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28 July 1999 <br /> • AGE-NC Protect No 96-0263 <br /> Page 2 of 9 <br /> 22 PREVIOUS INVESTIGATION <br /> On 24 June 1998, a total of nine soil probe borings (B 1 through 139)were advanced at the site Grab <br /> ground water samples were collected and analyzed from probe borings B1, B3, B5, B6, B7, B8 and <br /> 139 <br /> HYDROCARBON-IMPACTED SOIL <br /> TPH-g was detected in nine of fifteen soil samples analyzed from seven of the soil probe borings <br /> TPH-g was detected at concentrations as high as 670 mg/kg (sample 134-5') TPH-g was detected in <br /> soil from depths greater than 10 feet bsg at concentrations up to 240 mg/kg (135-12') TPH-g was not <br /> detected in soil samples collected at depths of 20 feet and 25 feet bsg <br /> BTEX compounds were detected in eleven of the fifteen soil samples analyzed The greatest <br /> concentrations of BTEX compounds detected were generally in soil samples collected at depths of <br /> five and ten feet bsg, however, in the former dispenser area BTEX compounds were detected in a <br /> soil sample collected from a depth of twelve feet bsg at a considerable concentration The <br /> concentrations detected dropped 2 orders of magnitude in a soil sample collected at 15 feet bsg in <br /> the same bonng In the former dispenser area, the concentrations of BTEX compounds detected in <br /> the deepest sample collected (25 feet bsg) were above the method detection limits, yet were low <br /> compared to concentrations in soil samples collected at depths of 5 feet to 15 feet bsg <br /> MTBE was detected in 12 of the fifteen soil samples analyzed MTBE concentrations detected in soil <br /> from depths less than 10 feet bsg were as high as 43,000 micrograms per kilogram (,ug/kg) (Sample <br /> 135-10') MTBE was detected In the soil sample collected at 25 feet bsg at a concentration of 58 <br /> ,ug/kg Laboratory results of soil samples analyzed for petroleum hydrocarbons area summarized in <br /> Tables 1 and 2 <br /> The most intensely hydrocarbon-impacted soil was encountered In the area of the former UST <br /> dispenser and product line The most intensely impacted soil was limited to soil above 20 feet bsg <br /> in the former UST area and to soil above 10 feet bsg west of the former USTs Clayey shallow soil <br /> was more intensely impacted than the deeper, saturated sandy/gravelly soil <br /> HYDROCARBON-IMPACTED GROUND WATER <br /> TPH-g was detected In four of the seven grab ground water samples collected from the site at <br /> concentrations ranging from 3,200 to 27,000 micrograms per liter (yg/1) BTEX compounds were <br /> detected in four of the water samples at significant concentrations ranging from 30 ,ug/l benzene In <br /> Advanced GeoEna ironmcnial,Inc <br />