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REGIONAL BOARD RESPONSE (S1J'RCB/0CC FILE A-1483) -5- <br /> PETITION FOR REVIEW OF WASTE DISCHARGE REQUIREMENTS <br /> ORDER NOS. R5-2002-0083 AND R5-2002-0084 <br /> CITY OF STOCKTON REGIONAL WASTEWATER CONTROL FACILITY <br /> TABLE 1 <br /> SJR Minimum Flows at Stockton During Above Average Wet Years <br /> (Dates of Record November 1995 —September 2001) <br /> Averaging Dates Stockton Vernalis Avg. <br /> Period Net Law Flow Flow <br /> 1-Day 16 January 1996 -6 cfs 1850 cfs <br /> 6 December 1999— 56 cfs 1775 cfs <br /> 4-Day 9 December 1999 <br /> 4 December 1999— 102 cfs 1783 cfs <br /> 7-Day 10 December 1999 <br /> 14-day 2 January 2000— 174 cfs 1644 cfs <br /> 15 January 2000 <br /> 30-Day 18 December 1999— 233 cfs 1626 cfs <br /> 16 January 2000 <br /> Note: Permitted flow for Stockton RWCF is 55 mgd(85 cfs). <br /> Since significant SIR flow data is available at Vernalis, comparisons of wet and dry year flows can be <br /> made using Vernalis flow data. For example, Table 1 shows the minimum 30-day average flow <br /> observed at Stockton during an above average wet year to be 233 cfs,whereas the 30-day average SIR <br /> flow at Vemalis was 1,626 cfs during the same time period. In contrast, Table 2 shows the minimum <br /> 30-day average SJR flow at Vernalis during 1991 and 1992 (during drought flow conditions)was only <br /> 445 cfs during the summer and 750 cfs during the winter. This comparison suggests that the minimum <br /> 30-day average SJR flow at Stockton during 1991 and 1992 (dry years)was much less than 233 cfs, as <br /> shown in Table 1, which was measured during a wet year. <br /> TABLE 2 <br /> SJR Minimum Flows at Vernalis During Drought Conditions <br /> Season Dates Vernalis 30-Day <br /> Average Flow <br /> Summer 23 June 1992— 445 cfs <br /> 22 July 1992 <br /> Winter 29 January 1991 — 750 cfs <br /> 27 February 1991 <br /> The State Board adopted Water Rights Decision 1641 (D-1641) on 29 December 1999. D-1641 <br /> implements flow objectives for the Bay-Delta Estuary, approves a petition to change points of diversion <br /> of the Central Valley Project and the State Water Project in the Southern Delta, and approves a petition <br /> to change places of use and purposes of use of the Central Valley Project. Increased SJR flows in the <br /> vicinity of Stockton could result from these objectives. D-1641 contains a salinity objective in the <br /> Southern Delta. One method of achieving the salinity objective is maintaining a minimum SJR flow of <br /> 1000 cfs at Vernalis. This means that the low flows, which occurred in 1991 and 1992, as shown in <br /> Table 2,may not occur in the future. However,the flows needed to meet the salinity objective are still <br /> significantly less than the lowest monthly Vernalis flows that occurred during the lowest SIR flows of <br />