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Asset Retirement Obligations (Tables)
12 Months Ended
Dec. 31, 2018
Asset Retirement Obligation [Abstract]  
Changes In Liability For Asset Retirement Obligations
Changes in our liability for asset retirement obligations for the years 2018 and 2017 are presented in the table below:
 
(in millions)
2018
 
2017
 
Beginning Balance
$
268.7

 
$
262.6

 
Accretion recorded as a regulatory asset/liability
11.1

 
10.3

 
Additions
63.3

(1) 
2.4

 
Settlements
(5.9
)
 
(15.6
)
 
Change in estimated cash flows 
14.8

(1) 
9.0

(2) 
Ending Balance
$
352.0

 
$
268.7

 

(1)In 2018, $59.8 million of additions and $17.7 million of the change in estimated cash flows are attributed to costs associated with refining the CCR compliance plan. See Note 18-D, "Environmental Matters," for additional information on CCRs.
(2)The change in estimated cash flows for 2017 is primarily attributed to changes in estimated costs and settlement timing for electric generating stations and the changes in estimated costs for retirement of gas mains.