This EPA Guide to Using Coal Fly Ash in Highway Construction includes a section on "environmental and health cautions" which may be of interest to residents, environmentalists, and local officials dealing with the Kingston fly ash spill.

The guide was developed by the Department of Energy, the Federal Highway Administration, the The American Coal Ash Association, and the Utility Solid Waste Activities Group in 2005.

Here is an abbreviated version with just the environmental section.

Regarding "encapsulated" (i.e. mixed in with concrete or pavement which hardens and binds the material), the guide says:

When coal ash is used in concrete for building roads and bridges, its constituents—such as heavy metals—are bound (encapsulated) in the matrix of the concrete and are very stable. Leaching of these constituents for all practical purposes does not occur.

Occupational issues associated with coal ash use in concrete include the handling of dry coal ash prior to or during its inclusion in a concrete mix or exposures during demolition of concrete structures. In these cases, work inhalation and skin contact precautions should be observed, as described on page 27 in the section called Occupational Issues: Inhalation and Skin Contact.

Regarding "unencapsulated" use (i.e. used for fill, roadbeds, and embankments), the guide says:

Studies and research conducted or supported by Electric Power and Research Institute (EPRI), government agencies, and universities4 indicates that the beneficial uses of coal combustion products in highway construction have not been shown to present significant risks to human health or the environment.

But, as with many other common substances, precautions and sound management practices should be applied when using coal ash in unencapsulated uses. Water and air are the two media most likely to be affected by coal ash or coal ash constituents.

Ingestion, inhalation, and skin contact are the ways that humans and other living things could be exposed to coal ash. Other issues that may need to be addressed are leaching of elements such as mercury and metals into ground water, contamination of vegetation and the impact of other elements on the food chain, and airborne dust. In most cases, however, the way that coal ash is used, the engineering requirements for that use, and the handling and management methods applied minimizes exposure to the ash.

The guidelines discuss all of these considerations in more detail and include worker safety recommendations.

Overall, the guidelines suggest that coal fly ash is relatively safe for use in construction, keeping in mind that construction involves an engineered and controlled process. Based on the precautions discussed, a massive, uncontrolled coal fly ash release into the environment poses a unique and different set of problems.

The report also raises another question: Why isn't TVA recycling fly ash for use in construction? The report suggests significant environmental benefits, including reduction of carbon emissions involved in manufacturing concrete and other building materials and conservation of virgin resources, in addition to reducing the landfill storage impacts.