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Departrnent of Toxic Substances Control Edwin F. Lowry, Director 8800 Cal Center Drive Winston H. Hickox Sacramento, California 95826-3200 Gray Davis Agency Secretary Governor California Environmental Protection Agency LR- D.MIHALOVICH IVL=D August 5, 2002 aw,t,�,��, 7 2002 Mr. Bryan Turner Chevron Environmental Management Company 6001 Bollinger Canyon Road San Ramon, California 94583 REVIEW OF THE OCTOBER 4, 2001 RESULTS OF THE UPDATED HUMAN HEALTH SCREENING RISK EVALUATION, POMBO PROPERTY(Report), AND THE MAY 9, 2002 RESPONSE TO COMMENTS-JANUARY2, 2002 LETTER (Letter), POMBO PROPERTY Dear Mr. Turner: The Department of Toxic Substances Control (DTSC) has completed its review of the subject Report and Letter for the Old Valley Pipeline (OVP), Pombo Property, prepared by Geomatrix Consultants and submitted by Chevron. Previously DTSC reviewed and (� commented on the Soil And Groundwater Investigation And Screening Health Risk Assessment Of The Old Valley Pipeline Right-Of-Way. The subject documents were submitted in response to additional Regional Water Quality Control Board requirements and a meeting held between DTSC, Chevron, and Geomatrix staff on April 22, 2002. The subject Report and Letter were reviewed by Karen W. DiBiasio, PH.D, and DTSC Staff Toxicologist (see enclosed internal memorandum dated July 11, 2002). The Report was reviewed for technical accuracy and validity with respect to the OVP- focused screening level risk assessment. The internal memorandum concludes that while the total risk for the focussed screening level risk assessment is in excess of the benchmark target of 1 x 10-6, it falls within the acceptable risk range of 1 x 10-¢ to 1 x lo-6. The current land use is acceptable within this risk range provided that a land use covenant (i.e. deed restriction) is applied to the site. This risk range would be unacceptable should the current land use designation change from commercial or industrial to residential or unrestricted. If a change in land use is necessary, DTSC would require further characterization, risk assessment and remediation at the site. This work could be accomplished under a follow-up Voluntary Cleanup Agreement. The energy challenge facing Ca;ifornia is real. Every caiifornian needs to take,immediate action to reduce energy consumption. For a list ofsimple ways you can reduce demand and cut your energy costs,see our Web-site at ww•wdtsc.ca.gov. © Printed on Recycled Paper V '