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• Mr Travis Bryant May 6, 2002 Page 3 Project No 2002-1426-01 (MTBE), tertiary amyl methyl ether (TAME), tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tertiary butyl ether (ETBE), and 1,2-dichloroethane (1,2-DCA) using USEPA Method 8260B Historical and first quarter 2002 groundwater analytical data are summarized in Tables 1 and 2 Certified analytical reports and chain-of-custody records are included in Appendix C TPHG was detected in the groundwater samples collected from monitoring wells MW-1 (87 micrograms per liter [µg/L]) and MW-2 (71 gg/L) TBA (24 µg/L) was detected in the sample collected from monitoring well MW-2 BTEX, MTBE, ETBE, TAME, or DIPE were not detected in either of the groundwater samples These data are consistent with previous monitoring events CONCLUSIONS AND RECOMMENDATIONS Concentrations of petroleum hydrocarbons in the monitoring wells have decreased since groundwater monitoring was initiated in 1997 Concentrations of TPHG and TBA detected in the groundwater samples were dust above laboratory reporting limits BTEX, MTBE, ETBE, TAME, or DIPE were not detected in either of the groundwater samples, consistent with previous sampling events To date, a total of three soil borings (BINW-1, B2/MW-1, and B3/MW-2), and two CPT borings (B-4/CPT-1 and B-5/CPT-2) have been advanced at the site A total of seven water samples and eleven soil samples were collected and analyzed during the CPT investigation conducted in May 2000 Fuel oxygenates were not detected in any of the soil or groundwater samples collected during the investigation TPHG was detected In soil samples (boring B-4) collected from 21, 49, and 64 feet bgs at concentrations dust above laboratory method reporting limits TPHG was detected in only two of the grab groundwater samples at concentrations of 0 057 milligrams per liter (mg/L) and 1 8 mg/L One groundwater sample collected from boring B-5 (at 85 feet bgs) contained concentrations of BTEX constituents (benzene at 580 µg/L, toluene at 4 6 gg/L, and total xylenes at 2 7 gg/L) Benzene concentrations in six other water samples collected between 40 and 116 bgs in borings B-4 and B-5 were below 17 µg/L The increase in concentrations of TPHG, benzene, toluene, and xylenes at 85 feet bgs possibly suggests that petroleum hydrocarbons have migrated beneath the site at this depth from an offsite source It is our understanding that the groundwater flow direction in the vicinity of Charter Way and Lincoln Street has generally been towards the east-northeast and east-southeast at a low gradient Given a similar flow direction beneath the IBC facility, well MW-2 is located downgradient of the former IBC UST tank pit Concentrations of TPHG detected in groundwater samples collected from well MW-2 show declining trends and are currently dust above laboratory method reporting limits (first quarter 2002) In addition, benzene has not been detected in samples collected from well MW-2 since third quarter 1999 Based on the low concentrations of dissolved petroleum hydrocarbons detected in groundwater samples during quarterly monitoring P 1I B C\StocktonlQrtly120021IBC Stockton-1Q02 doc 57RAW5 r