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7-Eleven/Stockton 23 <br /> October: 1988 <br /> The results of the groundwater sampling program have <br /> ^- continued to show non-detectable dissolved BTEX and TPH-as- <br /> gasoline levels in the off-site monitoring wells except for MW- <br /> 11. Hydrocarbon levels have increased in MW-11 during August and <br /> September, poss'bly due to the shifting of the groundwater <br /> gradient to a more easterly direction. Monitoring wells near the <br /> underground storage tanksand former pump island have contained <br /> 3 <br /> small amounts of free product or relatively high dissolved- <br /> hydrocarbon concentrations. The results of the laboratory <br /> analyses performed on domestic well samples have generally been <br /> Fi below the laboratory MDL. Minor BTEX and TPH-as-gasoline <br /> ' + constituents were detected in isolated wells, however, in each <br /> case the following sample round results indicated non-detectable <br /> f.a levels. <br /> w` The soil-vent system has been operating continuously at a <br /> flow rate of 100 cubic-feet-per-minute (c£m) . The system <br /> incorporates four carbon-adsorption canisters and the carbon life <br /> has increased to approximately 4 weeks before saturation. <br /> RECOMMENDATIONS <br /> LM1 <br /> _a Based on the current site conditions and the data <br /> accumulated to date, GTI makes the following recommendations for <br /> the site remediation effort: <br /> install one to two additional monitoring wells <br /> downgradient from MW-11. Due to increased <br /> t.� dissolved hydrocarbon levels in MW-11 in <br /> conjunction with the shifting of the groundwater <br /> gradient to a more easterly direction, it is <br /> important to acquire additional data for <br /> documenting the areal extent of the contaminant <br /> i <br /> plume. <br /> GR01'N1A%ATKR <br /> i L --j TEC11N01.()GV,INC. <br /> P�9 <br />