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7-Eleven/Stockton February 1990 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 on the influent to and effluent from the air-stripping tower for the presence of concentrations of BTEX and TPH-as-gasoline in order to verify compliance 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 for the samples analyzed during this period are tabulated on Table 2 (Appendix A) and the laboratory results are included in Appendix c. The air- stripping tower effluent sample results were below the laboratory method detection limits (MDI,) 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 and analyzed once a month for r„ the presence of metals. Laboratory analyses are performed for the presence of lead, cadmium, chromium, copper, nickel, and zinc. For all sampling rounds, the sample analyses results indicate that the levels of these metals in the discharge were - below the specified discharge limits. These results document that the air-stripping system is not exceeding the permitted discharge requirements. The results of the analyses for metals w are tabulated on Table 5 (Appendix A) and the laboratory results am included in Appendix C. SUMMARY Groundwater monitoring data have documented an increase of the water table elevation by approximately 1.30 feet during this reporting period. The groundwater gradient remains in an easterly direction, except in the areas within the capture mons of the pumping well. The gradient was approximately 0.002 ft/ft during the three month period. [4 GROUNDWATER - TECHNOLOGYINC.