10. | Asset Retirement Obligations |
The following table provides a summary of changes in asset retirement obligations, which are included in other liabilities in the accompanying consolidated balance sheets. Revisions in estimates for the periods presented relate primarily to revisions of current cost estimates, inflation rates and/or discount rates.
|
Years Ended December 31, |
|
|||||||||
|
2013 |
|
|
2012 |
|
|
2011 |
|
|||
|
(in thousands) |
|
|||||||||
Asset retirement obligations, beginning of period |
$ |
5,335 |
|
|
$ |
3,409 |
|
|
$ |
2,878 |
|
Additions |
|
— |
|
|
|
1,816 |
|
|
|
131 |
|
Revisions |
|
(1,314 |
) |
|
|
(133 |
) |
|
|
193 |
|
Accretion expense |
|
500 |
|
|
|
243 |
|
|
|
207 |
|
Deletions |
|
— |
|
|
|
— |
|
|
|
— |
|
Asset retirement obligations, end of period |
$ |
4,521 |
|
|
$ |
5,335 |
|
|
$ |
3,409 |
|