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Former Beacon Station No. 12474 March 18,2002 <br /> StocktonCalifornia __ _ Problem Assessment Report/Corrective Action Plan <br /> - 8.1.4 Excavation and Aboveground Treatment <br /> Excavation and aboveground treatment consists of various methods of aeration, soil vapor <br /> extraction, and bio-treatment. Aeration involves thin spreading of the excavated soils on an <br /> impermeable surface to allow removal of hydrocarbons through volatilization. Thin-spread <br /> soils are periodically turned to maximize surface exposure and aeration. Microbes naturally <br /> occurring in soils also convert both volatile and nonvolatile hydrocarbon components to <br /> primarily carbon dioxide (CO2) and water. <br /> Aboveground soil vapor extraction involves the in-situ venting of hydrocarbons in soil <br /> through a vapor recovery line network installed within the stockpiled excavated soils. <br /> Hydrocarbons contained in the soil vapors may be treated by combustion, adsorption, or <br /> directly discharged to the atmosphere, depending on the concentrations. <br /> Bio-treatment involves creating an environment in excavated soil that promotes <br /> decomposition of hydrocarbons by microbes. Fertilizer and oxygen are supplied to the <br /> excavated soils by cultivation, and forced ventilation enhances the performance and <br /> propagation of the microbes. Following treatment, the soils may be disposed of through an <br /> appropriate landfill or used as backfill material. <br /> 8.2 Groundwater Remediation Alternatives <br /> The following groundwater remediation alternatives are discussed in this section: <br /> • Passive Remediation <br /> • Aboveground Treatment <br /> • Air Sparging <br /> • In-Situ Bio-remediation <br /> • <br /> 474PARCAP3-02.doc 15 <br /> Project No. 1474.23 HORIZON ENVIRONMENTAL INC. <br />