HomeMy WebLinkAbout018 Water Sewer usage lot 12
190 NORTHSTAR LANE
BOZEMAN, MT 59718
406‐581‐5730
www.headwatersmt.net
Page 1 of 3
Cherry Creek Mixed Use
Lot 12 of Plat J‐300 of Gallatin Park Subdivision
Sanitary Sewer Usage
The proposed project includes 24 residential apartments and roughly 21,312 square feet of commercial on
approximately 2.01 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 = (24 units) x (2.11 people/unit) x (89 gpd/person) = 4,507 gpd
Average Commercial Daily Flowrate = 960 gal/acre/day x 2.01 acres = 1,929.6 gpd
Total Average Daily Sewer Flow = 6,437gpd
The City of Bozeman standard 2.11 persons per residential unit was multiplied by 24 units to determine an
equivalent residential population of 51 people plus the commercial estimated commercial equivalent of 149
people (13 gpd per employee per DEQ Circular 4). The total population of 200 people yielded a peaking factor
of 4.15. 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 4.15 was and adding the City’s infiltration allowance of 150 gallons per acre per day
resulted in a combined peak hourly flowrate of 27,015 gpd.
Peak Hourly Flowrate = ADF x PHF + 150 gpd/acre
Peak Hourly Flowrate = 6,437 gpd x 4.15 + 150 gpd x 2.01 ac = 27,015 gpd = 18.76 gpm
See the following page for sanitary sewer usage broken down by construction phase.
190 Northstar Lane, Bozeman, MT 59718 (406) 581‐5730 www.headwatersmt.net Page 2 of 3 Sanitary Sewer Usage by Construction Phase Residential Flows Commercial Flows Combined Flows Phase Dwelling units people/unit gpd/person Avg. Daily Flowrate Pro‐rated gallons/acre/day Avg. Daily Flowrate Total Average Daily Flow Peak Hour Factor Infiltration Peak Hourly Flowrate Phase 1 6 2.11 89 1126.74 0.5025 960 482.4 1609.14 4.15 75.375 6753.306 Phase 1A 4 2.11 89 751.16 0.335 960 321.6 1072.76 4.15 50.25 4502.204 Phase 2 6 2.11 89 1126.74 0.5025 960 482.4 1609.14 4.15 75.375 6753.306 Phase 3 8 2.11 89 1502.32 0.67 960 643.2 2145.52 4.15 100.5 9004.408 4506.96 1929.6 6436.56 27013.22
190 Northstar Lane, Bozeman, MT 59718 (406) 581‐5730 www.headwatersmt.net Page 3 of 3
Water Usage
The proposed project includes 24 residential apartments and roughly 21,312 square feet of commercial on
approximately 2.01 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 5.98 gallons per minute. Utilizing a
commercial rate of 10,000 gallons per 1,000 square foot of commercial area per year results in 0.41 gpm.
Using the City’s max day flow factor of 2.3, results in a maximum daily demand of 14.68 gpm. Multiplying the
average daily flow by the City’s peak hour factor of 3, results in a peak hour demand of 19.15 gpm. Local
landscape watering is included in the empirical data.
Average Residential Daily Flowrate = (24 units) x (2.11 people/unit) x (170 gpd/person) = 8,609 gpd
8,609 gpd /1440 min per day = 5.98 gpm
Average Commercial Daily Flowrate = 10,000 gallons per year /1,000 square feet x 21,312 sf / 365 days=
584 gpd = 0.41 gpm
Total Daily Flowrate = 6.38 gpm
Maximum Daily Flowrate = ADF x 2.3 = 6.38 gpm x 2.3 = 14.68 gpm
Maximum Hour Flowrate = ADF x 3.0 = 6.38 gpm x 3.0 = 19.15 gpm
Calculations completed by Garrett Schultz, P.E.
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