Alternatives for the specific media and site areas either can be conducted separately or confined to comprehensive alternatives for the entire site. The screening process involves evaluating alternatives with respect to their cost, implementability, effectiveness, and environmental and institutional considerations. Whenever Environmental Protection Agency (EPA) determines that there may be an imminent and substantial endangerment to the public health or welfare or the environment due to an actual release or a threat of release of a hazardous substance, pollutant, or contaminant, Comprehensive Environmental Response Compensation and Liability Act authorizes EPA to take a response action. The feasibility study involves the development, screening and detailed evaluation of alternative remedial actions. A preliminary site characterization summary is prepared to determine the feasibility of potential technologies and assist both the lead and support agencies with the initial identification of applicable or relevant and appropriate requirements.