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DUBLIN SAN RAMON SERVICE DISTRICT <br /> REGIONAL CONNECTION FEES <br /> actual capacity of the facility. The WWTP has to have adequate capacity to treat both average dry <br /> weather flow (ADWF) and peak wet weather flow (PWWF). The documented ADWF capacity is 17.0 <br /> million gallons per day (mgd) and the documented PWWF capacity is 49.0 mgd. The ADWF and <br /> PWWF capacities of the treatment facility do not match. This situation resulted because of budget <br /> concerns; some process units planned for inclusion in the Stage 4 project were eliminated before the <br /> project was advertised for bid. Therefore, major capital investments are required to expand elements of <br /> the WWTP to accommodate the existing ADWF capacity of 17.0 mgd. <br /> Historically, equalized peak wet weather flow (EPWWF) has also been a WWTP capacity rating <br /> parameter. At an ADWF capacity of 17.0 mgd, the EPWWF is 37.7 mgd. The relationship between the <br /> three flow conditions is shown in Figure 1. <br /> Figure 1 Wastewater Flow Relationships <br /> —ADWF --EPWWF -PWWF <br /> 80.0 <br /> 60.0 <br /> rn <br /> 40.0 <br /> 20.0 <br /> 0.0 T <br /> 0 5 10 15 20 <br /> Time <br /> Flow equalization to achieve an EPWWF has been utilized only through the secondary system after <br /> primary treatment. Prior to the Stage 4 project, effluent from the primary clarifiers could be diverted into <br /> storage basin no. 1 and then returned for treatment after the wastewater flow subsides. Because of odor <br /> control concerns' and with the construction of primary clarifier no. 4 during the Stage 4 expansion, the <br /> ability to equalize primary effluent was eliminated. Therefore, current plant capacity is defined by an <br /> ADWF of 17.0 mgd and a PWWF of 37.7 mgd as equalization is no longer available. A temporary <br /> project is planned to allow raw wastewater to hack up in holding basin no. 2 during extremely high storm <br /> flows to accommodate the ADWF and PWWF mismatch until such time the PWWF capacity through the <br /> secondary system can be increased. <br /> 3 "Plant Process Capacity: Dry Weather Capacity"; Brown and Caldwell; December 2004. <br /> "Wet Weather Capacity Study"; Brown and Caldwell; May 2005. <br /> "Odor Control Master Plan CI12M I lilt; May 1999. <br /> BLACK VEATCH 21 MAY 2010 <br />