ACCRUED CAPPING, CLOSURE AND POST CLOSURE

6 Months Ended

Oct. 31, 2011

ACCRUED CAPPING, CLOSURE AND POST CLOSURE

ACCRUED CAPPING, CLOSURE AND POST CLOSURE

4. ACCRUED CAPPING, CLOSURE AND POST CLOSURE

Accrued capping, closure and post-closure costs include the current and non-current portion of costs associated with obligations for closure and post-closure of our landfills. We estimate our future capping, closure and post-closure costs in order to determine the capping, closure and post-closure expense per ton of waste placed into each landfill. The anticipated timeframe for paying these costs varies based on the remaining useful life of each landfill, as well as the duration of the post-closure monitoring period. The changes to accrued capping, closure and post-closure liabilities for the six months ended October 31, 2011 and 2010 are as follows:

	Six Months Ended October 31,
	2011			2010
Beginning Balance	$	36,407		$	40,002
Obligations incurred	1,417			1,580
Revisions in estimates (1)	—			(338		)
Accretion expense	1,671			1,587
Payments	(648		)	(5,543		)
Ending Balance	$	38,847		$	37,288

(1) The revision in estimates for capping, closure and post-closure for the six months ended October 31, 2010 consists of changes in cost estimates and timing of capping and closure events, as well as changes to expansion airspace and tonnage placement assumptions.