The Green Scene: Coal Ash — a pond farewell

When you flip a light switch in Western North Carolina, odds are you’re drawing electricity from Progress Energy’s Skyland power plant, which burns mountains of West Virginia coal that comes in by rail. But ever since a dam at the Kingston coal-powered plant near Knoxville failed, spilling more than a billion gallons of toxic coal-ash sludge, similar facilities around the country have come under increased scrutiny.

“More people are asking what we do,” says Asheville Plant Manager Garry Whisnant. The Skyland facility’s much smaller coal-ash pond is well-monitored, says 27-year Progress Energy veteran, and the earthen dam is in good shape (see Xpress blog post “Progress Energy Says Asheville Coal Ash Ponds Safe”).

At the Asheville plant, built in 1964, pulverizers grind the coal, giant fans suck in the air needed for combustion, and humongous turbines generate steam.

Before viewing the pond, however, we get a PowerPoint science lesson from the plant’s environmental coordinator, Laurie Moorhead. Some elements in the coal, such as zinc and molybdenum, don’t burn, she explains. Instead, they melt during combustion and wind up as “bottom ash.” Another process removes toxic gases, and big catalytic converters like the one in your car scrub out the particulates (“fly ash”).

In the scrubber the utility installed in 2000 to meet more stringent Clean Air Act requirements, water and calcium carbonate (limestone) are added to the flue gases, which contain sulfur dioxide and nitrous oxides (SO2 and NOx), Moorhead explains. A limestone-based mixing-and-draining process converts some of the resulting waste to gypsum, which can be sold to wallboard manufacturers.

As we start our walking tour, Whisnant observes that what the plant does is really simple: “You grind coal, you burn coal, you make heat, you turn turbines … you get electricity.” He points out all the equipment mentioned by Moorhead—because speech is impossible amid the racket from the fans.

The control room, though, is eerily quiet. Computer screens detail every aspect of the plant’s operations, including emissions and even requests from headquarters to boost production as a cold front advances into the Carolinas. Like extreme summer weather, this puts the plant on “full load alert,” because energy from burning coal can’t be stored. “We have to burn it as we need it,” Mike Thomas explains.

Outside, we peer up at the “smoke” stack. But what actually billows out is white water vapor, because down below, the scrubber is removing the toxins and coal ash that used to be released into the air.

The cleaning process, though, creates more ash that has to be managed and stored. In a plant that uses a “dry” process, those solid wastes wind up in lined landfills. But the Skyland plant’s “wet” process washes the coal ash into the huge active retaining pond. Most coal-burning plants use the wet process, which is typically cheaper, says Whisnant.

Moorhead also shows off the artificial wetland system that helps filter the wastewater. It drains through a series of lined ponds that use bulrushes, cattails and bacteria to make mercury and other toxins settle out. After a little tumble through a rocky field, the water moves on to a second biological filtering process that removes more mercury, along with iron, manganese and selenium. “It’s a pretty groovy system,” says Moorhead.

After passing through a monitoring station, the water flows on to a small pond located below a dam. Water from the active ash pond also drains into this pond.

Progress Energy has a permit from the state to discharge this water into the French Broad River, she notes. The company regularly samples its effluent and reports the results to the state Division of Water Quality, as required by the Clean Water Act.

We drive down a road between the pond and the wetland to reach the 95-foot dam, which looms over Interstate 26. The highway didn’t exist when the plant was built, notes Whisnant. Looking back toward the plant from the top of the dam, we see water rippled by the wind, cattails growing wild along one bank. A grayish scum collects in a corner of the pond: cenopheres—a hollow, metallic material that contractors collect by boat, haul away and use to make bowling balls and some concretes, says Moorhead.

Some of the ash collects in globs near the pipes; these “clinkers,” as Whisnant calls them, are easily scooped up for reuse as infill in projects such as the Asheville Regional Airport’s ongoing expansion.

But most of the ash settles to the bottom of the pond, where it may sit indefinitely, barring an accident like the one at the Kingston plant. About 80 percent of this toxic sediment is fly ash from the scrubber, says Whisnant.

Asked if we’ll still be getting most of our electricity from fossil fuels such as coal in the future, he muses, “We need a scientific breakthrough [in] battery technology.” Alternatives such as electric cars and solar-power systems are limited by present technology, says Whisnant. “In the meantime, we’re trying to be good stewards for the environment with the process we have.”

He adds that an analysis of the cause of the Kingston plant disaster is being done—and when the conclusions are released, he hopes everyone will learn from them.

Send your environmental news to mvwilliams@mountainx.com.

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About Margaret Williams
Managing Editor Margaret Williams has been at Xpress since 1994. An Alabama native, she has lived in Western North Carolina since 1987.

One thought on “The Green Scene: Coal Ash — a pond farewell

  1. bobash

    Without a liner nothing just “sits” in the bottom of the pond. Are there any monitoring wells or a “witness” system that would collect any leachate created by the process beneath the pond. Without such monitoring points it is impossible to say no environmental damage is occurring. Just remember a guy by the name of Darcy said, “Nothing is Impermeable” not even the magical pond bottom

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