Sam Ziemann From - Region of Waterloo

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August 26, 2011Sam ZiemannPage 10 of 12Reference: Fluid Transient Analysis for Strange Street Raw Water Supply System – Draft TechnicalMemorandumseconds. Although it is unlikely the pressure sustaining valve could react fast enoughduring a rapid transient event such as a power failure, the pressure sustaining valve canhelp maintain positive pressures within the raw water supply system during a controlledshut-down of the wells. The pressure sustaining valve is set to maintain a hydraulicgrade of 365 m within the watermain upstream of the Strange Street Reservoir. Thissetting should result in a minimum pressure of 140 kPa within the raw water supplysystem during steady-state conditions.Scenario 7 results, which are shown in Figures 9a and 9b, indicate positive pressuresare maintained within the raw water delivery system during the shut-down of Well K18over a period of 60 seconds.Anticipated Future ConditionsAnticipated future improvements to the Strange Street Water Supply System include:• Replacement of an existing 300 mm main from the Glasgow Street/Knell Driveintersection near Well K11A to the Gage Avenue/Belmont Avenue intersectionwith 450 mm PVC DR25 pipe.• The addition of a new well(s) and replacement wells to increase the raw watersupply system capacity to 227 L/s.• Construction of a raw water storage tank to receive discharge from the wellsprior to providing iron and manganese water treatment and discharging thetreated water into the Strange Street Reservoir.As indicated previously in Table 1, it is anticipated that the new well(s) will have acapacity of 40 L/s. Scenario 8 was developed to model a power failure (pump trip) eventwith all of the wells pumps in operation at a total capacity of 227 L/s. For this scenario, anew 40 L/s capacity well was placed in the vicinity of the Well K18/K19 Well House.This scenario assumes the air valves referenced in Scenario 4 are installed.Figures 10a and 10b display the results of Scenario 8 and indicate full vacuumconditions and column separation (macro-cavitation) are avoided.Conclusions and RecommendationsThe following conclusions and recommendations are summarized regarding thetransient analysis of the Strange Street Water Supply System:Conclusions• Transient analysis results indicate it is likely that column separation occurswithin the SSRWS subsequent to a power failure induced pump trip with all wells
August 26, 2011Sam ZiemannPage 11 of 12Reference: Fluid Transient Analysis for Strange Street Raw Water Supply System – Draft TechnicalMemorandumin operation as well as subsequent to a sudden shut-down with one well inoperation.• Model results show the maximum pressures experienced along the raw watersupply system piping from the K18/K19 Well House to the end of the truncatedmodel can exceed steady-state pressures by approximately 330 kPa for a 5-second well pump start-up.• Model results indicate the maximum transient pressures experienced during allhydraulic transient simulations on the SSRWS did not exceed the pressure class(1,140 kPa) of PVC DR25 pipe or AWWA C106 Class 150 CI pipe.• Model results indicate the installation of double acting surge-suppression airvalves at each well and at high points within the SSRWSS prevents full vacuumconditions and column separation (macro-cavitation) from occurring within thesystem subsequent to power failure (pump trip) event with all of the wells pumpsin operation.• Model results indicate full vacuum conditions and column separation (macrocavitation)within the raw water supply system are avoided if the well pumps areshut-down over a period of 60 seconds.• Model results indicate the pressure increase within the water supply systemfrom the K18/K19 Well House to the end of the truncated model is limited toapproximately 135 kPa above steady-state conditions during pump start-up ifsoft-start controls are used to start-up the wells over a 30-second period.Recommendations• Confirm the type of air valves installed at each of the wells.• Determine existing soft-start and soft-stop ramp times for the wells.• Use a 60 second period for start-up and shut-down of the well pumps and do notstart-up or shut-down more than one well pump at a time.• Consider installing 100 mm combination air valves with 7.93 mm orifices on thedischarge piping at each of the wells and at high points along the raw watersupply system to prevent macro-cavitation.• Marco-cavitation should be prevented from occurring within the SSRWS underall conditions to minimize the risk of watermain breaks.
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Page 14 and 15: Pressure (kPa)K18/K19 Well House to
Page 16 and 17: Figure 4a - Existing ConditionsPump
Page 18 and 19: Figure 6a - Existing System w/Combi
Page 20 and 21: Figure 8a - Existing ConditionsWell
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HYDROGEOLOGICAL ASSESSMENTSTRANGE S
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25Pumping Rate20Pumping Rate (L/s)1
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TABLE 2SUMMARY OF GROUNDWATER ANALY
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CALCULATION OF SPECIFIC CAPACITY FR
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March 2, 2011Reference: 006-189Stan
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TABLE 1REGIONAL MUNICIPALITY OF WAT
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July 23, 2010Lisa Lachuta, P.Eng.Pa
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TECHNICAL MEMORANDUM A1 -STRANGE ST
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TECHNICAL MEMORANDUM A1 -STRANGE ST
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TABLE 1SUMMARY OF GROUNDWATER ANALY
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Sam Ziemann From - Region of Waterloo

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