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supply wells within a 1-mile radius of the site All of these wells are a minimum of 400 feet deep and are perforated below 200 feet CWS supplies water to residence and business users within the area surrounding the site and parts of the City of Stockton This groundwater is used to supplement water deliveries from New Hogan Reservoir According to the Stockton East Water District and CWS, groundwater from these wells represents 15 to 20 percent of the total domestic water supplied to the area near the site California Water Service well 77-01 (number 3 in Table 1 and Figure 5), ' 3500 feet to the north, is the nearest well to the site A cemetery is located immediately downgradient of the site The closest downgradient well is a 264 foot City of Stockton supply well approximately 4000 feet northwest of the site (number 18 in Table 1 and Figure 5) This well is used for municipal water supply and irrigation This well, as well as the other municipal water supply wells within one mile of the site, is perforated within the semiconfined deeper aquifer Site monitoring wells are completed within the unconfined shallow aquifer within 150 beet bgs 3 3 GROUNDWATER MONITORING This section summarizes all groundwater monitoring results up through the most recent round completed in May 1994 The May 1994 sampling round was conducted by Dames & Moore at the request of the RWQCB and the PHS-EHD The samples collected were analyzed for TPH/D and volatile organic compounds (VOC) (EPA Methods 8015 and 602) No detectable constituents were reported (Table 2) A description of sampling methods, chain of custody documentation, ground- water samples, quality assurance samples, and water level data for the May 1994 monitoring round is included in Appendix A Analytical laboratory reports for the May 1994 round are included in Appendix B The groundwater gradient in May 1994 was very flat, 0 00056 feet per foot, and to the west This was a change from previous monitoring rounds conducted between July 1987 and July 1991, which indicated a gradient of 0 0015 to 0 0019 feet per foot in a north/northwest direction Groundwater elevations measured in May had risen about 8 feet since the previous round in July 1991 The depth to groundwater ranged from 60 83 to 61 18 feet bgs, and from -45 92 to -46 06 feet in elevation Previous groundwater monitoring at the site is summarized below 3 3 1 Groundwater Sampling and Analysis Three groundwater monitoring wells, MW-1, MW-2, and MW-3 were installed by JHK in June 1987 Groundwater samples were collected by JHK in July of 1987 and analyzed for VOCs, SAC116 07 5 AUGUST 1994 DAMES & MOORE