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Y Yl .T K <br /> - 7-Eleven/Stockton 18 <br /> May, 1989 <br /> The soil-vent system is currently operational and is <br /> withdrawing vapors at an approximate flow rate of 90-cubic feet <br /> per minute (cfm) . Photo-ionization detector (PID) monitoring of <br /> ,.he two pre-filter, vapor-phase carbon canisters is conducted <br /> weekly For detection of carbon breakthrough. Upon detection of <br /> hydrocarbon vapors in the emissions from the two pre--filter <br /> carbon canisters, the canisters are replaced. The spent carbon <br /> canisters were replaced on February 17, 1989 and March 17, 1989. <br /> This method of emission treatment and monitoring results in <br /> maintenance of non-detectable hydrocarbon emissions to the <br /> atmosphere from the two final carbon canisters in the soil-vent <br /> system. <br /> SUMMARY <br /> Groundwater monitoring data have documented a gradual rise <br /> of the water table elevation during this reporting period. This <br /> .- rise in the groundwater surface elevation has enabled MW-4 to be <br /> monitored (it was previously dry) . Monitoring wells MW-2 and <br /> M14-3 remain dry despite the rise in groundwater level. During <br /> this reporting period the groundwater gradient has remained in an <br /> easterly direction at a 0.002 ft/ft slope, except in the areas <br /> within the capture zones of pumping wells. <br /> The results of the groundwater sampling indicate that the <br /> distribution of dissolved hydrocarbons in the groundwater beneath <br /> the site continues to be concentrated near the former <br /> underground-tank and pump-island locations, which is unchanged <br /> since previous reporting. The surrounding domestic wells did not <br /> contain detectable levels of dissolved hydrocarbons during this <br /> reporting period. <br /> -- GHUI:IPWATE:H <br />