Asset Retirement Obligations (AROs)

9 Months Ended

Sep. 30, 2012

Asset Retirement Obligations [Line Items]

Asset Retirement Obligations (AROs)

ASSET RETIREMENT OBLIGATIONS (AROs)

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL						WPL
	2012			2011			2012			2011			2012			2011
Balance, January 1		$91.1			$75.9			$56.2			$43.6			$34.9			$32.3
Revisions in estimated cash flows (a)	(9.9		)	7.8			(9.2		)	7.7			(0.7		)	0.1
Liabilities settled	(2.6		)	(0.5		)	(2.5		)	(0.4		)	(0.1		)	(0.1		)
Liabilities incurred (b)	16.0			4.0			—			3.1			7.6			0.9
Accretion expense	2.6			3.4			1.4			2.1			1.2			1.3
Balance, September 30		$97.2			$90.6			$45.9			$56.1			$42.9			$34.5

(a) For the nine months ended September 30, 2012 and 2011, IPL recorded revisions in estimated cash flows of ($8.2) million and $7.0 million, respectively, based on revised remediation timing and cost information for asbestos remediation at its Sixth Street Generating Station.

(b) For the nine months ended September 30, 2012, Resources recorded AROs of $8.4 million related to its Franklin County wind project and WPL recorded AROs of $7.6 million related to its Nelson Dewey generating station.

IPL [Member]

Asset Retirement Obligations [Line Items]

Asset Retirement Obligations (AROs)

ASSET RETIREMENT OBLIGATIONS (AROs)

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL						WPL
	2012			2011			2012			2011			2012			2011
Balance, January 1		$91.1			$75.9			$56.2			$43.6			$34.9			$32.3
Revisions in estimated cash flows (a)	(9.9		)	7.8			(9.2		)	7.7			(0.7		)	0.1
Liabilities settled	(2.6		)	(0.5		)	(2.5		)	(0.4		)	(0.1		)	(0.1		)
Liabilities incurred (b)	16.0			4.0			—			3.1			7.6			0.9
Accretion expense	2.6			3.4			1.4			2.1			1.2			1.3
Balance, September 30		$97.2			$90.6			$45.9			$56.1			$42.9			$34.5

(a) For the nine months ended September 30, 2012 and 2011, IPL recorded revisions in estimated cash flows of ($8.2) million and $7.0 million, respectively, based on revised remediation timing and cost information for asbestos remediation at its Sixth Street Generating Station.

(b) For the nine months ended September 30, 2012, Resources recorded AROs of $8.4 million related to its Franklin County wind project and WPL recorded AROs of $7.6 million related to its Nelson Dewey generating station.

WPL [Member]

Asset Retirement Obligations [Line Items]

Asset Retirement Obligations (AROs)

ASSET RETIREMENT OBLIGATIONS (AROs)

A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):

	Alliant Energy						IPL						WPL
	2012			2011			2012			2011			2012			2011
Balance, January 1		$91.1			$75.9			$56.2			$43.6			$34.9			$32.3
Revisions in estimated cash flows (a)	(9.9		)	7.8			(9.2		)	7.7			(0.7		)	0.1
Liabilities settled	(2.6		)	(0.5		)	(2.5		)	(0.4		)	(0.1		)	(0.1		)
Liabilities incurred (b)	16.0			4.0			—			3.1			7.6			0.9
Accretion expense	2.6			3.4			1.4			2.1			1.2			1.3
Balance, September 30		$97.2			$90.6			$45.9			$56.1			$42.9			$34.5

(a) For the nine months ended September 30, 2012 and 2011, IPL recorded revisions in estimated cash flows of ($8.2) million and $7.0 million, respectively, based on revised remediation timing and cost information for asbestos remediation at its Sixth Street Generating Station.

(b) For the nine months ended September 30, 2012, Resources recorded AROs of $8.4 million related to its Franklin County wind project and WPL recorded AROs of $7.6 million related to its Nelson Dewey generating station.