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1 <br /> 4.0 SOIL REMEDIATION <br /> This section presents a summary Yof the corrective actions taken <br /> for impacted sods at the site, <br /> along with a mass balance estimate of hydrocarbon discharged and recovered through corrective <br /> actions The soil remedial actions were proposed following a Feasibility Study (Dames & Moore, <br /> 1988) and a work plan describing the excavation and on-site treatment techniques, after the sods had <br /> been characterized as non-hazardous by the methods described in CCR Title 22 <br />' 4 1 CORRECTIVE ACTIONS <br />' Following a preliminary site assessment and Phase I soil sampling by BNI in 1985 and 1986, <br /> the 10,000 gallon tank on the eastern side of the maintenance shop and the 500 gallon waste oil tank <br /> on the western side of the building were taken out of service In May 1988 both USTs were <br /> removed under the direction of the PHS-EHD <br />' In June 1990 the former maintenance shop building was demolished, and demolition debris <br /> disposed of in a Class III landfill Following demolition of the building, approximately 2,000 cubic <br /> yards of soil was removed from two excavations,or slightly more than the 1,550 cubic yards planned <br /> to be removed following the Soil Remediation and Groundwater Monitoring Workplan (Dames & <br /> Moore, 1990) Additional soil was removed from both east and west excavations when samples from <br /> the floor samples exceeded 10,000 mg/Kg TPH/D <br /> When all confirmational soil samples fell below the remedial objective, the excavation was <br /> completed The excavation to the east of the former maintenance shop completed at 26 feet below <br /> grade, and the excavation to the west of the building was terminated at 22 feet below grade. The <br /> extent of these excavations is shown in Figure 9 Figures 16 and 17 also show lateral and vertical <br /> TPH/D distribution together with generalized geologic data inferred from boring logs <br /> Excavated soils impacted at levels greater than 100 mg/Kg TPH/D were treated in an on-site <br /> biotreatment cell After treatment to less than 1,000 ug/L, the soil was fully characterized and <br /> classified as a non-hazardous waste with diesel residues After all analyses were reviewed by <br /> Browning Ferris Industries (BFI), their CIass II landfill in Livermore, California accepted the soil <br /> for disposal The excavation pits were backfilled with approximately 2,000 cubic yards of imported <br /> clean fill, and 150 cubic yards of excavated soils with TPH/D concentrations of less than 100 <br /> mg/Kg The backfill was compacted as it was placed, and an asphalt cap constructed over the <br /> excavation area. The maintenance building pad was replaced with a four-inch thick layer of asphaltic <br /> SAC116 07 8 AUGUST 1994 <br /> DAMES &MOORE <br />