|
|
|
Years Ended December 31, | |||||
|
|
|
2013 |
|
2012 | |||
|
|
|
(Thousands) |
| ||||
|
Asset retirement obligation as of beginning of period |
|
$ |
109,034 |
|
$ |
102,439 |
|
|
Accretion expense |
|
8,342 |
|
7,716 |
| ||
|
Liabilities incurred |
|
2,510 |
|
1,141 |
| ||
|
Liabilities settled |
|
(3,353 |
) |
(2,408) |
| ||
|
Revisions in estimated cash flows |
|
(488 |
) |
146 |
| ||
|
Asset retirement obligation as of end of period |
|
$ |
116,045 |
|
$ |
109,034 |
|