SITE INFORMATION AND CORRESPONDENCE

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Michael Oliphant -3.- 8 May 2012 HHSE— US Can-Welty Road, . .,,nalis approximately 32 to 38 feet logs. It is unlikely groundwater wells would be installed at the Site, therefore, the direct exposure route is considered incomplete. Health risks and hazards for potential residential exposure to onsite groundwater were not evaluated quantitatively. • The California Natural Diversity Database, 2011, maintained by California Department of Fish and Game, was reviewed to search for threatened, endangered, or sensitive species in the vicinity of the Site. Six threatened and endangered species sightings were listed in the vicinity. However, there were no sightings within one-mile of the Site; the closest was 1.6 miles to the northwest. In summary, SAIC's report determined that the potential cancer risk to a potential future resident was 2E-06, which is within the range of risk management of 1 E-06 to 1 E-04. The non-cancer health hazard, of 0.02 is below the de minimus level of 1 which is a conservative estimate of risk. This level of cancer risk and non-cancer health hazard exposure to onsite soils does not present an unacceptable risk to hypothetical future onsite residents. Based on my review, I have the following comments: • Consistent with other TAOC/OVP sites, a Soil and Groundwater Management Plan (SGMP) needs to be submitted. The SGMP designates Chevron as the responsible party and serves as a guideline for Chevron to implement for handling soil and/or groundwater affected by degraded crude oil that may be encountered during future Site activities. • The areas of crude oil affected soil/groundwater are present within/beneath the Highway 33 easement, UPRR tracks, and active pipelines corridor, and large structures with paved surfaces. It is unlikely drinking water wells would be completed at or near these features. • Central Valley Water Board staff concurs with the findings of the HHSE and related supporting documentation, and that the Site is a candidate for closure. A request for a No Further Action Required (NFAR) determination may be prepared. • Documentation to support a NFAR closure determination should be completed in accordance with California Regional Water Quality Control Board, Central Valley Region's 16 April 2004 update to Appendix A of the Tri-Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites - No Further Action Requests. Section 6.5 - NFAR for Cases Exceeding Water Quality Objectives should be followed for documenting Site conditions.