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• • <br /> Penny T.Fourell -2- 28 February 2003 <br /> ChevronTexaco <br /> Surland Homes <br /> observed on groundwater in the TW-2 well in 1998. Monitoring well TW-3 is downgradient of TW-2. In <br /> the final two quarters of sampling in 2000, TPH-d concentration in both wells was less than the 100 pg/L <br /> taste and odor water quality objective (WQO) for TPH-d. The remaining constituents of concern were less <br /> than the laboratory method detection limits for the respective chemicals tested. <br /> According to the reports, the majority of residual petroleum hydrocarbons present at the site in soil were <br /> found at depths between 4.5 and 13.5 feet bgs. Total petroleum hydrocarbons as crude oil (TPH-c), BTEX <br /> (benzene, toluene, ethylbenzene, and total xylenes), and select polynuclear aromatic hydrocarbons (PAHs) <br /> were detected in soil samples collected from the site. Low concentrations of TPH as gasoline (TPH-g), <br /> TPH-d, toluene, ethylbenzene, xylenes, and select PAHs were detected in groundwater samples. <br /> For the purpose of the HSE, all concentrations detected for each chemical were quantitatively evaluated <br /> and the maximum detected concentration for each chemical was considered as representative. <br /> ChevronTexaco has forwarded a copy of the HSE report to the Department of Toxic Substances Control <br /> (DTSC) office for review and comment. <br /> Additional groundwater monitoring is needed to confirm that TPH-d concentrations are stable (or less <br /> than the WQO for the TPH-d [without silica gel] taste and odor threshold), and/or attenuating. <br /> ChevronTexaco needs to conduct a minimum of one additional quarter of groundwater sampling and <br /> analysis for the remaining two monitoring wells. Analysis should include the constituents of concern <br /> associated with the pipeline leak(s). <br /> By 1 April 2003, please provide a work plan and time schedule for the comments provided above. <br /> Regional Board staff cannot make a final determination about the site until the DTSC completes the <br /> human health risk assessment and the additional groundwater sampling has been conducted. <br /> If you have any questions or comments, please contact Dean Hubbard at (559) 445-5179. <br /> s� �� G;7 o),gL d�00 <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Associate Engineering Geologist <br /> RG No. 6357 <br /> cc: Mr. Ed Griswold, Surland Homes <br /> Mr. Michael Infuma, San Joaquin County Environmental Health, Stockto <br /> Mr. Bryan Turner, Geomatrix Consultants, San Ramon <br /> SLIC/EIChevronTexacaoOVPISurland Homes <br />