[Federal Register Volume 76, Number 85 (Tuesday, May 3, 2011)]
[Proposed Rules]
[Pages 24976-25147]
[FR Doc No: 2011-7237]

Vol. 76

Tuesday,

No. 85

May 3, 2011

Part II

Environmental Protection Agency

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40 CFR Parts 60 and 63

National Emission Standards for Hazardous Air Pollutants From Coal- and
Oil-Fired Electric Utility Steam Generating Units and Standards of
Performance for Fossil-Fuel-Fired Electric Utility, Industrial-
Commercial-Institutional, and Small Industrial-Commercial-Institutional
Steam Generating Units; Proposed Rule

Federal Register / Vol. 76, No. 85 / Tuesday, May 3, 2011 / Proposed
Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60 and 63

[EPA-HQ-OAR-2009-0234; EPA-HQ-OAR-2011-0044, FRL-9286-1]
RIN 2060-AP52

National Emission Standards for Hazardous Air Pollutants From
Coal- and Oil-Fired Electric Utility Steam Generating Units and
Standards of Performance for Fossil-Fuel-Fired Electric Utility,
Industrial-Commercial-Institutional, and Small Industrial-Commercial-
Institutional Steam Generating Units

AGENCY: Environmental Protection Agency.

ACTION: Proposed rule.

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SUMMARY: The United States (U.S.) Environmental Protection Agency (EPA
or Agency) is proposing national emission standards for hazardous air
pollutants (NESHAP) from coal- and oil-fired electric utility steam
generating units (EGUs) under Clean Air Act (CAA or the Act) section
112(d) and proposing revised new source performance standards (NSPS)
for fossil fuel-fired EGUs under CAA section 111(b). The proposed
NESHAP would protect air quality and promote public health by reducing
emissions of the hazardous air pollutants (HAP) listed in CAA section
112(b). In addition, these proposed amendments to the NSPS are in
response to a voluntary remand of a final rule. We also are proposing
several minor amendments, technical clarifications, and corrections to
existing NSPS provisions for fossil fuel-fired EGUs and large and small
industrial-commercial-institutional steam generating units.

DATES: Comments must be received on or before July 5, 2011. Under the
Paperwork Reduction Act (PRA), comments on the information collection
provisions are best assured of having full effect if the Office of
Management and Budget (OMB) receives a copy of your comments on or
before June 2, 2011.
    Public Hearing: EPA will hold three public hearings on this
proposal. The dates, times, and locations of the public hearings will
be announced separately. Oral testimony will be limited to 5 minutes
per commenter. The EPA encourages commenters to provide written
versions of their oral testimonies either electronically or in paper
copy. Verbatim transcripts and written statements will be included in
the rulemaking docket. If you would like to present oral testimony at
one of the hearings, please notify Ms. Pamela Garrett, Sectors Policies
and Programs Division (C504-03), U.S. EPA, Research Triangle Park, NC
27711, telephone number<PHONE_NUMBER>; e-mail<EMAIL_ADDRESS>
Persons wishing to provide testimony should notify Ms. Garrett at least
2 days in advance of each scheduled public hearing. For updates and
additional information on the public hearings, please check EPA's Web
site for this rulemaking, http://www.epa.gov/ttn/atw/utility/utilitypg.html. The public hearings will provide interested parties the
opportunity to present data, views, or arguments concerning the
proposed rule. EPA officials may ask clarifying questions during the
oral presentations, but will not respond to the presentations or
comments at that time. Written statements and supporting information
submitted during the comment period will be considered with the same
weight as any oral comments and supporting information presented at the
public hearings.

ADDRESSES: Submit your comments, identified by Docket ID. No. EPA-HQ-
OAR-2011-0044 (NSPS action) or Docket ID No. EPA-HQ-OAR-2009-0234
(NESHAP action), by one of the following methods:
     http://www.regulations.gov. Follow the instructions for
submitting comments.
     http://www.epa.gov/oar/docket.html. Follow the
instructions for submitting comments on the EPA Air and Radiation
Docket Web site.
     E-mail: Comments may be sent by electronic mail (e-mail)
to<EMAIL_ADDRESS>Attention EPA-HQ-OAR-2011-0044 (NSPS action)
or EPA-HQ-OAR-2009-0234 (NESHAP action).
     Fax: Fax your comments to:<PHONE_NUMBER>, Docket ID No.
EPA-HQ-OAR-2011-0044 (NSPS action) or Docket ID No. EPA-HQ-OAR-2009-
0234 (NESHAP action).
     Mail: Send your comments on the NESHAP action to: EPA
Docket Center (EPA/DC), Environmental Protection Agency, Mailcode:
2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460, Docket ID No.
EPA-HQ-OAR-2009-0234. Send your comments on the NSPS action to: EPA
Docket Center (EPA/DC), Environmental Protection Agency, Mailcode:
2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460, Docket ID.
EPA-HQ-OAR-2011-0044. Please include a total of two copies. In
addition, please mail a copy of your comments on the information
collection provisions to the Office of Information and Regulatory
Affairs, OMB, Attn: Desk Officer for EPA, 725 17th St., NW.,
Washington, DC 20503.
     Hand Delivery or Courier: Deliver your comments to: EPA
Docket Center, EPA West, Room 3334, 1301 Constitution Ave., NW.,
Washington, DC 20460. Such deliveries are only accepted during the
Docket's normal hours of operation (8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holiday), and special arrangements
should be made for deliveries of boxed information.
    Instructions: All submissions must include agency name and
respective docket number or Regulatory Information Number (RIN) for
this rulemaking. All comments will be posted without change and may be
made available online at http://www.regulations.gov, including any
personal information provided, unless the comment includes information
claimed to be confidential business information (CBI) or other
information whose disclosure is restricted by statute. Do not submit
information that you consider to be CBI or otherwise protected through
http://www.regulations.gov or e-mail. The http://www.regulations.gov
Web site is an ``anonymous access'' system, which means EPA will not
know your identity or contact information unless you provide it in the
body of your comment. If you send an e-mail comment directly to EPA
without going through http://www.regulations.gov, your e-mail address
will be automatically captured and included as part of the comment that
is placed in the public docket and made available on the Internet. If
you submit an electronic comment, EPA recommends that you include your
name and other contact information in the body of your comment and with
any disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some
information is not publicly available (e.g., 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 form. Publicly available docket materials are available either
electronically in http://www.regulations.gov or in hard copy at

the EPA Docket Center, Room 3334, 1301 Constitution Avenue, 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<PHONE_NUMBER>, and the telephone
number for the Air Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For the NESHAP action: Mr. William
Maxwell, Energy Strategies Group, Sector Policies and Programs
Division, (D243-01), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; Telephone number:<PHONE_NUMBER>; Fax number<PHONE_NUMBER>; E-
mail address<EMAIL_ADDRESS>For the NSPS action: Mr. Christian
Fellner, Energy Strategies Group, Sector Policies and Programs
Division, (D243-01), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina
27711; Telephone number:<PHONE_NUMBER>; Fax number<PHONE_NUMBER>; E-
mail address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: The information presented in this preamble
is organized as follows:

I. General Information
    A. Executive Summary
    B. Does this action apply to me?
    C. What should I consider as I prepare my comments to EPA?
    D. Where can I get a copy of this document?
    E. When would a public hearing occur?
II. Background Information on the NESHAP
    A. Statutory Background
    B. Regulatory and Litigation Background
III. Appropriate and Necessary Finding
    A. Regulating EGUs Under CAA Section 112
    B. The December 2000 Appropriate and Necessary Finding Was
Reasonable
    C. EPA Must Regulate EGUs Under Section 112 Because EGUs Were
Properly Listed Under CAA Section 112(c)(1) and May Not Be Delisted
Because They Do Not Meet the Delisting Criteria in CAA Section
112(c)(9)
    D. New Analyses Confirm That It Remains Appropriate and
Necessary To Regulate U.S. EGU HAP Under Section 112
IV. Summary of This Proposed NESHAP
    A. What source categories are affected by this proposed rule?
    B. What is the affected source?
    C. Does this proposed rule apply to me?
    D. Summary of Other Related D.C. Circuit Court Decisions
    E. EPA's Response to the Vacatur of the 2005 Action
    F. What is the relationship between this proposed rule and other
combustion rules?
    G. What emission limitations and work practice standards must I
meet?
    H. What are the startup, shutdown, and malfunction (SSM)
requirements?
    I. What are the testing requirements?
    J. What are the continuous compliance requirements?
    K. What are the notification, recordkeeping, and reporting
requirements?
    L. Submission of Emissions Test Results to EPA
    V. Rationale for This Proposed NESHAP
    A. How did EPA determine which subcategories and sources would
be regulated under this proposed NESHAP?
    B. How did EPA select the format for this proposed rule?
    C. How did EPA determine the proposed emission limitations for
existing EGUs?
    D. How did EPA determine the MACT floors for existing EGUs?
    E. How did EPA consider beyond-the-floor for existing EGUs?
    F. Should EPA consider different subcategories?
    G. How did EPA determine the proposed emission limitations for
new EGUs?
    H. How did EPA determine the MACT floor for new EGUs?
    I. How did EPA consider beyond-the-floor for new EGUs?
    J. Consideration of Whether To Set Standards for HCl and Other
Acid Gas HAP Under CAA Section 112(d)(4)
    K. How did we select the compliance requirements?
    L. What alternative compliance provisions are being proposed?
    M. How did EPA determine compliance times for this proposed
rule?
    N. How did EPA determine the required records and reports for
this proposed rule?
    O. How does this proposed rule affect permits?
    P. Alternative Standard for Consideration
VI. Background Information on the Proposed NSPS
    A. What is the statutory authority for this proposed NSPS?
    B. Summary of State of New York, et al., v. EPA Remand
    C. EPA's Response to the Remand
    D. EPA's Response to the Utility Air Regulatory Group's Petition
for Reconsideration
VII. Summary of the Significant Proposed NSPS Amendments
    A. What are the proposed amended emissions standards for EGUs?
    B. Would owners/operators of any EGUs be exempt from the
proposed amendments?
    C. What other significant amendments are being proposed?
VIII. Rationale for This Proposed NSPS
    A. How are periods of malfunction addressed?
    B. How did EPA determine the proposed emission limitations?
    C. Changes to the Affected Facility
    D. Additional Proposed Amendments
    E. Request for Comments on the Proposed NSPS Amendments
IX. Summary of Cost, Environmental, Energy, and Economic Impacts of
This Proposed NSPS
X. Impacts of These Proposed Rules
    A. What are the air impacts?
    B. What are the energy impacts?
    C. What are the compliance costs?
    D. What are the economic impacts?
    E. What are the benefits of this proposed rule?
XI. Public Participation and Request for Comment
XII. Statutory and Executive Order Reviews
    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 as Amended by the Small Business
Regulatory Enforcement Fairness Act (RFA) of 1996 SBREFA), 5 U.S.C.
601 et seq.
    D. Unfunded Mandates Reform Act of 1995
    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 Concerning Regulations 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

I. General Information

A. Executive Summary

    In December 2000, EPA appropriately concluded that it was
appropriate and necessary to regulate hazardous air pollutants (HAP)
from EGUs. Today, EPA confirms that finding and concludes that it
remains appropriate and necessary to regulate these emissions from
EGUs. Hazardous air pollutants from EGUs contribute to adverse health
and environmental effects. EGUs are by far the largest U.S.
anthropogenic sources of mercury (Hg) emissions into the air and emit a
number of other HAP. Both the finding in 2000 and our conclusion that
it remains appropriate and necessary to regulate HAP from EGUs are
supported by the CAA and scientific and technical analyses.
    Mercury is a highly toxic pollutant that occurs naturally in the
environment and is released into the atmosphere in significant
quantities as the result of the burning of fossil fuels. Mercury in the
environment is transformed into a more toxic form, methylmercury
(MeHg), and because it is also a persistent pollutant, it accumulates
in the food chain, especially the tissue of fish. When people consume
these fish they consume MeHg, the consumption of which may cause
neurotoxic effects. Children, and, in particular, developing

fetuses, are especially susceptible to MeHg effects because their
developing bodies are more highly sensitive to its effects. In the
December 2000 Finding, we estimated that about 7 percent of women of
child-bearing age are exposed to MeHg at a level capable of causing
adverse effects in the developing fetus, and that about 1 percent were
exposed to 3 to 4 times that level. 65 FR 79827. Moreover, in the 1997
Mercury Study Report to Congress (the ``Mercury Study''),\1\ we
concluded that exposures among specific subpopulations including
anglers, Asian-Americans, and members of some Native American Tribes
may be more than two-times greater than those experienced by the
average U.S. population (U.S. EPA 1997 Mercury Study Report to
Congress, Volume IV, page 7-2).
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    \1\ U.S. EPA. 1997. Mercury Study Report to Congress. EPA-452/R-
97-003 December 1997.
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    In addition to Hg, EGUs are significant emitters of HAP metals such
as arsenic (As), nickel (Ni), cadmium (Cd), and chromium (Cr), which
can cause cancer; HAP metals with potentially serious noncancer health
effect such as lead (Pb) and selenium (Se); and other toxic air
pollutants such as the acid gases hydrogen chloride (HCl) and hydrogen
fluoride (HF). Adverse noncancer health effects associated with non-Hg
EGU HAP include chronic health disorders (e.g., irritation of the lung,
skin, and mucus membranes, effects on the central nervous system, and
damage to the kidneys), and acute health disorders (e.g., lung
irritation and congestion, alimentary effects such as nausea and
vomiting, and effects on the kidney and central nervous system). Three
of the key metal HAP emitted by EGUs (As, Cr, and Ni) have been
classified as human carcinogens, while another (Cd) is classified as a
probable human carcinogen. Current national emissions inventories
indicate that EGUs are responsible for 62 percent of the national total
emissions of As, 22 percent of the national total emissions of Cr, and
28 percent of the national total emissions of Ni to the atmosphere.
Notably, EGUs are also responsible for 83 percent of the national total
emissions of Se to the atmosphere.
    Congress recognized the threats posed by emissions of HAP and was
dissatisfied with the pace of EPA's progress in reducing them prior to
1990. As a result, it enacted significant changes to the CAA that
required EPA to develop stringent standards for the control of these
pollutants from both stationary and mobile sources. Congress included
the requirements in the 1990 CAA amendments regarding acid rain that
would reduce emissions of certain criteria pollutants from EGUs and
result in the installation of controls that might achieve HAP emission
reduction co-benefits. For that reason, it added the requirement for
EPA to make a finding before it could regulate EGUs under section 112.
Specifically, Congress required in the air toxics provisions that EPA
conduct a study of the public health hazards anticipated to remain from
EGU HAP emissions after imposition of these other provisions and
regulate EGUs under section 112 if the Agency found, after considering
the results of the study, that such regulation was appropriate and
necessary. Congress also required EPA to conduct a study of Hg
emissions from EGUs and other sources and consider the health and
environmental effects of the emissions and the availability and cost of
control technologies.
    Responding to Congress, EPA published the required studies
detailing the hazards posed by emissions of Hg and the risks posed by
emissions of Hg and other HAP from fossil fuel-fired EGUs. Following
the publication of the studies and after collecting additional relevant
data, EPA concluded in December 2000 that the threats to public health
and the environment from emissions of Hg and other HAP from EGUs made
it both appropriate and necessary to adopt regulations under section
112 to reduce the emissions of Hg and other HAP from coal- and oil-
fired EGUs. As a result of its findings, EPA added these sources to the
list of stationary sources subject to regulations governing the
emissions of HAP. However, in a rulemaking effort completed in 2005,
EPA reversed its findings and instead adopted regulations under other
provisions of the CAA. The DC Circuit Court vacated the resulting
regulations, noting that EPA had sidestepped important legal
requirements in the CAA that govern the delisting of source categories.
Those requirements provide that EPA can delist a source category only
if it can demonstrate that no source within the listed category poses a
lifetime cancer risk above one in one million to the individual most
exposed and that emissions from no source in the category exceed the
level that is adequate to protect public health with an ample margin of
safety and that no adverse environmental effects will result from the
emissions of any source. CAA 112(c)(9)(B). The DC Circuit Court's
action restored EPA's December 2000 determination that it was
appropriate and necessary to regulate coal- and oil-fired EGUs under
section 112, and EGUs remain a listed source category.
    EPA reasonably concluded in December 2000, based on the information
available to the Agency at that time, that it was appropriate and
necessary to regulate EGUs under section 112. Now, more than 10 years
have passed since EPA's determination that toxic emissions from coal-
and oil-fired EGUs pose a threat to public health and the environment.
Although not required, EPA conducted additional, extensive technical
analyses based on more recent data, and those analyses confirm that it
remains appropriate and necessary to regulate HAPs from coal- and oil-
fired EGUs. Accordingly and without further delay, we are proposing a
set of HAP emission standards for coal- and oil-fired EGUs that can be
met with existing technology that has been available for a significant
time.
    EPA acknowledges that although EGUs contribute significantly to the
total amount of U.S. anthropogenic Hg emissions, other sources both
here and abroad also contribute significantly to the global atmospheric
burden and U.S. deposition of Hg. It is estimated that the U.S.
contributes 5 percent to global anthropogenic Hg and 2 percent the
total global Hg pool.\2\ However, as the U.S. Supreme Court has noted
in decisions as recently as Massachusetts v. EPA, regarding the problem
of climate change, it is not necessary to show that a problem will be
entirely solved by the action being taken, nor that it is necessary to
cure all ills before addressing those judged to be significant. 549
U.S. 497, 525 (2007).
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    \2\ Based on 2005 U.S. emissions of 105 tons, and global
emissions of 2,100 tons from UNEP. Mercury emissions are discussed
more fully in Section III.D.1 of this preamble.
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    At the time it published the December 2000 Finding, EPA identified
certain technologies capable of significantly reducing Hg and other HAP
emissions. Since then, additional technologies and improvements to
those previously identified have become available. These technologies
are also often effective at reducing significantly the emissions of
other conventional pollutants such as SO2 and PM, thereby
conferring even greater health co-benefits. As today's notice discusses
further, the reductions expected from the adopted final rule will
produce substantially greater co-benefits to health and the environment
than they will cost to affected companies. We further believe that
these reductions can be achieved without significantly affecting the
availability and cost of electricity to

consumers. In those instances in which such concerns do arise, the
Federal government will work with companies to ensure a reliable and
reasonably-priced supply of electricity. Moreover, in its assessment of
the impacts of today's proposed rule on jobs and the economy, EPA finds
that more jobs will be created in the air pollution control technology
production field than may be lost as the result of compliance with
these proposed rules.
    A number of EGUs operating today were built in the 1950s and 1960s,
using now-obsolete and inefficient technologies. Today, new units are
far more efficient in their production of electricity, their use of
fuel, and the relative quantities of pollution emitted. To the extent
that some of the oldest, least efficient, least controlled units are
retired by companies who elect not to invest in controlling them,
assessments included in the docket to today's notice of proposed
rulemaking indicate that there will be a sufficient supply of
electricity from newer units. In fact, one consequence of today's
proposed rule, if adopted as a final rule, will be that the market for
electricity in the U.S. will be more level and no longer skewed in
favor of the higher polluting units that were exempted from the CAA at
its inception on Congress' assumption that their useful life was near
an end. Thus, this proposed rule will require companies to make a
decision--control HAP emissions from virtually uncontrolled sources or
retire these sometimes 60 year old units and shift their emphasis to
more efficient, cleaner modern methods of generation, including modern
coal-fired generation.
    For the reasons summarized above and discussed in detail in this
document, the standards being proposed today will be effective at
significantly reducing emissions of Hg and an array of other toxic
pollutants from coal- and oil-fired EGUs. In addition, as a result of
the HAP reductions and co-benefits of these rules, many premature
deaths from exposure to air pollution will be avoided by the
application of controls that are well-known, broadly applied, and
available. To the extent that isolated issues remain concerning the
availability of electricity in some more remote parts of the country,
we believe that EPA has the ability to work with companies making good
faith efforts to comply with the standards so that consumers in those
areas are not adversely affected.
    Consistent with the recently issued Executive Order (EO) 13563,
``Improving Regulation and Regulatory Review,'' we have estimated the
cost and benefits of the proposed rule. The estimated net benefits of
our proposed rule at a 3 percent discount rate are $48 to 130 billion
or $42 to $120 billion at a 7 percent discount rate.

         Summary of the Monetized Benefits, Social Costs, and Net Benefits for the Proposed Rule in 2016
                                              [Millions of 2007$] a
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                                                  3% Discount rate                     7% Discount rate
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Total Monetized Benefits b............  $59,000 to $140,000................  $53,000 to $130,000.
Hg-related Benefits c.................  $4.1 to $5.9.......................  $0.45 to $0.89.
CO2-related Benefits..................  $570...............................  $570.
PM2.5-related Co-benefits d...........  $58,000 to $140,000................  $53,000 to $120,000.
Total Social Costs e..................  $10,900............................  $10,900.
Net Benefits..........................  $48,000 to $130,000................  $42,000 to $130,000.
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Non-monetized Benefits................  Visibility in Class I areas.
                                        Cardiovascular effects of Hg exposure.
                                        Other health effects of Hg exposure.
                                        Ecosystem effects.
                                        Commercial and non-freshwater fish consumption.
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a All estimates are for 2016, and are rounded to two significant figures. The net present value of reduced CO2
  emissions are calculated differently than other benefits. The same discount rate used to discount the value of
  damages from future emissions (SCC at 5, 3, 2.5 percent) is used to calculate net present value of SCC for
  internal consistency. This table shows monetized CO2 co-benefits at discount rates at 3 and 7 percent that
  were calculated using the global average SCC estimate at a 3 percent discount rate because the interagency
  workgroup on this topic deemed this marginal value to be the central value. In section 6.6 of the RIA we also
  report the monetized CO2 co-benefits using discount rates of 5 percent (average), 2.5 percent (average), and 3
  percent (95th percentile).
b The total monetized benefits reflect the human health benefits associated with reducing exposure to MeHg,
  PM2.5, and ozone.
c Based on an analysis of health effects due to recreational freshwater fish consumption.
d The reduction in premature mortalities from account for over 90 percent of total monetized PM2.5 benefits.
e Social costs are estimated using the MultiMarket model, in order to estimate economic impacts of the proposal
  to industries outside the electric power sector. Details on the social cost estimates can be found in Chapter
  9 and Appendix E of the RIA.

    For more information on how EPA is addressing EO 13563, see the
executive order discussion, later in the preamble.

B. Does this action apply to me?

    The regulated categories and entities potentially affected by the
proposed standards are shown in Table 1 of this preamble.

     Table 1--Potentially Affected Regulated Categories and Entities
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                                                        Examples of
           Category              NAICS code \1\    potentially regulated
                                                         entities
------------------------------------------------------------------------
Industry......................            221112  Fossil fuel-fired
                                                   electric utility
                                                   steam generating
                                                   units.
Federal government............        \2\ 221122  Fossil fuel-fired
                                                   electric utility
                                                   steam generating
                                                   units owned by the
                                                   Federal government.
State/local/tribal government.        \2\ 221122  Fossil fuel-fired
                                                   electric utility
                                                   steam generating
                                                   units owned by
                                                   municipalities.
                                          921150  Fossil fuel-fired
                                                   electric utility
                                                   steam generating
                                                   units in Indian
                                                   country.
------------------------------------------------------------------------
\1\ North American Industry Classification System.
\2\ Federal, State, or local government-owned and operated
  establishments are classified according to the activity in which they
  are engaged.

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by this
action. To determine whether your facility, company, business,
organization, etc., would be regulated by this action, you should
examine the applicability criteria in 40 CFR 60.40, 60.40Da, or 60.40c
or in 40 CFR 63.9982. If you have any questions regarding the
applicability of this action to a particular entity, consult either the
air permitting authority for the entity or your EPA regional
representative as listed in 40 CFR 60.4 or 40 CFR 63.13 (General
Provisions).

C. What should I consider as I prepare my comments to EPA?

    Do not submit information containing CBI to EPA through http://www.regulations.gov or e-mail. Send or deliver information identified
as CBI only to the following address: Roberto Morales, OAQPS Document
Control Officer (C404-02), Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711, Attention: Docket ID EPA-HQ-OAR-2011-0044
(NSPS action) or Docket ID EPA-HQ-OAR-2009-0234 (NESHAP action).
Clearly mark the part or all of the information that you claim to be
CBI. For CBI information in a disk or CD-ROM that you mail to EPA, mark
the outside of the disk or CD-ROM as CBI and then identify
electronically within the disk or CD-ROM the specific information that
is claimed as CBI. In addition to one complete version of the comment
that includes information claimed as CBI, a copy of the comment that
does not contain the information claimed as CBI must be submitted for
inclusion in the public docket. Information so marked will not be
disclosed except in accordance with procedures set forth in 40 CFR part
2.

D. Where can I get a copy of this document?

    In addition to being available in the docket, an electronic copy of
this proposed rule will also be available on the Worldwide Web (WWW)
through the Technology Transfer Network (TTN). Following signature, a
copy of the proposed rule will be posted on the TTN's policy and
guidance page for newly proposed or promulgated rules at the following
address: http://www.epa.gov/ttn/oarpg/. The TTN provides information
and technology exchange in various areas of air pollution control.

E. When would a public hearing occur?

    EPA will hold three public hearings on this proposal. The dates,
times, and locations of the public hearings will be announced
separately. If you would like to present oral testimony at one of the
hearings, please notify Ms. Pamela Garrett, Sectors Policies and
Programs Division (C504-03), U.S. EPA, Research Triangle Park, NC
27711, telephone number<PHONE_NUMBER>; e-mail<EMAIL_ADDRESS>
Persons wishing to provide testimony should notify Ms. Garrett at least
2 days in advance of the public hearings. For updates and additional
information on the public hearings, please check EPA's Web site for
this rulemaking, http://www.epa.gov/ttn/atw/utility/utilitypg.html.

II. Background Information on the NESHAP

    In 1990, Congress substantially rewrote provisions of the CAA
addressing emissions of HAP from large and small stationary sources in
the U.S. Collectively, these sources emit into the air millions of
pounds of HAP each year, chemicals that are known to cause or are
suspected of causing cancer, birth defects, reproduction problems, and
other serious health effects. Many of the sources that emit air toxics
are located in urban areas, which generally include predominantly low
income, minority or otherwise vulnerable communities, where dense
populations mean that large numbers of people may be exposed.
    Since 1990, EPA has promulgated regulations covering over 50
industrial sectors, requiring the use of available control technology
and other practices to reduce emissions. These standards have reduced
emissions of HAP from American industry by more than 60 percent. HAP
emissions from smaller sources such as dry cleaners and auto body shops
have declined by 30 percent, also due to CAA standards. Greater
reductions are expected as greater numbers of smaller sources adopt
pollution prevention, efficiency, or install control technologies to
comply with EPA emission standards. Emissions from the mobile source
sector have also been addressed. Controls for fuels and vehicles are
expected to reduce selected HAP from vehicles by more than 75 percent
by 2020.
    EGUs are the most significant source of HAP in the country that
remains unaddressed by Congress's air toxics program. EGUs emit
multiple HAP of concern and are by far the largest remaining source of
Hg, which is one of the more highly toxic chemicals on Congress's list
of HAP and which, once released, stays in the environment permanently.
Coal- and oil-fired EGUs also emit HAP such as As, other metals and
acid gases in amounts significantly higher than almost any other
industrial sector. They are located in nearly every state, and
emissions from their stacks affect people nearby as well as hundreds of
miles away.
    Congress provided a specific path for EPA to regulate HAP emissions
from EGUs. It gave explicit instructions about scientific studies EPA
needed to develop and then consider in determining whether it was
``appropriate and necessary'' to regulate HAP emissions from EGUs.
Congress anticipated that EPA would complete the studies by 1994. In
2000, EPA found that it was indeed ``appropriate and necessary'' to
regulate HAP emissions from EGUs under section 112. In the decade that
has passed since EPA made that finding, EGUs have continued to emit Hg
and other HAP, and there are still no national limits on the amount of
Hg and other HAP that EGUs can release into the air. And, although some
plants have installed available and effective control technologies that
reduce these emissions, there is no requirement for EGUs to control for
Hg and other HAP.
    As our new analyses demonstrate, it remains both appropriate and
necessary to set standards for coal- and oil-fired EGUs to protect
public health and the environment from the adverse effects of HAP
emissions from EGUs. The Agency's appropriate and necessary finding was
correct in 2000, and it remains correct today. EPA proposes to set
standards for coal- and oil-fired EGUs that will reduce emissions of
Hg, Ni and other metal HAP, acid gas HAP, and other harmful HAP. These
standards are based on available control technologies and other
practices already used by the better-controlled and lower-emitting
EGUs. They are achievable, we believe they can be implemented without
disruption to the reliable provision of electricity, and will deliver
health protection across the U.S.
    In this section, we provide an overview of the relevant statutory,
regulatory, and litigation background.

A. Statutory Background

    Congress enacted section 112 to address HAP emissions from
stationary sources. Section 112 contains provisions specific to EGUs,
which we will address in this preamble, but we begin with a summary of
the overall structure and purpose of the section 112 program.
    Prior to the 1990 Amendments, the CAA required EPA to regulate HAP
solely on the basis of risk to human

health. Legislative History of the CAA Amendments of 1990
(``Legislative History''), at 3174-75, 3346 (Comm. Print 1993).
Congress was dissatisfied with the slow pace of exclusively risk-based
regulation of HAP prior to 1990, however, and, as a result,
substantially amended the CAA in 1990, setting forth a two-stage
approach for regulating HAP emissions. Under the first stage, Congress
directed EPA to issue technology-based emission standards for listed
source categories. CAA sections 112 (c)-(d). In the second stage, which
occurs ``within eight years'' of the imposition of the technology-based
standards, EPA must consider whether residual risks remain after
imposition of the MACT standards that warrant more stringent standards
to protect human health or to prevent an adverse environmental effect.
CAA section 112(f)(2)(A).
    In addition to adopting this two-phased approach to standard-
setting, Congress included a series of rigorous deadlines for EPA,
including deadlines for listing categories and issuing emission
standards for such categories. See, e.g., CAA section 112(e)(1). Thus,
in substantially amending CAA section 112 in 1990, Congress sought
prompt and permanent reductions of HAP emissions from stationary
sources--first through technology-based standards, and then further, as
necessary, through risk-based standards designed to protect human
health and the environment.
    The criteria for regulation differ in section 112 depending on
whether the source is a major source or an area source. A ``major
source'' is any stationary source \3\ or group of stationary sources at
a single location and under common control that emits or has the
potential to emit 10 tons or more per year of any HAP or 25 tons or
more per year of any combination of HAP. See CAA 112(a)(1). An ``area
source'' is any stationary source of HAP that is not a ``major
source.'' See CAA 112(a)(2). For major sources, EPA must list a
category under section 112(c)(1) if at least one stationary source in
the category meets the definition of a major source.\4\ For area
sources, EPA must list if: (1) EPA determines that the category of area
sources presents a threat of adverse effects to human health or the
environment that warrants regulation under CAA section 112; or (2) the
category of area sources falls within the purview of CAA section
112(k)(3)(B) (the Urban Area Source Strategy). See CAA section
112(c)(3).
---------------------------------------------------------------------------

    \3\ A ``stationary source'' of HAP is any building, structure,
facility or installation that emits or may emit any air pollutant.
See CAA Section 112(a)(3).
    \4\ Congress required EPA to publish a list of categories and
subcategories of major sources and area sources by November 15,
1991. See CAA 112(c)(1) & (c)(3). EPA published the initial list on
July 16, 1992. See 57 FR 31576, July 16, 1992. EPA did not include
EGUs on the initial section 112(c) list because Congress required
EPA to conduct and consider the results of the study required by
section 112(n)(1)(A) before regulating these units. At the time of
the initial listing, EPA had not completed the study required by
section 112(n)(1)(A).
---------------------------------------------------------------------------

    Congress established a specific structure for determining whether
to regulate EGUs under section 112.\5\ Specifically, Congress enacted
CAA section 112(n)(1).
---------------------------------------------------------------------------

    \5\ ``Electric utility steam generating unit'' is defined as any
``fossil fuel fired combustion unit of more than 25 megawatts that
serves a generator that produces electricity for sale.'' See CAA
112(a)(8).
---------------------------------------------------------------------------

    In section 112(n)(1)(A), EPA is directed to conduct a study to
evaluate the hazards to public health reasonably anticipated to occur
as the result of HAP emissions from EGUs after imposition of the
requirements of the CAA, and to report the results of such study to
Congress by November 15, 1993 (Utility Study Report to Congress; \6\
the ``Utility Study''). We discuss this study further below in
conjunction with the other studies Congress required be conducted with
respect to EGUs under section 112(n)(1). The last sentence of section
112(n)(1)(A) provides that EPA shall regulate EGUs under CAA section
112 ``if the Administrator finds such regulation is appropriate and
necessary, after considering the results of the [Utility Study] * * *''
Thus, section 112(n)(1)(A) governs how the Administrator decides
whether to list EGUs for regulation under section 112. See New Jersey,
517 F.3d at 582 (``Section 112(n)(1) governs how the Administrator
decides whether to list EGUs; it says nothing about delisting EGUs.'').
---------------------------------------------------------------------------

    \6\ US EPA. Study of Hazardous Air Pollutant Emissions from
Electric Utility Steam Generating Units --Final Report to Congress.
EPA-453/R-98-004a. February 1998.
---------------------------------------------------------------------------

    Once a source category is listed pursuant to section 112(c), the
next step is for EPA to establish technology-based emission standards
under section 112(d). Under section 112(d), EPA must establish emission
standards for major sources that ``require the maximum degree of
reduction in emissions of the HAP subject to this section'' that EPA
determines is achievable taking into account certain statutory factors.
These are referred to as ``maximum achievable control technology'' or
``MACT'' standards. The MACT standards for existing sources must be at
least as stringent as the average emissions limitation achieved by the
best performing 12 percent of existing sources in the category (for
which the Administrator has emissions information) or the best
performing 5 sources for source categories with less than 30 sources.
See CAA section 112(d)(3)(A) and (B). This level of minimum stringency
is referred to as the MACT floor, and EPA cannot consider cost in
setting the floor. For new sources, MACT standards must be at least as
stringent as the control level achieved in practice by the best
controlled similar source. See CAA section 112(d)(3). EPA also must
consider more stringent ``beyond-the-floor'' control options. When
considering beyond-the-floor options, EPA must consider not only the
maximum degree of reduction in emissions of HAP, but must take into
account costs, energy, and nonair quality health and environmental
impacts when doing so. See Cement Kiln Recycling Coal. v. EPA, 255 F.3d
855, 857-58 (D.C. Cir. 2001).
    CAA section 112(d)(4) authorizes EPA to set a health-based standard
for a limited set of HAP for which a health threshold has been
established, and that standard must provide for ``an ample margin for
safety.'' 42 U.S.C. 7412(d)(4). As these standards are potentially less
stringent than MACT standards, the Agency must have detailed
information on HAP emissions from the subject sources and sources
located near the subject sources before exercising its discretion to
set such standards.
    For area sources, section 112(d)(5) authorizes EPA to issues
standards or requirements that provide for the use of generally
available control technologies (GACT) or management practices in lieu
of promulgating standards pursuant to sections 112(d)(2) and (3).
    As noted above, Congress required that various reports concerning
EGUs be completed. The first report, the Utility Study, required EPA to
evaluate the hazards to public health reasonably anticipated to occur
as the result of HAP emissions from EGUs after imposition of the
requirements of the CAA. This report was required by November 15, 1993.
The second report, due on November 15, 1994, directed EPA to ``conduct
a study of mercury emissions from [EGUs], municipal waste combustion
units, and other sources, including area sources.'' See CAA section
112(n)(1)(B). In conducting the Mercury study Congress directed EPA to
``consider the rate and mass of emissions, the health and environmental
effects of such emissions, technologies which are available to control
such emissions, and the costs of such technologies.'' Id. EPA completed
both of these reports by 1998.

    The last required report was to be completed by the National
Institute of Environmental Health Sciences (NIEHS) and submitted to
Congress by November 15, 1993. CAA section 112(n)(1)(C) directed NIEHS
to conduct ``a study to determine the threshold level of Hg exposure
below which adverse human health effects are not expected to occur.''
In conducting this study, NIEHS was to determine ``a threshold for
mercury concentrations in the tissue of fish which may be consumed
(including consumption by sensitive populations) without adverse
effects to public health.'' Id. NIEHS submitted this Report to Congress
in August, 1995.
    In addition, Congress, in conference report language associated
with EPA's fiscal year 1999 appropriations, directed EPA to fund the
National Academy of Sciences (NAS) to perform an independent evaluation
of the available data related to the health impacts of MeHg
(``Toxicological Effects of Methylmercury,'' hereinafter, NAS Study or
MeHg Study).\7\ H.R. Conf. Rep. No. 105-769, at 281-282 (1998).
Specifically, NAS was tasked with advising EPA as to the appropriate
reference dose (RfD) for MeHg, which is the amount of a chemical which,
when ingested daily over a lifetime, is anticipated to be without
adverse health effects to humans, including sensitive subpopulations.
65 FR 79826. In that same conference report, Congress indicated that
EPA should not make the appropriate and necessary regulatory
determination for Hg emissions until EPA had reviewed the results of
the NAS Study. See H.R. Conf. Rep. No. 105-769, at 281-282 (1998).
---------------------------------------------------------------------------

    \7\ National Research Council (NAS). 2000. Toxicological Effects
of Methylmercury. Committee on the Toxicological Effects of
Methylmercury, Board on Environmental Studies and Toxicology,
National Research Council. Many of the peer-reviewed articles cited
in this section are publications originally cited in the NAS report.
---------------------------------------------------------------------------

    The NAS Study evaluated the same issues as those required to be
considered under section 112(n)(1)(C). The NAS Study was completed 5
years after the NIEHS Study, and, thus, considered additional
information not available to NIEHS. Because Congress required that the
same issues be addressed in both the NAS and NIEHS Studies and the NAS
Study was issued after the NIEHS study, we discuss, for purposes of
this document, the content of the NAS Study, as opposed to the NIEHS
Study.

B. Regulatory and Litigation Background

    EPA conducted the studies required by section 112(n)(1) concerning
utility HAP emissions. Prior to issuance of the Mercury Study, EPA
engaged in two extensive external peer reviews of the document.
Although EPA missed the statutory deadline for completing the studies,
the Mercury Study and the Utility Study were complete by 1998. The
NIEHS study was completed in 1995, and the NAS Study was completed in
2000.
    In December 2000, after considering public input, the studies
required by section 112(n)(1) and other relevant information, including
Hg emissions data from EGUs, EPA determined that it was appropriate and
necessary to regulate EGUs under CAA section 112. Based on that
determination, the Agency listed such units for regulation under
section 112(c).
    Pursuant to a settlement agreement, the deadline for issuing
emission standards was March 15, 2005. However, instead of issuing
emission standards pursuant to section 112(d), on March 15, 2005, EPA
delisted EGUs, finding that it was neither appropriate nor necessary to
regulate such units under section 112. That attempt to delist was
subsequently invalidated by the DC Circuit Court.
1. Studies Related to HAP Emissions From EGUs
a. The Utility Study
    EPA issued the Utility Study in February 1998, over 4 years after
the statutory deadline. The Utility Study included numerous analyses.
EPA first collected HAP emissions test data from 52 EGUs, including a
range of coal-, oil-, and natural gas-fired units, and the test data
along with facility specific information were used to estimate HAP
emissions from all 684 utility facilities. EPA determined that 67 HAP
were emitted from EGUs. In addition, the study evaluated HAP emissions
based on two scenarios: (1) 1990 base year; and (2) 2010 projected
emissions. The 2010 scenario was selected to meet the section
112(n)(1)(A) mandate to evaluate hazards ``after imposition of the
requirements of the Act.'' EPA also considered potential control
strategies for the identified HAP consistent with section 112(n)(1)(A).
    EPA evaluated exposures, hazards, and risks due to HAP emissions
from coal-, oil-, and natural gas-fired EGUs. EPA conducted a screening
level assessment of all 67 HAP to prioritize the HAP for further
analysis. A total of 14 HAP were identified as priority HAP that would
be further assessed. Twelve HAP (As, beryllium (Be), Cd, Cr, manganese
(Mn), Ni, HCl, HF, acrolein, dioxins, formaldehyde, and radionuclides)
were identified as a priority for further assessment based on
inhalation exposure and risk. Six HAP (Hg, radionuclides, As, Cd, Pb,
and dioxins) were considered a priority for multipathway assessment of
exposure and risk.
    Based on the inhalation estimates for the priority HAP, EPA
determined that As and Cr emissions from coal-fired EGUs and Ni
emissions from oil-fired EGUs contributed most to the potential cancer
related inhalation risks, but those risks were not high. The non-cancer
risk assessment due to inhalation exposure indicated exposures were
well below the reference levels.
    The Agency also conducted multipathway assessments for the six HAP
identified above. Based on these analyses, EPA determined that Hg from
coal-fired EGUs was the HAP of greatest potential concern. In addition,
the screening multipathway assessments for dioxins and As suggested
that these two HAP were of potential for multipathway risk.
    In addition to the 1990 analysis, EPA also estimated emissions and
inhalation risks for the year 2010. HAP emissions from coal-fired
utilities were predicted to increase by 10 to 30 percent by the year
2010. Predicted changes included the installation of scrubbers for a
small number of facilities, the closing of a few facilities, and an
increase in fuel consumption of other facilities. For oil-fired plants,
emissions and inhalation risks were estimated to decrease by 30 to 50
percent by the year 2010, primarily due to projected reductions in use
of oil for electricity generation. Multipathway risks for 2010 were not
assessed.
    In estimating future emissions from EGUs, EPA primarily evaluated
the effect of implementation of the Acid Rain Program (ARP) on HAP
emissions from EGUs. The 2010 scenario also included estimated changes
in emissions resulting from projected trends in fuel choices and power
demands.
    Table 2 of this preamble presents estimated emissions for a subset
of priority HAP for 1990 and 2010.

                                                 Table 2--Nationwide Emissions for Six Priority HAP, tpy
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Coal                             Oil                         Natural gas
                           HAP                           -----------------------------------------------------------------------------------------------
                                                               1990            2010            1990            2010            1990            2010
--------------------------------------------------------------------------------------------------------------------------------------------------------
Arsenic.................................................              61              71            5               3             0.15             0.25
Chromium................................................              73              87            4.7             2.4   ..............  ..............
Mercury.................................................              46              60            0.25            0.13          0.0015           0.024
Nickel..................................................              58              69          390             200             2.2              3.5
Hydrogen chloride.......................................         143,000         155,000        2,900           1,500            NM               NM
Hydrogen fluoride.......................................          20,000          26,000          140              73            NM               NM
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Numerous potential alternative control strategies for reducing HAP
emissions from EGUs were identified. These included pre-combustion
controls (e.g., fuel switching, coal cleaning), post combustion
controls (e.g., PM controls, SO2 controls), and improving
efficiency in supply or demand. For example, coal cleaning tends to
remove at least some of all the trace metals. EPA also concluded that
PM controls tend to effectively remove the trace metals (excluding Hg).
The Utility Study also found that flue gas desulfurization (FGD) units
were less effective at removing trace metals and exhibited more
variability in removal of those metals than PM control, but FGD were
more effective at reducing acid gas HAP.
b. The Mercury Study
    EPA issued the Mercury Study in December 1997, 3 years after the
statutory deadline. The Mercury Study assessed the magnitude of U.S. Hg
emissions by source, the health and environmental implications of those
emissions, and the availability and cost of control technologies.
    According to the Mercury Study, Hg cycles in the environment as a
result of natural and human (anthropogenic) activities. Most of the Hg
in the atmosphere is elemental Hg vapor, which circulates in the
atmosphere for up to a year, and, hence, can be widely dispersed and
transported thousands of miles from likely sources of emission. The
Mercury Study also found that most of the Hg in water, soil, sediments,
or plants and animals is in the form of inorganic Hg salts and organic
forms of Hg (e.g., MeHg). The inorganic form of Hg, when either bound
to airborne particles or in a gaseous form, is readily removed from the
atmosphere by precipitation and is also dry deposited. Wet deposition
is the primary mechanism for transporting Hg from the atmosphere to
surface waters and land. Even after it deposits, Hg commonly is emitted
back to the atmosphere either as a gas or associated with particles, to
be re-deposited elsewhere.
    The Mercury Study estimated that in 1994-1995, anthropogenic U.S.
Hg emissions were about 158 tons annually. Roughly 87 percent of those
emissions were from combustion sources, including waste and fossil fuel
combustion. According to the Mercury Study, current anthropogenic
emissions were only one part of the Hg cycle. The Mercury Study noted
that current releases from human activities were adding to the Hg
reservoirs that already exist in land, water, and air, both naturally
and as a result of prior human activities. The Mercury Study concluded
that the flux of Hg from the atmosphere to land or water at any one
location is comprised of contributions from the natural global cycle,
including re-emissions from the oceans, international sources, regional
sources, and local sources.
    The Mercury Study further described a computer simulation of long-
range transport of Hg, which suggested that about one-third
(approximately 52 tons) of U.S. anthropogenic emissions are deposited,
through wet and dry deposition, within the lower 48 states. The
remaining two-thirds (approximately 107 tons) was estimated to be
transported outside of U.S. borders where it would diffuse into the
global reservoir. The computer simulation further suggested that
another 35 tons of Hg from the global reservoir outside the U.S. was
deposited annually in the U.S. for a total deposition in the U.S. of
roughly 87 tons per year (tpy).
    The Mercury Study also found that fish consumption dominates the
pathway for human and wildlife exposure to MeHg and that there was a
plausible link between anthropogenic releases of Hg from industrial and
combustion sources in the U.S. and MeHg in fish. In the Mercury Study,
EPA explained that, given the current scientific understanding of the
environmental fate and transport of this element, it was not possible
to quantify how much of the MeHg in fish consumed by the U.S.
population results from U.S. anthropogenic emissions, as compared to
other sources of Hg (such as natural sources and re-emissions from the
global pool).
    The Mercury Study noted that those who regularly and frequently
consume large amounts of fish--either marine species that typically
have much higher levels of MeHg than other species, or freshwater fish
that have been affected by Hg pollution--are more highly exposed.
Because the developing fetus may be the most sensitive to the effects
from MeHg, women of child-bearing age were the population of greatest
interest. EPA concluded in the Mercury Study that approximately 7
percent of women of child-bearing age (i.e., between the ages of 15 and
44) were exposed to MeHg at levels exceeding the RfD.
    Finally, the Mercury Study concluded that piscivorous (fish-eating)
birds and mammals were more highly exposed to Hg than any other known
component of aquatic ecosystems, and that adverse effects of Hg on
fish, birds and mammals include death, reduced reproductive success,
impaired growth and development, and behavioral abnormalities. The
Mercury Study also evaluated Hg emissions control technologies and the
costs of such technologies.
c. The NAS Methylmercury Study
    In the appropriations report for EPA's fiscal 1999 funding,
Congress directed EPA to fund the NAS to perform an independent study
on the toxicological effects of MeHg and to prepare recommendations on
the establishment of a scientifically appropriate MeHg exposure RfD. In
response, EPA contracted with NAS, which conducted an 18-month study of
the available data on the health effects of MeHg and reported its
findings to EPA in July 2000.
    The EPA included four charges to NAS: (1) Evaluate the body of
evidence that led to EPA's current RfD for MeHg, and on the basis of
available human epidemiological and animal toxicity data, determine
whether the critical study, end point of toxicity, and uncertainty
factors used by EPA in the derivation of the RfD for MeHg are
scientifically appropriate, including

consideration of sensitive populations; (2) evaluate any new data not
considered in the Mercury Study that could affect the adequacy of EPA's
MeHg RfD for protecting human health; (3) consider exposures in the
environment relevant to evaluation of likely human exposures
(especially to sensitive subpopulations and especially from consumption
of fish that contain MeHg), and include in the evaluation a focus on
those elements of exposure relevant to the establishment of an
appropriate RfD; and (4) identify data gaps and make recommendations
for future research.
    The NAS held both public and closed sessions wherein they evaluated
data and presentations from government agencies, trade organizations,
public interest groups, and concerned citizens. The NAS also evaluated
new findings that had emerged since the development of EPA's 1995 RfD
and met with the investigators of major ongoing epidemiological
studies.
    The NAS Study concluded that the value of EPA's 1995 RfD for MeHg,
0.1 micrograms per kilogram ([micro]g/kg) per day, was a scientifically
appropriate level for the protection of public health. The NAS Study
further concluded that data from both human and animal studies
indicated that the developing nervous system was a sensitive target
organ for low-dose MeHg exposure. The NAS Study indicated that there
was evidence that exposure to MeHg in humans and animals can have
adverse effects on both the developing and adult cardiovascular system.
Some of the studies observed adverse cardiovascular effects at or below
MeHg exposure levels associated with neurodevelopmental effects. The
weight of evidence for carcinogenicity of MeHg was inconclusive. There
was also evidence from animal studies that the immune and reproductive
systems are sensitive targets for MeHg toxicity.
    According to the NAS Study, the estimates of MeHg exposures in the
U.S. population indicated that the risk of adverse effects from then-
current MeHg exposures in the majority of the population was low.
However, the NAS Study concluded that individuals with high MeHg
exposures from frequent fish consumption might have little or no margin
of safety (i.e., exposures of high-end consumers are close to those
with observable adverse effects). The NAS Study also noted that the
population at highest risk was the children of women who consumed large
amounts of fish and seafood during pregnancy. The NAS Study further
concluded that the impact on that population was likely to be
sufficient to result in an increase in the number of children who
struggle to keep up in school and might require remedial classes or
special education.
2. EPA's December 2000 Appropriate and Necessary Finding
    On December 20, 2000, EPA issued a finding pursuant to CAA section
112(n)(1)(A) that it was appropriate and necessary to regulate coal-
and oil-fired EGUs under section 112 and added such units to the list
of source categories subject to regulation under section 112(d). In
making that finding, EPA considered the Utility Study, the Mercury
Study, the NAS Study, and certain additional information, including
information about Hg emissions from coal-fired EGUs that EPA obtained
pursuant to an information collection request (ICR) under the authority
of section 114 of the CAA. 65 FR 79826-27. EPA collected data on the Hg
content of coal from all coal-fired EGUs for the calendar year 1999 and
Hg emissions stack test data for certain coal-fired EGUs. 65 FR 79826.
EPA also solicited data from the public through a February 29, 2000,
notice (65 FR 10783). The public had an opportunity to provide their
views on what the section 112(n)(1)(A) appropriate and necessary
regulatory finding should be at a public meeting in Chicago, Illinois,
on June 13, 2000 (65 FR 18,992). 65 FR 79826.
    In the December 2000 notice, EPA explained that it evaluated EGUs
based on the type of fossil fuel combusted (i.e., coal, oil, and
natural gas). The December 2000 Finding focused primarily on Hg
emissions from coal-fired EGUs. Mercury was determined to be the HAP of
greatest concern in the Utility Study. In evaluating Hg emissions from
coal-fired EGUs, EPA stated that the quality of the Hg data available
in 2000 was considerably better than the data available for the Utility
Study because of the results of the 1999 ICR. The new data also
corroborated the Hg emissions estimates in the study. 65 FR 79828. In
the finding, EPA explained that Hg is highly toxic and persistent and
that it bioaccumulates in the food chain; that Hg air emissions from
all sources, including EGUs, deposit on the land where the Hg may
transform into MeHg, which is the primary type of Hg that accumulates
in fish tissue; and that eating Hg contaminated fish was the primary
route of exposure for humans. 65 FR 79827. The potential hazard of most
concern was determined to be consumption by subsistence fish-eating
populations and women of childbearing age because of the adverse
effects that Hg poses to the developing fetus. 65 FR 79827. Finally,
EPA noted that approximately 7 percent of women of child bearing age
were exposed to levels of MeHg that exceeded the RfD. 65 FR 79827.
    EPA further estimated that about 60 percent of the total Hg
deposited in the U.S. came from anthropogenic air emissions originating
in the U.S. and that EGUs contributed approximately 30 percent of those
anthropogenic air emissions. 65 FR 79827. Based on the record before
the Agency at the time, EPA determined that there was a plausible link
between Hg emissions from EGUs and MeHg in fish and that Hg emissions
from EGUs were a threat to public health and the environment. 65 FR
79827.
    In discussing the non-Hg HAP from coal- and oil-fired EGUs, EPA
stated that HAP metals such as As, Cr, Ni, and Cd are of potential
concern for carcinogenic effects. 65 FR 79827. EPA acknowledged that
the risk assessments conducted for these HAP indicated that cancer
risks were not high, but the Agency could not conclude the potential
concern for public health was eliminated for those metals. 65 FR 79827.
EPA further stated that dioxins, HCl, and HF were of potential concern
and could be evaluated further during the regulatory development
process. 65 FR 79827. EPA also concluded that the remaining HAP
evaluated in the Utility Study did not appear to be a public health
concern, but the Agency noted that there were limited data and
uncertainties associated with this conclusion, and we stated that
future data collection efforts could identify additional HAP of
potential concern. 65 FR 79827.
    EPA also explained that, consistent with Congress's direction in
section 112(n)(1)(A), we considered the alternative control strategies
available to control the HAP emissions that may warrant control. We
noted that currently available controls for criteria pollutants would
also be effective at controlling the HAP emissions from EGUs. 65 FR
79828.
    EPA then made nine specific conclusions based on the information in
the record, some of which are summarized above. 65 FR 79829-30. Based
on those conclusions, EPA found that it was ``appropriate'' to regulate
HAP emissions from coal- and oil-fired EGUs because EGUs ``are the
largest domestic source of Hg emissions, and Hg in the environment
presents significant hazards to public health and the environment.'' 65
FR 79830. EPA noted that the NAS Study confirmed EPA's own research
concluding that ``mercury in the environment presents a significant
hazard to public health.'' 65

FR 79830. EPA explained that it was appropriate to regulate HAP
emissions from coal- and oil-fired units because it had identified
certain control options that, it anticipated, would effectively reduce
HAP from such units. 65 FR 79830. In discussing its findings, EPA also
noted that uncertainties remained concerning the extent of the public
health impact from HAP emissions from oil-fired units. 65 FR 79830.
    Once EPA determined that it was ``appropriate'' to regulate coal-
and oil-fired EGUs under CAA section 112, EPA next concluded that it
was also ``necessary'' to regulate HAP emissions from such units under
section 112 ``because the implementation of other requirements under
the CAA will not adequately address the serious public health and
environmental hazards arising from such emissions identified in the
Utility RTC and confirmed by the NAS Study, and which section 112 is
intended to address.'' 65 FR 79830.
    For natural gas-fired EGUs, EPA found that regulation of HAP
emissions ``is not appropriate or necessary because the impacts due to
HAP emissions from such units are negligible based on the results of
the study documented in the utility RTC.'' 65 FR 79831.
    In light of the positive appropriate and necessary determination,
EPA in December 2000 listed coal- and oil-fired EGUs on the section
112(c) source category list. 65 FR 79831.
3. The 2005 Action
    On March 29, 2005, EPA issued the Section 112(n) Revision Rule
(``2005 Action'') that has since been vacated by the DC Circuit Court.
In that rule, EPA reversed the December 2000 Finding and concluded that
it was neither appropriate nor necessary to regulate coal- and oil-
fired EGUs under section 112 and delisted such units from the section
112(c) source category list. 70 FR 15994. EPA took the position that
the December 2000 Finding lacked foundation and that new information
confirmed that it was not appropriate or necessary to regulate coal-
and oil-fired EGUs under CAA section 112.
    In the final rule, EPA provided a detailed interpretation of
section 112(n)(1)(A), including the terms ``appropriate'' and
``necessary,'' as those terms relate to the regulation of EGUs under
section 112. In interpreting the statute, EPA recognized that section
112(n)(1)(A) provided no explicit guidance for determining whether
regulation of EGUs is appropriate and necessary. As such, EPA concluded
that Congress' direction on the Utility Study provided the only
guidance about the substance of the appropriate and necessary finding.
Accordingly, EPA extrapolated from Congress' description of the Utility
Study when interpreting the terms appropriate and necessary.
    Among other things, the Agency interpreted the focus on public
health in the Utility Study as precluding EPA from considering
environmental impacts. 70 FR 15998. EPA also looked at Congress' focus
on EGU emissions in the Study and took the position that EPA could only
consider hazards to public health that could be traced directly to HAP
emissions from EGUs in assessing whether it was appropriate to
regulate. EPA declined to consider the potential adverse public health
impacts that may occur as the result of the combination of EGU HAP
emissions and HAP emissions from other sources. 70 FR 15998.
    In making the determination as to whether it was appropriate to
regulate, EPA analyzed whether the level of HAP emissions from EGUs
remaining after imposition of the requirements of the CAA would result
in a hazard to public health. EPA concluded that if the HAP emissions
remaining after imposition of the requirements of the CAA do not pose a
hazard to public health, then regulation under section 112 is not
appropriate. EPA also maintained that even if it identified a hazard to
public health, regulation may still not be ``appropriate'' based on
other relevant factors, such as the cost effectiveness of regulation
under section 112. 70 FR 15600.
    In the 2005 Action, EPA interpreted the term ``necessary'' to mean
``that it is necessary to regulate EGUs under section 112 only if there
are no other authorities available under the CAA that would, if
implemented, effectively address the remaining HAP emissions from
EGUs.'' 70 FR 16001.
    Applying these interpretations, the Agency stated that it was
neither appropriate nor necessary to regulate HAP emissions from EGUs.
The Agency took the position that the December 2000 appropriate finding
lacked foundation because the finding was overbroad to the extent that
it relied on environmental effects. 70 FR 16002. The EPA next stated
that the appropriate determination in the December 2000 Finding lacked
foundation because EPA did not fully consider the Hg reductions that
would result after imposition of the requirements of the CAA and that
new information showed that the level of Hg emissions from EGUs
remaining after imposition of the requirements of the CAA do not pose a
hazard to public health. 70 FR 16003-4. Specifically, EPA pointed to
the promulgation of the Clean Air Interstate Rule (CAIR), issued
pursuant to CAA section 110(a)(2)(D), and the Clean Air Mercury Rule
(CAMR),\8\ issued pursuant to section 111, and, based on modeling,
determined that CAIR, and independently CAMR, could be expected to
reduce Hg emissions to levels that would not cause a hazard to public
health. Therefore, EPA concluded that it was not appropriate to
regulate EGUs under section 112. We note that CAMR was vacated by the
D.C. Circuit Court in New Jersey v. EPA, and that CAIR was remanded to
the Agency in North Carolina v. EPA, 531 F.3d 896, modified on reh'g,
550 F.3d 1176 (DC Cir. 2008).
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    \8\ On May 18, 2005, EPA issued the Clean Air Mercury Rule
(CAMR). 70 FR 28606. That rule established standards of performance
for emissions of mercury from new and existing coal-fired EGUs
pursuant to CAA section 111.
---------------------------------------------------------------------------

    As to the necessary finding, EPA took the position that the
December 2000 Finding was in error because EPA did not, at the time,
examine whether there were any CAA provisions other than section 112
that, if implemented, would address any identified hazards to public
health from HAP emissions from EGUs. 70 FR 16004. Specifically, EPA
stated that the error existed because EPA did not consider CAA sections
110(a)(2)(D) and 111 and that, considering actions under these
sections, hazard to public health from EGUs would be reduced. 70 FR
16005.
    EPA also determined that it was not appropriate and necessary to
regulate coal-fired EGUs on the basis of non-Hg HAP emission or oil-
fired EGUs on the basis of Ni and non-Ni HAP. 70 FR 16007.
4. Litigation History
    Shortly after issuance of the December 2000 Finding, an industry
group challenged that finding in the DC Circuit Court. UARG v. EPA,
2001 WL 936363, No. 01-1074 (DC Cir. July 26, 2001). The DC Circuit
Court dismissed the lawsuit holding that it did not have jurisdiction
because section 112(e)(4) provides, in pertinent part, that ``no action
of the Administrator * * * listing a source category or subcategory
under subsection (c) of this section shall be a final agency action
subject to judicial review, except that any such action may be reviewed
under section 7607 of (the CAA) when the Administrator issues emission
standards for such pollutant or category.'' (emphasis added)
    Environmental groups, States, and tribes challenged the 2005 Action
and CAMR. Among other things, the environmental and state petitioners
argued that EPA could not remove EGUs

from the section 112(c) source category list without following the
requirements of section 112(c)(9).
    On February 8, 2008, the DC Circuit Court vacated both the 2005
Action and CAMR. The DC Circuit Court held that EPA failed to comply
with the requirements of section 112(c)(9) for delisting source
categories. Specifically, the DC Circuit Court held that section
112(c)(9) applies to the removal of ``any source category'' from the
section 112(c) list, including EGUs. The DC Circuit Court rejected the
argument that EPA has the inherent authority to correct its mistakes,
finding that, by enacting section 112(c)(9), Congress limited EPA's
discretion to reverse itself and remove source categories from the
section 112(c) list. The DC Circuit Court found that EPA's contrary
position would ``nullify Sec.  112(c)(9) altogether.'' New Jersey, 517
F.3d at 583. The DC Circuit Court did not reach the merits of
petitioners' arguments on CAMR, but vacated CAMR for existing sources
because coal-fired EGUs were listed sources under section 112. The DC
Circuit Court reasoned that even under EPA's own interpretation of the
CAA, regulation of existing sources' Hg emissions under section 111 was
prohibited if those sources were a listed source category under section
112.\9\ The DC Circuit Court vacated and remanded CAMR for new sources
because it concluded that the assumptions EPA made when issuing CAMR
for new sources were no longer accurate (i.e., that there would be no
section 112 regulation of EGUs and that the section 111 standards would
be accompanied by standards for existing sources). Id. at 583-84. Thus,
CAMR and the 2005 appropriate and necessary finding became null and
void.
---------------------------------------------------------------------------

    \9\ In CAMR and the 2005 Action, EPA interpreted section 111(d)
of the Act as prohibiting the Agency from establishing an existing
source standard of performance under section 111(d) for any HAP
emitted from a particular source category, if the source category is
regulated under section 112.
---------------------------------------------------------------------------

    On December 18, 2008, several environmental and public health
organizations (``Plaintiffs'') \10\ filed a complaint in the DC
District Court (Civ. No. 1:08-cv-02198 (RMC)) alleging that the Agency
had failed to perform a nondiscretionary duty under CAA section
304(a)(2), by failing to promulgate final section 112(d) standards for
HAP from coal- and oil-fired EGUs by the statutorily mandated deadline,
December 20, 2002, 2 years after such sources were listed under section
112(c). EPA settled that litigation. The consent decree resolving the
case requires EPA to sign a notice of proposed rulemaking setting forth
EPA's proposed section 112(d) emission standards for coal- and oil-
fired EGUs by March 16, 2011, and a notice of final rulemaking by
November 16, 2011.
---------------------------------------------------------------------------

    \10\ American Nurses Association, Chesapeake Bay Foundation,
Inc., Conservation Law Foundation, Environment America,
Environmental Defense Fund, Izaak Walton League of America, Natural
Resources Council of Maine, Natural Resources Defense Council,
Physicians for Social Responsibility, Sierra Club, The Ohio
Environmental Council, and Waterkeeper Alliance, Inc.
---------------------------------------------------------------------------

III. Appropriate and Necessary Finding

    As required by the CAA, we determined in December 2000, and confirm
that finding here, that it is appropriate to regulate emissions of Hg
and other HAP from EGUs because manmade emissions of those pollutants
pose hazards to public health and the environment, and EGUs are the
largest or among the largest contributors of many of those HAP. It is
necessary to do so for a variety of reasons, including that hazards to
public health and the environment from EGUs remain after imposition of
the requirements of the CAA.
    In this section, we address the Agency's determination that it is
appropriate and necessary to regulate coal- and oil-fired EGUs under
CAA section 112. We first provide our interpretation of the critical
terms in CAA section 112(n)(1). As shown below, these interpretations
are wholly consistent with the CAA and the December 2000 Finding. We
then demonstrate that the December 2000 Finding was valid at the time
it was made based on the information available to the Agency at that
time. Finally, we explain that, although not required, we recently
conducted additional technical analyses given that several years have
passed since the December 2000 Finding was issued. Those analyses
include both a quantitative and qualitative assessment of the hazards
to public health and a qualitative analysis of hazards to the
environment associated with Hg and non-Hg HAP from EGUs. The analyses
confirm that it remains appropriate and necessary today to regulate
EGUs under CAA section 112. We also explain why these analyses and the
other information currently before the Agency confirm that regulation
of EGUs under section 112 is appropriate and necessary. Accordingly,
such units are properly listed pursuant to section 112(c).

A. Regulating EGUs Under CAA Section 112

    CAA section 112(n)(1)(A) requires the Agency to regulate EGUs under
section 112 ``if the Administrator finds such regulation is appropriate
and necessary after considering the results of the [Utility Study].''
(emphasis added). Congress did not define the phrase ``appropriate and
necessary'' in section 112(n)(1)(A). Rather, Congress expressly
delegated to the Agency the authority to interpret and apply those
terms. See Chevron U.S.A. Inc. v. Natural Resources Defense Council,
Inc., 467 U.S. 837, 843-44 (1984) (the Agency's interpretation of
statutory terms is entitled to considerable deference as long as it is
a reasonable reading of the statute).
    Courts have interpreted the terms ``appropriate'' and ``necessary''
in other provisions of the CAA and other statutes, and concluded that
those terms convey upon the Agency a wide degree of discretion. See,
e.g., National Association of Clean Air Act Agencies v. EPA, 489 F.3d
1221, 1229 (DC Cir. 2007) (finding ``both explicit and extraordinarily
broad'' the Administrator's authority under CAA section 231(a)(3) to
``issue regulations with such modifications as he deems appropriate.'')
(emphasis in original); see also Cellular Telecommunications & Internet
Association, et al. v. FCC, 330 F.3d 502, 510 (DC Cir. 2003), (finding
that ``[c]ourts have frequently interpreted the word `necessary' to
mean less than absolutely essential, and have explicitly found that a
measure may be `necessary' even though acceptable alternatives have not
been exhausted.'' (quoting Natural Res. Def. Council v. Thomas, 838
F.2d 1224, 1236 (DC Cir. 1998) (internal quotation marks omitted)).
    We evaluate the terms ``appropriate'' and ``necessary'' within the
statutory context in which they appear to determine the meaning of the
words. See Cellular Telecommunications, 330 F.3d at 510 (finding that
``it is crucial to understand the context in which the word [necessary]
is used in order to comprehend its meaning.'') (citations omitted). In
this case, we look for guidance in section 112 generally, and focus
specifically on section 112(n)(1), which addresses EGUs.
1. Statutory Framework for Evaluating EGUs
    As explained above, Congress, concerned by the slow pace of EPA's
regulation of HAP, ``altered section 112 by eliminating much of EPA's
discretion in the process.'' New Jersey, 517 F.3d at 578 (citations
omitted). We describe above the two-phased approach to standard
setting. Also, relevant, however, is that Congress set very strict
deadlines for listing source categories and issuing emission standards
for such

categories. See e.g., Section 112(c)(6), 112(e)(1); New Jersey, 517
F.3d at 578 (noting that ``EPA was required to list and to regulate, on
a prioritized schedule'' all categories and subcategories of major and
area sources). Thus, in substantially amending section 112 of the CAA
in 1990, Congress sought prompt and permanent reductions of HAP
emissions from stationary sources--first through technology-based
standards, and then further, as necessary, through risk-based standards
designed to protect human health and the environment.
    Congress' focus on protecting public health and the environment
from EGU HAP emissions is reflected in section 112(n)(1), titled
``[e]lectric utility steam generating units.'' That section directs EPA
to evaluate HAP emissions from EGUs. In addition to directing EPA to
regulate EGUs under section 112 if it determines that it is appropriate
and necessary to do so, section 112(n)(1) requires the completion of
three studies related to HAP emissions from EGUs. Those studies
include: (1) The Utility Study pursuant to section (n)(1)(A); (2) the
Mercury Study pursuant to section (n)(1)(B); and (3) the NIEHS Study
(NAS Study) pursuant to section 112(n)(1)(C).\11\
---------------------------------------------------------------------------

    \11\ As explained above, the NAS Study studied the same issues
Congress wanted addressed pursuant to section 112(n)(1)(C) and,
because it was conducted five years after the NIEHS study, it was a
more comprehensive study accounting for new information not
available to NIEHS. Congress directed both studies and wanted EPA to
consider the NAS Study before issuing the appropriate and necessary
finding so we are reasonably focusing our discussion on the content
of the later study.
---------------------------------------------------------------------------

    These studies are described above, in detail. In summary, for the
Utility Study, Congress required EPA to evaluate the hazards to public
health that are reasonably anticipated to occur as the result of EGU
emissions following imposition of the requirements of the CAA. Congress
also directed EPA to identify alternative control strategies for those
HAP that may warrant regulation under section 112.
    The Mercury Study required by section 112(n)(1)(B) is both broader
and narrower in scope, as compared to the Utility Study. For example,
the Mercury Study is narrower in scope, in that it focuses solely on
the impacts from Hg emissions, as opposed to all HAP. The Mercury Study
is broader in scope, however, in two important respects. First,
Congress required EPA to consider environmental effects in addition to
health effects. Second, Congress required the Agency to consider the
cumulative effects of Hg from all sources, including EGUs. In
considering the cumulative effects of Hg, the Agency was not required
to apportion the cause of any adverse effects among the various sources
of Hg. Both the Utility and Mercury Studies considered the control
technologies available to control Hg emissions, but only the Mercury
Study called for the evaluation of the costs of such controls. Section
112(n)(1)(B).
    EPA believes that Congress directed the Agency to conduct the
Utility Study so that the Agency would understand the hazards to public
health posed by HAP emissions from EGUs alone, and consider whether any
hazards that were identified would be addressed through imposition of
the requirements of the CAA applicable to EGUs at that time. Congress
provided EPA an additional year to examine the impacts of EGU emissions
of Hg on health and the environment in combination with other sources
of Hg emissions.
    The NAS Study required by section 112(n)(1)(C), which was due at
the same time as the Utility Study, was to focus on Hg only and the
adverse human health effects associated with Hg. The statute directed
the determination of the threshold level of Hg below which adverse
effects to human health are not expected to occur. The statute further
directed the determination of the threshold for Hg concentrations in
the tissue of fish which may be consumed, including by sensitive
populations, without adverse effects to public health. Here, unlike the
Utility Study and the Mercury Study, the statute specifically requires
an evaluation of the adverse human health effects of Hg on sensitive
populations.
    The remaining critical element of section 112(n)(1) is the
direction to EPA to determine whether it is appropriate and necessary
to regulate EGUs under section 112, considering the results of the
Utility Study. Although the Utility Study is a condition precedent to
making the appropriate and necessary determination, nothing in section
112(n)(1)(A) precludes the Agency from considering other information in
making that determination.
    Taken together, we believe these provisions provide a framework for
the Agency's determination of whether to regulate HAP emissions from
EGUs under section 112. Through these provisions, Congress sought a
prompt review and evaluation of the hazards to public health and the
environment associated with Utility HAP emissions. This prompt
consideration of health and environmental impacts is consistent with
the strict deadlines Congress imposed in section 112 on all other
source categories. See infra.
    Section 112(n)(1)(B) is direct evidence that Congress was concerned
with environmental effects and cumulative impacts of HAP emissions from
EGUs and other sources, particularly with regard to the bio-
accumulative HAP Hg. Section 112(n)(1)(C) provides further evidence
that Congress was concerned with limiting HAP emissions from EGUs to a
level that protects sensitive populations. We believe the scope of the
Utility Study was limited to HAP emissions from EGUs and hazards to
public health, not because Congress was unconcerned with adverse
environmental effects or the cumulative impact of HAP emissions, but
because the Utility Study, as required, was a significant undertaking
in itself and Congress wanted the Agency to complete the study within 3
years. Thus, section 112(n)(1) reveals, among other things, Congress'
concern for the health and environmental effects of HAP emissions from
EGUs, both alone and in conjunction with other sources, the impact of
Hg emissions from EGUs, and the availability of controls to address HAP
emissions from EGUs.
    Finally, significantly, nowhere in section 112(n)(1) does Congress
require the consideration of costs in assessing health and
environmental impacts. The only reference to costs is in section
112(n)(1)(B) and that reference required the Agency to consider the
costs of emission reduction controls for Hg.
2. Interpretation of Key Terms
    Section 112(n)(1)(A) itself provides no clear standard to govern
EPA's analysis and determination of whether it is ``appropriate and
necessary'' to regulate utilities under section 112. The statute simply
requires EPA to regulate EGUs under section 112 if it determines that
such regulation is appropriate and necessary, after considering the
results of the Utility Study. As noted above, courts have interpreted
the terms appropriate and necessary as conveying considerable
discretion to the Agency in determining what is appropriate and
necessary in a given context.
    As explained more fully below, in this context, we interpret the
statute to require the Agency to find it appropriate to regulate EGUs
under CAA section 112 if the Agency determines that the emissions of
one or more HAP emitted from EGUs pose an identified or potential
hazard to public health or the environment at the time the finding is
made. If the Agency finds that it is appropriate to regulate, it must
find it necessary to regulate EGUs under section 112 if the identified
or potential hazards to public health or the environment will not be
adequately addressed by the imposition of the requirements of the CAA.
Moreover, it

may be necessary to regulate utilities under section 112 for a number
of other reasons, including, for example, that section 112 standards
will assure permanent reductions in EGU HAP emissions, which cannot be
assured based on other requirements of the CAA.
    The following subsections describe in detail our interpretation of
the key statutory terms. We also explain below how the interpretations
set forth in this notice are wholly consistent with the December 2000
Finding. Further, to the extent our interpretation differs from that
set forth in the 2005 Action, we explain the basis for that difference
and why the interpretation, as set forth in this preamble, is
reasonable. See National Cable & Telecommunications Ass'n, et al. v.
Brand X Internet Services, et al., 545 U.S. 967, 981 (2005) (Discussing
the deference provided to an Agency when changing interpretations the
Court stated ``change is not invalidating, since the whole point of
Chevron deference is to leave the discretion provided by ambiguities of
a statute with the implementing agency.'') (Internal citations and
quotations omitted); see also Department of Treasury v. FLRA, 494 U.S.
922, 933 (1990) (Finding that EPA's judgment should only be overturned
if it is deemed unreasonable, not merely because other, reasonable
alternatives exist).
a. ``Appropriate'' To Regulate EGUs
    We interpret section 112(n)(1)(A) to require the Agency to find
regulation of EGUs under section 112 appropriate if we determine that
HAP emissions from EGUs pose a hazard to public health or the
environment at the time the finding is made. The hazard to public
health or the environment may be the result of HAP emissions from EGUs
alone or the result of HAP emissions from EGUs in conjunction with HAP
emissions from other sources. In addition, EPA must find that it is
appropriate to regulate EGUs if it determines that any single HAP
emitted by utilities poses a hazard to public health or the
environment. We further interpret the term ``appropriate'' to not allow
for the consideration of costs in assessing whether HAP emissions from
EGUs pose a hazard to public health or the environment. Finally, we may
conclude that it is appropriate, in part, to regulate EGUs if we
determine that there are controls available to address HAP emissions
from EGUs.
i. Basis for Interpretation
    As stated above, the appropriate finding may be based on hazards to
public health or the environment. Although we believe that Congress'
primary concern, as expressed in section 112(n)(1)(A) and 112(n)(1)(C),
related to hazards to public health, the inclusion of environmental
effects in section 112(n)(1)(B) indicates Congress' interest in
protecting the environment from HAP emissions from EGUs as well.
    Moreover, the term ``appropriate'' is extremely broad and nothing
in the statute suggests that the Agency should ignore adverse
environmental effects in determining whether to regulate EGUs under
section 112. Further, had Congress intended to prohibit EPA from
considering adverse environmental effects in the ``appropriate''
finding, it would have stated so expressly. Absent clear direction to
the contrary, and considering the purpose of the CAA (see e.g., CAA
section 101, 112(c)(9)(B)(ii)), it is reasonable to consider
environmental effects in evaluating the hazards posed by HAP emitted
from EGUs when assessing whether regulation of EGUs under section 112
is appropriate. Accordingly, we interpret the statute to authorize the
Agency to base the appropriate finding on either hazards to public
health or the environment.
    We also maintain that the Agency should base its ``appropriate''
evaluation on the hazards to public health or the environment that
exist at the time the determination is made, not after considering the
imposition of the other requirements of the CAA. The Agency evaluates
whether imposition of the requirements of the CAA will adequately
address any identified hazards only in the context of the necessary
finding. Thus, in assessing whether regulation of EGUs is appropriate
under section 112, we evaluate the current hazards posed by such units,
as opposed to projecting what such hazards may look like after
imposition of the requirements of the CAA.
    We further interpret the CAA as allowing the Agency to base the
appropriate finding on hazards to public health or the environment that
result from HAP emissions from EGUs alone or hazards to public health
and the environment that result from HAP emissions from EGUs in
conjunction with HAP emissions from other sources. Section 112(n)(1)
does not focus exclusively on EGU-only HAP emissions.
    As explained above, section 112(n)(1)(B) and (C) require either
expressly or implicitly the consideration of Hg emissions from all
sources, not just EGUs. Section 112(n)(1)(B) is of note because that
provision does not require the Agency to determine the hazard posed by
Hg from EGUs alone. Rather, Congress required EPA to evaluate the
health and environmental effects of Hg emissions from ``electric
utility steam generating units, municipal waste combustion units, and
other sources, including area sources.'' Section 112(n)(1)(C) is also
relevant because it requires a human health-based assessment of the
hazards posed by Hg without regard to the origin of the Hg. Congress
could have directed an evaluation of the human health risk attributable
to EGUs alone, but it did not. Congress also did not require such an
assessment be conducted in the NAS Study.
    In addition, Congress directed the Agency in section 112(n)(1)(A)
to regulate EGUs under section 112 if the results of the Utility Study
caused the Agency to conclude that regulation was appropriate and
necessary. Section 112(n)(1)(A) is not written in a manner to preclude
consideration of other information when determining whether it is
appropriate and necessary to regulate EGUs under section 112, and that
includes consideration of all hazards, both health and environmental,
posed by HAP emitted by EGUs. See United States v. United Technologies
Corp., 985 F.2d 1148, 1158 (2d Cir. 1993) (``based upon'' does not mean
``solely'').
    Finally, focusing on HAP emissions from EGUs alone when making the
appropriate finding ignores the manner in which public health and the
environment are affected by air pollution. An individual that suffers
adverse health effects as the result of the combined HAP emissions from
EGUs and other sources is harmed, irrespective of whether HAP emissions
from EGUs alone would cause that harm. For this reason, we believe we
may consider the hazards to public health and the environment posed by
HAP emissions from EGUs alone or in conjunction with HAP emissions from
other sources.
    Furthermore, the appropriate finding may be based on a finding that
any single HAP emitted from EGUs poses a hazard to public health or the
environment. Nothing in section 112(n)(1)(A) suggests that EPA must
determine that every HAP emitted by EGUs poses a hazard to public
health or the environment before EPA can find it appropriate to
regulate EGUs under section 112. Interpreting the statute in this
manner would preclude the Agency from addressing under section 112
identified or potential hazards to public health or the environment
associated with HAP emissions from EGUs unless

we found a hazard existed with respect to each and every HAP emitted.
    Indeed, Congress' focus in section 112(n)(1)(B) and (C) on Hg
indicates Congress' awareness that Hg was a problem and supports the
position that EPA could find it appropriate to regulate EGUs based on
the adverse health and environmental effects of a single HAP.
Furthermore, the statute does not directly or expressly authorize the
Agency to regulate only those HAP for which a hazard finding has been
made. In fact, the statute requires the Agency to regulate EGUs under
section 112 if the Agency finds regulation under section 112 is
appropriate and necessary, and regulation under section 112 for major
sources requires MACT standards for all HAP emitted from the source
category. See, e.g., National Lime Ass'n v. EPA, 233 F.3d 625, 633 (DC
Cir. 2000). For these reasons, we conclude we must find it appropriate
to regulate EGUs under section 112 if we determine that the emissions
of any single HAP from such units pose a hazard to public health or the
environment.
    We also maintain that the better reading of the term
``appropriate'' is that it does not allow for the consideration of
costs in assessing whether hazards to public health or the environment
are reasonably anticipated to occur based on EGU emissions. Had
Congress intended to require the Agency to consider costs in assessing
hazards to public health or the environment associated with EGU HAP
emissions, it would have so stated.
    This interpretation is consistent with the overall structure of the
CAA. Congress did not authorize the consideration of costs in listing
any source categories for regulation under section 112. In addition,
Congress did not permit the consideration of costs in evaluating
whether a source category could be delisted pursuant to the provisions
of section 112(c)(9).
    Under section 112(n)(1)(A), EPA is evaluating whether to regulate
HAP emissions from EGUs at all. It is reasonable to conclude that costs
may not be considered in determining whether to regulate EGUs under
section 112 when hazards to public health and the environment are at
issue.
    Finally, consistent with sections 112(n)(1)(A) and 112(n)(1)(B), we
conclude that we may base the appropriate finding on the availability
of controls to address HAP emissions from EGUs.
ii. The December 2000 Finding
    The Agency's interpretation of the term ``appropriate,'' as set
forth above, is wholly consistent with the Agency's appropriate finding
in December 2000. As noted above, in 2000, we concluded that it was
appropriate to regulate EGUs under section 112 because Hg in the
environment posed a hazard to public health and the environment. The
Agency also concluded it was appropriate because of uncertainties
associated with the hazards posed by other HAP emitted from EGUs. 65 FR
79827. Finally, the EPA concluded that it was appropriate because of
the availability of controls to reduce HAP emissions from EGUs. In
making the finding as it related to Hg, the Agency considered the
hazards posed by Hg in the environment and the contribution of EGUs to
that hazard. In addition, EPA did not consider costs when making the
appropriate determination. Further, the appropriate finding evaluated
the hazards at the time, as opposed to the hazards remaining after
imposition of the requirements of the CAA. EPA evaluated whether the
other requirements of the CAA would adequately address the hazards in
the necessary prong only.\12\
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    \12\ As explained below, EPA reasonably concluded in December
2000 that it was appropriate and necessary to regulate EGUs under
section 112 based on the record before the Agency at that time.
---------------------------------------------------------------------------

iii. The 2005 Action
    As noted above, in 2005, EPA revised its December 2000 Finding and
stated that the appropriate finding: (1) Could not be based on adverse
environmental effects; (2) must be made considering only HAP emissions
from EGUs; (3) must be made after consideration of the imposition of
the requirements of the CAA; and (4) must consider other factors (e.g.,
costs) even if we determine that HAP emissions from EGUs pose a hazard
to public health. This proposal differs from the 2005 Action, and we
address each of these differences below.
    First, we change the position taken in 2005 that the appropriate
finding could not be based on environmental effects alone. In 2005, we
did not properly consider all of the provisions of section 112(n)(1).
The Agency should not interpret the CAA to limit the Agency's
discretion to protect the environment absent clear direction to that
effect. In essence, the Agency's interpretation in 2005 would have
required the Agency to ignore a catastrophic environmental harm (e.g.,
the extinction of a species) if the Agency could not also identify a
hazard to public health. EPA took this position regarding environmental
effects in 2005 even though in that same rule it correctly interpreted
section 112(n)(1)(A) to allow the Agency to consider information beyond
the Utility Study in making the appropriate and necessary
determination. 70 FR 15,997-99. The 2005 interpretation that EPA cannot
consider environmental effects in evaluating whether it is appropriate
to regulate EGUs under section 112 was neither reasonable nor
consistent with the goals of the CAA, and, therefore, we are rejecting
that interpretation and returning to the approach taken in 2000 that
allowed consideration of environmental effects.
    Second, for all of the reasons stated above, we are revisiting the
2005 interpretation that required the Agency to consider HAP emissions
from EGUs without considering the cumulative impacts of all sources of
HAP emissions. Nothing in section 112(n)(1)(A) prohibits consideration
of HAP emissions from EGUs in conjunction with HAP emissions from other
sources of HAP. We believe it is more reasonable to interpret the
statute to authorize the Agency to consider the cumulative effects of
HAP that are emitted from EGUs and other sources. This interpretation
allows the Agency to evaluate more fully whether HAP emissions from
EGUs pose a hazard to public health or the environment consistent with
the manner in which the public and the environment are exposed to HAP
emissions.
    Third, we are revising the 2005 interpretation that required the
Agency to evaluate the hazards to public health after imposition of the
requirements of the CAA. We conclude today that in 2005 the Agency
improperly conflated the appropriate finding and the necessary finding
by requiring consideration of the ameliorative effects of other CAA
requirements in both prongs of the appropriate and necessary finding.
We believe the Agency must find it appropriate to regulate EGUs under
section 112 if we determine that HAP emitted by EGUs pose a hazard to
public health or the environment at the time the finding is made. The
issue of how and whether those hazards are reduced after imposition of
the requirements of the CAA is an issue for the necessary prong of the
finding.
    Finally, we are rejecting the 2005 interpretation that authorizes
the Agency to consider other factors (e.g., cost), even if the Agency
determines that HAP emitted by EGUs pose a hazard to public health (or
the environment). We reject the consideration of costs for all the
reasons set forth above. Furthermore, the better reading of section
112(n)(1)(A) is that the Agency should find it appropriate to regulate
EGUs under section 112 if a hazard to public health or the environment
is identified. We think it

unreasonable to decline to make the appropriate finding based on any
factor, cost or otherwise, if we determine that EGUs pose a hazard to
public health or the environment.
b. ``Necessary'' To Regulate EGUs
    Once the Agency has determined that it is appropriate to regulate
EGUs under section 112, the Agency must then determine whether it is
necessary to regulate EGUs under section 112. As stated above, we have
considerable discretion to determine whether regulation of EGUs under
section 112 is necessary. The DC Circuit Court has stated that ``there
are many situations in which the use of the word `necessary,' in
context, means something that is done, regardless of whether it is
indispensible, to achieve a particular end.'' Cellular
Telecommunication, 330 F.3d at 510.
    If the Agency concludes that it is appropriate to regulate EGUs, we
believe it is necessary to regulate HAP emissions from EGUs if we
determine that the imposition of the requirements of the CAA will not
sufficiently address the identified hazards to public health or the
environment posed by HAP that are emitted from EGUs. We maintain that
we must find it necessary based on such a finding even if regulation
under section 112 will not fully resolve the identified hazard to
public health or the environment.
    We may also determine it is necessary to regulate under section 112
if we are uncertain whether the imposition of the other requirements of
the CAA will sufficiently address the identified hazards. We may find
it necessary to regulate EGUs under section 112 even if we were to
conclude, based on reasonable estimations of emissions reductions, that
the imposition of the other requirements of the CAA would, or might,
significantly reduce the identified hazard, because the only way to
guarantee that such reductions will occur at all EGUs and be maintained
is through a section 112(d) standard that directly regulates HAP
emissions from utilities. Finally, we may also find it necessary to
regulate EGUs under section 112 to further the policy goal of
supporting international efforts to reduce HAP emissions, including Hg.
i. Necessary After Imposition of the Requirements of the CAA
    In the Utility Study, Congress directed the Agency to evaluate the
hazards to public health posed by HAP emissions from EGUs remaining
after imposition of the requirements of the CAA, and it gave EPA 3
years to complete that Study. We interpret the necessary requirement
first in the context of the phrase ``after imposition of the
requirements of [the CAA].'' Section 112(n)(1)(A).
    Congress did not define the phrase ``after imposition of the
requirements of the Act.'' The plain meaning of the term
``requirement'' is something that is necessary, or obligatory. See,
e.g., Random House Webster's Unabridged Dictionary, Deluxe Edition,
2001. Given that Congress intended the Utility Study to be completed by
1993, it is reasonable to interpret the phrase ``after imposition of
the requirements of the Act'', as requiring the Agency to consider only
those requirements that Congress directly imposed on EGUs through the
CAA as amended in 1990 and for which EPA could reasonably predict HAP
emission reductions at the time of the Utility Study. The most
substantial requirement in this regard was the newly enacted ARP.
    The purpose of the ARP was to reduce the adverse effects of acid
deposition (more commonly known as ``acid rain''), by limiting the
allowable emissions of SO2 and NOX primarily from
EGUs. In enacting the Acid Rain provisions of the Act, Congress
explained that the problem of acid deposition was one of ``national and
international significance,'' that technologies to reduce the
precursors to acid deposition were ``economically feasible,'' and that
``control measures to reduce precursor emissions from steam-electric
generating units should be initiated without delay.'' CAA section
401(a). The ARP also includes a series of very specific emission
reduction requirements. For example, the goals of the program include a
reduction of annual SO2 emissions by 10 million tons below
1980 levels and a reduction of NOX emissions by two million
tons from 1980 levels.
    Moreover, the ARP achieved the required reductions by allocating
allowances to emit SO2 at reduced levels to each affected
EGU. Sources were prohibited from emitting more SO2 than the
number of allowances held. To comply with these requirements, source
owners or operators could elect to install controls, such as scrubbers,
switch to lower sulfur fuels at their facilities, or purchase
allowances from other EGUs that had reduced their emissions beyond what
they were required by the ARP to achieve. It was known at the time of
enactment of the 1990 Amendments that the controls used to reduce
emissions of SO2, primarily scrubbers, had the co-benefit of
controlling HAP emissions, including Hg emissions. The ARP also
included requirements for limiting NOX emissions from EGUs.
Considering the Acid Rain requirements under section 112(n)(1) is
reasonable because the Act contained very specific emission reduction
requirements for EGUs, and a tight compliance time-frame. In fact, all
of the regulations implementing the SO2 allowance trading
portion of the ARP were completed by the mid-1990's.
    The other significant requirement that Congress imposed in the 1990
Amendments was to revise the NSPS for NOX emissions from
EGUs by 1994. CAA 407(c). However, unlike the SO2 allowance
requirements of the ARP, Congress did not specify the amount of
required reductions, but instead directed EPA to consider the
improvements in methods for reducing NOX when establishing
standards for new sources. Thus, in the 1990 Amendments, Congress
sought NOX reductions from EGUs both through the ARP and a
revision of the NSPS applicable to new sources. The Agency issued these
NSPS in 1997.
    There are other requirements of Title I of the Act that could
affect EGUs, and they include the National Ambient Air Quality
Standards (NAAQS). Congress did not impose these provisions directly on
EGUs, however. Instead, EPA is responsible for developing the NAAQS,
and states are primarily responsible for assuring attainment and
maintenance of the NAAQS. For example, EPA stated in the Utility Study
that implementation of the 1997 NAAQS for ozone and PM may lead to
reductions in Hg emissions, but those potential reductions could not be
sufficiently quantified because states have the ultimate responsibility
for implementing the NAAQS. See Utility Study, pages ES-25, 1-3, 2-32,
3-14, and 6-15. States use a broad combination of measures (mobile and
stationary) to obtain the reductions needed to meet the NAAQS. These
decisions are unique to each state, as each state must identify and
assess the sources contributing to nonattainment and determine how best
to meet the NAAQS. EPA cannot predict with any certainty precisely how
states will ensure that the reductions needed to meet the NAAQS will be
realized. Moreover, there are additional uncertainties even were a
state to impose requirements on EGUs through a State Implementation
Plan (SIP), because each EGU may choose to meet the required reductions
in a different manner, which could result in more or less HAP emission
reductions. Accordingly, we do not believe it would have been
appropriate to include such potential emissions reductions in
determining whether it is necessary to

regulate HAP emissions from EGUs under section 112.
    Further, it is reasonable to interpret the phrase ``after
imposition of the requirements of the Act'', as only requiring
consideration of those requirements that Congress directly imposed on
EGUs through the CAA as amended in 1990 and for which EPA could
reasonably predict emission reductions at the time of the Utility
Study. To interpret the phrase otherwise would require the Agency to
look ahead two to three decades to forecast what possible requirements
might be developed and applied to EGUs under some requirement of the
CAA at some point in the future.
    Indeed, such an interpretation would be inconsistent with the
structure and purpose of section 112. As noted above, Congress gave EPA
until 1993 to issue the Utility Study and expected the appropriate and
necessary finding would follow shortly thereafter. Congress also
required EPA to address HAP emissions rapidly from all source
categories. See CAA 112(e), supra. It is reasonable to presume that
Congress intended EPA to evaluate the need for EGU HAP controls in
light of the requirements imposed upon the industry via the new 1990
requirements. Obviously the central requirement that was new and
applied to EGUs was the ARP which would be implemented rapidly
following passage of the 1990 amendments to the Act.
    Although the above represents a reasonable interpretation of what
Congress contemplated the Utility Study would examine with regard to
``imposition of the requirements of the Act,'' we recognize that we
have discretion to look beyond the Utility Study in determining whether
it is necessary to regulate EGUs under section 112. Given that several
years have passed since the December 2000 Finding, we conducted
additional analysis. Although not required, we conducted this analysis
to demonstrate that even considering a broad array of diverse
requirements, it remains appropriate and necessary to regulate EGUs
under section 112.
    Specifically, we examined a host of requirements, which in our
view, far surpass anything Congress could have contemplated in 1990 we
would consider as part of our ``necessary'' determination. For example,
our analysis includes certain state rules regulating criteria
pollutants, Federal consent decrees, and settlement agreements for
criteria pollutants resolving state-initiated and citizen-initiated
enforcement actions.\13\ We did not include in our analysis any state-
only HAP requirements or voluntary actions to reduce HAP emissions, as
those are not requirements of the CAA, and are not required by Federal
law to remain applicable.\14\
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    \13\ In our analysis, we included state requirements and citizen
and state settlements associated with criteria pollutants because
those requirements may have a basis under the CAA. We did not,
however, conduct an analysis to determine whether that was the case
in each instance. As such, we believe there may be instances where
we should not have considered certain state rules or state and
citizen suit settlements in our analysis, because those requirements
are based solely in state law and are not required by Federal law.
    \14\ Although, as explained below, our technical analysis
examined impacts projected out to 2016, this is a very conservative
approach. Given that two decades have passed since the enactment of
the 1990 CAA Amendments, we believe we can find it appropriate and
necessary to regulate EGUs under section 112, if we determine EGU
HAP emissions pose a hazard to public health and the environment
today without considering future HAP emission reductions. Congress
could not have contemplated in 1990 that EPA would have failed in
2011 to have regulated HAP emissions from EGUs where hazards to
public health and the environment remain.
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ii. Necessary Interpretation
    If we determine that the imposition of the requirements of the CAA
will not address the identified hazards, EPA must find it necessary to
regulate EGUs under section 112. Section 112 is the authority Congress
provided to address hazards to public health and the environment posed
by HAP emissions and section 112(n)(1)(A) requires the Agency to
regulate under section 112 if we find regulation is ``appropriate and
necessary.'' If we conclude that HAP emissions from EGUs pose a hazard
today, such that it is appropriate, and we further conclude based on
our scientific and technical expertise that the identified hazards will
not be resolved through imposition of the requirements of the CAA, we
believe there is no justification in the statute to conclude that it is
not necessary to regulate EGUs under section 112.
    Furthermore, we believe it is necessary to regulate if we have
identified a hazard to public health or the environment that will not
be addressed by imposition of the requirements of the CAA even if
regulation of EGUs under section 112 will not fully resolve the
identified hazard. We conclude that this is particularly true for bio-
accumulative HAP such as Hg because EPA can only address such emissions
from domestic sources and mitigation of identified risks associated
with such HAP is a reasonable goal. See section 112(c)(6). EPA cannot
decline to find it ``necessary'' to regulate EGUs under section 112
when it has identified a hazard to public health or the environment,
simply because that regulation will not wholly resolve the identified
hazards. The statute does not require the Agency to conclude that
identified hazards will be fully resolved before it may find regulation
under section 112 necessary. See Massachusetts v. EPA, 549 U.S. 497,
525 (2007).
    In addition, we may determine it is necessary to regulate under
section 112 even if we are uncertain whether the imposition of the
requirements of the CAA will address the identified hazards. Congress
left it to EPA to determine whether regulation of EGUs under section
112 is necessary. We believe it is reasonable to err on the side of
regulation of such highly toxic pollutants in the face of uncertainty.
Further, if we are unsure whether the other requirements of the CAA
will address an identified hazard, it is reasonable to exercise our
discretion in a manner that assures adequate protection of public
health and the environment. Moreover, we must be particularly mindful
of CAA regulations we include in our modeled estimates of future
emissions if they are not final or are still subject to judicial review
(i.e., the Transport Rule \15\). If such rules are either not finalized
or upheld by the Courts, the level of risk would potentially increase.
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    \15\ Federal Implementation Plans To Reduce Interstate Transport
of Fine Particulate Matter and Ozone. Proposed Rule. August 2, 2010.
75 FR 45,210.
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    We also may find it necessary to regulate EGUs under section 112
even if we conclude, based on reasonable estimations of emissions
reductions, that the imposition of the other requirements of the CAA
will significantly reduce the identified hazard. We maintain this is
reasonable because the only way to guarantee that the necessary
reductions in HAP emissions will occur at all EGUs and be maintained is
through a section 112(d) standard that directly regulates HAP emissions
from EGUs. This is true because sources could discontinue use of
controls for criteria pollutants that achieve HAP reductions as a co-
benefit if new control technologies or practices are identified that
reduce the relevant criteria pollutants but do not also reduce HAP. For
example, scrubbers are often used to reduce SO2 emissions
and those scrubbers also reduce emissions of several HAP. However, if
an EGU with a scrubber started complying with its SO2
standard by switching to low sulfur coal or purchasing allowances, the
HAP

emission reduction co-benefits associated with the scrubber would no
longer be realized. In addition, at the time Congress passed the 1990
CAA amendments, there were many older EGUs that had few or no controls
in place. Over 20 years later, there remain a significant number of
older EGUs that are only minimally controlled. The Agency may find it
necessary to regulate EGUs under section 112 to ensure that these
minimally controlled EGUs and those units that switch to other criteria
pollutant compliance options, thereby no longer achieving the same HAP
reductions, are subject to HAP regulation, such that the estimated
reductions in the identified hazards are realized.
iii. December 2000 Finding
    Our interpretation of the necessary finding is reasonable and
consistent with the December 2000 Finding. In that finding, EPA
determined that the imposition of the requirements of the CAA would not
address the serious public health and environmental hazards resulting
from EGU HAP emissions. We also stated that section 112 is the
authority to address hazards from HAP emissions. Because we determined
that the imposition of the requirements of the CAA would not address
the identified hazards, we correctly concluded it was necessary to
regulate under section 112. Although the Agency did not expressly
interpret the term necessary in the December 2000 Finding, under the
interpretation set forth above, the Agency must find it necessary if we
conclude that the imposition of the other requirements of the CAA will
not address the identified hazards. Because EPA reached that
conclusion, the Agency correctly determined that it was necessary to
regulate EGU HAP emissions and did not need to base the 2000 necessary
finding on any of the other bases set forth above.
iv. The 2005 Action
    We stated in 2005 that ``it is necessary to regulate EGUs under
section 112 only if there are no other authorities under the CAA that,
if implemented, would effectively address the remaining HAP emissions
from EGUs.'' 70 FR 16,001.\16\ In essence, we stated in 2005 that
section 112(n)(1)(A) requires the Agency to scour the CAA to determine
whether there is a direct or indirect manner in which EPA could
regulate HAP emissions from EGUs, notwithstanding the fact that
Congress expressly provided section 112 for the purpose of regulating
HAP emissions from stationary sources. This interpretation is not
reasonable.
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    \16\ In the rule reconsidering the 2005 Action, we further
clarified that in evaluating the effectiveness of other CAA
authorities we considered whether those other authorities could be
implemented in a cost-effective and administratively effective
manner. 71 FR 33,391. We need not address this in detail because we
conclude that the threshold conclusion that the Agency must look for
alternative CAA authorities that could be used to regulate HAP
emissions from EGUs before finding it necessary is invalid.
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    Congress enacted section 112 for the express purpose of regulating
HAP emissions. It is not reasonable to interpret section 112(n)(1)(A)
to require the Agency to find another provision of the CAA to address
identified hazards to public health or the environment. This is
particularly the case where the Agency would not have certainty that
such alternative legal theory would withstand judicial scrutiny because
section 112 is the authority expressly provided to regulate HAP
emissions and no other provision provides express authority to regulate
HAP emissions from existing stationary sources.\17\ Although anyone can