SUPPLEMENTARY INFORMATION:

I. Participation in Virtual Public Hearing

To request to present at a virtual public hearing, or to pre-register to attend the hearing, if one is held, please use the online registration form available at https://www.epa.gov/​mn/​revision-taconite-regional-haze-federal-implementation-plan-mi-and-mn or contact Mayesha Choudhury at (312) 886-5909 or by email at choudhury.mayesha@epa.gov. EPA is asking all hearing attendees to register, even those who do not intend to present. The last day to request to present at the hearing will be May 6, 2025. If no request to present at the virtual public hearing is received by 11:59 p.m. Central Daylight Time (CDT) May 6, 2025, EPA will not hold the hearing. If a virtual hearing is held, EPA will accept registration until the start of the hearing.

EPA will announce the status of the hearing on May 7, 2025 on the public hearing website at https://www.epa.gov/​mn/​revision-taconite-regional-haze-federal-implementation-plan-mi-and-mn. Alternatively, interested parties may contact Mayesha Choudhury at (312) 886-5909 to find out if the hearing is being held.

If a request to present at the virtual public hearing is received by May 6, 2025, EPA will hold a virtual public hearing on May 12, 2025. EPA will post a general agenda for the hearing on May 8, 2025. The agenda will be available at https://www.epa.gov/​mn/​revision-taconite-regional-haze-federal-implementation-plan-mi-and-mn and will list pre-registered presenters in approximate order. The hearing will convene at 9:00 a.m. CDT and will conclude at 1:00 p.m. CDT, or 15 minutes after the last pre-registered presenter in attendance has presented if there are no additional presenters. EPA will announce further details on the virtual public hearing website at https://www.epa.gov/​mn/​revision-taconite-regional-haze-federal-implementation-plan-mi-and-mn.

If a request to present at the virtual public hearing is timely received, EPA will make every effort to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearing to run either ahead of schedule or behind schedule. Each commenter will have 5 minutes to provide oral testimony. EPA encourages commenters to provide EPA with a written copy of their oral testimony electronically by including it in the registration form or emailing it to choudhury.mayesha@epa.gov. EPA may ask clarifying questions during the oral presentations but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral comments and supporting information presented at the virtual public hearing.

Please note that any updates made to any aspect of the hearing will be posted online at https://www.epa.gov/​mn/​revision-taconite-regional-haze-federal-implementation-plan-mi-and-mn. Please monitor our website or contact Mayesha Choudhury at (312) 886-5909 or choudhury.mayesha@epa.gov to determine if there are any updates. EPA does not intend to publish a document in the Federal Register announcing updates concerning the virtual public hearing.

If you require the services of a translator or a special accommodation such as audio description/closed captioning, please pre-register for the hearing with Mayesha Choudhury at (312) 886-5909 or choudhury.mayesha@epa.gov and describe your needs by May 5, 2025. EPA may not be able to arrange accommodations without advance notice.

II. Background

A. Requirements of the CAA and EPA's Regional Haze Rule

In the CAA Amendments of 1977, Congress created a program for protecting visibility in the nation's national parks and wilderness areas. Section 169A of the CAA establishes as a national goal the “prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Class I Federal areas ^[1] which impairment results from manmade air pollution.” Congress added section 169B to the CAA in 1990 to address regional haze issues. EPA promulgated a rule to address regional haze on July 1, 1999 (64 FR 35714), codified at 40 CFR part 51, subpart P—Protection of Visibility (herein after referred to as the “Regional Haze Rule”). The Regional Haze Rule codified and clarified the BART provisions in the CAA at 40 CFR 51.308(e) and revised the existing visibility regulations to add provisions addressing regional haze impairment and establishing a comprehensive visibility protection program for Class I areas.

Section 169A of the CAA directs states, or EPA if developing a Federal Implementation Plan (FIP), to evaluate the use of retrofit controls at certain larger, often uncontrolled, older stationary sources to address visibility impacts from these sources. Specifically, section 169A(b)(2)(A) of the CAA requires that implementation plans contain such measures as may be necessary to make reasonable progress toward the natural visibility goal, including a requirement that certain categories of existing major stationary ( printed page 17235) sources ^[2] built between 1962 and 1977 procure, install, and operate BART ^[3] as determined by EPA.

Under the Regional Haze Rule, states (or in the case of a FIP, EPA) are directed to conduct BART determinations for such “BART-eligible” sources that may reasonably be anticipated to cause or contribute to any visibility impairment in a Class I area.

On July 6, 2005, (70 FR 39104), EPA published the Guidelines for BART Determinations Under the Regional Haze Rule at appendix Y to 40 CFR part 51 (hereinafter referred to as the “BART Guidelines”), to assist states and EPA in determining which sources should be subject to the BART requirements and in determining appropriate emission limits for each source subject to BART.

The process of establishing BART emission limitations follows three steps. First, states, or EPA if developing a FIP, must identify and list “BART-eligible sources.” ^[4] Once the state or EPA has identified the BART-eligible sources, the second step is to identify those sources that may “emit any air pollutant which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area. (Under the Regional Haze Rule, a source that fits this description is “subject to BART.”). Third, for each source subject to BART, the state or EPA must identify the level of control representing BART after considering the five factors set forth in CAA section 169A(g). The BART Guidelines provide a process for making BART determinations that states can use in implementing the BART requirements on a source-by-source basis. See40 CFR part 51, appendix Y, at IV.D.^[5]

States, or EPA if developing a FIP, must address all visibility-impairing pollutants emitted by a source in the BART determination process. The most significant visibility impairing pollutants are sulfur dioxide (SO₂), NO_X, and particulate matter (PM).

A State Implementation Plan (SIP) or FIP addressing regional haze must include source-specific BART emission limits and compliance schedules for each source subject to BART. Once a state or EPA has made a BART determination, the BART controls must be installed and operated as expeditiously as practicable, but no later than five years after the date of the final SIP or FIP. See CAA section 169A(g)(4) and 40 CFR 51.308(e)(1)(iv). In addition to what is required by the Regional Haze Rule, general SIP requirements mandate that the SIP or FIP include all regulatory requirements related to monitoring, recordkeeping, and reporting for the BART controls on the source. See CAA section 110(a).

B. BART FIP and Regulatory History for the Keetac Taconite Facility

On February 6, 2013 (78 FR 8706), EPA promulgated a FIP that included NO_X BART limits for indurating furnaces at seven taconite facilities subject to BART in Minnesota and Michigan (“Original 2013 FIP Rule”). The Original 2013 FIP Rule included NO_X BART limits for indurating furnaces at two U.S. Steel taconite facilities located in Minnesota—Keetac and Minntac. EPA took this action because Minnesota and Michigan had failed to meet a statutory deadline to submit their regional haze SIPs for the first planning period by December 17, 2007, and subsequently failed to require BART at the taconite facilities. The Original 2013 FIP Rule, among other requirements, established NO_X BART emission limits of 1.2 pounds (lbs) of NO_X per million British Thermal Unit (MMBtu) when burning natural gas and 1.5 lbs NO_X /MMBtu when using any fuel other than exclusively natural gas for Keetac's indurating furnace (along with indurating furnaces at six other taconite facilities in Michigan and Minnesota). These emission limits were based upon the performance of high stoichiometric (high-stoich) low-NO_X burners (LNBs) installed on taconite furnaces at Minntac.

In a related action, on September 30, 2013 (78 FR 59825), EPA finalized partial disapprovals of Minnesota and Michigan's regional haze SIPs for the first planning period for failing to require BART for the indurating furnaces at taconite facilities (“SIP Disapprovals”). Among other things, EPA found that Minnesota and Michigan had erred by determining that an undefined set of “good combustion practices” represented NO_X BART for Keetac and six other taconite facilities when U.S. Steel had successfully installed LNBs on Lines 6 and 7 at Minntac.

Subsequently, U.S. Steel filed a petition for review of the SIP Disapprovals in the U.S. Court of Appeals for the Eighth Circuit (“Eighth Circuit”) and submitted to EPA a petition for reconsideration of the SIP Disapprovals. In its petitions for review and reconsideration of the SIP Disapprovals, U.S. Steel simultaneously sought review and reconsideration of the Original 2013 FIP Rule.

On April 12, 2016 (81 FR 21672), EPA promulgated a revised FIP rule, which revised BART emission limits for certain taconite facilities owned by companies other than U.S. Steel (“2016 Revised FIP Rule”). Those companies, along with U.S. Steel, each filed a petition for review in the Eighth Circuit challenging the 2016 Revised FIP Rule. U.S. Steel also submitted to EPA a petition for reconsideration of the 2016 Revised FIP Rule.

On December 4, 2017 (82 FR 57125), EPA denied U.S. Steel's petitions for reconsideration of the Original 2013 FIP Rule, the SIP Disapprovals, and the 2016 Revised FIP Rule (“Denial of Reconsideration”). U.S. Steel filed a petition for review in the Eighth Circuit challenging EPA's Denial of Reconsideration. U.S. Steel's challenge of the Denial of Reconsideration has been in abeyance while the parties have been working toward resolution.

In November 2019, EPA executed a Settlement Agreement with U.S. Steel pertaining to NO_X BART requirements at Minntac.^[6] EPA subsequently proposed and finalized a FIP revision addressing NO_X BART requirements for Minntac.^[7] Most recently, in September 2024, EPA executed a Settlement Agreement with U.S. Steel pertaining to NO_X BART requirements at Keetac.^[8]

III. Basis for NO X Limits

The Original 2013 FIP Rule limits were set based upon the performance of high-stoich LNBs on indurating furnaces at Minntac. Between its two taconite facilities (Minntac and Keetac), U.S. Steel owns and operates six grate-kiln taconite furnaces: five indurating furnaces at Minntac, and one large indurating furnace at Keetac. While all six furnaces are of generally similar design, they each differ in size, gas flow, combustion air design, production throughput, fuels used, type of taconite pellets produced, and heat characteristics in the furnace, among ( printed page 17236) other differences.^[9] Keetac's pellet production is double that of Minntac's, which affects the magnitude of fuel input, number and design of combustion fans required, and burner system components needed to successfully operate a burner.^[10]

Between 2009 and 2019, U.S. Steel contracted a variety of manufacturers and engineering firms to evaluate different NO_X reduction technologies that could meet the requirements of the Original 2013 FIP Rule at its Minntac and Keetac facilities, which both operate grate-kiln indurating furnaces. Early computational fluid dynamics modeling performed by these contractors showed that a high-stoich low-NO_X burner system would be a feasible option at Minntac. This testing showed that low-NO_X main burner systems, when used in conjunction with other modifications, could achieve a significant decrease in NO_X emissions at those furnaces.

U.S. Steel also conducted NO_X reduction demonstrations with a selective non-catalytic reduction (SNCR) system at Minntac. The results of this testing at Minntac showed that SNCR could produce, at best case, 8-10% NO_X reduction from baseline NO_X emission levels at Minntac, and also in some cases a net increase in NO_X emissions with urea injected at the entrance to the preheater.^[11] In 2011, U.S. Steel reported the successful pilot testing of a low-NO_X main burner system on Line 7 at Minntac.^[12] Based on this testing at Minntac, U.S. Steel identified LNBs as the most effective method of reducing NO_X emissions from the indurating process and evaluated the feasibility of installing LNBs at Keetac. However, the emission and process data generated through subsequent modeling indicated that this specific LNB technology developed for Minntac would not consistently achieve the same results on all taconite indurating furnaces while operating under various fuel use and production scenarios while maintaining pellet quality.^[13] Keetac's pellet production is double that of Minntac's, which affects the magnitude of the fuel input, the number and design of combustion fans required, and the burner system components needed to successfully operate a burner. Subsequent modeling and engineering studies determined that a new low-NO_X main burner at Keetac would require additional natural gas and, as a result, would need double the amount of air to maintain an appropriate combustion efficiency.^[14] These additional requirements were deemed infeasible at Keetac due to several technical factors, including the need to maintain appropriate temperature profiles to ensure pellet quality, space and design constraints, and significant safety concerns.

In 2017, EPA asked U.S. Steel to evaluate additional technology options for Keetac, including evaluating application of water injection to the burner system, providing temperature data for further evaluation of SNCR, further engaging with burner manufacturers to design a low-NO_X main burner, and investigating the potential addition of preheat burners. A subsequent study of water injection at Keetac indicated that water injection would result in a significant reduction in pellet production along with adverse effects to pellet quality.^[15] U.S. Steel also collected process data to further evaluate the feasibility of SNCR at Keetac. Based on process temperature measurements, the downdraft drying sections are too cold or below the temperature window for SNCR injection, while the preheat section is too hot and above the temperature window. In addition, due to physical space limitations and flue gas velocity, adequate residence time is not available for the reaction to take place. Consequently, the facility-specific conditions of the operating line at Keetac do not allow for a suitable location to inject urea for SNCR.^[16]

U.S. Steel provided process and emission data and studies that set forth its concerns regarding potentially serious impacts from high-stoich LNB operation on the overall operation of the furnace, such as the heat balance of the furnace, the fuel used, pellet quality, airflow, safety, and other factors. U.S. Steel provided another engineering report containing a detailed analysis of how Keetac's process and pellet quality would be affected by changes to the burner operating parameters required to incorporate a high-stoich LNB system.^[17] The studies analyzed the effects of low and mid-stoich LNB systems on the Keetac furnace by using simulation modeling that compared Keetac's normal operating conditions with simulations of furnace operations while using LNBs with a higher stoichiometric rate, showing that a low-stoich LNB system may be a viable option to reduce NO_X emissions from the Keetac furnace, with the potential for additional reductions from preheat burners.

Following evaluation of these engineering studies and data, EPA concluded that while the specific LNB design implemented at Minntac would not be appropriate for Keetac, LNB continues to be the appropriate selection for BART at Keetac. Specifically, installation of a low-NO_X main burner combined with low-NO_X preheat burners is expected to yield a 40-45% NO_X reduction when compared to baseline emissions from a standard burner.^[18] Modeling of the Keetac indurating furnace with a low-NO_X main burner in conjunction with low-NO_X preheat burners indicated that a limit of 3.4 lbs NO_X /MMBtu represents BART for Keetac when firing exclusively natural gas.^[19] Modeling of a low-NO_X main burner also indicated that a limit of 2.0 lbs NO_X /MMBtu represents BART during production cycles when cofiring with coal.^[20] Modeling of mixed fuel production scenarios only reflects reductions based on the operation of the main burner since data indicate that reductions from preheat burners in these scenarios are limited.^[21]

Based on this most recent modeling data, EPA is proposing to replace the existing NO_X BART emission limits applicable to Keetac with the following NO_X BART emission limits: (1) 3.4 lbs NO_X /MMBtu on a 720-hour rolling average when firing exclusively natural gas, which will become enforceable beginning three years after promulgation ( printed page 17237) of a final rule, and (2) a NO_X BART limit of 2.0 lbs NO_X /MMBtu on a 720-hour rolling average when burning any fuel or combination of fuels other than exclusively natural gas, which will become enforceable five years after promulgation of a final rule, with the option for the owner or operator to seek an adjustment up to 2.5 lbs NO_X /MMBtu as discussed below. These values are based on modeling the use of both low-NO_X preheat burners and a low-NO_X main burner when firing exclusively natural gas and the use of a low-NO_X main burner when utilizing mixed fuels.

Due to the facility not utilizing mixed fuels after 2013, the modeling could not be validated for cofiring scenarios. Therefore, EPA is proposing to allow the owner or operator of Keetac, within a period of 52 months from the effective date of the final rule, the option to seek an adjustment of the NO_X BART cofiring emission limit based on collection of Continuous Emission Monitoring System (CEMS) data after installation of the NO_X -reduction technology.^[22] EPA is proposing that, upon receipt of complete emissions data from the owner or operator of Keetac as described in paragraph (b)(1)(i)(C)(1) of the proposed regulatory text, EPA will evaluate whether the data support adjusting the NO_X BART emission limit while burning any fuel or combination of fuels other than exclusively natural gas using the applicable equation set forth in 40 CFR 52.1235(f). If the results of the equation support adjustment of the NO_X BART emission limit, EPA shall initiate a rulemaking to adjust the emission limit. If revised, the NO_X BART emission limit when burning any fuel or combination of fuels other than exclusively natural gas may be no greater than 2.5 lbs NO_X /MMBtu, based on a 720-hour rolling average.

EPA's visibility impact analysis in the 2013 FIP was based on the assumption of a 70% reduction in NO_X emissions when firing natural gas. EPA now anticipates a 40-45% reduction in NO_X emissions when firing natural gas as a result of the control technologies and associated emission limits proposed in this rulemaking.^[23] EPA expects the Keetac LNB design to achieve substantial visibility improvements, although slightly less than what was projected to be achieved in the Original 2013 FIP Rule, in an amount roughly corresponding to the decrease in emission reductions.

IV. CAA Section 110(l)

Under CAA section 110(l), EPA cannot approve a plan revision “if the revision would interfere with any applicable requirement concerning attainment and reasonable further progress (as defined in section 7501 of this title), or any other applicable requirement of this chapter.” Based on the following analysis, we find that EPA's approval of this revision is consistent with CAA section 110(l) because it will not interfere with any applicable requirement concerning attainment, reasonable further progress, or any other applicable requirements of the CAA.

On June 12, 2012 (77 FR 34801), EPA approved Minnesota's regional haze plan for the first planning period as satisfying the applicable requirements in 40 CFR 51.308, except for BART emission limits for the taconite facilities. As previously discussed, EPA promulgated the Original 2013 FIP Rule to address the BART requirement for taconite facilities. The BART limits set forth in the Original 2013 FIP Rule were based on a LNB designed for Minntac. For reasons discussed above, U.S. Steel was unable to implement this LNB design at Keetac. Years of engineering studies and analysis identified an available LNB design solution for Keetac that will achieve NO_X reductions at the Keetac furnace. Since this analysis concluded Keetac could not meet the limits set forth in the Original 2013 FIP Rule, EPA is setting higher proposed BART limits that reflect the emission reductions achievable using the Keetac LNB design solution. EPA is proposing that these limits represent BART and therefore the BART requirements of the CAA are satisfied.

Minnesota's 2012 long-term strategy for making reasonable progress towards the national visibility goal was among the regional haze plan elements approved by EPA. Minnesota's 2012 long-term strategy did not rely on the achievement of any particular degree of emission control from the taconite facilities; therefore, the revised NO_X BART emission limits for Keetac represent greater control than was assumed in Minnesota's approved SIP and do not interfere with the reasonable progress goals required by 40 CFR 51.308(d)(1), as set forth in Minnesota's first planning period SIP.

With respect to requirements concerning attainment of the National Ambient Air Quality Standards (NAAQS) and reasonable further progress, all areas in Minnesota are designated as attainment for all NAAQS that are potentially impacted by NO_X emissions.^[24] Outside the state, the nearest ozone, particulate matter, or nitrogen dioxide nonattainment areas are the areas designated as nonattainment for the 2015 ozone NAAQS located along the western shore of Lake Michigan. The nearest of these ozone nonattainment areas along the western Lake Michigan shoreline, Sheboygan County, Wisconsin, is over 350 miles from Keewatin, Minnesota. At the time these areas were designated as nonattainment for the 2015 ozone NAAQS, EPA evaluated HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) trajectories to identify areas potentially contributing to monitored violations of the NAAQS. No areas designated as nonattainment for the 2015 ozone NAAQS showed trajectories indicating that emissions from the area near Keewatin, Minnesota, had the potential to contribute to any of the monitored violations of the ozone NAAQS.

Therefore, based on the information presented above, we find that EPA's approval of these revisions would be consistent with CAA section 110(l). The proposed FIP revision complies with applicable regional haze requirements and general implementation plan requirements and does not interfere with any regional haze program requirements, attainment and reasonable further progress, or any other requirement of the CAA.

V. Proposed Action

EPA is proposing to modify NO_X BART emission limits for the indurating furnace at Keetac. Specifically, EPA is proposing to approve the following NO_X BART emission limits for the Keetac Grate Kiln indurating furnace, with compliance to be determined on a rolling 720-hour average: (1) 3.4 lbs NO_X /MMBtu when firing exclusively natural gas, which will become ( printed page 17238) enforceable beginning three years after promulgation of a final rule, and (2) 2.0 lbs NO_X /MMBtu when firing any fuel or combination of fuels other than exclusively natural gas, which will become enforceable five years after promulgation of a final rule, unless before that date, EPA promulgates a modified limit in accordance with the following procedure. EPA is also proposing to allow Keetac, within a period of 52 months from the effective date of the final rule, the option to seek a potential adjustment of the cofiring emission limit, not to exceed 2.5 lbs NO_X /MMBtu as a 720-hour rolling average, based on collection of CEMS data after installation of the NO_X reduction technology.

VI. Statutory and Executive Order Reviews

Additional information about these statutes and executive orders can be found at https://www.epa.gov/​laws-regulations/​laws-and-executive-orders.

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

This action is exempt from review by the Office of Management and Budget (OMB), as it is not a rule of general applicability. This action, if finalized, will specifically regulate the Keetac taconite facility in Minnesota.

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

Executive Order 14192 does not apply because actions that are rules of particular applicability are exempt from review under Executive Order 12866. This action, if finalized, will specifically regulate the Keetac taconite facility in Minnesota.

C. Paperwork Reduction Act

This proposed action does not impose an information collection burden under the provisions of the Paperwork Reduction Act, 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 one taconite facility in Minnesota, the Paperwork Reduction Act does not apply. See5 CFR 1320(c).

D. Regulatory Flexibility Act (RFA)

I certify that this proposed action will not have a significant economic impact on a substantial number of small entities under the RFA. This proposed action will not impose any requirements on small entities. This action, if finalized, will add additional controls to one taconite source. This source, the Keetac taconite facility, is not owned by small entities, and therefore is not a small entity.

E. Unfunded Mandates Reform Act (UMRA)

This proposed action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect small governments. The proposed action imposes no enforceable duty on any state, local or Tribal governments or the private sector.

F. Executive Order 13132: Federalism

This proposed 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 proposed action does not have Tribal implications, as specified in Executive Order 13175. It will not have substantial direct effects on Tribal governments. Thus, Executive Order 13175 does not apply to this action. Consistent with the EPA Policy on Consultation and Coordination with Indian Tribes, EPA consulted with Tribal officials during the development of this action. On April 25, 2024, we met with Tribal leaders and presented an overview of the upcoming Keetac action. We encouraged the Tribes to contact us with any questions. Since that meeting we have provided updates on several monthly Tribal calls.

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

This action is not subject to Executive Order 13045 because it is not economically significant as defined in Executive Order 12866, and because EPA does not believe the environmental health or safety risks addressed by this action present a disproportionate risk to children. To the extent this action, if finalized, will limit emissions of NO_X emissions, 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 (66 FR 28355, May 22, 2001), because it is not a significant regulatory action under Executive Order 12866.

J. National Technology Transfer and Advancement Act

This rulemaking does not involve technical standards.

For the reasons stated in the preamble, EPA proposes to amend 40 CFR part 52 as follows:

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

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

3. Section 52.1235 is proposed to be amended by revising paragraph (b)(1)(i) to read as follows:

90 FR 17233