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►° t Mr Travis Bryant Project 792759 December 22, 1999 Page 2 gasoline The groundwater plume has not been delineated, but it extends downgradient (eastward) as far as Van Buren Street On February 25, 1997, an EMCON geologist observed V&W Drilling, Inc , of Rio Vista, California, drill three vertical soil borings (B-1, B-2, and B-3) Soil boring B-1 was converted to vapor extraction well VW-1, and borings B-2 and B-3 were converted to groundwater monitoring wells MW-1 and MW-2, respectively Residual hydrocarbons were detected in soil samples collected from borings B-1 through B-3 The highest concentrations were detected in soil boring B-1, drilled beneath the former UST Residual petroleum hydrocarbons were not detected in the vadose zone (0 to 215 feet below ground surface) soil borings B-2 and B-3, but were detected in the saturated zone Analytical results of groundwater indicated dissolved hydrocarbons were detected in monitoring wells MW-1 and MW-2 (EMCON, August 4, 1997) TPHG was detected in monitoring wells MW-1 and MW-2 at concentrations of 18,000 parts per billion (ppb) and 220 ppb, respectively Benzene was detected in monitoring wells MW-1 and MW-2 at concentrations of 4,400 and 33 ppb, respectively • GROUNDWATER MONITORING. FOURTH QUARTER 1999 On November 5, 1999, an IT technician was on site to measure depths to groundwater and collect groundwater samples from wells MW-1 and MW-2 for subjective and laboratory analyses Floating product was not observed in groundwater monitoring wells (see Table 1) IT's sampling and analysis procedures are presented in Appendix A- At the time of the monitoring event, groundwater levels were 2014 and 20 44 feet below ground surface in wells MW-1 and MW-2, respectively These levels are approximately 0 83 foot lower than the August 1999 monitoring event levels Groundwater samples were collected from monitoring wells MW-1 and MW-2 and were analyzed at Sequoia Analytical in Sacramento, California The groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPHG) DHS/LUFT, for benzene, toluene, ethylbenzene, and total xylenes (BTEX), and methyl tertiary butyl ether (MTBE) using USEPA Method 8020 Copies of the chain-of-custody records and laboratory analysis reports are presented in Appendix B Benzene, toluene, ethylbenzene, and total xylenes and MTBE were below laboratory detection limits in wells MW-1 and MW-2 TPHG was detected in wells MW-1 and MW-2 at concentrations of 65 7 micrograms per liter (µg/L) and 112 µg/L, respectively Results of laboratory analyses are presented in Tables 1 and 2 • CP\C\Archrve\IBC\IBC-Stkn\QtrlyISTKNQ499 doc 98Vsg I IT Corporation