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Mr. C.Dean Hubbard California Regional Water Quality Control Board Central Valley Region September 17,2004 Page 2 and 104 are within range of risk management, wherein otherfactors, along with risk, may be used to evaluate the acceptability of the risk." In Mr. Scharff s letter,there are three specific points that ChevronTexaco would like to address: Additional Investigation Mr. Scharff requests that an additional investigation"to ensure that a full and complete characterization of the potential threat to public health, safety and the environment" is conducted. The RWQCB and OEHHA have not required ChevronTexaco to perform an additional onsite investigation to support the conclusion of the HHRA. The RWQCB and OEHHA have found the investigations performed to date to be sufficient in characterizing the risk from petroleum hydrocarbons remaining onsite. Mr. Scharff has inferred that the RWQCB has,for several months, had an outstanding request for further investigation to delineate the extent of sub-surface crude oil. It appears that Mr. Scharff is referring to a comment in a July 15,2003 letter°from the RWQCB to ChevronTexaco (attached)providing comments on the first semi-annual 2003 groundwater monitoring reports. The RWQCB stated: "Based on previous and current monitoring events, it appears that the extent of impacted groundwater north of MW-1 and MW-6 has not been adequately characterized. ...After reviewing the next semi-annual report and analytical results, we will evaluate the possibility of conducting additional soil and groundwater testing downgradient(northerly)of monitoring wells MW-1 and MW-6." In this letter,the RWQCB is not discussing further characterization within the context of supporting the findings of the HHRA or characterizing the extent of crude oil impacts to soil or groundwater onsite, as Mr. Scharffs letter implies. Rather,the RWQCB's letter indicates that the RWQCB is considering the need for additional characterization of crude oil impacts to groundwater offsite (downgradient of the site). ChevronTexaco is submitting a workplan prepared by Science Applications International Corporation(SAIC)to address the RWQCB's request(attached). Request for RWQCB and DTSC Oversight It appears that Mr. Scharff is requesting regulatory oversight of the site by the RWQCB and Department of Toxic Substances Control(DTSC). The DTSC and the RWQCB have an agreement with ChevronTexaco regarding ChevronTexaco's Historical Pipeline Portfolio (HPP) of projects where the DTSC is the lead agency for"impacted soil only" sites and the RWQCB is the lead for"impacted groundwater" sites. The HPP includes management of property impacted by historical petroleum hydrocarbon releases from legacy ChevronTexaco pipelines. 3 Other factors may include but are not limited to:feasibility of remediation,available technology,and prohibitive cost. RWQCB,2003,Semiannual 2003 Groundwater Monitoring Report(January—June),Lyoth Loading Station, Tracy San Joaquin County letter,July 15. 5 SAIC,2003,Semiannual 2003 Groundwater Monitoring Report(January—June),Lyoth Loading Station, Tracy San Joaquin County,April 29.