FINAL CAPPING, CLOSURE AND POST-CLOSURE COSTS (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation Disclosure [Abstract]

Changes to Accrued Capping, Closure and Post-Closure Liabilities

The changes to accrued final capping, closure and post-closure liabilities are as follows:

	Fiscal Year Ended December 31,
	2017			2016
Beginning balance	$	44,207		$	41,041
Obligations incurred	3,022			2,441
Revisions in estimates (1)	11,498			(2,052		)
Accretion expense	4,401			3,606
Obligations settled (2)	(838		)	(829		)
Ending balance	$	62,290		$	44,207

(1) Relates to changes in estimates and assumptions concerning anticipated waste flow, cost and timing of future final capping, closure and post-closure activities at certain landfills, including the Subtitle D landfill in Southbridge, Massachusetts ("Southbridge Landfill"), as well as changes to expansion airspace. See Note 10, Commitments and Contingencies and Note 15, Other Items and Charges for disclosure regarding Southbridge Landfill.

(2) Includes amounts paid and amounts that are being processed through accounts payable as a part of our disbursement cycle.