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0 0 <br /> Scott Mansholt -2- 5 November 2003 <br /> ChevronTexaco <br /> Surland Homes Property <br /> Department of Toxic Substances Control (DTSC) office for review and comment. DTSC's comments have <br /> not yet been received for review by Regional Board staff. <br /> According to the reports, the majority of residual petroleum hydrocarbons, TPH-c, ethylbenzene, total <br /> xylenes, and select polynuclear aromatic hydrocarbons (PAHs) in soil were observed at depths between 6 and <br /> 9.5 feet below ground surface (bgs). Shallow soils less than six feet were not visually affected. <br /> Low concentrations of TPH-g, TPH-d, toluene, ethylbenzene, total xylenes, and select PAHs were detected in <br /> groundwater samples. Depth to groundwater is approximately 5 to 7 feet bgs and flows generally north- <br /> northwest. <br /> THIRD QUARTER 2003 MONITORING <br /> During the Third Quarter Sampling and Monitoring event in September 2003, TPH-d was detected at 88 µg/L <br /> in one groundwater sample, less than the 100-pg/L taste and odor water quality objective (WQO) for TPH-d. <br /> The remaining petroleum hydrocarbon constituents of concern were not detected for the respective chemicals <br /> tested in both monitoring wells. The analytical results for this quarter are consistent with previous sampling <br /> events where TPH-d did not exceed the WQO and/or was less than the method detection limit of<50 pg/L. <br /> In the quarterly report, SAIC concluded that the TPH-d remaining in the groundwater plume does not exceed <br /> the WQO for diesel, is stable, limited in extent, and No Further Action (NFA) should be granted for the site. <br /> SUMMARY <br /> Regional Board staff concurs with the reports' findings that the lateral and vertical extent of soil impacted by <br /> petroleum hydrocarbons has been adequately characterized. We also concur that the groundwater plume <br /> appears to be limited in extent, is stable, and meets the criteria for closure in accordance with the draft <br /> Regional Board "Low Risk Criteria", Appendix B —No Further Action Requests (1996, updated September <br /> 2001). However, as of this date, DTSC comments to the 22 August 2002 HSE report have not been <br /> provided to our office for review and comment. Regional Board staff cannot make a final determination <br /> about an NFA for the site until the DTSC completes their review of the human health risk assessment. <br /> If you have any questions or comments, please contact Dean Hubbard at (559) 445-5179. <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Associate Engineering Geologist <br /> RG No. 6357 <br /> cc: Mr. Michael Infurna, San Joaquin County Environmental Health, Stockton <br /> Mr. Gary Foote, Geomatrix, Oakland <br /> Mr. Luis Mercado, SAIC, Sacramento <br /> Mr. Ed Griswold, Surland Homes, Tracy <br />