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Federal Register / Vol. 86, No. 39 / Tuesday, March 2, 2021 / Rules and Regulations 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 113g, 42 U.S.C. 7413g. 84 FR 47945. EPA
did not receive any adverse comments relating to the proposed settlement agreement. Contrary to the commenters 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 4931249313, established low NOX burners as the basis for BART emission limits. That analysis and EPAs 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
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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. Steels 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 BARTeligible units that constitute BARTeligible 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 720hour 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 20122017.
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 facilitys 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 720hour values. Introducing the hourly values provides additional variability in
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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. 7410l 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 states 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 states 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
51.308d1. 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. EPAs proposal did not consider how relaxing the BART emission limits will impact the reasonable progress goals.
Response: Under section 110l of the Act, 42 U.S.C. 7410l, 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 Minnesotas regional haze plan as satisfying the applicable requirements in 40 CFR 51.308, except
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