PROPERTY, PLANT, AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

The Company depreciates and amortizes the cost of these assets, using the straight-line method as follows:

Asset Classification	Estimated Useful Life
Buildings and building improvements
Buildings	30–42 years
Leasehold and building improvements	2–45 years
Camp equipment	8–15 years
Vehicles	3–15 years
Equipment
Capitalized software and computer equipment	3–5 years
Solar equipment	30 years
Containers and railcars	15–20 years
All other equipment	8–25 years
Furniture and fixtures	5–8 years

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

	December 31, 2017		December 31, 2016
Land	$	121,658	$	120,575
Asset retirement costs (non-landfill)	14,593		14,567
Landfill assets	144,539		139,708
Buildings and improvements	414,384		373,160
Camp equipment	170,012		152,740
Vehicles	617,959		541,022
Equipment	1,644,102		1,483,736
Furniture and fixtures	5,708		5,492
Construction in progress	57,618		146,904
	3,190,573		2,977,904
Less - accumulated depreciation and amortization	1,603,208		1,366,077
Total property, plant and equipment, net	$	1,587,365	$	1,611,827