HomeMy WebLinkAbout004-water -sewer usage
190 NORTHSTAR LANE
BOZEMAN, MT 59718
406-581-5730
www.headwatersmt.net
Page 1 of 2
Nelson Meadows Business Park
Lot 4, Block 3 of Nelson Meadows Subdivision
Sanitary Sewer Usage
The proposed project includes 3 warehouse buildings on approximately 2.59 acres. The buildings area total for
all three buildings is 36,318 square feet. Of that, up to 12,900 square feet can be office.
Average Office Daily Flowrate = (12,900sf) x (10,000gallons/year)/(1,000 sf office) = 353 gpd
Average Manufacturing Flowrate = (30 employees) x (13 gpd/employee) = 390 gpd
Total Sewer Demand = 743 gpd
The Nelson Meadows Subdivision Water & Sewer Design Report estimates 749 people for the 69.47 acre
subdivision. This site makes up 3.73% of that or an equivalent population of 28 people. The total population of
28 people yielded a peaking factor of 4.36. 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 4.36 was and adding the City’s infiltration allowance of 150 gallons per acre per day
resulted in a combined peak hourly flowrate of 3,627 gpd.
Peak Hourly Flowrate = ADF x PHF + 150 gpd/acre
Peak Hourly Flowrate = 743 gpd x 4.36 + 150 gpd x 2.59 ac = 3,627 gpd = 2.52 gpm
Per the design report for the Nelson Meadows Subdivision, the original sewer demand was calculated at 960 gal/ac/day
or 2,486 gpd. A peaking factor of 3.87 was used within the report for a peak hourly flowrate of 9,620 gpd estimated for
this lot. This shows the proposed peak hour flow is substantially less than what was planned.
Water Usage
The proposed project includes 3 warehouse buildings on approximately 2.59 acres. The buildings area total for
all three buildings is 36,318 square feet. Of that, up to 12,900 square feet can be office. Headwaters estimates
a total average daily demand (ADD) of 743 gpd or 0.52 gallons per minute. Using the City’s max day flow factor
of 2.3, results in a maximum daily demand of 1.19 gpm. Multiplying the average daily flow by the City’s peak
hour factor of 3, results in a peak hour demand of 1.55 gpm. Local landscape watering is included in the
empirical data.
Average Office Daily Flowrate = (12,900sf) x (10,000gallons/year)/(1,000 sf office) = 353 gpd
Average Manufacturing Flowrate = (30 employees) x (13 gpd/employee) = 390 gpd
Total Water Demand = 743 gpd
Total Daily Flowrate = 743 gpd = 0.52 gpm
Maximum Daily Flowrate = ADF x 2.3 = 1.19 gpm
Maximum Hour Flowrate = ADF x 3.0 = 1.55 gpm
190 Northstar Lane, Bozeman, MT 59718 (406) 581-5730 www.headwatersmt.net Page 2 of 2
Per the design report for the Nelson Meadows Subdivision, the original water demand was calculated at 170 gpd for the
equivalent population. The equivalent population for the site was estimated at 28 persons as described above. 28
person at 170 gpd results in an average daily flow of 4,760 gpd or 3.31 gpm. One new hydrant is proposed for the site.
The Bozeman Water Department conducted a fire flow test from an existing hydrant on Prince Lane (hyd # 3049). The
test results were 1405 gpm at 70 psi. This results in roughly 5000 gpm at 20 psi. Static pressures in this area exceeded
100 psi, therefore no pressure or flow issues are anticipated.
________________
Jeremy May, P.E.
Headwaters Engineering, Inc.
www.headwatersmt.net
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