PROPERTY, PLANT AND EQUIPMENT

6 Months Ended

Jun. 30, 2018

Property, Plant and Equipment [Abstract]

Property, plant and equipment consisted of the following (in thousands):



	June 30, 2018		December 31, 2017
Land	$	123,984	$	121,658
Asset retirement costs (non-landfill)	14,780		14,593
Landfill assets	145,068		144,539
Buildings and improvements	429,880		414,384
Camp equipment	161,899		170,012
Vehicles	689,846		617,959
Equipment	1,675,920		1,644,102
Furniture and fixtures	5,623		5,708
Construction in progress	39,569		57,618
	3,286,569		3,190,573
Less - accumulated depreciation and amortization	1,677,187		1,603,208
Total property, plant and equipment, net	$	1,609,382	$	1,587,365

Interest in the amount of $0.1 million and $0.4 million was capitalized to property, plant and equipment during the three and six months ended June 30, 2018, respectively. Interest in the amount of $0.1 million and $0.2 million was capitalized to property, plant and equipment during the three and six months ended June 30, 2017, respectively. Depreciation expense, inclusive of landfill amortization, was $64.2 million and $129.8 million for the three and six months ended June 30, 2018, respectively. Depreciation expense, inclusive of landfill amortization, was $61.8 million and $125.2 million for the three and six months ended June 30, 2017, respectively.