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' ARCADIS Phase II Field <br /> Investigation and LNAPL <br /> Mobility Evaluation Report <br /> Union Pacific Railroad Company <br /> Former Maintenance Facility <br /> ' Tracy, California <br /> • Collecting 12 soil samples from the biotreatment beds <br /> ' Details of well installation activities and construction details were submitted to the <br /> Regional Water Quality Control Board (RWQCB) in the Well Installation Summary <br /> Report, prepared by ARCADIS and dated March 11, 2010(ARCADIS 2010a). <br /> Results from the biotreatment bed samples were presented in the Biotreatment Beds <br /> Post Remediation Investigation Report, prepared by ARCADIS and dated August 24, <br /> 2010 (ARCADIS 2010c). Biotreatment bed results are therefore not addressed in this <br /> report. <br /> ' 1.1 Objectives <br /> The overall objectives of the Phase 11 field investigation were to complete the LNAPL <br /> delineation that began in June 2008 and to complete additional characterization of <br /> groundwater in areas of the petroleum hydrocarbon-affected groundwater where data <br /> are sparse (i.e., in the transition zones). Specific objectives included the following: <br /> ' Delineate the extent of LNAPL to the east and west of the source area and in the <br /> ' vicinity of the track pan <br /> Assess potential LNAPL sources associated with the suspected underground <br /> piping in the vicinity of the track pan area and the Engine House <br /> ' - Assess potential impacts to groundwater from the former TPCA pond excavation <br /> • Refine the lateral extent of groundwater affected by total extractable petroleum <br /> hydrocarbons (TEPH), particularly along the upgradient(southwestern)edge <br /> • Assess TEPH distribution in the transition area groundwater between the source <br /> ' area and the perimeter of the plume <br /> Data collected during the Phase If field investigation were used to evaluate the mobility <br /> ' of LNAPL at the Site. Details of the LNAPL mobility evaluation are outlined in Section <br /> 5. <br /> ' 1.2 Background <br /> The Site was acquired by UPRR in 1997 from Southern Pacific Transportation <br /> ' Company. Current land use in the immediate site vicinity is a mix of industrial and <br /> residential. Beginning in the early 1960s, the Site served as a maintenance and <br /> 1 <br /> �upm4aAnVlmobftll-z 2010l doc <br /> ' 2 <br />