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Home My WebLink About007 - Roers Buildings A and B - Sewer Memo Roers - Bozeman Apartments SEWER IMPROVEMENTS SANITARY SEWER BASIS OF DESIGN REPORT January 2026 PREPARED BY: MMI #: 10549.002 No. 49499 CELINE M PROFESSIONAL E N G IN EERM O N TANA LICENS ED SAUCIER 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 ....................................................................................................................................... 4 7 ENVIRONMENTAL IMPACTS ........................................................................................................................ 4 APPENDICES Appendix A: Circular DEQ 4 Table 3.1-1: Typical Wastewater Flows 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.: 10549.002 INTRODUCTION This design report provides the criteria used as a basis of design for the sewer lines proposed to service Roers – Bozeman Apartments Buildings A and B. This report is submitted in conjunction with the completed plans and specifications to the City of Bozeman and is organized following the outline recommended in DEQ-2, Chapter 10. Section 11.1, Engineering Reports. Buildings A and B are located in Lot 1 Block 3 of Urban + Farms Phase 2. Lot 1 Block 3 is located north of Huffine Lane, west of South Laurel Parkway, south of Valley Commons Drive and east of Park C Block 3. This project is located within the City of Bozeman, Montana. 1 PROBLEM DEFINED This project involves the installation of two 8-inch sewer services that will tie into the existing 8-inch sewer stubs into Lot 1. Sewer facilities included in this project will be designed with adequate capacity to handle flow of the maximum peak hour flow rate within Building A and Building B, including residents, customers and employees. 2 DESIGN CONDITIONS Buildings A and B will be located on property zoned B-2M (Community Business District- Mixed) per the City of Bozeman’s zoning map. The capacity requirement for the sewer main extension is calculated as follows: Proposed Average Daily Flow The proposed Building A is residential (145 units), and Building B is mixed residential (148 units) and commercial (8,770 sq. ft.). The proposed demands for each space are based on Table V-1 in COB Design Standards and Specification Policies. The assumptions for each of the spaces are as follows: Assumptions: · New sanitary sewer lines to serve residential areas shall be designed to accommodate an average daily flow of 2.17 people per dwelling unit and 64.4 gal/capita/day. (COB Design Standards and Specifications Policy) · An infiltration rate of 150 gal/acre/day shall be added to all flow calculations when designing new sewers. (COB Design Standards and Specifications Policy) · The demand for commercial can be estimated from DEQ – 4 Table 3.1-1. A customer has a demand of 3 gal/capita/day and an employee of 10 gal/capita/day · Commercial in Building B has total square footage of 8,770 SF o Proposed commercial space has estimated occupancy of 100 SF/person o Population: 88 o Employees estimated: 6 Based on these criteria the demands predicted for the project are: Average Day Demand Residential: Building A (145 units) 145 units x 2.17 persons x 64.4 gpd = 20,263 gpd Building B (180 units) 148 units x 2.17 persons x 64.4 gpd = 20,683 gpd Commercial: 88 customers x 3 gpd = 264 gpd 6 employees x 10 gpd = 60 gpd Total Average Day Demand = 41,270 gpd or 28.7gpm Peaking Factor The same peaking factor will be used from the Urban + Farms Phase 2 Infrastructure Improvements Design report. The peaking factor for the west zone where Lot 1 Block 3 is located, is 3.62. Peak Hour Flow Average Day Demand x PF = 41,270 gpd x 3.62 =149,397 gpd or 103.7gpm Infiltration 6.81 ac x 150 gal/acre/day = 1,022 gpd or 0.7 gpm Total Peak Flow 149,397 gpd + 1,022 gpd = 150,419 gpd or 104.5gpm Please refer to the table below for comparison between maximum pipe capacity for the existing main and proposed flows to see that the proposed piping is adequate. LOT PEAK FLOW (gpm) PROPOSED CONVEYANCE *MAXIMUM FLOW FOR 8” MAIN (gpm) Lot 1 Block 3 101.7 8-inch sewer main @ 0.4% 313 Lot 1 Block 3 101.7 10-inch sewer main @ 0.28% 474 Lot 1 Block 3 101.7 15-inch sewer main @ 0.15% 1,024 *Roughness coefficient (n) value of 0.013, relative flow depth d/D = 0.75. Predicted Average Daily Flow from Urban + Farms Phase 2 The Urban + Farms Phase 2 Infrastructure Improvements Design report, (Hyalite Engineers, PLLC, November 2023), lists the water demand projections for the development for Lot 1 Block 3 of the subdivision. The original report provided in Appendix A, uses a flow rate of 2,000 gal/acre/day for B-2M zoning. Lot 1 Block 3 is 6.81 acres. The peaking factor used was 3.62. Using these assumptions, the predicted flows for the lot are as follows: Predicted Average Daily Flow = (6.81 acres)(2,000 gal/acre/day) = 13,620gpd or 9.46gpm Predicted Peak Hour Flow = 13,620gpd x 3.62 = 49,304gpd or 34.2 gpm Infiltration = 6.81 ac x 150 gal/acre/day = 1,022 gpd or 0.71gpm Predicted Total Peak Hour Flow = 49,304gpd +1,022gpd = 50,326gpd or 34.95 gpm 3 IMPACT ON EXISTING WASTEWATER FACILITIES The predicted flows in the engineering report for the buildings are more than the proposed demands calculated in this memo however it is shown that an 8” main has the capacity for the proposed building wastewater flow. The wastewater generated from the Roers – Bozeman Apartments flows to Norton Ranch Lift Station in the southeast quadrant of Laurel Parkway and Vaugh Drive. The Norton Ranch Lift Station is undergoing a redesign. The new lift station design assumes an average flow of 205,276 gpd for Urban + Farm Phase 2 from Table 1 of the City of Bozeman Norton Ranch Lift Station report dated November 5, 2024 prepared by HDR. The Urban + Farms Phase 2 sewer report, prepared by Hyalite Engineering uses an average flow below that rate, 170,515 gpd. The remaining capacity for the lift station average day flow designated for Urban + Farm Phase 2 Subdivision is 164,006 gpd after the construction of Roers Apartments. Average Flow Lift Station Capacity 205,276 gpd – 41,270 gpd = 164,006 gpd remaining 4 PROJECT DESCRIPTION This project involves the installation of 110 feet of 8-inch sewer service for Building A which ties into an existing 8-inch main via 48” manhole along Valley Commons Drive. And 146 feet of 8- inch sewer service for Building B which ties into an existing 8-inch main via 48” manhole along Valley Commons Drive. 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 system is to be constructed to the City of Bozeman and the 7th edition of Montana Public Works standard specifications (MPWSS). The sewer service shall be 8-inch diameter SDR 35 polyvinyl Chloride (PVC). 6 SITE INFORMATION The project site has been zoned B-2M by the City of Bozeman. The proposed site has existing grades of less than 4% slope. The site also has mostly Hyalite Beaverton complex with sections of Enbar Loam and Meadowcreek Loam (USDA Soil Survey). The ground water flows generally from the south to the north based on general groundwater flow in the valley. The groundwater depth at this site is likely seasonally varied. A groundwater depth of approximately 5’ was observed in multiple test pits in April. The project site has been receiving fill material placed and compacted in lifts to the desired grade. The site is not located in a floodway or floodplain. 7 ENVIRONMENTAL IMPACTS There are no expected environmental impacts from this sewer main extension, as the City of Bozeman Wastewater Treatment Plant has adequate capacity for the proposed development. Circular DEQ 4 Page 27 of 159 December 2023 Edition TABLE 3.1-1 TYPICAL WASTEWATER FLOWS FROM COMMERCIAL, INDUSTRIAL, AND OTHER NONRESIDENTIAL SOURCES Source Unit Wastewater Flow, gpd/unit Range Typical Airport Passenger 2-4 3 Automobile Service Station Vehicle Served 7-13 10 Employee 9-15 12 Bar Customer 5 3 Employee 10-16 13 Church Seat 3 (Not including a kitchen, food service facility, daycare, or camp) Church Seat 5 (Including kitchen, but not including a food service facility, day care, or camp) Daycare Child 10-30 25 Employee 10-20 15 Department Store Toilet Room 400-600 500 Employee 8-12 10 Hospital, medical Bed 125-240 165 Employee 5-15 10 Hospital, mental Bed 75-140 100 Employee 5-15 10 Hotel/Motel Guest 40-56 48 Employee 7-13 10 Industrial Building Employee 10-16 13 (Sanitary waste only) Laundry Machine 450-650 580 (Self-serve) Wash 45-55 50 Office Employee 7-16 13 Prison Inmate 75-150 115 Employee 5-15 10 Rest home Resident 50-120 85 Restaurant Meal 2-4 3 School, day: With cafeteria, gym, showers Student 15-30 25 With cafeteria only Student 10-20 15 Without cafeteria, gym, showers Student 5-17 11 School, boarding Student 50-100 75 Shopping Center Parking Space 1-2 2 Employee 7-13 10 Store Customer 1-4 3 Employee 8-12 10