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SOIL ASSESSMENT FOR PROPERTY ACQUISITION Intersection of Interstate 205 and Grant Line Road Tracy, California Delta Project No. 40-89-052 Page 4 3.0 RESULTS.OF SOIL BORING INVESTIGATION 3.1 Site Soils and Ground Water On July 20, 1989, Delta advanced six soil borings at the site in order to evaluate the condition of soils beneath the site. Soil boring locations are illustrated in Figure 2. Boring locations were chosen to provide efficient coverage of the site and to allow collection of representative soil samples for description and possible analysis. The surface of the site consists of silty gravel fill which ranges from 1/2 to 3 inches in thickness. A portion of the southern edge of the site is paved with a thin asphalt cover, 1 to 2 inches in thickness. It is in this paved area that the trucks are parked, and truckers have been observed draining oil onto the surface of the site. Soil samples retrieved from soil borings indicate that soils beneath the site consist of clayey sand and clayey silt with minor silty sand and clay strata. Data from the soil boring logs presented in Appendix A indicate that the upper 4 to 5 feet of soils beneath the site consist of clayey sand. Below this strata lies a clayey silt, which was encountered to a depth of 10.5 feet below ground surface in soil boring SB-6 (the maximum depth explored at the site). Ground water was encountered across the site at depths ranging from 5.5 to 9.5 feet below ground surface. Water samples were not collected at the site. All soil borings advanced at the site were sealed from the bottom of the borehole to ground surface with a cement/bentonite grout on July 20, 1989. A detailed description of grouting procedures is presented in Section 5.4. 3.2 Soil Sample Analytical Results Soil samples collected by Delta during the drilling of soil borings were submitted to a State-certified laboratory for analysis of TPH and BTEX. Five surface samples were submitted to and composited by the laboratory for analysis of pesticide/herbicide residues. Soil samples from only two of the six soil borings were submitted for laboratory analysis of hydrocarbon constituents for the following reasons: • The site is undeveloped. • There is no history at this site of underground tanks, leaks, or spills. • No organic vapors exceeding 1 part per million (ppm) were detected when soil samples were screened with a PID.