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7-Eleven/Stockton 21 <br /> August 1989 <br /> stripping system is not exceeding the permitted discharge <br /> _. requirements. The results of the metals analyses are tabulated <br /> on Table 5 (Appendix A) and the laboratory results are included <br /> in Appendix C. <br /> SOIL-VENT SYSTEM <br /> Four vapor-extraction points are located near the <br /> underground tank pit and are connected to a high-vacuum vapor.- <br /> control system designed to ventilate the subsurface and remove <br /> vapors from the soil. The four points are manifolded to four <br /> vapor-phase carbon-adsorption canisters to decrease air emissions <br /> to levels below 1.0 part per million (ppm) volatile organics, <br /> which is deemed acceptable by the San Joaquin County Air <br /> Pollution Control District. <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 (PTD) monitoring of <br /> the two prefilter, 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 prefilter carbon <br /> canisters, the canisters are replaced. The spent prefilter <br /> carbon canisters at the site were replaced on April 5, April 19, <br /> May S, May 24, and June 20, 1989. This method of emission treat- <br /> ment and monitoring results in maintenance of non-detectable <br /> hydrocarbon emissions to the atmosphere from the two final carbon <br /> _. canisters in the soil-vent system. <br /> In order to evaluate the possible integration of MW-1, MW-2, <br /> w MW-3 and MW-4 into the existing soil-vent system, a soil-vent <br /> test was conducted on April 28, 1989. Results of the soil-vent <br /> test indicate that at a total flow of 100 standard cubicr feet per <br /> ^� Cknl\U11t11.k <br /> TLti fI��N�h:1 Im <br />