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Home My WebLink About16 - Design Report - Rocky Mountain Credit Union - Sewer ROCKY MOUNTAIN CREDIT UNION SEWER IMPROVEMENTS SANITARY SEWER EXTENSION BASIS OF DESIGN REPORT May, 2016 PREPARED BY: Morrison ii Maierle engineers surveyors planners scientists `��•� ilrrtr ice'�,v,r�,C.;_+,;:.: `• MMI #: 2927.011 Table of Contents INTRODUCTION...........................................................................................................................................1 1 PROBLEM DEFINED............................................................................................................................1 2 DESIGN CONDITIONS.........................................................................................................................1 3 IMPACT ON EXISTING WASTEWATER FACILITIES ........................................................................3 4 PROJECT DESCRIPTION....................................................................................................................4 5 DESIGN CRITERIA...............................................................................................................................4 6 SITE INFORMATION............................................................................................................................4 7 ENVIRONMENTAL IMPACTS..............................................................................................................4 8 OPERATION AND MAINTENANCE.....................................................................................................4 APPENDICES None Prepared by: Morrison-Maierle, Inc. 2880 Technology Blvd. W. Bozeman, Montana 59771 Phone: (406) 587-0721 Fax: (406) 922-6702 Written By: DDK Checked By: MEE Approved By: MEE PROJECT NO.: 2927.011 INTRODUCTION This design report provides the criteria used as a basis of design for the Rocky Mountain Credit Union (RMCU) sewer main extension improvements project and is submitted in conjunction with the completed plans and specifications. This report is organized following the outline recommended in DEQ-2, Section 32. This project involves the installation of an 8" sewer main extension at the new site for the RMCU office building located just off of East Baxter Lane, on Lot 1A of the Corrected Amended Plat of the Saccoccia Minor Sub 207C. This project is located within the City of Bozeman, Montana. See the vicinity map for location details. 1 PROBLEM DEFINED RMCU has planned to construct an office building and parking lot off of East Baxter Lane in Bozeman, Montana. The RMCU site will need the sanitary sewer main on East Baxter Lane to be extended in order to serve the new office building. The project is proposing an 8-inch main to handle the proposed office building flow. The City of Bozeman has approved this extension, and the City's wastewater system has adequate capacity to accommodate the extension according to the sewer availability letter that the City of Bozeman Engineer provided for this submittal. Sewer facilities included in this project will be designed in accordance with Montana Department of Environmental Quality (MDEQ) regulations. Adequate capacity will be provided to allow for growth in areas adjacent to the actual project areas. Flow and population data for the project will be consistent with the City's approved Facilities Plan, where applicable. 2 DESIGN CONDITIONS The sewer main extension for the RMCU office building will serve one office building on Lot 1A and future construction on Lot 2A which is zoned B-2 (community business) per the City of Bozeman's zoning map. The capacity requirement for the sewer main extension is calculated as follows: 1 Non-Residential Flows: RMCU Office Building Lot 1A Flows: Assumptions: Employees 13 gpd per office typical employee (Per DEQ 4, Table 3.1-1) RMCU Daily Office Employees (Population) = 10 employees Average Daily Flow = (13 gpd/employee)*(10 employees/day) = 130 gpd Peaking Factor(PF) _ (18+(population/1000)^.5)/(4+(population/1000)^.5) Peaking Factor= 4.41 Peak Flow = 130 gpd (avg daily flow) x 4.41 = 574 gpd Peak Flow = 574 gpd = 0.40 gpm RMCU Customers (inside the building) Assume 6 tellers with 16.75 inside Customers/hour, at 8hours/day= 804 customers/day 3 Gallons per day per customer(Per DEQ 4, Table 3.1-1 Customers in store) Average Daily Flow = (804 Customers)*(3 gpd) = 2,412 gpd 13 Gallons per Capita per Day Population = (2,412 gpd)/(13 gallons per Capita per Day) = 186 people Peaking Factor(PF) _ (18+(population/1000)^.5)/(4+(population/1000)^.5) Peaking Factor= 4.16 Peak Flow = 2,412 gpd (avg daily flow) x 4.16 = 10,034 gpd Peak Flow= 10,034 gpd = 6.97 gpm Future Construction in Lot 2A Flows: Assumptions: COB Capital Planning Zone B-2 = 2,000 GAL./ACRE/DAY Lot 2A Building Site = 5.53 ACRES 2 Wastewater Flow Rate = (2,000 GAL./ACRE/DAY)(5.53 ACRES) Wastewater Flow Rate = 11,060 gpd 13 Gallons per Capita per Day Population = (11,060 gpd)/(13 gallons per Capita per Day) = 851 people Peaking Factor(PF) _ (18+(population/1000)1.5)/(4+(population/1000)^.5) Peaking Factor= 3.84 Peak Flow = 11,060 gpd (avg daily flow)x 3.84 = 42,470 gpd Peak Flow= 42,470 gpd = 29.49 gpm Infiltration: Assumptions: Lot 1A = 1.53 ACRES Lot 2A= 5.53 ACRES Total Acres = 7.06 ACRES Per COB standards (page 51), the infiltration rate is 150 gallons/acre/day Infiltration = 7.06 ACRES * 150 gallons/acre/day Infiltration = 1,059 gpd = 0.74 gpm Total Peak Flow = 0.40 gpm + 6.97 gpm + 29.49 gpm + 0.74 gpm = 37.60 qpm For comparison, the maximum flow in an 8-inch pipe at minimum grade (0.4%), with a roughness coefficient (n) value of 0.013 can be calculated as 498,240 gallons per day (346 gallons per minute). Thus, an 8-inch pipe size is adequate for all sewer mains included in this project. 3 IMPACT ON EXISTING WASTEWATER FACILITIES The City of Bozeman has existing sewer mains in this area for sewer service, and they have provided a letter, included in this submittal, stating that the existing sewer mains in the vicinity can handle the increase in flows from this project. 3 4 PROJECT DESCRIPTION The sewer main extension for the RMCU office will include the construction of approximately 165 lineal feet of 8-inch SDR 35 PVC sanitary sewer main and (1)48" diameter manholes to serve the proposed RMCU office building and surrounding area. The average sewer depth is approximately 13-feet. 5 DESIGN CRITERIA Design criteria including average and peak flows as well as sewer depth information were provided in previous sections. The proposed sewer mains conform to the State's minimum vertical and horizontal separation criteria from water mains. The proposed conventional gravity sewer collection system is to be constructed to City of Bozeman and the 6th Edition of Montana Public Works (MPW) standard specifications. In particular, the sewer mains shall be 8-inch diameter SDR 35 Polyvinyl Chloride (PVC) pipe. All manholes shall be standard concrete manholes spaced no more than 400 feet apart. 6 SITE INFORMATION The existing site is bound by East Baxter Lane to the north, Simmental Way to the west bordering a hotel (Hilton Garden Inn), an undeveloped field to the east and an existing Lowe's Home Improvement store to the South. The site has existing grades of less than 4% and Enbar loam soil deposits. 7 ENVIRONMENTAL IMPACTS There are no expected environmental impacts from this sewer main extension, as the City of Bozeman Wastewater Treatment Plant has more than adequate capacity for this extension. 8 OPERATION AND MAINTENANCE These sewer lines will be owned, operated, and maintained by the City of Bozeman. NA2927\01 1\Design Docs\Reports\RMCU water and sewer 041516\corrections on RMCU 052516\RMCU Sewer Extension Eng Report with corrections 052516.doc 4