PROPERTY, PLANT AND EQUIPMENT (Notes)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Line Items]

PROPERTY, PLANT AND EQUIPMENT

10. PROPERTY, PLANT AND EQUIPMENT

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

	December 31,			December 31,
	2018			2017
	(Thousands of dollars)
Natural gas distribution pipelines and related equipment	$	4,861,340		$	4,572,343
Natural gas transmission pipelines and related equipment	517,697			497,791
General plant and other	567,580			513,445
Construction work in process	126,526			130,333
Property, plant and equipment	6,073,143			5,713,912
Accumulated depreciation and amortization	(1,789,431		)	(1,706,327		)
Net property, plant and equipment	$	4,283,712		$	4,007,585

We compute depreciation expense by applying composite, straight-line rates of 2.0 percent to 3.0 percent that were approved by various regulatory authorities.

We recorded capitalized interest of $3.4 million, $3.0 million and $3.6 million for the years ended December 31, 2018, 2017 and 2016, respectively. We incurred liabilities for construction work in process and asset removal costs that had not been paid at December 31, 2018, 2017 and 2016 of $15.6 million, $21.7 million and $11.9 million, respectively. Such amounts are not included in capital expenditures or in the change of working capital items on our Consolidated Statements of Cash Flows.