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i <br /> 10 TreadwelOW10 <br /> ' • Pumping approximately 7,500 gallons of groundwater from the excavation into a Baker <br /> ' tank prior to testing and discharge to the sanitary sewer, <br /> • Collecting a soil and groundwater sample from the base of the shored excavation for <br /> 1 laboratory analyses, <br /> • Placing approximately 800 lbs of oxygen release compound (ORC) into the base of the <br /> shored excavation prior to backfilling, <br /> 1 • Backfilling and compacting P clean imported soil in the excavation and <br /> , <br /> ' • Disposing of contammated soil at Altamont Landfill in Stockton, California <br /> 4.1 Rationale for Remediation <br /> Site soil and groundwater data showed that significant concentrations of petroleum hydrocarbons <br /> were present at sampling location CPT-EXC-BT-19, and likely extended deeper As described <br /> in Section 3 0, rising groundwater at the Site has resulted in a smear zone of soil with TPH-g <br /> concentrations generally to at least 10 feet below the water table <br /> Excavation of contaminated soil <br /> pumping contaminated groundwater from the excavation, and <br /> ' adding ORC to the excavation to help create aerobic conditions that will enhance in-situ <br /> bioremediation was selected as the mitigation method because <br /> • In-situ remedial cleanup of contaminated soil is difficult at sites with significant <br /> concentrations of hydrocarbons in fine grained sediments below the water table, and <br /> • The planned development at the site could limit access for managing potential long-term <br /> ' in-situ cleanup <br /> Spreading ORC at the base of the excavation is an effective way to deliver time released <br /> oxygen to the subsurface <br /> 1 25971024 DGD 5 7 June 2005 <br />