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ISite Background Information K & S Gas & Grocery IPage 2 of 5 detected at a depth of 45 feet bsg or in samples analyzed from the three other borings Soil probe ' boring installations were described in theAGE-prepared Preliminary Site Assessment Report in August 1997 ' One 20,000-gallon UST was installed at the site following the 1998 UST removals Approximately 341 tons of hydrocarbon-impacted soil were excavated during removal of the old USTs and over- excavation for the installation of the new UST and piping Soil was disposed of at Forward Landfill ' During the UST installation, two conductor casings were installed through the pea gravel adjacent to the UST in anticipation of future site assessment needs The UST removal, over-excavation, and UST installation were described in the AGE-prepared UST Removal Report, dated 26 May 1998 Three ground water monitoring wells (MW-1 through MW-3) were installed in December 1998 as part of site assessment activities Petroleum hydrocarbon-impacted soil was encountered in all well borings The maximum concentration of TPH-g was 4,200 mg/kg (MW-1) Benzene and MTBE were detected only in soil sample MW2-35 at 0 0058 mg/kg and 0 011 mg/kg, respectively TPH-g was detected in initial ground water samples collected from MW-1 through MW-3 at a maximum concentration of 330,000 micrograms/liter (p.g/l) in the sample from MW-3 BTEX • compounds were detected at concentrations as high as 29,000 µg/1 benzene, 54,000 gg/1 toluene, 6,500 µg/l ethylbenzene, and 36,000 µg11 xylenes (MW-3) MTBE was detected in all three well samples at a maximum concentration of 510 µg/l(MW-1) In addition,TBA was detected in MW-1 and MW-2 at a maximum concentration of 830 µg/1(MW-1) Monitoring well installation and initial monitoring activities were described in the AGE-prepared Monitoring Well Installation Report, dated 02 June 1999 Between Februaryand November 2001,AGE advanced five paired cone penetrometer testing(CPT) soil borings(CPT-1 through CPT-5) at the site to depths between 100 feet and 150 feet bsg to assess ' the extent of petroleum hydrocarbon impact and to identify potential hydrologic units TPH-g was detected in grab ground water samples at concentrations as high as 14,000 gg/l (CPT-4), BTEX compounds were detected at concentrations as high as 4,000 gg/1 (benzene, CPT-4), MTBE was detected at concentrations as high as 1 3 gg/1(CPT-4), TBA was detected at concentrations as high as 5 0 µg/l (CPT-2) Based on CPT data,AGE developed a hydrogeologic model for the site consisting of a vadose zone and six potential hydrologic units informally identified as Hydrologic Unit 1 (HUI), located between 30 feet and 70 feet bsg,Hydrologic Unit 2 (HU2), located between 70 feet and 85 feet bsg, Hydrologic Unit 3 (HU3), located between 85 feet and 95 feet to 100 feet bsg, Hydrologic Unit 4 (HU4), located between 95 feet to 100 feet and 120 feet bsg, Hydrologic Unit 5 (HU5), located ' between 120 feet and approximately 135 feet bsg, and Hydrologic Unit 6 (HU6), located between 135 feet and at least 150 feet bsg Geologic cross sections A-A ' and B-B'were generated from the • CPT data, depicting the informal hydrologic units and petroleum hydrocarbon concentrations ' Advanced GeoEnvironmental,Inc