[Federal Register Volume 80, Number 212 (Tuesday, November 3, 2015)]
[Rules and Regulations]
[Pages 67837-67903]
[FR Doc No: 2015-25663]

Vol. 80

Tuesday,

No. 212

November 3, 2015

Part II

Environmental Protection Agency

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40 CFR Part 423

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

Federal Register / Vol. 80 , No. 212 / Tuesday, November 3, 2015 /
Rules and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 423

[EPA-HQ-OW-2009-0819; FRL-9930-48-OW]
RIN 2040-AF14

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

AGENCY: Environmental Protection Agency.

ACTION: Final rule.

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SUMMARY: This final rule, promulgated under the Clean Water Act (CWA),
protects public health and the environment from toxic metals and other
harmful pollutants, including nutrients, by strengthening the
technology-based effluent limitations guidelines and standards (ELGs)
for the steam electric power generating industry. Steam electric power
plants contribute the greatest amount of all toxic pollutants
discharged to surface waters by industrial categories regulated under
the CWA. The pollutants discharged by this industry can cause severe
health and environmental problems in the form of cancer and non-cancer
risks in humans, lowered IQ among children, and deformities and
reproductive harm in fish and wildlife. Many of these pollutants, once
in the environment, remain there for years. Due to their close
proximity to these discharges and relatively high consumption of fish,
some minority and low-income communities have greater exposure to, and
are therefore at greater risk from, pollutants in steam electric power
plant discharges. The final rule establishes the first nationally
applicable limits on the amount of toxic metals and other harmful
pollutants that steam electric power plants are allowed to discharge in
several of their largest sources of wastewater. On an annual basis, the
rule reduces the amount of toxic metals, nutrients, and other
pollutants that steam electric power plants are allowed to discharge by
1.4 billion pounds; it reduces water withdrawal by 57 billion gallons;
and, it has social costs of $480 million and monetized benefits of $451
to $566 million.

DATES: The final rule is effective on January 4, 2016. In accordance
with 40 CFR part 23, this regulation shall be considered issued for
purposes of judicial review at 1 p.m. Eastern time on November 17,
2015. Under section 509(b)(1) of the CWA, judicial review of this
regulation can be had only by filing a petition for review in the U.S.
Court of Appeals within 120 days after the regulation is considered
issued for purposes of judicial review. Under section 509(b)(2), the
requirements in this regulation may not be challenged later in civil or
criminal proceedings brought by EPA to enforce these requirements.

ADDRESSES: Docket: All documents in the docket are listed in the http://www.regulations.gov index. A detailed record index, organized by
subject, is available on EPA's Web site at http://www2.epa.gov/eg/steam-electric-power-generating-effluent-guidelines-2015-final-rule.
Although listed in the index, some information is not publicly
available, e.g., Confidential Business Information (CBI) or other
information whose disclosure is restricted by statute. Certain other
material, such as copyrighted material, will be publicly available only
in hard copy. Publicly available docket materials are available either
electronically in http://www.regulations.gov or in hard copy at the
Water Docket in the EPA Docket Center, EPA/DC, EPA West, Room 3334,
1301 Constitution Ave. NW., Washington, DC. The Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Public Reading Room is
202-566-1744, and the telephone number for the Water Docket is 202-566-
2426.

FOR FURTHER INFORMATION CONTACT: For technical information, contact
Ronald Jordan, Engineering and Analysis Division, Telephone: 202-566-
1003; Email<EMAIL_ADDRESS>For economic information, contact
James Covington, Engineering and Analysis Division, Telephone: 202-566-
1034; Email<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Organization of This Preamble

Table of Contents

I. Regulated Entities and Supporting Documentation
    A. Regulated Entities
    B. Supporting Documentation
II. Legal Authority for This Action
III. Executive Summary
    A. Purpose of the Rule
    B. Summary of Final Rule
    C. Summary of Costs and Benefits
IV. Background
    A. Clean Water Act
    B. Effluent Guidelines Program
    1. Best Practicable Control Technology Currently Available
    2. Best Conventional Pollutant Control Technology
    3. Best Available Technology Economically Achievable
    4. Best Available Demonstrated Control Technology/New Source
Performance Standards
    5. Pretreatment Standards for Existing Sources
    6. Pretreatment Standards for New Sources
    C. Steam Electric Effluent Guidelines Rulemaking History
V. Key Updates Since Proposal
    A. Industry Profile Changes Due to Retirements and Conversions
    B. EPA Consideration of Other Federal Rules
    C. Advancements in Technologies
    D. Engineering Costs
    E. Economic Impact Analysis
    F. Pollutant Data
    G. Environmental Assessment Models
VI. Industry Description
    A. General Description of Industry
    B. Steam Electric Process Wastewater and Control Technologies
    1. FGD Wastewater
    2. Fly Ash Transport Water
    3. Bottom Ash Transport Water
    4. FGMC Wastewater
    5. Combustion Residual Leachate From Landfills and Surface
Impoundments
    6. Gasification Wastewater
VII. Selection of Regulated Pollutants
    A. Identifying the Pollutants of Concern
    B. Selection of Pollutants for Regulation Under BAT/NSPS
    C. Methodology for the POTW Pass-Through Analysis (PSES/PSNS)
VIII. The Final Rule
    A. BPT
    B. BAT/NSPS/PSES/PSNS Options
    1. FGD Wastewater
    2. Fly Ash Transport Water
    3. Bottom Ash Transport Water
    4. FGMC Wastewater
    5. Gasification Wastewater
    6. Combustion Residual Leachate
    7. Non-Chemical Metal Cleaning Wastes
    C. Best Available Technology
    1. FGD Wastewater
    2. Fly Ash Transport Water
    3. Bottom Ash Transport Water
    4. FGMC Wastewater
    5. Gasification Wastewater
    6. Combustion Residual Leachate
    7. Timing
    8. Legacy Wastewater
    9. Economic Achievability
    10. Non-Water Quality Environmental Impacts, Including Energy
Requirements
    11. Impacts on Residential Electricity Prices and Low-Income and
Minority Populations
    12. Existing Oil-Fired and Small Generating Units
    13. Voluntary Incentives Program
    D. Best Available Demonstrated Control Technology/NSPS
    E. PSES
    F. PSNS
    G. Anti-Circumvention Provision
    H. Other Revisions
    1. Correction of Typographical Error for PSNS
    2. Clarification of Applicability
    I. Non-Chemical Metal Cleaning Wastes
    J. Best Management Practices
IX. Costs and Economic Impact
    A. Plant-Specific and Industry Total Costs

    B. Social Costs
    C. Economic Impacts
    1. Summary of Economic Impacts for Existing Sources
    2. Summary of Economic Impacts for New Sources
X. Pollutant Reductions
XI. Development of Effluent Limitations and Standards
XII. Non-Water Quality Environmental Impacts
XIII. Environmental Assessment
    A. Introduction
    B. Summary of Human Health and Environmental Impacts
    C. Environmental Assessment Methodology
    D. Outputs From the Environmental Assessment
    1. Improvements in Surface Water and Ground Water Quality
    2. Reduced Impacts to Wildlife
    3. Reduced Human Health Cancer Risk
    4. Reduced Threat of Non-Cancer Human Health Effects
    5. Reduced Nutrient Impacts
    E. Unquantified Environmental and Human Health Improvements
    F. Other Secondary Improvements
XIV. Benefit Analysis
    A. Categories of Benefits Analyzed
    B. Quantification and Monetization of Benefits
    1. Human Health Benefits From Surface Water Quality Improvements
    2. Improved Ecological Conditions and Recreational Use Benefits
From Surface Water Quality Improvements
    3. Market and Productivity Benefits
    4. Air-Related Benefits (Human Health and Avoided Climate Change
Impacts)
    5. Benefits From Reduced Water Withdrawals (Increased
Availability of Ground Water Resources)
    C. Total Monetized Benefits
    D. Other Benefits
XV. Cost-Effectiveness Analysis
    A. Methodology
    B. Results
XVI. Regulatory Implementation
    A. Implementation of the Limitations and Standards
    1. Timing
    2. Applicability of NSPS/PSNS
    3. Legacy Wastewater
    4. Combined Wastestreams
    5. Non-Chemical Metal Cleaning Wastes
    B. Upset and Bypass Provisions
    C. Variances and Modifications
    1. Fundamentally Different Factors Variance
    2. Economic Variances
    3. Water Quality Variances
    4. Removal Credits
    D. Site-Specific Water Quality-Based Effluent Limitations
XVII. Related Acts of Congress, Executive Orders, and Agency
Initiatives
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act (CRA)
Appendix A to the Preamble: Definitions, Acronyms, and Abbreviations
Used in This Preamble

I. Regulated Entities and Supporting Documentation

A. Regulated Entities

    Entities potentially regulated by this action include:

------------------------------------------------------------------------
                                                         North American
                                                            Industry
           Category              Example of regulated    Classification
                                        entity           System (NAICS)
                                                              Code
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Industry......................  Electric Power          22111
                                 Generation
                                 Facilities--Electric
                                 Power Generation.
                                Electric Power          221112
                                 Generation
                                 Facilities--Fossil
                                 Fuel Electric Power
                                 Generation.
                                Electric Power          221113
                                 Generation
                                 Facilities--Nuclear
                                 Electric Power
                                 Generation.
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    This section is not intended to be exhaustive, but rather provides
a guide for readers regarding entities likely regulated by 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 this
action, you should carefully examine the applicability criteria listed
in 40 CFR 423.10 and the definitions in 40 CFR 423.11 of the rule. If
you still have questions regarding the applicability of this action to
a particular entity, consult the person listed for technical
information in the preceding FOR FURTHER INFORMATION CONTACT section.

B. Supporting Documentation

    This rule is supported, in part, by the following documents:
     Technical Development Document for the Effluent
Limitations Guidelines and Standards for the Steam Electric Power
Generating Point Source Category (TDD), Document No. EPA-821-R-15-007.
     Environmental Assessment for the Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point
Source Category (EA), Document No. EPA-821-R-15-006.
     Benefits and Cost Analysis for the Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point
Source Category (BCA), Document No. EPA-821-R-15-005.
     Regulatory Impact Analysis for the Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point
Source Category (RIA), Document No. EPA-821-R-15-004.

These documents are available in the public record for this rule and on
EPA's Web site at http://www2.epa.gov/eg/steam-electric-power-generating-effluent-guidelines-2015-final-rule.

II. Legal Authority for This Action

    EPA promulgates this rule under the authority of sections 301, 304,
306, 307, 308, 402, and 501 of the CWA, 33 U.S.C. 1311, 1314, 1316,
1317, 1318, 1342, and 1361.

III. Executive Summary

A. Purpose of the Rule

    Steam electric power plants \1\ discharge large wastewater volumes,
containing vast quantities of pollutants, into waters of the United
States. The pollutants include both toxic and bioaccumulative
pollutants such as arsenic, mercury, selenium, chromium, and cadmium.
Today, these discharges account for about 30 percent of all toxic
pollutants discharged into surface

waters by all industrial categories regulated under the CWA.\2\ The
electric power industry has made great strides to reduce air pollutant
emissions under Clean Air Act programs. Yet many of these pollutants
are transferred to the wastewater as plants employ technologies to
reduce air pollution. The pollutants in steam electric power plant
wastewater discharges present a serious public health concern and cause
severe ecological damage, as demonstrated by numerous documented
impacts, scientific modeling, and other studies. When toxic metals such
as mercury, arsenic, lead, and selenium accumulate in fish or
contaminate drinking water, they can cause adverse effects in people
who consume the fish or water. These effects can include cancer,
cardiovascular disease, neurological disorders, kidney and liver
damage, and lowered IQs in children.
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    \1\ The steam electric power plants covered by the ELGs use
nuclear or fossil fuels, such as coal, oil, or natural gas, to heat
water in boilers, which generate steam. This rule does not apply to
plants that use non-fossil fuel or non-nuclear fuel or other energy
sources, such as biomass or solar thermal energy. The steam is used
to drive turbines connected to electric generators. The plants
generate wastewater composed of chemical pollutants and thermal
pollution (heated water) from their wastewater treatment, power
cycle, ash handling and air pollution control systems, as well as
from coal piles, yard and floor drainage, and other plant processes.
    \2\ Although the way electricity is generated in this country is
changing, EPA projects that, without this final rule, steam electric
power plant discharges would likely continue to account, over the
foreseeable future, for about thirty percent of all toxic pollutants
discharged into surface waters by all industrial categories
regulated under the CWA.
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    There are, however, affordable technologies that are widely
available, and already in place at some plants, which are capable of
reducing or eliminating steam electric power plant discharges. In the
several decades since the steam electric ELGs were last revised, such
technologies have increasingly been used at plants. This final rule is
the first to ensure that plants in the steam electric industry employ
technologies designed to reduce discharges of toxic metals and other
harmful pollutants discharged in the plants' largest sources of
wastewater.
    Steam electric power plant discharges occur in proximity to nearly
100 public drinking water intakes and more than 1,500 public wells
across the nation, and recent studies indicate that steam electric
power plant discharges can adversely affect surface waters used as
drinking water supplies. One study found that arsenic in ash and flue
gas desulfurization (FGD) wastewater discharges from four steam
electric power plants exceeded Safe Drinking Water Act (SDWA) Maximum
Contaminant Levels (MCLS) in the waterbodies into which they
discharged, indicating that these contaminants are present in surface
waters, and at levels above standards used to protect drinking water.
See DCN SE01984. A second, more recent study found increased levels of
bromide in rivers used as drinking water after FGD systems were
installed at upstream steam electric power plants. The study showed an
increase in bromides at four drinking water utilities' intakes after
wastewater from these FGD systems began to be discharged to the rivers,
whereas prior to the FGD wastewater discharges, bromides were not a
problem in the intake waters of the utilities. With bromides present in
their drinking water source waters at increased levels, carcinogenic
disinfection by-products (brominated DBPs, in particular
trihalomethanes (THMs)) began forming, and at one drinking water
utility, violations of the THM MCL began occurring. See DCN SE04503.
    Nitrogen discharged by steam electric power plants can also impact
drinking water sources by contributing to harmful algal blooms in
reservoirs and lakes that are used as drinking water sources. Ground
water contamination from surface impoundments (ash ponds) containing
steam electric power plant wastewater also threatens drinking water, as
evidenced by more than 30 documented cases. See EA Section 3.3.
    Steam electric power plant discharges also adversely affect the
quality of fish that people eat. Water quality modeling shows that
about half of waterbodies that receive steam electric power plant
discharges exhibit health risks to people consuming fish from those
waters (primarily from mercury). Nearly half of waterbodies that
receive steam electric power plant discharges exhibit pollutant levels
for one or more steam electric power plant pollutants in excess of
human health water quality criteria (WQC).\3\ See EA Section 4. People
who eat large amounts of fish from lakes and rivers contaminated by
mercury, lead, and arsenic are particularly at risk, and consumption of
such fish poses additional risk to the fetuses of pregnant women.
Compared to the general public, minority and low-income communities
have greater exposure to, and are therefore at greater risk from,
pollutants in steam electric power plant discharges, due to their
closer proximity to the discharges and greater consumption of fish from
contaminated waters. See Section XVII.J.
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    \3\ WQCs are established by states to protect beneficial uses of
waterbodies, such as the support of aquatic life and provision of
fishing and swimming.
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    Steam electric power plant discharges adversely affect our nation's
waters and their ecology. Pollutants in such discharges, particularly
mercury and selenium, bioaccumulate in fish and wildlife, and they
accumulate in the sediments of lakes and reservoirs, remaining there
for decades. Documented adverse impacts include the near eradication of
an entire fish population in the late 1970s in Belews Lake, North
Carolina, due to selenium discharges from a steam electric power plant
(DCN SE01842); a series of fish kills in the 1970s in Martin Lake,
Texas, also due to selenium discharges from a steam electric power
plant (elevated selenium levels and deformities persisted for at least
eight years after the plant ceased discharging) (DCN SE01861);
reproductive impairment and deformities in fish and birds from selenium
discharges (DCN SE04519); and other forms of impacts to surface waters,
as documented by numerous other damage cases associated with discharges
from surface impoundments containing steam electric power plant
wastewater. See EA Section 3.3.
    Waterbodies receiving steam electric power plant discharges have
routinely exhibited pollutant levels routinely in excess of state WQC
for pollutants found in the plant discharges. This includes pollutants
such as selenium, arsenic, and cadmium. Nutrients in steam electric
power plant discharges can cause over-enrichment of receiving waters,
resulting in water quality problems, such as low oxygen levels and loss
of critical submerged aquatic vegetation, further impairing beneficial
uses such as fishing. EPA's modeling corroborates such documented
impacts, revealing that nearly one fifth of waterbodies receiving steam
electric power plant discharges exceed WQC for protection of aquatic
life and nearly one third of such receiving waters pose potential
reproductive risks to birds that prey on fish.
    The steam electric ELGs that EPA promulgated and revised in 1974,
1977, and 1982 are out of date. They do not adequately control the
pollutants (toxic metals and other) discharged by this industry, nor do
they reflect relevant process and technology advances that have
occurred in the last 30-plus years. The rise of new processes for
generating electric power (e.g. coal gasification) and the widespread
implementation of air pollution controls (e.g., FGD and flue gas
mercury control (FGMC)) have altered existing wastestreams and created
new types of wastewater at many steam electric power plants,
particularly coal-fired plants. The processes employed and pollutants
discharged by the industry look very different today than they did in
1982. Many plants, nonetheless, still treat their wastewater using only
surface impoundments, which are largely ineffective at controlling
discharges of toxic pollutants and nutrients. This final rule addresses
an outstanding public health and environmental problem by

revising the steam electric ELGs, as they apply to a subset of power
plants that discharge wastestreams containing toxic and other
pollutants. As the CWA requires, this rule is economically achievable
(affordable for the industry as a whole) and is based on available
technologies. On an annual basis, the rule is projected to reduce the
amount of toxic metals, nutrients, and other pollutants that steam
electric power plants are allowed to discharge by 1.4 billion pounds;
reduce water withdrawal by 57 billion gallons; and, it has estimated
social costs of $480 million. Finally, of the benefits that were able
to be monetized, EPA projects $451 to $566 million in benefits
associated with this rule.

B. Summary of Final Rule

    To further its ultimate objective to ``restore and maintain the
chemical, physical, and biological integrity of the Nation's waters,''
the CWA authorizes EPA to establish national technology-based effluent
limitations guidelines and new source performance standards for
discharges from categories of point sources that occur directly into
waters of the U.S. The CWA also authorizes EPA to promulgate nationally
applicable pretreatment standards that control pollutant discharges
from existing and new sources that discharge wastewater indirectly to
waters of the U.S. through sewers flowing to publicly owned treatment
works (POTWs). EPA establishes ELGs based on the performance of well-
designed and well-operated control and treatment technologies.
    EPA completed a study of the steam electric category in 2009 and
proposed the ELG rule in June 2013. The public comment period extended
for more than three months. This final rule reflects the statutory
factors outlined in the CWA, as well as EPA's full consideration of the
comments received and updated analytical results.
    Existing Sources--Direct Discharges. For existing sources that
discharge directly to surface water, with the exception of oil-fired
generating units and small generating units (those with a nameplate
capacity of 50 megawatts (MW) or less), the final rule establishes
effluent limitations based on Best Available Technology Economically
Achievable (BAT). BAT is based on technological availability, economic
achievability, and other statutory factors and is intended to reflect
the highest performance in the industry (see Section IV.B.3). The final
rule establishes BAT limitations as follows: \4\
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    \4\ For details on when the following BAT limitations apply, see
Section VIII.C.
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     For fly ash transport water, bottom ash transport water,
and FGMC wastewater, there are two sets of BAT limitations. The first
set of BAT limitations is a numeric effluent limitation on Total
Suspended Solids (TSS) in the discharge of these wastewaters (these
limitations are equal to the TSS limitations in the previously
established Best Practicable Control Technology Currently Available
(BPT) regulations). The second set of BAT limitations is a zero
discharge limitation for all pollutants in these wastewaters.\5\
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    \5\ When fly ash transport water or bottom ash transport water
is used in the FGD scrubber, the applicable limitations are those
established for FGD wastewater on mercury, arsenic, selenium and
nitrate/nitrite as N.
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     For FGD wastewater, there are two sets of BAT limitations.
The first set of limitations is a numeric effluent limitation on TSS in
the discharge of FGD wastewater (these limitations are equal to the TSS
limitations in the previously established BPT regulations). The second
set of BAT limitations is numeric effluent limitations on mercury,
arsenic, selenium, and nitrate/nitrite as N in the discharge of FGD
wastewater.\6\
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    \6\ For plants that opt into the voluntary incentives program,
the second set of BAT limitations is numeric effluent limitations on
mercury, arsenic, selenium, and TDS in the discharge of FGD
wastewater.
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     For gasification wastewater, there are two sets of BAT
limitations. The first set of limitations is a numeric effluent
limitation on TSS in the discharge of gasification wastewater (this
limitation is equal to the TSS limitation in the previously established
BPT regulations). The second set of BAT limitations is numeric effluent
limitations on mercury, arsenic, selenium, and total dissolved solids
(TDS) in the discharge of gasification wastewater.
     A numeric effluent limitation on TSS in the discharge of
combustion residual leachate from landfills and surface impoundments.
This limitation is equal to the TSS limitation in the previously
established BPT regulations.
    For oil-fired generating units and small generating units (50 MW or
smaller), the final rule establishes BAT limitations on TSS in the
discharge of fly ash transport water, bottom ash transport water, FGMC
wastewater, FGD wastewater, and gasification wastewater. These
limitations are equal to the TSS limitations in the existing BPT
regulations.
    New Sources--Direct Discharges. The CWA mandates that new source
performance standards (NSPS) reflect the greatest degree of effluent
reduction that is achievable, including, where practicable, a standard
permitting no discharge of pollutants (see Section IV.B.4). NSPS
represent the most stringent controls attainable, taking into
consideration the cost of achieving the effluent reduction and any non-
water quality environmental impacts and energy requirements. For direct
discharges to surface waters from new sources, including discharges
from oil-fired generating units and small generating units, the final
rule establishes NSPS as follows:
     A zero discharge standard for all pollutants in fly ash
transport water, bottom ash transport water, and FGMC wastewater.
     Numeric standards on mercury, arsenic, selenium, and TDS
in the discharge of FGD wastewater.
     Numeric standards on mercury and arsenic in the discharge
of combustion residual leachate.
    Existing Sources--Discharges 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. PSES are analogous to BAT
effluent limitations for direct dischargers and are generally based on
the same factors (see Section IV.B.5). The final rule establishes PSES
as follows: \7\
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    \7\ For details on when PSES apply, see Section VIII.E.
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     A zero discharge standard for all pollutants in fly ash
transport water, bottom ash transport water, and FGMC wastewater.\8\
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    \8\ When fly ash transport water or bottom ash transport water
is used in the FGD scrubber, the applicable standards are those
established for FGD wastewater on mercury, arsenic, selenium and
nitrate/nitrite as N.
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     Numeric standards on mercury, arsenic, selenium, and
nitrate/nitrite as N in the discharge of FGD wastewater.
     Numeric standards on mercury, arsenic, selenium and TDS in
the discharge of gasification wastewater.
    New Sources--Discharges to POTWs. Pretreatment standards for new
sources (PSNS) are also designed to prevent the discharge of any
pollutant into a POTW that interferes with, passes through, or is
otherwise incompatible with the POTW. PSNS are analogous to NSPS for
direct dischargers, and EPA generally considers the same factors for
both sets of standards (see Section IV.B.6). The final rule establishes
PSNS that are the same as the rule's NSPS.

C. Summary of Costs and Benefits

    Table III-1 summarizes the benefits and social costs for the final
rule, at three percent and seven percent discount rates. EPA's analysis
reflects the Agency's understanding of the actions steam electric power
plants will take to meet the limitations and standards in the final
rule. EPA based its analysis on a baseline that reflects the expected
impacts of other environmental regulations affecting steam electric
power plants, such as the Clean Power Plan (CPP) rule that the Agency
finalized in July 2015 (as well as other relevant rules such as the
Coal Combustion Residuals (CCR) rule that the Agency promulgated in
April 2015). EPA understands that these modeled results have
uncertainty due to the possibility of unexpected implementation
approaches and thus that the actual costs could be somewhat higher or
lower than estimated. The current estimate reflects the best data and
analysis available at this time. In this preamble, EPA presents costs
and monetized benefits accounting for these other rules.\9\ Under this
final rule, EPA estimates that about 12 percent of steam electric power
plants and 28 percent of coal-fired or petroleum coke-fired power
plants will incur some costs.\10\ For additional information, see
Sections V and IX.
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    \10\ EPA estimates that the population of steam electric power
plants is about 1080.

                  Table III-1--Total Monetized Annualized Benefits and Costs of the Final Rule
                                                [Millions; 2013$]
----------------------------------------------------------------------------------------------------------------
                                               Total monetized social benefits         Total social costs
                Discount rate                -------------------------------------------------------------------
                                                     3%               7%               3%               7%
----------------------------------------------------------------------------------------------------------------
Final Rule..................................    $451 to $566     $387 to $478             $480             $471
----------------------------------------------------------------------------------------------------------------

    The remainder of this preamble is structured as follows. Section IV
provides additional background on the CWA and the ELG program. Section
V outlines key updates since the proposal, including updates to the
industry profile, estimated costs and economic impacts, and pollutant
data. Section VI gives an overview of the industry, and Section VII
reviews the identification and selection of the regulated pollutants.
Section VIII describes the final rule requirements, along with the
bases for EPA's decisions. Section IX presents the costs and economic
impacts, while Section X shows the accompanying pollutant reductions.
Section XI presents the numeric limitations and standards for existing
and new sources that are established in this final rule. Sections XII
through XIV explain the non-water quality environmental impacts
(including energy requirements), the environmental assessment, and the
resulting benefits analysis. Section XV presents results of the cost-
effectiveness analysis, and Section XVI provides information regarding
implementation of the rule.

IV. Background

A. Clean Water Act

    Congress passed the CWA to ``restore and maintain the chemical,
physical, and biological integrity of the Nation's waters.'' 33 U.S.C.
1251(a). In order to achieve this objective, the Act has, as a national
goal, the elimination of the discharge of all pollutants into the
nation's waters. 33 U.S.C. 1251(a)(1). 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 U.S., except as authorized under the CWA.
Under section 402 of the CWA, 33 U.S.C. 1342, discharges may be
authorized through a National Pollutant Discharge Elimination System
(NPDES) permit. The CWA establishes a dual approach for these permits,
technology-based controls that establish a floor of performance for all
dischargers, and water quality-based effluent limitations, where the
technology-based effluent limitations are insufficient to meet
applicable WQS. To serve as the basis for the technology-based
controls, the CWA authorizes EPA to establish national technology-based
effluent limitations guidelines and new source performance standards
for discharges from categories of point sources (such as industrial,
commercial, and public sources) that occur directly into waters of the
U.S.
    The CWA also authorizes EPA to promulgate nationally applicable
pretreatment standards that control pollutant discharges from sources
that discharge wastewater indirectly to waters of the U.S., through
sewers flowing to POTWs, as outlined in sections 307(b) and (c) of the
CWA, 33 U.S.C. 1317(b) and (c). EPA establishes national pretreatment
standards for those pollutants in wastewater from indirect dischargers
that pass through, interfere with, or are otherwise incompatible with
POTW operations. Generally, 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 (those discharging directly to surface waters)
must comply with effluent limitations in NPDES permits. Indirect
dischargers, who discharge through POTWs, must comply with pretreatment
standards. Technology-based effluent limitations and standards 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 limitation guideline or new source performance
standard (CWA section 402(a)(1)(B), 33 U.S.C. 1342(a)(1)(B)).
Additional limitations are also required in the permit where necessary
to meet WQS. CWA section 301(b)(1)(C), 33 U.S.C. 1311(b)(1)(C). The
ELGs are established by EPA 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, as specified in
the Act (e.g., BPT, BCT, BAT; see below).
    EPA promulgates national ELGs for major industrial categories for
three classes of pollutants: (1) Conventional pollutants (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 CWA section 307(a), 33 U.S.C. 1317(a); 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 TDS).

B. Effluent Guidelines Program

    EPA establishes ELGs based on the performance of well-designed and
well-operated 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 (principal author) (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).
    There are four types of standards applicable to direct dischargers,
and two types of standards applicable to indirect dischargers,
described in detail below.
1. Best Practicable Control Technology Currently Available
    Traditionally, EPA establishes effluent limitations based on BPT by
reference to the average of the best performances of facilities within
the industry, grouped to reflect various ages, sizes, processes, or
other common characteristics. EPA can 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
practically applied.
2. Best Conventional Pollutant Control Technology
    The 1977 amendments to the CWA require EPA to identify additional
levels of effluent reduction for conventional pollutants associated
with Best Conventional Pollutant Control Technology (BCT) for
discharges from existing industrial point sources. In addition to other
factors specified in section 304(b)(4)(B), 33 U.S.C. 1314(b)(4)(B), the
CWA requires that EPA establish BCT limitations after consideration of
a two-part ``cost reasonableness'' test. EPA explained its methodology
for the development of BCT limitations on July 9, 1986 (51 FR 24974).
Section 304(a)(4) designates the following as conventional pollutants:
BOD5, TSS, fecal coliform, pH, and any additional pollutants
defined by the Administrator as conventional. The Administrator
designated oil and grease as a conventional pollutant on July 30, 1979
(44 FR 44501; 40 CFR 401.16).
3. Best Available Technology Economically Achievable
    BAT represents the second level of stringency for controlling
direct discharges of toxic and nonconventional pollutants. 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,
non-water quality environmental impacts (including energy
requirements), and such other factors as the Administrator deems
appropriate. 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). Generally, EPA determines
economic achievability based on the effect of the cost of compliance
with BAT limitations on overall industry and subcategory (if
applicable) financial conditions. BAT is intended to reflect the
highest performance in the industry, and it 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 studies, or foreign plants. 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 Food Inst., 539 F.2d at 132, 140; Reynolds
Metals Co. v. EPA, 760 F.2d 549, 562 (4th Cir. 1985); Cal. & Hawaiian
Sugar Co. v. EPA, 553 F.2d 280, 285-88 (2nd Cir. 1977).
4. Best Available Demonstrated Control Technology/New Source
Performance Standards
    NSPS reflect ``the greatest degree of effluent reduction'' that is
achievable based on the ``best available demonstrated control
technology'' (BADCT), ``including, where practicable, a standard
permitting no discharge of pollutants.'' CWA section 306(a)(1), 33
U.S.C. 1316(a)(1). Owners of new facilities have the opportunity to
install the best and most efficient production processes and wastewater
treatment technologies. As a result, NSPS generally represent the most
stringent controls attainable through the application of 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).
5. Pretreatment Standards for Existing Sources
    Section 307(b) of the CWA, 33 U.S.C. 1317(b), authorizes EPA to
promulgate pretreatment standards for discharges of pollutants to
POTWs. 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. Congress
intended for the combination of pretreatment and treatment by the POTW
to achieve the level of treatment that would be required if the
industrial source were making a direct discharge. Conf. Rep. No. 95-
830, at 87 (1977), reprinted in U.S. Congress. Senate Committee on
Public Works (1978), A

Legislative History of the CWA of 1977, Serial No. 95-14 at 271 (1978).
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).
6. Pretreatment Standards for New Sources
    Section 307(c) of the CWA, 33 U.S.C. 1317(c), authorizes EPA to
promulgate PSNS at the same time it promulgates NSPS. As is the case
for PSES, PSNS are designed to prevent the discharge of any pollutant
into a POTW that interferes with, passes through, or is otherwise
incompatible with the POTW. In selecting the PSNS technology basis, the
Agency generally considers the same factors it considers in
establishing NSPS, along with the results of a pass-through analysis.
Like new sources of direct discharges, new sources of indirect
discharges have the opportunity to incorporate into their operations
the best available demonstrated technologies. As a result, EPA
typically promulgates pretreatment standards for new sources based on
best available demonstrated control technology for new sources. See
Nat'l Ass'n of Metal Finishers v. EPA, 719 F.2d 624, 634 (3rd Cir.
1983).

C. Steam Electric Effluent Guidelines Rulemaking History

    EPA provided a detailed history of the steam electric ELGs in the
preamble for the proposed rule, including an explanation of why EPA
initiated a steam electric ELG rulemaking following a detailed study in
2009. EPA published the proposed rule on June 7, 2013, and took public
comments until September 20, 2013. 78 FR 34432. During the public
comment period, EPA received over 200,000 comments. EPA also held a
public hearing on July 9, 2013.

V. Key Updates Since Proposal

    This section discusses key updates since EPA proposed its rule in
June 2013, including how these updates are reflected in the final rule.

A. Industry Profile Changes Due to Retirements and Conversions

    For the final rule, EPA adjusted the population of steam electric
power plants that will likely incur costs and the associated benefits
as a result of this final rule based on company announcements, as of
August 2014, regarding changes in plant operations. The steam electric
industry is a dynamic one, influenced by many factors, including
electricity demand, fuel prices, availability of resources, and
regulation. Since proposal, there have been some important changes in
the overall industry profile. Some companies have retired or announced
plans to retire specific steam electric generating units, as well as
converted or announced plans to convert specific units to a different
fuel source. See DCN SE05069 for information on the data sources for
these announced retirements and conversions. In addition to actual or
announced retirements and fuel conversions, in some cases, plants have
altered, or announced plans to alter, their wastewater treatment or ash
handling practices. To the extent possible, EPA adjusted its analyses
of costs, pollutant loadings, non-water quality environmental impacts,
and benefits for the final rule to account for these actual and
anticipated changes. The final rule accounts for plant retirements and
fuel conversions, as well as changes in plants' ash handling and
wastewater treatment practices, expected to occur by the implementation
dates in the final rule. For more details, see TDD Section 4.5 or
``Changes to Industry Profile for Steam Electric Generating Units for
the Steam Electric Effluent Guidelines Final Rule,'' DCN SE05059.

B. EPA Consideration of Other Federal Rules

    EPA made every effort to appropriately account for other rules in
its many analyses for this rule. Since proposal, EPA has promulgated
other rules affecting the steam electric industry: the Cooling Water
Intake Structures (CWIS) rule for existing facilities (79 FR 48300;
Aug. 15, 2014), the CCR rule (80 FR 21302; Apr. 17, 2015), the CPP rule
(see http://www2.epa.gov/cleanpowerplan/clean-power-plan-existing-power-plants), and the Carbon Pollution Standard for New Power Plants
(CPS) rule (see http://www2.epa.gov/cleanpowerplan/carbon-pollution-standards-new-modified-and-reconstructed-power-plants). One result of
taking into account these rules is a change in the population of units
and plants that EPA estimates would incur incremental costs, as well as
additional estimated benefits, under this final rule. In some cases,
EPA performed two sets of parallel analyses to demonstrate how the
other rules affected this final rule. For example, EPA conducted an
assessment of compliance costs and pollutant loadings for this rule
both with and without accounting for the CCR rule (this preamble only
presents results accounting for the CCR rule). Then, using results from
the analyses of costs and loadings accounting for the CCR rule, EPA
also conducted an additional set of analyses of compliance costs and
pollutant loadings accounting for the proposed CPP rule (this preamble
only presents results accounting for the proposed CPP rule). At the
time EPA conducted its analyses, the CPP had not yet been finalized,
and thus EPA used the proposed CPP for its analyses. EPA concluded that
the proposed and final CPP specifications are similar enough that using
the proposed rather than the final CPP will not bias the results of the
analysis for this rule. See Section IX for additional information.
Because EPA used the proposal as a proxy for the final rule, the rest
of the preamble simply refers to the CPP rule. Given that final CPP
state plans have not yet been determined, EPA recognizes that the
modeled results have uncertainty due to the possibility of unexpected
implementation approaches and that actual market responses may be
somewhat more or less pronounced than estimated. The current estimate
reflects the best data and analysis available at this time. For more
information on these federal rules, see TDD Section 1.3.3. For more
information on how EPA accounted for the effect of these rules on its
compliance cost, pollutant loadings estimates, and non-water quality
environmental impacts, see TDD Sections 9, 10, and 12. See Section V.D.
and Section IX, below, and the RIA regarding how EPA considered other
federal rules in its economic impact analysis.

C. Advancements in Technologies

    There have been advancements in several technologies since proposal
that reinforce EPA's decision regarding those technologies that serve
as the appropriate basis for the final rule. For proposal, EPA
evaluated a variety of technologies available to control and treat
wastewater generated by the steam electric industry. The final rule is
based on several treatment technologies discussed in depth at proposal.
As explained then, and further discussed in Section VIII, the record
demonstrates that the technologies that form the basis for the final
rule are available. Moreover, the record indicates that, based on the
emerging market for treatment technologies, plants will have many
options to choose from when deciding how to meet the requirements of
the final rule.
    The biological treatment technology that serves as part of the
basis for the final requirements for FGD wastewater

discharged from existing sources has been tested at power plants for
more than ten years and demonstrated in full-scale systems for more
than seven years. As this technology has matured, new vendors have
emerged to provide expertise in applying it to steam electric power
plants. In addition, other advanced technologies that plants may use to
achieve the effluent limitations and standards for FGD wastewater in
the final rule are now entering the marketplace, such as lower-cost
biological treatment systems that utilize a modular-based bioreactor,
which is prefabricated and can be delivered directly to the site.
Another advancement related to evaporation and crystallization
technology, operating at low temperatures to crystallize dissolved
solids, requires no chemical treatment of the wastewater and generates
no additional sludge for disposal, resulting in a simpler and more
economical application for treatment of both FGD wastewater and
gasification wastewater. Another development concerning the evaporation
system (which is the basis for the BAT limitations for FGD wastewater
in the voluntary incentives program, as well as the basis for the NSPS
for FGD wastewater) is a process that generates a pozzolanic material
instead of crystallized salts as a solid waste product of the treatment
system; although the pozzolanic material is expected to require
landfill disposal since it likely would not be a marketable material,
the capital and operating cost of the overall evaporation treatment
process would be reduced.
    Zero valent iron (ZVI) cementation, sorption media, ion exchange,
and electrocoagulation are also examples of emerging treatment
technologies that are being developed to treat FGD wastewater, and they
could be used to achieve the limitations in the final rule. See TDD
Section 7 for a more detailed discussion.
    The technologies used as the basis for the final requirements for
ash transport water (dry handling and closed-loop systems) have been in
operation at power plants for more than 20 years and are amply
demonstrated by the record supporting the final rule. Recent
advancements related to bottom ash handling technologies have focused
on providing more flexible retrofit solutions and improving the thermal
efficiency of the boiler operation. These advancements result in
additional savings related to electricity use, operation and
maintenance, water costs, and thermal energy recovery.
    In sum, the record demonstrates that there have been significant
advancements in relevant treatment technologies since proposal, and EPA
expects that the advancements will continue as this rule is implemented
by the industry.

D. Engineering Costs

    For the final rule, EPA updated its cost estimates to account for
public comments. The following list summarizes the main adjustments EPA
made to its cost estimates for the final rule:
     Adjustment of population of generating units and changes
in wastewater treatment or ash handling practices to account for
company-announced generating unit retirements/repowerings and
conversions of ash handling systems (see Section IV.A);
     Adjustment of population of generating units and changes
in wastewater treatment or ash handling practices to account for
implementation of the CCR rule and CPP rule (see Section IV.B);
     Adjustments to the direct capital costs factors to better
reflect all associated installation costs;
     Adjustments to the indirect capital cost factors to
account for appropriate engineering and contingency costs;
     Adjustment to plant population receiving one-time bottom
ash management costs;
     Addition of costs for denitrification pretreatment prior
to biological treatment of FGD wastewater (for certain plants);
     Updates to costing inputs to account for costs of
additional redundancy for the fly ash dry handling system;
     Addition of tank rental costs for surge capacity during
certain bottom ash handling system maintenance;
     Addition of building costs for certain bottom ash and FGD
wastewater systems; and
     Addition of costs for equipment that can be used to
mitigate high oxidation-reduction potential (ORP) levels in FGD
wastewater.
    See Section 9 of the TDD for additional information on the plant-
specific compliance cost estimates for the final rule.

E. Economic Impact Analysis

    For its analysis of the economic impact of the final rule, EPA
began with the same financial data sources for steam electric power
plants and their parent companies that were used and described in the
proposed rule, primarily collected through the Questionnaire for the
Steam Electric Power Generating Effluent Guidelines (industry survey)
\11\ and public sources. Since proposal, EPA updated some of the
analysis input data obtained from public sources to reflect the most
current information about the economic/financial conditions in, and the
regulatory environment of, the electric power industry, as well as data
on electricity prices and electricity consumption. Thus, EPA updated
its analysis to use the most current publicly available data from the
following sources: The Department of Energy's Energy Information
Administration (EIA) (in particular, the EIA 860, 861, and 906/920/923
databases),\12\ the U.S. Small Business Administration (SBA), the
Bureau of Labor Statistics (BLS), and the Bureau of Economic Analysis
(BEA). As was the case for the proposed rule, EPA performed an analysis
using the Integrated Planning Model (IPM), a comprehensive electricity
market optimization model that can evaluate impacts within the context
of regional and national electricity markets. For the final rule, EPA
used an updated IPM base case (v5.13) that incorporates improvements
and data updates to the previous version (v.4.10), notably regarding
electricity demand forecast, generating capacity, market conditions,
and newly promulgated environmental regulations also affecting this
industry (see Section IX).
---------------------------------------------------------------------------

    \11\ For details on the industry survey, see TDD Section 3 and
78 FR 34432; June 7, 2013).
    \12\ EIA-860: Annual Electric Generator Report; EIA-861: Annual
Electric Power Industry Database; EIA-923: Utility, Non-Utility, and
Combined Heat & Power Plant Database (monthly). The most current EIA
data at the time of the analysis was for the year 2012.
---------------------------------------------------------------------------

F. Pollutant Data

    For the final rule, EPA incorporated data submitted by public
commenters in its effluent limitations and standards development,
pollutants of concern identification, and pollutant loadings estimates.
Such data include:
     Industry-submitted data representing the FGD purge, FGD
chemical precipitation effluent, and FGD biological treatment effluent
for the plants identified as operating BAT systems;
     Industry-submitted ash transport water characterization
and source water data; \13\
---------------------------------------------------------------------------

    \13\ Industry also submitted bottom ash transport water data
approximately 14 months after the close of the public comment
period. EPA did not incorporate these late data into its analyses,
but it did perform a sensitivity analysis to determine how these
late data might have impacted EPA's analyses and decisions. EPA
concluded from the sensitivity analysis that the late bottom ash
transport water data would not have changed EPA's ultimate decisions
for this final rule. See DCN SE05581.

---------------------------------------------------------------------------

     Industry-submitted ash impoundment effluent
concentrations; and
     Industry-submitted pilot-test data related to treatment of
FGD wastewater.
    EPA subjected the new data to its data quality acceptance criteria
and, as appropriate, updated its analyses accordingly. See TDD Section
3 for additional information on the data sources used in the
development of the final rule.

G. Environmental Assessment Models

    Although not required to do so, EPA conducted an Environmental
Assessment for the final rule, as it did for the proposed rule. EPA
updated the environmental assessment in several ways to respond to
public comments, and improve the characterization of the environmental
and human health improvements associated with the final rule. EPA
performed dynamic water quality modeling of selected case-study
locations to supplement the results of the national-scale Immediate
Receiving Water (IRW) model. EPA supplemented the wildlife analysis by
developing and using an ecological risk model that predicts the risk of
reproductive impacts among fish and birds with dietary exposure to
selenium from steam electric power plant wastewater discharges. EPA
also updated and improved several input parameters for the IRW model,
including fish consumption rates for recreational and subsistence
fishers, the bioconcentration factor for copper, and benchmarks for
assessing the potential for impacts to benthic communities in receiving
waters. See Section XIII.A for additional discussion.

VI. Industry Description

A. General Description of Industry

    EPA provided a general description of the steam electric industry
in the proposed rule and provides a complete discussion of the industry
in TDD Section 4. As described in TDD Section 4.5 (and Section V.A,
above), EPA considered retirements, fuel conversions, ash handling
conversions, wastewater treatment updates, and other industry profile
changes in the development of the final rule and supporting technical
analyses; however, the data presented in the general industry
description represents 2009 conditions, as the industry survey (See TDD
Section 3) remains the best available source of information for
characterizing operations across the industry.

B. Steam Electric Process Wastewater and Control Technologies

    While almost all steam electric power plants generate certain
wastewater, like cooling water and boiler blowdown, the presence of
other wastestreams depends on the type of fuel burned. Coal- and
petroleum coke-fired generating units, and to a lesser degree oil-fired
generating units, generate a flue gas stream that contains large
quantities of particulate matter, sulfur dioxide, and nitrogen oxides,
which would be emitted to the atmosphere if they were not cleaned from
the flue gas prior to emission. Therefore, many of these generating
units are outfitted with air pollution control systems (e.g.,
particulate removal systems, FGD systems, nitrogen oxide
(NOX)-removal systems, and mercury control systems). Gas-
fired generating units generate fewer emissions of particulate matter,
sulfur dioxide, and nitrogen oxides than coal- or oil-fired generating
units, and therefore do not typically operate air pollution control
systems to control emissions from their flue gas. In addition, coal-,
oil-, and petroleum coke-fired generating units create fly and/or
bottom ash as a result of coal combustion. The wastewaters associated
with ash transport and air pollution control systems contain large
quantities of metals (e.g., arsenic, mercury, and selenium).
    See TDD Sections 4, 6, and 7 for details on these systems, the
wastewaters they generate, the number of facilities that operate the
systems and generate wastewater, and the control technologies used for
wastewater treatment prior to discharge.
1. FGD Wastewater
    FGD systems are used to remove sulfur dioxide from the flue gas so
that it is not emitted into the air. Dry FGD systems spray a sorbent
slurry into a reactor vessel so that the droplets dry as they contact
the hot flue gas. Although dry FGD scrubbers use water in their
operation, the water in most systems evaporates and they generally do
not discharge wastewater. Wet FGD systems contact the sorbent slurry
with flue gas in a reactor vessel producing a wastewater stream.
    Treatment technologies for FGD wastewater include chemical
precipitation, biological treatment, and evaporation. At some plants,
this wastewater is handled in surface impoundments, constructed
wetlands, or through practices achieving zero discharge. As described
above in Section V.C and TDD section 7, EPA identified other
technologies that have been evaluated or are being developed to treat
FGD wastewater, including iron cementation, ZVI cementation, reverse
osmosis, absorption or adsorption media, ion exchange, and
electrocoagulation.
2. Fly Ash Transport Water
    Plants use particulate removal systems to collect fly ash and other
particulates from the flue gas in hoppers located underneath the
equipment. Of the coal-, petroleum coke-, and oil-fired steam electric
power plants that generate fly ash, most of them transport fly ash
pneumatically from the hoppers to temporary storage silos, thereby not
generating any transport water. Some plants, however, use water to
transport (sluice) the fly ash from the hoppers to a surface
impoundment. The water used to transport the fly ash to the surface
impoundment is usually discharged to surface water as overflow from the
impoundment after the fly ash has settled to the bottom.
3. Bottom Ash Transport Water
    Bottom ash consists of heavier ash particles that are not entrained
in the flue gas and fall to the bottom of the furnace. In most
furnaces, the hot bottom ash is quenched in a water-filled hopper. For
purposes of this rule, boiler slag is considered bottom ash. Boiler
slag is the molten bottom ash collected at the base of the furnace that
is quenched with water. Most plants use water to transport (sluice) the
bottom ash from the hopper to an impoundment or dewatering bins. The
ash sent to a dewatering bin is separated from the transport water and
then disposed. For both of these systems, the water used to transport
the bottom ash to the impoundment or dewatering bins is usually
discharged to surface water as overflow from the systems, after the
bottom ash has settled to the bottom.
    Of the coal-, petroleum coke-, and oil-fired steam electric power
plants that generate bottom ash, most operate wet sluicing handling
systems. There are two types of bottom ash handling technologies that
can meet zero discharge requirements: (1) Dry handling technologies
that do not use any water, including systems such as dry vacuum or
pressure systems, dry mechanical conveyor systems, and vibratory belt
systems; and (2) wet systems that do not generate or discharge ash
transport water, including mechanical drag systems (MDS), remote MDS,
and complete-recycle systems.
4. FGMC Wastewater
    FGMC systems remove mercury from the flue gas, so that it is not
emitted into

the air. There are two types of systems used to control flue gas
mercury emissions: (1) Addition of oxidizing agents to the coal prior
to combustion; and (2) injection of activated carbon into the flue gas
after combustion. Addition of oxidizing agents to the coal prior to
combustion does not generate a new wastewater stream; it can, however,
increase the mercury concentration in the FGD wastewater because the
oxidized mercury is more easily removed by the FGD system. Injection of
activated carbon into the flue gas does have the potential to generate
a new wastestream at a plant, depending on the location of the
injection. If the injection occurs upstream of the primary particulate
removal system, then the mercury-containing carbon (FGMC waste) is
collected and handled the same way as, and together with, the fly ash.
Therefore, if the fly ash is wet sluiced, then the FGMC wastes are also
wet sluiced and likely sent to the same surface impoundment. In this
case, adding the FGMC waste to the fly ash can increase the amount of
mercury in the fly ash transport water. If the injection occurs
downstream of the primary particulate removal system, the plant will
need a secondary particulate removal system (typically a fabric filter)
to capture the FGMC wastes.
    Of the current or planned activated carbon injection systems, most
operate upstream injection. However, plants that wish to market their
fly ash will typically inject the activated carbon downstream of the
primary particulate removal system to prevent contaminating the fly ash
with carbon. For plants operating downstream injection, the FGMC
wastes, which would be collected with some carry-over fly ash, could be
handled separately from fly ash in either a wet or dry handling system.
5. Combustion Residual Leachate From Landfills and Surface Impoundments
    Combustion residuals comprise a variety of wastes from the
combustion process, which are generally collected by or generated from
air pollution control technologies. These combustion residuals can be
stored at the plant in on-site landfills or surface impoundments.
Leachate includes liquid, including any suspended or dissolved
constituents in the liquid, that has percolated through or drained from
waste or other materials placed in a landfill, or that passes through
the containment structure (e.g., bottom, dikes, berms) of a surface
impoundment. Based on data from the industry survey, most landfills and
some impoundments have a system to collect the leachate.
    In a lined landfill or impoundment, the combustion residual
leachate collected in the liner is typically transported to an
impoundment (e.g., collection pond). Some plants discharge the effluent
from these impoundments containing combustion residual leachate
directly to receiving waters, while other plants first send the
impoundment effluent to another impoundment handling the ash transport
water or other treatment system (e.g., constructed wetlands) prior to
discharge. Unlined impoundments and landfills usually do not collect
leachate, which would allow the leachate to potentially migrate to
nearby ground waters, drinking water wells, or surface waters.
    Using data from the industry survey and site visits, surface
impoundments are the most widely used systems to treat combustion
residual leachate. EPA also identified different management practices,
with approximately one-third of plants collecting the combustion
residual leachate from impoundments and recycling it back to the
impoundment from which it was collected. Some plants use their
collected leachate as water for moisture conditioning of dry fly ash
prior to disposal or for dust control around dry unloading areas and
landfills.
6. Gasification Wastewater
    Integrated Gasification Combined Cycle (IGCC) plants use a carbon-
based feedstock (e.g., coal or petroleum coke) and subject it to high
temperature and pressure to produce a synthetic gas (syngas), which is
used as the fuel for a combined cycle generating unit. After the syngas
is produced, it undergoes cleaning prior to combustion. The wastewater
generated by these cleaning processes, along with any condensate
generated in flash tanks, slag handling water, or wastewater generated
from the production of sulfuric acid, is referred to as ``grey water''
or ``sour water,'' and is generally treated prior to reuse or
discharge.
    EPA is aware of three plants that operate IGCC units in the U.S.
All three plants currently treat their gasification wastewater with
vapor-compression evaporation systems. One of these plants also
includes a cyanide destruction stage as part of the treatment system.

VII. Selection of Regulated Pollutants

A. Identifying the Pollutants of Concern

    In determining which pollutants warrant regulation in this rule,
EPA first evaluated the wastewater characteristics to identify
pollutants of concern (POCs). Constituents present in steam electric
power plant wastewater are primarily derived from the parent carbon
feedstock (e.g., coal, petroleum coke). EPA characterized the
wastewater generated by the industry and identified POCs (those
pollutants commonly found) for each of the regulated wastestreams. For
wastestreams where the final rule establishes numeric effluent
limitations or standards, the POCs are those pollutants that have been
quantified in a wastestream at sufficient frequency at treatable levels
(concentrations). For wastestreams where EPA is establishing zero
discharge limitations or standards, the POCs identified for each
wastestream are those pollutants that are confirmed to be present at
sufficient frequency in untreated wastewater samples of that
wastestream. In both cases, in response to public comments, where EPA
had available paired source water (intake water) data for a particular
pollutant in an untreated process wastewater sample, EPA compared the
two to confirm that the concentration in the untreated process
wastewater sample exceeded that of the source water. See TDD Section
6.6 for details on EPA's analysis of POCs.

B. Selection of Pollutants for Regulation Under BAT/NSPS

    For wastestreams where the final rule establishes numeric effluent
limitations or standards, effluent limitations or standards for all
POCs are not necessary to ensure that the pollutants are adequately
controlled because many of the pollutants originate from similar
sources, have similar treatability, and are removed by similar
mechanisms. Because of this, it is sufficient to establish effluent
limitations or standards for one or more indicator pollutants, which
will ensure the removal of other POCs. For wastestreams where the final
rule establishes zero discharge limitations or standards, all POCs are
directly regulated.
    For wastestreams where the final rule establishes numeric effluent
limitations or standards, EPA selected a subset of pollutants as
indicators for all regulated pollutants upon consideration of the
following factors:
     EPA did not set limitations or standards for pollutants
associated with treatment system additives because regulating these
pollutants could interfere with efforts to optimize treatment system
operation.
     EPA did not set limitations or standards for pollutants
for which the treatment technology was ineffective

(e.g., pollutant concentrations remained approximately unchanged or
increased across the treatment system).
     EPA did not set limitations or standards for pollutants
that are adequately controlled through the regulation of another
indicator pollutant because they have similar properties and are
treated by similar mechanisms as a regulated pollutant.
    See TDD Section 11 for additional detail on EPA's analysis and
rationale for selecting the regulated pollutants.

C. Methodology for the POTW Pass-Through Analysis (PSES/PSNS)

    Before establishing PSES/PSNS for a pollutant, EPA examines whether
the pollutant ``passes through'' a POTW to waters of the U.S. or
interferes with the POTW operation or sludge disposal practices. In
determining whether a pollutant passes through POTWs for these
purposes, EPA generally compares the percentage of a pollutant removed
by well-operated POTWs performing secondary treatment to the percentage
removed by the BAT/NSPS technology basis. A pollutant is determined to
pass through POTWs when the median percentage removed nationwide by
well-operated POTWs is less than the median percentage removed by the
BAT/NSPS technology basis. Pretreatment standards are established for
those pollutants regulated under BAT/NSPS that pass through POTWs.
    Under this rule, for those wastestreams regulated with a zero
discharge limitation or standard, EPA set the percentage removed by the
technology basis at 100 percent. Because a POTW would not be able to
achieve 100 percent removal of wastewater pollutants, it is appropriate
to set PSES at zero discharge, otherwise pollutants would pass through
the POTW.
    For wastestreams for which the final rule establishes numeric
limitations and standards, EPA determined the pollutant percentage
removed by the rule's technology basis using the same data sources used
to determine the long-term averages for each set of limitations and
standards (see TDD Section 13). As it has done for other rulemakings,
EPA determined the nationwide percentage removed by well-operated POTWs
performing secondary treatment using one of two data sources:
     Fate of Priority Pollutants in Publicly Owned Treatment
Works, September 1982, EPA 440/1-82/303 (50 POTW Study); or
     National Risk Management Research Laboratory Treatability
Database, Version 5.0, February 2004 (formerly called the Risk
Reduction Engineering Laboratory database).
    With a few exceptions, EPA performs a POTW pass-through analysis
for pollutants selected for regulation for BAT/NSPS for each
wastestream of concern. The exception is for conventional pollutants
such as BOD5, TSS, and oil and grease. POTWs are designed to
treat these conventional pollutants; therefore, they are not considered
to pass through.
    Section VIII, below, summarizes the results of the pass-through
analysis. EPA found that all of the pollutants considered for
regulation under BAT/NSPS pass through and, therefore, also selected
them for regulation under PSES/PSNS. For a more detailed discussion of
how EPA performed its pass-through analysis, see TDD Section 11.

VIII. The Final Rule

A. BPT

    The final rule does not revise the previously established BPT
effluent limitations because the rule regulates the same wastestreams
at the more stringent BAT/NSPS level of control. The rule does,
however, make certain structural modifications to the BPT regulations
in light of new and revised definitions. In particular, the final rule
establishes separate definitions for FGD wastewater, FGMC wastewater,
gasification wastewater, and combustion residual leachate, making clear
that these four wastestreams are no longer considered low volume waste
sources. Given these new and revised definitions, the final rule
modifies the structure of the previously established BPT regulations so
that they specifically identify these four wastestreams, but without
changing their applicable BPT limitations, which are equal to those for
low volume waste sources.

B. BAT/NSPS/PSES/PSNS Options

    EPA analyzed many regulatory options at proposal, the details of
which were discussed fully in the document published on June 7, 2013
(78 FR 34432). EPA proposed to regulate pollutants found in seven
wastestreams found at steam electric power plants, each based on
particular control technologies. Depending on the interests
represented, public commenters supported virtually all of the
regulatory options that EPA proposed--from the least stringent to the
most stringent, and many options in between. For this final rule, based
on public comments, EPA also considered a few additional regulatory
options. None of these additional regulatory options involve regulation
of different pollutants or wastestreams, or the application of
different control technologies, than those explicitly considered and
presented at proposal. Rather, they involve slight variations on the
overall packaging of the key options presented at proposal. Thus, in
developing this final rule, EPA named six main regulatory options,
Options A, B, C, D, E, and F.\14\ Table VIII-1 summarizes these six
regulatory options. In general, as one moves from Option A to Option F,
there is a greater estimated reduction in pollutant discharges from
steam electric power plants and a higher associated cost.
---------------------------------------------------------------------------

    \14\ Option B is equivalent to Proposed Option 3, Option C is
equivalent to Proposed Option 4a, Option E is equivalent to Proposed
Option 4, and Option F is equivalent to Proposed Option 5. Option A
is a slight variant of Proposed Options 1 and 3 and Option D is a
slight variant of Proposed Option 4.
---------------------------------------------------------------------------

    The following paragraphs describe the six options (Options A
through F), by wastestream, including the technology bases for the
requirements associated with each.

                                            TABLE VIII-1--Final Rule: Steam Electric Main Regulatory Options
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                            Technology basis for the main BAT/NSPS/PSES/PSNS regulatory options
          Wastestreams           -----------------------------------------------------------------------------------------------------------------------
                                           A                   B                   C                   D                   E                   F
--------------------------------------------------------------------------------------------------------------------------------------------------------
FGD Wastewater..................  Chemical            Chemical            Chemical            Chemical            Chemical            Evaporation.
                                   Precipitation.      Precipitation +     Precipitation +     Precipitation +     Precipitation +
                                                       Biological          Biological          Biological          Biological
                                                       Treatment.          Treatment.          Treatment.          Treatment.
Fly Ash Transport Water.........  Dry handling......  Dry handling......  Dry handling......  Dry handling......  Dry handling......  Dry handling.

Bottom Ash Transport Water......  Impoundment (Equal  Impoundment (Equal  Dry handling/       Dry handling/       Dry handling/       Dry handling/
                                   to BPT).            to BPT).            Closed loop (for    Closed loop.        Closed loop.        Closed loop.
                                                                           units >400 MW);
                                                                           Impoundment
                                                                           (Equal to
                                                                           BPT)(for units
                                                                           <=400 MW).
FGMC Wastewater.................  Dry handling......  Dry handling......  Dry handling......  Dry handling......  Dry handling......  Dry handling.
Gasification Wastewater.........  Evaporation.......  Evaporation.......  Evaporation.......  Evaporation.......  Evaporation.......  Evaporation.
Combustion Residual Leachate....  Impoundment (Equal  Impoundment (Equal  Impoundment (Equal  Impoundment (Equal  Chemical            Chemical
                                   to BPT).            to BPT).            to BPT).            to BPT).            Precipitation.      Precipitation.
Nonchemical Metal Cleaning        [Reserved]........  [Reserved]........  [Reserved]........  [Reserved]........  [Reserved]........  [Reserved].
 Wastes.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Consistent with the proposal, under all Options A through F, for
oil-fired generating units and small generating units (50 MW or
smaller) that are existing sources, the rule would establish BAT/PSES
effluent limitations and standards on TSS in fly ash transport water,
bottom ash transport water, FGD wastewater, FGMC wastewater, combustion
residual leachate, and gasification wastewater equal to the previously
promulgated BPT effluent limitations on TSS \15\ in fly ash transport
water, bottom ash transport water, and low volume waste sources, where
applicable. Under Options A through E, EPA would establish a voluntary
incentives program for plants that choose to meet BAT limitations for
FGD wastewater based on evaporation technology, as described in Section
VIII.C.13. Moreover, as EPA proposed, under all Options A through F,
the rule would establish an anti-circumvention provision designed to
ensure that the purpose of the rule is achieved, as further described
below, in Section VIII.G. Finally, as EPA proposed, under all Options A
through F, the rule would correct a typographical error in the
previously promulgated regulations, as well as make certain clarifying
revisions to the applicability provision of the regulations, as further
described below, in Section VIII.H.
---------------------------------------------------------------------------

    \15\ Although TSS is a conventional pollutant, whenever EPA
would be regulating TSS in this final rule, it would be regulating
it as an indicator pollutant for the particulate form of toxic
metals.
---------------------------------------------------------------------------

1. FGD Wastewater
    Under Option A, EPA would establish effluent limitations and
standards for mercury and arsenic in FGD wastewater based on treatment
using chemical precipitation. Under Options B through E, EPA would
establish effluent limitations and standards for mercury, arsenic,
selenium, and nitrate/nitrite as N in FGD wastewater based on treatment
using chemical precipitation (as under Option A) followed by biological
treatment. Under Option F, EPA would establish effluent limitations and
standards for mercury, arsenic, selenium, and TDS in FGD wastewater
based on treatment using an evaporation system. Under all options, to
facilitate implementation of the new BAT/NSPS/PSES/PSNS requirements,
EPA would also promulgate a definition for FGD wastewater, making clear
it would no longer be considered a low volume waste source.
2. Fly Ash Transport Water
    Under all Options A through F, EPA would establish (or in the case
of NSPS/PSNS, maintain) zero discharge effluent limitations and
standards for pollutants in fly ash transport water based on use of a
dry handling system.
3. Bottom Ash Transport Water
    Under Options A and B, EPA would establish effluent limitations and
standards for bottom ash transport water equal to the previously
promulgated BPT limitation on TSS, which is based on the use of a
surface impoundment. Under Options D, E, and F, EPA would establish
zero discharge effluent limitations and standards for pollutants in
bottom ash transport water based on one of two technologies: A dry
handling system or a closed-loop system. Under Option C, EPA would
establish, for bottom ash transport water, zero discharge limitations
and standards based on dry handling or closed-loop systems only for
generating units with a nameplate capacity of more than 400 MW. Units
with a nameplate capacity equal to or less than 400 MW would have to
meet new effluent limitations and standards equal to the previously
established BPT limitation on TSS, based on surface impoundments.
4. FGMC Wastewater
    Under all Options A through F, EPA would establish zero discharge
effluent limitations and standards for FGMC wastewater based on use of
a dry handling system. Under all Options A through F, EPA would
establish a separate definition for FGMC wastewater, making clear it
would no longer be considered a low volume waste source.
5. Gasification Wastewater
    The technology basis for control of gasification wastewater under
all Options A through F is an evaporation system. Under these options,
EPA would establish limitations and standards on arsenic, mercury,
selenium, and TDS in gasification wastewater. Under all Options A
through F, EPA would establish a separate definition for gasification
wastewater, making clear it would no longer be considered a low volume
waste source.
6. Combustion Residual Leachate
    Under Options A through D, EPA would establish effluent limitations
and standards for combustion residual leachate equal to the previously
promulgated BPT limitation on TSS for low volume waste sources. Under
Options E and F, EPA would establish additional limitations and
standards for arsenic and mercury in combustion residual leachate based
on treatment using a chemical precipitation system (the same technology
basis for control of FGD wastewater under Option A). Under all Options
A through F, EPA would establish a separate definition for combustion
residual leachate, making

clear it would no longer be considered a low volume waste source.
7. Non-Chemical Metal Cleaning Wastes
    Under all Options A through F, EPA would continue to reserve BAT/
NSPS/PSES/PSNS for non-chemical metal cleaning wastes, as the
previously established regulations do.

C. Best Available Technology

    After considering the technologies described in this preamble and
Section 7 of the TDD, as well as public comments, and in light of the
factors specified in CWA sections 304(b)(2)(B) and 301(b)(2)(A) (see
Section IV.B.3), EPA decided to establish BAT effluent limitations
based on the technologies described in Option D. Thus, for BAT, the
final rule establishes: (1) Limitations on arsenic, mercury, selenium,
and nitrate/nitrite as N in FGD wastewater, based on chemical
precipitation plus biological treatment; \16\ (2) a zero discharge
limitation for pollutants in fly ash transport water, based on dry
handling; (3) a zero discharge limitation for pollutants in bottom ash
transport water, based on dry handling or closed-loop systems; (4) a
zero discharge limitation on all pollutants in FGMC wastewater, based
on dry handling; (5) limitations on mercury, arsenic, selenium, and TDS
in gasification wastewater, based on evaporation; \17\ and (6) a
limitation on TSS in combustion residual leachate, based on surface
impoundments.\18\ The final rule also establishes new definitions for
FGD wastewater, FGMC wastewater, gasification wastewater, and
combustion residual leachate.
---------------------------------------------------------------------------

    \16\ For those plants that choose to participate in the
voluntary incentives program, the applicable limitations are for
arsenic, mercury, selenium, and TDS in FGD wastewater, based on the
use of an evaporation system (see Section VIII.C.13).
    \17\ For small (50 MW or less) generating units and oil-fired
generating units, the final rule establishes different BAT
limitations for FGD wastewater, fly ash transport water, bottom ash
transport water, FGMC wastewater, and gasification wastewater (see
Section VIII.C.12).
    \18\ The final rule also establishes BAT limitations on TSS in
discharges of ``legacy wastewater,'' which are equal to previously
established TSS limitations. See Section VIII.C.8.
---------------------------------------------------------------------------

1. FGD Wastewater
    This rule identifies treatment using chemical precipitation
followed by biological treatment as the BAT technology basis for
control of pollutants discharged in FGD wastewater. More specifically,
the technology basis for BAT is a chemical precipitation system that
employs hydroxide precipitation, sulfide precipitation (organosulfide),
and iron coprecipitation, followed by an anoxic/anaerobic fixed-film
biological treatment system designed to remove heavy metals, selenium,
and nitrates.\19\ After accounting for industry changes described in
Section V, forty-five percent of all steam electric power plants with
wet scrubbers have equipment or processes in place able to meet the
final BAT/PSES effluent limitations and standards.\20\ Many of these
plants use FGD wastewater management approaches that eliminate the
discharge of FGD wastewater.\21\ Other plants employ wastewater
treatment technologies that reduce the amount of pollutants in the FGD
wastestream. Both chemical precipitation and biological treatment are
well-demonstrated technologies that are available to steam electric
power plants for use in treating FGD wastewater. Based on industry
survey responses, 39 U.S. steam electric power plants (44 percent of
plants discharging FGD wastewater) use some form of chemical
precipitation as part of their FGD wastewater treatment system. More
than half of these plants (30 percent of plants discharging FGD
wastewater) use both hydroxide and sulfide precipitation in the process
to further reduce metals concentrations. In addition, chemical
precipitation has been used at thousands of industrial facilities
nationwide for the last several decades (see TDD Section 7).
---------------------------------------------------------------------------

    \19\ In estimating costs associated with this technology basis,
EPA assumed that in order to meet the limitations and standards,
certain plants with high FGD discharge flow rates (greater than or
equal to 1,000 gpm) would elect to incorporate flow minimization
into their operating practices (by reducing the FGD purge rate or
recycling a portion of their FGD wastewater back to the FGD system),
where the FGD system metallurgy can accommodate an increase in
chlorides. See Section 4.5.4 of EPA's Incremental Costs and
Pollutant Removals for the Final Effluent Limitations Guidelines and
Standards for the Steam Electric Power Generating Point Source
Category (DCNs SE05831 and SE05832).
    \20\ This value accounts for announced retirements, conversions,
and changes plants are projected to make to comply with the CPP and
CCR rules.
    \21\ A variety of approaches that depend on plant specific
conditions are used to achieve zero pollutant discharge at these
plants, including evaporation ponds, complete recycle, and processes
that combine the FGD wastewater with other materials for landfill
disposal. Although these technologies, as well as others currently
used for achieve zero pollutant discharge, may be available for some
plants with FGD wastewater, EPA determined they are not available
nationally. For example, evaporation ponds are only available in
certain climates. Similarly, complete recycle is only available at
plants with appropriate FGD metallurgy.
---------------------------------------------------------------------------

    Biological treatment has been tested at power plants for more than
ten years and full-scale systems have been operating at a subset of
plants for seven years. It has been widely used in many industrial
applications for decades, in both the U.S. and abroad, and it has been
employed at coal mines. Currently, six U.S. steam electric power plants
(approximately ten percent of those discharging FGD wastewater) use
biological treatment designed to substantially reduce nitrogen
compounds and selenium in their FGD wastewater. Other power plants are
considering installing biological treatment to remove selenium, and at
least one plant is scheduled to begin operating a biological treatment
system for selenium removal soon. Four of the six plants using
biological systems to treat their FGD wastewater precede the biological
treatment stage with chemical precipitation; thus, the entire system is
designed to remove suspended solids, particulate and dissolved metals
(such as mercury and arsenic), soluble and insoluble forms of selenium,
and nitrate and nitrite forms of nitrogen. These plants show that
chemical precipitation followed by biological treatment is
technologically available and demonstrated. The other two plants
operating anoxic/anaerobic bioreactors to remove selenium precede the
biological treatment stage with surface impoundments instead of
chemical precipitation. The treatment systems at these two plants are
likely to be less effective at removing metals (including many
dissolved metals) and would likely face more operational problems than
the plants employing chemical pretreatment, but they nevertheless show
the efficacy and availability of biological treatment for removing
selenium and nitrate/nitrite in FGD wastewater.
    A few commenters questioned the feasibility of biological treatment
at some power plants. Specifically, they claimed, in part, that the
efficacy of biological systems is unpredictable and is subject to
temperature changes, high chloride concentrations, scaling, and high
oxidation-reduction potential (ORP) in the absorber, which could kill
the microorganisms in the bioreactor. EPA's record does not support
these assertions for a well-designed and well-operated chemical
precipitation and biological treatment system.
    EPA's record demonstrates that proper pretreatment prior to
biological treatment and proper monitoring with adjustments to the
treatment system as necessary are key to reducing operational concerns
raised by commenters. Proper pretreatment includes chemical
precipitation, which can address wastewater containing high oxidant
loads through addition of a reducing agent in one of the treatment

system's reaction tanks.\22\ It also includes pretreatment of FGD
wastewater containing exceptionally high levels of nitrates (e.g.,
greater than 100 ppm nitrate/nitrite as N) using standard
denitrification technologies such as membrane bioreactors or stirred-
tank bioreactors. Moreover, recent pilot studies of biological
treatment systems for FGD wastewater treatment, along with data for
full-scale biological treatment systems, demonstrate that monitoring
ORP, pH, and total oxidant load is essential for proper operation of
these systems. Monitoring these parameters enables the plant to adjust
the system as necessary. For example, plants that monitor ORP in the
absorber or in the FGD purge will have sufficient advanced warning to
respond to elevated ORP levels by adding a chemical reductant to the
chemical precipitation system and/or increasing the feed rate of the
nutrient mix in the biological reactor. EPA's cost estimates account
for all of these pretreatment and monitoring steps. EPA's record,
moreover, shows that the treatment systems that form the bases for the
BAT limitations for FGD wastewater are able to effectively remove the
regulated pollutants at varying influent concentrations. See DCN
SE05733. Finally, as discussed in Section V.C, vendors continue to make
improvements to these systems and to develop non-biological systems for
selenium removal. For additional information on strategies to address
potential operational concerns, see DCNs SE04208 and SE04222.
---------------------------------------------------------------------------

    \22\ EPA included the equipment for chemical addition of a
reducing agent in its cost estimates for Options B through E.
---------------------------------------------------------------------------

    Some commenters also claimed that the efficacy of biological
systems in removing selenium is subject to changes in switching from
one coal type to another (also referred to as fuel flexing). Where EPA
had biological treatment performance data paired with fuel type, EPA
reviewed it and found that existing biological treatment systems
continue to perform well during periods of fuel switching. See DCN
SE05846. The data show that, in all cases except one, the plants met
the selenium limitations following fuel switches. In one instance when
a plant switched to a certain coal type, the plant exceeded the final
daily maximum selenium limitation for one out of thirteen observations
for the month while the average of all values for that month were below
the final monthly selenium limitation. This plant was not subject to a
selenium limit at the time data was collected. Moreover, EPA's record
demonstrates that effective communication between the operator(s) of
the generating unit and the boiler, as well as bench testing and
monitoring the ORP, and making proper adjustments to the operation of
the treatment system, would make it possible to prevent potential
selenium exceedances at this plant. Data for two other plants operating
full-scale biological treatment systems shows that fuel switches should
not result in exceeding the effluent limitations. EPA also has data
from a pilot project at another plant employing the same type of coal
used by the one plant that experienced elevated selenium effluent
concentrations following a coal switch. The data for this pilot project
demonstrate effective selenium removal by the BAT technology basis,
with all effluent values at concentrations below the BAT limitations
established in this rule.
    EPA also reviewed effluent data in the record for plants operating
combined chemical precipitation and biological treatment for FGD
wastewater to evaluate how cycling operation (i.e., changes in
electricity generation rate) and short or extended shutdown periods may
affect the ability of plants to meet the BAT effluent limitations.
These data demonstrate that cycling operations and shutdown periods,
whether short or long in duration, are manageable and do not result in
plants being unable to meet the ELG effluent limitations. See DCN
SE05846.
    EPA did not select surface impoundments as the BAT technology basis
for FGD wastewater because it would not result in reasonable further
progress toward eliminating the discharge of all pollutants,
particularly toxic pollutants (see CWA section 301(b)(2)(A)). Surface
impoundments, which rely on gravity to remove particulates from
wastewater, are the technology basis for the previously promulgated BPT
effluent limitations for low volume waste sources. Pollutants that are
present mostly in soluble (dissolved) form, such as selenium, boron,
and magnesium, are not effectively and reliably removed by gravity in
surface impoundments. For metals present in both soluble and
particulate forms (such as mercury), gravity settling in surface
impoundments does not effectively remove the dissolved fraction.
Furthermore, the environment in some surface impoundments can create
chemical conditions (e.g., low pH) that convert particulate forms of
metals to soluble forms, which are not removed by the gravity settling
process. Additionally, the Electric Power Research Institute (EPRI) has
reported that adding FGD wastewater to surface impoundments used to
treat ash transport water can reduce the settling efficiency in the
impoundments due to gypsum particle dissolution, thus increasing the
effluent TSS concentrations. Discharging wastewater containing elevated
levels of TSS would likely result in also discharging other pollutants
(e.g., metals) in higher concentrations. EPRI has also reported that
FGD wastewater includes high loadings of volatile metals, which can
increase the solubility of metals in surface impoundments, thereby
leading to increased levels of dissolved metals and higher
concentrations of metals in discharges from surface impoundments.
Finally, as described in Section 8 of the TDD, surface impoundments are
also subject to seasonal turnover, which adversely affects their
efficacy. Seasonal turnover occurs when the impoundment's upper layer
of water becomes cooler and denser, typically as the season changes
from summer to fall. The cooler, upper layer of water then sinks and
causes the entire volume of the impoundment to circulate, which can
result in resuspension of solids that had settled to the bottom and a
consequent increase in the concentrations of pollutants discharged from
the impoundment.
    Chemical precipitation and biological treatment are more effective
than surface impoundments at removing both soluble and particulate
forms of metals, as well as other pollutants such as nitrogen compounds
and TDS. Because many of the pollutants of concern in FGD wastewater
are present in dissolved form and would not be removed by surface
impoundments, and because of the relatively large mass loads of these
pollutants (e.g., selenium, dissolved mercury) discharged in the FGD
wastestream, EPA decided not to finalize BAT effluent limitations for
FGD wastewater based on surface impoundments.
    EPA also rejected identifying chemical precipitation, alone,
(Option A) as BAT for FGD wastewater because, while chemical
precipitation systems are capable of achieving removals of various
metals, the technology is not effective at removing selenium, nitrogen
compounds, and certain metals that contribute to high concentrations of
TDS in FGD wastewater. These pollutants of concern are discharged by
steam electric power plants throughout the nation, causing adverse
human health impacts and some of the most egregious environmental
impacts (see Section XIII and EA). In light of this, and the fact that
economically achievable technologies are available to

reduce these pollutants of concern, EPA determined that, by itself,
chemical precipitation would not result in reasonable further progress
toward the national goal of eliminating the discharge of all pollutants
(see CWA section 301(b)(2)(A)), and rejected that technology basis as
BAT in favor of chemical precipitation followed by anaerobic/anoxic
biological treatment.
    EPA also decided not to establish, for all steam electric power
plants, BAT limitations for FGD wastewater based on treatment using an
evaporation system. In particular, this technology basis would employ a
falling-film evaporator (also known as a brine concentrator) to produce
a concentrated wastewater stream (brine) and a distillate stream.\23\
While evaporation systems are effective at removing boron and
pollutants that contribute to high concentrations of TDS, EPA decided
it would not be appropriate to identify evaporation as the BAT
technology basis for FGD wastewater at all steam electric power plants
because of the high cost of possible regulatory requirements based on
evaporation for discharges of FGD wastewater at existing facilities.
The annual cost to the industry of limitations based on evaporation
would be more than 2 and \1/2\ times the cost to industry estimated for
the final rule (after tax) (approximately $570 million more expensive
than the final rule, on an annual basis, after tax). Given the high
costs associated with the technology, and the fact that the steam
electric industry is facing costs associated with several other rules
in addition to this rule, EPA decided not to establish BAT limitations
for FGD wastewater based on evaporation for all steam electric power
plants. Nevertheless, as described further below, in Section VIII.C.13,
the final rule does establish a voluntary incentives program under
which steam electric power plants can choose to be subject to more
stringent BAT limitations for FGD wastewater based on evaporation.
---------------------------------------------------------------------------

    \23\ This evaporation step would have been preceded by a
chemical precipitation step using hydroxide precipitation, sulfide
precipitation, and iron co-precipitation, as well as a softening
step.
---------------------------------------------------------------------------

    Finally, EPA decided not to establish a requirement that would
direct permitting authorities to establish limitations for FGD
wastewater using site-specific BPJ. Public commenters representing
industry, state, and environmental group interests urged EPA not to
establish any requirement that would leave BAT effluent limitations for
FGD wastewater to be determined on a BPJ basis. Sections 301 and 304 of
the CWA require EPA to develop nationally applicable ELGs based on the
best available technology economically achievable, taking certain
factors into account. EPA decided that it would not be appropriate to
leave FGD wastewater requirements in the final rule to be determined on
a BPJ basis because there are sufficient data to set uniform,
nationally applicable limitations on FGD wastewater at plants across
the nation. Given this, BPJ permitting of FGD wastewater would place an
unnecessary burden on permitting authorities, including state and local
agencies, to conduct a complex technical analysis that they may not
have the resources or expertise to complete. BPJ permitting of FGD
wastewater would also unnecessarily burden the regulated industry
because of associated delays and uncertainty with respect to permits.
2. Fly Ash Transport Water
    This rule identifies dry handling as the BAT technology basis for
control of pollutants in fly ash transport water. Specifically, the
technology basis for BAT is a dry vacuum system that employs a
mechanical exhauster to pneumatically convey the fly ash (via a change
in air pressure) from hoppers directly to a silo. Dry handling is
clearly available to control the pollutants present in fly ash
transport water. Today, the vast majority of steam electric power
plants use dry handling techniques to manage fly ash, and by doing so
avoid generating fly ash transport water. All new generating units
built since the ELGs were last revised in 1982 have been subject to a
zero discharge standard for pollutants in fly ash transport water. In
addition, many owners and operators with generating units that are not
subject to the previously established zero discharge NSPS for fly ash
transport water have chosen to retrofit their units with dry fly ash
handling technology to meet operational needs or for economic reasons.
The trend in the industry is, moreover, toward the conversion and use
of dry fly ash handling systems. See TDD Section 4.5. Based on data
collected in the industry survey, EPA estimates that approximately 80
percent of coal and petroleum coke-fired generating units operate dry
fly ash handling systems. Since the survey, companies have continued to
upgrade, or announce plans to upgrade, their ash handling systems at
generating units. See TDD Section 4.5.
    Dry ash handling does not adversely affect plant operations or
reliability, and it promotes the beneficial reuse of coal combustion
residuals. In addition, converting to dry fly ash handling eliminates
the need to treat fly ash transport water in a surface impoundment, and
it reduces the amount of wastes entering surface impoundments and the
risk and severity of structural failures and spills.
    EPA decided not to finalize a BAT limitation on fly ash transport
water equal to the previously promulgated BPT limitation on TSS, based
on the technology of surface impoundments, for the same reasons (where
applicable) that EPA did not identify surface impoundments as BAT for
FGD wastewater (see Section VIII.C.1).
3. Bottom Ash Transport Water
    This rule identifies dry handling or closed-loop systems as the BAT
technology basis for control of pollutants in bottom ash transport
water.\24\ More specifically, the first technology basis for BAT is a
system in which bottom ash is collected in a water quench bath and a
drag chain conveyor (mechanical drag system) then pulls the bottom ash
out of the water bath on an incline to dewater the bottom ash. The
second technology basis for BAT is a system in which the bottom ash is
transported using the same processes as a wet-sluicing system, but
instead of going to an impoundment, the bottom ash is sluiced to a
remote mechanical drag system. Once there, a drag chain conveyor pulls
the bottom ash out of the water on an incline to dewater the bottom
ash, and the transport (sluice) water is then recycled back to the
bottom ash collection system.
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    \24\ EPA identified two technologies, a mechanical drag system
or a remote mechanical drag system, as the BAT technology basis for
bottom ash transport water because of potential space constraints at
some plants' boilers.
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    These technologies for control of bottom ash transport water are
demonstrably available. Based on survey data, more than 80 percent of
coal-fired generating units built in the last 20 years have installed
dry bottom ash handling systems. In addition, EPA found that more than
half of the entities that would be subject to BAT requirements for
bottom ash transport water are already employing zero discharge
technologies (dry handling or closed-loop wet ash handling) or planning
to do so in the near future.
    Dry bottom ash handling does not adversely affect plant operations
or reliability, and shifting to dry bottom ash handling offers certain
benefits. As was the case for dry fly ash handling, shifting to dry
bottom ash handling eliminates the need to send bottom ash transport
water to a surface impoundment, and it reduces the

amount of waste entering surface impoundments and the risk and severity
of structural failures and spills. Furthermore, one way companies may
choose to comply with the final rule's requirements is to install a
completely dry bottom ash system, which increases the energy efficiency
of the boiler, thus reducing the amount of coal burned and associated
emissions of carbon dioxide (CO2) and other pollutants per
MW of electricity generated. On an annual basis, EPA calculated
significant fuel savings and reduced air emissions from such systems,
the value of which EPA estimates to be $41 million to $117 million per
year.\25\ See DCN SE05980.
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    \25\ Neither these savings nor the fuel and emissions reductions
have been incorporated into EPA's analyses for this final rule.
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    EPA did not identify surface impoundments as BAT for bottom ash
transport water for the same reasons (where applicable) that it did not
identify surface impoundments as BAT for FGD wastewater (see Section
VIII.C.1). Moreover, because the estimated overall cost of the rule has
decreased since proposal (see Section IX), EPA also decided that
establishing different bottom ash transport water limitations for
generating units of and below a certain size (other than 50 MW, as
described in Section VIII.C.12), as in Option C, was not warranted.
    At proposal and for the final rule, EPA considered an option that
would have established differentiated bottom ash transport water
requirements for units below 400 MW (Option C). Some public commenters
stated that EPA's record does not support differentiated requirements
for bottom ash transport water. They stated that BAT should be
established at a level at which the costs are affordable to the
industry as a whole, and that the cost to a unit in terms of dollars
per amount of energy produced (in MW) is not a relevant factor. They
cited EPA's record, which demonstrates that units of all sizes have
installed dry handling and closed-loop systems, as well as EPA's
economic achievability analysis, which does not show that units of 400
MW or less are especially likely to shut down if faced with a zero
discharge requirement. Other commenters supported EPA's consideration
of the relative magnitude of costs per amount of energy produced for
units below or equal to 400 MW, as compared to larger units, as well as
differentiated bottom ash transport water requirements for these units.
    EPA reviewed its record and re-evaluated whether it would be
appropriate to establish differentiated requirements for discharges of
bottom ash transport water from existing sources based on unit size, in
light of comments and the key changes since proposal discussed in
Section V. Annualized cost per amount of energy produced increases
along a smooth curve moving from the very largest units to the smallest
units. See DCN SE05813. That, however, is expected due to economies of
scale. There is no clear breaking point at which to establish a size
threshold for purposes of differentiated requirements for bottom ash
transport water.\26\ Furthermore, EPA collected information in the
industry survey that found that units of all sizes, including those
less than 400 MW, have installed dry handling and closed-loop systems.
And, as further described below, EPA projects a net retirement of only
843 MW under the final rule. This suggests that, as a group, units of
400 MW or less do not face particularly unique hardships under the
final rule with respect to the industry as a whole. For these reasons,
the final rule does not establish differentiated bottom ash transport
water requirements for units equal to or below 400 MW (or for units
equal to or below any other size threshold, other than 50 MW, as
explained in Section VIII.C.12).
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    \26\ At the same time, costs per amount of energy produced do
begin to increase very dramatically as one moves from units above 50
MW to units that are equal to 50 MW and smaller, and thus for
reasons described in Section VIII.C.12, the final rule establishes
different requirements for units of 50 MW or less for several
wastestreams, including bottom ash transport water.
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4. FGMC Wastewater
    This rule identifies dry handling as the BAT technology basis for
the control of pollutants in FGMC wastewater. More specifically, the
technology basis for BAT is a dry vacuum system that employs a
mechanical exhauster to convey the FGMC waste (via a change in air
pressure) from hoppers directly to a silo. Dry handling of FGMC waste
is available and well demonstrated in the industry; indeed, nearly all
plants with FGMC systems use dry handling systems. Plants using sorbent
injection systems (e.g., activated carbon injection) to reduce mercury
emissions from the flue gas typically handle the spent sorbent in the
same manner as their fly ash (see Section VI.B.4 and TDD Section 7.5).
As of 2009, 92 percent of the industry generating FGMC waste uses dry
handling to manage it. Only a few plants use wet systems to transport
the spent sorbent to disposal in surface impoundments. Based on the
industry survey, the plants using wet handling systems operate them as
closed-loop systems and do not discharge FGMC wastewater, or they
already have a dry handling system that is capable of achieving zero
discharge. Under the zero discharge limitation, these plants could
choose to continue to operate their wet systems as closed-loop systems,
or they could convert to dry handling technologies by managing the fly
ash and spent sorbent together in a retrofitted dry system (rather than
an impoundment) or by installing dedicated dry handling equipment for
the FGMC waste similar to the equipment used for fly ash.
    EPA decided that it would not be appropriate to establish BAT
limitations for FGMC wastewater based on surface impoundments for the
same reasons (where applicable) that it did not identify surface
impoundments as BAT for FGD wastewater (see Section VIII.C.1).
5. Gasification Wastewater
    This rule identifies evaporation as the BAT technology basis for
the control of pollutants in gasification wastewater. More
specifically, the technology basis for BAT is an evaporation system
using a falling-film evaporator (or brine concentrator) to produce a
concentrated wastewater stream (brine) and a reusable distillate
stream. This evaporation technology is available and well demonstrated
in the industry for treatment of gasification wastewater. All three
IGCC plants now operating in the U.S. (the only existing sources of
gasification wastewater) use evaporation technology to treat their
gasification wastewater.
    EPA did not identify surface impoundments as BAT for gasification
wastewater for the same reasons (where applicable) that it did not
identify surface impoundments as BAT for FGD wastewater (see Section
VIII.C.1). In addition, one existing IGCC plant previously used a
surface impoundment to treat its gasification wastewater, and the
impoundment effluent repeatedly exceeded its NPDES permit effluent
limitations necessary to meet applicable WQS. Because of the
demonstrated inability of surface impoundments to remove the pollutants
of concern, and given that current industry practice is treatment of
gasification wastewater using evaporation, EPA concluded that surface
impoundments do not represent BAT for gasification wastewater.
    EPA also considered including cyanide treatment as part of the
technology basis for BAT (as well as NSPS, PSES, and PSNS) for
gasification wastewater. EPA is aware that the Edwardsport IGCC plant,
which began commercial operation in June 2013, includes cyanide
destruction as one step

in the treatment process for gasification wastewater. EPA, however,
does not currently have sufficient data with which to calculate
possible ELGs for cyanide. Thus, EPA decided not to establish cyanide
limitations or standards for gasification wastewater in this rule. This
decision does not preclude permitting authorities from setting more
stringent effluent limitations where necessary to meet WQS. In those
cases, plants may elect to install additional treatment, like cyanide
destruction, to meet water quality-based effluent limitations.
6. Combustion Residual Leachate
    EPA received public comments expressing concern that the proposed
definition of combustion residual leachate would apply to contaminated
stormwater. Although this was not the Agency's intention, for the final
rule, EPA revised the definition to make it clear that contaminated
stormwater does not fall within the final definition of combustion
residual leachate. This rule identifies surface impoundments as the BAT
technology basis for control of pollutants in combustion residual
leachate. Based on surface impoundments, which relies on gravity to
remove particulates, this rule establishes a BAT limitation on TSS in
combustion residual leachate equal to the previously promulgated BPT
limitation on TSS in low volume waste sources. Few steam electric power
plants currently employ technologies other than surface impoundments
for treatment of combustion residual leachate. Throughout the
development of this rule, EPA considered whether technologies in place
for treatment of other wastestreams at steam electric power plants and
wastestreams generated by other industries, including chemical
precipitation, could be used for combustion residual leachate. At
proposal, noting the small amount of pollutants in combustion residual
leachate relative to other significant wastestreams at steam electric
power plants, and that this was an area ripe for innovation, EPA
requested additional information related to cost, pollutant reduction,
and effectiveness of chemical precipitation and alternative approaches
to treat combustion residual leachate. Commenters did not provide
information that EPA could use to establish BAT limitations. Thus, EPA
decided not to finalize BAT limitations for combustion residual
leachate based on chemical precipitation (Option E). The record
demonstrates that the amount of pollutants collectively discharged in
combustion residual leachate by steam electric power plants is a very
small portion of the pollutants discharged collectively by all steam
electric power plants (approximately 3 percent of baseline loadings, on
a toxic-weighted basis). Given this, and the fact that this rule
regulates the wastestreams representing the three largest sources of
pollutants from steam electric power plants (including by setting a
zero discharge standard for two out of the three wastestreams), EPA
decided that this rule already represents reasonable further progress
toward the CWA's goals. The final rule, therefore, establishes BAT
limitations for combustion residual leachate equal to the BPT
limitation on TSS for low volume waste sources.
7. Timing
    As part of the consideration of the technological availability and
economic achievability of the BAT limitations in the rule, EPA
considered the magnitude and complexity of process changes and new
equipment installations that would be required at facilities to meet
the rule's requirements. As described in greater detail in Section
XVI.A.1, where BAT limitations in this rule are more stringent than
previously established BPT limitations, those limitations do not apply
until a date determined by the permitting authority that is as soon as
possible beginning November 1, 2018 (approximately three years
following promulgation of this rule), but that is also no later than
December 31, 2023 (approximately eight years following promulgation).
    Consistent with the proposal and supported by many commenters, the
final rule takes this approach in order to provide the time that many
facilities need to raise capital, plan and design systems, procure
equipment, and construct and then test systems. It also allows for
consideration of plant changes being made in response to other Agency
rules affecting the steam electric industry (see Section V.B).
Moreover, it enables facilities to take advantage of planned shutdown
or maintenance periods to install new pollution control
technologies.\27\ EPA's decision is also designed to allow, more
broadly, for the coordination of generating unit outages in order to
maintain grid reliability and prevent any potential impacts on
electricity availability, something that public commenters urged EPA to
consider. In addition, as requested by industry and states, this final
rule and preamble clarify how the ``as soon as possible date'' is
determined and implemented for steam electric power plants. The final
rule specifies the factors that the permitting authority must consider
in determining the ``as soon as possible'' date, and Section XVI.A.1
provides guidance on implementation with respect to timing. In
addition, the rule includes a ``no later than'' date of December 31,
2023, for implementation because, as public commenters pointed out,
without such a date, implementation could be substantially delayed, and
a firm ``no later than'' date creates a more level playing field across
the industry. EPA's economic analysis assumes prompt renewal of permits
(no permits will be administratively continued) and, thus, that the
requirements of the rule will be fully implemented by 2023. While some
commenters requested that EPA give permitting authorities the ability
to extend the implementation period beyond December 31, 2023, in light
of public comments received on the proposal, and the fact that plants
can reasonably be expected to meet the new ELGs by December 31, 2023,
this timeframe is appropriate given the CWA's pollutant discharge
elimination goals (see CWA section 101(a)).