ARCHIVED REPORTS_DRAFT - PHASE I REMEDIAL INVESTIGATION REPORT

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r Kennedy/Jenks Consultants 1 sampling efforts on areas of detected impacts (if any), develop the initial site conceptual model and focus subsequent investigations to support achievement of the RI objectives. ' 1.3 Identification of Operable Units As described in the RI Work Plan and Addendum, the Railyard property was divided into five ' Operable Units (OUs) or investigation areas. The OUs were defined based on historical land use information, results of previous studies, and anticipated future use. The OU boundaries are shown on Figure 2. This division of the former Railyard into OUs allows for focused ' investigations or remedial actions where warranted, and may expedite future productive use of the OUs where the RI results indicate no future action is needed. 1.4 Site Description and History The full Railyard site covers approximately 34 acres, bounded by Sixth Street to the north, MacArthur Drive to the east and Tracy Avenue to the west, as shown on Figure 2. Areas adjacent to the site are a mix of commercial and residential development. The site was previously used as a Southern Pacific Transportation Company (Southern Pacific) maintenance facility, which was decommissioned in the 1940s. It was later used as a rail welding facility. A historical valuation map showing many of the site features and OU boundaries �. is provided as Figure 3. All operations had ceased and a majority of the structures and railroad tracks were removed in the 1980s. The site is currently vacant. Southern Pacific was acquired by Union Pacific in 1996. In 1991, the development firm Braddock and Logan Associates was considering purchase of the Railyard and an adjacent agricultural parcel for residential development. To that end, they initiated a Level One Environmental Site Investigation (ENGEO 1991). This study identified ' several areas of potential concern on the Railyard property, including former wastewater ponds, an aboveground storage tank, three metal standpipes and a concrete-lined sump filled with an oily substance, maintenance facilities and a large stockpile of soil and debris. To investigate whether environmental impacts had occurred in these areas, a Transfer Assessment Workplan was prepared (Anderson 1991), but this investigation was not implemented as proposed. Southern Pacific did subsequently proceed with a related scope of investigation for OU-1, as described below. Background information for each of the OUs is summarized as follows. 1.4.1 Operable Unit 1 OU-1 consists of approximately 17 acres in the eastern portion of the Railyard, bounded on the north by the railroad right-of-way that fronts Sixth Street, on the east by MacArthur Drive, on the south by Gonzalez Street, and on the west by the extended alignment of East Street that serves ' as the boundary between OU-1 and OU-2 (Figure 2). Past OU-1 improvements included railroad tracks, wheel shops, locker rooms, planking, oiled macadam, rail beds, a coal house, refuse pit, and various air and water pipelines. A rail welding facility was operated in OU-1 until the 1980s. In the late 1980s to early 1990s, the southeast portion of the OU, along MacArthur Drive, was leased to American Transit Mix Company, ' Inc./RMC Lonestar. Their operations included two underground storage tanks (USTs) DRAFT Phase I Remedial Investigation Report Page 2 Former Tracy Railyard, Tracy, California g.lis-groupladminljo610510565777.18_uprr109-reportslrirpAtexldoc