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f <br /> Mr Travis Bryant July 31, 2002 <br /> Page 3 Project No 2002-1426-01 <br /> ether (RIPE), ethyl tertiary butyl ether (ETBE), and 1,2-dichloroethane (1,2-DCA) using USEPA <br /> Method SW8260B <br /> Historical and second quarter 2002 groundwater analytical data are summarized in Tables 1 <br /> and 2 Certified analytical reports and chain-of-custody records are included in Appendix C <br /> TPHG (57 µg/1) and TBA (12 µg/1) were detected in the sample collected from well MW-2 <br /> Petroleum hydrocarbons or fuel oxygenates were not detected in the sample collected from well <br /> MW-1 <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Concentrations of petroleum hydrocarbons in the monitoring wells have decreased since <br /> groundwater monitoring was initiated in 1997 Concentrations of TPHG and TBA detected in <br /> the groundwater sample collected from well MW-2 were dust above laboratory reporting limits <br /> BTEX, MTBE, ETBE, TAME, or DIPE were not detected in either of the groundwater samples, <br /> consistent with previous sampling events <br /> To date, a total of three soil borings (BINW-1, B2/MW-1, and B3/MW-2), and two CPT <br /> borings (B-4/CPT-1 and B-5/CPT-2) have been advanced at the site A total of seven water <br />. samples and eleven soil samples were collected and analyzed during the CPT investigation <br /> conducted in May 2000 Fuel oxygenates were not detected in any of the soil or groundwater <br /> samples collected during the investigation TPHG was detected in soil samples (boring B-4) <br /> collected from 21, 49, and 64 feet bgs at concentrations dust above laboratory method reporting <br /> limits TPHG was detected in only two of the grab groundwater samples at concentrations of <br /> 0 057 milligrams per liter (mg/L) and 1 8 mg/L One groundwater sample collected from boring <br /> B-5 (at 85 feet bgs) contained concentrations of BTEX constituents (benzene at 580 µg/L, <br /> toluene at 4 6 �tg/L, and total xylenes at 2 7 µg/L) Benzene concentrations in six other water <br /> samples collected between 40 and 116 bgs in borings B-4 and B-5 were below 17 µg/L The <br /> increase in concentrations of TPHG, benzene, toluene, and xylenes at 85 feet bgs possibly <br /> suggests that petroleum hydrocarbons have migrated beneath the site at this depth from an offsite <br /> source <br /> It is our understanding that the groundwater flow direction in the vicinity of Charter Way and <br /> Lincoln Street has generally been towards the east-northeast and east-southeast at a low gradient <br /> Given a similar flow direction beneath the IBC facility, well MW-2 is located downgradient of <br /> the former IBC UST tank pit Concentrations of TPHG detected in groundwater samples <br /> collected from well MW-2 show declining trends and are currently just above laboratory method j <br /> reporting limits (second quarter 2002) In addition, benzene has not been detected in samples <br /> collected from well MW-2 since third quarter 1999 Based on the low concentrations of <br /> dissolved petroleum hydrocarbons detected in groundwater samples during quarterly monitoring <br /> of the site over the past 3 years, and in the analytical results of soil and groundwater samples j <br /> collected during the May 2000 site investigation, Stratus is recommending that the site be <br />�l considered for closure and requests authorization to proceed with preparation of California <br /> Regional Water Quality Control Board (CRWQCB) Appendix B documentation <br /> P 1113 C\Stockton\Qrt1y1200211BC Stockton-2Q02 doe 57RAT'U5 <br />