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ASSET RETIREMENT OBLIGATIONS Asset Retirement Obligations Level 3 (Tables)
 12 Months Ended
Dec. 31, 2019
Asset Retirement Obligation [Abstract]  
Schedule of Change in Asset Retirement Obligation
The following table presents the changes in the carrying amount of AROs (in thousands of dollars): 
 
 
2019
 
2018
Balance at beginning of year
 
$
26,792

 
$
26,415

Accretion expense
 
1,115

 
1,055

Revisions in estimated cash flows
 
365

 
(751
)
Liability incurred
 
—

 
129

Liability settled
 
(81
)
 
(56
)
Balance at end of year
 
$
28,191

 
$
26,792