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 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 retirement dates approved 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 (as described in further detail in the CCR section below), Columbia will be in compliance with ELG requirements.

The Elm Road Units must satisfy the ELG rule's requirements no later than December 2023, as determined by the permitting authority. In December 2021, the PSCW approved a CA application for installation of additional wastewater treatment equipment to comply with the ELG Rule. MGE's share of the costs to comply with the rule is estimated to be approximately $4 million. Construction began in March 2022 and is scheduled to be completed by the end of 2023.

In March 2023, the EPA published a proposed update to this rule that further regulates the wastewater discharges associated with coal-fired power plants. The proposed rule focuses on wastewater discharges from flue gas desulfurization, bottom ash transport water, and combustion residual leachate. The proposed rule includes some flexibility for plants that have already installed pollution controls based on previous versions of the rule, and flexibility for plants that will be retiring or switching to natural gas by certain dates. MGE expects this rule, if finalized as proposed, to impact our Elm Road Units. However, we will not know the impact of this rule with any certainty until the rule is finalized.

Blount received its most recent 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 in the next three years. 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 requires 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. BTA improvements may be limited or not required in the renewal permit given 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 retirements. MGE does not expect this rule to have a material effect on Columbia.

In May 2023, the EPA proposed a rule under section 111 of the Clean Air Act to establish NSPS and emission guidelines to limit GHG emissions from existing fossil fuel-fired EGUs and new, modified, and/or reconstructed fossil fuel-fired power plants. The EPA anticipates promulgating a final rule in

2024. MGE fossil fuel-fired generation units would be subject to the rule as proposed. MGE expects larger-sized units with long range retirement plans, West Riverside and the Elm Road units, may need to employ technology to achieve reduction. Columbia may not be impacted due to the owners' planned retirement of the existing fossil fuel fired units by 2026. However, we will not know the impact of this rule with any certainty until the rule is finalized.

The Elm Road Units are located in Milwaukee County, Wisconsin, a "moderate" nonattainment area. 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 will have a material effect on the Units based on final designations.

In January 2023, the EPA published a proposed rule to lower the average annual PM2.5 NAAQS from its current level. The EPA has also solicited comments on whether to lower the annual standard further than the proposed level, and whether to lower the maximum 24-hour limit to be consistent with recommendations from its Clean Air Scientific Advisory Committee (CASAC). Neither the proposed annual PM2.5 NAAQS nor the 24-hour limit recommended by the CASAC are expected to impact the counties where Columbia and the Elm Road Units are located. However, if the annual PM2.5 NAAQS is lowered further than the EPA's currently proposed value, Milwaukee County may be in nonattainment with the standard. A nonattainment designation would require the State of Wisconsin to develop a plan to get into attainment, which may include additional emission limitations for the Elm Road units. However, we will not know the impact of this rule until it is finalized, 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, the EPA finalized its Federal Implementation Plan (FIP) to address state obligations under the Clean Air Act "good neighbor" provisions for the 2015 Ozone NAAQS. The final rule impacts 23 states, including Wisconsin. For Wisconsin, the 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. The final rule became effective partway through the 2023 ozone season in August 2023. Emissions budgets can be met with planned retirements, fuel switching, and immediately available measures, including consistently operating emissions controls already installed at power plants. MGE expects to meet the emission reductions with immediately available measures. 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. MGE is reviewing the final rule. Based on our current evaluation, 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 evaluations are completed.

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 or operators of coal-fired power plants to stop transporting CCR and non-CCR wastewater to unlined surface impoundments. In addition, regulated entities must initiate impoundment closure as soon as feasible and in no event later than April 2021, unless the EPA grants an extension. A site-specific extension to initiate closure of the primary ash pond at Columbia by March 31, 2023, was requested, and was met. The EPA has confirmed that Columbia met the required extension requirements, has documented that Columbia ceased the receipt of waste on March 23, 2023, and has noted that Columbia's obligations under this portion of the CCR Rule are now complete.

In July 2021, the PSCW approved a CA application filed by MGE and the other owners of Columbia to install technology required to cease bottom ash transport water discharges rather than extend the longevity of the ash ponds. The coal combustion residuals system that replaced the unlined surface impoundment was placed in-service in March 2023. MGE's share of the costs of the project is approximately $4 million.

Review of the Elm Road Units has indicated that the costs to comply with the CCR rule are not expected to be significant.

In May 2023, the EPA proposed a CCR Legacy Rule that if finalized as currently written, will apply to previously closed CCR sites. Columbia's operator would likely need to complete a site evaluation to determine if the CCR Legacy Rule applies to Columbia's previously closed site. MGE is currently evaluating this proposed rule. However, we will not know the impact of this rule with any certainty until the rule is finalized.

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.

Certain environmental groups filed petitions against the PSCW challenging the fixed customer charge set in MGE's 2022/2023 rate settlement and 2023 electric limited reopener. 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 September 30, 2023:


(In thousands)	2023		2024		2025		2026		2027		Thereafter
Coal(a)	$	8,511	$	23,173	$	14,425	$	2,581	$	—	$	—
Natural gas(b)		20,009		41,502		25,517		14,873		2,165		11,995
	$	28,520	$	64,675	$	39,942	$	17,454	$	2,165	$	11,995

(a)

Total coal commitments for MGE's share of the Columbia and Elm Road Units, including transportation. Fuel procurement for MGE's jointly owned Columbia and Elm Road Units is handled by WPL and WEPCO, respectively, who are the operators of those facilities.

(b)

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.