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i 1.2 Site Background � ' Remcor, Inc. of Pittsburgh, Pennsylvania, conducted an environmental assessment in May, 1994 to determine the current environmental condition of the site. Remcor's report, dated July 21, 1994, indicated that the potential for soil or ground water contamination existed on the property. Of primary concern was a former underground gasoline storage tank that had been removed in the 1970's. No information regarding tank condition, ' possible soil or ground water contamination, or subsequent investigations was provided, however, it was reported that the tank was removed because it was known to be leaking. I ' On August 4 and 5, 1994, Remcor supervised the drilling of seven soil borings (Figure 2). Three of the borings were completed as ground water monitoring wells. Soil and ground water samples were collected for analysis of suspected or potential contaminants. Based ' upon the information obtained during this investigation, it was determined that an impact had occurred in the vicinity of the former gasoline tank, and that further investigation was warranted. On August 24 and 25, 1994, Remcor installed an additional seven soil borings and three monitoring wells to further define the lateral extent of soil and ground water contamination identified in the initial phase of work. On March 8, 1996, AGS installed three ground water monitoring wells to further define the lateral and vertical extent of contamination. Monitoring well MW-7 was installed in the upgradient direction to the southeast of the former UST pit. Monitoring well MW-8 was installed west of the former UST pit to assess ground water quality in that direction. These two wells were installed to a depth of 27 feet and 25 feet below the ground surface (bgs), respectively. Monitoring well MW-9 was installed adjacent to the previously installed well MW-6 to determine the vertical extent of contamination. This well was installed to a depth of 45 feet bgs and sealed with bentonite between the depths of 28 feet bgs and 38 feet bgs. A remedial excavation was conducted during July and August, 1998. Approximately 1,522 cubic yards of gasoline impacted soil was removed and aerated on-site. Monitoring wells MWA, MW-2, MW-3, MW-4 and MW-8 were abandoned prior to beginning the excavation. On September 17, 1998, monitoring well MW-lA was installed near the tformer location of MW-1. Following the December 1998 quarterly sampling event, AGS requested that the ground water monitoring program be modified to include the sampling of monitoring wells MW- 1A and MW-6 only. The request was approved by the San Joaquin Public Health Services in a letter dated February 9, 1999. There are currently five ground water • monitoring wells installed at the site. American Geological Service, Inc. CA95DE-029 4