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' November 22 1995 <br /> Page 9 <br />' contained no detectable to very low concentrations of TPH-g Benzene was not <br /> detected in any of the soil samples analyzed <br /> The clay horizon underlying the site at a depth of approximately 10 feet bgs appears <br /> to be laterally continuous The vertical extent of hydrocarbon-impacted soil appears <br /> to be hmited to the soils immediately above and below the water table in the <br /> northwest portion of the site, which generally correlates to the upper clay contact <br /> Petroleum hydrocarbon concentrations were found to attenuate to below detection <br /> limits within the clay, suggesting that the lower permeability clay horizon has <br />' inhibited vertical petroleum hydrocarbon migration <br /> In summary, the lateral extent of hydrocarbon-impacted groundwater has not been <br /> delineated in the northwestern portion of the site Although the vertical extent of <br /> groundwater impacted has not been quantified, it appears that based on soil analytical <br /> data and site bthology, the potential for vertical,migration of hydrocarbons is <br /> relatively low <br /> 1 RECOMMENDATIONS <br /> It is recommended that Monitoring Wells U-1, U-2, and U-3 be gauged for <br /> groundwater elevation and sampled for TPH-g, BTEX compounds, TPH-d, <br /> halogenated volatile organics, and priority pollutant metals on a quarterly schedule ✓ <br /> Quarterly groundwater monitoring should be performed for at least one full <br /> hydrologic cycle to evaluate trends in groundwater gradient and chemistry, and to <br /> determine if further site investigations are warranted <br /> The two USTs discovered at the north end of the site should be either removed or <br />' appropriately abandoned in place m accordance with PHS/EHD guidelines A <br /> corrective action work plan for the proper abandonment of the two USTs should be <br />' submitted to the PHS/EHD <br /> 1 <br /> _ 3100971 A/REPORT <br />