There is a nationwide push for the retirement of ash ponds across the country. Since the need for ash storage remains, many plants are looking toward ash recycle systems, dry ash handling systems, or other technologies to dispose of the ash differently.
Ash ponds, which have been in use for the past two centuries, store two unwanted byproducts of coal combustion: bottom ash and fly ash. These ash ponds, also called surface impoundment, use gravity to settle ash from power plant wastewater in large holding ponds. Some newer ash disposal systems do not use ponds and instead collect the ash in large hoppers or tanks where the ash may later be disposed of in a landfill or recycled. From an economic perspective, ash ponds are typically preferred. From an environmental perspective, alternative ash disposal systems are preferred.
Ash ponds are designed and constructed to prevent seepage and ensure slope stability through ring embankments to enclose the ponds. However, time has tested many of these ponds and unfortunately, extended use without proper inspections and maintenance has led to numerous ash spills to adjacent land and rivers across the country. These ash spills result in severe environmental damage with immeasurable long-term effects. Two examples of significant ash spills in recent history are:
At the Kingston Fossil Plant (TVA) in Tennessee, a dike used to contain an ash pond failed. This resulted in a release of approximately 1 billion gallons of coal-ash slurry containing 5.4 million cubic yards of coal ash to the Emory River Channel. The spill was an environmental disaster, and the cleanup cost TVA more than $1 Billion. The social cost of the potential harm to human health from the cleanup has yet to be determined.
At the Dan River Steam Station (Duke) in North Carolina, 27 million gallons of coal-ash slurry containing approximately 39 thousand tons of ash was deposited in the Dan River. At the Dan River Steam Station, the primary and secondary ash ponds are adjacent to the Dan River, and a storm pipe near the ash ponds broke, allowing the release of the ash slurry into the river.
How are Plants Replacing Ash Ponds?
Obviously, nobody wants toxic ash released into their local waterways where they fish, swim, and obtain drinking water. Power producers and energy conglomerates do not want to damage their reputations, pay fines, and fund enormously expensive cleanups. As a result, power producers and energy companies are retiring ash ponds and replacing them with ash recycle systems, dry ash handling systems, or other alternative ash disposal systems. When this is not practical, the risk of ash pond failures must be mitigated by increased inspection frequency and lining the ash ponds when leaks are discovered.
While many responsible power producers and energy companies are proactively taking steps to prevent ash pond seepage and leakage into local waterways, the EPA is going a step further to ensure disasters like those at Kingston and Dan River do not recur. In 2015, the EPA imposed new rules and regulations for the safe disposal of coal ash from power plants. Although the implementation of these new rules is currently on hold for amendments, it is expected that they will take effect over the next few years.
Plant ownership and management must be aware of the risk associated with continued use of ash ponds and ensure steps are taken to avoid ash spills and to comply with new EPA regulations. Further, operators and maintenance personnel must be adequately trained on new inspection and maintenance requirements required by the EPA. Lastly, if or when ash ponds are retired at a facility and replaced with an alternative ash disposal system, operators should be adequately trained on these new systems so that a spill from misoperation of the new system does not occur.
James Wiggins is a Senior Specialist with FCS. He provides engineering and technical services in support of operations and maintenance programs for power and process plants. As a former Mechanical Operator and Staff Instructor for the U.S. Navy, he was responsible for the initial qualification of students at the Nuclear Power Prototype. James is experienced in multiple training methods including one-on-one instruction, classroom instruction, and simulator operations.