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a. Groundwater Extraction and Air Stripping , Without Air Emission <br /> Control : This method has been used successfully since 1987 in the southern <br /> ' area of the site and a similar plant has been recently installed in the <br /> northern area of the site. Air stripping is also being considered for the <br /> central area. Extraction wells are used to pump contaminated groundwater out <br /> of the ground and into the air stripping towers. In the air stripping <br /> towers, the contaminant, primarily trichloroethene, is removed from the water <br /> and released to the air. Maximum air emissions are 0.4 pounds per day from <br /> the southern plant and 0.8 pounds per day from the northern plant. Average <br /> a emissions from both plants will be less than 0.1 pounds per day. <br /> E <br /> b. Groundwater Extraction and Air Stripping with Vapor Phase Carbon <br /> Absorption: The treatment method described in paragraph 5a may be modified <br /> by the addition of activated carbon to control air emissions. This <br /> alternative would be implemented by adding activated carbon beds to the air <br /> stripping towers to capture trichloroethene as it is removed from the <br /> groundwater. Air emission controls, such as carbon beds, may be deemed <br /> necessary based on health risks posed by releases of trichloroethene to air <br /> or by an ARAR requiring air emission control . The use of activated carbon is <br /> applicable to the existing air strippers as well as to the treatment plant <br /> planned for the central area. However, air emissions from the existing or <br /> planned treatment plants may be determined to be too low to make the use of <br /> carbon absorption necessary. <br /> c. Groundwater Extraction and Liquid Phase Carbon Absorption: Extracted <br /> groundwater may be treated directly with activated carbon without the use of <br /> air stripping. Contaminated groundwater would be pumped into carbon beds <br /> where the trichloroethene would be absorbed. Water leaving the carbon beds <br /> would be free of trichloroethene. Since the carbon beds will become filled <br /> ' with trichloroethene, they will have to be periodically cleaned or replaced. <br /> d. Groundwater Extraction and Ozonation with HpOyand UV Light: <br /> Trichloroethene in extracted groundwater could be reacted with ozone in the ? <br /> presence of ultraviolet light to form innocuous by-products. <br /> e. Groundwater Extraction and Biological Treatment in Fixed Bed Towers: <br /> Trichloroethene in extracted groundwater could be decomposed by micro- <br /> organisms. Contaminated water would be sprayed across the top of a tower <br /> filled with wood or plastic packing. Slime layers living on the packing <br /> would absorb and decompose the trichloroethene. <br /> 6. Treated Water Dis osal/Reuse Alternatives: An acceptable method for <br /> reusing or disposing o t e c eane water mast be selected. Treated l <br /> groundwater is expected to meet drinking water standards. Since some of the <br /> groundwater extraction wells will be shallow (less than 50 feet deep) , ' <br /> materials commonly found in shallow groundwater in the San Joaquin valley <br /> will be present. Treated water will be monitored to assure that water <br /> quality is acceptable for the intended reuse/disposal option. Flow rates for <br /> treated water are expected to be 300 gallons per minute (GPM) for the <br /> southern plant, 300 GPM for the northern plant, and 600 GPM for the central <br /> plant. i <br /> I <br />