The coal ash spill from Duke Energy’s Dan River power plant in Rockingham County on February 2 resulted in approximately 80,000 tons of coal ash entering the Dan River and is being cited as one of the nation’s largest coal ash spills. This unfortunate event serves as a reminder that our energy choices often result in unintended consequences from waste and/or byproducts of energy use, much like coal tar was a remnant of coal gas production at former manufactured gas plants. This local event can be used to help students discover and evaluate the consequences of human activities on the lithosphere, hydrosphere, atmosphere and biosphere.
Coal Ash Ponds
At some coal-fired power plants, the resulting coal ash from power production is stored in large ponds. The practice of transporting and storing coal ash in on-site ponds is known as wet ash handling. According to Duke Energy’s solid waste section on its website, it manages 23 active ash ponds in the Carolinas. A fact sheet published by Duke Energy on its management of coal ash reveals that these ponds were “the customary storage method when many coal plants were built. Since then, [it has] invested in millions of dollars to transition to storing fly ash in a dry form [dry ash handling] in lined landfills at many of [its] larger coal plants. This provides additional protection to surface and groundwater, and more conversion projects are under way.”
Components of Coal Ash
Coal ash, also known as coal combustion residuals (CCRs), varies in its composition depending on the type and origin of the coal, how the coal was burned, and the type of air pollution control equipment utilized at the power plant. The EPA indicates that “about 80 to 90 percent of [coal ash] is non-radioactive minerals, typically silicon, aluminum, iron and calcium.” In addition, the EPA cites that coal ash can “contain contaminants like mercury, cadmium and arsenic associated with cancer and various other serious health effects.” Furthermore, naturally occurring radionuclides such as uranium can become concentrated in coal ash.
Concern about Coal Ash Release to Dan River
During a Feb 17th, 2014 presentation to the General Assembly’s Environmental Review Commission (ERC) officials from NC’s Department of Environment and Natural Resources (DENR) stated that drinking water supplies were not adversely impacted. DENR officials have acknowledged that their primary concern is the settling of the ash onto the bottom of the Dan River and its longer-term impact on the aquatic habitat and to people who use the river for recreation. On February 12, 2014, the N.C. Department of Health and Human Services’ Division of Public Health issued two health advisories to minimize human exposure to contaminants downstream of the spill site. DHHS advises against the consumption of fish and shellfish and asks people to avoid recreational contact with water and sediment. To learn more about specific human health effects associated with many of the components of coal ash visit the Agency for Toxic Substances and Disease Registry and search for the chemical of interest.
The Connection between Coal Ash and Clean Air
An interesting aside on this topic that illustrates the link between water and air pollution management is worth noting. Some media stories correctly reported that a portion of the toxic materials found in the state’s coal ash ponds were a result of efforts to reduce air pollution through the passage of the Clean Smokestacks Act (CSA). Following passage of the CSA, which required significant emission reductions from the state’s coal-fired plants, scrubbers were placed on the facilities to keep ash from being discharged into the atmosphere. After capture by the scrubbers, the ash was subsequently disposed of into the coal ash ponds resulting in cleaner air “but the trade-off is significant enrichments of contaminants in solid wastes and wastewater discharged from power plants” according to a 2012 research study funded by the North Carolina Water Resources Research Institute.
Background Information and Teaching Resources
Dan River Coal Ash Spill, NC DENR
The Dan River Coal Ash Release: Description & Timeline of Events (PPT presentation from Feb 17th, 2014 DENR presentation to the ERC). This presentation includes graphics and photos that can be useful in helping students understand how coal ash is produced and captured in ponds.
Response to Dan River, Duke Energy
North Carolina coal ash spill raises questions about enforcement of environmental regulations, 7 minute video excerpt from PBS NewsHour, Feb 17, 2014
Coal Ash: Characteristics, Management and Environmental Issues (pdf), Electric Power Research Institute