Asset Retirement Obligations (Notes)

12 Months Ended

Dec. 31, 2018

Asset Retirement Obligation Disclosure [Abstract]

Asset Retirement Obligations

ASSET RETIREMENT OBLIGATIONS

Our accrued asset retirement obligations relate to our gas storage and transmission facilities. At the end of the useful life of our facilities, we are legally obligated to remove or plug and abandon certain transmission facilities including underground pipelines, major river spans, compressor stations and meter station facilities. These obligations also include restoration of the property sites after removal of the facilities from above and below the ground.

During 2018 and 2017, our overall asset retirement obligation changed as follows (in thousands):

	2018			2017
Beginning balance	$	67,100		$	60,762
Accretion	4,359			3,968
New obligations	—			149
Changes in estimates of existing obligations (1)	(2,095		)	2,510
Property dispositions/obligations settled	(14		)	(289		)
Ending balance	$	69,350		$	67,100

(1) Changes in estimates of existing obligations are primarily due to the annual review process, which considers various factors including inflation rates, current estimates for removal costs, the estimated remaining life of assets, and discount rates.