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PROPERTY, PLANT AND EQUIPMENT (Notes)
12 Months Ended
Dec. 31, 2016
Property, Plant and Equipment [Line Items]  
PROPERTY, PLANT AND EQUIPMENT
9.
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,
 
 
2016
 
2015
 
 
(Thousands of dollars)
Natural gas distribution pipelines and related equipment
 
$
4,321,429

 
$
4,114,090

Natural gas transmission pipelines and related equipment
 
481,953

 
462,654

General plant and other
 
530,459

 
498,906

Construction work in process
 
70,327

 
57,032

Property, plant and equipment
 
5,404,168

 
5,132,682

Accumulated depreciation and amortization
 
(1,672,548
)
 
(1,620,771
)
Net property, plant and equipment
 
$
3,731,620

 
$
3,511,911



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 $3.6 million, $2.6 million and $2.5 million for the years ended December 31, 2016, 2015 and 2014, respectively. We incurred liabilities for construction work in process and asset removal costs that had not been paid at December 31, 2016, 2015 and 2014 of $11.9 million, $15.0 million and $7.0 million, respectively. Such amounts are not included in capital expenditures on the Statements of Cash Flows.