Written by Mark Quarles, P.G., Senior Consultant, CCR Expert in BBJ Group's Nashville office
Multiple stakeholders are currently involved in how coal combustion residuals (CCR or coal ash) will be disposed of in the future, and what effects legacy disposal sites have had on the environment. For example, insurance carriers underwrite policies and process claims for disposal operations. Also, consultants are hired by utility companies to certify required environmental compliance documents. And non-governmental agencies and the public respond to, for example, public notices for disposal area closure plans and new disposal area designs. The science associated with coal ash compliance and risk mitigation is complex.
Coal ash became known to the general public after the 2008 collapse of a diked surface impoundment at the Tennessee Valley Authority, Kingston Plant. That collapse resulted in millions of cubic yards of coal ash flowing onto private property and into adjacent rivers. Some of the coal ash traveled many miles downstream, affecting private property and water resources along the way. As a result, the US EPA passed regulations in 2015 (aka the CCR Rule) to establish standards for closure of legacy disposal areas, designing and constructing new areas, and operating and monitoring those disposal areas.
Was the Kingston dike failure the first indication that coal ash disposal was risky? No. And was disposal previously unregulated like the wild, wild, west? No. Coal ash has been regulated as a solid waste by the Resource Conservation and Recovery Act (RCRA) since at least 1979. As such, utilities have long since been required to design and operate disposal sites in a manner that protects groundwater, for example. Also, the electrical power industry trade association—the Electric Power Research Institute (EPRI)—knew at least as early as the 1980s that coal ash could contaminate groundwater. EPRI even published manuals on how to design and install groundwater monitoring systems and to construct disposal areas with liners and leachate collection systems.
In my experience of researching coal ash disposal sites around the country since the 2008 TVA dike failure, the data are very clear:
- Unlined coal ash disposal sites, and especially unlined surface impoundments, have commonly contaminated groundwater. Many times, utilities even constructed unlined impoundments over existing streams, making connectivity with shallow groundwater inevitable.
- Legacy disposal operations complicate groundwater monitoring evaluations for old and new disposal areas because the required background sampling required by the CCR Rule might already show contamination from those old disposal areas. Background samples are meant to be the baseline to which future samples are compared to know whether or not a current disposal area is leaking in the future. So, unless the groundwater quality gets worse from possibly already high concentrations, the future data may not trigger the regulatory requirement to initiate assessment to define the nature and extent of contamination or the requirement to actually clean up groundwater.
- Groundwater monitoring wells are oftentimes drilled and screened too deep and can miss the uppermost portion of the uppermost aquifer nearest the bottom of the disposal area. As a result, groundwater samples may not represent the highest concentrations of contaminants that flow into streams and onto adjacent properties.
- Chemical contaminants commonly found in coal ash can be incorrectly blamed on naturally occurring conditions (e.g., metals such as arsenic), unless one understands such details as the leaching mechanisms of contaminants (e.g., changes in pH affect how constituents can leach); the chemical signatures of coal ash contaminants; and how water quality can vary substantially from the standing water in the impoundment, water in the pore space of saturated coal ash, and the deeper underlying groundwater.
- Groundwater quality may change and even worsen after a disposal site is closed in-place with an engineered cap over the wastes to minimize infiltration of precipitation, if coal ash remains saturated. Dewatering during closure in-place commonly only includes pumping of water standing in the impoundment and not water that submerges the coal ash beneath the standing water. As such, a cap-in-place closure may create a false sense of security for protecting groundwater into the future because leaching will continue, even though millions of dollars might have been spent constructing an engineered cap.
In summary, stakeholders beware. The complexities of coal ash disposal and compliance require a comprehensive understanding of the unique characteristics of the wastes and disposal history in order to define risks. Risks and risk transfer vary by the stakeholder. Without a clear understanding of coal ash complexities, insurance companies might pay claims outside the scope of a policy. Consultants might absorb professional liabilities for incorrectly certifying documents. There are plenty of ways to incorrectly interpret and assume risks for coal ash disposal.