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v i SITE ASSESSMENT INVESTIGA7TIONS !� d On 24 June 1997,a total of nine soil robe borings(B 1 through 139)were advanced at the site under i. EHD oversight. Soil in probe borings B1 through B5 were continuously sampled(cored),whereas soil inP robe boring B6 was sampled at the vadose zone/ground water interface. In addition, grab 1� ground water samples were collected from B1 through B9. The gmb ground water samples and selected soil samples were analyzed for TPH-g,TPH-d,BTEX and methyl tert-butyl ether(MTBE); however, soil samples collected from probe boring B1 were not analyzed, because field screening with a organic vapor monitor (OVM) indicated that the samples were not impacted by petroleum hydrocarbons. 9 • TPH-g was detected in six soil samples collected from four of the probe borings,B2,B3,B4 and B5. TPH-g was detected at concentrations as high as 5,000 mg/kg (135-6) at depths of 8 feet bsg or less. TPH-g concentrations detected in soil from depths greater than 8 feet bsg were as high as 550 mg/kg(144-9'). TPH-g was not detected at depths of 12 to 16 feet in the d area ofthe formerUSTs norwasTPH- detected in the soil sample collected from B6.Total J: g P petroleum hydrocarbons quantified as diesel (TPH-d) was detected in the soil sample collected from probe boringlB2 at a depth of 8 feet bsg at a concentration of 510 mg/kg. Ij BTEX compounds were detected in soil samples collected from depths of less than 8 feet bsg at concentrations ranging from 0.007 (ethyl benzene,1364) to 480 mg/kg (xylene, 135-6). q, BTEX compounds were also detected at a depth of 12 feet bsg in borings B2,B3 and B5.No I petroleum hydrocarbons or BTEX compounds were detected in the soil sample collected from a depth of 16 feet bsg in the former UST area. �i TPH-g was detected in each of the eight grab ground water samples collected from the site I at concentrations ranging from 220 micrograms per liter(µg/1)to 240,000 µg/1. TPH-d was detected in both of the grab ground water samples at concentrations of 44,000 µg/l and 310,000 µg/1. BTEX compounds were detected in each of the water samples analyzed at concentrations ranging from 0.56 µg/1 benzene in boring B1 to 20,000 µg/1 of benzene in 1 boring B7. MTBE was also,detected at concentrations up to 1,000 µg/1 by EPA Method 8020. However, the highest concentration of MTBE detected by EPA Method 8260 was 180 µg/1. On 12 and 13 February 1998 five ground water monitoring wells were installed on-site and off-site of the subject property. Soil borings B10 and B14 were completed as dual-screened ground water monitoring wells MW-2 and MW-11 respectively. Soil borings B 11,B 12, and B 13 were completed i; i as conventional ground water monitoring wells MW-3, MW-6 and MW-5, respectively. r TPH-g was detected in samples collected from well MW-IA and MW-1B at concentrations of 220 and 2,000µg/1,respectively.TPH-d was detected samples collected from well MW-1 B f at a concentration 160 µg/1.Benzene was detected in samples collected from wells MW-lA and MW-1B at concentrations of 15µg/1 and 530µg/1,respectively. Toluene,ethyl benzene j; and xylenes were also detected in MW-IA and MW-113 at concentration as high as 260 µg/1 ii (toluene, MW-1B). MTBE was detected in the sample collected from well MW-1B at a concentration 9.9 µg/1. t r