KAISER ALUMINUM CORP

6. Multiemployer Pension Plans

Overview. We contribute to multiemployer defined benefit pension plans under the terms of collective bargaining agreements that cover our union-represented employees at certain facilities. At December 31, 2023, approximately 37% of our total employees were union-represented employees at facilities participating in these multiemployer pension plans. We currently estimate that contributions will range from$5.0 million to$6.0 million in 2024.

The risks of participating in these multiemployer plans are different from single-employer plans in the following aspects:

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Assets contributed to the multiemployer plan by one employer may be used to provide benefits to employees of other participating employers.

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If a participating employer stops contributing to the plan, the unfunded obligations of the plan may be borne by the remaining participating employers.

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If we choose to stop participating in any of our multiemployer plans, we may be required to pay those plans an amount based on the underfunded status of the plan, referred to as a withdrawal liability.

The following table presents information about multiemployer pension plans in which we participate:

The zone status is based on information that we received from the plan and is certified by the plan’s actuary. Among other factors, plans in the green zone are at least 80% funded.

The “FIP/RP Status Pending/Implemented” column indicates if a Financial Improvement Plan (“FIP”) or a Rehabilitation Plan (“RP”) is either pending or has been implemented for the plan under the Pension Protection Act.

We are party tothree collective bargaining agreements with the USW that require contributions to the Steelworkers Pension Trust. As of December 31, 2023, USW collective bargaining agreements covering employees at our Newark and Trentwood facilities covered 87% of our USW-represented employees and expire in September 2025. Our monthly contributions per hour worked by each bargaining unit employee at our Newark and Trentwood facilities were (in whole dollars)$1.75 in 2023. The union contracts covering employees at our Richmond, Virginia facility and Florence, Alabama facility cover 10% and 3% of our USW-represented employees, respectively, and expire in November 2026 and March 2026, respectively. Our monthly contributions per hour worked by each bargaining unit employee at our Richmond, Virginia facility and Florence, Alabama facility were (in whole dollars) $1.50 and $1.35, respectively, in 2023.

Other Funds consists of plans that are not individually significant.

We were not listed in any of the plans’ Forms 5500 as providing more than 5% of the total contributions for any of the plan years disclosed. At the date the Company’s financial statements were issued, Forms 5500 were not available for the plan year ending in 2023. Further, there were no significant changes to the number of employees covered by our multiemployer plans that would affect the period-to-period comparability of the contributions for the years presented.