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' Quarterly Mnmtornns,Report July 1999 Canepa s Car Wash • 248E Park St Stockton CA August 24 1948 Page 4 ' 4 3 Groundwater Elevation Contours On July 23, 1998, the depth to groundwater was measured in each monitor well prior to the collection of groundwater samples The average depth to groundwater was approximately 24 2 feet below the monitor well ' measuring points Monitor wells MW-1, MW-2, and MW-3 are screened from approximately 45 to 65 feet bgs and monitor wells MW-4, MW-5, MW-6, and MW-7 are screened from approximately 40 to 60 feet bgs Therefore, water levels were substantially above the top of the screen in all of the monitor wells The ' groundwater elevation ranged from 14 09 to 12 13 feet below mean sea level (bmsl) at the site See Table 2, below, for groundwater elevation data Groundwater elevation contours are shown in Figure 3, Appendix A The groundwater elevation contours indicate a north-northeast groundwater flow towards the general vicinity of 1 MW-2 ' TABLE 2 Groundwater Elevation Data (July 23, 1998) MW-1 through MW-7 Well Well Casing Well Collar Depth to Groundwater ID Screen Elevation Water Elevation Interval(feet (feet) (feet) (feet) -bgs) MW-1 45 -65 1097 23 50 -1253 MW-2 45 - 65 1037 2446 -1409 ' MW-3 45 - 65 It 76 2505 -1329 MW-4 40 -60 1085 2298 -12 13 MW-5 40 - 60 1125 2490 -1365 MW-6 40 - 60 1172 2491 -13 19 IMW-7 40- 60 1 1 05 2392 -1287 5 DISCUSSION OF RESULTS Since September 1994, the depth to groundwater at the site has decreased from approximately 45 to 24 bgs The groundwater elevation contour map (Figure 3, Appendix A) indicates that groundwater flows in a north- northeast direction toward the general vicinity of MW-2 This is generally consistent with previous monitoring results A hydrograph of monitor wells MW-1 through MW-7 (Figure 4, Appendix A) illustrates the fluctuation of the groundwater table Historical groundwater measurements are provided in the accompanying Hydrograph Table (Appendix A) Analytical results for the July 1998, sampling are generally consistent with historical analytical results TPH-G and BTEX concentrations in the sample collected from MW-5 increased markedly between August 1995, and I �� CONDOR