Asset Retirement Obligations (AROs)

9 Months Ended

Sep. 30, 2011

Asset Retirement Obligations (AROs)

(15) 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
	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			—
Liabilities incurred		4.0			5.3			3.1			—			0.9			5.3
Accretion expense		3.4			3.1			2.1			2.1			1.3			1.0
Liabilities settled		(0.5	)		(0.6	)		(0.4	)		(0.5	)		(0.1	)		(0.1	)
Balance, Sep. 30	$	90.6		$	71.1		$	56.1		$	43.5		$	34.5		$	27.6

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

IPL [Member]

Asset Retirement Obligations (AROs)

(15) 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
	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
Liabilities incurred		4.0			5.3			3.1						0.9			5.3
Accretion expense		3.4			3.1			2.1			2.1			1.3			1.0
Liabilities settled		(0.5	)		(0.6	)		(0.4	)		(0.5	)		(0.1	)		(0.1	)
Balance, Sep. 30	$	90.6		$	71.1		$	56.1		$	43.5		$	34.5		$	27.6

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

WPL [Member]

Asset Retirement Obligations (AROs)

(15) 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
	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
Liabilities incurred		4.0			5.3			3.1						0.9			5.3
Accretion expense		3.4			3.1			2.1			2.1			1.3			1.0
Liabilities settled		(0.5	)		(0.6	)		(0.4	)		(0.5	)		(0.1	)		(0.1	)
Balance, Sep. 30	$	90.6		$	71.1		$	56.1		$	43.5		$	34.5		$	27.6

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