The US Environmental Protection Agency (EPA) approved the Tennessee Valley Authority’s (TVA) selected cleanup plan for the next phase of coal ash removal at the TVA Kingston disaster site in Roane County, Tenn.
The $268 million plan could serve as a model for best-practices in the disposal of coal ash produced from power generation. U.S. coal-fired power plants generate nearly 140 million tons of fly ash, scrubber sludge, and other combustion wastes every year, and the EPA has identified at least 70 impoundment sites in need of structural improvements.
The cleanup plan, one of three alternatives proposed to the public earlier this year, requires TVA to permanently store on-site all of the ash being removed from the Swan Pond Embayment, which includes land and bodies of water adjacent to the TVA coal ash disposal area. The embayment area will then be restored.
The plan calls for the removal and consolidation of approximately 2.5 million cubic yards of ash from the embayment. All the ash will be consolidated on-site in the re-engineered TVA coal ash disposal area, and no material will be taken off-site. Keeping all the ash on site will minimize heavy truck traffic in the Roane County community, reduce wear and tear on area roads, and be less disruptive to local traffic and commerce. On-site disposal also addresses community concerns about proper disposal and management of ash in off-site landfills.
TVA will place dry ash atop an engineered base layer of sand, gravel and geo-fabric. The dry ash will be placed into the on-site disposal area slowly so that it does not slide. A new dike will be installed around the entire perimeter of the coal ash disposal area to keep the ash from entering the embayment in the future. This dike will go 60 to 70 feet below the ground to the shale bedrock, and will consist of overlapping soil-cement columns that are able to withstand a local 6.0 magnitude earthquake. The coal ash area will incorporate measures to divert drainage and control runoff.
Once all the ash has been put in place, a two-foot clay cover and one foot of top soil will be put over it. Vegetation will then be planted to prevent erosion. Upon completion, the structure will be closely monitored, and regularly inspected to ensure public health and safety. Long-term groundwater monitoring will be conducted.
The height of the closed coal ash disposal area will be approximately 25 feet above the road surface, which is about 30 feet lower than the former dredge cell.
Following the removal of ash to native sediments, the embayment ecosystem will be restored to conditions the EPA says will protect human health and the environment. This includes the restoration of a complex mosaic of forested, scrub-shrub and emergent wetland plant communities that will provide diverse habitats for fish, semi-aquatic amphibians and bird species.
Drinking water, river water and groundwater in the area are sampled on a routine basis, and EPA said current results indicate no exceedances of drinking water standards or surface water quality criteria. Continued ecological, groundwater and river sampling will be conducted indefinitely after the cleanup is complete to monitor environmental conditions surrounding the site.
Field work to prepare for the cleanup is expected to begin in late May. This portion of the cleanup is estimated to take about four years to complete and will cost approximately $268.2 million, which includes an estimated $686,000 in annual maintenance costs for the first 30 years once the cleanup is complete. Ongoing five-year reviews will be conducted to ensure the integrity of the ash containment.
Earlier this month, EPA proposed the first-ever national rules for disposal and management of coal ash from coal-fired power plants.
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