Commitments. We have a variety of financial commitments, including purchase agreements, forward foreign exchange and forward sales contracts, indebtedness and letters of credit (see Note 3, Note 8 and Note 9).

CAROs. The inputs in estimating the fair value of CAROs include: (i) the timing of when any such CARO cash flows may be incurred; (ii) incremental costs associated with special handling or treatment of CARO materials; and (iii) the credit-adjusted risk-free rate applicable at the time additional CARO cash flows are estimated; all of these are considered Level 3 inputs as they involve significant judgment from us.

The following table summarizes activity relating to CARO liabilities (in millions of dollars):

	Year Ended December 31,
	2020			2019			2018
Beginning balance	$	6.5		$	6.3		$	5.9
Liabilities settled during the period		(0.1	)		(0.2	)		—
Accretion expense		0.5			0.5			0.4
Adjustment to accretion expense due to revisions to estimated cash flow and timing of expenditure¹		(0.2	)		(0.1	)		—
Ending balance	$	6.7		$	6.5		$	6.3

The estimated fair value of CARO liabilities were based upon the application of a weighted-average credit-adjusted risk-free rate of 8.7% at both December 31, 2020 and December 31, 2019. CAROs are included in Other accrued liabilities or Long-term liabilities, as appropriate.

Environmental Contingencies. We are subject to a number of environmental laws and regulations, to potential fines or penalties assessed for alleged breaches of such laws and regulations and to potential claims based upon such laws and regulations. We are also subject to legacy environmental contingencies related to activities that occurred at operating facilities prior to July 6, 2006, which

represent the majority of our environmental accruals. The status of these environmental contingencies are discussed below. We have established procedures for regularly evaluating environmental loss contingencies. Our environmental accruals represent our undiscounted estimate of costs reasonably expected to be incurred based on presently enacted laws and regulations, currently available facts, existing requirements, existing technology and our assessment of the likely remediation actions to be taken.

We continue to pursue remediation activities, primarily to address the historical use of oils containing polychlorinated biphenyls (“PCBs”) at our Trentwood facility. Our remediation efforts are in collaboration with the Washington State Department of Ecology (“Ecology”), to which we submitted a feasibility study in 2012 of remediation alternatives and from which we received permission to begin certain remediation activities pursuant to a signed work order. We have completed a number of sections of the work plan and have received satisfactory completion approval from Ecology on those sections. Additionally, in cooperation with Ecology, to determine the treatability and evaluate the feasibility of removing PCBs from ground water under the Trentwood facility, we constructed an experimental treatment facility and began treatment operations in 2015. During the year ended December 31, 2020, we increased our environmental accrual by $3.8 million based on a minimum cost estimate to implement a full‑scale experimental treatment facility for ground water PCB contaminants. As the long-term success of the new methodology cannot be reasonably determined at this time, it is possible we may need to make upward adjustments to our related accruals and cost estimates as the long term results become available.

Pursuant to a consent agreement with the Ohio Environmental Protection Agency (“OEPA”), we initiated an investigational study of our Newark facility related to historical on-site waste disposal. During the quarter ended December 31, 2018, we submitted our remedial investigation study to the OEPA for review and approval. The final remedial investigation report was approved by the OEPA during the quarter ended December 31, 2020. We are currently preparing the required feasibility study, which we expect to submit to the OEPA for review during the quarter ending June 30, 2021. The actual and final remediation cost estimates will not be fully determinable until the feasibility study has been accepted by the OEPA and the selected remediation design work plans are complete, which we expect to occur in the next 10 to 16 months.

During 2020, following the issuance of information requests under the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (“CERCLA”), to which we responded, the United States Environmental Protection Agency (“USEPA”) issued a general notice letter to us alleging that we are a potentially responsible party under CERCLA for response and other potential remedial actions concerning property owned by us near our former smelter site in Mead, Spokane County, Washington. In February 2020, we responded to the general notice letter and in August 2020, we entered into an administrative settlement agreement and an order on consent for removal actions (“EPA Order”). We performed the required remediation actions in October 2020 and, following its field evaluation, the USEPA notified us that the remediation actions taken were deemed to have completed the requirements of the EPA Order. As such, we have no remaining obligations or environmental accrual related to the EPA Order.

The following table presents the changes in our environmental accrual, which was primarily included in Long-term liabilities (in millions of dollars):

	Year Ended December 31,
	2020			2019			2018
Beginning balance	$	17.0		$	16.9		$	16.6
Additional accruals		5.2			1.8			1.7
Less: expenditures		(3.5	)		(1.7	)		(1.4	)
Ending balance	$	18.7		$	17.0		$	16.9

At December 31, 2020, our environmental accrual of $18.7 million represented our estimate of the incremental remediation cost based on: (i) proposed alternatives in the final feasibility study related to the Trentwood facility; (ii) currently available facts with respect to our Newark facility; and (iii) facts related to certain other locations owned or formerly owned by us. In accordance with approved and proposed remediation action plans, we expect that the implementation and ongoing monitoring could occur over a period of 30 or more years.

As additional facts are developed, feasibility studies are completed, remediation plans are modified, necessary regulatory approvals for the implementation of remediation are obtained, alternative technologies are developed and/or other factors change, there may be revisions to management’s estimates and actual costs may exceed the current environmental accruals. We believe at this time that it is reasonably possible that undiscounted costs associated with these environmental matters may exceed current accruals by amounts that could be, in the aggregate, up to an estimated $11.6 million over the remediation period. It is reasonably possible that our recorded estimate will change in the next 12 months.

Other Contingencies. We are party to various lawsuits, claims, investigations and administrative proceedings that arise in connection with past and current operations. We evaluate such matters on a case-by-case basis and our policy is to vigorously contest any such claims we believe are without merit. We accrue for a legal liability when it is both probable that a liability has been incurred and the amount of the loss is reasonably estimable. Quarterly, in addition to when changes in facts and circumstances require it, we review and adjust these accruals to reflect the impacts of negotiations, settlements, rulings, advice of legal counsel and other information and events pertaining to a particular case. While uncertainties are inherent in the final outcome of such matters and it is presently impossible to determine the actual cost that may ultimately be incurred, we believe that we have sufficiently accrued for such matters and that the ultimate resolution of pending matters will not have a material impact on our consolidated financial position, operating results or liquidity.