Lessons Learned from TVA-Kingston Coal Ash Spill

On March 19, 2014, the technical workgroup drafting the Dan River long-term monitoring and assessment plan heard a presentation by the U.S. Environmental Protection Agency’s remedial project officer for the Tennessee Valley Authority-Kingston incident that occurred in December 2008. There are significant differences between the TVA and Dan River events, but there also are similarities that government agencies can learn from and apply in the Dan River situation.

 

On December 22, 2008, the retention wall of a coal ash-holding pond failed at the TVA Fossil Plant in Roane County, Tenn., about 30 miles west of Knoxville. More than 5.4 million cubic yards of coal ash, mixed with 327 million gallons of water, spilled into the Emory River. The release covered approximately 300 acres outside the TVA coal ash dewatering and storage areas.

 

The coal ash slide disrupted electrical power and ruptured a gas line, causing the evacuation of 22 residents. The spill significantly affected the environment and disrupted people’s lives. Water quality in the Emory River at the site of the ash spill was impaired, and aquatic habitat was destroyed, principally by burial under the coal ash.

 

Differences between the two incidents:

 

  • The TVA spill was nearly 140 times larger than Duke Energy’s spill into the Dan River in Eden. N.C.
  • It is estimated that 90 percent of the material spilled at TVA was recovered by dredging in a two-year period. Nearly 510,000 cubic yards of coal ash were left in the Emory River, which is about 13 times more ash than was spilled at the Duke Energy site.
  • Because of several impoundments near the TVA location, the receiving area acted more like a lake than a river. Most of the ash stayed near the spill site, allowing for effective recovery. The Dan River is a free-flowing water body for most of its length, except for a few small dams between the spill site and Kerr Reservoir. As a result, the Duke Energy spill transported ash for approximately 70 miles, although the amount of ash moved and likely deposition sites are still being evaluated.

Similarities of the two incidents:

 

  • Both involved coal ash, which contains potentially toxic metals such as arsenic, selenium and mercury.
  • Both occurred during winter, when water temperatures are relatively low and biological activity is minimal.
  • Existing fish consumption advisories were in place, due to legacy PCB and mercury contamination not related to the ash spill. The Dan River advisory does not cover the entire length of the river; a section from Danville west to the North Carolina state line is not under the advisory.

Beginning around May 1, 2014 about 2,500 tons of coal ash will be vacuum-dredged from the Dan River from the Schoolfield Dam area in Danville.  The removal and 'de-watering' process is expected to be completed by July 1.

 

Although the scale of the two incidents sets them apart, concerns over potential environmental impacts are the same. The types of monitoring and analyses used in response to the TVA spill also will be part of the Dan River long-term assessment plan. Data review in the Dan River case will be in reference to the appropriate contaminant levels for sediment and fish tissue, as well as applicable water quality standards in Virginia and North Carolina.

 

In the TVA incident, ash recovery and ecosystem and human health assessments were conducted over a five-year period (2009-2013); long-term monitoring will continue for 30 years at five-year intervals. The final two-year period of monitoring and assessment was an ecosystem study and human health screening. It cost about $40 million; more than 16,000 samples were collected and 400,000 analyses were performed.

 

Current monitoring shows that the Emory River system essentially has returned to pre-spill conditions. Lessons learned at the TVA site include:

 

  • No impact on fishery reproduction detected; metals concentrations in fish tissue did not become elevated.
  • If the mixture ratio of ash to native sediment was at or below 40/60, the organisms that live on the river bottom were not significantly affected, though some mayfly larvae did accumulate low levels of selenium and arsenic.
  • Most of the ecological impact was due to “acute burial” by coal ash, not metals content of the ash.
  • Monitoring showed moderate to low ecosystem risks.
  • Human health risks have been deemed acceptable, based on nearly 200 university-conducted health assessments.
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Virginia Department of
Environmental Quality
P.O. Box 1105
Richmond, VA 23218
(804) 698-4000


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