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Statement of Need: On December 7, 2009, the EPA found that current and projected concentrations of greenhouse gases (GHG) in the atmosphere threaten the public health and welfare of current and future generations. Electric generating units (EGUs) are the single biggest stationary source of greenhouse gases and account for well over a third of all greenhouse gas emissions in the United States. Recognizing that greenhouse gases pose a threat to the public health and welfare and that EGUs are one of the largest sources of GHG emissions, the EPA has begun taking regulatory steps to ensure reductions of GHG emissions from EGUs. The regulatory path that the EPA has embarked upon commits the agency to regulating emissions from, not just new EGUs, but also existing EGUs (including those that are modified).

Summary of the Legal Basis: EPA will use the Clean Air Act authority under section 111 (b) to set GHG standards for modified EGU sources. The Clean Air Act (CAA) gives the Agency broad authority to set standards for emissions of "air pollutants." GHGs have been determined by the U.S. Supreme Court to be "air pollutants" that are subject to regulation under the CAA. Because of this and the fact that GHGs are not currently regulated under either National Ambient Air Quality Standards or under the National Emission Standards for Hazardous Air Pollutants, EPA has the authority to address them under the New Source Performance Standards (NSPS) program.

Alternatives: Not yet determined.

Anticipated Costs and Benefits: At this time we do not have any estimates regarding the benefits and costs of this action, but we do expect it to be a significant regulatory action with annual effects on the economy exceeding $100 million.

Risks: Not yet determined.