Asset Retirement Obligations

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligations

(19) ASSET RETIREMENT OBLIGATIONS

AROs recognized by Alliant Energy, IPL and WPL relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind projects, certain ash ponds, active ash landfills and above ground storage tanks. Alliant Energy's, IPL's and WPL's recognized AROs also include legal obligations for the management and final disposition of asbestos and PCB. Alliant Energy's, IPL's and WPL's AROs are recorded in "Other long-term liabilities and deferred credits" on the Consolidated Balance Sheets. Refer to Note 1(b) for information regarding regulatory assets related to AROs. A reconciliation of the changes in recognized AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL						WPL
	2011			2010			2011			2010			2011			2010
Balance, Jan. 1	$	75.9		$	63.3		$	43.6		$	41.9		$	32.3		$	21.4
Revisions in estimated cash flows (a)		7.8			—			7.7			—			0.1			—
Accretion expense		4.3			4.1			2.6			2.8			1.7			1.3
Liabilities incurred (b)		4.0			9.8			3.1			—			0.9			9.8
Liabilities settled		(0.9	)		(1.3	)		(0.8	)		(1.1	)		(0.1	)		(0.2	)
Balance, Dec. 31	$	91.1		$	75.9		$	56.2		$	43.6		$	34.9		$	32.3

(a) In 2011, IPL recorded revisions in estimated cash flows of $7.0 million based on revised remediation timing and cost information for asbestos remediation at Sixth Street.

(b) In 2010, WPL recorded AROs of $9.8 million related to its Bent Tree - Phase I wind project.

In addition, certain of Alliant Energy's, IPL's and WPL's AROs related to electric generating facility assets have not been recognized. Due to an indeterminate remediation date, the fair values of the AROs for these assets cannot be currently estimated. A liability for these AROs will be recorded when fair value is determinable.

IPL [Member]

Asset Retirement Obligations

(19) ASSET RETIREMENT OBLIGATIONS

AROs recognized by Alliant Energy, IPL and WPL relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind projects, certain ash ponds, active ash landfills and above ground storage tanks. Alliant Energy's, IPL's and WPL's recognized AROs also include legal obligations for the management and final disposition of asbestos and PCB. Alliant Energy's, IPL's and WPL's AROs are recorded in "Other long-term liabilities and deferred credits" on the Consolidated Balance Sheets. Refer to Note 1(b) for information regarding regulatory assets related to AROs. A reconciliation of the changes in recognized AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL						WPL
	2011			2010			2011			2010			2011			2010
Balance, Jan. 1	$	75.9		$	63.3		$	43.6		$	41.9		$	32.3		$	21.4
Revisions in estimated cash flows (a)		7.8			—			7.7			—			0.1			—
Accretion expense		4.3			4.1			2.6			2.8			1.7			1.3
Liabilities incurred (b)		4.0			9.8			3.1			—			0.9			9.8
Liabilities settled		(0.9	)		(1.3	)		(0.8	)		(1.1	)		(0.1	)		(0.2	)
Balance, Dec. 31	$	91.1		$	75.9		$	56.2		$	43.6		$	34.9		$	32.3

(a) In 2011, IPL recorded revisions in estimated cash flows of $7.0 million based on revised remediation timing and cost information for asbestos remediation at Sixth Street.

(b) In 2010, WPL recorded AROs of $9.8 million related to its Bent Tree - Phase I wind project.

In addition, certain of Alliant Energy's, IPL's and WPL's AROs related to electric generating facility assets have not been recognized. Due to an indeterminate remediation date, the fair values of the AROs for these assets cannot be currently estimated. A liability for these AROs will be recorded when fair value is determinable.

WPL [Member]

Asset Retirement Obligations

(19) ASSET RETIREMENT OBLIGATIONS

AROs recognized by Alliant Energy, IPL and WPL relate to legal obligations for the removal, closure or dismantlement of several assets including, but not limited to, wind projects, certain ash ponds, active ash landfills and above ground storage tanks. Alliant Energy's, IPL's and WPL's recognized AROs also include legal obligations for the management and final disposition of asbestos and PCB. Alliant Energy's, IPL's and WPL's AROs are recorded in "Other long-term liabilities and deferred credits" on the Consolidated Balance Sheets. Refer to Note 1(b) for information regarding regulatory assets related to AROs. A reconciliation of the changes in recognized AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL						WPL
	2011			2010			2011			2010			2011			2010
Balance, Jan. 1	$	75.9		$	63.3		$	43.6		$	41.9		$	32.3		$	21.4
Revisions in estimated cash flows (a)		7.8			—			7.7			—			0.1			—
Accretion expense		4.3			4.1			2.6			2.8			1.7			1.3
Liabilities incurred (b)		4.0			9.8			3.1			—			0.9			9.8
Liabilities settled		(0.9	)		(1.3	)		(0.8	)		(1.1	)		(0.1	)		(0.2	)
Balance, Dec. 31	$	91.1		$	75.9		$	56.2		$	43.6		$	34.9		$	32.3

(a) In 2011, IPL recorded revisions in estimated cash flows of $7.0 million based on revised remediation timing and cost information for asbestos remediation at Sixth Street.

(b) In 2010, WPL recorded AROs of $9.8 million related to its Bent Tree - Phase I wind project.

In addition, certain of Alliant Energy's, IPL's and WPL's AROs related to electric generating facility assets have not been recognized. Due to an indeterminate remediation date, the fair values of the AROs for these assets cannot be currently estimated. A liability for these AROs will be recorded when fair value is determinable.