NAAQS to a level of 0.08 parts per million (ppm), with a form based on
the 3-year average of the annual fourth-highest daily maximum 8-hour
average O3 concentration. On March 28, 2008 (73 FR 16436),
the EPA revised the O3 standards to a level of 0.075 ppm,
with a form based on the 3-year average of the annual fourth-highest
daily maximum 8-hour average O3 concentration. These changes
in the level and form of the O3 NAAQS, along with notable
decreases in O3 levels in most parts of the U.S., have
changed the landscape of O3 NAAQS violations in the U.S. At
the time of the first round of designations for the 8-hour standards
(June 15, 2005), only 5 areas were classified as serious or above for
the 8-hour standards as compared to 22 areas that were classified as
serious or above for the 1-hour standards. While the number of serious
and above areas decreased, the number of nonattainment areas remained
nearly the same. In addition to the change in the landscape of
O3 nonattainment issues, much of the equipment used at PAMS
sites is outdated and in need of replacement. New technologies have
been developed since the inception of the PAMS program that should be
considered for use in the network to simplify procedures and improve
data quality. For these reasons, the EPA determined that it would be
appropriate to re-evaluate the PAMS program as explained below.
    In 2011, the EPA initiated an effort to re-evaluate the PAMS
requirements in light of changes in the needs of PAMS data users and
the improvements in monitoring technology. The EPA consulted with the
Clean Air Science Advisory Committee (CASAC), Air

Monitoring and Methods Subcommittee (AMMS) to seek advice on potential
revisions to the technical and regulatory aspects of the PAMS program;
including changes to required measurements and associated network
design requirements. The EPA also requested advice on appropriate
technology, sampling frequency, and overall program objectives in the
context of the most recently revised O3 NAAQS and changes to
atmospheric chemistry that have occurred over the past 10-15 years in
the significantly impacted areas. The CASAC AMMS met on May 16 and May
17, 2011, and provided a report with their advice on the PAMS program
on September 28, 2011 (U.S. EPA, 2011f). In addition, the EPA met
multiple times with the National Association of Clean Air Agencies
(NACAA) Monitoring Steering Committee (MSC) to seek advice on the PAMS
program. The MSC includes monitoring experts from various State and
local agencies actively engaged in ambient air monitoring and many
members of the MSC have direct experience with running PAMS sites.
Specific advice obtained from the CASAC AMMS and the MSC that was
considered in making the proposed changes to the PAMS requirements is
discussed in the appropriate sections below.
    Based on the findings of the PAMS evaluation and the consultations
with the CASAC AMMS and NACAA MSC, the EPA proposed to revise several
aspects of the PAMS monitoring requirements including changes in (1)
network design, (2) VOC sampling, (3) carbonyl sampling, (4) nitrogen
oxides sampling, and (5) meteorology measurements. The following
paragraphs summarize the proposed changes, the comments received, and
the final changes and supporting rationale.
1. Network Design
    As discussed above, the current PAMS network design calls for two
sites (a Type 2, and a Type 1 or Type 3) per PAMS area. In their report
(U.S EPA, 2011f), the CASAC AMMS found ``that the existing uniform
national network design model for PAMS is outdated and too resource
intensive,'' and recommended ``that greater flexibility for network
design and implementation of the PAMS program be transferred to state
and local monitoring agencies to allow monitoring, research, and data
analysis to be better tailored to the specific needs of each
O3 problem area.'' While stating that the current PAMS
objectives were appropriate, the AMMS report also stated that
``objectives may need to be revised to include both a national and
regional focus because national objectives may be different from
regional objectives.'' The NACAA MSC also advised the EPA that the
existing PAMS requirements were too prescriptive and may hinder state
efforts to collect other types of data that were more useful in
understanding their local O3 problems.
    The EPA agrees with CASAC that the PAMS objectives include both
local and national objectives, and believes that the current PAMS
network design is no longer suited for meeting either sets of
objectives. As part of the PAMS evaluation, it was determined that at
the national level the primary use of the PAMS data has been to
evaluate photochemical model performance. Due to the locations of the
current PAMS areas and the current network design, existing PAMS sites
are clustered along the northeast and west coasts leading to
significant redundancy in these areas and very limited coverage
throughout the remainder of the country (Cavender, 2014). The resulting
uneven spatial coverage greatly limits the value of the PAMS data for
evaluation of model performance. CASAC (U.S. EPA, 2011f) noted the
spatial coverage issue and advised that the EPA should consider
requiring PAMS measurements in areas in addition to ``areas classified
as serious and above for the O3 NAAQS to improve spatial
coverage.'' The EPA also agrees with CASAC and NACAA that the PAMS
requirements should be revised to provide monitoring agencies greater
flexibility in meeting local objectives.
    The EPA proposed changes to the network design requirements to
better serve both national and local objectives. The EPA proposed a two
part network design. The first part of the design included a network of
fixed sites (``required PAMS sites'') intended to support O3
model development and the tracking of trends of important O3
precursor concentrations. The second part of the network design
required states with O3 non-attainment areas to develop and
implement Enhanced Monitoring Plans (EMPs) which were intended to allow
monitoring agencies the needed flexibility to implement additional
monitoring capabilities to suit the needs of their area.
    To implement the fixed site portion of the network design, the EPA
proposed to require PAMS measurements at any existing NCore site in an
O3 nonattainment area in lieu of the current PAMS network
design requirements.\222\ The NCore network is a multi-pollutant
monitoring network consisting of 80 sites (63 urban, 17 rural) sited in
typical neighborhood scale locations and supports multiple air quality
objectives including some of the objectives of the PAMS program
including the development and evaluation of photochemical models
(including both PM2.5 and O3 models), development
and evaluation of control strategies, and the tracking of regional
precursor trends.
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    \222\ The EPA noted that the proposed change would expand the
PAMS applicability beyond that required in 182(c)(1) of the CAA.
Thus, in this final rule, the EPA is relying on the authority
provided in Sections 103(c), 110(a)(2)(B), 114(a) and 301(a)(1) of
the CAA to expand the PAMS applicability to areas other than those
that are serious or above O3 nonattainment.
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    The EPA recognized that in limited situations existing NCore sites
may not be the most appropriate locations for making PAMS measurements.
For example, an existing PAMS site in an O3 nonattainment
area may be sited at a different location than the existing NCore site.
In this case, it may be appropriate to continue monitoring at the
existing PAMS site to support ongoing research and to maintain trends
information. To account for these situations, the EPA also proposed to
provide the EPA Regional Administrator the authority to approve an
alternative location for a required PAMS site where appropriate. The
EPA also solicited comments on alternative frameworks using other
benchmarks such as attainment status or population to ensure an
appropriately sized fixed PAMS monitoring network. The EPA received
several comments on the proposed changes to the network design,
primarily from state and local monitoring agencies. The following
paragraphs summarize the major comments made on the proposed network
design, our response, and final network design requirements.
    Most commenters agreed with the need to revise the existing network
design. One commenter agreed that ``requiring PAMS monitoring at
already existing NCore locations will benefit national and local
objectives to understand ozone formation and would also provide
significant cost efficiencies.'' Another commenter stated that they
supported the proposed changes, ``especially the flexibility provided
by EMPs designed to meet local objectives and achieve a better
understanding of photochemical precursors.'' Another commenter
supporting the changes stated that the ``proposed network revision will
provide states the flexibility to use their resources effectively.''
One commenter stated that the proposed changes ``reflect a more
efficient use of state and local monitoring resources by availing

monitoring agencies of existing NCore infrastructure to fulfill PAMS
requirements.''
    A number of concerns were also raised with the proposed network
design. Several commenters stated that the proposal ``would drastically
reduce the PAMS network in the Northeast.'' One commenter stated that
``this is not acceptable for the Northeast and Mid-atlantic Corridor,
which requires monitoring of the complex transport from multiple large
metropolitan areas in the region.'' One commenter recognized that the
EPA had intended to allow states to use EMPs to address upwind and
downwind data needs, but raised concerns that states with historically
important upwind and downwind sites in the Ozone Transport Region \223\
(OTR) may not be required to develop an EMP since those sites would be
in states that are attaining the O3 NAAQS. One commenter
suggested that ``the EPA consider the entire OTR when designing a PAMS
network rather than pockets of nonattainment areas in the region.'' The
EPA agrees that the reduction of sites in the OTR is a potential issue
and that many important existing PAMS sites would not be part of the
required PAMS sites based on the proposed network design. As noted by
several commenters, the EPA intended the state directed EMPs to give
states flexibility in determining data needed to understand local
O3 formation, including transport in the Northeast. However,
the EPA also agrees that as proposed many states in the OTR would not
be required to develop EMPs and, therefore, may not be provided PAMS
resources. To address these concerns and ensure adequate network
coverage in the OTR, the EPA is adding a requirement that all states in
the OTR develop and implement an EMP regardless of O3
attainment status. This change will help ensure that an EMP appropriate
for the entire OTR can be implemented.
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    \223\ Section 184(c) of the CAA establishes the OTR as comprised
of the states of Connecticut, Delaware, Maine, Maryland,
Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania,
Rhode Island, Vermont, and Consolidated Metropolitan Statistical
Area that includes the District of Columbia.
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    Concerns were raised by some states that existing NCore sites may
not be the most appropriate location for making PAMS measurements. One
commenter noted that their NCore site was inland but that their ``most
significant ozone problems occur along the shoreline due to transport
along the lake'', and that ``the NCore site cannot provide insight into
these important lakeshore ozone processes.'' Another commenter stated
that ``while it was laudable to leverage sites where data is already
being collected, it is unclear whether NCore sites adequately meet the
objectives of the PAMS program'', and that ``the current NCore network
may not be adequate to depict boundary conditions or areas of maximum
emissions.'' One commenter stated that ``in some nonattainment areas an
NCore site may be an appropriate location for a PAMS monitor, but in
other areas it would be preferable to install the PAMS monitoring in a
location downwind of a source region where higher ozone exposures
occur'' and that ``State and local boundaries should not be part of the
network design criteria.'' One commenter noted that while the EPA had
proposed to allow waivers, it was unclear if waivers would be allowed
where the alternative site was in a different CBSA or state than the
required PAMS site. As stated in our proposal, the EPA recognizes that
in some cases existing PAMS sites (or other sites) may be better suited
to meet local and national data needs. For this reason, we had proposed
to allow waivers in these situations. We do agree that it is
appropriate in some cases to allow these waivers to cross CBSA and
state boundaries. Therefore, we have added specific language to the
final waiver provisions to clarify that waivers can be allowed to cross
CBSA and state boundaries. Where a monitoring agency receives a waiver
from siting a monitor in reliance on a monitor operated by a different
monitoring agency (e.g., across state lines), the waiver will be
conditioned on the monitor being properly included in the other
agency's network plan, and operated in accordance with the requirements
of Part 58, including the relevant appendices.
    In addition to the concerns raised about closing important existing
PAMS sites discussed above, some commenters raised concerns that many
of the newly required PAMS sites would be in locations that were
expected to attain the revised O3 NAAQS soon after the new
sites would be installed. One commenter noted that ``requiring marginal
nonattainment areas to install PAMS sites would result in a large
undertaking at an area that would most likely be back in attainment at
or around the time the PAMS site started collecting data.'' One
commenter stated that by tying the network requirement to NAAQS
attainment ``threatens to underserve areas that are very close to
exceeding the revised ozone NAAQS and results in significant gaps in
the spatial coverage of the PAMS network'' and ``has the potential to
introduce undesirable uncertainty on the size and spatial extent of the
PAMS network over the long term.'' Another commenter was concerned that
the proposed network would be unstable, and would experience frequent
changes as areas came into attainment or went out of attainment thus
reducing the value of the data collected, and resulting in inefficient
use of resources. One commenter noted that ``a more stable monitoring
network design will allow for the examination of trends from spatially
robust, long running sites and will allow states to firmly establish
the infrastructure costs.''
    The EPA noted in the proposal that the size and locations of the
proposed required PAMS network is sensitive to the level of the revised
O3 NAAQS and future O3 concentrations. We
recognize and agree that if current downward trends in O3
concentrations continue, many initially required sites may no longer be
required to make PAMS measurements soon after the sites were installed.
Non-required sites could be closed, soon after being installed, at the
state's discretion. We agree this would result in an inefficient use of
resources. We also note that if these sites were closed following a
potential reclassification to attainment, the loss of those sites could
lead to a network with poor spatial coverage. Therefore, the EPA is
making changes to the proposed revisions to the network design to
improve the stability of the fixed site network. As explained below,
the final requirements are based on options for which we requested
comments in the proposal and the comments we have received.
    We requested comments on additional options to define the fixed
PAMS network component of the new network design. These options were
further discussed in a memorandum to the docket (Cavender, 2014). One
option discussed was to require PAMS measurements at all NCore sites
irrespective of the O3 attainment status of the area. One
commenter noted that ``requiring PAMS monitoring at all NCore sites,
regardless of ozone attainment status, provides the most spatially
robust and stable monitoring network.'' We noted that this requirement
would result in a network of approximately 80 sites, which would be
larger than the current network. In the supporting memorandum, we noted
that a fixed network of 80 sites would strain existing resources and
would not allow adequate resources to implement the state directed
EMPs.
    Another option discussed in the proposal included requiring PAMS
measurements at NCore sites in O3

nonattainment areas with a population greater than 1,000,000. We noted
that this option would result in a network of between 31 and 37 sites
depending on the level of the revised O3 NAAQS. We also
noted that focusing the applicability of PAMS to those NCore sites in
larger CBSAs would still provide the desired improvement in geographic
distribution while reducing the number of required sites down to a
level that would provide sufficient resources to implement the state-
directed EMP portion of the network. One commenter stated that they
``supported a 1,000,000 population threshold because it would help
prioritize resources to areas based on the greatest human health
impacts.'' In addition, a number of commenters, while not commenting on
the need for a population limit, did raise concerns about their ability
to acquire and retain staff with the necessary expertise to collect
PAMS measurements in less urbanized areas. As with the proposed network
design, we recognize that the total number of sites and the ultimate
spatial coverage under this option is also sensitive to changes in
O3 concentrations. If current downward trends in
O3 concentrations continue, many initially required sites
would not be required soon after they were installed. As with the
proposed option, this option could result in an unstable network
resulting in an inefficient use of resources and inadequate spatial
coverage to meet the network goals discussed above.
    Upon further consideration and in response to the comments
received, we are finalizing a network design that includes a
requirement for states to make PAMS measurements at all NCore sites in
CBSAs with a population of 1,000,000 people or more, irrespective of
O3 attainment status. We believe this requirement will
result in an appropriately sized network (roughly 40 sites) that will
provide adequate spatial coverage to meet national model evaluation
needs (Cavender, 2015). Redundancy is greatly reduced while important
network coverage is added in the midwest, southeast, and mountain west.
The improved spatial coverage will also strengthen the EPA's ability to
track trends in precursor concentrations regionally.
    Because the network requirement is not tied to attainment status,
this final requirement will ensure network stability and allows for
more efficient use of available resources. This final requirement also
removes uncertainty as to applicability and aids planning and logistics
involved with implementing the new requirements. Monitoring agencies
can determine the applicability of the fixed site requirements to their
areas today, and begin to make plans for investments in equipment,
shelter improvements, and staffing and training needs necessary to
implement the fixed site requirements without having to wait for the
designations process to be completed. In addition, this final
requirement should alleviate concerns raised by monitoring agencies in
more rural locations over the ability to attract and retain staff with
the skills necessary to make PAMS measurements.
    By adding the PAMS measurements to existing NCore sites,
significant efficiencies can be obtained which should further reduce
the costs of the fixed site network as NCore sites currently make many
of the PAMS measurements. Furthermore, adding the additional PAMS
measurements (e.g., speciated VOCs, carbonyls, and mixing height) to
existing NCore sites will improve our ability to assess other
pollutants (e.g., air toxics and PM2.5).
    Although, as discussed in comment and summarized above, we believe
there are good reasons for not tying the requirement for fixed PAMS
sites to O3 attainment status, we continue to believe that
requiring PAMS measurements in areas that historically have had low
O3 concentrations is unlikely to provide data of significant
value to warrant the expense and effort of making such measurements.
Therefore, we have included a provision that would allow a monitoring
agency to obtain a waiver, based on Regional Administrator approval, in
instances where CBSA-wide O3 design values are equal to or
less than 85% of the 8-hour O3 NAAQS and where the site is
not considered an important upwind or downwind site for other
nonattainment areas. The EPA selected 85% as the threshold for this
waiver provision as it has been used historically to identify locations
needing additional monitoring for both the O3 and
PM2.5 NAAQS. The EPA will work with the monitoring agencies
and the Regions to help ensure consistent implementation of this waiver
provision.
    The second part of the proposed PAMS network design included
monitoring agency directed enhanced O3 monitoring activities
intended to provide data needed to understand an area's specific
O3 issues. To implement this part of the PAMS network
design, the EPA proposed to add a requirement for states with
O3 nonattainment areas to develop an EMP. The purpose of the
EMP was to improve monitoring for ambient concentrations of
O3, NOX, total reactive nitrogen (NOy)
\224\, VOC, and meteorology. The EPA suggested that types of activities
that might be included in the state's EMP could include additional PAMS
sites (e.g., upwind or downwind sites), additional O3 and
NOX monitoring, ozonesondes or other aloft measurements,
rural measurements, mobile PAMS sites, additional meteorological
measurements, and episodic or intensive studies. The intent of the EMPs
is to allow monitoring agencies flexibility in determining and
collecting the information they need to understand their specific
O3 problems.
---------------------------------------------------------------------------

    \224\ NOy includes NO, NO2, and other
oxidized nitrogen compounds (NOz).
---------------------------------------------------------------------------

    We received comments on the proposed requirement for an EMP in
states with O3 nonattainment areas. Most comments supported
the requirement, but other comments raised a number of concerns. A
number of commenters questioned the need for EMPs in Marginal and
Moderate O3 nonattainment areas. They noted that in most
cases, Marginal O3 nonattainment areas were expected to come
into compliance without state-specific controls. One commenter stated
that ``nonattainment areas projected to attain the standard without
additional state-level actions may not need the PAMS resources and
additional monitoring to develop a better understanding of their ozone
issues.'' One commenter noted that ``marginal ozone nonattainment areas
are given only a few requirements because it is assumed that the areas
will reach attainment within three years.'' Another commenter stated
``requiring enhanced monitoring for any marginal or moderate area
should only be implemented where such analyses show the need for this
data.'' The EPA agrees that based on current trends in O3
concentrations and the EPA's own projections, states in Marginal
nonattainment areas likely will comply with the revised NAAQS without
additional state-directed controls, and as such, an EMP is not
necessary in Marginal O3 attainment areas. Accordingly, the
EPA is finalizing a requirement for EMPs in areas classified as
Moderate or above O3 nonattainment and, thereby, removing
the applicability of the requirement for Marginal areas. We believe
this final requirement will provide the desired flexibility to allow
states to identify enhanced monitoring needs while focusing resources
for EMPs in areas of greater need of enhanced monitoring data.
    Commenters expressed concerns over the lack of detail on what an
approvable EMP would entail. As proposed, the

EMPs would be reviewed and approved by the EPA Regional Administrator
as part of the annual monitoring plan review process. One commenter
recommended that the ``EPA detail the requirements of the EMPs for
ozone nonattainment areas in future implementation guidance.'' One
commenter stated that the ``EPA should provide some coordination
between regional offices and technical guidance to state agencies that
would be of assistance in developing and executing the EMPs.'' The
requirements for the EMPs were intentionally left quite general in
order to maximize the flexibility for states in identifying their
specific data needs. Regional approval of the plans is required to
ensure the enhanced monitoring planned will be commensurate with grant
funds provided for EMPs. Nonetheless, the EPA understands the need for
guidance on developing EMPs and commits to working with monitoring
agencies and the regions to develop appropriate guidance on developing
and reviewing EMPs.
2. Speciated VOC Measurements
    Measurement of speciated VOCs important to O3 formation
is a key aspect of the PAMS program. The existing PAMS requirements
allow for a number of options in measuring speciated VOCs at PAMS sites
which include (1) hourly measurements using an automatic gas
chromatograph (``autoGC''), (2) eight 3-hour samples daily using
canisters, or (3) one morning and one afternoon sample with a 3-hour or
less averaging time daily using canisters plus continuous Total Non-
methane Hydrocarbon (TNMHC) measurements.
    The EPA believes that the current options provided for VOC
measurement limit the comparative value of the data being collected,
and proposed that required PAMS sites must measure and report hourly
speciated VOCs, which effectively would require them to use an autoGC
to measure VOCs in lieu of canisters. More complete and consistent
speciated VOC data nationally would better help meet certain objectives
of the PAMS program described above (e.g., a speciated ambient air
database useful in evaluating control strategies, analyzing emissions
inventory issues, corroborating progress toward attainment, and
evaluating population exposure to air toxics). Furthermore, as noted by
the CASAC AMMS, hourly VOC data are ``particularly useful in evaluating
air quality models and performing diagnostic emission attribution
studies. These data can be provided on a near real-time basis and
presented along with other precursor species (e.g., oxides of nitrogen
and carbon monoxide) collected over similar averaging times.'' Longer
time-averaged data are of significantly lower value for model
evaluation. In addition, creating consistent monitoring requirements
across the network would provide better data for analyzing regional
trends and spatial patterns.
    At the time the original PAMS requirements were promulgated, the
canister options were included because the EPA recognized that the
technologies necessary to measure hourly average speciated VOCs
concentrations were relatively new and may not have been suitable for
broad network use. At that time, GCs designed for laboratory use were
equipped with auto-samplers designed to ``trap'' the VOC compounds from
a gas sample, and then ``purge'' the compounds onto the GC column. The
EPA did not believe that autoGCs were universally appropriate due to
the technical skill and effort necessary at that time to properly
operate an autoGC.
    While the basic principles of autoGC technology have not changed,
the hardware and software of modern autoGCs are greatly improved over
that available at the time of the original PAMS requirements. Based on
advice from the CASAC AMMS, the EPA initiated an evaluation of current
autoGCs potentially suitable for use in the PAMS network. Based on the
preliminary results, the EPA believes that typical site operators, with
appropriate training, will have the skill necessary to operate a modern
autoGC successfully. Considering the advances in autoGC technology, the
added value obtained from hourly data, and the proposed move of PAMS
measurements to NCore sites in O3 nonattainment areas, the
EPA proposed to require hourly speciated VOC sampling at all PAMS
sites. The EPA noted that this proposed requirement would effectively
prevent the use of canisters to collect speciated VOCs at the required
PAMS sites but that canister sampling may continue to be an appropriate
method for collecting speciated VOCs at other locations as part of
discretionary monitoring designed within the EMPs.
    While the EPA believes that the proposed transition to hourly
speciated VOC sampling is the appropriate strategy to take advantage of
improved technology and to broaden the utility of collected data, we
are also mindful of the additional rigidity that the proposed mandatory
use of autoGCs may have for monitoring agencies, especially those that
have experience with and have established effective and reliable
canister sampling programs. Therefore, the EPA requested comment on the
proposed requirement for hourly VOC sampling as well as the range of
alternatives that might be appropriate in lieu of a strict requirement.
    The EPA received a number of comments on the requirement to measure
hourly VOCs at required PAMS sites. Many commenters agreed with
requiring hourly VOC data. One commenter agreed that ``hourly VOC data
collection is the most appropriate and useful for PAMS monitors'' and
that ``it is only appropriate to approve an alternative data collection
interval if it is believed that the high ozone in an area is due to
other pollutants, such as NOX or methane.'' One commenter
stated they ``supported the movement towards hourly PAMS VOC speciated
measurements with flexibility to use canisters if programmatic or
logistical needs indicate.''
    However, some commenters raised concerns with the hourly VOC
requirement. Some commenters questioned if autoGCs would be capable of
measuring important VOC species in their environment. One commenter
noted that in their location (high desert) ``the largest VOC present in
our inventory is creosote, a compound not commonly measured with this
instrumentation.'' One commenter stated that the ``Southeastern United
States is dominated by biogenic VOC emissions'' and questioned ``the
benefits of an autoGC in understanding ozone formation in any potential
nonattainment area in our State.'' \225\ Some questioned the detection
capabilities of autoGCs as compared to canister sampling. One commenter
found that the method detection limit (MDL) for their canister sampling
was ``consistently equal to or less than the autoGC instrumentation''
based on the EPA's autoGC evaluation laboratory report (RTI, 2014).
Another commenter noted that the MDLs for many of the compounds and
systems reported in the laboratory report were too high to be useful at
PAMS sites. Another commenter stated that they found that ``retention-
time shifts made it difficult for instant identification of chemical
peaks'' and that ``states should be allowed the flexibility to continue
using canisters instead of autoGC.''
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    \225\ The EPA notes that isoprene (the dominant biogenic
compound in the Southeast) is well measured using autoGCs. The EPA
is also evaluating the potential of modern autoGC's to measure alpha
and beta pinene; however that work is not complete.
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    As noted in the preamble, and the comments received, the EPA is
currently completing an evaluation of

commercially available autoGCs. A copy of the report for the laboratory
phase of the study is available in the docket (RTI, 2014). As noted in
the laboratory report, the MDL estimates made for the laboratory study
were not conducted according to normal MDL testing procedures and as
such the results should only be used to compare the various instruments
being tested against each other.\226\ As part of the evaluation, the
EPA identified the manufacturer's specifications for MDL. Most of the
systems that are being evaluated have a manufacturer's estimated MDL in
the range of 0.1 ppb to 0.5 ppb. Based on the evaluation of MDL
capabilities and typical ambient concentrations of O3
precursors, the EPA believes that autoGCs are an appropriate method for
gathering VOC data at most urban locations. However, canister sampling
may be more appropriate in locations with low VOC concentrations.
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    \226\ Several factors combined to result in the high relative
MDL estimates reported in laboratory report. The MDL testing in the
laboratory was conducted during concurrent tests for interferences
from humidity and temperature. In addition, the MDL testing was
conducted at relatively high concentrations compared to the
concentrations testing would be conducted at for conventional MDL
testing. Finally, as noted in the laboratory report, a number of
instruments were having technical difficulties during the testing
which greatly impacted their MDL results. The EPA is continuing the
autoGC evaluation and has conducted a field study during the summer
of 2015. A final report is expected in early 2016.
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    For the reasons discussed above and in the proposed rule, the EPA
is finalizing a requirement for hourly speciated VOC measurements at
required PAMS sites. The EPA believes that hourly VOC measurements will
provide a more complete and consistent speciated VOC database to help
meet the PAMS program objectives described above. Hourly VOC data are
particularly useful in evaluating air quality models and performing
diagnostic emission attribution studies. Longer time-averaged data are
of lower value for model evaluation. Consistent monitoring requirements
across the network will provide better data for analyzing regional
trends and spatial patterns.
    However, the EPA agrees that there may be locations where an autoGC
may not be the most appropriate method for VOC measurement and that it
is appropriate to allow for canister sampling in limited situations.
Accordingly, the EPA is adding a waiver option (to be approved by the
EPA Regional Administrator) to allow three 8-hour average samples every
3rd day as an alternative in cases where VOCs are not well measured by
autoGC due to low concentrations of target compounds or where the
predominant VOC compounds cannot be measured using autoGC technology
(e.g., creosote in high desert environments). This alternative sampling
frequency was selected to be consistent with the sampling frequency
selected for carbonyls, which is discussed later in this preamble.
3. Carbonyl Measurements
    Carbonyls include a number of compounds important to O3
formation that cannot currently be measured using the autoGCs or
canisters used at PAMS sites to measure speciated VOCs. The current
method for measuring carbonyls in the PAMS program is Compendium Method
TO-11A (U.S. EPA, 1999). In this method, carbonyl compounds are
adsorbed and converted into stable hydrazones using
dinitrophenylhydrazine (DNPH) cartridges. These cartridges are then
analyzed for the individual carbonyl compounds using liquid
chromatography (LC) techniques. Three carbonyls are currently required
to be measured in the PAMS program--formaldehyde, acetaldehyde, and
acetone.
    In 2006, the EPA revised the PAMS requirements such that carbonyl
sampling was only required in areas classified as serious or above
nonattainment for O3 under the 8-hour O3 standard
which effectively reduced the applicability of carbonyl sampling to a
few areas in California. This change was made in recognition that there
were a number of issues with Method TO-11A that raised concerns with
the uncertainty in the carbonyl data being collected. These issues
include interferences (humidity and O3) and breakthrough
(i.e., overloading of the DNPH cartridge) at high concentrations. While
solutions for these issues have been investigated, these improvements
have not been incorporated into Method TO-11A.
    A recent evaluation of the importance of VOCs and carbonyls to
O3 formation determined that carbonyls, especially
formaldehyde, are very important to O3 formation (Cavender,
2013). CASAC AMMS (U.S. EPA, 2011f) also noted the importance of
carbonyls stating that ``There are many compelling scientific reasons
to measure carbonyls. They are a very important part of O3
chemistry almost everywhere.'' Although the EPA recognizes the issues
that have been raised about the current method of measuring carbonyls,
due to the importance of carbonyls to understanding O3
chemistry, the EPA proposed to require all required PAMS sites to
measure carbonyls.
    Several commenters agreed with the need for carbonyl data at PAMS
sites. However, a number of commenters questioned the proposed
frequency of eight 3-hour samples every day during the PAMS sampling
season (June through August). Several commenters indicated that the
frequency was too high. One commenter noted that the requirement would
require 800 samples per season at each PAMS site and pointed out that
this requirement, which was required at the inception of the PAMS
program in the 1990s was ``found to be prohibitively expensive,
technically unsustainable, and qualitatively compromised.'' Another
commenter stated that ``this level of sampling would require a
substantial amount of agency resources and seems unduly burdensome.'' A
number of commenters also questioned the commercial availability of an
8-channel carbonyl sampler that would be needed to take eight 3-hour
samples daily. In light of the comments and upon further review, the
EPA agrees that the proposed frequency is unduly burdensome and is
finalizing a requirement with a lower frequency.
    A number of alternative frequencies were suggested in the comments.
Several commenters suggested a frequency of three 8-hour samples on
either a 1-in-6 day or 1-in-3 day basis. Another commenter suggested a
frequency of eight 3-hour samples on a 1 in 6 day basis. The EPA notes
that sampling on a 1-in-6 day frequency would lead to as little as 15
sampling days per PAMS sampling season. The EPA believes that 15
sampling days is too few to provide a meaningful representation of
carbonyl concentrations over the PAMS sampling period. A sampling
frequency of 1-in-3 days would lead to 30 sampling days per season with
each day of the week being represented at least 4 times per sampling
season. With regards to samples per day, a 3-hour sampling duration
provides a better diurnal representation of carbonyl sampling compared
with an 8-hour sampling duration; however 8-hour sampling can provide
information useful for evaluating diurnal differences in carbonyl
concentrations. Upon further consideration and in light of the comments
received, the EPA is finalizing a carbonyl sampling requirement with a
frequency of three 8-hour samples on a 1-in-3 day basis. This final
requirement will result in approximately 90 samples per PAMS sampling
season which the EPA believes is not unduly burdensome and

will provide a reasonable representation of carbonyl concentrations.
    A number of commenters noted the ongoing development of continuous
formaldehyde instruments, and recommended that EPA allow for continuous
formaldehyde measurements as an alternative to the manual cartridge
based TO-11A method. The EPA agrees that continuous formaldehyde, with
the ability to obtain hourly averaged measurements, would be a
significantly more valuable that the longer averaged measurements. As a
result, the EPA has added an option to allow for continuous
formaldehyde as an alternative to the carbonyl measurements using TO-
11A.
4. Nitrogen Oxides Measurements
    It is well known that NO and NO2 play important roles in
O3 formation (U.S. EPA, 2013, Section 3.2.2). Under the
current network design, Type 2 PAMS sites are required to measure
NOX (which by definition is the sum of NO and
NO2), and Types 1, 3, and 4 sites are required to measure
NOy. NCore sites are currently required to measure
NOy but are not required to measure NO2
separately.
    In conventional NOX analyzers, NO2 is
determined as the difference between the measured NO and NOX
concentrations. However, due to the non-selective reduction of oxidized
nitrogen compounds by the molybedenum converter used in conventional
NOX monitors, the NO2 measurement made by
conventional NOX monitors can be biased high due to the
varying presence of NOz compounds that may be reported as
NO2. The unknown bias from the NOz compounds is undesirable
when attempting to understand O3 chemistry.
    Improvements in reactive nitrogen measurements have been made since
the original PAMS requirements were promulgated that allow for improved
NO2 measurements. Selective photolytic converters have been
developed that are not significantly biased by NOz compounds (Ryerson
et al., 2000). Monitors using photolytic converters are commercially
available and have been approved as FEMs for the measurement of
NO2. In addition, methods that directly read NO2
have been developed that allow for very accurate readings of
NO2 without some of the issues inherent to the ``difference
method'' used in converter-based NOX analyzers. However,
these direct reading NO2 analyzers generally do not provide
an NO estimate, and would need to be paired with a converter-based
NOX monitor or NOy monitor in order to also
measure NO.
    As discussed above, the EPA is finalizing a PAMS network design
such that PAMS measurements will be required at existing NCore sites in
CBSAs with a population of 1,000,000 people or more. NCore sites
currently are required to measure NO and NOy. NCore sites
are not currently required to measure NO2. Due to the
importance of accurate NO2 data to the understanding of
O3 formation, the EPA proposed to require NO2
measurements at required PAMS sites. Since existing NCore sites
currently measure NOy, either a direct reading
NO2 analyzer or a photolytic-converter NOX
analyzer could be used to meet the proposed requirement. The EPA
believes conventional NOX analyzers would not be appropriate
for making PAMS measurements due to the uncertainty caused by
interferences from NOz compounds.
    A number of commenters questioned the need for both NOy
and NO2 measurements at PAMS sites. One commenter stated
that ``in dense urban areas an NO/NO2/NOX
instrument may be adequate but in a more rural area an NO/
NOy instrument may be preferable.'' Another commenter stated
that due to the size of the grid cells used in grid models that ``the
impact of NOz interferences would be very small compared to other
modeling uncertainties such as emission inventories and mixing
heights.'' Another commenter suggested that ``EPA should provide clear
and specific guidance on how agencies can request that the
NOy monitoring be eliminated from the NCore suite based on
comparative data between the NO2 and NOy
monitors.''
    The comments suggest that the model's ability to simulate the
partitioning of reactive nitrogen is unimportant because there may be
other errors in the model. The EPA believes that measurements should be
routinely collected so that it can be demonstrated that the chemistry,
meteorology, and emissions in the model are all of sufficient
reliability for use in informing air quality management decisions.
Monitoring sites rarely fall into simple categories of urban or rural,
and the speciation of NOy varies considerably as a function
of meteorology and time of day at a given site. The state-of-the-
science in regulatory air quality modeling is such that accurate
measurements of key O3 precursors must be available to
demonstrate the credibility of the model predictions. The increased
availability of special field study observations is leading to
increased scrutiny of the chemical mechanisms used in regulatory
modeling. Comprehensive and accurate measurement sites are needed to
demonstrate the adequacy of the models and to respond to these
challenges.
    Measurements of NO, NO2, and NOy
concentrations are critical to understanding atmospheric aging and
photochemistry. These measurements will provide essential information
about whether NOy compounds are fresh or aged which is
important for understanding both local photochemistry (i.e. through
indicator ratios to distinguish NOX vs VOC limited
conditions) as well as for characterizing transport from upwind
regions. These evaluations may be conducted using observations, box
modeling or through complex photochemical grid based modeling. Accurate
speciated and total NOy measurements are necessary for all
three types of analysis. For these reasons, the EPA is finalizing the
requirement for required PAMS sites to measure true NO2 in
addition to NO and NOy.
5. Meteorology Measurements
    The current PAMS requirements require monitoring agencies to
collect surface meteorology at all required PAMS sites. As noted in the
EPA's Technical Assistance Document (U.S. EPA, 1998) for the PAMS
program, the PAMS requirements do not provide specific surface
meteorological parameters to be monitored. As part of the
implementation efforts for the original PAMS program, a list of
recommended parameters was developed and incorporated into the TAD
which includes wind direction, wind speed, temperature, humidity,
atmospheric pressure, precipitation, solar radiation, and ultraviolet
(UV) radiation. Currently, NCore sites are required to measure the
above parameters with the exceptions of atmospheric pressure,
precipitation, solar radiation, and UV radiation. In recognition of the
importance of these additional measurements for understanding
O3 formation, the EPA proposed to specify that
required PAMS sites are required to collect wind direction, wind speed,
temperature, humidity, atmospheric pressure, precipitation, solar
radiation, and UV radiation. Since NCore sites are currently required
to measure several of these surface meteorological parameters, the net
impact of the proposal was to add the requirement for the monitoring of
atmospheric pressure, precipitation, solar radiation, and UV radiation
at affected NCore sites. The EPA received no significant comments on
this portion of the proposal, and therefore is finalizing the
requirement as proposed.

    The existing PAMS requirements also require the collection of upper
air meteorological measurements at one site in each PAMS area. The term
upper air meteorological is not well defined in the existing PAMS
requirements. As part of the implementation efforts for the original
PAMS program, mixing height was added to the PAMS TAD as a recommended
meteorological parameter to be monitored. Most monitoring agencies
installed radar profilers to meet the requirement to collect upper air
meteorology. Radar profilers provide data on wind direction and speed
at multiple heights in the atmosphere. Radio acoustic sounding system
(RASS) profilers are often included with radar profilers to obtain
atmospheric temperature at multiple heights in the atmosphere and to
estimate mixing height. The EPA recognizes that the upper air data on
wind speed and wind direction from radar profilers can be very useful
in O3 modeling. However, many of the current PAMS radar
profilers are old and in need of replacement or expensive maintenance.
In addition, the cost to install and operate radar profilers at all
required PAMS sites would be prohibitive. Therefore, the EPA did not
propose to add upper air wind speed and direction as required
meteorological parameters to be monitored at required PAMS sites. Where
monitoring agencies find the radar profiler data valuable, continued
operation of existing radar profilers or the installation of new radar
profilers would be appropriate to consider as part of the state's EMP.
    As discussed above, mixing height is one upper air meteorological
measurement that has historically been measured at PAMS sites. A number
of methods can be used to measure mixing height in addition to radar
profiler technology discussed above. Recent developments in ceilometer
technology allow for the measurement of mixing height by changes in
particulate concentrations at the top of the boundary layer (Eresmaa et
al., 2006). Ceilometers provide the potential for continuous mixing
height data at a fraction of the cost of radar profilers. Due to the
importance of mixing height measurements for O3 modeling,
the EPA proposed to add the requirement for monitoring agencies to
measure mixing height at required PAMS sites.
    A number of commenters questioned the need for mixing height
measurements at PAMS sites. One commenter stated, ``the photochemical
modeling community has a long history of relying upon National Weather
Service measurements for mixing height.'' Another commenter stated that
``in some areas of the country the models used to predict mixing height
are adequate, but in other mountainous or marine areas model-predicted
mixing height data is inadequate.'' Accurate estimates of mixing height
are important for appropriately characterizing concentrations of
O3 and O3 precursors. Mixing height is also
important for characterizing how modeled O3 may change as a
result of changing NOX and VOC concentrations. For instance,
if the modeled mixing height is too low causing unrealistically high
concentration of NOX, then O3 destruction could
be predicted when O3 production may be happening in the
atmosphere. When this or the opposite situation exists in modeling it
may lead O3 response to emissions changes that are less
reliable for air quality planning purposes. While models are believed
to do a reasonable job of predicting mixing height during the day,
there is considerably more uncertainty in predicting this parameter
during morning and evening transition periods and at night. Model
O3 predictions are particularly sensitive to mixing height
during the time periods for which uncertainty in this parameter is
greatest.
    Several commenters noted that nearby National Oceanic and
Atmospheric Administration (NOAA) Automated Surface Observing System
(ASOS) sites may be a better alternative for collection of mixing
height data. As indicated in the proposal, the EPA is aware of the
network of ceilometers operated by NOAA as part of ASOS. The EPA has
been in discussions with NOAA regarding the potential for these systems
to provide the needed mixing height data. However, the ASOS ceilometers
are not currently equipped to provide mixing height data and NOAA has
no current plans to measure continuous mixing height in the future.
Nonetheless, the EPA will continue to work with NOAA to determine if
the ASOS ceilometers can be upgraded to meet the need for mixing height
data, and included proposed regulatory language that will allow states
a waiver to use nearby mixing height data from ASOS (or other sources)
to meet the requirement to collect mixing height data at required PAMS
sites when such data are suitable and available.
    The EPA is finalizing the requirement for the measurement of mixing
height at required PAMS sites due to the importance of mixing height in
O3 modeling. A waiver option, to be approved by the Regional
Administrator, is also being included to allow mixing height
measurements to be obtained from other nearby sites (e.g., NOAA ASOS
sites).
6. PAMS Season
    Currently, PAMS measurements are required to be taken during the
months of June, July, and August. This 3-month period is referred to as
the ``PAMS Season.'' As part of the PAMS re-evaluation, the EPA
considered changes to the PAMS season. The 3-month PAMS season was
originally selected to represent the most active period for
O3 formation. However, the EPA notes that in many areas the
highest O3 concentrations are observed outside of the PAMS
season. As an example, the highest O3 concentrations in the
mountain-west often occur during the winter months. Data collected
during the current PAMS season would have limited value in
understanding winter O3 episodes.
    The CASAC AMMS (U.S. EPA, 2011f) noted in their report to the EPA
that ``it would be desirable to extend the PAMS monitoring season
beyond the current June, July, August sampling period.'' But that ``the
monitoring season should not be mandated and rigid; it should be
flexible and adopted and coordinated on a regional airshed basis.'' The
EPA agrees with CASAC on the need for flexibility in determining when
PAMS measurements should be taken to meet local monitoring needs but
also agrees with CASAC that the flexibility ``should not conflict with
national goals for the PAMS program.'' A significant benefit of the
standard PAMS season is that it ensures data availability from all PAMS
sites for national- or regional-scale modeling efforts.
    While the EPA agrees with the potential benefit of extending the
availability of PAMS measurements outside of the current season, we
also considered the burden of requiring monitoring agencies to operate
additional PAMS measurements (e.g., hourly speciated VOC) for periods
that in some cases, might be much longer than the current 3-month
season, for example, if the PAMS season was extended to match each
state's required O3 monitoring season. Being mindful of the
potential burden associated with a lengthening of the PAMS season as
well as the potential benefits of the additional data, the EPA proposed
to maintain the current 3-month PAMS monitoring season for required
PAMS sites rather than extending the PAMS season to other periods where
elevated O3 may be expected. No significant comments were
received on the proposed PAMS season, and as such, for the reasons
stated here and in the proposal, the EPA is not changing the 3-month
PAMS season of June, July, and August.

    The EPA believes that the 3-month PAMS season will provide a
consistent data set of O3 and O3 precursor
measurements for addressing the national PAMS objectives. Monitoring
agencies are strongly encouraged to consider collecting PAMS
measurements in additional periods beyond the required PAMS season as
part of their EMP. The monitoring agencies should consider factors such
as the periods of expected peak O3 concentrations and
regional consistency when determining potential expansion of their
specific monitoring periods beyond the required PAMS season.
7. Timing and Other Implementation Issues
    The EPA recognizes that the changes to the PAMS requirements will
require resources and a reasonable timeline in order to be successfully
implemented. The PAMS program is funded, in part, as part of the EPA's
section 105 grants. The EPA believes that the current national funding
level of the PAMS program is sufficient to support these final changes,
but changes in the distribution of PAMS funds will need to be made. The
network design changes will require some monitoring agencies to start
collection of new PAMS measurements, while other monitoring agencies
will see reductions in PAMS measurement requirements. The EPA will work
with the NAACA, AAPCA, and other monitoring agencies to develop an
appropriate PAMS grant distribution strategy.
    In addition to resources, the affected monitoring agencies will
need time to implement the revised PAMS requirements. For the required
PAMS sites, monitoring agencies can determine now which NCore sites
will be required to make PAMS measurements based on readily available
census data. However, monitoring agencies will still need time to
evaluate and seek approval for alternative sites or alternative VOC
methods. In addition, monitoring agencies will need time to make
capital investments (primarily for the installation of autoGCs,
NO2 monitors, and ceilometers), prepare appropriate QA
documents, and develop the expertise needed to successfully collect
PAMS measurements via training or otherwise. In order to ensure
monitoring agencies have adequate time to plan and successfully
implement the revised PAMS requirements, the EPA is requiring that
monitoring agencies identify their plans to implement the PAMS
measurements at NCore sites in their Annual Network Plan due July 1,
2018, and to begin making PAMS measurements at NCore sites by June 1,
2019. The EPA believes some monitoring agencies may be able to begin
making PAMS measurements sooner than June 2019 and encourages early
deployment where possible.
    Monitoring agencies will need to wait until O3
designations are made to officially determine the applicability of the
EMP requirement. The EPA proposed to allow two years after designations
to develop EMPs, and that the EMPs would be submitted as part of their
Annual Network Plan. Several commenters stated that due to the level of
planning and coordination required for the EMPs, that the plans should
instead be included as part of the 5-year network assessment. While the
EPA agrees that the EMPs will require a substantial amount of planning
and coordination, the next 5 year network assessment will not be due
until July 1, 2020--nearly 5 years from the date of this final
rulemaking. The EPA believes that it would be inappropriate to wait 5-
years from the date of this rulemaking to develop plans for enhanced
O3 monitoring. In addition, the EPA believes that the first
round of EMP development should receive additional focus and review
that may not be afforded as part of the larger network assessment.
Finally, most monitoring agencies will be aware of their likely
O3 attainment status well in advance of the official
designations. In order to ensure timely development of the initial
EMPs, the EPA is requiring affected monitoring agencies to submit their
initial EMPs no later than two years following designations. States in
the OTR do not need to wait until designations to determine EMP
applicability and may not be classified as Moderate or above. As such,
the final rule includes a requirement for states in the OTR to submit
their initial EMPs by October 1, 2019 (which is consistent with the
expected timeline for the remaining EMPs). However, subsequent review
and revisions to the EMPs are to be made as part of the 5-year network
assessments beginning with the assessments due in 2025.

D. Addition of a New FRM for O3

    The use of FRM analyzers for the collection of air monitoring data
provides uniform, reproducible measurements of concentrations of
criteria pollutants in ambient air. FRMs for various pollutants are
described in several appendixes to 40 CFR part 50. For most gaseous
criteria pollutants (including O3 in Appendix D of part 50),
the FRM is described as a particular measurement principle and
calibration procedure to be implemented, with further reference to
specific analyzer performance requirements specified in 40 CFR part 53.
    The EPA allows new or alternative monitoring technologies--
identified as FEMs--to be used in lieu of FRMs, provided that such
alternative methods produce measurements closely comparable to
corresponding FRM measurements. Part 53 sets forth the specific
performance requirements as well as the performance test procedures
required by the EPA for determining and designating both FRM and FEM
analyzers by brand and model.
    To be used in a determination of compliance with the O3
NAAQS, ambient O3 monitoring data must be obtained using
either a FRM or a FEM, as defined in parts 50 and 53. For
O3, nearly all the monitoring methods currently used by
state and local monitoring agencies are FEM (not FRM) continuous
analyzers that utilize an alternative measurement principle based on
quantitative measurement of the absorption of UV light by
O3. This type of O3 analyzer was introduced into
monitoring networks in the 1980s and has since become the predominant
type of method used because of its all-optoelectronic design and its
ease of installation and operation.
    The existing O3 FRM specifies a measurement principle
based on quantitative measurement of chemiluminescence from the
reaction of ambient O3 with ethylene (ET-CL). Ozone
analyzers based on this FRM principle were once widely deployed in
monitoring networks, but now they are no longer used for routine
O3 field monitoring because readily available UV-type FEMs
are substantially less difficult to install and operate. In fact, the
extent of the utilization of UV-type FEMs over FRMs for O3
monitoring is such that FRM analyzers have now become commercially
unavailable. The last new commercial FRM analyzer was designated by the
EPA in 1979. The current list of all approved FRMs and FEMs capable of
providing ambient O3 data for use in NAAQS attainment
decisions may be found on the EPA's Web site and in the docket for this
action (U.S. EPA, 2014e). However, that list does not indicate whether
or not each listed method is still commercially available.
1. Proposed Changes to the FRM for O3
    Although the existing O3 FRM is still a technically
sound methodology, the lack of commercially available FRM O3
analyzers severely impedes the use of FRM analyzers, which are needed
for quality control purposes and as the standard to which candidate
FEMs are

required to be compared. Therefore, the EPA proposed to establish a new
FRM measurement technique for O3 based on NO-
chemiluminescence (NO-CL) methodology. This new chemiluminescence
technique is very similar to the existing ET-CL methodology with
respect to operating principle, so the EPA proposed to incorporate it
into the existing O3 FRM as a variation of the existing ET-
CL methodology, coupled with the same existing FRM calibration
procedure.
    A revised Appendix D to 40 CFR part 50 was proposed to include both
the original ET-CL methodology as well as the new NO-CL methodology,
such that use of either measurement technique would be acceptable for
implementation in commercial FRM analyzers. Currently, two
O3 analyzer models (from the same manufacturer) employing
the NO-CL methodology have been designated by the EPA as FEMs and would
qualify for re-designation as FRMs under the revised O3 FRM.
The rationale for selecting the new NO-CL FRM methodology, including
what other methodologies were also considered, and additional
information to support its selection are discussed in the preamble to
the proposal for this action (79 FR 75366-75368). No substantive change
was proposed to the existing O3 FRM calibration procedure,
which would be applicable to both chemiluminescence FRM methodologies.
    The proposed FRM in part 50, Appendix D also included numerous
editorial changes to provide clarification of some provisions, some
revised wording, additional details, and a more refined numbering
system and format consistent with that of two other recently revised
FRMs (for SO2 and CO).
    As noted in the proposal, there is substantial similarity between
the new and previously existing FRM measurement techniques, and
comparative field data show excellent agreement between ambient
O3 measurements made with the two techniques (U.S. EPA
2014f). Therefore, the EPA believes that there will be no significant
impact on the comparability between existing ambient O3
monitoring data based on the original ET-CL methodology and new
monitoring data that may be based on the NO-CL methodology.
    The proposed FRM retains the original ET-CL methodology, so all
existing FEMs, which were designated under part 53 based on
demonstrated comparability to that ET-CL methodology, will retain their
FEM designations. Thus, there will be no negative consequences or
disruption to monitoring agencies, which will not be required to make
any changes to their O3 monitors due to the revised
O3 FRM. New FEMs would be designated under part 53, based on
demonstrated acceptable comparability to either FRM methodology.
2. Comments on the FRM for O3
    Comments that were received from the public on the proposed new
O3 FRM technique are addressed in this section. Most
commenters expressed general support for the proposed changes, although
a few commenters expressed some concerns. The most significant issue
discussed in comments was the relatively small but nevertheless
potentially significant interference of water vapor observed in the ET-
CL technique. As some comments pointed out, this interference is
positive and could possibly affect NAAQS attainment decisions. The
available NO-CL FEM analyzers include a sample dryer, which minimizes
this interference. As noted previously, very few, if any, ET-CL FRM
analyzers are still in operation. The ET-CL (with and without a sample
dryer), the proposed NO-CL FRM, and all designated FEM analyzers have
demonstrated compliance with the substantially reduced water vapor
interference equivalent limit specified in 40 CFR part 53.
    The proposed FRM mentioned the need for a sample air dryer for both
ET-CL and NO-CL FRM analyzers. In response to these comments, the
wording of the ET-CL FRM has been augmented to clarify the requirement
for a dryer in all newly designated FRMs (the only change being made by
the EPA to the existing ET-CL FRM as proposed). Also, the interference
equivalent limit for water vapor in part 53 was proposed to be
substantially reduced from the current 0.02 ppm to 0.002 ppm. The
interference equivalent test for water vapor applicable to the new NO-
CL candidate FRM analyzers (specified in Table B-3 of part 53) was
proposed to be more stringent than the corresponding existing test for
ET-CL FRM analyzers by requiring that water vapor be mixed with
O3. This mixing requirement was not part of the existing
test for ET-CL candidate analyzers (denoted by footnote 3 in Table B-
3). However, in further response to these commenters' concerns, the EPA
has modified Table B-3 to extend this water vapor mixing requirement to
newly designated ET-CL analyzers, as well. These measures should insure
that potential water vapor interference is minimized in all newly
designated FRM analyzers.
    Several comments indicated concern that currently-designated FEM
analyzers retain their designation without retesting if the new FRM
were promulgated. The current ET-CL FRM is being retained; therefore,
it is not necessary to make these new requirements retroactive to
existing designated FEM analyzers. The existing FEM analyzers will not
be required to be retested, and their FEM designation will be retained
so that there will be no disruption to current monitoring networks.
    Although beyond the scope of this rulemaking, other comments
concerned potential hazards of the NO compressed gas supply required
for NO-CL analyzer operation, and the current non-availability of a
photolytic converter to provide an alternative source of NO from a less
hazardous nitrous oxide gas supply. With regard to the photolytic
converter, the EPA would approve such a converter as a source of NO if
requested by an FRM analyzer manufacturer, upon demonstration of
adequate functionality.
    A few commenters liked the ``scrubberless UV absorption'' (SL-UV)
measurement technique. The EPA has identified the SL-UV method as a
potentially advantageous candidate for the O3 FRM, but could
not propose adopting it until additional test and performance
information becomes available. A related comment requested
clarification that promulgation of the proposed revised FRM would not
preclude future consideration of other O3 measurement
techniques such as SL-UV. In response, the EPA can always consider new
technologies for FRMs under 40 CFR 53.16 (Supersession of reference
methods). However, a revised or amended FRM that included the SL-UV
technique, as set forth in Appendix D of 40 CFR part 50, would have to
be promulgated as part of a future rulemaking, before a SL-UV analyzer
could be approved as an FRM under 40 CFR part 53.
    One comment suggested that the value for the absorption cross
section of O3 at 254 nm used by the FRM's calibration
procedure should be changed. The comment indicated that the nearly 2%
difference effectively lowers the O3 NAAQS by that amount.
Using the corrected value would resolve much of the difference observed
between O3 measurements calibrated against the UV standard
reference photometer versus those calibrated using NO gas phase
titration and it would allow the EPA to adopt the less complex and more
economical Gas Phase Titration (GPT) technique as the primary
calibration standard for the

FRM. The EPA will await the results of further studies determining the
value of the O3 cross section at 254 nm before making a
change to the calibration procedures and will not finalize changes to
the calibration procedures in this final rule.

E. Revisions to the Analyzer Performance Requirements

1. Proposed Changes to the Analyzer Performance Requirements
    In close association with the proposed O3 FRM, the EPA
also proposed changes to the associated analyzer performance
requirements for designation of FRMs and FEMs for O3, as set
forth in 40 CFR part 53. These changes were largely confined to Table
B-1, which specifies performance requirements for FRM and FEM analyzers
for SO2, CO, O3, and NO2, and to Table
B-3, which specifies test concentrations for the various interfering
agent (interferent) tests. Minor changes were also proposed for Figure
B-5 and the general provisions in subpart A of part 53. All of these
proposed changes are described and discussed more fully in the preamble
to the proposal for this action (79 FR 75368-75369).
    Modest changes proposed for Table B-3 would add new interferent
test concentrations specifically for NO-CL O3 analyzers,
which include a test for NO2 interference.
    Several changes to Table B-1 were proposed. Updated performance
requirements for ``standard range'' analyzers were proposed to be more
consistent with current O3 analyzer performance
capabilities, including reduced limits for noise allowance, lower
detectable limit (LDL), interference equivalent, zero drift, span
drift, and lag, rise, and fall times. The previous limit on the total
of all interferents was proposed to be withdrawn as unnecessary and to
be consistent with that same change made previously for SO2
and CO analyzers. Also, the span drift limit at 20% of the upper range
limit (URL) was proposed to be withdrawn because it has similarly been
shown to be unnecessary and to maintain consistency with that same
change made previously for SO2 and CO analyzers.
    The form of the precision limits at both 20% and 80% of the URL was
proposed to be changed from ppm to percent. The proposed new limits (in
percent) were set to be equivalent to the previously existing limits
(in ppm) and thus remain effectively unchanged. This change in form of
the precision limits in Table B-1 has been previously made for
SO2 and CO analyzers, and was proposed to extend also to
analyzers for NO2, (again with equivalent limits) for
consistency and to simplify Table B-1 across all types of analyzers to
which the table applies. A new footnote proposed for Table B-1
clarifies the new form for precision limits as ``standard deviation
expressed as percent of the URL.'' Also proposed was a revision to
Figure B-5 (Calculation of Zero Drift, Span Drift, and Precision) to
reflect the changes proposed in the form of the precision limits and
the withdrawal of the limits for total interference equivalent.
    Concurrent with the proposed changes to the performance
requirements for candidate O3 analyzers, the EPA conducted a
review of all designated FRM and FEM O3 analyzers currently
in production or being used, and verified that all meet the proposed
new performance requirements. Therefore, none would require withdrawal
or cancellation of their current FRM or FEM respective designations.
    Finally, the EPA proposed new, optional, ``lower range''
performance limits for O3 analyzers operating on measurement
ranges lower (i.e., more sensitive) than the standard range specified
in Table B-1. The new performance requirements are listed in a new
``lower range'' column in Table B-1 and will provide for more stringent
performance in applications where more sensitive O3
measurements are needed.
    Two minor changes were proposed to the general, administrative
provisions in Subpart A of part 53. These include an increase in the
time allowed for the EPA to process requests for approval of
modifications to previously designated FRMs and FEMs in 53.14 and the
withdrawal of a requirement for annual submission of Product
Manufacturing Checklists associated with FRMs and FEMs for
PM2.5 and PM10-2.5 in 53.9. No comments were
received on these proposed changes and the EPA will be finalizing these
revisions in this rulemaking.
2. Comments on the Analyzer Performance Requirements
    Several comments were received related to the proposed changes to
the analyzer performance requirements of part 53, and most were
supportive. Comments from a few monitoring agencies suggested that the
more stringent performance requirements proposed might be difficult to
achieve or would increase monitor maintenance and cost. The EPA is also
clarifying that these requirements apply only to the performance
qualification requirements for designations of new FRM and FEM
analyzers and will have no impact on a monitoring agency's operation of
existing O3 analyzers.
    More specific comments from an analyzer manufacturer pointed out
that the proposed lower limits for noise and LDL may be too stringent,
the former because low-cost portable analyzers may have shorter
absorption cells, and the latter because of limitations of current
calibration technology. After further consideration of available
analyzer performance data in light of these comments, the EPA agrees
and is changing the noise limits from the proposed values of 1 ppb and
0.5 ppb (for the standard and lower ranges, respectively) to 2.5 ppb
and 1 ppb (respectively). The EPA is also changing the LDL limit from
the proposed values of 3 ppb and 1 ppb (respectively) to 5 ppb and 2
ppb (respectively). These new limits are still considerably more
stringent than the previous limits (for the standard range) and are
also consistent with those recommended by the commenter and the current
performance capabilities of existing analyzer/calibration technology.
    This commenter also pointed out that the proposed lower limit for
12-hour zero drift, together with the way the prescribed test is
carried out, resulted in the test being dominated by analyzer noise
rather than drift. The EPA agrees with this comment in general but
believes that further study is needed before any specific changes can
be proposed for the 12-hour zero drift test, particularly since any
such changes would affect analyzers for other gaseous pollutants, as
well.
    Other comments suggested that there was no need for the proposed
new, low-range performance requirements, because of cost and that
available calibrators would be inadequate for calibration of such low
ranges. The EPA disagrees with these comments and believes, as noted in
the proposal preamble, that there is a definite need for low-level
O3 measurements in some applications and that suitable
calibration for such low-level measurement ranges can be adequately
carried out. As stated previously, the new ``low range'' specifications
for O3 analyzers are optional.
    Several comments pointed out some typographical errors related to
footnotes in Table B-3, as proposed; these errors have been corrected
in the version of Table B-3 being finalized today.
    EPA is finalizing the proposed amendments to both the O3
FRM in Appendix D of part 50 and provisions in part 53, modified as
described above, in response to the comments received.

VII. Grandfathering Provision for Certain PSD Permits

    This section addresses the grandfathering provision for certain
Prevention of Significant Deterioration (PSD) permit applications that
is being finalized in this rule. Section VIII.C of this preamble
contains a description of the PSD and Nonattainment New Source Review
(NNSR) permitting programs and additional discussion of the
implementation of those programs for the O3 NAAQS.

A. Summary of the Proposed Grandfathering Provision

    The EPA proposed to amend the PSD regulations to add a transition
plan that would address the extent to which the revised O3
NAAQS will apply to pending PSD permit applications. This transition
plan is reflected in a grandfathering provision that applies to permit
applications that meet certain milestones in the review process prior
to either the signature date or effective date of the revised
O3 NAAQS. Absent such a grandfathering provision in the
EPA's regulations, the EPA interprets section 165(a)(3)(B) of the CAA
and the implementing PSD regulations at 40 CFR 52.21(k)(1) and
51.166(k)(1) to require that PSD permit applications include a
demonstration that emissions from the proposed facility will not cause
or contribute to a violation of any NAAQS that is in effect as of the
date the PSD permit is issued. The proposal included a grandfathering
provision that would enable eligible PSD applications to make the
demonstration that the proposed project would not cause or contribute
to a violation of any NAAQS with respect to the O3 NAAQS in
effect at the time the relevant permitting benchmark for grandfathering
was reached, rather than the revised O3 NAAQS. We proposed
that the grandfathering provision would apply specifically to either of
two categories of pending PSD permit applications: (1) Applications for
which the reviewing authority has formally determined that the
application is complete on or before the signature date of the final
rule revising the O3 NAAQS; and (2) applications for which
the reviewing authority has first published a public notice of the
draft permit or preliminary determination before the effective date of
the revised NAAQS.
    In the proposal, we also noted that for sources subject to the
federal PSD program under 40 CFR 52.21, the EPA and air agencies that
have been delegated authority to implement the federal PSD program for
the EPA would apply the grandfathering provision to any PSD application
that satisfies either of the two criteria that make an application
eligible for grandfathering. Accordingly, if a particular application
does not qualify under the first criterion based on a complete
application determination, it may qualify under the second criterion
based on a public notice announcing the draft permit or preliminary
determination. Conversely, a source may qualify for grandfathering
under the first criterion, even if it does not satisfy the second.
    The EPA also proposed revisions to the PSD regulations at 40 CFR
51.166 that would afford air agencies that issue PSD permits under a
SIP-approved PSD permit program the discretion to adopt provisions into
the SIP that allow for grandfathering of pending PSD permits under the
same circumstances as set forth in the federal PSD regulations. With
regard to implementing the grandfathering provision, we also explained
that air agencies with EPA-approved PSD programs in their SIPs would
have additional flexibility for implementing the proposed
grandfathering provision to the extent that any alternative approach is
at least as stringent as the federal provision. In addition, the
proposal recognized that some air agencies do not make formal
completeness determinations; thus, only the latter criterion based on
the issuance of a public notice would be relevant in such cases and the
state could elect to adopt only that criterion into its SIP.
Accordingly, the EPA proposed to add a grandfathering provision to 40
CFR 51.166 containing the same two criteria as proposed for 40 CFR
52.21.

B. Comments and Responses

    Many of the comments supported the concept of grandfathering. Some
of these comments, mostly by state and local air agencies, supported
the grandfathering provision as proposed. Many others recommended
alternative approaches to grandfathering based on several different
dates. Several comments recommended that air agencies be allowed to
grandfather certain PSD permit applications and issue a PSD permit
based on the 2008 O3 NAAQS after the area is designated
nonattainment for the revised O3 NAAQS. An opposing set of
comments, representing a coalition of eight environmental groups and
one health advocacy group, strongly objected to the proposal for
grandfathering, claiming that the EPA did not have any authority under
the CAA to exempt or grandfather permit applicants from the statutory
PSD permitting requirements. We are addressing some of these comments
below and others in the Response to Comment Document that is included
in the docket for this rule.
    Comments that recommended broadening the scope of the proposed
grandfathering provision suggested a variety of approaches. Some air
agency and industry comments recommended that the EPA adopt a
grandfathering provision applicable only to those PSD applications for
which the reviewing authority has determined the application to be
complete on or before the signature date of the revised NAAQS. Other
air agency and industry comments recommended that grandfathered status
be determined only on the basis of whether the relevant permitting
milestone has been achieved by the effective date of the revised NAAQS.
    The EPA disagrees with these comments; the final rule uses separate
dates for the two grandfathering milestones, as proposed. If the
effective date of the revised NAAQS were used as the date for the
complete application milestone, this could lead to pressure on state
permitting authorities to prematurely issue completeness determinations
in order to qualify for the grandfathering provision in the time period
between signature of this final rule and the effective date. Using the
signature date of the revised O3 NAAQS as the date for the
grandfathering milestone based on the completeness determination is
thus intended to help preserve the integrity of the completeness
determination process. Permit applications that have not yet been
determined complete can be supplemented or revised to address the
revised O3 standards before the completeness determination
is issued. Conversely, the amount and type of work required for a
preliminary determination or a draft permit reduces the risk that such
a document would be released prematurely merely to qualify for
grandfathering. Similarly, because these documents are released for the
purpose of providing an adequate opportunity for public participation
in the permitting process, it would not behoove a reviewing authority
to precipitately release such documents merely to satisfy the
grandfathering milestone. Accordingly, the EPA does not have the same
concerns about using the effective date of this final rule for the
preliminary determination or draft permit milestone and further finds
it reasonable to provide additional time for satisfying this milestone.
Moreover, using the proposed milestones and corresponding dates is
consistent with the milestones and corresponding dates that were used
in the grandfathering provisions for the 2012 PM2.5 NAAQS.

    Several other comments recommended that the grandfathering
provision apply to all PSD applications for which a final PSD permit
will be issued prior to the effective date of the area designations for
the revised NAAQS. Some of these comments explained that without some
transition provisions in the final rule, it may be impossible for a
source to demonstrate attainment if the current ambient air monitoring
data indicates a revised, lowered standard is not being met. The
comments also suggested that the extended period for grandfathering a
source from the revised NAAQS would provide states with additional time
to establish offset banks or similar systems for new nonattainment
areas.
    Other comments recommended that air agencies be allowed to
grandfather either all or certain PSD permit applications received
before the effective date of the final nonattainment designations for
the revised O3 NAAQS. These comments supported allowing air
agencies to issue PSD permits to grandfathered sources even after the
area in which the source proposes to locate is designated nonattainment
for the revised O3 NAAQS. One comment saw this as being
necessary because the development of the regulatory framework that will
support the revised NAAQS, such as development of a credit market or
even a transition into NNSR permitting, does not instantaneously
accompany the revised standard. Hence, the comment added that
``[d]uring the Interim Period (the time between the revision of the
NAAQS rule and development of the regulatory framework) the project may
be unable to secure offsets and no offsets would be available for
purchase.'' Another comment explained that the extended period for
grandfathering sources from the revised O3 NAAQS was needed
to ``minimize disruption to complex projects that may have been under
development since before the EPA published the proposed NAAQS
revision.'' This comment noted the ``PSD projects commonly undergo
years of engineering and other development resources before an air
permit application can be prepared.''
    The EPA does not agree with the comments recommending that the EPA
use a date after the effective date of the revised O3 NAAQS
as the date by which the permit application must reach the relevant
milestone to qualify for grandfathering. The EPA does not believe it is
appropriate to unreasonably or unnecessarily delay implementation of
these revised standards under the PSD program. As explained in more
detail below, the purpose of the grandfathering provision is to provide
a reasonable transition mechanism for certain PSD applications and the
EPA believes that the milestones proposed and finalized here strike the
appropriate balance in providing for such a reasonable transition.
Moreover, in some cases, some of these recommended approaches could
enable a situation where a PSD permit would be issued to a source
during a future period when the area is designated nonattainment for
the revised O3 NAAQS. As explained below, the EPA does not
believe that this specific outcome is permissible under the CAA.
    The EPA does not agree with the comments suggesting that the
grandfathering provision should be expanded to apply to any PSD
application received before the effective date of the final
nonattainment designations for the revised O3 NAAQS. Because
the process for reviewing PSD permit applications and issuing a final
PSD permit is time consuming, such an approach could allow issuance of
PSD permits to grandfathered sources even after the area in which the
source proposes to locate is designated nonattainment for the revised
O3 NAAQS. The EPA does not agree that grandfathering should
be extended in a way that would allow a source located in an area
designated as nonattainment for a pollutant at the time of permit
issuance to obtain a PSD permit for that pollutant rather than a NNSR
permit. The EPA does not interpret the CAA or its implementing
regulations to allow such an outcome. The PSD requirements under CAA
section 165 only apply in areas designated attainment or unclassifiable
for the pollutant. Alabama Power v. Costle, 636 F.2d 323, 365-66, 368
(D.C. Cir. 1980). Accordingly, the PSD implementing regulations at 40
CFR 52.21(i)(2) contain an exemption that provides that the substantive
PSD requirements shall not apply to a pollutant if the owner or
operator demonstrates that the facility is located in an area
designated nonattainment for that pollutant under CAA section 107 of
the Act. See also 40 CFR 51.166(i)(2) (allowing for the same exemption
in SIP-approved PSD permitting programs). In addition, under CAA
section 172(c)(5) implementation plans must require that permits issued
to new or modified stationary sources ``anywhere in the nonattainment
area'' meet the requirements of CAA section 173, which contains the
NNSR permit requirements. See 40 CFR part 51, Appendix S, IV.A
(providing that, if a major new source or major modification that would
locate in an area designated as nonattainment for a pollutant for which
the source or modification would be major, approval to construct may be
granted only if the specific conditions for NNSR are met, including
obtaining emission offsets and an emission limitation that specifies
the lowest achievable emissions rate). Moreover, given the adverse air
quality conditions that already exist in a nonattainment area and the
congressional directive to reach attainment as expeditiously as
practicable, construction of a major stationary source that
significantly increases emissions in such an area should be expected to
address all of the NNSR requirements, which are designed to ensure that
a new or modified major stationary source will not interfere with
reasonable progress toward attainment, even if this could cause delay
to the permit applicant.
    With respect to the comments that suggested the effective date of
the NAAQS should be used as the date for both milestones, the EPA does
not agree that such a change is necessary. The purpose of the
grandfathering provision is to provide a reasonable transition
mechanism in the following circumstances: first, the PSD application is
one for which both the applicant and the reviewing authority have
committed substantial resources; and, second, this situation is one
where the need to satisfy the demonstration requirement under CAA
section 165(a)(3) could impact the reviewing authority's ability to
meet the statutory deadline for issuing a permit within one year of the
completeness determination. In situations where the reviewing authority
has not yet issued a completeness determination as of the signature
date of the revised O3 NAAQS, both the permit applicant and
the reviewing authority have sufficient notice of the revised standard
so that it can be addressed before the completeness determination is
issued and the one-year clock begins to run. The grandfathering
provision issued in this rulemaking is crafted to draw a reasonable
balance that accommodates the requirements under both CAA sections
165(a)(3) and 165(c). Any modification of the dates further than is
necessary to accommodate these concerns could upset this balance.
    With respect to the comments that suggested adopting a
grandfathering provision applicable only to those PSD applications for
which the reviewing authority has determined the application to be
complete on or before the signature date of the revised NAAQS, the EPA
is not making this change because we understand that not all reviewing
authorities issue formal completeness determinations. Including

a grandfathering provision based on the publication of a public notice
of the draft permit or preliminary determination provides a reasonable
transition mechanism for PSD applications in situations where the
reviewing authority does not issue formal completeness determinations,
but the applicant and the reviewing authority have both committed
substantial resources to the pending permit application at the time the
revisions to the O3 NAAQS are finalized.
    An opposing set of comments--submitted by a consortium of eight
environmental groups and one health advocacy group--challenged the
proposed grandfathering provision on the basis that the EPA did not
have the legal authority to grandfather sources from PSD requirements.
These commenters argued that the plain language of CAA section 165
forecloses the EPA's proposed approach and raised several other legal
considerations. The EPA disagrees with these comments, including the
interpretations of the CAA that they offer. As summarized in the
rationale for the final action below in section VII.C of this preamble,
the EPA believes that the CAA provides it authority and discretion to
establish a PSD grandfathering provision such as the one being adopted
today through a rulemaking process. The EPA is providing a further,
detailed analysis fully responding to this set of comments, as well as
other comments related to the grandfathering provision, in the Response
to Comment Document in the docket for this rule.

C. Final Action and Rationale

    After consideration and evaluation of all the public comments
received on the grandfathering provision, the EPA is finalizing this
provision as proposed, with minor revisions that enhance the clarity of
the grandfathering provision, without changing its substantive effect.
While these revisions lead to slight differences in wording for the
grandfathering provision for the 2012 PM2.5 NAAQS and the
grandfathering provision finalized in this rulemaking, those
differences are not intended to create a different meaning; rather, the
grandfathering provision finalized in this rulemaking is intended to
have the same substantive effect and meaning for the revised
O3 standards as the grandfathering provision for the 2012
PM2.5 NAAQS had for the revised PM standards. Other than
those clarifying revisions, this final rule includes the same rule
language for the grandfathering provision as previously proposed for
the PSD regulations at 40 CFR 52.21(i)(12) and 51.166(i)(11),
respectively. The provision in the final rule reflects the same two
milestones and corresponding dates as the proposed grandfathering
provision. Thus, under the grandfathering provision as finalized,
either of the following two categories of pending PSD permit
applications would be eligible for grandfathering: (1) Applications for
which the reviewing authority has formally determined that the
application is complete on or before the signature date of the revised
O3 NAAQS, or (2) applications for which the reviewing
authority has first published a notice of a draft permit or preliminary
determination before the effective date of the revised O3
NAAQS. The EPA believes that it continues to be appropriate to include
the two proposed milestones for pending permit applications to be
eligible for grandfathering. While a completeness determination is
often the first event, some air agencies do not determine applications
complete as part of their permit process.
    Under 40 CFR 52.21, a permit application may qualify for
grandfathering under either of the two sets of milestones and dates
contained in the provision. Where the EPA is the reviewing authority,
the EPA intends to apply the grandfathering provision to PSD applicants
pursuant to PSD regulations at 40 CFR 52.21 primarily through the use
of the completeness determination milestone because the EPA Regional
Offices make a formal completeness determination for any PSD
application that they receive and review. The EPA is including the
second criterion in 40 CFR 52.21 so that pending applications can still
qualify for grandfathering under the second criterion if any air agency
that incorporates 40 CFR 52.21 into a SIP-approved program does not
make formal completeness determinations as part of its permit review
process.
    The EPA is also amending the PSD regulations at 40 CFR 51.166 to
enable states and other air agencies that issue PSD permits under SIP-
approved PSD programs to adopt a comparable grandfathering provision.
Nevertheless, such air agencies have discretion to not grandfather PSD
applications or to apply grandfathering under their approved PSD
programs in another manner as long as that program is at least as
stringent as the provision being added to 40 CFR 51.166. Accordingly,
an air agency may elect to rely on both sets of milestones and dates or
it may grandfather on the sole basis of only one set. However, the EPA
anticipates that once a decision is made concerning the use of either
set of milestones and dates, the air agency will apply grandfathering
consistently to all pending PSD permit applications.
    As explained in more detail in the proposal, absent a regulatory
grandfathering provision, the EPA interprets section 165(a)(3)(B) of
the CAA and the implementing PSD regulations at 40 CFR 52.21(k)(1) and
51.166(k)(1) to require that PSD permit applications include a
demonstration that emissions from the proposed facility will not cause
or contribute to a violation of any NAAQS that is in effect as of the
date the PSD permit is issued. However, reading CAA section
165(a)(3)(B) in context with other provisions of the Act and the
legislative history, the EPA interprets the Act to provide the EPA with
authority to establish grandfathering provisions through regulation.
The EPA has explained its interpretation of its authority to promulgate
grandfathering provisions in previous rulemaking actions, most recently
in the rule establishing the grandfathering provision for the 2012
PM2.5 NAAQS (78 FR 3086, 3254-56, January 15, 2013), as well
as in the proposal for this final action. The EPA is providing
additional discussion of this authority in the Response to Comment
Document contained in the docket for this final action.
    To summarize briefly, the addition of this grandfathering provision
is permissible under the discretion provided by the CAA for the EPA to
craft a reasonable implementation regulation that balances competing
objectives of the statutory PSD program found in CAA section 165.
Specifically, section 165(a)(3) requires a permit applicant to
demonstrate that its proposed project will not cause or contribute to a
violation of any NAAQS, while section 165(c) requires that a PSD permit
be granted or denied within one year after the permitting authority
determines the application for such permit to be complete. Section
109(d)(1) of the CAA requires the EPA to review existing NAAQS and make
appropriate revisions every five years. When these provisions are
considered together, a statutory ambiguity arises concerning how the
requirements under CAA section 165(a)(3)(B) should be applied to a
limited set of pending PSD permit applications when the O3
NAAQS is revised. The Act does not clearly address how the requirements
of CAA section 165(a)(3)(B) should be met for PSD permit applications
that are pending when the NAAQS are revised, particularly when the EPA
also determines that complying with the

demonstration requirement for the revised NAAQS could hinder compliance
with the requirement under section 165(c) to issue a permit within one
year of the completeness determination for a certain subset of pending
permits. The CAA also does not address how the requirements of CAA
sections 165(a)(3) and 165(c) should be balanced in light of the
statutory requirement to review the NAAQS every five years. As Congress
has not spoken precisely to this issue, the EPA has the discretion to
apply a permissible interpretation of the Act that balances the
statutory requirements to make a decision on a permit application
within one year and to ensure the new and modified sources will only be
authorized to construct after showing they can meet the substantive
permitting criteria. See Chevron, U.S.A., Inc. v. Natural Res. Def.
Council, Inc., 467 U.S. 837, 843-44 (1984).
    In addressing these gaps in the CAA and the tension that may arise
in section 165 in these circumstances, the EPA also applies CAA section
301, where the Administrator is authorized ``to prescribe such
regulations as are necessary to carry out his functions under this
chapter.'' Sections 165(a)(3) and 165(c) of the CAA make clear that the
interests behind CAA section 165 include both protection of air quality
and timely decision-making on pending permit applications. The
legislative history illustrates congressional intent to avoid delays in
permit processing. S. Rep. No. 94-717, at 26 (1976) (``nothing could be
more detrimental to the intent of this section and the integrity of
this Act than to have the process encumbered by bureaucratic delay'').
Thus, when read in combination, these provisions of the CAA provide the
EPA with the discretion to issue regulations to grandfather pending
permit applications from having to address a revised NAAQS where
necessary to achieve both CAA objectives--to protect the NAAQS and to
avoid delays in processing PSD permit applications. Accordingly, the
EPA is seeking in this action to balance the requirements in the CAA to
make a decision on a permit application within one year and to ensure
that new and modified sources will only be authorized to construct
after showing they can meet the substantive permitting criteria that
apply to them. The EPA is achieving this balance by determining through
rulemaking which O3 NAAQS apply to certain permit
applications that are pending when the EPA finalizes the revisions to
the O3 NAAQS in this final rule. We are clarifying, for the
limited purpose of satisfying the requirements under section
165(a)(3)(B) for those permits, which O3 NAAQS are
applicable to those permit applications and must be addressed in the
source's demonstration that its emissions do not cause or contribute to
a violation of the NAAQS.
    This approach is consistent with a recent opinion by the U.S. Court
of Appeals for the Ninth Circuit, which recognized the EPA's
traditional exercise of grandfathering authority through rulemaking.
The court observed that this approach was consistent with the statutory
requirement to ``enforce whatever regulations are in effect at the time
the agency makes a final decision'' because it involved identifying
``an operative date, incident to setting the new substantive standard,
and the grandfathering of pending permit applications was explicitly
built into the new regulations.'' Sierra Club v. EPA, 762 F.3d 971, 983
(9th Cir. 2014). As discussed in more detail in the EPA's Response to
Comment Document contained in the docket for this rule, this case
supports the EPA's action in this rulemaking. The court favorably
discussed prior adoption of regulatory grandfathering provisions that
are similar to the action in this rulemaking, such as the
grandfathering provision that the EPA promulgated when revising the
PM2.5 NAAQS that became effective in 2013. See id. at 982-
83.\227\
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    \227\ This case specifically involved an action by the EPA to
issue an individual PSD permit, which grandfathered a specific
permit applicant from certain requirements without any revision to
the regulations that were in effect. The court's reasoning in this
case distinguishes that type of permit-specific grandfathering from
establishing grandfathering provisions through a rulemaking process.
While the court was not persuaded that there was a conflict between
the requirements of sections 165(a)(3) and 165(c) of the CAA that
supported the permit-specific grandfathering at issue in that case,
it did not extend that uncertainty to its discussion of the EPA's
rulemaking authority. In fact, in its favorable discussion of the
EPA's authority to grandfather pending permit applications through
regulation, the court noted that the power of an administrative
agency ``to administer a congressionally created and funded program
necessarily requires the formulation of policy and the making of
rules to fill any gap left, implicitly or explicitly, by Congress''
though ``such decision cannot be made on an ad hoc basis.'' Sierra
Club v. EPA, 762 F.3d 971, 983 (9th Cir. 2014) (internal quotations
and marks omitted). This indicates that the court believed there is
a gap in the CAA that supports including grandfathering provisions
in regulations.
---------------------------------------------------------------------------

    This adoption of a grandfathering provision in this action is also
consistent with previous actions in which the EPA has recognized that
the CAA provides discretion for the EPA to establish grandfathering
provisions for PSD permit applications through regulations. Some
examples of previous references to the EPA's authority to grandfather
certain applications through rulemaking include 45 FR 52683, August 7,
1980; 52 FR 24672, July 1, 1987; and most recently 78 FR 3086, January
15, 2013.
    This grandfathering provision does not apply to any applicable PSD
requirements related to O3 other than the requirement to
demonstrate that the proposed source does not cause or contribute to a
violation of the revised O3 NAAQS. Sources with projects
qualifying under the grandfathering provision will be required to meet
all the other applicable PSD requirements, including applying BACT to
all applicable pollutants, demonstrating that emissions from the
proposed facility will not cause or contribute to a violation of the
O3 NAAQS in effect at the time of the relevant
grandfathering milestone, and addressing any Class I area and
additional O3-related impacts in accordance with the
applicable PSD requirements. In addition, this grandfathering provision
would not apply to any permit application for a new or modified major
stationary source of O3 located in an area designated
nonattainment for O3 on the date the permit is issued.

VIII. Implementation of the Revised O3 Standards

    This section provides background information for understanding the
implications of the revised O3 NAAQS and describes the EPA's
plans for providing revised rules or additional guidance on some
subjects in a timely manner to assist states with their implementation
efforts under the requirements of the CAA. This section also describes
existing EPA rules, interpretations of CAA requirements, and other EPA
guidance relevant to implementation of the revised O3 NAAQS.
Relevant CAA provisions that provide potential flexibility with regard
to meeting implementation timelines are highlighted and discussed. This
section also contains a discussion of how existing requirements to
reduce the impact on O3 concentrations from the stationary
source construction in permit programs under the CAA are affected by
the revisions to the O3 NAAQS. These are the PSD and
Nonattainment New Source Review (NNSR) programs. As discussed in
section VII of this preamble, to facilitate a smooth transition to the
PSD requirements for the revised O3 NAAQS, the EPA is
finalizing as part of this rulemaking a grandfathering provision that
applies to certain PSD permit applications that are pending and have
met certain milestones in the permitting process

when the revised O3 NAAQS is signed or before the effective
date of the revised O3 NAAQS, depending on the milestone.
    In the preamble for the O3 NAAQS proposal, the EPA
solicited comments on several issues related to implementing the
revised O3 NAAQS that the agency anticipated addressing in
future guidance or regulatory actions, but for which the EPA was not at
that time proposing any action. The EPA received numerous comments on
those and other implementation issues. Consistent with what the EPA
indicated in the O3 NAAQS proposal (79 FR 75370), the agency
is not responding to the implementation comments that are not related
to a specific proposal. However, the EPA intends to take these comments
under advisement as the agency develops rules and guidance to assist
with implementation of the revised NAAQS. Because the EPA did
specifically propose and is finalizing provisions in the regulations
addressing grandfathering for certain PSD permit applications and
requirements, as discussed in section VII of this preamble, the EPA is
responding to comments on the proposed PSD grandfathering provisions.

A. NAAQS Implementation Plans

1. Cooperative Federalism
    As directed by the CAA, reducing pollution to meet national air
quality standards always has been a shared task, one involving the
federal government, states, tribes and local air quality management
agencies. The EPA develops regulations and strategies to reduce
pollution on a broad scale, while states and tribes are responsible for
implementation planning and any additional emission reduction measures
necessary to bring specific areas into attainment. The agency supports
implementation planning with technical resources, guidance, and program
rules where necessary, while air quality management agencies use their
knowledge of local needs and opportunities in designing emission
reduction strategies that will work best for their industries and
communities.
    This partnership has proved effective since the EPA first issued
O3 standards more than three decades ago. For example, 101
areas were designated as nonattainment for the 1-hour O3
standards issued in 1979. As of the end of 2014, air quality in all but
one of those areas meets the 1-hour standards. The EPA strengthened the
O3 standards in 1997, shifting to an 8-hour standard to
improve public health protection, particularly for children, the
elderly, and other sensitive individuals. The 1997 standards drew
significant public attention when they were proposed, with numerous
parties voicing concerns about states' ability to comply. However,
after close collaboration between the EPA, states, tribes and local
governments to reduce O3-forming pollutants, significant
progress has been made. Air quality in 108 of the original 115 areas
designated as nonattainment for the 1997 O3 NAAQS now meets
those standards. Air quality in 18 of the original 46 areas designated
as nonattainment for the 2008 O3 NAAQS now meets those
standards.
    The revisions to the primary and secondary O3 NAAQS
discussed in sections II.D and IV.D of this preamble trigger a process
under which states \228\ make recommendations to the Administrator
regarding area designations. Then, the EPA promulgates the final area
designations. States also are required to review capacity and
authorities in their existing SIPs to ensure the CAA requirements
associated with the new standards can be carried out, and modify or
supplement their existing SIPs as needed. The O3 NAAQS
revisions also apply to the transportation conformity and general
conformity determinations, and affect which preconstruction permitting
requirements apply to sources of O3 precursor emissions, and
the nature of those requirements.
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    \228\ This and all subsequent references to ``state'' are meant
to include state, local, and tribal agencies responsible for the
implementation of an O3 control program.
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    The EPA has regulations in place addressing the general
requirements for SIPs, and there are also provisions in these existing
rules that cover O3 SIPs (40 CFR part 51). States likewise
have provisions in their existing SIPs to address air quality for
O3 and to implement the existing O3 NAAQS. In the
course of the past 45 years of regulating criteria pollutants,
including O3, the EPA has also provided general guidance on
the development of SIPs and administration of construction permitting
programs, as well as specific guidance on implementing the
O3 NAAQS in some contexts under the CAA and the EPA
regulations.
    The EPA has considered the extent to which existing EPA regulations
and guidance are sufficient to implement the revised standards. The CAA
does not require that the EPA promulgate new implementing regulations
or issue new guidance for states every time that a NAAQS is revised.
Likewise, the CAA does not require the issuance of additional
implementing regulations or guidance by the EPA before a revised NAAQS
becomes effective. It is important to note that the existing EPA
regulations in 40 CFR part 51 applicable to SIPs generally and to
particular pollutants, including O3 and O3
precursors, continue to apply unless and until they are updated.
Accordingly, the discussion below provides the EPA's current thoughts
about the extent to which revisions to existing regulations and
additional guidance are appropriate to aid in the implementation of the
revised O3 NAAQS.
2. Additional New Rules and Guidance
    The EPA has received comments from a variety of states and
organizations asking for rules and guidance associated with a revised
NAAQS to be issued in a timely manner. As explained above, and
consistent with the proposal, the EPA is not responding to these
comments at this time because they are not related to any changes to
existing regulations that EPA proposed in this rule. Moreover, although
issuance of such rules and guidance is not a part of the NAAQS review
process, National Ass'n of Manufacturers v. EPA, 750 F. 3d 921, 926-27
(D.C. Cir. 2014), toward that end, the EPA intends to develop
appropriate revisions to necessary implementation rules and provide
additional guidance in time frames that are useful to states when
developing implementation plans that meet CAA requirements.
    Certain requirements under the PSD preconstruction permit review
program apply immediately to a revised NAAQS upon the effective date of
that NAAQS, unless the EPA has established a grandfathering provision
through rulemaking. To ensure a smooth transition to a revised
O3 NAAQS, the EPA is finalizing a grandfathering provision
similar to the provision finalized in the 2012 PM2.5 NAAQS
Rule. See section VII.C of this preamble for more details on the PSD
program and the final grandfathering provision.
    Promulgation or revision of the NAAQS starts a clock for the EPA to
designate areas as either attainment or nonattainment. State
recommendations for area designations are due to the EPA within 12
months of promulgating or revising the NAAQS. In an effort to allow
states to make more informed recommendations for these particular
standards, the EPA intends to issue additional guidance concerning the
designations process for these standards within four months of
promulgation of the NAAQS, or approximately eight months before state
recommendations are due. The EPA generally completes

area designations two years after promulgation of a NAAQS. See section
VIII.B of this preamble for additional information on the initial area
designation process.
    Under CAA section 110, a NAAQS revision triggers the review and, as
necessary, revision of SIPs to be submitted within three years of
promulgation of a revised NAAQS. These SIPs are referred to as
``infrastructure SIPs.'' The EPA issued general guidance on submitting
infrastructure SIPs on September 13, 2013.\229\ It should be noted that
this guidance did not address certain state planning and emissions
control requirements related to interstate pollution transport. This
guidance remains relevant for the revised O3 NAAQS. See
section VIII.A.4 of this preamble for additional information on
infrastructure SIPs.
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    \229\ See memorandum from Stephen D. Page to Regional Air
Directors, ``Guidance on Infrastructure State Implementation Plan
(SIP) Elements under Clean Air Act Sections 110(a)(1) and
110(a)(2)'' September 13, 2013, which is available at http://www3.epa.gov/airquality/urbanair/sipstatus/docs/Guidance_on_Infrastructure_SIP_Elements_Multipollutant_FINAL_Sept_2013.pdf.
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    While much of the existing rules and guidance for prior ozone
standards remains applicable to the new standards, the EPA intends to
propose to adopt revised rules on some subjects to facilitate air
agencies' efforts to implement the revised O3 NAAQS within
one year after the revised NAAQS is established. The rules would
address nonattainment area classification methodologies and attainment
dates, attainment plan and NNSR SIP submission due dates, and any other
necessary revisions to existing regulations for other required
implementation programs. The EPA anticipates finalizing these rules by
the time areas are designated nonattainment. Finalizing rules and
guidance on these subjects by this time would assist air quality
management agencies with development of any CAA-required SIPs
associated with nonattainment areas. See section VIII.A.5 of this
preamble for additional information on nonattainment SIPs and section
VIII.C.3 for additional information on nonattainment New Source Review
requirements applicable to new major sources and major modifications of
existing sources.
3. Background O3
    The EPA and state, local and tribal air agencies, strive to
determine how to most effectively and efficiently use the CAA's various
provisions to provide required public health and welfare protection
from the harmful effects of O3. In most cases, reducing man-
made emissions of NOX and VOCs within the U.S. will reduce
O3 formation and provide additional health and welfare
protection. The EPA recognizes, however, that there can be infrequent
events where daily maximum 8-hour O3 concentrations approach
or exceed 70 ppb largely due to the influence of wildfires or
stratospheric intrusions, which contribute to U.S. background (USB)
levels but may also qualify for consideration under the Exceptional
Events Rule. See section I.D; but see section II.A.2.a above
(percentage of anthropogenic O3 tends to increase on high
O3 days relative to percentage of background, including in
intermountain west).
    The term ``background'' O3 is often used to refer to
O3 that originates from natural sources of O3
(e.g., wildfires and stratospheric O3 intrusions) and
O3 precursors, as well as from man-made international
emissions of O3 precursors. Using the term generically,
however, can lead to confusion as to what sources of O3 are
being considered. Relevant to the O3 implementation
provisions of the CAA, we define background O3 the same way
the EPA defines USB: O3 that would exist in the absence of
any man-made emissions inside the U.S.
    While the great majority of modeled O3 exceedances have
local and regional emissions as their primary cause, there can be
events where O3 levels approach or exceed the concentration
level of the revised O3 standards in large part due to
background sources. These cases of high USB levels on high
O3 days typically result from stratospheric intrusions of
O3 or wildfire O3 plumes. These events are
infrequent and the CAA contains provisions that can be used to help
deal, in particular, with stratospheric intrusion and wildfire events
with O3 contributions of this magnitude, including providing
varying degrees of regulatory relief for air agencies and potential
regulated entities. The EPA intends to work closely with states to
identify affected locations and ensure that the appropriate regulatory
mechanisms are employed.
    Statutory and regulatory relief associated with U.S. background
O3 may include: \230\
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    \230\ Note that the relief mechanisms discussed here do not
include the CAA's interstate transport provisions found in sections
110(a)(2)(D) and 126. The interstate transport provisions are
intended to address the cross-state transport of O3 and
O3 precursor emissions from man-made sources within the
continental U.S. rather than background O3 as it is
defined in this section. As noted in section II.A.2.a above, many of
the instances where commenters pointed to remote monitored locations
having O3 exceedances due to background O3 in
fact reflected sizeable contributions from domestic sources,
including interstate contributions (including from the Los Angeles
Basin and other California locations).
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     Relief from designation as a nonattainment area through
exclusion of data affected by exceptional events;
     Relief from the more stringent requirements of higher
nonattainment area classifications through treatment as a rural
transport area, through exclusion of data affected by exceptional
events, or through international transport provisions;
     Relief from having to demonstrate attainment and having to
adopt more than reasonable controls on local sources through
international transport provisions.
    Further discussion of these mechanisms is provided in sections
VIII.B.2 (exceptional events), VIII.B.1 (rural transport areas), and
VIII.E.2 (international transport).
    Although these relief mechanisms require some level of assessment
or demonstration by a state and/or the EPA to invoke, they have been
used successfully in the past under appropriate circumstances. For
example, the EPA has historically acted on every exceptional events
demonstration that has affected a regulatory decision regarding initial
area designations. See e.g., Idaho: West Silver Valley Nonattainment
Area--Area Designations for the 2012 primary annual PM2.5
NAAQS Technical Support Document, pp. 10-14, December 2014. For the
revised O3 standards, the areas that would most likely need
to use the mechanisms discussed in this section as part of attaining
the revised O3 standards are locations in the western U.S.
where we have estimated the largest seasonal average values of
background O3 occur. We expect some of these areas to use
the provisions in the Exceptional Events Rule during the designations
process for the revised O3 standards. The EPA will then give
priority to exceptional events demonstrations submitted by air agencies
with areas whose designation decision could be influenced by the
exclusion of data under the Exceptional Events Rule. In addition, as
discussed in more detail in sections V.D and VIII.B.2 of this action,
to streamline the exceptional events process, the EPA will soon propose
revisions to the 2007 Exceptional Events Rule and will release through
a Federal Register Notice of Availability a draft guidance document to
address Exceptional Events Rule criteria for wildfires that could
affect O3 concentrations. We expect to

promulgate Exceptional Events Rule revisions and finalize the new
guidance document before the October 2016 date by which states, and any
tribes that wish to do so, are required to submit their initial
designation recommendations for the revised O3 NAAQS.
4. Section 110 State Implementation Plans
    The CAA section 110 specifies the general requirements for SIPs.
Within three years after the promulgation of revised NAAQS (or such
shorter period as the Administrator may prescribe \231\) each state
must adopt and submit ``infrastructure'' SIPs to the EPA to address the
requirements of section 110(a)(1) and (2), as applicable. These
``infrastructure SIP'' submissions establish the basic state programs
to implement, maintain, and enforce revised NAAQS and provide
assurances of state resources and authorities. States are required 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. Because the revised primary NAAQS and secondary NAAQS are
identical, the EPA does not at present discern any need for there to be
any significant substantive difference in the infrastructure SIP
elements for the two standards and thus believes it would be more
efficient for states and the EPA if each affected state submits a
single section 110 infrastructure SIP that addresses both standards at
the same time (i.e., within three years of promulgation of the
O3 NAAQS). Accordingly the EPA is not extending the SIP
deadline for purposes of a revised secondary standard.
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    \231\ 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
for this revision to the O3 NAAQS.
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    It is the responsibility of each state to review its air quality
management program's compliance with the 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 the 2008 O3 NAAQS. We expect
that the result of these prior updates is that, in most cases, states
will already have adequate state regulations previously adopted and
approved into the SIP to address a particular requirement with respect
to the revised O3 NAAQS. For such portions of the state's
infrastructure SIP submission, the state may provide a
``certification'' specifying that certain existing provisions in the
SIP are adequate to meet applicable requirements. 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 SIP submission. If a state determines that its existing EPA-
approved SIP provisions are adequate in light of the revised
O3 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 CAA section 110(a)(2) infrastructure elements. In the case of
a certification, the submittal does not have to include another copy of
the relevant provision (e.g., rule or statute) itself. Rather, the
submission may provide citations to the already SIP-approved state
statutes, regulations, or non-regulatory measures, as appropriate,
which meet the relevant CAA requirement. Like any other SIP submission,
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