Canoe guide Brian Williams dipped his paddle downstream from where thousands of tons of coal ash has been spewing for days into the Dan River, turning the wooden blade flat to bring up a lump of gray sludge.
On the river bank, hundreds of workers at a Duke Energy power plant in North Carolina scrambled to plug a hole in a pipe at the bottom of a 27-acre pond where the toxic ash was stored.
Since the leak was first discovered by a security guard Sunday afternoon, Duke estimates up to 82,000 tons of ash mixed with 27 million gallons of contaminated water has spilled into the river.
Officials at the nation's largest electricity provider say they cannot provide a timetable for when the leak will be contained, though the flow has lessened significantly as the pond has emptied.
An Associated Press reporter canoed downstream of the spill at the Dan River Steam Station and saw gray sludge several inches deep, coating the river bank for miles.
Williams, a program manager with the Dan River Basin Association, worried that the extent of the damage might not be fully understood for years.
"How do you clean this up?" he said, shaking his head as he churned up the ash with his paddle. "Dredge the whole river bottom for miles? You can't clean this up. It's going to go up the food chain, from the filter feeders, to the fish, to the otters and birds, to people. Everything in the ecosystem of a river is connected."
Environmental regulators in North Carolina say they are still awaiting test results to determine if there is any hazard to people or wildlife. Coal ash is known to contain a witches' brew of toxic chemicals, including lead, arsenic, mercury and radioactive uranium.
Twenty miles downstream from the spill site and across the state line in Danville, Va., wary fishermen watched ash swirl in the water. A hand dipped into the water came out coated slate gray.
Municipal officials in Danville there say they are successfully filtering out contaminates in the drinking water for the city of about 43,000 people.
Meanwhile, officials in Virginia Beach, Va., announced they had stopped drawing water from Lake Gaston, a major reservoir fed by the Dan.
Personnel from Duke Energy and an alphabet soup of state and federal agencies, including the U.S. Environmental Protection Agency and U.S. Fish and Wildlife Service, traveled the river in motorboats Wednesday, collecting water and sediment samples. A command center has been set up at the power company's facility in Eden.
An EPA spokeswoman did not respond to questions Wednesday, including when the test results on the samples collected by the agency would be made public.
Environmentalists and government regulators have been warning for years that the 31 ash ponds at Duke's power plants in North Carolina had the potential for calamity, especially after a similar pond in Kingston, Tenn., burst open in 2008.
"Even without a spill, these settling ponds have been releasing continuous contamination into the rivers downstream from coal-fired power plants," said Avner Vengosh, a professor of geochemistry at Duke University, which was named for the same family that founded the power company.
Duke Energy officials have always insisted the ponds at its facilities were well-engineered and safe. At the Dan River plant, the waste pond was expanded more than 40 years ago over an older storm water drainage pipe. That pipe, which empties into the river, collapsed without warning sometime last weekend, draining the pond above.
Though the coal-fired turbines at the Dan River facility were shut down in 2012 and replaced with an adjacent plant fueled by natural gas, the company had no firm plans for when and how to clean up the ash ponds.