Asset Retirement Obligations (Notes)

12 Months Ended

Dec. 31, 2021

Asset Retirement Obligation Disclosure [Abstract]

These accrued obligations relate to underground storage caverns, offshore platforms, pipelines, and gas transmission facilities. At the end of the useful life of each respective asset, we are legally obligated to plug storage caverns and remove any related surface equipment, to dismantle offshore platforms, to cap certain gathering pipelines at the wellhead connection and remove any related surface equipment, and to remove certain components of gas transmission facilities from the ground.

During 2021 and 2020, our overall asset retirement obligation changed as follows (in thousands):


	2021		2020
Beginning balance	$	450,501	$	459,209
Accretion	22,343		23,142
New obligations	1,249		1,154
Changes in estimates of existing obligations (1)	59,460		(21,889)
Property dispositions/obligations settled	(15,166)		(11,115)
Ending balance	$	518,387	$	450,501

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(1) Changes in estimates of existing obligations are primarily due to the annual review process, which considers various factors including inflation rate, current estimates for removal costs, discount rates, and the estimated remaining life of assets. The increase in 2021 is primarily due to an increase in estimated removal cost for offshore AROs. The decrease in 2020 is primarily due to a decrease in the inflation rate.

We are entitled to collect in rates the amounts necessary to fund our ARO. All funds received for such retirements are deposited into an external trust account dedicated to funding our ARO (see Note 6 – ARO Trust).