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T r, • Mr Travis Bryant Project 792759 01000000 October 14, 1999 Page 2 east and northeast The primary hydrocarbon constituent detected in groundwater is 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: THIRD QUARTER 1999 On August 18, 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 analysts procedures are presented in Appendix A At the time of the monitoring event, groundwater levels were 19 35 and 19 57 feet below ground surface in wells MW-1 and MW-2, respectively These levels are approximately 101 feet lower than the May 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 (]rPHG) DHS/LUFT, for benzene, toluene, ethylbenzene, and total xylenes (BTEK), 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 TPHG, benzene, toluene, ethylben7ene, and total xylenes concentrations in MW-1/MW-2 were 68 3/124 micrograms per liter (µg/L), 178/2 0 µg/L, <0 510 585 [,g/L, <0 5/0 929 µg/L, and 0 961/0 748 µg/L, respectively MTBE was below laboratory detection limits in • wells MW-1 and MW-2. Results of laboratory analyses are presented in Tables 1 and 2 CP\C\Archive\TBCUI3C-Stkn\QtrlyISTKNQ399 doc-99%g I IT Corporation