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190 NORTHSTAR LANE
BOZEMAN, MT 59718
406‐581‐5730
www.headwatersmt.net
Page 1 of 2
January 28, 2022
City of Bozeman Community Development
Attn: Cody Flammond
20 East Olive Street
Bozeman, MT 59771
Re: The Ridge Lot 7A
Site Plan Submittal
Sewer Capacity Response
Cody,
In response to Comment #6 on The Ridge Lot 7A Site Plan DRC Review, dated 1/27/22, please consider the
following:
The subject property falls within the 135‐acre area described as “Bozeman Athletic Club West Annexation” in
the Valley West Trunk Main Report, dated 1998 (Report). The sewer demand for the property is detailed in
the Report as follows:
On Page 3 of the Report, 13.3 persons per acre was used to estimate the future population
On Page 4, 117 gallons per day per person was used to estimate wastewater by future
developments
On Page 4, 150 gallons per acre per day was assumed for infiltration of groundwater
135 acres x 13.3 persons per acre x 117 gallons per day = 210,132 gallons per day of
wastewater generated by the 135‐acre site
Pro‐rating the sewer demand based on the size of the subject property, compared to the entire 135‐acre
parcel in the report is detailed below:
The subject property makes up 0.264 acres, or .2% of the 135‐acre site
0.2% x 210,132 gpd = 399 gpd wastewater demand allocated
According to page 8 of the Report, a peak flow of 2252.9 gpm (including infiltration) was
allocated.
0.2% x 2,252.9 = 4.5 gpm peak flow rate allocated for Lot 7A
A comparison of the development’s estimated demand versus the demand allocated in the design report is
below:
The Ridge Lot 7A Site Plan includes 6,000 SF of commercial space on 0.264 acres
The calculated average daily sewer flow rate is 316.8 gpd
The calculated peak hourly sewer flow rate is 1,740 gpd, or 1.2 gpm
Based on the provided calculations, the amounts allocated to the subject property for average daily sewer
flow and peak hourly sewer rate are greater than the estimated demand of the development.
190 Northstar Lane, Bozeman, MT 59718 (406) 581‐5730 www.headwatersmt.net Page 2 of 2
Detailed calculations for the development, as well as the Valley West Trunk Main Design Report are included
with this letter.
If you should have any questions, please do not hesitate to contact me at 406‐570‐3676
Sincerely,
________________ _
Garrett Schultz, P.E.
Headwaters Engineering, Inc.
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