SITE INFORMATION AND CORRESPONDENCE

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Human Health Screening Evaluation Mountain House Development Site#6 January 18,2011 indicate that COPCs at the Site do not pose a significant health risk to potential residents or an environmental risk to sensitive ecological receptors, and therefore no further action is required with respect to on-site soil and groundwater. 1.2 SITE DESCRIPTION The Site is located in an agricultural area bordering the community of Mountain House, in San Joaquin County, California. The Mountain House study area is situated at elevations ranging from approximately 20 to 30 feet above mean sea level in relatively flat-lying areas. The Site is located along a '/2-mile stretch of West Byron Road,between Wicklund Road and West Bethany Road, approximately 3 miles northwest of the City of Tracy (Figure 1). The Site includes ROWS associated with the former OVP and TAOC pipelines. The OVP was installed between 1902 and 1904 as a"hot line" (i.e., the oil was heated to facilitate transmission), and carried San Joaquin Valley crude oil (SJV crude)north from the Kern River Oil Fields (in and near Bakersfield) to the Richmond Refinery. The pipeline and associated pump stations operated from 1903 until the early to mid 1930s. The OVP was again used during the early 1940s to primarily transmit Bunker C fuel oil from the Richmond Refinery to railroad hubs in Tracy. The former OVP alignment at the Site runs along the south side of West Byron Road. The former TAOC alignment at the Site lay within the UPRR ROW, located on the north side of West Byron Road. The TAOC pipeline system was constructed in 1907 and transmitted heavy crude oil from the southern San Joaquin Valley to the Bay Area. For a relatively short time span the pipelines reportedly transmitted a cutter stock with the crude oil between Coalinga and the Bay Area; the cutter stock was used to reduce the viscosity of the oil. The TAOC pipelines were abandoned in the 1970s. Where the pipelines were not abandoned in place, they were removed and the trenches likely backfilled with native soil. Active pipelines in the UPRR ROW include the Kinder Morgan Energy Partners, L.P. (KMEP) pipeline and Chevron Pipe Line Company's Bay Area Products Line (BAPL). The KMEP pipeline reportedly transports gasoline, diesel, and jet fuel. The BAPL reportedly transports gasoline and diesel fuel. The exact KMEP pipeline and BAPL locations have not been identified; therefore, those pipelines are not shown on Figure 2. West Byron Road is currently a two-lane thoroughfare serving southwest San Joaquin County and eastern Contra Costa County between Tracy and the Sacramento River Delta. The Site is located among agricultural areas in and near the community of Mountain House, California. Properties located to the north of West Byron Road are in the Mountain House community, and properties located to the south are in unincorporated San Joaquin County. Nearby development of the area consists of agricultural and light-industrial facilities. Mountain House is a master- planned development where single-family homes are planned or under construction in areas west of the Site. 1.3 PREVIOUS ENVIRONMENTAL INVESTIGATIONS Several environmental investigations were performed at the Site by Condor and SAIC under the direction of, and to the satisfaction of, the Central Valley RWQCB. Impacts from historical crude-oil pipeline operations to on-site soils were characterized and delineated. The Central Valley RWQCB agreed that no further investigation is required at the Site. A summary of site- from SuMnoe to SW"Noas