ACCRUED CAPPING, CLOSURE AND POST CLOSURE

9 Months Ended

Jan. 31, 2012

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 nine months ended January 31, 2012 and 2011 are as follows:

	Nine Months Ended January 31,
	2012			2011
Beginning balance	$	36,407		$	40,002
Obligations incurred	2,350			2,188
Revisions in estimates (1)	—			(1,120		)
Accretion expense	2,510			2,384
Payments	(1,298		)	(6,140		)
Ending balance	$	39,969		$	37,314

(1)The revision in estimates for capping, closure and post-closure for the nine months ended January 31, 2011 consists of changes in cost estimates and timing of capping and closure events, as well as changes to expansion airspace and tonnage placement assumptions.