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HUMAN HEALTH SCREENING EVALUATION <br /> US CAN—WELTY ROAD <br /> 1. INTRODUCTION <br /> SAIC Energy, Environment&Infrastructure, LLC (SAIC)performed this Human Health <br /> Screening Evaluation(HHSE) for the US Can—Welty Road site (the Site) located in Vernalis, <br /> San Joaquin County, California(Figure 1), on behalf of Chevron Environmental Management <br /> Company(CEMC). <br /> The Central Valley Regional Water Quality Control Board(RWQCB)is the lead regulatory <br /> agency for environmental issues related to former crude-oil pipelines at the Site. SAIC and <br /> others conducted soil and groundwater investigations at the Site to delineate the extent of <br /> affected soil and groundwater related to the former Old Valley Pipeline (OVP) and Tidewater <br /> Associated Oil Company(TAOC)pipelines. The former OVP system and former TAOC <br /> pipeline system are collectively referred to as the CEMC Historical Pipeline Portfolio— <br /> Bakersfield to Richmond(HPP-BTR). In an April 2011 letter, the Central Valley RWQCB <br /> agreed that the extent of petroleum-affected soil and groundwater were delineated, and requested <br /> ' that a human health risk assessment be submitted(Central Valley RWQCB, 2011; Appendix A). <br /> SAIC estimated potential human health cancer risks, non-cancer human health hazards, and <br /> potential threat to sensitive ecological receptors associated with exposure to on-site soils, soil <br /> vapor, and groundwater residuals from historical crude-oil pipeline operations. SAIC developed <br /> this HHSE using approaches and methodology consistent with those presented in the Preliminary <br /> Endangerment Assessment(PEA) Guidance Manual (California Environmental Protection <br /> Agency [Cal/EPA] Department of Toxic Substances Control [DTSC], 1999), and the Vapor <br /> Intrusion Guidance (DTSC and Cal/EPA, 2004). <br /> ' The methodology presented in both the PEA Guidance Manual and the Vapor Intrusion <br /> Guidance conform to standard regulatory human health risk assessment guidelines promulgated <br /> by Cal/EPA and the United States Environmental Protection Agency(EPA) for performing <br /> health risk assessments. Evaluating potential risks to human health using the procedures in both <br /> guidance documents is consistent with CEMC's Consistent Technical Approach(CTA)prepared <br /> by Geomatrix Consultants, Inc. (Geomatrix, 2005). It should be noted that the screening <br /> evaluation likely overestimates risks associated with the conditions at the Site, as the evaluation <br /> is based on conservative default assumptions. SAIC used default assumptions (i.e., a future <br /> residential land-use scenario)to ensure that the results of the evaluation are protective of human <br /> health. <br /> 1.1 SYNOPSIS <br /> SAIC evaluated cancer risks and non-cancer hazards from exposure to constituents of potential <br /> concern(COPCs) in soil and groundwater in a residential land-use scenario, and the potential for <br /> ' exposure of sensitive ecological receptors to COPCs at the Site. The results of this HHSE <br /> indicate that the lifetime cancer risk at the Site is 2E-06,within and at the lower end of the risk <br /> management range of 1E-06 to IE-04 established by Cal/EPA and EPA. Potential non-cancer <br /> health hazards are below the de minimis levels. Therefore, the Site does not appear to pose a <br /> health risk to potential residents or an environmental risk to sensitive receptors, and therefore no <br /> further action is required with respect to on-site soil and groundwater. <br /> 1 <br /> SAIC <br />