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Asset Retirement Obligation
 9 Months Ended
Sep. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligation Asset Retirement Obligation
The Company had a post-closure reclamation and site restoration obligation of $16,291 as of September 30, 2021. The following is a reconciliation of the total reclamation liability for asset retirement obligations.
Balance at December 31, 2020$14,996 
Additions737 
Accretion expense558 
Balance at September 30, 2021$16,291