SITE INFORMATION AND CORRESPONDENCE

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Human Health Screening Evaluation Former Vernalis Pump Station September 2,2010 1.2 SITE DESCRIPTION The site is situated in a rural and light-industrial area, and is bordered by Welty Road to the west, light-industrial facilities to the north and southeast, residential areas to the east, and agricultural areas to the south and east, beyond the residential area. The former pump station is transected by the San Joaquin/Stanislaus county line and consists of two properties: the Bellini property (formerly known as the Roberts property), San Joaquin County Assessor's Parcel Number(APN) 255-260-03; and the Arcos property, Stanislaus County APN 016-038-003. The Bellini property is on the northwestern part of the site, and the Arcos property is on the southeastern part of the site (Figure 2). The Bellini property(35500 Welty Road) is a triangular-shaped, 5.73-acre partially paved lot where heavy-duty agricultural equipment and transport trailers are staged. The Arcos property is irregularly shaped, and is currently used as a storage facility for equipment and materials. A residence and an office are also located on the Arcos property. The site also extends across the Union Pacific Railroad(UPRR)right of way (ROW), including a portion of Highway 33 and the Schaeffer property(APN 255-260-04). A residence is located on the Schaeffer property. The Vernalis Pump Station operated from 1902 to 1935 as part of the Old Valley Pipeline (OVP) system that transported heated heavy petroleum(crude oil) from the Kern River Oil Fields in and near Bakersfield to the Richmond Refinery. The former OVP was located along the northeastern side of the pump station and parallel to the existing UPRR tracks and Highway 33. Site features included a boiler house, a pump house, a sump, an incinerator, a rubbish pit, cottages, and three bulk-storage tanks with secondary containment structures. These surface structures were located on the Arcos property. The property located immediately southeast of the Arcos property is the former Tidewater Associated Oil Company(TAOC) Ohm Pump Station. Kinder Morgan Energy Partners, L.P. (KM) currently maintains a high-pressure,petroleum- product pipeline near the site that transports gasoline,jet fuel, and diesel. The KM pipeline is located within the UPRR ROW. 1.3 PREVIOUS ENVIRONMENTAL INVESTIGATIONS Several environmental investigations, including groundwater monitoring and sampling, were performed at the site. A summary of site investigation activities and results is provided as Appendix B. 2. EXPOSURE PATHWAYS AND MEDIA OF CONCERN An early step of the HHSE process is to construct a conceptual site model (CSM) for the site. The CSM identifies the on-site contaminant sources, release mechanisms, transport media, exposure pathways, exposure routes, and potential future human receptors associated with the site. SAIC-Benham evaluated the on-site residential land use scenario for this site as required in the PEA Guidance Manual. The CSM for this site is shown on Figure 3. Potentially complete soil-exposure pathways include incidental ingestion of soil, dermal contact with soil, and inhalation of wind-blown dust(for non-volatile constituents) and chemical vapors (for volatile constituents). 2 � The Benham Companies,LLC A Wholly Owned Subsidiary From&mxe to Solanoss