HomeMy WebLinkAbout009 - Water and Sewer Demands Design Report - Page 2 of 3
INTRODUCTION
The proposed site consists of two buildings is located on the remainder of tract 6 & 10’ of tract 7 of
the Smith Subdivision in Bozeman, Montana. The project includes construction of (2) live/work
apartment buildings with 8 total units.
The property is fronted on one side by a City street by Durston Road. A Water and sanitary sewer
main extension will be constructed on the site and connect to the existing mains located within
Durston Road and individual water, fire, and sanitary sewer services will connect to each of the
proposed buildings as shown on civil sheet C2.1.
Water Distribution System Demands
The design parameters used herein are according to the City of Bozeman Design Standards and
Specifications Policy (DSSP) dated May 2017.
Average Daily Residential Usage = 170 gallons per capita per day
Average Population Density = 2.17 persons/dwelling unit
Average Day Demand (Peaking Factor = 1.0)
Maximum Day Demand (Peaking Factor = 2.3)
Peak Hour Demand (Peaking Factor = 3.0)
Water Demands (8 dwelling units)
Average Day Demand = 16 d.u. x 2.17 persons/d.u. x 170 gpcpd = 2951 gpd = 2.05 gpm
Maximum Day Demand = 4.10 gpm x 2.3 = 4.72 gpm
Peak Hour Demand = 4.10 gpm x 3.0 = 6.15 gpm
Design Report - Page 3 of 3
Sanitary Sewer Design Load
The population estimates of 2.17 people per dwelling unit, and residential flow rate of 64.4 gpcd
used herein are according to the City of Bozeman Design Standards and Specifications. The
peaking factor for the design area is determined using the formula provided in the City of Bozeman
Design Standards and Specifications.
Using the city average of 2.17 persons per household the equivalent population is calculated.
Connection:
Equivalent Population = (2.17 persons/dwelling unit)(8 units) = 17.36 persons
Harmon Formula: Peaking Factor = (18 + P0.5)/(4 + P0.5)
where: P = Population in thousands
Peaking Factor = (18 + 0.0170.5)/(4 + 0.017.5)
Peaking Factor = 4.39
Assumed infiltration rate = 150 gallons/acre/day = 150 (.909 acres) = 136.35 gal/day
The peak flow rate is calculated by multiplying the City's design generation rate of 64.4 gallons per
capita per day by the population, multiplying by the peaking factor, and adding the infiltration rate:
Peak Flow Rate = 64.4 gpcpd (17.36 persons) (4.39) + 136 gpd = 5,044 gpd
= 3.50 gpm
= 0.0078 cfs