SITE INFORMATION AND CORRESPONDENCE

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M. Scott Mansholt - 3 - 18 November 2009 Vernalis Offsite NFAR environmental screening levels were not exceeded for Site COPCs attributable to historical crude oil pipeline leaks, and the site is a candidate for no further action determination. Based review of the reports, Central Valley Water Board staff finds that: • Data indicate that use of the historical crude oil pipelines ceased over 30 years ago. • According to the report findings, Central Valley Water Board staff concur that the extent of impacted soil and groundwater is limited in extent and has been delineated. • Central Valley Water Board staff concurs with the summary provided in the No Further Action Required Request for Vernalis Offsite and that the Site is a candidate for closure. Previously, SAIC assessed available cleanup technologies and various remedial alternatives for residual crude oil in soil and groundwater at OVP/TAOC projects. The assessment summarized that residual weathered crude oil is highly viscous, relatively immobile, and primarily occurs within low permeability soil found at the Site. Existing Site conditions limit most forms of remediation such as passive in-well recovery, pumping and extraction, and/or excavation. SAIC determined the low permeability soil generally limits the migration of the degraded crude oil in the subsurface. SAIC concluded that affected soil/groundwater has been delineated and in-place management of residual crude oil by natural attenuation is cost effective, feasible, and easily implemented. Concentrations of petroleum hydrocarbons will reduce with time. Based on the alternative cleanup technological assessment and consistent with State Water Resources Control Board Resolution No. 92-049, SAIC concluded there is no known feasible cost effective means, or easily implemented practical process to effectively remove the petroleum hydrocarbons identified on the Site. Future use of Site groundwater is not anticipated due to low yield, poor quality, and the availability of nearby existing water supplies. The Central Valley Water Board is required to provide the public the opportunity to comment on closure decisions under state law (including Health and Safety Code 25356.1). Central Valley Water Board staff will be notifying nearby landowners, residents, and occupants of closure cases we oversee. Pursuant to Section 2728 of the California Code of Regulations, Title 23, Division 3, Chapter 16, the Central Valley Water Board requests that Chevron conduct a property and offsite property owner survey (Survey). The Survey should determine: a) all properties overlying soil and groundwater determined to have been impacted by the historical pipelines' release and b) adjacent properties within a 200-foot radius of the impacted areas delineated at the Site. Upon completion of the Survey, submit a table or spreadsheet listing property owner names and mailing addresses, business and residence mailing addresses, and assessors' parcel numbers and a corresponding map(s).