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ameO 2.0 BACKGROUND The following sections provide information about the Off Site East Area setting, Off Site East Area geology and hydrogeology, and previous investigations conducted in the eastern portion of the Tracy Rail Yard adjacent to the Off Site East Area. 2.1 OFF SITE EAST AREA SETTING The Off Site East Area is centered along the former TAOC pipeline route east of the Tracy Rail Yard (Figure 2). The Off Site South Area lies to the west of the Off Site East Area, and it will be investigated separately. The majority of the Off Site East Area is currently developed as single family residential housing. The former TAOC pipeline passed through the Off Site East Area in a northwest to southeast alignment as shown on Figure 2. The former OVP extended onto the Tracy Rail Yard in a northeast to southwest alignment to the east of the Off Site West Area as shown on Figure 2. The TAOC pipeline and OVP 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 abandoned in 1970. 2.2 GEOLOGY AND HYDROGEOLOGY No previous investigations have been conducted in the Off Site East Area. Kennedy/Jenks and AMEC conducted previous investigations on the eastern portion of the Rail Yard site (area of interest [AOI]-4 and AOI-5). During these investigations, direct push borings were advanced to a maximum depth of 48 feet below ground surface (bgs; Figure 3). 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. 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 level data from monitoring wells formerly present in the eastern portion of the Tracy Rail Yard, north of the Off Site East Area (ARCADIS, 2008). This groundwater flow direction is consistent AMEC Geomatrix, Inc. X:\16000s\161130\4000\OffSiteEastWP061511\1 txt,cvrs,Itrs\text.docx 2