Asset Retirement Obligations (Notes)

12 Months Ended

Dec. 31, 2015

Asset Retirement Obligation Disclosure [Abstract]

ASSET RETIREMENT OBLIGATIONS

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 2015 and 2014, our overall asset retirement obligation changed as follows (in thousands):



	2015			2014
Beginning balance	$	296,475		$	273,987
Accretion	25,178			17,962
New obligations	256			1,346
Changes in estimates of existing obligations (1)	3,691			23,031
Property dispositions/obligations settled	(2,574		)	(19,851		)
Ending balance	$	323,026		$	296,475

(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 cost, discount rates, and the estimated remaining life of assets. The changes in estimates of existing obligations reflect an increase of $4 million and $23 million for 2015 and 2014, respectively, due to revisions in the estimated remaining life of assets, inflation rates, discount rates, and current estimates for removal costs.

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. Under our current rate settlement our annual funding obligation is approximately $36.4 million, with installments to be deposited monthly.