HomeMy WebLinkAbout29-PLNAPP-569_SewerDemandCertificationLetterAugust 10, 2022 | Page 1
Memorandum
August 10, 2022
To: City of Bozeman
121 N Rouse Ave,
Bozeman, MT 59715
(406) 582-2300
Project TRH Bozeman, MT
Project # 20210037
From Mike Haas, PE
Re Sewer Capacity Memo
SEWER
This memorandum is in response to the requirements of the City of Bozeman Unified Development
Ordinance Section 38.220.060 Water and Sewer Design Requirements. The proposed Texas Roadhouse
(TRH) is located on 870 Harmon Stream Boulevard, within the Bozeman Gateway Development. The
original Sanitary Sewer Design Report (May 17, 2006) for the Bozeman Gateway Development included the
TRH development as Lot 16. This memorandum will supplement the original Sanitary Sewer Design Report
by updating the design criteria as it pertains to the proposed restaurant.
Lot 16 / TRH is identified as part of the 50.6 Acre Westerly Drainage Basin. It is further subdivided into part
of the 18.32 Acre drainage basin served by segment 3W. Segment 3W consist of an 8-inch sewer pipe
running at 0.5% slope. Per Appendix A of the 2006 Sanitary Sewer Design Report, the pipe has a Planned
Peak Flow (Qp) versus Full Pipe Flow (Qf) ratio of 46.3%.
Since the report was written, the City of Bozeman Design Standards and Specifications have been revised
to lower the required flow rate for regional commercial areas from 3,495 gpd/ac to 1,600 gpd/ac. The
updated sewer flow rate from the TRH development is as follows:
Area – 0.446AC
Design Flow Rate – 1,600 gpd/ac
Population – 1,600 / 83 (18/ac) x 0.446 AC = 0.008 (in thousands)
Average Flow Rate = 0.446 ac x 1,600 gpd/ac = 713.6 gpd
Peaking Factor =
= 4.42
August 10, 2022 | Page 2
Peak flow (Qmax) = 713.6 gpd x 4.42 = 3,154 gpd = 2.19 gpm
Original Report Qmax (prorated) = .
. 177.7 = 4.32 gpm
Since the newly calculated peak flow (2.19 gpm) based on revised criteria is less than the original peak
flow (4.32 gpm) origination from the restaurant site, the proposed TRH is in conformance with the original
Sewer Design Report and the 8 inch sewer line would have sufficient capacity.
Attachments:
· Original Sewer Design Basin Map
· Appendix A from Original Sewer Design Report
End of Memorandum
Proj 20210037
expires 6/30/24
date 8/11/22
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