REVENUES - Geography (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of revenue
Revenue	$ 213,918	$ 155,802	$ 454,638	$ 286,839
United States
Disaggregation of revenue
Revenue	191,365	128,743	404,839	244,806
Canada
Disaggregation of revenue
Revenue	17,198	27,059	37,092	42,033
EMEA
Disaggregation of revenue
Revenue	3,915		9,154
Other
Disaggregation of revenue
Revenue	1,440		3,553
Environmental Services
Disaggregation of revenue
Revenue				205,177
Field and Industrial Services
Disaggregation of revenue
Revenue				81,662
Operating Segment | Environmental Services
Disaggregation of revenue
Revenue	110,409	112,844	237,154	205,177
Operating Segment | Environmental Services | United States
Disaggregation of revenue
Revenue	93,709	85,785	201,637	163,144
Operating Segment | Environmental Services | Canada
Disaggregation of revenue
Revenue	16,700	27,059	35,517	42,033
Operating Segment | Field and Industrial Services
Disaggregation of revenue
Revenue	103,509	42,958	217,484	81,662
Operating Segment | Field and Industrial Services | United States
Disaggregation of revenue
Revenue	97,656	$ 42,958	203,202	$ 81,662
Operating Segment | Field and Industrial Services | Canada
Disaggregation of revenue
Revenue	498		1,575
Operating Segment | Field and Industrial Services | EMEA
Disaggregation of revenue
Revenue	3,915		9,154
Operating Segment | Field and Industrial Services | Other
Disaggregation of revenue
Revenue	$ 1,440		$ 3,553