Prevention of Significant Deterioration (PSD) for Particulate Matter Less Than 2.5 Micrometers (PM2.5, 64864-64907 [2010-25132]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 75, Number 202 (Wednesday, October 20, 2010)]
[Rules and Regulations]
[Pages 64864-64907]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-25132]



[[Page 64863]]

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Part III





Environmental Protection Agency





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40 CFR Parts 51 and 52



Prevention of Significant Deterioration (PSD) for Particulate Matter 
Less Than 2.5 Micrometers (PM2.5)--Increments, Significant 
Impact Levels (SILs) and Significant Monitoring Concentration (SMC); 
Final Rule

Federal Register / Vol. 75 , No. 202 / Wednesday, October 20, 2010 / 
Rules and Regulations

[[Page 64864]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 51 and 52

[EPA-HQ-OAR-2006-0605; FRL-9210-9]
RIN 2060-AO24


Prevention of Significant Deterioration (PSD) for Particulate 
Matter Less Than 2.5 Micrometers (PM2.5)--Increments, 
Significant Impact Levels (SILs) and Significant Monitoring 
Concentration (SMC)

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The EPA is amending the requirements for particulate matter 
less than 2.5 micrometers (PM2.5) under the Prevention of 
Significant Deterioration (PSD) program by adding maximum allowable 
increases in ambient pollutant concentrations (``increments'') and two 
screening tools, known as the Significant Impact Levels (SILs) and a 
Significant Monitoring Concentration (SMC) for PM2.5. The 
SILs for PM2.5 are also being added to two other New Source 
Review (NSR) rules that regulate the construction and modification of 
any major stationary source locating in an attainment or unclassifiable 
area, where the source's emissions may cause or contribute to a 
violation of the national ambient air quality standards (NAAQS).

DATES: This final rule is effective on December 20, 2010.

ADDRESSES: The EPA has established a docket for this action under 
Docket ID No. EPA-HQ-OAR-2006-0605. All documents in the docket are 
listed on the https://www.regulations.gov Web Site. Although listed in 
the index, some information may not be publicly available, e.g., 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Certain other material, such as 
copyrighted material, is not placed on the Internet and will be 
publicly available only in hard copy form. Publicly available docket 
materials are available either electronically through https://www.regulations.gov or in hard copy at the Air Docket, EPA/DC, EPA 
West, Room 3334, 1301 Constitution Avenue, Northwest, Washington, DC. 
The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: Mr. Dan deRoeck, Air Quality Policy 
Division, Office of Air Quality Planning and Standards (C504-03), U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711, telephone number: (919) 541-5593, facsimile number: (919) 541-
5509, e-mail address: deroeck.dan@epa.gov.

SUPPLEMENTARY INFORMATION: The information in this Supplementary 
Information section of this preamble is organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related 
information?
II. Purpose
III. Overview of Final PM2.5 PSD Regulations
    A. Increments
    B. Significant Impact Levels
    C. Significant Monitoring Concentration
IV. Background
    A. PSD Program
    B. History of Particulate Matter (PM) NAAQS
    1. Total Suspended Particulate (TSP) and PM10 NAAQS
    2. PM2.5 NAAQS
    3. Revised PM2.5 and PM10 NAAQS
    C. Implementation of NSR for PM2.5
    D. Increments Under the PSD Program
    E. Historical Approaches for Developing Increments
    1. Congressional Enactment of Increments for PM and 
SO2
    2. EPA's Promulgation of Increments for NO2 and 
PM10
    a. Increments for NO2 Using the ``Contingent Safe 
Harbor'' Approach Under Section 166(a) of the Act
    b. Increments for PM10 Using ``Equivalent 
Substitution'' Approach Under Section 166(f) of the Act
V. Final Action on PM2.5 Increments
    A. Decision To Establish PM2.5 Increments Using 
``Contingent Safe Harbor Approach'' Under Section 166(a)
    B. Rationale for the Applicability of Section 166(a)
    C. EPA's Interpretation of the Requirements Under Sections 
166(a)-(d) of the Act
    1. Regulations as a Whole Should Fulfill Statutory Requirements
    2. Contingent Safe Harbor Approach
    3. The Statutory Factors Applicable Under Section 166(c)
    4. Balancing the Factors Applicable Under Section 166(c)
    5. Authority for States To Adopt Alternatives to Increments
    D. Framework for Pollutant-Specific PSD Regulations for 
PM2.5
    1. Increment System
    2. Area Classifications
    3. Permitting Procedures
    4. AQRV Review by Federal Land Manager (FLM) and Reviewing 
Authority
    5. Additional Impacts Analysis
    6. Installation of BACT
    E. Final PM2.5 Increments
    1. Identification of Safe Harbor Increments
    2. Data Used by EPA for the Evaluation of the Safe Harbor 
Increments for PM2.5
    3. Scope of Effects Considered
    4. Evaluation of the Health and Welfare Effects of 
PM2.5
    a. Health Effects
    b. Welfare Effects
    5. Fundamental Elements of Increments
    6. Evaluation of the Safe Harbor Increments
    7. Compliance Determinations for the PM2.5 Increments
    a. Modeling Compliance With PM2.5 Increments
    b. Condensable PM
    c. PM2.5 Precursors
    F. Final Action on Trigger and Baseline Dates for 
PM2.5 Increments
    G. Definition of ``Baseline Area'' for PM2.5
    H. No Final Action With Respect to the Proposed Revocation of 
PM10 Annual Increments
    I. Other Comments on Increments
VI. Final Action on PM2.5 SILs
    A. EPA's Determination on SILs for PM2.5
    B. Response to Comments Concerning the SILs
    1. Legal Basis for SILs
    2. Levels of the SILs
    a. Class I SILs
    b. Class II and III SILs
    3. Relationship Between SILs and AQRVs
    4. Form of the SILs
    5. SILs for Other Pollutants
VII. Final Action on the PM2.5 SMC
    A. EPA's Determination on the PM2.5 SMC
    B. Response to Comments Concerning the SMC
    1. Legal Issues
    2. Level of the SMC
    C. Correction of Cross Reference in PSD Ambient Monitoring 
Requirements
VIII. Dates Associated With Implementation of the Final Rule
    A. Effective Date of the Final Rule
    1. State PSD Programs
    2. Federal PSD Program
    B. Transition Period
    C. SILs and SMC for PM2.5
IX. Other Regulatory Changes
X. Statutory and Executive Order Reviews
    A. Executive Order 12866--Regulatory Planning and 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 That Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898--Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act
XI. Judicial Review
XII. Statutory Authority


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I. General Information

A. Does this action apply to me?

    Entities affected by this rule include sources in all industry 
groups. The majority of sources potentially affected are expected to be 
in the following groups:

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                  Industry group                                              NAICS \a\
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Electric services.................................  221111, 221112, 221113, 221119, 221121, 221122
Petroleum refining................................  32411
Industrial inorganic chemicals....................  325181, 32512, 325131, 325182, 211112, 325998, 331311,
                                                     325188
Industrial organic chemicals......................  32511, 325132, 325192, 325188, 325193, 32512, 325199
Miscellaneous chemical products...................  32552, 32592, 32591, 325182, 32551
Natural gas liquids...............................  211112
Natural gas transport.............................  48621, 22121
Pulp and paper mills..............................  32211, 322121, 322122, 32213
Paper mills.......................................  322121, 322122
Automobile manufacturing..........................  336111, 336112, 336712, 336211, 336992, 336322, 336312,
                                                     33633, 33634, 33635, 336399, 336212, 336213
Pharmaceuticals...................................  325411, 325412, 325413, 325414
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\a\ North American Industry Classification System.

    Entities affected by this rule also include State and local 
permitting authorities, and tribal authorities that implement these 
regulations.

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

    In addition to being available in the docket, an electronic copy of 
this final rule will also be available on the World Wide Web. Following 
signature by the EPA Administrator, a copy of this final rule will be 
posted in the regulations and standards section of our NSR home page 
located at https://www.epa.gov/nsr.

II. Purpose

    The purpose of this rulemaking is to finalize certain program 
provisions under the regulations to prevent significant deterioration 
of air quality due to emissions of PM2.5 (i.e., under the 
PM2.5 PSD regulations). This final rule supplements the 
final implementation rule for PM2.5, known as the Clean Air 
Fine Particle Implementation Rule (CAFPIR) that we promulgated on April 
25, 2007 (72 FR 20586), and the PM2.5 NSR Implementation 
Rule that we promulgated on May 16, 2008 (73 FR 28321). Together, these 
three rules encompass the elements necessary for implementation of a 
PM2.5 program in any area. This final rule is important 
because it establishes increments, SILs, and an SMC for 
PM2.5 to facilitate ambient air quality monitoring and 
modeling under the PSD regulations for areas designated attainment or 
unclassifiable for PM2.5.

III. Overview of Final PM2.5 PSD Regulations

A. Increments

    This rulemaking establishes increments for PM2.5 
pursuant to the legal authority contained in section 166(a) of the 
Clean Air Act (CAA or Act) for pollutants for which NAAQS are 
promulgated after 1977. The final PM2.5 increments were 
identified as Option 1 in the 2007 Notice of Proposed Rulemaking (NPRM) 
for this action, and are as follows:

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                                                                 NAAQS            Increments ([mu]g/m\3\)
                      Averaging period                          ([mu]g/   --------------------------------------
                                                                 m\3\)       Class I      Class II    Class III
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Annual......................................................           15            1            4            8
24-hour.....................................................           35            2            9           18
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    As discussed in more detail in sections V.F and VIII, the 
increments for PM2.5 will become applicable on October 20, 
2011 in order to comply with section 166(b) of the Act (providing that 
regulations under section 166(a) ``shall become effective one year 
after the date of promulgation'').
    This final rule does not revoke the annual increments for 
particulate matter less than 10 micrometers (PM10) as 
proposed under Option 1 in the 2007 NPRM. Thus, we are retaining the 
24-hour and annual PM10 increments in addition to adding 
PM2.5 increments. This outcome is discussed in greater 
detail in section V.H of this preamble.

B. Significant Impact Levels

    This rule establishes SILs for PM2.5 for evaluating the 
impact a proposed new source or modification may have on the NAAQS and 
PSD increments for PM2.5. The SILs for PM2.5 were 
developed by scaling the existing PM10 SILs using a 
PM2.5-to-PM10 NAAQS ratio. The final SILs were 
identified as Option 3 in the 2007 NPRM, and are as follows:

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                                             SILs ([mu]g/m\3\)
         Averaging period         --------------------------------------
                                     Class I      Class II    Class III
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Annual...........................         0.06          0.3          0.3
24-hour..........................         0.07          1.2          1.2
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    These values will be added to the State implementation plan (SIP) 
provisions for PSD at 40 CFR 51.166 (as an optional screening tool) and 
the Federal PSD program at 40 CFR 52.21, as well as under the 
preconstruction review permit requirements at 40 CFR 51.165(b) and part 
51, Appendix S. See a more detailed discussion of the SILs, as well as 
the relevant comments and our responses to them, in section VI of this 
preamble. The SILs for PM2.5 are incorporated into the 
Federal PSD program as well as into the regulations for State-
implemented PSD programs, although they are regarded as optional for 
State programs. The effective date for implementing the SILs under the 
Federal PSD program is the effective date of this final rule. See 
section VIII of this preamble for further discussion of the effective 
date.

C. Significant Monitoring Concentration

    This final rule establishes the SMC for PM2.5 as 4 
[mu]g/m\3\ PM2.5 (24-hour average). This value has been 
developed pursuant to proposed Option 1; however, it should be noted 
that the value being established in this final rule is lower than the 
proposed value of 10 [mu]g/m\3\ that was originally developed under 
Option 1. A more detailed discussion of the proposed SMC is presented 
in section VII of this preamble, describing the rationale for altering 
the proposed SMC, and the relevant comments on the proposed SMC and our 
responses to them. The SMC for PM2.5 is incorporated into 
the Federal PSD program as well as into the regulations for State-
implemented PSD programs, although they are regarded as optional for 
State programs. As with the SILs for PM2.5, the effective 
date for implementing the SMC under the Federal PSD program is the 
effective date of this final rule. See section VIII of this preamble 
for further discussion of the effective date.

IV. Background

A. PSD Program

    The NSR provisions of the Act are a combination of air quality 
planning and air pollution control technology program requirements for 
new and modified stationary sources of air pollution. In brief, section 
109 of the Act requires us to promulgate primary NAAQS to protect 
public health and secondary NAAQS to protect public welfare. Once we 
have set these standards, states must develop, adopt, and submit to us 
for approval SIPs that contain emission limitations and other control 
measures to attain and maintain the NAAQS and to meet the other 
requirements of section 110(a) of the Act. Part C of title I of the Act 
contains the requirements for a component of the major NSR program 
known as the PSD program. This program sets forth procedures for the 
preconstruction review and permitting of new and modified major 
stationary sources of air pollution locating in areas meeting the NAAQS 
(``attainment'' areas) and areas for which there is insufficient 
information to classify an area as either attainment or nonattainment 
(``unclassifiable'' areas). Most states have SIP-approved 
preconstruction permit (major NSR) programs. The Federal PSD program at 
40 CFR 52.21 applies in some states that lack a SIP-approved permit 
program, and in Indian country.\1\ The applicability of the PSD program 
to a major stationary source must be determined in advance of 
construction and is a pollutant-specific determination. Once a major 
source is determined to be subject to the PSD program (PSD source), 
among other requirements, it must undertake a series of analyses to 
demonstrate that it will use the best available control technology 
(BACT) and will not cause or contribute to a violation of any NAAQS or 
increment. For the latter demonstration, the PSD regulations generally 
require sources to submit for review and approval a source impact 
analysis and an air quality analysis.
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    \1\ We have delegated our authority to some states to implement 
the Federal PSD program. The EPA remains the reviewing authority in 
non-delegated states lacking SIP-approved programs and in Indian 
country.
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    The source impact analysis is primarily a modeling analysis 
designed to show that the allowable emissions increase from the 
proposed project, in conjunction with other emissions increases from 
existing sources, will not result in a violation of either the NAAQS or 
increments. In cases where the source's emissions may adversely affect 
an area classified as a Class I area, additional review is conducted to 
protect the increments and special attributes of such an area defined 
as ``air quality related values'' (AQRVs).
    The air quality analysis must assess the ambient air quality in the 
area that the proposed project would affect. For this analysis, the 
owner or operator of the proposed project must submit as part of a 
complete permit application air quality monitoring data that represent 
the air quality in the area affected by the proposed source for the 1-
year period preceding receipt of the application. Where data may 
already exist to represent existing air quality, it may be used by the 
applicant; otherwise, the source owner or operator is responsible for 
the installation and operation of monitors to collect the necessary 
data.
    Historically, EPA has allowed the use of several types of screening 
tools to facilitate implementation of the preconstruction review 
process to reduce the permit applicant's burden and streamline the 
permitting process for de minimis circumstances. These tools include a 
significant emissions rate (SER), SILs, and a SMC. The SER, defined in 
tons per year (tpy) for each regulated pollutant, is used to determine 
whether the emissions increase from any proposed source or modification 
can be excluded from review on the grounds that the increase of any 
particular pollutant is de minimis. An emission increase for a 
particular pollutant that is greater than the SER defined in the NSR 
regulations for that pollutant is considered to be a significant 
increase.
    The SIL, expressed as an ambient pollutant concentration 
(micrograms per cubic meter ([mu]g/m \3\)), is used to determine 
whether the ambient impact of a particular pollutant (once it is 
determined to be emitted in significant amounts) is significant enough 
to warrant a complete source impact analysis involving modeling the 
collective impacts of the proposed project and emissions from other 
existing sources.
    The PSD regulations generally require each PSD applicant to collect 
1 year of continuous air quality monitoring data for any pollutant 
determined to be subject to preconstruction review as part of complete 
PSD permit application. Using the SMC as a screening tool, expressed as 
an ambient pollutant concentration ([mu]g/m\3\), sources may be able to 
demonstrate that the modeled air

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quality impact of emissions from the new source or modification, or the 
existing air quality level in the area where the source would 
construct, is less than the SMC, i.e., de minimis, and may be allowed 
to forego the preconstruction monitoring requirement for a particular 
pollutant at the discretion of the reviewing authority.\2\ See 40 CFR 
51.166(i)(5) and 52.21(i)(5).
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    \2\ The basic monitoring exemption provision is part of the 
original monitoring requirements adopted in the 1980 PSD rulemaking. 
45 FR 52676, 52710, August 7, 1980.
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    When the reviewing authority reaches a preliminary decision to 
authorize construction of a proposed major new source or major 
modification, it must provide notice of the preliminary decision and an 
opportunity for comment by the general public, industry, and other 
persons that may be affected by the emissions of the proposed major 
source or major modification. After considering these comments, the 
reviewing authority may issue a final determination on the construction 
permit in accordance with the PSD regulations.

B. History of Particulate Matter (PM) NAAQS

1. Total Suspended Particulate (TSP) and PM10 NAAQS
    The EPA initially established NAAQS for PM in 1971, measured by the 
TSP indicator. Based on the size of the particles collected by the 
``high-volume sampler,'' which at that time was the reference method 
for determining ambient concentrations, TSP included all PM up to a 
nominal size of 25 to 45 micrometers. We established both annual and 
24-hour NAAQS for TSP.
    On July 1, 1987, we revised the NAAQS for PM and changed the 
indicator from TSP to PM10; the latter indicator includes 
particles with a mean aerodynamic diameter less than or equal to 10 
micrometers. The PM10 particles are the subset of inhalable 
particles small enough to penetrate to the thoracic region (including 
the tracheobronchial and alveolar regions) of the respiratory tract 
(referred to as thoracic particles). We established annual and 24-hour 
NAAQS for PM10, and revoked the NAAQS for TSP. (52 FR 
24634).
2. PM2.5 NAAQS
    On July 18, 1997, we again revised the NAAQS for PM in several 
respects. While we determined that the NAAQS should continue to focus 
on particles less than or equal to 10 micrometers in diameter, we also 
determined that the fine and coarse fractions of PM10 should 
be considered separately. We established new annual and 24-hour NAAQS 
using PM2.5 (referring to particles with a nominal mean 
aerodynamic diameter less than or equal to 2.5 micrometers) as the 
indicator for fine particles. The 1997 NAAQS rule also modified the 
PM10 NAAQS for the purpose of regulating the coarse fraction 
of PM10 (referred to as thoracic coarse particles or coarse-
fraction particles; generally including particles with a nominal mean 
aerodynamic diameter greater than 2.5 micrometers and less than or 
equal to 10 micrometers, or PM10-2.5); however, this part of 
the rulemaking was vacated during subsequent litigation, leaving the 
pre-existing 1987 PM10 NAAQS in place (62 FR 38652).
3. Revised PM2.5 and PM10 NAAQS
    On October 17, 2006, we promulgated revisions to the NAAQS for 
PM2.5 and PM10 with an effective date of December 
18, 2006 (71 FR 61144). We lowered the 24-hour NAAQS for 
PM2.5 from 65 [micro]g/m\3\ to 35 [micro]g/m\3\, and 
retained the existing annual PM2.5 NAAQS of 15 [micro]g/
m\3\. In addition, we retained the existing PM10 24-hour 
NAAQS of 150 [micro]g/m\3\, and revoked the annual PM10 
NAAQS (set at 50 [micro]g/m\3\).

C. Implementation of NSR for PM2.5

    After we established new annual and 24-hour NAAQS based on 
PM2.5 as the indicator for fine particles in July 1997, we 
issued a guidance document titled ``Interim Implementation for the New 
Source Review Requirements for PM2.5,'' John S. Seitz, 
Director, Office of Air Quality Planning and Standards, EPA, October 
23, 1997. As noted in that guidance, section 165 of the Act implies 
that certain PSD requirements become effective for a new NAAQS upon the 
effective date of the NAAQS. Section 165(a)(1) of the Act provides that 
no new or modified major source may be constructed without a PSD permit 
that meets all of the section 165(a) requirements with respect to the 
regulated pollutant. Moreover, section 165(a)(3) provides that the 
emissions from any such source may not cause or contribute to a 
violation of any increment or NAAQS. Also, section 165(a)(4) requires 
BACT for each pollutant subject to PSD regulation. The 1997 guidance 
stated that sources would be allowed to use implementation of a 
PM10 program as a surrogate for meeting PM2.5 NSR 
requirements until certain difficulties were resolved. These 
difficulties included the lack of necessary tools to calculate the 
emissions of PM2.5 and related precursors, the lack of 
adequate modeling techniques to project ambient impacts, and the lack 
of PM2.5 monitoring sites.
    On April 5, 2005, we issued a guidance document entitled 
``Implementation of New Source Review Requirements in PM-2.5 
Nonattainment Areas,'' Stephen D. Page, Director, Office of Air Quality 
Planning and Standards, EPA. This memorandum provided guidance on the 
implementation of the nonattainment major NSR provisions in 
PM2.5 nonattainment areas in the interim period between the 
effective date of the PM2.5 NAAQS designations (April 5, 
2005) and when we promulgate regulations to implement nonattainment 
major NSR for the PM2.5 NAAQS. In addition to affirming the 
continued use of the John S. Seitz guidance memo in PM2.5 
attainment areas, this memo recommended that, until we promulgated the 
PM2.5 major NSR regulations, states should use a 
PM10 nonattainment major NSR program as a surrogate to 
address the requirements of nonattainment major NSR for the 
PM2.5 NAAQS.
    On November 1, 2005, we proposed a rule to implement the 
PM2.5 NAAQS, including proposed revisions to the NSR 
program. For those states with EPA-approved PSD programs, we proposed 
to continue the 1997 NSR guidance to use PM10 as a surrogate 
for PM2.5, but only during the SIP development period. We 
also indicated in that proposal that we would be developing increments, 
SILs, and an SMC in a separate rulemaking, i.e., this final rule. Since 
there was an interim surrogate NSR program in place, i.e., the 
PM10 Surrogate Policy, EPA decided to first promulgate the 
non-NSR part of the implementation rule (including attainment 
demonstrations, designations, control measures, etc.). This rule was 
promulgated as the CAFPIR on April 25, 2007 (72 FR 20586).
    The NSR part of the implementation rule was issued separately as a 
final rule on May 16, 2008 (73 FR 28321), and included sets of NSR 
regulations for both attainment (PSD) and nonattainment areas 
(nonattainment NSR) for PM2.5. In the May 16, 2008 rule we 
added one of the important screening tools--the SER--for 
PM2.5. The SER for PM2.5 is defined as an 
emissions rate of 10 tpy for direct PM2.5 emissions. We also 
listed sulfur dioxide (SO2) and nitrogen oxides 
(NOX) as precursors of ambient PM2.5 and defined 
``significant'' as 40 tpy or more of either precursor pollutant. States 
were allowed up to 3 years from the date of publication in the Federal 
Register to

[[Page 64868]]

revise their SIPs and submit their revised NSR programs to EPA for 
approval.

D. Increments Under the PSD Program

    Under section 165(a)(3) of the Act, a PSD permit applicant must 
demonstrate that emissions from the proposed construction and operation 
of a facility ``will not cause, or contribute to, air pollution in 
excess of any (A) maximum allowable increase or maximum allowable 
concentration for any pollutant * * *.'' The ``maximum allowable 
increase'' of an air pollutant that is allowed to occur above the 
applicable baseline concentration for that pollutant is known as the 
PSD increment. By establishing the maximum allowable level of ambient 
pollutant concentration increase in a particular area, an increment 
defines ``significant deterioration'' of air quality in that area.
    For PSD baseline purposes, a baseline area for a particular 
pollutant emitted from a source includes the attainment or 
unclassifiable area in which the source is located, as well as any 
other attainment or unclassifiable area in which the source's emissions 
of that pollutant are projected (by air quality modeling) to result in 
a significant ambient pollutant increase. See, e.g., 40 CFR 
52.21(b)(15)(i). Once the baseline area is established, subsequent PSD 
sources locating in that area need to consider that a portion of the 
available increment may have already been consumed by previous 
emissions increases.
    In general, the submittal date of the first complete PSD permit 
application in a particular area is the operative ``baseline date.'' 
\3\ On or before the date of the first complete PSD application, 
emissions generally are considered to be part of the baseline 
concentration, except for certain emissions from major stationary 
sources, as explained in the following discussion of baseline dates. 
Most emissions increases that occur after the baseline date will be 
counted toward the amount of increment consumed. Similarly, emissions 
decreases after the baseline date restore or expand the amount of 
increment that is available.
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    \3\ Baseline dates are pollutant specific. That is, a complete 
PSD application establishes the baseline date only for those 
regulated NSR pollutants that are projected to be emitted in 
significant amounts (as defined in the regulations) by the 
applicant's new source or modification. Thus, an area may have 
different baseline dates for different pollutants.
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    In practice, three dates related to the PSD baseline concept are 
important in understanding how to calculate the amount of increment 
consumed-- (1) Trigger date; (2) major source baseline date; and (3) 
minor source baseline date. The first relevant date is the trigger 
date. The trigger date, as the name implies, triggers the overall 
increment consumption process nationwide. Specifically, this is a fixed 
date, which must occur before the minor source baseline date can be 
established for the pollutant-specific increment in a particular 
attainment area. See, 40 CFR 51.166(b)(14)(ii) and 52.21(b)(14)(ii). 
For PM (regulated as TSP) and SO2, Congress defined the 
applicable trigger date as August 7, 1977--the date of the 1977 
amendments to the Act when the original statutory increments were 
established by Congress. For nitrogen dioxide (NO2), we 
selected the trigger date as February 8, 1988--the date on which we 
proposed increments for NO2. See 53 FR 40656, 40658; October 
17, 1988. In this final rule, as described later, we are establishing a 
separate trigger date for purposes of implementing the PM2.5 
increments. See section V.F of this preamble for additional discussion 
of the trigger date for PM2.5.
    The two remaining dates--``minor source baseline date'' and ``major 
source baseline date''--as described later, are necessary to properly 
account for the emissions that are to be counted toward the amount of 
increment consumed following the national trigger date, in accordance 
with the statutory definition of ``baseline concentration'' in section 
169(4) of the Act. The statutory definition provides that the baseline 
concentration of a pollutant for a particular baseline area is 
generally the air quality at the time of the first application for a 
PSD permit in the area. Consequently, any increases in actual emissions 
occurring after that date (with some possible exceptions that we will 
discuss later) would be considered to consume the applicable PSD 
increment. However, the statutory definition in section 169(4) also 
provides that ``[e]missions of sulfur oxides and particulate matter 
from any major emitting facility on which construction commenced after 
January 6, 1975, shall not be included in the baseline and shall be 
counted in pollutant concentrations established under this part.''
    To make this distinction between the date when emissions resulting 
from the construction at a major stationary source consume the 
increment and the date when emissions changes in general (i.e., from 
both major and minor sources) begin to consume the increment, we 
established the terms ``major source baseline date'' and ``minor source 
baseline date,'' respectively. See 40 CFR 51.166(b)(14) and 
52.21(b)(14). Accordingly, the ``major source baseline date,'' which 
precedes the trigger date, is the date after which actual emissions 
increases associated with construction at any major stationary source 
consume the PSD increment. In accordance with the statutory definition 
of ``baseline concentration,'' the PSD regulations define a fixed date 
to represent the major source baseline date for each pollutant for 
which an increment exists. Congress defined the major source baseline 
date for the statutory increments for PM and SO2 as January 
6, 1975. For the NO2 increments, which we promulgated in 
1988 under our authority to establish an increment system under section 
166(a) of the Act, the major source baseline date we selected was 
February 8, 1988--the date on which we proposed increments for 
NO2. 53 FR 40656. In both instances, the major source 
baseline date for the individual increments was set as a date which 
preceded the date on which the regulations pertaining to those 
increments were issued. In this final rule, as described later, we are 
establishing a separate major source baseline date for implementing the 
PM2.5 increments. See section V.F of this preamble for 
further discussion of the major source baseline date for 
PM2.5.
    The ``minor source baseline date'' is the earliest date after the 
trigger date on which a source or modification submits the first 
complete application for a PSD permit in a particular area. After the 
minor source baseline date, any increase in actual emissions (from both 
major and minor sources) consumes the PSD increment for that area.
    Once the minor source baseline date is established, the new 
emissions increase from that major source consumes a portion of the 
increment in that area, as do any subsequent actual emissions increases 
that occur from any new or existing source in the area. When the 
maximum pollutant concentration increase defined by the increment has 
been reached, additional PSD permits cannot be issued until sufficient 
amounts of the increment are ``freed up'' via emissions reductions that 
may occur voluntarily, (e.g., via source shutdowns) or by mandatory 
control requirements imposed by the reviewing authority. Moreover, the 
air quality in a region cannot deteriorate to a level in excess of the 
applicable NAAQS, even if all the increment in the area has not been 
consumed. Therefore, new or modified sources located in areas where the 
air pollutant concentrations are near the level allowed by the NAAQS 
may not have full use of the amount of

[[Page 64869]]

pollutant concentration increase allowed by the increment.
    Under EPA guidance, the actual increment analysis that a proposed 
new or modified source undergoing PSD review must complete depends on 
the area impacted by the source's new emissions. We have provided 
approved air quality models and guidelines for sources to use to 
project the air quality impact of each pollutant (over each averaging 
period) for which an increment analysis must be done.\4\ In addition, 
we established SILs for each pollutant under the permit requirements 
applicable to new and modified major stationary sources locating in 
attainment areas that would cause or contribute to a violation of any 
NAAQS. See 40 CFR 51.165(b) and part 51, Appendix S, section III.A. 
These SILs have also been used for implementing the PSD program to 
identify levels below which the source's modeled impact of a particular 
pollutant is regarded as de minimis. In this final rule, we are 
establishing SILs (24-hour and annual) for PM2.5 that are 
being added to the aforementioned regulations containing SILs for other 
pollutants, as well as to the PSD regulations in 40 CFR 51.166 and 
52.21. See further discussion of the SILs for PM2.5 in 
section VI of this preamble.
---------------------------------------------------------------------------

    \4\ See EPA's ``Guideline on Air Quality Models'' at 40 CFR part 
51, Appendix W.
---------------------------------------------------------------------------

    In the event that a source's modeled impacts of a particular 
pollutant are below the applicable SIL at all ambient air locations 
modeled, i.e., de minimis everywhere, EPA's policy for PSD provides 
that no further modeling analysis is required for that pollutant. Our 
longstanding policy under the PSD program is that when a preliminary 
screening analysis based on the SIL is sufficient to demonstrate that 
the source's emissions throughout the area modeled will not cause or 
contribute to a violation of the increment, there is no need for a 
comprehensive source impact analysis involving a cumulative evaluation 
of the emissions from the proposed source and other sources affecting 
the area.
    Within the impact area of a source subject to PSD, that is, the 
area within which the proposed project's emissions increase does have a 
significant impact, increment consumption is calculated using the 
source's proposed emissions increase, along with other actual emissions 
increases or decreases of the particular pollutant from any sources in 
the area, which have occurred since the minor source baseline date 
established for that area. In addition, the emissions increases or 
decreases from any major source that has commenced construction since 
the major source baseline date (which precedes the minor source 
baseline date) will consume or expand increment. Thus, an emissions 
inventory of sources whose emissions, in whole or in part, of a 
particular pollutant consume or expand the available increment in the 
area must be compiled. The inventory of increment-consuming emissions 
includes not only sources located directly in the impact area, but 
sources outside the impact area that affect the air quality for the 
particular pollutant within the impact area.
    The inventory of increment-consuming emissions includes emissions 
from increment-affecting sources at two separate time periods--the 
baseline date and the current period of time. For each source that was 
in existence on the relevant baseline date (major source or minor 
source), the inventory includes the source's actual emissions on the 
baseline date and its current actual emissions. The change in emissions 
over these time periods represents the emissions that consume increment 
(or, if emissions have gone down, expand the available increment). For 
sources constructed since the relevant baseline date, all their current 
actual emissions consume increment and are included in the inventory.
    When the inventory of increment-consuming emissions has been 
compiled, computer modeling is used to determine the change in ambient 
concentration that will result from these emissions when combined with 
the proposed emissions increase from the new major source or major 
modification that is undergoing PSD review. The modeling has generally 
been guided by the ``Guideline on Air Quality Models'' (40 CFR part 51, 
Appendix W), which includes provisions on air quality models and the 
meteorological data input into these models. The model output 
(expressed as a change in concentration) for each relevant averaging 
period is then compared to the corresponding allowable PSD increment.

E. Historical Approaches for Developing Increments

1. Congressional Enactment of Increments for PM and SO2
    Congress established the first increments defining significant 
deterioration of air quality in the 1977 Amendments to the Act. These 
amendments, among other things, added part C to title I, setting out 
the requirements for PSD. In section 163, Congress included numerical 
increments for PM and SO2 for Class I, II, and III areas.
    The three area classes are part of the increment system originally 
established by Congress. Congress designated Class I areas (including 
certain national parks and wilderness areas) as areas of special 
national concern, where the need to prevent deterioration of air 
quality is the greatest. Consequently, the allowable level of 
incremental change is the smallest relative to the other area classes, 
i.e., most stringent, in Class I areas. The increments of Class II 
areas are larger than those of Class I areas and allow for a moderate 
degree of emissions growth. For future redesignation purposes, Congress 
defined a ``Class III'' classification to allow the redesignation of 
any existing Class II area for which a State may desire to promote a 
higher level of industrial development (and emissions growth). Thus, 
Class III areas are allowed to have the greatest amount of pollutant 
increase of the three area classes while still achieving the NAAQS. To 
date, there have been no redesignations made to establish a Class III 
area.
    In establishing these PSD increments, Congress used the then-
existing NAAQS for those pollutants as the benchmark for determining 
what constitutes ``significant deterioration.'' Congress established 
the increments for PM as a percentage of the then-existing PM NAAQS. At 
the time the Act was amended in 1977, the NAAQS for PM were expressed 
in terms of ambient concentrations of TSP. Thus, EPA interpreted the 
statutory increments for PM using the same ambient TSP ``indicator.''
2. EPA's Promulgation of Increments for NO2 and 
PM10
    Congress also provided authority for EPA to promulgate additional 
increments and to update the original PM increments created by statute. 
The EPA has promulgated two regulations pursuant to this authority.
a. Increments for NO2 Using the ``Contingent Safe Harbor'' 
Approach Under Section 166(a) of the Act
    Based on section 166(a) of the Act, on October 17, 1988, EPA 
promulgated increments for NO2 to prevent significant 
deterioration of air quality due to emissions of NOX (53 FR 
40656). The EPA based these increments on percentages of the NAAQS in 
the same way that Congress derived the statutory increments for PM and 
SO2. Those NO2 increments were challenged in 1988 
by the Environmental Defense Fund (EDF) when EDF filed suit in the U.S. 
Court of

[[Page 64870]]

Appeals for the District of Columbia Circuit against the Administrator 
(Environmental Defense Fund, Inc. v. Reilly, No. 88-1882). The EDF 
successfully argued that we failed to sufficiently consider certain 
provisions in section 166 of the Act. The court remanded the case to 
EPA ``to develop an interpretation of section 166 that considers both 
subsections (c) and (d), and if necessary to take new evidence and 
modify the regulations.'' See Environmental Defense Fund v. EPA, 898 
F.2d 183, 190 (D.C. Cir. 1990) (EDF v. EPA). Section 166(c) of the Act 
requires the PSD regulations to, among other things, meet the goals and 
purposes set forth in sections 101 and 160 of the Act. Section 166(d) 
requires these regulations be at least as effective as the increments 
established for PM (in the form of TSP) and SO2 in section 
163 of the Act. The court considered the NO2 increment 
values determined using the percentage-of-NAAQS approach as ``safe 
harbor'' increments which met the requirements of section 166(d) of the 
Act. However, the court also determined that EPA's reliance on such 
increment levels was contingent upon our completing the analyses 
required under section 166(c), which provided that the final increment 
values must address the goals of sections 101 and 160 of the Act to 
protect public health and welfare, parks, and AQRVs \5\ and to insure 
economic growth.
---------------------------------------------------------------------------

    \5\ The term ``air quality related values'' is not defined in 
the Act, but the legislative history provides language saying that 
``The term `air quality related values' of Federal lands designated 
as Class I includes the fundamental purposes for which such lands 
have been established and preserved by the Congress and the 
responsible Federal agency. For example, under the 1916 Organic Act 
to establish the National Park Service (16 U.S.C. 1), the purpose of 
such national park lands `is to conserve the scenery and the natural 
and historic objects and the wildlife therein and to provide for the 
enjoyment of the same in such manner and by such means as will leave 
them unimpaired for the enjoyment of future generations.' '' S. Rep. 
No. 95-127 at 36 (1977).
---------------------------------------------------------------------------

    In response to the court's decision, we proposed rulemaking on 
increments for NO2 on February 23, 2005 (70 FR 8880) and 
finalized the rule on October 12, 2005 (70 FR 59582). In the final 
rule, we established our policy on how to interpret and apply the 
requirements of sections 166(c) and (d) of the Act. In accordance with 
the court ruling, we conducted further analyses (considering the health 
and welfare effects of NOX) and concluded that the existing 
NO2 increments were adequate to fulfill the requirements of 
section 166(c). See 70 FR 59586 for our detailed analysis of how 
pollutant regulations satisfy the requirements of section 166 of the 
Act. Hence, we retained the existing NO2 increments along 
with other parts of the existing framework of pollutant-specific 
NO2 increment regulations. We also amended the PSD 
regulations under 40 CFR 51.166 to make it clear that states may seek 
EPA approval of SIPs that utilize a different approach than EPA used to 
establish these NO2 increments. To receive our approval of 
an alternative program, a State must demonstrate that its program 
satisfies the requirements of sections 166(c) and 166(d) of the Act and 
prevents significant deterioration of air quality from emissions of 
NOX.\6\
---------------------------------------------------------------------------

    \6\ Under the 2005 NOX regulation, states can adopt 
measures other than increments as long as they can demonstrate that 
the measures selected comply with the same criteria and goals of 
sections 166(c) and (d) of the Act that must be met for increments.
---------------------------------------------------------------------------

b. Increments for PM10 Using ``Equivalent Substitution'' 
Approach Under Section 166(f) of the Act
    On October 5, 1989, we proposed PM10 increments. See 54 
FR 41218. Although section 163 did not expressly define the existing 
statutory increments for PM in terms of a specific indicator, EPA 
reasoned that Congress' knowledge that TSP was the indicator for the PM 
NAAQS, and that the TSP standards were the starting point for the 
increments levels when the increments were established in 1977, meant 
that TSP was also the appropriate measure for the PM increments in 
section 163. As a consequence, EPA believed that the statutory PM 
increments could not simply be administratively redefined as 
PM10 increments, retaining the same numerical values, 
following the revision of the PM NAAQS. Rather, we stated our belief 
that with the promulgation of the PM10 NAAQS, EPA had both 
the responsibility and the authority under sections 166 and 301 of the 
Act to promulgate new increments for PM to be measured in terms of 
PM10. We further concluded that promulgating PM10 
increments to replace, rather than supplement, the statutory TSP 
increments under section 163 represented the most sensible approach for 
preventing significant deterioration with respect to PM. See 54 FR 
41220-41221.
    We promulgated PM10 increments to replace the then-
existing TSP increments on June 3, 1993 (58 FR 31622). In the interim 
between proposal and promulgation, Congress enacted the 1990 CAA 
Amendments. As part of these amendments, Congress amended section 166 
to add a new section 166(f). This section specifically authorized EPA 
to substitute PM10 increments for the existing section 163 
PM increments based on TSP, provided that the substituted increments 
are ``of equal stringency in effect'' as the section 163 increments.
    Thus, we were able to replace the TSP increments under section 163 
of the Act using PM10 increments based directly on the newly 
enacted authority under section 166(f) of the Act. In the 
PM10 rule, we maintained the existing baseline dates and 
baseline areas for PM that had been previously established using the 
TSP indicator. Also, as proposed, we promulgated PM10 
increments based on an approach we called the ``equivalent to statutory 
increments'' approach. Under this approach, we used the original TSP 
increments as a benchmark for calculating the PM10 
increments, thereby retaining roughly the same limitations on future 
deterioration of air quality as was allowed under the TSP increments.
    In using this approach, we considered the historical consumption of 
TSP increment by a sample population of permitted PSD sources, and then 
determined the PM10 increments for each area classification 
and averaging time that would provide approximately the same percentage 
of PM10 increment consumption, on average, by the same 
population of sources. Then, all future calculations of increment 
consumption after the PM10 implementation date would be 
based on PM10 emissions. See 58 FR 31622 and 31625.

V. Final Action on PM2.5 Increments

    In this section of the preamble, we will summarize the 
considerations that went into our proposed action and describe the 
final action being taken regarding new regulations for preventing 
significant deterioration of PM2.5 air quality--including 
PM2.5 increments (sections V.A through V.E, baseline dates 
and other permit requirements for PM2.5 (section V.F), 
baseline areas for PM2.5 (section V.G), and PM10 
increments (section V.H).

A. Decision To Establish PM2.5 Increments Using ``Contingent 
Safe Harbor Approach'' Under Section 166(a)

    The EPA's 2007 NPRM contained three options for developing 
numerical PM2.5 increments. Option 1 used the authority of 
section 166(a) of the Act to establish increments for PM2.5 
as a new pollutant for which NAAQS were established after August 7, 
1977, and established 24-hour and annual PM2.5 increments 
(Class I, II, and III) based on the ``contingent safe harbor'' 
approach. Options 2 and 3 used the contingent safe harbor approach 
under section 166(a) to only develop 24-hour PM2.5 
increments (Class I, II, and III), while using the ``equivalent 
substitution''

[[Page 64871]]

approach under section 166(f) of the Act to develop annual 
PM2.5 increments. Each of these options is discussed in 
detail in the 2007 NPRM. 72 FR 54123-54138. In addition, significant 
comments on each of the three options, and our responses to them, are 
provided in this section V of this preamble.
    In this final rule, after considering the available information and 
comments from interested parties, EPA has decided to select Option 1 
and establish increments for PM2.5 using the ``contingent 
safe harbor'' approach in accordance with the authority provided in 
section 166(a) of the Act.
    This final rule establishes increments for PM2.5 at the 
following levels:

----------------------------------------------------------------------------------------------------------------
                                                                 NAAQS           Increments ([micro]g/m\3\)
                      Averaging period                         ([micro]g/ --------------------------------------
                                                                 m\3\)       Class I      Class II    Class III
----------------------------------------------------------------------------------------------------------------
Annual......................................................           15            1            4            8
24-hour.....................................................           35            2            9           18
----------------------------------------------------------------------------------------------------------------

B. Rationale for the Applicability of Section 166(a)

    In the 2007 NPRM, we expressed our belief that it is permissible to 
interpret section 166(a) to apply to PM2.5. Section 166(a) 
requires EPA to develop regulations to prevent the significant 
deterioration of air quality due to emissions of certain named 
pollutants, and to develop such regulations for any pollutants for 
which NAAQS are subsequently promulgated. Although EPA has generally 
characterized the NAAQS for PM2.5 as a NAAQS for a new 
indicator of PM, EPA did not replace the PM10 NAAQS with the 
NAAQS for PM2.5 when the latter NAAQS were promulgated in 
1997. Rather, EPA retained the annual and 24-hour PM10 NAAQS 
(retaining PM10 as an indicator of coarse particulate 
matter), and established new annual and 24-hour NAAQS for 
PM2.5 as if PM2.5 was a new pollutant, even 
though EPA had already developed air quality criteria for PM generally. 
Thus, for purposes of section 166(a), the promulgation of a NAAQS for 
PM2.5 established a NAAQS for an additional pollutant after 
1977.
    Nine commenters supported our proposed Option 1, although only 
three of these explicitly expressed support for the use of section 
166(a) authority to promulgate PM2.5 increments. Ten other 
commenters specifically opposed the use of section 166(a) authority 
and/or supported the use of section 166(f) authority (on which the 
annual increments under Options 2A and 2B were based).
    One of the commenters who explicitly agreed with our proposed use 
of section 166(a) authority stated that it is the only option that is 
legally available. This commenter asserted that section 166(a) plainly 
applies to PM2.5 because PM2.5 is a pollutant for 
which NAAQS were promulgated after August 7, 1977. This commenter held 
that EPA's rulemaking duty under section 166(a) is not confined to 
``new pollutants,'' but is triggered by post-1977 NAAQS promulgations, 
regardless of whether for new or previously regulated pollutants. On 
the other hand, this commenter noted that by its terms, section 166(f) 
is limited to authorizing the adoption of PM10 increments as 
a substitute for the statutory TSP increments and does not provide for 
substitution of PM2.5 increments for TSP or PM10 
increments.
    The opposing commenters did not believe that section 166(a) 
provides a legal basis for EPA to promulgate PM2.5 
increments. One of these commenters stated that section 166(a) can only 
be used for a new pollutant, and PM2.5 is not a new 
pollutant.
    Another commenter who opposed the use of section 166(a) authority 
argued that nothing in section 166(a) of the Act can be interpreted to 
allow it to be used as the basis of increments when EPA revises an 
existing NAAQS. The commenter explained that, on its face, section 
166(a) can only be interpreted to apply to pollutants other than PM and 
SO2 since increments for these pollutants were enacted by 
Congress in section 163 of the Act. The commenter added that it can be 
argued that Congress intended to have section 166(a) apply to the four 
other pollutants specifically listed there.
    This commenter found unpersuasive our argument that we are not 
``substituting'' increments (as section 166(f) requires for 
PM10) but rather adding PM2.5 increments to the 
existing PM10 increments, and that only section 166(a) 
allows such an approach (72 FR 54121). The commenter asserted that if 
EPA had defined a coarse fraction to the particulate matter standards, 
then that fraction, together with the PM2.5 standards, would 
form the set of ``substituted'' new standards for the existing 
PM10 standards, and, thus, the increments.
    The commenter also disagreed with EPA's argument that it can treat 
PM2.5 as a new pollutant under section 166(a) of the Act 
since it has been demonstrated that sub-PM2.5 particles have 
distinctly different health and welfare effects than the other forms of 
PM (i.e., coarse or PM10). The commenter indicated that just 
as EPA replaced the TSP standards by PM10 as a better 
indicator of health effects, ongoing research has led to establishment 
of the PM2.5 standards as a better indicator of certain 
health effects, and it is the natural outcome of such research that has 
enabled EPA to separate the effect of total particulate matter into two 
fractions with distinct effects. The commenter added that given that 
the definition of particulate matter includes a vast conglomeration of 
solids and liquids, the finding of differing effects should not come as 
a surprise. The commenter explained that as is the case of different 
pollutants having similar effects that are, nonetheless, treated as 
separate pollutants, the same concept should apply to a range or 
fraction of particulate matter found to have different effects in 
establishing it as another indicator and not a different pollutant.
    The commenter did not disagree with the specific numerical 
increments proposed by EPA under Option 1, but did have concerns with 
the potential consequences of the section 166(a) approach. The 
commenter's primary concern was the proposal to allow states to 
substitute other measures in the place of uniform national increments 
for PM2.5. (This is discussed further in section V.C.5 of 
this preamble.) Another commenter also expressed this concern.
    Another commenter who opposed the section 166(a) approach believes 
that the legal and congressional history regarding the establishment of 
PM increments shows that Congress added section 166(f) to the Act based 
on the conviction that without it, EPA had no authority to revise the 
PM increments for PM10 (citing and quoting from S. Rep. No. 
228, 101st Cong., 2nd Sess. 75 (1990), reprinted in 1990 U.S.C.C.A.N. 
3385, 3461). The commenter concluded that EPA did not have authority in 
1987 under section 166(a) to adopt PM10 increments, and does 
not have authority now under section 166(a) to adopt PM2.5 
increments.
    We read section 166(a) to authorize EPA to promulgate pollutant-
specific PSD regulations meeting the

[[Page 64872]]

requirements of sections 166(c) and 166(d) for any pollutant for which 
EPA promulgates a NAAQS after 1977. Most of the pollutants identified 
in section 166(a) (NOX, photochemical oxidants, carbon 
monoxide) are pollutants for which EPA had established NAAQS in 1977 
when Congress adopted section 166 of the Act. There was no need for 
Congress to list other criteria pollutants, SO2 and PM, in 
section 166(a) because Congress had already established increments for 
these pollutants in section 163 of the Act. In addition to requiring 
regulations for the enumerated pollutants, we conclude that under 
section 166 of the Act Congress intended to authorize EPA to establish 
additional pollutant-specific PSD regulations, potentially containing 
increments, for any additional pollutants for which EPA promulgated a 
NAAQS under section 109 of the Act. Furthermore, because the Act refers 
to pollutants for which EPA promulgates NAAQS after 1977, and does not 
use the phrase ``additional pollutants,'' section 166(a) provides 
authority for EPA to promulgate new increments after revising an 
existing NAAQS (including NAAQS first promulgated before 1977), when we 
find that such action is appropriate.
    Moreover, any new increments developed pursuant to section 166(a) 
have no effect on existing increments, as there is no indication 
therein that an existing increment should be revoked or replaced when 
additional increments are promulgated. This was the situation following 
the promulgation of new NAAQS for PM in 1987 when EPA replaced the old 
NAAQS based on TSP with new ones based on PM10. Had Congress 
not added new section 166(f) in 1990, increments for PM10 
could have been developed pursuant to section 166(a) of the Act, but 
such increments would have had no effect on the original statutory 
increments for PM (based on TSP). Consequently, seeing no basis for 
retaining the original increments, Congress added section 166(f) which 
explicitly provides for the replacement of the existing increments with 
PM10 increments.
    One commenter asserted that if EPA establishes increments for 
PM2.5 under the authority of section 166(a) on the basis 
that PM2.5 is a new pollutant, then it must also establish 
PM10 increments under section 166(a) because (according to 
the commenter's analysis) PM10 is also a new pollutant. In 
the same analysis, the commenter concluded that EPA must adopt new 
measures to prevent significant deterioration from coarse PM based on 
section 166(a).
    In this final rule, EPA is not setting or amending any increments 
for PM10 or otherwise taking action with respect to 
PM10 increments. The preexisting annual and 24-hour 
increments for PM10 are being retained. See section V.H. 
Similarly, EPA is not taking any action with respect to coarse PM in 
this rule. For these reasons, the commenter's arguments on what 
authority must be used to set increments for PM10 and/or 
coarse PM, and that EPA has some obligation to take action with respect 
to coarse PM, are not on point for this rule. Thus, no substantive 
response to this comment is needed. Nevertheless, as mentioned earlier, 
Congress provided explicit authority under section 166(f) of the Act to 
address increments for PM10, because it intended