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Geomatrix compounds were below the soil screening level of 10 mg/l for TPHd (e.g. water quality goal of 0.100 mg/l multiplied by an attenuation factor of 1000) and 0.050 mg/1 for Cr and Cr VI (e.g., the Maximum Contaminant Level [MCL] for Cr). As noted in the FS/RO report, broken roof tile material was observed in shallow soil at boring LPW-3. At French Camp,THPd was detected at concentrations of 39 and 51 mg/kg in two shallow soil samples collected from a depth of 1 and 2.5 feet bgs, respectively, at boring FCW-1. The highest concentrations of total Cr(13 mg/kg) and Cr VI (0.010 mg/kg)were detected in soil samples from a depth of 15 feet bgs from boring FCW-3 and from a depth of 27 feet at boring FCW-2, respectively. The highest concentration of extractable Cr VI (0.0018 mg/1)was detected in a soil sample collected from a depth of 5 feet bgs at boring FCW-2. The extractable soil concentrations of Cr VI were below the soil screening level of 0.050 mg/l. Extractable concentrations of TPHd and total Cr were not detected in the shallow soil samples collected at depths of 1 and 5 feet bgs. In order to further assess the leaching potential of TPHd, Cr, and Cr VI in soil adjacent to the stockpiles, a vadose zone soil investigation was conducted under an approved Work Plan entitled Vadose Zone Investigation Work Plan (Brown and Caldwell, February 2002 and March 2002 Addendum). As part of the vadose zone investigation, three shallow borings were advanced to a depth of 10 feet bgs around the perimeter of each stockpile at locations between the groundwater monitoring wells. The boring locations are shown on Figures 2 and 3. Soil samples were collected at a depth of 1, 2.5, and 5 feet bgs and these samples were analyzed for extractable concentrations of TPHd, Cr, and Cr VI using the DIWET method. Analysis of the 10-foot soil samples were based on the findings of the 5-foot samples at four boring locations (LP-G6, LP-111, FC-G6, and FC-G7). A summary of the reported results and test methods is provided below: Concentration of Soil Extracts(mg/1) TPHd Cr Cr VI DIWET Method (EPA Method (EPA Method 6010) (EPA Method 8015M) 7199) Lathrop <0.05—2.7 <0.01—0.03 <0.0005—0.0019 French Camp <0.05—0.16 <0.01—0.02 <0.0005—0.0071 At Lathrop, extractable concentrations of TPHd were detected in two soil samples collected from a depth of 1 and 2.5 feet bgs at boring LP-H1 at concentrations of 0.67 to 2.7 mg/l, respectively. At French Camp, extractable concentrations of the TPHd were detected in one PAI 0626.000.O\Docs\MLT Soil Work Plan.doc 3