2003-09-24 CC Packet - Laserfiche WebLink

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t .; ~ r- I The model used in the 1997 report was updated to include all new trunk mains added to the system since the old report. Prior to this model upgrade, field hydrant flow tests were performed at three locations on portions of the City's water sytem. A hydrant was opened to create a demand on the system, the flow from the hydrant was determined, and the residual pressure for that flow rate was measured from a nearby downstream hydrant. This data was then compared with the model. Demands equal to the flows generated at the opened hydrants were incorporated into the model at the same locations. From this, a residual pressure was determined from the model. The following Table No.2 shows the comparison of the actual field test data and the model data in respect to both the static and residual pressures. Refer to Figure 1 for the locations of the nodes. Table No.2 - Pressure Comparisons I. :' , Street Static Pressures Residual Pressures Node Location Actual Model Actual Model J-96 Lakeland Circle 60-66 62.8 48 30.4 J-380 Beaver Pond Way 56-58 55.9 46 46.8 J-41O Deer Pass Drive 55 54.6 46 46.8 j ";.; i, . --, I I -ta-~~ \:- . I } - , As you can see from the data collected and generated in the above table, the pressures compare very favorably for two nodes but the residual pressure at Node J-96 (Lakeland Circle) did not. We cannot determine why the pressures for this node were better in the field than per the model. An extra looped water main that may have been missed or water main sizes shown too small would account for the extra pressure, but sizes and pipes were checked and confirmed by City staff. Another possible explanation to the residual pressures being higher in the field is that possibly one of the wells actually came on during the flow test which caused a greater reading in the field. The updated computer model is validated by the results of the actual field measurements for the other flow data. Water Tower Feasibility Report 12