Annual report pursuant to Section 13 and 15(d)

Accrued Closure Costs and ARO - Schedule of Change in Asset Retirement Obligation (Details)

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Accrued Closure Costs and ARO - Schedule of Change in Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]    
Balance at beginning $ 6,041 $ 6,750
Accretion expense 335 320
Spending (11) (1,359)
Adjustment to closure liability   330
Balance at end $ 6,365 $ 6,041