[Federal Register Volume 84, Number 26 (Thursday, February 7, 2019)]
[Proposed Rules]
[Pages 2670-2704]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-00936]



[[Page 2669]]

Vol. 84

Thursday,

No. 26

February 7, 2019

Part II





Environmental Protection Agency





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40 CFR Part 63





 National Emission Standards for Hazardous Air Pollutants: Coal- and 
Oil-Fired Electric Utility Steam Generating Units--Reconsideration of 
Supplemental Finding and Residual Risk and Technology Review; Proposed 
Rule

Federal Register / Vol. 84 , No. 26 / Thursday, February 7, 2019 / 
Proposed Rules

[[Page 2670]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2018-0794; FRL-9988-93-OAR]
RIN 2060-AT99


National Emission Standards for Hazardous Air Pollutants: Coal- 
and Oil-Fired Electric Utility Steam Generating Units--Reconsideration 
of Supplemental Finding and Residual Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing a 
revision to its response to the U.S. Supreme Court decision in Michigan 
v. EPA which held that the EPA erred by not considering cost in its 
determination that regulation under section 112 of the Clean Air Act 
(CAA) of hazardous air pollutant (HAP) emissions from coal- and oil-
fired electric utility steam generating units (EGUs) is appropriate and 
necessary. After considering the cost of compliance relative to the HAP 
benefits of regulation, the EPA proposes to find that it is not 
``appropriate and necessary'' to regulate HAP emissions from coal- and 
oil-fired EGUs, thereby reversing the Agency's prior conclusion under 
CAA section 112(n)(1)(A) and correcting flaws in the Agency's prior 
response to Michigan v. EPA. We further propose that finalizing this 
new response to Michigan v. EPA will not remove the Coal- and Oil-Fired 
EGU source category from the CAA section 112(c) list of sources that 
must be regulated under CAA section 112(d) and will not affect the 
existing CAA section 112(d) emissions standards that regulate HAP 
emissions from coal- and oil-fired EGUs. We are soliciting comment, 
however, on whether the EPA has the authority or obligation to delist 
EGUs from CAA section 112(c) and rescind (or to rescind without 
delisting) the National Emission Standards for Hazardous Air Pollutants 
(NESHAP) for Coal- and Oil-Fired EGUs, commonly known as the Mercury 
and Air Toxics Standards (MATS). The EPA is also proposing the results 
of the residual risk and technology review (RTR) of the NESHAP that the 
Agency is required to conduct in accordance with CAA section 112. The 
results of the residual risk analysis indicate that residual risks due 
to emissions of air toxics from this source category are acceptable and 
that the current standards provide an ample margin of safety to protect 
public health. No new developments in HAP emission controls to achieve 
further cost-effective emissions reductions were identified under the 
technology review. Therefore, based on the results of these analyses 
and reviews, we are proposing that no revisions to MATS are warranted. 
Finally, the EPA is also taking comment on establishing a subcategory 
for emissions of acid gas HAP from existing EGUs firing eastern 
bituminous coal refuse.

DATES: Comments. Comments must be received on or before April 8, 2019. 
Under the Paperwork Reduction Act (PRA), comments on the information 
collection provisions are best assured of consideration if the Office 
of Management and Budget (OMB) receives a copy of your comments on or 
before March 25, 2019.
    Public Hearing. The EPA is planning to hold at least one public 
hearing in response to this proposed action. Information about the 
hearing, including location, date, and time, along with instructions on 
how to register to speak at the hearing, will be published in a second 
Federal Register document.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No. 
EPA-HQ-OAR-2018-0794, at https://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. See SUPPLEMENTARY 
INFORMATION for detail about how the EPA treats submitted comments. 
Regulations.gov is our preferred method of receiving comments. However, 
the following other submission methods are also accepted:
     Email: a-and-r-docket@epa.gov. Include Docket ID No. EPA-
HQ-OAR-2018-0794 in the subject line of the message.
     Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2018-0794.
     Mail: To ship or send mail via the United States Postal 
Service, use the following address: U.S. Environmental Protection 
Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2018-0794, Mail 
Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: Use the following Docket Center 
address if you are using express mail, commercial delivery, hand 
delivery, or courier: EPA Docket Center, EPA WJC West Building, Room 
3334, 1301 Constitution Avenue NW, Washington, DC 20004. Delivery 
verification signatures will be available only during regular business 
hours.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Mary Johnson, 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: (919) 541-5025; fax number: (919) 541-4991; 
and email address: johnson.mary@epa.gov or Nick Hutson, 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: (919) 541-2968; fax 
number: (919) 541-4991; and email address: hutson.nick@epa.gov. For 
specific information regarding the risk modeling methodology, contact 
Mark Morris, Health and Environmental Impacts Division (C539-02), 
Office of Air Quality Planning and Standards, U.S. Environmental 
Protection Agency, Research Triangle Park, North Carolina 27711; 
telephone number: (919) 541-5416; and email address: 
morris.mark@epa.gov. For information about the applicability of the 
NESHAP to a particular entity, contact Sara Ayres, Office of 
Enforcement and Compliance Assurance, U.S. Environmental Protection 
Agency, U.S. EPA Region 5 (E-19J), 77 West Jackson Boulevard, Chicago, 
Illinois 60604; telephone number: (312) 353-6266; and email address: 
ayres.sara@epa.gov.

SUPPLEMENTARY INFORMATION: 
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2018-0794. All documents in the docket are 
listed in Regulations.gov. Although listed, some information is not 
publicly available, e.g., CBI (Confidential Business Information) or 
other information whose disclosure is restricted by statute. Certain 
other material, such as copyrighted material, is not placed on the 
internet and will be publicly available only in hard copy. Publicly 
available docket materials are available either electronically in 
Regulations.gov or in hard copy at the EPA Docket Center, Room 3334, 
EPA WJC West Building, 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 (202) 566-1744, and the telephone number for the EPA 
Docket Center is (202) 566-1742.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2018-0794. The EPA's policy is that all

[[Page 2671]]

comments received will be included in the public docket without change 
and may be made available online at https://www.regulations.gov, 
including any personal information provided, unless the comment 
includes information claimed to be CBI or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through https://www.regulations.gov or email. This type of information should be 
submitted by mail as discussed below.
    The EPA may publish any comment received to its public docket. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the Web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov website allows you to submit your 
comment anonymously, which means the EPA will not know your identity or 
contact information unless you provide it in the body of your comment. 
If you send an email comment directly to the EPA without going through 
https://www.regulations.gov, your email 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, the EPA recommends that you include your name and 
other contact information in the body of your comment and with any 
digital storage media you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should not include special characters or any form of encryption and be 
free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    The EPA is soliciting comment on numerous aspects of the proposed 
rule. The EPA has indexed each comment solicitation with an alpha-
numeric identifier (e.g., ``C-1,'' ``C-2,'' ''C-3'') to provide a 
consistent framework for effective and efficient provision of comments. 
Accordingly, the EPA asks that commenters include the corresponding 
identifier when providing comments relevant to that comment 
solicitation. The EPA asks that commenters include the identifier in 
either a heading, or within the text of each comment (e.g., ``In 
response to solicitation of comment C-1, . . .'') to make clear which 
comment solicitation is being addressed. The EPA emphasizes that the 
Agency is not limiting comment to these identified areas and encourages 
provision of any other comments relevant to this proposal.
    Submitting CBI. Do not submit information containing CBI to the EPA 
through https://www.regulations.gov or email. Clearly mark the part or 
all of the information that you claim to be CBI. For CBI information on 
any digital storage media that you mail to the EPA, mark the outside of 
the digital storage media as CBI and then identify electronically 
within the digital storage media the specific information that is 
claimed as CBI. In addition to one complete version of the comments 
that includes information claimed as CBI, you must submit a copy of the 
comments that does not contain the information claimed as CBI directly 
to the public docket through the procedures outlined in Instructions 
above. If you submit any digital storage media that does not contain 
CBI, mark the outside of the digital storage media clearly that it does 
not contain CBI. Information not marked as CBI will be included in the 
public docket and the EPA's electronic public docket without prior 
notice. Information marked as CBI will not be disclosed except in 
accordance with procedures set forth in 40 Code of Federal Regulations 
(CFR) part 2. Send or deliver information identified as CBI only to the 
following address: OAQPS Document Control Officer (C404-02), OAQPS, 
U.S. Environmental Protection Agency, Research Triangle Park, North 
Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2018-0794.
    Preamble Acronyms and Abbreviations. We use multiple acronyms and 
terms in this preamble. While this list may not be exhaustive, to ease 
the reading of this preamble and for reference purposes, the EPA 
defines the following terms and acronyms here:

AEGL acute exposure guideline level
AERMOD air dispersion model used by the HEM-3 model
ATSDR Agency for Toxic Substances and Disease Registry
CAA Clean Air Act
CalEPA California EPA
CAMR Clean Air Mercury Rule
CBI Confidential Business Information
CEMS continuous emissions monitoring systems
CFR Code of Federal Regulations
CPMS continuous parameter monitoring system
ECMPS Emissions Collection and Monitoring Plan System
EGU electric utility steam generating unit
EIA Energy Information Administration
EPA Environmental Protection Agency
EPRI Electric Power Research Institute
ERPG Emergency Response Planning Guideline
fPM filterable particulate matter
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model, Version 1.1.0
HF hydrogen fluoride
Hg mercury
HI hazard index
HQ hazard quotient
ICR information collection request
IGCC integrated gasification combined cycle
IRIS Integrated Risk Information System
km kilometer
lb/GWh pounds per gigawatt-hour
lb/MMBtu pounds per million British thermal units
lb/MWh pounds per megawatt-hour
lb/TBtu pounds per trillion British thermal units
MACT maximum achievable control technology
MATS Mercury and Air Toxics Standards
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
MMBtu million British thermal units
MMBtu/hr million British thermal units per hour
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NEEDS National Electric Energy Data System
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NOX nitrogen oxides
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PDF Portable Document Format
PM particulate matter
PM2.5 fine particulate matter
POM polycyclic organic matter
PRA Paperwork Reduction Act
RDL representative detection level
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RIA regulatory impact analysis
RTR residual risk and technology review
SAB Science Advisory Board
SO2 sulfur dioxide
TOSHI target organ-specific hazard index
tpy tons per year

[[Page 2672]]

TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and 
Ecological Exposure model
UARG Utility Air Regulatory Group
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
USGS United States Geological Survey

    Organization of this Document. The information in this preamble is 
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related 
information?
II. Appropriate and Necessary Finding
    A. Overview
    B. Background
    C. The EPA's Proposed Finding Under CAA Section 112(n)(1)(A)
    D. Effects of This Proposed Replacement of the Supplemental 
Finding
III. Criteria for Delisting a Source Category Under CAA Section 
112(c)(9)
IV. Background on the RTR Action
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP 
regulate its HAP emissions?
    C. What data collection activities were conducted to support 
this action?
    D. What other relevant background information and data are 
available?
V. RTR Analytical Procedures and Decision-Making
    A. How do we consider risk in our decision-making?
    B. How do we perform the technology review?
    C. How do we estimate post-MACT risk posed by the source 
category?
VI. RTR Analytical Results and Proposed Decisions
    A. What are the results of the risk assessment and analyses?
    B. What are our proposed decisions regarding risk acceptability, 
ample margin of safety, and adverse environmental effect?
    C. What are the results and proposed decisions based on our 
technology review?
VII. Consideration of Separate Subcategory and Acid Gas Standard for 
Existing EGUs That Fire Eastern Bituminous Coal Refuse
    A. Background
    B. Basis for Consideration of a Subcategory
    C. Potential Subcategory Emission Standards
VIII. Summary of Cost, Environmental, and Economic Impacts
IX. Request for Comments
X. Submitting Data Corrections
XI. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulation and Controlling 
Regulatory Costs
    C. Paperwork Reduction Act (PRA)
    D. Regulatory Flexibility Act (RFA)
    E. Unfunded Mandates Reform Act (UMRA)
    F. Executive Order 13132: Federalism
    G. Executive Order 13175: Consultation and Coordination with 
Indian Tribal Governments
    H. Executive Order 13045: Protection of Children from 
Environmental Health Risks and Safety Risks
    I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    J. National Technology Transfer and Advancement Act (NTTAA)
    K. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Does this action apply to me?

    Table 1 of this preamble lists the NESHAP and associated regulated 
industrial source categories that are the subject of this proposal. 
Table 1 is not intended to be exhaustive, but rather provides a guide 
for readers regarding the entities that this proposed action is likely 
to affect. The proposed standards, once promulgated, will be directly 
applicable to the affected sources. Federal, state, local, and tribal 
government entities that own and/or operate EGUs subject to 40 CFR part 
63, subpart UUUUU would be affected by this proposed action. The Coal- 
and Oil-Fired EGU source category was added to the list of categories 
of major and area sources of HAP published under section 112(c) of the 
CAA on December 20, 2000 (65 FR 79825). CAA section 112(a)(8) defines 
an electric utility steam generating unit as: Any fossil fuel fired 
combustion unit of more than 25 megawatts that serves a generator that 
produces electricity for sale. A unit that cogenerates steam and 
electricity and supplies more than one-third of its potential electric 
output capacity and more than 25 megawatts electrical output to any 
utility power distribution system for sale is also considered an EGU.

                Table 1--NESHAP and Industrial Source Categories Affected by This Proposed Action
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           Source category                         NESHAP                           NAICS code \1\
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Coal- and Oil-Fired EGUs.............  40 CFR part 63, subpart UUUUU  221112, 221122, 921150
----------------------------------------------------------------------------------------------------------------
\1\ North American Industry Classification System.

B. Where can I get a copy of this document and other related 
information?

    In addition to being available in the docket, an electronic copy of 
this action is available on the internet. Following signature by the 
EPA Administrator, the EPA will post a copy of this proposed action at 
https://www.epa.gov/mats/regulatory-actions-final-mercury-and-air-toxics-standards-mats-power-plants. Following publication in the 
Federal Register, the EPA will post the Federal Register version of the 
proposal and key technical documents at this same website. Information 
on the overall RTR program is available at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.

II. Appropriate and Necessary Finding

A. Overview

    The EPA proposes this revised action in response to the U.S. 
Supreme Court decision in Michigan v. EPA, 135 S.Ct. 2699 (2015), which 
held that the EPA erred by not considering cost in its determination 
that regulation of HAP emissions from coal- and oil-fired EGUs is 
appropriate and necessary under CAA section 112. In this action, after 
considering the cost of compliance relative to the HAP benefits of 
regulation, the EPA proposes to find that it is not ``appropriate and 
necessary'' to regulate HAP emissions from coal- and oil-fired EGUs, 
thereby reversing the Agency's conclusion under CAA section 
112(n)(1)(A), first made in 2000 and later affirmed in 2012 and 2016. 
This proposed response corrects flaws in the EPA's prior 2016 response 
to Michigan (82 FR 24420) and, if finalized, would supplant that 2016 
action. We also propose that finalizing this action will not remove the 
Coal- and Oil-Fired EGU source category from the CAA section 112(c)(1) 
list, nor will finalizing this action affect the existing CAA section 
112(d) emissions standards promulgated in 2012 that regulate HAP 
emissions from coal- and oil-fired EGUs, although this action requests 
comment on that proposed conclusion and whether the EPA has the 
authority or obligation to

[[Page 2673]]

delist the source category and rescind the standards, or to rescind the 
standards without delisting (Comment C-1).

B. Background

    In the 1990 Amendments to the CAA, Congress substantially modified 
CAA section 112, the provision of the CAA addressing HAP. That 
provision includes CAA section 112(b)(1), which sets forth a list of 
187 identified HAP, and CAA sections 112(b)(2) and (3), which give the 
EPA the authority to add or remove pollutants from the list. CAA 
section 112(a)(1) and (2) also specify the two types of sources to be 
addressed: Major sources and area sources. A major source is any 
stationary source or group of stationary sources at a single location 
and under common control that emits or has the potential to emit, 
considering controls, 10 tons per year (tpy) or more of any HAP or 25 
tpy or more of any combination of HAP. CAA section 112(a)(1). Any 
stationary source of HAP that is not a major source is an area source. 
CAA section 112(a)(2). All major source categories, besides EGUs, were 
required to be included on a published list of sources subject to 
regulation under CAA section 112, see CAA sections 112(a)(1) and 
(c)(1), and area sources ``which the Administrator finds presents a 
threat of adverse effects to human health or the environment (by such 
sources individually or in the aggregate) warranting regulation under 
this section'' were also required to be added to the list, see CAA 
section 112(c)(3). The EPA was to promulgate emission standards under 
CAA section 112(d) for those source categories on the list.
    This general CAA section 112(c) process of listing and regulation 
does not apply to EGUs. Instead, Congress enacted a special provision, 
CAA section 112(n)(1)(A), which established a separate process by which 
the EPA was to determine whether to regulate emissions of HAP from EGUs 
under CAA section 112. CAA section 112(n)(1)(A) directs the EPA to 
conduct a study to evaluate the hazards to public health that are 
reasonably anticipated to occur as a result of the HAP emissions from 
EGUs, after the imposition of other CAA provisions. The provision 
directs that the EPA shall regulate EGUs under CAA section 112 if the 
Administrator determines, after considering the results of the study, 
that such regulation is ``appropriate and necessary.'' CAA section 
112(n)(1)(A), therefore, sets a unique process by which the 
Administrator is to determine whether to establish CAA section 112(d) 
standards for EGUs. Moreover, the statute includes a separate 
definition of ``EGU'' which does not distinguish between major and area 
sources. CAA section 112(a)(8).
    On December 20, 2000, the EPA determined, pursuant to CAA section 
112(n)(1)(A), that it was appropriate and necessary to regulate coal- 
and oil-fired EGUs under CAA section 112(d) and added such units to the 
CAA section 112(c) List of Categories of Major and Area Sources. 65 FR 
79825 (2000 Finding). The EPA reversed that finding in 2005, concluding 
that it was neither appropriate nor necessary to regulate EGUs under 
CAA section 112(n)(1)(A), and stating that the effect of its reversal 
of the appropriate and necessary finding was removal of coal- and oil-
fired EGUs from the CAA section 112(c)(1) source category list. 70 FR 
15994 (March 29, 2005) (2005 Delisting Rule). The EPA concurrently 
issued the Clean Air Mercury Rule (CAMR), which regulated mercury (Hg) 
from new and existing coal-fired EGUs under CAA sections 111(b) and 
(d). The United States Court of Appeals for the District of Columbia 
(DC) Circuit (the Court) vacated the EPA's 2005 Delisting Rule in New 
Jersey v. EPA, 517 F.3d 574 (D.C. Cir. 2008). The Court ruled that the 
fact that the EPA had reversed its prior appropriate and necessary 
finding did not mean that the Agency could remove the Coal- and Oil-
Fired EGU source category from the CAA section 112(c)(1) list without 
going through the generally applicable CAA section 112(c)(9) delisting 
procedures. Id. Instead, the Court held that the Agency could only 
remove EGUs from the CAA section 112(c)(1) list after finding that the 
statutory criteria for delisting set forth in CAA section 112(c)(9) had 
been met. Id. In addition, the Court also vacated CAMR in light of the 
EPA's concession that it had no authority to regulate Hg from EGUs 
under CAA section 111 so long as EGUs remained on the CAA section 
112(c)(1) source category list. 517 F.3d 574 (D.C. Cir. 2008). (The 
Court did not address the merits of CAMR under CAA section 111; its 
vacatur was based solely on its holding that the delisting from CAA 
section 112 was improper.)
    On May 3, 2011, the EPA proposed to reaffirm the 2000 appropriate 
and necessary finding and proposed NESHAP for coal- and oil-fired EGUs, 
known as MATS. 76 FR 24976. The final MATS rule was subsequently issued 
on February 16, 2012. 77 FR 9304. Industry, states, environmental 
organizations, and public health organizations challenged many aspects 
of both the re-affirmed appropriate and necessary finding and the final 
MATS rule in the D.C. Circuit. The Court denied all challenges. White 
Stallion Energy Center v. EPA, 748 F.3d 1222 (D.C. Cir. 2014). Some 
industry and state petitioners sought further review of the final MATS 
rule, and the U.S. Supreme Court granted certiorari to determine 
whether the EPA erred when it concluded that it could properly make the 
appropriate and necessary finding under CAA section 112(n)(1)(A) 
without consideration of cost. On June 29, 2015, the Supreme Court 
ruled that the EPA ``strayed far beyond [the] bounds'' of reasonable 
interpretation when it determined cost was irrelevant to the 
appropriate and necessary finding. Michigan v. EPA, 135 S Ct. 2699, 
2707 (2015). Specifically, the Supreme Court held that cost was ``an 
important aspect of the problem'' and that the Agency was required to 
consider the cost of regulation before deciding whether it was 
appropriate and necessary to impose that regulation on EGUs under CAA 
section 112. Id. On remand from the Supreme Court, the D.C. Circuit 
left MATS in effect while the Agency addressed the Michigan decision. 
Order, White Stallion Energy Center v. EPA, No. 12-1100 (D.C. Cir. Dec. 
15, 2015) (ECF No. 1588459).
    On April 25, 2016, after public notice and comment,\1\ the EPA 
finalized a supplemental finding (2016 Supplemental Finding) concluding 
that its consideration of cost did not change its previous 
determination that regulation of HAP emissions from coal- and oil-fired 
EGUs is appropriate and necessary. 82 FR 24420. In the 2016 
Supplemental Finding, the EPA considered costs under two alternative 
approaches. Under the first approach, the EPA evaluated compliance 
costs in comparison to the industry's historical annual revenues and 
annual capital expenditures, and examined impacts of the rule on retail 
electricity prices. The EPA concluded that because these costs were 
within the range of historical variability, the cost of MATS was 
reasonable. The EPA also found that the power sector could continue to 
perform its primary function--the generation, transmission, and 
distribution of reliable electricity at reasonable cost--after 
imposition of the MATS rule. Based on the conclusion that the costs of 
the rule were ``reasonable'' and considering the benefits of reducing 
HAP that had been identified in earlier agency determinations, the 
Agency affirmed the appropriate and necessary finding under CAA section 
112(n)(1)(A).
---------------------------------------------------------------------------

    \1\ 80 FR 75025 (December 1, 2015).
---------------------------------------------------------------------------

    In the 2016 Supplemental Finding, the EPA also presented a second, 
alternative and independent, approach

[[Page 2674]]

to considering cost. This approach considered the results of the formal 
cost-benefit analysis that the Agency had previously performed for the 
regulatory impact analysis (RIA) for the final MATS rule.\2\ That RIA 
cost-benefit analysis accounted for the monetized and non-monetized 
benefits of MATS, including HAP-related benefits that could not be 
quantified or monetized, as well as the monetized co-benefits of 
reducing pollutants other than HAP. The RIA analysis found that its 
projection of these aggregated benefits ($37 to $90 billion each year) 
exceeded the costs of compliance ($9.6 billion) by three to nine times. 
The EPA, therefore, concluded that the RIA's cost-benefit analysis also 
supported its affirmation of the prior appropriate and necessary 
finding under CAA section 112(n)(1)(A). 82 FR 24420.
---------------------------------------------------------------------------

    \2\ U.S. EPA. 2011. Regulatory Impact Analysis for the Final 
Mercury and Air Toxics Standards. EPA-452/R-11-011. Available at 
https://www3.epa.gov/ttn/ecas/docs/ria/utilities_ria_final-mats_2011-12.pdf. Docket ID No. EPA-HQ-OAR-2009-0234-20131.
---------------------------------------------------------------------------

    A number of state and industry groups petitioned for review of the 
2016 Supplemental Finding in the D.C. Circuit. Murray Energy Corp. v. 
EPA, No. 16-1127 (D.C. Cir. filed April 25, 2016). In April 2017, given 
its interest in reviewing the 2016 action, the EPA moved the Court to 
continue oral argument and hold the case in abeyance in order to give 
the new Administration an opportunity to undertake that review. The 
Court granted the EPA's request for a continuance on April 27, 2017. 
Order, Murray Energy Corp. v. EPA, No. 16-1127 (D.C. Cir. April 27, 
2017) (ECF No. 1672987).

C. The EPA's Proposed Finding Under CAA Section 112(n)(1)(A)

    In this action, the EPA proposes to conclude that the 2016 
Supplemental Finding was flawed and that, after considering the cost of 
compliance relative to the HAP benefits of MATS, it is not appropriate 
and necessary to regulate coal- and oil-fired EGUs under section 112 of 
the CAA. CAA section 112(n)(1)(A) requires the EPA to determine that 
both the appropriate and the necessary prongs are met. Therefore, if 
the EPA finds that either prong is not satisfied, it cannot make an 
affirmative appropriate and necessary finding. Cf. 70 FR 16000. The 
EPA's reexamination of its determination in this proposal focuses on 
the first prong of that analysis: Whether regulation is 
``appropriate,'' after consideration of the costs and benefits of such 
regulation. The EPA has reexamined the cost analyses presented in the 
2016 Supplemental Finding and proposes to determine that neither of the 
Finding's approaches to considering cost satisfies the Agency's 
obligation under CAA section 112(n)(1)(A) as interpreted by the Supreme 
Court in Michigan. Instead, we use a different consideration of cost 
for purposes of the appropriate and necessary finding, one that we 
believe aligns with the purpose of CAA section 112(n)(1)(A) as set 
forth in Michigan.\3\ We propose to directly compare the cost of 
compliance with MATS with the benefits specifically associated with 
reducing emissions of HAP as the primary inquiry in this finding, in 
order to satisfy our duty to consider cost in the context of CAA 
section 112(n)(1)(A).
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    \3\ Agencies have inherent authority to reconsider past 
decisions and to revise, replace, or repeal a decision to the extent 
permitted by law and supported by a reasoned explanation. FCC v. Fox 
Television Stations, Inc., 556 U.S. 502, 515 (2009); Motor Vehicle 
Mfrs. Ass'n v. State Farm Mutual Auto. Ins. Co., 463 U.S. 29, 42 
(1983) (``State Farm''). The EPA's interpretations of the statutes 
it administers are not ``carved in stone,'' but must be evaluated 
``on a continuing basis,'' for example, ``in response to . . . a 
change in administrations.'' Nat'l Cable & Telecomms. Ass'n v. Brand 
X internet Servs., 545 U.S. 967, 981 (2005) (internal quotation 
marks and citations omitted). An agency's reasoning can include a 
change in policy on the basis that ``the agency believes it to be 
better,'' even if a court might disagree. White Stallion, 748 F.3d 
at 1235; see also Nat'l Ass'n of Home Builders v. EPA, 682 F.3d 
1032, 1038 & 1043 (D.C. Cir. 2012) (a revised rulemaking based ``on 
a reevaluation of which policy would be better in light of the 
facts'' is ``well within an agency's discretion,'' and `` `[a] 
change in administration brought about by the people casting their 
votes is a perfectly reasonable basis for an executive agency's 
reappraisal of the costs and benefits of its programs and 
regulations' '') (quoting State Farm, 463 U.S. at 59 (Rehnquist, J., 
concurring in part and dissenting in part)). The CAA complements the 
EPA's inherent authority to reconsider prior rulemakings by 
providing the Agency with broad authority to prescribe regulations 
as necessary to carry out the Administrator's authorized functions 
under the statute. 42 U.S.C. 7601(a). This broad discretion can be 
limited by Congress, however. In New Jersey v. EPA, the D.C. Circuit 
held that a reversal of the appropriate and necessary finding would 
not have the effect of removing Coal- and Oil-Fired EGUs from the 
CAA section 112(c)(1) source category list because Congress 
``unambiguously limit[ed] EPA's discretion'' by fashioning a 
statutorily mandated avenue for removing source categories from the 
list in CAA section 112(c)(9). 517 F.3d 574, 582-83. (D.C. Cir. 
2008).
---------------------------------------------------------------------------

    The EPA also proposes that, because a negative appropriate and 
necessary finding cannot by itself remove a source category from the 
CAA section 112(c) list, see New Jersey, 517 F.3d at 582, finalizing 
this finding will neither remove the Coal- and Oil-Fired EGU source 
category from the CAA section 112(c) list, nor will it alter or 
eliminate the CAA section 112(d) emissions standards imposed by MATS. 
The EPA solicits public comment on all aspects of this proposal, and 
retains the discretion, as always, to make changes in response to those 
comments prior to finalizing this rule or to decide not to finalize 
some or all aspects of this proposal after considering public comments.
1. The 2016 Supplemental Finding Was an Improper Response to Michigan 
v. EPA
a. The ``Cost Reasonableness'' Approach Does Not Satisfy the Agency's 
Obligation Under CAA Section 112(n)(1)(A)
    We propose to find that the Agency's 2016 Supplemental Finding 
erred in its consideration of cost. Specifically, we find that what was 
described in the 2016 Supplemental Finding as the preferred approach, 
or ``cost reasonableness test,'' does not meet the statute's 
requirements to fully consider costs, and was an unreasonable 
interpretation of CAA section 112(n)(1)(A)'s mandate, as informed by 
the Supreme Court's opinion in Michigan. In its 2016 Supplemental 
Finding, the EPA developed a ``cost reasonableness test'' based on D.C. 
Circuit opinions that had evaluated the Agency's consideration of cost 
in the context of setting new source performance standards under 
section 111 of the CAA. See Legal Memorandum Accompanying the Proposed 
Supplemental Finding that it is Appropriate and Necessary to Regulate 
Hazardous Air Pollutants from Coal- and Oil-Fired Electric Utility 
Steam Generating Units (EGUs) (2015 Legal Memorandum). Because those 
opinions interpreted CAA section 111 to only prohibit the Agency from 
adopting standards for new sources whose cost would be ``exorbitant,'' 
Lignite Energy Council v. EPA, 198 F.3d 930, 933 (D.C. Cir. 1999), 
``excessive,'' or ``unreasonable,'' Sierra Club v. Costle, 657 F.2d 
298, 383 (D.C. Cir. 1981), we concluded that we could consider cost for 
CAA section 112(n)(1)(A) by determining whether cost of compliance was 
``reasonable''--in other words, whether the cost of regulation could be 
absorbed by the power sector without negatively affecting the 
industry's ability to continue performing its primary function. That 
``cost reasonableness test'' compared compliance costs of MATS relative 
to historical annual revenues and annual capital expenditures, and 
evaluated the impacts of the rule on retail electricity prices. Because 
we found that the costs of compliance with the rule across the entire 
utility sector were within historical variability and would not shut 
down the sector as a whole, the EPA

[[Page 2675]]

concluded that the cost of compliance with MATS was reasonable.
    The Agency claimed that use of the ``cost reasonableness test'' for 
its CAA section 112(n)(1)(A) appropriate and necessary finding was 
supported by the ``overall statutory objectives of section 112,'' and 
stated that ``cost was but one factor among many'' that the EPA must 
consider. See Legal Memorandum at 20. We also interpreted CAA section 
112(n)(1)(A) and Michigan not to require the EPA to assume that a 
consideration of cost should predominate or take primary significance 
to the subordination of other considerations, because of CAA section 
112's overall concern with the nature of HAP emissions and populations 
that might be particularly sensitive to harms associated with those 
emissions. Id.
    In this notice, we are proposing to find that the EPA did not 
comply with its statutory duty to consider cost as part of the 
appropriate and necessary finding in the 2016 Supplemental Finding. The 
2016 Supplemental Finding repeatedly emphasized that the Michigan Court 
did not hold that the CAA ``unambiguously required'' the EPA to perform 
a formal cost-benefit analysis to satisfy CAA 112(n)(1)(A). 135 S. Ct. 
at 2711. But, as discussed below, the 2016 Supplemental Finding, among 
other flaws, ignored observations about the importance of the cost 
consideration to the appropriate and necessary finding, as provided by 
the Court in Michigan.
    Contrary to the 2015 Legal Memorandum's suggestion that cost should 
not ``trump'' or ``predominate'' other considerations, the Supreme 
Court observed that ``[a]gencies have long treated cost as a centrally 
relevant factor when deciding whether to regulate.'' Id. at 2707 
(emphasis added). The Supreme Court rejected arguments that the general 
goals of CAA section 112 make cost irrelevant to a CAA section 
112(n)(1)(A) appropriate and necessary finding. As such, the EPA must 
meaningfully consider cost when making this threshold finding. In 
addition, the Supreme Court emphasized that CAA section 112(n)(1)(A) 
reflects Congress's intent that the EPA treat EGUs differently from 
other sources. Id. at 2710. The attempt made in the 2016 Supplemental 
Finding to ``harmonize'' CAA section 112(n)(1)(A) with the remainder of 
CAA section 112 is, therefore, not consistent with Congress's intent 
and the Supreme Court's decision in Michigan v. EPA.
    The 2016 Supplemental Finding's reliance on case law pertaining to 
CAA section 111(b) new source rules was similarly misguided. The 
methodologies that courts have approved for considering costs of 
control technologies for new sources that have not yet been constructed 
are not particularly informative in the context of EPA's deciding 
whether it is appropriate to impose control requirements on sources 
that are already operating. Costs of control technologies for new 
sources are borne as each source is added to the fleet of existing 
sources and are not imposed on the entire fleet of existing sources 
within a period of a few years, as is required under CAA section 112. 
Moreover, the case law cited by the 2015 Legal Memorandum is 
distinguishable even without regard to the fact that different 
statutory provisions (CAA section 111 versus 112) are at issue. For 
example, in Lignite Council, the D.C. Circuit found that the ``new 
standards will only modestly increase the cost of producing electricity 
in newly constructed boilers.'' Lignite Energy Council v. United States 
EPA, 198 F.3d at 933. Even in its flawed conclusion that the cost of 
MATS was ``reasonable,'' the EPA did not go so far as to say that the 
costs of that rule were in any way ``modest.''
    The primary, fatal flaw of the 2016 Supplemental Finding's 
``preferred approach'' was its disregard for the Michigan Court's 
suggestion that, under CAA section 112(n)(1)(A), the Agency must 
meaningfully consider cost within the context of a regulation's 
benefits. The decision contemplated that a proper consideration of cost 
would be relative to benefits. For example, the Court questioned 
whether a regulation could be considered ``rational'' where there was a 
gross imbalance between costs and benefits and stated that ``[n]o 
regulation is ``appropriate'' if it does more harm than good.'' Id. The 
Court also made numerous references to a direct comparison of the costs 
of MATS with benefits from reducing emissions of HAP. For instance, the 
Court pointed out that ``[t]he costs [of MATS] to power plants were 
thus between 1,600 and 2,400 times as great as the quantifiable 
benefits from reduced emissions of hazardous air pollutants.'' Id. at 
2706. Although the decision established no bright-line rules, it 
suggested that CAA section 112(n)(1)(A)'s requisite consideration of 
cost would not be met if the cost analysis did not ``ensure cost-
effectiveness'' or ``prevent the imposition of costs far in excess of 
benefits.'' Id. at 2710.
    For these reasons, the 2016 Supplemental Finding's ``test'' of 
whether an industry can bear the cost of regulation does not 
demonstrate that the cost of MATS was ``reasonable'' under the 
particular statutory context. More importantly, the metrics ``tested'' 
by the Agency in the 2016 Supplemental Finding are irrelevant to the 
determination of whether it is ``appropriate and necessary'' to impose 
that regulation. Each cost metric the Agency examined compared the cost 
of MATS to other costs borne by the industry, but never in its 
``preferred approach'' did the Agency make the statutorily mandated 
assessment of whether the benefits garnered by the rule were worth it--
i.e., a direct comparison of costs and benefits. Because the ``cost 
reasonableness test'' failed to consider cost in a meaningful way 
relative to benefits, we, therefore, conclude that approach did not 
adequately address the Supreme Court's instruction that a reasonable 
regulation requires an agency to fully consider ``the advantages and 
the disadvantages'' of a decision. See Michigan, 135 S. Ct. at 2707 
(emphasis in original). Instead, we propose to reconsider cost using a 
more direct comparison of benefits and costs to address the Supreme 
Court's remand of the appropriate and necessary determination, as 
described below. As noted below, final action on this proposal would 
replace the 2016 Supplemental Finding.
b. The Cost-Benefit Approach in the 2016 Supplemental Finding's 
Alternative Approach Improperly Considered Co-benefits From Non-HAP 
Emissions Reductions
    In the 2016 Supplemental Finding's alternative approach, the EPA 
improperly made an independent finding under CAA section 112(n)(1)(A) 
that was based on a formal benefit-cost analysis, which evaluates 
whether a regulation will increase economic efficiency, to find that it 
was appropriate and necessary to regulate EGUs under CAA section 112. 
See 81 FR 24425.\4\ The formal benefit-cost analysis relied on 
information reported in the RIA performed for the MATS rule. The 
quantified benefits accounted for in the formal benefit-cost analysis 
in the 2016 Supplemental Finding's alternative approach included both 
HAP and non-HAP air quality benefits. In this action, we propose to 
find that the EPA's equal reliance on the particulate matter (PM) air 
quality co-benefits projected to occur as a result of the reductions in 
HAP was flawed as the focus of CAA section

[[Page 2676]]

112(n)(1)(A) is HAP emissions reductions.
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    \4\ We use the term ``formal benefit-cost analysis'' to refer to 
an economic analysis that attempts to quantify all significant 
consequences of an action in monetary terms in order to determine 
whether an action increases economic efficiency. Assuming that all 
consequences can be monetized, actions with positive net benefits 
(i.e., benefits exceed costs) improve economic efficiency.
---------------------------------------------------------------------------

    The EPA developed an RIA for the 2012 final MATS rule pursuant to 
Executive Orders 12866 and 13563 and other applicable statutes (e.g., 
the Regulatory Flexibility Act and the Unfunded Mandates Reform Act), 
as informed by OMB guidance \5\ and the EPA's Economic Guidelines.\6\ 
The analyses the EPA conducted generated an estimate of the 
quantifiable benefits of HAP reductions under the rule of $4 to $6 
million annually.\7\ The EPA also analyzed the PM air quality co-
benefits of MATS and attributed these benefits to the rule. The RIA 
included in its analysis a consideration of the co-benefit reductions 
in the emissions of pollutants other than the HAP regulated by MATS, 
such as nitrogen oxides (NOX) and sulfur dioxide 
(SO2), which contribute to the formation of fine particulate 
matter (PM2.5). Reductions of these NOX and 
SO2 emissions result from installing control technologies 
and implementing the compliance strategies necessary to reduce the HAP 
emissions directly regulated by MATS. The EPA projected that the co-
benefits associated with reducing these non-HAP pollutants would be 
substantial. Indeed, these projected co-benefits comprised the 
overwhelming majority (approximately 99.9 percent) of the monetized 
benefits of MATS reflected in the EPA's RIA ($36 billion to $89 
billion). By comparison, compliance costs of the final MATS rule were 
projected to be $9.6 billion in 2015, and $8.6 billion and $7.4 billion 
in 2020 and 2030, respectively.\8\ These compliance costs are an 
estimate of the increased expenditures in capital, fuel, and other 
inputs by the entire power sector to comply with the EPA's 
requirements, while continuing to provide a given level of electricity 
demand. In the 2016 Supplemental Finding's alternative approach, to 
satisfy the required consideration of cost when determining whether it 
is appropriate and necessary to regulate under CAA section 
112(n)(1)(A), the EPA compared these monetized costs to the monetized 
benefits, along with unquantified and unmonetized effects, to conclude 
that MATS would increase economic efficiency and, therefore, reaffirmed 
its earlier finding that it was appropriate and necessary to regulate 
EGUs.
---------------------------------------------------------------------------

    \5\ U.S. OMB. 2003. Circular A-4 Guidance to Federal Agencies on 
Preparation of Regulatory Analysis. Available at https://www.whitehouse.gov/sites/whitehouse.gov/files/omb/circulars/A4/a-4.pdf.
    \6\ U.S. EPA. 2014. Guidelines for Preparing Economic Analyses. 
EPA-240-R-10-001. National Center for Environmental Economics, 
Office of Policy. Washington, DC. December. Available at https://www.epa.gov/environmental-economics/guidelines-preparing-economic-analyses. Docket ID No. EPA-HQ-OAR-2009-0234-20503.
    \7\ Like the MATS RIA, all benefits and costs in this and 
subsequent sections are reported in 2007 dollars.
    \8\ See Table 3-5 of the RIA: https://www3.epa.gov/ttn/ecas/docs/ria/utilities_ria_final-mats_2011-12.pdf.
---------------------------------------------------------------------------

    The EPA's justification for its equal reliance on the co-benefits 
of non-HAP emissions when setting the MATS standards in its CAA section 
112(n)(1)(A) determination was flawed. The Agency erred in concluding 
that the statutory text of CAA section 112(n)(1)(A) and the legislative 
history of CAA section 112 more generally ``expressly support[ed]'' the 
position that it was reasonable to consider co-benefits, and give equal 
weight to those co-benefits, in a CAA section 112(n)(1)(A) appropriate 
and necessary finding. 81 FR 24439. The 2016 Supplemental Finding 
pointed to CAA section 112(n)(1)(A)'s directive to ``perform a study of 
the hazards to public health reasonably anticipated to occur as a 
result of emissions by electric utility steam generating units of [HAP] 
after imposition of the requirements of [the CAA],'' and noted that the 
requirement to consider co-benefit reduction of HAP resulting from 
other CAA programs highlighted Congress' understanding that programs 
targeted at reducing non-HAP pollutants can and do result in the 
reduction of HAP emissions. Id. The finding also noted that the Senate 
Report on CAA section 112(d)(2) recognized that maximum achievable 
control technology (MACT) standards would have the collateral benefit 
of controlling criteria pollutants. Id. However, these statements 
acknowledging that reductions in HAP can have the collateral benefit of 
reducing non-HAP emissions and vice versa, provides no support for the 
proposition that any such co-benefits should be the Agency's primary 
consideration when making a finding under CAA section 112(n)(1)(A). 
Indeed, it would be highly illogical for the Agency to make a 
determination that regulation under CAA section 112, which is expressly 
designed to deal with HAP, is justified principally on the basis of the 
criteria pollutant impacts of these regulations. That is, if the HAP-
related benefits are not at least moderately commensurate with the cost 
of HAP controls, then no amount of co-benefits can offset this 
imbalance for purposes of a determination that it is appropriate to 
regulate under CAA section 112(n)(1)(A). Cf. Michigan, 135 S. Ct. at 
2707 (``One would not say that it is even rational, never mind 
``appropriate,'' to impose billions of dollars in economic costs in 
return for a few dollars in health or environmental benefits.'').
    The 2016 Supplemental Finding's benefit-cost approach also erred in 
implying that the results of an economic efficiency test, as informed 
by the benefit-cost analysis presented in the MATS RIA, should govern 
the cost consideration assessment in CAA section 112(n)(1)(A). A formal 
benefit-cost analysis does not dictate how cost should be considered 
under CAA section 112(n)(1)(A), particularly where, as noted above, the 
statutory provision indicates Congress' particular concern about risks 
associated with HAP and the benefits that would accrue from reducing 
those risks. Although an analysis of all benefits and costs in 
accordance with generally recognized benefit-cost analysis practices is 
appropriate for informing the public about the potential effects of any 
regulatory action, as well as for complying with the requirements of 
Executive Order 12866, this does not mean that equal consideration of 
all benefits and costs, including co-benefits, is appropriate for the 
specific statutory appropriate and necessary finding called for under 
CAA section 112(n)(1)(A). Rather this finding is necessarily governed 
by the particular statutory language and context of this provision, as 
discussed below.
    In sum, the Agency did not provide any meaningful support for its 
conclusion that the statutory text and legislative history support 
placing consideration of co-benefits in a CAA section 112(n)(1)(A) 
determination on equal footing with the consideration of HAP-specific 
benefits and, as explained below, the statutory text strongly supports 
the use of a different approach.
2. It Is Not Appropriate and Necessary To Regulate EGUs Under CAA 
Section 112
    In this action, the EPA proposes to conclude that it is not 
appropriate and necessary to regulate HAP from EGUs under CAA section 
112 because the costs of such regulation grossly outweigh the HAP 
benefits. The EPA is taking comment on its proposal that direct 
comparison of the rule's costs and benefits is a reasonable approach, 
if not the only permissible approach, to considering costs in response 
to Michigan, and, further, that such a comparison performed under CAA 
section 112(n)(1)(A) should focus primarily on benefits associated with 
reduction of HAP (Comment C-2). A proper consideration of costs based 
on this approach demonstrates that the

[[Page 2677]]

total cost of compliance with MATS ($7.4 to $9.6 billion annually) 
dwarfs the monetized HAP benefits of the rule ($4 to $6 million 
annually). As discussed further below, while there are unquantified HAP 
benefits and significant monetized PM co-benefits associated with MATS, 
the Administrator has concluded that the identification of these 
benefits is not sufficient, in light of the gross imbalance of 
monetized costs and HAP benefits, to support a finding that it is 
appropriate and necessary to regulate EGUs under CAA section 112.
    The statutory text of CAA section 112(n)(1)(A) and the Michigan 
decision both support focusing the ``appropriate and necessary'' 
determination on HAP-specific benefits and costs. The study referenced 
in CAA section 112(n)(1)(A) specifically focuses on the hazards to 
public health that will reasonably occur as a result of HAP emissions, 
not harmful emissions in general. According to this section, ``The 
Administrator shall regulate electric utility steam generating units 
under this section, if the Administrator finds such regulation is 
appropriate and necessary after considering the results of the study 
required by this subparagraph.'' The text, on its face, thus, suggests 
that Congress wanted the Administrator's appropriate and necessary 
determination to be focused on the health hazards related to HAP 
emissions and the potential benefits of avoiding those hazards by 
reducing HAP emissions. As noted in section II.C.1.b. of this preamble, 
while the provision acknowledges the existence of the phenomenon of co-
benefits by referencing the potential for ancillary reductions of HAP 
emissions by way of CAA provisions targeted at other pollutants, 
acknowledgement of that fact does not address whether ancillary 
reductions of criteria pollutants should be part of the Administrator's 
determination under CAA section 112(n)(1)(A), which is undeniably 
focused on hazards resulting from HAP-specific emissions. Indeed, the 
direction to consider whether it is appropriate and necessary to 
regulate HAP after criteria pollutants have been addressed by the CAA's 
other requirements is, if anything, support for the conclusion that it 
is not proper to place much weight on the co-benefits of further 
criteria pollutant reductions as part of the CAA section 112(n)(1)(A) 
determination. Directing the EPA to study HAP effects under CAA section 
112 after other provisions of the CAA had been implemented suggests 
that Congress envisioned that the judgement about whether additional 
regulation was appropriate and necessary should be predicated primarily 
on an assessment of HAP emissions from this source category. Similarly, 
the general recognition of the existence of collateral benefits or 
controlling criteria pollutants in CAA section 112's legislative 
history \9\ does not shed any light on whether such benefits should be 
given equal consideration in a CAA section 112(n)(1)(A) determination. 
This is particularly so where that legislative history is unconnected 
to CAA section 112(n)(1)(A), a special provision written by Congress to 
address the unique circumstances facing EGUs. In fact, it would not be 
reasonable to rely on such legislative history in light of the Supreme 
Court's conclusion that the Agency erred attempting to ``harmonize'' 
CAA section 112(n)(1)(A) with the remainder of CAA section 112. As the 
Court noted, ``[t]his line of reasoning overlooks the whole point of 
having a separate provision about power plants: Treating power plants 
different from other stationary sources.'' Michigan, 135 S. Ct. at 
2710.
---------------------------------------------------------------------------

    \9\ See Legal Memorandum at 25 n.28 (citing A Legislative 
History of the Clean Air Act Amendments of 1990, Vol. 5, at 8512 
(CAA Amendments of 1989, at 172, Report of the Committee on 
Environment and Public Works, S.1630)).
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    Finally, we note that this action proposes to primarily consider 
the costs of MATS in comparison with the HAP benefits of the hazardous 
pollution reductions from MATS. In keeping with CAA section 
112(n)(1)(A) and the overall structure of the CAA, we think it is 
appropriate not to give equal weight to non-HAP co-benefits in this 
comparison. Congress established a rigorous system for setting 
standards of acceptable levels of criteria air pollutants and wrote a 
comprehensive framework directing the implementation of those standards 
in order to address the health and environmental impacts associated 
with those pollutants. See, e.g., 42 U.S.C. 7409; 7410; 7501; 7502; 
7505a; 7506; 7506a; 7507; 7509; 7509a; 7511; 7511a; 7511b; 7511c; 
7511d; 7511e; 7511f; 7512; 7512a; 7513; 7513a; 7513b; 7514; and 7515. 
As noted above, the vast majority of estimated monetized benefits 
resulting from MATS are associated with reductions in PM2.5 
precursor emissions, principally NOX and SO2. 
Both NOX and SO2 are criteria pollutants and 
precursors to criteria pollutants that are already addressed by the 
cavalcade of statutory provisions governing levels of these pollutants, 
including the National Ambient Air Quality Standards (NAAQS) provisions 
that require the EPA to set standards for criteria pollutants requisite 
to protect public health with an adequate margin of safety, and by 
state, regional, and national rulemakings establishing control measures 
to meet those levels. To the extent that additional reductions of these 
criteria pollutants are necessary to protect public health, regulation 
explicitly targeted at these pollutants is best reserved for the NAAQS 
program, under which Congress provided the EPA ample authority to 
regulate.
    The total cost of compliance with MATS ($7.4 to $9.6 billion 
annually) \10\ vastly outweighs the monetized HAP benefits of the rule 
($4 to $6 million annually).\11\ Even with the substantial monetized PM 
co-benefits and the significant unquantified HAP benefits associated 
with MATS, the gross disparity between monetized costs and HAP 
benefits, which we believe to be the primary focus of the 
Administrator's determination in CAA section 112(n)(1)(A), is too large 
to support an affirmative appropriate and necessary finding. As 
explained in the MATS RIA, the only health benefit attributed to 
reducing Hg emissions that the EPA could quantify and monetize was IQ 
loss in children born to a subset of recreational fishers who consume 
fish during pregnancy.\12\ The EPA also identified benefits associated 
with regulation of HAP from EGUs that could not be quantified. These 
effects include impacts of Hg on human health (including neurologic, 
cardiovascular, genotoxic, and immunotoxic effects), a variety of 
adverse health effects associated with exposure to certain non-Hg HAP 
(including cancer, and chronic and acute health disorders that 
implicate multiple organ systems such as the lungs and kidneys), and 
effects on wildlife and ecosystems.13 14
---------------------------------------------------------------------------

    \10\ See Table 3-5 on page 3-14 and Table 3-16 on page 3-31 of 
the MATS RIA.
    \11\ See Table ES-4 on page ES-6 of the MATS RIA.
    \12\ U.S. EPA, 2011. Revised Technical Support Document: 
National-Scale Assessment of Mercury Risk to Populations with High 
Consumption of Self-Caught Freshwater Fish In Support of the 
Appropriate and Necessary Finding for Coal- and Oil-Fired Electric 
Generating Units. Office of Air Quality Planning and Standards. 
November. EPA-452/R-11-009. Docket ID No. EPA-HQ-OAR-2009-0234-
19913.
    \13\ See Chapters 4 and 5 of the MATS RIA.
    \14\ In addition, the MATS RIA attributed unquantified health 
benefits to reductions in emissions of nitrogen dioxide 
(NO2) and SO2. However, as discussed above, 
these unquantified criteria pollutant co-benefits are no longer 
relevant given the different approach to considering such co-
benefits that the EPA is now proposing to take. See Chapter 5 of the 
MATS RIA.
---------------------------------------------------------------------------

    The EPA acknowledges the importance of these benefits and the 
limitations on the Agency's ability to monetize HAP-specific benefits. 
The

[[Page 2678]]

EPA agrees that such benefits are relevant to any comparison of the 
benefits and costs of a regulation. Because unquantified benefits are, 
by definition, not considered in monetary terms, the Administrator must 
evaluate the evidence of unquantified benefits and determine the extent 
to which they alter any conclusions based on the comparison of 
monetized costs and benefits. The MATS RIA accounts for all the 
monetized and unquantified benefits of the rule, and the EPA's proposed 
approach to the cost-benefit analysis in the RIA does not discount the 
existence or importance of the unquantified benefits of reducing HAP 
emissions.\15\ Instead, after fully acknowledging the existence and 
importance of such benefits, the EPA proposes to conclude that 
substantial and important unquantified benefits of MATS are not 
sufficient to overcome the significant difference between the monetized 
benefits and costs of this rule. As noted, the unquantified HAP-related 
benefits of MATS involve only a limited set of mercury and other HAP-
related morbidity effects in humans and ecosystems. The EPA has 
provided an updated comparison of costs and target pollutant benefits 
in a memorandum to the rulemaking docket.\16\ Table 1 of the memorandum 
estimates that the net target HAP benefits of the rule (HAP benefits--
costs) are negative. As noted elsewhere in the notice, the actual costs 
and benefits of the MATS rule may differ from the EPA's analysis. 
However, as explained in the memorandum, given that the CAA section 
112(n)(1)(A) finding is a threshold analysis that Congress intended the 
Agency would complete prior to regulation, the EPA believes it is 
reasonable for purposes of this reconsideration to rely on the 
estimates projected prior to the rule's taking effect, i.e., the 
estimates of costs and benefits calculated in the 2011 RIA. In 
addition, even assuming that actual costs and benefits differed from 
projections made in 2011, given the large difference between target HAP 
benefits and estimated costs, the outcome of the Agency's proposed 
finding here would likely stay the same.
---------------------------------------------------------------------------

    \15\ Id. The Agency is not in this proposed replacement to the 
2016 Supplemental Finding reopening the prior findings and risk 
assessments made over the last two decades. The EPA also explained 
in the MATS RIA that there are significant obstacles to successfully 
quantifying and monetizing the public health benefits from reducing 
HAP emissions. These obstacles include gaps in toxicological data, 
uncertainties in extrapolating results from high-dose animal 
experiments to estimate human effects at lower doses, limited 
monitoring data, difficulties in tracking diseases such as cancer 
that have long latency periods, and insufficient economic research 
to support the valuation of the health impacts often associated with 
exposure to individual HAP.
    \16\ Compliance Cost, HAP Benefits, and Ancillary Co-Pollutant 
Benefits for ``National Emission Standards for Hazardous Air 
Pollutants: Coal-and Oil-Fired Electric Utility Steam Generating 
Units--Reconsideration of Supplemental Finding and Residual Risk and 
Technology Review.''
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    For all of these reasons, and paying particular heed to the 
statutory text and purpose of CAA section 112(n)(1)(A) as well as the 
Supreme Court's direction in Michigan, we propose to find that it is 
not appropriate and necessary to regulate coal- and oil-fired EGUs 
under section 112 of the CAA.

D. Effects of This Proposed Replacement of the Supplemental Finding

1. Effects of This Proposed Replacement
    Final action on this proposed replacement of the 2016 Supplemental 
Finding will reverse the Agency's conclusion under CAA section 
112(n)(1)(A), first made in 2000 and later affirmed in 2012 and 2016, 
that it is appropriate and necessary to regulate HAP from EGUs. We 
propose to conclude that finalizing this replacement will not remove 
the Coal- and Oil-Fired EGU source category from the CAA section 
112(c)(1) list, nor will finalizing this revision otherwise affect the 
existing CAA section 112(d) emissions standards promulgated in 2012. 
Under D.C. Circuit case law, the EPA's determination that a source 
category was listed in error does not by itself remove a source 
category from the CAA section 112(c)(1) list--even EGUs, 
notwithstanding their special treatment under CAA section 112(n). New 
Jersey v. EPA, 517 F.3d 574 (D.C. Cir. 2008). Instead, in order to 
remove a source category from the CAA section 112(c)(1) list, the EPA 
must determine that the CAA section 112(c)(9) statutory criteria for 
delisting have been met. Id. The EPA requests comment on its 
interpretation of New Jersey in the context of this proposed finding 
(Comment C-3).
    In 2005, the EPA reversed the December 2000 Finding and concluded 
that it was neither appropriate nor necessary to regulate coal- and 
oil-fired EGUs under CAA section 112 and delisted such units from the 
CAA section 112(c) source category list. 70 FR 15994. In that rule we 
stated, ``EPA reasonably interprets section 112(n)(1)(A) as providing 
it authority to remove coal- and oil-fired units from the section 
112(c) list at any time that it makes a negative appropriate and 
necessary finding under the section.'' 70 FR 16032 (2005 Delisting 
Rule). In the 2005 Delisting Rule, the EPA ``identified errors in the 
prior [2000] finding and determined that the finding lacked 
foundation.'' Id. at 16033. Because we found that the 2000 Finding had 
been in error at the time of listing, we concluded that coal- and oil-
fired EGUs ``should never have been listed under section 112(c) and 
therefore the criteria of section 112(c)(9) do not apply'' in removing 
the source category from the list. Id. In addition, we pointed out that 
the inclusion of EGUs on the 112(c)(1) list was not a ``final agency 
action.'' Id. Therefore, we stated that we had ``inherent authority 
under the CAA to revise [the listing] at any time based on either 
identified errors in the December 2000 finding or on new information 
that bears upon that finding.'' Id.
    The D.C. Circuit rejected the EPA's interpretations and vacated the 
2005 Delisting Rule, holding that the CAA unambiguously requires the 
delisting criteria in CAA section 112(c)(9) to have been met before 
``any'' source category can be removed from the CAA section 112(c)(1) 
list. New Jersey, 517 F.3d at 582. It specified that, under the CAA's 
plain text and under step one of Chevron, ``the only way the EPA could 
remove EGUs from the section 112(c)(1) list'' was to satisfy those 
criteria. Id. (emphasis added). The Court expressly rejected the EPA's 
argument that, ``[l]ogically, if EPA makes a determination under 
section 112(n)(1)(A) that power plants should not be regulated at all 
under section 112 . . . [then] this determination ipso facto must 
result in removal of power plants from the section 112(c) list.'' Id. 
(quoting the EPA's brief). Instead, the Court maintained that CAA 
section 112(n)(1) governed only how the Administrator determines 
whether to list EGUs, and that any and all attempts to remove 
categories from the list were under the exclusive purview of CAA 
section 112(c)(9). See id. The Court further held that the existence of 
CAA section 112(c)(9) limited the normal discretion an Agency would 
typically have to reverse its position and undo the administrative 
determination to list EGUs as a source category. See Id. at 582-83.
    In this action, we propose to reverse the conclusions presented in 
the 2016 Supplemental Finding and to find that, after consideration of 
the cost of compliance with the CAA section 112(d) standards, it is not 
appropriate and necessary to regulate HAP emissions from EGUs under CAA 
section 112. Consistent with New Jersey, the EPA is proposing to find 
that this reversal of the CAA section 112(n)(1)(A) determination, if 
finalized, would not have the effect of removing EGUs from the CAA 
section 112(c)(1) source category list. Because EGUs would remain on 
the CAA section 112(c)(1)

[[Page 2679]]

source category list, the CAA section 112(d) standards for that 
category, as promulgated in the MATS rule, would be unaffected by final 
action on this proposal.
2. Alternative Interpretations of Effects of This Proposed Replacement: 
Requests for Comment
    The EPA also solicits comment on two alternative interpretations of 
the impact of reversing the 2016 Supplemental Finding. Specifically, 
the Agency solicits comment under two separate theories on whether, 
contrary to the interpretation discussed above, the EPA would have 
authority to rescind the MATS rule and delist EGUs from CAA section 112 
if, acting on remand following the Supreme Court's opinion in Michigan, 
it were to finalize its proposed conclusion that it is not appropriate 
and necessary to regulate HAP from coal- and oil-fired EGUs (Comment C-
4). The Agency also solicits comment on whether, in light of the fact 
that the CAA section 112(n)(1)(A) finding is a threshold determination 
to setting the CAA section 112(d) standards, we would be obligated to 
rescind the rule if we were to finalize our proposed finding that it is 
not appropriate and necessary to regulate HAP from these sources, even 
if such a finding did not remove EGUs from the list of covered sources 
under CAA section 112(c) (Comment C-5).
    In particular, we solicit comment on whether the EPA could 
reasonably conclude that the D.C. Circuit's holding in New Jersey v. 
EPA does not limit the Agency's authority to rescind the MATS rule, 
under two alternative interpretations (Comment C-6). Under the first 
alternative interpretation, we seek comment on whether New Jersey is 
distinguishable because the facts here are sufficiently different from 
those considered by the Court reviewing the 2005 Delisting Rule at 
issue (Comment C-7). In that case, the original 2000 Finding and CAA 
section 112(c)(1) listing were in place, but because the EPA had not 
yet promulgated CAA section 112(d) standards, the finding itself was 
not yet reviewable. CAA section 112(e)(4); see also UARG v. EPA, No. 
01-1074, 2001 U.S. App. LEXIS 18436, 2001 WL 936363 (D.C. Cir. July 26, 
2001). Here, the 2012 Finding was challenged and reviewed by the 
Supreme Court in Michigan v. EPA, which found that the EPA's 
determination that it was appropriate and necessary to regulate HAP 
from EGUs was flawed. Because the Supreme Court found that 
determination to be flawed, the EPA necessarily retains the discretion 
to reach a different conclusion from that reached in 2012 when we 
promulgated MATS. This proposed reversal of the 2016 Supplemental 
Finding is a continuation of the Agency's response to the Supreme 
Court's remand, and New Jersey does not limit the effect of an action 
made in response to a Supreme Court decision finding the original 
action flawed, nor does it limit the Agency's ability to revise its 
response to a Supreme Court decision. Therefore, the EPA would have 
authority to rescind MATS and remove EGUs from the list of source 
categories regulation under CAA section 112 after finalizing this 
reversal of the 2016 Supplemental Finding.
    Under the second alternative interpretation, the EPA seeks comment 
on whether, were the proposed reversal to be finalized, EGUs would 
remain on the CAA section 112(c) list of sources, but the EPA would 
have the authority to rescind the standards regulating those source's 
emissions under CAA section 112(d) in light of the fact that CAA 
section 112(n)(1)(A) plainly establishes that the Administrator must 
find regulation under CAA section 112 is appropriate and necessary as a 
prerequisite to undertaking such regulation (Comment C-8). New Jersey 
v. EPA held that the EPA may not remove a source category from the CAA 
section 112(c) list without demonstrating that the delisting analysis 
under CAA section 112(c)(9) has been satisfied, but the decision did 
not address the question whether, in the absence of a valid appropriate 
and necessary finding, the EPA must regulate EGUs for HAP.
    Finally, although the alternative interpretations described 
immediately above both suggest the EPA would have the discretionary 
authority to rescind MATS (either with or without delisting), the EPA 
solicits comment on whether, under either alternative interpretation, 
the Agency would instead be obligated to rescind MATS once it finalized 
a reversal of the 2016 Supplemental Finding (Comment C-9).
    We solicit comment on all aspects of these alternative 
interpretations of the impacts of replacing the 2016 Supplemental 
Finding and these potential alternate readings of the Court's decision 
in New Jersey (Comment C-10).

III. Criteria for Delisting a Source Category Under CAA Section 
112(c)(9)

    As noted above, New Jersey held that the EPA cannot remove a source 
category from the CAA section 112(c) source category list without 
addressing the delisting criteria in CAA section 112(c)(9). CAA section 
112(c)(9)(B) provides that ``[t]he Administrator may delete any source 
category'' from the CAA section 112(c) source category list if the 
Agency determines that: (1) For HAP that may cause cancer in humans, 
``no source in the category (or group of sources in the case of area 
sources) emits such hazardous air pollutants in quantities which may 
cause a lifetime risk of cancer greater than one in one million to the 
individual in the population who is most exposed to emissions of such 
pollutants from the source (or group of sources in the case of area 
sources)''; and (2) for HAP that may result in human health effects 
other than cancer or adverse environmental effects, ``a determination 
that emissions from no source in the category or subcategory concerned 
(or group of sources in the case of area sources) exceed a level which 
is adequate to protect public health with an ample margin of safety and 
no adverse environmental effect will result from emissions from any 
source.''
    In this action, the EPA is neither conducting a delisting analysis 
under CAA section 112(c)(9) for the Coal- and Oil-Fired EGU source 
category, nor soliciting comment on whether such an analysis should be 
conducted, or on what any such analysis would demonstrate. Any such 
comments would be outside the scope of this action.
    The Agency notes that the proposed results of its risk review 
indicate that with the MATS rule in place, the estimated inhalation 
cancer risk to the individual most exposed to actual emissions from the 
source category is 9-in-1 million. As noted above, the EPA is not 
proposing a delisting analysis and any such analysis would likely 
differ from the analysis done for the CAA section 112(f)(2) risk review 
in important aspects.
    In addition, on two previous occasions, the EPA has examined the 
statutory delisting criteria with respect to EGUs and found that the 
criteria were not met. We summarize without adding to those findings 
below.
    In 2011, in response to the EPA's request for comments on the 
proposed MATS rule, the Utility Air Regulatory Group (UARG) submitted a 
petition pursuant to CAA section 112(c)(9) requesting that coal-fired 
EGUs be removed from the CAA section 112(c) List of Categories of Major 
and Area Sources.\17\ In its petition, UARG

[[Page 2680]]

asserted that: (1) No coal-fired EGU or group of coal-fired EGUs emit 
HAP in amounts that will cause a lifetime cancer risk greater than 1-
in-1 million; and (2) no coal-fired EGU or group of coal-fired EGUs 
emit non-carcinogenic HAP in amounts that will exceed a level which is 
adequate to protect public health with an ample margin of safety or 
cause adverse environmental effects. The EPA denied this petition on 
several grounds.\18\ First, the EPA rejected UARG's request on the 
basis that, under D.C. Circuit precedent, the Agency is not permitted 
to delist a portion of a source category that poses cancer risks.\19\ 
Second, the EPA found that UARG's data and analyses identified a 
maximum individual cancer risk of 4-in-1 million, which exceeds the 
statutory threshold in CAA section 112(c)(9)(B)(i) of 1-in-1 million. 
Additionally, the EPA found that UARG's analysis did not fully 
characterize noncancer human health effects for the source category and 
further, that UARG failed to show that ``no adverse environmental 
effects will result from emissions from any source'' pursuant to CAA 
section 112(c)(9)(B)(ii). For all these reasons, the EPA denied UARG's 
petition to delist coal-fired EGUs from the CAA section 112(c) source 
category list. UARG challenged the EPA's denial of its delisting 
petition as arbitrary and capricious, and the D.C. Circuit dismissed 
UARG's challenge on the basis that the EPA had adequately demonstrated 
that the CAA section 112(c)(9) delisting criteria were not met by 
UARG's analysis. White Stallion, 748 F.3d at 1248.
---------------------------------------------------------------------------

    \17\ Petition of the Utility Air Regulatory Group for the De-
Listing of Coal-Fired Electric Utility Steam Generating Units as a 
Source Category Subject to Section 112 of the Clean Air Act. Docket 
ID No. EPA-HQ-OAR-2009-0234-17777.
    \18\ 77 FR 9365 (February 16, 2012).
    \19\ UARG petitioned the Agency to delist coal-fired EGUs, which 
represent only a portion of the listed source category. The EPA 
believed it was not permitted to delist a portion of a source 
category, where that source category poses cancer risks. NRDC v. 
U.S. EPA, 489 F.3d 1364 (D.C. Cir. 2007). Specifically, in NRDC, the 
D.C. Circuit held that the Agency's attempt to delist a ``low-risk'' 
subcategory was ``contrary to the plain language of the statute,'' 
and that the statute only authorized the Agency to remove source 
categories pursuant to CAA section 112(c)(9). Id. at 1373 (``Because 
EPA's interpretation of Section 112(c)(9) as allowing it to exempt 
the risk-based subcategory is contrary to the plain language of the 
statute, the EPA's interpretation fails at Chevron step one.'').
---------------------------------------------------------------------------

    The EPA also independently conducted an analysis which also 
confirmed that the Coal- and Oil-Fired EGU source category cannot be 
delisted pursuant to CAA section 112(c)(9).\20\ The EPA analyzed non-Hg 
inhalation risks from 16 EGU facility case studies, including both 
coal- and oil-fired EGUs. Of the 16 facilities analyzed, six had cancer 
risks greater than 1-in-1 million, exceeding the delisting criteria in 
CAA section 112(c)(9)(B)(i). Because EGUs failed to meet the first 
delisting requirement, the Agency did not need to determine whether the 
second delisting requirement was satisfied.
---------------------------------------------------------------------------

    \20\ U.S. EPA, 2011. Supplement to the Non-Hg Case Study Chronic 
Inhalation Risk Assessment in Support of the Appropriate and 
Necessary Finding for Coal- and Oil-Fired Electric Generating Units. 
November. EPA-452/R-11-013. Docket ID No. EPA-HQ-OAR-2009-0234-
19912.
---------------------------------------------------------------------------

IV. Background on the RTR Action

A. What is the statutory authority for this action?

    The statutory authority for this action is provided by sections 112 
and 301 of the CAA, as amended (42 U.S.C. 7401 et seq.). Section 112 of 
the CAA establishes a two-stage regulatory process to develop standards 
for emissions of HAP from stationary sources. Generally, the first 
stage involves establishing technology-based standards and the second 
stage involves evaluating those standards that are based on MACT to 
determine whether additional standards are needed to address any 
remaining risk associated with HAP emissions. This second stage is 
commonly referred to as the ``residual risk review.'' In addition to 
the residual risk review, the CAA also requires the EPA to review 
standards set under CAA section 112 every 8 years to determine if there 
are ``developments in practices, processes, or control technologies'' 
that may be appropriate to incorporate into the standards. This review 
is commonly referred to as the ``technology review.'' When the two 
reviews are combined into a single rulemaking, it is commonly referred 
to as the ``risk and technology review.'' The discussion that follows 
identifies the most relevant statutory sections and briefly explains 
the contours of the methodology used to implement these statutory 
requirements. A more comprehensive discussion appears in the document 
titled CAA Section 112 Risk and Technology Reviews: Statutory Authority 
and Methodology in the docket for this rulemaking.
    In the first stage of the CAA section 112 standard setting process, 
the EPA promulgates technology-based standards under CAA section 112(d) 
for categories of sources identified as emitting one or more of the HAP 
listed in CAA section 112(b). Sources of HAP emissions are either major 
sources or area sources, and CAA section 112 establishes different 
requirements for major source standards and area source standards. 
``Major sources'' are those that emit or have the potential to emit 10 
tpy or more of a single HAP or 25 tpy or more of any combination of 
HAP. All other sources are ``area sources.'' For major sources, CAA 
section 112(d)(2) provides that the technology-based NESHAP must 
reflect the maximum degree of emission reductions of HAP achievable 
(after considering cost, energy requirements, and non-air quality 
health and environmental impacts). These standards are commonly 
referred to as MACT standards. CAA section 112(d)(3) also establishes a 
minimum control level for MACT standards, known as the MACT ``floor.'' 
The EPA must also consider control options that are more stringent than 
the floor. Standards more stringent than the floor are commonly 
referred to as beyond-the-floor standards. In certain instances, as 
provided in CAA section 112(h), the EPA may set work practice standards 
where it is not feasible to prescribe or enforce a numerical emission 
standard. For area sources, CAA section 112(d)(5) gives the EPA 
discretion to set standards based on generally available control 
technologies or management practices (GACT standards) in lieu of MACT 
standards.
    The second stage in standard-setting focuses on identifying and 
addressing any remaining (i.e., ``residual'') risk according to CAA 
section 112(f). For source categories subject to MACT standards, 
section 112(f)(2) of the CAA requires the EPA to determine whether 
promulgation of additional standards is needed to provide an ample 
margin of safety to protect public health or to prevent an adverse 
environmental effect. Section 112(d)(5) of the CAA provides that this 
residual risk review is not required for categories of area sources 
subject to GACT standards. Section 112(f)(2)(B) of the CAA further 
expressly preserves the EPA's use of the two-step approach for 
developing standards to address any residual risk and the Agency's 
interpretation of ``ample margin of safety'' developed in the National 
Emissions Standards for Hazardous Air Pollutants: Benzene Emissions 
from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene 
Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery 
Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA 
notified Congress in the Risk Report that the Agency intended to use 
the Benzene NESHAP approach in making CAA section 112(f) residual risk 
determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently 
adopted this approach in its residual risk determinations and the Court 
upheld the EPA's interpretation that CAA section 112(f)(2) incorporates 
the approach established in the Benzene

[[Page 2681]]

NESHAP. See NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to 
evaluate residual risk and to develop standards under CAA section 
112(f)(2) is a two-step approach. In the first step, the EPA determines 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) 
\21\ of approximately 1 in 10 thousand.'' 54 FR 38045, September 14, 
1989. If risks are unacceptable, the EPA must determine the emissions 
standards necessary to reduce risk to an acceptable level without 
considering costs. In the second step of the approach, the EPA 
considers whether the emissions standards provide an ample margin of 
safety to protect public health ``in consideration of all health 
information, including the number of persons at risk levels higher than 
approximately 1 in 1 million, as well as other relevant factors, 
including costs and economic impacts, technological feasibility, and 
other factors relevant to each particular decision.'' Id. The EPA must 
promulgate emission standards necessary to provide an ample margin of 
safety to protect public health. After conducting the ample margin of 
safety analysis, we consider whether a more stringent standard is 
necessary to prevent, taking into consideration costs, energy, safety, 
and other relevant factors, an adverse environmental effect.
---------------------------------------------------------------------------

    \21\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk if an individual were exposed to the maximum 
level of a pollutant for a lifetime.
---------------------------------------------------------------------------

    CAA section 112(d)(6) separately requires the EPA to review 
standards promulgated under CAA section 112 and revise them ``as 
necessary (taking into account developments in practices, processes, 
and control technologies)'' no less often than every 8 years. In 
conducting this review, which we call the ``technology review,'' the 
EPA is not required to recalculate the MACT floor. Natural Resources 
Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008). 
Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 
2013). The EPA may consider cost in deciding whether to revise the 
standards pursuant to CAA section 112(d)(6).

B. What is this source category and how does the current NESHAP 
regulate its HAP emissions?

    The NESHAP for the Coal- and Oil-Fired EGU source category 
(commonly referred to as MATS) were initially promulgated on February 
16, 2012 (77 FR 9304), under title 40 part 63, subpart UUUUU. The MATS 
rule was amended on April 19, 2012 (77 FR 23399), to correct 
typographical errors and certain preamble text that was inconsistent 
with regulatory text; on April 24, 2013 (78 FR 24073), to update 
certain emission limits and monitoring and testing requirements 
applicable to new sources; on November 19, 2014 (79 FR 68777), to 
revise definitions for startup and shutdown and to finalize work 
practice standards and certain monitoring and testing requirements 
applicable during periods of startup and shutdown; and on April 6, 2016 
(81 FR 20172), to correct conflicts between preamble and regulatory 
text and to clarify regulatory text. In addition, the electronic 
reporting requirements of the rule were amended on March 24, 2015 (80 
FR 15510), to allow for the electronic submission of Portable Document 
Format (PDF) versions of certain reports until April 16, 2017, while 
the EPA's Emissions Collection and Monitoring Plan System (ECMPS) is 
revised to accept all reporting that is required by the rule, and on 
April 6, 2017 (82 FR 16736), and on July 2, 2018 (83 FR 30879), to 
extend the interim submission of PDF versions of reports through June 
30, 2018, and July 1, 2020, respectively.
    The MATS rule applies to coal- and oil-fired EGUs located at both 
major and area sources of HAP emissions. The sources subject to the 
MATS rule include each individual or group of coal- or oil-fired EGUs. 
An existing affected source is the collection of coal- or oil-fired 
EGUs in a subcategory within a single contiguous area and under common 
control. A new affected source is each coal- or oil-fired EGU for which 
construction or reconstruction began after May 3, 2011. As previously 
stated in section I of this preamble, an electric utility steam 
generating unit is a fossil fuel-fired combustion unit of more than 25 
megawatts (MW) that serves a generator that produces electricity for 
sale. A unit that cogenerates steam and electricity and supplies more 
than one-third of its potential electric output capacity and more than 
25 MW electric output to any utility power distribution system for sale 
is also considered an electric utility steam generating unit. The MATS 
rule defines additional terms for determining rule applicability, 
including, but not limited to, definitions for ``Coal-fired electric 
utility steam generating unit,'' ``Oil-fired electric utility steam 
generating unit,'' and ``Fossil fuel-fired.'' Certain types of electric 
generating units are not subject to 40 CFR part 63, subpart UUUUU: Any 
unit designated as a major source stationary combustion turbine subject 
to subpart YYYY of part 63 and any unit designated as an area source 
stationary combustion turbine, other than an integrated gasification 
combined cycle (IGCC) unit; any EGU that is not a coal- or oil-fired 
EGU and that meets the definition of a natural gas-fired EGU in 40 CFR 
63.10042; any EGU greater than 25 MW that has the capability of 
combusting either coal or oil, but does not meet the definition of a 
coal- or oil-fired EGU because it did not fire sufficient coal or oil 
to satisfy the average annual heat input requirement set forth in the 
definitions for coal-fired and oil-fired EGUs in 40 CFR 63.10042; and 
any electric steam generating unit combusting solid waste (i.e., a 
solid waste incineration unit) subject to standards established under 
sections 129 and 111 of the CAA.
    For coal-fired EGUs, the rule established standards to limit 
emissions of Hg, acid gas HAP, non-Hg HAP metals (e.g., nickel, lead, 
chromium), and organic HAP (e.g., formaldehyde, dioxin/furan). 
Standards for hydrochloric acid (HCl) serve as a surrogate for the acid 
gas HAP, with an alternate standard for SO2 that may be used 
as a surrogate for acid gas HAP for those coal-fired EGUs with flue gas 
desulfurization (FGD) systems and SO2 continuous emissions 
monitoring systems (CEMS) installed and operational. Standards for 
filterable particulate matter (fPM) serve as a surrogate for the non-Hg 
HAP metals, with standards for total non-Hg HAP metals and individual 
non-Hg HAP metals provided as alternative equivalent standards. Work 
practice standards limit formation and emission of the organic HAP.
    For oil-fired EGUs, the rule establishes standards to limit 
emissions of HCl and hydrogen fluoride (HF), total HAP metals (e.g., 
Hg, nickel, lead), and organic HAP (e.g., formaldehyde, dioxin/furan). 
Standards for fPM serve as a surrogate for total HAP metals, with 
standards for total HAP metals and individual HAP metals provided as 
alternative equivalent standards. Work practice standards limit 
formation and emission of the organic HAP.
    The MATS rule includes standards for existing and new EGUs for 
seven subcategories: Two for coal-fired EGUs, one for IGCC EGUs, one 
for solid oil-derived fuel-fired EGUs, and three for liquid oil-fired 
EGUs. EGUs in six of the subcategories are subject to numeric emission 
limits for the pollutants

[[Page 2682]]

described above except for organic HAP. Organic HAP are regulated by a 
work practice standard that requires periodic combustion process tune-
ups. EGUs in the subcategory of limited-use liquid oil-fired EGUs with 
an annual capacity factor of less than 8 percent of its maximum or 
nameplate heat input are also subject to a work practice standard 
consisting of periodic combustion process tune-ups, but are not subject 
to any numeric emission limits. Emission limits for existing EGUs and 
new or reconstructed EGUs are summarized in Table 2 and Table 3, 
respectively.

           Table 2--Emission Limits for Existing Affected EGUs
------------------------------------------------------------------------
         Subcategory                Pollutant        Emission limit \1\
------------------------------------------------------------------------
1. Coal-fired unit not low    a. fPM..............  3.0E-2 lb/MMBtu or
 rank virgin coal.                                   3.0E-1 lb/MWh.
                              OR..................  OR
                              Total non-Hg HAP      5.0E-5 lb/MMBtu or
                               metals.               5.0E-1 lb/GWh.
                              OR..................  OR
                              Individual HAP
                               metals:
                                 Antimony, Sb.....  8.0E-1 lb/TBtu or
                                                     8.0E-3 lb/GWh.
                                 Arsenic, As......  1.1 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Beryllium, Be....  2.0E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
                                 Cadmium, Cd......  3.0E-1 lb/TBtu or
                                                     3.0E-3 lb/GWh.
                                 Chromium, Cr.....  2.8 lb/TBtu or 3.0E-
                                                     2 lb/GWh.
                                 Cobalt, Co.......  8.0E-1 lb/TBtu or
                                                     8.0E-3 lb/GWh.
                                 Lead, Pb.........  1.2 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Manganese, Mn....  4.0 lb/TBtu or 5.0E-
                                                     2 lb/GWh.
                                 Nickel, Ni.......  3.5 lb/TBtu or 4.0E-
                                                     2 lb/GWh.
                                 Selenium, Se.....  5.0 lb/TBtu or 6.0E-
                                                     2 lb/GWh.
                              b. HCl..............  2.0E-3 lb/MMBtu or
                                                     2.0E-2 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  2.0E-1 lb/MMBtu or
                                                     1.5 lb/MWh.
                              c. Hg...............  1.2 lb/TBtu or 1.3E-
                                                     2 lb/GWh.
2. Coal-fired unit low rank   a. fPM..............  3.0E-2 lb/MMBtu or
 virgin coal.                                        3.0E-1 lb/MWh.
                              OR..................  OR
                              Total non-Hg HAP      5.0E-5 lb/MMBtu or
                               metals.               5.0E-1 lb/GWh.
                              OR..................  OR
                              Individual HAP
                               metals:
                                 Antimony, Sb.....  8.0E-1 lb/TBtu or
                                                     8.0E-3 lb/GWh.
                                 Arsenic, As......  1.1 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Beryllium, Be....  2.0E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
                                 Cadmium, Cd......  3.0E-1 lb/TBtu or
                                                     3.0E-3 lb/GWh.
                                 Chromium, Cr.....  2.8 lb/TBtu or 3.0E-
                                                     2 lb/GWh.
                                 Cobalt, Co.......  8.0E-1 lb/TBtu or
                                                     8.0E-3 lb/GWh.
                                 Lead, Pb.........  1.2 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Manganese, Mn....  4.0 lb/TBtu or 5.0E-
                                                     2 lb/GWh.
                                 Nickel, Ni.......  3.5 lb/TBtu or 4.0E-
                                                     2 lb/GWh.
                                 Selenium, Se.....  5.0 lb/TBtu or 6.0E-
                                                     2 lb/GWh.
                              b. HCl..............  2.0E-3 lb/MMBtu or
                                                     2.0E-2 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  2.0E-1 lb/MMBtu or
                                                     1.5 lb/MWh.
                              c. Hg...............  4.0 lb/TBtu or 4.0E-
                                                     2 lb/GWh.
3. IGCC unit................  a. fPM..............  4.0E-2 lb/MMBtu or
                                                     4.0E-1 lb/MWh.
                              OR..................  OR
                              Total non-Hg HAP      6.0E-5 lb/MMBtu or
                               metals.               5.0E-1 lb/GWh.
                              OR..................  OR
                              Individual HAP
                               metals:
                                 Antimony, Sb.....  1.4 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Arsenic, As......  1.5 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Beryllium, Be....  1.0E-1 lb/TBtu or
                                                     1.0E-3 lb/GWh.
                                 Cadmium, Cd......  1.5E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
                                 Chromium, Cr.....  2.9 lb/TBtu or 3.0E-
                                                     2 lb/GWh.
                                 Cobalt, Co.......  1.2 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Lead, Pb.........  1.9E+2 lb/MMBtu or
                                                     1.8 lb/MWh.
                                 Manganese, Mn....  2.5 lb/TBtu or 3.0E-
                                                     2 lb/GWh.
                                 Nickel, Ni.......  6.5 lb/TBtu or 7.0E-
                                                     2 lb/GWh.
                                 Selenium, Se.....  2.2E+1 lb/TBtu or
                                                     3.0E-1 lb/GWh.
                              b. HCl..............  5.0E-4 lb/MMBtu or
                                                     5.0E-3 lb/MWh.
                              c. Hg...............  2.5 lb/TBtu or 3.0E-
                                                     2 lb/GWh.
4. Liquid oil-fired unit--    a. fPM..............  3.0E-2 lb/MMBtu or
 continental (excluding                              3.0E-1 lb/MWh.
 limited-use liquid oil-
 fired subcategory units).
                              OR..................  OR
                              Total HAP metals....  8.0E-4 lb/MMBtu or
                                                     8.0E-3 lb/MWh.
                              OR..................  OR
                              Individual HAP
                               metals:
                                 Antimony, Sb.....  1.3E+1 lb/TBtu or
                                                     2.0E-1 lb/GWh.
                                 Arsenic, As......  2.8 lb/TBtu or 3.0E-
                                                     2 lb/GWh.
                                 Beryllium, Be....  2.0E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
                                 Cadmium, Cd......  3.0E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
                                 Chromium, Cr.....  5.5 lb/TBtu or 6.0E-
                                                     2 lb/GWh.

[[Page 2683]]

 
                                 Cobalt, Co.......  2.1E+1 lb/TBtu or
                                                     3.0E-1 lb/GWh.
                                 Lead, Pb.........  8.1 lb/TBtu or 8.0E-
                                                     2 lb/GWh.
                                 Manganese, Mn....  2.2E+1 lb/TBtu or
                                                     3.0E-1 lb/GWh.
                                 Nickel, Ni.......  1.1E+2 lb/TBtu or
                                                     1.1 lb/GWh.
                                 Selenium, Se.....  3.3 lb/TBtu or 4.0E-
                                                     2 lb/GWh.
                                 Hg...............  2.0E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
                              b. HCl..............  2.0E-3 lb/MMBtu or
                                                     1.0E-2 lb/MWh.
                              c. HF...............  4.0E-4 lb/MMBtu or
                                                     4.0E-3 lb/MWh.
5. Liquid oil-fired unit--    a. fPM..............  3.0E-2 lb/MMBtu or
 non-continental (excluding                          3.0E-1 lb/MWh.
 limited-use liquid oil-
 fired subcategory units).
                              OR..................  OR
                              Total HAP metals....  6.0E-4 lb/MMBtu or
                                                     7.0E-3 lb/MWh.
                              OR..................  OR
                              Individual HAP
                               metals:
                                 Antimony, Sb.....  2.2 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Arsenic, As......  4.3 lb/TBtu or 8.0E-
                                                     2 lb/GWh.
                                 Beryllium, Be....  6.0E-1 lb/TBtu or
                                                     3.0E-3 lb/GWh.
                                 Cadmium, Cd......  3.0E-1 lb/TBtu or
                                                     3.0E-3 lb/GWh.
                                 Chromium, Cr.....  3.1E+1 lb/TBtu or
                                                     3.0E-1 lb/GWh.
                                 Cobalt, Co.......  1.1E+2 lb/TBtu or
                                                     1.4 lb/GWh.
                                 Lead, Pb.........  4.9 lb/TBtu or 8.0E-
                                                     2 lb/GWh.
                                 Manganese, Mn....  2.0E+1 lb/TBtu or
                                                     3.0E-1 lb/GWh.
                                 Nickel, Ni.......  4.7E+2 lb/TBtu or
                                                     4.1 lb/GWh.
                                 Selenium, Se.....  9.8 lb/TBtu or 2.0E-
                                                     1 lb/GWh.
                                 Hg...............  4.0E-2 lb/TBtu or
                                                     4.0E-4 lb/GWh.
                              b. HCl..............  2.0E-4 lb/MMBtu or
                                                     2.0E-3 lb/MWh.
                              c. HF...............  6.0E-5 lb/MMBtu or
                                                     5.0E-4 lb/MWh.
6. Solid oil-derived fuel-    a. fPM..............  8.0E-3 lb/MMBtu or
 fired unit.                                         9.0E-2 lb/MWh.
                              OR..................  OR
                              Total non-Hg HAP      4.0E-5 lb/MMBtu or
                               metals.               6.0E-1 lb/GWh.
                              OR..................  OR
                              Individual HAP
                               metals:
                                 Antimony, Sb.....  8.0E-1 lb/TBtu or
                                                     7.0E-3 lb/GWh.
                                 Arsenic, As......  3.0E-1 lb/TBtu or
                                                     5.0E-3 lb/GWh.
                                 Beryllium, Be....  6.0E-2 lb/TBtu or
                                                     5.0E-4 lb/GWh.
                                 Cadmium, Cd......  3.0E-1 lb/TBtu or
                                                     4.0E-3 lb/GWh.
                                 Chromium, Cr.....  8.0E-1 lb/TBtu or
                                                     2.0E-2 lb/GWh.
                                 Cobalt, Co.......  1.1 lb/TBtu or 2.0E-
                                                     2 lb/GWh.
                                 Lead, Pb.........  8.0E-1 lb/TBtu or
                                                     2.0E-2 lb/GWh.
                                 Manganese, Mn....  2.3 lb/TBtu or 4.0E-
                                                     2 lb/GWh.
                                 Nickel, Ni.......  9.0 lb/TBtu or 2.0E-
                                                     1 lb/GWh.
                                 Selenium, Se.....  1.2 lb/Tbtu 2.0E-2
                                                     lb/GWh.
                              b. HCl..............  5.0E-3 lb/MMBtu or
                                                     8.0E-2 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  3.0E-1 lb/MMBtu or
                                                     2.0 lb/MWh.
                              c. Hg...............  2.0E-1 lb/TBtu or
                                                     2.0E-3 lb/GWh.
------------------------------------------------------------------------
\1\ Units of emission limits:
lb/MMBtu = pounds pollutant per million British thermal units fuel
  input;
lb/TBtu = pounds pollutant per trillion British thermal units fuel
  input;
lb/MWh = pounds pollutant per megawatt-hour electric output (gross); and
lb/GWh = pounds pollutant per gigawatt-hour electric output (gross).
\2\ Alternate SO2 limit may be used if the EGU has some form of FGD
  system and SO2 CEMS installed.


     Table 3--Emission Limits for New or Reconstructed Affected EGUs
------------------------------------------------------------------------
         Subcategory                Pollutant        Emission limit \1\
------------------------------------------------------------------------
1. Coal-fired unit not low    a. fPM..............  9.0E-2 lb/MWh.
 rank virgin coal.
                              OR..................  OR
                              Total non-Hg HAP      6.0E-2 lb/GWh.
                               metals.
                              OR..................  OR
                              Individual HAP        ....................
                               metals:
                                 Antimony, Sb.....  8.0E-3 lb/GWh.
                                 Arsenic, As......  3.0E-3 lb/GWh.
                                 Beryllium, Be....  6.0E-4 lb/GWh.
                                 Cadmium, Cd......  4.0E-4 lb/GWh.
                                 Chromium, Cr.....  7.0E-3 lb/GWh.
                                 Cobalt, Co.......  2.0E-3 lb/GWh.
                                 Lead, Pb.........  2.0E-2 lb/GWh.
                                 Manganese, Mn....  4.0E-3 lb/GWh.
                                 Nickel, Ni.......  4.0E-2 lb/GWh.

[[Page 2684]]

 
                                 Selenium, Se.....  5.0E-2 lb/GWh.
                              b. HCl..............  1.0E-2 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  1.0 lb/MWh.
                              c. Hg...............  3.0E-3 lb/GWh.
2. Coal-fired units low rank  a. fPM..............  9.0E-2 lb/MWh.
 virgin coal.
                              OR..................  OR
                              Total non-Hg HAP      6.0E-2 lb/GWh.
                               metals.
                              OR..................  OR
                              Individual HAP        ....................
                               metals:
                                 Antimony, Sb.....  8.0E-3 lb/GWh.
                                 Arsenic, As......  3.0E-3 lb/GWh.
                                 Beryllium, Be....  6.0E-4 lb/GWh.
                                 Cadmium, Cd......  4.0E-4 lb/GWh.
                                 Chromium, Cr.....  7.0E-3 lb/GWh.
                                 Cobalt, Co.......  2.0E-3 lb/GWh.
                                 Lead, Pb.........  2.0E-2 lb/GWh.
                                 Manganese, Mn....  4.0E-3 lb/GWh.
                                 Nickel, Ni.......  4.0E-2 lb/GWh.
                                 Selenium, Se.....  5.0E-2 lb/GWh.
                              b. HCl..............  1.0E-2 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  1.0 lb/MWh.
                              c. Hg...............  4.0E-2 lb/GWh.
3. IGCC unit................  a. fPM..............  7.0E-2 lb/MWh.\3\
                              ....................  9.0E-2 lb/MWh.\4\
                              OR..................  OR
                              Total non-Hg HAP      4.0E-1 lb/GWh.
                               metals.
                              OR..................  OR
                              Individual HAP        ....................
                               metals:
                                 Antimony, Sb.....  2.0E-2 lb/GWh.
                                 Arsenic, As......  2.0E-2 lb/GWh.
                                 Beryllium, Be....  1.0E-3 lb/GWh.
                                 Cadmium, Cd......  2.0E-3 lb/GWh.
                                 Chromium, Cr.....  4.0E-2 lb/GWh.
                                 Cobalt, Co.......  4.0E-3 lb/GWh.
                                 Lead, Pb.........  9.0E-3 lb/GWh.
                                 Manganese, Mn....  2.0E-2 lb/GWh.
                                 Nickel, Ni.......  7.0E-2 lb/GWh.
                                 Selenium, Se.....  3.0E-1 lb/GWh.
                              b. HCl..............  2.0E-3 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  4.0E-1 lb/MWh.
                              c. Hg...............  3.0E-3 lb/GWh.
4. Liquid oil-fired unit--    a. fPM..............  3.0E-1 lb/MWh.
 continental (excluding
 limited-use liquid oil-
 fired subcategory units).
                              OR..................  OR
                              Total HAP metals....  2.0E-4 lb/MWh.
                              OR..................  OR
                              Individual HAP        ....................
                               metals:
                                 Antimony, Sb.....  1.0E-2 lb/GWh.
                                 Arsenic, As......  3.0E-3 lb/GWh.
                                 Beryllium, Be....  5.0E-4 lb/GWh.
                                 Cadmium, Cd......  2.0E-4 lb/GWh.
                                 Chromium, Cr.....  2.0E-2 lb/GWh.
                                 Cobalt, Co.......  3.0E-2 lb/GWh.
                                 Lead, Pb.........  8.0E-3 lb/GWh.
                                 Manganese, Mn....  2.0E-2 lb/GWh.
                                 Nickel, Ni.......  9.0E-2 lb/GWh.
                                 Selenium, Se.....  2.0E-2 lb/GWh.
                                 Hg...............  1.0E-4 lb/GWh.
                              b. HCl..............  4.0E-4 lb/MWh.
                              c. HF...............  4.0E-4 lb/MWh.
5. Liquid oil-fired unit--    a. fPM..............  2.0E-1 lb/MWh.
 non-continental (excluding
 limited-use liquid oil-
 fired subcategory units).
                              OR..................  OR
                              Total HAP metals....  7.0E-3 lb/MWh.
                              OR..................  OR
                              Individual HAP        ....................
                               metals:
                                 Antimony, Sb.....  8.0E-3 lb/GWh.
                                 Arsenic, As......  6.0E-2 lb/GWh.

[[Page 2685]]

 
                                 Beryllium, Be....  2.0E-3 lb/GWh.
                                 Cadmium, Cd......  2.0E-3 lb/GWh.
                                 Chromium, Cr.....  2.0E-2 lb/GWh.
                                 Cobalt, Co.......  3.0E-1 lb/GWh.
                                 Lead, Pb.........  3.0E-2 lb/GWh.
                                 Manganese, Mn....  1.0E-1 lb/GWh.
                                 Nickel, Ni.......  4.1 lb/GWh.
                                 Selenium, Se.....  2.0E-2 lb/GWh.
                                 Hg...............  4.0E-4 lb/GWh.
                              b. HCl..............  2.0E-3 lb/MWh.
                              c. HF...............  5.0E-4 lb/MWh.
6. Solid oil-derived fuel-    a. fPM..............  3.0E-2 lb/MWh.
 fired unit.
                              OR..................  OR
                              Total non-Hg HAP      6.0E-1 lb/GWh.
                               metals.
                              OR..................  OR
                              Individual HAP        ....................
                               metals:
                                 Antimony, Sb.....  8.0E-3 lb/GWh.
                                 Arsenic, As......  3.0E-3 lb/GWh.
                                 Beryllium, Be....  6.0E-4 lb/GWh.
                                 Cadmium, Cd......  7.0E-4 lb/GWh.
                                 Chromium, Cr.....  6.0E-3 lb/GWh.
                                 Cobalt, Co.......  2.0E-3 lb/GWh.
                                 Lead, Pb.........  2.0E-2 lb/GWh.
                                 Manganese, Mn....  7.0E-3 lb/GWh.
                                 Nickel, Ni.......  4.0E-2 lb/GWh.
                                 Selenium, Se.....  6.0E-3 lb/GWh.
                              b. HCl..............  4.0E-4 lb/MWh.
                              OR..................  OR
                              SO2 \2\.............  1.0 lb/MWh.
                              c. Hg...............  2.0E-3 lb/GWh.
------------------------------------------------------------------------
\1\ Units of emission limits:
lb/MWh = pounds pollutant per megawatt-hour electric output (gross); and
lb/GWh = pounds pollutant per gigawatt-hour electric output (gross).
\2\ Alternate SO2 limit may be used if the EGU has some form of FGD
  system (or, in the case of IGCC EGUs, some other acid gas removal
  system either upstream or downstream of the combined cycle block) and
  SO2 CEMS installed.
\3\ Duct burners on syngas; gross output.
\4\ Duct burners on natural gas; gross output.

C. What data collection activities were conducted to support this 
action?

    The EPA did not issue a new information collection request (ICR) to 
affected coal- and oil-fired EGUs to obtain the data used to support 
this action, but did use some information from the 2010 ICR which 
collected data during development of the MATS rule. The data and data 
sources used to conduct the residual risk assessment and technology 
review for the Coal- and Oil-Fired EGU source category are described 
below in section IV.D of this preamble.

D. What other relevant background information and data are available?

    The EPA used multiple sources of information to support this 
proposed action. A comprehensive list of facilities and EGUs that are 
subject to the MATS rule was compiled primarily using publicly 
available information reported to the EPA and information contained in 
the Agency's National Electric Energy Data System (NEEDS) database.\22\ 
Affected sources are required to use the 40 CFR part 75-based ECMPS 
\23\ for reporting emissions and related data either directly for EGUs 
that use Hg, HCl, HF, or SO2 CEMS or Hg sorbent traps for 
compliance purposes or indirectly as PDF files for EGUs that use 
performance test results, PM continuous parameter monitoring system 
(CPMS) data, or PM CEMS for compliance purposes. Directly submitted 
data are maintained in ECMPS; indirectly submitted data are maintained 
in WebFIRE.\24\ The NEEDS database contains generation unit information 
used in the Agency's power sector modeling. Other sources used to 
refine the facility list included an EPA technical support document 
that contained a list of potentially affected EGUs in U.S. 
territories,\25\ the U.S. Department of Energy's Energy Information 
Administration's (EIA's) list of existing generators that reported for 
2016 under Form EIA-860,\26\ and the list of coal-fired EGUs included 
in a June 2018 Electric Power Research Institute (EPRI) technical 
report that summarizes EPRI's evaluation of HAP emissions and their 
associated inhalation health risks from coal-fired power plants after 
implementation of MATS.\27\ As of early 2018, we estimate

[[Page 2686]]

that there are 713 existing coal- and oil-fired EGUs located at 323 
facilities that are subject to 40 CFR part 63, subpart UUUUU.
---------------------------------------------------------------------------

    \22\ See https://www.epa.gov/airmarkets/power-sector-modeling-platform-v515.
    \23\ See https://ampd.epa.gov/ampd/.
    \24\ See https://cfpub.epa.gov/webfire; https://www.epa.gov/electronic-reporting-air-emissions/webfire.
    \25\ U.S. EPA, October 2014. Technical Support Document for 
Calculating Carbon Pollution Goals for Existing Power Plants in 
Territories and Areas of Indian Country. Available at https://archive.epa.gov/epa/sites/production/files/2014-10/documents/20141028tsd-supplemental-proposal.pdf.
    \26\ See https://www.eia.gov/electricity/data/eia860/.
    \27\ EPRI. June 8, 2018. Hazardous Air Pollutants (HAPs) 
Emission Estimates and Inhalation Human Health Risk Assessment for 
U.S. Coal-Fired Electric Generating Units: 2017 Base Year Post-MATS 
Evaluation. Available at https://www.epri.com/#/pages/product/3002013577/?lang=en. Note: There is a companion June 22, 2018 EPRI 
technical report, Multi-Pathway Human Health Risk Assessment for 
Coal-Fired Power Plants, that describes EPRI's multi-pathway human 
health assessment of HAP emissions from five coal-fired electric 
facilities based on 2017 configurations (available at https://www.epri.com/#/pages/product/3002013523/?lang=en).
---------------------------------------------------------------------------

    In developing the RTR emissions dataset for the risk review, the 
primary sources used to estimate annual HAP emissions were the 
emissions data as reported to the ECMPS and WebFIRE databases by 
facilities with affected EGUs. Emissions release point parameters and 
locations for each EGU were primarily based on information reported to 
the ECMPS and generator-level specific information about existing 
generators and their associated environmental equipment that is 
collected by the EIA under Form EIA-860. The EPA sources of information 
that were used to supplement the ECMPS, WebFIRE, and EIA data include 
emissions information collected through the 2010 ICR during development 
of the MATS rule and the 2014 National Emissions Inventory (NEI) 
database. The NEI is a database that contains information about sources 
that emit criteria air pollutants, their precursors, and HAP. The 
database includes estimates of annual air pollutant emissions from 
point, nonpoint, and mobile sources in the 50 states, the District of 
Columbia, Puerto Rico, and the Virgin Islands. The EPA collects this 
information and releases an updated version of the NEI database every 3 
years. The NEI includes information necessary for conducting risk 
modeling, including annual HAP emissions estimates from individual 
emission points at facilities and the related emissions release 
parameters. The June 2018 EPRI technical report was also used as a 
source of supplemental information.
    In conducting the technology review, the EPA examined information 
submitted to the EPA's ECMPS as well as information that supports 
previous 40 CFR part 63, subpart UUUUU actions to identify technologies 
currently being used by affected EGUs and determine if there have been 
developments in practices, processes, or control technologies. In 
addition to the ECMPS data, we reviewed regulatory actions for similar 
combustion sources and conducted a review of literature published by 
industry organizations, technical journals, and government 
organizations.

V. RTR Analytical Procedures and Decision-Making

    In this section, we describe the analyses performed to support the 
proposed decisions for the RTR and other issues addressed in this 
proposal.

A. How do we consider risk in our decision-making?

    As discussed in section IV.A of this preamble and in the Benzene 
NESHAP, in evaluating and developing standards under CAA section 
112(f)(2), we apply a two-step approach to determine whether or not 
risks are acceptable and to determine if the standards provide an ample 
margin of safety to protect public health. As explained in the Benzene 
NESHAP, ``the first step judgment on acceptability cannot be reduced to 
any single factor'' and, thus, ``[t]he Administrator believes that the 
acceptability of risk under section 112 is best judged on the basis of 
a broad set of health risk measures and information.'' 54 FR 38046, 
September 14, 1989. Similarly, with regard to the ample margin of 
safety determination, ``the Agency again considers all of the health 
risk and other health information considered in the first step. Beyond 
that information, additional factors relating to the appropriate level 
of control will also be considered, including cost and economic impacts 
of controls, technological feasibility, uncertainties, and any other 
relevant factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors 
the EPA may consider in making determinations and how the EPA may weigh 
those factors for each source category. The EPA conducts a risk 
assessment that provides estimates of the MIR posed by the HAP 
emissions from each source in the source category, the hazard index 
(HI) for chronic exposures to HAP with the potential to cause noncancer 
health effects, and the hazard quotient (HQ) for acute exposures to HAP 
with the potential to cause noncancer health effects.\28\ The 
assessment also provides estimates of the distribution of cancer risk 
within the exposed populations, cancer incidence, and an evaluation of 
the potential for an adverse environmental effect. The scope of the 
EPA's risk analysis is consistent with the EPA's response to comments 
on our policy under the Benzene NESHAP where the EPA explained that:
---------------------------------------------------------------------------

    \28\ The MIR is defined as the cancer risk associated with a 
lifetime of exposure at the highest concentration of HAP where 
people are likely to live. The HQ is the ratio of the potential 
exposure to the HAP to the level at or below which no adverse 
chronic noncancer effects are expected; the HI is the sum of HQs for 
HAP that affect the same target organ or organ system.

[t]he policy chosen by the Administrator permits consideration of 
multiple measures of health risk. Not only can the MIR figure be 
considered, but also incidence, the presence of non-cancer health 
effects, and the uncertainties of the risk estimates. In this way, 
the effect on the most exposed individuals can be reviewed as well 
as the impact on the general public. These factors can then be 
weighed in each individual case. This approach complies with the 
Vinyl Chloride mandate that the Administrator ascertain an 
acceptable level of risk to the public by employing his expertise to 
assess available data. It also complies with the Congressional 
intent behind the CAA, which did not exclude the use of any 
particular measure of public health risk from the the EPA's 
consideration with respect to CAA section 112 regulations, and 
thereby implicitly permits consideration of any and all measures of 
health risk which the Administrator, in his judgment, believes are 
---------------------------------------------------------------------------
appropriate to determining what will `protect the public health'.

See 54 FR 38057, September 14, 1989. Thus, the level of the MIR is only 
one factor to be weighed in determining acceptability of risk. The 
Benzene NESHAP explained that ``an MIR of approximately one in 10 
thousand should ordinarily be the upper end of the range of 
acceptability. As risks increase above this benchmark, they become 
presumptively less acceptable under CAA section 112, and would be 
weighed with the other health risk measures and information in making 
an overall judgment on acceptability. Or, the Agency may find, in a 
particular case, that a risk that includes an MIR less than the 
presumptively acceptable level is unacceptable in the light of other 
health risk factors.'' Id. at 38045. Similarly, with regard to the 
ample margin of safety analysis, the EPA stated in the Benzene NESHAP 
that: ``EPA believes the relative weight of the many factors that can 
be considered in selecting an ample margin of safety can only be 
determined for each specific source category. This occurs mainly 
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at 
38061. We also consider the uncertainties associated with the various 
risk analyses, as discussed earlier in this preamble, in our 
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information 
to date in making residual risk determinations. At this time, we do not 
attempt to quantify the HAP risk that may be associated with emissions 
from other facilities that do not include the

[[Page 2687]]

source category under review, mobile source emissions, natural source 
emissions, persistent environmental pollution, or atmospheric 
transformation in the vicinity of the sources in the category.
    The EPA understands the potential importance of considering an 
individual's total exposure to HAP in addition to considering exposure 
to HAP emissions from the source category and facility. We recognize 
that such consideration may be particularly important when assessing 
noncancer risk, where pollutant-specific exposure health reference 
levels (e.g., reference concentrations (RfCs)) are based on the 
assumption that thresholds exist for adverse health effects. For 
example, the EPA recognizes that, although exposures attributable to 
emissions from a source category or facility alone may not indicate the 
potential for increased risk of adverse noncancer health effects in a 
population, the exposures resulting from emissions from the facility in 
combination with emissions from all of the other sources (e.g., other 
facilities) to which an individual is exposed may be sufficient to 
result in an increased risk of adverse noncancer health effects. In May 
2010, the Science Advisory Board (SAB) advised the EPA ``that RTR 
assessments will be most useful to decision makers and communities if 
results are presented in the broader context of aggregate and 
cumulative risks, including background concentrations and contributions 
from other sources in the area.'' \29\
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    \29\ Recommendations of the SAB RTR Panel are provided in their 
report, which is available at https://yosemite.epa.gov/sab/
sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-
007-unsigned.pdf.
---------------------------------------------------------------------------

    In response to the SAB recommendations, the EPA incorporates 
cumulative risk analyses into its RTR risk assessments, including those 
reflected in this proposal. The Agency (1) conducts facility-wide 
assessments, which include source category emission points, as well as 
other emission points within the facilities; (2) combines exposures 
from multiple sources in the same category that could affect the same 
individuals; and (3) for some persistent and bioaccumulative 
pollutants, analyzes the ingestion route of exposure. In addition, the 
RTR risk assessments consider aggregate cancer risk from all 
carcinogens and aggregated noncancer HQs for all noncarcinogens 
affecting the same target organ or target organ system.
    Although we are interested in placing source category and facility-
wide HAP risk in the context of total HAP risk from all sources 
combined in the vicinity of each source, we are concerned about the 
uncertainties of doing so. Estimates of total HAP risk from emission 
sources other than those that we have studied in depth during this RTR 
review would have significantly greater associated uncertainties than 
the source category or facility-wide estimates. Such aggregate or 
cumulative assessments would compound those uncertainties, making the 
assessments too unreliable.

B. How do we perform the technology review?

    Our technology review focuses on the identification and evaluation 
of developments in practices, processes, and control technologies that 
have occurred since the MACT standards were promulgated. Where we 
identify such developments, we analyze their technical feasibility, 
estimated costs, energy implications, and non-air environmental 
impacts. We also consider the emission reductions associated with 
applying each development. This analysis informs our decision of 
whether it is ``necessary'' to revise the emissions standards. In 
addition, we consider the appropriateness of applying controls to new 
sources versus retrofitting existing sources. For this exercise, we 
consider any of the following to be a ``development'':

     Any add-on control technology or other equipment that 
was not identified and considered during development of the original 
MACT standards;
     Any improvements in add-on control technology or other 
equipment (that were identified and considered during development of 
the original MACT standards) that could result in additional 
emissions reduction;
     Any work practice or operational procedure that was not 
identified or considered during development of the original MACT 
standards;
     Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during development of the original MACT 
standards; and
     Any significant changes in the cost (including cost 
effectiveness) of applying controls (including controls the EPA 
considered during the development of the original MACT standards).

    In addition to reviewing the practices, processes, and control 
technologies that were considered at the time we originally developed 
(or last updated) the NESHAP, we review a variety of data sources in 
our investigation of potential practices, processes, or controls to 
consider. See sections IV.C and IV. D of this preamble for information 
on the specific data sources that were reviewed as part of the 
technology review.

C. How do we estimate post-MACT risk posed by the source category?

    In this section, we provide a complete description of the types of 
analyses that we generally perform during the risk assessment process. 
In some cases, we do not perform a specific analysis because it is not 
relevant. For example, in the absence of emissions of HAP known to be 
persistent and bioaccumulative in the environment (PB-HAP), we would 
not perform a multipathway exposure assessment. Where we do not perform 
an analysis, we state that we do not and provide the reason. While we 
present all of our risk assessment methods, we only present risk 
assessment results for the analyses actually conducted (see section 
VI.B of this preamble).
    The EPA conducts a risk assessment that provides estimates of the 
MIR for cancer posed by the HAP emissions from each source in the 
source category, the HI for chronic exposures to HAP with the potential 
to cause noncancer health effects, and the HQ for acute exposures to 
HAP with the potential to cause noncancer health effects. The 
assessment also provides estimates of the distribution of cancer risk 
within the exposed populations, cancer incidence, and an evaluation of 
the potential for an adverse environmental effect. The seven sections 
that follow this paragraph describe how we estimated emissions and 
conducted the risk assessment. The docket for this rulemaking contains 
the following document which provides more information on the risk 
assessment inputs and models: Residual Risk Assessment for the Coal- 
and Oil-Fired EGU Source Category in Support of the 2019 Risk and 
Technology Review Proposed Rule (risk document). The methods used to 
assess risk (as described in the seven primary steps below) are 
consistent with those described by the EPA in the document reviewed by 
a panel of the EPA's SAB in 2009;\30\ and described in the SAB review 
report issued in 2010. They are also consistent with the key 
recommendations contained in that report.
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    \30\ U.S. EPA. June 2009. Risk and Technology Review (RTR) Risk 
Assessment Methodologies: For Review by the EPA's Science Advisory 
Board with Case Studies--MACT I Petroleum Refining Sources and 
Portland Cement Manufacturing (EPA-452/R-09-006). Available at 
https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.

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[[Page 2688]]

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    Data for existing EGUs were used to create the RTR emissions 
dataset for the risk review as described in section IV.D of this 
preamble. The RTR emissions dataset includes information for 608 
emission release points (i.e., stacks). Because in some cases multiple 
EGUs are routed to a single stack or a single EGU is routed to two 
stacks, the number of stacks is not the same as the number of EGUs. The 
MATS rule regulates emissions of HAP in four pollutant categories: Hg, 
non-Hg metals, acid gases, and organics. As described in section IV.B 
of this preamble, EGUs in six subcategories are subject to numeric 
emission limits for specific HAP, or surrogates for those HAP, in the 
three pollutant categories of Hg, non-Hg metals, and acid gases. EGUs 
are not required to meet numeric emission limits for organic HAP or to 
test and report organic HAP emissions. During the 2010 ICR effort of 
the original MATS rulemaking process, most of the organic HAP emissions 
data for EGUs were at or below the detection levels of the prescribed 
test methods, even when long duration test runs (i.e., approximately 8 
hours) were required. In developing the RTR emissions dataset, the EPA 
reviewed the available organic HAP test results from the 2010 ICR. For 
each organic HAP tested, if 40 percent or more of the available test 
data were above test method detection limits, emissions estimates for 
that HAP were included in the modeling file. Emissions of the following 
HAP in each of the four pollutant categories were estimated for each 
emission release point and included in the RTR emissions dataset:

     Hg: elemental gaseous Hg, gaseous divalent Hg, 
particulate divalent Hg;
     Non-Hg metals: antimony, arsenic, beryllium, cadmium, 
hexavalent chromium, trivalent chromium, cobalt, lead, manganese, 
nickel, selenium;
     Acid gases: HCl, HF; and
     Organics: formaldehyde, naphthalene, 2-
methylnaphthalene, phenanthrene, two dioxin congeners, three furan 
congeners, and seven polychlorinated biphenyls congeners.

    As explained in section IV.D of this preamble, emissions estimates 
for the RTR emissions dataset were based primarily on data submitted 
via the EPA's ECMPS by facilities with affected EGUs. Calendar year 
2017 data were used where available because all affected EGUs subject 
to numeric emission limits would be required to submit compliance data 
by then. Where calendar year 2017 data were not available, the most 
recent data available were used. CEMS emissions data for Hg, HCl, and 
SO2 reported to the EPA's ECMPS were available as 2017 
actual annual values (i.e., pounds per year or tpy).
    Some emissions data for Hg, non-Hg HAP metals, HCl, and fPM was 
submitted to the EPA's ECMPS, but maintained in the WebFIRE database. 
For those sources, the EPA extracted data associated with operations in 
summer 2017, when EGUs would be expected to operate more frequently 
given increased demand for electricity, and used those summertime 
emissions to estimate annual emissions of the pollutants of interest. 
Specifically, test averages from third quarter performance stack tests 
(i.e., conducted between July and September 2017) for any pollutant and 
30-day rolling average values as of June 30, 2017, for PM CEMS and PM 
CPMS were extracted and then converted from pounds of pollutant per 
million British thermal units or trillion British thermal units (lb/
MMBtu or lb/TBtu) or pounds of pollutant per megawatt-hour or gigawatt-
hour (lb/MWh or lb/GWh) to actual annual emissions using 2017 total 
heat input (MMBtu) or total gross load (MWh) values, as appropriate. 
When ECMPS-submitted data for HAP in the RTR emissions dataset were not 
available, actual annual emissions estimates were based on data from 
the 2014 NEI and the June 2018 EPRI technical report. Some annual 
emissions estimates were also generated using the ratio of non-Hg 
metals to fPM and acid gases to SO2 from the 2010 ICR in 
conjunction with more recent fPM or SO2 emissions data. 
Emissions data from the 2010 ICR were used to develop emission factors 
for the non-Hg metals and acid gases included in the RTR emissions 
dataset and to develop ratios based on each of those emission factors 
divided by average fPM or SO2 values, respectively. 
Emissions data for EGUs no longer operating were excluded in the 
calculation of emission factors or average fPM or SO2 
values. In addition, we included in each emission factor and ratio 
calculation only the 2010 ICR data for EGUs where data for both the 
non-Hg metal HAP (e.g., antimony) and fPM, or the acid gas HAP (e.g., 
HCl) and SO2, were available. Emission factors and emission 
factor-based ratios were developed for the various combinations of fuel 
types and emissions control device types. Actual annual HAP-specific 
emissions for each stack were then estimated by multiplying each 
emission factor-based ratio by the most recent fPM or SO2 
annual emissions value (e.g., 2017 ECMPS or WebFIRE data or 2014 NEI 
data). Because EGUs in the subcategory of limited-use liquid oil-fired 
EGUs are not subject to any numeric emission limits, actual annual HAP-
specific emissions were estimated using 2014 NEI data or emission 
factor-based ratios along with 2014 NEI data for PM and SO2. 
Development of the emission factors and emission factor-based ratios is 
explained in the memorandum, Emission Factor Development for RTR Risk 
Modeling Dataset for Coal- and Oil-fired EGUs, which is available in 
the docket for this action.
    The majority of the total (i.e., non-speciated) Hg actual annual 
emissions estimates were based on data maintained in the EPA's ECMPS 
for CEMS data or sorbent traps or in WebFIRE for performance stack 
tests along with 2017 total heat input or total gross load values, as 
appropriate. Where such data were not available, total Hg actual annual 
emissions were estimated using the 2014 NEI or the June 2018 EPRI 
technical report. For a small number of oil-fired EGUs, EPA-developed 
emission factors and emission factor-based ratios were used to estimate 
total Hg actual annual emissions. Hg emissions were modeled as three 
different species: elemental gaseous Hg, gaseous divalent Hg, and 
particulate divalent Hg. The EPA utilized Hg speciation factors--
percentages based on fuel type and installed emissions control 
equipment--that were updated versions of those that had been used in 
the development of the MATS rule.\31\ Total Hg emissions were then 
multiplied by the factors to develop the speciated Hg actual annual 
emissions estimates.
---------------------------------------------------------------------------

    \31\ See Attachment E of the Risk Modeling Dataset Memo for the 
list of Hg speciation factors utilized in compiling the RTR 
emissions dataset for the risk review, available in the docket for 
this action. See Appendix G of the Technical Support Document for 
the Proposed Rule Emissions Inventories (available in the rulemaking 
docket at EPA-HQ-OAR-2009-0234-19908) for Hg speciation factors used 
in the development of MATS.
---------------------------------------------------------------------------

    For the several EGUs that submitted individual non-Hg HAP metals 
data to the EPA, actual annual emissions were estimated using the stack 
test values maintained in WebFIRE and 2017 total heat input or total 
gross load values, as appropriate. The majority of the non-Hg HAP 
metals actual annual emissions estimates were based on emission factor-
based ratios for non-Hg HAP metals and fPM annual emissions values. 
Chromium emissions were modeled as hexavalent chromium (Cr(VI)) and 
trivalent chromium (Cr(III)). Actual annual emissions of Cr(VI) and 
Cr(III) were estimated by multiplying total chromium emissions by the

[[Page 2689]]

speciation factors for coal or oil, as appropriate.
    Actual annual emissions estimates for HCl for EGUs that submitted 
data to the EPA's ECMPS were based on those ECMPS CEMS data or WebFIRE 
performance stack test data and 2017 total heat input or total gross 
load values, as appropriate. Where acid gas HAP data were not available 
in the WebFIRE database, but SO2 data were available in the 
ECMPS for requirements other than those in the MATS rule (e.g., the 
acid rain rule), emission factor-based ratios for the acid gas HAP 
(i.e., HCl and HF) and SO2 annual emissions values were used 
to estimate actual annual HCl and HF emissions. In some instances, 
actual annual HCl and HF emissions were estimated based on emission 
factor-based ratios and 2014 NEI data for SO2. In a small 
number of other instances, actual annual HCl and HF emissions were 
estimated using the June 2018 EPRI technical report.
    As previously explained, EGUs are not required to meet numeric 
emission limits for organic HAP or to test and report organic HAP 
emissions. Actual annual emissions for the 16 organic HAP included in 
the RTR emissions dataset are based on EPA-developed representative 
detection level (RDL) equivalent emissions values (lb/MMBtu) based on 
fuel type. RDL equivalent emissions values for 15 of the organic HAP 
are based on the averages of better-performing unit method detection 
levels across many source categories. Because we did not have an RDL 
analysis across source categories for formaldehyde, detection levels 
from the 2010 ICR data were used to develop the RDL equivalent 
emissions value for formaldehyde. Actual annual emissions of the 16 
organic HAP were estimated by multiplying the RDL equivalent emissions 
values by 2017 total heat input. Development of the RDL equivalent 
emissions values is explained in the memorandum, Development of 
Representative Detection Levels of Certain Organic HAP Expressed as 
Pounds per Million British Thermal Units of Fuel Input for RTR Risk 
Modeling Dataset for Coal- and Oil-fired EGUs, which is available in 
the docket for this action.
    Stack parameter values and locations for each emissions release 
point included in the RTR emissions dataset were primarily based on 
information reported to the ECMPS and generator-level specific 
information about existing generators and their associated 
environmental equipment that is collected under Form EIA-860. 
Specifically, the ECMPS was the primary source for stack height, 
diameter, and latitude/longitude coordinates, and the EIA-860 database 
was the primary source for stack temperature, velocity, and flow rate. 
Other sources of information that were used to fill gaps in the site-
specific emissions release point data included the 2014 NEI, parameters 
from similar stacks at a specific facility, and default parameter 
values based on MACT source category 2014 NEI information.
    The RTR emissions dataset was refined as necessary following a 
quality assurance check of source locations, emissions release 
characteristics, and annual emissions estimates. Latitude and longitude 
coordinates were checked using Google Earth[supreg] to ensure that 
stack locations were correct. Stack parameters were checked to ensure 
that they were within acceptable quality assurance range check 
boundaries. Emissions estimates were reviewed for completeness and 
accuracy. Additional details on the data and methods used to develop 
``actual'' emissions estimates for the RTR emissions dataset are 
provided in the memorandum, Development of the RTR Risk Modeling 
Dataset for the Coal- and Oil-Fired EGU Source Category (Risk Modeling 
Dataset Memo), included as Appendix 1 of the risk document, which is 
available in the docket for this action.
    A comparison of the actual annual HAP emissions in 2017 to the 
annual HAP emissions prior to promulgation of the MATS rule shows a 96-
percent reduction in total HAP emissions from coal- and oil-fired EGUs. 
The actual emissions from coal- and oil-fired EGUs for 2017 and 
estimated emissions from 2010 are shown in Table 4. Estimates of pre-
MATS emissions of organic HAP were not available. As discussed 
previously in this section, the 2017 emissions of organic HAP are based 
on RDL equivalent emissions values; the actual 2017 emissions are 
likely lower than the estimate of 3 tpy.

                     Table 4--HAP Emissions From Coal- and Oil-Fired EGUs Pre- and Post-MATS
----------------------------------------------------------------------------------------------------------------
                                                                  2010 Emissions  2017 Emissions
                            Pollutant                               (tons) \32\       (tons)       Reduction (%)
----------------------------------------------------------------------------------------------------------------
Hg..............................................................              29               4              86
Acid Gases......................................................         125,708           4,831              96
Non-Hg Metals...................................................           1,170             221              81
Organic HAP.....................................................               *              <3               *
                                                                 -----------------------------------------------
    Total.......................................................         126,907           5,059              96
----------------------------------------------------------------------------------------------------------------
Note: The compliance date for the vast majority of affected EGUs was on or before April 16, 2016.
* Not available.

2. How did we estimate MACT-allowable emissions?
---------------------------------------------------------------------------

    \32\ Memorandum: Emissions Overview: Hazardous Air Pollutants in 
Support of the Final Mercury and Air Toxics Standard. EPA-454/R-11-
014. November 2011; Docket ID No. EPA-HQ-OAR-2009-0234-19914.
---------------------------------------------------------------------------

    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during a specified annual time 
period. These ``actual'' emission levels are often lower than the 
emission levels allowed under the requirements of the current MACT 
standards. The emissions allowed under the MACT standards are referred 
to as the ``MACT-allowable'' emissions. We discussed the consideration 
of both MACT-allowable and actual emissions in the final Coke Oven 
Batteries RTR (70 FR 19998-19999, April 15, 2005) and in the proposed 
and final Hazardous Organic NESHAP RTR (71 FR 34428, June 14, 2006, and 
71 FR 76609, December 21, 2006, respectively). In those actions, we 
noted that assessing the risk at the MACT-allowable level is inherently 
reasonable since that risk reflects the maximum level facilities could 
emit and still comply with national emission standards. We also 
explained that it is reasonable to consider actual emissions, where 
such data are available, in both steps of the risk analysis, in 
accordance with the Benzene NESHAP approach. (54 FR 38044, September 
14, 1989.)

[[Page 2690]]

    MACT-allowable annual emissions of Hg, non-Hg HAP metals, and acid 
gas HAP were estimated using numeric emission limits for existing 
sources in the MATS rule along with 2017 total heat input. For Hg, 
allowable annual emissions of total Hg were estimated by multiplying 
subcategory-specific Hg emission limits by 2017 total heat input. 
Allowable annual emissions of elemental gaseous Hg, gaseous divalent 
Hg, and particulate divalent Hg were estimated by multiplying annual 
emissions of total Hg by EPA-developed Hg speciation factors which are 
based on fuel type and emissions control device type.
    With regard to non-Hg HAP metals, performance stack test data in 
almost all instances was for fPM, a surrogate for non-Hg HAP metals, 
and, as such, allowable annual emissions were estimated using the MATS 
rule's fPM emission limits. Specifically, allowable annual emissions of 
the non-Hg HAP metals were estimated by multiplying subcategory-based 
fPM emission limits by 2017 total heat input and by the emission 
factor-based ratios for non-Hg HAP metals that were calculated by the 
EPA. Allowable annual emissions of chromium as Cr(VI) and Cr(III) were 
estimated by multiplying the total chromium allowable emissions 
estimates by the chromium speciation factors for coal or oil, as 
appropriate.
    For acid gas HAP, allowable annual emissions of HCl and HF from 
oil-fired EGUs were estimated by multiplying subcategory-specific HCl 
and HF emission limits by 2017 total heat input. With regard to acid 
gas HAP for coal-fired EGUs, some coal-fired sources submitted data for 
HCl, a surrogate for acid gas HAP, whereas other sources submitted data 
for SO2, a surrogate for acid gas HAP for certain coal-fired 
EGUs. Allowable annual emissions of HCl and HF from coal-fired EGUs 
were estimated two different ways--one based on the MATS rule's HCl 
emission limits and HF actual emissions adjusted using an HCl emissions 
ratio and the other based on the MATS rule's SO2 emission 
limits and emission factor-based ratios--and the more conservative 
estimate was used. In the first approach, allowable annual emissions of 
HCl were estimated by multiplying subcategory-specific HCl emission 
limits by 2017 total heat input, and allowable annual emissions of HF 
were estimated by multiplying actual annual emissions of HF by a ratio 
of HCl allowable annual emissions to HCl actual annual emissions. In 
the second approach, allowable annual emissions of HCl and HF were 
estimated by multiplying subcategory-based SO2 emission 
limits by 2017 total heat input and by the emission factor-based ratios 
for HCl and HF that were calculated by the EPA.
    Because there are no numeric emission limits for organic HAP, 
allowable annual emissions for the 16 organic HAP were assumed equal to 
the actual annual emissions estimates for the 16 organic HAP. The Risk 
Modeling Dataset Memo, available in the docket for this action, 
contains additional information on the development of estimated MACT-
allowable emissions.
3. How do we conduct dispersion modeling, determine inhalation 
exposures, and estimate individual and population inhalation risk?
    Both long-term and short-term inhalation exposure concentrations 
and health risk from the source category addressed in this proposal 
were estimated using the Human Exposure Model (HEM-3).\33\ The HEM-3 
performs three primary risk assessment activities: (1) Conducting 
dispersion modeling to estimate the concentrations of HAP in ambient 
air, (2) estimating long-term and short-term inhalation exposures to 
individuals residing within 50 kilometers (km) of the modeled sources, 
and (3) estimating individual and population-level inhalation risk 
using the exposure estimates and quantitative dose-response 
information.
---------------------------------------------------------------------------

    \33\ For more information about HEM-3, go to https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem.
---------------------------------------------------------------------------

a. Dispersion Modeling
    The air dispersion model AERMOD, used by the HEM-3 model, is one of 
the EPA's preferred models for assessing air pollutant concentrations 
from industrial facilities.\34\ To perform the dispersion modeling and 
to develop the preliminary risk estimates, HEM-3 draws on three data 
libraries. The first is a library of meteorological data, which is used 
for dispersion calculations. This library includes 1 year (2016) of 
hourly surface and upper air observations from 824 meteorological 
stations, selected to provide coverage of the United States and Puerto 
Rico. A second library of United States Census Bureau census block\35\ 
internal point locations and populations provides the basis of human 
exposure calculations (U.S. Census, 2010). In addition, for each census 
block, the census library includes the elevation and controlling hill 
height, which are also used in dispersion calculations. A third library 
of pollutant-specific dose-response values is used to estimate health 
risk. These are discussed below.
---------------------------------------------------------------------------

    \34\ U.S. EPA. Revision to the Guideline on Air Quality Models: 
Adoption of a Preferred General Purpose (Flat and Complex Terrain) 
Dispersion Model and Other Revisions (70 FR 68218, November 9, 
2005).
    \35\ A census block is the smallest geographic area for which 
census statistics are tabulated.
---------------------------------------------------------------------------

b. Risk From Chronic Exposure to HAP
    In developing the risk assessment for chronic exposures, we use the 
estimated annual average ambient air concentrations of each HAP emitted 
by each source in the source category. The HAP air concentrations at 
each nearby census block centroid located within 50 km of the facility 
are a surrogate for the chronic inhalation exposure concentration for 
all the people who reside in that census block. A distance of 50 km is 
consistent with both the analysis supporting the 1989 Benzene NESHAP 
(54 FR 38044, September 14, 1989) and the limitations of Gaussian 
dispersion models, including AERMOD.
    For each facility, we calculate the MIR as the cancer risk 
associated with a continuous lifetime (24 hours per day, 7 days per 
week, 52 weeks per year, 70 years) exposure to the maximum 
concentration at the centroid of each inhabited census block. We 
calculate individual cancer risk by multiplying the estimated lifetime 
exposure to the ambient concentration of each HAP (in micrograms per 
cubic meter ([mu]g/m\3\)) by its unit risk estimate (URE). The URE is 
an upper-bound estimate of an individual's incremental risk of 
contracting cancer over a lifetime of exposure to a concentration of 1 
microgram of the pollutant per cubic meter of air. For residual risk 
assessments, we generally use UREs from the EPA's Integrated Risk 
Information System (IRIS). For carcinogenic pollutants without IRIS 
values, we look to other reputable sources of cancer dose-response 
values, often using California EPA (CalEPA) UREs, where available. In 
cases where new, scientifically credible dose-response values have been 
developed in a manner consistent with EPA guidelines and have undergone 
a peer review process similar to that used by the EPA, we may use such 
dose-response values in place of, or in addition to, other values, if 
appropriate. The pollutant-specific dose-response values used to 
estimate health risk are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.To estimate individual lifetime cancer risks 
associated with exposure to HAP emissions from each facility in the 
source category, we sum the risks for

[[Page 2691]]

each of the carcinogenic HAP \36\ emitted by the modeled facility. We 
estimate cancer risk at every census block within 50 km of every 
facility in the source category. The MIR is the highest individual 
lifetime cancer risk estimated for any of those census blocks. In 
addition to calculating the MIR, we estimate the distribution of 
individual cancer risks for the source category by summing the number 
of individuals within 50 km of the sources whose estimated risk falls 
within a specified risk range. We also estimate annual cancer incidence 
by multiplying the estimated lifetime cancer risk at each census block 
by the number of people residing in that block, summing results for all 
of the census blocks, and then dividing this result by a 70-year 
lifetime.
---------------------------------------------------------------------------

    \36\ The EPA's 2005 Guidelines for Carcinogen Risk Assessment 
classifies carcinogens as: ``carcinogenic to humans,'' ``likely to 
be carcinogenic to humans,'' and ``suggestive evidence of 
carcinogenic potential.'' These classifications also coincide with 
the terms ``known carcinogen, probable carcinogen, and possible 
carcinogen,'' respectively, which are the terms advocated in the 
EPA's Guidelines for Carcinogen Risk Assessment, published in 1986 
(51 FR 33992, September 24, 1986). In August 2000, the document, 
Supplemental Guidance for Conducting Health Risk Assessment of 
Chemical Mixtures (EPA/630/R-00/002), was published as a supplement 
to the 1986 document. Copies of both documents can be obtained from 
https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944. Summing 
the risk of these individual compounds to obtain the cumulative 
cancer risk is an approach that was recommended by the EPA's SAB in 
their 2002 peer review of the EPA's National Air Toxics Assessment 
(NATA) titled NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at https://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess the risk of noncancer health effects from chronic 
exposure to HAP, we calculate either an HQ or a target organ-specific 
hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is 
emitted. Where more than one noncancer HAP is emitted, we sum the HQ 
for each of the HAP that affects a common target organ or target organ 
system to obtain a TOSHI. The HQ is the estimated exposure divided by 
the chronic noncancer dose-response value, which is a value selected 
from one of several sources. The preferred chronic noncancer dose-
response value is the EPA RfC, defined as ``an estimate (with 
uncertainty spanning perhaps an order of magnitude) of a continuous 
inhalation exposure to the human population (including sensitive 
subgroups) that is likely to be without an appreciable risk of 
deleterious effects during a lifetime'' (https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary). In cases where an RfC 
from the EPA's IRIS is not available or where the EPA determines that 
using a value other than the RfC is appropriate, the chronic noncancer 
dose-response value can be a value from the following prioritized 
sources, which define their dose-response values similarly to the EPA: 
(1) The Agency for Toxic Substances and Disease Registry (ATSDR) 
Minimum Risk Level (https://www.atsdr.cdc.gov/mrls/index.asp); (2) the 
CalEPA Chronic Reference Exposure Level (REL) (https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-health-risk-0); or (3), as noted above, a scientifically 
credible dose-response value that has been developed in a manner 
consistent with EPA guidelines and has undergone a peer review process 
similar to that used by the EPA. The pollutant-specific dose-response 
values used to estimate health risks are available at https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants.
c. Risk From Acute Exposure to HAP That May Cause Health Effects Other 
Than Cancer
    For each HAP for which appropriate acute inhalation dose-response 
values are available, the EPA also assesses the potential health risks 
due to acute exposure. For these assessments, the EPA makes 
conservative assumptions about emission rates, meteorology, and 
exposure location. We use the peak hourly emission rate,\37\ worst-case 
dispersion conditions, and, in accordance with our mandate under 
section 112 of the CAA, the point of highest off-site exposure to 
assess the potential risk to the maximally exposed individual.
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    \37\ In the absence of hourly emission data, we develop 
estimates of maximum hourly emission rates by multiplying the 
average actual annual emissions rates by a factor (either a 
category-specific factor or a default factor of 10) to account for 
variability. This is documented in Residual Risk Assessment for 
Coal- and Oil-Fired EGU Source Category in Support of the 2019 Risk 
and Technology Review Proposed Rule and in Appendix 5 of the report: 
Analysis of Data on Short-term Emission Rates Relative to Long-term 
Emission Rates. Both are available in the docket for this 
rulemaking.
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    To characterize the potential health risks associated with 
estimated acute inhalation exposures to a HAP, we generally use 
multiple acute dose-response values, including acute RELs, acute 
exposure guideline levels (AEGLs), and emergency response planning 
guidelines (ERPG) for 1-hour exposure durations, if available, to 
calculate acute HQs. The acute HQ is calculated by dividing the 
estimated acute exposure by the acute dose-response value. For each HAP 
for which acute dose-response values are available, the EPA calculates 
acute HQs.
    An acute REL is defined as ``the concentration level at or below 
which no adverse health effects are anticipated for a specified 
exposure duration.'' \38\ Acute RELs are based on the most sensitive, 
relevant, adverse health effect reported in the peer-reviewed medical 
and toxicological literature. They are designed to protect the most 
sensitive individuals, including children and the elderly, in the 
population through the inclusion of margins of safety. Because margins 
of safety are incorporated to address data gaps and uncertainties, 
exceeding the REL does not automatically indicate an adverse health 
impact. AEGLs represent threshold exposure limits for the general 
public and are applicable to emergency exposures ranging from 10 
minutes to 8 hours.\39\ They are guideline levels for ``once-in-a-
lifetime, short-term exposures to airborne concentrations of acutely 
toxic, high-priority chemicals.'' Id. at 21. The AEGL-1 is specifically 
defined as ``the airborne concentration (expressed as ppm (parts per 
million) or mg/m\3\ (milligrams per cubic meter)) of a substance above 
which it is predicted that the general population, including 
susceptible individuals, could experience notable discomfort, 
irritation, or certain asymptomatic nonsensory effects. However, the 
effects are not disabling and are transient and reversible upon 
cessation of exposure.'' The document also notes that ``Airborne 
concentrations below AEGL-1 represent exposure levels that can produce 
mild and progressively increasing but transient and nondisabling odor, 
taste, and sensory irritation or certain asymptomatic, nonsensory 
effects.'' Id. AEGL-2 are defined as ``the airborne

[[Page 2692]]

concentration (expressed as parts per million or milligrams per cubic 
meter) of a substance above which it is predicted that the general 
population, including susceptible individuals, could experience 
irreversible or other serious, long-lasting adverse health effects or 
an impaired ability to escape.'' Id.
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    \38\ CalEPA issues acute RELs as part of its Air Toxics Hot 
Spots Program, and the 1-hour and 8-hour values are documented in 
Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The 
Determination of Acute Reference Exposure Levels for Airborne 
Toxicants, which is available at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary.
    \39\ National Academy of Sciences, 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2. Available at https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf. Note that the 
National Advisory Committee for Acute Exposure Guideline Levels for 
Hazardous Substances ended in October 2011, but the AEGL program 
continues to operate at the EPA and works with the National 
Academies to publish final AEGLs, (https://www.epa.gov/aegl).
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    ERPGs are ``developed for emergency planning and are intended as 
health-based guideline concentrations for single exposures to 
chemicals.'' \40\ Id. at 1. The ERPG-1 is defined as ``the maximum 
airborne concentration below which it is believed that nearly all 
individuals could be exposed for up to 1 hour without experiencing 
other than mild transient adverse health effects or without perceiving 
a clearly defined, objectionable odor.'' Id. at 2. Similarly, the ERPG-
2 is defined as ``the maximum airborne concentration below which it is 
believed that nearly all individuals could be exposed for up to one 
hour without experiencing or developing irreversible or other serious 
health effects or symptoms which could impair an individual's ability 
to take protective action.'' Id. at 1.
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    \40\ ERPGS Procedures and Responsibilities. March 2014. American 
Industrial Hygiene Association. Available at https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf.
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    An acute REL for 1-hour exposure durations is typically lower than 
its corresponding AEGL-1 and ERPG-1. Even though their definitions are 
slightly different, AEGL-1s are often the same as the corresponding 
ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from 
our acute inhalation screening risk assessment typically result when we 
use the acute REL for a HAP. In cases where the maximum acute HQ 
exceeds 1, we also report the HQ based on the next highest acute dose-
response value (usually the AEGL-1 and/or the ERPG-1).
    For the Coal- and Oil-Fired EGU source category, facility-level 
acute factors (i.e., multipliers) developed by the EPA were used to 
estimate acute emissions and the potential health risks due to acute 
exposure. First, 2017 total heat input (MMBtu) and boiler maximum rated 
heat input (MMBtu/hr) data were used to calculate an acute factor for 
EGUs where both values were available. Next, facility-level acute 
factors were calculated using a heat input-weighted average based on 
2017 heat input for each EGU located within a facility fenceline. The 
facility-level acute factor was used for each stack at the facility. 
For units at facilities that did not have a facility-level factor 
(e.g., 2017 total heat input and boiler maximum rated heat input were 
not available), a default facility-level value of 6 was used. The 
default facility-level value of 6 was developed by taking the average 
of the calculated facility-level factors. If the calculated facility-
level acute factor was greater than 10 (e.g., in cases where the EGU 
had a low 2017 heat input relative to the maximum rated heat input), 
the RTR program default acute emission adjustment factor of 10 was 
used. The default emission adjustment factor of 10 reflects a Texas 
study of short-term emissions variability, which showed that most peak 
emission events in a heavily-industrialized four-county area (Harris, 
Galveston, Chambers, and Brazoria Counties, Texas) were less than twice 
the annual average hourly emissions rate. The highest peak emissions 
event was 74 times the annual average hourly emissions rate and the 
99th percentile ratio of peak hourly emissions rate to the annual 
average hourly emissions rate was 9.\41\ Considering this analysis, to 
account for more than 99 percent of the peak hourly emissions, a 
conservative screening multiplication factor of 10 is applied to the 
average annual hourly emissions rate in the EPA's acute exposure 
screening assessments as the default approach. In this analysis, we 
inadvertently used allowable emissions (rather than actual emissions, 
which is our standard practice) in conjunction with the facility level 
acute factors in our screening assessment of acute risk. Because the 
results showed acute risks below a level of concern even with acute 
emissions being overstated due to the use of allowable emissions, we 
did not correct the analysis and consider it to clearly support the 
conclusion that acute risks are below a level of concern as shown in 
Table 5 of this preamble. A further discussion of the development of 
facility-level acute factors and emissions used to estimate acute 
exposure for the risk modeling can be found in the Risk Modeling 
Dataset Memo, available in the docket for this rulemaking.
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    \41\ Allen, et al., 2004. Variable Industrial VOC Emissions and 
their impact on ozone formation in the Houston Galveston Area. Texas 
Environmental Research Consortium. Available at https://www.researchgate.net/publication/237593060_Variable_Industrial_VOC_Emissions_and_their_Impact_on_Ozone_Formation_in_the_Houston_Galveston_Area.
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    In our acute inhalation screening risk assessment, acute impacts 
are deemed negligible for HAP for which acute HQs are less than or 
equal to 1 (even under the conservative assumptions of the screening 
assessment), and no further analysis is performed for these HAP. In 
cases where an acute HQ from the screening step is greater than 1, we 
consider additional site-specific data to develop a more refined 
estimate of the potential for acute exposures of concern.
4. How do we conduct the multipathway exposure and risk screening 
assessment?
    The EPA conducts a tiered screening assessment examining the 
potential for significant human health risks due to exposures via 
routes other than inhalation (i.e., ingestion). We first determine 
whether any sources in the source category emit any PB-HAP, as 
identified in the EPA's Air Toxics Risk Assessment Library (See Volume 
1, Appendix D, at https://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library.
    For the Coal- and Oil-Fired EGU source category, we identified PB-
HAP emissions of lead compounds, arsenic compounds, Hg compounds, 
cadmium compounds, polycyclic organic matter (POM), and dioxins, so we 
proceeded to the next step of the evaluation. In this step, we 
determine whether the facility-specific emission rates of the emitted 
PB-HAP are large enough to create the potential for significant human 
health risk through ingestion exposure under reasonable worst-case 
conditions. To facilitate this step, we use previously developed 
screening threshold emission rates for several PB-HAP that are based on 
a hypothetical upper-end screening exposure scenario developed for use 
in conjunction with the EPA's Total Risk Integrated Methodology.Fate, 
Transport, and Ecological Exposure (TRIM.FaTE) model. The PB-HAP with 
screening threshold emission rates are arsenic compounds, cadmium 
compounds, chlorinated dibenzodioxins and furans, Hg compounds, and 
POM. Based on EPA estimates of toxicity and bioaccumulation potential, 
the pollutants above represent a conservative list for inclusion in 
multipathway risk assessments for RTR rules. (See Volume 1, Appendix D 
at https://www.epa.gov/sites/production/files/201308/documents/volume_1_reflibrary.pdf). In this assessment, we compare the facility-
specific emission rates of these PB-HAP to the screening threshold 
emission rates for each PB-HAP to assess the potential for significant 
human health risks via the ingestion pathway. We call this application 
of the TRIM.FaTE model the Tier 1 screening assessment. The ratio of a 
facility's actual emission rate to the Tier 1 screening threshold 
emission rate is a ``screening value.''

[[Page 2693]]

    We derive the Tier 1 screening threshold emission rates for these 
PB-HAP (other than lead compounds) to correspond to a maximum excess 
lifetime cancer risk of 1-in-1 million (i.e., for arsenic compounds, 
polychlorinated dibenzodioxins and furans and POM) or, for HAP that 
cause noncancer health effects (i.e., cadmium compounds and Hg 
compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP 
or combination of carcinogenic PB-HAP in the Tier 1 screening 
assessment exceeds the Tier 1 screening threshold emission rate for any 
facility (i.e., the screening value is greater than 1), we conduct a 
second screening assessment, which we call the Tier 2 screening 
assessment.
    In the Tier 2 screening assessment, the location of each facility 
that exceeds a Tier 1 screening threshold emission rate is used to 
refine the assumptions associated with the Tier 1 fisher and farmer 
exposure scenarios at that facility. A key assumption in the Tier 1 
screening assessment is that a lake and/or farm is located near the 
facility. As part of the Tier 2 screening assessment, we use a United 
States Geological Survey (USGS) database to identify actual waterbodies 
within 50 km of each facility. We also examine the differences between 
local meteorology near the facility and the meteorology used in the 
Tier 1 screening assessment. We then adjust the previously-developed 
Tier 1 screening threshold emission rates for each PB-HAP for each 
facility based on an understanding of how exposure concentrations 
estimated for the screening scenario change with the use of local 
meteorology and USGS waterbody data. If the PB-HAP emission rates for a 
facility exceed the Tier 2 screening threshold emission rates and data 
are available, we may conduct a Tier 3 screening assessment. If PB-HAP 
emission rates do not exceed a Tier 2 screening value of 1, we consider 
those PB-HAP emissions to pose risks below a level of concern.
    There are several analyses that can be included in a Tier 3 
screening assessment, depending upon the extent of refinement 
warranted, including validating that the lakes are fishable, 
considering plume-rise to estimate emissions lost above the mixing 
layer, and considering hourly effects of meteorology and plume rise on 
chemical fate and transport. If the Tier 3 screening assessment 
indicates that risks above levels of concern cannot be ruled out, the 
EPA may further refine the screening assessment through a site-specific 
assessment.
    In evaluating the potential multipathway risk from emissions of 
lead compounds, rather than developing a screening threshold emission 
rate, we compare maximum estimated chronic inhalation exposure 
concentrations to the level of the current NAAQS for lead.\42\ Values 
below the level of the primary (health-based) lead NAAQS are considered 
to have a low potential for multipathway risk.
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    \42\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring, among other 
things, that the standard provide an ``ample margin of safety to 
protect public health''). However, the primary lead NAAQS is a 
reasonable measure of determining risk acceptability (i.e., the 
first step of the Benzene NESHAP analysis) since it is designed to 
protect the most susceptible group in the human population--
children, including children living near major lead emitting 
sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, 
applying the level of the primary lead NAAQS at the risk 
acceptability step is conservative, since that primary lead NAAQS 
reflects an adequate margin of safety.
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    For further information on the multipathway assessment approach, 
see the risk document, which is available in the docket for this 
action.
5. How do we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect, Environmental HAP, and Ecological 
Benchmarks
    The EPA conducts a screening assessment to examine the potential 
for an adverse environmental effect as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
    The EPA focuses on eight HAP, which are referred to as 
``environmental HAP,'' in its screening assessment: six PB-HAP and two 
acid gases. The PB-HAP included in the screening assessment are arsenic 
compounds, cadmium compounds, dioxins/furans, POM, Hg (both inorganic 
Hg and methyl Hg), and lead compounds. The acid gases included in the 
screening assessment are HCl and HF.
    HAP that persist and bioaccumulate are of particular environmental 
concern because they accumulate in the soil, sediment, and water. The 
acid gases, HCl and HF, are included due to their well-documented 
potential to cause direct damage to terrestrial plants. In the 
environmental risk screening assessment, we evaluate the following four 
exposure media: terrestrial soils, surface water bodies (includes 
water-column and benthic sediments), fish consumed by wildlife, and 
air. Within these four exposure media, we evaluate nine ecological 
assessment endpoints, which are defined by the ecological entity and 
its attributes. For PB-HAP (other than lead), both community-level and 
population-level endpoints are included. For acid gases, the ecological 
assessment evaluated is terrestrial plant communities.
    An ecological benchmark represents a concentration of HAP that has 
been linked to a particular environmental effect level. For each 
environmental HAP, we identified the available ecological benchmarks 
for each assessment endpoint. We identified, where possible, ecological 
benchmarks at the following effect levels: probable effect levels, 
lowest-observed-adverse-effect level, and no-observed-adverse-effect 
level. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we use all of the available 
effect levels to help us to determine whether ecological risks exist 
and, if so, whether the risks could be considered significant and 
widespread.
    For further information on how the environmental risk screening 
assessment was conducted, including a discussion of the risk metrics 
used, how the environmental HAP were identified, and how the ecological 
benchmarks were selected, see Appendix 9 of the risk document, which is 
available in the docket for this action.
b. Environmental Risk Screening Methodology
    For the environmental risk screening assessment, the EPA first 
determined whether any facilities in the Coal- and Oil-Fired EGU source 
category emitted any of the environmental HAP. For the Coal- and Oil-
Fired EGU source category, we identified emissions of lead compounds, 
arsenic compounds, Hg compounds, cadmium compounds, POM, dioxins, HCl, 
and HF. Because one or more of the environmental HAP evaluated are 
emitted by at least one facility in the source category, we proceeded 
to the second step of the evaluation.
c. PB-HAP Methodology
    The environmental screening assessment includes six PB-HAP, arsenic 
compounds, cadmium compounds, dioxins/furans, POM, Hg (both inorganic 
Hg and methyl Hg), and lead compounds. With the exception of

[[Page 2694]]

lead, the environmental risk screening assessment for PB-HAP consists 
of three tiers. The first tier of the environmental risk screening 
assessment uses the same health-protective conceptual model that is 
used for the Tier 1 human health screening assessment. TRIM.FaTE model 
simulations were used to back-calculate Tier 1 screening threshold 
emission rates. The screening threshold emission rates represent the 
emission rate in tpy that results in media concentrations at the 
facility that equal the relevant ecological benchmark. To assess 
emissions from each facility in the category, the reported emission 
rate for each PB-HAP was compared to the Tier 1 screening threshold 
emission rate for that PB-HAP for each assessment endpoint and effect 
level. If emissions from a facility do not exceed the Tier 1 screening 
threshold emission rate, the facility ``passes'' the screening 
assessment, and, therefore, is not evaluated further under the 
screening approach. If emissions from a facility exceed the Tier 1 
screening threshold emission rate, we evaluate the facility further in 
Tier 2.
    In Tier 2 of the environmental screening assessment, the screening 
threshold emission rates are adjusted to account for local meteorology 
and the actual location of lakes in the vicinity of facilities that did 
not pass the Tier 1 screening assessment. For soils, we evaluate the 
average soil concentration for all soil parcels within a 7.5-km radius 
for each facility and PB-HAP. For the water, sediment, and fish tissue 
concentrations, the highest value for each facility for each pollutant 
is used. If emission concentrations from a facility do not exceed the 
Tier 2 screening threshold emission rate, the facility ``passes'' the 
screening assessment and typically is not evaluated further. If 
emissions from a facility exceed the Tier 2 screening threshold 
emission rate, we evaluate the facility further in Tier 3.
    As in the multipathway human health risk assessment, in Tier 3 of 
the environmental screening assessment, we examine the suitability of 
the lakes around the facilities to support life and remove those that 
are not suitable (e.g., lakes that have been filled in or are 
industrial ponds), adjust emissions for plume-rise, and conduct hour-
by-hour time-series assessments. If these Tier 3 adjustments to the 
screening threshold emission rates still indicate the potential for an 
adverse environmental effect (i.e., facility emission rate exceeds the 
screening threshold emission rate), we may elect to conduct a more 
refined assessment using more site-specific information. If, after 
additional refinement, the facility emission rate still exceeds the 
screening threshold emission rate, the facility may have the potential 
to cause an adverse environmental effect.
    To evaluate the potential for an adverse environmental effect from 
lead, we compared the average modeled air concentrations (from HEM-3) 
of lead around each facility in the source category to the level of the 
secondary NAAQS for lead. The secondary lead NAAQS is a reasonable 
means of evaluating environmental risk because it is set to provide 
substantial protection against adverse welfare effects which can 
include ``effects on soils, water, crops, vegetation, man-made 
materials, animals, wildlife, weather, visibility and climate, damage 
to and deterioration of property, and hazards to transportation, as 
well as effects on economic values and on personal comfort and well-
being.''
d. Acid Gas Environmental Risk Methodology
    The environmental screening assessment for acid gases evaluates the 
potential phytotoxicity and reduced productivity of plants due to 
chronic exposure to HF and HCl. The environmental risk screening 
methodology for acid gases is a single-tier screening assessment that 
compares modeled ambient air concentrations (from AERMOD) to the 
ecological benchmarks for each acid gas. To identify a potential 
adverse environmental effect (as defined in section 112(a)(7) of the 
CAA) from emissions of HF and HCl, we evaluate the following metrics: 
The size of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas, in acres and km\2\; the 
percentage of the modeled area around each facility that exceeds the 
ecological benchmark for each acid gas; and the area-weighted average 
screening value around each facility (calculated by dividing the area-
weighted average concentration over the 50-km modeling domain by the 
ecological benchmark for each acid gas). For further information on the 
environmental screening assessment approach, see Appendix 9 of the risk 
document, which is available in the docket for this action.
6. How do we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine 
the risks from the entire ``facility,'' where the facility includes all 
HAP-emitting operations within a contiguous area and under common 
control. In other words, we examine the HAP emissions not only from the 
source category emission points of interest, but also emissions of HAP 
from all other emission sources at the facility for which we have data. 
For this source category, we conducted the facility-wide assessment 
using a dataset compiled from the 2014 NEI. The source category records 
of that NEI dataset were removed, evaluated, and updated as described 
in section IV.D of this preamble: What other relevant background 
information and data are available? Once a quality assured source 
category dataset was available, it was placed back with the remaining 
records from the NEI for that facility. The facility-wide file was then 
used to analyze risks due to the inhalation of HAP that are emitted 
``facility-wide'' for the populations residing within 50 km of each 
facility, consistent with the methods used for the source category 
analysis described above. For these facility-wide risk analyses, the 
modeled source category risks were compared to the facility-wide risks 
to determine the portion of the facility-wide risks that could be 
attributed to the source category addressed in this proposal. We also 
specifically examined the facility that was associated with the highest 
estimate of risk and determined the percentage of that risk 
attributable to the source category of interest. The risk document, 
available through the docket for this action, provides the methodology 
and results of the facility-wide analyses, including all facility-wide 
risks and the percentage of source category contribution to facility-
wide risks.
7. How do we consider uncertainties in risk assessment?
    Uncertainty and the potential for bias are inherent in all risk 
assessments, including those performed for this proposal. Although 
uncertainty exists, we believe that our approach, which used 
conservative tools and assumptions, ensures that our decisions are 
health and environmentally protective. A brief discussion of the 
uncertainties in the RTR emissions dataset, dispersion modeling, 
inhalation exposure estimates, and dose-response relationships follows 
below. Also included are those uncertainties specific to our acute 
screening assessments, multipathway screening assessments, and our 
environmental risk screening assessments. A more thorough discussion of 
these uncertainties is included in the risk document, which is 
available in the docket for this action. If a multipathway site-
specific assessment was performed for this source category, a full 
discussion of the uncertainties associated with that assessment can be

[[Page 2695]]

found in Appendix 11 of that document, Site-Specific Human Health 
Multipathway Residual Risk Assessment Report.
a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions dataset involved 
quality assurance/quality control processes, the accuracy of emissions 
values will vary depending on the source of the data, the degree to 
which data are incomplete or missing, the degree to which assumptions 
made to complete the datasets are accurate, errors in emission 
estimates, and other factors. The emission estimates considered in this 
analysis generally are annual totals for certain years, and they do not 
reflect short-term fluctuations during the course of a year or 
variations from year to year. The estimates of peak hourly emission 
rates for the acute effects screening assessment were based on an 
emission adjustment factor applied to the average annual hourly 
emission rates, which are intended to account for emission fluctuations 
due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration 
estimates associated with any model, including the EPA's recommended 
regulatory dispersion model, AERMOD. In using a model to estimate 
ambient pollutant concentrations, the user chooses certain options to 
apply. For RTR assessments, we select some model options that have the 
potential to overestimate ambient air concentrations (e.g., not 
including plume depletion or pollutant transformation). We select other 
model options that have the potential to underestimate ambient impacts 
(e.g., not including building downwash). Other options that we select 
have the potential to either under- or overestimate ambient levels 
(e.g., meteorology and receptor locations). On balance, considering the 
directional nature of the uncertainties commonly present in ambient 
concentrations estimated by dispersion models, the approach we apply in 
the RTR assessments should yield unbiased estimates of ambient HAP 
concentrations. We also note that the selection of meteorology dataset 
location could have an impact on the risk estimates. As we continue to 
update and expand our library of meteorological station data used in 
our risk assessments, we expect to reduce this variability.
c. Uncertainties in Inhalation Exposure Assessment
    Although every effort is made to identify all of the relevant 
facilities and emission points, as well as to develop accurate 
estimates of the annual emission rates for all relevant HAP, the 
uncertainties in our emission inventory likely dominate the 
uncertainties in the exposure assessment. Some uncertainties in our 
exposure assessment include human mobility, using the centroid of each 
census block, assuming lifetime exposure, and assuming only outdoor 
exposures. For most of these factors, there is neither an underestimate 
nor overestimate when looking at the maximum individual risk or the 
incidence, but the shape of the distribution of risks may be affected. 
With respect to outdoor exposures, actual exposures may not be as high 
if people spend time indoors, especially for very reactive pollutants 
or larger particles. For all factors, we reduce uncertainty when 
possible. For example, with respect to census-block centroids, we 
analyze large blocks using aerial imagery and adjust locations of the 
block centroids to better represent the population in the blocks. We 
also add additional receptor locations where the population of a block 
is not well represented by a single location.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and noncancer effects from both chronic and acute 
exposures. Some uncertainties are generally expressed quantitatively, 
and others are generally expressed in qualitative terms. We note, as a 
preface to this discussion, a point on dose-response uncertainty that 
is stated in the EPA's 2005 Guidelines for Carcinogen Risk Assessment; 
namely, that ``the primary goal of EPA actions is protection of human 
health; accordingly, as an Agency policy, risk assessment procedures, 
including default options that are used in the absence of scientific 
data to the contrary, should be health protective'' (the EPA's 2005 
Guidelines for Carcinogen Risk Assessment, page 1-7). This is the 
approach followed here as summarized in the next paragraphs.
    Cancer UREs used in our risk assessments are those that have been 
developed to generally provide an upper bound estimate of risk.\43\ 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit). In some circumstances, the true risk could be as low 
as zero; however, in other circumstances the risk could be greater.\44\ 
Chronic noncancer RfC and reference dose (RfD) values represent chronic 
exposure levels that are intended to be health-protective levels. To 
derive dose-response values that are intended to be ``without 
appreciable risk,'' the methodology relies upon an uncertainty factor 
(UF) approach,\45\ which considers uncertainty, variability, and gaps 
in the available data. The UFs are applied to derive dose-response 
values that are intended to protect against appreciable risk of 
deleterious effects.
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    \43\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \44\ An exception to this is the URE for benzene, which is 
considered to cover a range of values, each end of which is 
considered to be equally plausible, and which is based on maximum 
likelihood estimates.
    \45\ See A Review of the Reference Dose and Reference 
Concentration Processes, U.S. EPA, December 2002, and Methods for 
Derivation of Inhalation Reference Concentrations and Application of 
Inhalation Dosimetry, U.S. EPA, 1994.
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    Many of the UFs used to account for variability and uncertainty in 
the development of acute dose-response values are quite similar to 
those developed for chronic durations. Additional adjustments are often 
applied to account for uncertainty in extrapolation from observations 
at one exposure duration (e.g., 4 hours) to derive an acute dose-
response value at another exposure duration (e.g., 1 hour). Not all 
acute dose-response values are developed for the same purpose, and care 
must be taken when interpreting the results of an acute assessment of 
human health effects relative to the dose-response value or values 
being exceeded. Where relevant to the estimated exposures, the lack of 
acute dose-response values at different levels of severity should be 
factored into the risk characterization as potential uncertainties.
    Uncertainty also exists in the selection of ecological benchmarks 
for the environmental risk screening assessment. We established a 
hierarchy of preferred benchmark sources to allow selection of 
benchmarks for each environmental HAP at each ecological assessment 
endpoint. We searched for benchmarks for three effect levels (i.e., no-
effects level, threshold-effect level, and probable effect level), but 
not all combinations of ecological assessment/environmental HAP had 
benchmarks for

[[Page 2696]]

all three effect levels. Where multiple effect levels were available 
for a particular HAP and assessment endpoint, we used all of the 
available effect levels to help us determine whether risk exists and 
whether the risk could be considered significant and widespread.
    Although we make every effort to identify appropriate human health 
effect dose-response values for all pollutants emitted by the sources 
in this risk assessment, some HAP emitted by this source category are 
lacking dose-response assessments. Accordingly, these pollutants cannot 
be included in the quantitative risk assessment, which could result in 
quantitative estimates understating HAP risk. To help to alleviate this 
potential underestimate, where we conclude similarity with a HAP for 
which a dose-response value is available, we use that value as a 
surrogate for the assessment of the HAP for which no value is 
available. To the extent use of surrogates indicates appreciable risk, 
we may identify a need to increase priority for an IRIS assessment for 
that substance. We additionally note that, generally speaking, HAP of 
greatest concern due to environmental exposures and hazard are those 
for which dose-response assessments have been performed, reducing the 
likelihood of understating risk. Further, HAP not included in the 
quantitative assessment are assessed qualitatively and considered in 
the risk characterization that informs the risk management decisions, 
including consideration of HAP reductions achieved by various control 
options.
    For a group of compounds that are unspeciated (e.g., glycol 
ethers), we conservatively use the most protective dose-response value 
of an individual compound in that group to estimate risk. Similarly, 
for an individual compound in a group (e.g., ethylene glycol diethyl 
ether) that does not have a specified dose-response value, we also 
apply the most protective dose-response value from the other compounds 
in the group to estimate risk.
e. Uncertainties in Acute Inhalation Screening Assessments
    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that the EPA 
conducts as part of the risk review under section 112 of the CAA. The 
accuracy of an acute inhalation exposure assessment depends on the 
simultaneous occurrence of independent factors that may vary greatly, 
such as hourly emissions rates, meteorology, and the presence of humans 
at the location of the maximum concentration. In the acute screening 
assessment that we conduct under the RTR program, we assume that peak 
emissions from the source category and worst-case meteorological 
conditions co-occur, thus, resulting in maximum ambient concentrations. 
These two events are unlikely to occur at the same time, making these 
assumptions conservative. We then include the additional assumption 
that a person is located at this point during this same time period. 
For this source category, these assumptions would tend to be worst-case 
actual exposures, as it is unlikely that a person would be located at 
the point of maximum exposure during the time when peak emissions and 
worst-case meteorological conditions occur simultaneously.
f. Uncertainties in the Multipathway and Environmental Risk Screening 
Assessments
    For each source category, we generally rely on site-specific levels 
of PB-HAP or environmental HAP emissions to determine whether a refined 
assessment of the impacts from multipathway exposures is necessary or 
whether it is necessary to perform an environmental screening 
assessment. This determination is based on the results of a three-
tiered screening assessment that relies on the outputs from models--
TRIM.FaTE and AERMOD--that estimate environmental pollutant 
concentrations and human exposures for five PB-HAP (dioxins, POM, Hg, 
cadmium, and arsenic) and two acid gases (HF and HCl). For lead, we use 
AERMOD to determine ambient air concentrations, which are then compared 
to the secondary NAAQS standard for lead. Two important types of 
uncertainty associated with the use of these models in RTR risk 
assessments and inherent to any assessment that relies on environmental 
modeling are model uncertainty and input uncertainty.\46\
---------------------------------------------------------------------------

    \46\ In the context of this discussion, the term ``uncertainty'' 
as it pertains to exposure and risk encompasses both variability in 
the range of expected inputs and screening results due to existing 
spatial, temporal, and other factors, as well as uncertainty in 
being able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the model adequately represents 
the actual processes (e.g., movement and accumulation) that might occur 
in the environment. For example, does the model adequately describe the 
movement of a pollutant through the soil? This type of uncertainty is 
difficult to quantify. However, based on feedback received from 
previous EPA SAB reviews and other reviews, we are confident that the 
models used in the screening assessments are appropriate and state-of-
the-art for the multipathway and environmental screening risk 
assessments conducted in support of RTR.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the multipathway and environmental screening assessments, we 
configured the models to avoid underestimating exposure and risk. This 
was accomplished by selecting upper-end values from nationally 
representative datasets for the more influential parameters in the 
environmental model, including selection and spatial configuration of 
the area of interest, lake location and size, meteorology, surface 
water, soil characteristics, and structure of the aquatic food web. We 
also assume an ingestion exposure scenario and values for human 
exposure factors that represent reasonable maximum exposures.
    In Tier 2 of the multipathway and environmental screening 
assessments, we refine the model inputs to account for meteorological 
patterns in the vicinity of the facility versus using upper-end 
national values, and we identify the actual location of lakes near the 
facility rather than the default lake location that we apply in Tier 1. 
By refining the screening approach in Tier 2 to account for local 
geographical and meteorological data, we decrease the likelihood that 
concentrations in environmental media are overestimated, thereby 
increasing the usefulness of the screening assessment. In Tier 3 of the 
screening assessments, we refine the model inputs again to account for 
hour-by-hour plume rise and the height of the mixing layer. We can also 
use those hour-by-hour meteorological data in a TRIM.FaTE run using the 
screening configuration corresponding to the lake location. These 
refinements produce a more accurate estimate of chemical concentrations 
in the media of interest, thereby reducing the uncertainty with those 
estimates. The assumptions and the associated uncertainties regarding 
the selected ingestion exposure scenario are the same for all three 
tiers.
    For the environmental screening assessment for acid gases, we 
employ a single-tiered approach. We use the modeled air concentrations 
and compare those with ecological benchmarks.
    For all tiers of the multipathway and environmental screening 
assessments, our approach to addressing model input uncertainty is 
generally cautious. We

[[Page 2697]]

choose model inputs from the upper end of the range of possible values 
for the influential parameters used in the models, and we assume that 
the exposed individual exhibits ingestion behavior that would lead to a 
high total exposure. This approach reduces the likelihood of not 
identifying high risks for adverse impacts.
    Despite the uncertainties, when individual pollutants or facilities 
do not exceed screening threshold emission rates (i.e., screen out), we 
are confident that the potential for adverse multipathway impacts on 
human health is very low. On the other hand, when individual pollutants 
or facilities do exceed screening threshold emission rates, it does not 
mean that impacts are significant, only that we cannot rule out that 
possibility and that a refined assessment for the site might be 
necessary to obtain a more accurate risk characterization for the 
source category.
    The EPA evaluates the following HAP in the multipathway and/or 
environmental risk screening assessments, where applicable: Arsenic, 
cadmium, dioxins/furans, lead, Hg (both inorganic and methyl Hg), POM, 
HCl, and HF. These HAP represent pollutants that can cause adverse 
impacts either through direct exposure to HAP in the air or through 
exposure to HAP that are deposited from the air onto soils and surface 
waters and then through the environment into the food web. These HAP 
represent those HAP for which we can conduct a meaningful multipathway 
or environmental screening risk assessment. For other HAP not included 
in our screening assessments, the model has not been parameterized such 
that it can be used for that purpose. In some cases, depending on the 
HAP, we may not have appropriate multipathway models that allow us to 
predict the concentration of that pollutant. The EPA acknowledges that 
other HAP beyond these that we are evaluating may have the potential to 
cause adverse effects and, therefore, the EPA may evaluate other 
relevant HAP in the future, as modeling science and resources allow.

VI. RTR Analytical Results and Proposed Decisions

A. What are the results of the risk assessment and analyses?

1. Inhalation Risk Assessment Results
    Table 5 of this preamble provides a summary of the results of the 
inhalation risk assessment for the source category. More detailed 
information on the risk assessment can be found in the risk document, 
available in the docket for this action.

                                           Table 5--Coal- and Oil-Fired EGU Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                     Maximum individual cancer    Population at increased     Annual cancer incidence    Maximum chronic noncancer    Maximum screening
                      risk (in 1 million) \2\     risk of cancer >=1-in-1        (cases per year)                TOSHI \3\           acute noncancer HQ
                   ----------------------------           million          --------------------------------------------------------          \4\
                          Based on . . .       ----------------------------       Based on . . .              Based on . . .       ---------------------
     Number of     ----------------------------       Based on . . .       --------------------------------------------------------
  facilities \1\                               ----------------------------
                       Actual       Allowable      Actual       Allowable      Actual       Allowable      Actual       Allowable      Based on actual
                      emissions     emissions     emissions     emissions     emissions     emissions     emissions     emissions      emissions level
                      level \2\       level       level \2\       level       level \2\       level         level         level
--------------------------------------------------------------------------------------------------------------------------------------------------------
322...............            9            10       193,000       636,000          0.04           0.1           0.2           0.4   HQREL = 0.09
                                                                                                                                     (arsenic).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of facilities evaluated in the risk analysis.
\2\ Maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\3\ Maximum TOSHI. The target organ systems with the highest TOSHI for the source category are neurological and reproductive.
\4\ The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of HQ values. HQ values
  shown use the lowest available acute threshold value, which in most cases is the REL. When an HQ exceeds 1, we also show the HQ using the next lowest
  available acute dose-response value.

    As shown in Table 5 of this preamble, based on actual emissions, 
the estimated cancer MIR is 9-in-1 million, and nickel emissions from 
oil-fired EGUs are the major contributor to the risk. The total 
estimated cancer incidence from this source category is 0.04 excess 
cancer cases per year, or one excess case in every 25 years. 
Approximately 193,000 people are estimated to have cancer risks at or 
above 1-in-1 million from HAP emitted from the facilities in this 
source category. The estimated maximum chronic noncancer TOSHI for the 
source category is 0.2 (respiratory), which is driven by emissions of 
nickel and cobalt from oil-fired EGUs. No one is exposed to TOSHI 
levels above 1.
    Based on allowable emissions, the estimated cancer MIR is 10-in-1 
million, and, as before, nickel emissions from oil-fired EGUs are the 
major contributor to the risk. The total estimated cancer incidence 
from this source category is 0.1 excess cancer cases per year, or one 
excess case in every 10 years. Approximately 636,000 people are 
estimated to have cancer risks at or above 1-in-1 million from HAP 
emitted from the facilities in this source category. The estimated 
maximum chronic noncancer TOSHI for the source category is 0.4 
(respiratory), driven by emissions of nickel and cobalt from oil-fired 
EGUs. No one is exposed to TOSHI levels above 1.
2. Acute Risk Results
    Table 5 of this preamble provides the worst-case acute HQ (based on 
the REL) of 0.09, driven by actual emissions of arsenic. There are no 
facilities that have acute HQs (based on the REL or any other reference 
values) greater than 1. For more detailed acute risk results, refer to 
the risk document.
3. Multipathway Risk Screening Results
    Potential multipathway health risks under a fisher and gardener 
scenario were identified using a three-tier screening assessment of the 
PB-HAP emitted by facilities in this source category, and a site-
specific assessment of Hg using TRIM.FaTE for one location. Of the 322 
MATS facilities modeled, 307 facilities have reported emissions of 
carcinogenic PB-HAP (arsenic, dioxins, and POM) that exceed a Tier 1 
cancer screening value of 1, and 235 facilities have reported emissions 
of non-carcinogenic PB-HAP (lead, Hg, and cadmium) that exceed a Tier 1 
noncancer screening value of 1. For facilities that exceeded a Tier 1 
multipathway screening value of 1, we used additional facility site-
specific information to perform an assessment through Tiers 2 and 3, as 
necessary, to determine the maximum chronic cancer and noncancer 
impacts for the source category. For cancer, the highest Tier 2 
screening value was 200. This screening value was reduced to 50 after 
the plume rise stage of Tier 3. Because this screening value was much 
lower than 100-in-1 million, and because we expect the actual risk to 
be lower than the screening value (site-specific assessments typically 
lower estimates by an order of magnitude), we did not perform further 
assessment for cancer. For noncancer, the highest Tier 2 screening 
value was 30 (for Hg), with

[[Page 2698]]

four facilities having screening values greater than 20. These 
screening values were reduced to 9 or lower after the plume rise stage 
of Tier 3.
    An exceedance of a screening value in any of the tiers cannot be 
equated with a risk value or an HQ (or HI). Rather, it represents a 
high-end estimate of what the risk or hazard may be. For example, a 
screening value of 2 for a non-carcinogen can be interpreted to mean 
that we are confident that the HQ would be lower than 2. Similarly, a 
screening value of 30 for a carcinogen means that we are confident that 
the risk is lower than 30-in-1 million. Our confidence comes from the 
conservative, or health-protective, assumptions encompassed in the 
screening tiers: We choose inputs from the upper end of the range of 
possible values for the influential parameters used in the screening 
tiers; and we assume that the exposed individual exhibits ingestion 
behavior that would lead to a high total exposure.
    In evaluating the potential for multipathway effects from emissions 
of lead, we compared modeled maximum annual lead concentrations to the 
secondary NAAQS for lead (0.15 [micro]g/m\3\). The modeled maximum 
annual lead concentration is below the NAAQS for lead, indicating a low 
potential for multipathway impacts of concern due to lead.
4. Multipathway Site-Specific Assessment Results
    Because the final stage of Tier 3 (time-series) was unlikely to 
reduce the highest Hg screening values to 1, we conducted a site-
specific multipathway assessment of Hg emissions for this source 
category. Analysis of the facilities with the highest Tier 2 and Tier 3 
screening values helped identify the location for the site-specific 
assessment and the facilities to model with TRIM.FaTE. We also 
considered the effect multiple facilities within the source category 
could have on common lakes in the modeling domain. The selection of the 
facilities for the site-specific assessment also included evaluating 
the number and location of lakes impacted, watershed boundaries, and 
land-use features around the target lakes, (i.e., elevation changes, 
topography, rivers).
    The three facilities selected are located near Underwood, North 
Dakota. All three facilities had Tier 2 screening values greater than 
or equal to 20. Two of the facilities are near each other (16 km 
apart). The third facility is more distant, about 20 to 30 km from the 
other facilities, but it was included in the analysis because it is 
within the 50-km modeling domain of the other facilities and because it 
had an elevated Tier 2 screening value. We expect that the exposure 
scenarios we assessed for these facilities are among the highest, if 
not the highest, that might be encountered for other facilities in this 
source category. The refined site-specific multipathway assessment, as 
in the screening assessments, includes some hypothetical elements, 
namely the hypothetical human receptor (e.g., the fisher scenario which 
did not screen out in the screening assessments). It is important to 
note that although the multipathway assessment has been conducted, no 
data exist to verify the existence of the hypothetical human receptor. 
The refined multipathway assessment produced an HQ of 0.06 for Hg for 
the three facilities assessed. This risk assessment likely represents 
the maximum hazard for Hg through fish consumption for the source 
category and, with an HQ less than 1, is below the level of concern for 
exposure to emissions from these sources.
5. Environmental Risk Screening Results
    As described in section V.C of this preamble, we conducted an 
environmental risk screening assessment for the Coal- and Oil-Fired EGU 
source category for the following pollutants: Arsenic, cadmium, 
dioxins/furans, HCl, HF, lead, Hg (methyl Hg and mercuric chloride), 
and POMs.
    In the Tier 1 screening analysis for PB-HAP (other than lead, which 
was evaluated differently), POM emissions had no exceedances of any of 
the ecological benchmarks evaluated. Arsenic and dioxins/furans 
emissions had Tier 1 exceedances for surface soil benchmarks. Cadmium 
and methyl Hg emissions had Tier 1 exceedances for surface soil and 
fish benchmarks. Divalent Hg emissions had Tier 1 exceedances for 
sediment and surface soil benchmarks.
    A Tier 2 screening analysis was performed for arsenic, cadmium, 
dioxins/furans, divalent Hg, and methyl Hg emissions. In the Tier 2 
screening analysis, arsenic, cadmium, and dioxins/furans emissions had 
no exceedances of any of the ecological benchmarks evaluated. Divalent 
Hg emissions from two facilities exceeded the Tier 2 screen for a 
sediment threshold level benchmark by a maximum screening value of 2 at 
lake #35731. Methyl Hg emissions from the same two facilities exceeded 
the Tier 2 screen for a fish (avian/piscivores) no-observed-adverse-
effect-level (NOAEL) (merganser) benchmark by a maximum screening value 
of 2 at the same lake (lake #35731). A Tier 3 screening assessment was 
performed to verify the existence of lake #35731. Lake #35731 was found 
to be located on-site and is a man-made industrial pond, and, 
therefore, was removed from the assessment.
    Methyl Hg emissions from two facilities exceeded the Tier 2 screen 
for a surface soil NOAEL for avian ground insectivores (woodcock) 
benchmark by a maximum screening value of 2. Other surface soil 
benchmarks for methyl Hg, such as the NOAEL for mammalian insectivores 
and the threshold level for the invertebrate community, were not 
exceeded. Given the low Tier 2 maximum screening value of 2 for methyl 
Hg, and the fact that only the most protective benchmark was exceeded, 
a Tier 3 environmental risk screen was not conducted for methyl Hg.
    For lead, we did not estimate any exceedances of the secondary lead 
NAAQS. For HCl and HF, the average modeled concentration around each 
facility (i.e., the average concentration of all off-site data points 
in the modeling domain) did not exceed any ecological benchmark. In 
addition, each individual modeled concentration of HCl and HF (i.e., 
each off-site data point in the modeling domain) was below the 
ecological benchmarks for all facilities.
    Based on the results of the environmental risk screening analysis, 
we do not expect an adverse environmental effect as a result of HAP 
emissions from this source category.
6. Facility-Wide Risk Results
    Based on facility-wide emissions, the estimated cancer MIR is 9-in-
1 million, and nickel emissions from oil-fired EGUs are the major 
contributor to the risk. The total estimated cancer incidence from this 
source category is 0.04 excess cancer cases per year, or one excess 
case in every 25 years. Approximately 203,000 people are estimated to 
have cancer risks at or above 1-in-1 million from HAP emitted from the 
facilities in this source category. The estimated maximum chronic 
noncancer TOSHI for the source category is 0.2 (respiratory), driven by 
emissions of nickel and cobalt from oil-fired EGUs. No one is exposed 
to TOSHI levels above 1. These results are very similar to those based 
on actual emissions from the source category because there is not 
significant collocation of other sources with EGUs.
7. What demographic groups might benefit from this regulation?
    To examine the potential for any environmental justice issues that 
might be associated with the source category, we performed a 
demographic analysis,

[[Page 2699]]

which is an assessment of risk to individual demographic groups of the 
populations living within 5 km and within 50 km of the facilities. In 
the analysis, we evaluated the distribution of HAP-related cancer and 
noncancer risk from the Coal- and Oil-Fired EGU source category across 
different demographic groups within the populations living near 
facilities.\47\
---------------------------------------------------------------------------

    \47\ Demographic groups included in the analysis are: White, 
African American, Native American, other races and multiracial, 
Hispanic or Latino, children 17 years of age and under, adults 18 to 
64 years of age, adults 65 years of age and over, adults without a 
high school diploma, people living below the poverty level, people 
living two times the poverty level, and linguistically isolated 
people.
---------------------------------------------------------------------------

    The results of the demographic analysis are summarized in Table 6 
below. These results, for various demographic groups, are based on the 
estimated risk from actual emissions levels for the population living 
within 50 km of the facilities.

               Table 6--Coal- and Oil-Fired EGU Source Category Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                                    Population
                                                                                    with cancer
                                                                                   risk greater     Population
                                                                                   than or equal      with HI
                                                                                     to 1-in-1    greater than 1
                                                                                      million
----------------------------------------------------------------------------------------------------------------
                                                                      Nationwide          Source Category
----------------------------------------------------------------------------------------------------------------
Total Population................................................     317,746,049         193,000               0
----------------------------------------------------------------------------------------------------------------
                                                                           White and Minority by Percent
----------------------------------------------------------------------------------------------------------------
White...........................................................              62               1               0
Minority........................................................              38            * 99               0
----------------------------------------------------------------------------------------------------------------
                                                                                Minority by Percent
----------------------------------------------------------------------------------------------------------------
African American................................................              12               0               0
Native American.................................................             0.8               0               0
Hispanic or Latino (includes white and nonwhite)................              18            * 99               0
Other and Multiracial...........................................               7               0               0
----------------------------------------------------------------------------------------------------------------
                                                                                 Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.............................................              14              40               0
Above Poverty Level.............................................              86              60               0
----------------------------------------------------------------------------------------------------------------
                                                                               Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma.......................              14              25               0
Over 25 and with a High School Diploma..........................              86              75               0
----------------------------------------------------------------------------------------------------------------
                                                                        Linguistically Isolated by Percent
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.........................................               6            * 67               0
----------------------------------------------------------------------------------------------------------------
* Note: All the people with a cancer risk greater than or equal to 1 in 1 million reside in Puerto Rico.

    The results of the Coal- and Oil-Fired EGU source category 
demographic analysis indicate that emissions from the source category 
expose approximately 193,000 people to a cancer risk at or above 1-in-1 
million and no people to a chronic noncancer TOSHI greater than 1. 
There are only 4 facilities in the source category with cancer risk at 
or above 1-in-1 million, and all of them are located in Puerto Rico. 
Consequently, all of the percentages of the at-risk population in each 
demographic group associated with the Puerto Rican population are much 
higher than their respective nationwide percentages, and those not 
associated with Puerto Rico are much lower than their respective 
nationwide percentages.
    The methodology and the results of the demographic analysis are 
presented in a technical report, Risk and Technology Review--Analysis 
of Demographic Factors for Populations Living Near Coal- and Oil-Fired 
EGUs, available in the docket for this action.

B. What are our proposed decisions regarding risk acceptability, ample 
margin of safety, and adverse environmental effect?

1. Risk Acceptability
    As noted in section V.A of this preamble, the EPA sets standards 
under CAA section 112(f)(2) using ``a two-step standard-setting 
approach, with an analytical first step to determine an `acceptable 
risk' that considers all health information, including risk estimation 
uncertainty, and includes a presumptive limit on MIR of approximately 
1-in-10 thousand.'' (54 FR 38045, September 14, 1989). In this 
proposal, the EPA estimated risks based on actual and allowable 
emissions from coal- and oil-fired EGU sources, and we considered these 
in determining acceptability.
    The estimated inhalation cancer risk to the individual most exposed 
to actual emissions from the source category is 9-in-1 million. The 
estimated incidence of cancer due to inhalation exposures is 0.04 
excess cancer cases per year, or one excess case every 25 years. 
Approximately 190,000 people face an increased cancer risk at or above 
1-in-1 million due to inhalation exposure to HAP emissions from this 
source category. The estimated maximum chronic noncancer TOSHI from

[[Page 2700]]

inhalation exposure for this source category is 0.2. Based on allowable 
emissions, the estimated inhalation cancer risk to the individual most 
exposed is 10-in-1 million, and the estimated incidence of cancer due 
to inhalation exposures is 0.1 excess cancer cases per year, or one 
excess case every 10 years. Approximately 640,000 people face an 
increased cancer risk at or above 1-in-1 million due to inhalation 
exposure to allowable HAP emissions from this source category. The 
maximum chronic noncancer TOSHI from inhalation exposure is 0.4 based 
on allowable emissions. The screening assessment of worst-case acute 
inhalation impacts indicates that no facilities have actual emissions 
that result in an acute HQ greater than 1 for any pollutant, with an 
estimated worst-case maximum acute HQ of 0.09 for arsenic based on the 
1-hour REL.
    Potential multipathway human health risks were estimated using a 
three-tier screening assessment of the PB-HAP emitted by facilities in 
this source category. The only pollutants with elevated screening 
values are arsenic (cancer) and Hg (noncancer). The highest Tier 3 
cancer screening value is 50, mostly driven by arsenic. The highest 
Tier 3 noncancer screening value is 9, for Hg. We performed a site-
specific multipathway assessment which indicates that the highest Hg HQ 
expected from any facility in the source category is much less than 1. 
In evaluating the potential for multipathway effects from emissions of 
lead from the source category, we compared modeled maximum annual lead 
concentrations to the primary NAAQS for lead (0.15 [mu]g/m\3\). Results 
of this analysis estimate that the NAAQS for lead would not be exceeded 
at any off-site locations.
    In determining whether risks are acceptable for this source 
category, the EPA considered all available health information and risk 
estimation uncertainty as described above. The risk results indicate 
that both the actual and allowable inhalation cancer risks to the 
individual most exposed are well below 100-in-1 million, which is the 
presumptive limit of acceptability. Also, the highest chronic noncancer 
TOSHI, and the highest acute noncancer HQ, are well below 1, indicating 
low likelihood of adverse noncancer effects from inhalation exposures. 
There are also low risks associated with ingestion, with the highest 
cancer risk being less than 50-in-1 million based on a conservative 
screening assessment, and the highest noncancer hazard being less than 
1 based on a site-specific multipathway assessment.
    Considering all of the health risk information and factors 
discussed above, including the uncertainties discussed in section V of 
this preamble, the EPA proposes that the risks are acceptable for this 
source category.
2. Ample Margin of Safety Analysis
    As directed by CAA section 112(f)(2), we conducted an analysis to 
determine if the current emissions standards provide an ample margin of 
safety to protect public health. Under the ample margin of safety 
analysis, the EPA considers all health factors evaluated in the risk 
assessment and evaluates the cost and feasibility of available control 
technologies and other measures (including the controls, measures, and 
costs reviewed under the technology review) that could be applied to 
this source category to further reduce the risks (or potential risks) 
due to emissions of HAP identified in our risk assessment. In this 
analysis, we considered the results of the technology review, risk 
assessment, and other aspects of our MACT rule review to determine 
whether there are any cost-effective controls or other measures that 
would reduce emissions further to provide an ample margin of safety 
with respect to the risks associated with these emissions.
    Our risk analysis indicated the risks from the source category are 
low for both cancer and noncancer health effects, and, therefore, any 
risk reductions from further available control options would result in 
minimal health benefits. Moreover, as noted in our discussion of the 
technology review in section VI.C of this preamble, no additional 
measures were identified for reducing HAP emissions from affected 
sources in the Coal- and Oil-Fired EGU source category. Thus, we are 
proposing that the current MATS requirements provide an ample margin of 
safety to protect public health.
3. Adverse Environmental Effects
    Based on the results of our environmental risk screening 
assessment, we conclude that there is not an adverse environmental 
effect from the Coal- and Oil-Fired EGU source category. We are 
proposing that it is not necessary to set a more stringent standard to 
prevent, taking into consideration costs, energy, safety, and other 
relevant factors, an adverse environmental effect.
C. What are the results and proposed decisions based on our technology 
review?
    As described in section V.B of this preamble, our technology review 
focused on identifying developments in practices, processes, and 
control technologies that have occurred since the MATS rule was 
promulgated. Control technologies typically used to minimize emissions 
of pollutants that have numeric emission limits under the MATS rule 
include electrostatic precipitators and fabric filters for control of 
PM and non-Hg HAP metals; wet scrubbers and dry scrubbers for control 
of acid gases (SO2, HCl, and HF); and activated carbon 
injection for control of Hg. The existing air pollution control 
technologies that are currently in use are well-established and provide 
the capture efficiencies necessary for compliance with the MATS 
emission limits. Based on the effectiveness and proven reliability of 
these control technologies, and the relatively short period of time 
since the promulgation of the MATS rule, no developments in practices, 
processes, or control technologies, nor any new technologies or 
practices were identified for the control of non-Hg HAP metals, acid 
gas HAP, or Hg. Organic HAP, including emissions of dioxins and furans, 
are regulated by a work practice standard that requires periodic burner 
tune-ups to ensure good combustion. This work practice continues to be 
a practical approach to ensuring that combustion equipment is 
maintained and optimized to run to reduce emissions of organic HAP, and 
continues to be expected to be more effective than establishing a 
numeric standard that cannot reliably be measured or monitored. Based 
on the effectiveness and proven reliability of the work practice 
standard, and the relatively short amount of time since the 
promulgation of the MATS rule, no developments in work practices nor 
any new work practices or operational procedures have been identified 
for this source category regarding the additional control of organic 
HAP. Consequently, we propose that no revisions to the MATS rule are 
necessary pursuant to CAA section 112(d)(6). Additional details of our 
technology review can be found in the memorandum, Technology Review for 
the Coal- and Oil-fired EGU Source Category, which is available in the 
docket for this action.

VII. Consideration of Separate Subcategory and Acid Gas Standard for 
Existing EGUs That Fire Eastern Bituminous Coal Refuse

    The EPA is considering establishing a subcategory for emissions of 
acid gas HAP from existing EGUs firing eastern bituminous coal refuse. 
In this action, the EPA is soliciting comment on whether establishment 
of such a subcategory is needed (Comment C-11)

[[Page 2701]]

and on the acid gas HAP emission standards that would be established if 
we create this subcategory (Comment C-12).

A. Background

    In the MATS rule proposal, the EPA proposed a single acid gas 
emission standard for all coal-fired power plants--using HCl as a 
surrogate for all acidic gas HAP. See 76 FR 24976, May 3, 2011. The EPA 
also proposed an alternative emission standard for SO2 as a 
surrogate for the acid gas HAP. SO2 is also an acidic gas--
though not a HAP--and the controls used for SO2 emission 
reduction are also effective for control of the acid gas HAP. Further, 
most, if not all, affected EGUs were already measuring and reporting 
SO2 emissions as a requirement of the Acid Rain Program.
    The Appalachian Region Independent Power Producers Association 
(ARIPPA) \48\ submitted comments on the MATS proposal arguing that the 
characteristics of coal refuse made achievement of the standard too 
costly for its members and requested that the EPA create a subcategory 
for facilities burning coal refuse. The EPA determined that there was 
no basis to create such a subcategory and finalized emission standards 
for both HCl and SO2 that apply to all coal-fired EGUs. See 
77 FR 9304, February 16, 2012. ARIPPA, along with other petitioners, 
challenged the EPA's determination in the D.C. Circuit, and the Court 
upheld the final rule. White Stallion, 748 F.3d at 1249-50.
---------------------------------------------------------------------------

    \48\ ARIPPA is a non-profit trade association comprised of 
independent electric power producers, environmental remediators, and 
service providers located in Pennsylvania and West Virginia that use 
coal refuse as a primary fuel to generate electricity.
---------------------------------------------------------------------------

    In addition to challenging the final rule, ARIPPA also petitioned 
the Agency for reconsideration, again requesting a subcategory for the 
acid gas standards for facilities combusting all types of coal refuse. 
The EPA denied the petition for reconsideration on grounds that ARIPPA 
had adequate opportunity to comment on the ability of coal refuse-
combusting facilities to comply with the final standard. Furthermore, 
the EPA determined that the ARIPPA petition did not present any new 
information to support a change in the previous determination regarding 
the appropriateness of a subcategory for the acid gas HAP standard. 
ARIPPA subsequently sought judicial review of the denial of the 
petition for reconsideration. ARIPPA v. EPA, No. 15-1180 (D.C. 
Cir.).\49\ In petitioner's briefs, ARIPPA claimed that the EPA had 
misunderstood its reconsideration petition and pointed to a distinction 
between the control of acid gas emissions from units burning anthracite 
refuse and those burning bituminous coal refuse. See Industry Pets. Br. 
at 35-36, ARIPPA, No. 15-1180 (D.C. Cir. filed Dec. 6, 2016). The EPA 
disagrees with the assertion that the Agency misunderstood the basis 
for ARIPPA's reconsideration petition as we could not find a single 
statement in the rulemaking record that clearly or even vaguely 
requested a separate acid gas HAP limit based on the distinction 
between anthracite refuse and bituminous coal refuse. Nonetheless, the 
Agency recognizes that there are differences in anthracite and 
bituminous coal (and, thus, between anthracite refuse and bituminous 
coal refuse) and that those differences can influence the acid gas HAP 
emissions from EGUs firing those respective fuels. Those differences 
may also impact the unit's ability to control those emissions.
---------------------------------------------------------------------------

    \49\ ARIPPA's petition for review is currently being held in 
abeyance. ARIPPA v. EPA, No. 15-1180, Order, No. 1672985 (April 27, 
2017).
---------------------------------------------------------------------------

B. Basis for Consideration of a Subcategory

1. Differences Between Anthracite Refuse and Eastern Bituminous Coal 
Refuse
    Anthracite (or ``hard coal'') is the highest quality coal as it 
contains more carbon and fewer impurities--including sulfur and 
chlorine--than lower ranks of coal such as bituminous coal, sub-
bituminous coal, and lignite. Anthracite is rarely used in utility 
power plants, but anthracite refuse is used by a small number of EGUs 
located in Pennsylvania. Bituminous coal is a middle rank coal between 
subbituminous coal and anthracite. Bituminous coal typically has a high 
heating value and is commonly used in electricity generation in the 
United States. Bituminous coal is mined in the Appalachian region 
(northern Alabama through Pennsylvania), the Interior Region (primarily 
Illinois basin), and the Western Region (a small amount of bituminous 
coal mined primarily in Colorado and Utah). The bituminous coal in the 
Interior Region tends to have the highest sulfur content, followed by 
bituminous coals from the Appalachian Region. Coals (of all types) 
mined in the Western Region tend to have the lowest sulfur and chlorine 
content--and the highest content of free alkali (which can act as a 
natural sorbent to neutralize acid gases produced in the combustion 
process). The EPA is aware of currently operational coal-refuse EGUs 
that are firing anthracite refuse (10 units), subbituminous coal refuse 
(1 unit), western bituminous coal refuse (1 unit), and eastern 
bituminous coal refuse (12 units).
    The existing eastern bituminous coal refuse-fired EGUs that are 
currently in operation are listed below in Table 7 (excluding Seward, 
as discussed later). The table also lists the units' net summer 
capacity.

 Table 7--Eastern Bituminous Coal Refuse-Fired EGUs in Current Operation
                                    *
------------------------------------------------------------------------
    ORIS Plant code              Plant            State    Capacity (MW)
------------------------------------------------------------------------
10143.................  Colver Power Project..  PA                   110
10151.................  Grant Town Power Plant  WV                    40
                         Unit 1A.
10151.................  Grant Town Power Plant  WV                    40
                         Unit 1B.
10603.................  Ebensburg Power.......  PA                    50
10641.................  Cambria Cogen Unit 1..  PA                    44
10641.................  Cambria Cogen Unit 2..  PA                    44
10743.................  Morgantown Energy       WV                    25
                         Facility Unit 1.
10743.................  Morgantown Energy       WV                    25
                         Facility Unit 2.
50974.................  Scrubgrass Generating   PA                    42
                         Company LP Unit 1.
50974.................  Scrubgrass Generating   PA                    42
                         Company LP Unit 2.
------------------------------------------------------------------------
* Excluding the Seward units (as explained later).


[[Page 2702]]

2. Control Technologies for Acid Gas HAP
    All coal refuse fuels are fired in fluidized bed combustors (FBC) 
that use limestone injection to minimize SO2 emissions and 
to increase heat transfer efficiency. This limestone injection 
technology may be adequate for EGUs that are firing anthracite refuse, 
subbituminous, and western bituminous coal refuse to meet the MATS 
alternative (surrogate) emission standard for SO2 because, 
as previously mentioned, the anthracite coals are naturally much lower 
in impurities (including sulfur and chlorine) and western bituminous 
coals (and subbituminous coals) have lower sulfur and chlorine content 
and higher free alkalinity. All anthracite coal refuse-fired and 
western bituminous coal refuse-fired EGUs are currently emitting 
SO2 at rates that are below the final MATS emission standard 
for acid gas HAP and the subbituminous coal refuse-fired EGU is 
currently emitting HCl at a rate that is below the final MATS emission 
standard for acid gas HAP. Therefore, there is no need to consider a 
subcategory that would include those units. No anthracite coal refuse-
fired or western bituminous coal refuse-fired EGUs are currently 
reporting HCl emissions for compliance purposes; they are all opting 
to, instead, report the alternative standard for SO2.
    However, ARIPPA has argued that, for the eastern bituminous coal 
refuse-fired EGUs, limestone injection alone is not adequate to meet 
the final HCl or SO2 MATS emission standards. Operators 
cannot simply continue to inject more limestone to the combustor as 
that could negatively affect the operation of the combustor with 
limited impact on acid gas emissions.\50\ For this reason, bituminous 
coal refuse-fired EGUs are required to install some sort of downstream 
acid gas control technology in order to meet the final acid gas MATS 
standards. These downstream control devices could include wet FGD 
scrubbers, spray dryer absorbers (SDA), or dry sorbent injection (DSI) 
systems.
---------------------------------------------------------------------------

    \50\ ``[I]ncreased limestone injection consistent with current 
design and operational constraints cannot further reduce HCl 
emissions . . . to levels consistent with the Utility MACT limit.'' 
See ARIPPA Petition for Reconsideration, p. 5, See also p. 10, 
Docket ID No. EPA-HQ-OAR-2009-0234-20175.
---------------------------------------------------------------------------

    Available information suggests that wet FGD scrubbers and SDA 
systems would be particularly expensive retrofit control options for 
the small units that are currently firing eastern bituminous coal 
refuse. The cost effectiveness--i.e., the cost per incremental ton acid 
gas HAP reduced--may be excessive and may be technically and 
practically infeasible for these units. The EPA solicits comment on 
whether these controls are particularly costly for these units to adopt 
(Comment C-13).
    The eastern bituminous coal refuse-fired EGUs can also consider 
installation of DSI technology, which is a less costly control option. 
A DSI system is used to inject powdered alkaline sorbent (typically 
sodium- or calcium-based sorbents) into the flue gas stream. The 
alkaline sorbents neutralize acidic gases and the resulting solids are 
captured in a downstream PM control device (e.g., a fabric filter). DSI 
has been identified as a relatively low-cost technology for control of 
acid gases. Some commenters to the original MATS proposal stated that 
DSI will not work on units firing bituminous coals. Some commenters 
stated that DSI is only suitable for use on low-sulfur, low-chlorine 
western coals. In fact, in power sector modeling using the Integrated 
Planning Model (IPM) to support the development of MATS, the EPA 
restricted the availability of the DSI option to only those units that 
use or switch to relatively low-sulfur coal (up to 2 lb/MMBtu 
SO2).\51\ Some eastern bituminous coal refuse-fired EGUs 
have tested DSI systems and have identified the following problems that 
make the technology infeasible. The use of sodium-based sorbents 
negatively impacts the usability, and, thus, saleability, of the 
captured fly ash which can be utilized in many useful ways. One 
beneficial use includes using fly ash in mine reclamation activities. 
The increased sodium loading from the injection of sodium-based 
sorbents can increase the leachability and mobility of metals from the 
fly ash.\52\ Therefore, the saleability of the fly ash may be affected 
by the use of DSI. When both calcium-based and sodium-based sorbents 
were injected in testing, the emissions of Hg increased considerably 
(well above the final MATS emission standard for Hg). This is due to 
the alkaline sorbents scavenging free halides from the flue gas 
stream--which effectively helps to control acid gas emissions. However, 
the free halides are also helpful in oxidizing elemental Hg so that it 
can be captured in a downstream PM control device. All coal refuse-
fired EGUs are emitting at levels that are below the final MATS 
standard for Hg (and also with the standard for filterable PM). In 
fact, FBC units--including those firing coal refuse--are among the best 
performers for Hg control.\53\ Therefore, use of DSI technology for 
acid gas control (if feasible), would likely also require the 
installation of Hg-specific control technology. The EPA is soliciting 
comment on the technical feasibility of installing DSI, dry FGD, or 
other applicable control technologies at these units and whether the 
installation of acid gas HAP controls may create technical 
infeasibilities in meeting other MATS emission limits (Comment C-14).
---------------------------------------------------------------------------

    \51\ See 77 FR 9412.
    \52\ See ARIPPA comments on EPA's Proposed Supplemental Finding, 
available at Docket ID No. EPA-HQ-OAR-2009-0234-20530.
    \53\ Ibid.
---------------------------------------------------------------------------

    Further, most of the existing eastern bituminous coal refuse-fired 
EGUs are small (most are less than 100 MW) and may be constrained by 
space or other configurational limitations. However, there are two 
eastern bituminous coal refuse-fired EGUs at the Seward Generating 
Station in Pennsylvania that the EPA would not consider for inclusion 
in a potential subcategory. The Seward units are the newest and, at 260 
MW each, are by far the largest EGUs that are firing coal refuse. The 
Seward units were constructed with installed downstream acid gas 
controls that were part of the original design. The Seward facility, 
therefore, did not suffer from space and other configurational 
limitations that can affect other smaller existing eastern bituminous 
coal refuse-fired EGUs that are attempting to retrofit air pollution 
controls. Further, the Seward units were among the best performing 
units--with respect to HCl emissions--when the EPA developed the final 
MATS emission standards. And, MATS compliance reports submitted by the 
Seward EGUs show that the units' HCl emissions are well below the final 
MATS standard of 0.0020 lb/MMBtu.
    The EPA has incomplete information on the emissions controls that 
are installed at the currently operating eastern bituminous coal 
refuse-fired EGUs (i.e., those identified earlier in Table 7). The EPA 
solicits information on installed controls at those units, the types 
and amount of sorbents or reagents (if any) that are used, and, if 
present, the extent of the operation of these emissions controls 
(Comment C-15). The EPA also solicits comment on the cost of 
retrofitting DSI, dry FGD, or other applicable control technologies 
such that eastern bituminous coal refuse-fired EGUs are able to emit at 
or below the MATS standard for HCl or SO2 (Comment C-16). To 
better understand the economic characteristics of the eastern 
bituminous coal refuse-fired EGUs, the EPA additionally solicits 
information on the operating costs of these units, availability and 
cost

[[Page 2703]]

of their fuel supplies, and any planned retirements (Comment C-17).

C. Potential Subcategory Emission Standards

    As mentioned, the EPA is considering establishing acid gas emission 
standards for a subcategory of existing EGUs that fire eastern 
bituminous coal refuse; and we are soliciting comment on the need for 
such a standard (Comment C-18). The EPA has conducted an analysis to 
determine what such a numerical emission standard would be. The 
analysis is summarized in a separate memorandum available in the 
rulemaking docket.\54\ The results of that MACT floor analysis are 
shown below in Table 8. After the EPA establishes the MACT floor, it 
considers the costs and non-air quality health and environmental 
impacts and energy requirements to determine whether a more stringent, 
or ``beyond-the-floor,'' level of control should be established. The 
average SO2 lb/MMBtu emission rate was determined for each 
currently operating eastern bituminous coal refuse-fired EGU using 
monthly SO2 data available in the EPA's ECMPS for the period 
of January 2015 through June 2018. If the EPA were to establish a 
beyond-the-floor SO2 emissions limit, it would likely be in 
the range of 0.60--0.70 lb/MMBtu; a limit that, on average, the 
currently operating eastern bituminous coal refuse-fired EGUs have 
achieved based on their monthly emissions data for January 2015 through 
June 2018. Because no HCl emissions data have been submitted for the 
currently operating EGUs, and SO2 lb/MWh emissions data are 
available for only two of the EGUs, we could not use this same beyond-
the-floor methodology to evaluate beyond-the-floor standards for 
SO2 in lb/MWh or for HCl in either lb/MMBtu or lb/MWh. We, 
therefore, determined that the beyond-the-floor standards for those 
pollutants should reasonably be set based on the same percentage 
reduction as the SO2 lb/MMBtu described above (i.e., the 40-
percent reduction in the emissions rate for SO2 between the 
MACT floor value of 1.0 lb/MMBtu and the beyond-the-floor value of 0.60 
lb/MMBtu). The results of the MACT floor and the beyond-the-floor 
analyses are shown below in Table 8.
---------------------------------------------------------------------------

    \54\ Memorandum titled NESHAP for Coal- and Oil-Fired EGUs: MACT 
Floor Analysis and Beyond the MACT Floor Analysis for Subcategory of 
Existing Eastern Bituminous Coal Refuse-Fired EGUs Under 
Consideration, available in Docket ID No. EPA-HQ-OAR-2018-0794.

         Table 8--MACT Floor Results for Potential Eastern Bituminous Coal Refuse-Fired EGUs Subcategory
----------------------------------------------------------------------------------------------------------------
                                          Parameter                    HCl                        SO2
           Subcategory           -------------------------------------------------------------------------------
                                    Number in MACT floor                5                          5
----------------------------------------------------------------------------------------------------------------
Existing Eastern Bituminous Coal  99% UPL of top 5........  0.060 lb/MMBtu             1.0 lb/MMBtu
 Refuse-Fired EGUs.               (i.e., MACT floor)......  0.60 lb/MWh                15 lb/MWh
                                  Beyond-the-floor          0.040 lb/MMBtu             0.6 lb/MMBtu
                                   Standard.                0.40 lb/MWh                9 lb/MWh
----------------------------------------------------------------------------------------------------------------

    The EPA solicits comment on these analyses and the methodology 
presented in the accompanying memorandum (Comment C-19).\55\ 
Additionally, the EPA solicits comment on the appropriate definition of 
an eastern bituminous coal refuse-fired EGU (Comment C-20). 
Specifically, the EPA is seeking comment on the amount of eastern 
bituminous coal refuse that an EGU must fire to be an eastern 
bituminous coal refuse-fired EGU (e.g., must the EGU fire 100 percent 
of the fuel or should it be allowed to co-fire some small amount of 
another fuel if needed?) (Comment C-21). The EPA also solicits comment 
on distinctions in smaller FBC units as compared to larger FBC units 
(e.g., those less than 150 MW as compared to those greater than 150 MW 
in capacity) that fire eastern bituminous coal refuse (Comment C-22). 
The EPA further solicits comment on potential effects of establishing 
an acid gas HAP emission standard for a subcategory of small EGUs 
burning eastern bituminous coal refuse (Comment C-23).
---------------------------------------------------------------------------

    \55\ Ibid.
---------------------------------------------------------------------------

VIII. Summary of Cost, Environmental, and Economic Impacts

    The EPA estimates that there are 713 existing EGUs located at 323 
facilities that are subject to the MATS rule. The basis of our estimate 
of affected EGUs and facilities are provided in the Risk Modeling 
Dataset Memo, which is available in the docket for this action. Because 
the EPA is not proposing any amendments to the MATS rule, there would 
not be any cost, environmental, or economic impacts as a result of this 
proposed action.

IX. Request for Comments

    We solicit comments on this proposed action. In addition to general 
comments on this proposed action, we are also interested in additional 
data that may improve the risk assessments and other analyses (Comment 
C-24). We are specifically interested in receiving any improvements to 
the data used in the site-specific emissions profiles used for risk 
modeling (Comment C-25). Such data should include supporting 
documentation in sufficient detail to allow characterization of the 
quality and representativeness of the data or information. Section X of 
this preamble provides more information on submitting data. As 
described in section VII of this preamble, we also solicit comment on 
establishing a subcategory and acid gas emission standards for existing 
eastern bituminous coal refuse-fired EGUs.

X. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses (including instructions) are available 
for download on the RTR website at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html. The data files include detailed information for each HAP 
emissions release point for the facilities in the source category.
    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern, and provide any ``improved'' data that you have, if 
available. When you submit data, we request that you provide 
documentation of the basis for the revised values to support your 
suggested changes. To submit comments on the data downloaded from the 
RTR website, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information.
    2. Fill in the commenter information fields for each suggested 
revision (i.e., commenter name, commenter organization, commenter email 
address,

[[Page 2704]]

commenter phone number, and revision comments).
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft[supreg] Access format and all accompanying documentation to 
Docket ID No. EPA-HQ-OAR-2018-0794 (through the method described in the 
ADDRESSES section of this preamble).
    5. If you are providing comments on a single facility or multiple 
facilities, you need only submit one file for all facilities. The file 
should contain all suggested changes for all sources at that facility 
(or facilities). We request that all data revision comments be 
submitted in the form of updated Microsoft[supreg] Excel files that are 
generated by the Microsoft[supreg] Access file. These files are 
provided on the RTR website at https://www3.epa.gov/ttn/atw/rrisk/rtrpg.html.

XI. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is a significant regulatory action that was submitted 
to OMB for review. Any changes made in response to OMB recommendations 
have been documented in the docket. The EPA does not project any 
potential costs or benefits associated with this action.

B. Executive Order 13771: Reducing Regulation and Controlling 
Regulatory Costs

    This action is expected to be an Executive Order 13771 regulatory 
action. There are no quantified cost estimates for this proposed rule 
because this proposed rule is not expected to result in any changes in 
costs.

C. Paperwork Reduction Act (PRA)

    This action does not impose any new information collection burden 
under the PRA. OMB has previously approved the information collection 
activities contained in the existing regulations and has assigned OMB 
control number 2060-0567. This action does not impose an information 
collection burden because the EPA is not proposing any changes to the 
information collection requirements.

D. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. The EPA does 
not project any potential costs or benefits associated with this 
action.

E. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or 
more as described in UMRA, 2 U.S.C. 1531-1538, and does not 
significantly or uniquely affect small governments. The action imposes 
no enforceable duty on any state, local, or tribal governments or the 
private sector.

F. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

G. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications as specified in 
Executive Order 13175. It would neither impose substantial direct 
compliance costs on tribal governments, nor preempt Tribal law. Thus, 
Executive Order 13175 does not apply to this action.

H. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    This action is not subject to Executive Order 13045 because it is 
not economically significant as defined in Executive Order 12866, and 
because the EPA does not believe the environmental health or safety 
risks addressed by this action present a disproportionate risk to 
children. This action's health and risk assessments are contained in 
sections V.A and C, and sections VI.A and B of this preamble, and 
further documented in the risk document, available in the docket for 
this action.

I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. This action is not anticipated to have 
impacts on emissions, costs, or energy supply decisions for the 
affected electric utility industry.

J. National Technology Transfer and Advancement Act (NTTAA)

    This action does not involve technical standards.

K. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    The EPA believes that this action does not have disproportionately 
high and adverse human health or environmental effects on minority 
populations, low-income populations, and/or indigenous peoples, as 
specified in Executive Order 12898 (59 FR 7629, February 16, 1994). The 
documentation for this decision is contained in section VI.A of this 
preamble and the technical report, Risk and Technology Review--Analysis 
of Demographic Factors for Populations Living Near Coal- and Oil-Fired 
EGUs, available in the docket for this action.

    Dated: December 27, 2018.
Andrew R. Wheeler,
Acting Administrator.
[FR Doc. 2019-00936 Filed 2-6-19; 8:45 am]
BILLING CODE 6560-50-P