HomeMy WebLinkAboutwater -sewer usage-032321
190 NORTHSTAR LANE
BOZEMAN, MT 59718
406-581-5730
www.headwatersmt.net
Page 1 of 2
Gallatin Park Mixed Use
Lot 4A of Amended Plat of Gallatin Park Subdivision
Sanitary Sewer Usage
The proposed project includes 13 residential apartments and roughly 11,919 square foot of commercial on
approximately 1.06 acres. Average day residential flows were calculated using the City of Bozeman standard
of 2.11 persons per residential unit at 89 gpd per person. Utilizing the wastewater flow for Industrial or
Business Park from Tab V-2 of the City of Bozeman Design Regulations, the estimated commercial flow is 960
gallons per acre per day.
Average Residential Daily Flowrate = (13 units) x (2.11 people/unit) x (89 gpd/person) = 2,441 gpd
Average Commercial Daily Flowrate = 960 gal/acre/day x 1.061 acres = 1,018 gpd
Total Average Daily Sewer Flow = 3,459 gpd
The City of Bozeman standard 2.11 persons per residential unit was multiplied by 13 units to determine an
equivalent residential population 28 people plus the commercial estimated commercial equivalent of 78
people (13 gpd per employee per DEQ Circular 4). The total population of 106 people yielded a peaking factor
of 4.24. The peaking factor, PF, was calculated by the following formula, where P = population (thousands):
PF = 18 + P0.5
4 + P0.5
Using peak hour factor of 4.24 was and adding the City’s infiltration allowance of 150 gallons per acre per day
resulted in a combined peak hourly flowrate of 14,825 gpd.
Peak Hourly Flowrate = ADF x PHF + 150 gpd/acre
Peak Hourly Flowrate = 3,459 + gpd x 4.24 + 150 gpd x 1.061 ac = 14,825 gpd
Water Usage
The proposed project includes 13 residential apartments and roughly 11,919 square foot of commercial on
approximately 1.06 acres. Using the City of Bozeman empirical data of 170 gpd/person for residential flows,
Headwaters estimates a total residential average daily demand (ADD) of 3.24 gallons per minute. Utilizing a
commercial rate of 10,000 gallons per 1,000 square foot of commercial area per year results in Using the
City’s max day flow factor of 2.3, results in a maximum daily demand of 28.7 gpm. Multiplying the average daily flow by the City’s peak hour factor of 3, results in a peak hour demand of 37.4 gpm. Local landscape
watering is included in the empirical data. Watering of the major park areas will be completed using onsite
wells.
The average daily demands are exclusive of the suggested fire flow requirement of 2000 gallons per minute.
When modeled, the system design satisfies the fire flow occurring simultaneously with the maximum day
demands inclusive of the proposed subdivision.
Average Residential Daily Flowrate = (13 units) x (2.11 people/unit) x (170 gpd/person) = 4,663 gpd
4,663 gpd /1440 min per day = 3.24 gpm
Average Commercial Daily Flowrate = 10,000 gallons per year /1,000 square feet x 11,919 sf / 365 days=
327 gpd = 0.23 gpm
190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 2 of 2
Total Daily Flowrate = 3.47 gpm Maximum Daily Flowrate = ADF x 2.3 = 3.47 gpm x 2.3 = 7.98 gpm
Calculations completed by Jeremy May, P.E.
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