[Federal Register Volume 86, Number 39 (Tuesday, March 2, 2021)]
[Rules and Regulations]
[Pages 12095-12107]
[FR Doc No: 2021-04108]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R05-OAR-2010-0037; FRL-10019-32-Region 5]

Air Plan Approval; Minnesota; Revision to Taconite Federal
Implementation Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is revising a
Federal implementation plan (FIP) addressing the requirement for best
available retrofit technology (BART) for the United States Steel
Corporation's (U.S. Steel) taconite plant located in Mt. Iron,
Minnesota (Minntac or Minntac facility). We are revising the nitrogen
oxides (NOX) limits for U.S. Steel's taconite furnaces at
its Minntac facility because new information has come to light that was
not available when we originally promulgated the FIP on February 6,
2013. The EPA is finalizing this action pursuant to sections 110 and
169A of the Clean Air Act (CAA or the Act).

DATES: This final rule is effective April 1, 2021.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-R05-OAR-2010-0037. All documents in the docket are listed in
the http://www.regulations.gov website. Although listed in the index,
some information is not publicly available, e.g., Confidential Business
Information or other information whose disclosure is restricted by
statute. Certain other material, such as copyrighted material, is not
placed on the internet and will be publicly available only in hard copy
form. Publicly available docket materials are available either through
http://www.regulations.gov or at the EPA Region 5 office (please
contact the person identified in the FOR FURTHER INFORMATION CONTACT
section for availability information).

FOR FURTHER INFORMATION CONTACT: Kathleen D'Agostino, Environmental
Scientist, Attainment Planning & Maintenance Section, Air Programs
Branch (AR-18J), U.S. Environmental Protection Agency, Region 5, 77
West Jackson Boulevard, Chicago, Illinois 60604,<PHONE_NUMBER>,
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean EPA.

I. Background Information

    On February 6, 2013, EPA promulgated a FIP that included BART
limits for certain taconite furnaces in Minnesota and Michigan (2013
Taconite FIP; 78 FR 8706). On February 4, 2020, EPA proposed to revise
the 2013 Taconite FIP with respect to the NOX BART emission
limitations and compliance schedules for U.S. Steel's Minntac facility
in Minnesota. (85 FR 6125).
    Specifically, EPA proposed that an aggregate emission limit of 1.6
lbs NOX per million British Thermal Unit (MMBtu), based on a
30-day rolling average, averaged across Minntac's five production
lines, represents NOX BART for the Minntac facility. An
explanation of the CAA requirements, a detailed analysis of how these
requirements apply to U.S. Steel's Minntac facility, and EPA's reasons
for proposing the revised limit and compliance schedule were provided
in the notice of proposed rulemaking (NPRM) and will not be restated
here. The public comment period for this proposed rule ended on March
5, 2020.
    One commenter stated that EPA did not provide information regarding
a public hearing and did not ask the public if they were interested in
a public hearing. To address this comment, EPA held a virtual public
hearing on October 14, 2020, and reopened the public comment period.
The second comment period closed on November 13, 2020. The commenter
also stated that EPA did not demonstrate that the agency consulted with
Federal Land Managers (FLMs) regarding the proposed FIP revision. In
response to this comment, EPA engaged with the FLMs on the revision to
the taconite FIP for Minntac. The FLMs have indicated that they have no
comments on the FIP revision.

II. Public Comments

    During the first comment period EPA received adverse comments
submitted on behalf of the National Parks Conservation Association and
the Minnesota Center for Environmental Advocacy, an adverse comment
submitted anonymously, and a comment from a private citizen in support
of the February 4, 2020 proposal. We also received an anonymous comment
that addresses subjects outside the scope of our proposed action. The
adverse comments are summarized and addressed below. No one presented
testimony at the October 14, 2020 virtual public hearing. The
transcript of the hearing is available in the docket. We received no
comments during the second comment period.
    Comment 1: The 2013 FIP included case-by-case determinations and
emission limits for each of the BART units at Minntac, as follows: 1.2
lbs NOX/MMBtu when burning natural gas and 1.5 lbs
NOX/MMBtu when co-firing coal and natural gas. This was done
in accordance with the CAA where BART is defined as ``an emission
limitation based on the degree of reduction achievable through the
application of the best system of continuous emission reduction for
each pollutant which is emitted by an existing stationary facility.''
This emission limit is to be established on a case-by-case basis after
considering the five statutory factors.
    EPA's 2020 proposal would provide a single facility-wide
NOX BART limit of 1.6 lbs/MMBtu that will apply on a rolling
30-day basis. Contrary to the CAA and BART Guidelines, for each Minntac
source subject to BART, EPA abandons its 2013 BART determination and
now proposes a FIP revision that neglects its obligation to ensure
limits reflect BART emission rates that are of the appropriate type and
level for each source subject to BART. Without revised individual BART
determinations for each of the five Minntac units EPA cannot
demonstrate that reductions achieved by the facility-wide limit will be
equal to the reductions obtained by controlling the individual units.
While the Minntac Spreadsheet in the docket contains information on
95th and 99th percentile and highest 720-hour averages, it seems EPA
decided to ignore the percentile values, and rather propose U.S.
Steel's averaging approach.
    Response: The August 15, 2012 Proposed FIP (77 FR 49312-49313)
included a five-step BART analysis for Minntac's five lines (Lines 3-
7). The five-step analysis was conducted in accordance with the BART
Guidelines, appendix Y to 40 CFR part 51. EPA proposed BART emission
limits of 1.2 lbs NOX/MMBtu measured on a 30-day rolling
average based on the use of low NOX burners. EPA's analysis
and proposed determination that BART is based upon the use of low
NOX burners remains valid. In the February 6, 2013 Final FIP
(78 FR 8706), based on a comment from U.S. Steel regarding the
appropriate emission limit when burning solid fuels and supplementary
data submitted by U.S. Steel on October 15, 2012,\1\ EPA finalized a
limit for each of Minntac's five lines of 1.5 lbs NOX/MMBtu
measured on a 30-day rolling average; however, a limit of 1.2 lbs
NOX/MMBtu measured on a 30-day rolling average would apply
for any 30 or more consecutive days when only natural gas is used. The
final 2013 FIP limits reflected what EPA determined could be reasonably
achieved by the use of low NOX burners at taconite furnaces
based on the limited emission data available.
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    \1\ See ``US Steel Comments--Proposed FIP MN and MI'' and ``10-
15-2012 email from C. Bartovich to S. Rosenthal'' and attachments,
included in the docket.
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    At the time EPA promulgated the BART emission limits for Minntac,
low NOX burners had only been in operation on Minntac Lines
6 and 7 since April 2011 and May 2010, respectively, and there were
very little emission data available upon which to base a limit. Since
promulgation of the FIP, however, U.S. Steel submitted continuous
emission monitoring system (CEMS) data demonstrating that despite
having optimized each burner,\2\ Minntac is unable to comply with the
1.2 lbs NOX/MMBtu limit at all times when burning only
natural gas.
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    \2\ See ``IV.F. U.S. Steel Minntac Line 6 Low NOX
Burner Final Report, December 1, 2011,'' ``III.F. U.S. Steel
Minntac9.m. U.S. Steel Minntac Line 7 Burner Final Report, May 13,
2011,'' and ``Final Report Line 4 Burner 092917,'' included in the
docket.
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    EPA continues to rely on the BART analysis set forth in the August
15, 2012 proposal concerning the selection of low NOX
burners as the appropriate BART

technology. However, since EPA promulgated the BART limits for Minntac,
U.S. Steel has continued to operate low NOX burners on Lines
6 and 7 and has installed low NOX burners on Lines 4 and
5.\3\ There are significantly more data available from which to
determine whether the BART FIP emission limits are actually achievable
through the utilization of low NOX burners at Minntac. To
reevaluate the emission limit achievable by use of low NOX
burners, EPA analyzed available hourly CEMS data showing emissions in
lbs NOX/MMBtu by fuel type. These data were available for
the 2012-2017 time period. From this data set, EPA then compiled the
emission data available for each line after the installation of low
NOX burners. For Line 4, this included data from December
15, 2016 through November 19, 2017. For Line 5, this included data from
December 12, 2015 through November 11, 2017. For Lines 6 and 7,
emission data were available from May 8, 2012 and April 27, 2012
through November 11, 2017, respectively. There are necessarily
differing amounts of CEMS data for each line since the low
NOX burners were installed at different times.
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    \3\ U.S. Steel installed low NOX burners on Lines 4
and 5 on December 15, 2016, and December 20, 2015, respectively.
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    To ensure that any revised emission limit would be based upon
emission reduction capabilities during normal operations, EPA excluded
hours when a line was idle, when a measurement error was recorded, or
when process or CEMS codes indicated anything other than normal
operation. For each line, EPA separated hours when only natural gas was
burned from hours when the line was co-fired with coal (Lines 6 and 7)
or co-fired with biomass (Lines 4 and 5). EPA then calculated 720-hour
rolling averages based upon fuel type.\4\ To establish an achievable
emission limit, EPA assessed the highest 720-hour average, the 99th
percentile 720-hour average, and the 95th percentile 720-hour
average.\5\ The 99th percentile is the emission rate that the source
would be predicted to be below during 99 out of 100 720-hour averages.
The 95th percentile is the emission rate that the source would be
predicted to be below during 95 out of 100 720-hour averages. The
highest 720-hour average is the emission rate at which the source would
be predicted to be able maintain continual compliance.
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    \4\ Operations at Minntac in a given 30-day period, or even a
single day, may in some cases involve both operation with only
natural gas and operation with at least some firing of solid fuels.
To be able to evaluate emissions from all hours when different fuels
were used within a 30-day period, rather than only the times when a
line used solely natural gas or solely co-fired for 30 consecutive
days, EPA evaluated emissions based on 720-hour averages. Note that
operations are typically 24 hours per day and 720 is the number of
hours in a 30-day period.
    \5\ See Lines 3, 4, and 5 Data-L4_7 NOX Data files
combined,'' included in the docket.
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    Under the BART Guidelines, a source may be permitted to average
emissions across a set of BART-eligible emission units within a
fenceline, so long as the emission reductions from each pollutant being
controlled for BART would be equal to those reductions that would be
obtained by simply controlling each of the BART-eligible units that
constitute the BART-eligible source. See 40 CFR part 51, appendix Y, at
V. U.S. Steel expressed interest in utilizing this option. As shown in
Table 1 below, averaging the individual limits across Lines 4 through 7
for natural gas results in a combined emissions limit of 1.6 lbs
NOX/MMBtu averaged over 720 hours, regardless of whether the
single line emission limit basis for the cross-line average was the
highest 720-hour average, the 99th percentile 720-hour average, or the
95th percentile 720-hour average.

             Table 1--Individual Line and Cross-Line Averaging Emission Rates for Lines 4 Through 7
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                                                                   High  720-hr     99%  720-hr     95%  720-hr
                                                  Fuel             average  lbs    average  lbs    average  lbs
                                                                     NOX/MMBtu       NOX/MMBtu       NOX/MMBtu
----------------------------------------------------------------------------------------------------------------
Line 4................................  Natural Gas.............             1.5             1.5             1.5
                                        All Fuels...............             1.5             1.4             1.4
Line 5................................  Natural Gas.............             1.4             1.4             1.4
                                        All Fuels...............             1.4             1.4             1.3
Line 6................................  Natural Gas.............             1.7             1.6             1.6
                                        All Fuels...............             1.7             1.6             1.4
Line 7................................  Natural Gas.............             1.9             1.8             1.8
                                        All Fuels...............             1.9             1.8             1.7
                                                                 -----------------------------------------------
    Cross-line Average................  Natural Gas.............             1.6             1.6             1.6
                                        All Fuels...............             1.6             1.6             1.5
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    While Line 3 will not become subject to the FIP limits until July
2021, U.S. Steel has indicated that, when compared to the other lines,
the Line 3 burner is most similar to Line 4. Line 4 is more similar in
age, size and design to Line 3 than the other lines. Line 3 utilizes
the same fuels (natural gas and biomass) as Line 4, and both Lines are
managed by the same control room operators. In addition, operating
parameters on Line 3 are similar to Line 4 for such measured parameters
as Kiln Exit Temperature, Preheat Zone Temperature, Burner Temperature,
and Pellet Residence time on the grate and in the kiln. Absent an
engineering study for Line 3, using the emission rates for Line 4 as an
estimate of the emission rates that would be expected after
installation of a low NOX burner on Line 3 is reasonable.
Therefore, EPA also calculated a cross-line average considering actual
emissions from all four lines currently utilizing low NOX
burners (Lines 4 through 7), as well as the expected emissions from
Line 3. The resulting cross-line average is 1.6 lbs NOX/
MMBtu averaged over 720 hours, regardless of selection of statistical
analyses at the 99th or 95th percentiles, or highest 720-hour average.
    While the 1.6 lbs NOX/MMBtu limit for Minntac is
reflective of natural gas emission data, in response to the comment
received, EPA calculated 720-hour rolling averages for each line over
the entire period without separating fuel types. As provided in Table
1, the data

analysis showed that the cross-line averages at the highest 720-hour
average across all data and also at the 99th percentile is 1.6 lbs
NOX/MMBtu, and at the 95th percentile is 1.5 lbs
NOX/MMBtu. In addition, review of the CEMS data shows that
U.S. Steel has largely transitioned toward firing with natural gas and
away from co-firing with coal and natural gas. U.S. Steel stated that
it ``has been primarily combusting natural gas since December 2016.''
\6\ As previously stated, only two of Minntac's five lines (Lines 6 and
7) are capable of burning coal, and CEMS data show that U.S. Steel has
largely shifted its operations on Lines 6 and 7 away from co-firing
with coal and natural gas and toward firing exclusively natural gas.
While Lines 6 and 7 co-fired with coal and natural gas 85% of the time
in 2012, these lines co-fired with coal and natural gas only 3% of the
time in 2017.\7\
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    \6\ See Redacted ``U. S. Steel Confidential Settlement
Communication--Subject to FRE 408,'' May 1, 2018, included in the
docket.
    \7\ See ``Minntac CEMS Data and Analysis,'' included in the
docket.
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    EPA has determined that the 1.6 lbs NOX/MMBtu cross-line
emission limit constitutes the appropriate BART emission limit for
Minntac Lines 3 through 7, regardless of fuel type. As previously
discussed, the BART Guidelines provide that a source may be permitted
to average emissions across a set of BART-eligible units within a
fenceline, so long as the emission reductions from each pollutant
controlled for BART would be equal to those reductions that would be
obtained by separately controlling each of the BART-eligible units that
constitute the BART-eligible source. 40 CFR part 51, appendix Y, at V.
Minntac Lines 3, 4, 5, 6, and 7 are all BART-eligible units that
constitute a BART-eligible source within a fenceline. When averaging
the level of NOX emission reductions achievable on each of
Minntac Lines 3 through 7 individually, the resulting limit is 1.6 lbs
NOX/MMBtu when burning natural gas. Therefore, it is
reasonable for EPA to establish a single cross-line average emission
limit of 1.6 lbs NOX/MMBtu, to apply at all times, for
Minntac Lines 3 through 7. 1.6 lbs NOX/MMBtu is the most
stringent limit the facility can consistently meet while providing for
operational flexibility with regard to fuel choice, including burning
exclusively natural gas.
    Comment 2: EPA's proposal lacks alternative BART emission limits
based on the type of fuel each line will burn under the FIP. Although
the BART Guidelines are fuel-neutral, where a source wants to operate
under different scenarios and burn different fuels that create
different levels of BART pollutant emissions, EPA must first set
alternative BART emission limits for each unit based on fuel use. EPA's
2013 FIP promulgated two BART emission limits based on fuel use, which
apply to all five BART units: A limit when burning natural gas, and
second limit when co-firing coal and natural gas. The record indicates
the BART units historically used a variety of fuels, which included:
Coal; wood; co-firing; biomass; and natural gas. EPA's proposed
facility-wide BART limit relies on emission data collected when only
one fuel was used, natural gas. EPA fails to analyze the range of fuels
burned at Minntac and how the fuel burned impacts revising the prior
BART determinations.
    Response: EPA disagrees with the commenter's contention that EPA
must set alternative BART emission limits for each unit based on fuel
use. Neither the CAA nor the regional haze rule requires EPA to
establish separate BART limits based on fuel type. While the 1.6 lbs
NOX/MMBtu limit for Minntac is reflective of natural gas
emission data, EPA evaluated all available CEMS data for 2012-2017.
These data are reflective of scenarios where lines were burning
exclusively natural gas and scenarios when lines were co-firing with
solid fuels.
    We are under no obligation to set fuel-specific limits and are not
doing so here. EPA has determined that 1.6 lbs NOX/MMBtu is
the most stringent limit the facility can consistently meet while
providing for operational flexibility with regard to fuel choice,
including burning exclusively natural gas. As discussed previously in
response to Comment 1, in response to comments received, EPA calculated
720-hour rolling averages for each line over the entire period without
separating fuel types (the ``All Fuels'' scenario). The data
demonstrate that the cross-line averages at the highest 720-hour
average across all data and also at the 99th percentile is 1.6 lbs
NOX/MMBtu, and at the 95th percentile is 1.5 lbs
NOX/MMBtu. However, as previously explained, to allow for
fuel choice and a scenario in which the facility burns only natural
gas, 1.6 lbs NOX/MMBtu is the appropriate limit for the
facility.
    Comment 3: The agency suggests using the new data to revise the
five BART determinations in its 2013 FIP. EPA fails to provide a
reasoned analysis for using the new data to revise its prior
determination. EPA's prior determination found that once low
NOX burners were installed and burned natural gas,
NOX emissions were lower than when co-firing coal and
natural gas, and therefore, based the 2013 FIP BART emission limits on
its record and findings. EPA's 2020 proposal flips its prior
determination, contending that NOX emissions are higher when
burning only natural gas, as compared to co-firing coal and natural
gas.
    Response: EPA's August 15, 2012 proposed FIP approval includes an
analysis and proposed determination that BART for Minntac is based upon
the use of low NOX burners. In the 2013 FIP final rule, EPA
finalized this determination. EPA's analysis concerning low
NOX burners as representing BART for Minntac continues to
remain valid and it is appropriate for EPA to rely on it in this
action. As discussed above, at the time EPA established limits in the
2013 FIP, low NOX burners had only been in operation on
Lines 6 and 7 since April 2011 and May 2010, respectively, and there
were limited emission data available upon which to base a limit.
However, since that time, U.S. Steel has continued to operate low
NOX burners on Lines 6 and 7 and has installed low
NOX burners on Lines 4 and 5. Therefore, as discussed in the
response to Comment 1, there are significantly more data available from
which to determine whether the BART FIP emission limits are actually
achievable through the utilization of low NOX burners at
Minntac.
    Comment 4: EPA's approach is not permissible under the Act. Instead
of proposing BART emission limits based on maximum controls, EPA's
proposal uses the new data from the operating scenario that is the
least effective at controlling NOX emissions to derive a
BART emission limit, and then suggests applying the least effective
control at all five BART units, regardless of what the unit burns.
    Response: The control technology used as the basis for establishing
BART limits in the 2013 FIP has not changed. Since promulgation of the
2013 FIP, however, our understanding of the emissions levels achievable
through the use of this technology has changed. The emission limits
initially promulgated under the 2013 FIP were based on the installation
and optimization of a low NOX burner on Lines 6 and 7, and
the limited CEMS data available at that time. Since promulgation of the
2013 FIP, U.S. Steel has continued to collect CEMS data from Lines 6
and 7. U.S. Steel has also installed low NOX burners on
Lines 4 and 5, has adjusted and optimized each of those burners to
reduce NOX, and has collected CEMS data for each of the
lines. EPA based the 1.6 lbs NOX/MMBtu limit on the

emission rates demonstrated by the CEMS data to be achievable by low
NOX burners, which is the technology determined to be the
basis for BART. The 1.6 lbs NOX/MMBtu limit is the most
stringent limit the facility can consistently meet while providing for
operational flexibility with regard to fuel choice. Contrary to
commenter's assertion, EPA did not base the 1.6 lbs NOX/
MMBtu limit on the projected emission rates achievable by the least
effective control technology.
    Comment 5: There is nothing in the record to suggest all lines will
be capable of and restricted to burning natural gas nor that the
company plans to burn natural gas exclusively.
    Response: The CEMS data clearly demonstrate that all lines are
capable of burning natural gas. EPA is not restricting U.S. Steel to
only burning natural gas at Minntac. Should U.S. Steel choose to
periodically co-fire with coal or biomass on one or more of its lines,
the facility will remain subject to the 1.6 lbs NOX/MMBtu
limit regardless of fuel type.
    Comment 6: EPA fails to provide a basis for the cherry-picked and
incomplete data. EPA's NPRM notes it evaluated six years of CEMS data,
not specifying which years were evaluated. EPA provides neither an
analysis of nor a justification for using such disparate data. While
EPA explains the data represent operations at the taconite furnaces
under various production scenarios, it fails to explain what these
scenarios are and whether they represent the full range of future
scenarios. EPA provides no explanation to justify its use of this
limited data set.
    Response: As described previously, EPA used the full suite of CEMS
data available for each line after the installation of low
NOX burners. The document entitled ``Minntac CEMS Data and
Analysis,'' included in the docket, identifies the date and hour of
each emission data point used in the calculations. The earliest data
available that provided hourly NOX emission data in lbs
NOX/MMBtu along with the corresponding fuel type began in
2012 and was provided through 2017. From this data set, EPA then
compiled the emission data available for each line after the
installation of low NOX burners. For Line 4, this included
data from December 15, 2016 through November 19, 2017. For Line 5, this
included data from December 12, 2015 through November 11, 2017. For
Lines 6 and 7, emission data were available from May 8, 2012 and April
27, 2012, respectively, through November 11, 2017. There are
necessarily differing amounts of data for each line since the low
NOX burners were installed at different times. To establish
a limit based on emissions reflective of normal operating conditions,
EPA excluded hours when the process was idle, when a measurement error
was recorded, or when process or CEMS codes indicated anything other
than normal operation.
    With respect to operating scenarios, EPA does not claim that the
data evaluated represent the full range of possible future operating
scenarios. Rather, the initial emission limits in the 2013 FIP were
based upon very limited CEMS data from Lines 6 and 7. Operations at
Lines 6 and 7 over the 2012-2017 time period showed varying production
levels, fuels, pellet types and different ore mixes. In addition, we
now have CEMS data for Lines 4 and 5 reflecting the installation of low
NOX burners. The available CEMS data provide information on
NOX emissions over time which encompass more operating
scenarios than were represented by the limited data available at the
time EPA promulgated the 2013 FIP. As the CEMS data \8\ available in
the docket show, the 1.2 lbs NOX/MMBtu limit promulgated
under the 2013 FIP and intended to apply when burning only natural gas
cannot be consistently achieved at Minntac during normal operations
with low NOX burners.
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    \8\ See ``Minntac CEMS Data and Analysis,'' included in the
docket.
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    Comment 7: Although EPA's NPRM explains that U.S. Steel also
provided hourly NOX emissions data in lbs/MMBtu for Line 3,
which has not yet installed low NOX burner technology, the
NPRM provides no information on where this information is available.
    Response: This information was erroneously omitted from the docket.
The docket has been updated to include this information.\9\
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    \9\ See ``Lines 3, 4, and 5 Data-L4_7 NOX CEMS Data
files combined.''
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    Comment 8: For the past ten years, 2009 through 2018, the
NOX emissions reported by U.S. Steel have been relatively
constant. EPA fails to explain why emissions remain constant even
though U.S. Steel reports it installed low NOX burners on
four of the five lines subject to BART. EPA also fails to provide an
explanation for why there has been an increase in NOX
emissions in the years following installation of the low NOX
burner. This suggests that U.S. Steel did not optimize the low
NOX burners from 2014 through 2017.\10\
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    \10\ Commenter refers to a figure provided by commenter that
purports to show 2002 baseline emissions from Minnesota's state
implementation plan (SIP) submittal along with plots of facility-
wide NOX emissions in tons per year (tpy) and facility-
wide production for the period 2007 through 2018. See NPCA and MCEA
Comments on the Proposed Revision to Minnesota Taconite Federal
Implementation Plan for U.S. Steel Minntac, at p. 11, Figure 2.
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    Response: Commenter references a figure provided by commenter that:
(1) Shows the 2002 baseline annual emissions for Minntac included in
Minnesota's December 30, 2014 Five-Year Regional Haze Progress Report
SIP submittal,\11\ and (2) plots annual production and annual
NOX emissions at Minntac. The figure does not accurately
reflect U.S. Steel's implementation and optimization of low
NOX burners at Minntac. First, the annual NOX
emissions included in the commenter's figure do not represent annual
emissions from only the indurating furnaces, but rather represent
facility-wide NOX emissions. Second, by definition, BART is
``based on the degree of reduction achievable through the application
of the best system of continuous emission reduction.'' \12\ EPA is
setting a cross-line average for Minntac Lines 3 through 7 of 1.6 lbs
NOX/MMBtu, averaged over 30 days, which is a rate-based
limit based on the degree of reduction achievable through the use of
low NOX burners. Commenter conflates the rate-based emission
limit with total annual NOX emissions from the facility.
Since we are setting a rate-based emission limit, which does not
constrain production levels, total annual NOX emissions may
fluctuate in a given year even while the source is in compliance with
its BART emission rate. For example, if production increases, total
NOX emissions in tons per year would be expected to increase
as well. If production decreases, total NOX emissions in
tons per year (tpy) would be expected to decrease. Under all production
scenarios, the lbs of NOX/MMBtu rate-based emission limit
remains applicable. Finally, the production levels shown in the figure
represent facility-wide production. The figure provided by the
commenter does not differentiate production contributions by line,
i.e., what percentage of total production comes from individual lines
which had low NOX burners installed at the time vs. lines
which did not have low NOX burners installed at the time.
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    \11\ Note commenter used incorrect numbers 14,294 vs 14,924.
    \12\ See 40 CFR 51.301.
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    Notwithstanding the above-noted limitations regarding the figure
provided by the commenter, nonetheless, some information can be gained
by looking at the difference between production and emissions over
time, as represented by the distance

between the NOX line and production line in the figure. From
2007 through 2009, before the installation of low NOX
burners, these lines are relatively close together. In 2010, the year
when the low NOX burner was installed on Line 7, production
rose dramatically while annual NOX emissions did not.
Visually, there is a significant divergence between the NOX
and production lines in the figure, indicating an increase in
production without a commensurate increase in emissions.
Correspondingly, after the low NOX burner was installed on
Line 6 in 2011, the figure shows production increased between 2010 and
2011 while emissions decreased. Low NOX burners were
installed on Lines 5 and 4 in December 2015 and December 2016,
respectively. Similarly, the figure shows NOX emissions
between 2015 and 2017 did not increase at the same rate as production.
    Using the available CEMS data for the 2012-2017 time period, EPA
further evaluated the differences between various NOX
emission values pre and post-installation of low NOX burners
on Lines 4 and 5.\13\ Data for both lines showed a decrease in the
average lbs NOX/MMBtu, high 720-hour average lbs
NOX/MMBtu, and 99th percentile lbs NOX/MMBtu.
Even the average lbs NOX/hour, which does not account for
variations in production levels, decreased. U.S. Steel did not provide
CEMS data for Lines 6 and 7 for the period prior to the installation of
low NOX burners, so a similar comparison cannot be made for
these lines.
---------------------------------------------------------------------------

    \13\ See ``Emission reduction estimates'' and ``Lines 3, 4, and
5 Data-L4_7 NOX CEMS Data files combined for docket,''
included in the docket.
---------------------------------------------------------------------------

    Finally, the commenter asserts that the data suggest that U. S.
Steel failed to optimize operation of the low NOX burners
from 2014 through 2017. As discussed in detail in responses to comments
9 and 14 in this document, after installation of the low NOX
burner on each line, U.S. Steel optimized burner operation for
NOX reduction while maintaining pellet quality. In addition,
Minntac has remained subject to the limits in the 2013 FIP.
    Comment 9: EPA did not explain how U.S. Steel arrived at its
conclusion that the low NOX burners at each of the lines
were optimized and functioning at their best. In prior regional haze
actions, when the level of control has been uncertain at the time of
EPA's final action, EPA requires a control technology demonstration,
with explicit requirements for optimization of the control technology
system. EPA's 2014 final FIP requirements for Arizona plants included a
control technology demonstration project for the emission control
system at each plant, which entailed the collection of data and
preparation of an optimization protocol that would be used to determine
if a higher control efficiency would be achievable. There is no
evidence that EPA required and oversaw implementation of a control
technology project. Moreover, the BART Guidelines require the
consideration of improvements to the low NOX burner controls
(40 CFR part 51, appendix Y, at IV. D. Step 1] 9).
    Response: U.S. Steel has documented optimization studies at Lines
4, 5, 6, and 7 in final testing reports for each line. Final testing
reports for Lines 6 and 7 and preliminary data for Lines 4 and 5 are
included in the docket. In addition, U.S. Steel submitted final testing
reports for Lines 4 and 5, titled ``Final Report Line 4 Burner
092917.'' This document has also been added to the docket. In each
report, U.S. Steel describes challenges encountered over the course of
installing, operating, and testing each low NOX burner, and
discusses how certain design and operational changes were found to
optimize operation of each line's low NOX burners. As
explained in the reports, U.S. Steel evaluated operation of each low
NOX burner to ensure each burner can operate in a manner
that reduces NOX emissions while making pellets that meet
quality specifications. Each burner was evaluated according to hourly
CEMS data and during expected operating scenarios, including while
burning natural gas, solid fuels, and a combination of natural gas and
solid fuels. Over the course of the testing, U.S. Steel identified
several problems occurring at various stages of low NOX
burner operation and prescribed specific design and operational changes
to improve operation in each scenario. U.S. Steel states that each of
the proposed solutions and design changes--including adding blowers,
increasing combustion air fan speed and capacity, adding rings to
combustion air annuli, and adjusting and monitoring atomizing air and
gas splits--were implemented in consultation with the burner
manufacturer to optimize low NOX burner operation and
NOX reduction. In each case, U.S. Steel determined
optimization of the low NOX burners involves achieving
stoichiometric ratios of air to fuel at levels that create a tight
flame shape in order to minimize NOX while ensuring proper
process operation. U.S. Steel continues to monitor CEMS data and burner
parameters to ensure the burners are operating effectively.
    As explained in response to Comments 1 and 3, at the time EPA
established limits in the 2013 FIP, low NOX burners had only
been in operation on Lines 6 and 7 since April 2011 and May 2010,
respectively, and there were limited CEMS data available upon which to
base a limit. However, since EPA promulgated the initial BART limits
for Minntac in the 2013 FIP, U.S. Steel has continued to operate low
NOX burners on Lines 6 and 7 and has installed low
NOX burners on Lines 4 and 5.\14\ There are significantly
more data available from which to determine whether the 2013 FIP
emission limits are actually achievable through the utilization of low
NOX burners at Minntac. In addition, and as noted above,
U.S. Steel has submitted final testing reports for Lines 4 through 7
that detail U.S. Steel's optimization efforts for each of these low
NOX burners. In contrast to the scenario cited by commenter
where the control technology had not yet been installed and only
minimal data were available regarding performance of the control
technology at issue, EPA is basing the revised limit for Minntac on
actual CEMS data. U.S. Steel has also provided information concerning
its low NOX burner optimization efforts for Minntac Lines 4
through 7 and has provided post-optimization emissions data for Lines 4
through 7.
---------------------------------------------------------------------------

    \14\ U.S. Steel installed low NOX burners on Lines 4
and 5 on December 15, 2016, and December 20, 2015, respectively.
---------------------------------------------------------------------------

    In the Arizona 2014 Regional Haze FIP (79 FR 52420) cited by the
commenter, EPA stated the following with regard to Selective Non-
Catalytic Reduction (SNCR) at lime kilns: ``While this type of control
technology demonstration is not typically required as part of a
regional haze plan, we consider it to be appropriate here, given the
minimal data available about the performance of SNCR at lime kilns.''
(79 FR 52440). With regard to SNCR at cement kilns, we explained,
``While this type of control technology demonstration is not typically
required as part of a regional haze plan, we consider it to be
appropriate here, given the significant variability in control
efficiencies achievable with SNCR at cement kilns.'' (79 FR 52456; 79
FR 52462). The control technologies required for lime kilns and cement
kilns in the 2014 Arizona FIP had not yet been installed at the time
the Arizona FIP was promulgated. This is a different scenario than the
situation we are addressing with regard to Minntac.
    Commenter cites to the BART Guidelines at 40 CFR part 51, appendix

Y, at IV. D. Step 1] 9. However, section IV.D. addresses the five steps
of a case-by-case BART analysis, with Step 1 being the identification
of all available retrofit control technologies. As discussed in
response to Comment 1, the August 15, 2012 Proposed FIP (77 FR 49312-
49313) included a five-step BART analysis for Minntac's five lines
(Lines 3-7). The five-step analysis was conducted in accordance with
the BART Guidelines. EPA's analysis and proposed determination that
BART is based upon the use of low NOX burners remains valid
and EPA continues to rely upon that analysis. We are not conducting a
new five-step BART analysis. In this action, we are only revising the
NOX emission limits for Minntac to reflect the level of
emission reductions consistently achievable by low NOX
burners, which is the control technology determined to represent BART
for Minntac in the 2013 FIP.
    Comment 10: 42 U.S.C. 7607(d)(2) requires that EPA's proposed
action include ``the methodology used in obtaining the data.'' While
the docket includes an Excel spreadsheet of CEMS data, there is no
explanation provided regarding the methodology and test methods used to
obtain the data. Furthermore, there is nothing in the record to
indicate U.S. Steel's recent data was accompanied by a certification
statement. Therefore, EPA's proposal fails to comply with the Act's
methodology disclosure requirements and the public is unable to confirm
accuracy and completeness of the data.
    Response: 42 U.S.C. 7607(d)(2) includes requirements pertaining to
the establishment of a rulemaking docket. 42 U.S.C. 7607(d)(3),
however, does require EPA to include a summary of ``the methodology
used in obtaining the data and in analyzing the data.'' At proposal, we
explained how EPA obtained the CEMS data. Specifically, we stated,
``[t]o justify this limit, U.S. Steel provided EPA with hourly
NOX emissions data in lbs/MMBTU documenting actual emissions
levels after installation of [low NOX burner] technology on
Minntac Lines 4-7. U.S. Steel also provided hourly NOX
emissions data in lbs/MMBTU for Line 3, which has not yet installed
[low NOX burner] technology.'' (85 FR 6126).
    In response to EPA's CAA section 114 request for information
regarding Minntac, U.S. Steel provided CEMS data for Lines 3, 4 and 5
covering the time period from January 1, 2012 through August 9, 2016 as
well as CEMS data for Lines 6 and 7 covering the time period from July
24, 2015 through August 9, 2016. The response included a certification
of the accuracy and completeness of the information provided. U.S.
Steel's letter responding to the CAA section 114 information request,
as well as the certification, has been added to the docket.
    In response to additional requests from EPA that were not made
under CAA section 114, U.S. Steel provided CEMS data for Lines 6 and 7
for the period of April 27, 2012 through July 24, 2015 and for Lines 4
through 7 for the period of August 2016 to November 2017. However,
Minntac's CEMS were certified on Agglomerator Waste Gas Lines 6 & 7 on
June 2-3, 2005. The CEMS were certified on Waste Gas Lines 3, 4 & 5 on
January 24, 2007, January 31, 2007 and February 1, 2007, respectively.
Further, Minntac is subject to the CEMS requirements of the 2013 FIP,
which may be found at 40 CFR 52.1235(c) and include the requirement
that CEMS ``be installed, certified, calibrated, maintained, and
operated in accordance with 40 CFR part 60, appendix B, Performance
Specification 2 (PS-2) and appendix F, Procedure 1.'' Minntac's title V
permit also specifies that the CEMS meet the requirements of 40 CFR
part 60 appendix B and F and Minnesota rule 7017 for monitoring and
testing requirements. Pursuant to their title V permit, U.S. Steel must
annually certify its compliance with title V. EPA has no reason to
question the accuracy and completeness of the CEMS data supplied.
    In addition, the document, Minntac CEMS Data and Analysis, is
included in the docket and contains EPA's analysis of the data provided
by U.S. Steel.\15\
---------------------------------------------------------------------------

    \15\ See ``Minntac CEMS Data and Analysis,'' Docket ID # EPA-
R05-OAR-2010-0037-0110, available at https://www.regulations.gov/document?D=EPA-R05-OAR-2010-0037-0110. We note that the document,
Redacted US Steel Proposal to EPA Minntac 5-1-2018, was erroneously
listed on regulations.gov as an attachment to Minntac CEMS Data and
Analysis under Docket ID # EPA-R05-OAR-2010-0037-0110. Minntac CEMS
Data and Analysis and Redacted US Steel Proposal to EPA Minntac 5-1-
2018 are two distinct documents. Minntac CEMS Data and Analysis is
an Excel file containing EPA's analysis of CEMS data for Minntac.
Redacted US Steel Proposal to EPA Minntac 5-1-2018 is a redacted
version of a settlement communication provided by U.S. Steel to EPA.
While Redacted US Steel Proposal to EPA Minntac 5-1-2018 remains
available under Docket ID # EPA-R05-OAR-2010-0037-0110, it may also
be found under its own Docket ID # EPA-R05-OAR-2010-0037-0109,
available at https://www.regulations.gov/document?D=EPA-R05-OAR-2010-0037-0109.
---------------------------------------------------------------------------

    Comment 11: While U.S. Steel expressed apprehensions about
fluctuating emissions due to ``concerns regarding ore blend,'' and EPA
appears to rely on this in proposing to revise the FIP, there is no
information in the record to substantiate ore blend variability. Nor is
there any information in the record that explains how fluctuations in
ore blend impact the ability of low NOX burners to control
NOX emissions. EPA's assertions appear to suggest that it
assumes the fluctuations go in one direction, adding a ``safety
margin'' to the facility-wide limit, without providing a reasoned
basis.
    Response: EPA did not consider ore blends in proposing to revise
the FIP. EPA did provide a reasoned basis for the 1.6 lbs
NOX/MMBtu emission limit. This is the limit demonstrated by
the CEMS data to be achievable by low NOX burners, which is
the technology determined to be the basis for BART. The 1.6 lbs
NOX/MMBtu limit is the most stringent limit the facility can
consistently meet while providing for operational flexibility with
regard to fuel choice. EPA did not add a safety margin to the limit as
commenter suggests.
    Comment 12: EPA's proposal suggests that given the trajectory of
fuel markets, EPA has no reason to believe that U.S. Steel will not
continue to use natural gas at Minntac. EPA provides neither
information about fuel markets nor a trajectory. Even if such
information were provided, reliance on market projections is not an
acceptable justification. Projections are just that, merely
projections, and EPA lacks authority to rely on them. Moreover, in
responding to the Petitions for Reconsideration on its 2013 FIP, EPA
explained that ``the taconite industry has demonstrated that it can re-
engineer furnaces to adapt to market changes (such as fuel prices)''
and EPA found that ``at U.S. Steel's Minntac facility, where low
NOX burners have been installed and are in operation, there
has been no fuel penalty.''
    Response: The 1.6 lbs NOX/MMBtu limit for Minntac
represents the most stringent limit the facility can consistently meet
while providing for operational flexibility to burn exclusively natural
gas. As discussed previously in response to Comments 2 and 4, U.S.
Steel's production and fuel use data show that U.S. Steel has been
moving toward using natural gas rather than co-firing with coal.
Minntac Lines 6 and 7 (the only lines that capable of burning coal)
have shifted fuel use dramatically over the six years evaluated, from
15% natural gas in 2012 to 97% natural gas in 2017. The 1.6 lbs
NOX/MMBtu limit represents the most stringent limit the
facility can consistently meet while providing operational flexibility
with regard to fuel choice--including, for example, in response to
market changes, the option to burn exclusively natural gas. Should

U.S. Steel choose to co-fire with coal or biomass on one or more of its
lines, the facility will remain subject to the 1.6 lbs NOX/
MMBtu limit regardless of fuel type.
    Comment 13: Information in the docket indicates U.S. Steel
suggested the facility-wide emission limit needs to be set at a level
that includes approximately two months of historical emission data that
were above the 1.5 lbs NOx/MMBtu limit EPA offered during
the negotiations. EPA provides no explanation for what caused the
elevated levels. In fact, it's unclear whether EPA attempted to
ascertain the answer to that question. These elevated levels were not
seen at the other BART units. Without an explanation for this limited
data, and whether such instances will occur during normal operations,
it is unreasonable, arbitrary and capricious for EPA to set a limit
that includes these operations, which has the effect of providing a
``safety margin.''
    Response: It is unclear what information commenter is referencing.
However, as discussed in greater detail in response to Comment 1, EPA
evaluated and analyzed available hourly CEMS data showing emissions in
lbs NOX/MMBtu and fuel type. These data were available for
the 2012-2017 time period. From this data set, EPA compiled the
emission data available for each line after the installation of low
NOX burners. EPA then evaluated CEMS codes and process codes
for each line to ensure that the limit would be based upon emission
reduction capabilities during normal operations. EPA excluded hours
when the process was idle, when a measurement error was recorded, or
when process or CEMS codes indicated anything other than normal
operation. Based upon that data, EPA proceeded to calculate achievable
limits for the individual lines to use as a basis for the 1.6 lbs
NOX/MMBtu cross-line average limit proposed.
    Comment 14: Based on its experience with the low NOX
burner at Minntac Line 6, EPA denied U.S. Steel's Petition for
Reconsideration (at another facility), explaining that after installing
Line 6, U.S. Steel was able to make significant design changes before
installation at the next line planned for BART installation, Minntac
Line 7.\16\ EPA explained that the company identified the need for
increased air flow and the need to modify the burner size or physical
space to best accommodate the installation, and in doing so achieved
the NOX reductions at Line 7. EPA's current proposal fails
to explain why U.S. Steel cannot make design changes to all the lines
that will be capable of burning natural gas to achieve the
NOX emission limit when burning gas, when earlier it
demonstrated it was able to do so at Lines 6 and 7.
---------------------------------------------------------------------------

    \16\ Commenter seems to be confusing the order of low-
NOX burner installation on Lines 6 and 7. Low
NOX burners were installed on Lines 6 and 7 in April 2011
and May 2010, respectively.
---------------------------------------------------------------------------

    Response: U.S. Steel's final burner reports for Lines 4 and 5, 6,
and 7 provide detailed explanations of its efforts to optimize
NOX reduction at each line. As discussed in the reports,
U.S. Steel has made physical and operational changes and tuned each low
NOX burner to ensure each can operate in a manner that
reduces NOX emissions while making pellets that meet quality
specifications. Specifically, the September 2017 Line 4 final burner
report highlights how U.S. Steel installed a blower to add additional
combustion air to optimize stoichiometric ratios at Lines 4 and 5.
Subsequent information provided by U.S. Steel discusses how U.S. Steel
implemented a CEMS-based monitoring and process control program to
monitor NOX emissions at each line and allow for automated
process control system adjustments to ensure the low NOX
burners at each line are operating efficiently.
    Comment 15: One of EPA's purported reasons for providing U.S. Steel
with the higher limit is to provide the company with ``additional
flexibility.'' This rationale finds no basis in the CAA and is
therefore not a permissible reason for revising the 2013 FIP
determinations. Moreover, while EPA suggests that this flexibility is
appropriate because of ``unique issues U.S. Steel faced in trying to
comply with the individual limits in the 2013 FIP,'' EPA provides no
explanation of what those issues are, and what options were explored,
if any, to resolve those issues. EPA fails to provide an explanation
for its reversal of opinion and fails to explain the basis for its
decision.
    Response: As explained in the proposal, U.S. Steel faced issues
trying to comply with the limits in the 2013 FIP. As discussed in
response to Comment 1, the emission limits initially promulgated under
the 2013 FIP were based on the installation and optimization of low
NOX burners on Lines 6 and 7, and the limited CEMS data
available at that time. Since promulgation of the 2013 FIP, our
understanding of the emissions levels achievable through the use of low
NOX burner has changed. U.S. Steel has continued to collect
CEMS data from Lines 6 and 7. U.S. Steel has also installed low
NOX burners on Lines 4 and 5, adjusted and optimized each of
those burners to reduce NOX, and collected CEMS data for
each of the lines.
    EPA's proposal to set an aggregate emission limit averaged across
Minntac's five lines is permissible under the BART Guidelines. As
discussed in the proposal and in response to Comments 1 and 18, the
BART Guidelines provide that a source may be permitted to ``average''
emissions across a set of BART-eligible emission units within a
fenceline, so long as the emission reductions from each pollutant
controlled for BART would be equal to those reductions that would be
obtained by simply controlling each of the BART-eligible units that
constitute BART-eligible sources. See 40 CFR part 51, appendix Y, at V.
    EPA based the 1.6 lbs NOX/MMBtu cross-line average on
the emission rates demonstrated by the CEMS data to be achievable
through the use of low NOX burners. The 1.6 lbs
NOX/MMBtu limit is the most stringent limit the facility can
consistently meet while providing for operational flexibility with
regard to fuel choice. As stated in the proposal, EPA is confident that
allowing U.S. Steel to average NOX emissions levels across
Minntac Lines 3 through 7 will achieve NOX emission
reductions equal to the reductions that would have been obtained had
EPA revised the individual limits for Minntac Lines 3 through 7
separately. The ``additional flexibility'' provided by this cross-line
average is consistent with the BART Guidelines.
    Comment 16: EPA does not disclose that the proposal is apparently
the result of confidential settlement discussions. EPA's apparent
reliance on confidential information not disclosed as a part of this
proposal, contravenes the Act's requirements and does not allow the
public to review and consider the changes proposed, and is particularly
problematic in light of the history and level of pollution from these
sources. EPA has not provided documentation of the reasons for the
revisions in the form of publicly available information. Without the
opportunity to review the information EPA relies on, the public is
prohibited from critiquing the basis for EPA's action and cannot
meaningfully participate in the comment process. EPA is suppressing
``meaningful comment by failure to disclose the basic data relied upon
is akin to rejecting comment altogether.''
    In sum, EPA's emission limitation proposal appears to be based on
negotiations, rather than a technical analysis, since EPA did not
consider the

relevant statutory and regulatory factors in proposing the revisions
and fails to provide a basis for most of its assertions. It is
unlawful, arbitrary and capricious for EPA to assert it has authority
to revise BART emission limitations without the factual and analytical
support substantiating its decision.
    Response: The revised emission limit is the result of a settlement
agreement between EPA and U.S. Steel. On September 11, 2019, EPA
published a notice of proposed settlement agreement in the Federal
Register and provided the public an opportunity to comment on the
proposed settlement agreement, in accordance with CAA section 113(g),
42 U.S.C. 7413(g). (84 FR 47945). EPA did not receive any adverse
comments relating to the proposed settlement agreement. Contrary to the
commenter's assertion, EPA did not rely on confidential information in
determining the appropriate NOX BART emission limits for
Minntac. Rather, EPA relied upon CEMS data available in the docket.
    As discussed in the response to Comment 1, the five-step BART
analysis for Minntac in the August 15, 2012 proposed FIP (77 FR 49312-
49313), established low NOX burners as the basis for BART
emission limits. That analysis and EPA's determination that BART is
based upon the use of low NOX main burners remains valid and
EPA continues to rely on the BART analysis set forth in the August 15,
2012 proposal concerning the selection of low NOX burners as
the appropriate BART technology. However, since EPA promulgated the FIP
limits, U.S. Steel has continued to operate low NOX burners
and to collect CEMS data on Lines 6 and 7. Since promulgation of the
FIP, U.S. Steel has also installed low NOX burners and
collected CEMS data on Lines 4 and 5. Therefore, there are
significantly more data available now from which to evaluate the
emissions limits actually achievable through the use of low
NOX burners at Minntac than there were at the time the FIP
was promulgated. As discussed in greater detail in response to Comments
1 and 6, it is this combined data set, which has been included in the
docket, that provides the basis for the revision to the NOX
BART emission limit for Minntac.
    Comment 17: The proposal lacks clear, well-documented comparisons
between baseline emissions, the emission limitations from the 2013
final Taconite FIPs, and the new proposal. In particular, changes in
annual emissions are not provided, and thus not easily compared by the
public.
    Response: Upon implementation of limits of 1.5 lbs NOX/
MMBtu and 1.2 lbs NOX/MMBtu, the reductions estimated under
the 2013 FIP for Minntac range from 5,426 tpy to 6,077 tpy. The
estimated reductions under a revised Minntac limit of 1.6 lbs
NOX/MMBtu are 5,209 tpy. These data are included in the
docket as ``Emission reduction estimates.''
    Comment 18: EPA fails to explain why it now thinks it is reasonable
to use U.S. Steel's averaging approach, which it earlier found was not
defensible because it relies on the assumption that all furnaces will
emit at their highest values. Relying on the assumption that all
furnaces will emit at their highest values (and be burning natural gas
100 percent of the time) is yet another assumption that provides an
additional unjustified ``safety margin.''
    Response: Under the BART Guidelines, a source may be permitted to
``average'' emissions across a set of BART-eligible emission units
within a fenceline, so long as the emission reductions from each
pollutant controlled for BART would be equal to those reductions that
would be obtained by simply controlling each of the BART-eligible units
that constitute BART-eligible sources. See 40 CFR part 51, appendix Y,
at V. As shown in Table 1 in response to Comment 1, averaging the
individual limits across Lines 4 through 7 results in a combined
emissions limit of 1.6 lbs NOX/MMBtu averaged over 720 hours
(30 days).
    In determining the appropriate NOX emission limit for
Minntac, EPA analyzed CEMS data reflecting 720-hour rolling averages at
the 95th and 99th percentiles as well as the highest 720-hour rolling
average at each line. As noted in responses to Comments 1 and 2, while
the 1.6 lbs NOX/MMBtu limit for Minntac is reflective of
natural gas emission data, EPA evaluated all available CEMS data for
2012-2017. Based on this CEMS data, the resulting cross-line average is
1.6 lbs NOX/MMBtu averaged over 720 hours when the facility
is burning natural gas, regardless of selection of statistical analyses
at the 99th or 95th percentiles, or highest 720-hour average. As
discussed in response to Comments 1 and 13, 1.6 lbs NOX/
MMBtu limit is the most stringent limit the facility can consistently
meet while providing operational flexibility with regard to fuel
choice, including the facility's ability to burn natural gas as opposed
to co-firing. EPA did not add a safety margin to the limit as commenter
suggests.
    Comment 19: If EPA is already setting a 30-day rolling average
limit, it is inappropriate to further use the 720-hour values.
Introducing the hourly values provides additional variability in the
limit. EPA provides no authority to justify this approach, which
appears to have increased the BART limit.
    Response: Operations at Minntac in a given 30-day period, or even a
single day, may in some cases involve both operation with only natural
gas and operation with at least some firing of solid fuels. To be able
to evaluate emissions from all hours when different fuels were used
within a 30-day period, rather than only the times when a line used
solely natural gas or solely co-fired for 30 consecutive days, EPA
evaluated emissions based on 720-hour averages. Note that operations
are typically 24 hours per day and 720 is the number of hours in a 30-
day period.
    Comment 20: 42 U.S.C. 7410(l) prohibits the Administrator from
approving a SIP/FIP revision if the revisions would interfere with the
attainment and reasonable further progress requirements of the CAA, and
``any other applicable requirement.'' In addition to requiring BART,
each state's regional haze SIP must also set goals, expressed in
deciviews for each Class I area located within the state that will
assure reasonable progress toward achieving natural visibility.
Moreover, the state's haze SIP must establish reasonable progress goals
that ensure visibility conditions steadily progress, providing for
improvement in visibility on the most impaired days and ensure no
degradation in visibility on the least impaired days over the period of
the implementation plan. 40 CFR 51.308(d)(1). These goals are set after
considering the anticipated reductions in visibility impairing
pollution over the planning period of the SIP from anticipated BART
controls and other Federal or state programs, as well as controls
imposed on non-BART sources under the regional haze SIP to help achieve
reasonable progress. EPA's proposal did not consider how relaxing the
BART emission limits will impact the reasonable progress goals.
    Response: Under section 110(l) of the Act, 42 U.S.C. 7410(l), the
EPA Administrator may not approve a SIP or FIP revision ``if the
revision would interfere with any applicable requirements concerning
attainment and reasonable further progress, or any other applicable
requirements of [the Act].'' In the proposed action, EPA proposed to
find that the revisions to the FIP will comply with applicable regional
haze program requirements and general implementation plan requirements
such as enforceability.
    On June 12, 2012 (77 FR 34801), EPA approved Minnesota's regional
haze plan as satisfying the applicable requirements in 40 CFR 51.308,
except

for BART emission limits for the taconite facilities. Among the
regional haze plan elements approved was Minnesota's long-term strategy
for making reasonable progress toward visibility goals. Minnesota's
long-term strategy did not rely on the achievement of any particular
degree of emission control from the taconite plants to achieve
reasonable progress goals. Therefore, the revised NOX limits
for Minntac represent greater control than was assumed in Minnesota's
approved long-term strategy SIP and does not interfere with the
reasonable progress goals required by 40 CFR 51.308(d)(1). Thus, the
proposed FIP revision would not interfere with any regional haze
program requirements.
    Comment 21: The CAA requires that EPA provide a public hearing when
proposing a FIP. [42 U.S.C. 7607(d)(5)] EPA failed to comply with this
legislative mandate, since its proposal neither provided information
regarding a public hearing, nor asked the public if they were
interested in a hearing.
    Response: In response to this comment, EPA held a virtual public
hearing on the proposed rule to provide interested persons an
opportunity for the oral presentation of data, views, or arguments
concerning the proposed rule. EPA also reopened the comment period on
the proposed rule. Specifically, on September 29, 2020, EPA published a
NPRM in the Federal Register announcing the virtual public hearing on
the proposed rule to be held on October 14, 2020 and reopening the
public comment period on the proposed rule. (85 FR 60942). EPA held the
virtual public hearing on October 14, 2020. EPA accepted public
comments on the proposed rule for 30 days following the virtual public
hearing, and the public comment period closed on November 13, 2020. No
individuals presented at the virtual public hearing and EPA did not
receive any comments during the reopened comment period. The docket has
been updated with a transcript of the virtual public hearing.\17\
---------------------------------------------------------------------------

    \17\ Minnesota; Revision to Taconite Federal Implementation
Plan; October 14, 2020 Public Hearing Transcript, Docket ID # EPA-
R05-OAR-2010-0037-0117, available at https://www.regulations.gov/document?D=EPA-R05-OAR-2010-0037-0117.
---------------------------------------------------------------------------

    Comment 22: The CAA and Regional Haze Rule grant the FLMs,
regardless of whether a FLM manages a Class I area within or beyond the
state, a special role in the review of regional haze implementation
plans. There are obligations to consult on plan revisions under 40 CFR
51.308(i)(3) and EPA has not demonstrated it consulted with the Forest
Service, the Fish and Wildlife Service and the National Park Service on
the proposed FIP revision. Therefore, EPA has not met its obligations
under the Act.
    Response: In response to this comment, EPA contacted the FLMs to
provide the FLMs an opportunity to consult on the proposed action. EPA
reached out to representatives from the National Park Service, U.S.
Forest Service, and U.S. Fish and Wildlife Service. Each representative
indicated that they did not have any comments on the proposed rule. EPA
has updated the docket to include the relevant communications with the
FLMs.\18\
---------------------------------------------------------------------------

    \18\ See emails from March 23, 2020 to June 30, 2020 included in
the docket as ``3-23-2020 email from K. D'Agostino to D. Shepherd,
T. Wickman, T. Allen,'' etc.
---------------------------------------------------------------------------

    Comment 23: Should EPA wish to pursue this FIP revision, the agency
must prepare the required information and analyses, including a
comprehensive optimization study at Minntac, and then repropose its
action.
    Response: As noted in responses to Comments 1, 9 and 16, the five-
step BART analysis for Minntac in the August 15, 2012 proposed FIP (77
FR 49312-49313), established low NOX burners as the basis
for BART emission limits. That analysis and EPA's determination that
BART is based upon the use of low NOX main burners remains
valid and EPA continues to rely on the BART analysis set forth in the
August 15, 2012 proposal concerning the selection of low NOX
burners as the appropriate BART technology. However, since EPA
promulgated the FIP limits, U.S. Steel has continued to operate low
NOX burners and to collect CEMS data on Lines 6 and 7. Since
promulgation of the FIP, U.S. Steel has also installed low
NOX burners and collected CEMS data on Lines 4 and 5.
Therefore, there are significantly more data available now from which
to evaluate the emissions limits actually achievable through the use of
low NOX burners at Minntac than there were at the time the
FIP was promulgated. As discussed in greater detail in response to
Comments 1 and 6, it is this combined data set, which has been included
in the docket, that provides the basis for the revision to the
NOX BART emission limit for Minntac.
    In addition, as described in greater detail in responses to
Comments 9 and 14, U.S. Steel's final burner reports for Lines 4 and 5,
6, and 7 provide detailed explanations of its efforts to optimize
NOX reduction at each line. As discussed in the reports,
U.S. Steel has made physical and operational changes and tuned each low
NOX burner to ensure each can operate in a manner that
reduces NOX emissions while making pellets that meet quality
specifications. In each report, U.S. Steel discusses the process of
optimizing the low NOX burners and tuning each burner and
ancillary equipment to achieve optimal stoichiometric air to fuel
ratios. For each line, U.S. Steel determined achieving optimal air to
fuel ratios requires monitoring the atomizing air and gas split between
the core and annulus gas to reduce flame turbulence in order to create
a tight flame shape at each burner. In addition, in some cases, U.S.
Steel modified capacities of combustion fans and added blowers and
annulus rings to improve thrust and air to fuel ratios--each of which
served to minimize NOX emissions as demonstrated by CEMS
data.
    This action is limited to revising the FIP emission limit for
Minntac to reflect the level of NOX control achievable for
the source based on the use of low NOX burners. Regarding
commenter's assertion that EPA was required to prepare certain
information and analysis and repropose this action, as noted above, at
the time of our February 4, 2020 proposal, EPA already had the
information and analyses necessary to determine the appropriate revised
emission limit for Minntac. This information included CEMS data for
Minntac Lines 4 through 7 provided by U.S. Steel and EPA's analysis of
that information. In addition, U.S. Steel provided to EPA final burner
reports detailing U.S. Steel's efforts to optimize the low
NOX burners on Minntac Lines 4 through 7.
    As discussed in response to Comment 1, in the 2013 FIP, EPA
determined that low NOX burners reflect the appropriate
level of BART control for Minntac. EPA's analysis and proposed
determination that BART is based upon the use of low NOX
burners remains valid. (78 FR 8706). However, the emission limits
established in the 2013 FIP were based on limited CEMS data. Since
promulgation of the 2013 FIP, U.S. Steel has continued to collect CEMS
data on Minntac Lines 6 and 7. U.S. Steel has also installed low
NOX burners on Lines 4 and 5 and has collected CEMS data
reflecting the operation of low NOX burners on these lines.
To determine emission rates that would be consistently achievable at
each line, EPA evaluated all available CEMS data for 2012-2017, which
covered a wide range of different operating scenarios.
    Comment 24: How is the increase in NOX emissions at this
source not affecting nonattainment areas in downwind states such as New
York or

Connecticut? East coast states typically point to states like Minnesota
as significantly contributing to their ozone problems under CAA
110(a)(2)(D). Is EPA at this point conclusively deciding that this
increased FIP limit will not cause the state to violate CAA
110(a)(2)(D) for any of the relevant NAAQS like ozone PM or NO2? Did
EPA adjust its photochemical modeling performed for good neighbor SIPs
to account for this relaxation? EPA issued several memos detailing
Minnesota's contributions before this change, what is the quantitative
effect of increasing these emissions on Minnesota's contribution to
downwind states? EPA must figure this out before modifying this FIP
otherwise EPA is predetermining Minnesota's SIP under 110(a)(2)(D) and
concluding the state has met its obligations.
    Response: The CAA requires states to submit, within three years
after promulgation of a new or revised standard, SIPs meeting the
applicable ``infrastructure'' elements of sections 110(a)(1) and (2).
One of these applicable infrastructure elements, CAA section
110(a)(2)(D)(i), requires SIPs to contain ``good neighbor'' provisions
to prohibit certain adverse air quality effects on neighboring states
due to interstate transport of pollution. The commenter does not
specify which element of CAA section 110(a)(2)(D) it believes is
implicated by this action. Though, in questioning the effect of the FIP
revision on downwind nonattainment areas, the commenter may be
referring to the first two sub-elements of the good neighbor
provisions, at CAA section 110(a)(2)(D)(i)(I). These sub-elements
require that each SIP for a new or revised standard contain adequate
provisions to prohibit any source or other type of emissions activity
within the state from emitting air pollutants that will ``contribute
significantly to nonattainment'' or ``interfere with maintenance'' of
the applicable air quality standard in any other state.
    EPA has previously taken action to approve good neighbor SIPs for
several pollutants and the modifications being made to the FIP are not
expected to contradict those approvals. On October 20, 2015 (80 FR
63436), EPA approved Minnesota's SIP as addressing the State's CAA
section 110(a)(2)(D)(i)(I) obligations under the 2010 NO2
NAAQS. The approval of Minnesota's 2010 NO2 good neighbor
SIP was based on low design values for Minnesota and surrounding
states, with the highest neighboring state showing a design value of 49
parts per billion (ppb), less than half of the 100 ppb standard. This
approval was based on monitoring data from 2011 to 2013. Therefore, the
FIP, promulgated in 2013, but not immediately requiring reductions,
would not have had an impact on that data set.
    On October 10, 2018 (83 FR 50849), EPA approved Minnesota's SIP as
addressing the State's CAA section 110(a)(2)(D)(i)(I) obligations under
the 2012 PM2.5 NAAQS. In the proposed SIP approval, EPA
explained that Minnesota found, and EPA's review confirmed, that all
areas in other states where Minnesota emissions had the potential to
impact monitored PM2.5 air quality, with the exception of
one monitor in Allegheny County, Pennsylvania, were attaining the 2012
annual PM2.5 NAAQS based on 2014-2016 data. (83 FR 39970,
August 13, 2018). The emissions limits promulgated in the 2013 FIP were
not yet in effect during this period, and thus the associated
reductions did not impact the EPA's assessment of attainment. Minnesota
further determined that its impact on air quality monitors in
Pennsylvania was projected to be less than 1% of the 2012 annual
PM2.5 NAAQS, an insignificant contribution based on the air
quality threshold that EPA had previously used to identify linkages
between upwind states and downwind air quality problems under CAA
section 110(a)(2)(D)(i)(I). Minnesota's determination was based on
EPA's source apportionment modeling projecting upwind state
contributions to downwind monitors using 2011 base case emissions,
which was also conducted prior to the effectiveness of the emission
limits promulgated in the 2013 FIP. The revised FIP limit at Minntac
represents greater control than was assumed in Minnesota's and EPA's
analysis supporting approval of the 2012 PM2.5 good neighbor
SIP.
    To the extent EPA has not acted on a pending good neighbor SIP
under CAA section 110(a)(2)(D)(i)(I), EPA is not in this action pre-
determining its approvability. On October 1, 2018, the State of
Minnesota submitted to EPA a SIP submittal addressing Minnesota's
interstate transport requirements under CAA section 110(a)(2)(D)(i)(I)
with respect to the 2015 ozone NAAQS. EPA has not yet taken action on
Minnesota's October 1, 2018 SIP submittal. We will consider emissions
from the state and whether the state is significantly contributing to
or interfering with maintenance of the 2015 ozone NAAQS in any other
state when we take action on the SIP.

III. Final Action

    For the reasons stated in the proposed FIP revision, EPA is
finalizing the revised BART emission limit and related requirements for
the U.S. Steel Minntac facility as proposed.

IV. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive
Order 13563: Improving Regulation and Regulatory Review

    This action is exempt from review by the Office of Management and
Budget (OMB) because it is a rule of particular applicability and only
affects one facility, U.S. Steel's Minntac taconite plant located in
Mt. Iron, Minnesota.

B. Executive Order 13771: Reducing Regulations and Controlling
Regulatory Costs

    This action is not an Executive Order 13771 regulatory action
because this action is not significant under Executive Order 12866.

C. Paperwork Reduction Act (PRA)

    This action does not impose an information collection burden under
the provisions of the PRA, 44 U.S.C. 3501 et seq. Under the Paperwork
Reduction Act, a ``collection of information'' is defined as a
requirement for ``answers to . . . identical reporting or recordkeeping
requirements imposed on ten or more persons . . . .'' 44 U.S.C.
3502(3)(A). Because the FIP applies to just one facility, the PRA does
not apply. See 5 CFR 1320(c).

D. Regulatory Flexibility Act (RFA)

    After considering the economic impacts of this action on small
entities, I certify that this action will not have a significant
economic impact on a substantial number of small entities. EPA's action
revises control requirements at one source. The Regional Haze FIP that
EPA is promulgating for purposes of the regional haze program consists
of imposing Federal control requirements to meet the BART requirement
for NOX emissions on specific units at one source in
Minnesota. The net result of the FIP action is that EPA is finalizing
emission controls on the indurating furnaces at one taconite facilities
and this source is not owned by small entities, and therefore is not a
small entity.

E. Unfunded Mandates Reform Act (UMRA)

    EPA has determined that this rule does not contain a Federal
mandate as

described in UMRA, 2 U.S.C. 1531-1538, that may result in expenditures
that exceed the inflation-adjusted UMRA threshold of $100 million by
State, local, or Tribal governments or the private sector in any one
year. In addition, this rule does not contain a significant Federal
intergovernmental mandate as described by section 203 of UMRA nor does
it contain any regulatory requirements that might significantly or
uniquely affect small governments.

F. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have
substantial direct effects on the states, on the relationship between
the national government and the states, or on the distribution of power
and responsibilities among the various levels of government.

G. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    This rule does not have tribal implications, as specified in
Executive Order 13175. Thus, Executive Order 13175 does not apply to
this rule. However, EPA did discuss this action in conference calls
with the Minnesota Tribes.

H. Executive Order 13045: Protection of Children From Environmental
Health Risks and Safety Risks

    EPA interprets E.O. 13045 as applying only to those regulatory
actions that concern health or safety risks, such that the analysis
required under section 5-501 of the E.O. has the potential to influence
the regulation. This action is not subject to E.O. 13045 because it
does not establish an environmental standard intended to mitigate
health or safety risks. This action addresses regional haze and
visibility protection. Further, because this amendment to the current
regulation will require controls that will cost an amount equal to or
less than the cost of controls required under the current regulation,
it is not an economically significant regulatory action. However, to
the extent this rule will limit emissions of NOX,
SO2, and PM, the rule will have a beneficial effect on
children's health by reducing air pollution.

I. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use

    This action is not subject to Executive Order 13211, because it is
not a significant regulatory action under Executive Order 12866.

J. National Technology Transfer and Advancement Act

    Section 12 of the National Technology Transfer and Advancement Act
(NTTAA) of 1995 requires Federal agencies to evaluate existing
technical standards when developing a new regulation. To comply with
NTTAA, EPA must consider and use ``voluntary consensus standards''
(VCS) if available and applicable when developing programs and policies
unless doing so would be inconsistent with applicable law or otherwise
impractical.
    VCS are inapplicable to this action because application of those
requirements would be inconsistent with the CAA.

K. Executive Order 12898: Federal Actions To Address Environmental
Justice in Minority Populations and Low-Income Populations

    We have determined that this rule will not have disproportionately
high and adverse human health or environmental effects on minority or
low-income populations, as specified in Executive Order 12898 (59 FR
7629, February 16, 1994), because it increases the level of
environmental protection for all affected populations without having
any disproportionately high and adverse human health or environmental
effects on any population, including any minority or low-income
population.

L. Congressional Review Act (CRA)

    This rule is exempt from the CRA because it is a rule of particular
applicability.

M. Determination Under Section 307(d)

    Pursuant to CAA section 307(d)(1)(B), this action is subject to the
requirements of CAA section 307(d), as it revises a FIP under CAA
section 110(c).

N. Judicial Review

    Under section 307(b)(1) of the CAA, petitions for judicial review
of this action must be filed in the United States Court of Appeals for
the appropriate circuit by May 3, 2021. Filing a petition for
reconsideration by the Administrator of this final rule does not affect
the finality of this action for the purposes of judicial review nor
does it extend the time within which a petition for judicial review may
be filed, and shall not postpone the effectiveness of such rule or
action. This action may not be challenged later in proceedings to
enforce its requirements. See CAA section 307(b)(2).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by
reference, Intergovernmental relations, Nitrogen dioxide, Particulate
matter, Regional haze, Reporting and recordkeeping requirements, Sulfur
oxides, Volatile organic compounds.

    This document of the Environmental Protection Agency was signed on
January 11, 2021, by Andrew Wheeler, Administrator, pursuant to a
settlement agreement between EPA and U.S. Steel that required the final
rule to be signed no later than January 20, 2021. That document with
the original signature and date is maintained by EPA. For
administrative purposes only, and in compliance with requirements of
the Office of the Federal Register, the undersigned EPA Official re-
signs the document for publication, as an official document of the
Environmental Protection Agency. This administrative process in no way
alters the legal effect of this document upon publication in the
Federal Register.

Jane Nishida,
Acting Administrator.
    For the reasons stated in the preamble, EPA amends title 40 CFR
part 52 as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

    Authority:  42 U.S.C. 7401 et seq.

0
2. In Sec.  52.1235 revise paragraph (b)(1)(iii) to read as follows:

Sec.  52.1235   Regional haze.

* * * * *
    (b)(1) * * *
    (iii) United States Steel Corporation, Minntac: An aggregate
emission limit of 1.6 lbs NOX/MMBtu, based on a 30-day
rolling average, shall apply to the combined NOX emissions
from the five indurating furnaces: Line 3 (EU225), Line 4 (EU261), Line
5 (EU282), Line 6 (EU315), and Line 7 (EU334). To determine the
aggregate emission rate, the combined NOX emissions from
lines 3, 4, 5, 6 and 7 shall be divided by the total heat input to the
five lines (in MMBTU) during every rolling 30-day period commencing
either upon notification of a starting date by United States Steel
Corporation, Minntac, or with the 30-day period from September 1, 2019
to September 30, 2019, whichever occurs first. The aggregate emission
rate shall subsequently be determined on each day, 30 days after the
starting date contained in such

notification or September 30, 2019, whichever occurs first.
* * * * *
[FR Doc. 2021-04108 Filed 3-1-21; 8:45 am]
BILLING CODE 6560-50-P