Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2012

Schedule of Changes in Asset Retirement Obligations

The following shows the changes in the asset retirement obligations:

     years ended December 31:

(add 000)	2012			2011
Balance at January 1	$	43,233		$	41,079
Accretion expense		2,712			2,645
Liabilities incurred		204			3,062
Liabilities settled		(126	)		(2,091	)
Revisions in estimated cash flows		150			(1,462	)
Balance at December 31	$	46,173		$	43,233

Schedule of Contractual Purchase Commitments

The Corporation’s contractual purchase commitments as of December 31, 2012 are as follows:

(add 000)
2013	$	41,496
2014		8,659
2015		229
Total	$	50,384