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i American Geological Services, Inc. installed three additional monitoring wells on March 8, 1996. ' Two wells were installed to further define the lateral extent of soil and ground water contamination, and one well was installed in the down gradient direction to determine the vertical extent of the ground water plume. The lateral and vertical extent of ground water contamination was determined to have been defined during this last phase of investigation. A work plan was prepared and submitted to the San Joaquin Public Health Services, Environmental Health Division to conduct a remedial soil excavation. The work plan proposed the removal of approximately 2,000 cubic yards of gasoline contaminated soil. 1 1.3 Geology 1 The subsurface geology of the site was determined by logging soil samples collected at various intervals during the initial and supplemental site investigations performed by Remcor, and ' American Geological Services. The maximum depth of boring was 45 feet below grade. Remcor reported that dark brown silty clay dominates the stratigraphy from within one foot of ' the surface to the bottom of their borings installed to 18 feet below grade. In general, fine sand was found within the silty clay unit near the bottom of the borings. During the installation of the additional three monitoring wells, AGS encountered silty fine sands to a depth of approximately 20 feet. A fine to medium sand layer was found between 20 and 25 feet in MW-8, and between 25 and 35 feet, and 40 and 45 feet in MW-9. 1.4 Hydrology Groundwater at the site is contained in a semi-confined or unconfined aquifer typically 10 to 15 feet below grade. However, ground water was measured at an approximate depth of 8 feet bgs during the spring of 1998. Ground water was encountered at a depth of 12 feet below grade during the remedial excavation and stabilized once it had reached approximately 8 feet. Historically, groundwater at the site demonstrates a shallow gradient which slopes to the ' northwest. 2.0 OBJECTIVE AND SCOPE OF WORK 1 2.1 Objective ' The objective of this phase of the project was to remove gasoline contaminated soil caused by a release of gasoline from the former UST or its associated piping. This work was conducted in accordance with Section 2772(a) of the California Underground Storage Tank Regulations (Title 23, Division 3, Chapter 16 California Code of Regulations). In order to accomplish the above- stated objective, the following scope of work was conducted. ' American Geological Services,Inc. CA95DE-029 ' 3