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10 September 2004 <br /> AGE-NC Project No 04-1129 <br /> 1 Page 5 of 7 <br /> ' 2 4 2 Ground Water Depth and Gradient <br /> Based on ground water data collected during the four quarters of ground water monitoring,the depth <br /> '~ to ground water at the safe has ranged from approximately-335—feet to 36 7 feet below the tops of <br /> the well casings(btoc) The ground water flow direction near the foimer gasoline UST has generally <br /> been toward the southeast with'an average gradient 0 01 foot/foot <br /> i <br /> 3.0. ASSESSMENT OF PETROLEUM HYDROCARBON-IMPACTED SOIL AND <br /> ' 1, <br /> GROUND WATER FROM SOIL BORINGS <br /> Between May 2002 and May 2003, six soil borings were advanced at the site for collection of soil <br /> ' and grab ground water samples and installation of three-ground water monitoring wells (MW-1 <br /> through MW-3) <br /> ' 3 1 HYDROCARBON-IMPACTED SOIL <br /> The greatest concentration of petroleumhydrocarbon-impacted soil was encountered in soil borings <br /> B-5 and MW-1 between depths of 5 feet and 20 feet bsg(Table 1),petroleum hydrocarbons were not <br /> detected in soil samples collected from soil borings PB-2,PB-3,PB-20,MW-2 and MW-3 General <br /> lithology, soil sample locations and the vertical and Iateral extent of petroleum hydrocarbon- <br /> impacted soil are depicted in cross sectional views A-A' and B-B' (Figures 3 through 6), the <br /> approximate areal extent of adsorbed petroleum hydrocarbon-impacted soil is depicted on Figure 2 <br /> Based on the vertical and lateral extent ofhydrocarbon-impacted soil,the apparent maximum volume <br /> of petroleum impacted soil beneath the site is approximately 4,949 cubic yards (Appendix D) A <br /> mass-volume'calculatlon of TPH-d yields approximately 1,781 gallons of TPH-d in the remaining <br /> Impacted soil at the site (Appendix D) <br /> 3 2 HYDROCARBON-EAPACTED GROUND WATER <br /> Relatively low concentrations ofTPH-g and BTEX constituents were detected in a grab ground water <br /> sample collected from boring PB72,located near the former UST.area However,analytes of concern <br /> were not detected in ground water samples collected from monitoring wells MW-1 through MW-3 <br /> during the monitoring and. sampling period Analytical results of ground water samples. are <br /> summarized in Table 2 <br /> Advanced GeoEnvironmental,Inc <br /> d <br />