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AM S E C O R 76 Station 11195 September 13, 2004 Page 2 One 550-gallon fiberglass waste oil UST and associated remote fill line were removed in 1997. One soil sample was collected from the bottom of the waste oil UST excavation at 10 feet bgs. A second soil sample was collected from beneath the remote fill line at 3 feet bgs. Both samples were non-detect for petroleum hydrocarbons (GeoStrategies, Waste Oil UST and Remote Fill Line Soil Sampling Report, dated August 6, 1997). In July 1998, an abandoned water well, located north of the former UST pit adjacent to Louise Avenue, was properly destroyed. The well was destroyed by perforating the steel casing and grouting the well with neat cement placed by the use of a grout pump and tremie pipe. The well destruction was permitted and observed by the PHS-EHD. Five offsite wells (MW-8 through MW-12) were installed and one offsite well (MW-7) was destroyed in September 1998. Soil samples collected during the investigation at depths of 4 to 6 feet bgs contained petroleum hydrocarbon concentrations of up to 1.5 ppm of TPHg and 0.0034 ppm of benzene. Oxygenating compounds including methyl tert-butyl ether (MtBE) were not detected (Alisto, 1999). One 10,000-gallon, one 8,000-gallon, and one 6,000-gallon single-wall fiberglass gasoline =_ USTs, two dispenser islands, related product lines, and one canopy were replaced with two >= 12,000-gallon double-wall gasoline USTs, two dispenser islands, related product lines, and one canopy in December 1998. The new USTs were installed in an excavation located immediately adjacent to the former UST complex. These excavations are hydraulically connected with pea gravel backfill material encountered in the northeast corner of the former UST pit. Soil samples collected from the capillary fringe of the former and new UST excavations at depths of 11 to 12 feet bgs contained petroleum hydrocarbons at concentrations of up to 130 ppm of TPHg, 50 ppm of MtBE, 290 ppm of ethanol, and 51 ppm of tertiary butyl alcohol (TBA). All of the soil samples were non-detect for benzene and the oxygenate compounds. Soil samples collected from beneath the former product lines at depths of 3 to 4 feet bgs were non-detect for TPHg, benzene, MtBE, or the six oxygenate compounds. A set of first generation product lines were discovered during construction activities and removed. Soil samples were collected from beneath these product lines at depths of 2.5 to 4 feet bgs. Concentrations of TPHg (50 ppm), MtBE (0.17 ppm), and ethanol (64 ppm) were reported in these samples. The area surrounding these samples was overexcavated and four sidewall soil samples and one bottom sample were collected at depths ranging from 6 to 11.5 feet bgs. These samples contained TPHg concentrations up to 950 ppm, but were non-detect for all other analytes. Groundwater was encountered in the excavations at a depth of approximately 11 to 12 feet bgs. Two grab groundwater samples were collected from the former UST excavation and analyzed for TPHg, BTEX, MtBE, and six oxygenate compounds. Grab groundwater samples SW and CW, collected from beneath the former south and center USTs, contained ` 8,400 and 60,000 ppb of TPHg, 310 and 1,500 ppb of benzene, 100,000 and 130,000 ppb of CP 11195 Assessment WP 9-44.doc SECOR International Incorporated