Ending months of speculation, President Obama today announced Gina McCarthy as his nominee for administrator of the Environmental Protection Agency.

McCarthy, who has served since 2009 as the head of EPA's Office of Air and Radiation, issued several significant and controversial rules during her tenure, including the utility MACT rule and the proposed section 111 greenhouse gas emissions standard for new gas- and coal-fired power plants. Opponents of the new sources standard claim it will not only prevent construction of any new coal-fired utilities, but will also lay the groundwork for further regulation, effectively shuttering existing coal power plants as well.

Her track record of pushing through and defending difficult and controversial rules while head of EPA's air office likely made her an attractive candidate to the president, as EPA is poised to issue a suite of additional rules — some air, some not — that will continue to pressure coal-fired power plants. These include impending decisions on how to regulate coal ash, a 316(b) rule governing cooling water intakes for power plants, as well as the new sources standard.

McCarthy now faces an uncertain confirmation battle in the Senate, where Republicans worry her selection presages more aggressive administrative action on climate change. Meanwhile, environmental groups are likely satisfied with the administration's choice of a seasoned agency insider as a signal of the president's commitment to action on greenhouse gas emissions.

If confirmed, McCarthy will have to finalize a number of proposed rules under court-ordered deadlines, including the regulations for new gas- and coal-fired utilities, cooling water intake systems for power plants and effluent guidelines for coal-fired power plants and onshore oil and gas production.

She will also have to defend the agency's controversial Renewable Fuels Standard, as well as preside over other rulemakings affecting everything from the control of concentrated animal feeding operations under the Clean Water Act, to the treatment of coal ash under the Resource Conservation and Recovery Act.

A particular challenge for McCarthy will be juggling the administration's competing priorities on unconventional natural gas and oil. As environmentalists press for tighter regulation of hydraulic fracturing and a move away from fossil fuels, the president continues to tout natural gas as a bridge to the nation's clean energy future and to extol it as a cheap, abundant alternative to coal.

The agency promulgated new Clean Air Act rules in 2012 to control volatile organic compounds, sulfur dioxide and hazardous air pollutants at gas well sites and transmission and storage facilities, but delayed for three years the effective date of the most controversial provisions that would require energy companies to utilize so-called green completions to capture methane during gas well drilling. EPA has also begun the rulemaking process to set new Clean Water Act effluent limits for shale gas extraction. But while the agency looks poised to continue its energy extraction enforcement initiative for the next three fiscal years, to date that initiative has failed to yield big-ticket cases.

In the meantime, no one yet knows how the sequester will affect the agency's regulatory and enforcement efforts. Unlike other federal agencies that have already communicated final furlough plans to career staff, EPA has not yet announced a concrete plan to deal with the sharp budget cuts that became effective March 1, 2013.

Budget cuts over the last few cycles have already forced the agency to trim discretionary contract spending, so the sequester's impact on personnel will likely be significant. Even with rolling — rather than wholesale — furloughs, EPA will likely be hamstrung in moving forward aggressively on its regulatory agenda.

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