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' 30 March 1999 <br /> AGE-NC Project No 96-0263 <br /> Page 6 of 7 <br /> - <br /> prevailing ground water flow direction in this area of Tracy is generally toward th orth, <br />' based on ground water flow direction observations made on other sites in the vicinity <br /> • The most intensely hydrocarbon-impacted soil was encountered in the area of the former <br />' UST dispenser and_product-line <br /> • The most intensely Impacted soil was limited to soil above 20 feet bsg in the former UST <br />' area and to soil above 10 feet bsg west of the former USTs Clayey shallow soil was more <br /> Intensely Impacted than the deeper, saturated sandy/gravelly soil <br /> • The highest concentration of dissolved hydrocarbons quantified as TPH-g and overall BTEX <br />' compounds were limited to the former UST system area Hydrocarbons were not encountered a <br /> in the presumed down gradient direction from the USTs, soil boring B9 ` l P <br /> • The most Intensely Impacted ground water appeal s to underlie the former locations of the <br /> USTs and dispenser p'yAd 8_ <br />' • The lateral extent of the dissolved phase plume appears to have been delineated toward the p � <br /> south and west from the UST system M t <br /> 10 <br /> 6.0. RECOMMENDATIONS <br />' Based on the results of this Investigation, AGE recommends <br />' • Installation of ground water monitoring wells to define the lateral and vertical extent of the <br /> dissolved hydrocarbons and to monitor the hydrocarbon plume stability <br /> • Collection and field screening of grab ground \a atei samples prior to Installation of any <br />' monitoring wells to more completely define the lateial extent of the dissolved phase plume <br /> Additional well locations should be determined based upon new field observations and <br />' analytical results from previously collected grab ground water samples, with the concurrence <br /> of the PHS-EHD <br /> • Initiation of quarterly monitoring at the site upon installation of monitoring wells <br /> • If remediation of soil and/or ground water is necessai y at the site, a Corrective Action Plan <br /> (CAP) should be prepared The CAP should include iemediation feasibility studies (e g in- <br /> situ ai sparging pilot_test, sollyor extraction, soil excavation and bio-enhanced <br /> remediation or attenuation) to determine appropiiate remedial options for the site <br /> • <br /> Advanced GeoEnviron mental,Inc <br />