[Federal Register Volume 84, Number 71 (Friday, April 12, 2019)]
[Proposed Rules]
[Pages 15046-15077]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-07024]



[[Page 15045]]

Vol. 84

Friday,

No. 71

April 12, 2019

Part II





Environmental Protection Agency





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





40 CFR Part 63





National Emission Standards for Hazardous Air Pollutants: Stationary 
Combustion Turbines Residual Risk and Technology Review; Proposed Rule

  Federal Register / Vol. 84 , No. 71 / Friday, April 12, 2019 / 
Proposed Rules  

[[Page 15046]]


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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2017-0688; FRL-9991-97-OAR]
RIN 2060-AT00


National Emission Standards for Hazardous Air Pollutants: 
Stationary Combustion Turbines Residual Risk and Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: The Environmental Protection Agency (EPA) is proposing 
amendments to the National Emission Standards for Hazardous Air 
Pollutants (NESHAP) for Stationary Combustion Turbines to address the 
results of the residual risk and technology review (RTR) the EPA is 
required to conduct in accordance with the Clean Air Act (CAA). The EPA 
is proposing to find that the risks from this source category due to 
emissions of air toxics are acceptable and that the existing NESHAP 
provides an ample margin of safety to protect public health. The EPA 
identified no new cost-effective controls under the technology review 
that would achieve further emissions reductions from the source 
category. The EPA is also proposing to amend provisions addressing 
periods of startup, shutdown, and malfunction (SSM) and to require 
electronic reporting. In addition, the EPA is proposing to remove the 
stay of the effectiveness of the standards for new lean premix and 
diffusion flame gas-fired turbines that was promulgated in 2004.

DATES: 
    Comments. Comments must be received on or before May 28, 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 May 13, 2019.
    Public Hearing. If anyone contacts us requesting a public hearing 
on or before April 17, 2019, we will hold a hearing. Additional 
information about the hearing, if requested, will be published in a 
subsequent Federal Register document and posted at https://www.epa.gov/stationary-sources-air-pollution/stationary-combustion-turbines-national-emission-standards. See SUPPLEMENTARY INFORMATION for 
information on requesting and registering for a public hearing.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No. 
EPA-HQ-OAR-2017-0688, 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: [email protected]. Include Docket ID No. EPA-
HQ-OAR-2017-0688 in the subject line of the message.
     Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2017-0688.
     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-2017-0688, 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 Melanie King, 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) 541-2469; fax number: (919) 541-4991; 
and email address: [email protected]. 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; 
email address: [email protected]. 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, 77 West Jackson Boulevard (Mail Code E-19J), 
Chicago, Illinois 60604; telephone number: (312) 353-6266; and email 
address: [email protected].

SUPPLEMENTARY INFORMATION: 
    Public hearing. Please contact Adrian Gates at (919) 541-4860 or by 
email at [email protected] to request a public hearing, to register 
to speak at the public hearing, or to inquire as to whether a public 
hearing will be held.
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2017-0688. All documents in the docket are 
listed in Regulations.gov. Although listed, some information is not 
publicly available, e.g., Confidential Business Information (CBI) or 
other information whose disclosure is restricted by statute. Certain 
other material, such as copyrighted material, 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-
2017-0688. The EPA's policy is that all 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.

[[Page 15047]]

    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.
    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-2017-0688.
    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
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
CDX Central Data Exchange
CEDRI Compliance and Emissions Data Reporting Interface
CFR Code of Federal Regulations
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guideline
ERT Electronic Reporting Tool
HAP hazardous air pollutant(s)
HCl hydrochloric acid
HEM-3 Human Exposure Model
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
IRIS Integrated Risk Information System
km kilometer
MACT maximum achievable control technology
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NATA National Air Toxics Assessment
NEI National Emissions Inventory
NESHAP national emission standards for hazardous air pollutants
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
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
POM polycyclic organic matter
ppbvd parts per billion by volume, dry basis
ppm parts per million
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SSM startup, shutdown, and malfunction
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and 
Ecological Exposure model
UF uncertainty factor
[mu]g/m\3\ microgram per cubic meter
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
VCS voluntary consensus standards

    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. Background
    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?
III. 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?
IV. 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?
    D. What other actions are we proposing?
    E. What compliance dates are we proposing?
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulations 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) and 
1 CFR Part 51
    K. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

[[Page 15048]]

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 would be affected by this proposed action only if 
they own or operate stationary combustion turbines at major sources of 
hazardous air pollutants (HAP). As defined in the Initial List of 
Categories of Sources Under Section 112(c)(1) of the Clean Air Act 
Amendments of 1990 (see 57 FR 31576, July 16, 1992) and Documentation 
for Developing the Initial Source Category List, Final Report (see EPA-
450/3-91-030), the Stationary Turbines source category is any 
stationary combustion turbine used by electric and gas utilities, 
industrial establishments, and commercial/institutional operations to 
provide electricity, gas compression, or other functions. Included in 
the category are turbines fired by fuel oil, natural gas, and mixed or 
other fuel. The Stationary Turbine source category includes simple 
cycle and regenerative cycle turbines and the turbine portion of a 
combined cycle steam/electric generating system.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
------------------------------------------------------------------------
       Source category               NESHAP            NAICS code \1\
------------------------------------------------------------------------
Stationary Turbines.........  Stationary            2211, 486210,
                               Combustion Turbines.  211111, 211112,
                                                     221.
------------------------------------------------------------------------
\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/stationary-sources-air-pollution/stationary-combustion-turbines-national-emission-standards. 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.
    A redline version of the regulatory language that incorporates the 
proposed changes in this action is available in the docket for this 
action (Docket ID No. EPA-HQ-OAR-2017-0688).

II. Background

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 maximum 
achievable control technology (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, which is available 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 
tons per year (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

[[Page 15049]]

FR 38044, September 14, 1989). The EPA notified Congress in the 
Residual Risk Report to Congress 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 
United States Court of Appeals for the District of Columbia Circuit 
(the Court) upheld the EPA's interpretation that CAA section 112(f)(2) 
incorporates the approach established in the Benzene 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) 
\1\ 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.
---------------------------------------------------------------------------

    \1\ 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 source category for Stationary Combustion Turbines is all 
equipment including, but not limited to, the turbine, the fuel, air, 
lubrication and exhaust gas systems, control systems (except emissions 
control equipment), and any ancillary components and subcomponents 
comprising any simple cycle stationary combustion turbine, any 
regenerative/recuperative cycle stationary combustion turbine, or the 
combustion turbine portion of any stationary combined cycle steam/
electric generating system. Stationary means that the combustion 
turbine is not self-propelled or intended to be propelled while 
performing its function. A stationary combustion turbine may, however, 
be mounted on a vehicle for portability or transportability. The source 
category does not include stationary combustion turbines located at a 
research or laboratory facility, if research is conducted on the 
turbine itself and the turbine is not being used to power other 
applications at the research or laboratory facility. This NESHAP, 40 
CFR part 63, subpart YYYY, only applies to stationary combustion 
turbines located at major sources of HAP.
    Stationary combustion turbines have been divided into the following 
eight subcategories: (1) Emergency stationary combustion turbines, (2) 
stationary combustion turbines which burn landfill or digester gas 
equivalent to 10 percent or more of the gross heat input on an annual 
basis or where gasified municipal solid waste is used to generate 10 
percent or more of the gross heat input to the stationary combustion 
turbine on an annual basis, (3) stationary combustion turbines of less 
than 1 megawatt rated peak power output, (4) stationary lean premix 
combustion turbines when firing gas and when firing oil at sites where 
all turbines fire oil no more than an aggregate total of 1,000 hours 
annually (also referred to herein as ``lean premix gas-fired 
turbines''), (5) stationary lean premix combustion turbines when firing 
oil at sites where all turbines fire oil more than an aggregate total 
of 1,000 hours annually (also referred to herein as ``lean premix oil-
fired turbines''), (6) stationary diffusion flame combustion turbines 
when firing gas and when firing oil at sites where all turbines fire 
oil no more than an aggregate total of 1,000 hours annually (also 
referred to herein as ``diffusion flame gas-fired turbines''), (7) 
stationary diffusion flame combustion turbines when firing oil at sites 
where all turbines fire oil more than an aggregate total of 1,000 hours 
annually (also referred to herein as ``diffusion flame oil-fired 
turbines''), and (8) stationary combustion turbines operated on the 
North Slope of Alaska (defined as the area north of the Arctic Circle 
(latitude 66.5[deg] North)).
    The sources of emissions are the exhaust gases from combustion of 
gaseous and liquid fuels in a stationary combustion turbine. The HAP 
that are present in the exhaust gases from stationary combustion 
turbines include formaldehyde, toluene, benzene, and acetaldehyde. 
Metallic HAP are present in the exhaust from distillate oil-fired 
turbines; these metallic HAP are generally carried over from the fuel 
constituents.
    The NESHAP requires new or reconstructed stationary combustion 
turbines in the lean premix gas-fired, lean premix oil-fired, diffusion 
flame gas-fired, and diffusion flame oil-fired subcategories to meet a 
formaldehyde limit of 91 parts per billion by volume, dry basis (ppbvd) 
at 15-percent oxygen (O2). Compliance is demonstrated 
through initial and annual performance testing and continuous 
monitoring of operating parameters.
    During the original Stationary Combustion Turbine NESHAP 
rulemaking, the EPA received a petition from the Gas Turbine 
Association to delist two subcategories of stationary combustion 
turbines under CAA section 112(c)(9). The subcategories were lean 
premix firing natural gas with limited oil backup and a low-risk 
subcategory where facilities would make site-specific demonstrations 
regarding risk levels. On April 7, 2004, the EPA proposed to delist 
lean premix gas-fired turbines as well as three additional 
subcategories: Diffusion flame gas-fired, emergency, and turbines 
located on the North Slope of Alaska. At the same time, the EPA 
proposed to stay the effectiveness of the NESHAP for new lean premix 
gas-fired and diffusion flame gas-fired turbines. On August 18, 2004, 
the EPA finalized the stay of the effectiveness of the NESHAP for new 
lean premix gas-fired and diffusion flame gas-fired turbines, pending 
the outcome of the proposed delisting. As discussed further in section 
IV.D.3 of this preamble, the EPA is proposing to lift the stay as part 
of this action.

[[Page 15050]]

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

    The EPA used several means to collect the information necessary to 
conduct the RTR for the Stationary Combustion Turbine source category. 
Where possible, the EPA used data from the 2014 National Emissions 
Inventory (NEI) to estimate HAP emissions from affected facilities and 
turbines. More information about the sources of data used to estimate 
HAP emissions is provided in section III.C.1 of this preamble. The list 
of facilities potentially subject to the NESHAP was initially developed 
using the EPA's Enforcement and Compliance History Online database.\2\ 
To confirm whether facilities identified as potentially subject to the 
NESHAP were in fact subject to the standards, the EPA asked state and 
local air pollution control agencies and EPA Regional offices to review 
our draft list of affected facilities and turbines and revise it as 
necessary. The EPA also shared the draft list with a number of industry 
trade groups, including the American Petroleum Institute, Interstate 
Natural Gas Association of America, Council of Industrial Boiler 
Owners, National Waste & Recycling Association, American Public Power 
Association, National Rural Electric Cooperative Association, Utility 
Air Regulatory Group, Edison Electric Institute, and American Chemistry 
Council, and asked member companies to review and revise the list. The 
EPA also posted the draft list on the EPA website for the Stationary 
Combustion Turbine NESHAP so that other stakeholders could provide 
input on the list. The EPA also reviewed air permits for each facility 
to ensure the accuracy of our information. The facility-specific 
information from state and local agencies and companies with affected 
facilities provided support for this action's risk and technology 
reviews. No formal information collection request was performed.
---------------------------------------------------------------------------

    \2\ https://echo.epa.gov/.
---------------------------------------------------------------------------

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

    In order to determine whether there have been any developments in 
practices, processes, or control technologies since promulgation of the 
original NESHAP, the EPA reviewed several sources of information, 
including the EPA's Reasonably Available Control Technology/Best 
Available Control Technology/Lowest Achievable Emission Rate 
Clearinghouse,\3\ construction and operating permits for stationary 
combustion turbines, information provided by industry trade groups 
representing owners and operators of stationary combustion turbines, 
and manufacturers of emission control technologies and emission testing 
equipment. Additional details of the technology review can be found in 
the Technology Review for Stationary Combustion Turbines Risk and 
Technology Review (RTR) memorandum, which is available in the docket 
for this action. The EPA also reviewed the stationary combustion 
turbine performance test data that were collected for the original 
NESHAP rulemaking, as well as new HAP emissions data from tests of 
stationary combustion turbines conducted in recent years that were 
primarily provided by state and local air pollution control agencies.
---------------------------------------------------------------------------

    \3\ https://cfpub.epa.gov/rblc/.
---------------------------------------------------------------------------

III. 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 II.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.\4\ 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:
---------------------------------------------------------------------------

    \4\ 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 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.

[[Page 15051]]

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 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.'' \5\
---------------------------------------------------------------------------

    \5\ 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 
the NESHAP, we review a variety of data sources in our investigation of 
potential practices, processes, or controls to consider. See sections 
II.C and II.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 
IV.A).
    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

[[Page 15052]]

inputs and models: Residual Risk Assessment for the Stationary 
Combustion Turbines 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; \6\ and described in the SAB review 
report issued in 2010. They are also consistent with the key 
recommendations contained in that report.
---------------------------------------------------------------------------

    \6\ U.S. EPA. 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, June 2009. EPA-452/R-09-006. https://www3.epa.gov/airtoxics/rrisk/rtrpg.html.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    For each stationary combustion turbine that was determined to be 
subject to 40 CFR part 63, subpart YYYY, we gathered data for emissions 
of particulate matter (PM), volatile organic compounds (VOC), and HAP 
from Version 1 of the 2014 NEI. If a turbine had multiple processes 
reported in NEI, the emissions associated with each process were summed 
for a total emissions value for the turbine. The following HAP, which 
account for 98-99 percent of the HAP emissions from turbines subject to 
40 CFR part 63, subpart YYYY, regardless of fuel type, were modeled 
with the available NEI data per the applicable fuel types.

                                                      Table 2--HAP Modeled for Residual Risk Review
--------------------------------------------------------------------------------------------------------------------------------------------------------
               HAP                      Natural gas           Distillate oil           Landfill gas              Jet fuel               Process gas
--------------------------------------------------------------------------------------------------------------------------------------------------------
Formaldehyde....................  Yes                     Yes                     Yes                     Yes                     Yes
Toluene.........................  Yes                     Yes                     Yes
Xylenes (Mixed Isomers).........  Yes                     Yes                     Yes
Acetaldehyde....................  Yes                     Yes
Ethylbenzene....................  Yes                     Yes                     Yes
Propylene Oxide.................  Yes                     Yes
Benzene.........................  Yes                     Yes                     Yes                     ......................  Yes
Hexane..........................  Yes                     Yes                     Yes
Hydrochloric Acid...............  Yes                     Yes                     Yes
Acrolein........................  Yes                     Yes
Manganese Compounds.............  ......................  Yes                     ......................  Yes
Nickel Compounds................  ......................  Yes                     ......................  Yes                     Yes
Lead Compounds..................  ......................  Yes                     ......................  Yes                     Yes
Arsenic Compounds...............  ......................  Yes                     ......................  ......................  Yes
Chromium Compounds..............  ......................  Yes                     ......................  ......................  Yes
Cadmium Compounds...............  ......................  Yes                     ......................  ......................  Yes
Mercury Compounds...............  ......................  Yes                     ......................  Yes
Selenium Compounds..............  ......................  Yes
Cobalt Compounds................  ......................  Yes
Beryllium Compounds.............  ......................  Yes                     ......................  Yes
Antimony Compounds..............  ......................  Yes
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Whenever possible, the 2014 NEI HAP emissions values were used for 
each turbine unit included in the inputs for the residual risk modeling 
documented in section III.C.3 of this preamble, hereafter referred to 
as the modeling file. However, many of the turbine units used in the 
modeling file either were not included in the 2014 NEI or did not have 
reported emissions values for one or more of the expected HAP (see 
Table 2). For units with emissions values that were missing, a three-
tiered approach was developed for filling in emissions. In Tier 1, 
emissions were estimated using the NEI-reported VOC and/or PM of 10 
micrometers or less (PM10) emission values and the developed 
HAP emission factor speciation profiles per fuel type. For units that 
did not have a NEI-reported VOC and/or PM10 value available, 
or were not included in the 2014 NEI, the Tier 2 calculation 
methodology was used to estimate HAP emissions. In Tier 2, emissions 
were calculated using the design capacity (million British thermal 
units per hour) of each unit and developed HAP emission factor 
speciation profiles per fuel type. Tier 3 was used for estimating 
emissions for those units that did not have a design capacity value 
available. In Tier 3, emissions were conservatively estimated using the 
maximum HAP emission value reported to NEI for any turbine unit for the 
applicable fuel type. A more detailed discussion regarding the 
methodology for estimating actual emissions is provided in the 
Emissions Data Used for Stationary Combustion Turbines Risk and 
Technology Review (RTR) Modeling Files memorandum in the rulemaking 
docket.
    Stack parameters (height, diameter, temperature, exit velocity, and 
flow rate) and stack locations (latitudes and longitudes) were taken 
from the 2014 NEI when reported. For those units that did not have 2014 
NEI stack parameters, three sets of default stack parameters were 
developed based on the unit design capacity. The default parameters 
were created by averaging the NEI-reported values for each parameter in 
each data set.
    The modeling file input values were reviewed for completeness and 
accuracy. Data quality checks included reviewing turbine latitudes and 
longitudes using mapping tools and correcting as needed, performing 
statistical analysis of modeling inputs to flag outliers for review, 
and identifying and correcting stack parameters that were missing or 
outside of standard industry range.
2. How did we estimate MACT-allowable emissions?
    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

[[Page 15053]]

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.)
    For this source category, allowable emissions were determined using 
the emission limitations currently included in 40 CFR part 63, subpart 
YYYY. There are no current emission limits for existing source 
stationary combustion turbines in the rule. As such, allowable 
emissions have been set equal to the actual emissions for existing 
sources. For new or reconstructed gas-fired and oil-fired stationary 
combustion turbines where construction/reconstruction commenced after 
January 14, 2003, a formaldehyde emission limit of 91 ppbvd at 15-
percent O2 is established in 40 CFR part 63, subpart YYYY. 
However, the emission limits for new or reconstructed stationary 
combustion turbines that are lean premix gas-fired or diffusion flame 
gas-fired were stayed by the EPA. Therefore, as no emissions 
limitations currently apply to gas-fired turbine units, the allowable 
emissions have been set equal to the actual emissions for natural gas 
units constructed after January 14, 2003. For all new oil-fired units 
subject to the current emission limitation in 40 CFR part 63, subpart 
YYYY, allowable annual emissions were estimated using the 91 ppbvd 
formaldehyde limit and the NEI-reported operating hours.
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).\7\ 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.
---------------------------------------------------------------------------

    \7\ 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.\8\ 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 \9\ 
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.
---------------------------------------------------------------------------

    \8\ 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).
    \9\ 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 each of the carcinogenic HAP \10\ 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

[[Page 15054]]

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.
---------------------------------------------------------------------------

    \10\ 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 the 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 screening-level risk assessments, the 
EPA makes conservative assumptions about emission rates, meteorology, 
and exposure location. We use the peak hourly emission rate,\11\ 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.
---------------------------------------------------------------------------

    \11\ 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 the risk document 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.
---------------------------------------------------------------------------

    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.'' \12\ 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 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.\13\ 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 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.
---------------------------------------------------------------------------

    \12\ 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.
    \13\ 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).
---------------------------------------------------------------------------

    ERPGs are ``developed for emergency planning and are intended as 
health-based guideline concentrations for single exposures to 
chemicals.'' \14\ 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

[[Page 15055]]

health effects or symptoms which could impair an individual's ability 
to take protective action.'' Id. at 1.
---------------------------------------------------------------------------

    \14\ 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.
---------------------------------------------------------------------------

    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).
    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 
often consider additional site-specific data if available to develop a 
more refined estimate of the potential for acute exposures of concern. 
For this source category, we did not have short-term emissions data; 
therefore, we used the default multiplication factor of 10. The acute 
assessment methods are discussed more fully in the risk document, which 
is available in the docket for this action.
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 HAP known to be PB-
HAP, as identified in the EPA's Air Toxics Risk Assessment Library (See 
Volume 1, Appendix D, at https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library.
    For the Stationary Combustion Turbine source category, we 
identified PB-HAP emissions of arsenic, cadmium, lead, and mercury, 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, mercury compounds, 
and polycyclic organic matter (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.''
    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 mercury 
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 U.S. 
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 National Ambient Air Quality 
Standard (NAAQS) for lead.\15\ Values below the level of the primary 
(health-based) lead NAAQS are considered to have a low potential for 
multipathway risk.
---------------------------------------------------------------------------

    \15\ 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.
---------------------------------------------------------------------------

    For further information on the multipathway assessment approach, 
see the risk document, which is available in the docket for this 
action.

[[Page 15056]]

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, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. The acid 
gases included in the screening assessment are hydrochloric acid (HCl) 
and hydrogen fluoride (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 Stationary Combustion Turbine 
source category emitted any of the environmental HAP, and we identified 
emissions of arsenic, cadmium, mercury, lead, and HCl. 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, mercury (both 
inorganic mercury and methyl mercury), and lead compounds. With the 
exception of 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

[[Page 15057]]

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 that the EPA compiled from the 2014 NEI. We used the 
NEI data for the facility and did not adjust any category or ``non-
category'' data. Therefore, there could be differences in the dataset 
from that used for the source category assessments described in this 
preamble. We analyzed 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, we 
made a reasonable attempt to identify the source category risks, and 
these risks were compared to the facility-wide risks to determine the 
portion of 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 
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 under 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

[[Page 15058]]

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.\16\ 
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.\17\ 
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 \18\ 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.
---------------------------------------------------------------------------

    \16\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \17\ 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.
    \18\ 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.
---------------------------------------------------------------------------

    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 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

[[Page 15059]]

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, mercury, cadmium, and arsenic) 
and two acid gases (HF and hydrogen chloride). 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.\19\
---------------------------------------------------------------------------

    \19\ 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 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, mercury (both inorganic and methyl 
mercury), 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.

IV. Analytical Results and Proposed Decisions

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

    As described above, for the Stationary Combustion Turbines source 
category, we conducted an inhalation risk assessment for all HAP 
emitted and we also conducted multipathway and environmental risk 
screening assessments on the PB-HAP emitted. We present results of the 
risk assessment briefly below and in more detail in the risk document. 
Note that risk modeling was conducted for 253 facilities. Additional 
information obtained after the risk modeling was completed was used to 
refine our estimate of facilities in the source category to 242. The 
risk assessment results presented in this preamble and in the risk 
document are shown for the 253 facilities modeled.
1. Inhalation Risk Assessment Results
    Table 3 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.

[[Page 15060]]



                                       Table 3--Stationary Combustion Turbines Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                Maximum individual      Population at increased   Annual cancer incidence       Maximum chronic       Maximum  screening acute noncancer
                 cancer risk (in 1      risk of cancer >=1-in-1      (cases per year)        noncancer  TOSHI \3\                   HQ \4\
                   million) \2\                 million         ----------------------------------------------------------------------------------------
 Number of  ----------------------------------------------------      Based on . . .            Based on . . .
 facilities       Based on . . .            Based on . . .      ----------------------------------------------------
    \1\     ----------------------------------------------------
                Actual     Allowable      Actual     Allowable      Actual     Allowable      Actual     Allowable     Based on actual emissions level
              emissions    emissions    emissions    emissions    emissions    emissions    emissions    emissions
                level        level        level        level        level        level        level        level
--------------------------------------------------------------------------------------------------------------------------------------------------------
       253            3            3       42,000       42,000         0.04         0.04         0.04         0.04   HQREL = 2 (acrolein), HQAEGL-1 =
                                                                                                                      0.07.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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 system with the highest TOSHI for the source category is respiratory. The respiratory TOSHI was calculated using the
  CalEPA chronic REL for acrolein. The EPA is in the process of updating the IRIS RfC for acrolein. If the RfC is updated prior to signature of the
  final rule, we will use it in the assessment.
\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 3, based on actual and allowable emissions, the 
estimated cancer MIR is 3-in-1 million, and formaldehyde emissions 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 42,000 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 0.04 
(respiratory), which is driven by emissions of formaldehyde. No 
individuals are exposed to TOSHI levels above 1.
2. Acute Risk Results
    Table 3 provides the worst-case acute HQ (based on the REL) of 2, 
driven by actual emissions of acrolein. Only one facility has an HQ 
(REL) that exceeds 1. To better characterize the potential health risks 
associated with estimated worst-case acute exposures to HAP, and in 
response to a key recommendation from the SAB's peer review of the 
EPA's RTR risk assessment methodologies, we examine a wider range of 
available acute health metrics than we do for our chronic risk 
assessments. This is in acknowledgement that there are generally more 
data gaps and uncertainties in acute reference values than there are in 
chronic reference values. By definition, the acute REL represents a 
health-protective level of exposure, with effects not anticipated below 
those levels, even for repeated exposures; however, the level of 
exposure that would cause health effects is not specifically known. 
Therefore, when an REL is exceeded and an AEGL-1 or ERPG-1 level is 
available (i.e., levels at which mild, reversible effects are 
anticipated in the general public for a single exposure), we typically 
use them as an additional comparative measure, as they provide an upper 
bound for exposure levels above which exposed individuals could 
experience effects. As the exposure concentration increases above the 
acute REL, the potential for effects increases.
    The worst-case maximum estimated 1-hour exposure to acrolein 
outside the facility fence line is 0.004 mg/m\3\. This estimated worst-
case exposure exceeds the 1-hour REL by a factor of 2 (HQ=2) and is 
less than 10 percent of the 1-hour AEGL-1 and ERPG-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 evaluated using a three-tier screening assessment of the 
PB-HAP emitted by facilities in this source category. Of the 253 
facilities modeled, 35 facilities have reported emissions of 
carcinogenic PB-HAP (arsenic) that exceed a Tier 1 cancer screening 
value of 1, and 15 facilities have reported emissions of non-
carcinogenic PB-HAP (mercury and/or 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-specific 
information to perform an assessment through Tiers 2 and 3, as 
necessary, to determine the maximum chronic cancer and noncancer 
multipathway health risks for the source category. For cancer, the 
highest Tier 2 screening value was 20 and there were 17 facilities with 
Tier 2 screening values greater than 1. This highest screening value 
was reduced to 4 after Tier 3. For noncancer, the highest Tier 2 
screening value was 4 (for mercury), and there were 3 facilities with 
Tier 2 screening values greater than 1. After Tier 3, the highest 
screening value was 1.
    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 annual lead concentrations to the primary 
NAAQS for lead (0.15 [micro]g/m\3\). The highest annual lead 
concentration of 0.0003 [micro]g/m\3\ is well below the NAAQS for lead, 
indicating a low potential for multipathway impacts of concern due to 
lead.
4. Environmental Risk Screening Results
    As described in section III.C.5 of this document, we conducted an 
environmental risk screening assessment for the Stationary Combustion 
Turbine source category for the following pollutants: Arsenic, cadmium, 
mercury, lead, and HCl.
    In the Tier 1 screening analysis for PB-HAP (other than lead, which 
was evaluated differently), arsenic had no exceedances of any of the 
ecological benchmarks evaluated. Divalent mercury and methyl mercury 
emissions had Tier 1 exceedances for surface soil benchmarks. Cadmium 
emissions had Tier 1 exceedances for surface soil and fish benchmarks.
    A Tier 2 screening analysis was performed for cadmium, divalent 
mercury, and methyl mercury emissions. In the Tier 2 screening 
analysis, there were no exceedances of

[[Page 15061]]

any of the ecological benchmarks evaluated for any of the pollutants.
    For lead, we did not estimate any exceedances of the secondary lead 
NAAQS. For HCl, 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 (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.
5. Facility-Wide Risk Results
    Based on facility-wide emissions, the estimated cancer MIR is 
2,000-in-1 million, and ethylene oxide from chemical manufacturing is 
the major contributor to the risk. The total estimated cancer incidence 
based on facility-wide emissions is 0.7 excess cancer cases per year, 
or one excess case in every 1 to 2 years. Approximately 2.8 million 
people are estimated to have cancer risks at or above 1-in-1 million. 
The estimated maximum chronic noncancer TOSHI based on facility-wide 
emissions is 4 (respiratory), driven by emissions of chlorine from 
chemical manufacturing, and approximately 360 people are exposed to a 
TOSHI above 1.
6. 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, 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 Stationary Combustion 
Turbines source category across different demographic groups within the 
populations living near facilities.\20\
---------------------------------------------------------------------------

    \20\ 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 4 
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 4--Stationary Combustion Turbines Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                                 Source category
                                                               -------------------------------------------------
                                                  Nationwide     Population with cancer
                                                                  risk greater than or    Population with hazard
                                                                equal to 1-in-1 million    index greater than 1
----------------------------------------------------------------------------------------------------------------
     Stationary Combustion Turbines Source Category: Demographic Assessment Results--50 km Study Area Radius
----------------------------------------------------------------------------------------------------------------
Total Population..............................     317,746,049                   42,191                        0
----------------------------------------------------------------------------------------------------------------
                                          White and Minority by Percent
----------------------------------------------------------------------------------------------------------------
White.........................................              62                       52                        0
Minority......................................              38                       48                        0
----------------------------------------------------------------------------------------------------------------
                                               Minority by Percent
----------------------------------------------------------------------------------------------------------------
African American..............................              12                       11                        0
Native American...............................             0.8                      0.1                        0
Hispanic or Latino (includes white and                      18                       31                        0
 nonwhite)....................................
Other and Multiracial.........................               7                        6                        0
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level...........................              14                       19                        0
Above Poverty Level...........................              86                       81                        0
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without a High School Diploma.....              14                       13                        0
Over 25 and with a High School Diploma........              86                       87                        0
----------------------------------------------------------------------------------------------------------------
                                       Linguistically Isolated by Percent
----------------------------------------------------------------------------------------------------------------
Linguistically Isolated.......................               6                        9                        0
----------------------------------------------------------------------------------------------------------------

    The results of the Stationary Combustion Turbines source category 
demographic analysis indicate that emissions from the source category 
expose approximately 42,000 people to a cancer risk at or above 1-in-1 
million and no people to a chronic noncancer TOSHI greater than 1. 
Regarding cancer risk, the specific demographic results indicate that 
the percentage of the population potentially impacted by Stationary 
Combustion Turbine emissions is greater than its corresponding 
nationwide percentage for the following demographics: Hispanic or 
Latino (31 percent for the source category compared to 18 percent 
nationwide), minority (48 percent for

[[Page 15062]]

the source category compared to 38 percent nationwide), age 18 to 64 
(69 percent for the source category compared to 63 percent nationwide), 
below the poverty level (19 percent for the source category compared to 
14 percent nationwide), and linguistically isolated (9 percent for the 
source category compared to 6 percent nationwide). The remaining 
demographic group percentages are the same as or less than the 
corresponding 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 Stationary 
Combustion Turbines Source Category Operations, 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 III 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 
stationary combustion turbines located at major sources of HAP, and we 
considered these in determining acceptability.
    The estimated inhalation cancer risk to the individual most exposed 
to actual or allowable emissions from the source category is 3-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 42,000 people face an increased cancer risk at or 
above 1-in-1 million due to inhalation exposure to actual or allowable 
HAP emissions from this source category. The estimated maximum chronic 
noncancer TOSHI from inhalation exposure for this source category is 
0.04. The screening assessment of worst-case inhalation impacts 
indicates a worst-case maximum acute HQ of 2 for acrolein based on the 
1-hour REL and concentrations that are less than 10 percent of the 1-
hour AEGL-1 and ERPG-1. Only one facility has an HQ (REL) that exceeds 
1.
    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 Tier 1 and Tier 
2 screening values are arsenic (cancer), cadmium (noncancer), and 
mercury (noncancer). The Tier 3 screening values for these pollutants 
are low. For cancer, the Tier 3 screening value for arsenic is 4. For 
noncancer, the Tier 3 screening value for cadmium is less than 1, and 
the screening value for mercury is 1.
    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. In addition, the highest chronic 
noncancer TOSHI is well below 1, indicating low likelihood of adverse 
noncancer effects from inhalation exposures. There are also low 
estimated risks associated with ingestion, with the highest cancer risk 
being 4-in-1 million and the highest noncancer HI being 1, based on a 
Tier 3 multipathway screening assessment.
    The acute screening analysis results in a maximum acute noncancer 
HQ of 2 based on the acute REL for acrolein. This occurs at only one 
facility of the 253 that were modeled. For acute screening analyses, to 
better characterize the potential health risks associated with 
estimated worst-case acute exposures to HAP, we examine a wider range 
of available acute health metrics than we do for our chronic risk 
assessments. This is in acknowledgement that there are generally more 
data gaps and uncertainties in acute reference values than there are in 
chronic reference values. By definition, the acute REL represents a 
health-protective level of exposure, with effects not anticipated below 
those levels, even for repeated exposures; however, the level of 
exposure that would cause health effects is not specifically known. As 
the exposure concentration increases above the acute REL, the potential 
for effects increases. Therefore, when an REL is exceeded and an AEGL-1 
or ERPG-1 level is available (i.e., levels at which mild, reversible 
effects are anticipated in the general population for a single 
exposure), we typically use them as an additional comparative measure, 
as they provide an upper bound for exposure levels above which exposed 
individuals could experience effects.
    The highest estimated 1-hour concentration is less than 10 percent 
of the AEGL-1 and ERPG-1, well below the level at which mild, 
reversible effects would be anticipated. As stated previously, only one 
facility has an HQ (REL) that exceeds 1. In addition, the acute 
screening assessment includes the conservative (health protective) 
assumptions that every process releases its peak hourly emissions at 
the same hour, that the worst-case dispersion conditions occur at that 
same hour, and that an individual is present at the location of maximum 
concentration for that hour. As discussed previously in section 
III.C.3, we used a default multiplication factor of 10. A review of 
stack test data from turbines that were tested at different times shows 
that formaldehyde emissions during individual test runs generally vary 
by much less than a factor of 10 from the turbine's overall average 
emissions. Emissions of both acrolein and formaldehyde from stationary 
combustion turbines are primarily the result of incomplete combustion, 
so we expect acrolein emissions would not vary more significantly than 
formaldehyde emissions. Together, these factors lead us to conclude 
that adverse effects from acute exposure to emissions from this 
category are not anticipated.
    Considering all of the health risk information and factors 
discussed above, including the uncertainties discussed in section III 
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 whether 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 emission reduction measures 
necessary to provide an ample margin of safety with respect to the 
risks associated with these emissions.

[[Page 15063]]

    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 IV.C of this preamble, no additional cost-
effective measures were identified for reducing HAP emissions from 
affected sources in the Stationary Combustion Turbine source category. 
Thus, we are proposing that the current Stationary Combustion Turbine 
NESHAP provides an ample margin of safety to protect public health.
    Regarding the facility-wide risks due to ethylene oxide (described 
above), which are due to emission sources that are not part of the 
Stationary Combustion Turbines source category, we intend to evaluate 
those facility-wide estimated emissions and risks further and may 
address these in a separate future action, as appropriate. In 
particular, the EPA is addressing ethylene oxide based on the results 
of the latest NATA released in August 2018, which identified the 
chemical as a potential concern in several areas across the country 
(NATA is the Agency's nationwide air toxics screening tool, designed to 
help the EPA and state, local, and tribal air agencies identify areas, 
pollutants, or types of sources for further examination). The latest 
NATA estimates that ethylene oxide significantly contributes to 
potential elevated cancer risks in some census tracts across the U.S. 
(less than 1 percent of the total number of tracts). These elevated 
risks are largely driven by an EPA risk value that was updated in late 
2016. The EPA will work with industry and state, local, and tribal air 
agencies as the EPA takes a two-pronged approach to address ethylene 
oxide emissions: (1) Reviewing and, as appropriate, revising CAA 
regulations for facilities that emit ethylene oxide--starting with air 
toxics emissions standards for miscellaneous organic chemical 
manufacturing facilities and commercial sterilizers; and (2) conducting 
site-specific risk assessments and, as necessary, implementing emission 
control strategies for targeted high-risk facilities. The EPA will post 
updates on its work to address ethylene oxide on its website at: 
https://www.epa.gov/ethylene-oxide.
3. Adverse Environmental Effect
    Based on the results of our environmental risk screening 
assessment, we conclude that there is not an adverse environmental 
effect from the Stationary Combustion Turbine 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 III.B of this preamble, our technology 
review focused on identifying developments in practices, processes, and 
control technologies that have occurred since the Stationary Combustion 
Turbine NESHAP was originally promulgated in 2004. Our review of the 
developments in technology for the Stationary Combustion Turbine source 
category did not reveal any changes that require revisions to the 
emission standards. The only add-on HAP emission control technology 
identified in the original NESHAP rulemaking was an oxidation catalyst. 
No new or improved add-on control technologies that reduce HAP 
emissions from turbines were identified during the technology review. 
Our review also did not identify any new or improved operation and 
maintenance practices, process changes, pollution prevention 
approaches, or testing and monitoring techniques for stationary 
combustion turbines. Therefore, we propose that no revisions to the 
Stationary Combustion Turbine NESHAP are necessary pursuant to CAA 
section 112(d)(6). Additional details of our technology review can be 
found in the Technology Review for Stationary Combustion Turbines Risk 
and Technology Review (RTR) memorandum, which is available in the 
docket for this action.

D. What other actions are we proposing?

    In addition to the proposed actions described above, we are 
proposing additional revisions to the NESHAP. We are proposing 
revisions to the SSM provisions of the MACT rule in order to ensure 
that they are consistent with the Court decision in Sierra Club v. EPA, 
551 F. 3d 1019 (D.C. Cir. 2008), which vacated two provisions that 
exempted sources from the requirement to comply with otherwise 
applicable CAA section 112(d) emission standards during periods of SSM. 
We also are proposing to require electronic submittal of performance 
test results and semiannual compliance reports, and to remove the stay 
of standards for new lean premix and diffusion flame gas-fired 
stationary combustion turbines. Our analyses and proposed changes 
related to these issues are discussed below.
1. SSM
    In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C. 
Cir. 2008), the Court vacated portions of two provisions in the EPA's 
CAA section 112 regulations governing the emissions of HAP during 
periods of SSM. Specifically, the Court vacated the SSM exemption 
contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), holding that 
under section 302(k) of the CAA, emissions standards or limitations 
must be continuous in nature and that the SSM exemption violates the 
CAA's requirement that some CAA section 112 standards apply 
continuously.
    We are proposing the elimination of the SSM exemption in this rule 
which appears at 40 CFR 63.6105(a). Consistent with Sierra Club v. EPA, 
we are proposing standards in this rule that apply at all times. We are 
also proposing several revisions to Table 7 as is explained in more 
detail below. For example, we are proposing to eliminate the 
incorporation of the General Provisions' requirement that the source 
develop an SSM plan. We also are proposing to eliminate and revise 
certain recordkeeping and reporting requirements related to the SSM 
exemption as further described below.
    The EPA has attempted to ensure that the provisions we are 
proposing to eliminate are inappropriate, unnecessary, or redundant in 
the absence of the SSM exemption. We are specifically seeking comment 
on whether we have successfully done so. In proposing the standards in 
this rule, the EPA has taken into account startup and shutdown periods 
and, for the reasons explained below, has proposed alternate standards 
for startup and has not proposed alternate standards for shutdown.
    The EPA has determined that emissions from stationary combustion 
turbines during startup are significantly different than emissions 
during normal operation. The Gas Turbine Association provided the 
following information regarding the differences in turbine operation 
during startup that lead to changes in emissions: ``During startup the 
gas turbine combustor(s) transition through a variety of operational 
modes to ensure stable combustion and to minimize transient stresses on 
the gas turbine equipment. The equipment experiences extreme 
temperature transients during a startup event. The various operating 
modes result in low combustion efficiencies and incomplete combustion 
of the fuel which causes variations in the pollutant concentrations and 
fluctuations in the flow rate of the exhaust gas. Other

[[Page 15064]]

exhaust parameters/characteristics including temperature, molecular 
weight, water concentration, oxygen concentration, etc. change rapidly 
as the gas turbine is loaded from idle to a higher, steady state 
operating load.'' \21\ In addition, oxidation catalysts may not be 
fully effective until sufficient exhaust gas temperatures are reached.
---------------------------------------------------------------------------

    \21\ Email from Leslie Witherspoon, Solar Turbines to Melanie 
King, U.S. EPA. October 9, 2018. Available in the rulemaking docket.
---------------------------------------------------------------------------

    The EPA has determined that it is not feasible to prescribe or 
enforce a numerical emission limit during periods of startup for 
stationary combustion turbines because the application of measurement 
methodology during startup is not practicable. Test methods were 
developed for sampling stable operations. Changes in turbine operations 
during startup create rapid variations in exhaust gas flow rate, as 
well as pollutant and diluent gas concentrations. A concentration 
average over the startup period does not accurately reflect emissions 
over such a dynamically shifting concentration and flow scenario. 
Determining representative average emissions concentrations would 
require correlating the exhaust gas flow rates and the gas components 
concentration data for each fraction of time over the entire period of 
startup operation in order to apportion the values appropriately. The 
rapidly changing temperature (from ambient to approximately 1,800 
degrees Fahrenheit for a simple cycle unit), concentration, and flow 
profile would make it practically impossible to employ the proportional 
sampling technique that would be necessary to properly account for the 
effect of the variability in emissions. Additionally, the 
stratification of the gas stream with respect to both flow and 
concentration would be in flux over the startup period until steady 
state conditions are achieved. With existing methodologies, the ability 
to perform replicate testing within the normal bounds of variability of 
the test methods (typically 15-20 percent) under the conditions present 
at startup is not practicable, and work practice or operational 
standards are appropriate.
    The EPA is, therefore, proposing an operational standard in lieu of 
a numeric emission limit during periods of startup, in accordance with 
CAA section 112(h). The EPA is proposing that during turbine startup, 
owners and operators must minimize the turbine's time spent at idle or 
holding at low load levels and minimize the turbine's startup time to a 
period needed for appropriate and safe loading of the turbine, not to 
exceed 1 hour for simple cycle stationary combustion turbines and 3 
hours for combined cycle stationary combustion turbines, after which 
time the formaldehyde emission limitation of 91 ppbvd or less at 15-
percent O2 applies. Minimizing the time spent at idle or low 
load operation will minimize the time the turbine's combustion system 
is not at peak efficiency and the emission controls are not at minimum 
operating temperatures.
    For shutdown, the EPA does not have any information to show that 
emissions from stationary combustion turbines would be higher during 
shutdown than during normal operation. Therefore, the EPA is not 
proposing a different standard that applies during shutdown.
    Periods of startup, normal operations, and shutdown are all 
predictable and routine aspects of a source's operations. Malfunctions, 
in contrast, are neither predictable nor routine. Instead they are, by 
definition, sudden, infrequent, and not reasonably preventable failures 
of emissions control, process, or monitoring equipment (40 CFR 63.2; 
Definition of malfunction). The EPA interprets CAA section 112 as not 
requiring emissions that occur during periods of malfunction to be 
factored into development of CAA section 112 standards and this reading 
has been upheld as reasonable by the Court in U.S. Sugar Corp. v. EPA, 
830 F.3d 579, 606-610 (2016). Under CAA section 112, emissions 
standards for new sources must be no less stringent than the level 
``achieved'' by the best controlled similar source and for existing 
sources generally must be no less stringent than the average emission 
limitation ``achieved'' by the best performing 12 percent of sources in 
the category. There is nothing in CAA section 112 that directs the 
Agency to consider malfunctions in determining the level ``achieved'' 
by the best performing sources when setting emission standards. As the 
Court has recognized, the phrase ``average emissions limitation 
achieved by the best performing 12 percent of'' sources ``says nothing 
about how the performance of the best units is to be calculated.'' 
Nat'l Ass'n of Clean Water Agencies v. EPA, 734 F.3d 1115, 1141 (D.C. 
Cir. 2013). While the EPA accounts for variability in setting emissions 
standards, nothing in CAA section 112 requires the Agency to consider 
malfunctions as part of that analysis. The EPA is not required to treat 
a malfunction in the same manner as the type of variation in 
performance that occurs during routine operations of a source. A 
malfunction is a failure of the source to perform in a ``normal or 
usual manner'' and no statutory language compels the EPA to consider 
such events in setting CAA section 112 standards.
    As the Court recognized in U.S. Sugar Corp, accounting for 
malfunctions in setting standards would be difficult, if not 
impossible, given the myriad different types of malfunctions that can 
occur across all sources in the category and given the difficulties 
associated with predicting or accounting for the frequency, degree, and 
duration of various malfunctions that might occur. Id. at 608 (``the 
EPA would have to conceive of a standard that could apply equally to 
the wide range of possible boiler malfunctions, ranging from an 
explosion to minor mechanical defects. Any possible standard is likely 
to be hopelessly generic to govern such a wide array of 
circumstances.'') As such, the performance of units that are 
malfunctioning is not ``reasonably'' foreseeable. See, e.g. Sierra Club 
v. EPA, 167 F.3d 658, 662 (D.C. Cir. 1999) (``The EPA typically has 
wide latitude in determining the extent of data-gathering necessary to 
solve a problem. We generally defer to an agency's decision to proceed 
on the basis of imperfect scientific information, rather than to 
`invest the resources to conduct the perfect study.' '') See also, 
Weyerhaeuser v. Costle, 590 F.2d 1011, 1058 (D.C. Cir. 1978) (``In the 
nature of things, no general limit, individual permit, or even any 
upset provision can anticipate all upset situations. After a certain 
point, the transgression of regulatory limits caused by `uncontrollable 
acts of third parties,' such as strikes, sabotage, operator 
intoxication or insanity, and a variety of other eventualities, must be 
a matter for the administrative exercise of case-by-case enforcement 
discretion, not for specification in advance by regulation.''). In 
addition, emissions during a malfunction event can be significantly 
higher than emissions at any other time of source operation. For 
example, if an air pollution control device with 99-percent removal 
goes off-line as a result of a malfunction (as might happen if, for 
example, the bags in a baghouse catch fire) and the emission unit is a 
steady state type unit that would take days to shut down, the source 
would go from 99-percent control to zero control until the control 
device was repaired. The source's emissions during the malfunction 
would be 100 times higher than during normal operations. As such, the 
emissions over a 4-day malfunction period would exceed the annual 
emissions of the source during normal

[[Page 15065]]

operations. As this example illustrates, accounting for malfunctions 
could lead to standards that are not reflective of (and significantly 
less stringent than) levels that are achieved by a well-performing non-
malfunctioning source. It is reasonable to interpret CAA section 112 to 
avoid such a result. The EPA's approach to malfunctions is consistent 
with CAA section 112 and is a reasonable interpretation of the statute.
    Although no statutory language compels the EPA to set standards for 
malfunctions, the EPA has the discretion to do so where feasible. For 
example, in the Petroleum Refinery Sector RTR, the EPA established a 
work practice standard for unique types of malfunction that result in 
releases from pressure relief devises or emergency flaring events 
because the EPA had information to determine that such work practices 
reflected the level of control that applies to the best performers. 80 
FR 75178, 75211-14 (December 1, 2015). The EPA will consider whether 
circumstances warrant setting standards for a particular type of 
malfunction and, if so, whether the EPA has sufficient information to 
identify the relevant best performing sources and establish a standard 
for such malfunctions. We also encourage commenters to provide any such 
information.
    In the event that a source fails to comply with the applicable CAA 
section 112(d) standards as a result of a malfunction event, the EPA 
would determine an appropriate response based on, among other things, 
the good faith efforts of the source to minimize emissions during 
malfunction periods, including preventative and corrective actions, as 
well as root cause analyses to ascertain and rectify excess emissions. 
The EPA would also consider whether the source's failure to comply with 
the CAA section 112(d) standard was, in fact, sudden, infrequent, not 
reasonably preventable, and was not instead caused, in part, by poor 
maintenance or careless operation. 40 CFR 63.2 (definition of 
malfunction).
    If the EPA determines in a particular case that an enforcement 
action against a source for violation of an emission standard is 
warranted, the source can raise any and all defenses in that 
enforcement action and the federal district court will determine what, 
if any, relief is appropriate. The same is true for citizen enforcement 
actions. Similarly, the presiding officer in an administrative 
proceeding can consider any defense raised and determine whether 
administrative penalties are appropriate.
    In summary, the EPA interpretation of the CAA and, in particular, 
CAA section 112 is reasonable and encourages practices that will avoid 
malfunctions. Administrative and judicial procedures for addressing 
exceedances of the standards fully recognize that violations may occur 
despite good faith efforts to comply and can accommodate those 
situations. U.S. Sugar Corp. v. EPA, 830 F.3d 579, 606-610 (2016).
a. 40 CFR 63.6105 General Duty
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.6(e)(1)(i) by changing the ``yes'' in column 3 to a 
``no.'' Section 63.6(e)(1)(i) describes the general duty to minimize 
emissions. Some of the language in that section is no longer necessary 
or appropriate in light of the elimination of the SSM exemption. We are 
proposing instead to add general duty regulatory text at 40 CFR 63.6105 
that reflects the general duty to minimize emissions while eliminating 
the reference to periods covered by an SSM exemption. The current 
language in 40 CFR 63.6(e)(1)(i) characterizes what the general duty 
entails during periods of SSM. With the elimination of the SSM 
exemption, there is no need to differentiate between normal operations, 
startup and shutdown, and malfunction events in describing the general 
duty. Therefore, the language the EPA is proposing for 40 CFR 63.6105 
does not include that language from 40 CFR 63.6(e)(1).
    We are also proposing to revise the General Provisions table (Table 
7) entry for 40 CFR 63.6(e)(1)(ii) by changing the ``yes'' in column 3 
to a ``no.'' Section 63.6(e)(1)(ii) imposes requirements that are not 
necessary with the elimination of the SSM exemption or are redundant 
with the general duty requirement being added at 40 CFR 63.6105. We are 
also proposing to revise the General Provisions table (Table 7) to add 
an entry for 40 CFR 63.6(e)(1)(iii) and include a ``yes'' in column 3.
b. SSM Plan
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.6(e)(3) by changing the ``yes'' in column 3 to a 
``no.'' Generally, these paragraphs require development of an SSM plan 
and specify SSM recordkeeping and reporting requirements related to the 
SSM plan. As noted, the EPA is proposing to remove the SSM exemptions. 
Therefore, affected units will be subject to an emission standard 
during such events. The applicability of a standard during such events 
will ensure that sources have ample incentive to plan for and achieve 
compliance and, thus, the SSM plan requirements are no longer 
necessary.
c. Compliance With Standards
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.6(f)(1) by changing the ``yes'' in column 3 to a 
``no.'' The current language of 40 CFR 63.6(f)(1) exempts sources from 
non-opacity standards during periods of SSM. As discussed above, the 
Court in Sierra Club vacated the exemptions contained in this provision 
and held that the CAA requires that some CAA section 112 standards 
apply continuously. Consistent with Sierra Club, the EPA is proposing 
to revise standards in this rule to apply at all times.
d. 40 CFR 63.6120 Performance Testing
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.7(e)(1) by changing the ``yes'' in column 3 to a 
``no.'' Section 63.7(e)(1) describes performance testing requirements. 
The EPA is instead proposing to add a performance testing requirement 
at 40 CFR 63.6120(c). The performance testing requirements we are 
proposing to add differ from the General Provisions performance testing 
provisions in several respects. The regulatory text does not include 
the language in 40 CFR 63.7(e)(1) that restated the SSM exemption and 
language that precluded startup and shutdown periods from being 
considered ``representative'' for purposes of performance testing. The 
proposed performance testing provisions specify that representative 
conditions exclude periods of startup and shutdown. As in 40 CFR 
63.7(e)(1), performance tests conducted under this subpart should not 
be conducted during malfunctions because conditions during malfunctions 
are often not representative of normal operating conditions. The EPA is 
proposing to add language that requires the owner or operator to record 
the process information that is necessary to document operating 
conditions during the test and include in such record an explanation to 
support that such conditions represent normal operation. Section 
63.7(e) requires that the owner or operator make available to the 
Administrator such records ``as may be necessary to determine the 
condition of the performance test'' available to the Administrator upon 
request, but does not specifically require the information to be 
recorded. The regulatory text the EPA is proposing to add to this 
provision builds on that requirement

[[Page 15066]]

and makes explicit the requirement to record the information.
e. Monitoring
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.8(c)(1)(i) and (iii) by changing the ``yes'' in 
column 3 to a ``no.'' The cross-references to the general duty and SSM 
plan requirements in those subparagraphs are not necessary in light of 
other requirements of 40 CFR 63.8 that require good air pollution 
control practices (40 CFR 63.8(c)(1)) and that set out the requirements 
of a quality control program for monitoring equipment (40 CFR 63.8(d)).
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.8(d)(3) by changing the ``yes'' in column 3 to a 
``no.'' The final sentence in 40 CFR 63.8(d)(3) refers to the General 
Provisions' SSM plan requirement which is no longer applicable. The EPA 
is proposing to add to the rule at 40 CFR 63.6125(e) text that is 
identical to 40 CFR 63.8(d)(3) except that the final sentence is 
replaced with the following sentence: ``The program of corrective 
action should be included in the plan required under Sec.  
63.8(d)(2).''
f. 40 CFR 63.6155 Recordkeeping
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.10(b)(2)(i) by changing the ``yes'' in column 3 to 
a ``no.'' Section 63.10(b)(2)(i) describes the recordkeeping 
requirements during startup and shutdown. We are instead proposing to 
add recordkeeping requirements to 40 CFR 63.6155. When a source is 
subject to a different standard during startup, it will be important to 
know when such startup periods begin and end in order to determine 
compliance with the appropriate standard. Thus, the EPA is proposing to 
add language to 40 CFR 63.6155 requiring that sources subject to an 
emission standard during startup that differs from the emission 
standard that applies at all other times must report the date, time, 
and duration of such periods.
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.10(b)(2)(ii) by changing the ``yes'' in column 3 to 
a ``no.'' Section 63.10(b)(2)(ii) describes the recordkeeping 
requirements during a malfunction. The EPA is proposing to add such 
requirements to 40 CFR 63.6155. The regulatory text we are proposing to 
add differs from the General Provisions it is replacing in that the 
General Provisions requires the creation and retention of a record of 
the occurrence and duration of each malfunction of process, air 
pollution control, and monitoring equipment. The EPA is proposing that 
this requirement apply to any failure to meet an applicable standard 
and is requiring that the source record the date, time, and duration of 
the failure rather than the ``occurrence.'' The EPA is also proposing 
to add to 40 CFR 63.6155 a requirement that sources keep records that 
include a list of the affected source or equipment and actions taken to 
minimize emissions, an estimate of the quantity of each regulated 
pollutant emitted over the standard for which the source failed to meet 
the standard, and a description of the method used to estimate the 
emissions. Examples of such methods would include product-loss 
calculations, mass balance calculations, measurements when available, 
or engineering judgment based on known process parameters. The EPA is 
proposing to require that sources keep records of this information to 
ensure that there is adequate information to allow the EPA to determine 
the severity of any failure to meet a standard, and to provide data 
that may document how the source met the general duty to minimize 
emissions when the source has failed to meet an applicable standard.
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.10(b)(2)(iv) by changing the ``yes'' in column 3 to 
a ``no.'' When applicable, the provision requires sources to record 
actions taken during SSM events when actions were inconsistent with 
their SSM plan. The requirement is no longer appropriate because SSM 
plans will no longer be required. The requirement previously applicable 
under 40 CFR 63.10(b)(2)(iv)(B) to record actions to minimize emissions 
and record corrective actions is now applicable by reference to 40 CFR 
63.6155(a)(7)(iii).
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.10(b)(2)(v) by changing the ``yes'' in column 3 to 
a ``no.'' When applicable, the provision requires sources to record 
actions taken during SSM events to show that actions taken were 
consistent with their SSM plan. The requirement is no longer 
appropriate because SSM plans will no longer be required.
    We are proposing to revise the General Provisions table (Table 7) 
entry for 40 CFR 63.10(c)(15) by changing the ``yes'' in column 3 to a 
``no.'' The EPA is proposing that 40 CFR 63.10(c)(15) no longer apply. 
When applicable, the provision allows an owner or operator to use the 
affected source's SSM plan or records kept to satisfy the recordkeeping 
requirements of the SSM plan, specified in 40 CFR 63.6(e), to also 
satisfy the requirements of 40 CFR 63.10(c)(10) through (12). The EPA 
is proposing to eliminate this requirement because SSM plans would no 
longer be required, and, therefore, 40 CFR 63.10(c)(15) no longer 
serves any useful purpose for affected units.
g. 40 CFR 63.6150 Reporting
    Section 63.10(d)(5) describes the reporting requirements for 
startups, shutdowns, and malfunctions. Currently the General Provisions 
table (Table 7) entry for 40 CFR 63.10(d)(5) in 40 CFR part 63, subpart 
YYYY, states that 40 CFR 63.10(d)(5) does not apply because reporting 
of SSM is not required. To replace the General Provisions reporting 
requirement, the EPA is proposing to add reporting requirements to 40 
CFR 63.6150. The replacement language differs from the General 
Provisions requirement in that it eliminates periodic SSM reports as a 
stand-alone report. We are proposing language that requires sources 
that fail to meet an applicable standard at any time to report the 
information concerning such events in the semiannual compliance report 
already required under this rule. We are proposing that the report must 
contain the number, date, time, duration, and the cause of such events 
(including unknown cause, if applicable), a list of the affected source 
or equipment, an estimate of the quantity of each regulated pollutant 
emitted over any emission limit, and a description of the method used 
to estimate the emissions.
    Examples of such methods would include product-loss calculations, 
mass balance calculations, measurements when available, or engineering 
judgment based on known process parameters. The EPA is proposing this 
requirement to ensure that there is adequate information to determine 
compliance, to allow the EPA to determine the severity of the failure 
to meet an applicable standard, and to provide data that may document 
how the source met the general duty to minimize emissions during a 
failure to meet an applicable standard.
    We will no longer require owners or operators to determine whether 
actions taken to correct a malfunction are consistent with an SSM plan, 
because plans would no longer be required. The proposed amendments, 
therefore, eliminate the cross reference to 40 CFR 63.10(d)(5)(i) that 
contains the description of the previously required SSM report format 
and submittal schedule from this section. These specifications are no 
longer necessary because the events will be reported in

[[Page 15067]]

otherwise required reports with similar format and submittal 
requirements.
2. Electronic Reporting
    Through this proposal, the EPA is proposing that owners and 
operators of stationary combustion turbine facilities submit electronic 
copies of required performance test results and semiannual compliance 
reports through the EPA's Central Data Exchange (CDX) using the 
Compliance and Emissions Data Reporting Interface (CEDRI). A 
description of the electronic data submission process is provided in 
the memorandum, Electronic Reporting Requirements for New Source 
Performance Standards (NSPS) and National Emission Standards for 
Hazardous Air Pollutants (NESHAP) Rules, available in Docket ID No. 
EPA-HQ-OAR-2017-0688. The proposed rule requires that performance test 
results collected using test methods that are supported by the EPA's 
Electronic Reporting Tool (ERT) as listed on the ERT website \22\ at 
the time of the test be submitted in the format generated through the 
use of the ERT and that other performance test results be submitted in 
portable document format (PDF) using the attachment module of the ERT. 
The test methods required by 40 CFR part 63, subpart YYYY that are 
currently supported by the ERT are EPA Methods 3A and 4 of 40 CFR part 
60, appendix A.
---------------------------------------------------------------------------

    \22\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
---------------------------------------------------------------------------

    For periodic compliance reports the proposed rule requires that 
owners and operators use the appropriate spreadsheet template to submit 
information to CEDRI. A draft version of the proposed template for 
these reports is included in the docket for this rulemaking.\23\ The 
EPA specifically requests comment on the content, layout, and overall 
design of the template.
---------------------------------------------------------------------------

    \23\ See 
Draft_Stationary_Combustion_Turbine_Semiannual_and_Annual_Report.xlsm
, available at Docket ID. No. EPA-HQ-OAR-2017-0688.
---------------------------------------------------------------------------

    Additionally, the EPA has identified two broad circumstances in 
which electronic reporting extensions may be provided. In both 
circumstances, the decision to accept the claim of needing additional 
time to report is within the discretion of the Administrator, and 
reporting should occur as soon as possible. The EPA is providing these 
potential extensions to protect owners and operators from noncompliance 
in cases where they cannot successfully submit a report by the 
reporting deadline for reasons outside of their control. The situation 
where an extension may be warranted due to outages of the EPA's CDX or 
CEDRI which precludes an owner or operator from accessing the system 
and submitting required reports is addressed in 40 CFR 63.6150(h). The 
situation where an extension may be warranted due to a force majeure 
event, which is defined as an event that will be or has been caused by 
circumstances beyond the control of the affected facility, its 
contractors, or any entity controlled by the affected facility that 
prevents an owner or operator from complying with the requirement to 
submit a report electronically as required by this rule is addressed in 
40 CFR 63.6150(i). Examples of such events are acts of nature, acts of 
war or terrorism, or equipment failure or safety hazards beyond the 
control of the facility.
    The electronic submittal of the reports addressed in this proposed 
rulemaking will increase the usefulness of the data contained in those 
reports, is in keeping with current trends in data availability and 
transparency, will further assist in the protection of public health 
and the environment, will improve compliance by facilitating the 
ability of regulated facilities to demonstrate compliance with 
requirements and by facilitating the ability of delegated state, local, 
tribal, and territorial air agencies and the EPA to assess and 
determine compliance, and will ultimately reduce burden on regulated 
facilities, delegated air agencies, and the EPA. Electronic reporting 
also eliminates paper-based, manual processes, thereby saving time and 
resources, simplifying data entry, eliminating redundancies, minimizing 
data reporting errors, and providing data quickly and accurately to the 
affected facilities, air agencies, the EPA, and the public. Moreover, 
electronic reporting is consistent with the EPA's plan \24\ to 
implement Executive Order 13563 and is in keeping with the EPA's 
Agency-wide policy \25\ developed in response to the White House's 
Digital Government Strategy.\26\ For more information on the benefits 
of electronic reporting, see the memorandum, Electronic Reporting 
Requirements for New Source Performance Standards (NSPS) and National 
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, 
available in Docket ID No. EPA-HQ-OAR-2017-0688.
---------------------------------------------------------------------------

    \24\ EPA's Final Plan for Periodic Retrospective Reviews, August 
2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \25\ E-Reporting Policy Statement for EPA Regulations, September 
2013. Available at: https://www.epa.gov/sites/production/files/2016-03/documents/epa-ereporting-policy-statement-2013-09-30.pdf.
    \26\ Digital Government: Building a 21st Century Platform to 
Better Serve the American People, May 2012. Available at: https://obamawhitehouse.archives.gov/sites/default/files/omb/egov/digital-government/digital-government.html.
---------------------------------------------------------------------------

3. Stay of Standards for Certain New Turbines
    In August 2002, the Gas Turbine Association submitted a petition to 
delist two subcategories of stationary combustion turbines under CAA 
section 112(c)(9)(B). The subcategories were lean premix firing natural 
gas with limited oil backup and a low-risk subcategory where facilities 
would make site-specific demonstrations regarding risk levels. 
Additional information supporting the petition was provided in February 
2003. On April 7, 2004, the EPA proposed to delist lean premix gas-
fired turbines as well as three additional subcategories that were 
determined to meet the criteria for delisting in CAA section 
112(c)(9)(B): Diffusion flame gas-fired, emergency, and turbines 
located on the North Slope of Alaska. At the same time, the EPA 
proposed to stay the effectiveness of the NESHAP for new lean premix 
gas-fired and diffusion flame gas-fired turbines to ``avoid wasteful 
and unwarranted expenditures on installation of emission controls which 
will not be required if the subcategories are delisted.'' The standards 
for new oil-fired turbines were not stayed and have been in effect.
    On August 18, 2004, the EPA finalized the stay of the effectiveness 
of the NESHAP for new lean premix gas-fired and diffusion flame gas-
fired turbines, pending the outcome of the proposed delisting. The EPA 
stated that it would lift the stay if the subcategories were not 
ultimately delisted, and turbines constructed after January 14, 2003, 
would then be subject to the final standards. Those turbines would be 
given the same time to demonstrate compliance as they would have if 
there had been no stay.
    In 2007, the Court held in NRDC v. EPA, 489 F.3d 1364 (D.C. Cir. 
2007) that the EPA had no authority to delist subcategories under CAA 
section 112(c)(9)(B). According to the court decision, only entire 
source categories can be delisted under CAA section 112(c)(9)(B). Based 
on the proposed results of the residual risk analysis, we do not at 
this time have information to support a conclusion that the entire 
Stationary Combustion Turbines source category currently meets the 
criteria for delisting in CAA section 112(c)(9)(B). The results of the 
inhalation risk assessment show that the maximum individual cancer risk 
for this source category is above 1-in-1 million. Consequently, the EPA 
is proposing to remove the stay of the standards for new

[[Page 15068]]

lean premix and diffusion flame gas-fired turbines.

E. What compliance dates are we proposing?

    The EPA is proposing that affected sources must comply with the 
proposed amendments for SSM and electronic reporting no later than 180 
days after the effective date of the final rule. (The final action is 
not expected to be a ``major rule'' as defined by 5 U.S.C. 804(2), so 
the effective date of the final rule will be the promulgation date as 
specified in CAA section 112(d)(10).) For affected sources, we are 
proposing changes that would impact ongoing compliance requirements for 
40 CFR part 63, subpart YYYY. As discussed elsewhere in this preamble, 
we are proposing to add a requirement that performance test results and 
semiannual compliance reports be submitted electronically, and we are 
proposing to change the requirements for periods of SSM by removing the 
exemption from the requirement to meet the emission standards during 
periods of SSM and proposing a work practice standard for startup. Our 
experience with similar industries that are required to convert 
reporting mechanisms to install necessary hardware and software, become 
familiar with the process of submitting performance test results and 
compliance reports electronically through the EPA's CEDRI, test these 
new electronic submission capabilities, and reliably employ electronic 
reporting shows that a time period of a minimum of 90 days, and, more 
typically, 180 days is generally necessary to successfully accomplish 
these revisions. Our experience with similar industries further shows 
that this sort of regulated facility generally requires a time period 
of 180 days to read and understand the amended rule requirements; to 
evaluate their operations to ensure that they can meet the standards 
during periods of startup and shutdown as defined in the rule and make 
any necessary adjustments; and to update their operation, maintenance, 
and monitoring plans to reflect the revised requirements. The EPA 
recognizes the confusion that multiple different compliance dates for 
individual requirements would create and the additional burden such an 
assortment of dates would impose. From our assessment of the timeframe 
needed for compliance with the entirety of the revised requirements, 
the EPA considers a period of 180 days to be the most expeditious 
compliance period practicable and, thus, is proposing that affected 
sources must be in compliance with the revised requirements within 180 
days of the regulation's effective date. We solicit comment on this 
proposed compliance period, and we specifically request submission of 
information from sources in this source category regarding specific 
actions that would need to be undertaken to comply with the proposed 
amended requirements and the time needed to make the adjustments for 
compliance with any of the revised requirements. We note that 
information provided may result in changes to the proposed compliance 
date. All affected facilities would have to continue to meet the 
current requirements of 40 CFR part 63, subpart YYYY, until the 
applicable compliance date of the amended rule.
    As discussed previously, the EPA is proposing to lift the stay of 
the effectiveness of the standards for new lean premix and diffusion 
flame gas-fired turbines that was promulgated in 2004. Turbines that 
are subject to the stay would be required to comply with all applicable 
regulatory requirements of 40 CFR part 63, subpart YYYY, immediately 
upon a final action to remove the stay. Required initial performance 
tests must be conducted within 180 calendar days after the effective 
date of a final action to remove the stay.

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    The EPA has identified 719 turbines at 242 facilities that are 
subject to the Stationary Combustion Turbine NESHAP. We are projecting 
39 new stationary combustion turbines at 26 facilities will become 
subject over the next 3 years. The 39 turbines include 36 natural gas-
fired units, 1 oil-fired unit, and 2 landfill gas or digester gas-fired 
units. More information about the number of projected turbines over the 
next 3 years can be found in the Projected Number of Turbine Units and 
Facilities Subject to the Stationary Combustion Turbine National 
Emission Standards for Hazardous Air (NESHAP) memorandum in the docket 
for this rulemaking.

B. What are the air quality impacts?

    The baseline emissions of HAP for 719 stationary combustion 
turbines at 242 facilities subject to 40 CFR part 63, subpart YYYY, are 
estimated to be 5,331 tpy. The HAP that is emitted in the largest 
quantity is formaldehyde. The proposed amendments will require turbines 
subject to the Stationary Combustion Turbine NESHAP to operate without 
the SSM exemption. We were unable to quantify emission reductions 
associated with eliminating the SSM exemption. However, eliminating the 
SSM exemption will reduce emissions by requiring facilities to meet the 
applicable standard during periods of SSM. We are not proposing any 
other revisions to the emission limits, so there are no other air 
quality impacts as a result of the proposed amendments.

C. What are the cost impacts?

    Owners and operators of stationary combustion turbines that are 
subject to the proposed amendments to 40 CFR part 63, subpart YYYY, 
will incur costs to review the final rule. Nationwide annual costs 
associated with reviewing the final rule are estimated to be a total of 
$77,437 for the first year after the final rule only, or approximately 
$320 per facility. We do not believe that the proposed amendments 
revising the SSM provisions and requiring electronic reporting will 
impose additional burden and may result in a cost savings.

D. What are the economic impacts?

    Economic impact analyses focus on changes in market prices and 
output levels. If changes in market prices and output levels in the 
primary markets are significant enough, impacts on other markets may 
also be examined. Both the magnitude of costs needed to comply with a 
proposed rule and the distribution of these costs among affected 
facilities can have a role in determining how the market will change in 
response to a proposed rule. The total costs associated with reviewing 
the final rule are estimated to be $77,437, or $320 per facility, for 
the first year after the final rule. These costs are not expected to 
result in a significant market impact, regardless of whether they are 
passed on to the purchaser or absorbed by the firms.

E. What are the benefits?

    The EPA is not proposing changes to the emission limits and 
estimates that the proposed changes to the SSM requirements and 
requirements for electronic reporting are not economically significant. 
Because these proposed amendments are not considered economically 
significant, as defined by Executive Order 12866, and because no 
emission reductions were projected, we did not estimate any benefits 
from reducing emissions.

VI. 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

[[Page 15069]]

analyses. We are specifically interested in receiving any improvements 
to the data used in the site-specific emissions profiles used for risk 
modeling. Such data should include supporting documentation in 
sufficient detail to allow characterization of the quality and 
representativeness of the data or information. Section VII of this 
preamble provides more information on submitting data.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses and 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, 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-2017-0688 (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.

VIII. 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 not a significant regulatory action and was, 
therefore, not submitted to the OMB for review.

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

    This action is not expected to be an Executive Order 13771 
regulatory action because this action is not significant under 
Executive Order 12866.

C. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have 
been submitted for approval to the OMB under the PRA. The Information 
Collection Request (ICR) document that the EPA prepared has been 
assigned EPA ICR number 1967.08. You can find a copy of the ICR in the 
docket for this rule, and it is briefly summarized here.
    The information is being collected to assure compliance with 40 CFR 
part 63, subpart YYYY. The information requirements are based on 
notification, recordkeeping, and reporting requirements in the NESHAP 
General Provisions (40 CFR part 63, subpart A), which are mandatory for 
all operators subject to national emissions standards. The information 
collection activities also include paperwork requirements associated 
with initial and annual compliance testing and parameter monitoring. 
The proposed amendments to the rule would eliminate the paperwork 
requirements associated with the SSM plan and recordkeeping of SSM 
events and require electronic submittal of performance test results and 
semiannual compliance reports. The proposed amendments to the rule 
would also lift the stay on the performance testing and notification, 
recordkeeping, and reporting requirements for new lean premix gas-fired 
turbines and diffusion flame gas-fired turbines. These recordkeeping 
and reporting requirements are specifically authorized by CAA section 
114 (42 U.S.C. 7414).
    Respondents/affected entities: Owners and operators of stationary 
combustion turbines subject to 40 CFR part 63, subpart YYYY.
    Respondent's obligation to respond: Mandatory (40 CFR part 63, 
subpart YYYY).
    Estimated number of respondents: 90 per year.
    Frequency of response: The frequency of responses varies depending 
on the burden item. Responses include one-time review of rule 
amendments, reports of annual performance tests, and semiannual 
compliance reports.
    Total estimated burden: 3,751 hours (per year). Burden is defined 
at 5 CFR 1320.3(b).
    Total estimated cost: $1,983,088 (per year), includes $1,735,494 
annualized capital or operation and maintenance costs.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates and any suggested methods for 
minimizing respondent burden to the EPA using the docket identified at 
the beginning of this rule. You may also send your ICR-related comments 
to OMB's Office of Information and Regulatory Affairs via email to 
[email protected], Attention: Desk Officer for the EPA. Since 
OMB is required to make a decision concerning the ICR between 30 and 60 
days after receipt, OMB must receive comments no later than May 13, 
2019. The EPA will respond to any ICR-related comments in the final 
rule.

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. The 
small entities subject to the requirements of this action are small 
energy companies or governmental jurisdictions. The Agency has 
determined that 11 small entities representing approximately 4 percent 
of the total number of entities subject to the proposal may experience 
an impact of less than 1 percent of revenues.

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

[[Page 15070]]

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. None of the stationary combustion turbines that 
have been identified as being affected by this proposed action are 
owned or operated by tribal governments or located within tribal lands. 
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 III.A and C and sections IV.A and B of this preamble, and 
further documented in the risk document.

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

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

J. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR 
Part 51

    This action involves technical standards. The EPA proposes to use 
ANSI/ASME PTC 19-10-1981 Part 10 (2010), ``Flue and Exhaust Gas 
Analyses'' manual portion only as an alternative to EPA Method 3B and 
incorporate the alternative method by reference. The ANSI/ASME PTC 19-
10-1981 Part 10 (2010) method incorporates both manual and instrumental 
methodologies for the determination of O2 content. The 
manual method segment of the O2 determination is performed 
through the absorption of O2. The method is reasonably 
available from the American Society of Mechanical Engineers at http://www.asme.org; by mail at Three Park Avenue, New York, NY 10016-5990; or 
by telephone at (800) 843-2763. The EPA proposes to use ASTM D6522-11, 
``Standard Test Method for the Determination of Nitrogen Oxides, Carbon 
Monoxide, and Oxygen Concentrations in Emissions from Natural Gas-Fired 
Reciprocating Engines, Combustion Turbines, Boilers and Process Heaters 
Using Portable Analyzers'' as an alternative to EPA Method 3A for 
turbines fueled by natural gas and incorporate the alternative method 
by reference. The ASTM D6522-11 method is an electrochemical cell based 
portable analyzer method which may be used for the determination of 
nitrogen oxides, carbon monoxide, and O2 in emission streams 
form stationary sources. Also, instead of the current ASTM D6348-12e1 
standard (``Determination of Gaseous Compounds by Extractive Direct 
Interface Fourier Transform (FTIR) Spectroscopy''), the Stationary 
Combustion Turbine NESHAP references ASTM D6348-03 as an alternative to 
EPA Method 320. We are proposing to update the NESHAP to reference the 
most current version of the method. When using the method, the test 
plan preparation and implementation requirements in Annexes A1 through 
A8 to ASTM D6348-12e1 are mandatory. The ASTM D6348-12e1 method is an 
extractive FTIR Spectroscopy-based field test method and is used to 
quantify gas phase concentrations of multiple target compounds in 
emission streams from stationary sources. The ASTM standards are 
reasonably available from the American Society for Testing and 
Materials, 100 Barr Harbor Drive, Post Office Box C700, West 
Conshohocken, PA 19428-2959. See http://www.astm.org/.
    The EPA identified an additional seven voluntary consensus 
standards (VCS) as being potentially applicable to this proposed rule. 
After reviewing the available standards, the EPA determined that the 
seven VCS would not be practical due to lack of equivalency, 
documentation, validation data, and other important technical and 
policy considerations. For further information, see the memorandum 
titled Voluntary Consensus Standard Results for National Emission 
Standards for Hazardous Air Pollutants: Stationary Combustion Turbines 
Risk and Technology, in the docket for this proposed rule.

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 IV.A of 
this preamble and the technical report, Risk and Technology Review 
Analysis of Demographic Factors for Populations Living Near Stationary 
Combustion Turbines Source Category Operations.

List of Subjects in 40 CFR Part 63

    Environmental protection, Air pollution control, Hazardous 
substances, Incorporation by reference, Reporting and recordkeeping 
requirements.

    Dated: April 2, 2019.
Andrew R. Wheeler,
Administrator.

    For the reasons stated in the preamble, the EPA proposes to amend 
title 40, chapter I, part 63 of the Code of the Federal Regulations as 
follows:

PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS 
FOR SOURCE CATEGORIES

0
1. The authority citation for part 63 continues to read as follows:

    Authority: 42 U.S.C. 7401 et seq.

Subpart A--General Provisions

0
2. Section 63.14 is amended by revising paragraphs (e)(1) and (h)(85), 
redesignating paragraphs (h)(94) through (111) as (h)(95) through 
(112), and adding new paragraph (h)(94) to read as follows.


Sec.  63.14  Incorporations by reference.

* * * * *
    (e) * * *
    (1) ANSI/ASME PTC 19.10-1981, Flue and Exhaust Gas Analyses [Part 
10, Instruments and Apparatus], issued August 31, 1981, IBR approved 
for Sec. Sec.  63.309(k), 63.457(k), 63.772(e) and (h), 63.865(b), 
63.1282(d) and (g), 63.1625(b), 63.3166(a), 63.3360(e), 63.3545(a), 
63.3555(a), 63.4166(a), 63.4362(a), 63.4766(a), 63.4965(a), 63.5160(d), 
table 4 to subpart UUUU, table 3 to subpart YYYY, 63.9307(c), 
63.9323(a), 63.11148(e), 63.11155(e), 63.11162(f), 63.11163(g), 
63.11410(j), 63.11551(a), 63.11646(a), and 63.11945, table 5 to subpart 
DDDDD, table 4 to subpart JJJJJ, table 4 to subpart KKKKK, tables 4 and 
5 to subpart UUUUU, table 1 to subpart ZZZZZ, and table 4 to subpart 
JJJJJJ.
* * * * *
    (h) * * *
    (85) ASTM D6348-12e1, Standard Test Method for Determination of

[[Page 15071]]

Gaseous Compounds by Extractive Direct Interface Fourier Transform 
Infrared (FTIR) Spectroscopy, Approved February 1, 2012, IBR approved 
for Sec.  63.1571(a) and table 3 to subpart YYYY.
* * * * *
    (94) ASTM D6522-11, Standard Test Method for Determination of 
Nitrogen Oxides, Carbon Monoxide, and Oxygen Concentrations in 
Emissions from Natural Gas-Fired Reciprocating Engines, Combustion 
Turbines, Boilers, and Process Heaters Using Portable Analyzers, IBR 
approved for table 3 to subpart YYYY.
* * * * *

Subpart YYYY--National Emission Standards for Hazardous Air 
Pollutants for Stationary Combustion Turbines


Sec.  63.6095  [Amended]

0
3. Section 63.6095 is amended by removing paragraph (d).
0
4. Section 63.6105 is amended by revising paragraphs (a) and (b) and 
adding paragraph (c) to read as follows:


Sec.  63.6105  What are my general requirements for complying with this 
subpart?

    (a) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], you must be in compliance with the emission 
limitations and operating limitations which apply to you at all times 
except during startup, shutdown, and malfunctions. After [DATE 180 DAYS 
AFTER PUBLICATION OF FINAL RULE IN THE Federal Register], you must be 
in compliance with the emission limitations, operating limitations, and 
other requirements in this subpart which apply to you at all times.
    (b) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], if you must comply with emission and operating 
limitations, you must operate and maintain your stationary combustion 
turbine, oxidation catalyst emission control device or other air 
pollution control equipment, and monitoring equipment in a manner 
consistent with good air pollution control practices for minimizing 
emissions at all times including during startup, shutdown, and 
malfunction.
    (c) After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], at all times, the owner or operator must operate and 
maintain any affected source, including associated air pollution 
control equipment and monitoring equipment, in a manner consistent with 
safety and good air pollution control practices for minimizing 
emissions. The general duty to minimize emissions does not require the 
owner or operator to make any further efforts to reduce emissions if 
levels required by the applicable standard have been achieved. 
Determination of whether a source is operating in compliance with 
operation and maintenance requirements will be based on information 
available to the Administrator which may include, but is not limited 
to, monitoring results, review of operation and maintenance procedures, 
review of operation and maintenance records, and inspection of the 
source.
0
5. Section 63.6110 is amended by revising paragraph (a) to read as 
follows:


Sec.  63.6110  By what date must I conduct the initial performance 
tests or other initial compliance demonstrations?

    (a) You must conduct the initial performance tests or other initial 
compliance demonstrations in Table 4 of this subpart that apply to you 
within 180 calendar days after the compliance date that is specified 
for your stationary combustion turbine in Sec.  63.6095 and according 
to the provisions in Sec.  63.7(a)(2). New or reconstructed stationary 
combustion turbines that are lean premix gas-fired stationary 
combustion turbines or diffusion flame gas-fired stationary combustion 
turbines that commenced construction before April 12, 2019 and were 
subject to the stay of the standards for gas-fired subcategories in 
Sec.  63.6095(d) that was finalized on August 18, 2004, must conduct 
the initial performance test within 180 calendar days after the date 
the stay in Sec.  63.6095(d) is removed from this subpart.
* * * * *
0
6. Section 63.6120 is amended by revising paragraphs (b) and (c) to 
read as follows:


Sec.  63.6120  What performance tests and other procedures must I use?

* * * * *
    (b) Each performance test must be conducted according to the 
requirements in Table 3 of this subpart. Before [DATE 181 DAYS AFTER 
PUBLICATION OF FINAL RULE IN THE Federal Register], each performance 
test must be conducted according to the requirements of the General 
Provisions at Sec.  63.7(e)(1).
    (c) Performance tests must be conducted at high load, defined as 
100 percent plus or minus 10 percent. Before [DATE 181 DAYS AFTER 
PUBLICATION OF FINAL RULE IN THE Federal Register], do not conduct 
performance tests or compliance evaluations during periods of startup, 
shutdown, or malfunction. After [DATE 180 DAYS AFTER PUBLICATION OF 
FINAL RULE IN THE Federal Register], performance tests shall be 
conducted under such conditions based on representative performance of 
the affected source for the period being tested. Representative 
conditions exclude periods of startup and shutdown. The owner or 
operator may not conduct performance tests during periods of 
malfunction. The owner or operator must record the process information 
that is necessary to document operating conditions during the test and 
include in such record an explanation to support that such conditions 
represent normal operation. Upon request, the owner or operator shall 
make available to the Administrator such records as may be necessary to 
determine the conditions of performance tests.
* * * * *
0
7. Section 63.6125 is amended by adding paragraph (e) to read as 
follows:


Sec.  63.6125  What are my monitor installation, operation, and 
maintenance requirements?

* * * * *
    (e) After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], if you are required to use a continuous monitoring 
system (CMS), you must develop and implement a CMS quality control 
program that included written procedures for CMS according to Sec.  
63.8(d)(1)-(2). You must keep these written procedures on record for 
the life of the affected source or until the affected source is no 
longer subject to the provisions of this part, to be made available for 
inspection, upon request, by the Administrator. If the performance 
evaluation plan is revised, the owner or operator shall keep previous 
(i.e., superseded) versions of the performance evaluation plan on 
record to be made available for inspection, upon request, by the 
Administrator, for a period of 5 years after each revision to the plan. 
The program of corrective action should be included in the plan 
required under Sec.  63.8(d)(2).
0
8. Section 63.6140 is amended by revising paragraph (c) to read as 
follows:


Sec.  63.6140  How do I demonstrate continuous compliance with the 
emission and operating limitations?

* * * * *
    (c) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], consistent with Sec. Sec.  63.6(e) and 63.7(e)(1), 
deviations that occur during a period of startup, shutdown, and 
malfunction are not

[[Page 15072]]

violations if you have operated your stationary combustion turbine in 
accordance with Sec.  63.6(e)(1)(i).
0
9. Section 63.6150 is amended by:
0
a. Revising paragraph (a) introductory text, paragraph (a)(4) 
introductory text, paragraph (c) introductory text, and paragraph (e) 
introductory text, and
0
b. Adding paragraphs (a)(5), (f), (g), (h) and (i).
    The revisions and additions read as follows:


Sec.  63.6150   What reports must I submit and when?

    (a) Compliance report. Anyone who owns or operates a stationary 
combustion turbine which must meet the emission limitation for 
formaldehyde must submit a semiannual compliance report according to 
Table 6 of this subpart. The semiannual compliance report must contain 
the information described in paragraphs (a)(1) through (5) of this 
section. The semiannual compliance report must be submitted by the 
dates specified in paragraphs (b)(1) through (5) of this section, 
unless the Administrator has approved a different schedule. After [DATE 
180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE Federal Register], you 
must submit all subsequent reports to the EPA following the procedure 
specified in paragraph (g) of this section.
* * * * *
    (4) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], for each deviation from an emission limitation, the 
compliance report must contain the information in paragraphs (a)(4)(i) 
through (iii) of this section.
* * * * *
    (5) After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], if a source fails to meet an applicable standard, 
report such events in the semiannual compliance report. Report the 
information specified in paragraphs (a)(5)(i) through (iv) of this 
section.
    (i) Report the number of failures to meet an applicable standard. 
For each instance, report the start date, start time, duration, and 
cause of each failure, and the corrective action taken.
    (ii) For each failure, the report must include a list of the 
affected sources or equipment, an estimate of the quantity of each 
regulated pollutant emitted over any emission limit, a description of 
the method used to estimate the emissions.
    (iii) Information on the number, duration, and cause for monitor 
downtime incidents (including unknown cause, if applicable), as 
applicable, and the corrective action taken.
    (iv) Report the total operating time of the affected source during 
the reporting period.
* * * * *
    (c) If you are operating as a stationary combustion turbine which 
fires landfill gas or digester gas equivalent to 10 percent or more of 
the gross heat input on an annual basis, or a stationary combustion 
turbine where gasified MSW is used to generate 10 percent or more of 
the gross heat input on an annual basis, you must submit an annual 
report according to Table 6 of this subpart by the date specified 
unless the Administrator has approved a different schedule, according 
to the information described in paragraphs (d)(1) through (5) of this 
section. You must report the data specified in (c)(1) through (3) of 
this section. After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN 
THE Federal Register], you must submit all subsequent reports to the 
EPA following the procedure specified in paragraph (g) of this section.
* * * * *
    (e) If you are operating a lean premix gas-fired stationary 
combustion turbine or a diffusion flame gas-fired stationary combustion 
turbine as defined by this subpart, and you use any quantity of 
distillate oil to fire any new or existing stationary combustion 
turbine which is located at the same major source, you must submit an 
annual report according to Table 6 of this subpart by the date 
specified unless the Administrator has approved a different schedule, 
according to the information described in paragraphs (d)(1) through (5) 
of this section. You must report the data specified in (e)(1) through 
(3) of this section. After [DATE 180 DAYS AFTER PUBLICATION OF FINAL 
RULE IN THE Federal Register], you must submit all subsequent reports 
to the EPA following the procedure specified in paragraph (g) of this 
section.
* * * * *
    (f) Performance test report. After [DATE 180 DAYS AFTER PUBLICATION 
OF FINAL RULE IN THE Federal Register], within 60 days after the date 
of completing each performance test required by this subpart, you must 
submit the results of the performance test (as specified in Sec.  
63.6145(f)) following the procedures specified in paragraphs (f)(1) 
through (3) of this section.
    (1) Data collected using test methods supported by the EPA's 
Electronic Reporting Tool (ERT) as listed on the EPA's ERT website 
(https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert) at the time of the test. Submit the results of the 
performance test to the EPA via the Compliance and Emissions Data 
Reporting Interface (CEDRI), which can be accessed through the EPA's 
Central Data Exchange (CDX) (https://cdx.epa.gov/). The data must be 
submitted in a file format generated through the use of the EPA's ERT. 
Alternatively, you may submit an electronic file consistent with the 
extensible markup language (XML) schema listed on the EPA's ERT 
website.
    (2) Data collected using test methods that are not supported by the 
EPA's ERT as listed on the EPA's ERT website at the time of the test. 
The results of the performance test must be included as an attachment 
in the ERT or an alternate electronic file consistent with the XML 
schema listed on the EPA's ERT website. Submit the ERT generated 
package or alternative file to the EPA via CEDRI.
    (3) Confidential business information. If you claim some of the 
information submitted under paragraph (f)(1) of this section is CBI, 
you must submit a complete file, including information claimed to be 
CBI, to the EPA. The file must be generated through the use of the 
EPA's ERT or an alternate electronic file consistent with the XML 
schema listed on the EPA's ERT website. Submit the file on a compact 
disc, flash drive, or other commonly used electronic storage medium and 
clearly mark the medium as CBI. Mail the electronic medium to U.S. EPA/
OAQPS/CORE CBI Office, Attention: Group Leader, Measurement Policy 
Group, MD C404-02, 4930 Old Page Rd., Durham, NC 27703. The same file 
with the CBI omitted must be submitted to the EPA via the EPA's CDX as 
described in paragraph (f)(1) of this section.
    (g) If you are required to submit reports following the procedure 
specified in this paragraph, you must submit reports to the EPA via 
CEDRI, which can be accessed through the EPA's (CDX) (https://cdx.epa.gov/). You must use the appropriate electronic report template 
on the CEDRI website (https://www.epa.gov/electronic-reporting-air-emissions/compliance-and-emissions-data-reporting-interface-cedri) for 
this subpart. The date report templates become available will be listed 
on the CEDRI website. The report must be submitted by the deadline 
specified in this subpart, regardless of the method in which the report 
is submitted. If you claim some of the information required to be 
submitted via CEDRI is confidential business

[[Page 15073]]

information (CBI), submit a complete report, including information 
claimed to be CBI, to the EPA. The report must be generated using the 
appropriate form on the CEDRI website. Submit the file on a compact 
disc, flash drive, or other commonly used electronic storage medium and 
clearly mark the medium as CBI. Mail the electronic medium to U.S. EPA/
OAQPS/CORE CBI Office, Attention: Group Leader, Measurement Policy 
Group, MD C404-02, 4930 Old Page Rd., Durham, NC 27703. The same file 
with the CBI omitted must be submitted to the EPA via the EPA's CDX as 
described earlier in this paragraph.
    (h) If you are required to electronically submit a report through 
CEDRI in the EPA's CDX, you may assert a claim of EPA system outage for 
failure to timely comply with the reporting requirement. To assert a 
claim of EPA system outage, you must meet the requirements outlined in 
paragraphs (h)(1) through (7) of this section.
    (1) You must have been or will be precluded from accessing CEDRI 
and submitting a required report within the time prescribed due to an 
outage of either the EPA's CEDRI or CDX systems.
    (2) The outage must have occurred within the period of time 
beginning five business days prior to the date that the submission is 
due.
    (3) The outage may be planned or unplanned.
    (4) You must submit notification to the Administrator in writing as 
soon as possible following the date you first knew, or through due 
diligence should have known, that the event may cause or has caused a 
delay in reporting.
    (5) You must provide to the Administrator a written description 
identifying:
    (i) The date(s) and time(s) when CDX or CEDRI was accessed and the 
system was unavailable;
    (ii) A rationale for attributing the delay in reporting beyond the 
regulatory deadline to EPA system outage;
    (iii) Measures taken or to be taken to minimize the delay in 
reporting; and
    (iv) The date by which you propose to report, or if you have 
already met the reporting requirement at the time of the notification, 
the date you reported.
    (6) The decision to accept the claim of EPA system outage and allow 
an extension to the reporting deadline is solely within the discretion 
of the Administrator.
    (7) In any circumstance, the report must be submitted 
electronically as soon as possible after the outage is resolved.
    (i) If you are required to electronically submit a report through 
CEDRI in the EPA's CDX, you may assert a claim of force majeure for 
failure to timely comply with the reporting requirement. To assert a 
claim of force majeure, you must meet the requirements outlined in 
paragraphs (i)(1) through (5) of this section.
    (1) You may submit a claim if a force majeure event is about to 
occur, occurs, or has occurred or there are lingering effects from such 
an event within the period of time beginning five business days prior 
to the date the submission is due. For the purposes of this section, a 
force majeure event is defined as an event that will be or has been 
caused by circumstances beyond the control of the affected facility, 
its contractors, or any entity controlled by the affected facility that 
prevents you from complying with the requirement to submit a report 
electronically within the time period prescribed. Examples of such 
events are acts of nature (e.g., hurricanes, earthquakes, or floods), 
acts of war or terrorism, or equipment failure or safety hazard beyond 
the control of the affected facility (e.g., large scale power outage).
    (2) You must submit notification to the Administrator in writing as 
soon as possible following the date you first knew, or through due 
diligence should have known, that the event may cause or has caused a 
delay in reporting.
    (3) You must provide to the Administrator:
    (i) A written description of the force majeure event;
    (ii) A rationale for attributing the delay in reporting beyond the 
regulatory deadline to the force majeure event;
    (iii) Measures taken or to be taken to minimize the delay in 
reporting; and
    (iv) The date by which you propose to report, or if you have 
already met the reporting requirement at the time of the notification, 
the date you reported.
    (4) The decision to accept the claim of force majeure and allow an 
extension to the reporting deadline is solely within the discretion of 
the Administrator.
    (5) In any circumstance, the reporting must occur as soon as 
possible after the force majeure event occurs.
0
10. Section 63.6155 is amended by revising paragraph (a) introductory 
text and paragraphs (a)(3) through (5) and adding paragraphs (a)(6), 
(a)(7), and (d) to read as follows:


Sec.  63.6155   What records must I keep?

    (a) You must keep the records as described in paragraphs (a)(1) 
through (7) of this section.
* * * * *
    (3) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], records of the occurrence and duration of each 
startup, shutdown, or malfunction as required in Sec.  63.10(b)(2)(i).
    (4) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], records of the occurrence and duration of each 
malfunction of the air pollution control equipment, if applicable, as 
required in Sec.  63.10(b)(2)(ii).
    (5) Records of all maintenance on the air pollution control 
equipment as required in Sec.  63.10(b)(2)(iii).
    (6) After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], records of the date, time, and duration of each 
startup period, recording the periods when the affected source was 
subject to the standard applicable to startup.
    (7) After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], keep records as follows.
    (i) In the event that an affected unit fails to meet an applicable 
standard, record the number of failures. For each failure record the 
date, time, cause, and duration of each failure.
    (ii) For each failure to meet an applicable standard, record and 
retain a list of the affected sources or equipment, an estimate of the 
quantity of each regulated pollutant emitted over any emission limit 
and a description of the method used to estimate the emissions.
    (iii) Record actions taken to minimize emissions in accordance with 
Sec.  63.6105(c), and any corrective actions taken to return the 
affected unit to its normal or usual manner of operation.
* * * * *
    (d) Any records required to be maintained by this part that are 
submitted electronically via the EPA's CEDRI may be maintained in 
electronic format. This ability to maintain electronic copies does not 
affect the requirement for facilities to make records, data, and 
reports available upon request to a delegated air agency or the EPA as 
part of an on-site compliance evaluation.
0
11. Section 63.6175 is amended by revising the definition for 
``Deviation'' to read as follows:


Sec.  63.6175   What definitions apply to this subpart?

* * * * *
    Deviation means any instance in which an affected source subject to 
this subpart, or an owner or operator of such a source:
    (1) Fails to meet any requirement or obligation established by this 
subpart, including but not limited to any emission limitation or 
operating limitation;

[[Page 15074]]

    (2) Fails to meet any term or condition that is adopted to 
implement an applicable requirement in this subpart and that is 
included in the operating permit for any affected source required to 
obtain such a permit;
    (3) Fails to meet any emission limitation or operating limitation 
in this subpart during malfunction, regardless of whether or not such 
failure is permitted by this subpart;
    (4) Before [DATE 181 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], fails to satisfy the general duty to minimize 
emissions established by Sec.  63.6(e)(1)(i), or
    (5) After [DATE 180 DAYS AFTER PUBLICATION OF FINAL RULE IN THE 
Federal Register], fails to satisfy the general duty to minimize 
emissions established by Sec.  63.6105.
* * * * *
0
12. Table 1 to Subpart YYYY of Part 63 is revised to read as follows:

Table 1 to Subpart YYYY of Part 63--Emission Limitations

    As stated in Sec.  63.6100, you must comply with the following 
emission limitations.

------------------------------------------------------------------------
   For each new or reconstructed
   stationary combustion turbine         You must meet the following
 described in Sec.   63.6100 which        emission limitations . . .
              is . . .
------------------------------------------------------------------------
1. a lean premix gas-fired           limit the concentration of
 stationary combustion turbine as     formaldehyde to 91 ppbvd or less
 defined in this subpart,             at 15 percent O2, except during
2. a lean premix oil-fired            turbine startup. During turbine
 stationary combustion turbine as     startup, you must minimize the
 defined in this subpart,             turbine's time spent at idle or
3. a diffusion flame gas-fired        holding at low load levels and
 stationary combustion turbine as     minimize the turbine's startup
 defined in this subpart, or          time to a period needed for
4. a diffusion flame oil-fired        appropriate and safe loading of
 stationary combustion turbine as     the turbine, not to exceed 1 hour
 defined in this subpart.             for simple cycle stationary
                                      combustion turbines and 3 hours
                                      for combined cycle stationary
                                      combustion turbines, after which
                                      time the formaldehyde emission
                                      limitation of 91 ppbvd or less at
                                      15 percent O2 applies.
------------------------------------------------------------------------

0
13. Table 3 to Subpart YYYY of Part 63 is revised to read as follows:

Table 3 to Subpart YYYY of Part 63--Requirements for Performance Tests 
and Initial Compliance Demonstrations

    As stated in Sec.  63.6120, you must comply with the following 
requirements for performance tests and initial compliance 
demonstrations.

------------------------------------------------------------------------
                                                      According to the
       You must . . .              Using . . .            following
                                                     requirements . . .
------------------------------------------------------------------------
a. demonstrate formaldehyde   Test Method 320 of    formaldehyde
 emissions meet the emission   40 CFR part 63,       concentration must
 limitations specified in      appendix A; ASTM      be corrected to 15
 Table 1 by a performance      D6348-12e1 \1\        percent O2, dry
 test initially and on an      provided that the     basis. Results of
 annual basis and.             test plan             this test consist
                               preparation and       of the average of
                               implementation        the three 1 hour
                               provisions of         runs. Test must be
                               Annexes A1 through    conducted within 10
                               A8 are followed and   percent of 100
                               the %R as             percent load.
                               determined in Annex
                               A5 is equal or
                               greater than 70%
                               and less than or
                               equal to 130%; \2\
                               or other methods
                               approved by the
                               Administrator.
b. select the sampling port   Method 1 or 1A of 40  if using an air
 location and the number of    CFR part 60,          pollution control
 traverse points and.          appendix A.           device, the
                                                     sampling site must
                                                     be located at the
                                                     outlet of the air
                                                     pollution control
                                                     device.
c. determine the O2           Method 3A or 3B of    measurements to
 concentration at the          40 CFR part 60,       determine O2
 sampling port location and.   appendix A; ANSI/     concentration must
                               ASME PTC 19-10-       be made at the same
                               1981\1\ (Part 10)     time as the
                               manual portion        performance test.
                               only; ASTM D6522-
                               11\1\ if the
                               turbine is fueled
                               by natural gas.
d. determine the moisture     Method 4 of 40 CFR    measurements to
 content at the sampling       part 60, appendix A   determine moisture
 port location for the         or Test Method 320    content must be
 purposes of correcting the    of 40 CFR part 63,    made at the same
 formaldehyde concentration    appendix A, or ASTM   time as the
 to a dry basis.               D6348-12e1 \1\.       performance test.
------------------------------------------------------------------------
\1\ Incorporated by reference, see Sec.   63.14.
\2\ The %R value for each compound must be reported in the test report,
  and all field measurements must be corrected with the calculated %R
  value for that compound using the following equation:
 Reported Results = ((Measured Concentration in Stack)/(%R)) x 100.

0
14. Table 7 to Subpart YYYY of Part 63 is revised to read as follows:

Table 7 to Subpart YYYY of Part 63--Applicability of General Provisions 
to Subpart YYYY

    You must comply with the applicable General Provisions 
requirements:

----------------------------------------------------------------------------------------------------------------
           Citation                     Subject             Applies to subpart YYYY            Explanation
----------------------------------------------------------------------------------------------------------------
Sec.   63.1..................  General applicability of  Yes..........................  Additional terms defined
                                the General Provisions.                                  in Sec.   63.6175.
Sec.   63.2..................  Definitions.............  Yes..........................  Additional terms defined
                                                                                         in Sec.   63.6175.
Sec.   63.3..................  Units and abbreviations.  Yes..........................

[[Page 15075]]

 
Sec.   63.4..................  Prohibited activities...  Yes..........................
Sec.   63.5..................  Construction and          Yes..........................
                                reconstruction.
Sec.   63.6(a)...............  Applicability...........  Yes..........................
Sec.   63.6(b)(1)-(4)........  Compliance dates for new  Yes..........................
                                and reconstructed
                                sources.
Sec.   63.6(b)(5)............  Notification............  Yes..........................
Sec.   63.6(b)(6)............  [Reserved]..............
Sec.   63.6(b)(7)............  Compliance dates for new  Yes..........................
                                and reconstructed area
                                sources that become
                                major.
Sec.   63.6(c)(1)-(2)........  Compliance dates for      Yes..........................
                                existing sources.
Sec.   63.6(c)(3)-(4)........  [Reserved]..............
Sec.   63.6(c)(5)............  Compliance dates for      Yes..........................
                                existing area sources
                                that become major.
Sec.   63.6(d)...............  [Reserved]..............
Sec.   63.6(e)(1)(i).........  General duty to minimize  Yes before [DATE 181 DAYS
                                emissions.                AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register]. See
                                                          Sec.   63.6105 for general
                                                          duty requirement.
Sec.   63.6(e)(1)(ii)........  Requirement to correct    Yes before [DATE 181 DAYS
                                malfunctions ASAP.        AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.6(e)(1)(iii).......  Operation and             Yes..........................
                                Maintenance
                                Requirements.
Sec.   63.6(e)(2)............  [Reserved]..............
Sec.   63.6(e)(3)............  SSMP....................  Yes before [DATE 181 DAYS
                                                          AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.6(f)(1)............  Applicability of          Yes before [DATE 181 DAYS
                                standards except during   AFTER PUBLICATION OF FINAL
                                startup, shutdown, or     RULE IN THE Federal
                                malfunction (SSM).        Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.6(f)(2)............  Methods for determining   Yes..........................
                                compliance.
Sec.   63.6(f)(3)............  Finding of compliance...  Yes..........................
Sec.   63.6(g)(1)-(3)........  Use of alternative        Yes..........................
                                standard.
Sec.   63.6(h)...............  Opacity and visible       No...........................  Subpart YYYY does not
                                emission standards.                                      contain opacity or
                                                                                         visible emission
                                                                                         standards.
Sec.   63.6(i)...............  Compliance extension      Yes..........................
                                procedures and criteria.
Sec.   63.6(j)...............  Presidential compliance   Yes..........................
                                exemption.
Sec.   63.7(a)(1)-(2)........  Performance test dates..  Yes..........................  Subpart YYYY contains
                                                                                         performance test dates
                                                                                         at Sec.   63.6110.
Sec.   63.7(a)(3)............  Section 114 authority...  Yes..........................
Sec.   63.7(b)(1)............  Notification of           Yes..........................
                                performance test.
Sec.   63.7(b)(2)............  Notification of           Yes..........................
                                rescheduling.
Sec.   63.7(c)...............  Quality assurance/test    Yes..........................
                                plan.
Sec.   63.7(d)...............  Testing facilities......  Yes..........................
Sec.   63.7(e)(1)............  Conditions for            Yes before [DATE 181 DAYS
                                conducting performance    AFTER PUBLICATION OF FINAL
                                tests.                    RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.7(e)(2)............  Conduct of performance    Yes..........................  Subpart YYYY specifies
                                tests and reduction of                                   test methods at Sec.
                                data.                                                    63.6120.
Sec.   63.7(e)(3)............  Test run duration.......  Yes..........................
Sec.   63.7(e)(4)............  Administrator may         Yes..........................
                                require other testing
                                under section 114 of
                                the CAA.
Sec.   63.7(f)...............  Alternative test method   Yes..........................
                                provisions.
Sec.   63.7(g)...............  Performance test data     Yes..........................
                                analysis,
                                recordkeeping, and
                                reporting.
Sec.   63.7(h)...............  Waiver of tests.........  Yes..........................
Sec.   63.8(a)(1)............  Applicability of          Yes..........................  Subpart YYYY contains
                                monitoring requirements.                                 specific requirements
                                                                                         for monitoring at Sec.
                                                                                          63.6125.
Sec.   63.8(a)(2)............  Performance               Yes..........................
                                specifications.
Sec.   63.8(a)(3)............  [Reserved]..............
Sec.   63.8(a)(4)............  Monitoring for control    No...........................
                                devices.
Sec.   63.8(b)(1)............  Monitoring..............  Yes..........................
Sec.   63.8(b)(2)-(3)........  Multiple effluents and    Yes..........................
                                multiple monitoring
                                systems.
Sec.   63.8(c)(1)............  Monitoring system         Yes..........................
                                operation and
                                maintenance.
Sec.   63.8(c)(1)(i).........  General duty to minimize  Yes before [DATE 181 DAYS
                                emissions and CMS         AFTER PUBLICATION OF FINAL
                                operation.                RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.8(c)(1)(ii)........  Parts for repair of CMS   Yes..........................
                                readily available.

[[Page 15076]]

 
Sec.   63.8(c)(1)(iii).......  Requirement to develop    Yes before [DATE 181 DAYS
                                SSM Plan for CMS.         AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.8(c)(2)-(3)........  Monitoring system         Yes..........................
                                installation.
Sec.   63.8(c)(4)............  Continuous monitoring     Yes..........................  Except that subpart YYYY
                                system (CMS)                                             does not require
                                requirements.                                            continuous opacity
                                                                                         monitoring systems
                                                                                         (COMS).
Sec.   63.8(c)(5)............  COMS minimum procedures.  No...........................
Sec.   63.8(c)(6)-(8)........  CMS requirements........  Yes..........................  Except that subpart YYYY
                                                                                         does not require COMS.
Sec.   63.8(d)(1)-(2)........  CMS quality control.....  Yes..........................
Sec.   63.8(d)(3)............  Written procedures for    Yes before [DATE 181 DAYS
                                CMS.                      AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.8(e)...............  CMS performance           Yes..........................  Except for Sec.
                                evaluation.                                              63.8(e)(5)(ii), which
                                                                                         applies to COMS.
Sec.   63.8(f)(1)-(5)........  Alternative monitoring    Yes..........................
                                method.
Sec.   63.8(f)(6)............  Alternative to relative   Yes..........................
                                accuracy test.
Sec.   63.8(g)...............  Data reduction..........  Yes..........................  Except that provisions
                                                                                         for COMS are not
                                                                                         applicable. Averaging
                                                                                         periods for
                                                                                         demonstrating
                                                                                         compliance are
                                                                                         specified at Sec.  Sec.
                                                                                           63.6135 and 63.6140.
Sec.   63.9(a)...............  Applicability and State   Yes..........................
                                delegation of
                                notification
                                requirements.
Sec.   63.9(b)(1)-(5)........  Initial notifications...  Yes..........................  Except that Sec.
                                                                                         63.9(b)(3) is reserved.
Sec.   63.9(c)...............  Request for compliance    Yes..........................
                                extension.
Sec.   63.9(d)...............  Notification of special   Yes..........................
                                compliance requirements
                                for new sources.
Sec.   63.9(e)...............  Notification of           Yes..........................
                                performance test.
Sec.   63.9(f)...............  Notification of visible   No...........................  Subpart YYYY does not
                                emissions/opacity test.                                  contain opacity or VE
                                                                                         standards.
Sec.   63.9(g)(1)............  Notification of           Yes..........................
                                performance evaluation.
Sec.   63.9(g)(2)............  Notification of use of    No...........................  Subpart YYYY does not
                                COMS data.                                               contain opacity or VE
                                                                                         standards.
Sec.   63.9(g)(3)............  Notification that         Yes..........................
                                criterion for
                                alternative to relative
                                accuracy test audit
                                (RATA) is exceeded.
Sec.   63.9(h)...............  Notification of           Yes..........................  Except that
                                compliance status.                                       notifications for
                                                                                         sources not conducting
                                                                                         performance tests are
                                                                                         due 30 days after
                                                                                         completion of
                                                                                         performance
                                                                                         evaluations. Sec.
                                                                                         63.9(h)(4) is reserved.
Sec.   63.9(i)...............  Adjustment of submittal   Yes..........................
                                deadlines.
Sec.   63.9(j)...............  Change in previous        Yes..........................
                                information.
Sec.   63.10(a)..............  Administrative            Yes..........................
                                provisions for
                                recordkeeping and
                                reporting.
Sec.   63.10(b)(1)...........  Record retention........  Yes..........................
Sec.   63.10(b)(2)(i)........  Recordkeeping of          Yes before [DATE 181 DAYS
                                occurrence and duration   AFTER PUBLICATION OF FINAL
                                of startups and           RULE IN THE Federal
                                shutdowns.                Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.10(b)(2)(ii).......  Recordkeeping of          Yes before [DATE 181 DAYS
                                failures to meet a        AFTER PUBLICATION OF FINAL
                                standard.                 RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register]. See
                                                          Sec.   63.6155 for
                                                          recordkeeping of (1) date,
                                                          time and duration; (2)
                                                          listing of affected source
                                                          or equipment, and an
                                                          estimate of the quantity of
                                                          each regulated pollutant
                                                          emitted over the standard;
                                                          and (3) actions to minimize
                                                          emissions and correct the
                                                          failure.
Sec.   63.10(b)(2)(iii)......  Maintenance records.....  Yes..........................
Sec.   63.10(b)(2)(iv)-(v)...  Records related to        Yes before [DATE 181 DAYS
                                actions during SSM.       AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.10(b)(2)(vi)-(xi)..  CMS records.............  Yes..........................
Sec.   63.10(b)(2)(xii)......  Record when under waiver  Yes..........................
Sec.   63.10(b)(2)(xiii).....  Records when using        Yes..........................
                                alternative to RATA.
Sec.   63.10(b)(2)(xiv)......  Records of supporting     Yes..........................
                                documentation.
Sec.   63.10(b)(3)...........  Records of applicability  Yes..........................
                                determination.
Sec.   63.10(c)(1)-(14)......  Additional records for    Yes..........................  Except that Sec.
                                sources using CMS.                                       63.10(c)(2)-(4) and (9)
                                                                                         are reserved.

[[Page 15077]]

 
Sec.   63.10(c)(15)..........  Use of SSM Plan.........  Yes before [DATE 181 DAYS
                                                          AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register].
                                                         No after [DATE 180 DAYS AFTER
                                                          PUBLICATION OF FINAL RULE IN
                                                          THE Federal Register].
Sec.   63.10(d)(1)...........  General reporting         Yes..........................
                                requirements.
Sec.   63.10(d)(2)...........  Report of performance     Yes..........................
                                test results.
Sec.   63.10(d)(3)...........  Reporting opacity or VE   No...........................  Subpart YYYY does not
                                observations.                                            contain opacity or VE
                                                                                         standards.
Sec.   63.10(d)(4)...........  Progress reports........  Yes..........................
Sec.   63.10(d)(5)...........  Startup, shutdown, and    No. After [DATE 180 DAYS
                                malfunction reports.      AFTER PUBLICATION OF FINAL
                                                          RULE IN THE Federal
                                                          Register], see 63.6150(a)
                                                          for malfunction reporting
                                                          requirements.
Sec.   63.10(e)(1) and (2)(i)  Additional CMS reports..  Yes..........................
Sec.   63.10(e)(2)(ii).......  COMS-related report.....  No...........................  Subpart YYYY does not
                                                                                         require COMS.
Sec.   63.10(e)(3)...........  Excess emissions and      Yes..........................
                                parameter exceedances
                                reports.
Sec.   63.10(e)(4)...........  Reporting COMS data.....  No...........................  Subpart YYYY does not
                                                                                         require COMS.
Sec.   63.10(f)..............  Waiver for recordkeeping  Yes..........................
                                and reporting.
Sec.   63.11.................  Flares..................  No...........................
Sec.   63.12.................  State authority and       Yes..........................
                                delegations.
Sec.   63.13.................  Addresses...............  Yes..........................
Sec.   63.14.................  Incorporation by          Yes..........................
                                reference.
Sec.   63.15.................  Availability of           Yes..........................
                                information.
----------------------------------------------------------------------------------------------------------------

[FR Doc. 2019-07024 Filed 4-11-19; 8:45 am]
 BILLING CODE 6560-50-P


