Native American.....................................                 0.8                 0.2                   0
Hispanic or Latino (includes white and nonwhite)....                  18                  37                   0
Other and Multiracial...............................                   7                   4                   0
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level.................................                  14                  18                   0
Above Poverty Level.................................                  86                  82                   0
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without High School Diploma.............                  14                  23                   0
Over 25 and with a High School Diploma..............                  86                  77                   0
----------------------------------------------------------------------------------------------------------------

    The results of the Ethylene Production source category demographic
analysis indicate that emissions from the source category expose
approximately 2.8 million people to a cancer risk at or above 1-in-1
million and no people to a chronic noncancer TOSHI greater than 1. The
percentages of the at-risk population in the African American and the
Hispanic or Latino demographic groups are higher than their respective
nationwide percentages.
    The methodology and the results of the demographic analysis are
presented in a technical report, Risk and Technology Review--Analysis
of Demographic Factors For Populations Living Near Ethylene Production
Source Category Operations, available in the docket for this action.

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

1. Risk Acceptability
    As noted in section II.A of this preamble, the EPA sets standards
under CAA section 112(f)(2) using ``a two-step standard-setting
approach, with an analytical first step to determine an `acceptable
risk' that considers all health information, including risk estimation
uncertainty, and includes a presumptive limit on maximum individual
lifetime [cancer] risk (MIR) of approximately 1-in-10 thousand.'' 54 FR
38045, September 14, 1989. In this proposal, the EPA estimated risks
based on actual and allowable emissions from ethylene production
sources, and we considered these in determining acceptability.
    The estimated inhalation cancer risk to the individual most exposed
to actual emissions from the source category is 100-in-1 million. The
estimated incidence of cancer due to inhalation exposures is 0.1 excess
cancer cases per year, or one excess case every 10 years. Approximately
2.8 million people face an increased cancer risk greater than 1-in-1
million due to inhalation exposure to HAP emissions from this source
category. The Agency estimates that the maximum chronic noncancer TOSHI
from inhalation exposure for this source category is 1. Based on
allowable emissions, the estimated inhalation cancer risk to the
individual most exposed to actual emissions from the source category is
also 100-in-1 million, but the estimated incidence of cancer due to
inhalation exposures is 0.2 excess cancer cases per year, or one excess
case every 5 years. Approximately 4.6 million people face an increased
cancer risk greater than 1-in-1 million due to inhalation exposure to
allowable HAP emissions from this source category. The maximum chronic
noncancer TOSHI from inhalation exposure is 1 based on allowable
emissions. The screening assessment of worst-case acute inhalation
impacts indicates no facility is estimated to have an HQ greater than 1
based on the REL, AEGL-1 or ERPG-1.
    Potential multipathway human health risks were estimated using a
three-tier screening assessment of the PB-HAP emitted by facilities in
this source category, where the highest exceedance of a Tier 2
screening value is by a factor of 30. For noncancer, the highest
exceedance of a Tier 3 screening value is by a factor of 2 for mercury.
In evaluating the potential for multipathway effects from emissions of
lead from the source category, we compared modeled maximum annual lead
concentrations to the primary NAAQS for lead (0.15 [mu]g/m\3\). Results
of this analysis estimate that the NAAQS for lead would not be exceeded
at any off-site locations.
    For a summary of risk assessment report results for the source
category and facility-wide emission impacts, refer to Table 3 of this
preamble.
    In determining whether risks are acceptable for this source
category, the EPA considered all available health information and risk
estimation uncertainty as described above. The risk results indicate
that the inhalation cancer risks to the individual most exposed are no
greater than approximately 100-in-1 million, which is at the
presumptive limit of acceptability (see, for example, 54 FR 38045,
September 14, 1989). There is only one facility at this risk level and
only one person estimated to be exposed at this risk level based on
actual emissions, and only one facility and 60 people estimated to be
exposed at this risk level based on allowable emissions. The remaining
facilities have much lower estimated cancer risks, 30-in-1 million or
lower based on actual emissions and 80-in-1 million or lower based on
allowable emissions. There are no facilities with an estimated maximum
chronic noncancer HI greater than 1. There are no facilities with an
acute HQ >1 based on the REL, AEGL-1 or ERPG-1.
    Multipathway human health risks are also within limits of
acceptability. For cancer, the highest exceedance of a Tier 2 screening
value was by a factor of 30, which is well below the presumptive

limit of acceptability. For noncancer, there are two facilities that
exceed a Tier 3 screening value by a factor of 2 for mercury. In other
RTRs where we have exceeded either Tier 2 or Tier 3 screening values of
1 and performed refined facility-specific assessments, the refined
estimates have always been at least 80 percent lower than those
estimated by the Tier 2 or Tier 3 screening values. Given that only an
estimated 15-percent reduction in media concentrations for mercury are
needed in a refined facility-specific risk assessment to lower the
values to 1 (to one significant figure) compared to the Tier 3 screen,
and given the fact that results from facility-specific assessments
performed for other source categories always have significant trends
down in risk, we conclude that a refined facility-specific assessment
for the Ethylene Production source category would show a reduction of
noncancer risk by at least 15-percent to result in a value of 1 or
lower. For this reason and considering the conservative nature of the
multipathway exposure screening scenario, we conclude these levels are
acceptable. The multipathway screening analysis indicates that
emissions of lead do not result in concentrations that exceed the NAAQS
value.
    Considering all of the health risk information and factors
discussed above, including the uncertainties discussed in section III
of this preamble, the EPA proposes that the risks are acceptable
because the cancer risks do not exceed the presumptive limit of
acceptability and the noncancer results indicate there is minimal
likelihood of adverse noncancer health effects due to HAP emissions
from this source category.
2. Ample Margin of Safety Analysis
    We next considered whether the existing MACT standards provide an
ample margin of safety to protect public health. In addition to
considering all of the health risks and other health information
considered in the risk acceptability determination, in the ample margin
of safety analysis we evaluated the cost and feasibility of available
control technologies and other measures (including the controls,
measures, and costs reviewed under the technology review) that could be
applied to the source category to further reduce the risks due to
emissions of HAP. For purposes of the ample margin of safety analysis,
we evaluated the changes in risk that would occur through adoption of a
specific technology by looking at the changes to the risk due to both
actual and allowable emissions.
    As noted in our discussion of the technology review in section IV.D
of this preamble, we identified several developments in practices,
processes, or control technologies for reducing HAP emissions from
emission sources in the Ethylene Production source category. As part of
the risk review, we evaluated these developments to determine if any of
them could reduce risks and whether it is necessary to require any of
these developments to provide an ample margin of safety to protect
public health.
    We evaluated the health information and control options for all of
the emission sources located at ethylene production facilities,
including: storage vessels, heat exchange systems, ethylene process
vents, transfer racks, equipment leaks, waste operations, ethylene
cracking furnaces, flares, decoking operations of ethylene cracking
furnaces, and PRDs. For each of these sources, we considered chronic
cancer and noncancer risk metrics as well as acute risk. Regarding
chronic noncancer risk, we note that no facility in the source category
has a baseline TOSHI exceeding 1. Therefore, we did not quantitatively
evaluate reductions in the chronic noncancer TOSHI for any emission
source in the ample margin of safety analysis. Regarding our assessment
of potential acute effects, we note that baseline emissions are
unlikely to result in acute health effects because no facility is
estimated to have an HQ >1 based on the REL, AEGL-1 or ERPG-1.
Accordingly, the following paragraphs focus on cancer risk in the
determination of whether the standards provide an ample margin of
safety to protect public health.
    For storage vessels, as discussed in section IV.D of this preamble,
we identified three options that represent developments in practices,
processes or control technologies as part of our technology review
under CAA section 112(d)(6). We determined that only one of the
options, which we call option 1, is cost effective. We evaluated those
same control options to determine whether any of them are needed to
provide an ample margin of safety as part of our CAA section 112(f)(2)
risk analysis. Option 1 would affect only about 4 percent of the
storage vessel population in the Ethylene Production source category
(i.e., 12 storage vessels at six ethylene production facilities would
require additional controls resulting in approximately 34.6 tpy
reduction in HAP). Given that only one storage vessel at the facility
that is the cancer risk driver would be impacted and that all storage
vessels at that facility only contribute to an estimated cancer risk of
5-in-1 million (for both actual emissions and allowable emissions), we
estimate that option 1 would not change the cancer risk to the
individual most exposed (rounded to one significant figure).
Furthermore, given that all storage vessels account for only about 6
percent of the overall cancer incidence in the source category based on
actual emissions (and 3 percent based on allowable emissions) and that
option 1 will only impact a very small percentage of all storage
vessels in the source category, we estimate option 1 would not change
the cancer incidence and would have no discernible impact on the number
of people with an estimated cancer risk greater than 1-in-1 million.
For the same reasons mentioned above, we expect any reduction in cancer
incidence and MIR that would result from options 2 or 3, and reduction
in the number of people with a cancer risk greater than 1-in-1 million
from implementation of options 2 or 3, would be minimal. Therefore, we
are proposing that additional controls for storage vessels are not
necessary to provide an ample margin of safety.
    For heat exchange systems, as discussed in section IV.D of this
preamble, we identified one control option that represents a
development in practices, processes or control technologies as part of
our technology review under CAA section 112(d)(6). We determined the
control option is cost effective and would reduce HAP emissions by 25
tpy. We evaluated whether the control option would be needed to provide
an ample margin of safety as part of our CAA section 112(f)(2) risk
analysis. Given that heat exchange systems have a small contribution to
cancer risk to the individual most exposed (i.e., <1-in-1 million based
on actual emissions and 6-in-1 million based on allowable emissions),
we estimate that the control option would not change the cancer risk to
the individual most exposed (rounded to one significant figure). In
assessing the impacts of the control option on cancer incidence, given
that heat exchange systems contribute only 3 percent to the overall
cancer incidence based on actual emissions, and given that actual HAP
emissions would be reduced by about 30 percent, we estimate that this
reduction would not have a discernible impact on the cancer incidence
or the number of people with an estimated cancer risk greater than 1-
in-1 million. With respect to estimating the impacts of the control
option on cancer incidence based on allowable emissions, heat exchange
systems drive about half of the overall cancer

incidence, and we estimate that allowable emissions would be reduced by
the control option evaluated, bringing the allowable cancer incidence
down to a level approximately equal to that of the actual cancer
incidence (within one significant figure). Thus, in considering all the
health risks associated with emissions from heat exchange systems and
the minimal risk impact of the control option based on actual
emissions, we are proposing that additional controls for this emission
source is not necessary to provide an ample margin of safety.
    For ethylene process vents, we did not identify any additional
control options. Therefore, we are proposing that additional controls
for this emission source are not necessary to provide an ample margin
of safety.
    For transfer racks, we identified and evaluated one control option
discussed in the technology review section of this preamble (section
IV.D). We estimated that there would be no emission reductions
associated with this change, and hence, no reduction in risk. Thus, we
propose that this control option for transfer racks is not necessary to
provide an ample margin of safety.
    For equipment leaks and waste operations, we identified various
control options discussed in the technology review section of this
preamble (section IV.D). While we estimate that these control options
would reduce emissions and that most options would reduce overall
cancer risk, the control options evaluated for equipment leaks and
waste operations are not cost effective. Thus, considering all of the
health risks and other health information considered in the risk
acceptability determination, and considering that no cost-effective
options were identified for equipment leaks and waste operations, we
propose that additional controls for these emissions sources are not
necessary to provide an ample margin of safety.
    For ethylene cracking furnaces, as previously explained, we
requested under our CAA section 114 authority that ethylene production
facilities stack test this emissions source. The results of these stack
tests were then used to assess risk for the source category. We believe
that there is already an inherent level of HAP emissions control
realized for emissions generated from ethylene cracking furnaces given
the operational characteristics needed for the steam cracking reaction
to occur to produce ethylene and/or propylene. In particular, HAP
emissions, which are generated because of fuel combustion activities in
the ethylene cracking furnace firebox, are controlled as a result of
the high temperatures (i.e., in excess of 2,000 degrees Fahrenheit)
needed in the furnace firebox in order to provide process heat to the
steam cracking reaction. Thus, ethylene cracking furnaces effectively
function like a combustion APCD as a general result of the operating
parameters needed for the reaction kinetics driving the commercial
production of ethylene and/or propylene. Also, the fuels predominately
used in the ethylene cracking furnaces (e.g., natural gas, refinery
fuel gas, and/or tail gas from the production process (tail gas from an
ethylene production process primarily contains hydrogen, methane,
acetylene, and/or other olefins) contain little to no HAP. In addition,
emissions from this source are generally released at an elevated height
with high flow and high temperature, leading to better dispersion such
that impacts on nearby communities are minimized. In assessing the
baseline risk impacts from ethylene cracking furnaces, we note that
while ethylene cracking furnaces are the largest source of emissions in
the source category, these sources have a very small contribution to
cancer risk to the individual most exposed (i.e., <1-in-1 million) and
contribute to about 20 percent of the overall cancer incidence based on
actual emissions and to about 10 percent based on allowable emissions.
Thus, in considering all of the health risks associated with emissions
from ethylene cracking furnaces and the minimal risk impact of this
emissions source, we are proposing that additional controls for this
emission source are not necessary to provide an ample margin of safety.
    For flares, which are control devices that control emissions from
multiple emission source types within the Ethylene Production source
category, under CAA sections 112(d)(2) and (3), we are proposing
operating and monitoring requirements to ensure flares achieve the 98-
percent HAP destruction efficiency identified as the MACT floor in the
initial MACT rulemaking in 2002. Flares are critical safety devices
that effectively reduce emissions during startup, shutdown, and process
upsets or malfunctions, and in many cases, flares are the only means by
which emissions from PRDs can be controlled. Thus, we find that
properly functioning flares act to reduce HAP emissions, and thereby
risk, from this source category. The changes to the flare requirements
that we are proposing under CAA sections 112(d)(2) and (3) will result
in sources meeting the level required by the original standards. We did
not identify any control options that would further reduce the HAP
emissions from flares. Therefore, we are proposing that additional
controls for flares are not necessary to provide an ample margin of
safety.
    In summary, we propose that the existing EMACT standards provide an
ample margin of safety to protect public health. We are also
specifically requesting comment on whether there are additional control
measures for emission sources subject to the EMACT standards that are
necessary to provide an ample margin of safety to protect public
health.
    Further, we note that the decoking of ethylene cracking furnace
radiant tubes and PRD releases are emission sources with respect to
risk from ethylene production facilities. As described in section IV.A
of this preamble, we are proposing requirements for the decoking of the
ethylene cracking furnace radiant tube(s) and PRD releases. As part of
our risk assessment for this source category, we also considered the
risk reductions that would result from implementation of those
standards. Because we anticipate some small level of unquantifiable
emission reductions from decoking operations and PRD releases, these
reductions would likely have no discernable impact on the cancer risk
to the individual most exposed or cancer incidence. While our decisions
on risk acceptability and ample margin of safety are supported even in
the absence of these reductions, if we finalize the proposed
requirements for decoking operations and PRD releases, these proposed
requirements would further strengthen our conclusions that the
standards provide an ample margin of safety to protect public health.
    Lastly, regarding the facility-wide risks due to ethylene oxide
(described above), which are due to emission sources that are not part
of the Ethylene Production source category, we intend to evaluate those
facility-wide estimated emissions and risks further and may address
these in a separate future action, as appropriate. In particular, the
EPA is addressing ethylene oxide based on the results of the latest
NATA released in August 2018, which identified the chemical as a
potential concern in several areas across the country (NATA is the
Agency's nationwide air toxics screening tool, designed to help the EPA
and state, local, and tribal air agencies identify areas, pollutants,
or types of sources for further examination). The latest NATA estimates
that ethylene oxide significantly contributes to potential elevated
cancer risks in some census tracts across the U.S. (less than 1 percent
of the total number of tracts).

These elevated risks are largely driven by an EPA risk value that was
updated in late 2016. The EPA will work with industry and state, local,
and tribal air agencies as the EPA takes a two-pronged approach to
address ethylene oxide emissions: (1) Reviewing and, as appropriate,
revising CAA regulations for facilities that emit ethylene oxide--
starting with air toxics emissions standards for miscellaneous organic
chemical manufacturing facilities and commercial sterilizers; and (2)
conducting site-specific risk assessments and, as necessary,
implementing emission control strategies for targeted high-risk
facilities. The EPA will post updates on its work to address ethylene
oxide on its website at: https://www.epa.gov/ethylene-oxide.
3. Adverse Environmental Effects
    Based on the results of our environmental risk screening
assessment, we are proposing that HAP emissions from the Ethylene
Production source category do not present an adverse environmental
effect. Thus, we are proposing that it is not necessary to set a more
stringent standard to prevent, taking into consideration costs, safety,
and other relevant factors, an adverse environmental effect.

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

    The ethylene production source category is composed of the
following emission sources: Storage vessels, ethylene process vents,
transfer racks, equipment leaks, waste streams, heat exchange systems,
and ethylene cracking furnaces and associated decoking operations. 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, subsequent regulatory development efforts, and facility
responses to our CAA section 114 request. We then used information
provided by facilities that responded to our CAA section 114 request to
evaluate the impacts of requiring additional controls identified in the
technology review for the Ethylene Production source category. For
details about the information we requested under our CAA section 114
request from ethylene production facilities, see section II.C of this
preamble. After reviewing information from the aforementioned sources,
we have identified certain cost-effective developments in practices,
processes, or control technologies to reduce emissions from some of the
sources of HAP emissions regulated by the EMACT standards. Therefore,
we are proposing revisions to the EMACT standards for storage vessels
and heat exchange systems pursuant to CAA section 112(d)(6).
1. Storage Vessels
    Storage vessels are used for storing liquid and gaseous feedstocks
used in the ethylene production process, as well as to store liquid and
gaseous products from the ethylene production process. Types of storage
vessels used in the ethylene production process include atmospheric and
high pressure storage vessels. Most storage vessels, which are used for
storing process liquids and feedstocks, are designed for operation at
atmospheric or near atmospheric pressures. High pressure vessels are
used to store compressed gases and liquefied gases. Atmospheric storage
vessels are typically cylindrical with a vertical orientation, and are
constructed with either a fixed roof or a floating roof. Some,
generally small, atmospheric storage vessels are oriented horizontally.
High pressure vessels are either spherical or horizontal cylinders.
    Under Table 7 to 40 CFR 63.1103(e)(3), the owner or operator of a
storage vessel must reduce the organic HAP emissions by 98 weight-
percent for storage vessels with a maximum true vapor pressure (MTVP)
of total organic HAP of 76.6 kilopascals (kPa) or greater using a
closed vent system routed to a flare, non-flare APCD, or fuel gas
system or process meeting applicable requirements of 40 CFR part 63,
subpart SS. Owners or operators of storage vessels with an MTVP of
total organic HAP of 3.4 kPa or greater but less than 76.6 kPa and a
capacity of 95 cubic meters (m\3\) or greater can elect to comply with
this same control requirement or install either an internal floating
roof (IFR) with proper seals or an external floating roof (EFR) with
proper seals, and install enhanced fitting controls meeting applicable
requirements of 40 CFR part 63, subpart WW. Owners or operators of
smaller storage vessels (i.e., those with an MTVP of total organic HAP
of 3.4 kPa or greater but less than 76.6 kPa and a capacity of 4 m\3\
or greater but less than 95 m\3\) must, at a minimum, fill the storage
vessel through a submerged pipe.\30\
---------------------------------------------------------------------------

    \30\ These smaller storage vessels can also elect to comply with
the more stringent control requirements of reducing organic HAP
emissions by 98 weight-percent by routing emissions to closed vent
system and APCD (or fuel gas system) meeting 40 CFR part 63, subpart
SS or control emissions by using an EFR or IFR storage vessel that
meets the requirements of 40 CFR part 63, subpart WW.
---------------------------------------------------------------------------

    As part of our technology review for storage vessels, we identified
the following emission reduction options: (1) Revising the capacity and
MTVP thresholds of the EMACT standards to require storage vessels as
small as 59 m\3\ storing organic liquid with an MTVP of total organic
HAP of 0.69 kPa or greater but less than 76.6 kPa to reduce organic HAP
emissions by 98 weight-percent by routing emissions to closed vent
system and APCD (or fuel gas system) meeting 40 CFR part 63, subpart
SS, or controlling emissions through use of an EFR or IFR storage
vessel according to the requirements of 40 CFR part 63, subpart WW. For
storage vessels as small as 4 m\3\ but less than 59 m\3\ with an MTVP
of total organic HAP of 0.69 kPa or greater but less than 76.6 kPa,
they must either meet these same control requirements or fill the
vessel through use of a submerged pipe; (2) in addition to requirements
specified in option 1, requiring LDAR for fittings on fixed roof
storage vessels (e.g., access hatches) using EPA Method 21, and the use
of liquid level overfill warning monitors and roof landing warning
monitors on storage vessels with an IFR or EFR; and (3) in addition to
requirements specified in option 1, the conversion of EFRs to IFRs
through use of geodesic domes.
    We identified option 1 as a development in practices, processes,
and control technologies because it reflects requirements for similar
storage vessels that are located at chemical manufacturing facilities
subject to the new source Miscellaneous Organic Chemical Manufacturing
NESHAP (MON). We believe that option 1 is technologically feasible for
storage vessels used at ethylene production facilities. Option 2 is an
improvement in practices because these monitoring methods have been
required by other regulatory agencies since promulgation of the EMACT
and are being used by some of the sources covered by the Ethylene
Production source category. Finally, we consider option 3 to be a
development in control technology because we found that some storage
vessels with EFR have installed geodesic domes since promulgation of
the 2002 EMACT standards. A VOC recovery credit for product not lost to
the atmosphere from storage vessels was also considered for all three
of the options presented.\31\
---------------------------------------------------------------------------

    \31\ A VOC recovery credit for storage vessels of $380 per ton
(approximately $1.20/gallon) was used and is based on an August 2016
market price for naphtha. For more details, see the technical
memorandum titled Clean Air Act Section 112(d)(6) Technology Review
for Storage Vessels Located in the Ethylene Production Source
Category, which is available in Docket ID No. EPA-HQ-OAR-2017-0357.

---------------------------------------------------------------------------

    Under option 1, we considered the impacts of tightening the
capacity and MTVP thresholds of the EMACT standards to reflect the
capacity and MTVP threshold of the new source MON standards. This would
require tightening both the threshold for MTVP of total organic HAP
(i.e., decreasing it from 3.4 kPa or greater to 0.69 kPa or greater)
and the threshold for storage vessel capacity (i.e., decreasing it from
95 m\3\ to 38 m\3\) specified in Table 7 at 40 CFR 63.1103(e)(3)(a)(1)
and 40 CFR 63.1103(e)(3)(b)(1), respectively. However, upon further
evaluation of our CAA section 114 Ethylene Production source category
information specific to storage vessels, the smallest storage vessel
that would be required to add additional controls is an infrequently
used fixed roof storage vessel with a capacity of 58 m\3\. Based on the
response from the CAA section 114 request, this storage vessel reported
using a form of submerged fill to minimize emissions but did not
operate in 2013. We determined that it would not be cost effective for
this particular storage vessel to add additional controls due to its
infrequent use. Thus, in lieu of evaluating impacts for option 1 at the
new source MON capacity threshold of 38 m\3\, a threshold of 59 m\3\
was chosen so that this storage vessel could continue to use submerged
fill as a method of control. After reviewing the CAA section 114
request data, we identified only seven storage vessels that would be
impacted by option 1. All of these storage vessels have capacities
greater than or equal to 59 m\3\ and store material with an MTVP of
total organic HAP of 0.69 kPa or greater but less than 76.6 kPa.
Therefore, these storage vessels would need to either install an IFR or
EFR with proper seals and install enhanced fitting controls as required
in 40 CFR part 63, subpart WW. In the alternative, they would need to
reduce emissions of total organic HAP by 98 weight-percent by venting
emissions through a closed vent system to any combination of APCDs that
meet the requirements of 40 CFR 63.982(a)(1).
    For option 2, we evaluated the impacts of requiring leak detection
monitoring of fittings (e.g., access hatches) on fixed roof storage
vessels using EPA Method 21 (annually) and to repair a leak if it is
detected. A leak would be defined as an instrument reading greater than
500 ppmv using EPA Method 21. We also evaluated the impacts of enhanced
monitoring of the liquid level in the storage vessel (i.e., requiring
liquid level overfill warning monitors and roof landing warning
monitors on EFRs and IFRs). Levels below a low set point would provide
warning of a potential floating roof landing, and levels above a high
set point would provide warning of potential overfill. Based on the CAA
section 114 request data, we identified 78 storage vessels that would
be subject to option 2, of which 14 have fixed roofs (although, in this
analysis, seven of these are considered to have been converted to IFR
due to option 1, and six of the other seven fixed roof storage vessels
route emissions to a process or to a closed vent system and APCD) and
the remaining 64 have either an IFR or EFR. In addition, two of the
storage vessels with an IFR and one of the storage vessels with an EFR
route emissions to a closed vent system and APCD. In order to determine
costs for option 2, we added costs for enhanced monitoring requirements
to costs determined for option 1.
    Under option 3, we considered the impacts of converting storage
vessels with EFRs to IFRs through the use of geodesic domes. We assumed
for this option that only those storage vessels with EFRs with a
capacity greater than or equal to 59 m\3\ and that contain liquid with
an MTVP of total organic HAP of 0.69 kPa or greater but less than 76.6
kPa would be required to retrofit their storage vessel with a geodesic
dome. After reviewing the CAA section 114 request data, we identified
32 storage vessels with EFRs that would be subject to option 3.
Therefore, we estimated costs and emissions reductions for 32 EFRs. The
costs were added to the costs determined for option 1 to determine the
cost of option 3.
    Table 5 of this preamble presents the nationwide impacts for the
three options considered. See the technical memorandum titled Clean Air
Act Section 112(d)(6) Technology Review for Storage Vessels Located in
the Ethylene Production Source Category, which is available in Docket
ID No. EPA-HQ-OAR-2017-0357 for details on the assumptions and
methodologies used in this analysis, including the calculations we used
to account for additional ethylene production facilities that did not
receive a CAA section 114 request, additional facilities that would be
subject to the proposed control options and storage vessels from new
ethylene production facilities that are either under construction or
that started operation in 2017, and major expansions of currently
operating facilities. The calculation of the incremental cost
effectiveness allows us to assess the impacts of the incremental change
between option 1 and the other options.
    We determined that option 1 is cost effective and we are proposing
to revise the EMACT standards to reflect the more stringent storage
vessel capacity and MTVP thresholds of option 1 pursuant to CAA section
112(d)(6). Considering the emissions reductions and high incremental
cost effectiveness, we determined that storage vessel options 2 and 3
are not cost effective and are not proposing to revise the EMACT
standards to reflect the requirements of these options pursuant to CAA
section 112(d)(6).

                             Table 5--Nationwide Emissions Reduction and Cost Impacts of Control Options Considered for Storage Vessels at Ethylene Production Units
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                HAP
                                                                                Total                                         HAP cost          Total         HAP cost       incremental
                                                                   Total capital    annualized     VOC emission    HAP emission    effectiveness    annualized     effectiveness       cost
                         Control option                           investment ($)   costs w/o VOC    reductions      reductions    w/o credits ($/ costs with VOC   with credits    effectiveness
                                                                                credit ($/yr)       (tpy)           (tpy)           ton)        credit ($/yr)      ($/ton)      with credits
                                                                                ($/ton)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1...............................................................         820,000         152,000             309            34.6           4,400          34,000           1,000  ..............
2...............................................................       1,453,000         373,800             328            40.7           9,190         248,700           6,120          35,400
3...............................................................      19,909,000       2,723,000             383            58.3          46,700       2,547,000          44,100         107,100
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

2. Ethylene Process Vents
    Ethylene production units generate gaseous streams containing HAP.
These streams may be routed to other unit operations for additional
processing (e.g., a gas stream from a reactor that is routed to a
distillation unit for separation), may be sent to one or more recovery
devices, a process vent header collection system (e.g., blowdown
system) and APCD, and/or may be vented to the atmosphere. Ethylene
process vents are gas streams with a flow rate greater than 0.005
standard m\3\ per minute containing greater than 20 ppmv HAP that are
continuously discharged during operation of an ethylene production
unit.
    Under Table 7 to 40 CFR 63.1103(e)(3), the owner or operator must
reduce organic HAP emissions from ethylene process vents by 98 weight-
percent or reduce organic HAP or total organic compounds to a
concentration of 20 ppmv, whichever is less stringent, by venting
emissions through a closed vent system to any combination of APCDs
(e.g., a flare, thermal oxidizer, boiler, process heater, absorber,
condenser, or carbon adsorber) that meet applicable requirements of 40
CFR part 63, subpart SS.
    In the technology review for process vents, we did not identify any
practices, processes, or control technologies beyond those already
required by the EMACT standards for process vents. Therefore, we are
proposing that it is not necessary to revise EMACT standards for
ethylene process vents pursuant to CAA section 112(d)(6). For further
details on the assumptions and methodologies used in this analysis, see
the technical memorandum titled Clean Air Act Section 112(d)(6)
Technology Review for Ethylene Process Vents Located in the Ethylene
Production Source Category, which is available in Docket ID No. EPA-HQ-
OAR-2017-0357.
3. Transfer Racks
    Transfer racks at ethylene production units are equipment that are
used to transfer materials (primarily liquid products) from the
facility into either tank trucks or railcars. Emissions from transfer
racks may be released when material loaded into tank trucks or railcars
displaces vapors inside these transport vehicles.
    The EMACT standards at Table 7 to 40 CFR 63.1103(e)(3) allow
multiple options to control emissions from applicable transfer racks.
These options include the use of APCDs or collecting emissions for use
in the production process, a fuel gas system, or a vapor balance
system. To be subject to these requirements, the owner or operator must
load materials that have a true vapor pressure of total organic HAP of
3.4 kPa or greater and must load 76 m\3\ of HAP-containing material or
greater per day (averaged over any consecutive 30-day period).
    In our technology review for transfer racks, we identified one
emission reduction option which would require changing the transfer
rack applicability threshold (for volumetric throughput of liquid
loaded) from 76 m\3\ per day to 1.8 m\3\ per day to reflect the more
stringent applicability threshold of other chemical sector standards
that regulate emissions from transfer rack operations (i.e., 40 CFR
part 63, subparts F and G and 40 CFR part 63, subpart FFFF).
    Upon review of the CAA section 114 request data, we identified only
one transfer rack that would be subject to this revision. This transfer
rack loads red oil material (containing benzene, ethyl benzene,
toluene, and xylene) with a true vapor pressure of total organic HAP of
3.4 kPa or greater at a maximum 30-day average throughput of about 48
m\3\ per day into tank trucks. We also found that emissions from this
transfer rack are routed to a flare, and we, therefore, expect that the
owner or operator of this transfer rack is already complying with the
requirement to reduce emissions of organic HAP by 98 weight-percent as
specified in Table 7 to 40 CFR 63.1103(e)(3). As such, we determined
that none of the 21 facilities that responded to the CAA section 114
request would be impacted by changing the transfer rack applicability
threshold (for volumetric throughput of liquid loaded) from 76 m\3\ per
day to 1.8 m\3\ per day. We also estimated that there would be no
emission reductions associated with this change. While this change
would not have direct implementation costs, it would still impose a
certain burden on facilities because they would need to read the rule,
determine applicability, and meet additional recordkeeping and
reporting requirements. Because there are no emissions reductions, and
there would be a certain burden to industry, we do not consider this to
be a cost-effective option. Therefore, we are proposing that it is not
necessary to revise the EMACT standards for transfer racks pursuant to
CAA section 112(d)(6). For further details on the assumptions and
methodologies used in this analysis, see the technical memorandum
titled Clean Air Act Section 112(d)(6) Technology Review for Transfer
Racks Located in the Ethylene Production Source Category, which is
available in Docket ID No. EPA-HQ-OAR-2017-0357.
4. Equipment Leaks
    Emissions 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 valves,
pumps, compressors, PRDs, and certain types of process equipment.
    The requirements of 40 CFR part 63, subpart UU (National Emission
Standards for Equipment Leaks--Control Level 2 Standards), represent
the MACT floor for equipment leaks at both new and existing ethylene
production units. 40 CFR part 63, subpart UU, specifies LDAR
requirements for applicable equipment. The applicable equipment
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 hr/yr or more,
and are not in vacuum service. The LDAR requirements vary by equipment
(component) type but include EPA Method 21 monitoring at certain
frequencies (e.g., monthly, quarterly, every two 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
include sensory monitoring, and the use of EPA Method 21 monitoring if
a leak is identified.
    Our technology review for equipment leaks identified two
developments in LDAR practices and processes: (1) Lowering the leak
definition for valves in gas and vapor service or in light liquid
service from 500 ppm to 100 ppm and (2) lowering the leak definition
for pumps in light liquid service from 1,000 ppm to 500 ppm. The leak
definition for option 1 was identified in the petroleum refinery sector
technology review and, based on a recent air permit application, a new
ethylene production facility will comply with this leak definition. The
leak definition for option 2 was reported by seven ethylene production
facilities in the CAA section 114 responses, and this leak definition
is also applicable to certain facilities in Texas. We, therefore,
considered both options as developments in technology given that they
are either required by other regulatory agencies or are in use by some
sources covered by the Ethylene Production source category.
    Table 6 of this preamble presents the nationwide impacts for the
two options considered. A VOC recovery credit for

product not lost to the atmosphere from equipment leaks was also
considered for both options presented.\32\ See the technical memorandum
titled Clean Air Act Section 112(d)(6) Technology Review for Equipment
Leaks in the Ethylene Production Source Category, which is available in
Docket ID No. EPA-HQ-OAR-2017-0357 for details on the assumptions and
methodologies used in this analysis, including the calculations we used
to account for additional ethylene production facilities that did not
receive a CAA section 114 request, new ethylene production facilities
that are either under construction or that started operation in 2017,
and major expansions of currently operating facilities.
---------------------------------------------------------------------------

    \32\ A VOC recovery credit of $776 per ton was used and is based
on a November 2016 market price for ethylene.
---------------------------------------------------------------------------

    Based on the costs and emission reductions for each of the options,
we consider none of these identified options as cost effective for
reducing emissions from equipment leaks at ethylene production units.
We are proposing that it is not necessary to revise the EMACT standards
for equipment leaks pursuant to CAA section 112(d)(6).

                             Table 6--Nationwide Emissions Reduction and Cost Impacts of Control Options Considered for Equipment Leaks at Ethylene Production Units
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       Total           Total                                         VOC cost        VOC cost        HAP cost        HAP cost
                                                   Total capital    annualized      annualized     VOC emission    HAP emission    effectiveness   effectiveness   effectiveness   effectiveness
                 Control option                   investment ($)     costs w/o      costs with      reductions      reductions    w/o credits ($/  with credits   w/o credits ($/  with credits
                                                                  credits ($/yr)  credits ($/yr)       (tpy)           (tpy)           ton)           ($/ton)          ton)           ($/ton)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1...............................................       1,628,500         713,600         575,500             178            19.6           4,000           3,200          36,500          29,400
2...............................................         143,300          67,800          65,000             3.5            0.38          19,500          18,700         177,200         170,200
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

5. Waste Streams
    Examples of waste streams at ethylene production units include
process wastewater, product tank drawdown, sludge and slop oil removed
from waste management units, and landfill leachate. Owners and
operators of waste streams use wastewater collection systems (including
drains, manholes, trenches, lift stations, sumps, and/or junction
boxes) to combine waste streams prior to treatment. Wastewater
treatment systems are divided into three categories: Primary treatment
operations, which include oil-water separators and equalization basins;
secondary treatment systems, such as biological treatment units or
steam strippers; and tertiary treatment systems, which further treat or
filter wastewater prior to discharge to a receiving body of water or
reuse in a process. Emissions from these systems occur by
volatilization of organic compounds at any water/air interface.
    The EMACT standards apply to waste streams that contain benzene and
continuous butadiene waste streams and are dependent on a facility's
total annual benzene (TAB) quantity. For a TAB quantity of 10 megagrams
per year (Mg/yr) or greater, owners or operators of all waste streams
that have flow rates of at least 0.02 liters per minute (lpm),
wastewater quantities of at least 10 Mg/yr, and benzene concentrations
of at least 10 parts per million by weight (ppmw), must either manage
and treat these waste streams according to any of the options in the
Benzene Waste Operations NESHAP (BWON), or transfer the waste off-site.
For a TAB quantity of less than 10 Mg/yr, owners or operators of waste
streams that contain benzene and are either spent caustic waste streams
or dilution steam blowdown waste streams that have flow rates of at
least 0.02 lpm and wastewater quantities of at least 10 Mg/yr, must
manage and treat the waste streams according to the BWON, but are not
allowed to use any of the 1, 2, or 6 Mg/yr compliance options.\33\ For
any facility TAB quantity, owners and operators of all waste streams
that have flow rates of at least 0.02 lpm and 1-3-butadiene
concentrations of at least 10 ppmw, must also manage and treat these
waste streams according to the BWON (but the treatment and control
efficiencies required for benzene in BWON for these waste streams are
instead required for 1-3 butadiene, and owners and operators are also
not allowed to use any of the 1, 2, or 6 Mg/yr compliance options).
---------------------------------------------------------------------------

    \33\ The BWON requires removal of benzene from the waste stream
to 10 ppmw or by 99 weight-percent. For each closed vent system and
APCD used to comply with the BWON, a benzene reduction of 98 weight-
percent must be achieved. However, the BWON also includes three
compliance options that allow a facility to choose which streams to
manage and treat if certain conditions are met: either the TAB
quantity for the untreated waste streams cannot exceed 2 Mg/yr, the
facility TAB quantity for treated and untreated process wastewater
streams is less than 1 Mg/yr, or the facility TAB quantity for all
waste streams with at least 10-percent water content is less than 6
Mg/yr. These options are referred to as the 1, 2, and 6 Mg/yr
compliance options. The waste or wastewater streams that can be
exempted from management and treatment vary with the different
compliance options. Details of these compliance options are
specified in 40 CFR 61.342(c) through (e) of the BWON.
---------------------------------------------------------------------------

    The emission reduction options we identified in the waste stream
technology review are: (1) Specific performance parameters for an
enhanced biological unit (EBU) beyond those required in the BWON; and
(2) treatment of wastewater streams with a VOC content of 750 ppmv or
higher by steam stripping prior to any other treatment process for
facilities with high organic loading rates (i.e., facilities with total
annualized benzene quantity of 10 Mg/yr or more). Option 1 is intended
to improve the performance of wastewater treatment systems that use an
EBU, and thereby achieve additional emission reductions. The BWON, as
it applies to sources covered under EMACT, has limited operational
requirements for an EBU. Available data suggest that these systems are
generally effective for degrading benzene and other organic HAP;
however, without specific performance or operational requirements, the
effectiveness of the EBU to reduce emissions can be highly variable.
Under option 1, more stringent operating requirements are considered
for the EBU at ethylene production units. Option 2 considers segregated
treatment of wastewater streams with a volatile organic content of
greater than 750 ppmw, or high-strength wastewater streams, directly in
a steam stripper (i.e., not allowing these streams to be mixed and
treated in the EBU).
    Table 7 of this preamble presents the nationwide impacts for the
two options considered. See the technical memorandum titled Clean Air
Act Section 112(d)(6) Technology Review for Waste Streams Located in
the Ethylene Production Source Category, in Docket ID No. EPA-HQ-OAR-
2017-0357 for details on the assumptions and methodologies used in this
analysis, including the calculations we used to account for additional
ethylene production facilities that did not receive a CAA section 114
request, additional

impacted facilities from new ethylene production facilities under
construction or that started operation in 2017, and major expansions of
currently operating facilities. The costs and emissions impacts
presented in Table 7 of this preamble are not incremental between
options, but rather incremental from the baseline of compliance with
the BWON.
    Based on the costs and emission reductions for each of the options,
we consider none of the options identified to be cost effective for
reducing emissions from waste streams at ethylene production units. We
are proposing that it is not necessary to revise the EMACT standards
for waste streams pursuant to CAA section 112(d)(6).

         Table 7--Nationwide Emissions Reductions and Cost Impacts of Control Options Considered for Waste Streams at Ethylene Production Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Total       VOC emission    HAP emission      VOC cost        HAP cost
                     Control option                        Total capital    annualized      reductions      reductions     effectiveness   effectiveness
                                                          investment ($)   costs ($/yr)        (tpy)           (tpy)          ($/ton)         ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................................     224,050,000      24,727,000           1,986             529          12,450          46,700
2.......................................................      34,987,000      11,579,000           2,253             600           5,140          19,300
--------------------------------------------------------------------------------------------------------------------------------------------------------

6. 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). The term ``heat
exchange system'' is used in this preamble to refer collectively to
water-cooled heat exchangers and the associated cooling water handling
system. 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 river
water 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 EMACT standards include an LDAR program for owners or operators
of certain heat exchange systems. 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 63.1088. The current
EMACT standards for heat exchange systems allow the use of any method
listed in 40 CFR part 136 for sampling cooling water for leaks for the
HAP listed in Table 1 to 40 CFR part 63, subpart XX. Other
representative substances such as total organic carbon or VOC that can
indicate the presence of a leak can also be used. According to the
EMACT standards, 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 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, and the leak is at least 3.06 kg/hr. Individual
heat exchangers are considered leaking, according to the EMACT
standards, if the cooling water in the heat exchanger has an exit mean
concentration (of HAP or of another representative substance) that is
at least 1 ppmw or 10 percent greater than the entrance mean
concentration, whichever is greater. Furthermore, the EMACT standards
allow 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 63.1086(c) are
met. The EMACT standards for monitoring heat exchange systems according
to 40 CFR 63.1086(a) or for monitoring individual heat exchangers
according to 40 CFR 63.1086(b) initially require 6 months of monthly
monitoring for heat exchange systems at existing sources. If no leaks
are detected, the frequency decreases to quarterly monitoring for heat
exchange systems at existing sources, until a leak is detected. Once a
leak is detected, the frequency changes to monthly monitoring until the
leak is repaired and for the following 6 months, at which point the
heat exchange system's monitoring frequency can be reduced back to
quarterly. The EMACT standards initially require 6 months of weekly
monitoring for heat exchange systems at new sources. If no leaks are
detected, the frequency decreases to monthly monitoring for heat
exchange systems at new sources, until a leak is detected. Once a leak
is detected, the frequency changes to weekly monitoring until the leak
is repaired and for the following 6 months, at which point the heat
exchange system's monitoring frequency can revert to monthly
monitoring. Where surrogate monitoring is used for heat exchange
systems according to 40 CFR 63.1086(c), heat exchange systems at
existing sources must follow the same monitoring frequency as
previously discussed in this section; however, heat exchange systems at
new sources must always perform weekly monitoring.
    Our technology review identified one development in LDAR practices
and processes for heat exchange systems. Specifically, the use of the
Modified El Paso Method \34\ to monitor for leaks. The Modified El Paso
Method, which is included in the Petroleum Refinery Sector MACT 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 (including eight ethylene production facilities)
complying with their HRVOC rule (i.e., 30 TAC Chapter 115, Subchapter
H, Division 3). For heat exchange system LDAR programs, the compliance
monitoring option, leak

definition, and frequency of monitoring for leaks are all important
considerations for being able to identify when there is a leak and when
to take corrective actions to repair the leak. We, therefore, evaluated
the Modified El Paso Method for use at ethylene production facilities,
including an assessment of appropriate leak definitions and monitoring
frequencies.
---------------------------------------------------------------------------

    \34\ 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 Docket ID No. EPA-HQ-OAR-2017-0357.
---------------------------------------------------------------------------

    In order to identify an appropriate Modified El Paso Method leak
definition for ethylene production facilities, we identified two rules,
TCEQ's HRVOC rule and the Petroleum Refinery Sector MACT rule, that
incorporate this monitoring method and have leak definitions
corresponding to use of this methodology. We also reviewed data
submitted from our CAA section 114 request, where ethylene production
facilities performed sampling using the Modified El Paso Method. The
Petroleum Refinery MACT 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 MACT 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 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 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 ethylene
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 ethylene production facilities
are subject to, along with frequencies for the Petroleum Refinery
Sector MACT rule and the TCEQ HRVOC rule. 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 CAA section
114 data showed that no leaks were identified during the 6-month period
for any of the ethylene production 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 in 40 CFR part 63, subpart XX, for
where no leaks are found were, thus, considered the base frequencies:
i.e., quarterly monitoring for existing heat exchange systems and
monthly monitoring for new heat exchange systems. Once we determined
the base frequencies, we next considered more stringent monitoring
frequencies. Both the Petroleum Refinery Sector MACT rule, which
includes monthly (or quarterly) monitoring for existing sources, and
the TCEQ HRVOC rule, which includes continuous monitoring provisions
for existing and new sources, have more stringent monitoring
frequencies. However, analysis done for the Petroleum Refinery Sector
MACT rule showed that 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.
Given that the assumed leak distributions used in the analysis to
estimate emissions from heat exchange systems at ethylene production
facilities are considerably smaller than those used in the Petroleum
Refinery Sector MACT analysis (by over an order of magnitude), higher
incremental HAP cost effectiveness are expected for these options at
ethylene production facilities compared to petroleum refineries, making
them not cost-effective options. Thus, we chose to evaluate quarterly
monitoring for heat exchange systems at existing sources and monthly
monitoring for heat exchange systems at new sources (i.e., the base
monitoring frequency currently in the rule after the initial 6-months
of more frequent monitoring is performed).
    Based on this technology review, we identified the following
control option as a development in practice for heat exchange systems:
Quarterly monitoring for heat exchange systems at existing sources
(after an initial 6 months of monthly monitoring) and monthly
monitoring for heat exchange systems at new sources (after an initial 6
months of weekly monitoring) with the Modified El Paso Method, and
using a leak definition of 6.2 ppmv of total strippable hydrocarbon
concentration (as methane) in the stripping gas.
    We then reviewed the CAA section 114 request data to determine the
impacts of this control option. We identified 67 heat exchange systems
at 31 ethylene production facilities that would be impacted by
requiring the use of the Modified El Paso Method. As part of our
analysis, we assumed owners or operators conducting monthly monitoring
or 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 Method monitoring (because the total
annualized costs for in-house Modified El Paso Method monitoring is
less than the costs for contracted services for monthly monitoring and
because of logistics with facilities having three or more heat exchange
systems performing quarterly monitoring). In addition, because owners
and operators of 20 of these heat exchange systems (at eight
facilities) are required by TCEQ's HRVOC rule to conduct continuous
Modified El Paso Method monitoring, we assumed these owners or
operators would only incur an annualized repair cost (and no capital
costs). Further, we assumed repairs could be performed by plugging a
specific heat exchanger tube and, if a heat exchanger that 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 8 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. A VOC recovery credit for
product not lost to the atmosphere from leaks in heat exchange systems
was also considered for the option presented.\35\ See the technical
memorandum titled Clean Air Act Section 112(d)(6) Technology Review for
Heat Exchange Systems in the Ethylene Production Source Category, which
is available in Docket ID No. EPA-HQ-OAR-2017-0357 for details on the
assumptions and methodologies used in this analysis, including the
calculations we used to account for additional ethylene production
facilities that did not receive a CAA section 114 request, new ethylene
production facilities that are either under construction or that
started operation in 2017, and major expansions of currently operating
facilities.
---------------------------------------------------------------------------

    \35\ A VOC recovery credit of $776 per ton was used and is based
on a November 2016 market price for ethylene.
---------------------------------------------------------------------------

    Based on the costs and emission reductions for the identified
control option, we are proposing to revise the EMACT standards for heat
exchange systems pursuant to CAA section 112(d)(6). We are proposing at
40 CFR 63.1086(e)(4) to retain quarterly monitoring for heat exchange
systems at existing sources (after an initial 6-months of monthly
monitoring) and monthly monitoring for heat exchange systems at new
sources (after an initial 6-months of weekly 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 63.1088(d) 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 re-monitoring at the
monitoring location where a leak is identified to ensure that any leaks
found are fixed.

   Table 8--Nationwide Emissions Reductions and Cost Impact for Requiring the Modified El Paso Method for Heat Exchange Systems at Ethylene Production
                                                                          Units
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Total
                                          Total  capital       Total       VOC emission    HAP emission      HAP cost       annualized       HAP cost
             Control option                  investment     annualized      reductions      reductions     effectiveness    costs with     effectiveness
                                                ($)       costs w/o  VOC       (tpy)           (tpy)        w/o credits   VOC Credit  ($/  with credits
                                                          credit  ($/yr)                                      ($/ton)           yr)           ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................         136,000          26,400             227              25           1,060       (149,600)         (5,980)
--------------------------------------------------------------------------------------------------------------------------------------------------------

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 portions of 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 performance test results and reports, performance
evaluation reports, and NOCS reports, to remove certain exemptions for
once-through heat exchange systems, to include overlap provisions for
equipment at ethylene production facilities subject to both the EMACT
standards and synthetic organic chemicals manufacturing equipment leak
standards at 40 CFR part 60, subpart VVa, 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
    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.
a. Proposed Elimination of the SSM Exemption
    We are proposing the elimination of the SSM exemption in this rule
which appears at 40 CFR 63.1108(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 40 CFR part 63, subpart YY as is
explained in more detail below. For example, we are proposing to
eliminate the requirement that the source develop an SSM plan. We also
are proposing to eliminate and revise certain recordkeeping and
reporting requirements related to the SSM exemption as further
described below.
    The EPA has attempted to ensure that the provisions we are
proposing to eliminate are inappropriate, unnecessary, or redundant in
the absence of the SSM exemption. We are specifically seeking comment
on whether we have successfully done so.
    We are proposing that startups and shutdowns are normal operation
for the Ethylene Production source category. We, therefore, believe
that emissions from startup and shutdown activities should be included
when determining if all the standards are being attained. As currently
proposed in 40 CFR 63.1108(a)(4)(i), compliance with the emission
limitations (including operating limits) in this subpart is required
``at all times,'' except during periods of nonoperation of the affected
source (or specific portion thereof) resulting in cessation of the
emissions to which this subpart applies. Based on the information for
APCD operation

received in the CAA section 114 survey issued to the Ethylene
Production source category, we conclude that ethylene production
facilities will generally be able to comply with the standards during
periods of startup and shutdown for the reasons discussed below. Where
appropriate, we have also proposed in this preamble alternative
standards for certain emission points during periods of SSM to ensure a
standard applies ``at all 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. We do not expect startup and shutdown
events to affect emissions from storage vessels, equipment leaks, waste
sources (e.g., surface impoundments, oil-water separators, organic-
water separators), or heat exchange systems. Working and breathing
losses from storage vessels are the same regardless of whether the
process is operating under normal operating conditions or if it is in a
startup or shutdown event. Leak detection programs associated with
equipment leaks and heat exchange systems are in place to detect leaks,
and, therefore, it is inconsequential whether the process is operating
under normal operating conditions or is in startup or shutdown. Waste
emissions are also not expected to be significantly affected by startup
or shutdown events.
    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 (D.C. Cir. 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 APCD 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 we had
information to determine that such work practices reflected the level
of control that applies to the best performing sources. 80 FR 75178,
75211-14 (December 1, 2015). The EPA will consider whether
circumstances warrant setting standards for a particular type of
malfunction and, if so, whether the EPA has sufficient information to
identify the relevant best performing sources and establish a standard
for such malfunctions. As discussed in sections IV.A.1 and IV.A.2.a of
this preamble, we are proposing work practice standards that will apply
to PRD releases and flares, respectively, due to their similarities to
PRD releases and flares used in the Petroleum Refinery Sector source
category. As also previously explained, many parent companies that own
and operate facilities subject to the EMACT standards also own and
operate

petroleum refineries that are subject to the Petroleum Refinery Sector
Rule.
    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.
    Finally, in keeping with the elimination of the SSM exemption, we
are proposing in the EMACT standards at 40 CFR 63.1103(e)(11) to remove
the following SSM exemption provisions from the subparts referenced by
the EMACT standards.
     The second sentence of 40 CFR 63.181(d)(5)(i) of subpart
H.
     40 CFR 63.983(a)(5) of subpart SS.
     The phrase ``except during periods of start-up, shutdown
and malfunction as specified in the referencing subpart'' in 40 CFR
63.984(a) of subpart SS.
     The phrase ``except during periods of start-up, shutdown
and malfunction as specified in the referencing subpart'' in 40 CFR
63.985(a) of subpart SS.
     The phrase ``other than start-ups, shutdowns, or
malfunctions'' in 40 CFR 63.994(c)(1)(ii)(D) of subpart SS.
     40 CFR 63.996(c)(2)(ii) of subpart SS.
     40 CFR 63.997(e)(1)(i) of subpart SS.
     The term ``breakdowns'' from 40 CFR 63.998(b)(2)(i) of
subpart SS.
     40 CFR 63.998(b)(2)(iii) of subpart SS.
     The phrase ``other than periods of startups, shutdowns,
and malfunctions'' from 40 CFR 63.998(b)(5)(i)(A) of subpart SS.
     The phrase ``other than periods of startups, shutdowns,
and malfunctions'' from 40 CFR 63.998(b)(5)(i)(C) of subpart SS.
     The phrase ``except as provided in paragraphs (b)(6)(i)(A)
and (B) of this section'' from 40 CFR 63.998(b)(6)(i) of subpart SS.
     The second sentence of 40 CFR 63.998(b)(6)(ii) of subpart
SS.
     40 CFR 63.998(c)(1)(ii)(D), (E), (F), and (G) of subpart
SS.
     40 CFR 63.998(d)(1)(ii) of subpart SS.
     40 CFR 63.998(d)(3)(i) and (ii) of subpart SS.
     The phrase ``(except periods of startup, shutdown, or
malfunction)'' from 40 CFR 63.1026(e)(1)(ii)(A) of subpart UU.
     The phrase ``(except periods of startup, shutdown, or
malfunction)'' from 40 CFR 63.1028(e)(1)(i)(A) of subpart UU.
     The phrase ``(except periods of startup, shutdown, or
malfunction)'' from 40 CFR 63.1031(b)(1) of subpart UU.
b. General Duty
    We are proposing to remove the requirements at 40 CFR 63.1108(a)(5)
and 40 CFR 63.1111(a)(2) and are proposing instead to add general duty
regulatory text at 40 CFR 63.1108(a)(4)(ii) 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 63.1108(a)(5) and 40 CFR 63.1111(a)(2) 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 63.1108(a)(4)(ii) does not include that language from 40 CFR
63.1108(a)(5) and 40 CFR 63.1111(a)(2).
c. SSM Plan
    We are proposing to remove certain language at 40 CFR 63.1103(e)(3)
and 40 CFR 63.1111(a) requiring owners or operators to develop 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.
d. Compliance With Standards
    We are proposing to remove the current language of 40 CFR
63.1108(a)(1) and (2) which 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 standard apply continuously.
Consistent with Sierra Club, the EPA is proposing to revise standards
in this rule to apply at all times.
e. Performance Testing
    We are proposing to add a performance testing requirement at 40 CFR
63.1108(b)(4)(ii)(B) intended to replace the performance testing
requirements of 40 CFR 63.997(e)(1) (as referenced in 40 CFR
63.1108(b)(4)(ii)(A)). The proposal does not include the language that
precludes startup and shutdown periods from being considered
``representative'' for purposes of performance testing, and instead
allows performance testing during periods of startup or shutdown if
specified by the Administrator. As in 40 CFR 63.997(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 also
proposing to add language at 40 CFR 63.1108(b)(4)(ii)(B) that requires
the owner or operator maintain records of 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. Finally, the EPA is proposing to add language
clarifying that the owner or operator make such records available to
the Administrator upon request.
f. Recordkeeping
    We are not proposing to change the language at 40 CFR 63.1109(a)
requiring owners or operators of each affected source to keep copies of
reports. However, we are proposing to completely remove 40 CFR
63.1111(b), which eliminates periodic SSM reports, consequently
eliminating the requirement to keep a copy of this report. These
requirements are no longer appropriate for startup and shutdown because
SSM plans will no longer be required and the EPA is proposing that
recordkeeping and reporting applicable to normal operations will apply
to startup and shutdown. In the absence of special provisions
applicable to startup and shutdown, such as a startup and shutdown
plan, there is no reason to retain additional recordkeeping for startup
and shutdown periods. See section IV.E.1.a of this preamble for further
discussion of this proposed language removal.
    Furthermore, in lieu of the requirements applicable to malfunctions
in 40 CFR 63.1111(b), we are proposing new recordkeeping requirements
at 40 CFR 63.1111(c)(1). The regulatory text we are proposing to add at
40 CFR 63.1111(c)(1)(i) differs from 40 CFR 63.1111(b) in that 40 CFR
63.1111(b) requires the creation and retention of a record for each
malfunction during which excess emissions occurred, including total
duration of all malfunctions for a reporting period. 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 total duration of all malfunctions with which excess
emissions occurred. For each failure to meet an applicable standard,
the EPA is also proposing to add to 40 CFR 63.1111(c)(1)(ii) a
provision that sources keep records that include a list of the affected
source or equipment, 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. Furthermore,
the EPA is proposing to add 40 CFR 63.1111(c)(1)(iii) requiring sources
keep records of any corrective actions taken to return the affected
unit to its normal or usual manner of operations, and actions taken to
minimize emissions in accordance with the general duty regulatory text
at 40 CFR 63.1108(a)(4)(ii). 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.
g. Reporting
    We are proposing to completely remove 40 CFR 63.1111(b) which
describes the reporting requirements for SSM. When applicable, 40 CFR
63.1111(b)(1) requires sources to report actions taken during SSM
events to show that actions taken were consistent with their SSM plan.
When applicable, 40 CFR 63.1111(b)(2) requires sources to report
actions taken during SSM events when actions were inconsistent with
their SSM plan. To replace the 40 CFR 63.1111(b) reporting requirement,
the EPA is proposing to add reporting requirements to 40 CFR
63.1111(c)(2). The replacement language differs from the 40 CFR
63.1111(b) language in that it eliminates periodic SSM reports as a
stand-alone report. We are proposing language that requires sources
that fail to meet an applicable standard at any time to report the
information concerning such events in the periodic report already
required under this rule. We are proposing that the report contain the
number, date, time, and duration of such events (including unknown
cause, if applicable), a list of the affected source or equipment, an
estimate of the quantity of each regulated pollutant emitted over any
emission limit, and a description of the method used to estimate the
emissions.
    Regarding the proposed new requirement, discussed above, to
estimate the quantity of each regulated pollutant emitted over any
emission limit 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 (e.g., ethylene production rates and
control efficiencies). The EPA is proposing this provision to ensure
that there is adequate information to determine compliance, to allow
the EPA to determine the severity of the failure to meet an applicable
standard, and to provide data that may document how the source met the
general duty to minimize emissions during a failure to meet an
applicable standard.
    We will no longer require owners or operators to determine whether
actions taken to correct a malfunction are consistent with an SSM plan,
because plans would no longer be required. The proposed amendments,
therefore, eliminate 40 CFR 63.1111(b)(2) that requires reporting of
whether the source deviated from its SSM plan, including required
actions to communicate with the Administrator, and the cross-reference
to 40 CFR 63.1111(b)(1) that contains the description of the previously
required SSM report format and submittal schedule from this section.
These specifications are no longer necessary because the events will be
reported in otherwise required reports with similar format and
submittal requirements.
    We are proposing to completely remove 40 CFR 63.1111(b)(2) for
reasons discussed above and because 40 CFR 63.1111(b)(2) describes an
immediate report for startups, shutdown, and malfunctions when a source
failed to meet an applicable standard but did not follow the SSM plan.
We will no longer require owners and operators to report when actions
taken during a startup, shutdown, or malfunction were not consistent
with an SSM plan, because plans would no longer be required.
h. Waste
    The BWON provisions that are applicable to waste generated by
sources in the Ethylene Production source category are set forth in 40
CFR part 63, subpart XX, and are cross-referenced in Table 7 to 40 CFR
63.1103(e)(3). With the elimination of the SSM exemption, we are
proposing to remove the exemption language at 40 CFR 63.1095(a)(3) and
(b)(1) that exempts an owner or operator of continuous butadiene waste
streams and waste streams that contain benzene at a facility with a TAB
less than 10 Mg/yr from the BWON requirements during periods of SSM.
(For more information on how BWON applies to these streams, refer to
section IV.D.5 of this preamble.) This exemption does not apply to
facilities with a TAB of 10 Mg/yr or greater. An owner or operator of a
facility with a TAB less than 10 Mg/yr would be required to comply with
BWON at all times, including during periods of SSM for continuous
butadiene waste streams and waste streams that contain benzene. As part
of these proposed revisions, we are also proposing to remove language
from the definitions of ``dilution steam blowdown waste stream'' and
``spent caustic waste stream'' at 40 CFR 63.1082(b) such that the
definitions no longer exclude streams generated from sampling,
maintenance activities, or shutdown purges.
    We estimate that there would be no impact on any facility for
making these changes. In reviewing the data submitted to us from the
facilities who responded to our CAA section 114 survey, we determined
that there was only one facility with a TAB less than 10 Mg/yr;
however, this facility recently went through an expansion and we
believe their TAB has likely changed to 10 Mg/yr or greater such that
they are already complying with the BWON requirements at all times for
continuous butadiene waste streams and waste streams that contain
benzene. We solicit comment on whether there are any ethylene
production facilities that operate with a TAB less than 10 Mg/yr; and
if so, how this proposed change would impact them.
2. Electronic Reporting Requirements
    Through this proposal, the EPA is proposing that owners and
operators of ethylene production facilities submit electronic copies of
required performance test results and reports and NOCS reports 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, available in Docket ID No. EPA-HQ-OAR-2017-0357. 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 \36\ 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. The proposed rule requires that
NOCS reports be submitted as a PDF upload in CEDRI.
---------------------------------------------------------------------------

    \36\ https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.
---------------------------------------------------------------------------

    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
63.1110(a)(10)(iv). 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 63.1110(a)(10)(v). 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 \37\ to
implement Executive Order 13563 and is in keeping with the EPA's
Agency-wide policy \38\ developed in response to the White House's
Digital Government Strategy.\39\ 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,
available in Docket ID No. EPA-HQ-OAR-2017-0357.
---------------------------------------------------------------------------

    \37\ The EPA's Final Plan for Periodic Retrospective Reviews,
August 2011. Available at: https://www.regulations.gov/document?D=EPA-HQ-OA-2011-0156-0154.
    \38\ 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.
    \39\ 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. Exemptions for Heat Exchange Systems
    Heat exchange systems that meet any one of the criteria specified
in 40 CFR 63.1084 are exempt from the LDAR requirements in the EMACT
standards. We have also reviewed these criteria to see if the
exemptions were still reasonable to maintain. In addition, we compared
these exemptions to those requirements for heat exchangers that are
subject to the Petroleum Refinery Sector Rule given that this MACT
standard was more recently promulgated in 2009, relative to the EMACT
standard promulgated in 2002.\40\ Based upon this review, we are
proposing to remove the exemptions at 40 CFR 63.1084(c) and (d) for
once-through heat exchange systems and instead, proposing that
facilities comply with 40 CFR 63.1085 and 40 CFR 63.1086.
---------------------------------------------------------------------------

    \40\ The Refinery MACT standards for heat exchange systems were
promulgated on October 28, 2009 (see 74 FR 55685) and further
amended on June 30, 2010 (see 75 FR 37731) and June 20, 2013 (see 78
FR 37146).
---------------------------------------------------------------------------

    We identified two criteria in 40 CFR 63.1084 that are applicable to
once-through heat exchange systems meeting certain National Pollutant
Discharge Elimination System (NPDES) permit conditions (i.e., 40 CFR
63.1084(c) and (d)) that warranted further assessment. As discussed in
section IV.D.6 of this preamble, once-through heat exchange systems at
a petrochemical plant have systems open to the air (e.g., open sewer
lines, trenches, and ponds) that are utilized to transport used cooling
water to a discharge point (e.g., an outfall) of a facility. This
cooling water can also be mixed with other sources of water (e.g.,
cooling water used in once-through heat exchange systems in non-
ethylene source categories, stormwater, treated wastewater, etc.) in
sewers, trenches, and ponds prior to discharge from the plant. If this
point of discharge from the plant is into a ``water of the United
States,'' then the facility is required to have a NPDES permit and to
meet certain pollutant discharge limits. In reviewing the requirements
of 40 CFR 63.1084(c), we find that there is a disconnect between having
a NPDES permit that meets certain allowable discharge limits (i.e., 1
ppmv) or less above influent concentration, or 10 percent or less above
influent concentration, whichever is greater) at the discharge point of
a facility (e.g., outfall) as compared to being able to adequately
identify a leak from a once-through heat exchange system given that
these systems are open to the atmosphere prior to this discharge point
and, therefore, any volatile HAP leaking from a once-through heat
exchange system would likely be emitted to the atmosphere prior to the
NPDES outfall. Similarly, while the requirements of 40 CFR 63.1084(d)
allow facilities with once-through heat exchange systems that have
certain requirements (i.e., the requirements of 40 CFR 63.1084(d)(1)
through (4)) incorporated into their NPDES permit not to comply with
the EMACT standards for heat exchange systems, we find this exemption
to be problematic. Specifically, the NPDES requirements at 40 CFR
63.1084(d) lack the specificity of where a sample must be taken to
adequately find and quantify a leak from a once-through heat exchange
system. These include, for example, just prior to the outfall from the
plant versus from the exit of the once-through heat exchange system
prior to being open to atmosphere, what concentration and/or mass
emissions rate constitutes a leak that must be fixed, how quickly a
leak must be fixed, what pollutants must be adequately accounted for,
and what test method(s)/surrogate(s) facilities can use to demonstrate
compliance. As such, we

find 40 CFR 63.1084(d) to be inadequate for purposes of LDAR for leaks
that are at least as equivalent to those that would be identified if
once-through heat exchange systems were complying with 40 CFR 63.1085
and 40 CFR 63.1086 instead.
    Further, in reviewing the data submitted to us from the facilities
who responded to our CAA section 114 survey, we determined that there
are no facilities with once-through heat exchange systems complying
with the NPDES compliance options at 40 CFR 63.1084(c) and (d).
Accordingly, we are removing the exemption for once-through exchange
systems that are specified in 40 CFR 63.1084(c) and (d) and are
proposing that facilities that previously used either of these
exemptions comply with 40 CFR 63.1085 and 40 CFR 63.1086. Therefore, we
estimate that there would be no cumulative nationwide costs or emission
reductions associated with this change. We solicit comment on our
proposed decision.
4. Equipment Leak Overlap Provisions With Subpart VVa
    When an emission point is subject to multiple regulations, the
EMACT standards include overlap provisions at 40 CFR 63.1100(g) that
specify which regulations owners or operators must comply with. For
equipment leaks, overlap provisions are specified for 40 CFR part 60,
subpart VV; 40 CFR part 61, subpart J or subpart V; and 40 CFR part 63,
subpart H. However, since the promulgation of the EMACT standards in
2002, equipment leak regulations were finalized at 40 CFR part 60,
subpart VVa, in 2007 and did not address overlap with the EMACT
standards (or 40 CFR part 63, subpart UU, generally). As such, certain
equipment at newly constructed ethylene production facilities must
currently comply with both the EMACT standards and subpart VVa. Except
for calibration drift assessments required by subpart VVa, we are
proposing at 40 CFR 63.1100(g)(4)(iii) that equipment controlled
according to the EMACT standards and subpart VVa are required only to
comply with the EMACT standards. We believe this compliance option will
provide flexibility and reduce the burden on ethylene production
facilities. We are proposing that where equipment at ethylene
production facilities is subject to both the EMACT standards and
subpart VVa, an owner or operator that chooses to comply with the EMACT
standards only (instead of complying with both standards), must also
still comply with the calibration drift assessment provisions at 40 CFR
60.485a(b)(2). The calibration drift assessment helps ensure that the
EPA Method 21 monitoring results are accurate when demonstrating
compliance.
5. Other Corrections
    There are several additional revisions that we are proposing to 40
CFR part 63, subpart YY to clarify text or correct typographical
errors, grammatical errors, and cross-reference errors. These proposed
editorial corrections and clarifications are summarized in Table 9 of
this preamble.

 Table 9--Summary of Proposed Editorial and Minor Corrections to 40 CFR
                           Part 63, Subpart YY
------------------------------------------------------------------------
             Provision                        Proposed revision
------------------------------------------------------------------------
Table 1 to 40 CFR 63.1100(a)......  Format footnote ``a''; remove
                                     unnecessary periods; and correct
                                     reference to definition of heat
                                     exchange systems in footnote ``c.''
40 CFR 63.1100(b).................  Clarify applicability of General
                                     Provisions for ethylene production
                                     affected sources.
40 CFR 63.1100(g)(5)..............  Correct spelling of the word
                                     ``collocated.''
40 CFR 63.1100(g)(7)..............  Add paragraph to clarify flares that
                                     are subject to the provisions of 40
                                     CFR 60.18 or 40 CFR 63.11 and used
                                     as a control device for an emission
                                     point subject to the requirements
                                     in Table 7 to 40 CFR 63.1103(e) are
                                     only required to comply with the
                                     provisions specified in 40 CFR
                                     63.1103(e)(4).
40 CFR 63.1101....................  Clarify that the definition of
                                     ``pressure relief device or valve''
                                     does not apply to ethylene
                                     production affected sources (see
                                     section IV.A.2.a of this preamble
                                     for further details). Change
                                     ``ethylene production unit
                                     furnaces'' to ``ethylene cracking
                                     furnaces'' in the definition of
                                     ``shutdown'' for consistency.
40 CFR 63.1103(b)(2)..............  Change the word ``contracts'' to
                                     ``contacts'' in definition of ``in
                                     organic hazardous air pollutant or
                                     in organic HAP service.''
40 CFR 63.1103(e)(1)(F) and Table   Correct the reference to the
 7 at 40 CFR 63.1103(e)(3)(h).       definition of ``heat exchange
                                     systems.''
Table 7 at 40 CFR                   Correct typo by changing ``<='' to
 63.1103(e)(3)(a)(1).                ``<''.
Table 7 at 40 CFR                   Clarify concentration applicability
 63.1103(e)(3)(d)(1).                for ethylene process vents is on a
                                     dry basis based on original MACT
                                     floor determination.
Table 7 at 40 CFR                   Clarify concentration emission
 63.1103(e)(3)(d)(1)(i) and (ii),    limitation for ethylene process
 and (e)(1)(i) and (ii).             vents and transfer racks is on a
                                     dry basis corrected to 3.0-percent
                                     oxygen based on original MACT floor
                                     determination.
40 CFR 63.1107(a).................  Clarify how EPA Method 18 can be
                                     used when determining the percent
                                     organic HAP content of the process
                                     fluid that is contained in or
                                     contacts equipment for the ethylene
                                     production affected sources.
40 CFR 63.1108(a)(4)(ii)..........  Change ``which'' to ``that'' and
                                     clarify inspection of the
                                     ``affected'' source when
                                     determining whether a source is
                                     operating in compliance with
                                     operation and maintenance
                                     requirements.
40 CFR 63.1108(b)(4)(i)...........  Correct reference to paragraphs
                                     (b)(4)(i)(A) through (D).
------------------------------------------------------------------------

F. What compliance dates are we proposing?

    Amendments to the EMACT standards 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 CAA
section 112(i). For all of the requirements we are proposing under CAA
sections 112(d)(2) and (3), and CAA section 112 (d)(6), we are
proposing that all existing affected sources, and all new affected
source that commence construction or reconstruction after December 6,
2000 and on or before October 9, 2019, 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 provide for
compliance as expeditiously 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 by affected sources. As provided in CAA section
112(i), all ethylene production new affected sources that commenced
construction or reconstruction after October 9, 2019 would be required
to comply with these requirements by the effective date of the final
amendments to the EMACT 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 that most ethylene production units 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 ethylene
production unit to be shutdown. Therefore, for all existing affected
sources, and all new affected source that commence construction or
reconstruction after December 6, 2000 and on or before October 9, 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 ethylene production new affected
sources that commenced construction or reconstruction after October 9,
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 to provide 3 years after the effective date of
the final rule for owners or operators to install additional piping,
monitoring, and/or controls to correct any vent control bypasses. For
atmospheric PRDs in organic 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, all existing affected sources, and all new affected
source that commence construction or reconstruction after December 6,
2000 and on or before October 9, 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 ethylene
production new affected sources that commenced construction or
reconstruction after October 9, 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 CAA section 112(d)(2) and (3), we are also proposing work
practice standards for decoking operations that would require owners
and operators to institute procedures to reduce coke formation and coke
combustion emissions, and prevent non-coke combustion HAP emissions
from escaping to the atmosphere due to leaks in the transfer line and
decoking valves. We anticipate that most, if not all owners and
operators already have procedures in place that meet the proposed
criteria; however, the EPA recognizes the confusion that multiple
different compliance dates for individual requirements would create and
the additional burden such an assortment of dates would impose. Also,
facilities will still need some time to read and understand the amended
rule requirements, update standard operating procedures, and install
monitoring equipment; therefore, we are proposing that all existing
affected sources, and all new affected source that commence
construction or reconstruction after December 6, 2000 and on or before
October 9, 2019 must comply with the decoking work practice standards
no later than 3 years after the effective date of the final rule, or
upon startup, whichever is later. For all ethylene production new
affected sources that commenced construction or reconstruction after
October 9, 2019, we are proposing owners or operators comply with the
decoking work practice standards by the effective date of the final
rule (or upon startup, whichever is later).
    Under our technology review for storage vessels under CAA section
112(d)(6), we are revising the EMACT standards to reflect more
stringent storage vessel capacity and MTVP thresholds. We project that
some owners and operators will need to install new control equipment on
certain storage vessels because of the proposed applicability
revisions. The addition of new control equipment would require
engineering design, solicitation, and review of vendor quotes, and
contracting and installation of the equipment, which would need to be
timed with process unit outage and operator training. Therefore, we are
proposing a compliance date of 3 years after the effective date of the
final rule, or upon startup, whichever is later for all existing
affected sources, and all new affected source that commence
construction or reconstruction after December 6, 2000 and on or before
October 9, 2019 to comply with the proposed storage vessel
requirements. For all ethylene production new affected sources that
commenced construction or reconstruction after October 9, 2019, we are
proposing owners or operators comply with the proposed storage vessel
requirements 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 source that
commence construction or reconstruction after December 6, 2000 and on
or before October 9, 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 ethylene production new
affected sources that commenced construction or reconstruction after
October 9, 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).
    Finally, we are proposing to change the requirements for SSM by
removing both the exemption from the requirements to meet the standard
during SSM periods and the requirement to develop and implement an SSM
plan. We are also proposing electronic reporting requirements. We are
positing that facilities would need some time to successfully
accomplish these revisions, including time to read and understand the
amended rule requirements, to evaluate their operations to ensure that
they can meet the standards during periods of startup and shutdown, as
defined in the rule, and make any necessary adjustments, including
making adjustments to standard operating procedures, and to convert
reporting mechanisms to install necessary hardware and software. The
EPA recognizes the confusion that multiple different compliance dates
for individual requirements would create and the additional burden such
an assortment of dates would impose. From our assessment of the
timeframe needed for compliance with the entirety of the revised
requirements, the EPA considers a period of 3 years after the effective
date of the final rule to be the most expeditious compliance period
practicable and, thus, is proposing at 40 CFR 63.1102(c) and 40 CFR
63.1081 that all affected sources should be in compliance with all of
this regulation's revised requirements upon initial startup or within 3
years of the effective date of the final rule, whichever is later.

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    As of January 1, 2017, there were 26 ethylene production facilities
currently operating that are major sources of HAP, and the EPA is aware
of five ethylene production facilities under construction. As such, 31
ethylene production facilities will be subject to the proposed
amendments. A complete list of facilities that are currently subject,
or will be subject, to the EMACT standards is available in Appendix A
of the memorandum titled Review of the RACT/BACT/LAER Clearinghouse
Database for the Ethylene Production Source Category, in Docket ID No.
EPA-HQ-OAR-2017-0357.

B. What are the air quality impacts?

    At the current level of control, estimated HAP emissions were
approximately 4,040 tpy. We estimated HAP emissions reductions of 62
tpy and VOC emissions reductions of 540 tpy as a result of the proposed
amendments for storage vessels, heat exchange systems, and decoking
operations for ethylene cracking furnaces. We note that these emissions
reductions do not consider the potential excess emissions reductions
from flares that could result from the proposed monitoring
requirements; we estimated flare excess emissions reductions of 1,430
tpy HAP and 13,020 tpy VOC. When considering the flare excess
emissions, the total emissions reductions as a result of the proposed
amendments were estimated at 1,492 tpy HAP and 13,560 tpy VOC. These
emissions reductions are documented in the following memoranda, which
are available in Docket ID No. EPA-HQ-OAR-2017-0357: Assessment of Work
Practice Standards for Ethylene Cracking Furnace Decoking Operations
Located in the Ethylene Production Source Category, Clean Air Act
Section 112(d)(6) Technology Review for Storage Vessels Located in the
Ethylene Production Source Category, Clean Air Act Section 112(d)(6)
Technology Review for Heat Exchange Systems in the Ethylene Production
Source Category, and Control Option Impacts for Flares Located in the
Ethylene Production Source Category.

C. What are the cost impacts?

    We estimated the total capital costs of the proposed amendments to