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Home My WebLink About20 - Design Report - Cottonwood Subdivision - Water WATER MAIN DESIGN REPORT FOR: COTTONWOOD SUBDIVISION BOZEMAN, MT Prepared By: Madison Engineering 895 Technology Drive, Suite 203 Bozeman, MT 59718 (406) 586-0262 JANUARY 2020 -updated March 2020- Cottonwood Subdivision Water Design Report Page 1 of 4 COTTONWOOD SUBDIVISION WATER MAIN DESIGN REPORT A. General This design report will give an overview of the proposed 8” water main extensions for the development of the Cottonwood Subdivision, located at the intersection of Cottonwood Rd and Loyal Drive in Bozeman. The 28-acre subdivision is zoned R-5 and will consist of multi- residential units. The proposed improvements are anticipated to be phased, with the first phase being constructed in 2021. This report includes a description of the proposed water main extensions and design parameters. Once the water main is constructed and approved, the main will become a part of the City of Bozeman (COB) system. The following references were used in the preparation of this report: a. COB Design Standards and Specifications Policy, 2004. Addendum #5 b. COB Modifications to Montana Public Works Standard Specifications (MPWSS). c. WQB Circular No. 1 d. City of Bozeman Zoning Map e. Uniform Plumbing Code f. City of Bozeman Water Facility Plan Update, July 2017 A.1. Site Conditions Soil conditions on site consist of a native topsoil to a depth of approximately 12 inches, which is underlain by a thin, intermediate layer of stiff, silt/clay. Beginning at depths of 1.2 to 2.5 feet is an alluvial deposit of clean, sandy gravel that underlies much of the Bozeman area at relatively shallow depths. This clean, sandy gravel extended to the bottom of all 10 to 11 foot test pits. Groundwater depths on site are, on average, to a depth of 7 to 9 feet in the north, central, and east sides of the property, but at a shallower 5-foot depth on the south and southwest sides. Groundwater levels were monitored during the spring and summer of 2018. The highest groundwater levels were recorded in mid-April and showed shallow water conditions across the site. Throughout most of the site, the seasonal high water depths ranged from 3 to 4 feet, but rose to as high as 1.0 to 2.5 feet below the ground surface in the site’s southwest corner. Water flows on site in a in a northwesterly direction. No basements are advised on site. Crawl spaces are only recommended if the depth is limited below existing site grades, in-filling the crawl space up to the top of footings with a clean crushed rock layer, and installing subsurface drainage measure. Otherwise, at-grade slabs with perimeter footings and frost walls are recommended. The site is in an “Area of Minimal Flood Hazard” per the FEMA Panel 30031C0811D. B. Existing Water Supply The proposed water main extensions will be connected to the existing COB water distribution system in Cottonwood Road at Loyal Drive and Alpha Drive as well as in Huffine Road. The Cottonwood Subdivision Water Design Report Page 2 of 4 following information regarding pressures of the existing system was obtained from the City of Bozeman: Fire Hydrant – Golden Gate and Advanced Drive. Hydrants 2201 and 2202 Static Pressure: 115 psi Pitot Pressure: 80 psi Residual Pressure: 110 psi Hydrant Discharge During Test: 1,494 gpm Distribution Main Capacity – Fire flow at minimum residual pressure Qr = Qt[(Ps – Pr)/(Ps – Pt)]0.54 Qr = 1,494[(115 – 20)/(115 – 80)]0.54 Qr = 2,562 gpm Qt = Hydrant Discharge During Test (gpm) Qr = Fire Flow at Minimum Residual Pressure (psi) Ps = Static Pressure (psi) Pm = Minimum Residual Pressure (psi) Pr = Residual Pressure (psi) Pt = Pitot Pressure (psi) C. Proposed Water System The proposed water main extension will consist of approximately 4,030 lf of 8" Class 51 Ductile Iron Pipe within the subdivision's local streets. The proposed main will connect to an 8-inch stub in Cottonwood Road and Loyal Drive, and also be connected to the 10" water main in Huffine Lane. The layout of the proposed water main meets the City of Bozeman design criteria and will be located both within the right-of way and a proposed 30’ wide easement in which the water main will be installed from the subdivision north to Huffine. The water main will be separated from the proposed sanitary sewer main by a minimum distance of 10 feet. The layout of the proposed water main meets the COB design criteria. Fire hydrants will be installed so not to exceed 600’ spacing, fulfilling the distance requirement for fire hydrant spacing, as well as assisting in flushing of the main. Gate valves will be installed at the connection point to the existing mains as well as on property lines, per City standards. Blow-offs have been designed for all dead-end lines that will be extended in the future. Depending on lot layout, each building within the subdivision will either be served by a service line connecting directly to the water main or by a main extension looping through that lot. This system is not expected to be extended or expanded past what is proposed in this report, as all lots within the subdivision are accounted for in this report. If any extensions are required in the future, that developer will be required to analyze and submit a report to the City of Bozeman and the MDEQ for review (DEQ 1.1.2.c. and d., and 1.1.14). D. Capacity Analysis A capacity analysis was performed on the proposed water main extension for the 28-acre subdivision of R-5, residential mixed-use high density. The water main extension has been Cottonwood Subdivision Water Design Report Page 3 of 4 designed to meet the maximum day demand plus fire flow during the peak hour. The City does not have design standards for R-5 mixed-use high density residential. To determine the water demand for the entire subdivision, the density was assumed based on the proposed 400 units over the 16.76 developable acres, and the City of Bozeman design of 170 gpd per capita and 2.17 persons/unit. This equates to 23.89 units/acre. The main will be looped into the existing City of Bozeman system. Table 1 shows the water demand for the entire subdivision. TABLE 1 WATER DEMAND – RESIDENTIAL Zoning Units Density (residents/unit) Per Capita Flow (gpd/resident) Total Flow R-5 400 2.17 170 147,560 (gpd) 103 (gpm) It is anticipated that the average daily demand for the subdivision will be 103 gpm. In addition to the average daily demand, the water main extension must account for peak periods of daily use. Peaking factors are applied to the demand and account for these peak periods in daily use. The peaking factors used are maximum daily use and peak hour and are obtained from the City of Bozeman Design Standards. Table 2 shows the peaking factors and the resultant flows from those factors when applied to the average daily demand of 103 gpm. TABLE 2 PEAKING FACTORS Flow Designation Peaking Factor Flow (gpm) Average Day Demand 1 103 Maximum Day Demand 2.3 236.90 Maximum Hour Demand 3 309 The required fire flow for Type V-B structures is 1,500 gpm. With a fire flow demand of 1,500 gpm and a peak hour demand of 309 gpm, a peak hour flow of 1,809 gpm (4.04 cfs) is required. A Hazen-Williams “C” Factor of 130 was used in the pipe evaluation. The working residual water pressure shall not be less than 20 psi at any point in the water distribution system under maximum day plus fire flow. The velocity shall not exceed 15 feet per second through the main line. E. Results Flow analysis of the 8-inch D.I. pipe with a C value of 130 can provide the required 1,809 gpm. The maximum pipe velocity will not exceed 15 ft/s, as illustrated in the attached WaterCad Automated Fire Flow Analysis. Using the hydrant flow data listed on page 2 of this report, a three-point pump curve was generated to simulate existing conditions within the City of Bozeman water system. The residual pressure is typically used to model the low point on the pump curve. For this simulation however, the pitot pressure was used as the low point on the pump curve to ensure a conservative design (residual pressure = 110 psi, pitot pressure = 80 psi). The minimum system pressure during a fire event is 52 psi, which exceeds the minimum Cottonwood Subdivision Water Design Report Page 4 of 4 required pressure of 20 psi. Capacity analysis calculations outlining the capacity of the proposed 8-inch pipe are included in the appendix of this report. F. Conclusion Based on this analysis, the proposed 8-inch water main extensions for the proposed Cottonwood Subdivision provide adequate service to meet the peak hour demand and fire flows for the development. This project will require the approval of the City Engineer and MDEQ. Appendix 1. WaterCad Analysis 2. City of Bozeman Proposed Water Distribution System Figure 9-2 3. Exhibit A – Sewer and Water Main Exhibit Appendix Appendix 1: WaterCAD Analysis Scenario: Automated Fire Flow Analysis Current Time Step: 0.000 h Fire Flow Node FlexTable: Fire Flow Report G:\ACAD\2017\17-149 Cottonwood Sub\dwg\Civil\WaterCad\Cottonwood Subdivision WaterCad.wtg Label Zone Fire Flow Iterations Satisfies Fire Flow Constraints? Fire Flow (Needed) (gpm) Fire Flow (Available) (gpm) Flow (Total Needed) (gpm) Flow (Total Available) (gpm) Pressure (Residual Lower Limit) (psi) Pressure (Calculated Residual) (psi) Pressure (Zone Lower Limit) (psi) Pressure (Calculated Zone Lower Limit) (psi) Junction w/ Minimum Pressure (Zone) Pressure (System Lower Limit) (psi) Pressure (Calculated System Lower Limit) (psi) Junction w/ Minimum Pressure (System) Is Fire Flow Run Balanced? Velocity of Maximum Pipe (ft/s) Velocity (Upper Limit) (ft/s) Pipe w/ Maximum Velocity J-2 <None>3 True 1,500 2,350 1,500 2,350 20 75 20 77 J-1 (N/A)77 J-1 True 15.00 15.00 C-WATER-FS (Polyline)-30J-4 <None>3 True 1,500 2,350 1,500 2,350 20 75 20 77 J-3 (N/A)77 J-3 True 15.00 15.00 C-WATER-FS (Polyline)-29J-6 <None>3 True 1,500 2,350 1,500 2,350 20 74 20 76 J-5 (N/A)76 J-5 True 15.00 15.00 C-WATER-FS (Polyline)-31J-7 <None>3 True 1,500 2,311 1,500 2,311 20 73 20 75 J-8 (N/A)75 J-8 True 15.00 15.00 C-WATER-MAIN (Polyline)-37(2)(1)(1)J-9 <None>3 True 1,500 2,350 1,500 2,350 20 79 20 81 J-10 (N/A)81 J-10 True 15.00 15.00 C-WATER-FS (Polyline)-24 J-11 <None>3 True 1,500 2,350 1,500 2,350 20 70 20 72 J-12 (N/A)72 J-12 True 15.00 15.00 C-WATER-MAIN (Polyline)-6(1)(2) J-13 <None>3 True 1,500 2,350 1,500 2,350 20 63 20 65 J-14 (N/A)65 J-14 True 15.00 15.00 C-WATER-MAIN (Polyline)-6(1)(2) J-15 <None>3 True 1,500 2,350 1,500 2,350 20 77 20 79 J-16 (N/A)79 J-16 True 15.00 15.00 C-WATER-FS (Polyline)-25 J-18 <None>3 True 1,500 2,350 1,500 2,350 20 78 20 78 J-17 (N/A)78 J-17 True 15.00 15.00 C-WATER-HYDRANT (Polyline)-17 J-20 <None>3 True 1,500 2,350 1,500 2,350 20 77 20 77 J-19 (N/A)77 J-19 True 15.00 15.00 C-WATER-HYDRANT (Polyline)-14J-22 <None>3 True 1,500 2,350 1,500 2,350 20 80 20 80 J-21 (N/A)80 J-21 True 15.00 15.00 C-WATER-HYDRANT (Polyline)-18J-24 <None>3 True 1,500 2,350 1,500 2,350 20 52 20 52 J-23 (N/A)52 J-23 True 15.00 15.00 C-WATER-MAIN (Polyline)-6(2)(2)J-26 <None>3 True 1,500 2,350 1,500 2,350 20 75 20 75 J-25 (N/A)75 J-25 True 15.00 15.00 C-WATER-HYDRANT (Polyline)-9J-28 <None>3 True 1,500 2,350 1,500 2,350 20 81 20 81 J-27 (N/A)81 J-27 True 15.00 15.00 C-WATER-HYDRANT (Polyline)-8J-30 <None>3 True 1,500 2,350 1,500 2,350 20 77 20 78 J-29 (N/A)78 J-29 True 15.00 15.00 C-WATER-HYDRANT (Polyline)-35J-32 <None>3 True 1,500 2,272 1,500 2,272 20 62 20 63 J-31 (N/A)63 J-31 True 15.00 15.00 C-WATER-MAIN (Polyline)-36(1)(1)J-34 <None>3 True 1,500 2,272 1,500 2,272 20 64 20 65 J-33 (N/A)65 J-33 True 15.00 15.00 C-WATER-MAIN (Polyline)-16J-36 <None>3 True 1,500 2,272 1,500 2,272 20 76 20 76 J-68 (N/A)76 J-68 True 15.00 15.00 C-WATER-MAIN (Polyline)-36(1)(1) Page 1 of 1 3/24/2020file:///C:/Users/Tech7/AppData/Local/Temp/Bentley/WaterCAD/jvjauvuh.xml Appendix 2: City of Bozeman Proposed Water Distribution System Figure 9-2 Appendix 3: Exhibit A – Sewer and Water Main Exhibit LP LOYAL GARDEN SUBDIVISION ALPHA DRIVE HUFFINE LANE COTTONWOOD ROADSTAFFORD AVEGARFIELD ST RESORT DRPARK BLVD LOY A L D R LOT 2 BLOCK 2 LOT 2 BLOCK 1 LOT 1 BLOCK 1 LOT 1 BLOCK 2 LOT 1 BLOCK 3 LOT 2 BLOCK 3 LOT 1 BLOCK 5 LOT 1 BLOCK 6 PUBLIC PARK PUBLIC PARK PUBLIC PARK PUBLIC PARK TOWN PUMP -EXT'G-STAFFORD AVE(FUTURE)1 inch = 0 SCALE 200' 400'100'200' EXHIBIT AMADISON ENGINEERING 895 TECHNOLOGY BLVD, SUITE 203 BOZEMAN, MT 59718 PHONE (406) 586-0262 COTTONWOOD ROAD IMPROVEMENTS SEWER AND WATER MAIN EXHIBIT BOZEMAN, MT