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

Federal RegisterMar 29, 2023

Ask Donna

What actually matters in this document.

Text

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 423

[EPA-HQ-OW-2009-0819; FRL-8794-01-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:

Proposed rule; notification of public hearing.

SUMMARY:

The Environmental Protection Agency (EPA or the Agency) is proposing a 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 combustion residual leachate (CRL) at existing sources. EPA is also soliciting comment on ELGs for legacy wastewater. This proposal is estimated to cost $200 million dollars annually in social costs and reduce pollutant discharges by approximately 584 million pounds per year.

DATES:

Comments:

Comments on this proposal must be received on or before May 30, 2023. Comments intended for the associated direct final rule published elsewhere in this issue of the

Federal Register

Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category—Initial Notification Date Extension,

must be received on or before April 28, 2023.

Public hearing:

EPA will conduct two online public hearings about this proposed rule on April 20, 2023, and April 25, 2023. After a brief presentation by EPA personnel, the Agency will accept oral comments that will be limited to three (3) minutes per commenter. The hearing will be recorded and transcribed, and EPA will consider all the oral comments provided, along with the written public comments submitted via the docket for this rulemaking. To register for the hearing, please visit EPA's website at

www.epa.gov/eg/steam-electric-power-generating-effluent-guidelines-2023-proposed-rule.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-HQ-OW-2009-0819 at

www.regulations.gov.

Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from

www.regulations.gov.

EPA may publish any comment received to its public docket. Do not electronically submit any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (

e.g.,

audio, video) must be accompanied by a written comment. The written comment is considered the official comment and should include all points you wish to make. EPA will generally not consider comments or comment contents located outside of the primary submission (

i.e.,

on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI and multimedia submissions, and general guidance on making effective comments, please visit

www.epa.gov/dockets/commenting-epa-dockets.

All documents in the docket are listed on the

www.regulations.gov

website. Although listed in the index, some information is not publicly available, such as 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. Electronically available docket materials are available through

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.

EPA uses multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, EPA defines terms and acronyms used in Appendix A of this preamble.

Supporting Documentation.

The proposed rule is supported by a number of documents, including:

• Technical Development Document for Proposed Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (TDD), Document No. 821R23005. This report summarizes the technical and engineering analyses supporting the proposed rule. The TDD presents EPA's updated analyses supporting the proposed 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, corresponding non-water quality environmental impacts associated with updated FGD and BA methodologies, and calculation of the proposed 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 EPA's data collection, description of the industry, and underlying analyses supporting the 2015 and 2020 rules.

• Supplemental Environmental Assessment for Proposed Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (EA), Document No. 821R23004. This report summarizes the potential environmental and human health impacts estimated to result from implementation of the proposed revisions to the 2015 and 2020 rules.

• Benefit and Cost Analysis for Proposed Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (BCA Report), Document No. 821R23003. This report summarizes the societal benefits and costs estimated to result from implementation of the proposed revisions to the 2015 and 2020 rules.

• Regulatory Impact Analysis for Proposed Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (RIA), Document No. 821R23002. This report presents a profile of the steam electric power generating industry, a summary of estimated costs and impacts associated with the proposed revisions to the 2015 and 2020 rules, and an assessment of the potential impacts on employment and small businesses.

• Environmental Justice Analysis for Proposed Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating

Point Source Category (EJA), Document No. 821R23001. This report presents a profile of the communities and populations potentially impacted by this proposal, analysis of the distribution of impacts in the baseline and proposed changes, and a summary of inputs from potentially impacted communities that EPA met with prior to the proposal.

• Docket Index for the Proposed Supplemental Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category. This document provides a list of the additional memoranda, references, and other information EPA relied on for the proposed revisions to the ELGs.

Organization of this Document.

The information in this preamble is organized as follows:

I. Executive Summary

A. Purpose of Rule

B. Summary of Proposed Rule

II. Public Participation

III. General Information

A. Does this action apply to me?

B. What action is 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

1. Best Practicable Control Technology Currently Available

2. Best Available Technology Economically Achievable

3. New Source Performance Standards

4. Pretreatment Standards for Existing Sources

5. Pretreatment Standards for New Sources

6. Best Professional Judgment

C. 2015 Steam Electric Power Generation Point Source Category Rule

1. Final Rule Requirements

2. Vacatur of Limitations Applicable to CRL and Legacy Wastewater

D. 2020 Steam Electric Reconsideration Rule and Recent Developments

1. Final Rule Requirements

2. Fourth Circuit Court of Appeals Litigation

3. Executive Order 13990

4. Announcement of Supplemental Rule and Preliminary Effluent Guidelines Plan 15

E. Other Ongoing Rules Impacting the Steam Electric Sector

1. Coal Combustion Residuals Disposal Rule

2. Air Pollution Rules and Implementation

V. Steam Electric Power Generating Industry Description

A. General Description of Industry

B. Greenhouse Gas Reduction Targets, the Inflation Reduction Act, and Potential Impacts on Current Market Conditions

C. Control and Treatment Technologies

1. FGD Wastewater

2. BA Transport Water

3. CRL

4. Legacy Wastewater

VI. Data Collection Since the 2020 Rule

A. Information From the Electric Utility Industry

1. Data Requests and Responses

2. Meetings With Individual Utilities

3. Voluntary CRL Sampling

4. Electric Power Research Institute Voluntary Submission

5. Meetings With Trade Associations

B. Notices of Planned Participation

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

D. Other Data Sources

VII. Proposed Regulation

A. Description of the Options

1. FGD Wastewater

2. BA Transport Water

3. CRL

4. Legacy Wastewater

B. Rationale for the Proposed Rule

1. FGD Wastewater

2. BA Transport Water

3. Combustion Residual Leachate (CRL)

4. Legacy Wastewater

5. Clarification on the Interpretation of 40 CFR 423.10 (Applicability) With Respect to Inactive/Retired Power Plants and Solicitation of Comments on Potential Clarifying Changes to Regulatory Text

C. Proposed Changes to Subcategories

1. Plants With High FGD Flows

2. Low Utilization EGUs (LUEGUs)

3. EGUs Permanently Ceasing Coal Combustion by 2028

4. Subcategory for Early Adopters Retiring by 2032

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 Low-Income and Minority Populations

VIII. Costs, Economic Achievability, and Other Economic Impacts

A. Plant-Specific and Industry Total Costs

B. Social Costs

C. Economic Impacts

1. Screening-Level Assessment

2. Electricity Market 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 Four Regulatory Options

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

1. Human Health Effects From Surface Water Quality Changes

2. Ecological Condition and Recreational Use Effects From Changes in Surface Water Quality Improvements

3. Changes in Air-Quality-Related Effects

4. Other Quantified and/or Monetized Benefits

C. Total Monetized Benefits

D. Additional Benefits

XIII. Environmental Justice Impacts

A. Literature Review

B. Screening Analysis and Community Outreach

C. Distribution of Risks

1. Air

2. Surface Water

3. Drinking Water

4. Cumulative Risks

D. Distribution of Benefits and Costs

E. Results of the Analysis

F. Solicitations on Environmental Justice Analysis and Community Outreach

XIV. Development of Effluent Limitations and Standards

A. Criteria Used to Select Data as the Basis for the Limitations and Standards

B. Data Selection for Each Technology Option

C. CRL

XV. Regulatory Implementation

A. Continued Implementation of Existing Limitations and Standards

1. Reaffirmation of Expectation That Requirement that FGD and BA Transport Water BAT Limitations Apply “As Soon As Possible” Requires Careful Consideration of the Soonest Date That the Discharger Can Meet the Limitations

2. Reaffirmation That CRL and Legacy Wastewater BAT Limitations Require a Site-Specific BPJ Analysis and Careful Consideration of Technologies Beyond Surface Impoundments

3. Consideration of Late Notice of Planned Participation

B. Implementation of New Limitations and Standards

1. Availability Timing of Proposed Requirements

2. Conforming Changes for Transfers in §§ 423.13(o) and 423.19(i)

3. Conforming Changes for Voluntary and Involuntary Delays in §§ 423.18(a) and 423.19(j)

4. Recommended Information to be Submitted With a Permit Application for a Potential Discharge of CRL Through Groundwater

C. Reporting and Recordkeeping Requirements

1. Summary of Proposed Changes to the Annual Progress Reports for EGUs Permanently Ceasing Coal Combustion by 2028

2. Summary of the Proposed Reporting and Recordkeeping Requirements for Early Adopters

3. Summary of Proposed Reporting and Recordkeeping Requirements for CRL Discharges Through Groundwater

4. Proposed Deletion of Reporting and Recordkeeping Requirements for LUEGUs

5. Proposed Requirement To Post Information to a Publicly Available Website

6. Additional Solicitation on Providing a More Flexible Transition to Zero Discharge

D. Site-Specific Water Quality-Based Effluent Limitations

XVI. Related Acts of Congress, E.O.s, and Agency Initiatives

A. E.O.s 12866 (Regulatory Planning and Review) and 13563 (Improving Regulation and Regulatory Review)

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. E.O. 13132: Federalism

F. E.O. 13175: Consultation and Coordination With Indian Tribal Governments

G. E.O. 13045: Protection of Children From Environmental Health Risks and Safety Risks

H. E.O. 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer and Advancement Act

J. E.O. 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

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

I. Executive Summary

A. Purpose of Rule

EPA is proposing new regulations that apply to wastewater discharges from steam electric power plants, particularly coal-fired power plants. These plants are increasingly aging and uncompetitive sources of electric power in many portions of the United States and are subject to several environmental regulations designed to control (and in some cases eliminate) air, water, and land pollution over time. One of these regulations, the Steam Electric Power Generating Effluent Limitations Guidelines—or steam electric ELGs—was promulgated in 2015 (80 FR 67838; November 3, 2015) and revised in 2020 (85 FR 64650; October 13, 2020). The 2015 and 2020 rules apply 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 (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 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 EPA revised the steam electric ELGs in 2015 and 2020, pilot testing and full-scale use of various, more stringent compliance technologies have continued to expand. This proposal, if finalized, would revise requirements for discharges associated with the two wastestreams addressed in the 2020 rule: BA transport water and FGD wastewater at existing sources. The proposal would also address the 2015 rule CRL requirements that were vacated. Finally, while EPA is proposing technology-based limitations determined by permitting authorities on a site-specific basis using their best professional judgment (BPJ), an option discussed by the Court in

Southwestern Electric Power Co.

EPA.

B. Summary of Proposed Rule

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

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

• Numeric (non-zero) discharge limitations for mercury and arsenic in CRL.

The proposed rule would eliminate the separate, less stringent BAT requirements for two subcategories: high flow facilities and low utilization electric generating units (LUEGUs). The proposed rule does not seek to change the existing subcategories for oil-fired EGUs and small generating units (50 MW or less) established in the 2015 rule. The proposed rule also does not seek to change the existing subcategory for electric generating units (EGUs) permanently ceasing the combustion of coal by 2028, which was established in the 2020 rule (although the Agency does solicit comment on possible changes to this subcategory). Finally, the proposed rule would create separate requirements for a new subcategory of facilities that have already complied with either the 2015 or 2020 rule's requirements (hereafter referred to as “early adopters”) where such facilities would retire by 2032. For both the existing and new subcategory referenced immediately above, EPA proposes additional requirements for affected facilities to demonstrate permanent cessation of coal combustion or that permanent retirement will occur.

For the one known high flow facility (TVA Cumberland Fossil Plant) and the two known facilities with LUEGUs (GSP Merrimack LLC and Indiana Municipal Power Agency (IMPA) Whitewater Valley Station), the proposed rule would eliminate these two subcategories for FGD wastewater and BA transport water, subjecting those wastestreams to the otherwise applicable requirements for the rest of the industry. For early adopters retiring by 2032, the rule would retain the 2020 rule requirements for FGD wastewater and BA transport water rather than require the new, more stringent zero-discharge requirements for these wastestreams.

Where BAT limitations in this proposed rule are more stringent than previously established BPT and BAT limitations, EPA is proposing that any new limitations would not apply until a date determined by the permitting authority that is as soon as possible on or after [Final Rule Publication Date + 60 days], but no later than December 31, 2029.

For indirect discharges (

i.e.,

discharges to publicly owned treatment works (POTWs)), the proposed rule would establish pretreatment standards for existing sources that are the same as the BAT limitations.

C. Summary of Costs and Benefits

EPA estimates that the proposed rule will cost $200 million per year in social costs and result in $1,557 million per year in monetized benefits using a three percent discount rate and will cost $216 million per year in social costs and result in $1,290 million per year in monetized benefits using a seven percent discount rate.

Not all costs and benefits can be fully quantified and monetized, and in particular EPA anticipates the proposed rule would also generate important unquantified benefits (

e.g.,

improved habitat conditions for plants, invertebrates, fish, amphibians, and the wildlife that prey on aquatic organisms). Furthermore, while some health benefits and willingness to pay for water quality

improvements have been quantified and monetized, those estimates may not fully capture all important water quality-related benefits.

As discussed in Section XII of this preamble, not all benefits could be fully quantified and monetized at this time.

Table I-1 of this preamble summarizes the monetized benefits and social costs for the four regulatory options EPA analyzed at a three percent discount rate. 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 proposed rule. 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 impacts of relevant final rules affecting the power sector. Although the baseline does not reflect anticipated impacts on the industry because of the recently passed Inflation Reduction Act (IRA), EPA solicits comment on means by which the Agency could model the impacts of the IRA for the final rule. Because the primary effect of the IRA in the context of this rule would be to increase the number of facilities that permanently cease coal combustion in the baseline, EPA expects that it would proportionally reduce the benefits and costs estimated in this proposal.

EPA understands that these modeled results are uncertain and that the actual costs for individual plants could be higher or lower than estimated. The current estimate reflects the best data and analysis currently available. For additional information on costs and benefits, see Sections VIII and XII of this preamble, respectively.

Furthermore, because the cessation of coal combustion would occur in the baseline, EPA expects that the rule would continue to be economically achievable even after accounting for the IRA.

Table I-1—Total Monetized Annualized Benefits and Costs of Four Regulatory Options

[Millions of 2021$, three percent discount rate]

Regulatory option

Total social costs

Total

monetized

benefits

Total

monetized net

benefits

Option 1

$88.4

$696

$608

Option 2

167.0

1,336

1,169

Option 3 (Preferred)

200.3

1,557

1,357

Option 4

207.2

1,670

1,463

EPA estimated the air-related benefits for Option 3 using the Integrated Planning Model (IPM). EPA did not analyze Options 1, 2, and 4 using IPM. Instead, EPA extrapolated estimates for Options 1, 2, and 4 air-related benefits from the estimate for Option 3 in proportion to total social costs.

Includes benefits of changes in CO

air emissions monetized using the Interagency Working Group on the Social Cost of Greenhouse Gases (IWG) SC-CO

at 3% (average). See Section XII.B.3 of this preamble for benefits monetized using other SC-CO

values.

II. Public Participation

Submit your comments, identified by Docket ID No. EPA-HQ-OW-2009-0819, at

www.regulations.gov

(our preferred method), or the other methods identified in the

ADDRESSES

section. Once submitted, comments cannot be edited or removed from the docket. EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be CBI or other information whose disclosure is restricted by statute. Multimedia submissions (

e.g.,

audio, video) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. EPA will generally not consider comments or comment contents located outside of the primary submission (

i.e.,

on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit

www.epa.gov/dockets/commenting-epa-dockets.

III. General Information

A. Does this action apply to me?

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

see also Clean Water Action.

EPA,

No. 18-60079 (5th Cir.). On October 29, 2018, the District of Arizona case was dismissed upon 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. Final Rule Requirements

On August 31, 2020, EPA promulgated the

Steam Electric Reconsideration Rule

(hereinafter the “2020 rule”). 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 system 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. 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 compliance date(s) 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.

3. Executive Order 13990

On January 20, 2021, President Biden issued Executive Order (E.O.) 13990:

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

(86 FR 7037). E.O. 13990 directed Federal agencies to immediately review and, if necessary, 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. A list of regulations to be reviewed, including the 2020 rule, was released in conjunction with this E.O.

4. Announcement of Supplemental Rule and Preliminary Effluent Guidelines Plan 15

On July 26, 2021, EPA announced the new rulemaking to strengthen certain wastewater pollution discharge limitations for coal-fired power plants that use steam to generate electricity. EPA later clarified that, as part of its new rulemaking, it would be reconsidering all aspects of the 2020 rule.

EPA undertook an evidence-based, science-based review of the 2020 Steam Electric Reconsideration Rule under E.O. 13990, finding that there are opportunities to strengthen certain wastewater pollution discharge limitations. For example, 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, EPA also confirmed that until a new rule is promulgated, the 2015 and 2020 regulations will continue to be implemented and enforced to achieve needed pollutant reductions.

On April 8, 2022, the U.S. Court of Appeals for the Fourth Circuit granted EPA's motion for a long-term abeyance of the litigation challenging the 2020 rule, pending this rulemaking.

In September 2021, EPA issued

Preliminary Effluent Guidelines Program Plan 15

This document discussed the annual review of effluent limitations guidelines and pretreatment standards, rulemakings for new and existing industrial point source categories, and any new or existing sources receiving further analyses. Here, EPA not only discussed the wastestreams affected by the 2020 rule (FGD wastewater and BA transport water), but also the wastestreams from the 2015 rule which had limitations vacated and remanded to the Agency (

i.e.,

CRL and legacy wastewater). This was the first time EPA had publicly presented information that the supplemental rulemaking could cover these wastestreams as well. 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 Rules Impacting the Steam Electric Sector

1. Coal Combustion Residuals Disposal Rule

On April 17, 2015, EPA promulgated the Disposal of Coal Combustion Residuals from Electric Utilities final rule (2015 CCR rule). This rule finalized national regulations to provide a comprehensive set of requirements for the safe disposal of coal combustion residuals (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 between 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), 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) on July 29, 2020, and

A Holistic Approach to Closure Part B: Alternate Liner Demonstration

(CCR Part B rule) on October 15, 2020. EPA finalized five amendments to the 2015 CCR rule which continue to impact the wastewaters covered by this ELG. First, the CCR Part A rule established a new deadline of April 11, 2021, for all unlined surface impoundments, as well as those surface impoundments that failed the location restriction for placement above the uppermost aquifer, to stop receiving waste and begin closure or retrofitting. EPA established this date after evaluating the steps that owners and operators need to take for surface impoundments to stop receiving waste and begin closure, and the timeframes needed for implementation. (This would not affect the ability of plants to install new, composite-lined surface impoundments.) Second, the Part A rule established procedures for plants to obtain approval from EPA for additional time to develop alternative disposal capacity to manage their wastestreams (both coal ash and noncoal ash) before they must stop receiving waste and begin closing their coal ash 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 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 such a submission be approved, 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 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. EPA considered the interaction of these two rules during the development of this proposal. EPA's analysis builds in the final requirements of these rules in the baseline accounting for 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

2. Air Pollution Rules and Implementation

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 plants subject to Part 423. Other actions impact steam electric plants indirectly when implemented by states. In light of these

ongoing actions, EPA has worked to consider appropriate flexibilities in this proposed 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 are finalized and already impacting steam electric plant operations, EPA has accounted for these changed operations in its IPM modeling discussed in Section VIII of this preamble.

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

EPA recently completed a rulemaking to address “good neighbor” obligations for the 2008 ozone national ambient air quality standards (NAAQS) and proposed a rulemaking in 2022 with respect to the same statutory obligations for the 2015 ozone NAAQS. These actions implement the Clean Air Act's (CAA's) prohibition on emissions that significantly contribute to nonattainment or interfere with maintenance of the NAAQS in other states.

On April 30, 2021, 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). Between them, 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 oxides of nitrogen (NO

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

On February 28, 2022, the Administrator signed a proposed rule, Federal Implementation Plan Addressing Regional Ozone Transport for the 2015 Ozone National Ambient Air Quality Standards, 87 FR 20036 (April 6, 2022) (also called the Good Neighbor Plan). This proposed rule includes further ozone-season NO

pollution reduction requirements for fossil fuel-fired EGUs to address 25 states' good neighbor obligations for the 2015 ozone NAAQS. The proposed rule would establish an enhanced Group 3 market-based emissions trading program with NO

budgets for EGUs in those 25 states, beginning in 2023. Further information about this proposal is available on EPA's website.

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

b. Clean Air Act Section 111 Rule

On October 23, 2015, EPA finalized NSPSs for emissions from new, modified, and reconstructed fossil fuel-fired EGUs under CAA section 111(b). Specifically, the 2015 NSPS established separate standards for emissions of CO

from newly constructed, modified, and reconstructed fossil fuel-fired electric utility steam generating units (

i.e.,

utility EGUs and integrated gasification combined cycle units) and from newly constructed and reconstructed fossil fuel-fired stationary combustion turbines. The standards set in the 2015 NSPS reflected the degree of emission limitation achievable through application of the best system of emission reduction that EPA determined to have been adequately demonstrated for each type of unit and was codified in 40 CFR part 60, subpart TTTT. EPA is currently reviewing the 2015 NSPS—including new technologies to mitigate GHG emissions from new, modified, and reconstructed stationary combustion turbines—and will, if warranted, propose to revise the NSPSs in an upcoming rulemaking.

On August 3, 2015, under CAA section 111(d), EPA promulgated its first emission guidelines regulating emissions from existing fossil fuel-fired EGUs in the Clean Power Plan (CPP) (40 CFR part 60, subpart UUUU). The CPP was subsequently stayed by the U.S. Supreme Court. On June 19, 2019, EPA promulgated new emission guidelines, known as the Affordable Clean Energy (ACE) Rule (40 CFR part 60, subpart UUUUa), and issued a repeal of the CPP. On January 19, 2021, the U.S. Court of Appeals for the D.C. Circuit vacated the ACE Rule and remanded the rule to EPA for further consideration consistent with its decision. The Supreme Court then overturned portions of the D.C. Circuit Court's decision in

West Virginia

EPA,

No. 20-1530, in June 2022. EPA is now considering the implications of the Supreme Court's decision and is undertaking a new rulemaking to establish new emission guidelines under CAA section 111(d) to limit emissions from existing fossil fuel-fired EGUs.

c. Mercury and Air Toxics Standards Rule

After considering costs, EPA recently proposed to reaffirm the determination that it is appropriate and necessary to regulate hazardous air pollutants (HAPs), including mercury, from coal- and oil-fired steam generating power plants. These regulations are known as the Mercury and Air Toxics Standards (MATS) for power plants. The proposed MATS action would revoke a 2020 finding that it is not appropriate and necessary to regulate coal- and oil-fired power plants under CAA section 112, but which did not disturb the underlying MATS regulations. The MATS proposal would ensure that coal- and oil-fired power plants continue to control emissions of toxic air pollution, including mercury.

d. National Ambient Air Quality Standards Rules for Particulate Matter

EPA is currently reconsidering a December 7, 2020, decision to retain the primary (health-based) and secondary (welfare-based) NAAQS for particulate matter (PM).

EPA is reconsidering the December 2020 decision because available scientific evidence and technical information indicate that the current standards may not be adequate to protect public health and welfare, as required by the CAA.

See www.epa.gov/newsreleases/epa-reexamine-health-standards-harmful-soot-previous-administration-left-unchanged.

V. Steam Electric Power Generating Industry Description

A. General Description of Industry

EPA provided a general description of the steam electric power generating industry in the 2013 proposed rule, the 2015 final rule, the 2019 proposed rule, and the 2020 final rule, and has continued to collect information and update that 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 proposal, as described in the Supplemental TDD, Section 3, 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 the proposed rule use an updated baseline that incorporates these changes in the industry. The analyses then compare the effect of the proposed rule's requirements for FGD wastewater, BA transport water, CRL, and legacy wastewater to the effect on the industry (as it exists today) of the 2015 and 2020 rules' limitations for FGD wastewater,

BA transport water, CRL, and legacy wastewater.

The data presented in the general description continue to reflect some conditions existing in 2009, as the 2010 steam electric industry survey remains EPA's best available source of information for characterizing operations across the industry.

As described in the Regulatory Impact Analysis, of the 871 steam electric power plants in the country identified by EPA, only those coal-fired power plants that discharge FGD wastewater, BA transport water, CRL, and/or legacy wastewater may incur compliance costs under this proposal. EPA estimates that 69 to 93 such plants may incur compliance costs under the regulatory options in this proposal. For further information about plant retirements, fuel conversions, ash handling conversions, wastewater treatment updates, and updated information on capacity utilization, see

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

(DCN SE10241).

B. Greenhouse Gas Reduction Targets, the Inflation Reduction Act, and Potential Impacts on Current Market Conditions

While this proposal was motivated by the CWA and by the need to address water pollution, EPA acknowledges that there are also large changes happening in the industry, in part due to a series of actions targeted toward GHG reductions. First, in April 22, 2021, President Biden announced new 2030 GHG reduction targets for the United States.

As part of reaching net zero emissions by 2050, the nationally determined contribution submitted to the United Nations Framework Convention on Climate Change includes a 50-52 percent reduction from 2005 levels by 2030. These reduction targets were developed by the National Climate Task Force and support the United States' commitments under the Paris Agreement.

See www.whitehouse.gov/ceq/news-updates/2021/12/13/icymi-president-biden-signs-executive-order-catalyzing-americas-clean-energy-economy-through-federal-sustainability/.

The steam electric sector is one of the largest contributors of U.S. GHG emissions. Figure IV-1 of this preamble below is reproduced from EPA's website.

As shown in the figure, EPA estimates that 25 percent of 2020 GHG emissions in the United States came from electricity generation (largely comprised of emissions from steam electric power plants). Although this fraction continues to decline, several models looking at plausible pathways to meet the announced 2030 goal have estimated that substantial additional GHG reductions from coal combustion will be necessary.

See www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions.

Bistline, J., Abhyankar, N., Blanford, G., Clarke, L., Fakhry, R., Mcjeon, H., Reilly, J., Roney, C., Wilson, T., Yuan, M., and Zhao, A. 2022.

Actions for reducing US emissions at least 50% by 2030. Policies must help decarbonize power and transport sectors. Science.

Vol 376, Issue 6596. Pg 922-924. May 26. Available online at:

www.science.org/doi/10.1126/science.abn0661.

Total emissions in 2020 = 5,981 million metric tons of CO

equivalent. Percentages may not add up to 100 percent due to independent rounding.

Land use, land-use change, and forestry in the United States is a net sink and removes approximately 13 percent of these GHG emissions. This net sink is not shown in the above diagram. All emission estimates are from the

Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020.

Available online at:

www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks.

EP29MR23.059

The GHG reduction targets did not directly impose incentives on steam electric plants; however, on August 16, 2022, President Biden signed the IRA into law. The IRA includes many provisions that will affect the steam electric power generating industry. The IRA provides tax credits, financing programs, and other incentives that will accelerate the transition to forms of energy that produce little or no GHG emissions. An analysis conducted by the Department of Energy (DOE) shows that tax incentives included in the IRA will increase the growth of wind and

solar electricity generation while supporting the maintenance of the country's existing nuclear power fleet.

Thus, the DOE analysis suggests the IRA may reduce the number of coal burning power plants in operation.

See www.energy.gov/sites/default/files/2022-08/8.18%20InflationReductionAct_Factsheet_Final.pdf.

Based on these DOE analytic results EPA would expect reduced baseline emissions of air and water pollution, lower total incremental costs, and lower total incremental benefits of this rule. Lower costs and benefits would alter the regulatory impact analysis under E.O. 12866 and E.O. 13563. While the impacts of the IRA are not reflected in the detailed analyses included with this proposal (because the analyses were completed prior to the passage of the IRA), EPA is evaluating how the IRA can be incorporated into the baseline of the final rule (including IPM) and will update the analyses to reflect the IRA for any final rule. EPA solicits comment on the incorporation of the IRA into its analyses, including any specific recommendations or data supporting a particular approach.

EPA does not expect the IRA to affect the current findings of economic achievability of the rule. To evaluate economic achievability, EPA considers the costs of the technologies that form the basis for BAT and uses IPM to assess changes in the power sector, including closures. As discussed in Section VIII of this preamble, EPA expects the costs of the technologies discussed here to result in a single coal-fired power plant closure; thus, the rule would be economically achievable.

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 proposal, 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 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 as it is evaporated during operation, while wet FGD systems 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. EPA identified the following types of treatment and handling practices for FGD wastewater as part of the 2015 and 2020 rules:

•

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 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 to 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 rule.

•

High hydraulic residence time biological reduction (HRTR).

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 the BAT technology basis for the effluent limitations in the 2015 rule.

•

Low hydraulic residence time biological reduction (LRTR).

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 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 (FO), electrodialysis reversal (EDR), or reverse osmosis (RO)) designed specifically for high TDS and 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 the 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 gasses. The hot gasses 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 by 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 the 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 that 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 that evaporated or 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 chloride.

—

Evaporation impoundments.

Some plants located in warm, dry climates have been able to use surface impoundments as holding basins where the FGD wastewater is retained until it evaporates. The evaporation rate from the impoundments at these plants 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 would significantly reduce the potential of a discharge to groundwater.

—

FA conditioning

. Many plants that operate dry FA handling systems will utilize 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 by 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.

EPA also collected new 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. See Section 4.1 of the Supplemental TDD for more information on these technologies.

2. BA Transport Water

BA 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, boiler 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 either be operated as a closed-loop system (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 slip stream 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, allowing for the reduction of capital costs as facility needs allow. 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 proposed rule, 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 boiler. 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 boiler. The system uses ambient air to cool the BA in the boiler and then transports the ash out from under the boiler using a conveyor. There is no water used in this process.

•

Dry vacuum or pressure system.

These systems transport BA from the boiler 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 boiler 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.

See Section 4.2 of the Supplemental TDD for more information on these technologies.

3. CRL

In promulgating the 2015 rule, EPA determined that combustion residual leachate 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, EPA determined that certain treatment technologies identified for FGD wastewater could also be used to treat leachate from landfills and impoundments containing combustion residuals. 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. 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, that included using CRL from either an impoundment or landfill for moisture conditioning FA, dust control, or truck wash. EPA also identified plants that collect CRL from impoundments and recycle it directly back to the impoundment.

4. Legacy Wastewater

Legacy wastewater can be comprised 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 (

see

Section VII.B.4 of this preamble). 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, or 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 of 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.

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 also differ across CCR impoundments due to different types of fuels burned at the plant, duration of pond operation, and ash type. The list of treatment technologies identified for legacy wastewater above are all applicable to all legacy wastewaters; however, 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, 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 (CSC), 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 decanting or dewatering treatment.

• Costs associated with these technologies.

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

2. Meetings With Individual Utilities

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

The specific 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. EPA used this information to supplement the data collected in support of the 2015 and 2020 rules.

3. Voluntary CRL Sampling

In December 2021, 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. 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.

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, EPA reviewed 35 reports published between 2011 and 2018 that EPRI 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 proposed rule, EPRI provided an additional 25 reports generated in the intervening years. EPA used information presented in these reports to inform the development of numeric effluent limitations for FGD wastewater and to update methodologies for estimating costs and pollutant removals associated with candidate treatment technologies.

5. Meetings With Trade Associations

In 2021 and 2022, 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 current status of many utilities transitioning away from coal.

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 subcategory, or in the VIP (

see

40 CFR 423.19(e), (f), and (h), respectively). While EPA did not require that a copy be provided to the Agency, EPA nevertheless obtained a number of these filings. Some facilities provided EPA a courtesy copy when filing with the relevant permitting authority. The Agency received notice of other filings as part of its standard permit review process when a state permitting authority sent new draft permits or modifications to EPA for review. EPA also asked some states for NOPPs after those states asked EPA questions about the process or initiated discussions about specific plants. Environmental groups who had been tracking NOPPs at specific plants and states also shared with EPA the information they had collected.

EPA is currently aware of NOPPs covering 90 EGUs at 38 plants. Of these, four EGUs (at two plants) have requested participation in the LUEGU subcategory, an additional 12 EGUs (at four plants) have requested participation in the 2020 rule VIP, and the remaining 74 EGUs (at 33 plants) have requested participation in the permanent cessation of coal combustion subcategory.

EPA cautions that these counts are not a comprehensive picture of what facilities' plans are for two reasons. First, EPA was unable to obtain information for all plants and states, and thus solicits comment on whether the public is aware of additional NOPPs that are not yet known to the Agency. Second, even where a facility has filed a NOPP, it still retains the flexibility under the transfer provisions of 40 CFR 423.13(o) to transfer between subcategories, or between a subcategory and the 2020 VIP provisions until 2023 or 2025 (depending on the transfer desired). EPA therefore solicits comment on additional information that would inform the Agency's understanding of facilities' plans under the 2020 rule. For further detail, the NOPPs EPA is aware of have been placed in the docket along with a memo 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 Proposed Rule

(SE10241).

Plant Scherer filed a permanent cessation of coal combustion 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.

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

EPA gathered data on the availability and effectiveness of FGD wastewater, BA handling, CRL, and pond dewatering operations and wastewater treatment technologies in the industry 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

EPA gathered information on steam electric generating facilities from the Department of Energy's (DOE's) Energy Information Administration (EIA) Forms EIA-860 (Annual Electric Generator Report) and EIA-923 (Power Plant Operations Report). EPA used the 2019 and 2020 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.

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. 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. EPA used this information to inform the industry profile and identify process modifications occurring in the industry.

VII. Proposed Regulation

A. Description of the Options

This proposal evaluates four regulatory options and identifies one preferred option (Option 3), as shown in Table VII-1 of this preamble. All options include the same technology basis for CRL (chemical precipitation) and legacy wastewater (best professional judgment) while incrementally increasing controls on FGD wastewater, BA transport water, or both. Each successive option from Option 1 to 4 would achieve a greater reduction in wastewater pollutant discharges. Each subcategorization is described further in Section VII.C of this preamble. In addition to some specific requests for comment included throughout this proposal, EPA solicits comment on all aspects of this proposal, including the information, data, and assumptions EPA relied upon to develop the four regulatory options, as well as the proposed BAT, effluent limitations, and alternate approaches included in this proposal.

1. FGD Wastewater

Under Option 1, EPA proposes to eliminate the BAT and PSES subcategorizations for high FGD flow facilities and LUEGUs. Option 1 would establish the same mercury, arsenic, selenium, and nitrogen limitations applicable to the industrial category based on chemical precipitation, followed by low hydraulic residence time biological treatment and ultrafiltration. Under Options 2 and 3, EPA proposes to eliminate the BAT and PSES subcategorizations for high FGD flow facilities and LUEGUs and further proposes to require zero discharge of FGD wastewater based on chemical precipitation followed by membrane filtration with 100 percent recycle of the permeate. These proposed options would also create a subcategory for early adopters that have already installed compliant biological treatment systems and would retire no later than December 31, 2032. Under Option 4, EPA proposes to establish an industrywide zero-discharge requirement without establishing an early adopter subcategory. Note that for all four options EPA proposes to retain the subcategory for EGUs permanently ceasing coal combustion by 2028.

2. BA Transport Water

Under Options 1 and 2, EPA proposes to eliminate the BAT and PSES subcategorization for LUEGUs. Options 1 and 2 would establish the same volumetric purge limitation applicable to the industrial category based on high recycle rate systems. Under Option 3, EPA proposes zero discharge based on dry handling or closed-loop systems. This proposed option would also create a subcategory for early adopters that have already installed a compliant high recycle rate system and would retire no later than December 31, 2032. Under Option 4, EPA proposes to establish an industrywide zero-discharge requirement without establishing an early adopter subcategory. For all four options, EPA proposes to retain the subcategory for EGUs permanently ceasing coal combustion by 2028.

3. CRL

Under all four options, EPA proposes to establish BAT limitations and PSES for mercury and arsenic based on chemical precipitation treatment.

4. Legacy Wastewater

Under all four options, EPA proposes not to specify a nationwide technology basis for BAT/PSES applicable to legacy wastewater at this time, but rather proposes that such limitations are to be derived on a site-specific basis by the permitting authorities, using their BPJ. EPA does solicit comment on other options, as discussed below.

Table VII-1—Main Regulatory Proposed Options

Wastestream

Subcategory

Technology Basis for the BAT/PSES Regulatory Options

3 (Preferred)

FGD wastewater

N/A

Chemical precipitation + biological treatment + ultrafiltration

Chemical precipitation + membrane filtration

Chemical precipitation + membrane filtration.

High FGD flow facilities/LUEGUs

NS.

EGUs permanently ceasing coal combustion by 2028

Surface impoundments

Surface impoundments.

Early adopters permanently ceasing coal combustion by 2032

Chemical precipitation + biological treatment + ultrafiltration

NS.

BA transport water

N/A

High recycle rate systems

Dry handling or closed-loop systems

Dry handling or closed-loop systems.

LUEGUs

NS.

EGUs permanently ceasing coal combustion by 2028

Surface impoundments

Surface impoundments.

Early adopters permanently ceasing coal combustion by 2032

High recycle rate systems

NS.

CRL

N/A

Chemical precipitation

Chemical precipitation.

Legacy wastewater

N/A

Best professional judgment

Best professional judgment.

N/A = Not applicable.

NS = Not subcategorized.

Note: The table above does not present existing subcategories included in the 2015 rule or the 2020 VIP for FGD wastewater. EPA is not proposing any changes to the existing 2015 rule subcategorization of oil-fired units, units with a nameplate capacity of 50 MW or less, or the 2020 VIP.

B. Rationale for the Proposed Rule

In light of the criteria and factors specified in CWA sections 301(b)(2)(A) and 304(b)(2)(B) (

see

Section IV of this preamble, above), EPA proposes to establish BAT effluent limitations based on the technologies described in Option 3.

EPA proposes to include 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 EPA's intent that as many portions of the rule remain in effect as possible.

1. FGD Wastewater

EPA is proposing chemical precipitation, followed by membrane filtration, as the technology basis for establishing BAT limitations to control pollutants discharged in FGD wastewater. After considering the factors specified in CWA section 304(b)(2)(B), EPA proposes to find that this technology is technologically available, economically achievable, and has acceptable non-water quality environmental impacts. More specifically, the technology basis for BAT would include chemical precipitation to remove suspended solids and scaling compounds prior to treatment with one or more stages of nanofiltration, electrodialysis reversal (EDR), RO, and/or forward osmosis. The permeate from the final stage of treatment would then be recycled back into the plant either as FGD makeup water or boiler makeup water.

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

In the subsection immediately below, EPA discusses its rationale for proposing membrane filtration as BAT for the control of FGD wastewater. In the following subsection, EPA discusses why it is not proposing as its main option other zero discharge technologies as BAT but is taking comment on such technologies. In the final subsection, EPA discusses why it is not proposing a less stringent technology as BAT.

a. Membrane Filtration

Availability of membrane filtration.

EPA is proposing to determine that membrane filtration is available for use by the steam electric industry to control discharges of FGD wastewater. Such a finding is consistent with the technology forcing nature of BAT as described in the legislative history and legal precedents discussing this provision. “In setting BAT, EPA uses not the average plant, but the optimally operating plant, the pilot plant which acts as a beacon to show what is possible.” (

Kennecott

EPA,

780 F.2d 445, 448 (4th Cir. 1985) (citing

A Legislative History of the Water Pollution Control Act Amendments of 1972,

93d Cong., 1st Sess. (Comm. Print 1973), at 798). BAT is supposed to reflect the highest performance in the industry and may reflect a higher level of performance than is currently being achieved based on technology transferred from a different subcategory or category, bench scale or pilot plant studies, or foreign plants.

Southwestern Elec. Power Co.

EPA,

920 F.3d at 1006;

Am. Paper Inst.

Train,

543 F.2d 328, 353 (D.C. Cir. 1976);

Am. Frozen Food Inst.

Train,

539 F.2d 107, 132 (D.C. Cir. 1976). BAT may be based upon process changes or internal controls, even when these technologies are not common industry practice.

See Am. Frozen Foods,

539 F.2d at 132, 140;

Reynolds Metals Co.

EPA,

760 F.2d 549, 562 (4th Cir. 1985);

California & Hawaiian Sugar Co.

EPA,

553 F.2d 280, 285-88 (2nd Cir. 1977). As recently reiterated by the U.S. Court of Appeals for the Fifth Circuit, “Under our precedent, a technological process can be deemed available for BAT purposes even if it is not in use at all, or if it is used in unrelated industries. Such an outcome is consistent with Congress'[s] intent to push pollution control technology.”

Southwestern Elec. Power Co.

EPA,

920 F.3d at 1031 (citation and internal quotations omitted).

As further discussed below, EPA is proposing to base its determination that membrane filtration is available for control of pollutants found in FGD wastewater on the numerous full-scale foreign installations of membrane filtration to treat FGD wastewater, the large number of successful domestic and international pilot tests of membrane filtration on FGD wastewater, successful use of membrane filtration on other steam electric wastestreams, and the use of membrane filtration on wastestreams in a many different industries besides the steam electric industry.

In the 2020 rule, EPA determined that membrane filtration was not available to control FGD wastewater industrywide, primarily due to the lack of a full-scale membrane filtration system in use to control FGD wastewater discharges at a U.S. facility. There was also discussion of possible uncertainties or data gaps in the record regarding foreign plants, pilot tests, or use of membrane filtration on other wastestreams. When EPA promulgated the 2020 rule, however, the Agency was aware of membrane filtration being successfully used on FGD wastewater at 12 foreign plants, on FGD wastewater in 20 domestic pilots, and on several wastestreams with characteristics similar to those of FGD wastewater both within the steam electric sector and in other industries. The language and intent of the CWA, repeatedly confirmed by Federal appellate courts, demonstrates that Congress intended that BAT reflect the best performing plant (

see, e.g., Kennecott

EPA,

780 F.2d. at 447;

Southwestern Elec. Power Co.

EPA,

920 F.3d at 1018). Accordingly, some might argue that the amount of information in the 2020 record was sufficient to support a finding of membrane filtration as BAT for control of FGD wastewater discharges. Based on EPA's current record, which contains additional information regarding the application of membrane filtration to FGD wastewater and other wastestreams inside and outside the steam electric industry,

the weight of the evidence supports the Agency's proposed conclusion that membrane filtration is available in the industry to control FGD wastewater discharges, notwithstanding the uncertainties raised in the 2020 rule. 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). Thus, for the following reasons, EPA proposes coming to a different conclusion regarding the availability of membrane filtration than in it did in the 2020 rule.

Caselaw supports that EPA may base BAT on technologies used in other industries.

See, e.g., Kennecott

EPA,

780 F.2d at 453 (“Congress envisioned the scanning of broader horizons and asked EPA to survey related industries and current research to find technologies which might be used to decrease the discharge of pollutants.”).

EPA also recognizes that, while it 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). EPA has taken reliance interests into account in this rulemaking, as is clear from EPA's proposal in Section VII.C.4 of this preamble, below, to create a new subcategory for early adopters who relied on certain of EPA's past determinations. EPA also notes that no NPDES permittee has certainty of its limitations beyond its 5-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) & (d).

International installations.

At the time of the 2020 rule, the Agency cited 12 foreign installations of membrane filtration on FGD wastewater.

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

Since the 2020 rule, EPA has become aware of additional information about these international installations that supports its proposed determination that membrane filtration is available for control of FGD wastewater discharges. In particular, the Agency has learned that certain Chinese facilities with membrane installations have successfully achieved zero discharge of FGD wastewater, in part by adjusting the ratios and dosages of the specific chemicals used in their chemical precipitation pretreatment systems.

EPA also has learned that certain Chinese plants with later installations did not need to pilot membrane filtration systems before successfully installing and operating them at full scale. The operating information from the previous installations was sufficient to successfully install a full-scale membrane system without the need for an intermediate pilot.

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. 20177. 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. (13 November). DCN SE08624.; Broglio, Robert. 2019. Doosan. Vendor FGD Wastewater Treatment Details—Doosan. (15 July). 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. (27 June). DCN SE08628.

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

(SE10281).

SE06915.

SE08618.

In the 2020 rule, EPA stated that there were too many unknowns about the foreign installations to support a finding of availability, including not knowing enough about their configurations, operations, performance, or long-term maintenance. These American-made systems have continued to operate since the 2020 rule, with the oldest now

operating for seven years. This continued operation suggests that EPA's concerns in 2020 may have been overstated. Additional data on foreign system configurations and operations have also enhanced the Agency's understanding of these systems.

Particularly, EPA was able to learn more about the issues with pretreatment identified at the pilot stage for one of the first Chinese installations. These issues were a result of the FGD wastewater's high suspended solids and high hardness. While these issues were identified at the outset of pilot testing, they were sufficiently resolved through adjustment of the chemical precipitation pretreatment process, leading the facility to install the system at full scale. For later installations at different sites, this Chinese utility ceased conducting pilot tests since appropriate pretreatment steps had already been identified.

SE10245.

In the 2020 rule, EPA also stated that there was not enough information to know if the foreign installations could continually operate as zero discharge systems or whether there would be some periods during which discharges occur. EPA notes that two additional years of zero discharge operation for these foreign plants have occurred since the 2020 rule, which supports a finding that continuous zero discharge operations are achievable. As discussed in Section XIV of this preamble, while EPA proposes zero discharge of pollutants in FGD wastewater, the Agency solicits comment on alternative membrane filtration-based BAT limitations if comments demonstrate that a regular or intermittent discharge is necessary for some plants. For the reasons discussed above, the installation and operation of membrane filtration to treat FGD wastewater abroad supports the proposed BAT basis of membrane filtration for FGD wastewater discharges.

Pilot applications.

Although EPA has sufficient information to propose that membrane filtration is available based on foreign installations alone, pilot applications also support the availability of membrane filtration for control of FGD wastewater discharges. In the 2020 rule record, the Agency cited 20 pilot applications of membrane filtration on FGD wastewater (19 domestic and one international).

While EPA stated that there were data gaps associated with the pilot studies that prevented a finding that membrane filtration is available, these gaps primarily related to the development of numeric limitations, and EPA nevertheless established limitations based on membrane filtration technology in the VIP. Furthermore, the record showed that membrane filtration pilots in the United States 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.

While specifics of these reports are claimed as CBI, EPA notes that the authors of several pilot test reports gave glowing reviews of the technology and detailed a number of advantages that membrane filtration offered versus biological treatment.

One of the systems EPA was aware of for the 2020 rule was 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, EPA defers to the company's characterization of this system as a pilot. Thus, it is not considered 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.

One of these reports,

Performance Evaluation of a Vibratory Shear Enhanced Processing Membrane System for FGD Wastewater Treatment,

which was published in 2014 but recently made publicly available, found that the piloted membrane filtration technology reliably removed the vast majority of pollutants in FGD wastewater. This pilot of the Vibratory Shear Enhanced Processing/Spiral Reverse Osmosis (VSEP/RO) system from New Logic Research, Inc. was performed at the Water Research Center at Georgia Power's Plant Bowen. The pilot included operations in both single pass mode (

i.e.,

continuous operations) and batch mode (focused on maximizing water recovery) on moderate TDS FGD wastewater and high TDS VSEP/RO concentrate. As explained in the report, “The first stage, VSEP pilot unit, removed approximately 94% TDS, while the second stage, Spiral RO pilot unit, removed an additional 5.8% TDS, yielding an overall TDS removal efficiency of 99.8%.” Furthermore, the system successfully removed pollutants even when the pollutant concentrations were increased from an average of approximately 15,000 mg/L TDS to an average of approximately 54,000 mg/L TDS, demonstrating the versatility of the system across a range of concentrations. Finally, the system continued operation without decreased performance due to scaling/fouling. “In both modes of operation (single-pass and batch concentration), no irreversible membrane fouling, no irregular transmembrane pressure (TMP) increase was observed throughout the project.” This appeared to result from a combination of the acid/base cleanings and the VSEP membrane vibration design/mechanism. This pilot supports that membrane filtration systems can successfully remove pollutants under a variety of TDS concentrations and scaling potentials found in FGD wastewater.

Since the 2020 rule, EPA has also become aware of new information on three additional domestic pilot applications of membrane filtration on FGD wastewater. Each of these pilots was performed with a different technology and demonstrated successful removal of pollutants in FGD wastewater and recovery of usable permeate. In particular, the first-of-its-kind domestic pilot of an EDR pilot plant for FGD wastewater indicates that treatment with membrane filtration has continued to advance and become more available. This pilot is detailed in EPRI (2020), which found that “The Flex EDR Selective pilot plant reliably operated for 61 days, 24/7, including weekends and unattended overnights.” Other key findings included an average 93 percent water recovery, 98 percent uptime of continuous operations (more than 1440 hours), selective removal of chloride, the elimination of the need for soda ash softening, “demonstrated versatility to treat wastewater of different concentrations and water chemistries with the same treatment plant,” and the potential for cost savings when compared to comparable treatment systems. Thus, the weight of evidence available from a growing number of pilot studies supports the Agency's proposed conclusion that membrane filtration is BAT for FGD wastewater discharges.

Application to other wastestreams.

As EPA explained in the 2020 rule, membrane filtration is used in full-scale applications to other wastestreams in the steam electric power sector and other industrial sectors. The domestic steam electric power sector regularly uses membrane filtration for boiler makeup water,

cooling tower

blowdown,

and ash transport water.

Other industrial sectors with full-scale membrane filtration applications include the textiles,

chemical manufacturing,

mining,

agriculture, oil and gas extraction,

food and beverage,

microelectronics/semiconductors,

landfills,

and automotive industries.

EPRI (Electric Power Research Institute). 2015.

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

August. 3002002143.

See, e.g.,

5 Daniels, D.G. 2015.

Winning the Cooling Tower Trifecta: Controlling Corrosion, Scale, and Microbiological Fouling.

Power Magazine. August 21. Available online at:

www.powermag.com/winning-the-cooling-towertrifecta-controlling-corrosion-scale-andaqmicrobiological-fouling/

(DCN SE09088).

See, e.g., 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.

ERG. 2019. Final Notes from Meeting with Pall Water. (5 March). EPA-HQ-OW-2009-0819-7613; Wolkersdorfer, Christian et al. 2015. Intelligent mine water treatment—recent international developments. (21 July). DCN SE08581; U.S. EPA. 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.

CH2M Hill. 2010. Review of Available Technologies for the Removal of Selenium from Water. (June). DCN SE08583.

U.S. EPA. 2022. Notes from Meeting with BKT—April 9, 2021. DCN SE010253.

ERG. 2019. Sanitized_Saltworks Vendor Meeting Notes—Final. DCN SE07089.

U.S. EPA. 2022. Notes from Meeting with ProChem—April 9, 2021. DCN SE10254.

In the 2020 rule, EPA stated that some of these other applications did not show that membrane filtration was available for use on FGD wastewater by focusing on the differences between specific characteristics of these individual wastewaters and FGD wastewater. Information in the 2020 record and the current record, however, indicates that there are many similarities between FGD and the non-FGD wastestreams where membranes have been utilized. In the 2020 rule record, EPA discussed that cooling tower blowdown at steam electric plants and desalination in oil and gas extraction were examples where membrane filtration was used in full-scale applications for treating high TDS wastewaters, a characteristic of FGD wastewater (85 FR at 64664-64665, October 13, 2020). 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 was 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.

Thus, based on the information gathered in both EPA's prior and current records, the utilization of membrane technology on other wastestreams supports the Agency's proposed conclusion that membrane filtration technology is BAT for FGD wastewater discharges.

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, microelectronics/semiconductors, landfills, and automotive industries).

For all the foregoing reasons, EPA proposes to find that membrane filtration is technologically available for the control of discharges in FGD wastewater. Moreover, membrane filtration would make reasonable further progress toward the Act's goal of eliminating the discharge of all pollutants because it would result in zero discharge of FGD wastewater from steam electric power plants.

Economic achievability of membrane filtration.

EPA proposes to find that the costs of membrane filtration for control of FGD wastewater discharges are economically achievable. Under the CWA, BAT limitations must be economically achievable. Courts have interpreted that requirement as a test of whether the regulations can be “reasonably borne” by the industry as a whole.

Chem. Mfrs. Ass'n

EPA,

870 F.2d 177, 262 (5th Cir. 1989);

BP Exploration & Oil

EPA,

66 F.3d 784, 799-800 (6th Cir. 1996);

see also id.

at 252 n.337 (reviewing cases in which courts have upheld EPA's regulations that projected up to 50 percent closure rates). Although the 2020 rule cited the increased cost of membrane filtration as compared to the selected technology basis as a reason for rejecting membrane filtration,

the Agency did not go so far as to find that the costs of membrane filtration were not economically achievable at that time. EPA proposes to find that the costs of membrane filtration for FGD wastewater are economically achievable for the industry as a whole, as discussed further below and in Sections VII.F and VIII of this preamble.

While the relative costs of technologies differ from plant to plant, new information obtained during the 2022 information collection confirms what was shown in the 2020 record: 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.

Non-water quality environmental impacts of membrane filtration.

EPA proposes to find that the non-water quality environmental impacts of membrane filtration are acceptable. For further discussion of these impacts, see Sections VII.G and X of this preamble. There was one non-water quality environmental impact that the 2020 rule found was unacceptable. In that rule, EPA expressed concern that use of membrane filtration would unacceptably limit the beneficial use of FA. The 2020 rule record and the current record demonstrate that the beneficial use of FA as an admixture or to replace Portland cement in concrete provides a substantial environmental benefit. As such, the potential that using FA to help dispose of brine from membrane filtration would limit this beneficial use continues to be potentially the most substantial non-water quality environmental impact when considering whether membrane filtration is BAT. Nevertheless, in light of the facts and analyses described in the following paragraphs, EPA proposes to find that these non-water quality environmental impacts are acceptable, most importantly because EPA's record indicates that there is sufficient FA to accommodate both FGD brine encapsulation needs following membrane filtration of FGD wastewater and the beneficial use market.

At the outset, EPA notes that the 2020 rule record discusses two uses of FA: FA fixation and brine encapsulation. FA fixation occurs when a facility conditions its dry FA with FGD wastewater rather than fresh makeup water.

The use of FA fixation prior to the 2020 rule is partly due to the very low costs of FA conditioning compared to other wastewater treatment technologies for FGD wastewater, as well as the potential to eliminate the discharge of FGD wastewater. The 2020 rule record also included discussion of brine encapsulation. Brine encapsulation is the process of mixing raw FGD wastewater or concentrated

FGD wastewater brine with FA and lime, which results in pozzolanic reactions that bind additional pollutants into the final solid matrix. Since the 2020 rule, additional facilities have evaluated FA fixation with FGD wastewater and/or encapsulation of FGD wastewater using FA and lime. In at least one instance, fixation/encapsulation was less costly than biological treatment. Thus, even without a new regulation establishing BAT limitations based on membrane filtration, the record demonstrates that implementation of the baseline 2020 rule has resulted in the use of some FA for fixation or encapsulation.

Conditioning is required to avoid air dispersion of the fine FA particulates.

While FA fixation still may be an option for brine management, EPA evaluated the option most discussed in the record: brine encapsulation. Since the question in evaluating the impact of brine encapsulation is not whether the FA needed for these processes will be disposed of, but to what extent additional disposal curtails the FA available for beneficial use, EPA conducted an analysis of FA availability entitled

2021 Steam Electric Supplemental Proposed Rule: Fly Ash Availability

(SE10242). This analysis shows that the amount of FA needed to dispose of membrane filtration's byproduct would not have an unacceptable impact on the amount of FA that is used for beneficial purposes. In this analysis, consistent with EPA's costing methodology, the Agency conservatively assumed that all facilities generate brine from a single pass of a membrane filtration system, which is then encapsulated with FA and lime.

In other words, EPA conservatively assumed no further brine concentration (

e.g.,

additional membrane filtration, or thermal evaporation) would be performed that would further decrease the amount of FA needed for encapsulation.

While EPA's costs assume a polishing stage RO, the brine from that system in returned to the first stage system.

The results of EPA's conservative FA availability analysis support the finding that there is sufficient FA for the majority of the 22 plants that would be expected to make treatment upgrades to meet the proposed limitations. Based on EPA's analysis of 2019 and 2020 EIA data, 20 of these 22 power plants that would be expected to install membrane filtration under proposed Option 3 have enough FA for encapsulation before accounting for reported FA sales. For the two remaining plants, EPA estimates there would be a combined annual FA deficiency of approximately 240,000 tons. After accounting for reported FA sales, and assuming these sales continue, EPA estimates that an additional four power plants may not have enough FA available for encapsulation—a total of six plants with a combined annual FA deficiency of approximately 750,000 tons (or approximately one percent of all fly ash generated). In light of the relatively small on-site FA deficiency estimated using conservative assumptions and, as discussed more fully below, the potential for plants to use off-site FA or additional lime for their brine encapsulation needs or available brine management alternatives that do not rely on FA or use less FA, EPA proposes that its estimate of on-site FA that may no longer be available for beneficial use after implementation of this rule does not rise to the level of an unacceptable non-water quality environmental impact.

The 750,000 ton per year shortfall of FA described above is likely an overestimate for several reasons. First, based on the 2020 EIA data, coal-fired power plants reported more than 30 million tons of FA generated annually. While there are increasing FA sales reported each year, EPA identified more than 100 coal-fired power plants generating over 9.6 million tons of unsold FA that could be redirected from disposal towards either encapsulation or other beneficial uses.

Thus, EPA estimates that there is enough FA to accommodate both FGD brine encapsulation needs and the beneficial use market with millions of tons still requiring disposal. In the 2020 rule record, GenOn's plans to install membrane filtration at certain facilities did not include use of FA from those facilities. Instead, GenOn had plans to send the brine offsite to be mixed with other FA and lime for disposal and continued to seek options for beneficial use of the brine.

The concepts of use of off-site FA or beneficial use of brine are not unique to GenOn. With respect to alternate FA, the 2022 World of Coal Ash conference included 10 sessions with abstracts discussing the harvesting and beneficiation of previously disposed ash.

This further supports that, after accounting for FA availability across the entire industry, the non-water quality environmental impacts of potential FA disposal associated with membrane filtration are acceptable.

EPA also notes that the 2020 rule record failed to acknowledge that both the American Coal Ash Association and EPA have historically considered waste stabilization and solidification as a category of beneficial use.

See, e.g., www.acaa-usa.org/wp-content/uploads/coal-combustion-products-use/ACAA-Brochure-Web.pdf.

Notes from Call with GenOn (SE08614).

Session abstracts are available online at:

www.woca2022.conferencespot.org/event-data/activity.

Second, the Agency notes that multiple alternatives exist for handling the resulting brine that do not involve FA and thus would have no impact on the beneficial use of FA in other settings. EPA evaluated alternative scenarios including disposal of brine in a deep injection well and crystallization to a salt for disposal. With respect to disposal in a deep injection well, EPA has been encouraging efforts for water reuse rather than deep well injection, particularly in arid western climates. Most of the facilities in question here, however, are located in the Midwest and Southern U.S., places where water reuse may still be important when feasible, but not to the level that EPA would find injection to be unacceptable. With respect to crystallization and disposal of the resultant salt, none of the facilities that currently generates brine as part of a zero discharge system elects to encapsulate and dispose of that brine.

Rather, these facilities send the concentrated brine to a crystallizer, and these resulting salt crystals can then be disposed of without the use of FA. The costs and non-water quality environmental impacts of these alternatives are presented in

Alternative Brine Management Methodology

(SE10243). The 2015 rule record found crystallization to have acceptable non-water quality environmental impacts. Based on this most current analysis along with the 2015 record, EPA proposes to find that these alternative brine management strategies have acceptable non-water quality environmental impacts and that, while these costs are higher, they would be economically achievable.

While these systems are thermal systems rather than membrane systems, the brine generated would not differ substantially in its ultimate characteristics.

Third, EPA also notes that the six plants with potentially insufficient FA may still be able to sell their FA if the brine encapsulation were performed with additional lime use. EPA notes that extraction, processing, and transportation associated with additional lime use would result in some additional air emissions, but that these emissions would be less than those associated with Portland cement, the material that FA replaces in its most environmentally beneficial use.

Fourth, EPA's estimates regarding non-water quality environmental impacts associated with membrane filtration's byproduct are likely conservative (an overestimate) because, even where encapsulation will be the

ultimate brine management scenario, further concentration of the brine is not only possible, but probable for at least some facilities. For example, one utility evaluating 2020 rule VIP-compliant systems for a specific facility discussed how it would send the membrane reject brine to a thermal system to further reduce the volume of FGD brine to be encapsulated. This process would result in less demand for FA due to the decreased volume of brine.

Finally, the 2020 record indicated that the management of FGD brine could actually lead to new beneficial uses. At least one Chinese plant was taking its brine down to salts and then selling its salts for an industrial use.

Where companies are ultimately able to beneficially use some of the brine in lieu of disposal, this would be a positive non-water quality environmental impact. Thus, both ongoing evaluation and historical practice indicate EPA's assumptions regarding FA use to encapsulate FGD brine is likely a conservative estimate of the amount of ash that will be diverted from beneficial use to disposal. All of the above information supports EPA's proposed finding that the non-water quality environmental impacts of membrane filtration are acceptable.

Final DuPont Meeting Notes (SE08618), Notes from Vendor Call with DuPont October 29 and December 8, 2021 (SE10245).

b. Other Zero Discharge Technologies

For this proposal, EPA evaluated other zero discharge technologies that could also eliminate the discharge of FGD wastewater. However, EPA is not relying upon them as a basis for proposed BAT limitations because they achieve the same pollutant reductions as the proposed BAT technology basis (membrane filtration) but at a higher cost. Nevertheless, EPA solicits comment on whether the Agency should determine in a final rule that any one or more of these technologies constitutes an additional BAT technology basis for controlling pollutants discharged in FGD wastewater in addition to membrane technology, or alternatively, in place of membrane technology.

Currently, 36 coal-fired power plants in the United States 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 systems (

e.g.,

falling film evaporators), or SDEs. Since 2009, approximately 15 additional plants that also operated wet FGD systems and achieved zero discharge of FGD wastewater have retired or refueled such that the FGD wastewater has been eliminated. While some of these systems (evaporation ponds, fixation, and recycling) may not be available at every single site,

the number of thermal and SDE systems both domestically and internationally in use on FGD wastewater demonstrates that they are commercially available, and thus potentially technologically available, as technologies for treating FGD wastewater to meet zero-discharge limitations.

Specifically, at least some steam electric power plants have used the traditional thermal systems

and SDEs

to achieve zero discharge of FGD wastewater domestically and internationally for years, and several recent electric utility reports acknowledge this fact.

56 57 58 59

EPA has separately evaluated the costs of thermal and SDE systems. Costs per facility have decreased over time, and due to retirements and fuel conversions, total costs have decreased substantially. Although EPA has not estimated potential closures associated with these technologies using the same model it has for supporting the economic achievability of Option 3, as discussed more in Section VIII of this preamble below, EPA does not expect the costs associated with these technologies to have a significant impact on industry closures. In that case, the costs of these technologies, although higher than the costs estimated for industrywide membrane filtration,

would be reasonable for the category as whole, and thus economically achievable.

61 62

Furthermore, consistent with the findings of the 2015 rule, EPA proposes to find no unacceptable non-water quality environmental impacts from operation of thermal systems and proposes that SDEs have similarly acceptable non-water quality environmental impacts.

A 37th project that will result in zero discharge may have also been completed:

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

EPA acknowledged as much in both the 2015 and 2020 rules.

See, e.g.,

APEC (Asia-Pacific Economic Cooperation) Energy Working Group. 2015.

Water Energy Nexus: Coal-Based Power Generation and Conversion—Saving Water.

EWG 08/2014 A. December. Available online at:

www.apec.org/docs/default-source/Publications/2017/2/Water-Energy-Nexus-Coal-Based-Power-Generation-and-Conversion-----Saving-Water/217_EWG_APEC-Energy-Water-Nexus-Report-20161230-_CPAU_010217.pdf.

The Italian thermal 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” (SE07206).

SE10234.

SE09998.

EPRI (Electric Power Research Institute). 2017.

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

000000003002011665. (SE06971).

The record indicates that individual utilities have found thermal and/or SDE systems to be less expensive than membrane (and even biological) systems in some cases.

Thermal Evaporation Cost Methodology (SE10246).

Spray Dryer Evaporator Cost Methodology (SE10247).

EPA evaluated the non-water quality environmental impacts of these technologies in

Alternative Brine Management Methodology

(SE10243). EPA performed this evaluation in the context of brine management technologies for membrane filtration, and the types of impacts and findings would remain the same even if used as standalone technologies.

EPA solicits comment on whether the Agency should identify, in any final rule, one or more of the technologies of evaporation ponds, recycling of FGD wastewater, ash fixation, thermal systems (

e.g.,

falling film evaporators), or SDEs as a BAT technology basis for control of FGD wastewater discharges, in addition to membrane filtration technology. EPA solicits comment on whether such additional BAT basis or bases would be technologically available and economically achievable, and whether they would have acceptable non-water quality environmental impacts. EPA also solicits comment on whether any one or more of these alternative zero discharge technologies should be the BAT technology basis for control of FGD wastewater discharges in lieu of chemical precipitation plus membrane filtration.

c. EPA Proposes To Reject as BAT Less Stringent Technologies Than Membrane Filtration

Except for the early adopter subcategory discussed in Section VII.C.4 of this preamble, EPA is not proposing to base BAT on chemical precipitation followed by a low hydraulic residence time biological treatment including ultrafiltration, the technology which EPA determined to be BAT in the 2020 rule. Under CWA section 301(b)(2)(A), BAT is supposed to result in “reasonable further progress toward the national goal of eliminating the discharge of all pollutants” and “shall require the elimination of discharges of all pollutants if the Administrator finds . . . that such elimination is technologically and economically achievable” as determined in accordance with CWA section 304(b)(2)(B). The record shows that the 2020 rule industrywide BAT technology

basis for FGD wastewater removes fewer pollutants than the BAT basis of chemical precipitation plus membrane filtration identified in this proposal. Similarly, except for the permanent cessation of coal combustion subcategory discussed in Section VII.C.3 of this preamble, EPA is not identifying the less stringent (and previously rejected) technologies of surface impoundments or chemical precipitation, as these technologies too will remove fewer pollutants than the BAT in this proposal.

2. BA Transport Water

EPA is proposing dry handling or closed-loop systems as the technology basis for establishing BAT limitations to control pollutants discharged in BA transport water. EPA proposes to find that these technologies are technologically available, are economically achievable, and have acceptable non-water quality environmental impacts after evaluating the factors specified in CWA section 304(b)(2)(B). Specifically, dry handling systems include mechanical drag systems (

e.g.,

submerged chain conveyors), submerged grind conveyors (

e.g.,

compact submerged conveyors), air-cooled conveyor systems, and pneumatic systems. Closed-loop systems consist of remote mechanical drag systems paired with any necessary storage tanks, chemical addition systems, and/or RO treatment necessary to fully recycle BA transport water.

In addition to remote MDSs, non-BAT technologies include many dewatering bins (also known as hydrobins), and surface impoundments may also have the flexibility to operate as closed-loop systems. Like remote MDSs, the latter systems may need to install chemical addition systems (acid, caustic, and/or flocculants), RO systems, and/or additional storage tanks to operate as fully closed loop.

In the 2020 rule, EPA rejected dry handling or closed-loop systems as the BAT technology basis in favor of high recycle rate systems due to process changes plants made to comply with the CCR rule (

i.e.,

re-routing non-CCR wastes to their wet BA handling systems to avoid sending them to their unlined surface impoundments, as the CCR rule's cease-receipt-of-waste date approached), as well as the additional costs of dry handling or closed-loop systems. EPA also stated in 2020 that many plants may not, as a technical matter, be able to fully close their BA handling systems to operate without discharge. Upon further careful consideration of the record and the CCR rule, EPA does not think that plants need a purge allowance to comply with the CCR rule. While in some cases plants may incur additional costs to achieve zero discharge by making process changes, the widespread use of dry handling or closed-loop systems supports the view that these technologies are available. As explained below, EPA proposes to find that the technologies are available and economically achievable, and they have acceptable non-water quality environmental impacts. Thus, EPA is proposing dry handling or closed-loop systems as the BAT technology basis for BA transport water.

In the first subsection immediately below, EPA discusses its rationale for proposing dry handling or closed-loop systems as BAT for BA transport water. In the following subsection, EPA discusses why it is not proposing less stringent technologies than dry handling or closed-loop systems. In the final subsection, EPA solicits comment on issues associated with a BA transport water purge allowance and bottom ash contact water.

a. Dry Handling or Closed-Loop Systems

Availability of dry handling or closed-loop systems.

Based on the record, EPA proposes to find that dry handling or closed-loop systems are technologically available. At the time of the 2020 rule, EPA estimated that more than 75 percent of plants already employed dry handling systems or wet sluicing systems in a closed-loop manner, or had announced plans to switch to such systems in the near future. The high percentage of plants already employing these systems indicates that they are technologically available. Some of these systems have been in use since the 1970s, and today, most facilities have installed one or more such systems.

One vendor estimates that only seven ash conversions remain in the entire industry.

In the 2015 and 2020 rule preambles, EPA discussed the widespread use of dry handling systems for control of BA transport water servicing approximately 200 EGUs at over 100 plants. In the 2020 rule, EPA also discussed advances in dry BA handling systems. Specifically, the Agency discussed a newer technology called submerged grind conveyors (one example of which is called a compact submerged conveyor). At the time, compact submerged conveyors were known to be installed and in operation at two plants. EPA has since learned that about 12 compact submerged conveyors have been installed.

66 67

Partly due to the increased use of compact submerged conveyors, more dry handling systems are currently in place than EPA originally forecasted. For example, as indicated in the 2020 rule record, one utility commented that it had space constraints at a facility that would preclude the installation of a compact submerged conveyor, and EPA thus projected that this facility would employ a high recycle rate system under the 2020 rule. Since the 2020 rule, however, that utility ultimately proceeded to install a different dry handling system, which highlights the broad array of dry handling options available for coal-fired power plants, regardless of their configuration. Even where space constraints may prohibit certain dry systems, a plant could use a pneumatic system, albeit at a somewhat greater cost. The 2020 rule record included information on 50 pneumatic installations from as early as 1992. Given that BAT is to reflect the best performing plant in the field

Kennecott

EPA,

780 F.2d at 447, and the facts in the record support the use of dry handling technology to achieve zero discharge of BA transport water, EPA could propose to identify dry handling as the sole technology basis for control of BA transport water. Nonetheless, as it did in the 2015 rule, EPA is proposing to also identify closed-loop systems as a BAT technology basis for controlling discharges of BA transport water, given that a limited number of plants may find that option to be more attractive due to space constraints and lower costs when compared to a pneumatic system.

Some utilities have even suggested that the discussion of compact submerged conveyors in the final 2020 rule preamble and additional compliance timeframes have led them to consider these newer dry systems rather than a previously contemplated high recycle rate/closed-loop system.

Final Burns & McDonnell Meeting Notes (SE10248).

After the 2015 rule and throughout the 2020 rulemaking, certain industry representatives argued that there are challenges to operating a closed-loop BA handling system in a truly zero discharge manner. They argued that closed-loop systems, including remote MDS and dewatering bins, cannot maintain fully closed-loop operations due to chemistry issues or water imbalances in the system, such as those that might occur from unexpected maintenance or large precipitation events. However, even accounting for these issues, the 2020 rule did not find that closed-loop systems are not technologically available. Information in EPA's 2020 rule record indicated that plants can operate their closed-loop systems to achieve zero discharge, although this could require some process changes and their resulting costs. The 2020 record found that industry could achieve complete recycle

at an additional cost of $63 million per year in after-tax costs (beyond the costs of the systems themselves) over the 2015 rule's estimates. Moreover, EPA's cost estimates at the time were admittedly conservative, as the Agency assumed the need to treat 10 percent of the BA handling system's volume using RO for every facility with a closed-loop system. See Section VIII of this preamble for a further discussion of costs associated with the proposed closed-loop system technology basis.

In the 2020 rule record, EPA discussed four potential challenges with maintaining closed-loop systems: (1) managing non-BA transport water inflows, (2) managing precipitation-related inflows, (3) managing unexpected maintenance events, and (4) maintaining water system chemistry. As further discussed below, based on the current record, none of these previously discussed challenges provide a reasoned basis for finding closed-loop systems not to be technologically available, although these issues may in certain circumstances require a plant to incur additional costs.

First, in 2020, EPA stated that managing non-BA transport water inflows had the potential to result in water imbalances within a closed-loop system. With respect to the inflow of other wastestreams into the BA handling system, EPA's record in the 2015 and 2020 rules indicates that closed-loop systems (

i.e.,

remote MDSs) can be sized to handle these additional wastestreams.

To ensure effective operations when designing and procuring closed-loop systems, facilities should seek to size these systems for all wastestreams the system would handle. Moreover, there is no evidence in the record that unanticipated inflows cannot be addressed with reasonable steps.

EPA solicits comment on whether the best performing remote MDSs have documented non-BA transport water inflows regularly exceeding the ability of the systems to reuse their wastewater. EPA solicits comment providing data from any remote MDS that would suggest whether a purge allowance is or is not appropriate due to the technological availability of the system.

For example, the Belews Creek remote MDS discussed during the 2020 rulemaking also accepts economizer ash and pyrites (SE07137).

Even including dewatering bins, which are not the basis for either the 2015 BAT for BA transport water or this proposed BAT, the 2020 record included only a single facility where the water inflows to its dewatering bin system were too great to be recycled due to the presence of other wastewaters.

Second, in 2020, EPA stated that managing precipitation-related inflows had the potential to result in water imbalances in the BA handling system. However, EPA's record shows that precipitation-related inflows can be adequately managed with design improvements, including the use of roofing where appropriate. The 2015 BAT technology basis and 2020 rule remote MDS technology designs included and costed for covers to avoid collecting precipitation.

There is no record evidence that this previously discussed precipitation-related challenge cannot be overcome with reasonable steps and, therefore, this concern does not provide a basis for rejecting closed-loop systems as BAT. EPA solicits comment on whether the best performing remote MDSs have documented precipitation inflows that have exceeded the ability of the systems to reuse or store their wastewater, or whether the technology issue can be addressed by undertaking measures at a reasonable additional cost. EPA solicits comment providing data from such systems that would suggest whether a purge allowance is or is not warranted. EPA solicits comment on allowing for unlimited one-time purges due to large precipitation events exceeding a 10-year storm event of 24-hour or longer duration (

e.g.,

a 30-day storm event) where drains or other precipitation-collection components may not be amenable to roofs or other covers, including any necessary reporting or recordkeeping requirements. Due to the increasing storm severity associated with climate change, EPA also solicits comment on whether a different type of storm event would be more appropriate. Should EPA allow such discharges, the Agency solicits comment on whether to require facilities to submit information when they discharge, such as why the discharge was necessary, how much was discharged, or any other specific information (

e.g.,

meteorological information) that would be helpful to the permitting authority or public at large.

2020 Supplemental TDD (EPA-821-R-20-001).

A third previously discussed challenge mentioned in the 2020 rule to operating a remote MDS as a closed-loop system is the possibility of infrequent maintenance events that might fall outside the 2015 rule exemption of “minor maintenance” and “leaks” from the definition of BA transport water. EPRI (2018) listed several such maintenance events; most were expected to occur less than annually. EPRI provided information about the estimated frequency and volume of water associated with each maintenance event; however, EPRI did not provide information about a specific remote MDS unable to manage these maintenance events with existing maintenance tanks. Furthermore, even where maintenance wastewater volumes are too large to be managed in existing maintenance tanks, utilities can, at additional cost, lease storage tanks for short-term maintenance where these infrequent maintenance events are foreseeable.

There is no record evidence that infrequent maintenance events cannot be overcome with reasonable steps and, therefore, this concern does not provide a basis for rejecting closed-loop systems as BAT. EPA solicits comment on whether data from such systems would suggest a purge allowance is or is not warranted, as well as on the underlying data. EPA also solicits comment on whether the Agency should expand the existing “minor maintenance event” exemption from the definition of BA transport water in § 423.11(p). One example of such a potential expansion could include changing the current language that excludes “minor maintenance events (

e.g.,

replacement of valves or pipe section)” to instead state “minor maintenance (

e.g.,

replacement of valves or pipe sections) or infrequent (

i.e.,

occurring less than annually) maintenance events.” Another example would be to delete the term “minor” and associated parenthetical and merely say “maintenance events.” To the extent that EPA expands this exemption in 40 CFR 423.11(p), the Agency also solicits comment on any appropriate reporting or recordkeeping requirements. For example, EPA is interested in commenters' views on whether, when a facility discharges due to a maintenance event, facilities should submit information about why it was necessary to discharge, how much was discharged, or any other specific information that would be helpful to the permitting authority or broader public. Furthermore, EPA solicits comment on whether implementation of such a change to the definition of BA transport water should require, for example, a demonstration that the maintenance water could not be managed within the system.

In contrast, if the maintenance discharge is caused by an unforeseeable upset condition, the plant would have an affirmative defense to an enforcement action if the requirements of 40 CFR 122.41(n) are met.

The final engineering challenge discussed in the 2020 rule record as a reason for selecting high recycle rate systems rather than closed-loop systems was the need to maintain water system chemistry. The 2020 rule discussed

potentially problematic system chemistries, such as extreme acidic conditions, high scaling potential, and the buildup of fine particulates that could clog pumps and other equipment. The 2015 closed-loop system BAT design basis included a chemical addition system to manage these system chemistries. In particular, corrosivity could be managed through pH adjustment, scaling could be managed with acid and/or antiscalants, and fines could be further settled out with polymers and other coagulants. EPRI

documented that some systems went slightly further, pairing the chemical addition systems with changes in operations such as higher flow rates or longer contact time. Even where all else fails, the same slipstream of purge allowed under the 2020 rule could be treated with RO and recycled back in as clean makeup water. While it is possible that addressing these issues could entail additional costs, there is no record evidence that this chemistry-related challenge cannot be overcome with reasonable steps and, therefore, this concern does not provide a basis for rejecting closed-loop systems as BAT. EPA solicits comment on the extent to which any plant using a remote MDS has tried all the processes described above and still failed to adequately control system chemistry. EPA solicits comment on whether data from such systems would suggest a purge is or is not warranted, as well as on the underlying data.

SE08927.

For all the foregoing reasons, EPA proposes to find that the record indicates that dry handling or closed-loop systems are technologically available for control of discharges in BA transport water. Moreover, dry handling or closed-loop systems would result in reasonable further progress toward the Act's goal of eliminating the discharge of all pollutants, as the limitations based on this technology would require zero discharge of BA transport water from the steam electric industry.

Economic achievability of dry handling or closed-loop systems.

EPA proposes to find that the costs of dry handling or closed-loop systems are economically achievable for the industry as a whole. In the 2020 rule, EPA cited the additional costs of closed-loop systems as part of its basis for selecting high recycle rate systems. In the 2020 rule record, EPA noted that it had “conservatively” estimated costs of $63 million per year based on all facilities using a remote MDS needing a 10 percent purge to be treated with RO in order to achieve complete recycle (

i.e.,

zero discharge operations). However, EPA never found that the additional costs to achieve zero discharge were not economically achievable. Moreover, the 2020 rule record never demonstrated that a full 10 percent purge at all facilities was a realistic costing assumption. The primary basis for the 2020 rule purge allowance was a 2016 report from EPRI that involved continuous purges, the majority of which were well under one percent. Thus, in the 2020 rule record, EPA presented a sensitivity analysis with costs for a two percent purge treatment, which may better reflect actual operations.

Even using the more conservative cost estimates in the baseline IPM analysis for the 2020 rule (

i.e.,

full implementation of the 2015 rule),

the record demonstrated minimal changes in coal combustion and in steam electric power plant retirements. After updating these conservative cost estimates to $45 million per year pre-tax in proposed Option 3, the IPM analysis performed for this proposed rule continues to demonstrate that, after including the costs of treating all wastestreams

This text is long and has been trimmed here. Open the source document for the complete record.

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.