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Mr. C.Dean Hubbard • • <br /> California Regional Water Quality Control Board Central Valley Region <br /> September 17,2004 <br /> Page 3 <br /> Based on site data(the presence of impacted groundwater), the RWQCB has been and continues to be <br /> the lead regulatory agency for this site. On certain HPP sites, OEHHA or DTSC provide support to <br /> the RWQCB regarding the evaluation of potential human health risks associated with the residual <br /> crude oil remaining onsite. At this site,we believe OEHHA provided the appropriate technical <br /> review. <br /> Acceptable Risks <br /> Mr.Schaff characterized ChevronTexaco's position as"claiming that onsite risks are acceptable". <br /> In Geomatrix's February 26,2002 addendum submitted to OEHHA,they stated that the"potential <br /> risk to a future on-site resident is 2x10'5 in the GP-3 area and 7x10'6 in the Pipeline Area, within the <br /> acceptable risk range of 1x10-0 and 1x106. Hazard indexes for both areas were below an acceptable <br /> level of 1." In general,OEHHA agreed with the Geomatrix assessment,but clarified that the range of <br /> 10'4 to 10-6 is not necessarily an acceptable risk range but risks within this range are "....within the <br /> range of risk management, wherein other factors, along with risk, may be used to determine the <br /> acceptability of the risk." <br /> Any decision about risk management must be made within the context of potential future land use of <br /> the site, specifically in areas were the theoretical excess cancer risk is between 10-4 and 10-6. <br /> Overexcavation of Soil <br /> Mr.Scharff stated that the Hoffman Brothers "previously requested that Chevron remove and over- <br /> excavate the soil in areas where it poses excess risks, at levels in excess of 105. However, Chevron <br /> has not responded." <br /> ChevronTexaco does not believe this is an effective environmental management strategy for the site <br /> considering that OEHHA accepted the human health risk evaluation conducted for the site. <br /> In summary, ChevronTexaco is willing to cooperate with the RWQCB and the Hoffman Brothers to <br /> obtain no further action status for the site. <br /> If you have any questions or require additional information,please call either Bella Bakrania of SAIC <br /> at(925) 842-1343 or me at(925) 842-1804. <br /> Sincerely, <br /> M. Scott Mansholt <br /> Enclosures(chronological): <br /> OEHHA,2002,Response to Comments on the Health Risk Assessment,Former Lyoth Loading <br /> Station,Tracy,California,April 18. <br /> RWQCB,2003, Semiannual 2003 Groundwater Monitoring Report(January—June),Lyoth Loading <br /> Station,Tracy San Joaquin County,July 15. <br /> Scharff,Jeffory J.,2004,Letter to RWQCB and OEHHA,RE: Lyoth Loading Station,Tracy, San <br /> Joaquin County,May 7. <br /> Scharff,Jeffory J.,2004,Letter to ChevronTexaco Environmental Management Company,RE: <br /> Hoffman Brothers Trucking,Tracy, San Joaquin County, September 8. <br />