SITE INFORMATION AND CORRESPONDENCE_FILE 1

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r • -4 r d f ! Mr. Don O. Culbertson November 3, 1995 Page 2 Document Reviewed We reviewed the human health risk assessment portion of the document titled "Revised Screening Health Risk Assessment, Dividend Property, Tracy, California" prepared by Geomatrix Consultants for Chevron Pipe Line Co. and Texaco Trading& Transportation, Inc. dated September 28, 1995. Comments - 1. Most of the concerns raised by OSA in our July 19, 1995 memo have been adequately addressed in the revised screening health risk assessment. 2. In the August 28, 1995 meeting it was agreed that additional soil gas information would be incorporated. The revised screening health risk assessment does not contain any site maps and tables to specifically identify locations sampled and levels detected. However, it is our understanding that the soil gas sample locations are identical to the soil boring locations in Figure 2, and that the analyses were limited to PID readings of organic vapors. Since the PID readings lack precision in quantitation, the data included in the text are reported either as within a specific range of quantitation, or as non-detect. Additional text was incorporated discussing the non-specific nature of the PID readings and the potential degradation products from weathered crude oil; we recommend including interpretations of the chromatograms in Appendix C with respect to potential chemicals being detected by the PID in the soil gas survey. 3. In Appendix D the tables and appendices cited were not updated to agree with the designations in the revised risk assessment. Conclusions We agree with the conclusions in the screening health risk assessment. The results indicate that exposures by potential future on-site residents to levels of chemicals currently in soil or groundwater result in risks and hazards less than the acceptable benchmark levels of 1 x 10-6 and 1, respectively. If any changes are made in the document they should be clearly identified. This may be done in several ways: by submitting revised pages with the reason for the changes noted, by the use of strikeout and underline, or by the use of shading and italics. A cover letter stating how each of the above comments has been addressed may be included to further clarify changes made in the document. Any changes in the document that are not made in response to the reviewers comments should be identified and the reason for the changes clearly specified.