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Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2022
Asset Retirement Obligation [Abstract]  
Changes to Asset Retirement Obligation

The following table describes changes to the asset retirement obligation liability (dollars in millions):

 

 

 

Year Ended December 31,

 

 

 

2022

 

 

2021

 

Asset retirement obligation at beginning of period

 

$

29.4

 

 

$

31.8

 

Accretion expense

 

 

1.3

 

 

 

1.2

 

Liabilities incurred

 

 

—

 

 

 

1.0

 

Payments

 

 

(0.3

)

 

 

(0.1

)

Revisions in estimated cash flows (a)

 

 

(0.2

)

 

 

(4.5

)

Asset retirement obligation at end of period

 

$

30.2

 

 

$

29.4

 

 

(a)
For 2021, primarily consists of an asset retirement adjustment of $4.2 million related to the San Lorenzo, California facility closure.