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Home My WebLink About16 - Design Report - Graf Street Extension - Wastewater WASTEWATER SYSTEM DESIGN REPORT FOR: GRAF STREET EXTENSION BOZEMAN, MT Prepared By: MADISON ENGINEERING Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 E APRIL 2016 WASTEWATER SYSTEM DESIGN REPORT FOR: GRAF STREET EXTENSION BOZEMAN, MT Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 'i 0¢iPus LJDESK « No. 108 5 E APRIL 2016 o •� � C? GRAF STREET EXTENSION WASTEWATER SYSTEM DESIGN REPORT A. General This report will give an overview of the proposed wastewater collection system for the extension of Graf Street from S. 15th Ave to MacNab Street in Bozeman. The proposed system will serve the development of future phases of Allison Subdivision, which is zoned R-1 (Residential Single Household). The proposed Graf Street improvements are anticipated to be constructed during the summer of 2016. 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,2004. Addendum#5 b. COB Modifications to Montana Public Works Standard Specifications(MPWSS). c. City adopted MPWSS and Adopted Addenda d. COB Wastewater Facility Plan, 2015 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. d B. Capacity Analysis The proposed wastewater system will provide service to future phases of Allison Subd'wision.�l Manholes are proposed in Graf Street at the intersections of S. 15th Ave, Spring Ridge rive, and Keeton Street. Each manhole will have 8" PVC sanitary sewer stubs extending eight e beyond the right-of-way to the north and south. When the sanitary sewer mains are built out in the future they will be extended within the future right-of-ways to the north and south, and the effluent will travel to the north to the existing sanitary sewer system. The capacity of the proposed stubs was'determined based on the upstream demand, fut lots of Allison Subdivision. The wastewaterflemands were estimated on a per acre basis for 1 zoning. The City of Bozeman's Design Standards specify an average daily flow rate of 730 g /acre/day for R-1 development, obtained fr9m Table V-l. The proposed sewer mains have been sized to flow at no more than 75-percent,6f full capacity at peak hour conditions of full build out, and a Manning coefficient of 0.01�3, as used for PVC pipe. Sewer System Wastewater Area Average Flow Peaking Peak Flow Peak Flow Loading Served Rate (gpd) Factor Rate (gpd) Rate(cfs) d/acre (acres) S. 15th Ave 730 0.76 555 4.43 2,459 0.011 Spring Ridge Dr. 730 6.31 4,606 4.31 19,852 0.092 Keeton Street 730 3.79 2,767 4.35 1 12,037 0.056 Graf Street Extension Wastewater Design Report Page I of 2 A peaking factor was calculated based on the following formula: Qmax r Qave= (18 +P0'S)/(4+P0'5) (P=Population/thousands) The calculated peaking factors are included in the appendix of this report. The peak flow rate anticipated from the development was calculated by multiplying the average flow rate by the peaking factor. The peak flow rate was then converted from gpd to cfs using an 8-hour day. The sewer main sizes for the all streets will be 8-inch based on minimum required pipe size and slope. An 8-inch PVC sewer main at 0.4% slope has a capacity of 0.64 cfs at 75% of full flow capacity, which has adequate capacity for the proposed peak flows. Calculations are provided in the appendix of this report. C. Proposed Collection System i With the extension of Graf Street, three 48" manhole ith 8" san a sewer main s - e g north and south will be installed in S. 1 Sth Ave, Spring Ri�Drive, an e treetIn the future, when the lots south of Graf Street are developed as part of Allis Subd vision, the mains will be extended to serve these lots. PVC pipe meeting COB specifications will be used for all sewer mains. 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, an 8-inch sanitary sewer main in S. 15th Ave, Spring Ridge Drive, and Keeton Street will have the capacity for the effluent generated the from the future phases of Allison Subdivision. This project will require the approval of the City Engineer and MDEQ. Appendix 1. Calculations Graf Street Extension Wastewater Design Report Page 2 of 2 Calculations 8-inch PVC Pipe Capacity Project Description Friction Method Manning Formula Solve For Discharge Input Data Roughness Coefficient 0.013 Channel Slope 0.40000 Normal Depth 5.58 in Diameter 8.00 in Results Discharge 0.64 ft3/s Flow Area 0.26 ftz Wetted Perimeter 1.32 ft Hydraulic Radius 2.37 in Top Width 0.61 ft Critical Depth 0.38 ft Percent Full 69.8 % (93%full flow capacity x 75%flow depth) Critical Slope 0.00748 ft/ft Velocity 2.45 ft/s Velocity Head 0.09 ft Specific Energy 0.56 ft Froude Number 0.66 Maximum Discharge 0.82 ft'/s Discharge Full 0.76 ft'/s Slope Full 0.00278 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 in Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 in Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 Normal Depth Over Rise 69.75 Downstream Velocity Infinity ft/s Bentley Systems,Inc. Haestad Methods Sol tH mtl0pfftewMaster V8i(SELECTseries 1) [08.11.01.03] 4/11/2016 9:20:06 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Wastewater Design Graf Street Extension Peaking Factor S. 15th Ave Zoning Acres Units/Acre Density Total (residents/unit) Popoulation RI 0.76 3.9 2.11 6 Peaking = Q(max) = 18 +P 0.50 P =Population/thousands = 6/1000= 0.006 Factor Q(ave) 4 +P 0.50 Peaking Factor = 4.43 Spring Ridge Drive Density Total Zoning Acres Units/Acre (residents/unit) Population R1 6.31 3.9 2.11 52 Peaking = Q(max) = 18 +P 0.50 P=Population/thousands=52/1000 =0.052 Factor Q(ave) 4 +P 0.50 Peaking Factor = 4.31 Keeton Street Density Total Zoning Acres Units/Acre (residents/unit) Population R1 3.79 3.9 2.11 31 Peaking = Q(max) = 18 +P 0.50 P =Population/thousands= 52/1000 =0.031 Factor Q(ave) 4 +P 0.50 Peaking Factor = 4.35