A home in Harriman, Tenn. flooded with coal ash sludge from the Kingston plant. Credit: J. Miles Carey/Knoxville News Service.On December 22, 2008 an earthen retaining wall of a coal ash pond breached at the Kingston Fossil Plant in Tennessee, releasing more than 5.4 million cubic yards ( 1 billion gallons) of wet coal ash.  That quantity is enough to flood more than 3,000 acres one foot deep, or fill 1,660 Olympic-size swimming pools. The Kingston Fossil Plant is located at the confluence of the Emory and Clinch Rivers near Kingston, Tennessee.  The ash ponds were separated from the river only by earthen retaining walls.

The Kingston plant is owned by the Tennessee Valley Authority (TVA), a federally owned corporation that provides navigation, flood control, electricity generation, fertilizer manufacturing, and economic development in the Tennessee Valley.

The sludge flowed downhill in a wall as high as 6 feet, burying porches and garage doors. About a dozen homes were directly affected. Some were swamped with mud and another was swept off its foundation. Three have been declared uninhabitable.
 The slide also downed nearby power lines.  An estimated 78,000 cubic yards, or 15.7 million gallons, of sludge covered local railroad tracks and Swan Pond Road. In all, morfe than 300 acres of land were coated by the sludge.

The accidengt dumped a mix of ash and water in the Emory River, causing residents of nearby Kingston to worry about their drinking water. TVA has said the water is safe to drink.

TVA said that the utility will pay to test local wells for contamination and would start air quality testing.  The Tennessee Department of Environment and Conservation that the mixture of coal fly ash and water didn't pose an immediate risk to residents unless they ingested it.

Coal ash, a byproduct of burning coal, contains toxic heavy metals like arsenic, lead and selenium that can cause cancer and neurological problems.  The ash is stored in containment areas; thee one for which the retention wall failed covers about 40 acres.  It is one of three containment areas at the Kingston plant.

The extent of the environmental damage and human health risk will require careful follow-up monitoring and assessment.  A 2007 report by the U.S. Environmental Protection Agency found that fly ash contains significant amounts of carcinogens and retains the heavy metal present in coal in far higher concentrations. That EPA report found that the concentrations of arsenic to which people might be exposed through drinking water contaminated by fly ash could increase cancer risks several hundredfold.

A 2006 study by the National Research Council found that these coal-burning byproducts “often contain a mixture of metals and other constituents in sufficient quantities that they may pose public health and environmental concerns if improperly managed.” The study said “risks to human health and ecosystems” might occur when these contaminants entered drinking water supplies or surface water bodies.

The Kingston spill is far larger than the other two similar disasters. One spill in 1967 on the Clinch River in Virginia released about 130 million gallons, and the other in 2005 in Northampton County, Pa., released about 100 million gallons into the Delaware River.

Kingston is one of TVA’s larger fossil plants.  It generates 10 billion kilowatt-hours of electricity a year, enough to supply the needs of about 670,000 homes in the Tennessee Valley.

Sources

• CNN, Tennessee sludge spill estimate grows to 1 billion gallons, December 26, 2008
• New York Times, Coal Ash Spill Is Much Larger Than Initially Estimated, December 26, 2008.
• Tennessee Valley Authority, Ash Slide at TVA's Kingston Fossil Plant, December 25, 2008.
• Tennessean.com, TVA vows to test wells and air near ash spill, December 29, 2008.