Property, Plant and Equipment

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment [Text Block]

Property, Plant and Equipment

(a) Property, Plant and Equipment

Property, plant and equipment includes the following:



	Weighted Average Useful Lives	December 31,
	(in years)	2016		2015
		(in millions)
Natural Gas Distribution	32	$	6,219	$	5,762
Energy Services	25	83		86
Other property	9	49		50
Total		6,351		5,898
Accumulated depreciation and amortization:
Natural Gas Distribution		1,722		1,575
Energy Services		29		34
Other property		31		31
Total accumulated depreciation and amortization		1,782		1,640
Property, plant and equipment, net		$	4,569	$	4,258

(b) Depreciation and Amortization

The following table presents depreciation and amortization expense for 2016, 2015 and 2014:



	Year Ended December 31,
	2016		2015		2014
	(in millions)
Depreciation expense	$	230	$	211	$	195
Amortization expense	19		16		11
Total depreciation and amortization expense	$	249	$	227	$	206

A reconciliation of the changes in the ARO liability is as follows:



	December 31,
	2016		2015
	(in millions)
Beginning balance	$	156	$	139
Accretion expense	8		5
Revisions in estimates of cash flows	5		12
Ending balance	$	169	$	156

CERC recorded AROs associated with the removal of asbestos and asbestos-containing material in its buildings. CERC also recorded AROs relating to gas pipelines abandoned in place. The estimates of future liabilities were developed using historical information, and where available, quoted prices from outside contractors.

The increase of $5 million in the ARO from the revision in estimates in 2016 is primarily attributable to an increase in the labor rate associated with the abandonment of gas mains. The increase of $12 million in the ARO from the revision in estimates in 2015 is primarily attributable to a reduction in the estimated service lives of steel and plastic pipe. There were no material additions or settlements during the years ended December 31, 2016 or 2015.