Knife River Corp

Note 17 –Employee Benefit Plans

Pension and other postretirement benefit plans

We participate in self-sponsored qualified defined benefit pension plans which are accounted for as single-employer plans and are reflected in our audited consolidated financial statements. We use a measurement date of December 31 for all our pension and postretirement benefit plans. Prior to 2010, defined benefit pension plan benefits and accruals for the nonunion plan were frozen and on June 30, 2015, the remaining union plan was frozen. These employees were eligible to receive additional defined contribution plan benefits.

Prior to the Separation, we participated in a multiple-employer postretirement benefit plan sponsored by MDU Resources. In connection with the Separation, we assumed all the obligations and liabilities of our employees in that plan, along with all MDU Resources employees that transferred to Knife River as a result of the Separation. Subsequent to the Separation, the postretirement benefit plans in which we participate are single employer plans. Employees hired after December 31, 2010 are not eligible for retiree medical benefits. Effective January 1, 2011, eligibility to receive retiree medical benefits was modified such that eligible employees who attained age 55 with 10 years of continuous, full‐time service by December 31, 2010, will have an option to select one of two retiree medical insurance benefits. All other eligible employees must meet the new eligibility criteria of age 60 and 10 years of continuous, full‐time service at the time they retire. These employees will be eligible for a company funded retiree reimbursement account. Employees hired after December 31, 2014 are not eligible for retiree medical benefits.

In 2012, we modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage was replaced by a fixed-dollar subsidy for retirees and spouses to be used to purchase individual insurance through a healthcare exchange.

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Changes in benefit obligation and plan assets and amounts recognized in the Consolidated Balance Sheets at December 31, were as follows:

Employer contributions and benefits paid in the preceding table include only those amounts contributed directly to, or paid directly from, plan assets.

In 2025, the actuarial losses recognized in the pension and other postretirement benefit obligations was largely the combination of losses resulting from decreased discount rates, offset in part by higher asset gains. In 2024, the actuarial gains recognized in the pension and other postretirement benefit obligations was primarily the result of an increase in the discount rate. For more information on the discount rates, see the table below. Unrecognized pension actuarial gains and losses in excess of 10 percent of the greater of the projected benefit obligation or the market-related value of assets are amortized over the average life expectancy of plan participants for frozen plans. The market-related value of assets is determined using a 5 year average of assets.

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The pension plans all have plan assets in excess of accumulated benefit obligations. The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for these plans at December 31, were as follows:

The components of net periodic benefit cost, other than the service cost component, are included in other income (expense) on the Consolidated Statements of Operations. Prior service credit is amortized on a straight-line basis over the average remaining service period of active participants. The components related to our pension and other postretirement benefit plans for the years ended December 31, were as follows:

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Weighted average assumptions used to determine benefit obligations at December 31, were as follows:

Weighted average assumptions used to determine net periodic benefit cost for the years ended December 31, were as follows:

The expected rate of return on pension plan assets is based on a targeted asset allocation range determined by the funded ratio of the plan. As of December 31, 2025, the expected rate of return on pension plan assets is based on the targeted asset allocation range of 30 percent to 40 percent equity securities and 60 percent to 70 percent fixed-income securities and the expected rate of return from these asset categories.

Health care rate assumptions for our other postretirement benefit plans as of December 31, were as follows:

Our other postretirement benefit plans include health care and life insurance benefits for certain retirees. The plans underlying these benefits may require contributions by the retiree depending on such retiree’s age and years of service at retirement or the date of retirement. We contribute a flat dollar amount to the monthly premiums, which is updated annually on January 1.

We donot expect to contribute to our defined pension plans in 2026. We expect to contribute approximately $795,000 to our postretirement benefit plans in 2026.

The following benefit payments, which reflect future service, as appropriate, at December 31, 2025, are as follows:

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Outside investment managers manage our pension assets. Our investment policy with respect to the pension assets is to make investments solely in the interest of the participants and beneficiaries of the plans and for the exclusive purpose of providing benefits accrued and defraying the reasonable expenses of administration. We strive to maintain investment diversification to assist in minimizing the risk of large losses. Our policy guidelines allow for investment of funds in cash equivalents, fixed-income securities and equity securities. The guidelines prohibit investment in commodities and futures contracts, equity private placement, employer securities, leveraged or derivative securities, options, direct real estate investments, precious metals, venture capital and limited partnerships. The guidelines also prohibit short selling and margin transactions. Our practice is to periodically review and rebalance asset categories based on our targeted asset allocation percentage policy.

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The fair value ASC establishes a hierarchy for grouping assets and liabilities, based on the significance of inputs. The estimated fair values of our pension plans’ assets are determined using the market approach.

The carrying value of the pension plans’ Level 1 and Level 2 cash equivalents are based on quoted prices in active markets for identical instruments and approximates fair value by using observable inputs in active markets. The estimated fair value of the pension plans’ Level 1 and Level 2 cash equivalents is based on the net asset value of shares held at year end, based on quoted prices in active markets and is determined using other observable inputs, including pricing from outside sources.

The carrying value of the pension plan’s Level 2 money market funds are valued at the net asset value of shares held at the end of the period, based on published market quotations on active markets, or using other known sources including pricing from outside sources.

The estimated fair value of the pension plans’ Level 1 and Level 2 equity securities are based on the closing price reported on the active market on which the individual securities are traded or other known sources including pricing from outside sources. The estimated fair value of the pension plans’ Level 1 and Level 2 collective and mutual funds are based on the net asset value of shares held at year end, based on either published market quotations on active markets or other known sources, including pricing from outside sources.

Though we believe the methods used to estimate fair value are consistent with those used by other market participants, the use of other methods or assumptions could result in a different estimate of fair value.

The fair value of our pension plans’ assets by class were as follows:

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Nonqualified benefit plans

Prior to the Separation, we participated in unfunded, nonqualified defined benefit plans sponsored by MDU Resources. In connection with the Separation, we assumed all the obligations and liabilities of our employees in those plans, along with all MDU Resources employees that transferred to Knife River as a result of the Separation. Subsequent to the Separation, the unfunded, nonqualified defined benefit plans in which we participate are single employer plans for executive officers and certain key management employees. The plans generally provide for defined benefit payments at age 65 following the employee’s retirement or, upon death, to their beneficiaries for a 15-year period. In February 2016, the unfunded, nonqualified defined benefit plans were frozen to new participants and eliminated benefit increases. Vesting for participants not fully vested was retained.

The projected benefit obligation and accumulated benefit obligation for our participants in these plans at December 31, were as follows:

The components of net periodic benefit cost are included inother income (expense) on the Consolidated Statements of Operations. The components related to our participation in the nonqualified defined benefit plans for the years ended December 31, were as follows:

Weighted average assumptions used at December 31, were as follows:

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The amount of future benefit payments for the unfunded, nonqualified defined benefit plans at December 31, 2025 are expected to aggregate as follows:

Prior to the Separation, we participated in nonqualified defined contribution plans sponsored by MDU Resources. In connection with the Separation, we assumed all the obligations and liabilities of our employees in those plans, along with all MDU Resources employees that transferred to Knife River as a result of the Separation. In 2020, the plan established in 2012 was frozen to new participants and no new employer contributions were made to the plan after December 31, 2020. Vesting for participants not fully vested was retained.

Effective January 1, 2021, a new nonqualified defined contribution plan was adopted, to replace the plan originally established in 2012 with similar provisions. Expenses we incurred under these plans for 2025, 2024 and 2023 were $1.4 million, $800,000 and $1.5 million, respectively.

The amount of investments that we anticipate using to satisfy obligations under these plans at December 31, was as follows:

1 For more information on the insurance contract, see Note 8.

2 Investments of life insurance are carried on plan participants (payable upon the employee’s death).

Defined contribution plan

We sponsor a defined contribution plan in which our employees participate. The costs incurred by us under this plan for eligible employees were $31.7 million, $33.9 million and $31.1 million in 2025, 2024 and 2023, respectively.

Multiemployer plans

We contribute to a number of MEPPs under the terms of collective-bargaining agreements that cover our union-represented employees. The risks of participating in these multiemployer plans are different from single-employer plans in the following aspects:

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

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

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

Our participation in these plans is outlined in the following table. Unless otherwise noted, the most recent Pension Protection Act zone status available in 2025, 2024 and 2023 is for the plan’s year-end at December 31, 2024, December 31, 2023 and December 31, 2022, respectively. The zone status is based on information that we

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received from the plan and is certified by the plan’s actuary. Among other factors, plans in the “red zone,” or critical status, are generally less than 65 percent funded, plans in the “yellow zone,” or endangered status, are between 65 percent and 80 percent funded, and plans in the “green zone,” or healthy status, are at least 80 percent funded.

*Plan includes contributions required by collective bargaining agreements which have expired but contain provisions automatically renewing their terms in the absence of a subsequent negotiated agreement.

We were listed in the plans’ Forms 5500 as providing more than 5 percent of the total contributions for the following plans and plan years:

We also contribute to a number of multiemployer other postretirement plans under the terms of collective-bargaining agreements that cover our union-represented employees. These plans provide benefits such as health insurance, disability insurance and life insurance to retired union employees. Many of the multiemployer other postretirement plans are combined with active multiemployer health and welfare plans. Our total contributions to the multiemployer other postretirement plans, which also includes contributions to active multiemployer health and welfare plans, were $2.2 million, $2.0 million and $1.8 million for the years ended December 31, 2025, 2024 and 2023, respectively.