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Federal Register / Vol. 86, No. 229 / Thursday, December 2, 2021 / Rules and Regulations year emissions using the January 2020
IPM Reference Case, which was informed by actual 2018 compliance rates rather than anticipated compliance rates i.e., 2018 reported emission rates not a 0.1 lb/mmBtu assumption. This largely obviates the commenters concern regarding the 0.1 lb/mmBtu assumption at proposal. Moreover, the IPM modeling explicitly includes the CSAPR Update enforceable limits i.e., the states trading allowance budgets at both the regional and state level. With these enforceable limits included, the model allowed covered sources to emit up to those limits if it would be economically advantageous to do so, but this did not occur in the modeling.
EPA projected future 2021 and 2023
baseline EGU emissions using the version 6January 2020 reference case of the IPM.15 16 IPM, developed by ICF
Consulting, is a state-of-the-art, peerreviewed, multi-regional, dynamic, deterministic linear programming model of the contiguous U.S. electric power sector. It provides forecasts of least cost capacity expansion, electricity dispatch,
and emission control strategies while meeting energy demand and environmental, transmission, dispatch, and reliability constraints. EPA has used IPM for over two decades to better understand power sector behavior under future business-as-usual conditions and to evaluate the economic and emission impacts of prospective environmental policies. The model is designed to reflect electricity markets as accurately as possible. EPA uses the best available information from utilities, industry experts, gas and coal market experts, financial institutions, and government statistics as the basis for the detailed power sector modeling in IPM. The model documentation provides additional information on the assumptions discussed here as well as all other model assumptions and inputs.
The IPM version 6January 2020
reference base case accounts for updated federal and state environmental regulations, committed EGU retirements and new builds, and technology cost and performance assumptions as of late
2019. This projected base case accounts for the effects of the finalized Mercury and Air Toxics Standards rule, the CSAPR and the CSAPR Update, New Source Review settlements, final actions EPA has taken to implement the Regional Haze Rule, and other on-thebooks federal and state rules through 2019 impacting sulfur dioxide, NOX, directly emitted particulate matter, and CO2. For the new 2023 air quality modeling used to interpolate air quality projections in 2021, EPA relied on these 2023 EGU emissions to inform the broader emissions inventory.
The EGU emissions databoth historical and projectedare shown in Table 1, and compared with the CSAPR
Update enforceable budget, demonstrate: 1 The reasonableness of EPAs practice of not solely using enforceable levels in deriving projections of actual conditions and contribution at steps 1 and 2 of the interstate-transport framework for ozone, and 2 the robustness of its examination.

TABLE 1REPORTED OZONE SEASON NOX EMISSIONS FROM EGUS IN THE CSAPR UPDATE REGION 17
Reported ozone season NOX emissions tons
2015

2016

2017

2018

IPM
projection tons 18
2019

2020

CSAPR
Update budget enforceable tons
2021
2021

lotter on DSK11XQN23PROD with RULES1

398,831

371,994

294,483

289,988

251,763

227,325

222,900

313,626

In sum, EPAs EGUs assumptions show that its projected ozone-season EGU emissions levels from proposal of 283,164 tons in 2023 was, if anything, conservativethat is, it is likely that emissions levels from EGUs will be lower than what was projected in the proposal, not higher as suggested by the commenter. The 2019 ozone-season data reflected emissions that were already 20
percent below the CSAPR Update budgets, reflecting a 13 percent drop from the prior year, and at a pace of reduction that strongly suggests actual emissions from EGUs in 2021 will be well below the CSAPR Update budget levels. In other words, the emissions levels that the commenter claimed were not reasonable to expect in 2023 have already been achievedfour years ahead of that analytic year. The EGU

projections EPA used in its analysis for 2021, as discussed previously, are reasonable and properly inform its analysis of ozone levels and contribution in that analytic year. In order for emissions in 2021 to rise to total budget levels e.g., 313,626 tons, representing the aggregate budgets for the covered states, a decade-long decline in ozone-season NOX emissions would have to not only cease but reverse sharply.
Supported by the most recent reported emissions data, EPA concludes that its EGU projections used in the most recent modeling and in the interpolation of that modeling to 2021
are reasonable and conservative. Thus, EPA believes it is reasonable and appropriate to rely on these emissions projections in its air quality analysis for
2021 to approve the 2015 8-hour ozone transport SIP submissions for Florida, Georgia, North Carolina, and South Carolina.
Comment 3: A commenter states that EPAs 2023 modeling described in the March 2018 memorandum is also flawed given the modelings reliance on certain federal emissions reduction programs, which the commenter argues EPA is actively working to undermine. For example, the commenter points to EPAs proposed repeal of its rule regulating emissions from glider vehicles, glider engines, and glider kits, 82 FR 53442 November 16, 2017 Proposed Repeal of the Glider Rule, noting that EPA has estimated unregulated glider vehicles would increase emissions by approximately 300,000 tons annually in 2025. The
15 See https www.epa.gov/airmarkets/analysisrevised-cross-state-air-pollution-rule-update last accessed November 8, 2021.
16 The January 2020 IPM reference case is a later version than what was released with 2016v1.
17 This data analysis relies on 40 CFR part 75
emissions reporting data as available in EPA Air
Markets Program Data available at http
ampd.epa.gov/ampd/.
18 These values are available in the Air Quality Modeling Base Case State Emissions file fossil >25 MW worksheet available at https
www.epa.gov/airmarkets/analysis-revised-crossstate-air-pollution-rule-update. Additionally, as
noted in the Revised CSAPR proposal, EPAs earlier engineering analytics used a more conservative 283,164 tons for 2023. As a sensitivity analysis for the proposed Revised CSAPR Update Modeling using IPM, EPA also used an updated engineering analytics EGU estimate relying on 2019 data that resulted in a 2021 estimate of 238,798 tons.

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