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t a. Groundwater Ex6raction and Air Stripping, Without Air Emission Control: This method has been used successfully since 1987 in the southern area of the site and a similar plant has been recently installed in the northern area of the site. Air stripping is also being considered for the central area. Extraction wells are used to pump contaminated groundwater out of the ground and into the air stripping towers. In the air stripping towers, the contaminant, primarily trichloroethene, is removed from the water and released to the air. Maximum air emissions are 0.4 pounds per day from the southern plant and 0.8 pounds per day from the northern plant. Average emissions from both plants will be less than 0.1 pounds per day. b. Groundwater Extraction and Air Stripping with Vapor Phase Carbon Absorption: The treatment method described in paragraph 5a may be modified by the addition of activated carbon to control air emissions. This alternative would be implemented by adding activated carbon beds to the air stripping towers to capture trichloroethene as it is removed from the groundwater. Air emission controls, such as carbon beds, may be deemed necessary based on health risks posed by releases of trichloroethene to air or by an ARAR requiring air emission control. The use of activated carbon is applicable to the existing air strippers as well as to the treatment plant planned for the central area. However, air emissions from the existing or planned treatment plants may be determined to be too low to make the use of carbon absorption necessary. c. Groundwater Extraction and liquid Phase Carbon Absorption: Extracted groundwater.may be treated directly with activated carbon without the use of air stripping. Contaminated groundwater would be pumped into carbon beds where the trichloroethene would be absorbed. Water leaving the carbon beds would be free of trichloroethene. Since the carbon beds will become filled with trichloroethene, they will have to be periodically cleaned or replaced. d. Groundwater Extraction and Ozonation with H2O2and UV light: Trichloroethene in extracted groundwater could be reacted with ozone in the presence of ultraviolet light to form innocuous by-products. e. Groundwater Extraction and Biological Treatment in Fixed Bed Towers: Trichloroethene in extracted groundwater could be decomposed by micro- organisms. Contaminated water would be sprayed across the top of a tower filled with wood or plastic packing. Slime layers living on the packing would absorb and decompose the trichloroethene. 6. Treated Water Disposal/Reuse Alternatives: An acceptable method for reusing or disposing of the cleaned water mast be selected. Treated groundwater is expected to meet drinking water standards. Since some of the groundwater extraction wells will be shallow (less than 50 feet deep), materials commonly found in shallow groundwater in the San Joaquin valley will be present. Treated water will be monitored to assure that water quality is acceptable for the intended reuse/disposal option. Flow rates for treated water are expected to be 300 gallons per minute (GPM) for the southern plant, 300 GPM for the northern plant, and 600 GPM for the central plant.