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ameO 2.1 OFF SITE SOUTH AREA SETTING The Off Site South Area is centered along Central Avenue. The area west of Central Avenue includes a portion of the former Tracy Rail Yard property south and west of the area previously identified as the Tracy Rail Yard site (Figure 2) and extends south of the HPP alignment. The Off Site South Area east of Central Avenue is the area south of the Tracy Rail Yard site and TAOC pipeline alignment and is transected by the OVP. The majority of the Off Site South Area is currently developed as single family residential housing, with the exception of the area that was formerly part of the Tracy Rail Yard west of Central Avenue. The former TAOC pipeline passed through, or adjacent to, the north of the Off Site South Area in a northwest to southeast alignment as shown on Figure 2. The OVP passed through the Off Site South Area in a northeast-southwest alignment east of Central Avenue. The TAOC and OVP pipeline systems conveyed heated San Joaquin Valley crude oil from oil fields in southern San Joaquin Valley, California, to TAOC refineries in the San Francisco Bay Area. The TAOC pipelines were constructed in 1907, were reportedly operational from 1908 through 1968, and were removed in the early 1970s. Between Coalinga and the Bay Area, TAOC pipelines reportedly transmitted heated heavy crude oil with a cutter stock to reduce the viscosity of the oil. The OVP was installed between 1902 and 1904; the pipeline and associated pump stations operated from 1903 until the early to mid 1930s. The OVP was again used during the early 1940s primarily to transmit Bunker C fuel oil from the Richmond Refinery to railroad hubs in Tracy(such as the site). The OVP was reportedly put out of service in 1970. 2.2 GEOLOGY AND HYDROGEOLOGY ARCADIS advanced four cone penetrometer test (CPT) borings to a depth of approximately 25 feet below ground surface (bgs) at the Off Site South Area west of Central Avenue during previous investigations (CPT-10, CPT-11, CPT-21 and CPT-22). In these borings, lithology generally consisted of clay, silty sand, clayey silt, and sand. A sand unit was observed in three of the borings (CPT-10, CPT-11, and CPT-22)from approximately 21 to 25 feet bgs (the bottom of the borings). ARCADIS, Geocon Consultants, Inc. (Geocon), Kennedy/Jenks Consultants (Kennedy/Jenks), and AMEC conducted previous investigations on the southern portion of the Tracy Rail Yard site. During these investigations, direct push borings were continuously cored to a maximum depth of 35 feet below bgs. In general, the upper 25 feet of soil at the Tracy Rail Yard site are alluvial deposits consisting of clay, silt, silty sand, sandy silt, and sand. Below 25 feet bgs, clayey sand and poorly-graded gravel with sand was observed. During previous investigations at the Tracy Rail Yard site, AMEC observed groundwater at depths generally between 11 and 21.5 feet bgs(AMEC, 2010). ARCADIS reported a groundwater flow direction ranging between the north-northwest and the north based on water AMEC Geomatrix, Inc. X:\16000s\161140\4000 REG ULATORY\South WP 063011\1 W,cvrs, Itrs\Text.docx 2