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7-Eleven/Stockton 20 _- August 1989 w GROUNDWATER RE EDIATION SYSTEM During the three month reporting period, groundwater was extracted from PW-1 and recovery well RW-1. However, on w, June 6, 1989, the water table depression primp (WTDP) was removed from PW-1 due to a lack of groundwater. Prior to its removal, PW-1 was pumping at a rate of 0.25 to 0. ;-gallons per minute (gpm) . Pumping was maintained in RW-1 at an average rate of 1.0 gpm. The average total combined pumping rate prior to removal of the WTDP from PW-1 was 1.6 gpm. The areas being influenced by pumping are illustrated on the previously referenced gxounGwater- gradient maps (Figures 4, 5, and 6) . Groundwater extracted from the pumping wells is treated through an air-stripping .tower prior to discharge to the sanitary sewer system. Every two weeks, laboratory analyses are conducted f� on the influent to and effluent from the air-stripping tower for concentrations of BTEX and TPH-as-gasoline to verify compliance r , with requirements imposed by the Stockton Municipal Utilities District and the San Joaquin County Air Pollution Control District. The influent and effluent concentrations of BTEX and TPH-as-gasoline are tabulated on Table 2 (Appendix A) and the laboratory results are included in Appendix C. The air- stripping tower effluent samples were below the laboratory MDL for BTEX and TPH-as-gasoline during each sampling interval conducted during this reporting period. In addition to the BTEX and TPH-as-gasoline analyses, the air-stripping tower effluent is sampled every two weeks for metals analyses. Those metals analyzed include lead, cadmium, chromium, copper, nickel, and zinc. For all four sampling rounds, metals analyzed did not exceed the laboratory MDL. These results document that the air- ~ �� GHI\Ir4l U1.H - Ti k ii-I-A kt