[Federal Register Volume 88, Number 60 (Wednesday, March 29, 2023)]
[Proposed Rules]
[Pages 18824-18903]
[FR Doc No: 2023-04984]

Vol. 88

Wednesday,

No. 60

March 29, 2023

Part IV

Environmental Protection Agency

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40 CFR Part 423

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

Federal Register / Vol. 88, No. 60 / Wednesday, March 29, 2023 /
Proposed Rules

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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.

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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: [email protected]. For economic information, contact
James Covington, Water Economics Center, telephone:<PHONE_NUMBER>;
email: [email protected].

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 Sec. Sec.  423.13(o) and
423.19(i)
    3. Conforming Changes for Voluntary and Involuntary Delays in
Sec. Sec.  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. v. 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. v. 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.\1\ 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.
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    \1\ As discussed in Section XII of this preamble, not all
benefits could be fully quantified and monetized at this time.
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    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.\2\ 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.
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    \2\ 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]
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                                                                                Total           Total
                                                                   Total social      monetized     monetized net
                        Regulatory option                              costs       benefits \a\    benefits \a\
                                                                                \b\             \b\
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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
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\a\ 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.
\b\ Includes benefits of changes in CO2 air emissions monetized using the Interagency Working Group on the
  Social Cost of Greenhouse Gases (IWG) SC-CO2 at 3% (average). See Section XII.B.3 of this preamble for
  benefits monetized using other SC-CO2 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:

------------------------------------------------------------------------
                                                          North American
                                                             Industry
            Category               Example of regulated   Classification
                                          entity          System (NAICS)
                                                               Code
------------------------------------------------------------------------
Industry.......................  Electric Power                    22111
                                  Generation Facilities--
                                  Electric Power
                                  Generation.
                                 Electric Power                   221112
                                  Generation Facilities--
                                  Fossil Fuel Electric
                                  Power Generation.
------------------------------------------------------------------------

    This section is not intended to be exhaustive, but rather provides
a guide regarding entities likely to be regulated by any final rule
following this action. Other types of entities that do not meet the
above criteria could also be regulated. To determine whether your
facility is regulated by any final rule following this action,
carefully examine the applicability criteria listed in 40 CFR 423.10
and the definitions in 40 CFR 423.11. If you still have questions
regarding the applicability of any final rule following this action to
a particular entity, consult the person listed for technical
information in the preceding FOR FURTHER INFORMATION CONTACT section.

B. What action is EPA taking?

    The Agency is proposing to revise, and is soliciting comment on
possible revision to certain BAT effluent limitations guidelines and
pretreatment standards for existing sources in the steam electric power
generating point source category that apply to FGD wastewater, BA
transport water, CRL, and legacy wastewater.

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

    EPA is proposing to promulgate this rule under the authority of
sections 301, 304, 306, 307, 308, 402, and 501 of the Clean Water Act
(CWA), 33 U.S.C. 1311, 1314, 1316, 1317, 1318, 1342, and 1361.

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

    This proposed action is estimated to cost $200 million per year in
social costs and result in $1,557 million in benefits using a three
percent discount rate. Using a seven percent discount rate, the
estimated costs are $216 million per year and the benefits are $1,290
million.

IV. Background

A. Clean Water Act

    Congress passed the Federal Water Pollution Control Act Amendments
of 1972, also known as the Clean Water Act (CWA), to ``restore and
maintain the chemical, physical, and biological integrity of the
Nation's waters.'' 33 U.S.C. 1251(a). The CWA establishes a
comprehensive program for protecting our nation's waters. Among its
core provisions, the CWA prohibits the discharge of pollutants from a
point source to waters of the United States (WOTUS), except as
authorized under the CWA. Under section 402 of the CWA, discharges may
be authorized through a National Pollutant Discharge Elimination System
(NPDES) permit. The CWA also authorizes EPA to establish nationally
applicable, technology-based ELGs for discharges from different
categories of point sources, such as industrial, commercial, and public
sources.
    The CWA authorizes EPA to promulgate nationally applicable
pretreatment standards that restrict pollutant discharges from
facilities that discharge wastewater to WOTUS indirectly through sewers
flowing to Publicly Owned Treatment Works (POTWs), as outlined in CWA
sections 307(b) and (c), 33 U.S.C. 1317(b) and (c). EPA establishes
national pretreatment standards for those pollutants in wastewater from
indirect dischargers that may pass through, interfere with, or are
otherwise incompatible with POTW operations. Pretreatment standards are
designed to ensure that wastewaters from direct and indirect industrial
dischargers are subject to similar levels of treatment. See CWA section
301(b), 33 U.S.C. 1311(b). In addition, POTWs are required to implement
local treatment limits applicable to their industrial indirect
dischargers to satisfy any local requirements. See 40 CFR 403.5.
    Direct dischargers (i.e., those discharging directly to surface
waters rather than through POTWs) must comply with effluent limitations
in NPDES permits. Discharges that flow through groundwater before
reaching surface waters must also comply with effluent limitations in
NPDES permits if those discharges are the ``functional equivalent'' of
a direct discharge. County of Maui v. Hawaii Wildlife Fund, 140 S. Ct.
1462 (2020). Indirect dischargers, who discharge through POTWs, must
comply with pretreatment standards. Technology-based effluent
limitations in NPDES permits are derived from effluent limitations
guidelines (CWA sections 301 and 304, 33 U.S.C. 1311 and 1314) and new
source performance standards (CWA section 306, 33 U.S.C. 1316)
promulgated by EPA, or based on best professional judgment (BPJ) where
EPA has not promulgated an applicable effluent guideline or new source
performance standard. CWA section 402(a)(1)(B), 33 U.S.C.
1342(a)(1)(B); 40 CFR 125.3(c). Additional limitations based on water
quality standards are also required to be included in the permit in
certain circumstances. CWA section 301(b)(1)(C), 33 U.S.C.
1311(b)(1)(C); 40 CFR 122.44(d). EPA establishes ELGs by regulation for
categories of industrial dischargers and are based on the degree of
control that can be achieved using various levels of pollution control
technology.
    EPA promulgates national ELGs for major industrial categories for
three classes of pollutants: (1) conventional pollutants (i.e., total
suspended solids (TSS), oil and grease, biochemical oxygen demand
(BOD5), fecal coliform, and pH), as outlined in CWA section
304(a)(4) and 40 CFR 401.16; (2) toxic pollutants (e.g., toxic metals
such as arsenic, mercury, selenium, and chromium; toxic organic
pollutants such as benzene, benzo-a-pyrene, phenol, and naphthalene),
as outlined in section 307(a) of the Act, 40 CFR 401.15 and 40 CFR part
423 appendix A; and (3) nonconventional pollutants, which are those
pollutants that are not categorized as conventional or toxic (e.g.,
ammonia-N, phosphorus, and total dissolved solids (TDS)).

B. Relevant Effluent Guidelines

    EPA develops effluent guidelines that are technology-based
regulations for a category of dischargers. EPA bases these regulations
on the performance of control and treatment technologies. The
legislative history of CWA section 304(b), which is the heart of the
effluent guidelines program, describes the need to press toward higher
levels of control through research and development of new processes,
modifications, replacement of obsolete plants and processes, and other
improvements in technology, taking into account the cost of controls.
Congress has also stated that EPA need not consider water quality
impacts on individual water bodies as the guidelines are developed; see
Statement of Senator Muskie (October 4, 1972), reprinted in Legislative
History of the Water Pollution Control Act Amendments of 1972, at 170.
(U.S. Senate, Committee on Public Works, Serial No. 93-1, January
1973); see also Southwestern Elec. Power Co. v. EPA, 920 F.3d at 1005
(``The Administrator must require industry, regardless of a discharge's
effect on water quality, to employ defined levels of technology to meet
effluent limitations.'') (citations and internal quotations omitted).
    There are many technology-based effluent limitations (TBELs) that
may apply to a discharger under the CWA: four types of standards
applicable to direct dischargers, two types of standards applicable to
indirect dischargers, and a default site-specific approach. The TBELs
relevant to this rulemaking are described in detail below.
1. Best Practicable Control Technology Currently Available
    Traditionally, EPA defines Best Practicable Control Technology
(BPT) effluent limitations based on the average of the best
performances of facilities within the industry, grouped to reflect
various ages, sizes, processes, or other common characteristics. EPA
may promulgate BPT effluent limitations for conventional, toxic, and
nonconventional pollutants. In specifying BPT, EPA looks at a number of
factors. EPA first considers the cost of achieving effluent reductions
in relation to the effluent reduction benefits. The agency also
considers the age of equipment and facilities, the processes employed,
engineering aspects of the control technologies, any required process
changes, non-water quality environmental impacts (including energy
requirements), and such other factors as the Administrator deems
appropriate. See CWA section 304(b)(1)(B), 33 U.S.C. 1314(b)(1)(B). If,
however, existing performance is uniformly inadequate, EPA may
establish limitations based on higher levels of control than what is
currently in place in an industrial category, when based on an agency
determination that the technology is available in another

category or subcategory and can be practicably applied.
2. Best Available Technology Economically Achievable
    BAT represents the second level of stringency for controlling
direct discharge of toxic and nonconventional pollutants. Courts have
referred to this as the CWA's ``gold standard'' for controlling
discharges from existing sources. Southwestern Elec. Power Co. v. EPA,
920 F.3d at 1003. In general, BAT represents the best available,
economically achievable performance of facilities in the industrial
subcategory or category. As the statutory phrase intends, EPA considers
the technological availability and the economic achievability in
determining what level of control represents BAT. CWA section
301(b)(2)(A), 33 U.S.C. 1311(b)(2)(A). Other statutory factors that EPA
considers in assessing BAT are the cost of achieving BAT effluent
reductions, the age of equipment and facilities involved, the process
employed, potential process changes, and non-water quality
environmental impacts, including energy requirements, and such other
factors as the Administrator deems appropriate. CWA section
304(b)(2)(B), 33 U.S.C. 1314(b)(2)(B). The agency retains considerable
discretion in assigning the weight to be accorded these factors.
Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1045 (D.C. Cir. 1978). EPA
usually determines economic achievability on the basis of the effect of
the cost of compliance with BAT limitations on overall industry and
subcategory financial conditions. BAT reflects 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. v. EPA, 920 F.3d at
1006; American Paper Inst. v. Train, 543 F.2d 328, 353 (D.C. Cir.
1976); American Frozen Food Inst. v. 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
American Frozen Foods, 539 F.2d at 132, 140; Reynolds Metals Co. v.
EPA, 760 F.2d 549, 562 (4th Cir. 1985); California & Hawaiian Sugar Co.
v. EPA, 553 F.2d 280, 285-88 (2nd Cir. 1977).
3. New Source Performance Standards
    New Source Performance Standards (NSPS) reflect effluent reductions
that are achievable based on the Best Available Demonstrated Control
Technology (BADCT). Owners of new facilities have the opportunity to
install the best and most efficient production processes and wastewater
treatment technologies. As a result, NSPS should represent the most
stringent controls attainable through the application of the BADCT for
all pollutants (that is, conventional, nonconventional, and toxic
pollutants). In establishing NSPS, EPA is directed to take into
consideration the cost of achieving the effluent reduction and any non-
water quality environmental impacts and energy requirements. CWA
section 306(b)(1)(B), 33 U.S.C. 1316(b)(1)(B).
4. Pretreatment Standards for Existing Sources
    Section 307(b), 33 U.S.C. 1317(b), of the Act calls for EPA to
issue pretreatment standards for discharges of pollutants to POTWs.
Pretreatment standards for existing sources (PSES) are designed to
prevent the discharge of pollutants that pass through, interfere with,
or are otherwise incompatible with the operation of POTWs. Categorical
pretreatment standards are technology-based and are analogous to BPT
and BAT effluent limitations guidelines, and thus the agency typically
considers the same factors in promulgating PSES as it considers in
promulgating BAT. The General Pretreatment Regulations, which set forth
the framework for the implementation of categorical pretreatment
standards, are found at 40 CFR part 403. These regulations establish
pretreatment standards that apply to all non-domestic dischargers. See
52 FR 1586 (January 14, 1987).
5. Pretreatment Standards for New Sources
    Section 307(c), 33 U.S.C. 1317(c), of the Act calls for EPA to
promulgate Pretreatment Standards for New Sources (PSNS). Such
pretreatment standards must prevent the discharge of any pollutant into
a POTW that may interfere with, pass through, or may otherwise be
incompatible with the POTW. EPA promulgates PSNS based on best
available demonstrated control technology (BADCT) for new sources. New
indirect dischargers have the opportunity to incorporate into their
facilities the best available demonstrated technologies. The agency
typically considers the same factors in promulgating PSNS as it
considers in promulgating NSPS.
6. Best Professional Judgment
    The CWA section 301 and its implementing regulation at 40 CFR
125.3(a) indicate that technology-based treatment requirements under
section 301(b) of the CWA represent the minimum level of control that
must be imposed in an NPDES permit. Where EPA-promulgated effluent
guidelines are not applicable to a non-POTW discharge, or where such
EPA-promulgated guidelines have been vacated by a court, such treatment
requirements are established on a case-by-case basis using the
permitting writer's best professional judgment (BPJ). Case-by-case
TBELs are developed pursuant to CWA section 402(a)(1), which authorizes
EPA Administrator to issue a permit that will meet either: all
applicable requirements developed under the authority of other sections
of the CWA (e.g., technology-based treatment standards, water quality
standards, ocean discharge criteria) or, before taking the necessary
implementing actions related to those requirements, ``such conditions
as the Administrator determines are necessary to carry out the
provisions of this Act.'' The regulation at 40 CFR 125.3(c)(2) cites
this section of the CWA, stating that technology-based treatment
requirements may be imposed in a permit ``on a case-by-case basis under
section 402(a)(1) of the Act, to the extent that EPA-promulgated
effluent limitations are inapplicable.'' Further, section 125.3(c)(3)
indicates, ``[w]here promulgated effluent limitations guidelines only
apply to certain aspects of the discharger's operation, or to certain
pollutants, other aspects or activities are subject to regulation on a
case-by-case basis in order to carry out the provisions of the Act.''
The factors considered by the permit writer are the same. See 40 CFR
125.3(d)(1)-(3).

C. 2015 Steam Electric Power Generation Point Source Category Rule

1. Final Rule Requirements
    On September 30, 2015, EPA promulgated a rule revising the
regulations for the Steam Electric Power Generating point source
category (40 CFR part 423) (hereinafter the ``2015 rule''). The rule
set the first Federal limitations on the levels of toxic metals that
can be discharged in the steam electric industry's largest sources of
wastewater, based on technology improvements in the steam electric
power industry over the preceding three decades. Before the 2015 rule,
regulations for the industry were last updated in 1982.
    Over the last 30 years, new technologies for generating electric
power and the widespread implementation of air pollution controls

have altered existing wastewater streams or created new wastewater
streams at many steam electric facilities, particularly coal-fired
facilities. Discharges of these wastestreams include arsenic, lead,
mercury, selenium, chromium, and cadmium. Once in the environment, many
of these toxic pollutants can remain there for years and continue to
cause impacts.
    The 2015 rule addressed effluent limitations and standards for
multiple wastestreams generated by new and existing steam electric
facilities: BA transport water, CRL, FGD wastewater, FGMC wastewater,
FA transport water, gasification wastewater, and legacy wastewater. The
rule required most steam electric facilities to comply with the
effluent limitations ``as soon as possible'' after November 1, 2018,
and no later than December 31, 2023. NPDES permitting authorities
established 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 was projected to reduce the amount of metals defined
in the CWA as toxic pollutants, nutrients, and other pollutants that
steam electric facilities are allowed to discharge by 1.4 billion
pounds per year and reduce water withdrawal by 57 billion gallons. At
the time, EPA estimated annual compliance costs for the final rule to
be $480 million (in 2013 dollars) and estimated benefits associated
with the rule to be $451 to $566 million (in 2013 dollars).
2. Vacatur of Limitations Applicable to CRL and Legacy Wastewater
    Seven petitions for review of the 2015 rule were filed in various
circuit courts by the electric utility industry, environmental groups,
and drinking water utilities. These petitions were consolidated in the
U.S. Court of Appeals for the Fifth Circuit, Southwestern Electric
Power Co. v. EPA, Case No. 15-60821 (5th Cir.). On March 24, 2017, the
Utility Water Act Group submitted to EPA an administrative petition for
reconsideration of the 2015 rule. On April 5, 2017, the Small Business
Administration (SBA) submitted an administrative petition for
reconsideration of the 2015 rule.
    On August 11, 2017, the Administrator announced his decision to
conduct a rulemaking to potentially revise the new, more stringent BAT
effluent limitations and pretreatment standards for existing sources in
the 2015 rule that apply to FGD wastewater and BA transport water. The
Fifth Circuit subsequently granted EPA's request to sever and hold in
abeyance petitioners' claims related to those limitations and
standards, and those claims are still in abeyance. With respect to the
remaining claims related to limitations applicable to legacy wastewater
and CRL, the Fifth Circuit issued a decision on April 12, 2019,
vacating those limitations as arbitrary and capricious under the
Administrative Procedure Act and unlawful under the CWA, respectively.
Southwestern Elec. Power Co. v. EPA, 920 F.3d 999. In particular, the
Court rejected EPA's attempts to set BAT limitations for each
wastestream equal to previously promulgated BPT limitations based on
surface impoundments. In the case of legacy wastewater, the Court held
that EPA's record on surface impoundments did not support BAT
limitations based on surface impoundments. Id. At 1015. In the case of
CRL, the Court held that EPA's setting of BAT limitations equal to BPT
limitations was an impermissible conflation of the two standards, which
are supposed to be progressively more stringent, and that EPA's
rationale was not authorized by the statutory factors for determining
BAT. Id. At 1026. After the Court's decision, EPA announced its plans
to address the vacated limitations in a later action after the 2020
rule.
    In September 2017, using notice-and-comment procedures, EPA
finalized a rule (``postponement rule'') postponing the earliest
compliance dates for the more stringent BAT effluent limitations and
PSES for FGD wastewater and BA transport water in the 2015 rule, from
November 1, 2018, to November 1, 2020. EPA also withdrew a prior action
it had taken to stay parts of the 2015 rule pursuant to Section 705 of
the Administrative Procedure Act, 5 U.S.C. 705. The postponement rule
received multiple legal challenges, but EPA prevailed, and the courts
did not sustain any of them.\3\
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    \3\ See Center for Biological Diversity v. EPA, No. 18-cv-00050
(D. Ariz. filed January 20, 2018); see also Clean Water Action. v.
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.
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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.\4\ 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.
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    \4\ The 2015 rule's VIP compliance date was revised to December
31, 2028, in the 2020 rule.
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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. v. 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.\5\ 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.
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    \5\ 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.\6\ 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.
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    \6\ Available online at: www.epa.gov/system/files/documents/2021-09/ow-prelim-elg-plan-15_508.pdf.
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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 v. EPA, 901 F.3d 414 (D.C. Cir. 2018), and
Waterkeeper Alliance Inc. et al. v. 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 v. 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 (NOX) 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 NOX 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 NOX budgets for EGUs in those 25 states, beginning in
2023. Further information about this proposal is available on EPA's
website.\7\
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    \7\ See www.epa.gov/csapr/good-neighbor-plan-2015-ozone-naaqs.
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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 CO2 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 v. 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).\8\ 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.
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    \8\ See www.epa.gov/newsreleases/epa-reexamine-health-standards-harmful-soot-previous-administration-left-unchanged.
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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.\9\ 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.
---------------------------------------------------------------------------

    \9\ 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.\10\ 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.
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    \10\ See www.whitehouse.gov/ceq/news-updates/2021/12/13/icymi-president-biden-signs-executive-order-catalyzing-americas-clean-energy-economy-through-federal-sustainability/.
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    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.\11\ 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.\12\
---------------------------------------------------------------------------

    \11\ See www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions.
    \12\ 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.
    \13\ Total emissions in 2020 = 5,981 million metric tons of
CO2 equivalent. Percentages may not add up to 100 percent
due to independent rounding.
    \14\ 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.
[GRAPHIC] [TIFF OMITTED] TP29MR23.059

    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.\15\ Thus, the DOE analysis
suggests the IRA may reduce the number of coal burning power plants in
operation.
---------------------------------------------------------------------------

    \15\ 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.\16\
These impoundments must be large enough to accommodate extreme
precipitation events to prevent overtopping and runoff.
---------------------------------------------------------------------------

    \16\ 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.\17\ 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:
---------------------------------------------------------------------------

    \17\ 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).\18\
---------------------------------------------------------------------------

    \18\ 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.\19\ 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).
---------------------------------------------------------------------------

    \19\ 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
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Technology Basis for the BAT/PSES Regulatory Options
            Wastestream                    Subcategory      --------------------------------------------------------------------------------------------
                                                                        1                      2                3 (Preferred)                4
--------------------------------------------------------------------------------------------------------------------------------------------------------
FGD wastewater.....................  N/A...................  Chemical precipitation  Chemical               Chemical               Chemical
                                                              + biological            precipitation +        precipitation +        precipitation +
                                                              treatment +             membrane filtration.   membrane filtration.   membrane filtration.
                                                              ultrafiltration.
                                     High FGD flow           NS....................  NS...................  NS...................  NS.
                                      facilities/LUEGUs.
                                     EGUs permanently        Surface impoundments..  Surface impoundments.  Surface impoundments.  Surface impoundments.
                                      ceasing coal
                                      combustion by 2028.
                                     Early adopters          NS....................  Chemical               Chemical               NS.
                                      permanently ceasing                             precipitation +        precipitation +
                                      coal combustion by                              biological treatment   biological treatment
                                      2032.                                           + ultrafiltration.     + ultrafiltration.
BA transport water.................  N/A...................  High recycle rate       High recycle rate      Dry handling or        Dry handling or
                                                              systems.                systems.               closed-loop systems.   closed-loop systems.
                                     LUEGUs................  NS....................  NS...................  NS...................  NS.
                                     EGUs permanently        Surface impoundments..  Surface impoundments.  Surface impoundments.  Surface impoundments.
                                      ceasing coal
                                      combustion by 2028.
                                     Early adopters          NS....................  NS...................  High recycle rate      NS.
                                      permanently ceasing                                                    systems.
                                      coal combustion by
                                      2032.
CRL................................  N/A...................  Chemical precipitation  Chemical               Chemical               Chemical
                                                                                precipitation.         precipitation.         precipitation.
Legacy wastewater..................  N/A...................  Best professional       Best professional      Best professional      Best professional
                                                              judgment.               judgment.              judgment.              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.\20\
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    \20\ 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.
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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.\21\
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    \21\ 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.''
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    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 v. 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. v. EPA, 920 F.3d at 1006; Am. Paper Inst.
v. Train, 543 F.2d 328, 353 (D.C. Cir. 1976); Am. Frozen Food Inst. v.
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. v. EPA, 760 F.2d 549, 562 (4th Cir. 1985);
California & Hawaiian Sugar Co. v. 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. v. 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 v. EPA, 780 F.2d. at 447; Southwestern Elec. Power Co. v.
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,\22\
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 v. Fox
Television Stations, Inc., 556 U.S. 502, 515 (2009); Motor Vehicle
Mfrs. Ass'n v. 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.\23\
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    \22\ Caselaw supports that EPA may base BAT on technologies used
in other industries. See, e.g., Kennecott v. 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.'').
    \23\ 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 v. 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).
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    International installations. At the time of the 2020 rule, the
Agency cited 12 foreign installations of membrane filtration on FGD
wastewater.\24\ These systems began operating as early as 2015, and all
of the systems were designed to operate as zero discharge systems.\25\
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.\26\ 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.\27\
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    \24\ 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.
    \25\ Technologies for the Treatment of Flue Gas Desulfurization
Wastewater, Coal Combustion Residual Leachate, and Pond Dewatering
(SE10281).
    \26\ SE06915.
    \27\ SE08618.
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    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.\28\ 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.
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    \28\ SE10245.
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    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).\29\
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.\30\ 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.
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    \29\ 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.
    \30\ 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.
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    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,\31\ cooling tower

blowdown,\32\ and ash transport water.\33\ Other industrial sectors
with full-scale membrane filtration applications include the
textiles,\34\ chemical manufacturing,\35\ mining,\36\ agriculture, oil
and gas extraction,\37\ food and beverage,\38\ microelectronics/
semiconductors,\39\ landfills,\40\ and automotive industries.\41\
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    \31\ EPRI (Electric Power Research Institute). 2015. State of
Knowledge: Power Plant Wastewater Treatment--Membrane Technologies.
August.<PHONE_NUMBER>.
    \32\ 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).
    \33\ See, e.g., www.ge.com/in/sites/www.ge.com.in/files/GE_solves_ash%20pond_capacity_issue.pdf (DCN SE09090).
    \34\ ERG. 2020 Final Notes from Call with DuPont. DCN SE08618.
    \35\ ERG. 2020. Final Notes from Call with DuPont. DCN SE08618.
    \36\ 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.
    \37\ CH2M Hill. 2010. Review of Available Technologies for the
Removal of Selenium from Water. (June). DCN SE08583.
    \38\ U.S. EPA. 2022. Notes from Meeting with BKT--April 9, 2021.
DCN SE010253.
    \39\ U.S. EPA. 2022. Notes from Meeting with BKT--April 9, 2021.
DCN SE010253.
    \40\ ERG. 2019. Sanitized_Saltworks Vendor Meeting Notes--Final.
DCN SE07089.