Asset Retirement Obligations (Notes)

12 Months Ended

Dec. 31, 2021

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

	2021		2020
Beginning balance	$	95,777	$	91,251
Accretion	5,725		5,410
Changes in estimates of existing obligations (1)	21,148		(884)
Ending balance	$	122,650	$	95,777

(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 a decrease in the discount rate and an increase in the estimated life of the ARO assets.