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Asset retirement obligations (“ARO”)
 3 Months Ended
Mar. 31, 2012
Asset Retirement Obligation Disclosure [Abstract]  
Asset retirement obligations (“ARO”)
Asset retirement obligations (“ARO”)
Our asset retirement obligations consist primarily of costs associated with the disposal of spent pot liner used in the reduction cells of our domestic facilities.

The reconciliation of the changes in the asset retirement obligations is presented below:
 
Three months ended March 31, 2012
Year ended December 31, 2011
Beginning balance, ARO liability
$
15,171

$
14,274

Additional ARO liability incurred
291

1,110

ARO liabilities settled
(345
)
(1,315
)
Accretion expense
292

1,102

Ending balance, ARO liability
$
15,409

$
15,171


Certain conditional AROs related to the disposal costs of fixed assets at our primary aluminum facilities have not been recorded because they have an indeterminate settlement date. These conditional AROs will be initially recognized in the period in which sufficient information exists to estimate their fair value.