A structural fill is an engineered fill designed to improve land for an intended end use. Typically the land is unusable for the intended use unless fill material is imported to raise the elevation to the desired design elevations. Coal ash is a useful fill material due to its homogenous particle size, predictable geotechnical characteristics, low unit weight, relatively high shear strength and ease of handing and compaction. Charah utilizes coal ash and places and compacts it in accordance with approved ASTM design criteria.
As used in reference to structural fills, “lined” or “fully lined” refers to the protective measures employed in the design to prevent or limit water from penetrating or passing through the actual fill material. The liner can be a layer of low permeability soil and/or manufactured synthetic material. As implemented by Charah, in a fully lined structural fill, the ash is placed between a series of liners, with the top and bottom ultra-low permeability synthetic liners being heat-welded together to encapsulate and isolate the ash. The completed fully lined structural fill is then covered by soil to accommodate the final surface needs for the design purpose. Fully lined structural fills are designed to meet all ASTM, state and federal standards including strict groundwater monitoring and reporting. Charah uses the best practices, materials and technology for structural fills. Charah is currently nearing completion of a coal ash structural fill project at Asheville (North Carolina) Regional Airport. Click here to learn more about the construction process and components of a fully lined structural fill.
In June 2010 EPA proposed two different approaches to regulate coal ash disposal; one under RCRA Subtitle D (non-hazardous regulation) and a second approach under RCRA Subtitle C (hazardous regulation). After an exhaustive review process, and as agreed by EPA in a lawsuit settlement with industry and environmental groups, EPA released the final draft Coal Combustion Residuals (CCR) Regulations on December 19, 2014. EPA published the CCR Regulations in the Federal Register on Friday April 17, 2015. The new requirements will regulate CCRs as non-hazardous materials under Subtitle D. The new regulations establish national criteria under which States can govern CCRs in a manner similar to municipal solid wastes. The regulations address CCR disposal from utility boilers that burn 51% coal fuels and they exempt beneficial use of CCRs. The new regulations define “beneficial use” and provide a mechanism where structural fills can demonstrate that they meet the definition as “beneficial use.”
The CCR Regulations in the Federal Register finalizes the regulation development that started as a result of the ash impoundment failure at TVA’s Kingston Power Plant in Harriman, Tennessee. The rules become effective 180 days from publication and place requirements on utilities that electric operate coal plants to review existing sites and implement new operational requirements to comply with this broad reaching program. The Federal Register rules are at http://www.gpo.gov/fdsys/pkg/FR-2015-04-17/pdf/2015-00257.pdf.
Related to CCR disposal, the new criteria establishes measures that ensure groundwater monitoring at all active CCR disposal units and requires implementation of measures to ensure that CCRs are properly disposed of in units that are protective of human health and the environment. Design criteria and location restrictions are established for any new disposal unit.
By establishing the new criteria, EPA has once again confirmed that coal ash is not hazardous and can be adequately managed under a non-hazardous regulatory approach. This finding is supported by many years of research by the scientific community and states that currently manage solid wastes of all types. In addition to the CCR regulations, EPA has also released its report on the beneficial use of fly ash in concrete and gypsum in wallboard. The study titled “Coal Combustion Residual Beneficial Use Evaluation: Fly Ash Concrete and FGD Gypsum Wallboard” confirms that use of ash and CCPs in this type of construction products meets all the criteria for safety and should be encouraged as a best practice for utilizing these valuable resources.
If you are a user of coal ash, the rules provide continued assurance that products using recycled fly ash, bottom ash and gypsum are safe and protective of the environment. EPA’s criteria for disposal and the exemption of beneficial use both signal how important CCRs are to the national construction materials industries. The fact that EPA supports the continued beneficial use of CCRs paves the way for continued investment in science and projects which expand this resource utilization.
If you are an individual, the new EPA rules validate that CCRs are a valuable resource and can be safely used for various applications. This support for beneficial use saves natural resources by using recovered CCRs and avoids natural resource extraction while saving costs in producing new construction materials. Individuals can also take comfort in that EPA has established general criteria governing disposal of CCRs that is protective of health and the environment. States will be able to implement programs tailored to their specific needs of each state.