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4 0 SOIL REMEDIATION <br /> This section describes sal remediation activities undertaken at the site Section 4 1 briefly <br /> describes the regional geology, Section 4 2 describes excavation, backfilling, repavement, on-site <br /> treatment and disposal of impacted soil from the vicinity of the former maintenance shop Section 4 3 <br /> describes the removal, decontamination and disposal of all underground piping, soil excavation, <br /> backfilling, repavement and off-site treatment of impacted soil underneath the pipe and pump island <br /> 41 GEOLOGY <br /> The site is located on deep sediments deposited in the northern San Joaquin Valley The upper <br /> 1,000 feet of sediments consist of alluvium and unconsolidated Pleistocene sediments from the Victor <br /> Formation and Arroyo Seco Gravels probably deposited from floodwaters of the nearby Calaveras and <br /> San Joaquin Rivers The surface sediments directly underneath the site consist of recent flood-basin <br /> deposits including fine sands and silty clay deposits Generalized geologic cross sections in the vicinity <br /> of the maintenance shop are presented in Figures 4 1 to 4 3 These cross sections have been inferred <br />' from well installation boring logs (Appendix G), and previous soil boring information <br /> 4 2 MAINTENANCE SHOP <br /> The soil remedial actions in the vicinity of the maintenance shop were developed in the FS/RAP <br />' (Dames & Moore, 1988) approved by the RWQCB, and described in detail in the Soil Remediation and <br /> Groundwater Monitoring Workplan (Dames & Moore, 1990) This plan proposed the demolition of the <br /> maintenance shop, excavation and on-site treatment of impacted soils, backfilling, compaction and <br /> repaving the excavation, and installation of new groundwater monitoring wells (described above in <br /> Section 3 0) <br /> r <br /> 4 2 1 Demolition of Former Maintenance Shop <br />' Preconstruction activities including permitting,utility removal, and contractor mobilization which <br /> were conducted between May 15 and June 4, 1990 A Dames & Moore construction engineer was <br /> present on-site during all phases of site work to observe the operation and document observations as the <br /> work progressed The following sections describing demolition, excavation, and construction are based <br />' on the engineer's notes which are presented in Appendix I <br /> Demolition of the former maintenance shop was performed by Don Lawley Company of Stockton, <br /> California The demolition work began on June 5 and was completed on June 8, 1990 First, the wood <br /> frame metal-clad maintenance building was demolished and the concrete floor and service bays were <br /> SAC36 046 15 <br />