US Ecology (ECOL) 10-Q 5 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 02, 2021
Document Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2021
Entity File Number	001-39120
Entity Registrant Name	US ECOLOGY, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	84-2421185
Entity Address, Address Line One	101 S. Capitol Blvd., Suite 1000
Entity Address, City or Town	Boise
Entity Address, State or Province	ID
Entity Address, Postal Zip Code	83702
City Area Code	208
Local Phone Number	331-8400
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		31,512,324
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001783400
Amendment Flag	false
Common Stock
Document Information
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	ECOL
Security Exchange Name	NASDAQ
Warrants
Document Information
Title of 12(b) Security	Warrants to Purchase Common Stock
Trading Symbol	ECOLW

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 71,432	$ 73,848
Receivables, net	261,128	241,978
Prepaid expenses and other current assets	31,799	28,379
Income taxes receivable	18,340	18,279
Total current assets	382,699	362,484
Property and equipment, net	450,720	456,637
Operating lease assets	44,947	51,474
Restricted cash and investments	3,758	5,598
Intangible assets, net	497,636	523,988
Goodwill	413,101	413,037
Other assets	26,062	18,065
Total assets	1,818,923	1,831,283
Current Liabilities:
Accounts payable	66,402	35,881
Deferred revenue	17,475	15,267
Accrued liabilities	51,750	59,296
Accrued salaries and benefits	27,681	30,918
Income taxes payable	48	977
Current portion of long-term debt	3,359	3,359
Current portion of closure and post-closure obligations	8,234	6,471
Current portion of operating lease liabilities	15,114	17,048
Total current liabilities	190,063	169,217
Long-term debt	753,965	782,484
Long-term closure and post-closure obligations	90,107	89,398
Long-term operating lease liabilities	30,739	35,069
Other long-term liabilities	18,718	32,201
Deferred income taxes, net	119,358	120,983
Total liabilities	1,202,950	1,229,352
Commitments and contingencies (See Note 16)
Stockholders' Equity:
Common stock $0.01 par value per share, 50,000 authorized; 31,512 shares issued and outstanding	315	315
Additional paid-in capital	820,600	820,567
Retained deficit	(186,679)	(188,452)
Treasury stock, at cost, 249 and 358 shares, respectively	(10,919)	(15,841)
Accumulated other comprehensive loss	(7,344)	(14,658)
Total stockholders' equity	615,973	601,931
Total liabilities and stockholders' equity	$ 1,818,923	$ 1,831,283

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Sep. 30, 2021	Dec. 31, 2020
CONSOLIDATED BALANCE SHEETS
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	50,000	50,000
Common stock, shares issued	31,512	31,512
Common stock, shares outstanding	31,512	31,512
Treasury stock, shares	249	358

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue	$ 257,182	$ 238,142	$ 726,574	$ 692,780
Direct operating costs	194,028	173,849	555,994	511,028
Gross profit	63,154	64,293	170,580	181,752
Selling, general and administrative expenses	47,683	51,140	150,220	153,211
Goodwill impairment charges				300,300
Operating income (loss)	15,471	13,153	20,360	(271,759)
Other income (expense):
Interest income	485	9	1,148	251
Interest expense	(7,144)	(7,964)	(22,022)	(25,127)
Foreign currency gain (loss)	341	(421)	(385)	(155)
Other	114	86	4,020	382
Total other expense	(6,204)	(8,290)	(17,239)	(24,649)
Income (loss) before income taxes	9,267	4,863	3,121	(296,408)
Income tax expense (benefit)	2,535	(1,456)	1,348	542
Net income (loss)	$ 6,732	$ 6,319	$ 1,773	$ (296,950)
Earnings (loss) per share:
Basic	$ 0.22	$ 0.20	$ 0.06	$ (9.54)
Diluted	$ 0.21	$ 0.20	$ 0.06	$ (9.54)
Shares used in earnings (loss) per share calculation:
Basic	31,151	31,069	31,131	31,142
Diluted	31,400	31,324	31,377	31,142

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME
Net income (loss)	$ 6,732	$ 6,319	$ 1,773	$ (296,950)
Other comprehensive income (loss):
Foreign currency translation (loss) gain	(3,219)	1,923	(1,248)	(3,328)
Net changes in interest rate hedge, net of taxes of $286, $196, $2,276 and $(2,220) respectively	1,076	739	8,562	(8,353)
Comprehensive income (loss), net of tax	$ 4,589	$ 8,981	$ 9,087	$ (308,631)

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other comprehensive income (loss):
Net changes in interest rate hedge, tax	$ 286	$ 196	$ 2,276	$ (2,220)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income (loss)	$ 1,773	$ (296,950)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization of property and equipment	54,095	54,831
Amortization of intangible assets	26,501	27,812
Accretion of closure and post-closure obligations	3,571	3,812
Goodwill impairment charges		300,300
Unrealized foreign currency (gain) loss	(1,028)	87
Deferred income taxes	(3,822)	79
Share-based compensation expense	5,748	4,861
Share-based payments of business development and integration expenses	417	1,142
Unrecognized tax benefits	37	(8)
Net (gain) loss on disposition of assets	(337)	1,817
Amortization and write-off of debt issuance costs	1,851	1,640
Amortization and write-off of debt discount	121	121
Change in fair value of contingent consideration	282	(3,207)
Change in fair value of minority interest investment	(3,509)
Changes in assets and liabilities (net of effects of business acquisition):
Receivables	(19,064)	25,297
Income taxes receivable	(70)	(6,250)
Other assets	(7,093)	(8,345)
Accounts payable and accrued liabilities	20,666	(19,177)
Deferred revenue	2,185	930
Accrued salaries and benefits	(3,239)	(4,494)
Income taxes payable	(943)	287
Closure and post-closure obligations	(1,101)	(1,341)
Net cash provided by operating activities	77,041	83,244
Cash flows from investing activities:
Purchases of property and equipment	(45,347)	(45,124)
Proceeds from sale of property and equipment	2,431	1,079
Minority interest investment	(712)
Purchases of restricted investments	(1,014)	(1,113)
Proceeds from sale of restricted investments	3,192	970
Business acquisitions (net of cash acquired)		(3,309)
Insurance proceeds from damaged property and equipment		1,131
Net cash used in investing activities	(41,450)	(46,366)
Cash flows from financing activities:
Proceeds from short-term borrowings	61,326	72,353
Payments on short-term borrowings	(61,326)	(72,353)
Payments on long-term debt	(29,375)	(33,375)
Payment of equipment financing obligations	(4,344)	(4,827)
Payment of acquired contingent consideration liabilities	(2,553)	(2,085)
Deferred financing costs paid	(957)	(1,144)
Repurchase of common stock	(465)	(18,332)
Proceeds from long-term debt		90,000
Dividends paid		(5,667)
Other		28
Net cash (used in) provided by financing activities	(37,694)	24,598
Effect of foreign exchange rate changes on cash	26	(480)
(Decrease) increase in Cash and cash equivalents and restricted cash	(2,077)	60,996
Cash and cash equivalents and restricted cash at beginning of period	75,104	42,140
Cash and cash equivalents and restricted cash at end of period	$ 73,027	$ 103,136

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS - (Restricted cash and investments) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Cash and cash equivalents and restricted cash
Cash and cash equivalents	$ 71,432	$ 102,038	$ 73,848	$ 41,281
Restricted cash	1,595	1,098	1,256	859
Cash and cash equivalents and restricted cash	73,027	103,136	$ 75,104	$ 42,140
Supplemental Disclosures:
Income taxes paid, net of receipts	6,307	6,385
Interest paid	19,404	21,773
Non-cash investing and financing activities:
Capital expenditures in accounts payable	7,276	883
Restricted stock issued from treasury shares	$ 5,387	$ 2,041

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Total
Beginning balances at Dec. 31, 2019	$ 315	$ 816,345	$ 206,574		$ (11,854)	$ 1,011,380
Increase (Decrease) in Stockholders' Equity
Net income (loss)			(296,950)			(296,950)
Other comprehensive (loss) income					(11,681)
Share-based compensation		4,861
Share-based payments of business development and integration expenses		1,142
Stock option exercised and issuance of common stock and restricted common stock		(468)
Dividends paid			(5,667)
Other			(1)
Repurchase of common stock				$ (18,332)
Issuance of restricted common stock and common stock from treasury shares		(2,536)		2,041
Ending balances at Sep. 30, 2020	315	819,344	(96,044)	(16,291)	(23,535)	683,789
Beginning balances at Jun. 30, 2020	315	817,557	(102,362)	(16,366)	(26,197)	672,947
Increase (Decrease) in Stockholders' Equity
Net income (loss)			6,319			6,319
Other comprehensive (loss) income					2,662
Share-based compensation		1,773
Share-based payments of business development and integration expenses		170
Stock option exercised and issuance of common stock and restricted common stock		(31)
Other			(1)
Issuance of restricted common stock and common stock from treasury shares		(125)		75
Ending balances at Sep. 30, 2020	315	819,344	(96,044)	(16,291)	(23,535)	683,789
Beginning balances at Dec. 31, 2020	315	820,567	(188,452)	(15,841)	(14,658)	$ 601,931
Balance (in shares) at Dec. 31, 2020						31,512
Increase (Decrease) in Stockholders' Equity
Net income (loss)			1,773			$ 1,773
Other comprehensive (loss) income					7,314
Share-based compensation		5,748
Share-based payments of business development and integration expenses		417
Repurchase of common stock				(465)
Issuance of restricted common stock and common stock from treasury shares		(6,132)		5,387
Ending balances at Sep. 30, 2021	315	820,600	(186,679)	(10,919)	(7,344)	$ 615,973
Balance (in shares) at Sep. 30, 2021						31,512
Beginning balances at Jun. 30, 2021	315	818,913	(193,411)	(11,033)	(5,201)	$ 609,583
Increase (Decrease) in Stockholders' Equity
Net income (loss)			6,732			6,732
Other comprehensive (loss) income					(2,143)
Share-based compensation		1,713
Share-based payments of business development and integration expenses		119
Issuance of restricted common stock and common stock from treasury shares		(145)		114
Ending balances at Sep. 30, 2021	$ 315	$ 820,600	$ (186,679)	$ (10,919)	$ (7,344)	$ 615,973
Balance (in shares) at Sep. 30, 2021						31,512

GENERAL

GENERAL	9 Months Ended
	Sep. 30, 2021
GENERAL
GENERAL	NOTE 1. GENERAL ​ Basis of Presentation ​ The accompanying unaudited consolidated financial statements include the results of operations, financial position and cash flows of US Ecology, Inc. and its wholly-owned subsidiaries. All inter-company balances have been eliminated. Throughout these consolidated financial statements words such as “we,” “us,” “our,” “US Ecology” and “the Company” refer to US Ecology, Inc. and its subsidiaries. ​ In the opinion of management, the accompanying unaudited consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) necessary to present fairly, in all material respects, the results of the Company for the periods presented. These consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been omitted pursuant to the rules and regulations of the SEC. These consolidated financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the entire year ending December 31, 2021. ​ The Company’s consolidated balance sheet as of December 31, 2020 has been derived from the Company’s audited consolidated balance sheet as of that date. ​ Reclassifications ​ Effective in the first quarter of 2021, we changed our management structure resulting in the reclassification of certain overhead expenses from our Waste Solutions, Field Services and Energy Waste reportable segments to Corporate. As a result, certain regional overhead costs historically presented within our reportable segments as Direct operating costs were further reclassified to Corporate as Selling, general and administrative expenses to conform to the current period’s presentation. Throughout this Quarterly Report on Form 10-Q, all periods presented have been recast to reflect these changes. ​ Use of Estimates ​ The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from the estimates and assumptions that we use in the preparation of our consolidated financial statements. As it relates to estimates and assumptions in amortization rates and environmental obligations, significant engineering, operations and accounting judgments are required. We review these estimates and assumptions no less than annually. In many circumstances, the ultimate outcome of these estimates and assumptions will not be known for decades into the future. Actual results could differ materially from these estimates and assumptions due to changes in applicable regulations, changes in future operational plans and inherent imprecision associated with estimating environmental impacts far into the future. ​ Recently Issued Accounting Pronouncements ​ In March 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2020-04, “Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (Topic 848). The ASU provides optional expedients and exceptions for applying GAAP to transactions affected by reference rate (e.g., LIBOR) reform if certain criteria are met, for a limited period of time to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The ASU is effective as of March 12, 2020 through December 31, 2022. We will evaluate transactions or contract modifications occurring as a result of reference rate reform and determine whether to apply the optional guidance on an ongoing basis. The ASU is currently not expected to have a material impact on our consolidated financial statements. ​ Effective January 1, 2021, the Company adopted ASU No. 2019-12, “Income Taxes - Simplifying the Accounting for Income Taxes.” This ASU is intended to simplify various aspects of accounting for income taxes by eliminating certain exceptions within Accounting Standards Codification Topic 740, “Income Taxes” and to clarify certain aspects of the current accounting guidance. Adoption of this standard did not materially impact our consolidated statements of financial position, results of operations, or cash flows.

REVENUES

REVENUES	9 Months Ended
	Sep. 30, 2021
REVENUES
REVENUES	NOTE 2. REVENUES ​ Effective in the fourth quarter of 2020, we made changes to the manner in which we manage our business, make operating decisions and assess our performance. Throughout this Quarterly Report on Form 10-Q, all periods presented have been recast to reflect these changes. Our operations are now managed in three reportable segments, Waste Solutions, Field Services and Energy Waste, reflecting our internal reporting structure and nature of services offered. See Note 17 for additional information on our operating segments. ​ Effective in the second quarter of 2021, we made changes to the manner in which we evaluate revenues associated with our various response-based services, including emergency response, standby services and remediation. As a result, revenues from Emergency Response and Domestic Standby Services, which were formerly presented as discrete service lines, are now combined and presented as a single “Emergency Response” service line and certain revenues formerly classified as Domestic Standby Services are now classified as Remediation. Throughout this Quarterly Report on Form 10-Q, our disaggregated revenues for all periods presented have been recast to reflect these changes. ​ The following table presents our revenue disaggregated by our reportable segments and service lines: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 92,867 ​ $ 15,940 ​ $ 6,263 ​ $ 115,070 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 22,334 ​ ​ 6,483 ​ ​ 2,317 ​ ​ 31,134 Industrial Services (3) ​ ​ — ​ ​ 29,597 ​ ​ 730 ​ ​ 30,327 Small Quantity Generation (4) ​ ​ — ​ ​ 14,629 ​ ​ — ​ ​ 14,629 Total Waste Management (5) ​ ​ — ​ ​ 9,597 ​ ​ — ​ ​ 9,597 Remediation (6) ​ ​ — ​ ​ 16,310 ​ ​ — ​ ​ 16,310 Emergency Response (7) ​ ​ — ​ ​ 34,532 ​ ​ — ​ ​ 34,532 Other (8) ​ ​ — ​ ​ 4,494 ​ ​ 1,089 ​ ​ 5,583 Revenue ​ $ 115,201 ​ $ 131,582 ​ $ 10,399 ​ $ 257,182 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 88,601 ​ $ 13,861 ​ $ 2,625 ​ $ 105,087 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 18,648 ​ ​ 11,162 ​ ​ 1,257 ​ ​ 31,067 Industrial Services (3) ​ ​ — ​ ​ 28,464 ​ ​ 705 ​ ​ 29,169 Small Quantity Generation (4) ​ ​ — ​ ​ 13,056 ​ ​ — ​ ​ 13,056 Total Waste Management (5) ​ ​ — ​ ​ 9,998 ​ ​ — ​ ​ 9,998 Remediation (6) ​ ​ — ​ ​ 6,733 ​ ​ — ​ ​ 6,733 Emergency Response (7) ​ ​ — ​ ​ 37,993 ​ ​ — ​ ​ 37,993 Other (8) ​ ​ — ​ ​ 4,448 ​ ​ 591 ​ ​ 5,039 Revenue ​ $ 107,249 ​ $ 125,715 ​ $ 5,178 ​ $ 238,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 270,906 ​ $ 39,143 ​ $ 14,648 ​ $ 324,697 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 56,802 ​ ​ 21,169 ​ ​ 5,412 ​ ​ 83,383 Industrial Services (3) ​ ​ — ​ ​ 88,193 ​ ​ 1,841 ​ ​ 90,034 Small Quantity Generation (4) ​ ​ — ​ ​ 41,311 ​ ​ — ​ ​ 41,311 Total Waste Management (5) ​ ​ — ​ ​ 29,840 ​ ​ — ​ ​ 29,840 Remediation (6) ​ ​ — ​ ​ 40,055 ​ ​ — ​ ​ 40,055 Emergency Response (7) ​ ​ — ​ ​ 102,444 ​ ​ — ​ ​ 102,444 Other (8) ​ ​ — ​ ​ 12,336 ​ ​ 2,474 ​ ​ 14,810 Revenue ​ $ 327,708 ​ $ 374,491 ​ $ 24,375 ​ $ 726,574 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 266,129 ​ $ 33,744 ​ $ 16,102 ​ $ 315,975 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 53,555 ​ ​ 22,577 ​ ​ 6,206 ​ ​ 82,338 Industrial Services (3) ​ ​ — ​ ​ 85,529 ​ ​ 3,568 ​ ​ 89,097 Small Quantity Generation (4) ​ ​ — ​ ​ 35,292 ​ ​ — ​ ​ 35,292 Total Waste Management (5) ​ ​ — ​ ​ 25,315 ​ ​ — ​ ​ 25,315 Remediation (6) ​ ​ — ​ ​ 21,911 ​ ​ — ​ ​ 21,911 Emergency Response (7) ​ ​ — ​ ​ 103,756 ​ ​ — ​ ​ 103,756 Other (8) ​ ​ — ​ ​ 15,093 ​ ​ 4,003 ​ ​ 19,096 Revenue ​ $ 319,684 ​ $ 343,217 ​ $ 29,879 ​ $ 692,780 ​ (1) We categorize our treatment and disposal revenue as either “Base Business” or “Event Business” based on the underlying nature of the revenue source. We define Event Business as non-recurring projects that are expected to equal or exceed 1,000 tons, with Base Business defined as all other business not meeting the definition of Event Business. For the three months ended September 30, 2021 and 2020, 24% and 30% , respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76% and 70% of our treatment and disposal revenue for the three months ended September 30, 2021 and 2020, respectively. For the nine months ended September 30, 2021 and 2020, 24% and 28% , respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76% and 72% of our treatment and disposal revenue for the nine months ended September 30, 2021 and 2020, respectively. (2) Includes collection and transportation of non-hazardous and hazardous waste. (3) Includes industrial cleaning and maintenance for refineries, chemical plants, steel and automotive plants, marine terminals and refinery services such as tank cleaning and temporary storage. (4) Includes retail services, laboratory packing, less-than-truck-load service and household hazardous waste collection. Contracts for Small Quantity Generation may extend beyond one year and a portion of the transaction price can be fixed. (5) Through our total waste management (“TWM”) program, customers outsource the management of their waste compliance program to us, allowing us to organize and coordinate their waste management disposal activities and environmental compliance. TWM contracts may extend beyond one year and a portion of the transaction price can be fixed. (6) Includes site assessment, onsite treatment, project management and remedial action planning and execution. Contracts for Remediation may extend beyond one year and a portion of the transaction price can be fixed. (7) Includes services such as spill response, waste analysis and treatment and disposal planning as well as government-mandated, commercial standby oil spill compliance solutions and services that we provide to companies that store, transport, produce or handle petroleum and certain nonpetroleum oils on or near U.S. waters. Our standby services customers pay annual retainer fees under long-term or evergreen contracts for access to our regulatory certifications, specialized assets and highly trained personnel. When a customer with a retainer contract experiences a spill incident, we coordinate and manage the spill response, which results in incremental revenue for the services provided, in addition to the retainer fees. (8) Includes equipment rental and other miscellaneous services. ​ We provide services primarily in the United States, Canada and the Europe, Middle East, and Africa (“EMEA”) region. The following table presents our revenue disaggregated by our reportable segments and geographic location where the underlying services were performed: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2021 ​ Three Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services Waste Total Solutions Services Waste Total United States ​ $ 96,200 ​ $ 117,762 ​ $ 10,399 ​ $ 224,361 ​ $ 89,481 ​ $ 119,611 ​ $ 5,178 ​ $ 214,270 Canada ​ ​ 19,001 ​ ​ 1,453 ​ ​ — ​ ​ 20,454 ​ ​ 17,768 ​ ​ 990 ​ ​ — ​ ​ 18,758 EMEA ​ ​ — ​ ​ 11,123 ​ ​ — ​ ​ 11,123 ​ ​ — ​ ​ 4,195 ​ ​ — ​ ​ 4,195 Other (1) ​ — ​ 1,244 ​ — ​ 1,244 ​ — ​ 919 ​ — ​ 919 Total revenue ​ $ 115,201 ​ $ 131,582 ​ $ 10,399 ​ $ 257,182 ​ $ 107,249 ​ $ 125,715 ​ $ 5,178 ​ $ 238,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2021 ​ Nine Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services Waste Total Solutions Services Waste Total United States ​ $ 272,119 ​ $ 332,329 ​ $ 24,375 ​ $ 628,823 ​ $ 266,297 ​ $ 322,831 ​ $ 29,879 ​ $ 619,007 Canada ​ ​ 55,589 ​ ​ 2,896 ​ ​ — ​ ​ 58,485 ​ ​ 53,387 ​ ​ 2,565 ​ ​ — ​ ​ 55,952 EMEA ​ ​ — ​ ​ 35,052 ​ ​ — ​ ​ 35,052 ​ ​ — ​ ​ 13,349 ​ ​ — ​ ​ 13,349 Other (1) ​ — ​ 4,214 ​ — ​ 4,214 ​ — ​ 4,472 ​ — ​ 4,472 Total revenue ​ $ 327,708 ​ $ 374,491 ​ $ 24,375 ​ $ 726,574 ​ $ 319,684 ​ $ 343,217 ​ $ 29,879 ​ $ 692,780 ​ (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions. ​ Deferred Revenue We record deferred revenue when cash payments are received, or advance billings are charged, prior to performance of services, such as waste that has been received but not yet treated or disposed. Revenue is recognized when these services are performed. During the three months ended September 30, 2021 and 2020, we recognized $405,000 and $735,000 of revenue that was included in the deferred revenue balance at the beginning of each year, respectively. During the nine months ended September 30, 2021 and 2020, we recognized $13.7 million and $13.6 million of revenue that was included in the deferred revenue balance at the beginning of each year, respectively. ​ Receivables ​ Our receivables include invoiced and unbilled amounts where the Company has an unconditional right to payment. ​ Principal versus Agent Considerations ​ The Company commonly contracts with third-parties to perform certain waste-related services that we have promised in our customer contracts. We consider ourselves the principal in these arrangements as we direct the timing, nature and pricing of the services ultimately provided by the third-party to the customer. ​ Costs to obtain a contract ​ The Company pays sales commissions to employees, which qualify as costs to obtain a contract. Sales commissions are expensed as incurred as the commissions are earned by the employee and paid by the Company over time as the related revenue is recognized. Other commissions and incremental costs to obtain a contract are not material. ​ Practical Expedients and Optional Exemptions ​ Our payment terms may vary based on type of service or customer; however, we do not adjust the promised amount of consideration in our contracts for the time value of money as payment terms extended to our customers do not exceed one year and are not considered a significant financing component in our contracts. ​ We do not disclose the value of unsatisfied performance obligations as contracts with an original expected length of more than one year and contracts for which we do not recognize revenue at the amount to which we have the right to invoice for services performed is insignificant and the aggregate amount of fixed consideration allocated to unsatisfied performance obligations is not material.

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	9 Months Ended
	Sep. 30, 2021
BUSINESS COMBINATIONS
BUSINESS COMBINATIONS	NOTE 3. BUSINESS COMBINATIONS ​ Acquisition of Impact Environmental Services, Inc. ​ On January 28, 2020, we acquired Impact Environmental Services, Inc., an industrial cleaning and environmental services company based in Romulus, Michigan for $3.3 million. The acquired operations are reported as part of our Field Services segment, however, revenues, net income, earnings per share and total assets are not material to our consolidated financial position or results of operations. ​ We allocated the purchase price to the assets acquired and liabilities assumed based on estimates of the fair value at the date of the acquisition, resulting in $300,000 allocated to goodwill and $900,000 allocated to amortizing intangible assets (primarily customer relationships) to be amortized over a weighted average life of approximately 12 years. All of the goodwill recognized was assigned to our Field Services segment and is expected to be deductible for income tax purposes over a 15-year amortization period.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	9 Months Ended
	Sep. 30, 2021
ACCUMULATED OTHER COMPREHENSIVE LOSS
ACCUMULATED OTHER COMPREHENSIVE LOSS	NOTE 4. ACCUMULATED OTHER COMPREHENSIVE LOSS ​ Changes in accumulated other comprehensive income (loss) (“AOCI”) consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Unrealized Gain ​ ​ ​ ​ ​ Currency ​ (Loss) on Interest ​ ​ ​ $s in thousands Translation Rate Hedge Total Balance at December 31, 2020 ​ $ (7,870) ​ $ (6,788) ​ $ (14,658) Other comprehensive (loss) income before reclassifications, net of tax ​ (1,248) ​ 6,182 ​ 4,934 Amounts reclassified out of AOCI, net of tax (1) ​ — ​ 2,380 ​ 2,380 Other comprehensive (loss) income, net ​ (1,248) ​ 8,562 ​ 7,314 Balance at September 30, 2021 ​ $ (9,118) ​ $ 1,774 ​ $ (7,344) (1) Before-tax reclassifications of $743,000 ($587,000 after-tax) and $3.0 million ($2.4 million after-tax) for the three and nine months ended September 30, 2021, were included in Interest expense in the Company’s consolidated statements of operations. Amounts relate to the Company’s interest rate swap which is designated as a cash flow hedge. Changes in fair value of the swap recognized in AOCI are reclassified to interest expense when hedged interest payments on the underlying long-term debt are made or, for terminated swap agreements, amortized to interest expense over the period from termination to original maturity. Amounts in AOCI expected to be reclassified to interest expense over the next 12 months total approximately $2.9 million ($2.3 million after-tax). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Unrealized Gain ​ ​ ​ ​ ​ Currency ​ (Loss) on Interest ​ ​ ​ $s in thousands Translation Rate Hedge Total Balance at December 31, 2019 ​ $ (10,925) ​ $ (929) ​ $ (11,854) Other comprehensive loss before reclassifications, net of tax ​ (3,328) ​ (10,074) ​ (13,402) Amounts reclassified out of AOCI, net of tax (2) ​ — ​ 1,721 ​ 1,721 Other comprehensive loss, net ​ (3,328) ​ (8,353) ​ (11,681) Balance at September 30, 2020 ​ $ (14,253) ​ $ (9,282) ​ $ (23,535) (2) Before-tax reclassifications of $1.2 million ($921,000 after-tax) and $2.2 million ($1.7 million after-tax) for the three and nine months ended September 30, 2020, were included in Interest expense in the Company’s consolidated statements of operations. Amounts relate to the Company’s interest rate swap which is designated as a cash flow hedge. Changes in fair value of the swap recognized in AOCI are reclassified to interest expense when hedged interest payments on the underlying long-term debt are made or, for terminated swap agreements, amortized to interest expense over the period from termination to original maturity.

CONCENTRATIONS AND CREDIT RISK

CONCENTRATIONS AND CREDIT RISK	9 Months Ended
	Sep. 30, 2021
CONCENTRATIONS AND CREDIT RISK
CONCENTRATIONS AND CREDIT RISK	NOTE 5. CONCENTRATIONS AND CREDIT RISK ​ Major Customers ​ No customer accounted for more than 10% of total revenue for the three or nine months ended September 30, 2021 or 2020, respectively. No customer accounted for more than 10% of total trade receivables as of September 30, 2021 or December 31, 2020. ​ Credit Risk Concentration ​ We maintain most of our cash and cash equivalents with nationally recognized financial institutions. Substantially all balances are uninsured and are not used as collateral for other obligations. Concentrations of credit risk on accounts receivable are believed to be limited due to the number, diversification and character of the obligors and our credit evaluation process. Credit risk associated with a portion of the Company’s trade receivables may be reduced by our ability to submit claims to the Oil Spill Liability Trust Fund (“OSLTF”) for reimbursement of unpaid customer receivables related to services regulated under the provisions of the Oil Pollution Act of 1990. As of September 30, 2021, the Company did not have any trade receivables that are eligible for submission to the OSLTF for reimbursement. ​

RECEIVABLES

RECEIVABLES	9 Months Ended
	Sep. 30, 2021
RECEIVABLES
RECEIVABLES	NOTE 6. RECEIVABLES ​ Receivables consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands ​ 2021 2020 Trade ​ $ 198,948 ​ $ 186,502 Unbilled revenue ​ 61,320 ​ 52,858 Other ​ 4,458 ​ 5,554 Total receivables ​ 264,726 ​ 244,914 Allowance for credit losses ​ (3,598) ​ (2,936) Receivables, net ​ $ 261,128 ​ $ 241,978 ​

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	9 Months Ended
	Sep. 30, 2021
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS	NOTE 7. FAIR VALUE MEASUREMENTS ​ Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Assets and liabilities recorded at fair value are categorized using defined hierarchical levels directly related to the amount of subjectivity associated with the inputs to fair value measurements, as follows: ● Level 1 - Quoted prices in active markets for identical assets or liabilities; ● Level 2 - Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable; ● Level 3 - Unobservable inputs in which little or no market activity exists, requiring an entity to develop its own assumptions that market participants would use to value the asset or liability. The Company’s financial instruments consist of cash and cash equivalents, accounts receivable, restricted cash and investments, accounts payable and accrued liabilities, debt, interest rate swap agreements and contingent consideration. The estimated fair value of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate their carrying value due to the short-term nature of these instruments. In each of September 2019 and March 2021, the Company invested $7.9 million and $712,000, respectively, in the preferred stock of a privately held company. The investment does not have a readily determinable fair value therefore the investment is valued at cost, less impairment, plus or minus observable price changes of an identical or similar investment of the same issuer, if any. In March 2021, in connection with our incremental investment of $712,000, we observed that the fair value of our initial investment of $7.9 million increased by $3.5 million and, accordingly, recognized a gain on our minority interest investment of $3.5 million. The fair value of our minority interest investment is included in Other assets in the Company’s consolidated balance sheets. Changes in the fair value of our minority interest investment are included in Other income in the Company’s consolidated statements of operations. As of September 30, 2021, there have been no other identified events or changes in circumstances that would indicate the cost method investment should be impaired nor have there been any observable price changes of an identical or similar investment of the same issuer. The Company estimates the fair value of its variable-rate debt using Level 2 inputs, such as interest rates, related terms and maturities of similar obligations. At September 30, 2021, the fair value of the Company’s variable rate term loan was estimated to be $441.8 million, and the carrying value of the Company’s variable-rate revolving credit facility approximates fair value due to the short-term nature of the interest rates. The Company estimates the fair value of its contingent consideration liabilities using Level 3 inputs, including both observable and unobservable inputs. As a result, unrealized gains and losses may include changes in fair value that are attributable to both observable (e.g., changes in market interest rates) and unobservable (e.g., changes in unobservable long-dated volatilities) inputs. The Company’s assets and liabilities measured at fair value on a recurring basis consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 ​ ​ Quoted Prices in ​ Other Observable ​ Unobservable ​ ​ ​ ​ ​ Active Markets ​ Inputs ​ Inputs ​ ​ ​ $s in thousands (Level 1) (Level 2) (Level 3) Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fixed-income securities (1) ​ $ 1,708 ​ $ 455 ​ $ — ​ $ 2,163 Money market funds (2) ​ ​ 1,657 ​ ​ — ​ ​ — ​ ​ 1,657 Interest rate swap agreement (3) ​ ​ — ​ ​ 606 ​ ​ — ​ ​ 606 Total ​ $ 3,365 ​ $ 1,061 ​ $ — ​ $ 4,426 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Quoted Prices in ​ Other Observable ​ Unobservable ​ ​ ​ ​ ​ Active Markets ​ Inputs ​ Inputs ​ ​ ​ $s in thousands (Level 1) (Level 2) (Level 3) Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fixed-income securities (1) ​ $ 2,914 ​ $ 1,427 ​ $ — ​ $ 4,341 Money market funds (2) ​ ​ 1,319 ​ ​ — ​ ​ — ​ ​ 1,319 Total ​ $ 4,233 ​ $ 1,427 ​ $ — ​ $ 5,660 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap agreement (3) ​ $ — ​ $ 9,744 ​ $ — ​ $ 9,744 Contingent consideration (4) ​ ​ — ​ ​ — ​ ​ 2,173 ​ ​ 2,173 Total ​ $ — ​ $ 9,744 ​ $ 2,173 ​ $ 11,917 (1) We invest a portion of our Restricted cash and investments in fixed-income securities, including U.S. Treasury and U.S. agency securities. We measure the fair value of U.S. Treasury securities using quoted prices for identical assets in active markets. We measure the fair value of U.S. agency securities using observable market activity for similar assets. The fair value of our fixed-income securities approximates our cost basis in the investments. ​ (2) We invest portions of our Cash and cash equivalents and Restricted cash and investments in money market funds. We measure the fair value of these money market fund investments using quoted prices for identical assets in active markets. The portion of Restricted cash and investments that is invested in money market funds is considered restricted cash for purposes of reconciling the beginning-of-period and end-of-period amounts presented in the Company’s consolidated statements of cash flows. ​ (3) In order to manage interest rate exposure, we entered into an interest rate swap agreement in March 2020 that effectively converts a portion of our variable-rate debt to a fixed interest rate. The swap is designated as a highly-effective cash flow hedge, with gains and losses deferred in other comprehensive income to be recognized as an adjustment to interest expense in the same period that the hedged interest payments affect earnings. The interest rate swap has an effective date of March 31, 2020 in an initial notional amount of $500.0 million. The fair value of the interest rate swap agreement represents the difference in the present value of cash flows calculated (i) at the contracted interest rates and (ii) at current market interest rates at the end of the period. We calculate the fair value of interest rate swap agreements quarterly based on the quoted market price for the same or similar financial instruments. The fair value of the interest rate swap agreement is included in Other assets and Other long-term liabilities in the Company’s consolidated balance sheets as of September 30, 2021 and December 31, 2020, respectively. ​ (4) Our contingent consideration liabilities represent the estimated fair value of potential future payments the Company may be required to remit under the terms of historical purchase agreements entered into by NRC Group Holdings Corp. (“NRC”) prior to the Company’s acquisition of NRC (“NRC Merger”). The payments are contingent on the acquired businesses’ achievement of annual earnings targets in certain years and other events considered in the purchase agreements. The fair value of our contingent consideration liabilities is calculated using either a Monte Carlo simulation or modified Black-Scholes analyses based on earnings projections for the respective earn-out periods, corresponding earnings thresholds, and approximate timing of payments as outlined in the purchase agreements. The analyses utilize the following assumptions: (i) expected term; (ii) risk-adjusted net sales or earnings; (iii) risk-free interest rate; and (iv) expected volatility of earnings. Estimated payments, as determined through the respective models, are discounted by a credit spread assumption to account for credit risk. As of September 30, 2021, we have settled all acquired contingent consideration liabilities associated with the NRC Merger. The fair value of our contingent consideration liability as of December 31, 2020 was $2.2 million and is included in Accrued liabilities in the Company’s consolidated balance sheet. We revalue our contingent consideration payments each period and any increases or decreases to fair value are included in Selling, general and administrative expenses in our consolidated statements of operations. Fair values may be impacted by certain unobservable inputs, most significantly with regard to discount rates, expected volatility and historical and projected performance. Significant changes to these inputs in isolation could result in a significantly different fair value measurement. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended $s in thousands September 30, 2021 September 30, 2021 Contingent consideration, beginning of period ​ $ — ​ $ 2,173 Change in fair value of contingent consideration ​ — ​ 282 Contingent consideration paid ​ ​ — ​ ​ (2,553) Foreign currency translation ​ — ​ 98 Contingent consideration, end of period ​ $ — ​ $ — ​

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	9 Months Ended
	Sep. 30, 2021
PROPERTY AND EQUIPMENT
PROPERTY AND EQUIPMENT	NOTE 8. PROPERTY AND EQUIPMENT ​ Property and equipment consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands ​ 2021 2020 Cell development costs ​ $ 201,382 ​ $ 186,170 Land and improvements ​ 74,198 ​ 65,953 Buildings and improvements ​ 131,119 ​ 128,206 Railcars ​ 17,299 ​ 17,299 Vehicles, vessels and other equipment ​ 337,909 ​ 331,167 Construction in progress ​ 56,357 ​ 44,840 Total property and equipment ​ 818,264 ​ 773,635 Accumulated depreciation and amortization ​ (367,544) ​ (316,998) Property and equipment, net ​ $ 450,720 ​ $ 456,637 ​ Depreciation and amortization expense for the three months ended September 30, 2021 and 2020 was $17.9 million and $18.4 million, respectively. Depreciation and amortization expense for the nine months ended September 30, 2021 and 2020 was $54.1 million and $54.8 million, respectively.

LEASES

LEASES	9 Months Ended
	Sep. 30, 2021
LEASES
LEASES	NOTE 9. LEASES ​ We lease certain facilities, office space, land and equipment. Our lease payments are primarily fixed, but also include variable payments that are based on usage of the leased asset. Initial lease terms range from one may one None leases, however, amounts associated with these provisions are not material. Our leases do not include any material restrictive covenants. ​ Leases with an initial term of 12 months or less are not recorded on the balance sheet and expense is recognized on a straight-line basis over the lease term. We combine lease and non-lease components in our leases. We use the rate implicit in the lease, when available, to discount lease payments to present value. However, many of our leases do not provide a readily determinable implicit rate and we estimate our incremental borrowing rate to discount payments based on information available at lease commencement. ​ Lease assets and liabilities consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands 2021 2020 Assets: ​ ​ ​ ​ ​ ​ Operating right-of-use assets (1) ​ $ 44,947 ​ $ 51,474 Finance right-of-use assets (2) ​ ​ 18,601 ​ ​ 21,209 Total ​ $ 63,548 ​ $ 72,683 ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ Current: ​ ​ ​ ​ ​ ​ Operating (3) ​ $ 15,114 ​ $ 17,048 Finance (4) ​ ​ 4,974 ​ ​ 4,462 Long-term: ​ ​ ​ ​ ​ ​ Operating (5) ​ ​ 30,739 ​ ​ 35,069 Finance (6) ​ ​ 13,339 ​ ​ 17,501 Total ​ $ 64,166 ​ $ 74,080 (1) Included in Operating lease assets in the Company’s consolidated balance sheets. (2) Included in Property and equipment, net in the Company’s consolidated balance sheets. Finance right-of-use assets are recorded net of accumulated amortization of $12.0 million and $8.0 million as of September 30, 2021 and December 31, 2020, respectively. (3) Included in Current portion of operating lease liabilities in the Company’s consolidated balance sheets. (4) Included in Accrued liabilities in the Company’s consolidated balance sheets. (5) Included in Long-term operating lease liabilities in the Company’s consolidated balance sheets. (6) Included in Other long-term liabilities in the Company’s consolidated balance sheets. ​ Lease expense consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, $s in thousands 2021 2020 2021 2020 Operating lease cost (1) ​ $ 4,853 ​ $ 5,008 ​ $ 15,172 ​ $ 14,947 Finance lease cost: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization of leased assets (2) ​ ​ 1,311 ​ ​ 1,330 ​ ​ 3,947 ​ ​ 3,974 Interest on lease liabilities (3) ​ ​ 233 ​ ​ 292 ​ ​ 786 ​ ​ 925 Total ​ $ 6,397 ​ $ 6,630 ​ $ 19,905 ​ $ 19,846 (1) Included in Direct operating costs and Selling, general, and administrative expenses in the Company’s consolidated statements of operations. Operating lease cost includes short-term leases, excluding expenses relating to leases with a term of one month or less, which are not material. Operating lease cost excludes variable lease costs which are not material. (2) Included in Direct operating costs in the Company’s consolidated statements of operations. (3) Included in Interest expense in the Company’s consolidated statements of operations. ​ Supplemental cash flow information related to our leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, $s in thousands 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash flows from operating leases ​ $ 14,749 ​ $ 14,547 Operating cash flows from finance leases ​ $ 786 ​ $ 925 Financing cash flows from finance leases ​ $ 3,649 ​ $ 3,457 ​ ​ ​ ​ ​ ​ ​ Non-cash investing and financing activities: ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for new operating lease liabilities ​ $ 7,092 ​ $ 7,195 Right-of-use assets obtained in exchange for new finance lease liabilities ​ $ — ​ $ 6,089 ​

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2021
GOODWILL AND INTANGIBLE ASSETS
GOODWILL AND INTANGIBLE ASSETS	NOTE 10. GOODWILL AND INTANGIBLE ASSETS ​ Changes in goodwill for the nine months ended September 30, 2021 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Waste Solutions ​ Field Services ​ Energy Waste ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ Accumulated ​ ​ ​ Accumulated ​ ​ ​ $s in thousands Gross Impairment Gross Impairment Gross Impairment Total Balance at December 31, 2020 ​ $ 166,863 ​ $ (6,870) ​ $ 237,341 ​ $ (19,900) ​ $ 399,503 ​ $ (363,900) ​ $ 413,037 Foreign currency translation ​ 44 ​ ​ — ​ 20 ​ ​ — ​ ​ — ​ ​ — ​ 64 Balance at September 30, 2021 ​ $ 166,907 ​ $ (6,870) ​ $ 237,361 ​ $ (19,900) ​ $ 399,503 ​ $ (363,900) ​ $ 413,101 ​ Intangible assets, net consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ $s in thousands Cost Amortization Net Cost Amortization Net Amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Permits, licenses and lease ​ $ 174,940 ​ $ (26,127) ​ $ 148,813 ​ $ 174,885 ​ $ (23,005) ​ $ 151,880 Customer relationships ​ ​ 340,056 ​ ​ (81,407) ​ ​ 258,649 ​ ​ 340,032 ​ ​ (61,778) ​ ​ 278,254 Technology - formulae and processes ​ 7,159 ​ (2,471) ​ 4,688 ​ 7,142 ​ (2,293) ​ 4,849 Customer backlog ​ 3,652 ​ (2,661) ​ 991 ​ 3,652 ​ (2,387) ​ 1,265 Tradename ​ 10,390 ​ ​ (10,153) ​ ​ 237 ​ 10,390 ​ ​ (8,015) ​ ​ 2,375 Developed software ​ ​ 2,902 ​ ​ (2,402) ​ ​ 500 ​ ​ 2,902 ​ ​ (2,182) ​ ​ 720 Non-compete agreements ​ 5,572 ​ (5,171) ​ 401 ​ 5,571 ​ (4,318) ​ 1,253 Internet domain and website ​ ​ 536 ​ ​ (206) ​ ​ 330 ​ ​ 536 ​ ​ (184) ​ ​ 352 Database ​ ​ 390 ​ ​ (230) ​ ​ 160 ​ ​ 389 ​ ​ (214) ​ ​ 175 Total amortizing intangible assets ​ 545,597 ​ (130,828) ​ 414,769 ​ 545,499 ​ (104,376) ​ 441,123 Non-amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Permits and licenses ​ 82,733 ​ ​ — ​ 82,733 ​ 82,732 ​ ​ — ​ 82,732 Tradename ​ 134 ​ ​ — ​ ​ 134 ​ 133 ​ ​ — ​ ​ 133 Total intangible assets ​ $ 628,464 ​ $ (130,828) ​ $ 497,636 ​ $ 628,364 ​ $ (104,376) ​ $ 523,988 ​ On January 28, 2020, the Company acquired Impact Environmental Services, Inc. and recorded $300,000 of goodwill and $900,000 of amortizing intangible assets (consisting primarily of customer relationships). See Note 3 for additional information. ​ Amortization expense for the three months ended September 30, 2021 and 2020 was $8.6 million and $9.2 million, respectively. Amortization expense for the nine months ended September 30, 2021 and 2020 was $26.5 million and $27.8 million, respectively. Foreign intangible asset carrying amounts are affected by foreign currency translation.

DEBT

DEBT	9 Months Ended
	Sep. 30, 2021
DEBT
DEBT	NOTE 11. DEBT ​ Long-term debt consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands 2021 2020 Revolving credit facility ​ $ 321,000 ​ $ 347,000 Term loan ​ ​ 442,125 ​ ​ 445,500 Unamortized term loan discount and debt issuance costs ​ ​ (5,801) ​ ​ (6,657) Total debt ​ ​ 757,324 ​ ​ 785,843 Current portion of long-term debt ​ ​ (3,359) ​ ​ (3,359) Long-term debt ​ $ 753,965 ​ $ 782,484 ​ Future Maturities of long-term debt, excluding unamortized discount and debt issuance costs, as of September 30, 2021 consisted of the following: ​ ​ ​ ​ ​ $s in thousands Maturities 2021 (excluding the nine months ended September 30, 2021) ​ $ 1,125 2022 ​ ​ 4,500 2023 ​ ​ 4,500 2024 ​ ​ 4,500 2025 ​ ​ 4,500 Thereafter ​ ​ 744,000 ​ ​ $ 763,125 ​ ​ Credit Agreement ​ On April 18, 2017, US Ecology Holdings, Inc. (f/k/a US Ecology, Inc.) (“Predecessor US Ecology”), now a wholly-owned subsidiary of the Company, entered into a new senior secured credit agreement (as amended, restated, supplemented or otherwise modified through the date hereof, the “Credit Agreement”) with Wells Fargo Bank, National Association (“Wells Fargo”), as administrative agent for the lenders, swingline lender and issuing lender, and Bank of America, N.A., as an issuing lender, that initially provided for a $500.0 million, five-year revolving credit facility (the “Revolving Credit Facility”). ​ On August 6, 2019, Predecessor US Ecology entered into the first amendment (the “First Amendment”) to the Credit Agreement. Effective November 1, 2019, the First Amendment, among other things, extended the expiration of the Revolving Credit Facility to November 1, 2024, permitted the issuance of a $400.0 million incremental term loan to be used to refinance the indebtedness of NRC and pay related transaction expenses in connection with the NRC Merger, modified the accordion feature allowing Predecessor US Ecology to request up to the greater of (x) $250.0 million and (y) 100% of consolidated earnings before interest, taxes, depreciation and amortization (“EBITDA”) plus certain additional amounts, increased the sublimit for the issuance of swingline loans to $40.0 million and increased the maximum consolidated total net leverage ratio to 4.00 to 1.00. ​ On November 1, 2019, Predecessor US Ecology entered into the lender joinder agreement and second amendment (the “Second Amendment”) to the Credit Agreement. Effective November 1, 2019, the Second Amendment, among other things, amended the Credit Agreement to increase the capacity for incremental term loans by $50.0 million and provided for Wells Fargo lending $450.0 million in incremental term loans to Predecessor US Ecology to pay off the existing debt of NRC in connection with the NRC Merger, to pay certain fees, costs and expenses incurred in connection with the NRC Merger and to repay outstanding borrowings under the Revolving Credit Facility. The seven-year incremental term loan matures November 1, 2026, requires principal repayment of 1% annually, and bears interest at London Inter-Bank Offered Rate (“LIBOR”) plus 2.25% or a base rate plus 1.25% (with a step-up to LIBOR plus 2.50% or a base rate plus 1.50% in the event that US Ecology credit ratings are not BB (with a stable or better outlook) or better from S&P and Ba2 (with a stable or better outlook) or better from Moody’s). During the nine months ended September 30, 2021, the effective interest rate on the term loan, including the impact of the amortization of debt issuance costs, was 2.87%. ​ On June 26, 2020, Predecessor US Ecology entered into the third amendment (the “Third Amendment”) to the Credit Agreement. Among other things, the Third Amendment amended the Credit Agreement to provide a covenant relief period through the earlier of March 31, 2022 and the date Predecessor US Ecology elects to end such covenant relief period pursuant to the terms therein. During the covenant relief period, the Third Amendment increased Predecessor US Ecology’s consolidated total net leverage ratio requirement as of the end of each fiscal quarter to certain ratios above the 4.00 to 1.00 ratio in effect immediately before giving effect to the Third Amendment, subject to compliance with certain restrictions on restricted payments and permitted acquisitions during such covenant relief period. ​ On June 29, 2021, Predecessor US Ecology entered into the fourth amendment (the “Fourth Amendment”) to the Credit Agreement. Among other things, the Fourth Amendment amended the Credit Agreement to extend the maturity date for the existing revolving credit facility to June 29, 2026 (or such earlier date as the revolving credit facility may otherwise terminate pursuant to the terms of the Credit Agreement). The Fourth Amendment also amended the Credit Agreement (i) to extend the existing covenant relief period to end on the earlier of December 31, 2022 and the date Predecessor US Ecology elects to end such covenant relief period pursuant to the terms therein and (ii) to permanently increase Predecessor US Ecology’s consolidated total net leverage ratio requirement as of the end of each fiscal quarter ending on and after December 31, 2022 to 4.50 to 1.00. During the covenant relief period until the fiscal quarter ending December 31, 2022, the Fourth Amendment increased Predecessor US Ecology’s consolidated total net leverage ratio requirement as of the end of each fiscal quarter to certain ratios above the 4.50 to 1.00 ratio otherwise in effect after giving effect to the Fourth Amendment, subject to compliance with certain restrictions on restricted payments and permitted acquisitions during such covenant relief period. Furthermore, after giving effect to the Fourth Amendment and whether or not the covenant relief period is in effect, (i) if the Borrower’s consolidated total net leverage ratio is equal to or greater than 4.00 to 1.00 but less than 4.50 to 1.00, the interest rate on all outstanding borrowings of revolving credit loans under the Credit Agreement will step-up to the LIBOR plus 2.25% or a base rate plus 1.25% and the commitment fee will step-up to 0.375% and (ii) if Predecessor US Ecology’s consolidated total net leverage ratio is greater than 4.50 to 1.00, the interest rate on all outstanding borrowings of revolving credit loans under the Credit Agreement will step-up to LIBOR plus 2.50% or a base rate plus 1.50% and the commitment fee will step-up to 0.40%, in each case, pursuant to the terms of the Credit Agreement. The Fourth Amendment also reset any outstanding usage of certain negative covenant baskets, including baskets in connection with the indebtedness, liens, investments, asset dispositions, restricted payments and affiliate transactions negative covenants. ​ The Revolving Credit Facility provides up to $500.0 million of revolving credit loans or letters of credit with the use of proceeds restricted solely for working capital and other general corporate purposes (including acquisitions and capital expenditures). As modified by the Fourth Amendment, under the Revolving Credit Facility, revolving credit loans are available based on a base rate (as defined in the Credit Agreement) or LIBOR, at the Company’s option, plus an applicable margin which is determined according to a pricing grid under which the interest rate decreases or increases based on our ratio of funded debt to EBITDA (as defined in the Credit Agreement), as set forth in the table below: ​ ​ ​ ​ Consolidated Total Net Leverage Ratio LIBOR Rate Loans Interest Margin Base Rate Loans Interest Margin Equal to or greater than 4.50 to 1.00 2.50% 1.50% Equal to or greater than 4.00 to 1.00, but less than 4.50 to 1.00 2.25% 1.25% Equal to or greater than 3.25 to 1.00, but less than 4.00 to 1.00 2.00% 1.00% Equal to or greater than 2.50 to 1.00, but less than 3.25 to 1.00 1.75% 0.75% Equal to or greater than 1.75 to 1.00, but less than 2.50 to 1.00 1.50% 0.50% Equal to or greater than 1.00 to 1.00, but less than 1.75 to 1.00 1.25% 0.25% Less than 1.00 to 1.00 1.00% 0.00% ​ During the nine months ended September 30, 2021, the effective interest rate on the Revolving Credit Facility, after giving effect to the impact of our interest rate swap and the amortization of the loan discount and debt issuance costs, was 4.03%. Interest only payments are due either quarterly or on the last day of any interest period, as applicable. ​ As modified by the Fourth Amendment, Predecessor US Ecology is required to pay a commitment fee ranging from 0.175% to 0.40% on the average daily unused portion of the Revolving Credit Facility, with such commitment fee to be based upon Predecessor US Ecology’s total net leverage ratio (as defined in the Credit Agreement). At September 30, 2021, there were $321.0 million of revolving credit loans outstanding on the Revolving Credit Facility, which are presented as long-term debt in the consolidated balance sheets. ​ Predecessor US Ecology has entered into a sweep arrangement whereby day-to-day cash requirements in excess of available cash balances are advanced to the Company on an as-needed basis with repayments of these advances automatically made from subsequent deposits to our cash operating accounts (the “Sweep Arrangement”). Total advances outstanding under the Sweep Arrangement are subject to the $40.0 million swingline loan sublimit under the Revolving Credit Facility. Predecessor US Ecology’s revolving credit loans outstanding under the Revolving Credit Facility are not subject to repayment through the Sweep Arrangement. As of September 30, 2021, there were no ​ As of September 30, 2021, the availability under the Revolving Credit Facility was $62.2 million, subject to our leverage covenant limitation, with $14.7 million of the Revolving Credit Facility issued in the form of standby letters of credit utilized as collateral for closure and post-closure financial assurance and other assurance obligations. ​ Predecessor US Ecology may at any time and from time to time prepay revolving credit loans and swingline loans, in whole or in part, without premium or penalty, subject to the obligation to indemnify each of the lenders against any actual loss or expense (including any loss or expense arising from the liquidation or reemployment of funds obtained by it to maintain a LIBOR Rate Loan (as defined in the Credit Agreement) or from fees payable to terminate the deposits from which such funds were obtained) with respect to the early termination of any LIBOR Rate Loan. The Credit Agreement provides for mandatory prepayment at any time if the Revolving Credit Outstandings exceed the Revolving Credit Commitment (as such terms are defined in the Credit Agreement), in an amount equal to such excess. Subject to certain exceptions, the Credit Agreement provides for mandatory prepayment upon certain asset dispositions, casualty events and issuances of indebtedness. ​ Predecessor US Ecology’s obligations under the Credit Agreement are (or will be) jointly and severally and fully and unconditionally guaranteed on a senior basis by all of the Company’s existing and certain future domestic subsidiaries and are secured by substantially all of the assets of Predecessor US Ecology and the Company’s existing and certain future domestic subsidiaries (subject to certain exclusions), including 100% of the equity interests of the Company’s domestic subsidiaries and 65% of the voting equity interests of the Company’s directly owned foreign subsidiaries (and 100% of the non-voting equity interests of the Company’s directly owned foreign subsidiaries). ​ The Credit Agreement contains customary restrictive covenants, subject to certain permitted amounts and exceptions, including covenants limiting the ability of the Company to incur additional indebtedness, pay dividends and make other restricted payments, repurchase shares of our outstanding stock and create certain liens. Upon the occurrence of an Event of Default (as defined in the Credit Agreement), among other things, amounts outstanding under the Credit Agreement may be accelerated and the commitments may be terminated. ​ The Credit Agreement also contains financial maintenance covenants, a maximum consolidated total net leverage ratio and a consolidated interest coverage ratio. Except as further modified by the Third Amendment and Fourth Amendment as described above, our consolidated total net leverage ratio as of the last day of each fiscal quarter may not exceed 4.50:1:00. Our consolidated interest coverage ratio as of the last day of any fiscal quarter may not be less than 3.00 to 1.00. At September 30, 2021, we were in compliance with all of the financial covenants in the Credit Agreement. ​ Interest Rate Swap ​ In March 2020, the Company entered into an interest rate swap agreement with Wells Fargo, effectively fixing the interest rate on $450.0 million, or approximately 59%, of the Revolving Credit Facility and term loan borrowings outstanding as of September 30, 2021. In connection with our entry into the March 2020 interest rate swap, we terminated our existing interest rate swap prior to its scheduled maturity date of June 2021. As the original hedged forecasted transaction (periodic interest payments on our variable-rate debt) remained probable, the $1.8 million net loss related to the terminated swap reported in AOCI at the termination date was amortized as additional interest expense over its original maturity.

CLOSURE AND POST-CLOSURE OBLIGA

CLOSURE AND POST-CLOSURE OBLIGATIONS	9 Months Ended
	Sep. 30, 2021
CLOSURE AND POST-CLOSURE OBLIGATIONS
CLOSURE AND POST-CLOSURE OBLIGATIONS	NOTE 12. CLOSURE AND POST-CLOSURE OBLIGATIONS ​ Our accrued closure and post-closure liability represent the expected future costs, including corrective actions, associated with closure and post-closure of our operating and non-operating disposal facilities. We record the fair value of our closure and post-closure obligations as a liability in the period in which the regulatory obligation to retire a specific asset is triggered. For our individual landfill cells, the required closure and post-closure obligations under the terms of our permits and our intended operation of the landfill cell are triggered and recorded when the cell is placed into service and waste is initially disposed in the landfill cell. The fair value is based on the total estimated costs to close the landfill cell and perform post-closure activities once the landfill cell has reached capacity and is no longer accepting waste. We perform periodic reviews of both non-operating and operating facilities and revise accruals for estimated closure and post-closure, remediation or other costs as necessary. Recorded liabilities are based on our best estimates of current costs and are updated periodically to include the effects of existing technology, presently enacted laws and regulations, inflation and other economic factors. ​ Changes to closure and post-closure obligations consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended $s in thousands September 30, 2021 ​ September 30, 2021 Closure and post-closure obligations, beginning of period ​ $ 97,524 ​ $ 95,869 Accretion expense ​ 1,198 ​ 3,571 Payments ​ (337) ​ (1,104) Foreign currency translation ​ (44) ​ 5 Closure and post-closure obligations, end of period ​ 98,341 ​ 98,341 Less current portion ​ (8,234) ​ (8,234) Long-term portion ​ $ 90,107 ​ $ 90,107 ​

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2021
INCOME TAXES
INCOME TAXES	NOTE 13. INCOME TAXES ​ We have historically calculated the provision for income taxes during interim reporting periods by applying an estimate of the Annual Effective Tax Rate (“AETR”) for the full fiscal year to “ordinary” income or loss (pretax income or loss excluding unusual or infrequently occurring discrete items) for the reporting period. We used a discrete effective tax rate method to calculate taxes for the nine months ended September 30, 2021. We determined that since relatively small changes in estimated “ordinary” income would result in significant changes in the estimated AETR, that the historical method would not provide a reliable estimate for the nine months ended September 30, 2021. ​ Income tax expense for the three months ended September 30, 2021 was $2.5 million, resulting in an effective tax rate of 27.4%. Income tax benefit for the three months ended September 30, 2020 was $1.5 million resulting in an effective tax rate of (29.9)%. Income tax expense for the nine months ended September 30, 2021 was $1.3 million, resulting in an effective tax rate of 43.2%. Income tax expense for the nine months ended September 30, 2020 was $542,000, resulting in an effective tax rate of (0.2)%. The increase in our effective tax rate for the three and nine months ended September 30, 2021 compared to the three and nine months ended September 30, 2020 was primarily due to non-deductible goodwill impairment charges incurred during the nine months ended September 30, 2020, and lower pre-tax earnings, excluding impairments, for the nine months ended September 30, 2021, which resulted in income tax expense from the year-to-date earnings of our foreign operations, partially offset by an income tax benefit from the year-to-date loss of our U.S. operations. ​ Gross unrecognized tax benefits, included in Other long-term liabilities in the consolidated balance sheets, were $277,000 and $239,000 as of September 30, 2021 and December 31, 2020, respectively. The gross unrecognized tax benefits, if recognized by the Company, will result in a reduction of approximately $277,000 to the provision for income taxes. We do not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease within the next 12 months. Accrued interest and penalties related to unrecognized tax benefits are recorded in Interest expense and Selling, general and administrative expenses, respectively. The total accrued interest related to unrecognized tax benefits as of September 30, 2021 and December 31, 2020 were not significant. There is no accrual for penalties. ​ The Company files income tax returns in the U.S. federal and various state, local and foreign jurisdictions. The Company’s U.S. federal income tax returns are subject to examination by the Internal Revenue Service for tax years beginning in 2017. For tax years beginning in 2016, our state tax returns are subject to examination by state tax authorities. Stablex Canada, Inc. is currently under examination by the Canadian Revenue Agency for years 2018 through 2020. Tax years 2016 through 2020 remain subject to examination in our significant foreign jurisdictions. The Company does not anticipate any material change as a result of any current examinations in progress. ​ ​

EARNINGS (LOSS) PER SHARE

EARNINGS (LOSS) PER SHARE	9 Months Ended
	Sep. 30, 2021
EARNINGS (LOSS) PER SHARE
EARNINGS (LOSS) PER SHARE	NOTE 14. EARNINGS (LOSS) PER SHARE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ ​ 2021 ​ 2020 $s and shares in thousands, except per share amounts Basic Diluted Basic Diluted Net income ​ $ 6,732 ​ $ 6,732 ​ $ 6,319 ​ $ 6,319 Weighted average basic shares outstanding ​ 31,151 ​ 31,151 ​ 31,069 ​ 31,069 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Dilutive effect of share-based awards and warrants ​ ​ ​ ​ 249 ​ ​ ​ ​ 255 Weighted average diluted shares outstanding ​ ​ ​ ​ 31,400 ​ ​ ​ ​ 31,324 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share ​ $ 0.22 ​ $ 0.21 ​ $ 0.20 ​ $ 0.20 Anti-dilutive shares excluded from calculation ​ ​ ​ ​ 4,404 ​ ​ ​ ​ 4,233 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ 2021 ​ 2020 $s and shares in thousands, except per share amounts Basic Diluted Basic Diluted Net income (loss) ​ $ 1,773 ​ $ 1,773 ​ $ (296,950) ​ $ (296,950) Weighted average basic shares outstanding ​ 31,131 ​ 31,131 ​ 31,142 ​ 31,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Dilutive effect of share-based awards ​ ​ ​ ​ 246 ​ ​ ​ ​ — Weighted average diluted shares outstanding ​ ​ ​ ​ 31,377 ​ ​ ​ ​ 31,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings (loss) per share ​ $ 0.06 ​ $ 0.06 ​ $ (9.54) ​ $ (9.54) Anti-dilutive shares excluded from calculation ​ ​ ​ ​ 4,333 ​ ​ ​ ​ 4,208 ​

EQUITY

EQUITY	9 Months Ended
	Sep. 30, 2021
EQUITY
EQUITY	NOTE 15. EQUITY ​ Stock Repurchase Program ​ On June 6, 2020, the Company’s Board of Directors’ authorization to repurchase the Company’s outstanding shares of common stock and warrants under the share repurchase program expired. In the future, the Board of Directors may consider reauthorizing the repurchase program at any time, and the timing of any future repurchases of common stock or warrants will be based upon prevailing market conditions and other factors. The Company may from time to time also consider other options for repurchasing some or all of its warrants, including but not limited to a tender offer for all of the outstanding warrants. ​ Omnibus Incentive Plan ​ On May 27, 2015, the stockholders of Predecessor US Ecology approved the Omnibus Incentive Plan (as amended, “Pre-Merger Omnibus Plan”), which was approved by Predecessor US Ecology’s Board of Directors on April 7, 2015. In connection with the closing of the NRC Merger, the Company assumed the Pre-Merger Omnibus Plan, amended and restated such plan and renamed it the Amended and Restated US Ecology, Inc. Omnibus Incentive Plan (the “Omnibus Plan”) for the purpose of issuing replacement awards to award recipients under the Omnibus Plan pursuant to the NRC Merger Agreement and for the issuance of additional awards in the future. The Omnibus Plan was developed to provide additional incentives through equity ownership in US Ecology and, as a result, encourage employees, consultants and non-employee directors to contribute to our success. The Omnibus Plan provides, among other things, the ability for the Company to grant restricted stock, performance stock, options, stock appreciation rights, restricted stock units, performance stock units and other share-based awards or cash awards to employees, consultants and non-employee directors. The Omnibus Plan expires on March 31, 2031 and authorizes 3,272,000 shares of common stock for grant over the life of the Omnibus Plan. As of September 30, 2021, 2,014,301 shares of common stock remain available for grant under the Omnibus Plan. Subsequent to the approval of the Pre-Merger Omnibus Plan by Predecessor US Ecology in May 2015, we stopped granting equity awards under the American Ecology Corporation 2008 Stock Option Incentive Plan (“Pre-Merger 2008 Stock Option Plan”). However, in connection with the closing of the NRC Merger, the Company assumed the Pre-Merger 2008 Stock Option Plan, amended and restated such plan and renamed it in the Amended and Restated US Ecology, Inc. 2008 Stock Option Incentive Plan (the “2008 Stock Option Plan”) solely for the purpose of issuing replacement awards to award recipients thereunder and remains in effect solely for the settlement of awards granted under such plan and no future grants may be made under such plan. No shares that are reserved but unissued under the 2008 Stock Option Plan or that are outstanding under the 2008 Stock Option Plan and reacquired by the Company for any reason will be available for issuance under the Omnibus Plan. In addition, in connection with the closing of the NRC Merger, the Company assumed the NRC Group Holdings Corp. 2018 Equity Incentive Plan previously maintained by NRC by adopting the Amended and Restated US Ecology, Inc. 2018 Equity and Incentive Compensation Plan solely for the purpose of issuing replacement awards to award recipients thereunder pursuant to the NRC Merger Agreement, and no future grants may be made under such plan. ​ Performance Share Units (“PSUs”), Restricted Stock and Restricted Stock Units (“RSUs”) ​ A summary of our PSU, restricted stock and RSU activity for the nine months ended September 30, 2021 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ PSUs ​ Restricted Stock ​ RSUs ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ Average ​ ​ ​ Average ​ ​ ​ ​ Grant Date ​ ​ ​ Grant Date ​ ​ ​ Grant Date ​ Shares Fair Value Shares Fair Value Shares Fair Value Outstanding as of December 31, 2020 86,070 ​ $ 49.45 72,766 ​ $ 51.47 ​ 147,243 ​ $ 39.92 Granted — ​ ​ — 84,800 ​ ​ 36.49 ​ 62,759 ​ ​ 39.33 Vested (14,100) ​ 63.56 (47,002) ​ 47.08 ​ (55,876) ​ 42.03 Cancelled, expired or forfeited — ​ — — ​ — ​ (13,453) ​ 44.57 Outstanding as of September 30, 2021 71,970 ​ $ 46.69 110,564 ​ $ 41.85 ​ 140,673 ​ $ 38.38 ​ During the nine months ended September 30, 2021, 14,100 PSUs vested and PSU holders earned zero shares of the Company’s common stock. ​ Stock Options ​ A summary of our stock option activity for the nine months ended September 30, 2021 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ ​ Exercise ​ Shares Price Outstanding as of December 31, 2020 357,033 ​ $ 49.93 Granted 205,800 ​ ​ 35.30 Outstanding as of September 30, 2021 562,833 ​ $ 44.58 Exercisable as of September 30, 2021 299,568 ​ $ 48.29 ​ Treasury Stock ​ During the nine months ended September 30, 2021, the Company repurchased 12,788 shares of the Company’s common stock in connection with the net share settlement of employee equity awards at an average cost of $36.33. ​ Warrants ​ At September 30, 2021, there were a total of 3,772,753 warrants outstanding. Each warrant entitles the holder thereof to purchase one share of common stock at a price of $58.67 per share, subject to certain adjustments. The warrants may be exercised only for a whole number of shares of common stock. No fractional shares will be issued upon exercise of the warrants. The warrants will expire at 5:00 p.m. New York City time on October 17, 2023, or earlier upon redemption or liquidation. The warrants are listed on the Nasdaq Capital Market under the symbol “ECOLW”. The Company may call the warrants for redemption, in whole and not in part, at a price of $0.01 per warrant, upon not less than 30 days’ prior written notice of redemption to each warrant holder, if, and only if, the reported last sale price of common stock equals or exceeds $91.84 per share on each of 20 trading days within the 30 trading-day period ending on the business day prior to the date on which notice of the redemption is given and provided that there is an effective registration statement covering the shares of common stock issuable on exercise of the warrants and subject to the satisfaction of certain other requirements. The warrants were determined to be equity classified in accordance with ASC 815, Derivatives and Hedging Distinguishing Liabilities from Equity ​ Dividends ​ On March 31, 2020, the Board of Directors approved a plan to suspend quarterly cash dividends, beginning with the second quarter of 2020. The Company did not

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2021
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	NOTE 16. COMMITMENTS AND CONTINGENCIES ​ Litigation and Regulatory Proceedings ​ In the ordinary course of business, we are involved in judicial and administrative proceedings involving federal, state, provincial or local governmental authorities, including regulatory agencies that oversee and enforce compliance with permits. Fines or penalties may be assessed by our regulators for non-compliance. Actions may also be brought by individuals or groups in connection with permitting of planned facilities, modification or alleged violations of existing permits, or alleged damages suffered from exposure to hazardous substances purportedly released from our operated sites, as well as other litigation. We maintain insurance intended to cover property and damage claims asserted as a result of our operations. Periodically, management reviews and may establish reserves for legal and administrative matters, or other fees expected to be incurred in relation to these matters. In December 2010, National Response Corporation, a subsidiary of NRC acquired by the Company in the NRC Merger, was named as one of many “Dispersant Defendants” in multi-district litigation, arising out of the explosion of the BP Deepwater Horizon (“BP”) oil rig, filed in the U.S. District Court for the Eastern District of Louisiana (“ In re Deepwater Horizon On November 17, 2018, an explosion occurred at our Grand View, Idaho facility, resulting in one employee fatality and injuries to other employees. The incident severely damaged the facility’s primary waste-treatment building as well as surrounding waste handling, waste storage, maintenance and administrative support structures, resulting in the closure of the entire facility that remained in effect through January 2019. In addition to initiating and conducting our own investigation into the incident, we fully cooperated with the Idaho Department of Environmental Quality, the U.S. Environmental Protection Agency and the Occupational Safety and Health Administration (“OSHA”) to support their comprehensive and independent investigations of the incident. On January 10, 2020, we entered into a settlement agreement with OSHA settling a complaint made by OSHA relating to the incident for $50,000. On January 28, 2020, the Occupational Safety and Health Review Commission issued an order terminating the proceeding relating to such OSHA complaint. We maintain workers’ compensation insurance, business interruption insurance and liability insurance for personal injury, property and casualty damage. We believe that any potential third-party claims associated with the explosion in excess of our deductibles are expected to be resolved primarily through our insurance policies. Although we carry business interruption insurance, a disruption of our business caused by a casualty event, including the full and partial closure of our Grand View, Idaho facility, may result in the loss of business, profits or customers during the time of such closure. Accordingly, our insurance policies may not fully compensate us for these losses. In November 2020, we commenced a lawsuit against the generator and broker of the waste, the treatment of which we believe contributed to the Grand View explosion, seeking damages in connection with the losses suffered as a result of the incident. The Company is actively working with its insurance companies on comprehensive property and business interruption insurance claims related to the incident at our Grand View, Idaho facility. ​ In September 2021, Robert Dell, a Marine Technician for NRC from June 2021 to September 2021, filed a class action complaint against US Ecology in the Alameda Superior Court for the State of California (Robert Dell et. al. v. US Ecology Illinois, Inc., US Ecology, Inc., and US Ecology Vernon, Inc.) alleging the failure by the defendants to pay wages and/or overtime, failure to provide accurate itemized wage statements, and failure to provide meal and rest breaks as required by California law. Further, Mr. Dell has put the Labor & Workforce Development Agency on notice in an effort to exhaust administrative remedies and enable him to bring an additional claim under the California Labor Code Private Attorneys General Act, which permits an employee to assert a claim for violations of certain California Labor Code provisions on behalf of all aggrieved employees to recover statutory penalties. Given the recency of the filing, the Company has not yet filed a response to Mr. Dell’s complaint. The Company believes that Mr. Dell’s claims lack merit and intends to vigorously defend this action. The Company is currently unable to estimate the range of possible losses associated with this proceeding. ​ Other than as described herein, we are not currently a party to any material pending legal proceedings and are not aware of any other claims that could, individually or in the aggregate, have a materially adverse effect on our financial position, results of operations or cash flows. The decision to accrue costs or write-off assets is based on the pertinent facts and our evaluation of present circumstances.

OPERATING SEGMENTS

OPERATING SEGMENTS	9 Months Ended
	Sep. 30, 2021
OPERATING SEGMENTS
OPERATING SEGMENTS	NOTE 17. OPERATING SEGMENTS ​ Financial Information by Segment ​ Effective in the fourth quarter of 2020, we made changes to the manner in which we manage our business, make operating decisions and assess our performance. The energy waste business that was acquired through the NRC Merger now comprises our Energy Waste segment. Prior to this change, the energy waste business was included in the Waste Solutions segment (formerly “Environmental Services”). Throughout this Quarterly Report on Form 10-Q, all periods presented have been recast to reflect these changes. Under our new structure our operations are now managed in three reportable segments reflecting our internal management reporting structure and nature of services offered as follows: ​ Waste Solutions (formerly “Environmental Services”) ​ Field Services (formerly “Field & Industrial Services”) ​ Energy Waste ​ The operations not managed through our three reportable segments are recorded as “Corporate.” Corporate selling, general and administrative expenses include typical corporate items of a general nature such as certain labor, information technology, legal, accounting and other expenses not associated with a specific reportable segment. Income taxes are assigned to Corporate, but all other items are included in the segment where they originated. Inter-company transactions have been eliminated from the segment information and are not significant between segments. ​ Summarized financial information of our reportable segments is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 115,201 ​ $ 131,582 ​ $ 10,399 ​ $ — ​ $ 257,182 Depreciation, amortization and accretion ​ $ 10,500 ​ $ 11,062 ​ $ 5,334 ​ $ 786 ​ $ 27,682 Capital expenditures ​ $ 10,693 ​ $ 6,221 ​ $ 481 ​ $ 1,521 ​ $ 18,916 Total assets ​ $ 786,686 ​ $ 749,617 ​ $ 215,997 ​ $ 66,623 ​ $ 1,818,923 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 107,249 ​ $ 125,715 ​ $ 5,178 ​ $ — ​ $ 238,142 Depreciation, amortization and accretion ​ $ 10,377 ​ $ 12,129 ​ $ 5,566 ​ $ 820 ​ $ 28,892 Capital expenditures ​ $ 5,189 ​ $ 2,531 ​ $ 1,270 ​ $ 177 ​ $ 9,167 Total assets ​ $ 754,235 ​ $ 859,511 ​ $ 234,992 ​ $ 97,557 ​ $ 1,946,295 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 327,708 ​ $ 374,491 ​ $ 24,375 ​ $ — ​ $ 726,574 Depreciation, amortization and accretion ​ $ 32,905 ​ $ 33,794 ​ $ 15,108 ​ $ 2,360 ​ $ 84,167 Capital expenditures ​ $ 31,553 ​ $ 10,426 ​ $ 1,233 ​ $ 2,135 ​ $ 45,347 Total assets ​ $ 786,686 ​ $ 749,617 ​ $ 215,997 ​ $ 66,623 ​ $ 1,818,923 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 319,684 ​ $ 343,217 ​ $ 29,879 ​ $ — ​ $ 692,780 Depreciation, amortization and accretion ​ $ 31,119 ​ $ 36,420 ​ $ 16,729 ​ $ 2,187 ​ $ 86,455 Capital expenditures ​ $ 22,343 ​ $ 12,997 ​ $ 5,719 ​ $ 4,065 ​ $ 45,124 Total assets ​ $ 754,235 ​ $ 859,511 ​ $ 234,992 ​ $ 97,557 ​ $ 1,946,295 ​ Adjusted Earnings Before Interest, Taxes, Depreciation and Amortization (“Adjusted EBITDA”) ​ Management uses Adjusted EBITDA as a financial measure to assess segment performance. Adjusted EBITDA is defined as net income before interest expense, interest income, income tax expense, depreciation, amortization, share-based compensation, accretion of closure and post-closure liabilities, foreign currency gain/loss, non-cash goodwill impairment charges, business development and integration expenses and other income/expense. Adjusted EBITDA is a complement to results provided in accordance with GAAP and we believe that such information provides additional useful information to analysts, stockholders and other users to understand the Company’s operating performance. Since Adjusted EBITDA is not a measurement determined in accordance with GAAP and is thus susceptible to varying calculations, Adjusted EBITDA as presented may not be comparable to other similarly titled measures of other companies. Items excluded from Adjusted EBITDA are significant components in understanding and assessing our financial performance. Adjusted EBITDA should not be considered in isolation or as an alternative to, or substitute for, net income, cash flows generated by operations, investing or financing activities, or other financial statement data presented in the consolidated financial statements as indicators of financial performance or liquidity. Adjusted EBITDA has limitations as an analytical tool and should not be considered in isolation or a substitute for analyzing our results as reported under GAAP. Some of the limitations are: ● Adjusted EBITDA does not reflect changes in, or cash requirements for, our working capital needs; ● Adjusted EBITDA does not reflect our interest expense, or the requirements necessary to service interest or principal payments on our debt; ● Adjusted EBITDA does not reflect our income tax expenses or the cash requirements to pay our taxes; ● Adjusted EBITDA does not reflect our cash expenditures or future requirements for capital expenditures or contractual commitments; ● Although depreciation and amortization charges are non-cash charges, the assets being depreciated and amortized will often have to be replaced in the future, and Adjusted EBITDA does not reflect any cash requirements for such replacements; and ● Adjusted EBITDA does not reflect our business development and integration expenses. ​ A reconciliation of Net income (loss) to Adjusted EBITDA is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, $s in thousands 2021 2020 2021 2020 Net income (loss) ​ $ 6,732 ​ $ 6,319 ​ $ 1,773 ​ $ (296,950) Income tax expense (benefit) ​ ​ 2,535 ​ ​ (1,456) ​ ​ 1,348 ​ ​ 542 Interest expense ​ ​ 7,144 ​ ​ 7,964 ​ ​ 22,022 ​ ​ 25,127 Interest income ​ ​ (485) ​ ​ (9) ​ ​ (1,148) ​ ​ (251) Foreign currency (gain) loss ​ ​ (341) ​ ​ 421 ​ ​ 385 ​ ​ 155 Other income ​ ​ (114) ​ ​ (86) ​ ​ (4,020) ​ ​ (382) Goodwill impairment charges ​ ​ — ​ ​ — ​ ​ — ​ ​ 300,300 Depreciation and amortization of plant and equipment ​ ​ 17,898 ​ ​ 18,435 ​ ​ 54,095 ​ ​ 54,831 Amortization of intangible assets ​ ​ 8,586 ​ ​ 9,178 ​ ​ 26,501 ​ ​ 27,812 Share-based compensation ​ ​ 1,713 ​ ​ 1,773 ​ ​ 5,748 ​ ​ 4,861 Accretion and non-cash adjustment of closure & post-closure liabilities ​ ​ 1,198 ​ ​ 1,279 ​ ​ 3,571 ​ ​ 3,812 Business development and integration expenses ​ ​ 523 ​ ​ 1,627 ​ ​ 2,528 ​ ​ 7,507 Adjusted EBITDA ​ $ 45,389 ​ $ 45,445 ​ $ 112,803 ​ $ 127,364 ​ Adjusted EBITDA, by operating segment, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, Nine Months Ended September 30, $s in thousands ​ 2021 2020 ​ 2021 2020 Waste Solutions $ 43,439 ​ $ 45,556 $ 123,528 ​ $ 134,540 Field Services 21,507 ​ 24,362 55,810 ​ 57,869 Energy Waste ​ ​ 3,497 ​ ​ 90 ​ ​ 7,063 ​ ​ 4,163 Corporate (23,054) ​ (24,563) (73,598) ​ (69,208) Total $ 45,389 ​ $ 45,445 $ 112,803 ​ $ 127,364 ​ Property and Equipment and Intangible Assets Outside of the United States ​ We provide services primarily in the United States, Canada and the EMEA region. Long-lived assets, comprised of property and equipment and intangible assets net of accumulated depreciation and amortization, by geographic location are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands ​ 2021 2020 United States ​ $ 856,670 ​ $ 882,639 Canada ​ 65,616 ​ 68,623 EMEA ​ ​ 15,946 ​ ​ 18,042 Other (1) ​ ​ 10,124 ​ ​ 11,321 Total long-lived assets, net ​ $ 948,356 ​ $ 980,625 (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions.

GENERAL (Policies)

GENERAL (Policies)	9 Months Ended
	Sep. 30, 2021
GENERAL
Basis of Presentation	Basis of Presentation ​ The accompanying unaudited consolidated financial statements include the results of operations, financial position and cash flows of US Ecology, Inc. and its wholly-owned subsidiaries. All inter-company balances have been eliminated. Throughout these consolidated financial statements words such as “we,” “us,” “our,” “US Ecology” and “the Company” refer to US Ecology, Inc. and its subsidiaries. ​ In the opinion of management, the accompanying unaudited consolidated financial statements include all adjustments (consisting only of normal recurring adjustments) necessary to present fairly, in all material respects, the results of the Company for the periods presented. These consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States (“GAAP”) have been omitted pursuant to the rules and regulations of the SEC. These consolidated financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the entire year ending December 31, 2021. ​ The Company’s consolidated balance sheet as of December 31, 2020 has been derived from the Company’s audited consolidated balance sheet as of that date.
Reclassifications	Reclassifications ​ Effective in the first quarter of 2021, we changed our management structure resulting in the reclassification of certain overhead expenses from our Waste Solutions, Field Services and Energy Waste reportable segments to Corporate. As a result, certain regional overhead costs historically presented within our reportable segments as Direct operating costs were further reclassified to Corporate as Selling, general and administrative expenses to conform to the current period’s presentation. Throughout this Quarterly Report on Form 10-Q, all periods presented have been recast to reflect these changes.
Use of Estimates	Use of Estimates ​ The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from the estimates and assumptions that we use in the preparation of our consolidated financial statements. As it relates to estimates and assumptions in amortization rates and environmental obligations, significant engineering, operations and accounting judgments are required. We review these estimates and assumptions no less than annually. In many circumstances, the ultimate outcome of these estimates and assumptions will not be known for decades into the future. Actual results could differ materially from these estimates and assumptions due to changes in applicable regulations, changes in future operational plans and inherent imprecision associated with estimating environmental impacts far into the future.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements ​ In March 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2020-04, “Facilitation of the Effects of Reference Rate Reform on Financial Reporting” (Topic 848). The ASU provides optional expedients and exceptions for applying GAAP to transactions affected by reference rate (e.g., LIBOR) reform if certain criteria are met, for a limited period of time to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The ASU is effective as of March 12, 2020 through December 31, 2022. We will evaluate transactions or contract modifications occurring as a result of reference rate reform and determine whether to apply the optional guidance on an ongoing basis. The ASU is currently not expected to have a material impact on our consolidated financial statements. ​ Effective January 1, 2021, the Company adopted ASU No. 2019-12, “Income Taxes - Simplifying the Accounting for Income Taxes.” This ASU is intended to simplify various aspects of accounting for income taxes by eliminating certain exceptions within Accounting Standards Codification Topic 740, “Income Taxes” and to clarify certain aspects of the current accounting guidance. Adoption of this standard did not materially impact our consolidated statements of financial position, results of operations, or cash flows.

REVENUES (Tables)

REVENUES (Tables)	9 Months Ended
	Sep. 30, 2021
REVENUES
Schedule of disaggregation of revenues	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 92,867 ​ $ 15,940 ​ $ 6,263 ​ $ 115,070 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 22,334 ​ ​ 6,483 ​ ​ 2,317 ​ ​ 31,134 Industrial Services (3) ​ ​ — ​ ​ 29,597 ​ ​ 730 ​ ​ 30,327 Small Quantity Generation (4) ​ ​ — ​ ​ 14,629 ​ ​ — ​ ​ 14,629 Total Waste Management (5) ​ ​ — ​ ​ 9,597 ​ ​ — ​ ​ 9,597 Remediation (6) ​ ​ — ​ ​ 16,310 ​ ​ — ​ ​ 16,310 Emergency Response (7) ​ ​ — ​ ​ 34,532 ​ ​ — ​ ​ 34,532 Other (8) ​ ​ — ​ ​ 4,494 ​ ​ 1,089 ​ ​ 5,583 Revenue ​ $ 115,201 ​ $ 131,582 ​ $ 10,399 ​ $ 257,182 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 88,601 ​ $ 13,861 ​ $ 2,625 ​ $ 105,087 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 18,648 ​ ​ 11,162 ​ ​ 1,257 ​ ​ 31,067 Industrial Services (3) ​ ​ — ​ ​ 28,464 ​ ​ 705 ​ ​ 29,169 Small Quantity Generation (4) ​ ​ — ​ ​ 13,056 ​ ​ — ​ ​ 13,056 Total Waste Management (5) ​ ​ — ​ ​ 9,998 ​ ​ — ​ ​ 9,998 Remediation (6) ​ ​ — ​ ​ 6,733 ​ ​ — ​ ​ 6,733 Emergency Response (7) ​ ​ — ​ ​ 37,993 ​ ​ — ​ ​ 37,993 Other (8) ​ ​ — ​ ​ 4,448 ​ ​ 591 ​ ​ 5,039 Revenue ​ $ 107,249 ​ $ 125,715 ​ $ 5,178 ​ $ 238,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 270,906 ​ $ 39,143 ​ $ 14,648 ​ $ 324,697 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 56,802 ​ ​ 21,169 ​ ​ 5,412 ​ ​ 83,383 Industrial Services (3) ​ ​ — ​ ​ 88,193 ​ ​ 1,841 ​ ​ 90,034 Small Quantity Generation (4) ​ ​ — ​ ​ 41,311 ​ ​ — ​ ​ 41,311 Total Waste Management (5) ​ ​ — ​ ​ 29,840 ​ ​ — ​ ​ 29,840 Remediation (6) ​ ​ — ​ ​ 40,055 ​ ​ — ​ ​ 40,055 Emergency Response (7) ​ ​ — ​ ​ 102,444 ​ ​ — ​ ​ 102,444 Other (8) ​ ​ — ​ ​ 12,336 ​ ​ 2,474 ​ ​ 14,810 Revenue ​ $ 327,708 ​ $ 374,491 ​ $ 24,375 ​ $ 726,574 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services ​ Waste Total Treatment & Disposal Revenue (1) ​ $ 266,129 ​ $ 33,744 ​ $ 16,102 ​ $ 315,975 Services Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Transportation and Logistics (2) ​ ​ 53,555 ​ ​ 22,577 ​ ​ 6,206 ​ ​ 82,338 Industrial Services (3) ​ ​ — ​ ​ 85,529 ​ ​ 3,568 ​ ​ 89,097 Small Quantity Generation (4) ​ ​ — ​ ​ 35,292 ​ ​ — ​ ​ 35,292 Total Waste Management (5) ​ ​ — ​ ​ 25,315 ​ ​ — ​ ​ 25,315 Remediation (6) ​ ​ — ​ ​ 21,911 ​ ​ — ​ ​ 21,911 Emergency Response (7) ​ ​ — ​ ​ 103,756 ​ ​ — ​ ​ 103,756 Other (8) ​ ​ — ​ ​ 15,093 ​ ​ 4,003 ​ ​ 19,096 Revenue ​ $ 319,684 ​ $ 343,217 ​ $ 29,879 ​ $ 692,780 ​ (1) We categorize our treatment and disposal revenue as either “Base Business” or “Event Business” based on the underlying nature of the revenue source. We define Event Business as non-recurring projects that are expected to equal or exceed 1,000 tons, with Base Business defined as all other business not meeting the definition of Event Business. For the three months ended September 30, 2021 and 2020, 24% and 30% , respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76% and 70% of our treatment and disposal revenue for the three months ended September 30, 2021 and 2020, respectively. For the nine months ended September 30, 2021 and 2020, 24% and 28% , respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76% and 72% of our treatment and disposal revenue for the nine months ended September 30, 2021 and 2020, respectively. (2) Includes collection and transportation of non-hazardous and hazardous waste. (3) Includes industrial cleaning and maintenance for refineries, chemical plants, steel and automotive plants, marine terminals and refinery services such as tank cleaning and temporary storage. (4) Includes retail services, laboratory packing, less-than-truck-load service and household hazardous waste collection. Contracts for Small Quantity Generation may extend beyond one year and a portion of the transaction price can be fixed. (5) Through our total waste management (“TWM”) program, customers outsource the management of their waste compliance program to us, allowing us to organize and coordinate their waste management disposal activities and environmental compliance. TWM contracts may extend beyond one year and a portion of the transaction price can be fixed. (6) Includes site assessment, onsite treatment, project management and remedial action planning and execution. Contracts for Remediation may extend beyond one year and a portion of the transaction price can be fixed. (7) Includes services such as spill response, waste analysis and treatment and disposal planning as well as government-mandated, commercial standby oil spill compliance solutions and services that we provide to companies that store, transport, produce or handle petroleum and certain nonpetroleum oils on or near U.S. waters. Our standby services customers pay annual retainer fees under long-term or evergreen contracts for access to our regulatory certifications, specialized assets and highly trained personnel. When a customer with a retainer contract experiences a spill incident, we coordinate and manage the spill response, which results in incremental revenue for the services provided, in addition to the retainer fees. (8) Includes equipment rental and other miscellaneous services. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2021 ​ Three Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services Waste Total Solutions Services Waste Total United States ​ $ 96,200 ​ $ 117,762 ​ $ 10,399 ​ $ 224,361 ​ $ 89,481 ​ $ 119,611 ​ $ 5,178 ​ $ 214,270 Canada ​ ​ 19,001 ​ ​ 1,453 ​ ​ — ​ ​ 20,454 ​ ​ 17,768 ​ ​ 990 ​ ​ — ​ ​ 18,758 EMEA ​ ​ — ​ ​ 11,123 ​ ​ — ​ ​ 11,123 ​ ​ — ​ ​ 4,195 ​ ​ — ​ ​ 4,195 Other (1) ​ — ​ 1,244 ​ — ​ 1,244 ​ — ​ 919 ​ — ​ 919 Total revenue ​ $ 115,201 ​ $ 131,582 ​ $ 10,399 ​ $ 257,182 ​ $ 107,249 ​ $ 125,715 ​ $ 5,178 ​ $ 238,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2021 ​ Nine Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ Waste ​ Field ​ Energy ​ ​ ​ $s in thousands Solutions Services Waste Total Solutions Services Waste Total United States ​ $ 272,119 ​ $ 332,329 ​ $ 24,375 ​ $ 628,823 ​ $ 266,297 ​ $ 322,831 ​ $ 29,879 ​ $ 619,007 Canada ​ ​ 55,589 ​ ​ 2,896 ​ ​ — ​ ​ 58,485 ​ ​ 53,387 ​ ​ 2,565 ​ ​ — ​ ​ 55,952 EMEA ​ ​ — ​ ​ 35,052 ​ ​ — ​ ​ 35,052 ​ ​ — ​ ​ 13,349 ​ ​ — ​ ​ 13,349 Other (1) ​ — ​ 4,214 ​ — ​ 4,214 ​ — ​ 4,472 ​ — ​ 4,472 Total revenue ​ $ 327,708 ​ $ 374,491 ​ $ 24,375 ​ $ 726,574 ​ $ 319,684 ​ $ 343,217 ​ $ 29,879 ​ $ 692,780 ​ (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions. ​

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	9 Months Ended
	Sep. 30, 2021
ACCUMULATED OTHER COMPREHENSIVE LOSS
Schedule of changes in accumulated other comprehensive income (loss)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Unrealized Gain ​ ​ ​ ​ ​ Currency ​ (Loss) on Interest ​ ​ ​ $s in thousands Translation Rate Hedge Total Balance at December 31, 2020 ​ $ (7,870) ​ $ (6,788) ​ $ (14,658) Other comprehensive (loss) income before reclassifications, net of tax ​ (1,248) ​ 6,182 ​ 4,934 Amounts reclassified out of AOCI, net of tax (1) ​ — ​ 2,380 ​ 2,380 Other comprehensive (loss) income, net ​ (1,248) ​ 8,562 ​ 7,314 Balance at September 30, 2021 ​ $ (9,118) ​ $ 1,774 ​ $ (7,344) (1) Before-tax reclassifications of $743,000 ($587,000 after-tax) and $3.0 million ($2.4 million after-tax) for the three and nine months ended September 30, 2021, were included in Interest expense in the Company’s consolidated statements of operations. Amounts relate to the Company’s interest rate swap which is designated as a cash flow hedge. Changes in fair value of the swap recognized in AOCI are reclassified to interest expense when hedged interest payments on the underlying long-term debt are made or, for terminated swap agreements, amortized to interest expense over the period from termination to original maturity. Amounts in AOCI expected to be reclassified to interest expense over the next 12 months total approximately $2.9 million ($2.3 million after-tax). ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign ​ Unrealized Gain ​ ​ ​ ​ ​ Currency ​ (Loss) on Interest ​ ​ ​ $s in thousands Translation Rate Hedge Total Balance at December 31, 2019 ​ $ (10,925) ​ $ (929) ​ $ (11,854) Other comprehensive loss before reclassifications, net of tax ​ (3,328) ​ (10,074) ​ (13,402) Amounts reclassified out of AOCI, net of tax (2) ​ — ​ 1,721 ​ 1,721 Other comprehensive loss, net ​ (3,328) ​ (8,353) ​ (11,681) Balance at September 30, 2020 ​ $ (14,253) ​ $ (9,282) ​ $ (23,535) (2) Before-tax reclassifications of $1.2 million ($921,000 after-tax) and $2.2 million ($1.7 million after-tax) for the three and nine months ended September 30, 2020, were included in Interest expense in the Company’s consolidated statements of operations. Amounts relate to the Company’s interest rate swap which is designated as a cash flow hedge. Changes in fair value of the swap recognized in AOCI are reclassified to interest expense when hedged interest payments on the underlying long-term debt are made or, for terminated swap agreements, amortized to interest expense over the period from termination to original maturity.

RECEIVABLES (Tables)

RECEIVABLES (Tables)	9 Months Ended
	Sep. 30, 2021
RECEIVABLES
Schedule of receivables	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands ​ 2021 2020 Trade ​ $ 198,948 ​ $ 186,502 Unbilled revenue ​ 61,320 ​ 52,858 Other ​ 4,458 ​ 5,554 Total receivables ​ 264,726 ​ 244,914 Allowance for credit losses ​ (3,598) ​ (2,936) Receivables, net ​ $ 261,128 ​ $ 241,978

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
FAIR VALUE MEASUREMENTS
Schedule of assets and liabilities measured at fair value on a recurring basis	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 ​ ​ Quoted Prices in ​ Other Observable ​ Unobservable ​ ​ ​ ​ ​ Active Markets ​ Inputs ​ Inputs ​ ​ ​ $s in thousands (Level 1) (Level 2) (Level 3) Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fixed-income securities (1) ​ $ 1,708 ​ $ 455 ​ $ — ​ $ 2,163 Money market funds (2) ​ ​ 1,657 ​ ​ — ​ ​ — ​ ​ 1,657 Interest rate swap agreement (3) ​ ​ — ​ ​ 606 ​ ​ — ​ ​ 606 Total ​ $ 3,365 ​ $ 1,061 ​ $ — ​ $ 4,426 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Quoted Prices in ​ Other Observable ​ Unobservable ​ ​ ​ ​ ​ Active Markets ​ Inputs ​ Inputs ​ ​ ​ $s in thousands (Level 1) (Level 2) (Level 3) Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fixed-income securities (1) ​ $ 2,914 ​ $ 1,427 ​ $ — ​ $ 4,341 Money market funds (2) ​ ​ 1,319 ​ ​ — ​ ​ — ​ ​ 1,319 Total ​ $ 4,233 ​ $ 1,427 ​ $ — ​ $ 5,660 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Interest rate swap agreement (3) ​ $ — ​ $ 9,744 ​ $ — ​ $ 9,744 Contingent consideration (4) ​ ​ — ​ ​ — ​ ​ 2,173 ​ ​ 2,173 Total ​ $ — ​ $ 9,744 ​ $ 2,173 ​ $ 11,917 (1) We invest a portion of our Restricted cash and investments in fixed-income securities, including U.S. Treasury and U.S. agency securities. We measure the fair value of U.S. Treasury securities using quoted prices for identical assets in active markets. We measure the fair value of U.S. agency securities using observable market activity for similar assets. The fair value of our fixed-income securities approximates our cost basis in the investments. ​ (2) We invest portions of our Cash and cash equivalents and Restricted cash and investments in money market funds. We measure the fair value of these money market fund investments using quoted prices for identical assets in active markets. The portion of Restricted cash and investments that is invested in money market funds is considered restricted cash for purposes of reconciling the beginning-of-period and end-of-period amounts presented in the Company’s consolidated statements of cash flows. ​ (3) In order to manage interest rate exposure, we entered into an interest rate swap agreement in March 2020 that effectively converts a portion of our variable-rate debt to a fixed interest rate. The swap is designated as a highly-effective cash flow hedge, with gains and losses deferred in other comprehensive income to be recognized as an adjustment to interest expense in the same period that the hedged interest payments affect earnings. The interest rate swap has an effective date of March 31, 2020 in an initial notional amount of $500.0 million. The fair value of the interest rate swap agreement represents the difference in the present value of cash flows calculated (i) at the contracted interest rates and (ii) at current market interest rates at the end of the period. We calculate the fair value of interest rate swap agreements quarterly based on the quoted market price for the same or similar financial instruments. The fair value of the interest rate swap agreement is included in Other assets and Other long-term liabilities in the Company’s consolidated balance sheets as of September 30, 2021 and December 31, 2020, respectively. ​ (4) Our contingent consideration liabilities represent the estimated fair value of potential future payments the Company may be required to remit under the terms of historical purchase agreements entered into by NRC Group Holdings Corp. (“NRC”) prior to the Company’s acquisition of NRC (“NRC Merger”). The payments are contingent on the acquired businesses’ achievement of annual earnings targets in certain years and other events considered in the purchase agreements. The fair value of our contingent consideration liabilities is calculated using either a Monte Carlo simulation or modified Black-Scholes analyses based on earnings projections for the respective earn-out periods, corresponding earnings thresholds, and approximate timing of payments as outlined in the purchase agreements. The analyses utilize the following assumptions: (i) expected term; (ii) risk-adjusted net sales or earnings; (iii) risk-free interest rate; and (iv) expected volatility of earnings. Estimated payments, as determined through the respective models, are discounted by a credit spread assumption to account for credit risk. As of September 30, 2021, we have settled all acquired contingent consideration liabilities associated with the NRC Merger. The fair value of our contingent consideration liability as of December 31, 2020 was $2.2 million and is included in Accrued liabilities in the Company’s consolidated balance sheet. We revalue our contingent consideration payments each period and any increases or decreases to fair value are included in Selling, general and administrative expenses in our consolidated statements of operations. Fair values may be impacted by certain unobservable inputs, most significantly with regard to discount rates, expected volatility and historical and projected performance. Significant changes to these inputs in isolation could result in a significantly different fair value measurement.
Schedule of changes in Level 3 liabilities measured at fair value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended $s in thousands September 30, 2021 September 30, 2021 Contingent consideration, beginning of period ​ $ — ​ $ 2,173 Change in fair value of contingent consideration ​ — ​ 282 Contingent consideration paid ​ ​ — ​ ​ (2,553) Foreign currency translation ​ — ​ 98 Contingent consideration, end of period ​ $ — ​ $ —

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	9 Months Ended
	Sep. 30, 2021
PROPERTY AND EQUIPMENT
Schedule of property and equipment	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands ​ 2021 2020 Cell development costs ​ $ 201,382 ​ $ 186,170 Land and improvements ​ 74,198 ​ 65,953 Buildings and improvements ​ 131,119 ​ 128,206 Railcars ​ 17,299 ​ 17,299 Vehicles, vessels and other equipment ​ 337,909 ​ 331,167 Construction in progress ​ 56,357 ​ 44,840 Total property and equipment ​ 818,264 ​ 773,635 Accumulated depreciation and amortization ​ (367,544) ​ (316,998) Property and equipment, net ​ $ 450,720 ​ $ 456,637

LEASES (Tables)

LEASES (Tables)	9 Months Ended
	Sep. 30, 2021
LEASES
Summary of leased assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands 2021 2020 Assets: ​ ​ ​ ​ ​ ​ Operating right-of-use assets (1) ​ $ 44,947 ​ $ 51,474 Finance right-of-use assets (2) ​ ​ 18,601 ​ ​ 21,209 Total ​ $ 63,548 ​ $ 72,683 ​ ​ ​ ​ ​ ​ ​ Liabilities: ​ ​ ​ ​ ​ ​ Current: ​ ​ ​ ​ ​ ​ Operating (3) ​ $ 15,114 ​ $ 17,048 Finance (4) ​ ​ 4,974 ​ ​ 4,462 Long-term: ​ ​ ​ ​ ​ ​ Operating (5) ​ ​ 30,739 ​ ​ 35,069 Finance (6) ​ ​ 13,339 ​ ​ 17,501 Total ​ $ 64,166 ​ $ 74,080 (1) Included in Operating lease assets in the Company’s consolidated balance sheets. (2) Included in Property and equipment, net in the Company’s consolidated balance sheets. Finance right-of-use assets are recorded net of accumulated amortization of $12.0 million and $8.0 million as of September 30, 2021 and December 31, 2020, respectively. (3) Included in Current portion of operating lease liabilities in the Company’s consolidated balance sheets. (4) Included in Accrued liabilities in the Company’s consolidated balance sheets. (5) Included in Long-term operating lease liabilities in the Company’s consolidated balance sheets. (6) Included in Other long-term liabilities in the Company’s consolidated balance sheets.
Summary of lease cost	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, $s in thousands 2021 2020 2021 2020 Operating lease cost (1) ​ $ 4,853 ​ $ 5,008 ​ $ 15,172 ​ $ 14,947 Finance lease cost: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization of leased assets (2) ​ ​ 1,311 ​ ​ 1,330 ​ ​ 3,947 ​ ​ 3,974 Interest on lease liabilities (3) ​ ​ 233 ​ ​ 292 ​ ​ 786 ​ ​ 925 Total ​ $ 6,397 ​ $ 6,630 ​ $ 19,905 ​ $ 19,846 (1) Included in Direct operating costs and Selling, general, and administrative expenses in the Company’s consolidated statements of operations. Operating lease cost includes short-term leases, excluding expenses relating to leases with a term of one month or less, which are not material. Operating lease cost excludes variable lease costs which are not material. (2) Included in Direct operating costs in the Company’s consolidated statements of operations. (3) Included in Interest expense in the Company’s consolidated statements of operations.
Schedule of cash flow supplemental information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, $s in thousands 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: ​ ​ ​ ​ ​ ​ Operating cash flows from operating leases ​ $ 14,749 ​ $ 14,547 Operating cash flows from finance leases ​ $ 786 ​ $ 925 Financing cash flows from finance leases ​ $ 3,649 ​ $ 3,457 ​ ​ ​ ​ ​ ​ ​ Non-cash investing and financing activities: ​ ​ ​ ​ ​ ​ Right-of-use assets obtained in exchange for new operating lease liabilities ​ $ 7,092 ​ $ 7,195 Right-of-use assets obtained in exchange for new finance lease liabilities ​ $ — ​ $ 6,089

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2021
GOODWILL AND INTANGIBLE ASSETS
Schedule of changes in goodwill	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Waste Solutions ​ Field Services ​ Energy Waste ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ Accumulated ​ ​ ​ Accumulated ​ ​ ​ $s in thousands Gross Impairment Gross Impairment Gross Impairment Total Balance at December 31, 2020 ​ $ 166,863 ​ $ (6,870) ​ $ 237,341 ​ $ (19,900) ​ $ 399,503 ​ $ (363,900) ​ $ 413,037 Foreign currency translation ​ 44 ​ ​ — ​ 20 ​ ​ — ​ ​ — ​ ​ — ​ 64 Balance at September 30, 2021 ​ $ 166,907 ​ $ (6,870) ​ $ 237,361 ​ $ (19,900) ​ $ 399,503 ​ $ (363,900) ​ $ 413,101
Schedule of intangible assets, net	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ $s in thousands Cost Amortization Net Cost Amortization Net Amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Permits, licenses and lease ​ $ 174,940 ​ $ (26,127) ​ $ 148,813 ​ $ 174,885 ​ $ (23,005) ​ $ 151,880 Customer relationships ​ ​ 340,056 ​ ​ (81,407) ​ ​ 258,649 ​ ​ 340,032 ​ ​ (61,778) ​ ​ 278,254 Technology - formulae and processes ​ 7,159 ​ (2,471) ​ 4,688 ​ 7,142 ​ (2,293) ​ 4,849 Customer backlog ​ 3,652 ​ (2,661) ​ 991 ​ 3,652 ​ (2,387) ​ 1,265 Tradename ​ 10,390 ​ ​ (10,153) ​ ​ 237 ​ 10,390 ​ ​ (8,015) ​ ​ 2,375 Developed software ​ ​ 2,902 ​ ​ (2,402) ​ ​ 500 ​ ​ 2,902 ​ ​ (2,182) ​ ​ 720 Non-compete agreements ​ 5,572 ​ (5,171) ​ 401 ​ 5,571 ​ (4,318) ​ 1,253 Internet domain and website ​ ​ 536 ​ ​ (206) ​ ​ 330 ​ ​ 536 ​ ​ (184) ​ ​ 352 Database ​ ​ 390 ​ ​ (230) ​ ​ 160 ​ ​ 389 ​ ​ (214) ​ ​ 175 Total amortizing intangible assets ​ 545,597 ​ (130,828) ​ 414,769 ​ 545,499 ​ (104,376) ​ 441,123 Non-amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Permits and licenses ​ 82,733 ​ ​ — ​ 82,733 ​ 82,732 ​ ​ — ​ 82,732 Tradename ​ 134 ​ ​ — ​ ​ 134 ​ 133 ​ ​ — ​ ​ 133 Total intangible assets ​ $ 628,464 ​ $ (130,828) ​ $ 497,636 ​ $ 628,364 ​ $ (104,376) ​ $ 523,988

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2021
DEBT
Schedule of long-term debt	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands 2021 2020 Revolving credit facility ​ $ 321,000 ​ $ 347,000 Term loan ​ ​ 442,125 ​ ​ 445,500 Unamortized term loan discount and debt issuance costs ​ ​ (5,801) ​ ​ (6,657) Total debt ​ ​ 757,324 ​ ​ 785,843 Current portion of long-term debt ​ ​ (3,359) ​ ​ (3,359) Long-term debt ​ $ 753,965 ​ $ 782,484
Schedule of future maturities of long-term debt, excluding the unamortized discount and debt issuance costs	​ ​ ​ ​ ​ $s in thousands Maturities 2021 (excluding the nine months ended September 30, 2021) ​ $ 1,125 2022 ​ ​ 4,500 2023 ​ ​ 4,500 2024 ​ ​ 4,500 2025 ​ ​ 4,500 Thereafter ​ ​ 744,000 ​ ​ $ 763,125
Schedule of interest margins based on the total net leverage ratio	​ ​ ​ ​ Consolidated Total Net Leverage Ratio LIBOR Rate Loans Interest Margin Base Rate Loans Interest Margin Equal to or greater than 4.50 to 1.00 2.50% 1.50% Equal to or greater than 4.00 to 1.00, but less than 4.50 to 1.00 2.25% 1.25% Equal to or greater than 3.25 to 1.00, but less than 4.00 to 1.00 2.00% 1.00% Equal to or greater than 2.50 to 1.00, but less than 3.25 to 1.00 1.75% 0.75% Equal to or greater than 1.75 to 1.00, but less than 2.50 to 1.00 1.50% 0.50% Equal to or greater than 1.00 to 1.00, but less than 1.75 to 1.00 1.25% 0.25% Less than 1.00 to 1.00 1.00% 0.00%

CLOSURE AND POST-CLOSURE OBLI_2

CLOSURE AND POST-CLOSURE OBLIGATIONS (Tables)	9 Months Ended
	Sep. 30, 2021
CLOSURE AND POST-CLOSURE OBLIGATIONS
Schedule of changes to reported closure and post closure obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended $s in thousands September 30, 2021 ​ September 30, 2021 Closure and post-closure obligations, beginning of period ​ $ 97,524 ​ $ 95,869 Accretion expense ​ 1,198 ​ 3,571 Payments ​ (337) ​ (1,104) Foreign currency translation ​ (44) ​ 5 Closure and post-closure obligations, end of period ​ 98,341 ​ 98,341 Less current portion ​ (8,234) ​ (8,234) Long-term portion ​ $ 90,107 ​ $ 90,107

EARNINGS (LOSS) PER SHARE (Tabl

EARNINGS (LOSS) PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2021
EARNINGS (LOSS) PER SHARE
Schedule of earnings (loss) per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ ​ 2021 ​ 2020 $s and shares in thousands, except per share amounts Basic Diluted Basic Diluted Net income ​ $ 6,732 ​ $ 6,732 ​ $ 6,319 ​ $ 6,319 Weighted average basic shares outstanding ​ 31,151 ​ 31,151 ​ 31,069 ​ 31,069 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Dilutive effect of share-based awards and warrants ​ ​ ​ ​ 249 ​ ​ ​ ​ 255 Weighted average diluted shares outstanding ​ ​ ​ ​ 31,400 ​ ​ ​ ​ 31,324 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings per share ​ $ 0.22 ​ $ 0.21 ​ $ 0.20 ​ $ 0.20 Anti-dilutive shares excluded from calculation ​ ​ ​ ​ 4,404 ​ ​ ​ ​ 4,233 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ 2021 ​ 2020 $s and shares in thousands, except per share amounts Basic Diluted Basic Diluted Net income (loss) ​ $ 1,773 ​ $ 1,773 ​ $ (296,950) ​ $ (296,950) Weighted average basic shares outstanding ​ 31,131 ​ 31,131 ​ 31,142 ​ 31,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Dilutive effect of share-based awards ​ ​ ​ ​ 246 ​ ​ ​ ​ — Weighted average diluted shares outstanding ​ ​ ​ ​ 31,377 ​ ​ ​ ​ 31,142 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Earnings (loss) per share ​ $ 0.06 ​ $ 0.06 ​ $ (9.54) ​ $ (9.54) Anti-dilutive shares excluded from calculation ​ ​ ​ ​ 4,333 ​ ​ ​ ​ 4,208

EQUITY (Tables)

EQUITY (Tables)	9 Months Ended
	Sep. 30, 2021
EQUITY
Summary of PSU, restricted stock and RSU activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ PSUs ​ Restricted Stock ​ RSUs ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ Average ​ ​ ​ Average ​ ​ ​ ​ Grant Date ​ ​ ​ Grant Date ​ ​ ​ Grant Date ​ Shares Fair Value Shares Fair Value Shares Fair Value Outstanding as of December 31, 2020 86,070 ​ $ 49.45 72,766 ​ $ 51.47 ​ 147,243 ​ $ 39.92 Granted — ​ ​ — 84,800 ​ ​ 36.49 ​ 62,759 ​ ​ 39.33 Vested (14,100) ​ 63.56 (47,002) ​ 47.08 ​ (55,876) ​ 42.03 Cancelled, expired or forfeited — ​ — — ​ — ​ (13,453) ​ 44.57 Outstanding as of September 30, 2021 71,970 ​ $ 46.69 110,564 ​ $ 41.85 ​ 140,673 ​ $ 38.38
Summary of stock option activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ ​ ​ Exercise ​ Shares Price Outstanding as of December 31, 2020 357,033 ​ $ 49.93 Granted 205,800 ​ ​ 35.30 Outstanding as of September 30, 2021 562,833 ​ $ 44.58 Exercisable as of September 30, 2021 299,568 ​ $ 48.29

OPERATING SEGMENTS (Tables)

OPERATING SEGMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
OPERATING SEGMENTS
Summary of financial information of our reportable segments	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 115,201 ​ $ 131,582 ​ $ 10,399 ​ $ — ​ $ 257,182 Depreciation, amortization and accretion ​ $ 10,500 ​ $ 11,062 ​ $ 5,334 ​ $ 786 ​ $ 27,682 Capital expenditures ​ $ 10,693 ​ $ 6,221 ​ $ 481 ​ $ 1,521 ​ $ 18,916 Total assets ​ $ 786,686 ​ $ 749,617 ​ $ 215,997 ​ $ 66,623 ​ $ 1,818,923 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 107,249 ​ $ 125,715 ​ $ 5,178 ​ $ — ​ $ 238,142 Depreciation, amortization and accretion ​ $ 10,377 ​ $ 12,129 ​ $ 5,566 ​ $ 820 ​ $ 28,892 Capital expenditures ​ $ 5,189 ​ $ 2,531 ​ $ 1,270 ​ $ 177 ​ $ 9,167 Total assets ​ $ 754,235 ​ $ 859,511 ​ $ 234,992 ​ $ 97,557 ​ $ 1,946,295 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2021 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 327,708 ​ $ 374,491 ​ $ 24,375 ​ $ — ​ $ 726,574 Depreciation, amortization and accretion ​ $ 32,905 ​ $ 33,794 ​ $ 15,108 ​ $ 2,360 ​ $ 84,167 Capital expenditures ​ $ 31,553 ​ $ 10,426 ​ $ 1,233 ​ $ 2,135 ​ $ 45,347 Total assets ​ $ 786,686 ​ $ 749,617 ​ $ 215,997 ​ $ 66,623 ​ $ 1,818,923 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Waste ​ Field ​ Energy ​ ​ ​ ​ ​ ​ $s in thousands Solutions Services Waste Corporate Total Revenue ​ $ 319,684 ​ $ 343,217 ​ $ 29,879 ​ $ — ​ $ 692,780 Depreciation, amortization and accretion ​ $ 31,119 ​ $ 36,420 ​ $ 16,729 ​ $ 2,187 ​ $ 86,455 Capital expenditures ​ $ 22,343 ​ $ 12,997 ​ $ 5,719 ​ $ 4,065 ​ $ 45,124 Total assets ​ $ 754,235 ​ $ 859,511 ​ $ 234,992 ​ $ 97,557 ​ $ 1,946,295
Reconciliation of Net income (loss) to Adjusted EBITDA and adjusted EBITDA by operating segment	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, $s in thousands 2021 2020 2021 2020 Net income (loss) ​ $ 6,732 ​ $ 6,319 ​ $ 1,773 ​ $ (296,950) Income tax expense (benefit) ​ ​ 2,535 ​ ​ (1,456) ​ ​ 1,348 ​ ​ 542 Interest expense ​ ​ 7,144 ​ ​ 7,964 ​ ​ 22,022 ​ ​ 25,127 Interest income ​ ​ (485) ​ ​ (9) ​ ​ (1,148) ​ ​ (251) Foreign currency (gain) loss ​ ​ (341) ​ ​ 421 ​ ​ 385 ​ ​ 155 Other income ​ ​ (114) ​ ​ (86) ​ ​ (4,020) ​ ​ (382) Goodwill impairment charges ​ ​ — ​ ​ — ​ ​ — ​ ​ 300,300 Depreciation and amortization of plant and equipment ​ ​ 17,898 ​ ​ 18,435 ​ ​ 54,095 ​ ​ 54,831 Amortization of intangible assets ​ ​ 8,586 ​ ​ 9,178 ​ ​ 26,501 ​ ​ 27,812 Share-based compensation ​ ​ 1,713 ​ ​ 1,773 ​ ​ 5,748 ​ ​ 4,861 Accretion and non-cash adjustment of closure & post-closure liabilities ​ ​ 1,198 ​ ​ 1,279 ​ ​ 3,571 ​ ​ 3,812 Business development and integration expenses ​ ​ 523 ​ ​ 1,627 ​ ​ 2,528 ​ ​ 7,507 Adjusted EBITDA ​ $ 45,389 ​ $ 45,445 ​ $ 112,803 ​ $ 127,364 ​ Adjusted EBITDA, by operating segment, is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, Nine Months Ended September 30, $s in thousands ​ 2021 2020 ​ 2021 2020 Waste Solutions $ 43,439 ​ $ 45,556 $ 123,528 ​ $ 134,540 Field Services 21,507 ​ 24,362 55,810 ​ 57,869 Energy Waste ​ ​ 3,497 ​ ​ 90 ​ ​ 7,063 ​ ​ 4,163 Corporate (23,054) ​ (24,563) (73,598) ​ (69,208) Total $ 45,389 ​ $ 45,445 $ 112,803 ​ $ 127,364
Schedule of long-lived assets by geographic location	​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, $s in thousands ​ 2021 2020 United States ​ $ 856,670 ​ $ 882,639 Canada ​ 65,616 ​ 68,623 EMEA ​ ​ 15,946 ​ ​ 18,042 Other (1) ​ ​ 10,124 ​ ​ 11,321 Total long-lived assets, net ​ $ 948,356 ​ $ 980,625 (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions.

REVENUES (Details)

REVENUES (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)segment	Sep. 30, 2020USD ($)
Disaggregation of revenue
Number of reportable segments | segment			3
Revenue	$ 257,182	$ 238,142	$ 726,574	$ 692,780
Treatment and disposal
Disaggregation of revenue
Revenue	115,070	105,087	324,697	315,975
Transportation and Logistics
Disaggregation of revenue
Revenue	31,134	31,067	83,383	82,338
Industrial Services
Disaggregation of revenue
Revenue	30,327	29,169	90,034	89,097
Small Quantity Generation
Disaggregation of revenue
Revenue	14,629	13,056	41,311	35,292
Total Waste Management
Disaggregation of revenue
Revenue	9,597	9,998	29,840	25,315
Remediation
Disaggregation of revenue
Revenue	16,310	6,733	40,055	21,911
Emergency Response
Disaggregation of revenue
Revenue	34,532	37,993	102,444	103,756
Other Services
Disaggregation of revenue
Revenue	5,583	5,039	14,810	19,096
Operating Segment | Environmental Services
Disaggregation of revenue
Revenue	115,201	107,249	327,708	319,684
Operating Segment | Field & Industrial Services
Disaggregation of revenue
Revenue	131,582	125,715	374,491	343,217
Operating Segment | Energy Waste
Disaggregation of revenue
Revenue	10,399	5,178	24,375	29,879
Operating Segment | Treatment and disposal | Environmental Services
Disaggregation of revenue
Revenue	92,867	88,601	270,906	266,129
Operating Segment | Treatment and disposal | Field & Industrial Services
Disaggregation of revenue
Revenue	15,940	13,861	39,143	33,744
Operating Segment | Treatment and disposal | Energy Waste
Disaggregation of revenue
Revenue	6,263	2,625	14,648	16,102
Operating Segment | Transportation and Logistics | Environmental Services
Disaggregation of revenue
Revenue	22,334	18,648	56,802	53,555
Operating Segment | Transportation and Logistics | Field & Industrial Services
Disaggregation of revenue
Revenue	6,483	11,162	21,169	22,577
Operating Segment | Transportation and Logistics | Energy Waste
Disaggregation of revenue
Revenue	2,317	1,257	5,412	6,206
Operating Segment | Industrial Services | Field & Industrial Services
Disaggregation of revenue
Revenue	29,597	28,464	88,193	85,529
Operating Segment | Industrial Services | Energy Waste
Disaggregation of revenue
Revenue	730	705	1,841	3,568
Operating Segment | Small Quantity Generation | Field & Industrial Services
Disaggregation of revenue
Revenue	14,629	13,056	41,311	35,292
Operating Segment | Total Waste Management | Field & Industrial Services
Disaggregation of revenue
Revenue	9,597	9,998	29,840	25,315
Operating Segment | Remediation | Field & Industrial Services
Disaggregation of revenue
Revenue	16,310	6,733	40,055	21,911
Operating Segment | Emergency Response | Field & Industrial Services
Disaggregation of revenue
Revenue	34,532	37,993	102,444	103,756
Operating Segment | Other Services | Field & Industrial Services
Disaggregation of revenue
Revenue	4,494	4,448	12,336	15,093
Operating Segment | Other Services | Energy Waste
Disaggregation of revenue
Revenue	$ 1,089	$ 591	$ 2,474	$ 4,003

REVENUES - Treatment and Dispos

REVENUES - Treatment and Disposal Revenue (Details) - Treatment and disposal - T	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Event Business
Disaggregation of revenue
Threshold Tons of Non-recurring projects			1,000
Revenue (in percent)	24.00%	30.00%	24.00%	28.00%
Base Business
Disaggregation of revenue
Revenue (in percent)	76.00%	70.00%	76.00%	72.00%

REVENUES - Geography (Details)

REVENUES - Geography (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of revenue
Revenue	$ 257,182	$ 238,142	$ 726,574	$ 692,780
United States
Disaggregation of revenue
Revenue	224,361	214,270	628,823	619,007
Canada
Disaggregation of revenue
Revenue	20,454	18,758	58,485	55,952
EMEA
Disaggregation of revenue
Revenue	11,123	4,195	35,052	13,349
Other
Disaggregation of revenue
Revenue	1,244	919	4,214	4,472
Operating Segment | Environmental Services
Disaggregation of revenue
Revenue	115,201	107,249	327,708	319,684
Operating Segment | Environmental Services | United States
Disaggregation of revenue
Revenue	96,200	89,481	272,119	266,297
Operating Segment | Environmental Services | Canada
Disaggregation of revenue
Revenue	19,001	17,768	55,589	53,387
Operating Segment | Field & Industrial Services
Disaggregation of revenue
Revenue	131,582	125,715	374,491	343,217
Operating Segment | Field & Industrial Services | United States
Disaggregation of revenue
Revenue	117,762	119,611	332,329	322,831
Operating Segment | Field & Industrial Services | Canada
Disaggregation of revenue
Revenue	1,453	990	2,896	2,565
Operating Segment | Field & Industrial Services | EMEA
Disaggregation of revenue
Revenue	11,123	4,195	35,052	13,349
Operating Segment | Field & Industrial Services | Other
Disaggregation of revenue
Revenue	1,244	919	4,214	4,472
Operating Segment | Energy Waste
Disaggregation of revenue
Revenue	10,399	5,178	24,375	29,879
Operating Segment | Energy Waste | United States
Disaggregation of revenue
Revenue	$ 10,399	$ 5,178	$ 24,375	$ 29,879

REVENUES - Practical Expedients

REVENUES - Practical Expedients (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
REVENUES
Contract with Customer, Liability, Revenue Recognized	$ 405	$ 735	$ 13,700	$ 13,600
Revenue, Practical Expedient, Financing Component			true
Revenue, Practical Expedient, Initial Application and Transition, Nonrestatement of Modified Contract			true

BUSINESS COMBINATIONS - 2020 (D

BUSINESS COMBINATIONS - 2020 (Details) - USD ($)	Jan. 28, 2020	Sep. 30, 2021	Dec. 31, 2020
Acquisition
Goodwill		$ 413,101,000	$ 413,037,000
Impact Environmental Services Inc
Acquisition
Total purchase price	$ 3,300,000
Goodwill	300,000
Identifiable intangible assets	$ 900,000
Weighted average amortization period	12 years
Amortization period of goodwill recognized and expected to be deductible for income tax purposes	15 years

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated other comprehensive income (loss)
Beginning balances	$ 609,583	$ 672,947	$ 601,931	$ 1,011,380
Ending balances	615,973	683,789	615,973	683,789
Foreign Currency Translation
Accumulated other comprehensive income (loss)
Beginning balances			(7,870)	(10,925)
Other comprehensive income (loss) before reclassifications, net of tax			(1,248)	(3,328)
Other comprehensive income (loss), net			(1,248)	(3,328)
Ending balances	(9,118)	(14,253)	(9,118)	(14,253)
Unrealized Gain (Loss) on Interest Rate Hedge
Accumulated other comprehensive income (loss)
Beginning balances			(6,788)	(929)
Other comprehensive income (loss) before reclassifications, net of tax			6,182	(10,074)
Amounts reclassified out of AOCI, net of tax			2,380	1,721
Other comprehensive income (loss), net			8,562	(8,353)
Ending balances	1,774	(9,282)	1,774	(9,282)
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss)
Beginning balances	(5,201)	(26,197)	(14,658)	(11,854)
Other comprehensive income (loss) before reclassifications, net of tax			4,934	(13,402)
Amounts reclassified out of AOCI, net of tax			2,380	1,721
Other comprehensive income (loss), net	(2,143)	2,662	7,314	(11,681)
Ending balances	$ (7,344)	$ (23,535)	$ (7,344)	$ (23,535)

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE LOSS -Reclassifications Line Items (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reclassification adjustments
Interest expense	$ 7,144	$ 7,964	$ 22,022	$ 25,127
Unrealized Gain (Loss) on Interest Rate Hedge | Interest rate swap agreement
Reclassification adjustments
Amounts in AOCI expected to be recognized over the next 12 months before tax	2,900		2,900
Amounts in AOCI expected to be recognized over the next 12 months, net of taxes	2,300		2,300
Unrealized Gain (Loss) on Interest Rate Hedge | Interest rate swap agreement | Reclassification out of accumulated other comprehensive income
Reclassification adjustments
Interest expense	743	1,200	3,000	2,200
Interest expense, net of tax	$ 587	$ 921	$ 2,400	$ 1,700

RECEIVABLES (Details)

RECEIVABLES (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
RECEIVABLES
Trade	$ 198,948	$ 186,502
Unbilled revenue	61,320	52,858
Other	4,458	5,554
Total receivables	264,726	244,914
Allowance for credit losses	(3,598)	(2,936)
Receivables, net	$ 261,128	$ 241,978

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	1 Months Ended		9 Months Ended
	Mar. 31, 2021	Sep. 30, 2019	Sep. 30, 2021	Dec. 31, 2020	Mar. 31, 2020
Assets measured at fair value on a recurring basis
Initial notional amount					$ 500,000
Equity securities without readily determinable fair value
Investment in privately held company			$ 712
Investment in privately held company				$ 7,900
Variable rate			441,800
Interest rate swap agreement
Assets measured at fair value on a recurring basis
Initial notional amount					$ 450,000
Preferred Stock
Equity securities without readily determinable fair value
Fair value change	$ 3,500
Gain on investment	3,500
Preferred Stock | Other Assets
Equity securities without readily determinable fair value
Investment in privately held company	$ 712	$ 7,900
Level 3 | Contingent Consideration | Accrued Liabilities
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure				2,200
Recurring
Assets measured at fair value on a recurring basis
Assets fair value disclosure			4,426	5,660
Liabilities fair value disclosure				11,917
Recurring | Interest rate swap agreement
Assets measured at fair value on a recurring basis
Assets fair value disclosure			606
Liabilities fair value disclosure				9,744
Recurring | Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure			2,163	4,341
Recurring | Money market funds
Assets measured at fair value on a recurring basis
Assets fair value disclosure			1,657	1,319
Recurring | Contingent Consideration
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure				2,173
Recurring | Quoted Prices in Active Markets (Level 1)
Assets measured at fair value on a recurring basis
Assets fair value disclosure			3,365	4,233
Recurring | Quoted Prices in Active Markets (Level 1) | Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure			1,708	2,914
Recurring | Quoted Prices in Active Markets (Level 1) | Money market funds
Assets measured at fair value on a recurring basis
Assets fair value disclosure			1,657	1,319
Recurring | Other Observable Inputs (Level 2)
Assets measured at fair value on a recurring basis
Assets fair value disclosure			1,061	1,427
Liabilities fair value disclosure				9,744
Recurring | Other Observable Inputs (Level 2) | Interest rate swap agreement
Assets measured at fair value on a recurring basis
Assets fair value disclosure			606
Liabilities fair value disclosure				9,744
Recurring | Other Observable Inputs (Level 2) | Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure			$ 455	1,427
Recurring | Level 3
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure				2,173
Recurring | Level 3 | Contingent Consideration
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure				$ 2,173

FAIR VALUE MEASUREMENTS - Chang

FAIR VALUE MEASUREMENTS - Changes in Level 3 liabilities measured at fair value (Details) - Level 3 - Recurring $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, beginning of period	$ 2,173
Change in fair value of contingent consideration	282
Contingent consideration paid	(2,553)
Foreign currency translation	$ 98

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
PROPERTY AND EQUIPMENT
Total property and equipment	$ 818,264		$ 818,264		$ 773,635
Accumulated depreciation and amortization	(367,544)		(367,544)		(316,998)
Property and equipment, net	450,720		450,720		456,637
Depreciation and amortization of plant and equipment	17,898	$ 18,435	54,095	$ 54,831
Cell development costs
PROPERTY AND EQUIPMENT
Total property and equipment	201,382		201,382		186,170
Land and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	74,198		74,198		65,953
Buildings and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	131,119		131,119		128,206
Railcars
PROPERTY AND EQUIPMENT
Total property and equipment	17,299		17,299		17,299
Vehicles, vessels and other equipment
PROPERTY AND EQUIPMENT
Total property and equipment	337,909		337,909		331,167
Construction in progress
PROPERTY AND EQUIPMENT
Total property and equipment	$ 56,357		$ 56,357		$ 44,840

LEASES (Details)

LEASES (Details)	9 Months Ended
	Sep. 30, 2021
Leases
Operating lease - existence of option to renew	true
Finance lease - existence of option to renew	true
Minimum
Leases
Operating lease - term	1 year
Finance lease - term	1 year
Maximum
Leases
Operating lease - term	15 years
Operating lease - renewal term	40 years
Finance lease - term	15 years
Finance lease - renewal term	40 years

LEASES - Leased assets and liab

LEASES - Leased assets and liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Operating lease assets	$ 44,947	$ 51,474
Finance right-of-use lease assets	18,601	21,209
Total	63,548	72,683
Finance leased assets - accumulated amortization	12,000	8,000
Liabilities:
Operating lease, current	15,114	17,048
Finance lease, current	4,974	4,462
Long-term operating lease liabilities	30,739	35,069
Finance lease, long term	13,339	17,501
Total	$ 64,166	$ 74,080

LEASES - Lease cost (Details)

LEASES - Lease cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Lease cost
Operating lease cost	$ 4,853	$ 5,008	$ 15,172	$ 14,947
Amortization of leased assets	1,311	1,330	3,947	3,974
Interest on lease liabilities	233	292	786	925
Total	$ 6,397	$ 6,630	$ 19,905	$ 19,846

LEASES - Supplemental Cash Flow

LEASES - Supplemental Cash Flow information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
LEASES
Operating cash flows from operating leases	$ 14,749	$ 14,547
Operating cash flows from finance leases	786	925
Financing cash flows from finance leases	3,649	3,457
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 7,092	7,195
Right-of-use assets obtained in exchange for new finance lease liabilities		$ 6,089

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Changes in goodwill
Balance at the beginning of the period	$ 413,037
Foreign currency translation	64
Balance at the end of the period	413,101
Environmental Services
Changes in goodwill
Balance at the beginning of the period	166,863
Foreign currency translation	44
Balance at the end of the period	166,907
Accumulated Impairment
Accumulated impairment at the beginning	(6,870)
Accumulated impairment at the ending	(6,870)
Field & Industrial Services
Changes in goodwill
Balance at the beginning of the period	237,341
Foreign currency translation	20
Balance at the end of the period	237,361
Accumulated Impairment
Accumulated impairment at the beginning	(19,900)
Accumulated impairment at the ending	(19,900)
Energy Waste
Changes in goodwill
Balance at the beginning of the period	399,503
Balance at the end of the period	399,503
Accumulated Impairment
Accumulated impairment at the beginning	(363,900)
Accumulated impairment at the ending	$ (363,900)

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jan. 28, 2020
Intangible Assets
Amortizing intangible assets, Cost	$ 545,597,000		$ 545,597,000		$ 545,499,000
Accumulated amortization	(130,828,000)		(130,828,000)		(104,376,000)
Amortizing intangible assets, Net	414,769,000		414,769,000		441,123,000
Total intangible assets, cost	628,464,000		628,464,000		628,364,000
Total intangible assets, net	497,636,000		497,636,000		523,988,000
Goodwill	413,101,000		413,101,000		413,037,000
Amortization of intangible assets	8,586,000	$ 9,178,000	26,501,000	$ 27,812,000
Permits and licenses
Intangible Assets
Non-amortizing intangible assets	82,733,000		82,733,000		82,732,000
Tradename
Intangible Assets
Non-amortizing intangible assets	134,000		134,000		133,000
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	174,940,000		174,940,000		174,885,000
Accumulated amortization	(26,127,000)		(26,127,000)		(23,005,000)
Amortizing intangible assets, Net	148,813,000		148,813,000		151,880,000
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	340,056,000		340,056,000		340,032,000
Accumulated amortization	(81,407,000)		(81,407,000)		(61,778,000)
Amortizing intangible assets, Net	258,649,000		258,649,000		278,254,000
Technology - Formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	7,159,000		7,159,000		7,142,000
Accumulated amortization	(2,471,000)		(2,471,000)		(2,293,000)
Amortizing intangible assets, Net	4,688,000		4,688,000		4,849,000
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652,000		3,652,000		3,652,000
Accumulated amortization	(2,661,000)		(2,661,000)		(2,387,000)
Amortizing intangible assets, Net	991,000		991,000		1,265,000
Tradename
Intangible Assets
Amortizing intangible assets, Cost	10,390,000		10,390,000		10,390,000
Accumulated amortization	(10,153,000)		(10,153,000)		(8,015,000)
Amortizing intangible assets, Net	237,000		237,000		2,375,000
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,902,000		2,902,000		2,902,000
Accumulated amortization	(2,402,000)		(2,402,000)		(2,182,000)
Amortizing intangible assets, Net	500,000		500,000		720,000
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	5,572,000		5,572,000		5,571,000
Accumulated amortization	(5,171,000)		(5,171,000)		(4,318,000)
Amortizing intangible assets, Net	401,000		401,000		1,253,000
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	536,000		536,000		536,000
Accumulated amortization	(206,000)		(206,000)		(184,000)
Amortizing intangible assets, Net	330,000		330,000		352,000
Database
Intangible Assets
Amortizing intangible assets, Cost	390,000		390,000		389,000
Accumulated amortization	(230,000)		(230,000)		(214,000)
Amortizing intangible assets, Net	$ 160,000		$ 160,000		$ 175,000
Impact Environmental Services Inc
Intangible Assets
Amortizing intangible assets, Cost						$ 900,000
Goodwill						$ 300,000

DEBT - Schedule (Details)

DEBT - Schedule (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Nov. 01, 2020
Long-term debt
Loan amount	$ 763,125
Unamortized term loan discount and debt issuance costs	(5,801)	$ (6,657)
Total debt	757,324	785,843
Current portion of long-term debt	(3,359)	(3,359)
Long-term debt	753,965	782,484
Credit agreement
Long-term debt
Loan amount	321,000	347,000
Term Loan
Long-term debt
Loan amount	$ 442,125	$ 445,500	$ 400,000

DEBT - Future Maturities (Detai

DEBT - Future Maturities (Details) $ in Thousands	Sep. 30, 2021USD ($)
Future maturities of long-term debt, excluding unamortized net discount
2021 (excluding the nine months ended September 30, 2021)	$ 1,125
2022	4,500
2023	4,500
2024	4,500
2025	4,500
Thereafter	744,000
Total	$ 763,125

DEBT - Paragraph (Details)

DEBT - Paragraph (Details) $ in Thousands	Jun. 29, 2021	Jun. 26, 2020	Nov. 01, 2019USD ($)	Aug. 06, 2019	Apr. 18, 2017USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Nov. 01, 2020USD ($)
DEBT
Loan amount							$ 763,125
Notional amount						$ 500,000
Interest rate swap agreement
DEBT
Notional amount						$ 450,000
Percentage of outstanding debt						59.00%
Net loss related to terminated swap						$ 1,800
Credit agreement
DEBT
Maximum borrowing capacity					$ 500,000
Contractual term					5 years
Accordion feature			$ 250,000
Amount outstanding							$ 321,000
Effective interest rate (as a percent)							4.03%
Loan amount							$ 321,000	$ 347,000
Availability for borrowings under line of credit							$ 62,200
Voting equity interest in foreign subsidiaries pledged as security (as a percent)					65.00%
Non-voting equity interest in foreign subsidiaries pledged as security (as a percent)					100.00%
Equity interest in domestic subsidiaries pledged as security (as a percent)					100.00%
Percentage of EBITDA plus certain additional amounts used to determine additional borrowing capacity			100.00%
Total leverage ratio		4		4
Credit agreement | Minimum
DEBT
Commitment fee (as a percent)							0.175%
Credit agreement | Maximum
DEBT
Commitment fee (as a percent)							0.40%
Credit Agreement, Letter Of Credit
DEBT
Line of credit issued in the form of a standby letters of credit							$ 14,700
Credit Agreement, Swingline Loans
DEBT
Maximum borrowing capacity			$ 40,000
Credit Agreement, Swingline Loans | Sweep Arrangements
DEBT
Maximum borrowing capacity							40,000
Amount outstanding							0
Term Loan
DEBT
Maximum borrowing capacity			$ 450,000
Contractual term			7 years
Loan amount							$ 442,125	$ 445,500	$ 400,000
Increase in capacity			$ 50,000
Required annual principal repayment (as a percent)			1.00%
Effective interest rate (as a percent)							2.87%
Term Loan | Maximum
DEBT
Commitment fee (as a percent)	0.375%
Term Loan | LIBOR
DEBT
Percentage points added to the reference rate	2.25%		2.25%
Term Loan | Base rate
DEBT
Percentage points added to the reference rate	1.25%		1.25%

DEBT - Loan Interest Margin (De

DEBT - Loan Interest Margin (Details)	Jun. 29, 2021	Nov. 01, 2019	Apr. 18, 2017	Sep. 30, 2021
Credit agreement
DEBT
Minimum consolidated senior secured leverage ratio			3
Maximum consolidated senior secured leverage ratio			4.50
Credit agreement | Maximum
DEBT
Commitment fee (as a percent)				0.40%
Credit agreement | Equal to or greater than 4.50 to 1.00
DEBT
Minimum consolidated senior secured leverage ratio	4.50		4.50
Credit agreement | Equal to or greater than 4.00 to 1.00, but less than 4.50 to 1.00
DEBT
Minimum consolidated senior secured leverage ratio	4		4
Maximum consolidated senior secured leverage ratio	4.50		4.50
Credit agreement | Equal to or greater than 3.25 to 1.00, but less than 4.00 to 1.00
DEBT
Minimum consolidated senior secured leverage ratio			3.25
Maximum consolidated senior secured leverage ratio			4
Credit agreement | Equal to or greater than 2.50 to 1.00, but less than 3.25 to 1.00
DEBT
Minimum consolidated senior secured leverage ratio			2.50
Maximum consolidated senior secured leverage ratio			3.25
Credit agreement | Equal to or greater than 1.75 to 1.00, but less than 2.50 to 1.00
DEBT
Minimum consolidated senior secured leverage ratio			1.75
Maximum consolidated senior secured leverage ratio			2.50
Credit agreement | Equal to or greater than 1.00 to 1.00, but less than 1.75 to 1.00
DEBT
Minimum consolidated senior secured leverage ratio			1
Maximum consolidated senior secured leverage ratio			1.75
Credit agreement | Less than 1.00 to 1.00
DEBT
Maximum consolidated senior secured leverage ratio			1
Credit agreement | LIBOR | Equal to or greater than 4.50 to 1.00
DEBT
Percentage points added to the reference rate			2.50%
Credit agreement | LIBOR | Equal to or greater than 4.00 to 1.00, but less than 4.50 to 1.00
DEBT
Percentage points added to the reference rate			2.25%
Credit agreement | LIBOR | Equal to or greater than 3.25 to 1.00, but less than 4.00 to 1.00
DEBT
Percentage points added to the reference rate			2.00%
Credit agreement | LIBOR | Equal to or greater than 2.50 to 1.00, but less than 3.25 to 1.00
DEBT
Percentage points added to the reference rate			1.75%
Credit agreement | LIBOR | Equal to or greater than 1.75 to 1.00, but less than 2.50 to 1.00
DEBT
Percentage points added to the reference rate			1.50%
Credit agreement | LIBOR | Equal to or greater than 1.00 to 1.00, but less than 1.75 to 1.00
DEBT
Percentage points added to the reference rate			1.25%
Credit agreement | LIBOR | Less than 1.00 to 1.00
DEBT
Percentage points added to the reference rate			1.00%
Credit agreement | Base rate | Equal to or greater than 4.50 to 1.00
DEBT
Percentage points added to the reference rate			1.50%
Credit agreement | Base rate | Equal to or greater than 4.00 to 1.00, but less than 4.50 to 1.00
DEBT
Percentage points added to the reference rate			1.25%
Credit agreement | Base rate | Equal to or greater than 3.25 to 1.00, but less than 4.00 to 1.00
DEBT
Percentage points added to the reference rate			1.00%
Credit agreement | Base rate | Equal to or greater than 2.50 to 1.00, but less than 3.25 to 1.00
DEBT
Percentage points added to the reference rate			0.75%
Credit agreement | Base rate | Equal to or greater than 1.75 to 1.00, but less than 2.50 to 1.00
DEBT
Percentage points added to the reference rate			0.50%
Credit agreement | Base rate | Equal to or greater than 1.00 to 1.00, but less than 1.75 to 1.00
DEBT
Percentage points added to the reference rate			0.25%
Credit agreement | Base rate | Less than 1.00 to 1.00
DEBT
Percentage points added to the reference rate			0.00%
Term Loan | Maximum
DEBT
Commitment fee (as a percent)	0.375%
Term Loan | Equal to or greater than 4.50 to 1.00 | Maximum
DEBT
Commitment fee (as a percent)	0.40%
Term Loan | LIBOR
DEBT
Percentage points added to the reference rate	2.25%	2.25%
Term Loan | LIBOR | Equal to or greater than 4.50 to 1.00
DEBT
Percentage points added to the reference rate	2.50%
Term Loan | LIBOR | Step Up Rate Based On Credit Ratings
DEBT
Percentage points added to the reference rate		2.50%
Term Loan | Base rate
DEBT
Percentage points added to the reference rate	1.25%	1.25%
Term Loan | Base rate | Equal to or greater than 4.50 to 1.00
DEBT
Percentage points added to the reference rate	1.50%
Term Loan | Base rate | Step Up Rate Based On Credit Ratings
DEBT
Percentage points added to the reference rate		1.50%

DEBT - Leverage Ratio (Details)

DEBT - Leverage Ratio (Details)	Jun. 26, 2020	Aug. 06, 2019
Credit agreement
DEBT
Total leverage ratio	4	4

CLOSURE AND POST-CLOSURE OBLI_3

CLOSURE AND POST-CLOSURE OBLIGATIONS - Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Changes to reported closure and post-closure obligations
Closure and post-closure obligations, beginning of period	$ 97,524	$ 95,869
Accretion expense	1,198	3,571	$ 3,812
Payments	(337)	(1,104)
Foreign currency translation	(44)	5
Closure and post-closure obligations, end of period	98,341	98,341
Less current portion	(8,234)	(8,234)		$ (6,471)
Long-term portion	$ 90,107	$ 90,107		$ 89,398

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
INCOME TAXES
Income tax expense (benefit)	$ 2,535,000	$ (1,456,000)	$ 1,348,000	$ 542,000
Effective tax rate (as a percent)	27.40%	(29.90%)	43.20%	(0.20%)
Unrecognized Tax Benefits	$ 277,000		$ 277,000		$ 239,000
Possible reduction in the provision for income taxes if the unrecognized tax benefits were recognized			277,000
Penalties accrued on unrecognized tax benefits	$ 0		$ 0

EARNINGS (LOSS) PER SHARE (Deta

EARNINGS (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
EARNINGS (LOSS) PER SHARE
Net income (loss)	$ 6,732	$ 6,319	$ 1,773	$ (296,950)
Basic
Weighted average basic shares outstanding	31,151	31,069	31,131	31,142
Loss (earnings) per share-Basic (in dollars per share)	$ 0.22	$ 0.20	$ 0.06	$ (9.54)
Diluted
Net income, diluted	$ 6,732	$ 6,319
Dilutive effect of share-based awards (in shares)			246
Dilutive effect of share-based awards and warrants (in shares)	249	255
Weighted average diluted shares outstanding	31,400	31,324	31,377	31,142
Loss per share (in dollars per share)	$ 0.21	$ 0.20	$ 0.06	$ (9.54)
Anti-dilutive shares excluded from calculation	4,404	4,233	4,333	4,208

EQUITY - Omnibus Incentive Plan

EQUITY - Omnibus Incentive Plan (Details) - Omnibus Plan - shares	Sep. 30, 2021	May 27, 2015
Stock-Based Compensation Plans
Number of shares authorized for grant		3,272,000
Number of shares available for future grant	2,014,301
Number of shares outstanding	0

EQUITY - PSUs, Restricted Stock

EQUITY - PSUs, Restricted Stock and RSU (Details) - $ / shares	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Weighted Average Grant Date Fair Value
Common stock, shares issued	31,512,000	31,512,000
PSUs
Shares
Outstanding at the beginning of the year (in shares)	86,070
Vested (in shares)	(14,100)
Outstanding at the end of the year (in shares)	71,970
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 49.45
Vested (in dollars per share)	63.56
Outstanding at the end of the period (in dollars per share)	$ 46.69
Common stock, shares issued	0
Restricted stock
Shares
Outstanding at the beginning of the year (in shares)	72,766
Granted (in shares)	84,800
Vested (in shares)	(47,002)
Outstanding at the end of the year (in shares)	110,564
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 51.47
Granted (in dollars per share)	36.49
Vested (in dollars per share)	47.08
Outstanding at the end of the period (in dollars per share)	$ 41.85
RSUs
Shares
Outstanding at the beginning of the year (in shares)	147,243
Granted (in shares)	62,759
Vested (in shares)	(55,876)
Cancelled, expired or forfeited (in shares)	(13,453)
Outstanding at the end of the year (in shares)	140,673
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 39.92
Granted (in dollars per share)	39.33
Vested (in dollars per share)	42.03
Cancelled, expired or forfeited (in dollars per share)	44.57
Outstanding at the end of the period (in dollars per share)	$ 38.38

EQUITY - Stock Options (Details

EQUITY - Stock Options (Details) - Stock options	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Shares
Outstanding at the beginning of the period (in shares) | shares	357,033
Granted (in shares) | shares	205,800
Outstanding at the end of the period (in shares) | shares	562,833
Exercisable at the end of the period (in shares) | shares	299,568
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 49.93
Granted (in dollars per share) | $ / shares	35.30
Outstanding at the end of the period (in dollars per share) | $ / shares	44.58
Exercisable at the end of the period (in dollars per share) | $ / shares	$ 48.29

EQUITY - Treasury Stock (Detail

EQUITY - Treasury Stock (Details) - $ / shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Dividends
Dividends paid per share (in dollars per share)	$ 0	$ 0.18
Share repurchase program related to net share settlement
Treasury Stock
Repurchase of common stock (in shares)	12,788
Average cost of repurchase (in dollars per share)	$ 36.33

EQUITY - Warrants (Details)

EQUITY - Warrants (Details)	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Warrants
Number of warrants (in shares) | shares	3,772,753
Number of shares each warrant is entitled to purchase | shares	1
Exercise price	$ 58.67
Redemption price of warrants	$ 0.01
Minimum number of day for written prior notice for redemption	30 days
Share price of common stock required for redemption	$ 91.84
Number of trading days share price equals or exceeds required price within 30 consecutive trading days for redemption	20 days
Number of consecutive trading days	30 days

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Litigation and Regulatory Proceedings (Details) $ in Thousands	Jan. 10, 2020USD ($)	Nov. 17, 2018employee
Explosion at the Grand View, Idaho Facility
Litigation and Regulatory Proceedings
Number of fatalities | employee		1
Occupational Safety and Health Review Commission
Litigation and Regulatory Proceedings
Settlement | $	$ 50

OPERATING SEGMENTS - Summarized

OPERATING SEGMENTS - Summarized Financial Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)segment	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
OPERATING SEGMENTS
Number of reportable segments | segment			3
Revenue	$ 257,182	$ 238,142	$ 726,574	$ 692,780
Depreciation, amortization and accretion	27,682	28,892	84,167	86,455
Capital expenditures	18,916	9,167	45,347	45,124
Total assets	1,818,923	1,946,295	1,818,923	1,946,295	$ 1,831,283
Corporate
OPERATING SEGMENTS
Depreciation, amortization and accretion	786	820	2,360	2,187
Capital expenditures	1,521	177	2,135	4,065
Total assets	66,623	97,557	66,623	97,557
Environmental Services | Operating Segment
OPERATING SEGMENTS
Revenue	115,201	107,249	327,708	319,684
Depreciation, amortization and accretion	10,500	10,377	32,905	31,119
Capital expenditures	10,693	5,189	31,553	22,343
Total assets	786,686	754,235	786,686	754,235
Field & Industrial Services | Operating Segment
OPERATING SEGMENTS
Revenue	131,582	125,715	374,491	343,217
Depreciation, amortization and accretion	11,062	12,129	33,794	36,420
Capital expenditures	6,221	2,531	10,426	12,997
Total assets	749,617	859,511	749,617	859,511
Energy Waste | Operating Segment
OPERATING SEGMENTS
Revenue	10,399	5,178	24,375	29,879
Depreciation, amortization and accretion	5,334	5,566	15,108	16,729
Capital expenditures	481	1,270	1,233	5,719
Total assets	$ 215,997	$ 234,992	$ 215,997	$ 234,992

OPERATING SEGMENTS - Reconcilia

OPERATING SEGMENTS - Reconciliation of EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reconciliation of Net Income to Adjusted EBITDA
Net income (loss)	$ 6,732	$ 6,319	$ 1,773	$ (296,950)
Income tax expense (benefit)	2,535	(1,456)	1,348	542
Interest expense	7,144	7,964	22,022	25,127
Interest income	(485)	(9)	(1,148)	(251)
Foreign currency loss (gain)	(341)	421	385	155
Other income	(114)	(86)	(4,020)	(382)
Goodwill impairment charges				300,300
Depreciation and amortization of plant and equipment	17,898	18,435	54,095	54,831
Amortization of intangibles assets	8,586	9,178	26,501	27,812
Share-based compensation	1,713	1,773	5,748	4,861
Accretion and non-cash adjustment of closure & post-closure liabilities	1,198	1,279	3,571	3,812
Business development and integration expenses	523	1,627	2,528	7,507
Adjusted EBITDA	45,389	45,445	112,803	127,364
Operating Segment | Environmental Services
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA	43,439	45,556	123,528	134,540
Operating Segment | Field & Industrial Services
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA	21,507	24,362	55,810	57,869
Operating Segment | Energy Waste
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA	3,497	90	7,063	4,163
Corporate
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA	$ (23,054)	$ (24,563)	$ (73,598)	$ (69,208)

OPERATING SEGMENTS - Revenue an

OPERATING SEGMENTS - Revenue and Long-lived Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	$ 948,356	$ 980,625
United States
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	856,670	882,639
Canada
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	65,616	68,623
EMEA
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	15,946	18,042
Other
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	$ 10,124	$ 11,321