Intrepid recognizes a liability for future estimated costs associated with the reclamation of its mining properties. A liability for the estimated fair value of an asset retirement obligation and a corresponding increase to the carrying value of the related long-lived asset are recorded as the mining operations occur or as the assets are acquired.

Intrepid's asset retirement obligation is based on the estimated cost to remove assets and close the mining operations, the economic life of the properties, and federal and state regulatory requirements. The liability is discounted using the credit adjusted risk-free rate estimates at the time the liability is incurred or when there are revisions to estimated costs. The credit adjusted risk-free rates used to discount Intrepid's abandonment liabilities range from 6.9 percent to 8.5 percent. Revisions to the liability occur due to changes in estimated abandonment costs or economic lives, or if federal or state regulators enact new requirements regarding the abandonment of mines.

Following is a table of the changes to Intrepid's asset retirement obligations for the following periods (in thousands):

	Three months ended					Nine months ended

	September 30, 2011			September 30, 2010		September 30, 2011			September 30, 2010
Asset retirement obligation—beginning of period	$	9,860		$	8,981	$	9,478		$	8,619
Changes in estimated obligations		(287	)		—		(287	)		10
Accretion of discount		184			176		566			528

Total asset retirement obligation—end of period	$	9,757		$	9,157	$	9,757		$	9,157

The undiscounted amount of asset retirement obligation is $31.3 million as of September 30, 2011, and there are no significant payments expected in the next five years.