SITE INFORMATION AND CORRESPONDENCE_FILE 1

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DeceIber 19, 1986 Harding Lawson Associates 4167,154.02 Exxon Company, U.S.A. Mr. Kent Sanderson Page 4 Laboratory test results for stockpiled soil samples were transmitted to the S7CAPD and authorization was obtained to aerate the soils. The allow- able volume of soil at a given TPH concentration was spread on site by an AEMC backhoe operator to an approximate thickness of 6 inches and allowed to aerate for several days. Following aeration, our geologist conducted an OVA survey of the spread soils to determine 'worst case" locations. Survey locations were plotted on a site map and meter readings tabulated. One discrete soil sample was collected from the "worst case" location for each 100 cubic yanks of aerated soil. The samples were collected as des- cribed above and delivered to ASA under chain of custody for TPH and BIx analyses. ANALYTICAL RESULTS Three of the seven soil samples collected from the deepened excavation contained detectable hydrocarbons. 1986. See ASA report dated September 25, Ground water sample GW-1, collected from within the excavation at the east (fill) end of Tank 1, contained 130 ppm TPH and 40, 43, and 9.9 ppm BTX. All soils were aerated to concentrations of significantly less than 100 ppm TPH and were authorized by the SJCIM for use as backfill at the site. The laboratory analysis reports are attached. CONCLUSIONS AND RETTONS The presence of hydrocarbons in the soils beneath the former fill end of Tanks 1 and 2 suggests possible historical leaks or overfill spillage of these two gasoline tanks. Some product migration has probably occurred beneath Tank 2 toward the west (opposite of the fill end) , as indicated by the significantly lower hydrocarbon concentrations below the tank at this end. The laboratory results for ground-water Sample GW-1 indicate that hydro- carbograted to the shallow ground water beneath the tanks. We recommend that three ground-water monitoring wells be installed adja- cent to the tank excavation to determine the direction of ground-water flow at the site and to evaluate the upgradient and dcwngr dient ground- water quality. In addition, we recommend that the soils below the fuel delivery lines be sampled following removal to check for indication of Pipeline leaks.