Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category

Federal RegisterMay 9, 2024

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 423

[EPA-HQ-OW-2009-0819; FRL-8794-02-OW]

RIN 2040-AG23

Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

The Environmental Protection Agency (EPA or the Agency) is finalizing a Clean Water Act regulation to revise the technology-based effluent limitations guidelines and standards (ELGs) for the steam electric power generating point source category applicable to flue gas desulfurization (FGD) wastewater, bottom ash (BA) transport water and legacy wastewater at existing sources, and combustion residual leachate (CRL) at new and existing sources. Last updated in 2015 and 2020, this regulation is estimated to cost an additional $536 million to $1.1 billion dollars annually in social costs and reduce pollutant discharges by an additional approximately 660 to 672 million pounds per year.

DATES:

This final rule is effective on July 8, 2024. In accordance with 40 CFR part 23, this regulation shall be considered issued for purposes of judicial review at 1 p.m. Eastern time on May 23, 2024. Under section 509(b)(1) of the Clean Water Act (CWA), judicial review of this regulation can be had only by filing a petition for review in the U.S. Court of Appeals within 120 days after the regulation is considered issued for purposes of judicial review. Under section 509(b)(2), the requirements of this regulation may not be challenged later in civil or criminal proceedings brought by EPA to enforce these requirements.

ADDRESSES:

The EPA has established a docket for this action under Docket ID No. EPA-HQ-OW-2009-0819. All documents in the docket are listed on the

https://www.regulations.gov

website. Although listed in the index, some information listed in the index is not publicly available,

e.g.,

confidential business information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available electronically through

https://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT:

For technical information, contact Richard Benware, Engineering and Analysis Division, telephone: 202-566-1369; email:

benware.richard@epa.gov.

For economic information, contact James Covington, Water Economics Center, telephone: 202-566-1034; email:

covington.james@epa.gov.

SUPPLEMENTARY INFORMATION:

Preamble Acronyms and Abbreviations.

The EPA uses multiple acronyms and terms in this preamble. To ease the reading of this preamble and for reference purposes, the EPA defines terms and abbreviations used in appendix A (although the list of abbreviations in the appendix is not exhaustive).

Supporting Documentation.

The rule is supported by several documents, including the following:

•

Technical Development Document for the Final Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category

(TDD), Document No. 821R24004. This report summarizes the technical and engineering analyses supporting the rule. The TDD presents the EPA's updated analyses supporting the revisions to FGD wastewater, BA transport water, CRL, and legacy wastewater. The TDD includes additional data that has been collected since the publication of the 2015 and 2020 rules, updates to the industry (

e.g.,

retirements, updates to wastewater handling), cost methodologies, pollutant removal estimates, non-water quality environmental impacts associated with updated FGD and BA methodologies, and calculations for the effluent limitations. In addition to the TDD, the Technical Development Document for the Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (2015 TDD, Document No. EPA-821-R-15-007) and the Supplemental Technical Development Document for Revisions to the Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (2020 Supplemental TDD, Document No. EPA-821-R-20-001) provide a more complete summary of the EPA's data collection, description of the industry, and underlying analyses supporting the 2015 and 2020 rules.

•

Environmental Assessment for the Final Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (EA),

Document No. 821R24005. This report summarizes the potential environmental and human health impacts estimated to result from implementation of the revisions to the 2015 and 2020 rules.

•

Benefit and Cost Analysis for the Final Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category

(BCA), Document No. 821R24006. This report summarizes the societal benefits and costs estimated to result from implementation of the revisions to the 2015 and 2020 rules.

•

Regulatory Impact Analysis for the Final Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category

(RIA), Document No. 821R24007. This report presents a profile of the steam electric power generating industry, a summary of estimated costs and impacts associated with the revisions to the 2015 and 2020 rules, and an assessment of the potential impacts on employment and small businesses.

•

Environmental Justice Analysis for the Final Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category

(EJA), Document No. 821R24008. This report presents a profile of the communities and populations potentially impacted by this rule, an analysis of the distribution of impacts in the baseline scenario and with the revisions, and a summary of inputs from potentially impacted communities that the EPA met with prior to publishing the proposed rulemaking.

•

Docket Index for the Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category.

This document provides a list of additional memoranda, references, and other information the EPA relied on for the final revisions to the ELGs.

Organization of this Document.

The information in this preamble is organized as follows:

Table of Contents

I. Executive Summary

A. Purpose of Rule

II. Public Participation

III. General Information

A. Does this action apply to me?

B. What action is the EPA taking?

C. What is EPA's authority for taking this action?

D. What are the monetized incremental costs and benefits of this action?

IV. Background

A. Clean Water Act

B. Relevant Effluent Guidelines

C. 2015 Steam Electric Power Generation Point Source Category Rule

D. 2020 Steam Electric Reconsideration Rule and Recent Developments

E. Other Ongoing EPA Rules Impacting the Steam Electric Sector

V. Steam Electric Power Generating Industry Description

A. General Description of Industry

B. Current Market Conditions and Drivers in the Electricity Generation Sector

C. Control and Treatment Technologies

VI. Data Collection Since the 2020 Rule

A. Information from the Electric Utility Industry

B. Notices of Planned Participation

C. Information from Technology Vendors and Engineering, Procurement, and Construction Firms

D. Other Data Sources

VII. Final Regulation

A. Description of the Options

B. Rationale for the Final Rule

C. Subcategories

D. Additional Rationale for the Proposed PSES and PSNS

E. Availability Timing of New Requirements

F. Economic Achievability

G. Non-Water Quality Environmental Impacts

H. Impacts on Residential Electricity Prices and Communities with Environmental Justice Concerns

VIII. Costs, Economic Achievability, and Other Economic Impacts

A. Plant-Specific and Industry Total Costs

B. Social Costs

C. Economic Impacts

IX. Pollutant Loadings

A. FGD Wastewater

B. BA Transport Water

C. CRL

D. Legacy Wastewater

E. Summary of Incremental Changes of Pollutant Loadings from the Final Rule

X. Non-Water Quality Environmental Impacts

A. Energy Requirements

B. Air Pollution

C. Solid Waste Generation and Beneficial Use

D. Changes in Water Use

XI. Environmental Assessment

A. Introduction

B. Updates to the Environmental Assessment Methodology

C. Outputs from the Environmental Assessment

XII. Benefits Analysis

A. Categories of Benefits Analyzed

B. Quantification and Monetization of Benefits

C. Total Monetized Benefits

D. Additional Benefits

XIII. Environmental Justice Impacts

A. Literature Review

B. Proximity Analysis

C. Community Outreach

D. Distribution of Risks

E. Distribution of Benefits and Costs

XIV. Regulatory Implementation

A. Continued Implementation of Existing Limitations and Standards

B. Implementation of New Limitations and Standards

C. Reporting and Recordkeeping Requirements

D. Site-Specific Water Quality-Based Effluent Limitations

E. Severability

XV. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 14094: Modernizing Regulatory Review

B. Paperwork Reduction Act (PRA)

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments

G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks

H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer and Advancement Act

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations and Executive Order 14096: Revitalizing Our Nation's Commitment to Environmental Justice for All

K. Congressional Review Act (CRA)

Appendix A to the Preamble: Definitions, Acronyms, and Abbreviations Used in This Preamble

I. Executive Summary

A. Purpose of Rule

The EPA is promulgating this final supplemental rule to update requirements that apply to wastewater discharges from steam electric power plants, particularly coal-fired power plants. In 2015, the EPA set the first Federal limitations on the levels of toxic metals in several of the largest sources of wastewater that can be discharged from power plants after last updating these regulations in 1982 (80

Federal Register

(FR) 67838; November 3, 2015) (hereinafter the “2015 rule”). On an annual basis, the 2015 rule was projected to reduce the amount of toxic metals, nutrients, and other pollutants that steam electric power plants are allowed to discharge by 1.4 billion pounds and reduce water withdrawal by 57 billion gallons. This rule was reconsidered in 2020 and modified in part due to changing dynamics in the power sector (85 FR 64650; October 13, 2020) (hereinafter the “2020 rule”). Steam electric power plants are increasingly aging and less competitive sources of electric power in many portions of the United States.

Steam electric power plants, coal-fired power plants in particular, are subject to several environmental regulations designed to control (and in some cases eliminate) air, water, and land pollution over time. This rule, the Steam Electric Power Generating Effluent Limitations Guidelines and Standards—or steam electric ELGs—applies to the subset of the electric power industry where “generation of electricity is the predominant source of revenue or principal reason for operation, and whose generation of electricity results primarily from a process utilizing fossil-type fuel (

e.g.,

coal, oil, gas), fuel derived from fossil fuel (

e.g.,

petroleum coke, synthesis gas), or nuclear fuel in conjunction with a thermal cycle employing the steam-water system as the thermodynamic medium” (40 Code of Federal Regulations (CFR) 423.10). The 2015 rule addressed discharges from FGD wastewater, fly ash (FA) transport water, BA transport water, flue gas mercury control (FGMC) wastewater, gasification wastewater, CRL, legacy wastewater, and nonchemical metal cleaning wastes. The 2020 rule modified the 2015 requirements for FGD wastewater and BA transport water for existing sources only. The 2015 limitations for CRL from existing sources and legacy wastewater were vacated by the United States (U.S.) Court of Appeals for the Fifth Circuit in

Southwestern Electric Power Co., et al.

EPA,

920 F.3d 999 (5th Cir. 2019).

In the years since the EPA revised the steam electric ELGs in 2015 and 2020, new information has become available, which the EPA considered in finalizing this supplemental rule. For example, pilot testing and full-scale use of various, better performing treatment technologies have continued to develop, along with more data and information about their performance. The final supplemental rule updates requirements for discharges from two wastestreams addressed in the 2020 rule: BA transport water and FGD wastewater at existing sources. The final supplemental rule also replaces the court-vacated limitations for CRL (except for CRL discharges in one subcategory) and a subcategory of legacy wastewater. Finally, for the remaining CRL and legacy wastewaters, this rule finalizes a site-specific approach to developing technology-based limitations based on the permitting authorities' best professional judgment (BPJ), an option discussed by the Court in

Southwestern Electric Power Co.

EPA.

B. Summary of Final Rule

For existing sources that discharge directly to surface water, with the exception of the subcategories discussed below, the final rule establishes the following effluent limitations based on Best Available Technology Economically Achievable (BAT):

• A zero-discharge limitation for all pollutants in FGD wastewater, BA transport water, and CRL.

• Numeric (nonzero) discharge limitations for mercury and arsenic in unmanaged CRL

and for legacy wastewater discharged from surface impoundments during the closure process if those surface impoundments have not commenced closure under the Coal Combustion Residuals (CCR) regulations as of the effective date of this rule.

As discussed in section VII.C.5 of this document, the EPA is defining unmanaged CRL in this rule to mean CRL which either: (1) the permitting authority determines are the functional equivalent of a direct discharge to waters of the United States (WOTUS) through groundwater or (2) CRL that has leached from a waste management unit into the subsurface and mixed with groundwater prior to being captured and pumped to the surface for discharge directly to a WOTUS.

The final rule eliminates the separate, 2020 rule's less stringent BAT requirements for two subcategories: high-flow facilities and low-utilization electric generating units (LUEGUs), except to the extent they apply to one new permanent cessation of coal combustion subcategory. The final rule leaves in place the existing subcategories for oil-fired and small (50 megawatts (MW) or less) electric generating units (EGUs) established in the 2015 rule. The final rule also leaves in place the existing subcategory for EGUs permanently ceasing the combustion of coal by 2028, which was established in the 2020 rule and amended in a 2023 direct final rule by extending the date for filing a Notice of Planned Participation (NOPP).

See

88 FR 18440 (March 29, 2023). Lastly, the final rule creates a new subcategory for EGUs permanently ceasing coal combustion by 2034. For both the existing and new subcategories referenced immediately above, the EPA is finalizing additional reporting and recordkeeping requirements and zero-discharge limitations applicable after EGUs cease coal combustion, as well as procedural requirements for affected facilities to demonstrate permanent cessation of coal combustion or that permanent retirement will occur.

As stated above, the rule eliminates the 2020 rule subcategories for high flow and low utilization, except to the extent they apply to EGUs in the new permanent cessation of coal combustion by 2034 subcategory. The elimination of the 2020 rule's subcategories will affect the one known high-flow facility (the Tennessee Valley Authority (TVA) Cumberland Fossil Plant) that has indicated it is planning to close and the two known facilities with LUEGUs (GSP Merrimack LLC and Indiana Municipal Power Agency (IMPA) Whitewater Valley Station), one of which is also expected to close. For EGUs ceasing coal combustion by 2034, the final rule retains the 2020 rule requirements for FGD wastewater and BA transport water and the pre-2015 BPJ-based BAT requirements for CRL rather than requiring the new, more stringent zero-discharge requirements for these wastestreams. After the permanent cessation of coal combustion, however, EGUs in this subcategory must meet limitations on arsenic and mercury based on chemical precipitation for CRL.

Where BAT limitations in this final rule are more stringent than previously established Best Practicable Control Technology Currently Available (BPT) and BAT limitations, any new limitations for direct dischargers do not apply until a date determined by the permitting authority that is as soon as possible on or after July 8, 2024, but no later than December 31, 2029.

For indirect discharges (

i.e.,

discharges to publicly owned treatment works (POTWs)), the final rule establishes pretreatment standards for existing sources that are the same as the BAT limitations except where limitations are for total suspended solids (TSS), a pollutant that does not pass through POTWs. Pretreatment standards are directly enforceable and apply May 9, 2027.

While the EPA is not aware of any planned new sources that would be subject to the requirements of this final supplement rule, this action sets new source performance standards and pretreatment standards for discharges of CRL from new sources that are equivalent to the new BAT limitations—namely, zero discharge.

C. Summary of Costs and Benefits

The EPA estimates that the final rule will cost $536 million to $1.1 billion per year in social costs and result in $3.2 billion per year in monetized benefits using a 2 percent discount rate.

The EPA estimated the annualized value of future benefits and costs using a discount rate of 2 percent, following current Office of Management and Budget (OMB) guidance in Circular A-4 (OMB, 2023). In appendix B of the BCA, the EPA also provides results of analyses performed using 3 percent and 7 percent discount rates to allow comparison of the final rule costs and benefits with those estimated at proposal, which followed the guidance applicable at the time the prior analysis was conducted (OMB, 2003).

The EPA's analysis reflects the Agency's understanding of the actions steam electric power plants are expected to take to meet the limitations and standards in the final rule, including the implementation of additional treatment technologies to reduce pollutant discharges. The EPA based its analysis on a modeled baseline that reflects the full implementation of the 2020 rule, the expected effects of announced retirements and fuel conversions, and the anticipated impacts of relevant final rules affecting the power sector. Not all costs and benefits can be fully quantified and monetized. While some health benefits and willingness to pay (WTP) for water quality improvements have been quantified and monetized, those estimates may not fully capture all important water-quality-related benefits. Furthermore, the EPA anticipates the final rule would generate important additional benefits that the Agency was only able to analyze qualitatively (

e.g.,

improved habitat conditions for plants, invertebrates, fish, amphibians, and the wildlife that prey on aquatic organisms).

For additional information on costs and benefits,

see

sections VIII and XII of this preamble, respectively.

II. Public Participation

During the 60-day public comment period on the 2023 proposed supplemental rule (88 FR 18824, March 29, 2023) (from March 29, 2023, to May 30, 2023), the EPA received more than 22,000 public comment submissions from private citizens, industry representatives, technology vendors, government entities, environmental groups, and trade associations. The EPA also hosted two online public hearings during the public comment period—one on April 20, 2023, and one on April 25, 2023. These hearings had a combined total of 196 attendees, 46 of whom registered to provide comment on the proposed rule. Available documents from each public hearing include the presentations given by the EPA and two transcripts (document control number (DCN) SE10469, DCN SE10469A1, DCN SE10470 and DCN SE10470A1).

III. General Information

A. Does this action apply to me?

Entities potentially regulated by any final rule following this action include the following:

see also Clean Water Action.

EPA,

No. 18-60079 (5th Cir.). On October 29, 2018, the District of Arizona case was dismissed upon the EPA's motion to dismiss for lack of jurisdiction, and on August 28, 2019, the Fifth Circuit denied the petition for review of the postponement rule.

D. 2020 Steam Electric Reconsideration Rule and Recent Developments

1. 2020 Rule Requirements

On October 13, 2020, the EPA promulgated the

Steam Electric Reconsideration Rule

(85 FR 64650). The 2020 rule revised requirements for FGD wastewater and BA transport water applicable to existing sources. Specifically, the 2020 rule made four changes to the 2015 rule. First, the rule changed the technology basis for control of FGD wastewater and BA transport water. For FGD wastewater, the technology basis was changed from chemical precipitation plus high-hydraulic-residence-time biological reduction to chemical precipitation plus low-hydraulic-residence-time biological reduction. This change in the technology basis resulted in less stringent selenium limitations but more stringent mercury and nitrogen limitations. For BA transport water, the technology basis was changed from dry-handling or closed-loop systems to high-recycle-rate systems, allowing for a site-specific purge not to exceed 10 percent of the BA transport system's volume. This change in technology resulted in less stringent limitations for all pollutants in BA transport water. Second, the 2020 rule revised the technology basis for the voluntary incentives program (VIP) for FGD wastewater from vapor compression evaporation to chemical precipitation plus membrane filtration. This change in the technology basis resulted in less stringent limitations for most pollutants but added new limitations for bromide and nitrogen. Third, the 2020 rule created three new subcategories for high-flow facilities, LUEGUs, and EGUs permanently ceasing coal combustion by 2028. These subcategories were subject to less stringent limitations: high-flow facilities were subject to FGD wastewater limitations based on chemical precipitation; LUEGUs were subject to FGD wastewater limitations based on chemical precipitation and BA transport water limitations based on surface impoundments and a best management practice (BMP) plan; and EGUs permanently ceasing coal combustion by 2028 were subject to FGD wastewater and BA transport water limitations based on surface impoundments. Finally, the 2020 rule required most steam electric facilities to comply with the revised effluent limitations “as soon as possible” after October 13, 2021, and no later than December 31, 2025.

NPDES permitting authorities established the particular applicability date(s) of the new limitations within that range for each facility (except for indirect dischargers) at the time they reissued the facility's NPDES permit.

The 2015 rule's VIP compliance date was revised to December 31, 2028, in the 2020 rule.

2. Fourth Circuit Court of Appeals Litigation

Two petitions for review of the 2020 rule were timely filed by environmental group petitioners and consolidated in the U.S. Court of Appeals for the Fourth Circuit on November 19, 2020.

Appalachian Voices, et al.

EPA,

No. 20-2187 (4th Cir.). An industry trade group and certain energy companies moved to intervene in the litigation, which the Court granted on December 3, 2020. On April 8, 2022, the Court granted the EPA's motion and placed the case into abeyance pending the completion of the current rulemaking.

3. Executive Order 13990 and Announcement of Supplemental Rule

On January 20, 2021, President Biden issued Executive Order 13990:

Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis.

86 FR 7037. Executive Order 13990 directed Federal agencies to immediately review and, as appropriate and consistent with applicable law, take action to address the promulgation of Federal regulations and other actions during the previous four years that conflict with the national objectives of protecting public health and the environment.

On July 26, 2021, the EPA announced a new rulemaking to strengthen certain wastewater pollution discharge limitations for coal-fired power plants that use steam to generate electricity (86 FR 41801, August 3, 2021). The EPA later clarified that, as part of its new rulemaking, it would be reconsidering all aspects of the 2020 rule. The EPA undertook an evidence-based, science-based review of the 2020 rule under Executive Order 13990, finding that there are opportunities to strengthen certain wastewater pollution discharge limitations. For example, the EPA discussed how treatment systems using membranes have advanced since the 2020 rule's promulgation and continue to rapidly advance as an effective option for treating a wide variety of industrial pollution, including pollution from steam electric power plants. In the announcement, the EPA also clarified that, until a new rule is promulgated, part 423 will continue to be implemented and enforced to achieve needed pollutant reductions.

This includes both the 2020 rule and portions of the 2015 rule which were not revised or vacated.

4. Preliminary Effluent Guidelines Plan 15

In September 2021, the EPA issued

Preliminary Effluent Guidelines Program Plan 15.

This document discussed the annual review of ELGs, rulemakings for new and existing industrial point source categories, and any new or existing sources receiving further analyses. Here, in the context of the EPA's ongoing steam electric ELG rulemaking, EPA noted relevant wastestreams including pointing out that the 2015 rule limitations for CRL and legacy wastewater had been vacated and remanded to the Agency. For further discussion of the vacatur and remand of the 2015 limitations applicable to CRL and legacy wastewater, see section IV.D of this preamble.

Available online at:

www.epa.gov/system/files/documents/2021-09/ow-prelim-elg-plan-15_508.pdf.

E. Other Ongoing EPA Rules Impacting the Steam Electric Sector

The EPA has recently proposed or finalized several other rules to protect the nation's air, land, and water from pollution resulting from coal-fired power plants. The EPA has primarily considered these other rules to support this final rulemaking in two ways. First, when appropriate, the EPA has included the impacts of final rules in the baseline of its analyses. Second, the EPA has designed this final rule to harmonize compliance dates, subcategories, and other aspects of these rules to the extent possible and appropriate under different statutory schemes. The following sections summarize the solid waste and

air rules that are most directly relevant to the electric power sector.

1. Coal Combustion Residuals Disposal Rule

On April 17, 2015, the EPA promulgated the Disposal of Coal Combustion Residuals from Electric Utilities final rule (2015 CCR rule) (80 FR 21302). This rule finalized national regulations to provide a comprehensive set of requirements for the safe disposal of CCR, commonly referred to as coal ash, from steam electric power plants. The final 2015 CCR rule was the culmination of extensive study on the effects of coal ash on the environment and public health. The rule established technical requirements for CCR landfills and surface impoundments under subtitle D of the Resource Conservation and Recovery Act (RCRA), the Nation's primary law for regulating solid waste.

These regulations established requirements for the management and disposal of coal ash, including requirements designed to prevent leaking of contaminants into groundwater, blowing of contaminants into the air as dust, and the catastrophic failure of coal ash surface impoundments. The 2015 CCR rule also set recordkeeping and reporting requirements, as well as requirements for each plant to establish and post specific information to a publicly accessible website. The rule also established requirements to distinguish the beneficial use of CCR from disposal.

As a result of the D.C. Circuit Court decisions in

Utility Solid Waste Activities Group

EPA,

901 F.3d 414 (D.C. Cir. 2018) (“

USWAG

decision” or “

USWAG”

), and

Waterkeeper Alliance Inc. et al.

EPA,

No. 18-1289 (D.C. Cir. filed March 13, 2019), the Administrator signed two rules:

A Holistic Approach to Closure Part A: Deadline to Initiate Closure and Enhancing Public Access to Information

(CCR Part A rule) (85 FR 53516, August 28, 2020) on July 29, 2020, and

A Holistic Approach to Closure Part B: Alternate Liner Demonstration

(CCR Part B rule) (85 FR 72506, December 14, 2020) on October 15, 2020. The EPA finalized five amendments to the 2015 CCR rule which are relevant to the management of the wastewaters covered by this ELG because these wastewaters have historically been co-managed with CCR in the same surface impoundments. First, the CCR Part A rule established a new deadline of April 11, 2021, for all unlined surface impoundments in which CCR are managed (“CCR surface impoundments”), as well as CCR surface impoundments that failed the location restriction for placement above the uppermost aquifer, to stop receiving waste and begin closure or retrofitting. The EPA established this date after evaluating the steps that owners and operators need to take for CCR surface impoundments to stop receiving waste and begin closure, and the timeframes needed for implementation. (This did not affect the ability of plants to install new, composite-lined CCR surface impoundments.) Second, the Part A rule established procedures for plants to obtain approval from the EPA for additional time to develop alternative disposal capacity to manage their wastestreams (both CCR and non-CCR) before they must stop receiving waste and begin closing their CCR surface impoundments. Third, the Part A rule changed the classification of compacted-soil-lined and clay-lined surface impoundments from lined to unlined. Fourth, the Part B rule finalized procedures potentially allowing a limited number of facilities to demonstrate to the EPA that, based on groundwater data and the design of a particular surface impoundment, the unit ensures there is no reasonable probability of adverse effects to human health and the environment. Should the EPA approve such a submission, these CCR surface impoundments would be allowed to continue to operate.

As explained in the 2015 and 2020 ELG rules, the ELGs and CCR rules may affect the same EGU or activity at a plant. Therefore, when the EPA finalized the ELG and CCR rules in 2015, and revisions to both rules in 2020, the Agency coordinated the ELG and CCR rules to minimize the complexity of implementing engineering, financial, and permitting activities. Likewise, the EPA considered the interaction of the two rules during the development of this final rule. The EPA's analytic baseline includes the final requirements of these rules using the most recent data provided under the CCR rule reporting and recordkeeping requirements. This is further described in Supplemental TDD, section 3. For more information on the CCR Part A and Part B rules, including information about their ongoing implementation, visit

www.epa.gov/coalash/coal-ash-rule.

Concurrently with the final ELG, in a separate rulemaking, the EPA is also finalizing regulatory requirements for inactive CCR surface impoundments at inactive utilities (“legacy CCR surface impoundment” or “legacy impoundment”) (FR 2024-09157 (EPA-HQ-OLEM-2020-0107; FRL-7814-04-OLEM)). This action is being taken in response to the August 21, 2018, opinion by the U.S. Court of Appeals for the District of Columbia Circuit in the

USWAG

decision that vacated and remanded the provision exempting legacy impoundments from the CCR regulations. This action includes adding a definition for legacy CCR surface impoundments and other terms relevant to this rulemaking. It also requires that legacy CCR surface impoundments comply with certain existing CCR regulations with tailored compliance deadlines.

The EPA is also establishing requirements to address the risks from currently exempt solid waste management that involves the direct placement of CCR on the land. The EPA is extending a subset of the existing requirements in 40 CFR part 257, subpart D, to CCR surface impoundments and landfills that closed prior to the effective date of the 2015 CCR rule, inactive CCR landfills, and other areas where CCR is managed directly on the land. In this action, the EPA refers to these as CCR management units, or CCRMU. This rule will apply to all existing CCR facilities and all inactive facilities with legacy CCR surface impoundments subject to this final rule.

Finally, the EPA is making a number of technical corrections to the existing regulations, such as correcting certain citations and harmonizing definitions. For further information on the CCR regulations, including information about the CCR Part A and Part B rules' ongoing implementation, visit

www.epa.gov/coalash/coal-ash-rule.

2. Air Pollution Rules and Implementation

The EPA is taking several actions to regulate a variety of conventional, hazardous, and greenhouse gas (GHG) air pollutants, including actions to regulate the same steam electric power plants subject to part 423. In light of these ongoing actions, the EPA has worked to consider appropriate flexibilities in this ELG rule to provide certainty to the regulated community while ensuring the statutory objectives of each program are achieved. Furthermore, to the extent that these actions have been published before this rule's signature and are already impacting steam electric power plant operations, the EPA has accounted for these changed operations in its Integrated Planning Model (IPM) modeling discussed in section VIII of this preamble.

a. The Revised Cross State Air Pollution Rule Update and the Good Neighbor Plan for the 2015 Ozone National Ambient Air Quality Standards

On June 5, 2023, the EPA promulgated its final Good Neighbor Plan, which secures significant reductions in ozone-forming emissions of nitrogen oxides (NO

) from power plants and industrial facilities. 88 FR 36654. The Good Neighbor Plan ensures that 23 states meet the Clean Air Act's (CAA's) “Good Neighbor” requirements by reducing pollution that significantly contributes to problems attaining and maintaining EPA's health-based air quality standard for ground-level ozone (or “smog”), known as the 2015 Ozone National Ambient Air Quality Standards (NAAQS), in downwind states. Further information on this action is available on the EPA's website.

See https://www.epa.gov/csapr/good-neighbor-plan-2015-ozone-naaqs.

As of September 21, 2023, the Good Neighbor Plan's “Group 3” ozone-season NO

control program for power plants is being implemented in: Illinois, Indiana, Maryland, Michigan, New Jersey, New York, Ohio, Pennsylvania, Virginia, and Wisconsin. Pursuant to court orders staying the Agency's State Implementation Plan disapproval action in the following States, the EPA is not currently implementing the Good Neighbor Plan “Group 3” ozone-season NO

control program for power plants in: Alabama, Arkansas, Kentucky, Louisiana, Minnesota, Mississippi, Missouri, Nevada, Oklahoma, Texas, Utah, and West Virginia.

Further information on EPA's response to the stay orders can be found online at:

https://www.epa.gov/Cross-State-Air-Pollution/epa-response-judicial-stay-orders.

On January 16, 2024, the EPA signed a proposal to partially approve and partially disapprove State Implementation Plan submittals addressing interstate transport for the 2015 ozone NAAQS from Arizona, Iowa, Kansas, New Mexico, and Tennessee and proposed to include these States in the Good Neighbor Plan beginning in 2025 (89 FR 12666, February 16, 2024).

On April 30, 2021, the EPA published the final Revised Cross-State Air Pollution Rule (CSAPR) Update (86 FR 23054), which resolved 21 states' good neighbor obligations for the 2008 ozone NAAQS, following the remand of the 2016 CSAPR Update (81 FR 74504, October 26, 2016) in

Wisconsin

EPA,

938 F.3d 308 (D.C. Cir. 2019). Together, these two rules establish the Group 2 and Group 3 market-based emissions trading programs for 22 states in the eastern United States for emissions of NO

from fossil fuel-fired EGUs during the summer ozone season.

b. Clean Air Act section 111 Rule

Concurrently with the final ELG, the EPA is finalizing the repeal of the Affordable Clean Energy Rule, establishing Best System of Emissions Reduction (BSER) determinations and emission guidelines for existing fossil fuel-fired EGUs, and establishing BSER determinations and accompanying standards of performance for GHG emissions from new and reconstructed fossil fuel-fired stationary combustion turbines and modified fossil fuel-fired EGUs. Specifically, for coal-fired EGUs, the EPA is establishing final standards based on carbon capture and storage/sequestration with 90 percent capture with a compliance date of January 1, 2032 (FR 2024-09233 (EPA-HQ-OAR-2023-0072; FRL-8536-01-OAR)). For coal-fired EGUs retiring by January 1, 2039, the EPA is establishing final standards based on 40 percent natural gas co-firing with a compliance date of January 1, 2030.

While four subcategories for coal-fired EGUs were proposed, the EPA is finalizing just the two subcategories for coal-fired EGUs as described in the preceding paragraph. Consistent with 40 CFR 60.24a(e) and the Agency's explanation in the proposal, states have the ability to consider,

inter alia,

a particular source's remaining useful life when applying a standard of performance to that source.

See 88 FR 33240 (May 23, 2023) (invoking RULOF based on a particular coal-fired EGU's remaining useful life “is not prohibited under these emission guidelines”).

In addition, the EPA is creating an option for states to provide for a compliance date extension for existing sources of up to one year under certain circumstances for sources that are installing control technologies to comply with their standards of performance. States may also provide, by inclusion in their state plans, a reliability assurance mechanism of up to one year that under limited circumstances would allow existing EGUs that had planned to cease operating by a certain date to temporarily remain available to support reliability. Any extensions exceeding 1-year must be addressed through a state plan revision. Further information about the CAA section 111 rule is available online at

https://www.epa.gov/stationary-sources-air-pollution/greenhouse-gas-standards-and-guidelines-fossil-fuel-fired-power.

c. Mercury and Air Toxics Standards Rule

On March 6, 2023 (88 FR 13956), the EPA published a final rule which reaffirmed that it remains appropriate and necessary to regulate hazardous air pollutants (HAP), including mercury, from power plants after considering cost. This action revoked a 2020 finding that it was not appropriate and necessary to regulate coal- and oil-fired power plants under CAA section 112, which covers toxic air pollutants. The EPA reviewed the 2020 finding and considered updated information on both the public health burden associated with HAP emissions from coal- and oil-fired power plants, as well as the costs associated with reducing those emissions under the Mercury and Air Toxics Standards (MATS). After weighing the public risks these emissions pose to all Americans (and particularly exposed and sensitive populations) against the costs of reducing this harmful pollution, the EPA concluded that it remains appropriate and necessary to regulate these emissions. This action ensures that coal- and oil-fired power plants continue to control emissions of hazardous air pollution and that the Agency properly interprets the CAA to protect the public from hazardous air emissions.

Concurrently with the final ELG, the EPA is finalizing an update to the National Emission Standards for Hazardous Air Pollutants for Coal- and Oil-Fired Electric Utility Steam Generating Units (EGUs), commonly known as the Mercury and Air Toxics Standards (MATS) for power plants, to reflect recent developments in control technologies and the performance of these plants (FR 2024-0918 (EPA-HQ-OAR-2018-0794; FRL-6716.3-02-OAR)). This final rule includes an important set of improvements and updates to MATS and also fulfills the EPA's responsibility under the Clean Air Act to periodically re-evaluate its standards in light of advancements in pollution control technologies to determine whether revisions are necessary. The improvements consist of:

• Further limiting the emission of non-mercury HAP metals from existing coal-fired power plants by significantly reducing the emission standard for filterable particulate matter (fPM), which is designed to control non-mercury HAP metals. The EPA is finalizing a two-thirds reduction in the fPM standard;

Also, the EPA is finalizing the removal of the low-emitting EGU provisions for fPM and non-mercury HAP metals.

• Tightening the emission limit for mercury for existing lignite-fired power plants by 70 percent;

This level aligns with the mercury standard that other coal-fired power plants have been achieving under the current MATS.

• Strengthening emissions monitoring and compliance by requiring coal-and oil-fired EGUs to comply with the fPM standard using PM continuous emission monitoring systems (CEMS);

PM CEMS provide regulators, the public, and facility owners or operators with cost-effective, accurate, and continuous emission measurements. This real-time, quality-assured feedback can lead to improved control device and power plant operation, which will reduce air pollutant emissions and exposure for local communities.

• Revising the startup requirements in MATS to assure better emissions performance during startup.

Additional information on the final MATS is available on the EPA's website.

See https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards.

d. National Ambient Air Quality Standards Rules for Particulate Matter

On February 7, 2024, the EPA Administrator signed a final rule strengthening the National Ambient Air Quality Standards for Particulate Matter (PM NAAQS) to protect millions of Americans from harmful and costly health impacts, such as heart attacks and premature death (89 FR 16202, March 6, 2024). Particle or soot pollution is one of the most dangerous forms of air pollution, and an extensive body of science links it to a range of serious and in some cases deadly illnesses. The EPA set the level of the primary (health-based) annual particulate matter (PM

2.5

) standard at 9.0 micrograms per cubic meter to provide increased public health protection, consistent with the available health science. The EPA did not change the current primary and secondary (welfare-based) 24-hour PM

2.5

standards, the secondary annual PM

2.5

standard, and the primary and secondary PM

standards. The EPA also revised the Air Quality Index to improve public communications about the risks from PM

2.5

exposures and made changes to the monitoring network to enhance protection of air quality in communities overburdened by air pollution. More information about this action is available on the EPA's website.

See https://www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm.

V. Steam Electric Power Generating Industry Description

A. General Description of Industry

For each previous regulatory action—the 2013 proposed rule (78 FR 34432, June 7, 2013), the 2015 final rule, the 2019 proposed rule (84 FR 64620, November 22, 2019), the 2020 final rule, and the 2023 proposed rule—the EPA provided general descriptions of the steam electric power generating industry. The Agency has continued to collect information and update this industry profile. The previous descriptions reflected the known information about the universe of steam electric power plants and incorporated final environmental regulations applicable at that time. For this rule, as described in the Supplemental TDD, section 3, the EPA has revised its description of the steam electric power generating industry (and its supporting analyses) to incorporate major changes such as additional retirements, fuel conversions, ash handling conversions, wastewater treatment updates, and updated information on capacity utilization.

The analyses supporting this rule use an updated baseline that incorporates these changes in the industry and include the 2015 and 2020 rules' limitations for FGD wastewater, BA transport water, CRL, and legacy wastewater. The analyses then compare the effect of the new rule's requirements to this baseline.

The data presented in the general description continue to reflect some conditions existing in 2009.The 2010 steam electric industry survey remains the EPA's best available source of information for characterizing operations across the industry in cases where the EPA has not received newer information.

As described in the Regulatory Impact Analysis, of the 858 steam electric power plants in the country identified by the EPA, only those coal-fired power plants that discharge FGD wastewater, BA transport water, CRL, legacy wastewater and/or unmanaged CRL may incur compliance costs under this rule. The EPA estimates that 141 to 170 such plants may incur compliance costs under this rule, depending on the scenario used to model the occurrence of unmanaged CRL costs. See section VII.C.5 of this preamble for more information regarding subcategory for discharges of unmanaged CRL. See the EPA's memorandum,

Changes to Industry Profile for Coal-Fired Generating Units for the Steam Electric Effluent Guidelines Final Rule

(DCN SE11618), for more information about plant retirements, fuel conversions, ash handling conversions, wastewater treatment updates, and updated information on capacity utilization.

B. Current Market Conditions and Drivers in the Electricity Generation Sector

1. Inflation Reduction Act Implementation

On August 16, 2022, President Biden signed into law the Inflation Reduction Act (IRA). The IRA marks the most significant action Congress has taken on clean energy and climate change in the nation's history. The IRA provides tax credits, financing programs, and other incentives, some of which are administered by the EPA, that will accelerate the transition to forms of energy that produce little or no GHG emissions and other water and air pollutants. As such, it includes many provisions that will affect the steam electric power generating industry, causing both direct effects through changes in the production of electricity and indirect effects on electricity demand and changes to fuel markets.

In September 2023, the EPA published a report on the effect of the IRA on the electricity sector and on the economy in general.

The report found that the IRA would lead to emission reductions from the electric power sector of 49 to 83 percent below 2005 levels in 2030. The associated shifts from fossil fuel generation would also lead to reductions in water and air pollution from the sector. The study also found that the IRA would lower economy-wide CO

emissions, including emissions from electricity generation and use, by 35 to 43 percent below 2005 levels in 2030. Across the end-use sectors, the study found that buildings exhibit the greatest reductions from 2005 levels of direct plus indirect CO

emissions from electricity, followed by industry and transportation. Though it focuses on changes in climate-forcing emissions (in part attributable to the models it uses), the study also implies important changes in the emissions of other pollutants throughout the economy. The EPA used IPM to evaluate the impacts of the final ELG relative to a baseline that reflects impacts from other relevant policies and environmental regulations that affect the power sector, including the IRA and other on-the-books Federal and state rules (

see

section VIII.C.2 of this preamble for more information).

U.S. EPA (Environmental Protection Agency). 2023.

Electricity Sector Emissions Impacts of the Inflation Reduction Act: Assessment of Projected CO

Emission Reductions from Changes in Electricity Generation and Use.

U EPA 430-R-23-004. Available online at:

https://www.epa.gov/inflation-reduction-act/electric-sector-emissions-impacts-inflation-reduction-act.

2. Recent Developments in Ensuring Electric Reliability and Resource Adequacy

The nature and components of the bulk power sector have been evolving away from older and less efficient legacy fossil generation (mostly coal-fired power plants) towards more decentralized, renewable assets and flexible gas-fired generation. Stakeholders have raised concerns that centralized, dispatchable power plants are coming offline faster than new generation can replace the reliability attributes associated with them. However, a combination of technology innovation, revised market signals from the Regional Transmission Organizations (RTOs) and Independent System Operators (ISOs), and reforms recently completed and underway by Federal Energy Regulatory Commission (FERC) are collectively poised to address current reliability challenges associated with the transition along with expected higher load growth and the increasing frequency of extreme weather events. EPA has continued to learn and engage on reliability issues, particularly as part of the Agency's implementation of the

Joint Memorandum on Interagency Communication and Consultation on Electric Reliability.

As part of this process, EPA has engaged in regular meetings with Department of Energy (DOE), North American Electric Reliability Corporation (NERC), FERC, and the various ISOs/RTOs.

Available online at:

https://www.epa.gov/power-sector/electric-reliability-mou.

FERC, NERC, RTOs, and ISOs are already taking steps to ensure reliability during this period of asset evolution. Among FERC's actions to help address reliability is Order 2023, or “Improvements to Generator Interconnection Procedures,” which will help expedite interconnections for new assets waiting to connect to the grid. This is a very important development to ensure future resource adequacy because interconnection wait times for new energy assets entering energy markets have increased, which is stifling the ability of replacement generation to connect to the grid. FERC's final action on extreme cold weather preparedness will support the new peak demand hours, which have migrated to winter months. New reliability standards issued for inverter-based resources “will help ensure reliability of the grid by accommodating the rapid integration of new power generation technologies, known as inverter-based resources (IBRs), that include solar photovoltaic, wind, fuel cell and battery storage resources. . . .”

FERC has also undertaken various transmission-related efforts, from inter-regional transmission capacity efforts to reconductoring and dynamic line rating, that would help bolster reliability by increasing the transmission capacity of existing lines and creating incentives for new, inter-regional transmission. Increasing transmission capacity can enhance reliability by increasing the amount of generation that can access the grid to help meet demand.

For further information about FERC actions to address IBRs,

see https://www.ferc.gov/news-events/news/ferc-moves-protect-grid-transition-clean-energy-resources.

Furthermore, there are new technologies coming online that can also help provide reliability attributes. The deployment of many of these technologies has been accelerating due to the incentives in the IRA. The rapid increase in energy storage deployment across the nation is an important part of future grid reliability, particularly as the duration of storage assets expands. Examples of existing and emerging storage resources include various types of fuel cells, batteries, pumped hydro-electric reservoirs, and underground hydrogen caverns. Energy storage can help buttress reliability by storing renewable energy for dispatch when demand is high. Improved management of demand response assets, better designed electricity tariff structures, aggregation of distributed resources like roof-top solar panels, and integration of behind-the-meter battery storage can further support balancing peak demand on power grids. For example, programs to manage demand, which have shown value well before the recent energy transition, incentivize customers to shift their demand during periods when there is ample supply, which can help reduce instances when supply is tight.

Despite these concerns, there are also existing procedures in place to ensure electricity system reliability and resource adequacy over both the short and long-term. For example, regional planning organizations typically have incentive or planning procedures to ensure that there is sufficient capacity to meet future demand such as day-ahead reserve and capacity markets and seasonal reserve margins. Furthermore, the EPA understands that before a unit implements a retirement decision, the unit's owner will follow the processes put in place by the relevant RTO, balancing authority, or state regulator to protect electric system reliability. These processes typically include analysis of the potential impacts of the proposed EGU retirement on electrical system reliability, identification of options for mitigating any identified adverse impacts, and, in some cases, temporary provision of additional revenues to support the EGU's continued operation until longer-term mitigation measures can be put in place.

C. Control and Treatment Technologies

In general, control and treatment technologies for some wastestreams have continued to advance since the 2015 and 2020 rules. Often, these advancements provide plants with additional approaches for complying with any effluent limitations. In some cases, these advancements have also decreased the associated costs of compliance. For this rule, the EPA incorporated updated information and evaluated several technologies available to control and treat FGD wastewater, BA transport water, CRL, and legacy wastewater generated by the steam electric power generating industry. See section VIII of this preamble for details on updated cost information.

1. FGD Wastewater

FGD scrubber systems are used to remove sulfur dioxide from flue gas so it is not emitted into the air. Dry FGD systems use water in their operation but generally do not discharge wastewater because it evaporates during operation. Wet FGD systems do produce a wastewater stream.

Steam electric power plants discharging FGD wastewater currently employ a variety of wastewater treatment technologies and operating/management practices to reduce the pollutants associated with FGD wastewater discharges. The EPA identified the following types of treatment and handling practices for FGD wastewater:

• Chemical precipitation. Chemicals are added as part of the treatment system to help remove suspended solids and dissolved solids, particularly metals. The precipitated solids are then removed from the solution by coagulation/flocculation followed by clarification and/or filtration. The 2015 and 2020 rules focused on a specific design that employs hydroxide precipitation, sulfide precipitation (organosulfide), and iron coprecipitation to remove suspended solids and convert soluble metal ions to insoluble metal hydroxides or sulfides. Chemical precipitation was part of the BAT technology basis for the effluent limitations in the 2015 and 2020 rules.

• High-hydraulic-residence-time biological reduction (HRTR). The EPA

identified three types of biological treatment systems used to treat FGD wastewater: anoxic/anaerobic fixed-film bioreactors (which target removals of nitrogen compounds and selenium), anoxic/anaerobic suspended growth systems (which target removals of selenium and other metals), and aerobic/anaerobic sequencing batch reactors (which target removals of organics and nutrients). An anoxic/anaerobic fixed-film bioreactor designed to remove selenium and nitrogen compounds using high hydraulic residence times of approximately 10 to 16 hours was part of the BAT technology basis for the effluent limitations in the 2015 rule.

• Low-hydraulic-residence-time biological reduction (LRTR). LRTR is a biological treatment system that targets removal of selenium and nitrate/nitrite using fixed-film bioreactors in smaller, more compact reaction vessels. This system differs from the HRTR biological treatment system evaluated in the 2015 rule, in that the LRTR system is designed to operate with a shorter residence time (approximately one to four hours, compared to a residence time of 10 to 16 hours for HRTR) while still achieving significant removal of selenium and nitrate/nitrite. LRTR was part of the BAT technology basis for the effluent limitations in the 2020 rule.

• Membrane filtration. A membrane filtration system (

e.g.,

microfiltration, ultrafiltration, nanofiltration, forward osmosis, electrodialysis reversal, or reverse osmosis (RO)) is designed specifically for high-TDS and high-TSS wastestreams. These systems are designed to minimize fouling and scaling associated with industrial wastewater. These systems typically use pretreatment for potential scaling agents (

e.g.,

calcium, magnesium, sulfates) combined with one or more type of membrane technology to remove a broad array of particulate and dissolved pollutants from FGD wastewater. The membrane filtration units may also employ advanced techniques, such as vibration or creation of vortexes to mitigate fouling or scaling of the membrane surfaces. Membrane filtration can achieve zero discharge by recirculating permeate from an RO system back into plant operations.

• Spray evaporation. Spray evaporation technologies, which include spray dry evaporators (SDEs) and other similar proprietary variations, evaporate water by spraying fine misted wastewater into hot gases. The hot gases allow the water to evaporate before contacting the walls of an evaporation vessel, treating wastewater across a range of water quality characteristics such as TDS, TSS, or scale forming potential. Spray evaporation technologies use a less complex treatment configuration than brine concentrator and crystallizer systems (see the description of thermal evaporation systems) to evaporate water using a heat source, such as a slipstream of hot flue gas or an external natural gas burner. Spray evaporation technologies can be used in combination with other volume reduction technologies, such as membranes, to maximize the efficiency of each process. Concentrate from an RO system can then be processed through the spray evaporation technology to achieve zero discharge by recirculating permeate from the RO system back into plant operations.

• Thermal evaporation. Thermal evaporation systems use a falling-film evaporator (or brine concentrator), following a softening pretreatment step, to produce a concentrated wastewater stream and a distillate stream to reduce wastewater volume by 80 to 90 percent and reduce the discharge of pollutants. The concentrated wastewater is usually further processed in a crystallizer that produces a solid residue for landfill disposal and additional distillate that can be reused within the plant or discharged. These systems are designed to remove the broad spectrum of pollutants present in FGD wastewater to very low effluent concentrations.

• Some plants operate their wet FGD systems using approaches that eliminate the discharge of FGD wastewater. These plants use a variety of operating and management practices to achieve this, including the following:

—Complete recycle. The FGD wastestream is allowed to recirculate. Particulates (

e.g.,

precipitates and other solids) are removed and landfilled. Water is supplemented when needed to replace water that evaporated or was removed with landfilled solids. This process does not produce a saleable product (

e.g.,

wallboard grade gypsum) but it does not need a wastewater purge stream to maintain low levels of chlorides.

—Evaporation impoundments. Some plants located in warm, dry climates use surface impoundments as holding basins where the FGD wastewater is retained until it evaporates. The evaporation rate from these impoundments is greater than the flow rate of the FGD wastewater and amount of precipitation entering the impoundments; therefore, there is no discharge to surface water.

These impoundments must be large enough to accommodate extreme precipitation events to prevent overtopping and runoff.

Such impoundments must be lined based on the requirements in the CCR rule. This lining would significantly reduce the potential for a discharge through groundwater that would be the functional equivalent of a direct discharge to a WOTUS.

—FA conditioning. Many plants that operate dry FA handling systems use the water from their FGD system in the FA handling system to suppress dust or improve handling and/or compaction characteristics in an on-site landfill.

—Combination of wet and dry FGD systems. The dry FGD process involves atomizing and injecting wet lime slurry, which ranges from approximately 18 to 25 percent solids, into a spray dryer. The water contained in the slurry evaporates from the heat of the flue gas within the system, leaving a dry residue that is removed from the flue gas using a fabric filter (

i.e.,

baghouse) or electrostatic precipitator.

—Underground injection. These systems dispose of wastes by injecting them into a permitted underground injection well as an alternative to discharging wastewater to surface waters.

The EPA also collected information on other FGD wastewater treatment technologies, including direct contact thermal evaporators and ion exchange. These treatment technologies have been evaluated, in full- or pilot-scale, or are being developed to treat FGD wastewater. More information on these technologies is available in section 4.1 of the Supplemental TDD.

2. BA Transport Water

BA (bottom ash) consists of heavier ash particles that are not entrained in the flue gas and fall to the bottom of the furnace. In most furnaces, the hot BA is quenched in a water-filled hopper.

Some plants use water to transport (sluice) the BA from the hopper to an impoundment or dewatering bins. The water used to transport the BA to the impoundment or dewatering bins is usually discharged to surface water as overflow from the systems after the BA has settled to the bottom. The industry also uses the following BA handling systems that generate BA transport water:

Consistent with the 2015 and 2020 rule, EGU slag is considered BA.

• Remote mechanical drag system (MDS). These systems transport BA to a remote MDS using the same processes as wet-sluicing systems. A drag chain conveyor pulls the BA out of the water bath on an incline to dewater the BA. The system can be operated either as a

closed-loop system (part of the technology basis for the 2015 rule) or a high-recycle-rate system (technology basis for the 2020 rule).

In some cases, additional treatment may be necessary to maintain a closed-loop system. This additional treatment could include polymer addition to enhance removal of suspended solids or membrane filtration of a slipstream to remove dissolved solids.

• Mobile MDS. This technology is a smaller, mobile version of a remote MDS with an additional clarification system. It is not intended to be a permanent installation, which allows facilities to reduce capital costs. Once in place, the system works like a remote MDS—the incoming water is clarified and primary separation occurs. The clarified water is taken from the mechanical drag system to a mobile clarifier and polished to a level suitable for recirculation. The mobile clarifier thickens the collected solids, which are then sent back to the mechanical drag system portion and mixed with coarse BA. This mixture is sent up an incline, dewatered, and disposed of.

• Dense slurry system. These systems use a dry vacuum or pressure system to convey the BA to a silo (as described below for the “dry vacuum or pressure system”), but instead of using trucks to transport the BA to a landfill, the plant mixes the BA with a lower percentage of water compared to a wet-sluicing system and pumps the mixture to the landfill.

As part of the 2020 rule and this rule, the EPA identified the following BA handling systems that do not, by definition or practice, generate BA transport water.

• MDS. These systems are located directly underneath the EGU. The BA is collected in a water quench bath. A drag chain conveyor pulls the BA out of the water bath along an incline to dewater the BA.

• Dry mechanical conveyor. These systems are located directly underneath the EGU. The system uses ambient air to cool the BA in the boiler and then transports the ash out from under the EGU using a conveyor. There is no water used in this process.

• Dry vacuum or pressure system. These systems transport BA from the EGU to a dry hopper without using any water. Air is percolated through the ash to cool it and combust unburned carbon. Cooled ash then drops to a crusher and is conveyed via vacuum or pressure to an intermediate storage destination.

• Vibratory belt system. These systems deposit BA on a vibratory conveyor trough, where the ash is air-cooled and ultimately moved through the conveyor deck to an intermediate storage destination without using any water.

• Submerged grind conveyor. These systems are located directly underneath the EGU and are designed to reuse slag tanks, ash gates, clinker grinders, and transfer enclosures from the existing wet sluicing systems. The system collects BA from the discharge of each clinker grinder. A series of submerged drag chain conveyors transport and dewater the BA.

More information on these technologies is available in section 4.2 of the Supplemental TDD.

3. CRL

In promulgating the 2015 rule, the EPA determined that CRL from landfills and impoundments includes similar types of constituents as FGD wastewater, albeit at potentially lower concentrations and smaller volumes. Based on this characterization of the wastewater and knowledge of treatment technologies, the EPA determined that certain treatment technologies identified for FGD wastewater could also be used to treat CRL. These technologies, described in section V.C.1 of this preamble, include chemical precipitation, biological treatment (including LRTR), membrane filtration, spray evaporation, or other thermal treatment options. The EPA also identified other management and reuse strategies from responses to the 2010

Questionnaire for the Steam Electric Power Generating Effluent Guidelines,

or steam electric survey, which included using CRL from either an impoundment or landfill for moisture conditioning FA, dust control, or truck wash. The EPA also identified plants that collect CRL from impoundments and recycle it directly back to the impoundment.

4. Legacy Wastewater

Legacy wastewater can be composed of FGD wastewater, BA transport water, FA transport water, CRL, gasification wastewater and/or FGMC wastewater generated before the “as soon as possible” date that more stringent effluent limitations from the 2015 or 2020 rules would apply. Discharges of legacy wastewater may occur through an intermediary source (

e.g.,

a tank or surface impoundment) or directly into a surface waterbody, with the vast majority of legacy wastewater currently contained in surface impoundments resulting from treating the wastestreams listed above to the previously established BPT limitations. The record indicates that the following technologies can be applied to treat this type of legacy wastewater: chemical precipitation, biological treatment (including LRTR), membrane filtration, spray evaporation, and other thermal treatment options. These technologies are described in section V.C.1 of this preamble. Another option, which may be used in combination with other systems such as chemical and physical treatment, is zero valent iron (ZVI).

• ZVI. This technology can be used to target specific inorganics, including selenium, arsenic, nitrate, and mercury in this type of legacy wastewater. The technology entails mixing influent wastewater with ZVI (iron in its elemental form), which reacts with oxyanions, metal cations, and some organic molecules in wastewater. ZVI causes a reduction reaction in these pollutants, after which the pollutants are immobilized through surface adsorption onto iron oxide coated on the ZVI or generated from oxidation of elemental iron. The coated, or spent, ZVI is separated from the wastewater with a clarifier. The quantity of ZVI required and number of reaction vessels can vary based on the composition and amount of wastewater being treated.

The EPA recognizes that the characterization of legacy wastewater differs within the layers of a CCR impoundment as it is dewatered and prepared for closure. Therefore, treatment requirements may change as closure continues. Wastewater characteristics may also differ across CCR impoundments due to the different types of fuels burned at the plant, duration of pond operation, and ash type. Each of the treatment technologies identified for legacy wastewater above is applicable to all legacy wastewaters; treatment may require a combination of those technologies (

e.g.,

chemical precipitation and membrane filtration).

In addition, solids dewatering is necessary to dredge CCR materials from the impoundment. Mobile dewatering systems are typically self-contained units on a trailer, allowing for the entire system to be easily moved on-site and off-site. Legacy wastewater from a holding area (

e.g.,

pit, pond, collection tank) is pumped through a filter press to generate a filter cake and water stream. A shaker screen can be added to the treatment train to remove larger particles prior to the filter press. Furthermore, the filter press can be equipped with automated plate shifters to allow solids to drop from the end of the trailer directly into a loader or truck. The resulting wastestream may be further treated to meet any discharge requirements.

VI. Data Collection Since the 2020 Rule

A. Information from the Electric Utility Industry

1. Data Requests and Responses

In January 2022, the EPA requested the following pollution treatment system performance and cost information for coal-fired power plants from three steam electric power companies:

• FGD wastewater installations of the following technologies: thermal technology; membrane filtration technology; paste, solidification, or encapsulation of FGD wastewater brine; electrodialysis; and electrocoagulation.

• Overflow from an MDS, a compact submerged conveyor, or remote MDS installations, including purge rate and management from remote MDS systems, as well as any pollutant concentration data to characterize the overflow or purge.

• CRL treatment from on-site or off-site testing (full-, pilot-, or laboratory-scale).

• On-site or off-site testing (full-, pilot-, or laboratory-scale) and/or implementation of treatment technologies associated with surface impoundment dewatering treatment.

• Costs associated with these technologies.

In addition, after meeting with four additional power companies, the EPA sent each company a voluntary request inviting them to provide the same data described above.

In July 2023, the EPA requested any full-, pilot-, or laboratory-scale data associated with on-site or off-site testing or implementation of a recently commissioned spray dryer evaporator for FGD wastewater and legacy wastewater at a coal-fired power plant from Minnesota Power. The EPA also requested information on pretreatment or disposal systems necessary for continued spray dryer evaporator operations and any corresponding documentation (

e.g.,

wastestreams generated, process flow diagram).

2. Meetings With Individual Utilities

To gather information to support this supplemental rule, the EPA met with representatives from four utilities. Two of these utilities reached out to the EPA after the announcement of the supplemental rulemaking. The EPA contacted the remaining utilities due to their known or potential consideration of membrane filtration. At these meetings, the EPA discussed the operation of the utility's coal-fired EGUs and the treatment and management of BA transport water, FGD wastewater, legacy wastewater, and CRL since the 2020 rule. The EPA learned about updates associated with plant operations and studies at these plants, which were originally discussed during the 2015 and 2020 rules.

The objectives of these meetings were to gather general information about coal-fired power plant operations; pollution prevention and wastewater treatment system operations; ongoing pilot or laboratory scale study information for FGD wastewater treatment; BA system performance, characterization, and quantification of the overflow and purge from remote MDS installations; and treatment technologies and pilot testing associated with CRL and legacy wastewater. The EPA used this information to supplement the data collected in support of the 2015 and 2020 rules.

3. Voluntary CRL Sampling

In December 2021, the EPA invited eight steam electric power companies to participate in a voluntary program designed to obtain data to supplement the wastewater characterization data set for CRL. The EPA requested these data from facilities believed to have constructed new landfills pursuant to the 2015 CCR rule. Six power companies chose to participate in this program. The EPA incorporated these data into the CRL analytical dataset used to estimate pollutant loadings. More information on estimated CRL pollutant loadings is available in section 6 of the Supplemental TDD.

4. Electric Power Research Institute Voluntary Submission

The Electric Power Research Institute (EPRI) conducts industry-funded studies to evaluate and demonstrate technologies that can potentially remove pollutants from wastestreams or eliminate wastestreams using zero-discharge technologies. Following the 2015 rule, the EPA reviewed 35 EPRI reports published between 2011 and 2018 that were voluntarily provided regarding characteristics of FGD wastewater, FGD wastewater treatment pilot studies, BA transport water characterization, BA handling practices, halogen addition rates, and the effect of halogen additives on FGD wastewater. For this supplemental rule, EPRI provided an additional 25 reports generated since 2018. The EPA used the information in these reports to inform treatment technology performance and to update methodologies for estimating costs and pollutant removals associated with candidate treatment technologies.

5. Meetings With Trade Associations

In 2021 and 2022, the EPA met with the Edison Electric Institute and the American Public Power Association. These trade associations represent investor-owned utilities and community-owned utilities, respectively. They provided information and perspectives on the status of many utilities transitioning away from coal. The EPA also participated in meetings with one trade association following the 2023 proposed rule. This association requested meetings with the EPA to discuss the association's public comments.

B. Notices of Planned Participation

The 2020 rule required facilities to file a Notice of Planned Participation (NOPP) with their permitting authority no later than October 13, 2021, if the facility wished to participate in the LUEGU subcategory, the permanent cessation of coal combustion by 2028 subcategory, or in the VIP. For the permanent cessation of coal combustion by 2028 subcategory, this filing date was extended by a 2023 direct final rule to June 27, 2023. 88 FR 18440. While the facilities were not required to provide copies of the NOPPs to the Agency, the EPA nevertheless obtained a number of these filings. Some facilities provided the EPA a courtesy copy when filing with the relevant permitting authority. The Agency received notice of other filings when a state permitting authority sent new draft permits or modifications to the EPA for review. The EPA also asked some states for NOPPs after those states asked the EPA questions about the process or initiated discussions about specific plants. Environmental groups that collected some additional information about NOPPs also shared the information with EPA prior to the publication of the proposed rule.

The EPA is currently aware of NOPPs covering 94 EGUs at 38 plants. At the time of the proposed rule, four EGUs (at two plants) requested participation in the LUEGU subcategory, an additional 12 EGUs (at four plants) requested participation in the 2020 rule VIP, and the remaining 74 EGUs (at 33 plants) requested participation in the permanent cessation of coal combustion by 2028 subcategory.

Following the 2023 direct final rule, the EPA obtained one additional NOPP stating that two EGUs (at one plant) requested participation in the permanent cessation

of coal combustion subcategory by 2028 instead of the 2020 rule VIP. The EPA notes that these counts are not a comprehensive picture of facilities' plans for two reasons. First, the EPA was unable to obtain information for all plants and states. Second, even where a facility has filed a NOPP, under the transfer provisions of 40 CFR 423.13(o)(1)(ii), it still retains flexibility to transfer between subcategories, or between a subcategory and the 2020 VIP provisions, until December 31, 2025.

For example, the EPA made industry profile updates to some of the 90 EGUs with corresponding NOPPs based on public comments and other power company data (

e.g.,

integrated resource planning reports). For further detail, the NOPPs the EPA is aware of have been placed in the docket along with a memorandum summarizing the information and providing record index numbers for locating each facility, entitled

Changes to Industry Profile for Coal-Fired Generating Units for the Steam Electric Effluent Guidelines Final Rule

(DCN SE11618).

Plant Scherer filed a permanent cessation of coal combustion by 2028 NOPP for two EGUs and a 2020 rule VIP NOPP for the remaining two EGUs; thus, the plant count for the three groupings does not equal 38.

The ability to transfer into the LUEGU subcategory ended on December 31, 2023.

C. Information from Technology Vendors and Engineering, Procurement, and Construction Firms

The EPA gathered data on the availability and effectiveness of FGD wastewater, BA handling, CRL, and surface impoundment dewatering operations and wastewater treatment technologies from technology vendors and engineering, procurement, and construction firms through presentations, conferences, meetings, and email and phone contacts. These collected data informed the development of the technology costs and pollutant removal estimates for FGD wastewater, BA transport water, CRL, and legacy wastewater.

D. Other Data Sources

The EPA gathered information on steam electric generating facilities from the DOE's Energy Information Administration (EIA) Forms EIA-860 (Annual Electric Generator Report) and EIA-923 (Power Plant Operations Report). The EPA used the 2019, 2020, and 2021 data to update the industry profile, including commissioning dates, energy sources, capacity, net generation, operating statuses, planned retirement dates, ownership, and pollution controls at the EGUs. The EPA also referenced 2022 EIA data to support the analysis of FGD halogen (bromide and iodine) loads. Finally, the EPA used a 2024 EIA study as the basis for estimating the costs of a new coal-fired steam power plant.

U.S. Energy Information Administration (2024).

Capital Cost and Performance Characteristics for Utility-Scale Electric Power Generating Technologies,

available at:

https://www.eia.gov/analysis/studies/powerplants/capitalcost/pdf/capital_cost_AEO2025.pdf

The EPA conducted literature and internet searches to gather information on FGD wastewater treatment technologies, including information on pilot studies, applications in the steam electric power generating industry, and implementation costs and timelines. The EPA also used internet searches to identify or confirm reports of planned facility plant and EGU retirements and reports of planned unit conversions to dry or closed-loop recycle ash handling systems. The EPA used this information to inform the industry profile and identify process modifications occurring in the industry.

VII. Final Regulation

A. Description of the Options

The EPA analyzed four main regulatory options at proposal, the details of which were discussed in the proposed rule.

See

88 FR 18824, 18837-18838 (Mar. 29, 2023). For the final rule, the EPA evaluated three main regulatory options, as shown in table VII-1 of this preamble. Option A corresponds to the proposed regulation with modifications, while Options B and C would require controls that would achieve greater pollutant reductions. All three options include the same technology basis for FGD wastewater (zero-discharge systems) and BA transport water (dry-handling or closed-loop systems), while incrementally increasing controls on CRL and legacy wastewater and removing certain subcategories as one moves from Option A to Option C. Each successive option from Option A to Option C would achieve a greater reduction in wastewater pollutant discharges. Each subcategorization is described further in section VII.C of this preamble.

1. FGD Wastewater

Under all three main options, the EPA would require zero discharge of FGD wastewater based on zero-discharge technologies and retain the 2020 FGD wastewater limitations and standards as an interim step toward achievement of zero-discharge requirements. Under all three options, the EPA would also eliminate the BAT and PSES subcategorizations for high-FGD-flow facilities and LUEGUs. Options A and B would also create a subcategory for EGUs that will permanently cease coal combustion no later than December 31, 2034, and instead of zero discharge would require discharges from these facilities to meet the 2020 rule limitations as included in their CWA permit. This subcategory modifies the proposed early adopters subcategory and is described further in section VII.C of this preamble. Under Option C, the EPA would not finalize a subcategory for those EGUs planning to cease coal combustion by December 31, 2034. Note that, for all three options, the EPA would retain the 2020 subcategory for EGUs permanently ceasing coal combustion by 2028.

2. BA Transport Water

Under all three main options, the EPA would require zero discharge of BA transport water based on dry-handling or closed-loop systems and retain the 2020 BA transport water limitations and standards as an interim step toward achievement of zero-discharge requirements. For all three options, the EPA would also eliminate the BAT and PSES subcategorizations for LUEGUs. Options A and B would also create a subcategory for EGUs that will permanently cease coal combustion no later than December 31, 2034, and instead would require discharges from these facilities to meet the 2020 rule limitations as permitted. Under Option C, the EPA would not finalize this subcategory. Note that, for all three options, the EPA would retain the 2020 subcategory for EGUs permanently ceasing coal combustion by 2028.

3. CRL

Under Option A, the EPA would establish BAT limitations and PSES for mercury and arsenic based on chemical precipitation treatment. Under Options B and C, BAT limitations and PSES would be zero discharge and the EPA would establish BAT limitations for mercury and arsenic based on chemical precipitation for discharges of unmanaged CRL. Options A and B would also create a subcategory for EGUs that would permanently cease coal combustion no later than December 31, 2034; CRL discharges from EGUs in this subcategory would be subject to case-by-case BPJ decision-making until permanent cessation of coal combustion, after which they would be subject to mercury and arsenic limitations based on chemical precipitation. Under Option C, the EPA would not finalize this subcategory.

4. Legacy Wastewater

Under Option A, the EPA would not specify a nationwide technology basis for BAT/PSES applicable to legacy

wastewater at this time and such limitations would be derived on a site-specific basis by the permitting authorities, using their BPJ. Under Options B and C, the EPA would establish a subcategory for discharges of legacy wastewater discharged from surface impoundments commencing closure after July 8, 2024. For such discharges, the EPA would establish mercury and arsenic limitations based on chemical precipitation.

ER09MY24.039

ER09MY24.040

B. Rationale for the Final Rule

After considering the technologies described in this preamble and the TDD, as well as public comments, and in light of the factors specified in CWA sections 301(b)(2)(A) and 304(b)(2)(B) (

see

section IV of this preamble), the EPA is establishing BAT effluent limitations based on the technologies described in Option B.

While the EPA is establishing new BAT effluent limitations for FGD wastewater and BA transport water based on more stringent technologies than the 2020 rule, the EPA is retaining the 2020 rule BAT effluent limitations for discharges before the applicability dates for new limitations on these wastewaters.

The EPA is including severability language in the final rule that makes clear that if any provisions of the final rule are reviewed and vacated by a court, it is the EPA's intent that as many portions of the rule remain in effect as possible.

1. FGD Wastewater

The EPA is identifying zero-discharge systems as the technology basis for establishing BAT limitations to control pollutants discharged in FGD wastewater.

More specifically, the technology basis for BAT is membrane filtration systems, SDEs, and thermal evaporation systems, alone or in any combination, including any necessary pretreatment (

e.g.,

chemical precipitation) or post-treatment (

e.g.,

crystallization).

Furthermore, where a permeate or distillate is generated from the final stage of treatment, the BAT technology basis uses a process wherein this water would then be recycled back into the plant as either FGD makeup water or EGU makeup water.

After considering the factors specified in CWA section 304(b)(2)(B), the record shows that this suite of technologies is technologically available, is economically achievable, and has acceptable non-water quality environmental impacts. It is the EPA's intent that these three technologies considered together constitute BAT for FGD wastewater, and the EPA concludes that this BAT basis meets the requisite statutory factors. The EPA also finds, however, that each of the individual technologies within this suite supports a BAT determination on its own.

As described in section VII.B.5 of this preamble, the EPA is also finalizing a definitional change to certain wastewaters, including FGD wastewater, that excludes discharges necessary as a result of high intensity, infrequent storm events, as well as wastewater removed from FGD wastewater treatment equipment within the first 120 days of decommissioning the equipment.

While three main technologies are listed here and are used to evaluate costs and non-water quality environmental impacts, the list is not meant to exclude use of other known zero-discharge treatment processes, including FA fixation, direct encapsulation, or evaporation ponds.

The 2020 rule finalized a carve out from the definition of FGD wastewater applicable to “treated FGD wastewater permeate or distillate used as boiler makeup water.”

In the following subsections, the EPA discusses its rationale for selecting three zero-discharge systems as BAT for the control of FGD wastewater, as well as how each individual zero-discharge technology supports the BAT technology basis on its own. The EPA also explains why it is not selecting a less stringent technology as BAT. For further discussion of the changes (now being finalized by the EPA) to the definition of FGD wastewater related to infrequent storm events and decommissioning wastewater, see section VII.B.5 of this preamble. For further discussion of the EPA's retention of the 2020 rule limitations as interim limitations, see section VII.C.7 of this preamble.

a. The EPA selects zero-discharge systems as BAT for FGD wastewater.

Technological availability of zero-discharge systems.

At proposal, the EPA identified membrane filtration as a potential BAT on which to base zero-discharge limitations for FGD wastewater, but also solicited comment on several other zero-discharge technologies, such as thermal evaporation systems and SDEs, that the EPA thought might serve alone or in any combination as the BAT basis for a final rule.

The EPA received many comments that were specific to individual zero-discharge technologies, including both comments supporting and opposed to a finding of technological availability for these individual technologies as part of the BAT basis. Comments supporting zero-discharge limitations pointed to the large number of operating zero-discharge plants and pilot studies as evidence that more than just the best performing plant or pilot plants are using zero-discharge systems. Comments opposing such a finding primarily focused on membrane filtration, the EPA's proposed zero-discharge technology basis under the preferred regulatory option. The two concerns raised most commonly in opposition to the finding of membrane filtration availability were, first, that the EPA did not collect sufficient additional information to alter its findings in the 2020 rule regarding this technology's availability and, second, that the pilot studies and foreign plants cited by the EPA were conducted on small FGD wastewater flows that were not representative of domestic industry operations. For both membrane filtration systems and thermal evaporation systems, commenters who opposed a finding of availability also questioned whether back-end management options were available for the associated wastes from zero-discharge systems. To the extent it received comments suggesting that waste management alternatives are not available, the EPA has addressed these comments in the subsection discussing non-water quality environmental impacts, below.

After consideration of public comments and as further discussed below, the EPA is basing its determination that zero-discharge systems are available for control of pollutants found in FGD wastewater on the numerous full-scale domestic and foreign installations of zero-discharge systems to treat FGD wastewater, the large number of successful domestic and international pilot tests of zero-discharge systems on FGD wastewater, successful use of zero-discharge systems on other steam electric wastestreams, and the use of zero-discharge systems on wastestreams in many different industries besides the steam electric power generating industry. Alternatively, the EPA is basing its determination that each of the technologies that make up the suite of zero-discharge systems forming the BAT basis, standing alone, is available on the several full-scale domestic and/or

foreign installations of each of these technologies to treat FGD wastewater and/or the successful domestic and international pilot tests of each of these technologies on FGD wastewater. The availability of each technology standing alone is also supported by the successful use of each of these technologies on other steam electric wastestreams and/or the use of each of these technologies on wastestreams in different industries besides the steam electric power generating industry. The weight of the evidence supports the Agency's conclusion that the suite of zero-discharge systems (or each of the individual technologies alone) are available in the industry to control FGD wastewater discharges, notwithstanding certain uncertainties the EPA described in the 2020 rule about one of the technologies that form the zero-discharge BAT technology basis. Agencies have inherent authority to reconsider past decisions and to revise, replace, or repeal a decision to the extent permitted by law and supported by a reasoned explanation.

FCC

Fox Television Stations, Inc.,

556 U.S. 502, 515 (2009);

Motor Vehicle Mfrs. Ass'n

State Farm Mutual Auto. Ins. Co.,

463 U.S. 29, 42 (1983). A finding that zero-discharge systems are available, or that each of the zero-discharge technologies forming the BAT basis is available, is also consistent with the technology-forcing nature of BAT as described in the legislative history and legal precedents discussing this provision (

see

section IV.B.2 of this preamble).

Full-scale domestic zero-discharge systems.

In the 2020 rule, the EPA rejected membrane filtration as a standalone BAT technology basis due in part to the lack of a single full-scale domestic installation, which is still the case today. In that rule, however, the EPA did not evaluate a technology basis that includes the three zero-discharge technologies that form this final rule's BAT basis.

First, the EPA notes that 40 coal-fired power plants in the United States currently (as of 2024) operate wet FGD systems and manage their wastewater to achieve zero discharge.

These plants achieve zero discharge using evaporation ponds, recycling of FGD wastewater, ash fixation, thermal evaporation systems (

e.g.,

falling film evaporators), or SDEs. About 19 additional plants operated zero-discharge systems for FGD wastewater since 2009 but have since retired or converted fuels such that the FGD wastewater generation, and associated zero-discharge operations, have ceased. In total, more domestic facilities operate, or have operated, zero-discharge systems than the biological treatment systems used as the 2015 and 2020 rule bases.

Not only are there more of these systems, but the systems for which the EPA has information have achieved continuous, long-term zero discharge.

One of these 40 plants, which was already achieving zero discharge of its FGD wastewater, is now installing SDE. See

https://www.woodplc.com/insights/articles/engineering-solutions-for-wastewater-treatment

(DCN SE10284).

The EPA accounted for four plants operating biological treatment systems in the 2015 rule analyses (DCN SE05832) and nine plants in the 2020 rule analyses (DCN SE08629).

With respect specifically to the BAT basis identified in this final rule, the EPA finds that there are four U.S. coal-fired power plants currently operating full-scale thermal and three U.S. coal-fired power plants currently operating full-scale SDE systems.

The full-scale domestic application of the technologies identified in the BAT basis for this final rule support the EPA's finding that the BAT technology basis is available, as that term is used in the CWA. It also supports a finding that thermal evaporation systems are technologically available on their own and that SDEs are technologically available on their own.

In the 2020 rule and 2023 proposal, the EPA has continually deferred to one company's representations that, contrary to representations from the technology vendor, its membrane filtration system is a long-term pilot system rather than a full-scale installation. This is a distinction without a difference, as the EPA can rely on both full-scale installations and pilot plants in establishing BAT limitations. Therefore, the EPA addresses this system in the section on pilot systems below (even though it could arguably be used to treat the facility's entire wastestream in the future).

Full-scale, foreign zero-discharge systems and zero-discharge pilot plants.

While the full-scale, domestic operation of zero-discharge systems is sufficient to determine availability of the BAT technology basis, the EPA has also identified a number of full-scale, foreign zero-discharge systems, as well as domestic and international pilot systems; these could additionally or separately support the EPA's conclusion that the BAT basis identified in this final rule is available.

In 2020, the EPA declined to find that full-scale, foreign installations of membrane filtration demonstrated the availability of that technology, in large part because the EPA had not visited these systems or obtained long-term performance data on them, and thus stated there were uncertainties around these applications that prevented a finding of availability. At the time of the 2020 rule, the Agency cited 12 foreign installations of membrane filtration systems on FGD wastewater.

These systems began operating as early as 2015, and all of them were designed to operate as zero-discharge systems.

Importantly, however, the EPA did not dispute the availability of thermal evaporation systems in the 2020 rule. This is consistent with the record, as even at the time of the 2015 rule, the EPA visited three thermal evaporation systems operating in Italy, obtaining relevant performance data on these systems, which it then used to establish BAT limitations for a voluntary incentive program based on such technology, as well as NSPS for FGD wastewater.

ERG. 2020.

Technologies for the Treatment of Flue Gas Desulfurization Wastewater

(DCN SE09218); ERG. 2020.

Notes from Call with DuPont

(DCN SE08618); Beijing Jingneng Power. 2017.

Beijing Jingneng Power Company, Ltd. Announcement on Unit No. 1 of the Hbei Shuoshou Jingyuan Thermal Power Co., Ltd. Passing Through the 168-hours Trial Operation.

November 13 (DCN SE08624); Broglio, R. 2019.

Vendor FGD Wastewater Treatment Details—Doosan.

July 15 (DCN SE07107); Lenntech. 2020.

Lenntech Water Treatment Solutions. Flue Gas Desulfurization Treatment

(DCN SE08622); Nanostone. 2019.

China Huadian Jiangsu Power Jurong Power Plant FGD Wastewater Zero Liquid Discharge Project was Awarded the Engineering Star Award.

June 27 (DCN SE08623).

Technologies for the Treatment of Flue Gas Desulfurization Wastewater, Coal Combustion Residual Leachate, and Pond Dewatering

(DCN SE11695).

This information was also used as the basis for the 2015 rule NSPS for FGD wastewater.

Some commenters on the 2023 proposal reiterated the EPA's 2020 rule findings and argued that EPA has not collected sufficient new information on foreign installations of membrane filtration to reverse its 2020 findings. EPA first notes that, for this final rule, it has modified its BAT basis from proposal to consist of three zero-discharge systems (each of which was described in the proposal). Since the 2015 rule, EPA has collected information not just about membrane filtration systems abroad, but also about an additional four thermal evaporation systems and six SDE systems operating on FGD wastewater outside the United States.

The EPA finds that, when combined with the site visits and performance data EPA obtained on the three Italian thermal evaporation systems as part of the 2015 rulemaking, the current record is more than sufficient to determine, based on full-scale, foreign installations, that the suite of systems forming the BAT basis in this rule is available as that term is used in the CWA.

Technologies for the Treatment of Flue Gas Desulfurization Wastewater, Coal Combustion Residual Leachate, and Pond Dewatering

(DCN SE11695).

Furthermore, even looking at membrane filtration itself, as the EPA noted in the 2023 proposal, the foreign membrane filtration systems discussed in the 2020 rule have continued to successfully treat FGD wastewater and achieve zero discharge since 2020. Despite commenters arguing that this additional information is not important because it does not change the overall number of plants known to operate the technology or the number of influent and effluent concentration data points collected from these plants, the EPA finds that continued operations constitute significant new information. This is because the longer each zero-discharge system operates, the less probability that some yet unknown operational difficulty will appear and the more certainty the EPA has that the technology is capable of achieving long-term zero-discharge treatment of this wastewater. Thus, foreign installations of the suite of technologies forming the BAT basis support the EPA's conclusion that the BAT basis is available as that term is used in the CWA. At the same time, use of thermal evaporation systems abroad supports a finding that thermal evaporation systems are technologically available on their own, use of SDEs abroad supports a finding that SDEs are technologically available on their own, and use of membrane filtration systems abroad support a finding that membrane filtration is technologically available on its own.

With respect to pilot studies, the 2020 rule found that pilot projects on membrane filtration did not provide sufficient long-term concentration data on which to base a finding of availability or calculate limitations.

Commenters on the 2023 proposal reiterated the EPA's 2020 rule findings and suggested that the EPA had not supplemented the record with enough pilot studies to reach a new conclusion on availability. The EPA disagrees. The Agency first notes that the BAT technology basis in this final rule has been updated to consist of three zero-discharge systems. When the 13 thermal pilot projects and one SDE pilot project on FGD wastewater in the record are combined with the 30 membrane filtration pilots on FGD wastewater discussed in the proposed rule (including eight pilot studies conducted since the 2020 rule), the EPA has significant evidence of the ability of this suite of systems to handle a variety of operating conditions.

These domestic and foreign pilots have demonstrated success removing pollutants from FGD wastewater under a number of pretreatment settings, whether performed without chemical precipitation pretreatment, with chemical precipitation pretreatment, or following biological treatment.

Furthermore, while some systems will not generate a clean permeate or distillate that needs to be handled, those that do will recycle this clean water source back into the plant to meet the final zero-discharge limitations. Thus, long-term pollutant removal information is no longer as relevant as it was in 2020 because the EPA is not calculating nonzero limitations in this final rule. While this discussion of pilot projects is used to support the availability of the BAT technology basis comprised of multiple technologies, the large number of successful pilot projects of membrane filtration and thermal evaporation systems also supports the EPA's finding that these individual technologies are available on their own.

The EPA nevertheless established limitations based on membrane filtration technology in the 2020 VIP.

One of the systems is a long-term pilot project at one facility, which is a commercial-scale system that may have sufficient capacity to treat the full FGD wastestream moving forward. Nevertheless, because the company is still making changes to the operation of the plant's FGD system, has also pilot tested a biological treatment system, and has continued to leave the possibility of biological treatment for compliance open, the EPA defers to the company's characterization of this system as a pilot, rather than a domestic, full-scale installation.

In one case, a utility conducted a successful membrane pilot even when there were significant failures in the performance of upstream pretreatment systems leading to excessive TSS passthrough to the membrane system.

In comments, one recurring criticism of the 2023 proposal was that conclusions about membrane filtration system availability should not be drawn from foreign installations and pilot plants due to their small FGD wastewater flow rates. While the EPA acknowledges that foreign installations and pilot plants may have had smaller FGD wastewater flow rates than some of the plants the Agency expects would use this technology to meet the final limitations in this rule, this does not weigh against the EPA considering them as evidence of the technology's availability because the record shows that membrane filtration systems can be readily modified to handle different flow rates. This same comment was raised as far back as the 2015 rule with respect to thermal evaporation systems. At that time, the EPA responded to comments on the scalability of zero-discharge thermal evaporation systems:

Additionally, even if the flow rates were smaller, the fact that the technology can treat the FGD wastewater demonstrates that the system is available, and the size of the system does not matter because the system design can be scaled and designed to accommodate different flow rates.

U.S. EPA (Environmental Protection Agency). 2015.

Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category: EPA's Response to Public Comments.

Part 6 of 10. Page 6-40.

The EPA has not received information since 2015 that suggests that technologies are no longer scalable to higher flows. With respect to membrane filtration scalability, in particular, the most common system design for operating membrane filtration technologies is to place modules of these systems in parallel and simply add more and more stacks to treat higher and higher flows. Therefore, the EPA concludes that use of zero-discharge systems in smaller flow rate pilots and full-scale foreign facilities supports the finding that the BAT technology basis is available; these uses also support the EPA's finding that each of the individual technologies forming the BAT technology basis are available on their own.

It is also possible that some plants may choose to treat only a slipstream of FGD wastewater with a similarly small flow rate to keep the system closed loop.

Application to other wastestreams.

While the record above is sufficient to determine that the BAT basis of several zero-discharge systems is available, use of the BAT basis on other wastewaters also supports the EPA's finding regarding its availability. In the 2020 rule, the EPA declined to find that membrane filtration treatment of non-FGD wastewaters was sufficient to support a finding of availability. In that rule, EPA's conclusions were based on the ways in which each non-FGD wastewater appeared different from FGD wastewater. The EPA first notes that the BAT basis includes three zero-discharge systems, not just membrane filtration. When considering the success with which this suite of zero-discharge systems has operated on non-FGD wastewater that has similar characteristics to FGD wastewater, the EPA views application of these systems to such non-FGD wastewater as supporting EPA's conclusion that the suite of zero-discharge technologies identified as BAT in this rule is in fact available.

Examining all three zero-discharge systems that constitute the basis for BAT, these systems are used in full-scale applications to other wastestreams in the steam electric power sector and other industrial sectors. The domestic steam electric power sector applies

membrane filtration and thermal evaporation systems to EGU makeup water,

cooling tower blowdown,

and ash transport water.

Other industrial sectors with full-scale applications of membrane filtration, thermal evaporation, and SDE systems include the textiles,

chemical manufacturing,

mining,

agriculture,

oil and gas extraction,

food and beverage,

landfills,

and automotive industries.

EPRI (Electric Power Research Institute). 2015.

State of Knowledge: Power Plant Wastewater Treatment—Membrane Technologies.

August. 3002002143.

See, e.g.,

Drake, M., Wise, S., Charan, N., Venkatadri, R. 2012. ZLD Treatment of Cooling Tower Blowdown with Membranes.

WaterWorld.

December 1. Available online at:

https://www.watertechonline.com/process-water/article/16211541/zld-treatment-of-cooling-tower-blowdown-with-membranes

(DCN SE09089); ERG. 2019.

Final Notes from Meeting with New Logic Research.

July 22. (DCN SE07231) ERG. 2019.

Final Aquatech Meeting Notes.

July 26 (DCN SE07389).

See, e.g.,

https://www.ge.com/in/sites/www.ge.com.in/files/GE_solves_ash%20pond_capacity_issue.pdf

(DCN SE09090).

ERG. 2020.

Final Notes from Call with DuPont

(DCN SE08618).

ERG. 2020.

Final Notes from Call with DuPont

(DCN SE08618); U.S. EPA (Environmental Protection Agency). 2022.

Notes from Vendor Call with Vacom on October 27, 2021.

November 14 (DCN SE10367).

ERG. 2019.

Final Notes from Meeting with Pall Water.

March 5. EPA-HQ-OW-2009-0819-7613; Wolkersdorfer, C., et al. 2015.

Intelligent mine water treatment—recent international developments.

July 21 (DCN SE08581); U.S. EPA (Environmental Protection Agency). 2014.

Office of Superfund and Remediation and Technology Innovation. Reference Guide to Treatment Technologies for Mining-Influenced Water.

EPA 542-R-14-001. March (DCN SE08582); ERG. 2019.

Final Aquatech Meeting Notes.

July 26 (DCN SE07389); U.S. EPA (Environmental Protection Agency). 2022.

Notes from Vendor Call with Vacom on October 27, 2021.

November 14. (DCN SE10367).

U.S. EPA (Environmental Protection Agency). 2022.

Notes from Meeting with BKT—April 9, 2021

(DCN SE10253).

ERG. 2018.

Final Oasys Meeting Notes.

February 16 (DCN SE06915); ERG. 2019.

Final Aquatech Meeting Notes.

July 26 (DCN SE07389); ERG. 2019.

Final Veolia Meeting Notes.

August 30 (DCN SE07818); U.S. EPA (Environmental Protection Agency). 2022.

Notes from Vendor Call with Purestream on October 26, 2021.

November 14 (DCN SE10366); U.S. EPA (Environmental Protection Agency). 2022.

Notes from Vendor Call with Vacom on October 27, 2021.

November 14 (DCN SE10367).

U.S. EPA (Environmental Protection Agency). 2022.

Notes from Meeting with BKT—April 9, 2021

(DCN SE10253).

ERG. 2019.

Sanitized_Saltworks Vendor Meeting Notes—Final

(DCN SE07089); U.S. EPA (Environmental Protection Agency). 2022.

Notes from Vendor Call with Heartland on October 19, 2021.

September 26 (DCN SE10291).

U.S. EPA (Environmental Protection Agency). 2022.

Notes from Meeting with ProChem—April 9, 2021

(DCN SE10254).

Information in the record indicates that there are many similarities between the FGD and the non-FGD wastestreams where zero-discharge systems have been used. In the 2020 rule record, the EPA discussed that cooling tower blowdown at steam electric power plants and desalination in oil and gas extraction were examples of where membrane filtration has been used in full-scale applications for treating high-TDS wastewaters (high-TDS being a characteristic of FGD wastewater); 85 FR 64664-64665. The 2020 rule record also established that mining wastewaters, which are high in gypsum scaling potential (another characteristic of FGD wastewater), have been successfully treated with membrane filtration applications. Finally, the 2020 rule record established that, despite the high variability in ash transport water (a third characteristic of FGD wastewater), it has been successfully treated with membrane filtration. This information indicates that membrane filtration can operate effectively on wastestreams that contain several characteristics of FGD wastewater, including high TDS, high gypsum scaling potential, and high variability.

The similarities of other wastewaters to FGD wastewater are also relevant when considering the successful treatment by thermal evaporation systems. Thermal evaporation systems have been used to treat mining wastewaters, oil and gas wastewaters, and landfill leachate. SDE systems have been used to treat landfill leachate. Thus, based on the information, the use of zero-discharge systems on other wastestreams supports the Agency's conclusion that the BAT basis of zero-discharge systems is available for FGD wastewater discharges. These uses also support the Agency's conclusion that membrane filtration, thermal evaporation systems, or SDE systems are each available on their own.

Use of membrane filtration has since expanded into additional applications, treating wastewaters and industries beyond those where it was used at the time of the 2020 rule (

e.g.,

the food and beverage and automotive industries).

For all the foregoing reasons, the EPA finds that the BAT basis of zero-discharge systems is technologically available for the control of discharges in FGD wastewater. Steam electric power plants have used membrane filtration systems to achieve zero discharge of FGD wastewater internationally for years, and they have used traditional thermal evaporation systems

and SDEs

to achieve zero discharge of FGD wastewater domestically and internationally for years, as even recent electric utility reports acknowledge.

57 58 59 60

The widespread use across a variety of configurations of zero-discharge systems, when supplemented with the successful domestic and international pilot tests and use of such systems on other wastewaters in many industries (including the steam electric power generating industry itself and including wastewaters with characteristics that are similar to the FGD wastestream), further supports EPA's conclusion that the suite of zero-discharge technologies identified as the BAT basis in this rule is available. While this is not necessary to support its prior availability determination, the EPA further finds that any one of the technologies making up the BAT basis for FGD wastewater is available as that term is used in the Act. For membrane filtration, availability is demonstrated through full-scale use of membrane filtration abroad and in pilot projects both domestically and abroad, as well as its application to other wastestreams. For thermal evaporation, availability is demonstrated through use of full-scale thermal evaporation systems domestically and abroad and pilot projects both domestic and abroad, as well as their application to other wastestreams. For SDE systems, availability is demonstrated through use of full-scale SDE systems domestically and abroad, as well as their use in at least one known pilot project and application to a non-FGD wastestream.

The Italian thermal evaporation systems discussed first in the 2013 proposed rule have been in operation for over a decade.

Spray dry absorbers, effectively the same technology as the SDE, have been in use for decades to capture the same pollutants present in FGD wastewater.

“Proven technology (considered BAT for new sources by EPA). 3+ U.S. installations and 6+ European installations by Aquatech” (DCN SE07206).

DCN SE10234.

DCN SE09998.

EPRI (Electric Power Research Institute). 2017.

Thermal Evaporation Technologies for Treating Power Plant Wastewater: A Review of Six Technologies.

000000003002011665 (DCN SE06971).

Reliance interests in connection with 2020 BAT technologies.

Several commenters on the 2023 proposal criticized EPA for continuing to support implementation of the 2020 rule while simultaneously revising that rule with potentially more stringent limitations. These commenters stated that utilities relied upon materials announcing the Agency's decision to reconsider the 2020 rule and statements in the 2023 proposal which both confirmed that utilities should continue to implement the 2020 rule. Thus, in reliance, utilities claimed that they have continued to install compliant technologies and that such reliance should lead the EPA to a decision not to finalize more stringent BAT for these wastewaters. In the

alternative, some commenters recommended that such facilities reliance on, and compliance with, the 2020 rule should lead the EPA to build in additional flexibility for any more stringent BAT. Suggested flexibilities focused on subcategorization or longer timeframes for cost recovery before installation of more stringent technologies.

The EPA agrees that such reliance interests should be considered.

The EPA disagrees, however, with commenters who suggested these interests mean the Agency must retain only the 2020 limitations in all cases. First, no NPDES permittee has certainty of its limitations beyond its five-year NPDES permit term, as reissued permits must incorporate any newly promulgated technology-based limitations as well as potentially more stringent limitations necessary to achieve water quality standards.

See

40 CFR 122.44(a) and (d). The statute is designed for both technology-based and water quality-based effluent limitations to be revisited in each permit and, when necessary, revised consistent with these provisions and in light of the goal of ultimately eliminating pollutant discharges from point sources into WOTUS.

See

CWA section 101, 33 U.S.C. 1251.

The Supreme Court has held that, while an agency may change policies based upon a reasoned explanation, where a prior policy has engendered serious reliance interests, those interests must be taken into account.

FCC

Fox Television Stations, Inc.,

556 U.S. at 515 (citation omitted).

Moreover, the EPA has included enough time for facilities to build in any reasonable reliance interest. As discussed in section VII.E of this preamble, the Agency is finalizing a “no later than” date for the new FGD wastewater BAT limitations of December 31, 2029. Having a “no later than” date approximately five-and-a-half years following promulgation allows facilities to rely on permitted limitations for the remainder of any permit existing as of the effective date of this final rule.

Third, the EPA has considered the arguments that facilities have unrecoverable costs, particularly for biological treatment systems that the final rule may render obsolete, by evaluating both the existing costs of the 2020 rule and the costs of this final rule together in the IPM analysis. As discussed in sections VII.F and VIII.C, the EPA uses IPM to analyze electric sector impacts.

IPM shows small impacts across the industry and leads the EPA to the conclusion that even the cumulative cost of the two technologies is economically achievable (this concept is explained in section VII.F of this preamble). Where more stringent technologies are available, are economically achievable, and have acceptable non-water quality environmental impacts as zero-discharge systems do here, the fact that facilities may have to spend more to supplement or replace existing treatment systems, even relatively new ones, is not a sufficient reason on its own to reject selection of the technology.

While this modeling illustrates how the sector may comply with the rule, the EPA notes that the rule does not require any facilities to close.

Lastly, to the extent that the facilities claiming to be most impacted by having to add treatment are those that will be permanently ceasing coal combustion by 2034, the EPA has created a new subcategory for these facilities that would allow them to continue to meet only the 2020 BAT limitations and thereby avoid recovering the costs of two treatment systems (

i.e.,

biological treatment and a zero-discharge system), each one designed to meet the requirements of the 2020 or 2024 rules, over the facility's short remaining useful life. EPA anticipates that approximately nine EGUs may be able to avail themselves of this subcategory with respect to FGD wastewater.

Additional EGUs are projected to participate in this subcategory for BA transport water and CRL as discussed in the sections below.

Economic achievability of zero-discharge systems.

The EPA finds that the costs of zero-discharge systems for control of FGD wastewater are economically achievable. The 2020 rule cited the increased cost of membrane filtration as compared to the selected technology basis as a reason for rejecting membrane filtration

but did not find that the costs of membrane filtration were not economically achievable at that time. The EPA also declined in the 2020 rule to establish BAT based on thermal evaporation systems, which the Agency stated were 2.4 times the costs of the 2020 BAT technology basis of chemical precipitation plus low-residence-time-reduction biological treatment and 1.04 times the cost of membrane filtration. The Agency said that these costs were unreasonably high, and it cited this finding, together with the costs that the industry was facing due to other EPA rules, to reject thermal technologies as not economically achievable.

While the relative costs of technologies differ from plant to plant, the 2020 rule acknowledged, and additional information obtained during the 2022 information collection confirms, that, in some cases, technologies such as membrane filtration may be less costly than biological treatment at individual plants even where, on average, they would be more expensive to the industry as a whole.

After updating the cost analysis and IPM modeling for the final rule, the EPA finds that the costs of the BAT basis of zero-discharge systems for FGD wastewater are economically achievable for the industry, as discussed further below and in sections VII.F and VIII. Furthermore, the EPA notes that the estimates in IPM are conservative with respect to FGD wastewater. To the extent that costs would have been lower at six plants had the EPA used certain CBI costs for thermal evaporation systems in its primary cost analysis, the economic impacts modeled in IPM at these plants are overestimated.

To the extent that cost estimates for individual technologies are roughly of the same magnitude as indicated in the primary cost analysis, these costs would not be expected to alter the findings on economic achievability, even if the Agency were to rely on any one of the zero-discharge technologies as a standalone BAT basis.

Non-water quality environmental impacts of zero-discharge systems.

The EPA finds that the non-water quality environmental impacts of zero-discharge systems are acceptable.

The EPA proposed to find that the non-water quality environmental impacts of membrane filtration are acceptable. Specifically, the EPA proposed to reverse findings from the 2020 rule regarding FA use to encapsulate the brine generated by membrane filtration. The EPA also solicited comment on the non-water quality environmental impacts of other zero-discharge systems that might be used as a BAT technology basis.

Some commenters raised concerns relating to the non-water quality environmental impacts of zero-discharge systems. Specifically, commenters expressed concerns that the EPA had incorrectly evaluated FA availability because it did not use the most recent EIA data (which demonstrates that there is not enough FA available for brine encapsulation), did not use proper brine generation and encapsulation blending rates, and did not account for the costs of lost FA sales. Other commenters questioned the technological availability of one method of handling the solid waste generated from zero-discharge technologies—brine encapsulation—claiming that it has not been demonstrated to adequately retain pollutants in a landfill and, furthermore, that a particular form of brine encapsulation (paste encapsulation) has not been demonstrated and may not satisfy current disposal requirements. Finally, commenters claimed that pollutants in encapsulated brines and unencapsulated salt crystals could be

remobilized in a landfill setting or could damage the landfill-liner system. While some comments argued these disposal issues spoke to availability of the zero-discharge technology, the EPA views this rather as a non-water quality environmental impact (solid waste disposal issue) that it must consider. After considering these comments and the record, the EPA finds that the non-water quality environmental impacts of zero-discharge systems are acceptable.

With respect to comments on FA availability, the EPA agrees with commenters that it should evaluate the most recent EIA data, brine generation data, and data on encapsulation blends. Therefore, the EPA has updated its analysis to consider the most recent information in

2024 Steam Electric Supplemental Final Rule: Fly Ash Analysis

(DCN SE11692). As noted in that document, FA sold for beneficial use fluctuates from year-to-year, but over the last five years the amount sold would still be less than the amount available for sale even after assuming that every plant uses FA to encapsulate brine from an FGD wastewater and/or CRL treatment system. Thus, the EPA does not expect that under worst-case scenarios the use of FA to encapsulate brine would hamper the fly ash sales market, let alone constitute an unacceptable non-water quality environmental impact.

Furthermore, the assumption that all facilities use membrane filtration and generate a brine for encapsulation represents a conservative estimate on FA usage. The EPA has updated its cost estimates as discussed in section VIII and section 5 of the TDD. These revised cost estimates consist of least-cost analysis across the various zero-discharge systems. Part of this update also included adjustments to better account for the amount of FA available for encapsulation, brine generation rates, and brine encapsulation blends, all to respond to commenters and improve the accuracy of the Agency's analysis. The EPA finds that the now higher costs of membrane filtration lead thermal and SDE systems to be a less costly option at many plants. This finding is consistent with cost information received from some companies showing that membrane filtration would not be the least-cost technology. As a result of this analysis selecting non-membrane systems at a number of plants, the assumptions of FA usage presented above can be seen as a likely worst-case scenario. To the extent that FA sales would be even less hampered than the scenario already found to be acceptable above, it would only further support the Agency's conclusion that FA use in brine encapsulation has acceptable non-water quality environmental impacts. For a further discussion of EPA's revised cost estimates, see section 5 of the TDD.

With respect to comments about potential remobilization of pollutants from brine encapsulation and demonstration of paste encapsulation; as far back as the 2015 rule, the EPA pointed to multiple waste-handling alternatives that were being employed by facilities with zero-discharge systems. Some facilities at that time used the brine generated by thermal systems to condition ash for disposal. In the 2020 rule record, the EPA discussed facilities that directly engage in FA fixation of the FGD wastewater for this purpose, skipping the volume reduction step that a membrane or thermal system would offer (see section 4.1.5 of the 2020 TDD, DCN SE08650). When commenters express concern that contaminants from encapsulated brines could be remobilized, these comments assume less processing than EPA contemplates. The commenters reference situations where FGD wastewater or brine are merely used to condition ash without employing the further pozzolanic reactions that the EPA expects to occur in the full encapsulation process and that EPA included in its cost estimates of zero discharge. Encapsulation studies demonstrate that concentrations of leachate pass leachate toxicity tests and are of lower concentration than raw FGD wastewater. Encapsulation would also result in far less remobilization than exiting ash conditioning practices. Furthermore, to the extent that the EPA considered and discussed paste encapsulation, it was as a potentially cost-saving alternative to these conditioning and encapsulation techniques that are already well-demonstrated. Thus, to the extent that it is a less costly solid waste management alternative, it only provides the promise of cost savings compared to the EPA's estimates, but the EPA does not rely on this particular form of brine encapsulation in determining that solid waste disposal issues as a whole have acceptable non-water quality environmental impacts.

Even if brine encapsulation had not been adequately demonstrated as a solid waste handling practice, other solid waste handling alternatives are available. For example, facilities in the 2015 and 2020 rule records took the brine generated from a thermal system all the way down to a salt crystal using a crystallizer (DCN SE11695). The EPA evaluated these costs in the

FGD Wastewater, CRL, and Legacy Wastewater Zero Discharge Treatment Technologies Costs, Loadings, and Non-Water Quality Environmental Impacts

file (DCN SE11709) as an alternative and found it would increase annualized costs by three percent. These slightly higher overall costs would still be economically achievable.

Facilities could also consider deep-well injection of their brine. The EPA found that these costs on a nationwide basis would be three times the costs of encapsulation, and so are unlikely to be pursued by most facilities, though this too would constitute an alternative disposal practice available for the management of brine.

With respect to comments about remobilization of pollutants, the EPA agrees with commenters that pollutants in a landfill can be remobilized through percolation of rainwater through the disposed solid wastes. These solid wastes would include not only any encapsulated brines but also certain solids and salt crystals that would be disposed of following use of some thermal and SDE alternatives where no brine is generated. Here, absent the pozzolanic reactions from either ash conditioning or encapsulation, remobilization of pollution is more possible as rainfall percolates through these disposed solids. Nevertheless, proper landfill management is designed to reduce infiltration of water through a landfill and to capture leachate that makes it to the liner at the bottom of a landfill. The EPA received no comments that the facilities already generating these solids and salts have failed to properly operate their landfills such that contaminants were remobilized into the environment. Even where remobilization can reduce the overall effectiveness of the pollution treatment systems, as discussed in section VII.B.3 of this preamble, the EPA is also finalizing zero-discharge limitations for CRL during the life of the plant, unless they are discharges of unmanaged CRL.

This is designed to further ensure that these pollutants are kept in the landfill to the maximum extent possible rather than remobilized and released into the environment.

Note that the EPA is finalizing zero-discharge limitations for CRL, except as specified in the subcategories discussed in sections VII.C.4 and C.5. Where lined WMUs collect and treat CRL to zero-discharge standards during a facility's operation, permeate and distillate can be used to condition CCR for disposal in these WMUs.

Many of the facilities presented in the record as having zero-discharge systems have also successfully disposed of conditioned ash or FGD solids in landfills for years. The record supports that a properly designed, installed, and maintained landfill can operate as intended. As the EPA learned during implementation of the CCR rule, many

historical CCR landfills may suffer from the lack of an adequate liner system. However, the Agency has no evidence that, where liners are properly designed, installed, and maintained, they are incompatible with the additional pollutants in FGD wastewater that zero-discharge systems would capture.

In contrast, FGD gypsum is already removed from FGD wastewater before discharge and is known to loosen clay soils which sometimes form the base of older landfills designed without composite liners.

Finally, the EPA finds that, even to the extent that there are any negative non-water quality environmental impacts, the positive non-water quality environmental impacts outweigh the negative ones. In particular, the EPA estimates that there are significant decreases in air pollution and water withdrawals

as a result of this rule. While the rule is not being promulgated to reduce these impacts, these resulting non-water quality environmental impacts further support the Agency's conclusion that zero-discharge systems for FGD wastewater are BAT.

Reduced water withdrawals could also lead to reduced impingement and entrainment.

b. The EPA rejects less stringent technologies than zero-discharge systems as BAT for FGD wastewater.

Except for the new permanent cessation of coal combustion by 2034 subcategory discussed in section VII.C.4 of this preamble, and for discharges before the applicability dates of the new zero discharge-requirements in this final rule, the EPA is not selecting chemical precipitation followed by a low hydraulic residence time biological treatment including ultrafiltration, as the BAT technology basis. BAT is the “gold standard” for controlling water pollution from existing sources, and the Supreme Court has explained that BAT must achieve “reasonable further progress” toward the CWA's goal of eliminating pollution.

See Southwestern Elec. Power Co.

EPA,

920 F.3d at 1003, 1006 (citing

Nat'l Crushed Stone

EPA,

449 U.S. 64, 75 (1980)). The record shows that the 2020 rule industrywide BAT technology basis for FGD wastewater removes fewer pollutants than the zero-discharge BAT technology basis identified in this final rule that has been found to be technologically available, be economically achievable and have acceptable non-water quality environmental impacts.

Similarly, except for the permanent cessation of coal combustion by 2028 subcategory discussed in section VII.C.3 of this preamble, the EPA is not identifying the less stringent (and previously rejected in the 2015 and 2020 rules) technologies of surface impoundments or chemical precipitation, as these technologies too will remove fewer pollutants than the BAT technology basis in this rule.

In contrast, nothing in the record or public comments indicates that chemical precipitation plus low hydraulic residence time biological reduction has ceased to be available, be economically achievable, and have acceptable non-water quality environmental impacts for discharges before the applicability dates of the new, more stringent limitations of this rule.

2. BA Transport Water

The EPA is identifying the zero-discharge systems of dry-handling or closed-loop systems as the technology basis for establishing BAT limitations to control pollutants discharged in BA transport water.

Specifically, dry-handling systems include both waterless air-cooled conveyor systems and pneumatic systems, as well as under-boiler mechanical drag systems (

e.g.,

submerged chain conveyors) and submerged grind conveyors (

e.g.,

compact submerged conveyors), which use quench water to cool the ash but immediately remove the ash without generating BA transport water. Closed-loop systems consist of remote mechanical drag systems that actively sluice the ash (

i.e.,

transport the ash with water) and are paired with any necessary storage tanks, chemic

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