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OPERATING SEGMENTS - Summarized Financial Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
OPERATING SEGMENTS
Number of reportable segments \| segment			2
Revenue	$ 213,918	$ 155,802	$ 454,638	$ 286,839
Depreciation, amortization and accretion	28,878	13,125	57,563	25,186
Capital expenditures	16,826	17,434	35,957	24,657
Total assets	1,956,149	961,416	1,956,149	961,416	$ 2,231,244
Treatment and disposal
OPERATING SEGMENTS
Revenue	100,920	93,512	210,889	174,021
Transportation and Logistics
OPERATING SEGMENTS
Revenue	26,361	35,225	59,394	56,937
Remediation
OPERATING SEGMENTS
Revenue	3,117	889	13,349	2,616
Other
OPERATING SEGMENTS
Revenue	5,677	703	10,632	1,825
Corporate
OPERATING SEGMENTS
Depreciation, amortization and accretion	670	597	1,298	901
Capital expenditures	1,578	920	3,888	1,253
Total assets	109,133	68,120	109,133	68,120
Environmental Services
OPERATING SEGMENTS
Revenue				205,177
Environmental Services \| Treatment and disposal
OPERATING SEGMENTS
Revenue				168,092
Environmental Services \| Transportation and Logistics
OPERATING SEGMENTS
Revenue				37,085
Environmental Services \| Operating Segment
OPERATING SEGMENTS
Revenue	110,409	112,844	237,154	205,177
Depreciation, amortization and accretion	15,932	10,377	31,974	20,003
Capital expenditures	10,071	14,455	21,603	21,296
Total assets	990,441	725,311	990,441	725,311
Environmental Services \| Operating Segment \| Treatment and disposal
OPERATING SEGMENTS
Revenue	90,955	90,379	191,005
Environmental Services \| Operating Segment \| Transportation and Logistics
OPERATING SEGMENTS
Revenue	19,454	22,465	46,149
Field and Industrial Services
OPERATING SEGMENTS
Revenue				81,662
Field and Industrial Services \| Treatment and disposal
OPERATING SEGMENTS
Revenue				5,929
Field and Industrial Services \| Transportation and Logistics
OPERATING SEGMENTS
Revenue				19,852
Field and Industrial Services \| Remediation
OPERATING SEGMENTS
Revenue				2,616
Field and Industrial Services \| Other
OPERATING SEGMENTS
Revenue				1,825
Field and Industrial Services \| Operating Segment
OPERATING SEGMENTS
Revenue	103,509	42,958	217,484	81,662
Depreciation, amortization and accretion	12,276	2,151	24,291	4,282
Capital expenditures	5,177	2,059	10,466	2,108
Total assets	856,575	167,985	856,575	$ 167,985
Field and Industrial Services \| Operating Segment \| Treatment and disposal
OPERATING SEGMENTS
Revenue	9,965	3,133	19,884
Field and Industrial Services \| Operating Segment \| Transportation and Logistics
OPERATING SEGMENTS
Revenue	6,907	12,760	13,245
Field and Industrial Services \| Operating Segment \| Remediation
OPERATING SEGMENTS
Revenue	3,117	889	13,349
Field and Industrial Services \| Operating Segment \| Other
OPERATING SEGMENTS
Revenue	$ 5,677	$ 703	$ 10,632