Document ID: EPA-HQ-OAR-2003-0062-0247
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-04-25T04:00Z

6560-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 51

[EPA-HQ-OAR-2003-0062; FRL-    ]

RIN 2060-AK74

Clean Air Fine Particle Implementation Rule

AGENCY:	Environmental Protection Agency (EPA).

ACTION:	Final rule.  

SUMMARY:	This final action provides rules and guidance on the Clean Air
Act (CAA) requirements for State and Tribal plans to implement the 1997
fine particle (PM2.5) national ambient air quality standards (NAAQS). 
Fine particles and precursor pollutants are emitted by a wide range of
sources, including power plants, cars, trucks, industrial sources, and
other burning or combustion-related activities.  Health effects that
have been associated with exposure to PM2.5 include premature death,
aggravation of heart and lung disease, and asthma attacks.  Those
particularly sensitive to PM2.5 exposure include older adults, people
with heart and lung disease, and children.  	Air quality designations
became effective on April 5, 2005 for 39 areas (with a total population
of 90 million) that were not attaining the 1997 PM2.5 standards.  By 

April 5, 2008, each State having a nonattainment area must submit to EPA
an attainment demonstration and adopted regulations ensuring that the
area will attain the standards as expeditiously as practicable, but no
later than 2015.  This rule and preamble describe the requirements that
States and Tribes must meet in their implementation plans for attainment
of the 1997 fine particle NAAQS.  (Note that this rule does not include
final PM2.5 requirements for the new source review (NSR) program; the
final NSR rule will be issued at a later date.)

DATES:   This rule is effective on [INSERT DATE 60 DAYS FROM DATE OF
SIGNATURE].  

ADDRESSES:  The EPA has established a docket for this action under
Docket ID EPA-HQ-OAR-2003-0062.  All documents relevant to this action
are listed in the Federal docket management system at   HYPERLINK
"http://www.regulations.gov"  www.regulations.gov .  Although listed in
the index, some information is not publicly available (e.g. Confidential
Business Information or other information whose disclosure is restricted
by statute).   Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form.  Publicly available docket materials are available either
electronically through www.regulations.gov or in hard copy format at the
EPA Docket Center, EPA/DC, EPA West, Room 3334, 1301 Constitution
Avenue, NW, Washington, DC.  The Public Reading Room is open from 8:30
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays.  The
telephone number for the Public Reading Room is (202) 566-1744, and the
telephone number for the Office of Air and Radiation Docket and
Information Center is (202) 566-1742. A variety of information and
materials related to the fine particle NAAQS and implementation program
are also available on EPA’s web site: 
http://www.epa.gov/air/particles. 

FOR FURTHER INFORMATION CONTACT:  For general information, contact Mr.
Richard Damberg, U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, Mail Code C539-01, Research Triangle
Park, NC 27711, phone number (919) 54l-5592 or by e-mail at:   
HYPERLINK "mailto:damberg.rich@epa.gov"  damberg.rich@epa.gov .

SUPPLEMENTARY INFORMATION: 

 General Information

Does this Action Apply to Me?

	Entities potentially regulated by this action are State and local air
quality agencies.  

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

	In addition to being available in the docket, an electronic copy of
this final rule will also be available on the World Wide Web.  Following
signature by the EPA Administrator, a copy of this final rule will be
posted at http://www.epa.gov/particles/actions.html.  

C.	How is the preamble organized?

I.	Background

II.	Elements of the Clean Air Fine Particle Implementation Rule

A. 	Precursors and Pollutants Contributing to Fine Particle Formation

B.  	No Classification System

C.  	Due Dates and Basic Requirements for Attainment Demonstrations

D.  	Attainment Dates

E.	Modeling and Attainment Demonstrations

F.	Reasonably Available Control Technology and Reasonably Available
Control Measures

G.	Reasonable Further Progress

H.  	Contingency Measures

I.	Transportation Conformity

J. 	General Conformity

K.	Emission Inventory Requirements

L. 	Condensable Particulate Matter Test Methods and Related Data Issues

M.	Improving Source Monitoring 

N. 	Guidance Specific to Tribes

O.	Enforcement and Compliance

P.	Emergency Episodes

Q.	Ambient Monitoring

III.	Statutory and Executive Order Reviews

A.	Executive Order 12866: Regulatory Planning and Review

B.	Paperwork Reduction Act

C. 	Regulatory Flexibility Act

D.	Unfunded Mandates Reform Act

E.	Executive Order 13132: Federalism

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

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

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

I.	National Technology Transfer Advancement Act

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

K.	Congressional Review Act

IV.	Judicial Review

V.	Statutory Authority

I.	Background

Fine particles in the atmosphere are comprised of a complex mixture of
components.  Common constituents include:  sulfate (SO4); nitrate (NO3);
ammonium; elemental carbon; a great variety of organic compounds; and
inorganic material (including metals, dust, sea salt, and other trace
elements) generally referred to as ”crustal” material, although it
may contain material from other sources.  Airborne particles generally
less than or equal to 2.5 micrometers in diameter are considered to be
”fine particles” (also referred to as PM2.5).  (A micrometer is
one-millionth of a meter, and 2.5 micrometers is less than one-seventh
the average width of a human hair.)  ”Primary” particles are emitted
directly into the air as a solid or liquid particle (e.g., elemental
carbon from diesel engines or fire activities, or condensable organic
particles from gasoline engines). “Secondary” particles (e.g.,
sulfate and nitrate) form in the atmosphere as a result of various
chemical reactions.  (Section II of the proposed rule included detailed
technical discussion on PM2.5, its precursors, formation processes, and
emissions sources.)  

The EPA established air quality standards for PM2.5 based on evidence
from numerous health studies demonstrating that serious health effects
are associated with exposures to elevated levels of PM2.5. 
Epidemiological studies have shown statistically significant
correlations between elevated PM2.5 levels and premature mortality. 
Other important effects associated with PM2.5 exposure include
aggravation of respiratory and cardiovascular disease (as indicated by
increased hospital admissions, emergency room visits, absences from
school or work, and restricted activity days), changes in lung function
and increased respiratory symptoms, as well as new evidence for more
subtle indicators of cardiovascular health.  Individuals particularly
sensitive to PM2.5 exposure include older adults, people with heart and
lung disease, and children.  	

On July 18, 1997, we revised the NAAQS for particulate matter (PM) to
add new standards for fine particles, using PM2.5 as the indicator.  We
established health-based (primary) annual and 24-hour standards for
PM2.5 (62 FR 38652).  The annual standard was set a level of 15
micrograms per cubic meter, as determined by the 3-year average of
annual mean PM2.5 concentrations.  The 24-hour standard was set a level
of 65 micrograms per cubic meter, as determined by the 3-year average of
the 98th percentile of 24-hour concentrations.  

Attainment of the 1997 PM2.5 standards is estimated to lead to
reductions in health impacts, including tens of thousands fewer
premature deaths each year, thousands fewer hospital admissions and
emergency room visits each year, hundreds of thousands fewer absences
from work and school, and hundreds of thousands fewer respiratory
illnesses in children annually.  The EPA’s evaluation of the science
concluded that there was not sufficient information to either support or
refute the existence of a threshold for health effects from PM exposure.
 

We subsequently completed in October 2006 another review of the NAAQS
for PM.  With regard to the primary standards, the 24-hour PM2.5
standard was strengthened to a level of 35 micrograms per cubic meter,
based on the 3-year average of the 98th percentile of 24-hour
concentrations, and the level of the annual standard remained unchanged.
 Attainment of the 2006 PM2.5 standards is estimated to lead to
additional reductions in health impacts, including approximately 1,200
to 13,000 fewer premature deaths each year, 1,630 fewer hospital
admissions and 1,200 fewer emergency room visits for asthma each year,
350,000 fewer absences from work and school, and 155,300 fewer
respiratory illnesses in children annually.

In both 1997 and 2006 EPA established welfare-based (secondary)
standards identical to the levels of the primary standards.  The
secondary standards are designed to protect against major environmental
effects of PM2.5 such as visibility impairment, soiling, and materials
damage.  The EPA also established the regional haze regulations in 1999
for the improvement of visual air quality in national parks and
wilderness areas across the country.  Because regional haze is caused
primarily by light scattering and light absorption by fine particles in
the atmosphere, EPA is encouraging the States to integrate their efforts
to attain the PM2.5 standards with those efforts to establish reasonable
progress goals and associated emission reduction strategies for the
purposes of improving air quality in our treasured natural areas under
the regional haze program. 

The scientific assessments used in the development of the PM2.5
standards included a scientific peer review and public comment process. 
We developed scientific background documents based on the review of
hundreds of peer-reviewed scientific studies.  The Clean Air Scientific
Advisory Committee, a congressionally mandated group of independent
scientific and technical experts, provided extensive review of these
assessments, and found that EPA’s review of the science provided an
adequate basis for the EPA Administrator to make a decision.  More
detailed information on health effects of PM2.5 can be found on EPA’s
website at:  http://www.epa.gov/air/urbanair/pm/index.html.  Additional
information on EPA’s scientific assessment documents supporting the
1997 standards are available at   HYPERLINK
"http://www.epa.gov/ttn/oarpg/t1cd.html" 
http://www.epa.gov/ttn/oarpg/t1cd.html ; additional scientific
assessment information on the 2006 standards is available at:
http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_cr_cd.html.

The EPA issued final PM2.5 designations for areas violating the 1997
standards on December 17, 2004.  They were published in the Federal
Register on January 5, 2005 (70 FR 944).  On April 5, 2005, EPA issued a
supplemental notice which changed the designation status of eight areas
from nonattainment to attainment based on newly updated 2002-2004 air
quality data (70 FR 19844; published in the Federal Register on April
14, 2005).  A total of 39 areas were designated as nonattainment for the
1997 PM2.5 standards.  The population of these areas is estimated at
about 90 million (or more than 30% of the U.S. population).  Most of
these areas only violate the annual standard, but a few violate both the
annual and 24-hour standards. 

The nonattainment designation for an area starts the process whereby a
State or Tribe must develop an implementation plan that includes, among
other things, a demonstration showing how it will attain the ambient
standards by the attainment dates required in the CAA.  Under section
172(b), States have up to 3 years after EPA’s final designations to
submit their SIPs to EPA.  These SIPs will be due on April 5, 2008, 3
years from the effective date of the designations. 

Section 172(a)(2) of the Act requires States to attain the standards as
expeditiously as practicable but within 5 years of designation (i.e.
attainment date of April 2010 based on air quality data for 2007-2009),
or within up to 10 years of designation (i.e. to April 2015) if the EPA
Administrator extends an area’s attainment date by 1-5 years based
upon the severity of the nonattainment problem or the feasibility of
implementing control measures.  

Virtually all nonattainment problems appear to result from a combination
of local emissions and transported emissions from upwind areas.  The
structure of the CAA requires EPA to develop national rules for certain
types of sources which are also significant contributors to local air
quality problems, including motor vehicles and fuels.  It also provides
for States to address emissions sources on an area-specific basis
through such requirements as RACT, RACM, and RFP. 

We believe that to attain the PM2.5 standards, it is important to pursue
emissions reductions simultaneously on the local, regional, and national
levels.  The EPA issued the Clean Air Interstate Rule (CAIR) on March
10, 2005 to address the interstate transport of sulfur dioxide and
nitrogen oxide emissions primarily from power plants.  Section 110 gives
EPA the authority to require SIPs to ”prohibit ... any source or other
type of emission activity within the State from emitting any air
pollutant in amounts which will contribute significantly to
nonattainment in, or interfere with maintenance by, any other State with
respect to” any NAAQS, and to prohibit sources or emission activities
from emitting pollutants in amounts which will interfere with measures
required to be included in State plans to prevent significant
deterioration of air quality or to protect visibility (such as the
protection of 156 mandatory Federal class I areas under the regional
haze rule).  CAIR employs the same emissions trading approach used to
achieve cost-effective emission reductions under the acid rain program. 
It outlines a two-phase program with increasingly tighter power plant
emissions caps for 28 eastern states and the District of Columbia: SO2
caps of 3.6 million tons in 2010, and 2.5 million in 2015; NOx caps of
1.5 in 2009 and 1.3 in 2015; and NOx ozone season caps of 580,000 tons
in 2009 and 480,000 tons in 2015.  Emission caps are divided into State
SO2 and NOx budgets.  By the year 2015, the Clean Air Interstate Rule is
estimated to result in:

-- $85 to $100 billion in annual health benefits, including preventing
17,000 premature deaths, millions of lost work and school days, and tens
of thousands of non-fatal heart attacks and hospital admissions
annually.

-- nearly $2 billion in annual visibility benefits in southeastern
national parks, such as Great Smoky and Shenandoah.

-- significant regional reductions in sulfur and nitrogen deposition,
reducing the number of acidic lakes and streams in the eastern U.S.

Over the past several years, EPA has also issued a number of regulations
addressing emissions standards for new cars, trucks and buses.  These
standards are providing reductions in motor vehicle emissions of
volatile organic compounds (VOCs, also referred to as hydrocarbons),
NOx, and direct PM emissions (such as elemental carbon) as older
vehicles are retired and replaced.  Other existing rules are designed to
reduce emissions from several categories of nonroad engines.  The Tier 2
motor vehicle emission standards, together with the associated
requirements to reduce sulfur in gasoline, are estimated to provide
additional benefits nationally beginning in 2004.  When the new tailpipe
and sulfur standards are fully implemented, Americans are estimated to
benefit from the clean-air equivalent of removing 164 million cars from
the road.  These new standards require passenger vehicles to have
emissions 77 to 95 percent cleaner than those on the road today and
require fuel manufacturers to reduce the sulfur content of gasoline by
up to 90 percent.  In addition, the 2001 heavy-duty diesel engine
regulations will lead to continued emissions reductions as older
vehicles in that engine class are retired and fleets turn over.  New
emission standards began to take effect for model year 2007 and apply to
heavy-duty highway engines and vehicles.  These standards are based on
the use of high-efficiency catalytic exhaust emission control devices or
comparably effective advanced technologies.  Because these devices are
damaged by sulfur, the level of sulfur in highway diesel fuel was to be
reduced by 97 percent by mid-2006.  We project a 2.6 million ton
reduction of NOx emissions in 2030 when the current heavy-duty vehicle
fleet is completely replaced with newer heavy-duty vehicles that comply
with these emission standards.  By 2030, we estimate that this program
will reduce annual emissions of hydrocarbons by 115,000 tons and PM by
109,000 tons.  These emissions reductions are on par with those that we
anticipate from new passenger vehicles and low sulfur gasoline under the
Tier 2 program. 

The EPA also finalized national rules in May 2004 to reduce
significantly PM2.5 and NOx emissions from nonroad diesel-powered
equipment.  These nonroad sources include construction, agricultural,
and industrial equipment, and their emissions constitute an important
fraction of the inventory for direct PM2.5 emissions (such as elemental
carbon and organic carbon), and NOx.  The EPA estimates that affected
nonroad diesel engines currently account for about 44 percent of total
diesel PM emissions and about 12 percent of total NOx emissions from
mobile sources nationwide.  These proportions are even higher in some
urban areas.  The diesel emission standards will reduce emissions from
this category by more than 90 percent, and are similar to the onroad
engine requirements implemented for highway trucks and buses.  Because
the emission control devices can be damaged by sulfur, EPA also
established requirements to reduce the allowable level of sulfur in
nonroad diesel fuel by more than 99 percent by 2010.  In 2030, when the
full inventory of older nonroad engines has been replaced, the nonroad
diesel program will annually prevent up to 12,000 premature deaths, one
million lost work days, 15,000 heart attacks and 6,000 children's
asthma-related emergency room visits. 

The EPA expects the implementation of regional and national emission
reduction programs such as CAIR and the suite of mobile source rules
described above to provide significant air quality improvements for
PM2.5 nonattainment areas.  At the same time, analyses for the final
CAIR rule indicate that without implementation of local measures, a
number of PM2.5 areas are projected to remain in nonattainment status in
the 2010-2015 timeframe.  Thus, EPA believes that local and State
emission reduction efforts will need to play an important role in
addressing the PM2.5 problem as well.  The EPA will work closely with
States, Tribes, and local governments to develop appropriate in-state
pollution reduction measures to complement regional and national
strategies to meet the standards expeditiously and in a cost-effective
manner.  States will need to evaluate technically and economically
feasible emission reduction opportunities and determine which measures
can be reasonably implemented in the near term.  Local and regional
emission reduction efforts should proceed concurrently and
expeditiously.  

The promulgation of a revised 24-hour PM2.5 standard effective on
December 18, 2006 has initiated another process of State
recommendations, and the eventual designation by EPA of areas not
attaining the revised standard.  The additional designations are to be
completed within two years from the effective date, although EPA may
take an additional year to complete the designations if it determines it
does not have sufficient information.  State plans to attain the 24-hour
standard would then be due within three years of the final designations.
 A number of areas, including some that are already designated as not
attaining the 1997 standards, may be exceeding the revised 24-hour
standard.  The EPA encourages State and local governments to be mindful
of the strengthened 24-hour standard as they adopt emission reduction
strategies to attain the 1997 standards.  Such steps may help with
future attainment efforts, or even help some areas avoid a nonattainment
designation for the 24-hour standard in the first place.  

	The public health benefits of meeting the PM2.5 standards are estimated
to be significant.  Even small reductions in PM2.5 levels may have
substantial health benefits on a population level.  For example, in a
moderate-sized metropolitan area with a design value of 15.5 ug/m3,
efforts to improve annual average air quality down to the level of the
standard (15.0 ug/m3) are estimated to result in as many as 25-50 fewer
mortalities per year due to air pollution exposure.  In a smaller city,
the same air quality improvement from 15.5 to 15.0 ug/m3 still are
estimated to result in a number of avoided mortalities per year.  These
estimates are based on EPA’s standard methodology for calculating
health benefits as used in recent rulemakings.  In addition, because
many different precursors contribute to the formation of fine particles,
reductions in pollutants that contribute to PM2.5 also can provide
concurrent benefits in addressing a number of other air quality problems
- such as ground-level ozone, regional haze, toxic air pollutants, and
urban visibility impairment.  

	In order to assist States in developing effective plans to address the
local component of the PM2.5 nonattainment problem, EPA is issuing this
final fine particle implementation rule.  The EPA is issuing this rule
to implement the 1997 PM2.5 NAAQS in accordance with the statutory
requirements of the CAA forth in Subpart 1 of Part D of Title 1, i.e.,
sections 171 – 179B of the Act.  The EPA believes that the CAA directs
the Agency to implement new or revised NAAQS in nonattainment areas
solely in accordance with Subpart 1, unless another Subpart of the Act
also applies to the particular NAAQS at issue.  In this case, EPA has
concluded that Congress did not intend the Agency to implement
particulate matter NAAQS other than those using PM 10 as the indicator
in accordance with Subpart 4 of Part D of Title 1, i.e., sections 188
– 190 of the CAA.  Moreover, EPA believes that implementation of the
PM2.5 NAAQS under the provisions of Subpart 1 is more appropriate, given
the inherent nature of the PM2.5 nonattainment problem.  In contrast to
PM 10, EPA anticipates that achieving the NAAQS for PM2.5 will generally
require States to evaluate different sources for controls, to consider
controls of one or more precursors in addition to direct PM emissions,
and to adopt different control strategies.  As a result, EPA has
concluded that the provisions of Subpart 1 will allow States and EPA to
tailor attainment plans so that they can be based more specifically upon
the facts and circumstances of each nonattainment area.   

	The proposed clean air fine particle implementation rule was issued on
November 1, 2005 (70 FR 65984).  About 100 comments were received from
private citizens and parties representing industry, state and local
governments, environmental groups, and federal agencies.  Section II of
this notice describes the primary elements of the fine particle
implementation program.  Each section summarizes the relevant policies
and options discussed in the proposed rule, discusses the final policy
set forth by EPA in the final rule, and provides responses to the major
comments received on each issue.  

II.	Elements of the Clean Air Fine Particle Implementation Rule

A.	Precursors and Pollutants Contributing to Fine 

	Particle Formation

1.	Introduction

	The main precursor gases associated with fine particle formation are
SO2, NOx, volatile organic compounds (VOC), and ammonia.  This section
provides technical background on each precursor, discusses the policy
approach for addressing each precursor under the PM2.5 implementation
program, and responds to key issues raised in the public comment
process.  A subsection is also included on direct PM2.5 emissions to
address key comments received on this issue as well.  

	Gas-phase precursors SO2, NOx, VOC, and ammonia undergo chemical
reactions in the atmosphere to form secondary particulate matter. 
Formation of secondary PM depends on numerous factors including the
concentrations of precursors; the concentrations of other gaseous
reactive species; atmospheric conditions including solar radiation,
temperature, and relative humidity (RH); and the interactions of
precursors with preexisting particles and with cloud or fog droplets.
Several atmospheric aerosol species, such as ammonium nitrate and
certain organic compounds, are semivolatile and are found in both gas
and particle phases. Given the complexity of PM formation processes, new
information from the scientific community continues to emerge to improve
our understanding of the relationship between sources of PM precursors
and secondary particle formation.

	As an initial matter, it is helpful to clarify the terminology we use
throughout this notice to discuss precursors.  We recognize NOX, SO2,
VOCs, and ammonia as precursors of PM2.5 in the scientific sense because
these pollutants can contribute to the formation of PM2.5 in the ambient
air.  In section II.K on emission inventory issues, we make the point
that because of the complex and variable interaction of multiple
pollutants and precursors in the formation of fine particles, it is
important for States and EPA to continue to characterize and improve the
emissions inventories for all PM2.5 precursors.  The States and EPA need
to use the best available information available in conducting air
quality modeling and other assessments.  At the same time, the
refinement of emissions inventories, the overall contribution of
different fine particle precursors to PM2.5 formation, and the efficacy
of alternative potential control measures will vary by location.  This
requires that we further consider in this action how States should
address these PM2.5 precursors in their PM2.5 attainment plan programs. 
Thus, we require emission inventories to include the best available
information on all pollutants and precursors that contribute to PM2.5
concentrations, and at same time we use the term “PM2.5 attainment
plan precursor” to describe only those precursors that are required to
be evaluated for control strategies in a specific PM2.5 nonattainment
area or maintenance area plan. 

	In this rule, EPA has not made a finding that all precursors should be
evaluated for possible controls in each specific nonattainment area. 
The policy approach in the rule instead requires sulfur dioxide to be
evaluated for control measures in all areas, and describes general
presumptive policies for NOx, ammonia, and VOC for all nonattainment
areas.  The rule provides a mechanism by which the State and/or EPA can
make an area-specific demonstration to reverse the general presumption
for these three precursors.  States must also consider any relevant
information brought forward by interested parties in the SIP planning
and development process.  (See section II.A.8 for additional discussion
on these issues.)

	In the following sections, we discuss how States must evaluate PM2.5
precursors for nonattainment program issues in PM2.5 implementation
plans, including issues such as RACT, RACM, and reasonable further
progress.  This discussion in the final rule is linked to precursor
policies for the implementation of the new source review program, the
transportation conformity program, the general conformity program, and
the regional haze program.  All of these programs take effect prior to
approval of SIPs for attaining the PM2.5 NAAQS.  In the case of NSR, the
program applies on the effective date of the nonattainment area
designation.  In the case of transportation conformity and general
conformity, the program takes effect 1 year from the effective date of
designation of the nonattainment area (i.e., April 5, 2006 for areas
designated nonattainment effective April 5, 2005).  Thus, for each of
these programs there is an interim period between the date the program
becomes applicable to a given nonattainment area and the date the State
receives EPA approval of its overall PM2.5 implementation plan.  

2.  Legal Authority to Regulate Precursors

a. Background

	The CAA authorizes the Agency to regulate criteria pollutant
precursors.  The term “air pollutant” is defined in section 302(g)
to include “any precursors to the formation of any air pollutant, to
the extent the Administrator has identified such precursor or precursors
for the particular purpose for which the term ‘air pollutant’ is
used.”  The first clause of this second sentence in section 302(g)
explicitly authorizes the Administrator to identify and regulate
precursors as air pollutants under other parts of the CAA.  In addition,
the second clause of the sentence indicates that the Administrator has
discretion to identify which pollutants should be classified as
precursors for particular regulatory purposes.  Thus, we do not
necessarily construe the CAA to require that EPA identify a particular
precursor as an air pollutant for all regulatory purposes where it can
be demonstrated that various CAA programs address different aspects of
the air pollutant problem.  Likewise, we do not interpret the CAA to
require that EPA treat all precursors of a particular pollutant the same
under any one program when there is a basis to distinguish between such
precursors.  For example, in a rule addressing PM2.5 precursors for
purposes of the transportation conformity program, we chose to adopt a
different approach for one precursor based on the limited emissions of
that precursor from onroad mobile sources and the degree to which it
contributes to PM2.5 concentrations.  (70 FR 24280; May 6, 2005).   

  	Other provisions of the CAA reinforce our reading of section 302(g)
that Congress intended precursors to NAAQS pollutants to be subject to
the air quality planning and control requirements of the CAA, but also
recognized that there may be circumstances where it is not appropriate
to subject precursors to certain requirements of the CAA.  Section 182
of the CAA provides for the regulation of NOx and VOCs as precursors to
ozone in ozone nonattainment areas, but also provides in section 182(f)
that major stationary sources of NOx (an ozone precursor) are not
subject to emission reductions controls for ozone where the State shows
through modeling that NOx reductions do not decrease ozone.  Section
189(e) provides for the regulation of PM10 precursors in PM10
nonattainment areas, but also recognizes that there may be certain
circumstances (e.g. if precursor emission sources do not significantly
contribute to PM10 levels) where it is not appropriate to apply control
requirements to PM10 precursors.  The legislative history of Section
189(e) recognized the complexity behind the science of precursor
transformation into PM10 ambient concentrations and the need to
harmonize the regulation of PM10 precursors with other provisions of the
CAA:

The Committee notes that some of these precursors may well be controlled
under other provisions of the CAA.  The Committee intends that . . . the
Administrator will develop models, mechanisms, and other methodology to
assess the significance of the PM10 precursors in improving air quality
and reducing PM10.  Additionally, the Administrator should consider the
impact on ozone levels of PM10 precursor controls.  The Committee
expects the Administrator to harmonize the PM10 reduction objective of
this section with other applicable regulations of this CAA regarding
PM10 precursors, such as NOx.  See H. Rpt. 101-490, Pt. 1, at 268 (May
17, 1990), reprinted in S. Prt. 103-38, Vol. II, at 3292. 

	In summary, section 302(g) of the CAA clearly calls for the regulation
of precursor pollutants, but the CAA also identifies circumstances when
it may not be appropriate to regulate precursors and gives the
Administrator discretion to determine how to address particular
precursors under various programs required by the CAA.  Due to the
complexities associated with precursor emissions and their variability
from location to location, we believe that in certain situations it may
not be effective or appropriate to control a certain precursor under a
particular regulatory program or for EPA to require similar control of a
particular precursor in all areas of the country.

b.	Final Rule

	The final rule maintains the same legal basis for regulating precursors
as was described in the proposal and in the background section above. 
We also include a clarification of the term "significant contributor."

	In the proposal, when considering the impacts of the precursors NOx,
VOC and ammonia on ambient concentrations of particulate matter, we
referred to the possibility of reversing the presumed approach for
regulating or not regulating a precursor if it can be shown that the
precursor in question is or is not a “significant contributor” to
PM2.5 concentrations within the specific nonattainment area. 
“Significant contribution” in this context is a different concept
than that in Section 110(a)(2)(D).  Section 110(a)(2)(D) prohibits
States from emitting air pollutants in amounts which significantly
contribute to nonattainment or other air quality problems in other
states.  Consistent with the discussion of sections 189(e) and 302(g)
above, we are clarifying that the use in this implementation rule of the
term “significant contribution” to the nonattainment area’s PM2.5
concentration means that a significant change in emissions of the
precursor from sources in the state would be projected to provide a
significant change in PM2.5 concentrations in the nonattainment area. 
For example, if modeling indicates that a reduction in a state’s NOx
emissions would reduce ambient PM2.5 levels in the nonattainment area,
but that a reduction in ammonia emissions would result in virtually no
change in ambient PM2.5 levels, this would suggest that NOx is a
significant contributor but that ammonia is not.  The EPA in this rule
is not establishing a quantitative test for determining whether PM2.5
levels in a nonattainment area change significantly in response to
reductions in precursor emissions in a state.  However, in considering
this question, it is relevant to consider that relatively small
reductions in PM2.5 levels are estimated to result in worthwhile public
health benefits.

	This approach to identifying a precursor for regulation reflects
atmospheric chemistry conditions in the area and the magnitude of
emissions of the precursor in the area or State.  Assessments of which
source categories are more cost effective or technically feasible to
control should be part of the later RACT and RACM assessment, to occur
after the basic assessment of which precursors are to be regulated is
completed.

	In the proposed regulatory text, the provisions for reversing
presumptions for NOx, VOC and ammonia included consideration of whether
the precursor would significantly contribute to “other downwind air
quality concerns.” In the final rule we have removed that language to
clarify that identification of attainment plan precursors involves
evaluation of the impact on PM2.5 levels in a nonattainment area of
precursor emissions from sources within the state(s) where the
nonattainment area is located. Other parts of the Act, notably section
110(a)(2)(D) and section 126, focus on interstate transport of
pollutants. 

c.	Comments and Responses

	Comment:  The EPA received several comments supporting EPA’s
interpretation of 302(g) to determine the appropriate regulatory status
of each precursor pollutant.

Response:  The EPA agrees with the commenters.  In establishing section
302(g), Congress intended that precursors to NAAQS pollutants be subject
to the air quality planning and control requirements of the CAA. 
However, the CAA also recognizes that there may be circumstances where
it is not appropriate to subject precursors to certain requirements of
the CAA.   

	Comment:  The EPA received several comments regarding the applicability
of section 189(e), noting that it requires states to presumptively
control sources of PM10 precursors except where the EPA “determines
that such sources [of precursors] do not significantly contribute to
PM-10 levels which exceed the standard in the area.”  Several
commenters stated that EPA does not have the legal authority to regulate
PM2.5 precursors in a different manner.  Several commenters maintained
that all PM2.5 precursors presumptively should be subject to regulation
unless demonstrated by the State as not a significant contributor to
PM2.5 concentrations in a specific area.

	Response:  As stated above, EPA believes that section 302(g) allows the
Administrator to presumptively not require certain precursors to be
addressed in PM2.5 implementation plans generally, while allowing the
State or EPA to make a finding for a specific area to override the
general presumption.  In the following pollutant-specific sections of
this preamble, EPA finds that at this time there is sufficient
uncertainty regarding whether certain precursors significantly
contribute to PM2.5 concentrations in all nonattainment areas such that
the policy set forth in this rule does not presumptively require certain
precursors (ammonia, VOC) to be controlled in each area.  However, the
State or EPA may reverse the presumption and regulate a precursor if it
provides a demonstration showing that the precursor is a significant
contributor to PM2.5 concentrations in the area.  In addition, if in the
State’s SIP planning and adoption process a commenter provides
additional information suggesting an alternative policy for regulating a
particular precursor, the State will need to respond to this information
in its rulemaking action.  

3.  Policy for Ammonia

[Section II.E.2 of November 1, 2005 proposed rule (70 FR 65999); sec
51.1002 in draft and final regulatory text.]

a.	Background 

	Ammonia (NH3) is a gaseous pollutant that is emitted by natural and
anthropogenic sources. Emissions inventories for ammonia are considered
to be among the most uncertain of any species related to PM.  Ammonia
serves an important role in neutralizing acids in clouds, precipitation
and particles.  In particular, ammonia neutralizes sulfuric acid and
nitric acid, the two key contributors to acid deposition (acid rain). 
Deposited ammonia also can contribute to problems of eutrophication in
water bodies, and deposition of ammonium particles may effectively
result in acidification of soil as ammonia is taken up by plants.  The
NARSTO Fine Particle Assessment indicates that reducing ammonia
emissions where sulfate concentrations are high may reduce PM2.5 mass
concentrations, but may also increase the acidity of particles and
precipitation. An increase in particle acidity is suspected to be linked
with human health effects and with an increase in the formation of
secondary organic compounds.  Based on the above information and further
insights gained from the NARSTO Fine Particle Assessment, it is apparent
that the formation of particles related to ammonia emissions is a
complex, nonlinear process.

	Though recent studies have improved our understanding of the role of
ammonia in aerosol formation, ongoing research is required to better
describe the relationships between ammonia emissions, particulate matter
concentrations, and related impacts.  The control techniques for ammonia
and the analytical tools to quantify the impacts of reducing ammonia
emissions on atmospheric aerosol formation are both evolving.  Also,
area-specific data are needed to evaluate the effectiveness of reducing
ammonia emissions on reducing PM2.5 concentrations in different areas,
and to determine where ammonia decreases may increase the acidity of
particles and precipitation.  

	The proposal showed consideration for the uncertainties about ammonia
emissions inventories and about the potential efficacy of ammonia
control measures by providing for a case-by-case approach.  It was
recommended that each State should evaluate whether reducing ammonia
emissions would lead to PM2.5 reductions in their specific PM2.5
nonattainment areas.  The proposed policy did not require States to
address ammonia as a PM2.5 attainment plan precursor, unless a technical
demonstration by the State or EPA showed that ammonia emissions from
sources in the State significantly contribute to PM2.5 concentrations in
a given nonattainment area or to other downwind air quality concerns.
Where the State or EPA has determined that ammonia is a significant
contributor to PM2.5 formation in a nonattainment area, the State would
be required to evaluate control measures for ammonia emissions in its
nonattainment SIP due in 2008, in the implementation of the PM program,
and in other associated programs in that area.

b. Final Rule

	In the final rule, ammonia is presumed not to be a PM2.5 attainment
plan precursor, meaning that the State is not required to address
ammonia in its attainment plan or evaluate sources of ammonia emissions
for reduction measures.  This presumption can be reversed based on an
acceptable technical demonstration for a particular area by the State or
EPA.  If a technical demonstration by the State or EPA shows that
ammonia emissions from sources in the State significantly contribute to
PM2.5 concentrations in a given nonattainment area, the State must then
evaluate and consider control strategies for reducing ammonia emissions
in its nonattainment SIP due in 2008, in the implementation of the PM2.5
program.  Technical demonstrations on ammonia should also consider the
potential for atmospheric and particle acidity to increase with ammonia
reductions. Further discussion about technical demonstrations to support
reversing a PM2.5 precursor presumption is included in section II.A.8
below.

	This approach was retained from the proposal because of continued
uncertainties regarding ammonia emission inventories and the effects of
ammonia emission reductions.  Ammonia emission inventories are presently
very uncertain in most areas, complicating the task of assessing
potential impacts of ammonia emissions reductions.  In addition, data
necessary to understand the atmospheric composition and balance of
ammonia and nitric acid in an area are not widely available across PM2.5
nonattainment areas, making it difficult to predict the results of
potential ammonia emission reductions.  Ammonia reductions may be
effective and appropriate for reducing PM2.5 concentrations in selected
locations, but in other locations such reductions may lead to minimal
reductions in PM2.5 concentrations and increased atmospheric acidity. 
Research projects continue to expand our collective understanding of
these issues, but at this time EPA believes this case-by-case policy
approach is appropriate.  In light of these uncertainties, we encourage
States to continue efforts to better understand the role of ammonia in
its fine particle problem areas.  

c.  Comments and Responses

	Comment: One commenter stated that scientific understanding of the
complexities of PM formation from ammonia is limited. The commenter
claimed that the reduction of ammonia will not reduce PM in many areas,
and speciated PM data to investigate the potential decrease in PM from
ammonia emissions reductions is not available in all areas.

	Response:  The final rule takes these uncertainties into consideration
by allowing ammonia to be addressed on a case-by-case basis.  For any
area about which enough information is available to determine that
ammonia emission reductions would lead to a beneficial reduction in
PM2.5, the State can develop a technical demonstration justifying the
control of ammonia.  If the State chooses to develop such a
demonstration, preferably it should be completed as part of the SIP
development process and prior to the adoption of control measures, in
consultation with the appropriate EPA regional office.  

	Comment: Some commenters claimed that requiring no action on some
precursors is counter to the requirement in sections 172(a)(2) and 188
to attain the NAAQS as expeditiously as practicable.  They also asserted
that presuming that ammonia is not a PM2.5 attainment plan precursor
violates 302(g) by improperly delegating authority to the States.

	Response:  In many areas, reducing ammonia emissions could have little
effect on PM2.5 concentrations and could lead to the potentially harmful
effect of increased atmospheric acidity.  While States are not required
to take action on ammonia sources under this policy, States would be
required to address information on ammonia brought to their attention
during the planning and rule adoption process.  Under this approach,
States should assess whether ammonia reductions would lead to reduced
PM2.5 concentrations in specific nonattainment areas.  If the State
decides that ammonia reductions could yield beneficial reductions in
PM2.5, the State should complete a technical demonstration supporting a
reversal of the presumption.  The EPA does not believe that this
approach improperly delegates authority to the States.  It establishes a
general presumption for all areas through this rulemaking process, and
allows for the presumption to be modified by the State or EPA on a
case-by-case basis.  EPA still retains the ability to make a technical
demonstration for any area if appropriate to reverse the presumption and
require ammonia to be addressed in its attainment plan.  

	Comment: Some commenters stated that the results of a large study on
air emissions from concentrated animal feeding operations (CAFOs) should
be evaluated before requiring control of ammonia in areas where
agriculture is alleged to be a major source.

	Response:  The $15 million national CAFO consent agreement study
coordinated by Purdue University will greatly improve ammonia and VOC
emissions inventories and our understanding of the impacts of
agricultural emissions on particle formation.  The EPA recognizes that
the agricultural emissions study is expected to provide data for future
planning purposes, and we expect that some of the results of the study
will not be available in time to be considered in the development of
PM2.5 State Implementation Plans dues in April 2008.  However, if a
State believes it has sufficient technical information to warrant
regulation of ammonia emissions in their 2008 implementation plans, it
may include in its plan a demonstration to reverse the presumption as
well as emission reduction measures.  The EPA will review each submittal
on a case-by-case basis.  

	Comment: A presumption to not address ammonia will impede certain
states (i.e. those that have provisions requiring their regulations to
be “no stricter than Federal” provisions) from regulating ammonia.

	Response: This presumptive approach to ammonia will not restrict States
from addressing ammonia in their PM2.5 attainment plans.  If a State has
information indicating that reductions in ammonia emissions would cause
beneficial reductions in PM2.5 concentrations, the State can make a
technical demonstration to reverse the presumption.  In such cases,
inclusion of ammonia as a PM2.5 attainment plan precursor would not be
considered stricter than Federal requirements.  Under the policy in the
final rule, the Federal government or the State may assess the impact of
ammonia in a particular area and determine whether the presumption of
insignificance is appropriate or whether ammonia is in fact a
significant contributor to the PM2.5 problem in the area.

4.	Policy for VOC

[Section II.E.2 of November 1, 2005 proposed rule (70 FR 65999); sec
51.1002 in draft and final regulatory text.]

A	Background 

	The VOC policy in this rule addresses volatile and semivolatile organic
compounds, generally up to 24 carbon atoms. High molecular weight
organic compounds (typically 25 carbon atoms or more) are emitted
directly as primary organic particles and exist primarily in the
condensed phase at ambient temperatures.  Accordingly, high molecular
weight organic compounds are to be regulated as primary PM2.5 emissions
for the purposes of the PM2.5 implementation program.

	The organic component of ambient particles is a complex mixture of
hundreds or even thousands of organic compounds. These organic compounds
are either emitted directly from sources (i.e. primary organic aerosol)
or can be formed by reactions in the ambient air (i.e. secondary organic
aerosol, or SOA). Volatile organic compounds are key precursors in the
formation processes for both SOA and ozone. The relative importance of
organic compounds in the formation of secondary organic particles varies
from area to area, depending upon local emissions sources, atmospheric
chemistry, and season of the year. 

	The lightest organic molecules (i.e., molecules with six or fewer
carbon atoms) occur in the atmosphere mainly as vapors and typically do
not directly form organic particles at ambient temperatures due to the
high vapor pressure of their products. However, they participate in
atmospheric chemistry processes resulting in the formation of ozone and
certain free radical compounds (such as the hydroxyl radical [OH]) which
in turn participate in oxidation reactions to form secondary organic
aerosols, sulfates, and nitrates. These VOCs include all alkanes with up
to six carbon atoms (from methane to hexane isomers), all alkenes with
up to six carbon atoms (from ethene to hexene isomers), benzene and many
low-molecular weight carbonyls, chlorinated compounds, and oxygenated
solvents. 

	Intermediate weight organic molecules (i.e., compounds with 7 to 24
carbon atoms) often exhibit a range of volatilities and can exist in
both the gas and aerosol phase at ambient conditions. For this reason
they are also referred to as semivolatile compounds.  Semivolatile
compounds react in the atmosphere to form secondary organic aerosols. 
These chemical reactions are accelerated in warmer temperatures, and
studies show that SOA typically comprises a higher percentage of
carbonaceous PM in the summer as opposed to the winter.  The production
of SOA from the atmospheric oxidation of a specific VOC depends on four
factors: its atmospheric abundance, its chemical reactivity, the
availability of oxidants (O3, OH, HNO3), and the volatility of its
products.  In addition, recent work suggests that the presence of acidic
aerosols may lead to an increased rate of SOA formation. Aromatic
compounds such as toluene, xylene, and trimethyl benzene are considered
to be the most significant anthropogenic SOA precursors and have been
estimated to be responsible for 50 to 70 percent of total SOA in some
airsheds.  Man-made sources of aromatics gases include mobile sources,
petrochemical manufacturing and solvents.  Some of the biogenic
hydrocarbons emitted by trees are also   considered to be important
precursors of secondary organic particulate matter.  Terpenes (and
b-pinene, limonene, carene, etc.) and the sesquiterpenes are expected to
be major contributors to SOA in areas with significant   vegetation
cover, but isoprene is not.  Terpenes are very prevalent in areas with
pine forests, especially in the southeastern U.S.  The rest of the
anthropogenic hydrocarbons (higher alkanes, paraffins, etc.) have been
estimated to contribute 5–20 percent to the SOA concentration
depending on the area. 

	The contribution of the primary and secondary components of organic
aerosol to the measured organic aerosol concentrations remains a complex
issue.  Most of the research performed to date has been done in southern
California, and more recently in central California, while fewer studies
have been completed on other parts of North America.  Many studies
suggest that the primary and secondary contributions to total organic
aerosol concentrations are highly variable, even on short time scales. 
Studies of pollution episodes indicate that the contribution of SOA to
the organic particulate matter can vary from 20 percent to 80 percent
during the same day.

	Despite significant advances in understanding the origins and
properties of SOA, it remains probably the least understood component of
PM2.5.  The reactions forming secondary organics are complex, and the
number of intermediate and final compounds formed is voluminous.  Some
of the best efforts to unravel the chemical composition of ambient
organic aerosol matter have been able to quantify the concentrations of
hundreds of organic compounds representing only 10–20 percent of the
total organic aerosol mass. For this reason, SOA continues to be a
significant topic of research and investigation.

	Current scientific and technical information clearly shows that
carbonaceous material is a significant fraction of total PM2.5 mass in
most areas, that certain VOC emissions are precursors to the formation
of secondary organic aerosol, and that a considerable fraction of the
total carbonaceous material is likely from local as opposed to regional
sources.  However, while significant progress has been made in
understanding the role of gaseous organic material in the formation of
organic PM, this relationship remains complex.  We recognize that
further research and technical tools are needed to better characterize
emissions inventories for specific VOC compounds, and to determine the
extent of the contribution of specific VOC compounds to organic PM mass.

	In light of these factors, the proposed rule did not require States to
address VOCs as PM2.5 attainment plan precursors and evaluate them for
control measures, unless the State or EPA makes a finding that VOCs
significantly contribute to a PM2.5 nonattainment problem in the State
or to other downwind air quality concerns.  Many PM2.5 nonattainment
areas are also nonattainment areas for the 8-hour ozone standard;
control measures for VOCs will be implemented in some of these areas,
potentially providing a co-benefit for PM2.5 concentrations.

b.	Final Rule

	The final rule maintains the same policy as proposed.  States are not
required to address VOC in PM2.5 implementation plans and evaluate
control measures for such pollutants unless the State or EPA makes a
technical demonstration that emissions of VOCs from sources in the State
significantly contribute to PM2.5 concentrations in a given
nonattainment area.  Technical demonstrations are discussed in section
II.A.8 below.  If a State chooses to make a technical demonstration, it
should be developed in advance of the attainment demonstration.  

c.	Comments and Responses

	Comment:  One commenter stated that our understanding of the
complexities of PM2.5 formation from VOCs is limited, that speciated PM
data are not available in all areas, and that VOC reductions will not
reduce PM2.5 in many areas.  

	Response:  The EPA acknowledges the uncertainties regarding the role of
VOC in secondary organic aerosol formation.  For this reason the final
rule does not presumptively include VOC as a regulated pollutant for PM
planning.  However, if available data demonstrates that control of VOC
would reduce PM2.5 concentrations in an area, the State or EPA may
include VOC as an attainment plan precursor.

	Comment:  One commenter stated that the rationale that VOC should not
be considered a PM2.5 attainment plan precursor because most PM areas
are also ozone areas is not appropriate because many ozone areas will
attain soon and VOC reductions will still be needed for PM.

	Response:  The primary rationale for not including VOC as a PM2.5
attainment plan precursor in every nonattainment area is the uncertainty
regarding the contribution of anthropogenic VOCs to the formation of the
organic carbon portion of fine particles.  In certain areas, EPA expects
that VOC control measures will have some co-benefits in the reduction of
fine particulates.  However, this reason should not be considered the
principal reason for the policy in the final rule that VOCs
presumptively should not be considered PM2.5 attainment plan precursors.
 If a State or EPA determines that VOCs do contribute significantly to
PM2.5 concentrations in an area, the State will be required to evaluate
control measures for VOC as a PM2.5 attainment plan precursor for that
area.  This approach will provide for regulation of VOCs in locations
where it is most appropriate.  

	Comment:  One commenter suggested that EPA wait for the results of the
pending agricultural emissions study before requiring control of VOCs in
agricultural areas.  	Response:  The $15 million national CAFO consent
agreement study coordinated by Purdue University will greatly improve
ammonia and VOC emissions inventories and our understanding of the
impacts of agricultural emissions on particle formation.  The EPA
recognizes that the agricultural emissions study is expected to provide
data for future planning purposes, and we expect that some of the
results of the study will not be available in time to be considered in
the development of PM2.5 State Implementation Plans dues in April 2008. 
However, if a State believes it has sufficient technical information to
warrant regulation of VOC emissions in their 2008 implementation plans,
it may include in its plan a demonstration to reverse the presumption as
well as emission reduction measures.  The EPA will review each submittal
on a case-by-case basis.  

5.	Policy for NOx

[Section II.E.2 of November 1, 2005 proposed rule (70 FR 65999); sec
51.1002 in draft and final regulatory text.]

a.	Background 

	The sources of NOx are numerous and widespread.  The combustion of
fossil fuel in boilers for commercial and industrial power generation
and in mobile source engines each account for approximately 30 percent
of NOx emissions in PM2.5 nonattainment areas (based on 2001 emission
inventory information).  Nitrates are formed from the oxidation of
oxides of nitrogen into nitric acid either during the daytime (reaction
with OH) or during the night (reactions with ozone and water).  Nitric
acid continuously transfers between the gas and the condensed phases
through condensation and evaporation processes in the atmosphere. 
However, unless it reacts with other species (such as ammonia, sea salt,
or dust) to form a neutralized salt, it will volatilize and not be
measured using standard PM2.5 measurement techniques.  The formation of
aerosol ammonium nitrate is favored by the availability of ammonia, low
temperatures, and high relative humidity.  Because ammonium nitrate is
semivolatile and not stable in higher temperatures, nitrate levels are
typically lower in the summer months and higher in the winter months. 
The resulting ammonium nitrate is usually in the sub-micrometer particle
size range.  Reactions with sea salt and dust lead to the formation of
nitrates in coarse particles.  Nitric acid may be dissolved in ambient
aerosol particles.

	Based on a review of speciated monitoring data analyses, it is apparent
that nitrate concentrations vary significantly across the country. For
example, in some southeastern locations, annual average nitrate levels
are in the range of 6 to 8 percent of total PM2.5 mass, whereas nitrate
comprises 40 percent or more of PM2.5 mass in certain California
locations.  Nitrate formation is favored by the availability of ammonia,
low temperatures, and high relative humidity.  It is also dependent upon
the relative degree of nearby SO2 emissions because ammonia reacts
preferentially with SO2 over NOx.  NOx reductions are expected to reduce
PM2.5 concentrations in most areas.  However, it has been suggested that
in a limited number of areas, NOx control would result in increased
PM2.5 mass by disrupting the ozone cycle and leading to increased
oxidation of SO2 to form sulfate particles, which are heavier than
nitrate particles.  Because of the above factors, the proposed rule
presumed that States must evaluate and implement reasonable controls on
sources of NOx in all nonattainment areas, but allowed for the State and
EPA to develop a technical demonstration to reverse this presumption. 

b.	Final Rule

	The EPA is retaining the proposed approach in the final rule.  Under
this policy, States are required to address NOx as a PM2.5 attainment
plan precursor and evaluate reasonable controls for NOx in PM2.5
attainment plans, unless the State and EPA make a finding that NOx
emissions from sources in the State do not significantly contribute to
PM2.5 concentrations in the relevant nonattainment area.  This
presumptive policy is consistent with other recent EPA regulations
requiring NOx reductions which will reduce fine particle pollution, such
as the Clean Air Interstate Rule and a number of rules targeting onroad
and nonroad engine emissions.  

	Technical demonstrations that would reverse the presumption should be
developed in advance of the attainment demonstration and are discussed
in section II.A.8 below.  

c.	Comments and Responses

	Comment:  Most commenters generally agreed with the proposed inclusion
of NOx as a presumptive PM2.5 attainment plan precursor.  

	Response:  The EPA agrees with these commenters.  

	Comment:  Some commenters requested guidance on what would constitute
an acceptable demonstration to reverse the presumption that NOx is a
PM2.5 attainment plan precursor.  

	Response: Guidance on technical demonstrations to reverse the
presumptive inclusion of NOx in all state implementation plans is
discussed in section II.A.8 below.  

	Comment:  One commenter raised concerns that the proposed policy for
NOx would allow a State to find NOx to be an insignificant contributor
to an area’s PM2.5 nonattainment problem and effectively keep the
State from controlling the area’s NOx emissions for other purposes,
such as to address interstate transport under section 110 of the CAA. 
Section 110 requires SIPs to prohibit emissions within the State that
would contribute significantly to another State’s nonattainment
problem or interfere with another State’s maintenance plan. 

	Response:  The identification of precursors for regulation under this
rule is for purposes of PM2.5 nonattainment and maintenance plans under
Part D of the CAA.  The PM2.5 implementation rule does not prevent a
State from regulating NOx sources under any other Federal or State rule,
including interstate transport rules under Section 110. 

6.	Policy for SO2

	[Section II.E.2 of November 1, 2005 proposed rule (70 FR 65999); sec
51.1002 in draft and final regulatory text.]

a.	Background 

	Sulfur dioxide is emitted mostly from the combustion of fossil fuels in
boilers operated by electric utilities and other industry.  Less than 20
percent of SO2 emissions nationwide are from other sources, mainly other
industrial processes such as oil refining and pulp and paper production.
 The formation of sulfuric acid from the oxidation of SO2 is an
important process affecting most areas in North America.  There are
three different pathways for this transformation.  

	First, gaseous SO2 can be oxidized by the hydroxyl radical (OH) to
create sulfuric acid.  This gaseous SO2 oxidation reaction occurs slowly
and only in the daytime.  Second, SO2 can dissolve in cloud water (or
fog or rain water), and there it can be oxidized to sulfuric acid by a
variety of oxidants, or through catalysis by transition metals such as
manganese or iron.  If ammonia is present and taken up by the water
droplet, then ammonium sulfate will form as a precipitate in the water
droplet.  After the cloud changes and the droplet evaporates, the
sulfuric acid or ammonium sulfate remains in the atmosphere as a
particle.  This aqueous phase production process involving oxidants can
be very fast; in some cases all the available SO2 can be oxidized in
less than an hour.  Third, SO2 can be oxidized in reactions in the
particle-bound water in the aerosol particles themselves.  This process
takes place continuously, but only produces appreciable sulfate in
alkaline (dust, sea salt) coarse particles.  Oxidation of SO2 has also
been observed on the surfaces of black carbon and metal oxide particles.
 During the last 20 years, much progress has been made in understanding
the first two major pathways, but some important questions still remain
about the smaller third pathway.  Models indicate that more than half of
the sulfuric acid in the eastern United States and in the overall
atmosphere is produced in clouds.

	 The sulfuric acid formed from the above pathways reacts readily with
ammonia to form ammonium sulfate, (NH4)2SO4.  If there is not enough
ammonia present to fully neutralize the produced sulfuric acid (one
molecule of sulfuric acid requires two molecules of ammonia), part of it
exists as ammonium bisulfate, NH4HSO4 (one molecule of sulfuric acid and
one molecule of ammonia) and the particles are more acidic than ammonium
sulfate.  In certain situations (in the absence of sufficient ammonia
for neutralization), sulfate can exist in particles as sulfuric acid,
H2SO4.  Sulfuric acid often exists in the plumes of stacks where SO2,
SO3, and water vapor are in much higher concentrations than in the
ambient atmosphere, but these concentrations become quite small as the
plume is cooled and diluted by mixing.

	Because sulfate is a significant contributor (e.g. ranging from 9
percent to 40 percent) to PM2.5 concentrations in nonattainment areas
and to other air quality problems in all regions of the country, EPA
proposed that States would be required to address sulfur dioxide as a
PM2.5 attainment plan precursor in all areas. 

b.	Final Rule

	The final rule includes the same policy for sulfur dioxide as in the
proposal.  States are required to address sulfur dioxide as a PM2.5
attainment plan precursor and evaluate SO2 for possible control measures
in all areas.  Sulfate is an important precursor to PM2.5 formation in
all areas, and has a strong regional impact on PM2.5 concentrations. 
This policy is consistent with past EPA regulations, such as the CAIR,
the Clean Air Visibility Rule, the Acid Rain rules, and the Regional
Haze rule, that require SO2 reductions to address fine particle
pollution and related air quality problems.   

Under the transportation conformity program, sulfur dioxide is not
required to be addressed in transportation conformity determinations
before a SIP is submitted unless either the state air agency or EPA
regional office makes a finding that on-road emissions of sulfur dioxide
are significant contributors to the area's PM2.5 problem.  Sulfur
dioxide would be addressed after a PM2.5 SIP is submitted if the area's
SIP contains an adequate or approved motor vehicle emissions budget for
sulfur dioxide.  EPA based this decision on the de minimis level of
sulfur dioxide emissions from on-road vehicles currently, and took into
consideration the fact that sulfur dioxide emissions from on-road
sources will decline in the future due to the implementation of
requirements for low sulfur gasoline (which began in 2004) and for low
sulfur diesel fuel (beginning in 2006).  For more information, see the
May 6, 2005 transportation conformity rule on PM2.5 precursors at 70 FR
24283.

c.	Comments and Responses

	Comment:  Most commenters agreed with the proposed policy for SO2.  One
commenter stated, “…requiring states to address sulfur dioxide in
attainment planning in all areas is consistent with the science of PM2.5
formation and essential to effective implementation of the PM2.5
NAAQS.”  Another commenter concluded that EPA’s proposal “…is
justified based on the fact that SO2 has been found to be a significant
contributor to PM2.5 nonattainment in all areas.”

	Response:  The EPA agrees with these comments.  

	Comment:  Some commenters believe States should be able to make a
demonstration that SO2 not be addressed as an attainment plan precursor.
 The commenters claim that the urban increment of sulfate is generally
small, and SO2 control will not matter in many areas.  Commenters also
note that a large percentage of the SO2 emission inventory is being
reduced and will be reduced further through existing programs, and that
if attainment can be demonstrated without additional SO2 controls, a
State should be allowed to make that demonstration in its SIP.  One
commenter stated that whether SO2 emissions from a given source located
in a nonattainment area in fact contribute significantly to ambient
concentrations of sulfate and PM2.5 in that nonattainment area likely
will depend on a range of factors, including source type, stack height,
location, and meteorology.  The commenter asserted that sulfate forms
over significant geographic distances from the source of the SO2
emissions and may not form significant concentrations of PM2.5 in the
local nonattainment area.

	Response:  As in the proposal, the final rule requires SO2 to be
considered a PM2.5 attainment plan precursor in all cases.  Sulfate is a
significant fraction of PM2.5 mass in all nonattainment areas currently,
and although large SO2 reductions are projected from electric generating
units with the implementation of the CAIR program, sulfate is still
projected to be a key contributor to PM2.5 concentrations in the future.
 SO2 emissions also lead to sulfate formation on both regional and local
scales.  The EPA agrees that the extent of the contribution from a
particular source in a nonattainment area to PM2.5 concentrations in the
area will depend on a number of factors, and that at times the reaction
of SO2 emissions in the atmosphere to form sulfate particles may occur
less rapidly and extend over a significant distance.  However, at other
times the conversion of SO2 to sulfate can occur rapidly and local
impacts from a particular source can be more significant.  States are
required to develop plans to attain as expeditiously as practicable
through the identification of technically and economically feasible
control measures from the full range of source categories contributing
to PM2.5 nonattainment areas.  In developing these plans, each State
will need to consider whether controls on local SO2 sources would be
cost-effective and would be needed to attain expeditiously.  

7.	Policy for Direct PM

 	[Section II.E.2 of November 1, 2005 proposed rule (70 FR 65999); sec
51.1002 in draft and final regulatory text.]

a.	Background 

	This section addresses inorganic and organic forms of directly emitted
PM.  Although these direct emissions are by definition not precursors to
PM2.5, this section is included to provide information on the full range
of components that commonly make up fine particulate matter.  

	The main anthropogenic sources of inorganic (or crustal) particles are:
 entrainment by vehicular traffic on unpaved or paved roads; mechanical
disturbance of soil by highway, commercial, and residential
construction; and agricultural field operations (tilling, planting and
harvesting).  Industrial processes such as quarries, minerals
processing, and agricultural crop processing can also emit crustal
materials.  While much of these emissions are coarse PM, the size
distribution can have a tail of particles smaller than PM2.5.  

	In general, coarse PM is most important close to the source, and not
generally a significant contributor to regional scale PM problems.  Even
so, during certain high wind events, fine crustal PM has been shown to
be transported over very long distances.   

	Emission estimates of mechanically suspended crustal PM from sources
within the US are often quite high.  However, this PM is often released
very close to the ground, and with the exception of windblown dust
events, thermal or turbulent forces sufficient to lift and transport
these particles very far from their source are not usually present. 
Thus, crustal material is only a minor part of PM2.5 annual average
concentrations. 

 	Primary carbonaceous particles are largely the result of incomplete
combustion of fossil or biomass fuels.  This incomplete combustion
usually results in emissions of both black carbon and organic carbon
particles.  High molecular weight organic molecules (i.e., molecules
with 25 or more carbon atoms) are either emitted as solid or liquid
particles, or as gases that rapidly condense into particle form.  These
heavy organic molecules sometimes are referred to as volatile organic
compounds, but because their characteristics are most like direct PM
emissions, they will be considered to be primary emissions for the
purposes of this regulation.  Primary organic carbon also can be formed
by condensation of semi-volatile compounds on the surface of other
particles.  

 	The main combustion sources emitting carbonaceous PM2.5 are certain
industrial processes, managed burning, wildland fires, open burning of
waste, residential wood combustion, coal and oil-burning boilers
(utility, commercial and industrial), and mobile sources (both onroad
and nonroad).  Certain organic particles also come from natural sources
such as decomposition or crushing of plant detritus.  Most combustion
processes emit more organic particles than black carbon particles.  A
notable exception to this is diesel engines, which typically emit more
black carbon particles than organic carbon. Because photochemistry is
typically reduced in the cooler winter months for much of the country,
studies indicate that the carbon fraction of PM mass in the winter
months is likely dominated by direct PM emissions as opposed to
secondarily formed organic aerosol. 

	Particles from the earth’s crust may contain a combination of
metallic oxides and biogenic organic matter.  The combustion of surface
debris will likely entrain some soil.  Additionally, emissions from many
processes and from the combustion of fossil fuels contain elements that
are chemically similar to soil.  Thus, a portion of the emissions from
combustion activities may be classified as crustal in a compositional
analysis of ambient PM2.5.

The proposed rule required that States address the direct emissions of
particulate matter in their PM2.5 attainment plans.  During the comment
period, EPA received several comments regarding the definition of what
should be regulated as “direct PM2.5.”

b.	Final Rule

	This rule defines direct PM2.5 emissions as “air pollutant emissions
of direct fine particulate matter, including organic carbon, elemental
carbon, direct sulfate, direct nitrate, and miscellaneous inorganic
material (i.e. crustal material).”   Development of attainment plans
will include direct PM2.5 emissions and specific PM2.5 attainment plan
precursors.      

c.	Comments and Responses

	Comment:  A few commenters noted that 40 CFR 51.1000 of the proposed
rule includes definitions for both “direct PM2.5 emissions” and for
“PM2.5 direct emissions.”  They recommend including just one
definition in the final rule.  

	Response:  The EPA acknowledges this oversight and has included in the
final rule a single definition for “direct PM2.5 emissions.”  It
reads:  “Direct PM2.5 emissions means solid particles emitted directly
from an air emissions source or activity, or gaseous emissions or liquid
droplets from an air emissions source or activity which condense to form
particulate matter at ambient temperatures.  Direct PM2.5 emissions
include elemental carbon, directly emitted organic carbon, directly
emitted sulfate, directly emitted nitrate, and other inorganic particles
(including but not limited to crustal material, metals, and sea
salt).”

8.	Optional Technical Demonstrations for NOx, VOC, and Ammonia

	[Section II.E.2 of November 1, 2005 proposed rule (70 FR 65999); sec
51.1002 in draft and final regulatory text.]

a.	Background 

	The proposed rule required States to evaluate and consider control
strategies for sources of SO2 and direct PM2.5 emissions in all
nonattainment areas.  For the precursors NOx, VOC, and ammonia, the
proposed rule included presumptive policies that could be reversed with
an acceptable technical demonstration by the State or EPA.  (The policy
in the proposal presumptively required that NOx emissions must be
addressed in all areas, and that VOC and ammonia emissions do not need
to be addressed in all areas.)  A number of commenters requested
additional guidance on the criteria for an acceptable technical
demonstration.  

b.	Final Rule

	The final rule retains provisions for the State or EPA to conduct a
technical demonstration to reverse the presumptive inclusion of NOx or
to reverse the presumptive exclusions of ammonia and VOC as PM2.5
attainment plan precursors.  Demonstrations to reverse the presumptions
for ammonia, VOC, or NOx are to be based on the weight of evidence of
available information, and any demonstration by the State must be
approved by EPA.  The State must demonstrate that based on the sum of
available technical and scientific information, it would be appropriate
for a nonattainment area to reverse the presumptive approach for a
particular precursor.  The demonstration should include information from
multiple sources, including results of speciation data analyses, air
quality modeling studies, chemical tracer studies, emission inventories,
or special intensive measurement studies to evaluate specific
atmospheric chemistry in an area.  

	Because of the variation among nonattainment areas in terms of such
factors as local emissions sources, growth patterns, topography, and
severity of the nonattainment problem, EPA believes that it would not be
appropriate to define a prescriptive set of analyses that must be
included in all PM2.5 precursor technical demonstrations.  The key
criterion is that any technical demonstration must fairly represent
available information.  

	In developing the implementation plan for a nonattainment area, the
State should use all relevant information available (from EPA, the
State, or other sources) to determine the scientifically most
appropriate approach to regulating NOx, ammonia, and VOC emissions in
the area.  As required under any State rulemaking process, the State
must consider and provide a response in the record to any information or
evidence brought forward by commenters during the SIP planning,
development and review process which indicates that the presumption for
a precursor should be reversed.  In its review of the forthcoming State
implementation plan submittal, EPA will review the State’s proposed
precursor policies in light of all currently available information.  If
information brought forward by commenters or the State in the SIP
development process shows that the presumption in this rule for ammonia,
VOC or NOx is not technically justified for a particular nonattainment
area, the State must conduct a technical demonstration to reverse the
presumption.  In the case of ammonia or VOC, the State then would
evaluate control measures and implement those measures that are
technically and economically feasible and that will contribute to
expeditious attainment of the standards.	

	In the section below we suggest examples of the types of analyses that
would be appropriate to use in developing such a demonstration.  States
are encouraged to consult with EPA in formulating appropriate technical
demonstrations.

i.	Emission Inventory Information:  An analysis might show that a
precursor composes a significant fraction of the emissions inventory in
an area and therefore requires greater consideration.

Example: Several stationary sources emitting particular VOCs known to
contribute to SOA formation make up a significant portion of the
area’s VOC inventory.  This analysis may be useful in conjunction with
other analyses included in a weight of evidence demonstration.   

ii.	Speciation Data Information:  Analysis of data from speciation
networks might lead a State to determine the relative importance of a
precursor to seasonal or yearly average PM concentrations.  Individual
precursors require different approaches.  Collection of new data could
be used to understand the impacts of precursors in an area.

Example: Nitrate ion is a large portion of winter average PM2.5 mass. 
Nitrate ion is a major portion of PM2.5 mass on the 10 highest PM2.5
days in winter in the past 3 years.  The days with the highest mass
concentrations might be indicative of inversion conditions and/or local
impacts, rather than large-scale transport processes.  For these
reasons, nitrate should be addressed in the PM2.5 attainment plan.  

Example:  Ammonium ion data combined with total calculated nitrate data
indicates that reductions in ammonia would reduce PM concentrations
without a sharp related increase in particle acidity.  PM speciation
data shows that PM in the area is generally within 10% of calculated
neutralization.  In places for which the needed atmospheric data are
available to determine whether increased acidity is estimated to lead to
negative environmental effects, analysis showing that increased acidity
of particles and precipitation would likely result from ammonia
reductions would support the presumption against ammonia regulation. 
Analysis showing that ammonia reductions would be unlikely to increase
the acidity of particles and precipitation, and that potential
reductions in ammonia would significantly reduce PM2.5 levels, would
support a technical demonstration to reverse the presumption.  

iii.	Modeling Information:  Results of atmospheric modeling may help a
State characterize the impacts of potential precursor emission
reductions on PM2.5 concentrations in an area.

Example:  Modeling of SO2, NOx, and VOC emission reductions result in
lower sulfate and nitrate levels but not lower secondary organic aerosol
levels.  This likely indicates that VOC reductions are not as vital as
reductions of the other precursors.  

Example: Modeled reductions of NOx show a potential increase in sulfate
formation through disruption of the ozone cycle.  SO2 reductions may be
a better choice than NOx reductions.

Example:  Modeled ammonia reductions show a projected reduction in PM2.5
concentrations in selected areas.  Although dependant on good quality
inventory data, this type of an analysis would indicate that the area is
ammonia-limited and that ammonia reductions may be beneficial.

Example:  Modeling shows that reductions in SO2 in the absence of NOx
reductions in an area will not result in a significant PM2.5 reduction
because more nitrate particles form when less SO2 is available for
particle formation.  However, PM2.5 reductions are significant when both
SO2 and NOx are reduced concurrently.  This analysis would indicate that
NOx reductions should be included in the PM2.5 attainment plan for the
area.

iv.	Monitoring, Data Analysis, or Other Special Studies:  Could include
monitoring of gases and compounds not typically monitored under the
PM2.5 speciation network, receptor modeling analysis, or special
monitoring studies.  

Example:  Data from specialized monitoring studies can provide insights
about concentrations of ammonia gas and nitric acid in an area and
whether the area is ammonia-limited or not.  Ammonia reductions in
ammonia-limited areas typically yield reductions in PM2.5
concentrations.  Specialized monitoring and laboratory studies can also
assess the relative concentrations of organic compounds and provide
insights into the contributions of different anthropogenic and biogenic
VOCs to secondary organic aerosol formation.  

Example:  Receptor modeling and statistical analysis PM2.5 speciation
monitoring data can indicate relative contributions to PM2.5 mass from
sources with different chemical “fingerprints.”

Example:  Additional analysis of organic compounds on filters collected
through speciation monitoring may reveal insights about the relative
degree of carbonaceous material considered to be from fossil fuel
combustion as opposed to combustion of “modern” material (such as
wood or biomass).

c.	Comments and Responses

	Comment:  A number of commenters requested that the final rule include
guidance on acceptable technical demonstrations.

	Response:  The above section includes examples designed to help States
formulate appropriate demonstrations.  Prescribing specific technical
indicators to be used in all areas would ignore the scientific
uncertainty inherent in the relationships between precursor emissions
and the responses of atmospheric concentrations of PM2.5.  Therefore,
States are encouraged to review available information and consult with
EPA in formulating technical demonstrations appropriate to a particular
area.  

  SEQ CHAPTER \h \r 1 B.	No Classification System.  tc "B.
Classification Options Under Consideration for PM2.5 Nonattainment
Areas. " \l 2 

1.	No Classification System

a.	Background. 

	Section 172 of subpart 1 contains the general requirements for SIPs for
all nonattainment areas.  Section 172(a)(1) states that on or after the
date of designation, the Administrator may classify an area for the
purpose of applying an attainment date or for some other purpose.  Thus,
a classification system is allowed under section 172 of the CAA, but is
not required for the purposes of implementing a national ambient air
quality standard.  The CAA also states that EPA may consider certain
factors in making a decision concerning classification for areas, such
as the severity of nonattainment in such areas, and the availability and
feasibility of the pollution control measures that may be needed to
achieve attainment.  In the proposed rule, EPA provided two
implementation approaches for classifying PM2.5 nonattainment areas. 
Under the first approach, there would be no classification system. 
Under the second approach, a two-tiered classification system would
apply, with areas classified as either “moderate” or “serious”
based on specific criteria.  

	For example, the two classification tiers could be based on the
severity of nonattainment (e.g., serious areas would be those with a
design value above a specific threshold), or on the attainment date for
the area (e.g., serious areas would be those with attainment dates after
April 2010).  However, any moderate area that needs an attainment date
longer than 5 years would be reclassified as serious.  This would ensure
that areas with a more persistent PM2.5 problem are subject to more
stringent requirements, even if they are not one of the areas with the
highest current design values.  For such areas, the State would be
required to request reclassification for an area and ensure that the
2008 attainment SIP submission for the area includes all measures needed
to meet the serious area requirements. Under the two tiered
classification approach, we proposed that serious PM2.5 nonattainment
areas would be required to meet the more stringent requirements than
moderate areas that would be defined in this rulemaking action (e.g.,
lower thresholds for RACT, fixed percentage reduction for RFP, etc.). 
For serious areas, the attainment date would be as expeditious as
practicable, but no later than 10 years after designation, depending on
the year in which the area would be projected to attain considering
existing control requirements and the effect of RACM, RACT and RFP.

b.	Final Rule. 

	 The EPA believes that in the case of PM2.5, the no-classification
approach is the most appropriate approach.  An advantage of this
approach is that it provides a relatively simple implementation
structure for State implementation of the PM2.5 standards, and avoids
the need to define a classification system and determine classifications
for each area.  Without classifications, this rule still requires that
that SIPs include all reasonable measures that contribute to achieving
attainment as expeditiously as practicable.  (Further detail is provided
in sections D. and F. below.)  Because of differences in the nature and
sources of the PM2.5 problem in different parts of the country, EPA did
not find it appropriate to establish a tiered classification system with
increasing control measure requirements.  The no-classifications
approach provides States with greater flexibility to determine the
control strategies that will be most effective and efficient in bringing
specific areas into attainment as expeditiously as practicable. 	In
addition, EPA believes that States requesting additional time to attain
the standard beyond the initial 5 year attainment date, provided for
under Subpart I, will need to adopt additional or more stringent
measures to meet their obligations for RACT, RACM and attainment that is
as expeditious as practicable.   We believe that this addresses the main
concerns of those commenters who contend that a two tiered
classification system should be implemented.

c.	Comments and Responses.  

	Comment:   The majority of the commenters who commented on this issue
stated that they agreed with EPA’s preferred no classification
approach.  These commenters generally stated that they believed that EPA
has the authority not to establish a classification system for PM2.5
nonattainment areas.  Some commenters stated that it would also be
unreasonable, at this point in the process, for EPA to implement a
classification scheme for the PM2.5 standard.  Many commenters support
the no classification approach because it provides for a simple
implementation structure and/or allows greater implementation
flexibility to States, including flexibility to address specific
problems related to individual nonattainment areas in the most
cost-effective and expeditious manner, rather than through a one size
fits all approach.  Other commenters stated that they believe that a
classification system is not needed because nonattainment areas in the
Eastern United States are likely to attain the standard within a
timeframe that is consistent with the timeframe established under
Subpart 1.  

	Response: The EPA agrees with these commenters.

	Comment:   Several commenters disagreed with EPA’s preferred approach
and agreed with the two tiered classification approach featuring a
“moderate” and a “serious” area classification. These commenters
also stated that the threat of reclassification or “bump up” to a
higher classification was a powerful incentive for areas to attain as
expeditiously as practicable.  Commenters also indicated that areas
needing more time to attain the standard should be required to implement
more stringent measures or mandatory measures. 

	Response:   The EPA agrees that areas with more severe nonattainment
problems will need to implement more stringent measures to attain. 
However, EPA does not believe that a classification system is needed to
ensure that such measures are implemented.  The EPA believes that on
balance the no classification approach is the most appropriate
classification option for the implementation of the PM2.5 standard
because of the difference in contributing sources from area to area.  	

	Comment:  Several commenters stated that under EPA’s preferred
approach, each State would be required to submit an attainment
demonstration proposing an attainment date that is “as expeditious as
practicable” for each area.  They asserted that to allow States to
propose their own attainment dates would invite delay in the process of
cleaning up fine particle pollution.  These commenters further stated
that States would have no incentive to set an attainment date earlier
than the outer limit set by EPA, even if it would be practicable to
attain the NAAQS sooner.

	Response:   Section 172 of the CAA requires SIPs to demonstrate
attainment as expeditiously as practicable regardless of whether there
is a classification system, and under this rule states must justify that
their attainment date is as expeditious as practicable considering all
reasonable measures.  As noted above, EPA believes that States
requesting additional time to attain the standard beyond the initial 5
year attainment date will need to adopt additional or more stringent
measures to meet their obligations for RACT and RACM and to attain as
expeditiously as practicable.  More details on the analytical process
required for an attainment demonstration is included in section II.F.

	Comment:   Several commenters stated that the CAA requires regulation
of the PM2.5 standard under Subpart 4 of Part D.  These commenters state
that EPA takes the position that it must regulate PM2.5 under Subpart 1
of the CAA, which applies to nonattainment areas in general.  The
commenters state that section 7513, in Subpart 4 of Part D of the CAA,
contains specific provisions for classification of particulate matter
nonattainment areas, and that EPA must therefore regulate PM2.5 under
Subpart 4, which requires a moderate and serious area classification
system.  Other commenters argued that implementation of the PM2.5
standard must proceed under Subpart 1 of Part D of Title I of the CAA
and cannot be governed by Subpart 4 of Part D, which addresses the
implementation of the PM10 standard which is a different pollutant than
PM2.5.

	Response:   The EPA finds that the PM2.5 standard should be implemented
under subpart I of the CAA, which is the general provision of the CAA
related to NAAQS implementation.  Part D of Title I of the CAA sets
forth the requirements for SIPs needed to attain the national ambient
air quality standards.  Part D also includes a general provision under
Subpart I which applies to all NAAQS for which a specific subpart does
not exist.  Because the PM2.5 standards were not established until 1997,
the plan provisions found in section 172 of subpart 1  pertaining to
plans for nonattainment areas apply.  The EPA further agrees with
comments stating that subpart 4 on its face applies only to the PM10
standard.  In general, the emphasis in subpart 4 on reducing PM10
concentrations from certain sources of direct PM2.5 emissions can be
somewhat effective in certain PM2.5 nonattainment areas but not in all. 
Contributions to PM2.5 concentrations are typically from a complex mix
of sources of primary emissions and sources of precursor emissions which
form particles through reactions in the atmosphere.  PM2.5 also differs
from PM10 in terms of atmospheric dispersion characteristics, chemical
composition, and contribution from regional transport.

2. 	Rural Transport Classification  tc "2.  Rural Transport
Classification " \l 4 Option

a.	Background.	

	The 8-hour ozone implementation program includes a “rural transport
classification” for subpart 1 nonattainment areas.  In the proposal
for this rule we discussed whether an area classification of this type
would be appropriate for the PM2.5 implementation program in light of
the fact that no currently designated PM2.5 nonattainment area met the
criteria similar to those that apply to rural transport areas under the
ozone implementation program.

	As addressed in the proposal, a PM2.5 nonattainment area would qualify
for the “rural transport” classification if it met criteria similar
to those specified for rural transport areas for the 1-hour ozone
standard under section 182(h).  Section 182(h) defines “rural
transport” areas as those areas that do not include, and are not
adjacent to, any part of a Metropolitan Statistical Area (MSA) or, where
one exists, a Consolidated Metropolitan Statistical Area (CMSA). 
Section 182(h) further limits the category to those areas whose own
emissions do not make a significant contribution to pollutant
concentrations in those areas, or in other areas. 

	As discussed in the preamble to the proposed rule, potential criteria
for a State to identify an area for a rural transport classification
under the PM2.5 program could be similar to the criteria used in the
ozone implementation program:  a State with a PM2.5 “rural
transport” area would need to 1) demonstrate that the area meets the
above criteria,  2) demonstrate using EPA approved attainment modeling
that the nonattainment problem in the area is due to the “overwhelming
transport” of emissions from outside the area, and 3) demonstrate that
sources of PM2.5 and its precursor emissions within the boundaries of
the area do not contribute significantly to PM2.5 concentrations that
are measured in the area or in other areas. 

	An area which qualifies for the “rural transport” classification
would only be required to adopt local control measures sufficient to
demonstrate that the area would attain the standard by its attainment
date “but for” the overwhelming transport of emissions emanating
from upwind States.  RFP requirements under subpart 1 would still apply
to these areas.  As with other nonattainment areas, rural transport
nonattainment areas would be subject to NSR, transportation conformity,
and general conformity requirements.  In the proposal we solicited
comments on whether it would be appropriate to establish less burdensome
NSR requirements in the event that a classification for rural transport
areas is adopted in the final rule.  The EPA requested comment on
whether this type of classification option is needed at all under the
PM2.5 implementation program. 

b.	Final Rule.

	The final rule does not include a rural transport classification.  This
type of classification was included in the CAA for purposes of
implementing the ozone standards because of the phenomenon of the
formation of high ozone levels far downwind in very rural locations,
including on high elevation mountain peaks.  In reviewing the currently
designated PM2.5 nonattainment areas, it appears that all areas but one
are within or adjacent to a metropolitan area (i.e. core-based
statistical area or consolidated statistical area), and thus would not
meet the criteria discussed above.  Although PM2.5 concentrations are
greatly affected by long-range transport of air pollution, it appears
that nonattainment areas typically are located in urban areas and
include significant local pollutant sources. 

c.	Comments and Responses

	Comment:   Several commenters stated that they do not support the
adoption of a rural transport classification because it is not needed. 
Commenters stated that given the criteria for the rural transport
classification, which greatly limits its applicability, few if any PM2.5
nonattainment areas can qualify for the option. One commenter stated
that EPA modeled the rural transport classification after the “rural
transport areas” provision contained in subpart 2 of the CAA, which
applies only to the ozone standard.  The commenter further states that
neither Subpart 1 nor 4 contain any statutory authority for such a
classification.

	Response:  The EPA believes that it has sufficient statutory authority
under the CAA to establish a rural transport classification, but we do
not believe that such a classification is needed. 

	Comment:   One commenter generally supported the rural transport
concept and the proposed associated requirements, with the addition that
data analysis be included as appropriate in the required technical
demonstrations in addition to modeling.  While no PM2.5 area currently
meets the requirements for the rural transport classification option,
several commenters recommended that it be maintained for potential cases
in which the PM2.5 standards are made more stringent, or measured air
quality in areas change in such a way that areas would qualify for the
rural transport classification at a later date.

	Response: The EPA does not agree that a rural transport classification
is needed.  The EPA will re-evaluate the need for such a classification
as appropriate. 

C.	Due Dates and Basic Requirements for Attainment Demonstrations 

a.	Background. 

	 Part D of Title I of the CAA sets forth the requirements for SIPs
needed to attain the national ambient air quality standards.  Part D
includes a general subpart 1 which applies to all NAAQS for which a
specific subpart does not exist.  The 1990 CAA Amendments do not include
any subpart for PM2.5 because the PM2.5 standards were not yet
established.  The EPA has determined that for PM2.5, the nonattainment
area plan provisions found in section 172 of subpart 1 apply.  

	Section 172(b) of the CAA requires that at the time the Agency
promulgates nonattainment area designations, the EPA must also establish
a schedule for States to submit SIPs meeting the applicable requirements
of section 172(c) and of section 110(a)(2) of the CAA.  Nonattainment
area designations were finalized in December 2004, and a supplemental
notice was issued in April 2005.  Consistent with section 172(b) of the
CAA, 40 CFR 51.1002 of the proposed rule requires the State to submit
its attainment demonstration and SIP revision within 3 years, or by
April 2008.

	Section 51.1006 of the proposed rule addresses the situation in which
an area is initially designated as attainment/unclassifiable but is
later designated as nonattainment based on air quality data after the
2001-2003 period.  Under such circumstances, the SIP submittal date
would be 3 years from the effective date of the redesignation, and the
attainment date would be as expeditiously as practicable but no later
than 5 years from the effective date of the redesignation.  

	The section 172(c) requirements that States are to address under
section 172(c) (including RACT, RACM, RFP, contingency measures,
emission inventory requirements, and NSR) are discussed in later
sections of this notice.  Section 110(a)(2) of the CAA requires all
States to develop and maintain a solid air quality management
infrastructure, including enforceable emission limitations, an ambient
monitoring program, an enforcement program, air quality modeling, and
adequate personnel, resources, and legal authority.  Section
110(a)(2)(D) also requires State plans to prohibit emissions from within
the State which contribute significantly to nonattainment or maintenance
areas in any other State, or which interfere with programs under part C
to prevent significant deterioration of air quality or to achieve
reasonable progress toward the national visibility goal for Federal
class I areas (national parks and wilderness areas).  In order to assist
States in addressing their obligations regarding regionally transported
pollution, EPA has finalized the CAIR to reduce SO2 and nitrogen oxide
emissions from large electric generating units.

	To date, few states have submitted a SIP revision addressing the
section 110(a)(2) requirements for the purposes of implementing the
PM2.5 standards.  The EPA recognizes that this situation is due in part
to the fact that there were a series of legal challenges to the PM
standards which were not resolved until March 2002, at which time the
standards and EPA’s decision process were upheld (see section I.B. for
further discussion of past legal challenges to the standards).  To
address the States’ continuing obligation to address the requirements
of section 110(a), 40 CFR 51.1002 of the proposed rule also required
each State to address the required elements of section 110(a)(2) of the
CAA as part of the SIP revision adopting its attainment plan, if it has
not already done so.  On March 10, 2005, EPA entered into a consent
decree with Environmental Defense and American Lung Association
concerning EPA’s failure to find that States failed to submit SIPs to
address the section 110(a)(2) requirements.  As a part of that consent
decree, by no later than October 8, 2008, EPA is required to publish a
notice in the Federal Register related to its determinations of whether
each State has submitted SIPs for PM2.5 that meet the requirements as
stated under section 110(a)(2) of the CAA.     

b.	Final Rule. 

	The final rule maintains the regulatory approach described above.

c.	Comments and Responses.  

	There were no comments on this portion of the proposal.

D.	Attainment Dates

1.	Background on Statutory Requirements.  

	Establishing attainment dates.  Section 172(a)(2) states that an
area’s attainment date “shall be the date by which attainment can be
achieved as expeditiously as practicable, but no later than 5 years from
the date such area was designated nonattainment …, except that the
Administrator may extend the attainment date to the extent the
Administrator determines appropriate, for a period no greater than 10
years from the date of designation as nonattainment considering the
severity of nonattainment and the availability and feasibility of
pollution control measures.”

	Since PM2.5 designations have an effective date of April 5, 2005, the
initial 5-year attainment date for PM2.5 areas would be no later than
April 5, 2010.  For an area with an attainment date of April 5, 2010,
EPA would determine whether it had attained the standard by 

evaluating air quality data from the three previous calendar years (i.e.
2007, 2008, and 2009).  

	For any areas that are granted the full 5 year attainment date
extension under section 172, the attainment date would be no later than
April 5, 2015.  For such areas, EPA would determine whether they have
attained the standard by evaluating air quality data from 2012, 2013,
and 2014.  Section 51.1004 of the proposed regulations addressed the
attainment date requirement.  Section 51.1004(b) provided that in their
attainment demonstrations, States would propose an attainment date
representing attainment as expeditiously as practicable based upon
implementation of existing Federal and State measures, and all new
reasonable local and intrastate measures.  The EPA would approve a
particular attainment date based on its review of the attainment
demonstration.  

Determining Whether an Area Has Attained.  The EPA has the
responsibility for determining whether a nonattainment area has attained
the standard by its applicable attainment date.  Section 179(c)(1) of
the Act requires EPA to make determinations of attainment no later than
6 months following the attainment date for the area.  Under section
179(c)(2), EPA must publish a notice in the Federal Register identifying
those areas which failed to attain by the applicable attainment date. 
The statute further provides that EPA may revise or supplement its
determination of attainment for the affected areas based upon more
complete information or analysis concerning the air quality for the area
as of the area’s attainment date.

Section 179(c)(1) of the Act provides that the attainment determination
for an area is to be based upon an area’s “air quality data as of
the attainment date.”  The EPA will make the determination of whether
an area’s air quality is meeting the PM2.5 NAAQS by the applicable
attainment date primarily based upon data gathered from the air quality
monitoring sites which have been entered into EPA’s Air Quality System
(AQS) database.  No special or additional SIP submittal will be required
from the State for this determination.  

 μg/m3.  The 24-hour standard for PM2.5 is met when the average of 98th
percentile values for three consecutive calendar years at each
monitoring site is less than or equal to 65.5 μg/m3. 

The EPA will begin processing and analyzing data related to the
attainment of PM2.5 areas immediately after the applicable attainment
date for the affected areas.  Current EPA policy, under 40 CFR part 58,
sets the deadline for submittal of air quality data into the AQS
database for no later than 90 days after the end of the calendar year. 

While EPA may determine that an area’s air quality data indicates that
an area may be meeting the PM2.5 NAAQS for a specified period of time,
this does not eliminate the State’s responsibility under the Act to
adopt and implement an approvable SIP.  If EPA determines that an area
has attained the standard as of its attainment date, the area will
remain classified as nonattainment until the State has requested, and
EPA has approved, redesignation to attainment for the area. 

In order for an area to be redesignated as attainment, the State must
comply with the five requirements listed under section 107(d)(3)(E) of
the Act.  This section requires that :

- EPA has determined that the area has met the PM2.5 NAAQS; 

- EPA has fully approved the state’s implementation plan; 

- the improvement in air quality is due to permanent and enforceable
reductions in emissions;

- EPA has fully approved a maintenance plan for the area; 

- the State(s) containing the area have met all applicable requirements
under section 110 and part D.  

2.	Establishing Attainment Dates

a.	Background

	The EPA proposed rule language on attainment dates that closely tracks
the statutory language.  In the preamble, EPA noted that the attainment
date that is as expeditious as practicable should reflect the projected
impact of existing national and State programs (e.g. partial
implementation of the CAIR rule, final Acid Rain Program, motor vehicle
tier II standards and heavy-duty diesel engine standards, NOx SIP call,
State legislation such as Clean Smokestacks bill in North Carolina) as
well as additional reasonable measures required for the PM2.5
nonattainment SIP.

	With respect to its authority to extend an area’s date beyond 5
years, EPA stated in the preamble that the State can submit a SIP
demonstrating that it is impracticable to attain by the 5-year
attainment date:

“As stated previously, under section 172(a)(2)(A), EPA may grant an
area an extension of the initial attainment date for a period of one to
5 years.  States that request an extension of the attainment date under
this provision of the CAA must submit a SIP by April 5, 2008 that
includes, among other things, an attainment demonstration showing that
attainment within 5 years of the designation date is impracticable.  It
must also show that the area will attain the standard by an alternative
date that is as expeditious as practicable, but in no case later than 10
years after the designation date for the area (i.e. by April 5, 2015 for
an area with an effective designation date of April 5, 2005).  An
appropriate extension in some cases may be only 1 or 2 years - a 5-year
extension is not automatic upon request. 

	The attainment demonstration must provide sufficient information to
show that attainment by the initial attainment date is impracticable due
the severity of the nonattainment problem in the area, the lack of
available control measures, and any other pertinent information related
to these statutory criteria.   States requesting an extension of the
attainment date must also demonstrate that all local control measures
that are reasonably available and technically feasible for the area are
currently being implemented to bring about expeditious attainment of the
standard by the alternative attainment date for the area.  The State’s
plan will need to project the emissions reductions expected due to
Federally enforceable national standards, State regulations, and local
measures such as RACT and RACM, and then conduct modeling to project the
level of air quality improvement in accordance with EPA’s modeling
guidance.  The EPA will not grant an extension of the attainment date
beyond the initial 5 years required by section 172(a)(2)(A) for an area
if the State has not considered the implementation of all RACM and RACT
local control measures for the area (see section III.I for a more
detailed discussion of RACT and RACM).  The EPA also will examine
whether the State has adequately considered measures to address
intrastate transport of pollution from sources within its jurisdiction. 
In attainment planning, States have the obligation and authority to
address the transport of pollution from one area of the State to
another.  Any decision made by EPA to extend the attainment date for an
area beyond its original attainment date will be based on facts specific
to the nonattainment area at issue and will only be made after providing
notice in the Federal Register and an opportunity for the public to
comment.” 

b.	Final Rule

	We are adopting the approach described above from the proposed rule. 
We also wish to clarify language that was in the preamble to the
proposed rule regarding the criteria for an extension.  The preamble
stated that attainment date extensions would be based on the two
statutory extension criteria – “the severity of nonattainment, and
the availability and feasibility of pollution control measures,” - as
well as “other pertinent information which shows that additional time
is required for the area to attain the standard.”  The CAA does not
include this third clause and the regulatory text for the final rule
does not include this third clause.  The intent of this language in the
preamble to the proposal was that States could include “other
pertinent information” related to the two statutory criteria.     

c.	Comments and Responses

	Comment:  Some commenters expressed concern that EPA’s preamble
language appeared to assert a new basis for granting extensions not
provided by the statute.  They said EPA has authority to extend the
attainment date under Section 7502(a)(2) based solely on consideration
of  two enumerated factors:  the severity of nonattainment, and the
availability and feasibility of control measures.

	Response:  The EPA agrees that extensions must be based upon the two
factors in the statute, which are quite broad.  A clarification of the
preamble phrase cited by the commenter is provided above. The phrase in
question – “any other pertinent information which shows that
additional time is required for the area to attain the standard” --
refers to information that relates to the two statutory factors.

	Comment:  One commenter stated that an area should qualify for an
extension only if the area will implement stringent local controls, yet
still cannot practicably attain by the five-year deadline.  The
commenter stated that at a minimum, EPA must require states to adopt
RACM for both mobile and stationary sources before granting an
extension.  Another commenter said that given the difficulty many areas
will have in meeting the five-year deadline for attainment of the PM2.5
NAAQS (and especially in light of the fact that the deadline occurs only
2 years after states are to submit attainment SIPs), EPA should provide
maximum flexibility in allowing extensions to the full 10-year period.  

	Response:  The EPA agrees that extensions should be granted only if an
area cannot practicably attain within 5 years despite application of all
reasonable measures, including RACM.  Although some measures can be
implemented within a year or two, many measures require a longer period
for installation of controls or full program implementation.  In light
of the limited time period between the SIP submittal deadline and the
5-year date, EPA believes that a significant number of areas may warrant
extensions ranging from one to 5 years, with the length of extension
depending on the factors described above.

	Comment:  One commenter advocated that EPA include in this final rule a
determination of those areas for which attainment within 5 years is
impracticable.  Another commenter advocated that EPA establish guidance
based on EPA national modeling conducted last year to establish 2015 as
constituting expeditious attainment for certain areas.  

	Response:  The EPA is not determining in this rulemaking the areas that
should receive extensions or should receive the maximum 10-year
attainment date, for several reasons.  First, EPA did not propose such
an approach.  Therefore, the public has not had the opportunity to
comment on the approach or on the technical information on which EPA
would make such judgments.  

	Second, EPA believes that modeling being conducted by the states, with
updated inventories and finer grids, will generally provide a more
reliable basis for projecting future PM2.5 base case levels than
national modeling conducted by EPA with older information.  State
modeling of future year PM2.5 levels that has been conducted to date
indicates that some areas will start closer or farther from the standard
than EPA had projected.   

	Third, the SIP process provides a forum for states to identify
reasonable controls and conduct analyses to determine the appropriate
attainment date for an area.  This process provides for input from
expert stakeholders, the general public, other states which may share
the same multi-State nonattainment area, and EPA on decisions regarding
controls and attainment dates.  At this time, EPA does not have the
benefit of this process to inform a judgment as to when areas can
practicably attain.  States are responsible for developing RACM
demonstrations; at this time, EPA lacks the information to conduct a
credible RACM demonstration for all PM2.5 nonattainment areas.

	Fourth, no State commenter advocated that EPA attempt to make these
judgments on attainment dates in advance of the State SIP process.  The
statute gives the states the lead in developing State implementation
plans.

	Comment:  Another commenter recommends that an area should receive an
attainment date extension when collectively the following conditions
have been met:

It is proven through modeling that the region is adversely effected by
transport of PM2.5 emissions from up wind sources beyond that State’s
control; 

A State has submitted and committed to implementing all Federal PM2.5
emission reduction requirements in a timely manner; and,

The extension concept is approved through the State air agency or
through the MPO Interagency Consultation Process at the MPO level if
applicable.

	Response:  This commenter advocates for attainment date extensions
without any consideration of reasonable local measures.  As stated
above, EPA believes that extensions should be granted only if an area
cannot practicably attain within 5 years despite application of all
reasonable measures, including RACM.  Although some measures can be
implemented within a year or two, many measures may require a longer
period for installation of controls or full program implementation.  In
light of the limited time period between the SIP submittal deadline and
the 5-year date, EPA believes that a significant number of areas may
warrant extensions ranging from one to 5 years, with the length of
extension depending on the factors described above.

3.	Attainment Dates:  1-Year Extensions

a.	Background.  

 annual average of 15.0 μg/m3 or less, and a 98th percentile of 24-hour
monitoring values of 65 μg/m3 or less in order to qualify for a 1-year
extension.  (Given the rounding provisions specified in 40 CFR Part 50,
Appendix N, these criteria would be satisfied if the concentrations
before final rounding are less than an annual average of 15.05 μg/m3
and a 24-hour value of 65.5 μg/m3.)

	For example, suppose an area in violation of the annual standard has an
attainment date of April 2010, and its annual average for 2007 was 15.8
and for 2008 was 15.6.  If the annual average for the area in 2009 is
14.9, then the 3-year average would be 15.4, and it would not have
attained the standard.  We interpret section 172(a)(2)(C) as allowing
the area to submit a request to EPA for a 1-year extension of its
attainment date to 2011 (provided the State has also complied with its
requirements and commitments) since the 14.9 ambient air quality value
in the third year (2009) met the test of being at or below 15.0. 
Section 51.1005(a) of the proposed regulation addresses the initial
1-year attainment date extension.

	The air quality measured in 2010 in conjunction with prior data will
determine if the area attains the standard, qualifies for a second
1-year extension, or does not attain the standard.  For example, if the
area’s annual average for 2010 is 14.3, then its 3-year average for
2008-2010 would be 14.9 and it would have met the annual standard.  

	If the area’s annual average for 2010 is 14.9, however, then its
3-year average for 2008-2010 would be 15.1.  In this situation the area
would not have attained the standard, but the area would meet the air
quality test for the second of the 1-year extensions allowed under
section 172(a)(2)(C), because the 2010 annual average was at or below
15.0.  Section 51.1005(b) of the proposed rule addresses the second
1-year attainment date extension.  After obtaining a second 1-year
extension, the State would evaluate whether the air quality values in
2011, in conjunction with 2009 and 2010 data, bring the area into
attainment. 

	Pursuant to section 172(a)(2)(C), States must submit additional
information to EPA to demonstrate that they have complied with
applicable requirements, commitments, and milestones in the
implementation plan.  This information is needed in order for EPA to
make a decision on whether to grant a 1-year attainment date extension. 
The EPA will not be inclined to grant a 1-year attainment date extension
to an area unless the State can demonstrate that it has met important
requirements contained in the area’s implementation plan.  States must
demonstrate that: (1) control measures have been submitted in the form
of a SIP revision and substantially implemented to satisfy the
requirements of RACT and RACM for the area, (2) the area has made
emissions reductions progress that represents reasonable further
progress (RFP) toward attainment of the NAAQS, and (3) trends related to
recent air quality data for the area indicate that the area is in fact
making progress toward attainment of the standard.  Any decision made by
EPA to extend the attainment date for an area will be based on facts
specific to the nonattainment area at issue, and will only be made after
providing notice in the Federal Register and an opportunity for the
public to comment.

	If an area fails to attain the standard by the attainment date, EPA
would publish a finding to this effect in accordance with section 179 of
the CAA.  The area then would be required, within 1 year of publication
of this finding, to develop a revised SIP containing additional emission
reduction measures needed to attain the standard as expeditiously as
practicable.  

b.	Final Rule.  

	The final rule retains the proposed criteria for states to receive a
1-year attainment date extension for a nonattainment area.  

c.	Comments and Responses

	Comment:  A number of commenters supported EPA’s ability to grant a
1-year attainment date extension if monitoring data indicate that the
PM2.5 levels during the most recent year were below 15.05 ug/m3.  

	Response:  The EPA agrees with these comments.

	Comment:  Some commenters recommended that a 1-year extension be
provided if the trend line of the area’s emissions levels or air
quality data projects attainment in the extension year.  

	Response:  The EPA believes that 1-year extensions should be based on
air quality data, which can be assessed quickly after the end of the
year.  Basing such extensions solely on emissions trends would be
impractical due to the longer turnaround time needed to evaluate
emissions changes affecting a monitor. 

	Comment:  One commenter believes the current requirement is overly
stringent and inconsistent with the statute.  The commenter believes
that EPA’s proposed approach incorrectly defines the statutory
language referring to a “minimal number of exceedances” of the
standard in the previous year as “zero” exceedances.  
Alternatively, the commenter suggests EPA could withdraw this provision
and provide more detailed guidance giving the Agency and states some
flexibility to demonstrate that exceedances were minimal in a given case
since nothing in the statute requires the rigid definition of minimal
that EPA proposes.

	Response:  The EPA believes the policy in the final rule is a
reasonable application of the statutory language to a standard not based
on exceedances.  The EPA does not believe it would be appropriate to
provide a 1-year extension to an area with air quality data showing it
violating the standard over the 3 years prior to the attainment year. 

4.	Achieving “Clean Data” 

a.	Background 

	Section III.D of the preamble to the proposed rule describes the
incentives for attaining the standards prior to April 2008, when SIP
submittals are due, or prior to an area’s approved attainment date. 
Areas with design values just over the level of the standard may be able
to achieve reductions in the local area or in the State so that, when
their effect is considered in combination with reductions achieved under
national programs, they may be sufficient to attain the standards before
SIPs are due in 2008.  For example, if monitoring in a nonattainment
area shows that the air quality for 2004-2006 meets the standards, then
the area may be subject to reduced regulatory requirements and be
redesignated as “attainment.”  

	The EPA issued a “Clean Data” policy memorandum in December 2004
describing possible reduced regulatory requirements for areas that
attain the standards, but have not yet been redesignated as attainment.

b.	Final Rule

	In the proposed rule, EPA indicated that it had issued  this “Clean
Data” policy to apply for purposes of the PM2.5 standards.  In this
action EPA is finalizing as a rule the statutory interpretation that is
embodied in the policy.  Section 51.1004(c).  The text of the final rule
encapsulates the statutory interpretation set forth in the policy. 
Determinations as to whether individual areas have attained the PM2.5
standard and thus qualify for application of the new clean data rule
will be made in the context of rulemakings for those individual areas.

	The preamble to the proposed rule mistakenly stated that if an area
achieved “clean data,” it would be “relieved of the requirements
to implement the nonattainment NSR program otherwise required for
nonattainment areas, and instead would implement the PSD program.”  
The EPA wishes to clarify that the   SEQ CHAPTER \h \r 1 Clean Data
Policy does not provide for suspension of the requirements for NSR nor
for RACT.  The provisions at issue in the Clean Data Policy include the
requirements for an attainment demonstration and other related
requirements, reasonable further progress, and contingency measures.

c.	Comments and Responses

	Comment:  One commenter stated that EPA has absolutely no authority to
waive NSR or any of the CAA’s other requirements for nonattainment
areas merely because a nonattainment area has 3 years of clean data, nor
does EPA have authority to waive mandatory requirements of the CAA such
as NSR, RACT, and RFP merely because EPA or the State claims they are
not needed for attainment.  The commenter believes that the only way
that a nonattainment area can cease implementing controls and
requirements mandated for such areas is to seek and obtain redesignation
to attainment, and demonstrate in the process that the controls and
requirements are not needed for maintenance of standards.  The CAA has
explicit procedures and prerequisites for redesignating nonattainment
areas to attainment (CAA sections 107(d)(3)(E) and 175A).  The EPA’s
“clean data” proposal would illegally circumvent those requirements.

	Response:  The Clean Data policy does not waive requirements for NSR
nor for RACT.  However, EPA believes that “clean data” policies for
the ozone and fine particle programs are based on a reasonable
interpretation of the CAA.  The Clean Data Policy is the subject of two
EPA memoranda setting forth our interpretation of the provisions of the
Act as they apply to areas that have attained the relevant NAAQS.  The
EPA also finalized the statutory interpretation set forth in the policy
in a final rule, 40 CFR 51.918, as part of its Final Rule to Implement
the 8-Hour Ozone National Ambient Air Quality Standard – Phase 2
(Phase 2 Final Rule).  See discussion in the preamble to the rule at 70
FR 71645-71646 (November 29, 2005).  The legal rationale for the Clean
Data policy is explained in our Phase 2 Final Rule, in our December 14,
2004 memorandum from Stephen D. Page entitled “Clean Data Policy for
the Fine Particle National Ambient Air Quality Standards” (Page Memo),
and in our May 10, 1995 memorandum from John S. Seitz, entitled
“Reasonable Further Progress, Attainment Demonstration, and Related
Requirements for Ozone Nonattainment Areas Meeting the Ozone National
Ambient Air Quality Standard” (Seitz memo).  We adopt and reiterate
those explications here.

	The EPA has also explained its rationale for applying the Clean Data
policy in rulemaking actions associated with nonattainment areas for the
PM-10 and 1-hour ozone standards.  For rulemaking actions applying the
Clean Data policy to the PM-10 standards, see 71 FR 27440 (May 11, 2006)
(Weirton, WVA), 71 FR 13021 (March 14, 2006) (Yuma, AZ), 71 FR 6352
(February 8, 2006) (Ajo, AZ).  For a discussion of the legal rationale
supporting rulemaking actions applying the Clean Data policy to the
1-hour ozone standards, see, for example, 67 FR 49600 (July 31, 2002);
65 FR 37879 (June 19, 2000) Cincinnati-Hamilton, Ohio-Kentucky); 61 FR
20458 (May 7, 1996) (Cleveland Akron-Lorain, Ohio); 66 FR 53094 (October
19, 2001) (Pittsburgh-Beaver Valley, Pennsylvania); 61 FR 31832 (June
21, 1996 (Grand Rapids, Michigan); 60 FR 36723 (July 18, 1995) (Salt
Lake and Davis Counties, Utah); 68 FR 25418 (May 12, 2003) (St Louis,
Missouri); 69 FR 21717 (April 22, 2004) (San Francisco Bay Area).  

 	The EPA has further elaborated on its legal rationale for the Clean
Data Policy in briefs filed in the 10th, 7th, and 9th Circuits, and
hereby incorporates those briefs insofar as relevant here.  See Sierra
Club v. EPA, No. 95-9541 (10th Cir.), Sierra Club v. EPA, NO. 03-2839,
03-3329 (7th Cir.), Our Children’s Earth Foundation v. EPA, No.
04-73032 (9th Cir.).  As stated in the policy, the attainment
demonstration, RFP requirements, and contingency measure requirement are
designed to bring an area into attainment.  Once this goal has been
achieved, it is appropriate to suspend the obligation that States submit
plans to meet these goals, so long as the area continues to attain the
relevant standard.  The Tenth, Seventh and Ninth Circuits have all
upheld EPA rulemakings applying the Clean Data Policy.  See Sierra Club
v. EPA, 99 F. 3d 1551 (10th Cir. 1996); Sierra Club v. EPA, 375 F. 3d
537 (7th Cir. 2004); Our Children’s Earth Foundation v. EPA, No.
04-73032 (9th Cir.  June 28, 2005 (Memorandum Opinion).

	The EPA has explained in its memoranda on the Clean Data Policy for
PM2.5 and for ozone that it is reasonable to interpret the provisions
regarding RFP and attainment demonstrations, along with certain other
related provisions, as not requiring further submissions to achieve
attainment for so long as the area is in fact attaining the standard. 
Under the policy, EPA is not granting an exemption from any applicable
requirement under Part D.  Rather, EPA has interpreted these
requirements as not applying for so long as the area remains in
attainment with the standard.  This is not a waiver of requirements that
by their terms apply; it is a determination that certain requirements
are written so as to be operative only if the area is not attaining the
standard.  

CAA section 172(c)(2) provides that SIP provisions in nonattainment
areas must require “reasonable further progress.”  The term
“reasonable further progress” is defined in section 171(1) as
“such annual incremental reductions in emissions of the relevant air
pollutant as are required by this part or may reasonably be required by
the Administrator for the purpose of ensuring attainment of the
applicable NAAQS by the applicable date.”  Thus, by definition, the
“reasonable further progress” provision requires only such
reductions in emissions as are necessary to attain the NAAQS.  If an
area has attained the NAAQS, the purpose of the RFP requirement will
have been fulfilled, and since the area has already attained, showing
that the State will make RFP towards attainment will “have no meaning
at that point.”  The EPA’s General Preamble for the Implementation
of Title I of the Clean Air Act Amendments of 1990 (General Preamble) 57
FR 13498 , 13564 (April 16, 1992).  

CAA section 172(c)(1), the requirement for an attainment demonstration,
provides in relevant part that SIPs “shall provide for attainment of
the [NAAQS].”   The EPA has interpreted this requirement as not
applying to areas that have reached attainment.  If an area has attained
the standard, there is no need to submit a plan demonstrating how the
area will reach attainment.  In the General Preamble (57 FR 13564), EPA
stated that no other measures to provide for attainment would be needed
by areas seeking redesignation to attainment since “attainment will
have been reached.”  See also Memorandum from John Calcagni,
“Procedures for Processing Requests to Redesignate Areas to
Attainment,” September 4, 1992, at page 6.  

CAA section 172(c)(9) provides that SIPs in nonattainment areas
“[S]hall provide for the implementation of specific measures to be
undertaken if the area fails to make reasonable further progress, or to
attain the [NAAQS] by the attainment date applicable under this part. 
Such measures shall be included in the plan revision as contingency
measures to take effect in any such case without further action by the
State or [EPA].”  

	This contingency measure requirement is inextricably tied to the
reasonable further progress and attainment demonstration requirements. 
Contingency measures are implemented if reasonable further progress
targets are not achieved, or if attainment is not realized by the
attainment date.  Where an area has already achieved attainment by the
attainment date, it has no need to rely on contingency measures to come
into attainment or to make further progress to attainment.  As EPA
stated in the General Preamble:

“The section 172©(9) requirements for contingency measures are
directed at ensuring RFP and attainment by the applicable date.”   57
FR 13564.  Thus these requirements no longer apply when an area has
attained the standard.

It is important to note that should an area attain the PM2.5 standards
based on three years of data, its obligation to submit an attainment
demonstration is not waived but is only suspended.  If the area then has
air quality concentrations in the following year such that the area
exceeds the standard for years 2 through 4, then the area’s obligation
to submit an attainment demonstration is back in effect.  

The determination of attainment contemplated by the Clean Data Policy
does not purport to be a redesignation, and thus the requirements for
redesignation under section 107(d) are not applicable.  Nor does the
Clean Data Policy avoid or illegally circumvent the redesignation
requirements of section 107 of the CAA.  All of the requirements for
redesignation remain in effect and must be satisfied for an area to be
redesignated.  Sierra Club v. EPA, 99 F.3d at 1557-1558.  The Clean Data
Policy is simply an interpretation of certain provisions of the CAA,
whose express purpose is to achieve attainment of the standard, as not
requiring SIP revisions to be made by the State for so long as the area
continues to attain the standard.  The policy does not purport to exempt
areas from requirements that are inapplicable only if an area is
redesignated to attainment.  It interprets certain provisions which are
written in such a way as to impose requirements only upon areas that are
not attaining the NAAQS, regardless of whether they have been
redesignated to attainment.  The EPA has not provided for any waiver
from statutory requirements that was not provided by Congress.  The area
at issue remains designated nonattainment, and is subject to the risk
that if a violation occurs it will have to adopt and implement
reasonable further progress requirements, contingency measures, and an
attainment demonstration, unless it is redesignated to attainment.  In
order to be redesignated to attainment, however, the area will have to
satisfy all of the requirements of section 107(d)(3)(E), including the
requirement for a long-term maintenance plan.  

While a determination of attainment is not equivalent to a redesignation
to attainment, nothing in the Act compels EPA to wait until an area
meets all the requirements for redesignation before EPA makes a
determination that the area is in attainment with the standard, thereby
suspending the requirements for certain provisions related to
attainment.  Indeed, section 179(c) of the Act requires EPA to make an
attainment determination within six months after an area’s applicable
attainment date whether or not The EPA has made a finding with respect
to redesignation.  The EPA’s interpretation of the Act’s provisions
not to require, once attainment has been reached, certain plan
submissions whose purpose is to assure attainment, is not at odds with
the requirements for redesignation.  Nor does EPA’s construction of
the statute adversely impact planning for maintenance.  An area that is
monitoring attainment, but is still designated as a nonattainment area,
retains strong incentives to seek redesignation to attainment, and
remains subject to the requirement to demonstrate maintenance in order
to be redesignated.  For a detailed discussion of the relationship of
redesignation requirements and attainment determinations, see the
discussions in the EPA briefs in Our Children’s Earth Foundation v.
EPA, supra at pp. 43-60., Sierra Club v. EPA No. 95-9541 (10th Cir.) at
29-43, and Sierra Club v. EPA Nos. 03-2839, 03-3329 (7th Cir.) at 33-44
which are contained in the docket for this rulemaking. 

	  SEQ CHAPTER \h \r 1 Comment: A commenter noted that EPA’s proposal
suggested that areas attaining the standard would be subject to reduced
regulatory requirements.  The commenter believed that EPA’s
interpretation should be codified in regulatory form, in order to assure
that areas legally meeting the current PM2.5 standard and those
requesting redesignation be enabled to be redesignated and to benefit
from the interpretation through regulation, rather than by guidance or
policy.

	Response:  The EPA has adopted the commenter’s suggested approach of
codifying its Clean Data Policy interpretation for PM2.5 in regulatory
form.  Section 51.1004(c).  As it did for ozone in its Phase II Ozone
Implementation Rule, EPA is including in this rulemaking a regulation
that encapsulates the statutory interpretation  that is embodied in its
Clean Data Policy for PM2.5 , set forth above.  As noted in the response
to comment above, determinations as to whether individual areas have
attained the PM2.5 standard and thus qualify for application of the rule
will be made in the context of rulemakings for those individual areas. 
The EPA believes, however, that encapsulating its interpretation in
regulatory form will lend clarity and consistency to the process of
applying its interpretation.   

E.	Modeling and Attainment Demonstrations

1.	Background

[Section III.F.1 of November 1, 2005 proposed rule (70 FR 66007); sec
51.1007 in draft and final regulatory text]

	As noted in the proposal, Section 172(c) requires States with
nonattainment areas to submit an attainment demonstration.  An
attainment demonstration consists of: (1) technical analyses that
locate, identify, and quantify sources of emissions that are
contributing to violations of the PM2.5 NAAQS; (2) analyses of future
year emissions reductions and air quality improvement resulting from
already-adopted national and local programs, and from potential new
local measures to meet the RACT, RACM, and RFP requirements in the area;
(3) adopted emission reduction measures with schedules for
implementation; and (4) contingency measures required under section
172(c)(9) of the CAA.  

a.	Final Rule

	The requirements from the proposal are unchanged.  Each State with a
nonattainment area will be required to submit a SIP with an attainment
demonstration that includes analyses supporting the State’s proposed
attainment date.  States must show that the area will attain the
standards as expeditiously as practicable and it must include an
analysis of whether implementation of reasonably available measures will
advance the attainment date.  

2.	Areas That Need to Conduct Modeling

	[Section III.F.2 of November 1, 2005 proposed rule (70 FR 66007)]

a.	Background

	All nonattainment areas need to submit an attainment demonstration, but
in some cases, States may not need new, local-scale modeling analyses. 
In the proposed rule, EPA proposed that States may use in a PM2.5
attainment demonstration certain local, regional and/or national
modeling analyses that have been developed to support Federal or local
emission reduction programs, provided the modeling meets the attainment
modeling criteria set forth in EPA’s modeling guidance.  The proposal
also stated that nonattainment areas for which local, regional, or
national scale modeling demonstrates the area will not attain the
standard within 5 years of designation would be required to submit an
attainment demonstration SIP that includes new modeling showing
attainment of the standards as expeditiously as practicable.  

b.	Final Rule

	In the final rule, EPA is reaffirming the potential use of national
and/or regional modeling as part of an attainment demonstration.  We are
also clarifying the types of modeling analyses that may be useful as a
“primary” modeling analysis and as a “supplemental” analysis.  

The proposal suggested that it may be appropriate, in certain
circumstances, for a State to submit regional or national modeling as
the sole (primary) modeling analysis in its attainment demonstration. 
This implies that the State would not need to conduct local modeling
analyses.  

We wish to further define the differences between “national”,
“regional”, and “local” modeling analyses.  In this context,
national analyses are generally those conducted by EPA in support of
national or regional rules.  Regional and local modeling analyses are
generally those conducted by the RPOs and/or States for the purpose of
developing State Implementation Plans (SIPs).  

EPA has conducted national scale modeling for a variety of rules and
analyses.  Additionally, the RPOs and many States are conducting
regional and/or local scale modeling of PM2.5 and regional haze across
the country.  The national scale of the EPA modeling analyses requires
basic assumptions concerning local model inputs.  Compared to regional
or local modeling done by the States and/or RPOs, EPA modeling may, in
some cases, use coarser grid resolution, use inventories that are not as
refined, and model performance may be highly variable from area to area.
 For these reasons, national scale modeling may not always be
appropriate for local area attainment demonstrations.  

Therefore, we believe that regional or local modeling conducted by the
States or RPOs is best suited as the primary modeling analysis for a
modeled attainment demonstration.  The local modeling is more likely to
meet the recommendations contained in EPA’s modeling guidance. 
However, some areas having design values close to the standard may be
projected to come into attainment within five years based on modeling
analyses of national and regional emission control measures (e.g. CAIR)
that are scheduled to occur through 2009.  Regional scale modeling for
national rules such as the Tier II motor vehicle standards, the
Heavy-duty Engine standards, the Nonroad Engine standards, and CAIR
indicate major reductions in PM2.5 by 2010.  A portion of these benefits
will occur in the 2006-2009 PM2.5 attainment timeframe. 

Experience with past ozone attainment demonstrations has shown that the
process of performing detailed photochemical grid modeling to develop an
attainment demonstration can be very resource intensive for States.  The
EPA believes that it would be appropriate for States to leverage
resources by collaborating on modeling analyses to support SIP
submittals, or by making use of recent modeling analyses that are
completed prior to the SIP submittal date.  For this reason, EPA
recognizes that States may use in a PM2.5 attainment demonstration
certain local, regional and/or national modeling analyses that have been
developed to support Federal or local emission reduction programs,
provided the modeling meets the attainment modeling criteria set forth
in EPA’s modeling guidance (described below).  As with all SIPs under
subpart 1, the State must demonstrate that the area will attain the
PM2.5 standards as expeditiously as practicable.  The judgment of
whether the modeling is appropriate for an area should be made by the
State(s) and their respective EPA regional office on a case-by-case
basis. 

c.	Comments and Responses

	Comment:  There were many commenters that agreed that States should be
able to use EPA modeling or other national or regional modeling as a
modeled attainment demonstration.  One commenter recommended that the
final rule require States to show that the existing modeling
incorporates realistic assumptions, accurately reflects local emissions
and trends, and provides adequate model performance for the local
nonattainment area.

	Response:  We agree that national and/regional modeling may be used as
part of an attainment demonstration as long as it is shown to be
applicable to the local area.  This is consistent with the proposal
where we said that existing modeling should “meet the attainment
modeling criteria set forth in EPA’s modeling guidance.”  Part of
the analysis to determine if existing modeling meets the criteria in the
modeling guidance is to assess whether the modeling incorporates
realistic assumptions, accurately reflects local emissions and trends,
and provides adequate model performance for the local nonattainment
area. 

	Comment:  Some commenters thought States should be able to use EPA
modeling in the absence of an analysis of the applicability of the
modeling for a local nonattainment area.  One commenter said that EPA
should determine that States should not have to do any additional
modeling analyses if the CAIR modeling showed they were expected to
attain the NAAQS by 2010.  

	Response:  While we acknowledge there may be some circumstances in
which national or regional modeling would be appropriate to use without
local modeling and allow for such use, we disagree that national
modeling should be used in support of an attainment demonstration
without further analysis of the modeling assumptions for a particular
area.  National scale modeling may not always be appropriate for local
areas.  Most often, national scale EPA modeling is best suited for use
as a supplemental analysis or as part of a "weight of evidence"
demonstration.  The modeling guidance recommends supplemental analyses
for all attainment demonstrations.  The guidance specifically recommends
the examination of other modeling studies as a supplemental analysis. 
The EPA modeling as well as other “non-local” modeling can be used
for this purpose.  The “weight” of this alternative modeling in an
attainment demonstration should be guided by how well the modeling
system is suited for the local nonattainment area.  States should
consult with their EPA regional offices for further guidance and
recommendations. As such, we do not believe it to be appropriate to
determine a priori that CAIR or any other modeling analyses are
appropriate to use in a local attainment demonstration for any or all
nonattainment areas.  

	Comment:  Several commenters believe that States should be able to use
existing EPA modeling (such as CAIR), as the basis for an extension of
the area’s attainment date, if it shows that the nonattainment area
may not be able to attain the NAAQS by 2010.  They believe that the
State should not have to do additional modeling to show that they need
an attainment date extension. 

	Response:  We disagree with this comment.  The CAIR modeling included
national controls that are expected to be in place by 2010 (including
the CAIR rule itself), as well as existing state and local controls
reflected in the inventory used in the CAIR analysis.  It did not
include any additional local controls that could be implemented under
RACT and RACM requirements for the 1997 standards that may bring the
area into attainment sooner.  Nonattainment areas are required to attain
the NAAQS as expeditiously as practicable.  Therefore, updated modeling
of existing controls as well as additional local controls is needed
before an attainment date extension can be granted.  Additional
information on attainment dates and extensions is contained in the
preamble to the final rule, 

section II.D., and additional information on RACT and RACM requirements
is contained in section III.F.

	Comment:  Several commenters noted an apparent inconsistency in the
language concerning who would be required to perform “new”
local-scale modeling.  First, there are potentially conflicting
statements in the proposal when EPA states that areas with an attainment
date of 2010 will need to conduct local-scale modeling to project the
estimated level of air quality improvement in accordance with EPA’s
modeling guidance.  This conflicts with the proposed ability for States
to use existing national or regional modeling as their modeled
attainment demonstration.  Second, a portion of a sentence was removed
from the Federal Register version of the notice which differs from the
pre-Federal Register version.  The published version implies that all
nonattainment areas would be required to submit new modeling.  

	Response:  We agree that there are inconsistencies in the proposal
preamble text.  To clarify, new local-scale modeling is required for
areas that are not expected to come into attainment by 2010.  For other
areas, there may be national or regional modeling which may be
applicable to the area which shows they are likely to come into
attainment.  As noted earlier, national scale modeling is best suited
for use as a supplemental analysis, but in some cases may be acceptable
evidence that an area will attain by 2010.

	Additionally, the preamble language in the Federal Register contained
an error.  A portion of a sentence was mistakenly removed, which led to
some confusion.  The language in the FR notice (FR page 66008) stated
“Nonattainment areas would be required to submit an attainment
demonstration SIP that includes new modeling showing attainment of the
standards as expeditiously as practicable.  The new modeling will need
to include additional emissions controls or measures in order to
demonstrate attainment.”  The language should have read,
“Nonattainment areas for which local, regional, or national scale
modeling demonstrates the area will not be in attainment of the NAAQS
within 5 years of designation would be required to submit an attainment
demonstration SIP that includes new modeling showing attainment of the
standards as expeditiously as practicable.  The new modeling will need
to include additional emissions controls or measures in order to
demonstrate attainment.”  This should clarify that States that cannot
show attainment within 5 years will need to develop new modeling
analyses which contain additional control strategies which show how and
when they expect to attain the PM2.5 NAAQS.    

	Comment:  One commenter maintained that relying on large-scale regional
modeling alone may allow for PM2.5 hot spots (i.e. small unmonitored
areas projected to exceed the standard) to exist past the attainment
date.

	Response:  We agree that nonattainment areas with potential hotspot
issues (relatively high concentrations and/or gradients of primary
PM2.5) should not rely exclusively on regional modeling.  The EPA's
attainment demonstration modeling guidance attempts to address several
aspects of hotspot issues in both monitored and unmonitored areas.  The
modeled attainment tests contained in EPA's modeling guidance are
primarily monitor based tests.  Ambient data is combined with the model
predicted relative change in PM components to determine if attainment of
the standards is likely in the future.  There are several aspects of the
attainment test.  In most cases, States will run a photochemical grid
model to determine the future year predicted PM2.5 concentrations at
monitors.  The modeling guidance generally recommends that for urban
scale PM2.5 modeling, the State performs modeling analyses at 12
kilometer grid resolution or finer.  There is an additional component to
the attainment test for areas that have measured relatively high
concentrations and/or gradients of primary PM2.5 at monitors.  In these
cases, we recommend running a Gaussian dispersion model for potential
primary PM sources, to determine the local impact of changes in primary
PM emissions (from the modeled sources) on predicted concentrations at
the monitor(s).  

	In addition, we describe an "unmonitored area analysis" which uses
interpolated ambient data combined with gridded model outputs to examine
whether potential violations of the NAAQS may occur in unmonitored
areas.  If potential violations are indicated, we recommend further
analysis of the problem through additional local modeling.  Options for
State action to address such a situation could include imposition of
reasonably available control 

technology to reduce emissions, or the deployment of an air quality
monitor to further characterize the problem. 

	We believe that the combination of these model-based tests will
adequately determine whether attainment of the standards is likely by
the attainment date.  We also believe that these tests address the issue
of hotspots by recommending a combination of photochemical modeling,
dispersion modeling of local sources, and additional monitoring and/or
emissions controls. 

3.	Modeling Guidance

[Section III.F.3 of November 1, 2005 proposed rule (70 FR 66008)]

a.	Background.

	Section 110(a)(2)(K)(i) states that SIPs must contain air quality
modeling as prescribed by the Administrator for the purpose of
predicting the effect of emissions on ambient air quality.  The
procedures for modeling PM2.5 as part of an attainment SIP are contained
in EPA’s “Guidance for Demonstrating Attainment of Air Quality Goals
for PM2.5 and Regional Haze.”  The proposal summarized several of the
chapters in a draft version of the modeling guidance.

b.	Final Rule.  

	A draft of the PM2.5 attainment demonstration and regional haze
modeling guidance has now been revised (September 2006) and is available
at http://www.epa.gov/ttn/scram/guidance_sip.htm.  The draft PM2.5
attainment demonstration and regional haze guidance has been
incorporated into the ozone modeling guidance and is now called
“Guidance on the Use of Models and Other Analyses for Demonstrating
Attainment of Air Quality Goals for the 8-Hour Ozone and PM2.5 NAAQS and
Regional Haze”.  The final version of the modeling guidance will be
available at the same location by the end of the year.  

	The revised draft PM2.5 modeling guidance document is very similar to
the previous draft version, although there were several changes and
updates.  Among them are new methods in treating PM2.5 species
components as part of the PM2.5 attainment test; new methods for
determining potential future year violations in unmonitored areas; new
procedures for handling potential PM2.5 “hotspots”; and an increased
reliance on supplemental analyses, including “weight of evidence”
analyses.  The EPA notes that the PM2.5 attainment demonstration
modeling guidance that we have released is separate from the Agency’s
future hot-spot modeling guidance for transportation conformity
purposes.     

	The modeling guidance describes how to estimate whether a control
strategy to reduce emissions of particulate matter and its precursors
will lead to attainment of the annual and 24-hour PM2.5 NAAQS.  Part I
of the guidance describes a “modeled attainment test” for the annual
and 24-hour PM2.5 NAAQS.  Both tests are similar.  The output of each is
an estimated future design value consistent with the respective forms of
the NAAQS.  If the future design value does not exceed the concentration
of PM2.5 specified in the NAAQS, then the primary modeled test is
passed.  The modeled attainment test applies to locations with monitored
data. 

	A separate test is recommended to examine projected future year PM2.5
concentrations in unmonitored locations.  Interpolated PM2.5 ambient
data, combined with modeling data, is used to predict PM2.5
concentrations in unmonitored areas.  The goal of this analysis is to
identify areas without monitors that may be violating the PM2.5 NAAQS,
often due to high levels of primary PM2.5 (both now and in the future). 
The details of the analysis are contained in the final modeling
guidance.

	The guidance also discusses modeling PM2.5 at monitors where high
concentrations of primary PM2.5 are measured.  In these cases, it may be
beneficial to model the primary component of the PM2.5 with a Gaussian
dispersion model.  Dispersion models are better able to capture the
influence of primary PM sources where large concentration gradients may
exist.  Grid models spread out the PM emissions to the size of the grid
(typically 4 or 12 km). This makes it difficult to judge the benefits of
control strategies that may affect primary PM sources.  The final
modeling guidance recommends procedures for applying dispersion models
in these situations. 

	The guidance also recommends the submittal of supplemental analyses as
part of all attainment demonstrations.  Supplemental analyses are
modeling, emissions, and/or ambient data analyses that are submitted as
part of a SIP, in addition to the primary modeled attainment test.  The
evaluation of supplemental analyses when the predicted concentrations in
the primary attainment test are close to the NAAQS (slightly above or
slightly below) is called a weight-of-evidence (WOE) analysis.  This is
simply a collection of evidence that aims to show that attainment of the
standard is likely.  The final version of the modeling guidance puts
more emphasis on the submittal of supplemental analyses than in previous
versions.  

	Part II of the guidance describes how to apply air quality models to
generate results needed by the modeled tests for attainment. This
includes developing a conceptual description of the problem to be
addressed; developing a modeling/analysis protocol; selecting an
appropriate model to support the demonstration; selecting appropriate
meteorological episodes or time periods to model; choosing an
appropriate area to model with appropriate horizontal/vertical
resolution; generating meteorological and air quality inputs to the air
quality model; generating emissions inputs to the air quality model;
evaluating performance of the air quality model; and performing
diagnostic tests.  After these steps are completed, the model is used to
simulate the effects of candidate control strategies.

	Comment: Several commenters were supportive of the weight of evidence
concept.  They said that PM2.5 modeling is inherently more uncertain
than previous ozone modeling and the modeling guidance should reflect
that.  One commenter noted that weight of evidence demonstrations should
be “unbiased”, meaning that States should use all relevant analyses
and not only information that helps their case. 

	Response:  The EPA agrees with these comments.  The final modeling
guidance recommends supplemental analyses (including weight of evidence)
for all attainment demonstrations.  All States should submit modeling,
ambient data, and emissions analyses in addition to the primary modeling
demonstration.  A weight of evidence analysis is needed if the predicted
future year PM2.5 concentrations are slightly higher or slightly lower
than the NAAQS. 

	We also agree that a weight of evidence demonstration should include
all relevant information, including analyses which support attainment
and those that do not.  The idea of the analysis is to “weigh” the
evidence, both good and bad.  That cannot be fairly done if some
evidence is not presented.    

	Comment:  Several commenters suggested that a modeled attainment
demonstration should not be specifically required.  Instead they suggest
that all demonstrations should be weight of evidence demonstrations. 
This would include different analyses of ambient data, trends, and
modeling.  But due to the uncertainties in the current PM2.5 models and
emissions data, modeling would be but one part of a broader weight of
evidence approach.

Response:  We disagree with this comment.  Model results should be the
primary analysis of an attainment demonstration.  Regardless of current
uncertainties in the PM2.5 models and emissions, models are the only
tool that can predict future concentrations of PM2.5.  The uncertainties
in the model inputs and formulation should be taken into account when
evaluating the results.  We agree that a broad analysis of modeling,
ambient data and emissions trends should be part of the attainment
demonstration.  This is reflected in the final modeling guidance.  

4.	Modeled Attainment Test

[Section III.F.4 of November 1, 2005 proposed rule (70 FR 66008)]

a.	Background.

	The proposal described the nature of the attainment tests for the
annual average and 24-hour average PM2.5 NAAQS contained within the
modeling guidance.  Both tests use monitored data to estimate current
air quality.  The attainment test for a given standard is applied at
each monitor location within or near a designated nonattainment area for
that standard.  There is also an additional attainment test to be
performed in unmonitored areas.  Models are used in a relative sense to
estimate the response of measured air quality to future changes in
emissions.  Future air quality is estimated by multiplying current
monitored values times modeled responses to changes in emissions. 
Because PM2.5 is a mixture of chemical components, the guidance
recommends using current observations and modeled responses of major
components of PM2.5 to estimate future concentrations of each component.
 The predicted future concentration of PM2.5 is the sum of the predicted
component concentrations. 

b.	Final Rule.

	The nature of the PM2.5 attainment tests is unchanged.  The final
modeling guidance recommends refinements to the test and discusses the
treatment of individual PM2.5 species.  The speciated modeled attainment
test (SMAT) that was used to estimate future PM2.5 concentrations for
CAIR has been (mostly) implemented in the final guidance.  Among the new
recommendations is to better account for the known differences between
the PM2.5 Federal Reference Method (FRM) measurements and the PM2.5
speciation measurements.  For example, it is recommended to account for
the volatilization of nitrate from the FRM filters and to account for
uncertainties in organic carbon measurements by employing an “organic
carbon by mass balance” technique.  This assumes that all remaining
mass not accounted for by other species is organic carbon mass. 
Additional details are contained in the modeling guidance.

	The guidance also recommends, where necessary, to spatially interpolate
PM2.5 species data to estimate the species concentrations at FRM sites. 
It is necessary to estimate species concentrations when there are no
species measurements at FRM sites.  Several techniques can be used to
estimate species concentrations.  Spatial interpolation techniques may
be useful in many areas.  In other cases, it may be adequate to assume
that data from a speciation monitor may be representative of multiple
FRM monitors.  It is particularly important to develop credible
techniques to estimate species concentrations at the locations of the
highest FRM monitors.  

	The guidance lists several techniques that can be used. The EPA will
provide software which will apply the modeled attainment test, using
ambient data and model outputs.  Additionally, the software will
interpolate the PM2.5 species data to allow application of SMAT for all
FRM monitors.  The software will be available at the same location as
the final modeling guidance
(http://www.epa.gov/scram001/guidance_sip.htm).  

	Ultimately, it is up to the States to determine the best method to
represent the PM2.5 species concentrations, subject to EPA’s review
and approval.  These estimates are needed to perform the modeled
attainment test.

c.	Comments and Responses

	Comment:  Several commenters were concerned that interpolation of PM2.5
species concentrations may not be appropriate in certain areas or
situations.  The concentrations can vary significantly between urban and
rural areas and even between nearby urban areas.  One commenter
suggested that it might be useful to use older field study measurements
to derive current species concentrations.  Another commenter suggested
that it might be reasonable to assume that speciation measurements were
representative of nearby FRM sites.

	Response:  We agree that interpolations of species data may not always
be the best way to estimate species concentrations at FRM sites.  The
modeling guidance lists several different possible techniques.  States
should review their data and situation and choose the most reasonable
methodology to estimate species concentrations.  Nonattainment areas
that don’t have speciation measurements at the highest FRM site(s)
need to be especially careful.  The result of the speciated attainment
test can be heavily influenced by the assumed species concentrations at
the highest FRM sites.  The attainment test will be more straightforward
in areas with speciation monitors at the highest FRM sites.  States are
also encouraged to place speciation monitors at the highest FRM sites. 
This will aid in future assessments of attainment and ambient trends. 

5.  Multi-pollutant assessments 

[Section III.F.5 of November 1, 2005 proposed rule (70 FR 66009)]

a.	Background.

	The formation and transport of PM2.5 is in many cases closely related
to the formation of both regional haze and ozone.  There is often a
positive correlation between measured ozone and secondary particulate
matter.  Many of the same factors affecting concentrations of ozone also
affect concentrations of secondary particulate matter.  For example,
similarities exist in sources of precursors for ozone and secondary
particulate matter.  Emissions of NOx may lead to formation of nitrates
as well as ozone.  Sources of VOC may be sources or precursors for both
ozone and organic particles.  Presence of ozone itself may be an
important factor affecting secondary particulate formation.  The
proposal recommended multi-pollutant assessments for PM2.5 attainment
demonstrations.  A multi-pollutant assessment, or one-atmosphere
modeling, is conducted with a single air quality model that is capable
of simulating transport and formation of multiple pollutants
simultaneously.  This type of model simulates the formation and
deposition of PM2.5, ozone, and regional haze components, and it
includes algorithms simulating gas phase chemistry, aqueous phase
chemistry, aerosol formation, and acid deposition.

b.	Final Rule.

	The recommendation to conduct multi-pollutant assessments remains
unchanged.  It is recommended to model the impacts of future year
control strategies on PM2.5, ozone, and regional haze.  It may not
always be possible or convenient to do so, but it can be beneficial to
the strategy development process.  

	PM2.5 control strategies will have an impact on regional haze, and will
possibly impact ozone.  Even if high ozone and high PM2.5 concentrations
don’t typically occur during the same time of the year, controls that
affect precursors to PM2.5 may also affect ozone (e.g. NOx).

The SIP submittal dates for PM2.5, ozone, and regional haze do not
currently line up.  The PM2.5 SIPs are due almost 1 year later than
ozone.  But States can still do modeling analyses that can provide
information for multiple pollutants.  States can use one-atmosphere
models that are capable of simulating both ozone and PM2.5.  They can
also try to use consistent meteorological fields and emissions
inventories so that the same control strategies are relatively easy to
evaluate for both ozone and PM2.5.  Modeling the same future year(s) for
PM2.5 and ozone can also make it easier to evaluate the impacts of
controls on both pollutants.  

	It should be noted that there are no specific modeling requirements
other than the recommendation to try to harmonize the ozone, PM2.5, and
regional haze analyses whenever possible.

c.	Comments and Responses

	Comment: One commenter suggests that multi-pollutant assessments may
not be beneficial because their area experiences winter PM2.5
exceedances and summer ozone exceedances.

	Response:  We disagree with the comment.  Even in situations where high
PM2.5 and ozone don’t occur during the same time of year,
multi-pollutant assessments may be helpful.  NOx controls that may be
needed to reduce nitrates in the winter are likely to have an impact on
ozone in the summer.  As well, changes in VOCs may have an impact on
both PM2.5 and ozone.  Running potential control strategies through the
same modeling platform for ozone, PM2.5, and regional haze may allow the
development of optimized strategies.  

6.	Which Future Years(s) Should be Modeled?

[Section III.F.6 of November 1, 2005 proposed rule (70 FR 66009)]

a.	Background.  

	Modeling analyses consist of base year modeling and future year
modeling.  The attainment test examines the change in air quality
between the base and future years.  The proposal recommended, where
possible, future modeling years should be coordinated so that a single
year can be used for both PM2.5 and ozone modeling.  This coordination
will help to reduce resources expended for individual modeling
applications for PM2.5 and ozone and will facilitate simultaneous
evaluation of ozone and PM impacts.  

	Although there is some flexibility in choosing the future year modeling
time periods, unless the State believes it cannot attain the standards
within 5 years of the date of designation and must request an attainment
date extension, the choice of modeling years for PM2.5 cannot go beyond
the initial 5 attainment period.  Attainment date extensions will only
be granted under certain circumstances.  Among other things, the State
must submit an attainment demonstration showing that attainment within 5
years of the designation date is impracticable.

b.	Final Rule.  

	Further information is now known concerning the modeling years for
ozone.  Moderate nonattainment areas are presumed to be modeling 2009. 
This is consistent with the last year of the 5 year period allowed under
Subpart I for PM2.5.  Therefore, it is logical to presume that areas
that are able to attain the PM2.5 NAAQS within 5 years will model a
future year of 2009.  Areas that won’t be able to attain the standard
in 5 years will need to request an attainment date extension (of up to 5
additional years).  

	The NAAQS must be attained as expeditiously as practicable.  Therefore,
attainment date extensions must contain modeling analyses to justify the
extension.  Details of the required analyses are contained in the RACT
and RACM sections of the final rule.  See section F for more details.  

F.	Reasonably Available Control Technology and Reasonably Available
Control Measures.  

	This section of the preamble discusses the final rule requirements for
RACT and RACM.  In order to explain EPA’s approach in the final rule
more clearly, we first discuss the statutory and regulatory background
for the RACT and RACM requirements, and we then explain the key options
and interpretations upon which we took comment in the proposal. 
Thereafter, we discuss significant comments we received on the proposal
and provide brief responses to those comments. [Additional comments and
responses appear in the RTC for this final rule located in the docket.] 
Most of the comments received on this topic addressed the three options
EPA proposed for the RACT requirement, the relationship between the RACT
requirement and EPA’s Clean Air Interstate Rule (CAIR), and the
control measures to be required or considered for RACT and RACM.

1.	Background on Statutory Requirements for RACT and RACM  tc "General
Background " \l 3 	 Subpart 1 of Part D of the CAA (sections 171 –
179B) applies to all designated nonattainment areas.  Section 172 

of this subpart includes general requirements for all attainment plans. 

Notably, Congress provided EPA and States a great deal of deference for
determining what measures to include in an attainment plan. 
Specifically, Section 172(c)(1) requires that each attainment plan
“provide for the implementation of all reasonably available control
measures as expeditiously as practicable (including such reductions in
emissions from existing sources in the area as may be obtained through
the adoption, at a minimum, of reasonably available control technology),
and shall provide for attainment of the national primary ambient air
quality standards.”  By including language in Section 172(c)(1) that
only “reasonably available” measures be considered for RACT/RACM,
and that implementation of these measures need be applied only “as
expeditiously as practicable,” Congress clearly intended that the
RACT/RACM requirement be driven by an overall requirement that the
measure be “reasonable.”   Thus, the rule of “reason” drives the
decisions on what controls to apply, what should be controlled, by when
emissions must be reduced, and finally, the rigor required in a
State’s RACT/RACM analysis.  For example, we previously stated that
the Act “does not require measures that are absurd, unenforceable, or
impractical” or result in “severely disruptive socioeconomic
impacts” 55 FR 38327.  Moreover, we interpret the term “reasonably
available” to allow States to consider both the costs and benefits of
applying the measure, and whether the measure can be readily and
effectively implemented without undue administrative burden.  66 FR
26969. 

We also interpret the “reasonably available control measures” in
these provisions as referring to measures of any type that may be
applicable to a wide range of sources, whereas the parenthetical
reference to “reasonably available control technology” refers to
measures applicable to stationary sources.  RACM can apply to mobile
sources, areas sources and stationary sources not already subject to
PM2.5 RACT requirements.  Thus, RACT is a type of RACM specifically
designed for stationary sources.  As noted above, States are required to
implement RACM and RACT “as expeditiously as practicable” as part of
attainment plans designed to attain the standards.  

Section 172 does not include any specific applicability thresholds to
identify the size of sources that States and EPA must consider in the
RACT and RACM analysis.  Nor, does Section 172 specifically indicate
which pollutant(s) or precursor(s) must be subject to RACM or RACT
measures to attain the NAAQS.  Other pollutant-specific provisions of
the CAA do include applicability thresholds pertaining to attainment
plan requirements for NAAQS and precursor pollutants.  For example,
subpart 2 of part D, which establishes additional requirements for ozone
nonattainment areas, establishes thresholds ranging from 100 to 10 tons
per year for requirements applicable to “major sources” or “major
stationary sources,” depending on the area’s classification or level
of nonattainment.   Subpart 4 of part D, which provides additional plan
requirements for PM-10 nonattainment areas, establishes thresholds of
100 and 70 tons per year for requirements applicable to a “major
source” or “major stationary source.”

Moreover, subpart 1, unlike subparts 2 and 4, does not identify specific
source categories for which EPA must issue control technology documents
or guidelines, or  identify specific source categories for State and EPA
evaluation during attainment plan development.  For ozone, subpart 2
contains a list of specific requirements for control techniques
guidelines (CTGs) and alternative control techniques (ACT) documents.
For PM10, section 190 of the CAA (in subpart 4) places particular
emphasis on specific sources of area emissions, but does not identify
specific stationary source categories for which RACT guidance must be
issued.  Section 190 requires EPA to develop RACM guidance documents for
residential wood combustion, silvacultural and agricultural burning, and
for urban fugitive dust control. 

2.	What is the Overall Approach to Implementing RACT and RACM in the
Final Rule?

a.	Background for RACT. 

	Since the 1970s, EPA has interpreted RACT to mean “the lowest
emissions limitation that a particular source is capable of meeting by
the application of control technology that is reasonably available
considering technological and economic feasibility” as well as other
considerations. Presumptive RACT has been described as the 'norm
achievable by the source category.

	Section 110 of the 1970 Clean Air Act required States to develop SIPs
providing for attainment of the NAAQS by 1975 or 1977.  A number of
areas were having difficulty with developing attainment plans,
particularly for the ozone standard.  In response to the implementation
needs of this time period, EPA introduced the term “RACT” in a 1976
memorandum from Roger Strelow, Assistant Administrator for Air and Waste
Management to Regional Administrators, “Guidance for Determining
Acceptability of SIP Regulations in Non-attainment Areas” (Dec. 9,
1976).  In this early guidance relating to the acceptability of SIP
regulations, we indicated that our overriding concern in approving SIPs
was attaining the particular NAAQS as expeditiously as practicable
through reasonably available control technology and other reasonably
available control measures.  “The basis for fully approving
state-submitted SIP regulations continues to be demonstrated attainment
and maintenance of all national ambient air quality standards as
expeditiously as practicable,” the memo stated.

The 1977 Clean Air Act amendments added Part D to Title I of the Act,
and for the first time the Act specifically called for EPA to designate
nonattainment areas and for SIPs to require RACT and RACM in those
nonattainment areas.   In a 1979 Federal Register notice, EPA noted its
view that Congress adopted EPA’s pre-existing conception of RACT in
the 1977 amendments. (44 FR 53782, September 17, 1979).  Also during the
late 1970s, EPA developed a number of new control techniques guideline
(CTG) documents as directed in the 1977 amendments.  These CTGs provided
States with information on controls for a number of categories of
sources emitting VOCs, and recommended a “presumptive norm” for
State RACT determinations based on the control levels achievable by
sources in a given industry.   CTGs reduced the burden on States by
eliminating the need for each State to develop its own technical support
for implementing the RACT requirement.   Since the CTG-recommended
controls were based on general capabilities of an industry, EPA in the
1979 guidance (44 FR 53782) urged States in setting RACT to judge the
feasibility of the recommended controls on particular sources, and to
adjust accordingly.  

	As noted above, EPA’s early guidance related to the RACT requirement
indicated that our overriding concern in approving State RACT
requirements was attaining the particular NAAQS.   We initially required
States to apply RACT to qualify for attainment extensions, and in some
cases, for plans that could not demonstrate attainment.    

During the 1980s, EPA implemented the RACT requirements with a number of
CTGs and guidance documents.   These materials were aimed at addressing
the attainment deadlines of 1982 and 1987 under the 1977 Clean Air Act
amendments.   During this time, EPA, for pollutants other than ozone,
considered RACT to be dependent upon reductions needed for attainment as
expeditiously as practicable.  For ozone, where the State performed
photochemical grid modeling, the approach was the same, but where the
State used less sophisticated tools, we considered RACT to be
independent of whether the controls were needed to reach attainment as
expeditiously as practicable. We took this alternate approach because of
concerns related to the precision of modeling techniques.  In other
words, in those cases, we required that a stationary source of the
requisite type and size be subject to RACT, whether or not such controls
were actually demonstrated to be necessary for the area to attain by its
specified date.  (44 FR 20375-20376, April 4, 1979)  

	Congress followed a similar approach in the 1990 amendments to the CAA
for purposes of the ozone NAAQS in the subpart 2 provisions added at
that time.  For example, section 182(b)(2) requires the imposition of
RACT controls for all VOC source categories covered by a CTG and for all
other major stationary sources of VOC located within certain
nonattainment areas.  Thus, Congress required  these controls without
allowing for an area-specific demonstration by the State that the area
needed the controls for attainment as expeditiously as practicable. 
Extensive discussion of this requirement appeared in the 1992 general
preamble (57 FR 13541), in which EPA provided guidance for
implementation of the ozone NAAQS.  

	Notably, Congress did not significantly amend the generally applicable
provisions for nonattainment areas that appear in subpart 1 of Part D in
1990.  This indicates that Congress intended that the Agency retain the
authority to interpret the generally applicable nonattainment area plan
requirements of section 172(c), including the RACT and RACM
requirements, in the way that is most appropriate for new NAAQS that are
subject to subpart 1.  As discussed below, EPA has determined that an
approach to the RACT requirement in which RACT varies in different
nonattainment areas based on the reductions needed for attainment as
expeditiously as practicable, is appropriate for implementation of the
PM2.5 NAAQS.  We believe that the improved ability to model air quality
impacts of emissions controls allows for this approach.

b. Proposed options for RACT.

	The EPA proposed and requested comment on three alternative approaches
for interpretation of the RACT requirement of section 172(c)(1) for
implementation of the PM2.5 NAAQS.  The EPA proposed these approaches in
order to evaluate which method would best ensure that States consider
and adopt RACT measures for stationary sources in a way that is
consistent with the overarching requirement to attain the standards as
expeditiously as practicable, while providing flexibility for States to
focus regulatory 

resources on those sources of emissions that contribute most to local
PM2.5 nonattainment.  

	Under the first proposed alternative, EPA would require States to
conduct a RACT analysis and to identify and require reasonably available
controls for all affected stationary sources in the nonattainment area,
comparable to the implementation of RACT provided in subpart 2 governing
implementation of the 1-hour ozone NAAQS.  Under this option, covered
sources would be required to apply reasonable available controls
considering technical and economic feasibility, and there would be no
opportunity for States to excuse stationary sources from control on the
basis that the emissions reductions from those controls would not be
necessary to meet RFP requirements or to reach attainment.  Under this
alternative, EPA proposed to limit the universe of sources for which
States must conduct a RACT analysis and impose RACT controls, by
providing an applicability threshold based upon the amount of emissions
potentially emitted by the sources.  Under this first option, EPA
requested comment on a number of alternative emissions applicability
thresholds.  

Under the second proposed alternative, EPA would require States to
conduct a RACT analysis and to identify reasonably available controls
for all affected stationary sources.  Under this option, however, States
could thereafter determine that RACT does not include controls that
would not otherwise be necessary to meet RFP requirements or to attain
the PM2.5 NAAQS as expeditiously as practicable.  Under this approach,
RACT would be determined as part of the broader RACM analysis and
identification of all measures - for stationary, mobile, and area
sources - that are technically and economically feasible, and that would
collectively contribute to advancing the attainment date.  Because RACT
and RACM are considered together under this alternative, we did not
propose emissions threshold options for evaluation of stationary source
RACT.  In addition, consistent with existing policies, States would be
required to evaluate the combined effect of reasonably available
measures to determine whether application of such measures could advance
the attainment date by at least one year. 

The third proposed alternative, EPA’s preferred option in the
proposal, combined the first two options and is similar to the RACT
approach adopted in the final implementation rule for the 8-hour ozone
program.  Under the third option, EPA would require States to conduct a
RACT analysis and to require reasonably available controls for all
affected stationary sources in nonattainment areas with attainment dates
more than 5 years from the date of designation.  For areas with an
attainment date within 5 years of designation (e.g. by April 5, 2010 for
areas with an effective date for designation of April 5, 2005), EPA
would require RACT as under the second proposed alternative, in which
RACT would be determined as part of the broader RACM analysis.  For
these areas, States could determine that RACT does not include controls
that would not otherwise be necessary to meet RFP requirements or to
attain the PM2.5 NAAQS as expeditiously as practicable.  The same
proposed suboptions with respect to the size of sources for
consideration under the first alternative were also included under this
alternative.  

c.	Proposed Approach for RACM  

	The EPA proposed and asked for comment on one approach for interpreting
the RACM requirement for PM2.5.  The EPA based the proposal on the
approach that we adopted for other NAAQS implementation programs.  Under
this approach, a State provides a demonstration in its SIP that it
adopted all reasonably available measures needed to meet RFP
requirements and to attain the standard as expeditiously as practicable
and that no reasonably available additional measures would advance the
advance the attainment date by at least 1 year or would be necessary to
meet the RFP requirement for the area.

  	Under section 172(a)(2), the state implementation plan must provide
for a nonattainment area to attain as expeditiously as practicable, but
no later than 5 years after the effective date of designation of the
area (e.g., no later than April 2010 for the final designations
effective April 2005).  The statute thus creates a presumption for
attainment within 5 years of designation unless certain statutory
criteria are met for an extension of the attainment date.  Under the
proposed approach to RACM for PM2.5, each State would evaluate available
measures for sources of PM2.5 or its regulatory precursors in the area
to determine if reasonable measures were needed to meet the RFP
requirement or to achieve attainment as expeditiously as practicable. 
If modeling of all RACM and other state, regional and federal measures
indicates that the State will not be able to demonstrate attainment
within 5 years after designation based upon the severity of
nonattainment in that area or the availability or feasibility of
implementing controls in that area, then the State may request an
attainment date extension.  We proposed that under these circumstances,
the EPA could extend the attainment date for a period of 1 to 5 years,
when the State shows that it will implement all RACT and RACM as
expeditiously as practicable, has met its obligation to address
intrastate pollution transport from sources within its jurisdiction, and
still needs additional time to attain.

	 In the proposed rule, the EPA also took comment on the following
overall steps for implementing the statutory requirement for RACM.

(1) Identification of measures.  The State would begin the process of
determining RACM by identifying all available control measures for all
sources of PM2.5 and its precursors in the nonattainment area.  The RACM
can apply to mobile sources, area sources, and stationary sources.  

(2) Evaluation of measures.  After the State identifies the universe of
available measures for the sources in the area, the State would evaluate
them to determine whether implementation of such measures is technically
and economically feasible, and whether the measure will contribute to
advancing the attainment date. 

(3) Adoption of measures.  The State would adopt all reasonably
available measures for the area consistent with meeting the applicable
RFP requirements and attaining the NAAQS as expeditiously as
practicable, in accordance with applicable policy and guidance for
attainment demonstrations.  We would then approve or disapprove the
State’s plan through notice and comment rulemaking.  We also noted
that in reviewing the State’s selection of measures for RACM, or
determining that certain measures are not RACM, EPA may independently
supplement the rationale of the State or provide an alternative reason
for reaching the same conclusion as the State.	

c. Final Rule. 

	The EPA carefully considered our interpretation of section 172(c)(1)
for the PM2.5 NAAQS.  Because of the variable nature of the PM2.5
problem in different nonattainment areas, which may require States to
develop attainment plans that address widely disparate circumstances
(e.g., different source types and mixes, different precursors and mixes
of precursors, and different meteorological conditions), we determined
that the regulations implementing the PM2.5 NAAQS should provide for a
great degree of flexibility with respect to the RACT and RACM controls.

Selected approach to RACT and RACM. The final rule reflects EPA’s
decision to select option 2 for RACT and to require a combined approach
to RACT and RACM.  Under this approach, RACT and RACM are those measures
that a State finds are both reasonably available and contribute to
attainment as expeditiously as practical in the specific nonattainment
area.  

By definition, measures that are not necessary either to meet the RFP
requirement, or to help the area attain the NAAQS as expeditiously as
practicable, are not required RACT or RACM for such area.  The EPA
believes that this approach provides the greatest flexibility to a State
to tailor its SIP control strategy to the needs of a particular PM2.5
nonattainment area, but it may require the State to conduct a more
detailed analysis to identify the most effective RACT/RACM strategy to
attain the NAAQS.

During the comment period, commenters raised concerns that this approach
may be overly burdensome on States because of the number of potential
control measures a State would need to consider.  Today, we clarify that
although the State must conduct a thorough analysis of reasonably
available measures, States need not analyze every conceivable measure,
as explained in the guidance below.  Instead, “reason” should drive
States identification of potential measures, but States should remain
mindful of the public health risks of PM2.5. As long as a State’s
analysis is sufficiently robust in considering potential measures to
ensure selection of all appropriate RACT and RACM, and the State
provides a reasoned justification for its analytical approach, we will
consider approving that State’s RACT/RACM strategy.  

	Guidance on State analysis to identify RACT, RACM and appropriate
attainment date.  A State must consider RACT and RACM for all of its
nonattainment areas.  However, EPA believes that if the State projects
that an area will attain the standard within 5 years of designation as a
result of existing national measures (i.e. projected to have a design
value of 14.5 or lower), then the State may conduct a limited RACT and
RACM analysis that does not involve additional air quality modeling.  A
limited analysis of this type would involve the review of reasonably
available measures, the estimation of potential emissions reductions,
and the evaluation of the time needed to implement these measures.  If
the State could not achieve significant emissions reductions during 2008
due to time needed to implement the potential measures or other relevant
factors, then the State and EPA could conclude that there are no further
reasonably available control measures for that area that would advance
the attainment date by one year or more relative to the presumptive
outer limit for attainment dates, i.e., 5 years from designation.  In
lieu of conducting air quality modeling to assess the impact of
potential RACT and RACM measures, States may consider existing modeling
information to determine the magnitude of emissions reductions that
could significantly affect air quality and potentially result in
attaining prior to 2010 (e.g. in 2009 based on 2006-8 air quality data).
 If the State, in consultation with EPA, determines from this initial,
limited RACT and RACM analysis that the area may be able to advance its
attainment date through implementation of reasonable measures, then the
State would conduct a more detailed RACT and RACM analysis, including
appropriate air quality modeling analyses, to assess whether it can
advance the attainment date.  

	In general, the combined approach to RACT and RACM in the final rule
includes the following steps:  (1) identification of potential measures
that are reasonable; (2) modeling to identify the attainment date that
is as 

expeditious as practicable; and (3) selection of RACT and RACM.

	Identification of potential measures.  The State’s review of
potential measures must be sufficient to identify all appropriate RACT
and RACM.  As stated previously, inherent to RACT/RACM is the basic
requirement that the measure be “reasonable.”  A State need not
evaluate measures in its RACM/RACT analysis that it determines are
unreasonable such as measures that are “absurd, unenforceable, or
impractical” or that would cause “severely disruptive socioeconomic
impacts, (e.g. gas rationing and mandatory source shutdowns); such
measures are not required by the Act.  55 FR 38327  

	As we also stated earlier, a State’s RACT/RACM analysis not only
involves an assessment about what emissions sources to control and to
what level, but also a judgment as to when it is reasonable to require a
sector to comply with a given measure.  Accordingly, if the State or
Federal rules already heavily regulate a given sector, it is reasonable
for the State to first look to unregulated parts of the sector for
RACT/RACM measures, especially, in light of costs already realized by
the regulated sector.  A State may conclude that it is unreasonable to
further regulate the industry, or that it is only reasonable to impose
measures in the latter years of the attainment plan.

	Finally, the State should use reason in the extent of its efforts to
identify potential control measures.  For example, if a review of
monitoring data and modeling studies indicates that reductions in SO2
are much more effective in reducing ambient PM2.5 than reductions in
other pollutants, we expect that the State will more vigorously identify
RACT/RACM measures for SO2 than for other pollutants.  Conversely, if
reductions in a given pollutant, even in large quantities, would have
trivial impacts on PM2.5, less rigor is needed in the State’s
assessment of controls for that pollutant, because such controls could
not contribute to advancing the attainment date.  Likewise, where
reducing emissions of a pollutant is effective in reducing ambient
PM2.5, if the emissions inventory for that pollutant is dominated by a
given type of emissions source, then it would be appropriate to focus
the analysis on measures for that segment of the inventory. No RACT/RACM
analysis is needed for pollutants that are not 

attainment plan precursors for a particular PM2.5 nonattainment area.

	As supporting information for identification of RACT and RACM, the
State ordinarily provides data on technologically feasible control
measures:

-- A list of all emissions source categories, sources and activities in
the nonattainment area (for multi-State nonattainment areas, this would
include source categories, sources and activities from all states which
make up the area)

-- For each source category, source, or activity, an inventory of direct
PM2.5 and precursor emissions;

-- For each source category, source, or activity, a list of
technologically feasible emission control technologies and/or measures  

-- For each technologically feasible emission control technology or
measure, the State should provide the following information: (1) the
control efficiency by pollutant; (2) the possible emission reductions by
pollutant; (3) the estimated cost per ton of pollutant reduced; and (4)
the date by which the technology or measure could be reasonably
implemented.

	Based on this and other relevant information, the State will identify
the reasonable measures (potential RACT and RACM) to be included in air
quality modeling.  (At its option, the State may prefer not to make a
judgment on whether certain measures are technically and economically
feasible, if it believes they will not contribute to earlier attainment.
 In that case, the State could include those measures in the modeling,
and later exclude them from RACT and RACM by showing that all the
excluded measures together would not advance the attainment date by at
least 1 year.)  As previously mentioned, in determining the attainment
date that is as expeditious as practicable, the State should consider
impacts on the nonattainment area of intrastate transport of pollution
from sources within its jurisdiction, and potential reasonable measures
to reduce emissions from those sources.  

	Modeling to determine the attainment date that is as expeditious as
practicable.  Second, for purposes of determining the attainment date
that is as expeditious as practicable, the State will need to conduct
modeling to show the combined air quality impact of all of the potential
measures identified in the first step with a modeling analysis for the
year 2009.  A base case scenario for the year 2009 would project future
air quality given implementation of existing measures (Federal, State
and local).  If this base case scenario demonstrates attainment by 2010,
then the State must demonstrate why attainment could not be achieved in
an earlier year.  (As noted above, given the April 2008 due date for SIP
submissions, it may be difficult to achieve earlier attainment in many
cases).   

	If the base case scenario does not demonstrate attainment, then a
control case scenario (described below) is needed to examine whether the
reasonable, technically and economically feasible measures identified by
the State would result in attainment in 2009. The control case scenario
would add potential SIP measures -- e.g. potential RACT/RACM, plus any
candidate intrastate transport measures that the State has identified
and would be feasible to implement by that year.  States in multi-State
nonattainment areas are strongly encouraged to collaborate on their
modeling analyses.  This modeling, along with other information known as
weight of evidence considerations, would inform a judgment as to whether
reasonable measures could lead to attainment of the standards within 5
years after designation.  If the analysis does not demonstrate
attainment by April 2010 (2009 analysis year), then the analysis would
serve as the technical basis for the State to seek an extension of the
attainment date for that area.  Further analysis would then be necessary
and is required to identify the specific attainment date. 

	The choice of future years to model beyond 2010 may vary from area to
area.  Often, modeling potential controls in two different future years
may be necessary to support a judgment that a projected attainment year
is as expeditious as practicable.  If the area is projected to remain
over the standard in the early projection year (e.g., 2009) despite the
emission reductions from the modeled control measures, but is projected
to be well below the standard in the later projection year (e.g., 2012),
interpolation and emission inventory analysis could identify an
intermediate year as the appropriate attainment date.  There may be
cases in which modeling a single year is sufficient because modeling of
all technically and economically feasible controls results in attainment
by a narrow margin in that year.

	For many areas, EPA modeling analysis for CAIR and other modeling
analyses that have been performed suggest a number of nonattainment
areas will have a modest amount (in some cases only a few tenths of a
microgram) of needed reductions in ambient levels after 2010 to reach
attainment.  For any such area, and for areas otherwise expected to
attain relatively soon after 2010 (for example, due to substantial
reductions in a dominant local source), EPA believes that this analysis
should be for a year no later than 2012.  A later date (e.g., 2014) may
be appropriate for areas with very high PM2.5 levels that face
difficulty attaining within 10 years.

The EPA believes that it is not reasonable to require States to model
each and every year between 2009 and 2014 to determine the appropriate
attainment date.  Modeling future year inventories is a time consuming
and resource intensive process.  Multiple models and pre-processors are
needed in order to generate year specific emissions for the various
emissions sectors (e.g. mobile, non-road, non-EGU point, EGU point,
etc.).  Because it is not reasonable to model every year, a logical
choice often may be to model a year in the middle of the period.  As
such, we recommend modeling an emissions year no later than 2012 as the
initial extension date (which translates to a 2013 attainment date).  If
this modeling indicates that the area can reach attainment by 2012, then
the State can further analyze emissions and strategies to determine if
the attainment date can be advanced to an earlier year.  If the modeling
indicates that the area cannot reach attainment by 2012, then the
modeling will serve as further justification for granting a longer
attainment date extension (e.g., attainment date of 2015 with modeling
for 2014). In that case, additional modeling of 2014 with further
emissions controls would be required in order to show attainment. Again,
the State should then further analyze emissions and strategies to
determine if the attainment date can be advanced to an earlier year
between 2012 and 2015.

Additionally, in the discussion of air quality modeling issues in
section II.E above, we discuss the benefits of addressing control
strategies for multiple pollutants. Part of the challenge of
multi-pollutant modeling is coordinating the future modeling years for
different pollutants in order to minimize the number of required future
year model runs. As part of the requirements of the 8-hour ozone
implementation rule, States are currently working on modeling analyses
for 2009 and in some cases for 2012 (serious nonattainment areas).  For
an area that cannot attain the PM2.5 NAAQS by 2010, this may be reason
to select 2012 as the year to model, so that the State could conduct the
modeling for both ozone and PM2.5 in tandem.  This would, in some cases,
allow the pooling of resources (e.g., inventories, model runs, etc.) and
provide for faster development of a PM2.5 attainment demonstration. 

It may also be possible for the State to look at 2009 and 2014 only.  In
this instance, the State may find sufficient data to interpolate results
for the years in between based on estimated changes in emissions. 

	We emphasize that when a State models later years, that this analysis
must take into account potential controls that the State may have
determined would not be RACT or RACM for an earlier year.  For example,
some measures that are impractical to implement by 2009 could be
reasonable if implemented by 2010, 2011 or 2012.  Thus, when the State
models later years, the list of potential controls should be expanded to
include technically and economically feasible measures that can be
implemented by the analysis year.  

	Selection of RACT & RACM.  Based on this analysis, the State should
make decisions on RACT, RACM, intrastate measures, and the attainment
date that is as expeditious as practicable.  Because EPA is defining
RACT and RACM as only those reasonable, technically and economically
feasible measures that are necessary for attainment as expeditiously as
practicable, the State need not adopt all feasible, reasonable measures.
 The State may exclude those reasonable measures that, considered
collectively, would not advance the attainment date. 

Comments and Responses.

	Comment:  A number of commenters generally supported EPA’s second
proposed alternative to RACT (option 2).  Most of these commenters
expressed concern that the other options would require the imposition of
controls whether or not they were needed to attain the PM2.5 standards
as expeditiously as practicable. Some State and local commenters also
urged EPA to select option 2 as the best interpretation of the RACT
requirement for PM2.5 because they believe that it will be the most
appropriate approach for designing attainment strategies for their
particular nonattainment area or areas.   

	Response:  The EPA agrees that these two points are important
considerations. After carefully considering the options, we concluded
that Option 2 was the most suitable approach for the PM2.5 NAAQS.
Options 1 and 3 do not reduce the States’ burden to analyze potential
control measures as the States would still be required to look beyond
the mandated RACT for reasonably available control measures (RACM). 
Moreover, Options 1 and 3 could require imposition of controls on some
sources that would not strictly be necessary to attain the NAAQS as
expeditiously as practicable.  Given the nature of the PM2.5
nonattainment problem, EPA concluded that an interpretation that
provides the maximum flexibility is a better approach.

	Comment:   Some commenters recommended that EPA modify proposed option
2 to include a tons-per-year threshold.   Under such an approach, the
States and EPA would only require RACT for sources whose emissions were
above the threshold.  Most of these comments recommended a RACT
threshold of 100 tons per year.  These commenters expressed concern that
if option 2 were implemented without such a threshold, States would be
burdened with conducting RACT analyses for very small sources or source
categories with low emissions. 

	Response:  The EPA believes that under the approach chosen for the
final rule in which RACT is considered to be a part of the overall RACM
process, it would be difficult to define a threshold that would apply
for all types of sources and for all types of control measures in all
nonattainment areas.  It has not been common practice under past EPA
policy to establish or use an emissions threshold when considering
sources for possible emission reductions as part of a RACM analysis to
show attainment as expeditiously as practicable.  Indeed, many of the
control technique guidelines for VOC RACT do not recommend an emissions
threshold.   A state needing significant emission reductions to attain
the standards in a given area even by 2015 would likely conclude that
controls should be considered on smaller sources.  In contrast, a State
with an area that exceeds the standard by only a few tenths of a
microgram per cubic meter may not need to consider controls on smaller
source to reach attainment as expeditiously as practicable.  The EPA has
selected option 2 for interpretation of the RACT requirement for PM2.5,
in part, specifically because that approach contemplates that States
will conduct an appropriate analysis of the spectrum of source
categories and potential controls available.  To cut off such analysis
at a set emissions-based cut point for all sources and all areas would
undermine one of the key benefits of the approach.  Accordingly, EPA
disagrees with comments that option 2 should include a
nationally-defined threshold for the size of sources or source
categories that require RACT analyses. 

	Comment:   A number of commenters supported EPA’s first and third
proposed alternative approaches to RACT (option 1 and option 3). 
Commenters supporting these two options used similar reasoning. 
Commenters cited the statutory language in section 172(c)(1) requiring
that the attainment plan provide for “at a minimum” the adoption of
RACT.  Accordingly, these commenters argued that RACT is an independent,
minimum requirement of attainment plans irrespective of the attainment
demonstration and that option 2, which would not require the adoption of
RACT for all sources, has no policy or legal justification. Other
commenters noted that option 1 would be much easier to implement,
because RACT would be defined according to technical reasonableness and
would not hinge on complicated determinations involving attainment
demonstrations.  Some commenters argued that option 1 provides for
greater equity, because similar measures would be required for similar
sources for all nonattainment areas.   Finally, some commenters believed
that it is inherently inconsistent to assert that plans have met the
requirement for attainment “as expeditiously as practicable” without
applying RACT to all major sources. 

	Response:  The EPA disagrees with these comments.  The EPA believes
that option 2 is fully consistent with section 172(c)(1).  Section
172(c)(1) requires that attainment plans must provide for the
implementation of RACM as expeditiously as practicable (including such
reductions in emissions from existing sources in the area as may be
obtained through the adoption, at a minimum, of RACT).  Contrary to the
commenters’ assertions, this language does not demonstrate that RACT
is required for all sources, independent of RACM and attainment
demonstrations.   Moreover, this provision does not require RACT whether
or not imposition of technology would advance the attainment date. 
Instead, section 172(c)(1) explicitly provides that RACT is included
within the definition of RACM, and EPA has previously determined that
the CAA only requires such RACM as will provide for attainment as
expeditiously as practicable.  (See 57 FR 13498, 13560).   The courts
have deferred to this interpretation and concluded that EPA interprets
RACM as a collection of reasonable measures that would advance the
attainment date.   See Sierra Club v. EPA, 294 F.3d 155, 162 (D.C. Cir.
2002); see also Sierra Club v. EPA, 314 F.3d 735, 744 (5th Cir. 2002). 
The CAA does not “compel [ ] a State to consider whether any measure
is ‘reasonably available’ without regard to whether it would
expedite attainment in the relevant area.”  Sierra Club v. EPA, 294
F.3d at 162.  The EPA concludes that because section 172(c)(1)
establishes that RACT is a part of RACM, EPA is reasonably applying the
same interpretation to the RACT requirement for PM2.5.  The RACT is a
part of the collection of measures that are necessary to reach
attainment as expeditiously as practicable. It is thus directly related
to what a specific area needs to attain the NAAQS, and States need not
implement reasonably available measures that would not advance the
attainment date as part of the PM2.5 RACT requirement. 

	The EPA also finds that option 2 is consistent with the statutory
language providing that a State must apply RACT to existing sources,
“at a minimum,” to meet its requirement to apply RACM.  We interpret
the “at a minimum” clause to mean that when a State determines that
control of a specified existing stationary source(s) is necessary to
attain, the State must apply RACT to that source.  Further, EPA believes
this requirement for RACT applies to stationary sources as a group, and
not to each stationary source.  

The EPA finds sound policy reasons for choosing option 2.	While an
approach that provided for application of the same controls in all areas
would provide for more equity across areas, EPA emphasizes that equity
is only one of many factors considered by EPA when deciding between
options 1, 2 and 3. The EPA believes that it is also important to ensure
that control strategies focus on the most effective measures with the
greatest possibility for significant air quality improvements.   In
addition, while EPA agrees that options 1 and 3 could provide for
greater ease of implementation, this is also only one of the factors EPA
considered when deciding between the proposed options. Under option 2,
States have a greater burden and responsibility to identify the local
strategy that is tailored to their particular air quality problem.   At
the same time, the States have the ability to identify the sources with
the greatest impact on nonattainment and to identify a sound strategy
that achieves attainment in the most sensible manner.  The EPA believes
that approaching RACT and RACM in this manner is consistent with the
overall philosophy imbedded in the SIP program since its inception in
the late 1960s and early 1970s.

	Comment:   Some commenters believed that the proposed RACM requirement
was too broad.  These commenters believed that the requirement to
analyze the entire “universe” of possible measures was too
burdensome for States.  Commenters felt this was especially true in
light of the lack of federally issued CTG and ACT documents for PM2.5
and its precursors for all potential source categories.   

	Response:  As explained earlier, States should apply “reason” in
identifying measures to evaluate as potential RACM/RACT.  We recognize
that States are implementing the PM2.5 standard for the first time, and
do not have the long history and experience in implementing PM2.5 as
they have in implementing the PM10 and ozone standards.  Accordingly, we
expect that both the States and EPA will expend extra effort in
developing and evaluating attainment plans that contain appropriate
controls.  A number of resources exist to provide States with
information on potential control measure costs and emissions reductions.
 We intend to facilitate the sharing of information through a control
measure website and other efforts, and expect that States will develop
screening methods to reduce the burden of analysis.

	Comment:  One commenter asserted that EPA should not require the
analysis for, or implementation of, RACT and RACM for sources throughout
the entire nonattainment area, and should permit States to focus only on
sources located in smaller specific “problem areas” within the
nonattainment area.

	Response:   The EPA designated areas nonattainment based upon analysis
of the geographic area with sources that “contribute” to the
violation of the NAAQS in the area, in accordance with section 107(d).
These designations are based upon, among other things, a network of
monitors that the State and EPA previously agreed represented the
ambient air concentrations throughout the area.  Additional analysis of
information during the designation process indicated those areas that
contributed to the violations at the violating monitor because of, among
other things, the amount of emissions in such adjoining areas. 
Accordingly, the State in which a nonattainment area is located must
evaluate the full range of sources of PM2.5 and its precursors
throughout the designated nonattainment area during the development of
the SIP.  The EPA agrees that there are some nonattainment areas where
one or a few large emissions sources may be causing localized
concentrations at a monitor that are much higher than those within the
remainder of the nonattainment area.   For such areas, the nonattainment
strategy will likely not succeed without addressing those sources.   The
EPA does not, however, believe it is acceptable that the nonattainment
strategy focus only on those sources, because additional reductions
within the nonattainment area would still have the potential to advance
the attainment date.  Exempting portions of the nonattainment area could
expose a portion of the public residing downwind in the area to exposure
to levels of PM2.5 that exceed the NAAQS for longer than necessary, and
the health detriments from such exposure, merely to minimize the impact
of having to impose control strategies on sources upwind.   Moreover, to
the extent that monitoring in one portion of a nonattainment area
indicates violations in multiple portions of the area, a strategy that
solely focused upon the sources in the immediate vicinity of the monitor
might fail to assure that the NAAQS is achieved throughout the area. 
Because NAAQS violations generally reflect a combination of regional
scale, metropolitan scale, and local scale impacts, and all three scales
must be addressed, EPA requires RACT/RACM 

submittals to address sources throughout the nonattainment area.

Comment:  Some commenters agreed with EPA’s view   that State’s RACM
analysis must address those measures that a State declines to adopt and
must show  whether the combined measures would cumulatively advance the
attainment date by at least 1 year.  One commenter questioned the legal
basis for EPA’s determination that the only controls necessary to
attain the PM2.5 NAAQS as expeditiously as practicable are those that
would cumulatively advance an area’s projected attainment date by at
least one calendar year.  The commenter suggested that control measures
that would advance attainment by a smaller increment “would meet the
criteria endorsed in Sierra Club [Sierra Club v. EPA, 294 F.3d 155 (D.C.
Cir 2002)] by ‘expedit[ing] attainment in the relevant area.’”

Response:  The EPA has consistently interpreted RACM as a collection of
measures that would advance the attainment date by at least 1 year, and
the courts have determined that the statutory RACM requirement is
ambiguous and deferred to EPA’s interpretation of the requirement. 
See Sierra Club. v. EPA, 314 F.3d 735, 744 (5th Cir. 2002); see also
Sierra Club v. EPA, 294 F.3d, 155 162 (D.C. Cir. 2002).  Contrary to the
commenter’s suggestion, the court in Sierra Club v. EPA, did not
endorse specific criteria for identifying control measures that expedite
attainment, but instead deferred to EPA’s interpretation of an
ambiguous statutory term.  The courts deferred to EPA’s interpretation
after reviewing EPA’s approval of State SIP submissions.  The EPA
conducts such reviews consistent with its determination that the CAA
only requires such RACM as will provide for attainment as expeditiously
as practicable, and its belief that it would be unreasonable to require
implementation of measures that would not in fact advance attainment. 
See 57 FR 13498, 13560 (April 15, 1992); see also 44 FR 20372, 20374
(April 4, 1979).   In considering whether a collection of measures would
advance the attainment date of an area, EPA has previously interpreted
the phrase “advance the attainment date” as meaning that the
attainment date would be advanced by at least 1 year.   See e.g., 66 FR
57160, 57182 (Nov. 14, 2001) (approval of Houston SIP); 66 FR 586 (Jan
3. 2001) (approval of DC area SIP).  Further, EPA’s use of a one-year
increment in determining whether a collection of measures would advance
the attainment date is reasonable and consistent with the fact that all
areas will be designing attainment demonstrations for the annual PM2.5
standard.  Section 172(a)(2)(C) statute uses 1 year as the increment by
which attainment date extensions can be granted. Thus, requiring
evaluation of whether control measures would advance attainment by an
increment of 1 year is a reasonable approach for the PM2.5 NAAQS.

	Comment:   Some commenters recommended that EPA consider not requiring
a RACM analysis for areas projected to attain the standards within 5
years of designation, i.e., by April 2010 for the areas currently
designated nonattainment.  One commenter suggested that practical
considerations would make it impossible for any State projected to
attain by 2010 to advance the attainment date by a year.  This commenter
noted that because measures to provide for attainment by 2010 must be
implemented by the beginning of 2009, and SIPs are not submitted until
April 2008, it would impossible to advance the implementation of
measures by 1 year (that is, the beginning of 2008). 

	Response:  The EPA generally agrees that given the time constraints it
will be difficult for States with areas currently designated
nonattainment to devise, adopt, and implement RACM measures to advance
the attainment date before 2010.   At the same time, however, we note
that nothing precludes States from taking early action and we encourage
States to take actions to reduce PM2.5 concentrations where feasible
even before the SIPs are submitted.  RACM is required by the CAA and
thus EPA cannot waive the requirement for the analysis.  At the same
time, EPA recognizes that a streamlined analysis may be appropriate
given the short time periods involved.

3.	Observations and considerations in determining RACT and RACM tc
"15.What factors should States consider in determining whether control
measures are reasonably available? " \l 3 

a. Background. 

	The preamble to the proposed rule included a discussion of general
considerations for RACT (70 FR 66020 and 66021, latter part of section
III.I.6) and RACM (70 FR 66028, section III.1.15).   The preamble to the
final rule retains this discussion with some modifications and
restructuring to reflect the combined approach to RACT and RACM

b. Final rule.   

	General considerations.  Once the State has identified measures and
technologies that are available for implementation in the nonattainment
area, then it must evaluate those measures to determine whether
implementation of such measures are reasonable, and would collectively
advance attainment.  Many of the factors that the State should take into
consideration in determining whether a measure is “reasonable” are
related to the measure’s technical and economic feasibility. Since
RACM applies to area and mobile sources as well as stationary sources,
the State should consider other factors as well in conducting its RACM
analysis.  For example, in many cases obtaining emissions reductions
from area and mobile sources is achieved not by adding control
technology to a specific emissions source, but by reducing the level of
activity of a fleet of vehicles or by modifying a type of commercial
process.  In these situations, the State should also consider local
circumstances such as infrastructure, population, or workforce and the
time needed to implement the measure in light of the attainment date.

	The EPA believes that while areas projected to attain within 5 years of
designation as a result of existing national measures should still be
required to conduct a RACT and RACM analysis, such areas may be able to
conduct a limited RACT and RACM analysis that does not involve
additional air quality modeling.  A limited analysis of this type could
involve the review of available reasonable measures, the estimation of
potential emissions reductions, and the evaluation of the time needed to
implement these measures.  If the State could not achieve significant
emissions reductions by the beginning of 2008 due to time needed to
implement reasonable measures or other factors, then it could be
concluded that reasonably available local measures would not advance the
attainment date.  In lieu of conducting air quality modeling to assess
the impact of potential RACT and RACM measures, existing modeling
information could be considered in determining the magnitude of
emissions reductions that could significantly affect air quality and
potentially result in earlier attainment.  If the State, in consultation
with EPA, determines from this initial, more limited RACT and RACM
analysis that the area may be able to advance its attainment date
through implementation of reasonable measures, then the State would
conduct a more detailed RACT and RACM analysis.

	Observations on control opportunities.  The implementation of the PM2.5
NAAQS is in its initial stages, and many of the designated PM2.5
nonattainment areas are not current or former PM10 nonattainment areas. 
Thus, some existing stationary sources in these areas may currently be
uncontrolled or undercontrolled for PM2.5 or PM2.5 precursors.  Further,
to this point in time, emissions controls for existing sources in these
areas may have focused primarily on particulate matter that is
filterable at stack temperatures and thus may not adequately control
condensable emissions.  In addition, States should bear in mind that the
controlled sources may have installed emission controls 15 years ago or
more, and there may now be cost-effective opportunities available to
reduce emissions further through more comprehensive and improved
emissions control technologies, or through production process changes
that are inherently lower in emissions.  

	Moreover, improved monitoring methods may enhance the ability of
sources to maintain the effectiveness of installed emissions controls
and to reduce emissions by detecting equipment failures more quickly. 
For example, State imposition of requirements for more frequent
monitoring (e.g., continuous opacity monitors, PM continuous emissions
monitors, etc.) may provide greater assurance of source compliance and
quicker correction of inadvertent upset emissions conditions than
existing approaches. 

	Even in former or current PM10 nonattainment areas, existing
requirements for controlling direct PM emissions (e.g., with a baghouse
or electrostatic precipitator) may not have been revised significantly
since the 1970's.  When EPA established the PM10 standards in 1987, we
stated in the  preamble that it was reasonable to assume that control
technology that represented RACT and RACM for total suspended
particulates (TSP) should satisfy the requirement for RACT and RACM for
PM10.  52 FR 24672 (July 1, 1987).   The  basis for EPA’s belief was
that controls for PM10 and TSP would both focus on reducing coarse
particulate matter, and specifically that fraction of particulate matter
that is solid (rather than gaseous or condensable) at typical stack
temperatures.  However, emission controls to capture coarse particles in
some cases may be less effective in controlling PM2.5.  For this reason,
there may be significant opportunities for sources to upgrade existing
control technologies and compliance monitoring methods to address direct
PM emissions contributing to fine particulate matter levels with
technologies that have advanced significantly over the past 15 years.  

	Precursor Controls.  It will be important for States to conduct RACT
and RACM determinations for stationary sources of PM2.5 precursors as
well as direct PM2.5 emissions although, as noted above, the known
atmospheric chemistry of the area may dictate the necessary rigor of
this analysis.  A significant fraction of PM2.5 mass in most areas
violating the standards is attributed to secondarily-formed components
such as sulfate, nitrate, and some organic PM, and EPA believes that
certain stationary sources of precursors of these components in
nonattainment areas currently may be poorly controlled.  Accordingly, to
address these precursors, States should review existing sources for
emission controls or process changes that could be reasonably
implemented to reduce emissions from activities such as fuel combustion,
industrial processes, and solvent usage. 

Multi-State Nonattainment Areas.  States in multi-State nonattainment
areas will need to consult with each other on appropriate level of RACT
and RACM for that area. We anticipate that States may decide upon RACT
and RACM controls that differ from State to State, based upon the
State’s determination of the most effective strategies given the
relevant mixture of sources and potential controls in the relevant
nonattainment areas.  So long as each State can adequately demonstrate
that its chosen RACT and RACM approach will provide for meeting RFP
requirements and for attainment of the NAAQS as expeditiously as
practicable for the nonattainment area at issue, we anticipate approving
plans that may elect to control a somewhat different mix of sources or
to implement somewhat different controls as RACT and RACM. 
Nevertheless, States should consider RACT and RACM measures developed
for other areas or other States. EPA may consider such measures in
assessing the approvability of a State’s SIP. 

c.	Comments and Responses.

	Comment:  In the proposed rule, EPA indicated that States could
consider the “social acceptability” of measures as a factor in the
determination of what constitutes RACM in a given area.  A number of
commenters recommended that EPA eliminate use of this factor.  Some
commenters questioned whether States or EPA had the legal authority to
exclude measures from consideration based on social acceptability or
popularity, if the measures are technically and economically available,
and are needed to attain the NAAQS for protection of public health. 
Others expressed concerns that inclusion of such a factor would
inevitably result in the elimination of controls for area and mobile
sources and for this reason would unfairly focus emissions reduction
strategies on industrial sources of PM2.5 and precursors.

	Response:  The EPA believes that in developing RACM measures, it is
important that States not rely unduly on measures that would be very
difficult to enforce in practice.  We discourage States from relying on
measures that on paper may seem reasonably available but in practice
might fail to achieve benefits due to the problems and costs of
effectively enforcing these measures.  However, we recognize that the
CAA does not identify “social acceptability” as a factor in the
definition of what may constitute RACT or RACM, and more generally the
CAA does not establish a preference for measures that affect industrial
sources instead of the general public and are therefore more likely to
be “socially acceptable.”  Therefore, given the concerns raised by
commenters that establishment of “social acceptability” as a factor
in the RACM analysis is without basis in the CAA and might result in
inappropriate skewing of control strategies, we have removed this term
from the final rule. We reiterate, however, that capability of effective
implementation and enforcement are relevant considerations in the RACM
analysis, even though public “unpopularity” is not.  Moreover, in
assessing the efficacy of measures and the credit they should be given
in the context of attainment demonstrations or RFP calculations, EPA
believes that such considerations are important.  

4.	What factors should States consider in determining whether an
available control technology or measure is technically feasible?

a.	Background.

	 The following provides guidance for States to consider in determining
whether an available control technology is technologically feasible.  

b.	Final Rule. 

	The technological feasibility of applying an emission reduction method
to a particular source should consider factors such as the source’s
process and operating procedures, raw materials, physical plant layout,
and any other environmental impacts such as water pollution, waste
disposal, and energy requirements.  For example, the process, operating
procedures, and raw materials used by a source can affect the
feasibility of implementing process changes that reduce emissions and
the selection of add-on emission control equipment.  The operation and
longevity of control equipment can be significantly influenced by the
raw materials used and the process to which it is applied.  The
feasibility of modifying processes or applying control equipment also
can be influenced by the physical layout of the particular plant.  The
space available in which to implement such changes may limit the choices
and will also affect the costs of control. 

	Reducing air emissions may not justify adversely affecting other
resources by increasing pollution in bodies of water, creating
additional solid waste disposal problems or creating excessive energy
demands.  An otherwise available control technology may not be
reasonable if these other environmental impacts cannot reasonably be
mitigated.  For analytic purposes, a State may consider a PM2.5 control
measure technologically infeasible if, considering the availability (and
cost) of mitigating adverse impacts of that control on other pollution
media, the control would not, in the State's reasoned judgment, provide
a net benefit to public health and the environment.  However, in many
past situations, States and owners of existing sources have adopted
PM2.5 control technologies with known energy penalties and some adverse
effects on other media, based on the reasoned judgment that installation
of such technology would result in a net benefit to public health and
the environment.  States should consider this in determining technical
feasibility.  The costs of preventing adverse water, solid waste and
energy impacts should be included in assessing the economic feasibility
of the PM2.5 control technology.

	One particular cross-media issue relates to concentrated animal feeding
operations (CAFOs).  Should a State determine that reductions of direct
PM2.5 or PM2.5 precursors from CAFOs are necessary for attainment in a
nonattainment area, EPA strongly suggests that the State address these
reductions from a cross-media perspective.  Since 2003, EPA and many
stakeholders have been interested in developing a framework to enable
CAFOs to pursue superior environmental performance across all media.  We
are aware that today some CAFOs voluntarily conduct whole-farm audits to
evaluate releases of pollutants to all media through Environmental
Management Systems, self-assessment tools, performance track, ISO 14001
certification, and State-approved trade offs in meeting regulatory
thresholds between air and water that accomplish the best overall level
of environmental protection given State and local conditions.  The EPA
continues to believe the development of new and emerging technologies
offers the potential to achieve equivalent or greater pollutant
reductions than achieved solely by effluent guidelines and standards. 
Many of these are superior from a multimedia perspective, and EPA would
like to encourage superior multimedia solutions.  SIPs which need to
address ammonia may provide a unique opportunity to encourage multimedia
approaches at CAFOs.  For example, the addition of animal by-products
provides a valuable source of nutrients for crops, improves soil
structure which enhances soil permeability, and adds valuable organic
matter that improves soil health.  However, inappropriate application
can lead to air and water quality concerns or the improvement of one
media at the cost of another.  Optimal application technologies and
rates reduce potential air and water quality standards violations.  The
EPA does not want to discourage approaches that are superior from a
cross media perspective.

	The EPA recommends that States evaluate alternative approaches to
reducing emissions of particulate matter by reviewing existing EPA
guidance and other sources of control technology information.  The
EPA’s 1998 guidance presents information on topics such as the design,
operation and maintenance of general particulate matter control systems
such as electrostatic precipitators, fabric filters, and wet scrubbers. 
The filterable particulate matter collection efficiency of each system
is discussed as a function of particle size.  The guidance document also
provides information concerning other relevant considerations such as
energy and environmental considerations, procedures for estimating costs
of particulate matter control equipment, and evaluation of secondary
environmental impacts.  Because control technologies and monitoring
approaches are constantly being improved, the State should also consider
more updated or advanced technologies not referenced in this 1998
guidance when conducting a RACT determination.  Emissions reductions may
also be achieved through the application of monitoring and maintenance
programs that use critical process and control parameters to verify that
emission controls are operated and maintained so that they more
continuously achieve the level of control that they were designed to
achieve.

c.	Comments and Responses.

	Comment:  One commenter noted that the guidance for “technical
feasibility” implies that States look at individual sources with a
BACT-like case-by-case analysis.  The commenter recommended that source
owners conduct such a site-specific analysis and submit the analysis to
the State through the permitting process.

	Response:  While the analytical analysis to identify RACT is similar to
BACT, as noted above, EPA in the past has issued CTGs that describe the
presumptive norm for RACT controls for a given industry, but that allow
for case-by-case considerations for a given source.  Where States wished
to require source owners to conduct such a site-specific analysis as
part of the control technology review, EPA supports this type of
process.  On the other hand, EPA does not believe it would be
appropriate to require all RACT-eligible sources to conduct such an
analysis, given that States have the primary responsibility for
identifying and analyzing measures for such sources.

5.	What Factors Should States Consider in Determining Whether an
Available Control Technology or Measure is 

Economically Feasible?  tc "7.What Factors Should States 

Consider in Determining Whether an Available Control Ttechnology is
Economically Feasible? " \l 3 

a.	Background.

	The follow provides guidance for States to consider in determining
whether an available control technology is economically feasible for
purposes of identifying reasonably available control measures.  This
guidance is slightly modified from our proposal. 

b.	Final Rule.

	 Economic feasibility encompasses considerations such as whether the
cost of a potential measure is reasonable considering attainment needs
of the area and the costs of other measures, and whether the cost of a
measure is reasonable for the regulated entity to bear, in light of
benefits.

	While many States generally establish RACT requirements for a category
of sources, the Act does not require the same level of control on all
sources in a category, nor does the Act require that each source be
controlled individually.  Similar sources may have different marginal
costs, profit margins and abilities to pass costs through to the
consumer.  These factors are appropriate to consider in determining
whether a given level of control is appropriate for an individual source
or category of sources.  Accordingly, there is no presumption that a
given source must bear a cost similar to any other source.  

	States should consider the capital costs, annualized costs, cost
effectiveness of an emissions reduction technology, and effects on the
local economy in determining whether a potential control measure is
reasonable for an area or State.  One available reference for
calculating costs is the EPA Air Pollution Control Cost Manual, which
describes the procedures EPA uses for determining these costs for
stationary sources. The above costs should be determined for all
technologically feasible emission reduction options if such measure is
inherently “reasonably available” (e.g., not absurd or clearly
impractical).   States may give substantial weight to cost effectiveness
in evaluating the economic feasibility of an emission reduction
technology.  The cost effectiveness of a technology is its annualized
cost ($/year) divided by the emissions reduced (i.e., tons/year) which
yields a cost per amount of emission reduction ($/ton).  Cost
effectiveness provides a value for each emission reduction option that
is comparable with other options and other facilities.  Where multiple
control options exist for a given source or source category, States
should consider both the cost effectiveness (dollars per ton) of each
option, and the incremental cost effectiveness per ton between the
options (incremental increase in cost between options divided by the
incremental tons reduced).

In determining whether a given measure is reasonable, States may
consider costs per ton of other measures previously employed to reduce
that pollutant, but similar costs are not conclusive.  As discussed
above, States may evaluate equity considerations in weighing the
economic feasibility of imposing a measure on a given source or source
category.   

We anticipate that States may decide upon RACT and RACM controls that
differ from State to State, based on the State’s determination of the
most effective strategies given the relevant mixture of sources and
potential controls in the relevant nonattainment areas, and differences
in the difficulty of reaching attainment.  

	In considering what level of control is reasonable, EPA is not
proposing a fixed dollar per ton cost threshold for RACT, consistent
with the views of multiple commenters.  Areas with more serious air
quality problems typically will need to obtain greater levels of
emissions reductions from local sources than areas with less serious
problems.  Where essential reductions are more difficult to achieve
(e.g., because many sources are already controlled), the cost per ton of
control may necessarily be higher.  

It is not appropriate to assume that the same cost per ton range is
reasonable for direct PM2.5 and different precursors, because an equal
amount of emission reduction in different pollutants has a different
impact on PM2.5 ambient levels.  For example, in a given nonattainment
area, reductions of direct PM2.5 emissions may prove more expensive than
reductions of NOx emissions, but the resulting benefits of reductions of
direct PM2.5 might warrant the higher costs.  A State should consider
this differential impact on ambient PM2.5 in considering RACT for
controlling different pollutants.  During the SIP process, States and
regional planning organizations typically conduct sensitivity modeling
that can provide this information.  Also, the PM NAAQS RIA provides
information on the differential impact of PM2.5 and PM precursor
reductions on ambient PM2.5 levels in various areas.

One of the factors that could affect estimated compliance costs of an
emission reduction measure is the timing of its implementation. 
Hypothetically, if a short compliance period were contemplated for a set
of sources, and if the short compliance period resulted in high demand
for a limited supply of labor or other resources, compliance costs could
be higher than if the same measure were implemented by a later
compliance date.  In such a case it may be reasonable for the State to
find that the measure is reasonable only if implemented by the later
date. 

	If a source contends that a source-specific RACT level should be
established because it cannot afford the technology that appears to be
RACT for other sources in its source category, the source can support
its claim with such information as:

-- fixed and variable production costs ($/unit)

-- product supply and demand elasticity,

-- product prices (cost absorption vs. cost pass-through),

-- expected costs incurred by competitors,

-- company profits once the technology or measure is in operation
(considering the annualized costs and the marginal costs of alternative
technologies and measures), , 

-- employment costs, and

-- any other unique factor(s) particular to the individual source.

	Finally, the EPA clarifies that if the State demonstrates through
economic analysis that the imposition of the measure would cause
unacceptable economic disruption for the local economy, that is, a plant
shutdown or a severe curtailment in plant employment or output, a State
may reject the measure as not reasonable to reach attainment as
expeditiously as practicable.

c.	Comments and Responses. 

	Comment:   Some commenters agreed with EPA’s proposal not to
establish presumptive cost-effectiveness thresholds. 

	Response:  The EPA agrees with the commenters.

	Comment:  A number of commenters expressed concerns over the references
to health benefits as a consideration in whether measures are
technically or economically available.   Some commenters believed this
is a consideration not authorized by the CAA.  Others believed that
consideration of benefits, in combination with EPA’s estimates of
benefits per ton, would have the effect of converting RACT to more
stringent LAER levels.  Some commenters expressed concerns whether
States had the resources or expertise to conduct cost-benefit analyses
for this purpose.  

	Response:   The EPA wishes to clarify that the reference to health
benefits does not mean that a cost-benefit, or a detailed health
benefits assessment, is a necessary part of a control strategy
demonstration.   We also wish to clarify that EPA is not requiring that
the costs of all technologies and measures for PM2.5 and precursors be
deemed acceptable at any dollar/ton levels at or below the calculated
monetized benefits per ton of reduction.   We do, however, continue to
believe that the significant benefits associated with PM2.5 ambient
reductions is a relevant consideration in control strategy development. 
The EPA disagrees that this limited consideration of benefits would
convert the RACT process to the equivalent of LAER.  

	Comment:  One commenter objected to EPA’s proposed requirement that
States consider competitive factors such as production costs, demand
elasticity, product prices, and cost incurred by competitors in the
determination of RACT. The commenter believed that this information is
generally not accessible to States or industrial facility owners, and is
not necessary for a RACT determination.  

	Response:   The EPA generally disagrees that this type of information
is unavailable.  For example, EPA calculates or reviews this type of
data on a regular basis as part of our work on MACT, NSPS, and other
emissions standards.   A document that describes these types of analyses
and the data used to prepare them is the OAQPS Economic Resource Manual
found at     HYPERLINK "http://www.epa.gov/ttn/ecas/analguid.html" 
http://www.epa.gov/ttn/ecas/analguid.html .    EPA believes that this
issue is most relevant to category-wide RACT rules where a source seeks
a case-by-case exemption.  Further, EPA believes most RACT
determinations will be developed through case-by-case analyses rather
than rules affecting entire source categories.  Accordingly, this
analysis likely will be relevant in few cases.   

6.	What Specific Source Categories and Control Measures Should a State
Evaluate When Determining RACT and RACM for a Nonattainment Area?  tc
"16.What Specific Source Categories and Control Measures Should a State
Evaluate When Determining RACM for a Nonattainment Area? " \l 3 

a.	Background.

	Section 172 does not provide a specific list of source categories and
control measures that must be evaluated for RACT and RACM for PM2.5. 
However, section 172(c)(3) indicates that the attainment plan must
include a “comprehensive, accurate, current, inventory of actual
emissions from all sources of the relevant pollutant.”  This indicates
that States should look broadly at the different types of sources in the
nonattainment area.  We recognize that PM2.5 is a new NAAQS without a
long history of implementation as with ozone.  Therefore, we included a
list of potential RACM measures in the preamble to the proposed rule,
based upon a review of information about the contribution of various
sources to emissions inventories and a review of potential control
measures for such sources.  We requested comment on the specific sources
and potential control measures recommended for RACM analysis on this
list.   Based on comments received and additional information available
to EPA since the proposal, we have made some changes to the list. We
also refer to this list of potential “RACT and RACM” measures for
the combined approach to RACT and RACM in the final rule.

	In the preamble to the proposed rule, EPA indicated that due to the
short time available, it does not plan to develop new control techniques
guidance (CTG) or ACT documents specifically for purposes of PM2.5
implementation.  The EPA indicated that other information was available
on control technologies, and EPA also indicated its intention to
maintain an updated list of references for new PM2.5 control technology
information.  

b.	Final Rule.

Emission reduction measures constituting RACM should be determined on an
area-by-area basis.  We believe that a State should consider each of the
measures listed in this section to determine if each measure is
reasonably available in the applicable nonattainment area.  However, we
do not presume that each of these measures is reasonably available in
each nonattainment area. 

	We recommend that each State use the list of source categories in this
section as a starting point for identifying potentially available
control strategies (regulatory and voluntary) for a nonattainment area. 
States are encouraged and expected to add other potentially available
measures to the list based on its knowledge of the particular universe
of emissions sources in the area and comments from the general public. 
We expect that, depending on the potential measure being analyzed, the
State’s degree of evaluation will vary as appropriate.  Detailed
information on emission control technologies is available from a number
of sources.  The EPA intends to maintain a website with links to sources
of information for controlling emissions of direct particulate matter
and PM precursors.  

	As discussed in section II.J.5. above, EPA recognizes that control
technology guidance for certain source categories has not been updated
for many years.  Section 183(c) of the CAA, which addresses control
technologies to address ozone nonattainment problems, requires EPA to
“revise and update such documents as the Administrator determines
necessary.”  As new or updated information becomes available States
should consider the new information in their RACT determinations.  A
State should consider the new information in any RACT determinations or
certifications that have not been issued by the State as of the time
such updated information becomes available.

Stationary source measures

- Stationary diesel engine retrofit, rebuild or replacement, with
catalyzed particle filter

- New or upgraded emission control requirements for direct PM2.5
emissions at stationary sources (e.g., installation or improved
performance of control devices such as a baghouse or electrostatic
precipitator; revised opacity standard; improved compliance monitoring
methods)

- Improved capture of particulate emissions to increase the amount of
PM2.5 ducted to control devices, and to minimize the amount of PM2.5
emitted to the atmosphere, for example, through roof monitors

- New or upgraded emission controls for PM2.5 precursors at stationary
sources (e.g., SO2 controls such as wet or dry scrubbers, or reduced
sulfur content in fuel; desulfurization of coke oven gas at coke ovens;
improved sulfur recovery at refineries; increasing the recovery
efficiency at sulfuric acid plants)

- Energy efficiency measures to reduce fuel consumption and associated
pollutant emissions (either from local sources or distant power
providers)

- Measures to reduce fugitive dust from industrial sites

Mobile source measures

- Onroad diesel engine retrofits for school buses, trucks and transit
buses using EPA-verified technologies

- Nonroad diesel engine retrofit, rebuild or replacement, with catalyzed
particle filter

- Diesel idling programs for trucks, locomotive, and other mobile
sources

- Transportation control measures (including those listed in section
108(f) of the CAA as well as other TCMs), as well as other
transportation demand management and transportation systems management
strategies

- Programs to reduce emissions or accelerate retirement of high emitting
vehicles, boats, and lawn and garden equipment

- Emissions testing and repair/maintenance programs for onroad vehicles

- Emissions testing and repair/maintenance programs for nonroad
heavy-duty vehicles and equipment15

- Programs to expand use of clean burning fuels16

- Low emissions specifications for equipment or fuel used for large
construction contracts, industrial facilities, ship yards, airports, and
public or private vehicle fleets

- Opacity or other emissions standards for “gross-emitting” diesel
equipment or vessels

Area source measures					

- New open burning regulations and/or measures to improve program
effectiveness such as programs to reduce or eliminate burning of land
clearing vegetation

- Programs to reduce emissions from woodstoves and fireplaces including
outreach programs, curtailments during days with expected high ambient
levels of PM2.5, and programs to encourage replacement of woodstoves
when houses are sold

- Controls on emissions from charbroiling or other commercial cooking
operations

- Reduced solvent usage or solvent substitution (particularly for
organic compounds with 7 carbon atoms or more, such as toluene, xylene,
and trimethyl benzene)

Category-Specific Guidelines on innovative approaches.  The EPA has
issued a number of category specific guidelines on approaches to taking
into account innovative approaches to emissions reductions for purposes
of SIPs.   Categories currently covered by these guidelines include: (1)
Electric-sector Energy Efficiency and Renewable Energy Measures (2) Long
Duration Switch Yard Locomotive Idling (3) Long Duration Truck Idling
(4) Clean Diesel Combustion Technology (5) Commuter Choice Programs.  
See http://www.epa.gov/ttn/airinnovations/measure_specific.html

c.	Comments and Responses.

Comment:  Some commenters recommended that EPA provide new CTGs or other
control technology review documents for purposes of assisting States to
address PM2.5 and its precursors, because the information in some
current documents is out-dated.

Response: The EPA recognizes that issuance of new or updated CTGs
specifically tailored for PM2.5 would be useful.  Unfortunately,
limitations on time and resources preclude EPA from developing such CTGs
in advance of the SIP submission date.  The EPA cannot delay the
statutorily specified outer date for SIP submission.  However, EPA
believes that there are already many sources of information and guidance
on key source categories.  To the extent that States need to examine
potential control measures for sources never addressed before in any
area or other context for a previous NAAQS, EPA anticipates that it will
work closely with States during the process of plan development and
approval to ensure an appropriate approach.   

Comment:  A number of commenters expressed concerns with references to
the STAPPA and ALAPCO Menu of Options document.  Some commenters
believed that this document must be subject to formal review and comment
to ensure appropriate stakeholder input.     

Response:  The language in the final preamble has been changed to refer
to a website EPA maintains that provides access to a variety of
information sources regarding control technologies that may be useful to
States to consider in developing their PM2.5 SIPs.  These links include
evaluations developed by government and nongovernment organizations. 
One such source with potentially useful information is the STAPPA and
ALAPCO Menu of Options.  However, EPA is not specifically endorsing any
of the specific evaluations as being appropriate in any specific
situation.  Rather, we think documents such as the Menu of Options
provide potentially useful ideas.  Specifically, States would need to
assess which items on the menu are applicable in their areas, and will
have to assess the costs of applying controls locally.   Accordingly,
there would be ample opportunity for public review of the State’s
analysis of the local cost and air quality impacts of any measure listed
in the document which is included in a State’s SIP.  The EPA is not
requiring that States adhere to the list of measures in the Menu of
Options.  The EPA does not in any way mean to imply that the measures in
the Menu of Options are presumed to be RACM, merely that they are
potential controls for areas to consider.  The Menu of Options has no
regulatory significance and thus need not be issued through
notice-and-comment rulemaking.  The EPA notes, however, that the Menu of
Options does provide a broad list of potential sources and measures that
can help inform States in the development of their plans.  Similarly,
our own list of potential measures is not intended to be a categorical
list of measures which States must adopt, rather it is intended to
provide guidance about the types of sources and measures that States can
consider in constructing their attainment plans.  The EPA emphasizes
that whether a source category or potential measure is or is not on this
list is simply not conclusive as to whether a given measure is
appropriate to consider in the RACT and RACM analysis.  That can be
determined only through the State’s development of the attainment
plan, and EPA’s evaluation of such plan.

Comment:  A commenter representing the paper industry interpreted the
proposed rule as requiring electrostatic precipitator and tighter
sulfur-in-fuel requirements for the forest products industry.  The
commenter believed that  EPA was creating limits for such sources
without adequate rulemaking process.

Response:  The EPA disagrees that the listing of control technologies in
the table in the rule creates a “rebuttable presumption.”  Rather,
the table identifies potential opportunities for emissions reductions
which should be reviewed in light of technical and economic feasibility,
and which a State should consider in a list of possible RACT and RACM
measures for purposes of attaining the standards as expeditiously as
practicable.  The EPA is currently conducting a sector-based approach to
the paper industry.  One of the goals of the sector initiative on pulp
and paper is to work with the industry to identify reductions in SO2 and
PM2.5 that will assist us in meeting the NAAQS, considering facility
locations, magnitude of emissions, emission stream characteristics, and
cost effectiveness of controls.  

Comment:  A number of commenters believed that EPA should develop not
only a list of measures to consider for RACM, but should develop a list
of mandatory measures that States should include, particularly for areas
with attainment dates more than 5 years after designation.

Response:  See discussion in section II.D.3 regarding rule requirements
for attainment date extensions and the issue of whether certain measures
should be mandatory in order for an area to receive an extension. 

Comment:   Some commenters believed that the list of possible measures
was deficient in not including sources of PM2.5 and PM2.5 precursors
from agricultural sources.  One commenter believed the list is
incomplete without identifying the contribution of ammonia emissions
associated with livestock, poultry, and crop fertilizers.   

Response:   As we indicated in the proposal, we included a list of
potential RACM measures in the preamble to the proposed rule, based upon
a review of information about the contribution of various sources to the
emissions inventories and a review of potential control measures for
such sources.  We did not identify emissions from agricultural sources
in this review.  Because ammonia is not presumed to be a PM2.5 precursor
unless identified for a specific area by the State or EPA, regulation of
ammonia emissions from agricultural sources may not be necessary. 

We also note that the agricultural industry presents unique challenges
to regulators given the nature of relevant emissions sources.  Moreover,
we currently lack good methods to quantify agricultural emissions, and
we do not fully understand their contribution to nonattainment problems.
 We have entered into an agreement with several animal producer sectors
to monitor animal feeding operations to develop better tools to assess
emissions from this industry.  Hopefully, these tools will enhance our
knowledge of agricultural emissions and their contribution to
nonattainment problems.  Until emissions from these sources are better
understood, States should be judicious in determining whether any
specific measure is RACT/RACM for this industry.  

The EPA recognizes that the United States Department of Agriculture
(USDA) has been working with the agricultural community to develop
conservation systems and activities to control coarse particle
emissions.  Based on current ambient monitoring information, these
USDA-approved conservation systems and activities have proven to be
effective in controlling these emissions in areas where coarse particles
emitted from agricultural activities have been identified as a
contributor to a violation of the PM10 NAAQS.  The EPA has found that
where USDA-approved conservation systems and activities have been
implemented, these systems and activities have satisfied the Agency’s
reasonably available control measure and best available control measure
requirements for areas needing to attain the PM10 standards.  

The EPA believes that in the future, certain USDA-approved conservation
systems and activities that reduce agricultural emissions of fine
particles may be able to satisfy the requirements of applicable sources
to implement reasonably available control measures for purposes of
attaining the PM2.5 NAAQS.  The EPA will work with States to identify
appropriate measures to meet their RACM requirements, including
site-specific conservation systems and activities.  The EPA will
continue to work with USDA to prioritize the development of new
conservation systems and activities; demonstrate and improve, where
necessary, the control efficiencies of existing conservation systems and
activities; and ensure that appropriate criteria are used for
identifying the most effective application of conservation systems and
activities. 

	Comment:   Some commenters raised concerns about a statement in the
proposal that “[i]n addressing a nonattainment area having military
training, testing and operational activities occurring within it, the
State should not need to target these activities for emission
reductions.”  Some commenters interpreted this statement as an
exemption from any emission reduction requirements for military sources.
 

	Response:  The statement in the proposal was not intended as an
exemption for all military activities.  Emissions potentially
contributing to PM2.5 concentrations at military installations originate
from a variety of sources:  basic operational activities (such as power
generation, other fuel combustion, and transportation to and from
residences, offices, and schools); and from field training and testing
activities (such as personnel training, obscurants used in training,
operation of nonroad vehicles and equipment, and related prescribed
burning operations).  The EPA believes that in evaluating emissions for
a specific nonattainment area having military activities occurring
within it, the State should consult with DOD for information on the
nature of these activities and their associated emissions. 

	With regard to military training activities specifically, such
activities are periodic in nature, and when they do occur, the principal
type of emissions generated by these activities is dust (i.e. inorganic
direct PM emissions) from field operations.  Other pollutants may be
emitted to a lesser degree from certain onroad and nonroad motor
vehicles.  While military training activities may contribute some degree
of primary PM2.5 emissions to certain nonattainment area inventories,
the fugitive dust generated from military training activities is
predominantly composed of coarse PM rather than fine PM.  

	Based on data from the PM2.5 speciation monitoring network operated by
EPA and the States, the contribution of inorganic dust to total PM2.5
mass on an annual average basis is relatively low in most nonattainment
areas, on the order of 0.5 to 1.5 micrograms per cubic meter (generally
10% or less of total PM2.5 mass).  Dust from military training
activities would be a subset of these levels.  Depending on the
available information and specific circumstances for a particular area,
a State could find in its SIP development analyses that direct PM2.5
emissions from military training activities do not significantly
contribute to PM2.5 concentrations in the nonattainment area, and
therefore would not need to target military training activities for
emission reductions in its attainment plan.  

7.  How should States Consider EGU Reductions for CAIR in Meeting
RACT/RACM Requirements?  

a.	Background.

	 In section III.I.11 of the preamble to the proposed rule, we discussed
the nature of the SO2 and NOx RACT obligations of electric generating
unit (EGU) sources in states subject to the CAIR emission reduction
requirements.  The CAIR rulemaking was finalized in March 2005 and
published at 70 FR 25221 (May 12, 2005).  CAIR requires 28 states and
the District of Columbia to significantly reduce emissions of SO2 and/or
NOx.  The 26 jurisdictions in the CAIR PM2.5 region are required to
reduce annual emissions of SO2 and NOx, and the 26 jurisdictions in the
CAIR ozone region are required to reduce seasonal emissions of NOx.  
These jurisdictions also have the option of participating in
EPA-administered annual SO2, annual NOx, and seasonal NOx cap-and-trade
programs (the CAIR trading programs) to meet these emission reduction
requirements.  In addition, in March 2006, EPA promulgated a Federal
implementation plan (FIP) to implement CAIR in these jurisdictions until
they have EPA approved CAIR SIPs in place (71 FR 25328, April 28, 2006).
 The FIP adopts, as the control measure, the CAIR trading programs
slightly modified to allow for Federal instead of State implementation.
When fully implemented, CAIR will reduce SO2 emissions in these
jurisdictions by over 70 percent and NOx emissions by over 60 percent
from 2003 levels. This will result in $85 to $100 billion in health
benefits and nearly $2 billion in visibility benefits per year by 2015
and will substantially reduce premature mortality in the eastern United
States. The benefits will continue to grow over time as the program is
fully implemented (i.e., the SO2 emission bank is depleted and the final
cap is met), and as growth in populations and the aging of the
population continues (which increases the susceptible population).

	Sources subject to cap-and-trade programs such as the CAIR trading
programs generally have the option of installing emissions control
technology, adopting some other strategy to reduce emissions, or
purchasing emissions allowances and thereby effectively paying other
sources covered by the cap to reduce emissions. In the proposal, we
noted that a number of EGUs expected to be covered by the CAIR trading
programs are located in nonattainment areas. Based on emissions
projections for 2010 and 2015 using the Integrated Planning Model (IPM),
some of these EGUs are expected to comply with CAIR by purchasing
allowances under the trading program and some are expected to comply by
installing emission controls.  

	The proposal also described our past experience with the implementation
of the NOx SIP Call and our belief that many power companies will
develop their strategies for complying with CAIR based, in part, on
consultations with State and local air quality officials in order to
address local PM2.5 and ozone attainment planning needs.  The EPA
suggested that consultations on location of CAIR controls would be
timely during State development of the CAIR SIP, which is due in 2006,
prior to the April 2008 deadline for submitting PM2.5 nonattainment area
SIPs.

	The EPA proposed a determination that in states that fulfill their CAIR
SO2 emission reductions entirely through EGU emission reductions (i.e.
without reductions from non-EGU sources or allowing non-EGU sources to
opt-in to the CAIR SO2 trading program), participation in the CAIR SO2
trading program would satisfy the SO2 RACT requirement for the EGU
sources.  The EPA also proposed that in states that fulfill their CAIR
NOx emission reductions entirely through EGU emission reductions, CAIR
would satisfy NOx RACT for the EGU sources, provided that those sources
with existing selective catalytic reduction (SCR) emission control
technology installed on their boilers operate that technology on a
year-round basis beginning in 2009.  Note that direct PM2.5 emissions
are not addressed by the CAIR program, and EPA did not propose any
determination that compliance with CAIR would satisfy RACT for direct
PM2.5 emissions.  The proposal included a discussion of the rationale
for these proposed determinations for SO2 and NOx, and requested
comments on the issue.  

b.	Final Rule.

As discussed in section II.F.2 on our overall policy for RACT and RACM,
we consider an area’s obligation to implement RACT to be part of the
area’s overall RACM obligation – to adopt those reasonably available
measures needed to reach PM2.5 attainment as expeditiously as
practicable.  The final rule also reflects this combined RACT/RACM
approach regarding EGU control obligations under CAIR and the extent to
which meeting CAIR also satisfies a source’s RACT and RACM
requirements for attainment.  

Specifically, the final rule includes a presumption that in States that
fulfill their CAIR SO2 emission reduction requirements entirely through
EGU emission reductions (i.e. without reductions from non-EGU sources or
allowing non-EGU sources to opt in to the CAIR SO2 trading program),
compliance by EGU sources with an EPA-approved CAIR SIP or a CAIR FIP
would satisfy their SO2 RACT/RACM requirements for attaining the fine
particle NAAQS.  This section also includes a presumption that in States
that are subject to CAIR annual NOx emission reduction requirements and
fulfill these requirements entirely through EGU emission reductions
(i.e. without reductions from non-EGU sources or allowing non-EGU
sources to opt in to the CAIR annual NOx trading program), compliance by
EGU sources with an EPA-approved CAIR SIP or a CAIR FIP would satisfy
the NOx RACT/RACM requirement for the PM2.5 NAAQS, provided that the
sources with existing selective catalytic reduction (SCR) emission
control technology installed on their boilers operate that technology on
a year-round basis beginning in 2009.  This final position is based on a
number of factors identified in the proposal and discussed below.  

Many PM2.5 nonattainment areas are projected to achieve significant SO2
and NOx reductions under the CAIR program.  We do not believe that
requiring source-specific RACT/RACM controls on specified EGUs in
nonattainment areas would reduce total SO2 and NOx emissions from
sources covered by CAIR below the regionwide levels that will be
achieved under CAIR alone.  Nor do we believe that “beyond CAIR” EGU
controls for SO2 and NOx are “reasonably available” control measures
for most areas within the CAIR Region.  Accordingly, most States need
not evaluate additional control measures on EGUs to satisfy RACT/RACM
requirements as explained above.

As discussed previously, we are not requiring that States impose RACT on
any specific size or type of source.  Instead, States must conduct a
RACT/RACM analysis considering measures that are “reasonably
available” to meet the overarching requirement to attain the standards
as expeditiously as practicable.  Thus, the final rule imposes no
specific requirement on States to impose RACT/RACM on EGUs.  

Nonetheless, in evaluating RACT/RACM for EGUs, EPA believes it is
appropriate for States (states that achieve all reductions from EGUs) to
consider the special attributes of that group of facilities including
the unique interrelated nature of the power supply network, and their
participation in the CAIR program.  For EGUs in the CAIR region, based
upon the presumption explained here, States may define RACT/RACM as the
CAIR level of control on the collective group of sources in the region
rather than impose a specific level of control on an individual source. 
This approach is similar to the Agency’s past “bubble” policy, as
discussed in section (c) addressing comments on the proposal.   

As discussed more fully in the CAIR final rulemaking notice, EPA has set
the 2009 and 2010 CAIR caps for SO2 and NOx at a level that will require
EGUs to install emission controls on the maximum total capacity on which
it is feasible to install emission controls by those dates.  The EPA
concluded that the CAIR compliance dates represent an aggressive
schedule that reflects the limitations of the labor pool, and
equipment/vendor availability, and need for electrical generation
reliability for installation of emission controls. 

	Although the actual SO2 cap does not become effective until 2010, we
designed banking provisions in CAIR so that covered EGUs will begin to
reduce their SO2 emissions almost immediately after CAIR is finalized,
and will continue steadily to reduce their emissions in anticipation of
the 2010 cap and the more stringent cap that becomes effective in 2015. 
The 2015 SO2 and NOx caps are specifically designed to eliminate all SO2
and NOx emissions from EGUs that are highly cost effective to control
(the first caps represent an interim step toward that end).  

Moreover, we predicted that the majority of large coal-fired utilities
will install advanced control technologies under CAIR because the larger
and higher emitting source offer an opportunity to obtain more
cost-effective emissions reductions.  We expect that the
largest-emitting sources will be the first to install SO2 and NOx
control technology and that such control technology will gradually be
installed on progressively smaller-emitting sources until the ultimate
cap is reached.  As a result, few, if any coal-fired units with greater
than 600 MW of operating capacity should operate in PM2.5 nonattainment
areas without advanced control after full implementation of CAIR. Of the
remaining units operating without advanced pollution controls, a great
many of these units will have operating capacities below 300 MW.  We
predict that these units “will be utilized less often,” and
“typically have baghouses and electrostatic precipitators for
particulate control, have combustion controls for NOx control, and burn
low-sulfur coal.”  See “Contributions of CAIR/CAMR/CAVR to NAAQS
Attainment: Focus on Control Technologies and Emission Reductions in the
Electric Power Sector,” Office of Air and Radiation, U.S.
Environmental Protection Agency, April 18, 2006 (available at
http://www.epa.gov/airmarkets/cair/analyses/naaqsattainment.pdf).  In
light of these expected results, we generally believe that the cost to
install additional controls on these smaller units would be
unreasonable. 

We are also concerned that if States require specific EGUs to install
advanced pollution control measures, it could interfere with the
market-based incentives inherent in the cap and trade program.  This
could increase the cost of compliance and shift the location of the
units that would otherwise opt to install advanced emissions controls. 
Such a result may be counterproductive to that State’s attainment
efforts, as the State may forego a larger quantity of more beneficial
reductions in transported pollutants, in exchange for a smaller quantity
and less beneficial reduction in local emissions.  Moreover, it may
reduce the benefits expected in other nonattainment areas as well. 
Accordingly, even if a State found the cost to control an individual
unit acceptable on a cost per ton basis, the potential overall
disbenefit of control may nonetheless make imposition of the control not
“reasonably available.”  

	The EPA finds that the control installations projected to result from
CAIR NOx and SO2 caps in 2009 and 2010 are as much as feasible from EGUS
across the CAIR Region by those dates.  In fact, if states chose to
require smaller-emitting sources in nonattainment areas to meet
source-specific RACT requirements by 2009, they would likely use labor
and other resources that would otherwise be used for emission controls
on larger sources.  Because of economies of scale, more boiler-makers
may be required per megawatt of power generation for smaller units than
larger units.  In this case, the imposition of source-specific RACT/RACM
on smaller emitting sources by 2009 could actually reduce the amount of
banking that would otherwise occur and result in higher SO2 emissions in
2009 as compared to the level that would result from implementation of
CAIR alone.

In any event, the imposition of source-specific control requirements on
a limited number of sources also covered by a cap-and-trade program
would not reduce the total regionwide emissions from sources subject to
the program.  Under a cap-and-trade program such as CAIR, a given number
of allowances are issued in order to achieve a given emission level. 
Source-specific control requirements within the CAIR program may affect
the temporal distribution of emissions (by reducing banking and thus
delaying early reductions) or the spatial distribution of emissions (by
moving them around from one place to another), but they would not affect
total regional emissions under the program.  If source-specific
requirements were targeted at the units that could be controlled most
cost-effectively, then the imposition of source-specific controls would
likely achieve the same result as the cap-and-trade program.  If not,
however, the imposition of source-specific requirements would make any
given level of emission reduction more costly than it would be under the
cap-and-trade program alone.  Thus, the imposition of source-specific
RACT on EGUs covered by CAIR would not reduce total regionwide
emissions, but would likely achieve emission reductions under the
program in a more costly way.  

  Given the considerations described above, we think that in many areas
additional controls on EGUs generally would not be “reasonably
available.”  Notwithstanding these conclusions, we recognize that
States are in the best position to determine how best to achieve
attainment with the PM2.5 NAAQS in light of local needs and conditions. 
As we acknowledged in our proposed rule, power plant operators typically
have ongoing relationships with the state and local officials involved
in air quality planning.  We expect that power plants will continue to
collaborate with State officials to determine how best to address
multiple air quality goals, and which plant locations to control under
CAIR, considering local PM2.5 and ozone attainment needs.

The EPA expects States and local air agencies to identify reasonably
available control measures that are necessary and reasonable to attain
the standards as expeditiously as practicable; and that after consulting
with power companies, the State may conclude that establishing
additional “beyond CAIR” emission control requirements on specific
sources in nonattainment areas is warranted to provide for attainment as
expeditiously as practicable.  Nevertheless, in preparing the overall
attainment demonstration, States should be aware of the expected
benefits of the market-based incentives of the CAIR program, the cost
effectiveness of control, feasibility of implementation, and any
disbenefits that would result from requiring “beyond CAIR” controls
on any specific EGU before concluding that additional controls on EGUs
are “reasonably available” and necessary to satisfy RACT/RACM
requirements.  

	Year-round NOx controls.  In the CAIR final rulemaking notice, EPA
found that the operation of existing SCRs on a year-round basis, instead
of operating them only during the ozone season, could achieve NOx
reductions at low cost relative to other available NOx controls.  The
EPA projected that power generators would employ this control measure to
comply with CAIR SIPs.  Based on this control opportunity, EPA estimated
the average cost of non-ozone-season NOx control at $500/ton.  These
considerations support a finding that RACT should include year-round
operation of existing SCRs that are located in PM2.5 nonattainment
areas.  Because all PM2.5 nonattainment areas violate the annual form of
the PM2.5 standard and public health can be affected by high PM2.5
levels in the winter as well as the summer, we believe that year-round
operation of existing SCR that are located in nonattainment areas where
NOx is an attainment plan precursor will provide additional health
benefits for relatively low dollar cost per ton of pollutant reduced.

In the proposal notice, EPA proposed to define “existing” SCRs as
those units that were in place by the date of the proposed rule
(November 1, 2005).  We selected this date rather than the final date to
avoid creating an incentive to delay installation of new SCR.  Today, we
finalize our proposed approach with one clarification.  To avoid
confusion over the proper interpretation of the phrase “in place,”
we are clarifying that an existing SCR is one which is fully installed
and capable of operation by November 1, 2005.

We also proposed that these existing SCR begin year-round operations no
later than January 1, 2009 to qualify as RACT/RACM under our presumptive
approach. We noted that year round operation of existing SCR involves
little to no alteration of existing equipment, and that EGUs could
conduct any required work during normal outages.  Today, after taking
these factors into account, we finalize our proposed rule.  The
year-round operation requirement, however, will not be federally
enforceable to individual EGUs until EPA approves a State’s SIP
including the requirement.

C.	Comments and Responses.

	Comment:  Some commenters supported the proposed determination
described in section (a) that in States that fulfill their CAIR SO2
emission reduction requirements entirely through EGU emission reductions
(i.e. without reductions from non-EGU sources or allowing non-EGU
sources to opt in to the CAIR SO2 trading program), compliance by EGU
sources with an EPA-approved CAIR SIP or a CAIR FIP would satisfy the
SO2 RACT requirement for the sources; and in States that are subject to
CAIR annual NOx emission reduction requirements and fulfill these
requirements entirely through EGU emission reductions (i.e. without
reductions from non-EGU sources or allowing non-EGU sources to opt in to
the CAIR annual NOx trading program), compliance by EGU sources with an
EPA-approved CAIR SIP or a CAIR FIP would satisfy the NOx RACT
requirement for the sources, provided that the sources with existing
selective catalytic reduction (SCR) emission control technology
installed on their boilers operate that technology on a year-round basis
beginning in 2009.  One commenter supported EPA’s approach so long as
states may pursue additional reductions from EGUs if needed for
attainment as expeditiously as practicable.  A number of other
commenters opposed the proposed determination regarding RACT for EGUs
based on a number of issues.

	Response:  Based on the rationale described in the sections above, the
final rule includes a presumption that compliance with CAIR satisfies
SO2 and NOx RACT/RACM requirements for EGUs in many areas.  Nonetheless,
States can require “beyond CAIR” EGU controls if a State determines
that it is a necessary and reasonable means to attain the PM2.5
standards.  Comments opposing this approach are addressed in more detail
below.

	Comment:  A number of commenters objected to the proposed
determination, arguing that it would result in greater control
requirements and economic burden on non-EGU sources located in
nonattainment areas.  These commenters urged EPA to adopt a final rule
that provides for implementing the most cost-effective controls
necessary to attain the standard.  They assert that with the proposed
finding that compliance with CAIR satisfies RACT for EGUs, the proposed
rule would not provide for the most cost-effective approach to
attainment.  They argue EPA and States should develop cost-effectiveness
guidance that includes all stationary source control measures and they
should develop SIPs based on the most economic means to attain the
standard.  They make several arguments to support this position.  The
commenters asserted that if an EGU control is more cost-effective than a
non-EGU control, the EGU should be subject to “beyond-CAIR”
controls.  They also asserted that if EPA chooses to consider the CAIR
rule as satisfying SO2 and NOx RACT for EGUs, then other sources should
not be subjected to control costs greater than those found reasonable
under CAIR (i.e., $800/ton).  They believe it would be inequitable to
require smaller sources to pay a higher cost for emissions reductions
than larger sources, which are a more significant contributor to the
problem and which may be able to make more cost-effective emission
reductions.  One commenter also suggested that EPA should authorize a
presumption that emissions reductions required on electric utilities
under the CAIR will be equivalent to RACT only if a particular source in
a CAIR State has installed controls that achieve the average level of
control that EPA has projected will occur for the particular pollutant
under the CAIR requirements.

Response:  The EPA has determined that implementation of the CAIR
trading program represents highly cost-effective controls that will
achieve widespread regional SO2 and NOx emissions reductions from EGUs
and will provide significant air quality benefits for ozone and PM2.5
nonattainment areas. In developing attainment SIPs and identifying RACM,
States will need to consider additional cost-effective and reasonable
controls to reach attainment as expeditiously as practicable.  The EPA
does not agree with the commenter’s argument that controls on non-EGUs
should be no more than the projected cost of EGU controls under CAIR. 
The EPA expects that in order to achieve attainment as expeditiously as
practicable, some states may need to adopt control measures for some
sources which cost more per ton but which still are considered to be
reasonable and cost-effective.

In addition, States must consider the economic feasibility of
implementing a given control measure.  Because of facility-specific
factors, EPA believes it would be inappropriate to establish a threshold
of control effectiveness (e.g. dollars per ton) based on control of EGUs
and apply this threshold to all source categories.  The ability of a
source to cost-effectively reduce emissions is dependent on
case-specific factors, including the ability of the given source to
sustain the cost of control, and prevailing costs in the specific
geographical location.  A direct correlation between the size of an
emissions source and the economic feasibility of controls for that
source and location does not necessarily exist.

We also disagree with the commenter who suggests that RACT requirements
should only be satisfied if a source achieves an average level of
control that EPA projects to occur under CAIR.  The EPA maintains that
the presumption that CAIR satisfies SO2 and NOx RACT/RACM for EGUs in
most areas is an appropriate policy.  As discussed further below, we
have always recognized that States could determine RACT for a single
source or group of sources.   

Comment:  A number of commenters opposed the proposed determination that
CAIR would satisfy the SO2 and NOx RACT requirement for EGUs.  The
commenters argued that this determination is unlawful, that it does not
comply with section 172(c)(1) of the CAA which requires RACT (i.e.
controls that are technologically and economically feasible) “at a
minimum” for all existing sources in the nonattainment area, that it
would allow very large stationary sources to escape cost-effective
controls entirely, and that it is largely based on the
legally-irrelevant contention that CAIR will reduce emissions more
cost-effectively than RACT.  They claim that EPA has no authority to
displace the Congressionally-mandated RACT requirement, that CAIR was
designed to address regional pollution transport (not to be an
attainment strategy), and that EPA should remove these proposed
provisions in the final rule.  Commenters claim that the EPA’s
proposed approach to allow EGU emissions to be addressed solely through
CAIR would undermine states’ efforts to meet the Federal PM2.5 health
standard, particularly when EGU sources are among the most
cost-effective to control.  Another commenter claimed that EPA’s
proposal allowing states that choose to fulfill their CAIR requirements
entirely through emission reductions from EGUs to also use CAIR to
satisfy their SO2 and NOx PM2.5 RACT requirements, thereby equating
these two requirements for the EGU sector, is flawed. This commenter
argued that allowing a cap-and-trade program, such as the CAIR, to
substitute for the RACT requirement undermines the effectiveness of the
controls by allowing facilities to use allowances to offset emissions,
rather than control them at the source.  The purchase of allowances,
they assert, does not satisfy RACT requirements.  

	Response:  The EPA disagrees with these comments.  The final rule does
not displace the RACT requirement for any sources.  Instead, EPA is
exercising its authority to interpret the section 172 RACT and RACM
requirements for the purposes of implementing the 1997 PM2.5 standards. 
For the reasons described in section (b) above, we believe that states
can rely on EPA’s presumption that compliance with a CAIR SIP or FIP,
meeting certain requirements, will satisfy the RACT/RACM requirement for
certain EGU sources. The EPA historically issued control technology
guidelines setting forth presumptive levels of emissions control that
satisfy the RACT requirement for a given industry.  The final rule is
similar to this practice in establishing a presumption that SO2 and NOx
reductions under the CAIR program satisfy the RACT/RACM requirement for
EGUs in CAIR states.  In identifying reasonably available control
measures to ensure attainment as expeditiously as practicable, States
will need to take CAIR reductions into account as well as any additional
cost-effective reductions that are technologically and reasonably
available.  

We further find that the attempt by many commenters to characterize CAIR
as a strategy to address only regional pollution transport and not an
attainment strategy as overly simplistic.  The EPA analyses for CAIR
show that there are significant air quality benefits projected for
individual nonattainment areas as a result of SO2 and NOx reductions
across the multistate CAIR region.  The Act does not prevent States from
properly crediting measures that achieve multiple objectives (e.g.
regional transport or local nonattainment).  Moreover, Section
110(a)(2)(D) requires SIPs to contain adequate provisions to assure that
sources in the State do not contribute significantly to nonattainment in
any other State.  The CAIR rule is an integral element in meeting the
States’ Section 110 attainment obligations.  Accordingly, it is
reasonable to incorporate this consideration in determining what
measures qualify as RACT/RACM.

Finally, EPA does not interpret the provisions of Section 172(c)(1)
related to the RACT requirement as precluding States’ use of a cap and
trade approach as a means of regulating existing sources and achieving
RACT/RACM reductions, especially in light of Congresses’ expressed
authorization to auction emission rights in Section 172(c)(6). 

The EPA has long recognized that RACT need not apply to individual
sources.  As stated earlier, our early guidance on RACT requirements
stated that States could establish RACT for an “individual sources or
a group of sources.” (emphasis added)  See Memo. Strelow (Dec. 1976)
and 44 FR 71779.  Importantly, Congress ratified the early
interpretations of RACT and RACM when it enacted the 1990 Amendments.
See 42 U.S.C. Section 7515 (Clean Air Act section 193).  Our 1986
emissions trading policy also recognized a number of advantages offered
through application of a “bubble” approach including faster
compliance with RACT limits and earlier reductions. Moreover, Courts
have upheld EPA’s approval of States’ use of “bubbling” multiple
units to meet RACT requirements.  See e.g. Natural Resources Defense
Council v. EPA, 941 F.2d 1207 (finding that EPA need not adhere to a
source specific RACT determination to satisfy RACT requirements and
acknowledging EPA’s special knowledge and expertise in the area.) 

	Comment:  The EPA’s proposal to allow EGU emissions to be addressed
solely through CAIR undermines prospectively States’ efforts to meet
the Federal PM2.5 health standard.  EGU sources are among the most
cost-effective to control.

	Response:  For the reasons described in section (b) above, EPA believes
that states can rely on EPA’s presumption that compliance with a CAIR
SIP or FIP, meeting certain requirements, satisfies the SO2 and NOx
RACT/RACM requirement for certain EGU sources.  Areas can require
“beyond CAIR” EGU controls if a State determines that it is a
necessary and reasonable means to attain as expeditiously as
practicable.  Nonetheless, as discussed above, EPA believes that
implementation of the CAIR requirements will provide for substantial
progress in attaining the PM2.5 standards and that States may presume
that RACT/RACM requirements are equal to the CAIR level of control.

	Comment:  CAIR fails to address the need for short-term reductions in
PM2.5 and precursor emissions on high pollution days.  While RACT
restricts emissions over a 1-hour to 24-hour period, CAIR only provides
for an annual or seasonal cap. Reliance on CAIR therefore fails to
recognize the importance of reducing short-term emissions, which was
recently highlighted by the EPA’s own proposal to tighten the 24-hour
PM2.5 health standard.  Local and short-term adverse air quality effects
of PM2.5, must he addressed in the final rule by requiring RACT for all
major facilities in addition to CAIR.  

	Response:  The CAIR program is oriented toward reducing SO2 and NOx
emissions in order to reduce air quality concentrations on an annual and
seasonal basis.  Because all PM2.5 nonattainment areas were designated
due to violations of the annual standard (and the two designated areas
in California also violated the 24-hour standard), the focus of this
implementation rule is attainment of the annual standard.  CAIR is
projected to provide significant air quality benefits in 2010 and 2015
for eastern PM2.5 nonattainment areas on both an annual basis and on a
98th percentile 24-hour basis. 17  

	Comment:  The proposal is silent on the issue of whether EGUs are
subject to direct PM2.5 emissions RACT requirements.  It is critical
that RACT be required for all facilities with respect direct PM2.5
emissions, regardless of a facility’s participation in CAIR. 

	Response:  In the final rule and preamble, EPA has clarified that all
EGUs in nonattainment areas are subject to RACT/RACM for direct PM2.5
emissions.  The presumption described above applies only to SO2 and NOx
RACT/RACM, not RACT/RACM for direct PM2.5 emissions from EGUs.  

	Comment:  The EPA fails to consider the geographical distributional
impacts of the emission reductions.  Equating CAIR with RACT fails to
take into account the substantial contribution that emissions from EGUs
within a nonattainment area may make toward that area’s PM2.5
nonattainment problem.  The EPA does not attempt to explain how such a
generalized determination satisfies RACT for PM2.5.

	Response:  The establishment of recommended levels for RACT/RACM is an
area Congress delegated to the specific expertise of the Agency.  Based
on our analysis, we conclude that the CAIR emissions caps presumptively
represent the level of emissions control achievable through application
of “reasonably available” control technologies.  Nonetheless, in
developing attainment plans, each State will evaluate the impact of
stationary sources located within the nonattainment area in developing
its attainment strategies for the local area.

	Comment:  A few commenters stated that EPA should explain how this
proposal would be implemented for states that request an extension of an
attainment date because attaining in 5 years or less is impracticable;
i.e., whether EPA would still hold to its interpretation that CAIR
equals RACT for EGUs and not require additional reductions from EGUs
even if an area cannot attain in 5 years and controls on EGUs could lead
it to attain more expeditiously.  These commenters argue that, in
considering if additional RACT is needed in states that obtain
extensions of the attainment deadline after 2010, EPA cannot ignore
potential RACT for electric generating units any more than they would be
allowed legally to avoid consideration of any other RACT candidates. 
One commenter is particularly concerned that States would not include
EGUs in their RACT determinations and instead require smaller industrial
boilers or process heaters to control emissions.

	Response:  The EPA’s determination regarding CAIR and RACT is not
limited to areas attaining within five years.  The Agency’s rationale
is presented in the “final rule” section above.  We disagree that
the CAIR-RACT presumptions necessarily shift emission control burdens
from EGUs to smaller industry boilers and process heaters because, in
implementing the RACM requirement, the State may include an evaluation
of control options on those sources as part of their RACT/RACM analyses.
 As stated above, EPA concluded that the CAIR compliance dates represent
an aggressive schedule that reflects the limitations of the labor pool,
and equipment/vendor availability, and need for electrical generation
reliability for installation of emission controls.  Accordingly,
additional controls on EGUs may not be a reasonably available control
measure that can be effectively implemented in a manner that advances an
area’s attainment date.  

	Comment:  The EPA designated many partial counties nonattainment for
PM2.5 solely because the areas contained EGU emission sources thought to
cause or contribute to violations of the NAAQS.  In implementing
attainment plans, it makes sense to consider further control of these
sources, and because they are located in nonattainment areas, the
ability to do so is provided for and legal under the CAA.

	Response:  The EPA designated PM2.5 nonattainment counties because they
either had a violating monitor or they contributed to a nearby air
quality problem.  Importantly, EPA designated these areas without
considering the air quality benefits expected in the future from CAIR. 
Accordingly, the fact that an EGU is located in a partial county and we
included the partial county in the nonattainment area because we believe
that the EGU was causing or contributing to the nonattainment
violations, does not equate with a finding that more than CAIR is
required to remedy the nonattainment problem.  Nonetheless,   EPA
believes that States should evaluate the impact of stationary sources in
all designated counties, including those partial counties noted by the
commenter, in its assessment of reasonably available control strategies
to ensure attainment as expeditiously as practicable.  

	Comment:  The EPA should adopt the Ozone Transport Commission’s
(OTC’s) approach to cap-and-trade programs. When the OTC developed its
NOx Budget Program (which was the basis for EPA’s NOx SIP call and
subsequently CAIR), it assumed that RACT was applied first. Thus the
cap-and-trade program operated in an environment that assumed RACT was
in force, not in lieu of RACT.

	Response:  Under the ozone national ambient air quality standards, NOx
and VOC RACT have been implemented progressively for the past 30 years
or more, prior to development of the NOx SIP call regional control
program.  In contrast, the PM2.5 implementation program is the first
instance in which we have required RACT/RACM specifically for fine
particle pollution.  For this reason, the CAIR program is not operating
with SO2 and NOx RACT limits already in place for attainment of the
PM2.5 standards.  Nonetheless, as discussed above, EPA believes that
implementation of the CAIR requirements will provide for substantial
progress in attaining the PM2.5 standards and that States may presume
that RACT/RACM requirements are equal to the CAIR level of control.

	Comment: A few commenters stated that EPA should clarify and modify the
part of its proposal that explains why a State cannot rely on EPA’s
determination that CAIR can satisfy the NOx RACT requirement for PM2.5
if the State ‘elect[s] to allow non-EGU sources to voluntarily enter
the EPA-administered CAIR trading program through an opt-in provision in
the CAIR model rule.’ (70 FR 66025 col. 3). These commenters believe
that this part of the proposal might be construed to preclude states
subject to both the NOx SIP Call and included in the CAIR region for
ozone from relying on the NOx RACT determination for PM2.5 if the states
choose ‘to bring their non-CAIR [including non-EGU] NOx SIP Call
trading sources into the CAIR ozone season NOx cap and trade program. 
(70 FR 49708, 49728 col. 3)  (August 24, 2005). The commenters assert
that EPA gave states the option of bringing non-EGU NOx SIP Call sources
into the CAIR seasonal NOx trading program to ensure that non-CAIR
sources, including non- EGUs, that are subject to the NOx SIP Call rule
would not be ‘stranded,’ starting in 2009, by being left in an ozone
season NOx control program with no EGU trading partners.  The commenters
argued that “EGUs should not be penalized, in the form of denial of
CAIR=RACT treatment, as a result of states exercising their option to
avoid financial and compliance difficulties for non-EGUs that otherwise
would be left without allowance trading partners in the EGU sector after
the NOx SIP Call trading program ends in 2008.”  These commenters
point to EPA’s determination in the final Phase 2 ozone implementation
rule, that participation in the CAIR trading programs can satisfy NOx
RACT for ozone even if a State brings non-EGUs in the NOx SIP Call
trading program into the trading program after 2008, see 70 FR 71657
col. 2, provided the State retains an ‘EGU [emission] budget under
CAIR that is at least as restrictive as the EGU budget that was set in
the State’s NOx SIP call SIP,’ id. At 71658 col. 1. These commenters
argue that EPA should make a similar determination here regarding NOx
RACT for purposes of PM2.5 NAAQS implementation.

Response:  All states with EPA approved CAIR SIPs or subject to a CAIR
FIP implementing the annual NOx emission reduction requirements, and
obtaining those reductions solely from EGUs may rely on EPA’s
determination that CAIR presumptively satisfies NOx RACT/RACM for PM2.5
for these sources.  This determination is unaffected by whether or not a
State permits NOx SIP Call non-EGUs to participate in the CAIR ozone
season trading program.  In the final rule, we have included the
presumption that NOx RACT/RACM for PM2.5 is satisfied for EGUs complying
with a CAIR SIP or CAIR FIP implementing the annual CAIR NOx emission
reduction requirements (provided the State implementation of the CAIR
NOx annual trading program includes EGUs only).18

	In the final ozone implementation rule, EPA addressed numerous issues
relating to the transition from the NOx SIP Call to the CAIR ozone
season trading program, including the impact of bringing NOx SIP Call
non-EGUs into the CAIR ozone season trading program.  Commenters’
suggestion that these determinations are relevant to this PM2.5
implementation rule ignores the fact that both the NOx SIP Call and the
CAIR ozone season trading program are seasonal, not annual, trading
programs.  The NOx SIP Call EGU and non-EGU budgets are seasonal NOx
budgets and do not address annual NOx emissions.  As discussed above,
PM2.5 levels year-round contribute to an area’s annual average
concentration, and NOx emissions during non-summer months contribute to
nitrate concentrations, which are typically highest in cooler
temperatures.  For these reasons, EPA believes it would be inappropriate
to accept commenters’ suggestion.  

8.	What are the Required Dates for Submission and Implementation of
RACT?

a.	Background.  

	The EPA requested comment on a general approach for the dates for
submission and implementation of RACT rules.  The final rule retains the
proposed approach, as described in the following section.

b.Final Rule.  

The final rule requires the following:

(1) Date of submission.  States must submit adopted RACT rules to EPA
within 3 years of designation, at the same time as the attainment
demonstration due in April 2008. 

(2) Dates for implementation of control measures.  States should also
implement any measures determined to be RACT expeditiously, as required
by section 172.  Implementation of RACT measures should in no case start
later than the beginning of the year before the nominal attainment date.
  For example, if an area has an attainment date of April 2010, then any
required RACT measures should be in place and operating no later than
the beginning of 2009.  This is intended to help provide for clean air
in calendar year 2009.   As discussed in section II.D, if other criteria
are also met, EPA could then grant the area a 1-year attainment date
extension if the air quality level in the 3rd of the 3 years was below
the level of the standard. If the area observes a second year of clean
air, EPA could grant a second 1-year attainment date extension.  In this
case, the 2009 to 2011 period would then be reviewed to assess whether
the area attains the standards.)

(3) Provisions for a demonstration that additional time is needed. 
While EPA expects that States will implement required RACT controls by
January 2009 in most situations, there may be cases where additional
time is needed to implement an innovative control measure or to achieve
a greater level of reduction through a phased approach.  If a State has
provided an adequate demonstration showing that an attainment date
extension would be appropriate for an area, then the State may consider
phasing-in certain RACT controls after      January 2009.  The EPA would
allow the implementation of selected RACT controls after January 2009 if
the State can show why additional time is needed for implementation, and
such delayed implementation still would need to be on a schedule that
provides for expeditious attainment.  In no event could the State wait
to implement RACT controls until the last few years prior to the
attainment date without an adequate rationale for why earlier
implementation was not feasible.

c.	Comments and Responses. 

Comment: One commenter supported EPA’s position that implementation of
RACT and RACM by January 1, 2009 is necessary to achieve the effect on
air quality for calendar year 2009.   

Response:  The EPA agrees with this comment.

Comment:  Some commenters supported allowing for an implementation
schedule that allowed for implementation of RACT and RACM for a time
frame extending beyond 2009.    These commenters favored such an
approach if States provided an adequate demonstration of why the
measures cannot be implemented earlier.   Commenters noted that a phased
approach to emissions reductions in some cases could lead to additional
reductions that could not occur by 2009.  

	Response:  The EPA agrees with these comments.

	Comment:  One commenter believed that so long as a State demonstrates
attainment by 2015, EPA should not require implementation of any RACT
measures.  The commenter further asserted that it would be bad policy to
require costly emissions reductions through imposition of RACT on areas
expected to attain the standards through other means by 2015.

	Response:  The EPA disagrees with this comment.  The CAA requires
States to demonstrate that the attainment plan will attain the standards
as expeditiously as practicable and must include RACT and RACM.   The
requirement for “reasonable” measures does not require that any
theoretical measure be implemented, but does require implementation of
those reasonable measures which could advance the attainment date by at
least 1 year.  Given the health effects associated with PM2.5, EPA
believes this approach is sound public policy.     

9.	Which Pollutants Must be Addressed by States in Establishing RACT and
RACM Limits in Their PM2.5 Attainment Plans?

a.	Background.

	In the proposed rule, and in the final rule as discussed in detail in
section II.A above, EPA discusses the pollutants which States must
address in the attainment plans, in particular with respect to RACT,
RACM and NSR.   These pollutants include not only direct PM2.5, but also
gaseous precursors to the formation of PM2.5.  In general, the decisions
that States and EPA make with respect to which precursors are
significant contributors to an area’s PM2.5 nonattainment problem
define the pollutants and sources to be addressed by States in
developing RACT and RACM.  

b.	Final Rule.

	In the final rule, in establishing RACT and RACM limits, those RACT and
RACM limits must address:

-- direct emissions of PM2.5

-- SO2, a precursor to PM2.5 formation, and

-- NOx, unless a State makes a finding that NOx emissions from sources
in the State do not significantly contribute to the PM2.5 problem in a
given nonattainment area.  

	The EPA generally presumes that RACT and RACM limits are not needed for
ammonia or VOC unless that State or EPA determines otherwise for a given
nonattainment area.  RACT and RACM limits are needed for ammonia if a
State or EPA makes a finding that ammonia emissions significantly
contribute to the PM2.5 problem in a given nonattainment area, and thus
finds that control of ammonia would help address the PM2.5 problem. 
RACT and RACM limits are needed for VOC only if a State or EPA makes a
finding that VOC emissions significantly contribute to the PM2.5 problem
in a given nonattainment area.  (As a point of clarification,
“VOCs,” which are gaseous organic precursors to the chemical
formation of secondary organic aerosol, are treated differently from
semivolatile or nonvolatile organic compounds which are addressed as
directly emitted PM2.5).  Issues related to the finding of
“significant contribution” for these pollutants are discussed in
Section II.A above.

10.	Under the PM2.5 Implementation Program, When Does a State Need to
Conduct a RACT Determination for an Applicable Source That Already Has a
RACT, BACT, LAER, or MACT Determination in Effect?  tc "10.Under the
PM2.5 Implementation Program, Does a State Need to Conduct a RACT
Determination for an Applicable Source That Already Has a RACT
Determination in Effect? " \l 3  

a.	Background.

	For PM2.5 nonattainment areas, States are required to implement the
RACT requirement to reduce emissions of direct PM2.5 and PM2.5
precursors from applicable sources.  The EPA anticipates that for some
sources located in PM2.5 nonattainment areas, the State would have
previously conducted RACT determinations for VOC or NOx under the 1-hour
ozone standard, or for direct PM10 emissions under the PM10 standards. 
Some of the RACT determinations established under these other programs
would be relatively recent while other determinations may be more than
10 years old.  In some cases, a new RACT determination might reach the
conclusion that the preexisting determination is still valid and would
require the installation of similar control technology because the
relevant pollutant was addressed, the same emission points were
reviewed, and the same fundamental control techniques would still have
similar costs.  In other cases, however, a new RACT analysis could
determine, for example, that better technology has become available, and
that cost-effective emission reductions are achievable.  

	In the proposed rule, the EPA requested comments on a general approach
to taking prior RACT determinations into account, and within the general
approach, invited comments on two specific questions:  1) should new
RACT determinations be required for all existing determinations that are
older than a specified amount of time (such as 10 years old)?; and 2)
what supporting information should a State be required to submit as part
of its certification to demonstrate that a previous RACT analysis meets
the RACT requirement currently for purposes of the PM2.5 program?

	In the proposed rule, EPA also noted that sources subject to RACT may
also have been subject to other prior technology determinations such as
BACT, LAER or MACT determinations.  The proposed rule requested comment
on approaches to taking these prior technology determinations into
account. 

b.	Final Rule.

	The EPA has determined that it is appropriate to follow the approach in
the proposed rule, which is described below.  State RACT SIPs for PM2.5
must assure that RACT is met, either through a new RACT determination or
a certification that previously required RACT controls represent RACT
for PM2.5.    

Where a State adopted and EPA approved a control measure as RACT for a
pollutant emitted from a specific stationary source or source category
under another NAAQS program, the State may submit as part of its SIP
revision a certification, with appropriate supporting information, that
the previous determination represents a current RACT level of control
for those emissions for purposes of the PM2.5 program.  Otherwise, the
State should revise the SIP to reflect a modified RACT requirement for
specific sources or source categories.

	In cases where the State’s prior RACT analysis under another NAAQS
program concluded that no additional controls were necessary, a new RACT
determination is required for that source.  In cases where the previous
RACT determination did not require any controls on the source, it is
more likely that a new review might find that emission controls are now
economically and technically feasible.  This is because emissions
reductions from a potential control measure are likely to be greater,
and the cost per ton of emission reduction is likely to be lower, than
in the case of a source that previously installed controls to meet RACT
under another program.

	A RACT determination for a source or source category subject to a prior
RACT determination is also required for any pollutants that were not the
subject of the prior RACT determination, but which the State has
determined should be regulated for purposes of PM2.5.  The EPA advises
that the State should closely review any existing RACT determinations
established under another NAAQS program.  For RACT certifications and
determinations, States are to consider new information that has become
available since the earlier RACT determination.  For example, where
updated information on control technologies is presented as part of
notice-and-comment rulemaking, including a RACT SIP submittal for
sources previously controlled, States (and EPA) must consider the
additional information as part of that rulemaking.   Existing EPA
guidance on control technologies can be used to help inform RACT
decisions.  However, EPA believes it may not be sufficient for a State
to rely on technology guidance that is several years old and issued to
provide recommendations on control measures and levels for a different
NAAQS in evaluating RACT for PM2.5 

	With respect to prior technology determinations other than RACT, the
final rule provides that:

	(1) Prior BACT and LAER Determinations.  In many cases, but not all,
best available retrofit technology (BACT) or lowest achievable emission
rate (LAER) provisions for new sources would assure at least RACT level
controls on such sources.  The BACT/LAER analyses do not automatically
ensure compliance with RACT since the regulated pollutant or source
applicability may differ and the analyses may be conducted many years
apart.  States may, however, rely on information gathered from prior
BACT or LAER analyses for the purposes of showing that a source has met
RACT to the extent the information remains valid.  We believe that the
same logic holds true for emissions standards for municipal waste
incinerators under CAA section 111(d) and NSR/PSD settlement agreements.
 Where the State is relying on these standards to represent a RACT level
of control, the State should present its analysis with its determination
during the SIP adoption process.

	(2) Compliance With MACT Standards Affecting VOC.  In situations where
the State has determined VOC to be a significant contributor to PM2.5
formation in an area, compliance with MACT standards may be considered
in VOC RACT determinations.  For VOC sources subject to MACT standards,
States may streamline their RACT analysis by including a discussion of
the MACT controls and relevant factors such as whether VOCs are well
controlled under the relevant MACT air toxics standard, which units at
the facility have MACT controls, and whether any major new developments
in technologies or costs have occurred subsequent to establishment of
the MACT standards.  We believe that there are many VOC sources that are
well controlled (e.g., through add-on controls or through substitution
of non-VOC non-HAP materials for VOC HAP materials) because they are
regulated by the MACT standards, which EPA developed under CAA section
112.  Any source subject to MACT standards must meet a level that is as
stringent as the best-controlled 12 percent of sources in the industry. 
Examples of these HAP sources that may effectively control VOC emissions
include organic chemical plants subject to the hazardous organic NESHAP
(HON), pharmaceutical production facilities, and petroleum refineries. 
We believe that, in many cases, it will be unlikely that States will
identify VOC emission controls more stringent than the MACT standards
that are not prohibitively expensive and are thus unreasonable.  We
noted our view that this will allow States, in many cases, to conclude
that the control measures implemented to meet MACT standards satisfy any
requirement for VOC RACT.

	(3) Compliance With MACT Standards Affecting PM2.5 Emissions. 
Compliance with MACT standards may be considered in direct PM2.5 RACT
determinations.  For direct PM2.5 sources subject to MACT standards,
States may streamline their RACT analysis by including a discussion of
the MACT controls and relevant factors such as whether PM2.5 emissions
are well controlled under the relevant MACT air toxics standard, which
units at the facility have MACT controls, and whether any major new
developments in technologies or costs have occurred subsequent to the
MACT standards.  We believe that there are many direct PM2.5 sources
that are well controlled (e.g., through add-on controls that represent
State-of the art measures for PM2.5 reduction) because they are
regulated by the MACT standards which EPA developed under CAA section
112.  For some MACT standards, PM2.5 is used as a surrogate for
achieving MACT for HAPs such as heavy metals.  Any source subject to
MACT standards must meet a level that is as stringent as the
best-controlled 12 percent of sources in the industry.   We believe that
there will be sources for which it will be unlikely that States will
identify emission controls more stringent than the MACT standards that
are not prohibitively expensive and are thus unreasonable.   In
addressing whether a MACT standard represents best controls for PM2.5,
it is important that the State consider all PM2.5 sources at a given
facility and the nature of the PM limit (i.e., whether the limit ensures
control of the fine fraction of particulate matter).   Also, the State
should evaluate the degree of capture of PM2.5 -- that is, the amount of
PM2.5 that is collected and sent to a pollution control device in
addition to the efficiency of the device itself.   This evaluation
should consider the PM2.5 emissions reductions that could by achieved by
improving the degree of capture.  

	(4) Year-Round Controls for NOx.  In some cases, sources subject to NOx
RACT for PM will also be subject to controls under the NOx SIP Call.  In
the 8-hour ozone implementation rule, EPA concluded that certain sources
which have installed emission controls to comply with the NOx SIP call
would be deemed to meet NOx RACT for the purposes of the 8-hour ozone
implementation program.  Some of these sources subject to the NOx SIP
call may choose to control NOx emissions only or primarily during the
ozone season.  For purposes of PM2.5, however, EPA concludes that the
operation of emission controls only or primarily during the ozone season
would not constitute RACT for PM2.5 purposes.   Indeed PM2.5 control
programs must address annual average concentrations, and in many areas
nitrate concentrations are generally highest in the winter.  Therefore,
RACT for PM2.5 is year-round operation of controls.  For sources subject
to both the NOx SIP call and NOx RACT for PM, we believe that, in most
cases, the additional costs of running the NOx SIP call controls
year-round would impose only modest, reasonable additional costs and the
cost effectiveness would be better than the average cost effectiveness
for many other sources subject to PM RACT.  (See further discussion in
section F.7 above related to EGU sources subject to CAIR requirements
for NOx).   

c.	Comments and Responses.

	Comments:  A number of commenters agreed with the requirement for the
State to conduct a new RACT determination for any source for which the
State’s prior RACT analysis under another NAAQS program concluded that
RACT was defined as no additional controls.  One commenter noted that
for a source having a previous RACT determination for ozone or PM10 to
show that its level of control currently meets RACT for PM2.5 purposes,
the source must provide supporting documentation showing that the
previous RACT determination was based on the same universe of controls
that are “reasonably available” for the source in the present day.  

	Response:  The EPA agrees with these comments.

	Comments:  A few commenters recommended that EPA clarify that RACT
determinations resulting only in “operational changes” should be
treated in an equivalent manner as those resulting in no controls.   The
commenters suggested that, unlike “physical modification,” such
operational changes should always be revisited with a new RACT
determination.  

	Response:  The EPA does not agree with the implicit recommendation to
impose different RACT review requirements based on the types of control
previously implemented.  The EPA believes that a reassessment of RACT is
warranted, irrespective of the type of control previously implemented,
to consider the reasonableness of modifying or adding controls in the
particular circumstances.   Furthermore, we are concerned that making
such a distinction based upon the fairly broad term “operational
change” would be difficult to interpret and implement, and would
invite unnecessary disputes concerning the application of the term.  

	Comment:  Commenters differed on whether new RACT determinations should
be required for all existing determinations made before a specific date,
and on what that date should be.  Some commenters recommended that EPA
allow States to rely on any previous RACT determinations made after
1990, and one commenter recommended that EPA require states to review
only those older than 10-15 years, another recommended 10 years.    One
commenter believed that a 15-year period would be reasonable where
previous controls were installed, to allow for a 15-year amortization of
the cost of those controls.  Other commenters recommended that new RACT
determinations be made for any RACT determinations older than 5 years. 
Another commenter recommended that all RACT determinations should be
reviewed.

	Response:  The EPA has not included any specific time frame in the
final rule.  The EPA agrees that the more recent the RACT determination,
the greater the probability that technology advances or decreases in
control cost will not have occurred.  At the same time, technology
advances and decreases in control cost can and have occurred frequently.
 Accordingly, we believe it is necessary for States to review whether
such technology advances or decreases in control cost have occurred
before relying on previous RACT determinations.  We do not believe there
is any specific date or age that could be identified after which States
could ensure that no technology advances or decreases in control cost
will have occurred.

	Comment:  A number of commenters expressed concerns with the resources
required to conduct the certifications required by the proposed
approach, and argued that expending the resources required to review and
to certify previous RACT determinations would not be productive.  One
commenter recommended that EPA provide guidance on the previous RACT
categories for which old RACT determinations are believed to be out of
date.  Another commenter asserted that the only possible exception to
the acceptability of previous RACT measures for purposes of the ozone
standards would be when the new RACT is year-round for an existing
ozone-season RACT measure.

	Response:  The EPA believes that the proposed certification approach
strikes an appropriate balance in requiring States to verify whether
previous RACT determinations currently represent an appropriate RACT
level of control for PM2.5 purposes, while stopping short of requiring
an exhaustive re-analysis for all RACT sources.  The EPA believes that
much of the resource concerns expressed in comments were based upon
concerns that VOC sources are very numerous, and that this approach
would require detailed review for these sources.  As noted previously, a
RACT analysis for VOC sources is required only if a State makes a
finding that VOC sources significantly contribute to nonattainment in
the State.  We believe the commenters likely overestimate the resource
implications of the certification process for prior RACT determinations.
 Another mitigating factor is that many of these same sources would be
reviewed for purposes of implementing the eight-hour ozone standard.  On
the other hand, where a State or EPA determines that it is appropriate
to regulate VOC sources for PM2.5, EPA believes that it likely would be
productive to review the previous determination for such sources, some
of which have not been reviewed for many years.

	Comment:  One commenter believed that EPA should acknowledge detailed
RACT and RACM analyses for the South Coast and San Joaquin Valley in
California prepared during the 1990s for purposes of implementing the
ozone and PM10 standards.   The commenter believes that EPA acceptance
of these determinations as RACT for PM2.5 would enable States to focus
resources on developing new measures needed for attainment.

	Response:  The EPA agrees that States should focus resources on new
technologies and new developments.  At the same time, EPA recognizes
that for most source categories, new technology continues to be
developed, and new information continues to be generated.  Thus, even
recent RACT determinations for a given source category may be outdated. 
Hence, the certification approach in the rule for the relevant sources
or source categories is a reasonable approach which is designed to
provide for the type of focused efforts suggested by the commenter.   

	Comment:   One commenter believed that a State certification should
only have to identify the existing RACT levels in a SIP and pollutants
affected, but the State should not be required to provide any additional
information.  

	Response:   The EPA disagrees with this comment.  The EPA believes that
prior technology determinations should be taken into account in the RACT
determination process.  In reviewing existing RACT determinations, the
State should provide supporting information to show that the existing
technology in use should still be considered RACT, or it should show
that there have been technology advances or cost reductions that have
occurred since the previous RACT limits were developed that make lower
emissions technically and economically feasible in the context of RACT
and would contribute to advancing the attainment date by at least one
year.  

	Comment:  Some commenters supported EPA’s requirement for year-round
operation of NOx pollution control devices as RACT, given that PM2.5 is
an annual standard, while ozone is a summertime problem.

	Response:  The EPA agrees with these comments.

	Comment:   One commenter concluded that BACT and LAER determinations
should be considered to satisfy RACT, regardless of the date they were
made, because BACT and LAER by definition are more stringent than RACT. 
 

	Response:  The EPA disagrees with this comment.  The  EPA believes that
in many cases, but not all, BACT and LAER would assure RACT level of
controls.  Reasons that BACT and LAER might not satisfy RACT include:  
the pollutant of concern could have been different, the applicability
threshold for BACT and LAER may have excluded smaller sources
potentially subject to RACT controls, and technology advances or
reductions in control costs may have occurred since the old
determination was conducted.    

	Comment:   One commenter recommended that EPA allow States to use
information gathered from prior BACT or LAER analyses to complete the
RACT determination, as was allowed in the 8-hour ozone NAAQS
implementation rule. 

	Response:  The final rule allows for use of such information, to the
extent it remains valid, to inform a certification by the State that
BACT or LAER technology continues to exceed what would currently be
considered RACT.

	Comment:   Some commenters argued that any MACT determination that
controls the pollutants of concern should be more than sufficient to
satisfy RACT.  Some commenters made similar recommendations regarding
specific standards where PM limits were developed as a surrogate for
HAPs, such as the MACT standard for integrated iron and steel mills, the
MACT standard for iron and steel foundries, and the section 129
standards for waste to energy facilities.

	Response:  While agreeing that MACT controls are relevant, the EPA
disagrees that all MACT determinations should be automatically
considered to satisfy RACT.   Reasons include:  a MACT standard aimed at
toxics might not ensure that the relevant PM2.5 pollutant(s) are well
controlled, MACT applicability provisions might have excluded units
potentially subject to RACT, and technology advances or reductions in
control costs might have occurred since EPA conducted the MACT analysis.
 The EPA believes that the State should review whether technology
advances have occurred including available “beyond the MACT floor”
technologies that may be reasonable in the context of RACT for PM2.5
nonattainment, but which were not selected as MACT for purposes of
implementing section 112.  The EPA believes that RACT analyses should
evaluate whether increased capture of PM2.5 could be achieved, and
whether an increased efficiency in controlling the fine fraction of
particulate matter is reasonably available.   The EPA has, however,
added a specific recognition that MACT standards can reduce PM2.5 as
well as VOC, and that PM2.5 information gathered for MACT standards
development may inform a State’s conclusions on available technologies
for direct PM2.5 emissions.

	Comment:  One commenter expressed a concern that EPA should not presume
that MACT represents RACT where the MACT rule allows for a risk-based
exemption from the control technology requirement.

	Response:  The EPA agrees with this comment.

11.	How Should Condensable Emissions be Treated in RACT Determinations? 
tc "8.How Should Condensable Emissions be Treated in RACT
Determinations? " \l 3  

a.	Background.

	Certain commercial or industrial activities involving high temperature
processes (fuel combustion, metal processing, cooking operations, etc.)
emit gaseous pollutants into the ambient air which rapidly condense into
particle form.  The constituents of these condensed particles include,
but are not limited to, organic material, sulfuric acid, and metals.  In
general, condensable emissions are taken into account wherever possible
in emission factors used to develop national emission inventories, and
States are required under the consolidated emissions reporting rule
(CERR) to report condensable emissions in each inventory revision. 
Currently, some States have regulations requiring sources to quantify
condensable emissions and to implement control measures for them, and
others do not.  In 1990, EPA promulgated Method 202 in Appendix M of 40
CFR Part 51 to quantify condensable particulate matter emissions.  In
the proposed rule, EPA discussed and requested comment on issues related
to condensable emissions in RACT determinations.

	In the proposed rule, we noted that EPA is in the process of developing
detailed guidance on a new test method which quantifies and can be used
to characterize the constituents of the PM2.5 emissions including both
the filterable and condensable portion of the emissions stream.   We
also noted that when a source implements either of these test methods
addressing condensable emissions, the State will likely need to revise
the source’s emissions limit to account for those emissions that were
previously unregulated.  For the purposes of determining RACT
applicability and establishing RACT emission limits, EPA indicated in
the proposal that it intends to require the State to adopt the new test
method once EPA issues its detailed guidance.   This guidance would be
for use by all sources within a PM2.5 nonattainment area that are
required to reduce emissions as part of the area’s attainment
strategy.  

b.	Final Rule. 

	Issues and comments related to test method and emissions limit issues
for direct PM2.5 for RACT, including discussion of test methods for
condensable PM2.5, are discussed in section II.L.3 of this preamble. 
The EPA recognizes that in some cases condensable emissions are more
difficult to control than filterable emissions.  However, condensable
emissions may be assumed to be almost entirely in the 2.5 micrometer
range and smaller, so these emissions are inherently more significant
for PM2.5 than for prior particulate matter standards addressing larger
particles.  Therefore, EPA encourages States to consider the potential
for reducing condensable emissions when evaluating potential measures
for RACT.

12.	What Criteria Should be Met to Ensure Effective Regulations to
Implement RACT and RACM?

a.	Final Rule.

	After the State has identified a RACT or RACM measure for a particular
nonattainment area, it must then implement that measure through a
legally enforceable mechanism (e.g., a State rule approved into the
SIP).  The legally enforceable mechanism must meet four important
criteria.  

	First, the baseline emissions from the source or group of sources and
the future year projected emissions must be quantifiable so that the
projected emissions reductions from the sources can be attributed to the
specific measures being implemented.  It is important that the emissions
from the source category in question are accurately represented in the
baseline inventory so that emissions reductions are properly calculated.
 In particular, it is especially important to ensure that both the
filterable and condensable components of PM2.5 are accurately
represented in the baseline since traditional Federal and State test
methods have not included the condensable component of particulate
matter emissions and have not required particle sizing of the filterable
component.

	Second, the control measures must be enforceable.  This means that they
must specify clear, unambiguous, and measurable requirements.  When
feasible, the measurable requirements for larger emitting facilities
should include periodic source testing to establish the capability of
such facilities to achieve the required emission level.  Additionally,
to verify the continued performance of the control measure, specific
monitoring programs appropriate for the type of control measure employed
and the level of emissions must be included to verify the continued
performance of the control measure.  The control measures and monitoring
program must also have been adopted according to proper legal
procedures.

	Third, the measures must be replicable.  This means that where a rule
contains procedures for interpreting, changing, or determining
compliance with the rule, the procedures are sufficiently specific and
nonsubjective so that two independent entities applying the procedures
would obtain the same result.

	Fourth, the control measures must be accountable.  This means, for
example, that source-specific emission limits must be permanent and must
reflect the assumptions used in the SIP demonstration.  It also means
that the SIP must establish requirements to track emission changes at
sources and provide for corrective action if emissions reductions are
not achieved according to the plan.

b.	Comments and Responses

	There were no comments on this section.  The language above is very
similar to the language in the proposal.

G.	Reasonable Further Progress (RFP)

1.	Background

	Clean Air Act Section 172(c)(2) requires that plans for nonattainment
areas “shall require reasonable further progress,” which as defined
in Section 171(1) “means such annual incremental reductions in
emissions of the relevant air pollutant as are required by this part or
may reasonably be required by the Administrator for the purpose of
ensuring attainment of the applicable national ambient air quality
standard by the applicable date.”  This section describes the
requirements the Administrator is establishing for states to achieve
reasonable further progress.

	In general terms, the goal of these RFP requirements is for areas to
achieve generally linear progress toward attainment.  The RFP
requirements were included in the Clean Air Act to assure steady
progress toward attaining air quality standards, as opposed to deferring
implementation of all measures until the end date by which the standard
is to be attained.

2.	Requirements for Areas with Attainment Dates of 2010 or Earlier

a.	Background

	In 40 CFR 51.1009(b)(1) of the proposed rule, EPA proposed that a State
which submits an implementation plan that demonstrates that an area will
achieve attainment by 2010 (i.e., achieves attainment level emissions
during 2009) would not be required to submit a separate reasonable
further progress plan for that area.  In such cases, EPA proposed that
the attainment demonstration would also be considered to demonstrate
that the area is achieving RFP.

b.	Final Rule

	In the final rule, EPA is maintaining the approach described in the
proposed rule.  An area that demonstrates attainment by 2010 will be
considered to have satisfied the RFP requirement and need not submit any
additional material to satisfy the RFP requirement.  The EPA will view
the attainment demonstration as also demonstrating that the area is
making reasonable further progress toward attainment.  

c.	Comments and Responses

	Comment:  A number of commenters supported EPA’s view that a
demonstration of attainment by 2010 would also demonstrate that the area
is making reasonable further progress toward attainment.  

	Response:  The EPA appreciates the support and is adopting the
supported approach.

	Comment:  A set of commenters objects to EPA’s proposal, arguing that
EPA cannot waive RFP requirements for areas where the state purports to
demonstrate attainment.  These commenters believe that Subpart 4 of Part
D requires milestones prior to 2009, and these commenters believe that
even Subpart 1 requires a demonstration of interim progress that EPA
cannot waive.

	Response:  In brief, EPA is not waiving the RFP requirements for any
area.  Instead, EPA is concluding that a demonstration of attainment by
2010 also serves to demonstrate achievement of RFP.  If the state
submittal purports to demonstrate attainment but does not adequately
make this demonstration, then the submittal also would not demonstrate
achievement of RFP.  The nature of the RFP requirement would then depend
on whether the remedied attainment demonstration provides for attainment
by 2010.  Finally, as discussed above, EPA believes that Subpart 4
requirements do not apply to PM2.5 plans.  More detailed discussion of
this comment and EPA’s response are provided in the response to
comments document.

3.	Requirements for Areas With Attainment Dates Beyond 2010 

a.	Background  

	The proposed rule required a State to submit an RFP plan along with its
attainment demonstration and SIP due in April 2008 for any area for
which the State demonstrates that 2011 or later is the most expeditious
attainment date.    SEQ CHAPTER \h \r 1 EPA proposed that the 2008 RFP
plan must provide adequate emission reductions by 2009 and, in some
cases, by 2012.  The plan must demonstrate that emissions will decline
in a manner that represents generally linear progress from the 2002
baseline year to the attainment year.  

b.	Final Rule

	The final rule requires a State to submit an RFP plan along with its
attainment demonstration and SIP due in April 2008 for any area for
which the State justifies an extension of the attainment date beyond
2010.  The RFP plan must provide emission reductions such that emissions
in 2009 represent generally linear progress from the 2002 baseline year
to the attainment year.  Where the State justifies an extension of the
attainment deadline to 2014 or 2015, the state must additionally provide
emission reductions such that emissions in 2012 represent generally
linear progress from the 2002 baseline year to the attainment year. 

	If the State demonstrates that attainment will occur by 2010 or
earlier, EPA will consider the attainment demonstration to demonstrate
achievement of reasonable further progress, and the State will not be
required to submit an additional RFP plan for the area.  

c.	Comments and Responses

	Comment:  For areas that demonstrate attainment by 2015 without
adopting additional measures, a commenter recommended that the
attainment demonstration be viewed as also demonstrating that the area
is achieving RFP.  The commenter therefore recommended that the state
not be required to submit an RFP plan for such an area.

	Response:  A submittal that demonstrates attainment at the latest
allowable date and does not address interim air quality fails to show
that the path to attainment will yield interim incremental air quality
improvements.  States have ample opportunity to adopt measures that
would provide interim air quality improvement long before 2015.  Indeed,
as discussed elsewhere as part of the discussion of attainment dates, a
submittal that only addresses 2015 would also fail the attainment
demonstration requirement, insofar as it would not be addressing whether
attainment is as expeditious as practicable, because the submittal would
fail to assess whether attainment could be achieved earlier.  Therefore,
irrespective of whether additional measures are needed to attain by
2015, the Clean Air Act mandates assessing progress at reasonable
interim dates as well as mandating attainment.

4.	Generally Linear Progress and Associated Timeline

a.	Background

	The EPA proposed that states with areas needing an extension of the
attainment deadline beyond 2010 would be required to submit a plan
demonstrating that emissions would be sufficiently reduced by 2009 to
achieve a generally linear incremental improvement in air quality.  The
notice of proposed rulemaking provided an example calculation for an
area with a 2013 attainment date, i.e. an area that achieves attainment
level emissions in 2012.  (See section III.G.4.b.iv of the proposal, 70
FR 66013.)  In this example, the 2009 emissions year represents 7/10 of
the period extending from the baseline year of 2002 to the 2012 year of
attainment level emissions.  Therefore, for this example, EPA’s
proposed requirement would be for this area to achieve emission
reductions by 2009 representing approximately 7/10 of the emission
reductions needed to attain the standards.  For states with areas
needing the attainment deadline extended to 2014 or 2015, EPA proposed
to require achievement of generally linear emission reductions at two
RFP milestone years—the 2009 and 2012 emission years.

	The EPA received several comments on various elements of its proposed
approach.  Several commenters objected to EPA’s proposed requirement
to achieve linear progress toward attainment, asserting that EPA cannot
reasonably expect states to achieve a significant amount of progress
within a short time after plan submittals are due.  Some commenters
recommended requiring a specific emission reduction percentage, similar
to the rate of progress requirement for ozone.  These comments are
addressed below. 

b.	Final Rule

	The EPA is requiring States with areas needing an extension of the
attainment deadline to submit RFP plans.  These plans must demonstrate
that generally linear reductions in emissions will occur by 2009, i.e.
that emissions in 2009 will be reduced to the extent represented by a
generally linear progression from 2002 base year emissions to
attainment-level emissions.  For any area that needs an extension of the
attainment deadline to 2014 or 2015, the State’s RFP plan would also
need to demonstrate that generally linear reductions will be achieved in
the 2012 emissions year as well.  

c.	Comments and Responses

	Comment:  Several commenters objected to EPA’s proposed requirement
that states demonstrate linear progress toward attainment.  For example,
a commenter stated that a “generally linear reduction process may not
be practicable.”  A commenter stated that it “agrees that areas
should be able to take credit for reductions from 2002 forward, [but]
EPA should allow for fewer reductions (as opposed to linear reductions)
prior to 2008.”

	A commenter noted that EPA’s “proposed approach ignores several
important realities about PM NAAQS implementation.  First, . . . [n]ot
until SIP submittal in April 2008, some 6 years after the RFP baseline
date, will any local measures be finally adopted and approved.  Under
[the example EPA provided in its proposed rulemaking], states will be
required to play ‘catch-up’ by achieving 70 percent of the required
reductions in 2009. . . . Second, the ‘generally linear’ approach
ignores that EPA intends for states to rely in large part on mobile
source reductions and reductions in NOx and SOx from CAIR implementation
to achieve attainment in many areas.  These measures fail a ‘generally
linear’ test since most of the reductions they provide will not be
realized until after 2009.”  This commenter continues that the
incremental reductions in emissions required in the Clean Air Act need
not be equal increments, that the absence of a specific statutorily
mandated increment (such as the 3 percent per year requirement for
ozone) allows EPA to be more flexible and to rely more heavily on later
reductions.  The commenter also argues that EPA’s proposal is more
stringent than the ozone RFP requirement, insofar as the ozone RFP
requirement provides for averaging over 3 years.  Similar comments were
submitted by other commenters.  

	Another commenter supported EPA’s proposal.  This commenter supported
requiring demonstrations that areas achieve emission reductions that
will yield incremental improvement in air quality on a path toward
expeditious attainment.  

	Response:  The EPA believes that the requirement for generally linear
reductions is reasonable because it allows States to take credit for
early reductions achieved due to federal, State, and local programs.  We
find that it appropriately implements the RFP requirement in the Clean
Air Act.  For these reasons, EPA is finalizing the requirement that RFP
plans for areas needing an attainment deadline extension show generally
linear progress in reducing emissions from the base year through the
2009 emissions year.  EPA is also requiring that areas needing an
attainment deadline extension to 2014 or 2015 (i.e. attainment level
emissions projected to start in 2013 or 2014) show generally linear
progress in reducing emissions through the 2012 emissions year.

	The commenters objecting to the requirement for generally linear
progress appear to be assuming that only minimal emission reductions can
be expected before 2008, so that a requirement for generally linear
progress would require plans submitted in 2008 to compensate by
achieving unrealistically high levels of emission reductions.  The EPA
disagrees with this assumption.  

	In fact, substantial emission reductions have occurred in the past few
years and can be expected to occur through the 2009 emissions year.  The
EPA has promulgated significant mobile source rules recently that will
yield substantial benefits in the coming years, and these benefits
follow a series of prior rules that provide a steady progression of
emission reductions as newer, cleaner vehicles replace older, dirtier
vehicles.  For utilities, significant NOx reductions occurred in 2004
under the NOx SIP call, and substantial SO2 reductions are expected to
occur under the CAIR trading program prior to 2010 due to incentives for
early reductions and the banking of allowances.  

	The EPA has also promulgated many other regulations that will reduce
particulate matter and particulate matter precursor emissions before as
well as after 2009.  States have also been implementing a variety of
measures.  With use of a 2002 baseline, the assessment of RFP allows
credit for these measures.  The following is a partial list of the
measures that have been adopted and will contribute to achieving
generally linear reductions:

NOx SIP Call

Tightened emission limits for new gasoline and diesel vehicles

Numerous regulations requiring Maximum Achievable Control Technology,
including regulations for

		- Iron and steel plants, including coke plants

		- Industrial boilers

		- Cement plants

		- Lime plants

		- Primary aluminum plants	

Numerous consent decrees for refineries

Numerous consent decrees for power plants

The Clean Air Interstate Rule for utilities

Retrofitted controls on diesel vehicles, and related programs for
reducing diesel vehicle emissions

Closures of coke plants and other facilities (and, from a national
perspective, replacement with cleaner new facilities)

	While different control measures require various timelines for
implementation, EPA believes that many of the additional measures that
states might adopt for attainment planning purposes can be implemented
in a timely fashion for addressing RFP requirements.  Thus, EPA believes
that states can reasonably be expected to assure that the combination of
existing measures and additional measures as necessary will provide for
generally linear progress in reducing emissions.  Furthermore,
particularly with respect to the 2009 RFP milestone year, when EPA
evaluates whether the emission levels in a state plan represent
generally linear progress, EPA will consider the availability of
measures that can be implemented by 2009.  

It is difficult to compare the stringency of this RFP requirement to the
RFP requirement for ozone.  The RFP requirement for ozone measures one
form of progress that occurs after 3 years, and the requirement for
PM2.5 measures a different form of progress that occurs after 7 years
(and for some areas also after 10 years).  That is, the ozone RFP
requirement applies a fixed, universally applicable emission reduction
percentage for one pollutant (VOC), whereas EPA is defining the PM2.5
RFP requirement as an area-specific combination of emission reductions
for multiple pollutants, defined on the basis of each area’s
attainment demonstration.

	The EPA believes that the Clean Air Act mandates not merely eventual
attainment by 2015 but also that states demonstrate that emissions are
being incrementally reduced in earlier years.  (As discussed elsewhere,
states must also demonstrate attainment by earlier than 2015 if
feasible.)  The requirement for RFP reflects Congressional intent that
areas make steady progress toward attainment in the years before
attainment occurs, and states have ample opportunity to assure that
reductions occur well before 2015.  

	Comment:  A commenter observes that the PM2.5 nonattainment areas in
its state also violate the ozone standard.  The commenter observes,
“[i]n setting plan requirements, U.S. EPA should choose options that
best facilitate harmonization of fine particulate and ozone control
programs. This includes using a fixed percentage of emission reductions
per year for reasonable further progress (RFP). We recommend the ozone
RFP metric of three percent annual emission reductions averaged over
three years.”  Another commenter also supports a more prescriptive RFP
requirement, and comments that “As suggested by EPA, nonattainment
areas must be required to achieve ‘a fixed percentage reduction of the
emissions of direct PM2.5 and regulated PM2.5 precursors & in specific
milestone years’ between the base year and the attainment year
proposed in the attainment demonstration.”  A third commenter
supported establishing a requirement for a fixed emission reduction
percentage, set at “no less than the 3 percent rate” in Section 182,
with the possibility of higher rates in areas with more severe air
quality problems.

	Other commenters prefer the approach that EPA proposed.  For example
one commenter states that it agrees with EPA’s approach of using the
attainment demonstration to define the parameters for determining what
constitutes RFP, and the commenter supports the flexibility of EPA’s
proposed approach “rather than requiring fixed linear percentage
reductions.”  Regarding the proposed option to require 3 percent per
year emission reductions for areas classified as serious, some
commenters recommended against establishing classifications and a fixed
emission reduction percentage for any area. 

	Response:  Requiring a fixed annual emission reduction percentage would
impose a “one-size-fits-all” approach to address a range of
circumstances.  Requiring a fixed annual emission reduction percentage
would overstate the reductions needed to achieve timely attainment in
some areas and would understate the reductions needed to achieve timely
attainment in other areas.  The EPA believes that defining the RFP
requirement in terms of achieving generally linear progress toward the
emission reductions needed for timely attainment assures that each area
will achieve a steady rate of progress most appropriate for the area to
achieve timely attainment.

	The EPA recognizes that many areas are nonattainment for both PM2.5 and
ozone and that the control programs for the two pollutants are
sufficiently intertwined that harmonization of planning for meeting
requirements applicable to the two pollutants is important.  However,
because the statutory requirements set forth in section 182 do not apply
to PM2.5 RFP plans, EPA believes it is neither necessary nor appropriate
to impose these requirements for PM2.5.  Indeed, given the multiple
pollutants that contribute to PM2.5 and the variations that exist in the
nature and composition of PM2.5 across the country, EPA believes that
the PM2.5 RFP requirements for generally linear reductions are better
defined to reflect these variations and thus better targeted toward the
emission reductions that in each area can be expected to lead toward
timely attainment.  Further, EPA believes that application of a
different form of the RFP requirement does not cause conflicts in
implementation planning for the two standards.  For example, reductions
of NOx emissions will generally reduce concentrations of both ozone and
PM2.5, and NOx emission reductions are creditable for meeting both the
ozone and the PM2.5 RFP requirements.  

	An important distinction between PM2.5 and ozone is that fine particle
formation is in general a more complex process, affected by both direct
emissions and numerous precursor pollutants.  The EPA does not believe
that RFP targets for PM2.5 should be the same as those used for the
ozone implementation program, nor should the same percentage reduction
be used for all PM2.5 related pollutants.  Instead, EPA believes that
RFP plans should reflect an appropriate combination of pollutant
reductions that most effectively provides for attainment.  Therefore,
EPA has defined an RFP requirement in which target emission reductions
are established in conjunction with the area’s attainment plan.

5.	Geographic Coverage of Emissions Sources

a.	Background

	PM2.5 concentrations reflect a combination of impacts over a wide range
of geographic scales.  For some components of PM2.5, observed
concentrations typically arise predominantly from sources within the
nonattainment area.  For other components, PM2.5 concentrations may be
influenced by sources across a broad area extending outside the
nonattainment area.  The EPA’s intent is to define the RFP requirement
in terms of emissions reductions that can be expected to provide
generally linear improvements in air quality in the nonattainment area. 
For this purpose, EPA continues to believe that RFP requirements for
PM2.5 are best defined such that states evaluate emissions of each
pollutant throughout the area in which the emissions substantially
influence PM2.5 concentrations in the nonattainment area.  

	As described in the proposed rulemaking, EPA expects each area’s
attainment demonstration to identify many of the parameters used to
define the emission reductions that would represent RFP.  First, the
attainment plan will identify the pollutants that are being reduced to
achieve attainment.  Second, the attainment plan will identify the
amount of reduction of each pollutant and the date by which attainment
can be achieved.  This information suffices to calculate a baseline set
of reductions to be achieved by 2009 to provide for RFP.  Third, where a
state chooses to achieve RFP by reducing some pollutants earlier than
others, the attainment plan will provide the information needed to
assess whether the intended set of reductions can be expected to provide
a comparable level of air quality improvement.  Fourth, if the State
intends to include emissions sources located outside the nonattainment
area in its RFP plan, the information necessary to justify inclusion of
such sources will likely be found in the attainment plan.

 	The EPA’s proposed rulemaking identified several expectations
regarding regional versus local impacts.  For directly emitted PM2.5
(including organic and other carbonaceous particles as well as
miscellaneous inorganic particles and including condensable particulate
matter), EPA recognized that impacts are commonly localized, and that
direct emissions of PM2.5 outside the nonattainment area should not be
included in the RFP plan.  Conversely, EPA recognized the regional
nature of secondarily-formed sulfate and nitrate, and proposed that
states could justify inclusion in the RFP plan of SO2 and NOx emissions
sources located within 200 kilometers of the nonattainment area.

	The EPA recognizes that fine particles travel over long distances, and
that distant emissions of SO2 and NOx emissions can influence a
nonattainment area’s air quality.  At the same time, distant sources
can be expected to have less impact than sources closer to the
nonattainment area.  EPA’s procedures for assessing RFP rely on a
general assumption that all the sources included in the assessment have
a comparable impact per ton of emissions.  For this reason, it would be
inappropriate to include distant emission sources in the assessment. 
Indeed, limiting the consideration of SO2 and NOx emissions to a 200
kilometer range is intended to assure that only sources with comparable
impacts are included in the assessment.

b.	Final Policy

	The policy for addressing direct PM2.5 emissions in RFP plans remains
unchanged from the proposal:  only emissions from within the
nonattainment area may be included.  Conversely, for SO2 and NOx, EPA
believes that states could be able to justify considering not only all
emissions in the nonattainment area but also emissions within a distance
that may be up to 200 kilometers from the nonattainment area.  States
may also be able to justify consideration of VOC and ammonia emissions
outside the nonattainment area on a case-by-case basis.  As we explain
more fully below in responding to comments, in situations where the
state demonstrates that VOCs are a significant contributor to PM2.5
concentrations in the area, it may be appropriate to include VOC
emission sources within a distance of up to 100 kilometers of the
nonattainment area.  Given the uncertainties regarding ammonia emission
inventories and the effects of reducing ammonia, EPA is not establishing
a policy on this issue with respect to ammonia.  States that expect to
regulate ammonia should consult with their regional offices to determine
appropriate approaches for those areas.  The justification for
considering emissions outside the nonattainment area shall include
justification of the state’s recommended definition of the area used
in the RFP plan for each pollutant.

	The EPA received comments objecting to the possibility that RFP
inventories for areas outside the nonattainment area could include
selected sources expecting substantial emission reductions while
excluding other nearby sources expecting emission increases.  Based on
its review of these comments, EPA is revising its approach for
considering regional emissions.  If the state justifies consideration of
precursor emissions for an area outside the nonattainment area, EPA will
expect state RFP assessments to reflect emissions changes from all
sources in this area.  The State cannot include only selected sources
providing emission reductions in the analysis.  The inventories for
2002, 2009, 2012 (where applicable) and the attainment year would all
reflect the same source domain (i.e. the same set of sources except for
the addition of any known new sources or removal of known, creditably
and permanently shutdown sources).

	In cases where the state justifies consideration of emissions of
specified precursors from outside the nonattainment area, the state must
provide separate information regarding on-road mobile source emissions
within the nonattainment area for transportation conformity purposes. 
The EPA’s transportation conformity regulations (40 CFR Part
93.102(b)) only require conformity determinations in nonattainment and
maintenance areas, and these regulations rely on SIP onroad motor
vehicle emission budgets that address the designated boundary of the
nonattainment area.  For this reason, if the state addresses emissions
outside the nonattainment area for a pertinent precursor (i.e. a
precursor for which mobile sources are significant, as discussed in the
May 6, 2005 transportation conformity rule on PM2.5 precursors at 72 FR
24280), the on-road mobile source component of the RFP inventory will
not satisfy the requirements for establishing a SIP budget for
transportation conformity purposes.

	In such a case, the state must supplement the RFP inventory with an
inventory of onroad mobile source emissions to be used to establish a
motor vehicle emissions budget for transportation conformity purposes. 
This inventory must address on-road motor vehicle emissions that occur
within the designated nonattainment area, must be provided for the same
milestone year or years as the RFP demonstration (i.e. 2009 and 2012 as
applicable), and must satisfy other applicable requirements of the
transportation conformity regulations.  So long as the state provides
this separate emissions budget EPA believes that this approach will
optimally address both the RFP and the transportation conformity
provisions of the Act.

	The EPA is restricting the geographic area for RFP assessments to
include only areas within the state or states represented in the
nonattainment area.  For a single state nonattainment area, only
emissions within that state would be considered, even if other states
may be within 200 kilometers of the nonattainment area.  For multi-state
nonattainment areas, only regions within states represented in the
nonattainment area shall be included in the RFP assessment.  This
restriction is intended to address commenters’ concerns about the
enforceability of emission reductions included in the RFP assessment and
helps assure accountability for these reductions.  This topic is
discussed further in the discussion below about multi-state
nonattainment areas.

	The EPA is retaining the approach that RFP assessments may not include
direct PM2.5 emissions from sources outside the nonattainment area.  If
a State regulates VOC or ammonia emissions as part of its attainment
strategy, the RFP plan must include emissions of these pollutants.  In
the event that a State technical demonstration indicates that emissions
of VOC or ammonia from sources outside the nonattainment area contribute
significantly to PM2.5 concentrations in the nonattainment area, EPA
will consider on a case-by-case basis whether it would be appropriate to
include emissions from such sources in the RFP plan.  

c.	Comments and Responses.

	The EPA received numerous comments on its proposal regarding how
regional versus local impacts would be addressed.  Multiple commenters
objected to EPA’s proposal that states could consider sources reducing
emissions but ignore neighboring sources increasing emissions. Other
commenters recommended that EPA support granting credit for reductions
of direct PM2.5 emissions that occur outside nonattainment areas.  A few
commenters also recommended different treatment of selected pollutants. 

	Comment:  Several commenters object to the methods by which EPA
proposed to account for reductions outside the nonattainment area. 
According to a set of commenters, if indeed sources outside the
nonattainment area contribute to nonattainment, “then EPA cannot
lawfully or rationally allow the state to claim RFP credit from a single
source’s reductions without including in the baseline emissions from
all sources (mobile, area and stationary) within the same distance from
the nonattainment area, and without calculating the impacts of increases
and decreases in such emissions on RFP. Viewing reductions from a single
‘outside the area’ source in isolation will invariably provide an
incomplete and inaccurate picture of the actual increase or decrease in
emissions contribution to the nonattainment area from all ‘outside the
area’ sources.  Moreover, EPA’s proposal creates numerous
opportunities to game and undermine the system.  By allowing
nonattainment areas to rely on RFP reductions made outside the
nonattainment area, the proposed rule strays from the Act’s focus on
achieving emissions reductions from sources within the nonattainment
area.”  Another commenter insisted that states should not be allowed
to consider emissions from sources outside the area unless they can
demonstrate the impacts of these sources on nonattainment area
concentrations. 

	In addition, a commenter objects to consideration only of sources that
are reducing emissions and recommends that EPA allow credit for upwind
source reductions only “on the condition that all other major sources
in the 200 kilometer boundary are also not allowed to increase
emissions.” Another commenter supports an option which states would
only consider emissions within the nonattainment area, observing that to
consider emissions outside the nonattainment area would be difficult to
administer and might inappropriately “dilute the reductions needed in
the nonattainment area.”  This commenter also observes that a 200
kilometer limit does not include much of the emissions that yield long
range transport.  Another commenter supports crediting reductions
outside the nonattainment area but requests that EPA define the area to
be considered.

	Response:  The EPA agrees that examining emissions reductions of only
selected sources outside the nonattainment area gives an inaccurate
assessment of the progress that an area is making.  For example, if a
state took credit for emission reductions at Source A but ignored equal
emission increases at neighboring Source B, the state would claim
emission reductions in its RFP plan when in fact no net emission
reductions had occurred.  

	The commenters suggest various remedies for this problem.  One
suggestion is to include all sources within the area that is used. 
Another suggestion is to allow no consideration of emissions outside the
nonattainment area.  Yet another suggestion is to allow consideration of
selected sources so long as other sources do not increase emissions.  

	The EPA is adopting the first of these suggestions:  for the pertinent
area outside the nonattainment area, the RFP assessment must include
emissions (for all years evaluated) for all sources.  The EPA believes
that inclusion of all sources is needed to ensure that the RFP plan
reflects the actual net emissions changes that are occurring in the
relevant area.

	In cases where the state justifies consideration of emissions of
specified precursors from outside the nonattainment area, EPA is
accepting the recommendation of various commenters that the inventories
of these precursors used for RFP purposes shall include mobile source
emissions as well as stationary and area source emissions.  However, in
cases where onroad mobile source emissions are significant and are
therefore included, the state would need to submit additional
information for transportation conformity purposes.  As discussed above,
in accordance with existing transportation conformity regulations (40
CFR Part 93), the SIP's motor vehicle emissions budget(s) must reflect
an emissions inventory of on-road mobile source emissions for the
nonattainment area.  Consequently, in these cases, the state would need
to supplement its RFP inventory with information identifying the
inventory of on-road mobile source emissions within the nonattainment
area for the pertinent precursor(s) for the applicable year or years
(i.e. 2009 and potentially 2012) to be used to establish a motor vehicle
emissions budget for transportation conformity purposes.

	The relevant comments in general did not address the dimensions of
spatial domain of the sources outside the nonattainment area that would
be used in assessing RFP.  EPA agrees with a commenter urging, as a
prerequisite to including sources of the pertinent pollutants outside
the nonattainment area in the assessment, that states must justify the
inclusion of sources outside the nonattainment area.  This justification
would need to demonstrate that these emissions have a substantial impact
on nonattainment concentrations that warrants including these emissions
along with nonattainment area emissions in assessing RFP.  Another
commenter recommends that EPA define the area to be included.  Since the
demonstrations of impact are best done by states, in conjunction with
their attainment planning, EPA intends to allow States to justify the
area to be included, within distance limits discussed above.  

	Comment:  Numerous commenters recommend that EPA allow credit for
reductions of direct PM2.5 emissions outside the nonattainment area. 
Some of these commenters also recommend that EPA allow credit for mobile
source emission reductions outside the nonattainment area.  Other
commenters support EPA’s proposed approach, in which states may
justify considering precursor emissions outside the nonattainment area
but must evaluate direct PM2.5 emissions based solely on emissions
within the nonattainment area.

	Response:  Under Section 107 of the Clean Air Act, EPA is to designate
nonattainment areas that include areas nearby to the violations that
contribute to the violations.  Given the spatial scale of the impacts of
direct PM2.5 emissions, EPA believes that any direct PM2.5 emission
source that demonstrably influences nonattainment area violations (and
thus would contribute to these violations) would also be considered to
be nearby to the violations for designation purposes.  The EPA believes
that it has properly defined the nonattainment areas to include all
nearby contributing sources.  Nevertheless, EPA asks anyone with
evidence that an additional source or source area contributes to
violations in a nonattainment area to submit that information to EPA and
to recommend incorporation of that source or source area into the
nonattainment area.

	The EPA has commented on consideration of mobile source emissions
above.  For direct PM2.5 emissions, EPA believes that the nonattainment
area properly defines the area of consideration, and emissions from
mobile sources outside the nonattainment area, like emissions from
stationary sources outside the nonattainment area, should not be
considered.  For precursors for which consideration of emissions outside
the nonattainment area is justified, the applicable inventories would
include emissions from all sources including mobile sources as well as
stationary sources.

	Comment:   A commenter states that “RFP credits for VOC should be
granted for reductions achieved within the nonattainment area as well as
[within] geographical limits outside of the nonattainment area.”  This
commenter supports consistency with the ozone policy, which allows
credit for NOx reductions within 200 kilometers and VOC reductions
within 100 kilometers of the nonattainment area.  Another commenter
makes similar comments regarding VOC and comments that “[a]s the
science and understanding of PM2.5 formation increases, EPA must revisit
the 200 kilometer parameter and develop a possible proposal for
ammonia.”

	Response:   Conceptually, EPA agrees that in areas where anthropogenic
VOC emissions outside the nonattainment area are shown to be a
significant contributor to nonattainment area PM2.5 concentrations,
presumably by formation of organic particles that influence
nonattainment area concentrations, reduction of these VOC emissions
could help improve air quality in the nonattainment area.  Therefore,
EPA is revising its policy to accommodate consideration of these
potential impacts.  The EPA believes that as the impacts of
anthropogenic VOC on PM2.5 concentrations are better understood, it may
in some cases be appropriate to consider sources outside the
nonattainment area in RFP plans if the impacts from such sources can be
properly quantified and justified.

	Nevertheless, EPA must highlight the technical challenges involved in
assessing the impacts of VOC emission reductions.  First, it is
essential that the impacts of secondary organic particle formation from
anthropogenic VOC emissions be differentiated from the impacts caused by
biogenic VOC emissions and from the impacts of direct organic particle
emissions.  Second, the process of organic particle formation is highly
complex, and currently available atmospheric models typically perform
poorly in assessing the mass of particles thus formed.  Third, the
distance range of impacts, and to be more precise the distance range
over which source impacts are comparable, is especially uncertain. 
While the distance range for organic particle formation is not
necessarily the same as for the influence of VOC on ozone formation, it
may be appropriate to include sources within 100 kilometers of the
nonattainment area for both purposes, as the commenter recommended. 
However, any state wishing to include such sources outside the
nonattainment area must justify the distance range that is appropriate
for the area.

	The EPA is not prepared at this time to establish generally applicable
guidance with respect to how RFP plans should address ammonia in cases
where that precursor is found to be significant.  States that expect to
regulate ammonia emissions should consult their regional office
regarding appropriate approaches for their particular areas.

	Finally, EPA agrees with the commenter that EPA should revisit the
range of issues regarding geographic distances of impacts as more
information and understanding become available.

6.	Pollutants to be Addressed in the RFP Plan

a.	Background

	A number of commenters appeared to be confused by the discussion in the
notice of proposed rulemaking regarding the pollutants to be included in
the RFP assessment.  The EPA proposed that the attainment demonstration
would provide the key parameters of the RFP demonstration, and that the
list of pollutants to be addressed in the RFP demonstration would match
the list of pollutants regulated as part of the attainment
demonstration.  However, the notice of proposed rulemaking also
suggested that the presumptions regarding whether different pollutants
are to be regulated under NSR and RACM (including RACT) would also apply
to RFP.  This led some commenters to recommend different treatment of
specific pollutants.  

	In fact, the presumptions of applicability that EPA is promulgating for
RACM are not germane to RFP.  The pollutant coverage of RFP assessments
is determined on an area-specific basis according to each area’s
attainment demonstration, and EPA need not establish presumptions as to
what pollutants are included in the RFP assessment.  For example, if a
state includes no NOx emission reductions in its attainment plan, then
the RFP plan would not include NOx, irrespective of whether the
(uncontrolled) NOx emissions contribute significantly to the areas PM2.5
concentrations.    

	The contrast between establishment of presumptions for RACM and having
no such presumptions for RFP (or for attainment demonstrations) reflects
differences in regulatory context.  For RACM, at issue is whether the
impact of the pollutant is sufficient to warrant full implementation of
the RACM requirements.  In contrast, for RFP (as for attainment plans),
EPA is establishing an overall progress requirement that may be met by
applying various control levels to various pollutants, so long as
overall emission reductions are adequate.  Indeed, if the state chooses
not to control a particular pollutant in its attainment plan, then the
presumption is that that pollutant would not be reduced in the RFP plan
either.  Furthermore, states have the flexibility to meet the overall
progress with any adequate combination of control of relevant
pollutants, regardless of the significance or insignificance of these
pollutants’ impacts.  For these reasons, EPA is making no presumptions
as to what pollutants will be included in RFP plans.

b.	Final Policy

	As proposed, the pollutants to be addressed in the RFP plan are those
pollutants that are subject to control measures in the attainment plan.

c.	Comments and Responses

	Comment:  A commenter states that “VOC should be considered a
presumptive PM2.5 precursor.”  Another 

commenter recommends presuming that VOC and ammonia are included in the
RFP plan.  

	Response:   The EPA’s approach to RFP does not rely on presumptions
as to whether a pollutant does or does not warrant regulation as a
precursor.  Instead, pollutants are to be included or excluded according
to whether the attainment demonstration includes emission controls for
the pollutant that yield quantitative air quality benefits.  Thus,
irrespective of the presumptions applicable to RACM, the RFP plan would
not include VOC unless the attainment plan reflects air quality
improvements from VOC emission controls.  The challenges of addressing
VOC as part of an RFP plan were discussed earlier in this section. 
Similarly, ammonia would not be included in the RFP plan if the
attainment plan does not regulate ammonia emissions.

7.	Equivalent Air Quality Improvement

a.	Background

	The EPA proposed that states could use alternative combinations of
various types of emission control programs to meet RFP requirements if
the alternative would be expected provide air quality improvements that
are approximately equivalent to those of the benchmark emission
reductions.  Some control programs for some pollutants can be
implemented more quickly than other control programs.  EPA believes that
it is unnecessary to require that all pollutants be reduced at the same
rate or by the same fraction of the ultimate attainment plan reductions.
 The EPA believes instead that the states should have flexibility to
“mix and match” control strategies, so long as they provide a
demonstration that the adopted approach can be expected to yield
approximately the same air quality progress as an approach in which the
state achieves an identical fraction of the attainment strategy for all
pollutants by the RFP milestone date. 

	The notice of proposed rulemaking presented examples of the assessment
of RFP, illustrating EPA’s recommended approach for establishing a
benchmark set of emission reductions and illustrating EPA’s
recommended procedures for whether modified approaches that control some
pollutants earlier than other pollutants may be considered equivalent. 
While not repeated here, the examples remain appropriate for describing
the approach included in the final rule.  (See 70 FR 66012-66013). 

	Most commenters supported EPA’s proposal to allow alternative
combinations of control that can be shown by simple means to be
equivalent.  A set of commenters objected to this approach, given the
uncertainties involved in the equivalency assessment.  Nevertheless, for
this aspect of RFP policy, EPA’s final policy reflects the policy that
it proposed.

b.	Final Policy

	The EPA is adopting an approach that establishes a benchmark level of
controls but allows states the flexibility to adopt any combination of
controls of the various pollutants that can be shown to provide
equivalent benefits using procedures that EPA is recommending (or at the
State’s option, air quality modeling).  The first step is to determine
the ratio of the number of years from the baseline year to the RFP
review year (e.g., the 7 years from 2002 to 2009) divided by the number
of years from the baseline year to the year in which attainment level
emissions are achieved (e.g. the 10 years from 2002 to 2012, for an area
with a 2013 attainment deadline).  The benchmark level of controls is
then determined by multiplying this ratio times the level of control
being achieved for each pollutant.  For example, for an area with an
attainment deadline extended to 2013, the benchmark level of controls
would reflect 7/10 of the emission reductions of each pollutant that is
controlled in the attainment plan.

	The equivalency process involves consideration of the air quality
benefits for the emission reductions in the alternative plan for each
regulated pollutant.  In effect, the air quality benefits for each
pollutant are used as weighting factors, such that pollutants for which
controls yield larger benefits are weighted more heavily in determining
the adequacy of the resulting plan.  For each pollutant, the first step
is to find the ratio of the emission reductions achieved by the RFP
milestone date (e.g. the emission reductions achieved between 2002 and
2009) divided by the emission reductions achieved by the attainment
date.  The second step is to multiply this ratio times the air quality
improvement attributable to full implementation in the attainment year
of the attainment strategy relevant to that pollutant.  The third step
is to add these pollutant-specific results to obtain a total estimated
air quality benefit of the alternative plan.  

	The air quality benefits of the benchmark reductions are easier to
determine.  The first step, inherent to defining the benchmark
reductions, is to determine the ratio of the number of years to the RFP
review divided by the number of years to attainment level emissions (in
the example above, 7/10).  The second step is simply to multiply this
ratio times the quantity of air quality improvement achieved by the
attainment plan.  (Conceptually, the calculations are the same as are
done for the alternative plan, but the mathematics are simpler because
one is applying the same assumed fraction of the attainment plan
emission reductions (e.g. 7/10) for all pollutants, so that there is no
need to subdivide by pollutant.)  For each milestone date, any
alternative that provides estimated air quality benefits by the RFP
milestone date that at a minimum are generally equivalent to the
estimated benefits of the benchmark level of emission reductions will be
considered to satisfy RFP requirements.

c.	Comments and Responses

	Comment:  A set of commenters argues that the equivalency process is
too uncertain, and recommends instead that states be required to achieve
at least a fixed percentage reduction for all pollutants.  The
commenters cite the uncertainties acknowledged by EPA, including
potential nonlinearity (i.e. that a given percentage of an emission
reduction may yield a different percentage of the related air quality
benefit).  The commenters contrast EPA’s willingness to accommodate
these uncertainties, for purposes of giving states flexibility for
alternate RFP plan designs, with EPA’s unwillingness to accommodate
the uncertainties inherent in regulating ammonia emissions.  The
commenters state that “Rather than propose a standardized process for
coherently determining ‘equivalency,’ EPA embraces the possibility
that States will invent multiple and disparate methodologies.”  The
commenters argue that the need for certainty in achieving emission
reductions trumps the benefits of state flexibility, not the other way
around.  The commenters state that if “EPA decides nonetheless to
accept equivalency demonstrations, it should at least . . . require
States to conduct dispersion modeling” to confirm equivalency.  The
commenters further find unlawful the fact that EPA would allow “rough
equivalency” rather than full equivalency to the benchmark approach. 
The commenters would prefer that EPA required a fixed percentage
reduction of the emissions of direct PM2.5 emissions and of each
precursor.  

	Response:   The EPA believes that its proposed approach satisfies the
intent of the RFP requirement, which is to make ongoing, steady progress
toward attainment rather than backloading control strategies.  A
requirement to obtain at least a given percentage of each of the
pollutants that contribute to PM2.5 concentrations would impose an
inflexibility that EPA concludes is unnecessary where not required by
the statute.  The EPA proposed to require that areas achieve emission
reductions that are generally linear, and a plan that provides for rough
equivalency to the benchmark approach would indeed provide generally
linear reductions.  In response to commenters’ requests for a
standardized process for assessing equivalency, EPA believes the process
outlined in the final rule is responsive to this request.  It is not
clear whether the fixed reduction percentage that certain commenters
recommended would be an area-specific percentage (such as EPA uses to
define the benchmark approach) or a universally applicable percentage
(such as 3 percent per year).  If the former, then EPA would repeat the
response above regarding flexibility being consistent with the Act’s
requirements;  if the latter, then responses in III.H.4 regarding a
fixed reduction percentage apply.  The EPA believes that the procedures
it is establishing to assess equivalency are adequate for assessing RFP
and that dispersion modeling need not be required for this purpose.

8.	Other RFP Issues

a.	Multi-State Nonattainment Areas

	As stated in the proposed rulemaking, EPA seeks to ensure that
nonattainment areas that include more than one State meet RFP
requirements as a whole.  Some commenters expressed concern about how
one state’s submittal should address emissions in other states,
including how the state might address questions about the enforceability
of another state’s requirements.

	The issues here resemble the issues for attainment demonstrations.  In
that context as well, EPA seeks plans that reflect active consultation
by the affected states and provide a combination of reductions that are
enforceable by the respective states that collectively provide for
attainment.  The active involvement of regional planning organizations
helps assure a collective design of a plan with specific requirements to
be adopted by specific states.  Likewise for RFP, EPA would expect
states with multi-state nonattainment areas to consult with other
involved states, to formulate a list of the measures that they will
adopt and the measures that the other state(s) will adopt, and then to
adopt their list of measures under the assumption that the other
state(s) will adopt their listed measures.  That is, each state would be
responsible for adopting and thereby providing for enforcement of its
list of measures, and then that state and ultimately EPA (at such time
as the plan is approved) would be responsible for assuring compliance
with the SIP requirements.

	In accordance with this view of RFP, as is the case for attainment
plans, EPA expects states sharing a multi-state nonattainment area to
submit a common assessment of whether RFP will occur.  As a default, if
the assessment only includes emissions within the nonattainment area,
then each state would submit an assessment based on emissions from the
full nonattainment area including portions of the area in other states. 
If the assessment includes precursor emissions from additional area
outside the nonattainment area, then the states should have a common
rationale for the area included, and all affected states would use the
same inventory of the same multi-state area thus defined in assessing
whether RFP will occur.  The EPA would judge such submittals based on 1)
whether the overall projected emission reductions will achieve RFP and
2) whether the submitting state has adopted the necessary enforceable
measures to assure that the reductions projected within its boundaries
will in fact occur.

	As a point of clarification, even if a state justifies consideration of
emissions outside the nonattainment area in its RFP assessment, EPA
intends that these assessments not use emissions from outside the state
or states represented in the nonattainment area.  For single state
nonattainment areas, only emissions within that state would be
considered.  This will help assure accountability for the emission
reductions included in the plan.

b.	Tribal Areas

	The EPA received no comments on its proposed policy regarding RFP for
tribal areas, and EPA is finalizing the proposed policy.  Under its
Tribal Authority Rule (40 CFR 49.4), EPA found that it was not
appropriate to apply SIP schedule requirements to tribes.  For similar
reasons, EPA is not requiring tribes to submit RFP plans.  Generally
this exemption will have limited if any impact on the achievement of RFP
by an area.  Nevertheless, consistent with its general role in
implementing programs for tribes where “necessary and appropriate,”
EPA will work with the affected tribes and states to ensure that
emissions on tribal lands are addressed appropriately.  The EPA intends
to ensure that areas that include both state and tribal lands will
satisfy RFP on a collective basis, similar to the policy applicable to
multi-state nonattainment areas.

9.	Mid-Course Review 

a.	Background

	The EPA proposed requiring mid-course reviews on a case-by-case basis. 
The proposal described a mid-course review as a combination of reviews
aimed at assessing whether a nonattainment area is or is not making
sufficient progress toward attainment of the PM2.5 standards.  The
proposal described the mid-course review as involving “three basic
steps:  (1) Demonstrate whether the appropriate emission limits and
emission reduction programs that were approved as part of the original
attainment demonstration and SIP submittal were adopted and implemented;
(2) analyze available air quality, meteorology, emissions and modeling
data and document relevant findings; and (3) document conclusions
regarding whether progress toward attainment is being made using a
weight of evidence determination.”  (Cf. 70 FR 66010) 

	The EPA views mid-course review requirements as part of a set of
requirements for implementing the Clean Air Act requirements for
reasonable further progress.  For areas that demonstrate attainment by
April 5, 2010, EPA believes that this attainment demonstration also
demonstrates that reasonable further progress is being achieved.  For
areas that demonstrate attainment after April 5, 2010, EPA is requiring
states to submit an RFP plan, due on April 5, 2008, showing that
emissions in 2009 and, in some cases, in 2012, will be sufficiently
reduced to provide generally linear progress toward levels that are
expected to yield attainment.  At issue here is how then to conduct
ongoing tracking of whether the planned progress toward attainment is in
fact occurring.  Subparts 2 (for ozone) and 4 (for PM10) include
explicit requirements for ongoing milestone tracking.  Since Subpart 1
(applicable for PM2.5) allows EPA flexibility in determining how ongoing
progress is to be tracked, EPA may adopt other approaches for achieving
the necessary assurances that ongoing progress toward attainment is
occurring.  

	Milestone reviews can be confounded by changes in inventory methods (a
concern expressed by a commenter particularly with respect to
condensable emissions) and involve lengthy delays while inventories are
compiled before planning can begin.  Other approaches involving only air
quality data reviews also do not provide for timely planning, insofar as
such approaches involve waiting for three years of air quality data
after implementation of controls before planning can begin.  The EPA
believes that a mid-course review provides the most productive approach,
in lieu of establishing milestone tracking or other requirements, to
assure that reasonable further progress in reducing emissions is being
achieved.  For this reason EPA proposed a requirement for mid-course
reviews.

	The EPA proposed a process for establishing and implementing mid-course
review.  After the state submits an attainment plan (due in April 2008),
EPA would evaluate whether a mid-course review is warranted after
considering various factors including factors identified in the
proposal.  The EPA did not propose to conduct further rulemaking on
establishing this requirement, but EPA proposed that “[w]here EPA
finds that a MCR would be required, the approval of the [attainment]
demonstration would be contingent on a commitment from the State to
conduct the MCR.”   The mid-course review would then be due April
2010.  The EPA’s proposal also stated that “EPA would determine
[based on review of the mid-course review] whether additional emissions
reductions are necessary,” so that states would need to complete the
mid-course review “three or more years before the applicable
attainment date to ensure that any additional controls that may be
needed can be adopted [in timely fashion]”  Finally, EPA stated
“[i]f a mid-course review will be required for certain PM2.5
nonattainment areas, separate PM2.5 mid-course review guidance will be
written to address the specific requirements of PM2.5 nonattainment
areas.”

	The EPA received numerous comments objecting to EPA’s proposed
approach.  Several commenters noted the inconsistency between requiring
a mid-course review in April 2010 versus requiring a mid-course review
due 3 or more years before an attainment date of 2012 or earlier. 
Multiple commenters objected to EPA requiring a mid-course review only 2
years after the initial attainment plan is due.  A commenter requested
“nationally applicable guidance on when an MCR would be required and
what it would need to include.”  No commenters supported EPA’s
timeline for mid-course reviews.

	Based on the comments that EPA received, EPA has reevaluated the
process for mid-course reviews.  Upon reevaluation, EPA shares many of
the concerns expressed by commenters about the proposal.  The proposal
indeed presents conflicting dates for submittal.  The EPA agrees that a
deadline just two years after the initial SIP submittal is too soon for
states to conduct meaningful analyses of whether areas are making
progress towards attainment.  This problem would be exacerbated by the
proposed process, in particular the fact that states would not know to
begin work on a mid-course review until after they had submitted their
initial SIP and after EPA had sufficiently reviewed the submittal to
determine the need for a mid-course review.  An early mid-course review
also would defeat one of the purposes of the mid-course review, which is
to take advantage of advances in the science and understanding of the
nature of condensables and other components of PM2.5, to adjust plans to
be better targeted at solving problems. For these reasons, EPA is
significantly revising its approach to mid-course reviews as recommended
by the commenters.  The EPA is establishing a rule which provides more
certainty to the states as to applicability and content of mid-course
review requirements, thereby avoiding the need for future EPA
rulemakings on the subject.  The EPA’s rule clearly does not require
states with early attainment dates to conduct a mid-course review and
would clearly mandate a mid-course review only for areas with later
attainment dates.  The EPA’s final rule clarifies the content of
mid-course reviews and provides for states to make decisions on whether
further controls are needed rather than having EPA make this
determination.  The mid-course review shall include an updated modeled
attainment demonstration as well as a review of the implementation of
measures in the April 2008 SIP and a review of recent air quality data. 
The EPA believes that all of these elements are necessary and should be
sufficient for the state to identify whether additional measures are
needed to achieve attainment by the attainment date in the approved
plan.  The EPA believes that states, not EPA, should make the initial
determination as to whether additional measures are needed, and EPA has
designed its mid-course review requirements to provide for the states to
make this determination.

	The EPA is promulgating a fixed date of April 2011 as a date for
submittal of mid-course reviews for areas with attainment dates in 2014
or 2015.  This fixed date will facilitate joint planning for multiple
areas to apply common assumptions regarding regional transport.  This
date also gives states adequate notice for preparing these reviews and
adequate time after the April 2008 submittal to incorporate new
information and understanding of PM2.5 nonattainment problems to adjust
attainment strategies as appropriate.

	The EPA is not requiring areas demonstrating attainment by 2013 or
before to conduct a mid-course review.  Such areas plan to have
attainment level emissions by 2012, and EPA believes that an April 2011
mid-course review would not provide a timely reassessment of such
areas’ attainment plans.  Instead, EPA is clarifying that mid-course
reviews are only required for areas that demonstrate a need for an
attainment date extension at least to April 2014.  

b.	Final Rule

	For each area with an approved attainment date in 2014 or 2015, EPA is
requiring the State to submit a mid-course review by April 2011.  The
mid-course review shall include an updated attainment demonstration as
well as a review of the implementation status of measures included in
the April 2008 submittal and a review of recent air quality data.  The
state shall determine whether additional measures are needed for timely
attainment, just as the state is responsible for determining whether
additional measures are needed in the April 2008 attainment
demonstration, subject to formal EPA SIP review.  The EPA is not
requiring RFP milestone reviews, and EPA is requiring mid-course reviews
for areas with sufficiently extended attainment dates in lieu of any
other form of tracking reasonable progress.

c.	Comments and Responses

	Comment:  A number of commenters objected to EPA's proposed timeframe
that would have areas submit a mid-course review only two years after
the initial SIP is due.  They recommended, instead, that areas with
attainment dates two years or more beyond the first five-year period
submit mid-course reviews three years after the SIPs are due (April
2011) and every three years thereafter, if necessary.  Their reason for
this suggestion is that the timing of mid-course review requirements
needs to be clearer and should allow adequate time between plans and
mid-course reviews if they are to serve as meaningful reviews.  

	Several commenters also noted an inconsistency in the timing of
mid-course review requirements under EPA’s proposal.  The EPA proposed
that mid-course review submittals would be due 5 years after the initial
designation, which for all the original designations means 5 years after
April 2005, i.e. April 2010.  However, EPA also proposed that mid-course
reviews would be due 3 years before the attainment date, which for areas
with an April 2012 attainment date means April 2009.  The commenters
considered April 2009 for a mid-course review submittal to be too soon
after the initial SIP submittal in April 2008, arguing that EPA would
not have had time to review the 2008 SIP submittal, and the States would
not have time to prepare a mid-course review by 2009.  Some of these
commenters expressed a view that EPA should not require mid-course
reviews earlier than three years after the SIP submittal date.  

	Response:  The EPA agrees with these comments.  The EPA is remedying
the inconsistency in submittal dates by establishing the single
submittal due date of April 2011 that was recommended by the commenters.
 As requested by commenters, EPA is also clarifying the applicability of
the mid-course review requirement.  The requirement shall apply to areas
with attainment dates of 2014 or 2015; mid-course reviews shall not be
required for areas that are expected to attain the standards by 2013.  

	Comment:  A commenter supports mid-course reviews as a means of
assuring that areas with longer-term compliance dates are on track to
attain the NAAQS as expeditiously as practicable.

	Response:  The EPA agrees that mid-course reviews can be a critical
step in assuring expeditious attainment for areas with extended
attainment dates.  Indeed, EPA is relying on mid-course reviews rather
than milestone reviews or other forms of RFP tracking to serve this
purpose.

	Comment: A commenter recommended eliminating mid-course review
requirements for any area with less than seven years between SIP
submittal and attainment.  The commenter urged that EPA carefully
reconsider its overall time lines for PM2.5 while considering the
feasibility and practical usefulness of the steps required of States and
emission sources.

	Response:  The EPA agrees that the proposed timeline potentially
required mid-course reviews in areas where such reviews would not be
warranted, and the timeline did not provide the clarity as to the
applicability of the requirement that states need to fulfill their
planning responsibilities.  In response, EPA is not requiring mid-course
reviews for areas demonstrating attainment prior to 2014.  For those
areas that cannot demonstrate that attainment will occur prior to 2014,
EPA has streamlined the mid-course review process so that the state
bears responsibility for making the initial determination as to whether
additional measures are needed to achieve timely attainment, rather than
requiring additional steps of EPA rulemaking and initial findings by EPA
as to the level of controls needed in the state’s SIP.  With the
revised timetable, states can be assured of a meaningful mid-course
review effort that focuses on the areas that particularly warrant such a
review and for which time is available for a productive assessment of
the need for additional measures.  

	Comment: One commenter stated that the proposal that allows the Agency
to determine whether or not a State needs to submit a mid-course review
with their attainment demonstration on a case-by-case basis lacks
sufficient information.  Since these attainment demonstrations must meet
rigorous criteria, and require substantial work by the States, the
commenter is concerned that the proposal neglects to outline the
criteria EPA will use to make the case-by-case mid-course review
determinations. The commenter asks that EPA provide the States with
nationally applicable guidance on when an MCR would be required and what
it would need to include.	

	Response:  The EPA agrees with this comment.  In particular, EPA agrees
that establishing clear criteria for applicability and content of a
mid-course review requirement will provide states the opportunity to
plan for these reviews and conduct appropriate reviews in a timely
fashion.  Therefore, this final rule is establishing specific criteria
for the applicability of the mid-course review requirement, namely that
a mid-course review shall be conducted for any area that cannot
demonstrate attainment before 2014.  This final rule is also identifying
the necessary elements of this mid-course review, i.e. a review of the
implementation of measures in the 2008 SIP, and review of recent air
quality data, and an updated modeled attainment demonstration.  

H.	Contingency Measures

a.	Background.

	Under subpart 1 of the CAA, all PM2.5 nonattainment areas must include
in their SIPs contingency measures consistent with section 172(c)(9). 
Contingency measures are additional control measures to be implemented
in the event that an area fails to meet RFP or fails to attain the
standards by its attainment date.  These contingency measures must be
fully adopted rules or control measures that are ready to be implemented
quickly upon failure to meet RFP or failure of the area to meet the
standard by its attainment date.  The preamble to the proposal stated
that the SIP should contain trigger mechanisms for the contingency
measures, specify a schedule for implementation, and indicate that the
measures will be implemented without significant further action by the
State or by EPA. The contingency measures should consist of other
control measures for the area that are not included in the control
strategy for the SIP.

	The April 16, 1992 General Preamble provided the following guidance: 
(States must show that their contingency measures can be implemented
without further action on their part and with no additional rulemaking
actions such as public hearings or legislative review.  In general, EPA
will expect all actions needed to affect full implementation of the
measures to occur within 60 days after EPA notifies the State of its
failure.”  (57 FR at 13512.)  This could include Federal measures and
local measures already scheduled for implementation, as explained below.

	The EPA has approved numerous SIPs under this interpretation ( i.e.,
that use as contingency measures one or more Federal or local measures
that are in place and provide reductions that are in excess of the
reductions required by the attainment demonstration or RFP plan.  (62 FR
15844, April 3, 1997; 62 FR 66279, December 18, 1997; 66 FR 30811, June
8, 2001; 66 FR 586 and 66 FR 634, January 3, 2001.)  The key is that the
statute requires that contingency measures provide for additional
emission reductions that are not relied on for RFP or attainment and
that are not included in the demonstration.  The purpose is to provide a
cushion while the plan is being revised to meet the missed milestone. 
In other words, contingency measures are intended to achieve reductions
over and beyond those relied on in the attainment and RFP
demonstrations.  Nothing in the statute precludes a State from
implementing such measures before they are triggered.  In fact, a recent
court ruling upheld contingency measures that were previously required
and implemented where they were in excess of the attainment
demonstration and RFP SIP.  See LEAN v. EPA, 382 F.3d 575, 5th Circuit.,
2004.

	One basis EPA recommends for determining the level of reductions
associated with contingency measures is the amount of actual PM2.5
emissions reductions required by the control strategy for the SIP to
attain the standards. The contingency measures are to be implemented in
the event that the area does not meet RFP, or attain the standards by
the attainment date, and should represent a portion of the actual
emissions reductions necessary to bring about attainment in area. 
Therefore, the emissions reductions anticipated by the contingency
measures should be equal to approximately 1 year’s worth of emissions
reductions necessary to achieve RFP for the area. 

	As stated previously, EPA believes that contingency measures should
consist of other available control measures beyond those required to
attain the standards, and may go beyond those measures considered to be
RACM for the area.  It is important, however, that States make decisions
concerning contingency measures in conjunction with their determination
of RACM for the area, and that all available measures needed in order to
demonstrate attainment of the standards must be considered first; all
remaining measures should then be considered as candidates for
contingency measures.  It is important not to allow contingency measures
to counteract the development of an adequate control strategy
demonstration.

	The preamble to the proposal stated that contingency measures must be
implemented without “significant further action” after EPA
determines that the area has either failed to meet RFP, or has failed to
attain the standard by its attainment date.  The purpose of the
contingency measure provision is to ensure that corrective measures are
put in place automatically at the time that EPA makes its determination
that an area has either failed to meet RFP or failed to meet the
standard by its attainment date.  The EPA is required to determine
within 90 days after receiving a State’s RFP demonstration, and within
6 months after the attainment date for an area, whether these
requirements have been met.  The consequences for states which fail to
attain or to meet RFP are described in section 179 of the CAA. 

2.	Final Rule.

	The final rule includes regulatory text for contingency measures and
maintains the overall policy approach as described in the preamble to
the proposal.  The key requirements associated with contingency measures
are:

- Contingency measures must be fully adopted rules or control measures
that are ready to be implemented quickly upon failure to meet RFP or
failure of the area to meet the standard by its attainment date.  

- The SIP should contain trigger mechanisms for the contingency
measures, specify a schedule for implementation, and indicate that the
measures will be implemented without further action by the State or by
EPA.

- The contingency measures should consist of other control measures for
the area that are not included in the control strategy for the SIP.

- The measures should provide for emission reductions equivalent to
about 1 year of reductions needed for RFP, based on the overall level of
reductions needed to demonstrate attainment divided by the number of
years from the 2002 base year to the attainment year.  Contingency
measures are those measures that would not be included in the attainment
strategy for various reasons; for example, they may not be as
economically feasible as other measures that are considered to be RACM,
or it may not be possible to implement the measures soon enough to
advance the attainment date (e.g. federal mobile source measures based
on the incremental turnover of the motor vehicle fleet each year).  

3.	Comments and Responses

	Comment:  Several comments were received concerning the requirement for
contingency measures under section 172(c)(9).  The proposal indicated
that contingency measures adopted as part of the State plan are to be
equal to approximately 1 year’s worth of emissions reductions
necessary to achieve RFP, as determined by the attainment demonstration
for the area.  One commenter indicates that this amount of reductions
for contingency measures may be excessive in some cases.  The commenter
stated that States should be allowed to demonstrate appropriate amount
of reductions for contingency measures in each area based on the degree
of the PM2.5 nonattainment area problem and the progression of emission
reductions planned for the area as a part of the SIP.

	Response:   The EPA agrees that the CAA does not include the specific
level of  emission reductions that must be adopted to meet the
contingency measures requirement under section 172(c)(9).  One possible
interpretation of the CAA would assume that contingency measures should
be in place in the event that all of the State’s measures fail to
produce their expected emission reductions.  Under this scenario, the
State theoretically would be required to adopt sufficient contingency
measures to make up for the entire short fall.  In other words, the
State would have to adopt “double” the measures required to satisfy
the applicable emissions reduction requirements.  

	The EPA believes that this scenario would be highly unlikely and that
this interpretation would be an unreasonable requirement.  The adoption
of double the measures needed for attainment would be difficult for
States.  Therefore, the EPA believes that it is reasonable that
contingency measures should, at a minimum, ensure that an appropriate
level of emissions reduction progress continues to be made if attainment
or RFP is not achieved, or if an area fails to attain the standard by
its statutory attainment date and additional planning is needed by the
State.  The EPA believes that the contingency measures adopted by the
State for the affected area should represent a portion of the actual
emissions reductions necessary to bring about attainment in the area. 
Therefore, EPA believes that it is reasonable to require states to adopt
contingency measures equal to approximately 1 year’s worth of
emissions reductions necessary to achieve RFP for the area.

	Comment:  One commenter claimed that EPA incorrectly quoted the CAA as
requiring SIPs to provide for implementation of contingency measures
upon an attainment or RFP failure, without “significant” further
action by the State or EPA.   The commenter stated that section
172(c)(9) does not contain the word “significant.”  The CAA requires
that contingency measures take effect “without further action” by
the State or EPA.  

	Response:  The EPA agrees with the commenter that the general
requirements for attainment plans specified under section 172(c)(9)
State that each plan must contain additional measures that will take
effect without ‘further action’ by the State or EPA if an area
either fails to make RFP or fails to attain the standard by the
applicable attainment date.  Section 51.1012 of the final rule describes
the contingency measures requirement and does not include the word
“significant.” However, as a matter of practicality states need to
take minimal steps to make contingency measures effective and alert the
affected public that the measures are in force. Thus, EPA has indicated
based on conclusions first made in the 1992 General Preamble that states
should complete all of these administrative steps within 60 days and
that all regulatory steps be completed before SIP submission. 

	Comment:  The commenter further states that EPA is wrong in asserting
that contingency measures can include Federal measures and local
measures already scheduled for implementation, or previously implemented
measures that provide ‘excess’ reductions.  The CAA requires
contingency measures to consist of controls ‘to be undertaken if’
the area fails to meet attainment or RFP.  The commenter states that
this language clearly states that such measures are to be new measures
that will be undertaken upon the triggering event specifically to
address RFP or failure to attain, not measures already in place, or
measures required for other reasons.  

	Further, the commenter claims that EPA can not rationally refer to any
reductions prior to an attainment or RFP failure as ‘excess’ when
total reductions in the area in fact prove insufficient to meet
attainment RFP.  The commenter states that EPA cites a 5th Circuit case
as support, but the commenter respectfully submits that the case was
incorrectly decided on this issue for the aforementioned reasons.

	Response:  In response to comments claiming that EPA is wrong in
asserting that contingency measures can include Federal measures and
local measures already scheduled for implementation, or previously
implemented measures that provide ‘excess’ reductions, as stated
previously, the EPA has approved numerous SIPs under this
interpretation.  The statute requires that contingency measures provide
for additional emission reductions that are not relied on for RFP or
attainment and that are included in the attainment demonstration for the
area.  These measures are intended  to provide a “cushion” in terms
of emissions reductions for the area while the State is revising the SIP
for the area due to the failure to show RFP or attain.  In other words,
contingency measures are intended to achieve reductions over and beyond
those relied on in the attainment and RFP demonstrations.  Nothing in
the statute precludes a State from implementing such measures before
they are triggered. 

	As noted above, EPA’s General Preamble interpreted the control
measure requirements of sections 172(c)(9) and 182(c)(9) to allow
nonattainment areas to implement their contingency measures early.  57
FR 13498, 13511 (April 16, 1992).   The EPA has applied this
interpretation in rulemakings. See, for example, 67 FR 6,590, 6,591-92
(September 26, 2002).    See also rulemakings cited in the Background
section, above.  As set forth above, the Fifth Circuit has upheld
EPA’s interpretation.  Louisiana Environmental Action Network v. EPA,
382 F.3d 575 (Fifth Cir. 2004). (“LEAN”)  Commenters have not
provided a basis for concluding  that the Fifth Circuit in the LEAN case
wrongly interpreted the CAA.

	Commenters contend that the language in the CAA  regarding contingency
measure controls “to be undertaken” requires measures not already in
place or required for other reasons.  The Fifth Circuit disagreed,
finding that the terms in section 172(c)(9) — “to be undertaken”
and “to take effect” –  were ambiguous, and finding persuasive
EPA’s interpretation that this language allows measures already in
place or otherwise required.  The Court held:

“Here, the EPA’s allowance of early reductions to be used as
contingency measures comports with a primary purpose of the CAA  – the
aim of ensuring that nonattainment	areas reach NAAQS compliance in an
efficient manner – and necessary requirements of the CAA.”   382
F.3d at 583.

The Court further found that “By utilizing contingency measures early,
the contingency measures ensured that ‘an appropriate level of
emissions reduction progress’ would be implemented while the State
‘adopt[ed] newly required measures resulting from the bump-up to a
higher classification.” [citing the General Preamble].  Id.

	In addition, the Court agreed with EPA that “early reductions are
necessary in order to create an incentive for nonattainment areas to
implement ‘all reasonably available control measures as expeditiously
as practicable’” in accordance with section 172(c)(1) of the CAA. 
Thus the Court concluded  that it would be “illogical to penalize
nonattainment areas that are taking extra steps, such as implementing
contingency measures prior to a deadline, to comport with the CAA’s
mandate that such states achieve NAAQS compliance as ‘expeditiously as
practicable.’” Id. at 583-584.

The Fifth Circuit also endorsed the concept of “excess” reductions,
noting that the reductions credits at issue in that case, “although
already implemented, are in effect set aside, ‘to be applied in the
event that attainment is [not] achieved’ and such reduction credits
‘are not available for any other use.’ [citations omitted].  The
setting aside of a continuing, surplus emissions reduction fits neatly
within the CAA’s requirement that a necessary element of a contingency
measure is that it must ‘take effect without further action by the
State or [EPA]’.”   The Court concluded that “the early activation
of continuing contingency measures is consistent with the purpose and
requirements of the CAA statute.”  Id. at 584.

	Thus, EPA’s approval of early implemented contingency measures is
consistent with the CAA, as well as with EPA guidance.    For example,
EPA has consistently taken the position that ozone nonattainment areas
classified moderate and above must include sufficient contingency
measures so that “upon implementation of such measures, additional
emissions reductions of up to 3 percent of the emissions in the adjusted
base year inventory (or such lesser percentage that will cure the
identified failure) would be achieved in the year following the year in
which the failure has been identified.” 57 FR at 13,511 (EPA’s
General Preamble).  Thus the contingency measures are supposed to ensure
that progress towards attainment will occur while the relevant State
adopts whatever additional controls may be necessary to correct a
shortfall in emissions reductions. Id.  The EPA has historically allowed
early reductions – that is, reductions achieved before the contingency
measure is “triggered” – to be used as contingency measures.  See
also August 13, 1993 Memorandum from G.T. Helms: Early Implementation of
Contingency Measures for Ozone and Carbon Monoxide (CO) Nonattainment
Areas).  

The commenter’s argument that emission reductions cannot be valid
contingency measures if  they are otherwise required  is also misplaced.
 A State must have the legal authority to require whatever reductions it
may require as a contingency measure.  As EPA has previously stated,
“all contingency measures must be fully adopted rules or measures.” 
62 FR 15,844, 15,846 (April 3, 1997).  The fact that the State or
Federal government  has already exercised that authority is irrelevant
because, as noted above, contingency measures must “take effect
without further action by the State or [EPA].”  Section 172(c)(9). 
Thus, by definition, the State necessarily will have already exercised
its legal authority to require reductions as a contingency measure
before the measure is triggered.   It does not matter whether or not a
specific contingency measure is already required by law, as long as the
emissions reductions that will result from that contingency measure have
not been accounted for in the attainment and reasonable further progress
demonstrations.   If the reductions from the contingency measure are not
available for any other use, then they are surplus that is set aside in
the event reasonable further progress or attainment is not achieved.  

	A key element of a valid contingency measure reduction is that the
State may not use the reduction in its attainment or reasonable further
progress demonstrations if it is already using the reduction as a
contingency measure.  Those demonstrations must account for the actual
emissions reductions that will make reasonable further progress towards,
and achieve attainment of the NAAQS in the absence of contingency
measures.  

I.	Transportation Conformity

	Transportation conformity is required under CAA section 176(c) (42
U.S.C. 7506(c)) to ensure that Federally supported highway and transit
project activities are consistent with (“conform to”) the purpose of
the SIP.  Conformity currently applies to areas that are designated
nonattainment, and those redesignated to attainment after 1990
(“maintenance areas” with plans developed under CAA section 175A)
for the following transportation-related criteria pollutants:  ozone,
particulate matter (PM2.5 and PM10), carbon monoxide (CO), and nitrogen
dioxide (NO2).  Conformity to the purpose of the SIP means that
transportation activities will not cause new air quality violations,
worsen existing violations, or delay timely attainment of the relevant
NAAQS (or “standards”).

	The final PM2.5 implementation rule does not contain any revisions to
the transportation conformity regulation.  The EPA addressed the
transportation conformity requirements that apply in PM2.5 nonattainment
and maintenance areas in three separate rulemakings as described below.

	First, on July 1, 2004, EPA published a final rule (69 FR 40004) that
addressed the majority of requirements that apply in PM2.5 areas
including: 

regional conformity tests to be used in conformity determinations both
before and after SIPs are submitted and motor vehicle emissions budgets
are found adequate or are approved;

consideration of direct PM2.5 emissions in regional emissions analyses;

consideration of re-entrained road dust in PM2.5 regional emissions
analyses;

consideration of transportation construction-related fugitive dust in
PM2.5 regional emissions analyses; and

compliance with PM2.5 SIP control measures.

	Then on May 6, 2005, EPA promulgated a final rule (70 FR 24280) that
specified the transportation-related PM2.5 precursors and when they
apply in transportation conformity determinations in PM2.5 nonattainment
and maintenance areas.

	Finally, on March 10, 2006, EPA promulgated a final rule (71 FR 12468)
that establishes the criteria for determining which transportation
projects must be analyzed for local particle emissions impacts in PM2.5
and PM10 nonattainment and maintenance areas.  If required, an analysis
of local particle emissions impacts is done as part of a transportation
project’s conformity determination.

Transportation conformity for the PM2.5 standards  began applying in
PM2.5 nonattainment areas on April 5, 2006,  one year after the
effective date of EPA’s PM2.5 nonattainment designations (i.e., April
5, 2005).  CAA section 176(c)(6) and 40 CFR 93.102(d) provide a one-year
grace period before conformity applies in areas newly designated
nonattainment for a new standard.  PM2.5 SIP submissions such as RFP and
attainment demonstrations would identify motor vehicle emissions budgets
(“budgets”) for direct PM2.5 or PM2.5 precursors, as described
below.  These budgets would be used for satisfying transportation
conformity requirements, once the budgets are found adequate or the SIP
containing the budgets is approved by EPA.  For example, state and local
agencies would consider during the development of the PM2.5 SIP whether
reductions of on-road mobile source SO2 emissions are a significant
contributor to an area’s PM2.5 air quality problem, and if so,
establish a SO2 motor vehicle emissions budget for transportation
conformity purposes.

The EPA has previously addressed its intentions regarding when budgets
must be established in PM2.5 SIPs for transportation conformity
purposes.  RFP plans, attainment demonstrations, and maintenance plans
must include a budget for direct PM2.5 emissions, except for certain
cases as described below.  All PM2.5 SIP budgets would include directly
emitted PM2.5 motor vehicle emissions from tailpipe, brake wear, and
tire wear.  States should also consider whether re-entrained road dust
or highway and transit construction dust are significant contributors
and should be included in the PM2.5 budget.  For further information,
see 40 CFR 93.102(b) and 93.122(f) of the transportation conformity
regulation, as well as Sections VIII-X of the July 1, 2004 conformity
rule preamble at 69 FR 40031-40036.

Under certain circumstances, directly emitted PM2.5 from on-road mobile
sources may be found an insignificant contributor to the air quality
problem and NAAQS.  Section 93.109(k) of the conformity rule states that
“[s]uch a finding would be based on a number of factors, including the
percentage of motor vehicle emissions in the context of the total SIP
inventory, the current state of air quality as determined by monitoring
data for that NAAQS, the absence of SIP motor vehicle control measures,
and historical trends and future projections of the growth of motor
vehicle emissions.”  The EPA discussed its intentions for applying the
insignificance provision in the July 2004 final rule (69 FR
40061-40063).  

In the May 6, 2005 final rule, EPA provided details regarding when
states must establish SIP budgets for any PM2.5 precursor (i.e., NOx,
VOCs, SO2 and ammonia). If through the SIP process a state concludes
that on-road mobile source emissions of one or more precursors are
significant (i.e. need to be addressed in order to attain the PM2.5
standards as expeditiously as practicable), then EPA expects that the
state will include a budget in the SIP for each of the relevant
precursors.  (70 FR 24287)  The EPA also noted in the May 2005
conformity rule that, if inventory and modeling analyses demonstrating
RFP, attainment or maintenance indicate a level of emissions of a
precursor that must be maintained to demonstrate compliance with the
applicable requirement, then that level of emissions should be clearly
identified in the SIP as a budget for transportation conformity
purposes, even if the SIP does not establish particular controls for the
given precursor.  If the state fails to identify such a level of
emissions as a budget, EPA will find the submitted SIP budgets
inadequate because the SIP fails to clearly identify the motor vehicle
emissions budget as required by the conformity rule (40 CFR
93.118(e)(4)(iii)).  (70 FR 24287)  In determining whether the on-road
mobile source emissions of a PM2.5 precursor are significant, state and
local agencies would use the criteria for insignificance findings
provided in 40 CFR 93.109(k) of the transportation conformity
regulation.  A further discussion of the criteria to be considered in
establishing PM2.5 precursor budgets is contained in the May 2005 final
transportation conformity rule (70 FR 24282-24288).  If state and local
agencies conclude that on-road sources of a precursor are not a
significant contributor to the area’s PM2.5 air quality problem, as
described above, motor vehicle emissions budgets would not be
established even though emissions may be addressed in the area’s RFP
plan, attainment demonstration and/or maintenance plan.  

J.	General Conformity

a.	Background 

	The General Conformity regulations promulgated in 1993 establish an
implementation process where Federal agencies are responsible for making
their own determination of conformity with State implementation plans
(SIPs), and EPA plays an advisory role.  Recognizing that it was
impracticable to evaluate all Federal actions for conformity, EPA
created a number of exemptions in those regulations for actions with
insignificant or not reasonably foreseeable emission increases,
including exemptions for Federal actions with emissions below specified
de minimis levels.  When a Federal agency must demonstrate conformity
for an action, the regulations provide several methods for making that
demonstration.  With the designations of PM2.5 nonattainment areas on
April 5, 2005, requirements for demonstrating conformity become
effective in those areas on April 5, 2006.    

	On July 17, 2006 EPA issued a final rule (71 FR 40420) to amend the
General Conformity Regulations to establish de minimis levels for PM2.5
for the General Conformity program.  The final rule established 100
tons/year of direct PM2.5 emissions and its precursors as the de minimis
level where the General Conformity regulations would apply in PM2.5
nonattainment areas.  In the process of finalizing the de minimis level
for PM2.5 three comments were received.  One commenter was concerned
about emissions from burning by Federal agencies.  Another commenter
proposed that the de minimis level for emissions of direct PM2.5 should
be set significantly lower than 100 tons – in the range of 25-50 tons
per year (TPY) in areas that are likely to attain the PM2.5 national
ambient air quality standard within 5 years, and a level of 10-25 TPY in
areas that are likely to take more than 5 years to achieve the national
ambient air quality standard.  A third commenter supported the proposed
de minimis level.  

	The final rule revises the tables in sub-paragraphs (b)(1) and (b)(2)
of the General Conformity Regulations by adding a de minimis emission
level for PM2.5 and its precursors. This action maintained our past
policy of consistency between the conformity de minimis emission levels
and the size of a major stationary source under the New Source Review
program (70 FR 65984).  These levels are also consistent with the levels
promulgated for Reasonably Available Control Technology applicability
levels for volatile organic compound and nitrogen oxide emissions in
subpart 1 areas under the 8-hour ozone implementation strategy (68 FR
32843).  Since EPA is not finalizing any classifications for the PM2.5
nonattainment areas, we did not establish differing PM2.5 de minimis
emission levels for higher classified nonattainment areas.  

	 

b.	Comments and Responses

	Comment:   One commenter requests that EPA communicate to all Federal
agencies the value of the agencies advising the States as soon as
possible of any planned future projects in nonattainment areas that may
be above the General Conformity de minimis values or that will have to
be evaluated to show that they are below de minimis. This is for
projects that are very likely to proceed. The aim is to consider these
future emissions in any growth projections during SIP development since
such growth may not be anticipated well by the available growth model
(E-GAS). States can communicate with existing Federal facilities now
concerning this issue.

	Response:  The EPA sees the value in Federal agencies working with
States to anticipate growth in emissions and include those anticipated
emissions in the applicable SIP.  The EPA is in the process of proposing
regulatory amendments to the General Conformity regulations that provide
a framework for Federal facilities to work with States to account for
facility-wide emissions in SIPs and to include Federal facility
emissions in future SIPs.  The EPA anticipates that these rule
amendments should be proposed before the end of summer 2006.

	Comment:  Some commenters stated that the de minimis level for PM2.5
for conformity applicability should be less than 100 tons per year. A
level of 50 tons per year was suggested for direct PM2.5 emissions. 

	Response:  Similar comments were received when the PM2.5 de minimis
level was proposed on April 5, 2006.  The response to those comments can
be found in the preamble to the final rule setting the de minimis level
for PM2.5 at 71 FR 40420.

	Comment: Are the precursors for general conformity consistent with this
rulemaking or with the transportation conformity rulemaking?  

	Response:  The precursors for general conformity are generally
consistent both with this rule and the transportation conformity rule. 
The only difference between the transportation rule and this rule is
that SO2 is not considered a precursor for transportation conformity
determinations that occur prior to a PM2.5 SIP unless EPA or the State
air agency finds on-road mobile source emissions significant.  For more
information, see the May 6, 2005 transportation conformity rule on PM2.5
precursors at 70 FR 24283.  Since general conformity includes analysis
of stationary sources the general conformity rule requires SO2 as a
precursor both before and after a PM2.5 SIP is submitted.

	Comment:  When will rulemaking containing the de minimis levels for
PM2.5 and for the precursors be issued? There is some confusion, since
the proposed rule says that states should assume 100 tpy for all PM2.5
pollutants, as this would make it consistent with the levels for NOx and
VOC for the subpart 1 areas under 8-hour ozone. However, since New
Jersey’s classification is moderate under the 8-hour ozone standard
and we are in an Ozone Transport Region, the de minimis level for VOC is
50 tons per year.

	Response:  On July 17, 2006 EPA issued a final rule (71 FR 40420) to
amend the General Conformity Regulations to establish de minimis levels
for PM2.5 for the General Conformity program.  The final rule
established 100 tons/year of direct PM2.5 emissions and its precursors
as the de minimis level where the General Conformity regulations would
apply in PM2.5 nonattainment areas.  Since EPA is not finalizing any
classifications for the PM2.5 nonattainment areas, we did not establish
differing PM2.5 de minimis emission levels for based on a classification
scheme.  

	Comment:  If a Statement of Conformity has been issued on a project and
if the project has not been completed to date, are they required to
address PM2.5 prior to completion of the project or will they be
grandfathered in?  

	Response:  If a Federal action has completed a conformity determination
and the action has started (regardless of whether the project is
complete or not) then no new determination is needed.  If the conformity
determination was completed, but the action did not start in 5 years a
new determination is needed under the general conformity rules.  

	Comment:  What guidance should states use to establish budgets for
large facilities or military bases?

	Response:  The EPA has not issued any guidance for States and Federal
facilities to establish facility-wide budgets in the applicable SIP. 
There is nothing in the General Conformity regulations preventing this
approach which would allow Federal actions that do not increase total
facility emissions over the budget in the SIP from determining the
action conforms on the basis of its compliance with the budget limit. 
The EPA sees this practice as a positive step to encourage States and
Federal agencies to work together to account for emissions in a SIP so
they conform with the purposes and goals of the SIP.  The EPA intends to
address the approach and provide guidance in planned revisions to the
General Conformity regulations which are expected to be proposed in
2006.

K.	Emission Inventory Requirements

a.	Background.

Emission inventories are critical for the efforts of State, local,
tribal and federal agencies to attain and maintain the NAAQS that EPA
has established for criteria pollutants including PM2.5.  Pursuant to
its authority under section 110 of Title I of the CAA, EPA has long
required States to submit emission inventories containing information
regarding the emissions of criteria pollutants and their precursors. 
The EPA codified these requirements in 40 CFR part 51, subpart Q in 1979
and amended them in 1987.

The 1990 CAAA revised many of the provisions of the CAA related to
attainment of the NAAQS and the protection of visibility in mandatory
Class I Federal areas (certain national parks and wilderness areas). 
These revisions established new emission inventory requirements
applicable to certain areas that were designated nonattainment for
certain pollutants.  In the case of particulate matter, the emission
inventory provisions are in the general provisions under Section
172(c)(3).

In June 2002, EPA promulgated the Consolidated Emissions Reporting Rule
(CERR)(67 FR 39602; June 10, 2002), 40 CFR part 51 subpart A.  The CERR
consolidated the various emissions reporting requirements that already
existed into one place in the CFR, established new reporting
requirements for PM2.5 and ammonia, and established new requirements for
the statewide reporting of area source and mobile source emissions.

The CERR established two types of required emission inventories:  annual
inventories, and 3-year cycle inventories.  The annual inventory
requirement is limited to reporting statewide emissions data from the
larger point sources.  For the 3-year cycle inventory, States need to
report data from all of their point sources plus all of the area and
mobile sources on a statewide basis.  A special case existed for the
first 3-year cycle inventory for the year 2002 which was due on June 1,
2004.  

The EPA issued guidance suggesting that 2002 be used as the Base Year
for 8-hour ozone, PM2.5 and regional haze planning efforts (November 18,
2002 EPA memorandum (2002 Base Year Emission Inventory SIP Planning: 
8-hr Ozone, PM2.5 and Regional Haze Programs”   HYPERLINK
"http://www.epa.gov/ttn/chief/eidocs/2002baseinven_102502new.pdf" 
http://www.epa.gov/ttn/chief/eidocs/2002baseinven_102502new.pdf ).

  SEQ CHAPTER \h \r 1 States should estimate mobile source emissions by
using the latest emissions models and planning assumptions available at
the time the SIP is developed.  Information and guidance on the latest
emissions models is available at
http://www.epa.gov/otaq/stateresources/transconf/policy.htm#models and
at http://  HYPERLINK "http://www.epa.gov/otaq/models" 
www.epa.gov/otaq/models .htm.

By merging the information on point sources, area sources and mobile
sources into a comprehensive emission inventory, State, local and tribal
agencies may do the following:

set a baseline for SIP development.  

measure their progress in reducing emissions.  

have a tool to support future trading programs.

answer the public’s request for information.

	The EPA uses the data submitted by the States to develop the National
Emission Inventory (NEI).  The NEI is used by EPA to show national
emission trends, as modeling input for analysis of potential
regulations, and other purposes.

Most importantly, States need these inventories to help in the
development of control strategies and demonstrations to attain the
annual and 24-hour PM2.5 NAAQS.  In April 1999, EPA published the
“Emissions Inventory Guidance for Implementation of Ozone and
Particulate Matter National Ambient Air Quality Standards (NAAQS) and
Regional Haze Regulations,” EPA-454/R-99-006.  The EPA updated this
guidance in November 2005.  The current version of this guidance is
available at:   HYPERLINK
"http://www.epa.gov/ttn/chief/eidocs/eiguid/index.html" 
http://www.epa.gov/ttn/chief/eidocs/eiguid/index.html . The EPA
developed this guidance document to complement the CERR and to provide
specific guidance to State and local agencies and Tribes on how to
develop emissions inventories for 8-hour ozone, PM2.5, and regional haze
SIPs.  While the CERR sets forth requirements for data elements, EPA
guidance complements these requirements and indicates how the data
should be prepared for SIP submissions.  

The SIP inventory must be approved by EPA as a SIP element and is
subject to public hearing requirements, whereas the CERR is not. 
Because of the regulatory significance of the SIP inventory, EPA will
need more documentation on how the SIP inventory was developed by the
State as opposed to the documentation required for the CERR inventory. 
In addition, the geographic area encompassed by some aspects of the SIP
submission inventory will be different from the statewide area covered
by the CERR emissions inventory.    SEQ CHAPTER \h \r 1  The CERR
inventory was due June 1, 2004, while the SIP inventory due date is
later.  Because of this time lapse, the State may choose to revise some
of the data from the CERR when it prepares its SIP inventory to account
for improvements in emissions estimates.  If a State's 2005 emission
inventory (or a later one) becomes available in time to use for timely
development of a nonattainment area SIP, then that inventory can be
used.  We also encourage the cooperation of the Tribes and the State and
local agencies in preparing their emissions inventories.

b.	Final Rule.  

	  SEQ CHAPTER \h \r 1 In the proposed rulemaking, in section
51.1008(a), to meet the emission inventory requirements of section
172(c)(3),  EPA proposed to require submission of the CERR inventories
as well as “any additional emission inventory information needed to
support an attainment demonstration and RFP plan ensuring expeditious
attainment of the annual and 24-hour PM2.5 standards.” Section
51.1008(b) set forth specifications for baseline emissions inventories
for attainment demonstrations and RFP requirements.  Section 51.1008 of
the final rule reflects our proposed rule but is different from the
draft regulatory text.  The proposal did not specify a deadline for
submission of the emission inventory.  To ensure clarity, the final rule
contains language addressing the deadline for submission of emissions
inventories for nonattainment areas under section 172(c)(3) and section
172(b), and reflects the statutory requirement of no later than 3 years
after designation of the area.  See section 51.1008(a).  In addition,
section 51.1008(a)(1) of the proposed rule has been changed for purposes
of clarification.  The proposal referred to the requirement to submit
statewide emission inventories under the (CERR), contained in 40 CFR
part 51, subpart A.  The final regulatory text clarifies this to refer
to the requirements for data elements under 40 CFR part 51, subpart A. 
The EPA did not intend that the emissions inventories developed under
the CERR, which are statewide, would be appropriate for and satisfy all
aspects of SIP inventories developed for SIP submissions. Section
51.1008(b) has a minor change to clarify that this subsection refers to
the inventories required for submission under paragraph (a) of section
51.1008, and also clarifies the reference to 40 CFR Part 51 subpart A,
which currently contains the CERR.  In addition, section 51.1008(b) as
finalized provides that “The baseline emission inventory for calendar
year 2002 or other suitable year shall be used for attainment planning
and RFP plans for areas initially designated nonattainment for the PM2.5
NAAQS in 2004.”  The EPA added this flexibility to be consistent with
EPA’s ozone implementation rule, and to enable a State to use a more
recent and improved base year inventory if it is completed in time to
allow for timely development of the attainment plan.  As noted above, we
expect that States will consult the guidance document titled Emission
Inventory Guidance for Implementation of Ozone and Particulate Matter
National Ambient Air Quality Standards (“NAAQS”) and Regional Haze
Regulations, November 2005,and submit inventories that are appropriate
for the geographic area at issue and consistent with regulations and
this guidance.  We expect the States to include in their SIP submission
documentation explaining how the emissions data were calculated.

	In the proposed rulemaking, EPA asked “What emission inventory
requirements should apply under the PM2.5 NAAQS.”  Several specific
questions followed this general question to assess whether or not
additional emission inventory requirements or guidance are needed to
implement the proposed standard.  It was noted in the proposal that the
basis for EPA’s emission inventory program is specified in the
Consolidated Emissions Reporting Rule (CERR) and the related guidance
document titled Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards (NAAQS)
and Regional Haze Regulations.”

	Subsequent to the proposed rulemaking, EPA proposed the Air Emissions
Reporting Rule (AERR) at 71 FR 69 (Jan. 3, 2006).  The AERR would update
CERR reporting requirements by consolidating and harmonizing new
emissions reporting requirements with pre-existing sets of reporting
requirements under the Clean Air Interstate Rule (CAIR) and the NOx SIP
Call.  At this time, EPA is reviewing comments submitted on the AERR
proposal and expects to finalize this rulemaking during calendar year
2007.  The AERR is expected to be a means by which the Agency will
implement additional data reporting requirements for PM2.5 SIP emission
inventories.  Since the AERR rulemaking is in progress, EPA believes it
is appropriate to defer responding to certain comments on the proposed
PM2.5 Implementation Rule related to data reporting and emission
inventory requirements that were discussed in the AERR proposal.  Those
comments will be addressed in the final AERR rulemaking.  Significant
comments that are separable from the AERR rulemaking and relate to data
reporting and emission inventory requirements for the PM2.5 NAAQS are
addressed below and in EPA’s Responses to Comments document.

	With respect to SIP emission inventory requirements under this
rulemaking, EPA recognizes NOX, SO2, VOCs, and ammonia as potential
precursors of PM2.5 because these pollutants can contribute to the
formation of PM2.5 in the ambient air.  To provide a technical
foundation for understanding contributions to PM2.5 nonattainment
problems and for identifying potential future measures to reduce PM2.5
concentrations, EPA is requiring under 40 CFR part 51 subpart A and 40
CFR 51.1008 of this rule that States develop and submit inventories for
direct PM2.5 and all precursors of PM2.5.  This requirement stands apart
from the policies in this rule regarding the required treatment of
various precursor emissions in the development of control strategies for
attaining the PM2.5 standards.  With respect to the latter requirements,
EPA has not made a finding that all precursors should be evaluated for
potential control measures in each specific nonattainment area.  The
policy approach in the rule instead requires evaluation of control
measures for direct PM2.5 and sulfur dioxide in all areas, and describes
general presumptive policies that NOx sources need to be evaluated for
control measures in all areas unless findings of insignificance are
made, but that control measure evaluations are not required for sources
of ammonia and VOC unless findings of significance are made.  The rule
also provides a mechanism by which the State and/or EPA can make an
area-specific demonstration to reverse the general presumption for these
three precursors.  (See section II.A.8 for additional discussion on
these issues.)

c.	Comments and Responses

1.	Should EPA Specify an Inventory Approval Process?

	Comment:  Several commenters indicated that the current process of
approving SIP inventories by EPA regional offices is appropriate and did
not believe that additional approval requirements were necessary.  Some
commenters noted that flexibility is needed to address regional
concerns.  Several commenters noted that SIP emission inventories may
include requirements or information in addition to data required by the
Consolidated Emissions Reporting Rule (CERR).  One commenter observed
that States routinely develop information outside the CERR for purposes
of their SIP development and that additional requirements should not be
defined by EPA.  Another commenter recommended that requirements for
nonattainment area emission inventories be incorporated in the CERR or
AERR.  A few commenters felt that additional guidance was needed on the
SIP emission inventory approval process.	    

	Response:  The SIP emissions inventory is a plan provision that must be
approved by EPA under section 110(k) of the CAA and is subject to public
hearing requirements pursuant to section 110(a)(2).  The EPA believes
that it need not further specify a SIP approval process for emissions
inventories beyond that set forth in the statute, regulation (51.1008),
other related sections of this rulemaking and EPA’s current guidance. 
The EPA agrees with many of the commenters that the approval process for
SIP emission inventories need not be further defined and that approval
should be conducted at the regional level to provide flexibility to
address regional concerns.  The EPA also agrees that use of Quality
Assurance Project Plans developed for each state will be helpful in
establishing the proper approval process.  The EPA addresses the issue
of what data elements are needed for SIP approval in the responses to
comments below, including the responses to comments under Issue 2,
below.

	As noted by two commenters EPA describes procedures for approval of SIP
inventories in a document titled Emissions Inventory Guidance for
Implementation of Ozone and Particulate Matter National Ambient Air
Quality Standards (NAAQS) and Regional Haze Regulations, November 2005. 
Section 2.5, Inventory Approval, references a memorandum titled Public
Hearing Requirements for 1990 Base-Year Emissions Inventories for Ozone
and CO Nonattainment Areas, September 29, 1992.  The EPA intends to use
the procedures discussed in the guidance and memorandum to the extent
that they are applicable to approval of PM2.5 emission inventories
submitted as part of the SIP.  40 CFR 51.1008 sets forth the
requirements for emissions inventories under section 172(c)(3), which
will be reviewed in the context of the SIP approval process. See also 40
CFR 51.1007 and 51.1009 regarding attainment demonstrations and RFP
plans.  Thus, EPA believes that its existing SIP approval process is
adequately described in statute, regulation and guidance, and that it
provides flexibility to deal with issues that arise in individual
nonattainment areas.  

2.	Are the Data Elements Specified Within the CERR Sufficient to Develop
Adequate SIPs?  For Example, in the Determination of RACT, Should More
Information on Existing Control Devices be Required?

	Comment:  Several commenters recommended that any additional reporting
requirements should be addressed through the CERR/AERR and associated
guidance and that no additional reporting requirements should be
specified in the Rule.	 Another commenter stated that more detail
concerning control equipment would be helpful but was concerned about
the additional burden on industry compared to the benefit to State and
local agencies, and suggested  that this would be further addressed in
the context of comments on the AERR.  One commenter believed that the
reporting requirements within the CERR are sufficient to develop a PM2.5
SIP for most areas but noted that nonattainment areas may require
additional inventory information which will need evaluation on a
case-by-case basis.  The commenter further stated that any additional
inventory requirements should be identified during the SIP development
process, in cooperation with the EPA regional office, and should not be
part of this rule.

	Response:  In section 40 CFR 51.1008(a)(1) of the final rule, EPA
incorporates the requirements for data elements required under 40 CFR
part 51, subpart A, which contains the CERR, for inventories submitted
under this section.  The EPA notes, however, that the issue of whether
to require additional reporting requirements beyond those required in
the CERR is currently being addressed in the Air Emissions Reporting
Rule (AERR.) 71 FR 69 (January 3, 2006).  At this time EPA believes that
the requirements for data elements under the CERR, in conjunction with
the other provisions of 40 CFR 51.1008, as well as 40 CFR 51.1007 and
51.1009, are generally adequate to meet the needs for PM2.5
nonattainment emission inventory SIP development.  The AERR as proposed
includes additional provisions which may be helpful for PM2.5 SIP
emission inventory development.  The EPA will address this aspect of the
AERR, including comments received in this rulemaking on the issues
raised and the additional elements proposed in the AERR, in the final
AERR rulemaking. This final rule indicates that States shall include
data elements for PM2.5 inventories as required under 40 CFR part 51,
subpart A.  In addition, 40 CFR 51.1008(a)(2) requires that States
submit “any additional emission inventory information needed to
support an attainment demonstration and RFP plan ensuring expeditious
attainment of the annual and 24-hour PM2.5 standards.” See also 40 CFR
51.1007 and 51.1009.  Thus States should be aware that data elements in
addition to those required under the CERR may be needed to support
attainment demonstrations and RFP inventories.  Additional data elements
needed for other SIP emission inventory purposes should be handled on a
case-by-case basis.  Because of the nature of SIP development, which
varies depending on the nature and needs of individual areas, it may not
be possible to require a level of detail in regulations that will enable
a “one-stop-shop” information request as suggested by one of the
commenters.

     As recommended by one commenter, guidance on reporting requirements
is contained in Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards (NAAQS)
and Regional Haze Regulations (EPA-454/R-05-001, November 2005).  For
example, Section 3.2.1 for Pollutant and Pollutant Precursors to be
Inventoried presents guidance to states on PM2.5 pollutants and their
components that should be reported for PM2.5 SIP development.  See also
section 5, Emission Inventory Development, and other related sections of
the guidance.  

     With respect to the comment on additional detail on control
requirements, see also EPA’s Response to Comment Document.

3.	Is the Current Approach for Reporting Specific Pollutants Sufficient,
or Should EPA Require More Specific Emission Component Reporting Such as
Groups of Compounds or Reporting of Elemental Carbon and Organic Carbon?

	Comment:  Currently the CERR requires the reporting of SO2, VOC, NOx,
CO, Pb, PM10, PM2.5, and NH3.  VOC and PM are speciated by the emissions
processing models based on speciation profiles for specific source
categories.  Most commenters supported retaining the existing reporting
requirements under the CERR.  Others encouraged expansion of the
requirements to include reporting of specific organic compounds and
organic fractions although some thought this should be a requirement
while others thought it should be optional.  One commenter thought that
EPA should work with industry trade groups to develop and improve the
speciation profiles of the most important source categories rather than
asking the state and local agencies to characterize VOC and PM species. 
Several commenters thought that EPA should encourage the reporting of PM
components (filterable, condensable and total) for development of
control strategies and attainment demonstrations.  Another commenter
noted that including condensable emissions raises “uncertainty”
issues and urged EPA to devote resources to developing better test
methods.  One commenter believed that in addition to reporting PM2.5 and
its components, states should report all precursors to PM2.5 (SO2, NOx,
ammonia and VOC).  

	Response:  The EPA agrees with the commenters who argued that the need
for additional speciation should be determined based on specific SIP
needs.  40 CFR part 51, subpart A which contains the CERR, does not
require reporting of specific compounds or compound groups nor does it
require reporting of organic and elemental carbon fractions.  As
discussed in the response to comment above, EPA believes that the
requirements for data elements contained in 40 CFR part 51 subpart A, in
conjunction with the provisions of 40 CFR 51.1008, are generally
adequate to meet the needs for PM2.5 nonattainment emissions inventory
SIP development.  Section 51.1008(a)(1) applies the data element
requirements contained in 40 CFR part 51 subpart A.  Section
51.1008(a)(2) requires States to submit “any additional emission
inventory information needed to support an attainment demonstration and
RFP plan ensuring expeditious attainment of the annual and 24-hour PM2.5
standards.”  Thus data elements in addition to those required under
the CERR may be needed to support attainment demonstrations and RFP
inventories under 40 CFR 51.1008(a)(2).  Additional data elements needed
for other SIP emission inventory purposes should be handled on a
case-by-case basis.  Where States need to develop speciated emissions
for PM2.5 SIP emission inventories, EPA provides guidance in the
document titled Emissions Inventory Guidance for Implementation of Ozone
and Particulate Matter National Ambient Air Quality Standards (NAAQS)
and Regional Haze Ozone Regulations, November 2005.  Section 3.2.1,
Pollutants and Pollutant Precursors to be Inventoried identifies
pollutants and their components to be reported for PM2.5 SIPs.  Section
3.3.5, Speciation Procedures, discusses the preferred approach for
speciating PM2.5 emission inventories for use in ambient air quality
simulations.  The approach discussed in the guidance is application of
emission models which use speciation profiles to estimate the mass of
specific compounds and compound groups for VOC and elemental and organic
carbon fractions for PM. The EPA encourages further research and
development of technical tools to better characterize emissions
inventories for specific VOC compounds and to determine the extent of
specific VOC compounds and organic PM mass.  The EPA also encourages
States to continue efforts to refine their ammonia inventories.  See
Sections II A. 3 and II A. 4 of the Preamble.

	As discussed in the guidance document, EPA encourages reporting of
organic and elemental fractions of PM2.5 by state agencies (see Section
3.2.1, Pollutants and Pollutant Precursors to be Inventoried).  While
elemental or black carbon (EC/BC) and organic carbon (OC) will be
identified in default speciation profiles, more locally-specific data
should be collected where available as an input to model preprocessing. 
Where such data are available, they should be provided to EPA to help in
improving EPA’s speciation profiles.  Certain organic gases have been
identified as precursors to secondary organic aerosols (SOA).  Toluene,
xylene and ethyl benzene are known to be important SOA precursors. 
Additional organic gases may be identified by ongoing research.  While
these gases will be identified in default speciation profiles, more
locally-specific data should be collected, where available, as an input
to model preprocessing.  State, local and Tribal agencies can contact
EPA’s EIAG for more information.

	EPA agrees with the comment that it should take the lead in updating
VOC and PM profiles for most important source categories.  The Agency is
close to completing a multi-year effort to update the SPECIATE database.
 SPECIATE is EPA's repository of Total Organic Compound (TOC) and PM
speciated profiles for a wide variety of sources.  The profiles in this
system are provided for air quality dispersion modeling and as a library
for source-receptor and source apportionment type models.  This recent
initiative to update SPECIATE was needed because speciated emissions
profiles continue to be developed and the data in the existing EPA
database (SPECIATE 3.2) was becoming outdated.

	This work was coordinated with interested parties including industry
through an Agency sponsored workgroup.  It has depended largely on the
collection and review of existing profile data to accomplish, as the
commenter suggests, delivering the best results for the least amount of
resources spent.  Previously, these data were not widely available to
emission inventory developers and lacked the quality assurance review
and evaluation needed to develop profiles used by emissions models to
generate speciated emissions.  As suggested by the commenter, the
workgroup was used to help prioritize source categories for
investigation to ensure that updates to existing profiles and
development of new profiles focused on areas of greatest need.

	SPECIATE v4.0 contains more than 2500 source profiles and is currently
undergoing peer review.  The EPA expects the final work product to be
available for use by emission inventory preparers during early calendar
year 2007 and it will be distributed through EPA’s CHIEF Web site. 

	The EPA agrees with a commenter who noted that in order to meet the
requirements under section 172(c) of the CAA for “a comprehensive,
accurate, current inventory...,” condensable emissions of PM2.5 and
PM2.5 precursors are important to support development of local control
strategies and attainment demonstrations.  The EPA believes that the
final rule provides for the submission of PM2.5 nonattainment area
inventories meeting the requirements of section 172(c)(3).

	Section 51.1008(a)(1) requires that States submit emission inventories
for PM2.5 that satisfy the data elements reporting requirements under 40
CFR part 51 subpart A, which contains the CERR.  The CERR requires
reporting of “Primary PM2.5” which is defined as the sum of the
filterable and condensable portions of PM2.5.  Therefore, SIP base year
inventories will include the condensable fraction of PM which was of
concern to several commenters.  The CERR also requires reporting of SOx,
NOx, ammonia and VOC which are potential precursors to PM2.5.  EPA notes
that the AERR as proposed would require reporting of the same precursors
and would also require reporting of Primary PM2.5.  However, the
proposed AERR requires the reporting of the filterable and condensable
fractions of PM2.5 (optional under the CERR) in addition to the primary
PM2.5 total mass.  The EPA will address this requirement in its final
rulemaking on the AERR.

	As noted above, in addition to the data element requirements under
section 51.1008(a)(1), under section 51.1008(a)(2) States must submit
“any additional emission inventory information needed to support” an
attainment demonstration and RFP plan.  Thus States should be aware that
data elements in addition to those required under the CERR may be needed
to support attainment demonstrations and RFP inventories under 40 CFR
Part 51.1008(a)(2).  Additional data elements needed for other SIP
emission inventory purposes should be handled on a case-by-case basis.

	The EPA is aware of the issues raised by one commenter regarding
measurement uncertainty for condensable PM.  This issue is addressed in
detail under Section II. L of the preamble (“Condensable particulate
matter test methods and related data issues,”).  We believe that for
purposes of emissions inventories and attainment demonstrations, States
should continue to describe the impacts of baseline emissions and
develop future air quality strategies using information available on
primary PM2.5 emissions, including condensable PM2.5.  However, with
respect to developing enforceable emissions limits for condensable PM2.5
emissions, the final rule reflects EPA’s adoption of a transition
period during which we will allow time for development of emissions
limits for condensable PM2.5.  See 40 CFR 51.1002(c).  

     For additional comments and responses related to speciation issues,
see the Response to Comments Document.

4.	Should EPA Require That States Develop Their Own Estimates for Area
and Mobile Source Emissions?

	Comment:  The CERR allows states to adopt EPA developed emission
estimates from area and mobile sources in lieu of making those estimates
themselves if they accept these estimates for their emission inventory. 
One commenter thought that EPA should require States to develop their
own estimates for area and mobile sources based on the specified 2002
base year.  Three commenters thought that the existing process (under
the CERR) was adequate.  One of the commenters expressed concerns about
the reporting burden for States if they were required to compile their
own mobile and area source inventories.  Another commenter did not
believe that States should be required to submit data on area and mobile
sources but noted that many States would continue to run the MOBILE
model for onroad mobile sources and calculate area source data for SIP
emission inventories.  Two of the commenters thought that the existing
process provided flexibility needed by States to focus on source
categories of most concern and address problematic areas with special
inventory needs.  One commenter recommended that EPA continue developing
models for area and mobile sources.

	Response:  The EPA strongly encourages states to submit their own
estimates for area (nonpoint) and mobile sources unless they can
establish that it is impracticable to do so, given time and resources. 
We will continue, in appropriate circumstances, to allow a State to use
EPA-developed emission estimates for mobile and nonpoint sources in lieu
of making those estimates itself if the State accepts the estimates for
its emission inventory.  While this has been the case with respect to
reporting under the CERR for the 3-year cycle inventories, for
development of emission inventories to support PM2.5 SIPs, the ability
to rely on EPA-developed emission estimates for development of emission
inventories to support PM2.5 SIPS is more complex and problematic.  For
mobile sources, the practical use of these EPA-developed mobile source
inventories in a SIP may be very limited.  While EPA has developed
inventories for 2002, states will still have to develop attainment year
inventories, including projections of future activity and the effects of
control measures.  For mobile sources, future year inventories are not
developed by simply growing a base year inventory, but instead are
developed by running an emissions model with appropriate inputs for the
future year.  In order to develop an attainment demonstration that
accurately accounts for the change in emissions from the base year to
the attainment year, inventories for both of those years will need to be
developed using consistent methods and modeling assumptions.  For mobile
sources especially, it may be very difficult for states to replicate the
methods used by EPA for the base year when creating the attainment year
inventory.  

	In addition, states cannot use the EPA developed inventories for the
base year if newer models or planning assumptions are available at the
time they begin working on the SIP.  For example, if new or better
information about the composition of the local fleet of highway vehicles
in the base year becomes available to the state after the EPA developed
inventories were created, that information should be used by the state
to create a new base year inventory.

	Given the need for emissions modeling for mobile sources in the
projection year, the need for consistency in tools and methods between
the base year and attainment year, and the need to use latest available
models and planning assumptions, EPA believes that most if not all
states will choose to develop their own base year inventories for mobile
sources. 

	With respect to nonpoint (area) source emissions, States must make
every effort, consistent with available timing and resources to ensure
that their area source emission inventories are as accurate as possible.
 While EPA prepares a national area source emission inventory that
covers all counties, it is designed for national analyses.  EPA does not
have access to the more detailed information available to States that is
used to develop an area source inventory.  Therefore, states should
develop as much of their area source inventory as possible using local
and State information, and in particular should develop the inventory
for the most significant area source categories which are critical to
ensuring overall accuracy.  Where time and resources preclude a State
from developing the estimates for less-critical area source categories,
the State may rely on EPA-developed area source emissions information
for those categories. 

     The EPA points out that although guidance has recommended that 2002
be used as the base year for emissions inventories for states initially
designated nonattainment in 2004-5, states remain free to use an
alternate base year, as appropriate.  Section 51.1008(b) provides in
relevant part that “The baseline emission inventory for calendar year
2002 or other suitable year shall be used for attainment planning and
RFP plans for areas initially designated nonattainment for the PM2.5
NAAQS in 2004.”

EPA agrees with the comment that it should continue to develop models
and other emission estimation tools.  As an example, EPA’s Office of
Transportation and Air Quality (OTAQ) is developing a modeling system
termed the Motor Vehicle Emission Simulator (MOVES). This new system
will estimate emissions for on-road and nonroad sources, cover a broad
range of pollutants, and allow multiple scale analysis, from fine-scale
analysis to national inventory estimation. When fully implemented MOVES
will serve as the replacement for MOBILE6.2 and NONROAD.  In addition,
as the NEI is reengineered, OAQPS will examine the need for updating
emissions estimation guidance materials and developing tools which will
assist State agencies in estimating emissions from area source
categories.  See also EPA’s “Emissions Inventory Guidance for
Implementation of Ozone and Particulate Matter National Ambient Air
Quality Standards (NAAQS) and Regional Haze Regulations,”  November
2005.

5.	Other Inventory Issues

	The EPA’s responses to additional comments concerning  emission
inventory issues can be found in EPA’s Response to Comments Document.

L.	Condensable Particulate Matter Test Methods and Related Data Issues

a.	Background.  

	As noted in the preamble to the November 1, 2005 proposed rule, certain
commercial or industrial activities involving high temperature processes
(fuel combustion, metal processing, cooking operations, etc.) emit
gaseous pollutants into the ambient air which rapidly condense into
particle form.  The constituents of these condensed particles include,
but are not limited to, organic material, sulfuric acid, and metals. 
Because condensable emissions exist almost entirely in the 2.5
micrometer range and smaller, these emissions are inherently more
significant for PM2.5 than for prior particulate matter standards
addressing larger particles.  Therefore, we believe that it is important
that the air quality management of particulate matter promote a
comprehensive approach to condensable particulate matter.   

	We proposed to require a comprehensive inclusion of condensable PM for
all aspects of SIP development for PM2.5.   Under the proposal, EPA
would require condensable PM to be considered in the emissions
inventories and analyses used in attainment demonstrations.   Also under
the proposal, any stationary source emissions limits developed to
implement RACT or RACM would reflect control and measurement of
condensable PM.

	We received numerous comments on whether these requirements were
unreasonable in light of the current state of knowledge of and
uncertainties around the measurement of direct PM2.5.  Most commenters
supported the overall view that condensable PM should be addressed in
order to provide a complete air quality management program for PM2.5. 
On the other hand, many commenters raised concerns about the
availability and implementation of test methods and related issues about
the uncertainties in existing data for condensable PM2.5.  As a result
of the concerns, these commenters believed EPA would be premature in
requiring a comprehensive evaluation of condensable PM2.5, especially as
it related to developing any new emissions limits for stationary
sources.  In recognition of these concerns, the final rule reflects
EPA’s adoption of a transition period during which we will assess
possible revisions to available test methods and we will allow time for
States to update emissions inventories as needed to address direct PM2.5
emissions.  In this section of the preamble, we outline the elements of
the final rule addressing inventories reflecting control of direct
PM2.5.  We also discuss the specific comments raised regarding methods
for measuring direct PM2.5, both filterable and condensable PM, in
implementing the rule.  The particular comment areas include defining
test methods, quantifying direct PM2.5 for inventories, and a transition
period for developing effective regulations.  Below are also our
responses to those comments. 

b.	Final Rule

	For the final rule, EPA addresses two broad issues related to inclusion
of condensable PM.  The first issue is whether emissions inventories and
attainment demonstrations should include the condensable portion of
direct PM2.5 emissions.   The second issue is whether direct PM2.5
emissions limitations established by States for purposes of RACT and
RACM must include limits on condensable PM emissions or limits on total
direct PM2.5 that includes the condensable PM fraction.

For purposes of developing emissions inventories and attainment
demonstrations, the final rule reflects a requirement to account for
significant contributors of direct PM2.5 emissions, both filterable and
condensable PM2.5.  We recognize that some States have established
inventories consistent with requirements of the consolidated emissions
reporting rule (CERR) to report direct PM2.5 emissions, including
condensable PM, in each inventory revision.  While uncertainties remain
with significant issues to address related to our current knowledge base
on condensable PM emissions, we believe that for purposes of emissions
inventories and attainment demonstrations, States should continue to
describe the impacts of baseline emissions develop future air quality
strategies using information available on direct PM2.5 emissions
including condensable PM.

With respect to developing enforceable emissions limits for condensable
PM emissions, we note that some States have established emissions limits
or otherwise require PM emissions testing that includes measurement of
condensable PM.  We recognize that in some States there remain questions
about the viability of available test methods, the availability of
representative direct PM2.5 emissions data, the uncertainty of the
methods used to establish inventories, and the short time frame within
which States must develop SIPs.  In response we have decided to provide
a transition period for developing emissions limits and regulations for
condensable PM2.5.  During this transition period, we will provide
technical support to States as requested in establishing effective PM2.5
emissions limits and corresponding emissions testing requirements.

	As described further below, we will devote resources early during this
transition period to assessing and improving the available test methods
for condensable PM.  During this transition period, we will also solicit
the involvement of stakeholders with an interest in conducting emissions
testing to collect updated direct PM2.5 emissions data.  The purpose of
these stakeholder projects will be to collect new direct filterable and
condensable PM emissions data using methodologies that provide data more
representative of source direct PM2.5 emissions.  The EPA, States, and
others will use these data to improve emissions factors and to help
define or revise source emissions limits in permits and State
implementation plans.  

	The time required for our stakeholders and EPA to complete the test
method assessment will limit the degree to which State and local
agencies can address effectively the necessary direct PM2.5 regulations
in inventories and in the 2008 SIP submittals.  In recognition of this,
we will not require that the emissions limits included in the 2008
submittals account for the condensable fraction of direct PM2.5 or to
establish limits for total direct PM2.5, including condensable PM.  

We will expect States to continue developing more complete inventories
with regard to direct PM2.5 emissions, particularly for condensable PM,
during this transition period.  We expect no such allowance period for
method assessment or data collection to be necessary for implementing
regulations addressing precursor PM2.5 emissions.  

The period of transition for establishing emissions limits for
condensable direct PM2.5 will end January 1, 2011.  We expect States to
address the control of direct PM2.5 emissions, including condensable PM,
with any new actions taken after January 1, 2011.  For example, States
must address condensable PM emissions in any direct PM2.5 emissions
limits resulting from midcourse reviews.  Additionally, EPA expects that
any direct PM2.5 regulations or limits developed under any new NAAQS for
particulate matter would also address condensable PM emissions.

Notwithstanding the issues and uncertainties related to condensable PM,
EPA encourages States to identify measures for reducing condensable PM
emissions, particularly where those emissions are deemed significant
contributors to the control strategy needed for expeditious attainment. 
We wish to clarify that in order to take credit in the SIP for reduction
of any such condensable PM emissions, there must be enforceable
limitations that ensure that reduction in condensable PM emissions.  
These enforceable limits could take the form of a limitation on the
condensable PM emissions or total direct PM2.5 emissions (or a
commitment to develop such limitations after the end of the transition
period described above).  Alternatively, these enforceable limitations
could provide for enforceable conditions that ensure that the effect on
condensable PM emissions is assured (for example, enforceable
limitations on operating temperature, or limits on FGD scrubber
operations which have the effect of reducing condensable PM emissions). 

c. Comments and Responses.  

	We received many comments on quantification of direct PM2.5 emissions
particularly about the need to conduct further validations for the
available test methods, the availability of direct filterable or
condensable PM2.5 data or lack thereof for representative baselines, and
the procedures for applying baseline data for developing effective
regulations.

1.	Method 202

	Comment:  A majority of commenters characterized the performance of
Method 202 as lacking in reliability.  Some commenters characterized the
formation of artifacts in Method 202 as significant and the primary
reason for their recommendation to defer the inclusion of condensable
particulate matter in the baseline assessments and regulatory
development for the initial SIPs.  The commenters stated that the
principal artifact formed when using Method 202 was the result of SO2
dissolving in the impinger water and converting to sulfuric acid.

	Response:  We agree that SO2 in particular, and perhaps other gaseous
compounds, can react with the collecting liquids used in the method to
form materials (artifacts) that would not otherwise be solid or liquid
or would not condense upon exiting the stack.  We believe that when
Method 202 is applied appropriately (i.e., with the N2 purge as
prescribed), the SO2 artifact formation is reduced by as much as or more
than 90 percent; however, we agree that further verification and
refinement would be appropriate to verify the potential for artifact
formation.  

	In response, we are undertaking laboratory studies in collaboration
with several stakeholders to characterize the artifact formation and
other uncertainties associated with conducting Method 202, and to
identify procedures to be used in applying methods to minimize
uncertainties.  We are involving stakeholders representing industry and
State and local agencies in the project design and results review. 
Stakeholders who have expressed interest in participating in these
studies include the Electric Power Research Institute, companies
associated with the National Environmental Development Association’s
Clean Air Project (NEDA/CAP), the Portland Cement Association, the Lime
Manufacturing Association, the American Foundry Association, the
National Aluminum Association, and several governmental organizations
represented by National Association of Clean Air Agencies.  Other
parties may participate in the study as well.

	By the end of 2007, we intend to have conducted a comprehensive
laboratory study that examines the relationship between several critical
condensable PM sampling and analysis parameters (e.g., SO2
concentration, moisture concentration, sample duration, and water
acidity) and the artifact formation associated with the measurements. 
One intended result of the project will be identifying possible
modifications to Method 202 to minimize and quantify the uncertainties. 
We will publish the results of the laboratory study along with an
assessment of other input and data from stakeholders on the EPA website
and, to the extent possible, in a widely circulated peer review journal.
 Also, to the extent necessary, we intend to propose revisions to the
method to incorporate improvements and to clarify application.

2.	Conditional Test Methods 039 and 040

	Comment:  Several commenters cited as a deficiency that neither
conditional test method 040 (CTM-040) for measuring filterable PM2.5 nor
the dilution sampling method (CTM-039) has been thoroughly validated
through EPA Method 301.  There were also comments that neither of the
CTMs was published in the Federal Register.

	Response:  We agree with the comments that neither method has been
subjected to adequate public notice and comment rulemaking.  Taking that
step will facilitate application of the appropriate methods for
implementing the SIPs.  On the other hand, there are a number of levels
of validation already achieved for one or more of these methods that
will determine what, if any, additional validation work will be
necessary.  For example, while we could seek resources to evaluate
dilution sampling technology, including CTM-039, and to request public
involvement in the project planning, conduct, and review with the
possibility of a Federal Register proposal, our preference would be to
incorporate by reference an approved voluntary consensus test method
(e.g., ASTM standard).

	We believe that a dilution sampling method for measuring direct PM2.5
eliminates essentially all artifact formation and provides the most
accurate emissions quantification.  To the extent that we need to and
can secure resources and stakeholder interest, we plan to perform
additional validation testing of CTM-039 or other dilution sampling
technologies to characterize the precision of this approach.  In
conjunction with our validation efforts, we intend to continue
participation in the ASTM D22 committee to develop and publish a
dilution sampling method and encourage other volunteers on that
committee to approve the consensus based dilution sampling method.  We
believe that this work is nearly complete.  As outlined above, we are
already undertaking laboratory studies to assess the method and to
identify possible modifications to reduce formation of these artifacts. 
Preliminary laboratory evaluations conducted by EPA and by Environment
Canada indicate that additional artifact reductions of 60 to 90 percent
may be achieved with other minor modifications to Method 202.  These
preliminary findings indicate that Method 202 is essentially a viable
method that these proposed laboratory studies will serve to enhance. 
Within 18 months we intend to propose, if necessary, modifications to
Method 202 or similar methodologies suitable for measuring condensable
PM2.5.

	As for CTM-040, we believe that that further validation of this method
is unwarranted since the technology and procedures are based upon the
same as evaluated for promulgated Method 201A.  Method 201A has
undergone public review and comment (55 FR 14246, April 17, 1990). 
Also, as noted earlier, we have already begun laboratory and data
evaluation work the possible result of which would be a revised Method
202 to be proposed in the Federal Register to include improvements
indicated by the evaluation.  At that same time, we may propose CTM-040
to be used in combination with Method 202 for measuring direct PM2.5
with additional guidance on appropriate approaches to testing for direct
PM2.5 emissions from various types of control measures (e.g.,
electrostatic precipitator and flue gas desulphurization combinations).

3.	Role of Condensable PM Emissions in Defining RACT

	Comment:  Commenters indicated that States must reassess and revise
emissions limits if the States adopt methods for measuring direct PM2.5
including condensable PM where not required previously.  Commenters
noted that most existing PM emissions limits are not reflective of data
collected with methods that measure condensable or filterable PM2.5 and,
therefore, not enforceable using a new or different test method.  

	Response:  We agree that coordinating the test method with the
pollutant defined by the emissions limit is critical to an effective
regulation.  In the case of direct PM2.5 regulations, the methods for
measuring filterable and condensable PM provide data that are
significantly different than do methods often used in implementing many
current regulations (i.e., filterable plus condensable PM2.5 versus
filterable PM only).  The existing PM emissions regulations implementing
many current SIPs have focused almost exclusively on filterable PM at
stack conditions or other elevated temperatures (e.g., 250°F) with
little or no measurement of condensable PM, let alone filterable PM2.5. 
These deficiencies exist in spite of the Agency’s policies and
guidance presented in documents such as the 1987 PM10 SIP Development
Guideline and the General Preamble for the Implementation of Title 1 of
the Clean Air Act Amendments of 1990  issued in 1992.  These documents
set forth Agency policy stating that direct PM10 and direct PM2.5
emissions include both filterable and condensable particulate matter.

The policies are reinforced by a 2005 directive from the CAA Advisory
Committee.   

	More to the point, the use of test methods that quantify only
filterable PM would limit the capability of any assessment of control
measures available for developing cost effective strategies to achieve
attainment of the PM2.5 NAAQS.  Examples include an attainment
demonstration that includes control methodologies for PM precursors
which are likely to result in a significant decrease in the emissions of
direct PM2.5 (for example, alkaline scrubbers to reduce SO2 emissions)
and incorporate these direct PM2.5 emissions reductions in their
attainment demonstration or allow for the use of these reductions as
credits for other programs.

	Some States may decide to measure and control condensable PM emissions
prior to the end of the transition period.  To the extent that a State
has the supporting technical information and test methods, the State may
also assess the capabilities of current control technologies, possible
modifications to such technologies, or new technologies as appropriate
relative to control of condensable PM2.5 emissions in developing
effective control strategies and regulations.  As an example, a specific
approach for controlling condensable PM could be a change in control
device operating temperature to achieve necessary emissions reductions. 
We also note that it is important that implementation of any new or
revised rules and test methods should be prospective and clearly
differentiated from existing regulations to avoid confusion over status
of compliance relative to existing PM emissions limits.

4.	Sufficiency of Current Baselines Relative to Direct PM2.5 for
Regulatory Development

	Comment:  Many commenters indicated that the currently available
baselines for direct PM2.5 emissions are not sufficient for States to
develop effective emissions control regulations.  One commenter claimed
that States will need additional information regarding how to arrive at
enforceable PM2.5 emissions limitations through application of
correlations to existing PM10 emissions limitations. 

	Response:  We agree that State inventories accounting for direct PM2.5
emissions are important to the NAAQS implementation decision-making
process.  For example, the current national emissions inventories have
characterized the contribution of the condensable PM emissions to range
from 40 to 80 percent of the direct PM2.5 emissions particularly from
combustion source categories.  We also agree in many cases, the
emissions baselines are not sufficiently representative of significant
direct PM2.5 contributors to allow States to develop effective and
enforceable emissions limitations for sources that may require control
of direct filterable or condensable PM2.5 emissions in order for States
to come into attainment with the PM2.5 NAAQS.

	We note that States are already required under the consolidated
emissions reporting rule (CERR) to report direct PM2.5 emissions,
including condensable PM, in each inventory revision.  That means that
inventories and associated baselines must address sources and
contributions of direct PM2.5 emissions, both filterable and condensable
PM, from individual sources and groups of sources as well as for future
year projected emissions.  These data are important for the purposes of
calculating emissions reductions and demonstrating that such reductions
are attributable to the control measures being implemented.  

	In taking the process to the next step, we contend that many current
baselines established using the available direct filterable and
condensable PM2.5 national industry average emissions factors (e.g.,
those found in AP-42 and WebFIRE,
http://www.epa.gov/ttn/chief/efpac/index.html) often are of quality
insufficient to establish effective source-specific emissions limits. 
First, national industry average emissions factors are subject to
significant uncertainties as they usually represent data from a very
limited number of example facilities in a category and for a very
limited number of operating conditions.  Second, the available emissions
factors databases may not include direct PM2.5 emissions data for
specific source types that appear in some State and local inventories.  

	In short, we believe that States should rely on directly measured
emissions data in developing source category or pollutant-specific
emissions limits for regulations.  This approach is preferable to the
use of these national industry average emissions factors such as those
found in AP-42.  If there are no directly measured emissions data
available from the subject sources, national average emissions factors
should be used only with appropriate and significant adjustments for
uncertainty.  Based on our initial study of the uncertainties associated
with national average emissions factors when applied to site-specific or
rule-development activities, we would expect multipliers of 0.1 to 3.3
for an A-rated national average filterable and condensable direct PM2.5
emissions factors.  The level of a particular multiplier would depend on
how representative of the source category the applicable emissions
factor is, the quantity of data supporting that emissions factor, and
the specific application.  Determining what adjustment may apply for a
particular application requires detailed knowledge of the emissions
control variability, the expected range of operational and process
variability, and the statistical uncertainty in the measured emissions
data.  While more general adjustments to emissions factors are possible
for these purposes, we believe that the better approach is to improve
and update the emissions factors used in the database for a particular
area with measured direct PM2.5 emissions data.  For these reasons and
to allow time for data collection and analysis, we have determined the
need for a period of transition for States in developing direct PM2.5
emissions reduction strategies.

5.	Transition Period

	Comment:  Some commenters suggested that EPA should allow States to
base their initial 2008 SIPs on NOx, SO2, and filterable PM or PM10 (as
a surrogate for filterable PM2.5) rather than require State and local
agencies to develop direct PM2.5 emissions regulations immediately. 
Commenters suggested that EPA provide a transition period for sources to
adopt SIPs that address direct PM2.5 and to apply the appropriate test
methods.  The commenters proposed that during this transition period, a
source should be able to continue to use Method 5, Method 17, or
whatever method was used to set the underlying limit contained in the
source’s title V operating permit.  Commenters believe that such a
transition plan must provide additional time to collect data related to
condensable PM emissions.  Commenters believe that this additional time
is necessary because it is unrealistic to develop SIP revisions
addressing condensable emissions by April 2008.  Other commenters
suggested that source emissions inventories used for regulatory
decision-making and identifying regulatory control measures must be
based on accurate measurements.

	Response:  As outlined above, we agree that a transition period should
be allowed to allow time to resolve and adopt appropriate testing
procedures for condensable PM emissions, to collect total (filterable
and condensable) PM2.5 emissions data that are more representative of
the sources in their areas, and develop effective regulations for
control of direct PM2.5, including condensable PM.

6.	Data Collection for Regulatory Development  

	Comment:  Several commenters recommended that EPA should be responsible
for developing data of emissions from common sources of direct PM2.5.  

	Response:  We disagree with the commenters’ recommendation that EPA
should be primarily or solely responsible for developing baseline data
on common sources of direct PM2.5 emissions.  Commenters are suggesting
that we should collect data representative of direct PM2.5 emissions
from source categories potentially subject to regulation of direct PM2.5
emissions.  Furthermore, they suggest that we expand or improve the
current compilation of national industry average emissions factors such
as found in AP-42 and WebFIRE
(http://www.epa.gov/ttn/chief/efpac/index.html).  Given the limited
extent to which national industry average emissions factors are suitable
for developing State or local regulations that set limits on direct
PM2.5 emissions, we believe that it is inherent that States instead have
primary responsibility for reviewing and applying measured emissions
data collected from their sources in enhancing their current baselines. 
In some cases, this will mean that States and other stakeholders will
need to conduct more focused direct PM2.5 emissions data collection and
improve relevant emissions factors.

	This approach is appropriate for several reasons.   First, we believe
that stakeholders other than EPA are better equipped to identify
specific data needs and that they have the means to collect the data. 
Second, we believe we are better positioned to provide guidance on test
planning, data collection, and emissions factors calculations with a
less direct role in data collection and evaluation.  Third, we believe
that States in need of additional information can also benefit from
experience of other States with similar source types and who are
developing regulations to implement the NAAQS including the control of
condensable PM.   See also the discussion in section II.L.2.c.1 above on
the currently active collaborative study to assess direct PM2.5
emissions measurement technologies and to collect updated direct PM2.5
emissions data.

7.	Developing Effective Regulations for Direct PM2.5, Including
Condensable PM, Emissions.

	Most current PM regulations focus on the control and measurement of
filterable PM emissions and do not account for condensable PM emissions.
 At issue are assessing and accounting for the differences in
methodology and applicable limits when changing to a program designed to
achieve reductions in PM2.5 emissions, including condensable PM. 

	Comment:  A number of respondents commented that EPA needs to
promulgate a PM2.5 test method and adopt regulatory language that
determines the PM2.5 limits based on that promulgated PM2.5 test method
as soon as possible.  Other commenters suggested that EPA and States
have no choice but to revise the underlying standard by adopting new
monitoring requirements through a notice and comment rulemaking. 
Further, these commenters indicate that it is essential that EPA require
that no change in a test method or in methods of monitoring for
determining compliance until such time as EPA or the permitting agency
have undertaken a notice and comment process to determine how the
emissions limitations must be revised.  A number of commenters cited
specific components necessary for effective regulations.

	Response:  We agree that notice and comment rulemaking is appropriate
for establishing effective regulations.  As noted above, we are already
undertaking a study of the available test methods to determine the need
for regulatory revisions.  We also agree that new regulations limiting
direct PM2.5 emissions must include effective emissions limitations to
the extent that a State must reduce sources of direct PM2.5.  How a
State determines to take such regulatory action depends on the State’s
implementation plan.  Regarding the specific components necessary for
effective regulations, see section O below on enforcement and compliance
issues.  

M.	Improving Source Monitoring 

a.	Background.  

	In the November 1, 2005 proposal, we discussed a number of actions the
EPA would undertake to improve the effectiveness of existing and new
regulations with improved source monitoring provisions.  Specifically,
we repeated a plan outlined on January 22, 2004 (69 FR 3202; a Federal
Register notice describing requirements for monitoring in operating
permits), that includes a four-part strategy for improving monitoring of
emissions at the source where necessary through rulemaking.  One element
of that plan is for EPA to develop guidance on how States can reduce
PM2.5 emissions by improving source monitoring related to PM2.5
emissions limits.  We noted that we expect to describe in such guidance
methods of improving monitoring frequency or adopting more appropriate
monitoring for States to consider in developing their PM2.5 SIPs and to
illustrate the amount of credit that States could receive in PM2.5 SIPs
for adopting such improved monitoring.  We suggested that States with
areas where additional reductions are needed to help the area achieve
compliance with the NAAQS could implement improved monitoring measures
to obtain additional emissions reductions.  We put forward that State
agencies could receive SIP credits as a result of enforceable improved
monitoring or voluntary emissions monitoring programs meeting EPA
voluntary program policies.

	Specific examples of improved monitoring we outlined included: 1)
conducting the currently required monitoring more frequently (i.e.,
increased monitoring frequency), 2) changing the monitoring technique to
a parameter more closely related to control of direct or precursor PM2.5
emissions (i.e., a correlated parametric monitoring technique), 3)
changing the technique to more measurement of direct PM2.5 emissions and
PM2.5 precursors, or 4) a combination of these improvements.  These
types of monitoring improvements could be conducted for both controlled
and uncontrolled emissions units. The improved monitoring control
measure would require facilities to pay more attention to the operation
of add-on air pollution control devices, work practices, and other
control measure activities.  The additional attention will reduce
periods during which control devices and other control measures do not
operate as intended or required.  The result would be increased
emissions reductions from implementing existing and new rules.

	We discussed a range of currently applied and new monitoring
technologies.  We addressed concerns we have about the limitations of
the widespread use of visual emissions (VE) monitoring techniques, such
as visible emissions checks, to show compliance with PM emissions
limits.  We noted particular concerns about VE approaches, even with
frequent application, having the ability to verify compliance when the
margin of compliance is small or the ability to detect relatively
significant changes in emissions control performance.  The other concern
we noted about the use of VE tools is the limited frequency at which
they are conducted.  We cited studies on the availability of continuous
instrumental methods for monitoring opacity and operational parameters
closely related to PM control levels including the development of
repeatable correlations between parameter levels and PM emissions.  We
noted that PM continuous emissions monitoring systems (PM CEMS)
technology provides the opportunity to quantify PM emissions levels
(concentration or emissions rates).  These additional data provide the
source owner/operator with a level of information that can be useful for
understanding and operating the process and the control measures in ways
to minimize emissions, improve operating efficiencies, and reduce
enforcement liabilities.  Furthermore, we noted that this technology
will provide the State with quantitative information on PM emissions
which will help improve the inventories and to implement effective
control strategies to meet the NAAQS.

	We also discussed at some length what we believe constitutes improved
monitoring and the potential for monitoring-related emissions
reductions.  We discussed a study of how these emissions reductions
would be achieved by increasing the monitoring frequency or improving
the monitoring of an add-on air pollution control device or other
process activity above the level currently required in existing rules. 
The increased frequency or improved technique would allow owners or
operators to achieve greater emissions reductions by identifying and
responding more quickly to periods of ineffective control measure
operation.  States could use an improved monitoring control measure in
regulations or through other means to reduce emissions levels and
receive credits towards attainment.  Specifically, we cited materials
that indicate that source owners and operators who increase monitoring
frequency could achieve emissions reductions up to 13 percent and those
who improve the monitoring technique could achieve emissions reductions
up to 15 percent.  States with nonattainment areas in need of additional
reductions to achieve compliance with the NAAQS could implement an
improved monitoring measure and develop additional emissions reductions
credits.  We outlined several specific examples.

	In order to inform our improved monitoring guidance development
efforts, we used the 2005 proposal to solicit specific comments on 1)
how potentially inadequate source monitoring in certain SIPs could be
improved; 2) how improved PM2.5 monitoring relates to title V
monitoring; 3) whether instrumental techniques are more appropriate than
visual emissions (VE) techniques for monitoring compliance with PM
emissions limits; and 4) a basis for determining whether improved
monitoring would be effective and under what conditions should be
required.  We also requested comment on the feasibility of monitoring of
co-pollutant control measures and requested examples of improved
monitoring for any applications.

b.	Final Rule.  

	We maintain that improved monitoring is critical to implementing the
PM2.5 direct and precursor emissions reductions programs.  We also
believe that improving monitoring both in terms of increasing data
collection and analysis frequency and in measuring the pollutant of
interest more directly will accomplish several important and
advantageous outcomes.  First, improved monitoring will improve
verification of compliance and assurance of the intended emissions
reductions.  Second, improved monitoring can provide additional
emissions reductions through quicker detection and correction of control
measure problems.  Third, improved monitoring can improve operating
efficiencies that often result in cost savings to the facility exceeding
the cost of the monitoring.  We will continue to evaluate the effects of
improved monitoring on emissions reductions and ways to quantify the
benefits associated with improved monitoring.

	We intend to move forward with developing and providing additional
technical and informational materials regarding technologies
constituting improved monitoring and for developing regulations with
improved monitoring.  These materials may also include guidance and
tools for establishing emissions reductions credits and the economic
benefits associated with improved monitoring.  As noted in section L
above, we also reaffirm our policy that effective regulations must
include certain elements that define applicable emissions limitations,
the testing and monitoring requirements, and compliance, reporting, and
corrective action obligations.  

c.	Comments and Responses.

	We expected to receive practical advice concerning improved PM2.5
source emissions monitoring methods and field-tested examples.  Instead,
commenters focused on 1) critiquing PM CEMS technology 2) insisting that
improving monitoring changes stringency of existing rules and requires
rulemaking, and 3) critiquing the theoretical study linking emissions
reductions with improved monitoring.  

1.	Currently Available PM CEMS for Monitoring Direct PM2.5 Emissions

	Comment:  Commenters noted that because currently available PM CEMS
measure filterable PM at stack conditions or at other elevated
temperatures, the instruments do not measure the condensable portion of
PM2.5.  

	Response:  We agree with this comment relative to PM CEMS in use to
date and the ability to detect condensable PM.  PM CEMS as applied today
can be calibrated to measure filterable PM2.5 emissions with very good
sensitivity and repeatability.  Note that we are aware of a number of PM
CEMS vendors developing devices relying on much the same technology but
modified to measure condensable PM.  Further, we are aware of at least
one manufacturer offering a PM CEMS applicable to stationary sources
that also complies with ASTM requirements for mobile source emissions
monitoring.  We also believe that monitoring for filterable PM2.5 will
be as important in some cases as monitoring for condensable PM and that
PM CEMS in use today are markedly better at monitoring PM emissions than
other frequently used monitoring approaches.

	We realize that PM CEMS represent just one of a range of monitoring
options that constitute improvements over the current monitoring.  For
instance, we believe that improved monitoring would include replacing
current periodic VE measurements or daily recording of pressure drop of
fabric filters with continuous bag leak detectors.  We know of projects
(e.g., ASTM committee work) for continuing the development of optical,
as well as electromagnetic, monitoring tools to increase sensitivity and
cost-effectiveness.  Such monitoring would increase monitoring frequency
and would yield data much more closely related to and more sensitive to
control device operation than most currently applied monitoring.  To the
extent that condensable PM control is critical in implementing a
regulation, we believe that monitoring must address that need.  We will
continue to collect and also provide information on source monitoring
approaches that are improvements over current methods in both frequency
and representativeness relative to implementing PM2.5 emissions control
strategies.

2.	Status of Guidance Relative to Regulations

	Comment:  A significant majority of commenters suggested that improving
monitoring in an existing regulation increases its stringency and
requires notice and comment rulemaking, not guidance.  Just one
commenter suggested guidance could be developed and used.

	Response:  There are two aspects to the comments on this issue.  One is
whether improved monitoring would change source operations.  We agree
with the commenters that increasing the frequency of data collection or
providing data more directly related to the pollutant of concern with
improved monitoring could result in changes in how a facility is
operated relative to compliance.  We disagree with commenters that such
changes in process operation resulting from improved monitoring
constitute an increase in a regulation’s stringency with respect to
compliance.  First, as mentioned in the preamble to the Credible
Evidence rule (62 FR 8326, February 24, 1997), an emissions standard’s
required stringency is unaffected by the frequency of monitoring given
no decrease in averaging time or emissions limitation.  Secondly, data
from improved monitoring will provide a facility operator better
information on control measure performance more quickly and allow for
reducing the duration and the number of periods that may lead to
compliance problems.  Reducing the duration of excess emissions periods,
for example, with improved monitoring is not an increase in regulatory
stringency but a decrease in enforcement liability.  

	The second aspect to the comment is questioning whether we can issue
technical information about improved monitoring as guidance without
applying it to a Federal Register notice and comment process.  We
disagree with commenters who believe that our developing and
disseminating technical resource information is limited to notice and
comment rulemaking.  We note that making technical and other information
materials available to the public, states, and industry is an important
Agency function.  There are many examples of the Agency dispensing such
information including the Monitoring Knowledge Base (  HYPERLINK
"http://cfpub.epa.gov/mkb/"  http://cfpub.epa.gov/mkb/ ) that provides
just such information on improved monitoring.  On the other hand, we
agree with commenters that any significant change to an existing
regulation, including the addition of new monitoring requirements, would
be subject to notice and comment rulemaking.  To the extent that States
determine the need for changing existing or developing new regulations,
public notice and comment rulemaking is appropriate.  Our role in
developing technical resources and information informing the states in
developing those revised or new regulations does not require, nor should
be subject to the rulemaking process.  In that light, we recognize the
value in obtaining and responding to public comments and suggestions on
informative technical materials.  Further, we believe rulemaking is not
necessarily required for source owners or operators who volunteer to
participate in an optional improved monitoring program, such as the one
mentioned in the proposal.  That program seeks to provide SIP credits to
States where source owners or operators agree to improve their PM
monitoring approaches.  We plan on continuing to prepare and offer
non-regulatory incentives for source owners and operators who volunteer
to improve existing monitoring.  

3.	Study of Improved Monitoring-Induced Emissions Reductions

	Comment:  Commenters recommended that the proposal’s theoretical
study showing PM emissions reductions from the use of improved
monitoring needs to be validated with field data.  

	Response:  We agree with commenters that one should base any costs and
benefits findings as well as validating the approach on available data. 
To the extent that this applies to assessing the benefits of emissions
reductions achieved through improved monitoring, we requested that
commenters provide data or leads to other information or to other
alternatives that show how improved monitoring yields emissions
reductions and ways to quantify possible PM credits for SIPs.  In fact,
we are disappointed that commenters failed to provide these data or
examples of other approaches.  As resources allow, we will investigate
opportunities for field validation of the theoretical study, as well as
other means to offer incentives for use of improved monitoring.	

N.	Guidance Specific to Tribes

a.	Background.  

	The proposal set forth guidance for Tribes regarding various aspects of
air quality management, and this guidance remains largely the same as
described in the section below. 

b.	Final Rule.  

	The 1998 Tribal Authority Rule (TAR) (40 CFR part 49), which implements
section 301(d) of the CAA, gives Tribes the option of developing tribal
implementation plans (TIPs).  Specifically, the TAR provides for the
Tribes to be treated in the same manner as a State in implementing
sections of the CAA.  However, Tribes are not required to develop
implementation plans.  The EPA determined in the TAR that it was
inappropriate to treat Tribes in a manner similar to a State with regard
to specific plan submittal and implementation deadlines for
NAAQS-related requirements, including, but not limited to, such
deadlines in CAA sections 110(a)(1), 172(a)(2), 182, 187, and 191. (Add
footnote)  See 40 CFR 49.4(a). In addition, EPA determined it was not
appropriate to treat tribes similarly to states with respect to
provisions of the CAA requiring as a condition of program approval the
demonstration of criminal enforcement authority or providing for the
delegation of such criminal enforcement authority.  See   40 CFR
49.4(g).  To the extent a tribe is precluded from asserting criminal
enforcement authority, the Federal government will exercise primary
criminal enforcement responsibility.  See 40 CFR 49.8.  In such
circumstances, tribes seeking approval for CAA programs provide
potential investigative leads to an appropriate federal enforcement
agency. (end footnote)

If a Tribe elects to do a TIP, we will work with the Tribe to develop an
appropriate schedule which meets the needs of the Tribe, and which does
not interfere with the attainment of the NAAQS in other jurisdictions. 
The Tribe developing a TIP can work with the EPA Regional Office on the
appropriateness of addressing RFP and other substantive SIP requirements
that may or may not be appropriate for the Tribe’s situation.

The TAR indicates that EPA is ultimately responsible for implementing
CAA programs in Indian country, as necessary and appropriate, if Tribes
choose not to implement those provisions.  For example, an unhealthy air
quality situation in Indian country may require EPA to develop a FIP to
reduce emissions from sources on the reservation.  In such a situation,
EPA, in consultation with the Tribe and in consideration of their needs,
would work to ensure that the NAAQS are met as expeditiously as
practicable.  Likewise, if we determine that sources in Indian country
could interfere with a larger nonattainment area meeting the NAAQS by
its attainment date, we would develop a FIP for those sources in
consultation with the Tribe, as necessary or appropriate.

The TAR also provides flexibility for the Tribe in the preparation of a
TIP to address the NAAQS.  If a Tribe elects to develop a TIP, the TAR
offers flexibility to Tribes to identify and implement on a
Tribe-by-Tribe, case-by-case basis only those CAA programs or program
elements needed to address their specific air quality problems.  In the
proposed Tribal rule, we described this flexible implementation approach
as a modular approach.  Each Tribe may evaluate the particular
activities, including potential sources of air pollution within the
exterior boundaries of its reservation (or within non-reservation areas
for which it has demonstrated jurisdiction), which cause or contribute
to its air pollution problem.  A Tribe may adopt measures for
controlling those sources of PM2.5-related emissions, as long as the
elements of the TIP are reasonably severable from the package of
elements that can be included in a whole TIP.  A TIP must include
regulations designed to solve specific air quality problems for which
the Tribe is seeking EPA approval, as well as a demonstration that the
Tribal air agency has the authority from the Tribal government to
develop and run their program, the capability to enforce their rules,
and the resources to implement the program they adopt.  In addition, the
Tribe must receive an eligibility determination from EPA to be treated
in the same manner as a State and to receive authorization from EPA to
run a CAA program.

 The EPA would review and approve, where appropriate, these partial TIPs
as one step of an overall air quality plan to attain the NAAQS.  A Tribe
may step in later to add other elements to the plan, or EPA may step in
to fill gaps in the air quality plan as necessary or appropriate.  In
approving a TIP, we would evaluate whether the plan interferes with the
overall air quality plan for an area when Tribal lands are part of a
multi-jurisdictional area.

Because many of the nonattainment areas will include multiple
jurisdictions, and in some cases both Tribal and

State jurisdictions, it is important for the Tribes and the States to
work together to coordinate their planning efforts.  States need to
incorporate Tribal emissions in their base emission inventories if
Indian country is part of an attainment or nonattainment area.  Tribes
and States need to coordinate their planning activities as appropriate
to ensure that neither is adversely affecting attainment of the NAAQS in
the area as a whole.

c.	Comments and Responses

	No public comments were received on this section.

O.	Enforcement and Compliance

a.  Background.

	The proposed rule included a discussion of the specific requirements
that must be addressed in order for SIP regulations to be enforceable.  

b.	Final Rule.

	The final rule includes similar guidance on enforceable SIP
regulations, with some additional discussion about specific elements
that must be addressed regarding compliance testing and compliance
monitoring.  (Note that enforceable SIP regulations may address these
key elements in different ways depending on the type of source category
being regulated.)  

	In general, for a SIP regulation to be enforceable, it must clearly
spell out which sources or source types are subject to its requirements
and what its requirements (e.g., emission limits, work practices, etc.)
are.  The regulation also needs to specify the time frames within which
these requirements must be met, and must definitively state
recordkeeping and monitoring requirements appropriate to the type of
sources being regulated.  The recordkeeping and monitoring requirements
must be sufficient to enable the State or EPA to determine whether the
source is complying with the emission limit on a continuous basis.  An
enforceable regulation must also contain test procedures in order to
determine whether sources are in compliance.

	Complete and effective regulations that ensure compliance with an
applicable emissions limit must include requirements for both
performance testing of emissions and ongoing monitoring of the
compliance performance of control measures.  SIP regulations must
include the following critical elements of regulatory compliance
testing:

Indicator(s) of compliance - the pollutant or pollutants of interest
(e.g., filterable PM2.5 plus condensable PM2.5) and the applicable
measurable units for expressing compliance (e.g., ng/J of heat input,
lb/hr); 

Test method - reference to a specific EPA or other published set of
sample collection and analytical procedures, equipment design and
performance criteria, and the calculations providing data in units of
the indicator of compliance (see section II.P.4 below for descriptions
of available and potential improved test methods); 

Averaging time - the minimum length of each required test run and the
requirement to average the results of the test runs (e.g., three runs)
representing a specified period of time (e.g., 8 hours); and 

Frequency - the maximum time between conduct of emissions or performance
tests (e.g., within 30 days of facility start-up and once each
successive quarter, every 6-month period, yearly).  

	In order to be complete with regard to compliance monitoring
provisions, SIP regulations must include the following critical
elements:

  SEQ CHAPTER \h \r 1 Indicator(s) of performance - the parameter or
parameters measured or observed for demonstrating proper operation of
the pollution control measures or compliance with the applicable
emissions limitation or standard.  Indicators of performance may include
direct or predicted emissions measurements, process or control device
(and capture system) operational parametric values that correspond to
compliance with efficiency or emissions limits, and recorded findings of
verification of work practice activities, raw material or fuels
pollutant content, or design characteristics.  Indicators may be
expressed as a single maximum or minimum value, a function of process
variables (e.g., within a range of pressure drops), a particular
operational or work practice status (e.g., a damper position, completion
of a waste recovery task), raw material or fuel pollutant content, or an
interdependency between two or more variables;

Measurement technique - the means used to gather and record information
of or about the indicators of performance.  The components of the
measurement technique include the detector type or analytical method,
location and installation specifications, inspection procedures, and
quality assurance and quality control measures.  Examples of measurement
approaches include continuous emissions monitoring systems, continuous
opacity monitoring systems, continuous parametric monitoring systems,
performance testing, vendor or laboratory analytical data, and manual
inspections and data collection that include making records of process
conditions, raw materials or fuel specifications, or work practices;

Monitoring frequency - the number of times to obtain and record
monitoring data over a specified time interval.  Examples of monitoring
frequencies include at least one data value every 15 minutes for
continuous emissions or parametric monitoring systems, at least every 10
seconds for continuous opacity monitoring systems, upon receipt or
application of raw materials or fuel to the process, and at least once
per operating day (or week, month, etc.) for performance testing, work
practice verification, or equipment design inspections; and 

Averaging time - the period over which to average and use data to verify
compliance with the emissions limitation or standard or proper operation
of the pollution control measure.  Examples of averaging time include a
3-hour average in units of the emissions limitation, a 30-day rolling
average emissions value, a daily average of a control device operational
parametric range, periodic (e.g., monthly, annual) average of raw
materials or fuel pollutant content, and an instantaneous alarm.

These regulatory elements are essential for effective implementation of
the rules and clear and enforceable applicable requirements.  We believe
that approval of regulations implementing the SIPs must ensure that
these critical elements are present and clearly defined to be
approvable.  We reiterate that the compliance obligations, including
emissions limits and other applicable requirements, must be
representative of and accountable to the assumptions used in the SIP
demonstration.  This accountability includes the ability to transfer the
applicable regulatory requirements to an operating permit subject to EPA
and public review. 

Under the Title V regulations, sources have an obligation to include in
their Title V permit applications all emissions for which the source is
major and all emissions of regulated air pollutants.  The definition of
regulated air pollutant in 40 CFR 70.2 includes any pollutant for which
a NAAQS has been promulgated, which would include both PM10 and PM2.5. 
To date, some permitted entities have been using PM10 emissions as a
surrogate for PM2.5 emissions.  Upon promulgation of this rule, EPA will
no longer accept the use of PM10 as a surrogate for PM2.5.  Thus,
sources will be required to include their PM2.5 emissions in their Title
V permit applications, in any corrections or supplements to these
applications, and in applications submitted upon modification and
renewal.  The degree of quantification of PM2.5 emissions required will
depend on the types of determinations that a permitting authority needs
to address for a particular source, the requirements of title V, and the
informational needs and requirements of the particular State in
question.  Sources must continue to describe their PM10 emissions in
their applications as indicated above because the original PM10 NAAQS
remains in effect.

c.	Comments and Responses

	Comment:  One commenter disagreed with language in the preamble to the
proposal regarding Title V permitting requirements and the requirement
to include various emissions information in title V permit applications.
 As described in 40 CFR 70.5(c)(3)(i) and 71.5(c)(3)(i), sources are
required to include in their permit applications all emissions for which
the source is major and all emissions of regulated air pollutants.  In
the preamble to the proposal, the EPA stated that in the past some
permitted entities have been using PM10 emissions as a surrogate for
PM2.5 emissions in permit applications, or in corrections or supplements
to applications.  The EPA stated that upon promulgation of this rule,
the EPA will no longer accept the use of PM10 as a surrogate for PM2.5. 
 

	The commenter disagreed with language in the proposal stating that
sources would be required to detail or quantify PM2.5 emissions in
permit applications, or in corrections or supplements to applications. 
The commenter asserts that the inclusion of PM2.5 emissions information
is required in a Title V permit application only if there is an
applicable requirement in existence for which the source’s
applicability is in question and cited to various examples from the
memorandum entitled “White Paper for Streamlined Development of Part
70 Permit Applications,” from Lydia N. Wegman, Deputy Director, Office
of Air Quality Planning and Standards, to Air Division Directors,
Regions I-X, dated July 10, 1995.  

	Response:  The commenter is concerned that as a result of this rule all
applications (including initial, modification, and renewal applications)
will need to include a quantification of PM2.5 emissions, and that a
State will request that every source supplement or correct any existing
title V application in order to provide an estimation of PM2.5 emissions
at the source.  

	The EPA is not implying that this is the case.  The degree of
quantification of PM2.5 emissions required in an application (including
an initial, modification, or renewal application), or in a correction or
supplement to an existing application, depends on the types of
determinations that a permitting authority needs to address for a
particular source, the requirements of title V, and the informational
needs and requirements of the particular State in question.  For
example, if a source which emits PM2.5 emissions has submitted a title V
application, but a draft permit has not yet been issued, then the source
is required to submit information relative to the quantification of its
PM2.5 emissions if such information is needed or requested and it has
not previously submitted such information.  See 40 CFR 70.5(b) and
71.5(b).  

	Circumstances necessitating the quantification of PM2.5 emissions and
the submittal of this information include: (1) determining all of the
pollutants for which a source is major; (2) determining whether an
applicable requirement or program applies, e.g., determining the
applicability of a SIP requirement or a PSD or nonattainment NSR
program, etc.; or (3) determining what fees a source owes a permitting
authority as a result of considering PM2.5 emissions.  

In all circumstances, however, a State may require that a source
quantify its PM2.5 emissions information in an application, supplement,
or correction, even if it not needed for the particular determination at
issue.  The State, for example, may choose to obtain this information
for air quality planning purposes, developing emission inventories, or
for other purposes related to its air quality management goals. 
Requesting such emissions information is an option for any title V
permitting authority.  

The “White Paper for Streamlined Development of Part 70 Permit
Applications,” referenced by the commenter, was a confirmation of EPA
policy with respect to the fact that the specificity of emissions
quantification can vary significantly, depending on the circumstances of
a particular source.  It is also important to note that this guidance
document is a statement regarding the range of discretion available to
permitting authorities in implementing the emissions quantification
requirement, not a restriction of that discretion to minimum practices. 
Thus, States can implement this guidance document at their option,
either in part or in its entirety.  

	In summary, the purpose of the statements made in the preamble to the
proposal was to notify sources that as of the promulgation of this final
rule, the EPA will no longer accept the use of PM10 emissions
information as a surrogate for PM2.5 emissions information given that
both pollutants are regulated by a National Ambient Air Quality Standard
and therefore are considered regulated air pollutants.  See the
definition of regulated air pollutant in 40 CFR 70.2 and 71.2.  The
degree of quantification of PM2.5 emissions now required in an
application (including an initial, modification, or renewal
application), or provided in a correction or supplement to an existing
application, will depend on the types of determinations that a
permitting authority needs to address for a particular source, the
requirements of title V, and the informational needs and requirements of
the particular State in question.  

P.	Emergency episodes

a. 	Background.

In the proposal, we noted that subpart H of 40 CFR part 51 specifies
requirements for SIPs to address emergency air pollution episodes and
for preventing air pollutant levels from reaching levels determined to
cause significant harm to the health of persons.  We noted that we
anticipate proposing a separate rulemaking in the future to update
portions of that rule.

The preamble to the proposal 

b.  	Final Rule.

	We have not yet proposed any rule revision related to emergency
episodes.

c.	Comments and Responses.

	We received no comments on this section of the proposal.

Q.	Ambient monitoring

a. 	Background.

	Ambient air quality monitoring for PM2.5 plays an important role in
identifying areas violating the NAAQS, control strategy development, and
tracking progress to attainment.  We indicated in the proposal that
States are required to monitor PM2.5 mass concentrations using Federal
Reference Method devices to determine compliance with the NAAQS.  We did
not propose any revisions to current ambient monitoring requirements
listed in 40 CFR part 58.  

Currently, there are more than 1200 FRM monitors located across the
country.  States will need to maintain monitors in designated
nonattainment areas in order to track progress toward attainment and
ultimately determine whether the area has attained the PM2.5 standards.

In addition to the FRM network, EPA and the States have also deployed
more than 250 speciation monitoring sites around the country to sample
for chemical composition of PM2.5.  The data provided from these
speciation monitors are invaluable in identifying contributing source
categories and developing control strategies to reach attainment. 
Source apportionment and other receptor modeling techniques rely on the
detailed data on species, ions, and other compounds obtained from
chemical analysis.  Analyses of rural versus urban sites to identify
which PM2.5 components comprise the “urban excess” (urban minus
rural levels) portion of PM2.5 mass also rely on data from speciation
monitors.  The EPA encourages states to expand their data analysis
efforts using the wealth of information provided from the speciation
monitoring network.

b.	Final Rule.

	There is no change from the proposal.  We are not promulgating any
additional monitoring requirements as part of this rulemaking.  Revised
monitoring regulations were issued in 2006 along with the revised PM
NAAQS.  

c.	Comments and Responses.

	There were no comments on this section.  

III.	STATUTORY AND EXECUTIVE ORDER REVIEWS

A.	Executive Order 12866:  Regulatory Planning and Review

  SEQ CHAPTER \h \r 1 Under section 3(f)(1) of Executive Order (EO)
12866 (58 FR 51735, October 4, 1993), this action is an “economically
significant regulatory action.”  Implementation of the PM2.5 NAAQS is
likely to have an annual effect on the economy of $100 million or more. 
Accordingly, EPA submitted this action to the Office of Management and
Budget (OMB) for review under EO 12866 and any changes made in response
to OMB recommendations have been documented in the docket for this
action.  For clarity, we note that the estimated costs and benefits of
implementing the 1997 PM2.5 NAAQS are not created by this rule, because
the Clean Air Act requires state implementation of the 1997 PM2.5
standards (through state development of plans with enforceable
requirements for sources) on a statutory timetable regardless of whether
EPA issues this rule interpreting the statutory requirements.  The rule
reflects the statutory requirements.

As part of the “Regulatory Impact Analysis for Particulate Matter
National Ambient Air Quality Standards (September 2006),” EPA prepared
an assessment of the estimated costs and benefits associated with
attaining the 1997 PM2.5 NAAQS in 2015, incremental to currently
promulgated federal and state programs including for example the Clean
Air Interstate Rule, the Nonroad Diesel Rule, and other programs.  This
analysis is included as Appendix A of the report and is available in the
docket for this action and on EPA’s website at:    HYPERLINK
"http://www.epa.gov/ttn/ecas/regdata/RIAs/Appendix%20A--2015%20Analysis.
pdf" 
http://www.epa.gov/ttn/ecas/regdata/RIAs/Appendix%20A--2015%20Analysis.p
df .  This illustrative analysis finds that the estimated monetized
benefits of attaining the 1997 standards in 2015 are between $43 billion
and $97 billion annually, and the estimated monetized costs are $6.7
billion annually.  The RIA states: “Note that because this analysis
was intended to compare costs and benefits of attaining alternative
standards by fixed dates, it did not attempt to identify for each
designated PM2.5 area measures that may be needed to meet subpart 1
Clean Air Act requirements, such as reasonably available measures and
attainment as expeditiously as practicable.  It is expected that
additional costs and benefits will begin to accrue in earlier years as
states comply with these requirements.” (RIA, p. 1-4)  

B.	Paperwork Reduction Act

The information collection requirements in this rule have been submitted
for approval to the Office of Management and Budget (OMB) under the
Paperwork Reduction Act, 44 U.S.C. 3501 et seq.  In a separate Federal
Register notice published today, EPA is requesting comment on the
information collection requirements of this rule.  The information
collection requirements are not enforceable until OMB approves them.  

	The data collected from the State or local air agency respondents will
include the required SIP elements prescribed in CAA sections 110 and
part D, subpart 1 of title I for Implementation plans and the
requirements in this Implementation Rule (40 CFR 51.1000 – 51.1012). 
The PM2.5 SIP will contain rules and other requirements designed to
achieve the NAAQS by the deadlines established under the CAA, and it
also contains a demonstration that the State’s requirements will in
fact result in attainment.  The SIP must meet the requirements in
subpart 1 to adopt RACM, RACT, and provide for RFP toward attainment for
the period prior to the area’s attainment date.  

The Agency anticipates additional administrative burden during the 3
year period of the ICR for State governments and the Agency of 630,000
hours and 69,300 hours, respectively.  Fifty percent of the hours are
expended in the first year with the remainder evenly divided between the
second and third years of the ICR period.  Tribes are not required to
conduct attainment demonstrations or submit the RFP, RACT, or RACM
requirements.  

The present value of the total additional costs for State government
respondents is estimated at $33.4 million for the 3 year period.  On an
equivalent annual basis that is $12.7 million per year during the 3 year
period of the ICR.  The present value of the Agency administrative cost
burden is estimated at $3.7 million dollars for the 3 year period.  This
is equivalent to an equal annual stream of costs of $1.4 million per
year during the three year period. 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.  When this ICR is approved by
OMB, the Agency will publish a technical amendment to 40 CFR part 9 in
the Federal Register to display the OMB control number for the approved
information collection requirements contained in this final rule.

C.	Regulatory Flexibility Act

	The Regulatory Flexibility Act (RFA) generally requires an agency to
prepare a regulatory flexibility analysis of any rule subject to notice
and comment rulemaking requirements under the Administrative Procedure
Act or any other statute unless the agency certifies that the rule will
not have a significant economic impact on a substantial number of small
entities.  Small entities include small businesses, small organizations,
and small governmental jurisdictions.  

For purposes of assessing the impacts of this final action 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 that is independently owned and operated and
is not dominant in its field.

	After considering the economic impacts of this final rule on small
entities, I certify that this action will not have a significant
economic impact on a substantial number of small entities and it is not
necessary to prepare a regulatory flexibility analysis in conjunction
with this final rule.  The final rule governing SIPs will not directly
impose any requirements on small entities.  Rather, this rule interprets
the obligations established in the CAA for States to submit
implementation plans in order to attain the PM2.5 NAAQS. 

D. 	Unfunded Mandates Reform Act  tc \l2 "Unfunded Mandates Reform Act 

	Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public Law
104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and Tribal
governments and the private sector.  Under section 202 of the UMRA, 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
1 year.  Before promulgating an EPA rule for which a written statement
is needed, EPA is required by section 205 of the UMRA 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.

	This rule contains no Federal mandate that may result in expenditures
of $100 million or more for State, local, and Tribal governments, in the
aggregate, or the private sector in any 1 year.  The estimated
administrative burden hours and costs associated with implementing the
PM2.5 NAAQS are estimated in the ICR for this rule.  The estimated costs
presented there for States totals $33.4 million for a three-year period.
 Thus, this rule is not subject to the requirements of section 202 and
205 of the UMRA.  The EPA consulted with governmental entities affected
by this rule and has determined that this rule contains no regulatory
requirements that may significantly or uniquely affect small
governments, including Tribal governments.  

	The CAA imposes the obligation for States to submit SIPs to implement
the PM2.5 NAAQS.  In this rule, EPA is merely providing an
interpretation of those requirements.  However, even if this rule did
establish an independent requirement for States to submit SIPs, it is
questionable whether a requirement to submit a SIP revision would
constitute a Federal mandate in any case.  The obligation for a State to
submit a SIP that arises out of section 110 and section 172 (part D) of
the CAA is not legally enforceable by a court of law, and at most is a
condition for continued receipt of highway funds.  Therefore, it is
possible to view an action requiring such a submittal as not creating
any enforceable duty within the meaning of section 421(5)(9a)(I) of UMRA
(2 U.S.C. 658(a)(I)).  Even if it did, the duty could be viewed as
falling within the exception for a condition of Federal assistance under
section 421(5)(a)(i)(I) of UMRA (2 U.S.C. 658(5)(a)(i)(I)).

E.  Executive Order 13132: Federalism  tc \l2 "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 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.”

	 At the time of proposal, EPA concluded that the proposed rule would
not have any federalism implications.  The EPA stated that the proposed
rule would not have substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government, as specified in Executive Order 13132.  The CAA establishes
the scheme whereby States take the lead in developing plans to meet the
NAAQS.  This rule clarifies the statutory obligations of States in
implementing the PM2.5 NAAQS.  However, EPA recognized that States would
have a substantial interest in this rule and any corresponding revisions
to associated SIP requirements.  

Therefore, in the spirit of Executive Order 12132, and consistent with
EPA policy to promote communications between EPA and State and local
governments, EPA held a number of calls with representatives of State
and local air pollution control agencies and hosted a public hearing in
Washington, DC in November 2005. The EPA considered the comments from
State and local governments in developing the final rule.

	EPA concludes that this final rule does not have federalism
implications, for the reasons proposed.  The final rule will not modify
the relationship of the States and EPA for purposes of developing
programs to implement the NAAQS.  As noted above in section D on UMRA,
this rule does not impose significant costs on State and local
governments.  (EPA estimates the costs to States to implement the PM2.5
NAAQS to be $33.4 million.)  Thus, Executive Order 13132 does not apply
to this rule.

F.	Executive Order 13175: Consultation and Coordination with Indian
Tribal Governments  tc \l2 "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 defined in Executive Order 13175.  This rule concerns
the requirements for State and tribal implementation plans for attaining
the PM2.5 air quality standards.  The CAA provides for States to develop
plans to regulate emissions of air pollutants within their
jurisdictions.  The Tribal Air Rule (TAR) under the CAA gives Tribes the
opportunity to develop and implement CAA programs such as programs to
attain and maintain the PM2.5 NAAQS, but it leaves to the discretion of
the Tribe the decision of whether to develop these programs and which
programs, or appropriate elements of a program, they will adopt. 

Although Executive Order 13175 does not apply to this rule, EPA did
reach out to Tribal leaders and environmental staff in developing this
rule.  From 2001 – 2004, the EPA supported a National Designations
Workgroup to provide a forum for tribal professionals to give input to
the designations process.  In 2006, EPA supported a national "Tribal Air
call" which provides an open forum for all Tribes to voice concerns to
EPA about the NAAQS implementation process, including the PM2.5 NAAQS. 
In these meetings, EPA briefed call participants and Tribal
environmental professionals gave input as the rule was under
development. Furthermore, in December 2005, EPA sent individualized
letters to all federally recognized Tribes about the proposal to give
Tribal leaders the opportunity for consultation.   

	This final rule does not have Tribal implications as defined by
Executive Order 13175.  It does not have a substantial direct effect on
one or more Indian Tribes, since no Tribe has implemented a CAA program
to attain the PM2.5 NAAQS at this time.  The EPA notes that even if a
Tribe were implementing such a plan at this time, while the rule might
have Tribal implications with respect to that Tribe, it would not impose
substantial direct costs upon it, nor would it preempt Tribal law.

	Furthermore, this rule does not affect the relationship or distribution
of power and responsibilities between the Federal government and Indian
Tribes.  The CAA and the TAR establish the relationship of the Federal
government and Tribes in developing plans to attain the NAAQS, and this
rule does nothing to modify that relationship.  As this rule does not
have Tribal implications, Executive Order 13175 does not apply.

G.	Executive Order 13045: Protection of Children from Environmental
Health and Safety Risks tc \l2 "Executive Order 13045: Protection of
Children from Environmental Health and Safety Risks 

	EO 13045, “Protection of Children from Environmental Health and
Safety Risks,” (62 FR 19885, April 23, 1997) applies to any rule that
(1) is determined to be “economically significant” as defined under
Executive Order 12866, and (2) concerns an environmental health or
safety risk that EPA has reason to believe may have 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 subject to EO 13045 because it is economically
significant as defined in EO 12866, and we believe that the
environmental health risk addressed by this action may have a
disproportionate effect on children.  This rule implements a previously
promulgated health-based Federal standard – the PM2.5 NAAQS. The NAAQS
constitute uniform, national standards for PM pollution; these standards
are designed to protect public health with an adequate margin of safety,
as required by CAA section 109.  However, the protection offered by
these standards may be especially important for children because
children, along with other sensitive population subgroups such as the
elderly and people with existing heart or lung disease, are potentially
susceptible to health effects resulting from PM exposure.  Because
children are considered a potentially susceptible population, we have
carefully evaluated the environmental health effects of exposure to PM
pollution among children.  These effects and the size of the population
affected are summarized in section 9.2.4 of the Criteria Document and
section 3.5 of the Staff Paper.

 H. 	Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use tc \l2 "Executive Order 13211: Actions That
Significantly Affect Energy Supply, Distribution, or Use 

	This final rule is not a “significant energy action” as defined in
Executive Order 13211, “Actions 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.  This rule is not a “significant
energy action,” because it does not establish requirements that
directly affect the general public and the public and private sectors,
but, rather, interprets the statutory requirements that apply to States
in preparing their SIPs.  The SIPs themselves will likely establish
requirements that directly affect the general public, and the public and
private sectors.

I.	National Technology Transfer Advancement Act tc \l2 "National
Technology Transfer Advancement Act 

	Section 12(d) of the National Technology Transfer Advancement Act of
1995 (“NTTAA”), Public Law No. 104-113, section 12(d) (15 U.S.C. 272
note) directs EPA to use voluntary consensus standards (VCS) 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 VCS bodies.  The NTTAA directs EPA to provide Congress,
through OMB, explanations when the Agency decides not to use available
and applicable VCS.

This final rulemaking does not involve technical standards.  Therefore,
EPA is not considering the use of any VCS. The EPA will encourage the
States and Tribes to consider the use of such standards, where
appropriate, in the development of their implementation plans. tc \l2
"Executive Order 12898: Federal Actions to Address Environmental Justice
in Minority Populations and Low-Income Populations 

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

	EO 12898 (59 FR 7629 (Feb. 16, 1994) establishes Federal executive
policy on environmental justice.  Its main provision directs Federal
agencies, to the greatest extent practicable and permitted by law, to
make environmental justice part of their mission by identifying and
addressing, as appropriate, disproportionately high and adverse human
health or environmental effects of their programs, polices and
activities on minority populations and low-income populations in the
United States. 

	The EPA has determined that the final rule should not have
disproportionately high and adverse human health or environmental
effects on minority or low-income populations because it increases the
level of environmental protection for all affected poplations without
having any disproportionately high and adverse human health or
environmental effects on any population, including any minority or
low-income population.  The health and environmental risks associated
with fine particles were considered in the establishment of the PM2.5
NAAQS.  The level is designed to be protective with an adequate margin
of safety.  This final rule provides a framework for improving
environmental quality and reducing health risks for areas that may be
designated nonattainment.

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 to the United
State.  The EPA will submit a report containing the 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). 
This rule will be effective [INSERT DATE 60 DAYS FROM PUBLICATION].	

J.	Petitions for Judicial Review tc \l2 "L.  Petitions for Judicial
Review 

	Under section 307(b)(1) of the Act, petitions for judicial review of
this action must be filed in the United States Court of Appeals for the
District of Columbia Circuit by [INSERT DATE 60 DAYS FROM DATE OF
PUBLICATION].  Filing a petition for reconsideration by the
Administrator of this final rule does not affect the finality of this
rule for the purposes of judicial review nor does it extend the time
within which a petition for judicial review may be filed, and shall not
postpone the effectiveness of such 

rule or action.  This action may not be challenged later in proceedings
to enforce its requirements.  See Act section 307(b)(2).

K.	Judicial Review

	Under sections 307(d)(1)(E) and 307(d)(1)(V) of the CAA, the
Administrator determines that this action is subject to the provisions
of section 307(d).  Section 307(d)(1)(V) provides that the provisions of
section 307(d) apply to "such other actions as the Administrator may
determine."  While the Administrator did not make this determination
earlier, the Administrator believes that all of the procedural
requirements, e.g., docketing, hearing and comment periods, of section
307(d) have been complied with during the course of this rulemaking.

Page 487 of 508 

Clean Air Fine Particle Implementation Rule

List of Subjects in 40 CFR Part 51

Administrative practice and procedure, Air pollution control,
Intergovernmental relations, Nitrogen dioxide, Ozone, Particulate
matter, Sulfur oxides, Transportation, Volatile organic compound.

________________________________

Date

_______________________________

Stephen L. Johnson,

Administrator.

For the reasons set out in the preamble, title 40 ,   chapter I of the
Code of Federal Regulations is amended as follows:

1.  The authority citation for part 51 continues to read as follows: 
Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

2.  A new Subpart Y is added to read as follows:

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

Section

51.1000	Definitions.

51.1001	Applicability of part 51. 

51.1002  	Submittal of State implementation plan.

51.1003  	Classifications.

51.1004  	Attainment dates.

51.1005  	One-year extensions of the attainment date.

51.1006	Redesignation to nonattainment following initial designations
for the PM2.5 NAAQS.

51.1007  	Attainment demonstration and modeling requirements.

51.1008  	Emission inventory requirements for the PM2.5 NAAQS.

51.1009  	Reasonable further progress (RFP) requirements. 

51.1010  	Requirements for reasonably available control technology
(RACT) and reasonably available control measures (RACM) 

51.1011	Requirements for mid-Course review.

51.1012.	Requirements for contingency measures

§51.1000	Definitions.

The following definitions apply for purposes of this subpart.  Any term
not defined herein shall have the meaning as defined in 40 CFR 51.100.

(a) Act means the Clean Air Act as codified at 42 U.S.C. 7401-7671q.
(2003).

(b) Attainment date means the date by which an area, under an approved
State implementation plan, is required to attain the PM2.5 NAAQS (based
on the average of three consecutive years of ambient air quality data).

(c) Baseline year inventory for the RFP plan is the emissions inventory
for the year also used as the base year for the attainment
demonstration.  

(d) Benchmark RFP plan means the reasonable further progress plan that
requires generally linear emission reductions in pollutants from the
baseline emissions year through the milestone inventory year.

(e) Date of designation means the effective date of the PM2.5 area
designation as promulgated by the Administrator. 

(f) Direct PM2.5 emissions means solid particles emitted directly from
an air emissions source or activity, or gaseous emissions or liquid
droplets from an air emissions source or activity which condense to form
particulate matter at ambient temperatures.  Direct PM2.5 emissions
include elemental carbon, directly emitted organic carbon, directly
emitted sulfate, directly emitted nitrate, and other inorganic particles
(including but not limited to crustal material, metals, and sea salt).

(g) Existing control measure means any Federally enforceable national,
State, or local control measure that has been approved in the SIP and
that results in reductions in emissions of PM2.5 or PM2.5 precursors in
a nonattainment area. 

(h) Full implementation inventory is the projected RFP emission
inventory for the year preceding the attainment date, representing a
level of emissions that demonstrates attainment.

(i) Milestone year inventory is the projected RFP emission inventory for
the applicable RFP milestone year (i.e. 2009 and, where applicable,
2012).

(j) PM2.5 NAAQS means the particulate matter national ambient air
quality standards (annual and 24-hour) codified at 40 CFR 50.7.

(k) PM2.5 design value for a nonattainment area is the highest of the
three-year average concentrations calculated for the monitors in the
area, in accordance with 40 CFR part 50, appendix N.

(l) PM2.5 attainment plan precursor means SO2 and those other PM2.5
precursors emitted by sources in the State which the State must evaluate
for emission reduction measures to be included in its PM2.5
nonattainment area or maintenance area plan. 

(m) PM2.5 precursor means those air pollutants other than PM2.5 direct
emissions that contribute to the formation of PM2.5.  PM2.5 precursors
include SO2, NOx, volatile organic compounds, and ammonia. 

(n) Reasonable further progress (RFP) means the incremental emissions
reductions toward attainment required under sections 172(c)(2) and
171(1). 

(o) Subpart 1 means the general attainment plan requirements found in
subpart 1 of part D of title I of the Act.

§51.1001	Applicability of Part 51.  

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

§51.1002	Submittal of State Implementation Plan.

(a) For any area designated by EPA as nonattainment for the PM2.5 NAAQS,
the State must submit a State implementation plan satisfying the
requirements of section 172 of the Act and this subpart to EPA by the
date prescribed by EPA which will be no later than 3 years from the date
of designation.  

(b) The State must submit a plan consistent with the requirements of
section 110(a)(2) of the Act unless the State already has fulfilled this
obligation for the purposes of implementing the PM2.5 NAAQS. 

(c) Pollutants contributing to fine particle concentrations.  The State
implementation plan must identify and evaluate sources of PM2.5 direct
emissions and PM2.5 attainment plan precursors in accordance with
§§51.1009 and 51.1010.  After January 1, 2011, for purposes of
establishing emissions limits under 51.1009 and 51.1010, States must
establish such limits taking into consideration the condensable fraction
of direct PM2.5 emissions.  Prior to this date, States are not
prohibited from establishing source emission limits that include the
condensable fraction of direct PM2.5. 

(1) The State must address sulfur dioxide as a PM2.5 attainment plan
precursor and evaluate sources of SO2 emissions in the State for control
measures.

(2) The State must address NOx as a PM2.5 attainment plan precursor and
evaluate sources of NOx emissions in the State for control measures,
unless the State and EPA provide an appropriate technical demonstration
for a specific area showing that NOx emissions from sources in the State
do not significantly contribute to PM2.5 concentrations in the
nonattainment area.

(3)  The State is not required to address VOC as a PM2.5 attainment plan
precursor and evaluate sources of VOC emissions in the State for control
measures, unless:

(i) the State provides an appropriate technical demonstration for a
specific area showing that VOC emissions from sources in the State
significantly contribute to PM2.5 concentrations in the nonattainment
area, and such demonstration is approved by EPA; or

(ii) The EPA provides such a technical demonstration.

(4)  The State is not required to address ammonia as a PM2.5 attainment
plan precursor and evaluate sources of ammonia emissions from sources in
the State for control measures, unless:

(i) the State provides an appropriate technical demonstration for a
specific area showing that ammonia emissions from sources in the State
significantly contribute to PM2.5 concentrations in the nonattainment
area, and such demonstration is approved by EPA; or

(ii) The EPA provides such a technical demonstration. 

(5) The State must submit a demonstration to reverse any presumption in
this rule for a PM2.5 precursor with respect to a particular
nonattainment area, if the administrative record related to development
of its SIP shows that the presumption is not technically justified for
that area.

§51.1003 [Reserved] 

§51.1004	Attainment dates.  

(a) Consistent with section 172(a)(2)(A) of the Act, the attainment date
for an area designated nonattainment for the PM2.5 NAAQS will be the
date by which attainment can be achieved as expeditiously as
practicable, but no more than five years from the date of designation. 
The Administrator may extend the attainment date to the extent the
Administrator determines appropriate, for a period no greater than 10
years from the date of designation, considering the severity of
nonattainment and the availability and feasibility of pollution control
measures.

(b) In the SIP submittal for each of its nonattainment areas, the State
must submit an attainment demonstration justifying its proposed
attainment date.  For each nonattainment area, the Administrator will
approve an attainment date at the same time the Administrator approves
the attainment demonstration for the area, consistent with the
attainment date timing provision of section 172(a)(2)(A) and paragraph
(a) of this section.

(c) Upon a determination by EPA that an area designated nonattainment
for the PM2.5 NAAQS has attained the standard, the requirements for such
area to submit attainment demonstrations and associated reasonably
available control measures, reasonable further progress plans,
contingency measures, and other planning SIPs related to attainment of
the PM2.5 NAAQS shall be suspended until such time as:  the area is
redesignated to attainment, at which time the requirements no longer
apply; or EPA determines that the area has violated the PM2.5 NAAQS, at
which time the area is again required to submit such plans.  

§51.1005	One-year extensions of the attainment date.

(a) Pursuant to section 172(a)(2)(C)(ii) of the Act, a State with an
area that fails to attain the PM2.5 NAAQS by its attainment date may
apply for an initial 1-year attainment date extension if the State has
complied with all requirements and commitments pertaining to the area in
the applicable implementation plan, and:

 NAAQS as of its attainment date, the annual average concentration for
the most recent year at each monitor is 15.0 μg/m3 or less (calculated
according to the data analysis requirements in 40 CFR part 50, appendix
N).

(2) For an area that violates the 24-hour PM2.5 NAAQS as of its
attainment date, the 98th percentile concentration for the most recent
year at each monitor is 65 μg/m3 or less (calculated according to the
data analysis requirements in 40 CFR part 50, appendix N).

(b) An area that fails to attain the PM2.5 NAAQS after receiving a
1-year attainment date extension may apply for a second 1-year
attainment date extension pursuant to section 172(a)(2)(C)(ii) if the
State has complied with all requirements and commitments pertaining to
the area in the applicable implementation plan, and:

 15.0 μg/m3 or less (calculated according to the data analysis
requirements in 40 CFR part 50, appendix N).

(2) For an area that violates the 24-hour PM2.5 NAAQS as of its
attainment date, the two-year average of annual 98th percentile
concentrations at each monitor, based on the first extension year and
the previous year, is 65 μg/m3 or less (calculated according to the
data analysis requirements in 40 CFR part 50, appendix N).

§51.1006	Redesignation to nonattainment following initial designations
for the PM2.5 NAAQS.

Any area that is initially designated “attainment/unclassifiable”
for the PM2.5 NAAQS may be subsequently redesignated to nonattainment if
ambient air quality data in future years indicate that such a
redesignation is appropriate.  For any such area that is redesignated to
nonattainment for the PM2.5 NAAQS, any absolute, fixed date that is
applicable in connection with the requirements of this part is extended
by a period of time equal to the length of time between the effective
date of the initial designation for the PM2.5 NAAQS and the effective
date of redesignation, except as otherwise provided in this subpart.

§51.1007	Attainment demonstration and modeling requirements.

(a) For any area designated as nonattainment for the PM2.5 NAAQS, the
State must submit an attainment demonstration showing that the area will
attain the annual and 24-hour standards as expeditiously as practicable.
 The demonstration must meet the requirements of (51.112 and Appendix W
of this part and must include inventory data, modeling results, and
emission reduction analyses on which the State has based its projected
attainment date.  The attainment date justified by the demonstration
must be consistent with the requirements of §51.1004(a).  The modeled
strategies must be consistent with requirements in §51.1009 for RFP and
in §51.1010 for RACT and RACM.  The attainment demonstration and
supporting air quality modeling should be consistent with EPA’s PM2.5
modeling guidance.

(b) Required time frame for obtaining emissions reductions.  For each
nonattainment area, the State implementation plan must provide for
implementation of all control measures needed for attainment as
expeditiously as practicable, but no later than the beginning of the
year prior to the attainment date.  Consistent with section 172(c)(1) of
the Act, the plan must provide for implementation of all RACM and RACT
as expeditiously as practicable.  The plan also must include RFP
milestones in accordance with (51.1009, and control measures needed to
meet these milestones, as necessary.

(51.1008	Emission inventory requirements for the PM2.5 NAAQS. 

(a) For purposes of meeting the emission inventory requirements of
section 172(c)(3) of the Act for nonattainment areas, the State shall,
no later than three years after designation:

(1) Submit to EPA Statewide emission inventories for direct PM2.5
emissions and emissions of PM2.5 precursors.  For purposes of defining
the data elements for these inventories, the PM2.5 and PM2.5
precursor-relevant data element requirements under subpart A of this
part shall apply.

(2) Submit any additional emission inventory information needed to
support an attainment demonstration and RFP plan ensuring expeditious
attainment of the annual and 24-hour PM2.5 standards.  

(b) For inventories required for submission under paragraph (a) of this
section, a baseline emission inventory is required for the attainment
demonstration required under §51.1007 and for meeting RFP requirements
under §51.1009.  As determined on the date of designation, the base
year for this inventory shall be the most recent calendar year for which
a complete inventory was required to be submitted to EPA pursuant to
subpart A of this part.  The baseline emission inventory for calendar
year 2002 or other suitable year shall be used for attainment planning
and RFP plans for areas initially designated nonattainment for the PM2.5
NAAQS in 2004-2005.

§51.1009	Reasonable further progress (RFP) requirements. 

(a) Consistent with section 172(c)(2) of the Act, State implementation
plans for areas designated nonattainment for the PM2.5 NAAQS must
demonstrate reasonable further progress as provided in § 51.1009(b)
through (h).  

(b) If the State submits to EPA an attainment demonstration and State
implementation plan for an area which demonstrates that it will attain
the PM NAAQS within five years of the date of designation, the State is
not required to submit a separate RFP plan.  Compliance with the
emission reduction measures in the attainment demonstration and State
implementation plan will meet the requirements for achieving reasonable
further progress for the area. 

(c) For any area for which the State submits to EPA an approvable
attainment demonstration and State implementation plan that demonstrates
the area needs an attainment date of more than five years from the date
of designation, the State also must submit an RFP plan.  The RFP plan
must describe the control measures that provide for meeting the
reasonable further progress milestones for the area, the timing of
implementation of those measures, and the expected reductions in
emissions of direct PM2.5 and PM2.5 attainment plan precursors.  The RFP
plan is due to EPA within three years of the date of designation. 

(1) For any State that submits to EPA an approvable attainment
demonstration and State implementation plan justifying an attainment
date of more than five and less than nine years from the date of
designation, the RFP plan must include 2009 emissions milestones for
direct PM2.5 and PM2.5 attainment plan precursors demonstrating that
reasonable further progress will be achieved for the 2009 emissions
year.  

(2) For any area that submits to EPA an approvable attainment
demonstration and State implementation plan justifying an attainment
date of nine or ten years from the date of designation, the RFP plan
must include 2009 and 2012 emissions milestones for direct PM2.5 and
PM2.5 attainment plan precursors demonstrating that reasonable further
progress will be achieved for the 2009 and 2012 emissions years.  

(d) The RFP plan must demonstrate that in each applicable milestone
year, emissions will be at a level consistent with generally linear
progress in reducing emissions between the base year and the attainment
year.  

(e) For a multi-State nonattainment area, the RFP plans for each State
represented in the nonattainment area must demonstrate RFP on the basis
of common multi-State inventories. The States within which the area is
located must provide a coordinated RFP plan.  Each State in a
multi-State nonattainment area must ensure that the sources within its
boundaries comply with enforceable emission levels and other
requirements that in combination with the reductions planned in other
state(s) will provide for attainment as expeditiously as practicable and
demonstrate reasonable further progress 

(f) In the benchmark RFP plan, the State must identify direct PM2.5
emissions and PM2.5 attainment plan precursors regulated under the PM2.5
attainment plan and specify target emission reduction levels to be
achieved during the milestone years.  In developing the benchmark RFP
plan, the State must develop emission inventory information for the
geographic area included in the plan and conduct the following
calculations:  

(1) For direct PM2.5 emissions and each PM2.5 attainment plan precursor
addressed in the attainment strategy, the full implementation reduction
is calculated by subtracting the full implementation inventory from the
baseline year inventory.

(2) The "milestone date fraction" is the ratio of the number of years
from the baseline year to the milestone inventory year divided by the
number of years from the baseline year to the full implementation year.

(3) For direct PM2.5 emissions and each PM2.5 attainment plan precursor
addressed in the attainment strategy, a benchmark emission reduction is
calculated by multiplying the full implementation reduction by the
milestone date fraction

(4) The benchmark emission level in the milestone year is calculated for
direct PM2.5 emissions and each PM2.5 attainment plan precursor by
subtracting the benchmark emission reduction from the baseline year
emission level.  The benchmark RFP plan is defined as a plan that
achieves benchmark emission levels for direct PM2.5 emissions and each
PM2.5 attainment plan precursor addressed in the attainment strategy for
the area.

(5) In comparing inventories between baseline and future years for
direct PM2.5 emissions and each PM2.5 attainment plan precursor, the
inventories must be derived from the same geographic area. The plan must
include emissions estimates for all types of emitting sources and
activities in the geographic area from which the emission inventories
for direct PM2.5 emissions and each PM2.5 attainment plan precursor
addressed in the plan are derived.

(6) For purposes of establishing motor vehicle emissions budgets for
transportation conformity purposes (as required in 40 CFR part 93) for a
PM2.5 nonattainment area, the State shall include in its RFP submittal
an inventory of on-road mobile source emissions in the nonattainment
area.

(g) The RFP plan due three years after designation must demonstrate that
emissions for the milestone year are either:

(1) At levels that are roughly equivalent to the benchmark emission
levels for direct PM2.5 emissions and each PM2.5 attainment plan
precursor to be addressed in the plan; or 

(2) At levels included in an alternative scenario that is projected to
result in a generally equivalent improvement in air quality by the
milestone year as would be achieved under the benchmark RFP plan.

(h) The equivalence of an alternative scenario to the corresponding
benchmark plan must be determined by comparing the expected air quality
changes of the two scenarios at the design value monitor location.  This
comparison must use the information developed for the attainment plan to
assess the relationship between emissions reductions of the direct PM2.5
emissions and each PM2.5 attainment plan precursor addressed in the
attainment strategy and the ambient air quality improvement for the
associated ambient species.  

§51.1010	Requirements for reasonably available control technology
(RACT) and reasonably available control measures (RACM).

For each PM2.5 nonattainment area, the State shall submit with the
attainment demonstration a SIP revision demonstrating that it has
adopted all reasonably available control measures (including RACT for
stationary sources) necessary to demonstrate attainment as expeditiously
as practicable and to meet any RFP requirements.  The SIP revision shall
contain the list of the potential measures considered by the State, and
information and analysis sufficient to support the State’s judgment
that it has adopted all RACM, including RACT. 

(b) In determining whether a particular emission reduction measure or
set of measures must be adopted as RACM under section 172(c)(1) of the
Act, the State must consider the cumulative impact of implementing the
available measures.  Potential measures that are reasonably available
considering technical and economic feasibility must be adopted as RACM
if, considered collectively, they would advance the attainment date by
one year or more. 

§51.1011	Requirements for mid-course review. 

(a) Any State that submits to EPA an approvable attainment plan for a
PM2.5 nonattainment area justifying an attainment date of nine or ten
years from the date of designation also must submit to EPA a mid-course
review six years from the date of designation.  

(b) The mid-course review for an area must include:

(1) a review of emissions reductions and progress made in implementing
control measures to reduce emissions of direct PM2.5 and PM2.5
attainment plan precursors contributing to PM2.5 concentrations in the
area

(2) an analysis of changes in ambient air quality data for the area

(3) revised air quality modeling analysis to demonstrate attainment

(4) any new or revised control measures adopted by the State, as
necessary to ensure attainment by the attainment date in the approved
SIP of the nonattainment area.  

§51.1012	Requirement for contingency measures

(a) Consistent with section 172(c)(9) of the Act, the State must submit
in each attainment plan specific contingency measures to be undertaken
if the area fails to make reasonable further progress, or fails to
attain the PM2.5 NAAQS by its attainment date.  The contingency measures
must take effect without significant further action by the State or EPA.
 

 The original annual and daily standards for particles generally less
than or equal to 10 micrometers in diameter (also referred to as PM10)
were established in 1987. In the 1997 PM NAAQS revision, EPA also
revised the standards for PM10, but these revised PM10 standards were
later vacated by the court, and the 1987 PM10 standards remained in
effect.  In the 2006 NAAQS revision, the 24-hour PM10 standard was
retained but the annual standard was revoked.  Today’s implementation
rule and guidance does not address PM10.

	 Environmental Protection Agency.(2004a). Air Quality Criteria for
Particulate  Matter.  Research Triangle Park, NC: National Center for
Environmental Assessment-RTP, Office of Research and Development, U.S.
Environmental Protection Agency, Research Triangle Park, NC 27711;
report no. EPA/600/P-99/002aF and EPA/600/P-99/002bF. October 2004.

  The revised fine particle NAAQS were published on October 17, 2006 (71
FR 61144).  See EPA’s website for additional information: 
http://www.epa.gov/pm/index.html

 Regulatory Impact Analysis for Particulate Matter National Ambient Air
Quality Standards (September 2006), page ES-8.  The mortality range
includes estimates based on the results of an expert elicitation study,
along with published epidemiological studies.  

 See www.epa.gov/cair.

 See 64 FR 35714, July 1, 1999.  

 See Tier II emission standards at 65 FR 6698, February 10, 2000.

 See heavy-duty diesel engine regulations at 66 FR 5002, January 18,
2001.

 For more information on the proposed nonroad diesel engine standards,
see EPA(’s website:  http://www.epa.gov/nonroad/.

 See: U.S. EPA 2006.  Regulatory Impact Analysis for the Particulate
Matter National Ambient Air Quality Standards. Air Benefits and Cost
Group, Office of Air Quality Planning and Standards, Research Triangle
Park, N.C. October 6, 2006.  Appendix A provides an analysis of
estimated benefits and costs of attaining the 1997 PM NAAQS standards in
2015.  

 NARSTO (2004) Particulate Matter Assessment for Policy Makers: A NARSTO
Assessment. P. McMurry, M. Shepherd, and J. Vickery, eds. Cambridge
University Press, Cambridge, England. ISBN 0 52 184287 5.

 The policy is the same as proposed, with the clarification regarding
downwind areas discussed above (Section A.2.b).

 The policy is the same as proposed, with the clarification regarding
downwind areas discussed above (Section A.2.b).

 More information on the Clean Air Interstate RuleCAIR is available at:
www.epa.gov/cair. 

 See section 51.1005 of the proposed regulation. 

 Memorandum of December 14, 2004, from Steve Page, Director, EPA Office
of Air Quality Planning and Standards to EPA Air Division Directors,
(Clean Data Policy for the Fine Particle National Ambient Air Quality
Standards.(  This document is available at: 
http://www.epa.gov/pmdesignations/guidance.htm

 The recommendations contained in the modeled attainment demonstration
guidance are separate from the Agency’s future hot-spot modeling
guidance for transportation conformity purposes.

 In the March 10, 2006, final transportation conformity rule (71 FR
12468), EPA committed to develop PM2.5 and PM10 quantitative hot-spot
modeling guidance for transportation conformity determinations for
highway and transit projects of local air quality concern.

 Application of the unmonitored area analysis is limited to locations
which are appropriate to allow the comparison of predicted PM2.5
concentrations to the NAAQS, based on PM2.5 monitor siting requirements
and recommendations. 

 Under the Tribal Air Rule (TAR), requirements for RACT and RACM may be
considered to be severable elements of implementation plan requirements
for Tribes. ADVANCE \d 12 

 See, 44 FR 53782, September 17, 1979, and 1976 memorandum from Roger
Strelow, Assistant Administrator for Air and Waste Management to
Regional Administrators, “Guidance for Determining Acceptability of
SIP Regulations in Non-attainment Areas” (Dec. 9, 1976)

 See e.g. Workshop on Requirements for Non-attainment Area
Plans-Compilation of Presentations (OAQPS No. 1.2-103, revised edition
April 1978)

 Under the Tribal Air Rule (TAR), requirements for RACT and RACM may be
considered to be severable elements of implementation plan requirements
for Tribes. ADVANCE \d 12 

 In Sierra Club v. EPA, 294 F.3d 155 (D.C. Cir. 2002), the court stated
in upholding EPA’s statutory interpretation of RACM that the Act does
not compel a state to consider a measure without regard to whether it
would expedite attainment.  

 In this notice, where we use the shorthand phrase “advance the
attainment date,” it means “advance the attainment date by one year
or more.”

 In the context of the PM10 NAAQS, EPA has concluded that “advancement
of the attainment date” should mean an advancement of at least one
calendar year.  See State Implementation Plans; General Preamble for the
Implementation of Title I of the CAA Amendments of 1990, 57 FR 12498
(April 16, 1992).  See also Sierra Club v. EPA, 294 F.3d 155 (D.C. Cir.
2002). ADVANCE \d 12 

 The EPA believes that it is not necessary to identify every possible
variation of every type of control measure, or all possible combinations
of technologies and measures that would apply to a given source or
activity if the State has properly characterized the potentially
available emissions reductions and their costs.   For example, EPA
believes that the State can conduct a thorough analysis of VMT reduction
measures without including every possible level or stringency of
implementation of certain possible measures or combinations of measures
for reducing VMT, so long as those measures would not affect the overall
assessment of VMT reduction capabilities and the associated costs.  

 For example, see past EPA guidance on PM2.5 control technologies:
Stationary Source Control Techniques Document for Fine Particulate
Matter (EPA-452/R-97-001), EPA Office of Air Quality Planning and
Standards, October 1998.

 Stationary Source Control Techniques Document for Fine Particulate
Matter (EPA-452/R-97-001), EPA Office of Air Quality Planning and
Standards, October 1998. See also:  Controlling SO2 Emissions: A Review
of Technologies (EPA/600/R-00/093), EPA Office of Research and
Development, November 2000.

 See EPA’s website for more information: 
http://www.epa.gov/ttn/emc/monitor.html.

 EPA Air Pollution Control Cost Manual - Sixth Edition (EPA
452/B-02-001), EPA Office of Air Quality Planning and Standards,
Research Triangle Park, NC, Jan 2002. ADVANCE \d 12 

 See: U.S. EPA 2006.  Regulatory Impact Analysis for the Particulate
Matter National Ambient Air Quality Standards. Air Benefits and Cost
Group, Office of Air Quality Planning and Standards, Research Triangle
Park, N.C. October 6, 2006.  Appendix A provides an analysis of
estimated benefits and costs of attaining the 1997 PM NAAQS standards in
2015.

  There are a number of sources of information on technologies for
reducing emissions of PM2.5 and its precursors.  Links are provided to a
number of national, state and local air quality agency sites from
EPA’s PM2.5 website: http://www.epa.gov/pm/measures.html 

 See Clean School Bus USA program at http://www.epa.gov/cleanschoolbus/.
 See also:  What You Should Know About Diesel Exhaust and School Bus
Idling", (June 2003, EPA420-F-03-021) at
http://www.epa.gov/otaq/retrofit/documents/f03021.pdf. 

 See EPA’s voluntary diesel retrofit program web site at
http://www.epa.gov/otaq/retrofit/overfleetowner.htm.

 See EPA’s voluntary diesel retrofit program web site at   HYPERLINK
"http://www.epa.gov/otaq/retrofit/idling.htm" 
http://www.epa.gov/otaq/retrofit/idling.htm .  

 See EPA’s website on transportation control measures at
http://www.epa.gov/otaq/transp/traqtcms.htm. 

15 See EPA’s web site on nonroad engines, equipment, and vehicles at
http://www.epa.gov/otaq/nonroad.htm. ADVANCE \d 12 

16 Fuels adopted in SIPs must be consistent with the Energy Policy Act
of 2005 and EPA guidance on SIP-approved boutique fuels at 71 FR 78192
(December 28, 2006).  

 Windblown dust from agricultural tilling activities also can be a
periodic source of inorganic PM in some areas. In some cases such dust
would be expected to be predominantly composed of coarse PM rather than
fine PM.  Depending on the available information and specific
circumstances for a particular area, it is possible that a State could
find in its SIP development analyses that direct PM2.5 emissions from
agricultural tilling activities do not significantly contribute to
annual average PM2.5 concentrations in the nonattainment area, and
therefore would not need to require emission reductions from
agricultural tilling activities in the plan for attaining the annual
standard.  However, States should be mindful of the contribution of
these sources to 24-hour fine particle concentrations.

17 See the regulatory impact analysis chapter on air quality for the
2006 PM NAAQS review at
http://www.epa.gov/ttn/ecas/regdata/RIAs/Chapter%204--Air%20Quality.pdf.

18 EPA’s CAIR-RACT presumption also would not apply if a State
required sources other than EGUs to achieve a portion of the reductions
required by CAIR (e.g., the State’s CAIR SIP achieved some reductions
from EGUs but took credit for non-EGU reductions achieved under new,
more stringent requirements implemented to meet NOx SIP call caps). 
Under the CAIR rule such a State would not be eligible to participate in
the EPA-administered CAIR trading system.

19 There are some MACT categories for which it may not be possible to
determine the degree of VOC reductions from the MACT standard without
additional analysis; for example, the miscellaneous metal parts and
products (40 CFR part 60, subpart MMMM) due to the uncertainty of the
compliance method that will be selected.

 The consolidated emissions reporting rule was published in the Federal
Register on June 10, 2002, pages 39602-39616. ADVANCE \d 12 

 The RFP test uses inventories for the full year, e.g. the year of 2009
or the year of 2012.  EPA does not specifically require that the
relevant measures be implemented by the beginning of the year, but RFP
inventories must reflect the fact that measures that are implemented
later in the year have correspondingly less impact on the year’s
annual total emissions.

 Emissions Inventory Guidance for Implementation of Ozone and
Particulate Matter National Ambient Air Quality Standards (NAAQS) and
Regional Haze Regulations,(  EPA-454/R-05-001, November 2005.

  “Optimized Method 202 Sampling Train to Minimize the Biases
Associated with Method 202 Measurement of Condensable Particulate Matter
Emissions,” John Richards, Tom Holder, and David Goshaw, Air Control
Techniques, P.C.; Air & Waste Management Association, Hazardous Waste
Combustion Specialty Conference AWM, November 2-3, 2005, St. Louis, MO.

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Office of Air Quality Planning and Standards, Research Triangle Park,
NC. EPA Publication No. EPA-450/2-86-001. June 1987.

  The General Preamble is available online at   HYPERLINK
"http://www.epa.gov/ttn/oarpg/t1pfpr.html" 
http://www.epa.gov/ttn/oarpg/t1pfpr.html .

 Clean Air Act Advisory Committee, Recommendations to the Clean Air Act
Advisory Committee - Phase I and Next Steps, Air Quality Management Work
Group, Environmental Protection Agency,   HYPERLINK
"http://www.epa.gov/air/caaac/pdfs/report1-17-05.pdf" 
http://www.epa.gov/air/caaac/pdfs/report1-17-05.pdf , January 2005.

 Option Paper 4 - Providing Guidance Regarding The Use Of Emissions
Factors For Purposes Other Than Emissions Inventories, September 2005,
http://www.epa.gov/ttn/chief/efpac/projects.html

 See 40 CFR 70.5(c)(3)(i), 70.5(b), and 70.7(a)(1)(i); 40 CFR
71.5(c)(3)(i), 71.5(b), and 71.7(a)(1)(i).

 For background information on issues surrounding implementation of the
PM2.5 NAAQS, see the EPA memo entitled “Implementation of New Source
Review Requirements in PM2.5 Nonattainment Areas,” from Stephen D.
Page, Director, Office of Air Quality Planning and Standards, to
Regional Air Directors, Regions I-X, dated April 5, 2005.

 For background information on regulated air pollutants, see the EPA
memo entitled “Definition of Regulated Air Pollutant for Purposes of
Title V,” from Lydia N. Wegman, Deputy Director, Office of Air Quality
Planning and Standards, to Air Division Directors, Regions I-X, dated
April 26, 1993.

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