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1 , i. 6 29 April 2005 - `� AGE-NC'Project No'. 98-0440 ; Page 6 of 18 'The dissolved contaminant plume has migrated toward the northwest away from,the former,USTs towards the property of the Hay-Grower's Association truck scale and domestic well DW-5055 (Figures 7 and 8). Data further`suggests the dissolved contaminant plume rmaybe migrating;along a discontinuous sand body occurring at the top of the water table or 10-to'l3 feet bsg.The location and,, ' distribution of the sand body is depicted on Figures 7 and 8. The lateral and vertical extent of impacted soil has been defined; the lateral and'vertical extent of impacted ground water has also been defined. ' 4.1.' HYDROCARBON-IMPACTED SOIL ' Between July 1998 and March 2004, soil sampling was performed at seven soil borings(B 1 through ; B7) and twelve groundwater monitoring well pilot borings (MW-1 through MW-12) as part of a subsurface petroleum hydrocarbon investigation. ' Petroleum hydrocarbons (TPH-g) were"detected in soil samples,collected from borings Bl through ' . B7 and MW-1•through MW-6,delineating the maximum potential lateral extent of impacted soil. ' The veitical.extent of-TPH-g was delineated by the soil boring samples. Low concentrations of BTEX were detected in the majority of the same soil borings. The most significant concentrations of BTEX compound were detected in soil samples collected at depths of 15 feet bsg in borings B 1, ' 'B2 and MW-2. The plume of impacted soil at the site has'an estimated northeast-southwest dimerision of 155 feet- ' and northwest-southeast•dimension of 90'feet, at the former. UST release area..Mass .volume "calculations indicate that there,is approximately 65 i kg or 229 gallons of petroleum hydrocarbons :.''adsorbed in the soil• beneath:the site,(Appendix Q. Adsorbed soil`is depicted in plane view .in, ' :Figure 9. 4.2. HYDROCARBON-IMPACTED GROUND WATER A ' Between July 1998 and March 2005,twenty-five'ground water monitoring events were performed , at the.site to monitor dissolved petroleum hydrocarbon concentrations in ground water and to , characterize groundwater flow direction and gradient on the site. Generally,TPH-g and TVH-d were { detected in water samples collected from wells MW-2, MW-5 and MW-6 at concentrations as high as 11,000 µg11 and 3,600 µg/l` BTEX compounds from wells MW-2, MW-5 and MW-6 at . concentrations.as,high.as 1,200 ,14/1 (benzene), 52 µg/1 (toluene), 450 µg/l(ethylbenzene) and t1,300 µg/l (toluene). ' Advanced GeoEnvironmcntal,Inc.