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Mr George Takemort Project OF90-002 05 November 16, 1998 Page 2 contained detectable concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX), however, BTEX was not detected in the other sample Total petroleum hydrocarbons as gasoline (TPHG) were not detected in either sample In September 1988, the area was overexcavated Confirmation soil samples were collected from the bottom of the excavation Petroleum hydrocarbons were not detected in any of the confirmation soil samples collected during this overexcavation activity Between December 1987 and December 1994, following the removal of the tanks, soil borings were drilled and 14 groundwater monitoring wells were installed to characterize the lateral and vertical extents of soil and groundwater impact ("Problem Assessment Report and Final Remediation Pian," EMCON, December 16, 1992) Residual and dissolved hydrocarbons were detected in the vicinity of the USTs Well MW-1 was damaged and is inaccessible, and well MW-2 was abandoned during overexcavation activities In October 1993, EMCON performed a soil vapor extraction (SVE) test ("Problem Assessment Report and Final Remediation Plan," EMCON, December 16, 1992) Results of the test indicated that soil remediation using SVE was feasible In December 1994, a remediation system, consisting of an Environmental Instruments 250-cubic-foot-per- minute thermal oxidizer was permitted, installed, and started up The system operated until 1996 GROUNDWATER MONITORING. SEPTEMBER/OCTOBER 1998 On September 14, 1998, a Pinnacle technician measured depths to groundwater and performed subjective analyses of groundwater from monitoring wells MW-9 through MW-11 In addition, on October 9, 1998, the depth to groundwater was measured and groundwater samples were collected from monitoring wells AS-1 and MW-14 for laboratory analyses Well MW-9 was partially obstructed and well purging could not be performed, therefore, a groundwater grab sample was collected Wells MW-3 through MW-5 were dry during the site visit Floating product was not observed in any of the monitoring wells Sampling results and groundwater gradient are shown on Figures 2 and 3 Pinnacle's sampling and analysis procedures are presented in Appendix A The surveyed elevations and the depth to groundwater measurements, summarized in Table 2, were used to evaluate the flow direction beneath the site The flow direction on September 14 and October 9, 1998, was toward the northeast with a hydraulic gradient of 0 002 (see Figures 2) Groundwater elevations increased approximately 8 38 feet from the previous sampling event (May 17, 1996) in wells MW-9 through MW-14 CP1E\TEICHERTIQTRLYISTOCK-GW DOC-95Vsg 1