Note E — Asset Retirement Obligations (ARO)

The majority of the ARO recognized by the Company at September 30, 2013 and December 31, 2012 related to the estimated costs to dismantle and abandon certain of its retail gasoline stations. The Company has not recorded an ARO for certain of its marketing assets because sufficient information is presently not available to estimate a range of potential settlement dates for the obligation. These assets are consistently being upgraded and are expected to be operational into the foreseeable future. In these cases, the obligation will be initially recognized in the period in which sufficient information exists to estimate the obligation.

A reconciliation of the beginning and ending aggregate carrying amount of the ARO is shown in the following table.



	September 30,		December 31,
(Thousands of dollars)	2013		2012
Balance at beginning of period	$	15,401		13,190
Accretion expense		821		980
Liabilities incurred		491		1,231
Balance at end of period	$	16,713		15,401

The estimation of future ARO is based on a number of assumptions requiring professional judgment. The Company cannot predict the type of revisions to these assumptions that may be required in future periods due to the availability of additional information.