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Harding Lawson Associates <br /> volatilization of the residual hydrocarbons. In accordance with <br /> San Joaquin Valley Unified Air Pollution Control District <br /> (SJVUAPCD) regulations, only partial sections of the soil pile <br /> will be exposed at any one time to control the release of <br /> ' hydrocarbons to the atmosphere. The amount of soil exposed is <br /> determined by the concentration of hydrocarbon constituents. <br /> The other method of aeration is active aeration which <br /> would involve the VES. This method would be used to accelerate <br /> the process of reducing hydrocarbon concentrations so that the <br /> 1 soil can be removed from the property more quickly. Lateral <br /> screened vent pipes are laid into the pile as it is being formed <br /> which are manifolded to the VES. The vacuum blower induces the <br /> flow of air through the pile, volatilizing the hydrocarbons for <br /> removal. The exhaust of the blower passes through the carbon <br /> adsorption reactors for treatment. <br /> 2 . Task 2 - Install Vapor Manifold Trench <br /> ' a. Locate Existing Vapor Laterals in the Tank Pit <br /> Area. <br /> During excavation of the former underground tanks, <br /> Southland had placed five lateral 4-inch PVC pipes in the tank <br /> pit before backfilling and resurfacing the area of excavation. <br /> Three of these laterals were placed at a depth of six feet to be <br /> ' utilized as water extraction laterals. The other two were placed <br /> at three to four feet below grade to be utilized as vapor <br /> ' extraction laterals. All five laterals were extended to dust <br /> below the surface at the northern edge of the old excavation. By <br /> 26 <br />