From: Lydia Wegman/RTP/USEPA/US

To: "Frey, Nathan J." <Nathan_J._Frey@omb.eop.gov>

Cc: Joseph-J Dougherty/DC/USEPA/US@EPA, Michael Ling/RTP/USEPA/US@EPA

Date: 12/13/2012 04:57 PM

Subject: Minor edits to address interagency comments on transportation conformity and exceptional events

Nathan, 

Please find attached edits responding to two specific interagency comments on transportation conformity 

and exceptional events. Please let us know if you have any questions. 

Lydia
EPA intends that the changes to the monitoring regulations will be applied in a consistent 

manner in both the PSD and transportation conformity programs. The commenter is incorrect 

that the conformity program has been a forum for deciding what monitors were comparable to 

the NAAQS, or has been implemented in a manner inconsistent with the monitoring regulations 

to date and the PSD program. 

However, to ensure that there is no confusion in implementing the final rule’s monitoring 

requirements, we have clarified the PSD preamble as follows:

PSD section

In addition to the NAAQS revisions contained in today’s final rule, the EPA is 

finalizing certain clarifications to the existing monitoring regulations codified at 40 CFR 

58.30 (Special considerations for data comparisons to the NAAQS). These 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 also used the principles for making these 

determinations for monitoring sites to 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. Since the EPA interprets the regulation at 40 CFR 58.30 to apply in 

this context, the EPA will continue to use the principles in the revised regulations in 

guiding PSD modeling analysis design. Accordingly, the EPA recommends that air 

agencies qualify or disqualify specific receptor locations used in PSD air quality analyses 

consistent with the final monitoring regulations, as amended by today’s rule, and we 

intend to do so ourselves when we are the permitting authority. Accordingly, the EPA 

recommends that specific receptor locations used in PSD air quality analyses are 

evaluated consistent with the final monitoring regulations, as amended by today’s rule.

In addition, EPA will coordinate with DOT in the development of its revised receptor guidance 

for conformity analyses of the annual PM2.5 NAAQS. 
EO12866_PM NAAQS_2060-AO47_FRN Preamble_and_Reg_Text_20121120

6560-50-P

VII. Interpretation of the NAAQS for PM

B. Exceptional Events

The EPA is finalizing primary annual PM2.5-specific deadlines in 40 CFR 50.14 by which 

air agencies1 must flag ambient air quality data that they believe have been affected by 

exceptional events and submit initial descriptions of those events. The EPA is also finalizing the 

deadlines by which air agencies must submit detailed exceptional events documentation to 

support the exclusion of those data from the EPA’s monitoring-based determinations of 

attainment or nonattainment with the revised primary annual PM2.5 NAAQS. The final 

exceptional events-related schedule is aligned with the designations schedule, discussed in 

greater detail in section IX, and is promulgated as proposed and as supported by multiple 

commenters. Without revisions to 40 CFR 50.14, an air agency may not be able to flag and 

submit documentation for some relevant data either because the generic deadlines may have 

already passed by the time the new or revised NAAQS is promulgated or because the generic 

deadlines require documentation submission at least 12 months prior to the date that the EPA 

must make a regulatory decision.

The EPA acknowledges the concern raised by a few commenters that numerous wildfires 

occurred between 2010 and 2012 that air agencies may determine influenced ambient air quality 

concentrations potentially affecting compliance with the revised primary annual PM2.5 NAAQS, 

and that air agencies may want to submit detailed exceptional events documentation associated 

 

1 References to “air agencies” are meant to include state, local, and tribal air agencies responsible

for implementing the Exceptional Events Rule.
with multiplethese wildfires. Commenters further noted that 1 year to provide documentation of 

these potential exceptional events may not be sufficient. The EPA believes that the promulgated 

schedules provide sufficient time for air agencies to submit information related to the annual 

standard and for the EPA to fully consider and act on the submitted information during the initial 

area designation process. The EPA rRecently released draft exceptional events guidance that 

clarifies key provisions of the 2007 Exceptional Events Rule, provides examples of best 

practices, and streamlines the documentation development process. ,The guidance provides 

approaches that are broadly applicable to all event/pollutant combinations and would apply to 

many PM events, including wildfire/PM combinations. Additionally, the EPA has posted several 

concurred upon wildfire/PM exceptional event demonstration packages on its website at: 

http://www.epa.gov/ttn/analysis/exevents.htm. Considered together, the EPA believes this 

guidance will help air agencies submit information in a timely manner.

2

The EPA notes that 

under the promulgated schedule, except for events that occur in December 2012, air agencies 

will have more than 1 year to provide documentation for these potential events. The EPA intends 

to work with potentially affected areas to identify, screen, and prioritize events potentially 

influencing compliance with the primary annual PM2.5 NAAQS and associated area designations. 

Also in response to comments, the EPA is clarifying that this preamble language and the

associated promulgated exceptional events schedules apply only to the NAAQS that the EPA is 

newly promulgating or revising in this action, that is, the revised primary annual PM2.5 NAAQS. 

The promulgated exceptional event schedule revisions do not apply to the retained PM standards 

(i.e., secondary PM standards, primary 24-hour PM10, primary 24-hour PM2.5). Further, the 

 

2

The EPA released draft exceptional events guidance documents (U.S. EPA, 2012e) for public 

comment via a Notice of Availability in the Federal Register on July 6, 2012 (77 FR 39959). 
revised/extended exceptional event schedules apply only to those data the EPA will use to 

establish initial area designations for the revised primary annual PM2.5 NAAQS.

The “Treatment of Data Influenced by Exceptional Events; Final Rule” (72 FR 13560, 

March 22, 2007), known as the Exceptional Events Rule and codified at 40 CFR 50.14, contains 

generic deadlines for an air agency to submit to the EPA specified information about exceptional 

events and associated air pollutant concentration data. As discussed in the proposal, without 

revisions to 40 CFR 50.14, an air agency may not be able to flag and submit documentation for 

some relevant data because the generic deadlines may have already passed by the time the new 

or revised NAAQS is promulgated. Similarly, revisions to 40 CFR 50.14 are needed because air 

agencies may not be able to flag and submit documentation for events that occurred in December 

of 2013 by 1 year before the designations are made in 2014 as is required by the existing generic 

schedule requires. 

To support appropriate consideration of exceptional event data influencing ambient air 

quality concentrations potentially affecting compliance with the revised primary annual PM2.5

NAAQS, the EPA is adopting revisions to 40 CFR 50.14 to change the submission dates for 

claimed exceptional events information affecting PM2.5 data considered during the initial area 

designations process under the promulgated revised primary annual PM2.5 NAAQS. As 

proposed, for air quality data collected in 2010 or 2011, the EPA is extending to July 1, 2013 the 

otherwise applicable generic deadlines of July 1, 2011 and July 1, 2012, respectively, for 

flagging data and providing an initial description of an event (40 CFR 50.14(c)(2)(iii)). The EPA 

is retaining the existing generic deadline in the Exceptional Events Rule of July 1, 2013 for 

flagging data and providing an initial description of events occurring in 2012. Similarly, the EPA 

is revising to December 12, 2013, the deadline for submitting documentation to justify 
exceptional events occurring in 2010 through 2012 and potentially influencing compliance with

the revised primary annual PM2.5 NAAQS. The EPA believes these revisions/extensions will 

provide adequate time for air agencies to review potential PM2.5 exceptional events influencing 

compliance with the revised primary annual PM2.5 NAAQS from 2010 to 2012, to notify the 

EPA by flagging the relevant data and providing an initial description in AQS, and to submit

documentation to support claims for exceptional events. These schedule revisions will also allow 

the EPA to fully consider and act on the submitted information during the initial area designation 

process.

If an air agency intends the EPA to consider in the revised primary annual PM2.5

designations decisions whether PM2.5 data collected during 2013 influence compliance with the 

primary annual PM2.5 NAAQS, then the air agency must flag these data by the generic 

Exceptional Event Rule deadline of July 1, 2014. The EPA is finalizing August 1, 2014, as the 

deadline for submitting documentation to justify PM2.5-related exceptional events occurring in 

2013 and potentially influencing compliance with the revised primary annual PM2.5 NAAQS. 

The EPA believes that these deadlines provide air agencies with adequate time to review and 

identify potential exceptional events that occur in calendar year 2013 and for the EPA to fully 

consider and act on the submitted information during the initial area designation process.

While the EPA will make every effort to designate areas for the primary annual PM2.5

NAAQS on a 2 year schedule, the EPA recognizes that it may need up to an additional year for 

the designations process to ensure that states/tribes and the EPA base designations decisions on 

complete and sufficient information. If the EPA announces at a later date that it is extending the 

designations schedule beyond 2 years based on unavailability of data, the EPA will consider 
extending the 2013 exceptional event documentation submission schedule by promulgating 

additional revisions to 40 CFR 50.14. 

Therefore, using the authority provided in CAA section 319(b)(2) and in the Exceptional 

Events Rule at 40 CFR 50.14 (c)(2)(vi), the EPA is finalizing the schedule for data flagging and 

submission of demonstrations for PM2.5 exceptional events data potentially influencing 

compliance with the revised primary annual PM2.5 NAAQS considered for initial area 

designations under the promulgated primary annual PM2.5 NAAQS as presented in Table 3. 
Table 3. Revised Schedule for Exceptional Event Flagging and Documentation Submission for 

Data to be Used in Initial Area Designations for the 2012 PM2.5 NAAQS

NAAQS Pollutant/

Standard/(Level)/

Promulgation Date

Air Quality Data 

Collected for 

Calendar Year

Event Flagging & Initial 

Description Deadline

Detailed 

Documentation 

Submission Deadline

PM2.5/

Primary Annual 

Standard

(12.0 μg/m3) 

Promulgated 

December 14, 2012

2010 and 2011 July 1, 2013 December 12, 2013 

2012 July 1, 2013a December 12, 2013

2013 July 1, 2014aAugust 1, 2014

a

This date is the same as the general schedule in 40 CFR 50.14.

Note: The table of revised deadlines only applies to data the EPA will use to establish the initial 

area designations for the revised primary annual PM2.5 NAAQS. The general schedule applies for 

all other purposes, most notably, for data used by the EPA for redesignations to attainment.