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SY;R eport on Additional Excavation and Cb Armation Soil Sampling Bulk Transportation Facility, Stockton, California +� Hygienetics Environmental Services,Inc. suggested the diesel fuel in the soil was weathered. PIate 2 shows the locations at which soil samples were collected and the concentration of TPHd found in each sample. Table 1 presents �.. the results of laboratory analyses for TPHd and BTEX. Hygienetics also collected samples from three stockpiles of the backfill materials excavated during UST removal and submitted these samples to the laboratory for analysis for TPHd and BTEX. The results of these analyses are also presented in Table 1. �— The results of laboratory analyses of soil samples collected after removal of the UST, pipelines, and dispenser facilities showed diesel petroleum hydrocarbons were present at relatively high concentrations in the shallow soil (clay and silt) along a 20-foot-long portion of the diesel-fuel pipeline trench. Field observations made during excavation and removal work suggested the area of petroleum-hydrocarbon impact was local in this area of the pipeline trench. Diesel petroleum hydrocarbons were not present at concentrations of concern elsewhere in the excavations. V 2.0 FIELD AND LABORATORY WORK 2.1 Work Plan Field observations during the UST and pipeline removal in October 2002 suggested the extent of diesel fuel in the subsurface soil was restricted to an area beneath the pipeline trench where the elevated concentrations of TPHd were detected. In a work plan, dated April 17, 2003, Hygienetics (2003) proposed to excavate and remove diesel-impacted soil from the pipeline trench; the proposed excavation would be approximately 7 feet wide by 20 feet Ion maximum of 15 feet deep. The volume of soil to be removed was estimated to be 75 in-place cubic yards (100 uncompacted cubic yards). Hygienetics proposed to collect six samples o the native soil at staggered locations along the two sidewalls and on the bottom of the excavation. The work plan was submitted to the San Joaquin County Environmental Health Department (Environmental Health Department) for review. The Environmental Health Department .. conditionally approved the work plan in a letter to Bulk Transportation, dated May 30, 2003. Appendix A contains a copy of this approval letter. 2.2 Excavation Bulk Transportation identified and marked the locations of underground electrical and water lines present in the area before excavation began. On July 29, 2003, Foss cut and removed overlying concrete and excavated diesel-impacted soil using a Case 580 Extend-A-Hoe. Hygienetics observed much of the excavation and removal work performed on July 29. Diesel-hydrocarbon-impacted soil was observed to be discolored blue-gray in contrast to the yellow-brown color of the native silt. Excavation focused on removing visibly discolored soil and minimizing removal of soil that was not discolored. Hygienetics also used a portable photoionization detector,calibrated to detect diesel-fuel, to check soil that was not discolored for the presence of diesel vapors. During excavation, blue-gray discolored soil was encountered to a depth of approximately 12 feet below grade in the area of the central control dispenser island. Discolored soil was also observed �. to extend eastward approximately 3 feet beyond the former eastern end of this island and from 6 to 7 feet south of this island directly beneath the pipeline trench to the former southern satellite dispenser. In this latter case,most of the discolored soil was found between the depths of 4 and 9 3