SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2013

Schedule of asset classification and estimated useful life

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		30–40 years
Leasehold and building improvements		2–40 years
Camp equipment		12–15 years
Vehicles		3–12 years
Equipment
Capitalized software and computer equipment		3–5 years
Solar equipment		20 years
Containers and railcars		15–20 years
All other equipment		8–20 years
Furniture and fixtures		5–8 years

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



	December 31, 2013		December 31, 2012 (As Adjusted)
Land	$	99,794	$	104,379
Asset retirement costs (non-landfill)	10,938		10,111
Landfill assets	100,983		77,952
Buildings and improvements	327,956		359,816
Camp equipment	187,831		135,827
Vehicles	425,296		385,172
Equipment	1,201,296		1,034,856
Furniture and fixtures	5,260		3,735
Construction in progress	58,010		34,124
	2,417,364		2,145,972
Less - accumulated depreciation and amortization	815,194		612,919
Total property, plant and equipment, net	$	1,602,170	$	1,533,053

Schedule of Property, Plant and Equipment, Landfill Assets

As of December 31, 2013, the Company had 11 active landfill sites (including the Company's two non-commercial landfills), which have estimated remaining lives (based on anticipated waste volumes and remaining highly probable airspace) as follows:



		Remaining Lives (Years)	Remaining Highly Probable Airspace (cubic yards) (in thousands)
Facility Name	Location	Remaining Lives (Years)	Permitted	Unpermitted	Total
Altair	Texas	12	752	—	752
Buttonwillow	California	27	7,701	—	7,701
Deer Park	Texas	9	342	—	342
Deer Trail	Colorado	41	2,061	—	2,061
Grassy Mountain	Utah	29	2,058	—	2,058
Kimball	Nebraska	10	281	—	281
Lambton	Ontario	49	120	4,708	4,828
Lone Mountain	Oklahoma	17	2,769	—	2,769
Ryley	Alberta	11	912	880	1,792
Sawyer	North Dakota	16	4,007	—	4,007
Westmorland	California	64	2,732	—	2,732
			23,735	5,588	29,323

Remaining Highly Probable Airspace

The following table presents the remaining highly probable airspace from January 1, 2011 through December 31, 2013 (in thousands of cubic yards):



	2013		2012		2011
Remaining capacity at January 1,	29,643		27,557		28,557
Addition of highly probable airspace, net	1,218		3,598		102
Consumed	(1,538	)	(1,512	)	(1,102	)
Remaining capacity at December 31,	29,323		29,643		27,557