About Me. Overview. Seattle Regional Water System. Seattle Regional Water System. Water System Analysis and Design at Seattle Public Utilities

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1 About Me Water System Analysis and Design at Seattle Public Utilities Jon C. Ford, P.E. CEE 481 October 1, 8 Senior Civil Engineer, Seattle Public Utilities BSCE, Seattle University MSCE, University of Washington Registered Professional Engineer (Civil), WA My work Water System Planning and Analysis Hydraulic Modeling Replacement strategies for aging assets Overview Seattle Regional Water System Seattle s Water System Description of Hydraulic Modeling Water Demand Levels Example Water System Expansion Seattle Regional Water System The Great Seattle Fire June 6, million customers in King and Snohomish County 185, retail/1 wholesale service connections 1,6 mi. distribution/159 mi. transmission mains 15 reservoirs, 7 elevated tanks, 11 standpipes 18,35 fire hydrants 1

2 Cedar River Water Delivered to Seattle 191 Masonry Dam built 1914 Original Landsburg Dam Cedar River Pipelines South Fork Tolt 196s Wood Stave Pipe was used from 193 to 199 Landsburg Tunnel House (near Maple Valley) Tolt Filtration Plant 1 Cedar Treatment Facility 4 Cedar UV Treatment Building

3 Water Pressure Zone What is a Hydraulic Model? Simulation of pipe network Software application Graphical user interface Reservoir Pipe Example Pipe Network Junction Demand Sources Pipe Network Elements Reservoirs (fixed head) Tanks (variable head) Pipes Pipe junctions Pumps Valves 5 gpm Hydraulic Network Models Simulation of pressurized pipe network Solves for head loss in pipe loops (i.e., Hardy- Cross technique) Uses computers (instead of humans) for calculations Much faster, can analyze much larger networks Hydraulic Network Models Model Inputs: Pipe geometry (length, diameter, internal roughness, junction elevation) Source Head (flow into network) Demands (flow out of network) Pump and Valve Settings (Controls) Model Outputs: Pressure (or head) at pipe junctions Flow (or velocity) through pipe segments 3

4 Hydraulic Solution Algorithm Two relationships must be satisfied: The sum of head loss around a pipe loop must equal zero The flow into a pipe junction must equal the flow out Hydraulic modeling programs solve these equations simultaneously for the entire pipe network Equations Energy Equation p1 v1 p v z hp = z hl + hm + ht γ g γ g Head Loss Formulas Hazen-Williams Darcy-Weisbach 1.44 L Q h L = 1.85 C d f L v h L = D g Applications for Hydraulic Models Example Hydraulic Model Pressure Analyses Fire Flow Analyses Operational Reliability Analyses Water Quality Analyses Hydraulic Modeling Software Programs Model Calibration Using Field Tests EPANET Public domain Basic functionality Commercial Programs WaterGEMS HONet Licensed software Enhanced functionality 4

5 Determining Demand Levels Demand Pattern - ADD SCADA Flow Meter Data (best) Billing Records + Modeling (good) Estimates based on ERUs (very rough) Peaking Factor Richmond Highlands 59 ADD Demand Curve Morning Peak Afternoon Peak Time Demand Pattern - MDD Demand Pattern - MDD Richmond Highlands 59 MDD Demand Curve Richmond Highlands 59 MDD Demand Curve.4.4 Peaking Factor Peaking Factor Morning Peak Afternoon Peak Time Time Seasonal Demands Seasonal Demands RH59 7-Day Average Demand 7-8 RH59 7-Day Average Demand Demand (gpm) 4 3 Demand (gpm) 4 3 Off-Peak Demand Peak Season Demand 1 1 9//7 11/1/7 1//8 3//8 5/19/8 7/18/8 9/16/8 Date 9//7 11/1/7 1//8 3//8 5/19/8 7/18/8 9/16/8 Date 5

6 Elevation ft Diameter in Day 1, 1: AM Example Water System Expansion New development 1,8 new homes Commercial center Elementary School Elevation ranges from 5 to 5 feet Example Water System Expansion 31, feet of new watermains 1 new elevated storage tank Single point of supply (already treated) Hydraulic Model of System Expansion Water System Design Requirements System Design Standards Pressure Requirements Fire Flow Requirements Storage Requirements Other Considerations Design Standard Examples Watermain Sizing Commercial Areas 1 inches Residential Through Streets 8 inches Residential Dead Ends 6 inches Fire Hydrant Spacing Valve Spacing Pressure Analysis Minimum Peak Hourly Demand (PHD) Pressure 3 psi Design Pressure Range 4 to 8 psi Water Systems are organized into pressure zones to maintain 4-to-8 psi range 6

7 Pressure Simulation Water Demand Levels Pres sure psi Flow GPM Day 1, 1: AM ADD Average Day Demand MDD Maximum Day Demand MDD = MDD Factor x ADD PHD Peak Hourly Demand PHD = PHD Factor x ADD MDD and PHD Demand Pattern - ADD Maximum Day Demand Curve Richmond Highlands 59 ADD Demand Curve.4.4 Peaking Factor PHD Factor =.3 MDD Factor = 1.8 Peaking Factor Time Time Fire Flow Requirements Set by local fire jurisdictions Measured at psi under MDD conditions Depends on land use zoning Single-family residential 5 to 15 gpm Multi-family residential 1 to 3 gpm Commercial to 8 gpm Quality Diameter in Fire Flow Simulation Day 1, 1: AM 7

8 Storage Considerations Existing storage usually sufficient Large developments may require own storage Requirements depend on number of sources Single source strictest Multiple sources less strict Storage Requirements Operational Maintains pressure when pumps are cycled off Equalizing Makes up difference between peak demand and pumping capacity Fire Protection Provides fire flow capacity if pumps are unavailable Standby Provides domestic flows when pumps are unavailable OVERFLOW ELEVATION TOTAL VOLUME RESERVOIR STORAGE COMPONENTS PUMP OFF OPERATIONAL PUMP STORAGE (OS) ON EQUALIZING EFFECTIVE STORAGE (ES) VOLUME - ONLY THE ES AND SB STAND BY PORTIONS APPLY AND/OR FIRE TO ERU SUPPRESSION DETERMINATIONS STORAGE (SB AND FSS)* DEAD STORAGE (DS) PSIG OR 46 FEET OF HYDRAULIC BOTTOM OF FSS & 3 PSIG OR 69 FEET SB STORAGE OF HYDRAULIC BOTTOM OF EQUALIZING STORAGE TOTAL PUMPING HEAD Storage Calculations from Washington State Water System Design Manual Equalizing Storage ES = (PHD Total Available Supply)(15 min.) Fire Suppression Storage FSS = (Required FF)( Required Duration) Standby Storage For Single Sources: SB TSS = ( days) (ADD) For Multiple Sources: SB TMS = ( days)(add) - (Total supply less largest supply)(time required for pumping) DISTRIBUTION SYSTEM Equivalent Residential Units (ERUs) ERU represents one single-family household Accounts for demand of different land use types Typical daily demand per ERU: 15-3 gallons Number of ERUs:, ERUs ADD per ERU: 5 gallons per day ADD (gallons per minute) =? 8

9 Number of ERUs:, ADD per ERU: 5 gallons ADD = 347 gpm PHD Factor =.3 PHD =? Number of ERUs:, ADD per ERU: 5 gallons ADD = 347 gpm PHD Factor =.5 PHD = 799 gpm Total available supply: 6 gpm (single source) Fire flow requirement:, gpm x 4 hours Equalizing Storage Requirement PHD = 799 gpm Total Available Supply = 6 gpm ES = (PHD Total Available Supply)(15 min.) ES =? Equalizing Storage Requirement PHD = 799 gpm Total Available Supply = 6 gpm ES = (PHD Total Available Supply)(15 min.) ES = (799 6) x (15) = 9,85 gallons Fire Suppression Storage Requirement Maximum Required Fire Flow = 3, gpm (Commercial Area) Fire Flow Duration = 4 hours FSS = (Required FF)( Required Duration) FSS =? Fire Suppression Storage Requirement Maximum Required Fire Flow = 3, gpm (Commercial Area) Fire Flow Duration = 4 hours FSS = (Required FF)( Required Duration) FSS = 3 gpm x 4 min = 7, gallons 9

10 Standby Storage Requirement Average Day Demand = 347 gpm For Single Sources: SB TSS = ( days) (ADD) SB =? Standby Storage Requirement Average Day Demand = 347 gpm For Single Sources: SB TSS = ( days) (ADD) SB = days x 347 gpm = 999,36 gpm Equalizing Storage = 9,85 gallons Fire Suppression Storage = 7, gallons Standby Storage = days x 347 gpm = 999,36 gpm Note: FSS and Standby Storage can be combined Subtotal Volume = ES +max (FSS, SB) = 4, + 1,, gallons = 1,3, gallons Does not include operational storage Tank Design Tank geometry depends on volume and pressure requirements Bottom of Fire Suppression/Standby Storage needs to provide psi (46 feet net head) Bottom of Equalizing Storage needs to provide 3 psi (7 ft net head) Operational Storage is on top Tank Design Tank Diameter Calculation Operational Storage = 1 ft Diameter determined by FSS/SB requirement FSS/SB between 556 and 58 feet = 4 feet 58 ft 556 ft ES FSS/SB 3 psi = 7 ft psi = 46 ft FSS/SB Volume FSS/SB Area = 1,, gallons = 134, CF = Volume/Height = 557 SF Highest Service Elevation = 51 ft Tank Diameter = 85 feet 1

11 Tank Height Calculation ES Volume ES Height = 3, gallons = ~ 1 foot Combine with Operational Storage Operational Storage = 1 feet Total Tank Height = 51 feet + 7 feet + 1 feet = 59 feet Dead storage volume depends on geometry (less for elevated tank, more for standpipe) Other Design Considerations Redundancy Interconnectivity Water Quality Questions? 11