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Home My WebLink About07 Concept Review Response REF #10 - The Depot - Sewer The Depot at 112 S Church Ave SEWER IMPROVEMENTS SANITARY SEWER BASIS OF DESIGN REPORT November 2025 PREPARED BY: MMI #: 10758.001 2 Table of Contents INTRODUCTION ........................................................................................................................................................ 3 1 PROBLEM DEFINED ....................................................................................................................................... 3 2 DESIGN CONDITIONS .................................................................................................................................... 3 3 IMPACT ON EXISTING WASTEWATER FACILITIES ............................................................................. 5 4 PROJECT DESCRIPTION .............................................................................................................................. 5 5 DESIGN CRITERIA .......................................................................................................................................... 5 6 SITE INFORMATION ....................................................................................................................................... 5 7 ENVIRONMENTAL IMPACTS ........................................................................................................................ 6 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.: 10758.001 3 INTRODUCTION This design report provides the criteria used as a basis of design for the sewer lines proposed to service The Depot at 112 South Church Ave. 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. The proposed building is located at 112 South Church Ave and was previously a residential home. The site is approximately 0.304 acres. This project is located within the City of Bozeman, Montana. 1 PROBLEM DEFINED This project involves the installation of one 6-inch sewer services that will tie into the existing 8-inch sewer main in South Church Ave. Sewer facilities included in this project will be designed with adequate capacity to handle flow of the maximum peak hour flow rate within the building, including residents, customers and employees. 2 DESIGN CONDITIONS The proposed building will be located on property zoned B-3 (Downtown Business District) 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 is mixed residential (12 units), retail (1,663 sq. ft.) and office (4,021 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. The demand for an office from DEQ-4 Table 3.1-1 is 13 gal/employee/day 4 · Retail has total square footage of 1,663 SF o Proposed commercial space has estimated occupancy of 100 SF/person o Population: 17 o Employees estimated: 3 · Office has total square footage of 4,021 SF o Proposed office space has estimated occupancy of 100 SF/person o Population: 40 Based on these criteria the demands predicted for the project are: Average Day Demand Residential: 12 units x 2.17 persons x 64.4 gpd = 1,677 gpd Retail: 17 customers x 3 gpd = 51 gpd 3 employees x 10 gpd = 30 gpd Office: 40 employees x 13 gpd = 520 gpd Total Average Day Demand = 2,278 gpd or 1.6 gpm Peaking Factor The peaking factor is calculated to be 4.25 Peak Hour Flow Average Day Demand x PF = 2,278 gpd x 4.25=9,682 gpd or 6.7 gpm Infiltration 0.304 ac x 150 gal/acre/day = 45.6 gpd or 0.03 gpm Total Peak Flow 9,682 gpd + 45.6 gpd = 9,728 gpd or 6.8 gpm 5 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. Pipe PEAK FLOW (gpm) PROPOSED CONVEYANCE *MAXIMUM FLOW FOR 8” MAIN (gpm) Property Service 6.8 6-inch sewer main @ 2.0% 379 Church Ave Main 6.8 8-inch sewer main @ 0.4% 370 *Roughness coefficient (n) of 0.013 3 IMPACT ON EXISTING WASTEWATER FACILITIES The engineering report indicates that the predicted flows for the proposed buildings exceed those generated by the former residential use of the site. However, the sewer main along S. Church Avenue has not been identified as having any capacity limitations. The anticipated additional flow represents approximately 1.8% of the existing pipe’s capacity, which is sufficient to accommodate the proposed development. 4 PROJECT DESCRIPTION This project involves the installation of 30 feet of 6-inch sewer service for the proposed building which ties into an existing 8-inch main in S. Church Ave. 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-3 by the City of Bozeman. The proposed site has existing grades of less than 4% slope. The site is described as 100% Urban Land (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 seasonally varied but from geotechnical borings groundwater was not encountered at 9 feet deep as observed in multiple test pits in November. 6 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. Appendix A 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