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From: Lydia Wegman/RTP/USEPA/US

To: nfrey@omb.eop.gov

Cc: Anna Wood/RTP/USEPA/US@EPA, Rich Damberg/RTP/USEPA/US@EPA, Phil 

Lorang/RTP/USEPA/US@EPA, Peter Keller/RTP/USEPA/US@EPA, Raj Rao/RTP/USEPA/US@EPA, Beth 

Hassett-Sipple/RTP/USEPA/US@EPA, martin.karen@epa.gov, Joseph-J Dougherty/DC/USEPA/US@EPA, 

hannon.john@epa.gov, Sara Schneeberg/DC/USEPA/US@EPA

Date: 06/12/2012 01:03 PM

Subject: Redline of implementation section (section IX) in the PM NAAQS preamble 

Nathan, 

Attached is the redline mark-up of the implementation section (section IX) of the PM preamble. We hope that it is 

fully responsive to the comments we received in writing last Wednesday and in discussions Friday and this 

morning. The revisions address the implications of the proposed monitoring regulation clarifications for 

nonattainment area implementation (pp 13-14), permitting (pp 21-22) and transportation conformity (pp 41-42).

Please let us know if you have any questions. 

Lydia
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IX. Clean Air Act Implementation Requirements for the PM NAAQS 

The proposed revisions to the primary annual PM2.5 NAAQS and the proposed new secondary 

PM2.5 visibility index NAAQS discussed in sections III.F and VI.F above, if finalized, would trigger a 

process under which states1 will make recommendations to the Administrator regarding area 

designations, and the EPA will take final action on these designations. States will also be required to 

review, modify, and supplement their existing implementation plans. These proposed PM NAAQS 

revisions would also affect the applicable air permitting requirements and the transportation conformity 

and general conformity processes. This section provides background information for understanding the 

possible implications of the proposed NAAQS changes, and describes the EPA’s plans for providing 

states necessary guidance or rules in a timely manner to clarify how they are affected and to assist their 

implementation efforts. This section also describes existing EPA interpretations of CAA requirements 

and other EPA guidance relevant to implementation of new or revised NAAQS. Relevant CAA 

provisions that provide potential flexibility with regard to meeting implementation timelines are also 

discussed. 

This section also contains a discussion of several requirements of the stationary source 

construction permit programs under the CAA that may be affected by the proposed revisions of the PM 

NAAQS. These are the PSD and Nonattainment New Source Review (NNSR) programs. To facilitate 

implementation of the PSD requirements, which would be the first of the implementation requirements 

to become applicable upon the effective date of the final NAAQS rule, the EPA proposes as part of this 

rulemaking to add a grandfathering provision to its regulations that would apply to certain PSD permit 

applications that are pending on the effective date of the revised PM NAAQS. If the proposed NAAQS 

revisions are finalized, this rule could be finalized at the same time as the revised NAAQS. This section 

 

1

This and all subsequent references to “state” are meant to include state, local and tribal agencies 

responsible for the implementation of a PM2.5 control program. 
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also discusses other possible actions under consideration to facilitate implementation of the PSD and 

NNSR programs (see section IX.F). 

The EPA intends to propose additional appropriate regulations or issue guidance related to the 

implementation requirements for the revised PM NAAQS at a later date or dates. These may include 

additional revisions to both the PSD and NNSR regulations, as well as the promulgation of rules or 

development of guidance related to NAAQS implementation. These actions will be taken on a schedule 

that provides timely assistance to responsible states. Accordingly, in this section, the EPA solicits 

comment on several issues that the Agency anticipates will need to be addressed in future guidance or 

regulatory actions. Because these issues are not relevant to the establishment of the NAAQS, the EPA 

does not expect to respond, nor is the Agency required to respond, to these comments in the final action 

on this proposal, but the EPA expects these comments will be helpful as future guidance and regulations 

are developed. 

A. Designation of Areas

After the EPA establishes or revises a NAAQS, the CAA requires the EPA and the states to take 

steps to ensure that the new or revised NAAQS is met. The first step, known as the initial area 

designations, involves identifying areas of the country that either meet or do not meet the new or revised 

NAAQS along with the nearby areas contributing to violations. 

Section 107(d)(1) of the CAA states that, “By such date as the Administrator may reasonably 

require, but not later than 1 year after promulgation of a new or revised national ambient air quality 

standard for any pollutant under section 109, the Governor of each state shall ... submit to the 

Administrator a list of all areas (or portions thereof) in the State” that designates those areas as 

nonattainment, attainment, or unclassifiable.2Section 107(d)(1)(B)(i) further provides, “Upon 

promulgation or revision of a NAAQS, the Administrator shall promulgate the designations of all areas 

 

2 While the CAA says “designating” with respect to the Governor’s letter, in the full context of the CAA 

section it is clear that the Governor actually makes a recommendation to which the EPA must respond 

via a specified process if the EPA does not accept it.
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(or portions thereof) ... as expeditiously as practicable, but in no case later than 2 years from the date of 

promulgation. Such period may be extended for up to one year in the event the Administrator has 

insufficient information to promulgate the designations.” The term “promulgation” has been interpreted 

by the courts with respect to the NAAQS to be signature and widespread dissemination of a rule. By no 

later than 120 days prior to promulgating designations, the EPA is required to notify states of any 

intended modifications to their boundaries as the EPA may deem necessary. States then have an 

opportunity to comment on EPA's tentative decision. Whether or not a state provides a recommendation, 

the EPA must timely promulgate the designation that it deems appropriate. While section 107 of the 

CAA specifically addresses states, the EPA intends to follow the same process for tribes to the extent 

practicable, pursuant to section 301(d) of the CAA regarding tribal authority, and the Tribal Authority 

Rule (63 FR 7254; February 12, 1998). To provide clarity and consistency in doing so, the EPA recently 

issued a 2011 guidance memorandum to our Regional Offices on working with tribes during the 

designations process (Page, 2011).

Monitoring data are currently available from numerous existing aggregated PM2.5 mass and 

PM2.5 speciation sites to determine compliance with the proposed revised primary annual PM2.5 NAAQS 

and with for the proposed new PM2.5 visibility index NAAQS. As discussed in sections III and VI 

above, the EPA is proposing to: (1) revise the form and level of the primary annual PM2.5 standard, and 

retain the current primary 24-hour PM2.5 standard (section III.F); (2) retain the current secondary 24-

hour PM2.5 standard, and revise the form and retain the level of the secondary annual PM2.5 standard for 

non-visibility-related welfare protection (section VI.F); and (3) establish a new secondary PM2.5

visibility index standard (section VI.F). The EPA’s examination of air quality monitoring data current at 

the time of this proposal indicates that, for the proposed levels for the revised primary annual PM2.5

standard and the new secondary PM2.5 visibility index standard, it is likely that the vast majority of 

monitors violating theis secondary standard would overlap with monitors violating theis primary 

standard. Since the same types of emissions sources contribute to concentrations affecting attainment 
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status for both the proposed primary and secondary NAAQS, the EPA expects that the nonattainment 

area boundaries in locations with such overlap would be identical. The EPA will, consistent with 

previous area designations, use area-specific factor analysis3to support area boundaries decisions for 

both the primary and secondary standards. The EPA intends to more fully address issues affecting area 

designations in the designations guidance that will be issued around the same time as any accompanying 

the revised PM2.5 NAAQS are finalized. The EPA solicits comment and technical information related to 

establishing nonattainment area boundaries for the proposed revised primary annual PM2.5 NAAQS and 

the proposed new secondary PM2.5 visibility index NAAQS, including any relevant technical 

information that should be considered by the EPA, and any input on the extent to which different 

considerations may be relevant to establishing boundaries for a secondary PM2.5 NAAQS.

For the reasons stated above, upon promulgation of the revised NAAQS, the EPA currently 

intends to move forward on the same schedule with the initial area designations for both the revised 

primary annual PM2.5 standard and the new secondary PM2.5 visibility index standard. The EPA notes 

that promulgating initial area designations for these standards on the same schedule will provide early 

regulatory certainty for states. The EPA intends to promulgate the Thus, assuming for illustrative 

purposes that the revised PM NAAQS in December 2012are promulgated in June 2013, the EPA and 

would complete initial designations for both the revised primary annual PM2.5 NAAQS and the new 

secondary PM2.5 visibility index NAAQS by December 2014 June 2015 using available air quality data 

from the current PM2.5 and speciation monitoring networks. These designations would follow the 

standard 2-year process described previously and would be based on 3 consecutive years of certified air 

quality monitoring data from the years 20110 to 20132, or 20121 to 20143, if available. (Note, as 

discussed in sections IV.F and VI.F above, the EPA is proposing to retain the current primary 24-hour 

 

3

The EPA has used area-specific factor analyses to support nonattainment area boundary 

recommendations and final boundary determinations by evaluating factors such as air quality data, 

emissions data, population density and degree of urbanization, traffic and commuting patterns, 

meteorology, and geography/topography.

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PM10 standard and to revise the form of the secondary annual PM2.5 standard to remove the option for 

spatial averaging and to retain all other elements of the current suite of secondary PM standards to 

address non-visibility welfare effects. A new round of mandatory designations for these standards would 

occur only if these standards change.

4

) EPA requests comment on promulgating designations for both 

the revised primary and secondary PM2.5 NAAQS at the same time. 

In today’s action, as discussed in section VIII.B.3.b.i above, the EPA is proposing to add 

requirements for establishing near-road PM2.5 monitors in certain cities. If these requirements are 

finalized, the EPA anticipates that it will take up to 3 years to establish new monitoring sites for PM2.5

mass, plus an additional 3 years of monitoring thereafter to determine compliance with the mass-based 

primary and secondary PM2.5 NAAQS based on these new monitors. This means that a complete set of 

air quality data for use in designations from any near-road monitoring sites would not be available until 

20198. Also, as discussed in section VIII.B.3.d above, the EPA is proposing that each state with a CBSA 

over 1 million in population would need to have a CSN (or IMPROVE) monitoring site in at least one of 

its CBSAs to collect speciated PM2.5 data to support implementation of the proposed new secondary 

standard to address visibility impairment. This proposal may require the addition of new monitors, or the 

relocation of existing monitors, in some CBSAs. The EPA is also proposing in today’s action to extend 

the data certification period for speciation measurements by 12 months. Thus, even if EPA were to 

consider taking an additional year to complete the designations process (i.e., in December 2015June 

2016 instead of in December 2014June 2015 in the illustrative example), data from new PM2.5 near-road 

monitoring sites would not be available prior to the extended CAA designation deadline; and data from 

certain CSN (or IMPROVE) monitors also may not be available prior to the extended CAA designation 

deadline. For these reasons, the EPA does not currently intend to delay designations based on 

 

4 As discussed in section in VII.A.2 above, the EPA is proposing to remove the option for spatial 

averaging from the form of the secondary annual PM2.5 NAAQS consistent with the proposed change in 

the form of the primary annual PM2.5 standard. The EPA does not consider this change to trigger a new 

round of non-discretionary designations for this standard.

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unavailability of data for either the revised primary or new secondary standards in order to be able to 

include data from these new monitors. Initial area designations would not take into account monitoring 

data from any newly established near-road monitoring sites, nor from newly established speciation 

monitoring sites. Should any of these newly established monitoring sites indicate a violation of the 

relevant standard after completion of the initial designations, the EPA would consider at that time 

whether to redesignate the area from attainment to nonattainment. Such actions are discretionary under 

the CAA, and the EPA may use other means to assure attainment at any such monitors. 

The EPA recognizes that the number of PM2.5 speciation monitoring sites available to support the 

state Governors’ designation recommendations and EPA’s decisions for the proposed new secondary 

PM2.5 visibility index NAAQS will be much smaller than the number of PM2.5 FRM/FEM/ARM sites 

available to support designation recommendations and decisions for the revised annual primary PM2.5

NAAQS. Therefore, it may well be that more areas of the nation are designated unclassifiable (or 

unclassifiable/attainment) for the proposed new PM2.5 visibility index NAAQS than for the proposed 

revised primary annual PM2.5 NAAQS, if finalized. At this time the EPA does not believe that taking an 

additional year to complete designations for the new secondary PM2.5 visibility index NAAQS would 

change this outlook. However, the EPA intends to remain flexible with regard to the designation 

schedule for the proposed new and revised PM2.5 NAAQS and will reassess the potential need for an 

extended schedule upon issuance of the final NAAQS rule and thereafter.

In summary, the EPA intends to provide designation guidance to the states at the time of the 

promulgation of new or revised NAAQS or very shortly thereafter, to assist them in formulating these 

recommendations. iIn accordance with section 107(d)(4) of the CAA, the EPA currently believes that 

state Governors (and tribes, if they choose) should submit their initial designation recommendations for 

both the revised primary annual PM2.5 NAAQS and the new secondary PM2.5 visibility index NAAQS to 

the EPA no later than 1 year following promulgation of any new or revised NAAQS (e.g., byin

December 2013 assuming promulgation of the June 2014 if the revised PM NAAQS in December 
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2012are promulgated in June 2013). The EPA intends to provide designation guidance to the states at 

the time of the promulgation of a new or revised NAAQS or very shortly thereafter, to assist them in 

formulating these recommendations. If the Administrator intends to modify any state area 

recommendation, the EPA would notify the appropriate state Governor no later than 120 days prior to 

making final designations decisions. A state that believes the Administrator’s modification is 

inappropriate would have an opportunity to demonstrate to EPA why it believes its original 

recommendation (or a revised recommendation) is more appropriate before designations are 

promulgated. The Administrator would take any additional input from the state into account in making 

final designation decisions.

As previously stated, the EPA plans to issue guidance regarding designations for the revised

PM2.5 NAAQS at or very shortly after the time of their final promulgation. The EPA invites preliminary 

comment on all aspects of the designation process at this time, which the Agency will consider in 

developing that guidance.

B. Section 110(a)(2) Infrastructure SIP Requirements

The CAA directs states to address basic SIP requirements to implement, maintain, and enforce 

the standards. States are to develop and maintain an air quality management infrastructure that includes 

enforceable emission limitations, a permitting program, an ambient monitoring program, an enforcement 

program, air quality modeling capabilities, and adequate personnel, resources, and legal authority. Under 

CAA sections 110(a)(1) and 110(a)(2), states are to submit these SIPs within 3 years after promulgation 

of a new or revised primary standard. While the CAA allows the EPA to set a shorter time for 

submission of these SIPs, the EPA does not currently intend to do so. Section 110(b) of the CAA 

provides that the EPA may extend the deadline for the “infrastructure” SIP submission for a new 

secondary standard by up to 18 months beyond the initial 3 years. If both the annual PM2.5 NAAQS and 

the secondary PM2.5 visibility index NAAQS are revised, tThe EPA currently believes it would be more 

efficient for states and the EPA if each affected state submits a single section 110 infrastructure SIP that 
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addresses both standards the revised primary annual PM2.5 NAAQS and the new secondary PM2.5

visibility index NAAQS at the same time (i.e., within 3 years of promulgation of any revisions to the 

NAAQS for PM), because the EPA does not at present discern any need for there to be any substantive

difference in the infrastructure SIPs for the two standards. However, the EPA also recognizes that states 

may prefer the flexibility to submit the secondary NAAQS infrastructure attainment SIP at a later date. 

The EPA solicits comment on these infrastructure SIP submittal is timing aspect.considerations. The 

EPA intends to provide guidance regarding the required date(s) for submission of infrastructure SIPs at 

the same time as or very shortly after promulgation of the revised NAAQS. 

Section The CAA’s specific section 110(a)(2) of the CAA provisions includes the following 

paragraphs describing specific requirements specifying elements of infrastructure SIPs: (A) Emission 

limits and other control measures, (B) Ambient air quality monitoring/data system, (C) Programs for 

enforcement of control measures and for construction or modification of stationary sources, (D)(i) 

Interstate pollution transport; and (D)(ii) Interstate and international pollution abatement, (E) Adequate 

resources and authority, conflict of interest, and oversight of local governments and regional agencies, 

(F) Stationary source monitoring and reporting, (G) Emergency episodes, (H) SIP revisions, (I) Plan 

revisions for nonattainment areas, (J) Consultation with government officials, public notification, PSD 

and visibility protection, (K) Air quality modeling and submission of modeling data, (L) Permitting fees, 

and (M) Consultation and participation by affected local entities.

The EPA interprets the CAA such that for two of the section 110(a)(2) elements, both of which 

pertain to nonattainment area requirements in part D, title I of the CAA, the required submittal date 

should not be identified in section 110(a)(2) are not governed by the 3-year submission deadline of 

section 110(a)(1). The elements pertain to part D, in title I of the CAA, which addresses plan 

requirements for nonattainment areas. Therefore, for the reasons explained below, the following section

110(a)(2) elements are considered by EPA to be outside the scope of infrastructure SIP actions: (1)

section 110(a)(2)(C) to the extent it refers to permit programs (known as "nonattainment new source 
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review") under part D; and (2) section 110(a)(2)(I) (plan revisions for nonattainment areas) in its 

entirety. The EPA does not expect infrastructure SIP submittals to include regulations or emission limits 

developed specifically for attaining the relevant standard in areas designated nonattainment for the 

proposed new and revised PM2.5 NAAQS. Infrastructure SIPs for any final new and revised PM2.5

NAAQS will be due before PM2.5 SIPs are due to demonstrate attainment with the same NAAQS. (New 

emissions limitations and other control measures to attain a new or revised PM2.5 NAAQS will be due 3

years from the effective date of nonattainment area designation as required under CAA section 172(c) 

and will be reviewed and acted upon through a separate process.) For this reason, the EPA does not 

expect infrastructure SIP submissions to identify new nonattainment area emissions controls. 

It is the responsibility of each state to review its air quality management program's infrastructure 

SIP provisions in light of each new or revised NAAQS. Most states have revised and updated their 

infrastructure SIPs in recent years to address requirements associated with revised NAAQS. It may be 

the case that for a number of infrastructure elements, the state may believe it has adequate state 

regulations already adopted and approved into the SIP to address a particular requirement with respect to 

the revised PM NAAQS. For such portions of the state’s infrastructure SIP submittal, the state may 

provide a “certification” specifying that certain existing provisions in the SIP are adequate. Although the 

term "certification" does not appear in the CAA as a type of infrastructure SIP submittal, the EPA 

sometimes uses the term in the context of infrastructure SIPs, by policy and convention, to refer to a 

state's minimal SIP submittal (e.g., in the form of a letter to EPA from the state Governor or her/his 

designee). 

If a state determines that its existing SIP-approved provisions are adequate in light of the revised 

PM NAAQS with respect to a given infrastructure SIP element (or sub-element), then the state may 

make a "certification" that the existing SIP contains provisions that address those requirements of the 

specific section 110(a)(2) infrastructure elements. In the case of a certification, the submittal does not 

have to include a copy of the relevant provision (e.g., rule or statute) itself. Rather, the submittal may 
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provide citations to the SIP-approved state statutes, regulations, or non-regulatory measures, as 

appropriate, which meet the relevant CAA requirement. Like any other SIP submittal, such certification 

can be made only after the state has provided reasonable notice and opportunity for public hearing. This 

"reasonable notice and opportunity for public hearing" requirement for infrastructure SIP submittals 

appears at section 110(a), and it comports with the more general SIP requirement at section 110(l) of the 

CAA. Under EPA's regulations at 40 CFR part 51, if a public hearing is held, an infrastructure SIP 

submittal must include a certification by the state that the public hearing was held in accordance with 

EPA's procedural requirements for public hearings. See 40 CFR part 51, appendix V, paragraph 2.1(g), 

and 40 CFR 51.102.

In consultation with its EPA Regional Office, a state should follow applicable EPA regulations 

governing infrastructure SIP submittals in 40 CFR part 51 - e.g., subpart I (Review of New Sources and 

Modifications), subpart J (Ambient Air Quality Surveillance), subpart K (Source Surveillance), subpart 

L (Legal Authority), subpart M (Intergovernmental Consultation), subpart O (Miscellaneous Plan 

Content Requirements), subpart P (Protection of Visibility), and subpart Q (Reports). For the EPA's 

general criteria for infrastructure SIP submittals, refer to 40 CFR part 51, Appendix V, Criteria for 

Determining the Completeness of Plan Submissions. A recent EPA guidance memorandum identifies a 

number of alternatives that are available to states to reduce the administrative burden, cost, and time 

required to complete the CAA-required steps that are part of submitting infrastructure and other SIP 

revisions to EPA (McCabe, 2011). The EPA also notes that many of the infrastructure SIP provisions are 

not NAAQS-specific, and therefore are likely to have been approved as part of SIP actions associated 

with other recently promulgated NAAQS (e.g., 2006 PM2.5 and 2008 lead NAAQS). 

The EPA intends to issue a separate guidance document on section 110 infrastructure SIP 

requirements for theany revised PM NAAQS. The target date for issuing such guidance would be no 

later than 1 year after the revised PM NAAQS are finalized (2 years before state submittals are due). 

The EPA invites preliminary comment on all aspects of infrastructure SIPs at this time, which the
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Agency will consider in developing future guidance. 

C. Implementing the Proposed Revised Primary Annual PM2.5 NAAQS in Nonattainment Areas 

Part D of the CAA describes the various program requirements that apply to nonattainment areas 

for different NAAQS. Section 172 (found in subpart 1 of part D) includes the general SIP requirements 

that govern the PM2.5 program. Under section 172, states are required to submit SIPs within 3 years of 

the effective date of area designations by EPA. These plans need to show how the nonattainment area 

will attain the primary PM2.5 standards “as expeditiously as practicable,” but presumptively no later than 

within 5 years from the effective date of designations. However, in certain cases, the EPA can approve 

attainment dates up to 10 years from the effective date of designations, as appropriate, considering the 

severity of the air quality concentrations in the area, and the availability and feasibility of emission 

control measures per section 172(a)(2)(C).

Section 172(a)(1) of the CAA authorizes the EPA to establish classification categories for areas 

designated nonattainment for the primary or secondary PM NAAQS, but does not require the EPA to do 

so. The implementation program for the 1997 and 2006 primary and secondary PM2.5 standards did not 

include a tiered classification system. This provided a relatively simple implementation structure and 

flexibility for states to implement control programs tailored to the specific nature of the problem and 

source mix in each area. For this same reason, the EPA also does not intend to establish classifications 

for nonattainment areas for the proposed revised primary annual PM2.5 standard (or for a revised primary 

24-hour standard if one is promulgated). However, the EPA solicits comment on whether a 

classifications system would be appropriate and how asuch classifications system could be designed. 

In April 2007, the EPA issued a detailed PM2.5 implementation rule (72 FR 20586; April 25, 

2007) to provide guidance to states regarding development of SIPs to attain the 1997 PM2.5 NAAQS. 

The EPA believes that the overall framework and policy approach of the implementation rule for the 

1997 PM2.5 NAAQS provides effective and appropriate guidance on the general approach for states to 

follow in planning for attainment of the revised primary annual PM2.5 standard. The EPA intends to 
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develop and propose a revised implementation rule that will address any new implementation 

requirements as a result of the proposed revised primary annual PM2.5 NAAQS and the proposed revised 

monitoring regulations. The EPA intends to propose this implementation rule within 1 year after the 

revised PM NAAQS are promulgated, and finalize the implementation rule by no later than the time the 

area designations process is finalized (approximately 1 year later). The EPA believes that for many 

issues,much of the regulatory text similar to that of the existing implementation rule for the 1997 PM2.5

NAAQS can be included in this new implementation rule. In the implementation rule for the 1997 PM2.5

NAAQS, there are a few specific references to the 1997 annual PM2.5 NAAQS or associated 

implementation dates; in a proposed implementation rule for any revised PM2.5 NAAQS, such references

that would be updated as appropriateto reflect the final rule for today’s proposal. In addition, the EPA 

expects to consider options for potentially updating certain policies in the existing implementation rule 

based on new information or implementation experience (e.g., attainment demonstration requirements). 

For completeness, Tthe EPA solicits preliminary comment on the implementation issues that the Agency 

should consider for updating.

Under the basic approach outlined in the implementation rule for the 1997 PM2.5 NAAQS, the 

state begins the development of an attainment demonstration with the evaluation of the air quality 

improvements the nonattainment area can expect in the future due to “on the books” existing federal, 

state, and local emission reduction measures. The state then must conducts a further assessment of 

emission sources in the nonattainment area, and the additional reasonably available control measures 

(RACM) and reasonably available control technology (RACT) that can be implemented by these 

sources, in determining how soon the area can attain the standard. (Under the current implementation 

rule, the sources for consideration would be those emitting SO2, direct PM2.5, and presumptively NOx. 

Sources of the other PM2.5 precursors, VOC and ammonia, presumptively do not need to be evaluated 

for control measures unless demonstrated by the state or EPA as significant contributors to PM2.5

concentrations in the relevant nonattainment area.) Under section 172 of the CAA as interpreted by the 

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EPA, attainment demonstrations must include a RACM analysis showing that no additional reasonably 

available measures could be adopted and implemented such that the SIP could specify an advance the 

attainment date that is 1 by 1 year or more years earlier.

The evaluation of these potential emission reductions and associated air quality improvement is 

commonly performed with sophisticated air quality modeling tools. Given that fine particle 

concentrations are affected both by regionally-transported pollutants (e.g., SO2 and NOx emissions from 

power plants) and emissions of direct PM2.5 from local sources in the nonattainment area (e.g., steel 

mills, rail yards, and highway mobile sources), the EPA plans to recommends the use of regional gridbased models (such as CMAQ and CAMx) in combination with source-oriented dispersion models (such 

as AERMOD) to develop PM2.5 attainment strategies for the revised annual primary NAAQS. Although 

the EPA projects significant improvements in PM2.5 concentrations regionally from a number of recently 

promulgated rules such as the Cross State Air Pollution Rule (76 FR 48208, August 8, 2011) and the 

Mercury and Air Toxics Standards rule (77 FR 9304, February 16, 2012) that will result in SO2 and NOx

reductions from many geographically dispersed sources, local reductions of direct PM2.5 emissions also 

result in important health benefits. On a per ton basis, reductions of direct PM2.5 are more effective in 

reducing PM2.5 concentrations than reductions of precursor emissions. Therefore, reductions of direct 

PM2.5 emissions y should therefore play a key role in attainment planning as well.

Each nonattainment area needs to ensure that it will make “reasonable further progress” (RFP) in 

accordance with section 172(c)(2) of the CAA from the time of SIP submittal to its attainment date. 

Under the approach outlined in the implementation rule for the 1997 PM2.5 NAAQS, for an area that can 

demonstrate it will attain the standard within the presumptive 5-year period from designation, its 

attainment demonstration will be considered to meet the RFP requirement. The EPA believes it is 

appropriate to apply this same approach for the revised annual primary PM2.5 standard. The EPA 

believes there should be no additional RFP requirements for such an area because the SIP and attainment 

demonstration would be due 3 years after designations and its attainment date will be only 2 years after 

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that date. The EPA believes that two other provisions in the implementation rule for the 1997 PM2.5

NAAQS are also appropriately extended to a revised primary annual PM2.5 NAAQS: (1) aAn area that 

cannot demonstrate attainment within the presumptive 5 year period swhould be required to provide a 

separate RFP plan showing that the area will achieve emission reductions by certain interim milestone 

dates which provide for “generally linear” progress over the course of the implementation period. All 

PM2.5 attainment plans must also; and (2) a PM2.5 plan should be required to include contingency 

measures which would apply without significant delay in the event the area fails to attain by its 

attainment date. 

The EPA expects that the same general approach for determining attainment of the 1997 PM2.5

primary standard by the attainment deadline would be followed for determining attainment with any 

primary PM2.5 standard. Attainment would be evaluated based on the 3 most recent years of certified, 

complete, and quality-assured air quality data in the nonattainment area. The EPA also would expect to 

include similar flexibility provisions for an area to be able to obtain two 1-year attainment date 

extensions under certain circumstances. In the 1997 PM2.5 NAAQS implementation rule, an area whose 

design value based on the most recent 3 years of data exceeds the standard could receive a 1-year 

attainment date extension if the air quality concentration for the third year alone does not exceed the 

level of the standard. Similarly, an area that has received a 1-year extension could receive a second 1-

year extension if the average of the area’s air quality concentration in the “extension year” and the 

previous year does not exceed the level of the standard. 

The EPA notes that in other sections of today’s proposal, the EPA describes new requirements 

for deploying near-road monitors and clarifies certain existing monitoring provisions. As discussed in 

the designations section, the EPA would not expect that data from any new near-road PM2.5 monitors 

would be available in time to consider during the initial area designations process, and therefore such 

monitoring data would not be the basis for designating a new nonattainment area at the time of initial 

designations. The EPA plans to address any potential implications of the proposed monitoring changes 

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on attainment planning and development of attainment demonstrations by states in the future 

implementation rule. The EPA requests comment on any specific attainment planning considerations for 

future SIPs that may be associated with today’s proposed changes to monitoring provisions. 

With regard to implementation of the pre-existing standards for PM2.5, As noted above, the EPA 

expects to consider options for potentially updating certain policies in the existing implementation rule. 

One issue the EPA has identified for updating, as discussed in section VIII.B.3.b.i above, relates to the 

use of data from newly-deployed monitors. The EPA is proposing to require that by January 1, 2015, 

states establish one near road PM2.5 monitor in each CBSA with a population greater than 1 million, and 

that these monitors be collocated with NO2 near road monitors in these CBSAs. One implication of these 

changes is that a nonattainment area might have additional monitoring sites that violate the mass-based 

PM2.5 NAAQS. As noted earlier, this change in monitoring network requirements, if finalized, would not 

affect the initial area designations process for implementing the revised standards because of the timing 

of the deployment of new monitoring sites relative to the designations schedule. However, there are also 

implications for SIP development once the designations are made.

There are similar SIP development implications arising from the EPA’s proposal to change, as 

discussed in section VIII.B.2.b above, the current presumption that micro- and middle-scale monitoring 

sites are “unique” and are comparable only to the 24-hour PM2.5 standards, unless the Regional 

Administrator determines that the micro- or middle-scale site is not unique and can be compared to the 

annual PM2.5 standards. Today’s proposal, if finalized, would reverse this presumption, such that microand middle-scale monitoring sites would not be considered to be “unique,” and therefore would be 

comparable to the annual PM2.5 standards, unless otherwise determined by the Regional Administrator. 

This change conceivably could affect initial designations. In any case, however, these changes may 

necessitate changes in the requirements for air quality modeling analyses that are needed for PSD 

permitting, transportation conformity hotspot assessments, attainment demonstrations, and maintenance 

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plans to implement the existing and revised PM2.5 NAAQS. 5

Potential implications for and appropriate changes to attainment demonstration and maintenance 

plan SIP requirements will be more fully addressed in the implementation rule that we intend to finalize 

by the time that area designations would be finalized for the revised PM2.5 NAAQS. The EPA invites 

preliminary comment at this time on this and other possible implications. Tthe EPA’s current opinion is

that the changes in the monitoring regulations, if finalized, should not result in any new requirements 

with respect to attainment plans or maintenance plans for the 1997 or the 2006 PM2.5 NAAQS during 

some specified transition period.

6

For example, if the proposed PM NAAQS revisions and revised 

monitoring regulations are finalized in December 2012 June 2013, many states will have recently 

submitted, or will be close to submitting their implementation plans to attain the 2006 24-hour PM2.5

NAAQS (also due that are due in December 2012). In addition, state and EPA actions are still under way 

with regard to adopting and approving certain attainment plans and maintenance plans for nonattainment 

areas under the 1997 PM2.5 standards. These plans will still be under EPA review. If any states have 

experienced delays in completing their nonattainment SIPs for the 2006 NAAQS, they also should be 

close to such submittal. Also, some states may be developing or may have recently submitted 

maintenance plans for areas that have attained the 1997 or 2006 PM2.5 NAAQS. The EPA does not 

believe it would be reasonable for requirements applicable to such attainment implementation plans and 

maintenance plans to change beginning immediately upon any revision of the monitoring regulations., 

for example to demonstrate attainment at any monitoring sites newly considered to be violating the 

NAAQS as a result of the monitoring regulation changes.

7

It could be very burdensome on state air 

 

5

See sections IX.F and IX.G below for additional discussion of the potential effect on the PSD and 

transportation conformity programs, respectively.

6

For example, it may be possible that a new near-road monitoring site has collected 3 years of data and 

shown a violation before final EPA action has been taken on an attainment plan or maintenance plan for 

the 1997 or 2006 NAAQS.

7

For example, it may be possible that a new near-road monitoring site An additional monitoring site 

violating the PM2.5 NAAQS could be a new near road site, if the site has collected 3 years of data and 

shown a violation before final EPA action has been taken on an attainment plan to rmaintenance plan for 

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quality programs to revise SIPs that have already been submitted to EPA or that have been under 

development for some time and are about to be submitted. The EPA believes that a more reasonable 

approach would be to provide for a transition period before the revised monitoring network and data 

comparability provisions would affect implementation plan and maintenance plan requirements. The 

EPA believes it would be important for the transition period to provide enough time for the EPA to 

complete action on attainment and maintenance SIPs for the 1997 or 2006 PM2.5 NAAQS that were 

initiated and completed (or that are close to nearly completedion) by states before the finalization of the 

proposed changes in the monitoring regulations. The EPA believes that if a SIP for the 1997 or 2006 

PM2.5 NAAQS has been approved during the transition period, the state would not be under an 

obligation to revise it unless the EPA has made a SIP call. The EPA invites preliminary comment on 

theis transition period concept, and on an appropriate date by which the transition period should be 

concluded. 

D. Implementing the Primary and Secondary PM10 NAAQS

As summarized in sections IV.F and VI.F above, the EPA is proposing to retain the current 

primary and secondary 24-hour PM10 standards to protect against the health effects associated with 

short-term exposures to thoracic coarse particles and against welfare effects. If this approach is finalized, 

the EPA would retain the existing implementation strategy for meeting the CAA requirements for PM10. 

States and emission sources would continue to follow the existing guidance and regulations for 

implementing the current standards. 

E. Implementing the Proposed New Secondary PM2.5 Visibility Index NAAQS in Nonattainment 

Areas

 

by a date when the nonattainment or maintenance SIP for the 1997 or 2006 NAAQS. is still under 

development or review by EPA. It is also possible that after this PM NAAQS revision is finalized, a 

micro- or middle-scale site that previously was not comparable to the annual PM2.5 NAAQS will 

become comparable to that NAAQS and indicate a violation that was not officially a violation at the 

time of the nonattainment designation and SIP development for the 1997 or 2006 NAAQS. Because 

there are no existing monitors that are now officially considered not “population oriented” the proposed 

revision to remove population orientation as a condition for data comparability to the NAAQS would 

not by itself result in any monitoring sites newly being considered to be violating.

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In past actions, the EPA has set the secondary PM standards identical to the primary PM 

standards. In this action, as summarized in section VI.F above, the EPA is proposing a new distinct 

secondary PM2.5 visibility index NAAQS. In addition, as also summarized in section VI.F above, the 

EPA is proposing to retain the current annual and 24-hour secondary PM2.5 standards to provide 

protection against non-visibility welfare effects. Although the proposed new secondary PM2.5 visibility 

index NAAQS would differ from the primary PM2.5 NAAQS (and existing secondary PM2.5 NAAQS) 

with respect to indicator/index, statistical form, and level, attainment of this standard would, like the 

aggregated PM2.5 mass-based standards, depend on ambient measurements (i.e., specifically speciated 

PM2.5 mass concentrations). The EPA expects that implementation of emission reduction measures that 

will help to achieve the mass-based 1997 and 2006 primary and secondary PM2.5 standards and the 

proposed revised primary annual PM2.5 standard will also provide important improvements in visibility 

and substantial progress toward meeting the proposed new secondary PM2.5 visibility index standard, 

where necessary, because these emission reduction measures will address the same sources and 

pollutants which also contribute to PM-related visibility impairment. In fact, as discussed below in 

section IX.F.1, an analysis of the relationships between recent design values for the proposed primary 

(annual and 24-hour) PM2.5 standards and coincident design values for the proposed new PM2.5 visibility 

index standard indicates that all or nearly all areas in attainment of the proposed primary PM2.5 standards 

would also likely be in attainment of the proposed new secondary PM2.5 visibility index standard (Kelly,

et al.Wayland, 2012).

8

Section 172(a)(1) of the CAA authorizes the EPA to establish classification categories for areas 

designated nonattainment for the primary or secondary PM NAAQS, but does not require the EPA to do 

so. The implementation program for the 1997 and 2006 primary and secondary PM2.5 standards did not 

 

8

This analysis was based on 2008 to 2010 air quality data using the proposed level of 12 μg/m3for the 

primary annual PM2.5 standard and the existing 35 μg/m3level for the primary 24-hour PM2.5 standard 

and with the proposed level of either 30 or 28 dv in conjunction with a 24-hour averaging time and a 90th

percentile form for the secondary PM2.5 visibility index standard. The relationships between design 

values as characterized here are dependent upon the specific level and form of each of the standards.
Page 20 of 49

include a tiered classification system. This provided a relatively simple implementation structure and 

flexibility for states to implement control programs tailored to the specific nature of the problem and 

source mix in each area. For this same reason, the EPA also does not intend to establish classifications 

for nonattainment areas for the proposed new secondary PM2.5 visibility index standard. 

Section 172(a)(2) of the CAA provides the same statutory framework for implementing 

secondary standards in nonattainment areas as it does for primary standards, except that it provides

different attainment date requirements for secondary standards. The attainment date for the proposed 

revised primary annual PM2.5 standard is as expeditiously as practicable, but presumptively within 5

years of the date of designation, with the possibility of an attainment date of up to 10 years for certain 

areas with more severe air quality problems. For secondary NAAQS, however, section 172(a)(2)(B) 

defines the attainment date for an area designated nonattainment as “the date by which attainment can be 

achieved as expeditiously as practicable” but with no maximum limitation. Thus, it is possible for the 

EPA to approve an implementation plan part D SIP that provides for attainment of the secondary 

standards by a date more than 10 years after the date of designation with an appropriate demonstration. 

As noted in the above section on implementing the primary PM2.5 standard, the EPA expects that 

the same general approach for providing two possible 1-year extensions to the attainment date would 

also apply to any revised secondary PM2.5 standard. Attainment would be evaluated based on the 3 most 

recent years of certified, complete, and quality-assured air quality data in the nonattainment area. The 

EPA also would expect to include similar flexibility provisions for an area to be able to obtain two 1-

year attainment date extensions under certain circumstances. An area whose design value based on the 

most recent 3 years of data exceeds the standard could receive a 1-year attainment date extension if the 

deciview index for the third year alone does not exceed the level of the standard. Similarly, an area that 

has received a 1-year extension could receive a second 1-year extension if the average of the area’s 

deciview index in the “extension year” and the previous year does not exceed the level of the standard.

As noted previously, the EPA expects that implementation of control measures to achieve the 

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1997 and 2006 primary annual and 24-hour PM2.5 standards and the proposed revised primary annual 

PM2.5 standard will address the same sources and pollutants that contribute to PM-related visibility 

impairment, and, thus, great progress can be achieved toward attaining the proposed new secondary 

PM2.5 visibility index standard as a result of clean air programs designed principally to improve public 

health by attaining the primary PM2.5 standards. However, because the proposed new secondary PM2.5

standard is based on a visibility index rather than a mass concentration, implementation can be expected 

to present new challenges when developing part D SIPs. For example, while the proposed revision to the 

level and form of the primary annual PM2.5 standard does not pose any new issues with respect to air 

quality modeling methods, the speciated nature of the index for the proposed new secondary PM2.5

visibility index standard does pose new modeling issues. For this reason, the EPA invites commenters to 

present information concerning air quality modeling and other issues that are expected to be unique to 

implementing the proposed new secondary PM2.5 visibility index standard in nonattainment areas and

that should be considered by EPA in the development of the future implementation rule and related 

guidance. The EPA particularly seeks input on how implementation planning for the proposed new 

secondary PM2.5 visibility index standard can be integrated as much as possible with implementation 

planning for the proposed revised primary annual PM2.5 standard to increase the efficiency of the 

process and reduce administrative burden on state agencies and stakeholders. The EPA will consider 

these comments in developing a proposed implementation rule and related guidance for the new and 

revised standards. 

F. Prevention of Significant Deterioration and Nonattainment New Source Review Programs for the 

Proposed Revised Primary Annual PM2.5 NAAQS and the Proposed New Secondary PM2.5

Visibility Index NAAQS

The CAA requires states to include SIP provisions that address the preconstruction review of 

new stationary sources and the modification of existing sources. The preconstruction review of each new 

and modified source generally applies on a pollutant-specific basis and the requirements for each 

pollutant vary depending on whether the area is designated attainment or nonattainment for that 
Page 22 of 49

pollutant. Parts C and D of title I of the CAA contain specific requirements for the preconstruction 

review and permitting of new major stationary sources and major modifications, referred to as the PSD 

program and the NNSR program, respectively. Collectively, those permit requirements are commonly 

referred to as the “major NSR program.” 

The proposed revised primary annual PM2.5 NAAQS and proposed secondary PM2.5 visibility 

index NAAQS, if finalized, would affect certain PSD permitting actions as of the effective date for those 

NAAQS and would affect certain NNSR permitting actions after area designations are effective. In order 

to minimize the potential for disruption to NSR permitting, the EPA is proposing, in subsection IX.F.1.a 

of this preamble1(b), a grandfathering provision for certain PSD permits that are already in process, and 

is also proposing, in subsection IX.F.1.c1(c), a surrogacy approach for implementing PSD permitting 

requirements for the proposed secondary PM2.5 visibility index NAAQS. These provisions will assure 

that NSR permitting will be able to continue using the provisions and processes virtually identical to 

those already in place for the existing PM2.5 NAAQS, except that, in evaluating whether a source causes 

or contributes to a NAAQS violation, an applicants would need to compare the source’s their impacts to 

a different level and form of the primary annual standard if finalized as proposed. As discussed in more 

detail in the following sections, the EPA is not now proposing to change the PM2.5 increments, nor are 

we proposing to revise screening tools that are now used to implement PSD for PM2.5 such as the

significant emission rate, used as a threshold for determining whether a given project is subject to major 

NSR permitting requirements under both PSD and NNSR,; the significant impact levels, used to 

determine the scope of the required air quality analysis that must be carried out in order to demonstrate 

that the source’s emissions will not cause or contribute to a violation of any NAAQS or increment under 

the PSD program; or the significant monitoring concentrationSMC, a screening tool used to determine 

whether it may be appropriate to exempt a proposed source from the requirement to collect preconstruction ambient monitoring data as part of the required air quality analysis. 

1. Prevention of Significant Deterioration 
Page 23 of 49

The PSD requirements set forth under part C (sections 160 through 169) of the CAA apply to 

new major stationary sources and major modifications locating in areas designated as “attainment” or 

“unclassifiable” with respect to the NAAQS for a particular pollutant. The EPA regulations addressing 

the statutory requirements under part C for a PSD permit program can be found at 40 CFR 51.166 

(containing the PSD requirements for an approved SIP) and 40 CFR 52.21 (the federal PSD permit 

program). For PSD, a “major stationary source” is one with the potential to emit 250 tons per year (tpy)

or more of any air pollutant, unless the source or modification is classified under a list of 28 source 

categories contained in the statutory definition of “major emitting facility” in section 169(1) of the CAA. 

For those 28 source categories, a “major stationary source” is one with the potential to emit 100 tpy or 

more of any air pollutant. A “major modification” is a physical change or a change in the method of 

operation of an existing major stationary source that results in a significant net emissions increase of a 

regulated NSR pollutant. Under PSD, new major sources and major modifications must apply best 

available control technology (BACT) for each applicable pollutant and conduct an air quality analysis to

demonstrate that the proposed construction will not cause or contribute to a violation of any NAAQS or 

PSD increments (see CAA section 165(a)(3); 40 CFR 51.166(k); 40 CFR 52.21(k)). PSD requirements 

also include in appropriate cases an analysis of potential adverse impacts on Class I areas (see sections 

162 and 165 of the CAA). 

PSD permitting requirements first became applicable to PM2.5 in 1997 when EPA established a 

NAAQS for PM2.5 (Seitz, 1997). The EPA’s regulations define the term “regulated NSR pollutant” to 

include “[a]ny pollutant for which a national ambient air quality standard has been promulgated and any 

pollutant identified [in EPA regulations] as a constituent or precursor to such pollutant” (40 CFR 

51.166(b)(49); 40 CFR 52.21(b)(50)).9. In addition, on May 16, 2008, the EPA amended its rules to 

 

9 Under various provisions of the CAA, PSD requirements are applicable to each pollutant subject to 

regulation under the CAA, excluding hazardous air pollutants. The definition of “regulated NSR 

pollutant” also includes pollutants subject to any standard under section 111 of the CAA or any Class I 

or II substance subject to title VI of the CAA.
Page 24 of 49

identify certain PM2.5 precursors (SO2 and NOx) as regulated NSR pollutants and adopt other provisions, 

such as a significant emissions rate for PM2.5, to facilitate implementation of PSD and NNSR program 

requirements for PM2.5 (73 FR 28321). States were required to revise their SIPs by May 16, 2011 to 

incorporate the required elements of the 2008 final rule.

On October 20, 2010, the EPA again amended the PSD rules at 40 CFR 51.166 and 52.21 to add 

PSD increments as well as two screening tools for PM2.5 – significant impact levels (SILs) and a 

significant monitoring concentration (SMC) (75 FR 64864). The October 2010 final rule became 

effective on December 20, 2010. The EPA indicated that the SILs and SMC for PM2.5, while useful 

tools, are not considered mandatory elements of an approvable SIP; thus, no schedule was imposed on 

states for addressing those screening tools in their PSD rules. For the portions of the rule that addressed 

the PSD increments for PM2.5, states are required to submit the necessary SIP revisions (at least as 

stringent as the PSD requirements at 40 CFR 51.166) to EPA for approval within 21 months from the 

date on which the EPA promulgated the new PM2.5 increments – by July 20, 2012. This particular 

schedule is prescribed by the CAA specifically for the adoption of new PSD increments in state PSD 

programs. Sources for which PSD permits are issued pursuant to the Federal PSD program at 40 CFR 

52.21 after October 20, 2011, must determine their impact on the PM2.5 increments.

The PSD program currently regulates emissions of PM using several indicators of particles, 

including “particulate matter emissions” (as regulated under various new source performance standards 

under 40 CFR part 60), “PM10 emissions,” and “PM2.5 emissions.” The latter two emission indicators are 

designed to be consistent with the ambient air indicators for PM that the EPA currently uses in the PM 

NAAQS. As already noted, the PSD program also limits PM2.5 concentrations by regulating emissions of 

gaseous pollutants that result in the secondary formation of particulate matter. Those pollutants, known 

as PM2.5 precursors, generally include SO2 and NOx.

In addition to the NAAQS revisions themselves, for which proposed and other possible 

implementation approaches actions are described further below, the EPA is proposing certain 

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clarifications to the existing monitoring regulations codified at 40 CFR 58.30 (Special considerations for 

data comparisons to the NAAQS). These proposed clarifications are presented in detail in section 

VIII.B.2 of this preamble. The monitoring regulations provide a basis for determining whether specific 

monitoring sites are comparable to specific NAAQS. By extension, the EPA has used the principles for 

making these determinations for monitoring sites to also guide permitting authorities in assessing the 

comparability of specific receptor locations involved in PSD air quality analyses. Receptors are used in 

PSD modeling analyses to predict potential air quality impacts in the vicinity of the proposed new or 

modified facility and in some cases also at more distant Class I areas. The EPA will continue to use 

these principles in guiding PSD modeling analysis design. Accordingly, if the proposed PM NAAQS 

revisions and monitoring regulation clarifications described previously are finalized, the EPA will 

continue to advise permitting agencies to qualify or disqualify specific receptor locations used in PSD 

air quality analyses consistent with those provisions, and we will do so ourselves when we are the 

permitting authority. the EPA is 

proposing revisions to existing implementing regulations that will affect implementation of not 

only a revised annual PM2.5 NAAQS, but also the existing 24-hour PM2.5 NAAQS that the EPA is not 

proposing to change. Specifically, the EPA proposes to remove certain restrictions on the comparison of 

monitoring data to the PM2.5 NAAQS, currently codified at 40 CFR 58.30 (Special considerations for 

data comparisons to the NAAQS). These proposed changes include revoking the restriction that only 

“population-oriented” monitoring sites are comparable to the annual and 24-hour PM2.5 standards, and 

reversing the current presumption that micro- and middle-scale monitoring sites are “unique” and are 

comparable only to the 24-hour standard unless the Regional Administrator determines that a particular 

micro- or middle-scale site is not unique and can be compared to the annual standard. The latter 

proposed change would mean that micro- or middle-scale monitoring sites would be compared to the 

annual PM2.5 NAAQS unless the Regional Administrator determines that a particular micro- or middlescale site is unique and cannot be compared to these standards. See section VIII.B.2 of this preamble for 
Page 26 of 49

a more detailed discussion of the proposed changes regarding PM2.5 monitoring data.

Under PSD, modeling analyses are used to predict potential air quality impacts on “receptors” in 

the vicinity of the proposed new or modified facility, and in some cases also at more distant Class I areas 

where the emissions increase from the proposed source or modification could adversely affect applicable 

air quality related values, as defined for such areas. In the preamble to the 2008 final rule for PM2.5 NSR 

Implementation, the EPA stated that the PSD source impact analysis “must consider how a source, in 

combination with other sources in the area, will impact air quality at existing PM2.5 monitoring 

locations, as well as at locations that are appropriate for comparing predicted PM2.5 concentrations to the 

PM2.5 NAAQS based on PM2.5 monitor siting requirements and recommendations” (73 FR 28336, May 

16, 2008). This statement was intended to acknowledge the current provisions of 40 CFR 58.30 and to 

communicate that EPA did not expect PSD modeling for PM2.5 to include receptors representing sites 

that would not be eligible to be monitor locations (sites that are not population-oriented). The EPA has 

also interpreted 40 CFR 58.30 to mean that PSD modeling is not required to consider the effect of a new 

or modified facility on the annual standard at receptors that are micro- and middle-scale sites unless a 

monitor at the site of those receptors would be considered comparable to the annual standard. The 

proposed changes would eliminate restrictions in 40 CFR 58.30 and by extension mean that compliance 

with all the PM2.5 NAAQS should be considered at all ambient air receptors in a PSD modeling analysis 

unless the Regional Administrator determines that one or more micro- or middle-scale sites is unique 

and cannot be compared to the annual standard. While on first impression it might appear that these 

changes could make it more difficult for a source to show that it does not cause or contribute to a 

NAAQS violation, the EPA believes that few if any air quality analyses for PSD permits have relied 

upon the current EPA interpretation that allows the exclusion of some receptors in ambient air. 

With regard to the specific revisions being proposed to the PM NAAQS, today’s action, if 

finalized as proposed, would affect sources applying for PSD permits in several ways. We first discuss 

the implications for PSD with respect to the proposed revised primary annual PM2.5 standard (some of 
Page 27 of 49

which also apply to the proposed new secondary PM2.5 visibility index standard), and then the unique 

implications for PSD with respect to the proposed new secondary PM2.5 visibility index standard.

a. Grandfathering Provision

As discussed previously in this preamble, the EPA is proposing to revise the level of the primary 

annual PM2.5 NAAQS and establish a new secondary PM2.5 visibility index NAAQS.10 Longstanding 

EPA policy interprets the CAA and EPA regulations at 40 CFR 52.21(k)(1) and 51.166(k)(1) to 

generally require that PSD permit applications must include a demonstration that new sources and 

modifications will not cause or contribute to a violation of any NAAQS that is in effect as of the date the 

PSD permit is issued (Page, 2010a; Seitz, 1997). Thus, if the proposed revision to the primary annual 

PM2.5 NAAQS and the proposed new secondary PM2.5 visibility index NAAQS are promulgated, any 

proposed new and modified sources with permits pending at the time those PM2.5 NAAQS changes take 

effect would be expected to demonstrate compliance with them, absent some type of transition provision 

exempting such applications from the new requirements.

In order to provide for a reasonable transition into the new PSD permitting requirements that will 

result from the proposed revision of the primary annual NAAQS, the proposed addition of a secondary 

NAAQS for visibility protection, and the changes to the monitoring requirements discussed earlier, the 

EPA proposes to add a grandfathering provision to the federal PSD program codified at 40 CFR 52.21 

that would apply to certain PSD permit applications that are pending on the effective date of the revised 

PM NAAQS. The EPA proposes that the grandfathering provision would apply specifically to pending 

PSD permit applications for which the proposed permit (draft permit or preliminary determination) has 

been noticed for public comment before the effective date of the revised NAAQS. 

The proposed grandfathering provision would not be the first such grandfathering provision 

adopted by EPA. The Agency previously recognized that the CAA provides discretion for the EPA to 

 

10 The EPA is also proposing to revise the form of the annual primary standard by removing the option

for spatial averaging. However, this provision has played no role in PSD so its removal has no 

implications for PSD.
Page 28 of 49

grandfather PSD permit applications from requirements that become applicable while the application is 

pending (45 FR 52683, Aug. 7, 1980; 52 FR 24672, July 1, 1987; US EPA, 2011c, pp. 54 to 61). As 

discussed in more detail in these referenced actions, section 165(a)(3) of the CAA requires that a permit 

applicant demonstrate that its proposed project will not cause or contribute to a violation of any 

NAAQS. At the same time, section 165(c) of the CAA requires that a PSD permit be granted or denied

within 1 year after the permitting authority determines the application for such permit to be complete. In 

addition, section 301 of the CAA authorizes the Administrator “to prescribe such regulations as are 

necessary to carry out his functions under this chapter.” When read in combination, these three 

provisions of the CAA provide the EPA with the discretion to promulgate regulations to grandfather 

pending permit applications from having to address a revised NAAQS where necessary to achieve a 

balance between the CAA objectives to protect the NAAQS on the one hand, and to avoid delays in 

processing PSD permit applications on the other. The EPA has also construed section 160(3) of the 

CAA, which states that a purpose of the PSD program is to “insure that economic growth will occur in a 

manner consistent with the preservation of existing clean air resources” to call for a balancing of 

economic growth and protection of air quality (70 FR 59587 to 59588, Oct. 12, 2005). The reasoning of 

those prior EPA actions is also applicable to the promulgation of revised PM NAAQS.11

The CAA provides the EPA with discretion to establish the appropriate milestone within the 

permitting process for determining that a permit application is eligible for grandfathering (US EPA, 

2011c, p. 81). For example, in 1987, the EPA used the date of submittal of a complete permit application 

as the milestone upon which to base the grandfathering of a source from new permitting requirements 

 

11 In one extraordinary case where the EPA had not previously adopted a grandfathering provision in 

regulations and had significantly exceeded the deadline in section 165(c) of the CAA, the EPA has taken 

the position that it may grandfather through adjudication respecting a specific source, thus interpreting 

its regulations, as well as other authorities, to allow grandfathering in that extraordinary circumstance 

(US EPA, 2011c, pp. 67 to 71). Although grandfathering without a specific exemption in regulations 

was justified based on the particular facts in that specific instance, the EPA generally believes the 

preferred approach is to enable grandfathering through express regulatory exemptions of the type 

proposed in this action (US EPA, 2011c, p. 68).
Page 29 of 49

associated with the revisions made to the PM NAAQS at that time (52 FR 24672, July 1, 1987 at 

24703). In the context of the implementation of the revisions to the PM NAAQS that are being proposed

today, the EPA is proposing to use a different milestone to establish the date before which permits may 

be grandfathered. Accordingly, to avoid unreasonable delays in permit processing and issuance, and 

based on basic principles of fairness and equity, we believe that it is appropriate to allow pending permit 

applications that have reached the notice and comment period on a proposed permit (that is, a notice has 

been issued for public comment on the proposed permit action) by the effective date of the revised PM

NAAQS to continue being processed in accordance with the PM NAAQS requirements in place as the 

time of the public notice on the proposed permit.12

Before a proposed permit is issued for public comment, the applicant still has a reasonable 

opportunity to amend its permit application to address new or revised NAAQS that become effective 

while the reviewing authority’s preliminary consideration of the application is underway. Furthermore, 

the reviewing authority has the opportunity to review additional material and revise its fact sheet or 

statement of basis before beginning the public comment period on such a permit. However, if the EPA 

and other reviewing authorities were to apply new permitting requirements based on the revised PM 

NAAQS after the public comment period has begun, this would unduly delay the processing of the 

permit application by potentially requiring an additional public comment period and additional work by 

the reviewing authority at a time when it should be focused on considering public comments and 

preparing a final permit decision in order to conclude its review of a permit application in a timely 

manner. Through this proposal, the EPA is providing notice to current and future permit applicants that 

they may have to provide an analysis showing that their facility will not cause or contribute to a 

 

12 There may be proposed permits for which a public notice was issued prior to October 20, 2011, which 

is the date that PM2.5 increments became applicable requirements for any newly issued federal PSD 

permits under 40 CFR 52.21. It is not the EPA’s intention that the grandfathering provision proposed 

today should relieve such a permit from the requirement to demonstrate compliance with those new 

PM2.5 increments, for which the EPA did not adopt any grandfathering provisions but deferred 

implementation in accordance with the requirements of the CAA.
Page 30 of 49

violation of the revised NAAQS for PM if a proposed permit is not issued for public comment before 

such NAAQS become effective. 

Accordingly, the EPA proposes to amend the federal PSD regulations at 40 CFR 52.21 to 

provide a grandfathering provision to allow for the continued review of permits proposed before a 

revision to the 2006 PM NAAQS under the PM NAAQS that applied at the time of the public notice on 

the proposed permit. These requirements include not only the NAAQS as of that date, but also the 

modeling receptor restrictions based on the special considerations for comparability of PM2.5 ambient air 

monitoring data to the NAAQS, as discussed in section VIII.B.2 above.

The EPA also proposes that states that issue PSD permits under a SIP-approved PSD permit 

program should have the discretion to “grandfather” proposed PSD permits in the same manner under 

these same circumstances. Thus, the EPA also proposes to revise section 40 CFR 51.166 to provide a 

comparable exemption applicable to SIP-approved PSD programs.

In developing the proposed grandfathering provision, the EPA considered whether such a 

provision should include a sunset clause. A sunset clause would add a time limit beyond which an 

otherwise eligible permit action would no longer be grandfathered from PSD permitting requirements 

associated with a revised PM NAAQS. Consistent with past grandfathering actions described above, the 

EPA is not proposing to include a sunset clause for the proposed grandfathering provision. Permit 

applicants and reviewing authorities already have strong incentives to process applications and issue 

draft permits in a timely manner, and the EPA does not believe that the addition of a sunset clause to the 

proposed grandfathering provision would add meaningful additional incentive for sources or permitting 

authorities to expedite permitting processes. Furthermore, the EPA believes that a sunset clause could in 

fact result in further delays for permit actions that qualify for the proposed grandfathering provision in 

circumstances where unrelated and not reasonably avoidable factors cause draft permit issuance and

public notice to lapse beyond the sunset date. In such cases, the already delayed permit action would be 

further delayed to address PSD permitting requirements associated with the revised PM NAAQS, 
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potentially triggering a domino effect of newly applicable requirements. As such, the EPA believes a 

sunset clause would diminish the value of the grandfathering provision and likely introduce additional 

complexities in relation to specific permit actions. However, the EPA solicits comment on whether a 

sunset clause would be appropriate under certain circumstances, and if so, what time limits would be 

placed on the grandfathering period associated with the revised PM NAAQS.

b. Recent Guidance Applicable to the Proposed Revised Primary Annual PM2.5 NAAQS 

Today’s proposal to revise the level of the primary annual PM2.5 NAAQS from 15.0 μg/m3to a

level in the range between 12.0 and 13 μg/m3and to establish a new secondary PM2.5 visibility index 

NAAQS generally will require proposed new major stationary sources and modifications to take these 

changes into account as part of the required air quality analysis to demonstrate that the proposed 

emissions increase will not cause or contribute to a violation of the PM NAAQS. If the PM NAAQS are 

revised as proposed, and when effective, proposed sources that are not grandfathered from the new 

requirements (as described in section IX.F.1.a) would be required to demonstrate compliance with the 

suite of PM NAAQS, including the revised primary annual PM2.5 NAAQS and the proposed new 

secondary PM2.5 visibility index NAAQS upon their effective date.

PSD applicants are currently required to demonstrate compliance with the existing primary 

annual and 24-hour PM2.5 NAAQS and will need to consider their impact on the revised primary annual 

PM2.5 NAAQS, if finalized. To assist sources and permitting authorities in carrying out the required air 

quality analysis for PM2.5 under the existing standards, the EPA issued, on March 23, 2010, a guidance 

memorandum that recommends certain interim procedures to address the fact that compliance with the 

24-hour PM2.5 NAAQS is based on a particular statistical form, and that there are technical 

complications associated with the ability of existing models to estimate the impacts of secondarily 

formed PM2.5 resulting from emissions of PM2.5 precursors (Page, 2010b). For the latter issue, the EPA 

recommended that special attention be given to the evaluation of monitored background air quality data, 

since such data readily account for the contribution of both primary and secondarily formed PM2.5. To 

Comment [PAK1]: HEID check this language.
Page 32 of 49

provide more detail and to address potential issues associated with the modeling of direct and precursor 

emissions of PM2.5, the EPA is now developing additional permit modeling guidance that will 

recommend appropriate technical approaches for conducting a PM2.5 NAAQS compliance demonstration 

for the existing primary PM2.5 NAAQS, which includes more adequate accounting for contributions 

from secondary formation of ambient PM2.5 resulting from a proposed new or modified source’s

precursor emissions. (As discussed in the next section, these recommended approaches may be extended 

to the proposed secondary NAAQS as well under a surrogacy approach). To this end, the EPA discussed 

this draft guidance in March 2012 at the EPA’s 10th Modeling Conference.

13 Based on its review of 

public comments received and further technical analyses, the EPA intends to issue final guidance by the 

end of calendar year 2012.

c. Surrogacy Approach for the Proposed New Secondary PM2.5 Visibility Index NAAQS

As summarized in section VI.F of this preamble, the EPA is proposing a distinct secondary 

NAAQS for PM2.5 that will provide protection against visibility impairment, measured in terms of a 

visibility index using a calculated PM2.5 light extinction indicator (see section VI.D.1 above). The PM2.5

visibility index values are determined using a six-step procedure involving 24-hour speciated PM2.5

concentration data together with climatological relative humidity factors. The EPA plans to calculate 

design values for the proposed new secondary PM2.5 visibility index NAAQS using the procedures 

described in section VII.A.5 above, relying upon ambient PM2.5 speciation measurement data available 

through the CSN or IMPROVE methods and spatial interpolation of historical relative humidity data. 

As explained above, the PSD program requires individual new or modified stationary sources to 

carry out an air quality analysis to demonstrate that their proposed emissions increases will not cause or 

contribute to a violation of any NAAQS. Such a demonstration for the proposed new secondary PM2.5

visibility index NAAQS could require each PSD applicant to predict, via air quality modeling, the 

 

13 The presentation on this draft guidance was posted on the EPA website at: 

http://www.epa.gov/ttn/scram/10thmodconf.htm. 
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visibility impairment that will result from its proposed emissions in conjunction with an assessment of 

existing air quality (visibility impairment) conditions. Under 40 CFR 51.166(l)(1) and 40 CFR

52.21(l)(1), all applications of air quality modeling for purposes of determining compliance with 

awhether a new or modified source causes or contributes to a NAAQS violation, including a violation of

the proposed secondary NAAQS for PM2.5, must be based upon air quality models specified in appendix 

W to 40 CFR part 51. Currently there are no air quality models identified in Appendix W that are 

recommended for regulatory applications (Appendix W to 40 CFR part 51, Section 3.1.1(b)) for 

addressing the atmospheric chemistry associated with secondary formation of PM2.5. Thus, Iif this 

demonstration were to be attempted using the six-step procedure that the EPA is proposing to use for

calculating PM2.5 visibility index design values, significant technical issues with the modeling 

procedures could arise. Those technical difficulties include the current limitations on speciated sourcespecific emissions data for model input; the lack of an EPA-approved air quality model with the 

capability to address the atmospheric chemistry associated with secondary formation of PM2.5; and the 

lack of PSD screening tools for streamlining the air quality analysis process. In addition, due to the 

limited monitoring network for speciated PM2.5, some sources may not be able to rely on existing 

speciated monitoring data to adequately represent the background air quality and thereby satisfy 

preconstruction monitoring requirements. Consequently, those prospective PSD sources could be 

required to collect new data in order to determine the representative background concentrations of PM2.5

species (i.e., those required for calculating the PM2.5 visibility index values as described in section 

VII.A.5 above).

Recognizing these difficult technical issues, the EPA believes that there is an essential need to 

provide alternative approaches to enable prospective PSD sources to demonstrate that they will not 

cause or contribute to a violation of the secondary PM2.5 visibility index NAAQS, if finalized as 

proposed. To meet this need, the EPA believes that it is reasonable to allow the use of a surrogacy 

approach, as discussed below, for at least the interim period while technical issues are being resolved, 
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but which could potentially be continued beyond such time if shown to be appropriate. The EPA is 

providing notice of its intent to follow such an approach and is asking for comments on the approach as 

discussed in the remainder of this section. The Agency believes that following this approach will 

facilitate the transition to a workable PSD permitting approach under the proposed new secondary PM2.5

visibility index NAAQS.

To support consideration of alternative approaches that could be used by prospective PSD 

sources, the EPA conducted a two-pronged technical analysis of the relationships between the proposed

new PM2.5 visibility index standard and the proposed primary annual and 24-hour PM2.5 standards 

(Kelly, et al., Wayland, 2012). The first prong of the analysis addressed aspects of a PSD significant 

impact analysis by evaluating whether an individual source’s impact resulting in a small increase in 

PM2.5 concentration would produce a comparably small increase in visibility impairment. This analysis 

included estimates of PM2.5 speciation profiles based on direct PM2.5 emission profiles for a broad range 

of source categories and for theoretical upper and lower bound scenarios. The analysis indicated that 

small increases in PM2.5 concentrations caused by individual sources produce similarly small changes in 

visibility impairment for ambient conditions near the proposed standard level of either 30 dv or 28 dv. 

The second prong of the analysis addressed aspects of a PSD cumulative impact analysis by exploring

the relationship between the 3-year design values for the proposed primary and secondary annual and 

24-hour PM2.5 standards and coincident design values for the proposed new PM2.5 visibility index 

standard based on recent air quality data. This analysis showed that visibility generally decreases when 

daily PM2.5 concentrations increase, and vice versa. This analysis further explored the appropriateness of 

using a demonstration of attainment with the primary 24-hour PM2.5 standards as a surrogate for a 

demonstration of attainment with the proposed new secondary PM2.5 visibility index standard. The 

Kelly, et al. Wayland (2012) analysis was based on 2008 to 2010 air quality data and on the proposed 

retention of the primary 24-hour PM2.5 standards with a level of 35 μg/m3in conjunction with a 98th

percentile form (sections III.F and IV.F) and the proposed new secondary PM2.5 visibility index standard 
Page 35 of 49

with a level of either 30 dv or 28 dv in conjunction with 24-hour averaging time and a 90th percentile 

form (see section VI.F).14 This analysis indicated that all or nearly all areas in attainment of the primary 

24-hour PM2.5 standard would also likely be in attainment of the proposed new secondary PM2.5

visibility index standard. 

The EPA believes that this technical analysis is robust and will have broad national application. ;

thus, sources may choose to rely on the surrogacy demonstration even after resolution of the issues and 

limitations described previously, consistent with the case law on the use of surrogates. Based on this 

technical analysis, the EPA currently believes that there is sufficient evidence that, for the purposes of 

making a demonstration under the PSD program that a new or modified source will not cause or 

contribute to a violation of the proposed secondary 24-hour PM2.5 visibility index NAAQS, a 

demonstration that the source does not cause or contribute to a violation of compliance with the massbased primary 24-hour PM2.5 NAAQS serves as a suitable surrogate. for demonstrating compliance with 

the proposed secondary 24-hour PM2.5 visibility index NAAQS under the PSD program. As such, many 

or all sources undergoing PSD review for PM2.5 would be able to rely upon their analysis demonstrating 

that they do not cause or contribute to a violation of compliance with the mass-based 24-hour primary 

PM2.5 NAAQS to also demonstrate that they do not cause or contribute to a violation of show 

compliance with the proposed secondary PM2.5 visibility index NAAQS, if finalized. The described 

surrogate approach would thus serve to overcome the technical challenges discussed above and 

minimize otherwise burdensome and costly air quality analyses associated with individual sources being 

required to perform separate and distinct analyses with regard to the proposed new secondary PM2.5

visibility index standard. The EPA believes this surrogacy approach is appropriate to fulfill PSD 

requirements for individual sources in PSD areas, which, by definition, will not have been designated as 

nonattainment for the PM2.5 visibility index NAAQS. However, our proposed surrogacy approach for 

 

14 As identified in section IX.E above, the relationships between design values characterized in the 

WaylandKelly, et al. (2012) analysis and summarized here are dependent upon the specific level and 

form of each of these standards.
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PSD should not be construed as a proposal to use a surrogacy approach for designating nonattainment 

areas or for implementing programs to attain the visibility index NAAQS in those areas.

The surrogacyte approach is not intended to replace or otherwise undermine the validity of the 

analytical techniques employed for air quality related value (AQRV) assessments, including visibility, 

required under 40 CFR 51.166(p) and 40 CFR 52.21(p). The federal land managers (FLM) – the federal 

officials with direct responsibility for management of Federal Class I parks and wilderness areas – have 

an affirmative responsibility to protect the AQRVs of such lands, and to provide the appropriate 

procedures and analysis techniques for assessing AQRVs (Appendix W to 40 CFR part 51, Sections 6.1 

(b) and 6.2.3(a)). The FLMs have developed specific modeling approaches for AQRV assessments that 

are not specifically governed under the requirements set forth in 40 CFR 51.166(l)(1) and 40 CFR

52.21(l)(1), thus the surrogacyte approach is not applicable to the AQRV assessments under the PSD 

program.

The surrogate approach could be incorporated into the PSD program in any of three alternative 

ways. First, the decision as to whether the surrogate approach is adequate could be handled on a caseby-case basis in consultation with the permitting authority, similar to the existing consultation process 

under the EPA’s Guideline on Air Quality Models for ozone and secondary PM2.5 impacts (40 CFR part 

51, appendix W, section 5.2.1.c), with no presumption regarding its adequacy. Second, the EPA could 

establish a rebuttable presumption that the surrogate approach is applicable for all permits through either 

guidance or a notice-and-comment rulemaking. In either the first or second alternative, there would be a 

possibility that reliance on a surrogate-based demonstration could be subjected to challenge for any 

particular permit analysis. Third, the EPA could establish that the surrogate approach is applicable for 

all permits, also through a notice-and-comment rulemaking. The EPA seeks comment on all of the 

identified issues and proposed alternative implementation mechanisms associated with the proposed 

surrogate approach. It is the Agency’s intention to issue either guidance or new regulatory provisions as 

just described for a surrogacy approach by the time any final revisions to the PM NAAQS become
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effective, so that sources seeking permits will not be unnecessarily delayed. 

While noting the importance of the surrogacy approach as an essential initial strategy due to 

limitations on data and analytical tools, the EPA also notes that when a technically robust surrogate 

relationship exists there may not be a need to apply an end date for the use of a surrogacy approach. 

Without an end date, PSD applicants would always have the option of relying upon such a 

demonstration if they would so choose. This would offer long-term benefits in terms of simplification 

and resource savings for applicants and reviewing authorities. Accordingly, based on the technical 

analysis for the standards analyzed (Kelly, et alWayland, 2012) which supports the surrogacy approach 

for demonstrating compliance with the proposed secondary PM2.5 visibility index NAAQS, the EPA 

may determine that it is not necessary to announce an end date for using it. The EPA invites comment on 

this aspect of the proposal as well.

For context, the EPA notes that with regard to sources being required to demonstrate compliance 

with the 1997 PM2.5 NAAQS, the EPA has previously issued an interim policy for permit applicants that 

were required to demonstrate compliance with the PM2.5 NAAQS (Seitz, 1997). Under the 1997 policy, 

which is no longer in effect,15 the EPA stated that demonstrating compliance with the NSR requirements 

for controlling PM10 emissions and for analyzing impacts on PM10 air quality could be used to 

demonstrate compliance with the PM2.5 NSR requirements. This approach was designed to control PM2.5

emissions and protect PM2.5 air quality until certain technical difficulties concerning PM2.5 were 

resolved. At that time, however, we did not support the policy with any technical analysis to show how a 

demonstration of compliance with the PM10 NAAQS would satisfy the PM2.5 requirements and support 

the issuance of a PSD permit. Consequently, the EPA later concluded that, in keeping with numerous 

court opinions regarding the use of surrogates, PSD applicants and reviewing authorities seeking to rely 

specifically on the 1997 PM10 Surrogate Policy should consider certain overarching legal principles,

including that a surrogate may be used only after it has been shown to be reasonable (such as where the 

 

15 The 1997 PM10 Surrogate Policy formally ended on May 16, 2011. See 76 FR 28646 (May 18, 2011).
Page 38 of 49

surrogate is a reasonable proxy for the pollutant or has a predictable correlation to the pollutant) and that 

the relationship between the regulated pollutant and the surrogate pollutant can be shown to apply in the 

specific instance where an applicant or reviewing authority seeks to rely upon it. In keeping with these 

principles, the Agency believes that the surrogate approach now being proposed for use in 

demonstrating compliance with the new proposed secondary PM2.5 visibility index NAAQS is supported 

by a robust technical analysis. The EPA invites comment on this analysis, which is provided in the 

docket for this action.

The EPA notes that the analysis supporting the surrogacy approach for the PSD program is 

distinct from and serves a different purpose than the analyses conducted to inform the Administrator’s 

proposed conclusion on the appropriate indicator for a standard intended to protect against PM-related 

visibility impairment. As discussed in section VI.A above, the EPA has long recognized that the 

determination of a single, appropriate national level for a secondary standard to address PM-related 

visibility impairment is complicated by regional differences in several factors that influence visibility,

such as background and current PM2.5 concentrations, PM2.5 composition, and average relative humidity. 

Variations in these factors across regions could thus result in situations where attaining an appropriately 

protective concentration of fine particles in one region might or might not provide the appropriate 

degree of protection in a different region. Although the analysis upon which the surrogacy approach is 

based (Kelly, et al.,Wayland, 2012) generally shows that daily PM2.5 visibility index values decrease 

when daily PM2.5 mass concentrations decrease, and vice versa, there is nonetheless considerable 

variability in that relationship across the range of ambient fine particle concentrations. As a result, as 

discussed in section VI.D.1.d above, the Administrator provisionally concludes that a calculated PM2.5

light extinction indicator is an appropriate indicator to replace the current PM2.5 mass indicator and that 

such an indicator would afford a relatively high degree of uniformity of visual air quality protection in 

areas across the country by virtue of directly incorporating the effects of differences in PM2.5

composition and relative humidity across the country.
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d. PSD Screening Provisions: Significant Emissions Rates, Significant Impact Levels, and 

Significant Modeling Concentration.

The EPA has historically allowed the use of screening tools to help facilitate the implementation 

of the NSR program by reducing the permit applicant’s burden and streamlining the permitting process 

for circumstances where emissions or concentrations could be considered de minimis. These screening 

tools, which all provide de minimis thresholds of some kind, include a significant emissions rate (SER), 

significant impact levels (SILs), and a significant monitoring concentration (SMC). The EPA 

promulgated a SER for PM2.5 in the 2008 final rule on NSR implementation as part of the first phase of 

NSR amendments to address PM2.5 (74 FR 28333, May 16, 2008). The PM2.5 SER, defined as 10 tpy of 

direct PM2.5 emissions (including condensable PM)16, is used to determine whether any proposed new 

major stationary source or major modification will emit sufficient amounts of PM2.5 to require review 

under the PSD program.17 Under the terms of the existing EPA regulations, the applicable SER for PM2.5

is 10 tpy of direct PM2.5 emissions (including condensable PM) and, for precursors, 40 tpy of sulfur 

dioxide and 40 tpy of nitrogen dioxide emissions. 40 CFR 51.166(b)(23); 40 CFR 52.21(b)(23). This 

SER applies to permitting requirements based on both the annual and 24-hour PM2.5 NAAQS. The SERs 

are pollutant-specific but not specific to the averaging time of any NAAQS for a particular pollutant. At 

this time, the EPA is not proposing any change to the existing PM2.5 SER as a result of the proposed 

revisions to the primary annual PM2.5 NAAQS and the proposed new secondary PM2.5 visibility index 

NAAQS. However, the EPA intends to consider this issue in a subsequent rulemaking that will 

specifically address various PSD implementation issues that are being described herein. The EPA will 

solicit comment on any proposed changes to the SERs for PM2.5 and its precursors at that time, but also 

 

16 The SER for PM2.5 also includes de minimis thresholds for PM2.5 precursors of 40 tpy of SO2 and 40 

tpy of NOx emissions. The PM2.5 precursors emitted in significant amounts are also required to undergo 

preconstruction review for PM2.5. Any decision to propose changing the existing SER for PM2.5 will 

include consideration of the PM2.5 precursor SER values as well.

17 The PSD rules provide that a source that would emit major amounts of any regulated NSR pollutant 

must undergo review for that pollutant as well as any other regulated NSR pollutant that the source 

would emit in significant amounts.
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invites preliminary suggestions at this time that we may consider in developing that proposed 

rulemaking. Until any rulemaking to amend existing regulations is completed, permitting decisions

should continue to be based on the SERs for PM2.5 and its precursors in existing regulations.

Once it is determined that the proposed new source or modification is significant for PM2.5, the 

permit applicant must complete an air quality analysis. The SIL helps to determine the scope of the 

required air quality analysis that must be carried out in order to demonstrate that the source’s emissions 

will not cause or contribute to a violation of any NAAQS or increment. The EPA promulgated SILs for 

PM2.5 in 2010 under a final rule that established increments, SILs, and SMC for PM2.5 (75 FR 64890 to 

64894, October 20, 2010). A separate PM2.5 SIL is defined for each averaging period for which PM2.5

NAAQS and increments currently exist, as well as for each of the three area classifications, i.e., Class I, 

II and III, that Congress established in the CAA for PSD purposes. 

Historically, sources have been allowed to model their proposed emissions increase to predict 

ambient impacts associated with that emissions increase, and to compare this predicted ambient 

concentration of PM2.5 to the applicable SIL, which is also expressed as an ambient PM2.5 concentration 

over a prescribed averaging time consistent with the NAAQS and increments. At this time, the EPA is 

not proposing to revise the annual SIL for PM2.5 as a result of the proposed revision to the primary 

annual PM2.5 NAAQS. However, the EPA intends to review this issue and will consider any potential 

need to revise the existing SIL in a separate rulemaking addressing PSD implementation issues. The 

EPA welcomes preliminary comments concerning this issue, but will also provide an additional 

opportunity for comments at a later date in the event that a subsequent proposal is made to revise the 

annual PM2.5 SIL. 

While the proposed new secondary PM2.5 visibility index NAAQS is a 24-hour standard for 

which no PM2.5 SIL is currently defined, there is a question as to whether the existing 24-hour PM2.5

SIL, expressed on a PM2.5 mass basis (μg/m3), would be appropriate for this proposed new secondary 

NAAQS, expressed in terms of a PM2.5 visibility index. As discussed in section IX.F.1.c above, the EPA 
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conducted an analysis to evaluate whether an individual source’s impact resulting in a small increase in 

PM2.5 concentration would produce a comparably small increase in visibility impairment (WaylandKelly 

et al., 2012). The analysis indicates that small increases in PM2.5 concentrations caused by individual 

sources produce similarly small changes in visibility impairment for ambient conditions near the 

proposed standard level of either 30 dv or 28 dv. 

The EPA is not proposing any possible alternatives to the existing 24-hour PM2.5 SIL in this 

proposed rule, but instead intends to issue a separate rulemaking to assess this and other related PSD 

implementation issues. The EPA also wishes to note that the current PM2.5 SILs are the subject of a 

petition that challenges the EPA’s legal authority under the CAA to develop and implement those SILs, 

and also alleges that the existing PM2.5 SILs have not been adequately demonstrated to represent de 

minimis values. Sierra Club v. EPA, No. 10-1413 (D.C. Circuit filed December 17, 2010). In the course 

of this litigation, the EPA has recognized the need to correct the text of two PM2.5 SILs provisions in the 

regulations, and the EPA has asked the court to vacate those provisions so that the EPA may correct 

them. However, EPA does not believe this corrective action would preclude use of the PM2.5 SILs in the 

interim, and EPA intends to provide guidance on continued use of the PM2.5 SILs (in a manner 

consistent with principles articulated by the EPA in the rulemaking and litigation) pending this 

correction of the regulatory text. The proposed revised primary annual PM2.5 NAAQS and the proposed 

secondary PM2.5 visibility index NAAQS do not affect the continued used of the PM2.5 SILs in 

accordance with the forthcoming guidance described above. It is unclear at this time what implications 

this lawsuit will have on the continued use of the PM2.5 SILs. As a separate matter, the EPA intends to 

proceed with the process of evaluatingconsider the need for a new SIL specifically for implementing any 

new secondary PM2.5 visibility index NAAQS under the PSD program. In the event that we do proceed, 

the EPA now welcomes preliminary comments as to how such a SIL could be developed. The EPA will 

also provide an additional opportunity for comments at a later date in the event that a subsequent 

proposal is made to establish a separate unique SIL for the secondary PM2.5 visibility index NAAQS, if 
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such a secondary NAAQS is finalized 

Finally, the SMC, also measured as an ambient pollutant concentration (μg/m3), is a screening 

tool used to determine whether it may be appropriate to exempt a proposed source from the requirement 

to collect pre-construction ambient monitoring data as part of the required air quality analysis for a 

particular pollutant. The EPA promulgated the existing SMC for PM2.5 in 2010 on the basis of the 

defined minimum detection limit for PM2.5 and the current information at that time concerning the 

physical capabilities of the PM2.5 FRM samplers. In that rulemaking, the EPA addressed uncertainties 

introduced into the measurement of PM2.5 due to variability in the mechanical performance of the PM2.5

samplers and micro-gravimetric analytical balances that weigh filter samples. In a future NSR 

implementation rulemaking that will follow this rulemaking, the EPA intends to evaluate the types of 

additional ambient data, if any, that may need to be collected by a proposed source concerning the 

proposed new secondary PM2.5 visibility index NAAQS, and the feasibility of individual sources being 

required to gather such additional information. The EPA welcomes preliminary comments concerning 

this issue, but will provide additional opportunity for comment when a subsequent NSR implementation 

rulemaking is proposed concerning the proposed revisions to the PM NAAQS. 

e. PSD Increments

Section 166(a) of the CAA requires the EPA to promulgate “regulations to prevent the 

significant deterioration of air quality” for pollutants covered by the NAAQS“for which national 

ambient air quality standards. are promulgated after August 7, 1977.” Among other things, the EPA has 

implemented this requirement through promulgation of PSD increments. The EPA promulgated PM2.5

increments in 2010 to prevent significant air quality deterioration with regard to the primary and 

secondary annual and 24-hour PM2.5 NAAQS18 (75 FR 64864, October 20, 2010). The proposed revision 

to the primary annual PM2.5 NAAQS could raises the question of whether the EPA should consider 

 

18 The primary and secondary NAAQS for PM2.5 have been the same up until this time where EPA is 

proposing a new secondary NAAQS for PM-related visibility impairment.
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reviseing the annual PM2.5 increments. Similarly, tThe EPA’s proposed action to establish a new 

secondary PM2.5 visibility index NAAQS could raises the question of whether revisions to the EPA 

should promulgate a new increment or revise the existing PM2.5 increments are appropriate to to 

specifically address public welfare considerations protected by the this proposed new secondary

standard. 

In this proposal, the EPA is not proposing to revise the neither to revise the existing PM2.5

increments. nor to establish a new increment for the visibility index. The EPA will consider whether it 

is appropriate to take such an either of these actions in the future, and if so, would undertake 

rulemaking. Issues concerning the interpretation of section 166(a) of the CAA and EPA’s obligation to 

promulgate new or revised increments pursuant to that statutory provision have been raised in recent 

legal challenges. WildEarth Guardians v. Jackson, No. 3:11-CV-05651-YGR (N.D. Cal. filed Nov. 22, 

2011); Midwest Environmental Defense Center et al. v. Jackson, No. 3:11-CV-05694-YGR (N.D. Cal. 

filed Nov. 28, 2011). The decision to use section 166(a) to promulgate new increments for PM2.5, in 

light of the fact that the existing increments for PM measured air quality changes in terms of PM10, was 

based on EPA’s determination that “for purposes of section 166(a), the promulgation of a NAAQS for 

PM2.5 established a NAAQS for an additional pollutant after 1977”19 (75 FR 64871 to 64872, October 

20, 2010). 

While the determination of compliance with the proposed new secondary NAAQS would be 

based on a PM2.5 visibility index, it could be argued that such an indicator is actually based on a subset 

of the existing PM2.5 indicator and should not be considered a new pollutant for PSD purposes. Thus, 

there is a valid question as to whether the EPA should promulgate a new increment specifically designed 

to prevent significant deterioration with regard to PM-related visibility impairment, or revise the existing 

24-hour PM2.5 increment for that purpose. The EPA anticipates that its decision concerning the need for 

 

19 The EPA added new PM2.5 increments while retaining the existing PM10 increments, recognizing that 

two different indicators of PM were being used for the NAAQS.
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new or revised increments addressing a revised annual standard, and those addressing a PM-related 

visibility impairment will be made at a later date. The EPA invites preliminary comments at this time

on such a need, and on issues we should consider if we undertake a rule to revise the PM2.5 increments.

We would undertake any such action but also intends to address the issues associated with any new 

increments or equivalent measures in the separate NSR rulemaking discussed earlier in this section,

consistent with the timeframe provided by the CAA. In the meantime, the current PM2.5 increments 

remain in effect, and PSD permitting should continue pursuant to the current increments, with a 

minimum of disruption to the permitting process when the revised new NAAQS takes effect.

2. Nonattainment New Source Review 

The requirements under part D of the CAA pertain to the preconstruction review and permitting 

requirements for new major stationary sources and major modifications locating in areas designated 

“nonattainment” for a particular pollutant. Those requirements are commonly referred to as the NNSR 

program. The EPA regulations for the NNSR program are contained at 40 CFR 51.165, 52.24 and part 

51, appendix S. 

For NNSR, “major stationary source” is generally defined as a source with the potential to emit 

at least 100 tpy or more of a pollutant for which an area has been designated “nonattainment.” Thus, the 

NNSR program applies to pollutants for which the EPA has promulgated NAAQS. Because the EPA has 

defined the PM NAAQS, and has established area designations for PM, in terms of two separate 

indicators – PM10 and PM2.5 – each indicator is regulated separately for purposes of NNSR applicability. 

That is, for PM10, a “major stationary source” for NNSR applicability generally is a source that is 

located in a PM10 nonattainment area and has the potential to emit at least 100 tpy of PM10 emissions.20

For PM2.5, a “major stationary source” for NNSR applicability is a source that is located in a PM2.5

 

20 In some cases, however, the CAA and the EPA’s regulations define “major stationary source” for 

nonattainment area NSR in terms of a lower emissions rate dependent on the pollutant. For PM10, for 

example, a source having the potential to emit at least 70 tpy of PM10 is considered “major” if the source 

is located in a nonattainment area classified as a “Serious Area.”
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nonattainment area and has the potential to emit at least 100 tpy of direct PM2.5 (“PM2.5 emissions”) or a 

precursor of PM2.5.

For a major modification, the NNSR rules rely upon SERs described previously in the PSD 

discussion in section IX.F.1. For NNSR, a major modification is a physical change or a change in the 

method of operation of an existing stationary source that is major for the nonattainment pollutant and 

that results in a significant net emissions increase of that nonattainment pollutant. As described earlier, 

the EPA will be evaluating the existing SERs for PM2.5 and PM2.5 precursors, and will determine 

whether there is any basis for proposing changes to the existing values. Any decision to propose 

changing the existing SERs in a future rulemaking would also apply to their use in the NNSR program 

requirements.

The EPA has designated nonattainment areas for the existing primary annual and 24-hour PM2.5

NAAQS independently, and the EPA also approves redesignations to attainment separately for the two 

averaging periods. Thus, an area may be nonattainment for the annual standard and 

unclassifiable/attainment or attainment for the 24-hour standard. While no formal policy has yet been 

developed to address this situation, the EPA presently believes that it is reasonable to require that only 

NNSR (and not PSD) applies for PM2.5 in any area that is nonattainment for either averaging period.21

Looking forward, the EPA proposes that areas would be designated for a proposed new secondary PM2.5

visibility index NAAQS independently of designations for the mass-based annual and 24-hour PM2.5

NAAQS. Accordingly, the EPA intends to address this issue in a future NSR rulemaking, but invites 

comments now on whether it is appropriate to apply the NNSR program requirements for any pollutant 

that is designated nonattainment for at least one averaging period or at least one primary or secondary 

NAAQS for a particular pollutant. 

New major stationary sources or major modifications based on PM2.5 emissions (or emissions of 

 

21 However, transportation conformity requirements discussed in section IX.G below are dependent 

upon the averaging period(s) for which an area is designated nonattainment.
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a PM2.5 precursor) in a PM2.5 nonattainment area, must install technology that meets the lowest 

achievable emission rate (LAER); secure appropriate emissions reductions to offset the proposed 

emissions increases; and perform other analyses as required under section 173 of the CAA. Following

the promulgation of any new or revised NAAQS for PM2.5, some new nonattainment areas for PM2.5

may result. Where a state does not have any NNSR program or the current NNSR program does not 

apply to PM2.5, that state will be required to submit the necessary SIP revisions to ensure that new major 

stationary sources and major modifications for PM2.5 undergo preconstruction review pursuant to the 

NNSR program. Under section 172(b) of the CAA, the Administrator may provide states up to 3 years 

from the effective date of nonattainment area designations to submit the necessary SIP revisions meeting 

the applicable NNSR requirements. Nevertheless, permits issued to sources in nonattainment areas must 

satisfy the applicable NNSR requirements as of the effective date of the nonattainment designation; 

therefore states lacking the appropriate NNSR program requirements at that time will be allowed to 

issue such permits during the SIP revision period in accordance with the applicable nonattainment 

permitting requirements contained in the Emissions Offset Interpretative Ruling at 40 CFR part 51, 

appendix S, which would apply to the revised PM NAAQS upon their effective date. The EPA is not 

proposing any type of PM2.5 grandfathering provision at this time for purposes of NNSR. The timetable 

for adopting new provisions under the State NNSR program will not apply with regard to the new or 

revised NAAQS for PM2.5 until such time that an area is designated nonattainment for a particular 

standard. Further consideration of the need for a grandfathering provision for purposes of NNSR for the 

new or revised NAAQS for PM2.5 will be made and addressed in the future, as appropriate. 

G. Transportation Conformity Program

Transportation conformity is required under CAA section 176(c) to ensure that transportation 

plans, transportation improvement programs (TIPs) and federally supported highway and transit projects 

will not cause new air quality violations, worsen existing violations, or delay timely attainment of the 

relevant NAAQS or interim reductions and milestones. Transportation conformity applies to areas that 
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are designated nonattainment and maintenance for transportation-related criteria pollutants: carbon 

monoxide, ozone, NO2, and PM2.5, and PM10. Transportation conformity for any new or revised NAAQS 

for PM2.5 does not apply until 1 year after the effective date of the nonattainment designation for that 

NAAQS (See CAA section 176(c)(6) and 40 CFR 93.102(d)). The EPA’s Transportation Conformity 

Rule (40 CFR part 51, subpart T, and 40 CFR part 93, subpart A) establishes the criteria and procedures 

for determining whether transportation activities conform to the SIP. The EPA is not proposing changes 

to the transportation conformity rule in this proposed rulemaking. The EPA notes that the transportation 

conformity rule already addresses the PM2.5 and PM10 NAAQS. However, in the future, the EPA will 

review the need to issue or revise guidance describing how the current conformity rule applies in 

nonattainment and maintenance areas for any new or revised primary or secondary PM NAAQS, as 

needed. 

As discussed in section VIII above, the EPA is proposing certain clarifying changes to PM2.5 air 

quality monitoring regulations, one of which will be of interest to those who are involved in 

implementing transportation conformity requirements. The EPA is proposing to change the current 

presumption that micro- and middle-scale monitoring sites are unique and are comparable only to the 

24-hour PM2.5 standards unless the Regional Administrator determines that the micro- or middle-scale 

site is not unique and can be compared to the annual standard. Today’s proposal, if finalized, would 

reverse this presumption (section VIII.B.2.b). This would mean that micro- and middle-scale sites would 

be compared to the annual PM2.5 standards unless the Regional Administrator decides that the site is 

unique. The EPA is also proposing to remove population orientation as a condition for the NAAQScomparability of data from a monitoring site (section VIII.B.2.a). These proposed changes are designed 

to align different elements of the monitoring regulations for consistency, which will changes will help 

facilitate the interpretation of modeling results from quantitative PM2.5 conformity hot-spot analyses for 

the annual standards by clarifying as they will help to determine more objectively which receptors are 

comparable to the NAAQS.

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If the EPA finalizes these changes to the monitoring regulations, the EPA will update its 

guidance on quantitative PM2.5 hot-spot analyses as appropriate to make it consistent with the revised 

monitoring requirements (US EPA, 2010j). If the proposed revisions to the monitoring requirements are 

finalized, the EPA intends that the current quantitative PM2.5 hot spot guidance would continue to apply 

to any quantitative PM2.5 hot-spot analysis that was begun before the effective date of these proposed 

revisions to the monitoring regulations. Revised guidance on receptors to be compared to the annual 

PM2.5 standards for quantitative PM2.5 hot-spot analyses would apply to any quantitative PM2.5 hot-spot 

analysis begun after the effective date of the revised monitoring regulations. Nonattainment and 

maintenance areas are encouraged to use their interagency consultation processes to determine whether 

an analysis for a given project was started before the effective date of changes to the monitoring 

requirements. Applying the current guidance regarding whether or not a receptor can be compared to the 

annual PM2.5 NAAQS to analyses that had begun before the effective date of changes to the monitoring 

regulations is consistent with how the conformity rule and guidance address the transitional period for 

new emissions factor models or local planning assumptions (40 CFR 93.110(a) and 93.111(b) and (c)). 

In both of those cases, analyses begun before the new model or data became available can be completed 

using the data and/or model that were available when the analyses began. The EPA allows this in order 

to conserve state resources by not making transportation planning agencies redo analyses simply 

because a model has been revised, new data have become available, or in this case, the EPA has revised 

its regulations for PM2.5 monitoring.

H. General Conformity Program

General conformity is required by CAA section 176(c). This section requires that Federal 

agencies do not adopt, accept, approve, or fund activities that are not consistent with state air quality 

goals. General conformity applies to any Federal action (e.g., funding, licensing, permitting, or 

approving), other than projects that are Federal Highway Administration (FHWA)/Federal Transit 

Administration (FTA) projects as defined in 40 CFR 93.101 (which are covered under transportation 
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conformity described above), if the action takes place in a nonattainment or maintenance areas for 

ozone, PM, NO2, carbon monoxide, lead, or SO2. General conformity also applies to a Federal highway 

and transit project if it does not involve either Title 23 or 49 funding, but does involve FHWA or FTA 

approval such as is required for a connection to an Interstate highway or for a deviation from applicable 

design standards per 40 CFR 93.101. (The FHWA and FTA actions described here as not subject to 

general conformity are subject to transportation conformity.) General conformity for any revised PM 

NAAQS does not apply until 1 year after the effective date of a nonattainment designation for that 

NAAQS. The EPA’s General Conformity Rule (40 CFR 93.150 to 93.165) establishes the criteria and 

procedures for determining if a Federal action conforms to the SIP. The EPA is not proposing changes to 

the general conformity rule in this proposed rulemaking. The general conformity rule already addresses

the PM2.5 and PM10 NAAQS. The EPA will review the need to issue guidance describing how the 

current conformity rule applies in nonattainment and maintenance areas for the final revised primary and 

secondary PM NAAQS.