Sam Ziemann From - Region of Waterloo

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August 26, 2011Sam ZiemannPage 6 of 12Reference: Fluid Transient Analysis for Strange Street Raw Water Supply System – Draft TechnicalMemorandumthe Data Collection section. The model was then opened in Bentley Systems HAMMERtransient analysis software and saved.The following assumptions were made during model construction:• The Multiple Point pump type pump definitions provided in the model fromthe Kitchener Office were used in the transient analysis model. Thesedefinitions are based upon the pump curves.• A water elevation of 333.79 m was used as the downstream boundarycondition for the Strange Street Reservoir.• The following Hazen-Williams C-factors were used for watermains in themodel: 100-120 for CI and DI watermains; and 150 was used for high densitypolyethylene (HDPE) and PVC watermains.• Flow control valves were added to the model at each well to limit flows to therates provided in Table 1.• No air valves are installed on the Strange Street Water Supply System thathave the ability to allow air to enter the pipeline to prevent vacuumconditions.• Since the timing of well starts and stops was not provided, it was assumedwell starts occurred over a 5-second period and pump stops wereinstantaneous and the same as a power failure induced pump trip. Theseassumptions were made to estimate worst-case transient conditions withinthe raw water supply system.• The future raw water storage tank will be constructed at the Strange StreetReservoir site.• Operating pressure information was not provided. Therefore, the model wascalibrated based upon flow using the capacities within Table 1.Results for the water supply system indicate hydraulic conditions within the systemtransition from pressure to gravity flow approximately 1,150 m west of the GlaskowStreet/Belmont Avenue intersection. Therefore, a pressure sustaining valve was addedat the location where flow conditions transition from full pipe/pressurized flow to partiallyfull pipe/gravity flow to maintain pressurized flow upstream of this point. As shown inFigures 1 and 2, the slope of portions of the raw water supply system mains exceedsthe slope of the hydraulic grade. This will result in gravity flow conditions along portionsof the raw water supply system downstream of the pressure sustaining valve location.Figures 1 and 2 illustrate the hydraulic grade calculated by the model along the raw
August 26, 2011Sam ZiemannPage 7 of 12Reference: Fluid Transient Analysis for Strange Street Raw Water Supply System – Draft TechnicalMemorandumwater supply system piping from the K18/K19 Well House to the Strange StreetReservoir.The point where flow conditions transition from full pipe/pressurized flow to partially fullpipe/gravity flow conditions represents a boundary condition for the fluid transient modelas the model is limited to performing computations under pressure flow conditions.In order to perform the existing conditions transient analysis for the SSRWSS, themodel piping was truncated in the model at the location of the pressure sustaining valveand a Discharge to Atmosphere element was added to represent this transition point.The model was then rerun.Existing System Transient AnalysisThe first stage of the transient analysis was to develop and analyze scenarios of theexisting system for worst case transients. The following operational scenarios thatwould result in a change in steady-state flows were evaluated:1. Simultaneous shut-down of all wells due to power failure2. Sudden shut-down of one well (K18)3. Start-up of one well (K18) during normal operations (5 s start-up)Scenario 1 – Simultaneous shut-down of all wells due to power failureScenario 1 modeled a power failure (pump trip) event with all of the well pumps inoperation. The sudden shut-down of the well pumps induced a negative pressure wavethat propagated downstream. Figures 3a and 3b, which illustrate the pressure and headexperienced along the raw water supply system piping from the K18/K19 Well House tothe end of the truncated model, indicate that full vacuum conditions and columnseparation (macro-cavitation) occur along almost the entire segment of watermain.Macro-cavitation conditions occur when the negative pressures in the watermain dropor fall to the vapour pressure of the fluid. This phenomenon, which is known as columnseparation, results in the formation of large pockets of vapour within the watermain.Later, on the returning upsurge, these vapour pockets can collapse violently and thehigh pressure caused by the two liquid columns coming together can cause watermainruptures or damage to system components. Column separation places undesirablestresses on piping systems and should be avoided whenever possible.Scenario 2 – Well K18 Sudden Shut-downScenario 2 modeled a sudden shut-down event with one well in operation. This scenariois intended to represent normal operating conditions and assumes the wells within thesystem are shut-down one at a time. For this scenario the shut-down of Well K18 wasevaluated. Well K18 was chosen because it is the greatest distance away from the end
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Page 14 and 15: Pressure (kPa)K18/K19 Well House to
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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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