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DUBLIN SAN RAMON SERVICE DISTRICT o REGIONAL CONNECTION FEES CURRENT ADWF Wastewater flows are highly variable from year to year for a variety of reasons including: climatic conditions; vacancy rates; the economy; and flow meter performance. Flow metering at the WWTP is particularly challenging because of the number of flow meters required to determine the WWTP influent flow. Projects are in progress to reduce the number of meters that have to work accurately simultaneously to measure flow from 9 to 4'. The District has to plan to treat all the wastewater that could possibly enter the plant a result of current development. Because of the highly variable nature of wastewater flow from year to year, a generally accepted practice to evaluate flow over a period of time is to envelop the data within the 95 confidence level line. Shown in Figure 2 is the ADWF from 1997 to 2009. Also shown on the figure is the "least squares" fit 95 percentile trend line. Figure 2 Average Dry Weather Flow (ADWF) —ADWF —95th% -DUE 12.00 55000 11.00 50000 10.00 45000 0 2 9.00 40000 8.00 35000 1996 1998 2000 2002 2004 2006 2008 2010 Year Based upon the data in Figure 2, the ADWF in 2009 for planning purposes is 11 mgd. To confirm the growth trend over the time period is reasonable, the new connections sold, measured as dwelling units equivalent (DUE), over the same period are also shown on Figure 2. Considering that all the new connections sold are not yet occupied the correlation between the flow trend line increase and the increase in number of DUES is good. 6 `Influent Wastewater Metering Report"; Whitley Burchett Associates; January 2000. BLACK VEATCH 22 MAY 2010