Silver Lake Water & Sewer District 5-1 Comprehensive Water System Plan July 2010

CHAPTER 5

HYDRAULIC MODELING INTRODUCTION This Chapter presents the hydraulic model of the District’s water system and the results of hydraulic analyses, which are conducted to evaluate the existing and future capabilities of the water system. The operation of a municipal water system involves dynamic interactions between various water system components, including source, storage, transmission, and distribution system facilities. These interactions and their effect on the level of service provided to District customers are dependent on the distribution and magnitude of water demands within the system and the performance characteristics of the water system facilities. In addition to normal diurnal demands, infrequent and unanticipated demand events, such as fires and other emergencies, can significantly stress a municipal water system and its components. Such factors must be considered in analyzing the ability of a water system to provide for future demands, while maintaining an adequate level of water service to customers. The development of a computer hydraulic model, which can accurately and realistically simulate the response of a water system under a variety of conditions and scenarios, has become an increasingly important element in the planning, design, and analysis of municipal water systems. The Washington State Department of Health’s WAC 246-290 requires hydraulic modeling as a component of comprehensive water system plans. HYDRAULIC MODELING SOFTWARE The District’s water system is analyzed using MWHSoft’s H2ONet hydraulic modeling software, which operates in an AutoCAD computer aided design and drafting environment. The current model was created for the 2003 Water System Plan from a CYBERNET hydraulic model that was developed for the previous 1998 Water System Plan. The model has been updated continuously and is used regularly to evaluate District projects and developer extensions. The H2ONet model is configured with a graphical user interface. Each water system element, including pipes, valves, and reservoirs, is assigned a unique graphical representation within the model. Each element is assigned a number of attributes specific to its function in the actual water system. Typical element attributes include spatial coordinates, elevation, water demand, pipe lengths and diameters, and critical water levels for reservoirs. With attributes of each system element as the model input, the

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5-2 Silver Lake Water & Sewer District July 2010 Comprehensive Water System Plan

H2ONet software produces the model output in the form of flows and pressures throughout the simulated water system. MODEL ASSUMPTIONS Prior to the calibration of the hydraulic model, the basic layout of the water system is recreated within the model. The lengths, diameters, and connection points of system piping are assigned using an updated base map of the water system. The locations of normally closed valves, check valves, and PRVs are also found on the water system base map, while the critical elevations of the District’s reservoirs are taken from the District’s SCADA system settings. The assumptions regarding the modeling of the District’s water sources (CWSA and Everett master meters) and system demands are included in the following sections. SOURCE The District is currently served by five master meters; two on the west side of its service area, supplied by Everett, and three on the east side of its service area, supplied by the Clearview pipeline. The Clearview pipeline provides the majority of the supply to the District from the east side of the service area through Master Meters No. 4 and No. 5. Master Meter No. 7 is not used in normal system operation and is not modeled. The two west master meters are closed for model scenarios, as the District’s long-term options include the possibility of supplying demands exclusively from the Clearview master meters. For the purposes of the hydraulic model this is a worst-case condition. SYSTEM DEMANDS A key element in the hydraulic modeling process is the distribution of demands throughout the water system. Total demand on the system is based on the projected demands from Chapter 2. Five demand sets are used in the hydraulic analysis:

• 2010 Existing Demands: These demands were used to calibrate the model and verify current conditions.

• 2016 Peak Hour Demands: These demands are used to verify the system

is able to meet the DOH standards to supply domestic water at a minimum system wide pressure of 30 psi within the 6-year planning period.

• 2016 Peak Day Demands: These demands are used to evaluate the

system’s ability to meet the required fire flows at DOH’s requirement of 20 psi within the 6-year planning period.

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Silver Lake Water & Sewer District 5-3 Comprehensive Water System Plan July 2010

• 2030 Peak Hour Demands: These demands are used to verify the system is able to meet the DOH standards to supply domestic water at a minimum system wide pressure of 30 psi within the 20-year planning period.

• 2030 Peak Day Demands: These demands are used to evaluate the

system’s ability to meet the required fire flows at DOH’s requirement of 20 psi within the 20-year planning period.

PRESSURE REDUCING VALVES In the District’s water system the delivery of water from the reservoirs to various pressure zones is dependent on several PRV stations within the system. Each PRV has been set to maintain the hydraulic grade of the pressure zone that it serves. Two PRVs connect the 725 Zone to the 640 Zone and 11 PRVs connect the 640 Zone to the 485 Zone. The PRVs from the 725 Zone to the 640 Zone are closed for all model scenarios. DISTRIBUTION SYSTEM The District’s distribution system is currently interconnected with Everett’s system downstream of Master Meter No. 3 in the Silver Acres area. This is due to an interim arrangement between the District and the City of Everett to provide fire flow in an area recently annexed by Everett as a temporary measure until Everett resolves its system deficiencies. The area of the District’s system downstream of Master Meter No. 3 is isolated from the rest of the District by closed valves. The District has the facilities in place to isolate the two systems. Modeling for the 6-year and 20-year planning periods assumes that the District will be isolated from Everett. MODEL CALIBRATION Model calibration originally occurred during development of the model in 1998, it was updated as a part of the 2003 Water System Comprehensive Plan, and for this Plan, field measurements from 2010 were used for calibration. The update of the calibration of the hydraulic model provides a measure of assurance that the model is an accurate and realistic representation of the actual system. CALIBRATION TESTING The H2ONet hydraulic model of the District’s water system is calibrated using data obtained from fire hydrant tests at various locations throughout the water system. Nine fire hydrant tests were conducted with the assistance of District personnel in late February and early March 2010. During these tests, static and residual pressures were recorded as District staff opened hydrants and recorded the flow. Field results were used

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5-4 Silver Lake Water & Sewer District July 2010 Comprehensive Water System Plan

to calibrate the hydraulic model by verifying pipe type and size, and adjusting roughness coefficients. The testing locations include multiple points within each pressure zone. A description of each testing location is presented in Table 5-1.

TABLE 5-1

Hydrant Testing Locations

Test No. Pressure Zone Testing Location 1 640 21st Avenue SE and 103rd Street SE 2 485 46th Avenue SE and 110th Street SE 3 640 78th Avenue SE and 152nd Street SE 4 485 67th Avenue SE between 131st Place SE and 133rd Street SE 5 640 144th Street SE and 12th Drive SE 6 640 54th Avenue SE and 147th Street SE 7 640 North Creek Road and 153rd Street SE 8 725 Snohomish Cascade Drive and 65th Avenue SE 9 640 167th Street SE and 41st Avenue SE

The system conditions at the time of each test were recorded using the District’s SCADA system. Recorded parameters include outlet flow and pressure for each District reservoir booster station as well as flow from master meters. These parameters were input into the model during the calibration procedure. As the tests were performed on three separate days and system demands can vary, it was necessary to set booster station and master meter flow rates, as well as static demands, specifically for each hydrant test. CALIBRATION PROCEDURES Using the system conditions for each hydrant test, the hydraulic model is used to generate static pressure and residual pressure at the measured residual discharge. The total system demand at the time of the hydrant tests was assigned based on SCADA records. Model output is generated at points in the model equivalent to the locations of the hydrant tests. Model output for static pressure is generated by running the model at average system demands. Model output for residual pressure is generated at each model hydrant test point by placing an added demand equal to the measured residual discharge and recording the resulting pressure. The system pressures and pipe flow rates determined in the hydraulic analysis are highly dependent on the friction loss characteristics established for each pipe. Adjustments to assumptions of friction loss are made until the hydraulic model replicates the measured field conditions. Hazen-Williams C-factors between 100 and 130 are used throughout the

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Silver Lake Water & Sewer District 5-5 Comprehensive Water System Plan July 2010

system. These friction factors are typical values for most pipes and are generally conservative. However, the friction factors for the pipe also compensates for system losses through valves and pipe fittings. CALIBRATION RESULTS The model output is produced for two data comparisons, static pressure, and residual pressure. The values measured in the hydrant flow tests are compared to the model output values in Table 5-2.

TABLE 5-2

Calibration Results

Test No.

Flow (gpm)

Static Pressure (psi) Residual Pressure (psi) ΔF – ΔM(1)Field Model Difference Field Model Difference

1 1,100 65 66 1 48 53 5 4 2 800 104 104 0 72 66 -6 -6 3 1,400 96 92 -4 87 85 -2 2 4 1,200 62 61 -1 49 49 0 1 5 1,500 105 101 -4 97 90 -7 -3 6 1,200 66 65 -1 55 58 3 4 7 1,150(2) 124 124 0 100 96 -4 -4 8 1,000 73 74 1 74(3) 73 -1 -2 9 1,500 100 100 0 87 90 3 3

(1) ΔF – ΔM is equal to the model pressure difference minus the field pressure difference. (2) Hydrant flow rate calculate based on SCADA records, field measured value was 1,600 gpm by

pitot tube. (3) An increase in pressure is caused by additional pumps being called on at Reservoir No. 2 Booster

Station when the hydrant is opened. Calibration of the hydraulic model produced results that varied from 0 to 4 psi of actual field test data for static pressure. Modeled residual pressures are within 6 psi of the measured residual pressures in all cases. MODEL CONDITIONS Model input assumptions have significant impacts on peak hour and fire flow results. Table 5-3 shows reservoir levels as they were modeled for each scenario. All three District reservoirs operate below the hydraulic grade of the system and have outlet booster stations that maintain the hydraulic grade. The levels in Table 5-3 represent the hydraulic grade of each reservoir upstream of the booster station with the operation, equalizing, and demand management storage removed.

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5-6 Silver Lake Water & Sewer District July 2010 Comprehensive Water System Plan

TABLE 5-3

Model Reservoir Levels

Reservoir Capacity

(MG)

2016 2030 Peak Hour

Level (ft)

Fire Flow Level (ft)

Peak Hour Level (ft)

Fire Flow Level (ft)

No. 2 4.2 30 28 29 28 No. 3 4.2 30 28 29 28 No. 4 8 40 38 40 38 Clearview 12 60(1) 60(1) 60(1) 60(1) (1) The inlet pipe to the Clearview Reservoir discharges at an elevation of 660 feet,

which corresponds to a reservoir level of 60 feet. As the District’s master meters are upstream of the Clearview Reservoir, the hydraulic grade of water supplied to the master meters is always at 660 feet or greater.

Master meter settings for each future modeling scenario are shown in Table 5-4. Master Meters No. 4 and No. 5 provide supply from the Clearview pipeline. Both meters have been set such that no more than the projected peak day demand is supplied from the Clearview pipeline.

TABLE 5-4

Model Meter Settings

Master Meter2016 Scenarios

(gpm) 2030 Scenarios

(gpm) No. 4 3,698 4,299 No. 5 3,698 4,299

SYSTEM ANALYSIS PEAK HOUR ANALYSIS According to WAC 246-290, a water system must maintain a minimum pressure of 30 psi in the distribution system under peak hour demand conditions. The District’s existing distribution system has been modeled under 2016 and 2030 peak hour demand conditions. Results located in Appendix G illustrate the results of peak hour modeling for 2016 and 2030, respectively. Peak hour pressures for 2030 are shown on Figure 5-1. Peak hour analysis for 2016 and 2030 revealed no system deficiencies. The minimum system pressure at a customer connection in 2016 is 36 psi on 65th Drive SE south of 146th Place SE. In 2030, the pressure at this location is 32.8 psi. Low pressures were noted along a section of transmission main downstream of Master Meter No. 5. The

SILVER LAKE WATER & SEWER DISTRICT

WATER SYSTEM PLANFIGURE 5-1

2030 PEAK HOUR PRESSURE

M:\SLWD\08567 2009 Water Comp Plan\GIS\FIGURES\PEAK_HOUR.MXD

RESERVOIRNO. 2

MASTER METER NO. 6

MASTER METER NO. 8

MASTER METER NO. 7

MASTER METER NO. 2

MASTER METER NO. 5

MASTER METER NO. 4

CLEARVIEWRESERVOIR

RESERVOIRNO. 4

MASTER METER NO. 3

MASTER METER NO. 1

RESERVOIRNO. 3I-5

SR 9

SR 52

7

180TH STREET SE

CATHCART WAY

132ND STREET SE

LOWELL LARIMER ROAD

128TH

164TH STREET SE

100TH STREET SE

SEATTLE HILL ROAD

116TH STREET SE

35TH

AVE

NUE

SE

SEATTLE HILL ROAD

35TH

AVE

NUE

SE

0 3,000 6,0001,500Feet

SCALE 1" = 3000'

LEGEND:PEAK HOUR FLOW (2030):

0 - 3030 - 4040 - 6060 - 8080+MASTER METERRESERVOIRCLEARVIEW RESERVOIRSILVER LAKE WATER & SEWER DISTRICT BOUNDARYPRV / FLOW CONTROL VALVE STATION

DISTRICT PIPE:<12">=12"

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Silver Lake Water & Sewer District 5-7 Comprehensive Water System Plan July 2010

lowest pressure was located near Puget Park Drive and 67th Avenue SE. This pressure is 31.8 psi in 2016 and 29.8 psi in 2030. This main is a dedicated transmission main without any service connections and therefore does not represent a deficiency in the distribution system. The District also monitors this location with the SCADA system. PEAK DAY ANALYSIS According to WAC 246-290, a water system must be able to meet its peak day demand with its source of supply. As the District continues to grow and depend more on the CWSA as its primary source of supply and system demands continue to increase, it becomes more difficult to supply the peak day demands on a 24-hour basis and replenish reservoirs on the west side of the system. This is due to physical and geographical limitations to east-west transmission across the system. Based on results from the hydraulic model, the District will have difficulty delivering CWSA supply west of the Seattle City Light transmission easement in quantities beyond the current agreement capacity of 9.0 mgd without system improvements. These improvements will allow the District to replenish reservoir storage that is used to meet diurnal demands. Hydraulic modeling has identified potential improvements that can improve transmission for the District. These improvements include:

• Master Meter No. 9, which will supply CWSA supply directly to Reservoir No. 2, combined with improvements to PRV West to include a flow control feature. These improvements will allow the District to pump up to 3.0 mgd supply from Master Meter No. 9 via Reservoir No. 2, through the 725 Zone, and back to the 640 Zone through PRV West.

• A new 16-inch water main along 132nd Street SE from Seattle Hill Road to

65th Avenue SE (approximately 5,700 linear feet). This main will parallel an existing 12-inch main and provide additional east-to-west transmission capacity. This project will allow the District to fully maximize supply from Master Meters No. 4, No. 5, and No. 9.

• The Seattle Hill Road Booster Station would allow the District to wheel

up to 3.0 mgd of CWSA supply through the Cross Valley Water District. The booster station would be located along Seattle Hill Road near Master Meter No. 6 and would pump water up from Cross Valley Water District directly into the District’s 640 Zone. Due to its location west of the Seattle City Light transmission easement that provides a significant east-to-west transmission barrier to the District, it is ideally located for providing additional CWSA capacity to the District.

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5-8 Silver Lake Water & Sewer District July 2010 Comprehensive Water System Plan

Any two of these projects are sufficient improvements to provide the District with CWSA supply through the 20-year planning period. The third project would allow the District to meet its buildout supply needs using only the CWSA supply source. AVAILABLE FIRE FLOW ANALYSIS The DOH Design Manual states that a water system should be designed to provide adequate fire flow under peak day demand conditions, while maintaining a minimum system pressure of 20 psi. Fire flow availability is presented in Figure 5-2. The results of fire flow modeling are presented in Appendix H. Table 5-5 shows the identified 2030 available fire flow deficiencies. Individual projects that address fire flow deficiencies are identified as part of the District’s Capital Improvement Plan discussed in detail in Chapter 8.

TABLE 5-5

2030 Fire Flow Deficiency Locations

Location Nodes Pressure

Zone

Available Fire Flow

(gpm)

Required Fire Flow

(gpm) Reason for Deficiency

East end of 105th Pl. SE near 21st Ave. SE J-1127 640 473 1,000 Undersized

Dead-end Main West end of 105th Pl. SE near 21st Ave. SE J-1126 640 587 1,000 Undersized

Dead-end Main East end of 129th St. SE near 14th Dr. SE J-1418 640 661 1,000 Undersized

Dead-end Main 8th Dr. SE between 126th St. SE & Andrew Slater Rd. J-512 640 914(1) 1,000 Undersized Main

5th Ave. SE & Park Pl. J-577 640 973(2) 1,000 Undersized Main 10th Dr. SE between 129th St. SE & 126th St. SE J-535 640 977(3) 1,000 Undersized Main

(1) Fire flow availability at this location is currently 1,210 gpm with Master Meter No. 3 open. (2) Fire flow availability at this location is 1,027 gpm for 2016. (3) Fire flow availability at this location is 1,050 gpm for 2016. A portion of the District’s system is currently interconnected with Everett’s system downstream of Master Meter No. 3. Due to this, the deficiency at Node J-512 will not occur until after the two systems are disconnected. The deficiencies at Nodes J-577 and J-535 will not occur until after the 6-year planning period.

SILVER LAKE WATER & SEWER DISTRICT

WATER SYSTEM PLANFIGURE 5-2

2030 AVAILABLE FIREFLOW

M:\SLWD\08567 2009 Water Comp Plan\GIS\FIGURES\NODES.MXD

RESERVOIRNO. 2

MASTER METER NO. 6

MASTER METER NO. 8

MASTER METER NO. 7

MASTER METER NO. 2

MASTER METER NO. 5

MASTER METER NO. 4

CLEARVIEWRESERVOIR

RESERVOIRNO. 4

MASTER METER NO. 3

MASTER METER NO. 1

RESERVOIRNO. 3I-5

SR 9

SR 52

7

180TH STREET SE

CATHCART WAY

132ND STREET SE

LOWELL LARIMER ROAD

128TH

164TH STREET SE

100TH STREET SE

SEATTLE HILL ROAD

116TH STREET SE

35TH

AVE

NUE

SE

SEATTLE HILL ROAD

35TH

AVE

NUE

SE

0 3,000 6,0001,500Feet

SCALE 1" = 3000'

LEGEND:AVAILABLE FIREFLOW (2030):

0 - 999 GPM1000 - 1499 GPM1500 - 2999 GPM3000 - 5999 GPM6000 GPM AND GREATERMASTER METERRESERVOIRCLEARVIEW RESERVOIRPRV / FLOW CONTROL VALVE STATIONSILVER LAKE WATER & SEWER DISTRICT BOUNDARY

DISTRICT PIPE:<12">=12"