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The exhaust air Zrom the AST will be pas.-ed through a Vapor <br /> Control Unit to remove the hydrocarbons, primarily TCE and PCE. <br /> The AST top is connected to the VCUs by sixteen inch Fiber rein- <br /> forced Plastic (FRP) duct. A drain valve has been connected to <br /> drain the water from the duct and to collect influent samples to <br /> the VCU. <br /> The VCUs (Appendix H) are constructed by Westates Carbon Company <br /> of Los Angeles, California, under the supervision of Ensotech, <br /> Inc. They consist of two granular activated carbon (GAC) units, <br /> made of stainless steel for the carbon cells, and carbon steel <br /> for unit structure. Each unit, with a volume of 93 cu. ft. , has <br />~ 2, 500 lbs of GAC. Each VCU has an inlet damper, and is connected <br /> in parallel. One of the units is in line, whereas the other unit <br /> act as a standby. Each unit is capable of handling 2 , 700 cfm of <br /> ' air, contaminated with maximum TCE and PCE concentrations of 2. 1 <br /> and 1. 7 ppmv, respectively, which are the maximum concentrations <br /> expected. The system will remove a minimum 90% of TCE and PCE in <br /> the exhaust air to a maximum of 0. 21 ppmv of total hydrocarbon. <br /> The maximum pressure drop across the bed is four inches of water. <br /> When the GAC gets saturated, standby GAC unit will be placed in <br /> line and the saturated GAC unit will be isolated. The saturated <br /> GAC will be sent to the manufacturer for regeneration. <br /> A duct heater (Appendix H) , supplied by Westates is connected in <br /> between the AST and VCU. The heater 1 ' 10" x 1110" is made of <br /> stainless steel . The heater increases the temperature of the <br /> exhaust air from AST by an average of 20 degrees, thus increasing <br /> the efficiency of the VCUs . The heater has a temperature <br /> controller and is ON only when the blower is running. <br /> 5. 5 CONCRETE PAD <br /> A concrete pad, 25 feet wide, 35 feet long and 27 inches thick, <br /> was constructed on the site in order to support the treatment <br /> system without cracking as per specifications in the Drawing No. <br /> 9004-1, Appendix D. The plot plan was slightly changed and an as <br /> built plan is attached. See Drawing No. 9004-2 in Appendix D. <br /> E' <br /> a <br /> 11 <br />