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190 NORTHSTAR LANE
BOZEMAN, MT 59718
406-581-5730
www.headwatersmt.net
Page 1 of 2
Catalyst by Del Park Homes
Lot 3, Block 21 of Phase 3 of Cattail Creek Subdivision
Sanitary Sewer Usage
The proposed project includes 8 proposed residential units on approximately 0.56 acres. Average day
residential flows were calculated using the City of Bozeman standard of 2.11 persons per residential unit at
64.4 gpd per person.
Average Residential Daily Flowrate = (8 units) x (2.17 people/unit) x (64.4 gpd/person) = 1,118 gpd Contemplated with Subdivision = (8 units) x (2.54 people/unit) x (72 gpd/person) = 1,463 gpd
The City of Bozeman standard 2.17 persons per residential unit was multiplied by 8 units to determine an
equivalent residential population of 18 people. The total population of 18 people yielded a peaking factor of
4.37. The peaking factor, PF, was calculated by the following formula, where P = population (thousands):
PF = 18 + P0.5
4 + P0.5
Using a peak hour factor of 4.38 was and adding the City’s infiltration allowance of 150 gallons per acre per day
resulted in a combined peak hourly flowrate of 4,980 gpd.
Peak Hourly Flowrate = ADF x PHF + 150 gpd/acre
Peak Hourly Flowrate = 1118 gpd x 4.38 + 150 gpd x 0.56 ac = 4,980 gpd = 3.46 gpm
Water Usage
The proposed project includes 8 proposed residential units on approximately 0.56 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 2.05 gallons per minute. Using the City’s max day flow factor of 2.3, results in a
maximum daily demand of 4.71 gpm. Multiplying the average daily flow by the City’s peak hour factor of 3,
results in a peak hour demand of 6.15 gpm. Local landscape watering is included in the empirical data.
Average Residential Daily Flowrate = (8 units) x (2.17 people/unit) x (170 gpd/person) = 2,951 gpd
2,951 gpd /1440 min per day = 2.05 gpm
Average Daily Flowrate = 2.05 gpm
Maximum Daily Flowrate = ADF x 2.3 = 4.71 gpm
Maximum Hour Flowrate = ADF x 3.0 = 6.15 gpm
Fire
No new fire hydrants are proposed for the site. The Bozeman Water Department conducted a fire flow test
from an existing hydrant on Catalyst Street (hyd # 1889). The test results were 1555 gpm at 86 psi. This results
in roughly 5,000 gpm at 20 psi. Static pressures in this area exceeded 100 psi, therefore no pressure or flow
issues are anticipated.
190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 2 of 2
Calculations completed by Jeremy May, P.E.
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