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Hydraulic Model Development and Calibration City of Redwood City (0011239.02)2-16 Woodard & Curran, Inc. Sanitary Sewer Capacity Master Plan November 2023 2.4.1 Dry Weather Calibration The primary focus of the dry weather calibration was to confirm that the calculated average BWF based on winter water consumption, plus GWI if indicated, was consistent with the measured flows at the meter locations. During calibration, graphs of model-simulated flows for the dry weather calibration periods were compared to actual monitored flows for the same periods at each flow meter location to confirm that the flows match reasonably well on an overall average (total volume) basis and with respect to the diurnal flow pattern. The overall objective is to achieve a match to within about 10 percent of modeled to monitored average dry weather flows, and a reasonably good match to the diurnal flow pattern at most of the meter sites. While it is not possible to achieve a perfect match for all meters, emphasis is placed on the most downstream meters, as a good match at these sites indicates that, overall, the model is predicting flows with good accuracy. GWI was added when the observed dry weather hydrographs were greater than the model-simulated hydrographs by a relatively constant value throughout the day. It should be noted that it may be difficult to assess the actual amount of GWI in any given area, as the relative accuracy of the flow monitoring data, water consumption data, and other model assumptions may affect the amount of flow attributed to GWI. However, this methodology is considered adequate for master planning purposes. Figure 2-12 shows a 7-day calibration graph for the Maple Street Pump Station for the late January 2019 dry weather calibration period. The graph demonstrates that the model is accurately simulating the flows and flow patterns in the Main City Area. In the graph, the black line depicts the metered flow and the green line shows the model-simulated flow. Based on the model calibration, the total (wintertime) existing ADWF to the Maple Street Pump Station is approximately 6.4 MGD with a peak dry weather flow (PDWF) of approximately 10 MGD. Figure 2-12:Dry Weather Calibration Graph (Maple Street PS) __________ Metered flow __________ Modeled flow ATTY/RESO.0077/CC RESO SEWER SYSTEM MANAGEMENT PLAN - EXHIBIT A REV: 07-14-25 LF Page 132 of 317