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Mr George Takemort Project OF90-002 05 August 15, 1996 Page 2 gasoline (TPHG) were not detected to 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 to any of the confim-natton soil samples collected during this overexcavatton 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 Plan,"EMCON, December 16, 1992) Residual and dissolved hydrocarbons were detected to 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 • �l19�T E�? S��:.?� ��:��5 EMCON researched well locations within a 112-mile radius of the site at the State Department of Water Resources (DWR) Information obtained at the DWR identified three industrial wells, three domestic wells, and two municipal wells near the site Information from these wells is presented to Table 1, and well locations are depicted on Figure 1 The nearest well is a municipal well located approximately 1,200 feet northwest of the site LOCAL AND REGIONAL HYDROGEOLOGY During dnlhng activities, groundwater was encountered at approximately 39 feet bgs Depth to static groundwater has fluctuated from 39 feet bgs to 80 feet bgs during the last 8 years EMCON used the surveyed elevations and the depth to groundwater measurements (see Table 2) to evaluate the groundwater gradient The direction of groundwater flow has varied from southeast to northeast GROUNDWATER MONITORING. SECOND QUARTER 9996 On April 16 and May 17, 1996, a technician from EMCON measured depths to groundwater and performed subjective analyses of groundwater from monitoring wells SACNN\PJftF9MF900020 SAS 95Vw 1