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z ' i • personnel and subcontractors performing work on-site. A copy of the SHSP will be present on-site at all tames and kept in an easily accessed location 3.2 Soil Vapor Extraction and Emission Control System Design Soil vapor extraction system design parameters are based on data obtained during a VET performed by GTI (GTI, 1992) The pilot test was conducted to evaluate the radius of influence wells and the concentration of hydrocarbons in the soil vapor extracted from the wells. The VET showed that a radius of influence of approximately 25 feet at a flow rate of approximately 20 cfm could be expected from vapor extraction wells at the site In addition, the pilot study indicated that the average initial hydrocarbon concentration expected from the vapor extraction wells would be approximately 12,000 mg/m3. 3.2.1 Soil Vapor Extraction System Desi Soil vapor will be extracted from two zones at the site. The first zone comprises unsaturated soil extending from approximately 15 to 25 feet bsg; vapor extraction wells VEW-1A and VEW-2A are screened through this interval. The second zone also comprises unsaturated soil extending from approximately 25 to 40 feet bsg; vapor extraction wells . VEW-1B and VEW-213 are screened from 30 to 40 feet bsg (GTI, 1992). The radius of influence of vapor wells VEW-1A through VEW-4B encompasses the majority of this zone as presently defined (see Figure 4). The proposed soil vapor extraction system will utilize I a thermal oxidizer (thermox) manufacturing by AKI Systems, Inc. in Tomball, Texas with V-11, *� a blower to extract and abate hydrocarbon-bearing vapor from the vapor extraction wells 3 2.2 Emission Control System Based on the analytical results from the VET, a thermox is an appropriate abatement unit. The rated destruction efficiency for the thermox is 98% at higher concentrations and 92% at lower concentrations. The overall average destruction efficiency is expected to be approximately 95% The thermox is capable of effectively treating up to 600 cfm of soil vapor from the extraction wells. The thermox is equipped with an additional 200 cfm blower which is used for suppling oxygen for proper combustion. The total capacity of the thermox is 800 cfm. The supplemental fuel needed for the combustion process is natural gas The thermox is capable of automatically controlling the quantity of supplemental fuel (natural gas) supplied to the combustion chamber. The natural gas will be piped from the nearest main directly to the thermox. The thermox operates at a temperature of approximately 1400 degrees Fahrenheit. Automatic controls will shut the unit down should these operating parameters not be met. Influent and effluent hydrocarbon vapor samples, process temperature, and effluent temperature will all be measured as required for permit compliance and to ensure reliable operation of the system. Operation of the extraction system will further decrease emissions from the site over time As the hydrocarbon concentration of the process stream decreases over time, alternative TEXSTOCK SRW SEACOR N0001-006-01 4