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7-Eleven/Stockton 14 <br /> November 1989 <br /> are installed to a total depth of only 25 feet. These wells are <br /> removing adsorbed hydrocarbons from the permeable sands of the <br /> upper sequence, but do not penetrate the gravelly coarse sand <br /> unit. The expansion of the soil-vent system to include the dry <br /> on-site monitoring wells, MW-1, MW-2, MW-3 and MW-4, would enable <br /> the gravelly coarse sand unit to be more efficiently vented. <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 1 (Appendix A) . Groundwater monitoring was <br /> performed in accordance with GTI's SOP 8 (Appendix B) . <br /> Analyses of the groundwater monitoring data indicate that <br /> groundwater levels have declined an average of 1.85 feet during <br /> this three-month reporting period. <br /> Since the first set of groundwater monitoring data was <br /> collected in May 1986, local groundwater-table elevation has <br /> declined steadily. According to National Weather Service local <br /> climatological data for the Stockton area, below-normal annual <br /> precipitation was recorded for the past five years. However, in <br /> 1982 and 1983, just prior to this drought period, annual <br /> precipitation was nearly twice normal. Therefore, the steady <br /> decline in the groundwater-table elevation may be in response to <br /> prolonged, drought conditions combined with an abnormally-elevated <br /> w groundwater level at the beginning of the monitoring period <br /> induced by the 1982 and 1983 precipitation. The decline in the <br /> ,. groundwater levels is depicted in the hydrographs for MW-7, MW-8 <br /> and MW-9 (Figure 4) . Monitoring wells MW-7 and MW-8, are <br /> representative of the majority of Wells at. the site. The one <br />