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1a <br /> 7--Eleven/Stockton <br /> February 1990 <br /> o Maintained the groundwater treatment system, including <br /> sampling and analyses of the groundwater-treatment <br /> system influent and effluent. <br /> a installed a single-channel lower explosive limit (LEL) <br /> monitor with a strip-chart recorder to continuously <br /> monitor and record the total petroleum hydrocarbon <br /> vapor content in the discharge stream prior to entry to <br /> the sewer. <br /> GROUNDWATER MONITORING <br /> _. Monitoring of the groundwater elevation in the monitoring <br /> wells was conducted twice monthly. These monitoring data are <br /> presented in Table T (Appendix A) . Groundwater monitoring was <br /> performed in accordance with Groundwater Technology Standard <br /> Operating Procedure (sop) 8 (Appendix B) . <br /> Analyses of the groundwater smonitori.ng data indicate that <br /> ations h• ve increased an average of <br /> groundwater elev1.30 feet <br /> - -month reporting period. <br /> during this three <br /> Since the first set of groundwater monitoring data was <br /> collected in May 1965, local groundwater-table elevation has <br /> declined steadily. According to National Weather Service local <br /> e Stockton area, below-normal annual <br /> climatological data for th <br /> precipitation has been recorded for the past five years. <br /> However, in 1982 and 1983, just prior to this drought period, <br /> annual precipitation was nearly twice normal. Therefore, the <br /> steady decline in the groundwater-table elevation may be in <br /> response to prolonged drought conditions combined with an <br /> -,. <br /> at the beginning of the <br /> abnormally- <br /> elevated groundwater level <br /> monitoring period. The decline in the groundwater levels is <br /> �. (Figure 4) . <br /> depicted in the hydrographs for MW-7, Mw-8 and MW-9 GROUN[)%V,%TER <br /> TECHN�OLOCY-IaC. <br />