Definition Acronym
ac
wastewater flow that enters the wastewater collection system as a
constant flow. The flow varies throughout the year and is influenced
by t he ground water table an d seasonally by sprin g runoff/snowmelt
and by dr y or winter conditions.
from indoor plumbing and water use including residential, commercial,
and industrial activities.
affected by ra in events. This includes domestic flow and dry weather
BI.
diameter-mile of pipe
System
wastewater. The maximum value is reported as the maximum 30-day
flow.
hour.
averaging the flow over the number of days in the month. The
minimum value is reported as the minimum monthly flow.
WRF Wastewater treatment plant.
Wastewater Collection System Facility Plan – 2024 Update
2.0 – Definition of Terms and Acronyms
Montana State University MSU
Non-Irrigation Demand
Defined as metered water consumption during months that are not
impacted from seasonal outdoor water use. Used to define the
domestic flow entering the wastewater collection system.
North American Vertical NAVD 88
Operation and
Maintenance O&M
Optical Remote Sensor
Laboratory ORSL
Poly-vinyl-chloride pi pe PVC
Rainfall Derived Inflow and RDII
Defined as the portion of wastewater flow that originates from rain
Reinforced concrete pipe RCP
Supervisory Control and SCADA
Wastewater Duty Factor WWDF Wastewater flow generated per unit area associated with land use or
zoning - typically in units of gallons per acre per day.
Water Reclamation Facility
Wet Weather BI
A port ion of total wastewater flow defined as ground water that enters
the system during the wet months caused by h igh ground water due
to spring runoff.
Wet Weather Flow Defined as the total wastewater flow during the spring runoff season
Net Area
When discussing land use or zoning, net area refers to the area that is
developed and therefore generates wastewater flows. Net area
excludes right-of-way, riparian areas, and other protected areas.
Gross Area
When discussing land use or zoning, gross area refers to an area
Ultimate Build-Out UBO Complete development of the entire Growth Policy Boundary.
Universal Transverse
UTM
Urban Renewal District URD Areas within the City of Bozeman established to encourage
redevelopment by le veraging property tax within the district.
Tax Increment Finance TIF Districts
Areas within the City of Bozeman established to encourage
Vitrified clay pipe VCP
2.0 – Definition of Terms and Acronyms Page 2
National Association of
NASSCO
A prof essional organization providing standardization, education,
replacement.
technical resources, and advocacy for underground infrastructure
operation and maintenance, condition assessment, rehabilitation, and Organization
Sewer Service Companies
Datum 1988
events. Water that enters the system during and after the storm via
inflow and infiltration. Infiltration
Data Acquisition
encompassing developable land, potential streets, and protected
areas.
Mercator Coordinate
System
Districts development or redevelopment by le veraging property tax within the
district.
and includes domestic flow and wet weather BI flow. WWF
3.0
Data Collection
Technical Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Table of Contents
Chapter 1 Introduction and Purpose .................................................................................... 2
Chapter 2 Survey Data............................................................................................................ 3
2.1 Collection Methodology ..................................................................................................................................4
Chapter 3 Flow Monitoring Data........................................................................................... 6
3.1 Historical Monitoring Data..............................................................................................................................6
3.2 Spring 2020 Monitoring Data........................................................................................................................7
3.3 Monitoring Methodology ............................................................................................................................. 10
3.4 COVID-19 Pandemic Considerations ........................................................................................................ 10
Chapter 4 Operating Data ....................................................................................................12
4.1 Lift Stations......................................................................................................................................................... 12
Chapter 5 Water Reclamation Facility Inflow .................................................................... 14
Chapter 6 Water Meter Data (Domestic Water Meter Data)............................................ 15
Chapter 7 GIS Data................................................................................................................ 16
List of Tables
Table 3.1: Summary of Historic and Downtown Wastewater Flow Monitoring Efforts ........................7
Table 3.2: Summary of Spring 2020 Wastewater Flow Monitoring Efforts ..............................................8
Table 3.3: Summary of City Lift Stations..............................................................................................................12
List of Figures
Figure 2-1: Surveyed Manholes.................................................................................................................................5
Figure 3-1: Flow Monitoring Locations...................................................................................................................9
Figure 4-1: City of Bozeman Collection System ................................................................................................13
Technical Memorandum 3.0 Page 1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 1 Introduction and Purpose
The purpose of the Data Collection Technical Memorandum (TM) is to describe the data
structure, format, collection processes, and methodology required to update the City’s
Wastewater Collection System hydraulic sewer model. The TM is broken down into the following
sections:
1. Collection System Infrastructure Survey Data
a. Rim and Invert Elevations
2. Wastewater Flow Monitoring Data
3. Wastewater Collection System Operation Data
a. Lift Station Wetwell Dimensions, Pump Type, Pump Records
b. Water Reclamation Facility (WRF) Influent flow
c. Water Meter Data
d. GIS Data
In addition to this TM describing the data collected, a folder with pertinent digital data files was
provided to the City. The folder includes the following information:
• Survey Data
o Raw manhole survey data in .csv and .dwg format
o Note that this data was compiled to include in the hydraulic model and provided
through the electronic deliverables associated with TM 5 and TM 7.
• Flow Monitoring Information
o Single Excel spreadsheet with compiled 2020 manhole flow monitoring data
o WRF Inflow Excel spreadsheet
o Historic (2016-2019) monitoring data in individual Excel spreadsheets (by Others)
• Lift Station Information
o Excel spreadsheet with compiled list of lift station pump model and serial number
o SCADA Lift Station Levels at 1 min intervals (2016-2020)
o Note that lift station record drawings are available through the City’s online portal
Infrastructure Viewer:
https://gisweb.bozeman.net/Html5Viewer/?viewer=infrastructure
• Water Meter Data
o Excel spreadsheets with city-wide water meter information for 2015-2020
• GIS Data Shapefiles
o Surveyed manhole locations, surveyed pipes, split manholes, monitoring manhole
locations
Technical Memorandum 3.0 Page 2
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 2 Survey Data
The City’s Wastewater Collection System includes approximately 4,800 manholes and over
230 miles of sewer. In general, a majority of the City’s collection system has been constructed
from new development, which is required to submit final as-built record drawing information to
the City at the end of a project. Typically, the record drawings include manhole invert data,
material specifications, and locations of the asset. This information was reviewed and
incorporated into the GIS data and model. Sewer invert and size information was taken from the
drawings and manually added to the GIS pipe network data. The vertical datum was verified for
each record drawing to ensure consistency with GIS and subsequent model data. The North
American Vertical Datum 1988 (NAVD 88) is the standard datum used throughout this facility
plan unless otherwise noted.
After a detailed review of the City’s existing GIS and as-built information it was determined that
an additional survey was needed. It was decided by the City to survey approximately 1,400
manholes that lacked definitive invert information. Manholes selected for detailed surveying
were prioritized based on pipe diameter (10-inch or greater), material, and overall contributing
area, with the larger sewer trunk mains taking precedence. Manholes that were identified that
lacked invert and pipe-size information, but did not make the survey prioritization list, were
determined by assuming minimum pipe slope based on the Montana Department of
Environmental Quality (DEQ) Design Standards for Public Sewage Systems (DEQ Circular 2,
2018). Inverts were computed upstream or downstream from a known invert elevation (i.e.,
where record drawings or survey was available) by multiplying the minimum pipe slope
respective to the sewer size by the GIS pipe length.
Gathering additional detailed survey information was a critical path in developing the hydraulic
model. Accurate survey information helps ensure that the hydraulic calculations within the
model accurately represent system pipe slope, size, and, ultimately, capacity.
Moving forward, the City is refining its data standards to ensure this information is included in
all submittals and is in a user-friendly data format. It is recommended that the City continues to
collect invert information, specifically on larger diameter assets, to accurately reflect existing and
future pipe capacity within the hydraulic model. Figure 2-1 shows the City’s collection system
and highlights the surveyed manhole locations. Note that the shapefiles included in the figures
were provided to the City as part of the overall electronic deliverable for this Facility Plan.
Specific attribute fields within the hydraulic model were added so the City can easily determine
whether an invert was surveyed, manually calculated using the 10 state standards method, or
obtained from an as-built drawing.
Technical Memorandum 3.0 Page 3
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
2.1 Collection Methodology
All elevations associated with the survey are in the City’s adopted vertical datum NAVD 88. TM
10 provides a detailed description of the vertical and horizontal datum associated with this
project. The field survey was carried out between May and August 2020.
TD&H, a subcontractor of the facility plan update, was contracted to perform the field survey
using survey-grade Trimble GPS receiver models R6, R10, & R10-2 with a vertical measurement
tolerance of ±0.06 feet. Where GPS measurements were not feasible, a Trimble Robotic Total
Station model S7 was used with a vertical tolerance of ±0.03 feet. TD&H measured the top of
the visible pipe within the manhole using a Schneider Corp V. Depth measuring tool. This tool
uses a Leica Disto model D810 laser measuring device. The manufacturer’s specification states a
maximum measuring tolerance of 0.08 inches. The V. Depth measuring tool was provided by the
City of Bozeman. The stated measurement tolerance for the D810 does not consider human and
environmental factors associated with the measurements of underground pipes. The location of
some pipes within the sewer manholes prevented the use of the V. Depth measuring tool, so
these measurements were obtained using a survey leveling rod. Pipe inverts were calculated
using the measured top of pipe elevations and pipe diameters from the City GIS or record
drawings. Pipe sizes were field verified at split manholes. Split manholes were surveyed using a
LiDAR scanner (Leica BLK360), which generates scaled 3D renderings, enabling the user to
measure accurate pipe inverts and pipe sizes.
All inverts, pipe size, and pipe material information was transferred to the GIS data either
manually or through the ArcMap “spatial join” tool, which associates information from one data
source to another based on a shared location. A point shapefile representing manholes and a
polyline shapefile representing pipes with all gathered hydraulic modeling information (rim
elevations, invert elevations, pipe size, and pipe material) was compiled to provide integration
into the hydraulic model. The model integration process is further described in TM 6 FME and
GIS Data Exchange Routine.
Technical Memorandum 3.0 Page 4
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 3 Flow Monitoring Data
3.1 Historical Monitoring Data
The City of Bozeman periodically monitors wastewater flows throughout their system to assess
inflow and infiltration (I&I), evaluate system capacity against proposed development, and
recalibrate the hydraulic model. Historical flow monitoring data for 2016 through winter 2020
were obtained from TD&H Engineering, who the City has utilized to conduct flow monitoring.
It should be noted that the Midtown Urban Renewal District and the Downtown Urban Renewal
District conducted a joint sewer flow monitoring effort in 2018 with Sanderson & Stewart at a
number of different manhole locations in the downtown region. The goal of the joint effort
monitoring project was to better understand localized I&I associated with the downtown region
and the wastewater infrastructure required to serve the Midtown and Downtown Urban districts
at full buildout. The downtown metered locations are bolded in Table 3.1 for reference.
Table 3.1 summarizes the historical flow monitoring data.
Technical Memorandum 3.0 Page 6
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Table 3.1: Summary of Historic and Downtown Wastewater Flow Monitoring Efforts
MH ID1 Location Sewershed
K0005 Cattail & Vaquero Baxter Creek
K0147 Cattail & Vaquero Baxter Creek
L0424 Durston & Enboe Cattail Creek
L0548 Slough Creek Cattail Creek
I0421 20th & Durston Farmers Canal
I0406 Babcock & 19th Farmers Canal
G0418 10th & Beall Upper Rouse
G0426 9th & Mendenhall Upper Rouse
G0520 10th & Olive Spring Creek
G0583 Babcock & 8th Spring Creek
F0405 Grand & Villard Upper Rouse
F0517 Babcock & Tracy Upper Rouse
F0522 Black & Olive Upper Rouse
F0433 Beall & Bozeman Upper Rouse
F0431 Mendenhall & Bozeman Upper Bozeman Creek
F0429 Main & Bozeman Upper Bozeman Creek
E0505 Bogert Park Upper Bozeman Creek
F0307 Tamarack & Grand Upper Rouse
F0312 Tracy & Aspen Upper Rouse
F0320 Aspen & Bozeman Upper Rouse
F0405 Villard & Grand Upper Rouse
F0332 Rouse & Juniper Upper Rouse
F0328 Rouse & Cottonwood Upper Bozeman Creek
E0302 Rouse & Church Upper Bozeman Creek
D0421 Village Downtown Upper Bozeman Creek
D0503 Ellis & Highland Upper Bozeman Creek
G0135 Gallatin Park East Gallatin River
I0107 Simmental & Baxter Spring Creek
G0225 Walmart East Gallatin River
G0309 7th & Juniper East Gallatin River
1 Bold values represent downtown metered locations (Sanderson & Stewart 2018)
3.2 Spring 2020 Monitoring Data
Additional flow monitoring was necessary to fill in data gaps in the historical data set and
provide a basis for model calibration. To augment these data gaps, additional wastewater flow
was monitored at six locations around the City from April 16, 2020, to June 25, 2020. The
additional flow monitoring locations were selected based on where historical data was generally
not collected and in locations lower in the overall sewershed (North of Main Street), which
corresponded with larger trunk mains that collect substantial wastewater flow from the greater
network. It was decided to collect additional data at the Walmart location to bolster the previous
data set and quantify flow changes at this particular location.
Figure 3-1 shows the spring 2020, Sanderson & Stewart 2018, and historic monitoring locations
utilized in this analysis. Table 3.2 summarizes the flow monitoring location, GIS manhole
Technical Memorandum 3.0 Page 7
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
identification number (MH ID), sewershed, year, associated monitoring period, and number of
precipitation events observed during monitoring period.
The historical and spring 2020 flow data were used to calibrate the hydraulic model, which is
described in TM 7.
Table 3.2: Summary of Spring 2020 Wastewater Flow Monitoring Efforts
Location
Frontage Rd
Oak & Davis
Oak & Davis
Catamount &
Valley Creek
Walmart
Juniper & Oak
Park
Trunk Main
North Frontage
Road
Interceptor
Baxter
Interceptor
Davis-Fowler
Interceptor
27th Ave/Cattail
Creek
Interceptor
East Gallatin
River
Interceptor
19th Ave/11th
Ave
MH ID
I5012
K0319
J0306
I5009
G0225
H0325
Sewershed
East Gallatin River
Cattail Creek
Cattail Creek
Cattail Creek
East Gallatin River
Spring Creek
Year
2020
2020
2020
2020
2020
2020
Period of
Monitoring
4/16-6/25 2020
4/16-6/25 2020
4/16-6/25 2020
4/16-6/25 2020
4/16-6/25 2020
4/16-6/25 2020
Number of
Precipitation
Events+
10
10
10
10
10
10
+ Precipitation event defined as rain event producing at least 0.2 inches
Technical Memorandum 3.0 Page 8
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
During the spring 2020 monitoring period, a number of rainfall events were observed. However,
not all rainfall events solicited an I&I response within the system. For modeling and data
management purposes, a precipitation event was defined as a rain event that produced at least
0.2 inches of measurable precipitation.
The largest rain event during the spring 2020 monitoring period occurred on June 17; over 0.6
inches of precipitation was produced, and a noticeable I&I response was observed at the flow
monitoring locations deployed in the City’s collection system. Given the observed I&I response
and size of the rainfall event, the June 17 rain event was utilized for the wet-weather calibration
period in the hydraulic model.
In addition to the spring 2020 monitoring data, historical monitoring data were used to verify
model results and calibrate the Downtown and Midtown areas. The 2018 Sanderson & Stewart
monitoring data were specifically used to calibrate the Downtown and Midtown areas. A 1-inch
precipitation event that occurred on June 29th 2018, was used to assess and modify wet-weather
peaking factors for the areas monitored by Sanderson & Stewart within the hydraulic model.
The wet-and dry-weather model calibrations are described in TM 7.
3.3 Monitoring Methodology
The spring 2020 wastewater flow monitoring effort was coordinated with TD&H Engineering.
TD&H Engineering, with the help of City staff, ultimately installed and collected flow information
at the various locations.
Hach FL900 flow meters with Hach Flo-Dar Sensors were placed in the selected manhole
locations as defined in Table 3.2. Flow monitoring data were recorded at one-minute intervals,
downloaded from the devices fortnightly, and reviewed to ensure fidelity. Precipitation data for
the monitoring period were collected from the Optical Remote Sensor Laboratory (ORSL) at
Montana State University (MSU) at five-minute intervals. Through discussions with the City, the
MSU monitoring station was selected due to its proximity to the collection system and metered
manholes and its data reliability (consistent record since 2005).
3.4 COVID-19 Pandemic Considerations
Wastewater flow data were collected between April and June 2020 during the COVID-19
pandemic. The consequences of the pandemic, such as the spring quarantine and ongoing
restrictions, likely altered the wastewater flow characteristics normally observed in Bozeman. For
instance, Montana State University shifted to remote learning before students returned from
Spring Break, thereby decreasing wastewater contributions from campus. Many Bozeman
businesses instituted work-from-home policies during this time period, and most restaurants
had no in-restaurant food service. Given the unique impacts of COVID-19 on sewer flow
patterns, City staff, AE2S, and TD&H discussed whether to proceed with flow monitoring prior to
Technical Memorandum 3.0 Page 10
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
deploying the flow meters in April. Consensus was reached to move forward with collecting flow
data, understanding that the primary goal of this effort was to evaluate I&I contributions and
calibrate the hydraulic model, both of which are achievable regardless of impacts to dry-weather
flow patterns from COVID-19. After collecting flow meter data, an analysis was completed to
better understand the potential impacts of the COVID-19 quarantine. April 2019 and 2020
monitoring data were compared to evaluate how COVID-19 affected peak-hour factors. The
2020 peak hour factor was less than 3% lower than in 2019 during dry weather flow – causing
negligible change between the diurnal patterns. Based on this analysis, the City decided to use
the 2020 data for model calibration.
Technical Memorandum 3.0 Page 11
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 4 Operating Data
4.1 Lift Stations
The City provided lift station data, including:
• Lift Station record drawings (provided through Infrastructure Viewer
https://gisweb.bozeman.net/Html5Viewer/?viewer=infrastructure)
• Current pump operating set points, model, and serial numbers
• SCADA data records from 2016 through July 2020
Table 3.3 provides a high-level summary of the City’s lift stations, including the name, number
of pumps, pump manufacturer, and whether the lift station was included in the hydraulic model.
The lift station information provided by the City was utilized to update and calibrate the model.
Figure 4-1 shows the existing lift stations and associated sewershed.
Table 3.3: Summary of City Lift Stations
Lift Station Name
Baxter Meadows
Bridger Center
Burrup
Cattail Lake
Davis Lane
Laurel Glen
Loyal Gardens
Norton Ranch
Water Reclamation Facility
Cardinal Distribution
Links
MDT
Nelson Meadows
Overbrook Dr.
Seebna
Walker
Number of
Pumps
3
2
2
2
3
2
2
3
N/A
-
2
2
2
2
2
2
Pump Manufacturer
Flygt
Hydromatic
Flygt
Flygt
Flygt
Flygt
Flygt
Flygt
N/A
-
-
Pentair
Flygt
-
-
-
Lift Station
Owner
City
City
City
City
City
City
City
City
City
Private
Private
Private
Private
Private
Private
Private
Station Included
in Model
(Yes/No)
yes
yes
yes
yes
2yes
yes
yes
yes
3no
1no
yes
yes
yes
yes
yes
yes
1 No infrastructure modeled upstream
2 Not operational during flow monitoring or calibration period
3 End of network
Technical Memorandum 3.0 Page 12
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 5 Water Reclamation Facility Inflow
The City provided inflow data for the Water Reclamation Facility (WRF) from 2016 through July
2020 in five-minute increments. Figure 3.4 shows the average monthly WRF inflow annually
from 2016 through July 2020. April through June inflow is significantly higher due to the
influence of groundwater inflow and rainfall-derived infiltration, this was especially pronounced
in 2018 and 2019. The WRF data were used to calibrate the hydraulic model, specifically
downstream hydraulic and I&I conditions observed during periods of wet weather.
Figure 3.4: Water Reclamation Facility Inflow
It should be noted that the provided WRF influent flow generally correlates with seasonal high
groundwater conditions observed within the City. The Montana Bureau of Mines and Geology
(MBMG) records historic groundwater elevations for several wells in Bozeman, most of which
showed historically high groundwater levels in 2018. The higher groundwater appears to have
led to increased infiltration into the City’s sewers. Recognizing seasonal high groundwater
significantly influences both collection and treatment capacity, inflow from groundwater was
incorporated into the wet-weather model scenarios – this analysis and allocation methodology
is further discussed in TM 5.
Technical Memorandum 3.0 Page 14
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 6 Water Meter Data (Domestic Water Meter
Data)
Water meter data from the City’s water utility was compiled from 2015 through 2019. The data
was used to establish domestic wastewater flow allocation. The City provided data for all
domestic City water meters on monthly billing intervals. The City provided meter locations in a
point-feature shapefile. Additional details and analyses of the meter data are provided in TM 5.
Technical Memorandum 3.0 Page 15
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 3.0 – Data Collection
Chapter 7 GIS Data
The City provided multiple GIS datasets utilized in the model update process. Unless noted
otherwise, all GIS data are projected in UTM Zone 12N coordinate system. The data relevant for
this project include:
• Wastewater Collection System Network
o Manholes
o Gravity mains
o Force mains
• Water Meters
• Existing Land Use
• Existing Zoning
• Future Land Use
• Tax Increment Districts Overlay
All GIS data for this facility plan update was provided by the City in 2020. The City updated the
City’s GIS Wastewater Collection System Network database in early 2020 to correct manhole
locations, connectivity, and pipe attributes. The City and AE2S developed a feature manipulation
engine (FME) to populate the network database with relevant hydraulic modeling parameters.
This FME routine and model update methodology are described in detail in TM 6. Subsequently,
in 2023, a model network update was completed using updated GIS data from the City.
Technical Memorandum 3.0 Page 16
4.0
Manhole Condition
Assessment Technical
Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Table of Contents
Chapter 1 Purpose and Need................................................................................................. 2
Chapter 2 NASSCO Standards................................................................................................ 3
Chapter 3 Overview of Recommended Program................................................................. 4
Chapter 4 Recommended Inspection Schedule ................................................................... 6
Chapter 5 Recommended Data Synthesis and Analysis ...................................................... 8
Appendix A – Recommended Inspection Form .............................................................................................9
Appendix B – Survey 123 Workflow...................................................................................................................11
Appendix C – Manhole Imaging Technology................................................................................................ 12
List of Figures
Figure 4-1: Recommended Inspection Phasing Plan.........................................................................................7
Technical Memorandum 4.0 Page 1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Chapter 1 Purpose and Need
This Manhole Condition Assessment Program (MCAP) has been established to help the City of
Bozeman collect and synthesize manhole asset condition information. The City currently collects
closed circuit television (CCTV) data for wastewater pipes but has yet to implement a standard
practice for evaluating manhole condition.
The purpose of the MCAP is to provide the City staff with tools to help make informed data-
driven decisions on infrastructure operation, maintenance, and replacement. The City’s
wastewater collection system includes infrastructure dating back to the early 1900s. Much of the
aging infrastructure is located within areas of the City with higher population density (e.g.,
downtown) and the consequence of failure is greater. These areas are also experiencing
development pressure.
The City also experiences development pressure on the west end, where groundwater levels are
known to be high. This can lead to increased operation and maintenance (O&M) costs and
decrease the expected life of infrastructure. Manholes are susceptible to structural defects and
can be significant sources of inflow and infiltration (I&I). The addition of unwanted I&I can lead
to excessive wastewater flows and decrease the system’s overall capacity .
The MCAP will evaluate every manhole within the City with priority given to aging manholes and
manholes in areas with high groundwater and risk of I&I. Assessments performed on new
manholes will serve as condition baselines for future inspections. Manhole condition
assessments can be time-consuming and difficult to objectively complete. To streamline
inspections and improve consistency throughout the process, it is beneficial to follow an
established standard.
It is recommended that the City begin with simple manhole inspections collecting basic
condition information as outlined in Appendix A (modified National Association of Sewer
Service Companies Organization (NASSCO) inspection form). At a minimum, it is recommended
that the City establish an inspection protocol that is both simple and meaningful. Documenting
both the structural condition as well as operation and maintenance issues on a 1 to 10 scale will
help ensure the data collected will be compatible with future full scale NASSCO inspections
should the City decide to go that route.
Technical Memorandum 4.0 Page 2
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Chapter 2 NASSCO Standards
The National Association of Sewer Service Companies Organization (NASSCO) helps set industry
standards for the condition assessment of sewer infrastructure. The Manhole Assessment
Certification Program (MACP) focuses on condition scoring/codes for the assessment of sewer
manholes.
The MACP inspection form is broken into two types of inspections, which are described below:
• Level 1 MACP -“A level 1 MACP inspection will allow utility owners to gather basic
condition assessment information to evaluate the general condition of a manhole,
and to gather enough information to determine if a comprehensive Level 2
inspection is appropriate. A level 1 inspection can be completed without the use of
any special equipment or manned entry into a manhole.”
• Level 2 MACP -“The purpose of a Level 2 MACP inspection is to gather detailed
information to fully document all existing defects, determine the condition of a
manhole, and to provide specific information to recommend or specify corrective
actions. Level 2 inspections should be carried out via man-entry, camera, measurement
tools, and /or other specialized equipment.”
MACP provides comprehensive protocols and standards for managing and evaluating asset
conditions. Many of the procedures within the MACP standards require a higher level of effort
than what may be necessary for the City at this time. For example, the MACP inspection form
requires a total of 71 fields of information for City staff to fill out to complete a Level 2
inspection. Capturing data for all 71 fields can be beneficial once a program has been
established, however, given the City’s current staffing and resources, it is impractical to collect all
this data at this time. Therefore, City Staff and AE2S closely evaluated the inspection forms and
selected fields that capture the physical conditions of the manholes while also being easy to
collect for crews that are completing standard CCTV collection. Furthermore, these fields can be
incorporated into a risk assessment to evaluate the overall risk of the asset. Fields included in
the customized inspection form include inspection date, surface type, street location, size, and
surface material.
Technical Memorandum 4.0 Page 3
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Chapter 3 Overview of Recommended Program
The recommended MCAP provides an efficient method of data collection, utilizing tools that will
seamlessly integrate into the framework of the risk assessment model. A summary of how this
program will operate is provided below:
• A condensed manhole inspection form following NASSCO MACP standards will guide
the field inspection protocol. Appendix A shows this condensed form and highlights
the recommended data fields to complete during condition assessment inspections.
• The City’s current GIS production database of the sewer collection system will be used
as the foundation for a Survey 123 application developed by AE2S. Appendix B shows
screenshots of a similar Survey 123 inspection form and summarizes the typical Survey
123 field workflow.
o The Survey 123 application allows field crews to conduct manhole condition
assessments on a City provided mobile device by filling out the form created
by AE2S, with the survey results being automatically linked to their
respective manholes.
o The Manhole form will have selectable prepopulated answers/defect codes
that align with NASSCO MACP standards. Standard prepopulated forms
generally help reduce overall field time and help eliminate human error of
incorrectly typing defect codes.
• Photos of the manholes can also be directly loaded from the mobile device into
the Survey 123 application.
o It is recommended to capture images of the manhole using one of these
three options. Appendix C includes a matrix with pros, cons, and costs for
alternative imaging equipment:
▪A GoPro camera mounted on a long rod with an externally mounted
light.
▪CUES Lite Stick -City-owned manhole inspection imaging technology.
• Insta360 Camera – similar technology to GoPro and provides high-quality 360° still
images.
o The Bluetooth capabilities of the GoPro and Insta360 cameras will allow the
field crews to view the defects in real time, and appropriately log the defects
in the Survey 123 form.
o Photos and videos recorded should be geotagged to easily be joined to
the appropriate assets in GIS after the completion of the condition
assessments.
• With the completion of each manhole inspection, the color coding of the manhole
will change from red to green in the Survey 123 web map interface, making it easy
to keep track of which inspections have been completed.
Technical Memorandum 4.0 Page 4
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
• Once the inspections are completed, the results can be imported into InfoAsset
Planner where the formal risk assessment will be completed.
• Results from the manhole risk assessment can be provided to City staff for
incorporation into ongoing maintenance activities or relevant capital improvements.
Technical Memorandum 4.0 Page 5
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Chapter 4 Recommended Inspection Schedule
Recognizing that the City’s limited operations’ resources may not have the additional time
necessary to complete an all-inclusive MH inspection program, the recommended inspection
process described above is streamlined. This streamlined inspection process will provide the City
with the necessary flexibility to use in-house staff or contractors with minimal training to
conduct the field inspections. While the ideal situation would be to have staff NASSCO trained
and certified, this represents a significant investment of time and resources. To get this initial
MCAP up and running initially, we recommend the City train staff to recognize basic structural
defects in a manhole. This could include documenting cracks and their severity, any visible
infiltration with an estimate of the flow rate, and other visual defects that simply require an
observant eye. After the program is up and running, the City should conduct a review of the
compiled data set and assess if revisions should be made to the assessment/collection
procedure going forward.
To further increase the efficiency and usefulness of MCAP, a preliminary inspection schedule was
developed that prioritizes the most susceptible infrastructure. The inspection phasing plan is
based on infrastructure age and material, which are generally related in the City, with the oldest
portions of the collection system being either vitrified clay (VCP) or asbestos cement (AC) pipe.
The City’s Wastewater Collection System includes approximately 4,800 manholes. There are
approximately 1,000 manholes within the system connected to VCP and AC pipes. It is
recommended to inspect 20% (approximately 200) of these manholes each year over the next 5
years. Manholes with the lowest remaining useful life (RUL) should be inspected first. RUL can
be found by subtracting the current year from the sum of the installation year and the estimated
material lifecycle of the asset. For example, if the current year is 2021, the RUL of an AC pipe
installed in 1980 would be approximately 9 years since AC pipe has an estimated lifecycle of 50
years.
Following the completion of the 5-year initial inspection schedule and subsequent development
of the manhole risk assessment, it is recommended to use the results from the risk assessment
to create rehabilitation and replacement (R&R) and new inspection schedules for manholes and
provide scheduled updates to the risk assessment with new collected data.
Figure 4-1 shows a map of the collection system with priority manholes categorized by
inspection zone. Zoning prioritization is based on a preliminary risk analysis that ranks manhole
condition based on infrastructure age and is limited to only the manholes connected to VCP and
AC pipe.
Technical Memorandum 4.0 Page 6
Plan
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Chapter 5 Recommended Data Synthesis and Analysis
Managing the data from any infrastructure inspection program can become a hassle if a
standard procedure is not established at the program’s inception. Regardless of the camera
option the City chooses to utilize (GoPro, Insta360, etc.), it is important that personnel
performing manhole inspections complete the inspection form onsite. By completing the
inspection form onsite, this avoids the risk of accumulating mountains of inspection footage to
be reviewed and synthesized at some future date in the office. With the streamlined inspection
program recommended in this memorandum, the data feeding the future risk assessment will
be the completed inspection forms, not the actual photos/footage. Similar to the City’s Granite
XP database, the manhole inspection results will be tied to the City’s manhole ID, making it
simple to view and compile results in a spreadsheet or GIS interface.
It is recommended to utilize large external hard drives (2 TB+) to store the footage from the
inspections. Best practice would be to have at least two external hard drives, with one acting as
a backup in case of data corruption or loss. If the City chooses the GoPro option, cloud-based
storage is available for an annual fee.
It is also recommended that the City incorporates regularly scheduled reviews of the data
collected to ensure quality assurance. After the initial 5-year inspection schedule is completed, it
is recommended that the City consider incorporating all mandatory data fields outlined in both
Level 1 and Level 2 of the original MACP inspection form for new manholes inspections. The
increased details of the original MACP inspection form can provide a more robust condition
assessment and a more accurate risk assessment.
The end goal with MCAP is to help the City prioritize limited time and resources on the manhole
assets that pose the highest risk, as quantified from both the likelihood and consequence of
failure. To accomplish this goal, the recommended fields from the MACP inspection form can be
compiled using Survey 123 as outlined in this memo, or by simply expanding what’s currently
collected in CityWorks, as the City has indicated is a possibility.
The upcoming Wastewater Collection System Facility Plan Update will include a detailed risk
assessment and CIP update of the current wastewater pipes. It is recommended to update the
wastewater pipe risk assessment after 5 years so that both risk assessments can be used in
unison in future planning. The combination of the wastewater pipe and manhole risk
assessments will enable the City to better prioritize and plan CIP and R&R projects moving
forward.
Technical Memorandum 4.0 Page 8
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Appendix A – Recommended Inspection Form
Appendix A provides the recommended manhole condition assessment inspection form. This
inspection form is to be used by the City of Bozeman staff when completing manhole
inspections. The form has been condensed from the NASSCO MACP inspection form. Each
number corresponds to the number listed in the official inspection form. Additional numberings
in the official inspection form that designate either Level 1 or Level 2 MACP inspection have
been removed.
General Information
1. Surveyed By 11. Date 12. Time
Location
22. MH/Access Point No. 23. Street 26. Surface Type
Manhole
33. Evidence of Surcharge
Cover
47. Size 49. Size Width 50. Cover Material
56. Cover Condition
Cover Adjustment Ring Frame Chimney
61. Ring Condition 68. Frame Condition 81. Chimney Condition
Cone Wall Bench
87. Cone Condition 94. Wall Condition 98. Bench Condition
Channel
103. Channel Condition
Technical Memorandum 4.0 Page 9
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Sketch
Technical Memorandum 4.0 Page 10
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Appendix B – Survey 123 Workflow
Appendix B provides brief instructions on how to complete a survey in Survey 123. The steps are
as follows:
1) From a phone or tablet, click on a selectable element (i.e., manhole) preloaded into a
map.
2) Select survey form and fill out the condition assessment fields that have been
preloaded into Survey 123application.
• Use a Bluetooth-enabled GoPro or similar (e.g., Insta360) to capture images and upload
to each manhole inspectionform.
3) Once completed, the application automatically saves the information. The form can
then be reviewed or downloaded for further post-processing.
The figure below shows an example of how the Survey 123 process can be configured for
various fieldwork applications.
Technical Memorandum 4.0 Page 11
Camera is specific for
underwater photos
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Appendix C – Manhole Imaging Technology
Appendix C provides a summary of the available manhole inspection equipment.
Equipment Pros Cons Cost
Leica 3D scanner with integrated
Cost $19,000
Sealife
Fisheye
Lens
Camera
Waterproof to 200 feet/60
meters
Video and still images
Flashlight and video lights
Wide perspective
Weight: 1lb
$730
Camera
$600 Lens
Hero8 Black Four lenses: Narrow, distortion
Does not take $300
Technical Memorandum 4.0 Page 12
Scanner
BLK360
Imaging
spherical imaging system and
thermography panorama
sensor system
Captures 360,000 individual
measurements every second
as it rotates 360 degrees over
the course of 3 minutes
Open the images in any design
software of choice
Not easy to position
down in the manhole
Go-Pro with
Equipment
free Linear, Wide and Super
View
View -12MP + SuperPhoto with
improved HDR
Video: 4K60
Waterproof: 33ft (10m)
Auto Upload to the Cloud
Wifi+Bluetooth
measurements while
videoing
Mod
+$50 Light
GoPro
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 4.0 – Manhole Condition Assessment Program
Equipment
AutoFlex
Video
Inspection
System with
Macro Lens
Vision
Engineering
MCH-
001/MCS-
005/6X
Pros
Mighty Cam 1080p Auto Focus
Camera
18" Flexible Arm with Table Clamp
Allows manual adjustment of
image capture Magnification range
of 3X-80X at a 6 in. working
distance
360 ball joint allows the camera to
be rotated to any angle
Mantis compact series stereo
microscope visual inspection
system w/ universal stand & 6X
magnification lens
3D viewing Dust cover 16 pounds
Cons
Not waterproof
Not waterproof
Cannot video in
the dark
Cost
$1,940
$1,920
City
Owned
Imaging
Device
CUES Lite
Stick
Portable Video Inspection
Camera
Built-in wireless video
transmitter and battery in the
pole
Operates with TV unit’s
existing monitor, VCR, and data
system
Record distance and
information on a videotape if
utilizing an optional VCR
LED lighting for the dark
Includes a fiberglass extendable
telescoping pole, 6'-18' depth
No zoom option None
(City owned
technology)
Technical Memorandum 4.0 Page 13
5.0
Wastewater Flow
Characterization
Technical Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table of Contents
Chapter 1 Introduction...............................................................................................................3
Chapter 2 Study Area.................................................................................................................4
2.1 Study Area Boundary and Description........................................................................................................4
2.2 Existing Land Use and Zoning Conditions ................................................................................................8
2.3 Infill Zoning and Future Land Use................................................................................................................9
2.4 Urban Renewal Districts and Tax Increment Finance Districts ...........................................................11
Chapter 3 Population ...............................................................................................................12
3.1 Existing and Projected Population .............................................................................................................. 12
Chapter 4 Historic Wastewater Flows and Loading ....................................................................14
4.1 Historic WRF Flows ..........................................................................................................................................14
4.2 Wastewater Flow Analysis............................................................................................................................. 18
4.2.1 Domestic Flow based on Metered Customer Water Usage............................................ 18
4.2.2 Ground Water Infiltration............................................................................................................. 21
4.2.3 RDII Analysis..................................................................................................................................... 24
4.2.4 Summary of Existing System Model Loading...................................................................... 25
4.3 Population and Per Capita Loading Analysis......................................................................................... 25
Chapter 5 Wastewater Flow Characterization ...........................................................................27
5.1 Existing Land Use Wastewater Duty Factors............................................................................................27
5.2 Existing Zoning Wastewater Duty Factors .............................................................................................. 29
5.3 High Density Residential, Urban Renewal, and Tax Increment Financing Districts..................... 31
5.3.1 R-3, R-4, R-5 Wastewater Duty Factors................................................................................... 31
5.3.2 URD and TIF Wastewater Duty Factors .................................................................................. 32
Chapter 6 Wastewater Flow Projections and Recommended Duty Factors .................................33
6.1 Future Wastewater Flow Analysis............................................................................................................... 33
6.1.1 Infill Wastewater Flow Analysis ................................................................................................. 33
6.1.2 URD and TIF Redevelopment Wastewater Flow Analysis................................................ 35
6.1.3 Ultimate Build-Out (UBO) Wastewater Flow Analysis ...................................................... 35
6.1.4 Increased Density Scenario .........................................................................................................37
6.2 Wastewater Flow Analysis Summary........................................................................................................ 39
6.3 Wastewater Flow Recommendations for Planning and Design ...................................................... 39
Technical Memorandum 5.0 Page 1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
List of Tables
Table 2-1: Land Use Classification within City Limits (as of July 2020) .......................................................8
Table 2-4: Growth Area by Land Use Designation (as of July 2020)..........................................................10
Table 6-4: Future Land Use Wastewater Loading (summary of land use outside of 2020 City
Table 2-2: Zoning Classification within City Limits (as of July 2020) ...........................................................9
Table 2-3: Infill Area by Zoning Designation (as of July 2020) ....................................................................10
Table 2-5: URD and TIF Summary (as of July 2020) .........................................................................................11
Table 3-1: City of Bozeman Historic Population ...............................................................................................12
Table 3-2: City of Bozeman Projected Population............................................................................................13
Table 4-1: WRF Inflow Summary .............................................................................................................................15
Table 4-2: Detailed WRF Flow Summary (MGD)................................................................................................16
Table 4-3: Detailed WRF Flow Summary (gpcd)................................................................................................17
Table 4-4: Metered Water Use Summary (MGD) ..............................................................................................20
Table 4-5: Ground Water Flow Analysis at the WRF (MGD)..........................................................................24
Table 4-6: Daily Wastewater Loading Summary for Existing System Model Scenarios (MGD).......25
Table 4-7: AAF and DWF per Capita Flow Rates ...............................................................................................26
Table 5-1: Wastewater Duty Factors by Existing Land Use Classification................................................28
Table 5-2: Wastewater Loading Duty Factors by Zoning Classification ...................................................30
Table 5-3: R-3, R-4, R-5 Wastewater Planning Numbers...............................................................................32
Table 5-4: URD and TIF WWDF Summary (gpad) .............................................................................................32
Table 6-1: Infill Wastewater Loading .....................................................................................................................34
Table 6-2: URD and TIF Wastewater Loading.....................................................................................................35
Table 6-3: Future Land Use Correlated to Zoning Classification.................................................................36
Limits Boundary – see Figure 2-3) ....................................................................................................................37
Table 6-5: Increased Density Scenario Wastewater Loading Summary ...................................................38
Table 6-6: Summary of Overall System Wastewater Flow Parameters .....................................................39
Table 6-7: Summary of Existing and Buildout Wastewater Loading (MGD)...........................................39
Table 6-8: Summary of Recommended Duty Factors for Zoning and Future Land Use Classes ....41
List of Figures
Figure 2-1: Wastewater Collection Facility Plan Study Area Boundary.......................................................5
Figure 2-2: Zoning Designations for Infill Area....................................................................................................6
Figure 2-3: Ultimate Build-Out (UBO) Land Use Designations ......................................................................7
Figure 4-1: Average Annual Flow (2010 – 2019) ...............................................................................................14
Figure 4-2: WRF Average Annual Wastewater Flow Components .............................................................20
Figure 4-3: MDT Monitoring Well Static Water Level Data...........................................................................22
Technical Memorandum 5.0 Page 2
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Chapter 1 Introduction
Wastewater characterization involves the analysis of existing wastewater flows to better understand the
City’s wastewater generation trends. Wastewater characterization is necessary to assess the capabilities
of the City’s existing facilities to adequately address current wastewater demands and ensure the design
and functionality of proposed wastewater system components can sufficiently accommodate future
wastewater needs. This memorandum provides an overview of the City’s historical wastewater
generation trends and metered water usage applied to land use and zoning classes.
In addition, this memorandum presents the City’s projected future wastewater needs under ultimate-
build (UBO) conditions. Wastewater generated under UBO conditions is important to understand in
order for the City to address future growth concerns as well as appropriately size the infrastructure in
both existing and future areas to accommodate growth.
Technical Memorandum 5.0 Page 3
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Chapter 2 Study Area
Defining the study service area for the wastewater collection system model update is necessary to
provide a framework to 1) define system capacity milestones, 2) develop appropriate phasing of capital
improvements, and 3) strategically integrate improvements with existing infrastructure. The ultimate
goal of this approach is to maximize the economic benefit of the improvements.
2.1 Study Area Boundary and Description
The study area was developed by reviewing current planning documentation, considering recently
completed facility plans, evaluating geographical boundaries, and having discussions with City staff.
Ultimately, this resulted in using the City’s Growth Policy Boundary as the study area to ensure
consistency with other planning efforts. The Growth Policy Boundary was established in the Bozeman
Community Plan – Adopted by the Bozeman City Commission (Resolution No. 5133, November 17,
2020). Figure 2-1 shows the Growth Policy Boundary and current City limits. This results in a final
ultimate build-out (UBO) service area of approximately 45,342 acres, of which 13,393 acres are located
within the current City limits.
Future land use estimates were developed as follows:
• The 2020 Bozeman Community Plan was used to identify future land use for the service area
outside of the existing municipal City boundary.
• Areas located within the municipal City boundary that are currently vacant or undeveloped are
considered infill.
• Designations for infill areas were populated using existing City zoning classes.
• Future land use information for this study was provided by the City in a GIS database that
contained mapped polygons and attributes.
• Communication with City staff confirmed land use designations for future development; the City
also provided information with respect to identified known land use changes for known Urban
Renewal Districts (URD) and Tax Increment Financing (TIF) Districts. These two districts are
identified as areas that will continue to redevelop with higher density than existing conditions
and are analyzed further in this study.
Figure 2-2 and Figure 2-3 present the infill zoning designations and future land use for areas outside the
existing municipal City boundary, respectively.
Technical Memorandum 5.0 Page 4
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
2.2 Existing Land Use and Zoning Conditions
Table 2-1 summarizes the existing land use designations and acreages (based on net area) within the City
limits and the total acreage within the data set used to analyze existing wastewater loading duty factors.
Net area was used because of the format in which the City’s Existing land use shapefile was provided to
AE2S where right-of-way (ROW) was excluded from each land use polygon. Existing land use duty factors
were calculated to understand demands and help inform future planning but were not used to allocate
wastewater flows. The model analyses (both existing and future) rely on zoning duty factors for
allocation. Zoning Classification duty factors were used to allocate wastewater flows in the model for
infill areas as well as to establish future land use duty factors. The development of these duty factors is
discussed in more detail in Chapter 5. Table 2-2 summarizes current City zoning classifications and
acreages (based on gross area) within City limits used to analyze wastewater loading duty factors. Zoning
Classifications are in gross area because of the format in which the City’s zoning shapefile was provided
to AE2S where zone polygons include ROW.
Table 2-1: Land Use Classification within City Limits (as of July 2020)
Land Use
ROW
CA
CR
HM
LM
MIXED
RB
PFP
AP
CHURCH
DTR
MHMP
MFR
SFR
SEF
GOLF
RR
POS
MSU
Land Use Description
Right-of-Way
Commercial/Auto
Commercial/Rental
Hotel/Motel
Light Manufacturing
Mixed Use
Restaurant/Bar
Public Facility/Park
Administrative/Professional
Church
Duplex/Triplex Residential
Mobile Home/ Mobile Park
Multi-Family Residential
Single-Family Residential
School/Educational/Facility
Golf Course
Rural Residential
Parks or Open Space
Montana State University
Total
Area* (ac)
2,446
126
500
81
358
285
48
513
245
94
339
87
764
2,007
293
178
68
1,491
615
10,537
Percent of Total
23.2%
1.2%
4.7%
0.8%
3.4%
2.7%
0.5%
4.9%
2.3%
0.9%
3.2%
0.8%
7.2%
19.1%
2.8%
1.7%
0.6%
14.1%
5.8%
100.0%
*Total area excludes undeveloped and vacant land. Total City area as of July 2020 = 13,400
acres
Technical Memorandum 5.0 Page 8
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 2-2: Zoning Classification within City Limits (as of July 2020)
Zoning
R-S
R-1
R-2
R-3
R-4
R-5
R-O
R-MH
B-1
B-2
B-2M
B-3
M-1
M-2
BP
NEHMU
UMU
REMU
PLI
MSU**
Zoning Description
Residential Suburban District
Residential Single-Household Low Density District
Residential Two-Household Medium Density District
Residential Medium Density District
Residential High-Density District
Residential Mixed-Use High-Density District
Residential-Office District
Residential Manufactured Home Community District
Neighborhood Business District
Community Business District
Community Business District-Mixed
Central Business Park District
Light Manufacturing District
Manufacturing and Industrial District
Business Park District
Northeast Historic Mixed-Use District
Urban Mixed Use
Residential Emphasis Mixed Use
Public Lands and Institutions District
Montana State University
Area* (ac)
568
1,630
739
1,752
521
11
388
90
63
919
137
150
817
422
181
38
7
51
1,301
401
Percent of Total
5.6%
16.0%
7.3%
17.2%
5.1%
0.1%
3.8%
0.9%
0.6%
9.0%
1.3%
1.5%
8.0%
4.1%
1.8%
0.4%
0.1%
0.5%
12.8%
3.9%
*Area based on total gross area for each zoning class, less vacant and undeveloped land.
**MSU area represents Montana State campus area east of South 19th Avenue as of July 2020.
The wastewater duty factor analysis throughout this Facility Plan (both existing and future) rely on 2020
land use and zoning information provided by the City. There have been some changes to zoning and land
use classifications since 2020 but these changes will not impact the system-wide wastewater
characterization for the City.
2.3 Infill Zoning and Future Land Use
Table 2-3 summarizes the infill zoning designations which are based on current City zoning classifications
and acreages. Both infill and future land use information will be incorporated into the hydraulic model in
the future buildout scenario. Figure 2-2 presents the classifications for City infill zoning designations.
Technical Memorandum 5.0 Page 9
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 2-3: Infill Area by Zoning Designation (as of July 2020)
Zoning
R-S
R-1
R-2
R-3
R-4
R-5
R-O
R-MH
B-1
B-2
B-2M
B-3
M-1
BP
UMU
REMU
PLI
MSU West
Zoning Description
Residential Suburban District
Residential Single-Household Low Density District
Residential Two-Household Medium Density District
Residential Medium Density District
Residential High-Density District
Residential Mixed-Use High-Density District
Residential-Office District
Residential Manufactured Home Community District
Neighborhood Business District
Community Business District
Community Business District-Mixed
Central Business Park District
Light Manufacturing District
Business Park District
Urban Mixed Use
Residential Emphasis Mixed Use
Public Lands and Institutions District
Montana State University
Total
Infill Area*
(ac)
388
233
86
328
338
30
111
34
10
368
36
1
125
59
32
214
232
211
2,836
*Infill acreage excludes areas that are located within the URD and TIF districts.
Table 2-4 Summarizes the growth area land use classifications and gross acreages based on the 2020
Bozeman Community Plan. Figure 2-3 presents the future land designations assoacted with areas
outside the existing municipal City boundary.
Table 2-4: Growth Area by Land Use Designation (as of July 2020)
Growth Area Land Use
RC
GC
FU
ID
RD
CCMU
RDMU
PI
POS
Land Use Description
Regional Commercial and Services
Golf Course
No City Services
Industrial
Urban Neighborhood
Community Commercial Mixed Use
Residential Mixed Use
Public Institutions
Parks and Open Land
Total
Growth Area
(ac)
6
178
4,044
479
22,908
780
346
1,809
1,400
31,949
Technical Memorandum 5.0 Page 10
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
2.4 Urban Renewal Districts and Tax Increment Finance Districts
Table 2-5 summarizes the urban renewal districts and tax increment finance districts as identified by the
City. The area presented is gross acreage. The additional wastewater loading from redevelopment of
these areas will be added to the model in the buildout scenario. Figure 2-2 presents the areas associated
with URD and TIF districts.
Table 2-5: URD and TIF Summary (as of July 2020)
District Area (ac)
Midtown URD 460
North Park URD 345
North East Neighborhood URD 52
Downtown TIF 128
South Bozeman Tech District TIF 45
Pole Yard URD 273
Technical Memorandum 5.0 Page 11
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Chapter 3 Population
3.1 Existing and Projected Population
Past and projected Bozeman population trends can be found in Table 3-1 and Table 3-2, respectively.
Table 3-1 summarizes Bozeman’s historic population trends from 1960 to 2020. Table 3-2 displays the
City of Bozeman’s projected population over the next 40 years with an assumed growth rate of 4.0%
annually. The population growth rate of 4% is based on the approximate average growth over the past
seven years – this rate is being used in other ongoing planning efforts by the City. This growth rate
provides a conservative estimate for planning purposes and will set the basis for future water and
wastewater planning efforts.
Table 3-1: City of Bozeman Historic Population
Year
1960
1970
1980
1990
2000
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
Bozeman
Population
13,361
18,670
21,645
22,660
27,509
37,280
38,116
38,753
39,860
41,631
43,327
45,187
46,907
48,437
49,831
53,293
Annual Growth Rate
(%)
-
4.0
1.6
0.5
2.1
3.6
2.2
1.7
2.9
4.4
4.1
4.3
3.8
3.3
2.9
6.9
Source
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
2015 WW Facility Plan
Census
Census
Census
Census
Census
Census
This analysis was conducted during COVID-19 and the period of high development pressure that
followed the pandemic – future growth will likely ease off to more stable levels. Recent estimates by the
City show growth at 2.5%. However, this Facility Plan uses a conservative estimate for growth projections
which is appropriate for planning large infrastructure projects.
Technical Memorandum 5.0 Page 12
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 3-2: City of Bozeman Projected Population
Planning Period Year Population*
Existing 2020 53,293
Year 5 2025 63,952
Year 10 2030 76,742
Year 15 2035 92,090
Year 20 2040 110,508
Year 25 2045 132,610
Year 30 2050 159,132
Year 35 2055 190,958
Year 40 2060 229,150
Assumed growth rate is 4.0%
Technical Memorandum 5.0 Page 13
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Technical Memorandum 5.0 – Wastewater Flow Characterization
Chapter 4 Historic Wastewater Flows and Loading
4.1 Historic WRF Flows
Two primary considerations in this evaluation of flow are average annual flow and dry weather flow.
Average Annual Flow (AAF) is calculated by taking the annual wastewater influent flow volume divided
by the number of days each year. The AAF 10-year historic average is 5.3 million gallons per day (MGD).
Figure 4-1 shows the general trend of AAF for the City of Bozeman over the past decade. Detailed
analysis presented in the following sections focuses on five years of data from 2015 – 2019 which has an
AAF of 5.5 MGD. The past five years were selected as the basis of planning because the data better
represent the current system dynamics and trends better than a longer period with more historic data.
Figure 4-1: Average Annual Flow (2010 – 2019)
Dry Weather Flow (DWF) is the average flow that occurs on a day not influenced by rainfall. DWF is
determined by selecting days on which several conditions are met including the following:
o No rainfall occurred on that day
o No rainfall occurred on the preceding days
o Flow volumes were within a specified range:
o not less than 85 percent of the average
o or more than 115 percent of the average.
Table 4-1 summarizes the DWF and AAF from 2015-2019. For this analysis, dry weather flow was
calculated from the average WRF influent flow from the seasonal winter months of November through
February and reported for the year starting in November. For example, the DWF for November 2015 was
calculated as the average of the flows reported for November and December of 2015 and January and
February of 2016.
Technical Memorandum 5.0 Page 14
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 4-1: WRF Inflow Summary
Year
2015
2016
2017
2018
2019
Average
Average
Annual Flow
(MGD)
4.8
5.0
5.2
6.1
6.2
5.5
Dry Weather
Flow (MGD)
4.7
4.8
5.1
5.3
5.8
5.1
Maximum
Monthly Flow
(MGD)
5.2
5.6
5.9
8.9
8.2
6.8
Maximum 30
day* Flow
(MGD)
5.2
5.6
6.1
9.5
8.3
6.9
Maximum
Daily Flow
(MGD)
5.9
5.9
7.0
11.5
9.7
8.0
Peak Hourly
Flow (MGD)
7.5
9.6
9.5
14.0
12.2
10.6
*30-day rolling average.
Monthly detailed analysis of the WRF flow is presented in tables Table 4-2 and million gallons per day
(MGD) and in Table 4-3 as gallons per capita per day (gpcd). Monthly WRF flow is presented showing the
season variations of flow at the WRF. The following observations are derived from the detailed analysis:
• Average Annual Flow (AAF): From 2015 – 2019, the City had an average AAF of 5.5 MGD.
• Dry Weather Flow (DWF): From 2015 – 2019, the City had an average DWF of 5.1 MGD.
• Maximum Monthly Flow: From 2015 – 2019, the City had an average Maximum Monthly Flow of
6.8 MGD. The highest flow month occurred in April 2018 at 8.9 MGD.
• Maximum 30-day Flow: From 2015 – 2019, the City had an average Maximum 30-day Flow of
6.9 MGD. It is recommended that the City use the highest 30-day flow period from the review
period for planning purposes which occurred between April and May of 2018 at 9.5 MGD.
• Maximum Daily Flow: From 2015 – 2019, the City had an average maximum daily flow of 8.0
MGD. It is recommended that the City use the highest daily flow (11.5 MGD) from the review
period for planning purposes to account for wet years, potential impacts from climate change,
and provide conservatism.
• Maximum Hourly Flow: From 2015 – 2019, the City had an average maximum hourly flow of
10.6 MGD. It is recommended that the City use the highest hourly flow (14.0 MGD) from the
review period for planning purposes to account for wet years, potential impacts from climate
change, and provide conservatism.
Technical Memorandum 5.0 Page 15
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Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 4-2: Detailed WRF Flow Summary (MGD)
Month 2015 2016 2017 2018 2019 Avg.
January 4.7 4.5 4.6 5.0 5.2 4.8
February 4.9 4.9 4.9 5.2 5.2 5.0
March 4.7 5.0 5.2 6.2 5.6 5.3
April 4.4 5.3 5.7 8.9 8.2 6.5
May 4.9 5.6 5.9 8.3 6.8 6.3
June 4.9 5.2 5.6 6.6 6.6 5.8
July 4.9 5.0 5.2 5.7 6.3 5.4
August 5.2 4.8 5.0 5.6 5.8 5.3
September 5.1 4.9 5.2 5.5 6.4 5.4
October 5.0 5.3 5.2 5.6 6.2 5.4
November 4.9 5.0 5.3 5.5 6.1 5.4
December 4.4 4.6 5.0 5.1 5.6 5.0
Average Annual Flow
(AAF) 4.8 5.0 5.2 6.1 6.2 5.5
Minimum Monthly Flow
Maximum Monthly
4.4 (Apr) 4.5 (Jan) 4.6 (Jan) 5.0 (Jan) 5.2 (Feb) 4.7
Flow
Maximum 30-Day Flow
5.2 (Aug) 5.6 (May) 5.9 (May) 8.9 (Apr) 8.2 (Apr) 6.8
(rolling average)
Minimum Daily Flow
5.2 5.6 6.1 9.5 8.3 6.9
(December 25th for all
years)
3.4 3.6 4.0 4.2 4.7 4.0
5.9 (May 7.0 (May Maximum Daily Flow 5.9 (Sept 16) 11.5 (Apr 24) 9.7 (Apr 10) 8.0 21) 18)
9.6 (May Maximum Hourly Flow 7.5 (Mar 6) 9.5 (Sep 8) 14.0 (Apr 23) 12.2 (Apr 9) 10.6
Dry Weather Flow
21)
(DWF) 4.7 4.8 5.1 5.3 5.8 5.1
Tabulated bold values represent recommended planning numbers.
Technical Memorandum 5.0 Page 16
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Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 4-3: Detailed WRF Flow Summary (gpcd)
Month 2015 2016 2017 2018 2019 Average
January 108 100 97 103 105 103
February 112 109 105 108 104 108
March 108 110 110 128 112 114
April 102 118 122 184 165 138
May 113 124 126 172 136 134
June 112 115 120 135 133 123
July 113 111 111 119 126 116
August 119 106 107 115 117 113
September 119 109 111 113 128 116
October 115 116 111 115 125 116
November 113 111 112 114 123 115
December 102 102 106 105 113 106
Average Annual Flow (AAF) 111 111 112 126 124 117
Minimum Monthly Flow1 102 100 97 103 104 101
Maximum Monthly Flow1 119 124 126 184 165 144
Maximum 30-day Flow 121 130 140 219 191 160 (rolling average)
Minimum Daily Flow1 79 80 85 86 95 85
Maximum Daily Flow1 137 131 148 238 194 170
Maximum Hourly Flow1 173 213 202 289 245 224
Dry Weather Flow (DWF) 108 106 109 109 115 109
Population 43,327 45,187 46,907 48,437 49,831 -
1 See Table 4-2 for associated month/date
Technical Memorandum 5.0 Page 17
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Technical Memorandum 5.0 – Wastewater Flow Characterization
4.2 Wastewater Flow Analysis
The data presented in Table 4-2 was used to analyze the three main components that comprise
wastewater flow at the WRF. The three components to wastewater flow are generally described as
follows and discussed in more detail in the following sections:
• Domestic Flow: The portion of wastewater flow that originates from domestic water use
including residential, commercial, and industrial activities. Domestic flow is considered to be
relatively steady throughout the year and can be estimated from indoor metered potable water
use, calculated during non-irrigation months.
• Base Infiltration (BI): The portion of wastewater flow that originates from ground water and can
vary by season and is influenced by the depth of the ground water table.
• Rainfall Derived Inflow and Infiltration (RDII): The portion of wastewater flow that originates
from rainfall events and enters the collection system via inflow and infiltration.
4.2.1 Domestic Flow based on Metered Customer Water Usage
Water meter records are used to estimate the domestic flow portion of wastewater flow which
originates from domestic, commercial, and industrial water use. The City measures water consumption
through customer water meters. Historical water meter records from 2015 through 2019 were
evaluated to determine overall customer water consumption, water demand by land use class and
zoning, per capita usage, and seasonal variations in demand.
Table 4-4 summarizes the metered water customer analysis in MGD. The summary shows metered
customer non-irrigation demand which was calculated by taking the average monthly customer demand
for November through February. This method assumes that there is no irrigation during winter months
which is a conventional assumption for states in northern U.S. It is also standard convention for
American cities to assume that this non-irrigation season demand is near equivalent to base domestic
wastewater flow. These terms are defined in more detail below:
o Non-Irrigation Demand: is defined by taking an average of the daily flows for a period of the
year that is not influenced by irrigation. Non-irrigation demand is calculated seasonally during
winter months. For example, the non-Irrigation demand calculated for 2015 is calculated as the
average flow from Nov/Dec 2015 and Jan/Feb 2016. From 2015 – 2019, the City had an average
non-irrigation demand of 3.6 MGD.
o Domestic Flow: the Non-Irrigation Demand of 3.8 MGD will be used as the base domestic flow
allocated within the hydraulic model. The metered water demand showed a range of non-
irrigation demand during the review period from 3.3 to 3.8 MGD. Therefore, it is recommended
to assess the existing wastewater collection system using a non-irrigation demand of 3.8 MGD
as the domestic wastewater flow.
Figure 4-2 shows the comparison between the non-irrigation demand (domestic flow) and the WRF
wastewater inflow. Domestic flow seems to be on a slight upward trend, likely due to population
increase. Inflow and infiltration contribution to the total WRF inflow was calculated for wet-weather and
Technical Memorandum 5.0 Page 18
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
dry-weather periods and account for a large portion of annual flow to the WRF. The methods used to
calculate WWF and DWF I&I are discussed in more detail in Sections 4.2.2 and 4.2.3.
Technical Memorandum 5.0 Page 19
Month 2015
January
February 3.4 3.5 4.1 4.0 3.9 3.8
March 4.9
April 3.6 3.5 3.7 3.5 3.9 3.6
May
June 8.4 7.9 7.5 5.8 6.9 7.3
July
August 8.3 9.3 10.3 10.1 8.2 9.3
September
October 3.6 3.7 3.7 4.1 4.0 3.8
November
December 3.0 3.4 3.0 3.4 3.3 3.2
Average Annual Demand (AAD)
Non-Irrigation Demand
(Domestic Flow) 3.3 3.6 3.7 3.8 3.7 3.6
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 4-4: Metered Water Use Summary (MGD)
Figure 4-2: WRF Average Annual Wastewater Flow Components
Technical Memorandum 5.0 Page 20
2016 2017 2018 2019 Average
3.1 3.1 3.2 4.0 3.4
3.6 3.4 3.5 3.6 3.8
3.6
4.1 3.9 4.9 4.6 4.2 4.3
8.3 9.2 9.4 8.3 8.6 8.0
5.4 6.2 5.8 5.8 6.2 5.7
3.6 3.7 4.2 4.0 3.8 3.9
5.0 5.3 5.0 5.1 5.1 5.1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
4.2.2 Ground Water Infiltration
Inflow and Infiltration (I&I) is a critical consideration when evaluating collection system capacity. With
the presence of groundwater, infiltration can influence the system during dry weather. This is referred to
as base groundwater infiltration (BI), which is included in DWF and AAF at the WRF. During and after rain
events, flows within the collection system increase in response to the rainfall. This increase in
wastewater flow is known as rainfall derived inflow and infiltration (RDII), which is further described in
Section 4.2.3. The BI and RDII flow components are combined with diurnal peak domestic flows to define
the total wastewater flow conveyed by the wastewater collection system and treated at the WRF. This
peak wet weather flow condition is a worst-case scenario and used in evaluating a collection system.
As presented in Table 4-2, the detailed historic wastewater flow summary shows the range of flows and
trends that the WRF experiences over the course of winter, spring runoff, and wet weather seasons. BI
varies throughout the year and is influenced seasonally by spring runoff/snowmelt and by antecedent
conditions. Average monthly WRF inflow was compared to the non-irrigation monthly metered water
use – the difference between the two is assumed to conservatively represent base groundwater
infiltration. Table 4-5 shows these values by month for 2015 through 2019. This approach to estimating
base groundwater infiltration assumes that there is always some influence on collection system flows
from groundwater, and that average flows are representative of this influence. Rain event driven high
peak flows are accounted for separately in the RDII approach which is described in Section 4.2.3.
Figure 4-2 provides a visual representation of the average domestic and dry-and wet-weather BI flow
components of the WRF inflow. Dry weather BI and wet weather BI were relatively steady between 2015
and 2017. The dry weather BI increase in 2018 and 2019 is likely attributed to a high ground water table.
There is widespread seasonally shallow groundwater (less than 10’ deep) in Bozeman especially within
the northwestern portions of the City. As observed in the 2018 and 2019 WRF inflow data, even during
the dry-weather months (November through February), the shallow groundwater has a strong influence
on wastewater flows in the collection system. Groundwater static water level data from the MDT
monitoring well located southeast of the I-90 and 19th Ave interchange (GWIC Well #241692) was
examined to confirm and better visualize the correlation between high collection system flows and high
groundwater. Figure 4-3 shows the SWL for this well from 2015 through 2022. This data shows April/May
groundwater depths as shallow as 2 feet deep with spikes as shallow as 1 foot deep in April 2019. The I-
90 and N 19th interceptor runs through this area and likely receives a large amount of I&I during spring.
Technical Memorandum 5.0 Page 21
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Figure 4-3: MDT Monitoring Well Static Water Level Data
Based on the analysis of WRF inflow, metered water use, groundwater well data, and meetings with City
staff, it is recommended that the 2018 average DWF base groundwater infiltration value, 1.5 MGD, be
used throughout the collection system. This value provides a conservative and realistic estimation of dry-
weather groundwater infiltration for moderately wet years. Additionally, it is recommended that the
2018 wet-weather maximum 30-day rolling average BI, 5.7 MGD, be used for WWF groundwater
infiltration throughout the collection system for this Plan. This provides a very conservative estimate of
wet-weather flow but is appropriate for evaluating worst-case conditions and is supported by the 2018
data:
• During 2018, the domestic flow (non-irrigation metered water use) was 3.8 MGD and the
dry weather WRF inflow was 5.3 MGD. The conclusion from this analysis is that on
average, 1.5 MGD is contributed to Bozeman’s collection system as BI from ground
water infiltration during DWF.
• The peak months for WRF I&I are typically April and May primarily as a result of
snowmelt and spring rain events. The maximum 30-day flow of BI occurred during April
and May of 2018 as the WRF experience an average inflow of 9.5 MGD. With the
assumption that the domestic flow was 3.8 MGD, the estimated BI flow at the WRF
during the maximum 30-day flow is 5.7 MGD. This equates to 2,525 gpd/idm based on
the 2018 collection system pipe network.
• Following completion of this BI analysis, the City requested that additional areas be
added to the model that were not represented in the 2018 collection system pipe
network – these areas include the Front Street Interceptor, Davis Lane Interceptor, and
the Nelson Meadows Lift Station. As a result of these additions, the modeled WWF BI
increased proportionally to reflect the added pipe and results in an additional 0.2 MGD,
for a total WWF BI of 5.9 MGD. Note that the increase in DWF BI from these added pipes
is negligible (<0.05 MGD).
To summarize, it is recommended that BI flows be allocated within the model based on the
following:
Technical Memorandum 5.0 Page 22
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
• 1.5 MGD of BI will be allocated into the model for the DWF scenario.
• 5.9 MGD of BI will be allocated into the model for the WWF scenario.
The BI will be allocated based on the size and length of gravity main using the following
equation:
𝐵𝐼 𝐵𝐼 𝑐𝑡𝑡𝑥 𝑓𝑎𝑐𝑡𝑜𝑟 = ∑ (𝐷 𝑥 𝐿)𝑎𝑙𝑙 𝑔𝑟𝑎𝑣𝑖𝑟𝑦 𝑙𝑎𝑖𝑙𝑟
Where:
BI duty factor = ground water infiltration rate gallons per day per inch-
diameter-mile of pipe (gpd/idm)
BI = ground water infiltration (gpd)
D = Diameter = pipe diameter (inches)
L = Length = Pipe Length (miles)
• BI for DWF: 672 gpd/idm (or 1.5 MGD)
• BI for WWF: 2,525 gpd/idm (or 5.9 MGD)
The City’s BI varies considerably during dry and wet weather seasons. While the BI flow rate is high
during wet weather, it could be considered excessive according to EPA criteria. The EPA handbook
Facilities Planning, 1981 and the EPA handbook Procedures for Investigating Infiltration/Inflow EPA 68-
01-4913, 1981 state that the non-excessive BI rate should fall within the range of 2,000 to 3,000 gpd/idm
for systems with greater than 100,000 linear ft of sewer (Bozeman has over 1.2 million linear ft of
sewer).
Technical Memorandum 5.0 Page 23
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 4-5: Ground Water Flow Analysis at the WRF (MGD)
Month 2015 2016 2017 2018 2019 Average
January 1.4 0.9 0.9 1.1 1.6 1.2
February 1.6 1.3 1.2 1.4 1.5 1.4
March 1.4 1.4 1.4 2.4 1.9 1.7
April 1.1 1.7 2.0 5.0 4.6 2.9
May 1.6 2.0 2.2 4.5 3.1 2.7
June 1.6 1.6 1.9 2.7 3.0 2.1
July 1.6 1.4 1.5 1.9 2.6 1.8
August 1.9 1.2 1.3 1.7 2.1 1.7
September 1.8 1.3 1.5 1.7 2.7 1.8
October 1.7 1.6 1.5 1.7 2.6 1.8
November 1.6 1.4 1.6 1.7 2.5 1.7
December 1.1 1.0 1.3 1.3 2.0 1.3
Recommended
Average BI during DWF* 1.2 1.1 1.3 1.5 1.7 1.5
BI during Max Wet Weather Month 1.9 2.0 2.2 5.0 4.6
BI during Max 30-day Flow 1.9 2.0 2.4 5.7 4.6 5.7+
*Calculated seasonally (i.e., the value for 2015 is calculated with data from Nov/Dec 2015 and Jan/Feb 2016).
+ The maximum WWF BI over the 5-year span of analysis is 5.7 MGD. The recommended overall existing
conditions WWF BI is 5.9 MGD based on applying the unit rate (gpd/idm) calculated under the 2018
conditions to the existing conditions model network.
4.2.3 RDII Analysis
As discussed, the model scenarios have loading comprised of Domestic Flow and BI. In addition, rainfall
derived inflow and infiltration (RDII) causes water to enter the collection system. Typically, a design
storm is used to simulate RDII and respective peak flow rates that the sewer system has to handle during
these particular events.
The RDII design storm used to assess system capacity within the hydraulic model was selected off of a
number of different factors, which included the following:
• The purpose and scope of the modeling project
• The availability and quality of rainfall and flow data
• The characteristics and conditions of the sewer system and watershed
• The City’s engineering design standards
• The technical and economic feasibility
• The RDII response from monitored areas within the sewer system
• The ability to accommodate for future climate change
• The ability to handle growth changes related zoning changes
Based on these factors and discussions with City staff, a 25-year SCS design storm was used to simulate
RDII response and respective peak flow capacity within the hydraulic model.
Technical Memorandum 5.0 Page 24
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
The design storm used in RDII wet weather analysis is summarized below:
• NOAA Atlas 2, Volume I, 1973
• Recurrence Interval: 25 year
• Depth: 1.99 inches
• Distribution Type: SCS Type I
It should be noted there is no single best method or universally accepted design storm for RDII modeling.
Therefore, it is important to recognize that these results may vary from actual real world wet weather
storm events.
In general, the RDII design storm selected to assess system capacity is to some extent conservative based
on actual observed events. As such, additional flow monitoring and consideration of site-specific
characteristics (e.g. high groundwater, zoning changes) and conditions (e.g. pipe age, material, etc.) may
influence the timing of specific capacity driven capital improvements.
Additional RDII model results and calibration are discussed in the Model Development and Calibration
Technical Memorandum.
4.2.4 Summary of Existing System Model Loading
The summary below provides an overview of the sanitary loads allocated within the model to establish
the existing system baseline scenarios.
Table 4-6: Daily Wastewater Loading Summary for Existing System Model Scenarios (MGD)
Scenario Domestic Flow Ground Water BI Total Flow
Dry Weather 3.8 1.5 5.3
Wet Weather 3.8 5.7 9.5
4.3 Population and Per Capita Loading Analysis
Per capita wastewater flows (expressed in gallons per capita per day [gpcd]) were calculated by dividing
the WRF influent flow from Table 4-1 by the annual population estimates from Table 3-1. The per capita
wastewater flow analysis is presented Table 4-7.
Dry weather flow per capita trends from the last five years appear to be holding relatively steady at
around 109.5 gpcd with an increase noted in 2019. Average annual flows appear to fluctuate based on
ground water infiltration previously discussed in Section 4.2.2. The relatively steady dry weather flow is
likely attributable to infrastructure improvements, higher efficiency plumbing fixtures, and conservation
efforts. The per capita dry weather flow is expected to remain steady.
Average annual flow per person remained steady in the years 2015 through 2017. There was a
significant increase in flow for the years 2018 and 2019 notably caused by high groundwater I&I as
shown in Section 4.2.2.
Technical Memorandum 5.0 Page 25
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 4-7: AAF and DWF per Capita Flow Rates
Year
2015
2016
2017
2018
2019
Average
Population
43,327
45,187
46,907
48,437
49,831
Dry Weather Flow
(gpcd)
108
106
109
109
115
109
Average Annual
Flow (gpcd)
111
111
112
126
124
117
Per capita flow rates based on WRF inflow data
The per capita rate considers all water uses including residential, commercial, industrial, etc., and
includes those who commute to the City from the surrounding area for work and visit for commerce and
tourism. In addition, the per capita rate also takes into consideration base infiltration. The 2015
Wastewater Collection Facilities Plan used water meter categories to define the portion of per capita
wastewater flow generation associated with residential. In 2015, approximately 50% of the City’s water
meters were categorized as residential which remains consistent with the 2020 meter data; therefore,
following the same method previously used, approximately 59 gpcd (50% x 117 gpcd) is the estimated
residential wastewater flow generation. The 2015 value was 64.4 gpcd, given the two values are
relatively consistent, it is recommended that the City continue to use 64.4 gpcd when designing
collection system infrastructure, including for use in the development standards. This value provides an
appropriately conservative design standard.
Technical Memorandum 5.0 Page 26
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Chapter 5 Wastewater Flow Characterization
Chapter 5 expands the wastewater flow characterization by developing demands based on existing land
use and zoning classes. Wastewater flow generation defined by land use is a common and useful way of
projecting future demands. Chapter 5 defines the baseline (2015 – 2019) wastewater flow duty factors
and provides recommendations for establishing future scenarios, which are discussed in more detail in
Chapter 6.
5.1 Existing Land Use Wastewater Duty Factors
The first component of the land use projection method was to analyze historic non-irrigation water
usage by land use class and land use area to determine domestic flow generation by land use class.
Existing land use duty factors were not used to allocate wastewater loading in the model but were
calculated to understand loading and help inform future land use analyses. Table 5-1 summarizes the
analysis and presents the values as Domestic Flows.
The domestic flows do not include ground water I&I. As presented in Section 4.2.2, the dry weather BI
and wet weather BI were calculated as 1.5 and 5.7 MGD, respectively. The I&I duty factor was calculated
by taking the total BI divided by the total effective land use acreage of the system. The I&I duty factors
were calculated as follows:
• Dry Weather BI Duty Factor: 150 gpad (based on 10,537 acres)
• Wet Weather BI Duty Factor: 550 gpad (based on 10,537 acres)
The I&I duty factors were then added to the domestic flow and presented as the Recommended Dry and
Wet Weather Planning Values as shown in Table 5-1. These values are for planning purposes only, a more
in-depth discussion on planning and design standards recommendations is provided in Section 6.2
The wastewater duty factors from the 2015 WW Collection Facilities Plan Update are also presented in
Table 5-1 for reference. In general, the differences between the 2015 and 2020 values are due to more
detailed analysis for 2020 and differences between the City’s land use shapefile and designations.
Technical Memorandum 5.0 Page 27
=-=
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 5-1: Wastewater Duty Factors by Existing Land Use Classification
Land Use
CA
CR
HM
LM
MIXED
RB
PFP
AP
CHURCH
DTR
MHMP
MFR
SFR
SEF
GOLF
ROW
VACANT
MSU+
RR
POS
Land Use Description
Commercial/Auto
Commercial/Rental
Hotel/Motel
Light Manufacturing
Mixed Use
Restaurant/Bar
Public Facility/Park
Administrative/Professiona
l
Church
Duplex/Triplex Residential
Mobile Home/ Mobile Park
Multi-Family Residential
Single-Family Residential
School/Educational/Facility
Golf Course
Right of Way
Vacant
Montana State University
Rural Residential
Parks or Open Space
2020
2015 WW
Facility
Plan Flow
(gpad)
50
1,000
6,000
800
1,000
3,500
25
1,000
360
1,232
1,232
1,232
854
400
30
0
0
2,220
-
-
Domestic
Flow Non
Irrigation
Demand
(gpad)
670
370
2,050
230
610
1,490
80
420
80
700
1,600
1,080
500
120
20
0
0
740
-
10
Recommended
Dry Weather
Planning Value
Domestic Flow +
Dry Weather BI
(gpad)
820
520
2,200
380
760
1,640
230
570
230
850
1,750
1,230
650
270
170
0
0
890
-
160
Recommended Wet
Weather Planning
Value = Domestic
Flow + Wet Weather
BI (gpad)
1,220
920
2,600
780
1,160
2,040
630
970
630
1,250
2,150
1,630
1,050
670
570
0
0
1,290
-
560
Calculations based on net area.
+ MSU land use duty factor based on total campus area, east and west of South 19th Avenue (615 acres).
Technical Memorandum 5.0 Page 28
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
5.2 Existing Zoning Wastewater Duty Factors
Calculating wastewater duty factors for zoning classes mirrors the methodology used in the land use
analysis. Wastewater duty factors for zoning classifications were used to allocate wastewater demand
within infill and redevelopment areas. Table 5-2 summarizes the analysis and presents the values as
Domestic Flows and as Dry and Wet Weather Planning Values.
The wastewater duty factors from the 2015 WW Facility Plan are also presented in Table 5-2 for
reference. The 2015 WW Facility Plan used the planning flow numbers as dry weather loading factors.
The dry weather loading factors were then increased by 33 percent to obtain wet weather loading
factors.
The City currently uses the 2015 WW Facility Plan loading factors with an additional 150 gpad added on
the loading factors to represent I&I.
High density residential (R-3, R-4, R-5) were initially analyzed using the method described above. The
initial calculations showed that high-density residential developments generally have less flow when
compared with low density residential developments. A closer investigation of the City provided GIS data
showed that R-3, R-4, and R-5 had significant areas that were not completely built out. The domestic
flow duty factor calculation is based on metered water and total acreage. With developments at varying
stages of completion, the duty factor calculation was skewed due to the high number of acres.
Therefore, alternative analysis presented in Section 5.3 provides for high-density planning numbers.
Technical Memorandum 5.0 Page 29
=
-=
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 5-2: Wastewater Loading Duty Factors by Zoning Classification
Zoning
R-S
R-1
R-2
R-3
R-4
R-5
R-O
R-MH
B-1
B-2
B-2M
B-3
M-1
M-2
BP
NEHMU
UMU
REMU
PLI
MSU
Zoning Description
Residential Suburban District
Residential Single-Household
Low Density District
Residential Two-Household
Medium Density District
Residential Medium Density
District
Residential High-Density District
Residential Mixed-Use High-
Density District
Residential-Office District
Residential Manufactured
Home Community District
Neighborhood Business District
Community Business District
Community Business District-
Mixed
Central Business Park District
Light Manufacturing District
Manufacturing and Industrial
District
Business Park District
Northeast Historic Mixed-Use
District
Urban Mixed Use
Residential Emphasis Mixed Use
Public Lands and Institutions
District
Montana State University
2020 Analysis
2015 WW
Facility Plan
Flow (gpad)
910
546
728
910
1,456
-
728
728
1,000
2,000
-
3,000
960
960
960
910
1,456
1,456
1,030
2,200
Domestic
Flow
Non
Irrigation
Demand
(gpad)
60
280
490
420
710
1,580
400
660
1,100
480
1,000
1,040
100
420
130
470
1,000
610
50
1,140
Recommended
Dry Weather
Planning Value
Domestic
Flow + Dry
Weather BI
(gpad)
210
430
640
570
860
1,730
550
810
1,250
630
1,150
1,190
250
570
280
620
1,150
760
200
1,290
Recommended Wet
Weather Planning
Value = Domestic
Flow + Wet Weather
BI (gpad)
610
830
1,040
970
1,260
2,130
950
1,210
1,650
1,030
1,550
1,590
650
970
680
1,020
1,550
1,160
600
1,690
Zoning duty factors computed using gross area for each zone less undeveloped and vacant area.
MSU duty factor computed using gross campus area east of South 19th Avenue and water meters within “MSU”
meter classification.
UMU assumes the same duty factor as B-2M Zoning because as of July 2020 there were no meters within UMU
classification.
Technical Memorandum 5.0 Page 30
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
5.3 High Density Residential, Urban Renewal, and Tax
Increment Financing Districts
High density and mixed-use developments with multi-family units are becoming more common in
Bozeman and across the United States. Based on these trends it was decided to analyze several recently
completed high-density residential developments to better understand and develop representative
wastewater duty factors for these types of developments. The zoning classes associated with these
denser developments in Bozeman are R-3, R-4, and R-5. City staff provided data on several R-4
developments that had been completed and had representative water meter information. The
developments selected and further analyzed (Loyal Gardens, Baxter Lane, Graff Street, and Sundance
Meadows) were considered by City staff to be representative of development trends. All the
developments analyzed are classified as R-4 because the City was not able to identify any R-3 or R-5
areas that were considered fully built-out with representative water meter data.
The metered water use data for the selected developments was reviewed to establish the domestic
wastewater duty factors for R-4 Zoning. The average density of dwelling units for the R-4 subdivisions
was 19.1 dwelling units per acre. The domestic flow of 48.2 gpcd was calculated based on the number of
average units per acre and an assumed population density of 2.17 people per unit. This population
density (2.17 people per unit) is from the 2015 Plan which was computed using 2010 census data.
5.3.1 R-3, R-4, R-5 Wastewater Duty Factors
Using the R-4 duty factors developed from the representative developments discussed above, and input
from City Planning and Engineering staff, R-3 and R-5 duty factors were extrapolated. Table 5-3 shows
the recommended planning numbers for high-density residential zoning areas including domestic flow
and dry and wet weather BI. The planning values are based on the following assumptions:
• Dwelling units per acre:
o R-3: 15 dwellings/ac
o R-4: 20 dwellings/ac
o R-5: 20 dwellings/ac
• Domestic flow was calculated to be 48.2 gpcd for the sample R-4 developments provided by the
City (and assuming 2.17 people per dwelling units, from the 2015 Facility Plan)
• R-5 commercial flow:
o 910 gpad was added as the average domestic flow for B-1, B-2, B-2M, and B-3.
• Dry weather BI added to the domestic flow: 150 gpad
• Wet weather BI added to the domestic flow: 550 gpad
Technical Memorandum 5.0 Page 31
==
==
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 5-3: R-3, R-4, R-5 Wastewater Planning Numbers
Zoning
R-3
R-4
R-5
Dwellings per
Acre
15
20
20
Domestic Flow
(gpad)
1,570
2,100
3,010
Recommended
Dry Weather
Planning Value
Domestic Flow +
Dry Weather BI
(gpad)
1,720
2,250
3,160
Recommended
Wet Weather
Planning Value
Domestic Flow +
Wet Weather BI
(gpad)
2,120
2,650
3,560
R-5 Domestic Flow = R-4 domestic flow plus commercial flow (average of B-1, B-2, B-2M, and B-3).
5.3.2 URD and TIF Wastewater Duty Factors
As of 2020, the City of Bozeman had a total of six Urban Renewal Districts (URD) and Tax Increment
Financing (TIF) Districts. These are areas established by the City to support economic development
through the use of property taxes to fund infrastructure improvements. These six areas (Downtown TIF,
Midtown TIF, North Park URD, Northeast Neighborhood URD, Pole Yard URD, and South Bozeman
Technology District) will redevelop at a higher density. In order to account for the increased density and
wastewater generation for these areas, it was decided with City Planning and Engineering Staff to use
the average of the R-3, R-4, and R-5 domestic duty factors and I&I values established in Section 4.2
Table 5-4 summarizes the recommended URD and TIF district duty factors.
Table 5-4: URD and TIF WWDF Summary (gpad)
Zoning Domestic Flow Recommended Recommended
(gpad) Dry Weather Wet Weather
Planning Value
Domestic Flow +
Planning Value
Domestic Flow +
Dry Weather BI Wet Weather BI
(gpad) (gpad)
URD or TIF 2,230 2,380 2,780
Technical Memorandum 5.0 Page 32
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Chapter 6 Wastewater Flow Projections and
Recommended Duty Factors
Historical wastewater flow data is frequently used to project future loading. These future projections are
crucial in developing capital improvement plans. Future wastewater loading projections are based on a
combination of the following items:
• Historical domestic wastewater flow categorized by zoning class;
• 2020 Bozeman Community Plan future land use characteristics (anticipated land use type, and
associated area);
• Discussions with City Engineering and Planning staff; and
• Development of wastewater loading duty factors (WWDFs), which are a measurement of
wastewater flow in gallons per day per acre (gpd/ac). Adjustments to the WWDFs can be made
based on changes in development plans, water conservation, climate change, or any additional
factors that affect the amount of flow.
6.1 Future Wastewater Flow Analysis
Infill, TIF, and URD areas are assigned a duty factor based on their respective zoning. Future land use
classes are correlated to zoning classes based on the 2020 Bozeman Community Plan. Area weighted
duty factors were then calculated using the associated zones. Area weighting was generally based on
current City breakdown of the zones within each land use. The approach to developing future land use
duty factors is discussed in more detail in Section 6.1.3 Ultimate Build-Out.
6.1.1 Infill Wastewater Flow Analysis
Table 6-1 summarizes the additional wastewater flow rates expected from infill areas based on the
calculated zoning wastewater duty factors. The total additional infill DWF and WWF are estimated to be
2.6 and 3.7 MGD, respectively.
Technical Memorandum 5.0 Page 33
Infill Area (ac)
=
-
Dry Weather
Flow (MGD)
Wet
Weather
Flow
(MGD)
R-1 Residential Single-Household Low 233 280 430 830 0.10 0.19
Density District
R-3 Residential Medium Density 328 1,570 1,720 2,120 0.56 0.70
District
R-5 Residential Mixed-Use High- 30 3,010 3,160 3,560 0.09 0.11
Density District
Residential Manufactured Home 34 660 810 1,210 0.03 0.04
Community District
B-2 Community Business District 368 480 630 1,030 0.23 0.38
Central Business Park District 1 1,040 1,190 1,590 0.00 0.00
M-2 Manufacturing and Industrial 0 420 570 970 0.00 0.00
District
NEHMU Northeast Historic Mixed-Use 0 470 620 1,020 0.00 0.00
District
REMU Residential Emphasis Mixed Use 214 610 760 1,160 0.16 0.25
MSU West Montana State University 211 1,140 1,290 1,690 0.27 0.36
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 6-1: Infill Wastewater Loading
Total 2,836 2.6 3.7
Infill Acreage excludes areas that lie with URD and TIF districts.
Technical Memorandum 5.0 Page 34
Zoning Zoning Description
Domestic Flow
Non Irrigation
Demand (gpad)
Recommended Wet
Weather Planning
Value = Domestic Flow
+ Wet Weather BI
(gpad)
Recommended Dry
Weather Planning
Value = Domestic Flow
+ Dry Weather BI
(gpad)
R-S 388 60 610 0.08 Residential Suburban District 210 0.24
R-2 Residential Two-Household
Medium Density District 86 490 1,040 0.09 640 0.06
R-4 2,100 2,250 2,650 Residential High-Density District 338 0.76 0.90
R-O Residential-Office District 111 400 550 950 0.06 0.11
R-MH
B-1 Neighborhood Business District 1,250 1,650 0.01 0.02 10 1,100
B-2M
B-3
M-1
BP
PLI
UMU
Community Business District-
Mixed
Business Park District
Urban Mixed Use
Public Lands and Institutions
District
Light Manufacturing District
36 1,000
100
130
1,000
50
125
59
32
232
1,150 1,550 0.06 0.04
250
280 680 0.02 0.04
650 0.03 0.08
1,150 1,550 0.04 0.05
200 0.14 600 0.05
Midtown URD 460 0.8 0.8 0.8
Northeast Neighborhood URD 52 Less than 0.1
Downtown TIF 128 0.2 0.2 0.2
Total 1304 2.5 2.6 2.8
Domestic Flow Future Increase Allocation (MGD)
District Area (ac) Allocation Increase
Dry Weather Wet Weather (MGD)
North Park URD 345 0.8 0.8 1.0
Pole Yard URD 273 0.6 0.6 0.8
South Bozeman Tech District TIF 45 0.1 0.1 0.1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
6.1.2 URD and TIF Redevelopment Wastewater Flow Analysis
Table 6-2 summarizes the additional wastewater flows expected from redevelopment of URD and TIF
districts. These areas are expected to ultimately redevelop and increase in density over time. Therefore,
the URD and TIF redevelopments assumed higher domestic flows calculated from the high-density R3,
R4, and R5 domestic loading analysis established previously in Table 5-4. The domestic flow presented in
Table 6-2 is the assumed loading based on an increase in anticipated domestic loading from high
density planning values.
The total additional DWF and WWF for the URD and TIF areas are estimated to be 2.6 and 2.8 MGD,
respectively.
Table 6-2: URD and TIF Wastewater Loading
URD and TIF areas are assumed to rebuild at density consistent with domestic flow in Table 5-4.
Future allocation includes additional BI flows for North Park, Pole Yard, and Tech Districts. Midtown, Northeast Neighborhood, and
Downtown areas have existing BI loading and was not increased.
6.1.3 Ultimate Build-Out (UBO) Wastewater Flow Analysis
This section describes the methods used to assign wastewater loading for the Ultimate Build-Out (UBO)
scenario. Future land uses were related to zoning classes using the Bozeman 2020 Community Plan (pg.
58, Correlation with Zoning) and the Future Land Use map (presented in Figure 2-3).
Equivalent wastewater duty factors were calculated for each future land use using an assumed area-
weighting of the zoning categories specified in the Bozeman 2020 Community Plan. Table 6-4
summarizes the zoning categories per land use and assumed area-weighting. The weights for each zone
are generally based on current City characteristics with some modifications based on input from City
Engineering and Planning Staff taking into consideration recent development trends. For example, for
Urban Neighborhood (RD), the R-4 and R-5 percentages were increased to provide an appropriately
conservative estimate of overall average density for that land use (~9 dwelling units per acre). R4 and R5
are assumed to account for 20% each (40% total) of the 23,000 acres of Urban Neighborhood. Table 6-4
also summarizes the equivalent average residential densities (dwelling units per acre) for each land use
based on this analysis.
Technical Memorandum 5.0 Page 35
GC Golf Course 178 100% PLI 0.4
ID Industrial 479 30% M-1 | 15.5% M-2 | 6.7% BP | 47.8% PLI 0.9
20% R-4 | 20% R-5 | 4% R-O | 4% REMU 1.5% R-
13.4% R-O | 1.8% REMU | 2.2% B-1 Community CommercialCCMU 780 31.6% B-2 | 4.7% B-2M | 0.2% UMU 2.3 Mixed Use 1.3% NEHMU | 44.8% PLI
PI Public Institutions 1,809 100% PLI 0.4
Equiv. Avg. Gross Future Reference Zoning (from 2020 Community Plan) Density Land Use Description Growth Land Use and Percent of Total Area (dwelling units/ Area (ac) ac)
Regional Commercial and RC 6 25% B-2 | 25% B-2M | 25% UMU | 25% PLI 4.6 Services
FU No City Services 4,044 NA 0
15% R-S | 12% R-1 | 12% R-2 | 5% R-3
RD Urban Neighborhood 22,908 9.2
MH | 1.5% B-1 | 5% PLI
42.9% R-3 | 12.7% R-4 | 0.3% R-5
RDMU Residential Mixed Use 346 9.5% R-O | 1.2% REMU | 1.5% B-1 7.4
31.8% PLI
POS Parks and Open Land 1,400 100% PLI 0.4
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
It should be noted that approximately 70 percent of the future land use area has been classified as
Urban Neighborhood. Thus, the vast majority of the additional future flow in the UBO is generated from
the Urban Neighborhood land use. If the City refines the future UBO boundary or land use categories,
the model should be updated to better reflect wastewater projections.
Table 6-3: Future Land Use Correlated to Zoning Classification
-R-3, R-4, R-5 use the denser duty factors representing more current development trends (see Section 5.3 )
-Regional Commercial and Services assumed average of zoning categories (not weighted proportionate to current City because
future growth area assumed negligible)
-Equivalent Average Density calculated assuming 64.4 gallons per capita per day and 2.17 people per unit
Table 6-4 summarizes the resulting area-weighted duty factors and total additional wastewater flow for
the future land uses within the UBO. Areas are based on the future land use map presented in Figure 2-3
which was developed from the land use shapefile provided by the City in 2020. The future land use
shapefile provided by the City represents an unconstrained projection of development – due to
wastewater discharge, water supply, and other environmental and land ownership constraints, the actual
development characteristics will likely be very different.
The largest future land use is Urban Neighborhood, which is defined as approximately 9 dwelling units
per gross acre for the purposes of this Facility Plan. For comparison, the citywide average in 2020 was
6.5 dwelling units per gross acre.
The total UBO additional DWF and WWF are estimated to be 34.2 and 45.3 MGD, respectively. These
numbers are presented as a desktop analysis to provide the City with estimates of total wastewater
loading under the assumption the entire future growth area develops with similar densities and trends
seen in the City within the past 5 years.
Technical Memorandum 5.0 Page 36
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 6-4: Future Land Use Wastewater Loading
(summary of land use outside of 2020 City Limits Boundary – see Figure 2-3)
Growth Area
Land Use
RC
GC
FU
ID
RD
CCMU
RDMU
PI
POS
Land Use Description
Regional Commercial and
Services
Golf Course
No City Services
Industrial
Urban Neighborhood
Community Commercial
Mixed Use
Residential Mixed Use
Public Institutions
Parks and Open Land
Total
Gross
Growth
Area (ac)
6
178
4,044
479
22,908
780
346
1,809
1,400
31,949
Wastewater Duty Factor Wastewater Total
Dry
Weather
(gpad)
790
200
-
280
1,430
470
1,180
200
200
Wet
Weather
(gpad)
1,190
600
-
680
1,830
870
1,580
600
600
Dry
Weather
(MGD)
0.01
0.04
-
0.13
32.6
0.37
0.41
0.36
0.28
34.2
Wet
Weather
(MGD)
0.01
0.11
-
0.33
41.7
0.68
0.55
1.09
0.84
45.3
Dry weather duty factor includes 150 gallons per acre per day for BI
Wet weather duty factor includes 550 gallons per acre per day for BI
Equivalent population calculated using 64.4 gallons per capita per day and dry weather total flow
6.1.4 Increased Density Scenario
An alternative future growth scenario was evaluated to help City staff understand the impacts of growth
under denser conditions. The City recognizes the need to evaluate denser growth due to the recent
senate bill SB 382. SB 382 provides an avenue for Montana communities to develop with denser land
use. Denser development would increase domestic wastewater loading in the collection system. The
Increased Density Scenario helps the City identify potential future pinch-points or system deficiencies.
This Increased Density Scenario generally follows these assumptions:
• All single-family residential areas within current City limits experience increased domestic
loading by 25%;
• All infill residential zone areas R1, R2, and R3 are increased to R4 density and its respective duty
factor;
• Infill B2-M and REMU zoning was increased to R5 density and its respective duty factor.
• Select areas of varying Zoning and Future Land Use types as identified by the City where
increased density development is likely to occur.
• Urban Neighborhood land use areas within the 2020 City limit boundary are increased to R4
density; and
• Future land use outside of the current City limits is consistent with the planning as established in
Table 6-4.
Increased Density model results are presented in TM7. Table 6-5 summarizes the additional system-wide
loading under the Increased Density Scenario.
Technical Memorandum 5.0 Page 37
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 6-5: Increased Density Scenario Wastewater Loading Summary
Increase Density Area
Increase for Existing
Single Family Residential
Increase for Infill Residential Zoning
Increase for Urban Neighborhood
(within City Limits)
Increase for B2-M and REMU
Increase for select zoning and
land use areas.
Total Flow Increase
Increased Domestic Loading*
(gpm)
178
1,128
208
522
468
2,504
MGD
0.3
1.6
0.3
0.7
0.7
3.6
*Average annual flow.
Technical Memorandum 5.0 Page 38
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
6.2 Wastewater Flow Analysis Summary
Table 6-6 summarizes the overall planning numbers and takeaways for the existing system wastewater
flow characterization.
Table 6-7 summarizes the total system loading under each modeled scenario.
Table 6-6: Summary of Overall System Wastewater Flow Parameters
Parameter MGD GPCD
Average Annual Flow (AAF) 5.5 117
Minimum Month Flow 4.7 101
Maximum Month Flow 8.9 184
Maximum 30-Day Flow 9.5 219
Minimum Day Flow 4.0 85
Maximum Day Flow 11.5 238
Maximum Hour Flow 14.0 289
Dry Weather Flow (DWF) 5.3 109
Wet Weather Flow (WWF) 9.5 219
Table 6-7: Summary of Existing and Buildout Wastewater Loading (MGD)
Total System Loading
Dry Weather Wet Weather
Existing Allocation 5.3 9.5
Infill Allocation 2.6 3.7
URD & TIF Allocation Increase 2.6 2.8
UBO Increase 34.2 45.3
Total UBO 44.7 61.3
Increased Density Analysis Increase 3.6 3.6
The UBO increase wastewater flow is presented to provide a future growth estimate based on current
conditions and previous 5-year trends. The future UBO modeled allocation will be presented in TM 7
Future Conditions.
6.3 Wastewater Flow Recommendations for Planning and
Design
It is recommended the City use the wastewater duty factors presented in Table 6-8 below, which list all
the zoning classifications and future land use categories and their respective dry-weather duty factors
and equivalent residential densities. The residential densities were calculated using a per capita
domestic demand of 64.4 gallons per capita per day and 2.17 people per dwelling unit. The per capita
Technical Memorandum 5.0 Page 39
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
demand and average density are from the 2015 Facility Plan and were determined to be consistent with
the updated analysis and appropriate for this Plan.
The wet-weather BI duty factors provide conservative planning numbers by accounting for the 550
gallons per acre per day of groundwater inflow. The wet-weather BI analysis included relatively wet years
and is based on the City’s existing infrastructure. Because not all portions of the City have shallow
groundwater and newer collection system infrastructure decreases inflow susceptibility, it is
recommended that the City use the dry-weather duty factors; this approach is consistent with the 2015
Facility Plan, which used an assumption of 150 gallons per acre per day of inflow on top of domestic
loading.
These numbers should be used at a planning level only; for instance, they can be used to develop high-
level designs and costs for regional lift stations or regional interceptors.
Design Standards Recommendation:
It is recommended that developers continue to use the 64.4 gallons per person per day for base
domestic wastewater generation plus the 150 gallons per acre per day and 10-State Standard Peaking
unless valid justification and analysis are provided by a registered professional engineer.
If future developers are proposing densities beyond those assumed in this Facility Plan, an individual and
separate downstream analysis should be completed to verify the recommended plans conform to the
results and recommendations in this Facility Plan.
Technical Memorandum 5.0 Page 40
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 5.0 – Wastewater Flow Characterization
Table 6-8: Summary of Recommended Duty Factors for Zoning and Future Land Use Classes
R-S
R-2
R-3
R-5*
Residential Medium Density District
Residential Mixed-Use High-Density District
2,250
R-4
2,950
R-O
B-1
B-2M*
M-1
BP
UMU
PLI
B-2
B-3 Central Business Park District
Manufacturing and Industrial District
Community Business District
Northeast Historic Mixed-Use District
M-2
NEHMU
REMU*
Residential Suburban District
R-1 Residential Single-Household Low Density
District
430 2.0
Residential Two-Household Medium Density
District
Residential High-Density District
Residential -Office District
R-MH Residential Manufactured Home Community
District
810
Neighborhood Business District
Community Business District - Mixed
Light Manufacturing District
Business Park District
Urban Mixed Use
Public Lands and Institutions District
Montana State University 1,290
0.4
3.5
15.0
20.0
20.0
2.9
7.9
20.0
0.7
0.9
7.2
0.4
3.4
7.4
3.0
3.4
210
640
2,950
550
1,250
2,950
250
280
1,150
20.0
200
630
1,190
570
620
2,950
Future Land Use Classifications
RC Regional Commercial and Services 790 4.6
GC Golf Course 200 0.4
FU No City Services -
ID Industrial 280 0.9
RD Urban Neighborhood 1,430 9.2
CCMU Community Commercial Mixed Use 470 2.3
RDMU Residential Mixed Use 1,180 7.4
PI Public Institutions 200 0.4
POS Parks and Open Land 200 0.4
Zoning or Future Zoning or Land Use Class Planning Value Equivalent Density
Land Use (gpad) (dwelling units per
Classification acre)
Zoning Classifications
4.7
Residential Emphasis Mixed Use
MSU 8.2
* B-2M, R-5, and REMU zoning districts assume increased density planning values at 20.0 dwelling units per acre
for planning purposes. B-2M, R-5, and REMU allow a broad range of use and intensity of development and must be
verified by the design engineer.
Technical Memorandum 5.0 Page 41
6.0
Feature Manipulation
Engine and GIS Technical
Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Table of Contents
Chapter 1 Data Exchange Routine......................................................................................... 2
Update the Data Source Files (GIS output) ................................................................................................2
Open the GIS Exchange Window..................................................................................................................3
Verify/Update Source Data for Each Exchange and Attribute Mapping .........................................5
Run the Exchanges to Import/Update Junctions and Pipes............................................................... 13
Update the Map and Append Nodes to Pipes.......................................................................................14
Model Review.................................................................................................................................................... 17
Technical Memorandum 6.0 Page 1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Chapter 1 Data Exchange Routine
The purpose of this technical memorandum is to provide an overview of the process and steps
to import and update the wastewater collection system model using the InfoSWMM GIS
Exchange Tool. There are 5 main steps to update the model from a GIS database:
o Step 1: Update the data source files (GIS output).
o Step 2: Open the GIS Exchange Window.
o Step 3: Verify/Update source data for each Exchange and attribute mapping.
o Step 4: Run the Exchanges to Import/Update junctions and pipes.
o Step 5: Update the Map and Append nodes to pipes.
o Step 6: Review Tools for Checking General Connectivity.
These steps are covered in detail in this technical memorandum.
Update the Data Source Files (GIS output)
The City’s GIS department will provide updated wastewater collection system pipe shapefiles
and manhole shapefiles for the model update. Before exporting data, the GIS department
should first address any items identified for review or correction from previous model import
processes, as necessary.
Once the GIS system is ready for export, Use the FME program to export the following
shapefiles:
• SHYD_Junction Shapefile that contain all junctions.
• SHYD_Pipe Shapefile that contains all pipes.
The model uses the following Coordinate system: NAD_1983_UTM_Zone_13N.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Open the GIS Exchange Window
Open the model .mxd file and initialize the model. Activate an Existing model scenario (i.e.
EXIST_2020_DWF). Go the InfoSWMM Menu, select Exchange, and click on the GIS Gateway.
Click Here to
start the GIS
Gateway.
The GIS Gateway window will appear.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
The GIS Gateway
Window is shown
here.
There are four Exchanges listed in the GIS Gateway:
• SHYD_JUNCTION: Imports new manholes.
o i.e. imports manholes and force main nodes that were not previously in the
model.
• SHYD_PIPE: Imports new pipes.
o i.e. imports pipes (conduits) that were not previously in the model.
• SHYD_JUNCTION_UPDATE: Updates existing model manhole information.
o i.e. updates manhole rim elevation that was surveyed and entered into GIS.
• SHYD_PIPE_UPDATE: Updates existing model pipe information.
o i.e. updates pipe Manning’s n, diameter, and inverts for a pipe that was replaced
from 6” to 12”.
The four Exchanges
are shown here in
the GIS Gateway
Window.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Verify/Update Source Data for Each Exchange and Attribute
Mapping
Step 3A: Click on an Exchange and view the details in the lower window. Verify if the
Data source is correct for all Exchanges. If the data source is correct proceed to Step 4.
If the source is not correct proceed with Steps 3B through 3F.
Step 3B: If the source data needs to be corrected, click on an Exchange and select Edit.
The GIS Exchange Cluster window will appear.
3A: - To View
the Details of an
Exchange, Select
the Exchange
and view the
window below.
3B: To edit - select
the Exchange and
click Edit. The GIS
Exchange Cluster
window will
appear. Make
sure to click Save
after edits are
complete. **After Editing an exchange Click on the Exchange and Click Save.
Step 3C: Click the browse button to find and select the source shapefile.
Step 3D: In the InfoSWMM Data Source Area verify that the Type selected is appropriate
for the Exchange (i.e. Junction Tables is selected for Junction Exchanges as shown below).
Step 3E: Under the Exchange Options Area, verify that Tabular Join is selected, Load Only
is selected, and the appropriate record match is selected (i.e. Create New Records is
selected for the SHYD_JUNCTION exchange (importing new junctions).
Step 3F: Once the source file has been corrected, update the GIS ID Mapping Field to
the ID field.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
3D: -Verify that
the Table Type is
appropriately
selected for the
Exchange. (i.e.
Junction tables
selected for
Junction
Exchanges.)
3C: -To update the
source file click
here, browse to the
appropriate source
and select the
required Shapefile.
3E: -Under Exchange
Options select
Tabular Join, Load
Only, and the
appropriate record
match (Create New
vs. Update Existing)
for the Exchange.
3F: -Select the
dropdown button
and choose the
“ID” field for
mapping.
3F (cont.): -Select
the Field Mapping
Tab to verify
attribute mapping.
Note this window
shows no GIS fields
are mapped to the
model.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
3F (cont.): -Click
the Double Arrow
button to
automatically
match attributes
from the GIS Data
Fields to the
InfoSWMM Fields.
These will match
only if the Field
names are titled
exactly the same.
3F (cont.): -Note
this window shows
when the GIS
Fields are mapped.
3F (cont.): -Once mapped, the
Field is removed from the GIS
list.
Technical Memorandum 6.0 Page 7
3F (cont.): - To map Fields that do not automatically map:
Click on the GIS Data Fi eld, then Click on the corresponding
InfoSWMM Field, then Click on the Single Arrow.
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Ensure that the following Fields are mapped for both junction Exchanges:
3F (cont.): - Note these junction
Fields will not be Mapped.
3F (cont.): - Note
these highlighted
Fields must be
mapped.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Ensure that the following Fields are mapped for both pipe Exchanges:
3F (con t.): - Note
these pipe Fields will not be
Mapped.
3F (cont.): - Note
these highlighted
Fields must be
mapped.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
3F (cont.): -When
Mapping is
complete – Click
OK.
**After Editing an exchange Click on the Exchange and Click Save.
Step 3G: Complete steps 3B through 3F for all Exchanges.
Step 3H: Prepare model database for pipe connectivity update.
Prior to running the Exchanges, the pipe connectivity database within the model will
require edits. Perform the following steps.
• Close the GIS Exchange Window.
• Open the Database Editor:
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
• Select Element Geometry Data,
• Select Link Connectivity
• Click OK:
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
• In the DB Editor Window:
o Left Click on the From column header.
o Right Click and select Block Editing.
o Choose Operation Replace With.
o Delete any text in the Value field so it is blank.
o Click OK:
o Left Click on the To column header.
o Right Click and select Block Editing.
o Choose Operation Replace With.
o Delete any text in the Value field so it is blank.
o Click OK
o Click Exit
o Click Yes to confirm and save changes in Link Geometry
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Run the Exchanges to Import/Update Junctions and Pipes
Step 4A: Re-open the GIS Gateway window and select Load
To begin the Exchange
process, click on Load.
The Load Data from GIS Layer or Table window will appear. Select the Exchanges to run and
Load
• Choose Select All to use all Exchanges (recommended for initial update).
• Or: hold Control to pick and choose Exchanges to run (i.e. junctions only).
• Click on Load to run the selected Exchanges.
• Exchanges will then run.
Hold Control to select
multiple Exchanges.
Or Select All.
Select Load to run
the Exchange(s).
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Step 4B: Re-Run the Pipe Update Exchange to update pipe information in Future
scenarios.
Note: The model uses different hydraulic data sets for future scenarios. These hydraulic
data sets include diameter, roughness, length, minor loss, etc. The Pipe Update Exchange
will need to be applied to future modeling scenarios to update the data sets with pipe
diameter, roughness, or length originating from pipe replacement data or from GIS data
corrections.
Follow these steps to apply the Pipe Update Exchange to the Future Scenarios:
• Open the Scenario Explorer and Activate the future scenario:
• Open the GIS Gateway as outlined in Step 2.
• Load the PIPE_UPDATE Exchange only and Run.
• Repeat this process and apply the Pipe Update Exchange to all future Scenarios
Update the Map and Append Nodes to Pipes
Step 5A: Updating the Map: The import process will update X,Y coordinates of junctions
and the alignment of pipes. Follow these steps to update the map from the database and
visually see these changes.
• Go to the InfoSWMM Menu, select Utilities, Update MAP from DB, and Force All Network.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
**Note: Step 5A needs to be done prior to Appending nodes in the next step.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Step 5B: Appending Nodes: Following the import process the Start and End Node IDs
within the pipe geometry database will need to be updated.
Start/End Nodes
will no longer be
populated.
To rectify this issue, go the InfoSWMM Menu, select Exchange, and click on Append Nodes.
Click Here to
start the
Append Nodes
process.
In the Append Nodes Window:
• Use the searching distance (0.1) (distance in meters due to map units).
• Utilize Automatic Mode (keep box checked).
• Use the default Node Type as Junction and the default Link Type as Conduit.
• Uncheck Apply to Domain.
• Click Append to run.
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Technical Memorandum 6.0 –FME and GIS Data Exchange Routine
Model Review
This step discusses some of the tools that should be used to check for errors after completing
the GIS exchange process. Tools discussed in this step included:
General tools for cleaning/finding errors:
• To access the error cleaning/finding tools go to the InfoSWMM drop down menu, then
Utilities, then Network Review/Fix.
o Additional information is also provided in the InfoSWMM Help Menu which can be
accessed through the InfoSWMM drop down menu.
o Note: When using these tools it is generally recommend to NOT allow the
program to automatically fix the errors it finds. Use the tools to add the facilities
to a domain and review for further review..
• Locate/Fix Nodes in Close Proximity. Use this tool to find nodes that are in close
proximity to each other.
• Locate/Fix Pipe-Split Candidates. Use this tool to find pipes that should be connected. A
specified distance allows the user to find end nodes that are candidates to split pipes.
• Locate/Fix Crossing/Intersecting Pipes. Use this tool to find pipes that cross each other
but do not intersect with a common node.
• Trace Network, Connected Nodes, Upstream Network, or Downstream Network. Use
these tools to trace the network. The traced network will be added to a domain. Use
trace on the existing system to determine if any newly added pipe is not connected.
General Database Review:
• Review the manhole database to determine if there are missing rim elevations or missing
invert elevations. Correct as needed.
• Review the conduit database to determine if there are missing diameter, invert, length,
Manning’s n values. Correct as needed.
Complete Final Model Review:
• After completing a review of model connectivity try running the Model scenarios and
complete the following checks for all scenarios.
o Review d/D results and compare results from the updated model to the previous
model version.
o Spot Check peak flows at major interceptor locations and at the WRF.
o Check overall system loading.
Technical Memorandum 6.0 Page 17
7.0
Hydraulic Model
Development and
Results Technical
Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table of Contents
Chapter 1 Introduction...........................................................................................................5
Chapter 2 Existing Conditions Model Development and Calibration................................ 6
Data Summary.....................................................................................................................................................6
Model Network Update...................................................................................................................................7
Existing Wastewater Flow Allocation...........................................................................................................8
2.3.0 Domestic Flow Allocation ................................................................................................................8
2.3.1 Base Groundwater Infiltration ........................................................................................................9
2.3.2 Rainfall Derived Inflow and Infiltration Loading.......................................................................9
2.3.3 Summary of System Loading ....................................................................................................... 10
2.3.4 Wastewater Flow Hydrograph ......................................................................................................11
Model Calibration............................................................................................................................................ 13
2.4.0 Dry Weather Calibration ................................................................................................................13
2.4.1 Wet Weather Calibration.............................................................................................................. 20
2.4.2 Summary of RTK Factors from the 2020 Calibration............................................................27
2.4.3 2018 Midtown/Downtown Metering and Model Calibration............................................ 28
Chapter 3 Hydraulic Performance Standards..................................................................... 30
Gravity Main Design Criteria........................................................................................................................ 30
Force Main Design Criteria.......................................................................................................................... 32
Lift Station Design Criteria........................................................................................................................... 32
Peak Hour Design Factors ........................................................................................................................... 33
Dry Weather Criteria...................................................................................................................................... 33
Wet Weather Flow Event (Design Storm) Criteria................................................................................ 33
Chapter 4 Existing System Evaluation ................................................................................ 36
Existing Dry Weather Modeling Analysis................................................................................................. 40
Existing Wet Weather Modeling Analysis................................................................................................41
4.2.0 Wet Weather Lift Station Analysis ..............................................................................................41
4.2.1 WWF Interceptor and Gravity Main Analysis ......................................................................... 42
Chapter 5 Existing System Recommendations .................................................................. 50
Chapter 6 Future Conditions Model Development ........................................................... 51
Model Network Expansion............................................................................................................................ 51
Scenarios ........................................................................................................................................................... 52
Future Wastewater Allocation .................................................................................................................... 53
6.3.1 Domestic Flow Allocation ............................................................................................................. 53
6.3.2 Groundwater Baseflow .................................................................................................................. 53
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
6.3.3 Rainfall Derived Inflow and Infiltration Loading.................................................................... 54
6.3.4 Summary of Future System Loading ........................................................................................ 54
Chapter 7 Future System Evaluation and Recommendations .......................................... 56
Future Conditions Modeling Scenarios.................................................................................................... 56
7.1.1 Dry Weather Model Conditions ................................................................................................. 56
7.1.2 Wet Weather Model Conditions ................................................................................................ 56
Infill Evaluation and Improvements Summary .......................................................................................57
7.2.1 Modeling Results of Gravity Main and Interceptors for Infill Conditions ......................57
7.2.2 Infill Interceptor and Gravity Main Improvements ............................................................... 60
7.2.3 Infill Lift Station Summary ............................................................................................................ 62
UBO Improvements Summary ................................................................................................................... 65
7.3.1 Modeling Results of Gravity Main and Interceptors for UBO Conditions .................... 65
7.3.2 UBO Interceptor and Gravity Main Improvements ...............................................................70
7.3.3 UBO Lift Station Summary ............................................................................................................72
UBO West Improvements Summary .........................................................................................................73
7.4.1 UBO West Interceptor Improvements.......................................................................................73
7.4.2 UBO West Lift Station Summary ................................................................................................ 74
7.4.3 Modeling Results of Gravity Main and Interceptors for UBO West Conditions ..........75
Summary of Lift Stations and Force Main Improvements..................................................................78
Increased Density Improvements Summary.......................................................................................... 82
Technical Memorandum 7.0 Page 2
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
List of Tables
Table 2-1: Summary of Base Loading for Existing Conditions Model Scenarios ..................................11
Table 2-2: Summary of Dry Weather Flow Calibration Results....................................................................16
Table 2-3: Summary of Wet Weather Calibration Results .............................................................................23
Table 2-4: Summary of 2018 Rain Event Downtown Calibrated Peak Flows..........................................29
Table 3-1: Summary of Hydraulic Parameters and Design Criteria............................................................35
Table 4-1: Summary of Existing Lift Stations ......................................................................................................37
Table 4-2: Summary of Existing Interceptors......................................................................................................38
Table 4-3: Capacity Summary of Existing Lift Stations....................................................................................41
Table 4-4: Capacity Summary of Existing Interceptors ...................................................................................48
Table 6-1: Summary of Loading for Dry Weather Model Scenarios..........................................................55
Table 6-2: Summary of Loading for Wet Weather Model Scenarios.........................................................55
Table 7-1: Lift Station Capacity Summary............................................................................................................80
Table 7-2: Capacity Force Main ...............................................................................................................................81
List of Figures
Figure 2-1: Components of a Sewer Flow Hydrograph ..................................................................................12
Figure 2-2: Flow Monitoring Locations.................................................................................................................15
Figure 2-3: WRF Metered vs Modeled Dry Weather Flows...........................................................................17
Figure 2-4: I5012 Metered vs Modeled Dry Weather Flows .........................................................................17
Figure 2-5: G0225 Metered vs Modeled Dry Weather Flows .......................................................................18
Figure 2-6: H0325 Metered vs Modeled Dry Weather Flows.......................................................................18
Figure 2-7: K0319 Metered vs Modeled Dry Weather Flows........................................................................19
Figure 2-8: J0306 Metered vs Modeled Dry Weather Flows.........................................................................19
Figure 2-9: Calibration Storm Event: June 17, 2020 Rainfall Distribution................................................21
Figure 2-10: WRF Metered vs Modeled Wet Weather Flows .......................................................................24
Figure 2-11: I5009 Metered vs Modeled Wet Weather Flows .....................................................................24
Figure 2-12: I5012 Metered vs Modeled Dry Weather Flows.......................................................................25
Figure 2-13: G0225 Metered vs Modeled Wet Weather Flows....................................................................26
Figure 2-14: H0325 Metered vs Modeled Dry Weather Flows.....................................................................26
Figure 2-15: K0319 Metered vs Modeled Wet Weather Flows....................................................................26
Figure 2-16: J0306 Metered vs Modeled Wet Weather Flows.....................................................................27
Figure 3-1: Design Storm Rainfall Distribution..................................................................................................34
Figure 4-1: Existing Interceptors..............................................................................................................................39
Figure 4-2: Existing Wet Weather Gravity Main d/D Capacity Analysis....................................................44
Figure 4-3: Existing Wet Weather Interceptor d/D Capacity Analysis.......................................................49
Figure 7-1: Infill System Wet Weather d/D Capacity Analysis......................................................................59
Figure 7-2: Infill System Improvements................................................................................................................64
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
Figure 7-3: UBO Interceptor System......................................................................................................................66
Figure 7-4: UBO Interceptors and Sewershed Basins ......................................................................................67
Figure 7-5: UBO System Wet Weather d/D Capacity Analysis.....................................................................68
Figure 7-6: UBO System Improvements ...............................................................................................................69
Figure 7-7: UBO West System Improvements....................................................................................................76
Figure 7-8: UBO West Wet Weather d/D Capacity Analysis .........................................................................77
Figure 7-9: Increased Density Wet Weather d/D Capacity Analysis ..........................................................84
Figure 7-10: Increased d/D from UBO to Increased Density ........................................................................85
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Chapter 1 Introduction
The Hydraulic Model Development and Results Technical Memorandum (TM 7) provides a
summary of the data used, methods, assumptions, and results of the model update. TM 7
includes the following sections:
• Existing Conditions Model Development and Calibration;
• Hydraulic Performance Standards;
• Existing System Evaluation; and
• Future Conditions Scenario Development and Recommendations.
Additional details on the proposed improvements and recommendations are provided in the
Capital Improvements Plan Technical Memorandum (TM 9).
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Chapter 2 Existing Conditions Model Development
and Calibration
The City currently uses the Innovyze InfoSWMM software package for modeling the City’s
wastewater collection system, specifically InfoSWMM Executive Suite 14.7. Previous InfoSWMM
versions of the City’s collection system model were used as a reference model update, but were
not relied upon entirely because of questionable invert elevation data.
Data Summary
Several historic data sources and references, as well as newly collected data, were used in the
model update. TM 3 details these data sources and data collection methods. The following is a
list of key data sources used in the update, which include:
• Collection system geodatabase (City of Bozeman, initial updated with 2020, data, and
followed by an update with 2023 data);
• Planning land use and zoning GIS data (City of Bozeman, 2020);
• City of Bozeman Wastewater Collection System Model Update (City of Bozeman; 2018);
• City of Bozeman Wastewater Collection Facilities Plan Update Final (City of Bozeman;
2015);
• Collection System Field Survey (TD&H, 2020);
• Bozeman Community Plan 2020 (City of Bozeman, 2020);
• Historic wastewater flow monitoring at WRF and within the collection system (City of
Bozeman, 2015 through June 2020.);
• Spring 2020 wastewater flow monitoring (TD&H, 2020);
• Collection system infrastructure record drawings (City of Bozeman);
• Drinking water meter location shapefile (City of Bozeman, 2020);
• Drinking water metered account data (City of Bozeman, 2015 through June 2020);
• Bozeman Climate Plan (City of Bozeman, 2020);
• Climate Vulnerability Assessment and Resiliency Strategy (City of Bozeman, 2019); and
• Midtown/Downtown Sewer Capacity Analysis (Sanderson & Stewart, 2018).
• Baxter Creek Drainage Basin Analysis Technical Memorandum (AE2S, 2022).
Technical Memorandum 7.0 Page 6
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
Model Network Update
The following techniques were used to build the framework of the wastewater system model
network.
o Model Network Geospatial Updates:
o FME Routine: Feature Manipulation Engine (FME) scripting was used by the City
to consolidate relevant available information to import model network elements
(e.g., pipes and manholes). TM 6 describes the FME and model import method in
detail and provides a step-by-step process to complete the model network
update.
o GIS Gateway: TM 6 describes how the GIS shapefiles and InfoSWMM GIS
Gateway were used to geospatially update modeled sanitary sewer manholes
(junctions) and pipelines (conduits).
o Junction and Conduit Elevation Updates:
The following procedure details the elevation update approach.
o Survey: Survey data was collected along major sanitary sewers by TD&H
Engineering. The InfoSWMM GIS Gateway tool was used to import all field data
into the model based on junction and conduit IDs. Field data populated
included:
▪Manhole rim and invert elevations.
▪Conduit upstream and downstream invert elevations.
o Record Drawing: As-built record drawings were used to update lift stations and
surrounding developments.
o Upstream Invert Calculation: The InfoSWMM Upstream Invert Calculator tool
was used to calculate upstream conduit inverts of laterals and collector segments
that did not have field survey or as-built data. For these particular inverts that did
not have representative information, the nearest known invert (i.e., surveyed or
as-built) elevation was used to calculate the missing upstream invert based on
the pipe length from the known survey location and then utilizing the 10-states
Standards minimum pipe slope for that pipe’s known diameter.
o Manual Edits or Calculation: Residual conduit elevations were closely reviewed.
If an error was encountered in the model a manual edit or calculation was made
estimated based on engineering judgement and best available data. Edits
included interpolation between two known inverts and entering manually editing
inverts at locations where the upstream invert calculated started.
o Manhole Rim Elevation Extraction: For manholes that did not have survey or
as-built data, rim elevations were extracted from the City’s digital elevation
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
model (DEM), and manhole inverts were calculated using the InfoSWMM
Upstream Invert Calculator tool.
o The model has an attribute field INV_NOTE to denote the origin of conduit
inverts with the following labels: Surveyed, Record Drawing, Invert Calculator,
Manual Edit, or Manual Calc.
Existing Wastewater Flow Allocation
A wastewater flow and loading analysis was completed with water reclamation facility (WRF)
flow data from 2015 through 2019 along with water meter data from the same time period.
TM5 describes the wastewater characterization methodology and analyses in detail. This section
summarizes the key results and describes the model flow allocation methodology utilized in the
development of the model.
• Domestic Flow: The portion of wastewater flow that originates from residential,
commercial, and industrial sources, and also known as sanitary flow. This flow is
relatively steady throughout the year and can be estimated from non-irrigation (winter,
or indoor) metered water use.
• Base Infiltration (BI): The portion of wastewater flow that originates from groundwater
and can vary by depth of the groundwater table.
• Rainfall Derived Inflow and Infiltration (RDII): The portion of wastewater flow that
originates from rainfall events as inflow and infiltration into the collection system.
2.3.0 Domestic Flow Allocation
Water meter records were used to estimate wastewater flow from domestic (residential,
commercial, and industrial) water use throughout the City. Meter coverage is near 100-percent
across the City. Historical water meter records from 2015 through 2019 were evaluated to
determine overall customer water consumption, water demand by both land use class and
zoning, per capita water usage, and seasonal variations in water demand.
o Non-Irrigation Demand: Non-irrigation demand was calculated as an average of daily
flows during winter months. (i.e. The Non-Irrigation Demand calculated for 2015 is
calculated as the average flow from Nov/Dec 2015 and Jan/Feb 2016). From 2015 – 2019
the non-irrigation water demand ranged from 3.5 to 3.8 MGD, with an average of 3.6
MGD during the five-year period.
o Domestic Flow: Non-irrigation demand of 3.8 MGD was used as the base domestic
wastewater flow allocated within the hydraulic model as this was the highest flow
calculated for the review period.
o Allocation: The domestic flow was allocated (assigned geographically) in the model by
using georeferenced water meter points and February 2020 water usage data. The
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
metered data was allocated to the nearest gravity main and then to the manholes of
that gravity main.
2.3.1 Base Groundwater Infiltration
Inflow and Infiltration (I&I) is a critical consideration when evaluating collection system capacity.
Where groundwater is high, such as West Bozeman, infiltration can influence wastewater flows
even during dry conditions. This is referred to as base groundwater infiltration (BI), which makes
up a portion of the Dry Weather Flow (DWF), Wet Weather Flow (WWF), and Average Annual
Flow (AAF) at the Bozeman WRF.
TM 5 recommended the following BI flows be allocated within the following model scenarios:
• 1.5 MGD of BI for the base DWF scenario for existing conditions.
• 5.7 MGD of BI for the base WWF scenario for existing conditions.
o
The BI was allocated based on the size and length of gravity main using the following equation:
𝐴𝐼 𝐴𝐼 𝑐𝑟𝑟𝑥 𝑓𝑎𝑐𝑟𝑛𝑟 = ∑𝑎𝑙𝑙 𝑔𝑟𝑎𝑣𝑖𝑟𝑥 𝑙𝑎𝑖𝑙𝑟(𝐷 𝑥 𝐿)
Where:
BI duty factor = groundwater infiltration rate gallons per day per inch-
diameter-mile of pipe (gpd/idm)
BI = groundwater infiltration (gpd)
Diameter = pipe diameter (inches)
Length = pipe length (miles)
• BI for DWF: 672 gpd/idm (or 1.5 MGD)
• BI for WWF: 2,525 gpd/idm (or 5.7 MGD)
The BI was calculated for each conduit by multiplying the BI duty factor by the conduit length
and by the conduit diameter. The resulting BI flow was then allocated to the manholes on each
end of the conduit as a constant flow entering the manholes. The BI calculation was completed
for DWF and WWF scenarios.
2.3.2 Rainfall Derived Inflow and Infiltration Loading
During and after rain events, flows within the collection system increase, which is referred to as
rainfall derived inflow and infiltration (RDII). The RDII flow component is combined with BI and
diurnal peak domestic flows to define the total wastewater flow conveyed by the wastewater
collection system, which is ultimately routed and treated at the WRF. This peak WWF condition
is considered and representative of the City’s worst-case wastewater flow scenario and is
subsequently used to evaluate a collection system’s capacity.
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
The WWF scenario of the model update utilized a synthetic design storm event to allocate RDII.
RDII model calibration and design storm results are discussed in Section 2.3.4 and Chapter 4,
respectively.
2.3.3 Summary of System Loading
The following summary and Table 2-1 provide an overview of loading allocated within the
hydraulic model to establish the existing collection system scenarios. Refer to TM5 for a
detailed analysis of the following parameters.
o DWF Domestic Flow: A total of 3.8 MGD was assigned as the base domestic flow
rate for both DWF and WWF scenario based on the 2018 non-irrigation metered
water use.
▪Flow metering conducted in support of the model update indicated minor
irregularities from previously documented diurnal wastewater patterns in
Bozeman, due to the Covid-19 pandemic.
▪Diurnal peaking factors for the DWF and WWF design scenarios utilize the
diurnal patterns as calculated from data collected during the calibration
period. The demand patterns were then allocated across each flow
monitored area for the calibration period.
▪For the 2020 calibration, the total DWF was calculated as 6.0 MGD based
on WRF inflow. The domestic flow allocation used April 2020 water
metered data at 4.4 MGD. The metered flow was found to be too high, so
it was scaled down evenly to 3.9 MGD to reflect flows experienced at the
WRF. 3.9 MGD was applied to both the DWF and WWF calibration.
o BI: based on gpd/idm and findings within TM5 – Wastewater Flow
Characterization.
▪The base existing conditions DWF scenario: A total 1.5 MGD BI was
assigned as a representative DWF starting condition based on the 2018
DWF WRF inflow of 5.3 MGD.
• Calibration period occurred during April through June of 2020: A
total of 2.1 MGD BI was used for model calibration.
o The BI for the DWF calibration was initially modeled as 1.5
MGD. However, this was found to be too low and was
scaled evenly to 2.1 MGD to match flow monitoring
locations and WRF inflow for April through June, 2020
flows at the WRF. 2.1 MGD was applied to both the DWF
and WWF calibration.
▪The base existing conditions WWF scenario: A total of 5.7 MGD BI was
assigned as a representative WWF starting condition.
• The BI assigned for the WWF is based on the highest 30-day flow
of BI occurred during April and May of 2018 as the WRF
experience an average inflow of 9.5 MGD. With the assumption
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WWF 3.8 5.7 9.5
WWF Calibration 3.9 2.1 6.0
Ground Total Base Loading Domestic Flow Scenario Water BI (Domestic + Ground Water BI) (MGD) (MGD) (MGD)
DWF 3.8 1.5 5.3
DWF Calibration 3.9 2.1 6.0
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that the domestic flow was 3.8 MGD, the estimated BI flow at the
WRF during the maximum 30-day flow is 5.7 MGD.
o RDII: flow and peaking as determined by modeling analysis.
▪(peaking factors vary by flow monitored area)
▪RDII is not considered in the DWF modeling scenarios.
Table 2-1: Summary of Base Loading for Existing Conditions Model Scenarios
2.3.4 Wastewater Flow Hydrograph
A wastewater flow hydrograph is a useful way to display the components of the wastewater flow
over time. Figure 2-1 shows a conceptual hydrograph of the dry weather and wet weather
components of the City’s wastewater collection system flows.
Dry weather flow components consist of the domestic flow and base groundwater infiltration as
described above. Combined, these two flow components make up the average daily dry
weather flow. The base groundwater infiltration is generally a constant flow rate but may vary
based on the season and groundwater table elevation. Groundwater infiltration enters the
system through defective pipes, pipe joints, and manhole structures. The domestic flow
originates from indoor water use and varies throughout the day following a diurnal pattern that
typically peaks in the morning and afternoon or evening.
Wet weather flow components consist of the domestic flow, base groundwater infiltration, and
rainfall derived inflow and infiltration( RDII). Combined, these three flow components make up
the wet weather flow. The rainfall derived inflow is water that enters the collections system
through direct sources such as cross connection to storm sewers, private laterals, downspouts,
manhole defects, or other connections. Rainfall derived infiltration is in the additional
groundwater infiltration that occurs in the hours or days following the rainfall event due to
higher groundwater. RDII is influenced by the during and intensity of the rainfall event and
varies by each rainfall event. The wet weather peaking factor is the ratio of the peak wet weather
flow to the average dry weather flow.
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Figure 2-1: Components of a Sewer Flow Hydrograph
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Model Calibration
Model calibration is a process used to improve model results to match real-world observations
more closely. The model results can be adjusted by modifications to the physical attributes, to
the flow allocation, or flow patterns. A model that is more closely calibrated to observed
conditions generally improves the model’s ability to predict wastewater flows and overall
collection system performance. Examples of calibration adjustments include:
• Modifying pipe roughness coefficients;
• Varying flow diversion between wastewater sub-basins;
• Adjusting base flow volume;
• Changing base flow diurnal patterns; and
• Adjusting RDII contributing factors.
The calibration process ends when the model results are within a targeted range compared to
observed conditions, or when no further benefit is realized from reasonable model adjustments.
The following sections describe the DWF and WWF weather calibration processes and how
calibration was performed for the model update.
A total of six (6) flow meters were placed in the western and central portion of the City’s
collection system between April and June of 2020. The resulting flow data along with metered
flow data from the WRF (furthest downstream point in the collection system) was utilized to
calibrate the model. In addition to the six (6) flow meters utilized the City had collected
wastewater information for various past studies and new developments. These historical flow
monitoring locations where used to augment the data set and in model refinement and
calibration.
Figure 2-2 shows the six (6) 2020 flow monitoring locations, the upstream gravity main network
that represents the six (6) locations, and the historical flow monitoring locations used in the
analysis.
2.4.1 Dry Weather Calibration
The DWF is composed of BI and Domestic flow (DWF = BI + Domestic). DWF is the average flow
that occurs on a day not influenced by rainfall. Selection of the DWF is important since it is the
base flow that is carried into WWF calculations. DWF is identified using the following criteria:
• No rainfall occurred on that day or on the preceding days.
• Flow rates were within a specified range (not less than 85 percent of the average or
more than 115 percent of the average)
The day of the week is also considered since significant changes in wastewater generation
patterns can often be observed between weekdays and weekend days. Dry days for both
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weekdays and weekends were identified, and the rate of flow and shape of the hydrograph was
determined.
Sanitary sewer hydraulic model calibration standards have not been established at this time in
the U.S. Therefore, goals for DWF calibration were taken from the United Kingdom’s
Wastewater Planning Users Group (WaPUG1) and consisted of the following:
• The shape of the modeled versus metered data curves should be similar.
• The timing of the peaks, troughs, and recessions of the modeled versus metered curves
should be similar.
• Modeled total volume should be plus or minus 10 percent of measured total volume.
• Modeled peak flow rate should be plus or minus 10 percent of measured peak flow rate.
• Peak depth should be plus or minus 0.3 feet (3.6 inches)
During the calibration process, the DWF diurnal curves were adjusted within the model until
they closely matched the metered data. Once the timing of the peak flows and low flows in the
modeled diurnal curves visually matched the metered data, the hourly multipliers, BI, and
domestic flows were further adjusted to meet the numerical calibration goals.
WaPUG, Code of Practice for the hydraulic modelling of sewer systems, 3rd Edition WAPUG 2002 www.wapug.org.uk
Technical Memorandum 7.0 Page 14
1
2
Modeled vs Metered Meter Location Modeled vs Metered Volume Peak Flows
±10% of measured values ±10% of measured values
WRF -0.1 -2.6
I5009 * *
I5012 -0.1 -4.6
G0225 0.9 -21.4
H0325 1.3 -5.7
K0319 -4.6 -25.0
J0306 9.1 -11.7
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Table 2-2 provides a numerical comparison between modeled results versus observed metered
flow information at the six (6) 2020 monitoring locations as well as at the WRF. Specific flow
attributes of both volume and peak flow were compared and analyzed for differences.
Figure 2-3 through Figure 2-8 provides a visual comparison between the modeled results
versus observed metered information.
The comparisons show that the DWF model calibration falls within the calibration goals.
Therefore, considering the general shape similarity achieved for diurnal flow charts and diurnal
peak matching, the model was considered calibrated for DWF. The bullet summary below
provides a high-level summary of the results and variances from calibration goals:
• WRF, Meter I5012, and H0325 data fell within the calibration goals.
• Meter I5009 had lost data measurements during the DWF April metering period, could
not be compared to the model, and was not calibrated for DWF scenario. Calibration
results for Meter I5012 and the WRF, which are nearby and downstream, had acceptable
levels of calibration. Therefore no further monitoring or calibration at site I5009 was
deemed necessary as downstream results were found to be representative of field
conditions and no change in the outcome of the model is expected.
• Meter G0225 had large variances in diurnal peak flow when compared to the model.
These variances were brief high and low flows that could not be replicated in the model
and are likely due to varied commercial flow.
• Meter K0319 had a large diurnal peak flow variance. It appears this is due to upstream
pump station operation that could not be replicated within the model.
Table 2-2: Summary of Dry Weather Flow Calibration Results
*The flow meter at I5009 had errant measurements during the DWF flow monitoring time period.
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Figure 2-3: WRF Metered vs Modeled Dry Weather Flows
Figure 2-4: I5012 Metered vs Modeled Dry Weather Fl ows
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Figure 2-5: G0225 Metered vs Modeled Dry Weather Flows
Figure 2-6: H0325 Metered vs Modeled Dry Weather Flows
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Figure 2-7: K0319 Metered vs Modeled Dry Weather Flows
Figure 2-8: J0306 Metered vs Modeled Dry Weather Flows
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2.4.2 Wet Weather Calibration
Following DWF calibration, the hydraulic model was calibrated for WWF. June 17, 2020 was
chosen for calibrating the model for WWF because during this time period the City experienced
a recognizable rainfall event, which totaled 0.69 inches over a 24-hour time period. Figure 2-9
presents the observed rainfall distribution pattern utilized for the calibration. It should be noted
that the City did not experience any significant rainfall in the week prior to the June 17th event,
which allows the effects of this specific rainfall event to be evaluated without the influence of
prior rainfall events.
The following steps were taken for performing the WWF calibration:
• Establish the contributing flow area for each individual calibration point. Utilizing the
Thiessen polygon method, polygons were initially created for each manhole in model.
Each representative contributing area was assigned to the nearest representative
manhole in the model (i.e. rainfall that occurs within the model is routed to the assigned
manhole). These polygons were checked against the City’s current boundary area and
considered representative areas that could contribute RDII during periods of WWF.
• The Thiessen Polygon method produced a few large contributing drainage areas that
were determined unrealistic for a sanitary sewer system. To account for these unrealistic
areas, all contributing drainage areas greater than 5 acres were reduced to 5 acres, which
mirrored the previous 2015 wastewater facility plan, and considered representative for
this WWF analysis.
• Observed rainfall depth versus time model inputs were created and input into the model.
• For each contributing flow area, specific input based RDII factors were input in the
model. During calibration these RDII factors were manually adjusted until model results
closely matched the observed meter data.
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Figure 2-9: Calibration Storm Event: June 17, 2020 Rainfall Distribution
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The WWF calibration was evaluated against the following goals from the WaPUG:
• The shape of the modeled versus the metered flow curves should be similar.
• The timing of the peaks, troughs, and recessions of the modeled versus metered curves
should be similar.
• Modeled total volume should be within -10 percent and +20 percent of measured total
volume.
• Modeled peak flow rate should be within -15 percent and +25 percent of measured peak
flow rate.
WWF analysis is performed to determine how the collection system responds to rainfall events.
Understanding how WWF events influence a collection system allows subsequent mitigation
efforts (i.e. gravity main replacement, pipe lining, etc.) to be focused primarily in areas with the
most significant WWF responses. Typically areas that exhibit high WWF responses indicate
defects in the collection system, aging infrastructure, or infrastructure that has a direct conduit
into the collection system, such as rooftop stormwater downspout connections to name a few.
Extreme WWF responses resulting from RDII can result in flows that exceed the capacity of the
collection system, possibly leading to Sanitary Sewer Overflows (SSOs). SSOs can create serious
issues for the public and environment. RDII is composed of:
• The inflow component of RDII from defects directly connected to the surface. It is water
that enters the sewer system directly via depressed manhole lids and frames, connection
of downspouts, sump pumps, and foundation drains; and cross-connections with storm
sewers.
• The infiltration component of RDII originates from groundwater that infiltrates a sanitary
sewer system through damaged pipe sections, leaky joints, or leaky manhole
connections.
Of these two components, the inflow response most often dominates the peak flow of the RDII
hydrograph.
The flow data and rainfall are broken down into distinct DWF and RDII components for input
into the model. The DWF component was analyzed during the DWF calibration to construct a
DWF pattern. The RDII component was analyzed to determine RDII events and to calibrate
parameters of the RTK synthetic unit hydrograph (described below) to fit the RDII flow simulated
by the RTK method to the RDII flow. The calibrated RTK parameters and DWF patterns are then
used in the model to carry out detailed dynamic flow routing through the sewer system.
The RTK hydrograph is based on a set of parameters, which consist of the following:
• R (Percent) – the fraction of rainfall volume that enters the sewer system (areas with
greater than five percent are typically problem areas)
• T (Hours) – the time from the onset of rainfall to the peak of the unit hydrograph
Technical Memorandum 7.0 Page 22
- -
Modeled vs Metered Modeled vs Metered Meter Location Total Volume Peak Flow Rates
within 10% of and +20% of within 15% of and +25% of measured
measured values values
WRF -3.3 0.1
I5009 0.7 6.6
I5012 -1.0 0.4
G0225 -2.8 -3.7
H0325 5.3 0.3
K0319 -1.7 -1.6
J0306 -5.4 1.6
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• K – the ratio of time to recession of the unit hydrograph to the time to peak
Each of the RTK parameters has a fast, medium, and slow response variable that is adjusted
within the model to replicate the hydrograph created during a rainfall event. During the
calibration process, RTK parameters were adjusted and reviewed graphically until the model
results closely matched the metered data. The results were then checked to verify they met the
calibration goals. If modeled output did not meet the goals, the RTK parameters were further
adjusted within the model until the goals were met.
Table 2-3 provides a numerical comparison between modeled results versus overserved
metered flow information at the six (6) 2020 monitoring locations as well as the WRF. Specific
flow attributes of both volume and peak flow were compared and analyzed for differences.
Figure 2-10 through Figure 2-16 provides a visual comparison between modeled results versus
observed flow metered information.
The comparisons show that the WWF model calibration falls within the calibration goals.
Considering these results and the general shape of the diurnal flow curves and peak flows, the
model was considered calibrated for WWF.
Table 2-3: Summary of Wet Weather C alibration Results
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Figure 2-10: WRF Metered vs Modeled Wet Weather Flows
Figure 2-11: I5009 Metered vs Modeled Wet Weather Flows
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Figure 2-12: I5012 Metered vs Modeled Dry Weather Flows
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Figure 2-13: G0225 Metered vs Modeled Wet Weather Fl ows
Figure 2-14: H0325 Metered vs Modeled Dry Weather Flows
Figure 2-15: K0319 Metered vs Modeled Wet Weather Fl ows
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Figure 2-16: J0306 Metered vs Modeled Wet Weather Fl ows
2.4.3 Summary of RTK Factors from the 2020 Calibration
The RTK factors were adjusted until the difference between modeled and measured total volume
and modeled and measured peak flow rates fell within the calibration goals. Figure 2-2 provides
an overview of the metered areas for which the RTK factors were calculated and adjusted. The
RTK factors were applied within the model as summarized below:
2020 System Calibration:
• The network upstream of J0306 received the 2020 J0306 RTK factors.
• The network upstream of K0319 received the 2020 K0319 RTK factors.
• The network upstream of I5009 and downstream of J0306 and K0319 received the 2020
I5009 RTK factors.
• The network upstream of the WRF and downstream of H0325, J0306, and K0319 received
the 2020 WRF RTK factors.
• The network upstream of H0325 and downstream of previously monitored areas
received the 2020 H0325 RTK factors.
• The network upstream of I5012 and south of Interstate 90 kept the previously
established RTK factors.
• The network upstream of I5012 and north of Interstate 90 received the 2020 I5012 RTK
factors.
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• The network upstream of G0225 primarily kept the previously established RTK factors.
2.4.4 2018 Midtown/Downtown Metering and Model Calibration
The Midtown/Downtown Sewer Capacity Analysis (Sanderson & Stewart, 2018) was used to
further verify modeled peak flow rates. Figure 2-2 also shows a number of different historical
monitoring locations, which were utilized in the verification process. In general, a significant
amount of these historical locations were located in the Midtown/Downtown region and
monitored various flow conditions in 2018.
As with any significant monitoring effort, the Midtown/Downtown capacity analysis observed
various rainfall events. In particular, the Midtown/Downtown monitoring effort captured the
response from an approximately 1-inch storm event on June 29th, 2018. This precipitation
hyetograph (intensity vs time) was incorporated into the model as a unique calibration event to
verify peak flow rates observed at these historical locations. Initially, the simulated peak flows for
the Midtown/Downtown region were lower than the actual measured flow rates. The initial
discrepancy in peak flows was attributed to a change in the base groundwater allocation
method, updated domestic flow allocation, and a change in split flows within the model due to
updated invert data when compared to the City’s previous InfoSWMM model. Subsequently, to
account for these differences, the RTK factors within the Midtown/Downtown region were
adjusted until the model produced peak flows similar to the observed measured peak flows.
Table 2-4 presents a summary of the measured versus adjusted RTK peak flows. It should be
noted that this adjustment method is not considered a true model calibration, rather an
adjustment and verification of peak flow conditions. This approach was deemed necessary to
ensure the Midtown/Downtown peak flows accurately reflect observed conditions given the
substantial update in invert information.
This approach was thoroughly discussed with City staffed and deemed necessary and
appropriate given the historical information collected by the City in the region.
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Table 2-4: Summary of 2018 Rain Event Downtown Calibrated Peak Flows
Sanderson &
FM#1 G0225 842 960
FM#6A F0307 574 568
FM#9 F0431 229 237
FM#11 F0332 2,400 2,653
Technical Memorandum 7.0 Page 29
2020 Cal ibrated Model with
Adjusted RTK Factors
Meter
City
Manhole
ID
Stewart Flow
June 29,
2018
Measured
Peak Flow
(gpm)
Simulated Peak Flow
during 2018 Rainfall Event
(gpm)
FM#4B F0312 394 390
F0328 681 680
FM#10 F0405 471 477
FM#7
FM#12 G0309 398 660
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
Chapter 3 Hydraulic Performance Standards
This chapter summarizes the current City and Montana Department of Environmental Quality
(MDEQ) wastewater collection system standards, recommended design criteria, and hydraulic
performance evaluation criteria utilized in the analysis.
Design criteria was used to evaluate the performance of the City’s existing and future
wastewater collection system. Specific system components such as gravity mains, forces mains,
and pumping facilities were evaluated for conformance against the criteria. Components of the
collection system that did not satisfy design criteria were identified and further investigated. If
necessary, conceptual improvements were then evaluated, such as increasing the diameter of a
gravity main or increasing the capacity of an existing pumping facility. An iterative based
approach was employed until the upgrade satisfied design criteria. Lastly, improvements
identified where then carried into the capital improvement plan portion of the analysis for
further refinement and costing.
This approach is critical in order for the system to maintain existing reliability and accommodate
future growth and development of the system.
The criteria were established based on industry standards, MDEQ regulations and standards,
existing City codes and design standards, and professional engineering judgment. Design
criteria utilized in the evaluation of the system are outlined below, but generally include
parameters surrounding fluid dynamics and sizing (i.e. flow rate, flow depth compared to pipe
diameter, velocity, slope, pipe size, roughness, etc.). Design criteria include the following:
• Gravity Main Design Criteria: velocity, maximum depth of flow, diameter, minimum slope,
friction factor, and capacity;
• Force Main Design Criteria: velocity, diameter, and friction factor;
• Lift Station Design Criteria: firm capacity and peak hour flow;
• Peak Hour Design Factors;
• DWF Criteria; and
• WWF Event (Design Storm) Criteria.
Table 3-1 below summarize the performance standards and hydraulic design criteria pertinent
to the model development and analysis.
Gravity Main Design Criteria
The collection system model uses Manning’s Equation to calculate open channel pipe flow as
follows:
21.49 𝑃 = 𝐴 𝑃3√𝑃 𝑛
Where:
1.49 = Imperial unit conversion factor, ft^1/3/s
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Q = Flow, cfs
n = Manning’s roughness coefficient, unitless
A = Area, sq ft
R = Hydraulic radius, ft
S = Slope, ft/ft
Gravity mains must be designed to prevent deposition of solids within the main. MDEQ
suggests a minimum velocity of 2.0 ft/s when flowing full based on Manning’s formula “n” value
of 0.013. Recommended Manning’s n values are presented in Table 3-1
The designed level of service for a gravity main is typically described in terms of a ratio between
depth of flow to the diameter of the pipe or d/D. Bozeman’s design standards has established a
design criteria of 0.75 d/D meaning the depth within gravity sewers should be less than 75 % of
the full diameter of the pipe.
Gravity mains can be categorized and defined by size and area served as follows:
• Lateral or Collector Sewer: These sewers are generally the smallest diameter sewer within
the system at 8-inches or smaller. Laterals and collectors collect wastewater from small
areas and typically have numerous service connections. Layout varies widely but
generally follows streets of residential and commercial developments. There are over
166 miles of lateral and collector sewers which equates to 72 percent of the gravity
mains within the system.
• Trunk Sewer: Trunk sewers are sized larger (generally between 10 and 15-inches) and
collect wastewater from numerous collectors. Trunk sewers have little to no service
connections, serve large, topographic areas, and convey wastewater between collectors
and interceptors. There are over 34 miles of trunk sewers which equates to 15 percent of
the gravity mains within the system.
• Interceptor Sewer: Interceptor sewers are the largest gravity conveyance sewers with
diameters generally sized at 18-inch and larger. Several named interceptors include
segments less than 18-inches in diameter but are included for continuity between larger
segments or as critical conveyance corridors. Interceptors collect wastewater from
numerous sewersheds and trunk sewers and convey wastewater across long distances
typically along major traffic corridors. There are over 30 miles of interceptor sewers
which equates to 13 percent of the gravity mains within the system.
For the purposes of this study, gravity main performance was evaluated at 0.75 d/D consistent
with the previous Facility Plans and the 2024 COP Design and Construction Standards.
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Force Main Design Criteria
Force mains are designed to carry wastewater from lift stations to the wastewater treatment
facility or to other gravity mains or sewer interceptors. Undersized force mains can result in
backpressures exceeding lift station design standards. Oversized force mains can result in low
velocities and settling of solids.
MDEQ and other publications recommend a minimum velocity of 2 ft/s to keep solids
suspended while pumping. When no wastewater is flowing through the force main solids may
settle. A minimum velocity of 3 ft/s is recommended to resuspend settled solids.
MDEQ states that the maximum velocity shall not exceed 8 ft/s. Based on this criterion, it is
recommended that existing force mains be upsized if the velocity routinely exceeds 8 ft/s.
Velocities in excess of 8 ft/s can be acceptable for brief periods, as long as the upstream lift
station and piping can handle the backpressure associated with higher friction losses.
Recommended force main velocities are presented in Table 3-1.
Lift Station Design Criteria
Lift station capacity guidelines are based on firm capacity which is defined as the capacity of the
station with the largest pump out of service. The City equips all new lift stations with an on-site
backup power generator.
Lift station pumping capacity is sized to meet the meet hourly flow with firm capacity. Peak
hourly flow is the largest volume of flow to be received during a one-hour period expressed in
terms of flowrate such has gpm or MGD.
2024 COB Design and Construction Standards City standards do not have specific lift station
design requirements and relies on MDEQ Circular 2 for lift station parameters. MEDQ
recommends wet well filling time not to exceed 30 minutes and to follow pump manufacturer
requirements for minimum cycle time. When only two pumps are provided for a lift station,
industry practice suggests that they must be the same size, with firm capacity to handle peak
hour flow. They should also be sized to maintain the minimum force main velocity and deliver
uniform flow to minimum hydraulic surges.
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Peak Hour Design Factors
2024 COB Design and Construction Standards City standards requires a peak hour factor be
calculated for each pipe segment of new sewer infrastructure using the following formula (which
matches MDEQ requirements):
18 + √𝑃 𝑃𝑙𝑎𝑥 = (𝑃 = 𝑃𝑛𝑛𝑟𝑙𝑎𝑟�ℎ𝑛𝑛/𝑟�𝑛𝑟𝑟𝑎𝑛𝑐𝑟)𝑃𝑎𝑣𝑒 4 + √𝑃
The peaking formula based on population is a steady state calculation. As discussed in Section
2.3.4, the dynamic wastewater collection system model uses the hydrograph method with RTK
factors calculate peak flow which is different that the population based peaking formula. This
RTK method is an acceptable approach for evaluating the collection system network and master
planning efforts as the flow calculations represent wet weather conditions coupled with diurnal
peaking factors and are a result of a well-calibrated model.
Dry Weather Criteria
The existing system will be analyzed using the calibrated InfoSWMM model as discussed in
Section 2.3.4. The following DWF parameters will be used for analysis of the existing system:
• DWF equal to the average annual flow: 5.3 MGD.
• Diurnal patterns: as established during the flow monitoring period and calibration
efforts.
Wet Weather Flow Event (Design Storm) Criteria
The modeled design storm is an important part for determining the performance and capacity
of the collection system during periods of WWF. The 2019 Climate Vulnerability Assessment
and Resiliency Strategy indicates the City will likely experience more frequent and higher-
intensity storms compared to historic events. City staff and the design team reviewed the
previously modeled storm utilized in the 2015 wastewater facility plan and concluded that the
SCS Type I distribution is an appropriate design storm for planning purposes. High groundwater
is expected to continue to contribute a substantial amount of baseload infiltration into the
system. The 25-year, 24-hour rain event for the City has a rainfall depth of 1.99 inches. The
design storm coupled with base groundwater infiltration for the WWF scenario could be
considered conservative. However, City staff and the design team recognized that a slightly
conservative design event would reasonably provide flexibility within the collection system to
account for changes. These changes include climate change, varying localized groundwater
Technical Memorandum 7.0 Page 33
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
conditions found throughout the City, aging public infrastructure, and development patterns (i.e.
higher density growth). Based on the aforementioned considerations the design storm was
deemed appropriate for future planning.
It should be noted that timing and final sizing of system improvements could change depending
on updated local flow monitoring and survey information.
The existing system was analyzed during a design WWF scenario utilizing the distribution was
utilized with 0.1-hour increments. Figure 3-1 shows the 25-year, 24-hour rainfall SCS Type I
distribution storm pattern utilized in the WWF scenarios.
The WWF event was applied to the system with a total base loading of 9.5 MGD
distributed as follows:
• Domestic Loading: 3.8 MGD
• BI: 5.9 MGD
• Total Base Scenario Loading: 9.5 MGD
Figure 3-1: Design Storm Rainfall Distribution
Technical Memorandum 7.0 Page 34
-
F MDEQ Circular 2
5.3 MGD (existing) -
Based on h ourly pattern.
-
MDEQ Circular 2
2015 Wastewater Facility Plan
-
-
2 MDEQ Circular 2
Sized so one pump handles peak
hourly flow.
Emergency backup power and
bypass connection.
ill time not t o exceed 30 minutes
based on ave rage f low.
MDEQ Circular 2
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table 3-1: Summary of Hydraulic Parameters and Design Criteria
System Component Recommended Standard/Criteria Source
Gravity Mains
Gravity Main Minimum Velocity
(at full flow)
Gravity Main Manning's Roughness
Factor
Force Mains
Force Main Minimum Velocity1
Force Main Maximum Velocity1
Hazen-Williams Coefficient C-
Factor
Exit Loss Coefficient
Entrance Loss Coefficient
Lift Stations
Minimum Number of Pumps
Firm Capacity
Considerations for Emergency
Operations
Wet Well Size
Existing System Dry Weather
Average Annual Flow
(includes base flow and normal
ground water)
Diurnal Peaking Factors
Existing System Wet Weather
WWF (includes base flow and high
ground water)
Peaking Factor
WWF Analysis Design Storm
2 ft/s
0.011 – plastic
0.013 – all other pipe material
9.5 MGD (existing) -
RTK factors
(as determined during calibration) -
25-Year, 24-Hour Event
Depth = 1.99”
SCS Type I Distribution
City of Bozeman
MDEQ Circular 2
MDEQ Circular 2
City of Bozeman Design Request –
FME output
City of Bozeman Design and
Construction Standards, 2024
3 ft/s
8 ft/s
120
0.2
0.1
City of Bozeman Design Request
MDEQ Circular 2
1 2015 Wastewater Facility Plan update assumes force main design velocity= 5 fps
Technical Memorandum 7.0 Page 35
0.75
Gravity Main Maximum Velocity
(at full flow)
Target Design Depth (d/D)
15 ft/s
(varies by area, developed during
calibration)
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Chapter 4 Existing System Evaluation
This chapter presents the evaluation of the City’s existing wastewater collection system and its
ability to accommodate peak flows and meet performance criteria under various existing flow
conditions. Evaluations, findings, and recommendations for addressing any deficiencies
identified in the City’s existing wastewater collection system are summarized in this chapter. The
existing wastewater collection system was evaluated under both DWF and WWF loading
conditions as described in Section 2.3 using the performance standards summarized in
Chapter 3.
Table 4-1 provides a general overview of the existing lift stations within the City’s collection
system. The lift station summary includes the name, ownership, force main size, firm capacity,
standby power, receiving drainage area, and installation year. An overview of the locations of the
interceptors is presented in Figure 4-1.
Firm pumping capacity was evaluated to determine if the lift station has firm capacity issues
during the DWF and WWF assessment.
Table 4-2 provides an overview of the interceptor capacities based on pipe size and slope. In
general, the slopes for the interceptors are based off of field collected survey information. The
interceptor capacities were analyzed to identify existing capacity issues during the DWF and
WWF assessment and were used to assess the future system. An overview of the locations of the
interceptors is presented in Figure 4-1.
Invert elevations were assigned to model nodes as described in Section 2.2 and were used to
calculate gravity main slope. A review of the pipe slopes showed several existing gravity mains
having a slope that does not satisfy the current recommended MDEQ minimum slope standards.
In these cases, the sewers show flat to slightly adverse slope. However, no hydraulic issues were
found during review and model analysis.
Technical Memorandum 7.0 Page 36
Bridger Center City 4 100 no Rouse Interceptor 2004
Cattail Lake City 6 225 yes Cattail Interceptor 2007
Laurel Glen City 8 450 yes Valley West Interceptor 2003
Norton Ranch City 4/6 121 yes Valley West Interceptor 2010
Links Private 4 160 yes N. Frontage Interceptor 2008
Nelson
Meadows Private 6 190 yes Cottonwood-Davis
Interceptor 2019
11th Avenue Interceptor
1 Sebena Private 8 none n/a Rouse Interceptor unk
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table 4-1: Summary of Existing Lift Stations
1 The Cardinal lift station was not modeled due to lack of information and the Sebena lift station is not in service.
+ Davis Lane firm capacity is based on the Davis Lane Lift Station & Norton East Ranch Outfall Sewer Project, Issued
for Bid Plan set – 2 wetwell duty pumps and 1 wetwell jockey pump (HDR, March 2020).
Technical Memorandum 7.0 Page 37
Lift Station
Baxter
Meadows
Burrup
Davis Lane
Loyal Gardens
Cardinal
Distribution1
MDT
Overbrook
Walker
Ownership
City
City
City
City
Private
Private
Private
Private
18/18
6
4
2
4
8
Force Main
Size
(inches)
12
6
Approximate
Firm Pump
Capacity
(gpm)
690
450
5,000+
Standby
Power Interceptor Drainage Year
Installed
yes Cattail Interceptor 2002
yes Rouse Interceptor 1984
yes Cottonwood-Davis
Interceptor 2020
2007 364 yes Davis-Fowler Interceptor
unk unk N. Frontage Interceptor unk
unk
unk
1992
unk unk
unk unk
unk no
WRF Interceptor
WRF Interceptor
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table 4-2: Summary of Existing Interceptors
Interceptor Size
(inch)
Full Flow
Capacity1
(MGD)
Year Installed Drainage
19th Ave / Kagy Blvd
12
14
18
20
24
0.9 – 1.4
2.3 – 6.0
1.5 – 7.6
4.2 – 6.0
5.1 – 26.9
1972
1963, 1969
1969, 1998
1969
1969
Central
27th Ave / Davis Ln
21
24
27
6.7 – 22.7
10.5 – 29.3
10.9 – 56.7
2006
2002, 2006
2002
Western
Aajker Basin Diversion 21 3.8 – 9.7 2024 Western
Baxter Ln / Durston Rd
18
20
21
24
2.6 – 6.6
2.8 – 10.6
3.4 – 9.7
2.6 – 10.3
2007
1980, 2000, 2006
2005, 2007
1980
Western
Davis Ln / Cottonwood Rd
18
21
27
30
4.8 – 9.8
5.4 – 25.6
8.9 – 36.3
9.3 – 24.8
2019
2015
2021
2021
Western
Evergreen Dr
15
18
21
2.9 – 6.8
1.5 – 14.9
2.4 – 9.0
1952
1947, 1952, 1963
1994, 2004
1951
Eastern, Northern
Fowler Ave / 19th Ave
18
21
24
27
2.5 – 13.4
5.7 – 27.1
14.1 – 30.2
10.1 – 11.3
1980, 2022
2005, 2007, 2016
2007
2007
Western
Front St
18
21
24
5.5 – 20.1
6.0 – 9.6
1.7 – 31.3
2020
2020
2020
Eastern
Garfield St / Lincoln St 18 2.8 – 8.6 2016 Southern
North Frontage Rd
Parallel 20
and Parallel 36
Single 20
Single 30
Parallel 20
Single 20
1.0 – 11.7 (20-inch)
20.0 (36-inch)
5.3 – 12.6
6.3 – 38.4
2.6 – 13.8
8.0 – 9.0
1969, 1974, 1980
2020
1969
1992
1969, 1980
1969
Eastern, Northern
Rouse Ave
21
24
30
3.8 – 5.2
14.3 – 29.2
15.1 – 42.2
2017
2004
2004
Eastern
Tamarack St 18 4.3 – 7.9 1917 Eastern
WRF 30 17.6 – 20.5 1969 All
1Range based on full flow, Manning’s n, and surveyed inverts (slope). Capacity varies throughout interceptor due to
varying slopes of each segment of gravity main.
2North Frontage Road interceptors listed in order of upstream to downstream (east to west).
Technical Memorandum 7.0 Page 38
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Existing Dry Weather Modeling Analysis
Gravity main velocity, depth, and flow were evaluated during the DWF analysis. The minimum
gravity main velocity (2 ft/s) is not being met for most of the sewer system during DWF
conditions. The standard minimum velocity is intended to ensure adequate velocities are
maintained during full flow conditions so settled solids will be scoured downstream. Full flow
does not occur during DWF conditions and therefore minimum velocities are not met. No
gravity mains showed velocities greater than the maximum allowed.
Depths of flow in the gravity mains and at the manholes were also evaluated. DWF modeling
results showed no locations that surcharged indicating no issues within the collection system
under DWF conditions.
City owned lift stations and force mains were evaluated based on the velocity criteria presented
in Chapter 3. The DWF analysis results showed the lift stations have adequate capacity to
handle peak flows. All but three force mains satisfy the minimum velocities required by the City
(operating at 3 ft/s or above). The Baxter Meadows, Bridger Center, and Cattail Lake force mains
meet the minimum velocity recommended by MDEQ (2 ft/s or greater) at the firm pumping
capacity. Although these three force mains are not meeting minimum velocity required by the
City, it is not considered a major concern. Given these flow parameters, these particular force
mains could be more susceptible to solids deposition. Therefore, it is recommended that the
City’s operations and maintenance staff conduct more frequent monitoring and cleaning of
these assets.
Lift station pump curves were provided for the analysis and are stored within the model;
however, to improve model stability and reduce model runtimes, the model is set up to run peak
flow directly through the lift station using an ideal pump (inflow = outflow). Firm pumping
capacities provided by the City were used for analysis of force main capacity.
Technical Memorandum 7.0 Page 40
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Existing Wet Weather Modeling Analysis
The InfoSWMM model was utilized to simulate a WWF scenario which utilizes a design
storm. The WWF event is defined as a 25-yr rainfall event totaling 1.99 inches with a SCS
Type I rainfall distribution pattern w as selected to evaluate the systems response during
periods of WWF, which can untimely stress system capacities.
4.2.0 Wet Weather Lift Station Analysis
Lift stations and force mains were evaluated under the design rainfall event. For the
purposes of this analysis and based on the best information available, all lift stations
were assumed to operate at the firm capacity provided by the City. As a result,
velocities in the force mains remained the same during both WWF and DWF evaluations.
As expected, inflows into the lift stations increased significantly under the WWF
analysis. A summary of the lift station capacities and the modeled peak flows under
existing conditions during the WWF rainfall event are presented in Table 4-3.
Model results indicate that firm capacity of the lift station exceeds the peak hourly flows
for all lift stations excluding the Laurel Glen lift station. The peak flow entering the
Laurel Glen lift station is shown to exceed the lift station firm capacity by approximately
17 percent. For instance, the DWF flow peaked at 140 gpm while the WWF peaked at
507 gm. At this point, it is recommended that the City continues to further monitor the
Laurel Glen lift station during periods of seasonal high groundwater and large rain
events to determine how localized RDII affects the upstream sewershed and before
making any lift station improvements.
Table 4-3: Capacity Summary of Existing Lift Stations
City Lift Station
Baxter Meadows
Bridger Center
Burrup
Cattail Lake
Davis Lane
Laurel Glen
Loyal Gardens
Norton Ranch
Cardinal Distribution1
Links
MDT
Nelson Meadows
Overbrook
Sebena1
Walker
Approximate Firm
Capacity (gpm)
690
100
450
225
5,000+
450
364
121
unk
160
unk
190
unk
none
unk
Modeled Peak Inflow
(gpm)
270
30
102
16
365
507
177
70
-
8
16
75
32
-
34
Technical Memorandum 7.0 Page 41
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
1 The Cardinal lift station is not modeled and the Sebena lift station is not in service.
+ Davis Lane firm capacity based on Davis Lane Lift Station & Norton East Ranch Outfall Sewer Project,
Issued for Bid Plan set – 2 wetwell duty pumps and 1 wetwell jockey pump (HDR, March 2020)
4.2.1 WWF Interceptor and Gravity Main Analysis
Both Interceptors and gravity mains were evaluated under the design rainfall event
which included velocities, depths of flow in the gravity mains, and capacities of the
interceptors. No interceptors or gravity mains were identified with velocities that
exceeded the maximum recommended rates allowed.
Wet Weather Gravity Main Summary
Figure 4-2 presents the d/D as a ratio of the maximum modeled flow depth during
WWF in relation to the diameter of the gravity main conduit being evaluated. This
analysis was completed for the entire gravity main network of the City. The WWF
modeling analysis shows that a majority of the City’s collection system has sufficient
capacity to adequately handle additional inflow resulting from increased seasonal
groundwater coupled with a design storm. However, it should be noted that there are
several segments that reach model capacity. These segments include specific individual
manholes that show minimal surcharging during the design storm. Surcharging of a
sewer is the situation in which the sewer entrance and exit are submerged and the pipe
is flowing full under pressure. A surcharge is different than a node overflowing. If a node
is overflowing the hydraulic grade of the incoming flow is greater than the rim elevation
of the manhole (or ground elevation of lid), which indicates flow is no longer contained
in the conveyance system and is overflowing out of the system through the nodes.
Below is a list of manholes, which correlate to nodes within the model, that showed a
surcharge during the design storm. No overflows were shown in the modeling results
during WWF. Figure 4-2 shows the City’s existing collection system in relation to
modeled d/D results for WWF. The results are broken down into four flow classifications
(<.5 Blue), (0.5-0.75 Yellow), (0.75-0.99 Orange) and (1.0 full flow Red). Segments >.75
d/D where further evaluated to determine if mitigation is necessary or flagged for
further monitoring and evaluation as the City continues to grow.
The following is a list of manholes in which the hydraulic model indicated surcharge at
the node. The representative street intersection was listed for simplicity versus the
specific model node ID.
Technical Memorandum 7.0 Page 42
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
• Intersection of Westridge Dr and Wagon Wheel Road: The 10-inch sewer
experiences a grade change at this intersection which results in a surcharge of
less than 0.5 ft.
• Intersection of S Black Avenue and Hoffman Dr: The 10-inch sewer is at
capacity at this intersection which results in a surcharge of less than 0.25 ft.
• S Willson Avenue between W Mason Street and W Hayes St: The 14-inch
sewer is modeled to flow at capacity in this area with a surcharge of less than 1 ft.
• Intersection of E College Street and S Grand Ave: The 14-inch sewer along
College Street is at capacity and surcharges less than 0.25 ft.
• S Black Ave: 6-inch sewer between E Olive Street and E Babcock Street is at
capacity and modeled with a surcharge between 1 and 1.6 ft.
• Intersection of S 6th Avenue and W Curtiss St: The 18-inch sewer shows a dip
in this location causing the pipe to flow at capacity and a surcharge of less than
0.75 ft.
• Intersection of S 5th Avenue and W Olive St: The 6-inch sewer is modeled to
flow at capacity in this area with a surcharge of less than 1 ft.
• Manley Road: Parallel 20-inch Section: The north section of 20-inch parallel
interceptor between Manholes F0114 and G0132 is modeled to flow at capacity
with a surcharge of less than 1 ft.
• Manley Road: Single 20-inch Section: The single 20-inch interceptor between
Manholes G0132 and G0133 is modeled to flow at capacity with a surcharge of
less than 1 ft.
• Frontage Road: Parallel 20 inch Section: The north section of the 20-inch
parallel interceptor between model manhole IDs H0012 and H0005 flows at
capacity with a surcharge of 0.5 ft.
Technical Memorandum 7.0 Page 43
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Wet Weather Existing System Interceptor Summary
Understanding the capacity of the collection system interceptors is discussed in the
following paragraphs. Figure 4-1 provides an overview of the locations of the existing
interceptors.
Table 4-4 presents a summary of the existing system interceptor capacity, modeled
peak flow, and remaining capacity. Figure 4-3 highlights the existing d/D analysis for
the interceptor sewers segments. The existing system inceptor capacity analysis is
summarized below.
• 19th Avenue / Kagy Boulevard: The 19th Avenue / Kagy Boulevard interceptor
has varying levels of remaining capacity in the WWF scenario with the depth to
diameter ratio ranging from 0.25 to surcharging. The larger diameter
downstream sections (20 to 24-inch) can support additional loading from growth
or infill. However, the smaller diameter upstream sections (12 to 18-inch
between Kagy Boulevard and Babcock Street) need to be upsized to support
additional loading from growth or infill. The average depth to diameter ratio
during peak flows for the 12 to 18-inch sewer is 0.72 while the ratio is much
lower at 0.51 for the 20 to 24-inch sewers.
• 27th Avenue / Davis Lane: The 27th Avenue / Davis Lane interceptor has
sufficient capacity in the WWF scenario with the depth to diameter ratio ranging
from 0.25 to 0.5. The average depth to diameter ratio during peak flows is 0.33
indicating the 27th Avenue / Davis Lane interceptor can support additional
loading from growth or infill.
• Aajker Basin Diversion: The Aajker Basin Diversion is a new interceptor under
construction along Baxter Lane with little loading. The interceptor is under
construction and will server western growth areas when complete.
• Baxter Lane / Durston Road: The Baxter interceptor has sufficient capacity in
the WWF scenario with the depth to diameter ratio ranging from 0.25 to 0.5. The
average depth to diameter ratio during peak flows is 0.32 indicating the Baxter
Lane / Durston Road interceptor can support additional loading from growth or
infill.
• Davis Lane / Cottonwood Road: The newly constructed Davis Lane /
Cottonwood Road interceptor in the WWF shows a depth to diameter ratio less
than 0.25. The average depth to diameter ration during peak flows is 0.1
Technical Memorandum 7.0 Page 45
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
indicating the Davis Lane / Cottonwood Road interceptor can support additional
loading from growth or infill.
• Evergreen Drive: The Evergreen Drive interceptor has sufficient capacity in the
WWF scenario with depth to diameter ratio ranging from 0.25 to 0.75. The
average depth to diameter ratio during peak flows is 0.38 indicating the
Evergreen Drive interceptor can support additional loading from growth or infill.
• Fowler Avenue / 19th Avenue: The Fowler Avenue / 19th Avenue interceptor has
sufficient in the WWF scenario with depth to diameter ratio ranging from 0.1 to
0.6. The 18-inch portion of the interceptor has sections with less capacity
compared to the larger diameter sections. The average depth to diameter ratio
during peak flows is 0.21 indicating the Fowler Avenue / 19th Avenue interceptor
can support additional loading from growth or infill.
• Front Street: The Front Street interceptor has sufficient capacity in the WWF
scenario with depth to diameter ratios less than 0.25. It should be noted that the
Front Street interceptor was recently upsized by the City and incorporated into
the existing conditions model. The project included approximately 7,600 linear
feet of new gravity main, with pipe segments that ranged from 18-to 24-inchs.
The purpose of the project was to accommodate new development along East
Main Street, Haggerty Lane, and potential future expansions of Bozeman
Deaconess Hospital. The average depth to diameter ratio during peak flows is
0.21 indicating the interceptor can support additional loading from growth or
infill.
• Garfield Street / Lincoln Street: The Garfield Street / Lincoln Street interceptor
has sufficient capacity in the WWF scenario with depth to diameter ratio ranging
from 0.2 to 0.3. The average depth to diameter ratio during peak flows is 0.27
indicating the Garfield Street / Lincoln Street interceptor can support additional
loading from growth or infill.
• North Frontage Road: The North Frontage Road interceptor has various
segments that reach full flow capacity in the WWF scenario with the depth to
diameter ratio ranging from 0.25 to 1.00, meaning some sections have
underutilized capacity while others have no remaining capacity in the WWF
model scenario. Based on the modeling results additional large-scale
development or significant infill growth will further increase surcharging through
these sections. These results are generally in line with the previous facility plan, in
Technical Memorandum 7.0 Page 46
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
which the North Frontage Road was flagged for future mitigation. As of recent,
the City upgraded a section of the interceptor with their Manely Road upgrade.
However, the remaining segments of the Frontage Road have been incorporated
into the City’s short-term CIP program and discussed in further detail in the
capital improvement TM. Two sections within the hydraulic model that indicate
surcharging during the WWF scenario include:
o Area 1: Located along Manley Road, both upstream and downstream of
the transition from a parallel 20-inch and 36-inch section into the single
20-inch sewer at manhole ID G0132. The 20-inch sewer upstream of the
manhole and the 20-inch downstream of the manhole is surcharging
during the design storm.
o Area 2: Located northwest of transition from a single 30-inch sewer to
parallel 20-inch sewer at Manhole H0016. The model indicates the north
20-inch sewer is surcharging.
• Rouse Avenue: The Rouse Avenue interceptor has sufficient capacity during
WWF with the depth to diameter ratio ranging from 0.1 to 0.50, meaning the
interceptor flows less than half full. The average depth to diameter ratio during
peak flows is 0.24 indicating the Rouse Avenue interceptor can support additional
loading from growth or infill.
• Tamarack Street: The Tamarack Street interceptor has sufficient capacity during
WWF with the depth to diameter ratio ranging from 0.4 to 0.50, meaning the
interceptor flows slightly less than half full. The average depth to diameter ratio
during peak flows is 0.47 indicating the Tamarack Street interceptor can support
additional loading from growth or infill.
WRF: The WRF interceptor shows segments with the WWF scenario that that
nearly reach full flow capacity. Model results for this particular segment show the
segment near capacity with the depth to diameter ratio exceeding 0.75. However,
no significant surcharging was noted during peak flows in the analysis. The WRF
interceptor does not have any service connections and can support additional
loading from growth or infill before surcharging. These results are generally in
line with the previous facility plan, in which the WRF interceptor was flagged for
future mitigation. As such, the WRF interceptor has been incorporated into the
City’s short-term CIP program and discussed in further detail in the capital
improvement TM.
Technical Memorandum 7.0 Page 47
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table 4-4: Capacity Summary of Existing Interceptors
Interceptor Size
(inch)
Full Flow
Capacity1
(MGD)
Design
Capacity2
(MGD)
Modeled
Peak Flow
(MGD)
Percent
Capacity
Remaining
19th Ave / Kagy Blvd
12
14
18
20
24
0.9 – 1.4
2.3 – 6.0
1.5 – 7.6
4.2 – 6.0
5.1 – 26.9
0.7 – 1.1
1.7 – 4.5
1.1 – 5.7
3.2 – 4.5
3.8 – 20.2
1.2
2.6 – 3.2
1.5 – 3.5
2.8 – 4.5
4.5 – 8.8
0 to 20% (At Capacity)
0 to 50% (At Capacity)
0 to 60% (At Capacity)
30%
25 to 75%
27th Ave / Davis Ln
21
24
27
6.7 – 22.7
10.5 – 29.3
10.9 – 56.7
5.0 – 17.0
7.9 – 22.0
8.2 – 42.5
2.9
2.9 – 3.2
3.3
50 to 75%
50 to 75%
50 to 75%
Aajker Basin Diversion 21 3.8 – 9.7 2.9 – 7.3 2.4 at buildout < 50%
Baxter Ln / Durston Rd
18
20
21
24
2.6 – 6.6
2.8 – 10.6
3.4 – 9.7
2.6 – 10.3
2.0 – 5.0
2.1 – 8.0
2.6 – 7.3
2.0 – 7.7
0.5 – 0.8
0.5 – 1.8
0.8 – 1.2
1.8 – 1.9
50 to 75%
50 to 75%
50 to 75%
50 to 75%
Davis Ln / Cottonwood Rd
18
21
27
30
4.8 – 9.8
5.4 – 25.6
8.9 – 36.3
9.3 – 24.8
3.6 – 7.4
4.1 – 19.2
6.7 – 27.2
7.0 – 18.6
0.1
0.3
0.3
0.3
>75%
>75%
>75%
>75%
Evergreen Dr
15
18
21
2.9 – 6.8
1.5 – 14.9
2.4 – 9.0
2.2 – 5.1
1.1 – 11.2
1.8 – 6.8
1.4 – 1.7
2
2
25 to 75%
25 to 75%
50 to 75%
Fowler Ave / 19th Ave
18
21
24
27
2.5 – 13.4
5.7 – 27.1
14.1 – 30.2
10.1 – 11.3
1.9 – 10.1
4.3 – 20.3
10.6 – 22.7
7.6 – 8.5
2.2
1.6
1.6
0.8
25 to 75%
>75%
50 to 75%
>75%
Front St
18
21
24
5.5 – 20.1
6.0 – 9.6
1.7 – 31.3
4.1 – 15.1
4.5 – 7.2
1.3 – 23.5
0.3 – 0.9
0.9
0.9 – 1.0
>75%
>75%
>75%
Garfield St / Lincoln St 18 2.8 – 8.6 2.1 – 6.5 0.5 – 0.6 >75%
North Frontage Rd
Parallel 20
and
Parallel 36
Single 20
Single 30
Parallel 20
Single 20
1.0 – 11.7 (20-inch)
20.0 (36-inch)
5.3 – 12.6
6.3 – 38.4
2.6 – 13.8
8.0 – 9.0
0.8 – 8.8
15.0
4.0 – 9.5
4.7 – 28.8
2.0 – 10.4
6.0 – 6.8
2.7 – 4.8
2.9 – 3.2
6.5 – 6.6
5.6 – 7.5
3.7 – 7.6
7.6
0 to 50%
(Segments at Capacity)
>75%
0 to 50%
(Segments at Capacity)
25 to 75%
0 to 50%
(Segments at Capacity)
<25%
Rouse Ave
21
24
30
3.8 – 5.2
14.3 – 29.2
15.1 – 42.2
2.9 – 3.9
10.7 – 21.9
11.3 – 31.7
0.1 – 0.6
0.6 – 1.4
4.7 – 7.8
>75%
>75%
50 to 75%
Tamarack St 18 4.3 – 7.9 3.2 – 5.9 1.9 – 2.4 >50%
WRF 30 17.6 – 20.5 13.2 – 15.4 11.8 – 19.2 0 to 50%
(Segments at Capacity)
1Range based on full flow, Manning’s n, and surveyed inverts (slope). Capacity varies throughout interceptor due to varying slopes of
each segment of gravity main.
2Calculated as 75% of full flow capacity.
3North Frontage Road interceptors listed in order of upstream to downstream (east to west).
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Chapter 5 Existing System Recommendations
None of the current system deficiencies identified in the DWF and WWF analyses require
immediate attention.
Major recent interceptor improvements (Front Street, North Frontage Road, Davis Lane /
Cottonwood Road, and Garfield Street / Lincoln Street, and south end of the Fowler Avenue /
19th Avenue interceptors) have addressed some of the short-term improvement and growth
needs identified in the previous 2015 Collection System Facility Plan.
Identified deficiencies in the existing conditions analysis will be further evaluated in conjunction
with system risk and future system expansion. Surcharging exhibited in the existing WWF
scenario identified in Section 4.2.1 could likely be alleviated by upsizing specific segments of
gravity sewer. However, developing detailed improvement recommendations without
considering loading associated with future growth could result in underdeveloped CIP
mitigation recommendations.
Therefore, any system improvements will be developed in conjunction with the existing system
risk assessment results and future conditions analysis build-out analysis.
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Chapter 6 Future Conditions Model Development
As described in the City’s 2020 Community Plan, growth in Bozeman and Gallatin County has
been rapid and steady over the past several decades and will likely continue. The City must plan
its utilities and services to accommodate the growth. Development is occurring within the City
limits as well as expansion to the west and south – this growth will impact the collection system
facilities. To understand and evaluate these impacts, future condition scenarios based on the
City’s growth planning boundary were included in the hydraulic model. This chapter describes
the future conditions modeling and results. Future wastewater flow is described in detail in the
Wastewater Flow Characterization Technical Memorandum (TM 5).
Model Network Expansion
To serve the future development within the City limits and UBO planning area, extensions of
gravity mains and force mains were laid out. The following summarizes the approach used to
build the framework for the Future Conditions Wastewater Collection System Model Network.
o The topography within the growth area boundary was reviewed to verify and adjust the
2015 drainage basins.
o The topography within the growth area boundary was reviewed to verify and adjust the
2015 drainage basins. Drainage basin boundaries were analyzed to better reflect
anticipated development patterns and existing terrain. Subsequently, sewer
infrastructure sizing was planned for the service areas identified in this plan. Going
forward, the City should review detailed drainage basin boundaries in future Facility Plan
updates, with regional lift station planning and design, or with major trunk or interceptor
sewer design. The collection system gravity mains were extended to serve the entire
growth area by adding gravity mains to the existing system model network. The network
was established to approximately run at quarter sections where feasible, along major
drainage corridors within basins, and/or along arterial roads as identified in the COB
2017 Transportation Master Plan.
o Manholes were generally placed at quarter-to half-mile intervals along the proposed
gravity main network.
o A 2018 digital elevation model (DEM) was used to extract manhole rim elevations for the
proposed future network. Manhole inverts were initially assumed to be 8-ft below grade
and slopes were set to match ground topography between manholes. Where slopes did
not meet minimum grade standards, manhole depths, and thereby slopes, were
increased to achieve the minimum standard slope for the respective main size. When
manhole inverts were manually adjusted to achieve require slopes and collecting system
routing a maximum depth of 15 feet was used per City standards.
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o Gravity sewer mains were sized to handle modeled flows without exceeding 0.75 d/D
during peak flows of the wet-weather UBO scenario.
o Where required, lift stations and force mains were added to pump wastewater from a
low-lying areas to the near-by trunk sewers. No new proposed lift stations were added
beyond those identified in the 2015 Facility Plan. Additional information about the
proposed lift stations is provided in Section 7.3.3.
Scenarios
Four scenarios were developed in collaboration with City Engineering staff to evaluate future
growth and collection system infrastructure:
• Infill Scenario: The Infill scenario includes additional flow loading from the following
growth categories within City limits.
• Vacant Areas: Additional loading is added to the sanitary network using wastewater
duty factors established for existing land uses based on each land use type as
identified in TM 5.
• Zoned Areas: All zoned properties within City limits are added to the sanitary
network using wastewater duty factors established for existing zoning uses based on
each zone type as identified in TM 5.
• Redeveloped Areas: Urban renewal districts (URD) and tax increment finance (TIF)
areas modeled to have increased domestic loading as identified in TM 5.
• Ultimate Buildout (UBO)
• The UBO scenario includes all areas outside City limits and within the growth area
boundary added to the sanitary network using wastewater duty factors established
for land uses based on each land use type as identified in TM 5.
• Ultimate Buildout West (UBO West)
o The UBO West scenario includes the same loading as the UBO scenario but
includes wastewater flow diversion to a regional wastewater treatment facility
assumed to be located northwest of City limits and the growth area boundary.
• Increased Density
o The Increased Density scenario included additional domestic loading for
residential classification as identified in TM5. The increased density scenario was
only analyzed under WWF conditions.
▪Existing residential areas with R1 zoning experience increased domestic
loading by 25%.
▪Future residential growth areas with zoning of R2 or R3 experience
increased domestic loading to R4 zoning.
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Future Wastewater Allocation
Wastewater flow and loading analysis was completed using the wastewater duty factors
developed in TM 5. TM 5 describes the wastewater characterization methodology and analyses
in detail. This section summarizes the key results and describes the model flow allocation
methodology.
• Manhole Loading:
o Manholes were added to the growth network as described above in Section 6.1
o Thiessen polygons were automatically generated to determine the area of
influence for covering the growth area.
o Wastewater duty factors based on land use were applied to each manhole based
on the Thiessen polygon area of influence for each manhole.
o For RDII, the area of influence for future manholes was limited to 5 acres to
maintain realistic representations and consistency with the previous Facility Plan.
o RTK factors for calculating RDII in growth areas were assumed consistent with the
existing factors established during model calibration.
• Domestic Flow: The portion of wastewater flow that originates from residential,
commercial, and industrial sources. This flow is relatively steady throughout the year and
can be estimated from non-irrigation (winter, or indoor) metered water use.
• Base Infiltration (BI): The portion of wastewater flow that originates from groundwater
and can vary by depth of the groundwater table.
• Rainfall Derived Inflow and Infiltration (RDII): The portion of wastewater flow that
originates from rainfall events as inflow and infiltration into the collection system.
6.3.1 Domestic Flow Allocation
Wastewater duty factors were applied for each of the main growth scenarios including Infill,
UBO, UBO West, and Increased Density scenarios using factors established in TM5.
6.3.2 Groundwater Baseflow
The BI was calculated for each future manhole the ground water duty factors based on acreage.
The area of influence for future manholes was limited to 5 acres to have realistic representations
for area of influence and be consistent with previous master planning efforts. The resulting BI
flow was then assigned to the future manholes as constant inflow.
• BI for DWF: 150 gpad
• BI for WWF: 550 gpad
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6.3.3 Rainfall Derived Inflow and Infiltration Loading
The 2020 Model Update utilized a synthetic design storm event to allocate RDII, but also
included calibration to a WWF event that was captured with metering in 2020. RDII model
calibration and design storm results are discussed in Section 2.3.4 and Chapter 4, respectively.
For RDII, the area of influence for future manholes was limited to 5 acres to have realistic
representations for area of influence and be consistent with previous master planning efforts.
6.3.4 Summary of Future System Loading
The bulleted summary below, Table 6-1, and Table 6-2 provide an overview of loading
allocated within the model to establish the future collection system scenarios.
• DWF Domestic Flow:
o Existing: 3.8 MGD
o Infill Increase: 5.1 MGD
o UBO Increase: 30.2 MGD
o Increased Density: 2.2 MGD
o Diurnal peaking factors for the DWF and WWF design scenarios utilize
established diurnal peaking factors, which were allocated upstream of the
existing system network.
• BI for DWF:
o Existing: 1.5 MGD
▪Based on established 672 gpd/idm
o Infill Increase: 0.1 MGD
▪Based on established 150 gpad
o UBO Increase: 4.0 MGD
▪Based on established 150 gpad
o Increased Density: no change
• BI for WWF: based on gpd/idm
o Existing: 5.7 MGD
▪Based on established 2,525 gpd/idm
o Infill Increase: 1.3 MGD
▪Based on established 550 gpad
o UBO Increase: 15.2
▪Based on established 550 gpad
o Increased Density: no change.
Technical Memorandum 7.0 Page 54
Domestic Flow Ground Water BI Total Loading Scenario
(MGD) (MGD) (MGD)
Existing 3.8 1.5 5.3
Infill 8.9 1.6 10.5 (existing + infill)
UBO (and UBO West) 39.1 5.6 44.7 (existing + infill + UBO)
Increased Density 2.2 --
Domestic Flow Ground Water BI Total Loading Scenario
(MGD) (MGD) (MGD)
Existing 3.8 5.7 9.5
Infill 8.9 8.5 16.0 (existing + infill)
UBO (and UBO West) 39.1 22.2 63.3 (existing + infill + UBO)
Increased Density 2.2 - -
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Table 6-1: Summary of Loading for Dry Weather Mo del Scenarios
Table 6-2: Summary of Loading for Wet Weather Mo del Scenarios
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Chapter 7 Future System Evaluation and
Recommendations
This chapter presents the evaluation of the City’s future wastewater collection system and its
ability to accommodate peak flows and meet performance criteria under various future growth
conditions. Evaluations, findings, and recommendations for addressing deficiencies identified in
the City’s existing wastewater collection system along with additional loading from infill and
future growth and development are summarized in this chapter.
Future Conditions Modeling Scenarios
The future wastewater collection system was evaluated under four future growth conditions
including Infill, Ultimate Buildout (UBO), Ultimate Buildout with regional wastewater treatment
to the west (UBO West), and Increased Density. Recommended improvements under each of the
future scenarios are described in this Section; cost estimates and additional detail on the
improvements are provided in TM 9 (CIP Technical Memorandum).
7.1.1 Dry Weather Model Conditions
Gravity main velocity, depth, and flow were evaluated during the DWF analysis for the Infill, UBO,
and UBO West scenarios. The design standard minimum gravity main velocity is 2 ft/s to
minimize solids settling and reduce maintenance requirements. This minimum velocity standard
is not met under DWF conditions but is acceptable because it is achieved under WWF.
DWF depths in the gravity mains and at the manholes were also evaluated under the four future
growth condition scenarios. DWF modeling results show no locations that surcharge.
City owned lift stations and force mains were evaluated based on the velocity criteria discussed
in Chapter 3. Pump curves were provided for existing lift stations and are stored within the
model; however, to improve model stability and reduce model runtimes, the model is set up to
run peak flow directly through the lift station using an ideal pump (inflow = outflow). This pump
approach also provides a conservative estimate for capacity evaluations. Firm pumping
capacities provided by the City were used for analysis of force main capacity. Future lift stations
were modeled to run the peak flow directly through the lift stations using ideal pumps. The DWF
analysis results showed the lift stations have adequate capacity to receive peak flows.
7.1.2 Wet Weather Model Conditions
The InfoSWMM model was utilized to simulate the WWF event with additional loading as
described in Section 6.3 Gravity main velocity, depth, and flow were evaluated during four
WWF loading scenarios. The gravity main, force main, and lift stations analysis is summarized in
the following sections.
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Infill Evaluation and Improvements Summary
The collection system under the Infill scenario was sized to accommodate WWF peak flows for
the UBO and Infill loadings.
7.2.1 Modeling Results of Gravity Main and Interceptors for
Infill Conditions
Figure 7-1 presents the depth to diameter (d/D) ratio of maximum depth to full depth
for the infill loading on the existing gravity main network. A majority of the network
shows sufficient capacity to meet the design storm and support additional growth from
infill. However there are a number of locations that will require improvements to
support infill growth. The main corridors that show d/D that are shown to result in full
pipe flow (d/D = 1.0) include the following:
• Sections of the North Frontage Road Interceptor
• Sections of the 19th Avenue / Kagy Boulevard Interceptor between Kagy
Boulevard and Babcock Street.
• Black Avenue sewer between College Street and Main Street.
A detailed list of improvements required to correct these sewers for infill conditions is
presented in Section 7.2.2. In addition, Section 7.2.2 addresses improvements required
to correct sewers that are modeled to have a d/D between 0.75 and 1.0.
There are two gravity main sections that exceed the City’s design d/D criteria under Infill
Conditions after the identified improvements are completed. These two sections are
described in more detail below.
• North Frontage Road Interceptor: The primary recommended improvements
include paralleling the North Frontage Road in areas where there is currently a
single interceptor from N Rouse to Springhill Road and upsizing where
surcharging occurs under existing conditions. There are segments where old
smaller sections still show a peak d/D exceeding 0.75; however, these segments
are considered acceptable for the Infill scenario until the old, smaller trunk main
is replaced for UBO conditions.
• Fairway Dr: Fairway Dr shows capacity exceeding 0.75 d/D for Infill conditions.
Discussions with City staff indicate that there are no known issues or concerns
with sewer capacity in this sewer. Therefore it is recommended that the City
monitor the flow rate from this basin and complete further model calibration for
the subbasin before making a decision on upsizing sewer in this corridor.
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• S 3rd Ave: Short sections of sewer along S 3rd Ave between Westridge Dr and W
Graf St show capacity exceeding 0.75 d/D for Infill conditions. Discussions with
City staff indicate that there are no known issues or concerns with sewer capacity
in this sewer. Therefore it is recommended that the City monitor the flow rate
from this basin and complete further model calibration for the subbasin before
making a decision on upsizing sewer in this corridor.
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7.2.2 Infill Interceptor and Gravity Main Improvements
Figure 7-2 provides an overview of the required improvements to meet infill loading. The
projects described below include recommended improvements required for upsizing existing
gravity main as well as extensions required to serve future growth areas within the overall City
limit boundary.
7.2.2.1 Infill Upsizing Improvements:
Figure 7-1 highlights the existing sewer with modeled capacity issues when additional loading is
added for the Infill scenario. The projects described below address Infill capacity issues but are
sized to account for the UBO WWF. These projects and their estimated costs are discussed in
more detail in the CIP Technical Memorandum (TM 9). The list below notes with which CIP
Project # each of these segments is associated.
• North Frontage Road Interceptor:
o It is recommended to complete parallel segments along the entire Frontage Road
interceptor in places where there is currently a single interceptor segment.
Recommended parallel segments include:
▪27-inch parallel segment along North Frontage Road between Reeves
Road and Springhilll Road.
▪30-inch and 27-inch parallel segment from Manley Road westward along
North Frontage Road.
o It is recommended to upsize one of the existing parallel 20-inch segments
between North Rouse Avenue and Manley Road to a 36-inch Interceptor. It
should be noted that a 36-inch interceptor segment was completed west of
Manley Rd with the Manley Road Improvement project.
o This project was a previously identified City CIP: WWIF20
• WRF Interceptor:
o It is recommended to complete a 42-inch diameter parallel segment along
Springhill Road from North Frontage Road to the WRF.
o This project was a previously identified City CIP Project: WWIF44
• 19th Avenue / Kagy Boulevard Interceptor (South Wilson Avenue Kagy Boulevard to
Olive Street Sewer Improvements):
o Improvements to address both capacity and condition concerns needed. It is
recommend to upsize and replace various pipe segments from 10-to 18-inch.
o CIP Project: Project 1
• Front Street Interceptor and Highland Glen Sewer Main:
o The existing gravity main should be upsized from 8-inch to 12-inch and 18-inch
starting at Cherry Drive, through the Highland Glen open space, along Haggerty
Lane, and ending at intersection of South Main and Haggerty.
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o CIP Project: Project 11
• 4th Avenue, Babcock Street and Grand Avenue Sewer Main Replacement:
o The section of pipe between along W Babcock St and S 3rd Ave is recommended
to be upsized to a 10-inch main. Remaining sewer along 4th Ave is recommended
to be upsized to 8-inch main. In total, 1,300 feet of pipe will be replaced in this
project.
o CIP Project: Project 6
• South Black Avenue between E Story Street and W Main St:
o The existing gravity main should be upsized from 6-inch to 8-inch.
o CIP Project: Small-Pipe Project 1
• Olive Street between S 4th Avenue and S 6th Ave:
o The existing gravity main should be upsized from 6-inch to 8-inch.
o CIP Project: Small-Pipe Project 4
• Main Street between Tracy and S Rouse Ave to E Babcock St:
o The existing gravity main should be upsized from 6-onch and 8-inch to be 8-inch
and 10-inch. The new 10-inch sewer is on Main St between Black Ave and S
Rouse Ave.
o CIP Project: Small-Pipe Project 7
• S Bozeman Ave, E Story St, and Dell Pl Sewer Main Replacement:
o The existing gravity main should be upsized from 6-onch and 8-inch to be 8-inch
o CIP Project: Small-Pipe Project 8
7.2.2.2 Infill Interceptor Extensions
The dashed colored lines in Figure 7-2 show future collector, trunk, and interceptor sewer
extensions that are required to extend to serve the infill area. The proposed sewer size includes
capacity for the UBO scenario. The projects described below are limited to trunk and interceptor
sewers for planning purposes. The sizing and layout of these projects should be more carefully
considered as the need for them approaches.
• Bohart Lane Interceptor:
o This interceptor ranges in size from 21 to 24-inches and runs along the north side
of the interstate starting at the railroad crossing near mile post 309. This
interceptor extension would connect into the existing 30-inch Rouse Avenue
Interceptor.
• South Church Avenue Interceptor
o This interceptor ranges from 21 to 24-inch between Kagy Blvd and Olive Street
and ending at S Rouse Ave.
• Aajker Basin Diversion
o The 21-inch interceptor that will serve as the Aajker Basin Diversion will be
extended to serve growth. The interceptor opens up a significant portion of the
Aajker Creek sewershed basin south of Baxter Lane. The Diversion will take flow
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from the Aajker Creek basin and convey wastewater to the Davis Lane /
Cottonwood Road interceptor.
• Painted Hills Road Trunk Sewer:
o A12-inch sewer is required to serve the growth area southeast of Cherry Dr. The
trunk sewer is generally located within the Highland Glen open space, which is
the topographical low area of the drainage and follows the west side of the creek
between Kagy Road and Haggerty Lane. For infill conditions 12-inch sewer is
required between Painted Hills Road and the existing 8-inch sewer serving Cherry
Dr. UBO will require larger 18-inch main northward along Haggerty Lane.
• Farmhouse Lane Trunk Sewer
o A 12-inch sewer is required to serve the growth area south of the Haggerty Lane
and east of the Highland Glen drainage. The trunk sewer is generally located
within the Highland Glen open space, which is the topographical low area of the
drainage and follows the east side of the creek between Kagy Road and Haggerty
Lane.
7.2.3 Infill Lift Station Summary
No lift stations or lift station upgrades are required to meet the Infill loading scenario. However,
based on recent growth and development adjacent to the City’s existing service boundary, a
new lift station is required to support growth and development to the west. The identified lift
station necessary to meet expected near-term growth has been identified as the Valley Center
Lift Station (VCLS). The VCLS will reside within the Baxter Creek Drainage Basin, located on the
south side of East Valley Center Road, east of Stubbs Lane near the East Valley Center Spur Road
intersection.
The 2015 Facility Plan originally planned to serve the Baxter Creek Drainage Basin with the
Hidden Valley Regional Lift Station, which is northwest of the proposed VCLS. However,
development pressure within the Baxter Creek Drainage area requested the City to evaluate and
ultimately consider the possibility of splitting the Hidden Valley Regional Lift Station into two
separate lift stations. Based on feasibility criteria, modeling results, and input from City Staff,
AE2S recommended two smaller lift stations to service the Baxter Creek Drainage Basin and the
construction of the VCLS lift station in the near-term to help support anticipated future
development west of Davis Lane. The analysis also provided the City with long-term options for
a second lift station or regional alternative to service the Baxter Creek Drainage Basin as the City
continues to grow and develop to the west.
The detailed analysis of the Baxter Creek Drainage Basin and lift station alternatives was
completed in 2022 (Baxter Creek Drainage Basin Analysis Technical Memorandum (AE2S, 2022).
The recommendations were formally adopted by the City commission January 24, 2023. Thus,
amending the City’s adopted 2015 wastewater facility plan. These findings and
recommendations have been incorporated into the facility plan update and will be utilized as
the basis of planning for the Baxter Creek Drainage Basin.
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Currently, the City is in preliminary design phase for VCLS, with an anticipated construction
starting early 2025. Under the UBO loading, the City will need an additional lift station to serve
areas further west and north of the Valley Center Lift Station. Section 7.5 provides details
about the UBO scenario lift station analysis and recommendations.
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UBO Improvements Summary
7.3.1 Modeling Results of Gravity Main and Interceptors for
UBO Conditions
Figure 7-3 presents an overview of the interceptor system at UBO. Outlined in the figure
are existing and proposed interceptors by name along with highlights of proposed and
future trunk sewers. Figure 7-4 presents an overview of the interceptor system at UBO
overlaid with the sewershed basins for reference. Interceptor improvement projects are
discussed in more detail in the following sections.
Figure 7-5 presents the d/D as a ratio of maximum depth to full depth for the buildout
gravity main network. Figure 7-6 presents the infrastructure improvements by diameter
required to achieve the design criteria d/D. A majority of the network shows sufficient
capacity to meet the design storm and support additional growth from UBO conditions
while meeting design criteria. There are minor areas in which the City design criteria for
d/D (0.75) is not met; these are described in more detail below.
• There are a number of short segments scattered throughout the system that
exceed the design evaluation criteria. While they exceed the criteria, they do not
necessarily warrant upsizing as there is no manhole surcharging within the
system and the pipe segment d/D marginally exceeds 0.75. It is recommended
that the City continue to monitor growth and review modeling results to
determine if any of these areas begin to experience surcharging and require
improvements. Some of the areas include the following:
o Existing 21-inch on Fowler Ave just north of Main St.
o Existing 21-inch on Davis Lane just north of W Oak St.
o Existing 24-inch on Simmental Way just north of Baxter Ln
o Existing 15-inch to N 7th Ave between W Birch St and W Oak St.
o Existing 6-inch on S 6th Ave between Harrison St and Garfield St.
o Existing 8 and 10-inch sewer on S 3d Ave between Graf St and Kagy Blvd.
o Existing 18-inch in Blackwood Groves east of S 19th Ave.
• Davis Lane / Cottonwood Road Interceptor: There are three short segments of
this interceptor that marginally exceed 0.75 d/D at UBO conditions. However,
replacing or paralleling these sewers is not recommended at this time
because of the long duration for when buildout flows are realized in this
corridor These locations include the following segments on Cottonwood
Road: (1) 15-inch sewer just south of Alpha Drive, (2) 18-inch interceptor just
north of Babcock Street, and (3) existing 18-inch interceptor on Cottonwood
Road just south of Babcock St.
Technical Memorandum 7.0 Page 65
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7.3.2 UBO Interceptor and Gravity Main Improvements
Figure 7-6 provides an overview of the required improvements to meet UBO loading. The
improvements described below are required for the system to expand from the infill scenario to
the UBO scenario. These improvements are in addition to those listed in Section 7.1 .
7.3.2.1 UBO Upsizing and Interceptor Improvements
The solid-colored lines in Figure 7-6 show existing sewer with modeled capacity issues when
additional loading is added for the UBO scenario and include:
• North Frontage Road Interceptor:
o It is recommended to upsize the remaining interceptor sections along the North
Frontage that were not upsized under the Infill scenario.
o This improvement consists of 27-and 36-inch interceptors between North Rouse
Avenue and Springhill Road.
o Parallel segments are recommended east of the Cherry River fishing access, which
is located off of North Frontage Road.
• 27th Avenue / Davis Lane Interceptor:
o The 27th Avenue / Davis Lane Interceptor will require parallel segments at the
following locations:
▪24-inch between Davis Lane / Cattail Street intersection and the interstate
crossing near Honor Lane.
▪A secondary 30-inch interstate crossing parallel to the existing 30-inch
crossing.
▪Parallel the existing 21-inch along the Davis Lane / Fowler corridor with a
new 21-inch from Oak Street to north of Baxter Lane.
• Fowler Avenue / 19th Avenue Interceptor:
o The Fowler Avenue / 19th Avenue Interceptor will require a number of improved
segments for UBO conditions as follows:
▪Upsize existing sewer within Durston Road from 18-inch to 21-inch
between Meagher Avenue and Fowler Avenue.
▪Upsize existing sewer along the Davis Lane / Fowler corridor from 18-inch
to 24-inch between Durston Road and Oak Street.
• Davis Lane / Cottonwood Road Interceptor:
o The existing 8-inch sewer along Cottonwood Road between Huffine Lane and
Babcock Street is not sufficient to support future growth. The existing line can
continue to serve as a local collector in the near-term, however the existing
interceptor segment along this corridor will need to be extended to the south.
o It is recommended to install an 18-inch Interceptor within Cottonwood Road
between Huffine Lane to Babcock Street. A boring will be necessary as part of this
project to connect the upstream 15-inch section, which is located just south of
Huffine Lane in Cottonwood Road. Currently the existing 15-inch interceptor
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south of Huffine Lane within Cottonwood Road drains into the Loyal Garden Lift
station. This extension would allow the flow to gravity drain north into the new
18-inch interceptor and into the Cottonwood-Davis Interceptor network.
o Additionally, this connection will allow additional development to occur to the
south of Huffine lane, specifically along the Cottonwood Road corridor, which will
continue helping the City realize it’s recent investment in the Cottonwood-Davis
Interceptor.
• North Rouse Interceptor:
o The North Rouse Interceptor between the interstate and North Frontage Road
interceptor will require a parallel 30-inch interceptor under full buildout
conditions.
• Augusta Drive Interceptor (Bridger Creek Golf Course Area):
o The existing 12-inch trunk sewer along Augusta Drive westward toward the
Cherry Creek fishing access will need to be upsized to an 18-inch interceptor.
• 19th Avenue / Kagy Boulevard Interceptor (Babcock St Area):
o Buildout conditions modeled to be upsized to 21 and 24 under buildout
conditions. 21-inch sewer is modeled block upstream and one block downstream
of the intersection of Babcock St and S 6th Ave. 24-inch sewer is modeled
between S 9th Ave and S 11th Ave. It is recommended that the City continue to
monitor flows within this subbasin for future growth contributions which may
warrant upsizing this sewer.
• Fairway Drive Trunk Sewer:
o The existing 8-inch sewer along Fairway Drive (between Little Horse Dr and Kagy
Blvd) is modeled to be upsized to 10 and 12-inch trunk sewer under buildout
conditions. It is recommended that the City continue to monitor flows within this
subbasin for future growth contributions which may warrant upsizing this sewer.
7.3.2.2 UBO Interceptor Extensions
The dashed colored lines in Figure 7-6 show future collector, trunk, and interceptor sewer
extensions that are required to serve the UBO growth area. The projects described below are
limited to trunk and interceptor sewers for planning purposes. As development pressure
continues in these areas, the recommended sewer projects should be reevaluated and refined to
better reflect proposed conditions and ensure adequate capacity.
• Gooch Hill Interceptor:
o The Gooch Hill interceptor ranges in size from 18 to 21 inches and will serve the
far west extents of the growth area. The interceptor begins near Farmers Canal
and extends north along Gooch Hill Road, eventually meeting Harper Puckett
Road. The interceptor ends at East Valley Center Road at the proposed Gooch
Hill Lift station. The Gooch Hill lift station and force main will pump flow east to
the Davis Lane Lift Station. A planning study should be completed to determine
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
the connection point whether it will convey water to the Davis Lane Lift station to
be repumped, or if it will convey wastewater directly to the WRF.
▪There is a planned flow split between Oak Street and Baxter Lane to divert
some of the wastewater to the Davis Lane / Cottonwood Road
Interceptor. The diversion is planned to maximize the capacity within the
Cottonwood Davis Interceptor and minimize lifting the same wastewater
volume twice between Gooch Hill and Davis Lane Lift Stations.
o Additional trunk sewer sized at 15-inch and smaller will extend farther south
along Gooch Hill Road to serve further growth in the southern reaches of the
basin.
• McIlhattan Road Interceptor:
o The McIlhattan Road interceptor will serve the far northeast reaches of the
growth area and ranges in size from 18 to 21 inches. The Interceptor begins near
the intersection of Manley Road and McIlhattan Road. The Interceptor will follow
McIlhattan Road to Springhill Road where it will deliver wastewater to the
proposed Springhill Lift Station which pumps to the WRF.
• Sourdough Road Interceptor:
o As discussed under the Infill improvements, the Sourdough Road Interceptor will
need to be extended from Kagy Blvd southward to Gardner Park Drive generally
along the Sourdough Road corridor. Overall, the Sourdough Road Interceptor
ranges in size from 18 to 24 inches and will stretch from Garner Park Drive to
Olive Street.
• Bohart Lane Interceptor:
o As discussed under the Infill improvements, the Bohart Lane Interceptor will need
to be extended from the interstate east along Rocky Creek Road to Fort Ellis
Road. Overall, the Bohart Lane Interceptor ranges in size from 18 to 24 inches
and will stretch from Fort Ellis Road to N Rouse Avenue.
• South End Trunk Sewers:
o The southern portion of the future network will require a number of south-to-
north trunk sewers ranging in size from 10 to 15 inches. Figure 7-6 shows the
locations of trunk sewers. Trunk sewers in this area generally follow major
planned transportation corridors.
• North End Trunk Sewers:
o Trunk sewer extensions ranging from 10 to 15 inches are also required to serve
the northern extents of the growth area and are shown in in Figure 7-6.
7.3.3 UBO Lift Station Summary
Four primary regional lift stations are required to serve the UBO system:
• Coulee Drive Lift Station;
• Gooch Hill Lift Station;
• Hidden Valley Lift Station; and
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
• Spring Hill Lift Station.
Detailed lift station summaries for each are provided in Section 7.5 .
UBO West Improvements Summary
The natural topography of the City and surrounding area generally slopes downhill north and
west. Much of the western and northern growth areas lie at elevations below the WRF which is
why regional lift stations have been identified and required to pump wastewater to the
treatment facility. Large regional lift stations are generally expensive to build, operate, and
maintain so the City is exploring long-term future scenarios that would allow for gravity service
for the western and north growth areas of the City. As part of this evaluation, the “UBO West”
scenario was developed to analyze collection system infrastructure needs assuming wastewater
would be conveyed northwest under gravity flow conditions. Figure 7-7 shows the approximate
drainage split between what will continue to flow to the existing WRF and what will be able to
flow west to a new treatment facility under the UBO West scenario. The drainage boundary is
not exact because there would be flow splits and bypasses that allow some areas to drain both
directions. In this alternative scenario, wastewater would be treated at a different facility. This
scenario may be conducive for partnering with neighboring communities west of Bozeman to
increase feasibility.
The UBO West scenario includes the same loading as the UBO scenario but conveys wastewater
northwest of City limits and the growth area boundary along the Interstate 90 corridor to a
hypothetical treatment facility.
Figure 7-7 provides an overview of the proposed improvements under the UBO West scenario.
The Figure also highlights the existing lift stations that would be “decommissioned” to rely on
gravity flow. The proposed improvements include varying configurations of future interceptors
as well as diverting flows from existing lift stations in order to reduce overall system operation
and maintenance costs. The projects described below include recommended improvements and
conveyance infrastructure upsizing beyond those proposed under the base UBO scenario.
7.4.1 UBO West Interceptor Improvements
The primary changes for interceptors between the UBO and UBO West scenarios would occur in
the northwest corner of the study area west of Davis Lane and along Interstate 90. These
interceptor changes are shown in Figure 7-7 and include:
• Frontage Road Regional Interceptor:
o A new interceptor would start at the intersection of Springhill Road and the North
Frontage Road and tie into the existing Frontage Road interceptor allowing
wastewater to continue gravity flowing northwest. The interceptor is sized at
42 inches. The existing WRF maximum capacity is 14.6 MGD. Flows through the
Frontage Road interceptor beyond the 14.6 MGD would be diverted by this new
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
interceptor extension. The modeled peak flow in the UBO West scenario has
approximately 14 MGD heading the WRF and approximate 41 MGD heading
northwest to a hypothetical future treatment facility.
• Gooch Hill Road Interceptor:
o The Gooch Hill Road interceptor would require upsizing for the UBO West
conditions as compared to the base UBO conditions. This is due to higher flows
experienced by diverting flow from western lift stations allowing more
wastewater to flow through the primary interceptor through the Aajker Creek
Drainage Basin.
▪The Gooch Hill Interceptor will need to be increased as follows:
• Increases from 18 to 21 inches between the Aajker Diversion and
one mile south of Valley Center Road.
• Increase from 21 to 24 inches from one mile south of Valley Center
Road to Valley Center Road.
• Valley Center Road Trunk Sewer:
o It is recommended that the 15-inch trunk sewer be installed under either the UBO
and UBO West conditions to allow the City flexibility for future decommissioning
of the Valley Center Lift Station whether the flow is conveyed to a future regional
Hidden Valley Lift Station or the flow goes westward for regional treatment.
• Consideration of Additional Flow Diversion:
o It is possible to add additional flow diversions from the southwestern growth area
to be diverted towards the Gooch Hill Interceptor rather than sending the flow
northward through existing and planned improvements within City limits.
Additional flow diversions could come from/connect to:
▪Cottonwood Road south of Huffine Lane.
▪Fowler Lane South of Stucky Road.
Analysis of these alternative flow diversions were excluded from this
study.
7.4.2 UBO West Lift Station Summary
Two regional lift stations are required to serve the UBO West system; Coulee Drive and Spring
Hill lift stations. A detailed lift station summary is provided in Section 7.5 .
• Coulee Drive Lift Station:
o This station is required under both the base UBO and UBO West scenario. For
the UBO West scenario, this station will convey wastewater to the new Frontage
Road Regional Interceptor extension.
• Spring Hill Lift Station:
o This station is required under both the base UBO and UBO West scenario. For
the UBO West scenario, this station can convey wastewater to the WRF or to the
new Frontage Road Regional Interceptor.
Technical Memorandum 7.0 Page 74
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Four existing lift stations can be removed from service and replaced by gravity trunk sewers
conveying wastewater northwestward under the UBO West system. Additionally, the Valley
Center Lift Station, which is in the final design phase at the time of this analysis, can be removed
from service. A detailed lift station summary is provided in Section 7.5 . Existing lift stations
removed under the UBO West scenario:
• Laurel Glen Lift Station
• North Ranch Lift Station
• Loyal Garden Lift Station
• Davis Lane Lift Station
• Valley Center Lift Station (under design)
7.4.3 Modeling Results of Gravity Main and Interceptors for UBO West
Conditions
Figure 7-8 presents the d/D as a ratio of maximum depth to full depth for the UBO West
gravity main network. No manhole surcharging occurs under the UBO West scenario. A
detailed list of improvements specifically required for UBO West conditions is presented
in Section 7.4 .
Technical Memorandum 7.0 Page 75
Interceptor
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Summary of Lift Stations and Force Main Improvements
Lift station capacity was set to equal the modeled peak flow and force main sizing was
determined based on the velocity criteria discussed in Chapter 3. Proposed lift station locations
are the same as the 2015 Facility Plan with the exception of the Baxter Creek Drainage Basin
modifications and addition of the Valley Center Lift Station. Table 7-1 provides an overview of
lift station capacity analysis and improvements required for Infill, UBO, UBO West, and Increased
Density scenarios.
Table 7-2 summarizes the proposed of force main improvements. The following summarizes the
lift station improvements:
• Infill Lift Station Projects:
o No new lift station projects are identified to meet infill loading.
o Valley Center Lift Station: This lift station is currently under design by the City to
meet immediate growth needs adjacent to City limits and is included in the Infill
Scenario because it is expected to be online soon. This station is modeled with a
peak flow of 2,015 gpm. A 14-inch force main will convey wastewater along
Valley Center Road to the Davis Lane Interceptor.
• Improvements to Existing Lift Stations Required for UBO: The following lift station
improvements are required to meet UBO loading:
o Loyal Garden lift station would reach maximum capacity at UBO conditions with a
modeled peak flow to the lift station of 370 gpm. It is recommended that the City
continue to monitor growth within the basin and evaluate required capacity when
lift station maintenance or improvements projects are implemented.
o Davis Lane lift station would reach maximum capacity under the UBO conditions.
The peak flow is modeled to be in excess of 14,000 gpm which is nearly three
times the capacity of the existing station – the lift station was designed to be
phased with expansions allowing up to 10,400 gpm while operating 4 duty
pumps. In order to achieve 14,000 gpm at UBO, pump and wet well expansions
will be required. A third 18-inch force main (parallel to the existing two force
mains) is required to convey the UBO peak flow to the WRF.
• New Lift Stations Required for UBO: The following is a summary of proposed lift
stations to serve the UBO scenario. All of these proposed lift stations, with the exception
of the Coulee Drive station, are also recommended in the previous Facility Plan.
o Coulee Drive lift station is in the far northwest corner of the growth area and will
have a peak flow of 2,270 gpm under the UBO scenario. This lift station was not
identified in the 2015 Facility Plan because its service area was not within the
City’s growth boundary. This lift station will require a 14-inch force main
conveying wastewater directly to the WRF.
Technical Memorandum 7.0 Page 78
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Technical Memorandum 7.0 – Hydraulic Model Development and Results
▪Under the UBO-West condition, this lift station will convey wastewater
south toward the proposed Frontage Road interceptor rather than the
Davis Lane lift station.
o Spring Hill lift station is in the far north-center area of the collection system and
is modeled to have a UBO peak flow of 5,480 gpm. This lift station will require a
21-inch force main conveying wastewater directly to the WRF.
▪Under the UBO-West condition, this lift station could convey wastewater
to either the WRF or west to a future gravity main.
o Gooch Hill lift station in the northwest corner of the growth area and is modeled
to have a UBO peak flow of 6,770 gpm. This lift station will require a 24-inch
force main conveying wastewater to the Davis Lane lift station.
▪Under the UBO-West condition, this lift station will not be necessary as
wastewater can be conveyed northwest via gravity.
o Hidden Valley lift station is in the northwest corner of the growth area and is
modeled to have a UBO peak flow of 2,230 gpm. This lift station will require a
14-inch force main conveying wastewater to the Davis Lane lift station.
▪Under the UBO-West condition, this lift station will not be necessary as
wastewater can be conveyed northwest via gravity.
• UBO West Lift Station Decommissioning: The following existing lift stations could
potentially be decommissioned under the UBO West scenario:
o Valley Center Lift Station
▪Wastewater flow can be directed westward along Valley Center Road with
a 15-inch gravity main.
o Laurel Glen Lift Station
▪Wastewater flow can be directed northward with a 12-inch gravity main
towards the Baxter Lane interceptor.
o Norton Ranch
▪Wastewater flow can be directed westward with a 15-inch gravity main to
the Gooch Hill interceptor.
o Loyal Garden
▪Wastewater flow can be directed north and westward along Huffine Lane
with a 12-inch gravity main to the Gooch Hill interceptor.
Technical Memorandum 7.0 Page 79
City Lift Station Current Firm
Capacity
(gpm)
Existing Peak
Inflow (WWF)
(gpm)
Infill Peak
Flow
(gpm)
UBO Peak
Flow
(gpm)
UBO West
Peak Flow
(gpm)
Improvement
Type
Baxter Meadows 690 270 450 520 520
Bridger Center 100 30 20 20 20
Burrup 450 110 100 140 140
Cattail Lake 225 20 50 50 50
Davis Lane 3,000 310 620 14,040 Removed Increase Pump and Wetwell
Capacity for Growth
Laurel Glen 450 360 400 400 Removed
Loyal Gardens 364 180 270 370 Removed Monitor, Rehab for Growth if
Needed
Norton Ranch 450 70 450 450 Removed Monitor, Rehab for Growth if
Needed
Cardinal Distribution1 unk ---0
Links 160 30 30 40 40
MDT unk 20 20 50 50
Nelson Meadows 190 80 100 190 190
Overbrook unk 40 40 40 40
Sebena1 none ----
Walker unk 40 40 80 80
Coulee Drive 2,270 2,270 New for Growth
Spring Hill 5,480 5,480 New for Growth
Gooch Hill 6,770 New for Growth
Hidden Valley 2,230 New for Growth
Valley Center (Shallow)2 1,620 -New for Growth
(Reduce Hidden Valley by amount)
Valley Center (Deep)2
(reduce Hidden Valley by amount)
2,015 2,015 New for Growth
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table 7-1: Lift Station Capacity Summary
1 The Cardinal lift station is not modeled due to lack of information and the Sebena lift station is not in service.
2 Valley Center Lift Station under preliminary design at the time of this report
Technical Memorandum 7.0 Page 80
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7.0 – Hydraulic Model Development and Results
Table 7-2: Capacity Force Main
City Lift Station
Baxter Meadows
Bridger Center
Burrup
Cattail Lake
Davis Lane
Laurel Glen
Loyal Gardens
Norton Ranch
Cardinal Distribution1
Links
MDT
Nelson Meadows
Overbrook
Sebena1
Walker
Coulee Drive
Spring Hill
Gooch Hill
Hidden Valley
Valley Center (Shallow)2
(Reduce Hidden Valley by amount)
Valley Center (Deep)2
(reduce Hidden Valley by amount)
Existing Force
Main (inch)
12.00
4.00
6.00
6.00
18.00
8.00
6.00
4.00
4.00
6.00
14.00
21.00
24.00
14.00
14.00
14.00
Velocity at Firm
Capacity (ft/s)
1.96
2.55
5.11
2.55
6.53
2.87
4.13
3.09
4.09
2.16
Velocity at
UBO Flow (ft/s)
1.48
5.90
3.45
6.01
3.06
4.73
5.08
4.80
4.65
3.38
4.20
Force Main Improvement
Install third parallel 18-inch. (3,700 ft)
o
Use existing parallel 6-inch.
Install 14-inch force main. (17,200 ft)
Install 21-inch force main. (12,050 ft)
Install 24-inch force main. (11,200 ft)
Install 14-inch force main. (9,900 ft)
Install 14-inch force main. (3,200 ft)
Install 14-inch force main. (3,200 ft)
1 The Cardinal lift station is not modeled due to lack of information and the Sebena lift station is not in service.
2 Valley Center Lift Station under preliminary design at the time of this report
Technical Memorandum 7.0 Page 81
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7 – Hydraulic Model Development and Results
Increased Density Improvements Summary
Figure 7-9 shows areas that experience increased domestic loading based on increased
density. Flow increases under this scenario are described in detail in TM 5 and generally
follow:
• Existing residential areas with R1 zoning experience increased domestic loading
by 25%.
• Future residential growth areas with (Zoned R1, R2, or R3) experience increased
domestic loading to the R4 zoning duty factor (20 dwelling units per acre).
• Infill B2-M and REMU zoning was increased to R5 density and its respective duty factor.
• Select areas of varying Zoning and Future Land Use types as identified by the City where
increased density development is likely to occur.
• Any future land use within City Limits as identified in the 2020 Community Plan
was assigned the duty factor for Urban Neighborhood (~12 dwelling units per
acre).
Figure 7-9 presents the d/D as a ratio of maximum depth to full depth for the UBO
gravity main network under the increased density modeling scenario. A majority of the
network continues to show sufficient capacity to meet the design storm and support the
additional density. No manhole surcharging within manholes is modeled within the
increased density system with the assumption that the planned UBO recommended
improvements are implemented. Figure 7-10 shows the gravity main d/D increase from
the UBO scenario to the increased density scenario. Generally, the d/D ratio increases by
0.1 or less for most of the system. The City recognizes that densities beyond those
modeled in this scenario may be proposed by developers in the future and should be
carefully evaluated on a case-by-case basis using the system-wide model.
There are three gravity main sections (shown in Figure 7-9) that experience enough
increased flow to marginally exceed the City’s design d/D of 0.75:
• Davis Lane / Cottonwood Road Interceptor: The existing 15-inch trunk sewer
on Cottonwood Road just south of Alpha Drive and the existing 18-inch
interceptor on Cottonwood Road just north of Babcock Street remain below 0.9
d/D in the UBO conditions. Note that these sewers are new (2019-2020).
• Front Street Interceptor: The Front Street Interceptor between the Bozeman
Softball Complex through Tamarack Street would experience increased d/D but
remain below 0.90 d/D. Note that the portion of the interceptor north of the
Haggerty and Main intersection is new (2020) and is an 18 and 21-inch sewer.
Technical Memorandum 7.0 Page 82
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 7 – Hydraulic Model Development and Results
• Highland Glen Sewer Main: The sewer through the Highland Glen open space
between Cherry Drive and Ellis Street is modeled to experience increase d/D but
remain below 0.90. This sewer is currently 8 inches, proposed to be upsized to
12-to 15-inch in UBO, and would need to be further upsized under the Increased
Density loading to meet the d/D City standards.
While these corridors are shown to have increased flow, the recommendations under
the base UBO scenario are believed to be adequate currently. It is recommended that
the City continue to monitor these corridors to observe potential increases due to
increased density.
Technical Memorandum 7.0 Page 83
8.0
Risk Assessment Technical
Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
Table of Contents
Chapter 1 Risk Assessment Overview ................................................................................... 4
1.1 Risk Assessment Framework ...........................................................................................................................4
1.2 Risk Matrix ............................................................................................................................................................6
1.3 Likelihood of Failure Criteria and Weighting Factors .............................................................................7
1.3.1 Pipe Material........................................................................................................................................7
1.3.2 Hydraulic Model Output – Flow Depth-to-Diameter Ratio (d/D) ......................................8
1.3.3 NASSCO Pipe Ratings.......................................................................................................................8
1.3.4 Sewer Stoppage ............................................................................................................................... 10
1.3.5 Pipe Remaining Useful Life ........................................................................................................... 10
1.3.6 LOF Weighting Factors....................................................................................................................11
1.4 Consequence of Failure Criteria and Weighting Factors .....................................................................11
1.4.2 Pipe Flow............................................................................................................................................. 12
1.4.3 COF Weighting Factors..................................................................................................................13
Chapter 2 Sewer Main Risk Results .....................................................................................14
2.2 Renewal & Replacement Planning.............................................................................................................15
Chapter 3 Sewer Main Capital Replacement Projects ....................................................... 16
3.1 8-inch and Larger Sewer Main Replacement Projects.........................................................................16
3.1.1 Project 1: 19th Ave / Kagy Blvd Interceptor Improvement (between Kagy and
Olive)............................................................................................................................................. 17
3.1.2 Project 2: Durston Road and 17th Avenue Sewer Main Replacement............................21
3.1.3 Project 3: 7th Avenue to Oak Street Sewer Main Replacement ...................................... 22
3.1.4 Project 4: North 11th Avenue Sewer Main Replacement.................................................... 23
3.1.5 Project 5: Plum Avenue Sewer Main Replacement..............................................................24
3.1.6 Project 6: 4th Ave., Babcock Street and Grand Avenue Sewer Main
Replacement ............................................................................................................................. 25
3.1.7 Project 7: North 9th Avenue, West Villard Street, and South 9th Avenue Sewer
Main Replacement ...................................................................................................................27
3.1.8 Project 8: Harrison and 10th Avenue Sewer Main Replacement ..................................... 29
3.1.9 Project WWIF20: North Frontage Rd Interceptor................................................................. 30
3.2 6-inch Sewer Main Replacement Projects............................................................................................... 31
3.2.1 Likelihood of Failure Criteria and Weighting Factors...........................................................31
3.2.2 Consequence of Failure Criteria and Weighting Factors .................................................... 31
3.2.3 Small Pipe Risk Results .................................................................................................................. 32
3.3 Small Pipe Capital Replacement Projects ............................................................................................... 33
3.3.1 Small Pipe Project 1: South Black Avenue 6-inch Sewer Main ......................................... 34
Technical Memorandum 8.0 Page 1
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
3.3.2 Small Pipe Project 2: South Willson Avenue 6-inch Sewer Main .................................... 35
3.3.3 Small Pipe Project 3: South Grand Avenue 6-inch Sewer Main....................................... 36
3.3.4 Small Pipe Project 4: West Olive Street 6-inch Sewer Main...............................................37
3.3.5 Small Pipe Project 5: South 4th Avenue 6-inch Sewer Main.............................................. 38
3.3.6 Small Pipe Project 6: South 3rd Avenue 6-inch Sewer Main.............................................. 39
Chapter 4 Future Risk Model Updates ................................................................................ 41
4.1 GIS Updates .......................................................................................................................................................41
4.2 CCTV Updates ................................................................................................................................................. 43
4.3 Work Order (Sewer Stoppage) Updates.................................................................................................43
4.4 Risk Model Re-Run ........................................................................................................................................ 43
4.5 Conclusion ........................................................................................................................................................ 44
List of Tables
Table 1-1: Criteria Weighting Factors......................................................................................................................6
Table 1-2: Risk Matrix ..................................................................................................................................................6
Table 1-3: Risk Category and Response.................................................................................................................7
Table 1-4: Pipe Material LOF Scores ........................................................................................................................7
Table 1-5: d/D LOF Scores ...........................................................................................................................................8
Table 1-6: NASSCO LOF Scores .................................................................................................................................9
Table 1-7: Sewer Stoppage LOF ..............................................................................................................................10
Table 1-8: Pipe Lifespan by Material......................................................................................................................11
Table 1-9: RUL LOF Scores.........................................................................................................................................11
Table 1-10: LOF Weighting Factors........................................................................................................................11
Table 1-11: Pipe Flow COF Score ............................................................................................................................13
Table 1-12: COF Weighting Factors .......................................................................................................................13
Table 2-1: Risk Results by Pipe Diameter.............................................................................................................14
Table 2-2: Risk Results by Pipe Material...............................................................................................................15
Table 3-1: LOF Criteria Weighting ..........................................................................................................................31
Table 3-2: Small Pipe Risk Results ..........................................................................................................................32
List of Figures
Figure 1-1: Simplified Equation for calculating Asset Risk ..............................................................................4
Figure 3-1: Project 1 Extents (checkered line)....................................................................................................17
Figure 3-2: Project 1 Upsized Pipe Diameters....................................................................................................20
Figure 3-3: Project 2 Extents (checkered line)....................................................................................................21
Technical Memorandum 8.0 Page 2
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
Figure 3-4: Project 3 Extents (checkered line)....................................................................................................22
Figure 3-5: Project 4 Extents (checkered line)....................................................................................................23
Figure 3-6: Project 5 Extents (checkered line)....................................................................................................24
Figure 3-7: Project 6 Extents (checkered line)....................................................................................................25
Figure 3-8: Project 6 Upsized Pipe Diameters (checkered line)...................................................................26
Figure 3-9: Project 7 Extents (checkered line)....................................................................................................27
Figure 3-10: Project 7 Upsized Pipe Diameters (checkered line) ................................................................28
Figure 3-11: Project 8 Extents (checkered line)..................................................................................................29
Figure 3-12: Small Pipe Project 1 Extents (checkered line) ...........................................................................34
Figure 3-13: Small Pipe Project 2 Extents (checkered line) ...........................................................................35
Figure 3-14: Small Pipe Project 3 Extents (checkered line) ...........................................................................36
Figure 3-15: Small Pipe Project 4 Extents (checkered line) ...........................................................................37
Figure 3-16: Small Pipe Project 5 Extents (checkered line) ...........................................................................38
Figure 3-17: Small Pipe Project 6 Extents (checkered line) ...........................................................................39
Figure 4-1: Field Mapping for Sanitary Sewer Mains ......................................................................................42
Technical Memorandum 8.0 Page 3
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
Chapter 1 Risk Assessment Overview
The purpose of this memorandum is to explain the risk assessment performed for the City’s
sanitary sewer collection system (pipes). Following a methodical risk assessment process results
in a documented and consistent method for assessing risk associated with potential sewer
system failures. This process is not intended to be a one-time, static approach for assessing
sewer system failure risks. It is intended to be updated and refined over time as improvements
are conducted and additional data is continually collected.
The sewer system risk assessment includes data made available from the City’s GIS geodatabase,
hydraulic model results, the City’s sewer stoppage history, and CCTV records. InfoAsset
Planner® (Version 2023) software is used for development of the risk assessment model.
InfoAsset Planner® is a fully GIS integrated water and wastewater infrastructure assessment
software application. The risk assessment framework utilized for this project incorporates
consequence of failure (COF) and likelihood of failure (LOF) criteria for each asset type to fully
understand the components that contribute to asset risk.
1.1 Risk Assessment Framework
The first step of the risk assessment is to select the criteria to be included in the assessment.
The risk criteria are grouped into two categories – Consequence of Failure (COF) and Likelihood
of Failure (LOF). These two categories form the basis of risk and are important to fully
understand how asset risk levels are determined.
Figure 1-1 shows a simplified equation for how risk is calculated for each asset type. It is
simplified because it does not show all the specific COF and LOF criteria included when
calculating risk. The ‘union’ symbol between COF and LOF represents the combination of the
data sets in both categories; COF and LOF can be multiplied or added together when calculating
risk within InfoAsset Planner®. For this assessment, COF and LOF were multiplied together to
calculate risk.
Figure 1-1: Simplified Equation for calculating Asset Risk
Technical Memorandum 8.0 Page 4
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
Consequence of Failure (COF) Criteria
COF is defined as the consequence or impact a system would experience during a negative
event (most commonly an infrastructure failure). While all sewer system components are
important, some are more critical than others based on a variety of factors including but not
limited to customers served, critical facilities, physical location, etc. For example, a 24”
interceptor, that provides service to 50% of the customer base is more critical than an 8”
collector that only provides service to a few homes. Both sewer system components are
important, but the consequence of losing the 24” interceptor versus the 8” collector is much
greater. For these reasons, COF criteria were developed in order to understand the
consequence magnitude for all sewer system components. For each COF criteria evaluated, a
score of 1 to 10 was assigned to each asset with 1 being the lowest consequence of failure, and
10 being the highest consequence of failure.
Likelihood of Failure (LOF) Criteria
LOF is defined as the likelihood or probability that a negative event (most commonly an
infrastructure failure; could be either a structural or performance failure) will occur. All sewer
system components will eventually experience issues as time progresses. The LOF side of the
risk equation provides an understanding of which sewer system assets are most likely to fail and
why. By evaluating multiple relevant LOF criteria sets, the approach to determining which assets
are most likely to fail is practical and defendable. For each LOF criteria evaluated, a score of 1 to
10 is assigned to each asset with 1 being the lowest likelihood of failure, and 10 being the
highest likelihood of failure.
Weighting Factors
Not all criteria for this assessment are considered equal; like sewer system components, some of
the COF and LOF criteria developed are more important than others. A workshop was conducted
with City staff to determine appropriate weighting factors for the COF and LOF criteria.
Weighting factors are applied as multipliers to the criteria score assigned to the asset. For
example, if a large diameter sewer pipe received a COF score of 10 for the criteria of pipe
diameter, and the criteria weight selected by the City for pipe diameter was 3, the resultant COF
score would be 30 (10 x 3 = 30). Weighting factors selected by the City are shown in Table 1-1.
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Table 1-1: Criteria Weighting Factors
Criteria Weight Description
3 Criteria Extremely Critical
2 Criteria with Elevated Criticality
1 Criteria with Normal Criticality
Each of the COF criteria are individually evaluated for all pipes, scores of 1 to 10 are assigned, and weighting factors
are applied. The sum of the weighted COF scores is calculated for each pipe. The same procedure is followed for the
LOF criteria.
1.2 Risk Matrix
Bi-directional risk grading or a risk matrix is used to segregate assets into brackets of risk based
on the City’s defined risk parameters. In the bi-directional risk grading approach, the total COF
and total LOF scores are considered separately and independently. The brackets are simply
divided into thirds based on the distribution of COF and LOF scores. For example, if a sewer
pipe was ranked in the top third of all pipes based on COF scores, but only in the middle third of
all pipes based on LOF scores, it would land in the medium risk grade following the matrix in
Table 1-2. This ensures that an asset does not get flagged for risk driven replacement based on
a total risk score alone. To be classified as extreme risk, the pipe must be classified as both a
high likelihood and high consequence of failure.
Table 1-2: Risk Matrix
LOF Low LOF Medium LOF High
COF High Medium High Extreme
COF Medium Low Medium High
COF Low Negligible Low Medium
The observant reader will quickly note that the consequence of failure is always going to be high
for many pipes, and always going to be low for others based on their location and customers
served. This observation is correct. The thought behind the risk grading process is not that every
pipe will eventually cycle through the extreme risk grade and be replaced, but rather the
extreme risk grade will flag all pipes that the City cannot afford to let fail. It does not mean that
other pipes will not age, begin to deteriorate, and need replacement over time. As the highest
priority projects are addressed and the City begins to gain a comfort level with their acceptable
risk level, the bracket levels in the risk matrix can be adjusted so that projects are more driven by
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likelihood of failure, or more driven by consequence of failure depending on the City’s risk
appetite.
A description of the risk categories and an appropriate risk response is included in Table 1-3.
Table 1-3: Risk Category and Response
Risk Category Risk Response
Extreme Include in 5 Year CIP
High Prioritize for additional inspection. Budget
replacement for 20 Year CIP.
Medium Schedule inspection in <2 years
Low No Action Required
Negligible No Action Required
1.3 Likelihood of Failure Criteria and Weighting Factors
The following tables summarize how the pipe LOF criteria are evaluated for the collection
system which include:
• Pipe Material
• Hydraulic Model Output – Flow Depth-to-Diameter Ratio (d/D)
• NASSCO Pipe Rating from CCTV
• Pipe Main Repair History
• Pipe Remaining Useful Life
1.3.1 Pipe Material
A common LOF indicator is the material of the pipe. Over the last century, a number of materials
have been used to create pipes for use in a sewer system including vitrified clay pipe (VCP),
ductile iron (DI), and more recently polyvinyl chloride (PVC). Due to age, fragility, and corrosivity,
certain materials last longer than others and are thus given LOF scores that reflect the material’s
longevity. Table 1-4 details the scores assigned to each pipe material found in the City’s sewer
system. In the event of a pipe with unknown material, a score of 10 was given to help the City
prioritize identifying assets with missing information.
Table 1-4: Pipe Material LOF Scores
Pipe Material LOF Score
Vitrified Clay Pipe 10
Ductile Iron Pipe 6
Asbestos Cement Pipe 5
PVC Pipe 3
Unknown 10
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1.3.2 Hydraulic Model Output – Flow Depth-to-Diameter Ratio (d/D)
This factor uses the maximum flow depth to pipe diameter ratio (d/D) during a 25-year rainfall
event under existing flow conditions as produced by the hydraulic model to assess the capacity
of the mains to manage base loads and inflow and infiltration (I/I) from a frequent storm event.
Risk factors are distinguished by the fullness of a pipe as a percentage modeled under the
design event. The highest factor (10) represents a flow condition in a circular conduit where the
volumetric efficiency of the conduit to convey flow begins to diminish with increasing depth of
flow. This decreased efficiency occurs as water depth in a circular conduit exceeds approximately
85 percent of the pipe diameter. Conservatively, the acceptable d/D ratio before upsizing is
recommend for the City is 75 percent of the pipe diameter. Lower risk factors (1-6) represent
flow conditions modeled for the design event where the depth of flow is a smaller percentage of
total conduit diameter, and hence, has a lower likelihood of having problems conveying the
design flow event. Table 1-5 provides the risk categories and scoring based on performance
criteria.
Table 1-5: d/D LOF Scores
Hydraulic Model Output Flow
Depth to Diameter Ratio (d/D) LOF Score
>0.75 10
0.5 – 0.75 6
0.3 – 0.49 4
0.1 – 0.29 2
<0.1 1
1.3.3 NASSCO Pipe Ratings
CCTV data along with pipe defect ratings from the National Association of Sewer Service
Companies (NASSCO) are used to gauge the current condition of the sewer system. Defects are
ranked on a scale of 1 to 5 with 5 being worst-case defects. Two metrics are used two estimate
the severity of the pipe conditions, the Pipe Rating Score (PRS) and the Pipe Rating Index (PRI).
The PRS is the sum of the structural defect rating component and O&M defect rating
component for a given pipe segment. A rating is the sum of the defect occurrences multiplied
by the grade of each occurrence. The PRI is the average defect grade of a pipe segment. This is
accomplished by dividing the PRS by the total number of defect occurrences in the given pipe
segment. Using both metrics of defect analysis allows us to confidently rank potential pipe
replacement plans based on severity of occurrence and severity of defect simultaneously.
To ensure pipes with a high PRI are always given priority over pipes with a low PRI and high PRS
regardless of PRS, a secondary scoring system is applied that combines the LOFs for both the
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PRI and PRS. The resulting “Effective LOFs” assigned to each pipe segment are shown in Table
1-6.
Table 1-6: NASSCO LOF Scores
PRI PRS LOF Score
> 200 10
5 50 -200 9
< 50 8
> 200 8
4-5 50 -200 7
< 50 6
> 200 6
3-4 50 -200 5
< 50 4
> 200 4
2-3 50 – 200 3
< 50 2
1-2 > 200 2
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50 -200 1
< 50 0
< 1 0 0
1.3.4 Sewer Stoppage
Work orders are used to identify which pipe segments caused sewer stoppages over the last 15
years. The more stoppages occurring on a single segment of pipe indicates higher chances that
repairs may be required. Thus, the more stoppages along a pipe segment equals a higher LOF
score and vice versa. The LOF Scores for Sewer Main repairs can be found in Table 1-7.
Table 1-7: Sewer Stoppage LOF
Sewer
Stoppage LOF Score
Count
>4 10
4 8
3 6
2 4
1 2
1.3.5 Pipe Remaining Useful Life
The lifecycle of a pipe is the number of years the pipe can be in operation before recommended
replacement. Pipe lifecycles are determined from the material composition of the pipe. The
remaining useful life (RUL) of a pipe is calculated by subtracting the age of the pipe (current
year minus install year) from the pipe’s designated lifecycle.
𝑅𝑈𝐿 = 𝐿𝑖𝑒𝑒𝑐𝑦𝑐𝑙𝑒 − (𝐶𝑟𝑟𝑟𝑒𝑛𝑟 𝑌𝑒𝑎𝑟 − 𝐼𝑛𝑟𝑟𝑎𝑙𝑙 𝑦𝑒𝑎𝑟)
LOF scores were assigned based on the RUL of each pipe in the sewer system. Pipes with a RUL
of less than or equal to zero were given the highest scores to indicate the immediate need of
replacement. Table 1-8 provides the lifecycle associated to each pipe material found in the
sewer system while Table 1-9 details the LOF score ranges. The lifespan of a pipe is subject to
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numerous variables, and no estimate is perfect. Standard estimates provided by the EPA are
used for the purposes of this risk assessment.
Table 1-8: Pipe Lifespan by Material
Pipe Material Lifespan (Years)
Vitrified Clay Pipe 70
Ductile Iron Pipe 100
Asbestos Cement 70 Pipe
PVC Pipe 100
Table 1-9: RUL LOF Scores
RUL LOF Score
0 10
1-10 8
11-20 6
21-30 4
31-50 2
51-100 0
1.3.6 LOF Weighting Factors
LOF criteria and their respective weighting factors for the sewer system are summarized in Table
1-10. The weighting factor is a multiplier for the LOF score of each asset within the respective
category. For example, if a pipe received a LOF score of 5 for the pipe material, the multiplier of
4 would be applied and the overall LOF contribution of material for that pipe would be 20 (5 x 4
= 20).
Table 1-10: LOF Weighting Factors
LOF Criteria Weighting Factor
Pipe Material 1
d/D 3
NASSCO Rating 3
Sewer Stoppage 2
RUL 2
1.4 Consequence of Failure Criteria and Weighting Factors
Initially, the risk model included multiple COF criteria including pipe diameter, proximity to
critical facilities, road type, stream crossing, and expansion growth areas. After the first review of
the risk results and the sensitivity analysis, it became apparent that the analysis was too heavily
dependent on COF criteria and after a workgroup meeting with the City it was decided that
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reducing the COF criteria to focus on the core fundamental of pipe flow rates would eliminate
the “criteria dilution” previously experienced.
With the COF criteria limited to pipe flow, the analysis currently focuses on pipes with a high
likelihood of failure, that also experience elevated flow rates.
1.4.2 Pipe Flow
Results from the hydraulic model are used to assign COF scores based on the maximum flow
rate expected under a wet weather flow event. These scores are shown in Table 1-11 where
pipes with higher flow rates receive a higher COF score.
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Table 1-11: Pipe Flow COF Score
Pipe Flow COF Score (gpm)
>700 10
500 – 699 9
400 – 499 8
300 – 399 7
200 – 299 6
100 – 199 5
50 – 99 4
<50 3
1.4.3 COF Weighting Factors
Each of the sewer system COF criteria previously explained are assigned a weighting factor, as
summarized in Table 1-12. The weighting factor is a multiplier for the COF score of each asset
within the respective category. For example, if a pipe received a COF score of 5 for the
maximum flow rate, the multiplier of 1 would be applied and the overall COF contribution of
flow rate for that pipe would be 5 (5 x 1 = 5).
Table 1-12: COF Weighting Factors
Consequence of Failure
Criteria
Weighting
Factor
Pipe Flow 1
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Chapter 2 Sewer Main Risk Results
The pipe risk results shown by size and risk category are shown in Table 2-1. Additionally, risk
results shown by material and risk category are shown in Table 2-2. Overall, approximately 3%
of the system pipes fall in the “Extreme” risk category.
Table 2-1: Risk Results by Pipe Diameter
Pipe
Diameter (in)
Risk Category by Diameter (Length in Feet) Total
Length
(ft)
Percent
of
System Negligible Low Medium High Extreme
<=6 20,396 22,917 35,224 13,569 870 92,975 7%
8 630,187 133,350 36,009 20,814 4,316 824,676 66%
10 26,556 26,175 13,212 13,501 3,429 82,872 7%
12 12,408 14,368 19,713 7,812 5,576 59,877 5%
14 5,527 2,212 7,739 1%
15 14,674 4,333 10,204 5,305 3,244 37,760 3%
16 172 172 0.01%
18 5,805 5,200 6,990 14,568 3,075 35,637 3%
20 853 1,133 8,324 10,091 20,401 2%
21 1,708 4,679 18,294 2,532 27,213 2%
24 292 10 19,800 18,056 964 39,122 3%
27 7,340 1,001 4,357 12,698 1%
30 6,892 5,198 1,403 1,724 15,217 1%
Total Length
(ft)
726,430 212,885 170,132 108,879 38,033 1,256,360
Total Length
(mi)
138 40 32 21 7 238
% Of System 58% 17% 14% 9% 3%
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Table 2-2: Risk Results by Pipe Material
Pipe
Diameter (in)
Risk Category by Diameter (Length in Feet) Total
Length
(ft)
Percent
of
System Negligible Low Medium High Extreme
AC 1,123 4,852 3,111 40,678 18,156 67,920 5%
CMP 385 1,908 1,783 450 4,526 0.4%
DI 4,889 309 230 5,428 0.4%
PVC 719,483 112,390 92,542 19,956 1,380 945,750 75%
VCP 550 93,478 74,171 46,232 18,047 232,479 19%
Total Length
(ft)
726,430 212,885 170,132 108,879 38,033 1,256,360
Total Length
(mi)
138 40 32 21 7 238
% Of System 58% 17% 14% 9% 3%
The risk categories should not be viewed as definitive brackets of projects to be addressed in
different target years. Everything in the risk analysis needs to be viewed through the lens of
“prioritization based on the best available data at the time.” As the City continues to complete
CCTV inspection, better data will become available and should be used to re-prioritize. The
power of InfoAsset Planner is the ability to quickly assimilate new data and update risk analyses
and compare and evaluate changes in priorities for future years.
2.2 Renewal & Replacement Planning
A workshop was held with the City to review the preliminary asset renewal plan, or decision tree.
This decision tree provides a way to automate renewal and replacement decisions based on
predefined asset condition criteria. Throughout the course of this workshop the City expressed
that their experience with pipe rehabilitation activities such as slip lining have not been positive,
and at this time the City of Bozeman will only consider full replacement of sewer pipes. This
approach eliminates the need for a decision tree to help delineate projects into rehab vs.
replacement categories. If at a future date the City decides to consider rehabilitation activities
for sewer pipe, the decision tree functionality should be utilized within InfoAsset Planner to help
streamline these pipe renewal decisions.
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Chapter 3 Sewer Main Capital Replacement Projects
3.1 8-inch and Larger Sewer Main Replacement Projects
With the direction that all pipes needing rehabilitation should be budgeted for full replacement,
the pipes with the most extreme risk were assembled into logical project extents and reviewed
with City staff. The City’s sewer main replacement needs are much more extensive than what
can be funded under the current $1 million dollars per year allocated. The City has approved a
resolution to increase this budget up to $2.5 million dollars per year. The 5-year sewer pipe
replacement program outlined in this memo is based on a budget of $2.5 million dollars per
year. An interactive online dashboard detailing the extents, costs, and combined risk scores of
these projects can be found at the link below:
ArcGIS Insights CIP Dashboard
The following sections describe the extents of the replacement projects, as well as the factors
that caused these projects to be ranked as extreme risk in the analysis.
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3.1.1 Project 1: 19th Ave / Kagy Blvd Interceptor Improvement
(between Kagy and Olive)
Figure 3-1: Project 1 Extents (checkered line)
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A critical section of sewer main begins on Kagy Blvd and Hoffman Drive as a 10-inch diameter
AC line, and runs north through the park to Mason Street, and continues north on Wilson Ave.,
west on College Street, north on 4th Ave., west on Story Street, and finally north on 6th Ave. By
the time this sewer main reaches Olive Street it is an 18-inch diameter pipe. This is shown with a
checkered line in Figure 3-1.
This project is recommended for replacement (and upsizing) due to the following risk factors:
• d/D criteria of 75% is exceeded for much of the pipe in this critical sewer main, indicating
additional flow capacity is needed.
• The majority of this pipe was installed in the late 60’s and early 70’s. AC pipe typically
has a lifespan of around 70 years, but CCTV data indicates the condition of portions of
this pipe are not in great condition. There are also portions of PVC installed in the late
90’s running through the park. This section of pipe is included in the project due to the
additional needed flow capacity.
• As a critical sewer main, the flow in these pipes exceeds 2,400 gpm under wet weather
conditions.
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The recommended pipe diameters to be installed for this project are shown in
Figure 3-2.
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Figure 3-2: Project 1 Upsized Pipe Diameters
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3.1.2 Project 2: Durston Road and 17th Avenue Sewer Main
Replacement
Figure 3-3: Project 2 Extents (checkered line)
A 15-inch sewer main running west along Durston Road, turns north on 17th Ave. and becomes
an 18-inch sewer main. This project is recommended for replacement due to the following risk
factors:
• These VCP pipes were installed in the early 60’s and are near the end of their useful life.
• CCTV data indicates significant pipe defects in portions of this corridor.
• As a critical sewer main, the flow in these pipes exceeds 1,000 gpm under wet weather
conditions.
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3.1.3 Project 3: 7th Avenue to Oak Street Sewer Main Replacement
Figure 3-4: Project 3 Extents (checkered line)
A 15-inch sewer main running north in the fields west of 7th Avenue turns east on Birch Street
and becomes an 18-inch main. Just before reaching 7th Avenue, the 18-inch main turns north
until it intersects Oak Street. This project continues along Oak Street until approximately 5th
Avenue.
This project is recommended for replacement due to the following risk factors:
• These VCP pipes were installed in the early 50’s and have reached the end of their useful
life.
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• CCTV data indicates several pipe defects throughout portions of this corridor.
• As a critical sewer main, the flow in these pipes exceeds 1,100 gpm under wet weather
conditions.
3.1.4 Project 4: North 11th Avenue Sewer Main Replacement
On the west side of 11th Avenue immediately north of the High School, a 24-inch sewer main
wraps around the corner of Durston Road to the west until approximately Oaks Park Drive.
Figure 3-5: Project 4 Extents (checkered line)
This project is recommended for replacement due to the following risk factors:
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• These VCP pipes were installed in the late 60’s and are nearing the end of their useful
life.
• CCTV data indicates severe pipe defects throughout portions of this corridor, particularly
in front of the High School.
• As a critical sewer main, the flow in these pipes exceeds 3,100 gpm under wet weather
conditions.
3.1.5 Project 5: Plum Avenue Sewer Main Replacement
This project begins at the intersection of Plum Avenue and Peach Street with a 10-inch main
running north along Plum Avenue. The main continues up Plum Avenue and becomes a 12-inch
diameter at the intersection of Tamarack Street. The project extends along Juniper Street to the
intersection of Rouse Avenue.
Figure 3-6: Project 5 Extents (checkered line)
This project is recommended for replacement due to the following risk factors:
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• These VCP pipes were installed in the late 1930’s, making these pipes overdue for
replacement based on their expected useful life.
• CCTV data indicates several pipe defects throughout portions of this corridor.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 200 gpm.
3.1.6 Project 6: 4th Ave., Babcock Street and Grand Avenue Sewer
Main Replacement
This project includes the replacement and upsizing of the 8-inch main which starts at the corner
of Olive Street and 4th Avenue, extends north along 4th Avenue to Babcock Street, follows
Babcock Street to Grand Avenue, and wraps up to Main Street (see Figure 3-7).
Figure 3-7: Project 6 Extents (checkered line)
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This project is recommended for replacement due to the following risk factors:
• These VCP mains were installed in 1903, making them well past their expected lifespan
and overdue for replacement.
• d/D criteria of 75% is exceeded for much of the pipe in this main, indicating additional
flow capacity is needed.
• CCTV data indicates several pipe defects throughout portions of this corridor.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 500 gpm.
The recommended pipe diameters to be installed for this project are shown in Figure 3-8.
Figure 3-8: Project 6 Upsized Pipe Diameters (checkered line)
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3.1.7 Project 7: North 9th Avenue, West Villard Street, and South 9th
Avenue Sewer Main Replacement
Figure 3-9: Project 7 Extents (checkered line)
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This project includes the replacement of the 10-inch main that starts on South 9th Avenue just
south of Babcock Street. It continues to Willard Street, where it jogs east then north through
the alley where it continues to Durston Road. 370 feet of the 10-inch needs to be upsized to a
15-inch main. Further north, the slope increases and the pipe can be replaced with a 12-inch
diameter for the remainder of the project. This project is recommended for replacement due to
the following risk factors:
• These VCP mains were installed in between 1917 and 1952, making them well past their
expected lifespan and overdue for replacement.
• d/D criteria of 75% is exceeded for a small portion of the pipe in this main, indicating
additional flow capacity is needed.
• CCTV data indicates several pipe defects throughout portions of this corridor.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 600 gpm.
Figure 3-10: Project 7 Upsized Pipe Diameters (checkered line)
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3.1.8 Project 8: Harrison and 10th Avenue Sewer Main Replacement
Figure 3-11: Project 8 Extents (checkered line)
This project includes the replacement of the 10-inch main that starts at the corner of Harrison
Street and 6th Avenue and runs west to 10th Avenue. Roughly half of this stretch is 12-inch
diameter and should be replaced with 12-inch. From there the project extends north to Babcock
Street replacing the 12-inch main. A small segment of 12-inch main on Curtis Street is also
included. This project is recommended for replacement due to the following risk factors:
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• These VCP mains were installed in 1954, placing them at the end of their expected
lifespan and due for replacement.
• CCTV data indicates several pipe defects throughout portions of this corridor.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 1,300 gpm.
3.1.9 Project WWIF20: North Frontage Rd Interceptor
Figure 3-11: Project WWIF20 North Frontage Rd Interceptor (checkered line)
• As a critical sewer main, the flow in several of the pipes exceeds 3,100 gpm under wet
weather conditions.
• d/D criteria of 75% is exceeded for much of the pipe in this critical sewer main, indicating
additional flow capacity is needed.
• Average RUL of the pipes is around 15 years as of the date of this report.
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3.2 6-inch Sewer Main Replacement Projects
In addition to the risk assessment performed over the entire wastewater system, a secondary risk
assessment was performed on pipe segments that were 6-inches or less in diameter whose
material is VCP. These pipes, designated as Small Pipes in this document, were identified and
analyzed for their risk to the City. The second assessment was needed due to the grading
system used in the wastewater system risk assessment. In the wastewater system risk
assessment, priority is given to pipes of higher flows, which results in smaller sized pipes
receiving less severe risk grading regardless of their LOF factors. Performing a separate risk
assessment on smaller diameter pipes ensures all necessary projects and improvements are
captured.
3.2.1 Likelihood of Failure Criteria and Weighting Factors
LOF criteria for the Small Pipe Risk Analysis are adopted from the Wastewater System Risk
Analysis, excluding LOF for pipe material. No changes were made to the scoring systems for the
LOF criteria, however, the weighting factors for the LOF Criteria were adjusted to provide higher
accuracy.
Table 3-1: LOF Criteria Weighting
Likelihood of Failure Criteria Weighting Factor
RUL 2
Wet-Weather Depth-to-Diameter Ratio 1
NASSCO Pipe Ratings 3
Pipe Main Repair 2
3.2.2 Consequence of Failure Criteria and Weighting Factors
COF criteria for the Small Pipe Risk Analysis were also adopted from the Wastewater System Risk
Analysis. The COF Criteria of Pipe Flow was given a weighting factor of 1. No changes were
made to the scoring system for the Pipe Flow criteria.
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3.2.3 Small Pipe Risk Results
The pipe risk results shown by size and risk category are shown in Table 3-2.
Table 3-2: Small Pipe Risk Results
Pipe Risk Category by Diameter (Length in Feet) Total
Length
(ft)
Diameter (in)
Negligible Low Medium High Extreme
<=6 2,665 4,925 36,116 10,977 15,940 70,623
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3.3 Small Pipe Capital Replacement Projects
The results of the small pipe risk assessment are used to identify key projects to replace small,
old VCP pipes within the system. Pipes that fell within the “Extreme” and “High” risk category
rankings were deemed eligible for projects.
Once projects were identified, a process of elimination began that took into consideration City
budgetary constraints and removed projects that overlapped with preexisting projects. After the
process of elimination, six small pipe projects were identified. For a comprehensive breakdown
of each project, visit the interactive dashboard found here:
ArcGIS Insights Small Pipe Dashboard
The following sections describe the extents of the small pipe replacement projects, as well as the
factors that caused these projects to be flagged as extreme risk in the analysis.
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Wastewater Collection System Facility Plan – 2024 Update
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3.3.1 Small Pipe Project 1: South Black Avenue 6-inch Sewer Main
Figure 3-12: Small Pipe Project 1 Extents (checkered line)
This project includes the replacement of the 6-inch main on South Black Avenue with an 8-inch
PVC pipe from W Main St to E College St. This pipe is recommended for replacement due to the
following risk factors:
• This section of VCP main was installed in 1907, placing it at the end of its expected
lifespan and due for replacement.
• d/D criteria of 75% is exceeded for a portion of the pipe in this main, indicating
additional flow capacity is needed.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 300 gpm.
• These combined risk factors make this a segment of pipe the City should prioritize for
replacement.
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Wastewater Collection System Facility Plan – 2024 Update
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3.3.2 Small Pipe Project 2: South Willson Avenue 6-inch Sewer Main
Figure 3-13: Small Pipe Project 2 Extents (checkered line)
This project includes the replacement of the 6-inch main on South Willson Avenue with an 8-
inch PVC pipe from W Main St to W College St. This pipe is recommended for replacement due
to the following risk factors:
• This section of VCP main was installed in 1902, placing it at the end of its expected
lifespan and due for replacement.
• CCTV data indicates several pipe defects throughout portions of this corridor.
• These combined risk factors make this a segment of pipe the City should prioritize for
replacement.
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
3.3.3 Small Pipe Project 3: South Grand Avenue 6-inch Sewer Main
This project includes the replacement of the 6-inch main on South Grand Avenue with an 8-inch
PVC pipe from W Babcock St to W Dickerson St. This pipe is recommended for replacement due
to the following risk factors:
• This section of VCP main was installed in 1902, placing it at the end of its expected
lifespan and due for replacement.
• CCTV data indicates several pipe defects throughout portions of this corridor.
• These combined risk factors make this a segment of pipe the City should prioritize for
replacement.
Figure 3-14: Small Pipe Project 3 Extents (checkered line)
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
3.3.4 Small Pipe Project 4: West Olive Street 6-inch Sewer Main
Figure 3-15: Small Pipe Project 4 Extents (checkered line)
This project includes the replacement of the 6-inch main on South Grand Avenue with an 8-inch
PVC pipe along S 6th Ave and Olive Street to S 3rd Ave. This pipe is recommended for
replacement due to the following risk factors:
• This section of VCP main was installed in 1917, placing it at the end of its expected
lifespan and due for replacement.
• d/D criteria of 75% is exceeded for a portion of the pipe in this main, indicating
additional flow capacity is needed.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 250 gpm.
• These combined risk factors make this a segment of pipe the City should prioritize for
replacement.
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
3.3.5 Small Pipe Project 5: South 4th Avenue 6-inch Sewer Main
Figure 3-16: Small Pipe Project 5 Extents (checkered line)
This project includes the replacement of the 6-inch main on South 4th Ave with an 8-inch PVC
pipe from W College St to W Hayes St. This pipe is recommended for replacement due to the
following risk factors:
• This section of VCP main was installed in 1927, placing it at the end of its expected
lifespan and due for replacement.
• This pipe has had multiple sewer stoppage reports recorded throughout its life.
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Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
• CCTV data indicates several pipe defects throughout portions of this corridor.
• These combined risk factors make this a segment of pipe the City should prioritize for
replacement.
3.3.6 Small Pipe Project 6: South 3rd Avenue 6-inch Sewer Main
Figure 3-17: Small Pipe Project 6 Extents (checkered line)
Technical Memorandum 8.0 Page 39
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
This project includes the replacement of the 6-inch main on South 3rd Ave with an 8-inch PVC
pipe from W College St to W Garfield St. This pipe is recommended for replacement due to the
following risk factors:
• This section of VCP main was installed in 1907, placing it at the end of its expected
lifespan and due for replacement.
• d/D criteria of 75% is exceeded for a portion of the pipe in this main, indicating
additional flow capacity is needed.
• This project is less of a critical sewer main than most of the recommended projects in
this assessment, however the wet weather flow still exceeds 110 gpm.
• These combined risk factors make this a segment of pipe the City should prioritize for
replacement.
Technical Memorandum 8.0 Page 40
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
Chapter 4 Future Risk Model Updates
As mentioned previously in this report, the risk analysis results must be viewed as prioritization
based on the best available data at the time. To get the most value out of the risk model, as the
City continues to complete CCTV inspections, routine maintenance, and updates of GIS records,
the risk model should be updated. There is not a prescribed frequency for incorporating these
updates into the risk model, but a good practice would be to complete these updates on an
annual basis. This helps ensure that valuable data does not get overlooked and omitted from
the risk analysis.
If data collection standards are maintained and followed, updating the risk model is a very
simple and straightforward process. The following paragraphs summarize the steps to be taken
to update the risk model annually.
4.1 GIS Updates
The risk model is built 1:1 with the City’s GIS database. This means that the element locations
and ID’s in the risk model are identical to the export the City provided for the development of
the risk model. As the City adds more elements and improves the accuracy of the information
within GIS, those files simply need to be swapped out in InfoAsset Planner. When the new GIS
layer is referenced in InfoAsset Planner, the user will need to re-map the system fields with the
client fields, as shown in Figure 4-1.
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Technical Memorandum 8.0 – Risk Assessment
Figure 4-1: Field Mapping for Sanitary Sewer Mains
The same re-mapping process is followed for the shapefile containing the sewer manholes.
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Technical Memorandum 8.0 – Risk Assessment
4.2 CCTV Updates
For incorporation of CCTV updates, the City should follow the following steps:
1. Export coded CCTV results from GraniteNET to a csv file
2. Follow the CCTV LOF scoring process outlined in section 1.3.3, where the PRS and PRI
correspond to the Total_PR and Total_PRI columns from the GraniteNET query results.
3. The facility IDs in GraniteNET correspond to the facility IDs in the risk model, making the
updates as simple as a join based on facility ID in GIS.
4.3 Work Order (Sewer Stoppage) Updates
Future work order incorporation can be accomplished in a number of ways depending on how
the City tracks sewer stoppage going forward. For the initial development of the risk model, the
City’s sewer stoppage report was exported to a csv file and used to determine the number of
stoppages reported for each sewer main. The facility ID in the stoppage report aligns with the
facility ID in the risk model, making the updates as simple as a join based on facility ID in GIS.
Alternatively, if the City decides to start tracking sewer stoppage utilizing a geodatabase or
shapefile in GIS to record locations of stoppages with the corresponding facility ID, this shapefile
could simply be uploaded to the risk model to update the corresponding LOF criteria.
4.4 Risk Model Re-Run
Once any data updates are complete, re-running the risk model is completed in three simple
steps.
1. Within the “Operation Center,” the user should right
click on the heading “Consequence of Failure COF” and
select “Batch Run”. Each of the COF factors should be
re-run.
2. The same process is followed with “Likelihood of
Failure” factors, and a “Batch Run” should be
completed to update each of the factors.
3. Finally, the calculations are completed in a similar
fashion by right clicking on “Risk” within the
“Operation Center” and running a batch run of each of
the desired risk scenarios.
Technical Memorandum 8.0 Page 43
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 8.0 – Risk Assessment
Over time the City will likely develop multiple risk scenarios with additional criteria or weighting
factors to analyze model sensitivity. These updates can be simply incorporated by right clicking
on the respective field to be modified in the “Operation Center” and selecting “New”. This will
allow the City to add new COF criteria, new LOF criteria, or an additional risk scenario with
modified weighting factors.
4.5 Conclusion
Detailed cost estimates for the pipe replacement projects outlined in the risk assessment are
included in the subsequent Capital Improvement Project memo.
Following the risk assessment procedures outlined in this memo will allow the City to maintain a
transparent and defensible method for prioritizing sewer main replacements.
Technical Memorandum 8.0 Page 44
9.0
Capital Improvement Plan
Technical Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 9.0 – Capital Improvement Plan
Table of Contents
Chapter 1 Introduction...........................................................................................................6
1.1 Opinions of Probable Project Cost................................................................................................................6
1.2 Estimate Classification ......................................................................................................................................7
1.3 Estimate Exclusions............................................................................................................................................7
Chapter 2 Total Estimated Project Cost ................................................................................8
2.1 Hard Costs............................................................................................................................................................8
2.2 Component Unit Costs ....................................................................................................................................8
2.3 Paved Gravity Sewer Mains............................................................................................................................8
2.4 Other Sewer Main Items .................................................................................................................................9
2.5 Sewer Lift Station Facilities ........................................................................................................................... 10
2.6 Hard Cost Markups..........................................................................................................................................11
2.7 Soft Costs ............................................................................................................................................................11
2.8 Property Acquisition Costs ........................................................................................................................... 12
2.9 Contingency ...................................................................................................................................................... 12
2.10 Inflation ............................................................................................................................................................. 12
2.11 Summary of Estimate Markups..................................................................................................................13
Chapter 3 Recommended Improvements........................................................................... 14
3.1 Risk Assessment Improvements ..................................................................................................................14
3.2 Growth and Development Improvements ..............................................................................................14
3.3 Lift Station Improvements ............................................................................................................................ 15
Chapter 4 Near-Term (5-Year) Capital Improvement Plan...............................................16
4.1 8-inch and Larger Sewer Main Replacement Projects.........................................................................18
4.1.1 Project 1: 19th Ave / Kagy Blvd Interceptor Improvements ................................................. 18
4.1.2 Project 2: Durston Road and 17th Avenue Sewer Main Replacement........................... 22
4.1.3 Project 3: 7th Avenue to Oak Street Sewer Main Replacement ...................................... 23
4.1.4 Project 4: North 11th Avenue Sewer Main Replacement.................................................... 24
4.1.5 Project 5: Plum Avenue Sewer Main Replacement.............................................................. 25
4.1.6 Project 6: 4th Avenue, Babcock Street and Grand Avenue Sewer Main
Replacement ............................................................................................................................. 26
4.1.7 Project 7: North 9th Avenue, West Villard Street, and South 9th Avenue Sewer
Main Replacement .................................................................................................................. 28
4.1.8 Project 8: West Harrison Street, 10th Avenue, and West Curtiss Street Sewer
Main Replacement .................................................................................................................. 30
4.2 6-inch and Smaller Sewer Main Replacement Projects ...................................................................... 31
4.2.1 Small Pipe Project 1: South Black Avenue 6-inch Sewer Main ......................................... 32
4.2.2 Small Pipe Project 2: South Willson Avenue 6-inch Sewer Main .................................... 33
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4.2.3 Small Pipe Project 3: South Grand Avenue 6-inch Sewer Main....................................... 34
4.2.4 Small Pipe Project 4: West Olive Street 6-inch Sewer Main.............................................. 35
4.2.5 Small Pipe Project 5: South 4th Avenue 6-inch Sewer Main.............................................. 36
4.2.6 Small Pipe Project 6: South 3rd Avenue 6-inch Sewer Main .............................................37
4.3 Lift Station Improvement Projects ............................................................................................................ 38
4.3.1 Lift Station Project 1: Valley Center Lift Station ..................................................................... 38
4.4 Summary of Near-Term (5-Year) Capital Improvement Projects................................................... 38
Chapter 5 Long-Term (6-20-Year) Capital Improvement Plan.........................................40
5.1 8-inch and Larger Sewer Main Replacement Project...........................................................................41
5.1.1 Project 9: N Grand Ave Sewer Replacement...........................................................................41
5.1.2 Project 10: N 20th Ave Sewer Replacement............................................................................. 42
5.1.3 Project 11: Upper Front Street Interceptor and Highland Glen Sewer Main
Replacement ............................................................................................................................. 43
5.1.4 Project 12: S Grand Ave Sewer Replacement......................................................................... 44
5.1.5 Project 13: N 19th Ave Sewer Replacement ............................................................................. 45
5.1.6 Project 14: W Oak St Sewer Replacement............................................................................... 46
5.1.7 Project 15: E Lamme St Sewer Replacement .......................................................................... 46
5.1.8 Project 16: Plum Ave Sewer Replacement............................................................................... 47
5.2 6-inch and Smaller Sewer Main Replacement Projects ..................................................................... 48
5.2.1 Small Pipe Project 7: Main Street Sewer Main Replacement............................................48
5.2.2 Small Pipe Project 8: S Bozeman Ave, E Story St, and Dell Pl Sewer Main
Replacement ............................................................................................................................. 49
5.2.3 Small Pipe Project 9: S 5th Ave and Alleys Sewer Main Replacement............................ 50
5.2.4 Small Pipe Project 10: S 6th Ave Sewer Main Replacement ................................................ 51
5.2.5 Small Pipe Project 11: W Lamme St Sewer Main Replacement ........................................ 52
5.2.6 Small Pipe Project 12: S 4th Ave and S 3rd Ave Sewer Main Replacement.................... 53
5.2.7 Small Pipe Project 13: S 7th Ave Sewer Main Replacement................................................ 54
5.2.8 Small Pipe Project 14: S 3rd Ave Sewer Main Replacement ............................................... 55
5.2.9 Small Pipe Project 15: N Black Ave, E Cottonwood St, and N Tracy Ave Sewer
Replacement ............................................................................................................................. 56
5.2.10 Small Pipe Project 16: Ida Ave and Fridley St Sewer Replacement ..................................57
5.2.11 Small Pipe Project 17: E Cottonwood St Sewer Replacement........................................... 58
5.2.12 Small Pipe Project 18: E Aspen St Sewer Replacement....................................................... 58
5.2.13 Small Pipe Project 19: N 3rd Ave Sewer Replacement ......................................................... 59
5.2.14 Small Pipe Project 20: N 8th Ave Sewer Replacement......................................................... 60
5.2.15 Small Pipe Project 21: W Lamme St Sewer Replacement.................................................... 61
5.2.16 Small Pipe Project 22: W Mendenhall St .................................................................................. 61
5.2.17 Small Pipe Project 23: W Main St and W Babcock St Alley Sewer Replacement ....... 62
5.2.18 Small Pipe Project 24: W Main St Sewer Replacement....................................................... 62
5.2.19 Small Pipe Project 25: S 5th Ave Sewer Replacement.......................................................... 63
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5.2.20 Small Pipe Project 26: W Story St and S 6th Ave Sewer Replacement ........................... 64
5.2.21 Small Pipe Project 27: S 9th Ave and S 8th Ave Alley Sewer Replacement.................... 65
5.2.22 Small Pipe Project 28: S 8th Ave and S 7th Ave Sewer Main Replacement................. 66
5.2.23 Small Pipe Project 29: S Wallace Ave Sewer Replacement.................................................67
5.2.24 Small Pipe Project 30: E Main St Sewer Replacement......................................................... 68
5.2.25 Small Pipe Project 31: E Mendenhall St Sewer Replacement............................................ 68
5.2.26 Small Pipe Project 32: S Church Ave Sewer Replacement................................................. 69
5.2.27 Small Pipe Project 33: W Babcock St Sewer Replacement .................................................70
5.2.28 Small Pipe Project 34: S 6th Ave Sewer Replacement...........................................................70
5.2.29 Small Pipe Project 35: W Babcock Ave, W Olive St, and S 7th Ave Sewer Main
Replacement .............................................................................................................................. 71
5.2.30 Small Pipe Project 36: W Main St, S Tracy Ave, and E Babcock St Sewer Main
Replacement .............................................................................................................................. 71
5.3 Lift Station Improvement Projects..............................................................................................................72
5.3.1 Lift Station Project 2: Coulee Drive.............................................................................................72
5.3.2 Lift Station Project 3: Spring Hill..................................................................................................73
5.3.3 Lift Station Project 4: Gooch Hill ................................................................................................ 74
5.3.4 Lift Station Project 5: Hidden Valley...........................................................................................75
5.3.5 Lift Station Project 6: Davis Lane.................................................................................................76
5.3.6 Lift Station Project 7: Laurel Glen................................................................................................77
5.3.7 Lift Station Project 8: Loyal Gardens..........................................................................................78
5.4 Summary of Long-Term Capital Improvement Projects.....................................................................79
Chapter 6 Relevancy of Previously Recommended Yet to be Constructed CIP’s ........... 81
Chapter 7 Conclusion............................................................................................................ 86
List of Tables
Table 2-1: Paved Gravity Main Cost per Linear Foot .........................................................................................9
Table 2-2: Sewer Main Connection Costs............................................................................................................10
Table 2-3: Sewer Main Crossing Costs..................................................................................................................10
Table 2-4: Total Estimate Project Markup Summary .......................................................................................13
Table 3-1: Lift Station Existing and Needed Capacity Summary.................................................................15
Table 4-1: Summary of Near Term (5-year) Capital Improvement Projects ...........................................38
Table 5-1: Summary of Long-Term Capital Improvement Projects ...........................................................79
Technical Memorandum 9.0 Page 3
List of Figures
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 9.0 – Capital Improvement Plan
Figure 4-1: Project 1 Extents (checkered line)....................................................................................................19
Figure 4-2: Project 1 Upsized Pipe Diameters....................................................................................................20
Figure 4-3: Project 2 Extents (checkered line)....................................................................................................22
Figure 4-4: Project 3 Extents (checkered line)....................................................................................................23
Figure 4-5: Project 4 Extents (checkered line)....................................................................................................24
Figure 4-6: Project 5 Extents (checkered line)....................................................................................................25
Figure 4-7: Project 6 Extents (checkered line)....................................................................................................26
Figure 4-8: Project 6 Upsized Pipe Diameters (checkered line)...................................................................27
Figure 4-9: Project 7 Extents (checkered line)....................................................................................................28
Figure 4-10: Project 7 Upsized Pipe Diameters (checkered line) ................................................................29
Figure 4-11: Project 8 Extents (checkered line)..................................................................................................30
Figure 4-12: Small Pipe Project 1 Extents (checkered line) ...........................................................................32
Figure 4-13: Small Pipe Project 2 Extents (checkered line) ...........................................................................33
Figure 4-14: Small Pipe Project 3 Extents (checkered line) ...........................................................................34
Figure 4-15: Small Pipe Project 4 Extents (checkered line) ...........................................................................35
Figure 4-16: Small Pipe Project 5 Extents (checkered line) ...........................................................................36
Figure 4-17: Small Pipe Project 6 Extents (checkered line) ...........................................................................37
Figure 4-18: Valley Center Lift Station ..................................................................................................................38
Figure 5-1: Project 9 Extents (checkered line)....................................................................................................41
Figure 5-2: Project 10 Extents (checkered line)..................................................................................................42
Figure 5-3: Project 11 Extents (checkered line)..................................................................................................43
Figure 5-4: Project 12 extents (checkered line)..................................................................................................44
Figure 5-5: Project 13 Extents (checkered line)..................................................................................................45
Figure 5-6: Project 14 Extents (checkered line)..................................................................................................46
Figure 5-7: Project 15 Extents (checkered line)..................................................................................................46
Figure 5-8: Project 16 Extents (checkered line)..................................................................................................47
Figure 5-9: Small Pipe Project 7 Extents (checkered line)..............................................................................48
Figure 5-10: Small Pipe Project 8 Extents (checkered line) ...........................................................................49
Figure 5-11: Small Pipes Project 9 Extents (checkered line) .........................................................................50
Figure 5-12: Small Pipe Project 10 Extents (checkered line).........................................................................51
Figure 5-13: Small Pipe Project 11 Extents (checkered line).........................................................................52
Figure 5-14: Small Pipe Project 12 Extents (checkered line).........................................................................53
Figure 5-15: Small Pipe Project 13 Extents (checkered line).........................................................................54
Figure 5-16: Small Pipe Project 14 Extents (checkered line).........................................................................55
Figure 5-17: Small Pipe Project 15 Extents (checkered line).........................................................................56
Figure 5-18: Small Pipe Project 16 Extents (checkered line).........................................................................57
Figure 5-19: Small Pipe Project 17 Extents (checkered line).........................................................................58
Figure 5-20: Small Pipe Project 18 Extents (checkered line).........................................................................58
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Figure 5-21: Small Pipe Project 19 Extents (checkered line).........................................................................59
Figure 5-22: Small Pipe Project 20 Extents (checkered line).........................................................................60
Figure 5-23: Small Pipe Project 21 Extents (checkered line).........................................................................61
Figure 5-24: Small Pipe Project 22 Extents (checkered line).........................................................................61
Figure 5-25: Small Pipe Project 23 Extents (checkered line).........................................................................62
Figure 5-26: Small Pipe Project 24 Extents (checkered line).........................................................................62
Figure 5-27: Small Pipe Project 25 Extents (checkered line).........................................................................63
Figure 5-28: Small Pipe Project 26 Extents (checkered line).........................................................................64
Figure 5-29: Small Pipe Project 27 Extents (checkered line).........................................................................65
Figure 5-30: Small Pipe Project 28 Extents (checkered line).........................................................................66
Figure 5-31: Small Pipe Project 29 Extents (checkered line).........................................................................67
Figure 5-32: Small Pipe Project 30 Extents (checkered line).........................................................................68
Figure 5-33: Small Pipe Project 31 Extents (checkered line).........................................................................68
Figure 5-34: Small Pipe Project 32 Extents (checkered line).........................................................................69
Figure 5-35: Small Pipe Project 33 Extents (checkered line).........................................................................70
Figure 5-36: Small Pipe Project 34 Extents (checkered line).........................................................................70
Figure 5-37: Small Pipe Project 35 Extents (checkered line).........................................................................71
Figure 5-38: Small Pipe Project 36 Extents (checkered line).........................................................................71
Figure 5-39: Coulee Drive LS.....................................................................................................................................72
Figure 5-40: Spring Hill Lift Station ........................................................................................................................73
Figure 5-41: Gooch Hill Lift Station ........................................................................................................................74
Figure 5-42: Hidden Valley Lift Station................................................................................................................75
Figure 5-43: Davis Lane Lift Station........................................................................................................................76
Figure 5-44: Laurel Glen LS ......................................................................................................................................77
Figure 5-45: Loyal Gardens LS..................................................................................................................................78
Figure 6-1: North Frontage Road Interceptor ....................................................................................................81
Figure 6-2: Davis-Fowler Interceptor.....................................................................................................................82
Figure 6-3: WRF Interceptor......................................................................................................................................83
Figure 6-4: Cottonwood Rd Capacity ....................................................................................................................84
Technical Memorandum 9.0 Page 5
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 9.0 – Capital Improvement Plan
Chapter 1 Introduction
This Technical Memorandum presents recommended capital improvement projects identified
while evaluating hydraulic performance of the existing and future wastewater collection system.
This Capital Improvement Plan (CIP) includes recommended projects to address near-term (5
year) and long-term (6-20 year) needs. The recommended wastewater collection system
improvement projects are based on the results of:
1. The existing and future system evaluations -Hydraulic Model Development and Results
Technical Memorandum (TM 7).
2. The risk-based system assessment-Risk Assessment Technical Memorandum (TM 8); and
3. Multiple meetings with City staff.
An all-inclusive list of identified improvement projects was compiled for a comprehensive CIP
evaluation. Cost estimates were generated for each project and the projects were placed into
their respective planning periods to facilitate spending capital dollars in the most cost-effective
manner possible.
This memorandum includes descriptions of the CIP project categories, cost estimate
methodology, implementation considerations, and a summary of each recommended
improvement.
1.1 Opinions of Probable Project Cost
The opinion of probable project cost (OPPC) values are based on the total capital investment
necessary to complete a project from engineering design through construction. All estimates are
based on engineering experience and judgment, recent bid tabulations for projects of similar
scope, and input from area contractors and material suppliers. All costs are presented in 2022
dollars and inflated for each CIP project based on the estimated year it will be bid or
constructed.
Total estimated project costs were divided into five main components, as follows:
• Hard Costs – The actual physical construction of the project (i.e., excavation, materials,
labor, restoration).
• Soft Costs – Fees not directly related to labor and building materials (i.e., architecture
and engineering fees, permitting/environmental, contract administration, legal).
• Property Acquisition Costs – The cost to obtain property, right-of-way, and easements.
• Contingency – Amount added to the estimated cost to cover both identified and
unidentified risk events that occur on the project.
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Technical Memorandum 9.0 – Capital Improvement Plan
• Inflation – The application of the average annual inflation rate anticipated between the
time an estimate is prepared and when the project is bid or projected for construction.
The sum of these five components is the total OPPC. The OPPC values are based on the
preliminary concepts and layouts of the wastewater system components developed as a result of
the hydraulic modeling of the system and corresponding recommendations. The estimate is to
be an indication of fair market value and is not necessarily a reflection of the lowest bid. Fair
market value is assumed to be mid-range tender considering four or more competitive bids.
1.2 Estimate Classification
The Association for the Advancement of Cost Engineering (AACE) provides guidelines for
applying the general principles of estimate classification to project cost estimates (i.e., cost
estimates that are used to evaluate, approve, and/or fund projects). The purpose for following a
classification process is to align the level of estimating with the use of the information. The
estimates provided in the CIP are classified in accordance with the criteria established by AACE
cost estimating classification system referred to as Standard Practice 18R‐97.
In accordance with AACE criteria, the OPPC values are representative of Class 4 estimates. A
Class 4 estimate is defined as a study or feasibility estimate. Typically, the engineering effort is
from 1 to 15 percent complete. Class 4 estimates are used to prepare planning-level effort cost
scopes or complete an evaluation of alternative schemes, technical feasibility, and preliminary
budget approval or approval to proceed to the next stage of implementation.
Expected accuracy for Class 4 estimates typically range from -30 to +50 percent, depending on
the technical complexity of the project, appropriate reference information, and the inclusion of
an appropriate contingency determination. Ranges could exceed those shown in unusual
circumstances.
1.3 Estimate Exclusions
Unless specifically identified, the following estimating exclusions were assumed in the
development of the cost estimates:
• Environmental mitigation of hazardous materials and/or disposal.
• O&M costs for the project components.
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Technical Memorandum 9.0 – Capital Improvement Plan
Chapter 2 Total Estimated Project Cost
The following sections provide a breakdown of the different items included in each cost
component associated with developing the total OPPC for each project.
2.1 Hard Costs
Hard costs, sometimes referred to as contractor construction costs, represent the actual physical
construction of a project. This section was divided into component unit costs and hard cost
markups. The following sources of information were used to compile the hard cost estimates:
• Review of previous construction bid tabs for similar projects;
• Review of historical bid prices for the City;
• Vendor, supplier, and contractor estimates for specific equipment and materials.
2.2 Component Unit Costs
All estimates are based on engineering experience and judgment, recent bid tabulations for
projects of similar scope, cost indexing, and input from area contractors and material suppliers.
For specific equipment and materials, information was requested from vendors and suppliers
and the costs were increased by applying a multiplication factor to include the related costs and
expenses (such as labor, connections, and miscellaneous materials) required to complete the
installation.
2.3 Paved Gravity Sewer Mains
The pipe material assumed for new gravity sewer mains located within paved public right-of-
way was ASTM D3034 SDR35 PVC for pipes ranging from 8-inches to 16-inches in diameter,
while pipe sizes between 18-inches and 42-inches were assumed to be ASTM F679 PS46 PVC.
Table 2-1 presents the paved gravity main construction costs. The costs are based on the
following assumptions:
• Pipe Size with full depth import backfill (8’ to 12’ depth)
• Manhole every 200 ft plus extra vertical depth
• Pavement sawcut and removal
• 4” asphalt paving at 14 sq ft per foot
• Number of laterals replaced, assuming a 45-foot lateral length per connection.
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Table 2-1: Paved Gravity Main Cost per Linear Foot
Pipe Diameter PVC Pipe ($/linear foot)
(inches)
8 $210
10 $215
12 $222
14 $228
15 $231
16 $234
18 $240
20 $246
21 $248
24 $258
27 $267
30 $276
36 $306
42 $318
Please note that the costs of curb and gutter or sidewalk removal and replacement are not
included in the unit costs presented in Table 2-1.
2.4 Other Sewer Main Items
Additional items included in the sewer main cost estimates are presented below:
•Sewer Main Connections of proposed mains to other mains in the system (Table 2-2);
• Sewer Main Crossings (
• Table 2-3).
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Table 2-2: Sewer Main Connection Costs
Connecting Pipe Diameter (inches) Cost per Connection
($/each)
Existing Sewer Service Connection (including 45 feet $5,500
of lateral replacement)
Existing Sewer Main Connection $5,400
Lift Station Connection $5,400
10’H x 10’L x 5’W Specialty Manifold Structure $15,400
Table 2-3: Sewer Main Crossing Costs
Pipe Diameter (inches) Crossing Type Cost ($/linear foot)
18 -24 Highway Bore with Space Constraints $770
27 -36 Highway Bore with Space Constraints $1,030
8 -18 Road Crossing/Bore $410
2.5 Sewer Lift Station Facilities
Project costs for proposed lift station facilities were prepared for several different sizes. Costs
were based on information obtained from package lift station vendors, previous construction
experience, and recently bid projects for similar lift station projects. The cost is based on the
following assumptions:
•Wet well structures vary depending on associated capacity requirements;
•Includes major components (i.e., pumps, fittings, valves, electrical, emergency generator,
odor control, and communications).
Project cost estimates for construction of sewer lift stations were based on planning level costs
depending on overall capacity and whether it was for a retrofit of an existing lift station or
construction of a new lift station facility. Costs assigned to lift stations were general in definition
and items such as vault assemblies associated with force mains were not included but would
likely be covered as part of project contingencies if needed.
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2.6 Hard Cost Markups
Hard costs markups are applied to the hard costs and construction costs to calculate total
construction costs. The hard cost markups are reflected in the individual capital improvement
project cost estimates. Markups vary depending on the size and type of the project.
• Mobilization/demobilization/insurance/permits/bonds – 6 percent
o Mobilization costs include the administrative costs and expenses to mobilize
materials, equipment, and labor to the jobsite and demobilize upon project
completion. Costs associated with contractor insurance, permits, and bonding are
also included.
• Traffic Control – 2 percent
o Traffic control was assigned to projects that occur in the public right-of-way,
primarily gravity main replacement or force main projects.
• Erosion Control – 1 percent
o Erosion control is required for all construction projects to ensure compliance with
Storm Water Pollution Prevention Plans.
• Testing and Construction Surveying – 3 percent
o Costs associated with materials testing during construction in addition to
construction surveying and staking.
• Existing Utility Adjustments – 10 percent
o This hard cost markup was only applied to gravity sewer main installation projects
within urban areas where utility conflicts and associated re-routing are anticipated.
2.7 Soft Costs
To adequately complete the planning, design, and construction of projects listed in this CIP,
there are significant soft costs that will be required. Soft costs are non-construction labor costs
consisting of architecture and engineering fees, permitting and environmental compliance,
contract administration, legal fees, etc. Soft costs are applied to the hard costs plus the hard
cost markups. A breakdown and summary of the soft costs that were included in the cost
estimates are provided below.
• Engineering Design – 10 percent
o Costs include preliminary engineering through final design, which involves the
development of final project plans and specifications that will be stamped by a
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professional consulting engineer. Engineering costs include disciplines such as
process, civil, electrical, mechanical, architectural, and structural. Costs also include
surveying, testing, investigations, and inspections during the design phase. Examples
include surveys of pipeline alignments and facility parcels, security and safety
inspections, material and geological testing, and inspection services.
• Construction Administration and Management – 8 percent
o Costs include services to provide quality control, quality assurance, and construction
management during the construction phase and services associated with the initial
operation including training of operational, maintenance, and supervisory staff.
• Legal and Administrative – 5 percent
o Costs associated with the local and State project approval process, and any legal
costs, are included in this category. Responsible tasks may include road crossing
permits, construction permits, county building permits, inter-disciplinary team
meetings, NEPA compliance, expenses incurred by the City, etc.
2.8 Property Acquisition Costs
Property acquisition costs are associated with purchasing property and acquiring right-of-way or
easements for the project. Costs normally consist of payments to landowners. Costs for
purchasing property associated with a new lift station or lift station upgrades were generated
based on average 2022 real estate values of vacant lots with utilities within Bozeman urban
areas. Costs for acquiring right-of-way or easements were based on average 2022 real estate
values of City easements for rural land in Bozeman with generally no utilities. This was
appropriate for most of the identified CIP projects anticipated to be built outside of right-of-
way.
2.9 Contingency
A contingency is an amount added to the base cost to cover both identified and unidentified
risk events that occur on the project. The contingency value used was 30 percent. The
contingency values were added to the overall project base cost (i.e., hard and soft costs) in
anticipation of uncertainties inherent to the planning-level analysis completed for the BWWCS.
2.10 Inflation
Projects intended for construction several years in the future include a factor for inflationary
impacts to address the general trend of cost indices, which accounts for future labor, material,
and equipment cost increases beyond values at the time the estimate is prepared. For this
planning-level analysis, the 2022 project costs were inflated to the construction year anticipated
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for each CIP project. An annual average inflation rate was generated based on historic inflation
data to estimate inflation trends into the future.
2.11 Summary of Estimate Markups
Table 2-4 provides a summary of suggested hard costs markups, soft costs, and contingency
rate percentages.
Table 2-4: Total Estimate Project Markup Summary
Item
Mobilization/Demobilization/Insurance/Permits/Bonds
Erosion Control
Existing Utility Adjustments (as applicable)
Engineering Design
Legal and Administrative
Property Acquisition
Estimated Annual Inflation
6%
2%
1%
3%
10%
10%
8%
5%
Varies per acre
30%
5%
Technical Memorandum 9.0 Page 13
Hard Cost Markups
Traffic Control
Testing and Construction Surveying
Soft Costs
Construction Administration and Management
Other
Contingency
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 9.0 – Capital Improvement Plan
Chapter 3 Recommended Improvements
3.1 Risk Assessment Improvements
Projects identified through the collection system risk assessment target the replacement of
aging and failing infrastructure, which present a significant risk to the City. Failure can imply
infrastructure deterioration, or failure to meet the needed level of service such as flow capacity
limitations. It is important to note that all recommended pipe replacement projects in this
memo are sized for ultimate build out (UBO) conditions.
3.2 Growth and Development Improvements
The timing for growth and development projects can be difficult to predict. For this reason, the
City treats this class as its own separate category, and the prioritization of improvements is
evaluated as growth occurs. For the future system evaluation, needed improvements are broken
into four main categories:
1. Infill Internal Improvements
2. Infill Extensions
3. UBO Internal Improvements
4. UBO Extensions
Infill internal improvements include pipes that must be upsized when the undeveloped portions
of land within the existing City limits are developed as currently zoned. Infill extensions are
similar and include the new pipes needed to serve infill growth within the existing City limits.
UBO internal improvements include pipes within existing City limits that will need to be upsized
to serve the City at buildout conditions. UBO extensions are similar but include the pipe
extensions (not replacements) that will be needed to serve the City at buildout.
These pipe sizes and locations are discussed in detail in the Hydraulic Model Development and
Results Technical Memorandum (TM 7). For the purposes of the CIP, the majority of the “Infill
Internal Improvements” are addressed with the risk driven projects based on their age and
insufficient capacity (d/D between 0.5 and 0.75) and are included in the 5-year CIP. There are
two “Infill Internal Improvement” projects that are postponed to the 6–20-year CIP. Several “UBO
Internal Improvement” projects also overlap with the risk driven projects. All recommended pipe
replacement projects are sized to serve the City at buildout conditions.
Timing for the remainder of the growth projects should be driven based on the timing and
location of growth within the City. The Hydraulic Model Development and Results Technical
Memorandum (TM 7) includes details on the recommended pipe sizing for infill and UBO pipe
extensions and internal improvements.
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3.3 Lift Station Improvements
Lift station projects consist of existing lift stations that are anticipated to be under capacity prior
to full buildout and new lift stations that will serve future growth areas. Table 3-1 summarizes
the capacity of the three lift stations that must be upsized under infill and buildout conditions as
well as the new lift stations to be constructed for buildout conditions. This information is
provided to help understand the potential timing and priority of these projects which are driven
primarily by growth. The red text in the table indicates the time/growth period at which inflow is
anticipated to exceed existing firm capacity.
Table 3-1: Lift Station Existing and Needed Capacity Summary
Lift Station Name
Davis Lane
Laurel Glen
Loyal Gardens
Valley Center2,3
Hidden Valley2
Coulee Drive
Spring Hill
Gooch Hill
Existing Firm
Capacity (gpm)
5,000
450
364
-
-
-
-
-
Originally Planned
Buildout Capacity
(gpm)
10,400
600
N/A
Existing
Peak Flow
(gpm)
310
360
270
-
-
-
-
-
Infill Peak
Flow (gpm)
620
400
270
-
-
-
-
-
UBO Modeled
Peak Flow
(gpm)
14,040
400
370
1,620
2,230
2,270
5,480
6,770
2 The Valley Center lift station is being designed as of July 2024 to meet immediate growth needs adjacent to
City limits and will break the Baxter Creek Drainage Basin into two distinct sewersheds and allow for a
smaller Hidden Valley lift station than was presented in the 2015 Facility Plan.
3 The Valley Center lift station cost and capacity assumes the “shallow” alternative, as described in more
detail in the Baxter Creek Drainage Basin Analysis Technical Memorandum (AE2S, 2022).
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Chapter 4 Near-Term (5-Year) Capital Improvement
Plan
In coordination with City staff, the near-term (5-year) recommendations marked a departure
from previous strategies by utilizing both hydraulic models and risk assessment models to
prioritize capital planning needs. This dual approach provided a comprehensive view, identifying
high-risk areas, assets that have exceeded their useful service life, and specific infrastructure or
facilities needed to support future growth.
The comprehensive analysis revealed that the City's current replacement funding for FY23,
approximately $1 million per year, is insufficient to meet long-term needs. It should be increased
to maintain existing and future levels of service. Based on discussions with City staff and current
budgetary considerations, a $1.5 million per year increase to the City's wastewater replacement
fund was recommended. The proposed list of projects for the near term is approximately $12.5
million ($2.5 million per year). Depending on the project type, funding for the annual wastewater
pipe replacement is sourced either from utility rates or a combination of rates and impact fees.
Additionally, there are around 19 miles of existing 6-inch collection pipes (typically VCP) that
have reached the end of their useful life and require replacement and upsizing. These smaller
assets, typically serving single-family homes or smaller facilities, generally do not rank high in
the risk-based model when evaluating larger system assets (8-inch pipes and above). Moreover,
most of these pipes are located in existing service areas, which may not trigger growth-related
project upsizing.
Despite their lower risk ranking, City staff consider the replacement of these 6-inch pipes a
priority due to their age, material type, and service history. A separate risk assessment
specifically for the 6-inch pipes was completed and documented in TM8. Following discussions
with City staff, the establishment of a dedicated fund for the 6-inch replacement program was
recommended.
The 6-inch wastewater replacement program aims to replace approximately 19 miles of
undersized, aging collection pipes over a 25-year period. These pipes are not identified as high
risk for immediate replacement or rehabilitation under the City's annual wastewater pipe
replacement program. All 6-inch pipes will be upgraded to a minimum of 8-inch per city
standards or resized based on the City's Wastewater Facility Plan and hydraulic model.
Prioritization for the 6-inch replacement projects will generally align with the City's street
reconstruction program, new developments, and system risk compared to other 6-inch pipes.
Remaining funds will be used to update pipe condition data to better inform future capital
planning and project prioritization.
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The estimated cost for completing near-term projects involving 6-inch and smaller sewer
replacements is approximately $7.5 million. A fund of $1 million was recommended based on
discussions with City staff and the current budgetary framework.
Overall, considering the City's infrastructure needs, existing assets, and recommended
replacement cycles, the City should plan to spend approximately $4 million per year over the
next two decades to address existing replacement needs. Once the replacement of the 6-inch
assets is complete, the City may choose to roll this funding into the annual wastewater
replacement fund, depending on future needs. Additionally, if development partners collaborate
with the City on the 6-inch replacement, additional funding may become available sooner to
offset other emerging project needs.
A proactive approach will help maintain stable rates and consistent levels of service. The City
should periodically update these recommendations to reflect evolving needs and circumstances.
The near-term improvements presented include:
1. 8-inch and Larger Sewer Main Replacement
2. 6-inch and Smaller Sewer Main Replacement
3. Lift Station Improvements
Even if the identified projects take slightly longer than five years to complete at the current
funding level, the prioritization of these projects is suitable for addressing the challenge of aging
infrastructure. As each project is completed, the risk model should be updated, and the next
project should be identified and incorporated into the Capital Improvement Plan (CIP).
An interactive GIS dashboard showing the project extents and other pertinent details can be
accessed using the link below:
ArcGIS Insights CIP Dashboard
Additionally, the City’s complete capital improvement plan is included in an AE2S developed
web tool known as OptX. In addition to tracking capital improvement project timing and costs,
OptX can be used to track fund balances, revenue streams (utility rates, taxes, etc.), tie capital
projects to specific funds, evaluate revenue adequacy, and much more.
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4.1 8-inch and Larger Sewer Main Replacement Projects
4.1.1 Project 1: 19th Ave / Kagy Blvd Interceptor Improvements
The 19th Ave / Kagy Blvd Interceptor was flagged as lacking sufficient capacity under existing
and infill conditions at some locations, particularly in the upper sections between Kagy and West
Babcock Street. Additionally, this pipe is very old asbestos concrete and noted as high risk in the
risk analysis. Project 1 proposes to improve this interceptor from Kagy through the intersection
of South 9th Avenue and West Babcock Street. Project 1 is shown with a checkered line in Figure
4-1.
The total amount of pipe replaced in Project 1 is over 10,000 feet. It should be noted that some
portions of the existing 18-inch sewer at the downstream end of this project along South 6th
Avenue and West Babcock Street, may need to be upsized to a 21-inch under the UBO loading
in order for every segment to meet d/D standards.
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Figure 4-1: Project 1 Extents (checkered line)
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The recommended pipe diameters to be installed for this project are shown in Figure 4-2.
Figure 4-2: Project 1 Upsized Pipe Diameters
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Project 1 is needed to renew critical aging infrastructure identified in the risk analysis and
addresses infill capacity concerns. The recommended pipe sizes are set to provide sufficient
capacity for the UBO scenario.
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4.1.2 Project 2: Durston Road and 17th Avenue Sewer Main
Replacement
This project includes the 15-inch sewer main running west along Durston Road, which turns
north on 17th Ave. and becomes an 18-inch sewer main extending to Nelson Trailer Park. This
pipe should be replaced with the same diameter PVC pipe. The checkered line in Figure 4-3
below shows the project extents, and colored lines represent the current diameters of the pipe.
This project requires the replacement of 1,800 feet of pipe.
Figure 4-3: Project 2 Extents (checkered line)
Project 2 is needed to renew critical aging infrastructure identified in the risk analysis.
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4.1.3 Project 3: 7th Avenue to Oak Street Sewer Main Replacement
A 15-inch sewer main running north in the fields west of 7th Avenue turns east on Birch Street
and becomes an 18-inch main. Just before reaching 7th Avenue, the 18-inch main turns north
until it intersects Oak Street. This project continues along Oak Street until approximately 5th
Avenue. The total amount of pipe replaced in this project is 2,700 feet, which will match the
existing pipe diameters. The extents of the project can be seen below in Figure 4-4.
Figure 4-4: Project 3 Extents (checkered line)
Project 3 is needed to renew critical aging infrastructure identified in the risk analysis.
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4.1.4 Project 4: North 11th Avenue Sewer Main Replacement
On the west side of 11th Avenue immediately north of the High School, a 24-inch sewer main
wraps around the corner of Durston Road to the west until approximately Oak Park Drive. The
1,100 feet of pipe replaced in this project will be replaced with the same diameter pipe.
Figure 4-5: Project 4 Extents (checkered line)
Project 4 is needed to renew critical aging infrastructure identified in the risk analysis.
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4.1.5 Project 5: Plum Avenue Sewer Main Replacement
This project begins at the intersection of Plum Avenue and Peach Street with a 10-inch main
running north along Plum Avenue. The main continues up Plum Avenue and becomes a 12-inch
diameter at the intersection of Tamarack Street. The project extents continue along Juniper
Street to the intersection of Rouse Avenue. These pipes will be replaced with the same diameter,
with a total of 2,800 feet of pipe replaced between the 10-inch and 12-inch mains. The extents
of the project can be seen below in Figure 4-6.
Figure 4-6: Project 5 Extents (checkered line)
Project 5 is needed to renew critical aging infrastructure identified in the risk analysis.
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4.1.6 Project 6: 4th Avenue, Babcock Street and Grand Avenue Sewer
Main Replacement
This project includes the replacement and upsizing of the 10-inch main which starts at the
corner of Olive Street and 4th Avenue, extends north along 4th Avenue to Babcock Street, follows
Babcock Street to Grand Avenue, and wraps up to Main Street. The project extents can be seen
in Figure 4-7.
Figure 4-7: Project 6 Extents (checkered line)
The recommended pipe diameters to be installed for this project are shown in Figure 4-8. The
section of pipe between along W Babcock St and S 3rd Ave is recommended to be upsized to a
10-inch main. In total, 1,300 feet of pipe will be replaced in this project.
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Figure 4-8: Project 6 Upsized Pipe Diameters (checkered line)
Project 6 is needed to renew critical aging infrastructure identified in the risk analysis, but also
includes upsizing that is needed to alleviate existing capacity limitations.
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4.1.7 Project 7: North 9th Avenue, West Villard Street, and South 9th
Avenue Sewer Main Replacement
This project includes the replacement of the 10-inch main that starts on South 9th Avenue just
south of Babcock Street. It continues to Willard Street, where it jogs east then north through the
alley where it continues to Durston Road. 370 feet of the 10-inch needs to be upsized to a 15-
inch main as shown in Figure 4-9. Further north, the slope increases, and the pipe can be
replaced with a 12-inch diameter for the remainder of the project.
Figure 4-9: Project 7 Extents (checkered line)
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Figure 4-10 shows the pipe configuration with all the needed pipes upsized. In total, 3,000 feet
of pipe will be replaced and/or upgraded.
Figure 4-10: Project 7 Upsized Pipe Diameters (checkered line)
Project 7 is needed to renew critical aging infrastructure identified in the risk analysis.
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4.1.8 Project 8: West Harrison Street, 10th Avenue, and West Curtiss
Street Sewer Main Replacement
This project includes the replacement of the 10-inch main that starts at the corner of Harrison
Street and 6th Avenue and runs west to 10th Avenue. Roughly half of this stretch is 10-inch
diameter and should be replaced with 12-inch. From there the project extends north to Babcock
Street replacing the 12-inch main. A small segment of 12-inch main on W Curtiss Street is also
included. In total, 4,600 feet of pipe will be replaced. These pipes can be seen in Figure 4-11.
Figure 4-11: Project 8 Extents (checkered line)
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Project 8 is needed to renew critical aging infrastructure identified in the risk analysis.
4.2 6-inch and Smaller Sewer Main Replacement Projects
The projects included in this section are focused on replacing the old 6-inch VCP throughout the
sewer collection system. An interactive GIS dashboard showing the project extents and other
pertinent details can be accessed using the link below: ArcGIS Insights Small Pipe Dashboard
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4.2.1 Small Pipe Project 1: South Black Avenue 6-inch Sewer Main
This project includes the replacement of 3,000 feet of pipe along S Black Avenue. This pipe will
be upgraded to 8-inch PVC pipe as part of the replacement project. The extents of this project
are outlined with the checkered line in Figure 4-12.
Figure 4-12: Small Pipe Project 1 Extents (checkered line)
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4.2.2 Small Pipe Project 2: South Willson Avenue 6-inch Sewer Main
Project 2 involves the replacement of 3,000 feet of pipe along S Willson Ave. This pipe will be
upgraded from a 6-inch to an 8-inch diameter pipe as part of this project. The extents of this
project are outlined in Figure 4-13 with the checkered line.
Figure 4-13: Small Pipe Project 2 Extents (checkered line)
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4.2.3 Small Pipe Project 3: South Grand Avenue 6-inch Sewer Main
Project 3 involves the replacement of 2,500 feet of pipe along S Grand Ave. This pipe will be
upgraded from a 6-inch to an 8-inch diameter pipe as part of this project. The extents of this
project are outlined in Figure 4-14 with the checkered line.
Figure 4-14: Small Pipe Project 3 Extents (checkered line)
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4.2.4 Small Pipe Project 4: West Olive Street 6-inch Sewer Main
Project 4 involves the replacement of 1,000 feet of pipe along West Olive Street and South 6th
Avenue. This pipe will be upgraded from a 6-inch to an 8-inch diameter pipe as part of this
project. The extents of this project are outlined in Figure 4-15 with the checkered line.
Figure 4-15: Small Pipe Project 4 Extents (checkered line)
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4.2.5 Small Pipe Project 5: South 4th Avenue 6-inch Sewer Main
This project includes the replacement of 1,800 feet of pipe along S 4th Avenue. This pipe will be
upgraded to 8-inch pipe as part of the replacement project. The extents of this project are
outlined with the checkered line in Figure 4-16.
Figure 4-16: Small Pipe Project 5 Extents (checkered line)
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4.2.6 Small Pipe Project 6: South 3rd Avenue 6-inch Sewer Main
Project 6 involves the replacement of 1,500 feet of pipe along S 3rd Ave. This pipe will be
upgraded from a 6-inch to an 8-inch diameter pipe as part of this project. The extents of this
project are outlined in Figure 4-17 with the checkered line.
Figure 4-17: Small Pipe Project 6 Extents (checkered line)
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4.3 Lift Station Improvement Projects
Additional lift station capacity is needed under the Infill and UBO future condition scenarios. The
proposed lift stations and the existing lift station capacity expansions presented in this section
are sized to meet the UBO growth conditions. In the near-term improvements (5-year), only one
lift station project is recommended. The remainder of the projects are included in the long-term
improvements and will be driven by the timing of new growth.
4.3.1 Lift Station Project 1: Valley Center Lift Station
The Valley Center Lift Station (shown in Figure 4-18) is needed to support immediate growth
within the City. This 2.33 MGD lift station project includes 3,200 feet of new 12-inch diameter
force main.
Figure 4-18: Valley Center Lift Station
4.4 Summary of Near-Term (5-Year) Capital Improvement
Projects
A summary of the costs associated with the near-term capital improvement projects is included
in Table 4-1.
Table 4-1: Summary of Near Term (5-year) Capital Improvement Projects
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Improvement ID Location of Improvement
Project 1 19th Ave / Kagy Blvd Interceptor Improvements
Project 2 Durston Road and 17th Avenue Sewer Main
Replacement
Project 3 7th Avenue to Oak Street Sewer Main
Replacement
Project 4 North 11th Avenue Sewer Main Replacement
Project 5 Plum Avenue Sewer Main Replacement
Project 6 4th Avenue, Babcock Street and Grand Avenue
Sewer Main Replacement
Project 7 North 9th Avenue, West Villard Street, and
South 9th Avenue Sewer Main Replacement
Project 8 West Harrison Street, 10th Avenue, and Curtiss
Street Sewer Main Replacement
Subtotal for 8-inch and Larger Sewer Main Replacement Projects
Opinion of
Probable Cost
(2024 $)
$5,291,600
$959,900
$1,276,400
$574,400
$1,326,500
$665,000
$2,159,300
$2,478,600
$14,731,700
Lift Station Project 1 Valley Center Lift Station $5,962,700
Small Pipe Project 1 South Black Ave 6-inch Sewer Main
Replacement $1,817,000
Small Pipe Project 2 South Willson Ave 6-inch Sewer Main
Replacement $1,721,700
Small Pipe Project 3 South Grand Ave 6-inch Sewer Main
Replacement $1,377,600
Small Pipe Project 4 West Olive St 6-inch Sewer Main Replacement $691,400
Small Pipe Project 5 South 4th Ave 6-inch Sewer Main Replacement $961,100
Small Pipe Project 6 South 3rd Ave 6-inch Sewer Main Replacement
Subtotal for 6-inch and Smaller Sewer Main Replacement Projects
$971,800
$7,540,600
Total 5-Year Project Costs $28,235,000
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Chapter 5 Long-Term (6-20-Year) Capital
Improvement Plan
The most pressing infrastructure replacement needs are prioritized in the 5-year horizon.
However, additional needs exist beyond what can be funded in the next 5 years. These projects
are recommended for completion in the 6 to 20-year horizon. It should be noted that the risk
assessment completed to prioritize project needs is based on the best available information at
the time. As the City continues to complete CCTV inspections, new data should be incorporated
into the risk assessment. Although core elements driving project prioritization such as pipe
material, age, and diameter are unlikely to need revisions, CCTV inspections will help the City
have a clear understanding of the current condition of the infrastructure and adjustments to
project extents or timing can easily be completed.
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5.1 8-inch and Larger Sewer Main Replacement Project
5.1.1 Project 9: N Grand Ave Sewer Replacement
A section of 10-inch diameter sewer main begins at W Main St and travels along N Grand Ave.
Once the pipe reaches W Peach St, it transitions to a 15-inch diameter main. This is shown with a
checkered line in Figure 5-1. The total amount of pipe replaced in Project 9 totals 3,400 ft.
Figure 5-1: Project 9 Extents (checkered line)
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5.1.2 Project 10: N 20th Ave Sewer Replacement
A section of sewer begins at W Babcock St and travels under industrial lots and joins N 20th Ave
just before W Beall St. The main continues along N 20th Ave to Durston Rd. The entirety of this
section is 10-inch diameter pipe. The total pipe replaced in this project is 2,700 ft. The checkered
line in Figure 5-2 below shows the extents of the project.
Figure 5-2: Project 10 Extents (checkered line)
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5.1.3 Project 11: Upper Front Street Interceptor and Highland Glen
Sewer Main Replacement
Project 11 involves replacing the upper portion of the Front Street interceptor and the Highland
Glen sewer main extending south. Existing pipe will need to be upsized to meet Infill loading but
was sized to provide capacity for the UBO scenario. The project extents are shown below by the
checkered line in Figure 5-3. A total of approximately 6,300 feet of gravity main varying in size
from 12-to 18-inch will replace the existing pipe. Under the Increased Density scenario, this
interceptor would experience up to 0.90 d/D all the way to Tamarack Street. Additional
monitoring and analysis may be warranted as the area contributing builds out.
Figure 5-3: Project 11 Extents (checkered line)
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5.1.4 Project 12: S Grand Ave Sewer Replacement
This section of pipe begins in the neighborhood just south of the beginning of S Grand Ave.
Once the pipe reaches S Grand Ave, it follows S Grand Ave to W Dickerson St. The pipe starts as
an 8-inch main, then downsizes to a 6-inch main once the pipe exits the neighborhood. Project
12 encompasses 1,600 feet of pipe. Existing pipe diameters and planned project extents can be
seen in Figure 5-4.
Figure 5-4: Project 12 extents (checkered line)
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5.1.5 Project 13: N 19th Ave Sewer Replacement
This project includes a 24-inch sewer main that begins at the intersection of W Oak St and N
19th Ave, parallels N 19th Ave until Baxter Ln. The total length of pipe replaced in this project will
be 2,700 feet. The extents of Project 13 are outlined by the checkered line and can be seen in
Figure 5-5.
Figure 5-5: Project 13 Extents (checkered line)
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5.1.6 Project 14: W Oak St Sewer Replacement
Project 14 includes one section of sewer main that begins at N 19th AVE and follows W Oak St
until just beyond N 14th Ave. The section of pipe needing replacement is 2,200 feet long. The
extents of the pipe needing replacement in Project 14 can be seen in Figure 5-6.
Figure 5-6: Project 14 Extents (checkered line)
5.1.7 Project 15: E Lamme St Sewer Replacement
This section of sewer main follows E Lamme St from N Trace Ave to just before Plum Ave. This is
a combination of three different diameter mains. The first section from N Tracy Ave to N Rouse
Ave is a 10-inch main, the second section from N Rouse Ave to N Church Ave is an 8-inch main,
and the final section from N Church Ave to Plum Ave is a 6-inch diameter. In total, these three
sections add up to 2,650 feet of pipe that need to be replaced.
Figure 5-7: Project 15 Extents (checkered line)
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5.1.8 Project 16: Plum Ave Sewer Replacement
Project 16 includes upgrading 750 feet of 6-inch diameter pipe, and 1,200 feet of 8-inch
diameter pipe along Plum Ave and Davis St. In total 1,950 feet of pipe needs replacement. The
extents of this project can be seen below outlined by the checkered line in Figure 5-8.
Figure 5-8: Project 16 Extents (checkered line)
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5.2 6-inch and Smaller Sewer Main Replacement Projects
The projects included in this section are focused on replacing the old 6-inch vitrified clay pipe
(VCP) throughout the sewer collection system.
5.2.1 Small Pipe Project 7: Main Street Sewer Main Replacement
Small Pipe Project 7 includes the replacement of 2,100 feet of 8-inch and 6-inch sewer mains
along Main Street from South Tracy Avenue to Babcock Street. The extents of this project can be
seen below in Figure 5-9. All 6-inch and 8-inch VCP mains replaced in this project will be
upgraded to 8-or 10-inch diameter PVC pipes.
Figure 5-9: Small Pipe Project 7 Extents (checkered line)
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5.2.2 Small Pipe Project 8: S Bozeman Ave, E Story St, and Dell Pl
Sewer Main Replacement
This project includes the replacement of 6-inch sewer mains along S Bozeman Ave from E Olive
St to E Story St, along with a section along S Story St to Bogert Pl. The final section of this
project runs along Dell Pl from E Story St to E Alderson St. The pipe replaced in the project totals
2,250 feet. The extents of Small Pipe Project 8 can be seen below in Figure 5-10, outlined by the
checkered line. As part of this project, these 6-inch sewer mains will be upsized to 8-inch PVC
pipes.
Figure 5-10: Small Pipe Project 8 Extents (checkered line)
Technical Memorandum 9.0 Page 49
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5.2.3 Small Pipe Project 9: S 5th Ave and Alleys Sewer Main
Replacement
Small Pipe Project 9 involves the replacement of 4,804 feet of pipe along S 5th Ave from just
south of W Grant St to W Story Street. Three alley sewer lines are also included in this project.
The alleys are between W Dickerson St and W Alderson St, W College St and W Harrison St, and
W Story St and W Dickerson St. This sewer main will be upgraded to 8-inch diameter PVC pipe.
The extents of this project can be seen outlined by the checkered lines in Figure 5-11 below.
Figure 5-11: Small Pipes Project 9 Extents (checkered line)
Technical Memorandum 9.0 Page 50
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5.2.4 Small Pipe Project 10: S 6th Ave Sewer Main Replacement
The sewer main begins just south of W Grant St and continues north to the intersection of W
Harrison St. Most of the pipe in this project is a 6-inch diameter main; however, there is a small
46-foot section of 10-inch main included that connects the 6-inch main to W Harrison St. All 6-
inch diameter mains will be upsized to 8-inch PVC pipes as part of this project. In total, 1,800
feet of pipe will be upgraded as part of this project. The extents of Small Pipe Project 10 can be
seen below, outlined by the checkered line in Figure 5-12.
Figure 5-12: Small Pipe Project 10 Extents (checkered line)
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5.2.5 Small Pipe Project 11: W Lamme St Sewer Main Replacement
Small Pipe Project 11 includes replacement of a 6-inch main along W Lamme St from N 7th Ave
to N Willson Ave. The 1,900 foot 6-inch VCP main will be upgraded to a new, 8-inch PVC pipe.
The extents of this project are outlined by the checkered line in Figure 5-13 below.
Figure 5-13: Small Pipe Project 11 Extents (checkered line)
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5.2.6 Small Pipe Project 12: S 4th Ave and S 3rd Ave Sewer Main
Replacement
This project includes two sections of independent pipe. One segment extends along S 4th Ave
from W Hayes St to a block south of W Grant St. The other segment follows S 3rd Ave from W
Garfield St to a block south of W Grant St. Both pipes are 6-inch VCP mains that need to be
upsized to 8” PVC pipes. The checkered line in Figure 5-14 outlines the extents of the project. In
total, 1,900 feet of pipe will be replaced in this project.
Figure 5-14: Small Pipe Project 12 Extents (checkered line)
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5.2.7 Small Pipe Project 13: S 7th Ave Sewer Main Replacement
Small Pipe Project 13 includes the upsizing of a 6-inch sewer main that runs beneath S 7th Ave
from W Story St to W Cleveland St. The main is 1,940 feet long and should be upsized to 8-inch
diameter. An additional, small section of 12-inch main is also included in this project. The 12-
inch main that needs replacement is 50 feet long. The extents of this project can be seen in
Figure 5-15.
Figure 5-15: Small Pipe Project 13 Extents (checkered line)
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5.2.8 Small Pipe Project 14: S 3rd Ave Sewer Main Replacement
Small Pipe Project 14 includes the upsizing of a 2,200-foot section of 6-inch main to 8-inch
diameter along S 3rd Ave. The segment begins at W College Street and ends at W Olive St. The
extents of this project can be seen outlined by the checkered line in Figure 5-16 below.
Figure 5-16: Small Pipe Project 14 Extents (checkered line)
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5.2.9 Small Pipe Project 15: N Black Ave, E Cottonwood St, and N Tracy
Ave Sewer Replacement
This project contains 6-inch and 8-inch sewer mains. The 6-inch main follows N Black Ave from E
Beall St to E Cottonwood St, then upsizes to E Cottonwood St to N Tracy Ave, and goes back
down to 6-inches as it wraps around back onto N Tracy Ave. All 6-inch mains will be upgraded
to an 8-inch diameter in this project. The extents of the project can be seen below in Figure
5-17 outlined by the checkered line. 1,650 feet of pipe will be upgraded as part of this project.
Figure 5-17: Small Pipe Project 15 Extents (checkered line)
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5.2.10 Small Pipe Project 16: Ida Ave and Fridley St Sewer Replacement
The 6-inch main begins at the intersection of Fridley St and Brady Ave, then wraps around and
extends on Ida Ave to E Peach St. An alley sewer just north of Fridley St is included in this project
as well. The 6-inch main will be upgraded and upsized to an 8-inch PVC pipe as part of this
project. The extents of the project can be seen below, in Figure 5-18 outlined by the checkered
line. In total, 1,200 feet of pipe will be upgraded in this project.
Figure 5-18: Small Pipe Project 16 Extents (checkered line)
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5.2.11 Small Pipe Project 17: E Cottonwood St Sewer Replacement
An 1,100-foot section of 6-inch VCP will be upgraded to an 8-inch PVC main in Small Pipe
Project 17. The checkered line in Figure 5-19 below outlines the extents of this project. The
main runs along E Cottonwood St from N Church Ave to Plum Ave.
Figure 5-19: Small Pipe Project 17 Extents (checkered line)
5.2.12 Small Pipe Project 18: E Aspen St Sewer Replacement
Small Pipe Project 18 includes the 6-inch main along E Aspen St from N Church Ave to Plum
Ave. A total of 950 feet of pipe will be upgraded to 8-inch diameter PVC. The extents of the
project can be seen below outlined by the checkered line in Figure 5-20.
Figure 5-20: Small Pipe Project 18 Extents (checkered line)
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5.2.13 Small Pipe Project 19: N 3rd Ave Sewer Replacement
A 910-foot segment of 6-inch sewer main will be upgraded to 8-inch PVC along N 3rd Ave from
W Villard St to W Peach St. The checkered line in Figure 5-21 outlines the extents of this project.
Figure 5-21: Small Pipe Project 19 Extents (checkered line)
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5.2.14 Small Pipe Project 20: N 8th Ave Sewer Replacement
Small Pipe Project 20 includes the upsizing and replacement of two segments of 6-inch sewer
main. One segment starts at the intersection of N 8th Ave and W Mendenhall St and extends to
W Beall St. The second segment starts at N 9th Ave and ends at N 7th Ave. In total, 1,209 feet of
pipe will be replaced and upsized to 8-inch PVC. The extents of the project and two segments
can be seen below outlined by the checkered line in Figure 5-22.
Figure 5-22: Small Pipe Project 20 Extents (checkered line)
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5.2.15 Small Pipe Project 21: W Lamme St Sewer Replacement
A short, 500-foot section of pipe will be upgraded to 8-inch PVC in this project. The main starts
at the intersection of W Lamme St and an alley just east of N 11th Ave and extends to N 9th Ave.
The main is composed of both 8-inch and 6-inch VCP. The 6-inch portion will be upsized to 8-
inch as part of this project. The extents of this project can be seen outlined by the checkered line
in Figure 5-23 below.
Figure 5-23: Small Pipe Project 21 Extents (checkered line)
5.2.16 Small Pipe Project 22: W Mendenhall St
Small Pipe Project 22 includes the replacement of a sewer main along W Mendenhall St. The
portion replaced in this project begins at N 7th Ave and ends at N Tracy Ave. In total, 2,250 feet
of pipe will be upgraded to an 8-inch PVC pipe. The checkered line in Figure 5-24 below
outlines the extents of this project.
Figure 5-24: Small Pipe Project 22 Extents (checkered line)
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5.2.17 Small Pipe Project 23: W Main St and W Babcock St Alley Sewer
Replacement
The sewer main lies between W Main St and W Babcock St, and begins near S 11th Ave and
extends to S 7th Ave. The existing main is a 6-inch diameter pipe and will be upgraded to 8-inch
PVC as part of this project. In total, 1,250 feet of pipe will be replaced and upgraded. The scope
of the project can be seen outlined by the checkered line in Figure 5-25.
Figure 5-25: Small Pipe Project 23 Extents (checkered line)
5.2.18 Small Pipe Project 24: W Main St Sewer Replacement
This 6-inch diameter sewer main begins near the intersection of W Main St and N 7th Ave, and
continues along W Main St until N Grand Ave. This pipe will be upgraded to an 8-inch PVC as
part of this project. The extents of the 1,400 feet of pipe replaced is outlined below in Figure
5-26 by the checkered line.
Figure 5-26: Small Pipe Project 24 Extents (checkered line)
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5.2.19 Small Pipe Project 25: S 5th Ave Sewer Replacement
In Small Pipe Project 25, 1,350 feet of pipe will be upgraded to 8-inch PVC. Most of the pipe
upgraded in this project follows S 5th Ave from W Olive St to W Story St. A small portion extends
off this main segment between W Curtiss St and W Koch St. The project extents can be seen
below outlined by the checkered line in Figure 5-27.
Figure 5-27: Small Pipe Project 25 Extents (checkered line)
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5.2.20 Small Pipe Project 26: W Story St and S 6th Ave Sewer
Replacement
This project includes two sewer main segments, one which extends east on W Story St from
between S 9th Ave and S 8th Ave to S 6th Ave. The other extends south on S 6th Ave from W Story
St to W Harrison St. In total, 1,500 feet of pipe will be replaced and upsized to 8-inch PVC. The
project is outlined in Figure 5-28 below by the checkered line.
Figure 5-28: Small Pipe Project 26 Extents (checkered line)
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5.2.21 Small Pipe Project 27: S 9th Ave and S 8th Ave Alley Sewer
Replacement
This project includes upgrading a 6-inch main to 8-inch PVC between S 9th Ave and S 8th Ave.
The main extends from just below W Babcock St to W College St, with a break in the middle due
to the Irving Elementary School. 2,068 feet of pipe will be replaced in this project. The checkered
line in Figure 5-29 below outlines the extents of Small Pipe Project 27.
Figure 5-29: Small Pipe Project 27 Extents (checkered line)
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5.2.22 Small Pipe Project 28: S 8th Ave and S 7th Ave Sewer Main
Replacement
Small Pipe Project 28 involves the replacement of a 1,350-foot section of 6-inch sewer main. The
main begins on W Harrison St between S 8th Ave and S 7th Ave, and continues north before
turning right between W Story St and W Dickerson St to intersect S 7th Ave. This pipe will be
upgraded to an 8-inch PVC pipe as part of this project. The extents of this project are outlined in
Figure 5-30 below.
Figure 5-30: Small Pipe Project 28 Extents (checkered line)
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5.2.23 Small Pipe Project 29: S Wallace Ave Sewer Replacement
A total of 900 feet of 6-inch diameter sewer main along S Wallace Ave and just north of E
Babcock St will be replaced with an 8-inch diameter PVC pipe in this project. The extents of this
project can be seen below in Figure 5-31 outlined by the checkered line. Note that the segment
along Wallace Avenue between Babcock Street and the alley was replaced with an 8-inch PVC
sewer in 2020.
Figure 5-31: Small Pipe Project 29 Extents (checkered line)
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5.2.24 Small Pipe Project 30: E Main St Sewer Replacement
Two segments of 6-inch sewer main along E Main St will be replaced in Small Pipe Project 30.
The two segments combined total 800 feet that will be upgraded to 8-inch PVC. The project
extents are outlined by a checkered line in Figure 5-32 below.
Figure 5-32: Small Pipe Project 30 Extents (checkered line)
5.2.25 Small Pipe Project 31: E Mendenhall St Sewer Replacement
Small Pipe Project 31 includes the replacement of a 6-inch sewer main that follows E
Mendenhall St from N Tracy Ave to N Broadway Ave. In total, 2,900 feet of pipe will be upgraded
to 8-inch PVC. The checkered line in Figure 5-33 below shows the extents of the project.
Figure 5-33: Small Pipe Project 31 Extents (checkered line)
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5.2.26 Small Pipe Project 32: S Church Ave Sewer Replacement
The 1,700-foot 6-inch sewer main that runs from E Olive St to around E Story St along S Church
Ave will be replaced and upgraded with 8-inch PVC. An additional 350 feet of sewer main that
extends west above E Story St will also be replaced and upgraded. The extents of this project
can be seen below outlined by the checkered line in Figure 5-34.
Figure 5-34: Small Pipe Project 32 Extents (checkered line)
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5.2.27 Small Pipe Project 33: W Babcock St Sewer Replacement
In Small Pipe Project 33, 760 feet of 6-inch sewer main will be upgraded to 8-inch PVC along W
Babcock St. Outlined by a checkered line, the extents of this project can be seen in Figure 5-35.
Figure 5-35: Small Pipe Project 33 Extents (checkered line)
5.2.28 Small Pipe Project 34: S 6th Ave Sewer Replacement
Two segments of pipe will be replaced in this project, totaling 550 feet. These two pipes will be
upgraded from 6-inch to 8-inch PVC. One pipe extends north on S 6th Ave, and the other west
between W Curtiss St and W Koch St. The outline of the project extents can be seen below in
Figure 5-36.
Figure 5-36: Small Pipe Project 34 Extents (checkered line)
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5.2.29 Small Pipe Project 35: W Babcock Ave, W Olive St, and S 7th Ave
Sewer Main Replacement
In Small Pipe Project 35, 1,050 feet of 6-inch pipe will be upgraded to 8-inch PVC. The mains
extend along W Olive St, run north along S 7th Ave, and west between W Olive St and W
Babcock St. The checkered line outlines the project extents in Figure 5-37.
Figure 5-37: Small Pipe Project 35 Extents (checkered line)
5.2.30 Small Pipe Project 36: W Main St, S Tracy Ave, and E Babcock St
Sewer Main Replacement
Small Pipe Project 35 includes replacing the existing 6-inch with new 8-inch PVC along W Main
St from S Willson Ave to N Tracy Ave and along S Tracy Ave to E Babcock Ave. Additionally, the
existing 6-inch will be replaced with new 8-inch PVC along E Babcock St from S Bozeman Ave to
S Rouse Ave. In total, 1,100 feet of pipe will be replaced in this project. The checkered line in
Figure 5-38 below outlines the extents of this project.
Figure 5-38: Small Pipe Project 36 Extents (checkered line)
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5.3 Lift Station Improvement Projects
Additional lift station capacity will be needed to convey increased flows to the wastewater
reclamation facility under future growth conditions. Both the new lift stations and the existing
lift station capacity expansions presented in this section are sized to meet buildout growth
conditions. The need for the lift stations presented in this section will be driven by the timing of
new growth.
5.3.1 Lift Station Project 2: Coulee Drive
The Coulee Drive Lift Station (shown in Figure 5-39) is needed to support new growth within
the City. This 3.27 MGD lift station project includes 13,500 feet of new 14-inch diameter force
main.
Figure 5-39: Coulee Drive LS
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5.3.2 Lift Station Project 3: Spring Hill
The Spring Hill Lift Station (shown in Figure 5-40) is needed to support new growth within the
City. This 7.89 MGD lift station project includes 12,050 feet of new 21-inch diameter force main.
Figure 5-40: Spring Hill Lift Station
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5.3.3 Lift Station Project 4: Gooch Hill
The Gooch Hill Lift Station (shown in Figure 5-41) is needed to support new growth within the
City. This 9.75 MGD lift station project includes 11,200 feet of new 24-inch diameter force main.
Figure 5-41: Gooch Hill Lift Station
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5.3.4 Lift Station Project 5: Hidden Valley
The Hidden Valley Lift Station (shown in Figure 5-42) is needed to support new growth within
the City. This 3.21 MGD lift station project includes 9,900 feet of new 14-inch diameter force
main.
Figure 5-42: Hidden Valley Lift Station
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5.3.5 Lift Station Project 6: Davis Lane
The Davis Lane Lift Station upsizing (shown in Figure 5-43) is needed to support new growth
within the City. This 7.2 MGD lift station will need to be upsized to 22.72 MGD to meet buildout
conditions. This project includes 3,700 feet of a parallel 18-inch diameter force main. Since this
corridor is already full of pipes, and this would be the third parallel force main, it is likely that a
single line with the capacity of the combined force mains will be the preferred alternative.
Figure 5-43: Davis Lane Lift Station
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5.3.6 Lift Station Project 7: Laurel Glen
The Laurel Glen Lift Station upsizing (shown in Figure 5-44) is needed to support new growth
within the City. This 0.65 MGD lift station will need to be upsized to 0.78 MGD to meet buildout
conditions.
Figure 5-44: Laurel Glen LS
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5.3.7 Lift Station Project 8: Loyal Gardens
The Loyal Garden Lift Station upsizing (shown in Figure 5-45) is needed to support new growth
within the City. This 0.52 MGD lift station will need to be upsized to 0.76 MGD to meet buildout
conditions.
Figure 5-45: Loyal Gardens LS
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5.4 Summary of Long-Term Capital Improvement Projects
A summary of the costs associated with the long-term capital improvement projects is included
in Table 5-1.
Table 5-1: Summary of Long-Term Capital Improvement Projects
Improvement ID Location of Improvement
Project 9 N Grand Ave Sewer Main Replacement
Project 10 N 20th Ave Sewer Main Replacement
Upper Front Street Interceptor and Highland Glen Project 11 Sewer Main Replacement
Project 12 S Grand Ave Sewer Main Replacement
Project 13 N 19th Ave Sewer Main Replacement
Project 14 W Oak St Sewer Main Replacement
Project 15 E Lamme St. Sewer Main Replacement
Project 16 Plum Ave Sewer Main Replacement
Subtotal for 8-inch and Larger Sewer Main Replacement Projects
Opinion of
Probable Cost
(2024 $)
$2,081,600
$1,470,100
$2,488,300
$2,691,500
$1,316,700
$1,031,400
$1,489,800
$1,136,900
$13,706,300
Lift Station Project 2 Coulee Drive Lift Station
Lift Station Project 3 Spring Hill Lift Station
Lift Station Project 4 Gooch Hill Lift Station
Lift Station Project 5 Hidden Valley Lift Station
Lift Station Project 6 Davis Lane Lift Station
Lift Station Project 7 Laurel Glen Lift Station
Lift Station Project 8 Loyal Gardens Lift Station
Subtotal for Lift Station Projects
$13,673,200
$16,208,000
$17,366,100
$10,472,200
$12,091,700
$703,900
$1,008,400
$69,935,500
Small Pipe Project 7
Small Pipe Project 8
Small Pipe Project 9
Small Pipe Project 10
Small Pipe Project 11
Small Pipe Project 12
Small Pipe Project 13
Small Pipe Project 14
Small Pipe Project 15
Small Pipe Project 16
Small Pipe Project 17
Small Pipe Project 18
Small Pipe Project 19
Small Pipe Project 20
Small Pipe Project 21
Small Pipe Project 22
Main St and S Church Ave Sewer Replacement
S. Bozeman, E Story St, and Dell Pl. Sewer Main
Replacement
E Main St and Church Ave Sewer Main Replacement
S 6th Ave Sewer Main Replacement
E Main St and Church Ave Sewer Main Replacement
S 3rd Ave and S 4th Ave Sewer Main Replacement
S 7th Ave Sewer Main Replacement
S 3rd Ave Sewer Main Replacement
N Tracy Ave, E Cottonwood St, N Black Ave Sewer
Main Replacement
Ida Ave, Fridley St Sewer Main Replacement
E Cottonwood Ave Sewer Main Replacement
E Aspen St. Sewer Main Replacement
N 3rd Ave Sewer Main Replacement
N 8th Ave Sewer Main Replacement
W Lamme St Sewer Main Replacement
E Lamme St Ave Sewer Main Replacement
$1,207,400
$1,502,400
$2,907,400
$921,300
$1,221,400
$1,125,200
$1,131,200
$1,379,800
$1,278,700
$721,100
$609,500
$455,400
$627,000
$690,500
$274,500
$1,459,400
Technical Memorandum 9.0 Page 79
Small Pipe Project 23 W Main St/W Babcock St Sewer Main Replacement $699,300
Small Pipe Project 25 S 5th Ave Sewer Main Replacement $970,500
Small Pipe Project 27 S 9th Ave/S 8th Ave Sewer Main Replacement $1,229,600
Small Pipe Project 29 S 6th Ave Sewer Main Replacement $532,200
Small Pipe Project 31 E Mendenhall St Sewer Main Replacement $1,706,600
Small Pipe Project 33 W Babcock Ave Sewer Main Replacement $464,500
Small Pipe Project 35 W Babcock Ave/W Olive St, S 7th Ave Sewer Main
Replacement $530,700
Subtotal for 6-inch and Smaller Sewer Main Replacement Projects $28,916,400
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 9.0 – Capital Improvement Plan
Technical Memorandum 9.0 Page 80
Small Pipe Project 24
Small Pipe Project 26
Small Pipe Project 28
Small Pipe Project 30
Small Pipe Project 32
Small Pipe Project 34
Small Pipe Project 36
W Main St Sewer Main Replacement
W Story Ave and S 6th Ave Sewer Main Replacement
S 8th Ave/ S 7th Ave Sewer Main Replacement
E Main St Sewer Main Replacement
S Church Ave Sewer Main Replacement
S 6th Ave Sewer Main Replacement
W Main St, S Tracy Ave, E Babcock St Sewer Main
Replacement
Total 6-20-Year Project Costs
$869,600
$1,045,100
$844,300
$379,000
$1,020,300
$373,400
$739,100
$112,558,200
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 9.0 – Capital Improvement Plan
Chapter 6 Relevancy of Previously Recommended Yet
to be Constructed CIP’s
There are several collection system capital improvement projects yet to be completed from the
previous wastewater masterplan and the City’s ongoing 5-year CIP plan. A high-level review was
completed to assess if these projects are still recommended. These projects are summarized in
the following paragraphs.
North Frontage Road Interceptor (CIP Project WWIF20): Development of the east side of land
within the Community Plan Boundary will be collected by the North Frontage Road Interceptor.
Portions of the interceptor are at or near capacity and more segments will be at capacity when
the Existing and Obligated areas are developed. The buildout of the interceptor includes parallel
trunk sewers of varying sizes. This project consists of two main components: (1) replacement of
portions of existing parallel trunk sewer including upsizing 4,725 ft of existing pipe to 36-inch
diameter pipe and (2) installation of new parallel trunk sewer in areas with single trunk sewers
including 6,200 ft of 27-inch through 36-inch diameter pipe. This project is scheduled to be
completed in 2026, with an estimated cost of $4.6M. The results of the risk analysis also show
the need for this project, driven primarily by the material (vitrified clay) and remaining useful life
of most of the pipes along North Frontage Road.
Figure 6-1: North Frontage Road Interceptor
Technical Memorandum 9.0 Page 81
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Technical Memorandum 9.0 – Capital Improvement Plan
Davis-Fowler Interceptor (CIP Project WWIF22): The 2015 master plan states “The interceptor
between Durston Road and West Oak Street will eventually exceed capacity as the Baxter Creek
drainage basin develops. In order to convey the ultimate build-out flow, the interceptor will
need to be increased from an 18-inch diameter pipe to a 24-inch diameter pipe.” This project
was originally scheduled to be completed in 2023 at a cost of $1.25M. The timing of this project
will be dictated by the growth in the area and other City infrastructure projects (i.e., Fowler
Avenue Connection). The Hydraulic Model Development and Results Technical Memorandum
(TM 7) summarizes the recommended sizing for this project when it is needed. The results of the
risk analysis also show the need for this project, driven primarily by large flows and depth-to-
diameter ratios more than 50%.
Figure 6-2: Davis-Fowler Interceptor
Technical Memorandum 9.0 Page 82
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Technical Memorandum 9.0 – Capital Improvement Plan
WRF Interceptor (CIP Project WWIF44): Previous planning efforts identified the need to upsize
the existing 30-inch interceptor from I-90 to the WRF with a 48-inch interceptor. This project
was scheduled to be completed in 2024 with an estimated cost of $0.55M. The results of the
risk analysis also show the need for this project, driven primarily by large flows, depth-to-
diameter ratios more than 50%, and low remaining useful life. This project is still recommended,
and the previously recommended timing is appropriate.
Figure 6-3: WRF Interceptor
Technical Memorandum 9.0 Page 83
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Technical Memorandum 9.0 – Capital Improvement Plan
Cottonwood Road Sewer Capacity (CIP Project WWIF53): The City is mindful of growth and
has recognized that when annexation occurs in the western portion of the City, interceptor
capacity along Cottonwood Road will quickly become a priority. To extend the capacity of the
interceptor along Cottonwood Road, the City would install approximately 3,100 feet of 21-inch
sewer extending the Cottonwood-Davis Interceptor from Babcock Street to south of Huffine
Lane. The timing of this project will depend on growth. The current estimated cost to complete
this project is $2M.
Figure 6-4: Cottonwood Rd Capacity
Blackwood Groves Sewer Oversizing (CIP Project WWIF52): As the Blackwood Groves
Subdivision is developed, the City is participating in the oversizing of the sewer main for future
growth capacity. The construction of this project is ongoing and phase dependent. The
estimated completion date is 2028, at a total cost to the City of $0.2M.
Technical Memorandum 9.0 Page 84
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Technical Memorandum 9.0 – Capital Improvement Plan
Northwest Crossings Sewer Oversizing (CIP Project WWIF54): As the Northwest Crossing
Subdivision is developed, the City is participating in the oversizing of the sewer main for future
growth capacity. The construction of this project is ongoing and phase dependent. The
estimated completion date is 2028, at a total cost to the City of $0.3M.
Technical Memorandum 9.0 Page 85
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Technical Memorandum 9.0 – Capital Improvement Plan
Chapter 7 Conclusion
This collection system Capital Improvement Plan will allow the City to address the most pressing
infrastructure needs while continuing to maintain and operate at a high level of service. Below is
a summary of the key points discussed in more detail within this Technical Memorandum:
• The cost estimates developed for these recommendations are generally based on 2022
unit prices and assumptions and are considered Class 4 estimates typically ranging from
-30 to +50 percent accuracy.
• The near-term projects were selected based on risk and assumed immediacy of the
growth/development pressure.
• The Increased Density analysis flagged three interceptor projects that would require a
nominal pipe size increase to meet the increased demands. These projects include the
Cottonwood Road Interceptor (from Huffine to Babcock), the Front Street Interceptor
(from the Softball Complex to Tamarack), and the Bozeman Trail Interceptor through the
Highland Glen open space.
• When new information becomes available (e.g., CCTV data, pipe breaks, manhole backup
records), the City’s risk model should be updated which may impact the timing of the
recommended capital improvement projects
• The long-term improvement recommendations are growth dependent; and therefore,
implementation will vary with development pressure. Additionally, these long-term
recommendations should continue to be evaluated with each new Facility Plan update to
ensure adequate existing and future conditions are utilized in the analysis.
Technical Memorandum 9.0 Page 86
10.0
Asset Management
Coordinate System
Technical Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 10.0 – Asset Management Coordinate System
Table of Contents
Chapter 1 Introduction & Purpose........................................................................................ 2
Chapter 2 Current Methods ................................................................................................... 3
2.2 Vertical Datum....................................................................................................................................................3
2.2.2 Vertical Datum Conversions ...........................................................................................................3
2.3 Future Vertical Datum......................................................................................................................................4
2.4 Horizontal Coordinate System......................................................................................................................4
2.5 MSU CORS Base Station..................................................................................................................................4
2.6 PLSS Monumentation and Record Drawings ...........................................................................................5
2.7 Local Survey Control Monuments................................................................................................................5
Chapter 3 Summary of Recommendations .......................................................................... 7
3.1 Horizontal Coordinate System.......................................................................................................................7
3.2 Vertical Datum....................................................................................................................................................7
3.3 Global Positioning System City Base Station............................................................................................7
3.4 Permanent Control Point Monuments .......................................................................................................8
Appendix A -Example Monuments ............................................................................................ 9
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Technical Memorandum 10.0 – Asset Management Coordinate System
Chapter 1 Introduction & Purpose
The purpose of the Asset Management Coordinate System Technical Memorandum (TM 10) is to
provide recommendations to the City of Bozeman (City) to transition to a uniform coordinate
system. The City is growing rapidly and older methods are not keeping up with the times. This
report summarizes the currently adopted coordinate system and provides a recommendation to
ensure all drawings and surveys are in a uniform vertical and horizontal coordinate system
moving forward. This is critical for the City to effectively and efficiently manage the enormous
amount of data associated with the rapid expansion.
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Chapter 2 Current Methods
Currently, there is no official policy in the City requiring developers to submit digital .dwg or
shapefiles covering newly installed City assets. In the past, when the City received digital
information, there has not been a consistent vertical datum or horizontal coordinate system.
Recently, the City adopted Resolution 5113 (in coordination with Ordinance 2032), which
establishes North American Vertical Datum 1988 (NAVD 88) as the City’s vertical datum.
However, there is still no formal resolution setting a uniform horizontal coordinate system or
projection. The lack of consistency has led to inefficient workflows within and across City
departments.
Moving forward, the City should adopt a standard horizontal coordinate system and ensure it is
incorporated into the Engineering Design Standards. All future development review submittals
shall follow these standards. This report provides additional details on various coordinate
systems used in the area and recommends a path forward.
2.2 Vertical Datum
The City in the past used a local vertical datum based on benchmarks that are located on fire
hydrants. This datum is out of date and generally unreliable because of poor benchmark survey
and modifications to the hydrants due to new construction and distribution system updates.
Vertical datum conversions can be performed but should be carefully considered. Nationwide
vertical datum conversions are most widely used for the study of plate tectonics; therefore, the
conversions are not always helpful for local projects.
2.2.2 Vertical Datum Conversions
The approximate conversions from the City’s datum to the National Geodetic Vertical Datum of
1929 (NGVD 29) and the North American Vertical Datum of 1988 (NAVD 88) are shown in Table
2.1.
Table 2.1: Vertical Datum Conversions
City of Bozeman
Vertical Datum
Conversion to
NGVD 1929
+15.44 feet
Conversion to
NAVD 1988
+19.4 feet
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Technical Memorandum 10.0 – Asset Management Coordinate System
2.3 Future Vertical Datum
The National Geodetic Survey (NGS) will be replacing the North American Vertical Datum of
1988 (NAVD 88) in 2024. Additional information and details about this vertical datum update
can be accessed through the National Geodetic Survey webpage:
https://geodesy.noaa.gov/datums/newdatums/index.shtml.
With the integration of a City-wide vertical survey network tied into the existing National
Geodetic Survey (NGS) benchmarks and Montana State University (MSU) Continuously
Operating Reference Station (CORS), future vertical datum updates will be computed based on
the published vertical adjustments provided by NGS when the nationwide vertical datum is
updated. This allows simple conversion in the future to any new NGS datum. It is recommended
that the City adopt the latest NGS vertical datum when it becomes the national standard.
2.4 Horizontal Coordinate System
There is no standard horizontal coordinate system adopted by the City. Local Engineers and
Surveyors tend to use State Plane Coordinate System (SPCS) with a local projection established
by the MSU CORS station, which is known as the Bobcat projection. This coordinate system and
projection are very common in the area but are not officially required by the City.
Horizontal coordinate system conversions are normally made using computer programs such as
Geographic Information System (GIS) software or NGS’ Coordinate Conversion and
Transformation Tool (NCAT). The City should adopt a standard practice for receiving digital data
from Developers to ensure a consistent coordinate system.
It is recommended that the City adopt the State Plane Coordinate System Bobcat projection and
incorporate it into its Engineering Design Standards. All electronically submitted CAD and/or GIS
data shall be in this coordinate system.
2.5 MSU CORS Base Station
There is an NGS Continuously Operating Reference Station (CORS), which is a Global Positioning
System (GPS) station located on the Montana State University Campus. This station is
continuously maintained by Montana State University (MSU). The CORS station will allow for
conversions from NAVD 88 to the future vertical datum using the conversion provided by NGS.
The CORS station provides published horizontal coordinates in latitude & longitude, State Plane
& Universal Transverse Mercator (UTM). The CORS station will allow for horizontal coordinate
conversion between existing and future coordinate systems. The CORS station is a very useful
tool but has its dangers. The horizontal and vertical location being broadcasted can be altered
Technical Memorandum 10.0 Page 4
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Technical Memorandum 10.0 – Asset Management Coordinate System
by MSU when updates to the GPS unit are performed.
The City of Bozeman should consider developing its own permanent GPS base station or CORS
Station. The development of an additional permanent GPS base station within the city would
ensure that the surveying and engineering community has a reliable connection to precise
geodetic data.
2.6 PLSS Monumentation and Record Drawings
It is not recommended that Public Land Survey System (PLSS) monuments be used in the City
coordinate system. These monuments are easily disturbed by construction and over time are
recalculated by many different surveyors. The recalculated positions can sometimes differ
greatly to their original location resulting in errors. Therefore, it is recommended that the City
sets and maintains local survey control monuments.
2.7 Local Survey Control Monuments
To maintain spatial continuity, it is important for the City of Bozeman to create and adopt
Survey Design Standards that are required on all surveys and drawings. These standards will
outline the basis for how surveys are completed and ensure the necessary documentation is
provided to the City. The Survey Design Standards should generally include the elements listed
below.
• A City-wide horizontal and vertical control network should be set and maintained under
the direct supervision of a Licensed Professional Land Surveyor.
• The control network could consist of, but not be limited to, the existing NGS
benchmarks. It is recommended that the City sets and maintains additional monuments
beyond the current NGS monuments.
• These additional monuments should be set in safe and accessible locations, such as City
parks or rights-of-way (recommend approximately one-mile grid). Monuments should
be set in areas away from overhead impediments to allow for easier and more accurate
use by global positioning systems.
• Each monument should be documented using a standard form stating the date set,
horizontal & vertical coordinates, and a description of the monument and its location.
These forms should be readily available for use by engineering and surveying firms for
City projects.
• The monuments should be durable and built to standards to avoid disturbance.
Example monuments are provided in Appendix A and were obtained from the US Army
Corps of Engineers.
• The monuments can be referenced from the new City horizontal coordinate system to
the Montana State Plane Coordinate system to provide seamless integration into the
Technical Memorandum 10.0 Page 5
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Technical Memorandum 10.0 – Asset Management Coordinate System
City GIS with the use of the CORS station at MSU.
• The equipment required to maintain a horizontal and vertical survey network would
consist of survey grade GPS receivers, robotic or traditional total station, and a survey
grade spirit level.
• It is suggested that the initial control network be set up by a single entity to minimize
the errors.
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Technical Memorandum 10.0 – Asset Management Coordinate System
Chapter 3 Summary of Recommendations
3.1 Horizontal Coordinate System
It is recommended that the City adopt a coordinate system from the currently available and
published Low Distortion Projections (LDP) that encompasses the City limits. Low Distortion
Projections help minimize the difference between the distance on a map and the actual
distances on the ground. LDPs are conformal map projections and can cover large areas. The
published LDP for this area is called the Bobcat Coordinate System and is currently readily
available in GIS and AutoCAD software. Additionally, this projection is commonly used by
multiple local engineering and survey firms.
3.2 Vertical Datum
It is recommended that the City continue the use of NAVD 88 as the City-wide vertical datum
and incorporate it into the Engineering Design Standards.
3.3 Global Positioning System City Base Station
It is recommended that the City sets up and maintains a GPS base station to be used by the
public surveying and engineering community. Providing an easy-to-use public connection to the
precise geodetic position would promote the use of the available connection and willingness by
engineers and land surveyors to provide precise as built locations of city infrastructure. This
would provide a seamless way to tie into the City’s accepted horizontal coordinate system and
vertical datum. It is recommended that the City set up and maintain the GPS base station using
the procedures specified by the National Geodetic Survey (NGS) for the Continuously Operating
Reference Network (CORS) base stations. This will ensure the reliability of the base station and
integration into the NGS CORS network if the station at MSU becomes obsolete. Unfortunately,
at this time the City would not be able to enter the base station into the CORS network because
it would not meet the NGS requirements of being 70 km from an existing GPS base station
using the NGS requirements.
It is recommended that the City complete a study to determine the optimal location for a GPS
base station using the NGS requirements. This study would cost approximately $10,000 and
include the following tasks:
• Determine the best location for a GPS base station for complete city-wide coverage and
for future developments based on coverage, land availability/access, and security.
• Review NGS specifications for placement and permanent mounting requirements for
future integration to the NGS CORS network or the Montana State Reference Network
(MTSRN) that is currently in development.
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Technical Memorandum 10.0 – Asset Management Coordinate System
• Provide recommendations for available base station makes and models along with any
additional required components. Develop cost estimates for equipment and installation
of GPS units and additional components needed per manufacturer recommendations.
3.4 Permanent Control Point Monuments
It is recommended that the City sets permanent control point monuments around the City and
a study be performed to determine the best proposed location for setting permanent
monuments using the following requirements:
1. No overhead obstructions for the use of GPS survey equipment.
2. Within public parks or rights-of-way for easy public access.
3. Separation of a maximum of one mile between monuments.
4. Usable for future City-wide aerial survey control.
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Technical Memorandum 10.0 – Asset Management Coordinate System
Appendix A -Example Monuments
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Technical Memorandum 10.0 Page 10
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Technical Memorandum 10.0 Page 11
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 10.0 – Asset Management Coordinate System
Technical Memorandum 10.0 Page 12
11.0
Updating Model
Development Loading
Technical Memorandum
WastewaterCollection System
Facility Plan Update
December 2024
Wastewater Collection System Facility Plan – 2024 Update
Technical Memorandum 11.0 – Updating Model Development Loading
Table of Contents
Chapter 1 Updating Model Development Loading ............................................................. 1
Review of Existing System Model Scenarios ...............................................................................................1
Review of Development Analysis Scenarios ..............................................................................................3
Identify Manhole ID(s) Affected by the Development ...........................................................................5
Calculate Development Loading...................................................................................................................5
Update Model Loading ....................................................................................................................................6
1.5.1 Development Domestic Sanitary Loading .................................................................................6
1.5.2 Development Groundwater Loading...........................................................................................8
1.5.3 Development RDII.............................................................................................................................11
Query and Track Development Loading .................................................................................................. 13
1.6.1 Identify manholes that have development loading:.............................................................13
1.6.2 Add Development Manholes to a Domain.............................................................................. 15
Conclusion.......................................................................................................................................................... 17
Technical Memorandum 11.0 Page 1
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Technical Memorandum 11.0 – Updating Model Development Loading
Chapter 1 Updating Model Development Loading
The purpose of this technical memorandum is to provide an overview of the process and steps
used to update and track Development loading within the wastewater collection system model.
The process described herein is specifically for development loading review and includes the
following:
o Step 1: Review of Existing System Model Scenarios
o Step 2: Review of Development Demand Scenarios
o Step 3: Identify Manhole IDs Affected by the Development
o Step 4: Calculate Development Loading
o Step 5: Update Model Loading
o Step 6: Query and Track Model Loading
These steps are covered in detail in this technical memorandum.
Review of Existing System Model Scenarios
This section provides an overview of the scenarios and data sets for analyzing the existing
wastewater collection system. This review is presented to provide an understanding of the starting
point for scenarios created for the development review process. The hydraulic model has two
scenarios for dry weather and wet weather that are the base scenarios and used for the analysis
of existing system conditions. The scenarios and data sets used for dry weather and wet weather
analyses are summarized below:
• EXIST_2020_DWF Scenario: This scenario is the base scenario used to analyze dry
weather flow conditions for the existing wastewater collection system.
o External Flow Data Set: 2020_GW, Base GW during winter 1.5 MGD total
▪This data set represents a constant ground water base flow of 1.5 MGD.
o DWF Data Set: 2020_DWF, February 2020 Base Flow with Patterns
▪This data set represents a domestic sanitary flow of 3.8 MGD.
• EXIST_2020_WW Scenario: This scenario is the base scenario used to analyze wet weather
flow conditions.
o Raingage Data Set: DESIGN_STORM
▪This data set represents a 25-year, 24-hour, 1.99-inch rain event with a Soil
Conservation Service (SCS) Type I distribution.
o External Flow Data Set: 2020_WW, Base GW during spring 5.7 MGD total
▪This data set represents a constant ground water base flow of 5.7 MGD
representing high ground water and peak infiltration conditions.
o DWF Data Set: 2020_DWF, February 2020 Base Flow with Patterns
▪This data set represents a domestic sanitary flow of 3.8 MGD
▪This is the same data set that is used for the dry weather analysis.
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Technical Memorandum 11.0 – Updating Model Development Loading
o RDII Data Set: 2020_EXISTING_UPDATE_THIESSEN
▪This data set represents the sewershed area for each manhole and is used
in the model to calculate rainfall derived inflow and infiltration (RDII) during
the design storm.
The data sets for the existing scenarios are shown below as viewed in the InfoSWMM Scenario
Manager.
EXIST_2020_DWF
EXIST_2020_WW, Design Storm
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Technical Memorandum 11.0 – Updating Model Development Loading
Review of Development Analysis Scenarios
The existing system scenarios were cloned to create two development analysis scenarios to
analyze dry weather and wet weather conditions with additional development loading. These two
scenarios are used for assessing increased domestic sanitary loading, increased base groundwater
flow (if applicable), and additional acreage for rainfall derived inflow and infiltration (if applicable).
The scenarios and data sets used for development dry weather and wet weather flows are
summarized below:
• EXIST_2020_DWF_DEV Scenario: This scenario is used to analyze dry weather flow
conditions with additional development loading.
o External Flow Data Set: DEVELOPMENT_GW
▪This data set started as a copy of the 2020_GW data set.
▪Additional base dry weather groundwater can be added to this data set, if
required, for the Development.
o DWF Data Set: DEVELOPMENT_DWF
▪This data set started as a copy of the 2020_DWF data set.
▪Additional domestic sanitary flow can be added to this data set for the
Development.
• EXIST_2020_WW_DEV Scenario: This scenario is used to analyze wet weather flow
conditions with additional development loading.
o Raingage Data Set: DESIGN_STORM
▪This data set does not change and is the same as described in the existing
system scenario.
o External Flow Data Set: DEVELOPMENT_WW
▪This data set started as a copy of the 2020_WW data set.
▪Additional base wet weather groundwater can be added to this data set, if
required, for the development.
o DWF Data Set: DEVELOPMENT_DWF
▪This data set started as a copy of the 2020_DWF data set.
▪Additional domestic sanitary flow can be added to this data set for the
development.
▪This is the same data set that is used for the development dry weather
analysis.
o RDII Data Set: DEVELOPMENT_RDII
▪This data set started as a copy of the 2020_EXISTING_UPDATE_THIESSEN
data set.
▪Sewershed area contributing RDII to the manhole(s) can be adjusted, if
applicable, for the Development.
The data sets for the development scenarios are shown below as viewed in the InfoSWMM Scenario
Manager.
Technical Memorandum 11.0 Page 3
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Technical Memorandum 11.0 – Updating Model Development Loading
DEVOPMENT_DWF
DEVELOPMENT_WW
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Technical Memorandum 11.0 – Updating Model Development Loading
Identify Manhole ID(s) Affected by the Development
Modeling a development requires identification of manholes affected by the development
loading. A list of development manholes external to the model is recommended for record
keeping. The list can be used for comparison and verification of loading that gets added to the
model. The following information is recommended for external recording keeping and
development review:
• Development Name.
• Manhole ID(s) affected by the development.
• Allocated development loading including:
o Domestic Sanitary Flow.
o Groundwater Flow Adjustments (if applicable).
o RDII Adjustments (if applicable).
• Development Allocation Code (discussed further in Section 1.5).
Calculate Development Loading
Modeling a development requires three types of loading calculations. Calculations are
completed external to the modeling software. The calculations include determining domestic
sanitary flow and determination if groundwater flow or RDII acreage factors should be adjusted,
and if so, by the calculated amount.
• Domestic Sanitary Flow:
o Domestic sanitary flow needs to be calculated for the development. This
calculation excludes ground water and excludes rainfall derived inflow and
infiltration.
o Domestic sanitary flow is dependent on the characteristics of the development
and will require housing units, unit type (e.g. single family, medium density
residential, etc.), or zoning or land use classification.
o Refer to the Wastewater Collection System Facility Plan Update for recommended
loading values.
• Groundwater Flow:
o The existing system model includes base groundwater flow for dry weather and
wet weather scenarios.
o The Modeler must decide whether the development will require an increase to
the groundwater component of the modeling scenarios. This calculation will be
development specific. Values can be determined based on size and length of pipe
within the development or based on acreage of the development.
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Technical Memorandum 11.0 – Updating Model Development Loading
o Refer to the Wastewater Collection System Facility Plan Update for recommended
loading values.
▪Note that two values may be required.
• Ground Water for dry weather base infiltration.
• Ground Water for wet weather base infiltration.
• Area for RDII:
o Manholes within the model are assigned an acreage that represents a sewershed
area of influence. The acreages were calculated based on Thiessen polygons
generated from the modeling software. The acreage is used during the wet
weather scenario to calculate rainfall derived inflow and infiltration for each
manhole.
o The modeler will need to determine if the acreage assigned to the manholes
should be modified, calculate, and adjust accordingly. Acreage adjustments, if
any, will be development specific.
Update Model Loading
The process for updating development loading is a manual process and consists of updating
loading for three components:
• Updating Domestic Sanitary Loading,
• Updating Groundwater Loading, and
• Updating RDII Acreage.
Updating each factor is discussed further in the following paragraphs.
1.5.1 Development Domestic Sanitary Loading
Updating the development domestic sanitary loading within the model consists of the following
steps:
• Select the desired Manhole.
• In the InfoSWMM Browser, Select the Node Inflow Editor icon.
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Technical Memorandum 11.0 – Updating Model Development Loading
• The Node Inflow Editor Window opens.
• Click on the Dry Weather tab.
o This window shows any current loading assigned to the manhole.
• To add Development Loading:
o Click Add Row.
o Set the Constituent to be Flow.
o In the Allocation Code cell assign an Allocation Code.
• Start the allocation code using the prefix text: “_DEV”
• Follow the prefix text with an appropriate Development name:
o e.g. if the development is called the “Kings Development”
use and allocation code of “_DEV_KINGS”.
• The prefix “_DEV” is used to track, sort, and filter Development
loading.
o In the Average (gpm) cell assign the domestic sanitary loading.
▪Enter the average development domestic sanitary loading in gallons per
minute to represent the dry weather domestic sanitary flow.
o Assign the weekday Pattern 1 and weekend Pattern 2.
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▪The assigned pattern depends on the location of the manhole within the
system.
• If there is existing loading assigned to the manhole, use the same
patterns as the existing loading.
• If there is no existing loading assigned to the manhole, review
downstream manholes until existing loading is encountered. Then
assign the same patterns to the new Development loading.
1.5.2 Development Groundwater Loading
The following steps are used to update development groundwater loading should the Modeler
determine that the ground water base flow needs to be updated. Updating the development
groundwater loading within the model consists of the following steps:
• This process must be completed twice:
o First iteration: Complete for the Dry Weather Groundwater scenario.
▪Use appropriate dry weather groundwater infiltration loading factors.
o Second iteration: Complete for the Wet Weather Groundwater Scenario.
▪Use appropriate wet weather groundwater infiltration loading factors.
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• In the InfoSWMM Browser, Select the Node Inflow Editor icon.
• The Node Inflow Editor Window opens.
• Click on the External tab.
o This window shows any current loading assigned to the manhole.
• To add development groundwater loading:
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o Note: Only a single value can represent the groundwater flow in the database for
an individual manhole.
o Set the Constituent type to Flow.
o In the Baseline cell:
▪If no flow is present, then enter the new development groundwater flow
as a constant flow in gallons per minute.
▪If flow is present, then add the development groundwater flow to the
existing flow (gpm).
o Click Update to save changes.
o Track and acknowledge ground water adjustment in external documentation as
noted in Section 1.3.
o Reminder: this must be completed for both the Dry Weather scenario and the
Wet Weather scenario.
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1.5.3 Development RDII
The following steps are used to update development RDII acreage should the modeler
determine that the acreage needs to be updated. Updating the development RDII acreage
within the model is best done manually at each manhole.
• Select the desired Manhole.
• In the InfoSWMM Browser, Select the Node Inflow Editor icon.
• The Node Inflow Editor Window opens.
• Click on the RDII tab.
o This window shows any current acreage and unit hydrograph (UH) assigned to
the manhole.
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• To add development RDII acreage:
o Note: Only a single value can represent the acreage in the database for an
individual manhole.
o UH (Unit Hydrograph) Group:
▪If an UH is already selected, then do not change.
▪If an UH is not selected, then review downstream manholes and use the
same UH assigned to them.
o In the Sewershed Area (Acres) cell:
▪If no acreage is present, then enter the new development sewershed
area (acres).
▪If acreage is present, then add (or adjust as appropriate) the development
RDII area (acres).
o Click Update to save changes.
o Track and acknowledge RDII acreage adjusted as noted in Section 1.3.
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Query and Track Development Loading
Manholes with development domestic sanitary flow cannot be directly queried. There are two
options for querying development manholes in the model.
•
•
Option 1: Use the dry weather Allocation Code created in Section 1.5.1 to identify
manholes that have development loading.
o This method is discussed further in the following paragraphs.
Option 2: Create an attribute field that is specifically used to identify manholes that have
added Development loading. This will require the Modeler to manually update the
attribute field for each manhole used for development loading.
o This method is not discussed in this memorandum.
1.6.1 Identify manholes that have development loading:
• In the InfoSWMM drop down menu select Edit and then DB Editor to open the database
editor.
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• In the Database Editor Window select Extended Element Modeling Data, then Node DWF,
then OK.
• Sort the allocation code column (“ALLOC_CODE”) in ascending order.
o Left click on the “ALLOC_CODE” column header.
o Select the Sort Ascending icon or Right click and choose Sort Ascending.
• Scroll down until you reach the allocation codes starting with the text “_DEV”.
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• Left click on the row number of the first manhole that has the development code.
• Hold Shift and Left click on the on the row number of the last manhole that has the
Development code.
o The selected rows highlight in blue.
• The selected data can be copied (right click and copy) and then pasted into external
documents.
1.6.2 Add Development Manholes to a Domain
• The manholes can be added to a domain as well:
• Follow the steps in the previous paragraph. Once the manholes that have development
loading are highlight in the DB Editor table, complete the following:
o Right Click and choose “Append to Domain”.
▪Manholes with Development loading are now added to the domain.
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• Review Domain Data:
o You can now view element data using the “Domain” as the selection criteria.
▪Open the Database Editor.
▪Select Extended Element Modeling Data then Node DWF
▪Under Data Scope select Domain, then OK.
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o Note: DWF data will include ALL domestic sanitary flow assigned to the manholes
including existing and new development loading. The data can be copied out to
external files and filtered or organized as required.
o In the example database table below, each manhole has at least two different
loading allocation types. One type (e.g. MFR) is associated with a land use
loading and the other type is associated with Development loading. The
Allocation Code starting with the prefix “_DEV” identifies development loading.
Conclusion
Following the model loading update process within this memorandum will allow the City to
update and track development loads allocated within the model. The City will continually be
able to review new developments and assess capacity of the wastewater collection system and
determine if the system has the ability to handle the increased flow from development.
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