ARCHIVED REPORTS HUMAN HEALTH SCREENING EVALUATION

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1 HUMAN HEALTH SCREENING EVALUATION SURLAND HOMES—BRIDLE CREEK 1. INTRODUCTION This report presents the results of a Human Health Screening Evaluation (HHSE) performed by ' Science Applications International Corporation (SAIC) for the Surland Homes—Bridle Creek property (the site), in Tracy, California(see Figure 1). SAIC performed this HHSE on behalf of Chevron Environmental Management Company (CEMC), and at the request of the California Environmental Protection Agency (Cal/EPA) Department of Toxic Substances Control (DTSC). The Regional Water Quality Control Board (RWQCB)—Central Valley Region is the lead regulatory agency for environmental issues relating to former crude-oil pipeline operations for the site; however, HHSEs are typically evaluated by the DTSC. This HHSE has been prepared as outlined in a 2006 work plan prepared by SAIC (SAIC, 2006) and submitted to the DTSC. ' The work plan included responses to comments contained in a DTSC letter dated December 19, 2003 (DTSC, 2003), commenting on the 2002 Health Risk Screening Evaluation (HRSE) prepared for CEMC by Geomatrix Consultants, Inc. (Geomatrix, 2002; see Appendix A). The objective of the HHSE was to determine the potential human health cancer risks and non- cancer health hazards associated with exposure to soil residuals from historic crude-oil pipeline operations for hypothetical future construction and residential land use of the site. The results of the HHSE will be used to develop a remedial strategy for the site, if necessary. This HHSE was developed using approaches and methodology consistent with those presented in the Preliminary I Endangerment Assessment (PEA) Guidance Manual (Cal/EPA DTSC, 1999). It was prepared with data utilized in the initial HHSE prepared by Geomatrix, as well as additional soil data collected by SAIC in 2007. The PEA screening evaluation methodology conforms to standard regulatory human health risk assessment guidelines promulgated by Cai/EPA and the U.S. Environmental Protection Agency (EPA) for the performance of health risk assessments. Evaluating potential risks to human health using the PEA Manual's HHSE procedure is consistent with CEMC's Consistent Technical Approach (CTA; Geomatrix, 2005). It should be noted that the screening evaluation likely overestimates the risks associated with the conditions of the site as the evaluation is based on conservative default assumptions. Default assumptions (i.e., a residential land-use scenario) were used to ensure that the results of the evaluation are protective of human health. If necessary and appropriate, a site-specific human health risk assessment may be performed at a later date to further refine the estimate of potential health risks. This HHSE is being submitted to the DTSC Human and Ecological Risk Division for review and approval under the Voluntary Site Cleanup Program. 1.1 SITE DESCRIPTION The former Old Valley Pipeline (OVP) was operated by Standard Oil of California, and was located along the southern edge of the Union Pacific Railroad Company (UPRR) right of way (ROW), which lies immediately north of Byron Road and immediately south of the Laurelbrook residential subdivision. UPRR acquired the Southern Pacific Railroad (SPRR), and certain maps From Science to Solutions