Commitments and Contingencies 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 7 and Note 8 ). Rental expenses were $8.2 million , $7.9 million and $8.5 million for 2018 , 2017 and 2016 , respectively. There are renewal options in various leases subject to certain terms and conditions. Minimum rental commitments at December 31, 2018 were as follows (in millions of dollars): Year Ended December 31, Capital Leases Operating Leases 2019 $ 1.7 $ 6.1 2020 1.4 3.7 2021 1.2 2.8 2022 1.1 2.4 2023 1.0 2.2 2024 and thereafter 1.8 20.8 Total minimum lease payments $ 8.2 $ 38.0 Less: interest (1.2 ) Present value 1 $ 7.0 _________________________ 1. Of the $7.0 million in capital lease obligations as of December 31, 2018 , $1.4 million was included in Other accrued liabilities and $5.6 million was included in Long-term liabilities. Assets recorded under capital leases and the accumulated amortization thereon were $8.3 million and $1.3 million , respectively, as of December 31, 2018 , and $2.2 million and $0.9 million , respectively, as of December 31, 2017 . 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 the activity relating to our CARO liabilities (in millions of dollars): Year Ended December 31, 2018 2017 2016 Beginning balance $ 5.9 $ 5.5 $ 4.9 Liabilities settled during the period   (0.1 ) Accretion expense 0.4 0.4 0.5 Adjustment to accretion expense due to revisions to estimated cash flow and timing of expenditure 1   0.2 Ending balance $ 6.3 $ 5.9 $ 5.5 _________________________ 1. The adjustments in 2016 had a de minimis impact on the basic and diluted net income per share for 2016. 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, 2018 and December 31, 2017 . 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, existing requirements, currently available facts, 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 ("Washington State 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. As we have finished a number of sections of the work plan, we have received approval from Washington State Ecology on satisfactory completion of those sections. Additionally, in cooperation with Washington State 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 2016. 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. During 2013, at the request of the Ohio Environmental Protection Agency ("OEPA"), we initiated an investigational study of the Newark facility related to historical on-site waste disposal. In the fourth quarter of 2018, we submitted our remedial investigation study to the OEPA which is subject to their review and approval. Following OEPA approval of the remedial investigational study, we will then prepare the final feasibility study and update estimates for probable and estimable remediation, if any. The actual and final cost for remediation will not be fully determinable until a final feasibility study is submitted and accepted by the OEPA and work plans are prepared, which is expected to occur in the next 12 months . 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, 2018 2017 2016 Beginning balance $ 16.6 $ 17.2 $ 18.6 Additional accruals 1.7 0.3 0.1 Less: expenditures (1.4 ) (0.9 ) (1.5 ) Ending balance $ 16.9 $ 16.6 $ 17.2 At December 31, 2018 , our environmental accrual of $16.9 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. In July and September 2018, we filed a total of three requests for exclusion from certain import duties, as instituted in the Presidential Proclamation 9704 of March 8, 2018 (also known as Section 232 Tariff), with the Bureau of Industry and Security ("BIS"), an agency within the Department of Commerce. If such exclusions are approved by the BIS, we believe we will be able to apply for and recover approximately $2.4 million , which represents Section 232 Tariff related duties paid from the dates of filing the exclusion requests through December 31, 2018. However, the ultimate outcome of the exclusion requests, and subsequently the request for refund, cannot be determined. Therefore, no amount has been recognized in the 2018 financial results for the possible collection of a refund.