A summary of the changes to the environmental remediation liability associated with the Southbridge Landfill follows:



	Nine Months Ended September 30,
	2020		2019
Beginning balance	$	4,596	$	5,173
Accretion expense	90		94
Obligations incurred	28		—
Revisions in estimates (1)	(188)		—
Obligations settled (2)	(293)		(556)
Ending balance	$	4,233	$	4,711

(1)The revision of estimate is associated with the completion of the environmental remediation at the site. See Note 13, Other Items and Charges to our consolidated financial statements for further discussion.

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

A summary of the changes to the environmental remediation liability associated with the Potsdam follows:


	Nine Months Ended September 30,
	2020		2019
Beginning balance	$	1,151	$	5,614



Obligations settled (1)	(212)		(1,764)
Ending balance	$	939	$	3,850

(1)Includes amounts that are being processed through accounts payable as a part of our disbursements cycle.