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Seasonal Analysis <br />DA-21 sub-basin measured flow data from October 1995 to January 1996 were selected for <br />the pre-rehabilitation seasonal time period and from November 2001 to April 2002 and <br />October 2002 to February 2003 for the post-rehabilitation time period. <br />Dry weather flows were selected during the summer months. September 23-29, 1996 was <br />selected for the pre-rehabilitation seasonal flow time period and June 10-16, 2002 for post- <br />rehabilitation. <br />Figure 12 shows pre-rehabilitation measured flow data. These data exhibit random behavior <br />and an irregular diurnal pattern. There are time periods of increased sewer response without <br />rainfall. The figure also shows time periods when the sewer flow drops to zero during rain <br />events, at which time, the dry weather flow pattern is higher than the measured data. Because <br />of these issues, the pre-rehabilitation and post-rehabilitation seasonal analysis was not <br />completed for the DA-21 Basin. A variety of factors could potentially have influenced the <br />DA-21 data set including accuracy of monitoring data across range of storm events, spatial <br />variation of rainfall across the drainage area, and random fluctuations in dry-weather base <br />sanitary flow that cause the RDII calculation (RDII =monitoring data -dry-weather base <br />sanitary estimate). <br />0.5 <br />0.4 <br />0.3 <br />O <br />b <br />V <br />^ <br />~ 0.2 <br />0.1 <br />Q <br />Oct-95 <br />Nov-95 <br />Date <br />Figure 12 -Sub-basin 21 measured flow and rainfall <br />Dec-95 <br />0 <br />0.2 <br />0.4 <br />0.6 <br />r <br />4 <br />M <br />0.8 <br />^ <br />12 <br />1.4 <br />Event Analysis <br />The event based rehabilitation effectiveness analysis for sub-basin DA-21 only included event <br />RDII volume versus event rainfall. Six events were included for pre-rehabilitation and seven <br />for post-rehabilitation. A 26% RDII volume reduction was estimated. <br />24 <br />