Laserfiche WebLink
11 November 2004 <br /> AGE-NC Project No 99-0624 <br /> Tage6of13 <br /> 3 1 HYDROCARBON-IMPACTED SOIL <br /> Between March 1998 and April 2004, soil sampling was performed at sixteen soil borings <br /> (B1 through B4, P-1 through P-5), ground water monitoring well pilot borings (MW-1 through <br /> MW-7) and six shallow tank excavation samples as part of a subsurface petroleum hydrocarbon <br /> investigation <br /> Petroleum hydrocarbons(TPH-g)were detected in soil samples collected from boring P1 (50 feet), <br /> well MW-2 (45 feet) and boring MW-6 (25 feet), delineating the maximum potential lateral extent <br /> I of impacted soil The vertical extent of TPH-g was delineated by the soil borings, TPH-g was not <br /> detected below 60 feet bsg in any of the analyzed samples Low concentrations of BTEX were <br /> detected in the mai onty of the soil borings The most significant concentrations of BTEX compounds <br /> were detected In soil samples collected at depths between 45 and 55 feet bsg, possibly denoting a <br /> smear zone of the former water table level, from samples near the former UST release area <br /> Generally, BTEX was not detected in the shallow vadose zone, less than 40 feet bsg <br /> The fuel additives MTBE and TBA were detected in soil samples collected from the upper vadose <br /> p pp <br /> zone in significant concentrations, greater than 10 mg/kg and in one soil sample collected from the <br /> water table at 36 mg/kg (MW7-50) Lower concentrations of MTBE were detected in soil samples <br /> from throughout the soil profile The plume of impacted soil at the site has an estimated north-south <br /> dimension of 40 feet and east-west of dimension of 40 feet, at the former UST release area Minor <br /> volumes of soil may reside in the area of well MW-2 at the historically high water table level of 45 <br /> feet bsg The extent of soil contamination is defined laterally in all directions, vertically the soil is <br /> defined in the tank pit area, however the vertical extent has not bd'd' cfined in the area of MW-2 <br /> Analytical results of soil samples are included in Table 2 The lateral and vertical extent of soil <br /> contamination is depicted on Figures 5, 6 and 7 <br /> 3 2 HYDROCARBON-IMPACTED GROUND WATER <br /> Between November 1999 and May 2004,seventeen groundwater monitoring events were performed <br /> at the site to monitor dissolved petroleum hydrocarbon concentrations in ground water and to <br /> characterize ground water flow direction and gradient on the site Generally, TPH-g was detected <br /> in water samples collected from wells MW-1, MW-2 and MW-3 at concentrations as high as <br /> 33,000 µg/l, BTEX compounds frozra wells MW-1 through MW-3 at concentrations as high as <br /> 1,000 µg/1 (benzene), 100 µg/1 (toluene), 58 µg/l(ethylbenzene) and 1,700 µg/l (toluene), <br /> respectively, and MTBE from wells MW-1, MW-2,MW-3, MW-5 and MW-7 at concentrations as <br /> high as 33,000 µg/l(MW-2) The current limit of the shallow dissolved MTBE is not defined by the <br /> monitoring well network (Figure 8) <br /> IAdvanced GeoEnvironmental,Inc <br />