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Asset retirement obligations (“ARO”) (Tables)

3 Months Ended

Mar. 31, 2012

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Change in Asset Retirement Obligations

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

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- Definition

Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Topic 410

-SubTopic 30

-Publisher FASB

-Number

-Article

-Subparagraph

-Name Accounting Standards Codification

-Paragraph 5

-Section 50

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859

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