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Geomatrix soil sample collected from a depth of 5 feet bgs at boring FC-G6 at a concentration of 0.16 mg/l. The soil sample extract results suggested a limited extent of TPHd-impacted soil based on the concentrations reported below the screening level of 10 mg/l. Similarly, the extractable concentrations of Cr and Cr VI in soil samples were below the soil screening level of 0.050 mg/l. Based on the soil and groundwater monitoring data, and the limited extent of impacted soil, URS concluded that a feasibility study was not needed and soil remediation was not warranted (URS,December 2002). Since March 2002, nine groundwater monitoring events have been conducted at the Facilities, with the most recent event conducted in June 2005 (Geomatrix, June 2005). During the June 2005 monitoring event TPHd was detected in groundwater samples from both Facilities. At the Lathrop Facility, TPHd was detected for the first time in groundwater samples collected from monitoring wells LPW-1, LPW-2, and LPW-3, which included the upgradient well (LPW-3), at concentrations of 570,470, and 260 micrograms per liter (µg/Q, respectively. The laboratory identified these compounds as weathered diesel. At French Camp,TPHd was detected in groundwater samples from one groundwater well FCW-1 (cross-gradient well). Since November 2004, the concentration of TPHd detected in groundwater samples from monitoring well FCW-1 increased from 1900 µg/L to 3100 µg/L (FCW-1). 3.0 GEOLOGY AND HYDROGEOLOGY Regional and site-specific lithologic and hydrogeologic information for the Facilities was presented in the November Semi-Annual 2004 Groundwater Monitoring Report prepared by URS (December, 2004). For the purpose of this Work Plan this section briefly describes site- specific geology and hydrogeological conditions as presented by URS (December 2004). 3.1 REGIONAL The Facilities are located in the San Joaquin Valley of the Central Valley geomorphic province, which is a large, northwest-trending, asymmetric structural trough composed of interlayered gravels, sands, silts, and clays derived from the adjacent mountains and deposited in alluvial fan, fluvial, lacustrine, and marsh environments (USGS, 1986). The San Joaquin Valley is bounded by the Coast Ranges to the west, by the Delta to the north, the Tehachapi Mountains to the south, and the Sierra Nevada Mountains to the east. PA10626.000.00ocAMI-T Soil Work Plan.doc 4