ARCHIVED REPORTS_DRAFT - PHASE I REMEDIAL INVESTIGATION REPORT

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Kennedy/Jenks Consultants • Considering these results of past investigations and remedial actions, three general areas of interest (AOIs) were identified within OU-1 (Figure 2) that warranted further evaluation in the RI: • AOI 1 — Remediated Soils. This area encompasses several smaller isolated areas where remedial soil excavation was conducted until confirmation samples showed residual total lead concentrations were less than the 220 mg/kg remediation goal and soluble extract concentrations were less than 0.015 mg/I. These areas were backfilled with imported fill material. • AOI 2 — Stabilized Lead. In this area, remedial soil excavation was conducted, but confirmation samples indicated that total lead concentrations of soil remaining in-place may be above the 220 mg/kg remediation goal and/or the soluble extract concentrations may be greater than 0.015 mg/I. The area was backfilled within 1 foot of the original grade with excavated soil containing stabilized lead. The remaining excavated depth was backfilled with imported fill material. • AOI 3 — Residual Elevated Lead. This area includes three discrete areas along the perimeter of AOI 2 where soil samples collected from test pits indicated that lead concentrations in soils remaining in-place may be above the 220 mg/kg remediation goal and/or soluble extract concentrations may be greater than 0.015 mg/I. No remedial soil excavation has been conducted in these areas. 1.4.2 Operable Unit 2 OU-2 consists of approximately 16 acres occupying the central-southern portion of the Railyard, bounded on the north by the railroad right-of-way that separates OU-2 from OU-4, on the east by the extended alignment of East Street that serves as the boundary with OU-1, on the south by Fourth Street, and on the west by the railroad right-of-way that separates OU-2 from OU-3 ' (Figure 2). Based on inspection of the historic valuation map provided by Union Pacific (Figure 3) as well as historic aerial photographs, OU-2 appears to have been the primary industrial area of the Railyard. Aerial photographs show that three ponds were previously located in this area. No information on past uses of the ponds was found. Observations during a site visit in 2005, in comparison with aerial photography, indicate the former ponds have been filled with soil and ' concrete debris. Oil storage and transmission infrastructure were located in OU-2, including one large oil tank (believed to be aboveground), an oil pump house, grass swale, railroad tracks, and various oil drains, oil pipes, air pipes and water pipes (all believed to be underground). Given the proximity of these facilities to the ponds, it is possible that the ponds were used for waste disposal or storage. OU-2 also had a roundhouse area that included one turntable, two roundhouse structures, an engine pit, oil sump, tool house, store house, railroad tracks and associated oil pipes. Other facilities included settling tanks, pump houses, lumber shed, store houses, storage tanks, power • house, personnel offices/housing, railroad tracks, and various oil pipes, air pipes, and water pipes. ' DRAFT Phase I Remedial Investigation Report Page 6 Former Tracy Railyard, Tracy, California g:Vs-groupladminl obk0510565777.18_uprr\09-reports\ri rpMextdoc