Patrick Sullivan, Assistant Inspector General for Investigations, Office of Inspector General, EPA, testifies before the House Oversight and Government Reform full committee hearing, Wednesday, May 7, 2014 in Washington. A turf battle between the Environmental Protection Agency's inspector general and an EPA unit run by President Barack Obama's political staff gets an airing before Congress. (AP Photo/Molly Riley)
Bob Perciasepe, Deputy Administrator, EPA, testifies before the House Oversight and Government Reform full committee hearing, Wednesday, May 7, 2014 in Washington. A turf battle between the Environmental Protection Agency's inspector general and an EPA unit run by President Barack Obama's political staff gets an airing before Congress. (AP Photo/Molly Riley)
A presentation prepared in 2010 for then-EPA Administrator Lisa P. Jackson made clear that a pre-emptive veto "had never been done before in the history" of the Clean Water Act and could risk litigation. (Associated Press)
Environmental Protection Agency Administrator Gina McCarthy called for the inspector general to "temporarily halt" a probe after an investigator reported threatening behavior from an official inside the homeland security office, documents show. (Associated Press)
FILE - This July 1, 2013 file photo shows smoke rises from the Colstrip Steam Electric Station, a coal burning power plant in in Colstrip, Mont. The Supreme Court on Tuesday handed the Obama administration an important victory in its effort to reduce power plant pollution that contributes to unhealthy air in neighboring states. In a 6-2 decision, the court upheld a rule adopted by the Environmental Protection Agency in 2011 to limit emissions from plants in more than two-dozen Midwestern and Southern states. The pollution drifts into the air above states along the East Coast, and the EPA has long struggled to devise a way to control it. (AP Photo/Matthew Brown, File)