— Duke Energy failed to get permits it needed at six power plants to discharge rainwater from those sites into nearby rivers and streams, according to notices of violation the state Department of Environment made public Monday.

The state Department of Environment and Natural Resources issued two "notices of violation" on Friday to the Dan River Steam Station, the retired power plant where a ruptured stormwater pipe allowed nearly 40,000 tons of coal ash to spill into the Dan River near Eden on Feb. 2. Those notices threatened $25,000-per-day fines for discharging water into the river without a permit and undisclosed fines for other water-quality violations.

Coal ash is what's left over after coal is burned for fuel. It contains mercury, arsenic, selenium and other materials that can be toxic to humans and wildlife.

On Monday, the state announced it had issued similar notices to five more plants around the state, including plants in Goldsboro, Roxboro, Wilmington, Stokes County and Rutherford County. The notices indicate that the company never had permission to allow stormwater, which could be carrying pollutants concentrated by the coal-burning process, into nearby rivers.

Each notice says Duke is liable for $25,000-per-day fines because it neither has nor has applied for permits to discharge stormwater at those plants, but it's unclear for how long a period DENR could potentially enforce the fines.

Environmental advocates point out that the state has known for years the sites in question lacked stormwater permits, going back at least as far as 2008, when a massive coal ash spill in Tennessee prompted public concerns over the ash storage ponds. Asked why the state was cracking down now, DENR spokeswoman Bridget Munger said the Dan River spill had concentrated a lot of the state's attention on the issue of ash ponds.

"With regard to this (the Dan River) spill, there have been some surprises," Munger said.

For example, the pipe that failed under the Dan River site was made of corrugated metal, not concrete as the company had originally told the state.

"I think, at this point, we want to be extremely thorough so we don't have any more surprises like this," she said.

"Our agency is determined to make sure that all of these facilities are in compliance with state and federal law,” DENR Secretary John Skvarla said in a statement. “We’re doing everything in our power to prevent environmental disasters like what we’ve seen at the Dan River. We are committed to protecting public health and the natural resources of our state.”

DENR critic Frank Holleman, an attorney with the Southern Environmental Law Center, took issue with that statement.

Holleman said DENR knew that the six coal ash sites sites lacked stormwater permits when it filed its August 2013 lawsuit against Duke. However, the lawsuit doesn't include any mention of those violations.

"Why didn’t DENR enforce the law then, and why did it enforce the law only after the spill and a federal grand jury was empaneled?" Holleman asked. "If DENR had enforced the law then, would that have led to the most basic inspection of this unpermitted pipe and thereby discover that the pipe was rotting away?"

Agency spokesman Drew Elliot said DENR has been working since 2010 "to develop a stormwater permit template that can be used at all coal-fired facilities and had been asking for information from Duke as part of that process."

"In light of events at the Dan River facility and the subsequent investigation, DENR determined Duke Energy had been given enough time to comply, so the department issued a notice of violation," Elliot said.

Elliot also said the stormwater violations didn't appear in the 2013 lawsuit because the lawsuit was focused on groundwater contamination, which he said "was an active threat to the environment."

Duke has 14 working or shuttered coal-fired plants around the state, but these six are the only ones liable for this kind of violation.

Four other Duke plants have stormwater discharge permit applications under review by the state Division of Energy, Mineral and Land Resources, while two more have separate stormwater requirements included in their existing wastewater permits.

One Duke plant has withdrawn its stormwater permit, and the final one has had its stormwater conditions rescinded. In both instances, the plants no longer conducted the industrial activity covered by federal stormwater regulations.

Duke has 30 days to respond to each of the violation notices. They could make the case that they weren't required to have permits in these instances or try to negotiate some sort of settlement.

"We will respond to the state," Duke spokeswoman Paige Sheehan said.

Pressed for how the company could have operated without such a basic permit, Sheehan said she could not elaborate beyond her statement.