The URL can be used to link to this page

Home My WebLink About20 - Design Report - The Nest PUD - Water, Sewer DESIGN REPORT WATER & SEWER MANAGEMENT THE NEST PUD SUBDIVISION Prepared for: Center Arrow Partners, LLC P.O. Box 1633, Bozeman, MT 59771 Prepared by: C&H Engineering and Surveying, Inc. 1091 Stoneridge Drive, Bozeman, MT 59718 (406) 587-1115 Project Number: 180805 April 2020 INTRODUCTION The proposed Nest PUD Subdivision is a 15-lot condominium subdivision located on Lot R1, Block 5, Westbrook Subdivision, Phase 4 (5.41-acres) in the Westbrook Subdivision. This project will require connection to existing City of Bozeman water and sanitary sewer systems. WATER SYSTEM LAYOUT The Nest PUD Subdivision will extend the existing 8” class 51 ductile iron water main installed in Glenwood Drive and Annie Street and will tap into the existing 12” water main running along Durston Road. All new water mains are to be installed in the City standard location and will be located 10’ away from any proposed sewer mains. All water mains will be looped and no blowoffs will be required with this layout. A WaterCAD analysis is enclosed at the end of the report analyzing the 8-inch water main extension installed with this project. The connection to the existing system was modeled as a pump curve using data obtained from the City of Bozeman Water Department: static, residual and pitot pressures were read at hydrants #2005 and #1985, located at the intersections of Annie Street/Twin Lakes Ave and Annie Street/Rosa Way, respectively. This data was used to develop the pump curve used at the connection point to model the existing system. The following equation based off of the Hazen Williams method is used to generate the pump curve: Q = Qf x ((Ps - P) / (Ps - Pr))0.54 Where: Q = flow predicted at desired residual pressure, Qf = total flow measured during test, Pr= residual pressure during test, Ps = static pressure and P = residual pressure at the desired flow rate. In the model, the pump is connected to a reservoir which acts as a source of water. The elevation of the reservoir is fixed at the elevation of the pump, which is also equivalent to the elevation of the tie-in point. The reservoir does not create any head on the system; the head is generated entirely by the pumps. The input data and the pump curves are included at the end of the report. The pump curve table includes all calculations and equations used in determining flow characteristics at the connection point. A C-factor of 130 was chosen for ductile iron class 51 pipe. WATER DISTRIBUTION SYSTEM SIZING Residential Units: Average Daily Residential Usage = 170 gallons per capita per day Average Population Density = 2.17 persons/dwelling unit Minimum Fire Hydrant Flow = 1,500 gpm Residual Pressure Required = 20 psi for Fire Flow Average Day Demand (Peaking Factor = 1) Maximum Day Demand (Peaking Factor = 2.3) Maximum Hour Demand (Peaking Factor = 3.0) Residential Water Demands (Demand Junction 1) Average Day Demand = 33 d.u. x 2.17 persons/d.u. x 170 gpcpd = 12,240 gpd = 8.5 gpm Maximum Day Demand = 8.5 gpm x 2.3 = 19.4 gpm Peak Hour Demand = 8.5 gpm x 3.0 = 25.4 gpm Residential Water Demands (Demand Junction 2) Average Day Demand = 12 d.u. x 2.17 persons/d.u. x 170 gpcpd = 4,464 gpd = 3.1 gpm Maximum Day Demand = 3.1 gpm x 2.3 = 7.1 gpm Peak Hour Demand = 3.1 gpm x 3.0 = 9.2 gpm Available Pressure: 8-inch class 51 ductile iron main Annie Street and Rosa Way Static = 96 psi (Hydrant #2005) Residual = 88 psi (Hydrant #2005) Pitot (2.5” nozzle) = 80 (Hydrant #1985) Flowing = 1,500 gpm (Hydrant #1985) Design Report - Page 4 of 8 HYDRAULIC ANALYSIS A water distribution model was created using WaterCAD Version 10.01.00.72 for demand forecasting and describing domestic and fire protection requirements. In order to model the system, each junction node of the water distribution system was assessed a demand based on its service area. The table shown below quantifies the demands placed at the junction nodes and calculates the demands for Average Day, Maximum Day and Peak Hour within the subdivision. The peaking factor for each case is 1, 2.3 and 3.0 respectively. The Nest PUD Subdivision (Table 1): DEMAND JUNCTION NODE DWELLING UNITS (D.U.) POPULATION (RES.) 2.17 PEOPLE PER D.U. AVERAGE DAY GPM (170 GALLONS PER DAY PER PERSON) MAX. DAY GPM PEAK HOUR GPM DJ 1 33 72 8.5 19.4 25.4 DJ 2 12 26 3.1 7.1 9.2 Total 45 98 11.53 26.51 34.58 *See Demand Junction Map for more information on which lots contribute to each Demand Junction. CONCLUSION The proposed 8-inch DIP water mains provide adequate capacity to serve the subdivision under the Peak Hour Demand condition. The flows and pressures within the system for the Peak Hour Demands were generated with the WaterCAD program and can be found in Appendix A. The capacity of the system to meet fire flow requirements was tested by running a steady state fire flow analysis for all junctions at fire hydrant locations. The model shows that all hydrant junctions satisfy fire flow constraints (residual pressure > 20 psi, flow rate > 1500 gpm), while providing service to lots at peak hour. The results of the analysis at peak hourly flow are given in Appendix A. Design Report - Page 5 of 8 SANITARY SEWER SYSTEM An 8-inch PVC sanitary sewer line will be installed in the woonerf section and will flow north to connect with the existing 8-inch stub located just south of the Annie Street/Cassandra Lane intersection. DESIGN REQUIREMENTS The flow rates used herein are according to the City of Bozeman Design Standards and Specifications Policy (DSSP) dated March, 2004. The peaking factor for the design area is determined by figuring the equivalent population and inserting the population into the Harmon Formula. An 8-inch main is used because that is the minimum diameter allowed within the City of Bozeman. Using the city average of 2.17 persons per household the equivalent population is calculated. Connection: Equivalent Population = (2.17 persons/dwelling unit)(45 units) = 98 persons Harmon Formula: Peaking Factor = (18 + P0.5)/(4 + P0.5) where: P = Population in thousands Peaking Factor = (18 + 0.0980.5)/(4 + 0.0980.5) Peaking Factor = 4.25 Assumed infiltration rate = 150 gallons/acre/day = 150 (5.41 acres) = 812 gal/day The peak flow rate is calculated by multiplying the City's design generation rate of 65 gallons per capita per day by the population, multiplying by the peaking factor, and adding the infiltration rate: Peak Flow Rate = 65 gpcpd (98 persons) (4.25) + 812 gpd = 27,885 gpd = 19.36 gpm = 0.0431 cfs Design Report - Page 6 of 8 The capacity of an 8-inch main is checked using Manning’s Equation: Qfull = (1.486/0.013)AR2/3S1/2 For an 8-inch PVC main: Manning's n = 0.013 for PVC Pipe Minimum Slope = 0.004 ft/ft A = area = (3.14/4)d 2 = (3.14/4)(8/12)2 = 0.34907 ft2 P = perimeter = 2(3.14)r = 2(3.14)(4/12) = 2.0944 ft R = hydraulic radius = A/P = 0.34907/2.0944 = 0.16667 ft R2/3 = 0.30105 ft S = 0.004 ft/ft S1/2 = 0.0632 ft/ft Qfull = (1.486/0.013)(0.34907)(0.30105)(0.0632) = 0.7592 cfs Connection: Q/Qfull = 0.0431 /0.7592 = 0.0568 or 5.68% Based on these calculations, an 8-inch sewer line has adequate capacity to carry the design flows for the subdivision. Design Report - Page 7 of 8 APPENDIX A WATERCAD MODEL Scenario Summary Report Scenario: Base Scenario Summary 1ID BaseLabel Notes Base Active TopologyActive Topology Base PhysicalPhysical Base DemandDemand Base Initial SettingsInitial Settings Base OperationalOperational Base AgeAge Base ConstituentConstituent Base TraceTrace Base Fire FlowFire Flow Base Energy CostEnergy Cost Base TransientTransient Base Pressure Dependent DemandPressure Dependent Demand Base Failure HistoryFailure History Base SCADASCADA Base User Data ExtensionsUser Data Extensions Base Calculation OptionsSteady State/EPS Solver Calculation Options Base Calculation OptionsTransient Solver Calculation Options Hydraulic Summary Steady StateTime Analysis Type TrueUse simple controls during steady state? Hazen-WilliamsFriction Method FalseIs EPS Snapshot? 0.001Accuracy 12:00:00 AMStart Time 40Trials Fire FlowCalculation Type Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Pump Definition Detailed Report: HYD 1985 Element Details 49ID Notes HYD 1985Label Pump Curve Head(ft)Flow(gpm) 221.540 207.691,284 196.151,781 184.622,181 173.082,526 161.542,835 150.003,117 138.463,379 126.923,625 115.383,858 103.854,079 92.314,290 80.774,493 69.234,688 57.694,876 46.155,059 34.625,236 23.085,408 11.545,576 0.005,739 Pump Efficiency Type Best Efficiency Point Pump Efficiency Type %100.0Motor Efficiency %100.0BEP Efficiency FalseIs Variable Speed Drive? gpm0BEP Flow Transient (Physical) lb·ft²0.000Inertia (Pump and Motor)SI=25, US=1280Specific Speed rpm0Speed (Full)TrueReverse Spin Allowed? Page 1 of 227 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Pump Definition Detailed Report: HYD 1985 Page 2 of 227 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 5/7/2019 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Scenario: Base P-3P-4P-5P-7P-1Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 1/24/2020 WaterCAD CONNECT Edition Update 1[10.01.00.72]Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg FlexTable: Pipe Table Headloss Gradient (ft/ft) Hydraulic Grade (Stop) (ft) Hydraulic Grade (Start) (ft) Velocity (ft/s) Flow (gpm) Minor Loss Coefficient (Unified) Hazen-Williams C MaterialDiameter (in) Length (User Defined) (ft) Label 0.0004,975.474,975.470.0000.390130.0Ductile Iron8.022P-6 0.0004,975.474,975.470.0691.580130.0Ductile Iron8.0521P-7 0.0004,754.004,754.000.00350.000150.0PVC999.01P-1 0.0004,975.514,975.520.22351.880130.0Ductile Iron8.0430P-2 0.0004,975.474,975.470.0000.000130.0Ductile Iron6.010P-5 0.0004,975.494,975.510.22352.260130.0Ductile Iron8.0380P-3 0.0004,975.474,975.490.22352.860130.0Ductile Iron8.0406P-4 0.0004,975.494,975.490.0000.000130.0Ductile Iron6.028P-8 Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 1/24/2020 WaterCAD CONNECT Edition Update 1 [10.01.00.72]Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Fire Flow Node FlexTable: Fire Flow Report Junction w/ Minimum Pressure (System) Pressure (Calculated Zone Lower Limit) (psi) Pressure (Zone Lower Limit) (psi) Pressure (Calculated Residual) (psi) Pressure (Residual Lower Limit) (psi) Flow (Total Available) (gpm) Flow (Total Needed) (gpm) Fire Flow (Available) (gpm) Fire Flow (Needed) (gpm) Label DJ-222020202,6031,5002,6031,500HYD 2 DJ-219020202,2521,5002,2521,500HYD-1 Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 1/24/2020 WaterCAD CONNECT Edition Update 1 [10.01.00.72]Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg FlexTable: Junction Table Pressure (psi) Hydraulic Grade (ft) Demand (gpm) Demand CollectionElevation (ft) Label 934,975.4725<Collection: 1 items>4,760.00DJ-1 914,975.479<Collection: 1 items>4,765.00DJ-2 944,975.490<Collection: 0 items>4,757.17HYD 2 934,975.470<Collection: 0 items>4,760.00HYD-1 964,975.510<Collection: 0 items>4,754.50J-2 924,975.470<Collection: 0 items>4,762.00J-4 944,975.490<Collection: 0 items>4,757.17J-8 Page 1 of 127 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 1/24/2020 WaterCAD CONNECT Edition Update 1 [10.01.00.72] Bentley Systems, Inc. Haestad Methods Solution Center180805 The Nest PUD WaterCAD Model.wtg Design Report - Page 8 of 8 APPENDIX B DEMAND JUNCTION MAP & SANITARY SEWER MAP