We are involved in legal, tax, and regulatory proceedings before various courts, regulatory commissions, authorities, and governmental agencies with respect to matters that arise in the ordinary course of business, some of which involve substantial amounts of money. We believe that the final disposition of these proceedings, except as otherwise disclosed in the notes to our financial statements, will not have a material adverse effect on our results of operations, financial position, or liquidity.

To supply a portion of the fuel requirements of Ameren Missouri’s energy centers, Ameren Missouri has entered into various long-term commitments for the procurement of coal, natural gas, nuclear fuel, and methane gas. Ameren Missouri and Ameren Illinois also have entered into various long-term commitments for purchased power and natural gas for distribution. The table below presents our estimated minimum fuel, purchased power, and other commitments at December 31, 2020. Ameren’s and Ameren Illinois’ purchased power commitments include the Ameren Illinois agreements entered into as part of the IPA-administered power procurement process. Included in the Other column are minimum purchase commitments under contracts for equipment, design and construction, meter reading services, and service maintenance agreements related to Ameren Missouri’s High Prairie Renewable Energy Center, among other agreements, at December 31, 2020.


	Coal		Natural Gas(a)		Nuclear Fuel		Purchased Power(b)(c)(d)			Methane Gas		Other(e)		Total
Ameren:
2021	$	321	$	161	$	56	$	150	(f)	$	3	$	97	$	788
2022	194		111		12		64			3		29		413
2023	113		72		45		24			3		27		284
2024	94		31		26		7			3		25		186
2025	55		17		—		—			3		28		103
Thereafter	—		64		21		—			18		92		195
Total	$	777	$	456	$	160	$	245		$	33	$	298	$	1,969
Ameren Missouri:
2021	$	321	$	44	$	56	$	—		$	3	$	79	$	503
2022	194		40		12		—			3		30		279
2023	113		35		45		—			3		28		224
2024	94		15		26		—			3		26		164
2025	55		7		—		—			3		29		94
Thereafter	—		17		21		—			18		70		126
Total	$	777	$	158	$	160	$	—		$	33	$	262	$	1,390
Ameren Illinois:
2021	$	—	$	117	$	—	$	160	(f)	$	—	$	13	$	290
2022	—		71		—		67			—		—		138
2023	—		37		—		25			—		—		62
2024	—		16		—		7			—		—		23
2025	—		10		—		—			—		—		10
Thereafter	—		47		—		—			—		—		47
Total	$	—	$	298	$	—	$	259		$	—	$	13	$	570

(f)In January 2018, as required by the FEJA, Ameren Illinois entered into agreements to acquire zero emission credits, through 2026. Annual zero emission credit commitment amounts will be published by the IPA each May prior to the start of the subsequent planning year, which begins each June. The amounts above reflect Ameren Illinois’ commitment to acquire approximately $26 million of zero emission credits through May 2021.

Our electric generation, transmission, and distribution operations and natural gas transmission, distribution, and storage operations must comply with a variety of environmental laws that are enforced through statutory and regulatory requirements including permitting programs implemented by federal, state, and local authorities. Depending upon the business activity of specific facilities, such laws address emissions; discharges to water bodies; the storage, handling and disposal of hazardous substances and waste materials; siting and land use requirements; and potential ecological impacts. Complex and lengthy processes are required to obtain and renew approvals, permits, and licenses for new, existing, or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials require release prevention plans and emergency response procedures. We employ dedicated personnel knowledgeable in environmental matters to ensure our business activities comply with regulatory requirements.

Environmental regulations have a significant impact on the electric utility industry and compliance with these regulations could be costly for Ameren Missouri, which operates coal-fired power plants. Clean Air Act regulations that apply to the electric utility industry include the NSPS, the CSAPR, the MATS, and the National Ambient Air Quality Standards, which are subject to periodic review for certain pollutants. Collectively, these regulations cover a variety of pollutants, such as SO2, particulate matter, NOx, mercury, toxic metals, and acid gases, and CO2 emissions from new power plants. Clean Water Act regulations govern both water intake and discharges from power plants and require evaluation of the ecological and biological impact of our operations and could require modifications to water intake structures or more stringent limitations on wastewater discharges at Ameren Missouri’s energy centers. Depending upon the scope of modifications ultimately required by state regulators, these capital expenditures could be significant. The management and disposal of coal ash is regulated as a solid waste under the Resource Conservation and Recovery Act and the CCR rule, which require the closure of our surface impoundments at Ameren Missouri’s coal-fired energy centers. The individual or combined effects of existing and new environmental regulations could result in significant capital expenditures, increased operating costs, or the closure or alteration of operations at some of Ameren Missouri’s energy centers. Ameren and Ameren Missouri expect that such compliance costs would be recoverable through rates, subject to MoPSC prudence review, but the timing of costs and their recovery could be subject to regulatory lag.

Ameren and Ameren Missouri estimate that they will need to make capital expenditures of $175 million to $225 million from 2021 through 2025 in order to comply with existing environmental regulations. Additional environmental controls beyond 2025 could be required. This estimate of capital expenditures includes ash pond closure and corrective action measures required by the CCR regulations, potential modifications to cooling water intake structures at existing power plants under Clean Water Act rules, and by effluent limitation guidelines applicable to steam electric generating units, all of which are discussed below. This estimate does not include capital expenditures that may be required as a result of the NSR and Clean Air Act litigation discussed below. Ameren Missouri’s current plan for compliance with existing air emission regulations includes burning low-sulfur coal and installing new or optimizing existing air pollution control equipment. The actual amount of capital expenditures required to comply with existing environmental regulations may vary substantially from the above estimates because of uncertainty as to future permitting requirements made by state regulators and the EPA, potential revisions to regulatory obligations, and the cost of potential compliance strategies, among other things.

The following sections describe the more significant environmental laws and rules and environmental enforcement and remediation matters that affect or could affect our operations. The EPA has initiated an administrative review of several regulations and proposed amendments to regulations and guidelines, including to the effluent limitation guidelines and the CCR Rule, which could ultimately result in the revision of all or part of such rules.

Federal and state laws, including CSAPR, regulate emissions of SO2 and NOx through the reduction of emissions at their source and the use and retirement of emission allowances. CSAPR is implemented through a series of phases, and the second phase became effective in 2017. Additional emission reduction requirements may apply in subsequent years. To achieve compliance with the CSAPR, Ameren Missouri burns low-sulfur coal, operates two scrubbers at its Sioux Energy Center, and optimizes other existing air pollution control equipment. Ameren Missouri expects to incur additional costs to lower its emissions at one or more of its energy centers to comply with the CSAPR in future years. These higher costs are expected to be recovered from customers through the FAC or higher base rates.

The EPA’s Affordable Clean Energy Rule repealed the Clean Power Plan and replaced it with a new rule that had established emission guidelines for states to follow in developing plans to limit CO2 emissions and identified certain efficiency measures as the best system of emission reduction for coal-fired electric generating units. In January 2021, the United States Court of Appeals for the District of Columbia Circuit vacated the Affordable Clean Energy Rule, and ruled that the EPA had the discretion to consider emission reduction measures that include efficiency measures and generation shifting to lower carbon emissions. Additional litigation including reconsideration by the entire United States Court of Appeals for the District of Columbia Circuit or an appeal to the United States Supreme Court is possible. Regardless of the outcome of such potential legal challenges, the EPA is likely to develop new regulations to address carbon emissions from coal and natural gas electric generating units, which could take years to finalize. At this time, Ameren Missouri cannot predict the outcome of legal challenges or future rulemakings. As such, the impact on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri is uncertain.

In January 2011, the Department of Justice, on behalf of the EPA, filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri alleging that in performing projects at its coal-fired Rush Island Energy Center in 2007 and 2010, Ameren Missouri violated provisions of the Clean Air Act and Missouri law. In January 2017, the district court issued a liability ruling and, in September 2019, entered a final order that required Ameren Missouri to install a flue gas desulfurization system at the Rush Island Energy Center and a dry sorbent injection system at the Labadie Energy Center. There were no fines in the order. In October 2019, Ameren Missouri appealed the district court’s ruling to the United States Court of Appeals for the Eighth Circuit. The district court has stayed implementation of

the majority of the requirements of its order while the case is under appeal. Ameren Missouri believes that the district court both misinterpreted and misapplied the law in its ruling. In December 2020, the court of appeals heard oral arguments presented by the parties. Ameren Missouri is unable to predict the ultimate resolution of this matter. The court is under no deadline to issue a ruling in this case; however, Ameren Missouri expects a ruling during 2021.

The ultimate resolution of this matter could have a material adverse effect on the results of operations, financial position, and liquidity of Ameren and Ameren Missouri. Among other things and subject to economic and regulatory considerations, resolution of this matter could result in increased capital expenditures for the installation of air pollution control equipment, as well as increased operations and maintenance expenses. Based upon engineering studies from October 2019, capital expenditures to comply with the district court’s order for installation of a flue gas desulfurization system at the Rush Island Energy Center are estimated at approximately $1 billion. Further, the flue gas desulfurization system would result in additional operation and maintenance expenses of $30 million to $50 million annually for the life of the energy center. Engineering studies required to develop estimated capital expenditures and estimated additional operation and maintenance expenses for the Labadie Energy Center to comply with the district court’s order will not be undertaken while the case is under appeal. As a result of the district court’s stay, Ameren Missouri does not expect to make significant capital expenditures or incur operations and maintenance expenses related to the district court’s order while the case is under appeal.

The EPA’s Section 316(b) Rule requires power plant operators to evaluate cooling water intake structures and identify measures for reducing the number of aquatic organisms impinged on a power plant’s cooling water intake screens or entrained through the plant’s cooling water system. All of Ameren Missouri’s coal-fired and nuclear energy centers are subject to the cooling water intake structures rule. Requirements of the rule are being implemented through the permit renewal process of each energy center’s water discharge permit, which is expected to be completed by 2023.

In 2015, the EPA issued a rule to revise the effluent limitation guidelines applicable to steam electric generating units. These guidelines established national standards for water discharges, prohibits effluent discharges of certain waste streams, and imposes more stringent limitations on certain water discharges from power plants. To meet the requirements of the guidelines, Ameren Missouri installed dry ash handling systems and completed construction of wastewater treatment facilities at three of its four coal-fired energy centers in 2020. The Meramec Energy Center, which is the fourth coal-fired energy center and is scheduled to close permanently in 2022, will not have new wastewater and dry ash handling systems. Estimated capital expenditures to complete these projects are included in the CCR management compliance plan, discussed below.

The EPA’s CCR rule establishes requirements for the management and disposal of CCR from coal-fired power plants and will result in the closure of surface impoundments at Ameren Missouri’s energy centers. Ameren Missouri is in the process of closing surface impoundments at three facilities, and is scheduled to complete the last of such closures at all of its energy centers in 2023. While the EPA has issued a series of revisions to the CCR rule, none of those revisions or proposals is expected to materially impact our closure schedule. Ameren and Ameren Missouri have AROs of $111 million recorded on their respective balance sheets as of December 31, 2020, associated with CCR storage facilities. Ameren Missouri estimates it will need to make total capital expenditures of $75 million to $100 million from 2021 through 2025 to implement its CCR management compliance plan, which includes installation of dry ash handling systems, wastewater treatment facilities, and groundwater monitoring equipment.

As of December 31, 2020, Ameren Illinois has remediated the majority of the 44 former MGP sites in Illinois it owned or for which it was otherwise responsible. Ameren Illinois estimates it could substantially conclude remediation efforts at the remaining sites by 2023. The ICC allows Ameren Illinois to recover such remediation and related litigation costs from its electric and natural gas utility customers through environmental cost riders. Costs are subject to annual prudence review by the ICC. As of December 31, 2020, Ameren Illinois estimated the remaining obligation related to these former MGP sites at $94 million to $157 million. Ameren and Ameren Illinois recorded a liability of $94 million to represent the estimated minimum obligation for these sites, as no other amount within the range was a better estimate.

The scope of the remediation activities at these former MGP sites may increase as remediation efforts continue. Considerable uncertainty remains in these estimates because many site-specific factors can influence the ultimate actual costs, including unanticipated underground structures, the degree to which groundwater is encountered, regulatory changes, local ordinances, and site accessibility. The actual costs and timing of completion may vary substantially from these estimates.