In February 2021, MGE and the other co-owners of Columbia announced plans to retire that facility. The co-owners intend to retire Unit 1 and Unit 2 by June 2026. Final timing and unit retirement dates are subject to change depending on operational, regulatory, and other factors. Effects of the environmental compliance requirements discussed below will depend upon the final Columbia retirement dates approved, applicable regulations at that time, and required compliance dates.

MGE Energy and MGE are subject to frequently changing local, state, and federal regulations concerning air quality, water quality, land use, threatened and endangered species, hazardous materials handling, and solid waste disposal. These regulations affect the manner in which operations are conducted, the costs of operations, as well as capital and operating expenditures. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Regulatory initiatives, proposed rules, and court challenges to adopted rules could have a material effect on capital expenditures and operating costs. Management believes compliance costs will be recovered in future rates based on previous treatment of environmental compliance projects.

With the closure of the wet pond system in 2023 (as described in further detail in the CCR section below), Columbia complies with ELG requirements. With the installation of additional wastewater treatment equipment completed in 2023, the Elm Road Units comply with ELG requirements.

In May 2024, the EPA finalized the ELG rule that further regulates the wastewater discharges associated with coal-fired power plants. The rule focuses on wastewater discharges from flue gas

desulfurization and bottom ash transport water. The rule includes a reduction in requirements for plants that have already installed pollution controls based on previous versions of the rule, and for plants that will be retiring or switching to natural gas by certain dates. The operator of the Elm Road Units believes that pollution prevention installed under previous versions of the rule and the planned fuel switching will qualify the Elm Road Units for the reduced requirements. MGE and the operator of the Elm Road Units currently are evaluating the final rule.

Blount received its most recent Wisconsin Pollutant Discharge Elimination System (WPDES) permit from the Wisconsin Department of Natural Resources (WDNR) in October 2023. Blount's latest WPDES permit assumes that the plant meets BTA standards for entrainment for the duration of this permit which expires in 2028. The WDNR included a requirement to conduct an impingement study in the latest permit which needs to be completed by the end of 2027. Once the WDNR determines the impingement requirements at Blount, MGE will be able to determine any compliance costs of meeting Blount's permit requirements.

Intakes at Columbia are subject to this rule. The Columbia operator's most recent permit required that studies of intake structures be submitted to the WDNR by November 2023 to help determine BTA. Columbia's permit renewal application is due in 2024 and in November 2023 the Columbia operator timely submitted its renewal application to the WDNR. BTA improvements required by the renewal permit will be coordinated with the owners' plan to retire both units by June of 2026. MGE will continue to work with Columbia's operator to evaluate regulatory requirements in light of the planned retirement. MGE does not expect this rule to have a material effect on Columbia.

In May 2024, the EPA published its final performance standards and emission guidelines under section 111(b) of the Clean Air Act for carbon dioxide emissions from new combustion turbines and existing fossil-fuel fired boilers used to produce electricity. The final rule grants some emissions flexibility for existing coal-fired units that retire and/or fuel switch by certain dates. For existing natural gas boiler units, the final rule establishes a process where states must submit plans to the EPA for establishing standards. States will have two years from the publication date of these rules to submit plans to the EPA for review and approval. The EPA has indicated that it is separately developing performance standards and emission guidelines for GHG emissions from existing natural gas-fired combustion turbines. Our preliminary evaluation of the final ruling shows that MGE meets the requirements for our gas-fired boilers at Blount. Furthermore, MGE will meet the requirements for our coal-fired units at Columbia through planned unit retirements and the Elm Road Units through its transition to natural gas. MGE will monitor for upcoming rulemaking planned for gas-fired combustion turbines.

The Elm Road Units are located in Milwaukee County, Wisconsin, a "moderate" nonattainment area for the 2015 Ozone NAAQS. The deadline for moderate classified areas to meet attainment standards is August 2024. At this time, the operator of the Elm Road Units does not expect that the 2015 Ozone NAAQS or the Milwaukee County nonattainment designation will have a material effect on the Units.

In March 2024, the EPA published a final rule to lower the average annual PM2.5 NAAQS from 12 ug/m3 to 9 ug/m3 effective May 2024. The new annual PM2.5 NAAQS could impact Milwaukee County, where our Elm Road units are located, if the county is determined to be in nonattainment. A nonattainment designation would require the State of Wisconsin to develop a plan to get into attainment, which would likely include additional limitations for new and modified plants in the county. With the planned transition of the Elm Road Units to natural gas, there is a low probability for the need of additional emission limitations. However, we will not know the impact of this rule until PM data from 2023 and 2024 is evaluated and released, the EPA determines the attainment status of Wisconsin counties, and the State of Wisconsin develops an attainment implementation plan. MGE will continue to follow the rule's developments.

The EPA's CSAPR and its progeny are a suite of interstate air pollution transport rules designed to reduce ozone and PM2.5 ambient air levels in areas that the EPA has determined as being significantly impacted by pollution from upwind states. This is accomplished through a reduction in NOx and SO2 from qualifying fossil-fuel fired power plants and industrial boilers in upwind "contributing" states. NOx and SO2 contribute to fine particulate pollution and NOx contributes to ozone formation in downwind areas. Reductions are generally achieved through a cap-and-trade system. Individual plants can meet their caps through reducing emissions and/or buying allowances on the market.

In March 2023 (published June 2023), the EPA finalized its Federal Implementation Plan to address state obligations under the Clean Air Act "good neighbor" provisions for the 2015 Ozone NAAQS (FIP Rule). The FIP Rule impacts 23 states, including Wisconsin. For Wisconsin, the FIP Rule includes revisions to the current obligations for fossil-fuel power generation, which includes Blount, Columbia, the Elm Road Units, WCCF, West Riverside, and West Marinette. Emissions budgets can be met with planned retirements, fuel switching, and immediately available measures, including consistently operating emissions controls already installed at power plants. In 2026, additional obligations would go into effect, including a further reduction in emissions budgets. Wisconsin would need to submit a State Implementation Plan to meet its obligations or accept the EPA's FIP Rule. Legal challenges to the FIP Rule are pending in the United States Court of Appeals for the District of Columbia. In June 2024, the Supreme Court of the United States granted a request to stay the FIP Rule pending judicial review by the US Court of Appeals for the District of Columbia on the merits of petitioner's challenges to implementation of the rule. Based on our current evaluation, if the FIP Rule were to go into effect, the 2026 additional emission reductions may impact the Elm Road Units and additional upgrades may be needed to comply, however, we will not know the final impact until final decisions are issued in the pending litigation.

The CCR rule regulates the disposal of solid waste coal ash and defines what ash use activities would be considered generally exempt beneficial reuse of coal ash. The CCR rule also regulates landfills, ash ponds, and other surface impoundments used for coal combustion residuals by regulating their design, location, monitoring, and operation. The CCR rule requires owners and operators of coal-fired power plants to stop transporting CCR and non-CCR wastewater to unlined surface impoundments. With the coal combustion residuals system that replaced the unlined surface impoundment completed in 2023, Columbia complies with this rule.

In May 2024, the EPA published its final CCR Legacy Rule. The CCR Legacy Rule applies to previous closed disposal sites. In June 2024, MGE recorded $23.7 million asset retirement obligation for its estimated share of the legal liability associated with the effect of the CCR Legacy Rule for remediation and groundwater compliance monitoring. Actual costs of compliance may be different

than the amount recorded due to potential changes in compliance strategies that will be used, as well as other potential changes in cost estimate.

MGE is involved in various legal matters that are being defended and handled in the normal course of business. MGE accrues for costs that are probable of being incurred and subject to reasonable estimation. The accrued amount for these matters is not material to the financial statements. MGE does not expect the resolution of these matters to have a material adverse effect on its consolidated results of operations, financial condition, or cash flows.

Several environmental groups filed petitions against the PSCW challenging the fixed customer charge set in MGE's 2022/2023 rate settlement, 2023 electric limited reopener, and 2024/2025 rate order. MGE has intervened in the petitions in cooperation with the PSCW. See Footnote 9.a. for more information regarding this matter.

MGE Energy and MGE have entered into various commodity supply, transportation, and storage contracts to meet their obligations to deliver electricity and natural gas to customers. Management expects to recover these costs in future customer rates. The following table shows future commitments related to purchase contracts as of June 30, 2024:


(In thousands)	2024	2025	2026	2027	2028	Thereafter
Natural gas(a)	$22,421	$40,762	$15,492	$2,546	$2,546	$11,224

(a)

MGE's natural gas transportation and storage contracts require fixed monthly payments for firm supply pipeline transportation and storage capacity. The pricing components of the fixed monthly payments for the transportation and storage contracts are approved by FERC but may be subject to change. MGE's natural gas supply commitments include market-based pricing.