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Home My WebLink About18 - Design Report - Crestview Condos - Sewer SEWER MAIN DESIGN REPORT FOR: CRESTVIEW CONDOMINIUMS BOZEMAN, MT Prepared By: MADISON ENGINEERING Madison Engineering 895 Technology Drive, Suite 203 Bozeman, MT 59718 (406) 586-0262 NOVEMBER 2018 SEWER MAIN DESIGN REPORT FOR: CRESTVIEW CONDOMINIUMS BOZEMAN, MT ai�TA/�� <J • . CHINS G. ' QUDI:" 'I CC - Lu MIS Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 NOVEMBER 2018 i ,� � �- - SANITARY SEWER MAIN CALCULATIONS 8-Inch PVC_Pipe Capacity Project DeBcripUDn Friction Method Manning Formula Sohn For Discharge Input Data Roughness Coefiiclent 0.013 Channel Slope 0.40000 % Normal Depth 5.58 In Diameter 8.00 In Results Discharge 0.64 Via Flow Aron 0.28 IP Wetted perimeter 1.32 1t Hydraulic Rodiue 2.37 In Top VWdth 0.81 a Critical Depth 0.38 R Percent Full 49•8 % Critical Slope O.DD748 Mt yalocky 2.45 1Ns VMochy Head 0.09 A SpscMc Eiww 0.56 R Frauds Number 0.86 Maxin►um Discharge 0.82 ftl/s Discharge Full 0.76 Rh Slope Fug 0.00278 WR Flow Type SubCrMlcel GVF Input Data D0wno(rom Depth O.OD In Length 0.00 R Number OM" 0 GVF Output Data Upetmam Depth 0.00 In ProRle Description Profile Hoodlum 0.00 R Average End Depth Over Rise 0.00 % Normal Depth Over Rise 69.75 % Downstream Velocity Infinity R/a Bentley systems,Inc. Hassled Methods so~18~111aster Vol(SELECTssriss 1) 101.11.01.031 4/11/2016 940:06 AM 27 Blemons company Drive Suite 210 W Watertown,CT o6T66 USA+14103 T66-1666 Papa 1 of 2 i II �I CRESTVIEW CONDOMINIUMS SEWER MAIN EXTENSION REPORT A. General Project Description This report will give an overview of the proposed wastewater collection system for the development of the Crestview Condominiums in Lot 6 of the Baxter Lane Subdivision on the southwest corner of Sartain St and Thomas Dr in Bozeman. The zoning for the area is listed as R-4, residential high density. The proposed condominiums are designed as one 12-plex and one 10-plex for a total of 22 units. The improvements are anticipated to be constructed during the winter of 2018. Included in this report is a description of the proposed wastewater collection system and design parameters. Once the wastewater system is constructed and approved,the system will become a part of the City of Bozeman system. The following references were used in the wastewater facilities design and capacity analysis: a. COB Design Standards and Specifications Policy, 2017. Addendum#6 b. COB Modification to Montana Public Works Standard Specifications (MPWSS) c. City adopted MPWSS and adopted Addenda d. COB Wastewater Facility Plan, 2017 e. WQB Circular No. 2 f. City of Bozeman Zoning Map The procedures and parameters outlined in the COB Design Standards and Specifications Guide were used in the design of the sewer infrastructure for the proposed development. B. Capacity Analysis The effluent generated from the proposed condominiums will be collected by one 8-inch sanitary sewer main extending from the development to an existing COB SSMH. This 8-inch sewer main will flow east into a proposed sewer manhole before flowing north into an existing manhole near the intersection of Sartain Street and Thomas Drive. The wastewater demands from the proposed subdivision were estimated based on a flow per capita basis, which provided a more conservative flow than a per zoned acre basis. (COB Table V-1 specifies an average daily flow rate of 1,950 gal/ac-day for R-4 zoning, resulting in 1,658 gpd=0.85ac x 1,950 gal/ac-day). The proposed sewer mains have been sized to flow at no more than 75-percent of full capacity at peak hour conditions of full build out, and a Manning coefficient of 0.013 was used for PVC pipe. Crestview Condominiums Wastewater Design Report Page 1 of 3 Crestview Condominiums The average daily flow is based on the number of units, 2.11 residents per unit, and 89 gallons per capita per day, the latter two values based on COB design standards: ( residents gallons 22 units * 2.11 * 89 ) = 4,131gpd unit capita/day An approximate population for the condominiums is calculated as: residents 22 units * 2.11 = 47 persons unit This is a more realistic population value compared to utilizing the 10.4 units per acre (Table V-1 from COB design standards) applied to 0.85 acres, which only results in 19 persons. This equivalent population can be utilized to determine a peaking factor: Qmax _ 18 + P.5 _ 18 +.047.5 = 4.32 QAve 4 + P•5 4 +.047-5 (P =Population/thousands) Based on a total population of 47 people, a peaking factor of 4.32 was calculated. The peak flow rate anticipated from the development based on an average daily flow of 4,131 gallons per day is: Peak Flow Rate = (4,131 gpd x 4.32) = 17,846 gpd = 12.39 gpm = 0.028 cfs Additionally, an infiltration flow of 128 gpd(150 gal/acre/day x 0.85 acres)has been added to the flow, resulting in a total flow of 17,974 gpd (0.028 cfs). The sewer main size for the development will be an 8-inch, based on minimum required pipe size and slope. An 8-inch PVC sewer main at 0.40% slope has a capacity of 0.64 cfs at 1/4 pipe depth, which has adequate capacity for the proposed peak flow of 0.028 cfs effluent generated from the site. Calculations are included in the end of this report. C. Proposed Collection System PVC pipe meeting COB specifications will be used for the sewer mains. The effluent from the Crestview Condominiums will drain into a proposed 8-inch diameter sanitary sewer main via 4- inch sewer services. The effluent in the 8-inch will then flow east to a proposed manhole before turning north and flow to an existing manhole and existing 8" sewer main in Sartain Street. The Crestview Condominiums Wastewater Design Report Page 2 of 3 maximum manhole spacing will be 400 feet for the 8-inch main. Manholes will be constructed according to COB specifications. All sewer services will be 4-inch PVC installed at 2%minimum grade. Sewer services will connect into the main with in-line gasketed wyes. The sewer main will maintain a minimum separation of 10-feet horizontally and 18-inches vertically from any proposed or existing public water mains. D. Downstream Capacity Analysis The sanitary sewer mains were designed in conformance with the City of Bozeman Wastewater Improvement Plan. It is anticipated that the City of Bozeman sanitary sewer system has enough capacity to accommodate the main extension. A capacity letter from a City Engineer will be required prior to DEQ approval of the system. E. Conclusion As outlined above, one single 8-inch sanitary sewer main serving the Crestview Condominiums has the capacity for the effluent generated from the subdivision. This project will require the approval of the City Engineer and MDEQ. Crestview Condominiums Wastewater Design Report Page 3 of 3 I I I I I