Coal Ash Into Bridges

 

A Harriman, Tennessee, subdivision was swamped by coal ash sludge that spilled from a TVA pond in December. Duke University researchers say, “Our radioactive measurements of solid ash samples from Tennessee suggests the ash has radiation levels above those reported by the Environmental Protection Agency (EPA) for typical coal ash.”

A billion gallons of watery ash, laced with toxic materials, spilled from a holding pond and fouled 300 acres and two rivers near the Tennessee Valley Authority’s Kingston Fossil Plant on December 22,last year. Forty homes were affected, three became uninhabitable, roads were ruined, and residents were left wondering whether their water would ever be safe to drink.

The TVA estimates cleanup costs at $525 million to $825 million or more. There are about 300 similar wet impoundment facilities nationwide; most are regulated by the states, said an Environmental Protection Agency spokesperson. To reduce the need to store the materials, the EPA promotes beneficial reuse of coal combustion products such as fly ash, bottom ash and boiler slag.About 43 percent of the 131 million tons of coal combustion products generated in 2007 found beneficial uses, according to the American Coal Ash Association, based in Aurora, Colorado. However, some environmentalists are skeptical about that claim. Improperly handled ash can leach arsenic, lead, chromium, selenium and other toxic materials into ground and drinking water, she cautioned.

The EPA says that although hundreds of fish were killed, the water in the Tennessee spill zone meets safety standards. However, the Sierra Club alleged that the samples were taken upstream from the spill.

Soil in the zone shows elevated arsenic levels, although not enough to be considered a hazardous waste, the TVA reported.

In 2007, more than 80 percent of coal-plant boiler slag was utilized, mostly for sandblasting or as the grit on roofing shingles. Forty percent of bottom ash became a gravel substitute, fill for embankments or ice control agent, according to the coal ash group. However, use of coal ash as structural fill is a very, very dangerous use of ash About 44 percent of fly ash found uses, mostly as a substitute for some of the Portland cement in concrete, a use the EPA especially encourages because any heavy metals in the ash are trapped forever. (Concrete is composed of sand, gravel and Portland cement to hold it all together.

Fly ash makes concrete stronger and less porous, as well as generally less expensive, said Colin Lobo, engineering vice president of the National Ready Mixed Concrete Association, the concrete industry’s largest trade group.

Production of Portland cement releases large amounts of the greenhouse gas carbon dioxide, so reducing its use helps the environment. Not only does the concrete become greener in that sense, but it performs better.