[Federal Register Volume 70, Number 196 (Wednesday, October 12, 2005)]
[Rules and Regulations]
[Pages 59582-59618]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-20110]
[[Page 59581]]
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Part III
Environmental Protection Agency
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40 CFR Part 51
Prevention of Significant Deterioration for Nitrogen Oxides; Final Rule
Federal Register / Vol. 70, No. 196 / Wednesday, October 12, 2005 /
Rules and Regulations
[[Page 59582]]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 51
[AD-FRL-7981-1; E-Docket ID No. OAR-2004-0013 (Legacy Docket No. A-87-
16)]
RIN-2060-AM33
Prevention of Significant Deterioration for Nitrogen Oxides
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: In today's final action, EPA is retaining the existing
nitrogen dioxide (NO2) increments as part of the Agency's
regulations for the Prevention of Significant Deterioration (PSD) of
air quality from emissions of nitrogen oxides (NOX). These
regulations are designed to preserve the air quality in national parks
and other areas that are meeting the national ambient air quality
standards (NAAQS) for NO2 (hereafter called the
NO2 NAAQS). EPA reevaluated the original NO2
increments in response to a 1990 court ruling that directed the Agency
to consider and harmonize the statutory criteria for establishing PSD
regulations for NOX contained in sections 166(c) and 166(d)
of the Clean Air Act (CAA or Act). EPA is also amending its PSD
regulations to clarify that States otherwise meeting these requirements
of the Act may obtain approval to employ alternative approaches to the
existing increments for NO2. Under a separate action, we
will be publishing a Supplemental Notice of Proposed Rulemaking (SNPR)
to show how implementation of the model cap and trade program under the
2005 Clean Air Interstate Rule (CAIR) can meet the requirements for a
State to use this approach in lieu of the existing NO2
increments in order to prevent significant deterioration of air quality
from emissions of NOX.
DATES: This final rule is effective on November 14, 2005.
ADDRESSES: EPA has established a docket for this action under Docket ID
No. OAR-2004-0013. All documents in the docket are listed in the
EDOCKET index at http://www.epa.gov/edocket. Although listed in the
index, some information may not be publicly available, i.e., CBI or
other information whose disclosure is restricted by statute. Certain
other material, such as copyrighted material, is not placed on the
Internet and will be publicly available only in hard copy form.
Publicly available docket materials are available either electronically
in EDOCKET or in hard copy at the Air Docket, EPA/DC, EPA West, Room
B102, 1301 Constitution Ave., NW., Washington, DC. The Public Reading
Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday,
excluding legal holidays. The telephone number for the Public Reading
Room is (202) 566-1744, and the telephone number for the Air Docket is
(202) 566-1742.
FOR FURTHER INFORMATION CONTACT: Mr. Dan deRoeck, Information Transfer
and Program Integration Division (C339-03), U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, telephone (919)
541-5593, fax (919) 541-5509, or e-mail at [email protected].
SUPPLEMENTARY INFORMATION:
I. General Information
A. Does This Action Apply to Me?
Entities affected by this rule include sources in all industry
groups. The majority of sources potentially affected are expected to be
in the following groups:
----------------------------------------------------------------------------------------------------------------
Industry group SIC \a\ NAICS \b\
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Electric Services............................ 491 221111, 221112, 221113, 221119, 221121, 221122
Petroleum Refining........................... 291 324110
Industrial Inorganic Chemicals............... 281 325181, 325120, 325131, 325182, 211112, 325998,
331311, 325188
Industrial Organic Chemicals................. 286 325110, 325132, 325192, 325188, 325193, 325120, 325199
Miscellaneous Chemical Products.............. 289 325520, 325920, 325910, 325182, 325510
Natural Gas Liquids.......................... 132 211112
Natural Gas Transport........................ 492 486210, 221210
Pulp and Paper Mills......................... 261 322110, 322121, 322122, 322130
Paper Mills.................................. 262 322121, 322122
Automobile Manufacturing..................... 371 336111, 336112, 336211, 336992, 336322, 336312,
336330, 336340, 336350, 336399, 336212, 336213
Pharmaceuticals.............................. 283 325411, 325412, 325413, 325414
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\a\ Standard Industrial Classification.
\b\ North American Industry Classification System.
Entities affected by the rule also include States, local permitting
authorities, and Indian tribes whose lands contain new and modified
major stationary sources.
B. Where Can I Obtain Additional Information?
In addition to being available in the docket, an electronic copy of
today's final rule is also available on the World Wide Web. Following
signature by the EPA Administrator, a copy of today's final rule will
be posted on the EPA's New Source Review (NSR) Web site, under
Regulations & Standards, at http://www.epa.gov/nsr/index.html.
C. How is This Preamble Organized?
The information presented in this preamble is organized as follows:
I. General Information
A. Does This Action Apply to Me?
[[Page 59583]]
B. Where Can I Obtain Additional Information?
C. How Is This Preamble Organized?
II. Background
A. PSD Program
B. Existing PSD Increment System for NOX
C. SIP Requirements for Implementing PSD Program
D. Court Challenge to Increments for NOX
III. Overview of Today's Final Action
A. What We Proposed
B. Final Action and Differences From Proposal
IV. Legal Basis for Final Action
A. Clean Air Act Provisions and Court Opinion
1. Applicable Statutory Provisions
2. Opinion of the Court in EDF v. EPA
B. EPA's Interpretation of Section 166 of the Act
1. Regulations As a Whole Should Fulfill Statutory Requirements
2. Contingent Safe Harbor Approach
3. The Statutory Factors Applicable Under Section 166(c)
4. Balancing the Factors Applicable Under Section 166(c)
5. Authority for States To Adopt Alternatives To Increment
V. Health and Welfare Effects of NOX
A. Overview of the Potential Effects of Nitrogen Oxides
B. Scope of Our Analysis
C. Data Considered in Our Analysis
D. Analysis of Potential Effects
1. Health Effects
2. Welfare Effects
VI. Final Actions
A. Retain Existing Increment System for NOX
1. Existing Characteristics of the Regulatory Scheme Fulfill
Statutory Criteria
2. Characteristics of Increments for NOX
B. State Option To Employ Alternatives To Increment
1. States May Adopt ``Other Measures'' That Fulfill Section 166
of the Act
2. EPA Is Not Adopting Elements of Option 3
3. Benefits of an Alternative Approach
4. Future Actions Regarding Alternatives
VII. Measures Not Proposed as Options
VIII. Statutory and Executive Order Reviews
A. Executive Order 12866--Regulatory Planning and Review
B. Paperwork Reduction Act
C. Regulatory Flexibility Act (RFA)
D. Unfunded Mandates Reform Act
E. Executive Order 13132--Federalism
F. Executive Order 13175--Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045--Protection of Children From
Environmental Health and Safety Risks
H. Executive Order 13211--Actions That Significantly Affect
Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act
J. Executive Order 12898--Federal Actions To Address
Environmental Justice in Minority Populations and Low-income
Populations
K. Congressional Review Act
II. Background
A. PSD Program
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
Prevention of Significant Deterioration (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, i.e., ``attainment'' areas, or in areas for
which there is insufficient information to classify an area as either
attainment or nonattainment, i.e., ``unclassifiable'' areas.
The applicability of the PSD program to a particular source must be
determined in advance of construction and is pollutant-specific. Once a
source is determined to be subject to PSD, 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. 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'' (AQRV).
When the permitting 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 major source or major modification.
After considering and responding to the comments, the permitting
authority may issue a final determination on the construction permit in
accordance with the PSD regulations.
B. Existing PSD Increment System for NOX
On October 17, 1988, EPA promulgated pollutant-specific PSD
regulations for NOX under section 166 of the CAA. 53 FR
40656. As part of these regulations, the EPA decided to establish
NO2 increments following the pattern enacted by Congress for
the particulate matter (PM) and sulfur dioxide (SO2)
increments. These increments establish maximum increases in ambient air
concentrations of NO2 (expressed in micrograms per cubic
meter ([mu]g/m3)) allowed in a PSD area over a baseline
concentration. Emissions increases from both stationary and mobile
sources are considered in the consumption of the NO2
increments which are implemented through the PSD permitting provisions
in 40 CFR parts 51 and 52.
The NO2 increment system includes the three-tiered area
classification system originally established by Congress in section 163
for the statutory increments for SO2 and PM. Congress
designated Class I areas (including certain national parks and
wilderness areas) as areas of special national concern, where the need
to prevent air quality deterioration is the greatest. Consequently, the
allowable level of incremental change in air quality is smallest, i.e.,
most stringent, in Class I areas. Congress initially established as
Class II all areas not specifically designated in the Act as Class I
areas. The increments of Class II areas are less stringent than those
of the 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
higher levels of industrial development (and emissions growth). Thus,
Class III areas are allowed to have the greatest amount of pollutant
increase while still achieving the NAAQS. There have been no Class III
redesignations to date.
EPA based the levels of the original NO2 increments for
the three area classifications on the percentage-of-NAAQS approach that
Congress used to define the increments in the Act for SO2
and PM. Congress used different percentages of the NAAQS to calculate
the Class I increments for PM and SO2. For the
NO2 increments, we chose the percentage that Congress used
for SO2. This decision yielded a lower numerical value for
the Class I NO2 increment than would have resulted by using
the PM percentages.
The existing Class I NO2 increment is 2.5 [mu]g/
m3 (annual average), a level of 2.5 percent of the
NO2 NAAQS. It is based on the Class I SO2
increment, which is set at the same percentage (2.5 percent) of the
SO2 annual NAAQS. The Class II NO2 increment is
25 [mu]g/m3 - 25 percent of the NO2 NAAQS. The
Class III NO2 increment is 50 [mu]g/m3 - 50
percent of the NO2 NAAQS.
C. SIP Requirements for Implementing PSD Program
Air quality planning requirements for new and modified stationary
sources of air pollution are an integral part of the PSD program.
States must develop, adopt, and submit to EPA for approval a State
Implementation Plan (SIP) that contains emission limitations and other
[[Page 59584]]
control measures to attain and maintain the NAAQS and to meet other
requirements of section 110(a) of the Act. Each SIP must contain a
preconstruction review program for the construction and modification of
any stationary source of air pollution to assure that the NAAQS are
achieved and maintained. Further, each SIP must: protect areas of clean
air; not interfere with any other State's NAAQS maintenance; protect
AQRVs, including visibility, in national parks and other natural areas
of special concern; assure that appropriate emissions controls are
applied; maximize opportunities for economic development consistent
with the preservation of clean air resources; and ensure that any
decision to increase air pollution is made only after full public
consideration of all the consequences of such a decision.
D. Court Challenge to Increments for NOX
EPA's original 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). ED successfully argued that EPA failed to
sufficiently consider certain provisions in section 166 of the CAA. 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.''
Environmental Defense Fund v. EPA, 898 F.2d 183, 190 (D.C. Cir. 1990)
(``EDF v. EPA''). EPA initiated this action in response to the court
decision. We discuss the opinion of the court further below.
III. Overview of Today's Final Action
To ensure protection of the air quality in national parks and other
areas that meet the NAAQS for NO2, EPA is taking final
action today on its reevaluation of the Agency's pollutant-specific PSD
regulations for NOX, which include the existing
NO2 increments. We have decided to retain the existing
NO2 increments while also granting States the option to seek
approval of alternative approaches that protect parks and prevent
significant deterioration of air quality from emissions of
NOX.
A. What We Proposed
In accordance with the directions of a 1990 court ruling, EPA
conducted a review of the existing NO2 increments that are
part of the Agency's pollutant-specific PSD regulations for
NOX. We considered and harmonized the statutory criteria,
contained in sections 166(c) and 166(d) of the Act, that govern the
content of these PSD regulations for NOX. EPA proposed to
apply the statutory criteria using the ``contingent safe harbor''
approach that was suggested by the court as an appropriate way to
ensure that EPA's PSD regulations for NOX will prevent
significant deterioration of air quality in parks and other areas that
are designated to be in attainment with the NAAQS or are
unclassifiable. Applying this legal interpretation, we proposed three
options to satisfy the statutory requirements. See 70 FR 8880 (Feb. 23,
2005).
In the first option (option 1) of our February 2005 proposal, EPA
proposed to retain the existing regulatory framework and the original,
existing increments for NO2 that the Agency first
promulgated in 1988 to protect the air quality in national parks and
other areas that meet the NAAQS for NO2. These increments
were established as a percentage of the NAAQS, and were based on the
same ambient measure (NO2) and averaging period (annual) as
the NAAQS. We proposed to find that an increment with these
characteristics satisfied the minimum requirements of section 166(d) of
the Act for preserving the air quality in parks and other attainment
and unclassifiable areas. In addition, to address the requirements of
section 166(c), we reviewed the existing regulatory framework of the
Agency's PSD regulations for NOX and the scientific and
technical information pertaining to the health, welfare, and ecological
effects of NOX. In light of this review, EPA proposed to
find that the statutory requirements were met by retaining annual
NO2 increments that are based on the percentages of the
NAAQS that Congress employed to set the increments for SO2.
The available research on health and welfare effects indicated that the
existing NO2 increments, in conjunction with the case-by-
case permit reviews for additional impacts and impairment of AQRVs,
fulfilled the criteria in section 166(c).
In the second option (option 2), we proposed to allow States to
prevent significant deterioration of air quality due to emissions of
NOX by adopting an EPA-administered market-based interstate
cap and trade program, such as the model cap and trade program for EGUs
contained in our CAIR. Under this option, a State that implemented this
program to address NOX emissions would no longer be required
to conduct certain source-specific analyses, including the current
NO2 increment analysis. This option would require States to
submit revised SIPs that include a cap and trade program to reduce
NOX emissions in accordance with statewide emissions budgets
prescribed by EPA. Neither the statewide budget nor the regional cap
would be a legally enforceable limit on total NOX emissions
but would be used as an accounting technique to determine the amount of
emissions reductions that would be needed from specific source
categories to satisfy the budget or cap. The requirements of the cap
and trade program would be enforceable, and this would ensure that as
long as emissions from sources outside of the cap did not grow more
than projected, the overall regionwide budget would be met.
As a third option (option 3), we proposed to allow States to adopt
their own planning strategies to meet the requirements of section 166
of the CAA. We proposed to allow a State to forego implementation of
the NO2 increments if the State could demonstrate that
measures in its SIP, in conjunction with Federal requirements, would
prevent significant deterioration of air quality from emissions of
NOX. Under this option, in lieu of implementing the
increment system for NOX, a State would have to demonstrate
that specific planning goals and requirements contained in its SIP
would satisfy the requirements in section 166 of the Act and the goals
and purposes of the PSD program set forth in section 160. We proposed
to require that States establish a clear planning goal that satisfied
the requirements of sections 166(c) and 166(d) of the Act. Under this
option, EPA did not propose to require a State to demonstrate that its
SIP included a specific type of program. However, we indicated that we
believed a goal to keep statewide emissions of NOX from all
sources below 1990 levels would prevent significant deterioration of
air quality and satisfy the requirements of section 166 of the Act.
B. Final Action and Differences From Proposal
In this final action, we are adopting option 1 of the February 2005
proposal and retaining the existing NO2 increments along
with other parts of the existing framework of pollutant-specific PSD
regulations for NOX. However, we are also amending the text
of one of our PSD regulations in order to make clear that States may
seek EPA approval of SIPs that utilize an alternative approach to the
NO2 increments if the State can demonstrate that an
alternative program satisfies the requirements of sections
[[Page 59585]]
166(c) and 166(d) of the CAA and prevents significant deterioration
from emissions of NOX. States have always had the option to
submit alternative approaches in their SIPs that can be shown to be
more effective than the minimum program elements established by EPA,
but this regulatory change is intended to clarify that a system other
than increments may be utilized by a State to prevent significant
deterioration from emissions of NOX where the requirements
of the CAA are otherwise met.
In options 2 and 3, we proposed to address the requirements of
section 166 of the CAA for NOX through the review and
approval of State programs that employed alternative approaches to
fulfill the requirements of sections 166(c) and 166(d) of the Act. We
are codifying this basic principle in our regulations today without
defining any specific type of alternative program that we believe would
meet these requirements. We are simply making clear in our regulations
that States have the option to continue implementing the NO2
increment program or to design an alternative approach as part of the
SIPs and submit this program to EPA for approval. Rather than
promulgating a specific alternative program of the type we proposed in
option 2 and option 3, we are allowing States the flexibility to submit
any type of alternative for consideration on a case-by-case basis to
determine if the alternative meets the requirements of sections 166(c)
and 166(d) of the CAA as we interpret these provisions in this final
action. We are not establishing any additional regulatory criteria
(such as planning goals or emissions inventory requirements) that would
govern the review of such a program other than what is already
contained within the CAA. Thus, we make no final finding at this time
that any particular type of program other than the existing increment
framework meets the requirements of sections 166(c) and 166(d) of the
CAA. Instead, we plan to make such determinations on a case-by-case
basis whenever a State submits an alternative approach for EPA to
approve as part of a SIP.
Although we are not adopting a specific cap and trade (option 2) or
emissions inventory-based planning program (option 3) at this time, we
continue to see promise in using a cap and trade approach modeled on
the CAIR to meet the goals of the PSD program for NOX. As a
result, we intend to publish a supplemental notice of proposed
rulemaking that builds on option 2 and provides more details on how a
State that achieves the NOX emissions reductions required
under CAIR can fulfill the objectives of the PSD program, satisfy the
statutory requirements of section 166 of the Act, and obviate the need
to implement the NO2 increments program.
IV. Legal Basis for Final Action
A. Clean Air Act Provisions and Court Opinion
1. Applicable Statutory Provisions
EPA is taking this action in accordance with the requirements of
section 166 of the CAA for NOX. In section 166(a) of the
Act, Congress directed EPA to conduct a study and promulgate
regulations to prevent significant deterioration of air quality which
would result from emission of hydrocarbons, carbon monoxide,
photochemical oxidants, and NOX.
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.
In addition, the goals and purposes of the CAA described in section
101 of the Act are the following:
(b) * * * (1) 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;
(2) to initiate and accelerate a national research and
development program to achieve the prevention and control of air
pollution;
(3) to provide technical and financial assistance to State and
local governments in connection with the development and execution
of their air pollution prevention and control programs; and
(4) to encourage and assist the development and operation of
regional air pollution prevention and control programs [; and]
(c) * * * to encourage or otherwise promote reasonable Federal,
State, and local governmental actions, consistent with the
provisions of this Act, for pollution prevention.
2. Opinion of the Court in EDF v. EPA
In its 1990 opinion on the challenge to EPA's 1988 regulations for
NOX, the court held that EPA had satisfied its obligation
under section 166(d) but had not sufficiently considered whether
different increments should be established under the criteria in
section 166(c).
Environmental Defense Fund v. EPA, 898 F.2d 183 (D.C. Cir. 1990)
(``EDF v. EPA''). More specifically, the court held that EPA's
percentage-of-NAAQS approach for determining the increments satisfied
the duty under section 166(d) to promulgate regulations for
NOX that were ``at least as effective'' as the increments in
section 163. Id. at 188. As to subsection (c), however, the court held
that EPA's approach of using the percentage ambient concentrations as a
``proxy'' for meeting the subsection (c) criteria overlooked the
language of subsection (c) and turned subsection (c) into an option
despite its mandatory wording. Thus, 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.'' Id. at 190.
The court identified three steps that EPA took to develop PSD
regulations for NOX under section 166. The first two steps
reflected EPA's decisions to implement the PSD program for
NOX by adopting regulations for NOX that employed
increments with an area classification system. These first two steps
were not controverted in EDF v. EPA. See 898 F.2d at 184-85. The
dispute in the EDF case involved only
[[Page 59586]]
the third step, which was EPA's action to establish several
characteristics of the increments by reference to the NAAQS. The
characteristics that EPA derived from the NAAQS were (1) the level of
the increments using the percent-of-NAAQS approach; (2) the time period
(annual average) for the increments; and (3) the pollutant
(NO2) for which the increments were established. Since these
three characteristics of the increments were the only issues
controverted in the EDF v. EPA case, EPA interprets the court's remand
to direct the Agency only to reconsider these three questions. However,
in the proposal, we also believed it would be beneficial to consider
alternative approaches to an increment system and voluntarily
reconsidered the first two steps in the process of developing
pollutant-specific PSD regulations for NOX.
In EDF v. EPA, the court held that, in light of the criteria in
section 166(c), EPA could not use the NAAQS as the sole basis for
deriving increments. However, the court held that using the NAAQS as
the basis for deriving increments was permissible in determining
whether the ``at least as effective'' standard under subsection (d) was
met. But, with respect to subsection (c), the court stated: ``We find
nothing in the language or legislative history suggesting that this
duty [consideration of the goals and purposes of the statute] could be
satisfied simply by referencing the NAAQS.'' Id. at 190. The court
noted the differences between the health and welfare criteria on which
the NAAQS are based (sections 108 and 109) and the ``goals and
purposes'' of the PSD program set forth in section 160, highlighting
the special value the PSD program places on protection of national
parks. At the same time, the court recognized that ``[n]evertheless,
the ambient standards are the basic measure of air quality under the
[Clean Air Act], and the controlling standards by no means exclude any
value that is the subject of focus under the PSD provisions.'' Id. at
176 (internal citations and quotations omitted). In other words, the
court observed that NAAQS remain relevant to the inquiry under section
166 because they are a basic measure of air quality and may indirectly
reflect some consideration, among others, of the same values that are
the focus of the PSD program. However, the court indicated that we
could not rely solely upon the NAAQS to comply with section 166 because
this provision directs us to focus on the specific goals and purposes
of PSD which are not necessarily the factors that determine the NAAQS
under section 109.
Thus, the court directed EPA to reconsider the characteristics of
the existing increments in light of the criteria in both sections
166(c) and 166(d). The court indicated that one permissible
interpretation for harmonizing subsections (c) and (d) would be to
construe subsection (d) as a ``contingent safe harbor'' or presumptive
baseline. Thus, increments derived from the NAAQS could be authorized
if the Agency were to undertake additional analysis and make a reasoned
determination that the criteria under subsection (c) do not call for
different increments than the ``safe harbor'' that meets the criteria
in subsection (d) of the statute.
B. EPA's Interpretation of Section 166 of the Act
In the February 2005 notice of proposed rulemaking (February 2005
proposal), we responded to the court's opinion by describing in detail
how the EPA proposed to interpret and apply the relevant provisions of
the CAA in the course of reevaluating the existing PSD regulations for
NOX on remand. 70 FR at 8885-88. Our interpretation 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 adopted the ``contingent safe harbor''
approach suggested by the court 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 increment contained in a SIP
meet the requirements of sections 166(c) and 166(d).
We maintain this interpretation in this final action and summarize
the main points below. Further discussion of many of these points can
be found in the February 2005 proposal. 70 FR at 8885. In addition to
reiterating the main points below, the following discussion also
clarifies our interpretation in light of several comments that we
received.
1. Regulations As a Whole Should Fulfill Statutory Requirements
Commenters did not question our holistic approach, which is
grounded on the structure of section 166 of the Act. 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. In order to
develop pollutant-specific regulations under subsection (a), EPA must
establish an overall regulatory framework for those regulations and
fill in specific details around that framework. Thus, EPA interprets
section 166 to require that the entire system of PSD regulations for a
particular pollutant must, as a whole, satisfy the criteria in sections
166(c) and 166(d).
As a result, when we reevaluated the existing PSD regulations for
NOX, we did not look at increments in isolation, but also
considered how these increments work in conjunction with other measures
to satisfy the statutory criteria. The other measures that we
considered with the increments are the area classification system, AQRV
review in Class I areas, additional impacts analysis, and BACT
requirements. This approach is consistent with section 166(d), which
says that pollutant-specific PSD regulations ``may contain'' increments
or ``other measures.''
In option 1 of the proposal, we proposed to retain the increment
system and focused our reevaluation on the specific characteristics of
the increments (level, time period, and pollutant) in our existing PSD
regulations for NOX. This was because the dispute in EDF v.
EPA involved only EPA's decisions to define the characteristics of the
increments for NOX in relation to the NAAQS. Since the
increment and area classification system in EPA's PSD regulations for
NOX was not controverted, we interpreted the court's opinion
not to require that the Agency reconsider this basic framework for its
PSD regulations for NOX. Thus, in this action to finalize
option 1 of the proposal, we continue to focus on the level, time
period, and pollutant employed to establish increments for
NOX. However, under our holistic approach, we considered
these characteristics of the increment in conjunction with the other
measures
[[Page 59587]]
contained in our PSD regulations for NOX that were not
challenged in EDF v. EPA.
2. Contingent Safe Harbor Approach
Our proposal to harmonize the criteria set forth in sections 166(c)
and 166(d) by employing the ``contingent safe harbor'' approach was
also not opposed by any commenters. Several commenters took issue with
our ultimate decision not to establish increments more stringent than
the safe harbor, but no one questioned the analytical approach that we
used to harmonize sections 166(c) and 166(d) of the Act.
We continue to believe this is an appropriate reading of the
statute. 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 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. Then, subsection
(c) may 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). As in 1988, we construe subsection (d) to require that the
measures be ``at least as stringent'' as the statutory increments set
forth in section 163.
When we employ an increment and area classification system in our
section 166 PSD regulations, we interpret this language 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 identified the ``safe harbor'' increments for NOX
for each area classification (Class I, II, or III) to be increments
established in relation to the NO2 NAAQS that were set (1)
at 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 conducted further review to determine
whether these ``safe harbor'' increments, in conjunction with other
measures adopted under the PSD program and section 166, sufficiently
fulfilled the criteria in subsection (c).
After weighing and balancing the criteria set forth in subsection
(c) (and the incorporated goals and purposes of the CAA in section 101
and the PSD program in section 160), we have determined that the ``safe
harbor'' increments and associated measures satisfy the criteria in
subsection (c) for NOX. Thus, we are not adopting different
increments, additional increments, or additional measures to satisfy
the section 166(c) criteria. However, under the contingent safe harbor
approach, if we had determined that the ``safe harbor'' increments and
other measures did not satisfy the criteria applicable under section
166(c), we would have promulgated additional increments or other
measures as part of our pollutant-specific PSD regulations for
NOX under section 166.
3. The Statutory Factors Applicable Under Section 166(c)
We proposed to interpret 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. This fourth criterion in section 166(c) cannot
be understood without reference to other parts of the Act. Thus, we
construed 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.
A few commenters disagreed with our choice of words in an
introductory paragraph when we collectively described these eight parts
of the Act as ``factors to be considered.'' However, no one disagreed
that these eight objectives should be the focus of our analysis. For
instance, commenters did not question our decision to emphasize the
five goals and purposes in section 160, while looking to the more
general goals in section 101 of the Act to provide guidance on the
meaning of the more specific goals and purposes of the PSD program in
section 160.\1\
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\1\ 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. The
overall goals and purposes of the CAA listed in sections 101(b) and
101(c) are general goals regarding protecting and enhancing the
nation's air resources and controlling and preventing pollution.
Because these broad goals are given more specific meaning in section
160, EPA does not believe it is necessary to consider them in detail
when evaluating whether PSD regulations satisfy the criteria in
section 166(c). In addition, the court's inquiry in EDF v. EPA
focused exclusively on the specific goals and purpose of the PSD
program set forth in section 160. However, because the broad purpose
of the CAA set forth in section 101(b)(1) provides some additional
guidance as to the meaning of the more specific PSD goal set forth
in section 160(3), we considered section 101(b)(1) further in the
limited context of interpreting one of the factors applicable under
section 166.
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In this rulemaking action, we use the term ``factors'' as shorthand
to describe the group of eight statutory objectives (three criteria and
five goals and purposes) that we believe Congress directed us to
achieve in promulgating pollutant-specific PSD regulations under
section 166 of the Act. We do not intend for our use of ``factors'' to
suggest that EPA does not believe it must satisfy all four criteria in
section 166(c), one of which requires that EPA fulfill the five goals
and purposes in section 160. The Agency has used the term ``factors''
in this action to avoid confusion when referring to the combination of
criteria in section 166(c) and goals and purposes in section 160 that
the court directed us to consider further on remand. Regardless of the
semantics, our objective is to establish regulations that satisfy each
of these factors.
4. Balancing the Factors Applicable Under Section 166(c)
A few commenters questioned our interpretation of the Act to
establish a balancing test among many of the eight factors applicable
under section 166(c) of the Act. In the proposal, we described how we
believed the Act directed us to balance the goal to promote economic
growth with the factors that direct us to protect: (1) AQRVs; (2) the
public health and welfare from adverse effects, and (3) the air quality
in parks and special areas. We are not persuaded that this is an
impermissible reading of the Act. Section 166 of the CAA directs EPA to
promulgate pollutant-specific PSD regulations that simultaneously
satisfy each of the eight factors described above. While these
objectives are
[[Page 59588]]
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 at the same time. If not,
it might be impossible for EPA to establish one set of regulations that
fulfills all the factors applicable under section 166(c).
As discussed in the proposal, 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 CAA, 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 simultaneously 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 first part of the goal of the PSD program set forth in section
160(3) (``to insure that economic growth will occur'') makes clear that
the PSD program is not intended to stifle economic growth. However, the
second part of this goal indicates that economic growth should ``occur
in a manner that is consistent with the preservation of existing clean
air resources.'' 42 U.S.C. 7470(3). Section 101(b)(1) indicates that
these goals are not necessarily inconsistent because Congress sought to
``protect and enhance the Nation's air resources so as to promote the
public health and welfare and the productive capacity of its
population.'' When considered in light of the purpose of the Act set
forth in section 101(b)(1), it is clear that section 160(3) establishes
the goal of the PSD program to maximize opportunities for economic
growth and to protect clean air resources. Therefore, when applied as a
guiding factor for the content of pollutant-specific PSD regulations
under section 166(c), we construe section 160(3) to require that we
balance economic growth and environmental protection.
A few commenters objected to our characterization of the goal in
section 160(3) as establishing an objective to ``foster economic
growth.'' According to common usage, the term ``foster'' means to
``promote the growth or development of.'' Merriam-Webster's Collegiate
Dictionary, Tenth Edition, Page 459 (2001). We used ``foster'' in the
context of describing the goals in sections 160(3) and 101(b)(1) of the
Act, and considered the term to be consistent with the goal to
``insure'' economic growth under certain conditions and to ``promote''
the productive capacity of the population while protecting air quality.
However, to be more consistent with our terminology in recent NSR
rulemaking actions (67 FR at 80187), we will use the phrase ``maximize
opportunities for economic growth'' in this final action rather than
``foster economic growth.''
One commenter also argued that EPA was impermissibly departing from
an earlier interpretation that the goal in section 160(3) required EPA
``to ensure that economic growth in clean areas occurs only after
careful deliberation by State and local communities.'' 53 FR 3698, 3699
(Feb. 8, 1988). However, we believe our current view is consistent with
what we said in that earlier notice of proposed rulemaking. In 1988, we
also recognized that Congress had directed us to balance several of the
goals and purposes listed in section 160 of the Act. 53 FR at 3699. We
stated that the PSD program is required to balance the first goal to
protect public health and welfare, the second goal to protect air
quality in national parks and other special areas, and a third goal as
expressed above. 53 FR at 3699. From the language we used, however, it
is apparent that this ``third goal'' was actually a combination of the
goal in section 160(3) with the goal in section 160(5) of the Act.
Section 160(5) establishes the goal to ``assure that any decision to
permit increased air pollution in any area is made only after careful
evaluation of all the consequences of such decision and after adequate
opportunities for informed public participation in the decisionmaking
process.'' 42 U.S.C. 7470(5). We continue to believe that Congress
directed us to fulfill both the goals in sections 160(3) and 160(5) at
the same time. However, because, as we describe in more detail below,
we believe that other aspects of our existing PSD regulations for
NOX fulfill the goal in section 160(5), we have not
emphasized the language of section 160(5) in the balancing test we
utilized to analyze the characteristics of the increment.
In the present action, we are carrying this balancing approach an
additional step by seeking to harmonize the goals in section 160 with
other criteria applicable under section 166(c) of the Act. Thus, we
have not disavowed what we said in 1988, but rather have added to it.
Consistent with the direction of the court, we have analyzed the terms
of sections 166(c) and 160 more carefully after the court held that we
had not adequately considered these provisions of the Act. Having
considered these parts of the statute in more depth at this stage, we
believe our current interpretation is well-grounded in the terms of the
Act and in fact consistent with what we said in 1988.
The need to balance the applicable factors to achieve these
objectives simultaneously 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.
In the specific context of the PSD program, we construe this charge
to ``protect public health and welfare'' to require EPA to evaluate
whether 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 must consider how to
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
[[Page 59589]]
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
regulations, these factors must be weighed 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 Increment
We do not interpret section 166 to require that EPA (or that States
that implement our regulations) employ an increment system for every
pollutant listed in this section. Section 166(d) states that our
pollutant-specific PSD regulations ``may contain'' increments or
``other measures.'' Thus, EPA or the States may employ approaches other
than an increment system, so long as such an approach otherwise meets
the requirements of sections 166(c) and 166(d).
If a State adopts regulations in its SIP that meet the criteria of
sections 166(c) and 166(d), we believe section 166 would give EPA the
authority to allow the State to implement that program in lieu of the
NO2 increment program that we are reaffirming today. Thus,
one approach we proposed for fulfilling our obligation to promulgate
pollutant-specific regulations for NOX under section 166 was
to adopt regulations that allow States to demonstrate that alternative
programs satisfy section 166.
Under section 110(a)(1) of the Act, each State is required to
submit a SIP that provides for implementation, maintenance, and
enforcement of the primary and secondary NAAQS established by EPA. All
areas are required to submit SIPs within certain timeframes, and those
SIPs must include specified provisions identified under section
110(a)(2) of the Act. SIPs for nonattainment areas are required to
include additional specified control requirements, as well as controls
providing for attainment of any revised NAAQS and periodic reductions
providing ``reasonable further progress'' in the interim (see section
172(c) of the Act). For attainment areas subject to the PSD program,
section 161 of the Act requires that ``each applicable implementation
plan shall contain emissions limitations and such other measures as may
be necessary, as determined under regulations promulgated under this
part, to prevent significant deterioration of air quality in each
region * * * designated * * * as attainment or unclassifiable.'' We
have interpreted sections 166 and 161 to collectively require that EPA
promulgate a specific PSD regulatory program for each pollutant
identified in section 166 (such as the existing NO2
increments and associated regulations), and then to require the States
to adopt that program as part of their SIPs. Nothing in the CAA
precludes EPA from promulgating a minimum program, such as the
NO2 increments we reaffirm today, and giving States the
option to either adopt the minimum program or to design an alternative
program and demonstrate to EPA that such a program meets the
requirements of sections 166(c) and 166(d), as interpreted in this
action.
One commenter argued that EPA is authorized under sections 160,
161, and 166 of the Act to direct States to adopt SIPs that reduce
emissions of NOX from existing sources. However, we do not
completely agree with this interpretation. The PSD program was designed
to be a growth management program that limits the deterioration of air
quality beyond baseline levels that may be caused by the construction
of major new and modified sources. The commenter disputed this view by
pointing to language in section 160(2) which establishes the goal to
``preserve, protect, and enhance'' air quality in national parks.
However, considering the growth management goals of the PSD program, we
believe the use of the term ``enhance'' in section 160(2) was intended
to refer to the visibility provisions in sections 169A and 169B and
those situations where a PSD increment is violated. Section 160 lists
the goals and purposes of part C of the CAA, and this part includes
sections 169A and 169B which establish the Regional Haze program. An
explicit goal of this program is to ``remedy any existing impairment of
visibility in mandatory Class I Federal areas.'' 42 U.S.C. 7491(a)(1).
Thus, we believe the goal to ``enhance'' air quality in national parks
is implemented through the Regional Haze program while the PSD program
focuses on preserving and protecting air quality in these areas.
However, when a PSD increment is violated, we agree that EPA may
require a State to revise its SIP to correct a violation. See 40 CFR
51.166(a)(3). Otherwise, we do not interpret these PSD provisions to
authorize us to direct States in their SIPs to achieve reductions in
emissions from existing sources for PSD purposes.
However, we recognize that the growth management goals of PSD may
also be fulfilled when the States adopt controls on existing sources
that would reduce emissions and allow growth from new sources and major
modifications to existing sources without causing significant
deterioration. Under the increment approach, we have previously
recognized that States may choose to require reductions from existing
sources in order to expand the increments and allow for more growth
under the PSD program.\2\ However, we have never required States to do
so because, in the absence of an increment violation, we do not believe
section 166 and other provisions in part C give us the legal authority
to mandate such reductions for PSD purposes.
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\2\ 43 FR 26380, 26381 (June 19, 1978) (``States can expand the
available PSD increments by requiring emissions reductions from
existing sources.'')
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V. Health and Welfare Effects of NOX
As explained in the preceding section, the goals and purposes of
the PSD program that are especially relevant to the development of our
pollutant-specific PSD regulations for NOX address
protection of public health and welfare, with a particular emphasis on
the air quality in national parks and other natural areas. Thus, we
evaluated the available scientific and technical information on the
health and welfare effects of NOX to determine whether any
modification of those increments is warranted.
In this section, we summarize the scientific and technical
information that we considered, as well as the relevant health and
welfare findings that we believe support retaining the existing
NO2 increments. Additional discussion on the potential
effects of NOX is contained in the February 2005 proposal.
See 70 FR 8880 (February 23, 2005) at 8888-8894.
A. Overview of the Potential Effects of Nitrogen Oxides
``Nitrogen oxides'' is the generic term for a group of highly
reactive gases that contain nitrogen and oxygen in varying amounts. The
high-temperature combustion of fossil fuels, primarily
[[Page 59590]]
from electric utilities and mobile sources, is a major contributor to
the formation of nitric oxide (NO) and NO2.\3\ Most
NOX from combustion sources is emitted as NO (about 95
percent); the remainder are primarily NO2. Emissions of NO
are rapidly oxidized in the atmosphere to produce even more
NO2.\4\ In a relatively short time, however, NO2
in the atmosphere can be transformed into other nitrogen compounds,
including nitric acid and nitrates. We also know that nitrogen oxides
\5\ play a major role in the formation of other criteria pollutants--
ozone and PM (nitrogen-bearing particles and acid aerosols)--each with
their own set of adverse health and welfare effects.\6\ For example,
nitrate particles contribute to visibility impairment and regional haze
and nitrates are a major component of acidic deposition.
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\3\ Some forms of NOX are produced naturally (via
lightning, soils, wildfires, stratospheric intrusion, and the
oceans).
\4\ Because NO is readily converted to NO2 in the
atmosphere, the emissions of NOX reported by EPA assume
NOX in the form of NO2. In predicting ambient
impacts that may result from emissions of NOX, initially
is assumed to be emitted from sources as NOX. (40 CFR
part 50 app W sec. 6.2.4.)
\5\ Seven oxides of nitrogen are known to occur in the
atmosphere: nitric oxide (NO), nitrogen dioxide (NOX),
nitrate (NO3-), nitrous oxide N2O),
dinitrogen trioxide (N2O3), dinitrogen
tetroxide (N2O4) and dinitrogen pentoxide
(N2O5).
\6\ The term ``welfare'' is defined in the Act to include, inter
alia, ``effects on soils, water, crops, vegetation, man-made
materials, animals, wildlife, weather, visibility, and climate.''
Section 302(h).
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In addition, reduced nitrogen compounds, such as ammonia
(NH3) (derived largely from emissions from livestock waste
as well as the application of fertilizer to the ground) and ammonium
(NH4\+\), are also important to many of the public health
and environmental impacts associated with atmospheric nitrogen
compounds. However, because these nitrogen compounds are not associated
with emissions of NOX from the stationary sources subject to
review under the PSD program, we did not consider it appropriate to
factor them into the review of the adequacy of the existing
NO2 increments.
These varied origins of nitrogen in the atmosphere add to the
difficulty of determining the specific source contributing to the total
nitrogen concentration. This, in turn, increases the difficulty of
designing an emissions control strategy for reducing the nitrogen
contribution in a particular area.
B. Scope of Our Analysis
In the proposal, we explained that we did not believe our
pollutant-specific PSD regulations for NOX were the
appropriate place to address the effects of the secondary pollutants
ozone and PM. Some commenters disagreed with our proposed approach and
argued that EPA should address the adverse effects of ozone and PM as
part of our assessment of the existing NO2 increments.
Photochemical oxidants (ozone)\7\ and PM \8\ are formed in part by
reactions of NOX emissions with other pollutants in the
atmosphere. However, we do not agree that this fact alone dictates that
our pollutant-specific PSD regulations for NOX must address
ozone and PM impacts. Because nitrogen oxides are not the only
compounds that contribute to the formation of ozone and PM, we believe
we can more effectively address the effects of PM and ozone through
separate regulations for these pollutants under section 166 of the Act.
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\7\ Ozone is the oxidant found in the largest quantities in the
atmosphere. The EPA promulgated NAAQS for photochemical oxidants in
1971. The chemical designation of the standard was changed in 1979
from ``photochemical oxidants'' to ozone. See 44 FR 8202 (February
8, 1979).
\8\ Particulate matter (PM) is composed of directly emitted
particles and secondarily formed particles. Secondary particulates
are produced from gaseous pollutants, mainly NOX,
SO2, ammonia, and some VOCs. Emissions of NOX
can result in the formation of particulate nitrates whose
contribution to fine particles varies depending on geographic
location and other criteria.
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It would be unreasonable to establish pollutant-specific PSD
regulations to protect against the effects of ozone without also
considering the other major precursor for ozone--volatile organic
compounds. Any PSD regulation attempting to mitigate the ozone impacts
from NOX, notwithstanding the ozone NAAQS, would be
unfounded without also addressing this significant component. Thus, we
conclude that, for PSD purposes, the contribution of NOX to
the formation of ozone should be considered primarily in the context of
the establishment of pollutant-specific PSD regulations for ozone.\9\
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\9\ In the 1988 final preamble adopting the NO2
increments, we gave limited consideration to whether limiting
increases of NOX emissions would worsen ozone ambient
concentrations, in response to comments raising this issue. 53 FR at
40668. We did not, however, attempt to set the NO2
increments to address ozone public health and welfare impacts, nor
do we believe that is required here, for the reasons stated above.
Increments for ozone have not been established because of the
technical difficulty associated with predicting ambient
concentration changes resulting from a single stationary source. 61
FR 65764, 65776 (Dec. 13, 1996).
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Like ozone, PM has several precursors, of which NOX is
only one. NO2 may be transformed to nitrate particulates by
means of chemical reactions in the atmosphere.\10\ However, any PSD
strategy for PM should consider both direct PM emissions and all of the
regulated precursors instead of placing disproportionate emphasis on
only one component of the pollutant. Regulations for NOX
that address PM effects in a narrow manner (i.e., nitrates only) could
potentially affect the stringency of the PM increments and
considerations regarding the baseline concentration and baseline date.
Thus, we believe it would be inappropriate to promulgate pollutant-
specific regulations for NOX based on its transformation
into PM. In a separate notice, EPA intends to consider options for
regulating precursors to PM2.5.
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\10\ Nitrate is a major constituent of atmospheric PM. Due to
limited scientific literature addressing the health impacts of
nitrates, exposure currently is analyzed as exposure to fine PM.
(NAPAP, 1998.)
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Some commenters believe that the statutory PSD requirements
obligate EPA to promulgate NOX regulations to prevent
significant deterioration of air quality from ozone and PM. These
commenters cited language from section 166(a) of the Act which directs
EPA to ``promulgate regulations to prevent significant deterioration of
air quality which would result from the emissions of such pollutants.''
CAA Sec. 166(a).
However, we do not interpret this language to compel the action
commenters recommend. The phrase ``result from emissions of such
pollutants'' refers back to the first clause of the sentence which
lists several pollutants (``hydrocarbons, carbon monoxide,
photochemical oxidants, and nitrogen oxides'') that are subject to
section 166. We do not read this language to compel EPA to promulgate a
single regulation to address all such pollutants at once. Reading the
sentence as a whole, we interpret the language in section 166(a) to
provide EPA with the discretion to separately promulgate pollutant-
specific PSD regulations for each of these four groups of pollutants
(which include ozone because it is formed by photochemical oxidants).
Thus we believe our obligation in this action to promulgate pollutant-
specific PSD regulations for ``nitrogen oxides'' does not necessarily
have to include consideration of the effects of ozone.
For similar reasons, we do not read the provisions of section 166
of the Act to require that EPA consider effects attributable to PM when
promulgating pollutant-specific PSD regulations for ``nitrogen
oxides.'' Congress established separate increments for PM, originally
measured as total suspended particulate (or TSP), under the authority
of section 163 of the Act. Congress later authorized EPA to replace the
TSP increments with increments for PM10. See CAA Sec.
166(f). Section 166(a) of the Act also directs EPA to promulgate
pollutant-specific PSD regulations for any pollutants for which a NAAQS
is established after the
[[Page 59591]]
enactment of section 166. We interpret this language to apply to
pollutants such as PM2.5 for which we promulgated a NAAQS
after 1977. Thus, it does not follow that section 166 must be read to
require that EPA consider PM effects when promulgating regulations for
NOX.
Another commenter asserted that the court's opinion in EDF v. EPA
made it abundantly clear that EPA cannot use any single NAAQS or NAAQS
indicator as the sole basis for the regulations required by section 166
to address NOX. Rather, the commenter stated, EPA must
evaluate the impact of NOX with reference to the goals and
purposes in sections 101 and 160, which goals and purposes encompass
protection of public health and welfare from ``air pollution'' without
exception for any specific pollutants or class of pollutants. We
recognize that emissions of NOX contribute to a range of
direct and indirect effects on health, welfare, and AQRVs, but we
believe this rulemaking action should focus on those effects that were
considered by EPA in the development of the NAAQS for NO2.
This approach is appropriate because the need to develop PSD rules
is tied to the existence of the NAAQS. As the court in EDF v. EPA
acknowledged ``the ambient standards are the basic measure of air
quality under the [Clean Air Act] and the controlling standards by no
means exclude any value that is the subject of focus under the PSD
provisions.'' 898 F.2d at 190 (emphasis in original). Thus, the health
and welfare effects that were evaluated by EPA when it established the
NAAQS should also be considered when EPA establishes regulations under
section 166 to protect against significant deterioration of air quality
from NOX emissions.
The provisions of section 166 make clear that EPA is to establish
PSD regulations (including an increment, if appropriate) under this
provision after the establishment of a NAAQS for the applicable
pollutants. In 1971, EPA first established a single standard for
NO2 as both the primary and secondary NAAQS addressing
NOX. 36 FR 8186 (April 30, 1971). Congress then passed
section 166 of the Act in 1977 and gave EPA 2 years to complete its
study and promulgate PSD regulations for ``nitrogen oxides.'' 42 U.S.C.
7476(a). In addition, for pollutants for which a NAAQS had not been
promulgated by August 7, 1977, Congress gave EPA 2 years from the
promulgation of such standards to establish PSD regulation under
section 166 of the Act. Id. The establishment of PSD regulations (which
may include increments) must necessarily follow the NAAQS because the
NAAQS provides the benchmark against which we are to judge
``significant deterioration'' of air quality.
We do not believe that our decision to define the bounds of our
analysis as the range of effects considered in setting the NAAQS is
contrary to the court's holding in EDF v. EPA. The court held that EPA
cannot use the NAAQS as the ``sole basis'' for deriving the increment.
898 F.2d at 190. However, in this action, we did not simply focus on
the level of the NAAQS as a legal standard, as we did in 1988. In this
rulemaking action on remand, we considered the health and welfare
effects that EPA evaluated to establish the NAAQS. But rather than
considering those effects in relation to the standards set forth in
section 109, we evaluated those effects in relation to the factors in
sections 166(c) and 160 of the Act. The court held that we could not
rely solely on the NAAQS itself to establish increments because of the
emphasis in sections 166(c) and 160 on special considerations, such as
protection of national wilderness areas, whose special values may be
reflected in the NAAQS but are not necessarily the only factors that
determine the level of the NAAQS. See 898 F.2d at 190. Thus, within the
field of effects that EPA found relevant when establishing the NAAQS,
we narrowed our inquiry to focus on the special considerations of PSD
and those effects that may occur in some areas notwithstanding
attainment of the NAAQS. This approach follows directly from the
court's opinion in EDF v. EPA.
C. Data Considered in Our Analysis
In our February 2005 notice, we proposed to focus primarily on the
health and welfare information that we had compiled for the last
periodic review of the NO2 NAAQS. EPA is required to conduct
a periodic, comprehensive analysis of available scientific and
technical data as part of its process for promulgating NAAQS in
accordance with sections 108 and 109 of the Act. The last reevaluation
of the NAAQS for NOX was completed in 1996. 61 FR 52852,
November 8, 1996. The most recently reviewed data for NOX is
contained in the 1993 Criteria Document for NOX (``1993
Criteria Document'') and the associated 1995 OAQPS Staff Paper (``1995
Staff Paper for NOX''), as further explained below.\11\
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\11\ The official titles of these documents are, respectively,
``Air Quality Criteria for Oxides of Nitrogen,'' EPA, August 1993;
and ``Review of the National Ambient Air Quality Standards for
Nitrogen Oxides: Assessment of Scientific and Technical
Information,'' EPA, September 1995.
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Although we also considered the information contained in studies
published since the last NAAQS review, several commenters believed that
we should have given greater attention to such later studies. These
commenters believe these later studies show the growing seriousness of
NOX effects in the form of ozone, PM and atmospheric
nitrogen deposition (N deposition).\12\ One commenter felt that we
ignored a lot of scientific information on NOX effects on
ecosystems. Another commenter argued that our focus on the review of
the 1993 Criteria Document and 1995 Staff Paper for NOX was
a ``self-imposed limitation'' that relied on incomplete scientific
information considering the fact that new information has been
developed since then.
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\12\ The term ``atmospheric nitrogen deposition'' refers to the
process by which nitrogen compounds in the atmosphere are
transferred to various surfaces, including water, soil, etc.
Additional discussion on this is provided in sections V and VI of
this preamble as related to indirect effects of NO2.
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Although we did focus on the Criteria Document and 1995 Staff Paper
for NOX, we did not wholly ignore new information as the
commenters appear to suggest. We considered information contained in
more recent studies, particularly those concerning the types of effects
on ecosystems associated with atmospheric nitrogen deposition. We
evaluated information published since completion of the last NAAQS
review to determine whether there have been significant advances in
scientific and technical information. The more recent data we reviewed
has clearly broadened our understanding of the ecological changes
resulting from deposition in general and N deposition in particular.
Recent information also provides us with greater information about N
deposition trends and the speciation of various N components. The
collection of these types of information is an essential step in the
process of quantitatively defining the dose-response relationship
between emissions of NOX and the various adverse effects
being observed. However, even these later studies, including ones
supplied by some of the commenters, do not enable us to establish those
relationships at this time.
We focused on the effects described in the Criteria Document and
1995 Staff Paper for NOX because these documents are the
product of a rigorous process that is followed to validate and
interpret the information. 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
[[Page 59592]]
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). 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.
Our focus on the 1993 Criteria Document and the 1995 Staff Paper
for NOX is supported by the provisions of section 166 which
make clear that EPA is to establish pollutant-specific PSD regulations
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 purposes of establishing pollutant-specific PSD
regulations. We believe this timing was intended to enable EPA to rely
upon the same body of information concerning a pollutant's health and
welfare effects when it establishes the NAAQS and the subsequent PSD
increments (or other measure) defining significant air quality
deterioration for the same pollutant.
Thus, while we believe it would be consistent with congressional
intent to rely in the ordinary case on only the information used in the
most recent NAAQS review when establishing pollutant-specific PSD
regulations under section 166, the situation we faced with
NOX was unique. Because considerable time had passed since
the 1996 review of the NO2 NAAQS, we considered the more
recent studies discussed above.
Because EPA is taking this action to fulfill a court remand of an
increment originally established in 1988, the Act could be read to
suggest that we revert back to the information compiled in the NAAQS
review that predated our initial action in 1988. When the
NO2 increments were originally developed and promulgated,
the most recent Criteria Document for oxides of nitrogen was EPA's 1982
Criteria Document, used for completing the periodic review of the
NO2 NAAQS promulgated on June 19, 1985 (50 FR 25532).
However, because of the amount of time that has passed since then, we
do not believe it is reasonable to read the Act so narrowly in this
case. Thus, we relied on the most recent Criteria Document, because it
represented the most recent compilation of scientific and technical
evidence for purposes of NAAQS review, even though this was not the
Criteria Document we used to develop the 1988 NO2
increments.
In the last periodic review of the NO2 NAAQS, in 1996,
EPA compiled information that was not part of the scope of the previous
NAAQS review. Specifically, the 1993 Criteria Document and 1995 Staff
Paper for NOX considered as part of the secondary standard
review ``short- and long-term effects of nitrogen deposition on
biological, physical and chemical components of ecosystems and the
resulting effect of changes to these components on ecosystem structure
and function as well as the traditional issue of visibility impairment,
and materials damage.'' The expanded scope is particularly relevant to
the types of effects that should be used to consider the effectiveness
of the PSD increments.
We do not interpret the court decision in EDF v. EPA \13\ to mean
that we should not consider the same data when establishing both the
NAAQS and the PSD increments for a particular pollutant, but rather
that we would be expected to weigh the same data differently using the
different legal criteria as our guide. Consequently, we might arrive at
different conclusions for developing the NAAQS and increments because
of the differences in the legal criteria for the two types of
standards. As the court itself said, ``a pollutant that has only mild
public health effects but severe effects on wilderness areas might
demand a lower increment (measured as a percentage of its ambient
standards) than one with severe health effects but only mild effects on
wilderness areas.'' EDF v. EPA, 898 F.2d at 190. Thus, while the Act
seems to require that EPA establish NAAQS and increments for the same
pollutant using different legal standards, we believe it is important
nevertheless that the body of evidence used for both reviews should
initially be subjected to the same level of Agency validation and
review.
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\13\ The court pointed out that ``the `goals and purposes' of
the PSD program, set forth in Sec. 160, are not identical to the
criteria on which the ambient standards are based * * *''
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D. Analysis of Potential Effects
This section contains a summary of our review of the health and
welfare effects associated with NOX reviewed by EPA as part
of the reconsideration of the pollutant-specific PSD regulations for
NOX. Although EPA concluded from the available evidence that
there was no basis in 1996 for revising the NO2 NAAQS, the
objective of our latest review of the same body of scientific and
technical evidence was to determine whether there is any basis for
proposing to modify the NO2 increments, based on specific
percentages of those NAAQS, which are part of the PSD regulations for
NOX that we promulgated in 1988. Our analysis of the health
and welfare effects associated with NOX included adverse
health effects that were found to occur at levels at or near the NAAQS,
as well as a variety of direct NO2 welfare effects and
indirect welfare effects resulting from the transformation of
NO2 to other nitrogen compounds in the atmosphere which are
then transferred to other surfaces via N deposition.
We noted earlier that the 1993 Criteria Document and 1995 Staff
Paper for NOX added a level of review not contained in the
previous periodic review of the NAAQS for NOX. That is, the
most recent documents include evidence concerning ``short- and long-
term effects of N deposition on biological, physical and chemical
components of ecosystems and the resulting effect of changes to these
components on ecosystem structure and function as well as the
traditional issues of visibility impairment and materials damage.'' The
consideration of such effects was our primary focus for determining
whether the existing increments need to be modified to satisfy section
166(c) of the Act.
[[Page 59593]]
1. Health Effects
In 1996, EPA concluded that there was no need to change the
existing primary NAAQS for NO2 on the basis of the health
effects evidence available at that time. Nevertheless, for purposes of
evaluating the safe harbor NO2 increments, we examined those
effects which were found to occur at levels at or near NAAQS. Of
particular concern were possible health effects resulting from short-
term exposure (e.g., less than 3 hours), which might justify
consideration of a short-term increment.
The short-term health effects of most concern at ambient or near-
ambient concentrations of NO2 involved mild changes in
airway responsiveness (airway constriction and narrowing) and decrease
in pulmonary function. In neither case were the observed effects
considered serious: Observations of airway constriction did not reveal
airway inflammation and were fully reversible, and changes in pulmonary
function were considered small. Moreover, most of the observed effects
occurred at ambient concentrations of NO2 that were above
levels typically monitored in areas meeting the NAAQS, i.e., PSD areas.
We also considered effects based on longer-term (2-week periods),
low-level exposure to NO2 involving increased respiratory
illnesses among children. These studies involved situations of indoor
exposure to NO2 emitted from gas stoves. Various limitations
associated with these clinical studies made it difficult to extrapolate
the results in a manner that would yield estimates of health impacts
associated with outdoor NO2 exposure. See February 2005
proposal at 70 FR 8890-8891.
2. Welfare Effects
In our February 2005 proposal, we indicated that the 1996 periodic
review of the NO2 NAAQS concluded that the available body of
scientific and technical evidence did not provide an adequate basis for
setting a separate secondary standard to address welfare effects of
NOX. See 70 FR at 8891. However, as discussed earlier, the
goals and purposes of the PSD program give special weight to the
protection of welfare, air quality values and areas of special national
and regional interest (national parks, national wilderness areas, etc.)
Accordingly, EPA reviewed the information on welfare effects to
determine whether it supported a need on our part to modify the
existing NO2 increments to provide additional environmental
protection, especially for such areas as national parks, wilderness
areas and their natural, recreational, scenic, or historic value(s),
notwithstanding attainment of the NAAQS in PSD areas.
As mentioned earlier, the evidence we reviewed covered both direct
(NO2) and indirect (other NOX), short- and long-
term effects on biological, physical and chemical components of
ecosystems and the resulting effect of changes to these components on
ecosystem structure and function. Information from selected later
studies was also reviewed to determine the extent to which our
knowledge of the adverse effects of NOX had advanced since
the 1996 review. A summary of our review of both direct and indirect
effects of NO2 is presented below.
a. Direct Welfare Effects
The 1993 Criteria Document and 1995 Staff Paper for NOX
provided evidence that exposure to NO2 can cause potentially
adverse effects on plants and materials, and visibility impairment
(primarily in the form of local-scale plume discoloration). These
effects are summarized below. See also 70 FR 8892-8893.
Experimental studies involving exposure of plants to NO2
for periods less than 24 hours produced effects on the growth
development and reproduction of plants. However, the pollutant
concentrations used in these experiments were well above concentrations
observed in the ambient air and at a frequency of occurrence not
typically found in the U.S. The experimental effects were not
considered significant at concentrations at or below the level of the
NAAQS.
The effects of NO2 on materials were not well determined
according to the evidence contained in the 1993 Criteria Document. The
limited information showed that it was difficult to distinguish
NO2 or any other agent as the single causative agent for
observed damage; many agents, together with a number of environmental
stresses, act on the surface of materials over time.
Finally, NO2 can cause visibility impairment in the form
of a discoloration effect most noticeable as local-scale (within 50
kilometers of the source) or ``reasonably attributed impairment.'' This
effect can be observed as a contrast or color difference between a
plume and a viewed background, such as the sky or a distant object.
However, some studies have shown that brownish discoloration can result
from the presence of particles alone, thus making it difficult to
determine a reliable relationship between ground-level concentrations
of NO2 at any given point and discoloration caused by
particles that may also be in a source's plume. The 1995 Staff Paper
for NOX noted that despite the known light-absorbing
qualities of NO2, ``there are relatively little data
available for judging the actual importance of NO2 to visual
air quality.''
b. Indirect Welfare Effects
The predominant welfare effects of NO2 are indirect
effects caused by nitrogen compounds that have been transformed from
NO2 in the atmosphere, such as nitric acid and nitrates.
Studies have shown that nitrogen compounds can contribute to various
negative ecological effects when they are transferred from the
atmosphere to a variety of surfaces, e.g., water, soil, vegetation, and
other materials, by the process of N deposition.'' \14\
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\14\ Under certain conditions, in terrestrial or agricultural
systems, some amount of nitrogen deposition can enhance growth of
some forest species and crops. However, in areas where deposition
occurs in excess of plant and microbial demand (also known as
nitrogen saturation) the added nitrogen can disturb the nitrogen
cycle, contributing to such negative effects as increased plant
susceptibility to some natural stresses and modification of
interplant competition.
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Nitrogen deposition occurs in several forms, including wet (rain or
snow), dry (transfer of gases or particles), or occult (fog, mist or
cloud) deposition. Nitrogen deposition occurs primarily as nitrates,
which are formed in the atmosphere by the oxidation of NO and
NO2, or as ammonia, which is released by agricultural or
soil microbial activity. When the nitrogen transfer process involves
acids (e.g., nitric acid) or acidifying compounds, the deposition
process is referred to as ``acidic deposition.''
For the February 2005 proposal, we reviewed various indirect
effects resulting from N deposition and which can be categorized
according to the specific ecosystem being affected. These include
terrestrial, wetland, and aquatic ecosystems. These different effects
are summarized below. See also 70 FR 8888-8894.
As with the other effects we considered, we focused primarily on
the evidence contained in the 1993 Criteria Document and 1995 Staff
Paper for the NO2 NAAQS. Other more recent studies were also
summarized, although we did not consider ourselves to be under an
obligation to consider such evidence since it has not yet undergone the
extensive level of validation and review that will be necessary if it
is to be incorporated into the section 108 Criteria Document for
NOX.
The following subsections summarize the various indirect effects of
NO2 on
[[Page 59594]]
ecosystems, including terrestrial systems (i.e., plant communities),
wetlands, and aquatic systems. We believe that the effects summarized
are potentially relevant to an evaluation of the pollutant-specific PSD
regulations for NOX because these effects have been observed
in areas of the country that are attaining the NAAQS.
(1) Terrestrial ecosystems. Soils are the largest pool of nitrogen
in forest ecosystems, although such nitrogen is generally not available
for plants until it has been mineralized by bacteria (Fenn, 1998).
Another important source of nitrogen is atmospheric deposition, which
may cause or contribute to significant adverse changes in terrestrial
ecosystems, including soil acidification, increase in soil
susceptibility to natural stresses, and alterations in plant species
mix.
When excess nitrogen input causes soil acidification, it can alter
the availability of plant nutrients (i.e., calcium and magnesium) and
expose tree roots to toxic levels of aluminum and manganese, thereby
having an adverse effect on tree growth. It can also lead to the
mobilization of aluminum from the soil as nitrates are leached from the
soil and transported to waterways, where the aluminum can exhibit toxic
effects to aquatic organisms.\15\
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\15\ Aluminum from soil seldom appears in aquatic systems
because natural aluminum minerals are insoluble in the normal pH
range of natural waters. However, the term ``aluminum mobilization''
refers to the conversion of aluminum in acidic soils into dissolved
forms and its transport, as runoff or subsurface flow, to water
systems. Mobilized aluminum can then alter the acid/base property of
natural water systems (Wang, 2004).
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It is worth noting that air pollution is not the sole cause of soil
change; high rates of acidification are occurring in less polluted
regions of the western U.S. because of natural internal soil processes,
such as tree uptake of nitrate and nitrification associated with
excessive nitrogen fixation. Although N deposition can accelerate the
acidification of soils, the levels of nitrogen necessary to produce
measurable soil acidification are quite high. The 1993 Criteria
Document indicated that, at that time, N deposition had not been
directly associated with the acidification of soils in the U.S. More
recent information suggests that in parts of the Northeast, for
example, acid deposition has resulted in the accumulation of sulfur and
nitrogen in the soil beyond the levels that forests can use and retain,
and has accelerated the leaching of base cations, such as calcium and
magnesium, that help neutralize acid deposition. (Driscoll, 2001.) Some
western forest areas may also be experiencing nitrogen saturation
conditions, although the role of N deposition may vary from one
location to another (Fenn, 1998, 2003).
Aside from the effects of soil acidification, some studies have
shown that increased N deposition can alter tree susceptibility to
frost damage, insect and disease attack, and plant community structure.
However, other studies have not shown that similar results occur. In
all, the studies evaluated in the 1993 Criteria Document which focused
on the impact of excessive inputs of nitrogen in forest ecosystems
showed mixed results. The long response time of trees to environmental
stresses has made it difficult to fully understand how acid rain may
affect trees. It is also difficult to isolate the possible effects of
acid rain from stresses resulting from other natural and anthropogenic
origins. However, more recent studies appear to provide some evidence
that acid deposition has caused the death of red spruce trees,
particularly at higher elevations in the Northeast by decreasing cold
tolerance, and may be in part responsible for the extensive loss of
sugar maple in Pennsylvania. (Driscoll, 2001.)
Finally, in terrestrial systems in which the pre-existing balance
is marked by a competition among species for the available nitrogen,
additional nitrogen inputs, such as N deposition, may bring about an
alteration of the species mix. That is, a displacement of one kind of
vegetation (e.g., plants, grasses) with another may occur. While the
1995 Staff Paper for NOX noted that there were no documented
accounts of terrestrial ecosystems undergoing species shifts due to N
deposition in the U.S., later research provides some evidence
suggesting that elevated N deposition can contribute to shifts of
species compositions (e.g., Allen, 1998; Bowman, 2000).
(2) Wetlands. Wetlands include swamps, marshes, and bogs. In such
lands, water saturation is the dominant factor determining the nature
of soil development and the types of plants and animal communities
living in the soil and on its surface. These areas function as habitats
for plant and wildlife (among other useful environmental purposes),
including many rare and threatened plant species. Some of these plants
adapt to systems low in nitrogen or with low nutrient levels. Long-term
studies (greater than 3 years) of increased nitrogen loadings to
wetland systems in European countries have reported that increased
primary production of biomass can result in changes of interplant
competition. The 1995 Staff Paper for NOX reported that,
based on the evidence reviewed in the 1993 Criteria Document, ``the
staff believes we can anticipate similar effects from atmospheric N
deposition in the United States* * *.'' However, in the 1995 Staff
Paper for NOX, EPA found no documentation providing
sufficient evidence that such species changes have occurred or were
occurring at the time in the U.S.
(3) Aquatic ecosystems. Nitrogen deposition may adversely affect
aquatic ecosystems as a result of either acidification or
eutrophication. Both processes can cause a reduction in water quality
that makes the body of water unsuitable for many aquatic organisms.
The 1995 Staff Paper for NOX indicated that growing
evidence supported the concern that the impact of N deposition on
sensitive aquatic systems ``may be significant.'' Later studies have
shown much more clearly the harm that can result. Atmospheric nitrogen
can enter lakes and streams either as direct deposition to the water
surfaces or as N deposition to the watershed of which they are a part.
In some cases, nitrate may be temporarily stored in snow packs from
which it is subsequently released in more concentrated form in
snowmelt. In other cases, nitrogen deposited to the watershed may
subsequently be routed through plants and soil microorganisms and
transformed into other inorganic or organic nitrogen species which,
when they reach the water system, are only indirectly related to the
original deposition. To complicate matters, recent studies suggest
that, in addition to the contribution of nitrogen from anthropogenic
sources, nitrogen released from the weathering of nitrogen-bearing
bedrock, not commonly considered in the biogeochemical cycling of
nitrogen, may contribute a ``surprisingly large amount'' of nitrate to
natural waters. (Dahlgreen, 2002.)
Acidification may occur in two ways: Chronic (long-term)
acidification and episodic (short-term or seasonal) acidification.
Episodic acidification is more likely to be the primary problem in most
situations, with chronic acidification occurring mainly where excessive
nitrogen saturation exists. (NAPAP, 1998.) The main concern with
acidification of aquatic ecosystems is associated with freshwater
systems. Acidification impairs the water quality of lakes and streams
by lowering the pH levels, decreasing acid-neutralizing capacity, and
increasing aluminum concentrations (through the process of aluminum
mobilization from the soil, as
[[Page 59595]]
explained earlier). High levels of aluminum, considered toxic to fish
and other organisms, have been recorded in watersheds in the Northeast
associated with low levels of acid deposition. (Driscoll, 2001.)
Acid deposition may also increase the conversion of mercury to
organic (methyl) mercury in lakes where it is absorbed by aquatic
organisms and leads to increasing concentrations in the food chain.
Human consumption of fish containing high levels of methylmercury can
lead to problems with the central nervous system.
Regions of North America differ in their sensitivity to acidic
deposition and in the amount of acidic deposition they receive. Some
parts of the eastern U.S. are highly sensitive and chronically or
episodically receive damaging concentrations of acidic deposition. For
example, a 2001 report indicates that 41 percent of lakes in the
Adirondack Mountain region of New York and 15 percent of lakes in New
England show evidence of either chronic or episodic acidification, or
both. (Driscoll, 2001.) Other sensitive regions, such as the western
U.S., are unlikely to suffer adverse chronic effects but may experience
acidic conditions more on an episodic basis. Certain high-elevation
western lakes, in particular, are subject to episodes of acidic
deposition.
Eutrophication generally is a natural process by which aquatic
systems are enriched with the nutrients, including nitrogen, that are
presently limiting for primary production in that system. However, this
process can be accelerated by increased nutrient input resulting from
anthropogenic sources, e.g., agricultural runoff, urban runoff, leaking
septic systems, sewage discharge. Studies have also shown that N
deposition may directly and indirectly play a role in accelerated
eutrophication. When nitrogen is a limiting nutrient, input from
various origins can make a water system prone to eutrophication, with
impacts ranging from the increased turbidity and floating mats of macro
algae shading out beneficial submersed aquatic vegetation habitat, to
the exacerbation of noxious algae blooms, to the creation of low or no-
oxygen conditions which negatively affect fish populations. The
National Park Service (NPS) has reported that loadings of total N
deposition (wet and dry) have caused changes in aquatic chemistry and
biota in the Rocky Mountain National Park's high elevation ecosystems.
(U.S. Department of the Interior, 2002.) In the same report, the NPS
noted that increasing trends in N deposition at many parks in the
western U.S. result from both nitrate and ammonium.
The key to creating a linkage between levels of N deposition and
the eutrophication of aquatic systems is to demonstrate that the
productivity of the system is limited by nitrogen availability, and to
show that N deposition is a major source of nitrogen to the system.
Thus, while it appears that nitrogen inputs to aquatic systems may be
of general concern for eutrophic conditions, the significance of
nitrogen input will vary from site to site. (1995 Staff Paper for
NOX at 77.)
A 1993 National Research Council report identifying eutrophication
as the most serious pollution problem facing the estuarine waters of
the U.S. was reported in an EPA document issued in 1997, entitled
``Nitrogen Oxides: Impacts on Public Health and the Environment'' (p.
79). Nitrogen input is a major concern because nitrogen is the limiting
nutrient for algae growth in many estuaries and coastal water systems.
In contrast to the eutrophication concern, acidification typically is
not a concern, because estuaries and coastal waters receive substantial
amount of weathered material from terrestrial ecosystems and from
exchange with sea water.
Estimation of the contribution of atmospheric N deposition to the
eutrophication problem can be difficult because of the various direct
anthropogenic sources of nitrogen, including agricultural runoff and
sewage. Some studies have shown that nitrogen deposited from the
atmosphere can be a significant portion of the total nitrogen loadings
in specific locations, such as the Chesapeake Bay--the largest of the
130 estuaries in the U.S. It has been estimated that the proportion of
the total nitrate load to the Bay attributable to N deposition ranges
from 10 to 45 percent (NAPAP, 1998).
In most freshwater systems, including lakes and streams,
phosphorus, not nitrogen, is the limiting nutrient. Thus,
eutrophication by nitrogen inputs will only be a concern in lakes that
are chronically nitrogen limited and have a substantial total
phosphorus concentration. This condition is common only in lakes that
have received excessive inputs of anthropogenic phosphorus or, in rare
cases, have high concentrations of natural phosphorus. In the former
case, the primary dysfunction of the lakes is an excess supply of
phosphorus, and controlling N deposition would be an ineffective method
of gaining water quality improvement. In the latter case, N deposition
can measurably increase biomass and thus contribute to eutrophication
in lakes with high concentrations of natural phosphorus. Other lakes,
including some high-elevation lakes in the Rocky Mountains and Sierra
Nevada, are very low in both phosphorus and nitrogen; addition of
nitrogen can increase biomass and contribute to eutrophication in these
lakes also.
(4) Visibility impairment (Regional Haze). Nitrate particulates are
formed as a result of chemical reactions involving NO and
NO2 with other substances in the atmosphere, such as
ammonia. These particulates, as both fine and coarse particles, are
considered to be more responsible for visibility impairment than
NO2 directly. The fine particles can remain airborne for
considerable periods of time, may be transported long distances from
the NOX source, and impair visibility by either scattering
light or absorbing it.
The major cause of visibility impairment in the East is sulfates,
not nitrates which account for only 7 to 16 percent of the light
extinction in the East. However, nitrates in the West are responsible
for up to 45 percent of the light extinction.
Recent studies tend to provide more comprehensive documentation of
certain adverse effects than were reported earlier in the 1993 Criteria
Document. However, even in such later studies the inability to
establish quantifiable dose-response relationships NOX and
the various types of ecosystems remains to be a key problem. More study
is needed to resolve this problem.
VI. Final Actions
In the February 2005 proposal, we presented for public review and
comment the results of our review of the scientific and technical
evidence. We described the various health and welfare effects
associated with NO2 and other forms of NOX and
proposed our decision about the adequacy of the existing NO2
increments. On the basis of the available information, we proposed not
to change the existing PSD regulations for NOX. We also
proposed to find that the existing regulations, including the
increments for NOX expressed as annual average ambient
concentrations of NO2 satisfied the requirements under
sections 166(c) and 166(d) of the Act.
In today's action, we are retaining the existing NO2
increments without change. In addition, we are amending the text of our
PSD regulations at 40
[[Page 59596]]
CFR 51.166 \16\ to clarify that any State may employ an alternative
approach to the NO2 increments if the State's approach meets
certain requirements. Separately, we will soon publish a supplemental
notice of proposed rulemaking that provides more details on how a State
that achieves the NOX emission reductions under CAIR can
utilize its CAIR-related reductions as part of its alternative approach
to the NO2 increments. In this section of the preamble, we
describe our rationale for the final action we are taking today on the
NO2 increments and respond to significant comments we
received on the relevant portions of the proposal.
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\16\ Section 51.166 of the CFR contains minimum requirements for
the submittal and adoption of regulations that are part of a SIP. We
are not making similar changes to the Federal PSD regulations at 40
CFR 52.21.
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A. Retain Existing Increment System for NOX
1. Existing Characteristics of the Regulatory Scheme Fulfill Statutory
Criteria
In the February 2005 proposal, we addressed how several aspects of
our PSD regulations for NOX that were not controverted in
the EDF v. EPA court challenge served to satisfy many of the factors
applicable under section 166(c). This analysis helps show how our PSD
regulations for NOX, as a whole, satisfy the criteria in
section 166.
We continue to believe that many of the factors applicable under
section 166(c) are fulfilled by the elements of our regulations that
were not challenged in the EDF v. EPA case. Since we do not interpret
the court's decision to require us to reevaluate the entire regulatory
framework of the PSD regulations for NOX we established in
1988, with respect to option 1 of the proposal, we focused our review
on the level, time period, and pollutant form (NO2)
reflected in the increments we included in the 1988 PSD regulations for
NOX. Thus, when a factor applicable under section 166(c) was
fully satisfied by an aspect of the existing regulations that was not
questioned by the court, we did not consider that factor any further in
our evaluation of the characteristics of the increment.
In many cases, an aspect of our regulations that was not
controverted in the court challenge partially contributes to the
fulfillment of an applicable factor but does not fully satisfy that
factor. In these instances, to determine if changes to the increments
are necessary to satisfy the factors applicable under section 166(c),
we also considered the effectiveness of the unchallenged parts of our
regulations in conjunction with the three primary characteristics of
the increments that were challenged. We believe our obligations under
section 166(c) of the Act are satisfied when all of our pollutant-
specific PSD regulations for NOX (including the level and
other characteristics of any increment) collectively satisfy the
factors applicable under 166(c) of the Act.
a. Increment System
Two of the factors applicable under section 166(c) are fulfilled by
employing an increment system in our pollutant-specific PSD regulations
for NOX. In this action, we are retaining this basic
framework for our pollutant-specific PSD regulations for
NOX.
An increment-based program fulfills our obligation under section
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).
An increment is the maximum allowable increase of an air pollutant
that is allowed to occur above the applicable baseline concentration.
The baseline concentration in a particular area is generally the
ambient pollutant concentration at the time the first complete PSD
permit application is submitted (i.e., the baseline date) \17\ by a new
major stationary source or a major modification locating in or
otherwise affecting that area.\18\ By establishing the maximum
allowable level of ambient pollutant concentration increase in a
particular area, an increment defines ``significant deterioration.''
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 permitting
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. Thus, areas where the air pollutant
concentration is near the level allowed by the NAAQS may not be able to
use the full amount of pollutant concentration increase allowed by the
increment.
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\17\ This date is actually identified as the 'minor source
baseline'' date in EPA regulations. 40 CFR 51.166(b)(14); 40 CFR
52.21(b)(14). Because the baseline concentration does not include
emissions from certain major sources that consume increment, EPA has
distinguished between the 'minor source baseline'' date and the
'major source baseline date.'' See 40 CFR 51.166(b)(13)-(14); 40 CFR
52.21(b)(13)-(14).
\18\ For PSD baseline purposes, a source generally ``affects''
an area when its new emissions increase is projected to result in an
ambient pollutant increase of 1 [mu]g/m3 (annual average)
or more of the pollutant.
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Thus, an increment is a quantitative value that establishes the
``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 more stringent control
technologies in order to avoid violating the increment. Given that the
PSD increment level may be consumed by cumulative emissions increases
over time, it may become necessary to impose increasingly more
stringent levels of control on new sources in order to avoid violating
the increment or ensuring that there will be increment remaining for
additional economic growth. The more stringent control technologies
utilized in these areas 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'').
Because the existing increment-based regulatory framework, which
was not controverted in EPA v. EDF, satisfies these criteria we are
retaining the increment approach in this action.
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 its PSD regulations for
NOX but gave EPA the discretion to employ increments if
appropriate to meet the criteria and
[[Page 59597]]
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
allowing 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.
In addition, in a separate rulemaking action, we are continuing to
develop an alternative regulatory framework that would enable a State
to demonstrate that the requirements of section 166 are satisfied by
reducing NOX emissions from existing sources under the CAIR
and other similar programs.
b. Area Classifications
Having increments set at different levels for each class of PSD
area helps to fulfill two of the factors applicable under section
166(c) of the Act. Under the three-tiered area classification scheme
established by Congress, Class I areas are areas where especially clean
air is most desirable. The original Class I areas established by
Congress included national parks, wilderness areas, and other special
areas that require an extra level of protection. It stands to reason
that the most stringent increment is imposed in Class I areas. 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 least stringent 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.
The Petitioners in EDF v. EPA did not contest EPA's decision in 1988 to
employ this same classification scheme in our pollutant-specific PSD
regulations for NOX.
Establishing the most stringent increments in Class I areas helps
fulfill EPA's obligation to establish regulations for NOX
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 redesignating 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 stringent to allow the siting of new or modified
sources. The procedures specified by the Act for such a redesignation
require a commitment of the State government to the creation of such an
area, extensive public review, 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)). Our
1988 analysis, 53 FR at 3702-05, and the subsequent issuance of PSD
permits for major new and modified sources of NOX since that
time \19\ tend to confirm that, with the existing increment levels, the
three-tiered classification system has allowed for economic growth,
consistent with the preservation of clean air resources.
---------------------------------------------------------------------------
\19\ EPA does not formally track the issuance of PSD permits
across the country, but EPA's Regional Offices have confirmed that
various PSD permits for sources of NOX have been issued
by many of the States in their respective jurisdictions.
---------------------------------------------------------------------------
However, we do not believe that this framework alone completely
satisfies the factors applicable under section 166(c) of the Act. The
increment that is 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 increments further below.
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 sections 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 set forth in our proposal,
70 FR at 8896, we continue to believe these factors are fulfilled by
employing the permit review procedures.
d. Air Quality Related Values Review by Federal Land Manager and
Permitting Authority
Under an increment approach, we consider the review of AQRVs in
Class I areas by the Federal Land Manager (FLM) and State permitting
authority to be an additional measure that helps to satisfy the factors
in sections 166(c) and 160(2) which require that EPA's PSD regulations
for NOX protect air quality values, and parks and other
special areas, respectively. In the 1988 rulemaking addressing PSD for
NOX, EPA extended the AQRV review procedures set forth in
sections 51.166(p) and 52.21(p) to cover NO2. 53 FR at 3704.
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.
Section 165(d) creates a scheme in which the FLM and permitting
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. 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 permitting 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 permitting
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
[[Page 59598]]
impact on AQRVs.\20\ 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.\21\
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\20\ 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). In 1988, EPA made this provision applicable to the
PSD provisions for NOX, with a cap of 25 [mu]g/
m3 - the NO2 Class II increment. 53 FR at
3704; 40 CFR 51.166(p)(4) and 52.21(p)(5).
\21\ 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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In our February 2005 proposal, we referred to this process as the
``FLM review.'' However, we recognize this term is somewhat of an
oversimplification because it fails to account for the role of the
State permitting authority. In this final action, we more precisely
describe this process as the review of AQRVs by the FLM and permitting
authority.
Incorporating these AQRV review procedures into the PSD regulations
for NOX 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
we stated in the proposed 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.\22\
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\22\ 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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Section 166(d) of the CAA provides that EPA may promulgate measures
other than increments to satisfy the requirements of section 166.
Legislative history indicates 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 4 LH at 1401.
One commenter asserted that the AQRV review process is not
effective in protecting air quality in national parks and wilderness
areas because the FLM does not have unilateral authority to prevent the
issuance of a permit when it alleges that a proposed new source or
modification will have an adverse impact on an AQRV. We recognize that
the FLM has the burden to convince the permitting authority that there
will be an adverse impact on AQRVs in situations where the proposed
project will not cause an increment to be violated. Nevertheless, we do
not agree that the effectiveness of this process for reviewing impacts
on AQRVs is diminished simply because the ultimate decision to issue or
deny a permit does not rest with the FLM in all cases.
While the permitting authority has the discretion to disagree with
the FLM's analysis, that discretion is not unfettered. See In the
matter of Hadson Power 14--Buena Vista, 4 EAD 258, 276 (Oct. 5, 1992)
(opinion of EPA's Environmental Appeals Board in PSD Appeal No. 92-3,
92-4, 92-5). The permitting authority must carefully consider the FLM's
analysis. If a permitting authority is not convinced that there will be
an adverse impact on AQRVs from the proposed facility, the permitting
authority must provide a ``rational basis'' for such a conclusion. 50
FR 28549 (July 12, 1985); Hadson Power at 276. In addition, our
visibility regulations require that States provide an explanation when
they disagree with an FLM's conclusion that visibility will be
adversely impacted. 40 CFR 51.307(a)(3). The District of Columbia
Circuit Court has recently observed that a State must justify its
decision in writing when it disagrees with an FLM report finding an
adverse impact on visibility. See National Parks Conservation Ass'n v.
Manson, No. 04-5327, slip op. at 8 (D.C. Cir. July 1, 2005).
The value of the FLM review procedure is that it requires a review
of impacts on AQRVs by the FLM and permitting authority for each
project that may have an adverse impact on AQRVs in a specific,
localized area. In those cases where the increment is not violated and
the permitting authority agrees that a proposed project will adversely
affect AQRVs, the parks and other special areas will be protected by
denial of the permit or by requiring the applicant to modify the
project to alleviate the adverse impact. Although it is not the final
decisionmaker on this question in such a situation, the FLM plays an
important and material role by raising these issues for consideration
by the permitting authority, which in the majority of cases will be the
State.
Furthermore, we have not asserted that the AQRV review process
alone is sufficient to satisfy the requirements of section 166(c) for
NOX. As discussed below, we believe the statutory factors
are fulfilled when the review of AQRVs is applied in conjunction with
increments and other aspects of our PSD regulations.
Several commenters recommended that we improve the FLM review
process by providing specific guidance on how to evaluate and manage
adverse impacts on AQRVs from NOX emissions. These
commenters called for a more specific framework or systematic approach
for conducting the review of impacts on AQRVs and determining whether
impacts are adverse. Some requested that EPA provide more definition of
the concept of AQRVs and circumstances when an AQRV is adversely
impacted.
We recognize that the process of reviewing impacts on AQRVs is
somewhat ambiguous because it is loosely defined. The CAA does not
define AQRV, except to note that it includes visibility. Section
165(d)(1)(B). Some additional insight can be gained from the following
description in legislative history:
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. 95-127 at 36, reprinted at 3 LH at 1410.
However, we are not prepared at this time to provide further
definition for these concepts in this rulemaking action for pollutant-
specific PSD regulations for NOX. We believe the existing
AQRV review process provides the avenue to satisfy the factors
applicable under section 166(c) of the Act in conjunction
[[Page 59599]]
with other aspects of our PSD regulations.
The AQRV review process applies to SO2 and PM as well,
and thus is broader than the scope of this rulemaking for
NOX. We have been engaged in a separate action to consider
refinements to the AQRV review process. In 1996, the Agency, among
other refinements, proposed the following definition of AQRV:
* * * visibility or a scenic, cultural, physical, biological,
ecological, or recreational resource that may be affected by a
change in air quality, as defined by the Federal Land Manager for
Federal lands, or by the applicable State or Indian Governing Body
for nonfederal lands.
61 FR 38250, 38322 (July 23, 1996). However, we have not reached the
closure on the evaluation of these issues. We will continue to work
with Federal land management agencies and consult with States and other
stakeholder groups on potential reforms to the AQRV review process,
including evaluating the potential of a critical loads approach, as
discussed in section VII of this preamble.
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 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 CAA,
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. We agree with the commenter
who pointed out that our regulations under section 166 must also
provide protection for Class II and Class III areas. While not as
intensive a review as the AQRV analysis required in Class I areas, the
consideration of impairments to visibility, soils, and vegetation
through the additional impacts analysis contributes to the satisfaction
of the factors applicable under section 166(c) of the CAA 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 CAA, is included in
EPA's PSD regulations and thus is also part of the regulatory framework
for the Agency's pollutant-specific regulations for NOX. 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 is
rigorous and in practice has required significant reductions in the
pollutant emissions from new and modified sources. The control of
NOX emissions through the application of BACT helps to
protect air quality values, public health and welfare, and parks and
other special areas.
2. Characteristics of Increments for NOX
Because EDF v. EPA concerned certain characteristics of the
increments for NOX that we had established in 1988, we
sought comments in our proposal on the possible need to (1) create
additional increments for forms of NOX other than
NO2 alone; (2) promulgate additional increments for an
averaging period other than the existing annual period, i.e., ``short-
term'' increments; and (3) increase the stringency of the existing
NO2 increments by lowering the allowable levels. Several
commenters opposed our proposal to retain the annual NO2
increments at existing levels for all area classifications. However,
many commenters supported the existing increments, believing that they
provide adequate environmental protection and meet the requirements of
section 166(c) of the Act.
The majority of commenters that opposed retaining the existing
increments recommended we adopt various alternatives to the existing
NO2 increments, including new short-term increments,
increments measured by a different form of NOX, and the use
of critical loads in lieu of the present increment system. A few
commenters felt that the existing levels of the increments are not
adequate to protect the environment but did not recommend specific ways
to change them. One commenter supported the existing increments but
recommended that EPA enact additional mechanisms for protecting AQRVs
in Class I areas. Two commenters supported revising and retaining the
increment system on an interim basis but then emphasized the need for
additional studies to ultimately improve the PSD program for
NOX by switching to a critical loads approach.
After considering these comments, we have decided to retain the
existing increments for NOX without any of the changes
recommended by commenters. We have not been persuaded by comments
(including the information contained in studies provided by the
commenters) that there is sufficient basis for EPA to modify the ``safe
harbor'' increments. Thus, we are retaining annual NO2
increments for each area classification with a level based on the same
percentages of the NAAQS Congress employed to establish the
SO2 increments. As a result, the Class I increment for
NO2 remains at 2.5 [mu]g/m3 (annual average). The
Class II increment for NO2 is 25 [mu]g/m3 (annual
average) and the Class III increment for NO2 is 50 [mu]g/
m3 (annual average).
In evaluating the level, averaging period, and form of increments
for NOX, we applied the following four factors applicable
under section 166(c): (1) Protect air quality values; (2) protect
public health and welfare from adverse effects from air pollution that
occur even when the air quality meets the NAAQS; (3) protect air
quality in parks and special areas; and (4) ensure economic growth
consistent with preservation of clean air resources.\23\
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\23\ We have paraphrased these factors here and in other
sections to facilitate the explanation of our reasoning. However, we
recognize that the statutory language is broader than the shorthand
we use here for convenience.
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[[Page 59600]]
We continue to believe that the other four factors identified in
sections 166(c) and 160 of the Act do not relate to the level, time
period, and form of the increments and thus are more appropriately
considered when determining the overall framework for PSD regulations.
Since we believe that those other factors are satisfied by the
increment and area classification framework and other measures
contained within our PSD regulations, we do not believe that it is
necessary to further consider those other four factors when evaluating
the characteristics of increments of NOX.
a. Fundamental Elements of Increments
In the proposal, we described three elements which we believed were
fundamental to the PSD increments under the regulatory framework
established by Congress. We considered these elements in determining
whether to modify the existing increments. First, an increment
represents an allowable marginal increase in ambient air pollution
concentrations resulting from increases in the emissions of a
particular pollutant after the ``baseline'' date in the affected PSD
area. Second, increments are not intended to remedy the effects of pre-
existing sources of pollution in attainment areas, but rather prevent
excessive growth in emissions in these areas that already have ambient
air pollution levels below the NAAQS. The third fundamental element of
increments is that they are intended to allow the same level of growth
in each area with a particular classification and thus should be
uniform across the nation for each area classification. Most commenters
did not question these fundamental elements of increments, but some
concerns were raised.
(1) Marginal level of increase. Increments represent the maximum
allowable level of pollutant concentration increase in an area where
the air quality is in attainment with the NAAQS or has been designated
``unclassifiable.'' Thus, an increment is essentially a marginal level
of increase in air pollution that is allowable for particular areas.
The statutory increments are expressed as ambient concentrations rather
than mass values. An increment differs from the NAAQS in that an
increment is not an absolute air quality ceiling. The pollutant
increase allowed by an increment is added to the ``baseline'' air
pollution levels existing in an affected PSD area at the time a new or
modified major source submits an application for a PSD construction
permit. Thus, in applying the factors applicable under section 166(c),
we interpreted section 166 of the Act to require an analysis of the
impacts on air quality values, health and welfare, and parks and
special areas that could occur as a result of some marginal increase in
the concentration of air pollution in an area.
As noted earlier, EPA does not interpret the PSD program to require
it to set increments at a level where there will be no negative effects
from a marginal increase in air pollution in the amount of the
increment. Congress did not anticipate that an increment would be a
level of increase below which there would be no negative effects. An
increment is the level that defines ``significant'' deterioration; it
allows some deterioration of air quality. The PSD program allows for
some increase in effects when necessary to ensure that economic growth
may continue to occur consistent with the preservation of clean air
resources.
(2) Increments need not remedy existing air pollution. Because an
increment is an allowable level of increase, it does not function to
reduce air pollution in existence before the baseline dates. As its
name indicates, the PSD program is intended to protect against
significant deterioration of the air quality in attainment and
unclassifiable areas from the construction and operation of new and
modified sources of a particular size. Thus, the PSD program limits
increases in emissions of a pollutant (as measured by the increase in
ambient concentrations of the pollutant) but does not seek to reduce
existing emissions or ambient air pollutant concentrations to a
particular level.
Several commenters seemed to suggest that the increment system
should somehow be designed to improve the air quality to remedy
existing effects. However, we believe it is clear that the increments
established by Congress were only intended to define the allowable
levels of marginal increase in air pollution above a baseline
concentration that are established in each area when the first major
source applies for a PSD permit in that area. 42 U.S.C. 7479(4). As a
result, we do not believe we are required to set increments at a level
intended to alleviate existing negative effects.
When we evaluated the characteristics of increments necessary to
prevent significant deterioration of air quality, we also recognized
that EPA has adopted several other programs under the CAA that reduce
the adverse effects from existing air pollution sources. These programs
are designed to reduce emissions from existing sources, while the
increments serve the complementary function of limiting increases in
emissions from the construction of new major sources and the
modification of existing ones. Since our proposal, EPA has taken a
series of actions that require States to achieve substantial reductions
in NOX emissions.
On March 10, 2005, EPA finalized the CAIR (70 FR 25162, May 12,
2005), which requires substantial emissions reductions of
SO2 and NOX from sources in 28 eastern States and
the District of Columbia to help downwind PM2.5 and 8-hour
ozone nonattainment areas achieve the NAAQS. Under this program,
emissions of NOX are regulated as a precursor of either
ozone or fine PM, or both. EPA is requiring the affected States to
submit revised SIPs that include control measures to reduce emissions
of NOX to assist in achieving the NAAQS.\24\ This program is
based on State obligations to address interstate transport of pollution
under section 110(a)(2)(D) of the Act. The required NOX
reductions must be implemented by the States in two phases, with the
first phase beginning in 2009 (covering 2009-2014) and the second phase
beginning in 2015. The EPA estimates that the two-phase CAIR program
will reduce NOX emissions by a total of 2 million tons from
2003 emissions levels.
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\24\ The required reductions in NOX emissions will
also result in substantial visibility improvements and reductions in
nitrogen deposition in many parts of the eastern United States.
---------------------------------------------------------------------------
Reduction of NOX emissions from existing sources is also
required under EPA's 1998 NOX SIP Call, which also addresses
State obligations to address interstate transport of pollution. The
NOX SIP Call requires 22 eastern States and the District of
Columbia to submit SIP revisions that prescribe NOX
emissions reductions by a specified deadline. The EPA has projected
that approximately 900,000 tons of NOX per ozone season will
be reduced as a result of this particular program. While these
reductions are intended primarily to improve air quality in the East
with respect to ozone, it is clear that the required decreases in
NOX emissions will also decrease acid deposition, nitrogen
loadings to aquatic and terrestrial ecosystems, and ambient
concentrations of NO2.
In addition, EPA has taken further action to reduce NOX
emissions from existing sources that contribute to visibility problems,
through implementation of the Regional Haze program under sections 169A
and 169B of part C.\25\ On July 6, 2005, EPA issued
[[Page 59601]]
revised regulations for regional haze, including guidelines for Best
Available Retrofit Technology (BART) determinations. The regulations
require States to submit SIPs to address regional haze visibility
impairment in 156 mandatory Class I Federal areas located throughout
the U.S. 70 FR 39104. As required by the Act, the regulations require
certain major stationary sources, placed in service between August 7,
1962 and August 7, 1977, and which emit 250 tons or more per year of a
visibility-impairing pollutant, including NOX, to undergo a
BART analysis.
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\25\ When the visibility provisions were enacted, the House
committee report specifically recognized that the ``visibility
problem is caused primarily by emission into the atmosphere of
sulfur dioxide, oxides of nitrogen, and particulate matter * * *''
H.R. Rep. 95-294, at 204, reprinted in 4 LH at 2671. NOX
may result in visibility impairment either locally (a coherent plume
effect) or by contributing to regional haze, which has been
recognized as primarily a fine particle phenomenon. 1995 Staff Paper
for NOX at 89. For the reasons discussed earlier, we do
not believe we need to consider PM effects in this court-ordered
reevaluation of the NO2 increments.
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The BART requirements are in addition to other elements of the
Regional Haze program in regulations that EPA originally promulgated in
1999. 64 FR 35714 (July 1, 1999) (``Regional Haze rule''). The main
components of this rule require States to: (1) Submit SIPs that provide
for ``reasonable progress'' toward achieving ``natural visibility
conditions'' in Class I areas; (2) provide for an improvement in
visibility in the 20 percent most impaired days; (3) ensure no
degradation in visibility occurs on the 20 percent clearest days; and
(4) determine the annual rate of visibility improvement that would lead
to ``natural visibility'' conditions in 60 years.
At the time that Congress established the Regional Haze Program, a
Congressional committee recognized that the PSD program was not
necessarily created to alleviate adverse effects resulting from
contributions by existing sources. When it was writing section 169A of
the Act at the same time that it established the PSD program, the House
recorded the following observations in a committee report:
[T]he committee recognizes that one mechanism which has been
suggested for protecting these areas, the mandatory Class I
increments of new section 160 (`Prevention of Significant
Deterioration') do not protect adequately visibility in Class I
areas. First, inadequately controlled, existing gross emitters such
as the Four Corners plant would not be affected by the significant
deterioration provisions of the bill. Their emissions are part of
the baseline, and would not be required to be reduced by new section
160 of the act.
H. Rep. 95-294, at 205, 4 LH at 2672 (emphasis added). This statement
indicates that protection of air quality values under section 166(c) is
provided when an increment limits significant deterioration of air
quality resulting from increases in emissions after the baseline date,
but does not require an increment that addresses adverse impacts on air
quality values, such as visibility, that are caused by pre-existing
emissions.
In addition, in the 1990 Amendments, Congress enacted title IV to
address the problem of acid deposition. We believe this supports an
interpretation that the PSD measures called for in section 166 need not
address acid deposition impacts that are attributed to emissions that
existed prior to the baseline date. When we use an increment approach,
our view is that the PSD program is intended to focus on establishing a
marginal level of increase in emissions that will prevent significant
air quality deterioration and, in conjunction with AQRVs identified by
the FLM, provide protection against increases in adverse effects, such
as acidification, that may result from emissions increases after the
baseline date.
Thus, in areas where the PSD baseline has not yet been established,
the emissions reductions achieved by these programs will result in
lower PSD baseline concentrations. Then the increments will operate as
an allowable level of marginal increase that prevents the significant
deterioration of air quality beyond the baseline concentration in these
attainment areas. This approach is consistent with Congressional intent
that the baseline concentration, representing the air quality in an
attainment area subject to PSD, be established on the date of the first
application for a permit by a PSD source affecting that area. 42 U.S.C.
7479(4). See also Alabama Power v. Costle, 606 F.2d 1068, 1088-89 (D.C.
Cir. 1979).
(3) Increments should be uniform for each area classification.
Several commenters disagreed with our view that the increments should
be uniform throughout the U.S. in each area with the same
classification. These commenters argued that uniform national standards
are not required by the Act. We continue to believe that the PSD
program is intended to allow the air quality in each area of the
country attaining the NAAQS, and with the same area classification, to
``deteriorate'' by the same amount for each subject pollutant,
regardless of the existing air quality when the increment is initially
triggered in a particular area, as long as such growth allowed within
the constraints of the increment does not cause adverse impacts on
site-specific AQRVs or other important values.\26\ In this way, the PSD
increments avoid having a disproportionate impact on growth that might
disadvantage some communities, recognizing that the increments in
themselves would not address existing negative impacts but cannot allow
significant new adverse impacts. Congress established the foundation
for uniform national increments when it created increments for
SO2 and PM under section 165 of the Act.
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\26\ Congress also recognized that some areas may have air
pollution levels already near the levels allowed by the applicable
NAAQS, whereby the NAAQS would govern and the full amount of
increment might not be usable.
---------------------------------------------------------------------------
Thus, when we use the framework of an increment and area
classification system in the national PSD regulations for a particular
pollutant, we believe that we should establish a single increment for
each class of area such that this allowable level of increase applies
uniformly to all areas in the nation with that particular
classification. This is necessary for EPA to ensure equitable treatment
by allowing similar levels of emissions growth for all regions of the
country that a State elects to classify in a particular manner. The
following statement from the legislative history of the PSD program
supports this interpretation of what Congress intended:
Some suggestions were made that the pollution increments should
be calculated as a function of existing levels of pollution in each
area. But the inequities inherent in such an approach are readily
evident * * *. The committee's approach--increments calculated as a
percentage of the national standard--eliminates those inequities.
All areas of the same classification would be allowed the same
absolute increase in pollution, regardless of existing levels of
pollution.
H. Rep. 95-294, at 153, 4 LH at 2620. See also S. Rep. 95-127, at 30, 3
LH at 1404 (``These increments are the same for all nondeterioration
areas, thus providing equity for all areas''). This indicates that
Congress did not intend to impose more stringent restrictions under the
PSD program on particular areas of the country based on their current
levels of air pollution, unless, of course, the current levels of
pollution concentrations are so near the NAAQS that the full amount of
incremental change cannot be allowed.
Instead, Congress provided States with the authority to determine
situations when it might be desirable to allow a greater or lesser
level of air quality protection in a particular area. Except for
certain Federal lands designated as mandatory Class I areas
[[Page 59602]]
that could not be reclassified, Congress classified all other areas as
Class II areas and gave the States the power to reclassify these areas
to Class I or Class III to provide for greater protection of air
quality or allow more growth, depending on the values of the State and
the community in that area. The ability to reclassify most areas allows
the States to make their own choices about which areas require more
protection of air quality and which areas should be allowed more growth
consistent with the protection of air quality. See H.R. Rep. 95-294, at
153-154, 4 LH at 2620-2621.
The same equitable considerations are applicable when we establish
PSD regulations containing increments and area classifications under
section 166 of the Act. Since Congress did not intend for the
increments it established to impose a disproportionate impact on
particular areas, we do not believe it intended for EPA to do so under
section 166 of the Act. Thus, to treat all areas of the country in an
equitable manner, it is necessary for us to establish uniform national
increments for NO2 that define a maximum allowable increase
for each of the three area classifications. Then, States and tribes in
exercising their unique authority to manage their own air quality, in
accordance with their own unique and individual goals and objectives,
may decide how to best manage their air quality resources by
reassigning area classifications within any particular area (other than
mandatory Federal Class I areas).
Some of the commenters opposing uniform national increments
disagreed with our view that the increments should be uniform because
they felt we improperly focused on ``providing equal opportunity for
new emission sources without fulfilling [our] statutory duty to protect
ecological resources across the country.'' What is required, according
to these commenters, is ``the protection of air quality related values
and fulfillment of the Act's goals and purposes--which unquestionably
include protection of individual parks, wilderness areas, and other
areas of important value.'' Moreover, these commenters argued that
because of our insistence on the use of uniform increments no amount of
information would ever provide a ``nationally applicable'' basis for
EPA to revise the NO2 increments, because, as EPA
recognizes, ``the sensitivity of individual ecosystems varies greatly''
across locations.
We do not believe that our position supporting uniform national
increments under the national PSD program necessarily conflicts with
our responsibility to protect sensitive ecological resources located
throughout the U.S. The use of uniform national increments--only one
component of the PSD regulations for NOX--does not mean that
the PSD program is not responsive to different levels of adverse
effects in particularly sensitive areas, such as Class I areas.
We weighed Congress' goal to treat all areas with a particular
classification the same against the unique variability in ecosystem
effects that may result from NOX emissions (described
elsewhere in this preamble). We ultimately concluded that multiple
goals could be achieved by retaining uniform national increments for
NO2 for each area classification and augmenting them with an
additional case-by-case procedural review which can identify and
protect against variable effects that could occur in especially
sensitive areas, even when the increment is not fully consumed. Indeed,
this is what Congress did under its original PSD program requirements
for SO2 and PM.
This approach is embodied in the framework for the PSD regulations
for NOX that we adopted in 1988. As described in section
VI.A.1. above, each permit application is subject to an ``additional
impacts'' analysis that allows the permitting authority to consider the
sensitivity of a particular area. In Class I areas, the AQRV review
procedures provide further protection, notwithstanding the allowable
amount of pollutant concentration increase allowed by the Class I
increment, for the air quality values and the national parks and
wilderness areas included in Class I areas. These two sets of special
procedures are an important part of the overall regulations for
preventing significant air quality deterioration, while retaining the
uniform national increments. This approach allows EPA to achieve the
equity of setting a uniform increment level for all areas with a
particular classification, while directing that permitting authorities
conduct a more intensive, site-specific review to identify effects that
might occur in a more sensitive area but not necessarily in all areas
of the country with that classification.
As noted earlier, we read section 166 of the Act to direct EPA to
establish a system of regulations containing provisions that
collectively satisfy the content requirements in sections 166(c) and
166(d) of the Act. Thus, we think Congress contemplated that we would
consider all the provisions in our regulations as a group when
establishing particular aspects of those regulations. As a result, we
believe it is appropriate and consistent with our statutory obligations
to consider the protection provided by the additional impacts analysis
and the review of AQRVs in Class I areas when establishing increments.
We also believe that the factors applicable under section 166(c) of
the Act are met when we establish a uniform national increment for
NO2 for each class of area and augment the increment system
with an additional case-by-case procedural review to identify and
protect against variable adverse effects that could occur in especially
sensitive areas before the amount of pollutant increase defined by the
increment is reached.
We, nevertheless, understand the commenters' concern over our
position that the increments should be uniform, when they conclude that
no amount of evidence concerning ecological effects will be useful for
revising the increments, because of the highly variable sensitivity of
ecosystems throughout the U.S. While we have indicated that it would be
very difficult to use such variable data to modify the increments as
uniform increments, we believe it may be possible to develop uniform
increments that provide for a reasonable level of protection in most
areas if sufficient national critical loads data are available to
determine the range of adverse effects that must be considered.
Clearly, such extensive data are not available at this time.
Some commenters argued that we should establish local standards
under section 166 to address the known variable effects from
NOX. For the most part, however, the comments related to the
use of a critical loads approach rather than a set increment or
variable increments for NOX. In either case, however,
because of the equitable considerations and State prerogatives to
classify areas described above, we do not believe that Congress
intended for EPA to create a federally imposed system of regional or
locally based increments or to authorize EPA to do so to address any
variability in potential effects. Likewise, we do not believe it is
permissible or appropriate for us to establish uniform increments at
levels so stringent that they prevent any adverse impact on the most
sensitive receptors in any part of the U.S. Although such an approach
might achieve uniformity across all areas, it would unduly restrict
growth in those areas of the country where adverse effects may not
occur at the levels where the adverse effects occur in more sensitive
areas.
Furthermore, our regulations also provide protection against
localized impacts by requiring each new or
[[Page 59603]]
modified source subject to PSD to apply BACT. The BACT requirement
provides for a case-by-case State determination, taking into account
energy, environmental, and economic impacts and other costs to
determine the best method for minimizing a source's emissions. See
section 169(3) of the Act.
b. Analytical approaches for establishing increments. Mindful of
the above considerations about the characteristics of the increments,
we reviewed the scientific and technical evidence available for the
1996 review of the NO2 NAAQS in order to determine whether,
and to what extent, the ``safe harbor'' increments should be modified
to satisfy sections 166(c) and 160 of the Act. As summarized in section
V of this preamble, EPA's conclusions about whether nitrogen at levels
at or below the NAAQS caused negative environmental impacts were mixed,
but included findings that negative effects associated with nitrogen
deposition (1) did not likely exist (e.g., eutrophication of freshwater
systems); (2) were insignificant (e.g., impacts on terrestrial
vegetation); or (3) not clearly understood (e.g., chronic and episodic
acidification). There was some evidence that at levels below the NAAQS,
nitrogen was at least in part contributing to known negative
environmental effects. Ultimately, we tried two different analytical
approaches--a quantitative and a qualitative evaluation--to reach our
decision about whether we had a basis for modifying the safe harbor
NO2 increments so that the increments themselves could
provide greater protection against such adverse effects. These
approaches and the relevant findings are described below.
(1) Quantitative Evaluation. An increment is not like the NAAQS in
that it does not set a uniform pollutant concentration ``ceiling''
against which potential negative ecosystem responses could be
evaluated. Instead, an increment allows a uniform allowable pollutant
concentration increase above a baseline concentration in an area.
Therefore, we evaluated how protective the existing NO2
increments are by trying to compare the maximum pollutant concentration
increases allowed by the NO2 increments against the
pollutant concentrations at which various environmental responses
occur. See 70 FR 8900.
Unfortunately, this quantitative approach was hindered because the
available evidence we reviewed typically was inconclusive regarding the
pollutant concentrations at which negative environmental responses
associated with NOX could be expected to occur. As described
in section V, in many instances, there was uncertainty about the
specific relationship between the pollutant, NO2, and its
precise role in causing a particular negative response to an
environmental receptor.
The Agency encountered the same problem in the past during the last
periodic review of the NO2 NAAQS. Because of our inability
to derive from the available evidence a way to quantify how much of a
contribution atmospheric deposition of nitrogen is making to negative
environmental effects and what levels of reduction are necessary to
remedy the situation, we were precluded from recommending secondary
(welfare-based) NAAQS for NOX. See 1995 Staff Paper for
NOX, vol. 1, pp. 91-95. For similar reasons, we could not
quantitatively identify the level of increase in NOX
emissions at which significant negative environmental effects occur.
Thus, we do not have a quantitative way to determine whether or how to
modify the existing NO2 increments in order to prevent
significant deterioration.
Recognizing the inconclusive nature of the scientific and technical
evidence contained in the 1993 Criteria Document, we looked beyond that
information to later studies that might provide the information we
needed to determine the quantitative dose-response relationships
associated with NOX in the atmosphere. We found that later
studies enable us to better understand N deposition trends, the
mechanisms by which NOX contributes to N deposition, and the
ways in which sensitive ecosystem resources respond to excess nitrogen.
However, even in the later studies, there continues to be significant
uncertainty about the quantitative dose-response relationships that we
need to evaluate the effectiveness of the existing NO2
increments.
Some commenters saw the later studies, which provide evidence of
increased levels of N deposition in some areas of the U.S., and
scientific findings more closely linking nitrogen deposition to
observed negative ecosystem responses as ``proof'' that the existing
NO2 increments are ineffective. We disagree with the
commenters' claims that evidence of localized impacts in specific
sensitive areas, as reflected in later studies, necessarily proves that
the existing NO2 increments across the U.S. are ineffective.
It is not clear at this time whether a lower, more stringent increment
level that we might select for the national uniform increments would
prevent the adverse effects that are currently being observed in a
particular park or sensitive area of the U.S. We have already
acknowledged that increments are not intended to prevent all negative
impacts in all areas, and that the PSD regulations for NOX
contain other mechanisms for protecting sensitive resources where the
increment alone does not do so.
We cannot deny the commenters' claims that some areas of the U.S.
(primarily in the West) have continued to experience increased rates of
N deposition, as studies have shown. However, such information does not
change the fact that we are currently unable to find sufficient
evidence upon which to establish a dose-response relationship
associated with NOX so that we can scientifically support
more stringent numerical levels for the NO2 increments
should we otherwise conclude that a modification is appropriate.
Instead, as mentioned above, most published studies have still largely
focused on documenting the adverse effects and making links to N
deposition as a primary cause. These studies typically fall short of
defining a quantitative relationship between emissions of
NOX, N deposition rates, and the negative responses being
observed.
There are many recent studies that examine the various sources of
the nitrogen input (industry, transportation, agriculture), N
deposition budget, geographical location of different nitrogen
loadings, and trends in deposition rates, as well as the specific
effects of nitrogen deposition on specific ecosystems. These studies in
general emphasize the importance of reducing current emissions of
NOX as part of a strategy for reducing observed impacts and
promoting ecosystem recovery. However, such studies are not yet able to
provide the information needed to identify the dose-response
relationships associated with NOX.
There are several key difficulties associated with the ability to
establish a quantitative relationship between NOX and the
negative environmental responses to which nitrogen compounds are known
to contribute. Below, we summarize some of the key areas of difficulty
for which a better understanding is needed.
(1) Relationship between NOX emissions and N deposition.
It is generally recognized that reducing NOX emissions will
result in reductions in N deposition as well. However, the quantitative
relationship between the two is complex and still uncertain. Some
recent studies attempt to address the various parameters that together
could help to establish this relationship. For example, some recent
study results provide evidence of a quantitative
[[Page 59604]]
relationship between NOX emissions and precipitation (wet
deposition) NO3 in the eastern U.S. However, the results of
efforts to establish a quantitative relationship between NOX
emissions and total (wet and dry) nitrogen deposition have thus far
been inconclusive (Butler, 2000, 2003). These studies point to the
reactive nature of components of NOX as being part of the
problem. Besides producing nitric acid or nitrate aerosols, both
components of N deposition, NOX can also result in the
formation of peroxyacetyl nitrates (PAN), ozone and other oxidant
species. Also, it has been observed that high year-to-year variability
in N deposition does not match the relatively small total
NOX emissions changes in the eastern U.S.
(2) Nitrogen deposition budget. Another complication is that total
N deposition typically includes the combined contributions of emissions
from NOX (which form nitrates and nitric acid in the
atmosphere) and ammonia (ammonium). Emissions of ammonia can be
converted to any other nitrogen species and can contribute to all
nitrogen-related inputs. (Ammonia Workshop, 2003.) Ammonia and ammonium
found in the atmosphere, and in the soil, are generally the result of
agricultural activities that are neither regulated directly by the PSD
program nor counted towards the consumption of the NO2
increment (and would not be counted against the increment for
NOX measured as any other form of NOX). In order
to better understand the relationship between the different sources of
nitrogen and the ecosystems affected, it is important to also recognize
contributions from ammonia and ammonium.
One challenge with understanding the contributions from different
nitrogen species is that the mix of pollutant inputs that affect
sensitive ecosystems is dynamic. A 2005 report using data from the
National Atmospheric Deposition Program National Trends Network has
shown that from 1985 to 2002 marked changes in concentrations of
sulfate, nitrate and ammonium in wet deposition have occurred. The
reported trends indicate ``changes in the mix of gases and particles
scavenged by precipitation, possibly reflecting changes in emissions,
atmospheric chemical transformations, and weather patterns.'' (Lehmann,
2005.)
In some areas of the country, for example, it is reported that
emissions of ammonia are increasing at a greater rate than emissions of
NOX. At the same time, atmospheric ammonium concentrations
in wet deposition are increasing at a greater rate than are nitrate
concentrations (Fenn, 2003a). The same study indicated that
NOX emissions in the western U.S. are projected to decrease
28 percent by 2018, while ammonia emissions are projected to increase
by 16 percent. Another study reports the occurrence of significant
increases of ammonia and dissolved inorganic nitrogen in much of the
U.S., while reporting regionally significant increases and decreases in
nitrate. (Lehmann, 2005.)
Another challenge is that in many areas, particularly in the West,
the accuracy of the inventory for ammonia is very uncertain, and
historic deposition monitoring (collected mainly in the form of wet
deposition) typically has not included the ammonia component. (Fenn,
2003a.) This leads to problems in estimating total N deposition.
We believe that a better understanding of ammonia emissions and the
ammonia levels in the atmosphere, and their contribution to total N
deposition, is also needed in order to obtain a more complete picture
of the atmospheric partitioning of N emissions and total mass of N
deposition. This will help us better understand the dose-response
relationships between the different sources of nitrogen and the
ecosystems affected by them.
Finally, the N deposition budget and associated deposition rates
are determined by a complex interaction of multiple processes. Modeling
efforts to simulate the formation and deposition of nitrogen species in
the West involve a number of data inputs including emissions of
nitrogen from various sources of NOX and ammonia,
meteorological parameters, chemical transformation and partitioning of
nitrogen species, aerosol dynamics, and rates of wet and dry
deposition. (Fenn, 2003a.)
(3) Ecosystem variety and sensitivity. Even if a particular
threshold value could be identified to quantifiably relate ambient
NOX concentrations to an adverse effect in a given ecosystem
and location, the same threshold is not likely to apply to similar
ecosystems throughout the U.S. In our most recent review of the
NO2 NAAQS, we observed that ``a great degree of diversity
exists among ecosystem types, as well as in the mechanism by which
these systems assimilate nitrogen inputs.'' 60 FR 52831, October 11,
1995 at 52881. As a result, we concluded, ``the relationship between
nitrogen deposition rates and their potential environmental impact is
to a large degree site- or region-specific and may vary considerably
over broader geographical areas or from one system to another because
of the amount, form, and timing of nitrogen deposition, forest type and
status, soil types and status, the character of the receiving
waterbodies, the history of land management and disturbances across the
watersheds and regions, and exposure to other pollutants.'' Id.
A 2005 paper describes the progress being made by FLMs in
identifying the resources that are at risk or sensitive to air
pollution in the parks and wilderness areas under their jurisdiction.
(Porter, 2005.) Reportedly, the FLMs have also completed qualitative
descriptions of the various resources. It is noted that such
information is ``specific to each wilderness area or park, because of
the tremendous diversity in ecosystem characteristics, sensitivities,
and stressors on federal lands.''
Thus, for example, ecosystems in the Northeast have been more
strongly affected by acid deposition than have ecosystems in the
western U.S. On the other hand, the problem of greater concern in the
West results from nitrogen enrichment, which includes nitrogen
saturation, eutrophication and alterations in biological communities.
In addition, some areas in the West are noted for their sensitivity to
relatively low doses of N deposition, particularly at higher
elevations.
In addition to the difficulties described above, there are other
considerations that add to the complexity of determining dose-response
relationships for NOX. These include: (1) In addition to
multiple nitrogen compounds that must be identified, the observed
ecosystem responses to pollutant deposition can also be the result of
combined pollutant impacts, such as the acidification of lakes from
both sulfur and nitrogen deposition; (2) short-term increases of
nitrates in streams have occurred in the absence of concurrent
increases of N deposition but have been positively correlated with mean
annual air temperatures (Murdoch, 1998), and high levels of nitrogen
have occurred in the absence of anthropogenic sources; and (3) it may
take years before certain ecosystems come into balance with the
cumulative amounts of nitrogen inputs (making it difficult to determine
the level at which recovery begins).
The difficulty of establishing the dose-response relationships
associated with NOX is further illustrated by EPA's
experience in evaluating the feasibility of setting an acid deposition
standard. Under section 404 of the 1990 Amendments, Pub. L. 101-549,
Congress directed EPA to conduct a study of the feasibility and
effectiveness
[[Page 59605]]
of an acid deposition standard(s), to report to Congress on the role
that a deposition standard(s) might play in supplementing the acidic
deposition program adopted in title IV, and to determine what measures
would be needed to integrate an acid deposition standard with that
program.
The EPA completed this study, ``Acid Deposition Feasibility Study,
Report to Congress'' (1995), which concluded that current scientific
uncertainties associated with determining the level of an acid
deposition standard(s) are significant, and did not recommend setting
an acid deposition standard. See State of New York v. Browner, 50 F.
Supp. 2d 141, 149 (N.D.N.Y. 1999) (rejecting States' claim that section
404 required that the report include a deposition standard that would
be sufficient to protect sensitive aquatic and terrestrial resources,
and affirming EPA interpretation that duty was limited to
``consideration of a description'' of such standards).
While EPA has recognized that programs, such as the CAIR (70 FR
25162, May 12, 2005), that are intended to achieve NOX
emissions reductions pursuant to other statutory provisions will help
mitigate acid deposition problems, none of those programs purport to
set an acid deposition standard.
We note that one particular study, cited by two commenters, did
include a ``conservative recommendation'' for a threshold level (i.e.,
critical load) for nitrogen deposition based on ``wetfall for Class I
areas in the central Rocky Mountains.'' (Williams, 2000.) In addition,
it is reported that other efforts are underway by scientists using
empirical studies and modeling to estimate critical loads for other
areas of the U.S. Also, the NPS has spent considerable time evaluating
the effects of both sulfur and nitrogen deposition in several national
parks, and has estimated critical loadings associated with some of
their important natural resources. (Porter, 2005.)
We have considered whether the concept of a ``critical load'' could
be used to identify an alternative increment level. At this time, we do
not believe that the current status of such research can be used as a
basis for us to establish national increments, or other measures of
NOX, that could be applied throughout the U.S. We do,
however, provide further discussion in section VII concerning the
critical load concept and its potential for being an effective air
quality management tool.
As discussed in the welfare effects section (V.D.2), although we
are seeing effects at current nitrogen deposition rates, for the above
reasons we believe that it is not technically or practicably feasible
to identify a quantitative basis for concluding that the existing
NO2 increments are inadequate to provide protection against
the types of adverse effects on ecosystems that may occur in some areas
notwithstanding compliance with the NAAQS. In particular, it is not
possible to determine a different level of increment protection that
would define a significant deterioration level for ecosystem effects
associated with emissions of NOX. Thus, currently available
information does not provide a nationally applicable, quantitative
basis for revising the existing NO2 increments.
(2) Qualitative Evaluation. As explained above, the available
scientific and technical data do not yet enable us to adequately relate
ambient concentrations of NOX 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 existing NO2 increments or some alternative
increments meet the applicable factors.
In this situation, we believe that determining 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 no or
minimal increases in NOX emissions or establish an increment
for another form of NOX because there are data indicating
that an effect may be attributable to NOX emissions.
However, as explained earlier, 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 NOX
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' 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 a marginal increase of a particular level
below the ``safe harbor'' 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 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 NOX. This
[[Page 59606]]
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 permitting 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 are consistent with the values
of each State and individual communities within States.
c. Three characteristics of increments for NOX.
(1) Form of increment. A significant issue in the EDF v. EPA case
was EPA's action in 1988 to establish an increment for only one form of
NOX, i.e., NO2. We promulgated increments for
NO2 in 1988 because NO2 was the only form of
NOX for which we had established a NAAQS at that time.
However, the court held in EDF v. EPA that section 166(c) of the Act
``commands the Administrator to inquire into a pollutant's relation to
the goals and purposes of the statute, and we find nothing in the
language or legislative history suggesting that this duty could be
satisfied simply by referencing the ambient standards.'' 898 F.2d at
190. As a result, in this rulemaking action on remand, we weighed the
relevant evidence to determine whether the data supported the potential
use of other forms of NOX to serve as measures for the
increments and, if so, what numerical levels would be appropriate.
We requested comment on whether we should adopt increments for
other forms of NOX and received several comments
recommending that EPA do so. Some of these commenters claimed that the
statute requires EPA to examine and regulate nitrogen compounds other
than NO2, to protect the air quality, especially in Class I
areas. Therefore, these commenters called upon EPA to develop
increments that accounted for other forms of NOX, such as
nitric acid, nitrate, ammonium nitrate, and for ozone. Some commenters
recognized the complexity of the total nitrogen deposition problem and
recommended that EPA revise and retain the existing increments on an
interim basis, while undertaking the necessary steps to study the full
scope of the problems associated with NOX and revising the
PSD regulations for NOX accordingly. For the reasons
discussed below, we have decided not to add any additional increments
based on other forms of NOX to the existing increments for
NO2.
Under the ``contingent safe harbor'' approach discussed above, we
began our analysis with ``safe harbor'' increments that address
increases in ambient NO2 concentrations. Since 1988, EPA has
not identified a basis upon which to establish a NAAQS for any form of
NOX other than NO2. Thus, it remains the case
today that the only NAAQS established for NOX are the
current NO2 NAAQS which have not changed since 1971. We
believe that increments based on the same pollutant for which we have a
NAAQS are the ``safe harbor'' for the purposes of this rulemaking.
Establishing increments for this form of NOX is ``at
least as effective'' as the statutory increments in section 163 of the
Act. Congress established statutory increments in section 163 for only
those forms of PM and sulfur oxides for which we had promulgated a
NAAQS.\27\ As discussed above, the need for an increment necessarily
derives from the establishment of a NAAQS, which is the basic measure
of air quality under the CAA. Thus, an increment based on this basic
measure of air quality is ``at least as effective'' as the statutory
increments in section 163 of the Act. The court in EDF v. EPA rejected
the argument that increments based on the same form of NOX
as the NAAQS were not ``as effective as'' the increments in section
163. 898 F.2d at 190.
---------------------------------------------------------------------------
\27\ Since that time, we have refined the original NAAQS for PM
(then measured as TSP) to focus on coarse (PM10) and fine
(PM2.5) particulate matter. We subsequently established
increments for PM10 in accordance with section 166(f) of
the Act. 58 FR 31622 (June 3, 1993). We are considering establishing
increments for PM2.5.
---------------------------------------------------------------------------
We acknowledge that the available scientific and technical evidence
indicates that the range of adverse effects being observed in the
various ecosystems studied are the result of contributions from several
forms of NOX other than NO2. We noted earlier in
this preamble that seven species of oxides of nitrogen are known to
occur in the atmosphere. However, anthropogenic emissions of
NOX predominantly originate as NO and quickly oxidize into
NO2. As described in section V of the preamble, under the
discussion of environmental effects, many of the negative effects
indirectly related to emissions of NO and NO2 are caused (or
contributed to) largely by nitrogen compounds (e.g., nitrates, nitric
acid) which result from chemical transformations of NO2 in
the atmosphere.
In particular, nitrates (NO3-), primarily in
the form of nitric acid (HNO3) and nitrate aerosols such as
ammonium nitrate (NH4NO3), are primary
constituents of nitrogen deposition and can play a significant role in
producing welfare effects that are indirectly attributable to emissions
of NO and NO2. As a result, we examined the feasibility of
establishing numerical increments that would include measurement of
nitrates.
In the February 2005 proposal, we noted several reasons why we
believed that it was not necessary to adopt individual increments for
nitrate. First, the existing NO2 increments, which limit the
allowable increase of NO2 in a given area, serve also to
limit the amount of nitrate in the atmosphere.\28\ That is, by limiting
the allowable increase in ambient concentrations of NO2 in
the immediate area surrounding a proposed new or modified PSD source,
some limit can effectively be placed on downwind formations of nitrate
compounds as well.
---------------------------------------------------------------------------
\28\ Another source of nitrates, not associated with emissions
of NOX, is the nitrification of ammonium by bacteria in
stream beds.
---------------------------------------------------------------------------
We also noted that ambient nitrate often exists in the atmosphere
in particulate form, e.g., ammonium nitrate and nitrate salts formed
from nitric acid. These forms are known to contribute to regional haze.
Based on this, we indicated our belief that nitrates could be more
effectively regulated under our national PM program.
Notwithstanding these reasons for not needing a nitrate-based
increment, we further explained that the available scientific and
technical evidence available for our consideration did not exist (1) to
adequately establish a quantifiable relationship between NOX
emissions (NO/NO2) and nitrogen deposition products,
including nitrates, or (2) to set numerical levels for such increments.
Some of the commenters who supported the need for increments based
on a broader measure of NOX referenced more recent studies
which point to the worsening trends of nitrogen deposition, and
observations of adverse effects, in various areas of the country as
evidence that the existing NO2 increments are ineffective.
On this basis, the commenters claimed that the existing NO2
increments did not satisfy sections 166(c) and 160 of the Act. While we
do not discount the findings contained in these studies, we do not
believe that these more recent studies provide the necessary
information either to establish broader nitrogen-based increments or to
indicate that the NO2 increments are ineffective.
As was the case with the more recent studies that we reviewed, the
studies cited by commenters are based on observations of adverse
ecological effects in specific localized areas where sensitive
ecosystem receptors are known to exist. Such studies clearly have
[[Page 59607]]
enhanced our ability to understand the mechanics of the pollutant
deposition process, identify deposition trends, and document the
adverse effects to which nitrogen deposition contributes. Yet the same
studies in most cases continue to fall short of enabling us to quantify
the levels of deposition responsible for the recorded changes. In fact,
many of these studies conclude by calling for additional research to
collect the data necessary to quantify the dose-response relationships
associated with nitrogen.
Even considering more recent evidence, we continue to believe that
it is not feasible to develop broader-based increments for
NOX at this time, and the nitrate deposition effects in
local areas where sensitive ecosystems exist will be more effectively
addressed via the broader set of PSD regulations for NOX and
by various PM control programs that will apply in those local areas.
Finally, with regard to commenters' recommendations that we
establish increments to address the effects of ozone, we indicated
earlier that we do not believe Congress intended for us to consider the
effects of other regulated pollutants, such as ozone, when establishing
increments for NOX. We continue to believe that the
increments for NOX need only consider effects resulting from
ambient NO2 and other forms of NOX (resulting
from the transformation of NO2 in the atmosphere), rather
than secondary pollutants for which Congress expected separate PSD
regulations, including increments. See relevant comments concerning
increments for secondary pollutants associated with NOX and
our responses to those comments in section V.D. of this preamble.
A key problem that we have already discussed, however, is that
studies of nitrogen deposition indicate that the nitrogen input from
total atmospheric nitrogen deposition is not simply the result of
emissions of NOX, but of other nitrogen compounds as well,
including ammonia and ammonium. For example, when ambient
concentrations of ammonia and nitric acid are sufficiently high,
ammonium nitrate can be formed and both the ammonium and the nitrate
become components of nitrogen deposition contributing nitrogen to an
ecosystem. For these reasons, we do not believe it is feasible to adopt
an additional increment for another form of NOX to protect
air quality values, health and welfare, and parks and special areas,
from NOX emissions increases associated with new and
modified PSD sources. Thus we are adopting the ``safe harbor''
increments and retaining the existing increments for NO2.
Under these circumstances, the NAAQS provides a reasonable benchmark
for identifying the pollutant to be used in an increment.
Section 160(1) of the Act is expressed by using the NAAQS as a
benchmark and also uses standards that mirror the standards applicable
to the NAAQS-setting process-- ``protect public health and welfare.''
The court in EDF v. EPA rejected use of the NAAQS as the ``sole basis''
for deriving the increments for NOX but did not preclude EPA
from adopting only increments based on the same pollutant as the NAAQS
when EPA has determined that additional increments are not needed after
considering the factors applicable under section 166(c) of the Act. See
898 F.2d at 190. As we have explained earlier, several of the ``other
forms of NOX'' that commenters recommend be included in the
increments for NOX are more appropriately addressed under
programs for other criteria pollutants, as well as some of the multi-
pollutant emissions reductions programs that have been established
across the U.S.
(2) Increment averaging periods. The existing NO2
increments, promulgated in 1988, are based on an annual averaging
period, consistent with the NO2 NAAQS. In the 1988 rule, EPA
did not set short-term NO2 increments because a short-term
NAAQS for NO2 that would define short-term air quality for
NO2 did not exist. However, the court directed us to
evaluate whether, considering the factors applicable under section
166(c), we should promulgate additional increments for short-term
averaging times. 898 F.2d at 190. Thus, we have evaluated and requested
comment on the need to promulgate additional NO2 increments
based on a short-term averaging time to satisfy section 166(c) of the
Act. Several of the commenters that opposed EPA's proposed decision to
retain the existing increments without modifying them argued that
short-term increments were needed to meet our responsibility to provide
health and welfare protection under the requirements of section 166(c)
of the Act.
However, for the reasons discussed below, we are not persuaded that
short-term NO2 increments are necessary to satisfy the
factors applicable under section 166(c).
Under the ``contingent safe harbor'' approach discussed above, we
began our analysis with the ``safe harbor'' increments that are based
on the same annual averaging time used in the NAAQS. Since 1988, EPA
has not found cause to promulgate a NAAQS for any averaging period
other than the annual average. Thus, since this is the only averaging
time used in the current NAAQS, we consider an increment that employs
this averaging time to be a ``safe harbor'' that is ``at least as
effective'' as the statutory increments in section 163 of the Act. The
increments listed in section 163 of the Act are based on the same
averaging times that were contained in the NAAQS at the time Congress
adopted this provision. The NAAQS are the basic measure of air quality
under the CAA. Therefore, an increment that uses this standard as a
benchmark is ``at least as effective'' as the statutory increments in
section 163 of the Act. The court in EDF v. EPA rejected the argument
that an increment based on the same averaging time as the NAAQS was not
``as effective as'' the increments in section 163. 898 F.2d at 190.
We reviewed the scientific and technical evidence available in the
1993 Criteria Document for NOX in light of the section
166(c) criteria to determine whether it justified the need for a short-
term increment, even though no short-term NO2 NAAQS existed
from which to derive a short-term safe harbor increment. As we
indicated in the February 2005 proposal, the available evidence did not
identify any adverse health effects from short-term exposure to ambient
NO2 concentrations in areas with air quality meeting the
NO2 NAAQS. Thus, we proposed to find that a short-term
increment was not needed to provide any additional health protection
beyond assuring that the existing increments would keep ambient
NO2 concentrations at levels below the NO2 NAAQS.
Some commenters disagreed with us and expressed the need for a 1-
hour NO2 increment for health-related purposes. Some of
these commenters urged us to consider recent health data and the fact
that California has adopted a short-term health standard for
NO2 exposure. However, we continue to believe, based
primarily on the evidence in the 1993 Criteria Document and 1995 Staff
Paper for NOX, that there is insufficient evidence to
justify a national short-term NO2 increment to provide
additional health protection. As mentioned above, as part of the last
review of the NO2 NAAQS in 1996, EPA did not find adequate
evidence that health effects from short-term exposure NO2
occurred in areas where air quality levels met the NO2
NAAQS.
The Administrator concluded from that review that the annual
standard of 0.053 parts per million (ppm) NO2 provides
``substantial protection'' against the identified health effects (mild
changes in pulmonary function or airway responsiveness in sensitive
individuals) associated with short-term
[[Page 59608]]
peaks occurring in the range of 0.2 to 0.5 ppm--almost one order of
magnitude higher than the annual standard. 60 FR 52875, 52879-80
(October 11, 1995). The adequacy of the annual standard to protect
against these potential short-term effects was further supported by the
absence of documented effects in some studies at higher concentrations
(3 ppm to 4 ppm).
We continue to believe that the existing primary annual
NO2 NAAQS provides sufficient protection against the
likelihood of short-term NO2 concentrations that would cause
adverse human health responses in most areas of the U.S. We have no
evidence at this time showing that there is a problem from a national
perspective concerning short-term NO2 concentrations that
would represent a threat to human health, and the commenters have not
provided information indicating a national problem for us to consider.
We do know that high maximum 1-hour NO2 concentrations have
been measured in a few locations, including California--the only State
that has adopted a short-term air quality standard for NO2
(0.25 ppm, 1-hour).\29\
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\29\ It should be noted, however, that California's standard was
not established on the basis of new information since our last
periodic review of the NO2 NAAQS. California established
an ``Adverse Level'' for NO2 (0.25 ppm, 1-hour) in 1962.
In 1969, the California Air Resources Board set a short-term air
quality standard for NO2 using the original alert level.
---------------------------------------------------------------------------
We have reviewed NO2 air quality data collected from 592
monitoring site locations nationally from EPA's Air Quality System to
determine how effective the current primary annual NO2 NAAQS
is in preventing high short-term NO2 concentrations. These
data show that, since 1999, only 14 sites (a few with multiple
occurrences) across the U.S. have recorded peak 1-hour concentrations
exceeding 0.25 ppm NO2. Only one monitoring site recorded
such peaks from 2003-2004. Thus, from a national perspective, we do not
find support for a short-term NO2 increment to provide
health protection beyond that being provided by the existing annual
primary NO2 NAAQS.
We are aware of the fact that later studies have been published
concerning human responses to short-term exposure to ambient
NO2 concentrations. These studies will be considered in the
Agency's next periodic review of the NO2 NAAQS. To the
extent that any new relevant information is incorporated into the
Criteria Document for oxides of nitrogen, we will carefully evaluate
such evidence under the rigorous process described earlier in this
preamble, involving CASAC and a public review process, to determine
whether it is appropriate to adopt a short-term primary NO2
NAAQS. In accordance with the requirements of section 166 of the Act,
following promulgation of any revised NAAQS for NOX, based
on the same body of scientific and technical evidence, we will also
review that evidence against the requirements of section 166(c) to
determine the need to modify the existing NO2 increments.
However, at this time we do not believe there is a need to modify the
existing NO2 increments to provide a nationwide level of
health protection beyond what is being provided by the primary annual
NO2 NAAQS.
In addition, the information that we reviewed concerning welfare
effects associated with short-term exposure to NOX did not
convince us that there was a justification for a short-term increment
to provide additional protection against adverse welfare effects. The
available information indicated that known impacts were insignificant
in some cases (e.g., effects on terrestrial vegetation), while in other
cases (e.g., chronic acidification of surface waters) insufficient
information existed to quantify how much of a contribution nitrogen
deposition was making to the problem and what levels of reduction would
be needed to remedy the negative impact. The effects that we reviewed
are summarized in greater detail below and in section V of this
preamble.
Two commenters recommended that we adopt a 1-hour NO2
increment to prevent coherent plume (discoloration) visibility
impairment. We do not believe that a short-term NO2
increment for such purposes is supported by the available evidence. As
we indicated in our description of welfare effects in section V of this
preamble, NO2 can cause a discoloration effect in a plume
resulting in potential visibility impairment. However, the evidence
also indicates that the presence of particulate in the plume can result
in similar discoloration. Thus, the problem is not exclusively caused
by NO2. Moreover, the 1995 Staff Paper for NOX
noted that despite the known light-absorbing qualities of
NO2, ``there are relatively little data available for
judging the actual importance of NO2 to visual air
quality.''
Visibility impairment associated with coherent plumes is currently
addressed as part of the requirements for the AQRV review and the
additional impacts analysis. This methodology measures visibility
impairment resulting from multiple pollutants. The test for visibility
impairment of this type is typically applied to sources locating less
than 50 kilometers from a Class I area, and involves modeling the
potential plume impacts to calculate 1-hour impacts within the elevated
plume based on the concentrations of fine primary particulates and
NO2 emitted by the source. The effects of secondarily formed
sulfates can also be considered, where applicable and appropriate, in
the modeling procedure.
We do not believe it would be appropriate to establish a short-term
NO2 increment to address this visibility impairment problem
when it is known that the problem is associated with multi-pollutant
impacts. The problems associated with coherent plumes are currently
addressed through protection of AQRVs and the ``additional impacts''
analysis. (Congress explicitly identified visibility as an example of
an AQRV.) We believe that this is the most effective way to address
this multi-pollutant problem.
Some commenters recommended short-term increments to protect
against the increasing NOX pollution impacts. In this
regard, we do not find a justification to establish a short-term
increment for either NO2 or any other form of
NOX. In the latest review of the NO2 NAAQS, the
Administrator concluded that the impact on terrestrial vegetation from
short-term exposures to NO2 under existing ambient levels is
insignificant and did not warrant a short-term standard (1995 Staff
Paper for NOX, p. 91). The Administrator also considered the
welfare impacts from nitrate deposition during the last review of the
NO2 NAAQS. The evidence indicated, however, that none of the
welfare impacts from nitrates were directly attributed to short-term
ambient nitrate concentrations. In those cases where nitrogen
deposition was shown to cause episodic or ``short-term'' effects, such
as episodic acidification of streamwaters, the problem was typically
the result of a long-term accumulation of nitrogen compounds that were
released suddenly to the ecosystem (e.g., snowmelt runoff to lakes and
streams) rather than the direct result of short-term concentrations of
nitrates being transferred from the atmosphere.
The ability to quantitatively relate N deposition to episodic
acidification conditions is further hampered by evidence indicating
that, because of conditions of nitrogen saturation, episodic
acidification of surface waters and increased loadings to estuaries
could worsen even without concurrent increases in N deposition. Later
studies have verified this situation and have indicated that
temperature change, among other things, rather than direct changes in
the N deposition rate, can be
[[Page 59609]]
more influential in the increased acidification conditions. One later
study we reviewed subsequent to the proposal revealed a positive
correlation between short-term increases in stream nitrate
concentrations and mean annual air temperature (affecting nitrogen
movement in a watershed), while finding no statistically significant
correlation between deposition and stream nitrate concentrations.
(Murdoch, 1988.)
One commenter recommended a short-term ammonium nitrate increment
to address visibility problems associated with regional haze. However,
we do not believe it is necessary to address this pollutant through our
PSD regulations for NOX. Ammonium nitrate is a form of PM
(i.e., nitrate particulate), and we already addressed the contribution
of ammonium nitrates to total ambient PM levels and their effects on
visibility (regional haze) under the PM program.\30\ In revising the
NAAQS for PM in 1997, EPA considered the welfare effects of PM,
including nitrates, on visibility impairment in considering the need to
revise the secondary PM standards. In doing this, we considered the
pertinent scientific and technical information contained in the current
Criteria Document for PM and Staff Paper for PM to determine what an
appropriate level would be for a secondary standard to address adverse
effects of PM on visibility. We concluded from that process that a 24-
hour PM2.5 primary standard in conjunction with a national
regional haze program would be the more effective way to address
regional variations in the adverse effects of fine particulate on
visibility than by establishing national secondary standards for PM
that would be lower than the PM2.5 primary standards. See 62
FR 38652, July 18, 1997 at 38679-38683.
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\30\ ``Impairment of visibility in multi-State regions, urban
areas, and Class I areas is clearly an effect of particulate matter
on public welfare.'' OAQPS Staff Paper for Particulate Matter, July
1996 at p. VIII-15.
---------------------------------------------------------------------------
An important consideration in arriving at this decision was that
there were significant differences in then-current visibility
conditions in different areas of the country that could not effectively
be addressed by a uniform national standard. Because our national
control strategy for PM will include consideration of ammonium nitrate
particles, we find no basis for establishing a short-term increment for
ammonium nitrate to protect against visibility impairment as part of
the PSD regulations for NOX.
EPA has also recognized that NOX results in the
formation of ozone and nitrate particulates under certain conditions.
Although ozone, PM10, and PM2.5 have short-term
NAAQS to protect against public health effects associated with short-
term exposure to these pollutants, EPA does not consider the impacts
from these criteria pollutants, because it interprets section 166 to
require consideration of these criteria pollutants separate and
distinct from the duty to consider NOX.
Based on these considerations, we believe that an annual average
increment for NO2, coupled with the requirements for the
``additional impacts'' and AQRV protection in Class I areas, is
sufficient to protect air quality values, health and welfare, including
the sensitive ecosystems in parks and other special areas. Thus, we
revert to the ``safe harbor'' of the existing annual NO2
increments and decline to adopt additional increments for shorter
averaging periods under this final action.
(3) Level of NO2 increment. Having concluded from the
available scientific and technical evidence that additional increments
based on other forms of NOX or other averaging periods are
either not necessary or not feasible, the remaining issue we evaluated
in response to the court remand was whether there was a need for lower
annual NO2 increments. Our review of the applicable
scientific and technical evidence provided no basis for us to propose
modifying the levels of the existing NO2 increments.
As part of our proposal, the analysis of the appropriate levels for
NO2 increments began by establishing a ``safe harbor''
increment level that was ``at least as effective as'' the increments
established by Congress in section 163 of the Act. 42 U.S.C. 7476(d).
Under our interpretation of the Act, we preliminarily concluded that
these ``safe harbor'' levels established the minimum stringency levels
(or highest marginal increase in concentration levels) that we may use
as the increments for NO2 for each class of area.
The court in EDF v. EPA recognized that the ``at least as
effective'' standard in section 166(d) of the Act is satisfied when we
establish increments using the percentage-of-NAAQS approach that
Congress used to establish the statutory increments. See 898 F.2d at
188. This approach involves using the same percentages that Congress
used to calculate the PM and SO2 increments from the NAAQS
in effect at that time for these pollutants. Because Congress used
different percentages to calculate the Class I increments for PM and
SO2, we had to decide which of these percentages was
appropriate for the Class I NO2 increment. For the reasons
described in the 1988 NO2 increment rulemaking, we
considered it appropriate for NO2 increments to be derived
using the same percentages that Congress used for SO2
because NO2 more closely resembles SO2 than PM in
its characteristics and sources. See 53 FR 3698, 3700 (February 8,
1988).
Because the NO2 increments have not changed since 1988,
the percentage-of-NAAQS approach yields the same levels that we derived
in 1988. Thus, using this approach, the ``safe harbor'' level for the
Class I NO2 increment was calculated as 2.5 [mu]g/m\3\
(annual average), a level equal to 2.5 percent of the NO2
NAAQS. For the Class II NO2 increment, the ``safe harbor''
level is 25 [mu]g/m\3\--25 percent of the NO2 NAAQS. For the
Class III NO2 increment, the ``safe harbor'' level is 50
[mu]g/m\3\--50 percent of the NO2 NAAQS.
Our next step was to consider the factors applicable under section
166(c) and evaluate whether we needed to revise the ``safe harbor''
level to satisfy these factors. To the extent we were to find that the
marginal increase in concentration allowed by the ``safe harbor'' level
did not adequately protect against these effects and ensure economic
growth consistent with preservation of clean air resources, we were
obligated to attempt to identify an alternative level of marginal
increase that would satisfy the factors applicable under section
166(c).
In order to identify the appropriate level of increase for ambient
NO2 concentrations, we attempted to establish a quantitative
relationship between the emissions of NO2 and potential
adverse effects. Unfortunately, this approach was hindered for several
reasons. First, the available evidence we reviewed was inconclusive
regarding the pollutant concentrations at which the effects may occur.
As previously described, in some instances, the available scientific
and technical evidence revealed no significant effects, while in other
cases the evidence revealed uncertainty about the direct relationship
between the pollutant and its precise role in causing the effect. This
requires an understanding of the intermediate transformation processes
and the deposition patterns and total quantities of those nitrogen
compounds which may contribute to the known or observed effects, as
well as the nitrogen contribution to ecosystems from natural
geobiochemical processes.
Second, since many of the negative effects were associated with
total nitrogen deposition (indirectly associated with NO2),
i.e., caused by NOX compounds which have been transformed
from NO2 in the
[[Page 59610]]
atmosphere, it was also necessary to attempt to understand the
quantitative relationship between emissions of NO2 (the
regulated form of the increment) and the observed negative
environmental effects. Such relationships could not be sufficiently
identified from the available evidence.
As a result of these findings, we proposed to find that the
necessary scientific evidence was not yet available to determine that
the existing safe harbor NO2 increments are not adequately
protective for purposes of defining ``significant deterioration.''
Therefore, we proposed to retain the existing NO2 increments
to limit allowable increases in ambient pollution associated with
NOX emissions and protect against health and welfare effects
that might occur in areas where the air quality is better than the
NO2 NAAQS.
Some commenters objected to this proposed decision to retain the
existing increments, although most of them generally did not suggest
ways to revise the existing levels (other than to recommend short-term
NO2 increments) to make them more protective. For the most
part, the studies and information provided by these commenters advance
the knowledge about N deposition trends and how nitrogen inputs
adversely affect sensitive resources at various locations, but they
also support our original conclusions in the February 2005 proposal
that there is not yet sufficient evidence to quantify a dose-response
relationship between NOX and the various negative effects
being observed and reported.
We could establish more stringent increments simply by setting the
allowable levels of pollutant increases at lower numerical values;
however, we can find no basis for determining what particular lower
values would provide the ``correct'' level of protection against the
types of effects that have been identified. Consequently, we believe it
would be inappropriate to arbitrarily select more stringent values for
the NO2 increments that are not supported by the available
scientific and technical evidence.
Lacking a clear quantitative basis for establishing lower increment
levels, we conducted a qualitative evaluation of the safe harbor
increments in light of the considerations discussed above. To achieve
equity and protect against effects that are variable across regions of
the country, we believe each of the NO2 increments should be
set at a level that reasonably protects air quality values, health and
welfare, and parks and special areas across the country, while also
balancing the need to allow economic growth.
We continue to believe our ultimate obligation under section 166 of
the Act is to establish a set of regulations for NOX which
contain provisions that collectively satisfy the content requirements
in sections 166(c) and 166(d) of the Act. Thus, we think Congress
contemplated that we would consider the entire set of regulations when
we establish specific aspects of those regulations. As a result, we
believe it is appropriate and consistent with our statutory obligations
to consider the protection provided by the additional impacts analysis
and the FLM review of AQRVs when evaluating the level of NO2
increments that defines ``significant deterioration.''
Thus, based on the overall insufficiency of the available
scientific and technical evidences to enable us to define a
quantitative dose-response relationship, we believe the ``safe harbor''
approach for setting the increment levels is sufficient to satisfy the
factors applicable under section 166(c), when coupled with the overall
framework of PSD regulations applicable to NOX. This
approach generally maximizes opportunities for economic growth while
ensuring that each area receives a sufficient level of protection
against ``significant deterioration'' of air quality consistent with
Congressional policy. To the extent necessary, the case-by-case
additional impact analysis (in Class I and II areas) and AQRV review
(in Class I areas) will provide additional protection in particular
areas that may be more sensitive to nitrogen loadings resulting from
NOX emissions. Under these circumstances, we can find no
basis for modifying the safe harbor increments, based on the approach
established by Congress for the statutory increments. Thus, we retain
the existing NO2 increments that were established at the
``safe harbor'' level using the statutory ``percentage-of-NAAQS''
approach.
Several commenters seemed to suggest that we should no longer be
relying on increments promulgated in 1988 to protect the environment
and that it was time to update them. However, the Act does not provide
a mechanism for periodically reviewing the increments for a particular
pollutant. EPA's statutory responsibility for developing increments is
linked to its responsibility for promulgating NAAQS. Section 166
requires EPA to promulgate increments for a pollutant following the
promulgation of NAAQS for that pollutant. While the Act is silent in
section 166 on how EPA is to respond to future revisions to existing
NAAQS, we believe there may be certain circumstances when it is
appropriate to review the increments for certain types of NAAQS
revisions. For example, should EPA determine as part of a periodic
review of the NO2 NAAQS to promulgate a new, short-term
NAAQS, then we believe it may be appropriate to consider the
promulgation of a short-term increment as well. Nevertheless, this
final action being taken today regarding the NO2 increments
is not a periodic review of the increments but a response to a court
order requiring us to demonstrate the adequacy of the NO2
increments, which we promulgated in 1988, in accordance with the
relevant requirements that Congress provided for promulgating
pollutant-specific PSD increments under section 166 of the Act.
d. Future considerations.
We agree with the commenters who have recognized the complexity of
the total nitrogen deposition issue and suggested that it will take
time to better understand the problems and solutions. The Act does not
authorize EPA to reevaluate or upgrade the increments periodically, but
generally requires new PSD regulations, which may include increments,
following the promulgation of NAAQS.\31\ Thus, as new information comes
along to better document the dose-response relationships between
NOX and the various health- and welfare-related effects, we
are not necessarily obligated to revise the existing increments for
NOX unless such information results in changes to the NAAQS.
Hence, after any changes to the NAAQS, we would likely evaluate the PSD
regulations for NOX to determine what modifications, if any,
are appropriate to meet the requirements of section 166 of the Act.
---------------------------------------------------------------------------
\31\ Section 166(a) of the Act requires in part that ``In the
case of pollutants for which national ambient air quality standards
are promulgated after the date of enactment of this part, he [the
Administrator] shall promulgate such regulations not more than 2
years after the date of promulgation of such standards.''
---------------------------------------------------------------------------
This is not to say, however, that the advance of relevant
scientific and technical evidence could not be used to establish more
effective mechanisms as part of the PSD regulations where we deem them
to be appropriate. An example of this would be the use of the critical
loads concept. In the February 2005 proposal, we proposed not to
incorporate a critical loads approach as part of the national increment
system (see 70 FR at 8914). We continue to believe that it would not be
appropriate to do so at this time. Therefore, in today's final action,
we are not adopting a critical loads approach in lieu of the existing
NO2 increments, nor are we at
[[Page 59611]]
this time incorporating a critical loads approach into the overall PSD
regulations for NOX. However, we remain interested in the
concept and recognize its potential for addressing the adverse effects
of nitrogen deposition. We discuss the critical loads approach more in
section VII of this preamble.
Yet, we recognize that we may be obligated to consider
modifications to the existing increments as new scientific and
technical information becomes available, and when revisions to the
existing NO2 NAAQS are made. However, even as threshold
levels of adverse impact are able to be defined for individual
ecosystems, the diverse range of responses of nitrogen to different
ecosystem as well as the number of factors (and interactions of those
factors) which determine the response of ecosystems to anthropogenic
nitrogen input will make it very difficult to establish uniform
national increments which, by themselves, provide both an adequate
level of protection in the most sensitive areas and a reasonable
measure of ``significant'' deterioration in less sensitive areas.
B. State Option To Employ Alternatives to Increment
We are amending our regulations to explicitly give States the
option to continue implementing the NO2 increment program or
to design an alternative approach as part of its SIP and submit this
program to EPA for approval. If any States wish to pursue the latter
option, EPA will review State requests on a case-by-case basis to
determine if the State alternative program satisfies the requirements
of sections 166(c) and 166(d) of the CAA and prevents significant
deterioration of air quality from emissions of NOX.
We are not establishing any specific regulatory criteria to govern
the review and approval of such a program other than what is already
contained within section 166 of the CAA. EPA is not prepared at this
time to conclude that any particular type of program other than the
existing increment framework meets the requirements of sections 166(c)
and 166(d) of the CAA. However, as discussed in section IV above, we
continue to believe EPA's obligation under section 166 to promulgate
pollutant-specific regulations for NOX can be satisfied by
allowing States to demonstrate that ``other measures'' besides
increments will prevent significant deterioration of air quality due to
an increase in emissions of NOX, as long as those measures
are consistent with the requirements of sections 166(c) and 166(d) of
the Act.
1. States May Adopt ``Other Measures'' That Fulfill Section 166 of the
Act
In options 2 and 3 of the proposal, we proposed to address the
requirements of section 166 of the CAA for NOX through the
review and approval of State programs that employed alternative
approaches to fulfill the requirements of sections 166(c) and 166(d) of
the Act. We are codifying only this core principle in our regulations
today without identifying any specific type of alternative program that
would meet these requirements. EPA is postponing decisions on adequacy
of specific elements of a State's alternative approach until such time
as the State submits its plan to EPA in a case-by-case SIP approval
process. We believe this less prescriptive approach may allow some
States to employ an alternate approach sooner and more efficiently,
without waiting for EPA to develop a comprehensive one-size-fits-all
program through additional rulemaking.
Accordingly, we are amending our PSD rule at Sec. 51.166 to
reflect that an alternative approach to maximum allowable pollutant
concentrations or increments for NO2 that meet the
requirements of section 166 of the Act may be employed upon approval by
the Administrator. We are requiring that a State's alternative approach
meet three broad criteria, which will be explored in more detail on a
case-by-case basis. The approach must: prevent significant
deterioration of air quality due to emissions of NOX;
fulfill requirements of section 166 of the Act; and be demonstrated in
the SIP. We are not establishing criteria, other than the requirements
of the Act itself, by which to review a State's submittal, and we are
not defining any particular type of alternative approach for States to
use as a substitute for the NOX increments. Rather, we are
simply making clear in the regulations that States have the flexibility
to employ an alternative approach to the NOX increments.
2. EPA Is Not Adopting Elements of Option 3
Although this approach of allowing States to submit alternative
programs has some similarities to our proposed option 3, we are not
adopting several of the elements that we proposed as part of option 3
(the State planning approach). When we proposed option 3, we envisioned
that the EPA could establish a specific planning goal for States, or
require each State to establish one, and then provide a process by
which States would demonstrate how the measures in their SIPs would
achieve this goal. One specific planning goal we proposed was to keep
statewide emissions of NOX from all sources below 1990
levels.
Several commenters expressed concerns that option 3 of the proposal
did not include sufficient detail. We agree with the commenters that
there were numerous specific elements of the State planning approach
that we had not fully addressed in our proposal. The unresolved issues
related to option 3 included the following: (1) Timing of the SIP
approval with discontinuation of NOX increment tracking; (2)
a State plan's failure to prevent significant deterioration due to
NOX emissions; (3) periodic assessment of PSD cumulative
increment impacts; (4) additional measures (backstops); (5) potential
for localized adverse impacts; and (6) effects of an alternative
approach on air quality in neighboring States.
Because we have not yet resolved these issues, we have decided to
codify only the core element of options 2 and 3--the principle that a
State may employ alternatives to increment upon a proper demonstration.
Thus, instead of seeking to resolve these issues for every State in
advance through a rulemaking action, we will consider these types of
issues on a case-by-case basis during review of individual State plans.
At this time, we believe we can more effectively consider and address
such issues in the context of specific plan approvals.
Although option 3 of our proposal lacked detail, several commenters
tentatively supported the flexibility provided by option 3. Some
commenters preferred a case-by-case approach to having ``one-size-fits-
all'' criteria applicable to each State. Several commenters encouraged
flexibility to acknowledge the differences in the air quality and types
of sources among western and eastern States.
Other commenters opposed giving States flexibility on the grounds
that this would result in a lack of uniformity nationwide. One
commenter was concerned that State-to-State levels of NOX
protections would vary, resulting in an uneven playing field for
regulated sources.
We recognize there are reasons to support flexibility and reasons
to support uniform treatment. We addressed the juxtaposition of these
issues in evaluating the increment system and related provisions, as
discussed in more detail above. Our conclusion for those circumstances
was that we could to some extent balance these concerns by combining a
uniform increment system with a case-by-case review of additional
impacts and
[[Page 59612]]
AQRVs. We believe we can also consider the need for a level playing
field and the need to address regional variability when reviewing
individual State alternatives. Thus, we do not believe we should
foreclose permanently the option for States to demonstrate that they
can design an alternative program. We favor giving States the option to
experiment and consider approaches that are uniquely suitable to a
particular area, provided that such approaches do not result in
imbalances in NOX regulation across the country.
Some commenters were against option 3 because they believed EPA
might require States to develop an alternative to increments. Our final
action today does not require a State to develop an alternative to the
NO2 increments. States have the flexibility to continue
implementing the NO2 increments or to pursue approval of
other measures besides increments that achieve the same objectives.
Several commenters opposed option 3 on the grounds that it would
not provide adequate protection for parks and AQRVs. These commenters
were concerned that option 3 did not account for a source's distance
and direction from a Class I area. The commenters indicated that these
variables could have a major effect on whether a source's
NOX emissions adversely impact AQRVs. A State will be
required to demonstrate that any alternative approach to increments
protects parks and AQRVs. In addition, we recognized that an unresolved
issue under our option 3 was the potential for localized adverse
impacts. We will ensure that these issues are addressed before
approving an individual program submission.
One commenter suggested that State planning approach be used as the
foundation of a broader regional strategy to address air quality
impacts of NOX, and not only NO2. The commenter
believed that larger regional issues could not be addressed under
option 3, as proposed, given the increased population growth projected
for western States and attendant growth of urban areas. Our intent with
this regulation is to provide for the review of alternatives on a
State-by-State basis. However, to the extent that groups of States wish
to develop regional strategies, EPA will consider them to determine if
they meet the requirements of the Act. In addition, we will continue to
evaluate EPA's options for promulgating regional strategies to address
the commenter's concerns.
Tribal commenters were concerned that allowing States to implement
alternatives to increment could threaten the tribes' abilities to
regulate their own environmental quality and expose tribal
environmental resources to greater risk of pollution. These commenters
also expressed a concern that such alternatives would be inconsistent
with the Federal government's trust responsibility to tribes. We do not
believe this option will infringe the tribes' abilities to regulate
their environments, harm tribal environmental resources, or overlook
the Federal government's trust responsibility to federally-recognized
tribes. At this point, it is difficult to determine whether a specific
alternative program may affect adjacent areas, such as areas of Indian
country. We want to emphasize, however, that any State's alternative
program will be carefully evaluated to address potential concerns that
affected entities may have, whether it be another State, a tribal
governing body, or an FLM for a nearby Class I area. Each State
alternative program will be evaluated on a case-by-case basis and
subjected to public review and comment as part of the SIP review and
approval process. We believe that it is reasonable to expect that
States will communicate and cooperate with other potentially affected
governing entities as part of the process of developing an alternative
program. In addition, any such alternative program would need to be
approved by EPA. In determining whether to approve such programs, EPA
would act consistent with the Federal government's trust
responsibility, including conducting appropriate consultation with
tribes to help ensure that the interests of the tribes are considered
in this process. Although no specific process has been established for
tribes to consult with EPA on SIP approvals on a government-to-
government basis, we will endeavor to provide additional opportunities
for consultation and continue to carefully consider comments submitted
by tribal officials. This process should help ensure that all concerns
are considered and that environmental resources are protected prior to
approval of an alternative program through the SIP submittal process.
3. Benefits of an Alternative Approach
States have always had the option to submit alternative approaches
in their SIPs that can be shown to be more effective than the minimum
program elements established by EPA, but States may not have recognized
that a system other than increments may be utilized to prevent
significant deterioration from emissions of NOX. The
alternative approach provides States with the flexibility to employ a
program that may be more effective than increments in preventing
significant deterioration of air quality from emissions of
NOX. For example, a State could adopt an emissions reduction
plan for NOX, under authority other than the PSD program,
that limits NOX emissions from particular sources to a
greater extent than would occur under an increment approach that
focuses on marginal increase in emissions.
In addition, although we believe the increment program is effective
at limiting emissions increases, the process of tracking consumption of
increment and modeling changes in emissions concentrations can be time-
consuming and resource-intensive. A State that employs an EPA-approved
alternative approach to the NO2 increments program would not
be required to maintain an NO2 increment inventory. In
addition, PSD permit applicants in the State would not be required to
conduct an individual analysis to demonstrate that they do not cause or
contribute to a violation of the increments. Other measures would be
used to fulfill the requirements of the Act.
4. Future Actions Regarding Alternatives
Although we are not outlining a specific alternative program at
this time, we continue to see promise in using a cap and trade approach
modeled on the CAIR to reduce NOX emissions in order to meet
the goals of the PSD program for NOX. As a result, we intend
to publish a supplemental notice of proposed rulemaking that will
explore this option further. This notice will build on proposed option
2 and provide more details on how a State that achieves the
NOX emissions reductions required under CAIR can fulfill the
objectives of the PSD program, satisfy the statutory requirements of
section 166 of the Act, and obviate the need to implement the
NO2 increments program.
VII. Measures Not Proposed as Options
In the February 2005 proposal, we proposed not to use a ``critical
load'' as a means of identifying an alternative increment level or to
incorporate the concept of critical loads into the PSD regulations for
NOX at the present time. Critical loads can be defined as
``quantitative estimates of an exposure to one or more pollutants below
which significant harmful effects on specified sensitive elements of
the environment do not occur according to present knowledge.'' See 1995
Staff Paper for NOX at xi-xii.
[[Page 59613]]
Our proposal not to incorporate critical loads into our pollutant-
specific PSD regulations for NOX was based largely on our
preliminary conclusion that the scientific basis for developing and
applying critical loads was still emerging. We also raised an issue
about critical loads that related to the possible use of critical loads
to identify an alternative level for the existing NO2
increments. Because of the vastly differing sensitivities and potential
effects associated with ecosystem resources in different regions of the
United States, we expressed our belief that critical loads do not
represent an appropriate tool for setting a single, uniform, national
standard, such as a PSD increment level.
We did acknowledge, however, that States could propose to use a
critical loads concept. For example, where adequate information might
be available, States could use critical loads as part of their own air
quality management approaches, and EPA would consider it when
determining whether the overall air quality management approach
satisfied the PSD requirements. See 70 FR at 8914.
Five commenters agreed with our assessment that it would not be
appropriate at this time to use critical loads as part of the PSD
regulations for NOX. These commenters generally agreed that
the critical loads concept was not ready to be used for PSD purposes.
In addition, some felt that it would be inappropriate for EPA to use
critical loads as non-uniform national standards. One argued that the
use of critical loads would improperly prohibit economic growth.
On the other hand, nine commenters responded to our proposal by
opposing our decision not to use critical loads in some way under the
PSD regulations for NOX. These commenters recommended using
critical loads as either complete replacements for the existing
NO2 increments or as a supplemental measure for the
increment approach. The comments recommending the use of critical loads
as a supplemental measure suggested that critical loads could augment
the proposed uniform NOX increment approach by providing a
tool through which permitting authorities could consider ecosystem
changes in more sensitive areas. In such areas, they believed a
critical load could provide a science-based target for protection.
We agree that critical loads represent a promising mechanism for
addressing environmental impacts associated with atmospheric nitrogen
deposition. For example, once further developed, the critical load
concept could potentially be used as a location-specific means to
determine the goals of emissions control and management practices
related to ecosystem protection. Clearly, the ``critical loads''
concept is one way to describe the level at which a specific natural
area or system is negatively impacted by air pollution. With sufficient
information, critical load determinations for nitrogen deposition can
be related to location-specific indicators of ecological change, such
as episodic and chronic acidification of streams and rivers, chemical
changes in soils, or nutrient enrichment and eutrophication.
Over the past 20 years, the scientific community has gained
increasing knowledge regarding the impacts of atmospheric emissions of
certain criteria pollutants (NO2, SO2, and ozone)
on natural systems. Studies that we reviewed as part of this rulemaking
to determine the adequacy of the existing NO2 increments
illustrate that scientists now understand that both ambient exposure to
and deposition of various nitrogen compounds have gradually changed the
ecological balance of natural systems in many areas of the United
States. Detailed descriptions of the ecological effects of nitrogen
deposition can be found in many of the studies that we examined as part
of the review of the existing NO2 increments (see section V
of this preamble), but in most every case it is not yet possible to
quantify the levels of deposition responsible for such changes.
Commenters did not provide any information to show us that
sufficient information is available at this time to use the critical
load concept as part of the national PSD program for NOX.
Moreover, we believe that from the information that is available,
because ecological systems are quite heterogeneous, critical loads
would not serve as an appropriate replacement for the uniform national
NO2 increments. However, if the science is further
developed, we do agree with those commenters who suggest that location-
specific critical loads could be used effectively to augment the
existing increment system for NOX at those locations.
Two of the commenters supporting critical loads indicated that we
should revise the existing NO2 increments and continue using
the increment system as an interim approach, while studying the
critical load concept for future implementation as part of the PSD
program. These commenters agreed that ultimately the critical loads
approach was the most effective way to protect the environment from the
adverse effects of nitrogen deposition. Several other commenters also
urged EPA to further study the critical loads concept by initiating
pilot projects or a demonstration critical loads program by working
with States, FLMs, tribes, and others to select natural areas where
existing information is adequate to do so.
We agree with the commenters recommending that the current
increment system should continue to be applied under the PSD
regulations for NOX. However, as explained in section VI, we
do not agree that there is sufficient basis for modifying the existing
NO2 increments. Therefore, under today's final action, we
are not modifying the existing NO2 increments, but retaining
them at their existing levels and form.
We do agree with commenters that further research is necessary and
appropriate to further evaluate the critical loads concept. As
mentioned above, in recent years, ecosystems research has produced
findings that are sufficient to identify changes to many sensitive
elements of the environment at specific locations resulting from
atmospheric nitrogen deposition in its various forms. Nitrogen impacts
have been documented in areas ranging from East Coast estuaries to
high-elevation systems in the Colorado Front Range to southern
California chaparral communities. Nitrogen deposition in these areas
impacts diverse ecological communities ranging from fisheries to alpine
lakes to grasslands.
Even with advances in our understanding of nitrogen cycling in the
environment, scientific challenges remain in relation to setting
scientifically valid critical loads. These challenges include the
following:
Data requirements and availability: Critical loads for
acidification and nutrient-related ecosystem changes for sensitive
aquatic and terrestrial systems depend on many ecosystem
characteristics, compounded by the fact that these characteristics are
heterogeneous across space. Such characteristics include topography,
elevation, slope, bedrock geology, soil characteristics, soil
chemistry, land use history, water body and watershed surface area,
surface water chemistry, meteorology, climate, plant species
composition, biomass, and plant nutrient concentrations. Depending on
the critical loads calculation method used, some or all of the data
described above are necessary inputs for establishing critical loads.
Clearly, establishing critical loads is a very data-intensive exercise.
The challenge will be to determine the amount and types of data that
are necessary and available for
[[Page 59614]]
calculating critical loads at local to regional scales.
Multiple methods and models: In addition to data issues,
the current multiplicity of methods for calculating critical loads
poses a practical challenge that may complicate application of the
critical loads approach for air quality management. At least three
approaches are currently employed for calculating critical loads:
empirical approaches in which critical loads are based on the
relationship between an observed detrimental ecological effect and the
deposition level at which the effect occurred; steady-state approaches
using simple mass-balance models; and dynamic modeling approaches.
While each approach has advantages and disadvantages, the National
Research Council recently stated that reliance on steady-state models
can introduce uncertainty into critical loads calculations and observed
that ``the numerous methods for calculating both critical loads and
exceedance levels allow for inconsistency in implementation'' (NRC,
2004). Model comparison efforts will help to resolve issues regarding
critical load calculation approaches and enable evaluation of the data
needs and relative applicability of steady-state and dynamic modeling
approaches.
Critical load variations: Critical load values vary
depending upon factors such as the ecosystem response of interest or
the spatial context. At a given location, for example, critical loads
can vary depending upon the ecosystem response indicator of interest--
critical loads for soils are often different than critical loads for
freshwater systems. Similarly, critical loads for an ecosystem response
indicator may vary across local to regional spatial scales. The
challenge will be to integrate local-scale critical loads (e.g., for a
Class I area) and regional-scale critical loads when implementing air
quality management programs for ecosystem protection at multiple
scales.
We are aware that Federal land management agencies, other Federal
and State agencies, and the scientific community have developed a
substantial body of information related to nitrogen impacts for a
limited number of site-specific ecosystems around the country. EPA will
continue working to further develop the latest scientific research
results and information to explore the critical loads approach to
better manage air resources.
We agree with commenters that it is possible that a critical load
program could be developed by working collaboratively with States,
tribes, and FLMs to implement ``pilot projects'' in selected areas
where there may be sufficient information on nitrogen deposition and
ecosystem effects to establish critical loads. Under this final rule,
the Agency encourages States, tribes and FLMs to join with EPA in
exploring the voluntary use of critical loads as a basis to address
effects of nitrogen deposition on ecosystems for such areas. With
appropriate public input, cooperative critical load projects could lead
to implementation plans that demonstrate protection against
deterioration of AQRVs from nitrogen impacts, eliminate the need for
NO2 increment tracking, and reduce the extent of assessments
needed for permitting new sources that may impact AQRVs in Class I
areas. In addition, such an approach may fit within the structure of
existing requirements.
EPA will work with interested States, tribes, Federal land
management agencies and others to identify the components needed to
develop and implement cooperative projects to explore the feasibility
and usefulness of a critical loads approach. EPA believes such projects
are a means through which to explore whether a critical loads approach
could be an efficient approach to ensure protection of ecosystems and
other AQRVs as part of the existing increment system, and also meet
other purposes of the Act. Such an approach could reduce the
administrative burden on States and new sources. Collaborative efforts
to explore a critical loads approach for nitrogen would provide insight
into the general role of critical loads in future air quality
management programs.
The statutory PSD provisions authorize Federal land management
agencies, including NPS and the U.S. Forest Service, to play a special
role in protecting AQRVs in their Federal Class I lands.\32\ In this
context, the FLMs are also responsible for identifying AQRVs in Class I
areas and assessing whether they might be adversely impacted. For many
Class I area parks and wilderness areas, FLMs have already identified
the resources at risk from or sensitive to air pollution. In
conjunction with this effort, FLMs recently have explored the use and
setting of critical loads as a management tool to characterize the risk
from air pollution emissions and deposition to ecological systems on
Class I areas and Federal lands. (Porter, 2005.) For example, they have
used research on critical loads to assess ecosystem risk and to inform
air quality management decisions related to new source permit reviews
and comments on SIP pollution control strategies. These efforts could
serve as the basis for continuing review and evaluation by a
cooperative agreement with EPA, States and other interested parties.
---------------------------------------------------------------------------
\32\ Section 165(d)(2)(B) places an affirmative responsibility
on FLMs to protect the AQRVs in Federal Class I areas.
---------------------------------------------------------------------------
One commenter believed that EPA should elaborate on the way we
envision States' using critical loads within their State PSD programs.
This commenter further believed that States should be encouraged to
consider critical load data where such data indicate that the current
NO2 increments and current permitting procedures are not
providing adequate environmental protection.
In our February 2005 proposal, we indicated that States,
considering the state of the science, may propose use of critical load
information as part of their air quality management approach. If such a
proposal were made, EPA would consider it in determining whether the
State's approach satisfied its PSD requirements. We envision the
development of critical loads to be a phased, ongoing process. As
critical loads are calculated for specific receptors in a particular
area, such as forest soils, or surface waters, using a dose-response
relationship, and such critical loads are adequately peer-reviewed, we
encourage affected States to consider working closely with the
applicable FLM to establish agreements and procedures for incorporating
the critical load concept into their PSD permit process for protecting
AQRVs.
VIII. Statutory and Executive Order Reviews
A. Executive Order 12866--Regulatory Planning and Review
Under Executive Order 12866 (58 FR 51735, October 4, 1993), the
Agency must determine whether the regulatory action is ``significant''
and therefore subject to review by the Office of Management and Budget
(OMB) and the requirements of the Executive Order. The Order defines
``significant regulatory action'' as one that is likely to result in a
rule that may:
(1) Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal governments or
communities;
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
(3) Materially alter the budgetary impact of entitlements, grants,
user fees,
[[Page 59615]]
or loan programs, or the rights and obligations of recipients thereof;
or
(4) Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
Pursuant to the terms of Executive Order 12866, it has been
determined that this rule is a ``significant regulatory action''
because the State planning option in the proposal raises novel legal
and policy issues. As such, this action was submitted to OMB for
review. Changes made in response to OMB suggestions or recommendations
will be documented in the public record.
B. Paperwork Reduction Act
This action does not impose any new information collection burden.
Under this final action, we are retaining the existing increments and
regulatory framework of the PSD regulations for NOX. The
Office of Management and Budget (OMB) has previously approved the
information collection requirements contained in the existing
regulations (40 CFR parts 51 and 52) under the provisions of the
Paperwork Reduction Act, 44 U.S.C. 3501, et seq., and has assigned OMB
control number 2060-0003, EPA ICR number 1230.17. A copy of the OMB-
approved Information Collection Request (ICR) may be obtained from
Susan Auby, Collection Strategies Division, U.S. Environmental
Protection Agency (2822T), 1200 Pennsylvania Ave., NW., Washington, DC
20460, or by calling (202) 566-1672.
As an alternative to the existing increments, the State has
discretion in developing an alternative option that satisfies both the
requirements of the statutory PSD program requirements for
NOX and the State's air quality management goals. It is not
possible to determine at this time what additional burdens, if any, a
State alternative program may entail.
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.
An agency may not conduct or sponsor, and a person is not required
to respond to, a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for EPA's
regulations in 40 CFR are listed in 40 CFR part 9.
C. Regulatory Flexibility Act (RFA)
EPA has determined that it is not necessary to prepare a regulatory
flexibility analysis in connection with this final rule.
For purposes of assessing the impacts of today's final rule on
small entities, small entity is defined as: (1) A small business as
defined by the Small Business Administration's (SBA) regulations at 13
CFR 121.201; (2) a small governmental jurisdiction that is a government
of a city, county, town, school district or special district with a
population of less than 50,000; or (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 today's final rule on
small entities, EPA has concluded that this action will not have a
significant economic impact on a substantial number of small entities.
We are imposing no new requirements on small entities. We are retaining
existing regulations without change and thus imposing no new
requirements on small entities. Optionally, we allow States to adopt
alternative programs to relieve the burden of conducting specific
ambient air quality and increment analyses under the PSD program.
However, States do not meet the definition of a small entity under the
RFA.
D. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Pub.
L. 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, EPA
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
the aggregate, or to the private sector, of $100 million or more in any
one year.
Before promulgating an EPA rule for which a written statement is
needed, section 205 of the UMRA generally requires EPA 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 allows EPA 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 EPA establishes any regulatory requirements that may
significantly or uniquely affect small governments, including tribal
governments, it 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 EPA regulatory proposals with significant Federal
intergovernmental mandates, and informing, educating, and advising
small governments on compliance with the regulatory requirements.
Today's final action contains no Federal mandates (under the
regulatory provisions of Title II of the UMRA) for State, local, or
tribal governments or the private sector. The final rule imposes no
enforceable duty on any State, local or tribal governments or the
private sector.
We are retaining existing requirements and do not impose any new
Federal mandates. New rule language authorizes States to adopt an
alternative approach to meeting some of the rule's requirements, but
States have had such authority under the CAA and are not required to
adopt an alternative approach if they choose to continue implementing
the existing program provisions. In any event, EPA has determined that
this final 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 in the private sector in any one
year. Thus, today's final rule is not subject to the requirements of
sections 202 and 205 of the UMRA.
Because we have not required any new Federal mandates, EPA has also
determined that this rule contains no regulatory requirements that
might significantly or uniquely affect small governments.
E. Executive Order 13132--Federalism
Executive Order 13132, entitled ``Federalism'' (64 FR 43255, August
10, 1999), requires EPA 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
[[Page 59616]]
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 final rule does not have federalism implications. The rule
will not have substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government, as specified in Executive Order 13132. If the existing
regulations for increments are retained, no new regulatory requirements
will be imposed on States. Optionally, this final action permits States
to obtain relief from certain regulatory requirements by adopting
alternative programs but does not necessarily require adoption of a new
program in that a State may rely on a program that is already in place
or that is required by other EPA requirements. Direct compliance costs
associated with today's rule could be incurred when States incorporate
any changes into their SIPs, but these direct compliance costs would
not be significant. Thus, Executive Order 13132 does not apply to this
final rule.
F. Executive Order 13175--Consultation and Coordination With Indian
Tribal Governments
Executive Order 13175, entitled ``Consultation and Coordination
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000),
requires EPA 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 final rule does not have
tribal implications, as specified in Executive Order 13175. No tribes
are currently implementing the PSD program. Furthermore, this final
rule does not impose any new regulatory restrictions. In this final
action, EPA is retaining the existing NO2 increments and
making explicit that States implementing the PSD program have the
option to seek EPA approval of an alternative program that meets the
objectives of the PSD program without using increments. At the time it
reviews any alternative PSD program for NOX submitted by a
State, EPA will assess whether such program has tribal implications.
However, the final action we are taking today does not have a
substantial direct effect on tribes. Thus, Executive Order 13175 does
not apply to this final rule. Although Executive Order 13175 does not
apply to this rule, EPA has considered comments submitted by several
tribal officials. A summary of the concerns raised in these comments
and EPA's response to those concerns is provided in EPA's Comment-
Response Document located in the docket for this rule.
G. Executive Order 13045--Protection of Children From Environmental
Health and 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 ``economically significant'' as defined under
Executive Order 12866; and (2) concerns an environmental health or
safety risk that EPA has 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 final rule is not subject to the Executive Order because it is
not economically significant as defined in Executive Order 12866, and
because the Agency does not have reason to believe the environmental
health or safety risks of NOX addressed by this action
present a disproportionate risk to children. The final rule retains
existing regulations and does not impose any new regulatory
requirements. States may obtain relief from certain regulatory
requirements by choosing to adopt alternative programs.
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. The final
rule retains existing regulations and does not impose any new
regulatory requirements. States may obtain relief from certain
regulatory requirements by choosing to adopt alternative programs. This
option does not impose any new requirements but rather allows States to
obtain regulatory flexibility by implementing alternative requirements.
Further, we have concluded that this rule is not likely to have any
adverse energy effects.
I. National Technology Transfer and Advancement Act
As noted in the February 2005 proposal, section 12(d) of the
National Technology Transfer and Advancement Act of 1995 (``NTTAA''),
Pub. L. 104-113, 12(d) (15 U.S.C. 272 note), directs EPA to use
voluntary consensus standards in its regulatory activities unless to do
so would be inconsistent with applicable law or otherwise impractical.
Voluntary consensus standards are technical standards (e.g., materials
specifications, test methods, sampling procedures, and business
practices) that are developed or adopted by voluntary consensus
standards bodies. The NTTAA directs EPA to provide Congress, through
OMB, explanations when the Agency decides not to use available and
applicable voluntary consensus standards. This final rule does not
involve technical standards. Therefore, EPA did not consider the use of
any voluntary consensus standards.
J. Executive Order 12898--Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations
Executive Order 12898 requires that each Federal agency make
achieving environmental justice part of its mission by identifying and
addressing, as appropriate, disproportionate high and adverse human
health or environmental effects of its programs, policies, and
activities on minorities and low-income populations. The EPA concluded
that this final rule should not raise any environmental justice issues.
K. Congressional Review Act
The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General of the
United States. EPA will submit a report containing this rule and other
required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register. A major rule cannot
take effect until 60 days after it is published in the Federal
Register. This action is not a ``major rule'' as defined by 5 U.S.C.
804(2). Therefore, this action will be effective November 14, 2005.
[[Page 59617]]
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Cronan, C. Eagar, K.F. Lambert, G.E. Likens, J.L. Stoddard, and K.C.
Weathers, ``Acidic Deposition in the Northeastern United States,
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BioScience, vol. 51, no. 3 (p. 180-198), March 2001.
Driscoll, C.T., G.B. Lawrence, A.J. Bulger, T.J. Butler, C.S.
Cronan, C. Eagar, K.F. Lambert, G.E. Likens, J.L. Stoddard, and K.C.
Weathers, ``Acid Rain Revisited: Advances in Scientific
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LinksTM Publication. Vol. 1, no. 1, 2001.
Driscoll, C.T., K.M. Driscoll, M.J. Mitchell, and D.J. Raynal,
``Effects of Acidic Deposition on Forest and Aquatic Ecosystems in
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Fenn, M.E., M.A. Poth, J.D. Aber, J.S. Baron, B.T. Bormann, D.W.
Johnson, A.D. Lemly, S.G. McNulty, D.F. Ryan, and R. Stottlemyer,
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Clarke, D. Hope, D.A. Jaffe, S. Copeland, L. Geiser, H.M. Rueth, and
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2003.
Fenn M., L. Geiser, J. Peterson, E. Waddell, and E. Porter, ``Why
Federal Land Managers in the Northwest are Concerned About Nitrogen
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Fenn M.E., J.S. Baron, E.B. Allen, H.M. Rueth, K.R. Nydick, L.
Geiser, W.D. Bowman, J.O. Sickman, T. Meixner, D.W. Johnson, and P.
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2000), Chapter D.2. Visibility; Available at http://www2.nature.nps.gov/air/Permits/flag/htm/sub2.html
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Nitrogen in the United States.'' Office of Water Quality, USGS;
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Porter E., et al., ``Protecting Resources on Federal Lands:
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Nitrogen and Sulfur'' BioScience (2005) v. 55, no. 7, p. 603-612.
Taylor, G.E., D.W. Johnson, ``Air Pollution and Forest Ecosystems: A
Regional to Global Perspective.'' Ecological Applications, vol. 4,
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Parks: Second Edition.'' September 2002.
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for Oxides of Nitrogen. (3 volumes). Office of Air Quality Planning
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Ambient Air Quality Standards for Nitrogen Dioxide: Assessment of
Scientific and Technical Information. (1995 Staff Paper for
NOX.) Office of Air Quality Planning and Standards. EPA-
452/R-95-005, September 1995. Available at http://www.epa.gov/ttn/naaqs/standards/nox/s_nox_pr_sp.html
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Ambient Air Quality Standards for Particulate Matter: Policy
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List of Subjects in 40 CFR Part 51
Environmental protection, Administrative practices and procedures,
Air pollution control,
[[Page 59618]]
Intergovernmental relations, Nitrogen oxides, Ozone, Particulate
matter, Reporting and recordkeeping requirements.
Dated: September 29, 2005.
Stephen L. Johnson,
Administrator.
0
For the reasons set out in the preamble, title 40, chapter I of the
Code of Federal Regulations is amended as follows:
PART 51--[AMENDED]
0
1. The authority citation for part 51 continues to read as follows:
Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671 q.
Subpart I--[Amended]
0
2. Section 51.166 is amended by revising paragraph (c) to read as
follows:
Sec. 51.166 Prevention of significant deterioration of air quality.
* * * * *
(c) Ambient air increments and other measures. (1) The plan shall
contain emission limitations and such other measures as may be
necessary to assure that in areas designated as Class I, II, or III,
increases in pollutant concentrations over the baseline concentration
shall be limited to the following:
------------------------------------------------------------------------
Maximum
allowable
increase
Pollutant (micrograms
per cubic
meter)
------------------------------------------------------------------------
Class I
------------------------------------------------------------------------
Particulate matter:
PM10, annual arithmetic mean........................ 4
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
------------------------------------------------------------------------
Particulate matter:
PM10, annual arithmetic mean........................ 17
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
------------------------------------------------------------------------
Particulate matter:
PM10, annual arithmetic mean........................ 34
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
------------------------------------------------------------------------
For any period other than an annual period, the applicable maximum
allowable increase may be exceeded during one such period per year at
any one location.
(2) Where the State can demonstrate that it has alternative
measures in its plan other than maximum allowable increases that
satisfy the requirements in sections 166(c) and 166(d) of the Clean Air
Act for nitrogen oxides, the requirements for maximum allowable
increases for nitrogen dioxide under paragraph (c)(1) of this section
shall not apply upon approval of the plan by the Administrator.
* * * * *
[FR Doc. 05-20110 Filed 10-11-05; 8:45 am]
BILLING CODE 6560-50-P