New York Times: The federal Environmental Protection Agency will join North Carolina regulators in addressing potential violations of the Clean Water Act at Duke Energy power plants, including a massive spill of toxic coal ash last month in the Dan River, state officials said on Friday. The secretary of the state’s Department of Environment and Natural Resources, John Skvarla, invited the federal agency’s “participation and coordination” in a March 14 letter to the head of its regional office, the state department…