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• In May 1991, Emcon Associates installed one soil boring/groundwater monitoring well (MW1) in the approximate center of the backfilled tank pit. Analyses of soil samples collected during well installation indicated 0.10 parts-per-million (ppm) of benzene in the sample collected from 41 feet (ft) to 41.5 ft below ground surface. In January 1992, Kleinfelder, Inc. drilled two soil borings, B1 and B2 through the backfill near the southwest corner and north-central areas, respectively, of the previous investigation. No analytes were detected in the soil samples collected from B1. In B2, the sample from 30 ft below ground surface contained xylenes at a concentration of 0.0072 ppm. TPHd was detected at a concentration of 1.5 ppm in the sample collected from 40 ft below ground surface. In May 1993, following re-excavation of the tankpit, seven soil samples were collected from the sidewalls and floor at depths between 14 and 25 feet. No TPHg/BTEX analytes were detected in any sample nor were longer chain hydrocarbons. Based on these data the lateral and vertical extent of soil contamination had been defined. Tabulated analytical results for all soil samples and sampling locations are presented in the June 3, 1993 Soil Excavation Report included in Appendix A. Groundwater . In May 1991 a groundwater sample was collected from MW1 which was reported to contain 100 parts- per-billion (ppb) TPHg, and 1.6 ppb benzene. Depth to groundwater was measured at approximately 69 ft below groundsurface. In September 1991, groundwater samples were collected from MW1 and analyzed for TPHg, and BTEX by three different laboratories. One laboratory also analyzed the sample for TPHd. This lab reported a TPHg concentration of 60 ppb in the groundwater sample and no detectable TPHd or BTEX. A second lab reported a benzene concentration of 0.8 ppb, and a TPHg concentration of 220 ppb. The third laboratory did not detect TPHg or BTEX. In January 1992 a groundwater sample was collected from MW1 and depth to groundwater was again measured at approximately 69 ft below groundsurface. The sample was analyzed for TPHg and BTEX. No analytes were detected. In July 1993 a groundwater sample was collected from MW1 and analyzed for TPHg and BTEX. Toluene, ethylbenzene, and xylenes were reported at concentrations of 2.1 ppb, 0.7 ppb, and 4.2 ppb respectively. Depth to groundwater was measured to be 69.46 ft below groundsurface. Also in July 1993, a groundwater sample was collected. from a. hydropunch boring installed north- - northwest of MW 1 (downgradient of the UST pit and MW 1). The sample was analyzed for TPHg and BTEX. No analytes were detected. 3