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3.7 Laboratory Analysis of Soil Samples All soil samples collected for analysis were stored in a cooler chilled to 4° Celsius and shipped • under strict chain of custody protocol to the analytical laboratory. The samples were analyzed in ' Modesto, California by GeoAnalytical Laboratories, a' California State certified analytical laboratory for the following constituents: • TPH - gasoline, Method 5030/LUFT: Detection limit 2.5 mg/Kg. • Benzene, Toluene, Ethyl Benzene and Total Xylenes: EPA Method 8020: Detection limit 5.0 µg/Kg. 4.0 FINDINGS ' 4.1 Phase I Excavation Excavated soils were typically composed of silts, fine sandy silts and clayey silts. A distinct color change from brown to dark grey was noted between the depths of four and eight feet bgs that coincided with an increase in PID readings. Some fine sand layers were encountered along the eastern edge of the excavation, however these were very limited in thickness and extent. A ' brown highly plastic clay was encountered between 18 and 18.5 feet bgs across the bottom of the excavation. PID readings indicated no positive levels of volatile compounds in the clay collected from the bottom of the excavation. Ground water was initiallyencountered at a depth of 12 feet bgs but rose to a standing level of P g g approximately 8 feet bgs. Although moderate to strong hydrocarbon odors were noted in the water, no sheen was observed. Ground water was not removed from the excavation prior to backfilling. ' A volume of 1,147 cubic yards of gasoline contaminated soil was removed during performance of the phase I excavation. Eight sidewall samples, seven bottom samples, and four pit samples were collected during excavation. Analytical laboratory data are presented in Table I below along with PID readings obtained at each sample location. Laboratory data sheets and the chain of custody documents are included in Appendix A. Sidewall and bottom sample collection ' locations are shown on Figure 3. Pit interior sample collection locations are shown on Figure 4. The sidewall soil sample results indicate that gasoline and gasoline constituents remain along the ' western, northern and eastern boundaries of the excavation. Samples SW-1 through SW-4 all contain TPH gasoline levels in excess of 2,000 mg/Kg, with two of the samples, SW-1 and SW-3 having concentrations equal to or greater than 10,000 mg/Kg. The areas having residual ' contaminant levels are not accessible for remediation by excavation due to the presence of structural features including buildings and utility lines. ' American Geological Services,Inc. CA95DE-029 ' 10