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Water and Wastewater Design Report
ENTERPRISE SITE PLAN
150 Automotive Way
Bozeman, Montana
February 2023
Prepared By:
Genesis Engineering, Inc.
GEI Project #: 1134.008
Prepared For:
J & D Family Limited Partnership
270 Automotive Drive
Bozeman, MT 59718
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Water and Wastewater Design Report
Table of Contents
I. Project Background………………………………………………………………………………………………. 4
1. Introduction……………………………………………………………………………………………………………… 4
2. Soil and Groundwater………………………………………………………………………………………………. 4
3. Land Use…………………………………………………………………………………………………………………… 4
4. Design Standards……………………………………………………………………………………………………… 4
II. Sanitary Sewer System……………………………………………………………………………………. 5
1. Projected Flows…………………………………………………………………………………………………….….. 5
2. Collection System……………………………………………………………………………………………….……. 5
3. Service Connections………………………………………………………………………………………….……... 5
III. Water System……………………………………………………………………………………………….….… 6
1. Projected Usage………………………………………………………………………………………………….……. 6
2. Hydraulic Analysis……………………………………………………………………………………………….……. 6
3. Water Distribution System…………………………………………………………………………………….…. 6
4. Service Connections……………………………………………………………………………………………..….. 7
IV. Conclusion……………………………………………………………………………………………………..….. 7
List of Tables
Table 1. Projected Sewer Peak Flow ………………………..……………………………………………………………….… 5
Table 2. Projected Water Demands .………………………..……………………………………………………………….… 5
Appendix A—Drawings
Existing Water and Sewer Systems…………………………………………………………………………………………… W&S‐1
Appendix B—Calculations
Demand Calcs
Hydrant Flow Test
List of References
City of Bozeman Design Standards and Specifications Policy, March 2004, and all addenda.
Montana Public Works Standard Specifications (MPWSS), 6th Edition
City of Bozeman Modifications to the MPWSS, 6th Edition, March 31, 2011 & all addenda
Montana Department of Environmental Quality (MDEQ) Design Circulars DEQ‐1 and DEQ‐2
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I. Project Background
I‐1. Introduction
The Enterprise Site Plan encompasses approximately 2.7 acres of the 4.7 acres Lot 1 of Phase 2 of the J & D
Family Subdivision in Bozeman, Gallatin County, Montana. The proposed Enterprise Building will be fed from
the proposed J&D Family Subdivision main extension which is centrally located within Lot 1. The property lies
immediately west of Cottonwood Road, and south of West Babcock Street.
This report describes the water and wastewater systems that will be required to service the Enterprise Site
Plan. The proposed water and wastewater services will be connected to the public water and sewer systems
owned and maintained by the City of Bozeman.
I‐2. Soil and Groundwater
The NRCS Soil Survey identifies two major soil types on the proposed subdivision: Lamoose silt loam (537A)
and Enbar loam (509B). These soils belong to hydrologic soil group B & C as they are comprised primarily of
loams and silt loams with slow to moderate infiltration rates.
A geotechnical investigation by Rimrock Engineering in March and April, 2007 found static water levels
between three (3) and five (5) feet below existing grade in test pits and bore holes. Rimrock’s investigation
was conducted on the Norton East Ranch property immediately west of the proposed J & D Family Major
Subdivision.
I‐3. Land Use
The pre‐development land use on the proposed subdivision is pasture and open space, though the land is not
currently being used for grazing or other agricultural production. The proposed use is a rental car facility and
overflow parking lot.
I‐4. Design Standards
All sanitary sewer mains, water mains, service connections, and appurtenances will be designed and
constructed in accordance with the Montana Public Works Standard Specifications (MPWSS), 6th Edition; City
of Bozeman Design Standards and Specifications Policy (including all Addenda), March 2004; City of Bozeman
Modifications to the MPWSS, March 2011; the Montana Department of Environmental Quality (MDEQ) Design
Circulars DEQ‐1 and DEQ‐2, and any additional addenda thereof. The City of Bozeman will assume operation
and maintenance of the wastewater and water systems and appurtenances upon construction and acceptance
of the installation.
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II. Sanitary Sewer System
II‐1. Proposed Design Flow
Since the water demands for the Enterprise Building are not known at this time, Table V‐1 from the Design
Standards and Specifications Policy was used to estimate its generated sewage flows for the existing B‐1
zoning and compared to flows generated using Table 3.1‐1 in DEQ 4.
Table 1 shows the average daily demand and equivalent population calculation using Table V‐1.
Table 1. Wastewater Flow and Equivalent Population:
Parcel Use Lot Area ADF/Acre ADF Equivalent Pop
(acres) (gpd/acre) (gpd) (people)
Enterprise B‐1 Zoning 2.7 1,000 2,700 30
Infiltration 2.7 150g/ac/day 405
Total ADF = 3,105 gpd
The City of Bozeman standard of 89 gallons per capita per day was applied to the 2,700 gallons per day to
determine an equivalent population for the subdivision of 30 people, yielding a peaking factor of 4.51. The
peaking factor, PF, was calculated by the following formula, where P = population (thousands):
PF = 18 + P0.5
4 + P0.5
Multiplying the pre‐infiltration average daily flow of 2,700 by the peaking factor of 4.51 results in a calculated
peak flow of 12,177 gallons per day. Infiltration into the sanitary sewer system from the site plan was
calculated to be 405 gallons per day using the City’s rate of 150 gallons per day per acre over the 2.7 acre area.
Therefore, the combined estimated peak hour design flow for the entire lot is:
Peak Hour Flow: 12,582 gallons per hour
Utilizing Table 3.1‐1 in DEQ 4 and the existing rental car facility is a service station with 5 employees, the
existing flows are as follows:
5 employees at 16 gpd = 80 gpd
20 vehicle washes at 4 gpm for 8 min = 640 gpd
Total estimated average daily flow = 720 gpd
Peak hour flow = 720 gpd x 4.51=3,247 gpd + 405 gpd infiltration = 3,652 gallons per hour
Utilizing Table 3.1‐1 in DEQ 4 and the proposed expanded rental car facility is a service station with a total of
10 employees, the flows are as follows:
10 employees at 16 gpd = 160 gpd
35 vehicle washes at 4 gpm for 8 mins = 1,120 gpd
Total estimated average daily flow = 1,280 gpd
Peak hour flow = 1,280 gpd x 4.51 = 5,773 gpd + 405 gpd infiltration = 6,178 gallons per hour
Using Manning’s Equation and a minimum slope of 0.004 ft/ft for an 8‐inch diameter pipe, the full‐flow
capacity of the pipe is 0.76 cfs or 497,629 gallons per day. The empirically‐based peak hour design flow for the
entire Lot 1 occupies 2.5% of the proposed pipe. The full flow velocity of the 8‐inch diameter SDR‐35 main is
2.2 ft/sec exceeding the minimum of 2.0 ft/sec required.
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II‐2. Collection System
No new sewer main or manholes are proposed for the Enterprise Expansion Site Plan. The wastewater from
the existing Enterprise building is connected to the sewer main via a 4” SDR PVC sewer service. The sewage is
conveyed north into the gravity sewer main in West Babcock Street, then east via an 8‐inch SDR‐35 sewer main
to Cottonwood Road where it will join the Valley West Sewer Trunk Line and flow north. According to the
Morrison‐Maierle Design Report for Valley West Sewer Trunk Line (1998), the existing Trunk Line is designed
with development of the subject property and has adequate capacity to convey the peak design flow.
II‐3. Service Connections
All sewer connections associated with the expansion will occur within the internal plumbing of the existing
building. As always any future connections to the sanitary sewer mains will be designed in accordance with
the City’s Design Standards and Specifications Policy. Connections to the sewer main will be made with in‐line
gasketed wyes.
III. Water System
III‐1. Projected Usage
Using Table V‐1 from the Design Standards and Specifications Policy, Genesis estimated the development’s
typical water demands. Lot 1 has a total average daily demand (ADD) of 3.3 gallons per minute, a maximum
day demand of 7.5 gallons per minute, and a peak hour demand of 9.8 gallons per minute. The average daily
demands are exclusive of the suggested fire flow requirement of 2,000 gallons per minute. When modeled,
the system design satisfies the fire flow occurring simultaneously with the maximum day demands of Lot 1.
Table 2 below summarizes the projected usage.
Table 2. Projected Water Demand:
(1.0) (2.3) (3.0)
Parcel Use Lot Area ADF/Acre ADF ADD Max Day Peak Hr
(acres) (gpd/acre) (gpd) (gpm) (gpm) (gpm)
Enterp. B‐1 Zoning 2.7 1,000 2,700 1.9 4.3 5.6
Utilizing Table 3.1‐1 and assuming the proposed expanded rental car facility is a service station with 10 employees, the
flows are as follows:
10 employees at 16 gpd*1.10 = 176 gpd
35 vehicle washes at 4 gpm for 8 mins * 1.10 = 1,232 gpd
Total estimated average daily flow = 1,408 gpd
Average Daily Demand = 1.00 gpm
Max Day Demand = 2.30 gpm
Peak Hour Demand = 3.00 gpm
Genesis also looked at water usage through existing meter reading data from the years of 2021 and 2022. The
average daily demand from the meter readings is approximately 2,826 gpd. This suggests some irrigation is
may also be occurring and/or additional cars are being washed. The two years’ worth of data suggest the
water demand estimates are low.
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The Owner is using existing water rights and/or existing irrigation wells on the property to water the larger
landscaped areas along the perimeter of Lot 1.
III‐2. Hydraulic Analysis
The hydraulic modeling program WaterCAD was used to model domestic and fire protection demands for Lot
1. The results of the Phase 1 model were as follows:
Available Fire Flow ‐ 2,067 gpm at 20 psi at the Lot 1 hydrant
Maximum System Pressure – 62 psi at the new connection point
Minimum System Pressure – 20 psi within the Lot 1 main during fireflow.
It is noted that additional development has occurred in the area since the completion of Phase 1 and
therefore, a more recent hydrant flow test was requested from the City near the service connection in West
Babcock Street between Automotive Way Avenue and Cottonwood Road. The empirical test results can be
found in the appendix.
III‐3. Water Distribution System
No new water main is planned with this project. The existing 1.0” copper water service shall provide enough
water for the Enterprise Building including the expansion.
III‐4. Service Connections
Future service connections to the water mains will be designed in accordance with the City’s Design Standards
and Specifications Policy and sized based on the projected usage for each service line. Service lines less than 4
inches in diameter will be type “K” copper pipe, while those larger than 4 inches will be ductile iron. Water
services will meet all applicable design standards and flow requirements.
IV. Conclusion
The analysis and calculations included in this report demonstrate that the proposed designs for water
provision, including fire flow, and wastewater disposal satisfy state and local design requirements.
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