[Federal Register Volume 72, Number 183 (Friday, September 21, 2007)]
[Proposed Rules]
[Pages 54112-54156]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-18346]
[[Page 54111]]
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Part II
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);
Proposed Rule
Federal Register / Vol. 72, No. 183 / Friday, September 21, 2007 /
Proposed Rules
[[Page 54112]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 51 and 52
[EPA-HQ-OAR-2006-0605; FRL-8470-1]
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: Proposed rule.
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SUMMARY: The Clean Air Act (Act) authorizes EPA to establish
regulations to prevent significant deterioration of air quality due to
emissions of any pollutant for which a national ambient air quality
standard (NAAQS) has been promulgated. The NAAQS for particulate matter
using the PM2.5 indicator were promulgated in 1997. The EPA
is proposing to facilitate implementation of a PM2.5
Prevention of Significant Deterioration (PSD) program in areas
attaining the particulate matter less than 2.5 micrometers
(PM2.5) NAAQS by developing PM2.5 increments,
Significant Impact Levels (SILs), and a Significant Monitoring
Concentration (SMC). In addition, EPA is proposing to revoke the annual
PM10 increments.
``Increments'' are maximum increases in ambient PM2.5
concentrations (PM2.5 increments) allowed in an area above
the baseline concentration. The SILs and SMCs are numerical values that
represent thresholds of insignificant, i.e., de minimis, modeled source
impacts or monitored (ambient) concentrations, respectively. The EPA is
proposing such values for PM2.5 that will be used as
screening tools by a major source subject to PSD to determine the
subsequent level of analysis and data gathering required for a PSD
permit application for emissions of PM2.5.
DATES: Comments must be received on or before November 20, 2007. Under
the Paperwork Reduction Act, comments on the information collection
provisions must be received by the Office of Management and Budget
(OMB) on or before October 22, 2007.
Public Hearing. If anyone contacts us requesting to speak at a
public hearing by October 11, 2007, we will hold a public hearing.
Additional information about the hearing would be published in a
subsequent Federal Register notice.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2006-0605, by one of the following methods:
www.regulations.gov. Follow the on-line instructions for
submitting comments.
E-mail: [email protected].
Mail: Air and Radiation Docket and Information Center,
Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460. Please include a total of two
copies. In addition, please mail a copy of your comments on the
information collection provisions to the Office of Information and
Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk
Officer for EPA, 725 17th Street, Northwest, Washington, DC 20503.
Hand Delivery: Air and Radiation Docket and Information
Center, EPA/DC, EPA West, Room 3334, 1301 Constitution Avenue, NW.,
Washington, DC 20004. Such deliveries are only accepted during the
Docket Center's normal hours of operation, and special arrangements
should be made for deliveries of boxed information.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2006-0605. 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 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 www.regulations.gov
or e-mail. The www.regulations.gov Web site is an ``anonymous access''
system, which means EPA will not know your identity or contact
information unless you provide it in the body of your comment. If you
send an e-mail comment directly to EPA without going through
www.regulations.gov your e-mail address will be automatically captured
and included as part of the comment that is placed in the public docket
and made available on the Internet. If you submit an electronic
comment, EPA recommends that you include your name and other contact
information in the body of your comment and with any disk or CD-ROM you
submit. If EPA cannot read your comment due to technical difficulties
and cannot contact you for clarification, EPA may not be able to
consider your comment. Electronic files should avoid the use of special
characters, any form of encryption, and be free of any defects or
viruses. For additional instructions on submitting comments, go to
section I.B of the SUPPLEMENTARY INFORMATION section of this document.
Docket: All documents in the docket are listed in the
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 www.regulations.gov or in hard copy at the Air and Radiation Docket
and Information Center, 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 and Radiation Docket and
Information Center is (202) 566-1742.
FOR FURTHER INFORMATION CONTACT: Mr. Raghavendra (Raj) Rao, 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) 541-5344; fax number (919) 541-
5509; e-mail address: [email protected] or Dan deRoeck, 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) 541-5593; fax number (919) 541-
5509; e-mail address: [email protected]. To request a public hearing
or information pertaining to a public hearing on this document, contact
Ms. Pamela S. 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; e-mail address: [email protected].
SUPPLEMENTARY INFORMATION:
I. General Information
A. Does this action apply to me?
Entities potentially affected by this proposed action include
owners and operators of emission sources in all industry groups, as
well as the EPA and State, local, and tribal governments that are
delegated authority to implement these regulations. The majority of
sources potentially affected are expected to be in the following
groups:
[[Page 54113]]
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Category NAICS\a\ Industry group
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Industry......................... 221111, 221112, Electric services.
221113, 221119,
221121, 221122.
32411............... Petroleum refining.
325181, 32512, Industrial inorganic chemicals.
325131, 325182,
211112, 325998,
331311, 325188.
32511, 325132, Industrial organic chemicals.
325192, 325188,
325193, 32512,
325199.
32552, 32592, 32591, Miscellaneous chemical products.
325182, 32551.
211112.............. Natural gas liquids.
48621, 22121........ Natural gas transport.
32211, 322121, Pulp and paper mills.
322122, 32213.
322121, 322122...... Paper mills.
336111, 336112, Automobile manufacturing.
336712, 336211,
336992, 336322,
336312, 33633,
33634, 33635,
336399, 336212,
336213.
325411, 325412, Pharmaceuticals.
325413, 325414.
Federal government............... 924110.............. Administration of Air and Water Resources and Solid
Waste Management Programs.
State/local/tribal Government.... 924110.............. Administration of Air and Water Resources and Solid
Waste Management Programs.
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\a\ North American Industry Classification System.
This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action. To determine whether your facility is regulated by this action,
you should examine the applicability criteria in the PSD rules for
attainment areas (40 CFR 52.21). If you have any questions regarding
the applicability of this action to a particular entity, contact the
person listed in the preceding FOR FURTHER INFORMATION CONTACT section.
B. What should I consider as I prepare my comments for EPA?
1. Submitting CBI. Do not submit this information to EPA through
www.regulations.gov or e-mail. Clearly mark the part or all of the
information that you claim to be CBI. For CBI information in a disk or
CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as
CBI and then identify electronically within the disk or CD ROM the
specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2. Send or deliver information
identified as CBI only to the following address: Roberto Morales, OAQPS
Document Control Officer (C404-02), Environmental Protection Agency,
Research Triangle Park, NC 27711, Attention Docket ID No. EPA-HQ-OAR-
2006-0605.
2. Tips for Preparing Your 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 agency 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.
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, 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.
C. 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 proposal will also be available on the World Wide Web. Following
signature by the EPA Administrator, a copy of this notice will be
posted in the regulations and standards section of our NSR home page
located at http://www.epa.gov/nsr.
D. How can I find information about a possible Public Hearing?
Persons interested in presenting oral testimony should contact Ms.
Pamela Long, New Source Review Group, Air Quality Policy Division
(C504-03), Environmental Protection Agency, Research Triangle Park, NC
27711; telephone number (919) 541-0641 or e-mail [email protected] at
least 2 days in advance of the public hearing. Persons interested in
attending the public hearing should also contact Ms. Long to verify the
time, date, and location of the hearing. The public hearing will
provide interested parties the opportunity to present data, views, or
arguments concerning these proposed rules.
The information presented in this preamble is organized as follows:
I. General Information
A. Does this action apply to me?
B. What should I consider as I prepare my comments for EPA?
C. Where can I get a copy of this document and other related
information?
D. How can I find information about a possible Public Hearing?
II. Overview of Proposed Regulations
A. Summary of Proposed Options for Increments
B. Summary of Proposed Options for SILs
C. Summary of Proposed Options for the PM2.5 SMC
III. Background
A. PSD Program
B. History of PM NAAQS
1. TSP and PM10 NAAQS
2. PM2.5 NAAQS
3. Revised PM2.5 and PM10 NAAQS
C. Implementation of NSR for PM2.5
D. Background on Implementation of PSD Increments
[[Page 54114]]
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 NOX 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)
IV. EPA's Interpretation of Section 166 of the Clean Air Act
A. Which Criteria In Section 166 Should EPA Use to Develop
Increments for PM2.5?
1. Support for ``Contingent Safe Harbor'' Approach for
PM2.5 Under Section 166(a)
2. Support of ``Equivalent Substitution'' Approach for
PM2.5 Under Section 166(f)
B. Requirements of Sections 166(a)-(d) of the Clean Air 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
C. Requirements of Section 166(f) of the Clean Air Act
V. Increments and Other Measures to Prevent Significant
Deterioration
A. Option 1--Contingent Safe Harbor Approach for Annual and
Short-Term Increments--Section 166(a)
1. Proposed Framework for Pollutant Specific PSD Regulations for
PM2.5
a. Increment System
b. Area Classifications
c. Permitting Procedures
d. Air Quality Related Values Review by Federal Land Manager and
Reviewing Authority
e. Additional Impacts Analysis
f. Installation of Best Available Control Technology
2. Proposed Increments
a. Identification of Safe Harbor Increments
b. Data Utilized by EPA for the Evaluation of the Safe Harbor
Increments for PM2.5
c. Scope of Effects Considered
d. Evaluation of the Health and Welfare Effects of
PM2.5
e. Fundamental Elements of Increments
f. Evaluation of the Safe Harbor Increments
3. Proposed Baseline Dates for PM2.5 Increments Under
Option 1
4. Revocation of PM10 Annual Increments
B. Option 2--Equivalent Substitution Approach for Annual
Increments--Section 166(f)
1. Development of Equivalent Increments
2. Proposed Annual Increments for PM2.5
a. Option 2A
b. Option 2B
3. Baseline dates
VI. Significant Impact Levels (SILs)
A. EPA's Guidance on SILs in the PSD Program
B. Legal Basis for SILs
C. Relationship of SILs to AQRVs
D. Proposed Options for PM2.5 SILs (for PSD and NA-
NSR)
1. Option 1. Propose SILs using the approach we proposed for
PM10 in 1996
2. Option 2. PM2.5 to PM10 Emissions Ratio
3. Option 3. PM2.5 to PM10 NAAQS Ratio
VII. Significant Monitoring Concentrations (SMCs)
A. Background on SMCs
1. Preconstruction Monitoring and Its Role in NSR Program
2. History of SMC Rules Adopted by EPA
B. Legal Basis for SMCs
C. Proposed Options for PM2.5 SMC
1. Option 1. Lowest Detectable Concentration
2. Option 2. PM2.5 to PM10 Emissions Ratio
3. Option 3. PM2.5 to PM10 NAAQS Ratio
D. Correction of Cross References
VIII. Effective Date of the Final Rule, SIP Submittal/Approval
Deadlines and PM10 Revocation Deadline
A. Option 1: Increments promulgated pursuant to section 166(a)
of the Act.
1. Effective Date of Final Rule
2. State Program
3. Federal Program
B. Option 2: Increments Promulgated Pursuant to Section 166(f)
of the Act.
1. Effective date of Final Rule
2. State Program
3. Federal Program
C. Revocation of the PM10 Increment
D. Transition Period
E. Effective Date for SILs and SMCs
IX. 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 & 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
X. Statutory Authority
II. Overview of Proposed Regulations
This proposal is the first step in the rulemaking process for
promulgating PM2.5 increments, SILs, and a SMC. The purpose
of this proposed rulemaking is to develop the final elements that will
aid implementation of the PSD program for PM2.5. When final,
these elements will supplement the final NSR implementation rule for
PM2.5. Following final action on this proposal and the
PM2.5 implementation rule for NSR, the Federal
PM2.5 NSR programs will no longer have to rely on the
PM10 program as a surrogate, as has been the practice under
our existing guidance. A State implementing a NSR program in an EPA
approved State Implementation Plan (SIP) may continue to rely on the
interim surrogate policy until we approve a revised SIP addressing
these requirements. In this rulemaking, we \1\ are proposing several
options for increments, SILs and the SMC, respectively.
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\1\ In this proposal, the terms ``we,'' ``us,'' and ``our''
refer to the EPA and the terms ``you'' and ``your'' refer to the
owners or operators of stationary sources of air pollution.
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A. Summary of Proposed Options for Increments
We are proposing three sets of PM2.5 increments, based
on several approaches that are described in greater detail later in
this preamble. For the first set (option 1), we are relying on an
approach that treats PM2.5 as a new pollutant. This option
follows our statutory authority section 166(a) of the Act to develop
increments for ``pollutants for which national ambient air quality
standards are promulgated after the date of enactment of this part * *
* '' This is the same approach that we used to establish NOX
increment regulations on October 12, 2005 (70 FR at 59586). The second
and third options (options 2A and 2B) rely on an approach that we used
in 1993 to promulgate PM10 increments in lieu of the
statutory increments for particulate matter (PM) following our
replacement of the then existing indicator for the PM NAAQS based on
total suspended particulate with a new indicator based on
PM10. (58 FR 31622, June 3, 1993.) These two options
represent variations of the approach used under the authority of
section 166(f) of the Act to ``substitute'' PM10 increments
for TSP increments. The increment values resulting from each of these
three options are:
[[Page 54115]]
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Proposed increments ([mu]g/m\3\) NAAQS ([mu]g/m\3\)
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Option Class I Class II Class III
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Annual 24-hr Annual 24-hr Annual 24-hr
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1............................................................... 1 2 4 9 8 18 ......... .........
2A.............................................................. 1 2 4 9 8 18 15 35
2B.............................................................. 1 2 5 9 10 18 ......... .........
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B. Summary of Proposed Options for SILs
We are also proposing three options for SILs. The first option
utilizes the same approach we proposed for PM10 in the 1996
NSR Reform proposal. For option 2, we are proposing to scale the
PM10 SIL values by the ratio of direct PM2.5 to
direct PM10 emissions. The PM2.5/PM10
emissions ratio is the national average derived from the 2001
extrapolation of the 1999 National Emissions Inventory. For option 3,
we are proposing to scale the PM10 SIL values by the ratio
of the PM2.5 NAAQS to the PM10 NAAQS. The SIL
values resulting from each of these options are:
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Proposed SILs ([mu]g/m\3\)
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Option Class I Class II Class III
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Annual 24-hr Annual 24-hr Annual 24-hr
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1............................................. 0.04 0.08 1.0 5.0 1.0 5.0
2............................................. 0.16 0.24 0.8 4.0 0.8 4.0
3............................................. 0.06 0.07 0.3 1.2 0.3 1.2
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C. Summary of Proposed Options for the PM2.5 SMC
The first option we are proposing for the SMC is the ``Lowest
Detection Concentration'' or LDC approach that we used for establishing
the SMC for TSP and PM10. For option 2, we are proposing to
scale the PM10 SMC value by the ratio of direct
PM2.5 to direct PM10 emissions. The
PM2.5/PM10 emissions ratio is the national
average derived from the 2001 extrapolation of the 1999 National
Emissions Inventory. For option 3, we are proposing to scale the
PM10 SMC value by the ratio of the PM2.5 NAAQS to
the PM10 NAAQS. The proposed SMC values for each of these
options for the 24-hour averaging period are:
Option 1--10 [mu]g/m\3\
Option 2--7.9 [mu]g/m\3\
Option 3--2.3 [mu]g/m\3\
III. 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 new source
review (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.\2\ 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
incremental ambient pollutant concentration increase (increment). 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.''
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\2\ We have delegated authority to some States to implement the
Federal PSD program. The EPA remains the reviewing authority in non-
delegated States and in Indian country.
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As part of the analysis of air quality impacts to determine
compliance with the NAAQS and increment, the permit applicant and
reviewing authority may compare the source's impacts for a pollutant
with the corresponding SIL for that pollutant to show that a cumulative
air quality impacts analysis is not necessary. Similarly, the permit
applicant and reviewing authority may use the corresponding SMC for
that pollutant to determine if pre-application site-specific ambient
monitoring data is needed to conduct the air quality analysis.
When the reviewing authority reaches a preliminary decision to
authorize construction of each 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 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.
[[Page 54116]]
B. History of PM NAAQS
1. 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 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 promulgated new NAAQS for PM in which we
changed the indicator from TSP to PM10, the latter including
particles with a mean aerodynamic diameter less than or equal to 10
micrometers. These smaller 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
for 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. Our 1997 rules 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 action 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 micrograms per cubic meter ([mu]g/m\3\) to 35
[mu]g/m\3\, and retained the existing annual PM2.5 NAAQS of
15 [mu]g/m\3\. In addition, we retained the existing PM10
24-hour NAAQS of 150 [mu]g/m\3\, and revoked the annual PM10
NAAQS (previously set at 50 [mu]g/m\3\).
C. Implementation of NSR for PM2.5
After we established new annual and 24-hour NAAQS for
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 in July 1997, we issued a guidance
document ``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 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 provides 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 recommends that until we promulgate 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 indicate in that proposal that we will develop increments, SILs,
and SMC in a separate rulemaking--i.e. this proposed rulemaking. Since
there was an interim surrogate NSR program in place, EPA decided to
first promulgate the non-NSR part of the implementation rule (including
attainment demonstrations, designations, control measures etc.)--which
was promulgated on April 25, 2007. The NSR part of the implementation
rule is anticipated to be promulgated in September 2007. Additionally,
once this proposed rulemaking is finalized, States will be able to
fully implement a PM2.5 NSR program.
D. Background on Implementation of PSD Increments
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. * * *'' 42 U.S.C. 7475(a)(3). 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.''
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 an
ambient pollutant increase of at least 1 [mu]g/m\3\ (annual average).
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
[[Page 54117]]
``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) minor source baseline date; and (3)
major source baseline date. Chronologically, 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, e.g., 40 CFR 52.21(b)(14)(ii). For PM 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 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 action, as described later, we are proposing to add a
new trigger date for purposes of calculating the new PM2.5
increments.
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 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 changes in
general (i.e., from both major and minor sources) affect the increment
and the date when emissions resulting from the construction at a major
stationary source consume the increment, we established the terms
``minor source baseline date'' and ``major source baseline date,''
respectively. See 40 CFR 51.166(b)(14) and 52.21(b)(14). Accordingly,
the ``minor source baseline date'' is the date on which the first
complete application for a PSD permit is filed in a particular area.
Any change in actual emissions after that date affects the PSD
increment for that area.
The ``major source baseline date'' is the date after which actual
emissions increases associated with construction at any major
stationary source affect 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 is February 8, 1988--the date on which we
proposed increments for NO2. 53 FR 40656. In this action, as
described later, we are proposing to add a new major source baseline
date for PM2.5.
The PSD regulations set out the third date that is relevant to the
PSD baseline concept. These regulations provide that the earliest date
on which the minor source baseline date can be established is the date
immediately following the ``trigger date'' for the pollutant-specific
increment. See, e.g., 40 CFR 52.21(b)(14)(ii). For PM 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 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.
Once the minor source baseline date associated with the first PSD
permit application for a proposed new major stationary source or major
modification in an area is established, the new emissions from that
source consume 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 via 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 has not been consumed. Therefore, new or modified sources
located in areas where the air pollutant concentration is near the
level allowed by the NAAQS may not have full use of the amount of
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.\4\ We have also
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.\5\ In
addition, we established significant impact levels for each pollutant
under the nonattainment major NSR program that have also been used
under the PSD program to identify levels below which the source's
modeled impact is regarded as de minimis. See 40 CFR 51.165(b) and part
51, appendix S, section III.A. In the event that a source's modeled
impacts of a particular pollutant are below the applicable significant
impact level at all ambient air locations modeled, i.e., de minimis
everywhere, EPA policy provides that no further modeling analysis is
required for that pollutant. Our policy is that when a preliminary
screening analysis based on the significant impact level is sufficient
to demonstrate that the source's
[[Page 54118]]
emissions will not cause or contribute to a violation of the increment,
there is no need for a full impacts analysis involving a cumulative
evaluation of the emissions from the proposed source and other sources
affecting the area.
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\4\ We note that on June 6, 2007, we published a notice of
proposed rulemaking proposing to refine several aspects of the
increment calculation process to clarify how States and regulated
sources may calculate increases in pollutant concentrations for
purposes of determining compliance with the PSD increments. See 72
FR at 31372. When final, these revisions will amend the PSD
regulations at 40 CFR 51.166 and 52.21.
\5\ See EPA's ``Guideline on Air Quality Models'' at 40 CFR part
51, appendix W.
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Within the impact area of a source that does have a significant
impact, increment consumption is calculated using the source's proposed
emissions increase, along with other emissions increases or decreases
of the particular pollutant from sources in the area, which have
occurred since the minor source baseline date established for that
area. (For major sources, emissions increases or decreases that have
occurred since the major source baseline date consume or expand
increment.) Thus, an emissions inventory of sources whose emissions
consume or expand the available increment in the area must be compiled.
The inventory includes not only sources located directly in the impact
area, but sources outside the impact area that affect the air quality
within the impact area.
The inventory of 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 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 to the Act, among other things, added subpart C to title I,
setting out the requirements for PSD. In section 163, Congress included
numerical increments for PM and sulfur dioxide (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 as Class III 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. There have been no Class III redesignations
to date.
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 total suspended particulate
(TSP). Thus, EPA interpreted the statutory increments for PM using the
same ambient ``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 NOX Using the ``Contingent Safe Harbor''
Approach Under Section 166(a) of the Act
As enacted in 1977, subpart C of the Act also included sections
166(a) through 166(e), which set out requirements related to increments
for other pollutants. 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. Section 166(b) prescribes timelines for the effective date
of such regulations, and for corresponding SIP submittals and EPA
approvals. Specifically, regulations, including increments, developed
pursuant to section 166(a) become effective 1 year after the date of
promulgation, and State plan revisions containing the new regulations
are to be submitted to EPA for review within 21 months of promulgation.
The same provision then calls for EPA's approval or disapproval of the
revised plan within 25 months of promulgation. The legislative history
indicates that this 1-year delay before the new PSD requirements,
including the new increments, become effective is to allow Congress an
opportunity to review them before States are required to implement
them. H.R. Conf. Rep. 95-564, at 151 (1977), 1977 U.S.C.C.A.N. 1502,
1532. Section 166(c) and (d) set forth criteria and goals that such
regulations must meet.
Based on section 166 of the Act, on October 17, 1988, EPA
promulgated increments for nitrogen dioxide (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
(now Environmental Defense, or ``ED'') when ED filed suit in the U.S.
Court of Appeals for the District of Columbia Circuit against the
Administrator (Environmental Defense Fund, Inc. v. Reilly, No. 88-
1882). Environmental Defense 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).
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
[[Page 54119]]
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 air quality related
values (AQRVs) \6\ and to ensure economic growth.
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\6\ The term ``air quality related values'' is not defined in
the Act, but the legislative history provides 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)
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In response to the court's decision, we proposed rulemaking on
increments for NOX 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 PSD
regulations for NOX. We also amended the requirements of 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.\7\
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\7\ 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 166
(c) and (d) of the Act that must be met for increments.
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b. Increments for PM10 Using ``Equivalent Substitution''
Approach Under Section 166(f)
On October 5, 1989, we proposed new 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's 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 existing
TSP increments on June 3, 1993 (58 FR 31622). In the interim between
proposal and promulgation, Congress enacted the 1990 Act Amendments. As
part of these Act 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 developed 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.
IV. EPA'S Interpretation of Section 166 of the Clean Air Act
A. Which Criteria in Section 166 Should EPA Use to Develop Increments
for PM2.5?
The EPA interprets section 166 of the Act to give the Administrator
the discretion to use either the ``contingent safe harbor'' approach or
the ``equivalent substitution'' approach to establish increments for
PM2.5. Since sections 166(a) and section 166(f) contain or
incorporate different criteria for establishing PSD regulations
containing increments or other measures, the interpretation that EPA
chooses to follow could have an impact on the increments or other
measures that EPA adopts. Regulations promulgated under section 166(a)
must be based on the criteria in section 166(c) and 166(d). 42 U.S.C.
7476(c)-(d). Regulations promulgated under section 166(f) must ``be of
equal stringency in effect as those specific in the provisions for
which they are substituted.'' 42 U.S.C. 7476(f). Furthermore, section
166(a) calls broadly for regulations, which may include increments,
whereas section 166(f) addresses only increments.
Section 166(a) provides authority for EPA to promulgate additional
pollutant-specific PSD regulations, which may include increments, for
the pollutants specifically identified in that provision plus
additional pollutants for which EPA may promulgate a NAAQS after a
specific date 42 U.S.C. 7476(a). The last sentence of section 166(a)
provides the following:
In the case of pollutants for which national ambient air quality
standards are promulgated after August 7, 1977, [the Administrator]
shall promulgate such regulations not more than 2 years after the
date of promulgation of such standards.
Since EPA promulgated an additional NAAQS for PM, based on the
PM2.5 indicator, in 1997, one potential
[[Page 54120]]
approach for developing increments for PM2.5 is for EPA to
promulgate these increments under the authority of section 166(a).
Under this approach, EPA would promulgate increments or other measures
for PM2.5 that satisfy the standards set forth in
subsections (c) and (d) of section 166, as interpreted by EPA in our
recent rulemaking for nitrogen oxides.
However, in light of the provisions in section 163 and 166(f) of
the Act that address increments for TSP and PM10,
respectively, there is some ambiguity on the question of the legal
authority EPA should rely upon to establish increments for
PM2.5. In 1993, EPA construed section 166(f) to establish
the sole criteria for promulgation of a new PM increment and thus did
not base our final PM10 increment on section 166(a) of the
Act. Considering sections 163, 166(a), and 166(f) together, an
alternative interpretation of these provisions might be that Congress
intended that section 163 and 166(f) alone cover PM. Under this
reading, EPA would promulgate additional increments for particular
matter based on the section 163 increments and 166(f) of the Act, which
are the only provisions that specifically mention PM and PSD
increments. However, as discussed later, it may also be possible to
read sections 166(a) and 166(f) in harmony. Thus, we propose to adopt
one of the following legal theories to support promulgation of
increments for PM2.5 using either of the two methods that
EPA used in prior rules to develop PSD increments.
1. Support for ``Contingent Safe Harbor'' Approach for PM2.5
Under Section 166(a)
The EPA believes it is permissible to interpret section 166(a) to
apply to PM2.5. 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 in 1997. Rather, EPA established an additional NAAQS
for PM2.5 as if it were a new pollutant, even though EPA had
already developed air quality criteria for PM generally. Thus, for
purposes of section 166(a), the addition of a NAAQS for
PM2.5 is functionally the same as establishing a NAAQS for
an additional pollutant after 1977.
We read section 166(a) to authorize EPA to promulgate pollutant-
specific PSD regulations meeting the 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) (nitrogen
oxides, 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, sulfur dioxide and particular matter, 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, Congress clearly 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'' we believe that Section 166(a) provides authority for EPA
to promulgate new increments after revising an existing NAAQS
(including one first promulgated before 1977), when we find that such
action is appropriate.
In our 1989 proposal on the PM10 increments, EPA
construed section 166(a) to apply to PM10, even though EPA
regarded PM10 to be a new indicator for PM. 58 FR 31623-24.
Thus, before the adoption of section 166(f), EPA read the language of
section 166(a) to apply to the promulgation of increments using a new
indicator for PM and did not limit the application of section 166(a) to
wholly new criteria pollutants. Similarly, in the current proposal, EPA
believes it can continue to interpret section 166(a) to apply to the
promulgation of an additional increment for a new indicator of an
existing criteria pollutant since EPA promulgated a NAAQS for a new
indicator of that pollutant after 1977.
Although EPA ultimately applied the standard in section 166(f) as
the sole basis for our PM10 increments in 1993, that
provision does not necessarily govern the situation EPA currently faces
with PM2.5. One could read section 166(f) to address only
EPA's authority to substitute new PM increments for the
congressionally-established increments for TSP rather than the distinct
issue now faced by EPA concerning the promulgation of additional PM
increments for PM2.5 without necessarily revoking existing
increments. Furthermore, the language in section 166(f) could be read
to limit the scope of this provision to only increments using the
PM10 indicator. Thus, section 166(f) may not necessarily be
applicable to the substitution of PM10 increments with
PM2.5 increments.
The EPA believes that section 166(a) could apply to the adoption of
new increments, without the revocation of existing increments. As
reflected in the 2005 increments rule for NOX and the court
decision in EDF v. EPA, when sections 166(a)-(d) apply, EPA is
obligated to evaluate which indicator or form should be used in our
pollutant-specific PSD regulations to meet these requirements in the
Act. Based on this interpretation, we are proposing to use a contingent
safe harbor approach (option 1) that involves first deriving increment
values based on percentage of the NAAQS and then evaluating whether
alternative increments or additional measures are necessary to meet the
criteria in section 166(c).
2. Support of ``Equivalent Substitution'' Approach for PM2.5
Under Section 166(f)
The EPA believes it is also permissible for the Agency to construe
section 166(f) as a continuing grant of authority for the Administrator
to update the increments for particular matter whenever the
Administrator decides to adopt a new form of particular matter as the
indicator for the NAAQS. Although the terms of section 166(f) of the
Act appear to address PM10 alone, the overall intent of this
provision was to clarify that EPA had the authority to update the
original TSP increments to reflect changes in the NAAQS indicator.
Language describing the PM10 indicator was used in the Act
because this was the indicator for PM that EPA was seeking to
incorporate into the PSD program at the time of the 1990 Amendments
when section 166(f) was adopted. However, we believe it is reasonable
to conclude that Congress intended to authorize EPA to continue
updating the particular matter increments contained in section 163 if
EPA promulgated a NAAQS for another appropriate indicator for
particular matter.
We believe EPA is authorized to promulgate increments for
PM2.5 as a substitute for the PM10 increments, as
well as the original TSP increments, so long as the new increments for
PM2.5 are of ``equal stringency in effect as those specified
in the provisions for which they are substituted.'' 42 U.S.C. 7476(f).
Based on this interpretation, we propose two approaches (options 2A and
2B discussed later) for developing PM2.5 increments that
would meet the ``equal stringency in effect'' standard contained in
section 166(f).
While we believe section 166(f) may be construed to provide
continuing authority to ``update'' the increments for PM to conform to
the NAAQS, section
[[Page 54121]]
166(f) describes a process in which EPA would ``substitute'' one PM
increment for another. The language in section 166(f) does not address
whether EPA may adopt additional increments for other PM indicators
while retaining the existing PM increments. In contrast, section 166(a)
does contain language addressing the promulgation of PSD regulations
when EPA adds to the suite of NAAQS. Thus, we construe section 166(a)
to have the closest connection to the task of adding, rather than the
substituting or replacing, PSD increments for PM. As a result, for
purposes of establishing the proposed 24-hour PM2.5
increments, we propose only one option--using the contingent safe
harbor approach described in option 1--because we are not proposing to
replace the existing 24-hour PM10 increment with a new 24-
hour PM2.5 increment, since we have retained the 24-hour
PM10 NAAQS. However, we also seek comment on whether we
could rely on section 166(f) to promulgate the 24-hour PM2.5
increments using the same methodology as for the annual PM2.5
increments described later, even though the 24-hour PM10
NAAQS is not being revoked.
B. Requirements of Sections 166(a)-(d) of the Clean Air Act
If we determine that section 166(a) applies to PM2.5, we
propose to follow the interpretation of sections 166(a)-(d) that we
adopted in our most recent increments rule for NOX. This
interpretation was upheld in a recent court decision E.D. v. EPA, No.
05-1446 (June 19, 2007 DC Cir.). We summarize the key elements of this
interpretation later, but a more detailed discussion can be found in
our October 2005 final rule for NOX. 70 FR 59582.
In section 166(a) of the Act, Congress directed EPA to develop
pollutant-specific regulations to prevent significant deterioration of
air quality. Congress further specified that such regulations meet the
following requirements set forth in sections 166(c) and 166(d):
(c) Such regulations shall provide specific numerical measures
against which permit applications may be evaluated, a framework for
stimulating improved control technology, protection of air quality
values, and fulfill the goals and purposes set forth in section 101
and section 160.
(d) The regulations * * * shall provide specific measures at
least as effective as the increments established in section 163 [for
SO2 and PM] to fulfill such goals and purposes, and may
contain air quality increments, emission density requirements, or
other measures.
The goals and purposes of the PSD program set forth in section 160
are as follows:
(1) To protect public health and welfare from any actual or
potential adverse effect which in the Administrator's judgment may
reasonably be anticipate[d] to occur from air pollution or from
exposures to pollutants in other media, which pollutants originate
as emissions to the ambient air, notwithstanding attainment and
maintenance of all national ambient air quality standards;
(2) To preserve, protect, and enhance the air quality in
national parks, national wilderness areas, national monuments,
national seashores, and other areas of special national or regional
natural, recreational, scenic, or historic value;
(3) To insure that economic growth will occur in a manner
consistent with the preservation of existing clean air resources;
(4) To assure that emissions from any source in any State will
not interfere with any portion of the applicable implementation plan
to prevent significant deterioration of air quality for any other
State; and
(5) To assure that any decision to permit increased air
pollution in any area to which this section applies is made only
after careful evaluation of all the consequences of such a decision
and after adequate procedural opportunities for informed public
participation in the decisionmaking process.
As described in our 2005 rule for NOX, EPA's
interpretation of these provisions is grounded on five central
elements. First, we read section 166 of the Act to direct EPA to
conduct a holistic analysis that considers how a complete system of
regulations will collectively satisfy the applicable criteria, rather
than evaluating one individual part of a regulatory scheme in
isolation. Second, we use a ``contingent safe harbor'' approach which
calls for EPA to first establish the minimum level of effectiveness
necessary to satisfy section 166(d) and then to conduct further
analysis to determine if additional measures are necessary to fulfill
the requirements of section 166(c). Third, we interpreted section
166(c) of the Act to identify eight statutory factors that EPA must
apply when promulgating pollutant-specific regulations to prevent
significant deterioration of air quality. Fourth, we interpreted the
requirements to simultaneously satisfy each of these factors to
establish a balancing test in cases where certain objectives may be at
odds with each other. Fifth, we recognized that the requirements of
section 166 may be satisfied by adopting other measures besides an
increment and that EPA may allow States to demonstrate that
alternatives to an increment contained in a SIP meet the requirements
of sections 166(c) and 166(d).
1. Regulations as a Whole Should Fulfill Statutory Requirements
Section 166(a) directs EPA to develop pollutant-specific
regulations to prevent the significant deterioration of air quality.
Sections 166(c) and 166(d) provide detail on the contents of those
regulations, but do not necessarily require the same type of increment
system Congress created in section 163 of the Act. Thus, in order to
develop pollutant-specific regulations under subsection (a), EPA must
establish both the overall regulatory framework for those regulations
(such as system of increments) and fill details around that framework
(such as the level of the increments). Thus, EPA interprets section 166
to require that the entire system of PSD regulations (the framework and
details) for a particular pollutant must, as a whole, satisfy the
criteria in sections 166(c) and 166(d). We propose to use the same
approach to establish pollutant-specific regulations for PM2.5
under option 1 of this proposal.
When we propose a framework involving numerical increments under
section 166(a) of the Act, we do not look at increments in isolation,
but we also consider how these increments work in conjunction with
other measures to satisfy the statutory criteria. The other measures
that EPA may consider include new measures proposed by EPA for that
pollutant or measures applicable to other pollutants that EPA proposes
to apply to additional pollutants. Examples of other measures are an
area classification system, AQRV review in Class I areas, additional
impacts analysis, and control technology requirements. This approach is
consistent with section 166(d), which says that pollutant-specific PSD
regulations ``may contain'' increments or ``other measures.''
2. Contingent Safe Harbor Approach
The EPA continues to view the ``contingent safe harbor'' approach
to be an appropriate methodology for ensuring that our pollutant-
specific PSD regulations meet the requirements of sections 166(c) and
166(d). Subsection (c) of section 166 describes the kinds of measures
to be contained in the regulations to prevent significant deterioration
of air quality called for in section 166(a) and specifies that these
regulations are to ``fulfill the goals and purposes'' set forth in
sections 160 and 101 of the Act. Then, under subsection (d), to
``fulfill such goals and purposes,'' EPA must promulgate ``specific
measures at least as effective as the increments established in section
7473
[[Page 54122]]
of this title [section 163 of the Act].'' 42 U.S.C. 7476. Thus,
subsection (d) can be construed to require that EPA identify a minimum
level of effectiveness, or safe harbor, for the body of pollutant-
specific PSD regulations adopted under section 166. Subsection (c) may
then be read to require that EPA conduct further review to determine
whether, based on the criteria in subsection (c), EPA's pollutant-
specific PSD regulations under section 166 should contain measures that
deviate from the minimum ``safe harbor'' identified under subsection
(d). EPA construes subsection (d) to require that the measures be ``at
least as stringent'' as the statutory increments set forth in section
163.
When EPA employs an increment and area classification system in
regulations promulgated under section 166 of the Act, we interpret the
Act to require that EPA, at minimum, establish increments that are
consistent with the statutory increments established by Congress in
section 163 of the Act. Thus, we start by identifying ``safe harbor''
increments for each area classification (Class I, II, or III) that are
established (1) Using an equivalent percentage of the NAAQS as the
statutory increments; (2) for the same pollutants as the NAAQS; and (3)
for the same time period as the NAAQS. We then conduct further review
to determine whether these ``safe harbor'' increments, in conjunction
with existing elements of the PSD program or additional measures
proposed under section 166 to augment the increments, sufficiently
fulfill the criteria in subsection (c) of section 166. In this review,
we weigh and balance the criteria set forth in subsection (c) (and the
incorporated goals and purposes of the Act in section 101 and the PSD
program in section 160) to determine whether additional measures are
needed to satisfy the criteria in subsection (c).
3. The Statutory Factors Applicable Under Section 166(c)
The EPA interprets section 166(c) of the Act to establish eight
factors to be considered in the development of PSD regulations for the
pollutants covered by this provision. These factors are three of the
four criteria listed in section 166(c) and the five goals and purposes
identified in section 160 of the Act. The three stand-alone criteria in
section 166(c) indicate that PSD regulations for specific pollutants
should provide (1) Specific numerical measures for evaluating permit
applications; (2) a framework for stimulating improved control
technology; and (3) protection of air quality values. 42 U.S.C.
7476(c). The five goals and purposes in section 160 are incorporated
into the analysis by virtue of the fourth criterion in section 166(c),
which directs that EPA's pollutant-specific PSD regulations ``fulfill
the goals and purposes'' set forth in sections 160 and 101 of the Act.
We construe the term ``fulfill the goals and purposes,'' as used in
section 166(c), to mean that EPA should apply the goals and purposes
listed in section 160 as factors applicable to pollutant-specific PSD
regulations established under section 166. The Agency's view is that
PSD measures that satisfy the specific goals and purposes of section
160 also satisfy the more general purposes and goals identified in
section 101 of the Act.
4. Balancing the Factors Applicable Under Section 166(c)
The EPA interprets the Act to establish a balancing test among the
eight factors. Since, as discussed further later, many of the factors
can be satisfied by using an increment framework, when determining the
characteristics of numerical increments themselves within that
framework, EPA focuses on balancing the goal to promote economic growth
with the factors that direct us to protect: (1) AQRVs; (2) the public
health and welfare from reasonably anticipated foreseeable adverse
effects; and (3) the air quality in parks and special areas. Section
166 of the Act authorizes EPA to promulgate pollutant-specific PSD
regulations that satisfy each of the eight factors. While these
objectives are generally complementary, there are circumstances where
some of the objectives may be in conflict. In these situations, some
degree of balance or accommodation is inherent in the requirement to
establish regulations that satisfy all of these factors.
As discussed in our PSD regulations for NOX, we believe
this balancing test derives primarily from the third goal and purpose
set forth in section 160. Section 160(3) directs us to ``insure that
economic growth will occur in a manner consistent with the preservation
of existing clean air resources.'' To some extent, this goal of the PSD
program in section 160(3) more specifically articulates the broader
purpose of the Act, described in section 101(b)(1) of the Act, to
``protect and enhance the quality of the Nation's air resources so as
to promote the public health and welfare and the productive capacity of
its population.'' 42 U.S.C. 7401(b)(1). Sections 160(3) and 101(b)(1)
are similar in that both sections reflect the goal to protect air
quality and maximize opportunities for economic growth. Thus, in
interpreting the meaning of section 160(3) when used as a factor
applicable under section 166(c), we also consider the broader purpose
of the Act set forth in section 101(b)(1).
The need to balance the applicable factors to achieve these
objectives is also supported by our interpretation of the second goal
in section 160(2) of the Act to ``protect public health and welfare.''
The precise meaning of this goal in the context of the PSD program is
somewhat ambiguous because it appears to mirror the legal standards
applicable to the promulgation of the primary and secondary NAAQS.
Under section 109(b) of the Act, the primary NAAQS must ``protect the
public health'' with an adequate margin of safety (section 109(b)(1))
and the secondary NAAQS must ``protect the public welfare from any
known or anticipated adverse effects'' associated with ambient
concentrations of the pollutant (section 109(b)(2)). The term
``welfare'' is defined in the Act to include ``effects on soils, water,
crops, vegetation, man-made materials, animals, wildlife, weather,
visibility, and climate.'' Section 302(h) of the Act.
When applied as one of the factors applicable to pollutant-specific
PSD regulations under section 166(c) of the Act, we construe the goal
in section 160(3) of the to ``protect public health and welfare'' to
mean EPA should evaluate whether reasonably anticipated adverse effects
may occur as a result of increases in ambient pollutant concentrations
to levels below the NAAQS. If such effects may occur in some areas of
the country, then EPA would establish PSD regulations that protect
public health and welfare against those effects where they may occur.
However, we do not interpret the PSD program to require regulations
that eliminate all negative effects that may result from increases in
pollution in attainment areas.
The PSD program is, as its title indicates, designed to prevent
``significant deterioration'' from a baseline concentration. See S.
Rep. 95-127 at 11 (3 LH at 1385) (``This legislation defines
`significant deterioration' in all clean air areas as a specified
amount of additional pollution.* * * This definition is intended to
prevent any major decline in air quality currently existing in clean
air areas.'' (emphasis added)). Thus, some decline in air quality
(relative to the baseline air quality concentration) is permissible for
any particular area of the country that is currently achieving the
NAAQS, as long as it is not ``significant.''
When EPA employs an area classification system in its section 166
[[Page 54123]]
regulations, we generally weigh these factors in each type of area
(Class I, Class II, and Class III). However, the weight given to each
factor may be more or less, depending on the area involved and the
amount of deterioration deemed ``significant'' for that type of area.
For example, economic growth may be the most important factor in a
Class III area, but our PSD regulations for such areas should offer
some level of protection for existing clean air resources. In a Class I
area, our PSD regulations should allow some level of economic growth,
even though preservation of existing clean air resources may be the
dominant factor for these areas.
5. Authority for States To Adopt Alternatives to Increments
While section 166 of the Act authorizes EPA to promulgate
increments for pollutants listed under section 166(a), we also
interpret the section to authorize States to employ approaches other
than increments to prevent significant deterioration of air quality, so
long as such an approach otherwise meets the requirements of sections
166(c) and 166(d). As described earlier, we explained this
interpretation in the 2005 NOX increment rulemaking
whereupon we amended the PSD regulations at 40 CFR 51.166 by adding new
paragraph (c)(2) to codify this statutory authority (70 FR 59582,
October 12, 2005). However, in establishing the new provision, the
language at paragraph (c)(2) reflected the authority for States to
adopt alternative measures only with respect to increments for
NOX. In order to clarify our interpretation that the
authority to adopt alternative measures covers any pollutant listed in
section 166(a), we are proposing in this action to revise existing 40
CFR 51.166(c)(2) to make it inclusive to applicable pollutants rather
than just NOX.
C. Requirements of Section 166(f) of the Clean Air Act
If we decide to use the equivalent substitution options in this
proposal for PM2.5, EPA proposes to interpret section 166(f)
of the Act in the same manner that the Agency interpreted that
provision in our 1993 rule for PM10. In 1993, EPA construed
section 166(f) as authorizing EPA to follow the path that EPA laid out
in our 1989 proposal for developing equivalent increments for PM
measured as PM10. 58 FR 31626. Thus, in our 1993 rulemaking,
EPA developed our PM10 increments using the ``equivalent to
statutory increments'' option that EPA described in our notice of
proposed rulemaking. The EPA did not interpret the ``equivalent
stringency in effect'' standard in section 166(f) to require EPA to use
the second approach from the proposal, the ``percentage of NAAQS''
approach that Congress had originally used to establish TSP increments.
The Agency observed that if Congress intended to require EPA to update
the TSP increments using a straight percentage, Congress could have
easily revised the increments in section 163 instead of providing EPA
discretion to establish increments following the standard provided in
section 166(f). 58 FR 31626. The EPA thus construed section 166(f) as
providing EPA discretion to determine appropriate equivalent levels of
PM10. Id. The EPA identified equivalent levels by developing
a ratio based on a comparison of the TSP and PM10 impacts of
stationary sources. 58 FR 31627.
In this rulemaking, EPA proposes to apply the same type of ratio
approach to establish equivalent increments for PM10 under
section 166(f) of the Act. Since this ratio approach was the foundation
of EPA's equivalency method in the 1989 proposal, we believe it is
permissible, as we did in 1993, to construe section 166(f) as
authorizing EPA to continue utilizing this approach to establish
equivalent increments for PM.
In 1993, EPA disagreed with commenters who recommended that EPA
consider welfare effects and visibility impairments when establishing
PM10 increments under section 166(f) for class I areas. The
EPA observed that there was no evidence that Congress itself adopted
increments that would ensure specific levels of welfare and visibility
protection at each Class I area throughout the nation. The increments
established by Congress did not establish an absolute ceiling on air
quality, but rather limited the marginal amount of deterioration in air
quality above a baseline concentration that varies for each area, and
thus permitted each area with the same classification to deteriorate in
the same amount without regard to its particular sensitivities as
compared to other areas with the same classification. 58 FR 31625. The
EPA concluded that the PM10 increments should be designed to
protect each area from large adverse changes in air quality while the
air quality related values analysis was the main tool for protecting
specific ecologically-based attributes in particular class I areas. Id.
In this rulemaking for PM2.5, we maintain the view that
the ``equal stringency in effect'' language in section 166(f) does not
require EPA to consider welfare effects and visibility when
promulgating replacement increments under that provision. However, as
reflected in our recent increments rule for NOX, when
promulgating PSD increments under section 166(a), welfare effects and
visibility impacts are factors in the contingent safe harbor analysis
under the criteria in sections 166(c) and 160 of the Act. Consistent
with our recent PSD regulations for NOX, we continue to
believe that increments (whether promulgated under section 166(a) or
166(f)) should be designed to provide each area with a basic level of
protection from large adverse changes in air quality without
necessarily reflecting the unique air pollution sensitivities in each
class I area. The EPA considers welfare and visibility impacts across
the nation when establishing increments under section 166(a), but we
continue to believe that the Air Quality Related Values (AQRV) review
is the preferred tool for identification and protection of specific
ecologically-based attributes within particular class I areas. See 58
FR 31625.
V. Increments and Other Measures To Prevent Significant Deterioration
In this action, EPA is proposing three options for establishing
increments for PM2.5. The first option described uses the
``contingent safe harbor'' approach (using percentages of the NAAQS as
our initial basis) following section 166(a) of the Act. The other two
options are variations of the section 166(f) ``Equivalent Increment''
approach. The EPA is proposing option 1 as our preferred option and
seeking comments on the other two options.
A. Option 1--Contingent Safe Harbor Approach for Annual and Short-Term
Increments--Section 166(a)
Under the first option, we would consider PM2.5 to be a
new pollutant \8\ for which a NAAQS was promulgated after the date of
enactment of subpart C, and we would use the authority of section
166(a) of the Act to develop new increments for PM2.5. Using
this option, we are proposing to establish a system of increments at
the safe harbor level in conjunction with the other measures described
as follows:
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\8\ In our review of the PM NAAQS, we concluded that, because
the fine and thoracic coarse components of PM10 generally
have different sources, composition and formation processes, they
should be treated as separate pollutants. (OAQPS SP, December 2005,
page 3-1.)
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1. Proposed Framework for Pollutant Specific PSD Regulations for
PM2.5
Under this option, EPA proposes to apply the same basic
framework reflected in our regulation for NOX in
[[Page 54124]]
pollutant-specific PSD regulations for PM2.5. Thus, we
propose to adopt an increment and area classification system for
PM2.5 and to apply an AQRV review process to PM2.5
as well. As discussed further later, EPA believes that many of the
factors applicable under section 166(c) are fulfilled by using this
type of framework for pollutant-specific PSD regulations under section
166(a) of the Act. For other factors, this framework of regulations
partially contributes to the fulfillment of an applicable factor but
may not fully satisfy that factor. In these instances, the details of
our regulations (such as the characteristics of the increments
themselves) are also important and we evaluate the effectiveness of the
framework in conjunction with more detailed elements of our
regulations. The EPA believes our obligations under section 166(c) of
the Act are satisfied when the PSD regulations collectively satisfy the
factors applicable under 166(c) of the Act.
a. Increment System
An increment is the maximum allowable level of ambient pollutant
concentration increase that is allowed to occur above the applicable
baseline concentration in a particular area. As such, an increment
defines ``significant deterioration.'' Establishing an increment system
for PM2.5 will fulfill two of the factors applicable under
section 166(c).
An increment-based program satisfies the requirements under 166(c)
to provide ``specific numerical measures against which permit
applications may be evaluated.'' Under section 165(a)(3) of the Act, a
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.'' 42
U.S.C. 7475(a)(3). Once the baseline date associated with the first
proposed new major stationary source or major modification in an area
is established, the new emissions from that source consume a portion of
the increment in that area, as do any subsequent emissions increases
that occur from any 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 be
required by the reviewing authority. Thus, an increment is a
quantitative value that establishes a ``maximum allowable increase''
for a particular pollutant. It functions, therefore, as a specific
numerical measure that can be used to evaluate whether an applicant's
proposed project will cause or contribute to air pollution in excess of
allowable levels.
Increments also satisfy the second factor in section 166(c) by
providing ``a framework for stimulating improved control technology.''
Increments establish an incentive to apply improved control
technologies in order to avoid violating the increment and to ``free-
up'' available increment to promote continued economic growth. These
control technologies may become the basis of BACT determinations
elsewhere, as the technologies become more commonplace and the costs
tend to decline. See also S. Rep. 95-127 at 18, 30 (3 LH at 1392, 1404)
(``the incremental ceiling should serve as an incentive to technology,
as a potential source may wish to push the frontiers of technology in a
particular case to obtain greater productive capacity within the limits
of the increments'').
However, we recognize that an increment system is not the only way
to fulfill the requirements of section 166 of the Act. Congress did not
require EPA to utilize increments in our PSD regulations for
NOX but gave EPA the discretion to employ increments if
appropriate to meet the criteria and goals and purposes set forth in
sections 166 and 160 of the Act. 42 U.S.C. 7474(d); EDF v. EPA, 898
F.2d at 185 (``Congress contemplated that EPA might use increments'').
Thus, in this action, we are also proposing to allow States to develop
alternatives to an increment system at their discretion, and to submit
any such alternative program to EPA so that we can determine whether it
satisfies the requirements of section 166.
b. Area Classifications
The EPA proposes to establish the same three-tiered area
classification system for PM2.5 that is applicable to
NOX and other pollutants under the PSD program and the Clean
Air Act. Accordingly, areas that are currently Class I for other
pollutants would also be Class I for PM2.5 and all other
areas would be Class II for PM2.5 unless we redesignated the
area based on a request by a state or tribe pursuant to the process in
section 164 of the Act and EPA's regulations at 40 CFR 51.166(g) and
52.21(g).
As explained earlier, in section III.E.1, Class I areas are areas
where especially clean air is most desirable. In contrast, Class III
areas, which are those areas in which a State wishes to permit the
highest relative level of industrial development, have the largest
increment level. Areas that are not especially sensitive or that do not
wish to allow for a higher level of industrial growth are classified as
Class II. When Congress established this three-tiered scheme for
SO2 and PM, it intended that Class II areas be subject to an
increment that allows ``moderately large increases over existing
pollution.''
H.R. Rep. 95-294, 4 LH at 2609.
Establishing increments at different levels for each of the three
area classifications helps to fulfill two of the factors applicable
under section 166(c) of the Act. Establishing the smallest increments
in Class I areas helps fulfill EPA's obligation to establish
regulations that ``preserve, protect, and enhance the air quality'' in
parks and special areas. Class I areas are primarily the kinds of parks
and special areas covered by section 160(2) of the Act. With the air
quality in Class I areas subject to the greatest protection, this
scheme then provides two additional area classifications with higher
increment levels to help satisfy the goal in section 160(3) of the Act
that EPA ``insure that economic growth will occur in a manner
consistent with preservation of clean air resources.'' In those areas
where clean air resources may not require as much protection, more
growth is allowed. By employing an intermediate level (Class II areas)
and higher level (Class III areas), this classification scheme helps
ensure that growth can occur where it is needed (Class III areas)
without putting as much pressure on existing clean air resources in
other areas where some growth is still desired (Class II areas).
By requesting that EPA redesignate an existing Class II area to
Class III, States may accommodate economic growth and air quality in
areas where the Class II increment is too small to allow the siting of
new or modified sources. The procedures specified by the Act for such a
redesignation require a commitment by the State government to create
such an area, extensive public review, local government participation
in the SIP area redesignation process, and a finding that the
redesignation will not result in the applicable increment being
exceeded in a nearby Class I or Class II area. See 42 U.S.C. 7474(a)-
(b) (Section 164(a)-(b) of the Act). The EPA believes that the three-
tiered classification system has allowed for economic growth,
consistent with the preservation of clean air resources.
However, an area classification system alone may not completely
satisfy the factors applicable under section 166(c) of the Act. The
increment that is
[[Page 54125]]
employed for each class of area is also relevant to an evaluation of
whether the area classification scheme achieves the goals of the PSD
program. We discuss the characteristics of increments later.
c. Permitting Procedures
Two of the factors applicable under section 166(c) are fulfilled by
the case-by-case permit review procedures that are built into our
existing regulations. The framework of our existing PSD regulations
employs the preconstruction permitting system and procedures required
under section 165 of the Act. 42 U.S.C. 7475. These requirements are
generally reflected in 40 CFR 51.166 and 52.21 of EPA's PSD regulations
in Title 40 of the Code of Federal Regulations. These permitting and
review procedures, which we interpret to apply to construction of new
major sources and to major modifications at existing sources, fulfill
the goals set forth in sections 160(4) and 160(5) of the Act. These
goals require that PSD programs in one State not interfere with the PSD
programs in other States and that PSD programs assure that any decision
to permit increased air pollution is made after careful evaluation and
public participation in the decisionmaking process. For the same
reasons discussed in our proposal for the pollutant-specific PSD
regulations for NOX regulations, 70 FR 8896, we believe
these factors are also fulfilled for PM2.5 by employing the
permit review procedures.
d. Air Quality Related Values Review by Federal Land Manager and
Reviewing Authority
The EPA also proposes to apply the requirement to evaluate impacts
on AQRVs in Class I areas to PM2.5. The AQRV review provides
the Federal Land Managers (FLM) the opportunity to review source
impacts on site-specific AQRVs in Class I areas and to bring any
adverse impacts to the attention of the reviewing authority. Under an
increment approach, we consider this review to be an additional measure
that helps to satisfy the factors in sections 166(c) and 160(2) which
require that EPA's pollutant-specific PSD regulations protect air
quality values, and parks and other special areas, respectively.
In our rulemakings addressing PSD for NOX, EPA extended
the AQRV review procedures set forth in 40 CFR 51.166(p) and 52.21(p)
to cover NO2. These AQRV review procedures were established
based on section 165(d) of the Act, and they were originally applied
only in the context of the statutory increments for PM and
SO2. However, because they also address many of the factors
applicable under section 166(c) of the Act, EPA also applied them to
NOX through regulation. We propose the same approach for PM
2.5 in this rulemaking.
Section 165(d) creates a scheme in which the FLM and reviewing
authority must review the impacts of a proposed new or modified
source's emissions on AQRVs. The Act assigns to the FLM an
``affirmative responsibility'' to protect the AQRVs in Class I areas.
The FLM may object to or concur in the issuance of a PSD permit based
on the impact, or lack thereof, that new emissions may have on any
affected AQRV that the FLM has identified and for which information is
available to the general public. If the proposed source's emissions do
not cause or contribute to a violation of a Class I increment, the FLM
may still prevent issuance of the permit by demonstrating to the
satisfaction of the reviewing authority that the source or modification
will have an adverse impact on AQRVs. Section 165(d)(2)(C). On the
other hand, if the proposed source will cause or contribute to a
violation of a Class I increment, the reviewing authority (State or
EPA) shall not issue the permit unless the owner or operator
demonstrates to the satisfaction of the FLM that there will be no
adverse impact on AQRVs.\9\ Thus, the compliance with the increment
determines whether the FLM or the permit applicant has the burden of
satisfactorily demonstrating whether or not the proposed source's
emissions would have an adverse impact on AQRVs.\10\ In any event, the
FLM plays an important and material role by raising these issues for
consideration by the reviewing authority, which in the majority of
cases will be the State.
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\9\ Even if such a waiver of the Class I increment is allowed
upon a finding of no adverse impact, the source must comply with
such emissions limitations as may be necessary to ensure that the
Class II increment for SO2 or PM is not exceeded. Section
165(d)(2)(C)(iv). The EPA made this provision applicable to the PSD
provisions for NOX, with a cap of 25 g/m \3\--the NO
2 Class II increment. 53 FR 3704; 40 CFR 51.166(p)(4) and
52.21(p)(5).
\10\ In response to concerns that Class I increment would hinder
growth in areas surrounding the Class I area, Congress established
Class I increments as a means of determining where the burden of
proof should lie for a demonstration of adverse effects on AQRVs.
See Senate Debate, June 8, 1977 (3 LH at 725).
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Incorporating these AQRV review procedures into the PSD regulations
for PM2.5 helps to provide protection for parks and special
areas (which are generally the Class I areas subject to this review)
and air quality values (which are factors considered in the review). As
discussed later, we believe the factors applicable under section 166(c)
of the Act can be fulfilled when the review of AQRVs is applied in
conjunction with increments and other aspects of our PSD regulations.
In those cases where the increment is not violated and the reviewing
authority agrees that a proposed project will adversely affect AQRVs,
the parks and other special areas will be protected by denying issuance
of the permit or by requiring the applicant to modify the project to
alleviate the adverse impact. Legislative history suggests that the
AQRV review provisions of section 165(d) were intended to provide
another layer of protection, beyond that provided by increments. The
Senate committee report stated the following: ``A second test of
protection is provided in specified Federal land areas (Class I areas),
such as national parks and wilderness areas; these areas are also
subjected to a review process based on the effect of pollution on the
area's air quality related values.'' S. Rep. 95-127, at 17, 4 LH at
1401. As we stated in the NOX rule, we believe the term
``air quality values'' should be given the same meaning as ``air
quality related values.'' Legislative history indicates that the term
``air quality value'' was used interchangeably with the term ``air
quality related value'' (AQRV) regarding Class I lands.\11\
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\11\ See S. Rep. 95-127, at 12, reprinted at 3 LH at 1386, 1410
(describing the goal of protecting ``air quality values'' in
``Federal lands--such as national parks and wilderness areas and
international parks,'' and in the next paragraph and subsequent text
using the term ``air quality related values'' to describe the same
goal); id. at 35, 36 (``The bill charges the Federal land manager
and the supervisor with a positive role to protect air quality
values associated with the land areas under the jurisdiction of the
[FLM]'' and then describing the statutory term as ``air quality
related values''). H.R. Report 95-564 at 532 (describing duty of
Administrator to consider ``air quality values'' of the tribal and
State lands in resolving an appeal of a tribal or State
redesignation, which is described in the final bill as ``air quality
related values'').
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e. Additional Impacts Analysis.
The additional impacts analysis set forth in our regulations also
helps fulfill the criteria and goals and purposes in sections 166(c)
and 160. The additional impacts analysis involves a case-by-case review
of potential harm to visibility, soils, and vegetation that could occur
from the construction or modification of a source.
Sections 51.166(o)(1) and 52.21(o)(1) of the PSD regulations
require that a permit provide the following analysis:
An analysis of the impairment to visibility, soils and
vegetation that would occur as a result of the source or
modification, and general commercial, residential, industrial and
other growth associated with the source
[[Page 54126]]
or modification. The owner or operator need not provide an analysis
of the impact on vegetation having no significant commercial or
recreational value.
This requirement was based on section 165(e)(3)(B) of the Act, which
provides that EPA establish regulations that require ``an analysis of
the ambient air quality, climate and meteorology, terrain, soils and
vegetation, and visibility at the site of the proposed major emitting
facility and in the area potentially affected by emissions from such
facility * * * ''
42 U.S.C. 7475(e)(3)(B).
This portion of the additional impacts analysis is especially
helpful for satisfying the requirements of section 166(c) in Class II
and Class III areas. These areas are not subject to the additional AQRV
review that applies only in Class I areas. While not as intensive a
review as AQRV analysis required in Class I areas, considering
impairments to visibility, soils, and vegetation through the additional
impacts analysis contributes to satisfying the factors applicable under
section 166(c) of the Act in all areas, including Class II and Class
III areas.
f. Installation of Best Available Control Technology
The requirement that new sources and modified sources subject to
PSD apply BACT is an additional measure that helps to satisfy the
factors in sections 166(c), 160(1), and 160(2) of the Act. This
requirement, based on section 165(a)(4) of the Act, is already included
in EPA's PSD regulations and thus we consider it to be a part of the
regulatory framework for the Agency's pollutant-specific regulations
for PM2.5. 40 CFR 52.21(j); 40 CFR 51.166(j). Our existing
regulations define ``best available control technology'' as ``an
emission limitation * * * based on the maximum degree of reduction for
each pollutant subject to regulation under the Act * * * which the
Administrator, on a case-by-case basis, taking into account energy,
environmental, and economic impacts and other costs, determines is
achievable for such source through application of production processes
or available methods, systems, and techniques * * * '' 40 CFR
52.21(b)(12); 40 CFR 52.166(b)(12). This pollutant control technology
requirement in practice has required significant reductions in the
pollutant emissions increases from new and modified sources while also
stimulating the on-going improvement of control technology. The control
of PM2.5 emissions through the application of BACT helps to
protect air quality values, public health and welfare, and parks and
other special areas.
2. Proposed Increments
Based on our evaluation of the effects of PM2.5 and a
balancing of the criteria in section 166(c) of the Act (and the
incorporated goals and purposes of the Act in section 101 and the PSD
program in section 160), EPA proposes to find that the ``safe harbor''
increments for PM2.5 (which meet the minimum requirements in
section 166(d) of the Act) are sufficient to fulfill the criteria in
section 166(c) when combined with the other measures described earlier
that we propose to apply to PM2.5. Since several of the
eight factors applicable under section 166(c) are satisfied by adopting
the framework and other measures described earlier, our development of
the proposed increments for PM2.5 was guided by the four
remaining factors that may not be fully satisfied by the framework and
other measures: (1) Protecting AQRVs; (2) protecting the public health
and welfare from reasonably-anticipated adverse effects; (3) protecting
the air quality in parks and special areas; and (4) ensuring economic
growth.\12\ In accordance with the contingent safe harbor approach, to
determine the specific characteristics of the proposed increments, we
first established the minimum level of effectiveness necessary to
satisfy section 166(d) and then conducted further analysis to determine
if additional measures are necessary to fulfill the requirements of
section 166(c).
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\12\ We have paraphrased these factors here and in other
sections to facilitate the explanation of our reasoning. However, we
recognize, as we did in our regulation for NOX that the
statutory language is broader than the shorthand we use here for
convenience.
---------------------------------------------------------------------------
a. Identification of Safe Harbor Increments
Using the percentage-of-NAAQS approach, we derived the following
safe harbor increments for PM2.5:
------------------------------------------------------------------------
NAAQS Increments ([mu]g/m \3\)
Averaging period ([mu]g/m --------------------------------
\3\) Class I Class II Class III
------------------------------------------------------------------------
Annual...................... 15 1 4 8
24-hour..................... 35 2 9 18
------------------------------------------------------------------------
The PM2.5 levels of both the primary and secondary NAAQS
are 15 [mu]g/m \3\ for the annual averaging time and 35 [mu]g/m \3\ for
the 24-hour averaging time. See 40 CFR 50.7. We calculated the safe
harbor increments based on the same percentages that were used by
Congress to establish the original PM increments (measured as TSP) in
section 163 of the Act i.e. 6.6 percent of the NAAQS for Class I areas;
25 percent of the NAAQS for Class II areas and 50 percent of the NAAQS
for Class III areas. Increments with these characteristics are
sufficient to satisfy the requirement in section 166(d) requirement
that we adopt increments (or other PSD regulations) that are ``at least
as effective as'' the increments established in section 163 of the Act.
42 U.S.C. 7476(d); See EDF v. EPA, 898 F.2d at 188, 190.
b. Data Utilized by EPA for the Evaluation of the Safe Harbor
Increments for PM2.5
We evaluated whether measures other than the safe harbor increments
are necessary by analyzing primarily the scientific and technical
information on the health and welfare effects of PM2.5
contained in the June 2005 OAQPS Staff Paper (SP) used for the periodic
review of the 2004 PM air quality Criteria Document (CD).\13\
---------------------------------------------------------------------------
\13\ This periodic review of the PM NAAQS updates the last
review, which began in 1994 and resulted in revised standards for PM
in 1997.
---------------------------------------------------------------------------
Section 166 provides that EPA is to establish pollutant-specific
PSD regulations, including increments, after the establishment of a
NAAQS for the applicable pollutants. 42 U.S.C. 7476(a). Under normal
circumstances, the Act provides that EPA promulgate new PSD regulations
under section 166, including new increments if appropriate, within 2
years from the promulgation of any NAAQS after 1977. 42 U.S.C. 7476(a).
In such instances, the health and welfare information used for the
setting of the NAAQS would also be ``current'' for
[[Page 54127]]
purposes of establishing pollutant-specific PSD regulations. We believe
this timing reflects Congressional intent that EPA consider the same
body of information concerning a pollutant's health and welfare effects
when it promulgates the NAAQS and subsequent PSD increments (or other
measures) defining significant air quality deterioration for the same
pollutant. However, when we use that same information as the basis for
our pollutant-specific PSD regulations, we must evaluate that
information under the legal criteria in section 166 of the Act rather
than the criteria in section 109 applicable to the promulgation of
NAAQS. See EDF v. EPA, 898 F.2d at 190.
Since we just completed a review of the PM 2.5 NAAQS,
the information used in that review is current and timely for purposes
of this proposal to establish pollutant-specific PSD regulations for
PM2.5. As discussed earlier, on October 17, 2006, based
primarily on considerable new data on the air quality and human health
effects for PM2.5 directly, EPA revised the primary and
secondary NAAQS to provide increased protection of public health and
welfare by retaining the level of the annual standard and tightening
the level of the 24-hour standard from 65 to 35 [mu]g/m \3\ while
retaining the 24-hour PM10 NAAQS and revoking the annual
PM10 NAAQS. The information contained in the 2004 CD and
2005 SP that we also consider for purposes of this proposed rule was
used for this latest review of the PM NAAQS.
The 2004 CD and 2005 SP are the products of a rigorous process that
is followed to validate and interpret the available scientific and
technical information, and provided the basis for recommending the
PM2.5 NAAQS. In accordance with the Act, the NAAQS process
begins with the development of ``air quality criteria'' under section
108 for air pollutants that ``may reasonably be anticipated to endanger
public health or welfare'' and that come from ``numerous or diverse''
sources. Section 108(a)(1). For each NAAQS review, the Administrator
must appoint ``an independent scientific review committee composed of
seven members of the National Academy of Sciences, one physician, and
one person representing State air pollution control agencies,'' known
as the Clean Air Scientific Advisory Committee (CASAC). Section
109(d)(2)(A). The CASAC is charged with recommending revisions to the
criteria document and NAAQS, and advising the Administrator on several
issues, including areas in which additional knowledge is required to
appraise the adequacy and basis of existing, new, or revised NAAQS.
Section 109(d)(2)(B),(C).
``Air quality criteria '' must reflect the latest scientific
knowledge on ``all identifiable effects on public health or welfare ''
that may result from a pollutant's presence in the ambient air. 42
U.S.C. 7408(a)(2). The scientific assessments constituting air quality
criteria generally take the form of a ``criteria document,'' a rigorous
review of all pertinent scientific studies and related information. The
EPA also develops a ``staff paper '' to ``bridge the gap'' between the
scientific review and the judgments the Administrator must make to set
standards. See Natural Resources Defense Council v. EPA (``NRDC''), 902
F.2d 962, 967 ``D.C. Cir. 1990). Both documents undergo extensive
scientific peer-review as well as public notice and comment. See, e.g.,
62 FR 38654/1-2.
c. Scope of Effects Considered
The effects of ambient PM2.5 concentrations may include
secondarily-formed PM2.5. Hence, in this analysis we have
evaluated the health and welfare effects of both direct
PM2.5 and secondarily-formed PM2.5 that may
result from the transformation of other pollutants such as SO2
and NOX. This is consistent with the approach we described
for addressing these effects in the recently completed review of our
pollutant-specific PSD regulations for NOX. 70 FR 59590.
d. Evaluation of the Health and Welfare Effects of PM2.5
Airborne PM is not a specific chemical entity, but rather is a
mixture of liquid and solid particles from different sources and of
different sizes, compositions and properties. Particle size
distributions show that atmospheric particles exist in two classes:
fine particles and coarse particles. PM2.5 is an indicator
for fine particles and represents particles that are mostly less than
2.5 micrometers in size. PM10-2.5 is an indicator for
thoracic coarse particles and represents particles sized between 2.5
and 10 micrometers. In the last two reviews of the PM NAAQS, EPA
concluded that these two indicators, because of their different
sources, composition, and formation processes should be treated as
separate subclasses of PM pollution for purposes of setting ambient air
quality standards.
Coarse particles are generally primary particles, emitted directly
from their source as particles. These particles result from mechanical
disruption of large particles by crushing or grinding, from evaporation
of sprays, or from dust resuspension. In addition, some combustion-
generated particles may be found as coarse particles. By comparison,
fine PM is derived directly from combustion material that has
volatilized and then condensed to form primary PM or from precursor
gases, such as SO2 and NOX, reacting in the
atmosphere to form secondary PM. Because of the complexity of the
composition of ambient PM2.5 and PM10-2.5,
sources are best discussed in terms of individual constituents of both
primary and secondary PM2.5 and PM10-2.5. Each of
these constituents can have anthropogenic and natural sources. Major
components of fine particles are sulfates, strong acid, ammonium
nitrate, organic compounds, trace elements (including metals),
elemental carbon, and water. Primary and secondary fine particles have
long lifetimes in the atmosphere (days to weeks) and travel long
distances (hundreds to thousands of kilometers). They tend to be
uniformly distributed over urban areas and larger regions, especially
in the eastern United States. As a result, they are not easily traced
back to their individual sources. By contrast, coarse particles are not
readily transported across urban or broader areas. These particles can
settle rapidly from the atmosphere with lifetimes ranging from minutes
to days depending on their specific size, atmospheric conditions, and
altitude.
(1) Health Effects
The EPA reported important progress since the last PM NAAQS review
in advancing our understanding of potential mechanisms by which ambient
PM2.5, alone and in combination with other pollutants, is
causally linked to a number of key health effects. The more extensive
and stronger body of evidence used by EPA to study the health effects
of PM2.5 in our latest review identified a broader range of
effects than those previously documented, involving premature mortality
and indices of morbidity (including respiratory hospital admissions and
emergency room visits, school absences, work loss days, restricted
activity days, effects on lung function and symptoms, morphological
changes, and altered host defense mechanisms) associated with both
long- and short-term exposure to PM2.5.
An overview of the scientific and technical evidence considered in
the 2004 CD and 2005 SP can be found in our proposed rule for revising
the NAAQS for PM published at 70 FR 2619, January 17, 2006, beginning
at page 2626. The discussion which follows is only a brief summary of
those
[[Page 54128]]
effects, with an explanation of the range of PM2.5
concentrations that we examined in considering revisions to the primary
PM2.5 NAAQS.
While most epidemiological studies continue to be indexed by
PM2.5, some studies also implicate various components within
the mix of fine particles that have been more commonly studied (e.g.,
sulfates, nitrates, carbon, organic compounds, and metals) as being
associated with adverse effects. Furthermore, the available information
suggests that many different chemical components of fine particles and
a variety of different types of source categories are all associated
with, and probably contribute to, effects associated with
PM2.5. While there remains uncertainty about the role and
relative toxicity of various components of fine PM, the current
evidence continues to support the view that fine particles should be
addressed as a group for purposes of public health protection.
Short-term exposure (from less than 1 day up to several days) to
PM2.5 is likely causally associated with mortality from
cardiopulmonary diseases, increased hospitalization and emergency
department visits for cardiopulmonary diseases, increased respiratory
symptoms, decreased lung function, and changes in physiological
indicators for cardiovascular health. Effects associated with short-
term exposure identified since the last NAAQS review include increased
non-hospital medical visits (physician visits) and aggravation of
asthma associated with short-term exposure to PM2.5.
Although a growing body of studies provided evidence of effects
associated with exposure periods shorter than 24-hours (e.g., one to
several hours), EPA concluded in our 2004 SP that this information was
too limited to serve as a basis for establishing a primary fine
particle standard with less than a 24-hour averaging time. However, it
was concluded that this information added weight to the importance of a
24-hour standard. In addition, some studies suggested consideration of
a multiple-day averaging time, but EPA concluded that a multiple-day
averaging time would add complexity without providing more effective
protection than a 24-hour averaging time.
For setting the level of the short-term PM standard, EPA focused on
a range of 24-hour 98th percentile PM2.5 concentrations of
about 30 to 35 [mu]g/m\3\. Some new short-term mortality studies
considered for the last NAAQS review provided evidence of statistically
significant associations with PM2.5 in areas with air
quality levels below the level of the then-current primary 24-hour
PM2.5 NAAQS (65 [mu]g/m\3\). The EPA observed a strong
predominance of studies with 24-hour 98th percentile values down to
about 39 [mu]g/m\3\ showing statistically significant association with
mortality, hospital admissions, and respiratory symptoms. Within the
range of 24-hour average 98th percentile PM2.5
concentrations of about 30 to 35 [mu]g/m\3\, EPA no longer observed
this strong predominance of statistically significant results. Below 35
[mu]g/m\3\, EPA found increasing variation in the short-term exposure
studies, which indicated an increase in the uncertainty as to whether
likely causal associations could be extended. In considering what level
would be appropriate for the primary 24-hour PM2.5 standard,
the Administrator indicated that in the absence of evidence of any
clear effects thresholds, EPA had discretion to select a specific
standard level from within this range of values. In ultimately deciding
to set the level of the primary 24-hour PM2.5 standard at 35
[mu]g/m\3\, the Administrator concluded that a standard set at a higher
level would not likely result in improvement in air quality in areas
across the country in which short-term exposure to PM2.5 can
reasonably be expected to be associated with serious health effects.
Similarly, a standard set at a lower level was rejected because of
uncertainties in interpreting the available epidemiologic studies that
could causally relate the reported associations of health risks to
PM2.5 at those lower levels.
New epidemiologic studies have built upon earlier limited evidence
to provide fairly strong evidence that long-term exposure to
PM2.5 is likely causally associated with mortality from
cardiopulmonary disease, as well as development of chronic respiratory
disease and reduced lung function growth. The new studies also provide
evidence suggesting that long-term exposure to fine particles is
associated with lung cancer mortality. The 2004 CD placed the greatest
weight on re-analyses and extensions of two mortality studies (Six
Cities and American Cancer Society (ACS) studies) originally considered
in the previous NAAQS review. In the Six Cities study, the long-term
mean PM2.5 concentration was 18 [mu]g/m\3\, within an
overall range of 11 to 30 [mu]g/m\3\. In the extended ACS study, the
mean for the more recent time period used in the analysis was 14 [mu]g/
m\3\, while the confidence intervals around the relative risk functions
start to become appreciably wider (more uncertain) below approximately
12 to 13 [mu]g/m\3\. Based on this and other sets of evidence, EPA
decided to consider, for setting the level of the annual
PM2.5 standard, a range of annual PM2.5
concentrations beginning somewhat below 15 [mu]g/m\3\ (the then-
existing primary annual PM2.5 NAAQS) down to about 12 [mu]g/
m\3\. However, after carefully considering public comments and relevant
studies, including the uncertainties in interpreting the available
long-term exposure epidemiologic studies, the Administrator decided to
retain the level of the primary annual PM2.5 standard at 15
[mu]g/m\3\ to protect public health with an adequate margin of safety
from serious health effects. See 71 FR at 61177.
Despite the advances in knowledge about the effects of
PM2.5 on human health, the 2005 SP noted the continued
difficulty of being able to establish a dose-response relationship
between PM2.5 concentrations and specific health-related
effects. ``The available toxicologic studies have generally not been
designed to quantify dose-response relationships* * *. Among the
studies reviewed [in the 2004 CD] are some that report no evidence of a
dose-response relationship gradient, (CD, p. 7-152), while some do (CD,
p. 7-155), and the CD draws no overall conclusions regarding dose-
response relationships from toxicologic studies. Therefore, while
epidemiologic studies provide clear indication of increasing response
with increasing concentration, no conclusions can be drawn from
toxicologic evidence.'' 2005 SP at 3-30.
(2) Welfare Effects
Ambient PM alone, and in combination with other pollutants, can
have a variety of effects on public welfare. While visibility
impairment is the most noticeable effect of fine particles present in
the atmosphere, both fine and coarse particles can have other
significant welfare-related effects, including effects on vegetation
and ecosystems, materials (e.g., soiling and corrosion), and climate
change processes. In 1997, EPA established a suite of secondary PM
standards, including annual and 24-hour PM2.5 standards and
annual and 24-hour PM10 standards, to address visibility
impairment associated with fine particles, and materials damage and
soiling related to both fine and coarse particles. See 62 FR 38683. In
2006, EPA considered the then-currently available evidence and decided
to revise the current suite of PM2.5 secondary standards by
making them identical in all respects to the revised suite of primary
PM2.5 standards, retain the current 24-hour PM10
secondary
[[Page 54129]]
standard, and revoke the current annual PM10 secondary
standard.
In reaching our decision in 2006 to revise the suite of PM
secondary standards, EPA factored in several key conclusions from the
scientific and technical information contained in the 2004 CD and 2005
SP. These conclusions included the following: (1) PM-related visibility
impairment is principally related to fine particle levels, and most
directly related to instantaneous levels of visual air quality
associated with short-term averaging periods; (2) PM2.5
concentrations can be used as a general surrogate for visibility
impairment in urban areas; (3) any secondary NAAQS for visibility
protection should be considered in conjunction with the regional haze
program as a means of achieving appropriate levels of protection
against PM-related visibility impairment in urban, non-urban, and Class
I areas nationwide; (4) the available evidence is not sufficient to
support distinct secondary standards for fine or coarse particles for
any non-visibility related welfare effects; and (5) the secondary
standards should be considered in conjunction with protection afforded
by other programs intended to address various aspects of air pollution
effects on ecosystems and vegetation, such as the acid deposition
program and other regional approaches to reducing pollutants linked to
nitrate or acidic deposition.
Notwithstanding the conclusions reached in setting the NAAQS for
PM, EPA has reviewed the scientific and technical information
concerning welfare related effects considered in the 2004 CD and 2005
SP to determine whether there is any basis for modifying the safe
harbor increments developed for PM2.5 to satisfy the
criteria under sections 166(c) and 160 of the Act. The EPA's review
began with visibility impairment, followed by effects on vegetation and
other ecosystem components, materials and soiling, and climate changes.
(a) Visibility impairment.
The EPA has long recognized that impairment of visibility is an
important effect of PM on public welfare. Visibility can be defined as
the degree to which the atmosphere is transparent to visible light.
Visibility conditions are determined by the scattering and absorption
of light by particles and gases from both natural and anthropogenic
sources. The classes of fine particles principally responsible for
visibility impairment are sulfates, nitrates, organic matter, elemental
carbon, and soil dust.
Visibility impairment can occur in two principal ways: as local
visibility impairment (e.g., localized plumes) and as regional haze.
Local-scale impairment is generally the result of the plume from a
single source or small group of local sources, rather than from long-
range transport from more distant sources. With this type of
impairment, a band or layer of discoloration can be observed well above
the terrain, obscuring the sky or horizon relatively near the source,
or sources, which cause it. Such visibility problems in urban areas are
often dominated by local sources, which may include stationary, mobile
and area sources. Visibility impairment from the combined effects of
urban sources have been studied in several major cities because of
concerns about fine particles and their significant impacts on
residents of large metropolitan areas.
The second type of impairment, regional haze, generally results
from pollutant emissions from a multitude of sources located across a
broad geographic region. Regional haze can impair visibility in every
direction over a relatively large area, in some cases over multi-state
regions. Regional haze is principally responsible for impairment in
national parks and wilderness areas (Class I areas) across the country
where scenic views are considered an important attribute. Fine
particles transported from urban and industrialized areas may, in some
cases, be significant contributors to regional-scale impairment in
Class I and other rural areas.
Annual average visibility conditions vary regionally across the
United States. Higher visibility impairment tends to occur more in the
East, and is due to generally higher concentrations of anthropogenic
fine particles and higher relative humidity conditions. In addition,
the rural East generally has higher levels of impairment than remote
sites in the West. For Class I areas, visibility levels on the 20
percent haziest days in the West are about equal to levels on the 20
percent best days in the East. For urban areas, however, East/West
visibility differences from fine particles are substantially smaller
than they are in rural areas.
The EPA's latest PM NAAQS review focused on visibility impairment
primarily in urban areas for the following reasons: (1) The efforts now
underway to address all human-caused visibility impairment in Class I
areas through regional strategies under the regional haze program (65
FR 35713, July 1, 1999), and (2) new information from visibility and
fine particle monitoring networks since the last PM NAAQS review that
has allowed for updated characterizations of visibility trends and
current levels in urban areas. Given the strong link between visibility
impairment and short-term PM2.5 concentrations, EPA gave
significant consideration to the question of whether visibility
impairment in urban areas allowed by the original 24-hour secondary
NAAQS for PM2.5 could be considered adverse to public
welfare.
New data available on PM2.5, primarily in urban areas,
enabled EPA to better characterize urban visibility than was previously
possible. Such data includes Federal Reference Method (FRM)
measurements of PM2.5 mass, continuous measurements of
hourly PM2.5 mass, and PM2.5 chemical speciation
measurements. Using the new data EPA sought to explore the factors that
historically complicated efforts to address visibility impairment
nationally, including regional differences related to levels of
primarily fine particles and relative humidity. Using the most recent
monitoring information and analyses, as well as photographic
representations of visibility impairment in several urban areas to help
inform judgments about the acceptability of varying levels of visual
air quality in urban areas, EPA observed that:
(1) At concentrations at or near the level of the 24-hour
PM2.5 standard (65 [mu]g/m\3\), which equates to visual
ranges roughly around 10 kilometers (6 miles), scenic views around and
within the urban areas, are significantly obscured from view.
(2) Appreciable improvement in the visual clarity of the scenic
views occurs at PM2.5 concentrations below 35 to 40 [mu]g/
m\3\, which equates to visual ranges generally above 20 kilometers for
the urban areas considered.
(3) Visual air quality appears to be good at PM2.5
concentrations generally below 20 [mu]g/m\3\, corresponding to visual
ranges of approximately 25 to 35 kilometers.
While being mindful of the limitations in using visual
representations from a small number of areas as a basis for considering
national visibility-based secondary standards, EPA concluded that the
observations noted earlier supported consideration of revising the then
current PM2.5 secondary standards to enhance visual air
quality, particularly with a focus on urban areas. This led to the
evaluation of information related to indicator, averaging time, level,
and form to identify a range of alternative PM standards that would
protect visual air quality, primarily in urban areas. Notwithstanding
the selection process used in selecting the primary and
[[Page 54130]]
secondary NAAQS for PM, for this PM increment proposal we are examining
the same information to determine whether it might justify modifying
the safe harbor increments for PM2.5, which follow the
indicator, averaging times, and form of the NAAQS for PM2.5,
as described earlier as option 1.
PM indicator. While both fine and coarse particles contribute to
visibility impairment, visibility impairment is the most noticeable
effect of fine particles present in the atmosphere. Analyses of hourly
PM2.5 measurements and other information demonstrate that
fine particles contribute to visibility impairment directly in
proportion to their concentration in the ambient air. Moreover,
hygroscopic components of fine particles, in particular sulfates and
nitrates, contribute disproportionately to visibility impairment under
high humidity conditions, when such components reach particle diameters
up to and even above 2.5 [mu]m. The EPA's analyses of how well
PM2.5 concentrations correlated with visibility in urban
locations across the United States lead to the conclusion that the
observed correlations were strong enough to support the use of
PM2.5 as the indicator for standards to address visibility
impairment in urban areas, especially when the indicator is defined for
a relatively short period of daylight hours.
Averaging time. While EPA selected the 24-hour averaging time for
the PM2.5 secondary standard to address visibility
impairment primarily in urban areas, a range of shorter term (sub-
daily) daylight averaging times were also considered. Strong
correlations between visibility and PM2.5 concentrations
were found to occur at the 24-hour averaging time, but the strongest
correlations were found to occur at the sub-daily daylight averaging
times, e.g., 4-to 8-hour daylight averaging times. In fact, the
correlation was greatest in the 4-hour time period between 12 and 4
p.m. At the sub-daily daylight averaging times, correlations between
PM2.5 concentrations and light extinction were less
influenced by relative humidity and more consistent across regions.
A number of different daylight time periods was selected to compare
correlations between visibility and hourly PM2.5
concentrations in urban areas across the United States and in eastern
and western regions. Ultimately, EPA staff recommended consideration of
a short-term averaging time, within the range of 4 to 8 hours, within a
daylight time period between approximately 10 a.m. to 6 p.m., to target
the driest part of the day. Most CASAC Panel members supported the SP
recommendation of a sub-daily averaging time.
Following careful consideration of the various sets of data and
evidence concerning visibility impairment, the Administrator proposed
to revise the secondary 24-hour standard for PM2.5 to make
it identical to the proposed revised primary PM2.5 standard
(based on a 24-hour averaging time for the short-term standard).
Consistent with recommendations to consider a sub-daily averaging time,
the Administrator also solicited comment on 4-to 8-hour averaging time
for the secondary PM2.5 standard. In reaching his final
decision to rely on the 24-hour averaging period to set the secondary
standard for PM2.5, the Administrator concluded that the
relative protection against adverse effects on public welfare provided
by the proposed primary standards was equivalent or more protective
than several of the 4-hour secondary standard alternatives in the range
recommended by CASAC and the SP. He also believed that caution was
warranted in establishing a distinct secondary standard for visibility
impairment primarily in urban areas, given the limitations in the
underlying studies and the subjective nature of the judgment required.
Level of increment. In evaluating the adequacy of the levels of the
contingent safe harbor increments for PM2.5, we examined the
range of PM2.5 concentrations considered in setting a
national visibility standard primarily for urban areas. We had
established that range of concentrations by using the results of public
perception and attitude surveys conducted in the United States and
Canada, State and local visibility standards within the United States,
and visual inspection of photographic representations of several urban
areas across the United States. These approaches are detailed in the
2005 SP (pp. 6-18 to 6-23.)
The public perception and attitude studies were used to gain an
understanding of what the public regarded as an acceptable visible
range. In some urban areas, poor visibility has led to more localized
efforts to better characterize, as well as improve, urban visibility
conditions. Public perception surveys used in Denver, Phoenix, and
British Columbia studies yielded reasonably consistent results, with
each study indicating that a majority of citizens find value in
protecting local visibility to with a visual range of about 40 to 60
km. Visibility standards for the Lake Tahoe area in California and for
areas within the State of Vermont are both targeted at a visual range
of about 50 km. In contrast, California's longstanding general state-
wide visibility standard is a visual range of approximately 16 km.
Aided by photographic representations of varying levels of visual
air quality developed for several cities across the United States, EPA
staff reached the conclusion that a national visibility standard in the
PM2.5 concentration range of 30 to 20 [mu]g/m\3\ should be
considered. Further analyses to characterize the distributions of
PM2.5 concentrations, 4-hour averages in the 12 to 4 p.m.
time frame, by region, that correspond to various visual range target
levels, resulted in a finding that concentrations of 30, 25, and 20
[mu]g/m\3\ correspond to the target visual ranges of approximately 25,
30 and 35 km, respectively. Thus, it was determined that a standard set
within the range of 30 to 20 [mu]g/m\3\ could be expected to correspond
generally to media visual range levels of approximately 25 to 35 km in
urban areas across the United States. This range was generally
consistent with a national target visual range below 40 km, the level
suggested by the public perception surveys and the local visibility
standards and goals. Nevertheless, EPA staff noted that a standard set
at any specific PM2.5concentration will necessarily result
in visual ranges that vary somewhat in urban areas across the country,
reflecting in part the less-than-perfect correlation between
PM2.5 concentrations and reconstructed light extinction.
2005 SP at page 7-8.
Form of increment. In considering a reasonable range of forms for a
PM2.5 standard within the range of PM2.5
concentration levels being considered, EPA staff took into account the
same general factors that were taken into account in considering an
appropriate form for the primary PM2.5 standard. In that
case, EPA staff concluded that a concentration-based form should be
considered because of its advantages over the previously used expected-
exceedance form.\14\ For visibility, the advantages are that the
concentration-based form (1) Would give proportionally greater weight
to days when the PM-related visibility impairment is substantially
higher than to days just above the standard, and (2) has greater
stability. 2005 SP at 7-11. To identify a range of concentration
percentiles that would be appropriate for consideration, it was
concluded that
[[Page 54131]]
the upper end of the range of consideration should be the 98th to 99th
percentile, consistent with the forms being considered for the 24-hour
primary PM2.5 standard. For the lower end of the range, EPA
staff used the 92nd percentile because it represented the mean of the
distribution of the 20 percent worst days, consistent with the fact
that the regional haze program targets the 20 percent most impaired
days for improvements in visual air quality in Class I areas. 2005 SP
at 7-12.
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\14\ The form of the 1987 24-hour PM10 standard is
based on the expected number of day per year (averaged over 3 years)
on which the level of the standard is exceeded; thus, attainment
with the one-expected exceedance form is determined by comparing the
fourth-highest concentration in 3 years with the level of the
standard.
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While EPA staff regarded PM2.5 as the best indicator for
addressing visibility impairment in urban areas, they considered a
range of averaging times, levels, and forms for setting a
PM2.5 secondary standard. In summary, EPA staff recommended
that consideration be given to a short-term averaging time for a
PM2.5 standard, within the range of 4 to 8 hours, within a
daylight time period between approximately 10 a.m. to 6 p.m. In
addition, they recommended that consideration should be given to the
adoption of Federal equivalent methods for appropriate continuous
methods for measurement of short-term average PM2.5
concentrations to facilitate implementation of the standard. Within the
recommended 4- to 8-hour averaging time, the EPA staff recommended
consideration of a standard level within the range of 30 to 20 [mu]g/
m\3\, depending in part on the form of the standard selected. Finally,
staff recommended consideration of a percentile-based form, focusing on
a range from the 92nd percentile up to the 98th percentile of the
annual distribution of daily short-term PM2.5 concentrations
averaged over 3 years. 2005 SP at 7-13.
(b) Vegetation and other ecosystem components.
The 2004 CD found that then-current PM2.5 levels in the
United States ``[had] the potential to alter ecosystem structure and
function in ways that may reduce their ability to meet societal needs''
(CD, p. 4-153). However, studies show that vegetation and other
ecosystem components result predominantly from exposure to excess
amounts of specific chemical species than from particle source,
predominant form (particle, gas, or liquid) or size fraction. The 2004
CD discussed the effects of a number of different chemical species,
including dust, trace metals, and organics, found within ambient PM,
but ultimately focused on particulate nitrates and sulfates based on
the conclusion that these latter constituents of PM2.5 were
``of greatest and most widespread environmental significance.'' Thus,
the 2005 SP focused on the welfare effects of particulate nitrates and
sulfates, either individually, in combination, and/or as contributors
to total reactive nitrogen deposition and total deposition of
acidifying compounds on sensitive ecosystem components and essential
ecological attributes.
Nitrogen and sulfur in varying amounts are necessary and beneficial
nutrients for most organisms that make up ecosystems. It is when
unintentional additions of atmospherically derived nutrient and
acidifying compounds containing nitrogen and sulfur force unintended
change on ecosystems, resulting in adverse impacts on essential
ecological attributes, that deposited particulate nitrate and sulfate
are termed ecosystem ``stressors.'' In order for any specific chemical
stressor present in ambient PM to impact ecosystems, it must first be
removed from the atmosphere through any of three different types of
deposition: wet (rain/frozen precipitation), dry, or occult (fog, mist,
or cloud). At the national scale, all types of deposition must be
considered in determining potential impacts to vegetation and
ecosystems because each type may dominate over specific intervals of
time or space.
The most significant PM-related ecosystem-level effects result from
long-term cumulative deposition of a given chemical species (e.g.,
nitrate) or mix (e.g., acidic or acidifying deposition) that exceeds
the natural buffering or storage capacity of the ecosystem and/or
affects the nutrient status of the ecosystem. The 2005 SP examined the
environmental effects of both reactive nitrogen (of concern is the
reactive nitrogen resulting from the conversion of both atmospheric
nitrogen and fossil nitrogen during the combustion of fossil fuels) and
PM-related acidic and acidifying deposition on various ecosystems,
including vegetation, terrestrial ecosystems, threatened and endangered
species, and aquatic habitat.
Vegetation. Various studies indicate that at current ambient
levels, risks to vegetation from short-term exposures to dry deposited
particulate nitrate or sulfate are low; however, when found in
acidifying deposition, such particles do have the potential to cause
direct foliar injury. The 2005 SP concluded on the basis of available
information that the risk of injury occurring from acid precipitation
in the eastern United States is high, noting that acid precipitation
with levels of acidity associated with adverse foliar effects exist in
some locations of the United States. Such adverse effects may include
damage to leaf surface structure; increased permeability of leaf
surface to toxic material, water, and disease agents; increased
leaching of nutrients from foliage; altered reproductive processes; and
overall weakening of trees making them more susceptible to other
stressors. Having said all this, the 2005 SP also found that the
contribution of particulate sulfates and nitrates to the total acidity
found in the acid precipitation impacting eastern vegetation is not
clear.
Terrestrial ecosystems. The 2005 SP concluded that excess nitrogen
deposition is having a ``profound and adverse impact on the essential
ecological attributes associated with terrestrial ecosystems.''
Terrestrial ecosystems may be adversely impacted by (1) increased
nitrogen associated with atmospheric deposition, surface runoff, or
leaching from nitrogen saturated soils into ground or surface waters;
and (2) acidic and acidifying deposition.
Long-term, chronic additions of reactive nitrogen (including
nitrate deposition and ammonium from ambient PM) can cause the nitrogen
input to plants to exceed the natural capacity of plants and soil
microorganisms to utilize and retain the nitrogen needed for normal
growth. As this excess occurs over time, a detrimental ecological
condition known as ``nitrogen saturation'' is said to exist.
Nitrogen saturation does not occur at a specific point in time, but
reflects a set of gradually developing critical changes in the
ecosystem process. In addition, not all vegetation, organisms, or
ecosystems react in the same manner to increased nitrogen availability
from nitrogen deposition. Those plants that are predisposed to
capitalize on any increases in nitrogen availability gain an advantage
over those that are not as responsive to added nitrogen. Over time,
this shift in the competitive advantage may lead to shifts in overall
plant community composition. Whether this shift is considered adverse
would depend on the management context within which that ecosystem
falls and the ripple effects of this shift on other ecosystem
components, essential ecosystem attributes, and ecosystems.
The addition of nitrogen on plant community succession patterns and
biodiversity has been studied in several long-term nitrogen
fertilization studies in both the United States and Europe. These
studies suggest that some forests receiving chronic inputs of nitrogen
may decline in productivity and experience greater mortality. Some of
the U.S. forests that are showing severe symptoms of nitrogen
saturation are: the northern hardwoods and mixed conifer
[[Page 54132]]
forests in the Adirondack and Catskill Mountains of New York; the red
spruce forests at Whitetop Mountain, Virginia, and Great Smoky
Mountains National Park, North Carolina; mixed hardwood watersheds at
Fernow Experimental Forest in West Virginia; American beech forests in
Great Smoky Mountains National Park, Tennessee; and mixed conifer
forests and chaparral watersheds in southern California and the
southwestern Sierra Nevada in Central California. 2005 SP at 6-31.
Studies have shown that acid deposition has changed the chemical
composition of soils by depleting the content of available plant
nutrient cations (e.g., Ca\2+\, Mg\2+\, and K\+\) by increasing the
mobility of aluminum, and by increasing the sulfur and nitrogen
content. Effects of acidic deposition have been extensively documented,
as discussed in the 2004 CD and reports referenced therein. For
example, effects on some species of forest trees linked to acidic
deposition include increased permeability of leaf surfaces to toxic
materials, water, and disease agents; increased leaching of nutrients
from foliage; and altered reproductive processes; all of which serve to
weaken trees so that they are more susceptible to other stresses (e.g.,
extreme weather, pests, and pathogens). In particular, acidic
deposition has been implicated as a causal factor in the northeastern
high-elevation decline of red spruce. Although U.S. forest ecosystems
other than the high-elevation spruce-fir forests are not currently
manifesting symptoms of injury directly attributable to acid
deposition, less sensitive forests throughout the United States are
experiencing gradual losses of base cation nutrients, which in many
cases will reduce the quality of forest nutrition over the long term.
Threatened and endangered species. The adverse ecological effects
of PM include those effects on rare and unique ecosystems, including
both plant and wildlife species. Nitrogen deposition, including
particulate nitrate, may have a direct adverse affect on some plant
species, while for others the harm results when added nitrogen serves
as a nutrient for some invasive species that eventually replace the
more sensitive, rare species.
In some instances, as sensitive vegetation is harmed or lost,
wildlife species that depend on these plants are also adversely
affected. Several threatened or endangered species listed by the U.S.
Fish and Wildlife Service, such as the desert tortoise and checkerspot
butterfly have declined as a result of native food supplies being
replaced by invasive plant species whose productivity is enhanced in
part by nitrogen deposition.
Aquatic habitat. Adverse effects of PM on aquatic systems (streams,
rivers, lakes, estuaries, and oceans) can be the result of either
elevated levels of reactive nitrogen input or acidification. In either
case, the nitrogen input contribution from PM may be the result of
atmospheric deposition directly into the water body or on terrestrial
ecosystems, reaching the water body via surface runoff or leaching from
nitrogen saturated soils into ground or surface waters. However, it is
not clear how much of the total nitrogen input to aquatic systems
results from atmospheric deposition rather than from other nitrogen
sources.
Estuaries receive far greater nutrient inputs than other systems.
Excess nitrogen in estuaries results in eutrophic conditions whereupon
dissolved oxygen is significantly reduced; yielding an environment that
favors plant life over animal life. The 2005 SP describes research
being done in the Pamlico Sound in North Carolina, which is a key
fisheries nursery in the southeastern United States. Studies have shown
that direct nitrogen deposition onto waterways feeding into the Pamlico
Sound or onto the Sound itself and indirect nitrogen inputs via runoff
from the upstream watersheds contribute to conditions of severe water
oxygen depletion; formation of algae blooms in portions of the Pamlico
Sound estuarine complex; altered fish distributions, catches, and
physiological states; and increases in the incidence of disease. 2005
SP at p. 6-35.
Other studies have shown that under extreme rainfall events,
massive influxes of reactive nitrogen (in combination with excess
loadings of metals or other nutrients) into watersheds and sounds can
lead to dramatic decreases of oxygen in water and the creation of
widespread ``dead zones'' and/or increases of algae blooms that can
cause extensive fish kills and damage to commercial fish and sea food
harvesting. 2005 SP at p. 6-35.
The 2005 SP indicates that there is a clear link between acidic
water, which results from atmospheric deposition of strong acids, and
fish mortality. Studies have shown that inputs of acid deposition to
regions with base-poor soils have resulted in the acidification of soil
waters, shallow ground waters, streams, and lakes in a number of
locations with the United States. This can result in lower pH and
higher concentrations of inorganic monomeric aluminum, which causes
changes in chemical conditions that are toxic to fish and other aquatic
animals.
(c) Materials damage and soiling.
As part of the review for setting secondary standards for PM, the
2004 CD and 2005 SP considered the adverse effects that the deposition
of ambient PM can have on materials such as metals, paint finishes, and
building stone and concrete. Substantial evidence exists to show that
ambient PM plays a role in both physical damage and impaired aesthetic
qualities of materials. Physical damage to materials, including
corrosion, degradation, and deterioration, is known to result from
exposure to environmental factors such as sunlight, moisture, fungi,
and varying temperatures; however, to the extent that particles may
cause or contribute to physical damage of building materials, such
damage is primarily caused by chemically active--especially particulate
nitrates and sulfates--fine particles or hygroscopic coarse particles.
On the other hand, particles consisting of carbonaceous compounds are
responsible for soiling of commonly used building materials and
culturally important items (statues, works of art, etc.) Soiling or
exposure to PM can affect the aesthetic appeal of surfaces by giving
them a dirty appearance, resulting in an increased frequency of
cleaning. Nevertheless, while the role of ambient PM in specific
adverse effects is well documented in the available studies, the 2004
CD and 2005 SP also concluded that there remains insufficient evidence
to establish a quantitative relationship between ambient PM and any of
the various effects described.
The EPA believes that these observations and the underlying
available evidence continue to support consideration of retaining an
appropriate degree of control on both fine and coarse particles.
Lacking any specific quantitative basis for establishing distinct
standards to protect against PM related to adverse effects on
materials, EPA believes that reductions in fine and coarse particles
likely to result from the current suite of secondary PM standards, or
the range of recommended revisions to the primary PM standards and to
the secondary PM2.5 standard to address visibility
impairment, would contribute to protection against PM-related soiling
and materials damage.
(d) Climate and solar radiation effects.
The effects of PM on climate result from either the scattering or
absorption of radiation by ambient particles, resulting in a cooling or
warming effect on climate, respectively. Studies suggest
[[Page 54133]]
that global and regional climate changes could have both positive and
negative effects on human health and welfare, and the environment. Most
components of ambient PM, especially sulfates, scatter and reflect
incoming solar radiation back into space. However, some components of
ambient PM, especially black carbon, absorb incoming solar radiation or
outgoing terrestrial radiation. Sulfate particles indirectly affect
climate by serving as condensation nuclei which alter the size
distribution of cloud droplets (producing more droplets with smaller
sizes), causing the amount of solar radiation that clouds reflect back
to space to increase.
While substantial qualitative information has shown the important
role that ambient PM plays in both global and regional climatic
processes, that role is presently poorly quantified. There are
considerable uncertainties and difficulties in projecting likely
climate change impacts. The 2005 SP indicates that ``any complete
assessment of the direct radiative effects of PM would require
computationally intensive calculations that incorporate the spatial and
temporal behavior of particles of varying composition that have been
emitted from, or formed by precursors emitted from, different
sources.'' 2005 SP at 6-55. In addition, calculations of indirect
physical effects of particles on climate are subject to much larger
uncertainties than those related to the direct radiative effects of
particles.
Exposure to solar radiation may have direct effects on human health
and agricultural and ecological systems; indirect effects on human
health and ecosystems, and effects on materials. 2005 SP at 6-56ff.
Several studies cited in the 2004 CD reinforce the idea that particles
can play an important role in affecting the transmission of solar UV-B
radiation. However, none of these studies included measurements of
ambient PM concentrations, so that direct relationships between PM
levels and UV-B radiation transmission could not be determined. In
addition, the relationships between particles and UV-B radiation
transmission can vary considerably over location, conditions, and time.
2005 SP at 6-56. In summary, the EPA staff concluded that available
information is insufficient to project the extent to which, or even
whether, location-specific changes in ambient PM would indirectly
affect human health or the environment.
e. Fundamental Elements of Increments
As we have previously noted, under the model established in the Act
and prior EPA regulations, the function of an increment is not like
that of the NAAQS in that an increment is not intended to set a uniform
ambient pollutant concentration ``ceiling'' across the United States.
See 70 FR 59600. That is, while both increments and NAAQS generally
serve to limit air pollution levels, increments are designed to allow a
uniform degree of pollutant concentration increase for each area in the
United States with a particular classification, with the allowable
increase measured against a baseline air quality level for a particular
area.\15\ Because the baseline air quality level varies from one
location to another, and is not established until a PSD permit is
submitted, it is not possible to determine what the maximum pollutant
concentration attainable is for a given area (to be used to determine
the protection afforded by an increment against potential adverse
environmental effects) until the specific baseline air quality level is
known.
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\15\ It should be noted, however, that an increment does not
allow air pollution levels in an area to increase beyond the ambient
concentration of a pollutant that would exceed the level allowed by
the NAAQS.
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For the reasons described in our increments rule for
NOX, our objective is to establish uniform increments that
allow the same level of deterioration for each area of the country
having the same classification. 70 FR 59601. Our goal is not to
establish increments to reduce existing air pollutant concentrations
below baseline levels in each area, but rather to define a level of
increase in pollutant concentrations above baseline levels that
represents ``significant'' deterioration for each area classification.
70 FR 59600.
f. Evaluation of the Safe Harbor Increments
Mindful of the considerations we previously described about the
fundamental characteristics of the increments, we reviewed the
scientific and technical evidence available for the 2005 review of the
NAAQS for PM in order to determine whether, and to what extent, the
``safe harbor'' increments might need to be modified in order to
protect air quality values, health and welfare, and parks while
ensuring economic growth consistent with the preservation of clean air
resources in accordance with sections 166(c) and 160 of the Act. As we
did in our evaluation of the safe harbor NO2 increments, we
propose to rely on an approach that evaluates how protective the safe
harbor PM2.5 increments are by trying to compare the
marginal pollutant concentration increases allowed by the safe harbor
increment levels against the pollutant concentrations at which various
environmental responses occur. We analyzed the available evidence from
both a quantitative and qualitative perspective to reach a decision
about whether we should modify the contingent safe harbor
PM2.5 increments and whether we have sufficient information
to select a specific alternative level, averaging time, or pollutant
indicator for the increments.
(1) Non-Visibility Related Effects
In quantitatively evaluating the adequacy of the contingent safe
harbor increments for PM2.5 for non-visibility related
welfare effects, we experienced difficulties with identifying the
appropriate indicator, as well as to the level of the increments. In
the most recent evaluation of the NAAQS for PM, EPA staff concluded
that ``sufficient information is not available at this time to
recommend consideration of either an ecologically based indicator or an
indicator based distinctly on soiling and materials damage, in terms of
specific chemical components of PM.'' 2005 SP at 7-15. For
consideration of the effects of ambient PM on vegetation and other
ecosystems, the available data indicate that the chemical species of PM
(especially particulate nitrate and sulfate) has more relevance than
the size fraction (coarse or fine). Acid precipitation, including
particulate sulfate, has been found to be particularly damaging to
foliage, and along with ambient SO2 contributes
significantly to materials damage and soiling.
Determining the most effective levels for any indicator for PM from
the available data is difficult because the evidence is insufficient to
provide a quantitative relationship between ambient PM concentrations
and known and observed adverse ecological effects. Fundamental areas of
uncertainty preclude establishing predictable relationships between
ambient concentrations of particulate nitrogen and sulfur compounds and
associated ecosystem effects. One source of uncertainty hampering the
characterization of such relationships is the extreme complexity and
variability that exist in estimating particle deposition rates. These
rates are affected by numerous factors, including particle size and
composition, associated atmospheric conditions, and the properties of
the surfaces being impacted. A related source of uncertainty is
establishing the portion of the total nitrogen and sulfur deposition
occurring at a given site is attributable to ambient PM. Though several
national
[[Page 54134]]
deposition monitoring networks have been successfully measuring wet and
dry deposition for several decades, they often do not distinguish the
form (e.g., particle, wet, and dry gaseous) in which a given chemical
species is deposited. Further, it is not clear how well data from
monitoring sites may apply to non-monitored sites with different
surface cover, meteorology, or other deposition related factors.
Another fundamental problem that makes it difficult to establish a
meaningful dose-response relationship between ambient PM levels and
specific adverse environmental effects is that ecosystems have
different sensitivities and capacities to buffer or assimilate
pollutants. Many of the documented ecosystem-level effects only became
evident after long-term, chronic exposures to total annual loads of
reactive nitrogen (Nr) or acidifying compounds that eventually exceeded
the natural buffering or assimilative capacity of the system. In most
cases, PM deposition is not the only contributor to the total load of
Nr or acidifying compounds entering the affected system. Since it is
difficult to predict the rate of PM deposition, and thus, the PM
contribution to total deposition at a given site, it is difficult to
predict the ambient concentration of PM that would likely lead to the
observed adverse effects within any particular ecosystem. Equally
difficult is the prediction of recovery rates for areas already
affected, if PM deposition rates of various chemical species were to be
reduced.
In response to our 2005 proposal for NO2 increments,
some commenters expressed the opinion that a better way of identifying
acceptable pollutant loadings, particularly for protection against
ecological effects, is the use of a ``critical load'' concept.\16\ 70
FR 59612. At that time, EPA expressed support for the concept, but
indicated that our current knowledge about critical loads did not
``provide a sufficient basis for establishing a uniform, national
standard such as a PSD increment.''
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\16\ A ``critical load'' is a numerical estimate of the amount
of polloution that a sensitive ecosystem can absorb on a sustained
basis before it experiences a measurable amount of degradation. In
contrast to the units for increments, [mu]/m\3\, a critical load is
typicallly expressed as a loading rate in kilograms of a pollutant
per hectare per year.
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The critical load concept was once again reviewed in the 2005 SP
for PM. It was noted in that document that the ``[k]ey to the
establishment of a critical load is the selection of appropriate
ecological endpoints or indicators that are measurable characteristics
related to the structure, composition, or functioning of ecological
systems (i.e., indicators of condition).'' 2005 SP at 6-46. The EPA
recognized the value of using critical loads and acknowledged that a
number of different groups in the United States have begun to use or
develop critical loads. Nevertheless, while recognizing that current
activities ``hold promise,'' EPA concluded that ``widespread use of
[critical loads] in the U.S. is not yet possible.'' Among other things,
currently available data are insufficient to quantify the contribution
of ambient PM to total Nr or acid deposition, and it is not clear
whether a critical load could be developed just for the portion of the
total N or S input that is contributed by PM. SP at 4-49. Research, in
conjunction with the development of improved predictive models, could
help in future consideration within the United States of the critical
loads concept, and in determining how much of any given critical load
is contributed by different sources of pollutants.
As explained earlier, the available scientific and technical data
do not yet enable us to adequately relate ambient concentrations of
PM2.5 to ecosystem responses. Without such key information,
it is difficult to quantitatively evaluate the effectiveness of the
``safe harbor'' increments for protecting air quality values, health
and welfare, and parks while ensuring economic growth consistent with
the preservation of clean air resources. Alternatively, we must make a
qualitative judgment as to whether the contingent safe harbor
increments for PM2.5 or some alternative increments meet the
applicable factors.
In this situation, we believe that the determination of the
increment levels that satisfy the factors applicable under section
166(c) is ultimately a policy choice that the Administrator must make,
similar to the policy choice the Administrator must make in setting a
primary NAAQS ``with an adequate margin of safety.'' See Lead
Industries Ass'n v. EPA, 647 F.2d 1130, 1147 (D.C. Cir. 1980) (where
information is insufficient to permit fully informed factual
determinations, the Administrator's decisions rest largely on policy
judgments). Using a similar approach is warranted because both section
109 and section 160(1) direct the Administrator to use his or her
judgment in making choices regarding an adequate margin of safety or
protecting against effects that may still occur notwithstanding
compliance with the NAAQS--both areas of inquiry characterized by great
uncertainty. Thus, in the process for setting NAAQS, the Administrator
looks to factors such as the uncertainty of the science, the
seriousness of the health effects, and the magnitude of the
environmental problem (isolated or commonplace). E.g., 62 FR 38652
(July 18, 1997) (PM2.5 NAAQS).
Bearing on this policy decision for increments are various
considerations, based on the available information and the factors
applicable under section 166(c). The factors establishing particular
environmental objectives (protecting air quality values, health and
welfare, and parks) might suggest that, in some areas, we permit little
or no increase in PM2.5 emissions or establish an increment
for another form of PM because there are data indicating that an effect
may be attributable to PM emissions. However, as explained in the
NOX rule, we do not believe that Congress intended for the
PSD program to eliminate all negative effects. Thus, rather than just
seeking to eliminate all negative effects, we must attempt to identify
a level of increase at which any additional effects beyond existing (or
baseline) levels would be ``significant'' and protect against those
``adverse'' effects. Furthermore, we need to ensure that our increments
provide room for some economic growth. Congress intended for EPA to
weigh these considerations carefully and establish regulations that
balance economic growth and environmental protection.
Since we are unable to establish a direct, widely applicable,
quantitative relationship between particular levels of PM2.5
and specific negative effects, we give particular weight to the policy
judgment that Congress made when it set the statutory increments as a
percentage of the NAAQS and created increments for the same pollutant
form and time period that was reflected in the NAAQS. In section 166 of
the Act, Congress directed that EPA study the establishment of PSD
regulations for other pollutants for which Congress did not wish to set
increments at the time.
Congress's own reluctance to set increments to prevent significant
deterioration of air quality due to emissions of NOX, and
the provisions ensuring time for Congressional review and action,
suggest that Congress intended for EPA to avoid speculative judgments
about the science where data are lacking. Thus, in the absence of
specific data showing that an increment level that of the ``safe
harbor'' level would better protect health, welfare, parks, and air
quality values, while simultaneously maximizing opportunities for
economic growth, we give weight in our qualitative analysis of the
factors applicable under section
[[Page 54135]]
166(c) to the method that Congress used to establish the statutory
increments.
In making this qualitative judgment, we also consider the overall
regulatory framework that we have established in the PSD regulations
for PM2.5. This framework includes a case-by-case analysis
of each permit application to identify additional impacts (e.g., soils
and vegetation), a special review by the FLM and State reviewing
authority of potential adverse effects on air quality values in parks
and special areas, and a requirement that all new and modified sources
install BACT. In addition, the area classification system ensures that
there will be economic growth in particular areas that is consistent
with the values of each State and its individual communities. Based on
this qualitative analysis, we do not believe it is necessary to adopt
more stringent increments to satisfy section 166(c) of the Act with
respect to non-visibility related effects.
(2) Visibility Protection
In the case of visibility protection, the available evidence was
strong enough to enable EPA to conclude that PM2.5 is the
appropriate indicator for measuring the effects of ambient PM on
visibility impairment. Accordingly, using PM2.5
concentrations as the basis for review, EPA evaluated a range of
PM2.5 ambient concentrations, averaging times (24 hours and
less), and a range of concentration percentiles (using a concentration-
based form for the standard) in order to establish a recommendation for
setting the secondary NAAQS for PM to address visibility impairment in
urban areas. As explained in the 2005 SP, EPA considered, as a lower
bound for setting the short-term secondary PM2.5 standard, a
PM2.5 concentration of either 20 or 25 [mu]g/m\3\, averaged
over a 4- to 8-hour averaging time within daylight hours, depending on
the percentile range considered for the form of the standard.
The Class II, short-term safe harbor increment for PM2.5
is 9 [mu]g/m\3\. This level is well below the lower bound recommended
for setting the secondary PM2.5 standard, but is based on a
24-hour averaging time at the 98th percentile. The 2005 SP also notes
that the estimated 98th percentile values in distributions of daily
background levels are below 10 [mu]g/m\3\ in most areas. Thus, the
allowable deterioration from the safe harbor increment in addition to
the natural background level generally falls below the minimum values
recommended in the 2005 SP for the secondary short-term standard for
PM2.5.
With regard to the Class I increments for PM2.5, we note
that Congress explicitly included visibility as an air quality related
value (AQRV), enabling Federal land managers to protect significant
attributes of Federal Class I areas. Act section 165(d)(2)(B). The FLM,
assigned the affirmative responsibility to protect Federal Class I
areas, are to use AQRVs which are separate and distinct from
increments, to address individual Class I areas and the unique
attributes identified for each Class I area. Congress recognized that
AQRVs and increments were not the same thing and established
independent procedures for the implementation of each. For example, the
Act authorizes FLM to evaluate the effects of pollutant increases using
AQRVs as the basis regardless of the effect of such pollutant increases
on the increments. In using the AQRV, FLM are not limited in their
evaluation by the maximum allowable pollutant increase set by the
increment and may identify adverse impacts on visibility pursuant to
AQRVs even when the pollution increase will not cause or contribute to
an exceedance of an increment. Instead, the pollutant increase is
evaluated against the AQRV which considers the specific conditions
existing in the Class I area of concern. Thus, regardless of the
increased amount of pollution that an increment may allow, the FLM may
determine that the visibility in the Class I area is adversely affected
by an amount of pollutant increase less than that allowed by the
increment.
From a qualitative perspective, we believe that visibility
protection in Class I areas is more adequately provided by the AQRV
process, where each area can be addressed on the basis of the local
situation and the FLM's assessment of potential ambient impacts by a
particular source. Nevertheless, generally speaking an increment should
not be so large that it routinely results in substantially more
pollution in Class I areas than is generally acceptable under the AQRV
approach. The contingent safe harbor PM2.5 increments for
Class I areas are 1 [mu]g/m\3\ and 2 [mu]g/m\3\ for the annual and 24-
hour averaging periods, respectively.
We believe the importance of using distinct PM2.5
increments to protect against visibility impairment is also lessened by
the fact that Congress, aware of the statutory requirements for
prevention of significant deterioration of air quality, established
several visibility programs that specifically target emissions
reductions to achieve the desired visibility benefits. Under the
regional haze regulations, promulgated by EPA in 1999, States are
required to establish goals for improving visibility on the 20 percent
most impaired days in each Class I area, and for allowing no
degradation on the 20 percent least impaired days. Each State must
adopt emission reduction strategies which, in combination with the
strategies of contributing States, assure that Class I area visibility
improvement goals are met. Five multi-state planning organizations are
evaluating the sources of PM2.5 contributing to Class I area
visibility impairment to lay the technical foundation for developing
strategies, coordinated among many States, in order to make reasonable
progress in Class I areas across the United States.
We believe it is also important to consider the fact that some
State and local governments have also developed programs to improve
visual air quality in specific urban areas. These programs are
individually designed to focus on improving visibility to a visual
range defined by the specific area of concern. Such local programs can
more appropriately focus on the preferences of individual communities
where a uniform national increment for visibility protection generally
cannot.
In setting the NAAQS for PM, EPA ultimately concluded that a
distinct secondary standard with a different averaging time or form was
not warranted at that time. Instead, we concluded that a set of
secondary PM2.5 standards set identical to the revised
primary PM2.5 standards a reasonable approach when
considered in conjunction with the regional haze program as a means of
achieving appropriate levels of visibility protection in urban, non-
urban, and Class I areas across the United States. With regard to
evaluating the safe harbor increments for PM2.5, we had to
consider how much weight to give to visibility protection as a function
of the increments. That is, whether the increments were the appropriate
means of providing the most effective protection against visibility
impairment in urban areas as well as in rural areas, including Federal
Class I areas. In light of the other more direct approaches being used
to address visibility problems across the United States, we believe
that the use of distinct PM increments for visibility protection is not
the most effective means of addressing the visibility problem. Thus, we
do not believe it is necessary to modify the safe harbor increments for
PM2.5 to further protect visibility.
[[Page 54136]]
3. Proposed Baseline Dates for PM2.5 Increments Under Option
1
If we adopt option 1, we propose to require the implementation of
the PM2.5 increment system with new baseline areas, baseline
dates and trigger dates. Specifically, we are proposing that the major
source baseline date and trigger date, both fixed dates, will be
defined as the effective date of this rule after promulgation.
In light of current and expected trends in PM2.5
concentrations, EPA's judgment is that starting with new baseline dates
on or after the effective date of this rule would make the new PSD
increments more protective. Under our proposed approach, any emissions
reductions occurring prior to the effective date of this rule would be
counted toward the baseline concentration rather than expanding the
PM2.5 increment. If a retroactive baseline date were to
apply, emissions reductions occurring prior to the effective date of
this rule would serve to expand the available increments, enabling more
pollution than would otherwise be allowed to occur.
In addition, we believe starting with new baseline dates to
implement new increments for PM2.5 is appropriate under this
option because we would treat PM2.5 essentially as a ``new''
pollutant for purposes of PSD and section 166 of the Act. We believe
that establishing a new baseline overcomes significant implementation
concerns that would otherwise exist if the existing PM baseline were
maintained. If we were to require sources and reviewing authorities to
conduct PM2.5 increment analyses based on the minor source
baseline dates previously established under the TSP or PM10
program, they would have to attempt to recreate the PM2.5
emissions inventory as of the minor source baseline date in order to
determine the baseline PM2.5 concentration for the area. For
early minor source baseline dates in particular (e.g., 1976 in areas of
the United States), establishing the emissions inventory for PM2.5
would be extremely difficult, cumbersome and potentially inaccurate
because historic emissions inventories did not include PM2.5
emissions. For all of these reasons, we are proposing option 1 as our
preferred option and request comment on this contingent safe harbor
approach under option 1
4. Revocation of PM10 Annual Increments
If we use option 1 to adopt additional increments for
PM2.5, we propose to revoke the annual increments for
PM10 based on the same technical evidence that led us to
revoke the annual PM10 NAAQS. As discussed earlier, we do
not believe EPA is precluded from adopting new particular matter
increments under section 166(a) of the Act because we promulgated a
NAAQS for PM2.5 after 1977. However, if we read section
166(f) to address PM10 alone, the interaction of sections
166(a) and 166(f) could suggest that pollutant-specific PSD regulations
for PM promulgated on the basis of section 166(a) must be limited to
regulations that address fine PM. However, this view would create
tension with language in section 166(a) that calls for us to conduct a
holistic evaluation to establish a system of PSD regulations (including
numerical and other measures) for each pollutant covered by this
provision. Since it would be preferable to develop a system of
regulation for PM generally and select the appropriate indicator for PM
increments based on a comprehensive review of the effects of all forms
of PM (as we did in the recent NAAQS rule), we do not believe Congress
could have intended to constrain EPA's discretion to consider the
potentially differing effects of coarse and fine particles when
developing pollutant-specific PSD regulations under section 166(a).
Since EPA recently revised the NAAQS for PM10 and
eliminated the annual PM10 NAAQS, we believe it is
permissible for the Agency to interpret the phrase ``pollutants for
which national ambient air quality standards are promulgated after
August 7, 1977'' to apply to revisions to PM10 as well. In
our 1989 proposal to adopt PM10 increments, before the
addition of section 166(f) to the Act, we construed the language in
section 166(a) to be broad enough to support adoption of PM10
increments. Under a holistic approach, considering all forms of PM, we
do not believe the evidence supports retaining an annual increment for
PM10 under the PSD program. In our October 17, 2006 action
on the PM NAAQS, the Administrator concluded that an annual coarse
particle NAAQS was not warranted at this time. 71 FR 61198-99. The CD
concluded that the available evidence does not suggest an association
of adverse health effects with long-term exposure to coarse particles
and the SP concluded there is no quantitative evidence that directly
supports an annual standard. Id. at 61198. With respect to welfare
effects, the evidence indicated that a short-term PM2.5
standard was the best approach for addressing visibility. Id. at 61280.
For non-visibility welfare effects, the Administrator concluded that
the available evidence was not sufficient to support an additional
indicator, but that a secondary NAAQS identical to the primary NAAQS
directionally improves the level of protection afforded vegetation,
ecosystems, and materials. Id. at 61210.
When the evidence described in the Criteria Document and Staff
Paper is considered in light of the legal criteria applicable under
section 166(c), we believe it supports the conclusion that an annual
PM10 increment is no longer needed under the PSD program. In
the absence of a clear association between long-term exposure to coarse
particles and adverse health effects, we do not see a justification for
an annual PM10 increment to protect public health,
notwithstanding compliance with the NAAQS. In addition, the new
increments for PM2.5 that we propose to adopt, in
combination with the existing 24-hour increment for PM10,
will address welfare effects, air quality related values, and air
quality in national parks and other special areas. As described
earlier, visibility impacts are principally attributable to short-term
fine particle concentrations and thus will be addressed by the new
short-term PM2.5 increment. The evidence indicates that the
non-visibility welfare effects of concern are primarily attributable to
deposition of sulfate and nitrate particles of any size. Thus, the
combination of the new PM2.5 increments and the existing 24-
hour PM10 increment will address non-visibility welfare
impact attributable to deposition. Since we propose to retain the 24-
hour PM10 increment and adopt new annual and 24-hour fine
particle increments that will target all of these effects, we do not
consider it warranted to require continued tracking of changes in
annual concentrations of PM10 under the PSD program.
B. Option 2--Equivalent Substitution Approach for Annual Increments--
Section 166(f)
Under this option, we would recognize PM2.5 as a new
indicator for PM for NSR purposes, and develop annual PM2.5
increments to replace the annual PM10 increments using the
equivalent substitution approach under the authority of section 166(f)
of the Act.
The approach proposed under this option in this proposed rule would
be similar to the one we used in 1993, and discussed earlier to convert
from TSP increments to PM10 increments, to avoid having to
implement increments based on standards that no longer existed. On
October 17, 2006, EPA revoked the primary and secondary annual
PM10 standards and retained the primary and
[[Page 54137]]
secondary 24-hour PM10 standards. 71 FR 61144.
In this case, we therefore are developing annual PM2.5
increments to replace the annual PM10 increments. Also,
consistent with our prior action in 1993, we are proposing to eliminate
or revoke the PM10 increments in this notice. However, for
developing the 24-hour PM2.5 increments, we are proposing to
use the increment values derived under the contingent safe harbor
approach explained in option 1. We seek comment not only on the levels
of the proposed ``equivalent'' increments, but also on our use of this
equivalent increment option for only the annual PM2.5
increments. In addition, we seek comment on whether we should rely on
section 166(f) to also propose the 24-hour PM2.5 increments,
even though the primary and secondary 24-hour PM10 NAAQS are
not being revoked.
1. Development of Equivalent Increments
To establish equivalent PM10 increments in the 1993
rule, EPA compared the TSP and PM10 impacts of each of the
249 major sources subject to major NSR in our NSR database. EPA
observed that, in principle, for any source the equivalent PM10
increments was simply the product of the TSP increment to the source's
PM10/PM emissions ratio. 58 FR 31627.
In this rulemaking, EPA proposes to apply the same type of ratio
approach to establish equivalent increments for PM2.5 under
section 166(f) of the Act. Unlike the 1993 analysis where we evaluated
a database of 249 major sources, for this rulemaking EPA relied on a
more comprehensive analysis of the ``2001 National Emissions Estimates
by Source Categories'' for PM10 and PM2.5.\17\
From the 2001 National Emissions Inventory, the ratio of emission
estimates from utilities and industrial point source categories were
used to find the PM2.5 to the PM10 emissions
ratio. For purposes of deriving the ratio, area sources and non-road
and mobile sources were not included on the basis that for NSR
permitting virtually all of the permitted sources fall within the
utility and industrial point source categories.
---------------------------------------------------------------------------
\17\ 2001 National Emissions Estimates by Source Categories.
---------------------------------------------------------------------------
Utilities and industrial point source emission estimates were
combined and a ratio of 0.8 was calculated as the ratio of emissions of
PM2.5 to PM10. Hence, the annual increments
developed for PM2.5 would be equal to 0.8 multiplied by the
increment value for PM10. Although we believe that this
approach is based on a permissible interpretation of the statute, we
believe it results in increment values for PM2.5 that are
much higher than the values Congress envisioned when it established the
original increments for PM and SO2 based on percentages of
the then existing NAAQS. For example, an annual PM2.5
increment in Class II areas using this approach would be 13 [mu]g/m
\3\, which is 87 percent of the annual PM2.5 NAAQS of 15
[mu]g/m \3\. In contrast, Congress established the Class II Increments
for PM and SO2 to represent 25 percent of the NAAQS. To
avoid such an unreasonable outcome for PM2.5, we rejected
this approach and instead are proposing two variations (options 2A &
2B) of the equivalent increment approach as the second and third
option.
2. Proposed Annual Increments for PM2.5
a. Option 2A
In addition to an emissions ratio to reflect the shift in the
indicator from PM10 to PM2.5, we have also
considered the shift in the stringency of the NAAQS that resulted when
we changed the pollutant indicator from PM10 to
PM2.5. Accordingly, the ratio of emissions (0.8) that we
previously calculated would be multiplied by the ratio of the
PM2.5 NAAQS over the PM10 NAAQS (15/50 = 0.3
[mu]g/m \3\ for the annual standard) to derive an adjustment factor
(0.24 for the annual NAAQS) for calculating the Class I, II, and III
annual PM2.5 increments. Hence, multiplying the Class I, II,
and III annual PM10 increments, 4, 17, and 34 [mu]g/m \3\,
respectively, by the new adjustment factor yields the following
proposed increment values (rounded to the nearest whole number) under
option 2A:
------------------------------------------------------------------------
NAAQS Increments ([mu]g/m \3\)
Averaging period [mu]g/m --------------------------------
\3\) Class I Class II Class III
------------------------------------------------------------------------
Annual...................... 15 1 4 8
24-hr....................... 35 2 9 18
------------------------------------------------------------------------
Coincidentally, this new adjustment based on the PM2.5-
to-PM10 NAAQS ratio results in annual PM2.5
increment values identical to the values derived using option 1, the
percentage-of-NAAQS approach. As stated earlier, because the 24-hour
PM10 NAAQS have not been revoked, we do not consider section
166(f) to be the best fit for the development of the 24-hour PM2.5
increments. Thus, for new 24-hour PM2.5 increments, we are
proposing to rely on the authority of section 166(a) to derive 24-hour
increments as proposed under option 1.
b. Option 2B
This option represents another variation on the section 166(f)
equivalent increment approach. Under this option 2B, we are proposing
to develop annual PM2.5 increments based solely on the ratio
of the annual PM2.5 NAAQS to the primary annual
PM10 NAAQS (15/50 = 0.3 [mu]g/m \3\ for the annual NAAQS).
The values for the annual PM2.5 increments derived by
multiplying the Class I, II, and III annual PM10 increments,
4, 17, and 34 [mu]g/m \3\, respectively, by this adjustment ratio
yields the following proposed increment levels (rounded to the nearest
whole number) under option 2B:
------------------------------------------------------------------------
NAAQS Increments ([mu]g/m \3\)
Averaging period ([mu]g/m --------------------------------
\3\) Class I Class II Class III
------------------------------------------------------------------------
Annual...................... 15 1 5 10
[[Page 54138]]
24-hr....................... 35 2 9 18
------------------------------------------------------------------------
As with option 2A, for the 24-hour PM2.5 increments, we
are proposing to use increment values developed via the contingent safe
harbor approach as described in option 1.
3. Baseline Dates
Under these options (2A and 2B), since we will be replacing annual
PM10 increments with annual PM2.5 increments, we
propose to retain the existing TSP/PM10 baseline and trigger
dates and baseline areas for the PM2.5 program. Section
166(f) does not address how EPA should handle baseline dates for a
substituted increment. In 1993, we decided to retain the existing
baseline dates for TSP when we replaced the section 163 increment with
PM10 increments. We propose the same approach under this
option in this rulemaking because the continuation of the historic TSP/
PM10 baseline dates would ensure that no past case of
increment consumption is abandoned and serve as the closest measure of
a substitute. However, as discussed earlier, given PM2.5
emissions trends, our judgment is that establishing baseline dates for
PM2.5 after the effective date of this rule may be more
effective at preventing significant deterioration because the baseline
concentrations will reflect emissions reductions. We request comment on
whether this would provide sufficient justification for EPA to
establish new baseline dates under the section 166(f) substitution
approach.
However, in conjunction with the annual PM2.5 increments
discussed above, we are proposing to use option 1 increment levels for
24-hour PM2.5 increments which would use new baseline areas,
trigger and baseline dates. Thus, assuming the baseline date for the
PM10 increments has already been triggered, this results in
different baseline dates for the annual and 24-hour PM2.5
increments. This would also require a PSD applicant to develop two
separate emissions inventories of increment-consuming sources for
evaluating a new source's cumulative PM2.5 impacts in the
area of concern. We seek comment on this issue of multiple inventories
under the equivalent increments approach.
VI. Significant Impact Levels (SILs)
A. EPA's Guidance on SILs in the PSD Program
Significant Impact Levels or SILs are numeric values derived by EPA
that may be used to evaluate the impact a proposed major source or
modification may have on the NAAQS or PSD increment. The SILs currently
appear in EPA's regulations in 40 CFR 51.165(b), which are the
provisions that require States to operate a preconstruction review
permit program for major stationary sources that wish to locate in an
attainment or unclassifiable area but would cause or contribute to a
violation of the NAAQS. The SILs in that regulation are the level of
ambient impact that is considered to represent a ``significant
contribution'' to nonattainment.
Although 40 CFR 51.165 is the regulation that establishes the
minimum requirements for nonattainment NSR programs in SIPs, the
provisions of 40 CFR 51.165(b) are actually applicable to sources
located in attainment and unclassifiable areas. See 40 CFR
51.165(b)(4). Where a PSD source located in such areas may have an
impact on an adjacent non-attainment area, the PSD source must still
demonstrate that it will not cause or contribute to a violation of the
NAAQS in the adjacent area. This demonstration may be made by showing
that the emissions from the PSD source alone are below the significant
impact levels set forth in 40 CFR 51.165(b)(2). However, where
emissions from a proposed PSD source or modification would have an
ambient impact in a non-attainment area that would exceed the SILs, the
source is considered to cause or contribute to a violation of the NAAQS
and may not be issued a PSD permit without obtaining emissions
reductions to compensate for its impact. 40 CFR 51.165(b)(2)-(3).
The EPA has also applied SILs in other analogous circumstances
under the PSD program. Based on EPA interpretations and guidance, SILs
have also been widely used in the PSD program as a screening tool for
determining when a new major source or major modification that wishes
to locate in an attainment or unclassifiable area must conduct a more
extensive air quality analysis to demonstrate that it will not cause or
contribute to a violation of the NAAQS or PSD increment in the
attainment or unclassifiable area. SILs are also used to define the
extent of the Significant Impact Area (SIA) where a cumulative air
quality analysis accounting for emissions changes from all sources in
the SIA is performed.
The EPA's historical application of SILs to the analysis of major
source impacts on attainment and unclassifiable areas under the PSD
program has largely been based on interpretations reflected in EPA
guidance memorandum. The EPA has not previously incorporated the
concept of a SIL into our PSD regulations at 40 CFR 51.166 and 40 CFR
52.21. Nevertheless, EPA has long considered the ``significant
contribution'' test set forth in 40 CFR 51.165(b)(2) to apply to the
impact of PSD sources on attainment areas as well, since that provision
applies to major new sources and major modifications located in
attainment and unclassifiable areas. Thus, EPA has also supported the
use of SILs as screening mechanism when analyzing whether a source
located in a PSD area will cause or contribute to a violation of the
NAAQS or PSD increment in attainment or unclassifiable areas.
Although EPA's current PSD regulations do not contain SILs, EPA
initially developed SILs for TSP and other pollutants under the PSD
program in 1978. 43 FR 26380 (June 19, 1978). In the preamble to our
1978 regulations, EPA described SILs as a screening technique to
alleviate resource burdens (the costs and time involved in
sophisticated computer modeling of ambient air impacts) where there was
little or no threat to the PSD increments or NAAQS. 45 FR 26398.
However, as the threat to the increments increased, EPA intended for
more sophisticated techniques to be used. Id. Since EPA's analysis
indicated that the air quality impact of many sources fell off rapidly
to insignificant levels, the Agency did not intend to analyze the
impacts beyond the geographic point where the concentrations from the
source fell below certain levels derived from the class I increments.
Id. These levels were interpreted by EPA as representing the minimum
amount of ambient impact that is significant and hence came to be
[[Page 54139]]
known as the significant impact levels or SILs. Id.
When EPA substantially revised our PSD regulations in 1980 to
include significant emissions rates and significant monitoring
concentrations, EPA did not include the SILs in our PSD regulations. At
that time, EPA felt that there was no need for a separate table of SILs
because of the adoption of ``a de minimis exclusion for monitoring''
otherwise known as SMCs (described later). 45 FR 52707. In addition,
EPA saw little value in retaining SILs as an exemption from the air
quality analysis because the demonstration necessary to qualify for the
exemption was itself an air quality analysis. 45 FR 52707.
Subsequently, in draft guidance for permit writers, EPA advised
that SILs may be used to determine whether a source needs to conduct a
cumulative or ``full'' impact analysis to demonstrate that in
conjunction with all other increment consuming sources, it will not
cause or contribute to violation of the NAAQS or PSD increment in an
attainment or unclassifiable areas. New Source Review Workshop Manual,
at C.24-C.25 (Draft 1990); See also 40 CFR 51.166(k); 40 CFR 52.21(k).
Permitting authorities followed this guidance, and this approach
remains an accepted aspect of PSD program implementation. If based on a
preliminary impact analysis, a source can show that its emissions alone
will not increase ambient concentrations by more than the SILs, EPA
considers this to be a sufficient demonstration that a source will not
cause or contribute to a violation of the NAAQS or increment.
In light of the unique air quality considerations in Class I areas,
EPA has drawn a distinction between the use of SILs in Class II areas
and Class I areas. The EPA's draft 1990 guidance only identified SILs
to be used in Class II areas under the PSD program. Workshop Manual at
C.28. However, in 1991, EPA advised the State of Virginia that the
concept of a SIL might be applied to Class I areas if the levels were
determined in a reasonable manner. Memorandum from John Calcagni, Air
Quality Management Division, to Thomas J. Maslany, Air, Radiation, and
Toxics Divisions (Sept. 10, 1991). The EPA did not support the use of
SILs to determine whether a source should conduct an analysis of its
impact on air-quality related values (AQRVs). Since there are currently
no Class III areas for PSD in the United States, there has been no need
for EPA to apply SILs in these areas.
B. Legal Basis for SILs
The concept of a significant impact level is grounded on the de
minimis principles described by the court in Alabama Power Co. v.
Costle, 636 F.2d 323, 360 (D.C. Cir. 1980). In this case reviewing
EPA's 1978 PSD regulations, the court recognized that ``there is likely
a basis for an implication of de minimis authority to provide exemption
when the burdens of regulation yield a gain of trivial or no value.''
636 F.2d at 360. Based on this de minimis principle from the court's
opinion, EPA developed significant emissions rates and significant
monitoring concentrations in our 1980s regulations for PSD. The
significant emission rates reflect levels below which EPA considers an
emissions increase to be de minimis and thus not a major modification
that requires a PSD permit or NA-NSR permit. 45 FR 52676, 52705-07. See
also 40 CFR 51.166(b)(23); 40 CFR 52.21(b)(23). As discussed further
later, the significant monitoring concentrations in EPA regulations
define a de minimis level of impact that EPA has concluded does not
justify collecting pre-construction monitoring data for purposes of an
air quality impact analysis. 45 FR 52710.
Similarly, significant impact levels are intended to identify a
level of ambient impact on air quality concentrations that EPA regards
as de minimis. The EPA considers a source whose individual impact falls
below a SIL to have a de minimis impact on air quality concentrations.
Thus, a source that demonstrates its impact does not exceed a SIL at
the relevant location is not required to conduct more extensive air
quality analysis or modeling to demonstrate that its emissions, in
combination with the emissions of other sources in the vicinity, will
not cause or contribute to a violation of the NAAQS at that location.
In light of insignificance of the ambient impact from the source alone,
EPA considers the conduct of a cumulative air quality analysis and
modeling by such a source to yield information of trivial or no value
with respect to the impact of the proposed source or modification. The
EPA's Environment Appeals Board has recently reiterated and affirmed
EPA's interpretation of the Act to allow EPA to evaluate the
significance of a source's impact when determining whether it would
``cause or contribute'' to a NAAQS or increment violation under section
165(a)(3) of the Act. In Re: Prairie State Generating Company, PSD
Appeal No. 05-05, slip op. at 139-144 (Aug. 24, 2006).
Thus, in developing SILs for this proposal, EPA sought to derive
SILs for PM2.5 utilizing methods that would identify levels
representing a de minimis or insignificant impact on ambient air
quality. In choosing among the options set forth later, EPA proposes to
select an option that reflects the degree of ambient impact on
PM2.5 concentrations that can be considered truly de minimis
and would justify no further analysis or modeling of the air quality
impact of a source in combination with other sources in the area
because the source would not cause or contribute to an exceedance of
the PM2.5 NAAQS or the PM2.5 increments
established elsewhere in this proposal.
C. Relationship of SILs to AQRVs
We wish to emphasize that consistent with the original purpose of
the Class I SILs, the Class I SILs for PM2.5 we are
proposing are not intended to serve as thresholds for determining the
need for an AQRV analysis or whether an adverse impact on an AQRV will
occur. An adverse impact on an AQRV depends upon the sensitivity of the
particular AQRV. An ambient concentration that is considered
insignificant for purposes of increment consumption should not
automatically be considered inconsequential relative to the inherently
fact-specific demonstration upon which an adverse impact on an AQRV is
to be based. Accordingly, the fact that a source's predicted impact is
less than the SIL in a Class I area would neither relieve the source
from having to complete an analysis of impacts on AQRVs nor
automatically allow the reviewing authority to reject the FLM's
demonstration of adverse impact on an AQRV. See 61 FR at 38292.
D. Proposed Options for PM2.5 SILs (for PSD and NA-NSR)
We are seeking comment on the relative merits of each of the
following options for setting PM2.5 SILs.
1. Option 1. Propose SILs Using the Approach We Proposed for
PM10 in 1996
The first option that we are proposing utilizes the same approach
we proposed for PM10 in the 1996 NSR Reform proposal. For
Class I areas we would set the SIL to 4 percent of the Class I
PM2.5 increment. For Class II and Class III areas, we would
codify the SIL values of 1.0 [mu]g/m \3\ for the annual averaging
period and 5.0 [mu]g/m \3\ for the 24-hour averaging period, that
already exist for PM10 in 40 CFR 51.165(b)(2). If we adopt
this option, we would set the Class I SILs based on the Class I
increments
[[Page 54140]]
that we elect to adopt under the increment options. Based on the Class
I increment values proposed in the percent of NAAQS increment option 1,
the SILs under this option would be as follows:
------------------------------------------------------------------------
Class I SILs ([mu]g/m \3\)
increment --------------------------------
Averaging period ([mu]g/m
\3\) Class I Class II Class III
------------------------------------------------------------------------
Annual...................... 1 0.04 1.0 1.0
24-hour..................... 2 0.08 5.0 5.0
------------------------------------------------------------------------
As stated earlier, we had proposed this approach for setting
PM10 SILs in our 1996 NSR Reform proposal. Many commenters
supported this approach and believed that the proposed SIL values would
serve as appropriate de minimis values. In fact, EPA is aware that many
States have been using these proposed SILs for PM10 as
screening tools since 1996.
Regarding the proposal to set the level of Class I SILs at 4
percent of the Class I increments, we believe that where a proposed
source contributes less than 4 percent to the Class I increment,
concentrations are sufficiently low so as not to warrant a detailed
analysis of the combined effects of the proposed source and all other
increment-consuming emissions. We previously used a similar rationale
to establish the significant emissions rates for PSD applicability
purposes, concluding in part that emissions rates that resulted in
ambient impacts less than 4 percent of the 24-hour standards for PM and
SO2 were sufficiently small so as to be considered de
minimis.
The original SIL values of 1.0 and 5.0 [mu]g/m \3\ for TSP and PM10
were interpreted by EPA as representing the minimum amount of ambient
impact that is significant. This forms the basis of the proposed
PM2.5 SIL values of 1.0 and 5.0 [mu]g/m \3\ for the annual
and 24-hour standard for Class II and III areas.
2. Option 2. PM2.5 to PM10 Emissions Ratio
In our second proposed option for SILs, we would multiply the
PM10 SILs (proposed in 1996) by the emissions ratio of
PM2.5 to PM10 for point sources in the 2001
extrapolation of the final 1999 NEI. This is very similar to option 2A
for developing increments, and would use the same PM2.5/
PM10 emissions ratio (0.8). The Class I PM10 SILs
that we proposed in 1996 were 0.2 [mu]g/m3 (annual) and 0.3
[mu]g/m \3\ (24-hour). For Class II and III PM10 SILs, we
proposed 1.0 [mu]g/m \3\ (annual) and 5.0 [mu]g/m \3\ (24-hour) levels.
The SIL values determined in this option are as follows:
------------------------------------------------------------------------
SILs ([mu]g/m\3\)
Averaging period --------------------------------
Class I Class II Class III
------------------------------------------------------------------------
Annual................................. 0.16 0.8 0.8
24-hour................................ 0.24 4.0 4.0
------------------------------------------------------------------------
The SILs derived under this option are slightly more stringent for
Class II & III areas than those in option 1. Since PM2.5
emissions are a subset of PM10 emissions, we believe that an
emissions ratio of the PM10 SILs would serve as an
appropriate de minimis SIL value and represent insignificant impact on
ambient air quality.
3. Option 3. PM2.5 to PM10 NAAQS Ratio
Under the third option that we are proposing, we would multiply the
PM10 SILs by the ratio of the PM2.5 NAAQS to the
PM10 NAAQS. This is very similar to option 2B for developing
PM2.5 increments, and would use the same factors. We would
start with the same values for the PM10 SILs that we used
for option 2 above for SILs. The PM2.5 SILs determined using
this approach are as follows:
------------------------------------------------------------------------
SILs ([mu]g/m\3\)
Averaging period --------------------------------
Class I Class II Class III
------------------------------------------------------------------------
Annual................................. 0.06 0.3 0.3
24-hour................................ 0.07 1.2 1.2
------------------------------------------------------------------------
The SILs derived under this option are very stringent for Class II
and III areas compared to options 1 and 2. Nevertheless, we believe
that the NAAQS ratio approach is an appropriate alternative to
determine SILs, since it reflects the stringency in the NAAQS for
PM2.5 relative to that of PM10. We believe that
these SIL values would serve as appropriate de minimis values.
VII. Significant Monitoring Concentrations (SMCS)
A. Background on SMCs
1. Preconstruction Monitoring and Its Role in NSR Program
Under the Act and EPA regulations, an applicant for a PSD permit is
required to gather preconstruction monitoring data in certain
circumstances. Section 165(a)(7) calls for ``such monitoring as may be
necessary to determine the effect which emissions from any such
facility may have, or is having, on air quality in any areas which may
be affected by emissions from such source.'' 42 U.S.C. 7475(a)(7). In
addition, section 165(e) requires an analysis of the air quality in
areas affected by a proposed major facility or major modification and
calls for gathering 1 year of monitoring data unless the reviewing
authority determines that a complete and adequate analysis may be
accomplished in a shorter period. 42 U.S.C. 7575(e)(3). These
requirements are codified in
[[Page 54141]]
EPA's PSD regulations at 40 CFR 51.166(m) and 40 CFR 52.21(m).
In accordance with EPA's Guideline for Air Quality Modeling (40 CFR
part 51, Appendix W), the preconstruction monitoring data is primarily
used to determine background concentrations in modeling conducted to
demonstrate that the proposed source or modification will not cause or
contribute to a violation of the NAAQS. 40 CFR part 51, Appendix W,
section 9.2. For most areas where multiple sources of air pollution are
present, EPA's Guideline recommends using monitoring data to identify
the portion of background concentrations attributable to natural
background, minor sources, and distant major sources. 40 CFR part 51,
Appendix W, section 9.2.3.f. For nearby major sources, EPA recommends
explicitly modeling the emissions of such sources rather than relying
on monitored data as part of the NAAQS compliance demonstrations. As
described earlier, the compliance demonstration with respect to the PSD
increment compliance focuses on modeling the change in emissions from
sources in the Significant Impact Area.
2. History of SMC Rules Adopted by EPA
In 1980, EPA adopted regulations that exempt sources from
preconstruction monitoring requirements for a pollutant if the source
can demonstrate that its ambient air impact is less than a value known
as the Significant Monitoring Concentration or SMC. The pollutant-
specific SMCs are codified at 40 CFR 51.166(i)(5)(i) and 40 CFR
52.21(i)(5)(i). The EPA developed SMCs as a screening tool for sources
to determine whether they should conduct site-specific preconstruction
ambient monitoring. At the time they were adopted, EPA described the
SMCs as ``air quality concentration de minimis level[s] for each
pollutant * * * for the purpose of providing a possible exemption from
monitoring requirements.'' 45 FR 52676, 52707 (Aug. 7, 1980). The EPA
explained that it believed there was ``little to be gained from
preconstruction monitoring'' where a source could show that its
projected impact on the affected area was below these de minimis
levels. 45 FR 52710.
In 1980, EPA determined the SMCs based on the current capability of
providing a meaningful measure of the pollutants. The EPA promulgated
values that represented five times the lowest detectable concentration
in ambient air that could be measured by the instruments available for
monitoring the pollutants. 45 FR 52710. The EPA chose the factor of
five after reviewing test data for various methods and considering
instrument sensitivity, potential for sampling error, instrument
variability, and the capability to read recorded data. Id.
For PM, EPA set the SMCs for TSP at five times the lowest
detectable ambient concentration for TSP (2.0 [mu]g/m \3\) using the
Reference Method 5 for ambient sampling at that time. Memorandum from
Rehme, K. A., EPA/EMSL/QAD/MSB, to Peters, W., EPA/OAQPS/CPDD, on PSD
Monitoring (May 20, 1980). We set a SMC only for the 24-hour averaging
period, at a level of 10 [mu]g/m \3\. We retained the same numerical
level when we replaced the TSP NAAQS and increments with the
PM10 NAAQS and increments.
B. Legal Basis for SMCs
As with the SMCs adopted by EPA in 1980, the SMCs for
PM2.5 proposed in this action are supported by the de
minimis doctrine set forth in the Alabama Power v. Costle opinion. Like
the other pollutants for which EPA has promulgated SMCs, EPA believes
there is little to be gained from preconstruction monitoring of
PM2.5 concentrations when the increased emissions of
PM2.5 from a proposed source or modification has a de
minimis impact on ambient concentrations of PM2.5. If a
source can show through modeling of its emissions alone that its
impacts are less than the corresponding SMC, there is little to be
gained by requiring that source to collect additional monitoring data
on PM2.5 emissions to establish background concentrations
for further analysis.
Therefore, in developing SMCs for this proposal, EPA sought to use
methods that would identify levels representing a de minimis or
insignificant impact on PM2.5 ambient air quality that makes
the collection of additional monitoring data extraneous. In choosing
among the options set forth later, EPA proposes to select an option
that reflects the degree of ambient impact on PM2.5
concentrations that can be considered truly de minimis and would not
justify the gathering of monitoring data to establish background
concentrations for a demonstration of compliance with the NAAQS.
C. Proposed Options for PM2.5 SMC
1. Option 1. Lowest Detectable Concentration
For this approach, we would use the same methodology originally
used in 1980 to set the SMC for TSP, i.e., determining the lowest
detectable concentration and multiplying this value by five. The lowest
detectable 24-hour average concentration for PM2.5 is 2.0
[mu]g/m \3\ (40 CFR 50 App L, section 3). Thus, applying this
methodology for PM2.5 yields an SMC of 10 [mu]g/m \3\ for
the 24-hour averaging period.
As we indicated in 1980 when we originally used this methodology to
set the SMCs for TSP and the other PSD pollutants, the use of five
times the lowest detectable concentration was chosen to realistically
reflect pollutant levels at which low level concentrations or small
incremental changes in pollutant concentrations can reasonably be
determined. The factor of five takes into account the measurement
errors associated with the monitoring of these low pollutant levels or
small incremental changes in concentration. These measurement errors
arise from various sources, such as sample collection, analytical
measurement, calibration, and interferences (See Memorandum from Rehme,
K. A. mentioned earlier). We believe this is a reasonable approach,
since it has also been used for PM2.5 and TSP. We seek
comment on this approach.
2. Option 2. PM2.5 to PM2.5 Emissions Ratio
Proposed option 2 establishes the SMC for PM2.5 by
multiplying the existing PM10 SMC (10 [mu]g/m \3\) by the
ratio of PM2.5 emissions to PM10 emissions in the
2001 extrapolation of the final 1999 NEI. This is the same methodology
used in Increments option 2A and SIL option 2, and uses the same
emissions ratio (0.8). This yields a SMC value of 8.0 [mu]g/m \3\ for
PM2.5 for the 24-hour averaging period.
This approach gives a PM2.5 SMC value that is
equivalent, in terms of emissions, to the existing PM10 SMC.
We believe that this approach is consistent with the approach that
Congress set out for increments in section 166(f) of the Act and is, as
such, a reasonable approach for developing PM2.5 SMCs. We
seek comment on this approach.
3. Option 3. PM2.5 to PM10 NAAQS Ratio
Under the third option, we propose to multiply the PM10
SMC by the ratio of the PM2.5 NAAQS to the PM10
NAAQS. This is the same approach proposed for Increment option 2B and
SIL option 3. Because the PM10 SMC is for the 24-hour
averaging period, we would use the ratio of the 24-hour NAAQS for
PM2.5 (35 [mu]g/m \3\) and PM10 (150 [mu]g/m
\3\). The resulting factor is 0.233. Thus, the PM2.5 SMC
developed using this option would be 2.3 [mu]g/m \3\, for the 24-hour
averaging period.
[[Page 54142]]
The SMC developed using this approach is very stringent compared to
options 1 and 2, since it reflects the stringency of the 24-hour NAAQS
of PM2.5 relative to PM10. Nevertheless, we
believe this to be also a reasonable approach and seek comments on it.
D. Correction of Cross References
In addition to exempting sources that have emissions increases
below the SMCs, EPA also exempts sources from preconstruction
monitoring where the source demonstrates that existing ambient
concentrations of a pollutant in the affected area are currently below
the SMCs. 40 CFR 51.166(i)(5)(ii); 52.21(i)(5)(ii). This aspect of the
monitoring exemption was also adopted in the 1980 rulemaking. 45 FR
52710.
The EPA also proposes in this rulemaking to correct a cross
reference contained in these parts of the regulations. Paragraphs (ii)
and (iii) in 40 CFR 51.166(i)(5) and paragraph (ii) in 40 CFR
52.21(i)(5) each refer to concentrations listed in paragraphs
(i)(8)(i). However, there is no paragraph (i)(8)(i) in Sec. 51.166 and
no concentration values are contained in section (i)(8)(i) of Sec.
52.21. The cross references in these provisions were intended to
reference the SMCs in paragraph (i)(5)(i), but EPA failed to make this
change when the paragraphs were renumbered in a prior rulemaking. We
propose to correct that oversight in this rule.
VIII. Effective Date of the Final Rule, SIP Submittal/Approval
Deadlines and PM10 Revocation Deadline
This section sets forth EPA's proposed effective dates for the
PM2.5 increments (under different options), SILs and SMC. In
addition, we are setting forth the proposed deadlines for States to
submit revisions to their SIPs incorporating these changes to the PSD
regulations, and for EPA to approve or disapprove the revised plans.
Finally, this section describes EPA's proposed schedule for revoking
the PM10 annual increments in conjunction with the
commencement of the PM2.5 increment system under the part 51
and part 52 PSD regulations and we request comment on establishing a
transition period for processing complete permit applications. Please
see Table 1 in the docket (Docket ID No. EPA-HQ-OAR-2006-0605) for a
summary of the proposed options and alternatives on which we seek
comment.
A. Option 1: Increments Promulgated Pursuant to Section 166(a) of the
Act
1. Effective Date of Final Rule
As described in section III.E.2.a of this preamble, section 166(b)
of the Act specifies that new regulations for increments promulgated
pursuant to section 166(a) of the Act become effective 1 year after the
date of promulgation. Accordingly, if we promulgate the new PM2.5
increment under the authority of Section 166(a) following Option 1, we
propose a year's delay in the effective date.
Alternatively, EPA seeks comments on whether we could make the new
increment regulations effective 60 days from promulgation. Considering
the various timeframes outlined in section 166, it is clear that
Congress envisioned that increments or other measures would become
effective within 3 years of the promulgation of a NAAQS. In the current
circumstance, due to prolonged litigation and other implementation
concerns, there has been an extended delay of over 10 years since we
established the PM2.5 NAAQS. Given this extended delay, we
believe that the overall Congressional intent reflected in section 166
may best be met by advancing the effective date of the proposed
regulations.
States have to submit SIPs by April 5, 2008 to address the NSR
provisions of the final PM2.5 implementation rule after the
Federal NSR implementation rule is promulgated later this year. If EPA
decides to promulgate option 1 for increments and section 166(b)
timelines, the increments rule would not be implemented in SIP-approved
States until approximately January 2010 (assuming promulgation of this
rule in Spring 2008 and allowing 21 months for SIP submittal). Thus
from April 2008 to January 2010, PSD sources would be subject to a
PM2.5 applicability program, but would need to continue the
current PM10 air quality impacts analysis. Under these
circumstances, we expect that States, affected industry, and
environmental groups will see value in advancing the effective date of
the promulgated increments.
Legislative history indicates that, when section 166(b) was first
enacted in 1977, Congress established the delayed effective date in
order to allow time for ``contrary Congressional action.'' H.R. Conf.
Rep. 95-564, at 151 (1977). The Congressional Review Act (CRA) provides
Congress with an expedited means of reviewing and potentially
disapproving final actions issued by Federal agencies. Under the CRA, a
member of Congress can introduce a joint resolution to disapprove a
particular rule and have that resolution considered using expedited
procedures if the resolution is introduced within the designated time
period (generally 60 days depending on the Congressional calendar).
Furthermore, an agency rule meeting the CRA definition of ``major''
cannot take effect for 60 days. We request comment on whether, given
these procedures under the CRA, a 60-day delay in the effective date of
the proposed rule could satisfy the Congressional intent reflected in
section 166(b).
2. State Program
In this action, we propose to establish final PM2.5
increments as minimal program element for all State Programs.
Accordingly, States must submit revised SIPs for EPA's approval that
incorporate the final PM2.5 increments, or demonstrate that
an alternative approach is at least equivalent to this minimum program
element. Irrespective of whether we establish an effective date of the
final rule that falls 1 year after or 60 days after we promulgate the
final rule, we propose to require States to submit revised
implementation plans to EPA for approval within 21 months of
promulgation (9 months after the effective date of such regulations) in
accordance with the time frames specified in section 166(b) of the Act.
Section 166(b) also specifies that we must approve or disapprove these
revisions within 25 months of promulgation (4 months from the statutory
deadline for SIP submittal). We regard these statutory deadlines as
maximum allowed timeframes for action and do not believe that the Act
restricts our ability to approve SIP revisions requested by a State at
any time before these deadlines. We also propose to change the
regulatory provisions at 40 CFR 166(a)(6) to specifically articulate
these deadlines for these State SIP submittals.
3. Federal Program
The EPA must also decide how to apply the procedures set forth in
section 166(b) of the Act to the new PM2.5 increments under
our 40 CFR part 52 PSD regulations, which apply for States without
approved PSD programs as well as for Indian lands. We propose to begin
to implement the Part 52 PSD program upon the effective date of the
final rule. Accordingly, if we delay the effective date for 1 year
after the date of promulgation in accordance with Section 166(b), then
the Part 52 PSD program would become effective and implemented in the
applicable areas, on this date. Alternatively, if we establish an
effective date 60 days after we promulgate the final rules, the Part 52
PSD program would become effective on this same date.
Alternatively, we request comment on whether we should delay
implementation of the Federal Part 52
[[Page 54143]]
PSD program until 25 months after promulgation, or the outside date by
which EPA is required to approve State SIP revisions. This is the same
approach we took in 1988 to implement the then new NO2
increments. 53 FR at 40658. We are not offering this as our proposed
approach because of the significant delay that has already occurred
between the time we promulgated the PM2.5 NAAQS and the time
we will finalize this rule. However, we recognize that it may not be
equitable to begin implementation of the new program requirements in
those few areas where the Federal program applies before the majority
of States are required to implement the program. Nonetheless, we seek
comment on applying this alternative approach for the Federal Part 52
PSD program and specifically on the consequences of potential
inequities.
B. Option 2: Increments Promulgated Pursuant to Section 166(f) of the
Act
1. Effective Date of Final Rule
In contrast to the proposed delay of the effective date of the new
PM2.5 increments under option 1, we propose to make the new
PM2.5 increments proposed under option 2 effective 60 days
from the date of promulgation, consistent with the CRA timeframe. We do
not interpret section 166(b) of the Act to apply to increments
promulgated under the authority of section 166(f) because the first
sentence in section 166(b) describes only ``[r]egulations referred to
in subsection (a).''
2. State Program
We previously stated that we believe that it is appropriate to
establish a deadline for States to submit required SIP revisions
analogous to the deadline that applies to States when we promulgate or
revise a NAAQS. 67 FR 80241. We previously codified, conforming
regulatory text at 40 CFR 166(a)(6). Under Option 2 of this proposal,
we propose to follow the existing regulatory provisions that require a
State to adopt and submit for EPA approval its PM2.5 plan
revisions no later than 3 years after the date on which we promulgate
(i.e., publish in the Federal Register) the new regulations in the 40
CFR part 51 PSD regulations. Alternatively, we request comment on
whether we should require a timeframe shorter than 36 months, such as
the statutory maximum of 21 months required under Option 1. Given the
limited nature of the required changes, we believe that States
generally may not need more than 21 months to adopt and submit revised
plans to EPA for approval. If we select this alternative approach, we
propose to make conforming regulatory changes to 40 CFR 166(a)(6).
3. Federal Program
For the Federal part 52 PSD regulations, we propose under Option 2
to make the new PM2.5 increments effective 60 days from the
date we promulgate the final rules. However, unlike the proposed 3-year
period being proposed for States to submit their plan revisions to EPA
for review and approval, we propose to implement the new increments
under the part 52 PSD regulations upon the effective date of the final
rules. Since it would be difficult to know when States are planning to
revise their own PSD programs consistent with the new increment
regulations, it is not possible to ensure a consistent implementation
date between approved State programs and programs being implemented
under the part 52 PSD regulations unless we delayed implementation for
a full 4 years (3 years for SIP submission and 1 year for EPA to
approve the revision). We believe that this delay is excessive and does
not accomplish the goal of expedient implementation of a PM2.5
PSD program. We request comment on this approach.
C. Revocation of the PM10 Increment
While we believe it is appropriate to revoke the annual PM10
increment as explained earlier in this preamble, we propose to retain
the PM10 increments in both 40 CFR part 51 and part 52 PSD
regulations until the new PM2.5 increments are being
implemented either by a State through an approved SIP, or by EPA
through the Federal Part 52 PSD program. Accordingly, we propose to
approve the removal of the annual PM10 increments from any
SIP on or after the date we approve the new PM2.5 increments
in the same plan. We believe that States should request the removal of
the annual PM10 increments from their PSD programs at the
same time they submit plan revisions containing the new PM2.5
increments, allowing EPA to act on both actions simultaneously.
Similarly, we propose to retain the annual PM10
increments in the Part 52 PSD regulations until the effective date of
the new PM2.5 increments.
D. Transition Period
We believe that it is appropriate to establish a transition period
to clarify when PSD permit applications must contain an increment
analysis for the new PM2.5 increments following the date
they become effective and are approved as part of any State or Federal
PSD program. In the past, we have allowed for permit applications
submitted before the implementation date of new increment regulations
to continue to be processed under the existing rules, so long as the
reviewing authority has determined that the application is complete
before the implementation date. See e.g., existing 40 CFR
51.166(a)(i)(8) and (9). Consequently, we are also proposing a new
provision in both the 40 CFR parts 51 and 52 PSD regulations to provide
a transition process for initiating the requirement for analysis of the
new PM2.5 increments. Under the Part 51 regulations, we are
proposing that during the transition period, States have discretion to
continue the existing PM10 increment program or begin
implementing the new PM2.5 increment program. For the
federally administered programs under the Part 52 PSD regulations, the
provision would apply to each new PSD permit applicant upon the
effective date of the rule. However, we are also proposing a similar
transition period in these programs. See proposed 40 CFR 51.166(i)(10)
and 40 CFR 52.21(i)(11), respectively.
E. Effective Date for SILs and SMCs
Unlike the approach we propose for PM2.5 increments, we
are not proposing to make SILs and SMCs a minimum element of an
approved SIP. Accordingly, we are not proposing to establish specific
deadlines for submission of revisions to incorporate the final rules
into SIPs. We do not believe that SILs or SMCs are required elements of
an approvable State program because in the absence of these
requirements, States can satisfy the statutory requirements by
obtaining pre-construction monitoring data and conducting a cumulative
air quality analysis for every PSD permit application.
Nonetheless, we believe that availability of SILs and SMCs greatly
improve program implementation by streamlining the permit process and
reducing the labor hours necessary to submit and review a complete
permit application where the projected impact of the proposed source is
de minimis in the relevant area. For these reasons, we request comment
on whether we have authority to establish these as minimum program
elements based on the improved efficiency of the permit process. If we
require States to incorporate SILs and SMCs as mandatory elements of an
approvable program, then we would apply the existing regulations at 40
CFR 166(a)(6) for establishing the SIP submittal deadline. Under either
approach, the
[[Page 54144]]
final rules would become effective 60 days after we promulgate the
final rules.
IX. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review
Under Executive Order 12866 (58 FR 51735, October 4, 1993), this
action is a significant regulatory action because it raises novel legal
or policy issues arising out of legal mandates, the President's
priorities, or the principle set forth in the EO. Accordingly, EPA
submitted this action to the Office of Management and Budget (OMB) for
review under EO 12866 and any changes made in response to OMB
recommendations have been documented in the docket for this action.
B. Paperwork Reduction Act
The information collection requirements in this rule have been
submitted for approval to the OMB under the Paperwork Reduction Act, 44
U.S.C. 3501 et seq. The information collection requirements are not
enforceable until OMB approves them. The Information Collection Request
(ICR) document prepared by EPA has been assigned EPA ICR number
2276.01.
Certain records and reports are necessary for the State or local
agency (or the EPA Administrator in non-delegated States), for example,
to: (1) Confirm the compliance of status of stationary sources,
identify any stationary sources not subject to the standards, and
identify stationary sources subject to the rules; and (2) ensure that
the stationary source control requirements are being achieved. The
information would be used by EPA or State enforcement personnel to (1)
Identify stationary sources subject to the rules, (2) ensure that
appropriate control technology is being properly applied, and (3)
ensure that the emission control devices are being properly operated
and maintained on a continuous basis.
The proposed rule would increase the PSD permitting burden for
owners and operators of major stationary sources of PM2.5
emissions by adding PM2.5 to the list of regulated NSR
pollutants for which air quality impact analyses must be carried out to
track increment consumption and demonstrate compliance with the NAAQS.
At the same time, there would be a reduction in burden directly
associated with the revocation of the annual increment for
PM10, as proposed in this proposed rule. Over the 3-year
period covered by the ICR, we estimate an average annual burden
totaling about 14,000 hours and $920,000 for all industry entities that
would be affected by the proposed rule. For the same reasons, we also
expect the proposed rule (when fully implemented) to increase burden
for the State and local authorities reviewing PSD permit applications.
In addition, there would be additional burden for State and local
agencies to revise their SIPs to incorporate the proposed changes. Over
the 3-year period covered by the ICR, we estimate that the average
annual burden for all State and local reviewing authorities will total
about 4,150 hours and $180,000.
Burden means the total time, effort, or financial resources
expended by persons to generate, maintain, retain, or disclose or
provide information to or for a Federal agency. This includes the time
needed to review instructions; develop, acquire, install, and utilize
technology and systems for the purposes of collecting, validating, and
verifying information, processing and maintaining information, and
disclosing and providing information; adjust the existing ways to
comply with any previously applicable instructions and requirements;
train personnel to be able to respond to a collection of information;
search data sources; complete and review the collection of information;
and transmit or otherwise disclose the information.
Any 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 EPA's
regulations in 40 CFR are listed in 40 CFR part 9.
To comment on the Agency's need for this information, the accuracy
of the provided burden estimates, and any suggested methods for
minimizing respondent burden, including the use of automated collection
techniques, EPA has established a public docket for this ICR under
Docket ID number EPA-HQ-OAR-2007-0628. Submit any comments related to
the ICR for this proposed rule to EPA and OMB. See `Addresses' section
at the beginning of this notice for where to submit comments to EPA.
Send comments to OMB at the Office of Information and Regulatory
Affairs, Office of Management and Budget, 725 17th Street, NW.,
Washington, DC 20503, Attention: Desk Office for EPA. Since OMB is
required to make a decision concerning the ICR between 30 and 60 days
after September 21, 2007, a comment to OMB is best assured of having
its full effect if OMB receives it by October 22, 2007. The final rule
will respond to any OMB or public comments on the information
collection requirements contained in this proposal.
C. Regulatory Flexibility Act
The Regulatory Flexibility Act (RFA) generally requires an agency
to prepare a regulatory flexibility analysis of any rule subject to
notice and comment rulemaking requirements under the Administrative
Procedure Act or any other statute unless the agency certifies that 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 proposed rule on
small entities, ``small entity'' is defined as: (1) A small business as
defined by the Small Business Administration's regulations at 13 CFR
121.201; (2) a small governmental jurisdiction that is a government or
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 rule will not have a significant
economic impact on a substantial number of small entities. This
proposed rule will not impose any requirements on small entities. We
continue to be interested in the potential impacts of the proposed rule
on small entities and welcome comments on issues related to such
impacts.
D. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of the UMRA, we
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures to State, local, and tribal governments, in
aggregate, or to the private sector, of $100 million or more in any 1
year. Before promulgating an EPA rule for which a written statement is
needed, section 205 of the UMRA generally requires us to identify and
consider a reasonable number of regulatory alternatives and adopt the
least costly, most cost-effective, or least burdensome alternative that
achieves the objectives of the rule. The provisions of section 205 do
not apply when they are inconsistent with applicable law. Moreover,
section 205
[[Page 54145]]
allows us to adopt an alternative other than the least-costly, most
cost-effective, or least-burdensome alternative if the Administrator
publishes with the final rule an explanation why that alternative was
not adopted. Before we establish any regulatory requirements that may
significantly or uniquely affect small governments, including tribal
governments, we must have developed under section 203 of the UMRA a
small government agency plan. The plan must provide for notifying
potentially affected small governments, enabling officials of affected
small governments to have meaningful and timely input in the
development of our regulatory proposals with significant Federal
intergovernmental mandates, and informing, educating, and advising
small governments on compliance with the regulatory requirements.
We have determined that this proposed rule does not contain a
Federal mandate that may result in expenditures of $100 million or more
for State, local, and tribal governments, in the aggregate, or the
private sector in any one year. The proposed rule adds only a
relatively small number of new requirements to the existing permit
requirements already in place under the PSD program, since States are
currently implementing a PM10 surrogate program pursuant to
EPA guidance. Thus, this proposed rulemaking is not subject to the
requirements of sections 202 and 205 of the UMRA. We have also
determined that this rule contains no regulatory requirements that
might significantly or uniquely affect small governments because this
rule applies only to new major stationary sources. Thus, this proposed
rulemaking is not subject to the requirements of section 203 of the
URMA.
E. Executive Order 13132: Federalism
Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August
10, 1999), requires us to develop an accountable process to ensure
``meaningful and timely input by State and local officials in the
development of regulatory policies that have federalism implications.''
``Policies that have federalism implications'' is defined in the
Executive Order to include regulations that 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.''
This proposed rule does not have federalism implications. It would
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. Pursuant to the terms of
Executive Order 13132, it has been determined that this proposed rule
does not have ``federalism implications'' because it does not meet the
necessary criteria. Thus, the requirements of section 6 of the
Executive Order do not apply to this proposed rule.
In the spirit of Executive Order 13132, and consistent with our
policy to promote communications between us and State and local
governments, we specifically solicit comment on this proposed rule from
State and local officials.
F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments
Executive Order 13175, entitled ``Consultation and Coordination
with Indian Tribal Government'' (65 FR 67249, November 6, 2000),
requires us to develop an accountable process to ensure ``meaningful
and timely input by tribal officials in the development of regulatory
policies that have tribal implications.''
This proposed rule does not have tribal implications as defined in
Executive Order 13175. This rule provides the elements to implement a
PM2.5 PSD program in attainment areas. The CAA provides for
States to develop plans to regulate emissions of air pollutants within
their jurisdictions. The Tribal Air Rule (TAR) under the CAA gives
tribes the opportunity to develop and implement CAA programs such as
programs to attain and maintain the PM2.5 NAAQS, but it
leaves to the discretion of the Tribe the decision of whether to
develop these programs and which programs, or appropriate elements of a
program, they will adopt.
Although Executive Order 13175 does not apply to this rule, EPA did
reach out to national tribal organizations in 2006 to provide a forum
for tribal professionals to provide input to the rulemaking. However,
not much participation or input was received. It will neither impose
substantial direct compliance costs on tribal governments, nor preempt
tribal law. The EPA specifically solicits additional comment on this
proposed rule from tribal officials.
G. Executive Order 13045: Protection of Children From Environmental
Health & Safety Risks
Executive Order 13045 ``Protection of Children from Environmental
Health Risks and Safety Risks'' (62 FR 19885, April 23, 1997) applies
to any rule that: (1) Is determined to be ``economically significant''
as defined under Executive Order 12866, and (2) concerns an
environmental health or safety risk that we have reason to believe may
have a disproportionate effect on children. If the regulatory action
meets both criteria, the Agency must evaluate the environmental health
or safety effects of the planned rule on children, and explain why the
planned regulation is preferable to other potentially effective and
reasonably feasible alternatives considered by the Agency.
This proposed rule is not subject to the EO because it is not
economically significant as defined in EO 12866, and because the Agency
does not have a reason to believe the environmental health or safety
risks addressed by this action present a disproportionate risk to
children because one of the basic requirements of the PSD program is
that new and modified major stationary sources must demonstrate that
any new emissions do not cause or contribute to air quality in
violation of the national ambient air quality standards. The public is
invited to submit or identify peer-reviewed studies and data, of which
EPA may not be aware, that assessed resolutions of early life exposure
to ambient concentrations of fine particulate measured as
PM2.5.
H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use
This rule is not a ``significant energy action'' as defined in
Executive Order 13211, ``Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use'' (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. Further, we have
concluded that this rule is not likely to have any adverse energy
effects.
I. National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (NTTAA), Public Law No. 104-113, 12(d) (15 U.S.C. 272 note)
directs us to use voluntary consensus standards (VCS) in our regulatory
and procurement activities unless to do so would be inconsistent with
applicable law or otherwise impractical. The VCS are technical
standards (e.g., materials specifications, test methods, sampling
procedures, and business practices) developed or adopted by one or more
voluntary consensus bodies. The NTTAA directs us to provide Congress,
through annual reports to OMB, with explanations when we do not use
[[Page 54146]]
available and applicable VCS. This proposed rule does not involve
technical standards. Therefore, we are not considering the use of any
VCS.
J. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations
Executive Order 12898 (59 FR 7629 (February 16, 1994)) establishes
Federal executive policy on environmental justice. Its main provision
directs Federal agencies, to the greatest extent practicable and
permitted by law, to make environmental justice part of their mission
by identifying and addressing, as appropriate, disproportionately high
and adverse human health or environmental effects of their programs,
policies, and activities on minority populations and low-income
populations in the United States.
The EPA has determined that this proposed rule will not have
disproportionately high and adverse human health environmental effects
on minority or low-income populations because it does not affect the
level of protection provided to human health or the environment. This
regulation would provide regulatory certainty for implementing the
preconstruction NSR permitting program for PM2.5. However,
the requirements would be similar to the existing requirements of the
PM10 program and hence does not impact the human health
environmental effects.
X. Statutory Authority
The statutory authority for this proposed action is provided by
sections 101, 160, 163, 165, 166, 301, and 307(d) of the Act as amended
(42 U.S.C. 7401, 7470, 7473, 7475, 7476, 7601, and 7607(d)).
List of Subjects
40 CFR Part 51
Administrative practices and procedures, Air pollution control,
Environmental protection, Intergovernmental relations.
40 CFR Part 52
Administrative practices and procedures, Air pollution control,
Environmental protection, Intergovernmental relations.
Dated: September 12, 2007.
Stephen L. Johnson,
Administrator.
For the reasons set out in the preamble, title 40, chapter I of the
Code of Federal Regulations is proposed to be amended as follows:
PART 51--[AMENDED]
1. 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--[Amended]
2. Section 51.165 is amended by revising the table in paragraph
(b)(2) to read as follows:
Sec. 51.165 Permit requirements.
* * * * *
(b) * * *
(2) * * *
Option 1 for the table in paragraph (b)(2):
--------------------------------------------------------------------------------------------------------------------------------------------------------
Averaging time (hours)
Pollutant Annual --------------------------------------------------------------------------------------------
24 8 3 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2................................ 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... 25 [mu]g/m\3\.
PM10............................... ...................... ...................... ..................... ..................... 5 [mu]g/m\3\.
PM2.5.............................. 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.
NO2................................ 1.0 [mu]g/m\3\.
CO................................. ...................... ...................... 0.5 mg/m\3\.......... ..................... 2 mg/m\3\.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Option 2 for the table in paragraph (b)(2):
--------------------------------------------------------------------------------------------------------------------------------------------------------
Averaging time (hours)
Pollutant Annual --------------------------------------------------------------------------------------------
24 8 3 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2................................ 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... 25 [mu]g/m\3\.
PM10............................... ...................... 5 [mu]g/m\3\.
PM2.5.............................. 0.8 [mu]g/m\3\........ 4 [mu]g/m\3\.
NO2................................ 1.0 [mu]g/m\3\.
CO................................. ...................... ...................... 0.5 mg/m\3\.......... ..................... 2 mg/m\3\.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Option 3 for the table in paragraph (b)(2):
--------------------------------------------------------------------------------------------------------------------------------------------------------
Averaging time (hours)
Pollutant Annual --------------------------------------------------------------------------------------------
24 8 3 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2................................ 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... 25 [mu]g/m\3\.
PM10............................... ...................... 5 [mu]g/m\3\.
PM2.5.............................. 0.3 [mu]g/m\3\........ 1.2 [mu]g/m\3\.
NO2................................ 1.0 [mu]g/m\3\.
CO................................. ...................... ...................... 0.5 mg/m\3\.......... ..................... 2 mg/m\3\.
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 54147]]
* * * * *
3. Section 51.166 is amended as follows:
a. By revising the table in paragraph (c);
b. By revising paragraph (i)(5)(i)(c);
c. By revising paragraphs (i)(5)(ii) and (iii);
d. By revising paragraphs (i)(8) and (9);
e. By adding paragraph (i)(10);
f. By revising paragraph (k); and
g. By revising the table in paragraph (p)(4).
Sec. 51.166 Prevention of significant deterioration of air quality.
* * * * *
(c) * * *
Option 1 for the table in paragraph (c):
------------------------------------------------------------------------
Maximum
allowable
Pollutant increase
(micrograms per
cubic meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 1
24-hr maximum...................................... 3
PM10:
24-hr maximum...................................... 8
Sulfur dioxide:
Annual arithmetic mean............................. 2
24-hr maximum...................................... 5
3-hr maximum....................................... 25
Nitrogen dioxide:
Annual arithmetic mean............................. 2.5
------------------------------------------------------------------------
Class II
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 4
24-hr maximum...................................... 9
PM10:
24-hr maximum...................................... 30
Sulfur dioxide:
Annual arithmetic mean............................. 20
24-hr maximum...................................... 91
3-hr maximum....................................... 512
Nitrogen dioxide:
Annual arithmetic mean............................. 25
------------------------------------------------------------------------
Class III
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 8
24-hr maximum...................................... 18
PM10:
PM10, 24-hr maximum................................ 60
Sulfur dioxide:
Annual arithmetic mean............................. 40
24-hr maximum...................................... 182
3-hr maximum....................................... 700
Nitrogen dioxide:
Annual arithmetic mean............................. 50
------------------------------------------------------------------------
Option 2A for the table in paragraph (c):
------------------------------------------------------------------------
Maximum
allowable
Pollutant increase
(micrograms per
cubic meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 1
24-hr maximum...................................... 2
PM10:
24-hr maximum...................................... 8
Sulfur dioxide:
[[Page 54148]]
Annual arithmetic mean............................. 2
24-hr maximum...................................... 5
3-hr maximum....................................... 25
Nitrogen dioxide:
Annual arithmetic mean............................. 2.5
------------------------------------------------------------------------
Class II
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 4
24-hr maximum...................................... 9
PM10:
24-hr maximum...................................... 30
Sulfur dioxide:
Annual arithmetic mean............................. 20
24-hr maximum...................................... 91
3-hr maximum....................................... 512
Nitrogen dioxide:
Annual arithmetic mean............................. 25
------------------------------------------------------------------------
Class III
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 8
24-hr maximum...................................... 18
PM10:
24-hr maximum...................................... 60
Sulfur dioxide:
Annual arithmetic mean............................. 40
24-hr maximum...................................... 182
3-hr maximum....................................... 700
Nitrogen dioxide:
Annual arithmetic mean............................. 50
------------------------------------------------------------------------
Option 2B for the table in paragraph (c):
------------------------------------------------------------------------
Maximum
allowable
Pollutant increase
(micrograms per
cubic meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 1
24-hr maximum...................................... 2
PM10:
24-hr maximum...................................... 8
Sulfur dioxide:
Annual arithmetic mean............................. 2
24-hr maximum...................................... 5
3-hr maximum....................................... 25
Nitrogen dioxide:
Annual arithmetic mean............................. 2.5
------------------------------------------------------------------------
Class II
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 5
24-hr maximum...................................... 9
PM10:
24-hr maximum...................................... 30
Sulfur dioxide:
Annual arithmetic mean............................. 20
24-hr maximum...................................... 91
3-hr maximum....................................... 512
[[Page 54149]]
Nitrogen dioxide:
Annual arithmetic mean............................. 25
------------------------------------------------------------------------
Class III
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 10
24-hr maximum...................................... 18
PM10:
24-hr maximum...................................... 60
Sulfur dioxide:
Annual arithmetic mean............................. 40
24-hr maximum...................................... 182
3-hr maximum....................................... 700
Nitrogen dioxide:
Annual arithmetic mean............................. 50
------------------------------------------------------------------------
* * * * *
(i) * * *
(5) * * *
(i) * * *
(c) Particulate matter:
(1) 10 [mu]g/m\3\ of PM10, 24-hour average;
Option 1 for paragraph (i)(5)(i)(c)(2):
(2) 10 [mu]g/m\3\ of PM2.5, 24-hour average;
Option 2 for paragraph (i)(5)(i)(c):
(2) 8.0 [mu]g/m\3\ of PM2.5, 24-hour average;
Option 3 for paragraph (i)(5)(i)(c):
(2) 2.3 [mu]g/m\3\ of PM2.5, 24-hour average;
* * * * *
(ii) The concentrations of the pollutant in the area that the
source or modification would affect are less than the concentrations
listed in paragraph (i)(5)(i) of this section; or
(iii) The pollutant is not listed in paragraph (i)(5)(i) of this
section.
* * * * *
(8) The plan may provide that the permitting requirements
equivalent to those contained in paragraph (k)(1)(b) of this section do
not apply to a stationary source or modification with respect to any
maximum allowable increase for nitrogen oxides if the owner or operator
of the source or modification submitted an application for a permit
under the applicable permit program approved or promulgated under the
Act before the provisions embodying the maximum allowable increase took
effect as part of the plan and the reviewing authority subsequently
determined that the application as submitted before that date was
complete.
(9) The plan may provide that the permitting requirements
equivalent to those contained in paragraph (k)(1)(b ) of this section
shall not apply to a stationary source or modification with respect to
any maximum allowable increase for PM10 if (i) the owner or
operator of the source or modification submitted an application for a
permit under the applicable permit program approved under the Act
before the provisions embodying the maximum allowable increases for
PM10 took effect as part of the plan, and (ii) the reviewing
authority subsequently determined that the application as submitted
before that date was complete. Instead, the applicable requirements
equivalent to paragraph (k)(1)(b ) shall apply with respect to the
maximum allowable increases for TSP as in effect on the date the
application was submitted.
(10) The plan may provide that the permitting requirements
equivalent to those contained in paragraph (k)(1)(b ) of this section
shall not apply to a stationary source or modification with respect to
any maximum allowable increase for PM2.5 if (i) the owner or
operator of the source or modification submitted an application for a
permit under the applicable permit program approved under the Act
before the provisions embodying the maximum allowable increases for
PM2.5 took effect as part of the plan, and (ii) the
reviewing authority subsequently determined that the application as
submitted before that date was complete. Instead, the applicable
requirements equivalent to paragraph (k)(1)(b ) shall apply with
respect to the maximum allowable increases for PM10 as in
effect on the date the application was submitted.
* * * * *
(k) Source impact analysis--(1) Required demonstration. The plan
shall provide that the owner or operator of the proposed source or
modification shall demonstrate that allowable emission increases from
the proposed source or modification, in conjunction with all other
applicable emissions increases or reduction (including secondary
emissions), would not cause or contribute to air pollution in violation
of:
(a) Any national ambient air quality standard in any air quality
control region; or
(b ) Any applicable maximum allowable increase over the baseline
concentration in any area.
(2) Significant impact levels. The plan shall provide that, for
purposes of PM2.5, the demonstration required in paragraph
(k)(1) of this section is deemed to have been made if the emissions
increase of direct PM2.5 emissions from the new stationary
source alone or the net emissions increase of direct PM2.5
emissions from the modification alone would cause, in all areas, air
quality impacts less than the following amounts:
Option 1 for the table in paragraph (k)(2):
----------------------------------------------------------------------------------------------------------------
Class I significant Class II significant Class III significant
Averaging time impact levels impact levels impact levels
----------------------------------------------------------------------------------------------------------------
Annual............................... 0.04 [mu]g/m\3\........ 1.0 [mu]g/m\3\......... 1.0 [mu]g/m\3\.
24-hour.............................. 0.08 [mu]g/m\3\........ 5.0 [mu]g/m\3\......... 5.0 [mu]g/m\3\.
----------------------------------------------------------------------------------------------------------------
[[Page 54150]]
Option 2 for the table in paragraph (k)(2):
----------------------------------------------------------------------------------------------------------------
Class I significant Class II significant Class III significant
Averaging time impact levels impact levels impact levels
----------------------------------------------------------------------------------------------------------------
Annual............................... 0.16 [mu]g/m3.......... 0.8 [mu]g/m\3\......... 0.8 [mu]g/m\3\.
24-hour.............................. 0.24 [mu]g/m\3\........ 4.0 [mu]g/m\3\......... 4.0 [mu]g/m\3\.
----------------------------------------------------------------------------------------------------------------
Option 3 the table in paragraph (k)(2):
----------------------------------------------------------------------------------------------------------------
Class I significant Class II significant Class III significant
Averaging time impact levels impact levels impact levels
----------------------------------------------------------------------------------------------------------------
Annual............................... 0.06 [mu]g/m\3\........ 0.3 [mu]g/m\3\......... 0.3 [mu]g/m\3\.
24-hour.............................. 0.07 [mu]g/m\3\........ 1.2 [mu]g/m\3\......... 1.2 [mu]g/m\3\.
----------------------------------------------------------------------------------------------------------------
* * * * *
(p) * * *
(4) * * *
Option 1 for the table in paragraph (p)(4):
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean.............................. 4
24-hr maximum....................................... 9
PM10:
24-hr maximum....................................... 30
Sulfur dioxide:
Annual arithmetic mean.............................. 20
24-hr maximum....................................... 91
3-hr maximum........................................ 325
Nitrogen dioxide:
Annual arithmetic mean.............................. 25
------------------------------------------------------------------------
Option 2A for the table in paragraph (p)(4):
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean.............................. 4
24-hr maximum....................................... 9
PM10:
24-hr maximum....................................... 30
Sulfur dioxide:
Annual arithmetic mean.............................. 20
24-hr maximum....................................... 91
3-hr maximum........................................ 325
Nitrogen dioxide:
Annual arithmetic mean.............................. 25
------------------------------------------------------------------------
Option 2B for the table in paragraph (p)(4):
[[Page 54151]]
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean.............................. 5
24-hr maximum....................................... 9
PM10:
24-hr maximum....................................... 30
Sulfur dioxide:
Annual arithmetic mean.............................. 20
24-hr maximum....................................... 91
3-hr maximum........................................ 325
Nitrogen dioxide:
Annual arithmetic mean.............................. 25
------------------------------------------------------------------------
* * * * *
4. Appendix S to part 51 is amended by revising the table in
Section III.A to read as follows:
Appendix S to Part 51--Emission Offset Interpretative Ruling
* * * * *
III. * * *
A. * * *
Option 1 for the table in Section III.A:
--------------------------------------------------------------------------------------------------------------------------------------------------------
Averaging time (hours)
Pollutant Annual --------------------------------------------------------------------------------------------
24 8 3 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2................................ 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... 25 [mu]g/m\3\........ .....................
PM10............................... ...................... 5 [mu]g/m\3\.......... ..................... ..................... .....................
PM2.5.............................. 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... ..................... .....................
NO2................................ 1.0 [mu]g/m\3\........ ...................... ..................... ..................... .....................
CO................................. ...................... ...................... 0.5 mg/m\3\.......... ..................... 2 mg/m\3\.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Option 2 for the table in Section III.A:
--------------------------------------------------------------------------------------------------------------------------------------------------------
Averaging time (hours)
Pollutant Annual --------------------------------------------------------------------------------------------
24 8 3 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2................................ 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... 25 [mu]g/m\3\........ .....................
PM10............................... ...................... 5 [mu]g/m\3\.......... ..................... ..................... .....................
PM2.5.............................. 0.8 [mu]g/m\3\........ 4 [mu]g/m\3\.......... ..................... ..................... .....................
NO2................................ 1.0 [mu]g/m\3\........ ...................... ..................... ..................... .....................
CO................................. ...................... ...................... 0.5 mg/m\3\.......... ..................... 2 mg/m\3\.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Option 3 for the table in Section III.A:
--------------------------------------------------------------------------------------------------------------------------------------------------------
Averaging time (hours)
Pollutant Annual --------------------------------------------------------------------------------------------
24 8 3 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2................................ 1.0 [mu]g/m\3\........ 5 [mu]g/m\3\.......... ..................... 25 [mu]g/m\3\........ .....................
PM10............................... ...................... 5 [mu]g/m\3\.......... ..................... ..................... .....................
PM2.5.............................. 0.3 [mu]g/m\3\........ 1.2 [mu]g/m\3\........ ..................... ..................... .....................
NO2................................ 1.0 [mu]g/m\3\........ ...................... ..................... ..................... .....................
CO................................. ...................... ...................... 0.5 mg/m\3\.......... ..................... 2 mg/m\3\.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * ** * *
PART 52--[AMENDED]
5. The authority citation for part 52 continues to read as follows:
Authority: 42 U.S.C. 7401, et seq.
Subpart A--[Amended]
6. Section 52.21 is amended as follows:
a. By revising the table in paragraph (c);
b. By revising the third entry in paragraph (i)(5)(i);
c. By revising paragraphs (i)(5)(ii) and (iii);
d. By revising paragraphs (i)(9) and (10);
e. By adding paragraph (i)(11);
f. By revising paragraph (k); and
g. By revising the table in paragraph (p)(5).
Sec. 52.21 Prevention of significant deterioration of air quality.
* * * * *
(c) * * *
[[Page 54152]]
Option 1 for the table in paragraph (c):
------------------------------------------------------------------------
Maximum
allowable
Pollutant increase
(micrograms per
cubic meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 1
24-hr maximum...................................... 2
PM10:
24-hr maximum...................................... 8
Sulfur dioxide:
Annual arithmetic mean............................. 2
24-hr maximum...................................... 5
3-hr maximum....................................... 25
Nitrogen dioxide:
Annual arithmetic mean............................. 2.5
------------------------------------------------------------------------
Class II
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 4
24-hr maximum...................................... 9
PM10:
24-hr maximum...................................... 30
Sulfur dioxide:
Annual arithmetic mean............................. 20
24-hr maximum...................................... 91
3-hr maximum....................................... 512
Nitrogen dioxide:
Annual arithmetic mean............................. 25
------------------------------------------------------------------------
Class III
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 8
24-hr maximum...................................... 18
PM10:
PM10 24-hr maximum................................. 60
Sulfur dioxide:
Annual arithmetic mean............................. 40
24-hr maximum...................................... 182
3-hr maximum....................................... 700
Nitrogen dioxide:
Annual arithmetic mean............................. 50
------------------------------------------------------------------------
Option 2A for the table in paragraph (c):
------------------------------------------------------------------------
Maximum
allowable
Pollutant increase
(micrograms per
cubic meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 1
24-hr maximum...................................... 2
PM10:
24-hr maximum...................................... 8
Sulfur dioxide:
Annual arithmetic mean............................. 2
24-hr maximum...................................... 5
3-hr maximum....................................... 25
Nitrogen dioxide:
Annual arithmetic mean............................. 2.5
------------------------------------------------------------------------
[[Page 54153]]
Class II
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 4
24-hr maximum...................................... 9
PM10:
24-hr maximum...................................... 30
Sulfur dioxide:
Annual arithmetic mean............................. 20
24-hr maximum...................................... 91
3-hr maximum....................................... 512
Nitrogen dioxide:
Annual arithmetic mean............................. 25
------------------------------------------------------------------------
Class III
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 8
24-hr maximum...................................... 18
PM10:
24-hr maximum...................................... 60
Sulfur dioxide:
Annual arithmetic mean............................. 40
24-hr maximum...................................... 182
3-hr maximum....................................... 700
Nitrogen dioxide:
Annual arithmetic mean............................. 50
------------------------------------------------------------------------
Option 2B for the table in paragraph (c):
------------------------------------------------------------------------
Maximum
allowable
Pollutant increase
(micrograms per
cubic meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 1
24-hr maximum...................................... 2
PM10:
24-hr maximum...................................... 8
Sulfur dioxide:
Annual arithmetic mean............................. 2
24-hr maximum...................................... 5
3-hr maximum....................................... 25
Nitrogen dioxide:
Annual arithmetic mean............................. 2.5
------------------------------------------------------------------------
Class II
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 5
24-hr maximum...................................... 9
PM10:
24-hr maximum...................................... 30
Sulfur dioxide:
Annual arithmetic mean............................. 20
24-hr maximum...................................... 91
3-hr maximum....................................... 512
Nitrogen dioxide:
Annual arithmetic mean............................. 25
------------------------------------------------------------------------
[[Page 54154]]
Class III
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean............................. 10
24-hr maximum...................................... 18
PM10:
24-hr maximum...................................... 60
Sulfur dioxide:
Annual arithmetic mean............................. 40
24-hr maximum...................................... 182
3-hr maximum....................................... 700
Nitrogen dioxide:
Annual arithmetic mean............................. 50
------------------------------------------------------------------------
* * * * *
(i) * * *
(5) * * *
(i) * * *
Option 1 for the third entry in paragraph (i)(5)(i):
Particulate matter:
(a) 10 [mu]g/m\3\ of PM10, 24-hour average;
(b) 10 [mu]g/m\3\ of PM2.5, 24-hour average;
Option 2 for the third entry in paragraph (i)(5):
Particulate matter:
(a) 10 [mu]g/m\3\ of PM10, 24-hour average;
(b) 8.0 [mu]g/m\3\ of PM2.5, 24-hour average;
Option 3 for the third entry in paragraph (i)(5):
Particulate matter:
(a) 10 [mu]g/m\3\ of PM10, 24-hour average;
(b) 2.3 [mu]g/m\3\ of PM2.5, 24-hour average;
* * * * *
(ii) The concentrations of the pollutant in the area that the
source or modification would affect are less than the concentrations
listed in paragraph (i)(5)(i) of this section; or
(iii) The pollutant is not listed in paragraph (i)(5)(i) of this
section.
* * * * *
(9) The requirements of paragraph (k)(1)(a) of this section shall
not apply to a stationary source or modification with respect to any
maximum allowable increase for nitrogen oxides if the owner or operator
of the source or modification submitted an application for a permit
under this section before the provisions embodying the maximum
allowable increase took effect as part of the applicable implementation
plan and the Administrator subsequently determined that the application
as submitted before that date was complete.
(10) The requirements in paragraph (k)(1)(b) of this section shall
not apply to a stationary source or modification with respect to any
maximum allowable increase for PM10 if (i) the owner or
operator of the source or modification submitted an application for a
permit under this section before the provisions embodying the maximum
allowable increases for PM10 took effect in an
implementation plan to which this section applies, and (ii) the
Administrator subsequently determined that the application as submitted
before that date was otherwise complete. Instead, the requirements in
paragraph (k)(1)(b) shall apply with respect to the maximum allowable
increases for TSP as in effect on the date the application was
submitted.
(11) The requirements in paragraph (k)(1)(b) of this section shall
not apply to a stationary source or modification with respect to any
maximum allowable increase for PM2.5 if (i) the owner or
operator of the source or modification submitted an application for a
permit under this section before the provisions embodying the maximum
allowable increases for PM2.5 took effect in an
implementation plan to which this section applies, and (ii) the
Administrator subsequently determined that the application as submitted
before that date was otherwise complete. Instead, the requirements in
paragraph (k)(1)(b) shall apply with respect to the maximum allowable
increases for PM10 as in effect on the date the application
was submitted.
* * * * *
(k) Source impact analysis--(1) Required demonstration. The owner
or operator of the proposed source or modification shall demonstrate
that allowable emission increases from the proposed source or
modification, in conjunction with all other applicable emissions
increases or reductions (including secondary emissions), would not
cause or contribute to air pollution in violation of:
(a) Any national ambient air quality standard in any air quality
control region; or
(b) Any applicable maximum allowable increase over the baseline
concentration in any area.
(2) Significant impact levels. For purposes of PM2.5,
the demonstration required in paragraph (k)(1) of this section is
deemed to have been made if the emissions increase of direct
PM2.5 emissions from the new stationary source alone or the
net emissions increase of direct PM2.5 emissions from the
modification alone would cause, in all areas, air quality impacts less
than the following amounts:
Option 1 for the table in paragraph (k)(2):
----------------------------------------------------------------------------------------------------------------
Class I significant Class II significant Class III significant
Averaging time impact levels impact levels impact levels
----------------------------------------------------------------------------------------------------------------
Annual............................... 0.04 [mu]g/m\3\........ 1.0 [mu]g/m\3\......... 1.0 [mu]g/m\3\.
24-hour.............................. 0.08 [mu]g/m\3\........ 5.0 [mu]g/m\3\......... 5.0 [mu]g/m\3\.
----------------------------------------------------------------------------------------------------------------
Option 2 for the table in paragraph (k)(2):
[[Page 54155]]
----------------------------------------------------------------------------------------------------------------
Class I significant Class II significant Class III significant
Averaging time impact levels impact levels impact levels
----------------------------------------------------------------------------------------------------------------
Annual............................... 0.16 [mu]g/m\3\........ 0.8 [mu]g/m\3\......... 0.8 [mu]g/m\3\.
24-hour.............................. 0.24 [mu]g/m\3\........ 4.0 [mu]g/m\3\......... 4.0 [mu]g/m\3\.
----------------------------------------------------------------------------------------------------------------
Option 3 for the table in paragraph (k)(2):
----------------------------------------------------------------------------------------------------------------
Class I significant Class II significant Class III significant
Averaging time impact levels impact levels impact levels
----------------------------------------------------------------------------------------------------------------
Annual............................... 0.06 [mu]g/m\3\........ 0.3 [mu]g/m\3\......... 0.3 [mu]g/m\3\.
24-hour.............................. 0.07 [mu]g/m\3\........ 1.2 [mu]g/m\3\......... 1.2 [mu]g/m\3\.
----------------------------------------------------------------------------------------------------------------
* * * * *
(p) * * *
(5) * * *
Option 1 for the table in paragraph (p)(5):
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean.............................. 4
24-hr maximum....................................... 9
PM10:
24-hr maximum....................................... 30
Sulfur dioxide:
Annual arithmetic mean.............................. 20
24-hr maximum....................................... 91
3-hr maximum........................................ 325
Nitrogen dioxide:
Annual arithmetic mean.............................. 25
------------------------------------------------------------------------
Option 2 for the table in paragraph (p)(5):
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
PM2.5:
Annual arithmetic mean.............................. 4
24-hr maximum....................................... 9
PM10:
24-hr maximum....................................... 30
Sulfur dioxide:
Annual arithmetic mean.............................. 20
24-hr maximum....................................... 91
3-hr maximum........................................ 325
Nitrogen dioxide:
Annual arithmetic mean.............................. 25
------------------------------------------------------------------------
Option 3 for the table in paragraph (p)(5):
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
PM2.5:
[[Page 54156]]
Annual arithmetic mean.............................. 5
24-hr maximum....................................... 9
PM10:
24-hr maximum....................................... 30
Sulfur dioxide:
Annual arithmetic mean.............................. 20
24-hr maximum....................................... 91
3-hr maximum........................................ 325
Nitrogen dioxide:
Annual arithmetic mean.............................. 25
------------------------------------------------------------------------
* * * * *
[FR Doc. E7-18346 Filed 9-20-07; 8:45 am]
BILLING CODE 6560-50-P