PROPERTY, PLANT AND EQUIPMENT (Notes)

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

The following table sets forth our property, plant and equipment by property type, for the periods indicated:


	Estimated Useful Lives (Years)	December 31, 2020		December 31, 2019
		(Thousands of dollars)
Nonregulated
Gathering pipelines and related equipment	5 to 40	$	4,143,752	$	4,316,936
Processing and fractionation and related equipment	3 to 40	5,084,802		4,439,332
Storage and related equipment	3 to 54	798,785		684,635
Transmission pipelines and related equipment	5 to 54	810,434		797,678
General plant and other	2 to 60	647,675		610,013
Construction work in process	—	1,265,736		1,645,663
Regulated
Storage and related equipment	5 to 25	9,180		9,180
Natural gas transmission pipelines and related equipment	5 to 77	1,569,268		1,552,546
NGL transmission pipelines and related equipment	5 to 88	8,423,544		6,126,056
General plant and other	2 to 50	72,535		66,507
Construction work in process	—	247,224		1,802,946
Property, plant and equipment		23,072,935		22,051,492
Accumulated depreciation and amortization - nonregulated		(2,514,328)		(2,471,649)
Accumulated depreciation and amortization - regulated		(1,403,679)		(1,231,158)
Net property, plant and equipment		$	19,154,928	$	18,348,685

The average depreciation rates for our regulated property are set forth, by segment, in the following table for the periods indicated:


	Years Ended December 31,
	2020	2019	2018
Natural Gas Liquids	2.2%	2.0%	1.9%
Natural Gas Pipelines	2.1%	2.1%	2.1%

We incurred costs for construction work in process that had not been paid at December 31, 2020, 2019 and 2018, of $151.7 million, $544.8 million and $388.3 million, respectively. Such amounts are not included in capital expenditures (less AFUDC and capitalized interest) on the Consolidated Statements of Cash Flows.

Impairment Charges - In 2020, we evaluated our Natural Gas Gathering and Processing segment asset groups and determined that the carrying value of certain long-lived asset groups in the Powder River Basin, western Oklahoma and Kansas were not recoverable and exceeded their estimated fair value. As a result, we recorded noncash impairment charges of $362.3 million, which includes a natural gas processing plant and infrastructure in the Powder River Basin and its related supply contracts and natural gas processing plants and infrastructure in western Oklahoma and Kansas. In our Natural Gas Liquids segment, we recorded noncash impairment charges of $71.6 million related primarily to certain inactive assets, as our expectation for future use of the assets changed. These charges are included within impairment charges in our Consolidated Statement of Income for the year ended December 31, 2020. For additional information on our impairment charges, see Note A.