Exhibit 12

Statement re: Calculation of Ratios of Earnings to

Combined Fixed Charges and Preferred Unit Distributions

(Dollars in thousands)

	Three Months Ended March 31, 2009		Year Ended December 31, 2008		Year Ended December 31, 2007		Year Ended December 31, 2006		Year Ended December 31, 2005		Year Ended December 31, 2004
Income from continuing operations less preferred distributions	$	18,892	$	18,756	$	106,321	$	103,059	$	96,695	$	106,591
Preferred distributions		18,363		71,426		58,292		56,419		46,479		33,777
Interest expense		52,068		199,241		175,429		170,766		106,203		98,086
Earnings before fixed charges	$	89,323	$	289,423	$	340,042	$	330,244	$	249,377	$	238,454
Interest expense	$	52,068	$	199,241	$	175,429	$	170,766	$	106,203	$	98,086
Interest costs capitalized		7,499		53,456		59,167		36,260		9,510		5,961
Total fixed charges	$	59,567	$	252,697	$	234,596	$	207,026	$	115,713	$	104,047
Preferred distributions	$	18,363	$	71,426	$	58,292	$	56,419	$	46,479	$	33,777
Total fixed charges and preferred distributions	$	77,930	$	324,123	$	292,888	$	263,445	$	162,192	$	137,824
Ratio of Earnings to Fixed Charges		1.50		1.15		1.45		1.60		2.16		2.29
Ratio of Earnings to Combined Fixed Charges and Preferred Distributions		1.15		N/A		1.16		1.25		1.54		1.73

N/A—the ratio is less than 1.0; deficit of $34.7 million exists for the year ended December 31, 2008. The calculation of earnings includes $308.8 million of non-cash depreciation expense.