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1 <br /> III <br /> 6 SUMMARY AND RECOMMENDATIONS <br /> �I <br /> The following summarizes the results of this investigation <br /> • Sediments underlying the site consist of clayey silt to fine-to-coarse- grained sand <br /> I <br /> • Geologic conditions are similar to that observed in adjacent properties <br /> • The majority of residual hydrocarbons were detected in the viciruty of the former <br /> USTs and dispenser islands Residual hydrocarbons were detected in each bonng, <br /> except from soil samples collected from boring B-6R The highest concentrations were <br />' detected approximately 10 feet bgs near the former USTs TOG was detected in the <br /> sort sample collected near the former UST cavity (located near the station building) at <br /> a concentration of 10,000 ppm PCBs, TPHD, and CLHC were below laboratory <br /> detection limits in all soil samples analyzed from soil borings B-2R and B-6R <br /> • Groundwater was encountered at approximately 31 to 38 feet bgs On September 30, <br /> 1996, static groundwater was measured at 26 44 bgs in monitoring well MW-1R <br /> Groundwater elevations are consistent with groundwater elevations measured at <br /> adjacent properties <br /> ® The groundwater flow direction at the fuer ARCOService Station n August 22, <br /> 1996, was to the northeast with a hydraulic gradient of 0 002 <br />' • TPHG, BTEX, and MTBE compounds were detected in monitoring well MW-1R <br /> THPG and benzene were detected at a concentration of 33,000 ppb and 1,400 ppb, <br />' respectively MTBE was detected at a concentration of 550 ppb <br /> Based on the results of the investigation, EMCON recommends the following <br /> • Additional monitoring wells be installed upgradient and possibly north of the site to <br /> delineate the dissolved hydrocarbon plume <br />' • Quarterlygroundwater monitoring of monitoring well MW-1R and vapor extraction <br />' well <br />' SACS'\PJ2\2613\26131000 18S-9N]b 2 Rev 0,215/97 <br /> 22613 100 001 6-1 <br /> 1 <br />