Alarmed by toxic coal ash seeping into Illinois’ only national scenic river, a conservation group Tuesday declared it one of the nation's most threatened waterways.

Orange- and purple-hued muck often can be seen leaching from the banks of the Middle Fork of the Vermilion River as it meanders past a shuttered Dynegy coal plant near Oakwood, about 25 miles east of Urbana. The pollution problems led the nonprofit group American Rivers to list the stream as one of America’s most endangered rivers, adding another voice to local and national efforts intended to pressure Dynegy’s new owners to clean up the site.

Before Houston-based Dynegy closed the coal plant in 2011, more than 3.3 million cubic yards of coal ash had been dumped into pits next to the river — enough to fill the Empire State Building nearly 2½ times. Testing by Dynegy and the nonprofit Prairie Rivers Network shows the multicolored waste oozing into the water contains dangerous levels of heavy metals found in coal ash, including arsenic, chromium, iron, lead and manganese.

“There aren’t many ways to experience nature like this in Illinois,” said Andrew Rehn, water resources engineer for the network. “The Middle Fork needs to be protected from coal ash so future generations can enjoy its scenic beauty.”

What’s left of the Vermilion Power Station rises above the river about a mile downstream from a launch that draws thousands of paddlers, kayakers and tubers to the area every year. It also is along a 17-mile stretch of the river protected in 1989 under the federal National Wild and Scenic Rivers Act, a designation based in part on the dozens of endangered and threatened species in the river and surrounding woods.

In 2012, Dynegy was cited by the Illinois Environmental Protection Agency for water pollution violations at the site. The case is still open.

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Dynegy has said it is negotiating a settlement with regulators. The company recently was absorbed by another Texas-based electricity provider, Vistra Energy Corp.

Before the deal closed, Dynegy suggested it could protect the river by capping waste pits to prevent rain and snowmelt from washing coal ash into the water. But in November, Dynegy sent state regulators a report that estimated the normal flow of the Middle Fork is eroding the river banks by up to 3 feet a year, making it more likely the toxic slurry will be exposed below the proposed caps.

Because the power plant has been closed for so long, the ash pits are exempt from federal regulations enacted by the Obama administration in 2015. Opposition from Dynegy and other energy companies prompted the Trump administration last year to reconsider the safeguards; a separate proposal in Illinois also has been sidetracked.

Each year, American Rivers highlights 10 streams nationwide where policymakers are considering action to address significant threats to people and wildlife. Others in the Midwest on this year’s list include the Kinnickinnic River in northwest Wisconsin and the Mississippi River Gorge and Boundary Waters, both in Minnesota.

“We’ve seldom seen a collection of threats this severe, or an administration so bent on undermining and reversing protections for clean water, rivers and public health,” Bob Irvin, the group’s president, said in a statement. “This is the kind of destruction that will be difficult, and in some cases impossible, to reverse.”

mhawthorne@chicagotribune.com

Twitter @scribeguy

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