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Frank C. Alegre Trucking, Inc. 4203-172 Former Trucking Facility October 29, 1996 WORK PLAN FOR DRAINAGE POND MITIGATION AND Page 2 PIPING SURVEY BACKGROUND The drainage pond was operated until approximately 1980 when it was filled with sand and abandoned (Figure 2). According to Alegre Trucking personnel, the pond collected storm water runoff. In September 1996, San Joaquin County recovered a soil sample from a test pit excavation within the area of the pond. This sample was analyzed for solvents and metals. A bioassay was also performed for the sample. Results of the laboratory analyses found trace concentrations of Chlorobenzene and 1,4-Dichlorobenzene, toluene and xylenes. The reported concentrations are below existing regulatory criteria and/or guideline concentrations for these compounds. The reported metal concentrations were below state waste criteria. The soil sample passed the bioassay analysis. A number of drainage inlets and underground pipes have been observed within the former truck maintenance building. In addition, a±8-inch-diameter asbestos drainage pipe has been exposed along the north side of the building, parallel to the structure. Observation of this exterior drain pipe and several of the interior drain inlets indicates petroleum products or other hazardous materials may have been discharged to these lines. No as-built plans for the building and associated drainage systems are available. In October 1996, the San Joaquin County Department of Environmental Health requested the preparation of a work plan to address the abandoned pond and drain pipes. SCOPE OF SERVICES Soil Excavation A track-mounted excavator will be used for soil removal. The excavation will be extended laterally and vertically based on field observations and vapor screenings. The impacted soil will be removed to the extent feasible subject to equipment limitations. ENGEO anticipates an excavation 20 to 25 feet in depth over an area of x,000 ftz. The specific volume of soil to be excavated is not known, although, ENGEO estimates that 2,500 to 3,000 cubic yards of soil will be removed. Remnant pipes, if exposed will also be removed during the excavation work. Once field observations and screenings indicate the affected soils have been removed, discrete soil samples will be recovered from the excavation base and sidewalls at approximate 20 foot lineal intervals. The specific location and depth of the confirmation samples will be determined in the field. ENGEO estimates that 8 to 10 samples will be recovered from the excavation for laboratory analysis. Composite soil samples will also be recovered from the soil stockpile(s) on a one per 50 cubic yard basis.