Coal-fired plants were the backbone of TVA's power system, first using them in the 1950s. As TVA invests in a greener future—achieving a 61% carbon-free energy mix by 2026—the focus now moves to safely storing decades of ash to protect the environment.
When we burn coal, ash and other by-products called coal combustion residuals (CCRs) are created. TVA recycles 33 percent of its CCRs; they go into common building materials like concrete, roof shingles and wallboard. CCRs that cannot be recycled are removed from boilers and other equipment and currently are stored on site.
The U.S. Environmental Protection Agency (USEPA) regulates the management of coal ash. All of its plans for closure must be within the requirements set for by the USEPA, as well as those set for by the state in which its plants reside (Tennessee, Alabama and Kentucky). TVA is the industry leader in dry ash storage technology. TVA is the only utility in the world pioneering intelligent compaction technology to safely store dry coal ash – which turns dry powered ash into a rock-hard substance.
Closing a dry ash or wet ash pond is a complicated process that requires a lot of science, engineering and continual testing. Plus there are Federal reviews/approvals that must occur before starting work.
To put it simply, closing an ash pond or dry ash stack means covering it in a very careful way to prevent water from entering the ash. TVA is using the following closure method as seen in the illustration below. The geomembrane is a strong plastic cap that is welded together to prevent water from penetrating into the ash. Then we place a drainage net over the geomembrane so water can run off. To protect the geomembrane and net, soil is layered on with grass planted on top.
When the process is completed the closed structure looks like a lush green park.
What happens after the ash is capped?
TVA will monitor the ash facilities for 30 years. TVA’s closure method is approved by the EPA and follows the CCR and state guidelines. Actually, TVA exceeds these strict Federal rules having already installed over 7,000 real-time sensors to monitor our impoundments. Every five minutes, sensors send data to a centralized computer monitoring system within TVA. Our continuous ash pond monitoring will ensure the public and environment remains safe.
Continual testing. For more than 30 years we have been monitoring the biologic and ecologic health of the Tennessee River basin. For the next 30 years we will monitor and test groundwater at our facilities to ensure that the ash does not affect groundwater. Each state requires TVA to test groundwater and share that data with the appropriate state agency that regulates environmental issues.
To comply with the EPA Coal Combustion Residuals (CCR) Rule we established a groundwater sampling and analysis program and installed new wells to gather more data. The first year of monitoring will require eight background sampling events across the Valley at the facilities to capture baseline data. Once the background data has been established for these wells, groundwater monitoring will continue on a semi-annual basis, with a yearly report being posted to TVA’s CCR Website.