A large reservoir of coal ash is leaking into a river that flows through southern Virginia and North Carolina. The reservoir began leaking on Sunday after a pipe burst, and by Monday had released 50,000 to 82,000 tons of coal ash and 24 to 27 million gallons of contaminated water into the bordering Dan River — in total, enough ash to fill between 20 and 32 Olympic-size swimming pools. Leakage has slowed since, but work is still ongoing to fully seal the pipe.

The river and reservoir sit beside Duke Energy's Dan River Steam Station, a coal-fired power plant in Eden, North Carolina. The station was decommissioned in 2012, but Duke Energy has not finished closing its ash basin, which is around 27 acres in size (pictured above).

"We're working closely with local, state and federal authorities," Keith Trent, Duke Energy's executive vice president, said in a statement on Tuesday. "Company leaders, engineers, scientists, environmental specialists, industry experts and plant personnel assembled at the site have been working around the clock to safely devise both short- and long-term solutions, as well as to continually monitor the effects of the release."

Initial test results by North Carolina's Department of Environment and Natural Resources found normal levels of temperature, pH, dissolved oxygen, and conductivity in the river surrounding the station. The department is still awaiting lab results on the presence of heavy metals, sulfates, nutrients, and suspended solids; for now, Duke Energy says that its own test show that downstream water has remained safe and can be treated through normal processes.

"We’re working hard to get all those results back from our state laboratory and analyze them so we can provide the public with useful, timely information about any of the coal ash constituents we’re seeing in the Dan River," John Skvarla, secretary of North Carolina's environmental department, says in a statement. The department expects to publish results this week.

Duke Energy says that engineers and scientists remain on site today working to seal the pipe. Though its crews located the ruptured area Tuesday night, as of yesterday it had not devised a permanent solution.