Res 2016-137/approving a Water Master Plan to guide the future maintenance and extension of the City’s Water Infrastructure

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Alan Plummer Associates, Inc. Water Master Plan Update 2016 3 For the 2016 Water Master Plan Update, the hydraulic model software was upgraded from Bentley WaterCAD to Innovyze InfoWater which embeds within a geographic information systems (GIS) environment. Prior to evaluating future conditions, the hydraulic model needed to be updated and recalibrated to existing conditions. Field data collected in April 2014 were used to perform the updated model calibration. Much of the work regarding the existing system model development and calibration has been previously detailed in a November 2014 technical memorandum Existing System Subsequent sections of this chapter will summarize that work. 3.1 EXISTING DEMANDS In calibrating a hydraulic water distribution system model, often the most difficult component lies with the spatial distribution of demands. Unlike many utilities, the City of San Marcos has implemented advanced metering infrastructure (AMI) system-wide. This is a process by which itting data to a centralized data storage facility on an hourly basis. The availability of data from these meters vastly simplified the spatial distribution of demands within the model. In addition, having hourly data for all meters allowed the modelers to develop unique diurnal curves for each size meter based on actual data. The diurnal curves were then applied to nodes in the water distribution model based on the number and size of meters in close proximity. For the April 4-16, 2014 calibration data collection event, water metering data showed that the average daily system-wide demand was approximately 3,520 gpm (5.07 MGD). A complete 1 analysis of 2013 demands suggested the average day demand for all of 2013 was 4,651 gpm (6.7 mgd), with a maximum daily average demand of 5,953 gpm (8.6 mgd) and peak hour demand of 7,843 gpm (11.3 mgd). A detailed description of how these demands were spatially distributed is described in Appendix A. 3.2 WATER LOSS Like demand distribution, the distribution of water losses is also very difficult to determine by traditional means. However, the AMI data collected by the City was able to help distribute losses on a planar basis to some degree, improving the calibration. A full description of the process by which losses were calculated and distributed is available in Appendix A. By comparing SCADA-based production data to metered consumption over the course of the 72-hour April 9-11 calibration period, it was determined that approximately 24.5 percent of the water entering the distribution system via the SWTP High Service Pump Station, well pumpage, and net storage decrease was not metered upon exit. On average, water was supplied to the system at a rate of approximately 4,670 gpm (6.72 MGD) while the average metered demand 1 At the time of model calibration, 2013 was the last full year of demand data available. 3-1 m:\projects\0600\022-01\doc\report\draft\draftmasterplan-v15_hef.docx