formats provided by the EPA or (2) review rail yard data and annual
emission totals provided by EPA, submit comments on that data, and/or
notify the EPA that the State accepts that data. This second option is
available to States because rail companies voluntarily provide rail
yard data to the EPA (included as part of the voluntary burden
estimates for this proposed action). This voluntary data flow is likely
more convenient for rail companies than if each State needed to collect
data from them individually to meet the provisions of these proposed
requirements.
    The EPA is additionally proposing that States may voluntarily
submit annual total emissions for some or all rail yards, and if a
State chooses to report emissions would then be required to meet the
following requirements for the EPA to consider using such data. The EPA
is proposing to consider state-submitted emissions data for rail yards
only when the State: (1) submits all pollutants estimated by EPA's rail
yard emissions method to be used for the relevant inventory year
(described by the NEI Plan) and (2) submits documentation that
describes how States calculated annual total rail yard emissions and
performed QA steps.
    While the proposed approach above is EPA's preferred approach, the
EPA is also considering a ``Rail Companies'' Option that would
additionally regulate the rail companies directly to provide activity
data to EPA. For the Rail Companies Option, the EPA proposes that
owners/operators of rail companies would be required to report activity
data from of those yards to EPA. The Rail Companies Option would have a
disadvantage of imposing more requirements than continuing the ongoing
voluntary approach with rail companies. The EPA requests comment on the
Rail Companies Option and urges commenters to provide any additional
information that would be helpful to the EPA in deciding between a
voluntary and mandatory rail yard activity reporting approach.
3. New Requirements for Point Source Control Data
    Since the EPA started collecting emissions data through the EIS,
some States have made the EPA aware that allowing States to specify
controls was insufficient to appropriately allow specification of the
necessary details. In the current control device reporting requirements
of this subpart, States have been unable to describe fully how controls
are configured at a facility (e.g., series or parallel), define the
relationship among multiple control measures and the units, processes,
and/or release points at a facility, or reuse the definition of a
control measure in the dataset so that the same control measure can be
associated with more than one unit, process, or release point. Such
control configuration information is relevant to certain uses of the
NEI, such as Technical Reviews and Regulatory Impact Analyses.
    Based on this understanding, the EPA is proposing a requirement to
specify controls to remove the limitations of the current requirements.
This new proposed requirement would use a list of control measures for
a facility that is analogous to those control measures that exist in
the real world, wherein each control would define only a single piece
of control equipment or control measure, and a control path can be
defined that would allow control measures to be arranged in any
configuration of series and parallel control measures.
    This action proposes revisions to the data elements required for
specifying controls. This proposed action adds new data elements in
Table 2a to Appendix A of Subpart A to Part 51. These proposed data
elements include control paths, which are defined as one or more
controls at a facility that are linked. The path can consist of groups
of control measures or other paths in parallel or in series. The
proposed data elements also include control apportionment, which is
defined as the percentage of the emissions that flows to the next
control or path, and control assignment, which defines the sequence in
which controls are configured within a path. Other proposed data
elements to specify controls are similar to existing requirements, such
as the pollutants affected, and percent reduction achieved. to Appendix
A. More information on controls is available in Appendix A of the CAERS
User Guide.\55\
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    \55\ Combined Air Emissions Reporting System (CAERS) User's
Guide, Version 2.0, U.S. EPA, 2/25/2021, https://www.epa.gov/e-enterprise/combined-air-emissions-reporting-system-caers-users-guide.
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4. New Requirements for Point Source Throughput in Specific Units of
Measure
    The EPA has observed during past triennial inventory cycles a
potential for double counting of emissions from stationary sources of
fuel combustion, because those sources exist both in the point source
and nonpoint data categories. Stationary fuel combustion for point
sources occurs at sources that meet the point source reporting
thresholds while fuel combustion for nonpoint sources reflects
emissions from smaller commercial and institution facilities such as
shopping malls, office buildings, municipal buildings, and hospitals.
These nonpoint emissions are captured in the NEI through the
industrial, commercial and institutional (ICI) fuel combustion sectors,
and these sources are a significant portion of the total emissions
inventory for many areas. For example, according to the 2017 NEI,
statewide NOX from ICI combustion sources represented up to
27 percent of NOX, with a median of 9.1 percent over all
States, when calculated by excluding fires and biogenic sources from
the total. Using the same calculation approach, statewide
PM2.5 from ICI combustion sources represented up to 28
percent of statewide PM2.5 with a median of 3.2 percent.
Nonpoint commercial and institutional fuel combustion includes
emissions from boilers, engines, and other combustion sources that burn
natural gas, biomass, distillate fuel oil, residual fuel oil, kerosene,
liquefied petroleum gas (LPG), and coal.
    The EPA's approach to capture nonpoint ICI fuel combustion uses
statewide fuel consumption data from the U.S. Energy Information
Administration for the various fuel types and allocates it to counties
based on employment in the industrial or commercial sector from the
Census Bureau's County Business Patterns data. The EPA makes numerous
adjustments to the fuel consumption based on various data available to
EPA, such as subtracting nonroad source fuel consumption and non-
combustion uses from State total fuel use.
    To avoid double counting with point source emissions, the EPA
currently

provides, as part of the nonpoint data collection, various options for
States to supply point source fuel consumption. Some States, however,
do not provide such data in part because they do not have that data
from facilities. Over many triennial NEI years, the EPA has observed
that some States claim that their State does not have any nonpoint fuel
consumption; however, the EPA finds this claim implausible given that
those States do not include every shopping mall, office building,
municipal building, and hospital in their point source inventory. As a
result, the EPA has had to make assumptions about point source fuel
consumption to subtract it from the nonpoint fuel consumption totals.
These assumptions reduce the accuracy of the inventory. Such inaction
on the part of States directly contradicts the CAA section 172(c)(3)
requirement for ``comprehensive, accurate'' inventories. Furthermore,
this issue is not only significant for the NEI, but also is relevant
for emissions inventories required under the Ozone and PM2.5
SIP Implementation Rules.
    To date, the EPA has attempted to resolve the issue through
collection of total point source fuel use by each State as part of the
nonpoint ICI data collection. The EPA has experienced that some States
continue to avoid this requirement by making implausible claims that
all such sources for all fuel types do not exist or stating that States
lack the data. Given the importance of such information to States and
EPA, the EPA is proposing action to ensure States are aware of this
issue and to support creation of accurate ICI fuel combustion emissions
for both point and nonpoint sources.
    Further, the EPA recognizes the potential for directly receiving
such information from owners/operators of point sources as part of the
requirements proposed by this action. To address the connection with
direct reporting to the EPA by owners/operators, the following
paragraphs explain what owners/operators would potentially do to
support the Agency's need for fuel consumption data.
    The EPA has developed and implemented a point-nonpoint
reconciliation approach to resolve any double counting of ICI fuel
combustion sources, but challenges remain. The EPA has refined the
nonpoint ICI fuel combustion approach for each NEI triennial year,
resulting in the most recent approach as described in the 2020 NEI
TSD.\56\ The EPA's revisions to the approach have relied on States'
comments and concerns as part of each triennial NEI process. Based on
these activities, the EPA has concluded that to prevent double counting
of emissions between point and nonpoint ICI sources, the point-nonpoint
reconciliation must be based on subtracting point source fuel
consumption from the total fuel consumption within a State. This is in
contrast with past approaches that allowed subtraction of emissions,
which has been found to be insufficient because point source emissions
are often controlled such that subtracting emissions does not remove
the correct proportion of ICI activity from the nonpoint emissions.
---------------------------------------------------------------------------

    \56\ U.S. EPA, 2020 National Emissions Inventory, Technical
Support Document, March 2023, EPA Document number EPA-454/R-23-001,
https://www.epa.gov/air-emissions-inventories/2020-national-emissions-inventory-nei-technical-support-document-tsd.
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    When States use the approach currently provided, the EPA is
satisfied that the emissions estimates avoid double counting and
provide the best available emissions inventory estimates. While the
nonpoint approach may continue to evolve, the EPA expects that the
point source fuel use will continue to be a critical part of that
process. While the current approach is conceptually simple, the EPA has
concluded that this proposed action should ensure that the EPA and
States have access to the fuel consumption data from point sources.
    To ensure that the EPA and States have data to support point-
nonpoint reconciliation for ICI fuel combustion, this action proposes
to require States to collect and report point source fuel consumption
for certain emissions processes. These proposed changes are reflected
in the proposed Table 2b to Appendix A of this subpart. It is necessary
to collect fuel consumption from point sources, because under this
proposed action, point source data would be reported every year for all
sources. The annual reporting would allow the EPA and States to
subtract point source fuel consumption from State total fuel
consumption irrespective of whether States report nonpoint data on a
triennial year. The EPA is proposing that fuel consumption totals by
fuel to be required for all SCCs for a given inventory year that
reflect any fuel consumed after it has been produced and sold for
consumption. Thus, any in-process fuel combustion (such as combustion
of captured process gases) would be exempt from this proposed
requirement. For triennial years, States would have additional
requirements for nonpoint sources, which are described in section IV.J
of this preamble.
    EPA additionally proposes that owners/operators of point sources,
who are reporting directly to EPA, must include fuel consumption data.
The EPA has already added this collection approach into the CAERS for
use by owners/operators. To the extent that States wish to leverage
this feature of CAERS rather than comply with their fuel use reporting
requirement a different way, the EPA recommends that States evaluate
the possibility of using fuel consumption data provided by facilities
that report using CAERs.
    Depending on States' choices about reporting HAP on behalf of
owners/operators, the EPA recognizes that the fuel consumption data may
come from owners/operators for some facilities and processes (i.e.,
those with HAP emissions), but fuel consumption data for other
facilities and processes may come from States reporting CAP emissions.
As previously described, this proposed action would not require States
to participate in CAERS. This flexibility for States could result in
owners/operators needing to report the fuel consumption both to the EPA
through CAERS and to the State. To avoid this additional burden on
owners/operators, the EPA encourages States to participate with CAERS
in one of the data flows that would avoid duplicative burden on owners/
operators for fuel consumption.
5. New Requirement for Including Title V Permit Identifier
    Title V of the CAA forbids major sources and certain non-major
sources from operating without a permit. The vast majority of ``title
V'' operating permits are issued by State or local authorities under
State rules approved by the EPA to issue such. Title V operating
permits are required to address all applicable pollution control
obligations (i.e., applicable requirements) under the SIP or Federal
implementation plan (FIP), the acid rain program, the air toxics
program, or other applicable provisions of the CAA (e.g., NSPS
including solid waste incineration rules). Sources must also submit
periodic reports to the permitting authority concerning the extent of
their compliance with permit obligations. The EPA has adopted
regulations at 40 CFR part 70, which define the minimum elements
required for State operating permit programs. In certain circumstances,
the EPA also issues title V permits under 40 CFR part 71, the Federal
operating permit program.
    The EPA receives copies of permit applications, permits and
facility annual

compliance reports and is aware that a great deal of information is
available from title V operating permits and from the reports that
result from the monitoring and reporting requirements that the permits
are required to contain. For the same reason, users of the NEI data
often seek permitting information about facilities within the NEI.
States and the EPA have developed repositories of title V permits, with
much of that information available online. In most cases, perhaps all
cases, the title V operating permits have a permit identifier that
allow for distinguishing a permit from other title V operating permits.
While there is no requirement under 40 CFR part 70 for assigning a
unique identifier for title V operating permits, federally permitted
title V sources do have permit identifiers and the EPA is aware that
most, if not all, State permit programs also use permit identifiers.
Based on EPA's current information, States often rely on a variety of
numbers to uniquely identify various versions of a source's title V
permit, including the title V permit number, an application number,
project number, and the State's source identifier number. The EPA is
seeking comment on which unique identifiers it should collect as a
permit identifier.
    Given the importance of easily associating point sources within the
NEI with their Title V operating permits, this action proposes to
require States to report Title V operating permit identifiers for all
Title V sources that are also point sources as defined by the proposed
revision to 40 CFR 51.50. Similarly, this action proposes to require
owners/operators of facilities to report a Title V operating permit
identifier when they would report annual emissions totals and
associated data to the EPA under this action. The EPA additionally
proposes that this requirement would take effect starting with the 2026
inventory year. Because the definition of point sources in this action
does not necessarily include all Title V sources, it is possible that
this action will not collect all Title V operating permit identifiers,
but the EPA expects most of them to be collected under this proposed
action based on the proposed point source definition.
6. New Requirement To Use the Best Available Emission Estimation Method
    EPA guidance published in AP-42 has long established a hierarchy of
information quality on which States and sources should rely to estimate
emissions. The Introduction to AP-42, Volume I \57\ provides general
guidance about different ways to estimate emissions from sources.
Regarding stationary sources, page 1 of the Introduction to AP-42
describes that ``[d]ata from source-specific emission tests or
continuous emission monitors are usually preferred for estimating a
source's emissions because those data provide the best representation
of the tested source's emissions.'' The document goes on to acknowledge
on page 1 that such tests may not be available, and that in such cases,
emissions factors are ``the best or only method available for
estimating emissions.'' It also describes on page 2, ``because
emissions factors essentially represent an average of a range of
emission rates, approximately half of the subject sources will have
emission rates greater than the emissions factor and the other half
will have emission rates less than the factor.''
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    \57\ The Introduction to AP-42, Volume I, Fifth Edition, U.S.
EPA, January 1995, https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors.
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    Figure 1 of Introduction to AP-42 provides a hierarchy of emission
calculation methods whereby the methods near the top of the hierarchy
are methods with greater accuracy and methods near the bottom would
generally have lower accuracy. In reference to this figure, the
Introduction to AP-42 guides those who seek to estimate emissions by
stating on page 3, ``[s]electing the method to be used to estimate
source-specific emissions may warrant a case-by-case analysis
considering the costs and risks in the specific situation.'' In this
case, the ``cost'' consideration primarily applies to the decision
about whether to add a CEMS or perform a source test, since the costs
for simply looking up an emissions factor and applying it in a
calculation are negligible in comparison to those other measurement
options. Another cost could be incurred in cases where a new emissions
estimation method needs to be developed because none are available.
    As described previously, the EPA is interested in obtaining high
quality emissions data. Regulatory and other decisions are made by the
EPA based on the data collected by the AERR; however, the current AERR
requirements are silent on the question of how emissions should be
calculated. While this lack of specificity provides States and their
regulated sources flexibility in how emissions estimates are created,
the current AERR leaves open the possibility that the best available
emissions estimation approach may not be used in estimating and
reporting annual emission totals.
    The EPA is considering the advisability of adding requirements for
emissions testing at facilities for the purpose of improved emissions
estimates. In addition to a large burden any such requirement would
impose, the great variability of source types, source sizes,
pollutants, source measurement methods, and other factors would make
structuring such a requirement extremely difficult. Many requirements
on facilities to perform source tests and performance tests for
compliance purposes already exist. Given these considerations, an
addition of source testing requirements would likely be too unwieldy to
be successful.
    Without a requirement for sources to perform additional
measurements above and beyond what they are currently performing, the
EPA can still rely on the available data that States and owners/
operators of point sources have to estimate emissions. To ensure the
highest possible quality data be provided, the EPA proposes to require
in Sec.  51.5(a) that States and owners/operators of facilities use the
best available methods to report annual actual emissions. Further, the
EPA proposes to refer to Figure 1 of the Introduction of AP-42 and
include the expectation that States and owners/operators of facilities
should preferentially use available emissions calculation methods at
the top of the hierarchy over emissions calculation approaches lower in
the hierarchy. The EPA also proposes that the best available emissions
estimation method be used both to determine whether emissions exceed
any proposed reporting threshold and for reporting emissions to the EPA
when required or voluntarily reported. Finally, paragraph (a) of the
proposed regulatory text explains that where current guidance materials
are outdated or are not applicable to sources or source categories,
owners/operators should develop and document new techniques for
estimating emissions, which should rely on any available source
measurements applicable to the emissions source(s). In proposing this
approach, the EPA is seeking to strike the appropriate balance between
EPA's need to obtain the best information and the burden that would be
imposed by requiring additional source testing.
    The CAA delegates responsibility for estimating emissions of CAPs
to States and requires emission inventories reported by States to be
``comprehensive, accurate, and current'' in CAA section 172(c)(3).
Thus, when source tests, performance tests, or

continuous emissions monitor data are not available, States and owners/
operators of facilities may use available emission rates from EPA
compilations of emissions factors such as WebFIRE and AP-42 to estimate
emissions. The EPA proposes a clarification in Sec.  51.5(e) of the
proposed regulatory text that emissions factors should represent the
emissions process and controls at the facility.
    The EPA has observed that many States use EPA's emissions factor
compilations as the primary source of emission rates in their emissions
data collection tools. For this reason, States sometimes do not report
emissions from a process that does not have an EPA-provided emissions
factor. While the EPA strives for a complete compilation of emissions
factors, the CAA holds the States responsible for providing emission
inventory data for CAPs. Therefore, States may not claim that emissions
do not need to be reported simply because an EPA emissions factor is
not available through EPA's emissions factor compilations.
    Related to the possibility of missing emissions factors or
calculation methods, the SBAR Panel Report completed for this proposed
rule included a recommendation that the EPA avoid requiring small
entities to develop a new emissions estimation method when none
existed. Small entity representatives who participated in the panel
process indicated that such efforts are beyond their resources and
would impose an undue burden on small entities.
    To clarify the expectation of emissions reporting while avoiding
undue burden on small entities, the EPA proposes to include within
Sec.  51.5(a) a statement that ``where current guidance materials are
outdated or are not applicable to sources or source categories, an
owner/operator (other than a small entity) should develop and document
new techniques for estimating emissions, which should rely on any
available source measurements applicable to the emissions sources(s).''
States may estimate emissions with other approaches as described above.
    The EPA is responsible for quality assurance of emissions data
collected from owners/operators. While the requirements described in
this section should help ensure high quality data is reported, the EPA
may identify problems with the data as part of quality review. Based on
this consideration, the EPA is proposing a statement at Sec.  51.25(c)
that as part of this review, the EPA may require an owner/operator of a
point source to review and/or revise data that do not meet quality
assurance criteria. The EPA proposes that it may additionally require
an owner/operator of a point source to provide other data or
documentation to support their submissions when information provided
does not fully explain the source or quality of the data provided.
7. New Requirement To Use Source Test Reports for Emission Rates
    In the case of source test or performance test data being used for
emissions estimates, the tests that represent the typical operation of
a source during the year should be used. Fortunately, many source tests
are designed to measure emissions during typical operations of a
source. Because of this, the EPA expects that most source tests should
be relevant for estimation of emissions from the part of a facility
that has been measured.
    In addition to the use of the best available emission estimation
method as described above, the EPA proposes requirements specifically
regarding the use of source test data. The EPA proposes to require at
Sec.  51.5(c) that owners/operators of point sources that are
submitting point source emissions data directly to the EPA under this
subpart must use the most recent source test(s) or CEMS data applicable
to the operating conditions of the facility during that year to provide
annual actual emissions. When reporting directly to EPA, owners/
operators should determine which data to include in any averaged
emission rate used to estimate actual annual emissions. The EPA
additionally proposes that when an owner/operator has source test or
monitoring data for a unit, process, or release point that operated
during the reporting year and the owner/operator does not use that data
to estimate emissions, the owner/operator would be required to submit a
justification for that choice for each unit and pollutant for which
such data are not used to estimate emissions.
    States would not be subject to the requirements for emissions data
on owners/operators of point sources. To account for this, the EPA
proposes a related requirement on states in Sec.  51.5(d). The EPA
proposes that states submitting point source emissions on behalf of
owners/operators to the EPA under this subpart must ensure that owners/
operators of facilities submitting data to the State take the same
approaches as described in paragraphs Sec.  51.5(a) through (c) of this
subpart. If a State submits data for a facility that has not used
available source test data or continuous monitor data to estimate
emissions, then the State must submit a justification for that choice
for each unit and pollutant for which such data are not used to
estimate emissions. The EPA expects that the justification would be
collected by the State from owners/operators.
8. New Requirement To Identify Regulations That Apply to a Facility
    The EPA and States have numerous regulations that require owners/
operators to meet various requirements and emissions limits for a wide
variety of source categories. When the EPA or States issue a permit for
a facility (e.g., Title V operating permit), the permit includes the
regulations to which a facility is subject. This existing permitting
paradigm allows EPA, States, and the public to easily determine the
regulations that affect a specific facility. However, since these
permits are primarily on paper or an electronic format such as Portable
Document Format (PDF), the current permitting approach makes it
difficult for EPA, States, or the public to determine all the emissions
units across the U.S. that are affected by a given regulation. With
this action, the EPA is considering addressing this limitation by
collecting certain additional data elements from owners/operators and
States that would link key permit information with facilities and units
in the emissions inventory.
    An approach to provide such linking would be prudent because the
EPA routinely needs to identify all the facilities and units that are
regulated under Federal or State regulations that reduce emissions. For
example, the EPA needs to identify those facilities and units subject
to a particular NESHAP so that the EPA can evaluate the residual risk
associated with the source category or to perform a technology review.
Likewise, in making estimates of future-year emissions necessary for a
RIA or proposing solutions to transported emissions, the EPA needs to
understand which units are subject to state-imposed pollution reduction
programs that may go beyond EPA requirements as opposed to a State
implementing a particular EPA requirement. In addition, accurate
information about how a regulation affects facilities nationwide would
help the public know more about the ongoing benefits of EPA's
regulations.
    Using the current approach of paper of PDF permits, the EPA is able
to identify affected units for selected regulations; however, the EPA
has found such efforts to be labor intensive, time consuming, and
subject to error. While some States do have electronic permitting
systems that reduce these burdens for EPA, the systems are

typically not designed in a way that meets EPA's needs and even if such
a design were available, it would cover only those States that provided
it.
    In addition to the challenges posed by paper/PDF formatting versus
electronic datasets, the EPA has identified several reasons why the
current permitting approach is not sufficient for these emissions
inventory purposes. One reason is that unit identifiers included in
permits are not always the same as those identifiers used in the
emissions inventory. Thus, it is not necessarily possible to match the
unit(s) as identified in a permit with those units and their emissions
from an inventory. A second reason is that States do not have a uniform
permitting approach that could allow for automating the scanning of
paper/PDF documents. One way to eliminate these challenges would be a
wholesale revamping of permitting that connects permits to emissions
inventories (as some States have done) and to ensure facility IDs and
units are synchronized across permitting and emissions inventories.
However, this sort of endeavor would generate significant burden and
would affect much more about the permitting process than simply getting
the data that the EPA needs for inventory purposes.
    To create the data flow needed to address this issue and to
minimize burden, this action proposes to require certain additional
data elements for point sources from States and owners/operators of
point sources. For the major source designation, this action has
already described a proposed requirement for States and owners/
operators of facilities to provide a title V permit identifier, and
that requirement would help provide the Major source designation
information but does not address whether the source is a Major source
for CAPs, HAP, or both. To allow for full categorization, this action
proposes to include a reporting requirement in Table 2a to Appendix A
of this subpart, a Facility Source Category Code. This code would allow
a facility to be designated as one of the following: CAP major, HAP
major, HAP and CAP major, HAP, and nonattainment area major,
nonattainment area major, non-major, or synthetic non-major. The EPA
additionally proposes that this requirement would not take effect until
the 2026 inventory year (to be reported by May 31, 2027).
    This action additionally proposes to require States and owners/
operators of point sources with State or Federal operating permits to
report the regulatory applicability for each unit or process for which
a federally enforceable regulation applies and is included in EPA's
list of regulatory codes. Currently the list includes regulations
within 40 CFR parts 59, 60, 61, 63, and 65. The EPA provides the list
through the EIS and has included the current list in the EPA docket for
this action. As described in section IV.A.12 of this preamble, this
proposed requirement would include an optional accommodation for small
entities (that meet certain criteria) to require only reporting of
these additional data elements by unit, even when the regulation
applies only for a particular process of the unit. The EPA additionally
proposes that these requirements would not take effect until the 2026
inventory year (to be reported by May 31, 2027).
    Under this proposed action, States or owners/operators of permitted
sources would be required to provide the regulatory codes for a unit
when the entire unit is subject to a particular regulatory requirement
in EPA's list and would be required (if not a small entity) to provide
the regulatory codes for a process (e.g., a particular fuel burned at
that unit) if a single process within a unit is subject to a regulation
but not the entire unit. This requirement would apply to all facilities
for which a State/local/tribal CAA permitting authority (including the
EPA as the permitting authority) has issued a permit for construction
or for operation.
    If a State or owner/operator provides a regulatory code for a unit
(rather than a process at that unit), then the EPA would assume that
regulation applies to all processes at that unit. In addition, the
required data would include the start-year and any end-year of
applicability of the regulation to the unit or process. Finally, States
and owners/operators may optionally include any State regulations
associated with units and processes. If such optional regulations are
included, then the State or owner/operator would also need to include a
description of the State regulation.
    The EPA recognizes that this proposed requirement would impose some
incremental burden on owners/operators and States. Most of this burden
would occur in the first year of reporting under the new requirements
as proposed, and subsequent years would see a decline in that burden
because only changes to the information would be required to be
reported, as the EIS and CAERS carries forward data about regulations
from one year to the next.
9. Existing Regulatory Requirements To Be Required by EPA Data Systems
    The EPA has identified several data fields that are relevant to
perform its regulatory functions, for which States have not always
provided complete data. The current AERR requires reporting of design
capacity and associated data elements like unit of measure for any
point source combustion units. The current AERR additionally requires
the throughput that is used to calculate emissions when emissions are
calculated using emissions factors. EIS does not currently reject
States' data when it does not include these required data elements. The
current approach is based on feedback from States offered as part of
routine collaboration for the NEI in which States indicated that the
information was not available in their data systems when the EPA
started using the EIS for the 2008 inventory. After collecting 2008
inventory data, the EPA observed that some States used default values
rather than obtain accurate data for these fields. For this reason, the
EPA stopped requiring those fields so as not to clutter its
repositories with inaccurate data based on State defaults.
    Accurate information on design capacity and associated fields will
help the EPA better understand the size of combustion units when
evaluating alternative regulatory approaches to reducing emissions from
these sources. Accurate and complete data about throughputs used to
estimate emissions is critical to include so that the EPA can quality
assure the resulting emissions data and have all information needed to
transparently provide the origin of the emissions estimates in the NEI.
To achieve this, the EPA plans to reject data submitted to EIS that
does not include the unit design capacity and associated data elements
required under the current AERR and in this proposed revision to the
AERR for any combustion unit starting with the 2023 inventory cycle.
Likewise, the EPA plans to reject data submitted to EIS for emissions
estimation methods that require throughput to calculate emissions
(e.g., emissions factors) when the throughput data are not included in
the submitted emissions reports. The EPA is not reopening these
requirements included in the current AERR but rather is simply using
this preamble to explain the Agency's intent to start collecting these
data once again.

10. Option for Reporting Two-Dimensional Fugitive Release Points
    The current version of this subpart already allows for States to
report two-dimensional fugitive release points. These fugitive release
points can take the form of a series of vents near the top of a
manufacturing building, whereby any pollutants inside the building can
be vented to the ambient air. These two-dimensional releases can be
oriented in any position. The current version of this subpart provides
that these two-dimensional fugitive release points can be specified
using a latitude/longitude of the southwest corner of the release,
width, length, and an orientation angle in degrees from north, measured
positive in the clockwise direction from the western-most point. The
definition of the appropriate angle to use has been challenging for
States to understand and implement.
    Fugitive release parameters are very important because they impact
modeled risk. Often fugitive releases are lower to the surface and thus
may pose an increased risk to nearby communities as compared to tall
stacks that disperse the pollutants before they reach ground level. The
EPA's review of data from past inventory cycles shows that either
fugitive releases are not included in State submissions or when
submitted, the two-dimensional release parameters are incorrect. The
inaccuracy of these data is a significant reason for adjustments to the
NEI for use in EPA technology reviews and risk reviews, after the NEI
has been completed. This additional review takes time and delays
regulatory actions and consequently delays protection of public health.
These delays could be avoided if States (and/or owners/operators of
facilities reporting to EPA) were to submit correct information. To
address the challenges of the existing angle-based, two-dimensional
fugitive release points, the EPA is proposing a simpler approach.
    The EPA has devised a new approach that is easier to understand and
has been previously implemented as part of the RTR program's
information collections under CAA section 114 and in CAERS. This
approach relies only on the width of the two-dimensional releases
(e.g., the building width) and coordinates of the midpoints each end of
the length of the release. The latitude/longitude coordinates are
readily obtained through GPS devices on common cell phones, and the
building width can either be measured or obtained from building plans.
The greater simplicity of this proposed additional approach suggests
that it will assist States and owners/operators in complying with the
provisions of this subpart that include reporting fugitive release
points and their associated coordinates.
    Based on these considerations, the EPA proposes to allow States and
owners/operators to use either the existing angle-based approach for
this current subpart or the new approach as just described. The current
approach allows for States who have previously collected accurate two-
dimensional release point data to continue to provide that. The new
approach will help reduce burden, improve compliance with this subpart,
and improve data quality. It allows reporting the orientation of two-
dimensional fugitive releases by providing the latitudes and longitudes
for center of the sides of each release. For the example of a
rectangular building with vents (a common fugitive release), this
approach would allow a GPS-provided location to be collected by someone
while standing first at the midpoint of one side of the building, then
at the midpoint of the opposite side.
    While this action proposes to retain the angle-based approach, the
EPA continues to consider a second option that would phase-out the
angle-based approach in the future. This ``Single Fugitive Approach
Option'' would provide less overall complexity for the data system and
allow for easier quality control. It also would compel States that may
incorrectly assume that their data are accurate to regenerate that data
using the new approach, improving the accuracy of the emissions data.
If the EPA were to eliminate the angle-based approach from the
reporting structure, it would consider doing so as early as the 2023
inventory year (which would be due under this proposal by January 15,
2025) or as late as the 2032 inventory year (which would be due under
this proposal by May 31, 2033). The EPA urges commenters to provide
input on the advisability of retaining the angle-based approach
indefinitely or phasing it out during the periods suggested.
11. Changes To Reporting the North American Industrial Classification
System Code
    The current AERR requires that point source reports include a
single NAICS that applies to a facility. The EPA has observed that
multiple NAICS may apply to a single facility. To support the interest
that some States and owners/operators may have in reporting all
applicable NAICS codes, the EPA has included in its latest reporting
formats (as included in the docket for this proposal) a capability that
allows States to report multiple NAICS for the same facility. When
multiple NAICS are reported voluntarily, States need to provide an
additional data element to indicate which NAICS is considered the
primary NAICS and allows for labeling the other NAICS provided as
secondary, tertiary, etc.
    EPA is proposing to formalize this voluntary approach by including
an additional NAICS Type data element, and that this data element is
only required when multiple NAICS are reported. The EPA proposes that
reporting multiple NAICS and including the NAICS Type data element
would be voluntary for both States and owners/operators. However, when
multiple NAICS are voluntarily reported, the NAICS Type data for at
least one NAICS would be required to indicate the primary NAICS. The
EPA would assume that any State and owner/operator reporting a single
NAICS is reporting the primary NAICS.
    With the addition of the concept of primary NAICS, the EPA has
identified the need to define that term. The EPA considered definitions
available from the small business administration (13 CFR 127.102), the
GHGRP (40 CFR 98.3), and the TRI program (40 CFR 372.22). After
reviewing these available definitions, the EPA is proposing to define
primary NAICS as ``the NAICS code that most accurately describes the
facility or supplier's primary product/activity/service. The primary
product/activity/service is the principal source of revenue for the
facility or supplier.''
    In addition, the EPA is proposing to specify the number of digits
for the NAICS value that States and owners/operators must include when
reporting. The NAICS system allows for NAICS codes from 2-digits to 6-
digits, where more digits provide more specifics about the business
activity. As previously described in section IV.A.8, the EPA is
proposing a list of NAICS codes for which facilities with that primary
NAICS code would report HAP for those emitted pollutants that exceed
proposed reporting thresholds. This list of NAICS sometimes includes 5-
and 6-digit NAICS, so it will sometimes be necessary for facilities to
identify a NAICS at that degree of specificity.
    In its work with States, the EPA has learned that some State
systems continue to allow facilities to report emissions with only
Standard Industry Codes (SICs), which OMB replaced for use by Federal
agencies in 1997.\58\ In 2008, the EPA required that NAICS be used in
State reports under the AERR

(73 FR 76539); however, when States collect SIC, they must map it to a
NAICS code for reporting for this subpart. This mapping can result in
less specific NAICS. For this and other reasons, some States have been
unable to report NAICS beyond a 4-digit degree of specificity.
---------------------------------------------------------------------------

    \58\ See U.S. Census, North American Industry Classification
System, 2023. https://www.census.gov/naics/?99967.
---------------------------------------------------------------------------

    As will be described in section IV.R, the AERR is referenced as
providing a required data format for numerous SIP inventory
requirements. Given nearly every State has at some point since 2008
needed to prepare SIP emissions inventories, the EPA does not know why
some States do not collect NAICS from their facilities for meeting the
AERR and SIP inventory reporting requirements. The EPA seeks comment
from States on what obstacles exist for modernizing their collection.
Considering that the EPA now provides the CAERS for use by States and
CAERS includes collection of NAICS, the EPA expects all States should
update their emissions collections from facilities to meet the AERR
requirements for NAICS, originally issued in 2008.
    Additionally, the EPA describes in section IV.A.6 its proposal to
allow States to voluntarily report HAP on behalf of owners/operators,
which would require States to adopt the same reporting requirements for
HAP as the EPA has issued in a final AERR rulemaking. If finalized,
this provision would make collection of NAICS by States essential to
being able to report on behalf of owners/operators.
    As part of its efforts through CAERS to better share facility data
across emissions inventory programs, the EPA has evaluated the
requirements of the TRI, CEDRI, and GHGRP collections and the
requirement for NAICS. The TRI program requires a 6-digit NAICS code
(40 CFR 372.85(b)(5)). The CEDRI program does not require NAICS, but
when it is provided voluntarily, requires that it be provided with 6
digits. Finally, the GHGRP program requires at 40 CFR 98.3(c)(10) that
the NAICS be provided ``that most accurately describes the facility or
supplier's primary product/activity/service.'' The GHGRP has
implemented this using a 6-digit NAICS requirement.
    Given these considerations, the EPA is proposing to require 6-digit
NAICS in reports from States and owners/operators under this subpart.
In many cases, 5-digit NAICS are the same as 6-digit NAICS available by
appending a zero. In cases where there are more specific 6-digit NAICS
that correctly describe a facility, then States and owners/operators
should use it. When a 5-digit NAICS is the best representation of a
facility, such as when none of the more specific 6-digit NAICS
correctly describe the primary economic activity at a facility, States
and owners/operators may instead report a 5-digit NAICS. For those
owners/operators of facilities also reporting to other programs with a
6-digit NAICS, the EPA would encourage reporting with the same NAICS
when appropriate. In addition, a 6-digit NAICS would support
determination by States and owners/operators whether they are subject
to reporting requirements if the EPA finalizes the proposal to use
NAICS as one basis for HAP reporting requirements for non-major
sources. Further, if the EPA were to finalize the SBA Definition
Alternative for defining small entities (see section IV.A.14), 6-digits
would be necessary for implementing NAICS-specific criteria for small
business definitions. This proposed requirement would also provide the
EPA more specific information about activities at each facility and
better standardize the available data to the agency, States, and the
public.
12. Clarification About Definition of the Facility Latitude/Longitude
    Since the inception of the NEI program, the EPA has observed
problems with the accuracy of facility locations. In the current AERR,
Table 2a to Appendix A of this subpart specifies that for point
sources, States must report ``latitude and longitude at facility
level.'' However, the AERR provides no definition of this location.
    As described in sections IV.A.11, EPA is additionally proposing
requirements to collect coordinates for release points, to allow for
appropriately accurate estimation of cancer risk and other health
impacts associated with HAP. This ``facility-level'' coordinate serves
several purposes in implementing the NEI program. First, EPA uses the
facility-level coordinate to quality assure release point coordinates
as they are being submitted electronically, to make sure that the
release point coordinates are within a reasonable distance to the
facility-level coordinate (EPA has adjusted and may further customize
these ``reasonable'' distances for each facility to further improve the
quality assurance). In addition, the single facility-level coordinate
is used to provide a mapping location of the facility for displaying
facility-level emissions data for products such as AirToxScreen. Under
the current AERR, the facility-level coordinates serve as a default
location for all release points at a facility, and those release point
locations are used in air quality modeling that supports EPA's NAAQS
and air toxics programs. Under this proposal, those facility-level
locations would continue to serve as a default for certain small
businesses that choose to use the alternative reporting requirements
available as part of this proposal.
    Many ways exist for interpreting a facility-level coordinate. As a
result, States provide various interpretations of the location, which
includes geocoded addresses (which results in a coordinate at the
roadside) as well as points taken manually from a map. This variability
is understandable considering the lack of detail in the current rule.
Without a more specific definition, it is difficult for the EPA to
obtain quality data to best implement the NEI program.
    The EPA also recognizes that a single facility may have many
contexts in which a facility-wide coordinate could be used
appropriately. Thus, the EPA is considering which terms would best
describe the requirements of this subpart, while also allowing for
other contexts. Any such term would ideally not conflict with terms
that may be used to set geocoded addresses or locations in the context
of regulations related to other environmental mediate (e.g., water and
solid waste).
    Within the NEI program, the facility coordinates are important for
two primary reasons: (1) to display the location of the facility on
maps for end users and (2) to provide a centroid location that defines
a facility-specific quality assurance perimeter. Using the facility
coordinates and a facility-specific radius, the EIS can QA release
point coordinates to ensure that all such coordinates fall within such
a radius. To address these considerations, the EPA is proposing a
specific definition of facility coordinates in 40 CFR 51.50 to ensure
high quality data for mapping purpose and to allow for the effective
implementation of release point coordinates.
    The proposed definition reads as follows: ``Facility air centroid
coordinates means a latitude/longitude using the WGS84 or NAD83 datum
that maps to or near the centroid of the air emissions activities at a
facility.'' This definition would allow for separation of this
facility-wide coordinate from other coordinates that currently exist
outside of the NEI program. In addition to the definition, Table 2a to
Appendix A of this subpart would be modified to include the term
``facility air centroid coordinates'' rather than ``latitude and
longitude at facility level.''
    In addition to defining the term, this proposed change would add
the specification of which datum should be used when determining
coordinates to report. In past collections, the EPA has received other
types of datum without

specification. The previous AERR did not require specific datum or
require that a field identifying the datum be included in the report.
The EPA identified this error in the data after the data had been
reported, rather than before the data was accepted by the EPA from the
State. To allow for checking the datum used for the coordinates
reported, the EPA proposes to add a new required field for States and
owners/operators to fill in when reporting any coordinates (facility
air centroid coordinates and release point coordinates).
13. Clarification To Use the Latest Reporting Codes for Electronic
Reporting
    The EPA has observed that, in past emissions inventory reporting
cycles, States may try to report their emissions inventory data using
outdated emissions inventory reporting codes, such as SCCs, unit type
codes, or control measure codes. When States use outdated codes and
report to the EIS, the data records using such codes are rejected by
EIS. If States do not review the EIS feedback report notifying them
that certain data were rejected, correction of the error(s) is delayed,
creating unnecessary additional work for both States and EPA.
    To help avoid this problem for States and prevent this problem for
owners/operators who may be required to report directly to the EPA
under a final version of this proposed action, the EPA proposes to add
new requirements about use of the latest EPA codes in submitting
emissions inventories. The EPA is proposing to add a statement in 40
CFR 51.5(j) that would require States and owners/operators of point
sources reporting directly to the EPA under this subpart to use the
most current data reporting codes for electronic reporting that are
available at the time of reporting. Reporting codes can change over
time, and the EPA will strive to publish the reporting codes that can
be used for each inventory year by June 30th of each inventory year.
For example, the EPA would plan to publish codes that are to be used
for reporting 2024 emissions will be published by June 30, 2024. Since
the proposed regulations would require reporting in accordance with the
most current codes, entities responsible for reporting should check to
see if the EPA has published updated reporting codes before they
report.
14. Clarification About Reporting Individual Pollutants or Pollutant
Groups
    Some HAP pollutants have different degrees of specificity in how
they can be reported. For example, mercury could be reported as total
mercury compounds (i.e., compounds that include mercury but have other
elements that comprise the compound mass), total mercury (i.e., only
mercury), or reported separately for elemental gaseous mercury, gaseous
divalent mercury, and particulate divalent mercury. In proposing the
addition of HAP reporting to the AERR, the EPA is clarifying in this
proposed action whether individual pollutants or grouped pollutants
should be reported.
    EPA has developed experience in collecting HAP information based on
the existing voluntary HAP reporting from States. As part of this
voluntary program, the EPA has implemented choices for each case where
a pollutant group or a specific pollutant could be reported. This
choice depends on many factors that change over time, including source
measurement methods, available emissions factors, data system
capabilities, and QA approaches. To provide a degree of flexibility for
the data collection approach, the pollutants that are permitted to be
reported are listed via the EIS for State reporters and via CAERS for
use by owners/operators. The EPA lists the pollutants that may be
reported following the reporting codes schedule described in section
IV.I.13 of this preamble.
    The EPA is proposing that States or owners/operators would be
required to report the most detailed pollutants possible based on the
available data (e.g., continuous monitors, source tests, emissions
factors), so long as the system allows it to be reported. The
pollutants to be reported may be more detailed than when the pollutant
group is used to determine if a facility is a point source. For
example, in section IV.A.4 of this preamble, the EPA proposes that a
facility could be determined to be a point source when the sum of
dioxins/furans exceeds a mass-based reporting threshold. The EPA is
proposing to require the individual congeners of dioxins/furans to be
reported, in a manner similar to how dioxins/furans are reported to
TRI, because they have different degrees of toxicity. EPA would use the
latest available toxicity information to compute the TEQ of the dioxin/
furan group.
    To implement this approach, the EPA proposes to add Sec.  51.5(q)
to require owners/operators or States reporting on their behalf to
report the most detailed pollutants available (e.g., the component
pollutants from Table 1D to Appendix A of this subpart) preferentially
over pollutant groups. The specific cases listed are polychlorinated
biphenyls, and mercury. This action further proposes that, when the
detailed pollutants do not comprise the total mass of the pollutant
group, owners/operators report the remaining portion of mass for the
pollutant group. In all cases, owners/operators must only report
detailed compounds or pollutant groups that are supported by the EPA
electronic reporting system.
15. Clarification About How To Report HAP That Are Part of Compounds
    For pollutant groups such as ``Lead compounds'' or ``Nickel
compounds,'' the existing voluntary HAP program has caused confusion
about how to report such emissions. This confusion stems from the fact
that the HAP portion of such compounds can be a different amount of
mass than the total compound, which includes mass of other non-
hazardous elements.
    To avoid further confusion for States or owners/operators who may
report HAP, this action proposes at Sec.  51.5(p) to require that
emissions must be reported for the metal portion of the metal group (Pb
or Nickel in these examples). This proposed approach is consistent with
the guidance that the EPA has provided to States informally when NEI
reporting questions have arisen, but this proposed action attempts to
formalize the approach. If finalized, this proposed action would
further clarify that no adjustment is needed to estimate the metal
portion when using emissions factors and source tests, because the
source measurement methods used to create emissions factors and source
tests already reflect the metal portion of the compounds. Other
estimations methods such as material balance or engineering judgement
may need to include calculations to adjust the mass to reflect just the
toxic portion of the pollutant group. When no composition information
is known, the EPA proposes that the entire mass of the material emitted
be considered and reported as HAP.
16. Requirement To Include Certain Mobile Sources Within Point Source
Reports
    The EPA has received questions during past NEI years regarding
whether emissions from mobile sources operating within a facility site
should be included as emissions from that point source. These mobile
sources can include mining equipment and other vehicles and have
emissions both from combustion engines and from road dust

generated by the vehicles. To resolve any confusion that may exist, the
EPA proposes to include a statement to clarify that such emissions
should be included in point source reports.
    The EPA further proposes to define which mobile sources should be
included to distinguish the mobile sources that are part of the
functioning of the facility (which would be included) from vehicles
like cargo trains, employees' personal vehicles, or delivery trucks
(which would not be included). To accomplish this, the EPA proposes to
include a statement in 40 CFR 51.5(b) that would require States and
owners/operators to include in their point source reports the emissions
from those ``mobile sources (excluding aircraft and ground support
equipment (GSE)) operating primarily within the facility site
boundaries of a point source or multiple adjacent point sources''. The
EPA additionally proposes that this requirement applies when assessing
whether its facility emissions exceed the emissions reporting
thresholds in Tables 1A and 1B to Appendix A of this subpart and when
submitting point source emissions data under this subpart.
    EPA is proposing to exclude aircraft and GSE from 40 CFR 51.5(b) to
ensure that the section does not conflict with the proposed approach
for States to report data about aircraft and GSE described in section
IV.I.1 of this preamble. As previously described, the EPA is proposing
that for these sources, the EPA would provide LTO data for States to
review, accept, or provide comments about. Based on the LTO data, the
EPA would calculate emissions of aircraft and GSE. If those sources
were to be also included in 40 CFR 51.5(b) to determine point source
status of a facility, then States and owners/operators would need to
calculate those emissions independently of EPA. Rather than impose this
additional burden, the EPA is proposing to exclude those sources from
point source determinations. Other sources at airports such as
combustion units and other mobile sources as defined by 40 CFR 51.5(b)
should be included in making any determination of point source status
for airports.
    The proposed inclusion of the ``multiple adjacent'' phrase exists
account for co-located facilities that may share the use of such mobile
equipment or vehicles. This part of the proposed requirement is
intended to capture emissions from equipment used in the production and
operation of a facility, for example, nonroad vehicles and trucks at
mines, forklifts, and movable electricity generators. The proposed
requirement is intended to exclude vehicles of employees, temporary or
occasional on-site contractors (such as temporary construction,
landscapers, or repair services), and other mobile sources operated in
many other locations and/or for other purposes.
17. Cross-Program Identifiers Option
    During the SBAR panel, small entities asked about whether the EPA
would be able to use activity data about industrial throughput that the
EPA already collects as part of the Toxic Substances Control Act (TSCA)
section 8. They indicated that that activity data could be especially
relevant for helping small entities use facility-wide throughputs that
could be used to estimate emissions using EPA's emissions estimation
tool (see section IV.A.13 of this preamble). During discussions with
the panel, the EPA explained that to be able to use such information,
the EPA would need to be able to match facilities across the NEI and
TSCA programs. As a result of these discussions, the SBAR panel
recommended that the EPA take comment on whether small entities would
prefer to provide the EPA an additional data element with the TSCA
section 8 facility identifier, so that the EPA could use those
identifiers to support owners/operators use of the TSCA data, when
appropriate, for estimating facility-wide emissions. The EPA expects
that if TSCA identifiers were available, then connections between TSCA
section 8 data and emissions estimates for AERR could likely be
included in the emissions estimation tool and/or the CAERS collection
approach.
    Based on this recommendation and other information included in this
section, the EPA urges small entities and other commenters to provide
information about cross-program identifiers. In the case of the TSCA
section 8 identifiers, the EPA seeks to clarify our current
understanding that the throughput information from TSCA section 8 may
not be the relevant throughput for a particular facility, depending on
the emissions factors and other information available to EPA, to use to
estimate facility-wide air emissions. In addition, the EPA believes
that it would be impractical to require reporting of TSCA section 8
facility IDs only in certain circumstances. Thus, if the EPA
implemented this approach in any final action, the EPA expects that the
TSCA section 8 identifier would be an optional data field that could be
used to help small entities estimate emissions only when provided and
relevant.
    In addition to TSCA section 8 identifiers, the EPA has many air
emissions programs with different identifiers from the facility and
other identifiers that have been collected under the AERR for many
years and would continue to be collected. Through the CAERS program,
the EPA has developed a conceptual model of facilities, by which
emissions from each unit, process, and release point within a facility
are linked to different air emissions programs. If the detailed data
reported under the AERR also had cross-program identifiers, then EPA,
States, and other air emissions data users could better understand the
relationship among these programs. In some cases, facilities have the
same definitions across programs and a facility-level cross-program
identifier is sufficient to map across two programs. In other cases,
units within a facility as defined by the AERR may be grouped and
reported as two separate facilities based on the facility definition of
another program. Similarly, emissions processes (e.g., emissions from a
primary fuel) might be relevant for reporting separately to one program
from a different process at the same unit (e.g., emissions from a
secondary fuel, which happens to be biomass).
    Based on experience with cross-program mapping for air emissions
programs, the EPA has observed that its attempts to map across programs
can be error prone. While it is extremely difficult for the EPA to do
this mapping, the EPA believes that the owners/operators of facilities
are aware of which units and processes within a facility contribute
emissions for reporting to each program. Based on discussions with
owners/operators and States, the EPA is aware that owners/operators
often estimate emissions at a unit or process level before aggregating
emissions to a facility level before reporting facility total
emissions.
    For source test collections involving CEDRI, the EPA is aware that
owners/operators perform source tests on a specific unit and/or process
with control devices installed. When reporting these source tests
however, facilities are not required to use the identifiers that are
used for reporting emissions under the AERR. If these identifiers were
used, then EPA, States, and owners/operators could easily map the
source test data reported to CEDRI to use in calculating emissions when
it is appropriate to do so. If the EPA had this information from source
test reports, then it could use it in CAERS to provide the source test
data to owners/operators using CAERS for calculating their emissions.
This would lessen burden on owners/operators (and States adopting
CAERS) to meet the

proposed requirement to use source test data when it is available.
Under this scenario, CAERS could link to CEDRI and provide the
available source test data, and if not selected, require an explanation
for why it is not suitable as is also proposed to be required by this
action.
    As mentioned above, the EPA urges commenters to provide information
regarding the advisability of requiring or optionally allowing cross-
program identifiers, called the ``Cross-Program Identifiers Option''
for TSCA section 8, CEDRI, TRI, and GHGRP. If the EPA decided to
include such a provision in any final action, the EPA would include
additional data elements in Table 1A to Appendix A of this subpart that
would allow for owners/operators to report these identifiers. The EPA
seeks information about the availability of information, the burden
associated with providing such information, whether cross-program
identifiers should be required, which programs should be included, and
what the EPA can do to encourage such reporting, and other ideas for
using cross-program mapping information to reduce burden on owners/
operators and States.
18. New Requirements When Using Speciation Profiles To Calculate
Emissions
    One approach for estimation of emissions that may be used when
other approaches are not available includes speciation profiles. A
speciation profile is a set of pollutants with associated fractions of
some other related or ``base'' pollutant. For example, a speciation
profile could provide a ratio between a benzene and VOC to use to
estimate emissions of the benzene when a VOC emission value is
available. If the amount of VOC has been computed for a particular
source, the fraction of benzene from the speciation profile could be
multiplied by the mass of the base VOC emissions to calculate benzene.
This calculation would only be appropriate when the speciation profile
is relevant for the emissions source. A speciation profile is relevant
when it has been compiled based on measurements of sources like the one
for which the speciation profile is being applied.
    Emissions reporting by States under the current AERR allows States
to use speciation profiles to estimate emissions. Since this approach
is generally a lower quality method of estimating emissions as compared
to source tests, emissions factors, or mass balance approaches,
speciation profiles are typically used only if other sources of data
are not available.
    To address these considerations, the EPA proposes that a State or
owner/operator may use the SPECIATE database \59\ or other credible,
publicly available speciation profile data to calculate ratios of
related pollutants if relevant speciation profiles are available. In
addition, to allow the EPA to assess the quality of the information
provided, the EPA proposes to collect additional information about the
speciation profile. Specifically, the EPA proposes that starting with
the 2026 inventory year, when using a speciation profile, a State or
owner/operator must provide (1) the speciation factor used, (2) the
SPECIATE profile code when a SPECIATE profile is used or in the case of
other speciation profiles, the journal citation or reference to a
publicly available report, and (3) the actual emissions value and all
relevant required fields (e.g., throughput, emissions factor) used for
calculating the base pollutant emissions.
---------------------------------------------------------------------------

    \59\ SPECIATE Database available at https://www.epa.gov/air-emissions-modeling/speciate.
---------------------------------------------------------------------------

    This proposed change would require the emissions value and
associated required data fields for the base pollutant even if not
otherwise required by the AERR. For example, some SPECIATE profiles are
based on total organic gases (TOG), but the current AERR does not
require TOG reporting. Under this proposed change, however, if a State
or owner/operator used a TOG-based speciation profile to estimate and
report emissions, then the State or owner/operator would also need to
report TOG and the other required elements included in Table 2B to
Appendix A of this subpart.
19. New Requirement for Small Entity Type
    The EPA has a need to collect and retain information about which
facilities are owned by small entities and to be able to distinguish
which small entity definitions apply to a facility. As previously
described, the EPA expects the proposed revisions to impact small
entities, and the degree of that impact will depend on the definition
of small entity that the EPA uses in a final action. Irrespective of
that definition, the EPA expects States to continue to report emissions
for whatever businesses State regulations require, including voluntary
reporting of facilities smaller than the reporting thresholds included
in this proposal. If these reports included information about which
facilities are owned or operated by small entities, the EPA recognizes
that such information would be beneficial for several reasons as
follows.
    First, generally knowing whether a facility is owned or operated by
a small entity would allow the EPA to implement different reporting
options for small entities. Without a facility self-identifying as a
small entity, the EPA would not be able to provide such options or
analyze its data to know which facilities that owners/operators have
reported as a facility total versus which have been reported only a
single facility, unit, and process. Second, knowing which owners/
operators meet the CAA definition of small entities would support
implementation of the various expectations of SBEAPs for outreach and
support of these businesses. Third, knowing which owners/operators meet
the SBA Definition of small entities would allow the EPA to have more
information about such entities to more efficiently and effectively
analyze whether regulations being developed or revised may have a
significant impact on small entities, as is required by the RFA as
amended by the SBREFA. Finally, the EPA anticipates interest in
reviewing the AERR requirements as they apply to small entities in the
future. For example, the EPA may be expected to assess the utility of
collecting from small entities. By having this information in the data
for any small entities reporting under this proposed action, the EPA
would be able perform any such reviews and assessments.
    Based on these considerations, the EPA proposes to require
reporting of a Small Entity Type at the facility level starting with
the 2026 inventory year. This data element would be defined as the
small entity definitions that apply to an owner/operator responsible
for reporting emissions for a given facility, and it would be reported
as an attribute of a facility. We further propose that the available
types would be ``None'', ``CAA,'' and ``SBA,'' where ``CAA'' refers to
the definition of CAA section 507(c) and ``SBA'' refers to the
definition previously described as the SBA Definition Alternative (see
section IV.A.14 of this preamble).

J. Nonpoint Activity Data Reporting and Nonpoint Survey

    The current AERR requires States to report nonpoint emissions of
CAPs in triennial years. Nonpoint emissions can be estimated by
multiplying throughput or activity data (e.g., volume of fuel used) by
an emissions factor (e.g., quantity of nitrogen dioxide gas produced
per unit of fuel) to arrive at an emission value (e.g., amount of
NOX emitting in a year). Nonpoint emissions

estimates using emissions factors may also be adjusted by a control
factor when the emissions factor does not already account for emissions
reductions achieved by owners/operators due to their compliance with
regulations. More rarely, nonpoint emissions are estimated by
collecting point source data and summing it across counties to report
as a county total. In review of the current AERR, the EPA has
documented some significant reporting gaps that result from the current
requirements. As described below, the EPA is proposing to retain the
triennial reporting requirement for nonpoint sources and is proposing
to make other changes to reduce burden and improve the reporting
process.
    One key gap is that some States do not submit any nonpoint
emissions data. As part of the normal collaboration with States for the
NEI program, some States have explained that they do not have
sufficient resources to fulfil all AERR the requirements (i.e., lack of
staff or time). Another gap results when States submit incomplete
datasets that may exclude whole sectors or parts of sectors. Also, a
gap is caused when States do supply nonpoint emissions data but have
calculated emissions using an outdated method, a method that State
staff cannot explain, or a method without documentation. Another issue
is not knowing whether the State is using a different SCC or data
category to report emissions; in other words, some emissions may be
reported under an SCC that aligns with how the State categorizes a
sector, but this may not be the same categorization that the EPA uses
based on documented methods.
    The current AERR does not have a requirement to submit
documentation of emissions estimation methods alongside the data. Thus,
when States do submit their emissions estimates, they do not provide
documentation unless the EPA requests additional information. The
result can be a lengthy correspondence with State staff to try to
understand how they estimated emissions. The current AERR includes in
40 CFR 51.15(c) a provision for the EPA to ask States to voluntarily
provide supporting information, but the EPA has found this approach to
be very inefficient. Data quality issues, completeness problems, or
lack of documentation can be found months after the data have been
submitted, which has caused the EPA and State to redo work and creates
delays in completing the emissions inventory. For the 2020 triennial
inventory year, the EPA has developed enhanced nonpoint QA approaches
that could further improve quality control of NEI nonpoint sources with
additional adjustments.
    Since the last AERR revision in 2015, the EPA has observed the
problems just described in recent NEI cycles. While the EPA provides
emissions calculation methods with extensive documentation to ensure
robust methods and reduce State burden, the current AERR process does
not require use of those emissions methods. Further, when a State has
emissions calculation methods the State believes represents emissions
more accurately than EPA's methods, the EPA wants States to report
emissions totals for nonpoint sources; however, emissions data without
documentation explaining how it was calculated poses a problem. The EPA
needs to obtain documentation about those methods to assess State data
in comparison to the EPA methods and to consider it for possible
improvements to the EPA methods for future NEI years. Documentation is
also needed to support transparency of the data and for reproducibility
for subsequent inventory cycles or release of updated activity to
improve the estimates.
    Further, both the EPA and States benefit from a process that
considers the possibility of new information after a State submits and
other factors. For example, if a State reports emissions and the EPA
uses that data, the State's calculation method could be superseded by
improvements in an EPA method. Further, because the EPA uses the NEI to
estimate future emissions for use in regulatory development,
documentation of State emissions supports the EPA projecting those
emissions to the future with full understanding of the origin of those
data. Without a clear understanding of State methods, it is difficult
for the EPA to ensure emissions projections are consistent with the
assumptions a State may make to create their nonpoint emissions
submission. These considerations support EPA's interest in collecting
documentation of State emissions calculation methods.
    States continue to experience resource constraints, and any
approach taken by the EPA should consider that such resource
constraints could likely continue. At the same time, the nonpoint
emissions in the NEI are growing in relative importance to other
sources due to regulations that have significantly reduced point source
and onroad mobile source emissions over the past 20 years. This is
illustrated by research in Los Angeles County, CA, where VOC emissions
(among other pollutants) are important precursors to ozone and
PM2.5 formation. In Los Angeles, mobile-source VOC emissions
have decreased, but emissions from pesticides, coatings, printing inks,
adhesives, cleaning agents, and personal care products have decreased
less, or in some cases, have increased. In addition, recent studies
have shown that the chemical components of the VOC emissions from these
and other nonpoint categories can have an outsized influence on both
ozone and secondary PM2.5 formation. As a result, nonpoint
VOC sources have been identified as an increasingly important area of
study for contribution to public health harms.\60\ Thus, any adjustment
to the AERR for nonpoint sources should support States without
sufficient resources as well as promote high-quality and well
documented data collection.
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    \60\ McDonald et al. (2018), https://www.science.org/doi/10.1126/science.aaq0524.
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    Through EPA's work with States, the EPA has continued to refine and
publish new nonpoint emissions methods and tools for use by the EPA and
States. The EPA provides States with extensive opportunities to give
input on the nonpoint emissions methods and incorporates state-provided
emissions factors and ideas. As a result of this work and State input,
the EPA has developed a nonpoint estimation tool called the Wagon Wheel
(WW) as described most recently by the 2020 NEI TSD. The WW Tool
provides a central hub of the activity data inputs for estimation of
emissions for many nonpoint sectors. It also provides templates for
States to submit input activity data and estimation tool assumption
parameters, and it calculates emissions using county-specific data and
the latest emissions calculation methods. Under the current AERR,
States have been using the WW Tool (and its predecessors) voluntarily
because it reduces the burden of devising their own calculation
methods, tools, and submitting the emissions data to EIS.
    The EPA and States have also worked together to create other tools
and approaches (e.g., spreadsheets). Primary among these is the oil and
gas tool, which the EPA has revised each triennial inventory year since
2011. States and other stakeholders work closely with the EPA and
provide comments and input data to improve calculation approaches.
    When EPA's tools are used by States, this provides a consistent,
documented approach. Also, the burden on States who do not have the
resources to develop their own tools is greatly reduced with the WW
Tool and other EPA tools. Using these tools reduces the reporting
burden on States because the

process collects activity data in simpler formats (e.g., text, comma-
separated value) than the XML formats required when States report
emissions to EIS. In addition, when States provide activity data, the
States can upload this directly to the WW Tool to obtain updated
emission estimates and provide updated activity data to the EPA to
ensure more expedient error corrections in emissions estimates when the
EPA reruns these emissions calculation tools.
    Sometimes States are ahead of the EPA regarding the latest
emissions from certain nonpoint sectors, or the EPA tools do not yet
meet a State's needs. For example, some States are not yet able to use
the Oil and Gas Tool to estimate emissions from that sector while other
States do not believe that the WW Tool represents their residential
wood combustion emissions properly. The EPA has observed over the years
while collecting data for past inventories that there are cases where
States have better local input data and/or emissions calculation
methods for sectors that the EPA does not yet have tools for, or others
in which EPA's tools are not as appropriate for estimates in the State
as the State's own tools. For example, in past inventory years, States
have submitted emissions for such categories as cigarette smoke, human
perspiration, and industrial composting. In these situations, it is
appropriate for States to provide emissions totals. However, the EPA
must still be able to access documentation about emissions submissions.
    In addition to the WW Tool, input templates, and other calculation
tools, the EPA has implemented and used for the 2017 and 2020 triennial
years an online nonpoint survey as part of NEI collection, as most
recently explain in the 2020 NEI Plan.\61\ This ``Nonpoint Survey''
allows States to indicate their plans for nonpoint sources so that
States can communicate their intentions for accepting EPA data or
reporting their own data. This survey greatly assists States and the
EPA in QA to compare what States submitted to what they intended and to
allow States to accept EPA estimates.
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    \61\ 2020 NEI Plan, August 2020, U.S. EPA, https://www.epa.gov/air-emissions-inventories/2020-national-emissions-inventory-nei-plan.
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    As explained in the TSD, the EPA identified about 53,000 instances
for which State emissions data submissions for the 2017 triennial
inventory were inconsistent with EPA's expectations and were,
therefore, removed from the inventory. In these cases, the EPA needed
to use its own estimates from the WW Tool and other tools instead of
relying on state-submitted data. The EPA also prefers to use EPA
methods because of the consistency and transparency that approach
provides but wants to make sure that those methods best represent State
activity inputs. An improved process would both recognize the lack of
State reporting in many cases as well as steer towards a consistent and
transparent approach. Any such process might also allow for the case
where States want the EPA to consider their emissions totals even when
the calculation method is different from EPA methods and when the State
is obligated to report emissions that are not estimated by the
available EPA tools.
    Based on these considerations, the EPA proposes to include a
requirement at Sec.  51.15(d)(2) for States to complete and submit an
online survey (the ``nonpoint survey'') to indicate for which nonpoint
sources States intend to: (1) report input data for tools, (2) accept
EPA input data, (3) report emissions data, and (4) notify the EPA
whether or not to supplement data because the emissions are covered by
a different submitted SCC, the State does not have a particular source,
or the source is included in a point inventory submission. The EPA
further proposes at Sec.  51.15(d)(3)(i) that for nonpoint sources,
excluding commercial marine vessels and locomotives, States would be
required to report input data for EPA nonpoint tools using the formats
provided by EPA. In lieu of reporting tool inputs, the EPA proposes at
Sec.  51.15(d)(3)(ii) to allow States to comply with this requirement
by reviewing and accepting EPA-provided nonpoint tool inputs.
    For nonpoint sources with EPA tools excluding commercial marine
vessels and locomotives, the EPA additionally proposes to add an option
at Sec.  51.15(d)(3)(iii) that would allow States to optionally report
emissions of any pollutants allowed by the EPA electronic reporting
system and would require States to provide documentation that describes
how the emissions estimates were made and QA steps performed. The EPA
intends to evaluate the documentation provided to determine the best
approach for ensuring complete data from nonpoint sources that uses
sufficiently robust and transparent approaches. If documentation were
to be insufficient or approaches of lower quality than the EPA provided
approach, then some state-submitted nonpoint data may not be used.
    The EPA additionally proposes provisions for commercial marine and
locomotive sources. These requirements differ from those of other
nonpoint sources because of processes available to the Agency. In the
case of commercial marine vessels, the EPA processes satellite-based
data available from the Automatic Identification System (AIS), which is
an automatic tracking system that uses transceivers on ships. In the
case of locomotives, section IV.I.2 of this preamble describes that the
EPA works with rail companies to collect the data about locomotive
activity that is also connected to rail yard emissions. To accommodate
these special cases, the EPA proposes to add a requirement in Sec.
51.15(d)(4) that States must either (1) report annual actual emissions
of required pollutants, (2) provide comment on EPA-provided annual
actual emissions data, or (3) accept EPA-provided emissions data.
    In addition to those sectors for which the EPA provides tools, the
AERR must reflect all nonpoint sources for CAPs to support the need for
comprehensive emissions estimates. To address this need, the EPA
additionally proposes to add a requirement in Sec.  51.15(d)(5) that,
for nonpoint sources without EPA tools, States must report emissions
and documentation that describes how the emissions estimates were made
and QA steps performed. This proposed requirement would apply for any
additional sources not reported under Sec.  51.15(d)(3) or (4) of the
proposed regulatory text, not episodic windblown dust as described
under Sec.  51.15(d)(7) of the proposed regulatory text, and not such a
small source that it meets a de minimus standard described under Sec.
51.15(d)(8) of the proposed regulatory text. Paragraphs (7) and (8)
would be moved from the current AERR Sec.  51.20(d) to these new
paragraphs. The EPA intends to evaluate the documentation provided to
determine the best approach for ensuring complete data from nonpoint
sources that uses sufficiently robust and transparent approaches. If
documentation were to be insufficient, then some state-submitted
nonpoint data may not be used.
    The EPA has revised the windblown dust exemption from the current
AERR at 40 CFR 51.20(d) which states, ``[e]pisodic wind-generated
particulate matter (PM) emissions from sources that are not major
sources may be excluded, for example dust lifted by high winds from
natural or tilled soil.'' The EPA proposes at Sec.  51.15(d)(7) to
retain this exemption but remove the limitation of ``PM emissions''
from the exemption. The EPA proposes this change because the EPA does
not need to receive any emissions information about windblown dust,
which would also exclude HAP. While the EPA is not proposing to

require HAP from nonpoint sources for other categories, the EPA also
prefers States not to voluntarily report HAP from windblown dust
currently.
    In general, the goal of the documentation will be to replicate the
key information provided in the Nonpoint Emissions Method and Operation
(NEMO) documents. In some cases that type of documentation would not be
relevant because a State nonpoint estimate could be summed from data
collected from individual facilities. To define documentation to be
reported by States, the EPA would require different information in each
of these cases. For the general case of nonpoint emissions computed as
a county total, the EPA proposes that for each SCC and pollutant, the
State would need to provide any equations used to compute emissions,
all input values used for those equations, and all references for those
input values (e.g., government agency websites or publications). These
input values would need to include activity data, emissions factors,
and any other parameters of the equations.
    In the case of documentation needed when States provide nonpoint
emissions as a summed value from facilities, the EPA proposes to
require States to provide a spreadsheet that contains for each
facility: the State's facility identifier, a facility name, a facility
address, a primary NAICS code, the nonpoint SCC to which the emissions
were mapped, the facility emissions for each pollutant, the emissions
factor used to compute those emissions (when applicable), any control
measure applied to the emissions factor, and the type of control (using
EIS control measure codes). The EPA would provide a template for that
information for States to use, but States would be free to provide such
information in other formats.
    In cases where a State is both required to report input data for
EPA tools and voluntarily submits emissions data, the State burden
would be higher than under the current AERR. The EPA is considering
requiring documentation even though the trigger for that requirement is
a voluntary reporting of emissions by a State. The EPA is proposing
that such additional burden is warranted for the following reasons.
First, a State may believe its emissions estimates to be preferable to
EPA-methods, but the EPA must decide that issue on the merits of the
method documentation provided by the State. Second, the EPA would use
the required state-provided tool input data to be able to make a fair
comparison of EPA's method emissions totals compared to the state-
provided emissions totals. Third, the completion of the Nonpoint Survey
would remove confusion from differing SCCs, meaning potential
differences in State and EPA categorization of specific sectors could
be noted and resolved. Fourth, through discussions with States in past
NEI efforts, the EPA realizes that States may not be familiar with the
latest approaches and choose to report emissions even if they are
unable to find the underlying data that would be needed for complete
transparency. Finally, if the State later realizes that its provided
emissions totals are in error, or if the EPA revises its calculation
method to further improve the emissions estimations in a way the State
prefers, then the EPA would already have in hand the necessary EPA tool
input data to calculate emissions for the State.
    The EPA will QA all state-submitted input data and emissions with
associated documentation. Quality assurance will focus on the resulting
state-submitted emission estimates compared to EPA input data/methods,
if available, and previous state-submitted data, checking for data
completeness for pollutants and geographic coverage, and magnitude. The
EPA may not use state-submitted input data and/or emissions if it does
not pass QA checks, so the EPA can comply with the OAQPS Quality
Management Plan.\62\ Therefore, the EPA proposes to add paragraph Sec.
51.15(l) stating that the EPA may elect not to use the state-provided
data if it does not pass QA or if a State's documentation does not
adequately explain the origin and quality of the submitted data.
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    \62\ U.S. EPA, Office of Air Quality Planning and Standards
Quality Management Plan, May 20, 2020, https://www.epa.gov/sites/default/files/2021-05/documents/final_oapqs_qmp_2020-05-20.pdf.
---------------------------------------------------------------------------

K. Nonpoint Year-Specific Data and Timing of Reporting

    One key goal for the NEI program is to ensure emissions are
accurately reported for the year of the inventory, and an important
question for how to achieve that goal is when the submissions should be
due. This section discusses the considerations and EPA's proposal for
the timing of AERR submissions.
    Part of ensuring accurate nonpoint emissions is point-nonpoint
reconciliation as previously explained in section IV.I.4, which
prevents double counting and can be done with appropriate accuracy only
when nonpoint activity data are specific to the inventory year.
Furthermore, because the NEI is used as a starting point for SIPs that
require the use of ``accurate'' data (see CAA section 172(c)(3)), the
NEI program goal is consistent with that requirement and the
expectation of data users that the emissions reflect the listed year of
the inventory. Finally, when the EPA uses the NEI for regulatory
actions, it is appropriate for the EPA to follow the Agency's guidance
on inventories that emissions reflect the year in which they occurred
as best as possible. For these reasons, this action considers how best
to achieve year-specific nonpoint emissions inventories.
    On the issue of triennial versus annual reporting, the EPA intends
to retain the current triennial nonpoint reporting approach for
nonpoint sources. The EPA is not yet ready to support annual reporting
for nonpoint sources but may be able to do so in the future (in which
case we may conduct further rulemaking to require more frequent
reporting for nonpoint sources). Additionally, the EPA has successfully
used the data from States during triennial years, EPA tools, and data
collected from other Federal agencies to estimate emissions on years
other than triennial years. By retaining triennial nonpoint reporting,
the EPA additionally would not increase burden on States.
    The current AERR requires that, for each triennial inventory year,
States must report nonpoint emissions by December 31 of the following
year. As described in section IV.J of this preamble, this action
proposes to change the nonpoint requirement such that a State would:
(1) complete a nonpoint survey, (2) provide inputs for sources where
EPA tools are available, and (3) report emissions for other nonpoint
sources without EPA tools. As also described above, States may (4)
voluntarily report emissions for sources with EPA tools and (5) when
emissions data are provided, the State must also include documentation.
This section proposes when each of these required and optional
submissions would be due.
    In addition to collection of data, the EPA collaborates on a
continuous basis with States to improve nonpoint emissions calculation
tools. Based on input from States, peer reviewed literature, and EPA
research, the EPA develops NEMO documents for comment by States.\63\
States can voluntarily comment on these documents over some review
period provided by EPA. This work can be done independently of any
annual

reporting NEI cycle, but in many cases, new methods are developed in
time for their inclusion in a particular inventory reporting year. The
EPA has monthly webinars with States to provide many updates including
the review and discussion of NEMO documents and new methods.
---------------------------------------------------------------------------

    \63\ The EPA has provided the most recent NEMO documents with
the release of its 2017 NEI. These documents are available on the
EPA website at https://gaftp.epa.gov/air/nei/2017/doc/supporting_data/nonpoint/.
---------------------------------------------------------------------------

    Nonpoint emissions calculation methods rely on activity data from
other Federal agencies and other sources, and these data are released
after the current AERR deadline for nonpoint sources. For example, the
U.S. Census County Business Patterns dataset is important for nonpoint
calculations, but it is released approximately in April, about 16
months after the end of the inventory year. In the current AERR, States
must report emissions data 12 months after the end of the inventory
year and, thus, would need to use county business pattern data from the
prior year to estimate emissions.
    While using input data for a different year may be acceptable for
some sectors where the input data does not change much, other nonpoint
sectors can have significant local and national changes in emissions
from year to year (e.g., oil & gas exploration and extraction,
residential wood combustion). These sectors vary greatly depending on
unpredictable economic, weather, and other unexpected events. To
address this year-specific importance for some nonpoint categories and
the challenges caused by the current deadlines, the EPA is proposing
changes to the timing of nonpoint requirements.
    Another factor to consider is a current AERR provision that
undermines the argument for using year-specific data. Within the
current AERR, Sec.  51.35 provides States directions regarding how to
equalize the emission inventory effort from year to year, since a
triennial inventory means more effort on every third year. This section
explains that States may ease the workload spike by collecting one
third of their point sources that are not reported every year (i.e.,
the sources that are Type B but not Type A) and collect data for one-
third of the nonpoint, nonroad mobile, and onroad mobile sources. This
section further explains that States must use a consistent approach
between the 3 years for whatever source category is collected over 3
years. This section of the current AERR provides a burden equalization
approach for States but does not reflect the points made above about
the importance of year-specific inventories.
    In section IV.G of this preamble, the EPA proposes to require
States and owners/operators to use the same criteria each year to
determine which point sources should report. This provision would make
the current Sec.  51.35 ``burden equalization'' approach irrelevant for
point sources. In addition, this section has described the importance
of having year-specific data for nonpoint sources in some cases. At the
time that Sec.  51.35 was originally published, the EPA had a much less
robust support system to help States estimate emissions from nonpoint
sources. Now, many tools are available for States to estimate nonpoint
emissions, and it is important that States all use current methods to
do so. With the ongoing development of emissions methods by EPA,
allowing a State to make estimates based on an old methodology 2 years
before the data are due does not promote the data quality needed for
the NEI.
    Additionally, the EPA has realized that, even with this burden
reduction approach available to States, many States have not met their
nonpoint source reporting requirements in recent past NEI years. As a
result, the EPA has described in section IV.J of this preamble how
States would be able to comply with this proposed action simply by
reviewing and accepting EPA-provided activity data. Further, under this
proposed action, States would be required to use the emissions
calculation methods provided by the WW Tool. None of these provisions
would be workable under the current provisions of Sec.  51.35. As a
result of these considerations and in addition to the reasons described
in section IV.G of this preamble, the EPA proposes to remove the
equalization provisions of Sec.  51.35 and add a new set of timing
requirements that would allow the EPA to obtain appropriate, year-
specific data as needed while still including provisions that spreads
out the work for States.
    As previously described, nonpoint tool inputs can become available
after the current AERR reporting deadline. Depending on the data, they
are available to the EPA and States starting approximately 6 months
after the end of an inventory year (e.g., June of 2024 for the 2023
inventory year) through October of the second year (e.g., October of
2025 for the 2023 inventory year). As a result, the EPA targets March
of the third year after the inventory year for the final NEI nonpoint
data (e.g., March 2026 for the 2023 inventory year). Since the EPA does
not control the timing of release of that data, the EPA also recognizes
the importance of building flexibility into the process.
    Based on these considerations, the EPA proposes several changes to
the timing of the nonpoint collection. First, this action proposes that
States would complete the nonpoint survey in EIS by 15 months after
each triennial inventory year (e.g., March 31, 2025, for the 2023
inventory year). In addition, for any emissions sources without an EPA
tool, but not meeting the de minimis criteria included in this proposed
action, the State would report emissions and documentation by March 31,
15 months after a triennial inventory year. These deadlines and others
are summarized below in section IV.S of this preamble.
    Second, the EPA proposes to spread out requirements for submission
of input data for EPA tools, including the option to review and accept
EPA tool inputs. The EPA expects to release draft tool inputs and
emissions results on an incremental basis between July after the
inventory year (e.g., starting July of 2024 for the 2023 inventory
year) and December of the second year after the inventory year (e.g.,
through December 2025 for the 2023 inventory year). The EPA proposes to
add regulatory text stating that the States would have no fewer than 30
days to review, comment, and/or provide revised tool inputs based on
the information released by EPA, and that the EPA may allow a longer
period for review source categories with more complicated input data or
calculation approaches and would notify the States of this when the
data are released. To communicate a longer period, the EPA proposes to
indicate the period for review to States at the time the data are
provided for review. The EPA intends to include this information in its
periodic NEI newsletters included on the NEI Sharepoint site.
    After receiving the emissions based on EPA methods, States may
determine that the EPA tool calculation is insufficient. In this case,
the EPA proposes to add regulatory text stating that the States would
submit nonpoint tool inputs within 30 days of the EPA providing tool
inputs to the State, or within the period defined by the EPA at the
time the tool inputs are provided to States, whichever is longer. For
example, if the EPA released tool input data and draft emissions on
August 1 for State review with a 30-day review period (until August
31), States would have until September 30 to review/submit revised tool
inputs. Additionally, the EPA proposes to add regulatory text that
would set a timeline for States optionally submitting emissions and the
associated documentation within 60 days of the EPA providing inputs to
the State, or within the period defined by the EPA at the time the tool
inputs are provided, whichever is longer.
    In addition to collection of tool inputs, a key aspect of nonpoint

emissions work with States is the emissions calculation approach,
captured in the NEMO documents. While the EPA does not plan to require
States to contribute to these documents at this time, it anticipates
that many States will continue to do so voluntarily. To accommodate
this voluntary State collaboration, each NEI Plan gives States
timeframes during which they may provide these voluntary comments so
that the emission methods would be ready for use in a triennial
inventory. In cases where a State misses these deadlines, the Agency is
under no obligation to consider late-filed State comments but rather
intends to defer consideration of such late comments into the method
improvements that would be done for the next triennial inventory cycle.
    Under this proposal, the bulk of State's burden for nonpoint
submitting data would occur in the starting 6 months after the
triennial inventory year and continuing through the second year after
the triennial inventory year. Given this timing, the EPA plans to
coordinate the timing of the voluntary State review of emissions
methods so that States' work would be done primarily during periods the
EPA has proposed to require triennial nonpoint emissions data. For
example, for 2023 (the next triennial inventory year), the EPA would
plan to support voluntary comments from States on methods between
January 2023 and June 2024.

L. Nonpoint Reporting for Tribes and States With Counties Overlapping
Indian Country

    With this action, the EPA is proposing new requirements that would
resolve existing challenges associated with use of nonpoint emissions
submitted by tribes and prevent double counting with state-submitted
county total emissions. The EPA and States estimate nonpoint emissions
data with techniques that use county total activity data from other
agencies such as the U.S. Census Bureau. There are two cases that can
cause the potential for double counting without the approach that the
EPA proposes in this action.
    In the simplest case, EPA's nonpoint emissions tools multiply
county total activity data with emissions factors to estimate
emissions. When counties overlap with Indian country, the tools do not
automatically account for the portion of the county that is within
Indian country. When States report emissions for areas overlapping an
area reported by a tribe, the NEI could potentially double count
emissions unless those reporters take additional steps to adjust the
activity data prior to calculating emissions.
    The second case can occur when States accept emissions from EPA's
tools. In these cases, because EPA's tools include activity for the
entire county, double counting would occur when a tribe reports
nonpoint emissions data for Indian country overlapping those counties
using EPA's estimates. Further, the current AERR does not require
activity data for nonpoint categories from tribes that could be used to
subtract from the counties' data to avoid double counting. As a result
of this complexity, to date the EPA has chosen to use only the State
provided nonpoint data when using the NEI as an input for air quality
modeling. The EPA prefers and considers it more equitable for tribes to
be able to have tribal data used in the same ways as State data.
    The current AERR at 40 CFR 51.1 says that ``[s]tates must inventory
emission sources located on nontribal lands and report this information
to EPA.'' This is the only reference under the current AERR to the
concept of excluding Indian country from emissions estimates. Further,
this statement is confusing because, as explained in the preamble to
the original AERR (71 FR 69), the term ``states'' is defined in the
AERR as referring to States, locals, or tribes with a TAS agreement.
The EPA is proposing at Sec.  51.1(b) language that describes the
specific situation in which an Indian Tribe would be required to report
under Subpart A of 40 CFR part 51.
    In addition to the potential confusion created by the current text
of Sec.  51.1, other parts of the current AERR could be read to be
inconsistent with Sec.  51.1. First in Sec.  51.25, entitled ``What
geographic area must my state's inventory cover?'', the current AERR
makes no mention of Indian country but rather says ``because of the
regional nature of these pollutants, your State's inventory must be
statewide, regardless of any area's attainment status.'' ``Statewide''
could potentially be read as inclusive of Indian country. In addition,
the current version of Sec.  51.15(b)(2) explains that for nonpoint
submissions, ``states may choose to meet the requirements for some of
their nonpoint sources by accepting EPA's estimates for the sources for
which the EPA makes calculations.'' Given that EPA calculations have
not excluded (and are not planned to exclude) Indian country emissions
from the emissions that States report, this statement neglects to
clarify that a State would need to make an adjustment based on the
requirement to exclude Indian country as specified in the current AERR
at Sec.  51.1. As a result of these potentially confusing requirements,
the approach taken by States has been inconsistent in submitting
emissions data. Under the current AERR, some States exclude Indian
country emissions from their emissions while others do not.
    With this action, the EPA proposes an updated reporting approach
for nonpoint sources with EPA tools such that all agencies (including
tribes with TAS status) would report tool inputs, including activity
data. For those tribes that would report nonpoint activity data, the
EPA would need to have sufficient information from tribes to be able to
reconcile the county-total activity with the tribal activity to avoid
double counting.
    Based on these considerations, the EPA is proposing several
revisions intended to ensure clarity for States and tribes. First, the
EPA proposes to add paragraph (b) to Sec.  51.1 to clarify that tribes
that have obtained TAS status are subject to the AERR to the extent
allowed in their TIP, and that, to the extent a tribal government has
applied for and received TAS status for air quality control purposes
and is subject to the AERR under its TIP, the use of the term ``state''
in the AERR should be read to include that tribal government.
    Additionally, the EPA proposes additional nonpoint requirements to
address the issues described in this section. Taken together, these
requirements will allow both State/local and tribal nonpoint tool
inputs and emissions to avoid double counting and to be used as inputs
to air quality modeling. First, the EPA proposes at Sec.  51.15(d)(9)
of the proposed regulatory text that a State with counties that overlap
Indian country would avoid double counting by excluding the activity
and/or emissions associated with Indian country when the Tribe is
expected to report emissions. A State would need to become familiar
with which of the tribes with Indian country that overlaps a State's
counties would be required to report under this proposed action and
which tribes intend to voluntarily report. Similarly, tribes can assist
in preventing double counting by notifying States of their plans to
submit emissions (though the EPA is not proposing that tribes would be
required to do so).
    Second, the EPA proposes at Sec.  51.15(d)(10) of the proposed
regulatory text that tribes meeting the TAS and TIP criteria of the new
Sec.  51.1(b) of the proposed regulatory text would be required to
report nonpoint tool inputs or emissions from Indian country by
reporting those data separately for each portion of a county across
which Indian

country boundaries overlap. To assist tribes in making such
calculations, the EPA could provide tribes with ratios that they may
use for performing these calculations. A tribe meeting the criteria of
the proposed Sec.  51.1(b) would be subject to the nonpoint reporting
requirements associated with the new Sec.  51.15(d)(3) through (8) of
the proposed regulatory text when the tribe has sources that meet the
criteria for reporting a nonpoint source (i.e., sources that have the
EPA nonpoint tools or are not small enough to meet a de minimus
percentage of the tribe total emissions). The EPA believes that tribes
could use the EPA tools by adjusting the county values included in the
default templates to provide tribe-specific activity levels. Similarly,
tribes submitting emissions would report those data in association with
county boundaries by apportioning the total tribal emissions to each of
the county areas overlapping Indian country.

M. Requirements for Prescribed Burning

    Recent increases in the frequency of damaging wildfire events
underscore the need for improved management schemes that anticipate and
consider climate change factors like drought and temperature extremes.
Prescribed burning (of forestland, shrubland, grassland, wetlands,
wildland urban interfaces (WUIs), and timberland) \64\ is a way to
prepare for and mitigate wildfire events and manage grasslands, and
many States \65\ have implemented burning programs to improve ecosystem
health and reduce chances of catastrophic wildfires. The U.S.
Department of Agriculture Forest Service (USFS) Wildfire Crisis
Strategy,\66\ published in January 2022, indicates an interest in
increasing prescribed burning to treat up to an additional 20 million
acres on National Forest System lands and up to an additional 30
million acres of other Federal, State, Tribal, and private lands.\67\
While these prescribed burns are controlled and limit emissions as
compared to wildfires, they still produce significant emissions of CAPs
such as PM, VOC, HAP, and carbon dioxide, all of which are important
contributors to environmental health risks and climate change. The EPA
proposes additional requirements for States to report prescribed
burning data and consequently allow the EPA to have access to improved
data sources as compared to the data it has been collecting voluntarily
under the current AERR.
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    \64\ In this section, the use of the term ``prescribed fire''
and ``prescribed burning'' refers to burns that could occur on all
of these land types, unless otherwise specified.
    \65\ In Section III of this preamble, the EPA has previously
defined ``States'' to mean delegated local agencies and certain
tribes.
    \66\ U.S. Department of Agriculture, Forest Service, Confronting
the Wildfire Crisis: A Strategy for Protecting Communities and
Improving Resilience in America's Forests, January 2022. See also
https://www.fs.usda.gov/sites/default/files/Confronting-Wildfire-Crisis.pdf.
    \67\ U.S. Department of the Interior, ``Infrastructure
Investment and Jobs Act, Wildfire Risk Five-Year Monitoring,
Maintenance and Treatment Plan,'' April 2022. See also https://www.doi.gov/sites/doi.gov/files/bil-5-year-wildfire-risk-mmt-plan.04.2022.owf_.final_.pdf.
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    The EPA currently uses satellite data to identify the locations of
fires and uses various techniques and data from other agencies to label
fires as wildfires, prescribed fires, or agricultural fires. The EPA
has a goal of improving emissions estimates for all types of fires, and
this proposal strikes a balance between the information proposed to be
required and the burden that will be incurred by the many States that
will need to implement new data collection programs. The EPA's
experience over the past decade has determined that without more data,
it is not possible to accurately differentiate prescribed burning from
other types of fires in most States. The satellite data provide
estimates of the extent of burning each day but, in many cases, the EPA
must assume information about the type of fire, the biomass fuel type,
the amount of biomass consumed and other critical parameters. National-
level and other data sources are available to identify wildfires, and
these allow the EPA to reasonably conclude that other fires are
prescribed or agricultural fires. Using these sources of wildfire data
has also revealed that the additional fuel and burning data greatly
affect and improve the emissions estimates. For prescribed burning,
however, there is no central collection of national data, and few
States collect the information that the EPA would need to properly
label each fire.
    Available evidence indicates that wildfire acres burned have
increased over time,\68\ which, in turn, has drawn attention to
prescribed burns as a mitigating measure.\69\ Thus, the EPA expects
that prescribed burning activity will increase, making it important to
properly estimate the emission impacts from these sources.
Additionally, new satellites have become available in the last few
years that detect many more (and smaller) fire events. As a result, we
now have information about more fires and have an opportunity to
improve the current approach for estimating emissions from fire events.
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    \68\ U.S. EPA, Climate change indicators: Wildfires, Figure 5:
Change in Annual Burned Acreage by State Between 1984-2001 and 2002-
2018. https://www.epa.gov/climate-indicators/climate-change-indicators-wildfires.
    \69\ Hunter, M. E. and Robles, M. D, Tamm review: The effects of
prescribed fire on wildfire regimes and impacts: A framework for
comparison. Forest Ecology and Management, 475, 118435. https://www.sciencedirect.com/science/article/pii/S0378112720312044.
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    While some States currently submit data on prescribed burns
voluntarily, there is currently no national minimum approach to ensure
collection of information about prescribed burning. While some States
have permitting programs for prescribed burning to ensure that the
burns do not cause undue impact on communities, most of those programs
have not led to collection of data. Many permits may be issued that do
not result in a burn and its only possible to determine some aspects of
a burn (such as the acres burned) after it occurs. A minimum set of
prescribed burning data collected from all States would allow both for
higher quality emissions data and more equitable characterization of
the emissions that impact downwind communities.
    The 2015 AERR eliminated the requirement that States report
emissions from wildfires and prescribed fires, which had been required
via the 2008 AERR as county totals. At that time, the EPA had believed
that the satellite-based approach and other available datasets would be
sufficient to properly characterize emissions from these fires. While
EPA's expectation has come to pass for wildfire emissions, based on the
reasons described above, the satellite-based approach is too uncertain
to properly characterize prescribed burning. Further refinement of the
wildfire estimation technique will be sought, and EPA encourages
voluntary submission of wildfire data such as fuel type and consumption
information that provides refinement of these emissions estimates.
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    \70\ National Association of State Foresters and the Coalition
of Prescribed Fire Councils, 2020 National Prescribed Fire Use
Survey Report, December 2020, https://www.stateforesters.org/newsroom/2020-national-prescribed-fire-use-report/.
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    The National Interagency Coordination Center (NICC) estimates that
between 2009 and 2018, in the United States, on average about 86,300
prescribed fires burned about 3 million acres annually; however, these
data are known to be incomplete. The National Prescribed Fire Use
Survey Report \70\ is a more complete source for estimating prescribed
acres burned nationally, and the 2020 survey puts the national estimate
at about 9-10 million acres burned annually. About 75-80 percent of
these acres burned are in the eastern

U.S.; the amount of prescribed burning in the western States is small
in comparison. The 2018 National Prescribed Fire Use Survey Report
provided an estimate of 11.3 million acres treated with prescribed fire
in 2017.\71\
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    \71\ National Association of State Foresters and the Coalition
of Prescribed Fire Councils, 2018 National Prescribed Fire Use
Survey Report, December 2018, https://www.stateforesters.org/wp-content/uploads/2018/12/2018-Prescribed-Fire-Use-Survey-Report-1.pdf.
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    Other information suggests that even the National Prescribed Fire
Use Survey report is incomplete. The 2017 NEI estimate that includes
satellite-based observations and excludes wildfires as best as possible
put the national prescribed acreage burned for that year at about 14-15
million. While this may be an over-estimate because many of those fire
sizes were not documented, the difference in the satellite-based
estimate as compared documented fires suggests that the National
Prescribed Fire Use Survey may be incomplete. Another challenge in
determining whether a fire detection is a wildfire or prescribed fire
is that both activities sometimes occur at the same time especially in
areas with high use of prescribed fire such as the southeast.
    The importance of accurate wildfire and prescribed burning data is
highlighted by the many uses of that data by the EPA and States for air
quality management: exceptional event determinations, non-attainment
area inventories for PM and ozone, ozone and PM transport analysis, and
EPA's air quality modeling to support risk analysis, NAAQS review/risk
assessments, and regional haze. In addition, the EPA includes the fire
emissions data in emissions trends to provide environmental information
for the public and to meet international reporting agreements.
    For the 2017 NEI, prescribed fire emissions data (either activity
information or emissions) were estimated with voluntary help from 19
State air quality agencies.\72\ A mandatory prescribed burning
reporting program would be to the benefit of the many data uses listed
above. To assess how a mandatory program might be designed, the EPA is
considering what attributes would need to be part of any mandatory
prescribed burning reporting program. These attributes are (1) the
frequency of reporting, (2) the timing of reporting, (3) the size of
burn events to be reported, (4) the type of burn events to be reported,
and (5) the minimum data fields needed to address the current
limitations of the voluntary program. Each of these considerations is
described here.
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    \72\ While EPA received the 2017 NEI data from state air quality
agencies, EPA is aware that many of those states have coordinated
with their state forestry agencies to provide EPA the data.
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    The EPA has been estimating daily emissions of prescribed fires for
CAPs and HAP every year since 2005. These data inform annual fire
trends and the EPA uses the daily event data as input to annual air
quality modeling that supports both regulatory and non-regulatory
agency priorities. As previously described in section IV.G, regulatory
modeling needs may arise for the EPA and for State SIPs for any year
and not only triennial inventory years. Thus, the EPA must assume in
any policy the same potential need for data for every year.
Additionally, existing data shows that prescribed burning acres can
vary widely from year to year. As shown in Figure 1a (which is Figure
7-6 of the 2020 NEI TSD), from between 2006 and 2020, prescribed
burning acreage ranged from about 7 million acres per year to more than
15 million acres. Similarly, as shown in Figure 1b (which is Figure 7-5
of the 2020 NEI TSD), the PM2.5 emissions from prescribed
burning ranged from about 600,000 tpy to about 1,000,000 tpy. These
ranges suggest sufficient variability from year to year to support
annual collection of data.
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    In addition to an annual need for prescribed burning data, the
spatial and temporal differences across years should impact a decision
on reporting frequency. While grassland prescribed burning tends to
occur every year in the same locations, forest prescribed burning
usually occurs in different locations because the undergrowth burned in
one year is not in need of clearing again the following year. Further,