Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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OPERATING SEGMENTS - Summarized Financial Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
OPERATING SEGMENTS
Number of reportable segments \| segment			2
Total revenue	$ 126,057	$ 122,351	$ 236,291	$ 235,669
Depreciation, amortization and accretion	10,684	9,873	21,062	19,411
Capital expenditures	10,333	7,269	17,552	14,488
Total assets	789,446	778,252	789,446	778,252	$ 776,400
Treatment and disposal
OPERATING SEGMENTS
Total revenue	74,139	69,805	145,479	139,282
Transportation and Logistics
OPERATING SEGMENTS
Total revenue	23,296	20,844	41,216	41,031
Industrial Cleaning
OPERATING SEGMENTS
Total revenue	4,705	7,201	8,924	11,472
Technical Services
OPERATING SEGMENTS
Total revenue	19,802	19,167	35,464	36,772
Remediation
OPERATING SEGMENTS
Total revenue	3,217	4,653	3,823	5,490
Other
OPERATING SEGMENTS
Total revenue	898	681	1,385	1,622
Corporate
OPERATING SEGMENTS
Depreciation, amortization and accretion	128	125	258	247
Capital expenditures	723	673	1,603	1,553
Total assets	56,773	58,905	56,773	58,905
Environmental Services \| Operating Segment
OPERATING SEGMENTS
Total revenue	89,591	82,797	170,894	164,321
Depreciation, amortization and accretion	9,105	8,371	17,895	16,451
Capital expenditures	7,771	5,575	13,610	11,414
Total assets	608,207	591,511	608,207	591,511
Environmental Services \| Operating Segment \| Treatment and disposal
OPERATING SEGMENTS
Total revenue	71,238	66,908	139,941	133,633
Environmental Services \| Operating Segment \| Transportation and Logistics
OPERATING SEGMENTS
Total revenue	18,353	15,889	30,953	30,688
Field & Industrial Services \| Operating Segment
OPERATING SEGMENTS
Total revenue	36,466	39,554	65,397	71,348
Depreciation, amortization and accretion	1,451	1,377	2,909	2,713
Capital expenditures	1,839	1,021	2,339	1,521
Total assets	124,466	127,836	124,466	127,836
Field & Industrial Services \| Operating Segment \| Treatment and disposal
OPERATING SEGMENTS
Total revenue	2,901	2,897	5,538	5,649
Field & Industrial Services \| Operating Segment \| Transportation and Logistics
OPERATING SEGMENTS
Total revenue	4,943	4,955	10,263	10,343
Field & Industrial Services \| Operating Segment \| Industrial Cleaning
OPERATING SEGMENTS
Total revenue	4,705	7,201	8,924	11,472
Field & Industrial Services \| Operating Segment \| Technical Services
OPERATING SEGMENTS
Total revenue	19,802	19,167	35,464	36,772
Field & Industrial Services \| Operating Segment \| Remediation
OPERATING SEGMENTS
Total revenue	3,217	4,653	3,823	5,490
Field & Industrial Services \| Operating Segment \| Other
OPERATING SEGMENTS
Total revenue	$ 898	$ 681	$ 1,385	$ 1,622