HomeMy WebLinkAboutBabcock 5-Plex - Water and Sanitary Sewer Demand Memo M . �M� .�
ALPINE
SURVEYIIVO M
ENOINEERIN O
January 3, 2025
City of Bozeman Engineering Department
20 E. Olive Street
Bozeman, MT 59715
RE: Water& Sewer Demand Memo
Lot 10, Block 1 of Kirk Subdivision, S11,T02S,R05E,Bozeman,MT
To Whom it May Concern,
The intent of this memo is to outline the anticipated water and sanitary sewer demands for the
proposed 5-plex project on Lot 10, Block 1 of Kirk Subdivision. The 0.248-acre site is located on
the southeast corner of the intersection of W. Babcock Street and S. 20th Avenue and is currently
zoned B-2M.
The project site was previously developed with a single structure that was served by a 4" sanitary
sewer service draining to the sewer main in the alley, and a 1/4" water service extended from the
water main in S 20ffi Avenue. The structure has since been demolished and the proposed 5-unit
building will be served by a new 1" water service and 4" fire service from S 20'h Avenue. The
existing sanitary sewer service will be preserved and connected to the proposed building.
1.0 Water Demand
In order to be consistent with the sanitary sewer estimates, the water demand calculations for the
proposed project were computed using 2.17 people per dwelling unit, based on Section 2.3.5 of
the 2015 City of Bozeman Wastewater Collection Facilities Plan Update. Per the COB Design
Standards and Specifications Policy (COB DSSP), a water demand of 170 gallons per capita per
day is to be used when calculating water demand. As outlined in the COB DSSP,peaking factors
of 2.3 and 3.0 were used to calculate Maximum Day and Peak Hour Demand, respectively. The
below table provides the estimated water demands based on be above assumptions.
Peak water Demand Calculations
Type Dwelling Units Population Average Day GPM Max Day(GPM) Peak Hour(GPM)
Residential 5 10.85 1.28 2.95 3.84
714 Stoneridge Drive•Suite 3•Bozeman,MT 59718•(406)586-5599•www.alpinesuryeying.net
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2.0 Sanitary Sewer Demand
There are several ways to estimate Sanitary Sewer flows, including standards set forth by the
Montana DEQ Circular 2, Montana DEQ Circular 4, and the COB DSSP. However,the projected
wastewater flows in this memo are calculated using the values provided in the City of Bozeman
Wastewater Collection Facilities Plan Update Final — 2015. This document provides an updated
estimate of 2.17 persons per dwelling unit within the City of Bozeman Planning Area, which
differs slightly from the 2.11 person/du estimate outlined in the COB DSSP. The facilities plan
update also provides an updated wastewater generation estimate of 64.4 gallons per day per capita
based on extensive research of the existing system instead of the 89 gpcd estimate outlined in the
COB DSSP. The peaking factor is based on the Harmon Formula and an infiltration rate of 150
gallons per acre per day was also applied to the project,both as outlined in the COB DSSP. Based
on these criteria,the estimated demands from the proposed project are included in the table below.
Peak Sanitary Sewer Demand Calculation
Average Day Average Day Peaking Peak Hour Infiltration Design Flow sign
Dwelling Units Population Flow(GPD) Flow(GPM) Factor Flow(GPM) (GPM) Rate(GPM) Flow
Rate cfs
5 11 708.4 0.49 4.41 2.16 0.03 2.19 0.0049
Total Lot Area 0.25 lAcres
Infiltration Rate 150 Gal./Acre/Day
Total Infiltration 0.03 JGPM
4"PVC Pipe Capacity
Pipe Size(in) IFlow Depth-d(in)l Slope(ft/ft) I Manning's n I Flow(CFS)
4 1 3 1 0.02 1 0.012 1 0.27
Please feel free to contact me with any questions at(406) 586-5599, or by email at
ecote allpinesurveying.net.
N TA
Sincerely, •• �d '•
• ET HAN L •
COTE
No. 60593PE • w
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Ethan Cote, P.E 60593 %0ss,•
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714 Stoneridge Drive•Suite 3•Bozeman,MT 59718•(406)586-5599 www.alpinesurveying.net
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