By Robynn Andracsek, P.E., Burns & McDonnell and Contributing Editor
On Dec. 22, 2008, a retaining wall failed at the Tennessee Valley Authority’s Kingston Fossil Plant in Roane County, Tenn. More than 5.4 million cubic yards of coal ash spilled from an on-site holding pond. This is old news to anyone who follows the power generation industry. However, the related event we should be monitoring is the U.S. Environmental Protection Agency’s (over?) reaction to this environmental disaster.
EPA has undertaken two significant subsequent actions. First, a study of structural integrity of existing coal ash impoundments including plans to improve their safety has been made and, second, reclassification of coal ash as a hazardous waste is being considered.
The first is a crucial and somewhat obvious step. There are over 500 surface impoundments at more than 200 facilities in the U.S. Until EPA’s 2009 information request of the utility industry, the condition and vulnerability to failure of these “ash ponds” were both unknown. EPA’s survey will result in classifying each impoundment’s hazard potential based on the National Inventory of Dams criteria (whose ratings range from “less than low” to “high”). Information such as the ponds’ dimensions and contents, whether they were designed by professional engineers and when their last state inspection occurred (if ever) has been collated and made public.1 One hopes EPA will use this information to standardize coal ash impoundment inspections and prevent another dam collapse.
EPA’s second action is less linear in logic. Although a solid waste, coal ash is not a hazardous waste under the term’s current definition (ignitability, corrosivity, reactivity and toxicity). EPA twice declined to list coal ash as a hazardous waste, stating “we do not wish to place any unnecessary barriers on the beneficial use of fossil fuel combustion wastes so that they can be used in applications that conserve natural resources and reduce disposal costs” and “fossil fuel wastes infrequently exceed the hazardous waste characteristic.”2 Is it overkill now to call coal ash hazardous? Would it be more accurate simply to say that impoundments have been poorly regulated?
The uses for coal ash are numerous and some are as old as civilization. The Roman Empire used volcanic ash to produce concrete, similar to how modern man uses fly ash to improve concrete quality and reduce construction cost. Fly ash in concrete increases compressive strength, lowers permeability and increases resistance to sulfate attack and alkali-silica reactivity. The U.S. Green Building Council’s LEED system even recognizes fly ash as a post-industrial recycle material.3
Another beneficial use of coal ash is in mine filling to protect surface infrastructure, although this use is better regulated than impoundments. In parts of the country such as the Midwest, underground rock formations are appropriate for backfilling networks of mines in a safe and inexpensive manner. A network of abandoned mine voids can collapse and create sinkholes. Many surface land owners are unaware that these old mines exist beneath their feet, homes and businesses. Many highways and city streets are built over old mines. By using a low-cost cementitious material such as fly ash, these mines can be backfilled at reduced cost; oversight and labor, not materials, become the biggest expense.
Highway construction is another industry that benefits from fly ash use. Fly ash can replace 15 to 30 percent of the Portland cement needed in concrete. Fly ash can also stabilize base courses, provide structural fills and embankments and serve as grouts for pavement subsealing and asphalt pavement.
Should coal ash be classified as hazardous waste, these beneficial uses will virtually disappear. The risk of liability and potential legal exposure will preclude the power industry from allowing this “hazardous material” to leave their control. A product made of this now-hazardous waste could then be regulated for disposal as a hazardous waste. At present only a handful of hazardous waste landfills exist in the U.S., a capacity incapable of accommodating the quantities of “hazardous” coal ash that would have no home, other than surface impoundments.
EPA appears to be internally conflicted on this issue. The Coal Combustion Products Partnership is a cooperative effort between EPA, the Department of Energy, the Federal Highway Administration and industry groups to promote the beneficial use of coal combustion products. Its goals include increasing the use of coal combustion products as a supplementary cementitious material in concrete to 18.6 millions tons by 2011, thus avoiding 5 million tons a year of greenhouse gas emissions from the cement manufacturing industry. This target is unobtainable if coal ash becomes “hazardous.”
Keep in mind that although the fly ash involved in the Kingston spill was a non-cementitious type, EPA’s proposed hazardous reclassification would extend to beneficial cementitious ash as well. We live in a time of “reduce, reuse and recycle.” It is counter to the goal of sustainability to classify fly ash as hazardous. EPA’s decision is expected this spring.
2. 65 FR 32214
3. American Concrete Institute, Letter to EPA Administrator Lisa Jackson, Sept. 4, 2009.
Thanks to Bill Shefchik, Burns & McDonnell, for his input to this column.
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