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MEMORANDUM


TO:	Steam Electric Rulemaking Record

FROM:	Elizabeth Sabol, ERG
		TJ Finseth, ERG

DATE:	January 29, 2013

SUBJECT:	Steam Electric Effluent Guidelines  -  Methodology for Identifying Surface Impoundment Closures Based on Regulatory Options

As part of the compliance cost and pollutant removal estimates, ERG identified combustion residual surface impoundments at steam electric plants that will likely remain open, partially close, or completely close based on the regulatory options considered as part of the proposed rule. For additional details regarding the regulatory options considered as part of the rulemaking, see Section 8 of the Technical Development Document for the Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category. EPA used the results of the pond closure analysis to estimate costs for best management practices (BMP) for surface impoundments as part of the proposed rulemaking. For more information on the BMP costs see Section 5.6 of EPA's Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Generating Point Source Category [DCN SE01957]. Additionally, ERG estimated percent closures for surface impoundments determined to partially close based on combustion residual wastewater flow rates (in gallons per day (gpd)), capacity (ft[3]), and impoundment age. EPA used the results of the pond closure analysis, flow rate, capacity, and impoundment age to estimate benefits associated with avoided impoundment failures. See ERG's "Methodology for Estimating Impoundment Age, Capacity, and Reductions in Capacity Used to Estimate Benefits Associated with Avoided Impoundment Failures" memorandum [DCN SE02121] for more information on the percent closures methodology for combustion residual impoundments.
Overview
Implementation of the regulatory options evaluated as part of this rulemaking will reduce, and in some cases eliminate, FGD wastewater, fly ash transport water, bottom ash transport water, and combustion residuals managed in on-site surface impoundments. ERG used data from the Questionnaire for the Steam Electric Power Generating Effluent Guidelines (Steam Electric Survey) to develop a complete listing of combustion residual impoundments at steam electric power plants in the scope of this rule. ERG's complete listing of combustion residual surface impoundments contains 1,097 surface impoundments containing FGD and/or ash combustion residual wastewater, solids, or both. The listing also includes a flag for each type of combustion residual contained within the impoundment (i.e., FGD, fly ash, bottom ash). ERG flagged the waste as being contained in the pond if it was identified as a solid waste, process wastewater, or both. The Steam Electric Survey did not require plants to differentiate between CCR leachate from impoundments versus CCR leachate from landfills. For this reason, ERG was unable to evaluate which impoundments contained combustion residual landfill leachate and therefore, leachate was not included in the analysis.
ERG used the complete listing of surface impoundments in combination with the regulatory options considered as part of this rulemaking and those plants incurring costs to comply with the proposed rulemaking to determine the effect revisions to the ELGs would have on the population of surface impoundments. Table 1-1 presents the five regulatory options evaluated as part of this rulemaking and the types of combustion residual surface impoundments each option will affect.
Table 1-1. Regulatory Options and Effects on Surface Impoundment Types
                               Regulatory Option
   Combustion Residual Waste Stream(s) Affected by the Regulatory Option[a]
                                   Treatment
   Affects Surface Impoundments Containing the Combustion Residual Waste(s):
                                       1
FGD Wastewater
Chemical Precipitation
FGD
                                       2
FGD Wastewater
Chemical Precipitation + Biological Treatment
FGD
                                       3
FGD Wastewater
Chemical Precipitation + Biological Treatment
FGD, Fly Ash 
                                       
Fly Ash Transport Water
Dry Handling

                                       4
FGD Wastewater
Chemical Precipitation + Biological Treatment
FGD, Fly Ash, Bottom Ash
                                       
Fly Ash Transport Water
Dry Handling

                                       
Bottom Ash Transport Water
Dry Handling

                                       5
FGD Wastewater
Chemical Precipitation + Biological Treatment
FGD, Fly Ash, Bottom Ash

Fly Ash Transport Water
Dry Handling


Bottom Ash Transport Water
Dry Handling

[a] Other combustion residual wastestreams (i.e., combustion residual leachate, gasification wastewater, and flue gas mercury control wastewater) are also affected by the proposed effluent guidelines but either the associated surface impoundment(s) would be unaffected or those effects are not included in this analysis.

Based on the combustion residual types flagged during the development of the surface impoundment listing, ERG flagged surface impoundments as the following:
FGD Only;
Fly Ash Only;
Both FGD and Fly Ash;
Bottom Ash Only;
Both FGD and Bottom Ash;
Both Fly Ash and Bottom Ash; and
All Wastes (FGD, Fly Ash, and Bottom Ash).

ERG identified the following outcomes for surface impoundments for this analysis: 
Not Affected  -  The implementation of the regulatory option being evaluated will not affect the operation of the impoundments.
Closure  -  The implementation of the regulatory option being evaluated will eliminate all the combustion residual wastes (e.g., FGD wastewater, fly ash, and/or bottom ash) currently stored in the surface impoundment; therefore, ERG assumes the plant will close the surface impoundment.
Partial Closure  -  The implementation of the regulatory option being evaluated will eliminate at least one, but not all, of the combustion residual wastes currently stored in the surface impoundment; therefore, ERG assumes the plant will stop sending the affected combustion residual waste(s) to the surface impoundment, but the impoundment will continue receiving the other wastes (i.e., a "partial closure").

ERG also used information from the Steam Electric Survey to identify surface impoundments that will not be affected as part of the regulatory options because of assumptions ERG made in the compliance cost estimates. The impoundments determined unaffected, regardless of combustion residual type and regulatory option, are those impoundments identified as remaining functional as part of a complete recycle system, remaining functional as part of the FGD wastewater treatment system, or remaining functional for bottom ash complete recycle systems at plants incurring bottom ash management costs.
ERG analyzed the impoundment type (e.g., FGD only, All Wastes) to determine the type of outcome for each impoundment associated with a regulatory option. Table 1-2 presents the likely outcomes associated with each regulatory option, excluding the surface impoundments determined to be unaffected regardless of combustion residual type and regulatory option, described above.
Table 1-2. Outcomes for Types of Surface Impoundments Associated with Each Regulatory Option
                              Type of Impoundment
                               Regulatory Option

                                       1
                                       2
                                       3
                                       4
                                       5
FGD Only
                                    Closure
                                    Closure
                                    Closure
                                    Closure
                                    Closure
Fly Ash Only
                                 Not Affected
                                 Not Affected
                                    Closure
                                    Closure
                                    Closure
Both FGD and Fly Ash
                                Partial Closure
                                Partial Closure
                                    Closure
                                    Closure
                                    Closure
Bottom Ash Only
                                 Not Affected
                                 Not Affected
                                 Not Affected
                                    Closure
                                    Closure
Both FGD and Bottom Ash
                                Partial Closure
                                Partial Closure
                               Partial Closure 
                                    Closure
                                    Closure
Both Fly Ash and Bottom Ash
                                 Not Affected
                                 Not Affected
                               Partial Closure 
                                    Closure
                                    Closure
All Wastes
                                Partial Closure
                                Partial Closure
                               Partial Closure 
                                    Closure
                                    Closure
Note: This table does not reflect the outcomes for those surface impoundments determined to be unaffected because they remain functional as part of a complete recycle system, remain functional as part of the FGD wastewater treatment system, or remain functional for bottom ash complete recycle systems at plants incurring bottom ash management costs.

Identification of Impoundment Closures and Partial Closures
To identify impoundments that will be affected by the proposed rulemaking, ERG used the complete listing of combustion residual surface impoundments, complete with impoundment type flags, and the listing of plants incurring compliance costs for FGD wastewater, fly ash, and/or bottom ash. ERG used the following process for identifying surface impoundments as closures and partial closures.
First, ERG flagged impoundments for FGD costs, fly ash costs, and/or bottom ash costs based on the lists of plants incurring costs for FGD wastewater, fly ash, and/or bottom ash. For each plant incurring a cost, a corresponding cost flag was marked for all impoundments at the plant. Additionally, ERG also flagged impoundments marked as complete recycle, part of the FGD wastewater treatment, or bottom ash management.
ERG marked those impoundments flagged as complete recycle and part of the FGD wastewater treatment system for all regulatory options as "Not Affected" because ERG assumes these impoundments will remain open. ERG assumes that complete recycle impoundments will remain open so that the plant can continue operating a complete recycle system, which is in compliance with the proposed rulemaking for FGD wastewater, fly ash transport water, and bottom ash transport wastewater. Additionally, ERG determined that seven plants would continue to operate FGD impoundments as part of their FGD wastewater treatment because it would be more cost effective than installing equalization tanks to accommodate the large FGD wastewater flow. 
ERG marked those impoundments flagged as incurring bottom ash management costs and having bottom ash combustion residual wastes as "Not Affected" because ERG assumes that these plants will continue to operate their bottom ash impoundments to achieve complete recycle. ERG identified those plants receiving bottom ash management costs as those plants that recycle a majority (more than 90 percent) of their bottom ash transport water for reuse as bottom ash transport water or other plant operations that do not lead to discharges. Therefore, ERG expects these plants to adjust their recycle operations to achieve complete recycle, rather than install dry bottom ash handling.
For the remaining impoundments, ERG identified complete closures. Complete closures are impoundments that will likely close because all of the combustion residual waste currently transferred to the impoundment will likely no longer be transferred to the impoundment. ERG identified complete closures for each regulatory option using the following assumptions:
Regulatory Options 1 and 2:
The type of impoundment is "FGD Only;" and
The FGD cost flag for the impoundment is marked "Yes."

Regulatory Option 3:
The type of impoundment is "FGD Only" or "Fly Ash Only" or "Both FGD and Fly Ash;" and
The FGD and/or fly ash cost flag for the impoundment is marked "Yes."

Regulatory Options 4 and 5:
Any Cost Flag (FGD, fly ash, and/or bottom ash) is marked "Yes."

Additionally, ERG identified partial closures for each regulatory option. These closures represent ponds that will remain open because at least one type of combustion residual waste will continue to be transferred to the impoundment, but additionally, at least one type of combustion residual waste will likely no longer be transferred to the impoundment. ERG identified partial closures for each regulatory option using the following assumptions:
Regulatory Options 1 and 2:
The type of impoundment is "Both FGD and Fly Ash" or "Both FGD and Bottom Ash" or "All Wastes;" and
The FGD cost flag for the impoundment is marked "Yes."

Regulatory Option 3:
The type of impoundment is "Both Fly Ash and Bottom Ash" or "Both FGD and Bottom Ash" or "All Wastes;" and
The FGD and/or fly ash cost flag for the impoundment are marked "Yes."
                  OR
The impoundment is flagged as part of FGD wastewater treatment; and
The type of impoundment is "Both FGD and Fly Ash;" and
The fly ash cost flag for the impoundment is marked "Yes."
                  OR
The impoundment is flagged for complete recycle; and
The type of impoundment is "Both FGD and Fly Ash;" and
The FGD cost flag for the impoundment is marked "Yes."

Regulatory Options 4 and 5:
The impoundment is flagged as bottom ash management; and 
The type of impoundment is "Both Fly Ash and Bottom Ash" or "Both FGD and Bottom Ash" or "All Wastes;" and
The FGD and/or fly ash cost flag for the impoundment are marked "Yes."
                  OR
The impoundment is flagged as part of FGD wastewater treatment; and
The type of impoundment is "Both FGD and Fly Ash" or "Both FGD and Bottom Ash" or "All Wastes;" and 
The fly ash and/or bottom ash cost flag for the impoundment are marked "Yes."

The remaining impoundments not flagged as closures or partial closures were considered to be unaffected by the ELG.
The results of the impoundment closure analysis associated with the proposed ELG are presented in the file titled "Revised Pond Closure Analysis Including Partial Benefits (DCN SE01772).
