v2.4.0.6
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.