Document ID: EPA-HQ-OAR-2013-0691-0001
Agency: epa
Document Type: Proposed Rule
Title: Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements
Posted Date: 2015-03-23T04:00Z

[Federal Register Volume 80, Number 55 (Monday, March 23, 2015)]
[Unknown Section]
[Pages 15339-15474]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2015-06138]

[[Page 15339]]

Vol. 80

Monday,

No. 55

March 23, 2015

Part III

Environmental Protection Agency

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40 CFR Parts 50, 51, and 93

Fine Particulate Matter National Ambient Air Quality Standards: State 
Implementation Plan Requirements; Proposed Rule

  Federal Register / Vol. 80 , No. 55 / Monday, March 23, 2015 / 
Proposed Rules`  

[[Page 15340]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 50, 51, and 93

[EPA-HQ-OAR-2013-0691; FRL-9916-08-OAR]
RIN 2060-AQ48

Fine Particulate Matter National Ambient Air Quality Standards: 
State Implementation Plan Requirements

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing 
requirements that state, local and tribal air agencies would have to 
meet as they implement the current and future national ambient air 
quality standards (NAAQS) for fine particulate matter 
(PM2.5). Specifically, this notice provides details on how 
the EPA proposes that air agencies meet the statutory state 
implementation plan (SIP) requirements that apply to areas designated 
nonattainment for any PM2.5 NAAQS, such as: general 
requirements for attainment plan due dates and attainment dates; 
emissions inventories; attainment demonstrations; provisions for 
demonstrating reasonable further progress; quantitative milestones; 
contingency measures; and nonattainment New Source Review (NNSR) 
permitting programs, among other things. This proposed rule clarifies 
the specific attainment planning requirements that would apply to 
PM2.5 NAAQS nonattainment areas based on their 
classification (either Moderate or Serious), and the process for 
reclassifying Moderate areas to Serious. Additionally in this notice, 
the EPA is proposing to revoke the 1997 primary annual standard because 
the EPA revised the primary annual standard in 2012. The EPA first 
established the PM2.5 NAAQS in 1997, completed a review of 
those standards in 2006, and most recently completed a review of the 
PM2.5 NAAQS on December 14, 2012.

DATES: Comments. Comments must be received on or before May 22, 2015. 
Public Hearing. The EPA plans to hold one public hearing concerning the 
proposed rule in Washington, DC. The date, time and location will be 
announced separately. Please refer to SUPPLEMENTARY INFORMATION for 
additional information on the comment period and the public hearing. 
Information Collection Request. Under the Paperwork Reduction Act 
(PRA), comments on the information collection provisions are best 
assured of having full effect if the Office of Management and Budget 
(OMB) receives a copy of your comments on or before April 22, 2015.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2013-0691, by one of the following methods:
     http://www.regulations.gov. Follow the on-line 
instructions for submitting comments.
     Email: a-and-r-docket@epa.gov.
     Mail: Air and Radiation Docket and Information Center, 
Attention Docket ID No. EPA-HQ-OAR-2013-0691, Environmental Protection 
Agency, Mailcode: 28221T, 1200 Pennsylvania Avenue NW., Washington, DC 
20460. In addition, please mail a copy of your comments on the 
information collection (ICR) provisions to the Office of Information 
and Regulatory Affairs, Office of Management and Budget (OMB), Attn: 
Desk Officer for EPA, 725 17th Street NW., Washington, DC 20503.
     Hand Delivery: Air and Radiation Docket and Information 
Center, Attention Docket ID No. EPA-HQ-OAR-2013-0691, Environmental 
Protection Agency in the EPA Headquarters Library, Room No. 3334 in the 
EPA Docket Center, located at William Jefferson Clinton Building West, 
1301 Constitution Avenue NW., Washington, DC 20004. Such deliveries are 
only accepted during the Docket's normal hours of operation, and 
special arrangements should be made for delivery of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2013-0691. 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 http://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, 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 http://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 disk or CD-ROM 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 avoid the use of special characters, 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 http://www.epa.gov/epahome/dockets.htm. For additional instructions on 
submitting comments, go to the SUPPLEMENTARY INFORMATION section of 
this document.
    Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in http://www.regulations.gov or in hard copy at the Air and Radiation 
Docket and Information Center in the EPA Headquarters Library, Room No. 
3334 in the William Jefferson Clinton Building West, located at 1301 
Constitution Avenue NW., Washington, DC 20460. The Public Reading Room 
is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding 
legal holidays. The phone number for the Public Reading Room is (202) 
566-1744.

FOR FURTHER INFORMATION CONTACT: For general information on this 
proposed rule, contact Mr. Rich Damberg, Office of Air Quality Planning 
and Standards, U.S. Environmental Protection Agency, by phone at (919) 
541-5592 or by email at damberg.rich@epa.gov; or Ms. Megan Brachtl, 
Office of Air Quality Planning and Standards, U.S. Environmental 
Protection Agency, by phone at (919) 541-2648 or by email at 
brachtl.megan@epa.gov. For information on the public hearing, contact 
Ms. Pamela Long, Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, by phone at (919) 541-0641 or by email 
at long.pam@epa.gov. For information on the ICR, contact Mr. Butch 
Stackhouse, Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, by phone at (919) 541-5208 or by email 
at stackhouse.butch@epa.gov.

SUPPLEMENTARY INFORMATION: 

[[Page 15341]]

I. General Information

A. Preamble Glossary of Terms and Acronyms

    The following are abbreviations of terms used in the preamble.

AERR Air Emissions Reporting Rule
BACM Best Available Control Measures
BACT Best Available Control Technology
BART Best Available Retrofit Technology
BC Black Carbon
CAA Clean Air Act
CAIR Clean Air Interstate Rule
CAMx Comprehensive Air Quality Model with Extensions
CBI Confidential Business Information
CBSA Core-based Statistical Area
CDD Clean Data Determination
CFR Code of Federal Regulations
CMAQ Community Multi-Scale Air Quality Model
CSAPR Cross-State Air Pollution Rule
CSN Chemical Speciation Network
DOD Department of Defense
DOT Department of Transportation
EC Elemental Carbon
EGU Electric Generating Unit
EPA Environmental Protection Agency
Fe Iron
FEM Federal Equivalent Method
FIP Federal Implementation Plan
FRM Federal Reference Method
HCl Hydrogen Chloride
ICR Information Collection Request
LAER Lowest Achievable Emission Rate
MACT Maximum Achievable Control Technology
MATS Mercury and Air Toxics Standards
MSM Most Stringent Measures
MPO Metropolitan Planning Organization
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NAPAP National Acid Precipitation Assessment Program
NEI National Emissions Inventory
NESHAP National Emissions Standard for Hazardous Air Pollutants
NH3 Ammonia
NH4 Ammonium
NH4NO3 Ammonium Nitrate
NH4HSO4 Ammonium Bi-Sulfate
(NH4)2SO4 Ammonium Sulfate
NNSR Nonattainment New Source Review
NOX Nitrogen Oxides
NO3 Nitrate
NSPS New Source Performance Standards
O3 Ozone
OM Organic Mass
OMB Office of Management and Budget
PM Particulate Matter
PM2.5 Particulate Matter Equal to or Less than 2.5 
Microns in Diameter (Fine Particulate Matter)
PM10 Particulate Matter Equal to or Less than 10 Microns 
in Diameter
PRA Paperwork Reduction Act
PSD Prevention of Significant Deterioration
RACM Reasonably Available Control Measures
RACT Reasonably Available Control Technology
RFP Reasonable Further Progress
RICE Reciprocating Internal Combustion Engines
SIP State Implementation Plan
SOA Secondary Organic Aerosols
SO2 Sulfur Dioxide
SO4 Sulfate
TAR Tribal Authority Rule
TIP Tribal Implementation Plan
TIP Transportation Improvement Program
TSP Total Suspended Particles
[micro]m Micrometer (Micron)
VMT Vehicle Miles Traveled
VOC Volatile Organic Compounds

B. Does this action apply to me?

    Entities potentially affected directly by this proposed rule 
include state, local and tribal governments and air pollution control 
agencies responsible for attainment and maintenance of the NAAQS. 
Entities potentially affected indirectly by this proposed rule as 
regulated sources include owners and operators of sources that emit 
PM2.5, sulfur dioxide (SO2), oxides of nitrogen 
(NOX), volatile organic compounds (VOC) and/or ammonia 
(NH3). Others potentially affected indirectly by this 
proposed rule include members of the general public who live, work, or 
recreate in areas affected by elevated ambient PM2.5 levels 
in areas designated nonattainment for a PM2.5 NAAQS.

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

    1. Submitting CBI. Do not submit this information to the EPA 
through http://www.regulations.gov or email. Clearly mark the specific 
information that you claim to be CBI. For CBI in a disk or CD-ROM that 
you mail to the EPA, mark the outside of the disk or CD-ROM as CBI and 
then identify electronically within the disk or CD-ROM the specific 
information that is claimed as CBI. In addition to one complete version 
of the comment that includes information claimed as CBI, a copy of the 
comment that does not contain the information claimed as CBI must be 
submitted for inclusion in the public docket. Information so marked 
will not be disclosed except in accordance with procedures set forth in 
40 CFR part 2.
    2. Tips for preparing comments. When submitting comments, remember 
to:
     Identify the rulemaking by docket number and other 
identifying information (subject heading, Federal Register date and 
page number).
     Follow directions. The proposed rule may ask you to 
respond to specific questions or organize comments by referencing a 
Code of Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree, suggest alternatives 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used to support your comment.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
     Provide specific examples to illustrate your concerns 
wherever possible, and suggest alternatives.
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
     Make sure to submit your comments by the comment period 
deadline identified.

D. What information should I know about possible public hearings?

    For information pertaining to the one public hearing on this 
document, contact Ms. Pamela Long, Air Quality Policy Division, Office 
of Air Quality Planning and Standards (C504-03), Environmental 
Protection Agency, Research Triangle Park, North Carolina 27711; 
telephone number (919) 541-0641; fax number (919) 541-5509; email 
address: long.pam@epa.gov.

E. Where can I obtain a copy of this document and other related 
information?

    In addition to being available in the docket, an electronic copy of 
this Federal Register document will be posted at http://www.epa.gov/airquality/particlepollution/actions.html.

F. How is this Federal Register document organized?

    The information presented in this document is organized as follows:

I. General Information
    A. Preamble Glossary of Terms and Acronyms
    B. Does this action apply to me?
    C. What should I consider as I prepare my comments for the EPA?
    D. What information should I know about possible public 
hearings?
    E. Where can I obtain a copy of this document and other related 
information?
    F. How is this Federal Register document organized?
II. Background for Proposal
    A. Introduction
    B. Atmospheric Chemistry of PM2.5 and Its Precursors
    C. Historical Overview of PM2.5 NAAQS Setting and 
Implementation
    D. State Implementation Planning Process for PM2.5 
NAAQS
III. What is the EPA proposing with respect to the treatment of 
PM2.5 precursors in nonattainment area planning and 
permitting?
    A. Background
    B. Proposed Precursor Policy Options

[[Page 15342]]

    C. Technical Approaches for Demonstrating That a Precursor Does 
Not Need To Be Subject to Control Requirements
IV. What are the EPA's proposed requirements for Moderate area 
attainment plans?
    A. Plan Due Dates
    B. Emissions Inventory Requirements
    C. Pollutants To Be Addressed in the Plan
    D. Attainment Plan Control Strategy
    E. Modeling for Attainment Demonstrations
    F. RFP Requirements
    G. Quantitative Milestones
    H. Contingency Measures
    I. Attainment Dates
    J. Attainment Date Extensions
V. How would a PM2.5 Moderate nonattainment area be 
reclassified to Serious?
    A. Discretionary Authority
    B. Mandatory Duty
VI. What are the EPA's proposed requirements for Serious area 
attainment plans?
    A. Plan Due Dates
    B. Emissions Inventory Requirements
    C. Pollutants To Be Addressed in the Plan
    D. Attainment Plan Control Strategy
    E. Modeling for Attainment Demonstrations
    F. RFP Requirements
    G. Quantitative Milestones
    H. Contingency Measures
    I. Attainment Dates
    J. Attainment Date Extensions
VII. What are the EPA's proposed requirements for attainment plans 
under CAA section 189(d) for Serious areas that fail to attain the 
NAAQS by the applicable attainment date?
    A. Plan Due Dates
    B. Emissions Inventory Requirements
    C. Pollutants To Be Addressed in the Plan
    D. Attainment Plan Control Strategy
    E. Modeling for Attainment Demonstrations
    F. RFP Requirements
    G. Quantitative Milestones
    H. Contingency Measures
    I. Attainment Dates
VIII. What are the EPA's proposed NNSR permitting requirements?
    A. Statutory Requirements for NSR
    B. Federal NNSR Regulations
    C. What changes is the EPA proposing for NNSR for 
PM2.5 nonattainment areas?
    D. Plan Due Dates
    E. Avoidance of Dual Review for PSD and NNSR for 
PM2.5
IX. What other proposed requirements would apply in PM2.5 
nonattainment areas?
    A. Waivers Under Section 188(f)
    B. Conformity Requirements
    C. Clean Data Policy
    D. Section 179B/International Border Areas
    E. Enforcement and Compliance
    F. Efforts To Encourage a Multi-Pollutant Approach When 
Developing PM2.5 Attainment Plans
    G. Measures to Ensure Appropriate Protections for Overburdened 
Populations
    H. Tribal Issues
    I. Voluntary Programs for Reducing Ambient PM2.5
    J. Improved Stationary Source Emissions Monitoring
    K. Stationary Source Test Methods for Emissions of Condensable 
PM2.5
X. What is the EPA proposing with respect to revoking the 1997 
primary annual PM2.5 NAAQS?
    A. Background
    B. History of Revocation of Other NAAQS
    C. Proposed Options for Revocation and Related Anti-Backsliding 
Requirements for the 1997 Primary Annual PM2.5 NAAQS
    D. Discussion of Options
XI. Environmental Justice Considerations
XII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination with 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Determination Under Section 307(d)
Statutory Authority
List of Subjects

II. Background for Proposal

A. Introduction

    Ambient, or outdoor, air can contain a variety of pollutants, 
including particulate matter (PM). Airborne PM can be comprised of 
either solid or liquid particles, and can be a complex mixture of 
particles in both solid and liquid form. The most common constituents 
of airborne PM include: sulfate (SO4); nitrate 
(NO3); ammonium (NH4); elemental carbon (EC); 
organic mass (OM); and inorganic material, generally referred to as 
``crustal'' material, which can include metals, dust, sea salt and 
other trace elements. Airborne PM can be of different sizes, commonly 
referred to as ``coarse'' and ``fine'' particles. Fine particles, in 
general terms, are particulate matter with an aerodynamic diameter less 
than or equal to a nominal 2.5 micrometers ([mu]m). For this reason, 
particles of this size are referred to as PM2.5. 
PM2.5 particles commonly include ``primary'' particles and 
``secondary'' particles. Primary particles, or direct PM2.5, 
are emitted by sources directly into the air as solid or liquid 
particles (e.g., elemental carbon from diesel engines or wildfires, or 
condensable organic particles from gasoline engines). Secondary 
particles are formed in the atmosphere as a result of chemical 
reactions between specific pollutants known as PM2.5 
precursors (e.g., reactions between NOX and SO2 
emissions from mobile and stationary sources combined with ammonia to 
form NO3 and SO4).
    The human health effects associated with long- or short-term 
exposure to PM2.5 are significant and include premature 
mortality, aggravation of respiratory and cardiovascular disease (as 
indicated by increased hospital admissions and emergency room visits) 
and development of chronic respiratory disease. In addition, welfare 
effects associated with elevated PM2.5 levels include 
visibility impairment as well as effects on sensitive ecosystems, 
materials damage and soiling and climatic and radiative processes.\1\
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    \1\ For a complete discussion of the human health and welfare 
effects associated with exposure to elevated concentrations of 
particulate matter, see generally ``Integrated Science Assessment 
for Particulate Matter.'' U.S. Environmental Protection Agency, 
Office of Research and Development, National Center for 
Environmental Assessment-RTP Division, February 10, 2010. EPA/600/R-
08/139F. Available at: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_isa.html. See Chapter 2.
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    On December 14, 2012, the EPA made revisions to the suite of NAAQS 
for PM to provide requisite protection of public health and welfare 
with an adequate margin of safety. The EPA also made corresponding 
revisions to the data handling conventions for PM and the ambient air 
monitoring, reporting and network design requirements for PM. 
Specifically, the agency revised the primary annual PM2.5 
standard by lowering the level from 15.0 to 12.0 [mu]g/m\3\ to provide 
increased protection against health effects associated with long- and 
short-term PM2.5 exposures. The EPA did not revise the 
secondary annual PM2.5 standard which remains at 15.0 [mu]g/
m\3\.\2\ The EPA eliminated spatial averaging as part of the form of 
the PM2.5 annual standards to avoid potential 
disproportionate impacts on at-risk populations. In addition, the EPA 
retained the level and form of the primary and secondary 24-hour 
PM2.5 standards to continue to provide supplemental 
protection against health effects associated with short-term 
PM2.5 exposures. Although not directly relevant to this 
rulemaking with respect to the PM2.5 NAAQS, it should be 
noted that in December 2012, the EPA also did not revise the level or 
form of the

[[Page 15343]]

primary and secondary 24-hour PM10 standards, which remain 
at 150 [mu]g/m\3\.\3\
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    \2\ 78 FR 3086 (January 15, 2013).
    \3\ This proposed rulemaking is to develop implementation 
regulations with respect to the PM2.5 NAAQS. For the 
PM10 NAAQS, states and the EPA will continue to implement 
those NAAQS in accordance with the applicable statutory requirements 
of the Clean Air Act (CAA) and the EPA's existing guidance in the 
``The General Preamble for Implementation of Title I of the Clean 
Air Act (CAA) Amendments,'' 57 FR 13498 (April 16, 1992); and 
``State Implementation Plans for Serious PM-10 Nonattainment Areas: 
Addendum to the General Preamble for the Implementation of Title I 
of the Clean Air Act (CAA) Amendments,'' 59 FR 41998 (August 16, 
1994). Throughout this preamble, these documents will be referred to 
as the ``General Preamble'' and the ``Addendum,'' respectively.
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    Estimates show that attainment of the primary PM2.5 
standards will result in hundreds fewer premature deaths each year, 
prevent tens of thousands of hospital admissions each year and prevent 
hundreds of thousands of doctor visits, absences from work and school 
and respiratory illnesses in children annually.\4\ Attainment of the 
primary PM2.5 standards will have welfare co-benefits in 
addition to direct human health benefits. The term welfare co-benefits 
covers both environmental and societal benefits of reducing pollution, 
such as reductions in visibility impairment, materials damage and 
ecosystem damage.\5\
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    \4\ ``Regulatory Impact Analysis for the Final Revisions to the 
National Ambient Air Quality Standards for Particulate Matter.'' 
U.S. Environmental Protection Agency, Office of Air Quality and 
Planning Standards, Health and Environmental Impacts Division, 
February 28, 2013. EPA-452/R-12-005. See: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_2007_ria.html.
    \5\ Ibid.
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B. Atmospheric Chemistry of PM2.5 and Its Precursors

1. Overview
    In order to determine how to regulate sources of direct 
PM2.5 and PM2.5 precursors to attain the 
PM2.5 NAAQS in a given nonattainment area, it is necessary 
to understand the basic chemical processes that cause or contribute to 
the formation of ambient PM2.5. Accordingly, an 
understanding of these processes is necessary to design appropriate 
regulations for implementation of the PM2.5 NAAQS. Properly 
designed regulatory requirements will help to assure that the 
PM2.5 NAAQS are attained effectively and expeditiously in 
all areas.
    As noted earlier, the term PM2.5 refers to particles of 
solid and liquid material less than 2.5 microns in aerodynamic 
diameter.\6\ ``Primary'' PM2.5 is emitted directly from 
emissions sources or activities, such as from diesel fuel combustion, 
wood burning, construction activities or unpaved roads, and it includes 
both filterable and condensable particles.\7\ ``Secondary'' 
PM2.5 is formed as a result of emissions of certain 
precursor gases that undergo chemical reactions in the atmosphere. The 
principal precursor gases that contribute to secondary PM2.5 
formation are SO2, from the combustion of coal or other high 
sulfur fuels; NOX, from many types of fossil fuel 
combustion; VOC, from certain fuels, solvents and industrial processes; 
and ammonia, from sources such as animal feeding operations, wastewater 
treatment and fertilizer. Table 1 provides National Emissions Inventory 
(NEI) data for 2011 that represent nationwide anthropogenic emissions 
estimates for direct PM2.5 and the four main 
PM2.5 precursor gases from major source sectors.
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    \6\ The regulatory definition of PM2.5 includes 
particles with an upper 50 percent cut-point of 2.5[mu]m aerodynamic 
diameter (the 50 percent cut-point diameter is the diameter at which 
the sample collects 50 percent of the particles and rejects 50 
percent of the particles). PM2.5 particles have a 
penetration curve as measured by a reference method based on 
Appendix L of 40 CFR part 50 and designated in accordance with 40 
CFR part 53, by an equivalent method designed in accordance with 40 
CFR part 53, or by an approved regional method designated in 
accordance with Appendix C of 40 CFR part 58.
    \7\ Certain commercial or industrial activities involving high 
temperature processes (e.g., fuel combustion, metal processing, 
cooking operations) emit gaseous pollutants into the ambient air 
which rapidly condense into particle form. These ``condensable'' PM 
emissions exist almost entirely in the 2.5 or less micron range and 
can consist of organic material, sulfuric acid and metals.

                Table 1--Total Emissions of PM2.5 and Precursors for Major Sectors (in tons/year)
                           [Source: 2011 National Emissions Inventory (Version 1) \a\]
----------------------------------------------------------------------------------------------------------------
            Category               Direct PM2.5         SO2             NOX             VOC             NH3
----------------------------------------------------------------------------------------------------------------
Chemical and allied products....          16,464         125,768          49,867          79,236          23,044
Fuel combustion--electric                196,685       4,612,641       2,031,855          40,597          24,968
 generating utilities (EGUs)....
Fuel combustion --other.........         628,199         987,552       1,856,716         588,346          79,679
Other industrial................         273,857         185,859         348,561         328,222          53,039
Onroad mobile...................         208,629          28,969       5,785,570       2,413,026         119,654
Metals processing...............          48,451         144,630          70,655          34,277           1,140
Miscellaneous (mainly fire             4,489,694         219,318         434,547       5,810,566       3,934,405
 emissions, dust and some
 agricultural operations).......
Offroad mobile..................         207,543          92,036       3,133,798       2,159,368           3,270
Petroleum & related industries..          31,738         116,317         684,808       2,488,123           1,643
Solvent utilization.............           3,810             107             893       2,814,551             577
Storage and transport...........          20,098           9,109          19,079       1,221,185           5,734
Waste disposal and recycling....         172,144          16,842          83,469         131,777          68,281
----------------------------------------------------------------------------------------------------------------
\a\ For more details on the definitions of the emission categories listed in Table 1, see Sector/Tier crosswalk
  table for the 2011 NEI, available at: ftp://ftp.epa.gov/EmisInventory/2011/doc/scc_eis_crosswalk_2011neiv1.xlsx.

2. Composition and Sources of PM2.5 Constituents
    PM2.5 is a complex and highly variable mixture of 
particles, but the majority of PM2.5 by mass is often 
comprised of five constituents: (i) OM; (ii) EC; (iii) crustal 
material; (iv) ammonium sulfate 
((NH4)2SO4); and (v) ammonium nitrate 
(NH4NO3).\8\ The discussion that follows provides 
an overview of each of the five major components of PM2.5, 
all of which are known to contribute to ambient PM2.5 levels 
in areas throughout the U.S.\9\ Section II.B.3 provides more details on

[[Page 15344]]

the atmospheric chemistry involved in the formation of sulfate, nitrate 
and OM, to illustrate the importance of controlling emissions of 
PM2.5 precursors as part of any comprehensive strategy to 
reduce ambient PM2.5 levels in excess of the NAAQS. Section 
II.B.4 presents a brief overview of PM2.5 composition by 
region of the U.S.
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    \8\ Seinfeld J.H. and Pandis S.N., 2006. Atmospheric Chemistry 
and Physics: From Air Pollution to Climate Change. 2nd edition, J. 
Wiley, New York.
    \9\ U.S. Environmental Protection Agency, 2004. ``The Particle 
Pollution Report: Current Understanding of Air Quality and Emissions 
through 2003.'' Office of Air Quality Planning and Standards, 
Emissions, Monitoring, and Analysis Division, December 2004. 
Available at: http://www.epa.gov/airtrends/reports.html.
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    OM is the fraction of ambient PM2.5 with the most 
diverse chemical composition, containing potentially thousands of 
different organic compounds (i.e., those compounds containing carbon) 
composed primarily of carbon, hydrogen, oxygen and nitrogen. Both 
primary particles and secondary particles contribute to ambient OM 
concentrations, with combustion sources being the dominant type of 
emissions sources. Another portion of primary OM particles results from 
direct emissions of organic compounds from sources of incomplete 
combustion, such as gas and diesel engines. Secondary OM particle 
formation involves oxidation of both anthropogenic and biogenic (plant-
derived) VOC, and can involve other, more complex chemical reactions. 
Further details of the chemistry behind the formation of secondary OM, 
known more commonly as secondary organic aerosols (SOA), are described 
in Section II.B.3 of this preamble.
    EC refers to particulate carbon that has a graphitic molecular 
structure, and is sometimes referred to as ``black carbon'' (BC). It is 
emitted directly from emission sources and does not undergo any 
significant reactions with other gases in the atmosphere. EC particles 
result from primary emissions involving combustion, especially from 
diesel-fueled vehicles, but also from other processes involving the 
burning of fossil fuels. The latter includes anthropogenic sources such 
as boilers and waste disposal. In addition, some EC particles originate 
from biomass combustion such as from prescribed fires, wildfires and 
residential wood combustion.
    Crustal PM is comprised of particles of soil and oxides of metals 
from some industrial processes. Compounds comprised of elements such as 
silicon, aluminum, iron, calcium, titanium, magnesium and potassium, as 
well as oxygen, are major components.\10\ Sources of crustal 
PM2.5 include windblown dust, dust from mechanical 
resuspension (e.g. dust from construction activities or vehicles 
driving on unpaved roads) and some forms of combustion, especially of 
coal. Crustal PM2.5 comprised of elements, like iron (Fe), 
and their oxides can also be emitted from industrial sources.
---------------------------------------------------------------------------

    \10\ Appel, K.W., Pouliot, G.A., Simon, H., Sarwar, G., Pye, 
H.O.T., Napelenok, S.L., Akhtar, F., and Roselle, S.J., 2013. 
Evaluation of dust and trace metal estimates from the Community 
Multiscale Air Quality (CMAQ) model version 5.0, Geoscientific Model 
Development Discussions 61859-1899; Sorooshian, A., Shingler, T., 
Harpold, A., Feagles, C.W., Meixner, T., and Brooks, P.D., 2013. 
Aerosol and precipitation chemistry in the southwestern United 
States: spatiotemporal trends and interrelationships, Atmospheric 
Chemistry and Physics 13, 7361-7379.
---------------------------------------------------------------------------

    The remaining portion of ambient PM2.5 is mostly 
composed of SO4, NO3 and NH4, which 
react in the ambient air to form ammonium sulfate 
((NH4)2SO4) and ammonium nitrate 
(NH4NO3). Another common PM2.5 
particle is ammonium bi-sulfate (NH4HSO4). In 
some areas, less common ions such as chloride are also found in 
PM2.5 samples in the form of particles that include sodium 
chloride and ammonium chloride. Particle-bound water is often also 
associated with this fraction of PM2.5. Sulfate, nitrate and 
ammonium particles originate through both primary and secondary 
mechanisms, although the vast majority of these PM2.5 
particles are formed through secondary formation, as described in the 
following section.
3. Secondary Formation of PM2.5 From Gaseous Precursors
    a. Overview. The composition of PM2.5 is complex and 
highly variable due in part to the large contribution of secondary 
PM2.5 to total fine particle mass in most locations, and to 
the complexity of secondary particle formation processes. A large 
number of possible chemical reactions, often non-linear in nature, can 
convert the gases SO2, NOX, VOC and ammonia to 
PM2.5. Thus, these gases are precursors to PM2.5. 
A brief discussion of SO4, NO3 and SOA formation, 
as well as the role of ammonia in their formation, follows.
    b. SO4 formation. SO2 is emitted mostly from the 
combustion of fossil fuels in boilers operated by electric utilities 
and other industries, with less than 10 percent of SO2 
emissions nationwide coming from other industrial sources, such as oil 
refining and pulp and paper production.\11\ When SO2 
oxidizes it forms sulfuric acid, a highly corrosive compound toxic to 
humans and to ecosystems that contributes to acid deposition (acid 
rain). In the presence of ammonia, however, sulfuric acid will react to 
form (NH4)2SO4, a less acidic compound 
and one of the five major components of PM2.5. If there is 
not enough ammonia present to fully neutralize the sulfuric acid, part 
of it may convert to NH4HSO4, which is more 
acidic than (NH4)2SO4, but less so 
than sulfuric acid. There is a large amount of emerging scientific 
evidence that SO2 may also contribute to the formation of 
SOA from biogenic VOC emissions (see section later on SOA). Sulfate 
levels in the ambient air peak in summer months due to increased 
SO2 emissions, generally from electricity generating units, 
and from meteorological conditions that are conducive to sulfate 
formation.
---------------------------------------------------------------------------

    \11\ U.S. Environmental Protection Agency, 2013. ``2008 National 
Emissions Inventory: Review Analysis and Highlights.'' Office of Air 
Quality Planning and Standards, Air Quality Assessment Division, May 
2013. EPA-454/R-005. Available at: http://www.epa.gov/ttn/chief/net/2008report.pdf.
---------------------------------------------------------------------------

    c. NO3 formation. The main sources of NOX emissions are 
combustion of fossil fuel in boilers and mobile sources, accounting for 
more than 80 percent of national anthropogenic NOX emissions 
(based on the 2011 NEI), with boilers and electric generating units 
(EGUs) contributing about 27 percent and mobile sources contributing 56 
percent. Oxides of nitrogen react in the atmosphere to form nitric 
acid, another prime contributor to acid deposition in the environment. 
Nitric acid converts to ammonium nitrate, one of the five main 
components of PM2.5, in the presence of ammonia. Low 
temperatures and high relative humidity create ideal conditions for the 
formation of ammonium nitrate, typically leading to higher atmospheric 
levels in winter months and lower levels in summer months.\12\
---------------------------------------------------------------------------

    \12\ Carlton, A.G., Pinder, R.W., Bhave, P.B., Pouliout, G.A., 
2010. To What Extent Can Biogenic SOA Be Controlled, Environmental 
Science and Technology 44(9), 3376-80.
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    d. SOA formation. As discussed earlier, the OM component of ambient 
PM2.5 is a complex mixture of hundreds or even thousands of 
anthropogenic and biogenic organic compounds. These compounds are 
either emitted directly from sources (i.e., as ``primary'' 
PM2.5) or can be formed by reactions in the ambient air to 
make SOA (i.e., as ``secondary'' PM2.5).
    VOC (both anthropogenic and biogenic) are key precursors to the SOA 
component of PM2.5. The relative importance of these 
compounds in the formation of organic particles varies between 
geographic areas, depending upon local emission sources, atmospheric 
chemistry and season of the year. It should be further noted that not 
all inventoried VOC may be contributing to the formation of organic 
particles. For example, chemical reactions involving VOC are generally 
accelerated in warmer temperatures, and for this reason studies show 
that SOA typically comprises a higher

[[Page 15345]]

percentage of PM2.5 in the summer than in the winter.\13\
---------------------------------------------------------------------------

    \13\ Pandis S.N., Harley R.A., Cass G.R., and Seinfeld J.H., 
1992. Secondary Organic Aerosol Formation and Transport, Atmospheric 
Environment, 26, 2266-82.
---------------------------------------------------------------------------

    Anthropogenic sources of VOC include mobile sources, petrochemical 
manufacturing, oil and gas emissions and solvents.\14\ In addition, 
some biogenic VOC, emitted by vegetation such as trees, can also 
contribute significantly to SOA formation, especially in heavily 
forested areas, such as the southeastern U.S. It should be noted, 
however, that anthropogenic contributions to SOA are likely highest in 
the wintertime when biogenic SOA levels are lower; conversely, in the 
summertime, biogenic contributions to SOA are likely higher. Despite 
significant progress that has been made in understanding the origins 
and properties of SOA, it remains the least understood component of 
PM2.5 and continues to be a significant topic of research 
and investigation.
---------------------------------------------------------------------------

    \14\ Carlton, A.G., Bhave, P.B., Napelenok, S.L., Edney, E.O., 
Sarwar, G., Pinder, R.W., Pouliout, G.A., and Houyoux, M. (2010), 
Model Representation of Secondary Organic Aerosol in CMAQ4.7, 
Environmental Science and Technology 44(22), 8553-60.
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    e. Role of ammonia in sulfate, nitrate and SOA formation. Ammonia 
is a gaseous pollutant emitted by natural and anthropogenic sources. 
The EPA's 2011 NEI shows that the two main sources of ammonia emissions 
are fertilizer application (27 percent) and livestock raising (54 
percent). It should be noted that the 2011 NEI indicates that mobile 
sources in the aggregate contribute about 3 percent of nationwide 
ammonia emissions. Much of those emissions comes from catalytic 
converters installed on light-duty gasoline vehicles, which are 
designed to convert NOX to nitrogen (N2); 
however, some ammonia is formed as a secondary product during this 
process.
    As indicated earlier, ammonia plays an important role in 
neutralizing acids, such as sulfuric acid and nitric acid, in clouds, 
precipitation and particles. On the other hand, deposited ammonia can 
contribute to problems of eutrophication in water bodies due to its 
nutritive properties.\15\ Ammonia would not exist in particles if not 
for the presence of acidic species with which it can combine to form a 
particle. In the eastern U.S., sulfate, nitrate and the ammonium 
associated with them can together account for between roughly 30 
percent and 75 percent of the total PM2.5 mass in a given 
area. The ammonium portion by itself roughly accounts for between 5 
percent and 20 percent of the total PM2.5 mass in the 
East.\16\
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    \15\ Seinfeld, J.H. and Pandis, S.N. (1998), Atmospheric 
Chemistry and Physics: From Air Pollution to Climate Change, 1st 
edition, J. Wiley, New York.
    \16\ NARSTO, 2003. Particulate Matter Science for Policy Makers. 
A NARSTO Assessment. Parts 1 and 2. NARSTO. Management Office 
(Envair), Pasco, Washington. Available at: http://narsto.org/pm_science_assessment.
---------------------------------------------------------------------------

    f. Role of NOX in sulfate, nitrate and SOA formation. In addition 
to the contribution of NOX emissions to secondary 
particulate nitrate formation, NOX also reacts with 
anthropogenic and biogenic VOC that have an impact on secondary 
formation of organic compounds that make up SOA. NOX is thus 
involved in all secondary PM chemistry, not just in particulate nitrate 
formation.\17\
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    \17\ Carlton, A.G., Pinder, R.W., Bhave, P.B., and Pouliout, 
G.A., 2010. To what extent can Biogenic SOA be Controlled, 
Environmental Science and Technology 44(9), 3376-3380.
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4. Fine Particulate Composition By Location
    Table 2 shows regional 3-year mean concentrations (2009-2011) of 
PM2.5 and its main components at sites in the Chemical 
Speciation Network (CSN).\18\ In addition to the mean values for all 
sites in each region, the table includes the minimum and maximum 
observed PM2.5 and species concentrations for sites within 
each region. These data illustrate broad observed spatial patterns 
across the U.S. in PM2.5 concentrations and its composition. 
For example, PM2.5 concentrations are highest on average in 
the Central and West regions. Sulfate mass comprises a larger fraction 
of PM2.5 than nitrate mass in the northeastern U.S., whereas 
nitrate has a greater contribution than that of sulfate in the West. OM 
is the dominant component in all regions, with the highest 
concentrations of OM on average found in the West, Northwest and 
Southeast. On a percentage basis, the concentrations of EC and crustal 
material are relatively low throughout all regions of the U.S. compared 
to the other major PM2.5 components.
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    \18\ The organic matter (OM) values in Table 2 were calculated 
by multiplying the measured organic carbon (OC) concentrations by 
1.6 (Turpin and Lim (2001), Aerosol Science and Technology, 35, 602-
610). PM2.5 concentrations come from measurements of the 
Federal Reference/Equivalance Methods (FRM/FEM) rather than from the 
CSN PM2.5 measurement.
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    The composition of PM2.5 also varies between urban and 
rural areas. This is reflective of the distribution of urban and 
regional emission sources, atmospheric reactions and transport of fine 
particles. More details about the spatial distribution and origins of 
PM2.5 components can be found in the docket for this 
proposal.\19\
---------------------------------------------------------------------------

    \19\ Reff and Rao, Memo to the docket, 2013.

                                        Table 2--PM2.5 Chemical Composition Data at 2009-2011 Nonattainment Sites
                                                         [Source: EPA Speciation Trends Network]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                        Concentration ([mu]g/m\3\)
                    Region                                  Statistic            -----------------------------------------------------------------------
                                                                                      SOe         NO3         OM          EC          CrM        PM2.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
Central.......................................  Min ([mu]g/m\3\)................        1.46        0.3         2.73        0.31        0.01        8.92
                                                Mean ([mu]g/m\3\)...............        2.69        1.49        3.57        0.68        0.26       11.63
                                                Max ([mu]g/m\3\)................        4.19        3.34        4.81        1.1         1.0        13.51
                                                N...............................       61          61          50          50          61          42
East North Central............................  Min ([mu]g/m\3\)................        0.83        0.38        1.97        0.19        0.01        6.03
                                                Mean ([mu]g/m\3\)...............        1.68        1.8         2.84        0.48        0.19        9.86
                                                Max ([mu]g/m\3\)................        2.51        3.57        3.69        0.79        0.61       11.87
                                                N...............................       29          28          20          20          28          23
North East....................................  Min ([mu]g/m\3\)................        0.58        0.12        1.74        0.14        0           4.42
                                                Mean ([mu]g/m\3\)...............        2.06        0.97        3.14        0.69        0.17        9.33
                                                Max ([mu]g/m\3\)................        5.12        2.26        5.05        1.69        0.52       15.05
                                                N...............................       59          59          39          39          59          46
North West....................................  Min ([mu]g/m\3\)................        0.24        0.05        2.91        0.42        0.01        6.06
                                                Mean ([mu]g/m\3\)...............        0.54        0.4         5.02        0.81        0.15        8.33

[[Page 15346]]

 
                                                Max ([mu]g/m\3\)................        1.09        1.79        8.44        1.25        0.53       10.96
                                                N...............................       33          33          13          13          33          14
South.........................................  Min ([mu]g/m\3\)................        0.88        0.18        1.36        0.12        0.02        5.22
                                                Mean ([mu]g/m\3\)...............        2.06        0.8         3.32        0.57        0.5        10.05
                                                Max ([mu]g/m\3\)................        3.08        1.67        5.1         1.48        2.38       14.27
                                                N...............................       36          27          23          23          36          23
South East....................................  Min ([mu]g/m\3\)................        1.6         0.2         1.75        0.37        0.01        6.76
                                                Mean ([mu]g/m\3\)...............        2.39        0.53        4.12        0.63        0.26       10.77
                                                Max ([mu]g/m\3\)................        4.33        1.51        5.71        1.2         0.85       13.38
                                                N...............................       44          43          30          30          43          29
South West....................................  Min ([mu]g/m\3\)................        0.34        0.07        2.34        0.46        0.02        5.3
                                                Mean ([mu]g/m\3\)...............        0.63        0.49        3.01        0.7         0.5         7.93
                                                Max ([mu]g/m\3\)................        1.13        2.65        4.39        1.04        1.96        9.73
                                                N...............................       46          46          11          11          46          12
West..........................................  Min ([mu]g/m\3\)................        0.33        0.08        1.79        0.52        0.01        6.84
                                                Mean ([mu]g/m\3\)...............        0.9         1.4         5.22        0.85        0.32       11.49
                                                Max ([mu]g/m\3\)................        2.08        5.14       10.27        1.56        1.05       16.57
                                                N...............................       44          44          20          20          44          21
West North Central............................  Min ([mu]g/m\3\)................        0.29        0.06        1.22        0.09        0           3.23
                                                Mean ([mu]g/m\3\)...............        0.67        0.48        3.16        0.44        0.22        7.25
                                                Max ([mu]g/m\3\)................        1.79        2.02        8.28        1.21        0.53       13.72
                                                N...............................       30          30           7           7          30          10
--------------------------------------------------------------------------------------------------------------------------------------------------------

C. Historical Overview of PM2.5 NAAQS Setting and 
Implementation

    Sections 108 and 109 of the CAA govern the establishment, review 
and revision, as appropriate, of NAAQS for widespread pollutants 
emitted from numerous and diverse sources considered harmful to public 
health and the environment. The CAA requires two types of NAAQS: (i) 
Primary standards, which set limits to protect public health, including 
the health of at-risk populations; and (ii) secondary standards, which 
set limits to protect public welfare, including protection against 
visibility impairment, damage to animals, crops, vegetation and 
buildings.
    The EPA first promulgated annual and 24-hour NAAQS for 
PM2.5 in July 1997.\20\ Prior to that time, the EPA had 
addressed ambient particulate matter through other means, first by 
regulating ``total suspended particles'' (TSP) and then later by 
regulating PM10. After protracted litigation, the 1997 NAAQS 
for PM2.5 were upheld by the U.S. Court of Appeals for the 
District of Columbia Circuit in March 2002.\21\ The EPA subsequently 
promulgated designations for the 1997 PM2.5 NAAQS 
nationwide, and designated a number of areas as nonattainment for the 
1997 PM2.5 NAAQS, effective April 2005.\22\ In April 2007, 
the EPA issued a detailed implementation rule to assist states with the 
development of SIP submissions to meet attainment plan requirements for 
the 1997 NAAQS (the ``2007 PM2.5 Implementation Rule'').\23\ 
In May 2008, the EPA issued another rule to assist states with SIP 
submissions to meet the specific requirements for permitting programs 
for NNSR purposes in designated nonattainment areas (the ``2008 
PM2.5 NSR Rule'').\24\ The EPA premised both the 2007 
PM2.5 Implementation Rule and the 2008 PM2.5 NSR 
Rule on the EPA's interpretation of the statute that nonattainment 
areas for the PM2.5 NAAQS were subject solely to the general 
nonattainment plan requirements of subpart 1, part D of title I of the 
CAA (``subpart 1'').
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    \20\ 62 FR 38652 (July 18, 1997).
    \21\ For a complete summary of legal challenges and related 
court decisions on the PM NAAQS, see generally 78 FR 3086 (January 
15, 2013).
    \22\ 70 FR 944 (January 5, 2005).
    \23\ 72 FR 20583 (April 25, 2007).
    \24\ 73 FR 28231 (May 16, 2008).
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    Section 109(d)(1) of the CAA requires the EPA periodically to 
review the science upon which the standards are based and the standards 
themselves, and to revise the standards as may be appropriate. In 
October 2006, the EPA promulgated revisions to the suite of NAAQS for 
PM, and in particular the EPA revised the 24-hour PM2.5 
standards.\25\ In accordance with section 107(d), the EPA subsequently 
designated a number of areas as nonattainment for the revised 2006 24-
hour PM2.5 standards, effective December 2009.\26\ In March 
2012, the EPA issued a guidance document specifically to aid states in 
preparing their SIP submissions to meet attainment plan requirements 
for the 2006 24-hour PM2.5 NAAQS in designated nonattainment 
areas.\27\ The EPA's guidance for the 2006 PM2.5 NAAQS was 
based, in large part, on the requirements finalized in the 2007 
PM2.5 Implementation Rule, which the EPA based solely upon 
the statutory requirements of subpart 1.
---------------------------------------------------------------------------

    \25\ 71 FR 61144 (October 17, 2006).
    \26\ 74 FR 58688 (November 13, 2009).
    \27\ Memorandum of March 2, 2012 (withdrawn June 6, 2013), from 
Stephen D. Page, Director, Office of Air Quality Planning and 
Standards, to EPA Regional Air Directors, Regions I-X, 
``Implementation Guidance for the 2006 24-Hour Fine Particle 
(PM2.5) National Ambient Air Quality Standards (NAAQS).'' 
Available at: http://epa.gov/ttn/naaqs/pm/pm25_guide.html.
---------------------------------------------------------------------------

    The EPA initiated a review of the PM2.5 NAAQS in June 
2007, proposing revisions to the primary and secondary PM2.5 
NAAQS on June 29, 2012.\28\ The EPA issued its final rule on December 
14, 2012, in which it lowered the primary annual PM2.5 
standard from 15.0 [mu]g/m\3\ to 12.0 [mu]g/m\3\ to provide increased 
protection against health effects associated with long- and short-term 
fine particle exposures.\29\ The EPA also eliminated spatial averaging 
as part of the form of the annual standard to avoid potential 
disproportionate impacts on at-risk populations.\30\ The

[[Page 15347]]

EPA retained the level (35 [mu]g/m\3\) and form (98th percentile, 
averaged over 3 years) of the primary 24-hour PM2.5 
standard, as revised in 2006, to provide supplemental protection 
against health effects associated with short-term PM2.5 
exposures, especially in areas with high peak PM2.5 
concentrations.\31\ This suite of primary PM2.5 standards 
provides increased public health protection, including the health of 
at-risk populations which include children, older adults, persons with 
pre-existing health and lung disease and persons of lower socioeconomic 
status, against a broad range of PM2.5-related effects that 
include premature mortality, increased hospital admissions and 
emergency department visits and development of chronic respiratory 
disease.\32\ With regard to the secondary (welfare-based) standards, 
the EPA retained the existing annual PM2.5 standard of 15.0 
[mu]g/m\3\ and the existing 24-hour PM2.5 standard of 35 
[mu]g/m\3\ to protect against PM-related non-visibility welfare effects 
including ecological effects, effects on materials and climate impacts. 
In addition, the secondary 24-hour PM2.5 standard provides 
protection for PM-related visibility impairment.
---------------------------------------------------------------------------

    \28\ 77 FR 38890 (June 29, 2012).
    \29\ 78 FR 3086 (January 15, 2013).
    \30\ Spatial averaging of monitored ambient air quality data was 
a feature of the prior PM2.5 NAAQS monitoring regulations 
which had the potential for masking particularly high 
PM2.5 concentrations at certain monitored locations 
within nonattainment areas.
    \31\ 71 FR 61144 (October 17, 2006).
    \32\ General information regarding the health effects associated 
with PM2.5 exposures is available at: http://www.epa.gov/airquality/particlepollution/health.html. Additional information, 
such as the EPA's technical documents supporting the latest review 
of the standards, is available at: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_index.html.
---------------------------------------------------------------------------

    On January 4, 2013, shortly after the EPA promulgated the 2012 
revisions to the suite of PM NAAQS, the DC Circuit issued its decision 
in a challenge to the 2007 PM2.5 Implementation Rule and the 
2008 PM2.5 NSR Rule. In NRDC v. EPA, the court held that the 
EPA erred in implementing the 1997 PM2.5 NAAQS pursuant only 
to the general implementation requirements of subpart 1, rather than 
also to the implementation requirements specific to particulate matter 
(PM10) in subpart 4, part D of title I of the CAA (``subpart 
4'').\33\ The court reasoned that the plain meaning of the CAA requires 
implementation of the 1997 PM2.5 NAAQS under subpart 4 
because PM2.5 particles fall within the statutory definition 
of PM10 and are thus subject to the same statutory 
requirements. In addition, although the court stated that its decision 
that the EPA must implement the PM2.5 NAAQS pursuant to 
subpart 4 requirements meant that it did not have to reach decisions on 
other issues concerning the regulation of precursors to 
PM2.5, the court nonetheless noted that subpart 4 has 
specific requirements with respect to regulation of such precursors. As 
a result, the court remanded to the EPA both the 2007 PM2.5 
Implementation Rule and the 2008 PM2.5 NSR Rule, both of 
which were premised on the EPA's interpretation of the statute that 
subpart 1 was the only applicable subpart for the implementation of the 
1997 PM2.5 NAAQS. The court instructed the EPA ``to 
repromulgate these rules pursuant to Subpart 4 consistent with this 
opinion.'' Given the D.C. Circuit's opinion in NRDC v. EPA, the EPA 
withdrew its 2012 guidance document for the 2006 24-hour 
PM2.5 NAAQS in June 2013. Because the court had concluded 
that the EPA and states must implement the PM2.5 NAAQS 
consistent with the statutory requirements of subpart 4, the EPA 2012 
guidance for attainment plans for the 2006 PM2.5 NAAQS 
premised solely upon subpart 1 requirements was no longer appropriate.
---------------------------------------------------------------------------

    \33\ NRDC v. EPA, 706 F.3d 428 (D.C. Cir. 2013).
---------------------------------------------------------------------------

    The EPA intends to use this current rulemaking to accomplish 
multiple objectives. First, the EPA is taking this action to clarify 
how air agencies should meet the statutory SIP requirements that apply 
to areas designated nonattainment for any PM2.5 NAAQS under 
subparts 1 and 4. To this end, the EPA is proposing regulatory 
requirements that will be applicable to attainment plans for the 2012 
PM2.5 NAAQS and any future revisions of the PM2.5 
NAAQS, subject to revisions that may be necessary for implementation 
purposes in the future. Second, the EPA is taking this action to 
provide guidance, in addition to regulatory requirements, to assist air 
agencies in developing attainment plans for the 2012 PM2.5 
NAAQS and any future revisions of the PM2.5 NAAQS. Finally, 
the EPA is taking this action in response to the DC Circuit's remand of 
the 2007 PM2.5 Implementation Rule and the 2008 
PM2.5 NSR Rule. Through this rulemaking, the EPA intends to 
address requirements associated with states' ongoing implementation 
efforts for the 1997 and 2006 PM2.5 NAAQS. In the interim, 
the EPA will rely on the statutory attainment planning requirements 
\34\ contained in subparts 1 and 4 and on the EPA's General Preamble 
and Addendum for guidance on how to apply those requirements to current 
PM2.5 NAAQS nonattainment areas.
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    \34\ General Preamble, 57 FR 13498 (April 16, 1992).
---------------------------------------------------------------------------

D. State Implementation Planning Process for PM2.5 NAAQS

1. Overview
    The CAA establishes important roles both for state and tribal 
governments and for the EPA in implementing the NAAQS. In accordance 
with the principle of cooperative federalism, both state and tribal 
governments and the EPA have respective authorities and 
responsibilities under the CAA. At the outset, the EPA has the 
authority and responsibility to promulgate the NAAQS. In turn, state, 
local and tribal air agencies have the authority and primary 
responsibility for developing and implementing attainment plans that 
contain emission control measures needed to achieve the air quality 
standards in each nonattainment area, consistent with the requirements 
of the CAA. The EPA often assists air agencies by promulgating 
regulations or providing guidance for meeting implementation 
requirements and technical tools, including information on control 
measures.\35\ For example, the EPA intends this rulemaking to clarify 
the specific statutory requirements, and schedule for meeting those 
requirements, that state and tribal air pollution control agencies 
(``air agencies'') must address as they prepare SIP submissions for the 
PM2.5 standards in future.\36\
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    \35\ It is important to note that the EPA does not have a 
mandatory duty to promulgate an implementation rule for the 
PM2.5 NAAQS, and the obligations of state and tribal air 
agencies to develop and submit an attainment plan are independent 
obligations and not conditioned upon the EPA promulgating an 
implementation rule for the PM2.5 NAAQS.
    \36\ When the term ``state'' is used hereafter, it will refer 
generically to states, local air agencies, and tribal governments 
electing to be treated as states for the purposes of implementing 
the CAA. Of additional note is that the 1998 Tribal Authority Rule 
(TAR), which is found in 40 CFR part 49, which implements section 
301(d) of the CAA, provides that tribes be treated in the same 
manner as a state when implementing certain sections of the CAA. It 
gives tribes the option of developing tribal implementation plans 
(TIPs), but unlike states, tribes are not required to develop 
implementation plans. Section IX.I of this preamble provides further 
discussion of tribal issues.
---------------------------------------------------------------------------

    The EPA also promulgates nationally applicable control requirements 
and emission limits for many sources such as new motor vehicles, 
certain categories of new and modified major stationary sources and 
existing stationary sources of toxic air pollutants. These federal 
actions assist state and tribal air agencies by achieving emission 
reductions from certain categories of sources nationwide, which can 
help with local attainment needs in a given nonattainment area. In 
addition, the EPA has authority to address

[[Page 15348]]

interstate transport of pollutants, in the event that states fail to do 
so. Through this authority, the EPA has addressed regional transport of 
pollutants from upwind states to downwind states, and has previously 
done so for purposes of the PM2.5 NAAQS.\37\ In addition, 
the EPA has the authority and responsibility to review and take action 
to approve or disapprove submitted attainment plans based upon whether 
they meet applicable statutory and regulatory requirements, to provide 
funding and technical assistance to states and to initiate the process 
for imposition of sanctions and/or issue federal implementation plans 
(FIPs) when states fail to fulfill their CAA obligations. More 
information on area designations, the role of ambient air monitoring, 
the SIP development process and the role of federal measures in 
bringing an area into attainment is presented below.
---------------------------------------------------------------------------

    \37\ See 70 FR 25162 (May 12, 2005) and 76 FR 48208 (August 8, 
2011).
---------------------------------------------------------------------------

2. Initial Area Designations and Classifications
    The NAAQS implementation planning process begins with initial area 
designations, through which states and the EPA identify areas of the 
country that either meet or do not meet the new or revised NAAQS, along 
with identifying the nearby areas contributing to violations of the 
NAAQS. Section 107(d)(1) of the CAA requires that: ``By such date as 
the Administrator may reasonably require, but not later than 1 year 
after promulgation of a new or revised national ambient air quality 
standard for any pollutant under section 109, the Governor of each 
state shall . . . submit to the Administrator a list of all areas (or 
portions thereof) in the State'' that designates those areas as 
nonattainment, attainment, or unclassifiable.\38\ Thus, states are 
required to make their initial designation recommendations to the EPA 
by no later than 1 year after the promulgation of new or revised NAAQS. 
Section 107(d)(1)(B)(i) further provides: ``Upon promulgation or 
revision of a NAAQS, the Administrator shall promulgate the 
designations of all areas (or portions thereof) . . . as expeditiously 
as practicable, but in no case later than 2 years from the date of 
promulgation. Such period may be extended for up to 1 year in the event 
the Administrator has insufficient information to promulgate the 
designations.'' Thus, the EPA is required to promulgate the actual 
designations for all areas across the U.S. by no later than 2 years 
after the promulgation of any new or revised NAAQS, unless the EPA 
elects to take up to one additional year in situations where there is 
insufficient information. Under section 107(d)(1)(B)(ii), the EPA is 
authorized to modify the designations recommendations from the states, 
with respect to the designation of an area and the boundaries of an 
area, if the EPA deems that necessary. By no later than 120 days prior 
to promulgating final designations, the EPA is required to notify 
states of any intended modifications to their recommendations. States 
then have an opportunity to demonstrate to the EPA why the EPA's 
intended modification is inappropriate. Regardless of whether a state 
provides an initial designation recommendation for any area, the EPA 
must timely promulgate the designations it deems appropriate.\39\
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    \38\ While the CAA provides for ``designating'' with respect to 
the Governor's list, in the full context of the CAA section 107 it 
is clear that the Governor actually makes a recommendation, to which 
the EPA must respond using a specified process if the EPA does not 
accept the recommendation.
    \39\ While section 107 of the CAA specifically addresses states, 
the EPA is following the same process for tribes that choose to make 
a recommendation to the extent practicable, pursuant to section 
301(d) of the CAA regarding tribal authority, and the TAR. 63 FR 
7254 (February 12, 1998). To provide for clarity and consistency, 
the EPA issued a 2011 guidance memorandum for working with tribes 
during the designations process. Memorandum of December 20, 2011 
from Stephen D. Page, Director, Office of Air Quality Planning and 
Standards, to EPA Regional Administrators, Regions I-X re: 
``Guidance to Regions for Working with Tribes during the National 
Ambient Air Quality Standards (NAAQS) Designations Process.'' 
Available at: http://www.epa.gov/ttn/oarpg/t1/memoranda/20120117naaqsguidance.pdf.
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    Under subpart 4, the CAA provides for classification of 
PM2.5 nonattainment areas as either ``Moderate'' or 
``Serious.'' As provided in section 188(a) and reiterated in the 
General Preamble, all PM10 nonattainment areas and by 
extension all PM2.5 nonattainment areas are initially 
classified as Moderate by operation of law at the time of designation. 
Initial classifications are not subject to public notice-and-comment 
pursuant to section 107(d)(2)(B), although the EPA may elect to take 
comment on designations and classifications and its recent practice has 
been to do so.
    All areas designated as nonattainment for the 2012 PM2.5 
NAAQS and any future revised PM2.5 NAAQS will be initially 
classified as Moderate nonattainment areas upon designation, regardless 
of the severity of the PM2.5 problem in the area. This 
statutory approach to classifications for nonattainment areas under 
subpart 4 for the PM2.5 NAAQS is notably different from the 
approach for ozone NAAQS nonattainment areas under subpart 2 (of part 
D, title I of the CAA), wherein the statute includes several area 
classifications, and initial classifications are based on monitored 
ozone levels. Thus, unlike for ozone nonattainment areas, all 
PM2.5 nonattainment areas initially receive the same 
classification--Moderate--and the EPA only reclassifies such areas to 
Serious upon a showing by the state or a determination by the agency 
that the area cannot practicably attain by the statutory attainment 
date, or upon a finding that the area in fact failed to attain the 
NAAQS by the applicable Moderate area attainment date. The statute 
requires that Moderate nonattainment areas attain the NAAQS as 
expeditiously as practicable, but not later than the end of the sixth 
calendar year following designation. States have an incentive to avoid 
having a Moderate area reclassified to Serious because, as discussed 
later in this preamble, the specific subpart 4 requirements for areas 
classified as Serious include, among other things, a more stringent 
level of control for sources of direct PM2.5 and 
PM2.5 precursors than for Moderate areas.
    As of the date of this proposal, the first round of initial 
designations for most areas for the 2012 primary annual 
PM2.5 NAAQS has been completed, and those designations will 
become effective on April 15, 2015. All areas designated as 
nonattainment for the 2012 PM2.5 NAAQS were classified as 
Moderate nonattainment areas.\40\
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    \40\ See the Federal Register notice for the first round of 
designations for the 2012 PM2.5 NAAQS at 80 FR 2206 
(January 15, 2015).
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3. Ambient Air Monitoring for PM2.5
    Ambient air quality monitoring for PM2.5 plays an 
integral role in implementation of a NAAQS, including identifying areas 
violating the NAAQS, control strategy development and tracking progress 
toward attainment. States are required to monitor PM2.5 mass 
concentrations using approved methods to determine compliance with the 
NAAQS.\41\ The locations of monitors are identified in states' Annual 
Monitoring Network Plans, which are required to be submitted to the EPA 
by July 1 of each year.\42\ The EPA in turn reviews these annual plans 
for compliance with applicable regulations and consistency with 
relevant guidance. Currently there are more than 900

[[Page 15349]]

monitoring locations across the country eligible for comparison to the 
PM2.5 NAAQS. States are required to maintain monitors in 
designated nonattainment areas in order to track progress toward 
attainment and ultimately determine whether the area has attained the 
PM2.5 standards. In addition to the approved monitors for 
comparison to the NAAQS, the EPA and states also maintain a chemical 
speciation network (CSN) of about 200 stations around the country to 
support analyses of chemical composition of PM2.5 (e.g. 
sulfate, nitrate and organic carbon). The data provided by the CSN help 
states identify contributing source categories and develop control 
strategies to reach attainment.
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    \41\ The ambient air monitoring requirements that apply to the 
PM2.5 NAAQS are detailed in 40 CFR part 58. These 
monitoring requirements are applicable to state and local air 
agencies.
    \42\ See 40 CFR 58.10.
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    In conjunction with the promulgation of the 2012 PM2.5 
NAAQS, the EPA finalized a schedule for deployment of PM2.5 
monitors at near-road monitoring locations. Under revised monitoring 
requirements, states are required to locate a minimum of one 
PM2.5 monitor in each core-based statistical area (CBSA) 
with a population of 1 million or more, to be phased-in between January 
2015 and January 2017.\43\
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    \43\ Near-road monitors for CBSAs larger than 2.5 million in 
population are to be operational by 1/1/2015; and monitors for CBSAs 
with population larger than 1 million but less than 2.5 million are 
to be operational by 1/1/2017. CBSA is defined by OMB as a 
statistical geographic entity consisting of the county or counties 
associated with at least one urbanized area/urban cluster of at 
least 10,000 population, plus adjacent counties having a high degree 
of social and economic integration.
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    For initial area designations for any PM2.5 NAAQS, the 
EPA relies on monitoring data to identify areas to be designated 
nonattainment due to violations of the standard(s). The EPA uses other 
information to identify areas contributing to the monitored violations 
in those areas.\44\ The agency's protocol for designating areas and 
determining whether an area has attained the PM2.5 NAAQS is 
based on monitored air quality data collected over a period of 3 
calendar years. Data from the new PM2.5 near-road monitors 
were not available for the EPA to consider within the timeframe for 
initial area designations provided by the CAA for the 2012 
PM2.5 NAAQS; the agency will not be able to consider data 
from a near-road monitor in the implementation process until 3 years of 
data are available. The initial set of near-roadway PM2.5 
monitors are to be fully deployed by January 2015, with the first 3 
years of air quality data (2015-2017) available beginning in 2018; the 
second set of near-roadway monitors are to have the first 3 years of 
data available beginning in 2020.
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    \44\ See Catawba County v. EPA, 571 F.3d 20 (D.C. Cir. 2009).
---------------------------------------------------------------------------

4. SIP Development Process
    In general terms, a SIP is the compilation of EPA-approved state 
statutes, regulations and programs that a state develops and relies 
upon to carry out its NAAQS implementation responsibilities under the 
CAA, including the attainment, maintenance and enforcement of NAAQS. 
States use the SIP development process to identify the emissions 
sources that contribute to the nonattainment problem in a particular 
area, and to select the required emissions reduction measures most 
appropriate for that area, considering factors such as technological 
and economic feasibility. As part of developing an attainment plan, the 
states must meet specific requirements of the CAA to attain the NAAQS, 
e.g., a state with a Moderate PM2.5 nonattainment area must 
impose RACM (including RACT) and additional reasonable measures on 
sources located in the nonattainment area. Under the CAA, states must 
develop attainment plans that ensure that areas reach attainment as 
expeditiously as practicable, but no later than the applicable 
statutory attainment date. In these attainment plans, states may take 
into consideration emission reductions resulting from federally 
applicable national programs (such as mobile source regulations, the 
national acid rain program, or maximum achievable control technology 
(MACT) standards for air toxics), as well as from state or local 
programs not directly mandated, but authorized, under the CAA, if such 
measures are incorporated into the SIP and thus are made federally 
enforceable.
5. Geographic Extent of PM2.5 Problem
    The EPA recognizes the significant variability in the nature and 
sources of PM2.5 in different nonattainment areas and 
believes it is important to keep this variability in mind when 
providing guidance to states as they develop control strategies to 
bring their PM2.5 nonattainment areas into attainment with 
the relevant NAAQS. The variability of PM2.5 concentrations 
across the country has a substantial regional component because the 
formation and transport of secondarily formed particles, such as 
sulfates and nitrates, can extend over hundreds of miles. As a result, 
monitored violations of the PM2.5 NAAQS can often reflect 
the impact of the combination of ``local'' sources of emissions located 
within the designated nonattainment area and ``regional'' sources of 
emissions that may be located much farther away.
    In addition, data suggest that ambient PM2.5 
concentrations tend to rise and fall in a consistent manner across very 
large geographic areas. The transport phenomenon associated with 
PM2.5 and its precursors has been well documented for many 
years. For example, one significant source of information on long-range 
transport is the National Acid Precipitation Assessment Program (NAPAP) 
research from the 1980s and its associated reports published in 
1991.\45\ Additional studies and air quality modeling analyses since 
that time have added to the body of information documenting the 
regional nature of PM2.5.\46\
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    \45\ National Acid Precipitation Assessment Program. Acid 
Deposition: State of the Science and Technology. Washington, DC 
1991. See also Environmental Protection Agency. (2004) Air Quality 
Criteria for Particulate Matter. Research Triangle Park, NC: Office 
of Research and Development; report no. EPA/600/P-99/002a,bF. 
Available at: http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_cr_cd.html.
    \46\ For example, see technical information for the Cross-State 
Air Pollution Rule (CSAPR) at: http://www.epa.gov/airmarkt/programs/cair/index.html; and the Clean Air Interstate Rule (CAIR) at: http://www.epa.gov/airmarkt/programs/cair/index.html. See also: NARSTO 
(2004) Particulate Matter Assessment for Policy Makers: A NARSTO 
Assessment. P. McMurry, M. Shepherd, and J. Vickery, eds. Cambridge 
University Press, Cambridge, England. ISBN 0 52 184287 5.
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6. Strategies for Reducing Ambient PM2.5
    The control measures identified and adopted by a state through the 
SIP development process for bringing nonattainment areas into 
attainment constitute an important component of the CAA's overall 
strategy for meeting the PM2.5 standards, but they are not 
the only component. The CAA also includes requirements for national 
rules or programs that will reduce emissions and help achieve cleaner 
air. Specifically, the EPA has adopted a number of national rules over 
the past few years that require or will require emission reductions 
from sources of both direct PM2.5 and PM2.5 
precursors, especially of SO2 and NOX. The 
national rules that will help states meet their attainment dates 
include, but are not limited to: The Tier 2 Light-Duty Vehicle Rule; 
the Tier 3 Tailpipe and Evaporative Emission and Vehicle Fuel 
Standards; the Heavy-Duty Engine and Vehicle Standards and Highway 
Diesel Fuel Sulfur Control Requirements; the Clean Air Nonroad Diesel 
Rule; the Regional Haze Regulations and Guidelines for Best Available 
Retrofit Technology Determinations; the NOX Emission 
Standard for New Commercial Aircraft Engines; the CSAPR; the Emissions 
Standards for Locomotives and Marine

[[Page 15350]]

Compression-Ignition Engines; the Control of Emissions for Nonroad 
Spark Ignition Engines and Equipment; the C3 Oceangoing Vessels rule; 
area and major source Boilers NESHAPs, New Source Performance Standards 
and Emission Guidelines for Hospital/Medical/Infectious Waste 
Incinerators; the Reciprocating Internal Combustion Engines (RICE) 
NESHAPs; and the Mercury and Air Toxics Standards (MATS).\47\
---------------------------------------------------------------------------

    \47\ Compliance with the MATS emission standard for acid gas 
hazardous air pollutants (HAP) is demonstrated by direct measurement 
of either hydrogen chloride (HCl) or SO2 as surrogates 
for all acid gas HAP. Thus, compliance with MATS is expected to 
result in a substantial amount of new pollution controls (scrubbers 
and dry sorbent injection) and upgrading of existing acid gas 
controls that will significantly reduce acid gas emissions, 
including SO2 emissions, from power plants. MATS 
implementation is projected to reduce nationwide SO2 
emissions from power plants to a level more than 40 percent lower 
than the SO2 emissions projected under CSAPR without MATS 
in place. For more information, see: http://www.epa.gov/mats.
---------------------------------------------------------------------------

    Additionally, there are PM2.5 reductions that will be 
achieved as a result of previously adopted state and local agency 
regulations and voluntary programs to the extent they can be relied on 
under the EPA's voluntary measures policies, such as the use of low 
sulfur fuel for home heating and industrial purposes, curtailment of 
residential wood burning and burn bans. Furthermore, under the 
voluntary PM Advance program, the EPA works with states, tribes and 
local governments to ensure they are aware of the advantages of early 
action and to provide assistance in taking steps to achieve emission 
reductions in areas currently attaining the PM2.5 NAAQS but 
approaching levels that could lead to nonattainment in the future. 
Early reductions may help these areas maintain the annual and 24-hour 
PM2.5 NAAQS over the long-term. Furthermore, there may be 
emissions controls that can be implemented to meet NAAQS for ozone 
(O3) or SO2 that may have co-benefits for meeting 
and continuing to meet the current PM2.5 NAAQS and any 
future revised PM2.5 NAAQS.
    The EPA will continue to work closely with air agencies as they 
develop and use an appropriate combination of national, regional and 
local pollution reduction measures to meet the standards as 
expeditiously as practicable, as required by the CAA.

III. What is the EPA proposing with respect to the treatment of 
PM2.5 precursors in nonattainment area planning and 
permitting?

A. Background

    The EPA recognizes that a threshold question in developing 
PM2.5 attainment plans and implementing NNSR programs is the 
question of which precursors must be regulated in a given nonattainment 
area in order to attain the relevant NAAQS and to meet the statutory 
requirements of part D, including subpart 4, of the CAA. Before 
discussing the specific CAA attainment plan and NNSR requirements in 
detail in Sections IV through IX of this preamble, the EPA discusses in 
this section how a state should evaluate PM2.5 precursors in 
order to identify the specific precursors to which the PM2.5 
attainment plan and NNSR requirements will apply in a given 
nonattainment area. This section first provides a brief overview of the 
precursor policies that the agency included in the 2007 
PM2.5 Implementation Rule and in the 2008 PM2.5 
NSR Rule for the 1997 PM2.5 NAAQS that were remanded by the 
court. It then describes the EPA's three proposed options for 
addressing PM2.5 precursors under the attainment planning 
and NNSR programs to meet the statutory requirements of subpart 4. 
Lastly, this section discusses possible approaches for states to 
develop an adequate technical demonstration showing whether emissions 
of a given PM2.5 precursor significantly contribute to 
ambient concentrations that exceed the standard. The EPA requests 
public comment on the options and information presented below.
    The EPA's 2007 PM2.5 Implementation Rule included 
regulatory presumptions concerning the need to address certain 
PM2.5 precursors in attainment plans and through control 
measures related to those plans.\48\ The EPA has long recognized the 
scientific basis for concluding that there are multiple scientific 
precursors to PM10, and in particular to 
PM2.5.\49\ As described in Section II of this preamble (on 
technical background issues associated with PM2.5 and 
PM2.5 precursors), appropriate control of precursors is 
especially important because secondarily formed particles comprise a 
large fraction of ambient PM2.5 concentrations in many 
nonattainment areas.
---------------------------------------------------------------------------

    \48\ See 2007 PM2.5 Implementation Rule, 72 FR 20586, 
20589, 20590, 20591, 20592, 20593, 20594, 20595, 20596 and 20597 
(April 25, 2007).
    \49\ Ibid. For example, the EPA's 2007 PM2.5 
Implementation Rule discussed the fact that emissions of 
SO2, NOX, VOC and ammonia are factual and 
scientific precursors to PM2.5.
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    Section 302(g) of the CAA indicates that the term ``air pollutant'' 
includes ``any precursors to the formation of any air pollutant, to the 
extent the Administrator has identified such precursor or precursors 
for the particular purpose for which the term `air pollutant' is 
used.'' In the 2007 PM2.5 Implementation Rule and the 2008 
PM2.5 NSR Rule, the EPA recognized that the main scientific 
precursors of fine particle formation are SO2, 
NOX, VOC, and ammonia. Pursuant to the discretionary 
authority provided under section 302(g) to identify PM2.5 
precursors for a particular program, the EPA also included requirements 
describing which precursor gases states were to evaluate for potential 
emission reductions as part of the state's analysis of control measures 
to bring the area into attainment as expeditiously as practicable.
    To facilitate the evaluation and identification of reasonable 
control measures, the 2007 PM2.5 Implementation Rule 
included nationally applicable presumptions regarding the need to 
evaluate and potentially control emissions of certain precursors. 
Specifically, in 40 CFR 51.1002, the EPA provided that a state must 
evaluate sources of direct PM2.5 and SO2 for 
potential control measures; a state presumptively was required to 
evaluate sources of NOX for potential control measures; and, 
a state was presumptively not required to evaluate sources of VOC and 
ammonia emissions for potential control measures. The EPA established 
these presumptions concerning VOC and ammonia in the 2007 
PM2.5 Implementation Rule because of factors such as 
uncertainties regarding the emissions inventories for ammonia, 
uncertainties concerning the role of some VOC in the formation of 
particles, and uncertainties regarding the effectiveness of specific 
precursor control measures in various regions of the country in 
reducing PM2.5 concentrations. For example, in some areas of 
the U.S., emission reductions of a particular precursor may lead to 
large changes in PM2.5 concentrations because there are 
relatively few tons of such precursor emissions in the area in the 
first place. In other areas, the opposite may be true, where emission 
reductions of a particular precursor may lead to small changes in 
PM2.5 concentrations because the area has an abundance of 
emissions of that particular precursor.
    The rule also included provisions for potentially reversing the 
EPA's initial presumptions for certain precursors in a nonattainment 
area where the state or

[[Page 15351]]

the EPA had information demonstrating that the presumption was not 
valid for that area. The EPA left open the possibility in the 2007 
PM2.5 Implementation Rule for regulation of VOC and ammonia 
emissions as PM2.5 precursors in any nonattainment area 
where regulation was necessary for purposes of attaining the 1997 
PM2.5 NAAQS. Similarly, the EPA left open the possibility 
for not regulating NOX where NOX sources from 
within the state did not have a significant contribution to 
PM2.5 concentrations in the nonattainment area. The preamble 
to the 2007 PM2.5 Implementation Rule discussed that to 
``reverse'' the presumptions in the rule for NOX, VOC or 
ammonia, the state would need to provide an appropriate technical 
demonstration, and it provided examples of the types of analyses that 
could be included in such a demonstration. The EPA intended these to be 
rebuttable presumptions that either the state or the EPA might reverse 
through notice-and-comment rulemaking. These presumptions were not 
limited to precursor emissions only from major stationary sources, but 
rather were presumptions applicable to precursor emissions from all 
sources of such emissions within the area.\50\
---------------------------------------------------------------------------

    \50\ Ibid.
---------------------------------------------------------------------------

    The 2008 PM2.5 NSR Rule included similar policies for 
precursor presumptions in connection with the NSR requirements for 
nonattainment areas (the NNSR program).\51\ That rule provided a 
discussion of the possibility for the state or the EPA to provide a 
technical demonstration to reverse the presumptions for NOX, 
VOC or ammonia.\52\ The one significant difference between the two 
rules was the geographic scope of the requirements. The 2008 
PM2.5 NSR Rule indicated that a precursor presumption could 
be rebutted if the emissions of that precursor from sources within the 
nonattainment area (emphasis added) did not significantly contribute to 
PM2.5 concentrations in the nonattainment area. This 
distinction is logical because the requirements of the NNSR program 
apply only to sources located within a designated nonattainment area. 
Conversely, the 2007 PM2.5 Implementation Rule indicated 
that the evaluation of whether a given precursor should be regulated 
should be based on emissions from sources throughout the entire state 
(emphasis added), because the state air agency has jurisdiction over 
sources throughout the entire state in developing strategies to improve 
air quality specifically in nonattainment areas. A more complete 
discussion of the 2008 NNSR program requirements for the 
PM2.5 NAAQS and the proposed changes concerning the 
regulation of PM2.5 precursors from new or modified major 
stationary sources of PM2.5 precursors in PM2.5 
nonattainment areas is provided in Section VIII of this preamble.
---------------------------------------------------------------------------

    \51\ See the Federal Register published on May 16, 2008 (73 FR 
28321, 28326 and 28327).
    \52\ Ibid.
---------------------------------------------------------------------------

    The EPA's approach to the evaluation and regulation of 
PM2.5 precursors in both the 2007 and 2008 rules for 
implementing the 1997 PM2.5 NAAQS was called into question 
in the court's 2013 decision in NRDC v. EPA. As an example of the 
distinction between the divergent substantive requirements of subpart 1 
and subpart 4, the court noted that subpart 4 has specific provisions 
related to regulation of precursors not present in subpart 1. Although 
the court stated that it was not reaching a decision on the issue of 
regulation of precursors, the court's decision specifically discussed 
both the approach to precursors in the 2007 PM2.5 
Implementation Rule and the 2008 PM2.5 NSR Rule and compared 
those to section 189(e) of the CAA, which contains the sole explicit 
reference to the regulation of precursors in subpart 4. The court 
decision included the following statements with regard to precursors:

    Ammonia is a precursor to fine particulate matter, making it a 
precursor to both PM2.5 and PM10. For a 
PM10 nonattainment area governed by subpart 4, a 
precursor is presumptively regulated. See 42 U.S.C. 7513a(e) 
[section 189(e)]. But under the PM rules challenged here, the EPA 
established a rebuttable presumption against regulating ammonia 
unless a state or the EPA ``provides an appropriate technical 
demonstration'' that shows emissions from ammonia ``significantly 
contribute to PM concentration in the nonattainment area.'' 40 CFR 
51.1002(c)(4)(i). When Congress enacted subpart 4, it sought to end 
this administrative gamesmanship.\53\
---------------------------------------------------------------------------

    \53\ NRDC v. EPA, 706 F.3d 428, 437, n.7 (D.C. Cir. 2013).
---------------------------------------------------------------------------

* * * * *
    In light of our disposition, we need not address the 
petitioners' challenge to the presumptions in [40 CFR 51.1002] that 
volatile organic compounds and ammonia are not PM2.5 
precursors, as subpart 4 expressly governs precursor 
presumptions.\54\
---------------------------------------------------------------------------

    \54\ NRDC v. EPA, 706 F.3d 428, 437, n.10 (D.C. Cir. 2013).

    Section 189(e) for PM10 precursors (which the court 
concluded expressly includes PM2.5) provides that: ``The 
control requirements applicable under plans in effect under this part 
for major stationary sources of PM10 shall also apply to 
major stationary sources of PM10 precursors, except where 
the Administrator determines that such sources do not contribute 
significantly to PM10 levels which exceed the standard in 
the area.'' The court reasoned that the EPA's approach to precursors in 
the 2007 PM2.5 Implementation Rule and 2008 PM2.5 
NSR Rule had the effect of reversing the presumption embodied within 
subpart 4 that a state should address all PM10 precursors 
unless the state has made a specific showing why regulation of a 
particular precursor is not necessary.\55\
---------------------------------------------------------------------------

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

    The provisions of subpart 4 do not define the term ``precursor'' 
for purposes of PM10, nor do they explicitly require the 
control of any specifically identified particulate matter precursor. 
However, as stated above, the statutory definition of ``air pollutant'' 
provides that the term ``includes any precursors to the formation of 
any air pollutant, to the extent the Administrator has identified such 
precursor or precursors for the particular purpose for which the term 
`air pollutant' is used.'' CAA section 302(g). The EPA has determined 
that SO2, NOX, VOC and ammonia are factual and 
scientific precursors to PM, and thus the attainment plan requirements 
of subpart 4 initially apply equally to emissions of direct 
PM2.5 and all of its identified precursors, except as 
otherwise provided in the statute (e.g. CAA section 189(e)). Section 
189(e) explicitly requires the control of precursors from all major 
stationary sources, unless there is a demonstration to the satisfaction 
of the Administrator that such major stationary sources do not 
contribute significantly to PM levels that exceed the standards in the 
area.\56\ Section 189(e) contains the only express exception to control 
requirements under subpart 4. The control requirements for major 
sources referred to in this exception include requirements for RACM and 
RACT, additional reasonable measures, BACM and BACT, most stringent 
measures (as applicable) and NNSR on all major sources of precursors in 
the nonattainment areas. The General Preamble indicates that 
consideration of precursors is necessary for attainment plans, and it 
recognizes the specific applicability of section 189(e) to both 
existing and new major stationary sources, including new and modified 
sources subject to NNSR permitting requirements. Even though section

[[Page 15352]]

189(e) only explicitly contemplates exceptions to control requirements 
for PM2.5 precursors from major stationary sources, the EPA 
believes that by analogy it has authority to promulgate regulations 
that allow states to determine that it is not necessary to regulate 
PM2.5 precursors from other source categories as well, under 
appropriate circumstances.
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    \56\ The EPA notes that it has already addressed the 
requirements of subpart 4 for precursors, specifically within the 
context of the requirements of section 189(e), in the General 
Preamble. See the Federal Register published on April 16, 1992 (57 
FR 13498, 13539, 13541 and 13542).
---------------------------------------------------------------------------

    When Congress adopted the 1990 CAA Amendments, a NAAQS for 
PM10 was in effect, but no standard for PM2.5 had 
yet been established. At that time, it was understood that the 
interaction of PM precursors in the atmosphere led to the formation of 
particulate matter in many areas. However, in some of the 
PM10 nonattainment areas, air quality problems were caused 
primarily by area sources emitting direct PM emissions (e.g., a 
nonattainment area with numerous wood burning devices or with 
substantial sources of windblown coarse particles from construction 
sites), and precursor emissions from major stationary sources were not 
considered to make a significant contribution to the local 
nonattainment problem. For cases such as these, section 189(e) provided 
a possible exception to the requirement to control all PM2.5 
precursors from major sources in all nonattainment areas.
    While section 189(e) expressly requires control of precursors from 
major stationary sources where direct PM from major sources is to be 
controlled unless certain conditions are met, as stated above, it is 
clear that subpart 4 and other CAA provisions collectively require the 
control of direct PM and all PM2.5 precursors from all types 
of sources (i.e., stationary sources, area sources, and mobile sources) 
as may be needed for the purposes of demonstrating attainment as 
expeditiously as practicable in a given area.\57\ Long-standing EPA 
guidance for RACM has stated that the state should inventory all 
emissions of the relevant pollutants and precursors in the 
nonattainment area and evaluate all economically and technologically 
feasible control measures for the relevant pollutant and precursors, 
and that the state should adopt those measures that are deemed 
reasonably available and necessary in order to attain the NAAQS as 
expeditiously as practicable.\58\ The state also must ensure that there 
is no other collection of available control measures that if adopted 
would advance the attainment date by at least one year.\59\ Section 
IV.D of this preamble provides additional discussion on the development 
of emissions inventories and the identification, adoption and 
implementation of reasonable control measures for Moderate 
PM2.5 nonattainment areas. \60\
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    \57\ See CAA requirements for states to demonstrate attainment 
``as expeditiously as practicable'' (section 188(c)(1); section 
172(a)(2)).
    \58\ 57 FR 13498 (April 16, 1992).
    \59\ In the context of the PM10 NAAQS, the EPA has 
concluded that ``advancement of the attainment date'' should mean an 
advancement of at least 1 calendar year. See State Implementation 
Plans; General Preamble for the Implementation of Title I of the CAA 
Amendments of 1990, 57 FR 13498 (April 16, 1992). See also Sierra 
Club v. EPA, 294 F.3d 155 (D.C. Cir. 2002).
    \60\ See Section IV of this preamble for a thorough discussion 
of past reasonably available control measures (RACM) and reasonably 
available control technology (RACT) policy and guidance. Section IV 
discusses the EPA's proposed policy that under subpart 4, for 
Moderate areas that demonstrate that attainment by the statutory 
attainment date is impracticable, RACM and RACT would constitute all 
those technologically and economically feasible measures available 
for sources in the area that can be implemented within 4 years of 
designation, but they would not constitute the complete set of 
measures required to demonstrate attainment as expeditiously as 
practicable.
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B. Proposed Precursor Policy Options

    The EPA is proposing this rule to address the attainment plan and 
certain NNSR requirements for PM2.5 under subpart 4. In 
light of the court's decision in NRDC v. EPA, the EPA considers it 
necessary to address in this implementation rule how states must 
address regulation of PM2.5 precursor gases in attainment 
plans and NNSR programs for the PM2.5 NAAQS. As noted 
earlier, the court's decision made clear that appropriate regulation of 
all precursors is initially presumptively required under the CAA, and 
the regulation of precursors is a critical issue for attainment of the 
PM2.5 NAAQS because secondarily formed particles are a 
substantial component of the PM2.5 nonattainment problem in 
most areas of the U.S.
    For the purposes of this implementation rule, the EPA considers 
that for all nonattainment areas, the PM2.5 precursors for 
regulatory purposes are SO2, NOX, VOC and 
ammonia. This rule does not propose any national presumption that would 
simply allow a state to exclude sources of emissions of a particular 
precursor from further analysis for control requirements. However, the 
EPA's existing interpretation of subpart 4 requirements--with respect 
to precursors in attainment plans for PM10, as set out in 
the General Preamble--contemplates that the state may develop an 
attainment plan that regulates only those precursors that are necessary 
to control for purposes of timely attainment in the area, i.e., states 
may determine that only certain precursors need to be regulated for 
attainment purposes.\61\ Courts have upheld this approach to the 
requirements of subpart 4 for PM10.\62\
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    \61\ See the Federal Register published on April 16, 1992 (57 FR 
13498, 13540 and 13541).
    \62\ See, e.g., Assoc. of Irritated Residents v. EPA, et al., 
423 F.3d 989 (9th Cir. 2005).
---------------------------------------------------------------------------

    The EPA believes that application of a similar approach to 
PM2.5 precursors under subpart 4 is appropriate and 
reasonable. Thus, this proposal describes three proposed precursor 
options that provide for the possibility that, with appropriate 
justification provided by the state, further evaluation and 
implementation of control strategies for one or more PM2.5 
precursors in a given nonattainment area may not be needed or required. 
Under each option, a state may provide a technical demonstration and 
reasoned justification for the exclusion of a PM2.5 
precursor or precursors from control requirements for a particular 
nonattainment area.
    As explained above, the EPA interprets the CAA to require states to 
inventory and regulate all sources of PM2.5 precursors from 
all sources in the area, including area sources, mobile sources and 
stationary sources. This interpretation is based on CAA provisions 
requiring adoption of all RACM needed to attain the standard as 
expeditiously as practicable; section 302(g), which defines an air 
pollutant as including all precursors contributing to the formation of 
that pollutant; and, the EPA's identification of the four main 
PM2.5 precursors. For major stationary sources, section 
189(e) requires that the control requirements applicable for major 
stationary sources of PM2.5 must also apply to major 
stationary sources of PM2.5 precursors, unless the state 
provides a showing that emissions of a particular precursor from major 
stationary sources do not contribute significantly to levels which 
exceed the standard in the area. Thus, the statute generally requires 
control of all PM2.5 precursors, but it provides an express 
exception applicable to major stationary sources. Because the statutory 
provisions of subparts 1 and 4 are not explicit with respect to how 
states should address PM2.5 precursors from non-major 
sources, the EPA is proposing regulations to assure proper evaluation 
and regulation of PM2.5 precursor emissions in 
PM2.5 nonattainment areas. Moreover, even with respect to 
regulation of precursor emissions from major stationary sources, 
section 189(e) contains ambiguities that require interpretation. For 
example, section

[[Page 15353]]

189(e) does not specify the method by which the EPA should determine 
whether precursor emissions from major stationary sources contribute 
significantly to levels which exceed the standard in a given 
nonattainment area. Given that the provisions of subpart 4 are 
ambiguous with respect to these issues, the EPA believes that it is 
necessary to interpret those requirements in this rulemaking.
    The EPA is thus seeking comment on three potential approaches to 
address PM2.5 precursors pursuant to the specific statutory 
requirements of subpart 4 and the overarching requirements of the CAA. 
In these proposed options, particular emphasis is given to the 
situations and circumstances under which the state would or would not 
be required to evaluate emission controls for a particular precursor 
and to adopt those controls that are necessary to demonstrate 
attainment of the NAAQS as expeditiously as practicable. Note that 
these options describe analyses that the state may choose to pursue to 
demonstrate that control requirements should not apply to a particular 
precursor. However, the state also may choose to require controls for 
all PM2.5 precursors in attainment plans and in its NNSR 
permitting program, and choose not to conduct any analyses to eliminate 
one or more precursors from consideration for controls.
    The descriptions of the three precursor policy options being 
proposed in this section discuss how PM2.5 precursors would 
need to be addressed by the state with regard to three specific 
implementation situations: (1) A Moderate area for which attainment of 
the relevant NAAQS by the end of the sixth calendar year after 
designation can be demonstrated; (2) a Moderate area for which it can 
be demonstrated that the relevant NAAQS cannot practicably be attained 
by the end of the sixth calendar year after designation; and (3) an 
area that is reclassified to Serious and is obligated to develop a 
Serious area attainment plan to attain the relevant NAAQS. 
Additionally, the EPA describes how each of the proposed precursor 
policy options would apply to the implementation of NNSR in a Moderate 
or Serious PM2.5 nonattainment area. Later in this section, 
the EPA discusses specific issues related to the technical ``precursor 
demonstrations'' that states could choose to develop. The technical 
demonstration section includes a discussion of several types of 
analyses that a state could provide to the EPA to show that control 
measures for a specific PM2.5 precursor would not be needed 
for attainment or to expedite attainment, or to show that major 
stationary sources of a given precursor collectively do not 
significantly contribute to PM2.5 levels that exceed the 
relevant NAAQS in a given area.
    Before discussing the three precursor options, it is important to 
introduce a new term that is used throughout this section and other 
sections of the notice. Under subpart 4, RACM (including RACT) are 
those measures that can and must be implemented within 4 years of the 
area's designation as nonattainment (pursuant to section 189(a)(1)(C)). 
The EPA recognizes, however, that other, similarly reasonable emissions 
reduction measures could be implemented after this 4 year period, and 
as late as the end of the sixth calendar year following designation, to 
help an area attain as expeditiously as practicable. Therefore, in this 
proposal the EPA is proposing to define the term ``additional 
reasonable measures'' to describe those technologically and 
economically feasible control measures that could not be implemented 
within the 4 year period after designation, but could be implemented 
starting any time after that 4 year period through the end of the sixth 
calendar year after designation (note that this period could extend 
almost 3 additional years, depending on when during the year area 
designations are finalized). See proposed 40 CFR 51.1000. The EPA 
proposes to require implementation of these ``other'' control measures 
to the extent necessary to demonstrate attainment by the applicable 
attainment date pursuant to section 172(c)(6) of the CAA. That 
provision provides that nonattainment ``plan provisions shall include 
enforceable emissions limitations, and such other control measures . . 
. as may be necessary or appropriate to provide for attainment of such 
standard in such area by the applicable attainment date . . .'' 
Together, RACM and RACT and ``additional reasonable measures'' make up 
the set of control strategies referred to in this proposed rule as 
``reasonable control measures.'' \63\ (Section IV.D of this preamble 
provides a detailed discussion of how a state must determine reasonable 
control measures for a Moderate PM2.5 nonattainment area.) 
The EPA requests comment on each of the three proposed options 
discussed below which describe how a state may demonstrate that 
additional emissions reductions of a particular precursor would not be 
needed or appropriate for an area's attainment plan, and how it could 
demonstrate that emissions control requirements for a particular 
precursor would not be needed in NNSR permits for new or modified 
sources in the area. In particular, the EPA requests comment on whether 
only one of these approaches should be included in the final rule, or 
whether it would be appropriate to include multiple approaches (e.g., 
both Options 1 and 2), or only specific elements from the different 
options. The three proposed options are summarized as follows:
---------------------------------------------------------------------------

    \63\ In Section VI.D, the EPA describes a parallel approach for 
distinguishing control measures required under sections 172(c)(6) 
and 189(b)(1)(B) for Serious nonattainment areas.
---------------------------------------------------------------------------

     Option 1: Two independent analyses: (a) An attainment 
planning analysis demonstrating that control measures for a particular 
precursor are not needed for expeditious attainment, meaning that the 
precursor can be excluded from measures needed to attain as 
expeditiously as practicable for all types of sources; and (b) a 
section 189(e) technical demonstration showing that major stationary 
sources of a particular precursor do not contribute significantly to 
levels that exceed the PM2.5 standard, meaning that the 
precursor can be excluded from control requirements for major sources 
including NNSR permitting;
     Option 2: Single analysis demonstrating that all emissions 
of a particular precursor from within the area do not significantly 
contribute to PM2.5 levels that exceed the standard, meaning 
that control requirements for emissions of the precursor from major 
stationary and area sources, as well as mobile sources, would not be 
required for expeditious attainment, control requirements for major 
sources, or for NNSR permitting;
     Option 3: An attainment planning analysis demonstrating 
that control measures for all types of sources of a particular 
precursor are not needed for expeditious attainment also would be 
deemed to meet the section 189(e) technical demonstration requirement, 
meaning that the state would not need to regulate emissions of the 
particular precursor from major stationary sources under the NNSR 
permitting program or other control requirements for major stationary 
sources.

Each of these proposed options is presented in greater detail below.
    1. Option 1: Two independent analyses: (a) An attainment planning 
analysis demonstrating that control measures for a particular precursor 
are not needed for expeditious attainment, meaning that the precursor 
can be excluded from measures needed to attain as expeditiously as 
practicable for

[[Page 15354]]

all types of sources; and (b) a section 189(e) technical demonstration 
showing that major stationary sources of a particular precursor do not 
contribute significantly to levels that exceed the PM2.5 
standard, meaning that the precursor can be excluded from control 
requirements for major sources and from NNSR permitting.
    As with the other options discussed below, the critical first step 
in any precursor analysis is the development of a comprehensive 
inventory of all precursor emissions in the nonattainment area. A state 
will be unable to reasonably determine whether emissions of a given 
PM2.5 precursor contribute significantly to the 
nonattainment problem in an area if the state has failed to account 
adequately for all such emissions in the area in its emissions 
inventory.
    In general terms, Option 1 would require separate analyses for 
purposes of attainment planning and for NNSR. Section 189(a) of the CAA 
describes the requirements for Moderate nonattainment areas. Within 18 
months of designation as nonattainment, the state is required to submit 
a Moderate area plan that either demonstrates attainment as 
expeditiously as practicable but by no later than the end of the sixth 
year following designation, or demonstrates that attainment by such 
date would be impracticable.
    Under Option 1, the state would determine the precursors for which 
new control measures need to be adopted for a given nonattainment area 
through its determination of reasonable control measures needed for 
attainment. The state's analysis of reasonable measures for a given 
PM2.5 NAAQS nonattainment area should begin by identifying 
potential control measures (and factors related to technological 
feasibility, economic feasibility, and time needed for implementation) 
for all precursors from all types of sources in the area (i.e., 
stationary, area, mobile) included in the emissions inventory. The 
analysis of reasonable measures and selection by the state of those 
emissions reduction measures that would provide for attainment as 
expeditiously as practicable (but no later than the end of the sixth 
calendar year after designation) would determine which precursors must 
be regulated in the nonattainment area for purposes of attainment. 
Except for the requirement to determine whether implementation of all 
remaining reasonable measures could collectively advance attainment by 
a year, there would be no additional demonstration needed by the state 
to justify that attainment planning control requirements should not 
apply to a particular precursor. Therefore, the analysis of reasonable 
measures may result in the state controlling only a subset of the four 
main PM2.5 precursors as part of the attainment 
demonstration.
    a. Moderate area for which the state can demonstrate attainment by 
the statutory attainment date. For certain nonattainment areas, the 
state may be able to demonstrate that attainment of the standard ``as 
expeditiously as practicable'' is possible by the end of the sixth year 
after designation (the statutory Moderate area attainment date) or 
sooner, and could be achieved by adopting regulations to reduce 
emissions of only a subset of the four PM2.5 precursors. 
Under this scenario, the state would be expected to provide analytical 
information showing that, even though new economically and technically 
feasible control measures may be available for one or more precursors, 
the reductions in emissions of the precursor(s) that could be achieved 
are not necessary for expeditious attainment and would not advance the 
attainment date by at least a year. Under Option 1, if the state 
determined that new emissions reductions of a particular precursor are 
not necessary for attainment and would not accelerate the attainment 
date by at least 1 year, then for the purposes of this particular 
PM2.5 Moderate area attainment plan, the state would not 
need to adopt additional control measures for that PM2.5 
precursor. Given that additional regulation of that PM2.5 
precursor would not be necessary for attaining the standard as 
expeditiously as practicable, the EPA would be able to approve the 
attainment plan for the area as meeting the requirements of subpart 4.
    b. Moderate area for which the state can demonstrate that 
attainment by the statutory attainment date is impracticable. Section 
189(a)(1)(B) provides that for certain nonattainment areas, the state 
may demonstrate that, even with implementation of all reasonable 
control measures available for reducing emissions of all direct PM and 
PM2.5 precursors, it would be impracticable to attain the 
standard by the end of the sixth calendar year after designation. In 
other words, the analysis would need to demonstrate that implementing 
all economically and technically feasible control measures that are 
available in the area, and the expected air quality change from such 
measures, would not be able to provide for attainment by the end of the 
sixth year after designation.
    For states that can make the showing that they cannot attain the 
NAAQS by the end of the sixth calendar year after designation, the 
question arises as to whether the state should be required to adopt all 
reasonable measures (i.e. measures that represent RACM and RACT because 
they are technologically and economically feasible and can be 
implemented in 4 years and all additional reasonable measures that can 
be implemented within 6 years) through regulation as part of the 
Moderate area plan, even if a subset of these measures collectively 
would have a minimal effect on reducing ambient PM2.5 
concentrations. The EPA proposes two sub-options for areas that cannot 
demonstrate attainment during the Moderate area timeframe even with the 
implementation of all reasonable measures in the area. Under the first 
sub-option, the state would be required to adopt all available control 
measures for precursors through regulation as part of the Moderate area 
plan. The rationale supporting this approach would be that adopting all 
technologically and economically feasible measures would bring the area 
as close to attainment as possible during the timeframe prescribed for 
Moderate areas. Under this approach, if a measure can be implemented by 
the end of the sixth calendar year after the nonattainment designation 
and it meets the criteria for being considered ``reasonable,'' then the 
state must adopt and implement the measure.
    Under the second sub-option, the state would be able to elect not 
to impose those technologically and economically feasible measures that 
collectively have minimal effect on ambient PM2.5 levels in 
the area, based on the premise that such measures would be unreasonable 
to implement. To support this conclusion, the state would need to 
submit a technical demonstration showing that implementing available 
emissions controls for a particular precursor and/or a specific set of 
sources would provide only minimal changes in PM2.5 
concentrations in the area, and therefore such control measures should 
not be required during the timeframe prescribed for Moderate areas. The 
EPA requests comment on these two sub-options, including any technical 
information that would help support the commenter's position. Regarding 
the second sub-option, the EPA requests comment on what degree of air 
quality change should be considered minimal for purposes of this 
analysis.\64\
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    \64\ Note that under either sub-option, the state would be able 
to show that control of precursor emissions from major stationary 
sources would not be required if it could be demonstrated that such 
emissions do not contribute significantly to PM2.5 levels 
that exceed the standard, consistent with section 189(e).

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[[Page 15355]]

    c. Area reclassified to Serious. A Moderate area can be 
reclassified to a Serious area under two scenarios. Under the first 
scenario, if a Moderate area fails to attain the standard by the 
applicable attainment date, it would then be reclassified by the EPA as 
a Serious area and the state would be required to develop and submit a 
Serious area attainment plan within 18 months of reclassification. 
Under the second scenario, the EPA could reclassify an area to Serious 
prior to the Moderate area attainment date if the EPA determines that 
it would be impracticable for the area to attain by the Moderate area 
attainment date. (Section V of this preamble provides additional detail 
on reclassifying a Moderate area to Serious under subpart 4.)
    After an area has been reclassified to Serious, subpart 4 requires 
a state's Serious area attainment plan to include the imposition of 
more stringent control measures (best available control measures (BACM) 
and best available control technology (BACT)) intended to bring the 
area into attainment as expeditiously as practicable but no later than 
the end of the tenth calendar year after designation. Given that the 
CAA requires a more stringent new attainment plan for Serious areas, 
under Option 1 the state would be required to identify the best 
available measures for all sources of direct PM2.5 emissions 
and emissions of PM2.5 precursors and adopt those measures 
to attain the standard as expeditiously as practicable.\65\
---------------------------------------------------------------------------

    \65\ The EPA's two proposed options for determining BACM and 
BACT are discussed in detail in Section VI.D of this preamble.
---------------------------------------------------------------------------

    The BACM and BACT determination requires a more rigorous analysis 
than the RACM and RACT analysis, and such measures collectively should 
lead to a greater degree of emission reduction in the area than the 
analysis of reasonable control measures for the Moderate area plan. For 
this reason, under Option 1, if the state's previous Moderate area 
attainment plan had indicated that new emissions reduction measures 
from sources of one or more precursors were not needed to attain by the 
end of the sixth calendar year after designation, then for the Serious 
area plan the state would need to reevaluate the best control measures 
addressing all PM2.5 precursors (i.e. SO2, 
NOX, VOC, and ammonia) and require implementation of those 
``best'' available control measures for all precursors in order to 
bring the area into attainment as expeditiously as practicable, but no 
later than the end of the tenth year after designation. Under Option 1, 
any precursor demonstration that excluded one or more precursors from 
regulation in the Moderate area plan would not by itself also be 
sufficient to exclude the precursors from regulation in the Serious 
area plan. Further analysis would be needed to determine if control 
measures for those precursors qualify as ``best'' control measures. The 
EPA has interpreted the starting point for considering ``best'' control 
measures as including those control measures to reduce emissions of 
direct PM2.5 or PM2.5 precursors that have been 
adopted by any state, particularly those states with the most severe 
PM2.5 air quality problems. (Note that in Section VI.D of 
this preamble, more details are provided on BACM and BACT determination 
criteria. The EPA is taking comment on two options for BACM and BACT 
determinations--one that expresses it as a requirement independent of 
the attainment demonstration, and one that expresses it as only those 
``best'' measures that are needed for expeditious attainment no later 
than the end of the tenth calendar year after designation. The BACM and 
BACT determination approach adopted in the final rule accordingly will 
determine whether all best available emission controls for a particular 
precursor must be adopted or not in a Serious area).
    d. NNSR. Under Option 1, the initial expectation is that the state 
will need to address all four PM2.5 precursors under the 
NNSR program pursuant to the CAA and as reinforced by the January 2013 
NRDC v. EPA court decision. Pursuant to section 189(e), however, the 
state may provide a demonstration showing that emissions of a 
particular precursor from existing major stationary sources located in 
the nonattainment area do not contribute significantly to 
PM2.5 levels that exceed the standard in the area. Under 
Option 1, this analysis under section 189(e) for major sources would be 
completed independently from the analysis of reasonable control 
measures conducted for attainment planning purposes. Such an analysis 
would involve assessing the potential addition of precursor emissions 
in the area due to potential new major stationary sources, and would 
likely involve air quality modeling and other technical analyses by the 
state, developed in consultation with the EPA (see Section III.C. of 
this preamble for further discussion on such technical demonstrations). 
Note that under this provision of the CAA, it might be possible that a 
precursor would be considered important for attainment planning 
purposes, but would not be regulated as a PM2.5 precursor in 
NNSR permitting actions which, by definition, only apply to major 
sources of the nonattainment pollutant. For example, it might be 
possible that in a particular area the principal source of emissions of 
a certain precursor could be from mobile and area sources but not from 
major stationary sources of that precursor. The EPA requests comment on 
all aspects of proposed Option 1 as discussed above.
    2. Option 2: Single analysis demonstrating that all emissions of a 
particular precursor from within the area do not significantly 
contribute to PM2.5 levels that exceed the standard, meaning 
that control requirements for emissions of the precursor from 
stationary major and area sources, as well as mobile sources, would not 
be required for expeditious attainment, control requirements for major 
sources, or for NNSR permitting.
    Option 2 would provide the state the opportunity to provide the EPA 
with a scientifically credible technical analysis that would 
demonstrate that one or more precursors do not contribute significantly 
to the PM2.5 levels that exceed the standard, therefore 
controls on those emissions would not be effective in reducing 
PM2.5 levels in the area. As noted earlier in this section 
of the preamble, section 302(g) of the CAA includes ``precursors'' in 
the definition of ``air pollutant,'' but provides the EPA with some 
discretion in defining how these terms should be interpreted. In 
subpart 4, the CAA does not explicitly address control of precursors, 
except with regard to major stationary sources in section 189(e). The 
EPA interprets subpart 4 to require states to address PM2.5 
precursors from all source categories in the evaluation of controls 
needed for attainment in a given area, e.g., in the evaluation of RACM 
and RACT level controls. By analogy to section 189(e), the EPA also 
believes that there may be circumstances in which states may validly 
demonstrate that control of one or more PM2.5 precursors is 
not needed to attain the relevant NAAQS expeditiously.
    Section 189(e) provides that precursor control requirements apply 
to major stationary sources of precursors of PM2.5 if major 
sources of PM are regulated under the attainment plan, unless it can be 
shown that such precursor emissions do not contribute significantly to 
exceedances of the relevant NAAQS in the area. Under Option 2, the EPA 
relies on the discretion provided in section 302(g) and the section 
189(e) concept of precursor emissions in an area having a significant 
or insignificant effect on

[[Page 15356]]

PM2.5 concentrations that exceed the standard to propose two 
precursor technical demonstration suboptions. Option 2A would allow the 
state to provide a technical demonstration showing that all emissions 
(i.e., from area, mobile and stationary sources in the area) of a 
particular precursor collectively do not provide a significant 
contribution to PM2.5 levels that exceed the standard in the 
area. The kinds of analytical approaches that could be appropriate for 
this type of ``contribution demonstration'' are described later in this 
section.
    For Option 2B, the EPA proposes to allow states to provide a 
technical demonstration showing that PM2.5 concentrations in 
the area are not sensitive to potential reductions or increases in 
emissions of a particular precursor in the nonattainment area (e.g. 
because the particular precursor is not the limiting factor in 
secondary PM2.5 formation). More information is provided 
later in this section about possible analytical approaches to assess 
precursor ``sensitivities'' in an area (the optional technical 
demonstration described for Options 2A and 2B hereafter will be 
referred to as a ``precursor demonstration''). The EPA requests comment 
on which of the two options (Option 2A or Option 2B) would be more 
preferable, and why. The EPA encourages commenters to provide examples 
of specific situations and areas in support of their recommendations.
    These proposed options are consistent with the EPA's past practice 
for determining which technologically and economically feasible 
controls are necessary for expeditious attainment of the NAAQS. 
Specifically, the EPA has interpreted the RACM requirement in the CAA 
as requiring imposition of all reasonable controls as needed for 
expeditious attainment or to advance the attainment date by at least 1 
year. The statute does not require imposition of additional controls if 
collectively such measures would not advance the attainment date. The 
EPA maintains it is reasonable to treat regulation of PM2.5 
precursors in a manner similar to the agency's treatment of direct 
pollutants and therefore concludes that states should not be required 
to implement control measures for a particular precursor or precursors 
if such measures will have little or no impact on PM2.5 
concentrations in the area or if the state demonstrates that all 
emissions of a given precursor or precursors do not contribute 
significantly to the PM2.5 NAAQS exceedances in the area.
    a. Moderate area for which the state can demonstrate attainment by 
the statutory attainment date or for which the state can demonstrate 
that attainment by the statutory attainment date is impracticable. An 
approved precursor demonstration under Option 2A would show that 
emissions of the particular precursor from all types of sources do not 
contribute significantly to PM2.5 levels that exceed the 
standard. As proposed, this type of demonstration therefore by 
definition would also satisfy the section 189(e) provision (which 
allows the state to demonstrate that emissions from just major 
stationary sources are not significant and therefore should not be 
subject to control requirements, such as NNSR, that apply to major 
stationary sources of direct PM2.5). Thus, the state could 
possibly develop one precursor demonstration analysis that would serve 
the purposes of both attainment planning and the section 189(e) 
insignificant major source contribution demonstration.
    The sensitivity analyses required under Option 2B would need to 
assess a series of precursor emissions reductions and increases to 
determine the sensitivity to air quality in the area. For example, the 
analysis should evaluate the effect on PM2.5 concentrations 
of various precursor emissions reduction scenarios appropriate to 
determine the sensitivity of precursors for the area (as would be 
relevant for an attainment plan); the analysis should also evaluate the 
effect on PM2.5 concentrations of various precursor 
emissions increase scenarios appropriate to determine the sensitivity 
of precursors for the area, simulating the potential effect of the 
addition of potential new major stationary sources (or major 
modifications) to the nonattainment area under the NNSR program.
    The EPA would evaluate the relevant analyses and other supporting 
information provided by the state. By submitting a ``precursor 
demonstration'' of this type, the state would not need to compile 
additional information on precursor control measures, or to proceed 
with actions to adopt and implement local or state regulations for the 
precursor. Precursor demonstrations as described in Options 2A or 2B 
could be conducted for Moderate areas for which the state can show that 
it can attain the standard by the end of the sixth calendar year after 
designation and for Moderate areas where the state's plan demonstrates 
that attainment by such date would be impracticable.
    The EPA believes that general legal authorities under the CAA 
support the proposal of the overall precursor demonstration concept 
described above, and that requesting comment on these proposed options 
is appropriate from both a technical and a legal standpoint. This case 
specific approach is technically appropriate because the mix of 
PM2.5 precursor emissions and other relevant technical 
factors varies from area to area. For example, in some areas, one 
precursor may be abundant while the main precursor with which it reacts 
may be less abundant. In such cases, reducing emissions of the less 
abundant precursor (the ``limiting'' precursor) is generally more 
effective for reducing PM2.5 concentrations. In another type 
of area, the PM2.5 concentrations that exceed the standard 
may be commonly dominated by primary PM2.5 emissions rather 
than by secondarily formed PM2.5. The emissions of the 
particular precursor from sources in the nonattainment area could be 
found to have an insignificant contribution to PM2.5 levels 
that exceed the standard, and the potential air quality improvement 
from reducing emissions of the precursor in the area may be limited.
    The EPA believes that proposing Options 2A and 2B is appropriate 
from a legal standpoint based on authority provided the Administrator 
in sections 302(g) and 301(a)(1) of the CAA. Section 302(g) includes in 
the definition of ``air pollutant'' all the precursors to that 
pollutant, and it allows the EPA Administrator to regulate precursors 
for ``the particular purpose for which the term `air pollutant' is 
used.'' Under section 301(a)(1), ``[t]he Administrator is authorized to 
prescribe such regulations as are necessary to carry out his functions 
under this Act.'' Thus, with Option 2, the EPA proposes a framework by 
which the regulation of PM2.5 precursors for a specific 
nonattainment area can be modified if the state provides the EPA with a 
credible technical demonstration for exempting a particular precursor 
which meets certain criteria and can be approved by the EPA. In 
addition, as noted earlier the set of analyses described under Option 
2A could also satisfy the section 189(e) provision allowing the state 
to demonstrate that major stationary source emissions of a particular 
precursor do not significantly contribute to levels that exceed the 
standard. While this approach is not explicitly described in the 
statute, the EPA believes that the proposed Option 2 approach to 
precursor regulation is reasonable and allowed under the statutory 
authority provided in sections 302(g) and 301(a)(1) noted above.
    The EPA anticipates that development of an approvable 
PM2.5 precursor demonstration by the state at the

[[Page 15357]]

beginning of the attainment plan development process will require a 
substantial level of effort and consultation with the EPA. Such a 
demonstration by the state would likely involve a combination of 
technically rigorous and complex analyses, such as air quality modeling 
and ambient data analyses. The extensive nature of this type of a 
technical demonstration early in the attainment plan development 
process is necessary because the demonstration serves as the basis for 
limiting the applicability and associated control strategy decisions 
only to specific precursors for both the attainment plan and for the 
NNSR permitting program.
    b. Area reclassified to serious. As noted earlier in this section, 
a Moderate area can be reclassified to Serious under two scenarios. 
Under the first scenario, if a Moderate area fails to attain the 
standard by the end of the sixth calendar year after designation, it 
would then be reclassified by the EPA as a Serious area, and the state 
would be required to develop and submit a Serious area attainment plan 
within 18 months of reclassification. Under the second scenario, EPA 
could reclassify an area to Serious prior to the Moderate area 
attainment date if it can be shown that it would be impracticable for 
the area to attain by the Moderate area attainment date.
    Proposed Option 2 would allow a ``precursor demonstration'' 
approach for Serious area plans in the same manner as for Moderate area 
plans. However, if the state had previously submitted a precursor 
demonstration that the EPA approved for the Moderate area attainment 
plan, under either proposed Option 2A or 2B the state would be required 
to review and update the precursor demonstration, taking into account 
any changes in the emissions inventory and any other relevant 
information or advances in technical tools developed since the initial 
demonstration was approved. Examples of such information would be 
improved emission estimation methods or emission factors for key source 
categories; changes in precursor emissions inventories due to emissions 
control programs or new source growth; the development of more advanced 
technical tools to assess the effectiveness of precursor reductions; 
and, updated information about new or more effective control 
technologies or emission reduction techniques. Any precursor 
demonstration that is approved as part of the Serious area attainment 
plan would need to be revised and updated if the area cannot attain the 
standard by the end of the tenth calendar year after designation and 
seeks an extension under section 188(e) or does not attain the standard 
by the applicable Serious area attainment date and is subsequently 
subject to 5 percent annual emission reductions under section 189(d).
    One other important factor to consider is the substantial amount of 
time that can elapse between the submission of a Moderate area 
attainment plan for a particular nonattainment area, and submission of 
a Serious area attainment plan. The plan for a Moderate area is due 
within 18 months of designation. Under the EPA's overall proposed 
approach to attainment plan development, the state would be required to 
evaluate control measures for all types of sources and for all 
PM2.5 precursors in order to ensure attainment of the 
standard as expeditiously as practicable. The full assessment to 
identify reasonable control measures would involve a thorough 
compilation and analysis of information on control technologies and the 
technological feasibility of implementation of such measures for 
sources in the area; the assessment of associated control costs and 
economic feasibility of implementation; information on the time needed 
for deployment and implementation of such control measures; and, the 
resulting timeline for achieving emissions reductions.
    If the Moderate area does not attain the standard by the end of the 
sixth calendar year after designation, then as required by to the CAA, 
the EPA would have 6 months to make a determination to that effect, and 
the area would be reclassified to Serious. The state would then have 18 
months to submit, at a minimum, a new attainment demonstration and 
control strategy comprising BACM and BACT. Thus, under these 
circumstances, these key Serious area plan elements would be due at 
least 8 years after the EPA designated the area nonattainment, and more 
than 6 years after the state submitted the original Moderate area plan. 
Because of the potentially protracted timeline for developing, 
implementing and revising as necessary the SIP for a given 
PM2.5 nonattainment area under subpart 4, the EPA believes 
it is reasonable for the state to be required to update any precursor 
demonstration it had previously developed for the area if the area is 
reclassified as Serious.
    The EPA requests comment on the requirement for the state to review 
and update any previously approved ``precursor demonstration'' if the 
area fails to attain the standard by the applicable Moderate area 
attainment date. The EPA also requests comment on the requirement for 
the state to review and update any previously approved ``precursor 
demonstration'' if the area fails to attain the standard by the 
applicable Serious area attainment date.
    c. NNSR. An approvable precursor demonstration under either Option 
2A or Option 2B would evaluate emissions of a particular precursor from 
all types of sources. Accordingly, if the state provides an approvable 
precursor demonstration for all types of sources of a particular 
precursor as described above, then under Option 2A, the state would 
also be able to rely on the same technical demonstration to conclude 
that emissions of that precursor just from major stationary sources in 
the area do not provide a ``significant contribution'' to 
PM2.5 concentrations in the area pursuant to section 189(e). 
Thus, under Option 2A, the state would not need to apply the NNSR 
control requirements for PM2.5 to that precursor in the 
particular PM2.5 nonattainment area(s) for which the EPA 
approves the demonstration.
    Under Option 2B, the state would conduct analyses to determine the 
sensitivity of PM2.5 levels in the area (that exceed the 
standard) to potential increases in emissions (relevant for NNSR) and 
decreases (relevant for attainment demonstrations). If the state 
provided an approvable precursor demonstration showing that 
PM2.5 concentrations are insensitive to potential increases 
in emissions of a particular precursor in the area, then under Option 
2B the state would be able to rely on this technical demonstration as 
the basis for not regulating that precursor for major stationary 
sources under NNSR.
    Additionally, there could be a situation where the state finds that 
emissions of another precursor (i.e., a precursor that was not the 
subject of the initial precursor demonstration) from only major 
stationary sources located in the nonattainment area could be 
considered to have an insignificant contribution to PM2.5 
levels that exceed the standard in the area (under Option 2A). For 
example, mobile and area source emissions of a PM2.5 
precursor could be determined to provide a larger contribution to 
PM2.5 levels than major stationary sources in a given 
nonattainment area and would be the focus of the attainment strategy, 
and the major stationary source emissions of that same precursor might 
have only a minimal contribution to PM2.5 levels. In this 
situation, the state could develop a separate demonstration under 
section 189(e) to support the exclusion of the

[[Page 15358]]

additional precursor from implementation requirements applicable to all 
major stationary sources, including NNSR program requirements (assuming 
the state analysis includes appropriate consideration of potential new 
sources of the relevant precursor). With an approved demonstration 
under section 189(e), major stationary sources of that precursor could 
also be excluded from the NNSR control requirements for 
PM2.5. The EPA seeks comment on all aspects of proposed 
Option 2.
    3. Option 3: An attainment planning analysis demonstrating that 
control measures for all types of sources of a particular precursor are 
not needed for expeditious attainment also would be deemed to meet the 
section 189(e) technical demonstration requirement, meaning that the 
state would not need to regulate emissions of the particular precursor 
from major stationary sources under the NNSR permitting program or 
other control requirements for major stationary sources.
    Under proposed Option 3, the consideration of precursors in the 
attainment planning process for Moderate and Serious areas would 
closely follow the approach described for Option 1 (see Sections 
III.B.1.a-c of this preamble). As described for Option 1, after 
developing a comprehensive emissions inventory, the state would conduct 
an analysis to identify the new reasonable control measures that need 
to be adopted and implemented in order for the Moderate area to attain 
the standard as expeditiously as practicable, but no later than by the 
end of the sixth calendar year after designation (this analysis is 
described in greater detail in Section III.B.1.a in this preamble). If 
the state determines that adoption of additional economically and 
technically feasible emission reduction measures for a particular 
precursor are not necessary for expeditious attainment by the end of 
the sixth calendar year after designation, and that such measures 
collectively would not accelerate the attainment date by at least a 
year, then for the purposes of this Moderate area attainment plan, the 
state would not need to adopt such additional measures because they 
would not be considered reasonable. (Note that the need for additional 
emissions reductions of the particular precursor would have to be re-
evaluated if the area is reclassified to Serious, or if the area 
submitted a SIP revision requesting an extension of the Serious area 
attainment date under section 188(e)).
    To clarify the intent of Option 3, unlike under Option 1, a 
separate analysis to show that major stationary sources of a particular 
precursor do not contribute significantly to PM2.5 levels in 
a given PM2.5 nonattainment area for purposes of section 
189(e) would not be needed. If the state's single analysis shows that 
emission reduction measures are not needed from sources of a particular 
precursor in order to demonstrate expeditious attainment, then under 
proposed Option 3 the same analysis would also be considered adequate 
to meet the requirements of section 189(e). In effect, the attainment 
planning analysis would define the set of precursors that would be 
subject to control under both the attainment plan and the NNSR 
permitting program for the area.\66\
---------------------------------------------------------------------------

    \66\ Note that while the NNSR program needs to be implemented 
from the effective date of an area's nonattainment designation, in 
some situations the state would implement either its existing NNSR 
program for PM2.5 or, in the absence of such program, 40 
CFR part 51 Appendix S, the default NNSR program, until the EPA 
approves the state's PM2.5 attainment plan and revised 
NNSR regulations for PM2.5.
---------------------------------------------------------------------------

    The rationale supporting the Option 3 approach focuses on the 
section 189(e) emphasis on precursor control requirements. If control 
measures are not needed in a Moderate nonattainment area to reduce 
emissions of a particular precursor from all types of sources in order 
to demonstrate attainment or to advance the attainment date, then under 
the rationale of proposed Option 3, it would follow that the state 
would not need to include any other control requirements that apply to 
major stationary sources of that precursor, including control 
requirements for PM2.5 under the NNSR program. The theory 
for this option would be that if the state determines that new control 
requirements for emissions of the particular precursor are not needed 
for purposes of attainment planning because they would not contribute 
to reducing PM2.5 levels that exceed the standard, then 
other control requirements to address emissions of that precursor also 
would not be needed. Note that under this option, the state also would 
not be required to analyze the potential effect of increases in 
emissions of the particular precursor (e.g., from the possible 
permitting of new sources) on PM2.5 concentrations in the 
area. The EPA requests comment on the rationale supporting Option 3.
    Additionally, under Option 3, as was the case with Option 2, there 
could be a situation where the state determines that control measures 
for a particular precursor are generally needed in order to demonstrate 
attainment as expeditiously as practicable, but that the major 
stationary sources of that precursor that are located in the 
nonattainment area have an insignificant contribution to 
PM2.5 levels that exceed the standard in the area. Under 
this Option 3, the EPA believes that section 189(e) provides the state 
with the authority to develop a separate demonstration to show that, 
even though control measures for a specific precursor emitted by 
sources other than major stationary sources are necessary to 
demonstrate expeditious attainment in an area, major stationary sources 
of that precursor have an insignificant contribution to 
PM2.5 concentrations that exceed the standard in the area. 
Thus, controls from major stationary sources of that precursor would 
not be required for either the attainment plan or the NNSR program. 
More discussion on the potential options for precursor technical 
demonstrations is included in Section III.C of this preamble. The EPA 
seeks comment on all aspects of proposed Option 3.
    The EPA also seeks comment on whether only one of these approaches 
should be included in the final rule, or whether it would be 
appropriate to include multiple approaches (e.g., both Options 1 and 2) 
or a hybrid of two approaches by which a state could demonstrate that a 
particular precursor would not need to be addressed in the attainment 
plan or NNSR permitting program for a specific area.

C. Technical Approaches for Demonstrating That a Precursor Does Not 
Need To Be Subject to Control Requirements

    As noted earlier, in the preamble to the 2007 PM2.5 
Implementation Rule, the EPA included a discussion allowing for the 
state to submit a technical demonstration to show to the satisfaction 
of the EPA that emissions of a particular precursor do not 
significantly contribute to PM2.5 concentrations in the 
area. In that preamble discussion, the EPA indicated that such a 
demonstration should be based on the weight of evidence of available 
information, and that any such demonstration by the state must be 
approved by the EPA. The 2007 PM2.5 Implementation Rule also 
discussed a number of types of analyses that could inform this 
precursor demonstration, such as speciation data analyses, air quality 
modeling studies, chemical tracer studies, emissions inventories, or 
special intensive measurement studies to evaluate specific atmospheric 
chemistry in an area. In the 2007 PM2.5 Implementation Rule, 
the EPA intended to provide states with the flexibility to provide a 
range of different supporting analyses that would be appropriate for

[[Page 15359]]

the area, recognizing that nonattainment areas differed in terms of 
such factors as: (i) The mix of emissions sources located in the 
nonattainment area and outside the area that are contributing to 
PM2.5 concentrations in the area; (ii) the levels of 
PM2.5 species measured in the area; (iii) the times of year 
when highest PM2.5 concentrations are observed; (iv) the 
topography of the area; (v) the severity of the nonattainment problem; 
and, (vi) the patterns of emissions and population growth in and around 
the nonattainment area. Under the 2007 PM2.5 Implementation 
Rule, an important criterion for any technical precursor demonstration 
provided by a state, however, was that it had to fairly represent the 
information available to the state and the information made available 
to it by the public.
    For this proposed implementation rule, the EPA similarly proposes 
that the state should have the flexibility to present multiple types of 
analyses to support any demonstration for exempting a precursor from 
control requirements as long as they fairly represent the available 
information, and accordingly proposes that the EPA should review any 
such demonstration based on the weight of evidence. Unlike in the prior 
implementation rule, however, later in this section the EPA raises the 
question of whether certain specific types of analyses should be 
included as minimum required components of any precursor demonstration 
that a state chooses to submit to the EPA for approval.
    The preamble to the 2007 PM2.5 Implementation Rule 
indicated that if a state developed a precursor demonstration as part 
of its draft SIP, then in accordance with the state rulemaking process, 
the demonstration would be subject to public review at the state level. 
It also stated that, as required under any rulemaking process, the 
state had to consider and provide a response in the rulemaking record 
to any information or evidence brought forward by commenters during the 
state's SIP planning, development and review process. By insuring that 
this important issue was explicitly addressed and supported in the 
attainment plan submitted to the EPA, the EPA could better evaluate the 
precursor demonstration in accordance with its obligations under the 
CAA. The EPA believes these are sound procedural steps for a state 
rulemaking process, and the regulations being proposed as part of this 
rule include similar language providing for public review of any 
proposed precursor demonstration.
    The 2007 PM2.5 Implementation Rule did not provide a 
specific due date for submittal of any precursor demonstration, 
although it was assumed that if a state were to pursue such a 
demonstration, it would need to be done early in the attainment plan 
development process and submitted to the EPA no later than the date of 
the attainment plan submission itself. It was recommended that the 
state develop any such demonstration in consultation with the 
appropriate EPA Regional Office. In this proposal, the EPA is proposing 
that if a state is interested in developing a PM2.5 
precursor demonstration to support not regulating one or more 
PM2.5 precursors in the attainment plan for an area, it 
should consult with the EPA Regional Office as early as possible to 
discuss appropriate analyses to be included. In its review of any 
precursor demonstration provided by a state, the EPA will consider all 
currently available information.
    Under all three proposed precursor policy options described above, 
the state would have the opportunity to provide a precursor 
demonstration to meet the requirements of section 189(e) of the CAA. 
Precursor demonstrations pursuant to section 189(e) should evaluate the 
significance of the contribution of emissions of a particular precursor 
from existing major stationary sources to fine particle concentrations 
that exceed the standard. However, Options 2A and 2B differ from the 
others in that they would provide the state with the ability to conduct 
a precursor demonstration that comprehensively assesses the 
contribution of a particular precursor from all types of sources in the 
nonattainment area (not just from major stationary sources as 
specifically addressed by section 189(e)) for the purposes of informing 
which precursors must be addressed in both the attainment plan and in 
the NNSR program for a particular PM2.5 nonattainment area. 
(Note that Option 2 would not prevent the state from also conducting an 
additional analysis under section 189(e), if warranted, to further 
demonstrate that while all emissions of a particular precursor make a 
significant contribution to PM2.5 levels that exceed the 
standard, the emissions from just the major stationary sources of that 
precursor collectively do not contribute significantly to 
PM2.5 levels that exceed the NAAQS in the area.) The EPA has 
considered three important questions regarding the scope and the 
potential requirements associated with precursor demonstrations, and 
requests comment on the questions and technical analysis options 
presented below.
1. What is the geographic area from which precursor emissions should be 
assessed?
    In the 2007 PM2.5 Implementation Rule, the preamble 
indicated that a precursor demonstration analysis addressing all source 
types covered by the attainment plan should evaluate the impact of 
emissions from sources located throughout the entire state. In 
contrast, the 2008 PM2.5 NSR Rule suggested that a precursor 
demonstration for NNSR purposes should evaluate emissions from major 
stationary sources of a particular precursor located within the 
nonattainment area only.
    In determining which approach to include in the present proposal, 
the EPA believes that it continues to be reasonable that any precursor 
demonstration conducted to assess precursor significance for NNSR 
purposes should evaluate emissions from major stationary sources of the 
precursor from within the nonattainment area only. Section 189(e) is 
included in a part of the CAA that specifically sets forth 
nonattainment area requirements. For attainment planning purposes it is 
less clear that the evaluation of emissions should be limited only to 
sources from within the nonattainment area, because the state has 
jurisdiction over emissions sources located throughout the state, and 
can impose emission reduction requirements on contributing sources 
outside of nonattainment areas if necessary to help bring areas with 
violating monitors into attainment. At the same time, that argument 
would suggest that section 189(e) should be interpreted as requiring 
two different analyses of the impacts of precursors emitted from two 
different geographic scales (from within the nonattainment area, as 
well as from a broader area that influences air quality within the 
nonattainment area, which could include the entire state). The EPA does 
not believe such an interpretation is required, nor does it believe 
that such multiple analyses are warranted. The statute simply refers in 
general terms to precursor emissions from major stationary sources and 
does not differentiate between control requirements for attainment 
planning and control requirements for other purposes, such as NNSR 
permitting. The statute also does not indicate that multiple analyses 
must be done to assess major stationary source impacts from multiple 
geographic scales. For these reasons, the EPA is proposing that

[[Page 15360]]

any precursor demonstration must include an evaluation of emissions 
from sources located in the nonattainment area only. The EPA requests 
comment on this proposed approach.
2. Should the EPA's guidance provide a specific list of analyses as 
``minimum requirements'' that must be included in any proposed 
precursor demonstration?
    As noted above, the EPA encourages states to provide a range of 
analyses to thoroughly understand the effect of precursor emissions on 
PM2.5 concentrations in an area. In past discussions with 
state representatives regarding potential approaches to regulating 
PM2.5 precursors, some representatives have suggested that 
this PM2.5 implementation rulemaking should include more 
specificity about the minimum requirements for technical demonstrations 
to support exclusion of PM2.5 precursors from regulatory 
requirements in attainment plans, while others have recommended a less 
prescriptive approach. One overarching issue is how detailed the EPA's 
guidance should be with regard to the analytical requirements for any 
proposed precursor demonstration. As noted earlier, technical 
demonstrations can include data such as ambient speciation data 
analyses, air quality modeling studies, chemical tracer studies, 
emissions inventories, and/or special intensive measurement studies. 
Air quality modeling analyses are discussed in more detail below.
    a. Contribution analysis. Based on the statutory language of 
section 189(e), it appears that, at a minimum, any precursor 
demonstration conducted specifically pursuant to section 189(e) must 
evaluate the contribution of current emissions of the relevant 
precursor from existing major stationary sources to current (or most 
recent) PM2.5 concentrations observed in the nonattainment 
area (note that this type of analysis is possible under Option 1 and 
Option 3). In addition, as described above, any precursor demonstration 
under Option 2A must evaluate the contribution of emissions of the 
relevant precursor from all sources (not just major stationary sources) 
to current (or recent) PM2.5 concentrations observed in the 
nonattainment area.
    In light of the statutory language and the capabilities of existing 
technical tools, the EPA proposes to require that the state conduct 
such a contribution analysis at a minimum as part of any proposed 
precursor demonstration, and that the state conduct an analysis using 
an air quality modeling system that adequately accounts for the 
PM2.5 pollution problem within the nonattainment area. 
Several photochemical air quality models (e.g., Community Multi-Scale 
Air Quality Model (CMAQ) and the Comprehensive Air Quality Model with 
Extensions (CAMx)) can be used to quantify the contributions of 
precursor emissions to PM2.5 concentrations in the area.\67\ 
For example, states could compare base case conditions (at current 
precursor emissions levels) with a separate model simulation in which 
the relevant precursor emissions are reduced by a large percentage. The 
difference in the estimated PM2.5 concentrations provides 
one indication of the relative significance of the precursor emissions 
to PM2.5 concentrations in the area. This type of 
contribution analysis can also be accomplished by using existing 
advanced tools within photochemical air quality models, such as 
``source apportionment'' capabilities which allow one to track 
precursor emissions as they ``form'' PM2.5 (in the model) 
and then report their contributions separately. The EPA requests 
comment on including a contribution analysis as a minimum requirement 
in any proposed precursor demonstration under Option 2A.
---------------------------------------------------------------------------

    \67\ For more information on CMAQ, see http://www.epa.gov/AMD/Research/RIA/cmaq.html. For more information on CAMx, seehttp://
www.camx.com/.
---------------------------------------------------------------------------

    b. Sensitivity analysis. The EPA notes that changes in 
PM2.5 concentrations from current conditions in any area 
will not necessarily be linear with respect to changes in 
PM2.5 precursor emissions. Therefore, another important 
question is whether any precursor demonstration should be required to 
include an assessment of how ``sensitive'' the area will be to 
potential reductions or increases in emissions of the relevant 
precursor. Sensitivity analyses of potential reductions in emissions 
would be most appropriate for attainment planning (and relevant to 
Option 2B), whereas sensitivity analyses of potential increases in 
emissions (e.g., relevant to NNSR permitting) would be appropriate for 
all section 189(e) technical evaluations (possible under Options 1, 2B 
and 3). Sensitivity analyses are important because of the complexity 
and variability of the atmospheric chemistry affecting PM2.5 
concentrations in different areas across the country.
    The principal PM2.5 components that are secondarily 
formed in the atmosphere are the result of chemical reactions between 
various PM2.5 precursors (see Section II of this preamble 
for more information on specific precursor reactions). Thus, the most 
effective precursor strategies for reducing PM2.5 
concentrations as part of attainment planning will vary from area to 
area, depending upon which specific precursors play a role in forming 
or limiting PM2.5 formation in the particular area. 
Likewise, in evaluating which precursors would be appropriate to 
exclude from regulation for NNSR in an area, it is important to 
understand the current sensitivity of the atmosphere to potential 
increases in precursor emissions that could result from the addition of 
new sources to the nonattainment area.
    One approach to assessing precursor sensitivities would be to 
conduct a model simulation that evaluates the effect on 
PM2.5 concentrations in the area resulting from a given set 
of precursor emission reductions and emission increases. Simulations 
could be conducted to assess a set of emission reduction and emission 
increase scenarios deemed appropriate to determine the sensitivity of a 
particular precursor in a specific area. Another approach that could be 
used is a scientific technique called the ``decoupled direct method'' 
(DDM), which efficiently estimates the impacts on PM2.5 
concentrations as a result of reducing or increasing precursor 
emissions in the model.\68\
---------------------------------------------------------------------------

    \68\ See Simon et al., Memorandum to ozone NAAQS docket EPA-HQ-
OAR-2008-0699, ``Model-based Rollback Using the Higher Order Direct 
Decoupled Method (HDDM),'' August 14, 2012.
---------------------------------------------------------------------------

    For the reasons discussed above, the EPA also proposes that any 
precursor demonstration conducted under proposed Option 2B must provide 
a set of sensitivity analyses that evaluate the effect of a range of 
emissions changes associated with measures considered economically and 
technically feasible in a particular nonattainment area. Analyses that 
reduce emissions of a particular precursor will help the state and the 
EPA to understand how ``responsive'' the atmosphere would be to control 
measures and how effective such reductions would be relative to other 
precursor reductions. Although not specifically required for other 
options under this proposed rule, precursor sensitivity analyses 
evaluating the effect of varying degrees of potential precursor 
reductions would provide meaningful information for any precursor 
demonstration intended to show that a particular precursor does not 
need to be addressed for attainment planning. Conversely, sensitivity 
analyses that consider the effect of a range of potential emissions 
increases in the nonattainment area will help the state and the EPA to 
understand the potential response of PM2.5

[[Page 15361]]

concentrations to projected growth in the area, including potential 
increases in emissions associated with potential newly permitted 
sources that emit the precursor in question. Any precursor 
demonstration intended to show that a particular precursor does not 
need to be addressed for NNSR should include sensitivity analyses 
evaluating the effect of varying degrees of precursor emission 
increases in the area. The EPA recommends that the state conduct these 
analyses using air quality modeling tools, but the state could provide 
additional relevant analyses as well. The EPA requests comment on the 
proposed requirement for inclusion of sensitivity analyses in any 
precursor demonstration.
3. Should there be a ``bright line'' value to indicate that any 
estimated contribution to annual average or 98th percentile 
PM2.5 concentrations in the nonattainment area that exceeds 
this value would be considered ``significant''?
    In considering this question, it is helpful to first look to how 
the concept of a significant, or insignificant, contribution has been 
interpreted with regard to particulate matter in past PM10 
guidance (Addendum to the General Preamble) and in other 
PM2.5-related regulations, such as the CAIR. In the 
Addendum, the EPA introduced the concept of a ``de minimis'' impact 
from a source category for the purposes of the identification and 
evaluation of BACM.\69\ While a later discussion in this proposal 
addresses whether or not to maintain a similar de minimis source 
category-based policy approach for future BACM and BACT source category 
analyses, what is relevant for this precursor discussion is the EPA's 
guidance in the Addendum on what could be considered a ``de minimis,'' 
or ``insignificant,'' ambient impact for purposes of PM10. 
In the Addendum, the EPA indicated that a 1 [mu]g/m\3\ contribution to 
the annual PM10 standard of 50 [mu]g/m\3\ (equal to 2 
percent of the applicable NAAQS at the time), or a 5 [mu]g/m\3\ 
contribution to the 24-hour PM10 standard of 150 [mu]g/m\3\ 
(equal to 3.3 percent of the applicable NAAQS at the time) 
presumptively would be considered ``de minimis.'' The EPA set forth 
these levels in a Federal Register document, citing the discretionary 
authority of an administrative agency to exempt from regulation 
emissions (from source categories) ``which contribute only negligibly 
to ambient concentrations which exceed the NAAQS.''
---------------------------------------------------------------------------

    \69\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42011.
---------------------------------------------------------------------------

    Developed pursuant to subpart 4, this past guidance on what could 
be considered to be a de minimis or insignificant level of 
PM10 contribution from a source category can potentially 
inform this proposed rule for implementing the PM2.5 NAAQS. 
Accordingly, this proposal includes two options: (i) A ``no-threshold'' 
option, and (ii) a proposed threshold option derived from the ambient 
levels relied on for the PM10 source category de minimis 
thresholds, but adjusted to account for the 2012 PM2.5 
NAAQS.
    The concept of ``significant contribution'' also has been a central 
one with regard to interstate transport and the interpretation of 
section 110(a)(2)(D) of the CAA. In past programs to address interstate 
transport, such as the CAIR, an ``upwind'' state was identified as 
potentially subject to additional emission control requirements if the 
impact of SO2 and NOX emissions from the upwind 
state to any nonattainment area in a downwind state exceeded 1 percent 
of the relevant PM2.5 standard at a violating monitor in 
another state. This was merely the first step of the analysis, but it 
provided an initial threshold for determining whether further analysis 
was warranted. In this proposal, the concept of a significant 
contribution refers to the effect of emissions of a particular 
precursor from sources within the state or nonattainment area to local 
PM2.5 concentrations in the nonattainment area. The specific 
purpose and context for which the phrase ``contribute significantly'' 
is used in section 189(e) is very different from the purpose and 
context for which it is used in section 110(a)(2)(D). Thus, while a 
previous interstate transport rule under section 110(a)(2)(D) 
considered the combined impact of SO2 and NOX 
emissions from an upwind state on ambient PM2.5 at a 
violating monitor to be insignificant if it was less than 1 percent 
(i.e., 0.15 [mu]g/m\3\ on an annual average basis), it would not 
necessarily be appropriate to also consider the contribution from 
emissions of a specific precursor within a nonattainment area to be 
``insignificant'' if it does not exceed a similar 1 percent ambient 
concentration level.\70\
---------------------------------------------------------------------------

    \70\ See Rule To Reduce Interstate Transport of Fine Particulate 
Matter and Ozone (Clean Air Interstate Rule); Revisions to Acid Rain 
Program; Revisions to the NOX SIP Call, 70 FR 25162 (May 
12, 2005).
---------------------------------------------------------------------------

    There are a number of important distinctions between the section 
110(a)(2)(D) interstate transport provision and the section 189(e) 
provision addressing contributions of major stationary sources in a 
nonattainment area which would indicate that the 1 percent of the NAAQS 
significant contribution thresholds that have been included in section 
110(a)(2)(D) rulemakings may not be relevant for purposes of section 
189(e) precursor demonstrations. Section 110(a)(2)(D) was designed to 
address the collective contribution of interstate transport of 
pollution from multiple upwind states, while section 189(e) addresses 
contributions from major stationary sources in a single nonattainment 
area. In addition, section 110(a)(2)(D) requires that SIPs contain 
provisions to eliminate the contributions that are deemed significant, 
whereas section 189(e) merely requires that the emissions be 
controlled. Given the differences in purpose, scale, and scope, the EPA 
does not believe it is necessary for a threshold for ``significant 
contribution'' to be the same for the two programs.
    Based on the considerations discussed above regarding inclusion of 
a potential significance ``threshold'' for purposes of this 
PM2.5 implementation rulemaking, the EPA proposes and seeks 
comment on two options. The first option would not specify a threshold 
for what is a significant contribution to levels that exceed the 
relevant NAAQS in a given area. Rather, the state would be required to 
conduct a contribution analysis and sensitivity analyses as described 
above to determine the estimated level of ambient impact from the 
relevant precursor, and to provide the analyses to the EPA as part of 
its precursor demonstration. The EPA would then consider these analyses 
in addition to the other analyses provided by the state in determining 
whether to approve the precursor demonstration. This option would 
provide greatest flexibility for the state and the EPA to consider the 
contribution analysis in combination with other information relevant to 
the unique PM2.5 composition, source mix, and attainment 
needs of each individual nonattainment area. See proposed 40 CFR 
51.1006.
    The second option would specify a ``significance'' threshold of 3 
percent, such that if contribution modeling indicated that base year 
emissions of the precursor from the relevant sources in the 
nonattainment area (i.e. from major stationary sources for all analyses 
pursuant to section 189(e); from all types of sources for the upfront 
analysis in Option 2) leads to an ambient impact that exceeds 3 percent 
of the PM2.5 NAAQS (e.g.,, 0.36 [mu]g/m\3\ on an annual 
average basis for the 2012 primary annual PM2.5 NAAQS) at 
monitors in

[[Page 15362]]

the nonattainment area, then the precursor demonstration would not be 
approvable. The threshold equivalent to 3 percent of the relevant 
PM2.5 NAAQS is proposed as reasonable because it is between 
the two de minimis ambient contribution levels included in previous 
PM10 guidance issued under subpart 4 to identify a de 
minimis level of ambient contribution from a group of emissions 
sources. The EPA acknowledges that the context in which the proposed 
threshold is used here is different from the context in which it was 
used in previous guidance. Absent any explicit language provided in the 
statute to define significant contribution in the context of section 
189(e), however, the only other existing guidance that in some way 
addresses the concept of significant contribution for PM10 
is the de minimis source category threshold values from the Addendum. 
One benefit of having a specific threshold in the rule is that states 
will have more concrete guidance on what could potentially be 
approvable in a precursor demonstration.
    The EPA therefore seeks comment on: (1) Whether a specific 
significant contribution threshold should be included in the final rule 
or not; (2) if the commenter considers inclusion of a specific 
threshold to be appropriate, whether the proposed 3 percent of the 
relevant NAAQS threshold and its basis would be appropriate, and why; 
and (3) whether a threshold with an alternative level and supporting 
rationale would be more appropriate.

IV. What are the EPA's proposed requirements for Moderate area 
attainment plans?

    Sections 189(a), (c), and (e) of the CAA require that Moderate area 
attainment plans contain the following: (i) An approved permit program 
for construction of new and modified major stationary sources (section 
189(a)(1)(A)); (ii) a demonstration that the plan provides for 
attainment by no later than the applicable Moderate area deadline or a 
demonstration that attainment by that deadline is impracticable 
(section 189(a)(1)(B)); (iii) provisions for the implementation of RACM 
and RACT no later than 4 years after designation (section 
189(a)(1)(C)); (iv) quantitative milestones that will be used to 
evaluate compliance with the requirement to demonstrate reasonable 
further progress (RFP) (section 189(c)); and, (v) evaluation and 
regulation of PM2.5 precursors (in general to meet RACM and 
RACT and other attainment planning requirements, and as specifically 
required for major stationary sources by section 189(e)). Other subpart 
1 requirements for attainment plans continue to apply to 
PM2.5 nonattainment areas subject to subpart 4 and include 
the following: (i) a description of the expected annual incremental 
reductions in emissions that will demonstrate RFP (section 172(c)(2)); 
(ii) emissions inventories (section 172(c)(3)); (iii) other control 
measures (besides RACM and RACT) needed for attainment (section 
172(c)(6); and, (iv) contingency measures (section 172(c)(9)).
    Each of these statutory requirements is described more fully below. 
In certain cases, the EPA is proposing options for implementing a 
statutory requirement for purposes of the PM2.5 NAAQS. Based 
on comments the agency receives, the EPA will then promulgate 
regulations to implement the statutory requirements in the final action 
on this proposal, as appropriate. The EPA notes that its longstanding 
guidance on these statutory requirements is embodied in the General 
Preamble and the Addendum.\71\ Where appropriate, this proposal notes 
options that may vary from past EPA guidance and explains the EPA's 
reasons for considering an amended approach.
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    \71\ See the Federal Register published on April 16, 1992 (57 FR 
13498, 13536, 13537, 13538, 13539, 13540, 13541, 13542, 13543, 13544 
and 13545); and see the Federal Register published on August 16, 
1994 (59 FR 41988).
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A. Plan Due Dates

    Section 189 of the CAA specifies the schedule by which states must 
submit attainment plans for the PM2.5 NAAQS. Specifically, 
CAA section 189(a)(2)(B) requires states to submit an attainment plan 
that meets Moderate area attainment plan requirements no later than 18 
months from the date of a nonattainment designation.\72\ To be 
consistent with this subpart 4 deadline for the attainment plan 
submission, the EPA is proposing that states must also submit those 
elements of the attainment plan required under subpart 1 (i.e., 
emissions inventories and contingency measures) no later than 18 months 
from the date of designation of the area. The provisions of subpart 4 
do not explicitly specify when states must submit these attainment plan 
elements that carry over from subpart 1, so the EPA needs to interpret 
the requirements of the CAA to meet the objectives of the attainment 
plan requirements. The EPA believes that requiring states to submit the 
necessary emissions inventory (or inventories) either before or at the 
same time as the other attainment plan elements due under subpart 4 is 
necessary, given that a state will need information contained in the 
emissions inventory for other elements of its Moderate area attainment 
plan, such as its precursor analysis, analysis of RACM and RACT and 
additional reasonable measures, and attainment demonstration modeling. 
The EPA also believes it is reasonable to require the state to submit 
contingency measures, which need to be adopted and ready for immediate 
implementation in the event a nonattainment area fails to meet RFP 
requirements or fails to attain the PM2.5 NAAQS by the 
applicable attainment date, simultaneous with the other elements of the 
attainment plan. The state's evaluation of what emissions controls are 
appropriate to meet the contingency measure requirement is closely 
related to other aspects of the attainment plan, such as addressing the 
proper pollutants for control in a given area, the appropriate sources 
for controls beyond those already required for RACM and RACT for the 
area, and the amount of emission reductions that the contingency 
measures should achieve, based upon the facts and circumstances of the 
attainment plan for the area.
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    \72\ The EPA notes that Congress provided different statutory 
deadlines for submission of attainment plans under subpart 1 and 
subpart 4. Under section 172(b), the EPA is directed to establish 
the date for the attainment plan submission, but it can extend no 
later than 3 years from the date of a nonattainment designation. By 
contrast, under section 189(a)(2)(B), the statute provides that 
states must make the attainment plan submissions within 18 months 
after designation. Due to the December 2013 court decision in NRDC 
v. EPA, however, the EPA promulgated an alternative submission date 
of December 31, 2014 for attainment plans for the 1997 
PM2.5 and 2006 PM2.5 NAAQS in order to provide 
a reasonable, prospective due date for attainment plans that must 
comply with subpart 4 requirements and to clarify the requirements 
that a state must meet prior to redesignation of a PM2.5 
nonattainment area. See 79 FR 31566 (June 2, 2014).
---------------------------------------------------------------------------

    The EPA believes that the statutory deadline for submission of a 
Moderate area attainment plan for the PM2.5 NAAQS is 
straightforward and, absent unusual circumstances, the statute requires 
states to make such attainment plan submissions within 18 months after 
the effective date of a nonattainment designation for an area. See 
proposed 40 CFR 51.1003(a). Although nothing in the CAA prohibits 
states from making separate attainment plan submissions to meet the 
individual statutory requirements for attainment plans in advance of 
the required date, the EPA presumes that development and submission of 
all of the attainment plan elements simultaneously will be most 
effective, both for the state in the first instance and for the EPA in 
reviewing the state's submission. For example, the EPA designated areas 
as nonattainment for the 2012 PM2.5

[[Page 15363]]

NAAQS with an effective date of April 15, 2015; states will thus be 
required by statute to submit Moderate area attainment plans for any 
nonattainment areas to the EPA no later than October 15, 2016.

B. Emissions Inventory Requirements

    Pursuant to its authority under section 110 of title I of the CAA, 
the EPA has long required states to submit inventories of the emissions 
of criteria pollutants and their precursors. The EPA codified these 
requirements in 40 CFR part 51, subpart Q in 1979 and amended them in 
1987. Additionally, the 1990 CAA Amendments revised many of the 
provisions of the CAA related to attainment of the NAAQS and the 
protection of visibility in mandatory Class I federal areas (certain 
national parks and wilderness areas). These revisions established new 
emissions inventory requirements applicable to areas that were 
designated nonattainment for certain pollutants. In the case of 
particulate matter, Congress did not create a specific emissions 
inventory requirement in subpart 4 that would supersede the emissions 
inventory requirement under subpart 1. Thus, the section 172(c)(3) 
emissions inventory requirements continue to apply, and that provision 
explicitly requires ``a comprehensive, accurate, and current inventory 
of actual emissions of the relevant pollutants'' in the nonattainment 
area. In addition, the specific attainment plan requirements for the 
PM2.5 NAAQS set forth in section 189(a) and associated 
modeling requirements make an accurate and up-to-date emissions 
inventory a critical element of any viable attainment plan. Because of 
the nature of PM2.5, the EPA concludes that the statutory 
requirements for emissions inventories need further elaboration through 
additional regulatory requirements as described below.
    Emissions inventory data serve as the foundation for various types 
of analyses that enable states to evaluate the degree to which 
different emissions sources contribute to the nonattainment problem in 
a given nonattainment area and enable states to estimate the air 
quality improvement that can be achieved through different control 
measures. States should use the best available, current emissions 
inventory information for attainment plan development, because high 
quality emissions inventory data are essential for the development of 
an effective control strategy. To assist states in preparing complete, 
high quality inventories, the EPA provides guidance for developing 
emissions inventories called ``Emissions Inventory Guidance for 
Implementation of Ozone and Particulate Matter National Ambient Air 
Quality Standards (NAAQS) and Regional Haze,'' which is available from 
http://www.epa.gov/ttn/chief/eidocs/eiguid/index.html. This guidance is 
commonly called the ``SIP Emissions Inventory Guidance.'' The EPA 
recommends that states consult this guidance while developing the 
emissions inventories to meet statutory and regulatory requirements.
1. How do states meet the inventory requirements for the 
PM2.5 NAAQS?
    Neither section 172(c)(3), nor the provisions specifically 
applicable to attainment plans for the PM2.5 NAAQS in 
subpart 4, specify how states should meet statutory emissions inventory 
requirements. Although section 172(c)(3) explicitly requires that 
states submit only ``an'' emissions inventory in conjunction with other 
elements of an attainment plan, that term is ambiguous in the context 
of the PM2.5 NAAQS, and the EPA is authorized to interpret 
that term and to impose additional requirements as necessary and 
appropriate. In addition, pursuant to section 301, the EPA has 
additional authority to promulgate regulations as necessary for the 
implementation of the PM2.5 NAAQS, including requirements 
pertaining to emissions inventories. Accordingly, the EPA is proposing 
specific emissions inventory requirements it considers necessary to 
effectuate the attainment plan requirements of the CAA for the 
PM2.5 NAAQS.
    There are three key facets of the EPA's proposed emissions 
inventory requirements, as laid out below: (i) The type of inventories 
required; (ii) the timing of submittal of these inventories; and, (iii) 
the content of these inventories. These inventory requirements are 
being proposed to provide all of the requirements in a concise and 
direct way. In some cases, the EPA's rationale for the content 
requirements needs additional supporting description, which is provided 
in the subsequent text related to the use of seasonal inventories, 
required pollutants, etc.
    First, the EPA believes that in order to implement the 
PM2.5 NAAQS effectively, states will be required to submit 
at least two separate and distinct nonattainment area emissions 
inventories as elements of an attainment plan. The first emissions 
inventory is relevant for assessing the current or base year emissions 
in the nonattainment area; the second emissions inventory is a 
projected inventory relevant for assessing emissions in the target 
attainment year in the nonattainment area. The first type of inventory 
is expressly required by section 172(c)(3), and is called the ``base 
year inventory for the nonattainment area.'' The second type of 
inventory the EPA is proposing to require under section 301(a)(1) as 
necessary to implement the attainment demonstration requirement of 
section 189(a)(1)(B), and is called the ``attainment projected 
inventory for the nonattainment area.'' See proposed 40 CFR 51.1000. 
The need for this latter inventory stems from the need for both the EPA 
and the public to be able to compare, during their reviews of the plan, 
the base year inventory against the attainment projected inventory for 
the nonattainment area. For these reasons, the EPA is proposing to 
establish the regulatory requirement that attainment plans must include 
a base year inventory for the nonattainment area and an attainment 
projected inventory for the nonattainment area.
    Second, as noted above, to meet the statutory requirements for 
submission of attainment plans under subpart 4, the EPA believes that 
states must meet the same submission schedule for these emissions 
inventories as for the other elements of an attainment plan, i.e., 
within 18 months after the effective dates of the designation of the 
nonattainment area. This schedule must apply to both of these emissions 
inventories because they are necessary for effective evaluation of the 
attainment plan as a whole. Consequently, under the authority of 
section 172(b), the EPA is proposing to establish the regulatory 
requirement that emissions inventories be submitted by 18 months after 
designation.
    Third, the EPA proposes to establish specific requirements for both 
the base year inventory for the nonattainment area and for the 
attainment projected inventory for the nonattainment area in order to 
implement the PM2.5 NAAQS most effectively. Accordingly, the 
EPA proposes that the base year inventory for the nonattainment area 
must meet the following minimum criteria (a) through (g):
    (a) The inventory year must be one of the 3 years used for 
designations or another technically appropriate inventory year. Another 
inventory year may be chosen under specific circumstances (e.g., to 
account for a change in sources in the nonattainment area, changes in 
nonattainment area boundaries, or significant time lag between 
designations and preparation of the inventory) with consultation from 
the appropriate EPA Regional Office. This requirement is intended to 
ensure

[[Page 15364]]

that the inventory will represent the emissions sources whose 
contributions resulted in a nonattainment designation for the area.
    (b) The inventory must include actual emissions of all sources 
within the nonattainment area. This requirement stems directly from the 
wording of section 172(c)(3). Sources outside of the nonattainment area 
are explicitly not included in the section 172(c)(3) requirement with 
the words ``in such area.'' Furthermore, the EPA interprets the Act 
requirement for ``actual emissions from all sources'' in section 
172(c)(3) as intending to include all emissions that may contribute to 
the formation of PM2.5 within the nonattainment area.
    (c) The emissions values must either be annual total emissions or 
average-season-day emissions, as appropriate for the nonattainment 
problem. The rationale for providing annual or seasonal emissions must 
be included as part of the plan. A discussion of the EPA's rationale 
for proposing the option of seasonal or annual inventories is provided 
in Section IV.B.4 of this preamble.
    (d) As discussed above and consistent with past implementation rule 
requirements, the inventory must include emissions of direct 
PM2.5 (both filterable PM2.5 and condensable 
PM2.5), as well as all scientific PM2.5 
precursors (SO2, NOX, VOC and ammonia). A 
discussion of the EPA's rationale for proposing this requirement is 
provided in Section IV.B.5 of this preamble.
    (e) The emissions thresholds for which emissions sources must be 
reported as point sources must be followed from the Air Emissions 
Reporting Rule (AERR), 40 CFR part 51, subpart A. This requirement is 
consistent with past implementation rules and is needed to define the 
data structure (as opposed to the emissions values themselves) of the 
emissions submitted to the EPA. A discussion of the use of 40 CFR part 
51, subpart A, for the emissions thresholds and data reporting elements 
is provided in Section IV.B.6 of this preamble.
    (f) The detail of the emissions included in the inventory must be 
consistent with the detail required by 40 CFR part 51, subpart A. For 
example, all emissions must be subdivided to individual emissions 
processes within a facility or county. While these details should 
underlie the inventory, the emissions included in the attainment plan 
can be summarized. This requirement is consistent with the 2007 
PM2.5 Implementation Rule and is needed to define the data 
structure (as opposed to the emissions values themselves) of the 
emissions submitted to the EPA.
    (g) If the base year inventory for the nonattainment area is 
submitted to the EPA as a separate plan submission (i.e., severed from 
the overall attainment plan and provided separately), the inventory 
must still meet all public review requirements associated with that 
plan. See proposed 40 CFR 51.1008(a)(1).
    For the attainment projected inventory for the nonattainment area, 
the EPA also proposes to promulgate more specific requirements in order 
to implement the PM2.5 NAAQS most effectively. Accordingly, 
the EPA proposes that the attainment projected inventory must meet the 
following minimum criteria (a) through (g):
    (a) The year of the projected inventory must be the first year for 
which attainment is demonstrated by the modeled attainment plan.
    (b) The emissions values must be projected emissions of the same 
sources included in the base year inventory for the nonattainment area 
(i.e., only those located within the nonattainment area) and any new 
sources. The projected emissions values should be the best available 
representation of expected emissions, and thus should take into account 
emissions growth and contraction, facility closures, new facilities, 
new controls and other factors forecast to occur between the base year 
and the attainment year. In deciding what factors are relevant, states 
should consider factors affecting projected emissions that could 
significantly alter the conclusions of the attainment demonstration.
    (c) The temporal period of emissions must be the same temporal 
period (annual or average-season-day) as the base year inventory for 
the nonattainment area.
    (d) Consistent with the base year inventory for the nonattainment 
area, the inventory must include all emissions of direct 
PM2.5 (both filterable and condensable PM2.5), as 
well as all emissions of all scientific precursors (SO2, 
NOX, VOC and ammonia).
    (e) The same sources reported as point sources in the base year 
inventory for the nonattainment area must also be provided as point 
sources in the attainment projected inventory for the nonattainment 
area. Likewise, nonpoint and mobile source projected emissions must 
also be provided using the same detail (e.g., state, county and process 
codes) as the base year inventory.
    (f) The detail of the emissions included must be consistent with 
the level of detail in the base year inventory (i.e., as required by 40 
CFR part 41, subpart A).
    (g) If the attainment projected inventory for the nonattainment 
area is submitted to the EPA as a separate plan submission (e.g., 
severed from the overall attainment plan and provided separately), the 
inventory must still meet all public review requirements associated 
with that SIP submission. See proposed 40 CFR 51.1008(a)(2).
2. Are there new inventory requirements in this proposed rule that have 
not been included in previous rules?
    This proposed rule includes more specific requirements for 
emissions inventories than past implementation rules. First, the EPA 
proposes to require the attainment projected inventory for the 
nonattainment area. In practice, some states were providing this 
information at the request of their respective EPA Regional Offices, 
but it was not a specific requirement. The EPA believes that a specific 
requirement is necessary to ensure that the EPA and the public can 
reasonably assess the changes in emissions in the nonattainment area 
that the state maintains demonstrate that the area will attain the 
standard or that it is impracticable to attain the standard by the 
attainment date. Without such information, there is no way for the EPA 
to assess the projected emissions changes in the nonattainment area 
that the state asserts contribute to attainment. In addition, this 
proposed requirement would support the EPA's first proposed approach 
for conducting an RFP analysis as described in Section IV.F of this 
preamble.
    This proposed rule also is more specific about the requirements for 
the emissions inventories submitted. While the various criteria (a) 
through (g) listed above have been implicit in prior rules and 
associated guidance, the EPA believes that not having these specific 
requirements has caused confusion and inconsistencies across attainment 
plan inventories in the past. Thus, the EPA is proposing to require 
these minimum criteria in this proposed rule. Furthermore, the option 
for using only seasonal inventories in some attainment plans is a new 
facet of this rule, further described in Section IV.B.5 of this 
preamble.
3. Are there other inventory requirements from earlier PM2.5 
implementation rules that the EPA is proposing to retain or change?
    The 2007 PM2.5 Implementation Rule required states to 
submit specific emissions inventories in connection with the RFP 
requirements of section 172(c)(2) under subpart 1. The EPA believes 
that a separate emissions

[[Page 15365]]

inventory will be important to illustrate how a nonattainment area may 
achieve incremental emissions reductions toward attainment, and would 
be appropriate in light of the agency's proposed approaches for states 
to meet the statutory RFP requirements. Past EPA guidance with respect 
to RFP requirements under subpart 4 has not required any explicit, 
separate emissions inventory for this purpose for PM10 
NAAQS. For this reason, the EPA describes this issue and proposed 
approaches more fully in Section IV.F of this preamble.
    The 2007 PM2.5 Implementation Rule also required states 
to submit a statewide base year emissions inventory as part of the 
attainment plan. The EPA proposes not to include this statewide 
emissions inventory requirement in this rule. Subpart 4 does not 
expressly require such an inventory, and the EPA does not believe that 
it is needed for successful attainment of the PM2.5 NAAQS. 
Furthermore, statewide inventories are already required as part of the 
AERR (40 CFR part 51, subpart A) on a triennial basis. While these 
inventories do not receive the same level of scrutiny as inventories 
associated with attainment plans, the EPA believes that this existing 
statewide requirement is sufficient for understanding the 
PM2.5 nonattainment problems nationally and assessing the 
quality of inventories proposed to be required by this rule.
4. Why is the EPA proposing to permit seasonal inventories to meet the 
inventory reporting requirements?
    The statute does not explicitly address whether the emissions 
inventory required under section 172(c)(3) should include emissions 
throughout an entire calendar year or emissions during some shorter 
portion of the year that may be appropriate for implementation of a 
particular NAAQS. In the case of the PM2.5 NAAQS, the 
standards currently include both annual NAAQS and 24-hour NAAQS. With 
respect to the annual NAAQS, the form of the NAAQS includes monitored 
ambient PM2.5 values at all times throughout the course of 
the year and thus an annual emissions inventory is necessarily required 
for development of an appropriate attainment plan for a given area. In 
the case of the 24-hour NAAQS, however, the form of the NAAQS is based 
upon monitored ambient PM2.5 values on particular days with 
high levels of PM2.5, and in some nonattainment areas those 
days may occur only during a distinct and definable season of the year. 
The EPA considers it appropriate to interpret the emissions inventory 
requirements of the CAA in light of the specific inventory needs that 
are relevant for the NAAQS in question, and in the case of the 
PM2.5 NAAQS, the inventory requirement may thus include both 
an annual emissions inventory for the attainment area, and a seasonal 
emissions inventory for the area as appropriate for the attainment plan 
at issue.
    In contrast with the annual PM2.5 NAAQS, the 24-hour 
PM2.5 NAAQS are designed to protect against peak exposures. 
Thus, for the 24-hour PM2.5 NAAQS, there are circumstances 
in which the EPA believes that only seasonal emissions inventories may 
be required for attainment planning purposes. The EPA proposes to allow 
states to use only seasonal inventories for attainment plan development 
for attaining the 24-hour PM2.5 standard in areas that are 
nonattainment for only the 24-hour standard. In the event that it is 
appropriate to rely on a seasonal emissions inventory, the state should 
confer with the EPA concerning the exact length of the season and the 
start and stop dates of the season. The duration and start and stop 
dates of the season will be an important component of the attainment 
plan and must be approved by the EPA along with other elements of the 
attainment plan for a given nonattainment area. The EPA further 
proposes to require that seasonal inventories must use average-season-
day emissions values for this purpose. The average-season-day is 
defined as the sum of all emissions during the applicable season 
divided by the number of days in that season. The nature of some 
seasonal PM2.5 emissions sources (e.g., residential wood 
combustion) does not allow for only weekday emissions to be included in 
the inventory, therefore all days must be included. The state would 
need to explain the rationale for the duration of the season used for 
the inventory as part of the attainment plan submission. To justify the 
use of a seasonal inventory, the state must demonstrate why a seasonal 
attainment plan is appropriate for the particular PM2.5 
nonattainment area in question.
5. Why is the EPA requiring certain pollutants be included in the 
inventories?
    The EPA is proposing that states must submit emissions inventories 
that include all emissions of direct PM2.5 and all emissions 
of all PM2.5 precursors: SO2, NOX, VOC 
and ammonia. Furthermore, the inventory must differentiate between the 
condensable and filterable portions of direct PM2.5 
emissions. Section II.B of this preamble describes the background 
needed to understand the importance of including these precursors in 
emissions inventories for attainment plan purposes for the 
PM2.5 NAAQS. Emissions information about PM2.5 
and its precursors is a necessary precondition to meeting other core 
attainment plan requirements, such as effective evaluation of control 
measures and adequate demonstration of projected future attainment of 
the NAAQS through modeling. The EPA notes that with respect to 
requiring states to include emissions of direct PM2.5 and 
PM2.5 precursors in emissions inventories, the agency is 
following the requirements it established for the PM2.5 
NAAQS in the past. Section 172(c)(3) explicitly requires states to 
submit a ``comprehensive, accurate, and current inventory of actual 
emissions of the relevant pollutants'' and the EPA concludes that in 
order to meet these basic statutory requirements for the 
PM2.5 NAAQS, states must address PM2.5 and all 
PM2.5 precursors in their emissions inventories.
    The EPA requires air agencies to use the best available 
methodologies for estimating emissions of PM2.5 and its 
precursors. It should be noted that for ammonia, in particular, updated 
emissions estimating methodologies for animal feeding operations are 
under development using data collected during the period 2007-2009 from 
representative operations pursuant to the National Air Emissions 
Monitoring Study.\73\ The EPA is hopeful that such updated 
methodologies will help to reduce uncertainties in current ammonia 
inventories and will improve the quality of future emissions 
inventories needed for implementing the PM2.5 NAAQS.
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    \73\ For more information on the NAEMS study, see: http://www.epa.gov/agriculture/airmonitoringstudy.html.
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6. Why is the AERR used to define data elements and data methods that 
are required for the emissions inventories required by this rule?
    Because the provisions of the CAA do not specifically state the 
form of the emissions information to be reported to the EPA for meeting 
their attainment plan inventory requirement, it is necessary for the 
EPA to prescribe specifically the data elements of those emissions 
inventories. Distinct from the emissions values (i.e., how much 
emissions derive from each source or source category), the emissions 
elements (i.e., how they are reported) refer to the reporting 
definitions, data codes and required data fields. The EPA proposes

[[Page 15366]]

that states must use the emissions elements from 40 CFR part 51, 
subpart A, in preparing their inventories submitted to the EPA for 
implementing the PM2.5 NAAQS. This is consistent with past 
requirements for the form of emissions inventories.
    In addition to defining the data elements, 40 CFR part 51, subpart 
A also requires states to submit emissions information to the EPA. The 
EPA is not referring to those emissions submission requirements here, 
but rather the emissions elements--the definitions, data codes and 
required data fields. Below, the EPA addresses the issue of whether the 
emissions values submitted through the AERR are relevant to the 
inventory requirements of this proposed rule (see Section IV.B.8 of 
this preamble).
    As noted earlier, the EPA recommends that states consult the SIP 
Emissions Inventory Guidance in preparing the inventories needed for 
this rule. In addition to the AERR, this guidance includes definitions 
for data fields that are not required by the AERR, such as seasonal 
emissions values and other fields that are optional in the data system 
that collects data submitted for the AERR. The EPA is updating the SIP 
Emissions Inventory Guidance in coordination with this proposal. It 
provides specific guidance to air agencies on how to develop base year 
inventories for the nonattainment area and attainment projected 
inventories for 8-hour ozone, PM2.5, and regional haze SIPs. 
While the AERR sets forth requirements for data elements and 
definitions, the guidance complements these requirements, defines all 
data elements (even those that are voluntary AERR elements), and 
indicates how the data should be prepared, documented and publicly 
reviewed for attainment plan submissions.
7. How do emissions inventories support modeling for attainment 
demonstrations?
    This section attempts to clarify the difference between the 
inventories required to be a part of a state's Moderate area attainment 
plan submission (as described earlier) and other modeling inventories 
that are also relevant for attainment planning. While the EPA is not 
proposing additional modeling inventory requirements in this rule 
(i.e., for which a state must submit an emissions inventory to the 
EPA), to meet the attainment demonstration requirements of CAA sections 
189(a)(1) and 189(b)(1), states will need to submit an attainment 
demonstration (which includes air quality modeling) to show how the 
area will either attain the NAAQS by the applicable attainment date or 
that the area cannot attain by the attainment date. The modeled 
attainment demonstration requirements for Moderate areas are described 
fully in Section IV.E of this preamble.
    As part of this demonstration, the EPA presumes that states will 
need to prepare attainment demonstration modeling inventories for both 
a modeled base year and projected attainment year. Respectively, these 
are called the ``base year (baseline) inventory for modeling'' and the 
``attainment projected inventory for modeling.'' These inventories 
contain emissions for all regions (i.e., not just the nonattainment 
area) within the modeling domain being used for the attainment plan 
modeling demonstration, which typically includes counties and even 
states outside of the nonattainment area. They include detailed spatial 
and temporal elements needed to support air quality modeling. States 
should follow the requirements laid out in Section IV.E of this 
preamble and the procedures described in the SIP Emissions Inventory 
Guidance and the Air Quality Modeling Guidance to meet the minimum 
requirements for documentation and emissions summaries supporting 
modeling demonstrations.\74\
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    \74\ The EPA encourages states to consider in any baseline, 
modeling, and SIP attainment inventory used and/or submitted to 
include emissions expected from projects subject to general 
conformity and emissions from wildland fire that reasonably may be 
expected in the area.
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    The base year inventory and projected attainment year inventory 
include emissions from only within the nonattainment area. The EPA 
expects that modeling inventories will be consistent with those 
nonattainment area inventories; however, some exceptions may exist. 
Where possible, the nonattainment area base year and projected 
attainment year inventories can be a sum (for annual data) or average 
(for PM2.5 season-day data) of day-specific or hour-specific 
data used for modeling. In some cases, however, this approach may not 
be sufficient for modeling purposes. For example, greater spatial and 
temporal detail are needed for on-road mobile modeling inventories as 
compared to the base year inventory for the nonattainment area. For the 
nonattainment area base year inventory, one goal is to allow for the 
repeatability of the approach in order to create average, seasonal or 
annual inventories for use in rule requirements, such as reasonable 
further progress or conformity demonstrations. That goal is not 
necessarily compatible with the modeling need for greater spatial and 
temporal detail. In cases where some differences are unavoidable, air 
agencies should attempt to promote consistency where feasible.
    The AERR includes both triennial and annual statewide reporting 
requirements, with more extensive reporting requirements for triennial 
inventory years. For the interim annual inventories, reporting is 
limited to emissions data from only the larger point sources (Type 
``A'' sources), as defined by Appendix A of 40 CFR part 51, subpart A. 
For the triennial inventories, lower point source thresholds are given 
in Appendix A, consistent with the definition of major sources in 40 
CFR part 70, and all other sources of emissions must be reported as 
nonpoint or mobile sources on a county basis.
    In the past, some states have incorrectly asserted that their AERR 
submission meets the requirements for base year inventories required by 
past implementation rules. To avoid confusion, the EPA provides here 
the limited circumstances in which the AERR emissions inventories can 
meet the base year inventory for the nonattainment area requirement for 
Moderate areas. The following conditions must be met to use AERR 
inventories for attainment planning:
    (a) The AERR emissions inventory must have gone through the public 
review process required for attainment plans.
    (b) The AERR emissions inventory needs to include all sources of 
emissions and all pollutants required for the base year inventory for 
the nonattainment area. This is only possible if the inventory year for 
the base year inventory for the nonattainment area aligns with a 
triennial AERR year, because the data system implementing the AERR only 
accepts emissions from point sources and not other source categories in 
non-triennial years.
    (c) The EPA must be accepting data for the inventory year. 
Inventories are allowed to be submitted to the AERR for a given year 
for only a limited time during the development cycle of the National 
Emissions Inventory.
    (d) The AERR submission must include emissions from all relevant 
sources as described for the base year inventory for the nonattainment 
area requirements. In some cases, the AERR requirement can be met 
without electronically ``submitting'' emissions, which would not meet 
the requirements for the base year inventory for the nonattainment 
area. For example, states may elect to accept the EPA estimates for 
some nonpoint emissions sectors,

[[Page 15367]]

but this would not meet the requirements of section 172(c)(3). In 
addition, the AERR revision finalized in February 2015 replaces the 
prior requirement of reporting onroad mobile and nonroad mobile source 
emissions with a requirement for reporting the input parameters that 
can be used to run the EPA models to generate the emissions. If 
choosing to use an AERR submission to meet the base year inventory for 
the nonattainment area requirement, the state should submit the 
nonattainment area emissions, irrespective of the options provided to 
meet the AERR requirements. Since the ``statewide'' emissions are 
actually provided for individual point sources and counties, the EPA 
believes that these resolutions can be sufficient for most 
PM2.5 nonattainment areas.
8. What models should be used for mobile source emissions?
    A key part of emissions inventory development includes estimating 
mobile source emissions. For all of the mobile source inventories used 
for PM2.5 NAAQS implementation, states should use the latest 
emissions models available at the time the attainment plan inventory is 
developed.\75\ In general, the latest approved version of the MOVES 
model should be used by states other than California to estimate 
emissions from onroad transportation sources. States should use the 
latest available planning emission inputs including, but not limited 
to, vehicle miles traveled (VMT), speeds, fleet mix, SIP control 
measures and fuels. The current version of MOVES is available at http://www.epa.gov/otaq/models/moves/index.htm. The appropriate EPA-approved 
model(s) should similarly be used for California onroad source 
emissions.\76\ When using MOVES, states should follow the most current 
version of the MOVES Technical Guidance, available at http://www.epa.gov/otaq/models/moves/index.htm#sip. MOVES includes multiple 
options for estimating and processing emissions that could result in 
different emissions inventories. The EPA recommends that states use the 
same approach in any analysis that compares two or more emissions cases 
(e.g., different control scenarios, different years). If different 
approaches are taken for inventories that serve different purposes (for 
example between inventories developed for air quality modeling, which 
may require greater temporal and spatial detail, and inventories used 
as the motor vehicle emissions budget), states should seek to 
understand and minimize any differences in results. For example, an 
approach may be used for the modeled attainment demonstration that uses 
gridded temperatures and other meteorological data, but this approach 
could be too burdensome for use in the base year inventory for the 
nonattainment area. This is because emissions inventories created for 
purposes of RFP and transportation conformity analysis must use the 
same MOVES approach used in the base year inventory for the 
nonattainment area, and using a straightforward MOVES approach without 
gridded meteorology is more reasonable for that purpose.
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    \75\ Section 172(c)(3) requires that SIP inventories and control 
measures be based on the most current information and applicable 
models that are available when a SIP is developed.
    \76\ At this time, the California onroad mobile model is called 
EMFAC.
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    The most current version of the NONROAD model should be used for 
estimates of nonroad mobile source emissions, preferably with state-
supplied model input data. States can alternatively develop 
technologically equivalent or superior state-specific nonroad emissions 
estimates, but should explain why their approach gives a better 
estimate than the EPA model. For nonroad sources not estimated by the 
NONROAD model, the best available methods should be used, and the EPA 
recommends that states refer to the SIP Emissions Inventory Guidance 
for more information on emissions from these sources. Links to Federal 
Register documents and policy guidance memos on the latest approved 
versions of MOVES and NONROAD can be found at http://www.epa.gov/otaq/models.htm.
9. What special considerations exist for tribal areas?
    In the past, there have been instances where portions of tribal 
areas have been included in designated nonattainment areas, but when 
the base year inventory for the nonattainment area was prepared, 
emissions from the tribal lands were not included. This has had the 
effect of preventing tribes from generating emissions reductions from 
existing sources to develop emissions offsets, as well as impairing the 
ability of the state to prepare as accurate a modeling demonstration as 
possible. It could also cause sources in tribal areas to remain 
uncontrolled even though they are contributing to violations in a given 
nonattainment area. The EPA encourages states and tribes to work 
together to ensure that the information used in developing the baseline 
emissions inventory is inclusive of all emissions from a designated 
nonattainment area, including emissions from sources in tribal areas 
located therein.

C. Pollutants To Be Addressed in the Plan

    Under subpart 4 of the CAA, air agencies are initially required to 
analyze and evaluate emissions reduction measures for all sources of 
direct PM2.5 and PM2.5 precursors (i.e., 
SO2, NOX, VOC and ammonia) in developing 
PM2.5 attainment plans. As described in Section II of this 
preamble, and reiterated in the proposed emissions inventory 
requirements for Moderate area attainment plans under Section IV.B of 
this preamble, direct PM2.5 includes both filterable and 
condensable PM2.5 emissions. Thus, a state must evaluate 
control measures for sources of filterable and condensable 
PM2.5 emissions as part of an approvable control strategy 
for a Moderate PM2.5 nonattainment area.
    In addition, while evaluating sources of direct PM2.5 
for reasonably available controls is an implicit requirement in the 
context of implementing the PM2.5 NAAQS under any scenario, 
the EPA is proposing and seeking comment on several options for 
evaluating PM2.5 precursors under the PM2.5 NAAQS 
implementation program. The EPA interprets the requirements of the CAA 
to allow the air agency to provide a ``precursor demonstration'' to the 
EPA that supports a state's finding that one or more PM2.5 
precursors need not be subject to control requirements in a given 
nonattainment area. Section III of this preamble presents a complete 
discussion of the EPA's proposed options for states to address 
PM2.5 precursors in attainment plans and in the NNSR 
permitting program. Specifically, the EPA is proposing and seeking 
comment on three options describing different approaches to such 
precursor demonstrations, and requests comment on each. In general 
terms, the three options can be summarized as follows:
     Option 1: Two independent analyses: (a) an attainment 
planning analysis demonstrating that control measures for a particular 
precursor are not needed for expeditious attainment, meaning that the 
precursor can be excluded from measures needed to attain as 
expeditiously as practicable for all types of sources; and, (b) a 
section 189(e) technical demonstration showing that major stationary 
sources of a particular precursor do not contribute significantly to 
levels that exceed the PM2.5 standard, meaning that the 
precursor can be excluded from control requirements for major sources 
and from NNSR permitting;

[[Page 15368]]

     Option 2: Single analysis demonstrating that all emissions 
of a particular precursor from within the area do not significantly 
contribute to PM2.5 levels that exceed the standard, meaning 
that control requirements for emissions of the precursor from major 
stationary and area sources, as well as mobile sources, would not be 
required for expeditious attainment, control requirements for major 
sources, or for NNSR permitting;
     Option 3: An attainment planning analysis demonstrating 
that control measures for all types of sources of a particular 
precursor are not needed for expeditious attainment also would be 
deemed to meet the section 189(e) technical demonstration requirement, 
meaning that the state would not need to regulate emissions of the 
particular precursor from major stationary sources under the NNSR 
permitting program or other control requirements for major stationary 
sources.
    The EPA will finalize its approach to PM2.5 precursors 
and clarify the implications for states conducting analyses to identify 
required control measures after considering public comment received on 
this proposal.

D. Attainment Plan Control Strategy

1. General Approach to Designing a Control Strategy for a Moderate 
Nonattainment Area
    The statutory attainment planning requirements of subparts 1 and 4 
were established to ensure that the following goals of the CAA are met: 
(i) That states implement measures that provide for attainment of the 
PM2.5 NAAQS as expeditiously as practicable; and, (ii) that 
states adopt emissions reduction strategies that will be the most 
effective, and the most cost effective, at reducing PM2.5 
levels in nonattainment areas. In addition to having an obligation to 
meet the statutory requirements for specific control measures on 
sources located within a nonattainment area (e.g., RACM and RACT), a 
state has discretion to require reductions from any source inside or 
outside of a PM2.5 nonattainment area (but within the 
state's boundaries) in order to fulfill its obligation to demonstrate 
attainment in a PM2.5 nonattainment area as expeditiously as 
practicable. A state may need to require emissions reductions on 
sources located outside of a PM2.5 nonattainment area if 
such reductions are needed in order to provide for expeditious 
attainment of the PM2.5 NAAQS.
    With this in mind, the following sections describe the EPA's 
proposed approach for a state to follow in order to identify and select 
the complete suite of measures needed for an attainment plan submission 
for a Moderate PM2.5 nonattainment area. The proposed 
process consists of identifying all technologically and economically 
feasible control measures, including control technologies, for all 
sources of direct PM2.5 and PM2.5 precursors in 
the emissions inventory for the nonattainment area which are not 
otherwise exempted from consideration for controls.\77\ From that list 
of measures, the state must identify those that it can implement within 
4 years of designation of the area (and which would thus meet the 
statutory requirements for RACM and RACT) and any ``additional 
reasonable measures,'' which the EPA proposes to define as those 
technologically and economically feasible measures that the state can 
only implement on sources in the nonattainment area after the 4 year 
deadline for RACM and RACT has passed. See proposed 40 CFR 51.1000. The 
state must also assess whether there are other measures that it can 
implement to control sources within the state but outside the 
nonattainment area that contribute to the PM2.5 
nonattainment status of the area in order to bring the area into 
attainment as expeditiously as practicable.
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    \77\ Such exemptions could be due to a demonstrated lack of 
significant contribution of a certain PM2.5 precursor to 
the area's elevated PM2.5 concentrations or due to a 
presumptive determination that a certain source category contributes 
only a de minimis amount toward PM2.5 levels in a 
nonattainment area.
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    As discussed in Section II.D.6 of this preamble, one important 
component of a state's control strategy for a PM2.5 
nonattainment area is the suite of control measures that a state is 
already implementing or will be implementing to comply with national, 
regional, or state and local regulations already adopted or 
promulgated, as long as such measures will lead to permanent and 
enforceable reductions in emissions after the area is designated 
nonattainment. Such ``existing'' measures could apply to sources inside 
the nonattainment area, in which case the state must include them in 
the RACM and RACT and additional reasonable measures analysis for the 
area. The measures may also apply to sources located outside the 
nonattainment area but would achieve reductions in direct 
PM2.5 emissions or emissions of PM2.5 precursors 
to help bring the area into attainment. A state must evaluate the 
potential effects of all of these measures as part of its modeled 
attainment demonstration for the area, and must clearly indicate which 
of these measures will contribute toward timely attainment for the area 
in the attainment plan submission.
2. Identification and Selection of RACM and RACT and Additional 
Reasonable Measures
    a. Statutory requirements and existing guidance. CAA section 172(c) 
under subpart 1 describes the general attainment plan requirement for 
RACM and RACT, requiring that attainment plan submissions ``provide for 
the implementation of all reasonably available control measures as 
expeditiously as practicable (including such reductions in emissions 
from existing sources in the area as may be obtained through the 
adoption, at a minimum, of reasonably available control technology) and 
shall provide for attainment'' of the NAAQS. The attainment planning 
requirements specific to PM10, including PM2.5, 
under subpart 4 likewise impose upon states an obligation to develop 
attainment plans that impose RACM on sources of direct PM2.5 
and PM2.5 precursors within a Moderate nonattainment area. 
CAA section 189(a)(1)(C) requires that states with areas classified as 
Moderate have attainment plan provisions to assure that RACM are 
implemented by no later than 4 years after designation of the area.\78\ 
The EPA reads CAA sections 172(c)(1) and 189(a)(1)(C) together to 
require that attainment plans for Moderate nonattainment areas must 
provide for the implementation of RACM and RACT for existing sources of 
PM2.5 and PM2.5 precursors in the nonattainment 
area as expeditiously as practicable but no later than 4 years after 
designation.\79\
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    \78\ States with areas later reclassified as ``Serious'' 
nonattainment areas under subpart 4 must also develop and submit 
later plans to meet additional requirements for Serious areas.
    \79\ This interpretation is consistent with guidance described 
in the General Preamble. See 57 FR 13498 (April 16, 1992), at page 
13540.
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    The terms RACM and RACT are not defined within subpart 4, nor do 
the provisions of subpart 4 specify how states are to meet the RACM and 
RACT requirements. However, the EPA's longstanding guidance in the 
General Preamble described in detail considerations for determining 
what control measures constitute RACM and RACT for purposes of subpart 
4. The EPA's guidance for RACM for sources of PM10 and 
PM10 precursors under subpart 4 in the General Preamble 
included: (i) A list of some potential measures for states to consider; 
(ii) a statement of the EPA's expectation that the state will provide a 
reasoned explanation for a decision not to adopt

[[Page 15369]]

a particular control measure; (iii) recognition that some control 
measures might be unreasonable because the emissions from the sources 
that would be affected by the measure in the area are de minimis (i.e., 
aggregate emissions from all sources in a particular source category do 
not contribute significantly to PM2.5 concentrations in the 
area); (iv) an emphasis on state evaluation of potential control 
measures for reasonableness, considering factors such as technological 
and economic feasibility; and, (v) encouragement to states evaluating 
potential control measures imposed upon municipal or other governmental 
entities to include consideration of the impacts on such entities, and 
the possibility of partial implementation when full implementation 
would be infeasible (e.g., phased implementation of measures such as 
road paving).\80\ Thus, the RACM requirement under subpart 4 applies to 
all types of sources and is not necessarily focused upon forms of 
control that are strictly technology-based.
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    \80\ See 57 FR 13498 (April 16, 1992), at pages 13540-41.
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    With respect to RACT requirements, the EPA's guidance in the 
General Preamble: (i) noted that RACT has historically been defined as 
``the lowest emission limit that a source is capable of meeting by the 
application of control technology that is reasonably available 
considering technological and economic feasibility''; (ii) Noted that 
RACT generally applies to stationary sources, both stack and fugitive 
emissions; (iii) suggested that major stationary sources be the minimum 
starting point for a state's RACT analysis; and, (iv) recommended that 
states evaluate RACT not only for major stationary sources, but for 
other source categories as needed for attainment and considering the 
feasibility of controls.\81\ Thus, the RACT requirement under subpart 4 
is primarily focused on stationary sources and forms of emissions 
control that are technology-based.
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    \81\ Ibid.
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    In addition to the statutory requirements under sections 172(c)(1) 
and 189(a)(1)(C) for RACM and RACT, section 172(c)(6) requires that a 
state's attainment plan for a nonattainment area ``include enforceable 
emission limitations, and such other control measures, means or 
techniques (including economic incentives such as fees, marketable 
permits, and auctions of emission rights), as well as schedules and 
timetables for compliance, as may be necessary or appropriate to 
provide for attainment of such standard in such area by the applicable 
attainment date specified in this part.'' The EPA interprets this 
statutory provision to require a state to identify, select and 
implement additional measures to those identified as RACM and RACT for 
the area if needed to provide for timely attainment of the area. In the 
EPA's proposed approach detailed in this section, the EPA describes 
criteria for identifying and selecting ``additional reasonable 
measures'' for sources of direct PM2.5 and PM2.5 
precursors in a Moderate nonattainment area which may be necessary in 
order to bring the area into expeditious attainment.
    b. Proposed approach. This section describes the EPA's proposed 
approach for determining what measures qualify as RACM and RACT or as 
additional reasonable measures for controlling sources contributing to 
nonattainment in a Moderate PM2.5 nonattainment area. Under 
the proposed approach, the specific determination of RACM and RACT 
would be made within the broader context of assessing control measures 
for all stationary, area and mobile sources of direct PM2.5 
and PM2.5 precursors that would collectively contribute to 
meeting the statutory Moderate area attainment date as expeditiously as 
practicable.\82\ The proposed approach is designed to ensure that 
states consider and adopt control measures for sources in a way that is 
consistent with the statute's overarching requirement to attain the 
standards as expeditiously as practicable, yet to provide flexibility 
for states to focus regulatory resources on those sources of emissions 
whose control will most effectively and expeditiously contribute to 
attainment in a given area.
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    \82\ In Sierra Club v. EPA, 294 F.3d 155 (D.C. Cir. 2002), the 
court stated, in upholding the EPA's statutory interpretation of 
RACM, that the CAA does not compel a state to consider a measure 
without regard to whether it would expedite attainment.
---------------------------------------------------------------------------

    Specifically, the EPA proposes that a state must follow a process 
by which it would: (i) Identify all sources of emissions of direct 
PM2.5 and all PM2.5 precursors in the 
nonattainment area and all potential control measures to reduce 
emissions from those source categories not otherwise deemed de minimis; 
(ii) determine if any of the identified potential control measures are 
technologically infeasible; (iii) determine if any of the identified 
technologically feasible control measures are economically infeasible; 
(iv) determine which technologically and economically feasible measures 
can be implemented, in whole or in part, within 4 years from the date 
of designation of the area and which can be implemented, in whole or in 
part, by the end of the sixth calendar year following designation; and, 
(v) perform an analysis to determine the earliest practicable 
attainment date for the area and identify the control measures and 
control technologies that will be needed to achieve attainment by the 
demonstrated attainment date and to meet statutory control 
requirements.
    The statutory attainment date for Moderate nonattainment areas is 
as expeditiously as practicable, but not later than the end of the 
sixth calendar year after designation of the area as nonattainment. In 
the case of Moderate areas that can reach attainment by the statutory 
attainment date, and consistent with existing policies, states would be 
required to evaluate the combined effect of reasonably available 
control measures that are not necessary to demonstrate attainment 
within the maximum statutory timeframe to determine whether 
implementation of the remaining measures could advance the attainment 
date by at least 1 year. The EPA has long applied this particular 
test--whether reasonably available control measures that were not 
necessary to demonstrate attainment within the maximum statutory 
timeframe, collectively can advance an area's applicable attainment 
date by at least 1 year--to satisfy the statutory provision related to 
an area demonstrating attainment ``as expeditiously as practicable.'' 
\83\ The EPA continues to believe that this approach provides an 
appropriate degree of flexibility to a state to tailor its attainment 
plan control strategy to the needs of a particular PM2.5 
nonattainment area. In the case of Moderate areas that cannot 
practicably attain by the statutory attainment date, states would be 
required to implement all RACM and RACT, together with any additional 
reasonable measures on sources in the nonattainment area. In either 
case, the statute requires that a state's attainment plan provide for 
implementation of RACM and RACT within 4 years of designation.
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    \83\ The term ``expeditious attainment'' is used throughout this 
proposal to describe the ability of a nonattainment area to attain 
``as expeditiously as practicable'' based on the test described 
here.
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    The following discussion provides further detail on the specific 
steps and criteria that the EPA proposes states must apply when making 
their determinations for RACM and RACT and additional reasonable 
measures. The EPA seeks comment on the proposed steps, criteria and

[[Page 15370]]

considerations described below. See proposed 40 CFR 51.1009(a).
    Step 1: Identify sources to be controlled and existing and 
potential control measures
    i. Identify sources to be controlled. As described more fully in 
Section IV.B of this preamble, section 172(c)(3) of the CAA requires 
that attainment plans for PM2.5 nonattainment areas include 
a ``comprehensive, accurate, current inventory of actual emissions from 
all sources of the relevant pollutant or pollutants.'' As proposed, the 
inventory must include emissions information for all major stationary 
sources, nonpoint or area sources, and mobile sources of direct 
PM2.5 and PM2.5 precursors in the nonattainment 
area.
    The EPA proposes to require that a state must look at all of the 
sources reflected in the nonattainment area's base year inventory as 
part of the first step in identifying reasonable control measures for 
the area, as each of these sources may play a role in the area's 
PM2.5 problem and thus may be controlled currently or may 
need to be controlled to bring the area into attainment as 
expeditiously as practicable. Under this proposed approach, a state 
would need to consider all inventoried sources of direct 
PM2.5 emissions and sources of all four scientific 
PM2.5 precursors as it conducts its determination of 
reasonable control measures for an area. A possible exception to this 
comprehensive review requirement for all inventoried sources could 
arise if the EPA finalizes a precursor approach that would allow a 
state to demonstrate that one or more precursors in a nonattainment 
area do not significantly contribute to the PM2.5 problem in 
the area and/or that reducing emissions of one or more precursors in an 
area would not be effective in reducing PM2.5 concentrations 
in the area.\84\ In such a case, a state could exempt sources of any 
precursor for which the state has made such a demonstration from 
further consideration for measures to control emissions of that 
precursor. Independent of whether or not the EPA finalizes such an 
approach to precursors, however, a state could still determine that it 
is not necessary to control emissions of direct PM2.5 or any 
of the PM2.5 precursors in order to attain the 
PM2.5 NAAQS in a given area, or to advance the attainment 
date for that area, at a later point in this proposed process for 
determining RACM and RACT and additional reasonable measures.
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    \84\ See Section III of this preamble for further details on the 
agency's proposed options for how to handle precursors in attainment 
planning.
---------------------------------------------------------------------------

    ii. De minimis source category exemptions. The concept of exempting 
certain source categories from consideration for control measures due 
to their minimal (i.e., de minimis) contribution is discussed at length 
in the Addendum for sources located in Serious PM10 
nonattainment areas that would otherwise be subject to BACM and BACT 
requirements. The EPA's guidance in the General Preamble on Moderate 
PM10 nonattainment area requirements also provided support 
for exempting de minimis source categories from RACM and RACT 
requirements: ``If it can be shown that one or more measures are 
unreasonable because emissions from the sources affected are 
insignificant (i.e., de minimis), those measures may be excluded from 
further consideration as they would not represent RACM for that area.'' 
85 86
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    \85\ 57 FR 13498 (April 16, 1992), at page 13540.
    \86\ Where the sources at issue contribute only negligibly to 
ambient concentrations that exceed the NAAQS, the EPA's policy is 
that it would be unreasonable to regulate those sources, and, 
therefore, the sources would not be subject to RACM or other control 
requirements, unless it is determined that even sources identified 
as de minimis must be controlled in order for the area to attain the 
NAAQS. In this regard, it is worth noting that the inherent 
authority of administrative agencies to exempt de minimis situations 
from regulation has been recognized by courts as ``a tool to be used 
in implementing the legislative design'' (see Alabama Power Co. v. 
Costle, 636 F.2d 323, 360 (D.C. Cir. 1979)).
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    As with RACM for PM10, the EPA proposes to allow states 
to exempt de minimis source categories from further consideration as 
they determine reasonable control measures for bringing a Moderate 
PM2.5 nonattainment area into attainment with the relevant 
NAAQS. The EPA proposes that if a state can demonstrate that a 
particular source category does not contribute significantly to 
nonattainment of the PM2.5 NAAQS in a Moderate nonattainment 
area, then the state may eliminate the source category from further 
consideration for control measures.\87\ A state would be required to 
evaluate all other sources in the nonattainment area in source 
categories that do not qualify as de minimis for reasonable control 
measures.
---------------------------------------------------------------------------

    \87\ Ibid. See Alabama Power v. Costle, 636 F.2d 323, 360-61 
(D.C. Cir. 1979).
---------------------------------------------------------------------------

    The EPA notes that there are some challenges in establishing de 
minimis source categories for PM2.5 sources in the same 
manner as was performed for PM10 sources and seeks comment 
on the following proposed options.
    (1) Defining source categories. Source categories, in particular 
for stationary sources, can be defined very broadly or narrowly, and 
the definition could determine which sources are able to meet the 
thresholds for de minimis exemptions. The North American Industry 
Classification System (NAICS) is the standard industrial classification 
system used by federal agencies. NAICS codes are between 2 and 6 
digits, with greater industrial source specificity with increased 
digits.\88\ Each digit in the code is part of a series of progressively 
narrower categories, and the more digits in the code signify greater 
classification detail. The first two digits designate the economic 
sector, the third digit designates the subsector, the fourth digit 
designates the industry group, the fifth digit designates the NAICS 
industry, and the sixth digit designates the national industry. The 5-
digit NAICS code is the level at which there is comparability in code 
and definitions for most of the NAICS sectors across the three 
countries participating in NAICS (the United States, Canada and 
Mexico). The 6-digit level allows for the United States, Canada, and 
Mexico each to have country-specific detail. A complete and valid NAICS 
code contains six digits.
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    \88\ More information on the NAICS is available at: http://www.census.gov/eos/www/naics (last accessed August 12, 2013).
---------------------------------------------------------------------------

    Defining source categories by NAICS codes would still require a 
determination of how broadly to set the source category boundaries as 
NAICS codes with fewer digits represent larger source categories (e.g., 
sector `21' is for mining processes, while a further specification of 
`2122' is for metal mining processes, and `212210' is for iron ore 
mining). If source categories are defined in a very narrow or specific 
way, it is possible that many source categories will be below a set de 
minimis threshold, and therefore potentially inappropriately exempted 
from consideration for reasonable control measures. For this reason, 
the EPA proposes and seeks comment on a requirement that a state would 
need to define any source category for which a NAICS code exists at the 
four-digit industry group level. The EPA believes that relying on the 
four-digit industry group level to define ``source category'' for this 
purpose would provide an appropriate degree of distinction between 
industrial processes, while not making the source category definition 
overly broad. The EPA also seeks comment on two other alternative 
approaches for defining source category for this purpose, at the six-
digit level, and the two-digit level. The EPA notes that not all source 
categories have NAICS codes, and for these other categories, states 
would need to use the

[[Page 15371]]

appropriate recognized categories, e.g., on-road mobile sources. The 
EPA also seeks comment on alternative source categorization approaches 
that would ensure that sources that could be controlled with reasonable 
control measures to achieve meaningful reductions are not 
inappropriately excluded from consideration for such control measures 
as de minimis.
    (2) Determining the appropriate threshold for de minimis emissions. 
For the PM10 NAAQS, the EPA's guidance in the Addendum 
recommended that a source category is presumed not to be de minimis if 
the aggregate emissions from such source category have an impact that 
exceeds 5 [mu]g/m\3\ with respect to the then-applicable 24-hour 
PM10 NAAQS or an impact that exceeds 1 [mu]g/m\3\ with 
respect to the then-applicable annual PM10 NAAQS. The EPA 
designed these presumptive thresholds for de minimis source categories 
to apply to PM10 NAAQS nonattainment areas and to the level 
and form of the PM10 NAAQS at the time the Addendum was 
written. However, because of the differences in level and form of the 
PM10 and PM2.5 NAAQS, the agency finds that those 
levels are not appropriate for current or future PM2.5 NAAQS 
implementation.
    The EPA therefore proposes two options regarding the threshold for 
de minimis emissions. Under the first proposed option, the EPA would 
not establish a nationally applicable ``bright line'' threshold for 
defining a de minimis source category for purposes of implementing the 
PM2.5 NAAQS in a Moderate nonattainment area. Rather, under 
this option, the EPA proposes to allow a state to determine whether a 
particular source category should be considered de minimis given the 
particular facts and circumstances of a specific PM2.5 
nonattainment area and subject to approval by the EPA. See proposed 40 
CFR 51.1007.
    Under the second option, the EPA proposes to establish a nationally 
applicable de minimis source category threshold that would be a 
specific percentage of the level of the relevant PM2.5 
NAAQS. The EPA seeks comment on what value within the range of 1 and 3 
percent of the relevant NAAQS would represent an appropriate threshold 
level. The 3 percent upper end of the proposed range is generally 
derived from the de minimis source category contribution levels for 
PM10 as described in the General Preamble. The EPA defined 
these PM10 de minimis levels as follows: (i) For the annual 
standard of 50 [mu]g/m\3\, a source category contribution of 1 [mu]g/
m\3\ or less to the annual average design value (e.g., a contribution 
of about 2 percent or less); and, (ii) for the 24-hour standard of 150 
[mu]g/m\3\, a source category contribution of 5 [mu]g/m\3\ or less to 
the 24-hour design value (e.g., a contribution of about 3 percent or 
less). The 1 percent lower end of the proposed range is consistent with 
the value that the EPA established in the CAIR as a preliminary 
threshold for further evaluation of a state's contribution to 
interstate transport. That is, under the CAIR, a state was identified 
as potentially subject to additional emission control requirements if 
the impact of SO2 and NOX emissions from sources 
in that state to any nonattainment or maintenance area in another state 
exceeded 1 percent of the relevant PM2.5 standard at a 
receptor monitor in the other state. This value was merely the first 
step of the analysis, but it provided an initial threshold for 
determining whether further analysis was warranted.
    The EPA is requesting comment on the appropriateness of including 
de minimis threshold options for exempting certain source categories 
from consideration for reasonable control measure determinations, and 
seeks input on several key questions: First, if a de minimis threshold 
is included, what is the appropriate definition for source categories? 
In addition, what are the appropriate thresholds for impacts on ambient 
PM2.5 concentrations that would adequately reflect 
presumptive de minimis concentrations from a given source category 
comparable to those recommended for purpose of the PM10 
NAAQS? Also, should the de minimis source category thresholds be a 
percentage of the relevant NAAQS (i.e., similar to what was recommended 
for PM10, but set at a level that is more appropriate for 
the level and form of the relevant NAAQS)? The EPA requests that 
commenters submit any relevant data or analyses to support their 
comments with respect to these issues. Furthermore, the EPA notes that 
even in the event the agency finalizes this rulemaking with a de 
minimis source category policy of any kind, states are obligated under 
the CAA to demonstrate how their PM2.5 nonattainment area(s) 
will attain the standard as expeditiously as practicable. Accordingly, 
a state could not elect to treat source categories as de minimis if 
doing so would prevent the state from being able to demonstrate 
attainment for an area by the statutory attainment date.
    iii. Identify existing and potential control measures and 
technologies. The state's compilation of existing and potential control 
measures must be sufficiently broad to provide a basis for identifying 
all technologically and economically feasible controls that may be RACM 
or RACT for sources of direct PM2.5 and PM2.5 
precursor emissions in the nonattainment area at issue. Because RACM 
applies to area and mobile sources as well as stationary sources, the 
EPA proposes to require that states consider a variety of types of 
measures in conducting their control strategy analysis. As stated 
earlier, inherent to the concept of RACM and RACT is the basic premise 
that the measure be ``reasonable,'' thus the EPA believes that a state 
may decline to evaluate control measures that are plainly ``absurd, 
unenforceable, or impractical,'' for example, measures that would cause 
``severely disruptive socioeconomic impacts, (e.g. gas rationing and 
mandatory source shutdowns).'' It is the agency's interpretation that 
evaluation of such measures is not required by the CAA.\89\
---------------------------------------------------------------------------

    \89\ 55 FR 38327 and 57 FR 13560.
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    Furthermore, the EPA believes that reducing air emissions may not 
justify adversely affecting other resources, for example, by increasing 
pollution in bodies of water, creating additional solid waste disposal 
problems or creating excessive energy demands. An otherwise available 
control technology may not be reasonable if these other environmental 
impacts are sufficiently adverse and cannot reasonably be mitigated. 
The EPA proposes that a state may consider a control measure for direct 
PM2.5 or a PM2.5 precursor not reasonable if, 
considering the availability of mitigating adverse impacts of that 
control on pollution of other media, the control would not, in the 
state's reasoned judgment, provide a net benefit to public health and 
the environment. It should be noted that, in many past situations, 
states and owners of existing sources have adopted control technologies 
for direct PM2.5 and/or PM2.5 precursors with 
known energy penalties and some adverse effects on other media, based 
on the reasoned judgment that installation of such technology would 
result in a net benefit to public health and the environment. States 
should consider this before determining that a control technology is 
not reasonable because it may have other, negative environmental 
impacts that are, on balance, marginal.
    Generally, this proposed approach allows states to apply reasoned 
judgment as they identify potential control measures for sources of 
direct PM2.5 and PM2.5 precursors in their 
respective nonattainment areas, and the EPA expects that a state will 
provide a complete and reasoned explanation to support its selection of 
potential control

[[Page 15372]]

measures and control technologies as part of the attainment plan 
submission for any Moderate nonattainment area. The proposed 
regulations include language to require the inclusion of this 
explanation in a state's attainment plan submission.
    (1) Existing control measures. The EPA proposes that, as a starting 
point, a state must include in its initial list of control measures 
those measures and technologies that are being implemented or will be 
implemented due to promulgated and/or adopted (i.e., ``on the books'') 
regulations for sources of direct PM2.5 and PM2.5 
precursors in its Moderate PM2.5 nonattainment area. The EPA 
expects that the state will incorporate current or anticipated 
emissions reductions from these ``existing'' control measures (such as 
expected SO2 reductions from the MATS; reductions of 
NOX and direct PM2.5 from engine and fuel 
standards to reduce emissions from on-road and nonroad mobile sources) 
into its attainment demonstration modeling for the nonattainment area, 
and therefore the EPA believes it is appropriate for the state to 
clearly indicate such measures in the attainment plan for the area.
    The EPA recognizes that for some sources located in a Moderate 
PM2.5 nonattainment area, a state may have previously 
conducted RACM and RACT analyses to address emissions for other 
statutory purposes. Some of the RACM and RACT determinations could be 
relatively recent, while other determinations may be 15 years old or 
older. The EPA proposes that a state may not simply rely on a previous 
RACM or RACT determination for a particular source or source category 
when developing the attainment plan for a PM2.5 NAAQS, but 
rather that the state must consider all existing and potential new 
measures together as part of a comprehensive RACM and RACT analysis. In 
this way, the state's new RACM and RACT analysis will represent the 
most thorough, up-to-date review of control measures for its 
PM2.5 nonattainment area. For example, the state would still 
need to provide a RACT analysis for a stationary source that has 
installed new emissions controls recently (e.g., within the last 3 
years), but the state's determination may consider that recent 
installation when determining whether additional control is 
technologically and economically feasible.
    (2) Potential control measures. In addition to identifying existing 
control measures for sources in a Moderate PM2.5 
nonattainment area, a state must develop a comprehensive list of 
potential control measures for sources in the area. There are a number 
of resources available to assist states in identifying additional, 
potential control measures and control technologies for their RACM and 
RACT and additional reasonable measures determinations for their 
Moderate PM2.5 nonattainment areas. First, the EPA's Office 
of Air Quality Planning and Standards maintains a Menu of Control 
Measures document, available online at http://www.epa.gov/air/criteria.html. This document was developed to provide information 
useful in the development of local emissions reduction and NAAQS SIP 
scenarios, and identifying and evaluating potential control measures. 
It provides a broad, though not comprehensive, listing of potential 
emissions reduction measures for direct PM2.5 and precursors 
of ozone and PM2.5 from stationary, area and mobile sources. 
More complete information on mobile source control measures can be 
found on the EPA's Office of Transportation and Air Quality Web site at 
http://www.epa.gov/otaq.
    The RACT/BACT/LAER Clearinghouse (RBLC) provides a central database 
of air pollution technology information (including past RACT, BACT and 
LAER decisions contained in NSR permits) to promote the sharing of 
information among permitting agencies and to aid in future case-by-case 
control measure determinations. The RBLC permit database contains over 
5,000 determinations that can help a state identify appropriate 
technologies to mitigate most air pollutant emission streams. The RBLC 
includes data submitted by several U.S. territories and all 50 states 
on over 200 different air pollutants and 1,000 industrial processes. 
The RBLC can be found at: http://cfpub.epa.gov/rblc/.
    Additionally, the EPA maintains a Web site with links to other 
online sources of information on control measures for states to 
consider.\90\ Again, the EPA recognizes that some control technology 
guidance for certain source categories has not been updated for many 
years, and, for this reason, the agency expects states to identify and 
consider new and updated information in their RACM and RACT 
determinations as it becomes available.
---------------------------------------------------------------------------

    \90\ Links are provided to a number of national, state and local 
air quality agency sites from the EPA's PM2.5 Web site: 
http://www.epa.gov/pm/measures.html.
---------------------------------------------------------------------------

    (3) RACM for managing emissions from wildfire and prescribed fire. 
Wildfire emissions account for a large portion of direct 
PM2.5 emissions nationally and can significantly contribute 
to periodic high PM2.5 levels.\91\ Besides their effect on 
air quality, wildfires pose a direct threat to public safety--a threat 
that can be mitigated through management of wildland vegetation. 
Attempts to suppress wildfires have resulted in unintended 
consequences, including increased risks to both humans and 
ecosystems.\92\ The use of wildland prescribed fire can influence the 
occurrence, behavior, and effects of catastrophic wildfires which may 
help manage the contribution of wildfires to background 
PM2.5 levels and periodic peak PM2.5 events. 
Additionally prescribed fires can have benefits to those plant and 
animal species that depend upon natural fires for propagation, habitat 
restoration, and reproduction, as well as myriad ecosystem functions 
(e.g., carbon sequestration). The EPA understands the importance of 
prescribed fire which mimics a natural process necessary to manage and 
maintain fire-adapted ecosystems and climate change adaptation, while 
reducing risk of uncontrolled emissions from catastrophic wildfires, 
and is committed to working with federal land managers, tribes, and 
states to effectively manage prescribed fire use to reduce the impact 
of wildfire related emissions on PM2.5.
---------------------------------------------------------------------------

    \91\ For example, see ``miscellaneous'' category of direct 
PM2.5 emissions in Table 1.
    \92\ Indeed, ``fire policy that focuses on [wildfire] 
suppression only, delays the inevitable, promising more dangerous 
and destructive future . . . fires.'' Stephens, SL; Agee, JK; Fule, 
PZ; North, MP; Romme, WH; Swetnam, TW. (2013). Managing Forests and 
Fire in Changing Climates. Science 342: 41-42.
---------------------------------------------------------------------------

    If wildfire impacts are significant, contributing to exceedances of 
the standard, the EPA proposes that air agencies should consider RACM 
for this source. Fires play an important ecological role across the 
globe, benefiting those plant and animal species that depend upon 
natural fires for propagation, habitat restoration, and reproduction. 
Fires are one tool that can be used to reduce fuel load, unnatural 
understory, and tree density, helping to reduce the risk of 
catastrophic wildfires. Some wildfires and the use of prescribed fire 
can influence the occurrence of catastrophic wildfires which may reduce 
the probability of fire-induced smoke impacts and subsequent health 
effects. RACM must be determined for each area on a case-by-case basis. 
Possible RACM for wildfire may include measures that reduce wildland 
fuels through fuels management, including the use of prescribed fire 
and possibly allowing some wildfire to occur naturally in systems that 
are ecologically fire

[[Page 15373]]

dependent. Where appropriate, states, land managers, and landowners may 
consider developing plans to ensure that fuel accumulations are 
addressed and fuels management efforts, including prescribed fire, are 
not delayed. The EPA also proposes that air agencies should consider 
RACM for managing emissions from prescribed fires (including those 
prescribed fires conducted to reduce future wildfire emissions). 
Information is available from the DOI and the USDA Forest Service on 
smoke management programs and basic smoke management practices. The EPA 
requests comment on the concept of, and practical considerations 
associated with, RACM for wildfire and prescribed fire, including such 
issues as how such measures can be characterized in the emissions 
inventory and attainment demonstration and made federally enforceable 
for adoption in a SIP.
    (4) RACT for EGUs. Through guidance in the preamble to the 2007 
PM2.5 Implementation Rule, the EPA established a rebuttable 
presumption that compliance with the CAIR would satisfy RACM and RACT 
requirements for SO2 and NOX emissions from EGUs 
in states participating in the CAIR cap-and-trade program for such 
emissions.\93\ The EPA indicated that states could presume that EGUs 
located within a given nonattainment area were meeting the RACM and 
RACT requirements, based solely upon a regional program that imposed 
controls for SO2 and NOX emissions from sources 
both within and outside designated nonattainment areas.
---------------------------------------------------------------------------

    \93\ See the Federal Register published on April 25, 2007 (72 FR 
20586, 20623, 20624 and 20625).
---------------------------------------------------------------------------

    In June 2007, the EPA received a petition for reconsideration 
questioning the legality of this presumption, which the D.C. Circuit 
later found to be unlawful in the context of a similar presumption in 
the Phase 2 Ozone (NAAQS) Implementation Rule.\94\ The agency granted 
the petition for reconsideration in 2011 and proposed to withdraw from 
the 2007 PM2.5 Implementation Rule any presumption that 
compliance with the CAIR automatically satisfies RACM and RACT 
requirements for SO2 and NOX emissions from EGUs 
located in nonattainment areas for the 1997 PM2.5 
NAAQS.95 96 In that proposal, the EPA explained that given 
the explicit wording of section 172(c)(1) that sources ``in the area'' 
(i.e., in the nonattainment area) must at a minimum adopt RACT controls 
for that area, the agency believes that it is no longer appropriate to 
presume that this requirement is satisfied merely based upon the 
participation of a source in a regional cap-and-trade program. Indeed, 
implicit in a regional cap-and-trade program is that some sources, 
including those located within nonattainment areas, may elect to buy 
allowances in lieu of controlling emissions in order to meet the 
regional emissions reductions requirements.
---------------------------------------------------------------------------

    \94\ See ``Petition for Reconsideration,'' filed by Paul Cort, 
Earthjustice, on behalf of the American Lung Association, Medical 
Advocates for Healthy Air, Natural Resources Defense Council, and 
the Sierra Club (June 25, 2007). A copy of the petition is in the 
docket for this action. The EPA's decision to grant the petition for 
reconsideration on the issue of the CAIR being presumptively equal 
to RACT for EGUs was in part based on a D,C. Circuit decision 
related to a similar issue. Specifically, the Court decided that the 
provisions in the Phase 2 Ozone Implementation Rule indicating that 
a state need not perform (or submit) a NOX RACM/RACT 
analysis for EGU sources subject to a cap-and-trade program that 
meets the requirements of the NOX SIP Call are 
inconsistent with the statutory requirements of section 172(c)(1). 
The Court concluded that the phrase ``in the area'' means that 
reductions must occur from sources within the area and ``reductions 
from outside the nonattainment area do not satisfy the 
requirement.'' See NRDC v. EPA, 571 F.3d 1245 (D.C. Cir. 2009).
    \95\ Letter dated April 25, 2011, from former Administrator Lisa 
Jackson to Paul Cort, Earthjustice. A copy of this letter is located 
in the docket for this action.
    \96\ 79 FR 32892 (June 9, 2013).
---------------------------------------------------------------------------

    Accordingly, the EPA is not proposing any rebuttable presumption 
that the CAIR or any other regional control strategy constitutes RACM 
or RACT for EGUs or any other source category. Instead, the EPA is 
clarifying that in order to meet the RACM and RACT requirements for the 
PM2.5 NAAQS, states should evaluate EGU sources for RACM and 
RACT level controls just like any other source category, and not merely 
presume for EGUs located in a nonattainment area that compliance with a 
cap-and-trade program, including the CAIR or any other program, would 
satisfy their obligation to implement RACM and RACT. As required by the 
CAA, states are required to analyze what constitutes RACM and RACT for 
EGUs in each nonattainment area.
    Step 2: Determine whether an available control measure or 
technology is technologically feasible. Once a state has identified 
existing and potential control measures and technologies for sources of 
direct PM2.5 and PM2.5 precursors in the 
nonattainment area(s), it must evaluate these controls to determine if 
any of those controls would be technologically infeasible in the 
particular nonattainment area.
    i. Stationary sources. With respect to the technological 
feasibility of control technologies for stationary sources, the EPA has 
a longstanding approach to evaluating facts relevant to this criterion 
under subpart 4.\97\ The EPA interprets the term technological 
feasibility to include consideration of factors such as a source's 
processes and operating procedures, raw materials, physical plant 
layout, and potential environmental impacts such as increased water 
pollution, waste disposal and energy requirements. For example, the EPA 
recognizes that the process, operating procedures and raw materials 
used by a source can affect the feasibility of implementing process 
changes that reduce emissions and can also affect the selection of add-
on emissions control equipment. The feasibility of modifying processes 
or applying control equipment also can be influenced by the physical 
layout of the particular plant, if the physical space available in 
which to implement such changes limits the choices. The EPA proposes to 
retain its longstanding practice that a state should be allowed to 
consider such factors in order to eliminate from consideration control 
measures that are not technologically feasible to implement.\98\
---------------------------------------------------------------------------

    \97\ See the Federal Register published on April 16, 1992 (57 FR 
13498, 13540 and 13541).
    \98\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42013. Guidance is provided in the context of Serious 
area BACM determination, but the EPA is proposing to apply it here 
for Moderate area RACM determinations.
---------------------------------------------------------------------------

    ii. Area and mobile sources. With respect to determining whether a 
given control measure might not be technologically feasible for an area 
or mobile source, the EPA also proposes to retain its longstanding 
practice that a state may consider relevant factors in conducting its 
analysis, such as the social acceptability of the measure (e.g., 
residential woodstove change-out programs rely in large part on the 
willingness of individual citizens to participate in such a program) 
and local circumstances, such as the condition and extent of needed 
infrastructure, population size, or workforce type and habits, which 
may prohibit certain potential control measures from being 
implementable.
    The EPA seeks comment on the factors described above for states to 
consider when determining whether a control technology or measure is 
technologically feasible.
    Step 3: Determine whether an available control measure or 
technology is economically feasible. The EPA has a longstanding 
interpretation of the term ``economic feasibility'' in the context of 
evaluating potential RACM and RACT which involves considering the cost 
of reducing emissions and the difference between the cost of an 
emissions reduction measure at a particular source

[[Page 15374]]

and the cost of emissions reduction measures that have been implemented 
at other similar sources in the same or other areas.\99\ Absent other 
indications, the EPA presumes that it is reasonable for similar sources 
to bear similar costs of emissions reductions. Economic feasibility of 
RACM and RACT is thus largely informed by evidence that other sources 
in a source category have in fact applied the control technology, 
process change or measure in question in similar circumstances.
---------------------------------------------------------------------------

    \99\ See the Federal Register published on April 16, 1992 (57 FR 
13498, 13540 and 13541).
---------------------------------------------------------------------------

    In the preamble to the 2007 PM2.5 Implementation Rule, 
the EPA provided guidance on how to interpret the term ``economic 
feasibility'' which deviated from the agency's longstanding 
interpretation of the term. After promulgating the final rule, the EPA 
received and granted a petition for reconsideration on issues related 
to the agency's revised approach to interpreting the term 
``economically feasible.'' 100 101 Consistent with the EPA's 
granting of that petition for reconsideration, the EPA is proposing in 
this action an interpretation of economic feasibility that is 
consistent with the EPA's longstanding interpretation of what factors 
are appropriate for consideration of economic feasibility in a RACM and 
RACT analysis, instead of that adopted in the 2007 PM2.5 
Implementation Rule.
---------------------------------------------------------------------------

    \100\ ``Petition for Reconsideration,'' filed by Paul Cort, 
Earthjustice, on behalf of the American Lung Association, Medical 
Advocates for Healthy Air, Natural Resources Defense Council, and 
the Sierra Club (June 25, 2007). A copy of the petition is in the 
docket for this action.
    \101\ Letter dated April 25, 2011, from former Administrator 
Lisa Jackson to Paul Cort, Earthjustice. A copy of this letter is 
located in the docket for this action.
---------------------------------------------------------------------------

    Specifically, the EPA proposes that for each technologically 
feasible control measure or technology, a state must evaluate the 
economic feasibility of the measure or control, through consideration 
of the capital costs, operating and maintenance costs, and cost 
effectiveness (i.e., cost per ton of pollutant reduced by that measure 
or technology) associated with such measure or control. Furthermore, 
the EPA proposes that a state may not reject a technologically feasible 
control measure or technology as being economically infeasible if such 
a measure or technology has been implemented at other similar sources 
(i.e., at sources that would be included in the same source category in 
the emissions inventory data collection process), unless the state 
provides an adequate justification that clearly explains the specific 
circumstances of the source or sources in the nonattainment area that 
make such a measure or technology economically infeasible in that 
particular area.
    The EPA believes that it is appropriate for states to give 
substantial weight to cost effectiveness in evaluating the economic 
feasibility of an emission reduction measure or technology. The cost 
effectiveness of a measure is its annualized cost ($/year) divided by 
the emissions reduced (tons/year) which yields a cost per amount of 
emission reduction ($/ton). Cost effectiveness provides a relative 
value for each emissions reduction option that is comparable with other 
options and, in the case of control technologies, other facilities.
    The EPA also seeks comment on an alternative cost effectiveness 
metric that would allow a state to take into account the effect of 
controlling a particular precursor on reducing PM2.5 
concentrations in the area. Such a cost effectiveness metric would be 
the annualized cost ($/year) of a control measure divided by the 
emissions reduced (tons/year) multiplied by the amount of reductions 
needed in the precursor emissions to yield 1 [mu]g/m\3\ reduction in 
PM2.5 ($/([mu]g/m\3\)). Such a metric would allow a state to 
compare the relative cost effectiveness associated with each measure 
toward the attainment goal for the nonattainment area. The EPA notes 
the difficulty in determining the appropriate value to relate precursor 
reductions to reductions in ambient PM2.5 concentrations, 
and therefore seeks comment on the appropriateness of this approach and 
how a state might demonstrate the validity of the input values it 
chooses to use.
    In considering what level of control is reasonable, the EPA is not 
proposing a fixed dollar per ton cost threshold for economic 
feasibility of controls identified as potential RACM and RACT. In 
addition, if a state contends that a source-specific control-level 
should not be established because the source(s) cannot afford the 
control measure or technology that is demonstrated to be economically 
feasible for other sources in its source category, the EPA proposes 
that the state must support the claim with information regarding the 
impact of imposing the identified control measure or technology on the 
following financial indicators, to the extent applicable:
    1. Fixed and variable production costs ($/unit)
    2. Product supply and demand elasticity
    3. Product prices (cost absorption vs. cost pass-through)
    4. Expected costs incurred by competitors
    5. Company profits
    6. Employment costs
    7. Other costs (e.g., for RACM implemented by public sector 
entities).\102\
---------------------------------------------------------------------------

    \102\ These long-standing factors were established in EPA 
guidance in 1992 and are applicable to implementation programs for 
all NAAQS pollutants. See the appendices to the General Preamble, 57 
FR 18070 (April 28, 1992).
---------------------------------------------------------------------------

    The EPA seeks comment on the factors described above for states to 
consider when determining whether a control technology or measure is 
economically feasible.
    Step 4: Determine the earliest date by which a control measure or 
technology can be implemented in whole or in part. CAA section 
189(a)(1)(C) requires that the attainment plan for a Moderate 
PM2.5 nonattainment area provide for the implementation of 
RACM and RACT no later than 4 years after designation. The agency has 
long interpreted the term ``implement'' to mean that a control measure 
or technology has not only been submitted to the EPA for approval as 
part of a SIP but has also been built, installed and/or otherwise 
physically manifested, and is achieving the intended emissions 
reductions, and the EPA proposes to retain such a definition in this 
rule. See proposed 40 CFR 51.1000. However, the EPA recognizes that a 
state may be able to implement a given control measure only partially 
within 4 years after designation. The EPA addressed this situation in 
the General Preamble, stating: ``It is important to note that a State 
should consider the feasibility of implementing measures in part when 
full implementation would be infeasible.'' \103\ This guidance endorses 
the notion that a state should not reject an otherwise technologically 
and economically feasible control measure or technology as RACM or RACT 
even if it can be only partially implemented within the statutory 4-
year timeframe following designation of the area. Instead, the EPA 
interprets the statute to require states to adopt as RACM and RACT that 
portion of a control measure or technology that can feasibly be 
implemented within 4 years of the effective date of designation. For 
instance, if paving unpaved roads is a control measure that is 
technologically and economically feasible in a nonattainment area but a 
state cannot pave all roads within 4 years of designation, the state 
must adopt as RACM a measure that requires paving of that portion of 
roads that the state could feasibly accomplish within 4 years if

[[Page 15375]]

such a measure is needed for timely attainment of the PM2.5 
NAAQS in the area.
---------------------------------------------------------------------------

    \103\ 57 FR 13498 (April 16, 1992), at page 13541.
---------------------------------------------------------------------------

    The EPA thus proposes that a state must identify those 
technologically and economically feasible control measures and 
technologies that it can implement fully or partially within 4 years of 
designation of its Moderate PM2.5 nonattainment area. 
Depending on the severity of the PM2.5 nonattainment problem 
in the area, some or all of these measures identified as implementable 
within 4 years may be needed in order to bring the area into attainment 
as expeditiously as practicable. These measures will satisfy the EPA's 
criteria for RACM and RACT if the state determines, through its 
attainment demonstration that it needs to implement them to achieve 
timely attainment for the area.
    In addition, the EPA proposes that a state must separately identify 
those technologically and economically feasible control measures that 
can only be implemented after the statutory window for implementing 
RACM and RACT. The statutory 4-year timing requirement for implementing 
RACM and RACT under section 189(a)(1)(C) limits the control measures 
and technologies that can qualify as RACM and RACT for a Moderate 
PM2.5 nonattainment area. However, the statutory requirement 
of CAA 172(c)(6) also requires states to implement ``other measures'' 
necessary to provide for timely attainment in an area. The EPA proposes 
that among such other measures should be ``additional reasonable 
measures,'' which would be those measures and technologies that are 
otherwise technologically and economically feasible but can only be 
implemented in whole or in part later than 4 years after designation 
and initiated no later than the beginning of the sixth calendar year 
following designation of the area.\104\ Such additional reasonable 
measures would necessarily be implemented on sources in the 
nonattainment area. However, the EPA interprets the ``other measures'' 
required under section 172(c)(6) to apply to stationary, area and 
mobile sources located outside of the nonattainment area but within the 
state if the application of reasonable control measures on such sources 
would facilitate attainment of the PM2.5 NAAQS in the 
nonattainment area. See proposed 40 CFR 51.1009(b).
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    \104\ With respect to ``partial measures'' under this proposed 
approach, the EPA would require that a state implement as RACM that 
portion of any control measure determined to be technologically and 
economically feasible and implementable within 4 years after 
designation of a nonattainment area. The state would then be 
required to implement as an additional reasonable measure that 
portion of the same control measure that can be implemented starting 
4 years from designation through the sixth calendar year following 
designation.
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    Step 5: Model to determine the attainment date that is as 
expeditious as practicable and select the control measures necessary to 
achieve attainment and meet statutory requirements for control 
measures. Section 189(a)(1) of the CAA establishes a requirement that 
the attainment plan for a Moderate PM2.5 nonattainment area 
must demonstrate either that an area can attain the relevant NAAQS by 
the applicable attainment date or that it is impracticable for the area 
to do so. As noted previously, for Moderate PM2.5 
nonattainment areas, the ``applicable attainment date'' is as 
expeditious as practicable, but no later than the end of the sixth 
calendar year after designation as nonattainment. A complete discussion 
of the EPA's proposed requirements for attainment demonstration 
modeling is presented in Section IV.E of this preamble. However, one of 
the key features of attainment demonstration modeling is that it 
provides a means of synthesizing the effects of emissions reductions 
from all existing and potential new control measures identified for 
sources in a given nonattainment area on overall air quality in that 
area. States will be required to use the results of their attainment 
demonstration modeling to identify the appropriate combination of 
reasonable control measures for sources in their Moderate 
PM2.5 nonattainment area and any other control measures 
needed on sources outside the nonattainment area to ensure expeditious 
attainment of the relevant NAAQS in the area and to meet the statutory 
requirements of sections 189(a)(1)(B) and 172(c)(6) as explained 
below.\105\
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    \105\ Note that under section 110(l) of the CAA, after a state 
has adopted a control measure into the SIP for an attainment 
demonstration, it may remove or modify a measure if the state 
demonstrates to the satisfaction of the EPA that such removal or 
modification will not interfere with any applicable requirement of 
the CAA, such as attainment of the PM2.5 NAAQS or meeting 
RFP requirements.
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    Step 5a: If the state can demonstrate attainment in the area by the 
statutory attainment date for a Moderate area, then the state must 
implement those control measures needed for expeditious attainment of 
the NAAQS in the area. If a state determines that a Moderate 
nonattainment area can attain the PM2.5 NAAQS by the 
statutory attainment date, the state must adopt and implement any 
technologically and economically feasible control measures that are 
necessary to ensure that the area will attain the NAAQS as 
expeditiously as practicable. The EPA will consider any such measures 
that can be implemented within 4 years of designation of the area to 
fulfill the RACM and RACT requirements for the area. In addition, the 
EPA will consider any such measures that can only be implemented 
between 4 years and the sixth calendar year after designation to meet 
the requirements of section 172(c)(6) as ``additional reasonable 
measures'' for the area and necessary to demonstrate timely attainment 
under section 189(a)(1)(B).
    Under this approach, the state may reject any otherwise 
technologically or economically feasible measures that are not needed 
to demonstrate attainment or that will not advance the attainment date 
by at least 1 year. That is, for a Moderate area that can demonstrate 
attainment by the statutory Moderate area attainment date, the EPA 
proposes to define as ``reasonable'' only those technologically and 
economically feasible measures that are necessary for expeditious 
attainment of the NAAQS, as the CAA does not require a state to adopt 
measures that are not needed for expeditious attainment in a Moderate 
PM2.5 nonattainment area. Thus, a state may exclude those 
otherwise reasonably available measures that, if adopted and considered 
collectively, would not advance the attainment date for the area by at 
least 1 year, so long as the state can demonstrate attainment as 
expeditiously as practicable and no later than the statutory Moderate 
area attainment date. See proposed 40 CFR 51.1009(a)(4)(i).
    The EPA recognizes that identifying which measures could not 
collectively advance the attainment date for a Moderate area by at 
least 1 year may be an iterative process that requires additional 
analysis and/or modeling. The agency believes that such effort is 
reasonable for a state seeking to demonstrate the lack of need for 
certain controls that are determined to be technologically and 
economically feasible in light of the requirement for expeditious 
attainment in a given Moderate nonattainment area. The basis for 
deciding that it would be reasonable not to require imposition of 
otherwise available and appropriate controls because they would not be 
needed for attainment, or would not advance attainment, requires a 
suitably robust analysis and explanation.
    Step 5b: If the state cannot demonstrate attainment by the 
statutory attainment date for a Moderate area, then the state must 
adopt all reasonable control measures. As noted elsewhere in

[[Page 15376]]

this section, section 189(a)(1)(B) of the CAA requires a state to 
submit as part of the attainment plan either a demonstration that the 
plan will provide for attainment of the relevant NAAQS by the 
applicable attainment date, or a demonstration that attainment by such 
date is ``impracticable.'' This subpart 4 requirement anticipates that 
not all nonattainment areas initially classified as Moderate will 
necessarily be able to attain by the latest statutory attainment date 
for Moderate areas, and it incorporates the concept of an 
``impracticability demonstration'' for such areas.\106\ The CAA is thus 
structured to provide that Moderate areas that cannot timely attain the 
NAAQS through the required elements of a Moderate area attainment plan 
will be reclassified to Serious and will have to meet additional 
control requirements beyond those that are ``reasonable'' to assure 
attainment of the NAAQS by a later date that is as expeditious as 
practicable.
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    \106\ The concept of an ``impracticability demonstration'' is 
established in section 188(b), which addresses reclassifying 
Moderate PM2.5 areas to Serious. Section 188(b)(1) 
describes the EPA's discretionary authority to reclassify an area 
upon a determination that an area cannot practicably attain by the 
Moderate area attainment date. More relevant to this determination, 
however, section 189(a)(1)(B) specifically provides for submission 
of a demonstration addressing this concept in the case of Moderate 
areas that cannot attain the NAAQS by the applicable attainment 
date.
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    Existing guidance in the General Preamble on implementing this 
section of the CAA states that ``the EPA believes it is reasonable for 
all available control measures that are technologically and 
economically feasible to be adopted for areas that do not demonstrate 
attainment [by the applicable attainment date].'' \107\ The EPA 
maintains that it is reasonable to require a state to model the effects 
of emissions reductions from all technologically and economically 
feasible controls identified by the state for sources in a 
nonattainment area before asserting a claim that the area cannot 
practicably attain the relevant NAAQS by the Moderate area attainment 
date. However, the magnitude of certain PM2.5 precursor 
emissions and/or local atmospheric conditions of some PM2.5 
nonattainment areas may render certain technologically and economically 
feasible control measures ineffective in reducing ambient 
PM2.5 levels. Therefore, even in a Moderate PM2.5 
nonattainment area that cannot practicably attain the relevant NAAQS by 
the statutory attainment date, the EPA believes that it may not be 
reasonable in all cases to require that a state implement all 
technologically and economically feasible control measures identified 
for sources in the area.
---------------------------------------------------------------------------

    \107\ 57 FR 13498 (April 16, 1992), at page 13544.
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    Consistent with the EPA's long-standing interpretation that subpart 
4 Moderate area control requirements must be reasonable, the EPA 
proposes that, for a Moderate PM2.5 nonattainment area that 
cannot practicably attain the NAAQS by the statutory attainment date, a 
state must adopt and implement all technologically and economically 
feasible measures identified for sources in the area, except for any 
such measures that collectively will not effectively reduce ambient 
PM2.5 concentrations. See proposed 40 CFR 51.1009(a)(4)(ii). 
The EPA views this approach as similar to the agency's approach of 
allowing states to reject any otherwise technologically or economically 
feasible measures that are not needed to demonstrate attainment and 
that will not advance the attainment date by at least 1 year for 
nonattainment areas for which states can demonstrate attainment by the 
statutory attainment date. Once again, the EPA recognizes that 
identifying which measures collectively will not effectively reduce 
ambient PM2.5 concentrations will likely be an iterative 
process that requires specific analysis, potentially including 
modeling. However, the agency believes that such effort is appropriate 
for a state seeking to demonstrate the lack of need for certain 
controls that are determined to be technologically and economically 
feasible in a Moderate nonattainment area that cannot practicably 
attain the relevant PM2.5 NAAQS by the latest statutory 
Moderate area attainment date. The basis for establishing that it would 
not be reasonable to require imposition of otherwise available and 
appropriate controls because they would not be effective in reducing 
ambient PM2.5 concentrations requires an adequately robust 
analysis and explanation.
    The EPA also proposes an alternative approach to identifying all 
reasonable control measures for a Moderate nonattainment area that 
cannot practicably attain the PM2.5 NAAQS by the end of the 
sixth calendar year following designation. Under this alternative, 
states would be required to implement all technologically and 
economically feasible control measures that they have identified for 
sources of direct PM2.5 emissions and sources of emissions 
of significant PM2.5 precursors in the area. The EPA 
believes that this interpretation would be consistent with the agency's 
previous guidance in the General Preamble and is compelled by the 
language of section 189(a)(1)(C), which separately requires a state to 
submit a Moderate area attainment plan and meet the RACM and RACT 
requirement, even if the state submits a demonstration that it cannot 
attain the NAAQS through those measures by the applicable attainment 
date. In addition, as with a Moderate PM2.5 nonattainment 
area which a state demonstrates can attain the NAAQS by the end of the 
sixth calendar year following designation, the EPA interprets the 
provisions of section 172(c)(6) to require that such an area must 
implement all additional reasonable measures that it can implement 
through the sixth calendar year following designation of the area, in 
addition to those measures meeting the definition of RACM and RACT, in 
order to make progress toward attainment after the end of the fourth 
year following designation.
    As described in Section III of this preamble, the EPA is proposing 
three options for implementing CAA requirements applicable to 
PM2.5 precursors in the context of attainment planning and 
NNSR permitting. Proposed precursor Options 2A and 2B would provide an 
opportunity for a state to demonstrate that emissions of a particular 
precursor from all sources located in a Moderate PM2.5 
nonattainment area do not contribute significantly to ambient 
PM2.5 levels that exceed the standard in the area, or 
reductions of which will not be effective in reducing ambient 
PM2.5 concentrations, in which case the state would not be 
required to identify or otherwise evaluate control measures for the 
particular precursor. Under proposed precursor Options 1 and 3, on the 
other hand, states would rely on their control strategy analyses (e.g., 
for Moderate nonattainment areas, analyses to determine RACM and RACT 
and additional reasonable measures) to identify whether and/or which 
controls on sources of PM2.5 precursors are ``reasonable.'' 
The EPA believes that if proposed precursor Option 1 or 3 is finalized, 
it would be most appropriate to finalize the first approach to 
identifying reasonable control measures for Moderate areas that cannot 
practicably attain the NAAQS by the statutory attainment date, since 
states would not have an opportunity prior to evaluating the specific 
control measures for sources of PM2.5 precursors in the 
nonattainment area to demonstrate that controlling all sources of a 
particular precursor would not be effective in reducing ambient 
PM2.5 levels in the area. Likewise, if the agency finalizes 
proposed precursor Options 2A or 2B, the EPA believes that it would be 
most appropriate to finalize the alternative

[[Page 15377]]

proposed approach of requiring a state to implement all technologically 
and economically feasible measures identified by the state for sources 
in the area that can be implemented by the end of the sixth calendar 
year following designation if the state demonstrates that the area 
cannot practicably attain the NAAQS by the statutory attainment date, 
since the ``measures identified by the state'' would already implicitly 
exclude control measures on sources of any ``insignificant'' precursor. 
The EPA seeks comment on the two proposed approaches to selecting RACM 
and RACT and additional reasonable measures for Moderate nonattainment 
areas that cannot practicably attain the NAAQS by the statutory 
attainment date, and on the EPA's evaluation of the compatibility of 
these proposed approaches with the agency's proposed precursor options.
    The EPA's proposed analytical process for determining RACM and RACT 
is intended to result in a comprehensive list of such technologically 
and economically feasible controls that would include local and state 
measures that could achieve emissions reductions from sources within 
the area, beyond those that could or would be achieved through regional 
or national measures. Furthermore, the EPA is proposing to require that 
the Moderate area attainment plan must include modeling of all RACM and 
RACT and additional reasonable measures, and other state, regional and 
federal measures, to demonstrate that a state will not be able to 
attain the NAAQS by the end of the sixth calendar year after 
designation due to the severity of nonattainment in the area and/or due 
to the lack of availability or feasibility of implementing controls in 
the area by such date.
    Subpart 4 requires that Moderate areas that cannot or do not meet 
the Moderate area attainment date be reclassified as Serious 
nonattainment areas, in which case sources in the areas are then 
subject to BACM and BACT requirements. In the General Preamble, the EPA 
indicated that ``it may be reasonable, in some limited circumstances, 
for States to consider the compatibility of RACM and RACT with the BACM 
and BACT that will ultimately be implemented under the Serious area 
plans for those areas.'' \108\ Furthermore, for such areas that do not 
meet the Moderate area attainment date, the EPA indicated that ``in the 
case of RACM for area sources, EPA anticipates that any future 
implementation of BACM for these sources will be additive to, and hence 
compatible with, RACM. This is because BACM will generally consist of a 
more extensive implementation of the RACM measures . . . Since EPA 
anticipates that RACM and BACM for these sources will be compatible, 
the SIP's (sic) for these areas should reflect the application of 
available control measures to existing sources in moderate 
nonattainment areas as determined by the analysis described . . . for 
RACM.'' \109\ The EPA believes that a state should consider selecting 
and implementing controls that may qualify as BACM or BACT in a 
Moderate nonattainment area as part of their RACM and RACT analysis if 
they have reason to suspect that the area may not be able to attain the 
NAAQS by the applicable Moderate area attainment date as long as the 
control can be implemented by the statutory Moderate area attainment 
date. Early adoption of controls that would constitute BACM or BACT 
could be more efficient and could further the objectives of attaining 
the NAAQS expeditiously to protect public health and the environment.
---------------------------------------------------------------------------

    \108\ Ibid. at 13544.
    \109\ Ibid.
---------------------------------------------------------------------------

3. RACM and RACT and Additional Reasonable Measures Submission 
Requirements
    To ensure that attainment plan submissions contain the necessary 
supporting information to enable the EPA to review and approve a 
state's evaluation and selection of measures that constitute RACM and 
RACT in a given nonattainment area, the EPA proposes to require under 
the authority of section 301(a) that a state must submit the following 
information as part of its submission:
     A list of all source categories, sources and activities in 
the nonattainment area that emit direct PM2.5 or any 
PM2.5 precursor (for multi-state nonattainment areas, this 
would include source categories, sources and activities from all states 
which make up the area);
     For each source category, source or activity in the 
nonattainment area, an inventory of direct PM2.5 emissions 
and emissions of all PM2.5 precursors;
     For each non-de minimis source category, source or 
activity in the nonattainment area, a comprehensive list of potential 
control measures considered by the state for the nonattainment area; 
110 111
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    \110\ If the EPA finalizes proposed precursor Option 2A or 2B, 
which would effectively allow a state to demonstrate that a given 
precursor does not contribute significantly to PM2.5 
concentrations in a nonattainment area, then this step would require 
potential control measures only for sources of direct 
PM2.5 and precursors not exempted from further analysis.
    \111\ Menu of Control Measures document available at http://www.epa.gov/air/criteria.html.
---------------------------------------------------------------------------

     For each potential control measure considered by the state 
but eliminated from further consideration due to a determination by the 
state that the control measure or technology was not technologically 
feasible, a narrative explanation and quantitative or qualitative 
supporting documentation to justify the state's conclusion;
     For each technologically feasible emission control measure 
or technology, the state must provide the following information 
relevant to economic feasibility: (1) The control efficiency by 
pollutant; (2) the possible emissions reductions by pollutant; (3) the 
estimated cost per ton of pollutant reduced; and, (4) a determination 
of whether the measure is economically feasible, with narrative 
explanation and quantitative supporting documentation to justify the 
state's conclusion.
     For each technologically and economically feasible 
emission control measure or technology, the date by which the 
technology or measure could reasonably be implemented.
    Each of these elements will provide information needed by the EPA 
to evaluate correctly and efficiently whether the state is meeting the 
statutory requirements for an attainment plan, and in particular 
meeting the statutory requirement for states to implement RACM and RACT 
on sources within the nonattainment area. The EPA recognizes that the 
base year emissions inventory for the area that the state submits in 
conjunction with its attainment plan will likely contain some of the 
information proposed to be required under the first two items in this 
list. However, the EPA believes that it is incumbent on the state to 
ensure that the information needed for the EPA to evaluate the state's 
RACM and RACT analysis is presented more specifically as part of the 
RACM and RACT analysis and in a format that provides transparency, 
consistency and the ability for another party to evaluate the state's 
analysis effectively. For this reason, the EPA is including emissions 
inventory information specifically relevant to the RACM and RACT 
element of the state's attainment plan.
4. Criteria for Effective Regulations To Implement RACM and RACT and 
Additional Reasonable Measures
    After a state has identified a particular control measure as RACM 
or RACT or additional reasonable measure for a particular nonattainment 
area, it must

[[Page 15378]]

then implement that measure through a legally enforceable mechanism 
that will be included in the SIP (e.g., a state rule that the EPA will 
approve as a part of the federally enforceable SIP for the state). The 
EPA is proposing that in order for the EPA to be able to approve any 
such measure as part of the SIP, the state would have to provide 
information to meet the following four criteria. These criteria are 
similar to the criteria finalized as part of the remanded 2007 
PM2.5 Implementation Rule.
    First, the base year emissions from the source or group of sources 
to which the control measure applies and the future year projected 
emissions from those sources once controlled must be quantifiable so 
that the projected emissions reductions from the sources can be 
attributed to the specific measures being implemented. It is important 
that the emissions from the source category in question are accurately 
represented in the base year inventory so that emissions reductions are 
properly calculated. In particular, it is especially important to 
ensure that both the filterable and condensable components of direct 
PM2.5 emissions are accurately represented in the base year.
    Second, the control measures must be enforceable. This means that 
they must specify clear, unambiguous and measurable requirements. The 
measurable requirements for larger emitting facilities must include 
periodic source testing, monitoring or other viable means to establish 
whether the affected source meets the applicable emission limit. 
Additionally, to verify the continued performance of the control 
measure, specific emissions monitoring programs appropriate for the 
type of control measure employed and the level of emissions must be 
included to verify the continued performance of the control measure. 
The control measures and monitoring program must also have been adopted 
according to proper legal procedures.
    Third, the results of application of the control measures must be 
replicable. This means that where a rule contains procedures for 
interpreting, changing or determining compliance with the rule, the 
procedures are sufficiently specific and objective so that two 
independent entities applying the procedures would obtain the same 
result.
    Fourth, the control measures must be accountable. This means, for 
example, that source-specific emission limits must be permanent and 
must reflect the assumptions used in the attainment plan for the area, 
including the modeling conducted in conjunction with the attainment 
demonstration. It also means that the attainment plan must establish 
requirements to track emissions changes at sources and provide for 
corrective action if emissions reductions are not achieved according to 
the plan.
    The EPA seeks comment on these criteria for approval of any control 
measures adopted by a state for a Moderate area to assure that such 
measures are legally enforceable.
5. Determination of RACM and RACT and Additional Reasonable Measures in 
Multi-State Nonattainment Areas
    States in multi-state nonattainment areas will need to consult with 
each other on appropriate control measures for the shared nonattainment 
area. The agency anticipates that states could decide upon RACM and 
RACT and additional reasonable measures that differ from state to state 
in a shared nonattainment area, based upon each state's determination 
of the most effective strategies given the relevant mixture of sources 
and potential controls in the respective states' portions of a shared 
nonattainment area. As long as each state can adequately demonstrate 
that its chosen attainment strategy, including its selection and 
adoption of RACM and RACT and additional reasonable measures, will 
provide for meeting RFP requirements and for attainment of the NAAQS as 
expeditiously as practicable for the nonattainment area at issue, the 
EPA anticipates being able to approve individual state plans that may 
elect to control a different mix of sources or to implement different 
controls, under the proper circumstances. Nevertheless, in evaluating 
RACM and RACT and additional reasonable measures for a particular 
nonattainment area, states must consider potential reasonable control 
measures developed for other areas or other states, and particularly 
for other portions of an interstate nonattainment area. In addition, 
states in multi-state nonattainment areas must evaluate whether the 
reasonable measures each state may have identified as not being 
necessary for attainment could collectively advance the attainment date 
for the area by at least 1 year. The EPA may consider such measures in 
assessing the approvability of each state's individual attainment plan 
for a multistate nonattainment area.
6. Environmental Justice Considerations in Developing the Attainment 
Plan Control Strategy for a Moderate PM2.5 Nonattainment 
Area
    The EPA strongly urges states to consider environmental justice 
concerns with respect to any control measures they have identified as 
potential RACM or RACT or additional reasonable measures in an area, 
particularly to the extent that control measures that a state may be 
considering are otherwise approximately equal (in terms of 
technological and economic feasibility) but unequal with respect to 
their direct or indirect impacts on overburdened populations.\112\ In 
such cases, the EPA encourages the state to prioritize imposition of 
the control measures that will result in the least possible burden and 
greatest degree of health protection for overburdened populations in 
the nonattainment area. Section IX of this preamble discusses this and 
other possible approaches for states to incorporate ways to address 
environmental justice concerns associated with implementation of the 
PM2.5 NAAQS in their attainment plans and SIP development 
process, and the EPA seeks comment on ways to more fully address such 
concerns.
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    \112\ The term ``overburdened populations'' is defined in the 
EPA's ``Plan EJ 2014'' to describe the minority, low-income, tribal, 
and indigenous populations or communities in the U.S. that 
potentially experience disproportionate environmental harms and 
risks as a result of greater vulnerability to environmental hazards. 
This increased vulnerability may be attributable to an accumulation 
of both negative and lack of positive environmental, health, 
economic or social conditions within these populations or 
communities. For more information on Plan EJ 2014, see: http://www.epa.gov/environmentaljustice/plan-ej/.
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E. Modeling for Attainment Demonstrations

1. Statutory Requirements
    Section 189(a) generally requires a state with a designated 
Moderate nonattainment area to submit an attainment plan for such area. 
As discussed earlier, section 189(a)(1)(B) more specifically requires 
the state to submit an attainment demonstration including air quality 
modeling to establish either: (i) That the area will attain the 
relevant NAAQS by the applicable attainment date; or, (ii) that it is 
impracticable for the area to attain the relevant NAAQS by the 
applicable attainment date. For Moderate nonattainment areas, the 
attainment date is as expeditiously as practicable, but no later than 
the end of the sixth calendar year after designation as nonattainment. 
Section 189(a)(2)(B) of the CAA requires states with designated 
nonattainment areas to submit attainment plans no later than 18 months 
after designation.

[[Page 15379]]

2. What is an attainment demonstration?
    Section 189(a)(2)(B) does not define the term ``demonstration'' and 
does not specify precisely how a state should make the required 
demonstration. Thus, the EPA believes it is necessary to provide more 
specific parameters for such demonstrations in order to assure that 
they contain the requisite information to allow for meaningful 
evaluation of the issues that the demonstrations are intended to 
address. An attainment demonstration is a set of analyses that provide 
an explanation of how a state will attain the PM2.5 NAAQS by 
the applicable attainment date in a particular nonattainment area.\113\ 
The EPA is proposing that the demonstration must contain: (i) Technical 
analyses such as base year and future year modeling of emissions which 
identify sources and quantify emissions that are contributing to 
violations of the PM2.5 NAAQS; and, (ii) analyses of future 
year emissions reductions and air quality improvement resulting from 
existing (i.e., already-adopted or ``on the books'') national, regional 
and local programs, and potential new local measures needed for 
attainment, including RACM and RACT controls for the area. Each state 
with a Moderate nonattainment area must submit an attainment plan with 
an attainment demonstration that includes analyses supporting the 
state's determination of its proposed attainment date. In all cases, 
the state must show that the Moderate area will attain the NAAQS as 
expeditiously as practicable, but not later than the end of the sixth 
calendar year after designation. In order to establish that the 
attainment date is as expeditious as practicable, the state must 
explain why any control measures adopted in the attainment plan provide 
for the most expeditious attainment and, specifically, must demonstrate 
that collectively the reasonable measures that were not adopted as RACM 
or RACT or additional reasonable measures will not advance the 
attainment date by at least 1 year if implemented. See proposed 40 CFR 
51.1011(a).
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    \113\ An area is designated nonattainment for either the annual 
PM2.5 NAAQS or the 24-hr PM2.5 NAAQS or both. 
The attainment demonstration should show that the area is attaining 
the form of the NAAQS for which they have been designated 
nonattainment.
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    A state may alternatively submit a demonstration that shows that 
attainment by the statutory attainment date for a Moderate area is 
impracticable.\114\ The statute does not define the term 
``impracticable'' in this context, so it is necessary for the EPA to 
interpret this term in the context of a submission from the state for 
this purpose. In order to support this type of demonstration, the EPA 
proposes to require that the state must show that, even if all 
technologically and economically feasible controls that can be 
implemented within 6 years were implemented, the state could not attain 
the NAAQS within the statutory timeframe for a Moderate area. A state 
could do this by performing a modeling analysis which projects 
emissions to the sixth year after designations in order to predict 
future year PM2.5 design values in the area. The projected 
emissions would account for all existing federal and state SIP-adopted 
regulations on sources outside the nonattainment area that were in 
place at the time, plus all measures that were identified as 
technologically and economically feasible controls that can be 
implemented in the nonattainment area within 6 years of designation 
(i.e. all measures that would qualify as RACM or RACT or as additional 
reasonable measures), as well as any other reasonable measures 
available in the state that could aid in achieving timely attainment. 
If the modeling shows that attainment cannot be reached by the end of 
the sixth calendar year following designation, then the analysis could 
be used to demonstrate that it is impracticable for the area to attain 
the relevant NAAQS by the statutory attainment date. Other information 
can also be used to support the demonstration, including ambient data 
and emissions trends data. States are encouraged to work with their 
respective EPA Regional Office to identify appropriate information that 
could be used to support an impracticability demonstration. The EPA 
emphasizes that states that can make the required showing that a 
Moderate nonattainment area cannot attain the NAAQS by the statutory 
attainment date are nonetheless required to meet the substantive 
requirements for a Moderate area attainment plan, including the 
implementation of control measures that are RACM and RACT and 
additional reasonable measures in that area.
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    \114\ Pursuant to section 188(b)(1)(B), upon an EPA 
determination that attainment by the Moderate date is impracticable, 
the EPA shall reclassify the area as Serious within 18 months after 
the Moderate area attainment plan due date.
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3. What modeling is required?
    States are required to submit air quality modeling in support of an 
attainment demonstration for a Moderate PM2.5 nonattainment 
area. Although air quality modeling is not expressly required for a 
Moderate area demonstration showing that attainment by the attainment 
date is impracticable (per section 189(a)(1)(B)(ii)), the EPA proposes 
to interpret the CAA to require air quality modeling similar to that 
required for an attainment demonstration in order to demonstrate that 
attainment of the relevant PM2.5 NAAQS by the statutory 
attainment date is impracticable. Because air quality modeling is a 
required element of the attainment demonstration in section 
189(a)(1)(B), the EPA believes that it logically follows that similar 
modeling should also be required to show that an area will not be able 
to attain by the attainment date contemplated by the statute.
    There may be limited cases in which a state may be able to 
demonstrate through a rigorous technical analysis with supporting 
documentation that attainment by the statutory Moderate area attainment 
date is impracticable. Given that the statute may be interpreted as not 
requiring air quality modeling for an impracticability demonstration, 
the EPA proposes and seeks comment on an alternative option under which 
air quality modeling would not be a requirement for a Moderate area 
impracticability demonstration. The EPA would recommend that a state 
submit modeling as part of any Moderate area impracticability 
demonstration, but under this alternative option such modeling would 
not be a regulatory requirement.
    Given that secondarily formed PM2.5 (e.g. ammonium 
sulfate, ammonium nitrate and SOA) is a large fraction of the total 
measured PM2.5 in most PM2.5 nonattainment areas, 
the EPA assumes that photochemical grid modeling (which considers 
secondary PM2.5 formation) will be needed for a state to 
demonstrate attainment with the NAAQS. Most previous PM2.5 
attainment demonstrations for both the 1997 and 2006 PM2.5 
NAAQS have utilized photochemical grid models. However, in some 
nonattainment areas that are dominated by primary PM2.5 
emissions (e.g. residential wood smoke), more simplistic dispersion 
models, such as a combination of dispersion, receptor and box airshed 
models, may suffice to demonstrate that the area will attain the NAAQS. 
Regardless of the modeling approach selected to support the attainment 
demonstration, the analyses must be based on technically credible 
methods and provide for the timely submittal of the attainment 
demonstration and implementation of control measures. States should 
consult with their respective EPA Regional

[[Page 15380]]

Office to determine the appropriate type of modeling demonstration for 
the particular nonattainment area.
4. Do states need to develop new modeling for their attainment 
demonstrations?
    The EPA believes that the statutory provision requiring attainment 
demonstrations for Moderate PM2.5 nonattainment areas to 
include air quality modeling can be fulfilled in a variety of ways. 
Thus the EPA proposes to allow states to fulfill the statutory modeling 
requirement through either locally generated photochemical and/or 
dispersion modeling or, with proper justification, through appropriate 
regional or national modeling. The EPA seeks comment on what types of 
modeling demonstrations should be required to fulfill the CAA 
requirement to ``include air quality modeling'' as part of the 
attainment demonstrations for Moderate nonattainment areas.
    New modeling analyses that follow the EPA modeling guidance, 
conducted by the state for implementing the PM2.5 NAAQS, 
will presumably satisfy the attainment demonstration modeling 
requirement. However, many areas that were designated as nonattainment 
for the 1997 and/or 2006 PM2.5 NAAQS have already invested 
considerable resources in local and/or regional PM2.5 
modeling analyses. Most states with potential PM2.5 
nonattainment areas are already participating in regional modeling 
analyses through multi-jurisdictional organizations (MJOs). These MJOs 
(e.g. SESARM, LADCO and WRAP) represent most states with 
PM2.5 nonattainment areas in the country. There is ongoing 
PM2.5 modeling that may provide useful information for state 
PM2.5 NAAQS attainment demonstrations.
    In addition to local and regional modeling, the EPA conducts 
nationwide modeling (generally limited to the contiguous 48 states) in 
support of various national rulemakings. The base and future modeling 
year for national rule modeling varies depending on compliance dates 
for the rule being analyzed and on when the modeling was conducted. For 
example, there are several analyses of recent and ongoing rules which 
may provide useful PM2.5 modeling information for state 
attainment demonstrations. Among them are modeling to support the 2012 
PM2.5 NAAQS review, the final Tier 3 mobile source emissions 
standards, and the current ozone NAAQS review.\115\ While the analyses 
in these rulemaking actions may not be precisely relevant for the 
purposes of a PM2.5 attainment plan, they may nevertheless 
provide useful information or input relevant to states developing 
attainment plans for the PM2.5 NAAQS. Similar nationwide 
modeling efforts may be helpful for purposes of future PM2.5 
NAAQS.
---------------------------------------------------------------------------

    \115\ Even though the ozone NAAQS modeling will be focused on 
ozone, PM2.5 modeling results will likely be generated 
from the analysis in order to inform health benefits calculations.
---------------------------------------------------------------------------

    States may be able to use regional and/or EPA modeling to 
demonstrate that specific nonattainment areas will attain the relevant 
PM2.5 NAAQS by the applicable attainment date, but states 
must evaluate the relevant modeling information to show that it is 
suitable for that purpose. For example, the modeling should be 
evaluated to show that it is performing adequately for the area; that 
the future modeling year is appropriate for the particular attainment 
demonstration; and that the base year emissions and projected emissions 
and controls adequately represent the base year conditions and 
emissions expected to occur in the area in the future. States should 
work closely with the appropriate EPA Regional Office to determine what 
(if any) existing modeling may be suitable for use in an attainment 
demonstration (or an impracticability demonstration) for a Moderate 
PM2.5 nonattainment area.
    The EPA requests comment on how states can use existing regional 
and/or national modeling to meet their attainment demonstration 
requirements. The agency also notes that even when regional or EPA 
modeling is available to show that an area is expected to attain the 
PM2.5 NAAQS by the applicable attainment date, other CAA 
requirements may be difficult to satisfy through the use of regional or 
EPA modeling. For example, states may or may not be able to satisfy 
their CAA requirements for emissions inventory submittals or RFP 
demonstrations by using data derived from MJO or EPA modeling. The 
available regional/national modeling may not include an appropriate 
base year or future year, and the level of detail or how the emissions 
were derived may not be appropriate or compatible with inventories 
needed to satisfy specific CAA requirements. States may have to derive 
more local specific inventory data, for the appropriate years, to 
adequately satisfy these CAA requirements.
    Because it will be challenging for states to prepare new modeling 
analyses to meet the submission deadline for the Moderate area 
attainment plans, the EPA encourages states to start work on modeling 
analyses as soon as possible, in order to ensure that adequate time is 
devoted to developing a technically credible attainment demonstration. 
States that have the most challenging PM2.5 problems will 
likely need to develop new and/or updated photochemical modeling 
analyses for their nonattainment areas, with emissions (including 
potential new controls) projected to the appropriate future attainment 
year.
5. What guidance is available for using models to demonstrate 
attainment?
    The procedures for modeling PM2.5 as part of an 
attainment demonstration are described in the EPA's ``Guidance on the 
Use of Models and Other Analyses for Demonstrating Attainment of Air 
Quality Goals for Ozone, PM2.5, and Regional Haze.'' \116\ 
All modeling in support of an attainment demonstration should be 
consistent with the EPA's PM2.5 photochemical modeling 
guidance (referenced above) as well as the Guideline on Air Quality 
Models (40 CFR part 51, Appendix W).
---------------------------------------------------------------------------

    \116\ The 2007 modeling guidance can be found at the following 
Web site: http://www.epa.gov/scram001/guidance/guide/final-03-pm-rh-guidance.pdf. As noted, the EPA recently released revised draft 
modeling guidance.
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    The PM2.5 attainment demonstration modeling guidance 
describes how states can apply air quality models to generate results 
needed to demonstrate attainment. These recommendations include 
developing a conceptual description of the problem to be addressed; 
developing a modeling/analysis protocol; selecting an appropriate model 
to support the demonstration; selecting appropriate meteorological 
episodes or time periods to model; choosing an appropriate area to 
model with appropriate horizontal/vertical resolution; generating 
meteorological and air quality inputs to the air quality model; 
generating emissions inputs to the air quality model; and, evaluating 
performance of the air quality model. After these steps are completed, 
the state can apply a model to simulate effects of future year 
emissions and candidate control strategies.
    The EPA is not requiring a specific model for use in the attainment 
demonstration for the PM2.5 NAAQS. At present, there is no 
single model which has been extensively tested and shown to be clearly 
superior to other available models. The current modeling guideline, 40 
CFR part 51, Appendix W, does not identify a preferred model for use in 
attainment demonstrations of the PM2.5 NAAQS. Thus, states 
may choose from several alternatives so long as the

[[Page 15381]]

alternative is appropriate for the nonattainment area under evaluation.
    In some cases, a state may need to apply multiple models in the 
attainment demonstration. In most cases, a photochemical grid model is 
needed to predict base and future year concentrations of secondary 
PM2.5. Photochemical grid models can also be used to predict 
concentrations of primary particulate and are useful in assessing steep 
concentration gradients arising from area sources. However, in areas 
with high concentrations of primary PM2.5, or strongly 
stratified air at the surface, a Gaussian plume model or puff model may 
also be needed to more accurately represent steep concentration 
gradients (or lack of mixing to the surface) in locations with a large 
contribution from a single or multiple primary PM2.5 point 
sources or locations in near-road areas. The EPA's attainment 
demonstration modeling guidance provides details and recommendations on 
using multiple models.
    Models are used to test whether control measures in an attainment 
plan are likely to result in attainment of the relevant standard(s). 
The attainment demonstration modeling guidance recommends a modeled 
attainment test for the annual and 24-hour PM2.5 NAAQS that 
uses a combination of ambient PM2.5 and PM2.5 
species data and modeled PM2.5 concentrations to estimate 
future year air quality. In the recommended attainment test, the state 
applies the test at each PM2.5 ambient monitor location 
within or near a designated nonattainment area. Models are used in a 
relative sense to estimate the response of measured air quality to 
future changes in emissions. Future air quality is estimated by 
multiplying recent monitored PM2.5 values by the modeled 
relative response (percent change) to projected future changes in 
emissions. If the future design value at all monitoring locations in 
the nonattainment area does not exceed the concentration of 
PM2.5 specified in the NAAQS, the area is projected to 
attain the NAAQS.
    Because PM2.5 is a mixture of chemical components, 
states should use recent observations and modeled responses of major 
components of PM2.5 (i.e. sulfate, nitrate, organic carbon, 
etc.) to estimate future concentrations of each component.\117\ The 
predicted future concentration of PM2.5 is the sum of the 
future year predicted component concentrations.
---------------------------------------------------------------------------

    \117\ The exact years of the ``recent'' ambient data are defined 
by the base year selected for the modeling. The guidance recommends 
using 5 years of ambient data, centered about the base modeling 
year.
---------------------------------------------------------------------------

    The attainment demonstration modeling guidance contains additional 
details regarding the treatment of PM2.5 and speciation 
monitoring data. Because PM species data are not available at each 
PM2.5 FRM site, the EPA recommends a methodology which 
interpolates species data to each FRM site in order to estimate the 
species concentrations in the area. This information, combined with 
modeling results, may be used to calculate future air quality at each 
FRM monitoring site. The EPA has developed software to perform both the 
annual and 24-hour PM2.5 attainment test (including 
interpolating PM species data). The software is called the Modeled 
Attainment Test Software (MATS) and is available for no cost at: http://www.epa.gov/scram001/modelingapps_mats.htm. The software is provided 
to make it relatively easy for states to apply the recommended modeled 
attainment test. However, states are not required to use MATS and can 
develop their own post-processing software.
    The modeling guidance also describes the opportunity for states to 
supplement their modeling with a ``weight of evidence'' demonstration. 
States may use other information and analyses, in addition to the 
modeled attainment test, to estimate whether future attainment of the 
NAAQS in an area is likely. Other analyses may include, but are not 
limited to, emissions trends, ambient data trends and analyses, other 
modeling analyses, and documentation of other non-modeled emissions 
control strategies, including voluntary programs.
    The reliability of tests for estimating future attainment depends 
upon having reliable databases for inputs to those tests. The modeling 
guidance identifies and prioritizes key data-gathering activities and 
analytical capabilities that will increase credibility of analyses used 
to estimate if the NAAQS will be attained in the area by the statutory 
attainment date.
    The EPA is considering updates to the modeling guidance to address 
PM2.5 modeling for the 2012 PM2.5 NAAQS. The 
agency released a revised draft modeling guidance for developing 
demonstrations to meet PM2.5, ozone, and regional haze air 
quality goals in December 2014, and intends to revise the guidance 
after considering public comments received.\118\
---------------------------------------------------------------------------

    \118\ See ``Draft Modeling Guidance for Demonstrating Attainment 
of Air Quality Goals for Ozone, PM2s, and Regional Haze,'' issued by 
Richard Wayland, Director of Air Quality Assessment Division, EPA 
Office of Air Quality Planning and Standards, to EPA Regional Air 
Division Directors, Regions I-X, December 3, 2014. Available at: 
http://www.epa.gov/ttn/scram/guidance/guide/Draft_O3-PM-RH_Modeling_Guidance-2014.pdf.
---------------------------------------------------------------------------

    The application of air quality models requires a substantial effort 
by state and local agencies. Therefore, states should work closely with 
their respective EPA Regional Office in executing each step of the 
modeling process. Doing so will ensure that states know what EPA 
analyses they can rely on, if they wish, to simplify this task, and it 
will increase the likelihood of the EPA's approval of a state's 
demonstration submitted at the end of the modeling and overall 
attainment plan development process.
6. Demonstrating Attainment at Near-Road Monitors
    The 2012 PM2.5 NAAQS final rule contains new 
requirements for operating near-road monitors in the largest 
metropolitan areas.\119\ The first monitors were required to be in 
place as of January 1, 2015 (see Section II of this preamble for more 
details). These monitors will not have the requisite 3 years of 
monitoring data necessary to calculate a PM2.5 design value 
until 2018 at the earliest. Therefore, these data were not available to 
inform the first round of initial designations for the 2012 
PM2.5 NAAQS and there will be less than 3 years of data 
available when the initial attainment demonstrations for Moderate areas 
are due in October 2016. As a result of this timing, the agency is 
proposing that the initial set of Moderate area attainment 
demonstrations will not need to include projected design values for 
near-road monitor locations. However, subsequent attainment 
demonstrations for the PM2.5 NAAQS (after 2018, when 3 or 
more years of complete ambient data are available at near-road 
monitors) will need to address those monitor locations in attainment 
plans and will need to include a demonstration that those monitor 
locations will show attainment of the NAAQS by the applicable statutory 
attainment date. The revised modeling guidance document for the 
PM2.5 NAAQS includes procedures for applying a dispersion 
model or a combination of photochemical grid models and dispersion 
modeling to demonstrate attainment at near-road monitor locations.
---------------------------------------------------------------------------

    \119\ 78 FR 3085 (January 15, 2013), at page 3283.
---------------------------------------------------------------------------

7. Demonstrating Attainment in Unmonitored Areas
    As explained in the 2012 PM2.5 NAAQS final rule and 
summarized in Section II of this preamble, the EPA's

[[Page 15382]]

monitoring requirements for PM2.5 are designed to ensure a 
robust nationwide monitoring network in both nonattainment and 
attainment areas. Air agencies have achieved this by maintaining their 
PM2.5 networks in accordance with EPA's network design 
criteria. Historically, these criteria provided that CBSAs have at 
least one PM2.5 monitoring site located in an ``area-wide'' 
location of expected maximum concentration (within the CBSA).\120\ 
Thus, by assuring compliance with the NAAQS at the location of the 
expected highest area-wide concentration in the CBSA, air quality is 
protected throughout each CBSA. However, due to limited resources, 
there are limits to the number of air quality monitors that can be 
deployed and it therefore may be useful to consider what, if any, 
additional analysis needs there may be as agencies prepare their 
attainment plans.\121\
---------------------------------------------------------------------------

    \120\ As explained in the final 2012 PM NAAQS rule, the EPA 
expects that each CBSA will maintain its existing highest 
concentration area-wide monitoring site (referred to as the design 
value site), See 78 FR 3085 (January 15, 2013), at page 3240. These 
sites were set up during the period of time when the network design 
criteria required having at least one site in an area-wide location 
of expected maximum concentration. The EPA intends to maintain the 
highest priority sites in the existing network, which are often at 
the neighborhood scale, as the largest part of the PM2.5 
monitoring network to continue to support a number of monitoring 
objectives, while also allowing lower value sites to move to near-
road locations as that part of the network is phased in.
    \121\ Annual monitoring network plans and 5 year assessments are 
required by regulation in 40 CFR 58.10. The 5 year monitoring 
network assessment is a comprehensive evaluation of a monitoring 
agency's ambient air monitoring network, while the annual plan 
describes the existing network and changes being proposed to support 
implementing recommendations from the most recent 5 year assessment 
as well as any applicable changes finalized in association with 
NAAQS revisions.
---------------------------------------------------------------------------

    Under the 2007 PM2.5 Implementation Rule, the EPA 
required states to follow existing modeling guidance, which suggested 
that a state's PM2.5 attainment plan could be approved if it 
demonstrated attainment, through the modeled attainment test, at 
monitored locations only. But the guidance also recommended that states 
conduct further analyses based on the modeling results to determine 
whether there were unmonitored areas that merited additional analysis 
or investigation. The guidance further recommended that states either 
reduce emissions that, based on these recommended additional analyses, 
could cause violations in unmonitored areas, or that they place a new 
monitor in such an area. The EPA found that the minimum requirements 
for the unmonitored area analysis in the 2007 modeling guidance (and 
the 2007 PM2.5 Implementation Rule) were not sufficiently 
clear. The EPA is therefore proposing several alternative options in 
order to clarify the appropriate treatment of model results in 
unmonitored areas for purposes of implementing current and future 
PM2.5 NAAQS.
    The EPA is proposing four possible approaches to demonstrating 
attainment in unmonitored areas. Option 1 would only require states to 
perform the attainment test at locations that have current or recent 
FRM and/or FEM monitoring data. The EPA would not require states to 
analyze areas that have no monitoring data with which to anchor the 
attainment demonstration modeling results. The EPA is proposing this 
approach to evaluating monitored and unmonitored areas in order to be 
consistent with how attainment of the PM2.5 NAAQS is 
determined for purposes of designations and redesignations, and due to 
uncertainty in modeled projections in locations where there are no 
monitoring data to anchor the future year model results. As discussed 
in Section II of this preamble, the EPA promulgates designations for 
PM2.5 NAAQS nonattainment areas based primarily on ambient 
data measured at FRM and FEM monitors.\122\ Although the EPA considers 
other forms of information for purposes of evaluating areas with 
sources that contribute to those monitored violations for inclusion 
within the nonattainment area boundaries, the fundamental basis for 
designating an area as nonattainment for a PM2.5 NAAQS is 
the presence of one or more FRM or FEM monitors with data showing 
violations of the NAAQS in question. Similarly, determinations of 
attainment of the PM2.5 NAAQS for purposes of redesignation 
actions are based primarily on monitored data. When all FRM and FEM 
monitors in a nonattainment area measure attainment of the 
PM2.5 NAAQS, the state is eligible to submit a redesignation 
request for the area, assuming that it has complied with all other 
applicable requirements for purposes of redesignation. Specifically, 
the EPA's approval of a redesignation request is subject to meeting the 
requirements of CAA section 107(d)(3)(E). Among those requirements is 
that the area has attained the NAAQS. For the PM2.5 NAAQS, 
this determination is based on ambient data measured at the FRM and FEM 
monitors in the area in question. Thus, neither PM2.5 
designations nor redesignations currently take into account information 
regarding potential violations of the NAAQS at unmonitored locations 
throughout a given area. Therefore, consistent with how 
PM2.5 areas are designated and redesignated, the EPA is 
first proposing to require that states only show attainment at 
PM2.5 FRM and FEM monitoring locations as an element of 
their attainment demonstrations for the PM2.5 NAAQS.
---------------------------------------------------------------------------

    \122\ A monitor must have 3 years of quality-assured ambient 
data available to be used to calculate a PM2.5 design 
value and determine compliance with the NAAQS.
---------------------------------------------------------------------------

    In addition, the ``relative'' attainment test for PM2.5 
uses FRM or FEM ambient monitoring data, combined with future year 
modeled percentage changes in PM2.5 concentrations, to 
project future year design values. Since the attainment test relies on 
ambient monitoring data, an analysis of future year concentrations in 
unmonitored areas can only be accomplished by interpolating ambient 
data to a particular location where there is no existing monitor or 
recent monitoring data. Therefore, in the context of an attainment 
demonstration, the projection of future year PM2.5 
concentrations in unmonitored locations is inherently more uncertain 
than projections in monitored locations due to the fact that the 
ambient concentrations from which these projections are developed are 
unknown in the unmonitored locations.
    Proposed Option 2 for unmonitored area analyses would require the 
state to conduct an unmonitored area analysis as part of all attainment 
demonstrations (for Moderate and Serious areas) and require the state 
to eliminate potential violations in unmonitored areas through 
enforceable emissions reductions in the SIP. The requirement would be 
based on a premise that states must demonstrate attainment of the NAAQS 
in all locations of a nonattainment area, and models can and should be 
used for that purpose. Modeled attainment demonstrations using 
photochemical grid models provide modeling results for all grid cells 
in the nonattainment area. Therefore, notwithstanding the uncertainty 
that is inherent to this approach as discussed above, model outputs 
(optionally combined with interpolated ambient data) could be used to 
derive estimates of PM2.5 concentrations in unmonitored 
areas.
    Proposed Option 3 would require states to show attainment at all 
current and recent monitoring locations. In addition, states would be 
required to provide an unmonitored area analysis as part of all 
attainment demonstrations (for Moderate and Serious areas). However, 
rather than requiring states to impose additional enforceable emissions 
reductions in the SIP to address potential violations in these 
locations, states would be required to use the unmonitored area 
analysis

[[Page 15383]]

results to develop an assessment of the likelihood of violations in 
unmonitored areas. This assessment may be especially important in areas 
with a relatively sparse PM2.5 monitoring network or in 
locations where information such as modeling data, emissions 
inventories or non-FEM monitoring data (such as from special purpose 
monitors or saturation monitoring studies) may indicate potential high 
PM2.5 concentrations in areas that are currently 
unmonitored.
    The nature of the assessment of likelihood of violation that is 
required under proposed Option 3 would depend on local area modeling, 
but could include, as appropriate, elements such as an evaluation of 
the emissions inventory (particularly for local direct PM2.5 
sources), the existing ambient data for the area, and meteorological 
model inputs to determine if the modeled violations in unmonitored 
areas appear to be credible. If potential violations are found to be 
credible, additional steps may include imposition of enforceable 
emissions reductions at nearby emission sources or a commitment to 
deploy special purpose monitors and/or saturation monitors in the area 
(in order to further evaluate the problem). The state would be required 
to document the assessment, including analyses of emissions, 
meteorological inputs and ambient data and/or make a commitment to 
establish special purpose monitors as part of the attainment 
demonstration. Special purpose ambient air monitoring data that is 
collected after the attainment demonstration is submitted should be 
summarized for use in the area's 5-year monitoring assessment and, 
where appropriate, annual monitoring network plans.\123\ Additionally, 
monitoring data that is collected as a result of the unmonitored area 
analysis assessment (after the attainment demonstration is submitted) 
must be reported as a quantitative milestone required under section 
189(c)(1) (see Section IV.G of this preamble).
---------------------------------------------------------------------------

    \123\ All states are required to have an annual monitoring plan 
(see Section II of this preamble) which meets the siting criteria 
for PM2.5 monitors (40 CFR 58.10).
---------------------------------------------------------------------------

    In summary, Option 3 would clarify that an unmonitored area 
analysis would be required in all attainment demonstrations, and an 
assessment of the unmonitored area analysis results would be required 
as part of the attainment demonstration documentation. In contrast to 
Option 2, however, the unmonitored area analysis results would not be 
used as part of the specific analytical approach for determining 
whether a particular control strategy will result in the area attaining 
the NAAQS.
    Finally, proposed Option 4 would require states to show attainment 
at all current and recent monitoring locations. States would not be 
required to provide an unmonitored area analysis as part of the 
attainment demonstration. However, the EPA would encourage states to 
use information available to them to consider what, if any, impacts may 
be occurring in unmonitored areas. States could consider information 
such as modeling data, emissions inventories or non-FEM monitoring data 
(such as from special purpose monitors or saturation monitoring 
studies) which may indicate potential high PM2.5 
concentrations in areas that are currently unmonitored. Under this 
approach, states could consider model results to develop an assessment 
of the likelihood of violations in unmonitored areas. This proposed 
option differs from Option 3 in that it would not require an 
unmonitored area analysis. Rather, under proposed Option 4, an 
unmonitored area analysis would be recommended where the state and/or 
the EPA has reason to believe that potential violations may be 
occurring in unmonitored areas, or other available information 
indicates that further analysis is warranted. States would be expected 
to consult with the appropriate EPA Regional Office to evaluate 
available information to determine if an unmonitored area analysis is 
needed for a particular area.
    The four options presented above would lead to a range of potential 
analysis costs by requiring attainment demonstrations at more locations 
and with varying degrees of specificity. To the extent that these 
analyses reveal additional locations with potential violations, the 
effort needed to address these violations could also be higher, and may 
ultimately lead to additional reductions, with their associated costs 
and benefits. In terms of analysis costs, Option 1 would be expected to 
be the least costly option, whereas Option 2 would be expected to be 
the most resource intensive. Option 3 is similar to Option 2, except 
that if a potential violation is indicated in an unmonitored area, 
there would not be a regulatory requirement for the air agency to 
identify enforceable controls to eliminate the potential violation. For 
example, the air agency could instead elect to site a new monitor to 
further characterize air quality in the area. The analysis costs 
associated with Option 3 would thus be similar to Option 2.
    Option 4 most closely describes the current policy for the 
PM2.5 NAAQS implementation program. Currently, the EPA 
recommends that air agencies conduct an unmonitored area analysis, but 
there is no regulatory requirement for the air agency to either perform 
an unmonitored area analysis or to impose control requirements if the 
analysis indicates potential violations. Thus, under Option 4, if an 
unmonitored area analysis is performed, the analysis costs associated 
with this option would be the same as for Options 2 and 3. Under Option 
4, if it is determined by the EPA and the air agency to be unnecessary 
to perform an unmonitored area analysis, there would be no additional 
analysis costs beyond the monitor-only approach of Option 1. Regarding 
the costs and benefits of reductions resulting from additional efforts 
to address unmonitored locations (i.e., to the extent that efforts 
necessary to address monitored locations do not also address 
unmonitored locations), the EPA does not have enough information to 
determine the extent of such areas or the measures that would be needed 
to address them, nor can the agency predict the extent to which such 
measures would be adopted under one option but not another.
    The EPA's four proposed options reflect various combinations with 
respect to whether such an analysis is required and the purposes for 
which the state and the EPA might use the results of the analysis. The 
EPA requests comment on whether an unmonitored area analysis should be 
a required component of an attainment demonstration for a 
PM2.5 nonattainment area and, if required, how the results 
of an unmonitored area analysis should be used. The EPA also requests 
comment on the potential costs and benefits of each of the four 
specific options, and on which of the options the commenter believes 
should be included in the final rule and why.
8. What future year(s) should states model in attainment 
demonstrations?
    A state performing a modeling analysis for an attainment 
demonstration or impracticability analysis must select a future year 
for the analysis. For an attainment demonstration, a state should 
select the future modeling year such that all control measures relied 
on for attainment will have been fully implemented by the beginning of 
that year. To demonstrate attainment, the modeling results for the 
nonattainment area must predict that emissions controls implemented no 
later than the beginning of the last calendar year preceding the 
attainment date will

[[Page 15384]]

result in PM2.5 concentrations that meet the level of the 
standard.\124\
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    \124\ Note that for purposes of the PM2.5 NAAQS, a 
determination of attainment (or failure to attain), which the EPA is 
required to make after the attainment date has passed, is based on 
an average of the most recent 3 years of ambient data prior to the 
area's attainment date.
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    While states should choose the future modeling year based on a 
number of factors, the EPA recommends the last possible year permitted 
under the statute as a starting point for modeling. There are several 
reasons for this. First, states with Moderate areas that submit an 
impracticability demonstration must show that the area cannot attain 
the NAAQS by the end of the sixth calendar year following designation 
of the area. Therefore, the appropriate future modeling year for such a 
demonstration is the sixth calendar year after designation. Even if a 
state does not submit (or does not intend to submit) an 
impracticability demonstration, modeling the sixth calendar year is a 
logical starting point to determine if attainment by that year is 
likely. Second, even though attainment is determined based on 3 years 
of ambient data, states do not have to model 2 years before the 
attainment date to show modeled attainment. Since the design value is 
an average of the annual or 98th percentile value for 3 consecutive 
years of data, attainment can still be shown even if concentrations 
exceed the NAAQS in one or more of the 3 years used to determine 
attainment (as long as the average of the three annual values is below 
the level of the NAAQS). Therefore, it can be appropriate to model any 
of the 3 years used to determine attainment. Third, if ambient data 
show attainment level concentrations in the final statutory attainment 
year, a state may be eligible for up to two 1-year extensions of the 
attainment date, if the area meets the criteria for such extensions 
under CAA section 188(d). Therefore, modeling attainment level 
concentrations for the last year permitted by statute is acceptable.
    For all of the reasons stated above, it is both acceptable, and 
will in fact be most efficient, for a state to begin the attainment 
demonstration process by modeling the last year permitted under the 
statute to determine future year modeled PM2.5 
concentrations in the sixth year after designations. Thus, in the 
attainment demonstrations for areas designated nonattainment in the 
first round of designations for the 2012 PM2.5 NAAQS, it 
would be appropriate for states to model air quality for 2021.
    Because an area must attain ``as expeditiously as practicable'' 
according to the CAA, additional considerations are necessary before an 
attainment date can be established for a Moderate PM2.5 
nonattainment area. For purposes of determining the attainment date 
that is as expeditious as practicable, the state must conduct future 
year modeling which takes into account expected growth and known 
controls. For example, for a Moderate nonattainment area for the 2012 
PM2.5 NAAQS, a future base case scenario for the year 2021 
(6 years after designations) would project future air quality given 
implementation of existing federal, state and local measures. If this 
base case scenario demonstrates attainment, then the state must 
demonstrate whether attainment could be achieved in an earlier year. 
Therefore, the state needs to conduct an analysis to determine if, 
collectively, all technologically and economically feasible measures 
identified by the state for which the state can initiate implementation 
by the beginning of the sixth calendar year following designations, can 
advance the attainment date by at least 1 year. Results of this 
analysis may indicate attainment can be achieved earlier, through 
implementation of all reasonable control measures (i.e., RACM and RACT 
and additional reasonable measures).
    If the future base case scenario does not demonstrate attainment, 
then a control case scenario is needed to examine whether the 
implementation of all technnologically and economically feasible 
measures identified by the state would result in attainment in 2021 
(for purposes of this example based on the 2012 PM2.5 
NAAQS). The control case scenario would add to the model potential 
control measures (i.e., RACM and RACT and additional reasonable 
measures, plus any additional intrastate transport measures or other 
measures on sources outside of the nonattainment area that the state 
has identified as feasible to implement by the attainment date). This 
modeling, along with other relevant information, would inform a 
judgment as to whether attainment of the relevant NAAQS is practicable 
by the end of the sixth year after designation or earlier. In the case 
of areas designated nonattainment for the 2012 PM2.5 NAAQS 
in the first round of designations, if the analysis does not 
demonstrate attainment by December 31, 2021, then the analysis could 
serve as the technical basis for the state to submit a demonstration 
that attainment by the latest statutory attainment date for Moderate 
areas is impracticable. This demonstration in turn could serve as the 
technical basis for the Administrator to reclassify the area to 
Serious.\125\
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    \125\ A demonstration that the area cannot practicably attain by 
the Moderate area attainment date would not be the only trigger for 
a discretionary reclassification to Serious. The Administrator 
maintains wide discretion in making such a determination, with an 
impracticability demonstration serving as one potential source of 
analysis to inform such a determination.
---------------------------------------------------------------------------

    The EPA believes that it is not reasonable to require states to 
model each and every calendar year to determine the appropriate 
attainment date for a nonattainment area. Developing and modeling 
future year inventories is a time-consuming and resource intensive 
process. Multiple emissions models are needed in order to generate 
year-specific emissions for the various emissions sectors (e.g. mobile, 
non-road, non-EGU point and EGU point). In some cases it may be 
reasonable to model one additional interim year before the maximum 
statutory attainment date.\126\ However, in most cases, the air quality 
benefits of an identified set of RACM and RACT and additional 
reasonable measures can be estimated through model sensitivity analyses 
and the development of transfer factors (factors to relate tons of 
emissions reductions in the area to PM2.5 concentration 
changes in the area). For example, states can model across-the-board 
percentage reductions in direct PM2.5 and/or precursor 
emissions (in separate model runs) to determine the impact of emissions 
reductions on PM2.5 concentrations in the area. This 
modeling can be performed with a single attainment year modeling 
platform, which is much less resource intensive than modeling 
additional future years. The identified potential emissions reductions 
available from RACM and RACT and additional reasonable measures can be 
compared to the magnitude of the modeled PM2.5 reductions 
from the sensitivity analyses to determine if all such controls will 
advance attainment by a year. The EPA strongly recommends that states 
discuss the selection of the future year(s) to model with their 
respective EPA Regional Office as part of the modeling protocol 
development process and before embarking on running the model(s).
---------------------------------------------------------------------------

    \126\ If several future modeling years are available, in some 
cases it may be appropriate for states to interpolate 
PM2.5 concentrations between years.
---------------------------------------------------------------------------

9. Modeling Analysis of Controls That Have a De Minimis Impact on 
Ambient PM2.5 Concentrations
    In Section IV.D of this preamble, the EPA is proposing that if a 
state determines that a Moderate nonattainment area can attain the 
PM2.5

[[Page 15385]]

NAAQS by the statutory attainment date, the state must adopt and 
implement as reasonable control measures (i.e., as RACM and RACT and 
additional reasonable measures) only those technologically and 
economically feasible control measures that are necessary to ensure 
that the area will attain the NAAQS as expeditiously as practicable. In 
a Moderate PM2.5 nonattainment area that cannot practicably 
attain the relevant NAAQS by the statutory attainment date, the EPA 
similarly believes that it may not be reasonable in all cases to 
require that a state implement all technologically and economically 
feasible control measures. The EPA is thus proposing an option under 
which the state may evaluate the air quality impact of technologically 
and economically feasible control measures to determine if there is a 
subset of such measures that collectively will only achieve negligible 
reductions in ambient PM2.5 concentrations in the area. 
Similar to the EPA's proposed approach, described earlier in this 
section, to determine if a set of technologically and economically 
feasible control measures can collectively advance the attainment date 
by a year for a Moderate nonattainment area for which a state can 
demonstrate attainment by the statutory attainment date, the state 
would be required under this proposed option (for a Moderate area that 
cannot practicably attain the NAAQS by the statutory attainment date) 
to use an air quality model to determine the impact on ambient 
PM2.5 levels of the set of otherwise ``reasonable'' controls 
that it believes will not collectively reduce ambient PM2.5 
concentrations in the area. For this analysis, the state would have to 
show that the collective set of controls will have little to no effect 
on reducing PM2.5 concentrations in the area.
10. Attainment Year Motor Vehicle Emissions Budgets
    The transportation conformity rule requires that attainment plans 
establish motor vehicle emissions budgets for the area's attainment 
year. Therefore, once an area's attainment date has been established, 
the state would establish motor vehicle emissions budgets for direct 
PM2.5 and any relevant PM2.5 precursor for the 
attainment year.\127\ A motor vehicle emissions budget for the purposes 
of a PM2.5 attainment plan is that portion of the total 
allowable emissions within the nonattainment area allocated to on-road 
sources as defined in the submitted attainment plan.\128\ Such motor 
vehicle emissions budgets would be calculated using the latest planning 
assumptions and the latest approved motor vehicle emissions model 
available at the time that the attainment plan is developed.\129\
---------------------------------------------------------------------------

    \127\ For more information on PM2.5 precursor 
requirements, see section 93.102(b)(2)(iv) and (v) of the 
transportation conformity rule. See also the May 6, 2005, final 
transportation conformity rule that addressed requirements for 
PM2.5 precursors. (70 FR 24280).
    \128\ A state would also establish motor vehicle emissions 
budgets for an area's attainment year. Those budgets would be the 
motor vehicle emissions that the SIP establishes as being necessary 
to attain the NAAQS.
    \129\ If an area includes re-entrained road dust in the motor 
vehicle emissions budget, the latest approved version of AP-42 
should be used unless the EPA has approved an alternative model for 
the area.
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F. RFP Requirements

1. Statutory Requirements and Existing Guidance
    ``Reasonable further progress'' (RFP) is a concept included in the 
CAA under part D, title I to assure that states make steady, 
incremental progress toward attaining air quality standards in the 
years prior to the attainment date for a nonattainment area, rather 
than merely deferring implementation of control measures and therefore 
emissions reductions until the date by which the standards are to be 
attained. As discussed elsewhere in this preamble, section 172 of the 
CAA addresses nonattainment plan provisions in general. Section 
172(c)(2) requires attainment plans to provide for RFP, which is 
defined in section 171(l) as ``such annual incremental reductions in 
emissions of the relevant air pollutant as are required by [part D of 
title I] or may reasonably be required by the Administrator for the 
purpose of ensuring attainment of the applicable national ambient air 
quality standard by the applicable date.'' Section 172(c)(3) requires 
the state plan to include ``a comprehensive, accurate, current 
inventory of actual emissions from all sources of the relevant 
pollutant or pollutants in such area . . .'' Section 172(c)(1) requires 
the state plan to include ``all reasonably available control measures 
as expeditiously as practicable (including such reductions in emissions 
from existing sources in the area as may be obtained through the 
adoption, at a minimum, of reasonably available control technology) . . 
.''
    In general terms, the EPA interprets that the purpose of requiring 
RFP is to ensure that states with nonattainment areas develop 
attainment plans that achieve generally linear progress toward 
attainment, rather than deferring emissions reductions until the 
applicable attainment date for the area. In the context of implementing 
the PM2.5 NAAQS, ``generally linear progress'' means that 
emissions of direct PM2.5 and PM2.5 precursors 
from controlled sources generally decrease year by year such that the 
area ultimately attains the relevant NAAQS by the applicable attainment 
date. In the Addendum, the EPA provided guidance and identified four 
specific situations in which ``linear progress'' in emissions 
reductions to meet RFP may be appropriate:
    1. When pollutants are emitted by numerous and diverse sources.
    2. Where the relationship between any individual source and the 
overall air quality is not explicitly quantified.
    3. Where a chemical transformation is involved.
    4. Where the emission reductions necessary to attain the standard 
are inventory-wide.\130\
---------------------------------------------------------------------------

    \130\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42015.
---------------------------------------------------------------------------

    For example, a state with an area whose nonattainment problem is 
caused primarily by area sources, such as residential wood combustion, 
should be able to demonstrate generally linear progress toward 
attainment in that area. In such an area, the state might be able to 
require the replacement of a specified percentage of the residential 
woodstoves on an annual basis for each year to assure RFP on an annual 
basis.
    The EPA's guidance in the Addendum also provided examples of 
situations in nonattainment areas in which it might be less appropriate 
to expect RFP to be linear, including:
    1. Where there are a limited number of sources.
    2. Where the relationships between individual sources and air 
quality are relatively well defined.
    3. Where the emission control systems utilized (e.g., at major 
point sources) will result in swift and dramatic emission 
reductions.\131\
---------------------------------------------------------------------------

    \131\ Ibid.
---------------------------------------------------------------------------

    In nonattainment areas characterized by any of these circumstances, 
the EPA understands that RFP may be better represented as step-wise 
progress as controls are implemented and achieve significant reductions 
soon thereafter. For example, if an area's nonattainment problem can be 
attributed to a few major stationary sources, the EPA's guidance 
indicates that ``RFP should be met by `adherence to an ambitious 
compliance schedule' which is likely to periodically yield significant 
emission reductions.'' 132 133 While the EPA noted

[[Page 15386]]

in the Addendum that adherence to such a schedule does not necessarily 
mean it would be unreasonable to achieve generally linear progress, the 
agency has long interpreted the language of section 171(1) not to 
require some specific level of emissions reductions in any given year. 
Unlike certain provisions under subpart 2 governing ozone NAAQS 
implementation, subpart 4 does not specify a set percentage of 
emissions reductions to be achieved over a certain period of time. 
Accordingly, the EPA believes that the facts and circumstances of each 
specific area will be relevant to whether the emissions reductions meet 
the agency's expectations for ``generally linear progress.''
---------------------------------------------------------------------------

    \132\ USEPA, Office of Air Quality Planning and Standards, 
``Guidance Document for Correction of Part D SIP's for Nonattainment 
Areas,'' Research Triangle Park, NC, January 24, 1984, page 25.
    \133\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42015.
---------------------------------------------------------------------------

    With respect to implementation schedules, the EPA recommended in 
the Addendum that to meet the statutory RFP requirements, attainment 
plans must include ``detailed schedules for compliance with emission 
regulations in the [nonattainment] areas and accurately indicate the 
corresponding annual emission reductions to be realized from each 
milestone in the schedule. In reviewing the SIP, the EPA will determine 
whether the annual incremental emission reductions to be achieved are 
reasonable in light of the statutory objective to ensure timely 
attainment of the PM10 NAAQS. Additionally, the EPA believes 
that it is appropriate to require early implementation of the most 
cost-effective control measures . . . while phasing in the more 
expensive control measures.'' \134\
---------------------------------------------------------------------------

    \134\ Ibid. at 42016.
---------------------------------------------------------------------------

    The EPA believes that these prior interpretations of the Act's 
provisions for RFP continue to be appropriate for the PM2.5 
NAAQS. Accordingly, the following section describes the EPA's proposal 
for requirements to ensure that states meet the statutory provisions 
for RFP for Moderate PM2.5 nonattainment areas.
2. General Proposed Approach to RFP
    To satisfy the statutory requirements for RFP at section 172(c)(2), 
the EPA proposes that a state must submit an RFP plan as part of its 
Moderate area attainment plan submission. The RFP plan must contain 
appropriate information to demonstrate that adequate emissions 
reductions will be achieved through control measures in the attainment 
plan in order to meet the statutory definition of RFP. The plan must 
include an implementation schedule for control measures on sources in 
the nonattainment area and an analysis that demonstrates when--and 
through what control measures--emissions will decline from the 
applicable baseline year to the attainment year. As part of the 
analysis, the RFP plan must include a projected inventory for sources 
in the area for one (or more) interim year(s). The EPA is proposing and 
seeking comment on two options for developing an RFP plan, as well as 
on related requirements, as described below. See proposed 40 CFR 
51.1012. The EPA also notes that quantitative milestones required under 
section 189(c) are directly linked to the RFP plan, as interim 
quantifiable indicators intended to demonstrate that an area is making 
progress toward attaining the PM2.5 NAAQS, and are therefore 
related to the implementation schedule of control measures for a 
PM2.5 nonattainment area. Quantitative milestones are more 
fully discussed in Section IV.G of this preamble.
    a. Proposed Option 1. Under the first option, the EPA proposes that 
the RFP analysis for any Moderate PM2.5 nonattainment area 
that can demonstrate attainment by the statutory attainment date must 
demonstrate either: (i) Generally linear progress toward attainment by 
the applicable attainment date through emissions reductions to be 
achieved annually between a baseline year and the projected attainment 
date for the area; or, (ii) step-wise progress toward attainment by the 
applicable attainment date that will be achieved through adherence to 
an ambitious compliance schedule that would not necessarily achieve 
reductions on an annual basis. In the second case, the state would be 
required to submit a clear rationale and supporting information to 
explain why generally linear progress during the attainment period is 
not reasonable on an annual basis (e.g., due to the nature of the 
nonattainment problem and the types of sources contributing to 
PM2.5 levels in the area as discussed in Section IV.F.1 of 
this preamble). The EPA also proposes to require that RFP analyses need 
to show progress in achieving emissions reductions only for direct 
PM2.5 and any precursors that are controlled in the 
attainment plan for the nonattainment area.
    Note that the two approaches presented in Option 1 for 
demonstrating RFP within the nonattainment area are consistent with the 
pattern of emissions reductions of many nationally-applicable federal 
emissions reduction measures. For example, new emission standards for 
mobile sources may achieve reductions in a generally linear manner over 
time, as a portion of the existing vehicle fleet is replaced each year 
with new vehicles meeting the more stringent standards. On the other 
hand, regulations to reduce emissions from certain stationary source 
sectors often have a single compliance date by which controls must be 
in place, which typically result in a significant drop in emissions 
over a relatively short period (i.e., yield step-wise reductions).
    Because the statute does not clearly establish the applicable 
baseline year from which to begin calculating annual emissions 
reductions for purposes of demonstrating RFP, the EPA is proposing to 
require and seeks comment on a requirement that states use the same 
year as the base year inventory chosen for the area, as this inventory 
will serve as the basis for developing the control strategy necessary 
to bring the area into expeditious attainment. Furthermore, in 
developing their RFP analyses for specific nonattainment areas, the EPA 
expects that states will use the emissions inventories developed for 
those areas and air quality modeling they have completed for attainment 
planning purposes. This approach is consistent with the EPA's proposed 
approach, described later in this section, not to interpret the CAA as 
allowing states to take credit for emissions reductions from sources 
outside a nonattainment area when developing their plan to meet the 
statutory RFP requirements for PM2.5 nonattainment areas.
    For states with Moderate areas that cannot demonstrate attainment 
by the statutory Moderate area attainment date, the statutory RFP 
requirements still apply. However, the EPA proposes to require that, 
for such areas, the state must provide an analysis of the anticipated 
emissions reductions associated with implementing the control measures 
identified as RACM and RACT and additional reasonable measures for the 
area. The EPA notes that even if a state adequately demonstrates that 
it cannot attain the NAAQS in a given area by the statutory attainment 
date, the CAA still requires the state to submit a Moderate area 
attainment plan meeting the requirements for such attainment plans, 
including for RFP. An additional RFP analysis will be required as part 
of the Serious attainment plan for the area once the EPA reclassifies 
it to Serious.
    Similar to the approach taken for RFP in the remanded 2007 
PM2.5 Implementation Rule, the EPA is proposing under this 
option that all states must follow one primary

[[Page 15387]]

approach for conducting the RFP analysis, but that they also have an 
option to conduct a secondary analysis that will provide greater 
flexibility in setting RFP goals with alternative emissions reductions 
and air quality improvement scenarios. The primary approach would be to 
benchmark emissions reductions on a pollutant-by-pollutant basis 
starting from the pollutant's baseline emissions level. The state would 
then be required to calculate reductions in emissions of each pollutant 
on an annual basis that would be needed to bring the area into 
attainment by the projected attainment date.
    The EPA recognizes that different control measures address 
different pollutants, and that states may be able to implement some 
measures more quickly than others. Thus, in the optional secondary 
analysis, the state could present a different combination of emissions 
reductions at similar time intervals that would provide an equivalent 
or better result in terms of net air quality improvement. This 
``equivalency determination'' would allow states flexibility to address 
different pollutants (i.e., direct PM2.5 and 
PM2.5 precursors regulated under the control strategy for 
the area) according to different schedules so long as the EPA finds the 
projected net air quality improvements to be achieved through this 
alternative combination of emissions reductions to be equivalent to or 
better than those that would be achieved through generally linear 
emissions reductions across all pollutants in the area. This proposed 
approach recognizes that an important element of establishing 
appropriate emissions reductions targets for meeting RFP requirements 
for PM2.5 is quantifying the relative degrees of control of 
various pollutants.
    As discussed above, the primary approach for ensuring that RFP is 
met in a PM2.5 nonattainment area is to require that the 
state reduce each pollutant--that is, direct PM2.5 and all 
precursors not otherwise eliminated from control requirements--by some 
amount on an annual basis. The EPA's primary proposed RFP analysis, an 
emissions benchmark analysis, would reflect generally linear progress 
(or step-wise progress if more appropriate and adequately justified) to 
reduce those pollutants that the state intends to control to attain the 
PM2.5 NAAQS by the applicable attainment date. See proposed 
40 CFR 51.1012(b). For example, a state that can demonstrate that their 
Moderate nonattainment area can attain the 2012 PM2.5 NAAQS 
by an attainment date of December 31, 2021 would also need to achieve 
emissions levels that represent attainment in 2021. If the attainment 
plan requires a 10 percent reduction in NOX emissions and a 
14 percent reduction in PM2.5 direct emissions from 2011 
levels in order for the area to demonstrate attainment in 2021, then 
the RFP benchmark for NOX would reflect roughly a 1 percent 
reduction in NOX emissions per year, and the benchmark level 
for PM2.5 would be roughly a 1.4 percent reduction per year.
    The EPA proposes that states must provide an implementation 
schedule for control measures that would achieve emissions reductions 
consistent with those calculated as part of the RFP benchmark analysis. 
However, a state could choose to submit an ``equivalency'' analysis in 
addition to the RFP benchmark analysis and associated implementation 
schedule that presents an alternative combination of pollutant emission 
reductions (i.e., alternative implementation schedule for control 
measures) that achieves air quality improvements that are equivalent to 
or better than the RFP benchmark analysis. In such a case, the state 
would need to make an adequate showing that the alternative schedule 
for implementing control measures will provide estimated air quality 
improvements that are roughly the same as, if not better than, those 
that the emissions reductions determined through the RFP benchmark 
analysis would provide. If a state elects to follow this approach, it 
must provide in its RFP plan the information necessary to assess 
whether an alternative schedule of emissions reductions is generally 
equivalent, in air quality terms, to the RFP benchmark analysis 
reduction levels, such as attainment demonstration modeling results 
that link emissions reductions of various precursor emissions with air 
quality improvements. Under this proposed approach, the EPA would 
require states to use this information to evaluate the equivalence of 
alternative combinations of pollutant emissions reductions. The EPA 
would recommend that states estimate air quality improvements 
associated with intermediate emissions control levels (i.e., air 
quality improvement targets) by assuming that the same relationship 
between emissions and air quality applies at intermediate levels as 
would apply at attainment levels.
    The EPA continues to recognize that because atmospheric processes 
are quite complex, a specific percent change in emissions of 
PM2.5 precursors does not lead to an equivalent percent 
change in air quality, potentially creating uncertainty as to whether 
alternate emissions control scenarios will achieve equivalent benefits. 
Nevertheless, the EPA believes that it is important to provide the 
flexibility to address different pollutants on different timetables so 
long as the plan can reasonably be expected to achieve the intended air 
quality benefits represented by the RFP benchmark analysis. In general, 
the EPA would not expect a state to conduct dispersion modeling 
specifically to assess whether an alternative approach to meeting RFP 
will provide equivalent air quality benefits as the benchmark approach. 
Instead, the attainment plan modeling addresses the nonlinearities at 
attainment levels, and the EPA believes for RFP analysis purposes that 
the relationship between emissions and air quality at attainment levels 
provides an adequate approximation of the relationship at interim RFP 
levels.
    b. Proposed Option 2. Under the second option, the EPA proposes a 
simplified approach to developing an RFP plan that focuses on the 
emissions reductions anticipated from each of the particular control 
measures identified by the state as part of the analysis to identify 
RACM and RACT and additional reasonable measures for sources in the 
nonattainment area. Under this option, the first step in developing the 
RFP plan would be for the state to establish the implementation 
schedule on a year-by-year basis for all control measures contained in 
the control strategy for sources in the area beginning with the date of 
designation of the area and ending with the projected attainment date 
of the area. The schedule would need to comply with the statutory 
requirement that all RACM and RACT must be implemented within the first 
4 years following designation, but the state would have discretion 
beyond that requirement to schedule the implementation of any other 
measures necessary for expeditious attainment. Overall, the 
implementation schedule would need to demonstrate that control measures 
to bring the area into attainment will be implemented as expeditiously 
as practicable.
    The second step in developing an RFP plan under this second 
proposed option would be for the state to calculate the emissions 
reductions that would be achieved by all measures implemented on 
sources in the area corresponding with quantitative milestone dates 
(i.e., by 4.5 years and 7.5 years after designation of the area). These 
are the dates by which milestones for the area must be met, after which 
a report is due to the EPA from the state to verify that

[[Page 15388]]

the area has met the milestones identified for the area and thereby has 
also met the RFP requirements for the area. The EPA proposes that the 
state must calculate the emissions reductions to be achieved at each 
milestone year on a pollutant-by-pollutant basis.
    The third step under this proposed option would be for the state to 
conduct modeling or employ another quantitative method to predict the 
overall PM2.5 concentrations in the nonattainment area in 
each milestone year. This air quality target could simply be 
interpolated between the design value at the time of the area's 
designation and the design value in the projected attainment year. 
These air quality target values would serve as a points of comparison 
for the monitored ambient air data that the EPA is proposing that the 
state must submit as part of the milestone report due after the area 
reaches each milestone date.
    This simplified approach to determining RFP for a Moderate 
nonattainment area could apply equally well to areas that can 
demonstrate attainment with the relevant NAAQS by the statutory 
attainment date and those that cannot. See proposed 40 CFR 51.1012(c). 
In addition, the EPA believes it offers a reasonable approach to ensure 
that RFP is generally being met in the area without requiring extensive 
quantitative analysis so long as it is generally linear for purposes of 
achieving annual emissions reductions. The EPA seeks comment on these 
two options proposed for states to meet the statutory RFP requirements.
3. RFP Inventories for RFP Analyses
    The EPA proposes that a state with a Moderate PM2.5 
nonattainment area must submit one or more emissions projections as 
part of the RFP plan (the ``RFP inventory'') for the area that, at a 
minimum, includes projected emissions by different source types 
corresponding to the quantitative milestone date(s) for the area, 
described in greater detail in Section IV.H of this preamble. 
Specifically, the EPA proposes that the RFP plan for any Moderate area 
must contain a projected RFP inventory for each calendar year in which 
quantitative milestones for a Moderate nonattainment area must be met. 
For example, as explained in Section IV.H of this preamble, a state 
must identify as part of the attainment plan submission for a Moderate 
nonattainment area quantitative milestones to be achieved every 3 years 
from the Moderate area attainment plan due date, or 4.5 years from the 
effective date of designation of the area.\135\ For example, the first 
round of designations for the 2012 PM2.5 NAAQS become 
effective in April 2015; Moderate area attainment plans for these areas 
will thus be due 18 months later, or in October 2016. The first 
quantitative milestones for each of these areas would then have to be 
met in October 2019; the second quantitative milestones, in October 
2022; and so on, until the area attains the NAAQS. Under the EPA's 
proposed approach for projected emissions inventories for RFP analyses, 
the state would be required to submit such inventories as part of the 
Moderate area attainment plan due in October 2016 that project 
emissions from sources in the nonattainment area for the same calendar 
years as those for which quantitative milestones would be due.
---------------------------------------------------------------------------

    \135\ According to section 189(a)(2)(B), Moderate area 
attainment plans are due to the EPA 18 months after designation.
---------------------------------------------------------------------------

    The transportation conformity rule requires that attainment plans 
establish motor vehicle emissions budgets. RFP plans submitted as part 
of an attainment plan submission would therefore be required to 
establish motor vehicle emissions budgets for direct PM2.5 
and any relevant PM2.5 precursor.\136\ A motor vehicle 
emissions budget for the purposes of a PM2.5 RFP plan is 
that portion of the total allowable emissions allocated to on-road 
sources as defined in the submitted RFP plan for the relevant years as 
described above.\137\ Such motor vehicle emissions budgets would be 
calculated using the latest planning assumptions and the latest 
approved motor vehicle emissions model available at the time that the 
attainment plan is developed.\138\
---------------------------------------------------------------------------

    \136\ For more information on PM2.5 precursor 
requirements, see section 93.102(b)(2)(iv) and (v) of the 
transportation conformity rule. See also the May 6, 2005, final 
transportation conformity rule that addressed requirements for 
PM2.5 precursors. (70 FR 24280).
    \137\ A state would also establish motor vehicle emissions 
budgets for an area's attainment year. Those budgets would be the 
motor vehicle emissions that the SIP establishes as being necessary 
to attain the NAAQS.
    \138\ If an area includes re-entrained road dust in the motor 
vehicle emissions budget, the latest approved version of AP-42 
should be used unless the EPA has approved an alternative model for 
the area.
---------------------------------------------------------------------------

4. Geographic Coverage of Emission Sources for RFP
    The EPA is proposing that the RFP demonstration to be included with 
a state's PM2.5 nonattainment area plan must include 
emissions only for sources located in the nonattainment area, and not 
from an area larger than the nonattainment area. This policy approach 
differs from the remanded 2007 PM2.5 implementation rule. 
This section describes the evolution of policy on a similar RFP issue 
in the ozone NAAQS implementation program, and it discusses the 
reasoning behind this revised approach for PM2.5.
    In the preamble to the remanded 2007 PM2.5 
Implementation Rule, the EPA allowed states to incorporate reductions 
of NOX and SO2 emissions up to 200 km from 
outside the nonattainment area (and potentially for reductions of VOC 
or ammonia) into their RFP plan when certain conditions were met. This 
policy was included in the 2007 PM2.5 Implementation Rule in 
part to be consistent with a similar RFP policy for NOX and 
VOC that was included in the November 2005 Phase 2 ozone NAAQS 
implementation rule which provided guidance for states on implementing 
the 1997 ozone NAAQS.\139\
---------------------------------------------------------------------------

    \139\ See Phase 2 Ozone Implementation rule, 70 FR 71612 
(November 29, 2005).
---------------------------------------------------------------------------

    Under the policy in the 2007 PM2.5 NAAQS implementation 
rule, if a state intended to include emissions reductions from outside 
the nonattainment area in the RFP plan, the state would need to take on 
the additional work associated with developing: (i) An expanded 
baseline emissions inventory for the entire geographic area (i.e., the 
nonattainment area plus the additional area outside the nonattainment 
area) that characterizes emissions for all stationary, area and mobile 
sources (rather than for just a select few stationary sources) in the 
overall area; and, (ii) a projected attainment year inventory for this 
expanded area outside the boundaries of the designated nonattainment 
area. By requiring inclusion of all types of sources in these 
``expanded area'' emissions inventories, the EPA intended for this 
approach to reflect the projected net emissions reductions in this area 
(the difference between the ``expanded area'' base year inventory and 
the projected attainment year inventory). However, it should be noted 
that development of these more extensive inventories would likely have 
involved a substantial amount of additional time and resources. In 
addition, the state would have needed to have provided information 
supporting its decision regarding how far outside the nonattainment 
area the RFP inventory should extend. While this ``outside the 
nonattainment area'' RFP approach was theoretically available to states 
in developing their PM2.5 attainment plans due in 2008, 
there were no states to the agency's knowledge that elected to follow 
this approach.

[[Page 15389]]

    Both the 2005 Phase 2 ozone implementation rule and the 2007 
PM2.5 Implementation Rule were challenged on several issues. 
With regard to the Phase 2 ozone implementation rule, the EPA granted a 
petition for reconsideration and ultimately issued a final notice of 
reconsideration in June 2007. In November 2008, the U.S. Court of 
Appeals for the DC Circuit heard oral argument concerning multiple 
petitions for judicial review of the Phase 2 ozone rule and the notice 
of reconsideration. One of the issues in this case involved whether 
compliance by EGUs with a regional emissions trading program could be 
considered to meet the RACT requirement for those sources located in a 
nonattainment area. In its July 2009 decision, the court emphasized 
that: ``the RACT requirement calls for reductions in emissions from 
sources in the area; reductions from sources outside the nonattainment 
area do not satisfy the requirement . . . Accordingly, participation in 
the NOX SIP call would constitute RACT only if participation 
entailed at least RACT-level reductions in emissions from sources 
within the nonattainment area.''
    In light of this court decision, the EPA has determined that the 
best reading of the statute would be to interpret the term ``sources in 
the area'' in the same manner where it appears in different 
nonattainment provisions for ozone. The term appears in CAA section 182 
(requirements for ozone nonattainment areas) with regard to RFP as well 
as RACT. The decision on the Phase 2 ozone rule found that section 
182(b)(2) requires that a SIP must provide for implementation of RACT 
(under section 172(c)) for emissions sources ``in the area,'' meaning 
in the nonattainment area. Similarly, the EPA believes that when 
section 182(b)(1)(A)-(B) defines baseline emissions for RFP as ``the 
total amount of actual VOC or NOX emissions from all 
anthropogenic sources in the area,'' this also means sources in the 
nonattainment area.
    With regard to the 2007 PM2.5 Implementation Rule, the 
EPA received a petition for reconsideration in June 2007 that raised 
objections on several issues. One such issue dealt with the EPA's 
interpretation of the statutory RFP requirements to allow a state to 
take ``credit'' for emissions reductions from outside the nonattainment 
area when addressing RFP in its attainment plan.\140\ The EPA granted 
the petition for reconsideration on this issue in 2010, after the D.C. 
Circuit issued its decision on the Phase 2 Ozone Implementation 
Rule.141 142
---------------------------------------------------------------------------

    \140\ This same petition raised concerns regarding the criteria 
used to determine the economic feasibility of controls being 
considered for RACT for the 1997 PM2.5 NAAQS. See 
``Petition for Reconsideration,'' filed by Paul Cort, Earthjustice, 
on behalf of the American Lung Association, Medical Advocates for 
Healthy Air, Natural Resources Defense Council, and the Sierra Club 
(June 25, 2007). A copy of the petition is in the docket for this 
action.
    \141\ Letter dated May 13, 2010, from Gina McCarthy to David S. 
Baron and Paul Cort, Earthjustice. A copy of the letter is located 
in the docket for this action.
    \142\ See NRDC v. EPA, 571 F.3d 1245 (D.C. Cir. 2009).
---------------------------------------------------------------------------

    Specifically, the EPA believes that the DC Circuit's interpretation 
of the phrase ``sources in the area'' applies to RACT and RFP 
requirements for both the ozone NAAQS and the PM2.5 NAAQS. 
In particular, for PM2.5, the statutory language at section 
171(1) defines RFP in terms of ``reductions in emissions'' required in 
an attainment plan, which the EPA interprets as being directly linked 
to the baseline emissions inventory for sources located in a 
PM2.5 nonattainment area. The baseline emissions inventory 
is the foundation for the attainment plan. The emissions inventory 
requirement of section 172(c)(3) explicitly requires that the 
attainment plan inventory include all sources of the relevant 
pollutants ``in such area,'' which is a clear reference to the 
designated nonattainment area. Given that the baseline inventory must 
reflect the emissions ``in such area,'' and that this inventory 
provides the starting point for a state's RFP analysis, in which the 
state must calculate generally linear progress in emissions reductions 
that will lead to attainment of the NAAQS in the area, the EPA believes 
it is appropriate that a state should focus on sources located within 
the nonattainment area when conducting its analysis to determine the 
annual emissions reductions necessary for demonstrating RFP.
    The EPA believes that the most appropriate approach with regard to 
the geographic area required to be covered for demonstrating RFP in a 
PM2.5 attainment plan also should be limited to the 
nonattainment area for two other reasons. First, EPA believes that it 
makes policy sense for the PM2.5 implementation rule 
approach to be consistent with the approach in the ozone implementation 
rule. In the past, a number of areas have been designated as 
nonattainment for both standards, and the nonattainment area boundaries 
often are the same. For such areas, a common policy approach for the 
geographic area covered by the RFP plan will be more efficient to 
implement and would be expected to be less burdensome for the air 
agency than if the geographic areas covered by RFP plans for the two 
pollutants differed.
    Second, a policy allowing the geographic area of the RFP plan to be 
larger than the nonattainment area would conflict with a key provision 
of subpart 4 which requires annual incremental reductions in emissions 
from sources within the nonattainment area. Under subpart 4, an area 
that fails to attain the standard by the Serious area attainment date 
is then subject to the provisions of section 189(d). Section 189(d) 
specifies that the state must submit a plan revision within 12 months 
which provides for ``an annual reduction in PM10 or 
PM10 precursor emissions within the area of not less than 5 
percent of the amount of such emissions as reported in the most recent 
inventory prepared for such area'' (emphasis added). The EPA does not 
believe the rule should include an RFP policy approach which would not 
be consistent with section 189(d).
    After reconsideration of the approach to RFP that was opposed in 
the petition for reconsideration of the 2007 PM2.5 
Implementation Rule, and in light of the DC Circuit decision on the 
Ozone Phase 2 Implementation Rule, the EPA believes the best reading of 
the statute is that the CAA does not allow for a state to include 
emissions reductions from sources outside a nonattainment area when 
developing the plan to meet the CAA section 172(c)(2) RFP requirements 
for a PM2.5 nonattainment area. The EPA seeks comment on 
this proposed approach.
5. Other RFP Considerations
    In general, the EPA seeks to ensure that PM2.5 
nonattainment areas that are shared by more than one state or tribe 
meet RFP requirements as a whole. States and tribes that share a 
nonattainment area should therefore consult with one another to develop 
the RFP analysis and control strategy implementation schedule for the 
area as a whole. Such states and tribes should work with the EPA region 
or regions that oversee them to confirm that their collective approach 
is appropriate for RFP.
    The EPA's proposed approach for states to meet the RFP requirement 
is designed to ensure emissions reductions will yield incremental 
improvements in air quality on the path to attainment, while being 
sufficiently flexible to accommodate the range of control strategies 
necessary to address the complex mixtures of pollutants comprising 
PM2.5 in different areas. The EPA seeks comment on all of 
its proposed requirements and options for

[[Page 15390]]

RFP plans and analyses for Moderate PM2.5 attainment plans.

G. Quantitative Milestones

1. Statutory Requirements and Existing Guidance
    Section 189(c)(1) requires that a PM10 NAAQS attainment 
plan submission has ``quantitative milestones which are to be achieved 
every 3 years until the area is redesignated to attainment and which 
demonstrate reasonable further progress . . . toward attainment by the 
applicable date.'' Section 189(c)(2) further requires that, within 90 
days of each milestone, each affected state must submit a demonstration 
that all measures to assure RFP have been implemented and that the 
quantitative milestone has been met. Thus, the CAA imposes requirements 
upon states not only to make ``reasonable further progress'' toward 
attainment, but also to identify objective means (i.e., quantitative 
milestones) by which to measure this reasonable further progress every 
3 years, and to submit them as part of the attainment plan for the 
nonattainment area. In addition, according to section 189(c)(2), states 
must, within 90 days of the passage of each such milestone, submit to 
the EPA a demonstration that control measures have been implemented 
according to the approved RFP plan schedule and the milestone has been 
met.
    The EPA has previously described its interpretation of the 
requirements under section 189(c) for the PM10 NAAQS in the 
General Preamble and the Addendum and believes that these 
interpretations should also apply both in developing plans that 
demonstrate RFP and include appropriate quantitative milestones, and in 
demonstrating that those milestones have been met for the 
PM2.5 NAAQS.143 144 The EPA's guidance in the 
Addendum also noted that: ``Section 189(c) provides that the 
quantitative milestones submitted by a State for an area also must be 
consistent with RFP for the area. Thus, EPA will determine an area's 
compliance with RFP in conjunction with determining its compliance with 
the quantitative milestone requirement. Because RFP is an annual 
emission reduction requirement and the quantitative milestones are to 
be achieved every 3 years, when a state demonstrates an area's 
compliance with the quantitative milestone requirement, it should also 
demonstrate that RFP has been achieved during each of the relevant 3 
years.'' \145\
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    \143\ See the Federal Register published on April 16, 1992, 
General Preamble (57 FR 13498 and 13539).
    \144\ See the Federal Register published on August 16, 1994, 
Addendum to General Preamble (59 FR 41998, 42015, 42016 and 42017).
    \145\ Ibid.
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    The EPA's existing guidance in the Addendum with respect to the 
quantitative milestone requirements of CAA section 189(c) thus includes 
several important features: (i) That the control measures comprising 
the RFP plan should be implemented and in place to meet the statutory 
quantitative emissions reductions milestone requirement; (ii) that it 
is reasonable for the 3-year periods for quantitative milestones to run 
from the statutory due date for the Moderate area attainment plan 
submission; and, (iii) that the precise form that the quantitative 
milestones should take is not specified, but the state must choose 
milestones that will allow it to quantify or measure, track and report 
progress adequately and objectively.
    The EPA's proposed approach to identifying quantitative milestones 
for any Moderate PM2.5 nonattainment area and demonstrating 
compliance with the milestones is generally consistent with the 
existing guidance, as described in the following sections.
2. Proposed Approach
    The statute at section 189(c) is clear that quantitative milestones 
must be achieved every 3 years, however it does not make clear the 
starting date for counting the 3 year periods. In the General Preamble, 
the agency proposed that quantitative milestones must be achieved every 
3 years starting from the attainment plan submission due date (i.e., 
because the Moderate area attainment plan is due no later than 18 
months after designation of the area, the first set of milestones would 
need to be achieved 4.5 years after the area's designation) until the 
attainment date.\146\ The EPA proposes to maintain this approach for 
the PM2.5 NAAQS. Specifically, the EPA proposes that the 
attainment plan for a Moderate area that can demonstrate attainment by 
the statutory Moderate area attainment date must identify appropriate 
quantitative milestones to be achieved by 4.5 years following 
designation of the area. For a Moderate area that cannot practicably 
attain the relevant PM2.5 NAAQS within the statutory 
timeframe for a Moderate area, the EPA proposes that a state must 
submit two sets of quantitative milestones--one set to be achieved at 
year 4.5 from designation and the second set to be achieved at year 7.5 
from designation. The EPA believes that this proposed requirement will 
help to ensure that the state maintains progress toward bringing the 
area into attainment during the period in which such area is 
reclassified to Serious, the state works to develop a Serious area 
attainment plan for the area, and the EPA approves it. Pursuant to the 
statute, the EPA must reclassify a Moderate area for which a state 
submits an attainment impracticability demonstration within 18 months 
after the Moderate area attainment plan due date, or no later than 3 
years after the date of designation of the area. Even under a scenario 
in which the state develops and submits a Serious area attainment plan 
18 months after being reclassified to Serious, the milestone date of 
4.5 years after designation would likely come and go before the area 
had a new set of approved quantitative milestones with which to 
demonstrate compliance. Similarly, the milestone date of 7.5 years 
after designation could also come and go before the EPA is able to 
fully approve the Serious area plan and any quantitative milestones 
contained therein. Because of the timing of the various steps involved 
in reclassifying a Moderate area to Serious and a state developing a 
new Serious area plan, the EPA believes that requiring a state to 
identify quantitative milestones that the area must achieve 4.5 years 
and 7.5 years after designation as elements of its Moderate area 
attainment plan is reasonable and seeks comment on this proposed 
requirement.
---------------------------------------------------------------------------

    \146\ General Preamble, 57 FR 13498 (April 16, 1992), at page 
13539.
---------------------------------------------------------------------------

    The EPA is also proposing that the quantitative milestones 
contained in the attainment plan for a Moderate nonattainment area must 
be constructed such that they can be tracked, quantified and/or 
measured adequately in order for the state to meet its milestone 
reporting obligations, which come due 90 days after a given milestone 
date. In the Addendum, the EPA suggested some possible metrics that 
``support and demonstrate how the overall quantitative milestones 
identified for an area may be met,'' such as percent implementation of 
control strategies, percent compliance with implemented control 
measures, and adherence to a compliance schedule. This list was not 
exclusive or exhaustive but reflected the EPA's view that the purpose 
of the quantitative milestone requirement is to provide an objective 
way to assess that the state is making the necessary progress towards 
attainment in the area by the applicable attainment date.\147\ The EPA 
continues to believe that the quantitative milestone requirement

[[Page 15391]]

should be interpreted to allow states to devise milestones that are 
suitable for the specific facts and circumstances of the attainment 
plan for a particular area, so long as they provide an objective means 
to measure RFP.
---------------------------------------------------------------------------

    \147\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42016.
---------------------------------------------------------------------------

    The EPA therefore proposes to require that states select the 
quantitative milestones that are appropriate and quantifiable and that 
will provide for objective evaluation of progress toward attainment in 
their Moderate PM2.5 nonattainment area, whether the area 
can practicably attain the PM2.5 NAAQS by the statutory 
attainment date or not. For this approach, the EPA is not proposing to 
require that such quantitative milestones must take any particular 
form, merely that they provide a means to evaluate progress (i.e., 
demonstrate RFP) meaningfully. The EPA, in its attainment plan approval 
process, will determine if the specific quantitative milestones 
developed by the state for a specific nonattainment area satisfy the 
statutory requirements. The EPA recommends that states confer with 
their respective EPA regional office to develop appropriate 
quantitative milestones. See proposed 40 CFR 51.1013(a)(1).
    In addition to this general proposed approach for selecting 
quantitative milestones for a Moderate nonattainment area, the EPA is 
proposing and seeks comment on a requirement that, at a minimum, states 
must include in all attainment plans for Moderate PM2.5 
nonattainment areas a metric to confirm that all control measures 
identified and adopted as RACM and RACT for the area have been fully 
implemented within 4 years of designation. This metric specifically 
derives from the statutory provision that applies to all Moderate areas 
and thus represents a milestone that all Moderate areas must meet 
regardless of whether it is listed explicitly as an individual 
milestone. The EPA believes it would be appropriate to include it as a 
metric that any state with a Moderate nonattainment area would need to 
demonstrate compliance with when they submit their milestone report as 
described below, and thus seeks comment on this proposal.
3. Milestone Report Submittal
    Under the quantitative milestone requirement of section 189(c)(2), 
a state must demonstrate to the EPA that the RFP plan for the area and 
its approved milestones are being met within 90 days after the 
milestone due date. The EPA then has 90 days to determine whether or 
not a state's demonstration is adequate. Specifically, section 
189(c)(2) requires that: ``Not later than 90 days after the date on 
which a milestone applicable to the area occurs, each State in which 
all or part of such [nonattainment] area is located shall submit to the 
Administrator a demonstration that all measures in the plan approved 
under this section have been implemented and that the milestone has 
been met. A demonstration under this subsection shall be submitted in 
such form and manner, and shall contain such information and analysis, 
as the Administrator shall require.''
    In the event a state fails to submit a milestone demonstration 
report by the due date or the EPA determines that a milestone was not 
met, the state must submit a SIP revision within 9 months of either the 
missed reporting deadline or the EPA's determination of the state's 
failure to meet a milestone. According to the statutory requirements of 
section 189(c)(3), the new SIP revision must assure ``that the State 
will achieve the next milestone (or attain the national ambient air 
quality standard . . ., if there is no next milestone) by the 
applicable date.'' If a state fails to make a SIP submission to correct 
a failure to meet RFP expeditiously, sanctions under sections 110(m) 
and 179(b) may apply. If a state is unable to correct a failure to meet 
RFP, this may be evidence that the state cannot practicably attain the 
NAAQS by the applicable attainment date and may serve as a basis for 
reclassification of the area to Serious under the agency's 
discretionary authority. See proposed 40 CFR 51.1013(c).
    Because the statute does not define the parameters of these 
demonstrations, the statute grants the EPA discretion to determine the 
components of the required demonstration and the form and manner for 
submission. In the Addendum, the EPA offered guidance about what the 
milestone report should contain: ``This report must contain technical 
support sufficient to document completion statistics for appropriate 
milestones. For example, the demonstration should graphically display 
RFP over the course of the relevant 3 years and indicate how the 
emission reductions achieved to date compare to those required or 
scheduled to meet RFP and the required [quantitative] milestones. The 
calculations (and any assumptions made) necessary to determine the 
emission reductions to date should also be submitted. The demonstration 
should also contain an evaluation of whether the PM10 NAAQS 
will be attained by the projected attainment date.'' \148\ The EPA 
believes this guidance is still appropriate for states demonstrating 
compliance with RFP and quantitative milestones for PM2.5 
NAAQS and hereby proposes under the authority of section 301(a) to 
require that the milestone report submission must include the following 
four components:
---------------------------------------------------------------------------

    \148\ Ibid. at 42017.
---------------------------------------------------------------------------

    First, the report must include a certification by the Governor or 
Governor's designee that the state's attainment plan control strategy, 
including the RFP plan, is being implemented as described in the 
applicable attainment plan. Second, as described in the Addendum, the 
report must contain technical support, including calculations, 
sufficient to document completion statistics for appropriate milestones 
and to demonstrate that the quantitative milestones have been satisfied 
and how the emissions reductions achieved to date compare to those 
required or scheduled to meet RFP. Third, the state must submit an air 
quality screening analysis to determine if measured air quality 
progress is consistent with the expected air quality improvement target 
correlated with the RFP emissions reductions for the previous 3-year 
period. Fourth, the report must contain an evaluation of whether the 
PM2.5 NAAQS will be attained by the projected attainment 
date for the area. In addition, the EPA proposes that the milestone 
report must include a description and schedule for any remedial actions 
the state has taken or will take to address any failure to meet a 
quantitative milestone, including the implementation status of 
contingency measures for failing to meet RFP in the area. See proposed 
40 CFR 51.1013(b). The EPA seeks comment on these proposed components 
to a milestone report.
    The EPA stated in the Addendum that the milestone report must be 
submitted from the Governor or Governor's designee to the Regional 
Administrator of the respective EPA Regional Office serving the 
submitting state, and that the EPA will notify the state of its 
determination (regarding whether or not the state's report is adequate) 
by sending a letter to the appropriate Governor or Governor's designee. 
The EPA believes that it would be appropriate for states to submit 
milestone reports, including supporting documents, through the agency's 
electronic SIP (eSIP) submission system in order to simplify the 
process and reduce resource burden on all sides. The EPA seeks comment 
on how electronic reporting could facilitate a state's submittal of the 
required milestone report, how it could accommodate the various 
narrative and

[[Page 15392]]

data-dependent components that the EPA is proposing be part of such a 
submittal, and what particular system features might be desirable to 
accommodate milestone report submissions through the eSIP system.

H. Contingency Measures

    States with PM2.5 nonattainment areas must include 
contingency measures in their attainment plans consistent with section 
172(c)(9). Contingency measures are additional control measures to be 
implemented in the event that an area fails to meet RFP requirements or 
fails to attain the PM2.5 standard by the applicable 
attainment date. These measures must be fully adopted rules or control 
measures that are ready to be implemented quickly upon failure to meet 
RFP or failure of the area to meet the standard by its attainment date, 
and such measures are required to take effect without further action by 
the state or the EPA. The EPA provided extensive guidance on 
contingency measures in the General Preamble and Addendum, including 
the following: ``States must show that their contingency measures can 
be implemented with minimal further action on their part and with no 
additional rulemaking actions such as public hearings or legislative 
review. After the EPA determines that a moderate PM10 
nonattainment area has failed to attain the PM10 NAAQS, the 
EPA generally expects all actions needed to effect full implementation 
of the measures to occur within 60 days after the EPA notifies the 
state of the area's failure. The state should ensure that the measures 
are fully implemented as expeditiously as practicable after they take 
effect.'' \149\
---------------------------------------------------------------------------

    \149\ Ibid. at 42015.
---------------------------------------------------------------------------

    The EPA does not believe that the D.C. Circuit's decision in NRDC 
v. EPA affects the overall contingency measure requirements that were 
finalized in the remanded 2007 PM2.5 Implementation Rule, 
because section 172(c)(9) imposes the contingency measure requirement 
for attainment plans for the PM2.5 NAAQS and it is not 
superseded or subsumed by any specific contingency measure requirements 
under subpart 4. Although section 172(c)(9) requires contingency 
measures, the provision does not specify exactly what parameters such 
measures must meet. The EPA has longstanding interpretations of the 
statute with respect to the contingency measure requirement, both for 
PM and for other pollutants, in the General Preamble and Addendum. The 
EPA proposes to adopt an approach to contingency measures for the 
PM2.5 NAAQS similar to that recommended in earlier EPA 
guidance, but seeks comment on particular proposed approaches that 
differ in important ways from earlier guidance on contingency measures 
for the PM2.5 NAAQS. The EPA believes that it may be 
necessary to adopt a different approach to contingency measures for 
PM2.5 attainment plans due to proposed changes in 
determining RFP for a PM2.5 nonattainment area and in order 
to accommodate Moderate PM2.5 nonattainment areas that 
cannot practicably attain the standard by the statutory Moderate area 
attainment date.
    The EPA is proposing and seeking comment on the following general 
requirements for contingency measures to be approvable as part of a 
state's Moderate area attainment plan submission for the 
PM2.5 NAAQS:
    1. Contingency measures must be fully adopted rules or control 
measures that are ready to be implemented quickly upon a determination 
by the Administrator of the nonattainment area's failure to meet RFP or 
failure to meet the standard by its attainment date.
    2. The state's attainment plan submission must contain trigger 
mechanisms for the contingency measures, specify a schedule for 
implementation, and indicate that the measures will be implemented with 
minimal further action by the state or by the EPA.
    3. Contingency measures must consist of control measures that are 
not otherwise included in the control strategy for the attainment plan.
    4. Contingency measures must provide for emissions reductions 
approximately equivalent to 1 year's worth of reductions needed for 
RFP, based on the overall level of reductions needed to demonstrate 
attainment divided by the number of years from the base year to the 
attainment year, or approximately equivalent to 1 year's worth of air 
quality improvement or emissions reductions proportional to the overall 
amount of air quality improvement or emissions reductions to be 
achieved by the area's attainment plan. See proposed 40 CFR 51.1014.
    The EPA interprets the contingency measure requirement of section 
172(c)(9) to require control measures that are not already included in 
the attainment plan for other purposes, such as to meet RACM and RACT 
requirements. However, suitable contingency measures may be measures 
that were technologically and economically feasible for the area, but 
did not qualify as RACM or RACT or additional reasonable measures for 
one or more reasons. For example, a candidate contingency measure may 
have been deemed technologically and economically feasible, but it was 
not needed to achieve expeditious attainment in a Moderate area for 
which the state could demonstrate attainment by the statutory 
attainment date and therefore was not included as part of the 
attainment demonstration for the area. The agency believes it is 
important that states make decisions concerning contingency measures in 
conjunction with their determination of the overall control strategy 
for bringing the area into expeditious attainment, and that states 
first must identify those control measures needed in order to 
demonstrate expeditious attainment of the standards; any remaining 
measures should then be considered as candidates for contingency 
measures.
    For Moderate areas that cannot practicably attain the NAAQS by the 
statutory attainment date, the EPA is proposing that states must 
implement all control measures that they determine to be reasonable for 
sources in the area. In such cases, the EPA expects that contingency 
measures for such nonattainment areas would necessarily exceed the 
criteria for determining whether a measure is reasonable (i.e., 
technologically and economically feasible) as described in Section IV.D 
of this preamble. Such contingency measures would only be triggered in 
the event the area fails to meet RFP; the EPA does not interpret the 
requirement for contingency measures for failing to attain the NAAQS by 
the applicable attainment date to apply to a Moderate area that a state 
demonstrates cannot practicably attain the NAAQS by the statutory 
attainment date. Rather, the EPA believes it is appropriate for the 
state to identify and adopt contingency measures for failing to attain 
the NAAQS in a timely way as part of the Serious area attainment plan 
that it will develop once the EPA reclassifies such an area.
    The EPA proposes that for any Moderate PM2.5 
nonattainment area, contingency measures can include measures that 
achieve emissions reductions on sources located outside the 
nonattainment area as well as from sources within the nonattainment 
area, provided that the measures are factually demonstrated to produce 
the appropriate air quality impact within the nonattainment area. The 
EPA continues to believe it appropriate that a state might choose to 
rely on federal measures (e.g. federal mobile source measures based on 
the incremental turnover of the motor vehicle fleet each year) and 
local measures already scheduled for implementation for

[[Page 15393]]

purposes other than meeting attainment plan requirements, such as RACM 
and RACT, as meeting part or all of the contingency measure 
requirements, as the purpose of the contingency measures is to provide 
a cushion while the attainment plan for the area is being revised to 
meet the missed attainment milestone. The EPA has approved numerous 
attainment plans under an interpretation that one or more federal or 
local measures that are in place and provide reductions in the year 
following a failure to attain the relevant NAAQS or meet RFP in excess 
of the reductions required by the attainment demonstration or RFP plan 
can meet the contingency measure requirements.150 151
---------------------------------------------------------------------------

    \150\ See, e.g., 62 FR 15844 (April 3, 1997); 62 FR 66279 
(December 18, 1997); 66 FR 30811 (June 8, 2001); 66 FR 586 and 66 FR 
634 (January 3, 2001).
    \151\ A court ruling upheld contingency measures for ozone 
attainment plans that were previously required and implemented where 
they were in excess of the attainment demonstration and RFP SIP. See 
LEAN v. EPA, 382 F.3d 575 (5th Cir., 2004).
---------------------------------------------------------------------------

    The EPA recognizes that some states have historically relied on 
emissions reductions achieved through the implementation of control 
measures in excess of what was determined to be necessary to meet RFP 
in certain PM2.5 nonattainment areas in order to satisfy the 
contingency measure requirement in such areas. The EPA believes that 
this approach is reasonable for Moderate PM2.5 nonattainment 
areas that can demonstrate attainment by the statutory attainment date, 
as the state would calculate the emissions reductions needed for RFP 
separately from the control strategy determination for such an area. 
However, crediting an area for ``excess'' emissions reductions to 
satisfy the contingency measure requirement would not be possible for a 
Moderate area that cannot practicably attain by the statutory 
attainment date under the EPA's proposed approach for calculating RFP 
for such areas, as RFP would be calculated directly from the projected 
emissions reductions from all control measures identified for the area 
(as RACM and RACT or additional reasonable measures), such that there 
would be no difference between emissions reductions estimated from 
control measures and those estimated for demonstrating RFP.
    As mentioned earlier, contingency measures should represent a 
portion of the actual emissions reductions necessary to bring about 
attainment in the area. Consistent with the EPA's past approach for 
contingency measures for PM2.5 nonattainment areas, the EPA 
proposes to require that the emissions reductions anticipated by 
imposition of the contingency measures must be equal to approximately 1 
year's worth of emissions reductions while the state is revising its 
attainment plan for the area. The EPA has historically applied a policy 
of equating 1 year's worth of emissions reductions for contingency 
measures with those annual reductions determined to be necessary to 
achieve RFP for the area, unless the state demonstrates that some 
smaller reduction is appropriate. As described in Section IV.F of this 
preamble, the EPA is proposing an approach for interpreting the 
statutory RFP requirement that would require demonstrating RFP based on 
reductions from sources located inside the nonattainment area. Keeping 
with the historic linkage between RFP and contingency measures, the EPA 
is also proposing and seeking comment on a similar approach for 
calculating 1 year's worth of emissions reductions for purposes of 
adopting appropriate contingency measures. That is, the EPA's proposed 
approach for determining the level of emissions reductions for 
contingency measure purposes is to calculate the annual reductions in 
emissions of direct PM2.5 and PM2.5 precursors 
needed from sources located inside the nonattainment area. The EPA 
seeks comment on this proposed approach.
    The CAA requires that states must implement contingency measures 
after the EPA determines that the area has either failed to meet RFP 
requirements, or failed to attain the standards by the applicable 
attainment date. The purpose of the contingency measure provision is to 
ensure that corrective measures are put in place automatically at the 
time that the EPA makes its determination that an area has either 
failed to meet RFP or failed to meet the standard by its attainment 
date. The EPA is required to determine within 90 days after receiving a 
state's milestone demonstration, and within 6 months after the 
attainment date for an area, whether these requirements have been met. 
The consequences for states with areas that fail to attain the NAAQS or 
to meet RFP are described in section 179(d) of the CAA and discussed in 
Section V of this preamble.
    As noted earlier in this section, the EPA proposes to require that 
states must submit contingency measures at the same time as the rest of 
the Moderate area attainment plan elements, i.e., within 18 months 
after designation. Section 172(b) requires the Administrator to 
``establish a schedule according to which the State containing such 
[nonattainment] area shall submit a plan or plan revision (including 
the plan items) meeting the applicable [subpart 1 nonattainment plan] 
requirements. . . Such schedule shall, at a minimum, include a date or 
dates, extending no later than 3 years from the date of the 
nonattainment designation . . .'' The EPA believes it is reasonable to 
require the submittal of contingency measures for Moderate 
PM2.5 nonattainment areas on the same schedule as the other 
Moderate area attainment plan requirements because of the close 
relationship between an area's control strategy, RFP analysis and 
selection of quantitative milestones, and contingency measures. The EPA 
seeks comment on this proposed due date for submission of contingency 
measures.

I. Attainment Dates

1. Statutory Requirements
    Section 188 establishes the attainment dates for Moderate and 
Serious PM10 nonattainment areas, which also apply to 
Moderate and Serious PM2.5 nonattainment areas. Section 
188(c)(1) provides that for a Moderate area, ``the attainment date 
shall be as expeditiously as practicable but no later than the end of 
the sixth calendar year after the area's designation as 
nonattainment.'' The EPA has the responsibility for determining whether 
a nonattainment area has attained the standard by its applicable 
attainment date. Section 179(c)(1) requires the EPA to make 
determinations of attainment no later than 6 months following the 
attainment date for the area. Under section 179(c)(2), the EPA must 
publish a notice in the Federal Register identifying those areas which 
failed to attain by the applicable attainment date. The statute further 
provides that the EPA may revise or supplement its determination of 
attainment for the affected areas based upon more complete information 
or analysis concerning the air quality for the area as of the area's 
attainment date.
    Section 179(c)(1) provides that the EPA is to base the attainment 
determination for an area upon an area's ``air quality data as of the 
attainment date.'' The EPA will make the determination of whether an 
area's air quality is meeting the PM2.5 NAAQS by the 
applicable attainment date based upon data gathered from the air 
quality monitoring sites which have been entered into the EPA's Air 
Quality System (AQS) database. No special or additional attainment plan 
submission will be required from the state for this determination.
    A Moderate PM2.5 nonattainment area's air quality status 
is determined in accordance with Appendix N of 40 CFR

[[Page 15394]]

part 50. To show attainment of the current 24-hour and annual standards 
for PM2.5, the most recent 3 consecutive years' data prior 
to the area's attainment date must show that PM2.5 
concentrations over the prior 3-year period are at or below the levels 
of the standards. A complete year of air quality data, as described in 
part 50, Appendix N, is comprised of all 4 calendar quarters with each 
quarter containing data from at least 75 percent of the scheduled 
sampling days.
    The EPA will begin processing and analyzing data related to the 
attainment of Moderate PM2.5 nonattainment areas after the 
applicable attainment date for the affected areas. Current EPA 
regulations, under 40 CFR part 58, set the deadline for the state to 
submit air quality data into the AQS database as no later than 90 days 
after the end of the calendar year.
    While the EPA may determine that an area's air quality data 
indicates that an area may be meeting the PM2.5 NAAQS for a 
specified period of time, this does not eliminate the state's 
responsibility under the Act to adopt and implement an approvable 
attainment plan. If the area's monitored data indicates that the area 
is factually attaining the NAAQS, however, the EPA may issue a ``clean 
data determination'' which will suspend the obligation of the state to 
submit the elements of the attainment plan for the area that are 
related to planning requirements, as discussed in Section IX.C of this 
preamble. If the EPA determines that an area has attained the standard 
as of its attainment date, the area will remain classified as 
nonattainment until the state has requested, and the EPA has approved, 
redesignation to attainment for the area.
    In order for an area to be redesignated as attainment, the state 
must comply with the five requirements listed under section 
107(d)(3)(E) of the CAA. Briefly, this section requires that:
     The EPA has determined that the area has met the 
PM2.5 NAAQS;
     The EPA has fully approved the applicable state 
implementation plan;
     The improvement in air quality is due to permanent and 
enforceable reductions in emissions;
     The EPA has fully approved a maintenance plan for the 
area; and,
     The state(s) containing the area or portions of the area 
have met all applicable requirements under section 110 and part D.
2. Proposed Approach
    As noted earlier, section 188(c)(1) states that for a Moderate 
area, ``the attainment date shall be as expeditiously as practicable 
but no later than the end of the sixth calendar year after the area's 
designation as nonattainment.'' For purposes of clarity, the EPA 
proposes to interpret the reference to ``the area's designation'' in 
this provision as meaning ``the area's effective date of designation,'' 
consistent with the agency's approach for implementing the 1997 and 
2006 PM2.5 NAAQS and with its approach for implementing 
NAAQS for other criteria pollutants under part D, title I of the CAA. 
See proposed 40 CFR 51.1000. As discussed elsewhere in this preamble, 
the effective date of designation is April 15, 2015, for areas 
designated nonattainment in the first round of designations for the 
2012 PM2.5 NAAQS. For these areas, the Moderate area 
attainment date would be as expeditious as practicable, but no later 
than December 31, 2021 (i.e., the end of the sixth calendar year after 
designation). The EPA seeks comment on this proposed interpretation of 
the date of designation of a PM2.5 NAAQS nonattainment area 
and the resulting attainment date for such areas.
    As described in Sections IV.D and IV.E of this preamble, in the 
case of a Moderate PM2.5 nonattainment area for which a 
state can demonstrate attainment by the end of the sixth calendar year 
following designation, the state must follow a two-step process for 
determining the appropriate attainment date for the area. First, the 
state must demonstrate through air quality modeling that the area can 
attain the relevant NAAQS by the latest statutory attainment date and 
determine which control measures and technologies are needed for the 
area to attain by that date. Second, the state must determine whether 
implementing other reasonable controls (i.e., those not needed for 
attainment by the latest possible date but that are technologically and 
economically feasible) can cumulatively advance the attainment date for 
the area by at least 1 year. In the event that a state determines that 
the area can attain the relevant NAAQS earlier through the application 
of other measures, the state must propose the earlier date as part of 
the attainment plan submission for the area. When the EPA takes action 
to approve the different elements of the attainment plan for the area, 
one of the elements that the agency will take action on will be the 
state's proposed attainment date for the area. If the EPA approves an 
attainment date for the area that is earlier than the latest date 
allowed by statute, then the applicable attainment date for the area 
will be the approved date. See proposed 40 CFR 51.1004(a)(1)(i). If the 
area ultimately needs additional time to attain the relevant NAAQS, the 
state may request an attainment date extension for the Moderate 
nonattainment area under section 188 as long as certain conditions are 
met, as described in Section IV.J.
    The EPA's approach to approving an attainment date for a 
PM2.5 nonattainment area will be different for a Moderate 
area that cannot practicably attain the relevant PM2.5 NAAQS 
by the end of the sixth calendar year after designation. Given that the 
agency will reclassify any such area to Serious and thereby trigger 
additional Serious area requirements for the area, the EPA will approve 
an attainment date for the area when it takes action on the Serious 
area attainment plan submitted for the area. In the interim, before the 
EPA takes action to reclassify the area, the statutory Moderate area 
attainment date will continue to apply to such an area. See proposed 40 
CFR 51.1000 and 51.1004(a)(1)(ii). When the EPA reclassifies the area, 
then the presumptive attainment date for the area will be as 
expeditious as practicable, but no later than the end of the tenth 
calendar year following designation. A complete discussion of Serious 
area attainment dates is provided in Section VI.H of this preamble.

J. Attainment Date Extensions

1. Statutory Requirements
    The CAA under subpart 4 provides the EPA with authority to grant 
extensions of the attainment date for a Moderate area that otherwise 
could be found to have failed to attain the relevant PM2.5 
NAAQS, if the area can meet specific statutory criteria related to the 
implementation of measures contained in the attainment plan for the 
area, and to monitored air quality in the area. Specifically, under 
section 188(d), a state may apply to the EPA for an extension of a 
Moderate area's attainment date of one additional year (the ``Extension 
Year'') if ``(1) the state has complied with all requirements and 
commitments pertaining to the area in the applicable implementation 
plan; and (2) no more than one exceedance of the 24-hour [NAAQS] level 
for PM10 has occurred in the area in the year preceding the 
Extension Year, and the annual mean concentration of PM10 in 
the area for such year is less than or equal to the standard level.'' 
Section 188(d) limits the number of 1-year extensions that the EPA may 
grant for a Moderate nonattainment area to two.
    The provisions of section 188(d) thus allow a state an opportunity 
to demonstrate that a Moderate area should continue to be classified as

[[Page 15395]]

Moderate and not be reclassified to Serious even if the area exceeded 
the level of the applicable PM2.5 NAAQS in one or both of 
the 2 calendar years preceding the year in which the area is otherwise 
required to attain the NAAQS. Although section 188(d) provides the 
criteria for such an extension, the EPA believes that there are some 
ambiguities in the statutory language that warrant interpretation and 
clarification through regulations for the PM2.5 NAAQS. The 
EPA is thus proposing a preferred interpretation of section 188(d) to 
provide clarity to states about how and when they may qualify for a 
Moderate area attainment date extension for purposes of the 
PM2.5 NAAQS.
2. Proposed Interpretations of Attainment Date Extension Criteria
    With respect to the criterion in section 188(d)(1) that requires 
that ``the state has complied with all requirements and commitments 
pertaining to the area in the applicable implementation plan,'' the EPA 
proposes to interpret this provision to mean that the state has 
implemented the control measures in the SIP submission it made to 
address the attainment plan requirements for the applicable 
PM2.5 NAAQS, and not to require the area to have a fully 
approved attainment plan that meets all of the CAA's requirements for 
Moderate areas. This proposed interpretation is based on the plain 
language of section 188(d) that does not explicitly require that the 
state comply with all requirements pertaining to the area in the CAA, 
but merely requires that the state comply with all requirements in the 
applicable SIP.\152\ In other words, the EPA believes that section 
188(d)(1) should be interpreted to mean that so long as the state has 
submitted the necessary attainment plan for the area for the applicable 
PM2.5 NAAQs and is implementing the control measures in the 
submission, the fact that the EPA has not yet acted on such submission 
to make it an approved part of the applicable SIP should not be a 
barrier to the state obtaining an extension of the attainment date 
under section 188(d)(1). For the same reason, the EPA also proposes to 
read this provision not to bar an extension if all or part of an area's 
Moderate area plan is disapproved or has been promulgated by the EPA as 
a federal implementation plan (FIP). In the case that the ``applicable 
implementation plan'' is a FIP (or combination of SIP and FIP), then 
the EPA proposes that the state must have implemented the control 
measures contained therein in order to meet the statutory criteria at 
section 188(d)(1) for a Moderate area attainment date extension. The 
EPA seeks comment on this proposed interpretation of section 188(d)(1). 
See proposed 40 CFR 51.1005(a)(2).
---------------------------------------------------------------------------

    \152\ This interpretation as applied to section 188(e) for 
Serious area attainment date extensions was upheld by the Ninth 
Circuit Court of Appeals in Vigil v. Leavitt, 366 F.3d 1025, amended 
at 381 F.3d 826 (9th Cir. 2004).
---------------------------------------------------------------------------

    The EPA also proposes and seeks comment on an alternative 
interpretation of section 188(d)(1) that would require a state to have 
a Moderate area attainment plan fully approved by the EPA as meeting 
the applicable attainment plan requirements under sections 172 and 189 
for a Moderate PM2.5 nonattainment area before the state 
obtains an extension. Given that Moderate area attainment plans are due 
18 months from the date of designation, and that RACM and RACT must be 
implemented within 4 years after designation, states should have 
sufficient time under the statutory schedule to satisfy all applicable 
requirements in advance of seeking a Moderate area attainment date 
extension. Under this alternative approach, the EPA proposes that a 
state subject to a FIP (or SIP and FIP) for a Moderate PM2.5 
nonattainment area could qualify for an attainment date extension for 
the area if it had implemented all requirements and commitments of the 
FIP (or SIP and FIP), as the FIP (or SIP and FIP) would be the 
``applicable implementation plan'' for the area. Although this 
alternative interpretation could also be a reasonable reading of this 
criterion of section 188(d)(1), the EPA considers it less appropriate 
than the preferred interpretation because this approach could foreclose 
states from obtaining an otherwise appropriate extension merely because 
of logistical and timing considerations that might have prevented the 
EPA from acting on the state's attainment plan by the requisite point 
in time. Nevertheless, the EPA seeks comment on this alternative 
interpretation of section 188(d)(1).
    The second criterion that states must meet to qualify for an 
extension relates to the monitored ambient air in a nonattainment area 
in the year prior to the attainment date for the area. If a state has 
met the requirements of section 188(d)(1), the EPA may grant an 
extension of a Moderate area's attainment date if the state also 
satisfies the requirements of section 188(d)(2) that ``no more than one 
exceedance of the 24-hour national ambient air quality standard level 
for PM10 has occurred in the area in the year preceding the 
Extension Year, and the annual mean concentration of PM10 in 
the area for such year is less than or equal to the standard level.'' 
Again, the EPA may grant up to two such 1-year extensions and thus this 
criterion would apply to the calendar year prior to the applicable 
attainment date and to the Extension Year, in the case of a second 
extension.
    The EPA believes that the references to the ambient air quality 
standards in section 188(d)(2) are ambiguous in two significant ways in 
the context of the PM2.5 NAAQS implementation. First, the 
statutory language explicitly sets ambient air quality conditions for 
an attainment date extension in terms that relate factually to the 24-
hour PM10 NAAQS that was in effect at the time of the 1990 
Amendments of the CAA, which has a statistical form that is 
substantially different from the 24-hour PM2.5 NAAQS. 
Specifically, the form of the 24-hour PM10 NAAQS allows for 
no more than one ``exceedance'' of the standard per year on average 
over 3 years, and if there is more than one such exceedance on average 
over 3 years the area is violating the NAAQS. Thus, as a means of 
limiting extensions to areas that are close to attaining the NAAQS in 
the calendar year prior to the applicable attainment date, section 
188(d)(2) imposes the criterion of having ``no more than one exceedance 
of the 24-hour . . . standard level'' as a way of demonstrating that a 
nonattainment area has ``clean data'' for the year prior to the 
attainment date.\153\ This statutory language does not translate 
readily to the PM2.5 NAAQS, which postdate the creation of 
section 188(d) and are not structured with the same mathematical form. 
For example, the 2006 24-hour PM2.5 NAAQS incorporates a 3-
year average of the 98th percentile form, which means that an area with 
valid monitored ambient readings every day (or almost every day) could 
have seven readings above the numerical level of the standard (i.e., 
``exceedances'') in any given year and still have ``clean data'' for 
that year. A literal interpretation of section 188(d)(2) to permit only 
one exceedance of the 24-hour PM2.5 NAAQS, rather than the 
number of exceedances that is relevant for purposes of determining 
attainment of such NAAQS, is illogical. In light of the different form 
of the PM2.5 NAAQS, the statutory language of section 
188(d)(2) is thus ambiguous in how it should apply to implementation of 
the 24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \153\ The 24-hour PM10 NAAQS, set at 150 [mu]g/m\3\, 
cannot be exceeded more than once per year on average, over 3 years.
---------------------------------------------------------------------------

    Additionally, the language of section 188(d)(2) may be considered 
ambiguous

[[Page 15396]]

as to how it should apply to the PM2.5 NAAQS to the extent 
that it does not specify whether the air quality criteria for an 
attainment date extension apply equally for a Moderate area designated 
nonattainment for both the 24-hour and annual standards, or for just 
one of the standards. In practice, most areas designated nonattainment 
for the PM10 NAAQS following passage of the 1990 CAA 
Amendments were designated nonattainment only for the 24-hour 
PM10 NAAQS, with a few designated for only the annual 
PM10 NAAQS or for both the 24-hour and the annual 
PM10 NAAQS. The 24-hour NAAQS has served as the 
``controlling'' (i.e., functionally more stringent) PM10 
standard, such that the agency's experience to date in granting 
PM10 Moderate area attainment date extension requests has 
been limited to extending the attainment date for the 24-hour 
PM10 NAAQS.\154\
---------------------------------------------------------------------------

    \154\ For examples of the EPA actions to extend attainment dates 
for Moderate PM10 areas, see 61 FR 20730 (May 8, 1996), 
61 FR 66602 (December 18, 1996), and 66 FR 32752 (June 18, 2001).
---------------------------------------------------------------------------

    The situation is distinctly different for PM2.5 
nonattainment areas, as the specific facts and circumstances of a 
particular area may warrant a nonattainment designation for either the 
24-hour standard or the annual standard, but often not both. In most 
cases, for instance, the current nonattainment areas for 
PM2.5 are designated either for the 1997 annual NAAQS or for 
the 2006 24-hour NAAQS, but not both.\155\ For example, the EPA 
recently promulgated designations for areas violating only the annual 
PM2.5 NAAQS revised in 2012, not the 24-hour NAAQS which was 
retained at the level established during the 2006 p.m. NAAQS review. If 
a PM2.5 nonattainment area is designated only for the 24-
hour or only for the annual PM2.5 NAAQS, this situation 
raises the question of how section 188(d)(2) air quality criteria for 
both standards should apply to such a PM2.5 NAAQS 
nonattainment area if the state seeks an extension of the applicable 
attainment date for such area.
---------------------------------------------------------------------------

    \155\ Nonattainment areas designated for both the 24-hour and 
annual PM2.5 NAAQS are located in central and southern 
CA.
---------------------------------------------------------------------------

    Due to the ambiguities associated with applying this subpart 4 
requirement to current and future PM2.5 NAAQS, the agency 
believes it is important to propose a reasonable interpretation of the 
statutory requirement and seek public comment on this preferred 
interpretation as well as two alternative interpretations specifying 
the PM2.5 standard or standards for which a state would need 
to demonstrate a Moderate nonattainment area met the air quality 
criteria of section 188(d)(2) in order to qualify for an attainment 
date extension. The agency also believes it is important to clarify how 
the air quality criteria of section 188(d)(2) apply specifically for 
the 24-hour PM2.5 NAAQS. For this reason, the EPA is 
proposing a preferred interpretation of section 188(d)(2) for 
application to current and future PM2.5 NAAQS, and is 
seeking comment on two alternative interpretations that the agency 
considers less appropriate.
    The preferred proposed approach would only require a state to 
demonstrate that in the year prior to the applicable attainment date 
for the area, a Moderate area did not exceed the level of (i.e., had 
clean data for) the specific PM2.5 NAAQS for which the area 
is designated nonattainment (the ``applicable NAAQS'') and for which 
the state is seeking the extension of the attainment date. The second 
approach, on which the EPA seeks comment, would require that a state 
demonstrate that in the year prior to the applicable attainment date 
for an area, the Moderate area did not exceed the level of the specific 
PM2.5 NAAQS for which the area is designated nonattainment 
(the applicable NAAQS), and did not exceed the most stringent level of 
any other PM2.5 NAAQS in effect nationally at the time the 
area was designated for the applicable NAAQS. The third approach, on 
which the EPA also seeks comment, would require that a state 
demonstrate that in the year prior to the applicable attainment date 
for an area, the Moderate area did not have more than one exceedance of 
the level of the 24-hour PM2.5 standard, and that the annual 
mean concentration of PM2.5 in the area for the attainment 
year was less than or equal to the annual standard, regardless of the 
NAAQS for which the state is seeking an attainment date extension.
    The EPA prefers the proposed interpretation (described in more 
detail later in this section) for implementing the Moderate area 
attainment date extension criteria of section 188(d)(2) considering the 
fact that, due to the specific atmospheric conditions and source-
dependent nature of PM2.5 problems in different areas around 
the country, the EPA has historically designated, and may continue to 
designate, PM2.5 nonattainment areas for either the annual 
or the 24-hour NAAQS. As discussed earlier, the agency's designations 
processes for the 2006 revised 24-hour PM2.5 NAAQS and the 
2012 revised annual PM2.5 NAAQS have each been conducted to 
address only one standard individually. In addition, the current 24-
hour PM2.5 NAAQS does not have a ``one exceedance'' form of 
the standard, as cited in section 188(d)(2). Nevertheless, the EPA 
requests comment on the second and third interpretations of section 
188(d)(2) described later in this section because they more closely 
reflect the specific statutory wording.
    a. Proposed approach: the EPA preferred option. The EPA's proposed 
interpretation of section 188(d)(2) would simply require that a state 
demonstrate that in the year prior to the applicable attainment date 
for the area, a Moderate nonattainment area had clean data for the 
specific PM2.5 NAAQS for which the state was seeking an 
attainment date extension (the applicable NAAQS). Under this proposed 
approach, a state seeking an attainment date extension for a Moderate 
nonattainment area for a 24-hour PM2.5 NAAQS would be 
required to demonstrate that the area had clean data for that 
particular standard in the calendar year prior to the applicable 
attainment date for the area, rather than demonstrating that the area 
necessarily had no more than one exceedance of the 24-hour 
PM2.5 NAAQS.
    For example, under this proposed interpretation of section 
188(d)(2), in the case of a state seeking an extension of the 
attainment date for a Moderate area designated nonattainment for the 
2006 24-hour PM2.5 NAAQS, the state would need to 
demonstrate that the area had no more than the allowable number of 
valid monitored readings exceeding 35[mu]g/m\3\ to meet the 98th 
percentile statistical form of the standard in the year prior to the 
area's attainment date. The state would not have to demonstrate that 
the area also had clean data for any other PM2.5 NAAQS, 
including any annual PM2.5 NAAQS or later revision of the 
24-hour PM2.5 NAAQS.
    Likewise under the EPA's preferred approach, a state seeking an 
attainment date extension for a Moderate nonattainment area for an 
annual PM2.5 NAAQS would be required to demonstrate that the 
area had clean data for that particular standard in the calendar year 
prior to the applicable attainment date for the area. For example, in 
the case of a state seeking an extension of the attainment date for a 
Moderate area designated nonattainment for the 2012 annual 
PM2.5 NAAQS, the state would need to demonstrate that the 
annual mean concentration of PM2.5 at each monitor in the 
area as analyzed in accordance with Appendix N to 40 CFR part 50 for 
the year prior to the area's attainment date was less than or equal to 
12.0 [mu]g/

[[Page 15397]]

m\3\. Again, under this proposed approach, the state would not have to 
demonstrate that the area had clean data for any other PM2.5 
NAAQS.
    Under the EPA's preferred approach, if a state were to have an area 
that is designated nonattainment for both the 24-hour and the annual 
PM2.5 NAAQS, with the same applicable attainment date, then 
a state seeking attainment date extensions for both NAAQS would need to 
meet the ambient air quality criterion for both NAAQS. The EPA notes 
that this would not be a common occurrence, but under this 
interpretation, these would be the only circumstances under which a 
state should be required to have clean data for both NAAQS in order to 
qualify for an extension of the applicable attainment date under 
section 188(d)(2). If a state has a nonattainment area that is only 
designated for either the 24-hour or the annual PM2.5 NAAQS, 
the EPA believes that the state need only meet the air quality 
criterion of section 188(d)(2) for the NAAQS relevant to the attainment 
date at issue. See proposed 40 CFR 51.1005(a)(1)(ii) and (iii).
    The EPA believes this preferred interpretation of section 188(d)(2) 
is appropriate for two reasons. First, as discussed above, while most 
PM10 nonattainment areas were designated nonattainment for 
either just the 24-hour PM10 NAAQS or for both the 24-hour 
and annual PM10 NAAQS, the majority of current 
PM2.5 nonattainment areas are designated for either the 24-
hour or the annual PM2.5 NAAQS, and should arguably only 
need to demonstrate clean data for the NAAQS for which the area is 
designated nonattainment. For those few PM2.5 nonattainment 
areas designated for 24-hour and annual PM2.5 NAAQS, the EPA 
believes it may also be appropriate that a state must only demonstrate 
clean data for the specific NAAQS for which the state is seeking an 
attainment date extension because such an approach is consistent with 
the statute's overall approach to designating nonattainment areas and 
implementing control strategies for each separate PM2.5 
NAAQS.
    Second, as discussed earlier, the statutory language that requires 
that a nonattainment area have ``no more than one exceedance of the 24-
hour'' NAAQS level reflects a statistical form for the 24-hour 
PM10 standard that is different from the current form of the 
24-hour PM2.5 NAAQS. This difference, and the fact that the 
form could be subject to further revision in the future, leads the EPA 
to conclude that it is appropriate to describe this particular 
criterion more broadly so that it can apply to any 24-hour 
PM2.5 NAAQS, now or in the future regardless of the specific 
statistical form any such NAAQS may take. The EPA seeks comment on this 
preferred proposed approach.
    b. Alternative approach 1. The EPA also seeks comment on two 
alternative interpretations of section 188(d)(2). The EPA's first 
alternative interpretation of section 188(d)(2) would require that a 
state seeking an attainment date extension for a Moderate 
PM2.5 nonattainment area would have to demonstrate that the 
area met the level of the PM2.5 NAAQS for which it is 
seeking the attainment date extension, as well as met the numerical 
level of the most stringent PM2.5 NAAQS in effect at the 
time the area was designated nonattainment. That is, under this 
approach, the area would need to have clean data for the year preceding 
the attainment date for the PM2.5 NAAQS for which the state 
is seeking an attainment date extension and for the other 
PM2.5 NAAQS that were part of the same suite of 
PM2.5 standards (i.e., both the 24-hour and the annual 
PM2.5 NAAQS) in effect at the time the EPA designated the 
area nonattainment.
    For example, if a state seeks an extension of the attainment date 
for an area designated nonattainment only for the 2012 annual 
PM2.5 NAAQS, it would have to demonstrate that the annual 
mean concentration of PM2.5 at each monitor in the Moderate 
area as analyzed in accordance with Appendix N to 40 CFR part 50 in the 
attainment year was less than or equal to 12.0 [mu]g/m\3\. 
Additionally, the state would have to demonstrate that the 98th 
percentile of valid 24-hour monitored readings in the area for the year 
preceding the attainment date did not exceed 35 [mu]g/m\3\, the level 
of the 24-hour PM2.5 NAAQS set in 2006 and retained with the 
2012 p.m. NAAQS review as part of the suite of PM NAAQS, even if the 
area was not designated nonattainment for the 2006 24-hour 
PM2.5 NAAQS.\156\ As with the agency's preferred approach, a 
state seeking an attainment date extension for a Moderate nonattainment 
area for a 24-hour PM2.5 NAAQS would be required to 
demonstrate that the area had clean data for that particular standard 
in the calendar year prior to the applicable attainment date for the 
area in accordance with the statistical form of the 24-hour 
PM2.5 NAAQS, rather than demonstrating that the area had no 
more than one exceedance of the 24-hour PM2.5 NAAQS.
---------------------------------------------------------------------------

    \156\ Given the rounding provisions specified in 40 CFR part 50, 
Appendix N, these criteria would be satisfied if the concentrations 
before final rounding are less than an annual average of 12.05 
[mu]g/m\3\ and a 24-hour value of 35.5 [mu]g/m\3\.
---------------------------------------------------------------------------

    The EPA presents this first alternative interpretation of the 
statute for two reasons. First, as noted earlier, the statute at 
section 188(b)(2) does not specify whether the air quality criteria for 
an attainment date extension apply for Moderate areas designated 
nonattainment for both the 24-hour and annual PM10 
standards, or for just one of the standards. Read literally, however, 
the statute seems to require that an area seeking an extension of a 
Moderate area attainment date for any PM10 NAAQS must be 
meeting the level of both the 24-hour standard and the annual standard, 
even if it was only designated for just one of the standards. Under 
this interpretation of the statute for purposes of implementing the 
PM2.5 NAAQS, even though an area may be designated 
nonattainment for only one PM2.5 NAAQS and therefore seeking 
an attainment date extension only for that particular NAAQS, it would 
also have to meet the level of the other PM2.5 standards. As 
explained above, the EPA does not consider this the most appropriate 
interpretation of section 188(d). However, under this alternative 
interpretation the agency would take the position that the other 
PM2.5 standards whose level the state must show the Moderate 
nonattainment area met in the year preceding its attainment date would 
be the most stringent PM2.5 NAAQS in effect nationally at 
the time the area was designated nonattainment. For example, if the EPA 
were to strengthen the 24-hour PM2.5 standard below the 
current 35 [mu]g/m\3\ prior to December 31, 2021 (the anticipated 
statutory Moderate area attainment date for the 2012 PM2.5 
NAAQS), then an area seeking an extension of the Moderate area 
attainment date for the 2012 PM2.5 NAAQS would have to 
demonstrate that the area met the most stringent 24-hour 
PM2.5 NAAQS that applied at the time it was designated (35 
[mu]g/m\3\), and not the less stringent 24-hour NAAQS set in 1997 (65 
[mu]g/m\3\) or any more stringent standard set after designation but 
before the attainment date.
    Second, as with the proposed approach to interpreting section 
188(d)(2), the EPA believes it is appropriate to interpret the 
statutory language regarding ``no more than one exceedance of the 24-
hour'' NAAQS level broadly to mean that the area had clean data for the 
24-hour PM2.5 NAAQS, consistent with the form of the NAAQS 
at issue, so that the requirement can apply to any 24-hour 
PM2.5 NAAQS, now or in the future. Even if it were 
appropriate to interpret section

[[Page 15398]]

188(d)(2) to require that a state meet the air quality criterion for 
both the 24-hour and the annual PM2.5 NAAQS, the EPA 
believes that the statutory provision concerning the number of 
exceedances must still be read in light of the different form of the 
24-hour PM2.5 NAAQS. The EPA seeks comment on this first 
alternative interpretation of section 188(d)(2).
    c. Alternative approach 2. The EPA's second alternative 
interpretation of section 188(d)(2) would require that a state 
demonstrate that a Moderate area did not have more than one exceedance 
of the applicable 24-hour PM2.5 standard level, and the 
annual mean concentration of PM2.5 in the area was less than 
or equal to the applicable annual PM2.5 standard level, in 
the year preceding the applicable attainment date for the area. In 
other words, the EPA would not interpret the air quality criterion with 
respect to the 24-hour PM2.5 NAAQS in light of the 
significantly different form of the PM2.5 NAAQS. 
Furthermore, as with the first alternative interpretation, the 
``applicable'' PM2.5 standards would be those that applied 
at the time the Moderate area was designated for a given 
PM2.5 NAAQS, even if the area was not designated 
nonattainment for all of them. This interpretation would mean that 
regardless of the form of the applicable 24-hour PM2.5 
standard, the Moderate area seeking an attainment date extension could 
not have more than one exceedance of the numerical level of the 
applicable 24-hour standard in order to qualify for a Moderate area 
attainment date extension. This requirement would be more stringent--
and in some cases considerably so--than under the preferred proposed 
and first alternative interpretations, given the current statistical 
form of the 24-hour PM2.5 NAAQS. Additionally, under this 
reading of section 188(d)(2), any future changes to the 
PM2.5 NAAQS in terms of form or averaging time would also 
not be addressed, potentially creating confusion with respect to how a 
PM2.5 Moderate area could qualify for an attainment date 
extension in the future.
    The EPA believes that, while this interpretation of section 
188(d)(2) may appear to be a straightforward reading of the statutory 
language, it does not reasonably account for the important differences 
between the statistical form of the PM10 and 
PM2.5 NAAQS or between the EPA's longstanding convention for 
designating PM10 and PM2.5 nonattainment areas 
generally. The EPA therefore seeks comment on its preferred proposed 
approach and two alternative approaches for interpreting the air 
quality criteria of section 188(d)(2) that a state would need to 
demonstrate compliance with in order for the EPA to consider granting 
an extension of a Moderate PM2.5 area attainment date.
3. Proposed Process for Attainment Date Extension Request Submittals
    Regardless of which interpretation of section 188(d)(1) the EPA 
finalizes as part of this rulemaking, the EPA proposes to require 
states to submit sufficient information to demonstrate that they have 
complied with applicable requirements and commitments in the applicable 
implementation plan. This information would be needed in order for the 
EPA to make a decision on whether to grant a 1-year attainment date 
extension. The EPA would not be authorized to grant an attainment date 
extension to an area unless the state can demonstrate that it has met 
all of the requirements and commitments contained in the state's 
applicable implementation plan for the area. Under the EPA's first 
proposed approach for interpreting section 188(d)(1), a state would 
have to demonstrate that control measures have been submitted in the 
form of a SIP revision and that RACM and RACT and additional reasonable 
measures for sources in the area have been implemented. Under the 
agency's alternative proposal for interpreting section 188(b)(1), the 
attainment plan submitted by the state would have to have been fully 
approved by the EPA and the state would have to be in compliance with 
any elements required under any applicable FIP for the area. In 
addition, under the EPA's second proposed approach, the state would 
have to demonstrate that: (i) RACM and RACT and additional reasonable 
measures for sources in the area have been implemented, and (ii) the 
area has made emissions reductions progress that represents RFP toward 
attainment of the NAAQS and has met its quantitative milestones, and 
the state has submitted a milestone compliance demonstration (milestone 
report) to that effect if due. Any decision made by the EPA to extend 
the attainment date for an area would be based on facts specific to the 
nonattainment area at issue.
    Section 188(d) does not specify the process by which the EPA should 
evaluate and act upon requests from states for an extension of the 
Moderate area attainment date. However, the EPA proposes that an 
attainment date extension would only be granted after the agency 
provides notice in the Federal Register and an opportunity for the 
public to comment. This notice-and-comment process would allow for 
appropriate evaluation of the relevant criteria and facts in order to 
assure that the extension is granted or denied after full evaluation. 
This process also is consistent with past practice by the EPA in 
granting attainment date extensions, most recently for ozone 
nonattainment areas. In addition, for ease of implementation, the EPA 
proposes to interpret section 188(d) to authorize the EPA to stipulate 
that any extension would begin on January 1 and end on December 31 of 
the extension year and these dates would not depend on when the state 
submitted its request for an extension or was granted the extension by 
the EPA. The EPA believes this is a reasonable approach as the 
applicable attainment date for the area will either be the end of the 
sixth calendar year following designation of the area, or the end of an 
earlier calendar year if the state could advance attainment of the area 
by at least 1 year through the implementation of extra control 
measures. In addition, compliance with the relevant NAAQS will be 
evaluated based on monitored data collected over a full calendar year 
(i.e., over the period beginning January 1 and ending December 31), so 
starting the extension year on January 1 is logical.
    Because air quality criteria are part of the conditions that must 
be met in order for the EPA to grant a Moderate area attainment date 
extension, the EPA proposes to require that a state seeking such an 
extension must submit its complete attainment date extension request, 
including any available preliminary data for the year preceding the 
area's applicable Moderate attainment date, on or before the area's 
attainment date. The EPA also proposes to require that the state 
requesting such an extension must submit to the respective EPA Regional 
Office certified ambient PM2.5 monitoring data for the year 
preceding the attainment date for the area in question by no later than 
February 28 of the year following the area's attainment date. 
Submission of the necessary data by this date will allow the EPA to 
review the state's request and take appropriate action on the request 
prior to the date by which the EPA is required to make a determination 
that the area failed to attain by its Moderate area attainment date, 
i.e., within 6 months of the applicable attainment date (see the 
discussion of reclassification in Section V of this preamble). The EPA 
seeks comment on these proposed deadlines for a state to request an 
extension of a Moderate area's attainment date and submit certified air 
quality data as required under CAA section 188(d)(2).

[[Page 15399]]

    As noted earlier in this discussion of Moderate area attainment 
date extensions, the statute at section 188(d) provides that a state 
may seek up to two 1-year extensions of the Moderate area attainment 
date if it meets the applicable criteria of sections 188(d)(1) and 
188(d)(2). The statute makes no distinction between the criteria that 
must be met for the first 1-year extension and the criteria for the 
second 1-year extension, therefore the EPA plans to apply the same 
interpretations of the statutory criteria proposed throughout this 
section, including the proposed deadlines for the state to submit the 
extension request and the certified air quality data, for purposes of a 
state seeking a second 1-year attainment date extension for a Moderate 
nonattainment area.
    The EPA seeks comment on the proposed approaches described above 
for interpreting the criteria of section 188(d)(1) and 188(d)(2) and 
establishing a process for states to request attainment date extensions 
for Moderate areas.

V. How would a PM2.5 Moderate nonattainment area be 
reclassified to Serious?

    As discussed elsewhere in this preamble, subpart 4, part D of title 
I of the CAA establishes a two-tier classification system for areas 
designated nonattainment for the PM2.5 NAAQS. While all 
areas designated nonattainment are initially classified as Moderate, 
section 188(b) describes two pathways by which the EPA has the 
authority or the duty to reclassify a Moderate nonattainment area to a 
Serious nonattainment area. Pursuant to section 188 (b)(1), the EPA has 
general discretionary authority to reclassify from Moderate to Serious 
any area that the Administrator determines cannot practicably attain 
the NAAQS by the applicable Moderate area attainment date. Pursuant to 
section 188(b)(2), the EPA has a mandatory duty to reclassify from 
Moderate to Serious any area that fails to attain the NAAQS by the 
applicable Moderate area attainment date. Both of these pathways are 
more fully described below.

A. Discretionary Authority

    The EPA's discretionary authority to reclassify a Moderate area to 
Serious derives from language in section 188(b)(1) of the CAA which 
provides that: ``The Administrator may reclassify as a Serious 
PM10 nonattainment area . . . any area that the 
Administrator determines cannot practicably attain the [NAAQS] . . . by 
the attainment date . . . for Moderate Areas.'' The use of this 
discretionary authority thus would be triggered by the EPA making a 
determination that the Moderate area in question could not practicably 
attain by its statutory attainment date.
    The CAA does not specify the basis on which the EPA may make the 
determination that the area cannot practicably attain by the applicable 
attainment date. In the General Preamble, the EPA explained that the 
agency could base this determination upon whatever factors are 
pertinent and do so whether or not the state in question has submitted 
a Moderate area attainment plan, and whether or not the state has made 
the demonstration contemplated in section 189(a)(1)(B).\157\ The EPA 
may make such a determination based on evaluation of the attainment 
plan for the Moderate area in question or other facts known to the 
agency. As discussed earlier in this preamble, the attainment plan that 
a state would submit for a Moderate nonattainment area must include 
either a demonstration that the area will attain the NAAQS by the 
statutory Moderate area attainment date or a demonstration that 
attaining by the statutory Moderate area attainment date is 
impracticable. If the state makes and the EPA concurs with an 
impracticability demonstration submitted as part of the attainment 
plan, then the demonstration could serve as the basis for the EPA 
initiating a notice-and-comment rulemaking to reclassify the area to 
Serious. However, the CAA does not specify the basis for the EPA's 
exercise of its discretionary authority and does not require the EPA to 
make its determination based on a submission from the state. Indeed, 
such a prerequisite would be illogical in the case of a state that 
fails to make any attainment plan submission or fails to address the 
issue of the need for reclassification in such submission.
---------------------------------------------------------------------------

    \157\ See the Federal Register published on April 16, 1994 (57 
FR 13498, 13537 and 13538).
---------------------------------------------------------------------------

    Section 188(b)(1)(B) does establish mandatory timeframes by which 
EPA must act if it intends to exercise its discretionary authority to 
reclassify areas as appropriate following the Moderate area attainment 
plan due date, stating that ``the Administrator shall reclassify 
appropriate areas within 18 months after the required date for the 
state's submission of a SIP for the Moderate Area.'' In the case of 
areas designated nonattainment for the 2012 PM2.5 NAAQS in 
the first round of designations, states will be required by statute to 
submit a Moderate area attainment plan within 18 months of the date of 
designation (April 2015), or no later than October 2016. Pursuant to 
section 188(b)(1)(B), the EPA would then have until April 2018 (18 
months following the Moderate area attainment plan submission deadline) 
to use its discretionary authority to reclassify any area that the EPA 
determines at that time cannot practicably attain by the Moderate area 
attainment date of December 2021.
    As noted above, the EPA believes that while a Moderate area 
impracticability demonstration as contemplated in section 189(a)(1)(B) 
is desirable in order to help the agency make a determination that the 
area cannot practicably attain by its attainment date, such a 
demonstration is not necessary to trigger action by the EPA to 
reclassify a Moderate area to Serious. The statute does not prohibit 
the EPA from using the weight of available evidence, including 
information available in the public record of a state, to make such a 
determination, even in the absence of a complete attainment plan 
submission. Thus, the EPA expressed in the General Preamble that:

. . . under the plain meaning of the terms of section 188(b)(1) EPA 
has general discretion to reclassify at any time before the 
applicable attainment date any area EPA determines cannot 
practically attain the standards by such date. Accordingly, CAA 
section 188(b)(1) is a general expression of delegated rulemaking 
authority. In addition, subparagraphs (A) and (B) of CAA section 
188(b)(1) mandate that the EPA reclassify at specified timeframes 
any areas it determines appropriate for reclassification at those 
dates. These subparagraphs do not restrict the general authority but 
simply specify that, at a minimum, it must be exercised at certain 
times.\158\
---------------------------------------------------------------------------

    \158\ Ibid. at 13537.

The EPA continues to consider this the correct interpretation of the 
statutory requirements concerning its authority to reclassify a 
Moderate nonattainment area to Serious at any time prior to the area's 
Moderate area attainment date, if the agency determines that the area 
cannot practicably attain the relevant PM2.5 NAAQS by that 
date.
    The EPA emphasizes that states with an area designated as 
nonattainment for the PM2.5 NAAQS are required to meet all 
Moderate area attainment plan requirements, even after the EPA 
reclassifies the area to Serious. Section 189(b)(1) states clearly that 
``in addition to'' the Moderate area attainment plan requirements, 
states with areas reclassified to Serious must also meet Serious area 
attainment plan requirements, i.e., the reclassification does not 
eliminate the statutory obligation to meet Moderate area

[[Page 15400]]

attainment plan requirements.\159\ Thus, the EPA believes that 
reclassifying Moderate areas to Serious at any time under its 
discretionary authority does not reward areas who delay development and 
implementation of control measures by excusing states from meeting 
substantive Moderate area attainment plan requirements or by extending 
the applicable attainment date. The EPA articulated this position in 
the General Preamble, explaining that this interpretation:
---------------------------------------------------------------------------

    \159\ See, Vigil v. Leavitt, 366 F.3d 1025, amended at 381 F.3d 
826 (9th Cir. 2004).

. . . creates an incentive for the timely submittal and effective 
implementation of moderate area SIP requirements and facilitates the 
PM10 attainment objective. For example, if an area that 
fails to submit a timely moderate area SIP is reclassified, this does 
not obviate the requirement that the area submit and implement RACM 
consistent with the moderate area schedule. Accordingly, the area could 
be subject to sanctions for its delay in submitting the RACM SIP 
requirement . . . Further, reclassification before the applicable 
attainment date will ensure that additional control measures (i.e., in 
addition to RACM, serious areas must implement best available control 
measures (BACM)), are implemented sooner and will expedite the 
application of more stringent new source review requirements to the 
area . . . Similarly, where an area submits a timely moderate area SIP, 
EPA may not discover that the area cannot practicably attain until 
sometime after it begins implementing its moderate area control 
measures. The EPA then may want to reclassify the area in order to 
facilitate the development and implementation of BACM.\160\
---------------------------------------------------------------------------

    \160\ 57 FR 13498 (April 16, 1992), at page 13537.

    The EPA considers this the correct interpretation of the statutory 
requirements and proposes to apply this longstanding interpretation of 
section 188(b)(1) to nonattainment areas for the PM2.5 
NAAQS.

B. Mandatory Duty

    In addition to the EPA's discretionary authority to reclassify a 
Moderate area to Serious under certain circumstances, the CAA also 
directs the EPA to do so under other circumstances. The alternative 
circumstances under which the EPA will reclassify an area from Moderate 
to Serious are if that area fails to attain the relevant NAAQS by the 
applicable Moderate area attainment date, including any extension of 
that date under section 188(d) for which the area qualifies. Under such 
circumstances, the EPA has a mandatory duty to identify any area that 
fails to attain the PM2.5 NAAQS by the applicable Moderate 
area attainment date. Reclassification under such circumstances would 
happen by operation of law when the EPA determines that the area failed 
to attain the NAAQS by the applicable attainment date, in accordance 
with section 188(b)(2)(A). Section 188(b)(2) requires that ``within six 
months following the applicable attainment date for a PM10 
nonattainment area, the Administrator shall determine whether the area 
attained the standard by that date'' and publish its determination in 
the Federal Register. The EPA proposes that the date of 
reclassification for an area reclassified under the EPA's mandatory 
duty to reclassify an area would be the effective date of the Federal 
Register document announcing that the area had not attained the 
relevant PM2.5 NAAQS and is therefore reclassified by 
operation of law. Thus, for example in the case of the 2012 
PM2.5 NAAQS, assuming a Moderate PM2.5 
nonattainment area fails to attain the standard by its approved 
attainment date of December 31, 2021, the EPA would be required to 
publish in the Federal Register no later than June 30, 2022 its 
determination that the area failed to attain the NAAQS and is therefore 
reclassified as Serious by operation of law. The date of 
reclassification for the area would be the effective date of the 
Federal Register document, or sometime after June 30, 2022. To meet the 
requirements of section 189(b)(2), the Serious area attainment plan for 
the area would be due within 18 months thereafter, or no later than 
December 2023.
    An alternative approach for setting the date of reclassification 
for an area reclassified to Serious under the EPA's mandatory authority 
could be to make it the same date as the missed attainment date for the 
area. Applying this approach in the example above would yield an 
earlier date of reclassification of December 31, 2021, and an earlier 
Serious area attainment plan due date of June 30, 2023.
    Although section 188(b)(2) does not explicitly address this issue, 
the EPA believes that its proposed approach is a reasonable 
interpretation of statutory ambiguity in section 188(b)(2) and 
preferable over the alternative approach for two reasons. First, the 
statute at section 189(b)(2) gives a state 18 months from the date of 
reclassification of an area to submit for the EPA's approval an 
attainment demonstration with air quality modeling and provisions to 
assure timely implementation of BACM and BACT on sources in the 
nonattainment area. The EPA believes that it is reasonable for a state 
with a Serious PM2.5 nonattainment area to have 18 months 
plus the additional time needed by the EPA to issue a Federal Register 
document announcing the area's failure to attain by the applicable 
Moderate area attainment date and subsequent reclassification (up to 6 
additional months) to ensure that the state has time to develop and 
submit a thorough, complete and accurate Serious area attainment plan 
that will provide for timely attainment of the NAAQS. Second, the 
statutory attainment date for a Serious area reclassified under any 
circumstances is as expeditious as practicable but no later than the 
end of the tenth year following designation of the area, and is thus 
independent of the date of reclassification of the area. Allowing a 
state some additional amount of time beyond 18 months from the missed 
attainment date to develop and submit a complete Serious area 
attainment plan, including adopting BACM and BACT, will not change the 
statutory obligation on the state for the area to attain the relevant 
NAAQS by the applicable attainment date. On the contrary, the EPA 
believes that the extra time may in fact help the area timely attain 
the relevant NAAQS by allowing the state to develop a more effective 
attainment plan for the area.
    The EPA seeks comment on its proposed approach of basing the date 
of reclassification for an area reclassified under the agency's 
mandatory duty in section 188(b)(2) on the effective date for the 
Federal Register document in which the EPA announces that the area 
failed to attain the PM2.5 NAAQS by the applicable Moderate 
area attainment date and is reclassified by operation of law. The EPA 
intends to make determinations of whether or not an area attained the 
relevant NAAQS pursuant to section 188(b)(2) via notice-and-comment 
rulemaking.

VI. What are the EPA's proposed requirements for Serious area 
attainment plans?

    Sections 189(b) and (c) of the CAA include the following 
requirements for Serious area attainment plan submissions: (i) An 
attainment demonstration (section 189(b)(1)(A)); (ii) provisions for 
the implementation of best available control measures (BACM) no later 
than 4 years after reclassification of the area to Serious (section 
189(b)(1)(B)); (iii) quantitative milestones that will be used to 
evaluate compliance with the requirement to

[[Page 15401]]

demonstrate RFP (section 189(c)); and, (iv) regulation of 
PM2.5 precursors (in general to meet attainment and control 
strategy requirements and as specifically required for major stationary 
sources by section 189(e)). Other subpart 1 requirements for attainment 
plans not otherwise superseded under subpart 4 also apply to Serious 
areas for the PM2.5 NAAQS, including: (i) A description of 
the expected annual incremental reductions in emissions that will 
demonstrate RFP (section 172(c)(2)); (ii) emissions inventories 
(section 172(c)(3)); (iii) other control measures (besides BACM and 
BACT) needed for attainment (section 172(c)(6)); and, (iv) contingency 
measures (section 172(c)(9)).
    Additionally, section 189(b)(1) requires that ``in addition'' to 
the attainment plan requirements specific to Serious areas, states must 
also meet all Moderate area attainment plan requirements. The EPA 
interprets the statutory language of section 189(b)(1) to require 
states with areas that are reclassified to Serious to meet Moderate 
area attainment plan requirements, including any areas that the EPA 
reclassifies through rulemaking under its discretionary authority, even 
if that occurs before the area has met all of its Moderate area 
attainment plan requirements.\161\
---------------------------------------------------------------------------

    \161\ See Vigil v. Leavitt, 366 F.3d 1025, amended at 381 F.3d 
826 (9th Cir. 2004).
---------------------------------------------------------------------------

    The remainder of this section presents the EPA's proposed 
regulatory approaches to implement the requirements for attainment plan 
submissions for Serious areas.

A. Plan Due Dates

    The timing of Serious area attainment plan elements is dictated by 
two provisions of the CAA: Section 189(b)(2) for certain subpart 4 
elements and section 172(b) for subpart 1 elements not superseded by 
subpart 4 requirements. Section 189(b)(2) addresses the due dates for 
Serious area attainment demonstrations due under section 189(b)(1)(A) 
and provisions for BACM and BACT implementation under section 
189(b)(1)(B). Specifically, section 189(b)(2) stipulates two 
alternative schedules for states to submit Serious area attainment 
demonstrations, depending upon the statutory authority invoked by the 
EPA to reclassify the area from Moderate to Serious. For an area 
reclassified to Serious by operation of law under section 188(b)(2) 
upon a determination by the EPA that the area failed to attain the 
relevant NAAQS by the applicable Moderate area attainment date, a state 
must submit a new attainment demonstration for the area no later than 
18 months after reclassification. For an area reclassified to Serious 
pursuant to the agency's discretionary authority provided under section 
188(b)(1), a state must submit a new attainment demonstration no later 
than 4 years after reclassification of the area.\162\ For all Serious 
nonattainment areas, section 189(b)(2) requires a state to submit 
within 18 months of an area's reclassification ``provisions to assure 
that the best available control measures [BACM] for the control of 
PM10 shall be implemented no later than 4 years after the 
date the area is classified (or reclassified) as a Serious Area.''
---------------------------------------------------------------------------

    \162\ Section V of this preamble provides a more detailed 
discussion of the process for reclassifying areas with severe 
nonattainment problems to Serious.
---------------------------------------------------------------------------

    In contrast, section 172(b) provides the EPA discretion to set a 
due date for subpart 1 attainment plan elements that is no later than 3 
years after designation of the area. In the Addendum, the EPA 
interpreted the date of reclassification of an area to Serious to be 
analogous to the date of designation of the area to nonattainment 
generally.\163\ If the EPA selects the proposed option, discussed later 
in this section, to adopt this convention, the subpart 1 attainment 
plan elements of provisions to demonstrate RFP, emissions inventories, 
additional control measures beyond BACM and BACT needed for expeditious 
attainment of the PM2.5 NAAQS, and contingency measures 
could in theory be due as late as 3 years after reclassification of an 
area to Serious. For the reasons discussed below, the EPA believes that 
it is necessary to harmonize the submission dates of the various 
elements of a Serious are attainment plan for the PM2.5 
NAAQS to provide for more effective evaluation of such attainment plan 
submissions by states, the EPA and members of the general public.
---------------------------------------------------------------------------

    \163\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42015.
---------------------------------------------------------------------------

    As with Moderate area attainment plans consisting of both subpart 1 
and 4 elements, the EPA presumes that simultaneous development and 
submission of most, if not all, of the Serious area attainment plan 
elements will be most effective, both for the state in developing the 
plan and for the EPA in reviewing the state's submission, given the 
interplay between all plan elements in the formation of a successful 
control strategy for the area. Just as importantly, a complete 
attainment plan submission facilitates the general public's review of 
the entire control strategy adopted by the state. Therefore where there 
is ambiguity in the statutory provisions, the EPA is proposing one or 
more approaches to schedule submission of the various elements of 
Serious area attainment plans in a way that will facilitate better 
development and evaluation of such attainment plan submissions. The 
EPA's proposed options for due dates for specific elements of a Serious 
area attainment plan are described below.
1. Area Reclassified to Serious After Failing To Attain the 
PM2.5 NAAQS
    If the EPA reclassifies a Moderate area to Serious because of a 
failure to attain the relevant NAAQS by the applicable attainment date, 
section 189(b)(2) requires that the state must submit both the 
attainment demonstration for the area and provisions to ensure timely 
BACM and BACT implementation to the EPA within 18 months after 
reclassification. Because an up-to-date base year emissions inventory, 
required under section 172(c)(3), will serve as the foundation of a 
state's BACM and BACT determination, and additional control measures 
(beyond BACM and BACT) that are necessary for expeditious attainment of 
the PM2.5 NAAQS as required under section 172(c)(6) will 
need to be identified in order to complete the control strategy for the 
area, the EPA proposes that both the base year inventory and additional 
control measures (beyond BACM and BACT) needed for expeditious 
attainment must also be submitted within 18 months after 
reclassification of the area to Serious by operation of law.
    The EPA also proposes and seeks comment on two possible due dates 
for the remaining Serious area attainment plan elements for areas that 
failed to attain the NAAQS by the applicable Moderate area attainment 
date. Those plan elements are provisions for RFP, quantitative 
milestones and contingency measures. The first proposed due date for 
these remaining Serious area attainment plan elements would be no later 
than 18 months after reclassification of the area, consistent with the 
due date for the plan elements already described above. As noted above, 
the EPA maintains that requiring states to submit all elements of an 
attainment plan by the same date is reasonable because it allows for a 
complete review of the state submission by the EPA, regulated entities, 
and the general public, and it also may prove most efficient for 
states. See proposed 40 CFR 51.1003(b)(2)(ii).
    The alternate proposed due date for the remaining elements would be 
3 years following reclassification to

[[Page 15402]]

Serious, which would be consistent with guidance the EPA provided in 
the Addendum specific to the due date for contingency measures for 
Serious areas.\164\ This guidance references the EPA's discretion under 
section 172(b) to establish due dates up to 3 years after designation 
for attainment plan elements required under section 172(c), which also 
include RFP provisions. Subpart 4 meanwhile requires quantitative 
milestones to demonstrate RFP but does not specify a due date for 
submitting such milestones as part of the attainment plan for the area 
(as separate and distinct from the clear statutory requirements related 
to demonstrating compliance with those milestones established in the 
attainment plan). When taken together, the EPA believes that these 
statutory provisions may be read to permit a state to submit these 
three elements of the plan as late as 3 years after reclassification of 
the area. While the EPA does not believe that such a reading is as 
logical as the agency's first proposed approach, the EPA seeks comment 
on this alternative proposed approach to setting due dates for a state 
to submit an RFP plan, quantitative milestones and contingency measures 
for a Serious area reclassified under the EPA's mandatory authority.
---------------------------------------------------------------------------

    \164\ Ibid. at 42015.
---------------------------------------------------------------------------

2. Area Reclassified to Serious Due to an Inability To Practicably 
Attain the NAAQS by the Statutory Moderate Area Attainment Date
    If the EPA determines that a Moderate area cannot practicably 
attain the relevant NAAQS by the applicable attainment date and 
reclassifies the area to Serious pursuant to its discretionary 
authority under section 188(b)(1), section 189(b)(2) requires the state 
to submit provisions to ensure timely implementation of BACM and BACT 
to the EPA within 18 months after reclassification. As stated earlier, 
because an up-to-date emissions inventory serves as the foundation for 
a state's BACM and BACT determination and pursuant to the authority 
granted to the EPA under section 172(b), the EPA proposes that the 
state must meet the emissions inventory requirement under section 
172(c)(3) also within 18 months after reclassification of the area by 
submission of an up-to-date emissions inventory.
    With respect to the attainment demonstration requirement for 
Serious areas reclassified pursuant to section 188(b)(1), section 
189(b)(2) allows the state up to 4 years after reclassification to 
submit a new attainment demonstration for an area reclassified to 
Serious because it cannot practicably attain the PM2.5 NAAQS 
by the applicable Moderate area attainment date. This due date could 
generally be appropriate, notwithstanding the related issues discussed 
in the following paragraphs, if the EPA finalizes an approach for 
determining the overall control strategy for the area in which BACM and 
BACT are identified independent of the attainment demonstration for the 
area (see proposed Option 1 for BACM and BACT determinations described 
in Section VI.D of this preamble).
    However, the EPA is also proposing an alternative approach for 
determining the control strategy for a Serious area, under which BACM 
and BACT and additional feasible measures would be identified in 
conjunction with the attainment demonstration for the area (see 
proposed Option 2 for BACM and BACT determinations described in Section 
VI.D of this preamble). Under such an approach, the EPA proposes that 
the due date for the Serious area attainment demonstration would be no 
later than 18 months after reclassification if the EPA finalizes its 
proposed Option 2 for determining BACM and BACT for the area, as the 
attainment demonstration would be necessary in order for the EPA and 
the public to determine whether the control strategy identified for the 
area is adequate, and the statute requires that a state submit its BACM 
provisions within 18 months after reclassification of an area.
    With respect to other elements of a Serious area attainment plan, 
under the EPA's prior interpretation as described in the Addendum, the 
EPA had suggested that states could submit contingency measures no 
later than 3 years after reclassification of an area to Serious because 
of the language of section 172(b).\165\ The EPA believes it may be 
appropriate to extend a similar approach to establishing due dates for 
some other attainment plan elements required under subpart 1. 
Therefore, the EPA proposes to provide a state with the maximum time 
permitted under section 172(b)--3 years from the date of 
reclassification of the area--to submit the following plan elements: 
Provisions to demonstrate RFP, other control measures (beyond BACM and 
BACT) needed to bring the area into expeditious attainment, and 
contingency measures. The EPA proposes that quantitative milestones, 
required under subpart 4 but linked to RFP which is required under 
subpart 1, would also be included with the plan elements due 3 years 
following reclassification.
---------------------------------------------------------------------------

    \165\ Ibid. at 42015.
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    The EPA believes that this proposed due date for certain attainment 
plan elements required under subparts 1 and 4 would be most appropriate 
if finalized in conjunction with proposed Option 2 for BACM and BACT, 
which would require the state to submit the attainment demonstration 
for the area within 18 months after reclassification of the area to 
Serious. However, in the event the EPA finalizes proposed Option 1 for 
determining BACM and BACT for a Serious nonattainment area independent 
of the attainment demonstration for the area, the attainment 
demonstration for the area would be due no later than 4 years after the 
date of reclassification of the area to Serious. Given the integral 
role that the attainment demonstration plays in helping to identify 
additional feasible measures (beyond BACM and BACT) that an area may 
need to attain the relevant standard expeditiously (and which are 
required under section 172(c)(6)), to calculate emissions reductions 
needed on an annual basis to demonstrate RFP, and to calculate the 
emissions reductions that contingency measures need to achieve and 
identify what controls could constitute such measures, the EPA is 
proposing and seeking comment on an alternative submittal deadline for 
provisions for RFP and quantitative milestones, additional control 
measures needed for expeditious attainment, and contingency measures 
that would align their due date with the statutory Serious area 
attainment demonstration due date, no later than 4 years from the date 
of reclassification. See proposed 40 CFR 51.1003(b)(2)(i). The EPA 
believes that coordinating submission of attainment plan elements so 
that they may be developed and reviewed together can prove most 
efficient for the submitting state, the EPA, and the general public, 
and therefore this proposed alternative is the agency's preferred 
approach. However, the EPA seeks comment on all of its proposed due 
date options for the various elements of a Serious area attainment 
plan.

B. Emissions Inventory Requirements

1. What emissions inventory requirements apply to Serious area 
attainment plans?
    As with PM2.5 nonattainment areas classified as 
Moderate, Congress did not create a specific emissions inventory 
requirement in subpart 4 that would supersede the emissions inventory 
requirement under subpart 1 for Serious areas. Thus, the statutory 
emissions

[[Page 15403]]

inventory requirements that apply for Serious area attainment plans 
continue to be those of section 172(c)(3), which explicitly requires 
``a comprehensive, accurate, and current inventory of actual emissions 
of the relevant pollutants'' in the nonattainment area. In addition, 
the specific attainment plan requirements for the PM2.5 
NAAQS set forth in section 189(a) and associated modeling requirements 
make an accurate and up-to-date emissions inventory a critical element 
of any viable attainment plan. Finally, the additional attainment plan 
requirements for the PM2.5 NAAQS for Serious areas contained 
in subpart 4 at section 189(b) have additional requirements that affect 
the emissions inventory requirements for Serious areas.\166\
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    \166\ All definitions described in Section IV.B of this preamble 
for areas classified as Moderate apply in this section.
---------------------------------------------------------------------------

    As noted earlier in this preamble, states must use the best 
available, current emissions inventory information for attainment plan 
development, because complete, high quality emissions inventory data 
are essential for the development of an effective control strategy. To 
assist states in preparing complete, high quality inventories, the EPA 
provides guidance for developing emissions inventories in its SIP 
Emissions Inventory Guidance, available at http://www.epa.gov/ttn/chief/eidocs/eiguid/index.html. The EPA recommends that states consult 
this guidance while developing emissions inventories to meet 
requirements for Serious area attainment plans.
2. How do states meet the inventory requirements for the 
PM2.5 NAAQS for areas classified as Serious?
    As with Moderate PM2.5 nonattainment areas, neither 
section 172(c)(3) nor the provisions specifically applicable to 
attainment plans for the PM2.5 NAAQS in subpart 4 specify 
how states should meet statutory emissions inventory requirements for 
Serious PM2.5 nonattainment areas. Section 172(c)(3) 
requires that states submit ``a comprehensive, accurate, current 
inventory of actual emissions from all sources of the relevant 
pollutant or pollutants in such area, including such periodic revisions 
as the Administrator may determine necessary to assure that the 
requirements of this part are met'' (emphasis added). The EPA 
interprets this provision to authorize the agency to require states to 
revise their base year emissions inventories whenever the state is 
required to submit a new attainment plan because of a change in the 
nonattainment area's status (e.g. failure to attain by the applicable 
attainment date resulting in reclassification). In addition, pursuant 
to CAA section 301, the EPA has additional authority to promulgate 
regulations as necessary for the implementation of the PM2.5 
NAAQS, including requirements pertaining to emissions inventories. 
Accordingly, the EPA is proposing specific emissions inventory 
requirements it considers necessary to effectuate the attainment plan 
requirements of the CAA for the PM2.5 NAAQS.
    Like Moderate areas, there are three key facets of the EPA's 
proposed emissions inventory requirements, as laid out below: (i) The 
types of inventories required; (ii) the content of these inventories; 
and, (iii) the timing of submittal of these inventories. The three 
facets are addressed in the following paragraphs.
    First, the EPA proposes that the same two types of inventories 
required for Moderate areas are also required for Serious areas. While 
these inventories are the same types and names of inventories as for 
Moderate areas, they must be created specifically for Serious area 
attainment plans in accordance with the applicable Serious area 
requirements. The first type of inventory, the ``base year inventory 
for the nonattainment area,'' is expressly required by section 
172(c)(3). The second type of inventory the EPA is proposing to require 
under section 301(a)(1) is necessary to implement the attainment 
demonstration requirement of section 189(a)(1)(B). This second 
inventory is called the ``attainment projected inventory for the 
nonattainment area.'' See proposed 40 CFR 51.1008(b)(1) and (2).
    Second, the EPA proposes that the content of the inventories will 
follow the content requirements for Moderate area inventories, with one 
exception needed to meet the requirements of section 189(b)(3). For 
Serious areas, section 189(b)(3) defines a separate emissions threshold 
for major sources in Serious nonattainment areas (70 tpy potential to 
emit of PM10), and this major source threshold is used in 40 
CFR part 51, subpart A (the AERR) to define which sources must be 
reported as point sources for PM10. This threshold is lower 
than the 100 tpy potential to emit general requirement for major 
sources of PM10, PM2.5 or one of its precursors 
that is used for Moderate area emissions inventories. Inventories for 
Serious area attainment plans must include these smaller sources as 
point sources (rather than the nonpoint source category that would 
apply for these in Moderate area plans) using the lower threshold 
specified in the CAA and codified in 40 CFR part 51, subpart A. Also as 
described above and in 40 CFR part 51, subpart A, this means that all 
other smaller stationary sources must be included in the inventory as 
nonpoint sources.
    Third, Section VI.A of this preamble describes the EPA's proposal 
to require that a state submit the base year inventory for a Serious 
nonattainment area at the same time that it submits provisions to 
implement BACM and BACT on sources in the area (due no later than 18 
months from reclassification of the area pursuant to section 189(b)(2)) 
as the base year inventory serves as the starting point for conducting 
a BACM and BACT determination. On the other hand, because the 
attainment projected inventory is more closely related to the Serious 
area attainment demonstration, the EPA believes that a state should be 
required to submit its attainment projected inventory with the 
attainment demonstration for a given Serious area in order to allow 
effective evaluation of the attainment plan as a whole. Consequently, 
the EPA is proposing to establish the regulatory requirement that 
attainment projected emissions inventories be submitted at the same 
time as the Serious area attainment demonstration, which would mean no 
later than 18 months after reclassification for areas reclassified 
after failing to attain the NAAQS by the applicable Moderate area 
attainment date, or no later than 4 years after reclassification for 
areas reclassified by the EPA because the area cannot practicably 
attain the NAAQS by the statutory attainment date if the EPA finalizes 
proposed Option 1 for determining BACM and BACT for area. See proposed 
40 CFR 51.1008(b)(3) and (4). If the EPA finalizes an approach for 
determining BACM and BACT that links the control strategy analysis to 
the attainment demonstration, then the attainment demonstration 
including the attainment projected emissions inventory would be due no 
later than 18 months after reclassification (i.e., at the same time 
BACM provisions are due under the statute).
    The EPA seeks comment on these proposed requirements and due dates 
for emissions inventories for Serious area attainment plans.

C. Pollutants To Be Addressed in the Plan

    Section III of this preamble includes a detailed discussion about 
how states should address PM2.5 precursors in attainment 
plans and in the NNSR

[[Page 15404]]

program for purposes of implementing current and future 
PM2.5 NAAQS. While evaluating sources of direct 
PM2.5 for BACM and BACT is an implicit requirement in the 
context of implementing the PM2.5 NAAQS under any scenario, 
the EPA is proposing and seeking comment on several options for 
addressing PM2.5 precursors under the PM2.5 NAAQS 
implementation program. The EPA interprets the requirements of the CAA 
to allow an air agency to provide a ``precursor demonstration'' that 
can seek to make a technical case to the EPA that one or more 
PM2.5 precursors need not be subject to control requirements 
in a given nonattainment area, whether from sources in general or from 
major stationary sources. Section III presented three options 
describing different proposed approaches to such precursor 
demonstrations, and requested comment on each. The discussion for each 
option described how precursors would be addressed for Moderate areas 
and for Serious areas.
    In general terms, the three options can be summarized as follows:
     Option 1: Two independent analyses: (a) An attainment 
planning analysis demonstrating that control measures for a particular 
precursor are not needed for expeditious attainment, meaning that the 
precursor can be excluded from measures needed to attain as 
expeditiously as practicable for all types of sources; and, (b) a 
section 189(e) technical demonstration showing that major stationary 
sources of a particular precursor do not contribute significantly to 
levels that exceed the PM2.5 standard, meaning that the 
precursor can be excluded from control requirements for major sources 
and from NNSR permitting. For an area reclassified to Serious, the 
state would once again need to evaluate potential control measures for 
all sources of direct PM2.5 and all PM2.5 
precursor emissions as part of the control strategy determination 
process (described more fully in Section VI.D of this preamble).
     Option 2: Single analysis demonstrating that all emissions 
of a particular precursor from within the area do not significantly 
contribute to PM2.5 levels that exceed the standard, meaning 
that control requirements for emissions of the precursor from major 
stationary and area sources, as well as mobile sources, would not be 
required for expeditious attainment, control requirements for major 
sources, or for NNSR permitting. For an area reclassified to Serious 
for which a precursor had previously been demonstrated to not 
significantly contribute to PM2.5 levels that exceed the 
standard, the air agency would be required to update the precursor 
demonstration taking into account any relevant information or technical 
tools that had been developed since the initial demonstration was 
approved, but could still conclude that control requirements are not 
required for Serious area attainment planning if the updated 
demonstration still shows that all source emissions of a precursor do 
not significantly contribute to PM2.5 levels that exceed the 
standard.
     Option 3: An attainment planning analysis demonstrating 
that control measures for all types of sources of a particular 
precursor are not needed for expeditious attainment also would be 
deemed to meet the section 189(e) technical demonstration requirement, 
meaning that the state would not need to regulate emissions of the 
particular precursor from major stationary sources under the NNSR 
permitting program or other control requirements for major stationary 
sources. As under proposed precursor Option 1, for an area reclassified 
to Serious, the state would once again need to evaluate potential 
control measures for all sources of direct PM2.5 and all 
PM2.5 precursor emissions as part of the control strategy 
determination process (see Section VI.D of this preamble).
    The EPA will finalize its approach to PM2.5 precursors 
and clarify the implications for states conducting analyses to 
determine the appropriate control strategy for a Serious area after 
considering public comment received on this proposal.

D. Attainment Plan Control Strategy

1. General Approach To Designing a Control Strategy for a Serious 
Nonattainment Area
    As noted in Section IV.D of this preamble, the statutory attainment 
planning requirements of subparts 1 and 4 were established to ensure 
that states meet the following goals of the CAA: (i) Implement measures 
that provide for attainment of the PM2.5 NAAQS as 
expeditiously as practicable, and (ii) adopt emission reduction 
strategies that will be the most effective, and the most cost 
effective, at reducing PM2.5 levels in nonattainment areas. 
A state has discretion to require reductions from any source inside or 
outside of a PM2.5 nonattainment area (but within the 
state's boundaries) in order to fulfill its obligation to demonstrate 
attainment in a PM2.5 nonattainment area as expeditiously as 
practicable, in addition to having an obligation to meet the statutory 
requirements for specific control measures on sources located within a 
nonattainment area (e.g., BACM and BACT). A state may need to require 
emissions reductions on sources located outside of a PM2.5 
nonattainment area if such reductions are needed in order to provide 
for expeditious attainment of the PM2.5 NAAQS.
    The following sections describe the EPA's proposed approach for a 
state to follow in order to identify and select the complete suite of 
measures needed for an approvable attainment plan submission for a 
Serious PM2.5 nonattainment area.
2. Identification and Selection of BACM and BACT and Additional 
Feasible Measures
    a. Statutory requirements and existing guidance. As discussed 
earlier, a state must prepare a new attainment plan for any Moderate 
area reclassified to Serious. Such a plan must include provisions to 
implement BACM on sources in a Serious nonattainment area, as provided 
by section 189(b)(1)(B), no later than 4 years after reclassification. 
Under section 189(b)(2), a state has 18 months following 
reclassification to submit these BACM provisions.
    Section 189(b)(1)(B) refers only to BACM, but the EPA has long 
interpreted this term to include BACT, just as the analogous term for 
RACM includes RACT for Moderate areas. The legislative history for the 
1990 Amendments to the CAA supports this interpretation, as the EPA has 
explained in past guidance.\167\ Additionally, the requirement for BACT 
in the context of PM2.5 NAAQS implementation in 
nonattainment areas is separate and distinct from the requirement for 
BACT under the Prevention of Significant Deterioration (PSD) permitting 
program for new stationary sources in areas designated as attainment or 
unclassifiable for the PM2.5 NAAQS. As described later in 
this section, the process and criteria that states have historically 
used to determine BACT for PSD have been applied to determine BACT for 
PM10 NAAQS implementation, but these requirements are 
otherwise unrelated.
---------------------------------------------------------------------------

    \167\ Ibid. at 42008-09.
---------------------------------------------------------------------------

    Longstanding guidance in the General Preamble and Addendum, 
together with past practice associated with implementing the 
PM10 NAAQS under subpart 4, have helped to establish a 
general approach for states and the EPA to determine BACM and BACT for 
Serious PM10 nonattainment areas. This approach has served 
as the basis for developing a more stringent control strategy for a 
Serious PM10 nonattainment area than that developed

[[Page 15405]]

for such area when it was classified as Moderate. Indeed, as BACM and 
BACT are required to be implemented when a Moderate nonattainment area 
is reclassified as Serious due to its actual or projected inability to 
attain the relevant NAAQS by the Moderate area attainment date through 
the implementation of ``reasonable'' measures, it is logical that 
``best'' control measures should represent a more stringent and 
potentially more costly level of control.\168\ The level of stringency 
generally refers to the overall level of emissions reductions of a 
control measure or technology, or of such measures and technologies 
combined.
---------------------------------------------------------------------------

    \168\ Ibid. at 42009.
---------------------------------------------------------------------------

    Congress first defined BACT in CAA section 169(3) for the PSD 
permitting program as: ``an emission limitation based on the maximum 
degree of reduction of each pollutant . . . which the permitting 
authority, on a case-by-case basis, taking into account energy, 
environmental, and economic impacts and other costs, determines is 
achievable for such facility through application of production 
processes and available methods, systems, and techniques . . .''
    In the Addendum, the EPA provided guidance concerning the 
requirements for BACM and BACT for Serious area attainment plan 
requirements for the PM10 NAAQS.\169\ The EPA discussed in 
the Addendum that when Congress amended the CAA, Congress selected the 
same ``best'' terminology for PM10 nonattainment areas as 
they did for the language selected for the PSD program in 1977. The EPA 
interpreted this word choice at the time to mean that PSD BACT and 
PM10 nonattainment area BACM should be generally analogous 
in definition and implementation, but with some differences due to 
different end policy goals between the PSD and nonattainment area 
programs.\170\ The EPA thus defined BACM for PM10 Serious 
nonattainment area planning to be the maximum degree of emission 
reduction achievable from a source or source category which is 
determined on a case-by-case basis, considering energy, economic and 
environmental impacts and other costs.\171\
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    \169\ Ibid. at 42009.
    \170\ Ibid. at 42010. ``EPA will interpret PSD BACT and PM-10 
BACM as generally similar because, despite the similarity in 
terminology, certain key differences exist between control measures 
applicable in the PSD and PM-10 serious nonattainment area programs. 
The BACT under the PSD program applies only in areas already meeting 
the NAAQS, while PM-10 applies in areas which are seriously 
violating the NAAQS. The difference in policy goals, arguably, 
suggests that the PM-10 BACM control standard should be more 
stringent than that for PSD BACT. . . . EPA considers it reasonable 
to use the approach adopted in the PSD BACT program as defined in 
section 169(3) of the Act as an analogue for determining appropriate 
PM-10 nonattainment control measures in serious areas, while at the 
same time retaining the discretion to depart from that approach on a 
case-by-case basis as particular circumstances warrant.''
    \171\ Ibid.
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    The EPA has described BACM as a generally independent requirement, 
to be determined without regard to the specific attainment analysis 
(i.e., attainment demonstration) for the area.\172\ The EPA established 
that such an interpretation is in accordance with the structural scheme 
of the CAA, which by its definition requires that when an area is 
classified as Serious, BACM are implemented in addition to RACM. 
Because of the two types of measures employed, the EPA found it 
reasonable in the past to interpret the statute as requiring a 
different analysis for determining BACM, i.e., that while RACM has been 
interpreted as those reasonable measures necessary to bring a 
nonattainment area into expeditious attainment, BACM has been 
interpreted as those measures that best control sources' emissions 
without regard to whether such measures are needed for purposes of 
attainment of the relevant NAAQS in the area. The view that BACM and 
BACT measures are generally independent of the attainment needs of the 
area is also consistent with the statutorily specified submission date 
for BACM and BACT control measures, versus the statutorily specified 
submission date for the attainment demonstration for Serious areas. 
Specifically, states with Serious nonattainment areas must submit BACM 
and BACT measures within 18 months of reclassification of areas to 
Serious, whereas they are given up to 4 years from reclassification to 
submit the attainment demonstration for such areas.
---------------------------------------------------------------------------

    \172\ Ibid. at 42011.
---------------------------------------------------------------------------

    In addition, the EPA has historically provided an exemption from 
BACM and BACT for source categories that contribute only de minimis 
levels to ambient PM10 concentrations in a Serious 
nonattainment area. In the Addendum, the EPA proposed that all sources 
in a Serious area are subject to BACM unless ``the state adequately 
demonstrates that a particular source category does not contribute 
significantly to nonattainment of the NAAQS.''\173\ Because the 
language regarding BACM implementation in section 189(b)(1)(B) of the 
CAA requires ``provisions to assure that best available control 
measures (BACM) for the control of PM10 shall be implemented 
. . .'' without stating that ``all'' BACM must be implemented, the EPA 
has interpreted this language as providing the EPA discretion to 
exclude from BACM requirements source categories that do not contribute 
significantly to an area's nonattainment status. Additionally, in the 
Addendum, the EPA argued that based on the decision in Alabama Power 
Co. v. Costle, the courts have supported the interpretation that 
sources that contribute negligibly to an area's nonattainment status 
can be excluded from regulation.\174\ The EPA further indicated that 
the same criteria used in the NSR permitting program at the time to 
determine if a source category contributes significantly to an area's 
nonattainment status should apply, such that a source category would be 
considered a significant contributor to an area's nonattainment status 
if its emission contribution was expected to exceed 5 [micro]g/m\3\ for 
the 24-hour PM10 NAAQS (150 [micro]g/m\3\ at the time), or 1 
[micro]g/m\3\ for the annual PM10 NAAQS (50 [micro]g/m\3\ at 
the time).
---------------------------------------------------------------------------

    \173\ Ibid. at 42011.
    \174\ See Alabama Power Co. v. Costle, 636 F.2d 323, 360-61 
(D.C. Cir. 1979).
---------------------------------------------------------------------------

    A discussion of the EPA's existing process and criteria for 
determining BACM and BACT for Serious PM10 nonattainment 
areas and the agency's proposed options for defining the criteria by 
which a state must determine BACM and BACT and additional feasible 
measures for a Serious PM2.5 nonattainment area are 
presented in the sections that follow.
    In accordance with the PM10 guidance in the Addendum, 
the EPA has applied a four-step process for states to use to identify 
measures that constitute BACM or BACT for sources located in 
PM10 Serious areas. The four-step BACM selection process was 
designed to take into account the local facts and circumstances and the 
nature of the air pollution problem in a given nonattainment area. The 
BACM determination process for PM10 Serious nonattainment 
areas has historically entailed: (i) Developing a comprehensive 
inventory of sources and source categories of directly emitted 
PM10 and PM10 precursors; (ii) evaluating source 
category impact and determining if any source categories are de minimis 
and thus do not need further evaluation for emission controls; (iii) 
evaluating alternative control measures available for significant 
source categories for technological feasibility; and, (iv) evaluating 
costs (i.e., economic feasibility) of the technologically

[[Page 15406]]

feasible control measures.175 176 These steps are described 
more fully below.
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    \175\ For additional information, see ibid. at 42012-13.
    \176\ For examples of how states have applied these steps and 
criteria for Serious PM10 nonattainment areas and how the 
EPA has evaluated them, see generally Approval and Promulgation of 
Implementation Plans for California--San Joaquin Valley PM-10 
Nonattainment Area; Serious Area Plan for Attainment of the 24-Hour 
and Annual PM-10 Standards, 69 FR 5412 (February 4, 2004); Approval 
and Promulgation of Implementation Plans for California--San Joaquin 
Valley PM-10 Nonattainment Area; Serious Area Plan for Attainment of 
the 24-Hour and Annual PM-10 Standards, 69 FR 30006 (May 26, 2004); 
Approval and Promulgation of Implementation Plans for Arizona; 
Maricopa County PM--10 Nonattainment Area; Serious Area Plan for 
Attainment of the 24-Hour and Annual PM-10 Standards, 73 FR 45542 
(August 14, 2008); Approval and Promulgation of Implementation 
Plans; Arizona--Maricopa County PM-10 Nonattainment Area; Serious 
Area Plan for Attainment of the Annual PM-10 Standard, 65 FR 19964 
(April 13, 2000), at page 19972.
---------------------------------------------------------------------------

    Step 1: Inventory sources and precursors. As with any control 
strategy analysis for a nonattainment area, the EPA recommended that a 
state begin with a current emissions inventory as the first step toward 
determining what constitutes BACM or BACT for a particular Serious 
PM10 nonattainment area. The EPA expected that a state would 
start with the base year emissions inventory submitted with the 
Moderate area attainment plan for the area as required under section 
172(c)(3), and update it as necessary to reflect new source 
construction, facility shutdowns, growth in certain source categories, 
and any other relevant changes. The EPA reiterated in the Addendum that 
the emissions inventory for the area must identify both 
nonanthropogenic and anthropogenic emissions sources.\177\
---------------------------------------------------------------------------

    \177\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42012.
---------------------------------------------------------------------------

    Step 2: Evaluate source category impact. The next step in the BACM 
analysis for PM10 Serious areas was for the state to 
identify source categories having significant (i.e., non-de minimis) 
impacts on air quality in the Serious area. The EPA suggested in the 
Addendum that receptor modeling, screening modeling, or refined 
dispersion modeling would likely be necessary to identify key source 
categories, which the state may have performed during the development 
of the Moderate area attainment plan.\178\
---------------------------------------------------------------------------

    \178\ Ibid.
---------------------------------------------------------------------------

    Step 3: Evaluate alternative control techniques. Once the 
significant source categories were identified for a PM10 
Serious nonattainment area, the state was expected to evaluate the 
technological and economic feasibility of control measures ``discussed 
in the BACM guidance documents and other relevant materials for all 
source categories impacting the nonattainment area except those with a 
de minimis impact considering emission reductions achieved with RACM.'' 
\179\ Control measures were supposed to be expanded to include options 
not previously considered RACM as well as consider additional measures 
not previously evaluated in the RACM analysis.
---------------------------------------------------------------------------

    \179\ Ibid. at 42012. At the time of publication of the 
Addendum, the EPA had already issued BACM guidance documents 
pursuant to section 190 for residential wood combustion, prescribed 
burning, and fugitive dust. The agency referred to these documents 
as establishing the control measures that a state should consider, 
at a minimum, as BACM for those PM10 sources in Serious 
PM10 nonattainment areas.
---------------------------------------------------------------------------

    Under the Addendum, the test for determining technological 
feasibility could differ depending on the type of source category 
evaluated. For area sources, the EPA's guidance suggested that 
technological feasibility depended on the ability to alter the 
characteristics that affect emissions from the sources, such as the 
size or extent of the area sources and operation procedures. The EPA's 
guidance suggested that for specific point sources, technological 
feasibility should consider factors such as layout of the plant, space 
available to make changes in the plant, energy requirements, operating 
procedures, and materials used, among others.\180\
---------------------------------------------------------------------------

    \180\ Ibid. at 42013 (discussing in detail factors which affect 
the selection of mobile, area, and point source alternative control 
techniques for particulate matter).
---------------------------------------------------------------------------

    Step 4: Evaluate costs of control. The EPA's previous guidance 
recommended that a control should be considered economically feasible 
by the state when ``the control technology in question has previously 
been implemented at other sources in a similar source category without 
unreasonable economic impacts.'' \181\ Feasibility of public funding 
for BACM could have been a consideration that states evaluated for all 
of the technologically feasible control measures determined in Step 3. 
Other costs that could be considered included capital costs, operating 
and maintenance costs, and the cost effectiveness of a particular 
control measure or technology.\182\
---------------------------------------------------------------------------

    \181\ Ibid. at 42013.
    \182\ EPA Air Pollution Control Cost Manual, Sixth Edition, 
(EPA/452/B-02-001), July 2002 (explaining how to determine costs 
under a BACT analysis).
---------------------------------------------------------------------------

    The EPA believes that the difference between RACM and BACM 
primarily lies in the extent of the actual emissions reductions 
achieved through the application of a given suite of candidate 
measures. For example, a state may have deemed a candidate RACM or RACT 
measure economically infeasible because its cost effectiveness (dollar 
per ton of pollutant reduced) was high relative to other measures, but 
the same measure could qualify as BACM if, for the increased cost, it 
would ultimately provide substantial PM2.5 attainment 
benefits. An example of RACM might be to implement a particular control 
in a limited way, while BACM could mean a more widespread 
implementation of that same measure, even though wider implementation 
would incur greater cost. In the PM10 context, states and 
the EPA have determined that BACM have sometimes been measures that 
were first implemented as RACM, but were then later implemented on a 
broader scale as BACM in the nonattainment area after it was 
reclassified as Serious.\183\
---------------------------------------------------------------------------

    \183\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42014. The Addendum provides one example of RACM to 
reduce PM10, to ``[p]ave 4 miles of unpaved city 
streets.'' Ibid. BACM for PM10 for the same nonattainment 
area could later mean to ``[p]ave 10 miles of the most heavily-
traveled, unpaved county roads.'' Ibid. Therefore, the measure 
itself was not necessarily changed, but the extent to which the 
measure was implemented was significantly expanded. Such a measure 
would also contribute to more expeditious attainment of the NAAQS.
---------------------------------------------------------------------------

    While the proposed approaches and criteria for identifying 
appropriate control measures for a Serious area are necessarily 
different than for a Moderate area, it is important to note two 
similarities: first, that the EPA interprets the requirement under 
section 172(c)(6) for a state to adopt ``other measures'' needed for 
attainment to apply to sources located inside and outside of any 
PM2.5 nonattainment area (but within the state's 
boundaries), whether the area is classified as Moderate or Serious; 
and, second, similar to the RACM requirement for Moderate nonattainment 
areas under subpart 4, section 189(b)(1)(B) requires that BACM must be 
implemented no later than 4 years after a Moderate area is reclassified 
to Serious.
    Taking these two statutory provisions together, the EPA proposes 
that the other measures required under section 172(c)(6) must include 
``additional feasible measures,'' which would be those measures and 
technologies that otherwise meet the criteria for BACM and BACT but 
that can only be implemented in whole or in part beginning 4 years 
after reclassification of an area, but no later than the statutory 
attainment date for the area. See proposed 40 CFR 51.1000. Such 
measures would necessarily be implemented on sources in the 
nonattainment area, and a state would only be required to implement 
them if they were needed in addition to BACM and BACT to bring the area 
into expeditious attainment. The state must

[[Page 15407]]

also assess whether there are other control measures that it can 
implement to control sources within the state but outside the 
nonattainment area that contribute to the PM2.5 
nonattainment status of the area in order to bring the area into 
attainment as expeditiously as practicable, and may consider existing 
measures that, applied more extensively, could meet the more stringent 
criteria for control measures that must be adopted to bring a Serious 
nonattainment area into expeditious attainment.
    These ``additional feasible measures'' would be analogous to the 
``additional reasonable measures'' in the proposed RACM and RACT 
analysis process, which are technologically and economically feasible 
measures that cannot qualify as RACM or RACT because they cannot be 
implemented within 4 years of designation of a Moderate nonattainment 
area. Under either of the two proposed approaches for determining BACM 
and BACT for sources in a Serious nonattainment area descrfibed later 
in this section, a state would identify additional feasible measures as 
part of the BACM and BACT determination process, just as additional 
reasonable measures would be identified as part of the state's RACM and 
RACT determination process.
    The EPA recognizes that only a nonattainment area that is 
reclassified under the agency's discretionary authority might have 
sufficient time between the required date for implementing BACM and 
BACT and the statutory Serious area attainment date to implement 
additional measures beyond BACM and BACT. BACM and BACT must be 
implemented no later than 4 years after reclassification of the area; 
areas reclassified to Serious because they cannot practicably attain 
the relevant NAAQS by the applicable attainment date could potentially 
have significantly more than 4 years between the date of 
reclassification and the statutory Serious area attainment date, during 
which time the area could continue to implement additional measures to 
bring the area into attainment. By way of illustration, for areas 
designated in the first round of designations for the 2012 
PM2.5 NAAQS, the statutory Moderate area attainment date 
will be no later than December 31, 2021. If a state submits a Moderate 
area attainment plan by the statutory attainment plan due date (18 
months after designation, or in this example, October 2016) and the 
plan demonstrates that the area cannot practicably attain the NAAQS by 
December 31, 2021, then the EPA has a statutory duty to reclassify such 
an area within 18 months of the attainment plan due date (i.e., by 
April 2018). The statutory Serious area attainment date would be the 
end of the tenth year following designation, or December 31, 2025. In 
such a case, the state would need to implement BACM for the area within 
4 years of reclassification, or by April 2022, leaving over 3.5 years 
between the statutory deadline for implementing BACM and the statutory 
attainment date for the area. The EPA's proposal to require the state 
to identify and adopt additional feasible measures for the area would 
mean that the state would need to identify those control measures and 
technologies that are feasible (according to the proposed BACM and BACT 
criteria described later in this section) and that can be implemented 
between April 2022 and December 2025. The EPA expects that while such a 
long span of time may be available only to a very few Serious 
nonattainment areas, it would be appropriate to require such areas to 
implement measures in addition to BACM and BACT if, taken together, 
they can advance the attainment date for the area by at least 1 year. 
The EPA seeks comment on its proposal to require additional feasible 
measures for Serious nonattainment areas as described here.
    b. Proposed approaches for determining BACM and BACT and additional 
feasible measures for Serious PM2.5 nonattainment areas. The EPA 
proposes and seeks comment on two approaches for a state to meet the 
statutory control requirements that apply for Serious nonattainment 
areas. The EPA is first proposing an approach consistent with prior 
guidance summarized in the preceding section of this preamble which 
would center on determining BACM and BACT and additional feasible 
measures ``generally independent'' of whether such measures are needed 
for expeditious attainment of the relevant NAAQS in a Serious 
PM2.5 nonattainment area. Under this first proposed 
approach, states would have the option, with the proper evidence and 
justification, to eliminate de minimis source categories from 
consideration for controls.
    The EPA's second proposed approach would require states to identify 
BACM and BACT and additional feasible measures simply within the 
context of what is necessary to bring an area into attainment as 
expeditiously as practicable. In other words, the second proposed 
option would take a different approach to determining Serious area 
control measures from the approach included in prior EPA guidance, in 
that it would allow states not to impose specific measures that would 
otherwise be BACM or BACT (or additional feasible measures) in the 
area, if those measures would not be necessary to bring the area into 
attainment with the relevant NAAQS by the statutory attainment date, 
and the collective emissions reductions from such measures would not be 
sufficient to advance the attainment date by at least 1 year in the 
area. A discussion of the proposed options follows.
    i. Proposed Option 1. The EPA seeks comment on a proposed approach 
to maintain, with some modifications, the existing approach to 
determining BACM and BACT for Serious PM10 nonattainment 
areas to BACM and BACT determinations for Serious PM2.5 
nonattainment areas. Under this approach, a state would be required to 
determine BACM and BACT and additional feasible measures for a Serious 
PM2.5 nonattainment area independent of an analysis of the 
specific attainment needs of the Serious area; in other words, the BACM 
and BACT analysis would need to be conducted without regard to whether 
all such controls are needed to bring the area into expeditious 
attainment. Keeping in mind that the overall objective of the 
implementation of BACM and BACT and additional feasible measures is to 
bring a Serious PM2.5 nonattainment area into attainment as 
expeditiously as practicable, this option would continue to provide 
that the test for BACM puts a ``greater emphasis on the merits of the 
measure or technology alone,'' rather than on ``flexibility in 
considering other factors,'' in contrast to the approach for 
determining RACM and RACT described in both the EPA's past guidance and 
in this proposal in Section IV.D.\184\ This Option 1 is consistent with 
the statutory provisions governing the timing for submission of BACM 
and BACT measures versus the timing for attainment demonstrations for 
Serious areas. By interpreting the statutory requirement for BACM and 
BACT for Serious PM2.5 nonattainment areas as a requirement 
that a state must meet independent of the attainment planning needs of 
the area, the EPA would not consider such requirement to be a 
``planning'' requirement tied to the actual attainment status of the 
area, and thus would not suspend such a requirement in the event the 
agency determines that a Serious area is attaining the relevant 
PM2.5 NAAQS and

[[Page 15408]]

in turn grants a clean data determination for the area.\185\
---------------------------------------------------------------------------

    \184\ Ibid.
    \185\ For a complete discussion of the EPA's Clean Data Policy 
and the EPA's proposal for applying this policy for purposes of 
implementing the PM2.5 NAAQS, see Section IX.C of this 
preamble.
---------------------------------------------------------------------------

    Under the EPA's first proposed approach, a state would be required 
to follow a multi-step process similar to the existing BACM process for 
PM10 (outlined earlier in this section) to identify and 
select control measures and technologies more stringent than RACM and 
RACT and additional reasonable measures for non-de minimis source 
categories in the nonattainment area. This process would involve 
analyzing the impact of the different source categories identified in 
the up-to-date base year emissions inventory for the area to identify 
those with a significant contribution to the area's PM2.5 
concentrations. Any source categories found not to have such an impact 
would be considered de minimis and therefore exempt from further 
consideration. The specific steps the EPA is proposing for this 
approach are explained below. See proposed 40 CFR 51.1010(a) for 
proposed Option 1.
    Step 1: Update base year emissions inventory for the area. The 
first step under this proposed approach would be for the state to 
develop a detailed emissions inventory of the various sources and 
source categories that emit direct PM2.5 and 
PM2.5 precursors in the Serious area. This inventory should 
be the most comprehensive and accurate inventory available. The EPA 
expects that the work for this step would be completed in order to meet 
the emissions inventory requirements for Serious area plans as 
described in Section VI.B, and would start with reviewing and updating 
the emissions inventory submitted as part of the Moderate area 
attainment plan for the area.
    Step 2: Evaluate source category impacts. As with BACM for 
PM10, the EPA proposes to allow states to exempt from 
further consideration de minimis source categories in Step 2 of the 
agency's first proposed approach for determining BACM and BACT for a 
Serious PM2.5 nonattainment area. The EPA proposes to apply 
the same overarching test for identifying de minimis source categories 
as that described in the Addendum.\186\ That is, if a state can 
demonstrate that a particular source category does not contribute 
significantly to nonattainment of the PM2.5 NAAQS after the 
application of any RACM or RACT controls on the sources in the source 
category, then the state may eliminate the source category from further 
consideration for BACM or BACT.\187\ A state would be required to 
evaluate for BACM and BACT controls all other sources in the 
nonattainment area in source categories that do not qualify as de 
minimis.
---------------------------------------------------------------------------

    \186\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42011.
    \187\ Ibid. See also Alabama Power v. Costle, 636 F.2d 323, 360-
61 (D.C. Cir. 1979).
---------------------------------------------------------------------------

    This option could be beneficial for some states that may already 
exclude de minimis PM10 source categories from BACM in 
Serious PM10 nonattainment areas or that may exclude de 
minimis PM2.5 source categories from RACM and RACT and 
additional reasonable measures in Moderate PM2.5 
nonattainment areas. As discussed earlier, a state may rely on receptor 
or dispersion modeling conducted for the area as part of its Moderate 
area attainment plan. Alternative or additional modeling, including 
screening modeling, or filter analysis may also be necessary to 
identify significant contributors to PM2.5 levels in the 
area. More discussion on the EPA's proposal regarding how to evaluate 
source category impacts and identify those that are de minimis can be 
found in Section IV.D of this preamble. The EPA notes that a state may 
face the same challenges in establishing de minimis source categories 
for PM2.5 sources in a Serious nonattainment area as it did 
in establishing de minimis source categories for PM2.5 
sources when the area was classified as Moderate. Therefore, the EPA 
seeks comment on its proposed options, described in Section IV.D, for 
defining source categories and determining the appropriate threshold 
for de minimis emissions. The EPA requests that commenters submit any 
relevant data or analyses to support their comments. In the absence of 
compelling evidence to support establishing a nationally-applicable 
``bright line'' threshold for defining a de minimis source category for 
purposes of implementing the PM2.5 NAAQS in a Serious 
nonattainment area, the EPA would apply a presumptive approach allowing 
a state to apply its own reasoned judgment to determine whether a 
particular source category should be considered de minimis in the event 
the EPA finalizes proposed Option 1 for BACM and BACT determinations.
    Step 3: Identify existing and potential control measures. After 
evaluating source category impacts to eliminate de minimis source 
categories from further consideration, the state would identify all 
existing and potential measures (including those measures that were 
rejected in the RACM and RACT determination and additional new 
potential measures) for reducing emissions from the remaining (i.e., 
non-de minimis) source categories listed in the latest base year 
emissions inventory for the area. For purposes of identifying new 
measures to consider in its BACM and BACT analysis, the EPA proposes to 
require that the state conduct a survey of other nonattainment areas 
for the PM2.5 NAAQS and other NAAQS (i.e., PM10, 
ozone, SO2 and NOX) both in the same state and in 
other states to identify potential control measures that other air 
agencies are implementing, and the state must incorporate such measures 
into the list of potential control measures for the source categories 
in the Serious nonattainment area. The EPA would expect the state to 
identify an array of existing and potential new measures at least as 
broad as that identified for the same area as part of the RACM and RACT 
analysis, in order to ensure that the state has a sufficiently 
expansive and comprehensive set of potential measures to evaluate. 
Therefore, at a minimum, the EPA proposes that the list of potential 
measures must include all measures identified as potential control 
measures for the nonattainment area when it was classified as Moderate 
or, for a given source category, one or more alternative control 
measures or technologies that would control emissions even more 
stringently than the measures and technologies included in the RACM and 
RACT analysis. In this way, the state will begin its BACM and BACT 
determination with a list of potential control options that is as 
complete and up-to-date as possible.
    In addition to identifying existing control measures for sources in 
a Serious PM2.5 nonattainment area, a state must develop a 
comprehensive list of potential control measures for sources in the 
area. The EPA's RACT/BACT/LAER Clearinghouse provides a central data 
base of air pollution technology information that may be highly 
relevant to states seeking information on stationary source control 
technology that may qualify as BACT for PM2.5 NAAQS 
implementation, and is available online at http://cfpub.epa.gov/RBLC/. 
There are also other resources available to assist states in 
identifying other potential control measures and control technologies 
for their BACM and BACT determinations. The EPA encourages states with 
Serious PM2.5 nonattainment areas to visit the agency's Web 
site to find links to other online sources of information on potential

[[Page 15409]]

control measures for states to consider.\188\
---------------------------------------------------------------------------

    \188\ Links are provided to a number of national, state and 
local air quality agency sites from the EPA's PM2.5 Web 
site: http://www.epa.gov/pm/measures.html.
---------------------------------------------------------------------------

    Specific to potential control measures for mobile source emissions, 
the EPA's past guidance has indicated that where mobile sources 
contribute significantly to PM2.5 violations, ``the state 
must, at a minimum, address the transportation control measures listed 
in CAA section 108(f) to determine whether such measures are achievable 
in the area considering energy, environmental and economic impacts and 
other costs.'' \189\ The EPA proposes to retain this guidance and 
require that a state include for evaluation as BACM for mobile sources 
those measures listed in section 108(f), and the agency seeks comment 
on this specific requirement.
---------------------------------------------------------------------------

    \189\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42013.
---------------------------------------------------------------------------

    Step 4: Determine whether an available control measure or 
technology is technologically feasible. After developing a list of 
existing and potential new measures to evaluate for BACM and BACT, the 
state would then need to determine the technological feasibility of 
each identified control measure in light of a number of considerations, 
including each measure's individual energy and environmental 
impacts.\190\
---------------------------------------------------------------------------

    \190\ Ibid. at 42012.
---------------------------------------------------------------------------

    (1) Stationary sources. As described under the technological 
feasibility criteria for the control measures analysis for Moderate 
area attainment plans in Section IV.D, the EPA's prior guidance on 
factors to consider for judging whether a particular control technology 
is technologically feasible should include a source's processes and 
operating procedures, raw materials, physical plant layout and 
potential environmental impacts such as increased water pollution, 
waste disposal and energy requirements. For example, the EPA recognizes 
that the process, operating procedures and raw materials used by a 
source can affect the feasibility of implementing process changes that 
reduce emissions and can also affect the selection of add-on emission 
control equipment. The feasibility of modifying processes or applying 
control equipment also can be influenced by the physical layout of the 
particular plant, if the physical space available in which to implement 
such changes limits the choices.\191\
---------------------------------------------------------------------------

    \191\ Ibid. at 42013.
---------------------------------------------------------------------------

    (2) Area and mobile sources. With respect to determining whether a 
given control measure might not be technologically feasible as BACM for 
an area or mobile source, the EPA proposes that a state may consider 
factors in conducting its analysis that are similar to factors the 
state may have considered during the RACM and RACT determination 
process, such as the social acceptability of the measure, and local 
circumstances, such as the condition and extent of needed 
infrastructure, population size or workforce type and habits, which may 
prohibit certain potential control measures from being implementable. 
However, in the instance where a given control measure has been applied 
in another NAAQS nonattainment area (for PM2.5 or other 
pollutant), the EPA proposes that the state will need to provide a 
detailed justification for rejecting any potential BACM measure as 
technologically infeasible. Furthermore, if the state identifies a 
certain control measure for area or mobile sources that has been 
implemented in another nonattainment area and may qualify as BACM or 
BACT for the state's Serious nonattainment area, the state must provide 
a reasoned justification if it deems it technologically infeasible to 
implement the same control measure to the same extent or magnitude as 
it was applied in the other nonattainment area.
    The EPA seeks comment on the factors described above for states to 
consider when evaluating the technological feasibility of a control 
measure or technology for BACM and BACT.
    Step 5: Determine whether an available control technology or 
measure is economically feasible. The fifth step under this proposed 
approach is to evaluate the costs of implementing each of the 
technologically feasible control measures and technologies in order to 
eliminate from further consideration any measures determined to be 
economically infeasible. As discussed elsewhere in this proposal, in 
assessing ``best'' control measures and technologies, states with 
Serious PM2.5 nonattainment areas must identify a control 
strategy for the area that overall is more stringent than that 
identified for the area when the state considered only the 
``reasonableness'' of potential control measures. Thus the EPA is 
proposing to require states to consider emission reduction measures 
with higher costs per ton when assessing the economic feasibility of 
BACM and BACT controls (and, where applicable, additional feasible 
measures) as compared to the economic feasibility criteria applied in 
their RACM and RACT analysis (and analysis for additional reasonable 
measures) for the same nonattainment area.
    Indeed, consistent with prior guidance on evaluating costs of a 
potential BACM or BACT control, the EPA maintains that while the 
economic feasibility of a control measure is as important as its 
technological feasibility under the RACM and RACT determination 
process, economic feasibility is a less significant factor in the BACM 
and BACT determination process. In other words, a state must apply a 
higher standard for eliminating a technologically feasible control 
measure from further consideration as BACM due to cost alone.
    In the Addendum, the EPA stated that ``for PM10 BACM 
purposes, it is reasonable for similar sources to bear similar costs of 
emission reduction.'' \192\ Additionally, the EPA indicated that 
``economic feasibility for PM10 BACM purposes should focus 
upon evidence that the control technology in question has previously 
been implemented at other sources in a similar source category without 
unreasonable economic impacts.'' \193\ Thus, a state may not eliminate 
a particular control measure from further consideration as potential 
BACM if similar sources have successfully implemented such a measure. 
That is, a state must at a minimum continue to consider as potential 
BACM any technologically feasible control measures or technologies 
implemented by similar sources.
---------------------------------------------------------------------------

    \192\ Ibid.
    \193\ Ibid.
---------------------------------------------------------------------------

    In addition, the EPA seeks to clarify that a state may not 
automatically eliminate a particular control measure merely because 
other sources have not implemented the measure. In other words, a state 
must continue to consider technologically feasible measures that have 
not been implemented by similar sources but that can nonetheless 
effectively reduce emissions from the source category in question at a 
cost that is not wholly cost prohibitive.
    As with the EPA's proposed approach for evaluating economic 
feasibility of potential reasonable measures for Moderate area 
attainment plans, the EPA proposes that for each technologically 
feasible control measure or technology, a state must evaluate the 
economic feasibility of the measure or control through consideration of 
the capital costs, operating and maintenance costs, and cost 
effectiveness (i.e., cost per ton of pollutant reduced by that measure 
or technology) associated with such measure or control. While the EPA 
is

[[Page 15410]]

not proposing a fixed dollar per ton cost threshold for economic 
feasibility of controls identified as potential BACM and BACT, the EPA 
proposes that the threshold should be higher for the BACM and BACT 
analysis than it was for the RACM and RACT analysis for the same 
nonattainment area. In addition, if a state contends that a source-
specific control-level should not be established because the source(s) 
cannot afford the control measure or technology that is demonstrated to 
be economically feasible for purposes of BACM for other sources in its 
source category, the state must support the claim with information 
regarding the impact of imposing the identified control measure or 
technology on the following financial indicators, to the extent 
applicable:
    1. Fixed and variable production costs ($/unit);
    2. Product supply and demand elasticity;
    3. Product prices (cost absorption vs. cost pass-through);
    4. Expected costs incurred by competitors;
    5. Company profits
    6. Employment costs;
    7. Other costs (e.g., for BACM implemented by public sector 
entities).
    The EPA seeks comment on the factors described above for states to 
consider when determining whether a control measure or technology is 
economically feasible as BACM or BACT.\194\
---------------------------------------------------------------------------

    \194\ These long-standing factors were established in EPA 
guidance in 1992 and are applicable to implementation programs for 
all NAAQS pollutants. See the appendices to the General Preamble, 57 
FR 18070 (April 28, 1992).
---------------------------------------------------------------------------

    Step 6: Determine the earliest date by which a control measure or 
technology can be implemented in whole or in part. Section 189(b)(1)(B) 
requires that Serious area attainment plans provide for the 
implementation of BACM no later than 4 years after reclassification of 
the area to Serious. As with the EPA's proposed approach to RACM and 
RACT, the EPA proposes the term ``implement'' to mean that the control 
measure or technology has not only been adopted into the SIP for the 
area but has also been built, installed and/or otherwise physically 
manifested and the affected sources are required to comply. See 
proposed 40 CFR 51.1000. The EPA thus expects a state with a Serious 
nonattainment area to take deliberate and timely action to implement 
BACM and BACT in the area. The EPA proposes that if a state evaluates a 
potential BACM or BACT measure and determines that it can be 
implemented only partially within 4 years after reclassification, the 
state must adopt the partial measure as BACM.
    The EPA proposes that a state must identify those technologically 
and economically feasible control measures and technologies that it can 
implement fully or partially within 4 years of reclassification of its 
Serious PM2.5 nonattainment area. These measures will be 
considered BACM and BACT for the area. ``Additional feasible measures'' 
would be ``best''-level, feasible measures that a state could implement 
in whole or in part on sources in the area sometime after the fourth 
year following reclassification and prior to the statutory attainment 
date for the area.
    ii. Proposed Option 2. The second proposed approach for evaluating 
control measures and technologies and determining which qualify as BACM 
or BACT or additional feasible measures for a Serious PM2.5 
nonattainment area would directly link the control strategy 
determination process with the attainment demonstration for the area, 
allowing a state to eliminate potential measures that are not necessary 
to demonstrate attainment of the relevant NAAQS in the area and would 
not collectively advance the attainment date for the area by at least 1 
year. For this second proposed approach, the EPA proposes a process 
similar to the one proposed for Moderate area control strategy 
determinations. However, the specific potential control measures to be 
evaluated as BACM and BACT and additional feasible measures would 
continue to be distinguished by stricter criteria to yield a set of 
control measures that reflects an overall higher level of stringency in 
the control strategy for the nonattainment area than that provided by 
the implementation of reasonable control measures (i.e., RACM and RACT 
and additional reasonable measures).
    Under the EPA's second proposed approach for determining which 
measures must be part of the control strategy for a Serious 
PM2.5 nonattainment area, a state would follow many of the 
same steps as described under the EPA's first proposed approach for the 
such determinations, with two important differences. First, Step 2 as 
described above would be eliminated from the process. That is, after a 
state updates the baseline emissions inventory for sources located in 
the area, the state would be required to identify existing and 
potential new measures for all sources in the inventory for evaluation 
as potential BACM and BACT and additional feasible measures without 
exempting any source categories as de minimis. Second, Step 6 as 
described above would not be the last step in the control strategy 
determination process, but rather would serve as another interim step 
in the process prior to making a final determination of what 
constitutes BACM and BACT and additional feasible measures for the area 
through modeling for the attainment demonstration. The EPA's proposed 
requirements for what the state would need to evaluate during this step 
under this second proposed approach are described in greater detail in 
the following section.
    The EPA emphasizes that proposed Option 2 for determining BACM and 
BACT and additional feasible measures depends on the state submitting 
its attainment demonstration earlier than may otherwise be required 
under the statute so that it can be contemporaneous with the submission 
of BACM and BACT measures, due 18 months after the date of 
reclassification of a PM2.5 nonattainment area to Serious.
    Given all of the above, the EPA is proposing and seeking comment on 
a second approach for determining BACM and BACT and additional feasible 
measures for a Serious PM2.5 nonattainment area comprised of 
the following steps. See proposed 40 CFR 51.1010(a) for proposed Option 
2. Note that Steps 1 through 5 would incorporate the same 
considerations and requirements as those in the equivalent steps 
described in the EPA's first proposed approach with the two important 
exceptions discussed in the preceding section:
    Step 1: Update base year emissions inventory for the area.
    Step 2: Identify existing and potential control measures for all 
emissions sources in the emissions inventory for the area.
    Step 3: Determine whether an available control measure or 
technology is technologically feasible.
    Step 4: Determine whether an available control measure or 
technology is economically feasible.
    Step 5: Determine the earliest date by which a control measure or 
technology can be implemented in whole or in part.
    During this step in the process, the state would be required to 
identify two groups of measures. The first group of measures would be 
potential BACM and BACT; that is, ``best''-level, feasible measures 
that the state could implement in whole or in part within 4 years of 
reclassification. The second group of measures would be additional 
feasible measures, defined as ``best''-level, feasible measures that a 
state could implement in whole or in part on sources in the area 
sometime after the fourth year following reclassification

[[Page 15411]]

and prior to the statutory attainment date for the area.
    Step 6: Model to determine the attainment date that is as 
expeditious as practicable. As with the proposed Moderate area 
attainment plan control strategy analysis, the EPA proposes that states 
would need to model air quality impacts to determine the Serious area 
attainment date that is as expeditious as practicable for the area. 
After developing an inventory, identifying potential measures, 
determining economic and technological feasibility, and determining 
whether a measure would be able to be implemented in 4 years or between 
4 years from reclassification and the statutory attainment date for the 
area, the state would conduct modeling that shows the combined air 
quality impact of all BACM and BACT measures and additional feasible 
measures as applicable. The purpose of this modeling would be to 
determine the attainment date that is as expeditious as practicable and 
to identify whether there are certain control measures that a state 
could eliminate from the Serious area attainment plan because they 
cannot collectively expedite attainment of the area by 1 year or more. 
A complete discussion of the EPA's proposed modeling requirements for 
Serious area attainment demonstration is presented in Section VI.E 
below.
    Step 6a: If area can demonstrate attainment by the statutory 
attainment date, then select only those control measures needed for 
expeditious attainment as BACM or BACT or additional feasible measures. 
Under this second proposed approach to BACM and BACT determinations, 
the EPA proposes that if a Serious area will be able to demonstrate 
attainment by the statutory Serious area attainment date, then the 
state must adopt all measures identified as potential BACM and BACT, 
and additional feasible measures if applicable, that will ensure that 
the attainment date is as expeditious as practicable. The state may, 
however, reject those potential BACM and BACT and additional feasible 
measures that would not collectively contribute to emissions reductions 
that could advance the attainment date for the area by at least 1 year.
    The EPA recognizes that identifying the measures that would not 
collectively advance the attainment date for a Serious area by at least 
1 year will likely be an iterative process that requires additional 
modeling. As with modeling for Moderate area attainment demonstrations, 
the EPA believes that such extra effort is reasonable for a state 
seeking to reject certain potential BACM or BACT or additional feasible 
measures from implementation in a given Serious nonattainment area.
    One notable point of discussion in the Addendum indicates that 
short-term BACM measures are not preferred by the EPA unless such a 
measure is the only way to implement BACM within 4 years.\195\ This is 
because the ultimate goal of selection of BACM controls is that those 
measures will prevent future emissions, rather than a temporary 
reduction of emissions. Therefore, consistent with this previous 
guidance, the EPA proposes that those measures that a state must reject 
first under this proposed approach would be those that offer only 
short-term emissions reductions.
---------------------------------------------------------------------------

    \195\ Ibid.
---------------------------------------------------------------------------

    Step 6b: If an area cannot demonstrate attainment by the statutory 
attainment date, then submit request for Serious area attainment date 
extension including adopting MSM. Section 189(b)(1)(A) of the CAA 
requires a state to submit as part of its Serious area attainment plan 
either a demonstration that the plan will provide for attainment by the 
statutory Serious area attainment date, or a demonstration that 
attainment by such date is ``impracticable.'' If the state cannot 
demonstrate attainment based on the implementation of all BACM and BACT 
and additional feasible measures by the end of the tenth calendar year 
following designation of the area, then under sections 189(b)(1)(A)(ii) 
and 188(e), the state must submit as part of its Serious area 
attainment plan a complete request to extend the attainment date for 
the area that meets the statutory provisions of section 188(e) and 
meets all of the regulatory criteria proposed under Section VII in this 
preamble, including the evaluation and adoption of MSM.
    The EPA acknowledges that this second proposed approach for 
determining BACM and BACT and additional feasible measures for a 
Serious area, which would authorize states to link the attainment 
control strategy to the attainment needs for an area, is different from 
the approach the agency has historically applied to BACM determinations 
for PM10. The EPA believes that effectively eliminating the 
step of exempting de minimis source categories the beginning of the 
control strategy determination process and linking the determination of 
BACM and BACT and additional feasible measures with the attainment 
analysis for a Serious area would not be a relaxation of the statutory 
requirement for implementation of ``best'' measures in Serious 
PM2.5 nonattainment areas as Congress required in section 
189(b)(1)(B), however. Rather, the agency believes that in order to 
ensure that a state develops an appropriately stringent control 
strategy for a Serious PM2.5 nonattainment area, it is 
appropriate to require that state to identify and evaluate potential 
control measures for all sources of direct PM2.5 emissions 
and emissions of any PM2.5 precursors not otherwise found to 
contribute insignificantly to PM2.5 levels in the area. 
Eliminating the possibility for de minimis source category exemptions 
means that a state's evaluation of potential control measures and 
technologies will be more thorough and comprehensive and potentially 
lead to the implementation of controls on a wider variety of source 
categories. Additionally, the test of whether the potential BACM and 
BACT and additional feasible measures not needed for an area to attain 
the NAAQS by the outside statutory attainment date could collectively 
advance the attainment date for the area by at least 1 year could 
result in a state implementing such measures on source categories 
which, if they had each been evaluated separately for purposes of a de 
minimis source category analysis, might have been exempted from 
control. Furthermore, as noted earlier in this section, in order for 
the state, the EPA, and the general public to be able to fully evaluate 
whether the selected control strategy (i.e., BACM and BACT and 
additional feasible measures) will provide for expeditious attainment 
of the NAAQS in a Serious PM2.5 nonattainment area, the 
state would be required to submit the attainment demonstration for the 
area at the same time as it submits provisions to meet the BACM and 
BACT requirement under section 189(b)(1)(B), 18 months after 
reclassification of the area to Serious. This date would be stricter 
than the statutory due date for a Serious area attainment demonstration 
for areas reclassified to Serious under the EPA's discretionary 
authority of section 188(b)(1), which is no later than 4 years from the 
date of reclassification of the area.
    By defining a process for determining BACM and BACT and additional 
feasible measures in a way that is similar to the process for 
determining RACM and RACT and additional reasonable measures for the 
same area, the EPA believes that a state with a Serious 
PM2.5 nonattainment area may be able to conserve resources 
by relying in part on the analytical work performed for the RACM and 
RACT analysis for the area when it was classified as Moderate. 
Furthermore, the challenges associated

[[Page 15412]]

with properly identifying de minimis source categories as described 
earlier in this section may be avoided. Finally, the EPA believes that 
tying the final selection of BACM and BACT and additional feasible 
measures to the specific attainment needs of a nonattainment area could 
help to focus limited air agency resources on control measures that are 
most needed to bring a Serious area into expeditious attainment for the 
PM2.5 NAAQS.
    The EPA seeks comment on all aspects of both proposed approaches 
and criteria for determining BACM and BACT and additional feasible 
measures for a Serious nonattainment area. The agency may finalize 
either of the proposed approaches or various elements of each after 
analyzing submitted comments.
3. BACM and BACT Submittal Requirements
    To ensure that attainment plan submissions contain the necessary 
supporting information for EPA review and approval of the state's 
selected BACM and BACT and additional feasible measures as applicable, 
the EPA proposes to require under the authority of section 301(a) that 
a state must submit the following information as part of its Serious 
area attainment plan submission:
     A list of all emissions source categories, sources and 
activities in the nonattainment area that emit direct PM2.5 
or any PM2.5 precursor (for multi-state nonattainment areas, 
this would include source categories, sources and activities from all 
states which make up the area);
     For each source category, source or activity in the 
nonattainment area, an inventory of direct PM2.5 and all 
PM2.5 precursor emissions;
     For each source category, source or activity in the 
nonattainment area, a comprehensive list of potential control measures 
considered by the state for the nonattainment area; \196\ \197\
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    \196\ The EPA believes that it is not necessary to identify 
every possible variation of every type of control measure, or all 
possible combinations of technologies and measures that would apply 
to a given source or activity, as long as the state has properly 
characterized the potentially available emissions reductions and 
their costs. For example, the EPA believes that the state can 
conduct a thorough analysis of VMT reduction measures without 
including every possible level or stringency of implementation of 
certain possible measures or combinations of measures for reducing 
VMT, so long as those measures would not affect the overall 
assessment of VMT reduction capabilities and the associated costs.
    \197\ The Menu of Control Measures document is available at: 
http://www.epa.gov/air/criteria.html.
---------------------------------------------------------------------------

     For each potential control measure considered by the state 
but eliminated from further consideration due to a determination by the 
state that the control measure or technology was not technologically 
feasible, a narrative explanation and quantitative or qualitative 
supporting documentation to justify the state's conclusion;
     For each technologically feasible emission control measure 
or technology, the state must provide the following information 
relevant to economic feasibility: (i) The control efficiency by 
pollutant; (ii) the possible emission reductions by pollutant; (iii) 
the estimated cost per ton of pollutant reduced; and, (iv) a 
determination of whether the measure is economically feasible, with 
narrative explanation and quantitative supporting documentation to 
justify the state's conclusion;
     For each technologically and economically feasible 
emission control measure or technology, the date by which the 
technology or measure could be implemented.
    As with a Moderate area attainment plan submission, the EPA 
recognizes that the base year emissions inventory for the area that the 
state submits in conjunction with its Serious area attainment plan will 
likely contain the information proposed to be required under the first 
two items in this list. However, the EPA believes that it is incumbent 
on the state to ensure that the information needed for the EPA to 
evaluate the state's BACM and BACT and additional feasible measures 
analysis is presented as part of that analysis and in a format that 
provides transparency, consistency and the ability for another party to 
evaluate the state's analysis effectively and to duplicate the state's 
results. For this reason, the EPA is proposing to require the state to 
include the base year emissions inventory information with the BACM and 
BACT submittal and as one element of the state's attainment plan due 18 
months after reclassification of the area to Serious.
4. Criteria for Effective Regulations To Implement BACM and BACT and 
Additional Feasible Measures
    As with control measures identified as part of a Moderate area's 
attainment control strategy, after a state has identified its BACM and 
BACT and additional feasible measures for a particular nonattainment 
area, it must implement those measures through a legally enforceable 
mechanism to be included in the SIP. As with Moderate area control 
measures, the EPA is proposing that in order for the agency to be able 
to approve any Serious area control measure and approve it as part of 
the SIP, the state will have to provide information to meet the 
following four criteria.
    First, the base year emissions from the source or group of sources 
to which the control measure applies and the future year projected 
emissions from those sources once controlled must be quantifiable so 
that the projected emissions reductions from the sources can be 
attributed to the specific measures being implemented. Once again, it 
is important that the emissions from the source category in question 
are accurately represented in the base year inventory so that emissions 
reductions are properly calculated. In particular, it is especially 
important to ensure that both the filterable and condensable components 
of PM2.5 are accurately represented in the base year.
    Second, the control measures must be enforceable, meaning that they 
must specify clear, unambiguous and measurable requirements. The 
measurable requirements for larger emitting facilities must include 
periodic source testing to establish the capability of such facilities 
to achieve the required emission level. Additionally, to verify the 
continued performance of the control measure, specific emissions 
monitoring programs appropriate for the type of control measure 
employed and the level of emissions must be included to verify the 
continued performance of the control measure. The control measures and 
monitoring program must also have been adopted according to proper 
legal procedures.
    Third, the results of application of the control measures must be 
replicable. This means that where a rule contains procedures for 
interpreting, changing or determining compliance with the rule, the 
procedures are sufficiently specific and objective so that two 
independent entities applying the procedures would obtain the same 
result.
    Fourth, the control measures must be accountable. For example, 
source-specific emission limits must be permanent and must reflect the 
assumptions used in the attainment plan for the area, including the 
modeling conducted in conjunction with the attainment demonstration. 
The attainment plan must establish requirements to track emissions 
changes at sources and provide for corrective action if emissions 
reductions are not achieved according to the plan.
    The EPA seeks comment on these criteria for approval of any control 
measures adopted by a state for a Serious area to assure that such 
measures are legally enforceable.

[[Page 15413]]

5. Relevance of Prior BACT, LAER and BART Determinations
    The EPA believes that BACT or lowest achievable emission rate 
(LAER) provisions for new sources (as distinct from BACT for existing 
sources), or best available retrofit technology (BART) for existing 
sources, could qualify as BACM or BACT for purposes of meeting the 
Serious area attainment plan requirements. However, the EPA does not 
believe it is appropriate for a state to assume that just because a 
certain control technology was determined to meet BACT, LAER, or BART 
criteria for a new source, such a control will also automatically meet 
the criteria for BACM or BACT or additional feasible measures for 
attainment planning purposes because the regulated pollutant or source 
applicability may differ and the analyses may be conducted many years 
apart. Thus, a state may not simply rely on prior BACT, LAER or BART 
analyses for the purposes of showing that a source has also met BACT 
for the relevant PM2.5 NAAQS. Rather, the EPA expects that 
in Step 2 of either of the agency's proposed approaches to the BACM and 
BACT determination process, the state would identify such measures as 
``existing measures'' that should be further evaluated as potential 
BACM or BACT or additional feasible measures.
6. Multi-State Nonattainment Areas
    States that share a multi-state Serious PM2.5 
nonattainment area must consult with one another on BACM and BACT and 
additional feasible measures that will be required for the 
nonattainment area in the different states. This requirement would be 
consistent with the overall requirements for BACM and BACT and 
additional feasible measures determinations, as all states with Serious 
areas need to consider implementing BACM and BACT-level measures that 
have been implemented in other states, even if those measures incur 
higher costs. The EPA anticipates that states may potentially adopt 
controls that differ from state to state, based upon each state's 
determination of what qualifies as ``best'' given the mixture of 
sources and potential controls in the state portions of relevant 
nonattainment areas, subject to EPA approval. If the state can 
adequately demonstrate that its chosen BACM and BACT and additional 
feasible measures fully meet the EPA's proposed criteria for such 
measures, then the agency may consider approving individual state plans 
that differ in implementation of control measures.
7. Environmental Justice Considerations for Developing the Attainment 
Plan Control Strategy for a Serious PM2.5 Nonattainment Area
    The EPA strongly urges states to consider the environmental justice 
aspect of any control measures they have identified as BACM and BACT or 
additional feasible measures. Because the criteria for determining BACM 
and BACT will lead in most cases to the selection of an overall more 
stringent control strategy in a Serious area than what RACM and RACT 
could provide, an appropriate control strategy for a Serious 
nonattainment area will likely implicitly include the best measures for 
ensuring that overburdened populations are appropriately protected. 
Nonetheless, the EPA encourages states when possible to select BACM and 
BACT measures that will result in the least possible burden and 
greatest degree of health protection for overburdened populations in 
the nonattainment area.

E. Modeling for Attainment Demonstrations

    Section IV.E. describes the EPA's proposed attainment demonstration 
and modeling requirements for Moderate area plans, and the EPA is 
proposing that the same general requirements should apply to Serious 
area attainment demonstrations. However, Serious area plans have 
additional statutory requirements, which the EPA proposes to address as 
described below.
1. Statutory Requirements
    Section 189(b) generally requires a state with a designated Serious 
nonattainment area to submit an attainment plan for such area. As 
discussed earlier, section 189(b)(1)(A) more specifically requires the 
state to submit an attainment demonstration including air quality 
modeling to establish either: (i) That the area will attain the 
relevant NAAQS by the applicable attainment date, or (ii) if the state 
is seeking an extension of the attainment date, that it is 
impracticable for the area to attain the relevant NAAQS by the 
statutory Serious area attainment date. For Serious nonattainment 
areas, the attainment date is as expeditiously as practicable, but no 
later than the end of the tenth calendar year after designation as 
nonattainment. An attainment demonstration that shows that it is 
impracticable for the area to attain within this timeframe must also 
provide for attainment of the NAAQS by the most expeditious alternative 
date practicable, but no later than 5 years after the maximum statutory 
Serious area attainment date (based on the criteria specified in 
section 188(e)).
    Attainment demonstrations are due 18 months after reclassification 
if the EPA reclassifies the area to Serious after failure of the area 
to attain the applicable Moderate area deadline. Alternatively, section 
189(b)(2) requires states with designated Serious nonattainment areas 
to submit attainment demonstrations no later than 4 years after 
reclassification of the area to Serious if the reclassification occurs 
before the Moderate area attainment deadline. However, the EPA is 
proposing an approach for determining an appropriate attainment plan 
control strategy for a Serious PM2.5 nonattainment area that 
would require the state to submit the attainment demonstration for the 
area within 18 months after reclassification regardless of when or the 
authority under which an area was reclassified to Serious. Sections 
VI.A and VI.D of this preamble describe more fully the EPA's proposed 
approach for control strategy analyses and due dates for all elements 
of a Serious area attainment plan. Section VI.J of this preamble 
provides a complete discussion of the EPA's proposed criteria for 
granting a Serious area attainment date extension.
2. Attainment Demonstrations for Serious Areas
    As described in Section IV.E of this preamble, an attainment 
demonstration is a plan that demonstrates how a state will attain the 
PM2.5 NAAQS by the applicable attainment date. The EPA is 
proposing that the demonstration for Serious areas must consist of: (i) 
Technical analyses such as base year and future year modeling of 
emissions which identify sources and quantify emissions that are 
contributing to violations of the PM2.5 NAAQS; and, (ii) 
analyses of future year projected emissions reductions and air quality 
improvement resulting from existing (i.e. already-adopted or ``on the 
books'') national, regional and local programs, and potential new local 
measures needed for attainment, including RACM and RACT and BACM and 
BACT controls for the area, as well as other measures either inside the 
nonattainment area or outside the nonattainment area but within the 
state that could potentially accelerate attainment. Each state with a 
Serious nonattainment area must submit an attainment plan with an 
attainment demonstration that includes analyses supporting the state's 
determination of its proposed attainment date. In all cases, the state 
must show that the area

[[Page 15414]]

will attain the NAAQS as expeditiously as practicable, but not later 
than the tenth calendar year after designation. In order to establish 
that the attainment date is as expeditious as practicable, the state 
must explain why the control measures adopted in the attainment plan 
provide for the most expeditious attainment and must either: (i) Under 
proposed Option 1 for the BACM and BACT determination include all BACM 
and BACT controls in the analysis, or (ii) under proposed Option 2 for 
BACM and BACT, provide the requisite analysis to show that 
implementation of additional emissions controls, including any 
potential BACM and BACT, would not advance the attainment date for the 
area by at least 1 year if considered collectively.
    A state with a Serious nonattainment area can also submit an 
impracticability demonstration (under section 189(b)(1)(A)(ii)) as part 
of seeking an extension of the attainment date under section 188(e). 
The impracticability demonstration for a Serious area would be similar 
to an impracticability demonstration for Moderate areas because it must 
include air quality modeling which shows that the area will not be able 
to attain the PM2.5 NAAQS by the outside statutory 
attainment date, which in this case is by the end of the tenth calendar 
year following designation. However, in order to support a Serious area 
impracticability demonstration, the state must also show (through 
modeling) that attainment cannot be reached by the statutory Serious 
area attainment date, even if all RACM and RACT and BACM and BACT 
controls, as well as other measures either inside the nonattainment 
area or outside the nonattainment area but within the state, were 
implemented before the attainment date. Moreover, in addition to the 
Serious area impracticability demonstration, to support an extension of 
the attainment date, the Serious area plan must demonstrate (again, 
using air quality modeling) that it provides for attainment by the most 
expeditious alternative date practicable employing MSM, as specified in 
section 188(e). As a result, the required plan is both an 
impracticability demonstration (to justify an extension beyond the 
statutory attainment date) and an attainment demonstration which serves 
as the basis for proposing an appropriate alternative attainment date.
3. What modeling is required?
    States are required to submit air quality modeling in support of an 
attainment demonstration for a Serious PM2.5 nonattainment 
area. Unlike the impracticability demonstration for Moderate areas 
described in section 189(a)(1)(B)(ii), the impracticability 
demonstration for Serious areas in section 189(b)(1)(A)(ii) also 
requires air quality modeling establishing the most expeditious 
alternative attainment date practicable. Therefore, air quality 
modeling is a required element in all attainment demonstrations for 
Serious areas.
    Other than the timing of plan submissions and additional required 
elements of a Serious area plan (such as BACM and BACT), the relevant 
air quality modeling procedures and guidance for Moderate and Serious 
area plans are the same. See Section IV.E. of this preamble for more 
details on proposed modeling requirements and guidance for all 
PM2.5 nonattainment areas.
4. Will areas reclassified to Serious need to submit two separate 
attainment demonstrations?
    Under section 189(a)(1)(B), a state is required to submit as part 
of an area's Moderate area attainment plan a demonstration that the 
area either will attain or cannot practicably attain the NAAQS by the 
statutory Moderate area attainment date. Regardless of whether the 
state submits an attainment demonstration or an impracticability 
demonstration for a Moderate area, if such area is reclassified to 
Serious prior to or after failing to attain the applicable NAAQS, the 
state is required under section 189(b)(1)(A) to submit a new attainment 
demonstration as part of an area's Serious area attainment plan. The 
separate statutory requirements for Moderate and Serious nonattainment 
areas anticipate two separate attainment plan submissions, and the 
EPA's existing guidance in the General Preamble and Addendum further 
support this expectation. While the state would be required to submit a 
separate Serious area attainment plan, the EPA anticipates that certain 
control strategies may build upon those previously adopted and 
implemented as part of the Moderate area plan. For example, it could be 
the case that an area dominated by woodsmoke emissions could not attain 
the standard by the statutory Moderate area attainment date because all 
necessary woodstove change-outs could not occur in that timeframe, but 
additional woodstove change-outs could occur by the statutory Serious 
area attainment date.
5. What future year(s) should be modeled in attainment demonstrations?
    A state performing a modeling analysis for an attainment 
demonstration or a Serious area impracticability analysis must select a 
future year for the analysis. For an attainment demonstration, a state 
should select the future modeling year such that all emissions control 
measures relied on for attainment will have been implemented by the 
beginning of that year. To demonstrate attainment, the modeling results 
for the nonattainment area must predict that emissions reductions 
implemented by the beginning of the last calendar year preceding the 
attainment date will result in PM2.5 concentrations that 
meet the level of the standard.\198\
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    \198\ Note that for purposes of the PM2.5 NAAQS, a 
determination of attainment (or failure to attain), which the EPA is 
required to make after the attainment date has passed, is based on 
ambient data from the most recent 3 years prior to the attainment 
date for the area.
---------------------------------------------------------------------------

    While states should choose the future modeling year based on a 
number of factors, the EPA recommends the last year of the statutory 
attainment date as a starting point for modeling for two reasons. 
First, a state with a Serious area for which it submits an attainment 
date extension request under section 188(e) must show that the area 
cannot practicably attain the NAAQS by the end of the tenth calendar 
year following designation of the area. Therefore, the appropriate 
future modeling year for making such a demonstration would be the tenth 
year after designations. Even if a state does not submit (or does not 
intend to submit) a Serious area attainment date extension request, 
modeling the tenth year is a logical starting point to determine if 
attainment by year 10 is likely. If attainment-level concentrations of 
PM2.5 are not expected in the tenth calendar year after 
designations, then the area must also, as a requirement to receive an 
extension of the Serious area attainment date, submit a demonstration 
(using air quality modeling) that provides for attainment by the most 
expeditious alternative date practicable, but no later than the end of 
the fifteenth year after designation, with the implementation of MSM 
(see Section VI.J of this preamble for details about MSM 
determinations).
    Second, even though attainment of any PM2.5 NAAQS is 
determined based on 3 years of ambient data, states do not have to 
model 2 years before the attainment date to show modeled attainment. 
Since the design value is an average of the annual or 98th percentile 
value for 3 consecutive years, attainment can still be shown even if 
concentrations exceed the NAAQS in one or more of the 3 years used to 
determine attainment (as long as the average of the 3 annual values is 
less

[[Page 15415]]

than the NAAQS). Therefore, it can be appropriate to model any of the 3 
years used to determine attainment. For these reasons, it is 
acceptable, and may in fact be most efficient, for a state to begin the 
Serious area attainment demonstration process by modeling the final 
year of the statutory attainment date to determine future year modeled 
PM2.5 concentrations in the tenth year after designations.
    Because an area must attain ``as expeditiously as practicable,'' 
additional considerations are necessary before an attainment date can 
be established. For purposes of determining the attainment date that is 
as expeditious as practicable, the state must conduct future year 
modeling which takes into account growth and known controls (including 
any controls that were previously determined to be RACM and RACT for 
the area). For example, for an area designated nonattainment for the 
2012 PM2.5 NAAQS during the first round of designations and 
subsequently reclassified to Serious, a future case scenario for the 
year 2025 (10 years after the initial nonattainment designation) would 
be needed to examine whether the the BACM and BACT identified by the 
state would result in attainment. Under the proposed BACM and BACT 
determination Option 1 (where BACM and BACT must be determined 
independent of the attainment demonstration for the area), the future 
case scenario must include BACM and BACT controls in the analysis plus 
any additional measures on sources inside and outside of the 
nonattainment area (but within the state) that the state has identified 
as feasible to implement by the attainment date. Under proposed Option 
2 for determining BACM and BACT (where BACM and BACT is determined 
according to what is needed to expeditiously attain the NAAQS), the 
future case scenario must show whether implementation of emissions 
controls, including all BACM and BACT and additional feasible measures 
on sources inside and outside of the nonattainment area (but within the 
state), collectively would advance the attainment date by at least 1 
year. Note that similar to RACM and RACT, BACM and BACT controls must 
be implemented within 4 years after reclassification to Serious 
nonattainment. In order to justify an extension of the attainment date 
beyond the end of the tenth year after designation, the state must show 
that attainment by that date (including the anticipated emissions 
reductions from RACM and RACT and additional reasonable measures, and 
BACM and BACT and additional feasible measures) would be impracticable. 
Any proposed attainment date after the 10 year period must include 
modeling of BACM and BACT controls plus the most stringent measures 
that are included in the implementation plan of any state and can be 
feasibly implemented in the area. The attainment date extension beyond 
10 years can be for up to 5 additional years, but the proposed 
attainment date must also be shown to be as expeditious as practicable. 
Section VI.J of this preamble provides a complete discussion of the 
EPA's proposed interpretation of the statutory requirements for a 
Serious area attainment date extension under section 188(e).
    As with Moderate area attainment demonstrations, the EPA believes 
that it is not necessary or reasonable to require states to model each 
and every year to determine the appropriate attainment date for a 
Serious PM2.5 nonattainment area given the resource demands 
associated with modeling.\199\ In some cases it may be reasonable to 
model one additional interim year before the maximum statutory 
attainment date. However, in most cases, the air quality benefits of an 
identified set of reasonable control measures, BACM and BACT and 
additional feasible control measures can be estimated through model 
sensitivity analyses and the development of transfer factors (factors 
to relate tons of emissions reductions in the area to PM2.5 
concentration changes in the area). The EPA strongly recommends that 
states discuss the selection of the future year(s) to model with their 
respective EPA Regional Office as part of the modeling protocol 
development process prior to embarking on the modeling.
---------------------------------------------------------------------------

    \199\ States with Serious areas that request an attainment date 
extension beyond 10 years must model the tenth year after 
designation of the area as part of an impracticability 
demonstration, plus an additional year beyond that which represents 
the attainment date.
---------------------------------------------------------------------------

6. Attainment Year Motor Vehicle Emissions Budgets
    As with Moderate areas, the transportation conformity rule requires 
that Serious area attainment plans establish motor vehicle emissions 
budgets for the area's attainment year. Therefore, once a Serious 
area's attainment date has been established, the state is required to 
establish motor vehicle emissions budgets for direct PM2.5 
and any relevant PM2.5 precursor for the attainment 
year.\200\ A motor vehicle emissions budget for the purposes of a 
Serious area PM2.5 attainment plan is that portion of the 
total allowable emissions within the nonattainment area allocated to 
on-road sources as defined in the submitted attainment plan.\201\ Such 
motor vehicle emissions budgets would be calculated using the latest 
planning assumptions and the latest approved motor vehicle emissions 
model available at the time that the attainment plan is developed.\202\
---------------------------------------------------------------------------

    \200\ For more information on PM2.5 precursor 
requirements, see section 93.102(b)(2)(iv) and (v) of the 
transportation conformity rule. See also the May 6, 2005, final 
transportation conformity rule that addressed requirements for 
PM2.5 precursors. (70 FR 24280).
    \201\ A state would also establish motor vehicle emissions 
budgets for an area's attainment year. Those budgets would be the 
motor vehicle emissions that the SIP establishes as being necessary 
to attain the NAAQS.
    \202\ If an area includes re-entrained road dust in the motor 
vehicle emissions budget, the latest approved version of AP-42 
should be used unless the EPA has approved an alternative model for 
the area.
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F. RFP Requirements

1. Statutory Requirements
    As with Moderate area attainment plans, Serious PM2.5 
nonattainment area plans must provide for RFP as required under CAA 
section 172(c)(2). Section IV.F of this preamble fully describes the 
statutory requirements and overall proposed approaches for states to 
fulfill the RFP requirement in the context of Moderate area attainment 
plans. The EPA believes that the proposed approaches described for RFP 
for Moderate area plans can apply to Serious area attainment plans as 
well. The following section offers additional detail about how the EPA 
proposes that the approach to RFP should apply specifically to Serious 
area attainment plans.
2. Proposed Approach
    As with a Moderate area attainment plan, the EPA is generally 
proposing that a state must submit an RFP plan as part of any 
attainment plan submission for a Serious nonattainment area in order to 
satisfy the statutory requirements for RFP. The plan must include a 
schedule and an analysis that collectively demonstrate when and through 
what control measures emissions from sources in the nonattainment area 
will decline from the applicable baseline year to the projected 
attainment year. The EPA is proposing that the applicable baseline year 
must be the same year as that represented by the latest base year 
inventory for the Serious area. The projected attainment year may be up 
to the end of the tenth year following designation of the area for a 
Serious area

[[Page 15416]]

that can demonstrate attainment pursuant to section 189(b)(1)(A), or up 
to the end of the fifteenth year following designation for a Serious 
area that is seeking an extension to the statutory attainment date 
pursuant to section 188(e).\203\ The RFP analysis must clearly convey 
how the schedule for implementing BACM and BACT and any additional 
control measures will provide for generally linear progress towards 
attainment or, if step-wise progress is more appropriate for the 
specific nonattainment area in question, the analysis must convey an 
appropriate implementation schedule and must explain why generally 
linear progress towards emissions reductions in the area is not 
appropriate (e.g., due to the nature of the nonattainment problem and 
the types of sources contributing to PM2.5 levels in the 
area). For a Serious area that cannot demonstrate attainment by the 
statutory Serious area attainment date, the EPA proposes that the state 
must include in its RFP analysis the anticipated emissions reductions 
expected to be achieved through the implementation of BACM and BACT and 
MSM on sources in the nonattainment area. As with RFP plans for 
Moderate areas, the EPA proposes that a state must submit one or more 
projected emissions inventories as part of the RFP plan for any Serious 
PM2.5 nonattainment area following the same guidance that 
applies to emissions inventories for attainment plans (see Section VI.B 
of this preamble for a complete discussion of emissions inventories for 
Serious area attainment plans). These projected inventories must 
correspond with the quantitative milestone date(s) for the area as 
described in Section VI.H of this preamble. The EPA proposes that motor 
vehicle emissions budgets must also be established for direct 
PM2.5 and any relevant PM2.5 precursor using the 
latest planning assumptions and the latest approved motor vehicle 
emissions model available at the time that the Serious area attainment 
plan is developed.\204\
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    \203\ As noted in Section VI.B of this preamble, depending upon 
when the area is reclassified from Moderate to Serious, this base 
year inventory may need to be more recent than the inventory 
submitted with the Moderate area attainment plan.
    \204\ If an area includes re-entrained road dust in the motor 
vehicle emissions budget, the latest approved version of AP-42 
should be used unless the EPA has approved an alternative model for 
the area.
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    The EPA seeks comment on all aspects of the agency's proposal for 
meeting the statutory RFP requirements as they apply to Serious 
nonattainment areas. Furthermore, the EPA seeks comment on the proposed 
options described in Section IV.F of this preamble regarding how to 
prepare an RFP plan, geographic coverage of emission sources for RFP, 
and RFP requirements for multi-state nonattainment areas, which would 
also apply to Serious area attainment plans.

G. Quantitative Milestones

    The attainment plan for any Serious nonattainment area must include 
quantitative milestones pursuant to section 189(c). These quantitative 
milestones would be in addition to those identified in the area's 
Moderate area attainment plan, and would need to continue to be 
achieved every 3 years until the area attains the NAAQS. Specifically, 
the Serious area plan for an area that can demonstrate attainment by 
the statutory Serious area attainment date would have to contain 
quantitative milestones to be achieved by 7.5 years from the area's 
date of designation as nonattainment. This date would be 3 years after 
the first quantitative milestones for the area, to be met 4.5 years 
from designation of the area and 3 years after the Moderate area 
attainment plan was due to the EPA. The EPA also proposes and seeks 
comment on a requirement that a Serious area plan for an area that can 
demonstrate attainment by the statutory Serious area attainment date 
must also include quantitative milestones to be reached 10.5 years from 
designation, to help assess the state's progress toward attaining the 
PM2.5 NAAQS in the event the area fails to attain by the 
applicable attainment date. For a Serious area that cannot demonstrate 
attainment by the statutory Serious area attainment date, the EPA 
proposes that the state must include in the Serious area attainment 
plan quantitative milestones to be achieved at years 7.5, 10.5 and 13.5 
from the area's date of designation.
    The Addendum included guidance that recommended milestones ``should 
be addressed by quantifying and comparing the annual incremental 
emission reductions which result from implementation of BACM and BACT 
(required within 4 years after the area is reclassified as serious) and 
from additional measures included in the final serious area SIP to 
those reductions which were identified in the SIP as quantitative 
milestones necessary to achieve the NAAQS by the applicable attainment 
date.'' \205\
---------------------------------------------------------------------------

    \205\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42016.
---------------------------------------------------------------------------

    The EPA continues to agree with the fundamental concept conveyed in 
the existing guidance, but believes that it is impractical to expect 
that a state will always be able to quantify and compare real and 
projected emissions reductions, and submit a report to the EPA within 
90 days of a given milestone, as required under section 189(c)(2). 
Therefore, the EPA proposes that the general proposed approach to 
selecting quantitative milestones, described in Section IV.G, should 
apply to any attainment plan for a PM2.5 nonattainment area, 
independent of its classification. Specifically, the EPA proposes that 
states be allowed to select the quantitative milestones that they 
identify as appropriate and quantifiable and that will provide for 
objective evaluation of progress toward attainment in their Serious 
PM2.5 nonattainment area, and that the EPA, in its 
attainment plan approval process, will determine if they satisfy the 
statutory requirements of section 189(c).
    In addition to this general proposed approach for selecting 
quantitative milestones and similar to an option proposed for Moderate 
area attainment plans, the EPA proposes to require that, at a minimum, 
states must include in all attainment plans for Serious 
PM2.5 nonattainment areas a measure to confirm that some 
specific portion of BACM and BACT for the area has been implemented as 
appropriate in order to comply with the statutory requirement at 
section 189(b)(1)(B). The EPA acknowledges that the precise 
quantifiable metric (e.g., 50 percent of BACM and BACT measures 
implemented by milestone date 7.5 years from designation) would need to 
be determined on a case-by-case basis, as it would depend upon the date 
of reclassification of the area, whether the metric is to be achieved 
at year 7.5 or year 10.5 from designation, and the anticipated 
implementation timing and nature of the BACM and BACT controls 
themselves. Nonetheless, the EPA believes it would be appropriate to 
include it as a metric that any state with a Serious nonattainment area 
must adopt as a quantitative milestone to demonstrate RFP (and thus 
must demonstrate compliance with when they submit their milestone 
report), as it derives from a statutory provision that applies to all 
Serious areas and thus represents a milestone that all Serious 
nonattainment areas must meet.
    The EPA seeks comment on these proposed options for interpreting 
the statutory quantitative milestone requirements for Serious areas.

H. Contingency Measures

    As noted in Section IV.G of this preamble, all PM2.5 
nonattainment areas must include in their attainment plans

[[Page 15417]]

contingency measures consistent with section 172(c)(9). Contingency 
measures are additional control measures to be implemented in the event 
that an area fails to meet RFP requirements or fails to attain the 
PM2.5 standard by the applicable attainment date. These 
measures must be fully adopted rules or control measures that are ready 
to be implemented quickly upon a determination by the EPA that the area 
failed to meet RFP or failed to meet the standard by the applicable 
attainment date, and such measures are required to take effect without 
significant further action by the state or the EPA.
    The statutory contingency measure requirement at section 172(c)(9) 
is not superseded or subsumed by any requirement under subpart 4, nor 
does it apply only to Moderate area attainment plans. Thus, contingency 
measures are required for Serious PM2.5 nonattainment areas 
as part of a state's Serious area attainment plan submission. The EPA 
proposes that the criteria for identifying and selecting contingency 
measures for a Serious area attainment plan should be the same as those 
for Moderate area plans. Specifically, the EPA proposes that the 
following requirements must be met in order for contingency measures to 
be approvable as part of a state's Serious area attainment plan 
submission:
    1. Contingency measures must be fully adopted rules or control 
measures that are ready to be implemented quickly upon a determination 
by the Administrator of the nonattainment area's failure to meet RFP or 
failure to meet the standard by its attainment date.
    2. The SIP must contain trigger mechanisms for the contingency 
measures, specify a schedule for implementation, and indicate that the 
measures will be implemented without significant further action by the 
state or by the EPA.
    3. Contingency measures must consist of control measures that are 
not otherwise included in the control strategy for the SIP, or must 
require further implementation of partial measures already included in 
the SIP as BACM or BACT, additional feasible measures, or MSM.
    4. Contingency measures must provide for emissions reductions 
equivalent to 1 year's share of reductions needed to demonstrate 
attainment (i.e., the overall needed reductions divided by the number 
of years from the base year to the attainment year), or equivalent to 1 
year's worth of air quality improvement or emissions reductions 
proportional to the overall amount of air quality improvement or 
emissions reductions to be achieved by the area's attainment plan.
    The EPA further proposes that a state may elect to rely on 
contingency measures that achieve emissions reductions on sources 
located outside the nonattainment area, but within the state, as well 
as from within the nonattainment area, provided that the measures on 
sources outside the designated nonattainment area are demonstrated to 
produce the appropriate air quality impact within the nonattainment 
area.
    As with contingency measures for Moderate nonattainment areas, the 
EPA believes it appropriate that a state might rely on additional 
reductions in the years following a failure to meet RFP requirements or 
a failure to attain the NAAQS by the applicable attainment date from 
federal or local measures already scheduled for implementation as part 
or all of their contingency measures. The EPA could potentially 
consider such measures as meeting the contingency measure requirement 
as long as they produce emissions reductions in excess of those 
required to meet other statutory provisions, such as to meet BACM and 
BACT requirements, and they can be relied on to achieve a sufficient 
portion of the actual emissions reductions necessary to reduce 
emissions in the area while the state develops a new plan to bring the 
area into attainment.\206\ As with contingency measures for Moderate 
area attainment plans, the EPA proposes that the emissions reductions 
associated with contingency measures for Serious area plans must be 
equal to approximately 1 year's worth of emissions reductions necessary 
to achieve RFP for the area, unless the state adequately demonstrates 
that some smaller amount of reductions is appropriate while the state 
is revising its attainment plan for the area. The EPA seeks comment on 
this requirement.
---------------------------------------------------------------------------

    \206\ See LEAN v. EPA, 382 F.3d 575 (5th Cir. 2004).
---------------------------------------------------------------------------

    The Addendum provided guidance related specifically to the 
selection and implementation of contingency measures for Serious 
nonattainment areas. First, the EPA guidance indicated that ``for those 
moderate areas reclassified as serious, if all or part of the moderate 
area plan contingency measures become part of the required serious area 
control measures (i.e., BACM), then additional contingency measures 
must be submitted whether or not the previously submitted contingency 
measures had already been implemented. Further, the affected states 
must ensure that serious areas have adequate contingency measures 
considering, among other things, new information about the potential 
attainment shortfall for the newly reclassified serious area.'' \207\ 
The EPA continues to believe that this approach to the statutory 
contingency measure requirement is appropriate and proposes to adopt it 
for purposes of implementing the PM2.5 NAAQS in Serious 
nonattainment areas.
---------------------------------------------------------------------------

    \207\ Addendum to General Preamble, 59 FR 41988 (August 16, 
1994), at 42015.
---------------------------------------------------------------------------

    With regard to the timing for implementing contingency measures, 
the EPA reiterates that the purpose of contingency measures is to 
ensure that corrective measures are put in place automatically at the 
time that the EPA makes a determination that an area has failed to meet 
RFP or failed to meet the NAAQS by the applicable attainment date. For 
any nonattainment area, the EPA is required to determine within 90 days 
after receiving a state's RFP demonstration, and within 6 months after 
the attainment date for an area, whether the state has met their 
statutory obligations for demonstrating RFP or attaining the standard, 
as appropriate. As with Moderate areas, the EPA believes that 
contingency measures should become effective for Serious areas within 
60 days of the EPA making its determination that the area failed to 
meet RFP or attain the NAAQS and proposes to require this for purposes 
of PM2.5 NAAQS implementation in Serious nonattainment 
areas.
    Finally, while section 172(b) gives discretion to the Administrator 
to establish a deadline for submitting contingency measures up to 3 
years from designation of the area, it does not explicitly address the 
appropriate submittal date for contingency measures for areas 
reclassified to Serious. In the Addendum, the EPA indicated that 
``states must submit contingency measures for serious areas or 
otherwise demonstrate that adequate measures are in place within 3 
years of reclassification.'' \208\ The EPA proposes and seeks comment 
on applying this guidance to Serious nonattainment areas for current 
and future PM2.5 NAAQS.
---------------------------------------------------------------------------

    \208\ Id.
---------------------------------------------------------------------------

    In addition, as described in Section VI.A, the EPA proposes an 
alternative submission deadline for Serious area contingency measures 
that would align the contingency measure due date with the Serious area 
attainment demonstration due date. If an area is reclassified under the 
EPA's discretionary authority, the Serious area

[[Page 15418]]

attainment demonstration is due 4 years from the date of 
reclassification; under this alternative proposed approach, contingency 
measures would also be due 4 years from the date of reclassification 
for such areas. If an area is reclassified under the EPA's mandatory 
duty upon failure of the area to attain the NAAQS by the Moderate area 
attainment date, then the Serious area attainment demonstration is due 
18 months from the date of reclassification; accordingly, under this 
alternative proposed approach, contingency measures would also be due 
18 months from the date of reclassification for such an area. In either 
case, the BACM and BACT provisions for the Serious area would be due at 
or before the time contingency measures would be due, which is 
appropriate given that the EPA expects a state to consider its BACM and 
BACT measures as it develops its contingency measures. The state may 
ascertain that measures not otherwise required or necessary for BACM or 
BACT may nevertheless be suitable for purposes of contingency measures. 
The EPA seeks comment on this alternative approach to setting Serious 
area contingency measure due dates.

I. Attainment Dates

    As explained earlier, section 188 establishes the attainment dates 
for both Moderate and Serious areas. For a Serious area, section 
188(c)(2) provides that ``the attainment date shall be as expeditiously 
as practicable but no later than the end of the tenth calendar year 
beginning after the area's designation as nonattainment.'' \209\ For 
example, for an area initially designated as nonattainment effective in 
April 2015 that is reclassified to Serious at some future date, the 
Serious area attainment date, absent any approved Serious area 
attainment date extension, would be no later than December 31, 2025 
(the end of the tenth calendar year after designation). As discussed in 
Section IV.I, the EPA proposes to interpret the references to 
``designation'' in CAA section 188(c) as meaning ``effective date of 
designation,'' consistent with the agency's prior approach for 
implementing the previous PM2.5 NAAQS under subpart 1 and 
other NAAQS.
---------------------------------------------------------------------------

    \209\ The EPA believes that there is no real effect on 
attainment date determinations due to the small difference in 
statutory language in section 188(c) basing the Moderate area 
attainment date on the ``sixth calendar year after the area's 
designation'' and the Serious area attainment date on the ``tenth 
calendar year beginning after the area's designation,'' (emphasis 
added).
---------------------------------------------------------------------------

    The process for a state to determine the most expeditious 
attainment date practicable for a Serious area will depend upon the 
final approach selected for determining BACM and BACT for the area. 
Therefore the EPA is proposing two approaches for determining the 
appropriate attainment date for a Serious area. Under the first 
approach, which would correspond to the agency's proposed Option 1 for 
determining BACM and BACT--independent of the attainment demonstration 
for the area--the state would simply include the control measures 
determined to be BACM and BACT for the area in its air quality 
modeling, and would report the results of the modeling, including the 
earliest projected attainment date.
    Under the second proposed approach, which would correspond to the 
EPA's proposed Option 2 for determining BACM and BACT--tied to the 
attainment needs of the particular nonattainment area--the state would 
be required to follow a two-step process for determining the 
appropriate attainment date for the area. First, the state would be 
required to demonstrate through air quality modeling that the area can 
attain the relevant NAAQS by the latest statutory attainment date and 
determine which control measures and technologies are needed for the 
area to attain by that date. Second, the state would be required to 
determine whether implementing any remaining BACM or BACT controls 
(i.e., those not needed for attainment by the latest date) or any other 
additional controls can cumulatively advance the attainment date for 
the area by at least 1 year. In the event that a state determines that 
the area can attain the relevant NAAQS earlier through the application 
of these other measures, the state must propose the earlier date as 
part of the attainment plan submission for the area. This second 
approach is similar to the proposed approach for determining the most 
expeditious attainment date for a Moderate area.
    As with Moderate area attainment dates, when the EPA takes action 
to approve the different elements of the attainment plan for the 
Serious area, one of the elements that the agency will take action on 
will be the state's proposed attainment date for the area. If the EPA 
approves an attainment date for the area that is earlier than the 
latest date allowed by statute, then the applicable attainment date for 
the area will be the approved date. If the state demonstrates that the 
Serious area cannot practicably attain the NAAQS by the end of the 
tenth calendar year following designation, the state may request a 
Serious area attainment date extension as long as certain conditions 
are met, as described next in Section VI.J.

J. Attainment Date Extensions

1. Statutory Requirements
    As with Moderate areas, the EPA may grant an extension of the 
attainment date for a Serious PM2.5 nonattainment area if 
certain statutory criteria are met. Specifically, section 188(e) 
provides that the EPA may allow one attainment date extension of no 
more than 5 years ``upon application by any state . . . if attainment 
by the [original Serious area attainment date] would be impracticable, 
the state has complied with all requirements and commitments pertaining 
to that area in the implementation plan, and the state demonstrates to 
the satisfaction of the Administrator that the plan for that area 
includes the most stringent measures that are included in the 
implementation plan of any state or are achieved in practice in any 
state, and can feasibly be implemented in the area.'' In addition to 
the required preconditions for such an extension, the statute also 
includes factors which the Administrator may use as she considers 
whether to grant the extension and the length of the extension, 
including ``the nature and extent of nonattainment, the types and 
numbers of sources or other emitting activities in the area (including 
the influence of uncontrollable natural sources and transboundary 
emissions from foreign countries), the population exposed to 
concentrations in excess of the standard, the presence and 
concentrations of potentially toxic substances in the mix of 
particulate emissions in the area, and the technological and economic 
feasibility of various control measures.'' \210\
---------------------------------------------------------------------------

    \210\ Notably, these statutory criteria do not include specific 
ambient air quality criteria like the criteria that need to be met 
in the year prior to a Moderate area attainment date in order for 
the area to qualify for an attainment date extension under section 
188(d).
---------------------------------------------------------------------------

2. Proposed Approach
    In the Addendum, the EPA generally described the statutory 
requirements listed above and expressed an intent to issue guidance on 
applying for an extension of the Serious area attainment date, if 
appropriate. While ultimately the EPA did not deem it necessary to 
issue such guidance, the EPA has interpreted these statutory 
requirements through actual exercise of its authority under section 
188(e) in past rulemakings for specific PM10 nonattainment 
areas. For example, the EPA interpreted section 188(e) in approving an 
extension of a Serious area

[[Page 15419]]

attainment date for purposes of the PM10 NAAQS for the 
Maricopa area (AZ).\211\ The EPA believes that the steps finalized in 
the Maricopa County PM10 Serious area SIP approval notice 
provide an appropriate starting point for a proposed regulatory 
approach, with some potential modification, for states to meet the 
statutory requirements that could apply nationally. The EPA is thus 
proposing to require that states adhere to the following steps when 
preparing and submitting a request for a Serious area attainment date 
extension:
---------------------------------------------------------------------------

    \211\ Maricopa County PM10 Serious area attainment 
date extension, proposal: 65 FR 19964 (April 13, 2000); and final: 
67 FR 48718 (July 25, 2002).
---------------------------------------------------------------------------

    Step 1: Demonstrate that attainment by the statutory Serious area 
attainment date is impracticable. In order to demonstrate 
impracticability, the state would have to show that the implementation 
of all BACM and BACT and all additional feasible measures required 
under section 172(c)(6) will not bring the area into attainment by the 
statutory Serious area attainment date (i.e., by no later than the end 
of the tenth calendar year after designation).\212\ The statutory 
provision for demonstrating impracticability requires that the 
demonstration be based on air quality modeling (see section 
189(b)(1)(A)). Additional guidance on this demonstration is provided in 
Section VI.E of this preamble.
---------------------------------------------------------------------------

    \212\ This proposed approach parallels the EPA's proposed 
approach, described earlier in this preamble, for the 
impracticability option for Moderate areas under CAA section 
189(a)(1)(B) in which all measures that qualify as RACM and RACT and 
all additional reasonable measures are required before a Moderate 
area plan could show impracticability of attainment by the statutory 
Moderate area attainment date (the end of the sixth calendar year 
after designation).
---------------------------------------------------------------------------

    Step 2: Comply with all requirements and commitments in the 
applicable implementation plan. Similar to the proposed approach 
described in Section IV.J of this preamble for Moderate area attainment 
date extensions, the EPA proposes to interpret the criterion under 
section 188(e) that requires a state to have ``complied with all 
requirements and commitments pertaining to that area in the 
implementation plan'' simply to mean that the state has implemented the 
control measures in the SIP revisions it has submitted to address the 
applicable requirements in sections 172 and 189. For a Serious area 
attainment date extension request being submitted contemporaneously 
with the ``original'' Serious area attainment plan for the area, the 
EPA proposes to read section 188(e) not to require the area to have a 
fully approved attainment plan that meets the CAA's requirements for 
Moderate areas. The agency proposes to base this reading on the plain 
language of section 188(e) which requires the state to comply with all 
requirements and commitments pertaining to that area in the 
implementation plan but does not require that the state comply with all 
requirements pertaining to the area in the CAA.\213\ For the same 
reason, the EPA also proposes to read this provision not to bar an 
extension if all or part of an area's Moderate area plan is disapproved 
or has been promulgated as a FIP, provided the area has complied with 
all of the requirements in the applicable FIP, or in the applicable SIP 
and FIP.
---------------------------------------------------------------------------

    \213\ This interpretation as applied to section 188(e) for 
Serious area attainment date extensions was upheld by the Ninth 
Circuit Court of Appeals in Vigil v. Leavitt, 366 F.3d 1025, amended 
at 381 F.3d 826 (9th Cir. 2004).
---------------------------------------------------------------------------

    However, for a Serious area attainment date extension request being 
submitted sometime after submission of an ``original'' Serious area 
attainment plan that contained an attainment demonstration meeting the 
requirements of section 189(b)(1)(A)(i), the EPA proposes to read 
section 188(e) not to require the area to have a fully approved 
attainment plan that meets the CAA's requirements for Serious areas, 
but to have a fully approved Moderate area attainment plan. The 
rationale for this distinction is due to the timing of the Serious area 
attainment date extension request under these circumstances, which is 
discussed in greater detail later in this section. The EPA believes 
that this proposed interpretation of this criterion would apply whether 
the area was reclassified to Serious under the EPA's discretionary 
authority (section 188(b)(1)) or by operation of law upon failing to 
attain by the Moderate area attainment date (section 188(b)(2)).
    The EPA also seeks comment on an alternative interpretation of the 
implementation plan compliance criterion that would require a state to 
have a Moderate area attainment plan fully approved by the EPA, not 
just fully implemented by the state, at the time of the Serious area 
attainment date extension request, regardless of when such a request is 
submitted to the EPA. The EPA believes that one may reasonably argue 
that a state seeking an extension of the Serious area attainment date 
should have fully implemented all elements of an approved Moderate area 
attainment plan. The EPA believes that while such a condition may be 
reasonable, generally speaking, there may be circumstances in which a 
state submits a Moderate area attainment plan that the EPA is unable to 
approve in a timely way, potentially creating a situation in which the 
state cannot qualify for a Serious area attainment date extension (due 
to its unapproved Moderate area plan) even if the area is reclassified 
to Serious and cannot practicably attain by the statutory attainment 
date for a Serious area. The EPA seeks comment on this alternate 
proposed interpretation of the applicable implementation plan 
compliance criterion under section 188(e). Recognizing that a situation 
such as that described above may be rare, the agency also seeks comment 
on what remedy might be available under the statute if such a situation 
comes to pass if the EPA were to finalize this alternative proposed 
interpretation of the applicable implementation plan criterion.
    Step 3: Demonstrate the inclusion of MSM. To qualify for any 
extension of a Serious area attainment date, section 188(e) requires a 
state to ``demonstrate to the satisfaction of the Administrator that 
the plan for the area includes the most stringent measures that are 
included in the implementation plan of any state, or are achieved in 
practice in any state, and can feasibly be implemented in the area.'' 
In its prior guidance in the Addendum, the EPA interpreted the term 
``most stringent measure'' (MSM) to mean the maximum degree of emission 
reduction that has been required or achieved from a source or source 
category in any other attainment plans or in practice in any other 
states and that can feasibly be implemented in the area seeking the 
extension, such as what LAER represents for new or modified sources 
under the NNSR permit program.\214\
---------------------------------------------------------------------------

    \214\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42010.
---------------------------------------------------------------------------

    The agency proposes that a state would need to follow a process for 
determining MSM for a Serious nonattainment area that is generally 
similar to proposed Option 2 for BACM and BACT described in Section 
VI.D of this preamble, which would include exemptions from MSM for 
sources in de minimis source categories if such measures did not 
collectively advance the attainment date for the area by at least 1 
year. The EPA is also proposing an alternative approach for determining 
MSM for a Serious nonattainment area that would provide for de minimis 
source category exemptions for MSM only for those source categories 
that do not contribute significantly to ambient PM2.5 
concentrations in the Serious nonattainment area, an approach more 
closely aligned with proposed Option 1 for determining BACM and BACT.

[[Page 15420]]

    Under proposed approach #1 for MSM, the EPA would prescribe a five-
step process for states to follow when selecting and implementing MSM. 
This proposed approach is similar to that used in practice for 
approving the PM10 Serious area attainment plan and Serious 
area attainment date extension request submitted for Maricopa County 
(AZ) in 2000.\215\
---------------------------------------------------------------------------

    \215\ Maricopa County PM10 Serious area attainment 
date extension, 67 FR 48718 (July 25, 2002).
---------------------------------------------------------------------------

    The first step of this proposed approach would be for the state to 
update as needed the emissions inventory of direct PM2.5 and 
PM2.5 precursor sources and source categories in the Serious 
nonattainment area required under section 172(c)(3) for any attainment 
plan submission. The EPA expects that the state would meet this 
inventory requirement as part of its Serious area attainment plan 
submittal without any additional work if the state submits the Serious 
area attainment date extension request simultaneously with the plan 
itself. However, in the event the attainment date extension request is 
submitted after the ``original'' Serious area attainment plan for the 
area (i.e., toward the end of the Serious area attainment period), then 
the EPA proposes to require that the state must submit a more recent, 
complete and accurate emissions inventory that meets the same emissions 
inventory requirements for Moderate and Serious PM2.5 
nonattainment areas pursuant to section 172(c)(3), as well as an 
attainment projected inventory as part of the new Serious area 
attainment plan for the area. The inventories submitted to support a 
Serious area attainment plan must also include point sources meeting 
the lower major stationary source threshold in 40 CFR part 51, subpart 
A.
    The second step in this proposed MSM determination process would 
require the state to perform air quality modeling in order to evaluate, 
for each of the various source categories included in the emissions 
inventory for the area, the impact on PM2.5 concentrations 
in excess of the applicable NAAQS in order to determine which 
categories are significant for the purposes of adopting MSM. Those 
source categories for which such modeling indicates potential control 
measures collectively would have only a de minimis effect on advancing 
the attainment date for the area could be eliminated from further 
consideration. In the context of the EPA's action to approve the 
Maricopa County PM10 Serious area attainment plan and 
attainment date extension request, the agency finalized an approach for 
judging what constitutes a de minimis source category for MSM by 
applying a test of whether MSM controls on the allegedly de minimis 
sources would result in more expeditious attainment, rather than 
applying a test of whether or not requiring the application of controls 
for such sources would make the difference between attainment and 
nonattainment by the statutory Serious area deadline, as the latter 
test implicitly would be met through the controls chosen for 
demonstrating attainment by the alternate attainment date for the area. 
In the agency's explanation of the proposed approach, the EPA explained 
that ``Our responsibility under section 188(e) . . . is to grant the 
shortest practicable extension of the attainment date by assuring the 
plan provides for attainment as expeditiously as practicable. Thus, one 
means of determining an appropriate de minimis level is to determine if 
applying MSM to the proposed de minimis source categories would 
meaningfully expedite attainment. If it did, then the de minimis level 
is too high, and if it did not, then the de minimis level is 
appropriate.'' \216\ The EPA thus proposes to determine whether any 
source categories should be eliminated from MSM controls through a de 
minimis exemption based on a demonstration that collectively applying 
MSM controls to such source categories would not advance attainment of 
the NAAQS in the area by at least 1 year. This test would presumably 
result in a more stringent threshold for what is considered a de 
minimis source category for MSM as compared to the threshold for de 
minimis source categories for BACM and BACT as described in the EPA's 
proposed Option 1 for BACM and BACT determination criteria (see Section 
VI.D of this preamble). The EPA proposes and seeks comment on this test 
for determining whether any source categories could be found to be de 
minimis and thus not subject to MSM controls.
---------------------------------------------------------------------------

    \216\ Maricopa County PM10 Serious area attainment 
date extension proposal, 65 FR 19964
    (April 13, 2000), at page 19969.
---------------------------------------------------------------------------

    The third step in the EPA's first proposed approach to determining 
MSM for a Serious nonattainment area would involve identifying the 
potentially most stringent measures in other implementation plans for 
PM2.5 or other NAAQS, or used in practice in other states 
for controlling emissions from each of the remaining source categories 
listed in the emissions inventory that were not determined to be de 
minimis. For each measure, the state would be required to determine its 
technological and economic feasibility for sources in the area. The EPA 
proposes generally to apply more stringent criteria for determining the 
feasibility of potential MSM than that described for BACM and BACT in 
Section VI.D. In some situations, MSM could involve increasing the 
coverage of measures that were already adopted and implemented as BACM 
and BACT (for example, changing out an even greater percentage of 
woodstoves in an area, or paving even more roads, if such source 
categories were major contributors to the air quality problem in the 
nonattainment area).
    However, because BACM and BACT represent the ``best'' level of 
control feasible for an area, it would be possible for the MSM 
requirement to result in no more controls and no more emissions 
reductions in an area than result from the implementation of BACM and 
BACT. Stated another way, there may be sources or categories for which 
no other feasible controls exist beyond what a state has already 
adopted as BACM or BACT. Given the strategy in the nonattainment 
provisions of the CAA to offset longer attainment timeframes with more 
stringent control requirements, the EPA therefore proposes to interpret 
the MSM provision in order to increase the potential that it will 
result in additional controls beyond the set of measures adopted as 
BACM and BACT by requiring a state to reanalyze any measures that were 
rejected during the state's BACM and BACT analysis for the area to see 
if they are now feasible for the area given the potentially longer 
attainment date (up to 5 years after the statutory Serious area 
attainment date) or given the changes that have occurred in the interim 
that improve the feasibility of previously rejected measures.
    The fourth step of this first proposed approach would require the 
state to compare the potential MSM for each non-de minimis source 
category against the measures, if any, already adopted for that source 
category in the Serious nonattainment area to determine if such MSM 
would provide any additional reductions.
    The fifth step would then require that the plan provide for the 
adoption and expeditious implementation of any MSM that is more 
stringent than existing measures or, in lieu of adoption, provide a 
reasoned justification for rejecting the potential MSM, i.e., provide 
an explanation as to why such measures cannot be feasibly implemented 
in the area.

[[Page 15421]]

    As noted earlier, the EPA expects that this first proposed approach 
to determining MSM would be most compatible with the agency's proposed 
Option 2 for determining BACM and BACT, described in Section VI.D. 
Under proposed Option 2 for BACM and BACT determinations, a state would 
be required to implement only those ``best'' control measures necessary 
to bring a Serious nonattainment area into attainment expeditiously. 
Such an approach to BACM and BACT determinations would not incorporate 
an explicit step in the process for a state to exempt de minimis source 
categories from consideration for potential control measures. However, 
it would allow a state to eliminate any potential BACM or BACT or 
additional feasible measures that are not needed to bring a Serious 
area into attainment by the statutory attainment date and that cannot, 
collectively, advance the attainment date for the area by at least 1 
year. Proposed Option 2 for determining BACM and BACT for an area is 
thus similar to the proposed approach to MSM described above, in which 
a state could eliminate from further consideration those source 
categories for which potential control measures collectively would have 
only a de minimis effect on advancing the attainment date for the area 
(see proposed step 2).
    The EPA's proposed Option 1 for BACM and BACT determinations would 
include an explicit step in the process for exempting de minimis source 
categories from further consideration for potential control measures. 
However, under such approach, a state would need to assess whether 
emissions of a particular pollutant from a given source category 
contributed significantly to PM2.5 concentrations in the 
nonattainment area. If the state determined that the source category 
contributed only a de minimis amount of emissions, then the state could 
exempt the source category from further consideration for potential 
control measures. Thus, while it incorporates a step to identify de 
minimis source categories, the EPA's proposed Option 1 for BACM and 
BACT determinations is not wholly consistent with the agency's proposed 
approach #1 for determining MSM.
    Therefore, the EPA is also proposing an alternative approach for 
determining MSM for a Serious nonattainment area that would be more 
compatible with the EPA's proposed approach #1 for determining BACM and 
BACT. Under this alternative proposed approach for determining MSM, a 
state could exempt de minimis source categories from further 
consideration, but de minimis source categories would be identified by 
virtue of their lack of significant contribution to PM2.5 
levels in the area, not by virtue of whether controlling such sources 
categories collectively could expedite attainment of the relevant 
NAAQS. In this way, de minimis source categories for MSM would be 
defined in a similar way, or subject to a similar ``significant 
contribution'' test, as de minimis source categories for BACM and BACT 
determinations under proposed Option 1. Thus under proposed approach #2 
for MSM, the steps described for determining MSM would generally be the 
same as under proposed approach #1, with the exception of step 2. 
Rather, the EPA proposes an alternative step 2 in the MSM determination 
process in which a state could identify de minimis source categories to 
exempt from further control based on an analysis of the particular 
contribution made by a given source category to ambient 
PM2.5 levels in the nonattainment area. The EPA believes 
that defining de minimis source categories and ``significant 
contribution'' for determining de minimis source categories would be 
equally challenging in the context of MSM determinations as in the 
context of BACM and BACT determinations.\217\ However, in the event the 
agency finalizes proposed Option 1 for BACM and BACT determinations, 
the EPA believes it would be appropriate to finalize proposed approach 
#2 for MSM, and would require that a state seeking to exempt from MSM 
sources in a given source category apply more stringent criteria for 
evaluating whether a certain source category's contributions to the 
area's PM2.5 concentrations are indeed de minimis.
---------------------------------------------------------------------------

    \217\ See the discussion of de minimis source categories in 
Section VI.D in this preamble.
---------------------------------------------------------------------------

    The EPA believes that either of these proposed approaches for 
determining MSM for a Serious nonattainment area would be consistent 
with the EPA's guidance in the Addendum to define MSM as those measures 
that can ``feasibly be implemented in the relevant area from among 
those which are either included in any other SIP or have been achieved 
in practice by any other state.'' One of the key features of this 
guidance relates to identifying control measures implemented elsewhere, 
which is also a key feature of the EPA's proposed process for 
identifying RACM and RACT and additional reasonable measures (and BACM 
and BACT and additional feasible measures, if necessary) for a 
PM2.5 nonattainment area. For these processes, the EPA is 
proposing that a state identify potential measures for consideration as 
RACM or RACT or additional reasonable measures (or BACM or BACT or 
additional feasible measures) by looking at measures implemented by 
other states to meet PM2.5 NAAQS or other NAAQS. Thus, a 
state seeking to identify MSM should be able to start its process using 
with the work already undertaken for the nonattainment area's RACM and 
BACM determinations and to make updates to the list of potential 
control measures accordingly.
    The EPA notes that section 188(e) does not identify a deadline for 
a state to implement MSM, while elsewhere the statute establishes a 
deadline for implementing RACM and RACT and BACM and BACT (see CAA 
sections 189(a)(1)(C) and 189(b)(1)(A), respectively). However, because 
the clear intent of section 188(e) is to minimize the length of a 
Serious area attainment date extension, the EPA proposes that the 
implementation of MSM must be as expeditious as practicable but no 
later than 1 year prior to the alternative Serious area attainment date 
identified by the state in its extension request.
    The EPA seeks comment on whether the two proposed approaches to 
determine MSM are sufficiently consistent with the agency's respective 
proposed approaches to BACM and BACT determination. The agency also 
seeks comment on whether considerations regarding its MSM approach 
should influence the final selection of a BACM and BACT approach.
    Step 4: Demonstrate attainment by the most expeditious alternative 
date practicable. Section 189(b)(1)(A) requires that a Serious area 
plan demonstrate attainment, using air quality modeling, by the most 
expeditious date practicable after the statutory Serious area 
attainment date. This demonstration is the final criterion that must be 
met before the EPA may consider granting an extension. The agency's 
determination of whether the plan provides for attainment by the most 
expeditious date practicable would depend on whether the plan provides 
for implementation of BACM and BACT by the statutory implementation 
deadline and MSM as expeditiously as practicable. In no case would a 
state be able to seek an extension of a Serious area attainment date to 
a date more than 5 years past the statutory attainment date for Serious 
areas. Section VI.E of this preamble describes the EPA's proposed 
requirements for attainment

[[Page 15422]]

demonstration modeling for Serious area attainment plans.
    Step 5: Apply for an attainment date extension. The state would 
have to apply to the EPA for any extension of a Serious area attainment 
date. The request would have to accompany an attainment plan submission 
containing an attainment demonstration showing attainment by the most 
expeditious alternative date practicable, and the state would need to 
submit modeling as part of the attainment demonstration in accordance 
with Section VI.E. Furthermore, the state would have to provide the 
public reasonable notice and a public hearing on the attainment date 
extension request before submitting it to the EPA, as the EPA would 
consider it an integral part of the attainment demonstration and part 
of the revised SIP submission which is subject to the requirements of 
the CAA and federal regulations for public notice and hearing on SIP 
revisions.
3. Timing of Extension Request Submittal
    The EPA believes that a state may submit a request for an extension 
of the Serious area attainment date either at the time the original 
Serious area attainment plan is submitted following reclassification of 
the area or at a point in time closer to the Serious area attainment 
date. In the first case, when taken together with language under 
section 189(b)(1)(A)(ii) which describes the possibility of including 
an impracticability demonstration in a Serious area attainment plan 
that parallels the impracticability demonstration for a Moderate area 
attainment plan, section 188(e) appears to set an expectation that a 
state may request an extension of the attainment date for a Serious 
area when the state initially submits its Serious area plan. Therefore, 
the EPA would deem such a request as timely and appropriate.
    On the other hand, the EPA also recognizes that a state may prepare 
and fully implement a timely Serious area plan that includes modeling 
demonstrating attainment no later than the statutory Serious area 
attainment date (the end of the tenth calendar year following 
designation), and yet may see as the attainment date nears that the 
Serious area will in fact fail to attain by its projected attainment 
date. While the statute provides a remedy to be instituted immediately 
upon failure of a Serious area to attain the standard (through 
contingency measures and other measures stipulated in section 189(d)), 
the EPA also believes that the criteria of section 188(e) could be 
applied after a state submits a Serious area attainment plan but prior 
to the area failing to attain, as long as the area had not already been 
granted a prior Serious area attainment date extension under section 
188(e). In such a case, the EPA believes that it would be acceptable 
for a state to submit a Serious area attainment date extension request 
similar to that described above (for submissions made simultaneous with 
initial Serious area attainment plans) together with a new Serious area 
attainment plan meeting all of the statutory requirements that apply to 
such plans. In this case, the complete submission would have to be made 
in a timely way such that the EPA could fully review the new attainment 
plan for the area and the accompanying attainment date extension 
request, including the status of compliance with all requirements and 
commitments in the Moderate area attainment plan for the area, the 
justification for the selection of the alternate attainment date, and 
provisions for the implementation of MSM, prior to making its 
determination of failure of the area to timely attain the relevant 
NAAQS.
    The EPA seeks comment on this option, particularly with respect to 
whether the criteria proposed above are appropriate in a situation in 
which a state seeks a Serious area attainment date extension after 
submitting a Serious area attainment plan that initially demonstrated 
attainment by the statutory Serious area attainment date. For example, 
the EPA seeks comment in particular on whether it would be appropriate 
to interpret the section 188(e) requirement for a state to have 
``complied with all requirements and commitments pertaining to that 
area in the implementation plan'' as referencing those requirements and 
commitments contained in the area's Moderate area plan (as proposed 
above for areas seeking a Serious area attainment date extension 
simultaneous with submittal of their Serious area plan) or whether, for 
areas that already submitted Serious area plans demonstrating 
attainment, it is more appropriate that the state must have complied 
with all requirements and commitments pertaining to the area in the 
area's original Serious area attainment plan. The EPA believes this 
second interpretation is the more appropriate interpretation as it 
pertains to Serious areas seeking an extension of their attainment date 
as they approach their statutory Serious area attainment date, and 
therefore the agency is proposing and seeking comment on this approach. 
The EPA believes that this second interpretation is especially 
preferable if the EPA finalizes its proposal that interprets the SIP 
compliance requirement for areas seeking an attainment date extension 
simultaneous with their Serious area attainment plan submittal to mean 
that the state need only have implemented the control measures in the 
SIP revisions it has submitted to the EPA to address the CAA 
requirements in section 189 (i.e., to mean that the area need not have 
a fully approved attainment plan that meets the CAA's requirements for 
Serious areas).
    The EPA seeks comment on these proposed options for interpreting 
and implementing the statutory language at section 188(e) for Serious 
area attainment date extensions.

VII. What are the EPA's proposed requirements for attainment plans 
under CAA section 189(d) for Serious areas that fail to attain the 
NAAQS by the applicable attainment date?

    In the event that a Serious area fails to attain the 
PM2.5 NAAQS by the applicable attainment date, section 
189(d) requires that ``the state in which such area is located shall, 
after notice and opportunity for public comment, submit within 12 
months after the applicable attainment date, plan revisions which 
provide for attainment of the . . . standard and, from the date of such 
submission until attainment, for an annual reduction in PM10 
or PM10 precursor emissions within the area of not less than 
5 percent of the amount of such emissions as reported in the most 
recent inventory prepared for such area.''
    A state with a Serious nonattainment area subject to section 189(d) 
must submit to the EPA its plan to meet the requirements of section 
189(d) in the form of a complete attainment plan submission that 
contains the following elements: (i) An attainment demonstration and 
provisions for the implementation of measures that will achieve annual 
emissions reductions of not less than 5 percent from the most recent 
emissions inventory for the area for each year until attainment 
(section 189(d)); (ii) quantitative milestones that will be used to 
measure compliance with the RFP requirement (section 189(c)); and, 
(iii) regulation of PM2.5 precursors (in general to meet 
attainment and control strategy requirements and as specifically 
required for major stationary sources by section 189(e)). Subpart 1 
requirements that apply to Serious PM2.5 nonattainment areas 
also subject to the requirements of section 189(d) include the 
following: (i) A description of the expected annual incremental 
reductions

[[Page 15423]]

in emissions that will demonstrate RFP (section 172(c)(2)); (ii) 
emissions inventories (section 172(c)(3)); and, (iii) contingency 
measures (section 172(c)(9)). A state with a Serious PM2.5 
nonattainment area that fails to attain the NAAQS by the applicable 
Serious area attainment date must also address any statutory 
requirements relevant to Moderate nonattainment areas and Serious 
nonattainment areas under sections 172 and 189 of the CAA that have not 
already been satisfied. In addition, the EPA must approve a new 
attainment date for the area under sections 172(a)(2) and 179(d)(3).
    The remainder of this section presents the EPA's proposed 
requirements for attainment plan submissions under section 189(d).

A. Plan Due Dates

    Section 189(d) requires a state with a Serious PM10 
nonattainment area that failed to attain the NAAQS by the applicable 
Serious area attainment date to submit a new attainment plan submission 
for the area within 12 months after the missed attainment date. 
Therefore a state with a nonattainment area subject to section 189(d) 
must submit a new attainment plan for the area--with all required 
elements of the attainment plan--within 12 months after the missed 
attainment date.

B. Emissions Inventory Requirements

    As with all other attainment plan submissions required for Moderate 
and Serious PM2.5 nonattainment areas, a state must develop 
its submission to meet section 189(d) based on ``the most recent 
emissions inventory prepared for such [nonattainment] area.'' This 
inventory must meet the same requirements that would apply to any other 
emissions inventory submitted for a PM2.5 nonattainment area 
to meet the requirements of section 172(c)(3), which requires ``a 
comprehensive, accurate, and current inventory of actual emissions of 
the relevant pollutants'' in the nonattainment area. Therefore the EPA 
proposes that the inventory submitted with an attainment plan to meet 
section 189(d) requirements must also meet the EPA's proposed 
regulatory requirements for such emissions inventories as described 
earlier in this preamble under Section IV.B (for Moderate area 
attainment plans) and Section VI.B (for Serious area attainment plans).
    One important aspect of the emissions inventory required to be 
submitted with an attainment plan under section 189(d) is its role as 
the basis for calculating the emissions reductions of direct 
PM2.5 and PM2.5 precursors necessary to satisfy 
the 5 percent annual reduction criteria of section 189(d). For this 
reason, the EPA proposes that the ``most recent inventory'' for the 
area must not only meet the criteria as that described for a base year 
inventory submitted pursuant to section 172(c)(3) and in Section VI.B 
of this preamble, but also must fully account for emissions reductions 
achieved to date through the implementation of all RACM and RACT, BACM 
and BACT and additional reasonable and feasible measures submitted with 
the Moderate and original Serious area attainment plans for the area. 
In this way, the state will calculate the additional reductions that 
the nonattainment area will need beyond those already required in order 
to fulfill the requirements of section 189(d) and bring the area into 
attainment as expeditiously as practicable.
    In order to ensure that the ``most recent inventory'' is 
representative of the nonattainment problem in the area current at the 
time of the section 189(d) submission, the EPA proposes that the 
inventory year must be one of the 3 years from which monitored data was 
used to determine that the area failed to attain the PM2.5 
NAAQS by the applicable Serious area attainment date. The EPA believes 
that associating the inventory with one of these 3 years is reasonable 
in light of the fact that some BACM and BACT controls and additional 
feasible controls (required under section 172(c)(6)) for sources in the 
area may not be implemented until the beginning of the attainment year. 
Thus, requiring that a state use an emissions inventory for one of 
those 3 years will help ensure that the inventory adequately captures 
the emissions reductions already achieved through the prior 
implementation of BACM and BACT and additional feasible measures.
    The EPA recognizes the additional level of effort that may be 
needed to produce an up-to-date emissions inventory for a nonattainment 
area, and therefore is proposing and seeking comment on an alternative 
approach that would allow a state to select an inventory year earlier 
than one of the 3 years from which monitored data were used to 
determine that the area failed to attain the NAAQS by the applicable 
attainment date. Under this alternative proposed approach, another 
inventory year may be included in the plan under specific circumstances 
with the submission of a written justification for selecting the 
earlier year and in consultation with the appropriate EPA Regional 
Office. At a minimum, the state would need to demonstrate that the 
inventory for the alternative year adequately incorporates emissions 
reductions projected to be achieved through the implementation of BACM 
and BACT and additional feasible control measures submitted with the 
original Serious area attainment plan for the area. The EPA proposes 
that modification of an older inventory to incorporate those emissions 
reductions would be an acceptable way to meet this requirement. In 
considering use of this option, states could be obligated to achieve a 
larger annual reduction than 5 percent if the older inventory has 
higher emissions levels than the ``most recent inventory'' for the 
area.
    The EPA seeks comment on these proposed criteria and options for 
emissions inventories to be submitted as part of the attainment plan 
due for a Serious area under section 189(d).

C. Pollutants To Be Addressed in the Plan

    Section 189(d) requires states to develop a new attainment plan for 
an area that failed to attain by the applicable Serious area attainment 
date that provides for ``an annual reduction in PM10 or 
PM10 precursor emissions within the area of not less than 5 
percent of the amount of such emissions'' reported in the latest 
emissions inventory for the area. In Section III of this preamble, the 
EPA is proposing several options on how a state may evaluate which 
PM2.5 precursors to control for purposes of attaining the 
NAAQS in a particular nonattainment area. The EPA interprets the 
requirements of the CAA generally to allow an air agency to provide a 
``precursor demonstration'' that can support a determination that one 
or more precursors need not be subject to control requirements in a 
given nonattainment area, even if the area has failed to attain the 
relevant NAAQS by the applicable Serious area attainment date.
    Section III presents three options describing different proposed 
approaches to such precursor demonstrations, and requests comment on 
each. The discussion for each option describes how states and the EPA 
should address precursors for Moderate areas and for Serious areas, 
including Serious areas that fail to attain the PM2.5 NAAQS 
by the applicable attainment date. This section describes, for each of 
the three options, how the given precursor approach would apply to 
plans required to be submitted where the area has failed to attain by 
the Serious area attainment date.
     Option 1: Two independent analyses: (a) An attainment 
planning

[[Page 15424]]

analysis demonstrating that control measures for a particular precursor 
are not needed for expeditious attainment, meaning that the precursor 
can be excluded from measures needed to attain as expeditiously as 
practicable for all types of sources; and (b) a section 189(e) 
technical demonstration showing that major stationary sources of a 
particular precursor do not contribute significantly to levels that 
exceed the PM2.5 standard, meaning that the precursor can be 
excluded from control requirements for major sources and from NNSR 
permitting. Consistent with this approach, for an area subject to the 
requirements of section 189(d), the state would need to evaluate 
control measures to identify those needed to achieve a minimum 5 
percent reduction in emissions of direct PM2.5 or precursors 
on an annual basis, and identify those control measures for direct 
PM2.5 and all precursors that would bring the area into 
attainment as expeditiously as practicable.
     Option 2: Single analysis demonstrating that all emissions 
of a particular precursor from within the area do not significantly 
contribute to PM2.5 levels that exceed the standard, meaning 
that control requirements for emissions of the precursor from major 
stationary and area sources, as well as mobile sources, would not be 
required for expeditious attainment, control requirements for major 
sources, or for NNSR permitting. For an area subject to section 189(d) 
requirements for which a precursor had previously been demonstrated not 
to significantly contribute to PM2.5 levels that exceed the 
standard, the air agency would be required to update the precursor 
demonstration taking into account any relevant information or technical 
tools that had been developed since the demonstration was approved. 
Consistent with this approach, if, upon failure to attain, the state 
continued to demonstrate that the precursor did not contribute 
significantly to PM2.5 concentrations in the area, then the 
state would not need to identify or implement any measures to control 
that precursor's emissions.
     Option 3: An attainment planning analysis demonstrating 
that control measures for all types of sources of a particular 
precursor are not needed for expeditious attainment also would be 
deemed to meet the section 189(e) technical demonstration requirement, 
meaning that the state would not need to regulate emissions of the 
particular precursor from major stationary sources under the NNSR 
permitting program or other control requirements for major stationary 
sources. Consistent with this approach, for an area subject to the 
requirements of section 189(d), the state would need to evaluate 
control measures to identify those needed to achieve a minimum 5 
percent reduction in emissions of direct PM2.5 or precursors 
on an annual basis, and identify those control measures for direct 
PM2.5 and all precursors that would bring the area into 
attainment as expeditiously as practicable.
    The EPA will finalize its approach to PM2.5 precursors 
and clarify the implications for states conducting analyses to identify 
measures to satisfy the requirements of section 189(d) after 
considering public comment received on this proposal.

D. Attainment Plan Control Strategy

    The control strategy to be developed for the attainment plan 
submission for a Serious area subject to section 189(d) should place 
particular emphasis on control measures that can be implemented 
quickly, in order to ensure that the area attains the PM2.5 
NAAQS as expeditiously as practicable. The control strategy would need 
to include any additional measures that are beyond those already 
adopted for the area as RACM and RACT and additional reasonable 
measures, or BACM and BACT and additional feasible measures, and that 
are necessary to achieve annual reductions in emissions of direct 
PM2.5 and PM2.5 precursors from sources in the 
area of at least 5 percent of the amount of such emissions reported in 
the most recent emissions inventory for the area. The EPA is proposing 
to interpret section 189(d) in this way to address the ambiguity of how 
the statutory language should apply to the PM2.5 NAAQS, as 
section 189(d) requires ``an annual reduction in PM10 or 
PM10 precursor emissions . . . as reported in the most 
recent inventory prepared for such area.''
1. Proposed Approach
    The EPA believes that in light of the important role that 
PM2.5 precursors play in the formation of PM2.5, 
it is appropriate to require a state to implement control measures for 
all types of sources in a Serious nonattainment area subject to section 
189(d) to achieve the requisite 5 percent annual reduction in emissions 
of both direct PM2.5 and PM2.5 precursors from 
sources in that area. Accordingly, the EPA is proposing that, for 
direct PM2.5 and for PM2.5 precursors that the 
state and the EPA have determined are necessary to be controlled for 
purposes of attainment in the area, the attainment plan required by 
section 189(d) would have to include control measures that will achieve 
at least 5 percent reductions from the latest emissions inventory of 
each such pollutant on an annual basis until the area attains the 
relevant PM2.5 NAAQS. The EPA believes this is an 
appropriate interpretation of the 5 percent requirement of section 
189(d) and seeks comment on this proposed approach.
    The EPA also proposes and seeks comment on an alternative reading 
of the statute that would require a state to achieve 5 percent 
reductions of inventoried emissions of either direct PM2.5 
or of any relevant PM2.5 precursors. This approach, while 
consistent with past guidance on how to interpret section 189(d) 
requirements for PM10 NAAQS implementation, could 
potentially allow a state to delay the implementation of measures to 
control the relevant pollutants. However, paired with the requirement 
for the area to reach attainment of the NAAQS as expeditiously as 
practicable, the EPA believes that such an interpretation may be 
reasonable and seeks comment on this approach.
    It is important to note that under implementation of either of the 
options presented above, and as described more fully in Section III of 
this preamble, the EPA is proposing that in the event that a state has 
demonstrated and can continue to demonstrate that emissions of a given 
precursor from all sources in a nonattainment area do not contribute 
significantly to PM2.5 concentrations in the area, then the 
state would not need to achieve 5 percent reductions in emissions of 
that precursor even if the nonattainment area becomes subject to the 
requirements of section 189(d).
    The statute requires that the requisite minimum 5 percent emissions 
reductions must be calculated from the total emissions for each 
precursor and for direct PM2.5 contained in the most recent 
inventory for the area, as described earlier in this section. In 
addition, the EPA proposes that these required reductions must then be 
achieved every year between the section 189(d) plan submission date and 
the new projected attainment date for the area. For example, assume it 
is 2025, and a Serious area has failed to attain the 2012 
PM2.5 NAAQS within 10 years of designation. Assume also that 
the most recent inventory available for an area subject to section 
189(d) is for the year 2023. This inventory would serve as the base 
inventory for determining the emissions reduction requirement under 
section 189(d). If the most recent inventory indicates that emissions 
of direct PM2.5 from all sources in the area are 100 tons/
day, then the area would need to reduce emissions of direct 
PM2.5

[[Page 15425]]

by 5 percent of the base inventory (in this example, 5 percent of the 
2023 base inventory, or 5 tons/day) each year until the area attains 
the NAAQS. Thus, in the first year following submission of the section 
189(d) plan for the area, emissions of direct PM2.5 could 
not exceed 95 tons/day; in the second year, emissions could not exceed 
90 tons/day; and so forth.
    Although section 189(d) requires that a state develop measures that 
will obtain annual emissions reductions of ``not less than 5 percent'' 
from the most recent inventory, the EPA interprets this language to 
authorize states to elect to front-load emissions reductions in earlier 
years and still meet the 5 percent per year requirement. The EPA notes 
that interpreting the statute in this way will encourage states to 
implement measures earlier, where possible, rather than delay 
implementation of measures merely to assure that the 5 percent 
requirement can be met in later years. Thus, using the example 
described above, the annual reduction requirement for the area would be 
5 tons/day from a base year emissions level of 100 tons/day. The 
required level after year 1 would be 95 tons/day, after year 2 the 
level would be 90 tons/day, and so on. If the area reached a level of 
81 tons/day by the end of year 3, then by the end of year 4 it would 
only need to reduce emissions by 1 ton/day to yield an emissions level 
of 80 tons/day. Consistent with its past action to approve a Serious 
area attainment plan for the San Joaquin Valley (CA) PM10 
nonattainment area under section 189(d), the EPA therefore proposes and 
seeks comment on an approach to allow states to carry forward any 
emissions reductions beyond the required minimum 5 percent in a given 
year to the next year as a means to encourage states to achieve 
emissions reductions as quickly as possible.\218\
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    \218\ 69 FR 30006 (May 26, 2004).
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    The EPA also proposes to clarify its interpretation of the 
statutory language under section 189(d) that requires a state to submit 
a new attainment plan to achieve annual reductions ``from the date of 
such submission until attainment,'' to mean annual reductions beginning 
from the due date of such submission until the new projected attainment 
date for the area based on the new or additional control measures 
identified to achieve at least 5 percent emissions reductions annually. 
This proposed clarification is intended to make clear that even if a 
state is late in submitting its section 189(d) plan, the area must 
still achieve its annual 5 percent emissions reductions beginning from 
the past due date for the section 189(d) plan submission. Because 
attainment dates for PM2.5 nonattainment areas established 
under subpart 4 occur at the end of the calendar year, any section 
189(d) plan, which is required within 12 months of the missed 
attainment date for the area, would also be due by the end of the 
calendar year.
2. Additional Guidance on Section 189(d) Control Measures
    The EPA believes that an appropriate starting point for a state to 
identify measures to achieve the requisite minimum 5 percent annual 
emissions reductions of direct PM2.5 and PM2.5 
precursors is the list of potential control measures initially required 
as part of the RACM and RACT determination for the area, then updated 
as part of the required BACM and BACT determination for the area. The 
EPA anticipates that a state should be able to rely on much of the work 
it previously undertook to develop this list of potential control 
measures and analyze their technological and economic feasibility, and 
the time required to implement them. However, for purposes of meeting 
the requirements of section 189(d), the EPA recommends that the state 
first identify any additional potential measures not previously 
identified for the area, and then analyze any new or additional 
measures that the state has not already adopted in a previous 
attainment plan for the area. The EPA expects that such an analysis to 
identify new control measures would necessarily take into account 
recent technological advances in control technologies, the possibility 
of a greater availability of funding to expand implementation of 
control measures for area sources, and the additional time the area 
will have to attain the PM2.5 NAAQS under sections 189(d) 
and 179(d)(3).
    In addition, a state may include in the section 189(d) plan control 
strategy for the area any control measures triggered as contingency 
measures upon the EPA's determination that area failed to attain the 
PM2.5 NAAQS by the applicable attainment date. In order to 
be included as control measures that will help the area meet its 
requisite minimum 5 percent reductions in direct PM2.5 and 
PM2.5 precursor emissions, such measures would have to meet 
the same requirements as all other approvable control measures for 
being quantifiable, enforceable, replicable and accountable. The EPA 
believes that reliance on such measures is appropriate given the short 
timeline provided for in the statute for states to revise and submit 
their SIP revisions (12 months from the missed attainment date) and the 
fact that the contingency measures included in the prior attainment 
plan for the area under section 172(c)(9) must be activated once the 
EPA publishes its finding of the area's failure to attain the NAAQS by 
the applicable attainment date. If contingency measures from the 
Serious area attainment plan are relied on in the new attainment 
demonstration as part of the control strategy, the state will need to 
submit additional contingency measures for the section 189(d) 
attainment plan submission.
3. Control Strategy Submission Requirements
    To ensure that attainment plan submissions contain the necessary 
supporting information for the EPA to review and approve the state's 
new control strategy to achieve at least 5 percent reductions in 
emissions of direct PM2.5 and significant PM2.5 
precursors, the EPA proposes to require under the authority of section 
301(a) that a state must submit the following information as part of 
its section 189(d) plan submission:
     A list of all emissions source categories, sources and 
activities in the nonattainment area (for multi-state nonattainment 
areas, this would include source categories, sources and activities 
from all states which make up the area);
     For each source category, source or activity in the 
nonattainment area, an inventory of direct PM2.5 and all 
PM2.5 precursor emissions;
     For each source category, source or activity in the 
nonattainment area, a comprehensive list of potential control measures 
considered by the state for those sources in the nonattainment area; 
\219\
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    \219\ Menu of Control Measures document available at http://www.epa.gov/air/criteria.html.
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     For each potential control measure considered by the state 
but eliminated from further consideration due to a determination by the 
state that the control measure or technology was not technologically 
feasible, a narrative explanation and quantitative or qualitative 
supporting documentation to justify the state's conclusion;
     For each technologically feasible emission control measure 
or technology, the state must provide the following information 
relevant to economic feasibility: (i) the control efficiency by 
pollutant; (ii) the possible emission reductions by pollutant; (iii) 
the estimated cost per ton of pollutant reduced; and, (iv) a 
determination of whether the measure is economically

[[Page 15426]]

feasible, with narrative explanation and quantitative supporting 
documentation to justify the state's conclusion;
     For each technologically and economically feasible 
emission control measure or technology, the date by which the 
technology or measure could be implemented.
    As with other PM2.5 attainment plan submissions, the EPA 
believes that it is incumbent on the state to ensure that the 
information needed for the EPA to evaluate the state's analysis of new 
control measures needed to achieve annual 5 percent reductions is 
presented separately as part of the control strategy analysis and in a 
format that provides transparency, consistency and the ability for 
another party to evaluate the state's analysis effectively and to 
duplicate the state's results. For this reason, the EPA is including 
the section 189(d) plan base year emissions inventory information as a 
necessary part of the control strategy submittal and as one element of 
the state's section 189(d) plan due 12 months after the missed 
attainment date for the area. In addition, the EPA proposes that the 
state must provide information as part of any attainment plan submitted 
to meet the requirements of section 189(d) consistent with the criteria 
described in Section VI.D.5 of this preamble to ensure that a state 
adopts effective regulations to implement the control measures 
identified as being needed to meet those requirements. Specifically, 
all control measures must be quantifiable, enforceable, replicable and 
accountable.
    The section 189(d) requirement to reduce emissions by 5 percent per 
year is in effect a fixed level of RFP to be achieved annually. 
Accordingly, just as quantitative milestones are used to track progress 
with RFP requirements, the EPA proposes that the state would be 
required to submit quantitative milestone reports to describe the 
area's progress in meeting the 5 percent annual emissions reduction 
requirement under section 189(d). See Section VII.G of this preamble 
for more details.

E. Modeling for Attainment Demonstrations

    Section 189(d) requires a state with a Serious nonattainment area 
that failed to attain the relevant NAAQS by the applicable Serious area 
attainment date to submit a new attainment plan for such area within 12 
months after the missed attainment date. The EPA is proposing that the 
same general requirements for attainment demonstrations and modeling 
that apply to Moderate area plans and Serious area plans due under 
sections 189(a) and 189(b) should also apply to section 189(d) 
attainment plans. However, the EPA is proposing additional requirements 
specific to plans states submitted pursuant to section 189(d) as 
described below.
1. Attainment Demonstrations for Serious Areas That Fail To Attain the 
NAAQS by the Applicable Attainment Date
    The EPA is proposing that the attainment demonstration for Serious 
areas subject to section 189(d) requirements must consist of: (i) 
technical analyses such as base year and future year modeling of 
emissions which identify sources and quantify their emissions that are 
contributing to violations of the PM2.5 NAAQS; and, (ii) 
analyses of future year projected emissions reductions and air quality 
improvement resulting from national, regional and local programs 
already implemented as part of previous Moderate and/or Serious area 
attainment plans for the area (including reasonable control measures, 
BACM and BACT and additional feasible measures), and additional 
measures needed for expeditious attainment, including measures needed 
to achieve 5 percent emissions reductions on an annual basis. Each 
state with a nonattainment area subject to the requirements of section 
189(d) must submit an attainment plan with an attainment demonstration 
that includes analyses supporting the state's determination of its 
proposed new attainment date. In all cases, the state must show that 
the area will attain the NAAQS as expeditiously as practicable.
2. What modeling is required?
    The EPA proposes that states are required to submit air quality 
modeling in support of an attainment demonstration for a nonattainment 
area subject to the requirements of section 189(d). The modeling 
demonstration must show how and when the area will attain the NAAQS. 
Other than the timing of plan submissions and requirement to achieve 5 
percent emissions reductions in direct PM2.5 and 
PM2.5 precursors, the relevant air quality modeling 
procedures and guidance for all PM2.5 nonattainment area 
plans are the same. See Sections IV.E. and VI.E of this preamble for 
more details on proposed modeling requirements and guidance for 
Moderate and Serious PM2.5 nonattainment areas, 
respectively.
3. What future year(s) should be modeled in attainment demonstrations?
    As discussed more fully in Section VII.I of this preamble, the EPA 
must establish a new attainment date for a PM2.5 
nonattainment area subject to section 189(d) and must do so according 
to the provisions of sections 179(d)(3) and 172(a)(2), which require 
that the new attainment date must be as expeditious as practicable, but 
no later than 5 years from the date of publication in the Federal 
Register of the EPA's determination that the area failed to attain the 
relevant NAAQS. The EPA may extend the attainment date by up to 5 
additional years (thus to 10 years from the date of publication of the 
notice of finding of failure to attain by the applicable attainment 
date for the area) if the agency deems it appropriate ``considering the 
severity of nonattainment and the availability and feasibility of 
pollution control measures.''
    For purposes of determining the attainment date that is as 
expeditious as practicable, the state must conduct future year modeling 
which takes into account emissions growth, known controls (including 
any controls that were previously determined to be RACM or RACT or 
additional reasonable measures, or BACM or BACT or additional feasible 
measures for the area), the 5 percent per year emissions reductions 
required by section 189(d), plus any other emissions controls that are 
needed for expeditious attainment of the NAAQS. A state performing a 
modeling analysis for a plan submitted under section 189(d) must select 
a future modeling year such that all emissions control measures relied 
on for attainment will have been implemented by the beginning of that 
year. To demonstrate attainment, the modeling results for the 
nonattainment area must predict that emissions reductions implemented 
by the beginning of the last calendar year preceding the attainment 
date will result in PM2.5 concentrations that meet the level 
of the standard.\220\
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    \220\ Note that for purposes of the PM2.5 NAAQS, a 
determination of attainment (or failure to attain), which the EPA is 
required to make after the attainment date has passed, is based on 
an average of the most recent 3 years of ambient data prior to the 
area's attainment date.
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    For a PM2.5 nonattainment area subject to section 
189(d), the EPA expects that the state will adopt any control measures 
necessary to demonstrate expeditious attainment within 5 years of the 
area failing to attain the NAAQS by the applicable Serious area 
attainment date.
4. Attainment Year Motor Vehicle Emissions Budgets
    As with all other PM2.5 NAAQS attainment plans, the 
transportation

[[Page 15427]]

conformity rule requires that attainment plans for areas subject to 
section 189(d) establish motor vehicle emissions budgets for the area's 
attainment year. Therefore, for such an area, the state would first 
determine the new attainment date as described in Section VII.I of this 
preamble. Once an area's attainment date has been established, the 
state would establish motor vehicle emissions budgets for direct 
PM2.5 and any relevant PM2.5 precursor for the 
attainment year.\221\ A motor vehicle emissions budget for the purposes 
of a PM2.5 attainment plan is that portion of the total 
allowable emissions within the nonattainment area allocated to on-road 
sources as defined in the submitted attainment plan.\222\ Such motor 
vehicle emissions budgets would be calculated using the latest planning 
assumptions and the latest approved motor vehicle emissions model 
available at the time that the attainment plan is developed.\223\
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    \221\ For more information on PM2.5 precursor 
requirements, see section 93.102(b)(2)(iv) and (v) of the 
transportation conformity rule. See also the May 6, 2005, final 
transportation conformity rule that addressed requirements for 
PM2.5 precursors. (70 FR 24280).
    \222\ A state would also establish motor vehicle emissions 
budgets for an area's attainment year. Those budgets would be the 
motor vehicle emissions that the SIP establishes as being necessary 
to attain the NAAQS.
    \223\ If an area includes re-entrained road dust in the motor 
vehicle emissions budget, the latest approved version of AP-42 
should be used unless the EPA has approved an alternative model for 
the area.
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    The EPA seeks comment on these proposed attainment demonstration 
and modeling requirements for new attainment plans due for Serious 
areas subject to section 189(d).

F. RFP Requirements

    As with other PM2.5 attainment plans, a plan submitted 
to meet the requirements of section 189(d) must provide for RFP as 
required under sections 172(c)(2) and 189(c)(1). Section 171(1) defines 
RFP as ``such annual incremental reductions in emissions of the 
relevant air pollution as are required by this part or may reasonably 
be required by the Administrator for the purpose of ensuring attainment 
of the applicable [NAAQS] by the applicable attainment date.'' The 
purpose of RFP requirements is to assure that a state is making 
progress towards attainment on an annual basis through the attainment 
plan, rather than deferring emissions reductions until just before the 
attainment date for the area. This requirement is similar to, though 
less prescriptive than, the requirement under section 189(d) for 5 
percent emissions reductions of direct PM2.5 or 
PM2.5 precursors from the most recent emissions inventory on 
an annual basis until the area attains. Therefore, the EPA proposes to 
determine that a state has satisfied the RFP requirement if the state 
submits an approvable control strategy under section 189(d) that 
demonstrates that the state will achieve at least 5 percent reductions 
in direct PM2.5 and PM2.5 precursor emissions 
from sources in the area annually until attainment.
    The EPA proposes that motor vehicle emissions budgets must also be 
established as part of any RFP plan for direct PM2.5 and for 
any relevant PM2.5 precursor using the latest planning 
assumptions and the latest approved motor vehicle emissions model 
available at the time that the plan is developed for a Serious area 
subject to 189(d).\224\
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    \224\ If an area includes re-entrained road dust in the motor 
vehicle emissions budget, the latest approved version of AP-42 
should be used unless the EPA has approved an alternative model for 
the area.
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    The EPA seeks comment on this proposed approach related to RFP 
requirements for new attainment plans due under section 189(d).

G. Quantitative Milestones

    The revised attainment plan for any Serious nonattainment area that 
fails to attain the relevant PM2.5 NAAQS by the applicable 
attainment date must include quantitative milestones pursuant to 
section 189(c). These quantitative milestones would be additional to 
those previously identified in the Moderate area and original Serious 
area attainment plans, and would need to reflect the projected 
emissions reductions or air quality improvements expected through the 
implementation of specific control measures identified to achieve the 
minimum 5 percent annual reductions required under section 189(d). Such 
milestones would need to be achieved every 3 years until the area 
attains the relevant NAAQS, such that the EPA proposes that, at a 
minimum, quantitative milestones selected for an attainment plan 
submitted under section 189(d) would need to demonstrate a reduction of 
at least 15 percent in emissions of direct PM2.5 and 
significant precursors below those emissions reported in the most 
recent inventory for the area.
    The section 189(d) plan for an area that failed to attain the 
standard by the applicable Serious area attainment date would have to 
contain quantitative milestones to be achieved by 13.5 years from the 
area's date of designation and every 3 years thereafter until the 
area's new projected attainment date. In the event a state is 
developing a revised attainment plan pursuant to section 189(d) that 
will be due sometime after 13.5 years following designation of the 
area, the EPA proposes to allow the state to submit quantitative 
milestones beginning for the year 16.5 from designation and every 3 
years thereafter until the area's projected attainment date.
    The EPA believes that its proposed requirements for quantitative 
milestones, described in Sections IV.G and VI.G of this preamble, 
should also apply to quantitative milestones submitted with any revised 
attainment plan pursuant to section 189(d), and thus proposes and seeks 
comment on the agency's proposed milestone requirements for application 
to attainment plans due under section 189(d).

H. Contingency Measures

    All PM2.5 attainment plans, including plans for areas 
subject to section 189(d), must contain contingency measures that are 
consistent with section 172(c)(9). Section VI.H of this preamble 
describes the EPA's proposed criteria for contingency measures for a 
Serious area attainment plan, and the agency proposes that contingency 
measures for a section 189(d) plan must meet the same criteria. The EPA 
proposes that the emissions reductions associated with contingency 
measures for section 189(d) plans must be at least 5 percent of direct 
PM2.5 and significant PM2.5 precursor emissions 
as reported in the most recent inventory for the area. The EPA believes 
this requirement would appropriately align the proposed requirement for 
selecting contingency measures with the agency's proposed approach to 
RFP for these areas. In other words, if RFP for an area is equivalent 
to about 1 year's worth of emissions reductions, or 5 percent emissions 
reductions in direct PM2.5 and PM2.5 precursors, 
then the adopted contingency measures should likewise achieve about 1 
year's worth of emissions reductions, or 5 percent emissions reductions 
in direct PM2.5 and PM2.5 precursors.
    The EPA recognizes that identifying contingency measures for a 
Serious PM2.5 nonattainment area that failed to attain the 
relevant NAAQS by the applicable attainment date may be challenging for 
a state that should already have fully implemented all control measures 
identified as ``reasonable'' and ``best,'' and potentially ``most 
stringent,'' in addition to identifying new control measures to achieve 
the requisite minimum 5 percent reductions in direct PM2.5 
and significant PM2.5 precursor emissions

[[Page 15428]]

necessary for expeditious attainment. Nonetheless, given the statutory 
language of section 172(c)(9), the EPA seeks comment on applying the 
same proposed requirements for contingency measures for section 189(d) 
plans, and on the agency's proposed approach for calculating the 
emissions reductions that such measures must be able to achieve.

I. Attainment Dates

    As previously discussed, section 189(d) requires a minimum 5 
percent annual reduction in emissions of direct PM2.5 and 
PM2.5 precursors until the area attains the relevant NAAQS. 
However, neither section 189(d) nor other sections in subpart 4 
explicitly establish or provide the authority to establish a new 
attainment date for the area; other subpart 4 attainment date 
provisions for Moderate or Serious areas are likewise not applicable to 
areas in this situation. Therefore, once an area is beyond the 
attainment dates that Congress specified in subpart 4 for the 
PM10 NAAQS, the EPA must look to the existing provisions of 
the CAA to provide authority for a new attainment date. Sections 
179(d)(3) and 172(a)(2) provide generally applicable attainment dates 
that fill the gap in the statute left for areas subject to the 
requirements of section 189(d). Thus, for a PM2.5 
nonattainment area subject to section 189(d) requirements, the EPA must 
establish a new attainment date, and must do so according to the 
provisions of section 179(d)(3) and 172(a)(2). The EPA has followed 
this same approach in the past for PM10 nonattainment areas 
governed by subpart 4 nonattainment requirements.\225\
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    \225\ For example, see the Federal Register notice from June 6, 
2007 (72 FR 31183) in which the EPA found that the Phoenix 
PM10 Serious nonattainment area failed to attain the 
standard by the 2006 attainment date.
---------------------------------------------------------------------------

    The new attainment date must be as expeditious as practicable, but 
no later than 5 years from the date of publication in the Federal 
Register of the EPA's determination that the area failed to attain the 
relevant NAAQS. The EPA may extend the attainment date by up to 5 
additional years (thus to 10 years from the date of publication of the 
notice of finding of failure to attain by the applicable attainment 
date for the area) if the agency deems it appropriate ``considering the 
severity of nonattainment and the availability and feasibility of 
pollution control measures.'' For a PM2.5 nonattainment area 
subject to section 189(d), the EPA expects that the state will adopt 
any control measures necessary to demonstrate expeditious attainment 
within 5 years of the area failing to attain the NAAQS by the 
applicable Serious area attainment date.
    As discussed earlier in this section, the EPA will consider the 
state's attainment demonstration and proposed attainment date for the 
area, in addition to the state's revised control strategy and the 
relevant facts and circumstances, in order to identify the most 
expeditious attainment date practicable for the area.
    The EPA seeks comment on this proposal for interpreting the 
statutory requirements under section 189(d) for a Serious area that 
fails to attain the PM2.5 NAAQS by the applicable attainment 
date.

VIII. What are the EPA's proposed NNSR permitting requirements?

A. Statutory Requirements for NSR

    Section 110(a)(2)(C) of the CAA requires states to include in their 
SIPs a preconstruction review permitting program that regulates the 
construction and modification of stationary sources as necessary to 
ensure that NAAQS are achieved. To address the regulation of the larger 
pollutant-emitting sources (defined as major stationary sources), 
Congress provided specific permitting requirements in the CAA in parts 
C and D of title I. The requirements for preconstruction permits under 
parts C and D of the CAA are commonly known collectively as the major 
NSR program because they apply specifically to the preconstruction 
review and permitting of new major stationary sources, and major 
modifications at existing sources. As explained in Sections VIII.A.1 
and 2 of this preamble, the preconstruction review of each new and 
modified major stationary source generally is carried out on a 
pollutant-specific basis and the requirements with regard to each 
pollutant apply based on whether the area in which the proposed major 
source or major modification would locate is designated attainment (or 
unclassifiable) or nonattainment for that pollutant at the time the 
permit is issued.
1. PSD
    Part C of title I of the CAA (hereafter referred to simply as part 
C) contains implementation plan requirements that apply to new major 
stationary sources and major modifications in areas designated 
attainment or unclassifiable for any NAAQS. These requirements 
constitute the PSD program. Pursuant to part C, the EPA has adopted PSD 
regulations at 40 CFR 51.166 (minimum requirements for an approvable 
state PSD program in the SIP) and 40 CFR 52.21 (the federal PSD 
program, applicable in areas where the state does not have an EPA-
approved PSD program in its SIP). The EPA last amended the PSD 
regulations for PM2.5 on January 15, 2013, in the final rule 
revising the PM2.5 NAAQS.\226\ This proposal does not relate 
to the PSD program, nor does it propose further changes to the PSD 
regulations. Any future revisions to the PSD regulations for 
PM2.5 would be done through a separate notice-and-comment 
rulemaking.
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    \226\ More information on the PSD requirements for 
PM2.5 as well as the public comments and the EPA's 
responses to those comments and the related issues for which 
comments were received is contained in the January 15, 2013 Federal 
Register document (78 FR 3086, beginning at page 3251).
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2. NNSR
    Part D of title I of the CAA (hereafter referred to as part D) 
contains implementation plan requirements for nonattainment areas, 
which include the requirements for permitting new major stationary 
sources and major modifications in designated nonattainment areas, 
referred to as the NNSR program. As noted earlier, part D contains 
several subparts that include various requirements for addressing 
nonattainment areas. Subpart 1 addresses plan requirements for 
nonattainment areas generally, including section 172(c)(5) which 
requires preconstruction and operating permits for new major stationary 
sources and major modifications in nonattainment areas. Section 173 
outlines the minimum statutory requirements for a state's NNSR permit 
program and serves as the basis for the EPA's NNSR regulations for 
PM2.5 as promulgated in the 2008 PM2.5 NSR Rule. 
Subpart 4 was added to part D as part of the 1990 CAA Amendments and 
includes additional plan provisions for designated PM10 
nonattainment areas. Relevant here, section 189(a)(1)(A) of subpart 4 
requires states to include in their implementation plan a permit 
program addressing major stationary sources of PM10 that 
meets the requirements under section 173 of subpart 1. Subpart 4 also 
includes some additional preconstruction review requirements for which, 
to date, the EPA has promulgated NSR regulations applying only to major 
stationary sources of PM10 in PM10 nonattainment 
areas. The specific NNSR requirements contained in both subparts 1 and 
4 are described below including the changes to the NNSR regulations 
needed to address PM2.5 specifically that the EPA is 
proposing in this notice.

[[Page 15429]]

B. Federal NNSR Regulations

    Federal regulations pertaining to the preconstruction permitting of 
new major stationary sources and major modifications in areas 
designated nonattainment are contained at 40 CFR 51.165; part 51, 
appendix S; and, Sec.  52.24. An approved NNSR program in a state's 
implementation plan must, at a minimum, meet the program requirements 
set forth in the federal NNSR requirements at 40 CFR 51.165, which for 
PM2.5 are currently based on changes made under the 2008 
PM2.5 NSR Rule. States are required to adopt regulations 
consistent with those plan requirements and submit them to the EPA for 
approval as part of their SIP within a period of time consistent with 
the schedule prescribed by the CAA.
    The EPA interprets the requirement established under section 
110(a)(2)(C) of the CAA for states to regulate the construction and 
modification of sources to apply in nonattainment areas as of the 
effective date of a new nonattainment area designation.\227\ Although 
section 110(a)(2)(C) does not contain specific requirements a state 
must follow for issuing major source permits during the interim period 
between effective date of designation and the date when a state has an 
EPA-approved NNSR program, the EPA regulation at 40 CFR 52.24(k) 
authorizes states to apply 40 CFR part 51, Appendix S, known as the 
Emission Offset Interpretative Ruling, during the interim period. 
228 229
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    \227\ See the Federal Register published on November 29, 2005 
(70 FR 71612, 71677 and 71678).
    \228\ States with designated PM2.5 nonattainment 
areas were required to submit SIPs satisfying the requirements of 
the 2008 PM2.5 NSR Implementation Rule by May 16, 2011, 3 
years from the date of publication of that rule. See 73 FR 28321 
(May 16, 2008), at page 28342. Such approved state programs can 
continue to be implemented to issue permits to new major stationary 
sources and major modifications until the state's revised program 
containing the subpart 4 NNSR provisions promulgated in this 
rulemaking is approved under the applicable SIP.
    \229\ Appendix S was originally promulgated in 1976 to address 
whether, and to what extent, new and modified sources would be 
allowed to construct in nonattainment areas whose attainment 
deadlines had already passed, in light of the regulatory requirement 
that new or modified sources be disapproved where the source would 
interfere with attainment of the NAAQS (41 FR 55524 (December 21 
1976)). When Congress added the part D provisions in the 1977 CAA 
Amendments, it also added the requirement that SIPs contain NNSR 
provisions as set forth in Part D. Additionally, Congress provided 
that Appendix S would govern preconstruction permitting in 
nonattainment areas lacking approved part D SIPs before a 
construction ban went into effect. When Congress removed the 
construction ban via the 1990 CAA Amendments (except as provided for 
in section 110(n)(3)) it left in place the use of the interim NNSR 
program under Appendix S.
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    Accordingly, states with newly designated nonattainment areas for 
the revised primary PM2.5 NAAQS have two possible means by 
which they can implement NNSR requirements for PM2.5 
following the effective date of designations and until the EPA approves 
a SIP submission meeting the NNSR requirements for PM2.5 
promulgated in this rule under subpart 4. First, any state that has an 
approved NNSR program for PM2.5 can continue to apply those 
permitting requirements in the interim. Second, states that lack any 
approved NNSR program for PM2.5 may rely upon the NNSR 
provisions in Appendix S until the EPA approves a SIP submission from 
the state to address PM2.5 in order to ensure that proposed 
new major stationary sources and major modifications for 
PM2.5 in newly designated PM2.5 nonattainment 
areas undergo the appropriate type of preconstruction review in the 
interim.
1. General Applicability
    New major stationary sources are subject to the NNSR requirements 
when they are major for the pollutant for which an area is designated 
nonattainment. See 40 CFR 51.165(a)(2)(i). With regard to major 
modifications, NNSR applies to proposed physical changes or changes in 
the method of operation of an existing stationary source that (1) is 
major for the nonattainment pollutant (or a precursor for that 
pollutant) and (2) results in both a significant emissions increase and 
a significant net emissions increase of that nonattainment pollutant 
(or a precursor for that pollutant).\230\
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    \230\ As will be explained in ensuing discussions, the 
nonattainment pollutant and any applicable precursors for that 
pollutant are considered separately for NNSR applicability purposes. 
See 40 CFR 51.165(a)(1)(v)(A), (a)(2)(ii)A).
---------------------------------------------------------------------------

    For each proposed major new source and major modification, the 
general NNSR requirements that are required to be included in a state's 
SIP include: (i) the installation and continuous operation of pollution 
control technology that complies with the LAER; (ii) the acquisition of 
creditable emissions reductions to adequately offset the proposed 
emissions increase of the nonattainment pollutant; and, (iii) a 
demonstration of compliance with other analyses as required under 
section 173 of the CAA.\231\ These NNSR requirements must be satisfied 
by a major new source or major modification as a prerequisite for 
receipt of a construction permit and apply as of the effective date of 
designation of an area as nonattainment for the pollutant.
---------------------------------------------------------------------------

    \231\ The basic NNSR requirements are set forth in section 173 
of subpart 1. Subpart 4 adds a more stringent definition of ``major 
source'' for PM10 sources in PM10 
nonattainment areas classified as Serious and sets forth provisions 
for the regulation and potential exemption of major sources of 
PM10 precursors in PM10 nonattainment areas. 
Until the decision in NRDC v. EPA was issued, the additional subpart 
4 requirements had not been directly applied with regard to 
PM2.5.
---------------------------------------------------------------------------

2. Historical Overview of NNSR for PM10 and PM2.5 
NAAQS
    Following the adoption of new PM NAAQS based on the PM10 
indicator in 1987 (replacing the original Total Suspended Particulate 
indicator), the EPA announced that it did not intend to designate areas 
as nonattainment for PM10. As a result, the EPA initially 
determined that part D, which at that point consisted only of generally 
applicable requirements, did not apply to the PM10 
NAAQS.\232\ Thus, nonattainment area requirements, including the NNSR 
program, did not initially apply with respect to PM10. 
Consequently, all new major stationary sources and major modifications 
of PM10 were required to undergo PSD review as a 
prerequisite for construction or modification.
---------------------------------------------------------------------------

    \232\ At the time the EPA promulgated the new PM10 
NAAQS, part D of the CAA did not include subpart 4. See 52 FR 24672 
(July 1, 1987).
---------------------------------------------------------------------------

    The approach for implementing the NNSR program for PM changed when 
in 1990 Congress established a new subpart 4 specifically to address 
implementation plan requirements for PM10 nonattainment 
areas, including new preconstruction permit requirements for major 
stationary sources and major modifications with respect to 
PM10 and PM10 precursors. Moreover, Congress 
created new PM10 nonattainment areas through designations 
that became effective upon enactment of the 1990 Amendments on November 
15, 1990.\233\ In section 189(a)(2)(A), Congress also required states 
to submit the necessary NNSR permit program SIP revisions for these 
areas to the EPA by June 30, 1992.
---------------------------------------------------------------------------

    \233\ See section 107(d)(4)(B) of the CAA. The EPA subsequently 
published a list of the statutorily created PM10 areas in 
a Federal Register document at 55 FR 45799 (October 31, 1990).
---------------------------------------------------------------------------

    In a letter to its Regional Offices dated March 11, 1991,\234\ the 
EPA initially indicated that states should implement such new 
requirements by operation of law, without the need for formal 
rulemaking by the EPA to establish the necessary requirements for 
states to adopt. In the General Preamble, the EPA offered states 
additional guidance and described the EPA's preliminary views on how 
the states and the EPA should interpret various provisions of the 1990

[[Page 15430]]

Amendments, primarily those provisions concerning planning and control 
measure requirements for the attainment of the NAAQS in nonattainment 
areas. In a 2005 final rule, the EPA formally amended the NNSR 
regulations to incorporate the requirements contained in subpart 4 of 
part D of the 1990 CAA Amendments concerning PM10 
nonattainment areas. \235\
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    \234\ The EPA memorandum titled ``New Source Review (NSR) 
Program Transition Guidance,'' signed by John S. Seitz, Director, 
Office of Air Quality Planning & Standards.
    \235\ See ``Final Rule to Implement Certain Aspects of the 1990 
Amendments Relating to New Source Review and Prevention of 
Significant Deterioration as They Apply in Carbon Monoxide, 
Particulate Matter and Ozone NAAQS.'' 70 FR 71611 (November 29, 
2005).
---------------------------------------------------------------------------

    The EPA revised the PM NAAQS in 1997, establishing new annual and 
24-hour NAAQS using PM2.5 particles as a new indicator, 
while retaining the NAAQS for PM10.\236\ In 2006, the EPA 
again revised the suite of PM NAAQS by tightening the 24-hour 
PM2.5 standards and retaining the level of the annual 
PM2.5 standards.\237\ In 2008, the EPA issued the 
PM2.5 NSR Rule that established various provisions ensuring 
that proposed new major stationary sources or major modifications of 
sources of direct PM2.5 emissions or emissions of applicable 
PM2.5 precursors would be required to undergo 
preconstruction review.\238\ The EPA included specific provisions in 
the 2008 PM2.5 NSR Rule to apply when such sources are 
located in a designated PM2.5 nonattainment area. Unlike the 
NNSR requirements for PM10 developed under subpart 4, the 
EPA determined that the applicable implementation requirements for the 
PM2.5 NAAQS were contained in the general nonattainment 
provisions under subpart 1.
---------------------------------------------------------------------------

    \236\ See 62 FR 38652 (July 18, 1997).
    \237\ See 71 FR 61144 (October 17, 2006).
    \238\ See 73 FR 28321 (May 16, 2008).
---------------------------------------------------------------------------

    With regard to NSR applicability for PM2.5 precursors in 
the 2008 PM2.5 NSR Rule, the EPA recognized NOX, 
SO2, VOC and ammonia as precursors of PM2.5 in 
the scientific sense (because those pollutants under the appropriate 
conditions can contribute to the formation of PM2.5 in the 
ambient air) but did not require that states subject all of these 
precursors to control as part of the attainment plan or NSR permitting 
requirements applicable to a given nonattainment area.\239\ Instead, 
based on the authority in section 302(g) of the CAA, the EPA 
established the initial presumptions for nonattainment areas that 
SO2 and NOX should be regulated precursors for 
PM2.5, but VOC and ammonia need not be regulated precursors. 
The EPA or the states could rebut the initial presumptions regarding 
NOX, VOC or ammonia on an area-by-area basis with a 
demonstration approved by the Administrator and thus reverse any of 
those presumptions in the state's implementation plan for that 
area.\240\
---------------------------------------------------------------------------

    \239\ See 72 FR 20589.
    \240\ In the 2008 PM2.5 NSR Rule, the EPA concluded 
that SO2 should be regulated as a precursor for 
PM2.5 in all areas. See 73 FR 28327.
---------------------------------------------------------------------------

    As described above in Section II.C of this preamble, in January 
2013 the court in NRDC v. EPA held that the EPA erred in implementing 
the PM2.5 NAAQS pursuant only to the general implementation 
requirements in subpart 1, rather than also to the implementation 
requirements specific to particulate matter in subpart 4. Accordingly, 
the court directed the EPA to comply with the requirements of subpart 4 
when developing implementing regulations for PM2.5 
nonattainment areas.
    The court decision, requiring that the EPA implement the 
PM2.5 NAAQS consistent with the requirements of subpart 4, 
clearly has specific implications for implementing the NNSR program for 
PM2.5. Two provisions of subpart 4 impose additional 
requirements on the existing NNSR program requirements for 
PM2.5. The first relates to the definition of ``major 
stationary source.'' Section 188(b) provides that some areas initially 
designated as Moderate areas for PM10 subsequently may be 
reclassified as Serious areas. For any PM10 nonattainment 
area reclassified as a Serious area, section 189(b)(3) provides that a 
major stationary source of PM10 be defined to include any 
stationary source or group of stationary sources located within a 
contiguous area and under common control that emits or has the 
potential to emit at least 70 tpy of PM10. In accordance 
with the statute, the EPA is proposing to establish a major source 
emissions threshold for stationary sources of PM2.5 that 
satisfies the intent of section 189(b)(3).
    The second relevant subpart 4 provision governs the treatment of 
major sources of PM10 precursors. As previously explained in 
Section III.A of this preamble, the court specifically criticized the 
EPA's prior establishment of the rebuttable presumptions for addressing 
PM2.5 precursors, specifically citing the requirement of 
section 189(e). Section 189(e) requires that the control requirements 
in the plan applicable to major stationary sources of PM10 
must also apply to major stationary sources of PM10 
precursors. Section 189(e) also provides that states may elect not to 
impose control requirements on major stationary sources of 
PM10 precursor emissions if such emissions do not contribute 
significantly to ambient PM10 concentrations that exceed the 
standard in the PM10 nonattainment area. Section 189(e) 
requires that the EPA must make this determination, and thus the EPA 
must approve the decisions of a state that elects to use this provision 
to exempt any major stationary sources of PM2.5 precursors 
from controls in its attainment plan or NNSR program.
    The court's observation that the EPA's prior presumptions regarding 
precursors were inconsistent with the explicit requirements of section 
189(e) that major sources of all PM2.5 precursors are 
subject to control requirements thus necessitates that the agency 
revise the NNSR regulations governing precursors for PM2.5. 
As explained in greater detail later in this section, the EPA is 
proposing different potential options to make the necessary changes to 
the NNSR regulations in order to address the precursor requirements 
contained in subpart 4.

C. What are the changes the EPA is proposing for NNSR for PM2.5 
nonattainment areas?

    In this section, the EPA presents for comment certain proposed 
revisions to the NNSR regulations as well as alternative approaches for 
incorporating the subpart 4 requirements into the NNSR regulations for 
PM2.5. The proposed changes would affect the existing 
regulations at 40 CFR 51.165 and part 51 Appendix S. The agency does 
not intend to propose any changes to the regulations at 40 CFR 52.24, 
which provide the authorization for states to issue NNSR permits to 
major new sources and major modifications ``during the period between 
the date of designation as nonattainment and the date the NSR permit 
program meeting the requirements of part D is approved.''
1. What are the changes the EPA is proposing for the NNSR requirements 
for PM2.5 at 40 CFR 51.165?
    As explained above, the existing NNSR regulations applicable to 
PM2.5 are based solely on the permit requirements contained 
in section 173 of subpart 1. In subpart 4, section 189(a)(1)(A) 
requires states to include in their SIPs for PM10 
nonattainment areas a permit program meeting the requirements of 
section 173; however, other provisions in subpart 4 add additional 
requirements for the NNSR permit program. Those additional provisions 
concern (i) the definition of ``major stationary source'' in 
nonattainment areas classified as Serious areas, and (ii) control

[[Page 15431]]

requirements for applicable major stationary sources of PM10 
precursors. While those particular requirements in subpart 4 refer 
specifically to PM10, the EPA is proposing to add similar 
requirements for PM2.5 in accordance with the court's 
holding in NRDC v. EPA that subpart 4 also governs implementation of 
the PM2.5 NAAQS.
    a. Definition of ``major stationary source'' in Serious PM2.5 
nonattainment areas. In Section III.A of this preamble, the EPA 
indicated its intention to propose new provisions based on the 
requirements in subpart 4 for reclassifying certain PM2.5 
nonattainment areas as Serious areas. Because the NNSR regulations for 
PM2.5 set forth in the 2008 PM2.5 NSR Rule were 
developed pursuant to subpart 1, which does not provide for the 
classification of designated nonattainment areas, the EPA has not yet 
developed regulations to address subpart 4 requirements concerning 
nonattainment areas classified as Serious. With respect to NNSR, 
section 189(b)(3) provides that, for any PM10 nonattainment 
area classified as Serious, the major source threshold with regard to 
the terms ``major source'' and ``major stationary source'' shall be 70 
tpy of PM10. Accordingly, the EPA is proposing to amend the 
NNSR regulations at 40 CFR 51.165 consistent with this provision to 
establish a major source threshold for new major stationary sources and 
major modifications in PM2.5 nonattainment areas classified 
as Serious consistent with subpart 4. The EPA is proposing to set the 
major source threshold for direct PM2.5 emissions at 70 tpy. 
See proposed 40 CFR 51.165(a)(1)(iv)(A)(1)(vii).
    While the court decision did not mandate that the EPA define 
``major source'' and ``major stationary source'' for PM2.5 
at a threshold of 70 tpy of PM2.5 emissions for areas 
reclassified as Serious, the most straightforward and consistent 
application of section 189(b)(3) to PM2.5 nonattainment 
areas is to establish the same numerical threshold for Serious 
PM2.5 nonattainment areas as that which applies to Serious 
PM10 nonattainment areas. Moderate nonattainment areas for 
both PM10 and PM2.5 are already subject to the 
same major source thresholds by statute, so the EPA believes that it is 
also reasonable to establish the threshold for PM2.5 in 
Serious areas at the same level as the threshold that applies to 
PM10 in Serious areas. For the reasons explained below, the 
EPA believes that potential alternative approaches to setting the major 
source threshold for Serious PM2.5 nonattainment areas could 
have significant drawbacks. Nevertheless, the EPA is proposing and 
requesting comments on other possible thresholds for Serious areas.
    A possible alternative approach would be to promulgate a 
PM2.5 major source threshold lower than 70 tpy of 
PM2.5 emissions, recognizing that PM2.5 is a 
subset of PM10. Generally, any source's PM2.5 
emissions will be a fraction of that source's PM10 
emissions. However, determining the appropriate major source emissions 
threshold for PM2.5 that would be equivalent to 70 tpy of 
PM10 on a national basis is problematic because, while 
PM2.5 is generally a subset of PM10, there is not 
a consistent ratio of PM2.5 to PM10 emissions for 
all stationary sources. Combustion sources, such as industrial and 
commercial boilers that burn fossil fuels, and selected industrial 
processes emit primarily finer particles within the PM2.5 
size range, while other industrial processes--typically involving 
crushing and grinding operations--tend to emit more coarse particles in 
the PM10 size range. While the PM10: 
PM2.5 ratio for most sources decreases when the overall 
emissions of PM are controlled, the quantitative difference between 
PM2.5 emissions and PM10 emissions from specific 
sources can still be significant, thus making a national 
PM2.5 major source threshold based on a single ratio 
difficult to define. The EPA seeks comments on possible ways in which a 
PM2.5 emissions rate different from the statutory 70 tpy 
rate for PM10 emissions can be established, taking into 
account variations in the PM10: PM2.5 ratio for 
different source categories and activities.
    Accordingly, while the EPA seeks comment on this alternative 
approach, because of the associated limitations just described, the 
first option (i.e., a major source threshold of 70 tpy of 
PM2.5 emissions for stationary sources proposing to 
construct or modify in PM2.5 nonattainment areas 
reclassified as Serious) represents the agency's preferred approach.
    b. Control requirements for new major stationary sources and major 
modifications of PM2.5 precursors. The second key provision contained 
in subpart 4 that is not contained in subpart 1 relates to the control 
of major stationary sources and major modifications of precursor 
pollutants. Section 189(e) provides that, with respect to NNSR, the 
control requirements applicable to major stationary sources of 
PM10 also apply to major stationary sources of 
PM10 precursors, except that major stationary sources of a 
particular precursor may be exempt from the control requirements that 
apply to major stationary sources of PM10 if the state can 
demonstrate (based on guidance provided by the EPA) that the precursor 
emissions from those sources do not contribute significantly to ambient 
PM10 concentrations that exceed the standard in the 
nonattainment area.
    The specific ``control requirements'' for new or modified major 
stationary sources of PM2.5 are contained in section 173 of 
the CAA (outlining requirements for the state permit program required 
to be submitted in a state plan under section 189(a)(1)(A)) and 
189(b)(3) (establishing a major source threshold for sources in Serious 
areas). Consistent with these requirements, the EPA is proposing a 
series of revisions to address PM2.5 precursors in the NNSR 
regulations at 40 CFR 51.165, including: Revision of the definition of 
``regulated NSR pollutant'' to require regulation under the permitting 
program of all PM2.5 precursors; the establishment of major 
stationary source thresholds (for both Moderate areas and Serious 
areas) for all PM2.5 precursors; and, a provision for an 
exemption from the NNSR requirements, pursuant to section 189(e) of the 
CAA, for major stationary sources of any PM2.5 precursor 
where such sources do not contribute significantly to ambient 
concentrations of PM2.5 that exceed the standard in a 
particular nonattainment area. As described in greater detail below, 
the EPA is not at this time proposing any new significant emissions 
rates for the PM2.5 precursors.
    As described in Section VIII.A.2.b of this preamble, the NNSR 
regulations at 40 CFR 51.165 currently require states to regulate new 
major stationary sources and major modifications of SO2 and 
NOX as precursors under the NNSR requirements for 
PM2.5.\241\ Optionally, a state may avoid regulating new 
major stationary sources and major modifications of NOX 
under the NNSR requirements for PM2.5 if that state 
demonstrates to the satisfaction of the EPA that NOX is not 
a significant contributor to PM2.5 concentrations in a 
particular PM2.5 nonattainment area. Similarly, the existing 
regulations provide that a state may opt to regulate new major 
stationary sources and major modifications of VOC or ammonia under the 
NNSR requirements for PM2.5 if that state demonstrates to 
the satisfaction of the EPA that VOC or ammonia are precursors for 
PM2.5 that need to be controlled in a particular

[[Page 15432]]

PM2.5 nonattainment area.\242\ In accordance with the 
court's statement that section 189(e) requires all PM2.5 
precursors to be addressed, the EPA is proposing to revise the NNSR 
regulations to require that new major stationary sources and major 
modifications of SO2, NOX, VOC and ammonia meet 
the NNSR requirements for PM2.5 in PM2.5 
nonattainment areas. In doing so, the EPA believes that it is necessary 
to propose several revisions to 40 CFR 51.165 to ensure that the NNSR 
requirements for PM2.5 adequately address the regulated 
precursors consistent with the requirements of subpart 4.
---------------------------------------------------------------------------

    \241\ See the definition of ``regulated NSR pollutant'' at 
existing 40 CFR 51.165(a)(1)(xxxvii)(C)(2) and (3).
    \242\ Ibid at (a)(1)(xxxvii)(C)(3) and (4).
---------------------------------------------------------------------------

    First, the EPA is proposing to revise the regulations at 40 CFR 
51.165 to ensure that new major stationary sources and major 
modifications of the four scientific precursors for PM2.5 
are subject to the same requirements under the NNSR regulations that 
apply to new major stationary sources and major modifications of direct 
PM2.5 emissions. As explained earlier in this preamble, the 
court decision in NRDC vs. EPA concluded that section 189(e) 
``expressly governs precursor presumptions'' and thus necessitates that 
the EPA revise its existing provisions in the NNSR rules that indicate 
that VOC and ammonia are not regulated PM2.5 precursors. The 
EPA is thus proposing to revise the NNSR definition of ``regulated NSR 
pollutant'' to ensure that the NNSR regulations are consistent in 
establishing that SO2, NOX, VOC and ammonia are 
all regulated PM2.5 precursors for purposes of NNSR 
requirements, except under certain conditions explained below. See 
proposed 40 CFR 51.165(a)(1)(xxxvii)(C)(2).
    While section 189(e) generally requires that major stationary 
sources of PM2.5 precursors must apply the control 
requirements (including those for NNSR) for major stationary sources of 
direct PM2.5 emissions, the section also provides for an 
exemption from such requirements for any precursor for which ``the 
Administrator determines that such sources do not contribute 
significantly'' to the levels of PM2.5 that exceed the 
standard in the nonattainment area. Section 189(e) further authorizes 
the EPA to issue guidelines concerning the application of the exemption 
process.
    In Section III of this preamble, the EPA described the agency's 
proposed approaches for interpreting requirements for states to control 
PM2.5 precursors in their attainment plans for the 
PM2.5 NAAQS, which includes several proposed options to 
enable states to exempt a precursor from the attainment plan control 
requirements (including NNSR) for a particular PM2.5 
nonattainment area with the appropriate factual and analytical basis. 
In summary, the options included: (i) Separate analyses to determine 
which precursors are subject to the control requirements for attainment 
plans and which precursors are subject to the control requirements for 
NNSR for PM2.5; (ii) a technical demonstration showing that 
all sources of a particular precursor do not significantly contribute 
to the PM2.5 levels that exceed the standard in an area, 
thus exempting the precursor from control under both the attainment 
plan and NNSR programs; and, (iii) one analysis to determine whether 
control measures for a precursor are not needed for expeditious 
attainment for purposes of the attainment plan, which would also define 
the precursors that should be addressed for NNSR for PM2.5. 
Accompanying the description of each of the above options, Section 
III.C of this preamble discusses the potential analytical requirements 
for any proposed demonstration that any particular precursor should be 
exempted from the control requirements for PM2.5 in a given 
nonattainment area. The EPA is requesting comments on the three 
precursor options and the technical approaches for requesting a 
precursor exemption. Any comments received will be considered in 
developing the agency's final policy for addressing PM2.5 
precursors under the NNSR program for PM2.5.
    The second proposed change with regard to the nonattainment area 
control requirements for PM2.5 precursors involves the 
definition of ``major stationary source'' as it relates specifically to 
precursors. The EPA is proposing to revise the definition of ``major 
stationary source'' contained in the NNSR regulations to ensure that 
new sources that emit major amounts of any PM2.5 precursor 
that the state is regulating in the attainment plan for the area are 
appropriately considered major stationary sources subject to the NNSR 
requirements for PM2.5. See proposed 40 CFR 
51.165(a)(1)(iv)(A)(1). The proposed change concerning the regulation 
of precursors for PM2.5 is being accomplished by adding to 
the term ``regulated NSR pollutant'' the phrase ``(as defined in 
paragraph (a)(1)(xxxvii) of this section).'' It should be noted that 
the definition of ``major modification'' already contains this phrase. 
As described above, the EPA is also proposing to revise the definition 
of ``regulated NSR pollutant'' to clarify that four precursors are 
being regulated for PM2.5 in nonattainment areas for 
PM2.5. The EPA is proposing to set the major source 
threshold for each PM2.5 precursor (SO2, 
NOX, VOC and ammonia) at 100 tpy of each precursor for 
sources locating in Moderate areas, and 70 tpy of any precursor for 
sources locating in Serious areas. See proposed 40 CFR 
51.165(a)(1)(iv)(A)(1) and (a)(1)(viii), respectively. For example, in 
order to be a major source for purposes of the PM2.5 NAAQS, 
the source would need to emit at least 100 tpy of PM2.5 
emissions or at least 100 tpy of any individual PM2.5 
precursor that is a regulated precursor in a Moderate PM2.5 
nonattainment area. The individual treatment of pollutants and 
precursors for applicability purposes is consistent with the EPA's 
policy as explained in previous rulemakings.\243\
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    \243\ ``Different pollutants, including precursors, are not 
summed to determine applicability.'' See 73 FR 28231 (May 16, 2008), 
at page 28331.
---------------------------------------------------------------------------

    In proposing to set the major source threshold for each 
PM2.5 precursor at 100 tpy for Moderate areas, the EPA is 
following the precedent established in the 2008 PM2.5 NSR 
Rule in which the agency set the same 100 tpy major source threshold 
for PM2.5 and each of its precursors (at that time 
SO2 and NOX).\244\ As the EPA stated in that 2008 
notice, sections 169 and 302(j) of the CAA contain definitions of 
``major emitting facility'' and ``major stationary source'' that apply 
to programs implemented under subpart 1, which contain the PSD and NNSR 
program requirements, respectively.\245\ Those definitions also apply 
to programs implemented under subpart 4 to the extent that they 
regulate areas classified as Moderate PM2.5 nonattainment 
areas, as subpart 4 does not establish a different threshold for such 
areas. This proposal to set the same 100 tpy major source thresholds 
for sources of PM2.5 emissions and applicable 
PM2.5 precursor emissions is also consistent with the 
requirements of section 189(e), which make the control requirements 
applicable to major stationary sources of PM10 also 
applicable to major stationary sources of applicable PM10 
precursors.\246\
---------------------------------------------------------------------------

    \244\ Ibid.
    \245\ Ibid.
    \246\ See 57 FR 13498 (April 16, 1992), at page 13538.
---------------------------------------------------------------------------

    As noted above, section 189(b)(3) sets a lower major source 
threshold of 70 tpy of PM10 emissions for sources locating 
in PM10 nonattainment areas reclassified as Serious. Because 
subpart 4 NNSR requirements must be applied to PM2.5, the 
EPA must set a lower major source

[[Page 15433]]

threshold for PM2.5, pursuant to section 189(b)(3), in 
PM2.5 nonattainment areas that are reclassified as Serious 
areas. Thus, the EPA's preferred approach proposed above is to set a 
major source threshold of 70 tpy of PM2.5 emissions for 
sources in PM2.5 nonattainment areas reclassified as 
Serious.
    Consistent with this proposal, the EPA is also proposing to set the 
major source threshold for Serious areas for each precursor at 70 tpy 
of that particular precursor. As noted above, section 189(e) makes the 
control requirements for major stationary sources of PM10 
also applicable to major stationary sources of PM10 
precursors; thus, in accordance with the provision of the statute, the 
control requirements applicable to major stationary sources of 
PM2.5 emissions are also applicable to major stationary 
sources of PM2.5 precursors. Accordingly, the EPA must 
develop a major source threshold for PM2.5 precursors that 
is consistent with the threshold for direct PM2.5 that will 
apply in PM2.5 nonattainment areas reclassified as Serious. 
See proposed 40 CFR 51.165(a)(1)(iv)(1)(viii).
    The EPA's proposal to set a major source threshold of 70 tpy for 
Serious areas for each PM2.5 precursor is also consistent 
with the approach the EPA has taken for establishing a major source 
threshold for each PM10 precursor under subpart 4. In the 
Addendum to the General Preamble offering guidance as to how to apply 
the new subpart 4 requirements in Serious areas, the EPA indicated that 
it interpreted the statute as applying the 70 tpy threshold to sources 
of PM10 precursors.\247\
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    \247\ See Addendum to the General Preamble, 59 FR 41998 (August 
16, 1994), at page 42012 (defining major point sources in Serious 
areas as ``sources with the potential to emit at least 70 tons per 
year of PM10 (or PM10 precursors) as required 
in sections 189(b)(3) and 189(e) of the Act'').
---------------------------------------------------------------------------

    The EPA also solicits comments on the appropriateness of setting 
the precursor major source thresholds at a different rate, particularly 
if, as alternatively proposed above, the agency defines ``major 
stationary source'' for sources of direct PM2.5 in Serious 
PM2.5 nonattainment areas at a rate lower than 70 tpy of 
PM2.5 emissions. For example, if the agency sets the major 
source threshold at 60 tpy of PM2.5 emissions in Serious 
PM2.5 nonattainment areas, the agency would also consider 
setting the major source threshold for each PM2.5 precursor 
at 60 tpy of that particular precursor.
    Moreover, the EPA believes that a reasonable argument can be made 
that whatever threshold is set for PM2.5 emissions, the same 
level would be too low to be regarded as ``major'' for each precursor 
when considering the effects that such precursor sources could have on 
ambient PM2.5 concentrations. The EPA previously analyzed 
the relationship between emissions of SO2 and NOX 
and the formation of secondary PM2.5 in the ambient air 
expressly for purposes of determining an appropriate ratio for allowing 
interprecursor offsets for PM2.5. Those studies resulted in 
the EPA providing in the 2008 PM2.5 NSR Rule ``preferred'' 
ratios for both SO2 and NOX, whereby a source 
could obtain reductions of a PM2.5 precursor to offset an 
increase of direct PM2.5 emissions or another 
PM2.5 precursor based on the ``preferred'' offset 
ratios.\248\ In brief, the preferred ratios were as follows: For 
NOX-to-primary PM2.5: 200 to 1 (NOX 
tons to PM2.5 tons) for areas in the eastern U.S, and 100 to 
1 for areas in the western U.S.; and for SO2-to-primary 
PM2.5: 40 to 1 (SO2 tons for PM2.5 
tons). In each case, the ratio illustrates that it requires 
considerably more precursor emissions than direct PM2.5 
emissions to result in a particular ambient concentration of 
PM2.5. It should be noted that at that time the EPA did not 
consider using the preferred ratios for the purpose of adjusting the 
major source thresholds or significant emissions rates for 
SO2 and NOX when regulating them as 
PM2.5 precursors.
---------------------------------------------------------------------------

    \248\ The technical assessment, with details on data and 
modeling inputs, was fully described in a technical memo titled 
``Details on Technical Assessment to Develop Interpollutant Trading 
Ratios for PM2.5 Offsets,'' which was placed in the 
docket to the 2008 final rule. See also 73 FR 28321 (May 16, 2008), 
at page 28339.
---------------------------------------------------------------------------

    The preferred ratios as presented in the 2008 notice were later 
challenged in a petition for reconsideration and the EPA withdrew them 
via an EPA memorandum issued in 2011.\249\ In withdrawing the preferred 
ratios, the EPA cited several concerns. First, it was determined that 
the preferred ratios were not sufficiently conservative to be 
representative of conditions in all areas of the country. Second, the 
EPA determined that the preferred ratios were not adequate for 
addressing the precursor relationship to ambient PM2.5 
concentrations for the short-term (daily) averaging period.\250\ In 
addition, the EPA believes that the overall analysis conducted for the 
2008 notice generally illustrates that the threshold for defining 
``major'' for either SO2 or NOX as precursors for 
PM2.5 could reasonably be set at an emissions rate 
considerably higher than 70 tpy of that particular precursor and be 
equally protective of air quality as the 70 tpy threshold applied to 
PM2.5 emissions.
---------------------------------------------------------------------------

    \249\ Memorandum from Gina McCarthy, then EPA Assistant 
Administrator, dated July 21, 2011, titled ``Revised Policy to 
Address Reconsideration of Interpollutant Trading Provisions for 
Fine Particles (PM2.5)'' and sent to Regional Air 
Division Directors.
    \250\ Nevertheless, while the ratios are no longer considered 
appropriate to use presumptively to meet the NNSR requirements for 
emissions offsets, a state may still conduct its own analysis and 
propose area-specific ratios for EPA approval on a case-by-case 
basis for interpollutant offset trading.
---------------------------------------------------------------------------

    Although the statutory definition at section 189(b)(3) applicable 
to PM10 does not explicitly apply to other pollutants, the 
EPA is considering the possibility that it may not have the legal 
authority to set a higher major source threshold for PM2.5 
precursors, even if it were technically justified. As previously noted, 
section 189(e), as interpreted in light of the court decision in NRDC 
v. EPA, requires that the same control requirements applicable to major 
stationary sources of PM2.5 also apply to major stationary 
sources of PM2.5 precursors. Courts have determined in other 
contexts that the term ``controls'' under the CAA includes NSR 
requirements, and in particular includes major source thresholds as 
specified in the statute.\251\ Thus, if the holding of South Coast 
directs the EPA's actions, section 189(e) must be read to require the 
same major source threshold be applied to PM2.5 precursors 
as applies to direct emissions of PM2.5.
---------------------------------------------------------------------------

    \251\ See South Coast Air Quality Management District v. EPA, 
472 F.3d 882, 900-902 (D.C. Cir. 2006) (holding that ``controls'' in 
section 172(e) anti-backsliding provision include NSR requirements 
such as LAER, offset ratios, and major source thresholds).
---------------------------------------------------------------------------

    This conclusion is also consistent with the limited legislative 
history on this issue. A House (of Representatives) Report accompanying 
the 1990 amendments to the CAA described the effects of adding section 
189(b)(3) to include the requirement that ``new or modified sources 
emitting 70 tons or more per year of VOC will be subject to new source 
review requirements.'' \252\ Thus, Congress seems to have contemplated 
that the same major source threshold would apply to sources of 
PM2.5 emissions and PM2.5 precursors in Serious 
areas.
---------------------------------------------------------------------------

    \252\ H.R. Rep. 101-490.
---------------------------------------------------------------------------

    The EPA does not believe that a sufficient technical basis exists 
at this time to enable the agency to propose specific higher major 
source thresholds for any of the four PM2.5 precursors 
presumptively regulated in PM2.5 nonattainment areas. The 
EPA intends to continue its analysis of the relationship between each 
precursor and ambient PM2.5 concentrations with the 
possibility that higher major source thresholds for specific precursors 
could be established in the future. In the meantime, the agency 
solicits comments

[[Page 15434]]

on the general appropriateness of setting higher major source 
thresholds for one or more PM2.5 precursors in 
PM2.5 nonattainment areas, as well as legal and technical 
considerations that should be made as part the EPA's future analysis of 
NNSR requirements with respect to PM2.5 precursors.
    c. Significant emissions rates for PM2.5 precursors. As explained 
above, a modification to an existing major stationary source of a 
nonattainment pollutant such as PM2.5 is a major 
modification and subject to the NNSR requirements for that pollutant 
when the source proposes to make a physical or operational change that 
results in both a significant emissions increase and a significant net 
emissions increase of that nonattainment pollutant. With regard to 
PM2.5 precursors, a modification to a major stationary 
source of any such precursor is likewise a major modification subject 
to the NNSR requirements for PM2.5 when the source proposes 
a physical or operational change resulting in a significant net 
emissions increase of that precursor. The EPA defined ``significant'' 
for SO2 and NOX as PM2.5 precursors in 
the 2008 PM2.5 NSR Rule. For both precursors, the EPA set 
the significant emissions rate for each pollutant when it is regulated 
as a precursor to PM2.5 at 40 tpy, the same level as the 
existing significant emissions rate for the pollutant as independently 
regulated as a criteria pollutant for purposes of the SO2 
and NO2 NAAQS.\253\ Also, in the preamble to the 2008 
PM2.5 NSR Rule, the EPA indicated that it would consider 40 
tpy for VOC as a PM2.5 precursor; however, that rate was not 
codified in any of the NSR regulations because the regulations provided 
that VOC was generally presumed not to be a precursor to 
PM2.5. Instead, the agency explained that any state making a 
demonstration that VOC should be treated as a PM2.5 
precursor in a particular nonattainment area ``would be required to 
adopt the 40-tpy significant emissions rate unless it demonstrated that 
a more stringent significant emissions rate (lower rate) is more 
appropriate.'' \254\
---------------------------------------------------------------------------

    \253\ See the Federal Register published on May 16, 2008 (73 FR 
28321, 28333 and 28334); and existing 40 CFR 51.165(a)(1)(x)(A).
    \254\ See the Federal Register published on May 16, 2008 (73 FR 
28321 and 28333).
---------------------------------------------------------------------------

    The 2008 PM2.5 NSR Rule codified the presumption that 
ammonia, like VOC, need not be regulated as a PM2.5 
precursor and the EPA did not set a significant emissions rate for 
ammonia. Instead, the agency indicated that it was allowing states that 
determine that ammonia significantly contributes to PM2.5 
concentrations in a given PM2.5 nonattainment area to set 
the significant emissions rate for ammonia based on information 
developed for each individual attainment plan.\255\
---------------------------------------------------------------------------

    \255\ Ibid.
---------------------------------------------------------------------------

    As explained in the 2008 PM2.5 NSR Rule, the EPA set the 
significant emissions rates for the presumed PM2.5 
precursors at the levels for those pollutants already included in NSR 
programs. The EPA explained that the use of the existing rates where 
the PM2.5 precursor is also regulated as a separate criteria 
pollutant harmonizes the NSR program for PM2.5 with the NSR 
programs for those other criteria pollutants. The agency further 
explained that this approach for setting the significant emissions 
rates for PM2.5 precursors follows the precedent for setting 
the significant emissions rate for NOX as a precursor to 
ozone, where the same 40 tpy threshold was used for NOX 
emissions as both a criteria pollutant (NO2) and a precursor 
for ozone.\256\
---------------------------------------------------------------------------

    \256\ See 73 FR 28321 (May 16, 2008), at page 28334.
---------------------------------------------------------------------------

    Nevertheless, the EPA gave some consideration in the development of 
the 2008 PM2.5 NSR Rule to setting the significant emissions 
rates for the individual PM2.5 precursors at different 
levels based on the effect of each precursor on ambient 
PM2.5 concentrations. The EPA concluded that it did not have 
adequate data on the impacts of precursor emissions from individual 
sources to override the administrative advantages of setting the 
significant emissions rates for SO2, NOX and VOC 
for purposes of the PM2.5 NSR program at the same levels 
that are already used for other purposes in the major NSR program for 
other NAAQS. The EPA continues to believe, however, that when more data 
are available, these data could provide a reasonable basis for 
considering subsequent changes to the significant emissions rates for 
each PM2.5 precursor for purposes of implementing the 
PM2.5 NAAQS, whereby the significant emissions rates for the 
individual PM2.5 precursors could more realistically reflect 
the effect that each precursor has on ambient PM2.5 
concentrations.
    The EPA is currently undertaking a separate rulemaking for both 
NNSR and PSD in which it intends to include a technical analysis of 
each PM2.5 precursor to better understand the relationship 
of emissions of each precursor to ambient PM2.5 
concentrations. The agency intends to consider the results of that 
analysis and other factors and may propose new significant emissions 
rates accordingly for SO2 and NOX as 
PM2.5 precursors. The EPA also intends to propose individual 
significant emissions rates for VOC and ammonia as PM2.5 
precursors at that time. Thus, the EPA is not proposing any changes to 
the existing significant emissions rates for SO2 and 
NOX as PM2.5 precursors in this document.
    It is the EPA's expectation that any new or revised significant 
emissions rates for the individual PM2.5 precursors will 
become effective in that separate rulemaking not long after the date of 
that final rule, allowing states to adopt and use them in their own 
NNSR regulations once the EPA approves their individual SIPs. However, 
in the event that the timing of that rule does not allow ample time for 
states to rely on it to adopt any new or revised significant emissions 
rates in their rules, it was explained earlier that individual 
significant emissions rates already exist for SO2 and 
NOX at 40 tpy. Additionally, the significant emissions rate 
for VOC was identified as 40 tpy in the 2008 PM2.5 NSR Rule 
notice (though not in the final regulations), but the EPA is proposing 
to add that precursor and emissions rate to the list of 
PM2.5 precursors. See proposed 40 CFR 51.165(a)(1)(x)(A). 
Hence, only the ammonia significant emissions rate would remain to be 
defined by each state that needs to control major stationary sources of 
ammonia as part of their NNSR program.
    d. Transition provisions for PM2.5. The CAA requires proposed major 
stationary sources and major modifications to meet major NSR permitting 
requirements that apply on the basis of the area's attainment 
designation.\257\ Accordingly, the EPA's longstanding interpretation of 
the CAA is that a proposed new major stationary source or major 
modification must satisfy the appropriate major NSR requirements (PSD 
vs. NNSR) for a particular pollutant that are in effect on the date 
that a permit is issued to the source, rather than the requirements 
that may have been applicable when the permit application was 
submitted.\258\
---------------------------------------------------------------------------

    \257\ Compare CAA section 165(a) (permitting requirements for 
sources locating in attainment and unclassifiable areas) with 
sections 172(c)(5) and 173 (permitting requirements for sources 
locating in nonattainment areas).
    \258\ See Memorandum from John S. Seitz, Director, EPA Office of 
Air Quality Planning and Standards, on March 11, 1991, titled ``New 
Source Review (NSR) Transitional Guidance,'' Attachment p. 6, sent 
to Regional Air Division Directors.
---------------------------------------------------------------------------

    In the final 2012 PM NAAQS rule, the EPA established a 
grandfathering provision that would enable some proposed new and 
modified sources

[[Page 15435]]

that had already submitted a PSD application prior to the effective 
date of the revised primary annual PM2.5 NAAQS to continue 
being reviewed under the pre-existing PSD requirements for 
PM2.5. This provision applies where the PSD program 
continues to be the applicable set of major NSR requirements for the 
area of concern. In response to the EPA's proposal to add this 
grandfathering provision for certain PSD permit applications pending 
upon the effective date of the new NAAQS, the EPA received comments 
concerning the need for a transition period for implementing the NNSR 
requirements in newly designated PM2.5 nonattainment areas 
as a result of the tightening of the primary annual PM2.5 
NAAQS.\259\ The commenters recommended that the EPA establish a 
grandfathering provision to enable pending permit applications to 
continue under review for the pre-existing requirements. A subset of 
the commenters recommended that grandfathering be accomplished by 
establishing an effective date for designations 1 year after initial 
publication in the Federal Register. Presumably, these commenters 
believed that by delaying the effective date of any new nonattainment 
designations for the primary annual PM2.5 NAAQS, sources 
with pending PSD permit applications could continue to be reviewed 
under the PSD permitting requirements rather than the NNSR requirements 
for PM2.5.
---------------------------------------------------------------------------

    \259\ See 78 FR 3086 (January 15, 2013), at page 3263.
---------------------------------------------------------------------------

    In the final 2012 PM NAAQS rule, the EPA expressed its disagreement 
with those commenters, explaining that the obligation to adopt new 
provisions under a state's NNSR program will not apply with regard to 
the revised NAAQS until such time as an area is designated 
nonattainment, and beginning on the effective date of the new area 
designations for PM2.5 proposed new and modified major 
sources would be required to meet the applicable NNSR requirements for 
PM2.5.\260\ However, the EPA further indicated that it would 
continue to consider the need to establish a grandfathering provision 
under the NNSR program for PM2.5, and would propose such 
provision, if appropriate, as part of a subsequent NSR implementation 
rulemaking with additional opportunity for public comment.\261\
---------------------------------------------------------------------------

    \260\ The applicable NNSR requirements would be either the NNSR 
requirements for PM2.5 in the state's existing SIP or the 
requirements found at 40 CFR part 51 Appendix S, where a state's SIP 
does not currently include NNSR requirements for PM2.5. 
States will be required to submit to the EPA for approval SIP 
revisions containing the amended NNSR program requirements for 
PM2.5 contained in the final PM2.5 NAAQS 
implementation rule being proposed in this notice, but those 
additional requirements will not apply in states with SIPs that 
include NNSR requirements for PM2.5 until the EPA 
approves the SIP revision. See ibid.
    \261\ Ibid.
---------------------------------------------------------------------------

    After further considering the issue during the development of this 
proposal, the EPA has decided not to propose a grandfathering provision 
that would apply to pending PSD permit applications that were submitted 
but not approved prior to the effective date of the new nonattainment 
designations for the 2012 primary annual PM2.5 NAAQS. The 
EPA does not believe it would be acceptable for the EPA or a state to 
issue a PSD permit, instead of a NNSR permit, with regard to a 
particular pollutant for which an area is designated nonattainment on 
the date the permit is to be issued. Instead, if the PSD permit has not 
been issued by the effective date of the new nonattainment designation, 
then the applicant should be required to withdraw that part of the 
permit application that addresses the nonattainment pollutant and 
submit an application that satisfies the applicable NNSR or minor NSR 
requirements in effect in the implementation plan on the date the 
permit will be issued. Given adverse conditions that already exist in a 
nonattainment area and the congressional directive to reach attainment 
as expeditiously as practicable, construction at a major stationary 
source that significantly increases emissions in such an area should be 
expected to address NNSR requirements, even if this could cause delay 
to the permit applicant.
    As explained in Section VIII.D of this preamble, states will have 
18 months from the date of the new nonattainment designations to revise 
their existing NNSR programs or establish new programs in accordance 
with the applicable requirements under subpart 4. Where the area was 
already designated nonattainment for any prior PM2.5 NAAQS 
before the effective date of designations for the 2012 NAAQS, the state 
should continue to apply the NNSR requirements contained in the 
approved SIP to issue the final permit addressing all PM2.5 
NAAQS until the new SIP revisions required by this rule are approved. 
In areas already designated nonattainment for any PM2.5 
NAAQS but lacking an approved NNSR program that applies to 
PM2.5, the requirements of Appendix S may continue to be 
applied for issuing permits in that area. However, any changes to the 
Appendix S requirements that the EPA may make via this rulemaking must 
be implemented in any area that applies Appendix S once these revisions 
become effective. Section VIII.C.2 that follows discusses the possible 
changes to the NNSR requirements in Appendix S that the agency is 
proposing in this action.
    The EPA is not proposing to add any grandfathering provisions that 
would apply to changes in NNSR permitting requirements in areas that 
the EPA may already have designated nonattainment for PM2.5 
at the time the source submitted a permit application. For reasons 
similar to those identified above in cases where an area designation 
changes, the EPA generally believes that major sources that would 
contribute to the air quality in an area that is not meeting the NAAQS 
for a particular pollutant should be expected to address the most 
current requirements that apply in the nonattainment area. The agency 
acknowledges it is possible that a proposed new or modified source may 
need to address additional precursor control requirements that did not 
apply when a permit application was submitted once the EPA's final rule 
is promulgated and the appropriate revisions are approved into a 
state's NNSR SIP. However, based on the terms of section 189(e) of the 
CAA, the EPA generally believes that those requirements should be 
addressed in pending permit applications unless the air agency has 
determined, and the EPA has approved such demonstration, that major 
stationary sources of that precursor do not contribute significantly to 
PM2.5 levels in the nonattainment area. Nevertheless, the 
agency recognizes that there may be certain circumstances where 
proposed construction might be delayed and an applicant may feel 
fundamental fairness would support exempting a particular pending 
permit from newly established requirements; therefore, the EPA seeks 
comment on what circumstances, if any, would justify a grandfathering 
provision for pending nonattainment NSR permits similar to the 
grandfathering provision promulgated in the final 2012 PM NAAQS Rule 
for PSD permitting purposes. See 40 CFR 51.166(i)(10) 52.21(i)(11). In 
addition, the EPA requests comment on how such a grandfathering 
provision would be consistent with the relevant provisions of the CAA. 
The EPA does not believe the statutory deadline in section 165(c) that 
forms part of the EPA's basis for grandfathering in the PSD context is 
applicable to NNSR permit decisions.
2. What are the changes the EPA is proposing in Appendix S?
    As described above, 40 CFR 52.24(k) provides that the Emission 
Offset

[[Page 15436]]

Interpretative Ruling, 50 CFR part 51, Appendix S, shall govern permits 
to construct and operate for which a NNSR permit application is 
submitted between the effective date of designation as nonattainment 
and the date a state's NSR permit program meeting the requirements of 
part D is approved and effective. The EPA is considering a range of 
options concerning how and whether to address the proposed subpart 4 
requirements in the interim NNSR program requirements contained in 
Appendix S.
    Permitting requirements for new major stationary sources and major 
modifications in PM2.5 nonattainment areas were originally 
added to Appendix S in the 2008 PM2.5 NSR Rule. The 
amendments generally followed the NNSR requirement contained in subpart 
1 of part D. However, in the 2008 PM2.5 NSR Rule, the EPA 
determined that, in light of the transitional function of Appendix S, 
it would be appropriate to regulate PM2.5 precursors under 
Appendix S in a manner that differed slightly from the regulatory 
approach taken in 40 CFR 51.165.
    As explained in Section VIII.B.2 of this preamble, under the 
existing requirements for NNSR plans at 40 CFR 51.165, SO2 
is regulated as a PM2.5 precursor, NOX is 
presumed to be a regulated PM2.5 precursor, and VOC and 
ammonia are presumed not to be regulated precursors (with either states 
or the EPA having authority to rebut any such presumption for a 
particular nonattainment area). However, in developing Appendix S, the 
EPA determined that it would be premature to presume that 
NOX is a regulated PM2.5 precursor in all 
PM2.5 nonattainment areas that proposed new major sources 
and major modifications in those areas should be required to address as 
a prerequisite to obtaining a NNSR permit, while at the same time the 
states were in the process of determining whether in fact 
NOX emissions contribute significantly to ambient 
PM2.5 concentrations in those areas. Accordingly, the EPA 
decided to delay implementing any control requirements for 
NOX as a PM2.5 precursor until the states 
completed the necessary analyses to determine the need for 
NOX controls as part of their SIP revisions addressing the 
revised PM2.5 NAAQS. Thus, the existing NNSR requirements 
for PM2.5 under Appendix S do not contain a requirement for 
proposed sources to consider the control of NOX emissions as 
a PM2.5 precursor. Moreover, as states presumptively did not 
need to regulate VOC and ammonia in accordance with the 2008 
PM2.5 NSR Rule in 40 CFR 51.165, the EPA similarly did not 
require sources seeking permits pursuant to the Appendix S requirements 
to address those precursors.
    As an interim measure to facilitate permitting while states develop 
NNSR rules for PM2.5, the EPA believes that the NNSR 
requirements under Appendix S need not be identical to those governing 
states' development of approvable programs pursuant to subpart 4, which 
requires regulation of all PM2.5 precursors unless a state 
provides, and the EPA approves, a demonstration that such control is 
not necessary for major stationary sources in the area under section 
189(e). This is reasonable because the EPA anticipates that many states 
may be able to demonstrate to the EPA that there is not a need to 
regulate one or more PM2.5 precursors from major stationary 
sources in a given nonattainment area, as described in Section III of 
this preamble.
    Accordingly, the EPA is proposing to revise the definition of 
regulated NSR pollutant as contained in Appendix S to provide for the 
regulation of some precursors during the transition period, but not 
others. Specifically, for reasons explained below, the EPA is proposing 
to require that both SO2 and NOX be considered 
regulated PM2.5 precursors in Appendix S and is proposing a 
significant emissions rate of 40 tpy for NOX as a 
PM2.5 precursor. See proposed Sections II.A.31(iii)(b) and 
II.A.10(i) of Appendix S, respectively. However, this proposal would 
not provide states the option of submitting a demonstration that could 
relieve them of the obligation to regulate SO2 and 
NOX as PM2.5 precursors during the transition 
period. The EPA believes that it is not necessary or efficient to 
expend effort on such a demonstration for the transitional program, 
when states are developing the demonstration for submittal with the 
NNSR SIP submission that, when approved, would replace the Appendix S 
transitional program for that area.
    The EPA is proposing to include SO2 and NOX 
in Appendix S based on the principle that the national application of a 
transition program should correspond to the general expectation of what 
the prevailing regulation of precursors will ultimately be when SIPs 
are submitted. Although such expectations are uncertain at this time, 
it is nonetheless appropriate to base the transition program on them. 
The EPA believes it is likely in many cases that states will determine 
that emissions of VOC and/or ammonia do not contribute significantly to 
PM2.5 concentrations in the affected PM2.5 
nonattainment area, although such determinations should be made on a 
case-by-case basis for individual PM2.5 nonattainment areas.
    On the other hand, the EPA expects that the cases where 
NOX does not contribute significantly to PM2.5 
concentrations in the affected PM2.5 nonattainment area will 
be few in number. Accordingly, given this likelihood, the EPA believes 
that it is reasonable to require the regulation of SO2 and 
NOX as PM2.5 precursors during the interim period 
when states are developing their PM2.5 attainment plans for 
newly designated areas (including the necessary revisions to the NNSR 
programs based on subpart 4). An added benefit of this proposed 
approach is that it will also ensure that states using the permitting 
requirements contained in Appendix S will regulate the same precursors 
that are required to be regulated in states that have already adopted 
NNSR for PM2.5 based on the 2008 PM2.5 NSR Rule. 
The EPA seeks comment on this approach as part of this proposal.
    As one alternative approach that the EPA is presenting for public 
comment, the agency is proposing to amend Appendix S to regulate not 
only SO2 and NOX, but also VOC and ammonia, as 
PM2.5 precursors that must be controlled during this interim 
period. This alternative would more closely match the basic NNSR 
program requirements of subpart 4, which indicate that states should 
regulate precursors from major stationary sources in the nonattainment 
area unless the EPA has determined that such emissions do not 
significantly contribute to violations of the NAAQS in the area. 
However, it would require states to control new major stationary 
sources and major modifications of each PM2.5 precursor 
during the interim period prior to submission of the required SIP 
revisions without the benefit of first allowing states to determine 
whether the control of each precursor is warranted. The EPA does not 
prefer this option for amending Appendix S as an interim NNSR program; 
however, the EPA is seeking comment on the approach to address the 
policy and legal implications associated with it. This alternative, 
while being proposed for comment, is not shown in the proposed 
regulatory text.
    Another alternative that the agency is proposing for comment is for 
the EPA to establish a phased-in process for regulating 
PM2.5 precursors in the NNSR program whereby states would 
initially require sources issued a permit to control only 
SO2 and NOX as PM2.5 precursors (as 
under the preferred option), with a second requirement to later require 
sources issued a permit

[[Page 15437]]

after the prescribed date (e.g., the date on which SIP revisions based 
on subpart 4 requirements are due) to control emissions of VOC and 
ammonia as well. For each precursor, the requirement to control would 
apply to major stationary sources of that particular precursor. The EPA 
believes that by phasing in the requirement to address all precursors, 
states that are ultimately able to demonstrate to the EPA's 
satisfaction that VOC and/or ammonia do not need to be subject to 
control under the NNSR requirements for PM2.5, but that have 
not yet submitted such demonstration, will have ample time to make the 
necessary demonstration and will not have to control such precursors 
even temporarily. At the same time, the phase-in provision could 
address concerns about delays in SIP submittal or approval in states 
with PM2.5 nonattainment areas in which VOC and ammonia need 
to be regulated. Such delays could result in prolonged exclusion of 
these precursors from control requirements beyond the time when an EPA-
approved state NNSR program is expected to be in place. This 
alternative, while being proposed for comment, is not shown in the 
proposed regulatory text.
    Separately, the EPA is proposing to amend Appendix S by revising 
the definition of ``major stationary source'' to include a separate 
PM2.5 major source threshold applicable to new major 
stationary sources and major modifications in PM2.5 
nonattainment areas reclassified as Serious areas. See proposed section 
II.A.4(i)(a)(7). Inclusion of the new definition is not an immediate 
concern for the revised 2012 primary annual PM2.5 NAAQS or 
any future revision to the PM2.5 NAAQS because the possible 
reclassification of any Moderate area to a Serious area will not occur 
for several years and states are required to submit their SIP revisions 
addressing NNSR requirements prior to such time. There is a 
possibility, however, that existing PM2.5 nonattainment 
areas (for the 1997 and/or 2006 PM2.5 NAAQS) could be 
reclassified as Serious areas sooner. States that still do not have 
approved NNSR programs addressing PM2.5 would be without the 
appropriate NNSR provisions to address new major stationary sources and 
major modifications in those Serious areas until they submit revisions 
to their existing programs and the EPA approves those revisions. The 
EPA solicits comments on this proposal to incorporate a definition of 
``major stationary source'' for PM2.5 nonattainment areas 
reclassified as Serious.
    The EPA is not proposing any Appendix S provisions for 
grandfathering proposed new and modified sources from newly established 
permit requirements applicable to PM2.5 nonattainment areas. 
The EPA generally believes that it would not be appropriate to 
grandfather sources from requirements that apply in areas that are not 
meeting the NAAQS. Nevertheless, the EPA seeks comment on possible 
circumstances where grandfathering, similar to the grandfathering 
provision established for pending PSD permits under the final 2012 p.m. 
NAAQS Rule, may be appropriate with respect to changes made to Appendix 
S.

D. Plan Due Dates

    For Moderate areas, section 189(a)(2)(B) requires that states make 
an attainment plan submission satisfying the requirements contained 
therein, including applicable NNSR programs for PM10 (and 
PM2.5), to the EPA for approval within 18 months of an area 
being designated nonattainment. The agency recognizes that this 
submittal date represents a considerably earlier date than anticipated 
when it issued the final 2012 p.m. NAAQS rule.\262\ However as the CAA 
requires, the EPA will apply the 18 month deadline from the effective 
date of designation of a Moderate PM2.5 nonattainment area 
for the submission of any applicable NNSR program revisions for 
PM2.5 as included in any final implementation rule.
---------------------------------------------------------------------------

    \262\ Ibid.
---------------------------------------------------------------------------

    In the event a Moderate area is reclassified as a Serious 
PM2.5 nonattainment area, it will be required to implement 
the NNSR program with a ``major stationary source'' threshold of 70 
tons per year (per CAA section 189(b)(3)). However, the CAA does not 
specify a deadline for the state's submittal of any NNSR program 
revisions (e.g., to lower the major stationary source threshold from 
100 tpy to 70 tpy) that would be needed to implement the program in a 
Serious area. Pursuant to the EPA's gap-filling authority in CAA 
section 301(a), and to effectuate the statutory control requirements in 
section 189 of the CAA, the EPA proposes to require the state to submit 
these NNSR SIP revisions no later than 18 months from the effective 
date of final reclassification of the area as a Serious nonattainment 
area. This timeframe is consistent with the 18 month timeframe required 
for submittal of certain Serious area plan elements, and it is 
consistent with the 18 month time for submittal of Moderate area plan 
revisions. We also request comment on a 12-month timeframe for 
submittal of the NNSR revisions for Serious areas. An approach that 
requires the NNSR revisions to be submitted on the same 18-month 
schedule as other Serious area plan elements is expected to be more 
administratively efficient than one that would require the NNSR 
revisions on a different schedule. On the other hand, this type of 
revision to the NNSR regulations may be relatively straightforward and 
potentially could be completed within 12 months of the reclassification 
date, thereby assuring that new major sources or modified major sources 
in the area will be subject to the lower statutory major source 
thresholds expeditiously. The EPA requests comment on both the proposed 
18-month timeframe for submission of the NNSR SIP revisions for Serious 
areas and the alternative 12-month option.

E. Avoidance of Dual Review for PSD and NNSR for PM2.5

    Because the EPA designates nonattainment areas for the primary 
annual and 24-hour PM2.5 NAAQS independently, some areas 
ultimately may be designated nonattainment for one of these standards 
and unclassifiable/attainment or attainment for another. This may raise 
concerns that the sources locating in such an area may be subject to 
both PSD and NSSR for the same pollutant. In the preamble to the final 
2012 p.m. NAAQS rule, the EPA explained that the existing PSD 
regulations resolved this issue.\263\ Specifically, the PSD regulations 
at 40 CFR 51.166(i)(2) and 52.21(i)(2) provide that the PSD 
requirements do not apply to a major stationary source or major 
modification with respect to a pollutant when ``as to that pollutant, 
the source or modification is located in an area designated as 
nonattainment . . . .'' \264\ [emphasis added]. This policy was 
explained in the preamble to the final rule promulgating the revised 
primary annual PM2.5 NAAQS.\265\ The EPA is simply 
reiterating in this action the agency's policy for addressing NSR 
applicability for areas that may be designated nonattainment for one 
averaging period and attainment or unclassifiable for another averaging

[[Page 15438]]

period. Thus, for PM2.5 only the NNSR requirements would 
apply with regard to major stationary sources of PM2.5 
locating in that nonattainment area.
---------------------------------------------------------------------------

    \263\ See ibid.
    \264\ The policy for applying the PSD exemption is clear with 
regard to the federal PSD program at 40 CFR 52.21; however, the 
requirements for a SIP-approved PSD program state that ``[t]he plan 
may provide . . .'' Accordingly, a state may choose to apply a 
different applicability strategy if it so wishes.
    \265\ Ibid.
---------------------------------------------------------------------------

IX. What other proposed requirements would apply in PM2.5 
nonattainment areas?

A. Waivers Under Section 188(f)

1. Statutory Requirements and Existing Guidance
    Section 188(f) of the CAA provides a means for the EPA to waive a 
specific date for attainment and certain control and planning 
requirements for PM2.5 nonattainment areas if certain 
conditions are met in the nonattainment area. Specifically, the statute 
provides that: ``The Administrator may, on a case-by-case basis, waive 
any requirement applicable to any Serious Area . . . where the 
Administrator determines that anthropogenic sources of PM10 
do not contribute significantly to the violation of the PM10 
standard in the area.'' In addition, ``the Administrator may also waive 
a specific date for attainment of the [PM10] standard where 
the Administrator determines that nonanthropogenic sources of 
PM10 contribute significantly to the violation of the 
PM10 standard in the area.'' In the Addendum, the EPA 
provided extensive guidance on how the agency interpreted section 
188(f) and how it intended to apply the statutory waiver provisions for 
purposes of implementing the PM10 NAAQS.\266\ At this time, 
the EPA is not proposing to revise the guidance presented in the 
Addendum with respect to section 188(f), but the agency requests 
comment on whether the existing guidance in the Addendum is appropriate 
when implementing the current and any future PM2.5 NAAQS.
---------------------------------------------------------------------------

    \266\ 59 FR 41998 (August 16, 1994), at page 42004.
---------------------------------------------------------------------------

2. Relationship Between the CAA Section 188(f) Waiver Provisions and 
the EPA's Exceptional Events Rule
    On March 22, 2007, the EPA promulgated the ``Treatment of Data 
Influenced by Exceptional Events; Final Rule'' (72 FR 13560), known as 
the Exceptional Events Rule, pursuant to the 2005 amendment of CAA 
section 319.\267\ The Exceptional Events Rule provides a mechanism by 
which the EPA can concur with an air agency's request to exclude from 
regulatory decisions air quality monitoring data determined by the EPA 
to have been affected by exceptional events.\268\ The Exceptional 
Events Rule applies to all NAAQS pollutants, including 
PM2.5. Section 188(f) and the Exceptional Events Rule 
provide separate mechanisms by which states and/or other air agencies 
can seek to have event-influenced monitoring data excluded from certain 
regulatory requirements or decisions associated with the PM NAAQS 
implementation process, under appropriate circumstances. This section 
explains the EPA's views on how these two mechanisms can operate.
---------------------------------------------------------------------------

    \267\ Section 319 of the CAA, as amended by section 6013 of the 
Safe Accountable Flexible Efficient-Transportation Equity Act: A 
Legacy for Users (SAFE-TEA-LU) of 2005, required the EPA to propose 
and promulgate regulations governing the review and handling of air 
quality monitoring data influenced by exceptional events.
    \268\ References to ``air agencies'' are meant to include state, 
local and tribal air agencies responsible for implementing the 
Exceptional Events Rule.
---------------------------------------------------------------------------

    The Exceptional Events Rule addresses elevated emissions from 
specific events that influence monitored air quality concentrations. 
The EPA's regulations at 40 CFR 50.1(j) define an ``exceptional event'' 
as one that ``affects air quality, is not reasonably controllable or 
preventable, is an event caused by human activity that is unlikely to 
recur at a particular location or a natural event, and is determined by 
the Administrator in accordance with 40 CFR 50.14 to be an exceptional 
event.'' Further, 40 CFR 50.1(j) explicitly provides that exceptional 
events do ``. . . not include stagnation of air masses or 
meteorological inversions, a meteorological event involving high 
temperatures or lack of precipitation, or air pollution relating to 
source noncompliance.'' At 40 CFR 50.1(k), the EPA's regulations define 
a ``natural event'' as an event in which human activity plays little or 
no direct causal role to the event in question.\269\ The Exceptional 
Events Rule allows the EPA to exclude from regulatory decisions air 
quality monitoring data that it determines to have been influenced by 
emissions that result from exceptional events. Air quality monitoring 
data that the EPA determines to have been influenced by an exceptional 
event under the procedural steps, substantive criteria, and schedule 
specified in the Exceptional Events Rule may be excluded from 
regulatory decisions such as initial area designations decisions and 
decisions associated with implementing the PM2.5 NAAQS such 
as clean data determinations, evaluation of attainment demonstrations, 
and discretionary or mandatory reclassifications of nonattainment areas 
from Moderate to Serious. While the EPA may agree with an air agency's 
request to exclude event-influenced air quality monitoring data from 
regulatory decisions, these regulatory actions require the EPA to 
provide an opportunity for public comment on the claimed exceptional 
event and all supporting data prior to the EPA taking final agency 
action.
---------------------------------------------------------------------------

    \269\ The EPA will generally consider human activity to have 
played little or no direct role in causing emissions of the dust 
generated by high wind for purposes of the regulatory definition of 
``natural event'' if contributing anthropogenic sources of the dust 
are reasonably controlled at the time of the event, regardless of 
the amount of dust coming from these reasonably controlled 
anthropogenic sources, and thus the event could be considered a 
natural event. In such cases, the EPA believes that it would 
generally be a reasonable interpretation of its regulations to find 
that the anthropogenic source had ``little'' direct causal role. If 
anthropogenic sources of windblown dust that are reasonably 
controllable but that did not have those reasonable controls applied 
at the time of the high wind event have contributed significantly to 
a measured concentration, then the event would not be considered a 
natural event. See preamble to the Exceptional Events Rule at 72 FR 
13560 (March 22, 2007), footnote 11 on page 13566.
---------------------------------------------------------------------------

    If wildfire is a potential contributor to exceedances of the NAAQS 
and exceptional events, the EPA urges state and local agencies to 
coordinate with the land management agencies, as appropriate, in 
developing plans and appropriate public communications regarding public 
safety and reducing exposure. This action can directly help states meet 
their Exceptional Events Rule obligation whereby ``states must provide 
public notice, public education, and must provide for implementation of 
reasonable measures to protect public health when an event occurs.'' 
When wildfire impacts are significant in a particular area, air 
agencies and communities may be able to lessen the impacts of wildfires 
by working collaboratively with land managers and land owners to employ 
various mitigation measures including taking steps to minimize fuel 
loading in areas vulnerable to fire.\270\
---------------------------------------------------------------------------

    \270\ Because of previously expressed stakeholder feedback 
regarding implementation of the Exceptional Events Rule and specific 
stakeholder concerns regarding the analyses that can be used to 
support wildfire-related exceptional event demonstrations, the EPA 
intends to propose revisions to the Exceptional Events Rule in a 
future notice-and-comment rulemaking and will solicit public comment 
at that time. Depending on the nature and scope of any interstate 
emissions events affecting downwind air quality, the EPA may be able 
to assist states in developing approvable exceptional events 
demonstrations.
---------------------------------------------------------------------------

    The EPA notes that there could be some potential overlap between 
the application of the Exceptional Events Rule and section 188(f). The 
EPA believes that this potential for overlap can best be addressed by 
considering the applicability of the Exceptional Events Rule and 
section 188(f) in sequence. Thus, the EPA recommends

[[Page 15439]]

that air agencies first consider whether the monitored air quality data 
on specific days were influenced by an exceptional event. If the air 
agency requests and the EPA agrees with this request and determines 
that the monitored air quality data should be excluded from 
consideration in regulatory decisions, then using the provisions in the 
Exceptional Events Rule could address the situation adequately. 
Thereafter, if the air agency determines that the waiver provisions of 
section 188(f) may also be applicable, then the EPA can evaluate that 
question based on the remaining data that are representative for the 
area in question.

B. Conformity Requirements

1. What requirements apply to both transportation and general 
conformity?
    a. What are transportation and general conformity? Conformity is 
required under CAA section 176(c) to ensure that federal actions are 
consistent with (``conform to'') the purpose of the SIP. Conformity to 
the purpose of the SIP means that federal activities will not cause new 
air quality violations, worsen existing violations, or delay timely 
attainment of the relevant NAAQS or interim reductions and milestones. 
Conformity applies to areas that are designated nonattainment, and 
those nonattainment areas redesignated to attainment with a CAA section 
175A maintenance plan after 1990 (``maintenance areas'').
    The EPA's Transportation Conformity Rule (40 CFR 51.390 and part 
93, subpart A) establishes the criteria and procedures for determining 
whether transportation activities conform to the SIP. These activities 
include adopting, funding or approving transportation plans, 
transportation improvement programs (TIPs) and federally supported 
highway and transit projects. The EPA first promulgated the 
Transportation Conformity Rule on November 24, 1993 (58 FR 62188), and 
subsequently published several amendments. For example, the EPA 
published a final rule on July 1, 2004 (69 FR 40004) that provided 
conformity procedures for state and local agencies under the 1997 
PM2.5 NAAQS, among other things. On May 6, 2005 (70 FR 
24280) the EPA published a final rule that addressed transportation 
conformity requirements for PM2.5 precursors.\271\ The EPA 
published another final rule on March 24, 2010 (75 FR 14260) that 
addressed additional requirements for the 2006 PM2.5 NAAQS. 
Finally, the EPA published a final rule on March 14, 2012 (77 FR 14979) 
that restructured portions of the transportation conformity rule so 
that they would clearly apply to nonattainment and maintenance areas 
for new and revised NAAQS, including the 2012 PM2.5 NAAQS. 
All of these rules apply to the current PM2.5 NAAQS 
including the 1997 PM2.5 NAAQS, the 2006 24-hour 
PM2.5 NAAQS and the 2012 primary annual PM2.5 
NAAQS and will apply to future PM2.5 NAAQS. For further 
information on conformity rulemakings, policy guidance and outreach 
materials, see the EPA's Web site at http://www.epa.gov/otaq/stateresources/transconf/index.htm. The EPA may issue future 
transportation conformity guidance as needed to implement the 2012 
primary annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \271\ This final rule was not challenged or affected in any way 
by the January 2013 D.C. Circuit Court decision requiring the EPA to 
implement the PM2.5 NAAQS pursuant to subpart 4 of the 
CAA.
---------------------------------------------------------------------------

    With regard to general conformity, the EPA first promulgated 
general conformity regulations in November 1993 (40 CFR part 51, 
subpart W, 40 CFR part 93, subpart B). Subsequently the EPA finalized 
revisions to the general conformity regulations on April 5, 2010 (75 FR 
17254). Besides ensuring that federal actions not covered by the 
transportation conformity rule will not interfere with the SIP, the 
general conformity program also fosters communications between federal 
agencies and state/local air quality agencies, provides for public 
notification of and access to federal agency conformity determinations 
and allows for air quality review of individual federal actions. More 
information on the general conformity program is available at http://www.epa.gov/air/genconform/.
    b. Why is the EPA discussing transportation and general conformity 
in this proposed rulemaking? The EPA is discussing transportation and 
general conformity in this proposed rulemaking in order to provide 
affected parties with information on when conformity must be 
implemented after nonattainment areas are designated for a new or 
revised PM2.5 NAAQS. At this time the EPA is using the 2012 
PM2.5 NAAQS as an example. The agency is also discussing how 
it plans to make the transition from demonstrating conformity for the 
1997 annual PM2.5 NAAQS to the 2012 primary annual 
PM2.5 NAAQS because this transition is unique in that the 
1997 annual PM2.5 NAAQS was retained as a secondary NAAQS. 
The information presented here is consistent with existing conformity 
regulations and statutory provisions that are not addressed by this 
PM2.5 implementation rulemaking. Affected parties would 
include state and local transportation and air quality agencies, 
metropolitan planning organizations (MPOs), and federal agencies 
including the U.S. Department of Transportation (DOT), the U.S. 
Department of Defense, the U.S. Department of Interior and the U.S. 
Department of Agriculture.
    c. When would transportation and general conformity apply to areas 
designated nonattainment for the 2012 primary annual PM2.5 NAAQS? 
Transportation and general conformity apply 1 year after the effective 
date of nonattainment designations for a new or revised 
PM2.5 NAAQS including the 2012 primary annual 
PM2.5 NAAQS. This is because CAA section 176(c)(6) provides 
a 1-year grace period from the effective date of initial designations 
for any new NAAQS before transportation and general conformity apply in 
areas newly designated nonattainment for a specific pollutant and 
NAAQS. With regard to general conformity, the EPA's April 2010 
revisions to its general conformity regulations (see 75 FR 17277; April 
5, 2010) apply the same 1-year grace period for purposes of general 
conformity.
    With regard to transportation conformity, the conformity grace 
period applies to all areas designated nonattainment for a new or 
revised PM2.5 NAAQS including the 2012 primary annual 
PM2.5 NAAQS. The requirements differ depending on whether 
the nonattainment area is within or adjacent to a MPO designated under 
23 U.S.C. 134. Within 1 year after the effective date of the initial 
nonattainment designation for a given pollutant and NAAQS, the MPOs and 
DOT must make a conformity determination with regard to that pollutant 
and standard for all of the transportation plans and TIPs in the 
nonattainment area. The conformity requirements for surrounding ``donut 
areas,'' including the application of the 1-year conformity grace 
period, are generally the same as those for metropolitan areas.\272\ 
For the purposes of the implementation of the 2012 PM2.5 
NAAQS, MPOs and any adjacent donut areas in a 2012 PM2.5 
NAAQS nonattainment area must continue to meet conformity requirements 
during the grace period for any other applicable NAAQS, including the 
1997 annual PM2.5 NAAQS and the 2006 24-hour 
PM2.5 NAAQS. If, at the end of the grace period for the 2012 
annual PM2.5 NAAQS, the MPO and DOT have not made a 
transportation plan and TIP

[[Page 15440]]

conformity determination for that NAAQS, the area would be in a 
conformity ``lapse.'' During a conformity lapse, only certain projects 
can receive additional federal funding or approvals to proceed. The 
practical impact of a conformity lapse will vary from area to area. 
Finally, the 1-year conformity grace period also applies to project 
level conformity determinations.
---------------------------------------------------------------------------

    \272\ For the purposes of transportation conformity, a ``donut'' 
area is the geographic area outside a metropolitan planning area 
boundary, but inside a designated nonattainment or maintenance area 
boundary that includes an MPO (40 CFR 93.101).
---------------------------------------------------------------------------

    Isolated rural nonattainment and maintenance areas are areas that 
do not contain or are not part of an MPO (40 CFR 93.101). Conformity 
requirements for isolated rural nonattainment and maintenance areas can 
be found at 40 CFR 93.109(g). One year after the effective date of the 
initial nonattainment designation for a given pollutant and NAAQS, 
conformity requirements with regard to that pollutant and standard 
would apply in any nonattainment areas that are isolated rural areas. 
Per the transportation conformity rule, an isolated rural area would be 
required to make a transportation conformity determination only at the 
point when a transportation project needs funding or approval. This 
project level conformity determination may occur significantly after 
the 1-year grace period has ended. See the EPA's July 1, 2004 final 
rule for further background on how the EPA has implemented this 
conformity grace period in metropolitan, donut and isolated rural areas 
(69 FR 40008; July 1, 2014; see also 69 FR 40009, 40010, 40011, 40012, 
40013 and 40014).
    d. How will transportation and general conformity apply with regard 
to the 1997 annual PM2.5 NAAQS, which was retained as a secondary 
NAAQS? In the final 2012 p.m. NAAQS rule the EPA established a new 
health-based primary annual PM2.5 NAAQS of 12.0 [mu]g/m\3\. 
In that same action the EPA retained the 1997 annual PM2.5 
NAAQS of 15.0 [mu]g/m\3\ as a secondary NAAQS to protect against 
certain welfare effects. In the 1997 PM2.5 designations rule 
(70 FR 944; January 5, 2005), the EPA designated areas nonattainment 
for both the 1997 primary and secondary annual PM2.5 NAAQS 
(which have identical levels of 15.0 [mu]g/m\3\). Designations for the 
2012 primary annual PM2.5 NAAQS were made in January 2015 
(80 FR 2205; January 15, 2015). This action did not make any changes to 
the designations that apply for the 1997 secondary annual 
PM2.5 standard. Therefore, at this time, all areas 
designated nonattainment in 2005 for the 1997 annual PM2.5 
standard are considered as having been designated nonattainment for 
both the 1997 primary annual PM2.5 NAAQS and for the 1997 
secondary annual PM2.5 NAAQS where such distinctions are 
made below. Similarly, for any 1997 PM2.5 nonattainment 
areas that have approved redesignation requests for attainment of the 
1997 PM2.5 NAAQS, the redesignation applies to both the 
primary and secondary standards of the 1997 PM2.5 NAAQS. A 
discussion of how transportation and general conformity apply in this 
situation follows.
    CAA section 176(c)(5) establishes that conformity applies to: a 
nonattainment area and each pollutant for which the area is designated 
as a nonattainment area; and an area that was designated as a 
nonattainment area but that was later redesignated by the Administrator 
as an attainment area and that is required to develop a maintenance 
plan under CAA section 7505a with respect to the specific pollutant for 
which the area was designated nonattainment. Section 176(c)(5) is clear 
that transportation and general conformity apply in nonattainment areas 
and in areas that have been redesignated to attainment and are required 
to develop a maintenance plan under section 175A.
    Section 175A(a) establishes the requirements for areas that are 
required to submit a maintenance plan as one of the requirements that 
must be fulfilled in order for an area to be redesignated to 
attainment.
    Section 175A(a) requires nonattainment areas for primary NAAQS to 
submit maintenance plans in order to be redesignated, and such plans 
must ensure maintenance of the standard for at least 10 years after 
redesignation. Section 175A(a) does not require nonattainment areas for 
secondary NAAQS to submit maintenance plans in order to be designated 
to attainment. Therefore, the EPA concludes that transportation and 
general conformity do not apply in areas that have been redesignated 
for any secondary NAAQS, such as the 1997 secondary annual 
PM2.5 NAAQS, since conformity does not apply in areas that 
have been redesignated without maintenance plans.
    Elsewhere in this notice, the EPA is proposing options for revoking 
the 1997 primary annual PM2.5 NAAQS, which has been replaced 
by the more health protective 2012 primary annual PM2.5 
NAAQS. If the EPA finalizes an option that results in the revocation of 
the 1997 primary annual PM2.5 NAAQS, nonattainment and 
maintenance areas would not be required to make transportation or 
general conformity determinations for the 1997 primary annual 
PM2.5 NAAQS after the effective date of the revocation of 
the 1997 primary annual NAAQS. The revocation would leave designations 
in place for the 1997 secondary annual NAAQS. Any area that is 
designated as nonattainment for the 1997 secondary annual NAAQS would 
have to continue to make transportation and general conformity 
determinations for that NAAQS as conformity applies in nonattainment 
areas for secondary NAAQS.
    However, for any area that has been redesignated to attainment for 
the 1997 secondary NAAQS and is not designated nonattainment for the 
2012 primary annual PM2.5 NAAQS, the relevant planning 
organization will not have to make conformity determinations for any 
annual PM2.5 NAAQS after the effective date of the 
revocation of the 1997 primary annual PM2.5 NAAQS because, 
as discussed above, the CAA does not require maintenance areas for 
secondary NAAQS to make conformity determinations. This means that if 
the EPA finalizes any of the options for revoking the 1997 primary 
annual PM2.5 NAAQS, after the effective date of the 
revocation, areas redesignated to attainment for the 1997 secondary 
annual PM2.5 NAAQS will no longer be required to make 
transportation plan, TIP, or project-level transportation conformity 
determinations for that NAAQS. In addition, federal agencies will no 
longer be required to make general conformity determinations for that 
NAAQS. Areas that remain designated nonattainment for the 1997 
secondary annual PM2.5 NAAQS will continue to make 
transportation plan, TIP, and project-level conformity determinations 
for that NAAQS and federal agencies will be required to continue to 
make general conformity determinations for that NAAQS in these areas 
until such time as they attain that NAAQS and are redesignated to 
attainment.
    e. What impact will the implementation of a new or revised PM2.5 
NAAQS such as the 2012 PM2.5 NAAQS have on a state's transportation 
and/or general conformity SIP? As long as the EPA does not make 
specific changes to its transportation or general conformity 
regulations states should not need to revise their transportation and/
or general conformity SIPs. The EPA is not proposing any changes to its 
transportation conformity regulations. The EPA is proposing to change 
the de minimis levels in its general conformity regulations as 
discussed in Section IX.B.2.b. of this preamble. States with a general 
conformity SIP should evaluate the need to revise those SIPs if this 
change is finalized. States with new nonattainment areas may also need 
to revise conformity SIPs in order to

[[Page 15441]]

ensure the state regulations apply in any newly designated areas.
    However, if this is the first time that transportation conformity 
will apply in a state, such a state is required by the statute and EPA 
regulations to submit a SIP revision that addresses three specific 
transportation conformity requirements that address consultation 
procedures and written commitments to control or mitigation measures 
associated with conformity determinations for transportation plans, 
TIPs or projects (40 CFR 51.390). Additional information and guidance 
can be found in the EPA's ``Guidance for Developing Transportation 
Conformity State Implementation Plans'' (http://www.epa.gov/otaq/stateresources/transconf/policy/420b09001.pdf).
2. What additional requirements apply to general conformity?
    a. What de minimis emissions levels will apply for direct PM2.5 and 
its precursors?
    Federal actions estimated to have an annual net emissions increase 
less than the de minimis levels established in the general conformity 
regulations are not required to demonstrate conformity under those 
regulations. For direct PM2.5 and its precursors 
(SO2, NOX, VOC and ammonia), the existing de 
minimis emissions levels are set forth in the EPA's general conformity 
regulations at 40 CFR 93.153(b)(1). Those levels were based on the 
definition of a major stationary source for nonattainment NSR programs 
as established by sections 182, 183 and 302 of the CAA. The EPA 
believes it is appropriate to continue this practice for implementing 
the current and any future PM2.5 NAAQS.
    However, because the definition of precursors currently in the 
general conformity regulations at 40 CFR 93.152(b)(1) does not reflect 
the elimination of rebuttable presumptions for certain PM2.5 
precursors, the EPA is proposing changes to these conformity provisions 
to make them consistent with the agency's revised precursor 
requirements. Specifically, the current definition of precursors for 
PM2.5 in the general conformity regulations reflects the 
rebuttable presumptions for VOC and ammonia finalized in the 2007 
PM2.5 Implementation Rule (72 FR 20583; April 25, 2007). It 
also does not reflect the subpart 4 definitions for ``major source'' 
and ``major stationary source'' that apply for Serious PM2.5 
nonattainment areas. Therefore, through this proposal the EPA proposes 
to change the PM2.5 precursor de minimis levels currently in 
40 CFR 93.153(b)(1) to be consistent with the statutory requirements 
for major stationary source thresholds under subpart 4 and any relevant 
changes being proposed in Section III of this preamble. The EPA 
proposes to set the de minimis levels that apply to direct 
PM2.5 and PM2.5 precursors for PM2.5 
nonattainment areas for purposes of general conformity as identified in 
Table 3 below.

                   Table 3--General Conformity De Minimis Emission Levels for PM2.5 Precursors
----------------------------------------------------------------------------------------------------------------
                                                     Tons/year in moderate PM2.5
                 Type of  emission                   nonattainment areas and all     Tons/year in Serious PM2.5
                                                          maintenance areas             nonattainment areas
----------------------------------------------------------------------------------------------------------------
Direct emissions..................................                           100                             70
SO2...............................................                           100                             70
NOX...............................................                           100                             70
VOC...............................................                           100                             70
Ammonia...........................................                           100                             70
----------------------------------------------------------------------------------------------------------------

    b. Are there any other impacts related to general conformity based 
on implementation of the 2012 PM2.5 NAAQS? The EPA is not proposing any 
other revisions to the general conformity regulations at this time. 
However, as states develop SIP revisions for the 2012 and future 
PM2.5 NAAQS, the agency recommends that state and local air 
quality agencies work with federal agencies with large facilities 
(e.g., commercial airports, ports and large military bases) that are 
subject to the general conformity regulations to establish an emissions 
budget for those facilities in order to facilitate future conformity 
determinations under the conformity regulations. Such a budget could be 
used by federal agencies in determining conformity or identifying 
mitigation measures if the budget level is included and identified in 
the SIP.
    Significant tracts of land under federal management may also be 
included in nonattainment area boundaries. The role of fire in these 
areas should be assessed and emissions budgets developed in concert 
with those federal land management agencies. In such areas the EPA 
encourages states to consider in any baseline, modeling and SIP 
attainment inventory used and/or submitted to include emissions 
expected from projects subject to general conformity, including 
emissions from wildland fire that may be reasonably expected in the 
area. Where appropriate, states may consider developing plans for 
addressing wildland fuels in collaboration with land managers and 
owners. Information is available from DOI and USDA Forest Service on 
the ecological role of fire and on smoke management programs and basic 
smoke management practices.\273\
---------------------------------------------------------------------------

    \273\ USDA Forest Service and Natural Resources Conservation 
Service, Basic Smoke Management Practices Tech Note, October 2011, 
http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046311.pdf.
---------------------------------------------------------------------------

C. Clean Data Policy

    This section describes the ongoing status of the EPA's Clean Data 
Policy and proposes provisions applicable to any determinations of 
attainment under current and future PM2.5 NAAQS. This 
section also sets forth the regulatory consequences of an EPA 
determination, made after notice and comment rulemaking, that an area 
designated nonattainment for a PM2.5 standard has air 
quality attaining that standard. Upon such a determination by the EPA, 
the state's requirement for the area to submit the separate required 
elements of an attainment plan (including an attainment demonstration, 
but not the emissions inventory requirement), shall be suspended until 
such time as the area is redesignated to attainment, at which time the 
requirements no longer apply. If the EPA determines that the area, 
after reaching attainment, has again violated that PM2.5 
NAAQS, the requirements are again applicable. The following discussion 
of this interpretation, known as the EPA's Clean Data Policy, explains 
the basis for the EPA's interpretation and is relevant to all 
PM2.5 NAAQS under subpart 4.
1. What is a clean data determination?
    The EPA's interpretation of the CAA applies when the agency, after 
notice-and-comment rulemaking, issues a ``clean data determination'' 
(CDD), in

[[Page 15442]]

which it determines that a specific nonattainment area has attained the 
relevant standard. For such areas, the EPA interprets the CAA as 
suspending the state requirements to submit to the EPA the planning 
elements of an attainment plan related to attaining the NAAQS for as 
long as the area continues to attain the standard.\274\ These planning 
elements generally include reasonable further progress (RFP) 
requirements, attainment demonstrations, RACM and RACT, nonattainment 
area contingency measures, and other state planning requirements 
related to the attainment of the NAAQS.\275\ The suspension of the 
obligation to submit applies regardless of when the plan submissions 
are due. The CDD does not suspend CAA requirements that are independent 
of helping the area achieve attainment, such as the requirements to 
submit an emissions inventory and nonattainment new source review 
requirements.
---------------------------------------------------------------------------

    \274\ In the context of CDDs, the EPA distinguishes between 
attainment planning requirements of the CAA, which relate to the 
attainment demonstration for an area and related control measures 
for bringing an area into attainment for a given NAAQS as 
expeditiously as practicable, and other types of requirements, such 
as permitting requirements under the NNSR program, and any specific 
control requirements independent of those strictly needed to ensure 
timely attainment of a given NAAQS.
    \275\ See December 14, 2004 memorandum from Stephen D. Page, 
Director, EPA Office of Air Quality Planning and Standards, to Air 
Division Directors, EPA Regions I-X, entitled ``Clean Data Policy 
for the Fine Particle National Ambient Air Quality Standards.'' 
Available at: http://www.epa.gov/airquality/urbanair/sipstatus/docs/pm25_clean_data_policy_14dec2004.pdf.
---------------------------------------------------------------------------

    The emissions inventory is a basic compilation of information used 
to characterize the sources of emissions of the nonattainment area. 
Section 172(c)(3), the statutory provision requiring submission of an 
emissions inventory, is not tied to attainment of the NAAQS, unlike the 
attainment planning provisions which are suspended by a CDD. A base 
year inventory continues to be relevant to a nonattainment area that is 
attaining the NAAQS and has obtained a CDD because, for example, the 
inventory is a necessary component to an approvable redesignation 
request. In addition, in the event the air quality in the area exceeds 
the standard in a subsequent year, the state would be obligated to 
submit an attainment demonstration and other planning elements for the 
area, and a base year inventory would need to be available immediately 
in order for the state to submit an approvable attainment plan 
expeditiously. Similarly, the new source review requirement is not 
suspended because section 172(c)(5) is not tied to attainment of the 
NAAQS, and an area with a CDD is still designated nonattainment. NNSR 
permitting is required in each nonattainment area until the area is 
redesignated to attainment.'' For the past two decades, and for many 
NAAQS, the EPA has consistently applied its Clean Data Policy 
interpretation to attainment-related provisions of subparts 1, 2 and 4 
of Part D, Title I of the CAA. The Clean Data Policy is the subject of 
several EPA memoranda and regulations and numerous individual 
rulemakings published in the Federal Register. These rulemakings have 
applied the interpretation to a broad spectrum of NAAQS, including the 
1-hour and 1997 ozone standards, PM10, 1997 and 2006 
PM2.5 standards and the carbon monoxide (CO) and lead 
standards. The D.C. Circuit has upheld the Clean Data Policy 
interpretation as embodied in the EPA's 8-hour ozone Implementation 
Rule, 40 CFR 51.918.\276\ NRDC v. EPA, 571 F. 3d 1245 (D.C. Cir. 2009). 
Other U.S. Circuit Courts of Appeals that have considered and reviewed 
the EPA's Clean Data Policy interpretation have upheld it and the 
rulemakings applying the EPA's interpretation. Sierra Club v. EPA, 99 
F.3d 1551 (10th Cir. 1996); Sierra Club v. EPA, 375 F. 3d 537 (7th Cir. 
2004); Our Children's Earth Foundation v. EPA, N. 04-73032 (9th Cir. 
June 28, 2005) (memorandum opinion); Latino Issues Forum, v. EPA, Nos. 
06-75831 and 08-71238 (9th Cir. March 2, 2009) (memorandum opinion). 
The EPA incorporated its Clean Data Policy interpretation in both its 
1997 8-hour ozone implementation rule and in its remanded 2007 
PM2.5 Implementation Rule in 40 CFR 51.1004(c). See the 
Federal Register published on April 25, 2007 (72 FR 20583, 20585 and 
20665. The D.C. Circuit, in its January 4, 2013 decision remanding the 
PM2.5 implementation rule, did not address the merits of 
that regulation or the EPA's existing interpretation of the statutory 
provisions as they pertained to the EPA's Clean Data Policy.
---------------------------------------------------------------------------

    \276\ ``The EPA's Final Rule to implement the 8-hour Ozone 
National Ambient Air Quality Standard--Phase 2 (Phase 2 Final 
Rule).'' See the Federal Register published on November 29, 2005 (70 
FR 71612, 71645 and 71646).
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    The EPA has previously articulated its Clean Data Policy 
interpretation under subpart 4 in implementing the PM10 
standard. See, e.g., 75 FR 27944 (May 19, 2010) (determination of 
attainment of the PM10 standard in Coso Junction, 
California); 71 FR 13021 (March 14, 2006) (Yuma, Arizona area); 71 FR 
40023 (July 14, 2006) (Weirton, West Virginia area); 71 FR 44920 
(August 8, 2006) (Rillito, Arizona area); 71 FR 63642 (October 30, 
2006) (San Joaquin Valley, California area) 72 FR 14422 (March 28, 
2007) (Miami, Arizona area). In the EPA's proposed and final 
rulemakings determining that the San Joaquin Valley nonattainment area 
attained the PM10 standard, the EPA set forth at length its 
rationale for applying the Clean Data Policy to PM10 under 
subpart 4. 71 FR at 63643-45. The Ninth Circuit upheld the EPA's final 
rulemaking, and specifically the EPA's Clean Data Policy, in the 
context of subpart 4. Latino Issues Forum v. EPA, supra. Nos. 06-75831 
and 08-71238 (9th Cir. March 2, 2009) (memorandum opinion). In 
rejecting the petitioner's challenge to the Clean Data Policy under 
subpart 4 for PM10, the Ninth Circuit stated, ``As the EPA 
explained, if an area is in compliance with PM10 standards, 
then further progress for the purpose of ensuring attainment is not 
necessary.'' Thus the EPA has previously established its interpretation 
that, under subpart 4, a clean data determination suspends the 
obligations to submit an attainment demonstration, RACM/RACT, RFP and 
quantitative milestones, contingency measures, and other measures 
related to attainment. The EPA is proposing to codify this 
interpretation in this implementation rule for the PM2.5 
NAAQS.
    As with its Clean Data Policy interpretation for 8-hour ozone, 
which the EPA embodied in a regulation that was upheld by the D.C. 
Circuit in NRDC v. EPA, 571 F. 3d 1245 (D.C. Cir. 2009), the EPA 
intends to embody its interpretation for the Clean Data Policy for 
current and future PM2.5 NAAQS in a regulation as part of 
this proposed rulemaking. This interpretation complies with the D.C. 
Circuit's ruling (NRDC v. EPA, 706 F.3d 428 (D.C. Cir. 2013)) that both 
subparts 1 and subpart 4 apply to implementation, and reflects the 
interpretation upheld by the Latino Issues Forum Court. Latino Issues 
Forum v. EPA, supra. Nos. 06-75831 and 08-71238 (9th Cir. March 2, 
2009) (memorandum opinion). Under this proposed regulation, if the EPA 
determines, after notice-and-comment rulemaking, that an area has 
attained the applicable PM2.5 NAAQS based on the most recent 
3 years of complete, quality-assured data meeting the requirements of 
40 CFR part 50, Appendix N, the area's obligation to submit the 
following Moderate or Serious area attainment-related planning 
requirements is suspended for so long as the area continues to attain 
the PM2.5 standard: (i) the part D, subpart 4 and subpart 1

[[Page 15443]]

obligation to provide an attainment demonstration pursuant to section 
189(a)(1)(B); (ii) the RACM and RACT provisions of section 
189(a)(1)(C); (iii) the RFP and quantitative milestones provisions of 
section 189(c); and, (iv) related attainment demonstration, RACM and 
RACT, RFP and contingency measure provisions requirements of subpart 1, 
section 172.
    A final determination of attainment, also known as a clean data 
determination, would not constitute a redesignation to attainment under 
CAA section 107(d)(3). The state would still have to meet the statutory 
requirements for redesignation in order to be redesignated to 
attainment. A determination of attainment for purposes of the Clean 
Data Policy is also not linked to any particular attainment deadline, 
and is not necessarily equivalent to a determination that an area has 
attained the standard by its applicable attainment deadline, e.g., 
under section 189(c).
2. Planning Requirements Suspended With a CDD
    a. Control measure requirements for Moderate areas. Both sections 
172(c)(1) and 189(a)(1)(C) require ``provisions to assure that 
reasonably available control measures'' (i.e., RACM) are implemented in 
a nonattainment area. Reasonably available control technology (i.e., 
RACT) is a subset of RACM. The General Preamble states that the EPA 
interprets section 172(c)(1) so that RACM requirements are a 
``component'' of an area's attainment demonstration.\277\ Thus, for the 
same reason the obligation to submit an attainment demonstration is 
suspended, the requirement for a state to submit RACM is suspended if 
the nonattainment area reaches attainment. For PM2.5, the 
EPA has consistently interpreted this provision to require only 
implementation of potential RACM that could contribute to RFP or to 
timely attainment (General Preamble, 57 FR 13498). Thus, where an area 
is already attaining the standard, no additional RACM are required, but 
all measures adopted into the SIP prior to attainment would 
remain.\278\ The EPA is interpreting section 189(a)(1)(C) consistent 
with its interpretation of section 172(c)(1).
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    \277\ 57 FR 13498 (April 16, 1992), at page 13560.
    \278\ The EPA's interpretation that the statute requires 
implementation only of RACM that would advance attainment was upheld 
by the Fifth Circuit Court (Sierra Club v. EPA, 314 F.3d 735, 743-
745 (5th Cir. 2002), and by the D.C. Circuit Court (Sierra Club v. 
EPA, 294 F.3d 155, 162-163 (D.C. Cir. 2002)).
---------------------------------------------------------------------------

    b. RFP and quantitative milestones. The EPA has long interpreted 
the provisions of part D, subpart 1 of the CAA (sections 171 and 172) 
as not requiring the submission of RFP for an area already attaining 
the PM10 NAAQS. For an area that is attaining, showing that 
the state will make RFP towards attainment ``will, therefore, have no 
meaning at that point.'' \279\ Section 189(c)(1) states that: ``Plan 
revisions demonstrating attainment submitted to the Administrator for 
approval under this subpart shall contain quantitative milestones which 
are to be achieved every 3 years until the area is redesignated 
attainment and which demonstrate reasonable further progress, as 
defined in section [171(1)] of this title, toward attainment by the 
applicable date.''
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    \279\ 57 FR 13498 (April 16, 1992), at page 13564. See 71 FR 
40952 (July 19, 2006) and 71 FR 63642 (October 30, 2006) (proposed 
and final determination of attainment for San Joaquin Valley); 75 FR 
13710 (March 23, 2010) and 75 FR 27944 (May 19, 2010) (proposed and 
final determination of attainment for Coso Junction).
---------------------------------------------------------------------------

    With respect to RFP, section 171(1) states that, for purposes of 
part D, RFP ``means such annual incremental reductions in emissions of 
the relevant air pollutant as are required by this part or may 
reasonably be required by the Administrator for the purpose of ensuring 
attainment of the applicable NAAQS by the applicable date.'' 42 U.S.C. 
7501(1). Thus, whether dealing with the general RFP requirement of 
section 172(c)(2), the ozone-specific RFP requirements of sections 
182(b) and (c), or the specific RFP requirements for PM10 
areas of part D, subpart 4, section 189(c)(1), the stated purpose of 
RFP is to ensure attainment by the applicable attainment date. Although 
section 189(c) states that revisions shall contain milestones which are 
to be achieved until the area is redesignated to attainment, such 
milestones are designed to show reasonable further progress ``toward 
attainment by the applicable attainment date,'' as defined by section 
171. Thus, it is clear that once the area has attained the standard, no 
further milestones are necessary or meaningful. This interpretation is 
supported by language in section 189(c)(3), which mandates that a state 
that fails to achieve a milestone must submit a plan that assures that 
the state will achieve the next milestone or attain the NAAQS if there 
is no next milestone. Thus, section 189(c)(3) itself assumes that the 
requirement to submit and achieve milestones does not continue after 
attainment of the NAAQS.
    In the General Preamble, the EPA noted with respect to section 
189(c) that the purpose of the milestone requirement is ``to provide 
for emission reductions adequate to achieve the standards by the 
applicable attainment date (H.R. Rep. No. 490 101st Cong., 2d Sess. 267 
(1990)).'' 57 FR 13498 (April 16, 1992), at page 13539. If an area has 
in fact attained the standard, the stated purpose of the RFP 
requirement will have already been fulfilled.\280\ Similarly, the 
requirements of section 189(c)(2) with respect to milestones no longer 
apply so long as an area has attained the standard. Section 189(c)(2) 
provides in relevant part that: Not later than 90 days after the date 
on which a milestone applicable to the area occurs, each State in which 
all or part of such area is located shall submit to the Administrator a 
demonstration . . . that the milestone has been met.
---------------------------------------------------------------------------

    \280\ Thus, the EPA believes that it is a distinction without a 
difference that section 189(c)(1) speaks of the RFP requirement as 
one to be achieved until an area is ``redesignated attainment,'' as 
opposed to section 172(c)(2), which is silent on the period to which 
the requirement pertains, or the ozone nonattainment area RFP 
requirements in sections 182(b)(1) or 182(c)(2), which refer to the 
RFP requirements as applying until the ``attainment date,'' since 
section 189(c)(1) defines RFP by reference to section 171(1) of the 
CAA. Reference to section 171(1) clarifies that, as with the general 
RFP requirements in section 172(c)(2) and the ozone-specific 
requirements of section 182(b)(1) and 182(c)(2), the PM-specific 
requirements may only be required ``for the purpose of ensuring 
attainment of the applicable national ambient air quality standard 
by the applicable date.'' 42 U.S.C. 7501(1). As discussed in the 
text of this proposed rulemaking, the EPA interprets the subpart 4 
RFP requirements, in light of the definition of RFP in section 
171(1), and its incorporation into section 189(c)(1), to no longer 
apply once the EPA makes a determination that the standard has been 
attained.
---------------------------------------------------------------------------

    Where the area has attained the standard and there are no further 
milestones, there is no further requirement to make a submission 
showing that such milestones have been met. This is consistent with the 
position that the EPA took with respect to the general RFP requirement 
of section 172(c)(2) in the General Preamble and in the May 10, 1995 
Seitz memorandum \281\ with respect to the requirements of sections 
182(b) and (c). In the Seitz memorandum, the EPA also noted that 
section 182(g), the milestone requirement of subpart 2, which is 
analogous to provisions in section 189(c), is suspended upon a 
determination that an area has attained. The memorandum, citing 
additional provisions related to attainment

[[Page 15444]]

demonstration and RFP requirements, stated:
---------------------------------------------------------------------------

    \281\ Memorandum from John S. Seitz, titled ``Reasonable Further 
Progress, Attainment Demonstration, and Related Requirements for 
Ozone Nonattainment Areas Meeting the Ozone National Ambient Air 
Quality Standard,'' (Seitz Memo). May 10, 1995.

    Inasmuch as each of these requirements is linked with the 
attainment demonstration or RFP requirements of section 182(b)(1) or 
182(c)(2), if an area is not subject to the requirement to submit 
the underlying attainment demonstration or RFP plan, it need not 
---------------------------------------------------------------------------
submit the related SIP submission either. (Seitz memo, page 4).

    c. Contingency measures. Other SIP submission requirements are 
linked with these attainment demonstration and RFP requirements, and 
similar reasoning applies to them. These requirements include the 
contingency measure requirements of sections 172(c)(9). The EPA has 
interpreted the obligation to submit contingency measure requirements 
of sections 172(c)(9) as suspended when an area has attained the 
standard because those ``contingency measures are directed at ensuring 
RFP and attainment by the applicable date.'' 57 FR at 13564; see also 
Seitz memo at pgs. 5-6.
    Section 172(c)(9) provides that: ``SIPs in nonattainment areas 
shall provide for the implementation of specific measures to be 
undertaken if the area fails to make reasonable further progress, or to 
attain the [NAAQS] by the attainment date applicable under this part. 
Such measures shall be included in the plan revision as contingency 
measures to take effect in any such case without further action by the 
state or the EPA.''
    The contingency measure requirement is inextricably tied to the RFP 
and attainment demonstration requirements. Contingency measures are 
implemented if RFP targets are not achieved, or if attainment is not 
realized by the attainment date. Where an area has already achieved 
attainment and continues to do so it has no need to rely on contingency 
measures to come into attainment or to make further progress to 
attainment. As the EPA stated in the General Preamble: ``The section 
172(c)(9) requirements for contingency measures are directed at 
ensuring RFP and attainment by the applicable date.'' See 57 FR 13564.
    d. Attainment demonstrations. With respect to the attainment 
demonstration requirements of section 172(c) and section 189(a)(1)(B), 
the EPA proposes to find that, as with the RFP requirements, if an area 
is already monitoring attainment of the standard, there is no need for 
an area to make a further submission containing additional measures to 
achieve attainment. The plain language of section 189(a)(1)(B) requires 
that the attainment plan provide for ``a demonstration (including air 
quality modeling) that the [SIP] will provide for attainment by the 
applicable attainment date . . . .'' Where the area has attained the 
standard, such a demonstration no longer serves a purpose. This 
interpretation is consistent with the interpretation of the section 
172(c) requirements provided by the EPA in the General Preamble, the 
Page memo, and the section 182(b) and (c) requirements set forth in the 
Seitz memo.\282\ As the EPA stated in the General Preamble, no other 
measures to provide for attainment would be needed by areas seeking 
redesignation to attainment since ``attainment will have been reached'' 
(57 FR at 13564). See also Latino Issues Forum, v. EPA, Nos. 06-75831 
and 08-71238 (9th Cir.), Memorandum Opinion, March 2, 2009.
---------------------------------------------------------------------------

    \282\ Memorandum from Stephen D. Page titled ``Clean Data Policy 
for the Fine Particle National Ambient Air Quality Standards'' are 
equally pertinent to all NAAQS. December 14, 2004.
---------------------------------------------------------------------------

    e. Control measure requirements for Serious areas. Under proposed 
Option 1 for BACM and BACT determinations, described in Section VI.D of 
this preamble, BACM and BACT for sources in the nonattainment area 
would be determined independent of the attainment needs of the area, 
and thus the requirement for BACM and BACT would not be considered an 
attainment planning requirement. Therefore, under such an approach, a 
determination of attainment (i.e., a clean data determination) would 
not suspend the obligation to submit any applicable outstanding BACM 
and BACT requirements. Under proposed Option 2 for BACM and BACT 
determinations, BACM and BACT would be identified based on the specific 
attainment needs of the area, thus tying the BACM and BACT requirement 
directly to attainment planning for the area. Consistent with this 
second proposed approach for determining BACM and BACT, issuance of a 
CDD would therefore also suspend BACM and BACT requirements.
    In addition, for a Serious area that failed to attain the relevant 
PM2.5 NAAQS by the applicable attainment date and that is 
therefore subject to the annual 5 percent emissions reduction 
requirement under section 189(d), but is nevertheless now attaining the 
relevant NAAQS, the EPA believes that the Clean Data Policy may apply 
to the obligations of the state to make an attainment plan submission 
to meet the requirements of section 189(d). Once such an area is 
attaining the relevant NAAQS, a clean data determination would suspend 
the section 189(d) submission requirement.
3. Planning Requirements Not Suspended With a CDD
    For Moderate nonattainment areas, the planning elements that are 
not suspended with a clean data determination are: Emissions 
inventories, nonattainment new source review including 189(e) control 
requirements for major stationary source precursors, and conformity. 
For Serious nonattainment areas, the planning elements not suspended 
with a clean data determination are: Emissions inventories, 
nonattainment NSR including section 189(e) control requirements for 
major stationary sources of PM2.5 precursors, the Most 
Stringent Measures (MSM) requirements (if the area has elected to seek 
an extension of the attainment date under section 188(e)), and 
conformity. In addition, for a Serious PM2.5 nonattainment 
area, if the EPA finalizes proposed Option 1 for BACM and BACT 
determinations, in which BACM and BACT would be determined independent 
of the attainment needs for the area, then the requirement for 
implementation of BACM and BACT would not be considered an attainment 
planning requirement and would thus not be suspended with a clean data 
determination for the area.
4. Violations of the NAAQS After a CDD
    The suspension of the state's obligations to submit attainment plan 
elements such as provisions for RACM and RACT, RFP and quantitative 
milestones, contingency measures, an attainment demonstration and other 
related attainment planning requirements exists only for as long as the 
area continues to monitor attainment of the relevant NAAQS prior to 
redesignation. If the EPA determines, after notice-and-comment 
rulemaking but prior to redesignation, that the area has monitored a 
violation of the relevant NAAQS, the basis for the suspension of the 
requirements no longer exists. In that case, the area would again be 
subject to the requirement to submit the pertinent attainment plan 
elements or SIP revisions and would need to address those requirements. 
Thus, a final determination that the area need not currently submit one 
of the required attainment plan elements amounts to no more than a 
suspension of the obligation to make the submission for so long as the 
area continues to attain the standard. Only if and when the EPA 
redesignates the area to attainment under section 107(d)(3) would the 
area be permanently relieved of these attainment plan submission 
obligations.

[[Page 15445]]

    Upon the EPA's determination that an area is currently attaining 
the applicable PM2.5 standard, the EPA proposes that the 
obligations to submit attainment planning provisions to meet the 
requirements for an attainment plan for the PM2.5 NAAQS, 
including RFP plans, RACM and RACT, quantitative milestones, 
contingency measures and an attainment demonstration are suspended for 
as long as the area continues to monitor attainment of the applicable 
PM2.5 standards. If in the future, prior to redesignation of 
the nonattainment area to attainment, the EPA determines after notice-
and-comment rulemaking that the area again violates the applicable 
PM2.5 standard, then the basis for suspending the obligation 
of the state to make one or more of these submissions would no longer 
exist and these attainment plan elements would again be due. Since all 
attainment planning requirements had been suspended for this area and 
the area attained by its attainment date, the CAA attainment plan 
contingency measures would not apply at the time of the NAAQS 
violation. In addition, because the area did not have a maintenance 
plan, the CAA section 175A maintenance plan contingency measures would 
also not apply. When an area violates after a CDD, and the statutory 
submission date has passed, CAA section 110(k)(5) applies, requiring 
that if the EPA finds that the applicable implementation plan is 
substantially inadequate to attain or maintain the NAAQS, the 
Administrator shall establish a reasonable deadline (not to exceed 18 
months) for a state to submit a SIP plan revision.

D. Section 179B/International Border Areas

    The EPA recognizes that some states are affected not only by local 
and regional sources of PM2.5 and PM2.5 
precursors, but also international sources that can contribute to an 
area's PM2.5 NAAQS nonattainment status. As discussed in 
Section II of this preamble, direct PM2.5 and more 
importantly PM2.5 precursors can be transported long 
distances and can be found in the air thousands of miles from where the 
emissions occurred and the particles were formed. Nitrates and sulfates 
formed from NOX and SO2 emissions are generally 
transported over wide areas leading to substantial background 
contributions to NAAQS violations in urban areas. Organic carbon, which 
has both a primary and secondary component, can also be transported, 
but to a far lesser degree. In general, higher concentrations of 
elemental carbon and crustal matter are found closer to the sources of 
these emissions.
    Section 179B of the CAA, entitled ``International Border Areas,'' 
applies to areas that could attain the relevant NAAQS by the statutory 
attainment date ``but for'' emissions emanating from outside the U.S. 
Specifically, section 179B(a) provides that the EPA shall approve an 
attainment plan for such an area if: (i) the attainment plan meets all 
other applicable requirements of the CAA, and (ii) the submitting state 
can satisfactorily demonstrate that ``but for emissions emanating from 
outside of the United States,'' the area would attain and maintain the 
relevant NAAQS. In addition, section 179B(d) applies specifically to 
PM10 NAAQS (which would include the PM2.5 NAAQS) 
and provides that if a state demonstrates that an area would have 
timely attained the NAAQS but for emissions emanating from outside the 
U.S., then the area is not subject to the mandatory reclassification 
element of section 188(b)(2) for Moderate areas that fails to attain 
the PM10 NAAQS by the applicable attainment date.
    Under section 179B, areas affected by emissions from outside the 
U.S. continue to have attainment plan obligations. First, even if the 
area is impacted by emissions from outside the U.S., that fact does not 
affect the designation of the area. An area that is violating the 
relevant NAAQS, even if emissions from outside the U.S. contribute to 
that violation, will be designated nonattainment. Section 179B does not 
affect designation. Second, as a result of that designation, the state 
is required to meet the applicable attainment plan requirements for the 
relevant NAAQS. Section 179B does not negate the attainment plan 
requirements, it only eliminates the obligation for an attainment 
demonstration that demonstrates attainment and maintenance of the 
NAAQS, and elimination of that obligation is conditioned upon the state 
meeting all other attainment plan requirements.
    Under section 179B, states remain obligated to meet the attainment 
plan requirements other than the requirement to demonstrate timely 
attainment. The applicable requirements for an attainment plan for 
PM2.5 include those requirements that apply to a Moderate 
area attainment plan, including an emissions inventory, RACM and RACT 
measures, RFP and quantitative milestones, and contingency measures. 
The Addendum includes a discussion of the applicable attainment plan 
requirements in the context of developing a SIP subject to section 
179B. In it, the EPA clarified that ``RACM/RACT must be implemented to 
the extent necessary to demonstrate attainment by the applicable 
attainment date if emissions emanating from outside the U.S. were not 
included in the analysis.'' \283\ The EPA further encouraged states 
``to reduce emissions beyond the minimum necessary to satisfy the `but 
for' test in order to reduce the PM concentrations to which their 
populations are exposed''.\284\ However, the EPA acknowledged that ``if 
. . . States . . . were also required, because of contributions to 
PM10 violations caused by foreign emissions, to shoulder 
more of a regulatory and economic burden than States not similarly 
affected . . . such a requirement would unfairly penalize States 
containing international border areas and effectively undermine the 
purpose of section 179B. Indeed, to the extent an affected State can 
satisfactorily demonstrate that implementation of such measures clearly 
would not advance the attainment date, EPA and the state could conclude 
they are unreasonable and hence do not constitute RACM.'' \285\
---------------------------------------------------------------------------

    \283\ Addendum to the General Preamble, 59 FR 41998 (August 16, 
1994), at page 42001.
    \284\ Ibid.
    \285\ Ibid.
---------------------------------------------------------------------------

    The EPA has considered this past interpretation of RACM and RACT 
requirements in the context of section 179B attainment plans for 
PM2.5 NAAQS and no longer views it as appropriate or 
consistent with the agency's guidance that encourages states ``to 
reduce emissions beyond the minimum necessary to satisfy the `but for' 
test in order to reduce the PM10 concentrations to which 
their populations are exposed.'' \286\ That is, given that the primary 
purpose of an attainment plan is to achieve emission reductions so that 
people living in a nonattainment area receive the public health 
protection intended by the NAAQS, adopting an interpretation that would 
allow those people to continue to be subjected to levels of 
PM2.5 above the NAAQS that the state could reasonably 
reduce--in this case not to attainment level, but to a level below the 
current level--would be antithetical to the objectives of the CAA. In 
addition, as with all other Moderate PM2.5 nonattainment 
areas, the EPA interprets the provisions of section 172(c)(6) to 
require that such areas must implement all additional reasonable 
measures that it can implement through the sixth calendar year 
following designation of the area, in addition to those measures 
meeting

[[Page 15446]]

the definition of RACM and RACT, in order to make progress toward 
attainment after the end of the fourth year following designation.
---------------------------------------------------------------------------

    \286\ Ibid.
---------------------------------------------------------------------------

    Therefore, the EPA is proposing and seeking comment on two proposed 
approaches that would give greater clarity to the agency's existing 
interpretation of control strategy requirements for Moderate area 
attainment plans to be approved under section 179B. The first proposed 
interpretation would clarify that the control strategy for an area that 
could attain by the Moderate area attainment date, ``but for'' foreign 
emissions of direct PM2.5 or its precursors, must include 
all control measures identified by the state to be technologically and 
economically feasible and implementable on sources in the area by the 
end of the sixth calendar year following designation of the area, thus 
satisfying requirements for RACM and RACT and additional reasonable 
measures, with a possible exception for any such measures that 
collectively would not be effective in reducing ambient 
PM2.5 levels in the area. This interpretation would closely 
align the EPA's interpretation of what constitutes a reasonable control 
strategy for a Moderate area attainment plan submitted pursuant to 
section 179B with the EPA's proposed interpretation of what constitutes 
a reasonable control strategy for a Moderate area attainment plan 
submitted pursuant to section 189(a)(1) for an area that cannot 
practicably attain by the statutory Moderate area attainment date.
    More specifically, under the first proposed approach for 
identifying appropriate control measures on sources in a Moderate 
PM2.5 nonattainment area that could attain the NAAQS ``but 
for'' foreign emissions, the EPA is proposing that the state would be 
required to implement all technologically and economically feasible 
measures that can be implemented on sources in the area by the end of 
the sixth calendar year following designation of the area in order to 
ensure that the area makes reasonable progress toward attaining the 
standard even if such measures are not expected to yield attainment by 
the statutory Moderate area attainment date. However, because the EPA 
recognizes that it may not be reasonable to require that a state 
implement those technologically and economically feasible control 
measures that collectively will not effectively reduce ambient 
PM2.5 concentrations, the agency is proposing to allow the 
state not to implement such measures if it can demonstrate that 
collectively they will not be effective in reducing PM2.5 
levels in the area. The EPA seeks comment on this proposed approach for 
Moderate PM2.5 nonattainment areas potentially subject to an 
attainment demonstration waiver under section 179B, and seeks comment 
on an alternative proposed approach that would not allow such an 
exception based on the collective effectiveness of otherwise 
``reasonable'' measures. This alternative proposed option parallels a 
similar option described in Section IV.D in this preamble for Moderate 
PM2.5 nonattainment areas that cannot practicably attain the 
NAAQS by the latest statutory attainment date for the area.
    The EPA also seeks comment on a distinct, second proposed approach 
for interpreting what would constitute an acceptable control strategy 
for sources in an area for which a state is seeking an attainment plan 
approval under section 179B. Under this second option, a state would 
need to demonstrate that its selected control measures for a Moderate 
nonattainment area would achieve reductions in PM2.5 levels 
that exceeded the applicable NAAQS in proportion to their contribution 
to overall PM2.5 levels. For example, if monitors in a 
Moderate nonattainment area reveal that the area is exceeding the 2012 
PM2.5 NAAQS of 12 [mu]g/m\3\ by 2 [mu]g/m\3\, for a total of 
14 [mu]g/m\3\, and the state concludes that foreign sources are 
contributing 3 [mu]g/m\3\, then the state would be responsible for the 
remaining 11 [mu]g/m\3\ and would need to implement enough reasonable 
control measures to achieve reductions in monitored ambient 
PM2.5 concentrations equal to (11/14)*2 [mu]g/m\3\ or 1.6 
[mu]g/m\3\. The EPA recognizes that this approach could require a high 
level of precision to be able to quantify accurately contributions from 
sources inside and outside the nonattainment area as well as projected 
emission reductions to be achieved with the implementation of each 
potential control measure for sources inside the area. However, the 
agency believes that such precision may be justified to support any 
``but for'' demonstration submitted to the EPA and to support any 
claims that a state should only be required to implement a subset of 
otherwise ``reasonable'' control measures on sources of direct 
PM2.5 emissions or emissions of PM2.5 precursors 
located in the nonattainment area.
    The EPA seeks comment on these two approaches to clarify what 
constitutes a reasonable control strategy in the context of a SIP 
submitted pursuant to section 179B. The EPA is also proposing 
regulations for the PM2.5 NAAQS consistent with the existing 
guidance with respect to requirements for RFP and quantitative 
milestones and contingency measures for areas seeking Moderate area 
attainment plan approval under section 179B. The General Preamble 
states that:

    In international border areas, EPA will not require the 
contingency measures for PM10 to be implemented after the 
area fails to attain if EPA determines that the area would have 
attained the NAAQS, but for emissions emanating from outside the 
U.S. However, the EPA will require contingency measures to be 
implemented if it determines that the area failed to make RFP in 
achieving the required reductions in PM10 emissions from 
sources within the U.S., or if the area does not, in fact, obtain 
the emission reductions that were necessary to demonstrate timely 
attainment of the NAAQS, but for emissions emanating from outside 
the U.S.\287\
---------------------------------------------------------------------------

    \287\ Ibid.

    The EPA is proposing that this interpretation of section 179B(a)(1) 
with respect to contingency measures and RFP requirements should apply 
to Moderate nonattainment areas for the PM2.5 NAAQS. 
Specifically, the EPA proposes that as part of any Moderate area 
attainment plan submitted under section 179B, a state must include an 
RFP plan developed consistent with proposed Option 2 for RFP analyses 
for Moderate nonattainment areas that cannot practicably attain the 
relevant NAAQS by the statutory attainment date, described in Section 
IV.F of this preamble. Furthermore, the state must include as part of 
any attainment plan submission made for such an area contingency 
measures that can be implemented without significant effort in the 
event the EPA finds that such area failed to meet RFP requirements. The 
contingency measures should achieve approximately 1 year's worth of 
emissions reductions as calculated by the state for purposes of the RFP 
analysis. In addition, the EPA proposes that the state must identify 
quantitative milestones for the area to be achieved 4.5 years and 7.5 
years from the date of designation of the area. The EPA proposes to 
apply the same proposed requirements for establishing and reporting on 
quantitative milestones for Moderate nonattainment areas seeking 
attainment date waivers under section 179B as for all other Moderate 
nonattainment areas, described fully in Section IV.G of this preamble. 
The agency seeks comment on these proposed requirements for Moderate 
area plans submitted pursuant to section 179B.
    The EPA has historically evaluated section 179B ``but for'' 
demonstrations on a case-by-case basis, based on the

[[Page 15447]]

individual circumstances and data provided by the submitting state. 
These demonstrations have included information such as ambient air 
quality monitoring data, modeling scenarios, emissions inventory data 
and meteorological or satellite data.\288\ The Moderate area attainment 
demonstration modeling and other elements of the attainment 
demonstration must show timely attainment of the NAAQS but for the 
emissions from outside of the U.S. Section 179B does not, however, 
provide authority to exclude monitoring data influenced by 
international transport from regulatory determinations related to 
attainment and nonattainment. Thus, even if the EPA approves a section 
179B ``but for'' demonstration for an area, the area would continue to 
be designated as nonattainment and subject to the applicable 
requirements, including nonattainment new source review, conformity and 
other measures prescribed for nonattainment areas by the CAA. Section 
179B requires states to continue to meet attainment plan requirements, 
notwithstanding the contribution of emissions from sources outside the 
U.S., in order to provide the public health protection intended by the 
NAAQS. However, if the EPA approves a ``but for'' demonstration for a 
Moderate nonattainment area, the area would not be subject to 
reclassification for failure to attain by the applicable attainment 
date as explained earlier.
---------------------------------------------------------------------------

    \288\ Ibid. The Addendum includes further examples of 
information a state may present for the EPA to consider as part of 
the ``but for'' demonstration, including additional monitors in 
international border areas, more detailed emissions inventories, and 
speciation data that identifies PM2.5 components from 
foreign sources.
---------------------------------------------------------------------------

    Although monitor data cannot be excluded for a determination of 
whether an area has attained based solely on the fact the data are 
affected by emissions from outside the U.S., such data may be excluded 
from consideration if they were significantly influenced by exceptional 
events under section 319(b)(3) of the CAA. Where international 
transport of emissions contributes to an exceedance or violation and 
comes from natural sources such as wildfires, and otherwise meets the 
criteria contained in the EPA's Exceptional Events Rule, it can be 
addressed by that rule.\289\ Specifically, if the EPA concurs with an 
air agency's request to exclude affected data, the event-influenced 
data are officially noted and removed from the data set used to 
calculate official design values. Because of previously expressed 
stakeholder feedback regarding implementation of the Exceptional Events 
Rule and specific stakeholder concerns regarding the analyses that can 
be used to support wildfire-related exceptional event demonstrations, 
the EPA intends to propose revisions to the Exceptional Events Rule in 
a future notice-and-comment rulemaking and will solicit public comment 
at that time. The EPA has approved PM2.5 wildfire influenced 
exceptional events demonstrations in the past, which are posted on the 
agency's Exceptional Events Rule Web site.\290\
---------------------------------------------------------------------------

    \289\ See 40 CFR 50.14.
    \290\ The EPA's Exceptional Events Rule Web site is located at: 
http://www.epa.gov/ttn/analysis/exevents.htm.
---------------------------------------------------------------------------

    Depending on the nature and scope of international emissions events 
affecting air quality in the U.S., the EPA may be able to assist states 
in developing approvable exceptional events demonstrations. More 
generally, the EPA believes that the best approach for evaluating the 
potential impacts of international transport on nonattainment is for 
states to work with the EPA on a case-by-case basis to determine the 
most appropriate information and analytical methods for each area's 
unique situation. The EPA will work with states that are developing 
attainment plans for which section 179B is relevant, and ensure the 
states have the benefit of the EPA's understanding of international 
transport of PM2.5 and PM2.5 precursors.

E. Enforcement and Compliance

    Section 172(c)(6) in subpart 1 of the CAA requires nonattainment 
SIPs to ``include enforceable emission limitations, and such other 
control measures, means or techniques . . . as well as schedules and 
timetables for compliance, as may be necessary or appropriate to 
provide for attainment.'' In the remanded 2007 PM2.5 
Implementation Rule, the EPA described the general elements that 
characterize an enforceable SIP regulation, recognizing that 
enforceable SIP regulations may address the elements in different ways 
depending on the type of source category being regulated. The agency 
continues to believe and hereby proposes that in general, in order for 
a SIP regulation to be enforceable, it must clearly spell out which 
sources or source types are subject to its requirements and what its 
requirements (e.g., emission limits or work practices) are. An 
enforceable regulation would also specify the timeframes within which 
these requirements must be met, and definitively state the 
recordkeeping and monitoring requirements appropriate to the type of 
sources being regulated. The recordkeeping and monitoring requirements 
would have to be sufficient to enable the state or the EPA to determine 
whether the source is complying with the emission limit on a continuous 
basis. An enforceable regulation would also contain test procedures in 
order to determine whether sources are in compliance.
    The EPA continues to believe that complete and effective 
regulations that ensure compliance with an applicable emissions limit 
would have to include requirements for both performance testing of 
emissions and ongoing monitoring of the compliance performance of 
control measures, and the agency proposes to require that SIP 
regulations that establish emission limits include the following:
    (a) Indicator(s) of compliance--the pollutant or pollutants of 
interest (e.g., filterable and condensable PM2.5) and the 
applicable units of measurement for expressing compliance (e.g., ng/J 
of heat input, lb/hr);
    (b) Test method--reference to a specific EPA or other published set 
of sample collection and analytical procedures, equipment design and 
performance criteria, and the calculations providing data in units of 
the indicator of compliance (Section IX.K of this preamble presents a 
discussion of specific test methods for condensable PM2.5 
emissions);
    (c) Averaging time--the minimum length of each required test run 
and the requirement to average the results of the test runs (e.g., 
three runs) representing a specified period of time (e.g., 8 hours); 
and,
    (d) Frequency--the maximum time between emissions or performance 
tests (e.g., within 30 days of facility start-up and once each 
successive quarter, every 6-month period, or yearly).
    In order to be complete with regard to compliance monitoring 
provisions, the EPA proposes that regulations adopted into the SIP must 
include the following critical elements:
    (a) Indicator(s) of performance--the parameter or parameters 
measured or observed for demonstrating proper operation of the 
pollution control measure or compliance with the applicable emissions 
limitation or standard. Indicators of performance could include direct 
or predicted emissions measurements, process or control device (and 
capture system) operational parametric values that correspond to 
compliance with efficiency or emissions limits, and recorded findings 
of verification of work practice activities, raw material or fuel 
pollutant content, or design

[[Page 15448]]

characteristics. Indicators could be expressed as a single maximum or 
minimum value, a function of process variables (e.g., within a range of 
pressure drops), a particular operational or work practice status 
(e.g., a damper position, completion of a waste recovery task), raw 
material or fuel pollutant content, or an interdependency between two 
or more variables;
    (b) Measurement technique--the means used to gather and record 
information of or about the indicators of performance. The components 
of the measurement technique include the detector type or analytical 
method, location and installation specifications, inspection 
procedures, and quality assurance and quality control measures. 
Examples of measurement approaches include continuous emissions 
monitoring systems (CEMS), continuous opacity monitoring systems 
(COMS), continuous parametric monitoring systems (CPMS), performance 
testing, vendor or laboratory analytical data, and manual inspections 
and data collection that include making records of process conditions, 
raw materials or fuel specifications, or work practices. Directly 
enforceable emission measurements, such as PM CEMs, are preferred 
wherever feasible. Where COMS are feasible, it should be clear that 
opacity is a directly enforceable standard, not merely an indicator of 
compliance;
    (c) Averaging time--the period over which to average data to verify 
compliance with the emissions limitation or standard or proper 
operation of the pollution control measure. Examples of averaging time 
include a 3-hour average in units of the emissions limitation, a 30-day 
rolling average emissions value, a daily average of a control device 
operational parametric range, periodic (e.g., monthly, annual) average 
of raw materials or fuel pollutant content, and an instantaneous alarm;
    (d) Monitoring frequency--the number of monitoring data values 
recorded over a specified time interval. Examples of monitoring 
frequencies include at least one data value every 15 minutes for CEMS 
or CPMS, at least every 10 seconds for COMS, upon receipt or 
application of raw materials or fuel to the process, or at least once 
per operating day (or week, month, etc.) for performance testing, work 
practice verification, or equipment design inspections; and,
    (e) Reporting and record retention requirements--criteria for 
retaining monitoring and test data in an electronic form and periodic 
electronic reporting of information as needed to the compliance office. 
Electronic record retention and submission have been widely adopted, 
and the EPA believes that such readily accessible documentation could 
be used by state, federal and other analysts to spot trends and non-
compliance more easily than if these entities conducted reviews of 
paper documents. The EPA also recommends that compliance reports be 
made available online so that the general public can readily access the 
information without the need to submit Freedom of Information Act 
(FOIA) requests to the EPA. The EPA is in the process of revising 
federal rules to make similar requirements apply.
    The EPA continues to believe that approval of regulations adopted 
into SIPs would have to ensure that these critical elements are present 
and clearly defined to be approvable. In particular, the compliance 
obligations, including emissions limits and other applicable 
requirements, would need to be representative of and accountable to the 
assumptions used in a state's attainment demonstration. This 
accountability would include the ability to transfer the applicable 
regulatory requirements to a title V operating permit subject to the 
EPA and public review.\291\
---------------------------------------------------------------------------

    \291\ Under the title V regulations, sources have an obligation 
to include in their title V permit applications, among other 
components, all emissions of pollutants for which the source is 
major, and all emissions of regulated air pollutants. See, e.g., 40 
CFR 70.5(c)(3). The definition of regulated air pollutant in 40 CFR 
70.2 includes any pollutant for which a NAAQS has been promulgated, 
including PM2.5.
---------------------------------------------------------------------------

    The EPA seeks comment on the elements proposed to be required to 
ensure that regulations adopted into a SIP are enforceable.

F. Efforts To Encourage a Multi-Pollutant Approach When Developing 
PM2.5 Attainment Plans

1. General Guidance
    From a planning and resource perspective, the EPA believes that it 
can be efficient for states to develop integrated control strategies 
that address multiple pollutants rather than separate strategies for 
each pollutant or NAAQS individually. An integrated air quality control 
strategy that reduces multiple pollutants can help ensure that 
reductions are efficiently achieved and produce the greatest overall 
air quality benefits. For example, it is widely known that certain 
control measures that reduce emissions of NOX and VOC, and 
thus reduce ambient PM2.5 levels, can also result in reduced 
ambient concentrations of ground-level ozone.\292\ Many VOC are also 
hazardous air pollutants (HAP), so a control strategy for a 
PM2.5 nonattainment area that reduces VOC emissions may 
provide the additional benefit of reducing air toxics. It is also 
widely known that many sources of PM2.5 also emit toxic 
metals as particulates, so controlling directly emitted 
PM2.5 emissions from these sources would also reduce the 
emissions of toxic metals. In addition, due to expected changes in 
meteorology resulting from climate change, the EPA encourages states to 
assess climate change and air pollution together and account for the 
potential effects of climate change in their multi-pollutant planning 
efforts.
---------------------------------------------------------------------------

    \292\ For a list of potential control measures for 
PM2.5 and PM2.5 precursors, see http://www.epa.gov/air/pdfs/MenuOfControlMeasures.pdf.
---------------------------------------------------------------------------

    In June 2007, the EPA's CAA Advisory Committee (CAAAC) recommended 
that the agency allow states to integrate SIP requirements and other 
air quality goals into a comprehensive plan.\293\ The recommended plan 
would demonstrate attainment/maintenance of multiple NAAQS, accomplish 
sector-based reductions, realize risk reductions of HAPs and make 
improvements in visibility. It could also be structured to integrate 
programs addressing land use, transportation, energy and climate.
---------------------------------------------------------------------------

    \293\ Recommendations to the Clean Air Act Advisory Committee: 
Phase II, June 2007, http://www2.epa.gov/caaac/caaac-reports.
---------------------------------------------------------------------------

    The EPA has encouraged states to take a multi-pollutant approach to 
managing air quality.\294\ Specifically, the agency has encouraged 
states to involve all stakeholders when planning to meet air quality 
standards and to provide a basic outline for how local jurisdiction(s) 
could address air pollutants in an integrated manner.
---------------------------------------------------------------------------

    \294\ Memorandum from Stephen D. Page to Regional Air Division 
Directors, ``Consideration of Multiple Pollutants in Control 
Strategy Development.'' August 10, 2005.
---------------------------------------------------------------------------

    While the agency encourages states to develop multi-pollutant 
plans, it recognizes that the requirement for the agency to review and, 
as necessary, revise NAAQS every 5 years, which can trigger new 
statutory attainment plan submission and attainment dates, as well as 
the ever-evolving understanding of pollutants and many control programs 
that may be available to reduce emissions, can sometimes make such 
efforts challenging. For example, under the current law, the 2007 
submission date for Regional Haze SIPs has already passed while RACT 
SIPs for nonattainment areas classified as Moderate or higher for the 
2008 ozone NAAQS were due more than 2 years before the due date for 
Moderate area

[[Page 15449]]

attainment plans for areas designated nonattainment for the 2012 annual 
PM2.5 NAAQS. Although it is not feasible to integrate fully 
these planning requirements, states could potentially use common 
databases and modeling tools for all three SIP submissions for these 
different requirements and rely on similar control measures as 
appropriate. Furthermore, as states develop plans to meet any current 
or future PM2.5 NAAQS, they may wish to modify existing 
plans for implementing the ozone NAAQS or other NAAQS, or for regional 
haze, as they consider strategies more comprehensively. However, it is 
important to note that states and the EPA must continue to meet all the 
CAA mandated planning and program elements for individual NAAQS. The 
EPA seeks comment on alternative approaches to integrate the planning 
requirements for multiple NAAQS and other CAA programs that are 
promulgated at different times.
2. What is the EPA doing beyond encouraging states to integrate their 
air quality planning activities to the extent feasible?
    Ideally, an air quality management plan (AQMP) is a set of 
pollution reduction strategies/planning activities for an area 
demonstrating: attainment/maintenance of one or more NAAQS; risk 
reductions from HAPs; improvements in visibility and ecosystem health; 
and, integration of land use, transportation, energy and climate 
activities in the area. Three areas in the country--North Carolina, New 
York and the City of St. Louis (involving both Missouri and Illinois)--
participated in an EPA-led pilot effort to develop multi-pollutant 
AQMPs. The pilot projects provided lessons regarding AQMP development 
that should prove useful to other areas interested in better 
integrating their air quality planning. The areas' initial AQMPs and 
other materials are available on the EPA's Web site.\295\
---------------------------------------------------------------------------

    \295\ See http://www.epa.gov/air/aqmp/.
---------------------------------------------------------------------------

    Implementation of the 2012 PM2.5 NAAQS provides an 
opportunity for states to consider how to use a multi-pollutant 
approach from the beginning of their planning process. The EPA 
recommends that states and tribes wishing to take a comprehensive 
approach consider the following activities:
     Develop models for the attainment demonstration that 
include previously implemented or planned measures to reduce 
PM2.5 precursors and secondary fine particles, ozone 
precursors, pollutants that contribute to regional haze and, where 
appropriate, air toxics and any potential negative impacts on 
ecosystems;
     Conduct an integrated assessment of the impact that 
controls have on ambient levels of PM2.5, ozone, regional 
haze, and, where applicable, air toxics, greenhouse gases, ecosystem 
protection and environmental justice to identify those controls with 
the greatest potential co-benefits; and,
     Use common data bases and analytical tools, where 
possible.
    The EPA is requesting comment on what incentives or assistance the 
agency might be able to provide to encourage states to integrate their 
planning activities.
3. Multi-Pollutant Assessments/One-Atmosphere Modeling
    A multi-pollutant assessment, or one-atmosphere modeling, is 
conducted with a single air quality model that is capable of simulating 
transport and formation of multiple pollutants simultaneously.\296\ For 
example, this type of model can simulate formation and deposition 
involving pollutants associated with PM2.5, ozone and 
regional haze, and it can include algorithms simulating gas phase 
chemistry, aqueous phase chemistry, aerosol formation and acid 
deposition. This type of model could also include the formation and 
deposition of key air toxics and the chemical interactions that occur 
with these individual toxic species to produce PM2.5 and 
ozone.
---------------------------------------------------------------------------

    \296\ Depending on the context, ``multi-pollutant'' can be 
defined in different ways. In this context the agency is defining 
multi-pollutant modeling as simultaneous modeling of 
PM2.5, ozone, key air toxics, and regional haze. Future 
multi-pollutant models may include the ability to model a broader 
array of air toxics as well as greenhouse gases.
---------------------------------------------------------------------------

    Multi-pollutant assessments are recommended for PM2.5 
attainment demonstrations because the formation and transport of VOC 
and NOX are closely related to the formation of both ozone 
and regional haze. There is often a positive correlation between 
measured secondary particulate matter and ozone. Many of the same 
factors affecting PM2.5 concentrations also affect ozone 
concentrations because similarities exist in sources of precursors for 
both pollutants. For example, emissions of NOX may lead to 
formation of nitrates, which affect both ambient PM2.5 and 
ozone levels and impair visibility. Many VOC (such as toluene) are air 
toxics and may also be sources of precursors for both organic particles 
and ozone. In addition, the presence of ozone itself may be an 
important factor affecting secondary particle formation.
    Because of these relationships, models and data analysis intended 
to address PM2.5 could be beneficial for use in addressing 
ozone and visibility impairment. When performing a multi-pollutant 
assessment, the modeling should take into account previously 
implemented or planned measures to reduce PM2.5, ozone, and 
regional haze. States that undertake multi-pollutant assessments as 
part of their attainment demonstration should consider assessing the 
impact of their PM2.5 strategies on ozone and visibility 
impairment to ensure that optimal emission reduction strategies are 
developed for the three programs to the extent possible. This could 
facilitate addressing all of these pollutants in a more cost effective 
manner.
    States may also find it desirable to assess the impact of 
PM2.5, ozone, and/or regional haze control strategies on 
toxic air pollutants regulated under the CAA or under state air toxic 
initiatives. Given the relationships that exist between air toxics and 
the formation of PM2.5 and ozone, states may find that 
controls can be selected to meet goals for PM2.5 and/or 
ozone attainment as well as those of specific air toxic programs.

G. Measures To Ensure Appropriate Protections for Overburdened 
Populations

1. Review of PM NAAQS and At-Risk Populations
    As discussed in Section II of this preamble, when the EPA sets a 
primary NAAQS, the CAA directs the Administrator to establish a 
standard that is ``requisite'' to protect public health with ``an 
adequate margin of safety.'' \297\ In setting the NAAQS, the EPA 
considers available, relevant scientific information on the health 
effects that may occur in the general

[[Page 15450]]

population, as well as specific groups within the general population 
that are at increased risk for experiencing adverse pollutant-related 
health effects (i.e., at-risk populations).\298\ These groups could 
exhibit a greater risk of pollutant-related health effects than the 
general population for a number of reasons including being adversely 
affected at lower pollutant concentrations, experiencing a larger 
health impact at a given pollutant concentration, and/or being exposed 
to higher pollutant concentrations than the general population. Thus, 
the NAAQS review process inherently takes into consideration certain 
environmental justice factors as part of the standard-setting process. 
In setting a secondary standard, the CAA directs the Administrator to 
establish a standard that ``is requisite to protect the public welfare 
from any known or anticipated adverse effects.''
---------------------------------------------------------------------------

    \297\ The requirement that primary standards provide an adequate 
margin of safety was intended to address uncertainties associated 
with inconclusive scientific and technical information available at 
the time of standard setting. It was also intended to provide a 
reasonable degree of protection against hazards that research has 
not yet identified. Both kinds of uncertainties are components of 
the risk associated with pollution at concentrations below those at 
which human health effects can be said to occur with reasonable 
scientific certainty. Thus, in selecting primary standards that 
provide an adequate margin of safety, the EPA Administrator is 
seeking not only to prevent pollution levels that have been 
demonstrated to be harmful but also to prevent lower pollutant 
levels that may pose an unacceptable risk of harm, even if the risk 
is not precisely identified as to nature or degree. The CAA does not 
require the Administrator to establish a primary NAAQS at a zero-
risk level or at background concentration levels, but rather at a 
level that reduces risk sufficiently so as to protect public health 
with an adequate margin of safety.
    \298\ The legislative history of section 109 of the CAA 
indicates that a primary standard is to be set at the ``maximum 
permissible ambient air level . . . which will protect the health of 
any [sensitive] group of the population'' and that for this purpose 
``reference should be made to a representative sample of persons 
comprising the sensitive group rather than to a single person in 
such a group.''
---------------------------------------------------------------------------

    Section 109(d) of the CAA requires the EPA to periodically review 
(every 5 years) the science upon which the standards are based and the 
standards themselves. As discussed elsewhere in this proposal, in its 
2012 review of the PM NAAQS, the EPA revised the primary annual 
PM2.5 standard by lowering the level to 12.0 micrograms per 
cubic meter ([mu]g/m\3\) so as to provide increased protection against 
health effects associated with long- and short-term PM2.5 
exposures.\299\ The agency also revised the form of the primary annual 
PM2.5 standard to eliminate the spatial averaging provisions 
to avoid potential disproportionate impacts on at-risk populations. In 
conjunction with these revisions, the EPA retained the primary 24-hour 
PM2.5 standard, as revised in 2006 (71 FR 61144, October 17, 
2006), to provide supplemental protection against health effects 
associated with short-term PM2.5 exposures, especially in 
areas with high peak PM2.5 concentrations. This suite of 
primary annual PM2.5 standards provides increased public 
health protection, including the health of at-risk populations which 
include children, older adults, persons with pre-existing health and 
lung disease, and persons of lower socioeconomic status, against a 
broad range of PM2.5-related effects that include premature 
mortality, increased hospital admissions and emergency department 
visits, and development of chronic respiratory disease.\300\
---------------------------------------------------------------------------

    \299\ 78 FR 3086 (January 15, 2013).
    \300\ In the final 2012 p.m. NAAQS rule, based on information 
presented in the Integrated Science Assessment for Particulate 
Matter (U.S. EPA, 2009, sections 2.2.1 and 8.1.7), the EPA made a 
finding that persons with lower socioeconomic status are at 
increased risk for experiencing adverse health effects related to PM 
exposures (78 FR 3085, January 15, 2013, at page 3104). Persons with 
lower socioeconomic status (SES) have been generally found to have a 
higher prevalence of pre-existing diseases, limited access to 
medical treatment, and increased nutritional deficiencies, which can 
increase this population's risk to PM-related effects (77 FR 38911, 
June 29, 2012).
---------------------------------------------------------------------------

    In addition, the Policy Assessment (U.S. EPA, 2011a, p. 2-60) 
observed that the highest concentrations of PM2.5 in an area 
tend to be measured at monitors located in areas where the surrounding 
populations are more likely to live below the poverty line and to have 
higher percentages of minorities. The EPA directed states to relocate a 
limited number of existing monitors to near-roadway sites in large 
urban areas. Both of these revisions were informed by scientific 
evidence that underscored the potentially disproportionate exposure to 
high PM2.5 concentrations and therefore disproportionate 
risk to low-income and minority populations.
2. Relationship Between Direct PM2.5 Emissions and 
PM2.5 Precursor Emissions Reductions and At-Risk Populations
    Sources of direct PM emissions have their greatest impact on 
PM2.5 concentrations and public health in the general 
vicinity of the source (e.g., within 10 miles), while sources of 
precursor emissions can contribute to PM2.5 concentrations 
more than 100 miles away and are considered to have a more regional 
impact. To date, state PM2.5 attainment plans have generally 
relied to a greater extent on reductions of precursor pollutants rather 
than on reductions of direct PM2.5 emissions. Studies show, 
however, that on a per ton basis, the reduction of a ton of direct 
PM2.5 emissions leads to greater health benefits than the 
reduction of a ton of SO2 or NOX.\301\
---------------------------------------------------------------------------

    \301\ See Fann, N., Fulcher, C., and B. Hubbell, 2009. The 
Influence of location, source, and emission type in estimates of the 
human health benefits of reducing a ton of air pollution. Air 
Quality, Atmosphere & Health. Volume 2, Number 3, 169-176, June 
2009. See also Fann et. al., 2011. Maximizing health benefits and 
minimizing inequality: incorporating local-scale data in the design 
and evaluation of air quality policies. Society for Risk Analysis, 
vol. 31, no. 6, p. 908-922, June 2011.
---------------------------------------------------------------------------

    The process for developing attainment plans for the current and 
future PM2.5 NAAQS presents a potential opportunity to 
target the health protections afforded by the NAAQS, as the EPA expects 
that attainment for the 2012 PM2.5 NAAQS and future 
PM2.5 NAAQS in nonattainment areas with the most severe 
pollution problems may need to give greater emphasis to reducing direct 
PM2.5 emissions in combination with efforts already underway 
to further reduce precursor emissions. Placing greater emphasis on 
reducing emissions from sources of direct PM2.5 (e.g., 
certain industrial facilities located in more densely populated areas; 
areas with high motor vehicle and other diesel engine emissions, such 
as rail yards and near major roadways; and, areas with high wood smoke 
emissions) could provide the added benefit of reducing exposure to 
PM2.5 in low-income and minority communities.
    With this in mind, the EPA is seeking comment on additional ways 
that air agencies can provide public health protection specifically for 
overburdened populations when preparing attainment plans for the 
PM2.5 NAAQS. The discussion that follows provides some 
examples of points in the attainment plan development process at which 
a state could assess opportunities for providing such additional 
protections, and examples of what those additional protections might 
look like.
3. Options for States To Consider To Ensure Appropriate Protections 
From PM2.5 Exposure for Overburdened Populations
    The EPA believes that states have sufficient flexibility and 
discretion under the CAA in implementing their attainment strategies to 
focus resources on controlling those sources of emissions that directly 
and adversely affect low-income and other at risk populations. By 
reducing impacts on at-risk populations, states can maximize health 
benefits, thereby creating greater net benefits for the state in a 
cost-effective manner.\302\ In addition, reducing adverse impacts to 
low-income and minority populations advances the environmental justice 
goal of fair treatment for these populations.
---------------------------------------------------------------------------

    \302\ Wesson, K., Fann, N., Morris, M, Fox, T., Hubbell, T., 
2010. A multipollutant, risk-based approach to air quality 
management. Case study for Detroit. Atmospheric Pollution Research, 
1, 296-304. The study compared air quality control strategies and 
concluded that the multi-pollutant, risk-based approach was able to 
produce approximately two times greater monetized benefits through 
avoided health impacts and was more cost effective than a pollutant-
by-pollutant approach.
---------------------------------------------------------------------------

    There are a number of actions that states could take to focus 
resources in this way. Some of these actions can help identify areas 
where additional ambient monitoring may be needed in low income and 
overburdened communities.

[[Page 15451]]

Such information can be used to support updates to the state's annual 
monitoring plan. Examples of actions to support updates to the annual 
monitoring plan include:
     Develop databases and online mapping tools that enable 
users (including state staff, public, and the regulated community) to 
understand where sources of direct PM2.5 emissions are 
located and where new or modified sources of emissions could have 
potential impacts on low income and other overburdened communities;
     Incorporate existing mapping tools which identify target 
areas in the attainment plan development process and related actions; 
and,
     Analyze emissions data, ambient data, and available 
modeling to identify potential unmonitored PM2.5 hotspots in 
areas with a high percentage of low income, minority or indigenous 
persons (see Section IV.E of this preamble for further discussion of 
this option).
    Once target areas for addressing these sensitive population needs 
within a nonattainment area have been identified, the state could 
consider taking any of the following actions which help target 
emissions reductions that may be needed to attain the PM2.5 
NAAQS:
     Prioritize the selection of control measures that target 
reductions of direct PM2.5, particularly from sources 
located in ``at-risk'' areas as part of the state's RACM and RACT 
analysis (for Moderate nonattainment areas) or BACM and BACT analysis 
(for Serious nonattainment areas), as well as other measures needed to 
demonstrate attainment (see Sections IV.D and VI.D, respectively, of 
this preamble for further discussion of this option);
     Improve the understanding of the potential impact of minor 
sources by improving or generating an emissions inventory for such 
minor sources, including sources that are not currently required to 
report emissions, to generate options on how emissions can be reduced 
in the target area;
     Design voluntary programs to reduce VMT and mobile source-
related PM2.5 emissions (e.g., diesel retrofits);
     Incorporate environmental justice criteria into the 
alternatives analysis to ensure appropriate siting and require 
cumulative impact studies for proposed projects;
     Eliminate exemptions from and/or raise thresholds for 
minor source permitting;
     Develop a list of potential supplemental environmental 
projects (SEPs) \303\ that could be applied in the target area; and,
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    \303\ For more information on SEPs, go to www2.epa.gov/enforcement/supplemental-environmental-projects-sep.
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     Prioritize targeted enforcement strategies.
    In addition to the above, states could increase opportunities for 
meaningful involvement of community groups in attainment plan 
development, annual monitoring network plan reviews, and permitting 
processes \304\ for at-risk and minority populations by taking the 
following steps:
---------------------------------------------------------------------------

    \304\ See 78 FR 27220 (May 9, 2013) notice of availability, 
``EPA Activities To Promote Environmental Justice in the Permit 
Application Process.''
---------------------------------------------------------------------------

     Develop advisory boards and/or develop enhanced notice-
and-comment requirements for low income and minority communities to 
assure meaningful involvement relative to projects that impact their 
communities;
     Provide special notice of important actions affecting 
target areas in appropriate languages and with attention to cultural 
barriers;
     Provide advance notification for low income and minority 
communities of upcoming opportunities for public comment on SIPs, 
ambient air monitoring plans, and other relevant actions;
     Maintain multi-lingual Web sites and offer translators for 
public meetings and hearings;
     Coordinate with the state's EJ coordinator to assist with 
outreach efforts; and,
     Provide states with appropriate federal EJ guidance tools.
    The EPA is seeking comment on these examples and whether and how 
the EPA might provide recommendations to states preparing attainment 
plans for the 2012 and any future PM2.5 NAAQS on additional 
ways to ensure equal protections for overburdened populations.

H. Tribal Issues

    The 1998 Tribal Air Rule (TAR) (40 CFR part 49), which implements 
section 301(d) of the CAA, gives tribes the option of developing TIPs. 
Specifically, the TAR provides for the tribes to be treated in the same 
manner as a state in implementing certain sections of the CAA. However, 
tribes are not required to develop implementation plans. The EPA 
determined in the TAR that it was inappropriate to treat tribes in a 
manner similar to a state with regard to specific plan submittal and 
implementation deadlines for NAAQS-related requirements, including, but 
not limited to, such deadlines in CAA sections 110(a)(1), 172(a)(2), 
182 187, and 191. See 40 CFR 49.4(a). In addition, the EPA determined 
it was not appropriate to treat tribes similarly to states with respect 
to provisions of the CAA requiring as a condition of program approval 
the demonstration of criminal enforcement authority or providing for 
the delegation of such criminal enforcement authority. See 40 CFR 
49.4(g). To the extent a tribe is precluded from asserting criminal 
enforcement authority, the federal government will exercise primary 
criminal enforcement responsibility. See 40 CFR 49.8. In such 
circumstances, tribes seeking approval for CAA programs provide 
potential investigative leads to an appropriate federal enforcement 
agency.
    If a tribe elects to do a TIP, the agency will work with the tribe 
to develop an appropriate schedule which meets the needs of the tribe, 
and which does not interfere with the attainment of the NAAQS in other 
jurisdictions. The tribe developing a TIP can work with the EPA 
Regional Office on the appropriateness of addressing RFP and other 
substantive SIP requirements that may or may not be appropriate for the 
tribe's situation.
    The CAA and the TAR provide tribes opportunities and flexibility 
for the tribe in the preparation of a TIP to address the NAAQS. If a 
tribe elects to develop a TIP, the TAR offers flexibility for the tribe 
to identify and implement on a case-by-case basis only those CAA 
programs or reasonably severable program elements needed to address 
their specific air quality problems. In the TAR, the EPA described this 
flexible implementation approach as a modular approach. Each tribe may 
evaluate the particular activities, including potential sources of air 
pollution within the exterior boundaries of its reservation (or within 
non-reservation areas for which it has demonstrated jurisdiction), 
which cause or contribute to its air pollution problem. A tribe may 
adopt measures for controlling those sources of PM2.5-
related emissions, as long as the elements of the TIP are reasonably 
severable from the package of elements that can be included in a whole 
TIP. A TIP must include regulations designed to solve specific air 
quality problems for which the tribe is seeking the EPA's approval, as 
well as a demonstration that the tribal air agency has the authority 
from the tribal government to develop and run their program, the 
capability to enforce their rules, and the resources to implement the 
program they adopt. In addition, the tribe must receive an eligibility 
determination from the EPA to be treated in the same manner as a state 
for the particular

[[Page 15452]]

matter at issue and to receive authorization from the EPA to run a CAA 
program.
    The EPA would review and approve, where appropriate, these partial 
TIPs as one step of an overall air quality plan to attain the NAAQS. A 
tribe may step in later to add other elements to the plan, or the EPA 
may step in to fill gaps in the air quality plan as necessary or 
appropriate. In approving a TIP, the agency would evaluate whether the 
plan appropriately coordinates with the overall air quality plan for an 
area when tribal lands are part of a multi-jurisdictional area.
    Because many PM2.5 nonattainment areas will include 
multiple jurisdictions, and in some cases both Indian country and state 
lands, it is particularly important for the tribes and the states to 
work together to coordinate their planning efforts. States need to 
incorporate Indian country emissions in their base emissions 
inventories if Indian country is part of an attainment or nonattainment 
area.\305\ Tribes and states should coordinate their planning 
activities as appropriate to ensure that neither is adversely affecting 
attainment of the NAAQS in the area as a whole. Coordinated planning in 
these areas will help ensure that the planning decisions made by the 
states and tribes complement each other and that the nonattainment area 
makes reasonable progress toward attainment and ultimately attains the 
applicable PM2.5 NAAQS. In reviewing and approving 
individual TIPs and SIPs, the EPA will determine if together they are 
consistent with the overall air quality needs of an area.
---------------------------------------------------------------------------

    \305\ On January 17, 2014, the United States Court of Appeals 
for the District of Columbia Circuit issued a decision vacating the 
EPA's 2011 rule entitled ``Review of New Sources and Modifications 
in Indian Country'' (76 FR 38748, July 1, 2011) with respect to non-
reservation areas of Indian country (See, Oklahoma Department of 
Environmental Quality v. EPA, 740 F.3d 185 (D.C. Cir. 2014)). Under 
the court's reasoning, with respect to CAA state implementation 
plans, a state has primary regulatory jurisdiction in non-
reservation areas of Indian country (i.e., Indian allotments located 
outside of reservations and dependent Indian communities) within its 
geographic boundaries unless the EPA or a tribe has demonstrated 
that a tribe has jurisdiction over a particular area of non-
reservation Indian country within the state.
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    To date, very few tribes have submitted for the EPA's approval TIPs 
covering areas over which they have jurisdiction. In the absence of a 
TIP, the EPA is authorized under the TAR to implement CAA programs in 
such areas as necessary or appropriate. For example, an unhealthy air 
quality situation on an Indian reservation may require the EPA to 
develop a FIP to reduce emissions from sources on the reservation. 
Likewise, if the agency determines that sources in an area under tribal 
jurisdiction could interfere with a larger nonattainment area meeting 
the NAAQS by its attainment date, it would develop a FIP for those 
sources in consultation with the tribe, as necessary or appropriate.
    States have an obligation to notify other states in advance of any 
public hearing(s) on their state plans if such plans will significantly 
impact such other states. 40 CFR 51.102(d)(5). Under section 301(d) of 
the CAA and the TAR, tribes may become eligible to be treated in a 
manner similar to states (TAS) for this purpose. Affected tribes with 
this status must also be informed of the contents of such state plans 
and given access to the documentation supporting these plans. In 
addition to this mandated process, the EPA encourages states to extend 
the same notice to all affected tribes, regardless of their TAS status.
    Executive Orders and the EPA's Indian policies generally call for 
the EPA to coordinate and consult with tribes on matters that affect 
tribes. Executive Order 13175, titled, ``Consultation and Coordination 
with Indian Tribal Governments'' requires the EPA to develop a process 
to ensure ``meaningful and timely input by tribal officials in the 
development of regulatory policies that have Tribal implications.'' In 
addition, the EPA's policies include the agency's 1984 Indian Policy 
relating to Indian tribes and implementation of federal environmental 
programs, the April 10, 2009, Office of Air Quality Planning and 
Standards guidance ``Consulting with Indian Tribal Governments,'' and 
the ``EPA Policy on Consultation and Coordination With Indian Tribes.'' 
Consistent with these policies, the EPA intends to meet with tribes on 
activities potentially affecting the attainment and maintenance of the 
current and future PM2.5 NAAQS in Indian country, including 
agency actions on SIPs. As such, it would be helpful for states to work 
with tribes with land that is part of the same air quality area during 
the SIP development process and to coordinate with tribes as they 
develop their SIPs.

I. Voluntary Programs for Reducing Ambient PM2.5

1. PM Advance Program
    The EPA believes there are significant advantages for states, 
tribes and local agencies to take steps to reduce direct 
PM2.5 emissions and emissions of PM2.5 precursors 
as early as possible. First and foremost, early reductions help to 
achieve cleaner air sooner, and help to ensure continued health 
protection. Second, early steps could help an area avoid a 
nonattainment designation in the first place, or for an area eventually 
designated as nonattainment, early reductions could help bring the area 
back into attainment sooner, which may lead to qualifying for a CDD and 
subsequent suspension of attainment planning requirements as described 
in Section IX.C of this preamble. In addition, early action to improve 
air quality can help an eventual nonattainment area, particularly an 
area that has never been designated nonattainment before, to establish 
working relationships between key stakeholders. The EPA's expectation 
is that early actions to reduce emissions in such areas would be less 
resource-intensive than actions taken once a nonattainment designation 
has been made, since at that point the implementation of controls would 
need to occur in conjunction with actions to comply with other 
requirements such as nonattainment NSR and transportation conformity.
    In January 2013, the EPA began a new early emissions reduction 
program for attainment areas called ``PM Advance,'' which is much like 
the related ``Ozone Advance'' program that began in April 2012. 
Additional information about the PM Advance program for the annual and 
24-hour PM2.5 NAAQS is provided in a separate guidance 
document that is available at http://www.epa.gov/ozonepmadvance.
2. Residential Wood Smoke Programs
    The EPA recognizes that residential wood smoke is a concern for 
many nonattainment areas. The EPA estimates that wood stoves, hydronic 
heaters and fireplaces emit more than 345,000 tons of PM2.5 
into the air throughout the country each year--mostly during the winter 
months. Residential wood smoke can increase fine particle pollution to 
levels that cause significant health concerns (e.g., asthma attacks, 
heart attacks, premature death). Wood smoke causes many counties 
throughout the U.S. to either exceed the national health-based 
standards for fine particles, or places them on the cusp of exceeding 
the standards. Because wood stoves, hydronic heaters and other similar 
appliances can be used around the clock in residential areas, they can 
cause significant and varying health and quality of life issues.
    To reduce fine particle pollution, many PM2.5 
nonattainment areas will need to address residential wood smoke. The 
EPA has developed the ``Strategies for Reducing Residential Wood 
Smoke''

[[Page 15453]]

document that provides education and outreach tools, information on 
regulatory approaches to reduce wood smoke, as well as information 
about voluntary programs that communities around the country have 
used.\306\ In addition, it includes methods for calculating emissions 
reductions, funding ideas and the basic components of a wood smoke 
reduction plan that can be adopted into a SIP as an enforceable control 
measure.\307\ To access the document, go to http://epa.gov/burnwise/pdfs/strategies.pdf. For more information on the EPA's wood smoke 
reduction program, visit http://www.epa.gov/burnwise.
---------------------------------------------------------------------------

    \306\ On February 3, 2015, the EPA strengthened the New Source 
Performance Standards (NSPS) for new residential wood heaters and 
established NSPS for other new wood heaters, including outdoor and 
indoor wood-fired boilers (also known as hydronic heaters). The 
standards will reduce emissions of direct PM2.5 as well 
as carbon monoxide, VOC, air toxics (including formaldehyde, benzene 
and polycyclic organic matter), and black carbon. See http://www2.epa.gov/residential-wood-heaters/new-source-performance-standards-new-residential-wood-heaters-new.
    \307\ For further guidance on incorporating voluntary measures 
into a SIP, see ``Incorporating Emerging and Voluntary Measures in a 
State Implementation Plan (SIP).'' U.S. EPA. Office of Air and 
Radiation. September 2004. Available at http://www.epa.gov/ttn/caaa/t1/memoranda/evm_ievm_g.pdf.
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J. Improved Stationary Source Emissions Monitoring

1. Background
    For purposes of demonstrating compliance with the EPA's air quality 
regulatory requirements, the EPA, air agencies, and sources rely on two 
basic types of monitoring: ambient air quality monitoring and 
stationary source emissions monitoring. Ambient air quality monitoring, 
as discussed in Section II of this preamble, entails collecting and 
measuring samples of criteria pollutants in ambient air to evaluate air 
quality as compared to clean air standards and historical information. 
Stationary source emissions monitoring, on the other hand, entails 
collecting and using measurement data (or other information) from 
individual stationary sources to demonstrate compliance with emissions 
standards, to assess process or control device performance, or to 
verify work practices. While ambient air quality monitoring is used to 
assess compliance with the NAAQS, stationary source emissions 
monitoring is used to assess compliance with source-specific 
regulations under programs like the New Source Performance Standards 
(NSPS), the National Emissions Standards for Hazardous Air Pollutants 
(NESHAP), the compliance assurance monitoring (CAM) program, the title 
V air operating permits program, and the acid deposition control 
program, as well as specific SIP control measures.\308\
---------------------------------------------------------------------------

    \308\ Regulations governing the implementation of these programs 
are located at 40 CFR parts 60, 61, 63, 64, 70, 71 and 75.
---------------------------------------------------------------------------

    Accurate stationary source emissions monitoring is critical for 
purposes of developing accurate emissions inventories and in order to 
identify appropriate control measures to reduce emissions from 
stationary sources. In addition, after control measures are in place, 
stationary source emissions monitoring provides process and control 
device performance information to the facility operator so that 
appropriate corrective action can be taken if emission levels exceed 
applicable thresholds. Thus, appropriate stationary source emissions 
monitoring requirements, like the control measures with which they are 
associated, are a fundamental element of an approvable attainment plan.
    By way of example, in a limited study on improving stationary 
source emissions monitoring, the EPA found that revising the 
measurement technique at a stationary source could provide information 
to the facility operator to take corrective action that could 
potentially reduce emissions up to 15 percent, and that increasing 
monitoring frequency at the facility could provide information that 
could be used to inform corrective actions that could yield potential 
stationary source emissions reductions of up to 13 
percent.309 310 Implementation of stationary source 
emissions monitoring improvements could thus lead to actions to achieve 
additional emissions reductions not only at individual sources but also 
in the nonattainment areas where these sources are located.
---------------------------------------------------------------------------

    \309\ Impact of Improved Monitoring on PM2.5 
Emissions, memorandum from L. Barr and K. Schaffner, RTI 
International, to B. Parker, U.S. Environmental Protection Agency. 
December 2003.
    \310\ As discussed in Section IX.E of this preamble, emissions 
monitoring has four essential components: (i) indicator(s) of 
performance; (ii) measurement technique(s); (iii) monitoring 
frequency; and, (iv) averaging time.
---------------------------------------------------------------------------

2. Guidance To Help Improve Stationary Source Emissions Monitoring
    Because of the important role that effective stationary source 
emissions monitoring can play in informing the development of 
attainment strategies for PM2.5 NAAQS nonattainment areas, 
the EPA is interested in applied best practices for stationary source 
emissions monitoring that could be included in guidance for other 
stationary sources and air agencies. The EPA seeks to gather 
information about ways to make the source emissions monitoring data 
collection process easier and more transparent. The EPA therefore seeks 
appropriate examples and supporting data from individual sources and 
air agencies with experience in this area to inform such future 
guidance. The EPA also seeks comment on the specific topics and 
questions that follow, which the agency may address in future guidance 
related to improved source monitoring. Specifically:
    (1) Based on your experience, in which cases do you believe 
improved monitoring techniques are more appropriate than visual 
emissions (VE) techniques for monitoring compliance with 
PM2.5 (or PM, in general) emissions limits? Please identify 
monitoring techniques that you would recommend in lieu of VE, and 
describe the instances in which VE remains appropriate.
    (2) Based on your experience, are bag leak detection systems, PM 
continuous parameter monitoring systems (CPMS), or PM continuous 
emissions monitoring systems (CEMS) reliable, cost-effective methods 
for monitoring compliance with PM emissions? Please provide additional 
information on reliability and cost to support your position.
    (3) Will increasing the frequency of VE observations resolve the 
issue of applicability of VE techniques for monitoring compliance with 
PM2.5 emissions? In other words, are there situations in 
which increased VE frequency (i.e., daily versus weekly) would be 
expected to have no impact on compliance with PM2.5 emission 
limits? If so, please provide relevant data and explanation of such 
situations.
    (4) Should the EPA consider mandating through rulemaking the use of 
alternatives to VE techniques for monitoring compliance with 
PM2.5 and PM emissions limits in certain situations and 
applications? If so, in what cases?
    (5) Should the EPA's effort with regard to the use of improved 
monitoring techniques in lieu of VE monitoring be focused on applicable 
requirements established/relied upon for compliance with the 
PM2.5 NAAQS, or should the agency more broadly address other 
applicable requirements where VE techniques are commonly used (e.g., to 
estimate TSP and PM10 emissions)?
    (6) Should the EPA consider mandating through rulemaking the use of 
alternatives to continuous opacity monitoring systems (COMS) for 
monitoring compliance with PM2.5 and PM emissions limits in 
certain situations and applications? If so, in what cases?

[[Page 15454]]

    (7) In its study published in 2003, the EPA identified stationary 
source emission reduction techniques that air agencies should consider 
when developing their potential list of control measures for a 
PM2.5 NAAQS nonattainment area.\311\ Specifically, the EPA 
identified improved measurement techniques and increased monitoring 
frequency as practices that could better inform sources and air 
agencies of excess emissions from individual sources which, if 
responded to more quickly, could yield significant reductions and 
assist in bringing the area into attainment for the NAAQS. Please 
comment on whether these techniques remain appropriate, given that they 
were based on the best technical information available at the time. Are 
there ways to improve the methodologies described in the study?
---------------------------------------------------------------------------

    \311\ Ibid.
---------------------------------------------------------------------------

    (8) Please submit any examples of improved stationary source 
emissions monitoring, including a description of the measure, 
monitoring data, etc.
    (9) Please submit any other methodologies--complete with equations 
and explanations--for estimating emissions reductions due to improved 
monitoring.
    The EPA will continue to explore and implement innovative, cost-
effective ideas that offer tangible incentives for improved source 
monitoring to be adopted as part of the associated emissions 
limitations that will help achieve additional reductions from 
stationary sources and bring areas into attainment for the 
PM2.5 NAAQS in a timely way.

K. Stationary Source Test Methods for Emissions of Condensable PM2.5

1. Background
    As discussed in Section II of this preamble, direct 
PM2.5 comprises of two components: Filterable 
PM2.5 and condensable PM2.5 emissions. Accurate 
test methods for quantifying filterable PM emissions have been 
available for air agencies and states to apply since the early 1970s. 
In addition, controls have improved over the past 40 years and most 
sources now achieve substantially lower emissions than required by 
state and federal emissions limits. With the filterable portion of 
PM2.5 emissions being relatively well controlled, the 
condensable portion of PM2.5 emissions now represents a 
larger share of overall PM2.5 emissions for several 
categories of stationary sources. However, accurate test methods for 
condensable PM2.5 emissions have only been recently 
developed and approved by the EPA. Thus, many states may have 
stationary source emission limits adopted into their existing SIPs 
based only on filterable PM2.5 emissions or based on 
outdated methods for measuring or estimating condensable 
PM2.5 emissions.
    The following discussion focuses on current test methods for 
quantifying condensable PM2.5 emissions and the EPA's 
proposed requirements for states developing control strategies for 
PM2.5 nonattainment areas.
2. Test Methods for Condensable PM From Stationary Sources
    Since January 1, 2011, the EPA has required that states take into 
consideration condensable PM2.5 emissions when establishing 
emission limits for stationary sources as part of any control strategy 
for PM2.5 NAAQS nonattainment areas.\312\ This date 
coincided with the effective date of the agency's revisions to test 
methods for measuring filterable PM10 emissions from 
stationary sources (Method 201A) and for measuring condensable PM 
emissions from stationary sources (Method 202).\313\ The revisions 
increased the precision of Method 202 and improved the consistency in 
the measurements obtained between source tests performed under 
different regulatory authorities.
---------------------------------------------------------------------------

    \312\ 72 FR 20586 (April 25, 2007).
    \313\ 75 FR 80118 (December 21, 2010).
---------------------------------------------------------------------------

    In the preamble to the 2007 PM2.5 Implementation Rule, 
the EPA explained that the use of the (then anticipated) revisions to 
the EPA Method 201A combined with Method 202 to obtain measured source 
specific emissions of PM2.5 would improve the quality of 
emissions inventories for stationary sources and would aid in the 
development of a more reliable attainment strategy, as sources that may 
have a considerable amount of condensable PM2.5 emissions 
could be better characterized with the new methods. The EPA continues 
to believe that using these improved test methods can help identify 
sources of direct PM2.5 emissions which, if better 
controlled, can help to bring a PM2.5 nonattainment area 
into attainment. Likewise, use of these test methods may help a state 
identify sources whose condensable emissions may have been incorrectly 
estimated and therefore may not provide meaningful PM2.5 
control opportunities.
3. Proposed SIP Requirements for Test Methods For Condensable 
PM2.5 Emissions
    The EPA proposes to require that, where a state needs to adopt 
control measures for direct PM2.5 from sources in a 
nonattainment area, the state must specify PM2.5 emission 
limits in its SIP that include both filterable and condensable 
emissions. In addition, compliance testing of those sources must 
include measurement of condensable emissions (such as through the use 
of Method 202). Under this proposal, any new or revised emission limit 
used as a control measure to bring an area into attainment for any 
current or future PM2.5 NAAQS must use methods that measure 
PM2.5 or total PM including both filterable and condensable 
particulate matter. Existing emission limitations that are not being 
revised as part of a Moderate area or Serious area attainment plan can 
remain as filterable PM or whatever test method is used by the state 
for compliance determination. In these cases, the acceptability of 
existing stationary source test methods for PM2.5 attainment 
plans will depend upon what is required under the state's current test 
methods for PM emissions. The EPA believes that this proposed 
requirement is appropriate because the addition of the condensable 
portion of PM2.5 to filterable PM2.5 may increase 
direct PM2.5 emissions by a factor of five or more, and the 
use of test methods that only measure filterable emissions potentially 
limit the control measures available for developing cost effective 
strategies to achieve attainment of the PM2.5 NAAQS.
    The EPA seeks comment on this proposed requirement for states to 
quantify condensable PM2.5 emissions in their attainment 
plans for PM2.5 nonattainment areas.

X. What is the EPA proposing with respect to revoking the 1997 primary 
annual PM2.5 NAAQS?

A. Background

    If the 1997 primary annual PM2.5 NAAQS were to remain in 
place after conformity requirements begin to apply for the 2012 primary 
annual PM2.5 NAAQS (1 year after the effective date of 
designations), a number of federal agencies, metropolitan planning 
organizations (MPOs) and other state, local, and federal transportation 
and air quality agencies in areas that are currently designated 
nonattainment or maintenance for the 1997 annual PM2.5 NAAQS 
and will be designated nonattainment for the 2012 primary annual NAAQS 
would be required to implement conformity requirements for both annual 
PM2.5 NAAQS concurrently. Additionally, some areas would 
also be implementing conformity requirements for the 2006 24-hour 
PM2.5

[[Page 15455]]

NAAQS, and two areas remain subject to conformity requirements for the 
1997 24-hour PM2.5 NAAQS. This could lead to unnecessary 
complexity for transportation conformity determinations, especially if 
an area's boundaries for the various PM2.5 NAAQS differ from 
one another and the same test of conformity cannot be used for all of 
the PM2.5 NAAQS. Even where an area's boundaries are 
unchanged, different analysis years under the conformity rules may be 
required for each PM2.5 NAAQS. It could also lead to general 
conformity determinations being made in areas that are attainment for 
the 2012 primary annual PM2.5 NAAQS. Finally, state and 
local air quality agencies would be required to continue attainment 
planning activities for the 1997 primary annual PM2.5 NAAQS 
even if they had air quality data that resulted in their being 
designated attainment for the 2012 primary annual PM2.5 
NAAQS.
    The EPA believes that it is more important and consistent with CAA 
requirements to determine conformity for the new 2012 primary annual 
PM2.5 NAAQS, which is more stringent and thus more 
protective of health than the 1997 PM2.5 NAAQS. This section 
therefore describes the EPA's proposed approaches for transitioning 
from the 1997 primary annual PM2.5 NAAQS to the 2012 primary 
annual PM2.5 NAAQS. This section discusses a number of 
options for revoking the 1997 primary annual PM2.5 NAAQS and 
addresses anti-backsliding requirements that would apply, as 
appropriate, under each of the revocation options. The EPA is not 
proposing to revoke the 1997 secondary annual PM2.5 NAAQS in 
this action because that NAAQS has been retained in order to prevent 
certain welfare effects associated with PM2.5.\314\
---------------------------------------------------------------------------

    \314\ 78 FR 3086 (January 15, 2013).
---------------------------------------------------------------------------

    The proposed options are framed in the context of the CAA 
requirements that apply to NAAQS transitions to ensure that states and 
nonattainment areas continue to make progress and do not reverse 
progress, or backslide, from improvements already made in air quality. 
The CAA contains several provisions indicating congressional intent not 
to allow a state to alter or remove provisions from an approved 
attainment plan if the revision would reduce air quality protection. 
Section 193 of the CAA prohibits modification of a control requirement 
in effect or required to be adopted as of November 15, 1990 (the date 
of enactment of the 1990 CAA Amendments), unless such a modification 
would ensure equivalent or greater emissions reductions. Section 
172(e), which addresses relaxations of a NAAQS, requires protections 
for areas that have not attained a NAAQS prior to a relaxation by 
requiring controls which are at least as stringent as the controls 
applicable in nonattainment areas prior to any such relaxation. Section 
110(l) provides that a SIP revision cannot be approved if it will 
interfere with attainment or other CAA requirements. Under section 
175A(d), an area that is redesignated to attainment may, with an 
appropriate showing of no interference, cease to implement a measure 
that is contained in the SIP at the time of redesignation, but only if 
that measure is retained as a contingency measure in the area's 
maintenance plan.315 316
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    \315\ Nonattainment areas that were redesignated to attainment 
with an approved section 175A maintenance plan are referred to 
throughout this document as ``maintenance areas.''
    \316\ Unimplemented requirements in the SIP or those shown to be 
unnecessary for maintenance can be shifted to the contingency 
measures portion of the SIP upon redesignation. See ``Procedures for 
Processing Requests to Redesignate Areas to Attainment,'' Memorandum 
from John Calcagni, Director, Air Quality Management Division, 
September 4, 1992; ``State Implementation Plan (SIP) Requirements 
for Areas Submitting Requests for Redesignation to Attainment of the 
Ozone and Carbon Monoxide (CO) National Ambient Air Quality 
Standards (NAAQS) On or After November 15, 1992,'' Memorandum from 
Michael H. Shapiro, Acting Assistant Administrator for Air and 
Radiation, September 17, 1993. As discussed elsewhere in this 
document, an exception is made for NNSR, which can be removed from 
the SIP completely and need not be retained as a contingency measure 
after redesignation to attainment.
---------------------------------------------------------------------------

    The transition from the 1997 to the 2012 primary annual 
PM2.5 NAAQS is a straightforward tightening of the level 
with little change in the form of the standard, so it is unambiguous 
that the 2012 primary annual PM2.5 NAAQS is more stringent 
than the 1997 primary annual PM2.5 NAAQS. In the final 2012 
PM NAAQS rule the EPA eliminated the provisions that allowed for an 
area to use spatial averaging of monitoring data to determine whether 
or not it is attaining the 1997, 2012 and any future annual 
PM2.5 NAAQS.\317\ Eliminating spatial averaging provides 
additional protection for populations that may be at a greater risk to 
exposures of elevated levels of PM2.5. In these 
circumstances where the annual PM2.5 NAAQS has clearly been 
strengthened, section 172(e) on its face does not apply. The EPA's 
interpretation that anti-backsliding provisions consistent with the 
purposes of section 172(e) by analogy should apply as upheld by the 
court in South Coast as appropriate in the absence of statutory 
provisions addressing tightened air quality standards. In proposing 
anti-backsliding requirements that would apply as appropriate to the 
options that are being considered, the EPA seeks to apply the 
principles of section 172(e).\318\
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    \317\ See the Federal Register published on January 15, 2013 (78 
FR 3085, 3124, 3125, 3126, 3137 and 3229).
    \318\ South Coast Air Quality Management District v. EPA, 472 
F.3d 882 (D.C. Cir. 2006).
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B. History of Revocation of Other NAAQS

    The EPA has either adopted or has proposed to adopt transition 
policies for other NAAQS, including the policies for the transitions 
from:
     The 1-hour ozone NAAQS to the 1997 ozone NAAQS;
     The 1997 ozone NAAQS to the 2008 ozone NAAQS;
     The prior lead NAAQS to the 2008 lead NAAQS; and,
     The prior sulfur dioxide (SO2) NAAQS to the 
2010 SO2 NAAQS.
    It is important to note that for all previous NAAQS transitions, 
the EPA has used revocation to reduce the burden associated with 
implementing a NAAQS that has been replaced with a more stringent 
NAAQS.
    In its Phase 1 Rule for the transition from the 1-hour ozone NAAQS 
to the 1997 ozone NAAQS, the EPA stated that the 1-hour ozone NAAQS 
would be revoked (i.e., no longer apply) 1 year after the effective 
date of initial area designations for the 1997 ozone NAAQS. The EPA 
also included anti-backsliding requirements in the Phase 1 Rule to 
address the transition between the two standards.
    The Phase 1 Rule for implementation of the 1997 ozone NAAQS was the 
subject of legal challenges, and the resulting court decision in South 
Coast upheld the EPA's authority to revoke the 1-hour ozone NAAQS as 
long as adequate anti-backsliding measures were retained to prevent 
backsliding.\319\ The decision directed the EPA to provide additional 
1-hour ozone NAAQS anti-backsliding requirements for NNSR, section 185 
fees, and section 172(c)(9) and 182(c)(9) contingency measures for 
failure to attain the 1-hour ozone NAAQS by the applicable attainment 
date or to make reasonable further progress toward attainment of that 
standard, in addition to the anti-backsliding measures contained in the 
Phase 1 rule.\320\
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    \319\ South Coast Air Quality Management District v. EPA, 472 
F.3d 882 (D.C. Cir. 2006).
    \320\ For a more complete discussion of the requirements for the 
transition from the 1-hour ozone NAAQS to the 1997 ozone NAAQS, see 
the Federal Register dated April 30, 2004 (69 FR 23951, 23969, 
23970, 23971, 23972, 23973, 23974, 23975, 23976, 23977, 23978, 
23979, 23980, 23981, 23982, 23983, 23984, 23985, 23986, 23987, 23988 
and 23989).

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[[Page 15456]]

    As part of its final SIP requirements rule for the 2008 ozone 
NAAQS, the EPA included requirements for the transition from the 1997 
ozone NAAQS to the 2008 ozone NAAQS.\321\ In developing that 
rulemaking, the EPA built upon its experience in implementing the Phase 
1 rule for the transition from the 1-hour ozone NAAQS to the 1997 ozone 
NAAQS and the decision in the South Coast litigation. The EPA revoked 
the 1997 ozone NAAQS on the effective date of the final SIP 
requirements rule and finalized anti-backsliding requirements 
consistent with the implementation of the court decision for the 
previous ozone transition that would apply in areas designated 
nonattainment for the 1997 ozone NAAQS at the time of revocation.\322\
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    \321\ See the published proposal at 78 FR 34178 (June 6, 2013) 
and the final SIP requirements rule for the 2008 ozone NAAQS at 
http://www.epa.gov/groundlevelozone/implement.html.
    \322\ Ibid.
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    It should be noted that as part of the transition from the 1997 
ozone NAAQS to the 2008 ozone NAAQS, the EPA revoked the 1997 ozone 
NAAQS for transportation conformity purposes only in a separate action 
related to classifications for the 2008 ozone NAAQS that was finalized 
prior to the time that the full implementation rule had been 
proposed.\323\ The EPA took this action because the D.C. Circuit Court 
in litigation on the transportation conformity rule and in its decision 
in the South Coast litigation affirmed that the use of motor vehicle 
emissions budgets that have been approved or found adequate for use in 
transportation conformity determinations for the prior NAAQS must be 
used in transportation conformity determinations for the new NAAQS 
until a state submits motor vehicle emissions budgets for the new NAAQS 
and those budgets are either found adequate or are 
approved.324 325 These cases seemed to indicate that the use 
of these existing budgets until new budgets are available is the 
appropriate anti-backsliding measure with respect to transportation 
conformity to support revocation for that purpose.\326\ It should be 
noted, however, that the revocation of the 1997 ozone NAAQS for 
transportation conformity purposes was the subject of litigation in the 
D.C. Circuit Court.\327\ The court issued its decision on December 23, 
2014, and held that the EPA lacked authority to revoke the 1997 ozone 
NAAQS only for transportation conformity purposes because for areas 
that remain designated as nonattainment or maintenance for the 1997 
ozone NAAQS, CAA section 176(c) requires transportation conformity 
determinations in nonattainment and maintenance areas.
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    \323\ 77 FR 30160 (May 21, 2012).
    \324\ See South Coast Air Quality Management District v. EPA, 
472 F.3d 882 (D.C. Cir. 2006).
    \325\ 40 CFR 93.101 defines ``motor vehicle emissions budget'' 
as ``that portion of the total allowable emissions defined in the 
submitted or approved control strategy implementation plan revision 
or maintenance plan for a certain date for the purpose of meeting 
reasonable further progress milestones or demonstrating attainment 
or maintenance of the NAAQS, for any criteria pollutant or its 
precursors, allocated to highway and transit vehicle use and 
emissions.''
    \326\ In addition, the Court affirmed that conformity 
determinations need not be made for a revoked standard.
    \327\ NRDC v. EPA, No. 12-1321 (D.C. Cir.) (challenging EPA 
actions taken at 77 FR 30160 (May 21, 2012)).
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    Following promulgation of the 2008 lead NAAQS and 2010 
SO2 NAAQS, the EPA revoked the prior lead and SO2 
NAAQS for all purposes in areas that had attained the prior NAAQS and 
had been redesignated to attainment, as well as in areas that had 
initially been designated as attainment for those NAAQS. The EPA 
retained the prior NAAQS in areas that had not yet attained those NAAQS 
until those areas had an approved attainment plan for the revised 
NAAQS. Because the EPA revoked the prior lead and SO2 NAAQS 
in areas that had been redesignated to attainment for those NAAQS, the 
EPA primarily relied on the CAA's anti-backsliding provisions found in 
sections 110(l) and 193 in order to provide anti-backsliding 
protection.\328\
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    \328\ For details on the requirements for the lead NAAQS and the 
SO2 NAAQS, respectively, see 73 FR 66964 (November 12, 
2008), at page 67043; and 75 FR 35519 (June 22, 2010), at page 
35580.
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    In developing the options for revoking the 1997 primary annual 
PM2.5 NAAQS contained in this proposal, the EPA has drawn 
from these prior anti-backsliding approaches.

C. Proposed Options for Revocation and Related Anti-Backsliding 
Requirements for the 1997 Primary Annual PM2.5 NAAQS

    The EPA is proposing and seeking comment on two options for 
revoking the 1997 primary annual PM2.5 NAAQS and is seeking 
comment on whether to revoke the NAAQS at the current time. Under 
either of the options to revoke the 1997 NAAQS, revocation would take 
effect no sooner than 1 year after the effective date of designations 
for the 2012 primary annual PM2.5 NAAQS. One of these 
options would provide for revocation at a later date for some areas.
    After revocation of the 1997 primary annual PM2.5 NAAQS, 
the designations (and the classifications associated with those 
designations) for that standard would no longer be in effect, and the 
designations that would remain in effect would be those for the 1997 
secondary annual PM2.5 NAAQS, the 2006 primary and secondary 
24-hour PM2.5 NAAQS and the 2012 primary annual 
PM2.5 NAAQS. However, the EPA would retain the listing of 
the designated nonattainment areas for the revoked 1997 primary annual 
PM2.5 NAAQS in 40 CFR part 81, for the sole purpose of 
identifying the anti-backsliding requirements that may apply to the 
areas at the time of revocation. Accordingly, such references to 
historical designations for the revoked standard should not be viewed 
as current designations under CAA section 107(d).
    For any proposed option that allows for revocation in nonattainment 
areas for the 1997 primary annual PM2.5 NAAQS, the EPA is 
also proposing anti-backsliding provisions to ensure that in these 
areas: (i) There is protection against degradation of air quality 
(e.g., the areas do not backslide in terms of air quality 
improvements); (ii) the areas continue to make progress toward 
attainment of the new, more stringent 2012 primary annual 
PM2.5 NAAQS; and, (iii) there is consistency with the 
PM2.5 NAAQS implementation framework outlined in subpart 4 
of part D, title I of the CAA. At the current time, there are 14 areas 
that continue to be designated as nonattainment for the 1997 annual 
PM2.5 NAAQS; however all but 2 of these areas have 2011-2013 
air quality data showing that they are attaining that NAAQS. Therefore, 
the EPA expects many of these current nonattainment areas will be 
eligible to seek redesignation to attainment prior to any revocation. 
The EPA is proposing and seeking comment on the following two options:
     Option 1: Revoke the 1997 primary annual PM2.5 
NAAQS for all purposes in attainment areas for that NAAQS 1 year after 
the effective date of the designations for the 2012 primary annual 
PM2.5 NAAQS; or,
     Option 2: Revoke the 1997 primary annual PM2.5 
NAAQS for all purposes in all nonattainment and attainment areas for 
that NAAQS 1 year after the effective date of the designations for the 
2012 primary annual PM2.5 NAAQS.
    More details on the proposed options and associated rationale are 
included below.

[[Page 15457]]

1. Option 1: Revoke the 1997 Primary Annual PM2.5 NAAQS for 
All Purposes in Attainment Areas for That NAAQS 1 Year After the 
Effective Date of the Designations for the 2012 Primary Annual 
PM2.5 NAAQS
    The EPA's first proposed option would revoke the 1997 primary 
annual PM2.5 NAAQS for all purposes in areas that are 
designated as attainment for that NAAQS 1 year after the effective date 
of designations for the 2012 primary annual PM2.5 NAAQS, as 
well as in future areas that are redesignated as attainment areas after 
the initial revocation. The areas addressed by this option are those 
that were originally designated as attainment areas for the 1997 
primary PM2.5 NAAQS and those that were originally 
designated as nonattainment but have since or will in the future be 
redesignated to attainment for that NAAQS. Under this option, the EPA 
would not revoke the 1997 primary annual PM2.5 NAAQS in any 
area that is designated nonattainment for that NAAQS.
    Areas that are designated nonattainment for the 1997 annual 
PM2.5 NAAQS at the time of the initial revocation would be 
required to continue to meet all applicable requirements for such 
NAAQS, and could continue to seek redesignation to attainment for the 
1997 primary annual PM2.5 NAAQS. For example, even if the 
revocation were to become effective in April 2016, redesignations could 
continue to be approved after that date. For such areas, the effective 
date of the revocation would be the effective date of the area's 
redesignation to attainment for the 1997 annual PM2.5 NAAQS.
    The EPA notes that under proposed Option 1 it is unnecessary to 
propose anti-backsliding requirements for the 1997 primary annual 
PM2.5 NAAQS, since Option 1 would only revoke this NAAQS in 
attainment areas. Anti-backsliding requirements are not applicable to 
attainment areas (i.e., for former nonattainment areas that have been 
redesignated to attainment the EPA has already determined through the 
redesignation process and approval of maintenance plans that all 
applicable requirements for the 1997 primary annual PM2.5 
NAAQS--including anti-backsliding requirements--have been fulfilled and 
areas that have always been designated attainment for this NAAQS).
    For areas that were initially designated as attainment for both the 
1997 and 2012 annual PM2.5 NAAQS the EPA is proposing that 
the approved PSD SIPs for these areas satisfy the obligation to submit 
an approvable maintenance plan for the 2012 primary annual 
PM2.5 NAAQS under section 110(a)(1).
    The EPA also notes that areas designated nonattainment for the 2012 
primary annual PM2.5 NAAQS would be required to comply with 
applicable conformity requirements beginning 1 year after the effective 
date of designations for that NAAQS. For transportation conformity 
purposes these requirements would include using adequate or approved 
motor vehicle emissions budgets for the 1997 annual PM2.5 
NAAQS where they exist until the area has approved or adequate budgets 
for the 2012 primary annual PM2.5 NAAQS.\329\ The use of 
such budgets serves as the appropriate anti-backsliding measure for 
transportation conformity purposes.
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    \329\ Areas that do not have adequate or approved motor vehicle 
emissions budgets for the 1997 annual PM2.5 NAAQS or the 
2006 24-hour PM2.5 NAAQS would use one of the two interim 
emissions tests required by 40 CFR 93.109(c)(3) and 40 CFR 
93.119(b).
---------------------------------------------------------------------------

    In general, Option 1 builds upon the EPA's practice in the 
transition from the 1-hour to the 1997 ozone NAAQS in that areas will 
not only be able to be redesignated to attainment up to the date of the 
initial revocation, but any remaining nonattainment areas will be able 
to be redesignated after the initial revocations occur 1 year after the 
effective date of designations.\330\ This approach is also consistent 
with the approach established for the transition from the prior lead 
and SO2 NAAQS to the current lead and SO2 NAAQS.
---------------------------------------------------------------------------

    \330\ Although section 51.905(a) specified that the anti-
backsliding requirements ``attached'' at the time of designation for 
the 1997 ozone NAAQS, areas were still able to redesignate to 
attainment for the 1-hour ozone NAAQS up to the date of revocation 
of that standard.
---------------------------------------------------------------------------

2. Option 2: Revoke the 1997 Primary Annual PM2.5 NAAQS for 
All Purposes in All Nonattainment and Attainment Areas for That NAAQS 1 
Year After the Effective Date of Designations for the 2012 Primary 
Annual PM2.5 NAAQS
    Under this second proposed option, the EPA would revoke the 1997 
primary annual PM2.5 NAAQS for all purposes in all 
nonattainment and attainment areas 1 year after the effective date of 
designations for the 2012 primary annual PM2.5 NAAQS. The 
requirements for revoking the 1997 primary annual NAAQS in attainment 
areas for that NAAQS are discussed under proposed Option 1. However, 
revoking the 1997 primary annual PM2.5 NAAQS in 
nonattainment areas for that NAAQS would require anti-backsliding 
measures. Therefore, the EPA is proposing the following anti-
backsliding measures for any designated nonattainment areas that exist 
for the 1997 primary annual PM2.5 NAAQS upon the effective 
date of the proposed revocation:
     For areas designated attainment for the 2012 primary 
annual PM2.5 NAAQS and nonattainment for the 1997 primary 
annual PM2.5 NAAQS, the EPA's preferred proposed option is 
not to require these areas to adopt any outstanding applicable 
requirements for the revoked 1997 primary annual PM2.5 
standard. However, the EPA proposes that the approved PSD SIPs for 
these areas satisfy the obligation to submit an approvable maintenance 
plan for the 2012 primary annual PM2.5 NAAQS under section 
110(a)(1).
     For these same areas (i.e., those designated attainment 
for the 2012 primary annual PM2.5 NAAQS and nonattainment 
for the 1997 primary annual PM2.5 NAAQS), the EPA is also 
proposing an alternative anti-backsliding option where these areas 
would be required to show maintenance for the 2012 primary annual 
PM2.5 NAAQS. This maintenance showing would be due 3 years 
after the effective date of designations for the 2012 primary annual 
PM2.5 NAAQS. The maintenance showing would contain a 
demonstration of continued maintenance of the 2012 primary annual 
PM2.5 NAAQS in the area for 10 years from the effective date 
of the area's designation as attainment for the 2012 primary annual 
PM2.5 NAAQS. The EPA would take further action to specify 
the elements of such a maintenance showing should the agency require it 
in the final rule. For areas designated nonattainment for the 2012 
primary annual PM2.5 NAAQS and also designated nonattainment 
for the 1997 annual PM2.5 NAAQS, the EPA is proposing that 
these areas continue to implement their approved SIPs for the 1997 
annual PM2.5 NAAQS and fulfill any outstanding requirements, 
and that they comply with the applicable requirements for the current 
2012 primary annual PM2.5 NAAQS. For example, at some time 
in the future there may be an area that is reclassified as Serious for 
the 1997 PM2.5 NAAQS while also classified as Moderate for 
the 2012 PM2.5 NAAQS. In such an area, the lower Serious 
area major source threshold of 70 tpy (PTE) would apply. In addition to 
these proposed requirements, if a state seeks to revise any measure 
already approved into its SIP for a nonattainment area for the 1997 
annual PM2.5 NAAQS, the state must meet the requirements of 
sections 110(l) and 193, if applicable.
    The EPA notes that Option 2 for 2012 attainment/1997 nonattainment 
would

[[Page 15458]]

be similar to the approach to revocation of the 1-hour ozone NAAQS 
consistent with court decisions and the approach to revocation of the 
1997 ozone NAAQS in the final 2008 ozone NAAQS SIP requirements 
rule.\331\ The EPA also notes that areas designated nonattainment for 
the 2012 primary annual PM2.5 NAAQS would be required to 
comply with applicable conformity requirements beginning 1 year after 
the effective date of designations for that NAAQS. For transportation 
conformity purposes these requirements would include using adequate or 
approved motor vehicle emissions budgets for the 1997 annual 
PM2.5 NAAQS where they exist until the area has approved or 
adequate budgets for the 2012 primary annual PM2.5 
NAAQS.\332\ The use of such budgets serves as the appropriate anti-
backsliding measure for transportation conformity purposes. Further 
details regarding this option and associated rationale are in Section 
X.D of this preamble.
---------------------------------------------------------------------------

    \331\ See the final SIP requirements rule for the 2008 ozone 
NAAQS at http://www.epa.gov/groundlevelozone/implement.
    \332\ Areas that do not have adequate or approved motor vehicle 
emissions budgets for the 1997 annual PM2.5 NAAQS or the 
2006 24-hour PM2.5 NAAQS would use one of the two interim 
emissions tests required by 40 CFR 93.109(c)(3) and 40 CFR 
93.119(b).
---------------------------------------------------------------------------

    Lastly, the EPA requests comment on the possible approach of not 
revoking the 1997 primary annual PM2.5 NAAQS at this time. 
Under this concept, the EPA would not revoke the 1997 primary annual 
PM2.5 NAAQS for any purpose at this time. As a result, all 
nonattainment and maintenance areas would be required to continue 
planning activities associated with the 1997 annual PM2.5 
NAAQS such as submitting attainment SIPs and maintenance plans, NNSR, 
and transportation and general conformity requirements for the 1997 
primary annual PM2.5 NAAQS, in addition to any new 
requirements associated with the more health-protective 2012 primary 
annual PM2.5 NAAQS. Under this approach the EPA would not 
have to establish any anti-backsliding requirements.
    The EPA again notes that if this approach were finalized it would 
be the first time that the EPA has not taken some action to reduce the 
burden associated with implementing a NAAQS that has been replaced with 
a more stringent NAAQS.\333\ If the EPA were to finalize this approach, 
it would result in state and local agencies being required to implement 
the requirements associated with two primary annual PM2.5 
NAAQS. These agencies would be required to continue attainment planning 
activities for the 1997 primary annual PM2.5 NAAQS even if 
they had air quality data that resulted in their being designated 
attainment for the 2012 primary annual PM2.5 NAAQS. State, 
local and federal agencies would be required to continue to make 
transportation and general conformity determinations for the less 
protective 1997 primary annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \333\ As discussed in Section IX.B of this preamble, the EPA has 
taken action to revoke previous ozone, SO2 and lead NAAQS 
when the previous NAAQS has been revised.
---------------------------------------------------------------------------

D. Discussion of Options

    Until the 1997 primary annual PM2.5 NAAQS is revoked, 
that NAAQS remains in effect, in parallel with the 2012 primary annual 
PM2.5 NAAQS, and continues to apply independently and by its 
own terms. The EPA believes that all of the proposed options to revoke 
the 1997 primary annual PM2.5 NAAQS are consistent with the 
CAA and previous precedent in transitioning from a previous NAAQS to a 
new, more stringent NAAQS, and would ensure that attainment areas 
continue to attain the revoked NAAQS into the future. If the 1997 
primary annual PM2.5 NAAQS is revoked, the EPA is proposing 
that the anti-backsliding requirements for the 1997 primary annual 
PM2.5 NAAQS, as proposed in this rulemaking, will become 
applicable. However, the EPA notes that most of the areas that were 
initially designated as nonattainment for the 1997 primary annual 
PM2.5 NAAQS where the NAAQS would be revoked have already 
been redesignated to attainment (i.e., they are maintenance areas) or 
could qualify for redesignation based on current air quality data, and 
in such cases their approved maintenance plan for the 1997 primary 
annual PM2.5 would prevent backsliding.\334\ Under Option 2 
there would be a limited number of nonattainment areas where the 1997 
primary annual NAAQS would be revoked and where anti-backsliding 
measures would be required. Under all of the proposed options, 
conformity would apply in areas that are designated nonattainment for 
the more health protective 2012 primary annual PM2.5 NAAQS. 
In the case of transportation conformity, adequate or approved motor 
vehicle emissions budgets for the 1997 primary annual PM2.5 
NAAQS would be used in conformity determinations until motor vehicle 
emissions budgets for the 2012 primary annual PM2.5 NAAQS 
are found adequate or are approved. Once a NAAQS is revoked in a 
nonattainment area, the EPA would not designate or redesignate areas 
for that NAAQS after the revocation of that NAAQS except as described 
in Option 1. The extent of continued implementation of a revoked 
standard derives from administration of anti-backsliding requirements 
for that standard.
---------------------------------------------------------------------------

    \334\ Based on 2011-13 air quality data, many of the areas that 
were initially designated nonattainment for the 1997 annual 
PM2.5 NAAQS will have already met the 1997 annual 
PM2.5 NAAQS and will have been redesignated to attainment 
by the time it is revoked (projected to be in or around April 2016), 
and thus after revocation of the 1997 primary annual 
PM2.5 NAAQS, the number of areas with 1997 anti-
backsliding requirements will be correspondingly reduced.
---------------------------------------------------------------------------

    Under Option 1, the 1997 primary annual PM2.5 NAAQS 
would be revoked only in areas that have attained the 1997 annual 
PM2.5 NAAQS and have been redesignated to attainment with an 
approved section 175A maintenance plan for the 1997 primary annual 
PM2.5 NAAQS; under Option 2, many of the areas where the 
1997 primary annual NAAQS would be revoked would have been redesignated 
to attainment with an approved maintenance plan. The EPA also 
anticipates that states will continue to request that areas be 
redesignated to attainment and the EPA will continue to act on those 
requests under Option 2. As a result the EPA anticipates that a number 
of such requests will be approved prior to the point in time that the 
EPA has proposed for the revocations to become effective (i.e., 1 year 
after the effective date of designations for the 2012 primary annual 
PM2.5 NAAQS). Therefore, the number of nonattainment areas 
for the 1997 primary annual PM2.5 NAAQS will continue to 
decrease and fewer areas will be required to comply with anti-
backsliding requirements, and a correspondingly larger number of areas 
will be required to continue to implement their approved section 175A 
maintenance plan for the 1997 primary annual PM2.5 NAAQS.
    It should also be noted that, for either proposed option, after the 
effective date of any revocation of the 1997 primary annual 
PM2.5 NAAQS, transportation and general conformity 
determinations would continue to be required in areas that are 
designated nonattainment for the 1997 secondary annual PM2.5 
NAAQS until such areas are redesignated to attainment pursuant to the 
requirements of section 107(d)(3). Areas that are initially designated 
as nonattainment for the 2012 primary annual NAAQS are subject to 
transportation and general conformity requirements after the end of the 
grace period that ends 1 year after the effective date of designations 
for the 2012 primary annual PM2.5 NAAQS. See further 
information for how conformity will be implemented for the 2012 
PM2.5 NAAQS in Section IX.B of this preamble. Under Options 
1 and 2 the

[[Page 15459]]

timing that the EPA is proposing means that any area that was 
previously a 1997 annual PM2.5 NAAQS nonattainment area, but 
has been redesignated to attainment for the 1997 annual 
PM2.5 NAAQS by the time of revocation of the 1997 primary 
annual PM2.5 NAAQS (e.g., April 2016 for most areas), will 
not be subject to the anti-backsliding requirements for the 1997 annual 
PM2.5 NAAQS. This is because when an area has been 
redesignated to attainment for a PM2.5 NAAQS while that 
NAAQS is in effect, it has fulfilled all applicable requirements for 
that NAAQS, including applicable anti-backsliding requirements for the 
1997 annual PM2.5 NAAQS. The area is, therefore, not subject 
to anti-backsliding requirements for the revoked 1997 primary annual 
PM2.5 NAAQS. These areas are required instead to implement 
their approved CAA section 175A maintenance plan for the 1997 primary 
annual PM2.5 NAAQS and implement a PSD program for this 
NAAQS, if they are designated attainment for the 2012 primary annual 
PM2.5 NAAQS.335 336 Revisions to the approved 
maintenance plan can only be made if the revisions meet the 
requirements of section 110(l) and, if applicable, section 193. The EPA 
proposes that these areas not be required to submit a second 10-year 
maintenance plan for the 1997 primary annual PM2.5 NAAQS 
because there is no justification for additional maintenance plan 
burdens to be imposed on these areas solely because at one time they 
were designated nonattainment under the revoked 1997 primary annual 
PM2.5 NAAQS. Not requiring a second 10-year maintenance plan 
for these areas would help to minimize the burden associated with 
preparing SIPs for a succession of NAAQS of increasing stringency.
---------------------------------------------------------------------------

    \335\ Areas initially designated as attainment for the 1997 
annual PM2.5 NAAQS would also be required to continue to 
implement a PSD program unless an area was designated nonattainment 
for the 2012 primary annual PM2.5 NAAQS. Such an area 
would be required to implement a NNSR program for that NAAQS.
    \336\ Areas designated nonattainment for the 2012 primary annual 
PM2.5 NAAQS would implement a NNSR program for that 
NAAQS.
---------------------------------------------------------------------------

    As explained previously, for areas redesignated to attainment under 
Options 1 and 2, the section 175A maintenance plan for the 1997 primary 
annual PM2.5 NAAQS satisfies the anti-backsliding 
requirements of these areas. The EPA believes that for these areas any 
further 110(a)(1) maintenance plan requirement under the 2012 primary 
annual PM2.5 NAAQS for areas designated attainment for that 
NAAQS would be unnecessarily burdensome.
    For Option 2, the EPA is applying a general principle to apply 
transition requirements depending on how the area is designated--
attainment or nonattainment--for the 2012 primary annual 
PM2.5 NAAQS, while taking into account the area's status 
with respect to the 1997 primary annual PM2.5 NAAQS. For 
those areas which have already incorporated measures into their 
approved SIPs that satisfy the nonattainment requirements for that 
standard, section 110(l) functions to require continued implementation 
of such measures unless revised in accordance with its provisions.
    Under Option 2, the EPA is proposing as one alternative that areas 
designated attainment for the 2012 primary annual PM2.5 
NAAQS and nonattainment for the 1997 annual PM2.5 NAAQS (as 
of revocation of the 1997 primary annual PM2.5 NAAQS) not be 
required to adopt any outstanding applicable requirements for the 
revoked 1997 primary annual standard. This approach is similar to the 
approach followed in the transition from the 1-hour ozone NAAQS to the 
1997 ozone NAAQS. However, instead of submitting a maintenance plan the 
EPA is also proposing that the approved PSD SIPs for these areas 
satisfy the obligation to submit an approvable maintenance plan for the 
2012 primary annual PM2.5 NAAQS under section 110(a)(1). 
This is similar to what the EPA finalized for the transition from the 
1997 ozone NAAQS to the 2008 ozone NAAQS.\337\ The EPA's rationale for 
this approach is as follows: Areas designated attainment for the 2012 
primary annual PM2.5 NAAQS and nonattainment for the 1997 
primary annual PM2.5 NAAQS (as of revocation of the 1997 
primary annual PM2.5 NAAQS) have already attained the most 
stringent existing standard. These areas thus have developed 
nonattainment plans that in combination with federal measures and 
emissions controls in upwind areas have produced sufficient emissions 
reductions to achieve the more protective 2012 primary annual 
PM2.5 NAAQS. They remain subject to the 1997 nonattainment 
area requirements already approved into the SIP, which can be revised 
only upon a showing that such revision is consistent with sections 
110(l) and 193, if applicable. At this time, and given the succession 
of NAAQS of increasing stringency that has occurred, the EPA believes 
that the burden of developing an approvable maintenance plan for the 
2012 primary annual PM2.5 NAAQS would outweigh any 
compensating benefit for an area that is already attaining that more 
stringent NAAQS and that is subject to prior nonattainment requirements 
which are already incorporated into the SIP.
---------------------------------------------------------------------------

    \337\ See the the final SIP requirements rule for the 2008 ozone 
NAAQS at http://www.epa.gov/groundlevelozone/implement.html.
---------------------------------------------------------------------------

    Under Option 2, the EPA is also proposing, for areas that are 
attainment for the 2012 primary annual PM2.5 NAAQS, that the 
NNSR anti-backsliding requirement(s) for the 1997 annual 
PM2.5 NAAQS cease to apply, since PSD will then be in 
effect. The state may request that the corresponding NSR requirements 
be removed entirely, rather than be retained in the SIP as a 
maintenance plan contingency measure.\338\ Areas that are designated 
nonattainment for the more stringent 2012 primary annual 
PM2.5 NAAQS will be subject to NNSR and other nonattainment 
requirements for their classification under the more stringent 2012 
primary annual PM2.5 NAAQS.
---------------------------------------------------------------------------

    \338\ See 40 CFR 51.905(a)(3), the comparable provision for 
transitions from the 1-hour NAAQS to the 1997 ozone NAAQS, which 
allows such areas to request that the 1-hour NNSR provisions be 
removed from the SIP.
---------------------------------------------------------------------------

    The revocation of the 1-hour ozone NAAQS and the associated anti-
backsliding provisions were the subject of past litigation. In its 
December 2006 decision on that challenge, as modified following 
rehearing, the Court held with respect to the anti-backsliding approach 
for conformity that 1-hour ozone motor vehicle emissions budgets must 
be used in transportation conformity determinations for the more 
protective 1997 ozone NAAQS where such SIP motor vehicle emissions 
budgets have been found adequate or approved, until SIP motor vehicle 
emissions budgets for the 1997 ozone NAAQS are available.\339\ In 
addition, the Court affirmed more broadly that in order for 
transportation conformity determinations to fulfill the requirements of 
CAA section 176(c)(1), motor vehicle emissions budgets for a prior 
NAAQS must be used in transportation conformity determinations under a 
revised NAAQS until emissions budgets for the revised NAAQS are either 
found adequate or are approved, but that conformity determinations need 
not be made for a revoked standard. Therefore, areas designated 
nonattainment for the 2012 primary annual PM2.5 NAAQS that 
have adequate or approved SIP budgets for the 1997 annual 
PM2.5 NAAQS must continue to use such budgets in 
transportation conformity determinations until budgets for the

[[Page 15460]]

2012 primary annual PM2.5 NAAQS are found adequate or are 
approved.\340\
---------------------------------------------------------------------------

    \339\ See South Coast Air Quality Management District v. EPA, 
472 F.3d at 882 (D.C. Cir. 2006).
    \340\ Areas that do not have adequate or approved motor vehicle 
emissions budgets for the 1997 annual PM2.5 NAAQS or the 
2006 24-hour PM2.5 NAAQS would use one of the two interim 
emissions tests requied by 40 CFR 93.109(c)(3) and 40 CRR 93.119(b).
---------------------------------------------------------------------------

    With regard to general conformity, the D.C. Circuit Court did not 
address the need for specific anti-backsliding measures in its initial 
decision or in the modified decision on the South Coast litigation. 
Therefore, if the EPA finalizes either Option 1 or 2 and revokes the 
1997 primary annual PM2.5 NAAQS, general conformity 
determinations will be required in nonattainment areas for the 2012 
primary annual NAAQS as required by section 176(c)(5) to ensure that 
the action of federal agencies do not cause a violation of that NAAQS, 
make an existing violation worse or delay timely attainment of the 
NAAQS or an interim milestone.\341\ The EPA believes that revoking the 
1997 primary annual PM2.5 NAAQS under Option 1 or 2 is 
logical because it would result in only one primary annual 
PM2.5 NAAQS--the 2012 primary annual PM2.5 
NAAQS--applying for purposes of transportation and general conformity 
in most areas, after the end of the 1-year conformity grace period that 
applies to newly designated nonattainment areas. (CAA section 
176(c)(6)).
---------------------------------------------------------------------------

    \341\ It should be noted that some areas will remain designated 
nonattainment for 1997 secondary annual PM2.5 NAAQS. Such 
areas will remain subject to transportation and general conformity 
for that NAAQS until such time that they are redesignated to 
attainment for that NAAQS pursuant to the requirements of section 
107(d)(3).
---------------------------------------------------------------------------

    Areas that are attaining the more health protective 2012 primary 
annual PM2.5 NAAQS would no longer have to expend resources 
to make conformity determinations for any of the current primary annual 
PM2.5 NAAQS after the 1997 primary annual PM2.5 
NAAQS is revoked and the area is redesignated as attainment for the 
1997 secondary annual PM2.5 NAAQS. Some of these areas would 
be required to continue to make conformity determinations for the 2006 
24-hour PM2.5 NAAQS and based on 2011-13 air quality data 
two areas would be required to make conformity determinations for the 
1997 24-hour PM2.5 NAAQS. It should be noted that any areas 
that are attaining the more health protective 2012 primary annual NAAQS 
are also necessarily attaining the less stringent 1997 annual 
PM2.5 NAAQS by a wide margin. Therefore, the options of this 
proposal would provide a seamless transition from demonstrating 
conformity for the 1997 annual PM2.5 NAAQS to demonstrating 
conformity for the more stringent 2012 primary annual PM2.5 
NAAQS.
    Areas designated nonattainment for the 2012 primary annual 
PM2.5 NAAQS will likely need the full 1-year grace period 
provided in section 176(c)(6) to complete the required initial 
transportation conformity determination. Those areas that were 
designated as either nonattainment or maintenance for the 1997 annual 
PM2.5 NAAQS at the time of designation as nonattainment for 
the 2012 primary annual PM2.5 NAAQS will need certainty as 
to the specific requirements for that conformity determination. For 
example they need to know what analysis years must be addressed and, if 
the boundaries for the PM2.5 NAAQS are different, they need 
to know whether to address conformity for both areas and which test or 
tests would apply.
    The EPA seeks comment on the options proposed in the preceding 
discussion regarding revoking the 1997 primary annual PM2.5 
standard, as well as on whether the agency should take no action to 
revoke the standard as this time.

XI. Environmental Justice Considerations

    The EPA believes the human health or environmental risk addressed 
by this action will not have disproportionately high and adverse human 
health or environmental effects on minority, low-income, or indigenous 
populations because it would not negatively affect the level of 
protection provided to human health or the environment under the 
PM2.5 NAAQS. When promulgated, these proposed regulations 
will clarify the state implementation plan requirements and the NNSR 
permitting requirements to be met by states in order to attain the 
PM2.5 NAAQS as expeditiously as practicable. These 
requirements are designed to protect all segments of the general 
population. The EPA included specific discussion in this preamble about 
actions that could be considered for the protection of minority, low-
income or indigenous populations in Section IV.D.6 on Moderate area 
attainment plan control strategies; Section VI.D.7 on Serious area 
attainment plan control strategies; and Section IX.G, measures to 
ensure appropriate protections for overburdened populations. In 
addition, as part of the consultation activities conducted in 
developing this rule, the EPA participated in training and outreach 
activities with representatives from environmental justice 
organizations in a March 2014 conference held in Research Triangle 
Park, NC titled, ``Clean Air Act Rulemaking and Permitting Training for 
EJ Communities.'' These proposed regulations are designed to protect 
and enhance the health and safety of these and other populations, and 
they will not adversely affect the health or safety of minority, low-
income or indigenous populations.

XII. Statutory and Executive Order Reviews

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

    This action is a significant regulatory action that was submitted 
to the Office of Management and Budget (OMB) for review because it 
raises novel policy issues. Any changes made in response to OMB 
recommendations have been documented in the docket.\342\
---------------------------------------------------------------------------

    \342\ Note that a regulatory impact analysis evaluating the 
costs and benefits associated with attaining the 2012 
PM2.5 NAAQS was released at the time the NAAQS review was 
finalized. See ``Regulatory Impact Analysis for the Final Revisions 
to the National Ambient Air Quality Standards for Particulate 
Matter.'' U.S. Environmental Protection Agency, Office of Air 
Quality and Planning Standards, Health and Environmental Impacts 
Division, February 28, 2013. EPA-452/R-12-005.
---------------------------------------------------------------------------

B. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the PRA. The Information Collection Request (ICR) document 
prepared by the EPA has been assigned the EPA ICR number 2258.03, OMB 
Control No. 2060-0611. You can find a copy of the ICR in the docket for 
this rule, and it is briefly summarized here.
    The EPA is proposing this PM2.5 NAAQS SIP Requirements 
Rule to describe the CAA requirements that must be met by states with 
nonattainment areas required to develop attainment plans for attaining 
and maintaining the NAAQS. The intended effect of the SIP Requirements 
Rule is to provide certainty to states regarding their planning 
obligations such that states may begin SIP development. Only states 
with nonattainment areas are required to submit SIPs under this rule.
    For purposes of analysis of the estimated paperwork burden, the EPA 
assumed there were 21 existing nonattainment areas for the 1997 and 
2006 PM2.5 NAAQS, and 15 hypothetical, newly-designated 
nonattainment areas.\343\ The attainment

[[Page 15461]]

plan requirements would appear as 40 CFR 51.1000 through 51.1015 which 
implement CAA subsections 172(c)(1) and (2), and 189(a)(1)(B) and (C), 
189(b)(1)(A) and (B) and 189(c). Some states have new nonattainment 
areas and some states should already have information from emission 
sources, as facilities should have provided this information to meet 
1997 and 2006 PM2.5 NAAQS SIP requirements, operating 
permits and/or emissions reporting requirements. Such information does 
not generally reveal the details of production processes. But, to the 
extent it may, confidential business information for the affected 
facilities is protected. Specifically, submissions of emissions and 
control efficiency information that is confidential, proprietary and 
trade secret and is not emission data is protected from disclosure 
under the requirements of subsections 503(e) and 114(c) of the CAA.
---------------------------------------------------------------------------

    \343\ These hypothetical nonattainment areas were developed 
based on 2010-12 air quality data and state recommendations. Actual 
nonattainment designations and boundaries are based on the most 
recent, complete air quality data available.
---------------------------------------------------------------------------

    The annual state burden for this information collection for the 15 
hypothetical newly designated 2012 PM2.5 nonattainment 
areas, averaged over the first 3 years of this ICR, is estimated to be 
a total of 54,000 labor hours per year at an annual labor cost of $3.2 
million (present value) over the 3-year period, or approximately 
$649,000 per state for the 5 state respondents. The average annual 
reporting burden is approximately 3,600 hours per response, with 
approximately 3 responses per state for 15 state responses. There are 
no capital or operating and maintenance costs associated with the 
proposed rule requirements. Burden is defined at 5 CFR 1320.3(b).
    The annual state burden for this information collection for the 21 
existing nonattainment areas for the 1997 and 2006 PM2.5 
NAAQS, averaged over the first 3 years of this ICR, is estimated to be 
a total of 43,400 labor hours per year at an annual labor cost of $2.6 
million (present value) over the 3-year period, or approximately 
$370,000 per state for the 7 state respondents. The average annual 
reporting burden is approximately 2,000 hours per response, with 
approximately 3 responses per state for 21 state responses. There are 
no capital or operating and maintenance costs associated with the 
proposed rule requirements. Burden is defined at 5 CFR 1320.3(b).
    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 
oria_submissions@omb.eop.gov, 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 
April 22, 2015. The EPA will respond to any ICR-related comments in the 
final rule.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any regulation subject 
to notice-and-comment rulemaking requirements under the Administrative 
Procedures Act or any other statute unless the agency certifies the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations and small governmental jurisdictions.
    For purposes of assessing the impacts of this rule on small 
entities, small entity is defined as: (1) A small business as defined 
in the Small Business Administration's (SBA) regulations at 13 CFR 
121.201; (2) a small governmental jurisdiction that is a government of 
a city, county, town, school district or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise which is independently owned and operated 
and is not dominant in its field.
    After considering the economic impacts of this proposed rule on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. This 
proposed rule will not impose any requirements directly on small 
entities. Entities potentially affected directly by this proposal 
include state, local and tribal governments and none of these 
governments are small governments. Other types of small entities are 
not directly subject to the requirements of this rule. The EPA 
continues to be interested in the potential impacts of the proposed 
rule on small entities and welcomes comments on issues related to such 
impacts.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. This action imposes no enforceable duty on any 
state, local or tribal governments or the private sector. The CAA 
imposes the obligation for states to submit attainment plans to 
implement the PM2.5 NAAQS. In this rule, the EPA is 
clarifying those requirements. Therefore, this action is not subject to 
the requirements of sections 202, 203, and 205 of the UMRA.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government, as 
specified in Executive Order 13132. The requirement to submit 
attainment plans to meet a PM2.5 NAAQS is imposed by the 
CAA. This proposed rule, if made final, would interpret those 
requirements as they apply to current and future PM2.5 
NAAQS. Thus, Executive Order 13132 does not apply to these proposed 
regulations.
    In the spirit of Executive Order 13132 and consistent with the EPA 
policy to promote communications between the EPA and state and local 
governments, the EPA specifically solicits comments on this proposed 
action from state and local officials. In addition, the EPA intends to 
meet with organizations representing state and local officials during 
the comment period for this action.

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

    This proposed action does not have tribal implications, as 
specified in Executive Order 13175 (65 FR 67249, November 9, 2000). It 
would not have a substantial direct effect on one or more Indian 
tribes. Furthermore, these proposed regulation revisions do not affect 
the relationship or distribution of power and responsibilities between 
the federal government and Indian tribes. The CAA and the TAR establish 
the relationship of the federal government and tribes in characterizing 
air quality and developing plans to attain the NAAQS, and these 
revisions to the regulations do nothing to modify that

[[Page 15462]]

relationship. Thus, Executive Order 13175 does not apply to this 
action.
    Although Executive Order 13175 does not apply to this action, the 
EPA solicits comment on this proposed action from tribal officials. The 
EPA also intends to offer to consult with any tribal government to 
discuss this proposal.

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

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive Order. This action is not subject to 
Executive Order 13045 because it implements a previously promulgated 
health or safety-based federal standard established pursuant to the 
CAA.
    These proposed regulatory provisions are designed to help implement 
the current and future PM2.5 NAAQS, promulgated to protect 
the health and welfare of individuals, including children, who are 
susceptible to the adverse effects of exposure to unhealthy levels of 
ambient PM2.5.

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

    This action is not a ``significant energy action'' as defined in 
Executive Order 13211 (66 FR 28355 (May 22, 2001)), because it is not 
likely to have a significant adverse effect on the supply, 
distribution, or use of energy.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272 
note) directs the EPA to use voluntary consensus standards in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus standards 
are technical standards (e.g., materials specifications, test methods, 
sampling procedures and business practices) that are developed or 
adopted by voluntary consensus standards bodies. NTTAA directs the EPA 
to provide Congress, through OMB, explanations when the agency decides 
not to use available and applicable voluntary consensus standards.
    This proposed rulemaking does not involve technical standards. 
Therefore, the EPA is not considering the use of any voluntary 
consensus standards.

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

    The EPA believes the human health or environmental risk addressed 
by this action will not have disproportionately high and adverse human 
health or environmental effects on minority, low-income, or indigenous 
populations. The results of this evaluation are contained in Section XI 
of this preamble.

K. Determination Under Section 307(d)

    Pursuant to sections 307(d)(1)(E) and 307(d)(1)(V) of the CAA, the 
Administrator proposes to determine that this action is subject to the 
provisions of section 307(d). Under section 307(d)(1)(V), the 
provisions of section 307(d) apply to ``such other actions as the 
Administrator may determine.''

Statutory Authority

    The statutory authority for this action is provided by 42 U.S.C. 
7403, 7407, 7410, and 7601.

List of Subjects

40 CFR Part 50

    Environmental protection, Air pollution control, Intergovernmental 
relations, Particulate matter.

40 CFR Part 51

    Environmental protection, Air pollution control, Intergovernmental 
relations, Particulate matter.

40 CFR Part 93

    Environmental protection, Air pollution control, Intergovernmental 
relations, Particulate matter.

    Dated: March 10, 2015.
Gina McCarthy,
Administrator.

    For the reasons stated in the preamble, Title 40, Chapter I of the 
Code of Federal Regulations is proposed to be amended as follows:

PART 50--NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY 
STANDARDS

0
1. The authority citation for part 50 continues to read as follows:

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

0
2. In Sec.  50.13, add paragraph (d) to read as follows:

Sec.  50.13  National primary and secondary ambient air quality 
standards for PM2.5.

* * * * *
    (d) The standards set forth in this section will remain applicable 
to all areas notwithstanding the promulgation of the 2012 primary 
annual PM2.5 national ambient air quality standards (NAAQS) 
in Sec.  50.18. The 1997 primary annual PM2.5 NAAQS set 
forth in this section will no longer apply to an area 1 year after the 
effective date of the designation of that area, pursuant to section 107 
of the Clean Air Act, for the primary annual PM2.5 NAAQS set 
forth in Sec.  50.18; except that for areas designated nonattainment 
for the 1997 annual PM2.5 NAAQS set forth in this section as 
of 1 year after the effective date of the designations for the primary 
annual PM2.5 NAAQS established in Sec.  50.18, the 
requirements applicable to the 1997 annual PM2.5 NAAQS set 
forth in this section will apply until the effective date of an area's 
redesignation to attainment for the 1997 annual NAAQS pursuant to the 
requirements of section 107 of the Clean Air Act. The 1997 secondary 
annual PM2.5 NAAQS and the 1997 24-hour PM2.5 
NAAQS shall remain in effect.

PART 51--REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF 
IMPLEMENTATION PLANS

0
3. The authority citation for part 51 continues to read as follows:

    Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

Subpart I--Review of New Sources and Modifications

0
4. In Sec.  51.165:
0
a. Revise paragraphs (a)(1)(iv)(A)(1), (a)(1)(x)(A), and 
(a)(1)(xxxvii)(C)(2);
0
b. Remove paragraphs (a)(1)(xxxvii)(C)(3), and (4); and
0
d. Revise paragraphs (a)(2)(i) and (a)(2)(ii)(A).
    The revisions read as follows:

Sec.  51.165  Permit requirements.

    (a) * * *
    (1) * * *
    (iv)(A) * * *
    (1) Any stationary source of air pollutants that emits, or has the 
potential to emit, 100 tons per year or more of any regulated NSR 
pollutant (as defined in paragraph (a)(1)(xxxvii) of this section), 
except that lower emissions thresholds shall apply in areas subject to 
subpart 2, subpart 3, or subpart 4 of part D, title I of the Act, 
according to paragraphs (a)(1)(iv)(A)(1)(i) through (viii) of this 
section.
    (i) 50 tons per year of volatile organic compounds in any serious 
ozone nonattainment area.

[[Page 15463]]

    (ii) 50 tons per year of volatile organic compounds in an area 
within an ozone transport region, except for any severe or extreme 
ozone nonattainment area.
    (iii) 25 tons per year of volatile organic compounds in any severe 
ozone nonattainment area.
    (iv) 10 tons per year of volatile organic compounds in any extreme 
ozone nonattainment area.
    (v) 50 tons per year of carbon monoxide in any serious 
nonattainment area for carbon monoxide, where stationary sources 
contribute significantly to carbon monoxide levels in the area (as 
determined under rules issued by the Administrator).
    (vi) 70 tons per year of PM10 in any serious 
nonattainment area for PM10.
    (vii) 70 tons per year of PM2.5 in any serious 
nonattainment area for PM2.5.
    (viii) 70 tons per year of any precursor for PM2.5 in 
any serious nonattainment area for PM2.5.
* * * * *
    (x)(A) Significant means, in reference to a net emissions increase 
or the potential of a source to emit any of the following pollutants, a 
rate of emissions that would equal or exceed any of the following 
rates:

Pollutant Emission Rate

Carbon monoxide: 100 tons per year (tpy)
Nitrogen oxides: 40 tpy
Sulfur dioxide: 40 tpy
Ozone: 40 tpy of volatile organic compounds or nitrogen oxides
Lead: 0.6 tpy
PM10: 15 tpy
PM2.5: 10 tpy of direct PM2.5 emissions; 40 tpy 
of sulfur dioxide emissions; 40 tpy of nitrogen oxide emissions; 40 tpy 
of VOC emissions;
* * * * *
    (xxxvii) * * *
    (C) * * *
    (2) Sulfur dioxide, nitrogen oxides, volatile organic compounds and 
ammonia are precursors to PM2.5 in any PM2.5 
nonattainment area, unless the State demonstrates to the 
Administrator's satisfaction or the EPA demonstrates that major 
stationary sources of a particular precursor do not contribute 
significantly to PM2.5 levels that exceed the 
PM2.5 ambient standards in a particular area.
* * * * *
    (2) Applicability procedures. (i) Each plan shall adopt a 
preconstruction review program to satisfy the requirements of sections 
172(c)(5) and 173 of the Act for any area designated nonattainment for 
any national ambient air quality standard under subpart C of 40 CFR 
part 81. Such a program shall apply to any new major stationary source 
or major modification that is major for the pollutant (as defined in 
paragraph (a)(1)(xxxvii) of this section) for which the area is 
designated nonattainment under section 107(d)(1)(A)(i) of the Act, if 
the stationary source or modification would locate anywhere in the 
designated nonattainment area. Different pollutants, including 
individual precursors, are not summed to determine applicability of a 
major stationary source or major modification.
    (ii) * * *
    (A) Except as otherwise provided in paragraphs (a)(2)(iii) and (iv) 
of this section, and consistent with the definition of major 
modification contained in paragraph (a)(1)(v)(A) of this section, a 
project is a major modification for a regulated NSR pollutant (as 
defined in paragraph (a)(1)(xxxvii) of this section), if it causes two 
types of emissions increases--a significant emissions increase (as 
defined in paragraph (a)(1)(xxvii) of this section), and a significant 
net emissions increase (as defined in paragraphs (a)(1)(vi) and (x) of 
this section). The project is not a major modification if it does not 
cause a significant emissions increase. If the project causes a 
significant emissions increase, then the project is a major 
modification only if it also results in a significant net emissions 
increase.
* * * * *
0
5. In Appendix S to part 51:
0
a. Revise paragraph II.A.4.(i)(a) introductory text;
0
b. Add paragraphs II.A.4.(a)(7) and (8); and
0
c. Revise paragraphs II.A.10.(i) and II.A.31.(ii)(b)(2).
    The revisions and addition read as follows:

Appendix S to Part 51--Emission Offset Interpretative Ruling

* * * * *
    II. * * *
    A. * * *
    4. (i) * * *
    (a) Any stationary source of air pollutants which emits, or has 
the potential to emit, 100 tons per year or more of a regulated NSR 
pollutant (as defined in paragraph II.A.31 of this Ruling), subject 
to regulation under the Act, except that lower emissions thresholds 
shall apply in areas subject to subpart 2, subpart 3, or subpart 4 
of part D, title I of the Act, according to paragraphs 
II.A.4(i)(a)(1) through (6) of this ruling.
* * * * *
    (7) 70 tons per year of PM2.5 in any serious 
nonattainment area for PM2.5.
    (8) 70 tons per year of any PM2.5 precursor (as 
defined in paragraph II.A.31 of this Ruling) in any Serious 
nonattainment area for PM2.5.
* * * * *
    10. (i) Significant means, in reference to a net emissions 
increase or the potential of a source to emit any of the following 
pollutants, a rate of emissions that would equal or exceed any of 
the following rates:

Pollutant and Emissions Rate

Carbon monoxide: 100 tons per year (tpy)
Nitrogen oxides: 40 tpy
Sulfur dioxide: 40 tpy
Ozone: 40 tpy of volatile organic compounds or nitrogen oxides
Lead: 0.6 tpy
Particulate matter: 25 tpy of particulate matter emissions
PM10: 15 tpy
PM2.5: 10 tpy of direct PM2.5 emissions; 40 
tpy of sulfur dioxide emissions; 40 tpy of nitrogen oxides emissions
* * * * *
    31. * * *
    (ii) * * *
    (b) * * *
    (2) Sulfur dioxide and nitrogen oxides are precursors to 
PM2.5 in all PM2.5 nonattainment areas.
* * * * *
0
6. Revise subpart Z to read as follows:

Subpart Z--Provisions for Implementation of PM2.5 
National Ambient Air Quality Standards

Sec.
51.1000 Definitions.
51.1001 Applicability of part 51.
51.1002 Classifications.
51.1003 Attainment plan submittals and due dates.
51.1004 Attainment dates.
51.1005 Attainment date extensions.
51.1006 Requirements for demonstrating insignificant contribution of 
PM2.5 precursors.
51.1007 Requirements for de minimis source category determinations 
for direct PM2.5 and PM2.5 precursors.
51.1008 Emissions inventory requirements.
51.1009 Moderate area attainment plan control strategy requirements.
51.1010 Serious area attainment plan control strategy requirements.
51.1011 Attainment demonstration and modeling requirements.
51.1012 Reasonable further progress (RFP) requirements.
51.1013 Quantitative milestone requirements.
51.1014 Contingency measures requirements.
51.1015 Clean data requirements.

Sec.  51.1000  Definitions.

    The following definitions apply for purposes of this subpart. Any 
term not defined herein shall have the meaning as defined in 40 CFR 
51.100 or Clean Air Act section 302.
    Act means the Clean Air Act as codified at 42 U.S.C. 7401-7671q 
(2003).

[[Page 15464]]

    Additional feasible measure is any control measure that otherwise 
meets the definition of ``best available control measure'' (BACM) but 
can only be implemented in whole or in part beginning 4 years after the 
date of reclassification of an area as Serious and no later than the 
statutory attainment date for the area.
    Additional reasonable measure is any control measure that otherwise 
meets the definition of ``reasonably available control measure'' (RACM) 
but can only be implemented in whole or in part during the period 
beginning 4 years after the date of designation of a nonattainment area 
and no later than the end of the sixth calendar year following the date 
of designation of the area.
    Applicable annual standard is the annual PM2.5 NAAQS 
established, revised, or retained as a result of a particular 
PM2.5 NAAQS review.
    Applicable attainment date means the latest statutory date by which 
an area is required to attain a particular PM2.5 NAAQS, 
unless EPA has approved an attainment plan for the area to attain such 
NAAQS, in which case the applicable attainment date is the date 
approved under such attainment plan. If EPA grants an extension of an 
approved attainment date, then the applicable attainment date for the 
area shall be the extended date.
    Applicable 24-hour standard is the 24-hour PM2.5 NAAQS 
established, revised, or retained as a result of a particular 
PM2.5 NAAQS review.
    Attainment projected inventory means the projected emissions of 
direct PM2.5 and all PM2.5 precursors from 
sources included in the base year inventory, and from any additional 
sources of such emissions expected within the boundaries of the 
nonattainment area by the projected attainment date for the area.
    Base year inventory means the actual emissions of direct 
PM2.5 and all PM2.5 precursors from all sources 
within the boundaries of a nonattainment area in one of the 3 years 
used for purposes of designations or another technically appropriate 
year.
    Benchmark RFP analysis means the analysis submitted as part of the 
RFP plan for a PM2.5 nonattainment area that requires 
generally linear emissions reductions in direct PM2.5 and in 
each PM2.5 precursor from the base year through the 
projected attainment year.
    Best available control measure (BACM) is any technologically and 
economically feasible control measure that can be implemented in whole 
or in part within 4 years after the date of reclassification of a 
PM2.5 nonattainment area and that generally can achieve 
greater permanent and enforceable emissions reductions in direct 
PM2.5 emissions and/or emissions of PM2.5 
precursors from sources in the area than can be achieved through the 
implementation of RACM on the same source(s). BACM includes best 
available control technology (BACT).
    Date of designation means the effective date of a PM2.5 
area designation as promulgated by the Administrator.
    Date of reclassification means the effective date of a 
PM2.5 area reclassification from Moderate to Serious as 
promulgated by the Administrator.
    Direct PM2.5 emissions means solid particles emitted directly from 
an air emissions source or activity, or gaseous emissions or liquid 
droplets from an air emissions source or activity which condense to 
form particulate matter at ambient temperatures. Direct 
PM2.5 emissions include filterable and condensable 
PM2.5 emissions composed of elemental carbon, directly 
emitted organic carbon, directly emitted sulfate, directly emitted 
nitrate, and other inorganic particles (including but not limited to 
crustal material, metals, and sea salt).
    Existing control measure means any federally enforceable national, 
state, or local control measure that results in reductions in direct 
PM2.5 emissions or emissions of PM2.5 precursors 
in a nonattainment area in that state.
    Implemented means adopted by the state and fully approved into the 
SIP by EPA for the nonattainment area; built, installed, and/or 
otherwise physically manifested; and, fully complied with by the 
affected sources.
    Most stringent measure (MSM) is any permanent and enforceable 
control measure that achieves the most stringent emissions reductions 
in direct PM2.5 emissions and/or emissions of 
PM2.5 precursors from among those control measures which are 
either included in any other SIP for any NAAQS or have been achieved in 
practice by any state and that can feasibly be implemented in the 
relevant PM2.5 NAAQS nonattainment area.
    PM2.5 design value (DV) for a PM2.5 nonattainment area 
is the highest of the three-year average concentrations calculated for 
the ambient air quality monitors in the area, in accordance with 40 CFR 
part 50, appendix N.
    PM2.5 NAAQS are the fine particulate matter National Ambient Air 
Quality Standards codified at 40 CFR part 50.
    PM2.5 precursors are sulfur dioxide (SO2), oxides of 
nitrogen (NOX), volatile organic compounds (VOC), and 
ammonia (NH3).
    Reasonably available control measure (RACM) is any technologically 
and economically feasible measure that can be implemented in whole or 
in part within 4 years after the date of designation of a 
PM2.5 nonattainment area and that achieves permanent and 
enforceable reductions in direct PM2.5 emissions and/or 
PM2.5 precursor emissions from sources in the area. RACM 
includes reasonably available control technology (RACT).
    Reasonable further progress (RFP) means such annual incremental 
reductions in emissions of direct PM2.5 and PM2.5 
precursors regulated in the attainment plan as are required for the 
purpose of ensuring attainment of the applicable PM2.5 NAAQS 
in a nonattainment area by the applicable attainment date.
    Subpart 1 means subpart 1 of part D of title I of the Act.
    Subpart 4 means subpart 4 of part D of title I of the Act.

Sec.  51.1001  Applicability of part 51.

    The provisions in subparts A through X of this part apply to areas 
for purposes of the PM2.5 NAAQS to the extent they are not 
inconsistent with the provisions of this subpart.

Sec.  51.1002  Classifications.

    (a) Initial classification as Moderate PM2.5 nonattainment area. 
Any area designated nonattainment for a PM2.5 NAAQS shall be 
classified at the time of such designation, by operation of law, as a 
Moderate PM2.5 nonattainment area.
    (b) Reclassification as Serious PM2.5 nonattainment area. A 
Moderate nonattainment area shall be reclassified to Serious under the 
following circumstances:
    (1) The EPA shall reclassify as Serious through notice-and-comment 
rulemaking any Moderate PM2.5 nonattainment area that the 
EPA determines cannot practicably attain a particular PM2.5 
NAAQS by the applicable Moderate area attainment date.
    (2) A Moderate PM2.5 nonattainment area shall be 
reclassified by operation of law as a Serious nonattainment area if the 
EPA finds through notice-and-comment rulemaking that the area failed to 
attain a particular PM2.5 NAAQS by the applicable Moderate 
area attainment date.

Sec.  51.1003  Attainment plan submittals and due dates.

    (a) Nonattainment areas initially classified as Moderate.
    (1) For any area designated as nonattainment and initially 
classified as Moderate for a PM2.5 NAAQS, the

[[Page 15465]]

state(s) shall submit a Moderate area attainment plan that meets all of 
the following requirements:
    (i) Emissions inventory requirements set forth at Sec.  
51.1008(a)(1);
    (ii) Emissions inventory requirements set forth at Sec.  
51.1008(a)(2);
    (iii) Moderate area attainment plan control strategy requirements 
set forth at Sec.  51.1009;
    (iv) Attainment demonstration and modeling requirements set forth 
at Sec.  51.1011;
    (v) Reasonable Further Progress (RFP) requirements set forth at 
Sec.  51.1012;
    (vi) Quantitative milestone requirements set forth at Sec.  
51.1013;
    (vii) Contingency measure requirements set forth at Sec.  51.1014; 
and,
    (viii) Nonattainment new source review plan requirements pursuant 
to section 189(a)(1)(A) and section 172(c)(5) of the CAA.
    (2) The state(s) shall submit its Moderate area attainment plan to 
EPA no later than 18 months from the date of designation of the area.
    (b) Nonattainment areas reclassified to Serious.
    (1) For any nonattainment area reclassified to Serious for a 
PM2.5 NAAQS under Sec.  51.1002(b), in addition to meeting 
the Moderate area attainment plan submittal requirements set forth at 
Sec.  51.1003(a), the state(s) shall submit a Serious area attainment 
plan that meets all of the following requirements:
    (i) Emissions inventory requirements set forth at Sec.  
51.1008(b)(1);
    (ii) Emissions inventory requirements set forth at Sec.  
51.1008(b)(2);
    (iii) Serious area attainment plan control strategy requirements 
set forth at Sec.  51.1010;
    (iv) Attainment demonstration and modeling requirements set forth 
at Sec.  51.1011;
    (v) Reasonable Further Progress (RFP) requirements set forth at 
Sec.  51.1012;
    (vi) Quantitative milestone requirements set forth at Sec.  
51.1013;
    (vii) Contingency measure requirements set forth at Sec.  51.1014; 
and,
    (viii) Nonattainment new source review plan requirements pursuant 
to section 189(b)(3) and section 172(c)(5) of the CAA.
    (2) The state(s) shall submit its Serious area attainment plan to 
EPA according to the following schedule:
    (i) For any nonattainment area reclassified to Serious for a 
particular PM2.5 NAAQS under Sec.  51.1002(b)(1), the 
state(s) shall submit to EPA the portion of the Serious area attainment 
plan that meets the requirements set forth at paragraphs (b)(1)(i), 
(iii) and (viii) of this section no later than 18 months from the date 
of reclassification. The state(s) shall submit to EPA the portion of 
the Serious area attainment plan that meets the requirements set forth 
at paragraphs (b)(1)(ii) and (b)(1)(iv) through (vii) of this section 
to EPA no later than 4 years from the date of reclassification.
    (ii) For any nonattainment area reclassified to Serious for a 
particular PM2.5 NAAQS under Sec.  51.1002(b)(2), the 
state(s) shall submit to EPA a Serious area attainment plan meeting the 
requirements set forth at paragraphs (b)(1)(i) through (viii) of this 
section no later than 18 months from the date of reclassification.
    (iii) If the state(s) submits to EPA a request for a Serious area 
attainment date extension simultaneous with the Serious area attainment 
plan due under paragraph (b)(1) of this section, such a plan shall meet 
the most stringent measure (MSM) requirements set forth at Sec.  
51.1010(b) in addition to the BACM and BACT and additional feasible 
measure requirements set forth at Sec.  51.1010(a).
    (c) Serious nonattainment areas subject to CAA section 189(d) for 
failing to attain the PM2.5 NAAQS by the applicable Serious 
area attainment date.
    (1) For any Serious nonattainment area that fails to attain a 
particular PM2.5 NAAQS by the applicable Serious area 
attainment date, the state(s) shall submit a revised Serious area 
attainment plan that demonstrates that the area annually will achieve 
at least 5 percent reductions in emissions of direct PM2.5 
and PM2.5 precursors based on the most recent emissions 
inventory for the area and that meets the following requirements:
    (i) Emissions inventory requirements set forth at Sec.  
51.1008(c)(1);
    (ii) Emissions inventory requirements set forth at Sec.  
51.1008(c)(2);
    (iii) Demonstration of attainment and modeling requirements set 
forth at Sec.  51.1011;
    (iv) Reasonable Further Progress (RFP) requirements set forth at 
Sec.  51.1012;
    (v) Quantitative milestone requirements set forth at Sec.  51.1013; 
and,
    (vi) Contingency measure requirements set forth at Sec.  51.1014.
    (2) The state(s) shall submit to EPA the revised attainment plan 
meeting the requirements set forth at paragraphs (c)(1)(i) through (vi) 
of this section no later than 12 months from the missed applicable 
Serious area attainment date.
    (d) Any attainment plan submitted to EPA under this section shall 
establish motor vehicle emissions budgets for the projected attainment 
year for the area, if applicable. The state shall develop such budgets 
according to the requirements of the transportation conformity rule as 
they apply to PM2.5 nonattainment areas (40 CFR part 93).

Sec.  51.1004  Attainment dates.

    (a) The state shall submit a projected attainment date as part of 
its attainment plan submission under Sec.  51.1003 for any 
PM2.5 NAAQS nonattainment area located in whole or in part 
within its boundaries. The state shall justify the projected attainment 
date for each such nonattainment area (or portion of a nonattainment 
area) as part of the demonstration of attainment developed and 
submitted according to the requirements set forth at Sec.  51.1011 and 
according to the following:
    (1) Nonattainment areas initially classified as Moderate.
    (i) Except for nonattainment areas that meet the criterion under 
paragraph (a)(1)(ii) of this section, the projected attainment date for 
a Moderate PM2.5 nonattainment area shall be as expeditious 
as practicable with the implementation of all control measures required 
under Sec.  51.1009 and may be as late as the end of the sixth calendar 
year after the date of designation if the state demonstrates that the 
implementation of certain control measures that qualify as RACM or RACT 
or additional reasonable measures, but that are not necessary for 
demonstrating attainment by the end of the sixth calendar year after 
the date of designation, will not collectively advance the attainment 
date by at least 1 year.
    (ii) The projected attainment date for a Moderate PM2.5 
nonattainment area which the state demonstrates cannot practicably 
attain the applicable PM2.5 NAAQS by the end of the sixth 
calendar year after the date of designation of the area with the 
implementation of all control measures required under Sec.  51.1009 
shall be such date unless and until the area is reclassified as Serious 
according to Sec.  51.1002.
    (2) Nonattainment areas reclassified to Serious.
    (i) Except for nonattainment areas that meet the criterion under 
paragraph (a)(2)(ii) of this section, the projected attainment date for 
a Serious PM2.5 nonattainment area shall be as expeditious 
as practicable with the implementation of all control measures required 
under Sec.  51.1010 but no later than the end of the tenth calendar 
year after the date of designation.

[ALTERNATIVE PROPOSED REGULATORY TEXT]

    (i) Except for nonattainment areas that meet the criterion under 
paragraph (a)(2)(ii) of this section, the projected attainment date for 
a Serious PM2.5 nonattainment area shall be as

[[Page 15466]]

expeditious as practicable with the implementation of all control 
measures required under Sec.  51.1010 and may be as late as the end of 
the tenth calendar year after the date of designation if the state 
demonstrates that the implementation of certain control measures that 
qualify as BACM or BACT or additional feasible measures, but that are 
not necessary for demonstrating attainment by the end of the tenth 
calendar year after the date of designation, will not collectively 
advance the attainment date by at least 1 year.]
    (ii) A state that submits an attainment plan that demonstrates that 
a Serious PM2.5 nonattainment area cannot practicably attain 
the PM2.5 NAAQS by the end of the tenth calendar year 
following the date of designation of the area with the implementation 
of all control measures required under Sec.  51.1010(a) must request an 
extension of the Serious area attainment date consistent with Sec.  
51.1005(b). The request must propose a projected attainment date for 
the nonattainment area that is as expeditious as practicable, but no 
later than the end of the fifteenth calendar year from the date of 
designation of the area.
    (3) Serious nonattainment areas subject to CAA section 189(d) for 
failing to attain by the applicable Serious area attainment date. The 
projected attainment date for a Serious PM2.5 nonattainment 
area that failed to attain the PM2.5 NAAQS by the applicable 
Serious area attainment date shall be as expeditious as practicable 
based on annual reductions in direct PM2.5 and significant 
PM2.5 precursor emissions within the area of not less than 5 
percent of the amount of such emissions as reported in the most recent 
emissions inventory prepared for the area, but no later than 5 years 
following the missed Serious area attainment date.
    (b) Except for attainment plans that meet the conditions of 
paragraphs (a)(1)(ii) or (a)(3) of this section, the Administrator 
shall approve an attainment date at the same time and in the same 
manner in which the Administrator approves the attainment plan for the 
area.
    (1) In accordance with paragraph (a)(1)(ii) of this section, if a 
state demonstrates that a Moderate PM2.5 nonattainment area 
cannot practicably attain the PM2.5 NAAQS by the end of the 
sixth calendar year following the date of designation of the area, EPA 
shall proceed under the provisions of Sec.  51.1002(b)(1) to reclassify 
the area to Serious through notice-and-comment rulemaking.
    (2) In accordance with paragraph (a)(3) of this section, if a 
Serious PM2.5 nonattainment area fails to attain the 
PM2.5 NAAQS by the applicable Serious area attainment date, 
EPA will proceed to establish a new attainment date through a direct 
final action published in the Federal Register.

Sec.  51.1005  Attainment date extensions.

    (a) Nonattainment areas initially classified as Moderate.
    (1) A state with a Moderate PM2.5 nonattainment area may 
apply for a 1-year attainment date extension for the area if the 
following conditions are met in the year preceding the applicable 
attainment date for the area:
    (i) The state has complied with all requirements and commitments 
pertaining to the area in the applicable implementation plan;
    (ii) For an area designated nonattainment for a particular 24-hour 
PM2.5 NAAQS for which the state seeks an attainment date 
extension, the 98th percentile concentration at each monitor in the 
area for the calendar year prior to the applicable attainment date is 
less than or equal to the level of the applicable 24-hour standard 
(calculated according to the data analysis requirements in 40 CFR part 
50, appendix N);
    (iii) For an area designated nonattainment for a particular annual 
PM2.5 NAAQS for which the state seeks an attainment date 
extension, the annual average concentration at each monitor in the area 
for the calendar year prior to the applicable attainment date is less 
than or equal to the level of the applicable annual standard 
(calculated according to the data analysis requirements in 40 CFR part 
50, appendix N).
    (2) The applicable implementation plan for a Moderate 
PM2.5 nonattainment area for which a state seeks an 
attainment date extension is the plan submitted to EPA to meet the 
requirements of Sec.  51.1003(a).
    (3) For a Moderate PM2.5 nonattainment area, the 
requesting state (or states) shall submit a written request by February 
28 of the year following the applicable attainment date for the area.
    (4) A state with a Moderate area that received an initial 1-year 
attainment date extension may apply for a second 1-year attainment date 
extension for the area if the state meets the conditions described in 
paragraph (a)(1) of this section in the year preceding the approved 
attainment date.
    (b) Nonattainment areas reclassified as Serious.
    (1) A state may apply for one attainment date extension not to 
exceed 5 years for a Serious nonattainment area if the following 
conditions are met:
    (i) The state demonstrates that attainment of the applicable 
PM2.5 NAAQS by the approved attainment date for the area 
would be impracticable or, in the absence of an approved attainment 
date, attainment of the applicable PM2.5 NAAQS by the 
applicable statutory attainment date for the area would be 
impracticable;
    (ii) The state has complied with all requirements and commitments 
pertaining to the area in the applicable implementation plan; and,
    (iii) The state demonstrates that the attainment plan for the area 
includes the most stringent measures (MSM) that are included in the 
attainment plan of any state or are achieved in practice in any state, 
and can feasibly be implemented in the area consistent with Sec.  
51.1010(b).
    (2) At the time of application for an attainment date extension, 
the state shall submit to EPA a Serious area attainment plan that meets 
the following requirements:
    (i) Emissions inventory requirements set forth at Sec.  51.1008(b);
    (ii) Most stringent measures (MSM) requirement described under 
paragraph (b)(1)(iii) of this section and Sec.  51.1010(b);
    (iii) Attainment demonstration and modeling requirements set forth 
at Sec.  51.1011 that justify the state's conclusion under paragraph 
(b)(1)(i) of this section;
    (iv) Reasonable Further Progress (RFP) requirements set forth at 
Sec.  51.1012;
    (v) Quantitative milestone requirements set forth at Sec.  51.1013; 
and,
    (vi) Contingency measure requirements set forth at Sec.  51.1014.
    (3) The applicable implementation plan for a Serious 
PM2.5 nonattainment area for which a state seeks an 
attainment date extension under Sec.  51.1004(a)(2)(ii) is the plan 
submitted to EPA to meet the requirements set forth at Sec.  
51.1003(a).
    (4) The applicable implementation plan for a Serious 
PM2.5 nonattainment area for which a state seeks an 
attainment date extension under Sec.  51.1004(a)(2)(i) is the plan 
submitted to EPA to meet the requirements set forth at Sec.  
51.1003(b)(1).
    (5) A state applying for an attainment date extension for a Serious 
nonattainment area under Sec.  51.1004(a)(2)(ii) shall submit to EPA a 
request for an extension at the same time as it submits the Serious 
area attainment plan due under Sec.  51.1003(b)(1).
    (6) A state applying for an attainment date extension for a Serious 
nonattainment area subsequent to submitting an initial Serious area 
attainment plan that demonstrated

[[Page 15467]]

attainment of the NAAQS by the applicable attainment date consistent 
with Sec.  51.1004(a)(2)(i) at the time of submittal may apply for such 
an extension no later than 60 calendar days prior to the approved 
attainment date for the area or, in the absence of an approved 
attainment date, no later than 60 calendar days prior to the applicable 
statutory attainment date for the area.
    (c) Serious nonattainment areas subject to CAA section 189(d) for 
failing to attain by the applicable Serious area attainment date. If a 
Serious area fails to attain a particular PM2.5 NAAQS by the 
applicable Serious area attainment date, the area is then subject to 
the requirements of section 189(d) of the Act, and, for this reason, 
the state is prohibited from requesting an extension of the applicable 
Serious area attainment date for such area.
    (d) For any attainment date extension request submitted pursuant to 
this section, the requesting state (or states) shall submit a written 
request and evidence of compliance with these regulations which 
includes both of the following:
    (i) Evidence that all control measures submitted in the applicable 
attainment plan have been implemented, and
    (ii) Evidence that the area has made emission reduction progress 
that represents reasonable further progress toward timely attainment of 
the applicable PM2.5 NAAQS.
    (e) For a PM2.5 nonattainment area located in two or 
more states or jurisdictions, all states and/or jurisdictions in which 
such area is located shall submit separate attainment date extension 
requests for the area consistent with the requirements set forth at 
paragraph (d) of this section.

Sec.  51.1006  Requirements for demonstrating insignificant 
contribution of PM2.5 precursors.

    (a) For purposes of determining that a particular PM2.5 
precursor does not contribute significantly to ambient PM2.5 
concentrations in a PM2.5 nonattainment area, the state 
shall conduct a technical analysis that accounts for all emissions of 
such PM2.5 precursor from all sources located within the 
area.
    (b) The state shall submit results and supporting documentation for 
any technical analyses conducted pursuant to paragraph (a) of this 
section as part of any attainment plan for the area.

Sec.  51.1007  Requirements for de minimis source category 
determinations for direct PM2.5 and PM2.5 
precursors.

    (a) All categories of sources of direct PM2.5 emissions 
and of emissions of PM2.5 precursors in a PM2.5 
nonattainment area shall be considered non-de minimis unless and until 
the state conducts a technical analysis to determine whether a 
particular source category may qualify for a presumptive de minimis 
source category exemption from evaluation for potential control 
measures due to its minimal contribution to the ambient 
PM2.5 concentrations in the area.
    (b) The state shall define source categories for stationary sources 
classified under the North American Industry Classification System 
(NAICS) at the level represented by four (4) digits or fewer.
    (c) The state shall define a single source category for on-road 
mobile sources, including on-road vehicles and engines, and a single 
source category for nonroad mobile sources, including nonroad engines, 
equipment, and vehicles, or may define a single source category for all 
mobile sources in the aggregate.

Sec.  51.1008  Emissions inventory requirements.

    (a) For any nonattainment area initially classified as Moderate, 
the state shall submit to EPA all of the following:
    (1) A base year inventory for the nonattainment area for all 
emissions sources that meets the following minimum criteria:
    (i) The inventory year shall be one of the 3 years used for 
designations or another technically appropriate inventory year if 
justified by the state in the plan submission.
    (ii) The inventory shall include actual emissions of all sources 
within the nonattainment area.
    (iii) The emissions values shall be either annual total emissions 
or average-season-day emissions. The state shall include as part of the 
plan a rationale for providing annual or seasonal emissions.
    (iv) The inventory shall include direct PM2.5 emissions 
and emissions of all PM2.5 precursors.
    (v) The state shall report emissions as point sources according to 
the point source emissions thresholds of the Air Emissions Reporting 
Rule (AERR), 40 CFR part 51, subpart A.
    (vi) The detail of the emissions inventory shall be consistent with 
the data elements required by 40 CFR part 51, subpart A.
    (2) An attainment projected inventory for the nonattainment area 
that meets the following minimum criteria:
    (i) The year of the projected inventory shall be the most 
expeditious year for which attainment is demonstrated by the modeled 
attainment plan.
    (ii) The emissions values shall be projected emissions of the same 
sources included in the base year inventory for the nonattainment area 
(i.e., those only within the nonattainment area). The state shall 
include in this inventory projected emissions growth and contraction 
from both controls and other causes during the relevant period.
    (iii) The temporal period of emissions shall be the same temporal 
period (annual or average-season-day) as the base year inventory for 
the nonattainment area.
    (iv) Consistent with the base year inventory for the nonattainment 
area, the inventory shall include direct PM2.5 emissions and 
emissions of all PM2.5 precursors.
    (v) The same sources reported as point sources in the base year 
inventory for the nonattainment area shall be provided as point sources 
in the attainment projected inventory for the nonattainment area. 
Nonpoint and mobile source projected emissions shall be provided using 
the same detail (e.g., state, county, and process codes) as the base 
year inventory.
    (vi) The same detail of the emissions included shall be consistent 
with the level of detail in the base year inventory (i.e., as required 
by 40 CFR part 41, subpart A).
    (b) For any nonattainment area reclassified as Serious, the state 
shall submit to EPA all of the following:
    (1) For purposes of meeting the emissions inventory requirements of 
CAA section 172(c)(3), a base year inventory for the nonattainment area 
for all emissions sources that meets the requirements listed under 
paragraph (a)(1) of this section, and in addition, uses the Serious 
area definition of a major source listed under Sec.  
51.165(a)(1)(iv)(A)(vii) and (viii) in determining sources to include 
as point sources.
    (2) An attainment projected inventory for the nonattainment area 
that meets the criteria listed under paragraph (a)(2) of this section.
    (c) Serious nonattainment areas subject to CAA section 189(d) for 
failing to attain a PM2.5 NAAQS by the applicable Serious 
area attainment date. No later than 12 months after EPA finds through 
notice-and-comment rulemaking that a Serious nonattainment area, or 
portion thereof contained within a state's borders, fails to attain a 
PM2.5 NAAQS by the applicable attainment date and thus 
becomes subject to the requirements under CAA section 189(d), the state 
shall submit to EPA all of the following:
    (1) For purposes of meeting the emissions inventory requirements of

[[Page 15468]]

CAA section 172(c)(3), a base year inventory for the nonattainment area 
for all emissions sources that meets the requirements listed under 
paragraph (a)(1) of this section, and in addition, uses the Serious 
area definition of a major source listed under Sec.  
51.165(a)(1)(iv)(A)(vii) and (viii) in determining sources to include 
as point sources.
    (2) An attainment projected inventory for the nonattainment area as 
defined by Sec.  51.1000(e) and that meets the criteria listed under 
paragraph (a)(2) of this section.

Sec.  51.1009  Moderate area attainment plan control strategy 
requirements.

    (a) The state shall identify, adopt, and implement control 
measures, including control technologies, on sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors located in any Moderate PM2.5 nonattainment area 
or portion thereof located within the state consistent with the 
following:
    (1) The state shall identify all sources of direct PM2.5 
emissions and all sources of emissions of PM2.5 precursors 
in the nonattainment area in accordance with the emissions inventory 
requirements of Sec.  51.1008(a);
    (2) The state shall identify all potential control measures to 
reduce emissions from all sources of direct PM2.5 emissions 
and all sources of emissions of PM2.5 precursors in the 
nonattainment area identified under paragraph (a)(1) of this section.
    (i) The state may elect not to identify potential control measures 
to reduce emissions from any sources of a particular PM2.5 
precursor if the state demonstrates that all sources of such 
PM2.5 precursor contribute insignificantly to ambient 
PM2.5 concentrations in the area under Sec.  51.1006.
    (ii) The state may elect not to identify potential control measures 
to reduce emissions from sources in any source category of direct 
PM2.5 emissions or emissions of PM2.5 precursors 
determined to be a de minimis source category under Sec.  51.1007.
    (3) For any potential control measure identified under paragraph 
(a)(2) of this section, the state may make a demonstration that such 
measure is not technologically or economically feasible to implement in 
whole or in part by the end of the sixth calendar year following the 
date of designation of the area, and the state may eliminate such whole 
or partial measure from further consideration under this paragraph.
    (i) For purposes of evaluating the technological feasibility of a 
potential control measure, the state may consider factors including but 
not limited to a source's processes and operating procedures, raw 
materials, physical plant layout, and potential environmental impacts 
such as increased water pollution, waste disposal, and energy 
requirements.
    (ii) For purposes of evaluating the economic feasibility of a 
potential control measure, the state may consider factors including but 
not limited to capital costs, operating and maintenance costs, and cost 
effectiveness of the measure.
    (iii) The state must submit to EPA as part of its Moderate area 
attainment plan a detailed written justification for eliminating from 
further consideration any potential control measure identified under 
paragraph (a)(2) of this section on the basis of technological or 
economic infeasibility.
    (4) The state shall use air quality modeling that meets the 
requirements of Sec.  51.1011(a) and that accounts for emissions 
reductions estimated due to all technologically and economically 
feasible control measures identified for sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors in the Moderate PM2.5 nonattainment area to 
demonstrate that the area can attain the applicable PM2.5 
NAAQS as expeditiously as practicable but no later than the end of the 
sixth year following the date of designation of the area, or to 
demonstrate that the Moderate PM2.5 nonattainment area 
cannot practicably attain the applicable PM2.5 NAAQS by such 
date.
    (i) If the state demonstrates through air quality modeling that the 
area can attain the applicable PM2.5 NAAQS by the end of the 
sixth calendar year following the date of designation of the area, the 
state shall adopt and implement all technologically and economically 
feasible control measures identified under paragraph (a)(3) of this 
section that are necessary to bring the area into attainment by such 
date. The state shall also adopt and implement all other 
technologically and economically feasible measures identified under 
paragraph (a)(3) of this section that, when considered collectively, 
would advance the attainment date for the area by at least 1 year.
    (A) Any control measure identified for adoption and implementation 
under this paragraph that can be implemented in whole or in part by 4 
years after the date of designation of the Moderate PM2.5 
nonattainment area shall be considered RACM for the area. Any such 
control measure that is also a control technology shall be considered 
RACT for the area.
    (B) Any control measure identified for adoption and implementation 
under this paragraph that can only be implemented in whole or in part 
during the period beginning 4 years after the date of designation of 
the Moderate PM2.5 nonattainment area and the beginning of 
the calendar year containing the applicable attainment date for the 
area shall be considered an additional reasonable measure for the area.
    (ii) If the state demonstrates through air quality modeling that 
the area cannot practicably attain the applicable PM2.5 
NAAQS by the end of the sixth calendar year following the date of 
designation of the area, the state shall adopt all technologically and 
economically feasible control measures identified under paragraph 
(a)(3) of this section unless the state makes a demonstration that one 
or more such measures, when considered collectively, would have minimal 
effect on reducing ambient PM2.5 concentrations in the area.
    (A) Any control measure identified for adoption and implementation 
under this paragraph that can be implemented in whole or in part by 4 
years after the date of designation of the Moderate PM2.5 
nonattainment area shall be considered RACM for the area. Any such 
control measure that is also a control technology shall be considered 
RACT for the area.
    (B) Any control measure identified for adoption and implementation 
under this paragraph that can only be implemented in whole or in part 
during the period beginning 4 years after the date of designation of 
the Moderate PM2.5 nonattainment area through the end of the 
sixth calendar year following the date of designation of the area shall 
be considered an additional reasonable measure for the area.
    (b) The state shall identify, adopt, and implement control 
measures, including control technologies, on sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors located outside the Moderate PM2.5 nonattainment 
area, or portion thereof, located within the state if doing so is 
necessary to provide for attainment or will expedite attainment of the 
applicable PM2.5 NAAQS in such area.
    (c) For control measures on sources of direct PM2.5 
emissions in the form of source emissions limitations, the state shall 
establish such limitations taking into account the filterable and 
condensable fractions of such emissions.

[[Page 15469]]

Sec.  51.1010  Serious area attainment plan control strategy 
requirements.

[PROPOSED REGULATORY TEXT FOR OPTION 1:

    (a) The state shall identify, adopt, and implement control 
measures, including control technologies, on sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors located in any Serious PM2.5 nonattainment area 
or portion thereof located within the state to yield a control strategy 
for the area that is more stringent than that developed for the area 
when it was classified as Moderate, and consistent with the following:
    (1) The state shall identify all sources of direct PM2.5 
emissions and all sources of emissions of PM2.5 precursors 
in the nonattainment area in accordance with the emissions inventory 
requirements of Sec.  51.1008(b);
    (2) The state shall identify all potential control measures to 
reduce emissions from all sources of direct PM2.5 emissions 
and sources of emissions of PM2.5 precursors in the 
nonattainment area identified under paragraph (a)(1) of this section.
    (i) The state shall survey other NAAQS nonattainment areas in the 
U.S. and identify any measures not previously identified by the state 
during the development of the Moderate area attainment plan for the 
area.
    (ii) The state may elect not to identify potential control measures 
to reduce emissions from any sources of a particular PM2.5 
precursor if the state demonstrates that all sources of such 
PM2.5 precursor contribute insignificantly to ambient 
PM2.5 concentrations in the area under Sec.  51.1006.
    (iii) The state may elect not to identify potential control 
measures to reduce emissions from sources in any source category of 
direct PM2.5 emissions or emissions of PM2.5 
precursors determined to be a de minimis source category under Sec.  
51.1007.
    (3) The state may make a demonstration that any measure identified 
under paragraph (a)(2) of this section is not technologically or 
economically feasible to implement in whole or in part by the end of 
the tenth calendar year following the date of designation of the area, 
and may eliminate such whole or partial measure from further 
consideration under this paragraph.
    (i) For purposes of evaluating the technological feasibility of a 
potential control measure, the state may consider factors including but 
not limited to a source's processes and operating procedures, raw 
materials, physical plant layout, and potential environmental impacts 
such as increased water pollution, waste disposal, and energy 
requirements.
    (ii) For purposes of evaluating the economic feasibility of a 
potential control measure, the state may consider capital costs, 
operating and maintenance costs, and cost effectiveness of the measure.
    (iii) The state shall submit to EPA as part of its Serious area 
attainment plan submission a detailed written justification for 
eliminating from further consideration any potential control measure 
identified under paragraph (a)(2) of this section on the basis of 
technological or economic infeasibility. The state shall provide as 
part of its written justification an explanation of how its criteria 
for determining the technological and economic feasibility of potential 
control measures under paragraphs (a)(3)(i) and (ii) of this section 
are more stringent than its criteria for determining the technological 
and economic feasibility of potential control measures under Sec.  
51.1009(a)(3)(i) and (ii) for the same sources in the PM2.5 
nonattainment area.
    (4) Except as provided under paragraph (a)(3) of this section, the 
state shall adopt and implement all potential control measures 
identified under paragraph (a)(2) of this section.
    (i) Any control measure that can be implemented in whole or in part 
by the end of the fourth year following the date of reclassification of 
the area to Serious shall be considered a best available control 
measure for the area. Any such control measure that is also a control 
technology for a stationary source in the area shall be considered a 
best available control technology for the area.
    (ii) Any control measure that can be implemented in whole or in 
part between the end of the fourth year following the date of 
reclassification of the area to Serious and the applicable attainment 
date for the area shall be considered an additional feasible measure.
    (5) The state shall use air quality modeling that meets the 
requirements of Sec.  51.1011(b) and that accounts for emissions 
reductions estimated due to all best available control measures, 
including best available control technologies, and additional feasible 
measures identified for sources of direct PM2.5 emissions 
and sources of emissions of PM2.5 precursors in the area to 
demonstrate that the area can attain the PM2.5 NAAQS as 
expeditiously as practicable but no later than the end of the tenth 
calendar year following the date of designation of the area, or to 
demonstrate that the Serious PM2.5 nonattainment area cannot 
practicably attain the applicable PM2.5 NAAQS by such date.]

[PROPOSED REGULATORY TEXT FOR OPTION 2:

    (a) The state shall identify, adopt, and implement control 
measures, including control technologies, on sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors located in any Serious PM2.5 nonattainment area 
or portion thereof located within the state to yield a control strategy 
for the area that is more stringent than that developed for the area 
when it was classified as Moderate, and consistent with the following:
    (1) The state shall identify all sources of direct PM2.5 
emissions and sources of emissions of PM2.5 precursors in 
the nonattainment area in accordance with the emissions inventory 
requirements of Sec.  51.1008;
    (2) The state shall identify all potential control measures to 
reduce emissions from all sources of direct PM2.5 emissions 
and sources of emissions of PM2.5 precursors in the 
nonattainment area identified under paragraph (a)(1) of this section.
    (i) The state shall survey other NAAQS nonattainment areas in the 
U.S. and identify any measures not previously identified by the state 
during the development of the Moderate area attainment plan for the 
area.
    (ii) The state may elect not to identify potential control measures 
to reduce emissions from any sources of a particular PM2.5 
precursor if the state demonstrates that all sources of such 
PM2.5 precursor contribute insignificantly to ambient 
PM2.5 concentrations in the area under Sec.  51.1006.
    (3) The state may make a demonstration that a measure identified 
under paragraph (a)(2) of this section is not technologically or 
economically feasible to implement in whole or in part by the end of 
the tenth calendar year following the date of designation of the area, 
and may eliminate such whole or partial measure from further 
consideration under this paragraph.
    (i) For purposes of evaluating the technological feasibility of a 
potential control measure, the state may consider factors including but 
not limited to a source's processes and operating procedures, raw 
materials, physical plant layout, and potential environmental impacts 
such as increased water pollution, waste disposal, and energy 
requirements.
    (ii) For purposes of evaluating the economic feasibility of a 
potential control measure, the state may consider

[[Page 15470]]

capital costs, operating and maintenance costs, and cost effectiveness 
of the measure.
    (iii) The state shall submit to EPA as part of its Serious area 
attainment plan submission a detailed written justification for 
eliminating from further consideration any potential control measure 
identified under paragraph (a)(2) of this section on the basis of 
technological or economic infeasibility. The state shall provide as 
part of its written justification an explanation of how its criteria 
for determining the technological and economic feasibility of potential 
control measures under paragraphs (a)(3)(i) and (ii) of this section 
are more stringent than its criteria for determining the technological 
and economic feasibility of potential control measures under Sec.  
51.1009(a)(3)(i) and (ii) for the same sources in the PM2.5 
nonattainment area.
    (4) The state shall use air quality modeling that meets the 
requirements of Sec.  51.1011(b) and that accounts for emissions 
reductions estimated due to all technologically and economically 
feasible control measures identified for sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors in the area to demonstrate that the area can attain the 
applicable PM2.5 NAAQS as expeditiously as practicable but 
no later than the end of the tenth calendar year following the date of 
designation of the area, or to demonstrate that the Serious 
PM2.5 nonattainment area cannot practicably attain the 
applicable PM2.5 NAAQS by such date.
    (5) For a Serious PM2.5 nonattainment area which air 
quality modeling demonstrates that the area can attain the applicable 
PM2.5 NAAQS by the end of the tenth calendar year following 
the date of designation of the area, the state shall adopt and 
implement all technologically and economically feasible control 
measures needed to bring the area into attainment by such date and 
additionally any other such measures that, when considered 
collectively, would advance the attainment date for the area by at 
least 1 year.
    (i) Any control measure that can be implemented in whole or in part 
by the end of the fourth year following the date of reclassification of 
the area to Serious shall be considered a best available control 
measure for the area. Any such control measure that is also a control 
technology for a stationary source in the area shall be considered a 
best available control technology for the area.
    (ii) Any control measure that can only be implemented in whole or 
in part between the end of the fourth year following the date of 
reclassification of the area to Serious and the applicable attainment 
date for the area shall be considered an additional feasible measure.]
    (b) For a Serious PM2.5 nonattainment area which air 
quality modeling demonstrates cannot practicably attain the applicable 
PM2.5 NAAQS by the end of the tenth calendar year following 
the date of designation of the area, the state shall identify, adopt, 
and implement the most stringent control measures that are included in 
the attainment plan for any state or are achieved in practice in any 
state, and can be feasibly implemented in the area, consistent with the 
following:
    (1) The state shall identify all sources of direct PM2.5 
emissions and sources of emissions of PM2.5 precursors in 
the nonattainment area in accordance with the emissions inventory 
requirements of Sec.  51.1008(b).
    (2) The state shall identify all potential control measures to 
reduce emissions from all sources of direct PM2.5 emissions 
and sources of emissions of PM2.5 precursors in the 
nonattainment area identified under paragraph (a)(1) of this section 
and not otherwise determined to contribute insignificantly to ambient 
PM2.5 concentrations in the area according to Sec.  51.1006 
or to be de minimis according to Sec.  51.1007.
    (i) The state shall survey other NAAQS nonattainment areas in the 
U.S. and identify the most stringent measures adopted into any SIP for 
any NAAQS or used in practice to control emissions from any non-de 
minimis source categories.
    (ii) The state shall reanalyze any measures previously rejected by 
the state during the development of any Moderate area or Serious area 
attainment plan control strategy for the area, unless the extension 
request is made at the same time as the Serious area attainment plan 
required after the area is reclassified in accordance with Sec.  
51.1005(b)(5).
    (3) The state may make a demonstration that a measure identified 
under paragraph (b)(2) of this section is not technologically or 
economically feasible to implement in whole or in part by 5 years after 
the applicable attainment date for the area, and may eliminate such 
whole or partial measure from further consideration under this 
paragraph.
    (i) For purposes of evaluating the technological feasibility of a 
potential control measure, the state may consider factors including but 
not limited to a source's processes and operating procedures, raw 
materials, physical plant layout, and potential environmental impacts 
such as increased water pollution, waste disposal, and energy 
requirements.
    (ii) For purposes of evaluating the economic feasibility of a 
potential control measure, the state may consider capital costs, 
operating and maintenance costs, and cost effectiveness of the measure.
    (iii) The state shall submit to EPA as part of its Serious area 
attainment plan submission a detailed written justification for 
eliminating from further consideration any potential control measure 
identified under paragraph (b)(2) of this section on the basis of 
technological or economic infeasibility. The state shall provide as 
part of its written justification an explanation of how its criteria 
for determining the technological and economic feasibility of potential 
control measures under paragraphs (b)(3)(i) and (ii) of this section 
are more stringent than its criteria for determining the technological 
and economic feasibility of potential control measures under paragraphs 
(a)(3)(i) and (ii) of this section and under Sec.  51.1009(a)(3)(i) and 
(ii) for the same sources in the PM2.5 nonattainment area.
    (4) Except as provided under paragraph (b)(3) of this section, the 
state shall adopt and implement all control measures identified under 
paragraph (b)(2) of this section that may achieve greater emissions 
reductions from any non-de minimis sources of direct PM2.5 
emissions or sources of emissions of PM2.5 precursors in the 
area than previously adopted measures have achieved and that shall 
achieve attainment as expeditiously as practicable but no later than 5 
years after the applicable attainment date for the area.
    (c) The state shall identify, adopt, and implement control 
measures, including control technologies, on sources of direct 
PM2.5 emissions and sources of emissions of PM2.5 
precursors located outside the Serious PM2.5 nonattainment 
area or portion thereof, located within the state if doing so will 
expedite attainment of the applicable PM2.5 NAAQS within the 
area.
    (d) For control measures on sources of direct PM2.5 
emissions in the form of source emissions limitations, the state shall 
establish such limitations taking into account the filterable and 
condensable fractions of such emissions.

Sec.  51.1011  Attainment demonstration and modeling requirements.

    (a) Nonattainment areas initially classified as Moderate. The 
attainment demonstration due to EPA as part of any

[[Page 15471]]

Moderate area attainment plan required under Sec.  51.1003(a) shall 
meet all of the following criteria:
    (1) The attainment demonstration shall show the projected 
attainment date for the Moderate nonattainment area that is as 
expeditious as practicable in accordance with the requirements of Sec.  
51.1004(a)(1).
    (2) The attainment demonstration shall meet the requirements of 
Appendix W of this part and shall include inventory data, modeling 
results, and emission reduction analyses on which the state has based 
its projected attainment date.
    (3) The base year for the emissions inventory required for an 
attainment demonstration under this paragraph shall be one of the 3 
years used for designations or another technically appropriate 
inventory year if justified by the state in the plan submission.
    (4) The control strategies modeled as part of the attainment 
demonstration shall be consistent with the following as applicable:
    (i) For a Moderate area that can demonstrate attainment of the 
applicable PM2.5 NAAQS no later than the end of the sixth 
calendar year following the date of designation of the area with the 
implementation of RACM and RACT and additional reasonable measures, the 
control strategies modeled as part of the attainment demonstration 
shall be consistent with control strategy requirements under Sec.  
51.1009(a).
    (ii) For a Moderate area that cannot practicably attain the 
applicable PM2.5 NAAQS by the end of the sixth calendar year 
following the date of designation of the area with the implementation 
of RACM and RACT and additional reasonable measures, the control 
strategies modeled as part of the attainment demonstration shall be 
consistent with control strategy requirements under Sec.  51.1009(b).
    (5) The attainment demonstration and supporting air quality 
modeling should be consistent with the most current version of EPA's 
PM2.5 attainment demonstration modeling guidance.
    (6) Required time frame for obtaining emissions reductions. For 
each Moderate nonattainment area, the attainment plan must provide for 
implementation of all control measures needed for attainment as 
expeditiously as practicable. All control measures in the attainment 
demonstration must be implemented no later than the beginning of the 
year prior to the attainment date, notwithstanding RACM implementation 
deadline requirements in Sec.  51.1009.
    (b) Nonattainment areas reclassified as Serious. The attainment 
demonstration due to EPA as part of a Serious area attainment plan 
required under Sec.  51.1003(b) shall meet all of the following 
criteria:
    (1) The attainment demonstration shall show the projected 
attainment date for the Serious nonattainment area that is as 
expeditious as practicable in accordance with the requirements of Sec.  
51.1004(a)(2).
    (2) The attainment demonstration shall meet the requirements of 
Appendix W of this part and shall include inventory data, modeling 
results, and emission reduction analyses on which the state has based 
its projected attainment date.
    (3) The base year for the emissions inventories required for 
attainment demonstrations under this paragraph shall be one of the 3 
years used for designations or another technically appropriate 
inventory year if justified by the state in the plan submission.
    (4) The control strategies modeled as part of the attainment 
demonstration shall be consistent with the following as applicable:
    (i) For a Serious area that can demonstrate attainment of the 
applicable PM2.5 NAAQS no later than the end of the tenth 
calendar year following the date of designation of the area with the 
implementation of best available control measures (BACM), including 
best available control technologies (BACT), and additional feasible 
measures, the control strategies modeled as part of the attainment 
demonstration shall be consistent with control strategy requirements 
under Sec.  51.1010(a).
    (ii) For a Serious area that cannot practicably attain the 
applicable PM2.5 NAAQS by the end of the tenth calendar year 
following the date of designation of the area with the implementation 
of best available control measures (BACM), including best available 
control technologies (BACT), and additional feasible measures, the 
control strategies modeled as part of the attainment demonstration 
shall be consistent with control strategy requirements under Sec.  
51.1010(b).
    (5) The attainment demonstration and supporting air quality 
modeling should be consistent with the most current version of EPA's 
PM2.5 attainment demonstration modeling guidance.
    (6) Required timeframe for obtaining emissions reductions. For each 
Serious nonattainment area, the attainment plan must provide for 
implementation of all control measures needed for attainment as 
expeditiously as practicable. All control measures must be implemented 
no later than the beginning of the year prior to the attainment date, 
notwithstanding BACM implementation deadline requirements in Sec.  
51.1010.

Sec.  51.1012  Reasonable further progress (RFP) requirements.

    (a) Consistent with CAA section 172(c)(2), the state shall submit 
in each attainment plan for a PM2.5 nonattainment area a 
plan that demonstrates that the area will achieve, on an annual basis, 
reasonable further progress (RFP) in reducing emissions of direct 
PM2.5 and any PM2.5 precursors from sources in 
the area that the state has determined are necessary to be controlled 
in order for the area to attain the applicable PM2.5 NAAQS 
as expeditiously as practicable. The RFP plan shall include all of the 
following:
    (1) A description of each control measure adopted by the state to 
satisfy the control strategy requirements of Sec.  51.1009 (for 
Moderate area attainment plans) or Sec.  51.1010 (for Serious area 
attainment plans), as appropriate, and the projected reductions in 
direct PM2.5 emissions and emissions of PM2.5 
precursors that each control measure will achieve by the projected 
attainment date for the area.
    (2) A schedule for implementing the measures described in paragraph 
(a)(1) of this section.
    (3) An analysis that demonstrates that by the end of the calendar 
year for each milestone date for the area determined in accordance with 
Sec.  51.1013(a), emissions will be at a level that reflects generally 
linear progress in reducing emissions on an annual basis between the 
base year and the attainment year.
    (b) Except as provided under paragraph (c) of this section, the RFP 
analysis required under paragraph (a)(3) of this section shall include, 
at a minimum, a benchmark RFP analysis, and may include an alternative 
RFP analysis, consistent with the following:
    (1) The base year for the RFP emissions inventory shall be one of 
the 3 years used for designations or another technically appropriate 
inventory year if justified by the state in the plan submission.
    (2) In the benchmark RFP analysis, the state must identify direct 
PM2.5 emissions and PM2.5 precursors regulated in 
the control strategy for the area and specify target emission reduction 
levels to be achieved during the milestone years. In developing the 
benchmark RFP analysis, the state must develop emissions inventory 
information for the area and calculate the following:
    (i) For direct PM2.5 emissions and each PM2.5 
precursor addressed in the control strategy, the full implementation 
reduction is calculated by subtracting

[[Page 15472]]

the full implementation inventory from the base year inventory.
    (ii) The ``milestone date fraction'' is the ratio of the number of 
years from the base year to the milestone year divided by the number of 
years from the baseline year to the full implementation year.
    (iii) For direct PM2.5 emissions and each 
PM2.5 attainment plan precursor addressed in the attainment 
strategy, a benchmark emission reduction is calculated by multiplying 
the full implementation reduction by the milestone date fraction.
    (iv) The benchmark emission level in the milestone year is 
calculated for direct PM2.5 emissions and each 
PM2.5 precursor by subtracting the benchmark emission 
reduction from the base year emission level.
    (v) In comparing inventories between the base year and future years 
for direct PM2.5 emissions and emissions of PM2.5 
precursors, the inventories must be derived for sources located within 
the nonattainment area.
    (vi) For purposes of establishing motor vehicle emissions budgets 
for transportation conformity purposes (as required in 40 CFR part 93) 
for a PM2.5 nonattainment area, the state shall include in 
its RFP submittal an inventory of on-road mobile source emissions in 
the nonattainment area for each milestone year.
    (3) The RFP analysis must demonstrate that emissions for the 
milestone year are either:
    (i) At levels that are roughly equivalent to the benchmark emission 
levels for direct PM2.5 emissions and emissions of 
PM2.5 precursors addressed in the attainment plan; or
    (ii) At levels included in an alternative RFP analysis that 
projects generally equivalent improvement in air quality by the 
milestone year as would be achieved under the benchmark RFP plan.
    (iii) The equivalence of an alternative RFP analysis to the 
corresponding benchmark analysis must be determined by comparing the 
expected air quality changes from the two analyses at the design value 
monitor location. This comparison must use the information developed 
for the attainment plan to assess the relationship between emissions 
reductions of the direct PM2.5 emissions and emissions of 
PM2.5 precursors addressed in the control strategy for the 
area and the ambient air quality improvement.
    (c) For an attainment plan submittal that demonstrates that a 
Moderate PM2.5 nonattainment area cannot practicably attain 
the applicable PM2.5 NAAQS by the end of the sixth calendar 
year following the effective date of designation of the area with the 
implementation of control measures as required under Sec.  51.1009, the 
RFP analysis required under paragraph (a)(3) of this section shall 
demonstrate generally linear emissions reductions in direct 
PM2.5 emissions and emissions of PM2.5 precursors 
projected from the Moderate area control strategy determined according 
to Sec.  51.1008 for each milestone year.
    (d) For a multi-state or multi-jurisdictional nonattainment area, 
the RFP plans for each state represented in the nonattainment area 
shall demonstrate RFP on the basis of common multi-state inventories. 
The states or jurisdictions within which the area is located must 
provide a coordinated RFP plan. Each state in a multi-state 
nonattainment area must ensure that the sources within its boundaries 
comply with enforceable emission levels and other requirements that in 
combination with the reductions planned in other state(s) within the 
nonattainment area will provide for attainment as expeditiously as 
practicable and demonstrate RFP consistent with these regulations.

Sec.  51.1013  Quantitative milestone requirements.

    (a) Consistent with CAA section 189(c)(1), the state must submit in 
each attainment plan for a PM2.5 nonattainment area specific 
quantitative milestones that demonstrate reasonable further progress 
toward attainment of the applicable PM2.5 NAAQS in the area 
and that meet the following requirements:
    (1) Nonattainment areas initially classified as Moderate.
    (i) For an attainment plan submittal that demonstrates that a 
Moderate PM2.5 nonattainment area can attain the applicable 
PM2.5 NAAQS by the end of the sixth calendar year following 
the date of designation of the area or earlier with the implementation 
of control measures as required under Sec.  51.1009, the state shall 
submit quantitative milestones to be achieved no later than a milestone 
date of 4.5 years from the date of designation of the area.
    (ii) For an attainment plan submittal that demonstrates that a 
Moderate PM2.5 nonattainment area cannot practicably attain 
the applicable PM2.5 NAAQS by the end of the sixth calendar 
year following the effective date of designation of the area with the 
implementation of control measures as required under Sec.  51.1009, the 
state shall submit quantitative milestones to be achieved no later than 
milestone dates of 4.5 years and 7.5 years, respectively, from the date 
of designation of the area.
    (iii) The state shall select quantitative milestones that coincide 
with the milestone due dates specified in paragraphs (a)(1)(i) and (ii) 
of this section, as applicable, and that provide for objective 
evaluation of emissions reductions and/or air quality improvements 
representing progress toward attainment of the applicable 
PM2.5 NAAQS in the area, including, at a minimum, a 
milestone that all control measures identified and adopted as RACM and 
RACT for the area will be fully implemented within 4 years after the 
date of designation.
    (2) Nonattainment areas reclassified to Serious.
    (i) For an attainment plan submittal that demonstrates that a 
Serious PM2.5 nonattainment area can attain a particular 
PM2.5 NAAQS by the end of the tenth calendar year following 
the effective date of designation of the area with the implementation 
of control measures as required under Sec.  51.1010(a), the state shall 
submit quantitative milestones to be achieved no later than milestone 
dates of 7.5 years and 10.5 years, respectively, from the date of 
designation of the area.
    (ii) For an attainment plan submittal that demonstrates that a 
Serious PM2.5 nonattainment area cannot practicably attain a 
particular PM2.5 NAAQS by the end of the tenth calendar year 
following the date of designation of the area with the implementation 
of control measures required under Sec.  51.1010(a), the state shall 
submit quantitative milestones to be achieved no later than milestone 
dates of 7.5 years, 10.5 years, and 13.5 years, respectively, from the 
date of designation of the area.
    (iii) The state shall select quantitative milestones that coincide 
with the milestone due dates specified in paragraphs (a)(2)(i) and (ii) 
of this section, as applicable, and that provide for objective 
evaluation of emissions reductions and/or air quality improvements 
representing progress toward attainment of the applicable 
PM2.5 NAAQS in the area, including, at a minimum, a 
milestone that all control measures identified and adopted as BACM and 
BACT for the area will be fully implemented within 4 years of 
reclassification of the area to Serious.
    (3) Serious areas that fail to attain by the applicable Serious 
area attainment date. For an attainment plan submittal for a Serious 
area that failed to attain a particular PM2.5 NAAQS by the 
applicable Serious area attainment date and is therefore subject to the 
requirements of CAA section 189(d) and Sec.  51.1003(c), the state 
shall submit

[[Page 15473]]

quantitative milestones to be achieved no later than a milestone date 
of 13.5 years from the date of designation of the area and every 3 
years thereafter until the projected attainment date for the area. The 
state shall select quantitative milestones that coincide with the 
milestone due dates for the area, and that provide for objective 
evaluation of emissions reductions and/or air quality improvements 
representing progress toward attainment of the applicable 
PM2.5 NAAQS in the area.
    (b) Not later than 90 days after the date on which a milestone 
applicable to a PM2.5 nonattainment area occurs, each state 
in which all or part of such area is located shall submit to the 
Administrator a milestone report that contains all of the following:
    (1) A certification by the Governor or Governor's designee that the 
state's attainment plan control strategy, including the RFP plan, is 
being implemented as described in the applicable attainment plan;
    (2) A technical demonstration, including calculations, to document 
completion statistics for appropriate milestones and to demonstrate 
that the quantitative milestones have been satisfied and how the 
emission reductions achieved to date compare to those required or 
scheduled to meet RFP;
    (3) An air quality screening analysis to determine if measured air 
quality progress is consistent with the expected air quality 
improvement target correlated with the RFP emissions reductions for the 
previous 3-year period calculated in accordance with Sec.  51.1012;
    (4) An evaluation of whether the area will attain the applicable 
PM2.5 NAAQS by the projected attainment date for the area; 
and,
    (5) A description and schedule for any remedial actions the state 
has taken or will take to address any failure to meet a quantitative 
milestone, including the implementation status of contingency measures 
required under Sec.  51.1014(a)(1)(i) for failing to meet RFP.
    (c) In the event a state fails to submit a milestone report that 
meets the requirements of paragraph (b) of this section by the due date 
or the Administrator determines that the state failed to meet a 
milestone by the milestone date, the state shall submit an attainment 
plan revision within 9 months of the missed due date or the 
Administrator's determination of the state's failure to meet a 
milestone that assures that the state will achieve the next milestone 
or attain the applicable NAAQS by the applicable date, whichever is 
earlier.

Sec.  51.1014  Contingency measure requirements.

    (a) The state must include as part of each attainment plan 
submitted under this subpart for a PM2.5 nonattainment area 
specific contingency measures that shall take effect with minimal 
further action by the state or EPA within 60 days of the Administrator 
making a determination that the area has failed to meet either of the 
following conditions:
    (1) The area failed to meet the RFP requirements of Sec.  51.1012 
or to submit a milestone report due to EPA in accordance with Sec.  
51.1013(b); or,
    (2) The area failed to attain the applicable PM2.5 NAAQS 
by the applicable attainment date.
    (b) The contingency measures adopted as part of a PM2.5 
attainment plan shall meet all of the following requirements:
    (1) The contingency measures shall consist of control measures that 
are not otherwise included in the control strategy for the area.
    (2) The contingency measures shall provide for emissions reductions 
approximately equivalent to 1 year's worth of reductions needed for 
RFP, based on the overall level of reductions needed to demonstrate 
attainment divided by the number of years from the base year to the 
attainment year, or approximately equivalent to 1 year's worth of air 
quality improvement or emissions reductions proportional to the overall 
amount of air quality improvement or emissions reductions to be 
achieved by the area's attainment plan.
    (c) The attainment plan submission shall contain a description of 
the specific trigger mechanisms for the contingency measures and 
specify a schedule for implementation.

Sec.  51.1015  Clean data requirements.

    (a) Nonattainment areas initially classified as Moderate. Upon a 
determination by EPA that a Moderate PM2.5 nonattainment 
area has attained the PM2.5 NAAQS, the requirements for the 
state to submit an attainment demonstration, provisions demonstrating 
that reasonably available control measures, including reasonably 
available control technology for stationary sources, shall be 
implemented no later than 4 years following the date of designation of 
the area, reasonable further progress plan, and contingency measures 
for the area shall be suspended until such time as:
    (1) The area is redesignated to attainment, after which such 
requirements are permanently discharged; or,
    (2) EPA determines that the area has re-violated the 
PM2.5 NAAQS, at which time the state shall submit such 
attainment plan elements for the Moderate nonattainment area by a 
future date to be determined by EPA and announced through publication 
in the Federal Register at the time EPA determines the area is 
violating the PM2.5 NAAQS.
    (b) Nonattainment areas reclassified as Serious. Upon a 
determination by EPA that a Serious PM2.5 nonattainment area 
has attained the PM2.5 NAAQS, the requirements for the state 
to submit an attainment demonstration, reasonable further progress 
plan, and contingency measures for the area shall be suspended until 
such time as:
    (1) The area is redesignated to attainment, after which such 
requirements are permanently discharged; or,
    (2) EPA determines that the area has re-violated the 
PM2.5 NAAQS, at which time the state shall submit such 
attainment plan elements for the Moderate nonattainment area by a 
future date to be determined by EPA and announced through publication 
in the Federal Register at the time EPA determines the area is 
violating the PM2.5 NAAQS.

[ALTERNATIVE PROPOSED REGULATORY TEXT:

    (b) Nonattainment areas reclassified as Serious. Upon a 
determination by EPA that a Serious PM2.5 nonattainment area 
has attained the PM2.5 NAAQS, the requirements for the state 
to submit an attainment demonstration, provisions demonstrating that 
best available control measures, including best available control 
technology for stationary sources, shall be implemented no later than 4 
years following the date of reclassification of the area to Serious, 
reasonable further progress plan, and contingency measures for the area 
shall be suspended until such time as:
    (1) The area is redesignated to attainment, after which such 
requirements are permanently discharged; or,
    (2) EPA determines that the area has re-violated the 
PM2.5 NAAQS, at which time the state shall submit such 
attainment plan elements for the Serious nonattainment area by a future 
date to be determined by EPA and announced through publication in the 
Federal Register at the time EPA determines the area is violating the 
PM2.5 NAAQS.]

[[Page 15474]]

PART 93--DETERMINING CONFORMITY OF FEDERAL ACTIONS TO STATE OR 
FEDERAL IMPLEMENTATION PLANS

0
7. The authority citation for part 93 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart B--Determining Conformity of General Federal Actions to 
State or Federal Implementation Plans

0
8. In Sec.  93.153, revise paragraphs (b)(1) and (2) to read as 
follows:

Sec.  93.153  Applicability.

* * * * *
    (b) * * *
    (1) For purposes of paragraph (b) of this section the following 
rates apply in nonattainment areas (NAA's):

------------------------------------------------------------------------
                                                            Tons/year
------------------------------------------------------------------------
Ozone (VOC's or NOX):
    Serious NAA's.....................................                50
    Severe NAA's......................................                25
    Extreme NAA's.....................................                10
    Other ozone NAA's outside an ozone transport                     100
     region...........................................
Other ozone NAA's inside an ozone transport region:
    VOC...............................................                50
    NOX...............................................               100
    Carbon Monoxide: All maintenance areas............               100
    SO2 or NO2: All NAA's.............................               100
PM10:
    Moderate NAA's....................................               100
    Serious NAA's.....................................                70
PM2.5 (direct emissions, SO2, NOX, VOC, and ammonia):
    Moderate NAA's....................................               100
    Serious NAA's.....................................                70
    Pb: All NAA's.....................................                25
------------------------------------------------------------------------

    (2) For purposes of paragraph (b) of this section the following 
rates apply in maintenance areas:

------------------------------------------------------------------------
                                                            Tons/year
------------------------------------------------------------------------
Ozone (NOX, SO2 or NO2):
    All maintenance areas.............................               100
Ozone (VOC's):
    Maintenance areas inside an ozone transport region                50
    Maintenance areas outside an ozone transport                     100
     region...........................................
    Carbon monoxide: All maintenance areas............               100
    PM10: All maintenance areas.......................               100
    PM2.5 (direct emissions, SO2, NOX, VOC, and                      100
     ammonia).........................................
    All maintenance areas.............................               100
    Pb: All maintenance areas.........................                25
------------------------------------------------------------------------

* * * * *
[FR Doc. 2015-06138 Filed 3-20-15; 8:45 am]
BILLING CODE 6560-50-P