ARCHIVED REPORTS_XR0004020 - Laserfiche WebLink

Home Browse Search

Mr Travis Bryant February 11, 2002 Page 3 ProjectNo 2002-1426-01 Historical and fourth quarter 2001 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 sample collected from monitoring well MW-2 at 66 micrograms per liter (µg/L) BTEX, MTBE, TBA, ETBE, TAME, DIPE, and 1,2-DCA were not detected in either of the groundwater samples, 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 Only TPHG was detected in the sample collected from well MW-2 at a concentration dust above laboratory method reporting limit (66 µg/L) Petroleum hydrocarbons or fuel oxygenates were not detected in the sample collected from well MW-1 To date, a total of three soil bonngs (B1/VW-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 µg/L, and total xylenes at 2 7 µg/L) Benzene concentrations in six other water samples collected between 40 and 116 bgs in bonngs 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 (fourth quarter 2001) 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 of the site over the past 3 years, and in the analytical results of soil and groundwater samples collected during the May 2000 site investigation, Stratus is recommending that the site be considered for closure and requests authorization to proceed with preparation of California Regional Water Quality Control Board (CRWQCB) Appendix B documentation • P 11 B C1Stockton\Qrt1y\200111BC Stockton-4Q01 doe 5TRATU