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' 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 g g ' 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 grade, respectively. Monitoring well MW-9 was installed adjacent to the previously installed well MW-6 to determine the vertical extent bf contamination. This well was installed to a depth of 45 feet below grade and sealed with bentonite between the depths of 38 feet and 28 feet. A remedial excavation was conducted during July and August, 1998. Approximately 1522 cubic yards of gasoline impacted soil was removed and aerated on-site. Monitoring rwells MW-1, MW-2, MW-3, MW-4 and MW-8 were abandoned prior to beginning the excavation. On September 17, 1998, monitoring well MW-1A was installed near the 10 former 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- IA 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. ' 1.3 Geology The subsurface geology of the site was determined by logging soil samples collected at various intervals during the initial and supplemental site investigations. Dark brown silty clay dominates the stratigraphy from within one foot of the surface to ' the bottom of the borings. In general, fine sand was found within the silty clay unit near the bottom of the borings at an approximate depth of 20 feet. The moisture content increased with depth and reached saturation between 12 and 16 feet below grade. American Geological Services, Inc. ' CA95DE-029 4