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• Mr. George Takemori Project OF90-002.07 <br /> April 30, 1999 <br /> Page 2 <br /> contained detectable concentrations of benzene, toluene, ethylbenzene, and xylenes <br /> (BTEX); however, BTEX was not detected in the other sample. Total petroleum <br /> hydrocarbons as gasoline (TPHG) were not detected in either sample. In September 1988, <br /> the area was overexcavated. Confirmation soil samples were collected from the bottom of <br /> the excavation. Petroleum hydrocarbons were not detected in any of the confirmation soil <br /> samples collected during this overexcavation activity. <br /> Between December 1987 and December 1994, following the removal of the tanks, soil <br /> borings were drilled and 14 groundwater monitoring wells were installed to characterize the <br /> lateral and vertical extents of soil and groundwater impact ("Problem Assessment Report <br /> and Final Remediation Plan," EMCON, December 16, 1992). Residual and dissolved <br /> hydrocarbons were detected in the vicinity of the USTs. Well MW-1 was damaged and is <br /> inaccessible, and well MW-2 was abandoned during overexcavation activities. <br /> In October 1993, EMCON performed a soil vapor extraction (SVE) test ("Problem <br /> Assessment Report and Final Remediation Plan," EMCON, December 16, 1992). Results <br /> of the test indicated that soil remediation using SVE was feasible. In December 1994, a <br /> remediation system, consisting of an Environmental Instruments 250-cubic-foot-per- <br /> minute thermal oxidizer was permitted, installed, and started up. The system operated <br /> until 1996. <br /> GROUNDWATER MON3TORING: MARCH 1999 <br /> On March 16, 1999, a Pinnacle technician measured depths to groundwater and <br /> performed subjective analyses of groundwater from monitoring wells MW-9 through <br /> MW-11. Floating product was not observed in any of the monitoring wells. Sampling <br /> results and groundwater gradient are shown on Figures 2 and 3. Pinnacle's sampling and <br /> analysis procedures are presented in Appendix A. <br /> The surveyed elevations and the depth to groundwater measurements, summarized in <br /> Table 2, were used to evaluate the flow direction beneath the site. The flow direction on <br /> March 16, 1999 was toward the southwest with a hydraulic gradient of 0.0016 ft/ft(see <br /> Figures 2). Groundwater elevations increased approximately 4.7 feet from the previous <br /> sampling event (September 14 and October 9, 1998) in wells MW-3 through MW-5 and <br /> MW-9 through MW-14. <br /> CPIE:\TEICIIERT1STOCKTOMQTRLYISTKNQ 199.DOC-9511sg:I �ioftiLGiC�E <br />