Annual report pursuant to Section 13 and 15(d)

ASSET RETIREMENT OBLIGATIONS

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ASSET RETIREMENT OBLIGATIONS
12 Months Ended
Dec. 31, 2020
Environmental Remediation Obligations [Abstract]  
Asset Retirement Obligation Disclosure
The following is a summary of our asset retirement obligations:
(In Millions)
December 31,
2020 2019
Asset retirement obligations1
$ 342  $ 165 
Less: current portion 7 
Long-term asset retirement obligations $ 335  $ 163 
1 Includes $190 million and $22 million related to our active operations as of December 31, 2020 and 2019, respectively.
The accrued closure obligation provides for contractual and legal obligations related to our indefinitely idled and closed operations and for the eventual closure of our active operations. We performed a detailed assessment of our asset retirement obligations related to our active operations most recently in 2020 in accordance with our
accounting policy, which requires us to perform an in-depth evaluation of the liability every three years in addition to routine annual assessments. In 2020, we employed third-party specialists to assist in the evaluation.
Additionally, we have included in our asset retirement obligation $172 million for our integrated steel facilities and other operations acquired in the Acquisitions. The closure date for each of our active mine sites was determined based on the exhaustion date of the remaining mineral reserves and the amortization of the related asset and accretion of the liability is recognized over the estimated mine lives. The closure date and expected timing of the capital requirements to meet our obligations for our indefinitely idled or closed mines is determined based on the unique circumstances of each property. For indefinitely idled or closed mines, the accretion of the liability is recognized over the anticipated timing of remediation. As the majority of our asset retirement obligations at our steelmaking operations have indeterminate settlement dates, asset retirement obligations have been recorded at present values using estimated ranges of the economic lives of the underlying assets.
The following is a roll-forward of our asset retirement obligation liability:
(In Millions)
2020 2019
Asset retirement obligation as of January 1 $ 165  $ 172 
Increase from acquisitions 172  — 
Accretion expense 14  10 
Remediation payments (9) (1)
Revision in estimated cash flows   (16)
Asset retirement obligation as of December 31 $ 342  $ 165 
The revision in estimated cash flows during the year ended December 31, 2019 for $16 million primarily relates to an extension of the life-of-mine plan for Tilden mine based on the economic reserve analysis performed during 2019.