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Home My WebLink About20 - Design Report - Nexus Point - Water B. Water Main Design Report - Exhibit WATER MAIN DESIGN REPORT FOR: NEXUS POINT DEVELOPMENT BOZEM^ MT .•'CHRIS G. f • • i.. :3 w= Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 MARCH 2O20 NEXUS POINT DEVELOPMENT WATER SYSTEM DESIGN REPORT A. General This design report will give an overview of the proposed water main extension for the development of Nexus Point Multi-Unit Residential & Office Building Development Infrastructure Improvements. The proposed Phase 1 improvements are anticipated to be constructed during the fall of 2019. Once the water main is constructed and approved, the main will become a part of the City of Bozeman system. The following references were used in the preparation of this report: a. COB Design Standards and Specifications Policy,2017. Addendum#6 b. COB Modifications to Montana Public Works Standard Specifications (MPWSS). c. WQB Circular No. 1 d. City of Bozeman Zoning Map e. City of Bozeman Water Facility Plan f. 2015 International Fire Code Existing System The proposed water maul extension will be served by the existing City of Bozeman water distribution system, which will be looped. The two connection locations are the existing stub of Lantern Lane and future stub at intersection of Lantern Lane and S 21" Avenue, which will continue south and connect to the intersection of Graf Street and S 215t Avenue. The following information was obtained by the City of Bozeman at the intersection of Lantern Lane and Enterprise Boulevard. Fire Hydrants: 2077 Static Pressure: 65 psi Pitot Pressure: 56 psi Residual pressure: 57 psi Hydrant discharge: 1450 gpm from 2.5" port Distribution Main Capacity—Fire flow at minimum residual pressure Q,=Qt[(Ps—P. ps—Pt)i0.54 Qr= 1,250 [(65 20)/(65 —56]0.54 Q, =2,981 gpm at 20 psi Qt= Hydrant Discharge during Test Qr= Fire Flow at Residual Pressure P,= Static Pressure Pill = Minimum Residual Pressure =20 psi Pr= Residual Pressure Pt= Pitot Pressure Nexus Point Development Water Design Report Page 1 of 3 B. Proposed Water System The proposed water main extension for the Nexus Point development consists of approximately 2,499 linear feet of 8"ductile iron pipe that will connect to the existing water main stub on Lantern Lane and at the future intersection of Lantern Lane and S 2 1"Avenue, which is to be installed with the Graf Street Apartment project. The layout of the proposed water main meets the COB design criteria and will be located within the easements/right of way and separated from the proposed sanitary sewer main by a minimum of 10 feet horizontally. Fire hydrants will be installed per COB design criteria and will not exceed the recommended distance. C. Capacity Analysis The Nexus Point development water main extension is proposed for the development of the 14- buildings comprised of 240-units (120 units per phase) & 2 — office buildings, which sits on an estimated 19.99 acres of R-O (Residential Office District) zoned land. An estimation of the water flow rate was based on the City of Bozeman's design standards and specification policy, which suggests using an average daily flow rate of 2.11 people per dwelling unit and 170-gallons per capita per day. Applied to the 240 units, the required water flow rate is calculated: residents gallons (240 units * 2.11 unit * 170 ca ita day) = 86,088 gpd P The 2 future 2-story office buildings consist of 11,300 sf and 9,900 sf at full build out. Based on a conservative basis the office buildings will produce 0.273 gpd/sf. per water supply planning book by David W. Prasifka. Taking these factors into consideration the office buildings will contribute: 0.273 gallons per day ) * (11,300 + 9,900)square feet = 12,985 gpd square feet Based on these parameters, the development at full build out(240 units + 2 office buildings) will have an estimated water usage of 99,073 gpd (68.80 gpm). The main will connect to the existing City of Bozeman system and will serve the future Nexus Point apartment buildings. 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 1 shows the peaking factors and the resultant flows from those factors when applied to the average daily demand of 68.80 gpm. TABLE l PEAKING FACTORS Flow Designation Peakine Factor Flow (gnm) Average Dav Demand l 68.8 Maximum Day Demand 2.3 152.2 Maximum Hour 3 206.4 Demand Nexus Point Development Water Design Report Page 2 of 3 Based on communication with the architect, four types of buildings will be installed and will consist of two (2) —multi-floor office buildings, six (6)— 12 plex 2-bedroom units, four (4) — 30 plex 1 & 2—bedroom units and two (2) —24 plex 2-bedroom units along with a club house for a total of 14 individual buildings. The square footage for each type of building are as follows: 12 Plex = 12,552sf, 30 Plex = 38,800sf, 24 Plex = 24,046sf and the club house = 9,989sf. The units are expected to be type V-A and V-B construction with fire sprinklers. A Type V-A 38,800sf building requires 3,500 gpm for a 3-hour flow duration per the 2015 International Fire Code,Table B 105.1(2). The flow capacity for the largest building was chosen to be more conservative. Based on the 2015 International Fire Code's Table B105.2, the 3,500 gpm fire flow can be reduced but shall not be less than the minimum of 1,500 gpm. Results Based on the analysis outlined above, the required minimum fire flow is 1,500 gpm and the maximum hour demand is 206.4 gpm. The combination of these results is a maximum hour flow of 1,706.4 gpm. The attached WaterCAD analysis was designed to incorporate the maximum hour demand throughout the system. A fire flow analysis was performed at each node throughout the system(including the base max. hour demand)where a building has a potential fire flow demand. The flow analysis shows that an 8-inch DI pipe can provide the development with the required flow of 1,706.4 gpm and remain above the minimum pressure of 20 psi. See attached flow analysis for calculations. D. Conclusion Based on this analysis, the proposed 8-inch ductile iron water main serving the Nexus Point residential development extension provides adequate service to meet the 240-unit peak hour demand and fire flows requirements for the development. The water main was designed on conservative premise for future development. For instance, only one connection point(intersection of Lantern Lane and Enterprise Blvd.) was modeled, when in reality there will be two connection points for the system. The water main design is consistent with the City of Bozeman Water Facility Plan. This project will require the approval of the City of Bozeman Engineer and MDEQ. 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