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f CONESTOGA-ROVERS &ASSOCIATES 1985 UST Replacement: During October 1985, J.H. Kleinfelder & Associates drilled four soil borings in the vicinity of the USTs. Petroleum hydrocarbons were detected with a trace gas analyzer in soil samples collected from 10 feet below grade (fbg) from three of the four soil borings. The source of the hydrocarbons was not identified. During November 1985, three steel USTs were removed and replaced with three 10,000 gallon double-walled fiberglass tanks in the same location. Canonie Engineers, Inc. collected soil samples from beneath the USTs and water samples from the bottom of the excavation. Laboratory analysis of these samples indicated total petroleum hydrocarbons (TPH)were present in soil and groundwater during this investigation. The source of these hydrocarbons was not identified. 1989 Investigation: During August and September 1989 Delta Environmental Consultants, Inc (Delta) drilled and sampled 12 soil borings and converted three of the borings to monitoring wells (MW-1,MW-2, and MW-3). TPH was detected in soil samples from 3 of the 12 borings at concentrations up to 140 milligrams per kilogram(mg/Kg),and benzene was detected in only one boring at a concentration of 0.01 mg/Kg. TPH and benzene were not detected in groundwater samples collected from the three monitoring wells. These findings are documented in Delta's November 22, 1989 Pretank Closure Assessment Report. 1990 Tank Replacement and Overexcavation: During May 1990, three 10,000 gallon USTs were removed from the site. Delta performed soil sampling and overexcavation activities associated with the UST removal. Delta directed overexcavation in the eastern portion of the site to depths ranging from 3.5 to 18 fbg, removing approximately 1,700 cubic yards of soil. Approximately 400 cubic yards of soil containing TPH concentrations up to 250 mg/Kg were transported to appropriate disposal facilities. Approximately 1,300 cubic yards of soil containing no detectable concentrations of benzene,toluene, ethylbenzene, or xylenes(BTEX), or TPH were used onsite as backfill. These activities are documented in Delta's November 28, 1990 Preliminary Report and Tank Closure Report. Soil sample locations from the historical tank excavations are shown on Figure 2,along with the limits of excavation. 1990 Monitoring Well Replacement: During July 1990, wells MW-1, MW-2, and MW-3 were damaged during site remodeling activities and were subsequently properly destroyed. These wells were replaced in August 1990 by wells MW-lA, MW-2A, and MW-3A. 0813 2 Worldwide Engineering, Environmental,Construction,and IT Services