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Home My WebLink About010 Sewer Demand ReportSEWER USAGE DEMAND REPORT FOR: HIDDEN CREEK RESIDENTIAL DEVELOPMENT BOZEMAN, MT Prepared By: WWC Engineering/Madison 895 Technology Blvd, Suite 203 Bozeman, MT 59718 (406) 586-0262 July 2025 SEWER USAGE DEMAND REPORT FOR: HIDDEN CREEK RESIDENTIAL DEVELOPMENT BOZEMAN, MT WWC Engineering/Madison 895 Technology Blvd, Suite 203 Bozeman, MT 59718 (406) 586-0262 July 2025 Hidden Creek Residential Development Sewer Design Report Hidden Creek Residential Development Sewer Demand Report Summary This report outlines the wastewater daily flow analysis calculations for the proposed Hidden Creek Residential Development. The development is located on a 5.35-acre lot located southwest of the intersection between Juniper Street and Oak Park Drive. The project is proposed to consist of five apartment buildings with supportive services and infrastructure creating 182 new residential units and the south extension of Oak Park Drive. The City will review the sewer demands calculated in this report and evaluate the adjacent system’s capacity to accommodate the estimated demands. Proposed Project Demand An existing 24” concrete sewer main runs along the East boundary line of the property. An additional existing 18” concrete sewer main runs west-east across the northern half of the property. For Buildings 1, 3, 4, and 5, 6” PVC sewer service lines will branch off the existing 24” concrete sewer main which will be located under the Oak Park Drive extension. Buildings 1, 3, 4, and 5 will consist of 24, 34, 36 and 52 residential units respectively. The proposed 6” PVC sewer service for Building 2 will extend from the existing 18” concrete sewer main. Building 2 will consist of 36 residential units. The proposed sewer services will range in length from 16’ to 162’. A 6” PVC sewer service stub will be installed off the existing 24” concrete sewer extending to the County lot to allow for future connection. Two 6” PVC sewer service stubs will be installed off the existing 24” concrete sewer extending to the CLT lot to allow for future connection. All 6” PVC sewer services will be run at a minimum slope of 1/8 inch per foot. The wastewater demand of the HRDC lot was calculated using the values per City of Bozeman Design Standards which outlines an average daily domestic flow rate of 64.4 gallons per capita per day at 2.17 people per dwelling unit with the proposed number of 182 residential units plus an additional infiltration rate of 150-gallon/acre/day. (64.4 gallons per capita day ∗2.17 people dwelling unit ∗182 dwelling units)=𝟎𝟎,𝟎𝟎𝟎 𝐠𝐩𝐝 The sewer demand of the HRDC lot is predicted to be an average daily flow of 25,434 gpd or 17.7 gpm. As the development plans of the County and CLT lots are not fully known, the average daily demand for these lots was estimated on a per acre basis using the duty factor for R-4 zoning of 2,800 gpad. Hidden Creek Residential Development Sewer Design Report County Lot: (2,800 average daily demand per day acre ∗0.18 acres)=𝟎𝟎𝟎 𝐠𝐩𝐝 The County lot is predicted to have an average daily flow of 504 gpd or 0.35 gpm. CLT Lot: (2,800 average daily demand per day acre ∗0.43 acres)=𝟎,𝟎𝟎𝟎 𝐠𝐩𝐝 The CLT lot is predicted to have an average daily flow of 1,204 gpd or 0.84 gpm. An infiltration rate of 150 gallons/acre/day was added to the estimated domestic flow. The base infiltration was applied to the 5.20 acre gross area of the development and was calculated to contribute 780 gpd or 0.54 gpm. The total development is predicted to have an average daily flow of 27,922 gpd or 19.4 gpm. A peaking factor based on the estimated population of development was calculated to account for peak flow. The HRDC Lot, based on 182 dwelling units multiplied by a density of 2.17 residents per unit is estimated to have a population of 395 persons. As the development plans of the County and CLT lots are not fully known, an equivalent population for these lots was calculated by dividing the total design flow of these lots by domestic per capita flow. Based on a combined design flow of 1,708 gpd and a domestic per capita flow of 64.4 gpd, the County and CLT lots are estimated to contribute 27 persons to the development’s population resulting in a total site population of (𝑃𝑚𝑎𝑥 𝑃𝐴𝑣𝑒 )=18 +𝑃.5 4 +𝑃.5 =18 +.𝟎𝟎𝟎.5 4 +.𝟎𝟎𝟎.5 =𝟎.𝟎𝟎 (P = Population/thousands) A peaking factor of 4.01 was calculated and when applied to the average daily demand concluded a peak hour sewer demand of 111,967 gpd or 77.8 gpm. This project will require the approval of the City of Bozeman Engineer. Wastewater Daily Flow Analysis Hidden Creek Residential Development Average Daily Flow Hidden Creek Residences Number of Units 182 Residents/unit 2.17 Gallons per Capita/day 64.4 Average Daily Flow 25,434 gpd County Lot Zoning R-4 Acres 0.18 acres Average Day Demand 2,800 gpad Average Daily Flow 504 gpd CLT Lot Zoning R-4 Acres 0.43 acres Average Day Demand 2,800 gpad Average Daily Flow 1,204 gpd Added Infilration Total Site Acreage 5.2 acres Infilration Rate 150 gpad Added Infilration Flow 780 gpd Total Average Daily Flow 27,922 gpd Peaking Factor Calculations Hidden Creek Residences Number of Units 182 Residents/unit 2.17 Population 395 persons County and CLT Lots Design Average Flow 1,708 Domestic Per Capita Flow 64.4 Population 26 persons Total Equivalent Population 421 =Q(max)= 18 + P 0.50 P = Population/thousands = 421/1000 = 0.421Q (ave)4 + P0.50 Peaking Factor = Peak Hour Sewer Demand Average Daily Flow 27,922 gpd 1163.4 gph 19.4 gpm Peaking Factor 4.01 Peak Hour Sewer Demand 4667.1 gph 77.8 gpm 4.01 Peaking Factor