The URL can be used to link to this page

Home My WebLink About12 - Design Report - Town Pump - Baxter & 19th - Sewer Sewer Main Extension Engineer's Report Town Pump — Baxter Lane and North 19t" Avenue February 2012 Submitted to: City of Bozeman Engineering Department 20 East Olive Bozeman, MT 59715 Montana Department of Environmental Quality Permitting and Compliance Division Public Water and Subdivisions Bureau PO Box 200901 Helena, MT 59620-0901 Prepared by: Stahly Engineering and Associates pNTA 7585 Shedhorn Drive Bozeman, MT 59718 (406) 522-9526 60M '* PE STAH LY �9f i9�o ' focIRV%. Engineer's Report Contents Note: The Engineer's Report format for the Town Pump Sewer Main Extension follows DEQ-2 organization. Additional information required by the City of Bozeman Design Standards is added where required. Report Narrative Chapter 10 — Engineering Reports & Facility Plans 11.1 Engineering Report 11.11 Problem Defined 11.12 Design Conditions 11.13 Impact on Existing Wastewater Facilities 11.14 Project Description 11.15 Design Criteria 11.16 Site Information 11.17 Environmental Impacts Figures and Tables Figure 1. Vicinity Map Figure 2. Sewer System Map Table 1. Estimated Water Use Data Sewer Mains 1 3/22/2012 11.1 Engineering Report The proposed new Town Pump is located within the City of Bozeman at 5851 East Baxter Lane. The site is comprised of Lot 1 B of Gardner Simmental Plaza Subdivision owned by Town Pump with a total acreage of 4.03 acres. The site is currently occupied by the existing Anderson Pre- cast building and storage yard. The current building will be demolished prior to construction of the proposed Town Pump. The property owner's contact information is: Town Pump, Inc. c/o Dan Sampson, Construction and Development Manager 600 South Main Street Butte, MT 59701 Water supply and wastewater treatment will be provided by the City of Bozeman's municipal systems. The system owner's contact information is: City of Bozeman Public Service Department Debra Arkell, Director PO Box 1230 Bozeman, MT 59771-1230 The location of the Town Pump is shown on the Vicinity Map in Figure 1, included as a separate map. 11.11 Problem Defined City of Bozeman sewer mains currently exist adjacent to the property in Baxter Lane. The existing facility is currently connected to the existing sewer main in Baxter Lane. The new Town Pump facility will also utilize this connection. A sewer extension is proposed on the east side of the lot to serve an RV dump station. This extension will connect to an existing manhole located in Baxter Lane. The location of the existing mains and proposed extension are shown in Figure 2, a large map included separately. The City of Bozeman Facility Plan has included this property in its capacity analysis and the existing system has capacity to accept flows from the proposed development. Sewer Mains 2 3/22/2012 11.12 Design Conditions Wastewater flows from the new Town Pump are assumed to be similar to estimated water use. Flow estimation for the proposed development was estimated from MDEQ values provided in Table 5-1 of DEQ-4 for stores. Estimated flows from the proposed Town Pump are shown in Table 1. TABLE 1. Estimated Water Use-Town Pump User Class Proposed Town Pump Customers 500 Average Day Flow d/customer 3 Subtotal Inmate Water Use 1,500 Staff 25 Average Day Flow(gpd/staM 10 Subtotal Staff Water Use 2,500 Average Day Flow d 4,000 The customer estimation is based on previous similar facilities constructed by Town Pump and the staff estimation is based on anticipated staffing needs by Town Pump. 11.13 Impact on Existing Wastewater Facilities Sewer capacity for the 24" trunk sewer main located in Baxter Lane was determined using data obtained from the City of Bozeman Wastewater Facility Plan (COBWWFP). Because this main currently receives wastewater flow from the existing building at the site and the proposed development does not significantly increase that flow, the capacity of the existing main is sufficient for the anticipated flows. 11.14 Project Description The project has been adequately described in previous sections. Complete Plans and Specifications for the project are included with the submittal showing the proposed sewer main relocations. 11.15 Design Criteria The Town Pump sewer service and sewer main extension were designed in accordance with Montana Department of Environmental Quality Circular 2, Montana Public Works Standards and Specifications, City of Bozeman Modifications to Montana Public Works Standards and Specifications, the Sewer Mains 3 3/22/2012 Uniform Plumbing Code, and the City of Bozeman Wastewater Facility Plan. 11.16 Site Information The site is typical of Bozeman with fine grained soils overlying gravel deposits. Geotechnical borings have determined the depth to gravel ranges from 5 to 6 feet. Estimated depth to groundwater obtained from the geotechnical borings is 3 feet. If mains are installed during high groundwater times dewatering may be required. 11.17 Environmental Impacts Continued use and new extensions of City of Bozeman municipal sewer mains has the least environmental impact. No new environmental impacts will be caused by these sewer main extensions. Sewer Mains 4 3/22/2012 Town Pump - Baxter Lane and North 19th Avenue Sewer Extension Capacity Calculations Total Area Served = 6.31 acre Community Commercial (Table V-2)= 2400 gal/acre/day Inflow and Infiltration (150 gal/acre/day)= 946.5 gal/day Total Daily Flow= 16091 gat/day Total Daily Flow= 670 gal/hr Total Daily Flow= 11.2 gal/min Pipe Capacity Calculation - 8-inch (75% depth) Use Mannings Slope= 0.004 ft/ft Area = 0.28 ft2 Manning's"n"= 0.013 Wetted Perimeter= 1.4 ft Hydraulic Radius = 0.2 ft Flow Capacity= 0.69 Wisec Flow Capacity= 311.6 gal/min Capacity(311.6 gpm)greater than daily flow(11.2 gpm)so OK.