sampling and analysis is performed to demonstrate that the process
equipment does not meet the definition of being in ethylene oxide
service. We are proposing sampling and analysis procedures at 40 CFR
63.2492. Examples of information that could suggest ethylene oxide is
present in a process stream include calculations based on safety data
sheets, material balances, process stoichiometry, or previous test
results provided the results are still relevant to the current
operating conditions.
    Based on the proposed applicability thresholds, we expect that
eight facilities will be affected by the proposed ethylene oxide-
specific standards. Five of these eight facilities will be subject to
the process vent and/or storage tank provisions; specifically, three
facilities have process vents in ethylene oxide service and three
facilities have storage tanks in ethylene oxide service. All eight
facilities are expected to be subject to the equipment leak provisions.
    To reduce risks from process vents in ethylene oxide service, we
are proposing to either reduce emissions of ethylene oxide by (1)
venting emissions through a closed-vent system to a control device that
reduces ethylene oxide by greater than or equal to 99.9 percent by
weight, or to a concentration less than 1 ppmv for each process vent,
or to less than 5 pounds per year for all combined process vents; or
(2) venting emissions through a closed-vent system to a flare meeting
the proposed flare operating requirements discussed in section IV.A.1
of this preamble. To reduce risks from storage tanks in ethylene oxide
service, we are proposing to either reduce emissions of ethylene oxide
by (1) venting emissions through a closed-vent system to a control
device that reduces ethylene oxide by greater than or equal to 99.9
percent by weight or to a concentration less than 1 ppmv for each
storage tank vent; or (2) venting emissions through a closed-vent
system to a flare meeting the proposed flare operating requirements
discussed in section IV.A.1 of this preamble. Additionally, we propose
removing the option to allow use of a design evaluation in lieu of
performance testing to demonstrate compliance for both process vents
and storage tanks in ethylene oxide service to ensure that the required
level of control is achieved. We are also proposing that after
promulgation of the rule, owners or operators that choose to control
emissions with a non-flare control device conduct an initial
performance test according to 40 CFR 63.997 and 40 CFR 63.2450(g) on
each existing control device in ethylene oxide service and on each
newly installed control device in ethylene oxide service to verify
performance at the required level of control. Subsequently, we propose
that owners or operators conduct periodic performance testing on non-
flare control devices in ethylene oxide service every 5 years.
    As previously stated, we are aware that MON facilities with
ethylene oxide emissions from process vents and storage tanks commonly
use scrubbers to control emissions. Based on our knowledge of these
scrubbers, there is a difference in how these scrubbers operate in
order to achieve high control efficiencies versus how a normal wet
scrubber operates. The higher removal efficiency of ethylene oxide in
these scrubbers is based on the absorption of ethylene oxide into the
scrubber water and then conversion of ethylene oxide to ethylene
glycol. This conversion is dependent on several factors--maintaining an
acid environment to catalyze the reaction and having enough residence
time in the scrubber for the reaction to occur. We are proposing
continuous monitoring of operating parameters for these scrubbers to
ensure that the factors needed for the reaction to occur are met,
namely liquid-to-gas ratio, pressure drop across the scrubber, liquid
feed pressure, liquid temperature, and pH. However, we are aware that
several other parameters may also be important to monitor, such as
maximum liquid flow rate, tank levels for the reactant and solution
feed tanks, and ethylene glycol content of the tanks. We are requesting
comment on the operating parameters we have proposed for these
scrubbers and whether these additional operating parameters are
necessary, and if so, how these parameter limits should be set and at
what frequency they should be monitored.
    To reduce risks from equipment leaks, we identified two options
that we are co-proposing for controlling emissions from MON equipment
in ethylene oxide service, referred to here as equipment leak Control
Option 1 and equipment leak Control Option 2. These two co-proposed
options, presented in Table 6 and summarized here, provide a level of
control beyond what is being proposed in the technology review for all
MON equipment in HAP service.
    In equipment leak co-proposed Control Option 1, we are proposing
that all light liquid pumps in ethylene oxide service be monitored
monthly at a leak definition of 1,000 ppm, and when a leak is detected,
it be repaired as soon as practicable, but not later than 15 calendar
days after it is detected. Additionally, under co-proposed Control
Option 1, we are proposing that the leak repair exemption available for
pumps at 40 CFR 63.1026(b)(3), 40 CFR 63.163(c)(3), and 40 CFR
65.107(b)(3) would not apply to equipment in ethylene oxide service.
Also, as part of co-proposed Control Option 1, we are proposing that
all gas/vapor and light liquid connectors in ethylene oxide service be
monitored annually at a leak definition of 500 ppm, and when a leak is
detected, it be repaired as soon as practicable, but not later than 15
calendar days after it is detected.
    As an alternative to Control Option 1, we are co-proposing
equipment leak Control Option 2. Under co-proposed Control Option 2, we
are proposing that more stringent equipment leak standards would apply
to the facilities with a MIR greater than 100-in-1 million after
imposition of the proposed standards for process vents and storage
tanks, as determined by this risk analysis (i.e., Lanxess Corporation
and

Huntsman Performance), and detailed in Appendix 10 of the document
titled Residual Risk Assessment for the Miscellaneous Organic Chemical
Manufacturing Source Category in Support of the 2019 Risk and
Technology Review Proposed Rule, which is available in the docket for
this rulemaking. For these two facilities, pumps in ethylene oxide
service would be required to be leakless (i.e., have zero emissions)
and monitored annually to verify there are no emissions. Additionally,
valves in ethylene oxide service would be required to either be
leakless and monitored annually, or not be leakless and be monitored
quarterly. For pumps and valves in ethylene oxide service, equipment is
considered leaking if an instrument reading above background is found.
Furthermore, at the two higher risk facilities with a MIR greater than
100-in-1 million, connectors in ethylene oxide service would be
monitored monthly at a leak definition of 100 ppm. We are proposing
that when a leak is detected, it be repaired as soon as practicable,
but not later than 15 calendar days after it is detected, and a first
attempt at repair be made no later than 5 calendar days after the leak
is detected. As part of co-proposed Control Option 2, all other
facilities with MON equipment in ethylene oxide service would be
subject to the standards previously described in equipment leak co-
proposed Control Option 1.
    We solicit comment on each of the proposed requirements for process
vents, storage tanks, and equipment in ethylene oxide service.

    Table 6--Summary of Equipment Leak Co-Proposed Control Options for MON Facilities Emitting Ethylene Oxide
----------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------
Equipment Leak Control                            Applicability                       Control option description
 Option
----------------------------------------------------------------------------------------------------------------
1..........................  MON equipment in ethylene    Light Liquid Pumps........  Require leak definition of
                              oxide service.                                           1,000 ppm, monthly
                                                                                monitoring.
                                                          Gas/Vapor and Light Liquid  Require leak definition of
                                                           Connectors.                 500 ppm, annual
                                                                                monitoring.
2..........................  MON equipment in ethylene    Light Liquid Pumps........  Require pumps to have zero
                              oxide service at the two    Gas/Vapor and Light Liquid   emissions (e.g.,
                              facilities with cancer       Connectors.                 leakless), annual
                              risks >=100-in-1 million                                 monitoring.
                              (specifically, Lanxess                                  Require leak definition of
                              Corporation and Huntsman                                 100 ppm, monthly
                              Performance).                                            monitoring.
                                                          Gas/Vapor and Light Liquid  Require valves to have
                                                           Valves.                     zero emissions (e.g.,
                                                                                leakless) with annual
                                                                                monitoring or non-
                                                                                leakless with quarterly
                                                                                monitoring.
                             MON equipment in ethylene    Light Liquid Pumps........  Require leak definition of
                              oxide service at all other  Gas/Vapor and Light Liquid   1,000 ppm, monthly
                              facilities (excluding        Connectors.                 monitoring.
                              Lanxess Corporation and                                 Require leak definition of
                              Huntsman Performance).                                   500 ppm, annual
                                                                                monitoring.
----------------------------------------------------------------------------------------------------------------

    Finally, in considering possible control options for equipment
leaks, it is important to understand the uncertainties related to the
modeled ethylene oxide equipment leak emissions. For Lanxess
Corporation, the modeled equipment leak emissions were our best
estimate, using component counts from the facility's title V permit
application and emission factors, and were not based on measured
emissions. Notably, this calculated emission estimate was higher than
what was reported to the 2014 NEI and the 2014 Toxics Release
Inventory. We used the highest emission estimate in our model run to be
conservatively health protective but recognize that this may result in
an overestimation of risk. For Huntsman Performance, the modeled
equipment leak emissions were also our best estimate, using calculated
emissions that were reported to the 2014 NEI, and were also not based
on measured emissions. Although Huntsman Performance did report their
equipment leak emissions, we do not know which components (e.g., pumps,
valves, connectors, etc.) were responsible for these emissions, which
introduces uncertainty regarding the effect that the proposed equipment
leak controls would have on reducing equipment leak emissions. At
Huntsman Performance, we are also aware that the ethylene oxide
equipment leak emissions are not entirely from MON processes; however,
we did not have enough information to distinguish between emissions
attributed to MON processes versus other processes (e.g., 40 CFR part
63, subparts H and PPP). Therefore, the risk for this facility is
likely biased high due to our inability to distinguish between co-
located emissions. For both Lanxess Corporation and Huntsman
Performance, because the ethylene oxide equipment leak emissions were
derived from engineering calculations and are not based on measured
values, there is considerable uncertainty regarding the appropriateness
of the proposed LDAR and control provisions for light liquid pumps,
gas/vapor and light liquid connectors, and gas/vapor and light liquid
valves. As such, modeled risk reductions may not accurately reflect the
actual effects of implementing the proposed controls. Furthermore, we
have limited information regarding the use of leakless valves on
streams that are in ethylene oxide service and, therefore, are
soliciting comment on the applicability of these valves for MON
equipment in ethylene oxide service.
3. Determination of Risk Acceptability
    As noted in sections II.A and III.A of this preamble and in the
Benzene NESHAP, the EPA sets standards under CAA section 112(f)(2)
using a two-step approach, with an analytical first step to determine
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) of
approximately 1 in 10 thousand'' (54 FR 38045, September 14, 1989). A
MIR of 1-in-10,000 (i.e., 100-in-1 million) alone does not constitute a
bright line for making a risk acceptability determination. The level of
the MIR is only one factor weighed in determining acceptability of
risk. As risks increase above this benchmark, they become presumptively
less acceptable under CAA section 112

and are weighed with other health risk measures and information,
including risk estimation uncertainty, in making an overall judgment on
acceptability.
    In some cases, the health risk measures and information taken
together may provide a more realistic description of the magnitude of
risk in the exposed population than that provided by the MIR alone. As
such, we considered the results of the risk assessment (including the
risk estimation uncertainty) and evaluated available control
technologies and other measures (including the controls reviewed under
the technology review) that could be applied to this source category to
reduce the risks due to emissions of ethylene oxide from process vents,
storage tanks, and equipment leaks without considering costs or
technological feasibility. Additionally, as described previously in
section IV.C.2, we are co-proposing two options for control of ethylene
oxide emissions from equipment leaks (e.g., co-proposed Control Options
1 and 2). Therefore, we present the risk impacts using health risk
measures and information, including the MIR, cancer incidence,
population exposed to cancer risks greater than 100-in-1 million, and
associated uncertainty in emissions estimates after incremental
application of controls for storage tanks, process vents, and either
co-proposed equipment leak Control Option 1 or 2, in Table 7 and in the
discussion below.

                                       Table 7--Nationwide Risk Impacts After Implementation of Proposed Controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Population
                                                                       --------------------------------     Cancer
             Control scenario                  MIR (x-in-1 million)        >=1-in-1        >100-in-1       incidence               Uncertainty
                                                                            million         million
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pre-Control Baseline.....................  2,000 (Lanxess, 300               2,900,000          18,000             0.4  ................................
                                            (Huntsman).
+ Storage Tank Controls..................  500 (Lanxess), 300                2,600,000           1,500             0.1  The effect of process vent and
                                            (Huntsman).                                                                  storage tank controls on
                                                                                emissions is well understood
                                                                                and generally certain.
+ Process Vent Controls..................  400 (Lanxess), 300                2,400,000             780             0.1
                                            (Huntsman).
Either, + Equipment Leak Control Option 1  200 (Lanxess), 300                2,300,000             300             0.1  Fugitive emissions estimates are
                                            (Huntsman).                                                                  uncertain and based on
                                                                                engineering calculations.
                                                                                Therefore, there is uncertainty
                                                                                regarding the relevance of the
                                                                                proposed equipment leak
                                                                                controls (Lanxess, Huntsman).
                                                                                Modeled fugitive emissions may
                                                                                be subject to other NESHAP
                                                                                which likely results in an
                                                                                overestimation of risk
                                                                                (Huntsman).
Or, + Equipment Leak Control Option 2....  100 (Lanxess), 200                2,100,000              30             0.1
                                            (Huntsman).
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Although the post-control risks are greater than 100-in-1 million
(i.e., 200 to 300-in-1 million), due to the inherent health protective
nature of our risk assessment methods and the uncertainties in this
assessment, we believe that this risk assessment is more likely to
overestimate rather than underestimate the risks. A brief discussion of
the health protective aspects of the assessment, including
uncertainties in the RTR emissions dataset, dispersion modeling,
inhalation exposure estimates, and dose-response relationships was
covered in section III.C.8. A more thorough discussion of these
uncertainties is included in the Residual Risk Assessment for the
Miscellaneous Organic Chemical Manufacturing Source Category in Support
of the 2019 Risk and Technology Review Proposed Rule, which is
available in the docket for this action.
    We note that the modeled risks due to emissions of ethylene oxide
are sensitive to the URE applied. In this assessment, the modeled risks
are largely driven by use of an EPA URE for ethylene oxide that was
updated in December 2016 (i.e., 5 x 10-3 per ug/m\3\) on the
basis of new human data.34 35 This updated URE is about 60
times greater than the value used previously by EPA in its risk
assessments (i.e., California EPA URE of 8.8 x 10-5 per ug/
m\3\, based on animal data).
---------------------------------------------------------------------------

    \34\ U.S. EPA. Evaluation of the Inhalation Carcinogenicity of
Ethylene Oxide (CASRN 75-21-8) In Support of Summary Information on
the Integrated Risk Information System (IRIS). December 2016. EPA/
635/R-16/350Fa. https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/1025tr.pdf.
    \35\ SAB. (2015). Science Advisory Board Review of the EPA's
Evaluation of the Inhalation Carcinogenicity of Ethylene Oxide:
Revised external review draft--August 2014 [EPA Report]. (EPA-SAB-
15-012). Washington, DC: U.S. EPA, SAB. https://yosemite.epa.gov/
sab/sabproduct.nsf/fedrgstr_activites/
BD2B2DB4F84146A585257E9A0070E655/$File/EPA-SAB-15-012+unsigned.pdf.
---------------------------------------------------------------------------

    The UREs we use in our risk assessments generally provide an upper
bound estimate of risk \36\ to be health protective in light of dose-
response modeling uncertainties. As noted above and in Section
III.C.8.d, there are uncertainties inherent in all risk assessments,
including uncertainties in the development of dose-response values.
Consistent with EPA SAB recommendations,\37\ where a HAP is a risk
driver, as is the case with ethylene oxide for this risk assessment, we
examine the underlying technical information, including sources of risk
estimation uncertainties. To better characterize the risks, we reviewed
EPA's 2016 ethylene oxide dose-response assessment and the
uncertainties in the dose-response relationships.
---------------------------------------------------------------------------

    \36\ IRIS glossary (https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
    \37\ Recommendations of the SAB Risk and Technology Review
Methods Panel are provided in their report, which is available at:
https://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
---------------------------------------------------------------------------

    For the EPA's 2016 ethylene oxide URE, two aspects of uncertainty
stand out as potentially contributing to the conservative (i.e., health
protective) nature of the final 2016 URE. This is documented in the
memorandum titled Sensitivity of Ethylene Oxide Risk Estimates to Dose-
Response Model Selection, which is available in the docket for this
rulemaking, and as discussed further below.

    First, the updated IRIS URE for ethylene oxide is based on the
upper confidence limit on the slope of the dose response curve.
However, according to the 2005 Guidelines for Carcinogen Risk
Assessment, when human data are available, it is reasonable to consider
the central estimate rather than upper confidence limit for a URE.\38\
In the case of ethylene oxide, we do have human health data and,
therefore, it is reasonable to consider the central estimate. The
central estimate of the URE for ethylene oxide is 3 times lower than
the upper confidence limit, as documented in the memorandum titled
Sensitivity of Ethylene Oxide Risk Estimates to Dose-Response Model
Selection, which is available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \38\ Guidelines for Carcinogen Risk Assessment. Risk Assessment
Forum. U.S. EPA. Washington, DC. March 2005.
---------------------------------------------------------------------------

    Second, we note that several dose-response models were considered
during the 2016 IRIS assessment for two types of cancer: Breast cancer
and lymphoid cancer. Considering multiple models ensures the selected
model provides the best fit to the exposure data and helps quantify and
characterize model and statistical uncertainty. The choice of model
also has significant implications for the URE, particularly at the low
end of the dose-response range.
    With regard to lymphoid cancer, the selected model provided the
best fit and satisfied all SAB recommendations.\39\ However, there were
statistical challenges associated with modeling the data. Therefore, in
developing the dose-response value, the EPA considered other lymphoid
cancer models that provided reasonably good fits to the exposure data
and met some, but not all, of the SAB modeling criteria
recommendations. For purposes of characterizing the uncertainty around
the final 2016 IRIS URE, it is useful to consider the extent to which
choosing an alternative lymphoid cancer model would have affected the
value. In fact, one of the alternative lymphoid cancer models evaluated
by the EPA would result in a URE 2 to 3 times lower than the IRIS URE,
as documented in the memorandum titled Sensitivity of Ethylene Oxide
Risk Estimates to Dose-Response Model Selection, which is available in
the docket for this rulemaking.\40\ For breast cancer, there was a high
level of statistical certainty with the model selected, and, therefore,
we did not include alternative models in this uncertainty discussion.
---------------------------------------------------------------------------

    \39\ SAB advice on modeling criteria included (1) the
recommendation to prioritize models with good fits in the low
exposure range (e.g., spline models), (2) preference for using
continuous individual-level exposure data over categorical results,
and (3) selecting models that have a dose-response shape that is
both biologically plausible and consistent with observed data.
    \40\ The memorandum notes that higher estimates of risk were
obtained using other models that statistically fit the data. There
were limitations with these models and they were not considered in
the uncertainty analysis. However, a comprehensive analysis of
alternative models would likely include some risk estimates higher
than the IRIS unit risk.
---------------------------------------------------------------------------

    The EPA concludes that these uncertainties, noted in the 2016 IRIS
assessment, provide important context for interpreting whether risks
remaining post-control can be considered acceptable. In particular, we
note that the central estimate compared to the upper confidence limit
could result in a URE 3 times lower than the IRIS URE and an
alternative dose-response model for lymphoid cancer could result in a
URE 2-3 times lower. While EPA followed SAB recommendations regarding
lymphoid model choice, we acknowledge the uncertainty inherent in this
model selection, which is important for interpreting risk results. In
fact, both the central estimate and an alternative dose-response model
combined could result in a URE 5 times lower. This would reduce
potential post-control risks to 60- to 100-in-1 million (from 200- to
300-in-1 million).
    The updated URE was used in EPA's 2014 National Air Toxics
Assessment (NATA). In September 2018, the ACC submitted a Request for
Correction under the Information Quality Act asking that the ``NATA
risk estimates for E.O.\41\ should be withdrawn and corrected to
reflect scientifically-supportable risk values''.
---------------------------------------------------------------------------

    \41\ In this instance, ``E.O.'' refers to ``ethylene oxide.''
---------------------------------------------------------------------------

    Given the ACC's Request for Correction, in the HCl Production RTR
proposed rule, the EPA requested comment on the use of the updated
ethylene oxide URE for regulatory purposes (84 FR 1584; February 4,
2019). The comment period for the proposed rule closed on April 26,
2019, and the Agency received a number of comments on the updated
ethylene oxide URE and its use for regulatory purposes. Those comments
are included in Docket ID No. EPA-HQ-OAR-2018-0417, and the EPA is
incorporating those comments into the docket for this rulemaking.
Commenters provided comments both in support of and opposed to the 2016
updated URE for ethylene oxide and its use for regulatory purposes. One
commenter noted that the application of the URE would have wide-ranging
implications on regulatory decision making. Commenters supporting the
use of the 2016 updated URE noted that the IRIS assessment for ethylene
oxide used the best available science, underwent review by Agency and
non-Agency experts, as well as public review, and was published in a
peer-reviewed journal. Commenters opposing the use of the 2016 updated
URE noted concerns with the model and variables used to estimate pre-
1978 worker exposure estimates (and suggested an alternative model and
alternative pre-1978 worker exposure estimates that would reflect
higher pre-1978 exposures and affect the final URE), and another
commenter indicated that they are developing their own cancer dose-
response value for ethylene oxide.
    In June 2019, the Texas Commission on Environmental Quality (TCEQ)
issued a draft document for public review (``Ethylene Oxide
Carcinogenic Dose-Response Assessment''), which concluded that
``USEPA's ethylene oxide inhalation URF \42\ is not adequately
supported by scientific data'' and instead proposed a unit risk factor
(URF) of 1.4 x 10-6 per ug/m\3\. Specifically, TCEQ
disagreed with the EPA's model selection as the basis for deriving a
URE. TCEQ highlighted uncertainties in the URE arising from what it
considered to be errors in the assumptions and calculations used to
determine the best model fit of the data. TCEQ's concerns with the
EPA's URE derivation have not been peer reviewed and the public comment
period closed on September 26, 2019.
---------------------------------------------------------------------------

    \42\ In this instance, ``URF'' is intended to be functionally
equivalent to the EPA's unit risk estimate for ethylene oxide.
---------------------------------------------------------------------------

    Because of the robustness of the comments received and their
relevance to this rulemaking, the Agency will consider those comments
in the final rule for the Miscellaneous Organic Chemical Manufacturing
source category. In this proposed rule, we are requesting any
additional comments on the use of the 2016 updated URE for ethylene
oxide for regulatory purposes beyond those already received for the HCl
Production RTR proposed rule (84 FR 1584-1597; February 4, 2019), as
well as comments on the use of an alternative URE for ethylene oxide in
the final rule for this source category. The EPA believes it is
reasonable to assume that, allowing for the uncertainties in the URE,
estimated risks for the Miscellaneous Organic Chemical Manufacturing
source category could be lower, even potentially lower than the 100-in-
1 million benchmark.

    It is also important to note that there is considerable uncertainty
regarding the estimated equipment leak emissions that are responsible
for the remaining modeled risk. As described previously in section
IV.C.2 and summarized here, the estimated ethylene oxide equipment leak
emissions are based on engineering calculations, not actual measured
emissions, and, therefore, it is uncertain whether the proposed
controls are appropriate for the actual source(s) of fugitive emissions
at these facilities. Furthermore, at Lanxess Corporation, a
conservatively high equipment leak emissions estimate was used, and at
Huntsman Performance, equipment leak emissions are also thought to be
overestimated due to knowledge that the modeled emissions are not
entirely from MON equipment. Due to these emissions uncertainties, the
post-control MIRs of 300-in-1 million at Huntsman Performance and 200-
in-1 million at Lanxess Corporation are likely biased high; the actual
MIRs would be expected to be lower at both facilities. Given that the
number of people estimated to have a cancer risk greater than 100-in-1
million would be reduced from 18,000 to 300, the incidence would be
reduced from 0.4 to 0.1, and considering that the MIR is expected to be
lower than 300-in-1 million, we propose that, after application of the
ethylene oxide-specific controls for process vents, storage tanks, and
equipment leak co-proposed Control Option 1, risks would be acceptable.
    Alternatively, additional equipment leak controls (e.g., beyond
equipment leak co-proposed Control Option 1) could be applied to the
two highest risk facilities to further reduce risks. After application
of the ethylene oxide-specific controls for process vents, storage
tanks, and equipment leak co-proposed Control Option 2, ethylene oxide
emissions would be reduced by 94-percent for the source category, the
estimated MIR would be reduced from 2,000-in-1 million to 200-in-1
million at Huntsman Performance and 100-in-1 million at Lanxess
Corporation, the number of people estimated to have a cancer risk
greater than 100-in-1 million would be reduced from 18,000 to 30, and
the incidence would be reduced from 0.4 to 0.1.
    Finally, we note that the proposed control measures provide for a
significant risk reduction. Application of the ethylene oxide-specific
controls for process vents and storage tanks would reduce ethylene
oxide emissions by an estimated 89 percent for the source category, and
the estimated MIR would be reduced from 2,000-in-1 million to 400-in-1
million at Lanxess Corporation, and the next highest estimated MIR
would be 300-in-1 million at Huntsman Performance. In both cases, the
remaining risk is primarily from equipment leak emissions of ethylene
oxide. Subsequent application of equipment leak co-proposed Control
Option 1 would further reduce ethylene oxide emissions by 4 percent,
for a total estimated 93-percent reduction in ethylene oxide emissions
for the source category, with the MIR at Lanxess Corporation being
further reduced to 200-in-1 million and the MIR at Huntsman Performance
remaining at 300-in-1 million.
    In summary, after implementation of the proposed controls for
process vents and storage tanks at MON facilities emitting ethylene
oxide, as well as implementation of either of the co-proposed control
options for equipment leaks, and considering all of the health risk
information and factors discussed above, including the uncertainties
regarding the equipment leak emissions, the uncertainties inherent in
all risk assessments (i.e., the emissions dataset, dispersion modeling,
exposure estimates, and dose-response relationships) and the EPA's use
of the updated URE for ethylene oxide (which is developed to be health
protective but, given uncertainties in the value, could be as much as 5
times lower), the EPA proposes that the resulting risks would be
acceptable for this source category. We are soliciting comment on which
of the two ethylene oxide equipment leak co-proposed control options
should be implemented in the final rulemaking in order to ensure that
risks from the source category are acceptable.
4. Ample Margin of Safety Analysis
    The second step in the residual risk decision framework is
determination of whether the emission standards proposed to achieve an
acceptable risk level would protect public health with an ample margin
of safety, or whether more stringent emission standards would be
required. In making this determination, we considered the estimate of
health risk and other health information, along with additional factors
relating to the appropriate level of control, including costs and
economic impacts of controls, technological feasibility, uncertainties,
and other relevant factors, consistent with the approach of the 1989
Benzene NESHAP. Table 8 of this preamble presents the summary of costs
and ethylene oxide emission reductions we estimated for the proposed
control options. For details on the assumptions and methodologies used
in the costs and impacts analyses, see the technical memoranda titled
Analysis of Control Options for Storage Tanks and Process Vents
Emitting Ethylene Oxide Located in the Miscellaneous Organic Chemical
Manufacturing Source Category and Analysis of Control Options for
Equipment Leaks at Processes that use Ethylene Oxide Located in the
Miscellaneous Organic Chemical Manufacturing Source Category, which are
available in the docket for this rulemaking.

    Table 8--Nationwide Emission Reductions and Cost Impacts of Control Options Considered for Process Vents,
                        Storage Tanks, and Equipment in Ethylene Oxide (EtO) Service \1\
----------------------------------------------------------------------------------------------------------------
                                                                                Cost
                                                   Total capital       Total       EtO emission    effectiveness
                 Control option                     investment      annualized      reductions      ($/ton EtO)
                                                        ($)        costs  ($/yr)     (tpy) \2\          \3\
----------------------------------------------------------------------------------------------------------------
A--Process Vent Controls........................       2,180,000         914,000             1.2         783,000
B--Storage Tank Controls........................         466,000         796,000             8.6          93,100
C--Equipment Leak co-proposed Control Option 1..          76,000          48,000             3.6          13,200
                                                 ---------------------------------------------------------------
    Total (A + B + C)...........................       2,720,000       1,760,000            13.3         132,000
D--Equipment Leak co-proposed Control Option 2..         673,000         148,000             4.5          33,000
                                                 ---------------------------------------------------------------
    Total (A + B + D)...........................       3,320,000       1,860,000            14.2         131,000
----------------------------------------------------------------------------------------------------------------
\1\ Costs are calculated for the year 2016 and assume that a scrubber was installed as the control device.
\2\ Reductions shown are based on model plant emission estimates, not on emissions that were modeled in the risk
  assessment.
\3\ Cost effectiveness presented is without recovery credits, which represent the savings in product that would
  not be lost from equipment leaks.

    For the ample margin of safety analysis, we evaluated the cost and
feasibility of available control technologies that could be applied in
this source category to further reduce the risks (or potential risks)
due to emissions of HAP, considering all of the health risks and other
health information considered in the risk acceptability determination
described above. We note that we did not identify any other controls
for ethylene oxide emission sources so we are considering all the
available options to reduce risk.
    In the case that we apply the process vent, storage tank, and
equipment leak co-proposed Control Option 1 in the first step (i.e.,
determination of acceptable risk), we considered this option as well as
three additional options in the second step to establish an ample
margin of safety. For the three additional options, first, we
considered implementing equipment leak co-proposed Control Option 2,
which would require that the two facilities with cancer risks greater
than 100-in-1 million comply with more stringent standards. Second, we
considered expanding the applicability of equipment leak co-proposed
Control Option 2 so that the more stringent controls would apply to all
facilities with equipment in ethylene oxide service, regardless of
cancer risks. Third, we considered the options identified in the
technology review (i.e., controls to equipment leaks for MON equipment
not in ethylene oxide service and heat exchange systems). The ample
margin of safety analysis for these options is discussed below.
    First, in the case of implementing the ethylene oxide equipment
leak co-proposed Control Option 2, we compared the costs of co-proposed
Control Option 1 to co-proposed Control Option 2 ($76,000 vs. $673,000
total capital investment; $48,000 vs. $148,000 total annualized cost).
From the ethylene oxide equipment leak co-proposed Option 1 to Option
2, the MIR would be reduced from 300-in-1 million to 200-in-1 million,
the population exposed to cancer risks >=1-in-1 million would be
reduced from 2,300,000 to 2,100,000, and the incidence would remain
unchanged at 0.1.
    Second, in the case that we expand the applicability of equipment
leak co-proposed Control Option 2 so that the more stringent controls
would apply to all facilities with equipment in ethylene oxide service,
costs were also found to be considerably higher compared to ethylene
oxide equipment leak co-proposed Control Option 1 ($76,000 vs.
$1,600,000 total capital investment; $48,000 vs. $300,000 total
annualized cost). The estimated ethylene oxide emissions reductions are
5.8 tons per year with a cost effectiveness of $51,000 per ton of
ethylene oxide. The population exposed to cancer risks greater than or
equal to 1-in-1 million would be reduced by 14,000, but there are no
additional reductions in the MIR or incidence when expanding these more
stringent standards to apply to all facilities with equipment in
ethylene oxide service. We solicit comment on whether we should apply
the requirements of equipment leak co-proposed Control Option 2 that
are specific to the two highest risk facilities more broadly, so that
they apply to all facilities with equipment in ethylene oxide service.
    Third, we considered control options identified in the technology
review (section IV.D of this preamble), which apply to all HAP and are
not specific to ethylene oxide. These options include controls for (1)
equipment leaks for MON equipment not in ethylene oxide service
(options 1 through 4), and (2) heat exchangers. For controls for
equipment leaks for MON equipment not in ethylene oxide service (option
1, described in section IV.D.1 of this preamble) and heat exchangers,
while cost-effective, neither lowered the source category MIR,
incidence, or population exposed to cancer risks >=1-in-1 million. For
equipment leak controls for MON equipment not in ethylene oxide
service, options 2, 3, and 4 (described in section IV.D.1 of this
preamble) were not cost-effective and did not reduce the source
category MIR, incidence, or population exposed to risks >=1-in-1
million, with the exception of the equipment leak option 3 controls
which lowered the population exposed to cancer risks >=1-in-1 million
by approximately 250,000 people.
    Based on our ample margin of safety analysis, including all health
information and the associated cost and feasibility as discussed above,
we propose that the requirements that we are proposing to achieve
acceptable risks would also provide an ample margin of safety to
protect public health. We are soliciting comment on which of the
available control options should be applied in order to provide an
ample margin of safety to protect public health.
5. Adverse Environmental Effects
    We do not expect there to be an adverse environmental effect as a
result of HAP emissions from this source category, and 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?

    Sources of HAP emissions regulated by the MON are process vents,
storage tanks, transfer racks, equipment leaks, wastewater streams, and
heat exchange systems. MON processes can either be batch or continuous
operations. Batch operations mean a non-continuous operation involving
intermittent or discontinuous feed into equipment and, in general,
involve the emptying of the equipment after the operation ceases and
prior to beginning a new operation. To inform our technology reviews
for these emissions sources, we reviewed the EPA's Reasonably Available
Control Technology/Best Available Control Technology/Lowest Achievable
Emission Rate (RACT/BACT/LAER) clearinghouse and regulatory development
efforts published after the MON for similar sources. (See the
memorandum titled Review of the RACT/BACT/LAER Clearinghouse Database
for the Miscellaneous Organic Chemical Manufacturing Source Category,
which is available in the docket for this rulemaking.) After reviewing
information from the afore-mentioned sources, we have identified
certain developments in practices, processes, or control technologies
to reduce emissions from some of the sources of HAP emissions regulated
by the MON. We then evaluated the impacts of applying these
developments to the Miscellaneous Organic Chemical Manufacturing source
category and are proposing revisions to the MON for equipment leaks and
heat exchange systems pursuant to CAA section 112(d)(6).
1. Equipment Leaks
    Emissions of HAP (e.g., beyond ethylene oxide) from equipment leaks
occur in the form of gases or liquids that escape to the atmosphere
through many types of connection points (e.g., threaded fittings) or
through the moving parts of certain types of process equipment during
normal operation. Equipment regulated by the MON includes pumps,
compressors, agitators, PRDs, sampling collection systems, open-ended
valves or lines, valves, connectors, and instrumentation systems that
contain or contact material that is 5 percent by weight or more of
organic HAP, operate 300 hours per year or more, and are not in vacuum
service.
    Depending on the type of equipment, the equipment leak requirements
of the MON provide the option of meeting the

control requirements of 40 CFR part 63, subparts H (National Emission
Standards for Organic Hazardous Air Pollutants for Equipment Leaks), or
UU (National Emission Standards for Equipment Leaks--Control Level 2
Standards), or 40 CFR part 65, subpart F (the Consolidated Air Rule for
Equipment Leaks) for existing MON processes and 40 CFR part 63, subpart
UU, or 40 CFR part 65, subpart F, for new MON processes. The equipment
leak requirements vary by equipment (component) type but require LDAR
using monitoring with EPA Method 21 of appendix A-7 to 40 CFR part 60
at certain frequencies (e.g., monthly, quarterly, every 2 quarters,
annually) and leak definitions (e.g., 500 ppm, 1,000 ppm, 10,000 ppm)
if the component is in either gas and vapor service or in light liquid
service. The LDAR requirements for components in heavy liquid service
require sensory monitoring and the use of EPA Method 21 monitoring if a
leak is identified.
    The practices, processes, and control technologies considered
during MACT development for equipment leaks at MON facilities included
LDAR. To identify developments for the technology review, we reviewed
the control options that were considered for the proposed MON in 2003.
As mentioned previously in section IV.C.2 of this preamble, the EPA
conducted a general analysis in the 2011 equipment leaks study \43\ to
identify the latest developments in practices, processes, and control
technologies for equipment leaks at chemical manufacturing facilities
and petroleum refineries and estimated the impacts of applying those
practices, processes, and control technologies to model facilities. We
also used this 2011 equipment leaks analysis as a reference for
conducting the technology review for equipment leaks at MON facilities.
Additionally, we evaluated other federal regulations (i.e., the
finalized Petroleum Refinery Sector MACT,\44\ NSPS subpart VVa,\45\ and
the Hazardous Organic NESHAP \46\) and state regulations (e.g., the
Texas fugitive emissions rules applicable to petrochemical processes
47 48) as part of this review.
---------------------------------------------------------------------------

    \43\ Hancy. 2011. Memorandum from Hancy, C., RTI International
to Howard, J., EPA/OAQPS. Analysis of Emissions Reduction Techniques
for Equipment Leaks. December 21, 2011. EPA Docket ID No. EPA-HQ-
OAR-2010-0869.
    \44\ 40 CFR part 63, subpart CC: National Emission Standards for
Organic Hazardous Air Pollutants from Petroleum Refineries.
    \45\ 40 CFR part 60, subpart VVa: Standards of Performance for
Equipment Leaks of VOC in the Synthetic Organic Chemicals
Manufacturing Industry for Which Construction, Reconstructions, or
Modification Commenced After November 7, 2006.
    \46\ 40 CFR part 63, subpart H: National Emission Standards for
Organic Hazardous Air Pollutants for Equipment Leaks.
    \47\ 30 TAC 115, subchapter D, Division 3: Control of Air
Pollution from Volatile Organic Compounds; Petroleum Refining,
Natural Gas Processing, and Petrochemical Processes; Fugitive
Emission Control in Petroleum Refining, Natural Gas/Gasoline
Processing, and Petrochemical Processes in Ozone Nonattainment
Areas.
    \48\ 30 TAC 115, subchapter H, Division 3: Control of Air
Pollution from Volatile Organic Compounds; Highly-Reactive Volatile
Organic Compounds; Fugitive Emissions (referred to as the TX HRVOC
rule).
---------------------------------------------------------------------------

    Our technology review for equipment leaks of HAP (e.g., beyond
ethylene oxide) identified several developments in LDAR practices and
processes: Option 1, lowering the leak definition for pumps in light
liquid service at existing batch processes from 10,000 ppm to 1,000 ppm
with monthly monitoring; option 2, lowering the leak definition for
pumps in light liquid service at existing batch processes from 10,000
ppm to 500 ppm and at existing continuous processes from 1,000 ppm to
500 ppm with monthly monitoring; option 3, requiring monitoring of
connectors in gas and vapor service or light liquid service at a leak
definition of 500 ppm with monitoring every 8 years; and option 4,
lowering the leak definition for valves in gas and vapor service or
light liquid service from 500 ppm to 100 ppm at both batch and
continuous processes with quarterly monitoring. For all other component
types, we did not identify developments in LDAR practices and
processes.
    Emissions reductions were estimated for the new developments that
we identified using component counts and emission factors. The
component counts were derived using data from the original MON rule,
which included model component counts for 224 facilities, with 167
using batch processes, 57 using continuous processes, and three not
having information. The batch facilities contained 1,049 batch
processes, or an average of 6.3 per facility. The continuous facilities
contained 88 continuous processes, or an average of 1.5 per facility.
These values were scaled to estimate the number of batch and continuous
processes for the current count of 201 facilities, resulting in 943
batch processes and 79 continuous processes nationwide. The number of
nationwide processes was then multiplied by the component counts to
estimate the nationwide component counts. Subsequently, baseline
emissions and emissions after implementation of the controls for each
component were calculated for continuous and batch processes using the
nationwide component counts for continuous and batch processes derived
from the 2003 MON analysis and emission factors and leak frequencies
for the chemical manufacturing industry from the 2011 equipment leaks
study.\49\
---------------------------------------------------------------------------

    \49\ Hancy. 2011. Memorandum from Hancy, C., RTI International
to Howard, J., EPA/OAQPS. Analysis of Emissions Reduction Techniques
for Equipment Leaks. December 21, 2011. EPA Docket ID No. EPA-HQ-
OAR-2010-0869.
---------------------------------------------------------------------------

    Costs were then calculated for the baseline and control options,
which reflect the cost to implement an LDAR program for each component.
Note that the difference between the costs for the baseline and control
options is the incremental cost to comply with the controls. Costs were
calculated for the year 2016, and capital costs were annualized using a
5-percent interest rate. Furthermore, because the control options
result in chemicals in process lines not leaking and, therefore, not
being lost, we present costs both with and without this consideration.
To estimate savings in chemicals not being emitted (i.e., lost) due to
the equipment leak control options, we applied a recovery credit of
$900 per ton of VOC to the VOC emission reductions in the analyses. The
$900 per ton recovery credit has historically been used by the EPA to
represent the variety of chemicals that are used as reactants and
produced at synthetic organic chemical manufacturing facilities,\50\
however, we recognize that this value is from a 2007 analysis and may
be outdated. Therefore, we solicit comment on the availability of more
recent information to potentially update the value used in this
analysis to estimate the recovery credits. The complete cost
calculation methodology is documented in the memorandum, Clean Air Act
Section 112(d)(6) Technology Review for Equipment Leaks Located in the
Miscellaneous Organic Chemical Manufacturing Source Category, which is
available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \50\ U.S. EPA. 2007. Standards of Performance for Equipment
Leaks of VOC in the Synthetic Organic Chemicals Manufacturing
Industry; Standards of Performance for Equipment Leaks of VOC in
Petroleum Refineries (https://www.federalregister.gov/documents/2007/07/09/E7-13203/standards-of-performance-for-equipment-leaks-of-voc-in-the-synthetic-organic-chemicals-manufacturing). EPA-HQ-OAR-
2006-0699.
---------------------------------------------------------------------------

    We calculated the VOC and HAP cost effectiveness by dividing the
incremental annual costs by the emissions reductions. Table 9 of this
preamble presents the nationwide costs and impacts for the suite of
equipment leak control options considered. See the technical memorandum
titled Clean Air Act Section 112(d)(6) Technology

Review for Equipment Leaks Located in the Miscellaneous Organic
Chemical Manufacturing Source Category, which is available in the
docket for this rulemaking, for details on the assumptions and
methodologies used in this analysis.
    Based on the costs and emission reductions for each of the options,
we determined that option 1 is a cost-effective strategy for further
reducing HAP emissions from equipment leaks from MON equipment not in
ethylene oxide service, and we are proposing at 40 CFR 63.2480(b)(6)
and (c)(10) to revise the MON for equipment leaks to lower the leak
definition for pumps in light liquid service at existing batch
processes from 10,000 ppmv to 1,000 ppmv with monthly monitoring,
pursuant to CAA section 112(d)(6). We are also clarifying at 40 CFR
63.2480(b)(7) and (c)(11) that you must initially monitor for leaks
within 30 days after initial startup of the equipment. We solicit
comment on these proposed revisions. Considering the high cost per ton
estimate, we determined that equipment leak options 2, 3, and 4 are not
cost effective for the entire source category; therefore, we are not
proposing to revise the MON to reflect the requirements of these
options pursuant to CAA section 112(d)(6).

                 Table 9--Nationwide Emissions Reduction and Cost Impacts of Control Options Considered for Equipment Leaks for MON Equipment Not in Ethylene Oxide Service \1\
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Total         Total
                                                                    Total      annualized    annualized        VOC           HAP         VOC cost       VOC cost       HAP cost       HAP cost
                        Control  option                            capital      costs w/o    costs with     emission      emission    effectiveness  effectiveness  effectiveness  effectiveness
                                                                 investment    credits \2\   credits \2\   reductions    reductions     w/o credits   with credits    w/o credits   with credits
                                                                     ($)         ($/yr)        ($/yr)         (tpy)         (tpy)      \2\ ($/ton)    \2\ ($/ton)    \2\ ($/ton)    \2\ ($/ton)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1.............................................................       863,100       156,600        85,200          79.3          7.93          1,980          1,075         19,760         10,760
2.............................................................     1,416,800       303,000       223,900          87.9          8.79          3,450          2,550         34,480         25,480
3.............................................................     9,326,800     1,381,900       910,600           524          52.4          2,640          1,740         26,390         17,390
4.............................................................       650,800       116,300        93,300          25.5          2.55          4,560          3,660         45,630         36,630
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Costs are calculated for the year 2016.
\2\ Recovery credits represent the cost savings in chemicals not being emitted (i.e., lost) due to the equipment leak options.

2. Heat Exchange Systems
    Heat exchangers are devices or collections of devices used to
transfer heat from process fluids to another process fluid (typically
water) without intentional direct contact of the process fluid with the
cooling fluid (i.e., non-contact heat exchanger). There are two types
of heat exchange systems: Closed-loop recirculation systems and once-
through systems. Closed-loop recirculation systems use a cooling tower
to cool the heated water leaving the heat exchanger and then return the
newly cooled water to the heat exchanger for reuse. Once-through
systems typically use surface freshwater (e.g., from rivers) as the
influent cooling fluid to the heat exchangers, and the heated water
leaving the heat exchangers is then discharged from the facility. At
times, the internal tubing material of a heat exchanger can corrode or
crack, allowing some process fluids to mix or become entrained with the
cooling water. Pollutants in the process fluids may subsequently be
released from the cooling water into the atmosphere when the water is
exposed to air (e.g., in a cooling tower for closed-loop systems or
trenches/ponds in a once-through system). The term ``heat exchange
system'' is not defined in the MON; therefore, we are proposing a
definition for this term at 40 CFR 63.2550(i) that would apply only to
the MON standards. We are proposing to define ``heat exchange system''
as a device or collection of devices used to transfer heat from process
fluids to water without intentional direct contact of the process fluid
with the water (i.e., non-contact heat exchanger) and to transport and/
or cool the water in a closed-loop recirculation system (cooling tower
system) or a once-through system (e.g., river or pond water). For
closed-loop recirculation systems, the heat exchange system consists of
a cooling tower, all miscellaneous organic chemical manufacturing
process unit heat exchangers that are in organic HAP service, serviced
by that cooling tower, and all water lines to and from these
miscellaneous organic chemical manufacturing process unit heat
exchangers. For once-through systems, the heat exchange system consists
of all heat exchangers that are in organic HAP service, servicing an
individual miscellaneous organic chemical manufacturing process unit
and all water lines to and from these heat exchangers. Sample coolers
or pump seal coolers are not considered heat exchangers for the purpose
of this proposed definition and are not part of the heat exchange
system. Intentional direct contact with process fluids results in the
formation of a wastewater.
    The MON includes an LDAR program for owners or operators of certain
heat exchange systems which meets the requirements of 40 CFR 63.104
(National Emission Standards for Organic Hazardous Air Pollutants from
the Synthetic Organic Chemical Manufacturing Industry). The LDAR
program specifies that heat exchange systems be monitored for leaks of
process fluids into cooling water and that owners or operators take
actions to repair detected leaks within 45 days. Owners or operators
may delay the repair of leaks if they meet the applicable criteria in
40 CFR 63.104. The current MON, for heat exchange systems, allows the
use of any method listed in 40 CFR part 136 for sampling cooling water
for leaks for the HAP listed in Table 4 to 40 CFR part 63, subpart F,
for recirculating systems and Table 9 to 40 CFR part 63, subpart G for
once-through systems. A leak in the heat exchange system is detected if
the exit mean concentration of HAP (or other representative substance)
in the cooling water is at least 1 ppmw or 10 percent greater than
(using a one-sided statistical procedure at the 0.05 level of
significance) the entrance mean concentration of HAP (or other
representative substance) in the cooling water. Furthermore, the MON
allows owners or operators to monitor for leaks using a surrogate
indicator of leaks (e.g., ion-specific electrode monitoring, pH,
conductivity), provided that certain criteria in 40 CFR 63.104(c) are
met. The MON initially requires 6 months of monthly monitoring for
existing heat exchange systems. Thereafter, the frequency can be
reduced to quarterly. The leak monitoring frequencies are the same
whether water sampling and analysis or surrogate monitoring is used to
identify leaks.
    Our technology review identified one development in LDAR practices
and processes for heat exchange systems, the

use of the Modified El Paso Method \51\ to monitor for leaks. The
Modified El Paso Method, which is included in the Petroleum Refinery
Sector rule (i.e., 40 CFR part 63, subpart CC), was identified in our
review of the RACT/BACT/LAER clearinghouse database. It is also
required by the TCEQ for facilities complying with their HRVOC rule
(i.e., 30 TAC Chapter 115, Subchapter H, Division 3). The Modified El
Paso Method measures a larger number of compounds than the current
methods required in the MON and is more effective in identifying leaks.
For heat exchange system LDAR programs, the compliance monitoring
option, leak definition, and frequency of monitoring for leaks are all
important considerations affecting emission reductions by identifying
when there is a leak and when to take corrective actions to repair the
leak. Therefore, we evaluated the Modified El Paso Method for use at
MON facilities, including an assessment of appropriate leak definitions
and monitoring frequencies.
---------------------------------------------------------------------------

    \51\ The Modified El Paso Method uses a dynamic or flow-through
system for air stripping a sample of the water and analyzing the
resultant off-gases for VOC using a common flame ionization detector
(FID) analyzer. The method is described in detail in Appendix P of
the TCEQ's Sampling Procedures Manual: The Air Stripping Method
(Modified El Paso Method) for Determination of Volatile Organic
Compound (VOC) Emissions from Water Sources. Appendix P is included
in the docket for this rulemaking.
---------------------------------------------------------------------------

    In order to identify an appropriate Modified El Paso Method leak
definition for MON facilities, we identified two rules, TCEQ's HRVOC
rule and the Petroleum Refinery Sector rule, both of which incorporate
this monitoring method and have leak definitions corresponding to the
use of this methodology. We also reviewed data submitted in response to
a CAA section 114 request for the Ethylene Production RTR where
facilities performed sampling using the Modified El Paso Method.
    The Petroleum Refinery Sector rule and TCEQ's HRVOC rule have leak
definitions of total strippable hydrocarbon concentration (as methane)
in the stripping gas ranging from 3.1 ppmv to 6.2 ppmv. In addition,
sources subject to the Petroleum Refinery Sector rule may not delay the
repair of leaks for more than 30 days where, during subsequent
monitoring, a total strippable hydrocarbon concentration (as methane)
in the stripping gas of 62 ppmv or higher is found. In reviewing the
Ethylene Production RTR CAA section 114 data, a clear delineation in
the hydrocarbon mass emissions data was noticed at 6.1 ppmv of total
strippable hydrocarbon (as methane) in the stripping gas. In addition,
given that both the leak concentration and water recirculation rate of
the heat exchange system are key variables affecting the hydrocarbon
mass emissions from heat exchange systems, the overall Ethylene
Production RTR CAA section 114 data for all heat exchange systems
sampled generally showed lower hydrocarbon mass emissions for leaks at
or below 6.1 ppmv of total strippable hydrocarbon (as methane) in the
stripping gas compared to leaks found above 6.1 ppmv of total
strippable hydrocarbon (as methane) in the stripping gas. Taking into
account the range of actionable leak definitions in use by other rules
that require use of the Modified El Paso Method currently (i.e., 3.1
ppmv-6.2 ppmv of total strippable hydrocarbon (as methane) in the
stripping gas), and the magnitude of emissions for leaks of total
strippable hydrocarbon (as methane) in the stripping gas above 6.1 ppmv
compared to other leaks identified in the CAA section 114 sampling
data, we chose to evaluate a leak definition at the upper end of
identified actionable leak definitions in our analysis. Thus, the
Modified El Paso Method leak definition we evaluated was 6.2 ppmv of
total strippable hydrocarbon concentration (as methane) in the
stripping gas for both new and existing heat exchange systems, along
with not allowing delay of repair of leaks for more than 30 days where,
during subsequent monitoring, a total strippable hydrocarbon
concentration (as methane) in the stripping gas of 62 ppmv or higher is
found.
    We determined an appropriate leak monitoring frequency by reviewing
the current monitoring frequencies that MON facilities are subject to,
along with frequencies for the Petroleum Refinery Sector rule and the
TCEQ HRVOC rule, and information gathered in the Ethylene Production
RTR CAA section 114 survey. As a first step, we reviewed whether it was
still reasonable to specify more frequent monitoring for a 6-month
period after repair of leaks. Our review of the Ethylene Production RTR
CAA section 114 data showed that no leaks were identified during the 6-
month period post repair for any of the facilities that reported heat
exchange system compliance data that had leaks. Thus, we find that re-
monitoring once after repair of a leak, at the monitoring location
where the leak was identified, is sufficient from a continuous
compliance perspective to demonstrate a successful repair. The
monitoring frequencies currently required by MON for where no leaks are
found were, thus, considered the base frequencies (i.e., quarterly
monitoring for existing and new heat exchange systems). Once we
determined the base frequencies, we next considered more stringent
monitoring frequencies. Both the Petroleum Refinery Sector rule, which
includes monthly monitoring for existing sources, under certain
circumstances, and the TCEQ HRVOC rule, which includes continuous
monitoring provisions for existing and new sources, have more stringent
monitoring frequencies. However, the incremental HAP cost effectiveness
to change from quarterly to monthly monitoring and monthly to
continuous monitoring was found to be $40,000/ton and $500,000/ton,
respectively. We conclude that these costs are not reasonable for MON
facilities. Thus, we chose to evaluate quarterly monitoring for
existing and new heat exchange systems (i.e., the base monitoring
frequency currently in the rule).
    Based on this technology review, we identified the following
control option for heat exchanger systems as a development in practice
that can be implemented at a reasonable cost: Quarterly monitoring for
existing and new heat exchange systems (after an initial 6 months of
monthly monitoring) with the Modified El Paso Method and a leak
definition of 6.2 ppmv of total strippable hydrocarbon concentration
(as methane) in the stripping gas.
    We then estimated the impacts of this control option assuming that
all 201 MON facilities would be affected by requiring the use of the
Modified El Paso Method. As part of our analysis, we assumed owners or
operators conducting quarterly monitoring for three or more of these
heat exchange systems would elect to purchase a stripping column and
FID analyzer and perform in-house Modified El Paso monitoring (because
the total annualized costs for in-house Modified El Paso monitoring are
less than the costs for contracted services). In addition, we assumed
repairs could be performed by plugging a specific heat exchanger tube,
and if a heat exchanger is leaking to the extent that it needs to be
replaced, then it is effectively at the end of its useful life.
Therefore, we determined that the cost of replacing a heat exchanger is
an operational cost that would be incurred by the facility as a result
of routine maintenance and equipment replacement, and it is not
attributable to the control option.
    Table 10 of this preamble presents the nationwide impacts for
requiring owners or operators to use the Modified El Paso Method and
repair leaks of total strippable hydrocarbon concentration (as methane)
in the stripping gas of 6.2

ppmv or greater. See the technical memorandum titled Clean Air Act
Section 112(d)(6) Technology Review for Heat Exchange Systems Located
in the Miscellaneous Organic Chemical Manufacturing Source Category,
which is available in the docket for this rulemaking, for details on
the assumptions and methodologies used in this analysis.
    Based on the costs and emission reductions for the identified
control option, we are proposing to revise the MON for heat exchange
systems pursuant to CAA section 112(d)(6). We are proposing at 40 CFR
63.2490(d)(1) to specify quarterly monitoring for existing and new heat
exchange systems (after an initial 6 months of monthly monitoring)
using the Modified El Paso Method and a leak definition of 6.2 ppmv of
total strippable hydrocarbon concentration (as methane) in the
stripping gas. We are also proposing at 40 CFR 63.2490(d)(4) a delay of
repair action level of total strippable hydrocarbon concentration (as
methane) in the stripping gas of 62 ppmv, that if exceeded during leak
monitoring, would require immediate repair (i.e., the leak found cannot
be put on delay of repair and would be required to be repaired within
30 days of the monitoring event). This would apply to both monitoring
heat exchange systems and individual heat exchangers by replacing the
use of any 40 CFR part 136 water sampling method with the Modified El
Paso Method and removing the option that allows for use of a surrogate
indicator of leaks. We are also proposing at 40 CFR 63.2490(d)(2) and
(3) re-monitoring at the monitoring location where a leak is identified
to ensure that any leaks found are fixed. Finally, we are proposing
that none of these proposed requirements would apply to heat exchange
systems that have a maximum cooling water flow rate of 10 gallons per
minute or less. We solicit comment on the proposed requirements.

   Table 10--Nationwide Emissions Reductions and Cost Impact for Requiring the Modified El Paso Method for Heat Exchange Systems at MON Facilities \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Total                                                           Total
                                                            annualized     VOC emission    HAP emission      HAP cost       annualized       HAP cost
             Control option                Total capital     costs w/o      reductions      reductions     effectiveness    costs with     effectiveness
                                          investment ($)  credits \2\ ($/      (tpy)           (tpy)        w/o credits   credits \2\ ($/  with credits
                                                                yr)                                         \2\ ($/ton)         yr)         \2\ ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................       1,483,000         261,000             306              31           8,530        (14,000)           (470)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Costs are calculated for the year 2016.
\2\ Recovery credits represent the cost savings of chemicals in process lines not leaking into heat exchange systems and, therefore, not being lost, due
  to application of the El Paso Method.

3. Process Vents, Storage Tanks, Transfer Racks, Wastewater
    We did not identify any cost-effective developments in practices,
processes, or control technologies for process vents, storage tanks,
transfer racks, and waste streams that achieve a greater HAP emission
reduction beyond the emission reduction already required by MON, with
the exception of developments presented in section IV.C of this
preamble to specifically control ethylene oxide emissions from process
vents and storage tanks. Therefore, we are not proposing any changes to
the NESHAP for these emission process groups based on our technology
review. For further details on the assumptions and methodologies used
in these analyses, see the technical memoranda titled Clean Air Act
Section 112(d)(6) Technology Review for Process Vents, Wastewater,
Transfer Racks, and Storage Tanks Located in the Miscellaneous Organic
Chemical Manufacturing Source Category, which is available in the
docket for this rulemaking.

E. What other actions are we proposing?

    In addition to the proposed actions described above, we are
proposing additional revisions to the NESHAP. We are proposing
revisions to the SSM provisions of the MACT rule in order to ensure
that they are consistent with the Court decision in Sierra Club v. EPA,
551 F.3d 1019 (D.C. Cir. 2008), which vacated two provisions that
exempted sources from the requirement to comply with otherwise
applicable CAA section 112(d) emission standards during periods of SSM.
We also are proposing revisions to require electronic reporting of
emissions test results and to clarify text or correct typographical
errors, grammatical errors, and cross-reference errors. Our analyses
and proposed changes related to these issues are discussed below.
1. SSM Requirements
    In its 2008 decision in Sierra Club v. EPA, 551 F.3d 1019 (D.C.
Cir. 2008), the Court 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 40 CFR 63.6(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 CAA section 112 standards apply
continuously.
    We are proposing the elimination of the SSM exemption in this rule
which appears at 40 CFR 63.2450(a). Consistent with Sierra Club v. EPA,
we are proposing standards in this rule that apply at all times. We are
also proposing several revisions to Table 12 (the General Provisions
Applicability Table) as is 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. In addition, we are proposing to make the portion of
the ``deviation'' definition in 40 CFR 63.2550(i) that specifically
addresses SSM periods no longer applicable beginning 3 years after
publication of the final rule in the Federal Register. Finally, we are
proposing at 40 CFR 63.2450(e)(4), 40 CFR 63.2480(f), and 40 CFR
63.2485(p) and (q) to make references that are related to an SSM
exemption in 40 CFR part 63, subpart G (for wastewater), 40 CFR part
63, subpart SS (for process vents, storage tanks, transfer racks), and
40 CFR part 63, subparts H and UU, and 40 CFR part 65, subpart F (for
equipment leaks), will no longer be applicable.
    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.

    We are proposing that emissions from startup and shutdown
activities be included when determining if all the standards are being
attained. As currently proposed in 40 CFR 63.2450(a)(2), compliance
with the emission limitations (including operating limits) in this
subpart is required ``at all times.'' We solicit comment on whether
owners and operators in the Miscellaneous Organic Chemical
Manufacturing source category will be able to comply with the standards
during these times. Emission reductions for process vents and transfer
rack operations are typically achieved by routing vapors to an APCD
such as a flare, thermal oxidizer, or carbon adsorber. It is common
practice in this source category to start an APCD prior to startup of
the emissions source it is controlling, so the APCD would be operating
before emissions are routed to it. We expect APCDs would be operating
during startup and shutdown events in a manner consistent with normal
operating periods, and that these APCDs will be operated to maintain
and meet the monitoring parameter operating limits set during the
performance test.
    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 (40 CFR 63.2)
(Definition of malfunction). 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 and this reading
has been upheld as reasonable by the Court in U.S. Sugar Corp. v. EPA,
830 F.3d 579, 606-610 (2016). Under CAA 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 CAA 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
Court 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. The EPA is not required to treat
a malfunction in the same manner as the type of variation in
performance that occurs during routine operations of a source.
    As the Court recognized in U.S. Sugar Corp., accounting for
malfunctions in setting 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. Id. at 608 (``the
EPA would have to conceive of a standard that could apply equally to
the wide range of possible boiler malfunctions, ranging from an
explosion to minor mechanical defects. Any possible standard is likely
to be hopelessly generic to govern such a wide array of
circumstances.''). As such, 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 APCD 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. As such, 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.
    Although no statutory language compels the EPA to set standards for
malfunctions, the EPA has the discretion to do so where feasible. For
example, in the Petroleum Refinery Sector RTR, the EPA established a
work practice standard for unique types of malfunction that result in
releases from PRDs or emergency flaring events because the EPA had
information to determine that such work practices reflected the level
of control that applies to the best performers. 80 FR 75178, 75211-14
(December 1, 2015). The EPA will consider whether circumstances warrant
setting standards for a particular type of malfunction in the
Miscellaneous Organic Chemical Manufacturing source category, and, if
so, whether the EPA has sufficient information to identify the relevant
best performing sources and establish a standard for such malfunctions.
We also encourage commenters to provide any such information.
    In the event that a source fails to comply with the applicable CAA
section 112(d) 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.
a. General Duty
    We are proposing to revise the General Provisions table (Table 12)
entry for 40 CFR 63.6(e)(1)(i) by adding a separate row for 40 CFR
63.6(e)(1)(i) and changing the ``yes'' in column 3 to a ``no'' in which
40 CFR 63.6(e)(1)(i) would no longer be applicable beginning 3 years
after publication of the final rule in the Federal Register. We are
proposing to add general duty regulatory text at 40 CFR 63.2450(u) that
reflects the general duty to minimize emissions ``at all times'' 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
63.2450(u) does not include that language from 40 CFR 63.6(e)(1).
    We are also proposing to revise the General Provisions table (Table
12) entry for 40 CFR 63.6(e)(1)(ii) by adding a separate row for 40 CFR
63.6(e)(1)(ii) and changing the ``yes'' in column 3 to a ``no'' in
which 40 CFR 63.6(e)(1)(ii) would no longer be applicable beginning 3
years after publication of the final rule in the Federal Register.
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 63.2450(u).
b. SSM Plan
    We are proposing to revise the General Provisions table (Table 12)
entries for 40 CFR 63.6(e)(3)(i), (ii), (v) through (viii), and (ix) by
changing the ``yes'' in column 3 to a ``no'' in which these provisions
would no longer be applicable beginning 3 years after publication of
the final rule in the Federal Register. 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 (Table 12)
entry for 40 CFR 63.6(f)(1) by changing the ``yes'' in column 3 to a
``no'' in which 40 CFR 63.6(f)(1) would no longer be applicable
beginning 3 years after publication of the final rule in the Federal
Register. 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 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 standards in this rule to apply at all times.
    We are proposing to revise the General Provisions table (Table 12)
entry for 40 CFR 63.6(h)(1) by adding a separate row for 40 CFR
63.6(h)(1) and changing the ``yes'' in column 3 to a ``no'' in which 40
CFR 63.6(h)(1) would no longer be applicable beginning 3 years after
publication of the final rule in the Federal Register. The current
language of 40 CFR 63.6(h)(1) exempts sources from opacity standards
during periods of SSM. As discussed above, the Court in Sierra Club
vacated the exemptions contained in this provision and held that the
CAA requires that some CAA section 112 standard apply continuously.
Consistent with Sierra Club, the EPA is proposing to revise standards
in this rule to apply at all times.
d. Performance Testing
    We are proposing to revise the General Provisions table (Table 12)
entry for 40 CFR 63.7(e)(1) by changing the ``yes'' in column 3 to a
``no'' in which 40 CFR 63.7(e)(1) would no longer be applicable
beginning 3 years after publication of the final rule in the Federal
Register. Section 63.7(e)(1) describes performance testing
requirements. The EPA is instead proposing to add performance testing
at 40 CFR 63.2450(g)(6). The performance testing we are proposing to
add differs from the General Provisions performance testing provisions
in several respects. The proposed 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 exclude periods of startup
or shutdown as representative conditions for conducting performance
testing. 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 upon request such records
``as may be necessary to determine the condition of the performance
test,'' 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 (Table 12)
entries for 40 CFR 63.8(c)(1)(i) through (iii) by changing the ``yes''
in column 3 to a ``no'' in which these provisions would no longer be
applicable beginning 3 years after publication of the final rule in the
Federal Register. 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
practices (40 CFR 63.8(c)(1)) and that set out the requirements of a
quality control program for monitoring equipment (40 CFR 63.8(d)).
    We are proposing to revise the General Provisions table (Table 12)
entry for 40 CFR 63.8(d) by adding separate rows for 40 CFR 63.8(d)(1)
through (3) and changing the ``yes'' in column 3 to a ``no'' in which
40 CFR 63.8(d)(3) would no longer be applicable beginning 3 years after
publication of the final rule in the Federal Register. The final
sentence in 40 CFR 63.8(d)(3) refers to the General Provisions' SSM
plan requirement which is no longer applicable. The EPA is proposing to
add to the rule at 40 CFR 63.2450(j)(6) text that is identical to 40
CFR 63.8(d)(3) except that the final sentence is replaced with the
following sentence: ``The program of corrective action should be
included in the plan required under Sec.  63.8(d)(2).''
f. Recordkeeping
    We are proposing to revise the General Provisions table (Table 12)
entry for 40 CFR 63.10(b)(2)(i), (ii), (iv), and (v) by adding separate
rows for each provision and changing the ``yes'' in column 3 to a
``no'' in which 40 CFR 63.10(b)(2)(ii), (iv), and (v) would no longer
be applicable beginning 3 years after publication of the final rule in
the Federal Register. 40 CFR 63.10(b)(2)(ii) describes the
recordkeeping requirements during a malfunction. The EPA is proposing
to add such requirements to 40 CFR 63.2525(h) and (l). The regulatory
text we are proposing to add differs from the General Provisions it is
replacing in that the

General Provisions requires the creation and retention of a record of
the occurrence and duration of each malfunction of process, air
pollution control, and monitoring equipment. The EPA is proposing that
this requirement apply to any failure to meet an applicable standard
and is requiring that the source record the date, time, and duration of
the failure rather than the ``occurrence.'' The EPA is also proposing
to add to 40 CFR 63.2525(l) a provision that sources keep records that
include a list of the affected source or equipment and actions taken to
minimize emissions, an estimate of the quantity of each regulated
pollutant emitted over the standard for which the source failed to meet
the standard, and a description of the method used to estimate the
emissions. Examples of such methods would include product-loss
calculations, mass balance calculations, measurements when available,
or engineering judgment based on known process parameters. The EPA is
proposing to require that sources keep records of this information to
ensure that there is adequate information to allow the EPA to determine
the severity of any failure to meet a standard, and to provide data
that may document how the source met the general duty to minimize
emissions when the source has failed to meet an applicable standard.
    When applicable, 40 CFR 63.10(b)(2)(iv) requires sources to record
actions taken during SSM events when actions were inconsistent with
their SSM plan. The requirement is no longer appropriate because SSM
plans will no longer be required. The requirement previously applicable
under 40 CFR 63.10(b)(2)(iv)(B) to record actions to minimize emissions
and record corrective actions is now applicable by reference to 40 CFR
63.2525(l). Finally, when applicable, 40 CFR 63.10(b)(2)(v) requires
sources to record actions taken during SSM events to show that actions
taken were consistent with their SSM plan. The requirement is no longer
appropriate because SSM plans will no longer be required.
    We are proposing to revise the General Provisions table (Table 12)
entry for 40 CFR 63.10(c)(15) by adding a separate row for this
provision and changing column 3 to a ``no'' in which 40 CFR
63.10(c)(15) would no longer be applicable to CEMS beginning 3 years
after publication of the final rule in the Federal Register. When
applicable, the provision allows an owner or operator to use the
affected source's SSM plan or records kept to satisfy the recordkeeping
requirements of the SSM plan, specified in 40 CFR 63.6(e), to also
satisfy the requirements of 40 CFR 63.10(c)(10) through (12). The EPA
is proposing to eliminate this requirement because SSM plans would no
longer be required, and, therefore, 40 CFR 63.10(c)(15) no longer
serves any useful purpose for affected units.
2. Monitoring, Recordkeeping, and Reporting Requirements
a. Monitoring for Adsorbers That Cannot Be Regenerated and Regenerative
Adsorbers That Are Regenerated Offsite
    We are proposing to add monitoring requirements at 40 CFR
63.2450(e)(7) for adsorbers that cannot be regenerated and regenerative
adsorbers that are regenerated offsite because the MON does not
currently include specific monitoring requirements for this type of
APCD. We are proposing owners and operators of this type of APCD use
dual adsorbent beds in series and conduct daily monitoring. We have
prescribed a dual bed system because the use of a single bed does not
ensure continuous compliance unless the bed is replaced significantly
before breakthrough.\52\ A dual bed system will allow one bed to be
saturated before it is replaced and, therefore, makes efficient use of
the adsorber bed without exceeding the emission limits. Facilities
utilizing non-regenerative adsorbers must typically replace the
adsorber bed at the end of the absorbent life and already have a second
bed onsite. Therefore, we have determined that these proposed
requirements would not impose a cost increase; it would only require a
second adsorber bed to be purchased earlier than it would have under
previous rules. In addition, once the second adsorber was purchased,
the source would need to purchase and install canisters at the same
rate they would have under previous rules. In fact, the source could
likely reduce costs over time because the adsorber beds can be used to
a greater saturation level without risking non-compliance. Without the
proposed requirement to use dual adsorbent beds in series, sources
might replace the beds based on temperature readings, the vendor's bed
life expectancy estimates or past history, and may replace the bed
prematurely in order to avoid non-compliance. The burden of purchasing
the initial additional adsorber bed, when compared to the large
increase in compliance assurance, is small.
---------------------------------------------------------------------------

    \52\ We are proposing to define the term ``breakthrough'' at 40
CFR 63.2550(i) to mean the time when the level of HAP or total
organic compound (TOC) detected is at the highest concentration
allowed to be discharged from an adsorber system.
---------------------------------------------------------------------------

    Similar to regenerative adsorbers, in order to monitor performance
deterioration, we are proposing measurements of HAP or TOC using a
portable analyzer or chromatographic analysis for non-regenerative
absorbers. We are proposing that these measurements be taken daily on
the outlet of the first adsorber bed in series using a sample port.
Furthermore, in order to relieve some monitoring burden, we have
included the option to reduce the frequency of monitoring with the
portable analyzer from daily to weekly or monthly. If you choose this
option, you would first be required to establish an average adsorber
bed life. For periods when more than 2 months remain on the bed life,
monthly monitoring can be conducted, and when more than 2 weeks remain
on the bed life, weekly monitoring can be conducted.
b. Electronic Reporting
    The EPA is proposing that owners and operators of MON facilities
submit electronic copies of required flare management plans (at 40 CFR
63.2450(e)(5)(iv)), compliance reports (at 40 CFR 63.2520(e)),
performance test reports (at 40 CFR 63.2520(f)), and performance
evaluation reports (at 40 CFR 63.2520(g)) through the EPA's Central
Data Exchange (CDX) using the Compliance and Emissions Data Reporting
Interface (CEDRI). A description of the electronic data submission
process is provided in the memorandum, Electronic Reporting
Requirements for New Source Performance Standards (NSPS) and National
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, which
is available in the docket for this rulemaking. The proposed rule
requires that performance test results collected using test methods
that are supported by the EPA's Electronic Reporting Tool (ERT) as
listed on the ERT website \53\ at the time of the test be submitted in
the format generated through the use of the ERT and that other
performance test results be submitted in portable document format (PDF)
using the attachment module of the ERT. Similarly, performance
evaluation results of continuous monitoring systems measuring relative
accuracy test audit pollutants that are supported by the ERT at the
time of the test must be submitted in the format generated through the
use of the ERT and other performance evaluation results be submitted in
PDF using the attachment module of the ERT. Flare

management plans would be uploaded as a PDF file. For compliance
reports, the proposed rule requires that owners and operators use the
appropriate spreadsheet template to submit information to CEDRI. A
draft version of the proposed template for these reports is included in
the docket for this rulemaking.\54\ The EPA specifically requests
comment on the content, layout, and overall design of the template.
---------------------------------------------------------------------------

    \53\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
    \54\ See MON_Compliance_Report_Draft_Template.xlsx, which is
available in the docket for this rulemaking.
---------------------------------------------------------------------------

    Additionally, the EPA has identified two broad circumstances in
which electronic reporting extensions may be provided. In both
circumstances, the decision to accept the claim of needing additional
time to report is within the discretion of the Administrator, and
reporting should occur as soon as possible. The EPA is providing these
potential extensions to protect owners and operators from noncompliance
in cases where they cannot successfully submit a report by the
reporting deadline for reasons outside of their control. The situation
where an extension may be warranted due to outages of the EPA's CDX or
CEDRI which precludes an owner or operator from accessing the system
and submitting required reports is addressed in 40 CFR 63.2520(h). The
situation where an extension may be warranted due to a force majeure
event, which is defined as an event that will be or has been caused by
circumstances beyond the control of the affected facility, its
contractors, or any entity controlled by the affected facility that
prevents an owner or operator from complying with the requirement to
submit a report electronically as required by this rule is addressed in
40 CFR 63.2520(i). Examples of such events are acts of nature, acts of
war or terrorism, or equipment failure or safety hazards beyond the
control of the facility.
    The electronic submittal of the reports addressed in this proposed
rulemaking will increase the usefulness of the data contained in those
reports, is in keeping with current trends in data availability and
transparency, will further assist in the protection of public health
and the environment, will improve compliance by facilitating the
ability of regulated facilities to demonstrate compliance with
requirements and by facilitating the ability of delegated state, local,
tribal, and territorial air agencies and the EPA to assess and
determine compliance, and will ultimately reduce burden on regulated
facilities, delegated air agencies, and the EPA. Electronic reporting
also eliminates paper-based, manual processes, thereby saving time and
resources, simplifying data entry, eliminating redundancies, minimizing
data reporting errors, and providing data quickly and accurately to the
affected facilities, air agencies, the EPA, and the public. Moreover,
electronic reporting is consistent with the EPA's plan \55\ to
implement Executive Order 13563 and is in keeping with the EPA's
agency-wide policy \56\ developed in response to the White House's
Digital Government Strategy.\57\ For more information on the benefits
of electronic reporting, see the memorandum, Electronic Reporting
Requirements for New Source Performance Standards (NSPS) and National
Emission Standards for Hazardous Air Pollutants (NESHAP) Rules, which
is available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \55\ EPA's Final Plan for Periodic Retrospective Reviews, August
2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \56\ E-Reporting Policy Statement for EPA Regulations, September
2013. Available at: https://www.epa.gov/sites/production/files/2016-03/documents/epa-ereporting-policy-statement-2013-09-30.pdf.
    \57\ Digital Government: Building a 21st Century Platform to
Better Serve the American People, May 2012. Available at: https://obamawhitehouse.archives.gov/sites/default/files/omb/egov/digital-government/digital-government.html.
---------------------------------------------------------------------------

3. Other Corrections
    There are several additional revisions that we are proposing to 40
CFR part 63, subpart FFFF, to clarify text or correct typographical
errors, grammatical errors, and cross-reference errors. These proposed
editorial corrections and clarifications are summarized in Table 11 of
this preamble.

          Table 11--Summary of Proposed Editorial and Minor Corrections to 40 CFR Part 63, Subpart FFFF
----------------------------------------------------------------------------------------------------------------
                                   Provision                                            Proposed revision
----------------------------------------------------------------------------------------------------------------
40 CFR 63.2435(c)(3)..........................................................  Remove the word ``future.''
40 CFR 63.2450(c)(2)..........................................................  Correct cross-reference error by
                                                                                changing ``Sec.   63.2525(f)''
                                                                                to ``Sec.   63.2525(e)(3) and
                                                                                (4).''
40 CFR 63.2450(j)(1)(i).......................................................  Correct typo by changing ``an
                                                                                Fourier'' to ``a Fourier''; and
                                                                                clarify performance
                                                                                specification requirements.
40 CFR 63.2450(k)(4)(iv)......................................................  Correct cross-reference error by
                                                                                changing ``(b)(2)(ii)'' to
                                                                                ``(c)(2)(ii).''
40 CFR 63.2450(l).............................................................  Correct typo by adding the
                                                                                ``Sec.   '' symbol.
40 CFR 63.2460(b)(5)..........................................................  Change ``under either'' to ``if
                                                                                you comply with one.''
40 CFR 63.2470(e)(3)..........................................................  Replace the phrase ``pounds per
                                                                                square inch gage pressure
                                                                                (psig)'' with ``psig'' because
                                                                                the term is defined earlier in
                                                                                the rule text.
40 CFR 63.2475(a).............................................................  Correct cross-reference error by
                                                                                changing ``in paragraphs (b)
                                                                                and (c) of this section'' to
                                                                                ``in paragraph (b) of this
                                                                                section.''
40 CFR 63.2520(c)(2)..........................................................  Correct cross-reference error by
                                                                                changing ``Sec.
                                                                                63.2460(c)(5)'' to ``Sec.
                                                                                63.2450(k)(6).''
40 CFR 63.2520(e)(5)(iii)(A)..................................................  For clarification, change ``The
                                                                                date and time'' to ``The start
                                                                                date, start time, and duration
                                                                                in hours.''
40 CFR 63.2520(e)(5)(iii)(B)..................................................  For clarification, change ``The
                                                                                date, time, and duration that
                                                                                each CEMS was out-of-control,
                                                                                including the information in
                                                                                63.8(c)(8).'' to ``The start
                                                                                date, start time, and duration
                                                                                in hours that each CEMS was out-
                                                                                of-control and a description of
                                                                                the corrective actions taken.''
40 CFR 63.2520(e)(5)(iii)(D)..................................................  For clarification, change ``A
                                                                                summary of the total duration
                                                                                of the deviation during the
                                                                                reporting period'' to ``The
                                                                                total duration in hours of all
                                                                                deviations for each CMS during
                                                                                the reporting period'' and add
                                                                                ``the total operating time in
                                                                                hours of the affected source
                                                                                during the reporting period.''
40 CFR 63.2520(e)(5)(iii)(F)..................................................  For clarification, change ``A
                                                                                summary of the total duration
                                                                                of CMS downtime'' to ``The
                                                                                total duration in hours of CMS
                                                                                downtime for each CMS.''
40 CFR 63.2520(e)(5)(iii)(I)..................................................  For clarification, change ``A
                                                                                brief description of the CMS''
                                                                                to ``The monitoring equipment
                                                                                manufacturer(s) and model
                                                                                number(s) and the pollutant or
                                                                                parameter monitored.''

40 CFR 63.2520(e)(8)..........................................................  For clarification, change
                                                                                ``Records of process units
                                                                                added to a PUG as specified in
                                                                                Sec.   63.2525(i)(4) and
                                                                                records of primary product
                                                                                redeterminations as specified
                                                                                in Sec.   63.2525(i)(5)'' to
                                                                                ``For process units added to a
                                                                                PUG, you must report the
                                                                                description and rationale
                                                                                specified in Sec.
                                                                                63.2525(i)(4). You must report
                                                                                your primary product
                                                                                redeterminations specified in
                                                                                Sec.   63.2525(i)(5).''
40 CFR 63.2525(f).............................................................  Correct cross-reference error by
                                                                                changing ``Sec.   63.2450(s)''
                                                                                to ``Sec.   63.2450(p).''
40 CFR 63.2550(i).............................................................  Add definition for ``bench-scale
                                                                                process.''
40 CFR 63.2550(i).............................................................  Change ``it is up to and
                                                                                including the extruder, die
                                                                                plate'' to remove ``extruder,''
                                                                                in the definition of
                                                                                ``miscellaneous organic
                                                                                chemical manufacturing
                                                                                process'' in bullet (6).
40 CFR 63.2550(i).............................................................  Define ``loading rack'' as a
                                                                                single system used to fill tank
                                                                                trucks and railcars at a single
                                                                                geographic site. Loading
                                                                                equipment and operations that
                                                                                are physically separate (i.e.,
                                                                                do not share common piping,
                                                                                valves, and other equipment)
                                                                                are considered to be separate
                                                                                loading racks. The term
                                                                                ``loading rack'' is used in the
                                                                                definition of ``transfer rack''
                                                                                but ``loading rack'' is not
                                                                                defined in the MON.
All Equations.................................................................  For clarification, renumber
                                                                                equations in numerical order.
Table 12 to 40 CFR part 63, Subpart FFFF......................................  Add a row for ``Sec.
                                                                                63.7(e)(4).''
----------------------------------------------------------------------------------------------------------------

F. What compliance dates are we proposing?

    Amendments to the MON proposed in this rulemaking for adoption
under CAA section 112(d)(2) and (3) and CAA section 112(d)(6) are
subject to the compliance deadlines outlined in the CAA under section
112(i).
    For all of the requirements we are proposing under CAA sections
112(d)(2), (3), and (d)(6), we are proposing all affected sources must
comply with all of the amendments no later than 3 years after the
effective date of the final rule, or upon startup, whichever is later.
For existing sources, CAA section 112(i) provides that the compliance
date shall be as expeditious as practicable, but no later than 3 years
after the effective date of the standard. (``Section 112(i)(3)'s three-
year maximum compliance period applies generally to any emission
standard . . . promulgated under [section 112].'' Association of
Battery Recyclers v. EPA, 716 F.3d 667, 672 (D.C. Cir. 2013)). In
determining what compliance period is as expeditious as practicable, we
consider the amount of time needed to plan and construct projects and
change operating procedures. As provided in CAA section 112(i), all new
affected sources would be required to comply with these requirements by
the effective date of the final amendments to the MON standards or
startup, whichever is later.
    We are proposing new operating and monitoring requirements for
flares under CAA section 112(d)(2) and (3). We anticipate that these
requirements would require the installation of new flare monitoring
equipment and we project most MCPUs would install new control systems
to monitor and adjust assist gas (air or steam) addition rates. Similar
to the addition of new control equipment, these new monitoring
requirements for flares would require engineering evaluations,
solicitation and review of vendor quotes, contracting and installation
of the equipment, and operator training. Installation of new monitoring
and control equipment on flares will require the flare to be taken out
of service. Depending on the configuration of the flares and flare
header system, taking the flare out of service may also require a
significant portion of the MCPU to be shutdown. Therefore, for all
existing affected sources, and all new affected sources that commence
construction or reconstruction after April 4, 2002, and on or before
December 17, 2019, we are proposing that it is necessary to provide 3
years after the effective date of the final rule (or upon startup,
whichever is later) for owners or operators to comply with the new
operating and monitoring requirements for flares. For all new affected
sources that commenced construction or reconstruction after December
17, 2019, we are proposing owners or operators comply with the new
operating and monitoring requirements for flares by the effective date
of the final rule (or upon startup, whichever is later).
    Under CAA section 112(d)(2) and (3), we are proposing new vent
control requirements for bypasses. These requirements would typically
require the addition of piping and potentially new control
requirements. As these vent controls would most likely be routed to the
flare, we are proposing, for all existing affected sources, and all new
affected sources that commence construction or reconstruction after
April 4, 2002, and on or before December 17, 2019, to provide 3 years
after the effective date of the final rule for owners or operators to
allow coordination of these bypass modifications with the installation
of the new monitoring equipment for the flares. For all new affected
sources that commenced construction or reconstruction after December
17, 2019, we are proposing owners or operators comply with the new vent
control requirements for bypasses by the effective date of the final
rule (or upon startup, whichever is later).
    For atmospheric PRD in HAP service, we are establishing a work
practice standard that requires a process hazard analysis and
implementation of a minimum of three redundant measures to prevent
atmospheric releases. Alternately, owners or operators may elect to
install closed-vent systems to route these PRDs to a flare, drain (for
liquid thermal relief valves), or other control system. We anticipate
that sources will need to identify the most appropriate preventive
measures or control approach; design, install, and test the system;
install necessary process instrumentation and safety systems; and may
need to time installations with equipment shutdown or maintenance
outages. Therefore, for all existing affected sources, and all new
affected sources that commence construction or reconstruction after
April 4, 2002, and on or before December 17, 2019, we are proposing a
compliance date of 3 years from the effective date of the final rule
(or upon startup, whichever is later) for owners or operators to comply
with the work practice standards for atmospheric PRD releases. For all
new affected sources that commenced construction or reconstruction
after December 17, 2019, we are proposing owners or operators comply
with the work practice standards for atmospheric PRD releases

by the effective date of the final rule (or upon startup, whichever is
later).
    Under our technology review for equipment leaks under CAA section
112(d)(6), we are revising the leak definition for light liquid pumps
at batch processes from 10,000 ppm to 1,000 ppm. Affected sources are
currently monitoring light liquid pumps on a monthly basis, and the
change we are proposing to lower the leak definition would require no
additional equipment and would only result in identifying smaller leaks
that require repair. Therefore, we believe that this change could be
implemented quickly and are proposing a compliance date of 1 year after
the effective date of the final rule, or upon startup, whichever is
later, for all existing affected sources, and all new affected sources
that commence construction or reconstruction after April 4, 2002, and
on or before December 17, 2019 to comply with the proposed leak
definition for light liquid pumps at batch processes. For all new
affected sources that commenced construction or reconstruction after
December 17, 2019, we are proposing owners or operators comply with the
proposed leak definition for light liquid pumps at batch processes by
the effective date of the final rule (or upon startup, whichever is
later).
    As a result of our technology review for heat exchange systems, we
are proposing to replace the existing leak definition and monitoring
method with a new leak definition and monitoring method. We project
some owners and operators would require engineering evaluations,
solicitation and review of vendor quotes, contracting and installation
of monitoring equipment, and operator training. In addition, facilities
will need time to read and understand the amended rule requirements and
update standard operating procedures. Therefore, we are proposing that
all existing affected sources, and all new affected sources that
commence construction or reconstruction after April 4, 2002, and on or
before December 17, 2019 must comply with the new monitoring
requirements for heat exchange systems no later than 3 years after the
effective date of the final rule, or upon startup, whichever is later.
For all new affected sources that commenced construction or
reconstruction after December 17, 2019, we are proposing owners or
operators comply with the new monitoring requirements for heat exchange
systems by the effective date of the final rule (or upon startup,
whichever is later).
    Additionally, as previously mentioned in this preamble, we are
proposing under CAA section 112(f), new provisions for process vents
and storage tanks at MON facilities emitting ethylene oxide, as well as
proposing to implement one of two co-proposed control options for
equipment leaks. The proposed provisions may require additional time to
plan, purchase, and install equipment for ethylene oxide control. For
example, for process vents, if the affected source cannot demonstrate
99.9-percent control of ethylene oxide emissions, or reduce ethylene
oxide emissions to less than 1 ppmv (from each process vent) or 5
pounds per year (for all combined process vents), then a new control
system will need to be installed. Therefore, we are proposing a
compliance date of 2 years after the effective date of the final rule,
or upon startup, whichever is later for all existing affected sources,
and all new affected sources that commence construction or
reconstruction after April 4, 2002, and on or before December 17, 2019
to comply with the proposed ethylene oxide requirements. For all new