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Asset Retirement Obligation
12 Months Ended
Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]  
Asset Retirement Obligation
Asset Retirement Obligation
The Company had a post-closure reclamation and site restoration obligation of $13,322 as of December 31, 2018. The following is a reconciliation of the total reclamation liability for asset retirement obligations.
Balance at December 31, 2016
$
1,384

Additions and revisions of prior estimates
7,084

Accretion expenses
514

Balance at December 31, 2017
$
8,982

Additions and revisions of prior estimates
7,546

Accretion expenses
(26
)
Settlement of liability
$
(3,180
)
Balance at December 31, 2018
$
13,322