HomeMy WebLinkAbout20 - Design Report - Mountain Vista - Water
INTRODUCTION
The proposed Mountain Vista Housing Complex is a 25-unit development consisting of Duplex
and Single Units, located on the property described in Doc. No. 2046120 in the Southwest Quarter,
Section 11, Township 2 South, Range 5 East of P.M.M.. The project will require connection to the
existing City of Bozeman water and sanitary sewer systems.
WATER SYSTEM LAYOUT
The Mountain Vista Housing complex will require tapping in to an existing 10” ductile iron water
main in West Babcock Street with 8” Class 51 ductile iron pipe. All new water mains are to be
installed in the City standard location and will be located 10’ away from any proposed sewer
mains. The 8” main extending into the property will have 4 stubs with blowoff valves.
A WaterCAD analysis is enclosed at the end of the report analyzing the 8-inch water main to be
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 hydrant #968, located on Donna Avenue, south of Babcock Street. 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 = 2.11 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 = 10 d.u. x 2.11 persons/d.u. x 170 gpcpd = 3,587 gpd = 2.6 gpm
Maximum Day Demand = 2.6 gpm x 2.3 = 5.9 gpm
Peak Hour Demand = 2.6 gpm x 3.0 = 7.8 gpm
Residential Water Demands (Demand Junction 2)
Average Day Demand = 15 d.u. x 2.11 persons/d.u. x 170 gpcpd = 5,380 gpd = 3.8 gpm
Maximum Day Demand = 3.8 gpm x 2.3 = 8.8 gpm
Peak Hour Demand = 3.8 gpm x 3.0 = 11.5 gpm
Available Pressure: 10-inch class 51 ductile iron main Babcock Street
Static = 114 psi (Hydrant #986)
Residual = 88 psi (Hydrant #986)
Pitot (2.5” nozzle) = 108 (Hydrant #986)
Flowing = 1,575 gpm (Hydrant #1985)
HYDRAULIC ANALYSIS
Design Report - Page 4 of 6
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.
Mountain Vista Housing Complex (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 10 22 2.6 5.9 7.7
DJ 2 15 33 3.8 8.8 11.5
Total 25 54 6.40 14.73 19.21
*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 development 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 the junction where the hydrant is located. 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 6
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
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FlexTable: Junction Table
Pressure
(psi)
Hydraulic
Grade
(ft)
Demand
(gpm)
Demand CollectionElevation
(ft)
Label
1145,086.568<Collection: 1 items>4,822.50DJ-1
1135,086.5612<Collection: 1 items>4,826.10DJ-2
1135,086.560<Collection: 0 items>4,826.30HYD #1
1145,086.570<Collection: 0 items>4,822.00J-1
1145,086.570<Collection: 0 items>4,822.00J-2
1145,086.560<Collection: 0 items>4,823.40J-3
1145,086.560<Collection: 0 items>4,823.40J-4
1135,086.560<Collection: 0 items>4,826.40J-5
1135,086.560<Collection: 0 items>4,826.30J-6
1135,086.560<Collection: 0 items>4,826.30J-7
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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
0.0004,823.504,823.500.00190.000150.0PVC999.01P-51
0.0005,086.565,086.570.12190.500130.0Ductile Iron8.0157P-3
0.0005,086.565,086.560.07120.390130.0Ductile Iron8.0173P-7
0.0005,086.575,086.570.12190.390130.0Ductile Iron8.0261P1
0.0005,086.575,086.570.08190.390130.0Ductile Iron10.0305P-2
0.0005,086.565,086.560.0001.280130.0Ductile Iron8.0132P-4
0.0005,086.565,086.560.0000.000130.0Ductile Iron8.098P-5
0.0005,086.565,086.560.0000.350130.0Ductile Iron8.043P-8
0.0005,086.565,086.560.0000.000130.0Ductile Iron8.045P-9
0.0005,086.565,086.560.0000.000130.0Ductile Iron6.011P-10
0.0005,086.565,086.560.0001.280130.0Ductile Iron8.0137P-6
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Pump Definition Detailed Report: HYD 968
Element Details
168ID Notes
HYD 968Label
Pump Curve
Head(ft)Flow(gpm)
263.080
251.541,427
240.002,075
228.462,583
216.923,017
205.383,404
193.853,756
182.314,082
170.774,387
159.234,675
147.694,949
136.155,210
124.625,461
113.085,702
101.545,935
90.006,160
78.466,379
66.926,591
55.386,798
43.856,999
32.317,196
20.777,388
9.237,575
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?
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Pump Definition Detailed Report: HYD 968
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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
J-723020203,4371,5003,4371,500HYD #1
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Design Report - Page 6 of 6
APPENDIX B
DEMAND JUNCTION MAP