EPA issued a (Clean Data( policy memorandum in December 2004 describing
possible reduced regulatory requirements for areas that attain the
standards early, 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.”
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 Clean Air Act(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).  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.  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.

	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).

 	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).

	EPA has explained in its memoranda on the Clean Data Policy for PM 2.5
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.”  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].”   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 Clean Air Act.  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.  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 EPA has made a finding with respect to
redesignation.  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.

4.  Determining attainment

[to be added]

	  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:  EPA has adopted the commenter’s suggested approach of
codifying its Clean Data Policy interpretation for PM 2.5 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.  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

a.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.

b.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.

While States are encouraged to submit national modeling that supports
their attainment demonstrationTherefore, we believe that this modeling
is best served as a supplemental analysis and/or part of a weight of
evidence demonstration.  Regional 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:  WeWhile 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 only
included national controls that are expected to be in place by 2010
(including the CAIR rule itself).  It did not include any additional
local controls that could be implemented under RACT and RACM
requirements that may bring the area into attainment sooner.
Nonattainment areas are required to attain the NAAQS as expeditiously as
practicable.  Therefore, additional 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
xxxxII.D., and additional information on RACT and RACM requirements is
contained in section III.J.(?)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:  The EPA’s modeling guidance for PM2.5 generally recommends
that for urban scale PM2.5 modeling, the State performs modeling
analyses at 12 kilometer grid resolution or finer.  The guidance
contains procedures for examining modeled results in areas without
monitors.  The "unmonitored area analysis" procedure recommended in the
guidance is intended to address large scale unmonitored areas (on the
order of 12km resolution) that may be in danger of violating the NAAQS.
These areas may be influenced by a large range of sources including
direct PM2.5 emissions from point sources.  In areas where potential
NAAQS violations are indicated, EPA recommends that the State conduct
further analyses to better understand the sources potentially
contributing to the projected high values.  For example, the State could
run a dispersion model to further evaluate the contributions of sources
of direct PM2.5 emissions.	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.  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.

	TheA draft of the PM2.55 attainment demonstration and regional haze
modeling guidance has now been finalizedrevised (September 2006) and is
available at   HYPERLINK "http://www.epa.gov/ttn/scram/xxxxx"
http://www.epa.gov/ttn/scram/xxxxx
.http://www.epa.gov/ttn/scram/guidance_sip.htm.  The final 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 in 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 finalrevised 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.  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 iswill be available at xxxxx.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
exceedences and summer ozone exceedences.

	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 and SO2 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 XX J.F for more
details.

7.  Mid course reviews

[Section III.F.7 of November 1, 2005 proposed rule (70 FR 66010)]

F.  What requirements apply for RACT and RACM for PM2.5 nonattainment
areas?	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 nonattainment area plans.

Notably, Congress provided EPA and States a great deal of deference for
determining what measures to include in a nonattainment plan.
Specifically, Section 172(c)(1) requires that each nonattainment area
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.” In this provision,
“reasonably available control measures” or RACM, are understood to
be controls  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” or RACT are
understood to be technology based controlsrefers to measures applicable
primarily to stationary sources. Thus, RACT areis a subsettype 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 nonattainment area plans designed to attain
the standards as expeditiously as practicable.

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.  However, the RACT requirement applies both to
sources of direct PM2.5 emissions and to sources of PM2.5 precursors in
the given nonattainment area.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 suchapplicability thresholds pertaining to
nonattainment area plan requirements for thoseNAAQS 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
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.”

SimilarlyMoreover, subpart 1, unlike subparts 2 and 4, does not
identify specific source categories for which EPA must issue control
technology documents or guidelines, thereby identifyingor  identify
specific source categories for State and EPA evaluation during
nonattainment area  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, prescribed silvacultural and agricultural burning for forest
management and agricultural activities, 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 late 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 (44 FR 53762;
September 17, 1979).  Because RACT is a control technology requirement
and because modeling techniques were not precise in the past, we have
generally considered RACT to be independent of the need to demonstrate
attainment.  In other words, we have generally required that a
stationary source of the requisite type and size be subject to the
controls that were deemed to be RACT, whether or not such controls were
actually demonstrated to be necessary for the area to attain by its
specified attainment date.  The EPA’s approach to RACT was affirmed in
the 1990 amendments to the CAA, which adopted this approach for purposes
of ozone in the subpart 2 provisions added at that time.  [Thus, 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 that are located within certain nonattainment
areas.  The statute thus requires these controls in such an area,
without a specific showing that they are necessary for the area to
attain, and without the possibility of a showing that they are not
necessary to attain as a means to exclude them from the plan.  Extensive
discussion of this issue appeared in the 1992 general preamble (57 FR
13541), in which EPA provided guidance for implementation of the ozone
NAAQS.  ” as well as other considerations. In practice, RACT is
generally described as the “norm achievable” by the source category.

	Significantly, Congress did not amend the generally applicable
provisions for nonattainment areas that appear in subpart 1 in 1990.
This indicates that the Agency retains 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 a more flexible approach to the
RACT requirement is appropriate for implementation of the PM2.5 NAAQS.
The EPA believes that the improved ability to model the impacts of
controls allows for this more flexible approach, so long as the analysis
of what controls are necessary to achieve the NAAQS as expeditiously as
practicable in a given area is sufficiently robust.]

	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 technicallyreasonable available
controls considering technical and economically feasible
controlseconomic 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 expeditereach 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, underconsistent with existing policies, States would
be required to evaluate the second alternative, areas cannot avoid the
impositioncombined effect of eitherreasonably available RACT or RACM
measures without a demonstration that there is no combinationto
determine whether application of such declined RACT and RACM measures
that would could advance the date of 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 2010 for
areas with an effective date for designation of  April 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.  EPA based the proposal on
the approach that it has we adopted for other   NAAQS implementation
programs.  Under this approach, EPA requires the a State to provide
provides a demonstration in its SIP that it has adopted all reasonably
available measures needed to meet RFP requirements and to attain the
standard as expeditiously as practicable.  Reasonable measures are those
measures  and that are technologically and economically feasible for the
area in question.  The required demonstration must show that there are
no reasonably available additional reasonable measures available in the
nonattainment area that 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 attainment datestate implementation plan
must provide for a nonattainment area isto 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, EPA each State would
require each State to evaluate all RACM for all available measures for
sources of PM2.5 or its regulatory precursors in the area to determine
if any suchreasonable measures could contributewere needed to meeting
the RFP requirement or  or to achievingto achieve attainment as
expeditiously as practicable.  If this evaluationmodeling of all RACM
findsand 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, provided thatwhen the State has presented
an adequate demonstration showing they 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 needneeds 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 have the initial
responsibility for demonstrating to EPA that it has has adopted adopt
all reasonably available measures for the area consistent with meeting
the applicable RFP requirements and attaining  the standardsNAAQS as
expeditiously as practicable, in accordance with applicable policy and
guidance for attainment demonstrations.  The EPA notes that it must take
action on State nonattainment plansWe would then approve or disapprove
the State’s plan through notice and comment rulemaking, and failure of
a State to supply adequate reasoning and support for its submission with
respect to RACM measures would be a basis for disapproval of the
submission.   In .  We also noted that in reviewing the State’s
selection of measures for RACM, or determinationdetermining that certain
measures are not RACM, EPA couldmay independently supplement the
rationale of the State or provide an alternative reason for reaching the
same conclusion as the State, but only where EPA deems it appropriate. .

 	In the proposal, EPA also confirmed its past interpretation that the
RACM requirement requires the collective evaluation of measures and the
assessment of whether they will advance the attainment date when taken
together.  Thus, for any measure or measures that would otherwise be
RACM in the area, the State would be required to provide a reasoned
rationale for declining to adopt such measure or measures, and an
analysis to show that adoption of all such measures cumulatively would
not advance the attainment for that area by at least 1 year.

c. Final rule.

	The EPA has carefully considered the properour 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 nonattainment area plans that address widely disparate
circumstances (e.g., different source types and mixes, different
precursors and mixes of precursors, and different meteorological
conditions), EPA haswe 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 (subject to special considerations for electric
generating units participating in CAIR as discussed in section F.6). .
Under   this approach, RACT and RACM are those measures whichthat a
State finds are both reasonably available considering technical and
economic feasibility, and which contribute to advancing the attainment
date by 1 year or more as expeditiously as practical in the specific
nonattainment area.

By definition, those 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.  In exchange for this flexibility, however, States
will need to , but it may require the State to conduct a more rigorous
and systematic analysisdetailed analysis to identify the most effective
RACT/RACM strategy to determine what constitutes  RACT and RACM measures
and what  attainment date  is as expeditious as practicable for each
area.  The final rule requires States to demonstrate that they have
adopted all appropriate RACT and RACM measures attain the attainment
demonstrations that States must submit to EPA in early 2008NAAQS.

The EPA stresses that under the approach in the final rule, it is
inappropriate to reject a single measure under consideration as RACT or
RACM because the emission reduction benefits from that measure alone
would not advance the attainment date by 1 year. For any measure or
measures that would otherwise be RACM in the area, the State is required
to provide a reasoned rationale for declining to adopt such measure or
measures, and an analysis to show that adoption of all such declined
measures cumulatively would not advance the attainment for that area by
at least 1 year.  Th  EPA believes that PM2.5 nonattainment is typically
the result of the cumulative impact of emissions from a large number of
different sources of varying sizes.  Implementation strategies,
therefore, will require consideration of controls on a broad variety of
sources that might not individually cause nonattainment but whose
contribution to nonattainment must nevertheless be reduced in order to
achieve the NAAQS.  Therefore, an approach to RACM that would excuse
control measures that would not singlehandedly bring an area into
attainment would be an inappropriate way to implement the RACM
requirement for PM2.5.

Under the final rule, the State’s analysis must   provide a reasoned
justification for rejecting any available control measures that would
constitute RACT or RACM in such area.  The supporting information must
show why each rejected measure, including any measure raised during  the
State's public hearing or public comment process, is technologically or
economically infeasible or unreasonable, or will not contribute to
advancing attainment by 1 year.  Note that special considerations for
EGUs apply as discussed in section F.6 below.

	Guidance on State analysis to identify RACT, RACM and appropriate
attainment date.  For each nonattainment area, the State must provide a
demonstration showing that the area will attain the standards as
expeditiously as practicable considering implementation of existing
Federal measures, plus implementation of RACT, RACM, and potential
measures to reduce intrastate pollution transport that contributes to
the nonattainment problem.

All nonattainment areas are subject to RACT and RACM requirements.
However, EPA believes that areas clearly projected to attain 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) 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 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 reasonably available  measures in the area could
not advance the attainment date 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, EPA believes that it would be appropriate for States
to consider existing modeling information  in determining 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 must 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;
(2) modeling to identify the attainment date that is as expeditious as
practicable; and (3) selection of RACT and RACM.

	Identification of potential measures:  As supporting information for
identification of RACT and RACM, the State  must provide data on
technologically feasible control measures:

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 expeditiously 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 judgement 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 nonattainment 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
technically and economically feasiblethe reasonable measures (potential
RACT and RACM) for 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
expeditiousexpeditiously as practicable, the State is also   responsible
for considering 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.  The State should provide its rationale for including, or not
including, such measures in its SIP (e.g., based on potential emissions
reductions, costs and air quality impacts).

	Modeling to determine the attainment date that is as
expeditiousexpeditiously as practicable:  Second, for purposes of
determining the attainment date that is as expeditiousexpeditiously 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 “expeditious” 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 for 2009(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 – specifically, all
technically and economically feasible nonattainment area measures which
could be implemented by the beginning of calendar year 2009-- 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 beyond April 2010 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 expeditiousexpeditiously 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 dominentdominant 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 that States
shouldto model each and every year between 2009 and 2014 in order 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 compromise is 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 futherfurther 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 previously
have determined not to be RACT or RACM either because they could not
implement the controls in time to meet an earlier nonattainment date
(e.g., because of technological, economic, or timing reasons) or because
the controls would not sufficiently advance the attainment date.  For
example, some reasonable 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 expeditiousexpeditiously as practicable.  Because EPA is
defining RACT and RACM as only those reasonable, technically and
economically feasible measures that are necessary for expeditious
attainment of the NAAQS as expeditiously as practicable, the State need
not adopt all measures that are all technically and economically
feasible measures feasible, reasonable measures.  The State may exclude
those reasonable measures that, considered collectively, would not
advance the attainment date by at least 1 year.  Given the public health
risks of PM2.5, we believe that the State should carefully consider a
decision to forego a measure that would otherwise be RACT or RACM, and
we will require that the State present an adequate rationale and
technical support for exclusion of such measures.  The EPA notes that
States retain the authority under section 116 of the CAA to require more
emission reductions, beyond what is required for RACT and RACM, and
without regard to whether it would advance the attainment date.    .

d.  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 PN 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.  Th  EPA initially believed that option 1 or option 3
would provide advantages, in that they would automatically require RACT
controls on larger sources of emissions in all areas (under option 1) or
on all larger sources of emissions in areas which need longer than five
years from designation to attain (in the case of option 3).  This might
allow States to focus control efforts on such sources, to use their
analytical resources to evaluate other sources, and to simplify and
streamline somewhat the SIP development process.  After further
consideration, however, EPA has concluded that these options have at
least the potential to 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 measures.  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.  Moreover, even under options 1 or 3, States would have
had an obligation to consider the full range of sources for control
under in the process of conducting a RACM analysis, so either option
would not necessarily have significantly reduced the degree of analysis
that many States would need to conduct under any of the options. as
practicable.  Given the nature of the PM2.5 nonattainment problem, EPA
has concluded that an interpretation that provides the maximum
flexibility, coupled with the requirement of a robust analysis to
justify the resulting nonattainment area plans, 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 inappropriatedifficult 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. Also, identification of   A state needing
significant emission reductions to attain the standards in a specific
threshold in this rule would not be consistent with the case-by-case
nature of the RACT and RACM analysis for eachgiven area.  For example,
an area needing significant emission reductions to attain the standards
even by 2015 would likely conclude that controls should be considered on
smaller sources than would be needed for.  In contrast, a
nonattainmentState 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 a fullan appropriate analysis of the full 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 therefore subvertundermine 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 nonattainment plan provide for “at a minimum” the adoption
of RACT.  Accordingly, these commenters argued that RACT is an
independent, minimum requirement of nonattainment 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 nonattainment 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
commentercommenters’ 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
expeditious attainment as expeditiously as practicable.  (See 57 FR
13498, 13560).   The courts have deferred to this interpretation and
concluded that EPA has reasonably interpreted 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 would advance the attainment date. 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 need not be implemented 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.  Th  EPA
interprets We interpret the “at a minimum” clause to mean that the
states must include, as part of RACM, RACT controls onwhen 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.  While a State may also
chose to impose RACM on other source categories such as mobile sources,
RACT controls are only required for existing stationary sources.
Section 172(c)(1) requires that RACM include, at a minimum, RACT on
existing stationary sources and the final rule is fully consistent with
that requirement.

The EPA believes that there arefinds 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:  The EPA recognizesAs 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 be
required to expend extra effort in developing and evaluating
nonattainment plans that contain appropriate controls.  Given the nature
of PM2.5 and the needA number of resources exist to address emissions of
both direct PM2.5 and its precursors from a variety of sources, however,
EPA cannot artificially curtail the RACM requirement solely to those
sources and potential controls for which the most extensive information
exists.  The EPA believes that there are a number of resources available
to States that provide States with information on potential control
measure costs and emissions reductions.   EPA also intendsWe intend to
facilitate the sharing of information through a control measure website
and other efforts.   In addition, given the provisions allowing
exclusion of a set of measures that collectively would not advance the
attainment date by 1 year, , and expect that States will likely only
need to adopt an appropriate subset of the full “universe” of
measures that have a potential for substantial air quality benefit, and
it is likely thatdevelop screening approaches will be available to
demonstrate that this is the case.    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 has 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 had previously agreed upon as
representative of 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 would subvert the goal of
achieving 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 decided to deferdeferred 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
expeditious 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 and.  At the
expeditious implementation of measuressame time, EPA recognizes that
will advance attainment in the area, although 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 would be technically and economically
feasibleare 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 are described in sections
F.4 and F.5 below. . 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 must would
conduct a more detailed RACT and RACM analysis, involving air quality
modeling analyses, to assess whether it can advance the attainment date.
 .

	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 and address RACT and RACM measures
developed for other areas or other States as part of a well reasoned
RACT and RACM analysis.  The EPA’s own evaluation of State SIPs for
compliance with the RACT and RACM requirements will include comparison
of measures considered or adopted by 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 achieve enforce in practice.  The EPA’s intent was to We
discourage States from relying on measures that on paper may seem
reasonably available but in practice might fail to achieve benefits due
to resistance to implementing the 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.

	 In the preamble to the proposed rule, EPA includedThe following
provides guidance for States to consider in determining whether an
available control technology is technologically feasible.  We include
this guidance in this preamble as well.

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 adverseadversely affecting other
resources by increasing the pollution of 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.  In However, in many
instances, however,past situations, States and owners of existing
sources have adopted PM2.5 control technologies have with known energy
penalties and some adverse effects on other media, but based on the
reasoned judgment that installation of such effects and the cost of
their mitigation are also knowntechnology would result in a net benefit
to public health and have been borne by owners of existing sources in
numerous cases.  Such well-established adverse effects and their costs
are normal and assumed to be reasonable and should not, in most cases,
justify rejection of the potential PM2.5 control technology.the
environment.  States should consider this in determining technical
feasibility.  The costs of preventing adverse water, solid waste and
energy impacts will also influenceshould 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).  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 informatinoinformation 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