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ARCADIS Phase II Field Investigation Work Plan 1. Introduction Union Pacific Railroad Company Former Maintenance Facility On behalf of the Union Pacific Railroad Company(UPRR),ARCADIS U.S., Inc., Tracy, California (ARCADIS)presents this Phase II Field Investigation Work Plan for the UPRR Former Maintenance Facility in Tracy, California (the Site; Figures 1 and 2). The Site is located southeast of the corner of Sixth Street and Macarthur Drive in Tracy,California (Figure 1). In June 2008,ARCADIS implemented Phase I of this investigation, which consisted of advancement of 16 17 cone penetrometer testing (CPT)/laser-induced fluorescence (LIF)borings to evaluate the distribution of Liquid Phase Hydrocarbon (LPH)in the source area. The site closure requirements and purpose of the investigation are described in the first work plan (ARCADIS 2008b).The initial phase of the investigation provided data to delineate the LPH in most of the source area. LPH impacts(identified as diesel product)were observed in LIF borings between the railroad tracks and the Engine House and in the vicinity of the oil/water separator(former above ground storage tanks[ASTs]),which are shown on Figure 3. A description of the historic uses of the Site, past investigation and remedial actions, and other background information are included in the LPH Investigation Work Plan (ARCADIS 2008b). 1.1 LIF Data from Phase 1 LIF data were collected from 16 locations during the Phase I investigation (Figure 3). Locations with medium to high (greater than 20 percent)fluorescence are shown in yellow,orange, and red,and those where fluorescence was low are shown in green. As shown on Figure 3,the extent of LPH impacts have not yet been defined outside the area investigated by the Phase I LIF borings. 1.2 Current Groundwater Data Soil at the Site, to a depth of approximately 100 feet below ground surface (bgs), is composed primarily of clay and silt with varying amounts of sand and fine gravel. Shallow groundwater(referred to as the A-Zone)typical occurs at approximately 10 to 25 feet bgs. In March 2008,groundwater flow direction was to the north and depth-to- water was approximately 9 to 13 feet bgs. These data are generally consistent with historical data. Deeper groundwater, referred to as the B-and C-Zones,typically occurs from 35 to 45 feet bgs and 65 to 75 feet bgs(ARCADIS 2008b), respectively. C:\Do nts and Settings\kbrandl Lod Semngs\Temporary Internet F,ks\Content.O,Iwk\52SXLSSI�Phase 11 WP_01_05_09(2).d 1/6