an individual compound in a group (e.g., ethylene glycol diethyl ether)
that does not have a specified reference value, we also apply the most
protective reference value from the other compounds in the group to
estimate risk.
e. Uncertainties in the Multipathway Assessment
    For each source category, we generally rely on site-specific levels
of PB-HAP emissions to determine whether a refined assessment of the
impacts from multipathway exposures is necessary. This determination is
based on the results of a three-tiered screening analysis that relies
on the outputs from models that estimate environmental pollutant
concentrations and human exposures for four PB-HAP. Two important types
of uncertainty associated with the use of these models in RTR risk
assessments and inherent to any assessment that relies on environmental
modeling are model uncertainty and input uncertainty.\25\
---------------------------------------------------------------------------

    \25\ In the context of this discussion, the term ``uncertainty''
as it pertains to exposure and risk encompasses both variability in
the range of expected inputs and screening results due to existing
spatial, temporal and other factors, as well as uncertainty in being
able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the selected models are
appropriate for the assessment being conducted and whether they
adequately represent the actual processes that might occur for that
situation. An example of model uncertainty is the question of whether
the model adequately describes the movement of a pollutant through the
soil. This type of uncertainty is difficult to quantify. However, based
on feedback received from previous EPA SAB reviews and other reviews,
we are confident that the models used in the screen are appropriate and
state-of-the-art for the multipathway risk assessments conducted in
support of RTR.
    Input uncertainty is concerned with how accurately the models have
been configured and parameterized (i.e., represented in terms of
measurable or estimable variables) for the assessment at hand. For Tier
1 of the multipathway screen, we configured the models to avoid
underestimating exposure and risk. This was accomplished by selecting
upper-end values from nationally representative datasets for the more
influential parameters in the environmental model, including selection
and spatial configuration of the area of interest, lake location and
size, meteorology, surface water and soil characteristics and structure
of the aquatic food web. We also assume an ingestion exposure scenario
and values for human exposure factors that represent reasonable maximum
exposures.
    In Tier 2 of the multipathway assessment, we refine the model
inputs to account for meteorological patterns in the vicinity of the
facility versus using upper-end national values and we identify the
actual location of lakes near the facility rather than the default lake
location that we apply in Tier 1. By

refining the screening approach in Tier 2 to account for local
geographical and meteorological data, we decrease the likelihood that
concentrations in environmental media are overestimated, thereby
increasing the usefulness of the screen. The assumptions and the
associated uncertainties regarding the selected ingestion exposure
scenario are the same for Tier 1 and Tier 2.
    For both Tiers 1 and 2 of the multipathway assessment, our approach
to addressing model input uncertainty is generally cautious. We choose
model inputs from the upper end of the range of possible values for the
influential parameters used in the models, and we assume that the
exposed individual exhibits ingestion behavior that would lead to a
high total exposure. This approach reduces the likelihood of not
identifying high risks for adverse impacts.
    Despite the uncertainties, when individual pollutants or facilities
do screen out, we are confident that the potential for adverse
multipathway impacts on human health is very low. On the other hand,
when individual pollutants or facilities do not screen out, it does not
mean that multipathway impacts are significant, only that we cannot
rule out that possibility and that a refined multipathway analysis for
the site might be necessary to obtain a more accurate risk
characterization for the source category.
    For further information on uncertainties and the Tier 1 and 2
screening methods, refer to Appendix 4 of Modeling File Preparation
Memo.
f. Uncertainties in the Environmental Risk Screening Assessment
    For each source category, we generally rely on site-specific levels
of environmental HAP emissions to perform an environmental screening
assessment. The environmental screening assessment is based on the
outputs from models that estimate environmental HAP concentrations. The
same models, specifically the TRIM.FaTE multipathway model and the
AERMOD air dispersion model, are used to estimate environmental HAP
concentrations for both the human multipathway screening analysis and
for the environmental screening analysis. Therefore, both screening
assessments have similar modeling uncertainties.
    Two important types of uncertainty associated with the use of these
models in RTR environmental screening assessments--and inherent to any
assessment that relies on environmental modeling--are model uncertainty
and input uncertainty.\26\
---------------------------------------------------------------------------

    \26\ In the context of this discussion, the term
``uncertainty,'' as it pertains to exposure and risk assessment,
encompasses both variability in the range of expected inputs and
screening results due to existing spatial, temporal and other
factors, as well as uncertainty in being able to accurately estimate
the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the selected models are
appropriate for the assessment being conducted and whether they
adequately represent the movement and accumulation of environmental HAP
emissions in the environment. For example, does the model adequately
describe the movement of a pollutant through the soil? This type of
uncertainty is difficult to quantify. However, based on feedback
received from previous EPA SAB reviews and other reviews, we are
confident that the models used in the screen are appropriate and state-
of-the-art for the environmental risk assessments conducted in support
of our RTR analyses.
    Input uncertainty is concerned with how accurately the models have
been configured and parameterized for the assessment at hand. For Tier
1 of the environmental screen for PB-HAP, we configured the models to
avoid underestimating exposure and risk to reduce the likelihood that
the results indicate the risks are lower than they actually are. This
was accomplished by selecting upper-end values from nationally-
representative datasets for the more influential parameters in the
environmental model, including selection and spatial configuration of
the area of interest, the location and size of any bodies of water,
meteorology, surface water and soil characteristics and structure of
the aquatic food web. In Tier 1, we used the maximum facility-specific
emissions for the PB-HAP (other than lead compounds, which were
evaluated by comparison to the secondary lead NAAQS) that were included
in the environmental screening assessment and each of the media when
comparing to ecological benchmarks. This is consistent with the
conservative design of Tier 1 of the screen. In Tier 2 of the
environmental screening analysis for PB-HAP, we refine the model inputs
to account for meteorological patterns in the vicinity of the facility
versus using upper-end national values, and we identify the locations
of water bodies near the facility location. By refining the screening
approach in Tier 2 to account for local geographical and meteorological
data, we decrease the likelihood that concentrations in environmental
media are overestimated, thereby increasing the usefulness of the
screen. To better represent widespread impacts, the modeled soil
concentrations are averaged in Tier 2 to obtain one average soil
concentration value for each facility and for each PB-HAP. For PB-HAP
concentrations in water, sediment and fish tissue, the highest value
for each facility for each pollutant is used.
    For the environmental screening assessment for acid gases, we
employ a single-tiered approach. We use the modeled air concentrations
and compare those with ecological benchmarks.
    For both Tiers 1 and 2 of the environmental screening assessment,
our approach to addressing model input uncertainty is generally
cautious. We choose model inputs from the upper end of the range of
possible values for the influential parameters used in the models, and
we assume that the exposed individual exhibits ingestion behavior that
would lead to a high total exposure. This approach reduces the
likelihood of not identifying potential risks for adverse environmental
impacts.
    Uncertainty also exists in the ecological benchmarks for the
environmental risk screening analysis. We established a hierarchy of
preferred benchmark sources to allow selection of benchmarks for each
environmental HAP at each ecological assessment endpoint. In general,
EPA benchmarks for programmatic levels (e.g., Office of Water,
Superfund Program) were used if available. If not, we used EPA
benchmarks used in regional programs (e.g., Superfund Program). If
benchmarks were not available at a programmatic or regional level, we
used benchmarks developed by other agencies (e.g., NOAA) or by state
agencies.
    In all cases (except for lead compounds, which were evaluated
through a comparison to the NAAQS), we searched for benchmarks at the
following three effect levels, as described in section III.A.5 of this
preamble:
    1. A no-effect level (i.e., NOAEL).
    2. Threshold-effect level (i.e., LOAEL).
    3. Probable effect level (i.e., PEL).
    For some ecological assessment endpoint/environmental HAP
combinations, we could identify benchmarks for all three effect levels,
but for most, we could not. In one case, where different agencies
derived significantly different numbers to represent a threshold for
effect, we included both. In several cases, only a single benchmark was
available. In cases where multiple effect levels were

available for a particular PB-HAP and assessment endpoint, we used all
of the available effect levels to help us to determine whether risk
exists and if the risks could be considered significant and widespread.
    The EPA evaluates the following seven HAP in the environmental risk
screening assessment: Cadmium, dioxins/furans, POM, mercury (both
inorganic mercury and methyl mercury), lead compounds, HCl and HF,
where applicable. These seven HAP represent pollutants that can cause
adverse impacts for plants and animals either through direct exposure
to HAP in the air or through exposure to HAP that is deposited from the
air onto soils and surface waters. These seven HAP also represent those
HAP for which we can conduct a meaningful environmental risk screening
assessment. For other HAP not included in our screening assessment, the
model has not been parameterized such that it can be used for that
purpose. In some cases, depending on the HAP, we may not have
appropriate multipathway models that allow us to predict the
concentration of that pollutant. The EPA acknowledges that other HAP
beyond the seven HAP that we are evaluating may have the potential to
cause adverse environmental effects and, therefore, the EPA may
evaluate other relevant HAP in the future, as modeling science and
resources allow.
    Further information on uncertainties and the Tier 1 and 2
environmental screening methods is provided in Appendix 5 of the
document, Technical Support Document for TRIM-Based Multipathway Tiered
Screening Methodology for RTR: Summary of Approach and Evaluation.
Also, see the Residual Risk Assessment for the Aerospace Manufacturing
and Rework Facilities Source Category in Support of the January, 2015
Risk and Technology Review Proposal, January 2015, available in the
docket for this action.

B. How did we consider the risk results in making decisions for this
proposal?

    As discussed in section II.A of this preamble, in evaluating and
developing standards under CAA section 112(f)(2), we apply a two-step
process to address residual risk. In the first step, the EPA determines
whether risks are acceptable. This determination ``considers all health
information, including risk estimation uncertainty, and includes a
presumptive limit on maximum individual lifetime [cancer] risk (MIR)
\27\ of approximately [1-in-10 thousand] [i.e., 100-in-1 million].'' 54
FR 38045, September 14, 1989. If risks are unacceptable, the EPA must
determine the emissions standards necessary to bring risks to an
acceptable level without considering costs. In the second step of the
process, the EPA considers whether the emissions standards provide an
ample margin of safety ``in consideration of all health information,
including the number of persons at risk levels higher than
approximately 1-in-1 million, as well as other relevant factors,
including costs and economic impacts, technological feasibility, and
other factors relevant to each particular decision.'' Id. The EPA must
promulgate emission standards necessary to provide an ample margin of
safety.
---------------------------------------------------------------------------

    \27\ Although defined as ``maximum individual risk,'' MIR refers
only to cancer risk. MIR, one metric for assessing cancer risk, is
the estimated risk were an individual exposed to the maximum level
of a pollutant for a lifetime.
---------------------------------------------------------------------------

    In past residual risk actions, the EPA considered a number of human
health risk metrics associated with emissions from the categories under
review, including the MIR, the number of persons in various risk
ranges, cancer incidence, the maximum non-cancer HI and the maximum
acute non-cancer hazard. See, e.g., 72 FR 25138, May 3, 2007; 71 FR
42724, July 27, 2006. The EPA considered this health information for
both actual and allowable emissions. See, e.g., 75 FR 65068, October
21, 2010; 75 FR 80220, December 21, 2010; 76 FR 29032, May 19, 2011.
The EPA also discussed risk estimation uncertainties and considered the
uncertainties in the determination of acceptable risk and ample margin
of safety in these past actions. The EPA considered this same type of
information in support of this action.
    The agency is considering these various measures of health
information to inform our determinations of risk acceptability and
ample margin of safety under CAA section 112(f). As explained in the
Benzene NESHAP, ``the first step judgment on acceptability cannot be
reduced to any single factor'' and, thus, ``[t]he Administrator
believes that the acceptability of risk under [previous] section 112 is
best judged on the basis of a broad set of health risk measures and
information.'' 54 FR 38046, September 14, 1989. Similarly, with regard
to the ample margin of safety determination, ``the Agency again
considers all of the health risk and other health information
considered in the first step. Beyond that information, additional
factors relating to the appropriate level of control will also be
considered, including cost and economic impacts of controls,
technological feasibility, uncertainties, and any other relevant
factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors
the EPA may consider in making determinations and how the EPA may weigh
those factors for each source category. In responding to comment on our
policy under the Benzene NESHAP, the EPA explained that:

[t]he policy chosen by the Administrator permits consideration of
multiple measures of health risk. Not only can the MIR figure be
considered, but also incidence, the presence of non-cancer health
effects, and the uncertainties of the risk estimates. In this way,
the effect on the most exposed individuals can be reviewed as well
as the impact on the general public. These factors can then be
weighed in each individual case. This approach complies with the
Vinyl Chloride mandate that the Administrator ascertain an
acceptable level of risk to the public by employing [her] expertise
to assess available data. It also complies with the Congressional
intent behind the CAA, which did not exclude the use of any
particular measure of public health risk from the EPA's
consideration with respect to CAA section 112 regulations, and
thereby implicitly permits consideration of any and all measures of
health risk which the Administrator, in [her] judgment, believes are
appropriate to determining what will `protect the public health'.

See 54 FR at 38057, September 14, 1989. Thus, the level of the MIR is
only one factor to be weighed in determining acceptability of risks.
The Benzene NESHAP explained that ``an MIR of approximately 1-in-10
thousand should ordinarily be the upper end of the range of
acceptability. As risks increase above this benchmark, they become
presumptively less acceptable under CAA section 112, and would be
weighed with the other health risk measures and information in making
an overall judgment on acceptability. Or, the Agency may find, in a
particular case, that a risk that includes MIR less than the
presumptively acceptable level is unacceptable in the light of other
health risk factors.'' Id. at 38045. Similarly, with regard to the
ample margin of safety analysis, the EPA stated in the Benzene NESHAP
that: ``EPA believes the relative weight of the many factors that can
be considered in selecting an ample margin of safety can only be
determined for each specific source category. This occurs mainly
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at
38061. We also consider the uncertainties associated with the various
risk analyses, as discussed earlier in this preamble, in

our determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information
to date in making residual risk determinations. At this time, we do not
attempt to quantify those HAP risks that may be associated with
emissions from other facilities that do not include the source
categories in question, mobile source emissions, natural source
emissions, persistent environmental pollution or atmospheric
transformation in the vicinity of the sources in these categories.
    The agency understands the potential importance of considering an
individual's total exposure to HAP in addition to considering exposure
to HAP emissions from the source category and facility. We recognize
that such consideration may be particularly important when assessing
non-cancer risks, where pollutant-specific exposure health reference
levels (e.g., RfCs) are based on the assumption that thresholds exist
for adverse health effects. For example, the agency recognizes that,
although exposures attributable to emissions from a source category or
facility alone may not indicate the potential for increased risk of
adverse non-cancer health effects in a population, the exposures
resulting from emissions from the facility in combination with
emissions from all of the other sources (e.g., other facilities) to
which an individual is exposed may be sufficient to result in increased
risk of adverse non-cancer health effects. In May 2010, the SAB advised
the EPA ``that RTR assessments will be most useful to decision makers
and communities if results are presented in the broader context of
aggregate and cumulative risks, including background concentrations and
contributions from other sources in the area.'' \28\
---------------------------------------------------------------------------

    \28\ EPA's responses to this and all other key recommendations
of the SAB's advisory on RTR risk assessment methodologies (which is
available at: http://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf)
are outlined in a memo to this rulemaking docket from David Guinnup
entitled, EPA's Actions in Response to the Key Recommendations of
the SAB Review of RTR Risk Assessment Methodologies.
---------------------------------------------------------------------------

    In response to the SAB recommendations, the EPA is incorporating
cumulative risk analyses into its RTR risk assessments, including those
reflected in this proposal. The agency is: (1) Conducting facility-wide
assessments, which include source category emission points as well as
other emission points within the facilities; (2) considering sources in
the same category whose emissions result in exposures to the same
individuals; and (3) for some persistent and bioaccumulative
pollutants, analyzing the ingestion route of exposure. In addition, the
RTR risk assessments have always considered aggregate cancer risk from
all carcinogens and aggregate non-cancer hazard indices from all non-
carcinogens affecting the same target organ system.
    Although we are interested in placing source category and facility-
wide HAP risks in the context of total HAP risks from all sources
combined in the vicinity of each source, we are concerned about the
uncertainties of doing so. Because of the contribution to total HAP
risk from emission sources other than those that we have studied in
depth during this RTR review, such estimates of total HAP risks would
have significantly greater associated uncertainties than the source
category or facility-wide estimates. Such aggregate or cumulative
assessments would compound those uncertainties, making the assessments
too unreliable.

C. How did we perform the technology review?

    Our technology review focused on the identification and evaluation
of developments in practices, processes and control technologies that
have occurred since the MACT standards were promulgated. Where we
identified such developments, in order to inform our decision of
whether it is ``necessary'' to revise the emissions standards, we
analyzed the technical feasibility of applying these developments and
the estimated costs, energy implications, non-air environmental
impacts, as well as considering the emission reductions. We also
considered the appropriateness of applying controls to new sources
versus retrofitting existing sources.
    Based on our analyses of the available data and information, we
identified potential developments in practices, processes and control
technologies. For this exercise, we considered any of the following to
be a ``development'':
     Any add-on control technology or other equipment that was
not identified and considered during development of the original MACT
standards.
     Any improvements in add-on control technology or other
equipment (that were identified and considered during development of
the original MACT standards) that could result in additional emissions
reduction.
     Any work practice or operational procedure that was not
identified or considered during development of the original MACT
standards.
     Any process change or pollution prevention alternative
that could be broadly applied to the industry and that was not
identified or considered during development of the original MACT
standards.
     Any significant changes in the cost (including cost
effectiveness) of applying controls (including controls the EPA
considered during the development of the original MACT standards).
    We reviewed a variety of data sources in our investigation of
potential practices, processes or controls to consider. Among the
sources we reviewed were the NESHAP for various industries that were
promulgated since the MACT standards being reviewed in this action. We
reviewed the regulatory requirements and/or technical analyses
associated with these regulatory actions to identify any practices,
processes and control technologies considered in these efforts that
could be applied to emission sources in the Aerospace Manufacturing and
Rework Facilities source category, as well as the costs, non-air
impacts and energy implications associated with the use of these
technologies. Additionally, we requested information from facilities
regarding developments in practices, processes or control technology.
Finally, we reviewed information from other sources, such as state and/
or local permitting agency databases and industry-supported databases.

IV. Analytical Results and Proposed Decisions

A. What actions are we taking pursuant to CAA sections 112(d)(2) and
112(d)(3)?

    We are not proposing any new emissions limitations to the NESHAP
other than with respect to specialty coatings. In this action, we are
proposing the following revisions to the Aerospace NESHAP to ensure the
standards are consistent with the requirements of the CAA as
interpreted by the courts: adding standards to limit organic and
inorganic HAP emissions from specialty coating application operations
and updating the provisions regulating emissions during periods of SSM.
Additionally, we are adding an alternative compliance demonstration
provision for all types of coating application operations (primers,
topcoats, specialty coatings and chemical milling maskants) in certain
situations. The results and proposed decisions based on the analyses
performed pursuant to CAA section 112(d)(2) and (3) are presented
below.
    We are proposing to establish MACT standards specific to specialty
coating application operations to ensure the standards are consistent
with the

requirements of the CAA as interpreted by the courts. Under CAA section
112(d)(3), the EPA is required to promulgate emissions limits for all
HAP emitted from major source categories.\29\ Specialty coatings are a
source of HAP emissions from the Aerospace Manufacturing and Rework
Facilities source category that is not currently regulated under the
Aerospace NESHAP. We are proposing organic HAP content limits to reduce
organic HAP emissions and equipment and work practice standards to
reduce inorganic HAP emissions associated with specialty coating
application. Refer to section IV.E.1 of this preamble for a description
of specialty coating application operations, associated emissions and
how this emissions source is addressed in the current Aerospace NESHAP,
and how the EPA established the MACT floor for specialty coating
application operations. Section IV.E.1 of this preamble also includes
the EPA's rationale for proposing this standard, as well as how the EPA
established the MACT floor for specialty coating application operations
and the estimated costs for complying with the proposed standard. The
EPA is proposing to add these standards for specialty coatings because
they are a source of HAP emissions from the Aerospace Manufacturing and
Rework Facilities source category and EPA had not previously
established MACT standards for these emissions points. These proposed
changes are necessary to ensure the emissions standards are consistent
with the requirements of the CAA as interpreted by the courts and are
unrelated to the risk findings.
---------------------------------------------------------------------------

    \29\ For more details see the discussion of Sierra Club v. EPA,
479 F. 3d 875 (D.C. Cir. 2007) in section II.E of this preamble,
which found that the EPA may not set ``no emissions reductions''
MACT floors.
---------------------------------------------------------------------------

    The EPA is also proposing to revise the provisions affecting
periods of SSM to clarify that the emission limitations in the
Aerospace NESHAP apply at all times, including during these SSM
periods. Refer to section IV.E.3 of this preamble for a description of
the EPA's proposed revisions to the SSM provisions for aerospace
manufacturing and rework operations. These proposed changes to the SSM
provisions are necessary to ensure the emissions standards are
consistent with the requirements of the CAA as interpreted by the
courts and are unrelated to the risk findings.
    The EPA also collected emissions data and performed a risk analysis
for certain emissions points outside of the source category--chemical
milling and metal finishing operations, waste water operations, storage
tanks and composite operations that are related to aerospace
manufacturing and rework, but are not surface coating operations. The
data collected for these non-surface coating operations were used to
characterize the risk presented from these operations in order to
estimate the total risk from the entirety of each aerospace
manufacturing and rework facility. The EPA is not proposing to expand
the Aerospace Manufacturing and Rework Facilities source category to
include these operations, which are not surface coating operations and
were not part of the original source category and which, as explained
below, did not present unacceptable risks. The initial and subsequent
listings of source categories for regulation under section 112 of the
CAA included Aerospace Manufacturing and Rework Facilities only as a
surface coating source category.\30\ \31\
---------------------------------------------------------------------------

    \30\ Initial List of Categories of Sources Under Section
112(c)(1) of the Clean Air Act Amendments of 1990. 57 FR 31576, July
17, 1992.
    \31\ National Emission Standards for Hazardous Air Pollutants;
Revision of Initial List of Categories of Sources and Schedule for
Standards Under Sections 112(c) and (e) of the Clean Air Act
Amendments of 1990. 61 FR 28197, June 4, 1996.
---------------------------------------------------------------------------

B. What are the results of the risk assessment and analyses?

1. Inhalation Risk Assessment Results
    Table 2 of this preamble provides an overall summary of the results
of the inhalation risk assessment.

            Table 2--Aerospace Manufacturing and Rework Facilities Inhalation Risk Assessment Results
----------------------------------------------------------------------------------------------------------------
                                                        Estimated
                              Estimated  population  annual  cancer      Maximum
Maximum  individual  cancer    at  increased risk       incidence     chronic  non-  Maximum screening acute non-
 risk  (-in-1 million) \a\      levels of cancer       (cases per     cancer  TOSHI         cancer HQ \c\
                                                          year)            \b\
----------------------------------------------------------------------------------------------------------------
                                                Actual Emissions
----------------------------------------------------------------------------------------------------------------
10.........................  >= 1-in-1 million:                0.02             0.5  HQREL = 2 (ethylene glycol
                              180,000.                                                ethyl ether acetate).
                             >= 10-in-1 million:
                              1,500.
                             >= 100-in-1 million: 0
----------------------------------------------------------------------------------------------------------------
                                             Allowable Emissions \d\
----------------------------------------------------------------------------------------------------------------
10.........................  >= 1-in-1 million:                0.02             0.5  ...........................
                              180,000.
                             >= 10-in-1 million:
                              2,000.
                             >= 100-in-1 million: 0
----------------------------------------------------------------------------------------------------------------
\a\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\b\ Maximum TOSHI. The target organ with the highest TOSHI for the Aerospace Manufacturing and Rework Facilities
  source category for both actual and allowable emissions is the kidney system.
\c\ See Section III.A.3 of this preamble for explanation of acute dose-response values. Acute assessments are
  not performed on allowable emissions.
\d\ The development of allowable emission estimates can be found in the memorandum titled, Aerospace
  Manufacturing and Rework Facilities RTR Modeling File Preparation, December 2014, which is available in the
  docket.

    The inhalation risk modeling performed to estimate risks based on
actual and allowable emissions relied primarily on emissions data from
the ICRs and calculations described in the memorandum titled, Aerospace

Manufacturing and Rework Facilities RTR Modeling File Preparation,
December 2014, which is available in the docket for this action. The
results of the chronic baseline inhalation cancer risk assessment
indicate that, based on estimates of current actual emissions, the MIR
posed by the Aerospace Manufacturing and Rework Facilities is 10-in-1
million, with emissions of strontium chromate, from coating operations
accounting for the majority of the risk. The total estimated cancer
incidence from Aerospace Manufacturing and Rework Facilities based on
actual emission levels is 0.02 excess cancer cases per year or one case
every 50 years, with emissions of strontium chromate and chromium
compounds contributing 66 percent and 15 percent, respectively, to the
cancer incidence. In addition, we note that approximately 1,500 people
are estimated to have cancer risks greater than or equal to 10-in-1
million, and approximately 180,000 people are estimated to have risks
greater than or equal to 1-in-1 million as a result of actual emissions
from this source category.
    When considering MACT-allowable emissions, the MIR is estimated to
be up to 10-in-1 million, driven by emissions of strontium chromate
from coating operations. The estimated cancer incidence is estimated to
be 0.02 excess cancer cases per year, or one excess case in every 50
years. Approximately 2,000 people are estimated to have cancer risks
greater than or equal to 10-in-1 million and approximately 180,000
people are estimated to have cancer risks greater than or equal to 1-
in-1 million considering allowable emissions from Aerospace
Manufacturing and Rework Facilities.
    The maximum modeled chronic non-cancer HI (TOSHI) value for the
source category based on actual emissions is estimated to be 0.5,
driven by cadmium compounds emissions from blast depainting. When
considering MACT-allowable emissions, the maximum chronic non-cancer
TOSHI value is estimated to be 0.5, also driven by cadmium compounds
emissions from blast depainting.
2. Acute Risk Results
    Our screening analysis for worst-case acute impacts based on actual
emissions indicates the potential for one pollutant, ethylene glycol
ethyl ether acetate, from one facility, to have HQ values above 1,
based on its REL value. One hundred forty-three of the 144 Aerospace
Manufacturing and Rework Facilities had an estimated worst-case HQ less
than or equal to 1 for all HAP.
    To better characterize the potential health risks associated with
estimated worst-case acute exposures to HAP from the source category at
issue and in response to a key recommendation from the SAB's peer
review of the EPA's CAA section 112(f) RTR risk assessment
methodologies, we examine a wider range of available acute health
metrics than we do for our chronic risk assessments. This is in
acknowledgement that there are generally more data gaps and
inconsistencies in acute reference values than there are in chronic
reference values.
    By definition, the acute CalEPA REL represents a health-protective
level of exposure, with no risk anticipated below those levels, even
for repeated exposures; however, the health risk from higher-level
exposures is unknown. Therefore, when a CalEPA REL is exceeded and an
AEGL-1 or ERPG-1 level is available (i.e., levels at which mild effects
are anticipated in the general public for a single exposure), we have
used them as a second comparative measure. Historically, comparisons of
the estimated maximum off-site 1-hour exposure levels have not been
typically made to occupational levels for the purpose of characterizing
public health risks in RTR assessments. This is because occupational
ceiling values are not generally considered protective for the general
public since they are designed to protect the worker population
(presumed healthy adults) for short-duration (less than 15-minute)
increases in exposure. As a result, for most chemicals, the 15-minute
occupational ceiling values are set at levels higher than a 1-hour
AEGL-1, making comparisons to them irrelevant unless the AEGL-1 or
ERPG-1 levels are also exceeded.
    The worst-case maximum estimated 1-hour exposure to ethylene glycol
ethyl ether acetate outside the facility fence line for the source
categories is 0.3 mg/m\3\. This estimated worst-case exposure exceeds
the 1-hour REL by a factor of 2 (HQREL = 2). All other HAP
in this analysis have worst-case acute HQ values of 1 or less (maximum
HQAEGL-1 = 0.02 for phenol, maximum HQERPG-1 =
0.03 for phenol) indicating that they carry no potential to pose acute
concerns.
    In characterizing the potential for acute non-cancer impacts of
concern, it is important to remember the upward bias of these exposure
estimates (e.g., worst-case meteorology coinciding with a person
located at the point of maximum concentration during the hour) and to
consider the results along with the conservative estimates used to
develop peak hourly emissions as described in the Modeling File
Preparation Memo (which is available in the docket for this action) for
a detailed description of how the hourly emissions were developed for
this source category.
3. Multipathway Risk Screening Results
    Results of the worst-case Tier I screening analysis indicate that
PB-HAP emissions of cadmium compounds or mercury compounds did not
exceed the screening emission rates. Neither dioxins nor polycyclic
aromatic hydrocarbons (PAH) are emitted by any source in the source
category.
4. Environmental Risk Screening Results
    As described in section III.A of this preamble, we conducted a
screening-level evaluation of the potential adverse environmental risks
associated with emissions of the following environmental HAP from the
Aerospace Manufacturing and Rework Facilities source category: lead,
mercury, cadmium, HCl and HF.
    In the Tier 1 screening analysis for PB-HAP (other than lead
compounds, which were evaluated differently), the individual modeled
Tier 1 concentrations for mercury and cadmium did not exceed any
ecological benchmark for any facility in the source category. For lead
compounds, we did not estimate any exceedances of the secondary lead
NAAQS.
    For HF and HCl, the average modeled concentration around each
facility (i.e., the average concentration of all off-site data points
in the modeling domain) did not exceed the ecological benchmarks. In
addition, each individual modeled concentration of HCl and HF (i.e.,
each off-site data point in the modeling domain) was below the
ecological benchmarks for all facilities.
5. Facility-Wide Risk Results
    The facility-wide chronic MIR and TOSHI were estimated based on
emissions from all sources at the identified facilities (both MACT and
non MACT sources). The results of the facility-wide assessment for
cancer risks indicate that 44 facilities with aerospace manufacturing
and rework processes have a facility-wide cancer MIR greater than or
equal to 1-in-1 million. The maximum facility-wide cancer MIR is 20-in-
1 million, primarily driven by arsenic and chromium (VI) compounds,
from internal combustion engines. The maximum facility-wide TOSHI for
the source category is estimated to be 0.5, primarily driven by
emissions of hexamethylene-1,6-diisocyanate from specialty coatings
operations.

6. What demographic groups might benefit from this regulation?
    To examine the potential for any environmental justice (EJ) issues
that might be associated with the source category, we performed a
demographic analysis, which is an assessment of risks to individual
demographic groups, of the population close to the facilities. In this
analysis, we evaluated the distribution of HAP-related cancer risks and
non-cancer hazards from the Aerospace Manufacturing and Rework
Facilities across different social, demographic and economic groups
within the populations living near facilities identified as having the
highest risks. The methodology and the results of the demographic
analyses are included in a technical report, Risk and Technology
Review--Analysis of Socio-Economic Factors for Populations Living Near
Aerospace Facilities, available in the docket for this action.
    The results of the demographic analysis are summarized in Table 3
of this preamble. These results, for various demographic groups, are
based on the estimated risks from actual aerospace manufacturing and
rework emissions levels for the population living within 50 km of the
facilities.

            Table 3--Aerospace Manufacturing and Rework Facilities Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                                Population with    Population
                                                                                cancer risk at   with chronic
                                                                                or above 1-in-1   hazard index
                                                                   Nationwide     million due to  above 1 due to
                                                                                emissions from  emissions from
                                                                                aerospace        aerospace
                                                                                facilities      facilities
----------------------------------------------------------------------------------------------------------------
Total Population...............................................     312,861,265        179,074                 0
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White..........................................................              72             64                NA
All Other Races................................................              28             36                NA
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White..........................................................              72             64                NA
African American...............................................              13             19                NA
Native American................................................               1              1.5              NA
Other and Multiracial..........................................              14             16                NA
----------------------------------------------------------------------------------------------------------------
                                              Ethnicity by Percent
----------------------------------------------------------------------------------------------------------------
Hispanic.......................................................              17             16                NA
Non-Hispanic...................................................              83             84                NA
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level............................................              14             19                NA
Above Poverty Level............................................              86             81                NA
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without High School Diploma........................              15             17                NA
Over 25 and with a High School Diploma.........................              85             83                NA
----------------------------------------------------------------------------------------------------------------

    The results of the Aerospace Manufacturing and Rework Facilities
baseline risk assessment indicate that emissions from the source
category expose approximately 180,000 people to a cancer risk at or
above 1-in-1 million and no one is predicted to have a chronic non-
cancer TOSHI greater than 1.
    The analysis indicates that the percentages of the population
exposed to a cancer risk greater than or equal to 1-in-1 million and
living within 50 km of the 144 aerospace facilities is higher for
minority populations, 36-percent exposed versus the national minority
population average of 28 percent. The specific demographics of the
population within 50 km of the facilities indicate potential
disparities in certain demographic groups, including the ``African
American'' and ``Below the Poverty Level.''

C. What are our proposed decisions regarding risk acceptability, ample
margin of safety and adverse environmental effects?

1. Risk Acceptability
    As noted in section II.A.1 of this preamble, the EPA sets standards
under CAA section 112(f)(2) using ``a two-step standard-setting
approach, with an analytical first step to determine an `acceptable
risk' that considers all health information, including risk estimation
uncertainty, and includes a presumptive limit on MIR of approximately 1
in 10 thousand.'' 54 FR 38045, September 14, 1989. For the Aerospace
Manufacturing and Rework Facilities source category, we estimate, based
on both actual and allowable emissions, an MIR of 10-in-1 million
driven by emissions of strontium chromate from coating operations. We
estimate that, based on actual emissions, about 1,500 people are
estimated to have cancer risks greater than or equal to 10-in-1 million
and, based on allowable emissions, about 2,000 people have cancer risks
greater than or equal to 10-in-1 million. We estimate that
approximately 180,000 people are estimated to have risks greater than
or equal to 1-in-1 million based on both actual and allowable emissions
from this source category. The total estimated incidence of cancer for
this source category due to inhalation exposures, based on both actual
and allowable emissions, is 0.02 excess cancer cases

per year, or 1 case in 50 years. The agency estimates that the maximum
chronic non-cancer TOSHI from inhalation exposure, based on both actual
and allowable emissions, from this source category, is 0.5, with
cadmium compounds emissions from blast depainting accounting for the
majority of the TOSHI.
    The multipathway screening analysis, based upon actual emissions,
indicates that PB-HAP emissions of both cadmium compounds and mercury
compounds did not exceed the screening emission rates. Neither dioxins
nor PAH are emitted by any source in the source category. In evaluating
the potential for multipathway effects from emissions of lead, modeled
maximum annual lead concentrations were compared to the secondary NAAQS
for lead (0.15 [mu]g/m\3\). Results of this analysis estimate that the
NAAQS for lead would not be exceeded at any off-site locations.
    The screening assessment of worst-case acute inhalation impacts
from baseline actual emissions indicates that the worst-case maximum
estimated 1-hour exposure to ethylene glycol ethyl ether acetate
outside the facility fence line exceeds the 1-hour REL by a factor of 2
(HQREL = 2). This exceedance was only predicted to occur in
a remote, non-inhabited area just adjacent to the facility fence line
for 2 hours a year. All other HAP in this analysis have worst-case
acute HQ values of 1 or less (maximum HQAEGL-1 = 0.02 for
phenol, maximum HQERPG-1 = 0.03 for phenol) indicating that
they carry no potential to pose acute concerns.
    In determining whether risks are acceptable for this source
category, the EPA considered all available health information including
any uncertainty in risk estimates. Also, as noted above, the agency
estimated risk from both actual and allowable emissions. While there
are uncertainties associated with both the actual and allowable
emissions, we consider the allowable emissions to be an upper bound,
based on the conservative methods we used to calculate allowable
emissions.
    The risk results indicate that both the actual and allowable
inhalation cancer risks to the individual most exposed are no greater
than approximately 10-in-1 million, which is considerably less than the
presumptive limit of acceptability (i.e., 100-in-1 million). The
maximum chronic non-cancer hazard indices for both the actual and
allowable inhalation non-cancer risks to the individual most exposed of
0.5 is less than 1.
    The maximum acute non-cancer HQ for all pollutants was 2 based on
the REL for ethylene glycol ethyl ether acetate. This value was only
predicted to occur during 2 hours per year in a remote location
adjacent to a single facility's fenceline. All other acute risks are
estimated to be below a noncancer HI threshold of 1.
    The multipathway screening analysis indicates that PB-HAP emissions
did not exceed the screening emission rates for any compound evaluated.
    Considering all of the health risk information and factors
discussed above, including the uncertainties discussed in section
III.A.8 of this preamble, the EPA proposes that the risks at baseline
are acceptable since the cancer risks are well below the presumptive
limit of acceptability and the non-cancer results indicate there is
minimal likelihood of adverse non-cancer health effects due to HAP
emissions from this source category.
2. Ample Margin of Safety Analysis and Proposed Controls
    Under the ample margin of safety analysis, we evaluate the cost and
feasibility of available control technologies and other measures
(including the controls, measures and costs evaluated under the
technology review) that could be applied in this source category to
further reduce the risks due to emissions of HAP identified in our risk
assessment, as well as the health impacts of such potential additional
measures. As noted in our discussion of the technology review in
section III.C of this preamble, no measures (beyond those already in
place or that we are proposing today under CAA sections 112 (d)(2) and
(d)(3)) were identified for reducing HAP emissions from the Aerospace
Manufacturing and Rework Facilities source category. Therefore, we
propose that the current standards provide an ample margin of safety to
protect public health.
    Although the current standards were found to provide an ample
margin of safety to protect public health, we are proposing additional
standards under CAA sections 112(d)(2) and (3) that address previously
unregulated emissions of HAP from specialty coating application
operations. The additional standards are being proposed to address a
deficiency in the Aerospace NESHAP as discussed previously in section
II.E. of this preamble. We are proposing organic HAP and volatile
organic compound (VOC) content limits for specialty coatings that are
equal to the VOC content limits specified in the Aerospace CTG for
specialty coatings. Facilities that do not use specialty coatings and
those in nonattainment areas that are currently complying with the
Aerospace CTG limits for their specialty coating operations will not
have to do anything new to meet these requirements. The 74 facilities
located in attainment areas that reported using specialty coatings in
the 2011 ICR may not be using compliant coatings and may need to use
alternative coatings, direct the emissions stream to an add-on control
device or use the averaging option to demonstrate compliance with
implement the standards. We are also proposing that specialty coating
application operations be subject to the same equipment standards
(i.e., use high-efficiency application equipment) currently required
for primer and topcoat application operations. Further, we are
proposing to require that specialty coating application operations meet
current work practice standards for primer and topcoat application
operations for inorganic HAP emissions. The estimated emission
reductions resulting from these proposed HAP content limits, equipment
standards and work practice standards for specialty coatings are 58
tons of HAP per year. As noted above, we are proposing that the MACT
standard, prior to the implementation of these proposed standards for
specialty coatings, provides an ample margin of safety to protect
public health. Therefore, we maintain that, after the implementation of
these standards for specialty coatings, the rule will continue to
provide an ample margin of safety to protect public health.
Consequently, based on current information, we do not expect it will be
necessary to conduct another residual risk review under CAA section
112(f) for this source category 8 years following promulgation of new
emission limits and equipment and work practice standards for specialty
coatings, merely due to the addition of these MACT requirements. While
our decisions on risk acceptability and ample margin of safety are
supported even in the absence of these reductions for specialty
coatings, if we finalize the proposed requirements for these sources,
they would further strengthen our conclusions that risk is acceptable
with an ample margin of safety to protect public health.
    Although we did not identify any new technologies, other than for
specialty coatings application operations, to reduce risk for this
source category, we are specifically requesting comment on whether
there are additional control measures that may be able to reduce risks
from the source category. We request any information on potential
emission reductions of such measures, as well the cost and health
impacts of

such reductions to the extent they are known.
3. Adverse Environmental Effects
    Based on the results of our environmental risk screening
assessment, we conclude that there is not an adverse environmental
effect as a result of HAP emissions from the Aerospace Manufacturing
and Rework Facilities source category. We are proposing that it is not
necessary to set a more stringent standard to prevent, taking into
consideration costs, energy, safety and other relevant factors, an
adverse environmental effect.

D. What are the results and proposed decisions based on our technology
review?

    As described in section III.C of this preamble, our technology
review focused on identifying developments in practices, processes and
control technologies for the Aerospace Manufacturing and Rework
Facilities source category. The EPA reviewed various information
sources regarding emission sources that are currently regulated by the
Aerospace NESHAP, which include primer and topcoat application
operations, maskant application operations, cleaning operations,
chemical and blast depainting operations and waste storage and handling
operations.
    For the technology review, we conducted a search of the EPA's RACT/
BACT/LAER Clearinghouse (RBLC) and regulatory actions (MACT standards,
area sources standards and residual risk standards) subsequent to
promulgation of the 1995 Aerospace NESHAP.\32\ We reviewed Washington
State's records of Prevention of Significant Deterioration (PSD)
permits. Further, we considered numerous relevant regional and state
regulations (e.g., California, Missouri, Delaware and Arizona), the
Ozone Transport Commission serving the Northeastern United States and
state implementation plans. We reviewed the database of responses to
the 2011 ICR to determine the technologies and practices reported by
industry.
---------------------------------------------------------------------------

    \32\ See the EPA's ``Coatings and Composites Coordinated Rule
Development'' Web page at http://www.epa.gov/ttnatw01/coat/coat.html
for a full list of surface coating-related NESHAP, and links to Web
pages specific to each surface coating NESHAP.
---------------------------------------------------------------------------

    We reviewed these sources for information on add-on control
technologies, other process equipment, work practices and procedures
and process changes or pollution prevention alternatives that were not
considered during development of the Aerospace NESHAP. We also looked
for information on improvements in add-on control technology, other
process equipment, work practices and procedures and process changes or
pollution prevention alternatives that have occurred since development
of the Aerospace NESHAP. Regarding process changes or pollution
prevention alternatives, we searched for advancements in the use of
low-HAP coatings and solvents, advancements in the use of high solids
coatings and the adoption of lower VOC content limits for coatings and
solvents.
    The following sections summarize our technology review results for
each of these emission sources.
1. Primer and Topcoat Application Operations
    As defined in the Aerospace NESHAP (see 40 CFR 63.742), a coating
is a material that is applied to the surface of an aerospace vehicle or
component to form a decorative or functional solid film, or the solid
film itself. A primer is the first layer and any subsequent layers of
coating prior to the topcoat and is typically used for corrosion
prevention, protection from the environment, functional fluid
resistance and adhesion of subsequent coatings. A topcoat is a coating
that is applied over one or more layers of a primer for appearance,
identification, camouflage or protection. Specialty coatings are not
included in the categories of primers or topcoats currently subject to
regulation under 40 CFR 63.745.
    Most aerospace coatings contain a mixture of organic solvents that
may be HAP, and also inorganic pigments, such as various metal
compounds, which may also be HAP. The organic HAP emissions from the
application of primers and topcoats occur from the evaporation of
organic solvents during mixing, application and drying. Emissions of
inorganic HAP from spray-applied coating operations, typically metal
compounds (e.g., chromium, cadmium compounds), occur when coating
particles do not adhere to the surface being coated (i.e., overspray).
The organic and inorganic emissions from coating application occur in
large open areas, such as hangars or in partially or fully enclosed
spaces, such as within spray booths.
    The existing Aerospace NESHAP requires the following organic HAP
and VOC content limits for uncontrolled primers and topcoats (40 CFR
63.745(c)):
     Primers: 2.9 lb/gal (less water) as applied; or 4.5 lb/gal
(less water) as applied for general aviation rework facilities, or 5.4
lb/gal (less water) as applied, to large commercial aircraft components
(parts or assemblies) or fully assembled, large commercial aircraft.
     Topcoats: 3.5 lb/gal (less water) as applied; or 4.5 lb/
gal (less water) as applied for general aviation rework facilities.
    Alternatively, a control system can be used to capture and control
organic HAP and VOC emissions from the primer or topcoat application
operations. The system must achieve an overall control efficiency of 81
percent of organic HAP and VOC emissions (40 CFR 63.745(d)).
    In addition, the Aerospace NESHAP requires the use of one of the
following coating application techniques (40 CFR 63.745(f)):
     Flow/curtain coat application.
     Dip coat application.
     Roll coating.
     Brush coating.
     Cotton-tipped swab application.
     Electrodeposition (dip) coating.
     High volume low pressure (HVLP) spraying.
     Electrostatic spray application.
     Other coating application methods that achieve emission
reductions equivalent to HVLP or electrostatic spray application
methods.
    The Aerospace NESHAP also includes operating requirements for the
application of primers or topcoats that contain inorganic HAP,
including control of spray booth exhaust streams with either
particulate filters or waterwash spray booths (40 CFR 63.745(g)).
    Based on the technology review for primers and topcoats, we did not
identify any practices, processes or control technologies beyond those
already required by the Aerospace NESHAP. A brief summary of the EPA's
findings in conducting its RTR review of primer and topcoat application
operations follows. For a detailed discussion of the EPA's findings,
refer to the memorandum, Technology Review for Primer and Topcoat
Application Operations in the Aerospace Source Category, January 2015,
available in the docket for this action.
    In reviewing add-on control technologies or other equipment and
work practices and procedures, we did not identify any add-on control
technologies, other equipment or work practices and procedures that had
not previously been considered during development of the Aerospace
NESHAP, nor did we identify any developments in the same since the
promulgation of the NESHAP.
    Based on our search of the RBLC, we did not find any more stringent
requirements. We identified one facility

in Washington State, for which a Best Achievable Control Technology
(BACT) analysis was completed in September 2014, for constructing new
buildings needed for producing new models of large commercial
airplanes, including the building and surface coating of composite
aircraft wings. The surface coating operations on these aircraft wings
would involve the use of primers and topcoats that are subject to the
limits in 40 CFR 63.745. The BACT analysis concluded that there are no
demonstrations of add-on controls at facilities performing surface
coating comparable to large commercial aircraft wing components. The
analysis also concluded that add-on controls would not be cost
effective for surface coating of large components, such as wings, much
less fully assembled large commercial aircraft.
    In reviewing improvements in add-on control technologies or other
equipment that had previously been considered during development of the
Aerospace NESHAP, specifically in conducting a technology review of the
wood manufacturing industry, we found that the Wood Furniture
Manufacturing NESHAP, 40 CFR part 63, subpart JJ, requires the use of
high-efficiency spray guns (e.g., airless spraying, air assisted
airless spraying, electrostatic spraying and HVLP spray guns) and
prevents the use of conventional spray guns. Although the Aerospace
NESHAP does not specifically prohibit the use of conventional spray
methods, it does specify that only spray application methods that are
equivalent to HVLP or electrostatic spray application methods may be
used. Because conventional spray guns can be used only if they can
achieve the same efficiency as HVLP or electrostatic spray application
methods, the Aerospace NESHAP and the Wood Furniture Manufacturing
NESHAP are essentially equivalent. No other new developments in add-on
control technologies or other equipment were found.
    The EPA reviewed the 2011 ICR data for advancements in the use of
low-HAP liquid primers and topcoats as process changes and pollution
prevention alternatives that could be transferred to and used in this
source category and that were not identified and considered during
development of the Aerospace NESHAP. In this review, we found some
facilities with weighted-average HAP content values below the HAP and
VOC content limits for primers and topcoats in the Aerospace NESHAP.
However, the data collected by the ICR cannot be compared directly with
the HAP and VOC content limits in the Aerospace NESHAP because the
NESHAP limits are based on grams of HAP per liter of coating, less
water. The ICR asked for readily available data, such as data from
product sheets and material safety data sheets, which did not provide
data on the water content of the coatings. As a result, we cannot
accurately convert the reported HAP contents from the ICR to the same
basis as in the Aerospace NESHAP. Moreover, we believe that if the
coatings in the ICR contained water and the water content of the
coatings is removed, then the corrected HAP content of the coatings
would increase and the apparent difference between the ICR data and the
NESHAP limits would be reduced.
    Finally, many of the currently used coatings have already been
reformulated to meet the current MACT HAP content limits. Manufacturers
of aerospace vehicles are constrained to using certain types of primers
and topcoats based on the market segment for which the coating is
intended (i.e., military original equipment manufacturer (OEM),
military rework, commercial OEM or commercial rework) and the unique
circumstances and design considerations within each market segment. In
addition to being regulated by the Aerospace NESHAP, aerospace vehicle
manufacturing and rework operations are also regulated by the Federal
Aviation Administration (FAA), the Department of Defense and specific
customer requirements. As outlined in the EPA's 1998 promulgation of
amendments to the Aerospace NESHAP,\33\ affected sources must comply
with FAA Airworthiness Directives (AD) that can potentially require the
use of chemicals containing HAP, and affected sources may have to
obtain alternative means of compliance for AD to allow for the
substitution of non-HAP materials. These multiple regulations can
result in lengthy processes for qualifying new paint systems.
---------------------------------------------------------------------------

    \33\ 63 FR 46525, September 1, 1998.
---------------------------------------------------------------------------

    Based on a finding of no new developments in practices, processes
and control technologies in the technology review for primer and
topcoat application operations, we are not proposing to revise the
Aerospace NESHAP HAP and VOC content limit requirements for primer and
topcoat application operations pursuant to CAA section 112(d)(6). For
further discussion of the technology review results, refer to the
memorandum, Technology Review for Primer and Topcoat Application
Operations in the Aerospace Source Category, January 2015, available in
the docket for this action.
2. Chemical Milling Maskant Application Operations
    In the process of chemical milling, an etchant solution is used to
chemically reduce the thickness of selected areas of metal parts. The
process is typically used when the size or shape of the part precludes
mechanical milling or when chemical milling is advantageous due to
shorter processing time or its batch capability. Before chemical
milling, a maskant is applied to the part, allowed to cure and is then
removed from selected areas of the part where metal is to be removed by
the etchant. The maskant remaining on the part protects those areas
from the etchant. Maskants are applied by brushing, dipping, spraying
or flow coating. Organic HAP emissions occur through evaporation of the
solvent in the maskant, typically toluene, xylene or perchloroethylene,
as the maskant is applied and while it cures.
    There are two subcategories of chemical milling maskants in the
Aerospace NESHAP. Type I maskants are used with chemical milling
etchants that contain dissolved sulfur and no amines, and Type II
maskants are used with etchants that are strong sodium hydroxide
solutions containing amines. The Aerospace NESHAP requires the
following organic HAP and VOC content limits for uncontrolled chemical
milling maskants (40 CFR 63.747(c)):
     Type I: 5.2 pounds organic HAP per gallon (622 g/L) less
water, as applied.
     Type II: 1.3 pounds of organic HAP per gallon (160 g/L)
less water, as applied.
    These requirements do not apply to touch-up of scratched surfaces
or damaged maskant and touch-up of trimmed edges. Alternatively, a
control system can be used to capture and control emissions from the
maskant application operation. The system must achieve an overall
control efficiency of 81 percent (40 CFR 63.747(d)).
    Based on the technology review for chemical milling maskants, we
did not identify any add-on control technologies, other equipment or
work practices and procedures that had not previously been considered
during development of the Aerospace NESHAP. Additionally, we did not
identify any improvements that could be transferred to this source
category. In our search of the RBLC, we also did not find any more
stringent requirements. We did find that some California air quality
management districts require more stringent VOC content limits than
those in the Aerospace NESHAP and have higher overall minimum control
requirements for the use of add-on control technology.

However, the EPA did not find any chemical milling maskant application
operations located in these two districts that are subject to these
more stringent limits.
    Based on a finding of no new developments in practices, processes
and control technologies in this technology review, we are not
proposing revisions to the Aerospace NESHAP for chemical milling
maskant application operations pursuant to CAA section 112(d)(6). Refer
to the memorandum, Technology Review for Chemical Milling Maskant
Application Operations in the Aerospace Source Category, January 2015,
available in the docket for this action, for more a more detailed
description of the technology review results.
3. Cleaning Operations
    At Aerospace Manufacturing and Rework Facilities, cleaning
operations are used at essentially every processing step of aerospace
surface coating, from preparing surfaces to be coated to cleaning the
coating application equipment. The cleaning operations regulated by the
current Aerospace NESHAP include hand-wipe cleaning, spray gun cleaning
and flush cleaning, as well as housekeeping measures for storage,
handling and transfer of cleaning solvents and solvent-laden materials.
    The liquid cleaning solutions used in cleaning operations for the
aerospace industry contain organic solvents, and some of these organic
solvents are HAP. Organic HAP emissions from the cleaning operations
are often fugitive in nature, resulting from the evaporation of the
volatile portion of the cleaning solvent in large open areas, such as
hangars. They may also be emitted from stacks when the solvents are
used in partially or fully enclosed spray booths that are ventilated
through stacks.
    The current Aerospace NESHAP requires that hand-wipe and flush
cleaning solvents meet certain composition requirements, or that the
cleaning solvents have a composite vapor pressure of no more than 45 mm
Hg (24.1 inches water) (40 CFR 63.744(b) and (d)). The NESHAP specifies
work practice standards for spray gun cleaning (e.g., cleaning a spray
gun in an enclosed gun cleaning system) and flush cleaning operations
(e.g., for flush cleaning events, empty used cleaning solvent into an
enclosed container) (40 CFR 63.744(c) and (d)). Work practice measures
are also specified for the storage and handling of solvents and
solvent-laden materials (e.g., solvent-laden cloth, paper or other
absorbent materials) (40 CFR 63.744(a)).
    Based on the technology review for cleaning operations, we did not
identify any practices, processes or control technologies beyond those
already required by the Aerospace NESHAP that could be transferred to
the source category. A brief summary of the EPA's findings in
conducting its RTR review of cleaning operations follows. For a
detailed discussion of the EPA's findings, refer to the memorandum,
Technology Review for Cleaning Operations in the Aerospace Source
Category, January 2015, available in the docket for this action.
    In the technology review, we did not identify any improvements in
add-on control technologies, other equipment or work practices and
procedures since promulgation of the Aerospace NESHAP. The EPA
identified one aerospace manufacturing and rework facility that routes
the air flow from a spray booth to a carbon adsorption control device
when performing spray gun cleaning and residual spray gun hand-wipe
cleaning. We found that this was the same spray booth in which surface
coating is performed, and it is not a spray booth dedicated to spray
gun cleaning. Based on the results of the responses to the EPA's 2011
information collection survey for other facilities, the EPA concluded
that this practice could not be applied to the source category without
impacting facility operations. First, very few facilities have carbon
adsorbers controlling emissions from spray booths. Second, it is not
always practical to move the spray gun cleaning operations into a spray
booth without affecting the surface coating operations in that spray
booth because of space limitations within the booth.
    The EPA also identified one aerospace manufacturing and rework
facility that, for certain cleaning operations, uses a non-HAP solvent
blend that has a vapor pressure of 36 mm Hg for certain cleaning
operations; the facility does not use this solvent for all cleaning
operations. The use of non-HAP cleaning solvent is already a compliance
option that was considered in the development of the Aerospace NESHAP
and is included in 40 CFR 63.744.
    Based on a finding of no new developments in practices, processes
and control technologies in the technology review, we are not proposing
any revisions to the Aerospace NESHAP standard requirements for
cleaning operations pursuant to CAA section 112(d)(6). For further
discussion of the technology review results, refer to the memorandum,
Technology Review for Cleaning Operations in the Aerospace Source
Category, January 2015, available in the docket for this action.
4. Chemical and Dry Media Blasting Depainting Operations
    At Aerospace Manufacturing and Rework Facilities, chemical and dry
media blasting depainting operations remove unwanted or old surface
coatings (e.g., primers, topcoats and specialty coatings) to prepare
the surface for painting. As defined in the Aerospace NESHAP, a
depainting operation means the use of a chemical agent, media blasting
or any other technique to remove permanent coatings from the outer
surface of an aerospace vehicle or components, excluding hand and
mechanical sanding or other non-chemical removal processes that do not
involve blast media or other mechanisms that would result in airborne
particle movement at high velocity. The depainting operation includes
washing of the aerospace vehicle or component to remove residual
stripper, media or coating residue. Depainting is most often done in
the rework of existing aircraft, but may also be done in limited
circumstances in the manufacture of new aircraft.
    The liquid chemical agents (i.e., strippers) used to remove
permanent coatings in the aerospace industry contain organic solvents.
Organic HAP emissions from strippers occur from the evaporation of the
chemical stripper during mixing, application and possibly during
washing of the vehicle or component to remove residual stripper. The
organic emissions from depainting operations that occur within a booth
or hangar are typically captured and exhausted through a stack,
although some emissions may be fugitive in nature (e.g., open
containers of stripper).
    Inorganic HAP, typically metal compounds (e.g., compounds of lead,
chromium or cadmium), can be emitted during dry media blasting if these
compounds are present in the paint layer that is being removed. These
inorganic HAP would be emitted as particulate matter as the dry media
blasting removes the existing coating through abrasion.
    The Aerospace NESHAP restricts facilities to using organic HAP-
containing chemical strippers for only spot stripping and decal
removal. The amount of stripper used for spot stripping and decal
removal is limited to no more than 26 gallons of HAP-containing
chemical stripper (or alternatively 190 pounds of organic HAP) for each
commercial aircraft, and 50 gallons (or 365 pounds of organic HAP) for
each military aircraft. As an alternative, facilities may use controls
for organic HAP emissions from

chemical depainting, and emissions must be reduced by 81 percent for
controls installed before the effective date, and by 95 percent for
controls installed on or after the effective date (40 CFR 63.746(b)(1)
through (3) and (c)).
    For non-chemical depainting operations that generate inorganic HAP
emissions from dry media blasting, the operation must be performed in
an enclosed area or in a closed cycle depainting system and the air
stream from the operation must pass through a dry filter system meeting
a minimum efficiency specified in the rule, through a baghouse or
through a waterwash system before being released to the atmosphere (40
CFR 63.746(b)(4)).
    Based on the technology review for depainting operations, we did
not identify any practices, processes or control technologies that were
not already required by the Aerospace NESHAP or considered in its
development, nor did we identify any improvements to those practices,
processes or control technologies that could be transferred and applied
to this source category. A brief summary of the EPA's findings in
conducting the RTR review of chemical and dry media blast depainting
operations follows. For a detailed discussion of the EPA's findings,
refer to the memorandum, Technology Review for Depainting Operations in
the Aerospace Source Category, January 2015, available in the docket
for this action.
    In reviewing Washington State's records of permits for Aerospace
Manufacturing and Rework Facilities, we identified a 2013 PSD permit
amendment that requires the VOC vapor pressure of cleaning solvents and
chemical strippers used in depainting operations to be less than 45 mm
Hg. The Aerospace NESHAP does not prescribe vapor pressure limits to
chemical depainting strippers, but instead has capture and control and
volume usage limits for chemical depainting operations that use HAP-
containing chemical strippers. Otherwise, facilities must use non-HAP
chemical strippers. Therefore, we believe that the Aerospace NESHAP is
at least as stringent as the Washington State PSD permit requirements.
    Based on a finding of no new developments in practices, processes
and control technologies in the technology review, we are not proposing
to revise the Aerospace NESHAP standard requirements for chemical or
dry media blast depainting operations pursuant to CAA section
112(d)(6). For further discussion of the technology review results,
refer to the memorandum, Technology Review for Depainting Operations in
the Aerospace Source Category, January 2015, available in the docket
for this action.
5. Waste Storage and Handling Operations
    At Aerospace Manufacturing and Rework Facilities, waste is produced
primarily from cleaning, coating and depainting operations. Cleaning
operations produce solvent-laden cloth and paper and spent solvent
which can emit organic HAP from the evaporation of the solvents.
Coating operations produce waste paint and waste solvent that also emit
organic HAP through evaporation.
    Depainting operations can produce either a liquid or solid waste
stream depending on the type of process used. Chemical depainting
processes produce a waste sludge that consists of the stripper solution
and paint residue. Emissions occur from the evaporation of the solvent
from the stripper solution in the waste sludge.
    Blast depainting processes produce a solid waste stream that
consists of paint chips and particles and spent blasting media.
Emissions do not directly occur from this waste stream, although
particulate emissions are generated during the blasting process.
    The requirements for waste storage and handling in the Aerospace
NESHAP apply to each waste storage and handling operation, which is
defined as the total of all waste handling and storage at the facility.
In 40 CFR 63.748, the Aerospace NESHAP requires that all waste must be
handled and transferred to or from containers, tanks, vats, vessels and
piping systems in such a manner that spills are minimized.
    Because the EPA did not want to create possible conflicts over the
handling of waste between the Aerospace NESHAP and regulations under
the Resource Conservation and Recovery Act (RCRA) of 1976 (Pub. L. 94-
580), as implemented by 40 CFR parts 260 and 261, the Aerospace NESHAP
specifically exempted wastes covered under the RCRA regulations.\34\
Per 40 CFR 63.741(e), all wastes that are determined to be hazardous
wastes under RCRA as implemented by 40 CFR parts 260 and 261, and that
are subject to RCRA requirements as implemented in 40 CFR parts 262
through 268, are exempt from the requirements of the Aerospace NESHAP.
---------------------------------------------------------------------------

    \34\ See the preamble to the proposed rule, 59 FR 29216, June 6,
1994.
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    The practical effect of the provisions in 40 CFR 63.741(e) is that
all HAP-containing wastes generated by aerospace manufacturing and
rework operations are subject to RCRA and are exempt from the
requirements of 40 CFR 63.748. Because all of these HAP-containing
wastes are covered under RCRA and exempt from 40 CFR 63.748, there is
no need to do a technology review for the standards for handling and
storage of waste.

E. What other actions are we proposing?

    In addition to the proposed actions described above, we are
proposing additional revisions. As stated previously in this preamble,
the United States Court of Appeals for the District of Columbia Circuit
found that the EPA had erred in establishing emissions standards for
sources of HAP in the NESHAP for Brick and Structural Clay Products
Manufacturing and Clay Ceramics Manufacturing, 67 FR 26690 (May 16,
2003), and consequently vacated the rules.\35\ Among other things, the
court found EPA erred by failing to regulate processes that emitted
HAP, in some instances by establishing a MACT floor of ``no control.''
In this action we are proposing to correct the same error in the
Aerospace NESHAP by proposing to remove the exemption for specialty
coatings found at 40 CFR 63.741(f) and instead add limits for specialty
coatings (including adhesives, adhesive bonding primers and sealants).
---------------------------------------------------------------------------

    \35\ Sierra Club v. EPA, 479 F. 3d 875 (D.C. Cir. March 13,
2007).
---------------------------------------------------------------------------

1. Specialty Coating Application
    At Aerospace Manufacturing and Rework Facilities, specialty
coatings are those coatings that have additional performance criteria
for specific applications that are beyond the criteria for primers,
topcoats and self-priming topcoats, although specialty coatings may
still meet the definition of a primer or topcoat. These additional
performance criteria may include, for example, temperature or fire
resistance, substrate compatibility, antireflection, temporary
protection or marking, sealant properties, adhesive properties,
electrical insulation, lubrication or enhanced corrosion protection (40
CFR 63.742).
    Specialty coatings contain a mixture of organic solvents and/or
inorganic HAP. The organic HAP emissions from the application of
specialty coatings occur from the evaporation of organic solvents
during mixing, application and drying. Emissions of inorganic HAP from
spray-applied coating operations, typically metal compounds (e.g.,
chromium, cadmium compounds), occur when particles do not adhere to the
surface being coated (i.e.,

overspray). The organic and inorganic emissions from coating
application operations occur in large open areas, such as hangars or
partially or fully enclosed spaces, such as within spray booths.
    The current Aerospace NESHAP explicitly excludes specialty coatings
from meeting any control requirements, as specified in 40 CFR 63.741(f)
and in 40 CFR 63.742 (i.e., the definitions for ``exterior primer,''
``primer,'' and ``topcoat''). Appendix A of the Aerospace NESHAP
defines 59 separate categories of specialty coatings.
    Although the EPA did not include emission limitations for specialty
coatings in the Aerospace NESHAP finalized in 1995 or in any subsequent
amendments, the EPA included VOC content limits for the 59 categories
of specialty coatings in the 1997 Aerospace CTG. The Aerospace CTG is
intended to provide state and local air pollution control authorities
with an information base, recommended emissions limitations and
monitoring, recordkeeping and reporting requirements for proceeding
with their analyses of reasonably available control technology (RACT)
for their own regulations to reduce VOC emissions from aerospace
surface coating operations. The Aerospace CTG includes presumptive VOC
limits for specialty coating operations that are based on a review of
the contemporary knowledge and data concerning the technology, impacts
and costs associated with various emission control techniques. During
their development, the specialty coating categories and VOC limits in
the CTG were also subject to a period of public comment and review, and
the final CTG categories and VOC limits were revised after proposal to
reflect the EPA's analysis of those comments on the proposed CTG.
    In this action, we are proposing to establish standards for
specialty coatings. Based on a MACT analysis for specialty coatings, we
are proposing to require aerospace manufacturing and rework specialty
coating application operations to achieve organic HAP content limits
that are equivalent to the VOC content limits for specialty coatings
included in the Aerospace CTG. As discussed previously in section
IV.E.1 of this preamble, the Aerospace CTG may be adopted by state and
local agencies in nonattainment areas to assist them in meeting their
state implementation plan requirements. Of the 109 facilities that
reported the use of specialty coatings, 35 are in nonattainment areas
and likely currently complying with the specialty coating limits in the
Aerospace CTG. The remaining facilities would need to take action to
comply with the specialty coating application operations limits.
    In the MACT analysis for specialty coatings, the EPA considered
data provided in response to a comprehensive information collection
request (ICR) sent out in February 2011 and consulted the EPA's RACT/
BACT/LAER Clearinghouse, the California Statewide Best Available
Control Technology (BACT) Clearinghouse and regional and state
regulations for sources of data on control technologies and
limitations. We reviewed state rules to compare the VOC limits in those
rules to the VOC limits in the Aerospace CTG. This review of state
rules was in addition to a review of the database of responses to the
2011 ICR and the RBLC for information on add-on control technology or
other equipment, work practices and procedures and process changes or
pollution prevention alternatives not identified and considered during
development of the Aerospace CTG, or improvements in the same since the
CTG development. A brief summary of the EPA's findings in conducting
its MACT analysis of specialty coating application operations follows.
For a detailed discussion of the EPA's findings, refer to the
memorandum, Maximum Achievable Control Technology for Specialty Coating
Operations in the Aerospace Source Category, January 2015, available in
the docket for this action.
    For specialty coatings, where there were sufficient data, the EPA
compared the emissions for the best performing coatings with the
Aerospace CTG limits. The results of this comparison showed that the
CTG VOC limits were equivalent in performance to the best performing
specialty coating. Therefore, we determined that the current Aerospace
CTG limits represent MACT for specialty coatings.
    Based on the results of the MACT analysis, we determined that the
VOC limits in the Aerospace CTG for specialty coatings are currently
being achieved by about half of all operating sources subject to the
Aerospace NESHAP. The facilities complying with the CTG limits for
specialty coatings are located in ozone non-attainment areas where
state VOC rules have been developed based on the Aerospace CTG. From
our review of industry responses to the 2011 ICR, we determined that
some facilities complying with these state VOC limits employ use of
add-on control devices to reduce organic HAP emissions (i.e., thermal
oxidizers and carbon adsorbers); however, these add-on controls are not
widely used in the source category. Other facilities achieve equivalent
emission reductions without add-on controls by using coatings that meet
the VOC content limits.
    Based on our review of state and regional regulations for specialty
coating operations in the aerospace industry, we identified several
cases in which limits are specified for certain specialty coating
categories that are lower than the VOC content limits for the same
specialty coating categories in the Aerospace CTG. These differences
generally affect about one-quarter of the specialty coating categories
(although each state or regional regulation may differ from the CTG in
only a handful of categories), and the limits differ by less than 200
grams VOC per liter of coating. However, these state and regional rules
and the Aerospace CTG differ in certain ways, such that the lower VOC
limits in the state and regional rules do not represent a more
stringent limit as compared to the Aerospace CTG.
    First, in many cases where a state rule has a lower VOC limit than
the CTG, the state rule has also added coating categories with VOC
limits equal to or higher than the CTG limits. For example, one state
rule has a lower limit for fuel tank coatings, but has an additional
category for ``rapid cure'' fuel tank coatings that is the same as the
CTG VOC limit.
    Second, not all categories of specialty coatings are used at all
Aerospace Manufacturing and Rework Facilities. For the specialty
categories with more stringent VOC limits, the EPA does not have data
to confirm that facilities exist in those jurisdictions that are using
those coatings and actually have to comply with the more stringent VOC
limits. These data on facilities actually using coatings subject to
these more stringent limits would be needed to confirm that these more
stringent limits constitute the MACT floor according to section
112(d)(3) of the CAA.
    Finally, many of the areas with more stringent VOC limits than in
the CTG have climates that are warmer and drier than in most other
parts of the United States, and this type of climate is more conducive
to the use of low-VOC coatings because it helps promote expeditious
curing of the coatings under ambient conditions. In cooler and more
humid areas, the coatings require the use of a solvent carrier and/or
thermal curing. The Aerospace NESHAP and CTG, on the other hand, must
establish HAP and VOC limits that are applicable across the United
States. It is not practical to establish MACT limits for coatings based
on regional climate differences for this source category.

    Based on the issues noted above, the EPA concludes that the noted
differences between the state and regional rules and the Aerospace CTG
limits do not constitute more stringent limits compared to those in the
Aerospace CTG. The EPA does not have sufficient data to determine
whether these differences in VOC limits, compared to the limits in the
Aerospace CTG, actually constitute MACT. Therefore, the EPA is
specifically soliciting comment and additional data on the differences
noted between state and regional rules and the aerospace CTG.
    Based on its analysis, the EPA is proposing the MACT floor for
specialty coatings to be organic HAP content limits equal to the VOC
limits specified in the Aerospace CTG for specialty coatings.
Additionally, the low-volume exemption provisions in the current
Aerospace NESHAP for primers, topcoats and chemical milling maskants
may be used for specialty coatings. The EPA has not identified any
options more stringent than the MACT floor as documented in the review
of specialty coatings discussed earlier in this section, so the
proposed organic HAP content limits are equal to the MACT floor VOC
content limits. The EPA is proposing this MACT floor based on the fact
that these VOC limits are currently being achieved by at least 12
percent of the operating facilities in a total population of 109
operating aerospace and rework facilities that reported using specialty
coatings in the 2011 ICR. For more information on the MACT floor
analysis, please refer to the memorandum, Maximum Achievable Control
Technology for Specialty Coating Operations in the Aerospace Source
Category, January 2015, available in the docket for this action.
    In reviewing the state and district VOC rules, the EPA determined
that the aerospace surface coating rules in many of the California
district rules, in addition to the requirement to meet VOC limits,
require that all spray-applied coating operations use high-efficiency
application equipment (i.e., HVLP, electrostatic spray or an
equivalent). This requirement is more stringent than the model rule
found in the Aerospace CTG, which exempts specialty coatings from the
requirement to use high-efficiency application equipment. The
California rules examined by the EPA require the use of high-efficiency
application equipment for all spray applied coatings, unless an add-on
control system was used, or certain other exemptions apply. Other state
rules that follow the CTG require high-efficiency application methods
only for primer and topcoat application operations. The facilities
located in California that are required to use high-efficiency
application equipment for specialty coatings constitute the MACT floor
for the application of these coatings. This determination is based on
the fact that at least 11 facilities in California's air pollution
control districts are currently subject to district rules that require
high-efficiency application equipment for all coating operations,
including specialty coatings. Therefore, the EPA is proposing that
specialty coatings be subject to the same application requirements in
40 CFR 63.745(f) as primers and topcoats. Compared to conventional
spray application methods, high-efficiency application methods, such as
HVLP spray guns or electrostatic deposition, can achieve HAP and VOC
emission reductions because of reduced coating consumption that results
from reduced coating overspray. The EPA has not identified any control
options more stringent than the use of high-efficiency application
methods for spray-applied coating operations.
    In our review of the RBLC, we did not identify any control options
for aerospace specialty surface coating operations that were not
already reflected in the VOC content limits in the Aerospace CTG.
However, we identified one facility in the state of Washington for
which a BACT analysis was completed in September 2014, for constructing
new buildings needed for producing new models of large commercial
airplanes, including the building and surface coating of composite
aircraft wings. The BACT analysis described the facility as currently
using HVLP spraying and electrostatic airless and modified high-
efficiency air-assisted airless spray equipment in all spray applied
surface coating operations. The BACT analysis concluded that there were
no demonstrations of add-on controls at facilities performing surface
coating comparable to large commercial aircraft wing components.
    In our review of Washington State's record of permits, we
determined that the current PSD permit for this facility identified
BACT for VOC from coating operations to be the equivalent of complying
with ``all applicable VOC emission standards of the Aerospace NESHAP.''
The PSD permit for the facility did not consider add-on control
technologies to be BACT after taking into account energy, environmental
and economic impacts. Based on this information from the RBLC and the
Washington State BACT analysis, we determined that add-on control
techniques would not be MACT for specialty coating application
operations for the aerospace industry.
    Instead, MACT is being proposed as the use of low-HAP coatings
(with HAP content limits equal to the VOC content limits in the
Aerospace CTG) and high-efficiency application methods for spray-
applied coating operations. As the EPA did with primers and top coats
in the current NESHAP, the EPA is proposing to use VOC limits that are
currently in effect as the basis for proposed organic HAP limits.
    The EPA is also proposing to establish MACT to limit emissions of
inorganic HAP from spray-applied specialty coatings that contain
inorganic HAP. The predominant method used to control inorganic HAP
emissions from all spray-applied coating operations (including
specialty coatings) is the use of a spray booth with a particulate
filter, which generally achieves a high (i.e., greater than 99 percent)
control efficiency. The Aerospace NESHAP currently requires the use of
spray booths with filters meeting minimum efficiency requirements for
the spray application of primers and topcoats that contain inorganic
HAP. Based on the results of the 2011 ICR, the EPA has determined that
the vast majority of spray-applied specialty coatings are currently
applied in spray booths. It is likely that these specialty coatings are
applied in the same spray booths as primers and topcoats, or at least
in spray booths that are very similar to those used for primer and
topcoat operations. Therefore, the same inorganic HAP emission
limitations that are applied to primer and topcoat operations should
also be applicable to specialty coating operations, and the EPA is
proposing to extend these limitations to specialty coating operations.
The EPA has not identified any control options more stringent than the
use of spray booths with high-efficiency filters to control inorganic
HAP emissions from spray-applied coating operations.
    In summary, the EPA is proposing to add a requirement to the
Aerospace NESHAP that Aerospace Manufacturing and Rework Facilities
comply with organic HAP or VOC content limits for specialty coatings
that are equal to the VOC content limits specified in the Aerospace
CTG. The EPA is also proposing that specialty coating application
operations be subject to the same application equipment requirements in
40 CFR 63.745(f), and the standards for inorganic HAP emissions in 40
CFR 63.745(g) that apply to primer and topcoat application operations.
We request comment on our analysis and supporting info on any

other practices that may be used to limit emissions from specialty
coatings.
    The EPA believes that the proposed HAP and VOC content limits for
specialty coatings are achievable because they are based on the VOC
content limits in the Aerospace CTG, which have been adopted in many
state and local VOC rules. In the development of these proposed
amendments, the EPA made repeated efforts to reach out to and solicit
input from aerospace manufacturers on the coating performance and
reformulation challenges, if any, presented by complying with specialty
coating limits based on the current CTG. However, the information
presented so far has been only anecdotal, and not for the full range of
specialty coating categories in the CTG.
    Therefore, the EPA is specifically soliciting comment and
additional data on any changes needed to the definitions of specialty
coating categories and the proposed organic HAP and VOC limits. The EPA
will consider comments on changes to the definitions of specialty
coating categories that may be needed to clarify the scope of each of
the individual specialized coating categories, based on industry
experience, including complying with those categories in rules derived
from the Aerospace CTG. The EPA will consider data and information on
specific cases (not just general examples) of specialty coatings that
could not meet the current definitions of the specialty coating
categories or the proposed organic HAP or VOC content limits for those
categories. Please provide with your comments information on the
following: The annual volume of the coating used, the container size,
the container type, the military specification or FAA AD that applies,
the specialty category that applies, documentation of the organic HAP
or VOC content of the coating and suggested changes to category
definitions (if applicable and feasible) that would include the coating
in a more appropriate category with a higher HAP or VOC limit. The EPA
will consider any submitted data that supports a comment that a
specific coating cannot meet the proposed organic HAP or VOC content
limit for a particular specialty coating category.
    The estimated costs, emission reductions, other (non-air)
environmental impacts and energy impacts associated with the proposed
regulation of specialty coatings are presented in section V of this
preamble.
2. Electronic Reporting Requirements
    In this proposal, the EPA is describing a process to increase the
ease and efficiency of performance test data submittal while improving
data accessibility. Specifically, the EPA is proposing that owners and
operators of Aerospace Manufacturing and Rework Facilities submit
electronic copies of required performance test and performance
evaluation reports by direct computer-to-computer electronic transfer
using EPA-provided software. The direct computer-to-computer electronic
transfer is accomplished through the EPA's Central Data Exchange (CDX)
using the Compliance and Emissions Data Reporting Interface (CEDRI).
The CDX is the EPA's portal for submittal of electronic data. The EPA-
provided software is called the Electronic Reporting Tool (ERT), which
is used to generate electronic reports of performance tests and
evaluations. The ERT generates an electronic report package which will
be submitted using the CEDRI. The submitted report package will be
stored in the CDX archive (the official copy of record) and the EPA's
public database called WebFIRE. The WebFIRE database was constructed to
store performance test data for use in developing emissions factors.
All stakeholders would have access to all reports and data in WebFIRE
and accessing these reports and data will be very straightforward and
easy (see the WebFIRE Report Search and Retrieval link at http://cfpub.epa.gov/webfire/index.cfm?action=fire.searchERTSubmission). A
description of the WebFIRE database is available at http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main. A description of the
ERT and instructions for using ERT can be found at http://www.epa.gov/ttn/chief/ert/ert_tool.html. CEDRI can be accessed through the CDX Web
site (www.epa.gov/cdx).
    The proposal to submit performance test data electronically to the
EPA would apply only to those performance tests conducted using test
methods that will be supported by the ERT. The ERT contains a specific
electronic data entry form for most of the commonly used EPA reference
methods. A listing of the pollutants and test methods supported by the
ERT is available at http://www.epa.gov/ttn/chief/ert/index.html. We
believe that industry would benefit from this proposed approach to
electronic data submittal. Specifically, by using this approach,
industry would save time in the performance test submittal process.
Additionally, the standardized format that the ERT uses allows sources
to create a more complete test report resulting in less potential
failure to include all data elements required to be submitted. Also
through this proposal, industry may only need to submit a report once
to meet the requirements of the applicable subpart because stakeholders
can readily access these reports from the WebFIRE database. This also
would benefit industry by cutting back on recordkeeping costs as the
performance test reports that are submitted to the EPA using CEDRI are
no longer required to be retained in hard copy, thereby reducing staff
time needed to coordinate these records. Another benefit to industry is
that, because the EPA would already have performance test data in hand,
industry would be subject to fewer or less substantial data collection
requests from EPA in conjunction with required future residual risk
assessments or technology reviews. This would result in a decrease in
industry staff time needed to respond to data collection requests.
    State, local and tribal air pollution control agencies (S/L/Ts) may
also benefit from having electronic versions of the reports they are
now receiving. For example, S/L/Ts may be able to conduct a more
streamlined and accurate review of electronic data submitted to them.
The ERT would allow for an electronic review process, rather than a
manual data assessment, which will make review and evaluation of the
source provided data and calculations easier and more efficient. In
addition, the public will benefit from electronic reporting of
emissions data because the electronic data will be easier for the
public to access. How the air emissions data are collected, accessed
and reviewed will be more transparent for all stakeholders.
    Further, the EPA must have performance test data to conduct
effective reviews of CAA sections 112 and 129 standards, as well as for
many other purposes including compliance determinations, emissions
factor development and annual emissions rate determinations. In
conducting these required reviews, the EPA has found it ineffective and
time consuming, not only for the EPA, but also for regulatory agencies
and source owners and operators, to locate, collect and submit
performance test data because of varied locations for data storage and
varied data storage methods. In recent years, though, stack testing
firms have typically collected performance test data in electronic
format, making it possible to move to an electronic data submittal
system that would increase the ease and efficiency of data submittal
and improve data accessibility.

    One major advantage of the proposed submittal of performance test
data through the ERT is a standardized method to compile and store much
of the documentation required to be reported by this rule. Another
advantage is that the ERT clearly states what testing information would
be required. Another important proposed benefit of submitting these
data to the EPA at the time the source test is conducted is that it
should substantially reduce the effort involved in data collection
activities in the future. When the EPA has performance test data in
hand, the EPA will be able to conduct fewer or less substantial data
collection requests in conjunction with future required residual risk
assessments or technology reviews. This would result in a reduced
burden on both affected facilities (in terms of reduced staff time to
respond to data collection requests) and the EPA (in terms of preparing
and distributing data collection requests and assessing the results).
    Finally, another benefit of the proposed data submittal to WebFIRE
electronically is that these data would greatly improve the overall
quality of existing and new emissions factors by supplementing the pool
of emissions test data for establishing emissions factors and by
ensuring that the factors are more representative of current industry
operational procedures. A common complaint heard from industry and
regulators is that emissions factors are outdated or not representative
of a particular source category. With timely receipt and incorporation
of data from most performance tests, the EPA would be able to ensure
that emissions factors, when updated, represent the most current range
of operational practices.
    In summary, in addition to supporting regulation development,
control strategy development and other air pollution control
activities, having an electronic database populated with performance
test data would save industry, state, local, tribal agencies and the
EPA significant time, money and effort while also improving the quality
of emissions inventories and, as a result, air quality regulations.
3. Startup, Shutdown and Malfunction Requirements
    In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C.
Cir. 2008), cert. denied, 130 S. Ct. 1735 (U.S. 2010), the United
States Court of Appeals for the District of Columbia Circuit vacated
portions of two provisions in the EPA's CAA section 112 regulations
governing the emissions of HAP during periods of SSM. Specifically, the
court vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and
(h)(1), holding that under section 302(k) of the CAA, emissions
standards or limitations must be continuous in nature and that the SSM
exemption violates the CAA's requirement that some section 112
standards apply continuously.
    We are proposing the elimination of the SSM exemption in this rule.
Consistent with Sierra Club v. EPA, we are proposing changes so that
standards in this rule would apply at all times. We are also proposing
several revisions to Table 1 to subpart GG of Part 63 (the General
Provisions Applicability Table, hereafter referred to as the ``General
Provisions table'') as explained in more detail below. For example, we
are proposing to eliminate the incorporation of the General Provisions'
requirement that the source develop an SSM plan. We also are proposing
to eliminate and revise certain recordkeeping and reporting
requirements related to the SSM exemption as further described below.
    The EPA has attempted to ensure that the provisions we are
proposing to eliminate are inappropriate, unnecessary or redundant in
the absence of the SSM exemption. We are specifically seeking comment
on whether we have successfully done so.
    In proposing the standards in this rule, the EPA has taken into
account startup and shutdown periods and, for the reasons explained
below, has not proposed alternate standards for those periods.
    Periods of startup, normal operations and shutdown are all
predictable and routine aspects of a source's operations. Malfunctions,
in contrast, are neither predictable nor routine. Instead they are, by
definition sudden, infrequent and not reasonably preventable failures
of emissions control, process or monitoring equipment. The EPA
interprets CAA section 112 as not requiring emissions that occur during
periods of malfunction to be factored into development of CAA section
112 standards. Under section 112, emissions standards for new sources
must be no less stringent than the level ``achieved'' by the best
controlled similar source and, for existing sources, generally must be
no less stringent than the average emission limitation ``achieved'' by
the best performing 12 percent of sources in the category. There is
nothing in section 112 that directs the agency to consider malfunctions
in determining the level ``achieved'' by the best performing sources
when setting emission standards. As the D.C. Circuit has recognized,
the phrase ``average emissions limitation achieved by the best
performing 12 percent of'' sources ``says nothing about how the
performance of the best units is to be calculated.'' Nat'l Ass'n of
Clean Water Agencies v. EPA, 734 F.3d 1115, 1141 (D.C. Cir. 2013).
While the EPA accounts for variability in setting emissions standards,
nothing in CAA section 112 requires the agency to consider malfunctions
as part of that analysis. A malfunction should not be treated in the
same manner as the type of variation in performance that occurs during
routine operations of a source. A malfunction is a failure of the
source to perform in a ``normal or usual manner'' and no statutory
language compels the EPA to consider such events in setting CAA section
112 standards.
    Further, accounting for malfunctions in setting emission standards
would be difficult, if not impossible, given the myriad different types
of malfunctions that can occur across all sources in the category and
given the difficulties associated with predicting or accounting for the
frequency, degree and duration of various malfunctions that might
occur. As a result, the performance of units that are malfunctioning is
not ``reasonably'' foreseeable. See, e.g. Sierra Club v. EPA, 167 F.3d
658, 662 (D.C. Cir. 1999) (``The EPA typically has wide latitude in
determining the extent of data-gathering necessary to solve a problem.
We generally defer to an agency's decision to proceed on the basis of
imperfect scientific information, rather than to `invest the resources
to conduct the perfect study.' '') See also, Weyerhaeuser v. Costle,
590 F.2d 1011, 1058 (D.C. Cir. 1978) (``In the nature of things, no
general limit, individual permit, or even any upset provision can
anticipate all upset situations. After a certain point, the
transgression of regulatory limits caused by `uncontrollable acts of
third parties,' such as strikes, sabotage, operator intoxication or
insanity and a variety of other eventualities, must be a matter for the
administrative exercise of case-by-case enforcement discretion, not for
specification in advance by regulation.''). In addition, emissions
during a malfunction event can be significantly higher than emissions
at any other time of source operation. For example, if an air pollution
control device with 99-percent removal goes off-line as a result of a
malfunction (as might happen if, for example, the bags in a baghouse
catch fire) and the emission unit is a steady-state type unit that
would take days to shut down, the source would go from 99-percent
control to zero control until the control device was repaired. The
source's emissions during the malfunction

would be 100 times higher than during normal operations and the
emissions over a 4-day malfunction period would exceed the annual
emissions of the source during normal operations. As this example
illustrates, accounting for malfunctions could lead to standards that
are not reflective of (and significantly less stringent than) levels
that are achieved by a well-performing non-malfunctioning source. It is
reasonable to interpret CAA section 112 to avoid such a result. The
EPA's approach to malfunctions is consistent with CAA section 112 and
is a reasonable interpretation of the statute.
    In the event that a source fails to comply with the applicable CAA
section 112 standards as a result of a malfunction event, the EPA would
determine an appropriate response based on, among other things, the
good faith efforts of the source to minimize emissions during
malfunction periods, including preventative and corrective actions, as
well as root cause analyses to ascertain and rectify excess emissions.
The EPA would also consider whether the source's failure to comply with
the CAA section 112 standard was, in fact, sudden, infrequent, not
reasonably preventable and was not instead caused in part by poor
maintenance or careless operation.
    If the EPA determines that an enforcement action against a source
for violation of an emission standard is warranted, the source can
raise any and all defenses in that enforcement action and the federal
district court will determine what, if any, relief is appropriate. The
same is true for citizen enforcement actions. Similarly, the presiding
officer in an administrative proceeding can consider any defense raised
and determine whether administrative penalties are appropriate.
    In summary, the EPA interpretation of the CAA and, in particular,
CAA section 112 is reasonable and encourages practices that will avoid
malfunctions. Administrative and judicial procedures for addressing
exceedances of the standards fully recognize that violations may occur
despite good faith efforts to comply and can accommodate those
situations.
    In several prior CAA section 112 rules, the EPA had included an
affirmative defense to civil penalties for violations caused by
malfunctions in an effort to create a system that incorporates some
flexibility, recognizing that there is a tension, inherent in many
types of air regulation, to ensure adequate compliance while
simultaneously recognizing that despite the most diligent of efforts,
emission standards may be violated under circumstances entirely beyond
the control of the source. Although the EPA recognized that its case-
by-case enforcement discretion provides sufficient flexibility in these
circumstances, it included the affirmative defense to provide a more
formalized approach and more regulatory clarity. See Weyerhaeuser Co.
v. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 1978) (holding that an
informal case-by-case enforcement discretion approach is adequate); but
see Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 (9th Cir. 1977)
(requiring a more formalized approach to consideration of ``upsets
beyond the control of the permit holder''). Under the EPA's regulatory
affirmative defense provisions, if a source could demonstrate in a
judicial or administrative proceeding that it had met the requirements
of the affirmative defense in the regulation, civil penalties would not
be assessed. Recently, the United States Court of Appeals for the
District of Columbia Circuit vacated an affirmative defense in one of
the EPA's CAA section 112 regulations. NRDC v. EPA, 749 F.3d 1055 (D.C.
Cir., 2014) (vacating affirmative defense provisions in CAA section 112
rule establishing emission standards for Portland cement kilns). The
court found that the EPA lacked authority to establish an affirmative
defense for private civil suits and held that under the CAA, the
authority to determine civil penalty amounts in such cases lies
exclusively with the courts, not the EPA. Specifically, the court
found: ``As the language of the statute makes clear, the courts
determine, on a case-by-case basis, whether civil penalties are
`appropriate.''' See NRDC, 2014 U.S. App. LEXIS 7281 at *21 (``[U]nder
this statute, deciding whether penalties are `appropriate' in a given
private civil suit is a job for the courts, not EPA.'').\36\ In light
of NRDC, the EPA is not including a regulatory affirmative defense
provision in the proposed rule. As explained above, if a source is
unable to comply with emissions standards as a result of a malfunction,
the EPA may use its case-by-case enforcement discretion to provide
flexibility, as appropriate. Further, as the United States Court of
Appeals for the District of Columbia Circuit recognized, in an EPA or
citizen enforcement action, the court has the discretion to consider
any defense raised and determine whether penalties are appropriate. Cf.
NRDC, 2014 U.S. App. LEXIS 7281 at *24 (arguments that violation were
caused by unavoidable technology failure can be made to the courts in
future civil cases when the issue arises). The same is true for the
presiding officer in EPA administrative enforcement actions.\37\
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    \36\ The court's reasoning in NRDC v. EPA focuses on civil
judicial actions. The Court noted that ``EPA's ability to determine
whether penalties should be assessed for Clean Air Act violations
extends only to administrative penalties, not to civil penalties
imposed by a court.'' Id.
    \37\ Although the NRDC v. EPA case does not address the EPA's
authority to establish an affirmative defense to penalties that is
available in administrative enforcement actions, the EPA is not
including such an affirmative defense in the proposed rule. As
explained above, such an affirmative defense is not necessary.
Moreover, assessment of penalties for violations caused by
malfunctions in administrative proceedings and judicial proceedings
should be consistent. CF. CAA section 113(e) (requiring both the
Administrator and the court to take specified criteria into account
when assessing penalties).
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a. 40 CFR 63.743(e) General Duty
    We are proposing to revise the entry in the General Provisions
table for 40 CFR 63.6(e)(1)(i) by changing the ``yes'' in column 2 to a
``no.'' Section 63.6(e)(1)(i) describes the general duty to minimize
emissions. Some of the language in that section is no longer necessary
or appropriate in light of the elimination of the SSM exemption. We are
proposing instead to add general duty regulatory text at 40 CFR
63.743(e) that reflects the general duty to minimize emissions while
eliminating the reference to periods covered by an SSM exemption. The
current language in 40 CFR 63.6(e)(1)(i) characterizes what the general
duty entails during periods of SSM. With the elimination of the SSM
exemption, there is no need to differentiate between normal operations,
startup and shutdown and malfunction events in describing the general
duty. Therefore the language the EPA is proposing for 40 CFR 63.743(e)
does not include that language from 40 CFR 63.6(e)(1).
    We are also proposing to revise the General Provisions table entry
for 40 CFR 63.6(e)(1)(ii) by changing the ``yes'' in column 2 to a
``no.'' Section 63.6(e)(1)(ii) imposes requirements that are not
necessary with the elimination of the SSM exemption or are redundant
with the general duty requirement being added at 40 CFR 63.743(e).
b. SSM Plan
    We are proposing to revise the General Provisions table entry for
40 CFR 63.6(e)(3) by changing the ``yes'' in column 2 to a ``no.''
Generally, these paragraphs require development of an SSM plan and
specify SSM recordkeeping and reporting requirements related to the SSM
plan. As noted, the EPA is proposing to remove the SSM exemptions.
Therefore, affected units will be subject to an

emission standard during such events. The applicability of a standard
during such events will ensure that sources have ample incentive to
plan for and achieve compliance and, thus, the SSM plan requirements
are no longer necessary.
c. Compliance With Standards
    We are proposing to revise the General Provisions table entry for
40 CFR 63.6(f)(1) by changing the ``yes'' in column 2 to a ``no.'' The
current language of 40 CFR 63.6(f)(1) exempts sources from non-opacity
standards during periods of SSM. As discussed above, the court in
Sierra Club v. EPA vacated the exemptions contained in this provision
and held that the CAA requires that some CAA section 112 standards
apply continuously. Consistent with Sierra Club, the EPA is proposing
to revise some standards in this rule to apply at all times.
d. 40 CFR 63.749(j) Performance Testing
    We are proposing to revise the General Provisions table entry for
40 CFR 63.7(e)(1) by changing the ``yes'' in column 2 to a ``no.''
Section 63.7(e)(1) describes performance testing requirements. The EPA
is instead proposing to add a performance testing requirement at 40 CFR
63.749(j). The performance testing requirements we are proposing to add
differ from the General Provisions performance testing provisions in
several respects. The regulatory text does not include the language in
40 CFR 63.7(e)(1) that restated the SSM exemption and language that
precluded startup and shutdown periods from being considered
``representative'' for purposes of performance testing. The proposed
performance testing provisions will specify that performance testing of
controls must be conducted during representative operating conditions
of the applicable source, and may not take place during startup,
shutdown or malfunction of the applicable controlled surface coating
operations, controlled chemical milling maskant application operations
or controlled chemical depainting operations. As in 40 CFR 63.7(e)(1),
performance tests conducted under this subpart should not be conducted
during malfunctions because conditions during malfunctions are often
not representative of normal operating conditions. The EPA is proposing
to add language that requires the owner or operator to record the
process information that is necessary to document operating conditions
during the test and include in such record an explanation to support
that such conditions represent normal operation. Section 63.7(e)
requires that the owner or operator make available to the Administrator
such records ``as may be necessary to determine the condition of the
performance test'' available to the Administrator upon request, but
does not specifically require the information to be recorded. The
regulatory text the EPA is proposing to add to this provision builds on
that requirement and makes explicit the requirement to record the
information.
e. Monitoring
    We are proposing to revise the General Provisions table entry for
40 CFR 63.8(c)(1)(i) and (iii) by changing the ``yes'' in column 2 to a
``no.'' The cross-references to the general duty and SSM plan
requirements in those subparagraphs are not necessary in light of other
requirements of 40 CFR 63.8 that require good air pollution control