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September 18, 1996 Page 3 PREVIOUS SITE INVESTIGATIONS _ November 18, 1987 A soil vapor contaminant assessment (SVCA) was performed on site by EA Ten sample points were driven to depths ranging from ') to 8 feet bgs at locations in the area of the waste-oil tank, dispenser islands, and the gasoline UST complex Petroleum hydrocarbons were not detected above 1 part per million (ppm) in the 21 soli vapors samples collected February 24, 1988. One 1,000-gallon fiberglass waste-oil UST and three 10,000-gallon fiberglass gasoline USTs were excavated and removed during the site demolition activi- ties No holes were observed in any of the tanks Laboratory results indicated that the j soil sample collected beneath the waste oil tank (Sample,WOF41) reported 26 ppm of high-boiling point hydrocarbons and 10 ppm of low-boiling point hydrocarbons No chlorinated solvents, benzene, toluene, ethylbenzene, and xylenes (BTEX compounds), or polychlonnated biphenyls (PCBs) were detected (Table 2) After removing the three 10,000-gallon gasoline USTs, the northeast portion of the tank pit was overexcavated to a depth of 25 feet bgs One soil sample (AOP#1) was collected from the bottom of the gasoline tank excavation and reported high- and low-boiling point hydrocarbons at 55 and 340 ppm, respectively, but no benzene was detected (Table 2) - ' November 1988. EA drilled six bonngs on site to depths between,41 and 50 feet bgs �+ and converted the borings into 4-inch diameter monitonng wells (MW-1 through MW-6) The maximum concentration of petroleum hydrocarbons (3,300 ppm total purgeable petroleum hydrocarbons calculated as gasoline [TPPH-g] and 9 6 ppm benzene) detected in soil was reported from the samples collected from Well MW-4, located proximal to the northeast corner of the former UST complex (Table 2) While installing Well MW-5, an abandoned 550-gallon steel UST was encountered and accidentally punctured (Figure 2) The liquid inside the tank was sampled and character- ized as weathered gasoline Soil around the UST was later excavated to expose the s tank Dunng tank excavation, product piping was uncovered leading to two additional steel USTs (3,000- and 4,000-gallon) that had been abandoned in place and filled with soil December 1988 The three additional steel USTs were removed and documented by Blaine Tech Services, Inc (Blaine) Prior to excavation the liquid inside of the 550-gallon UST was pumped, and soil inside the 3,000- and 4,000-gallon tanks was removed. Upon excavation, no holes in the tanks were observed One soil sample was collected below each end of the 4.000- and 3,000-gallon tanks, and one soil sample was obtained from below the middle of the 550-gallon tank (Table 2) No petroleum hydro- , r carbons, ethylene dibromide, or orgaruc lead was detected in any sample analyzed - (Table 2) 320133M CLOSURE] 4