HomeMy WebLinkAbout007 Boulder Creek Lots 3 & 4 - Sewer Service Eng Report
BOULDER CREEK APARTMENTS PHASE 2 - BOZEMAN
SEWER IMPROVEMENTS
SANITARY SEWER BASIS OF DESIGN REPORT
March 202
PREPARED BY:
MMI #: 4192.025
Table of Contents
INTRODUCTION ........................................................................................................................................... 1
1 PROBLEM DEFINED ........................................................................................................................... 1
2 DESIGN CONDITIONS ......................................................................................................................... 1
3 IMPACT ON EXISTING WASTEWATER FACILITIES ........................................................................ 3
4 PROJECT DESCRIPTION .................................................................................................................... 3
5 DESIGN CRITERIA .............................................................................................................................. 3
6 SITE INFORMATION ............................................................................................................................ 3
7 ENVIRONMENTAL IMPACTS .............................................................................................................. 3
8 OPERATION AND MAINTENANCE .................................................................................................... 3
APPENDICES
Appendix A – Laurel Glen Lift Station Capacity Design Report, May 3, 2020
Appendix B – Northwest Crossing Subdivision Phase 1, April 6, 2021
Prepared by:
Morrison-Maierle, Inc.
2880 Technology Blvd. W.
Bozeman, Montana 59771
Phone: (406) 587-0721
Fax: (406) 922-6702
Written By: CMS Checked By: MEE
Approved By: MEE
PROJECT NO.: 4192.025
1
INTRODUCTION
Phase 2 of Boulder Creek Apartments is located off Abigail Lane on Lots 3 & 4 of the Boulder
Creek Subdivision (see the vicinity map for location details). As a part of this project, three
apartment buildings are currently proposed, one 12-plex and two 18-plexes. During the
construction of Phase 1, located on Lots 1 & 2, a sewer main extension will be installed which
will service two of the buildings in Phase 2. The sewer main extension was designed and
installed in accordance with the Montana Department of Environmental Quality (MDEQ) Circular
No. 2, Chapter 10, Section 11.1, Engineering Reports; Montana Public Works Standard
Specifications (MPWSS); The City of Bozeman Modifications to MPWSS; and the City of
Bozeman Wastewater Facility Plan.
The design report is to verify that there is an adequate capacity to receive wastewater flows
from Phase 2 of the Boulder Creek Apartment development. The following design report follows
the section numbering of the Circular DEQ-2 Standards for Public Sewage Systems, June 3,
2016.
1 PROBLEM DEFINED (DEQ 11.11)
This project involves the installation of an 8-inch sewer services for three proposed multifamily
apartment buildings as a part of Phase 2 of Boulder Creek Apartments. Building 1 (12-plex) will
utilize a proposed service that will tie into an existing 8-inch stub from the main within Abigail Ln.
Building 2 & 3 (18-plexes) will be serviced using stubs off of the sewer main extension within
Lots 2 & 3 that was installed as a part of the Phase 1 development.
Sewer facilities included in this project will be designed in accordance with Montana Department
of Environmental Quality (MDEQ) regulations. Adequate capacity will be provided to allow for
growth in areas adjacent to the actual project areas. Flow and population data for the project
will be consistent with the City’s approved Facilities Plan, where applicable.
2 DESIGN CONDITIONS
The Boulder Creek Apartments – Phase 2 are located off of Abigail Lane on Lots 3 & 4 of the
Boulder Creek Subdivision. Three apartment buildings are currently proposed, one 12-plex and
two 18-plexes. The two 18-plexes will be serviced from the sewer main proposed from the
Boulder Creek Apartments – Phase 1 Sewer Extension. The 12-plex will be serviced from the
existing 8” main that runs along Abigail Lane.
The sewer main extension installed as a part of Phase 1 was intended to service four apartment
buildings, two 12-plexes (Phase 1) and two 18-plexes (Phase 2). The Phase 2 contribution to
the sewer main will be the same as calculated as a part of the original Boulder Creek
Apartments Sewer Improvements report dated October 2021.
From the previous design report the flows to the sewer main extension was calculated as
follows:
Flows to Existing 8” Sewer Main in Lots 2 & 3
Residential
2
60 each apartment units proposed x 2.17 people per dwelling unit (COB Design Standards V-
B4) = 131 people
Wastewater Flow Rate = 131 people x 64.4 gallons per capita day (COB Design Standards V-
B4)
= 8,436.4 gallons per day (gpd) = 5.86gpm
Infiltration
2.52 acres x 150 gallons/acre/day (COB Design Standards V-B4) = 378 gallons/day
Total Average Flow
Total Average Flow = 8,436.4 gpd + 378 gpd = 8,814.4 gpd = 6.12 gpm
Total Peak Flow
Population = 131 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.21
Peak Flow = 8,814.4 gpd (avg daily flow) x 4.21 = 37,108.62gpd = 25.8gpm
Total Flows from Lots 3 & 4
Residential
48 each apartment units proposed x 2.17 people per dwelling unit (COB Design Standards V-
B4) = 104 people
Total Average Flow
Wastewater Flow Rate = 104 people x 64.4 gallons per capita day (COB Design Standards V-
B4)
= 6,697.6 gallons per day (gpd) = 4.65gpm
Total Peak Flow
Population = 104 people
Peaking Factor (PF) = (18+(population/1000)^.5)/(4+(population/1000)^.5)
Peaking Factor = 4.24
Peak Flow = 6,697.6gpd (avg daily flow) x 4.24 = 28,397.82gpd = 19.72gpm
Please refer to the table below for comparisons between maximum flows and proposed flows
and see that that proposed piping is adequate.
LOT
PEAK FLOW
(gpm) PROPOSED CONVEYANCE
*MAXIMUM FLOW
FOR 8” MAIN (gpm)
3 & 4 19.72 Existing 8-inch sewer main 346
*8-inch pipe at minimum grade (0.4%) with a roughness coefficient (n) value of 0.013
3
3 IMPACT ON EXISTING WASTEWATER FACILITIES
The original Laurel Glen Lift Station Capacity Analysis Design Report which was prepared by
C&H on May 3, 2020 indicated that the full build out of the Boulder Creek Subdivision would not
be possible until additional sewer capacity was provided. This sewer capacity would come from
the construction of the sanitary sewer main diversion from Flanders Way to the NERI in
Cottonwood Road. This diversion would provide sufficient capacity in the Laurel Glen Lift Station
(LGLS) to handle the full build out of the Boulder Creek Subdivision.
However, as a part of Northwest Crossing Phase 1, the City of Bozeman required NWX to
accommodate the existing wastewater flow from the area south of NWX, specifically the existing
flow in the mains where Rosa Way meets West Oak Street (Appendix C of NWX Sewer Report
attached). While the Boulder Creek Subdivision is not included in this area, the NWX sewer
infrastructure alleviated approximately 73.5 acres or 353.3 gpm of peak flow which was
originally flowing to LGLS and diverted it to the Davis Lift Station. For this reason, the Laurel
Glen Lift Station will be able to handle the flows from the proposed development.
4 PROJECT DESCRIPTION
This project involves connecting to two sewer service stubs to existing sewer main of 732 feet of
an 8-inch sewer which then flows into an existing 8-inch main along Abigail Lane. There will be
another sewer service connection to and existing sewer stub along Abigail Lane. This project
also includes the abandonment of two existing sewer service stubs along Abigail Lane.
5 DESIGN CRITERIA
Design criteria including average and peak flows as well as sewer depth information were
provided in previous sections. The proposed sewer service conforms to the State’s minimum
vertical and horizontal separation criteria for sewer services.
The proposed conventional gravity sewer collection system is to be constructed to City of
Bozeman and the 6th Edition of Montana Public Works (MPW) standard specifications. The
sewer service shall be 8-inch diameter SDR 35 Polyvinyl Chloride (PVC) pipe.
6 SITE INFORMATION
The project site has been zoned R-4 by the City of Bozeman. The existing site is bound by
Boulder Creek Apartments- Phase 1 to the South, Oak St to the North, Abigail Lane to the West
and Sacco Drive to the East. The site has existing grades of less than 4% and has Turner
loam, Hyalite-Beaverton complex and Meadowcreek loam soil deposits (see the USDA Soil
Survey information attached). The site is not located in a floodway or floodplain.
7 ENVIRONMENTAL IMPACTS
There are no expected environmental impacts from the sewer services, as the City of Bozeman
Wastewater Treatment Plant has adequate capacity for this extension.
8 OPERATION AND MAINTENANCE
Sewer mains will be owned, operated, and maintained by the City of Bozeman.
4
Appendix A
Laurel Glen Lift Station Capacity Design Report, May 3, 2020
5
Appendix B
Northwest Crossing Subdivision Phase 1, April 6, 2021
NORTHWEST CROSSING SUBDIVISION
PHASE 1
SANITARY SEWER SYSTEM IMPROVEMENTS
SANITARY SEWER EXTENSION BASIS OF DESIGN REPORT
April 6, 2021 (Revised)
January, 2021 (Original)
PREPARED BY:
MMI #: 5659.006
Table of Contents
1 PROBLEM DEFINED (DEQ 11.11) ...................................................................................................... 1
2 DESIGN CONDITIONS (DEQ 11.12) ................................................................................................... 1
3 IMPACT ON EXISTING WASTEWATER FACILITIES (11.13) ............................................................ 2
4 PROJECT DESCRIPTION (11.14) ....................................................................................................... 3
5 DRAWINGS (11.15) .............................................................................................................................. 3
6 DESIGN CRITERIA (11.16) .................................................................................................................. 3
7 SITE INFORMATION (11.17) ............................................................................................................... 4
8 ALTERNATIVE SELECTION/ANALYSIS (11.18) ................................................................................ 4
9 ENVIRONMENTAL IMPACTS (11.19) ................................................................................................. 4
EXHIBITS
Exhibit A Vicinity Map Exhibit B Framework Plan – by Norris Design Exhibit C Rosa Way Sewer Flow
APPENDICES
Appendix A NRCS Soils Report
Prepared by:
Morrison-Maierle, Inc.
2880 Technology Blvd. W.
Bozeman, Montana 59771
Phone: (406) 587-0721
Fax: (406) 922-6702
1
Northwest Crossing Subdivision: Phase 1
Sanitary Sewer Design Report
EXECUTIVE SUMMARY
The proposed Northwest Crossing Subdivision encompasses a total of 160.5 acres and is generally located at the northwest corner of West Oak Street and Cottonwood Road. The property is within the boundaries of the City of Bozeman, Montana and was annexed and zoned REMU (130.994 acres) and B2-M (29.513 acres) in January of 2019. Phase 1 consists of development tracts A-D for a total of 32.9 acres as detailed in the Master Plan Framework developed by Norris Design (Exhibit B). See the vicinity map on Exhibit A for details. The following is the legal description for the property. Tract 5 of Certificate of Survey No. 2552, located in the NE1/4 of Section 4, Township 2 South, Range 5 East, Principal Meridian, Gallatin County, Montana.
Sewer collection for the project will consist of sewer mains located in the right-of-way or easements with individual services stubbed to each property or building location. Sewer mains
will generally flow to the north and east and connect to an existing 21” PVC main in Cottonwood Road, which drains to a 27” interceptor in Baxter Lane.
This design report provides a basis of design for the sewer collection system for the Northwest Crossing Subdivision Phase 1. The sewer collection will be designed and installed in accordance with the Montana Department of Environmental Quality (MDEQ) Circular No. 2; Montana Public Works Standard Specifications (MPWSS); The City of Bozeman Modifications to MPWSS; City of Bozeman Design Standards and Specifications Policy March of 2004, and all Addendum’s; and the City of Bozeman Wastewater Facility Plan. 1 PROBLEM DEFINED (DEQ 11.11)
The purpose of this design report is to quantify the anticipated sewer flows from the Northwest Crossing Subdivision and provide preliminary sizing for the proposed sewer infrastructure. The flows from Phase 1 of the Northwest Crossing Subdivision will discharge into the existing 21” sewer main in the Cottonwood Road right of way and the 27” sewer interceptor in Baxter Lane.
The following design report follows the section numbering of the Circular DEQ-2 Standards for Public Sewage Systems, 2018. 2 DESIGN CONDITIONS (DEQ 11.12)
Phase 1 consists of parcels with two different zoning designations. For the purpose of this report, we will use the areas associated with the Master Site Plan (see the Framework Plan by Norris Design in Exhibit B). Using the areas from the Framework Plan is more conservative than using the areas from the Preliminary Plat (Framework Plan = 32.9 ac and Preliminary Plat = 28.4). The Preliminary Plat areas exclude the road rights-of-way. The Framework Plan is based off gross area. Parcels A, B and C are zoned B2-M and D is zoned REMU. At this point in the design, A and B are planned to be used as commercial centers while C and D will be multifamily housing.
The wastewater generation for the proposed development includes sewer services for B2-M and REMU Zoning designation includes uses outlined in the UDO Sec. 38.300.110. Design flowrates for this development are based on the “City of Bozeman Wastewater Collection
2
Facilities Plan Update” prepared my Morrison-Maierle, Inc. in 2015. Based on Table 2-13, the REMU zoned parcels use a flowrate of 1,456 gal/acre/day which is developed from an estimate
of 2.17 people per dwelling and a maximum of 10.4 units per acre. The B-2M parcels are designated a flowrate of 2,000 gal/acre/day. The peak hour factor is calculated based on the City Design Standards and Specification Policy). The final addition to projected wastewater
generation is infiltration/inflow (I/I) which is 150 gpd/acre per the City Design Standards and Specifications Policy (Section V.B.4 - Page 48).
The anticipated sewer flows are calculated as follows:
Table 1 – Project Anticipated Demand
1 2015 City of Bozeman Wastewater Facility Plan (Table 2-14, Community Commercial) 2 2015 City of Bozeman Wastewater Facility Plan Phase 1: Total Average Daily Flow Total Average Daily Flow = 29.2 + 1.8 + 15.5 + 1.6 gpm
= 48.1 gpm = 69,264 gpd
Phase 1: Total Peak flow Total Peak Flow = 120.5 + 66.2 gpm = 186.7 gpm Sewer Capacity Calculations 3 IMPACT ON EXISTING WASTEWATER FACILITIES (11.13)
The property is within the wastewater planning boundary for the City of Bozeman as described in the 2015 City of Bozeman Wastewater Collection System Facilities Plan. The property is planned to be served by the proposed Davis Lift Station. This lift station and associated piping to serve the drainage basin is currently under design by HDR Engineering. We have contacted
HDR / COP Construction and they have confirmed that infrastructure is currently being installed with completion anticipated July of 2021. All of Phase 1 will flow into the existing Cottonwood main in two locations. New manholes will be placed on the main approximately 1200 ft and
1800 ft north of the Oak Street intersection. Capacity for the entire Northwest Crossing subdivision was addressed in the Master Site Plan Sewer Design Report.
From a treatment perspective, the City of Bozeman’s Water Reclamation Facility has adequate capacity to serve the development.
3
4 PROJECT DESCRIPTION (11.14)
The purpose of this design report is to quantity the anticipated sewer flows from Phase 1 of the
Northwest Crossing Subdivision and provide preliminary sizing for the proposed sewer infrastructure. The flows from the Northwest Crossing Subdivision will discharge into the existing 21” sewer main in the Cottonwood Road right of way and continue on to the 27” sewer
main in Baxter Lane. 5 DRAWINGS (11.15) Drawings identifying the site of the project, including the location and alignment of proposed facilities are included in this submittal (see infrastructure plans for details). 6 DESIGN CRITERIA (11.16)
Design criteria including average and peak flows were provided in previous sections. The
proposed sewer mains will conform to the State’s minimum vertical and horizontal separation criteria from water mains.
The proposed conventional gravity sewer collection system is to be constructed to City of Bozeman and the 6th Edition of Montana Public Works (MPW) standard specifications. The sewer mains shall be SDR 35 PVC pipe. All manholes shall be standard concrete manholes
spaced no more than 400 feet apart. 12” Sewer Main
As part of the review of the preliminary plat for Phase 1, the City of Bozeman has required NWX to accommodate the existing wastewater flow from the area south of this subdivision. More particularly, the existing flow in the mains where Rosa Way meets West Oak Street. The contributing area can be seen in Exhibit C. Our estimation of this flow is: Based on the the area shown in Exhibit C, the contributing area is approximately 73.5 acres. Assuming the entire area is R-4 zoning at 1,950 gal/acre/day, the potential flow from this area is estimated at 143,325 gallons/day. This equates to average flow ~99.5 gpm. Assuming 64.4 gpd/person/day (COB Facility Plan), this equates to a population of 2,226 persons. A peaking factor is then calculated to be 3.55 using the standard equation listed in COB Section V.B.6.
A peak flow for this line is estimated to be 99.5 gpm * 3.55 = 353.3 gpm.
For NWX Phase 1, the total peak flow was calculated to be 187.4 gpm. That means the 12” Northwest Crossing sewer mains must be able to convey 187.4 gpm + 353.3 gpm = 540.7 gpm.
To accommodate the Rosa Way sewer flow and the Phase 1 NWX flows, our design proposes a 12” main in Rosa Way and Harvest Parkway. A 12” main at minimum slope and 75% capacity can accommodate 651 gpm, which is greater than the estimated peak flow of 540.7 gpm.
4
8” Sewer Main
The proposed design includes 8” sewer mains along Twin Lakes Avenue, Dayspring Avenue, and Wellspring Drive. An 8” main installed at minimum slope and running at 75% capacity can accommodate 305 gpm. Conservatively assuming that all flow from Parcels A and B, plus half
of flow from Parcels C and D will be conveyed into the 8” main in Twin Lakes, the largest peak flow expected would be 153.6 gpm. Therefore 8” mains are sufficient to serve the remainder of the development. Cottonwood Sewer Main Lowering A portion of the 21” sewer main within cottonwood is proposed to be lowered. The lowering of the existing Cottonwood sewer main is proposed at the existing manhole at Harvest Parkway (Sheets SS-10 thru SS-12) was designed to accommodate the western portion of Phase 1 for NWX plus intercept and route flow from an existing manhole south of Oak Street that serves portions of the existing Traditions Subdivision and Flanders Creek Subdivision (Sheet SS-7).
This connection at Rosa Way will divert flow from the Laurel Glen Lift Station as desired by the City.
Per the 2007 Facility Plan, the peak flow requirement within the 21” sewer main in Cottonwood is 4,210 gpm. The lowered 21” pipe is proposed at a slope 0.45%, which is above the minimum slope requirement. A 21” PVC pipe has a 75% full flow capacity of 4,350 gpm when installed at
the proposed 0.45% slope and is therefore sufficient to convey the required flow. 7 SITE INFORMATION (11.17) The development is bounded by Cottonwood Street (principal arterial) to the east, Baxter Lane (minor arterial) to the north, Laurel Parkway (collector) to the west and West Oak Street (principal arterial) to the south. The proposed development is currently undeveloped agricultural land which slopes gently to the north with existing grades of less than 4% and mostly Meadowcreek, Turner and Amsterdam silt loam soil deposits (USDA, Natural Resources Conservation Service, Web Soil Survey). See the soils report located in Appendix A for details. 8 ALTERNATIVE SELECTION/ANALYSIS (11.18) No proposed alternatives were considered 9 ENVIRONMENTAL IMPACTS (11.19) There are no expected environmental impacts from this sewer main extension, as the City of Bozeman Wastewater Treatment Plant has more than adequate capacity for this extension.
N:\5659\006_NWX_Phase1Design\04 Design\Reports\Water and Sewer\Sewer Report- Phase 1.doc
Exhibit A
Vicinity Map
11THSAVE19THNAVE27THNAVE15THNAVEINTERSTATE
90
191HUFFINELN
W LINCOLN ST
W GARFIELD ST
W COLLEGE
W BABCOCK ST MAIN STW
COTTONWOODRD235
BAXTER LN
F
R
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A
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D
OAK STW 27THAVENDURSTON RDDAVISLNPROJECT
LOCATION HARPER-RDPUCKETTSPRINGHILLRDV
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NAVEFERGUSONengineerssurveyorsplannersscientists
2880 Technology Boulevard West
Bozeman, MT 59718
Phone: (406) 587-0721
Fax: (406) 922-6702
VICINITY MAP
SCALE:1" = 3000'
Exhibit B
Framework Plan- by Norris Design
REVISION DATENORTHWEST CROSSING | FRAMEWORK PLAN AND ZONING
4 DECEMBER 2020
1000 200
SCALE: 1” = 200’
400
NORTHBAXTER CREEKSINGLE FAMILYATTACHED & DETACHED
MULTI-FAMILY/COMMERCIAL
COMMERCIAL
PLANNING AREAS
HOMESTEAD PARK
LEGEND
Compliance with City of Bozeman Regulations and Development Review The vision for NWX centers on the two underlaying zoning districts; “Community Business -Mixed” (B-2M) located in the southeastern area of the community and the “Residential Emphasis Mixed-Use” (REMU) zoning district designated across the remainder of the property. NWX is designed to meet the standards of these two underlying zoning designations.
Compliance with the Underlying REMU and B2-M Zoning StandardsAs specified herein and in the NWX Master Plan and Design Guidelines, all new development will meet the development standards of the underlying zoning district. With future development, should any modifications or variances to these standards be necessary to achieve better design or to meet the intent of the Master Plan, then such requests will be addressed through the applicable City review process.
Development of properties zoned REMU will meet the standards set forth within the City of Bozeman Unified Development Code. All new public streets will be complete streets that accommodate pedestrians, bicycles, automobiles, and snow storage. Collector streets and arterial streets external to the site will also accommodate buses. These complete streets create an interconnected and vibrant community. Front-loaded streets are designed to meet the requirements of Section 38.330.020.
Permitted UsesThe range of land uses permitted under REMU and B2-M allows for a dynamic mix of homes and businesses at NWX. The B-2M area will function as a vibrant mixed-use district to accommodate substantial growth and enhance the character of the city. The area will have a range of commercial and office uses that serve the immediate area and City as a whole and will include the integration of multi-family residential structures as a secondary use. The area will be designed to emphasize pedestrian oriented design with enhanced pedestrian connections.
The REMU district will be mixed-use in character and will provide options for a variety of housing, employment, retail and neighborhood service opportunities. Residential uses, with varying product types and densities will be the primary use in this area. The neighborhoods will be compact and walkable and promote a healthy lifestyle and social interactions.
It is intended that the permitted uses in the zoning districts be in accordance with the uses set forth under Table 38.310.040.A.
MSP 1.03LAUREL PARKWAY (90’ ROW)HAVENWOOD DRIVEABIGAIL LANEROSA WAYDAYSPRING AVENUETWIN LAKES AVENUECOTTONWOOD ROAD (120’ ROW)BAXTER LANE (100’ ROW)
WEST OAK STREET (125’ ROW)
HARVEST PARKWAY
TOUCHSTONE LANE
BOZEMAN SPORTS PARK
FLANDERS CREEK SUBDIVISIONLAUREL GLEN SUBDIVISION PHASE 2 FUTURE HIGH SCHOOL
B
A
D
B2-M ZONING
REMU ZONING
EXISTING ZONING BOUNDARY
REVISED ZONING BOUNDARY
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BR I A R W O O D L A N EP1
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Exhibit C
Rosa Way Sewer Flow
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MWMWMWMWMWMWMWMWMWUPSTREAM AREA~73.5 ACRESOAK STCOTTONWOOD RDNORTWESTCROSSING