They allege the NC Department of Environment and Natural Resources officials deliberately misled the public about when they knew about the pumping.
Duke has been cited by the state for illegally pumping 61 million gallons of contaminated water from two coal ash dumps into a canal leading to the river. State officials said so much water was removed it may have cracked one of the dams.
The ABC11 I-Team was the first to ask the state about the pumping after Chopper 11 spotted a pump at the side of one of the ponds.
DENR told ABC11 their inspectors also found those pumps on that very same day. What DENR didn't tell us was that a month earlier, another inspector was at the same site and reported that the "liquid level had been lowered to investigate joint-hole leakage and potential repairs."
Documents show DENR knew Duke was pumping and knew there could be structural problems weeks before they told us they found those pumps.
For some environmentalists, it all adds up to a smoking gun.
"By all appearances, they were concealing information from the public about these first inspections, concealing information about these ponds that had pipes that were leaking, and that they were actually lowering the ponds by emptying their contents out in the river," offered Pete Harrison with the environmental group Waterkeeper Alliance.
ABC11 has contacted DENR for a response and we haven't heard back yet.
The coal ash ponds have been under scrutiny since Feb. 2 spill at a Duke coal ash dump in Eden coated 70 miles of the Dan River in toxic sludge.
North Carolina officials said they will partner with the U.S. Environmental Protection Agency to pursue joint enforcement actions against Duke for Clean Water Act violations at Dan River and other sites.
Duke operates 14 facilities in North Carolina with leaky unlined coal ash dumps, all of which have been cited for polluting groundwater.
Federal prosecutors are also conducting a criminal investigation of the Dan River spill and probing the relationship between Duke and the state officials charged with enforcing clean water laws. There have been at least 23 subpoenas issued since the spill and a grand jury met this week at the federal courthouse in Raleigh