HomeMy WebLinkAbout013 North Wallace Residences SANITARY DEMAND MEMO
MEMO
32 Discovery Drive ♦ Bozeman, MT 59718 ♦ (406) 582-0221 ♦ Fax (406) 582-5770
Project Name: North Wallace Residences
Project Number: AESI 22-058
Date and Time: August 18, 2023
Re: Sanitary Sewer Demand
MEMO DETAILS:
The purpose of this memo is to outline the estimated peak sanitary sewer demand for the residential site development of Babcock and Davis Addition to Bozeman Subdivision, W2 Lot 3 (428 North Wallace). The
demand is estimated based on guidelines provided in the Montana Department of Environmental Quality (MDEQ) Circular 4 and the City of Bozeman Design Standards and Specifications.
One new service line will serve the ADU and main residence from within the site coming from the existing 8” sewer main on North Wallace Ave. A second service line will extend from the existing service line coming from North Wallace Ave. and provide service to the duplex. The City of Bozeman Design Guidelines states that new sanitary sewer lines to serve residential areas shall be designed to accommodate an average daily flow rate of 2.l 1 people per dwelling unit and 89-gallons per capita per day. In addition, an infiltration rate of 150 gal/acre/day was added to the flow demand calculations per the COB Design Standards and Specifications. Please see the attached calculations for additional information. A
summary is provided below. The estimate should be conservative as one of the units is an accessory dwelling unit (ADU) and anticipated to have few residents that the average used.
• Number of units = 4
• Average Daily Flow = 4 units x 2.11 people x 89-gallons per capita = 751.2 gpd
• Gross area of site = 0.299 acres
• Infiltration rate = 44.9 gpd (0.03 gpm)
• Average day demand + infiltration = 796.0 gpd (0.55 gal/min)
• Peaking factor (P=0.0084) = 4.42
• Peak hour demand = 3,321gpd (2.31 gpm)
Please contact Emma Raeside and/or Rory Romey at 406-582-0221 or eraeside@alliedengineering.com; rromey@alliedengineering.com with any questions or if additional information is required.