GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Changes in goodwill
Balance at the beginning of the period	$ 191,823
Foreign currency translation	1,090
Balance at the end of the period	192,913
Intangible Assets
Amortizing intangible assets, Cost	212,848		$ 210,759
Accumulated amortization	(24,056)		(21,061)
Amortizing intangible assets, Net	188,792		189,698
Total intangible assets, cost	262,729		260,632
Total intangible assets, net	238,673		239,571
Amortization expense	2,610	$ 3,302
Permits and licenses
Intangible Assets
Nonamortizing intangible assets	49,750		49,750
Tradename
Intangible Assets
Nonamortizing intangible assets	131		123
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	111,056		109,652
Accumulated amortization	(7,575)		(6,682)
Amortizing intangible assets, Net	103,481		102,970
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	82,226		82,021
Accumulated amortization	(10,424)		(9,015)
Amortizing intangible assets, Net	71,802		73,006
Technology - formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	7,017		6,560
Accumulated amortization	(1,184)		(1,054)
Amortizing intangible assets, Net	5,833		5,506
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652		3,652
Accumulated amortization	(652)		(561)
Amortizing intangible assets, Net	3,000		3,091
Tradename
Intangible Assets
Amortizing intangible assets, Cost	4,318		4,318
Accumulated amortization	(2,570)		(2,210)
Amortizing intangible assets, Net	1,748		2,108
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,917		2,899
Accumulated amortization	(771)		(678)
Amortizing intangible assets, Net	2,146		2,221
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	732		732
Accumulated amortization	(732)		(732)
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	540		540
Accumulated amortization	(51)		(44)
Amortizing intangible assets, Net	489		496
Database
Intangible Assets
Amortizing intangible assets, Cost	390		385
Accumulated amortization	(97)		(85)
Amortizing intangible assets, Net	293		$ 300
Environmental Services
Changes in goodwill
Balance at the beginning of the period	147,692
Foreign currency translation	1,090
Balance at the end of the period	148,782
Field & Industrial Services
Changes in goodwill
Balance at the beginning of the period	44,131
Balance at the end of the period	$ 44,131