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Adsorption and Leaching Potential Leachability and adsorption potential tests were also run on soil samples collected from the two elastic silt units. In addition to the bioamenability tests run on samples S-SB8-25.5 and S-SB8- 36, TOC was determined as an indicator of adsorption potential. TOC was 0.18 % in sample e S-SB8-25.5 and 0.20% in sample S-SB8-36, relatively high levels from a silt/clay at depth and f, indicating a relatively high adsorption potential. In addition to TOC, physical analyses were conducted on's11 amples collected from the two elastic silt units. Grain size analysis indicate that the unit from!!,which S-SB8-25.5 was collected is actually a clayey silt and the unit from which S-SB8-36 was collected is actually a clay with sand. These data, along with the high TOC content of the units. describe effective barriers to vertical transport of hydrocarbon contaminants. This is confirmed by the non -detect chemical results from samples collected at 41 and 45.5 feet bgs in SB8 (Table 1). Laboratory data sheets g are included in Appendix E. 3.3 REMEDIAL ACTIONS 3.3.1 Soil Soil remedial actions consisted of source removal excavation conducted in 1990. Approximately 1530 cubic yards of soil were removed. The tank pit was excavated to an estimated depth of approximately 20 feet in order to remove contaminated soil previously found to exist above the water table. Presumably, excavation continued until field evidence indicated that no petroleum i hydrocarbon contamination remained in the vadose zone. i The soil was aerated under permit from the San Joaquin County Air Pollution Control District (APCD) and, subsequent to verification of successful remediation through sampling of the stockpiled soil, was used to backfill the excavation. The soil excavation and remediation reports prepared by Uriah Environmental is included in Appendix B. groundzeVanuioklosure 8 c