Asset Retirement Obligations
 3 Months Ended
Mar. 31, 2016
Asset Retirement Obligation [Abstract]  
Asset Retirement Obligations
Asset Retirement Obligations
Changes in the Partnership’s liability for asset retirement obligations for the three months ended March 31, 2016 and 2015 are presented in the table below:
 
(in millions)
2016
 
2015
Balance as of January 1,
$
25.3

 
$
23.2

Noncontributed net parent investment adjustments(1)
—

 
(0.4
)
Accretion expense
0.3

 
0.3

Additions
—

 
—

Settlements
—

 
—

Change in estimated cash flows
(0.9
)
 
—

Balance as of March 31,
$
24.7

 
$
23.1


(1) Reflects the removal of amounts related to Crossroads Pipeline Company, which was included in the Predecessor but was not contributed to the Partnership.
The asset retirement obligations above relate to the modernization program of pipelines and transmission facilities, the retiring of offshore facilities, polychlorinated biphenyl ("PCB") remediation and asbestos removal at several compressor and measuring stations. The Partnership recognizes that certain assets, which include gas pipelines and natural gas storage wells, will operate for an indeterminate future period when properly maintained. A liability for these asset retirement obligations will be recorded only if and when a future retirement obligation with a determinable life is identified.