SITE INFORMATION AND CORRESPONDENCE

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- - - Jerry Lile December 10, 2003 Page 2 northwest. Petroleum sheen has been reported in grab groundwater samples. DOCUMENTS REVIEWED We reviewed the August 2002, `Health Risk Screening Evaluation, Sudand Homes Property, Tracy, Califomia"and the August 1998 `Soil and Groundwater Investigation and Site Status Report, Surland Homes Property, Tracy, Califomia" prepared for Chevron by Geomatrix Consultants, Inc. in Oakland, CA and San Francisco, CA, respectively. SCOPE OF REVIEW The-document was reviewed for technical accuracy and validity of the human health screening-level risk evaluation for releases from the OVP onto the Surland Homes property. Site characterization data was reviewed to a limited extent, to determine adequacy with respect to use in a screening-level human health risk appraisal. Sampling details, analytical methodology, and technical approach were evaluated. The screening-level human health risk appraisal was evaluated for consistency with DTSC guidance and technical accuracy and validity. Neither the screening-level risk assessment, nor HERD's review, is reflective of the potential risks from any other potential or actual sources of release on the Suriand Homes property. Furthermore, releases from the OVP that have migrated off the Surland Homes property, particularly via groundwater, were not included in the scope of the risk appraisal or HERD's review of the document. GENERAL COMMENTS 1. HERD disagrees with the conclusion that no further action is required. There are not sufficient data to support a risk-based no further action declaration. Soil and groundwater data demonstrate impacts by petroleum contamination; however the data are not sufficient to draw conclusions regarding potential human health risks. 2. The screening-level human health risk appraisal was generally conducted as per DTSC guidance. The conceptual site model, exposure pathways, exposure parameters, potentially exposed populations, exposure scenarios, toxicity criteria, calculations of exposure point concentrations and intakes, and risk characterization were all evaluated and determined to be in accordance with DTSC's recommendations, except as noted below. SPECIFIC COMMENTS - Site Characterization: 1. The location of the pipelines, or former pipelines, need to be depicted in the maps. Include in the text the information regarding the depths of the OVP and APL, whether each is in place or removed, and if removed please specify the source of backfill used.