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Evaluation of Encapsulated Beneficial Uses:
Fly Ash Concrete and FGD Gypsum Wallboard Frequent Questions

  1. Can fly ash be used as a replacement for portland cement in concrete and flue gas desulfurization (FGD) gypsum as a substitute for mined gypsum in wallboard?

    EPA applied the steps of the Methodology for Evaluating Encapsulated Beneficial Uses of Coal Combustion Residuals (PDF) (22 pp, 475 KB) ("the Methodology") to the beneficial use of fly ash used as a replacement for portland cement in concrete and flue gas desulfurization (FGD) gypsum used as a replacement for mined gypsum in wallboard. The evaluation considered products that meet relevant physical and performance standards, that conform to standard design specifications, and that incorporate fly ash and FGD gypsum from pollution control devices currently used in the United States. Based on the findings of the evaluation, the Agency concluded that fly ash concrete and FGD gypsum wallboard are both appropriate beneficial uses. Thus, the Agency continues to support the beneficial use of fly ash in concrete and FGD gypsum in wallboard.

  2. What is "encapsulated beneficial use" of coal combustion residuals (CCR)?

    The Agency has defined "beneficial use" as the reuse of CCRs in a product that provides a functional benefit; that replaces a product made from virgin raw materials on the market, thus conserving natural resources that would otherwise need to be obtained through practices, such as extraction; and that meets relevant product specifications and regulatory standards. An encapsulated beneficial use is one that binds the CCRs into a solid matrix that minimizes their mobilization into the surrounding environment. Examples of encapsulated uses include, but are not limited to:

    • Filler or lightweight aggregate in concrete
    • A replacement for, or raw material used in production of, cementitious components in concrete or bricks
    • Filler in plastics, rubber, and similar products
    • Raw material in wallboard production

  3. Will EPA evaluate other encapsulated beneficial uses? If not, who is responsible for conducting evaluations of other encapsulated CCR beneficial uses? What is EPA’s role in evaluating these beneficial uses?

    EPA has no plans to evaluate other encapsulated beneficial uses of CCRs. However, the Methodology is being made available so that federal or state authorities, beneficial users, and other interested parties can, if they choose, use the methodology to evaluate other encapsulated beneficial uses of CCRs. Use of this methodology is voluntary, not regulatory, and is not a replacement for existing regulatory requirements. Many states have beneficial use programs, and they should be consulted to determine whether a specific CCR beneficial use is allowed. Other parties who use the Methodology should consult with their state to determine whether the application of the methodology is consistent with all applicable state requirements. EPA has no role in reviewing or approving evaluations conducted by others, but can assist with any questions about how to properly apply the methodology.

  4. How does EPA’s encapsulated beneficial use methodology work?

    The Methodology is composed of five steps. The party conducting the evaluation does not need to follow these steps in the order that they are outlined in the Methodology or necessarily use all of the steps. They can begin the evaluation at any step, can apply the individual steps in an order that makes best use of the available data, and can stop the evaluation at any step when they determine that the beneficial use product will not release constituents of potential concern (COPC) greater than releases found in analogous products (i.e., products without CCRs) or if there is no exposure pathway in which a person or ecological organism may come into contact with the COPC. The methodology’s five steps are:

    • Step 1: (Literature Review and Data Collection): This step involves the collection and review of available literature on a CCR and its beneficial use. The purpose of this step is twofold: 1) to establish whether existing evaluations are sufficient to demonstrate that releases from the CCR beneficial use are comparable to or lower than those from an analogous product, or are at or below relevant regulatory and health-based benchmarks, and 2) to collect data on any COPCs that may be present in and released from the CCR beneficial use product, but were not sufficiently addressed by existing evaluations. If existing evaluations have already sufficiently addressed all potential releases, then no further evaluation is warranted and the beneficial use of the product is appropriate.
    • Step 2: (Comparison of Available Data): This step involves a comparison of the COPC releases from the CCR beneficial use product with those from an analogous product that it replaces. The purpose of this step is to determine whether there is the potential for higher COPC releases from the beneficial use product than from the analogous product. If releases of all COPCs are found to be comparable to or lower than those from the analogous product, then no further evaluation is warranted and the beneficial use of the product is appropriate.
    • Step 3: (Exposure Review): The purpose of this step is to identify the ways that different receptors may be exposed to the remaining COPCs. This information is then summarized through a conceptual model. Any COPC releases that do not have a complete exposure pathway are eliminated from further consideration and, if none of the COPCs have a complete exposure pathway, then no further evaluation is warranted and the beneficial use of the product is appropriate.
    • Step 4: (Screening Assessment): This step uses a combination of conservative (i.e., likely to overestimate exposures) environmental, fate and transport, and/or exposure data to estimate potential COPC exposures. These conservative exposures are then compared to relevant screening benchmarks. If all exposures are below these screening benchmarks, then no further evaluation is warranted and the beneficial use of the product is appropriate.
    • Step 5: (Risk Assessment): This step uses environmental, fate and transport, and/or exposure data that are more representative of real world conditions to estimate potential COPC exposures. These more realistic exposures are then compared to relevant risk benchmarks. If all exposures are below these risk benchmarks, then no further evaluation is warranted and the beneficial use of the product is appropriate.

  5. What coal combustion residual (CCR) uses did EPA evaluate in the Application document and how was the methodology applied?

    EPA applied the methodology to the two largest CCR uses - coal fly ash concrete and FGD gypsum wallboard. Below is a summary of the evaluation made in each step of the Methodology as described in Question 4:

    • Step 1: The following types of releases that may occur during use of fly ash concrete and FGD gypsum wallboard were identified: 1) generation of dust, 2) leaching to ground and surface water, 3) emissions to air, and 4) decay of naturally occurring radionuclides.

      From a literature review, a number of existing studies were found to be of sufficient applicability and quality to rely upon to draw the following conclusions:

      • For both fly ash concrete and FGD gypsum wallboard, the findings from the cumulative body of evidence from existing studies were used to eliminate radioactive decay from further consideration.
      • For FGD gypsum wallboard, the findings from the cumulative body of evidence from existing studies were used to eliminate all releases from further consideration, except for emissions to air.
      • For fly ash concrete, the findings from the cumulative body of evidence from existing studies were used to identify COPCs that had not been sufficiently addressed for particular releases: 23 COPCs for generation of dust, 9 COPCs for leaching to ground and surface water, and 1 COPC for emissions to air.

      For more information, see Table 1-2: List of COPCs Remaining Following Step 1 in the Coal Combustion Residual Beneficial Use Evaluation: Fly Ash Concrete and FGD Gypsum Wallboard (PDF) (95 pp, 1.33 MB)

    • Step 2: All of the data identified in Step 1 was aggregated to allow a comparison of releases from CCR fly ash concrete and FGD gypsum wallboard to releases from their respective non-CCR analogous products (i.e., portland cement concrete and mined gypsum wallboard) during use. The evaluation found that concentrations of 2 COPCs in dust from fly ash concrete were comparable to or lower than those in dust from portland cement concrete. The evaluation also found that concentrations of 5 COPCs in leachate from fly ash concrete and portland cement concrete were comparable. Therefore, the evaluation did not carry these COPCs forward for further consideration, but retained all other COPCs from fly ash concrete and FGD gypsum wallboard for further consideration. For more information, see Table 2-4: List of COPCs Remaining Following Step 2 in the Coal Combustion Residual Beneficial Use Evaluation: Fly Ash Concrete and FGD Gypsum Wallboard (PDF) (95 pp, 1.33 MB)
    • Step 3: No releases or associated COPCs were eliminated at this step. For more information, see Table 3-1: List of COPCs Remaining Following Step 3 in the Coal Combustion Residual Beneficial Use Evaluation: Fly Ash Concrete and FGD Gypsum Wallboard (PDF) (95 pp, 1.33 MB)
    • Step 4: The evaluation conservatively estimated COPC exposures that may occur during use of fly ash concrete and FGD gypsum wallboard, and compared these exposures to relevant regulatory or health-based screening benchmarks. The evaluation found that the remaining 21 COPCs for generation of dust, 4 COPCs for leaching to ground and surface water, and 1 COPC for emissions to air were below all relevant screening benchmarks and the beneficial uses of these products are appropriate. Therefore, the evaluation did not proceed to Step 5. EPA’s evaluation concluded that the beneficial use of encapsulated CCRs in concrete and wallboard is appropriate because they are comparable to virgin materials or below the agency’s health and environmental benchmarks.
  6. Will EPA be evaluating "unencapsulated beneficial uses" of coal combustion residuals (CCR)?

    EPA plans to develop a conceptual framework for evaluating unencapsulated CCR beneficial uses. In addition, EPA is working with the US Department of Agriculture to assess the use of FGD gypsum in agriculture.

  7. What types of literature sources did the Agency rely upon in this application of the Methodology?

    This evaluation used studies and data pertaining to either beneficial use products or their raw materials. In most cases, the literature sources were drawn from peer reviewed journals. An assessment determined whether data sources were relevant, sufficiently explained the data and assumptions relied upon, accounted for sources of uncertainty and variability, and had undergone an independent review in some form. Some data were submitted directly to EPA by generators, regulatory entities, and other interested parties. These data have been made available for comment to both the public and a panel of independent peer reviewers through the 2010 Human and Ecological Risk Assessment of Coal Combustion Wastes.

  8. Does EPA require the use of data from certain test methods when applying the Methodology?

    EPA’s encapsulated beneficial use Methodology does not require any specific test methods, only that the data generated is of sufficient quality to support the final conclusions of the evaluation.

  9. Can EPA’s encapsulated beneficial use methodology be used to determine if a specific encapsulated use of coal combustion residuals (CCR) is “safe”?

    The Agency developed this methodology to evaluate the potential impacts to human health and the environment that may result from the encapsulated beneficial uses of CCRs. This methodology may be used to show whether releases of constituents of potential concern, such as metals from encapsulated beneficial uses, are comparable to or lower than those from analogous non-CCR products, or are at or below relevant regulatory and health-based benchmarks for human and ecological receptors.

  10. Can EPA’s encapsulated beneficial use methodology be used to determine if the “unencapsulated” beneficial reuse of coal combustion residuals (CCR) is safe?

    This methodology is not intended to be applied to unencapsulated beneficial uses of CCRs. EPA plans to develop a conceptual framework for evaluating non-encapsulated uses of CCRs.

 

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