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t i= Geomatrix At the French Camp Facility, groundwater monitoring data indicated a groundwater flow direction that ranged from the west to the northeast at a gradient between 0.001 ft/ft and 0.009 ft/ft (URS, May 2004). Although the measured groundwater elevations in June 2005 ' were approximately 5 feet higher than the elevations reported for the November 2004 event, the groundwater flow direction was consistent with the variable directions reported previously. In June 2005, the groundwater gradient at this Facility was reported at 0.001 ft/ft with a flow direction to the north-northwest (Geomatrix 2005). 4.0 OBJECTIVES AND APPROACH The objective of this soil investigation is to assess the vertical distribution of diesel-range ' petroleum hydrocarbons in soil beneath the two stockpiles and to determine whether additional assessment of groundwater is warranted. In addition, soil below each stockpile will be further evaluated for Cr and Cr VI. ' The scope of work for the soil investigation includes: • Drilling and sampling three soil borings using direct push methods to depths of approximately 10 feet bgs. Soil borings will be placed below the footprint of each stockpile after the stockpile at each Facility has been consumed (recycled back into the tile manufacturing process); • Analyzing soil samples from depths of 1, 2.5, 5, and 10 feet bgs from each soil boring. These samples will be analyzed for total and extractable concentrations of TPHd, Cr, and Cr VI. The analyses will be conducted using EPA Method 8015 M, Method 6010, and Method 7199,respectively, for the total and extractable concentrations. Extractable concentrations of TPHd, Cr, and Cr VI will be obtained by Title 22 WET Method using de-ionized water as the extraction media (DIWET); and • Reviewing the results of the soil investigation activities and developing conclusions regarding the vertical extent of TPHd, Cr, and Cr VI in soil directly below the stockpiles, and comparison of the data to the soil screening levels for TPHd I (10 mg/1) and for Cr and Cr VI (0.050 mg/1). 5.0 SOIL INVESTIGATION ACTIVITIES This section describes the pre-field activities and the procedures to be followed during the proposed soil investigation activities. The proposed soil investigation will be conducted during two separatelield events. It is anticipated that the investigation will occur in January 2006 at the French Camp Facility and in June 2006 at the Lathrop Facility. The soil investigation will PAl0626.000.O\Docs\MLT Soil Work Plan.doc 6 �R`