HomeMy WebLinkAboutWS1 - Water and Sewer Demand Memo A& M . �=� .�
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August 12, 2025
City of Bozeman Engineering Department
20 E. Olive Street
Bozeman, MT 51715
RE: Valley Glass Water& Sewer Demand Memo
Lot 3 of Tract 6,Plus Vacated Single Tree Court,
Gardner Simmental Plaza Subdivision
Sec. 35,T1S, R5E of P.M.M.
To Whom it May Concern,
The intent of this memo is to outline the anticipated water and sanitary sewer demands for the
proposed commercial development on Lot 3 of Tract 6, Plus Vacated Single Tree Court, Gardner
Simmental Plaza Subdivision. The proposed development includes an 11,800 Sq. Ft. commercial
building in addition to an existing 12,000 Sq. Ft existing commercial building on the 2.267-acre
site.
The existing building is served by a 4" existing sanitary sewer service and, a water service of
unknown diameter. The proposed building will be served by a proposed 4" sanitary sewer service
and a proposed 1"domestic water service installed per the City of Bozeman's Modifications to the
Montana Public Works Standards and Specifications dated 10/2024. Neither the proposed or
existing building require fire suppression,therefore fire suppression is not included in calculations
for domestic water demand. An existing well on the site is currently used for irrigation will be
abandoned. The existing and proposed landscaping will be connected to the existing domestic
water service.
1.0 Water Demand
Water demand within the M-1 Light Manufacturing Zoning District is 134 gallons per acre per
day. 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. Using this method for estimating domestic
water demand results in an estimate that is significantly lower that the proposed sanitary sewer
demand. A domestic water demand estimate can also be calculated using domestic wastewater
flows estimates and the peaking factors from above. The below table provides the estimated water
demands based both based on the M1 — Light Manufacturing Zoning demand, and based on
domestic waste water demand. Domestic water used for irrigation was estimated using two
numbers included in the landscaping and irrigation design. The total gallons throughout the
irrigating season are included in the water budget calculator from the City of Bozeman. This
714 Stoneridge Drive•Suite 3•Bozeman,MT 59718•(406)586-5599•www.alpinesurveying.net
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number was divided by the total number of minutes in the irrigation year(May-September)to get
a gallon per minute flow rate for irrigation uses. This number is then added to the maximum day
demand. Additionally, instantaneous flow rates for irrigation are estimated on the irrigation plan
and associated Worst Case Station Pressure Loss scenario. This value is added to the peak water
demand estimate for both of the water demand estimates.
Landsca in Irrigation Estimate
Total Irrigation Water Use(Gal/year) 254983
Average Day Irrigation Demand during 1.1
Irri ation Season(GPM)
Peak Irrigation Demand(GPM) 14
Peak Water Demand Calculations(Using M1Zoning Estimate)
Type Demand ad) Acres Average Da GPM
M1-Light Manufacturin 134 2.27 0.21
Max Da (GPM) P ok Hour(GPM)
0.49 0.63
Max Day+Average Day Irrigation(GPM) Peak Hour+Peak Irrigation Demand(GPM)
1.65 14.63
Peak Water Demand Claculations(Using Waste Water Demand)
(Peak Waste Water Demand( pm) Maximum Da (GPM) Peak Hour(GPM)
0.87 2.00 2.61
Max Day+Average Day Irrigation(GPM) Peak Hour+Peak Irrigation Demand(GPM)
3.17 16.61
2.0 Sanitary Sewer Demand
The projected wastewater flows are estimated using the COB DSSP dated 10/2024 and Circular
DEQ-4. Table 3.1-1 from Circular DEQ-4 provides typical and average wastewater flows for non-
residential sources.The source best representing the proposed light manufacturing from Table 3.1-
1 is Industrial Building where wastewater is measured per employee and has an average flow rate
of 13 gallons per day. Using existing and proposed staffing numbers an estimate of 22 employees
was used to calculate wastewater flow. 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.
714 Stoneridge Drive•Suite 3•Bozeman,MT 59718•(406)586-5599•www.alpinesurveying.net
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Peak Sanitary Sewer Demand Calculation
Industrial Building Flow Employees Average Day Average Day Peaking Peak Hour Infiltration Design Flow Flow
(gpd/employee) Flow(GPD) Flow(GPM) Factor Flow(GPM) (GPM) Rate(GPM) Design
Rate cfs
13 1 22 286.0 0.20 1 4.37 1 0.87 1 0.24 1 1.11 1 0.0025
Total Lot Area 2.267 Acres
Infiltration Rate 150 Gal./Acre/Da
Total Infiltration 0.24 GPM
Total Infiltration 0.00053 CFS
Total Design Flow w/Infil 0.00301 CFS
4"PVC Pipe Capacity
Pipe Size(in) Flow Depth-d(in) Slope(ft/ft) Manning-s n Flow(CFS)
4 3 1 0.02 0.012 0.27
Please feel free to contact me with any questions at(406) 586-5599, or by email at
dkirsch@alpinesurveying.net.
.•''•'p N T A N''••.
Sincerely, �. "' '9
' ANDREW M.
. �,
Drew Kirsch, P.E. 86489 No. 86489PE
/CENSI.0 ',etc, •
714 Stoneridge Drive Suite 3 Bozeman,MT 59718•(406)586-5599 www.alpinesurveyint:.net
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