— State environmental regulators have known for about five years that some coal-fired power plants in North Carolina didn't have required permits to discharge stormwater into nearby lakes and rivers, according to internal emails.

The state Department of Environment and Natural Resources last week issued notices of violation against six Duke Energy power plants, charging that the utility never obtained stormwater permits for them and threatening $25,000-a-day fines.

DENR said a Feb. 2 spill of nearly 40,000 tons of toxic coal ash into the Dan River from a shuttered Duke plant in Eden prompted a review of all environmental permits there and at Duke's 13 other current or retired coal-fired plants statewide.

More than 400 pages of emails obtained by the Southern Environment Law Center as part of the group's legal efforts to shut down the coal ash ponds show that DENR has been studying the permit issue since a massive coal ash spill in Tennessee in late 2008.

Regulators even created a color-coded spreadsheet of North Carolina power plants to determine which ones needed permits and which didn't.

By 2011, emails show, state tests found mercury in runoff from coal ash in Lumberton and bromide in coal ash runoff near Eden, and DENR officials asked the Duke and Raleigh-based Progress Energy, which Duke acquired in 2012, obtain stormwater permits for their plants.

The two utilities pushed back against the demand.

"Why we would do this when we are looking for a kinder gentler regulatory framework according to the Governor?" Duke environmental and legislative director George Everett asked in a July 20, 2011, email, referring to then-Gov. Beverly Perdue.

DENR regulators held their own against the utilities until early 2012, when Republican lawmakers cut the agency's budget. That's when the permitting process ground to a halt, according to emails from DENR environmental engineer Bethany Georgoulis.

"We were told to wait to do anything with those 'new' draft permits until Matt (Matthews) could speak with George (Everett) again. To our knowledge, Matt and George could never get a hold of one another," Georgoulis wrote on Sept. 12, 2013.

"Over the last year and a half, we repeatedly asked for a status and direction on these (permits), and we have been given none," she wrote. "We stopped asking."

DENR spokesman Drew Elliott couldn't explain Tuesday why Matthews, the agency's surface water protection section chief, was unable to reach Duke's environmental director for a year and a half.

"While our focus is on how to protect the environment and public health going forward, we will continue to look into decisions made under previous administrations," Elliott said in an email to WRAL News.