US Ecology (ECOL) 10-K28 Feb 222021 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2021	Feb. 22, 2022	Jun. 30, 2021
Document Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Firm ID	34
Auditor Location	Boise, Idaho
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	FY
Entity Central Index Key	0001783400
Amendment Flag	false
Entity Public Float			$ 1,170
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	Dec. 31, 2021	Dec. 31, 2020
Current Assets:
Cash and cash equivalents	$ 67,487	$ 73,848
Receivables, net	250,154	241,978
Prepaid expenses and other current assets	32,136	28,379
Income taxes receivable	14,441	18,279
Total current assets	364,218	362,484
Property and equipment, net	456,384	456,637
Operating lease assets	43,607	51,474
Restricted cash and investments	1,567	5,598
Intangible assets, net	489,573	523,988
Goodwill	413,126	413,037
Other assets	36,923	18,065
Total assets	1,805,398	1,831,283
Current Liabilities:
Accounts payable	64,793	35,881
Deferred revenue	15,950	15,267
Accrued liabilities	51,265	59,296
Accrued salaries and benefits	29,438	30,918
Income taxes payable	559	977
Current portion of long-term debt	3,359	3,359
Current portion of closure and post-closure obligations	5,771	6,471
Current portion of operating lease liabilities	15,799	17,048
Total current liabilities	186,934	169,217
Long-term debt	735,125	782,484
Long-term closure and post-closure obligations	93,149	89,398
Long-term operating lease liabilities	28,477	35,069
Other long-term liabilities	13,907	32,201
Deferred income taxes, net	123,482	120,983
Total liabilities	1,181,074	1,229,352
Commitments and contingencies (See Note 18)
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	821,970	820,567
Retained deficit	(183,115)	(188,452)
Treasury stock, at cost, 242 and 358 shares, respectively	(10,652)	(15,841)
Accumulated other comprehensive loss	(4,194)	(14,658)
Total stockholders' equity	624,324	601,931
Total liabilities and stockholders' equity	$ 1,805,398	$ 1,831,283

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Thousands	Dec. 31, 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	242	358

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF OPERATIONS
Revenue	$ 988,001	$ 933,854	$ 685,509
Direct operating costs	754,923	683,703	475,675
Gross profit	233,078	250,151	209,834
Selling, general and administrative expenses	199,732	206,169	141,123
Goodwill and intangible asset impairment charges		404,900
Operating income (loss)	33,346	(360,918)	68,711
Other income (expense):
Interest income	1,417	258	605
Interest expense	(28,966)	(32,595)	(19,239)
Foreign currency loss	(171)	(1,134)	(733)
Other	4,476	788	455
Total other expense	(23,244)	(32,683)	(18,912)
Income (loss) before income taxes	10,102	(393,601)	49,799
Income tax expense (benefit)	4,765	(4,242)	16,659
Net income (loss)	$ 5,337	$ (389,359)	$ 33,140
Earnings (loss) per share:
Basic	$ 0.17	$ (12.51)	$ 1.41
Diluted	$ 0.17	$ (12.51)	$ 1.40
Shares used in earnings (loss) per share calculation:
Basic	31,138	31,126	23,521
Diluted	31,373	31,126	23,749

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ 5,337	$ (389,359)	$ 33,140
Other comprehensive income (loss):
Foreign currency translation (loss) gain	(1,505)	3,055	3,772
Net changes in interest rate hedge, net of taxes of $3,182, $(1,557) and $(488), respectively	11,969	(5,859)	(1,835)
Comprehensive income (loss), net of tax	$ 15,801	$ (392,163)	$ 35,077

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other comprehensive income (loss):
Net changes in interest rate hedge, tax	$ 3,182	$ (1,557)	$ (488)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ 5,337	$ (389,359)	$ 33,140
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization of property and equipment	70,799	66,561	41,423
Amortization of intangible assets	34,614	37,344	15,491
Accretion of closure and post-closure obligations	5,363	4,000	4,388
Goodwill and intangible asset impairment charges		404,900
Integration-related property and equipment charges		3,067
Property and equipment impairment charges			25
Unrealized foreign currency gain	(1,647)	(1,472)	(666)
Deferred income taxes	(635)	(4,148)	6,601
Share-based compensation expense	7,478	6,651	5,544
Share-based payments of business development and integration expenses	411	1,182	3,717
Unrecognized tax benefits	16	(8)	(238)
Net (gain) loss on disposition of assets	(116)	1,504	426
Gain on insurance proceeds from damaged property and equipment			(12,366)
Amortization and write-off of debt issuance costs	2,440	2,217	1,007
Amortization and write-off of debt discount	161	161	27
Change in fair value of contingent consideration	282	(3,682)	349
Change in fair value of minority interest investment	(3,509)
Changes in assets and liabilities (net of effects of business acquisition):
Receivables	(14,685)	8,381	(9,357)
Income taxes receivable	3,830	(7,049)	(4,163)
Other assets	(5,271)	(5,443)	(2,163)
Accounts payable and accrued liabilities	15,985	(13,628)	(10,706)
Deferred revenue	658	(1,619)	967
Accrued salaries and benefits	(1,483)	(121)	8,326
Income taxes payable	(430)	(549)	(244)
Closure and post-closure obligations	(3,279)	(1,744)	(1,912)
Net cash provided by operating activities	116,319	107,146	79,616
Cash flows from investing activities:
Purchases of property and equipment	(68,666)	(57,399)	(58,100)
Proceeds from sale of property and equipment	2,431	1,897	1,182
Minority interest investment	(712)		(7,870)
Proceeds from sale of short-term investments	2,142
Purchases of restricted investments	(1,017)	(1,615)	(1,197)
Proceeds from sale of restricted investments	1,267	1,483	1,145
Business acquisitions (net of cash acquired)		(3,309)	(399,599)
Insurance proceeds from damaged property and equipment		1,305	12,714
Payment of acquired contingent consideration liabilities			(4,000)
Net cash used in investing activities	(64,555)	(57,638)	(455,725)
Cash flows from financing activities:
Proceeds from short-term borrowings	61,326	72,353	77,997
Payments on short-term borrowings	(61,326)	(72,353)	(77,997)
Payments on long-term debt	(48,500)	(74,500)	(80,000)
Payment of equipment financing obligations	(5,616)	(6,327)	(1,539)
Payment of acquired contingent consideration liabilities	(2,553)	(2,517)
Deferred financing costs paid	(957)	(1,144)	(9,416)
Repurchase of common stock	(465)	(18,332)	(915)
Proceeds from long-term debt		90,000	491,875
Dividends paid		(5,667)	(15,890)
Other		28	319
Net cash (used in) provided by financing activities	(58,091)	(18,459)	384,434
Effect of foreign exchange rate changes on cash	277	1,915	1,062
(Decrease) increase in Cash and cash equivalents and restricted cash	(6,050)	32,964	9,387
Cash and cash equivalents and restricted cash at beginning of year	75,104	42,140	32,753
Cash and cash equivalents and restricted cash at end of year	$ 69,054	$ 75,104	$ 42,140

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS - (Restricted cash and investments) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Cash and cash equivalents and restricted cash
Cash and cash equivalents	$ 67,487	$ 73,848	$ 41,281	$ 31,969
Restricted cash	1,567	1,256	859	784
Cash and cash equivalents and restricted cash	$ 69,054	$ 75,104	$ 42,140	$ 32,753

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Total
Beginning balances at Dec. 31, 2018	$ 220	$ 183,834	$ 189,324	$ (370)	$ (13,791)	$ 359,217
Balance (in shares) at Dec. 31, 2018	22,040,144
Increase (Decrease) in Stockholders' Equity
Net income (loss)			33,140			33,140
Other comprehensive (loss) income					1,937	1,937
Share-based compensation		5,544				5,544
Share-based payments of business development and integration expenses		3,717				3,717
Dividends paid			(15,890)			(15,890)
Issuance of restricted common stock	$ 2	(1,516)				(1,514)
Issuance of restricted common stock (in shares)	78,175
Stock option exercises		319				319
Stock option exercises( Shares)	8,235
Repurchase of common stock				(916)		(916)
Issuance of restricted common stock and common stock from treasury shares		(514)		514
Issuance of performance common stock		(634)				(634)
Issuance of performance common stock (in shares)	9,540
Common stock issued in NRC Merger	$ 93	581,008				581,101
Common stock issued in NRC Merger (in shares)	9,337,949
Replacement warrants, restricted stock and stock options issued in NRC Merger		45,359				45,359
Cancellation of treasury shares		(772)		772
Cancellation of treasury shares (in shares)	(13,359)
Ending balances at Dec. 31, 2019	$ 315	816,345	206,574		(11,854)	1,011,380
Balance (in shares) at Dec. 31, 2019	31,460,684
Increase (Decrease) in Stockholders' Equity
Net income (loss)			(389,359)			(389,359)
Other comprehensive (loss) income					(2,804)	(2,804)
Share-based compensation		6,651				6,651
Share-based payments of business development and integration expenses		1,182				1,182
Dividends paid			(5,667)			(5,667)
Issuance of restricted common stock		(286)				(286)
Issuance of restricted common stock (in shares)	45,111
Stock option exercises		28				28
Stock option exercises( Shares)	3,142
Repurchase of common stock				(18,332)		(18,332)
Issuance of restricted common stock and common stock from treasury shares		(3,143)		2,491		(652)
Issuance of performance common stock		(210)				(210)
Issuance of performance common stock (in shares)	3,387
Ending balances at Dec. 31, 2020	$ 315	820,567	(188,452)	(15,841)	(14,658)	$ 601,931
Balance (in shares) at Dec. 31, 2020	31,512,324					31,512,000
Increase (Decrease) in Stockholders' Equity
Net income (loss)			5,337			$ 5,337
Other comprehensive (loss) income					10,464	10,464
Share-based compensation		7,478				7,478
Share-based payments of business development and integration expenses		411				411
Repurchase of common stock				(465)		(465)
Issuance of restricted common stock and common stock from treasury shares		(6,486)		5,654		(832)
Ending balances at Dec. 31, 2021	$ 315	$ 821,970	$ (183,115)	$ (10,652)	$ (4,194)	$ 624,324
Balance (in shares) at Dec. 31, 2021	31,512,324					31,512,000

CONSOLIDATED STATEMENTS OF ST_2

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY
Repurchase of common stock, number of shares	12,788	414,769	14,462

DESCRIPTION OF BUSINESS

DESCRIPTION OF BUSINESS	12 Months Ended
DESCRIPTION OF BUSINESS	Dec. 31, 2021
GENERAL
DESCRIPTION OF BUSINESS	NOTE 1. DESCRIPTION OF BUSINESS US Ecology Holdings, Inc., the predecessor to the Company (“Predecessor US Ecology”), was incorporated as a Delaware corporation in March 1987 as American Ecology Corporation. On February 22, 2010, Predecessor US Ecology changed its name from American Ecology Corporation to US Ecology, Inc. On November 1, 2019, in connection with the Company’s acquisition of NRC Group Holdings Corp. (“NRC”), a new parent entity of US Ecology completed a merger transaction with Predecessor US Ecology and became the successor to Predecessor US Ecology and changed its name to “US Ecology, Inc.” In connection with the closing of the NRC Merger (as defined below), Predecessor US Ecology changed its name to “US Ecology Holdings, Inc.” US Ecology, Inc., through its subsidiaries, is a leading North American provider of environmental services to commercial and government entities. The Company addresses the complex waste management needs of its customers, offering treatment, disposal and recycling of hazardous and radioactive waste, as well as a wide range of complementary field services. US Ecology, Inc. and its predecessors have been protecting the environment since 1952, with operations primarily in the United States, Canada, the Europe, Middle East, and Africa (“EMEA”) region and Mexico. Throughout these consolidated financial statements words such as “we,” “us,” “our,” “US Ecology” and the “Company” refer to US Ecology, Inc. and its subsidiaries. On November 1, 2019, pursuant to and subject to the conditions set forth in the Agreement and Plan of Merger (the “NRC Merger Agreement”) by and among the Company, NRC, Predecessor US Ecology, Rooster Merger Sub, Inc. (“NRC Merger Sub”), and ECOL Merger Sub, Inc. (“ECOL Merger Sub”), ECOL Merger Sub merged with and into Predecessor US Ecology, with Predecessor US Ecology continuing as the surviving company and as a wholly-owned subsidiary of the Company. Substantially concurrently therewith, NRC Merger Sub merged with and into NRC, with NRC continuing as the surviving company and as a wholly-owned subsidiary of the Company. Following the completion of the mergers (collectively, the “NRC Merger”), the Company contributed all of the issued and outstanding equity interests of NRC to Predecessor US Ecology so that, after such contribution, NRC became a wholly-owned subsidiary of Predecessor US Ecology. Effective as of November 1, 2019, the Company changed its name from “US Ecology Parent, Inc.” to “US Ecology, Inc.,” the Company’s common stock and warrants began trading on Nasdaq under the symbol “ECOL” and “ECOLW,” respectively. The Company identified itself as the successor issuer to Predecessor US Ecology pursuant to Rule 12g-3(c) under the Securities Exchange Act of 1934, as amended. 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 Annual Report on Form 10-K, all periods presented have been recast to reflect these changes. Under our new structure our operations are 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 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 Annual Report on Form 10-K, all periods presented have been recast to reflect these changes.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Dec. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Principles of Consolidation The accompanying financial statements are prepared on a consolidated basis. All inter-company balances and transactions have been eliminated in consolidation. Our year-end is December 31. Cash and Cash Equivalents Cash and cash equivalents consist primarily of cash on deposit, money market accounts or short-term investments with original maturities of 90 days or less at the date of acquisition. Cash and cash equivalents totaled $67.5 million and $73.8 million at December 31, 2021 and 2020, respectively. At December 31, 2021 and 2020, we had $54.4 million and $59.3 million, respectively, of cash at our operations outside the United States. Receivables Our receivables include invoiced and unbilled amounts where the Company has an unconditional right to payment. Receivables are stated at an amount management expects to collect. Based on management’s assessment of the credit history of the customers having outstanding balances and factoring in current economic conditions, management has concluded that potential unidentified losses on balances outstanding at year-end will not be material. Unbilled receivables are recorded for work performed under contracts that have not yet been invoiced to customers and arise due to the timing of billings. Substantially all unbilled receivables at December 31, 2021, were billed in the following month. Restricted Cash and Investments Restricted cash and investments of $1.6 million and $5.6 million at December 31, 2021 and 2020, respectively, represent funds held in third-party managed trust accounts as collateral for our financial assurance obligations for post-closure activities at our non-operating facilities and other restricted funds related to deferred compensation plans. These funds are primarily invested in money market accounts. Revenue Recognition Revenues are recognized when control of the promised services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those services. We recognize revenue from three primary sources: (1) waste treatment, recycling and disposal services, (2) field and industrial waste management services, and (3) waste transportation services. Our waste treatment and disposal customers are legally obligated to properly treat and dispose of their waste in accordance with local, state, and federal laws and regulations. As our customers do not possess the resources to properly treat and dispose of their waste independently, they contract with the Company to perform these services. Waste treatment, recycling, and disposal revenue results primarily from fixed fees charged to customers for treatment and/or disposal or recycling of specified wastes. Waste treatment, recycling, and disposal revenue is generally charged on a per-ton or per-yard basis based on contracted prices and is recognized over time as the services are performed. Our treatment and disposal services are generally performed as the waste is received and considered complete upon final disposal. Field and industrial waste management services revenue results primarily from specialty onsite services such as high-pressure cleaning, tank cleaning, decontamination, remediation, transportation, spill cleanup and emergency response at refineries, chemical plants, steel and automotive plants, and other government, commercial and industrial facilities. We also provide hazardous waste packaging and collection services and total waste management solutions at customer sites and through our 10-day transfer facilities. These services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. Generally, the pricing in these types of contracts is fixed, but the quantity of services to be provided during the contract term is variable and revenues are recognized over the term of the agreements or as services are performed. As we have a right to consideration from our customers in an amount that corresponds directly with the value to the customer of the Company’s performance completed to date, we have applied the practical expedient to recognize revenue in the amount to which we have the right to invoice. Additionally, we have customers that pay annual retainer fees, primarily for our standby services, under long-term or evergreen contracts. Such retainer fees are recognized over time as the services are performed and it is probable that a significant reversal in the amount of cumulative revenue recognized on the contracts will not occur. Transportation and logistics revenue results from delivering customer waste to a disposal facility for treatment and/or disposal or recycling. Transportation services are generally not provided on a stand-alone basis and instead are bundled with other Company services. However, in some instances we provide transportation and logistics services for shipment of waste from cleanup sites to disposal facilities operated by other companies. For such arrangements, we allocate revenue to each performance obligation based on its relative standalone selling price. We generally determine standalone selling prices based on the prices charged to customer or using expected cost-plus margin. Transportation revenue is recognized over time as the waste is transported. Taxes and fees collected from customers concurrent with revenue-producing transactions to be remitted to governmental authorities are excluded from revenue. Our Richland, Washington disposal facility is regulated by the Washington Utilities and Transportation Commission (“WUTC”), which approves our rates for disposal of low-level radioactive waste (“LLRW”). Annual revenue levels are established based on a rate agreement with the WUTC at amounts sufficient to cover the costs of operation, including facility maintenance, equipment replacement and related costs, and provide us with a reasonable profit. Per-unit rates charged to LLRW customers during the year are based on our evaluation of disposal volume and radioactivity projections submitted to us by waste generators. Our proposed rates are then reviewed and approved by the WUTC. If annual revenue exceeds the approved levels set by the WUTC, we are required to refund excess collections to facility users on a pro-rata basis. Refundable excess collections, if any, are recorded in Accrued liabilities in the consolidated balance sheets. The current rate agreement with the WUTC was extended in 2019 and is effective until December 31, 2025. 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, and is recognized when these services are performed. During the year ended December 31, 2021 and 2020, we recognized $15.1 million and $14.7 million of revenue that was included in the deferred revenue balance at the beginning of each year, respectively. Property and Equipment Property and equipment are recorded at cost and depreciated on the straight-line method over estimated useful lives. Replacements and major repairs of property and equipment are capitalized and retirements are made when assets are disposed of or when the useful life has been exhausted. Minor components and parts are expensed as incurred. Repair and maintenance expenses were $29.5 million, $26.9 million and $20.5 million for the years ended December 31, 2021, 2020 and 2019, respectively. We assume no salvage value for our depreciable fixed assets. The estimated useful lives for significant property and equipment categories are as follows: Useful Lives Vehicles, vessels and other equipment 3 to 10 years Disposal facility and equipment 3 to 20 years Buildings and improvements 5 to 40 years Railcars 40 years Disposal Cell Accounting Qualified disposal cell development costs such as personnel and equipment costs incurred to construct new disposal cells are recorded and capitalized at cost. Capitalized cell development costs, net of recorded amortization, are added to estimated future costs of the permitted disposal cell to be incurred over the remaining construction of the cell, to determine the amount to be amortized over the remaining estimated cell life. Estimates of future costs are developed using input from independent engineers and internal technical and accounting managers. We review these estimates at least annually. Amortization is recorded on a unit of consumption basis, typically applying cost as a rate per cubic yard disposed. Disposal facility costs are expected to be fully amortized upon final closure of the facility, as no salvage value applies. Costs associated with ongoing disposal operations are charged to expense as incurred. We have material financial commitments for closure and post-closure obligations for certain facilities we own or operate. We estimate future cost requirements for closure and post-closure monitoring based on RCRA and conforming state requirements and facility permits. RCRA requires that companies provide the responsible regulatory agency acceptable financial assurance for closure work and subsequent post-closure monitoring of each facility for 30 years following closure. Estimates for final closure and post-closure costs are developed using input from our technical and accounting managers as well as independent engineers and are reviewed by management at least annually. These estimates involve projections of costs that will be incurred after the disposal facility ceases operations, through the required post-closure care period. The present value of the estimated closure and post-closure costs are accreted using the interest method of allocation to direct costs in our consolidated statements of operations so that 100% of the future cost has been incurred at the time of payment. Business Combinations We account for business combinations under the acquisition method of accounting. The cost of an acquired company is assigned to the tangible and identifiable intangible assets purchased and the liabilities assumed on the basis of their fair values at the date of acquisition. Any excess of purchase price over the fair value of net tangible and intangible assets acquired is assigned to goodwill. The transaction costs associated with business combinations are expensed as they are incurred. Goodwill Goodwill represents the excess of the fair value of the consideration transferred over the fair value of the underlying identifiable assets and liabilities acquired. Goodwill is not amortized, but instead is assessed for impairment annually in the fourth quarter as of October 1 and also if an event occurs or circumstances change that may indicate a possible impairment. In the event that we determine that the value of goodwill has become impaired, we will incur an accounting charge for the amount of impairment during the period in which the determination has been made. See Note 3 for additional information related to the use of estimates in the Company’s goodwill impairment tests and Note 13 for additional information related to our annual assessment of goodwill. Intangible Assets Intangible assets are stated at the fair value assigned in a business combination net of amortization. We amortize our amortizing intangible assets using the straight-line method over their estimated economic lives ranging from 1 to 60 years. We review intangible assets with indefinite useful lives for impairment during the fourth quarter as of October 1 of each year. We also review both non-amortizing and amortizing intangible assets for impairment whenever events or changes in circumstances indicate that the carrying value of an intangible asset may not be recoverable. See Note 3 for additional information related to the use of estimates in the Company’s intangible assets impairment tests and Note 13 for additional information related to our annual assessment of non-amortizing intangible assets. Our acquired permits and licenses generally have renewal terms of approximately 5-10 years. We have a history of renewing these permits and licenses as demonstrated by the fact that each of the sites’ treatment permits and licenses have been renewed regularly since the facility began operations. We intend to continue to renew our permits and licenses as they come up for renewal for the foreseeable future. Costs incurred to renew or extend the term of our permits and licenses are recorded in Selling, general and administrative expenses in our consolidated statements of operations. Impairment of Long-Lived Assets Long-lived assets consist primarily of property and equipment facility development costs and amortizing intangible assets. The recoverability of long-lived assets is evaluated periodically through analysis of operating results and consideration of other significant events or changes in the business environment. If an operating unit had indications of possible impairment, we would evaluate whether impairment exists on the basis of undiscounted expected future cash flows from operations over the remaining amortization period. If an impairment loss were to exist, the carrying amount of the related long-lived assets would be reduced to their estimated fair value. We did not observe any events or changes in circumstances in 2021 that indicated the carrying value of our long-lived assets may not be recoverable. Share-Based Payments The Company has elected to account for forfeitures of share-based awards as they occur, rather than estimate expected forfeitures. See Note 19 for additional information related to our accounting policies for share-based payments. Debt Issuance Costs & Debt Discount Debt issuance costs and debt discount are amortized over the scheduled maturity of the underlying debt instrument. Amortization of debt issuance costs and debt discount is included as a component of interest expense in the consolidated statements of operations. Unamortized debt discount and debt issuance costs associated with our term loan were $5.5 million and $6.7 million at December 31, 2021 and 2020, respectively, and have been recorded as a reduction of the Current portion of long-term debt and Long-term debt in the consolidated balance sheets. Unamortized debt issuance costs associated with our Revolving Credit Facility were $4.8 million and $5.3 million at December 31, 2021 and 2020, respectively, and have been recorded in Prepaid expenses and other current assets and Other assets in the consolidated balance sheets. Derivative Instruments 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. Changes in the fair value of the interest rate swap are recorded as a component of accumulated other comprehensive income within stockholders’ equity, and are recognized in interest expense in the period in which the payment is settled, or for terminated swap agreements, amortized to interest expense over the period from termination to original maturity. The interest rate swap has an effective date of March 31, 2020 in an initial notional amount of $500.0 million. The Company does not hold or issue derivative financial instruments for trading or speculative purposes. Foreign Currency The assets, liabilities and results of operations of certain of our foreign subsidiaries are measured using their functional currency which is the currency of the primary foreign economic environment in which they operate. Assets and liabilities are translated to U.S. dollars (“USD”) at the exchange rate in effect at the balance sheet date and revenue and expenses at the average exchange rate for the period. Gains and losses from the translation of the consolidated financial statements of our foreign subsidiaries into USD are included in stockholders’ equity as a component of Accumulated other comprehensive loss. Gains and losses resulting from foreign currency transactions are recognized in the consolidated statements of operations. Recorded balances that are denominated in a currency other than the functional currency are re-measured to the functional currency using the exchange rate at the balance sheet date and gains or losses are recorded in the statements of operations. Income Taxes We account for income taxes using an asset and liability method, which requires the recognition of taxes payable or refundable for the current year and deferred tax assets and liabilities for the expected future tax consequences of temporary differences that currently exist between the tax basis and the financial reporting basis of our taxable subsidiaries’ assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in operations in the period that includes the enactment date. The measurement of deferred tax assets is reduced, if necessary, by the amount of any tax benefits that, based on available evidence, are not expected to be realized. The unrecognized tax benefits that are not expected to result in payment or receipt of cash within one year are classified as “Other long-term liabilities” in the Consolidated Balance Sheets. We regularly assess the need for a valuation allowance against our deferred tax assets. In making that assessment, we consider both positive and negative evidence related to the likelihood of realization of the deferred tax assets on a jurisdictional basis to determine, based on the weight of available evidence, whether it is more-likely-than-not that some or all of the deferred tax assets will not be realized. Examples of positive and negative evidence include future growth, forecasted earnings, future taxable income, the mix of earnings in the jurisdictions in which we operate, historical earnings, taxable income in prior years, if carryback is permitted under the law and prudent, and feasible tax planning strategies. In the event we were to determine that we would not be able to realize all or part of our net deferred tax assets in the future, an adjustment to the deferred tax assets valuation allowance would be charged to earnings in the period in which we make such a determination, or goodwill would be adjusted at our final determination of the valuation allowance related to an acquisition within the measurement period. If we later determine that it is more-likely-than-not that the net deferred tax assets would be realized, we would reverse the applicable portion of the previously-provided valuation allowance as an adjustment to earnings at such time. We account for unrecognized tax benefits using a more-likely-than-not threshold for financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. We establish reserves for tax-related uncertainties based on estimates of whether, and the extent to which, additional taxes will be due. We record an income tax liability, if any, for the difference between the benefit recognized and measured and the tax position taken or expected to be taken on our tax returns. We recognize interest assessed by taxing authorities or interest associated with uncertain tax positions as a component of interest expense. We recognize any penalties assessed by taxing authorities or penalties associated with uncertain tax positions as a component of selling, general and administrative expenses. Our income tax expense, deferred tax assets and deferred tax liabilities, and liabilities for uncertain tax benefits reflect management’s best estimate of current and future taxes to be paid. We are subject to income taxes in the United States and numerous foreign jurisdictions. Significant judgments and estimates are required in the determination of the consolidated income tax expense. See Note 17 for additional information regarding income taxes. Insurance Accrued costs for our self-insured healthcare coverage were $3.4 million and $3.3 million at December 31, 2021 and 2020, respectively. Earnings (Loss) Per Share Basic earnings per share is calculated based on the weighted-average number of outstanding common shares during the applicable period. Diluted earnings per share is based on the weighted-average number of outstanding common shares plus the weighted-average number of potential outstanding common shares. Potential common shares that would increase earnings per share or decrease loss per share are anti-dilutive and are excluded from earnings per share computations. Earnings per share is computed separately for each period presented. Treasury Stock Shares of common stock repurchased by us are recorded at cost as treasury stock and result in a reduction of stockholders’ equity in our consolidated balance sheets. Treasury shares are reissued using the weighted average cost method for determining the cost of the shares reissued. The difference between the cost of the shares reissued and the issuance price is added or deducted from additional paid-in capital. 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.

USE OF ESTIMATES

USE OF ESTIMATES	12 Months Ended
USE OF ESTIMATES	Dec. 31, 2021
USE OF ESTIMATES
USE OF ESTIMATES	NOTE 3. USE OF ESTIMATES The preparation of financial statements in conformity with accounting principles generally accepted in the United States 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. Listed below are the estimates and assumptions that we consider to be significant in the preparation of our consolidated financial statements. ● Allowance for Credit Losses - We estimate losses for uncollectible accounts based on the aging of the accounts receivable and an evaluation of the likelihood of success in collecting the receivable. ● Recovery of Long-Lived Assets - We evaluate the recovery of our long-lived assets periodically by analyzing our operating results and considering significant events or changes in the business environment. ● Income Taxes - We assume the deductibility of certain costs in our income tax filings, and estimate our income tax rate and future recovery of deferred tax assets. ● Legal and Environmental Accruals - We estimate the amount of potential exposure we may have with respect to litigation and environmental claims and assessments. ● Disposal Cell Development and Final Closure/Post-Closure Amortization - We expense amounts for disposal cell usage and closure and post-closure costs for each cubic yard of waste disposed of at our operating facilities. In determining the amount to expense for each cubic yard of waste disposed, we estimate the cost to develop each disposal cell and the closure and post-closure costs for each disposal cell and facility. The expense for each cubic yard is then calculated based on the remaining permitted capacity and total permitted capacity. Estimates for closure and post-closure costs are developed using input from third-party engineering consultants, and our internal technical and accounting personnel. Management reviews estimates at least annually. Estimates for final disposal cell closure and post-closure costs consider when the costs would actually be paid and, where appropriate, inflation and discount rates. ● Business Acquisitions - The Company records assets and liabilities of the acquired business at their fair values. Acquisition-related transaction and restructuring costs are expensed rather than treated as part of the cost of the acquisition. Goodwill represents the excess of the cost of an acquired business over the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed in a business acquisition. ● Contingent Consideration – The Company records liabilities for 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, prior to the NRC Merger. The payments are contingent on the acquired business’ achievement of annual earnings targets in certain years and other events considered in the purchase agreement. ● Goodwill - We assess goodwill for impairment during the fourth quarter as of October 1 of each year or sooner if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The assessment consists of comparing the estimated fair value of the reporting unit to the carrying value of the net assets assigned to the reporting unit, including goodwill. Fair values are generally determined by using both the market approach, applying a multiple of earnings based on guideline for publicly traded companies, and the income approach, discounting projected future cash flows based on our expectations of the current and future operating environment. The rates used to discount projected future cash flows reflect a weighted average cost of capital based on our industry, capital structure and risk premiums including those reflected in the current market capitalization. Estimating future cash flows requires significant judgment about factors such as general economic conditions and projected growth rates, and our estimates often vary from the cash flows eventually realized. Failure to execute on planned growth initiatives within the related reporting units, coupled with the other factors mentioned above, could lead to the impairment of goodwill and other long-lived assets in future periods. ● Intangible Assets - We review intangible assets with indefinite useful lives for impairment during the fourth quarter as of October 1 of each year. Fair value is generally determined by considering a discounted projected cash flow analysis. If the fair value of an asset is determined to be less than the carrying amount of the intangible asset, an impairment in the amount of the difference is recorded in the period in which the annual assessment occurs. We also review amortizing intangible assets for impairment whenever events or changes in circumstances indicate that the carrying value of an intangible asset may not be recoverable. In order to assess whether a potential impairment exists, the assets’ carrying values are compared with their undiscounted expected future cash flows. Estimating future cash flows requires significant judgment about factors such as general economic conditions and projected growth rates, and our estimates often vary from the cash flows eventually realized. Impairments are measured by comparing the fair value of the asset to its carrying value. Fair value is generally determined by considering: (i) the discounted projected cash flow analysis; (ii) a third-party valuation; and/or (iii) information available regarding the current market environment for similar assets. If the fair value is determined to be less than the carrying amount of the intangible assets, an impairment in the amount of the difference is recorded in the period in which the events or changes in circumstances that indicated the carrying value of the intangible assets may not be recoverable occurred. 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.

REVENUES

REVENUES	12 Months Ended
REVENUES	Dec. 31, 2021
REVENUES
REVENUES	NOTE 4. REVENUES Disaggregation of Revenue 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 Annual Report on Form 10-K, all periods presented have been recast to reflect these changes. Our operations are managed in three reportable segments, Waste Solutions, Field Services and Energy Waste, reflecting our internal reporting structure and nature of services offered. See Note 21 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 Annual Report on Form 10-K, 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: 2021 Waste Field Energy $s in thousands Solutions Services Waste Total Treatment & Disposal Revenue (1) $ 372,204 $ 50,327 $ 20,997 $ 443,528 Services Revenue: Transportation and Logistics (2) 79,045 29,096 8,978 117,119 Industrial Services (3) — 121,357 2,814 124,171 Small Quantity Generation (4) — 55,158 — 55,158 Total Waste Management (5) — 39,949 — 39,949 Remediation (6) — 48,224 — 48,224 Emergency Response (7) — 138,425 18 138,443 Other (8) — 17,651 3,758 21,409 Revenue $ 451,249 $ 500,187 $ 36,565 $ 988,001 2020 Waste Field Energy $s in thousands Solutions Services Waste Total Treatment & Disposal Revenue (1) $ 354,055 $ 47,781 $ 18,884 $ 420,720 Services Revenue: Transportation and Logistics (2) 71,358 34,218 7,184 112,760 Industrial Services (3) — 118,584 4,178 122,762 Small Quantity Generation (4) — 48,049 — 48,049 Total Waste Management (5) — 35,401 — 35,401 Remediation (6) — 30,225 — 30,225 Emergency Response (7) — 140,253 — 140,253 Other (8) — 19,243 4,441 23,684 Revenue $ 425,413 $ 473,754 $ 34,687 $ 933,854 2019 Waste Field Energy $s in thousands Solutions Services Waste Total Treatment & Disposal Revenue (1) $ 359,847 $ 18,523 $ 6,039 $ 384,409 Services Revenue: Transportation and Logistics (2) 80,700 40,670 2,877 124,247 Industrial Services (3) — 38,861 1,200 40,061 Small Quantity Generation (4) — 37,471 — 37,471 Total Waste Management (5) — 33,794 — 33,794 Remediation (6) — 13,307 — 13,307 Emergency Response (7) — 41,088 — 41,088 Other (8) — 8,688 2,444 11,132 Revenue $ 440,547 $ 232,402 $ 12,560 $ 685,509 (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 years ended December 31, 2021, 2020 and 2019, 24% , 27% and 22% , respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76% , 73% and 78% of our treatment and disposal revenue for the years ended December 31, 2021, 2020 and 2019, 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-then-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 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 EMEA region. The following table presents our revenue disaggregated by our reportable segments and geographic location where the underlying services were performed: 2021 Waste Field Energy $s in thousands Solutions Services Waste Total United States $ 374,414 $ 450,276 $ 36,565 $ 861,255 Canada 76,835 3,785 — 80,620 EMEA — 41,218 — 41,218 Other (1) — 4,908 — 4,908 Total revenue $ 451,249 $ 500,187 $ 36,565 $ 988,001 2020 Waste Field Energy $s in thousands Solutions Services Waste Total United States $ 355,226 $ 445,405 $ 34,687 $ 835,318 Canada 70,187 3,064 — 73,251 EMEA — 19,947 — 19,947 Other (1) — 5,338 — 5,338 Total revenue $ 425,413 $ 473,754 $ 34,687 $ 933,854 2019 Waste Field Energy $s in thousands Solutions Services Waste Total United States $ 354,625 $ 221,942 $ 12,560 $ 589,127 Canada 85,922 2,577 — 88,499 EMEA — 5,079 — 5,079 Other (1) — 2,804 — 2,804 Total revenue $ 440,547 $ 232,402 $ 12,560 $ 685,509 (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions. 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	12 Months Ended
BUSINESS COMBINATIONS	Dec. 31, 2021
BUSINESS COMBINATIONS
BUSINESS COMBINATIONS	NOTE 5. BUSINESS COMBINATIONS NRC Group Holdings Corp. On November 1, 2019, the Company completed its merger with NRC, a provider of comprehensive environmental, compliance and waste management services to the marine and rail transportation, general industrial and energy industries. The addition of NRC’s substantial service network strengthens and expands US Ecology’s suite of environmental services, including new oil and gas exploration and production landfill disposal capabilities, and provides expanded opportunities to establish US Ecology as a leader in standby and emergency response services. The total merger consideration was $1,024.8 million, comprised of the following: November 1, $s in thousands 2019 Fair value of US Ecology common stock issued (1) $ 581,101 Fair value of replacement warrants issued (2) 44,858 Fair value of replacement restricted stock units issued (3) 141 Fair value of replacement stock options (4) 360 Repayment of NRC’s term loan and revolving credit facility 398,373 Total merger consideration $ 1,024,833 (1) The fair value of US Ecology common stock issued was calculated based on 9,337,949 shares of US Ecology common stock multiplied by the closing price of US Ecology common stock of $62.23 per share on October 31, 2019, the day immediately preceding the closing of the NRC Merger. (2) The fair value of replacement warrants issued was calculated based on 3,772,753 replacement warrants multiplied by the fair value per warrant of $11.89 . The fair value per warrant was based on the closing price of the replaced NRC warrants (NYSE: NRCG.WS) of $2.33 on October 31, 2019, the day immediately preceding the closing of the NRC Merger, divided by the exchange ratio of 0.196 pursuant to the NRC Merger Agreement. (3) The fair value of replacement restricted stock units issued was calculated based on 118,239 replacement restricted stock units multiplied by the closing price of US Ecology common stock of $62.23 per share on October 31, 2019, the day immediately preceding the closing of the NRC Merger, further multiplied by the ratio of the precombination service period to the remaining vesting period, or approximately 1.9% . (4) The fair value of replacement stock options issued was calculated based on 29,400 replacement stock options multiplied by the fair value per option of $12.26 . The fair value per option was calculated using the Black-Scholes option pricing model, with the following weighted-average assumptions: strike price of $52.30 per option, dividend yield of 1.2% ; expected volatility of 28.9% ; average risk-free interest rate of 1.5% ; and an expected term of 1 year. The replacement stock options became fully vested at the merger date therefore the entire fair value is considered merger consideration. The payment of transaction fees and expenses and repayment of $398.4 million of NRC’s debt were funded using proceeds from a $450.0 million seven-year term loan. See Note 16 for additional information on the Company’s debt. As of October 31, 2020, the Company finalized the purchase accounting for the NRC Merger. The following table summarizes the final NRC Merger purchase price allocation: Purchase Price $s in thousands Allocation Current assets $ 130,110 Property and equipment 170,208 Identifiable intangible assets 309,500 Other assets 41,687 Current liabilities (89,733) Deferred income tax liabilities (54,974) Other liabilities (59,363) Total identifiable net assets 447,435 Goodwill 577,398 Total purchase price $ 1,024,833 Goodwill of $577.4 million arising from the acquisition is primarily attributable to the assembled workforce of NRC and expected synergies from combining operations. $399.5 million of the goodwill recognized was allocated to our Energy Waste segment and $177.9 million of the goodwill recognized was allocated to our Field Services segment. We expect $33.3 million of the acquired goodwill to be deductible for income tax purposes. The fair value of identifiable intangible assets related to the acquisition of NRC by major intangible asset class and corresponding weighted average amortization period are as follows: Average Amortization $s in thousands Fair Value Period (Years) Amortizing intangible assets: Customer relationships - noncontractual $ 199,600 14 Customer relationships - contractual 34,400 7 Permits and licenses 8,700 16 Tradenames 6,100 2 Non-compete agreements 3,300 2 Total identified amortizing intangible assets 252,100 Non-amortizing intangible assets: Permits and licenses 57,400 n/a Total identified intangible assets $ 309,500 The following unaudited pro forma financial information presents the combined results of operations as if NRC had been combined with US Ecology as of January 1, 2019. The pro forma financial information includes the accounting effects of the business combination, including the amortization of intangible assets, depreciation of property, plant and equipment, and interest expense. The unaudited pro forma financial information is presented for informational purposes only and is not indicative of the results of operations that would have been achieved if the acquisition had taken place at the beginning of the periods presented, nor should it be taken as indication of our future consolidated results of operations. (unaudited) $s in thousands 2019 Pro forma combined: Revenue $ 1,048,745 Net income (loss) $ 11,775 The amounts of revenue and operating loss from NRC included in the Company’s consolidated statements of operations for the year ended December 31, 2019 was $70.2 million and $9.1 million, respectively. NRC Merger-related business development and integration expenses of $2.4 million, $11.5 million and $24.4 million are included in Selling, general and administrative expenses in the Company’s consolidated statements of operations for the years ended December 31, 2021, 2020 and 2019, respectively. 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 W.I.S.E. Environmental Solutions Inc. On August 1, 2019, we acquired 100% of the outstanding shares of W.I.S.E. Environmental Solutions Inc. (“US Ecology Sarnia”), an equipment rental and waste services company based in Sarnia, Ontario, Canada for 23.5 million Canadian dollars, which translated to $17.9 million at the time of transaction and was funded with borrowings under the Credit Agreement. US Ecology Sarnia is reported as part of our Field Services segment. The Company assessed the revenues, net income, earnings per share and total assets of US Ecology Sarnia and concluded they are not material to our consolidated financial position or results of operations. As such, pro forma financial information has not been provided. 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 $7.7 million allocated to goodwill and $6.2 million allocated to intangible assets (primarily customer relationships) to be amortized over a weighted average life of approximately 14 years. Goodwill of $7.7 million arising from the acquisition is attributable to the assembled workforce and the future economic benefits of synergies with our other regional facilities and expansion into new markets. All of the goodwill recognized was assigned to our Field Services segment and is not expected to be deductible for income tax purposes.

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	12 Months Ended
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	Dec. 31, 2021
ACCUMULATED OTHER COMPREHENSIVE LOSS
ACCUMULATED OTHER COMPREHENSIVE LOSS	NOTE 6. ACCUMULATED OTHER COMPREHENSIVE INCOME (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, 2019 $ (10,925) $ (929) $ (11,854) Other comprehensive income (loss) before reclassifications, net of tax 3,055 (8,494) (5,439) Amounts reclassified out of AOCI, net of tax (1) — 2,635 2,635 Other comprehensive income (loss), net 3,055 (5,859) (2,804) Balance at December 31, 2020 $ (7,870) $ (6,788) $ (14,658) Other comprehensive (loss) income before reclassifications, net of tax (1,505) 9,010 7,505 Amounts reclassified out of AOCI, net of tax (2) — 2,959 2,959 Other comprehensive (loss) income, net (1,505) 11,969 10,464 Balance at December 31, 2021 $ (9,375) $ 5,181 $ (4,194) (1) Before-tax reclassifications of $3.3 million ( $2.6 million, after-tax) for the year ended December 31, 2020 were included in Interest expense in the Company’s consolidated statements of operations. Amount relates 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. (2) Before-tax reclassifications of $3.7 million ( $3.0 million, after-tax) for the year ended December 31, 2021 were included in Interest expense in the Company’s consolidated statements of operations. Amount relates 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 recognized as interest expense over the next 12 months total approximately $2.8 million ( $2.2 million after tax).

DISCLOSURE OF SUPPLEMENTAL CASH

DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION	12 Months Ended
DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION	Dec. 31, 2021
DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION
DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION	NOTE 7. DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION For the Year Ended December 31, $s in thousands 2021 2020 2019 Income taxes and interest paid: Income taxes paid, net of receipts $ 1,951 $ 7,774 $ 14,777 Interest paid 25,771 28,433 17,204 Non-cash investing and financing activities: Fair value of equity issued for acquisition of NRC $ — $ — $ 626,460 Adjustments to closure/post-closure retirement asset 732 5,422 (221) Capital expenditures in accounts payable 7,702 4,712 2,882 Acquisition of equipment with financing arrangements — 6,197 2,481 Restricted common stock and common stock issuances from treasury shares 5,654 2,491 514

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
FAIR VALUE MEASUREMENTS	Dec. 31, 2021
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS	NOTE 8. 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 December 31, 2021, there have been no 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 December 31, 2021, the fair value of the Company’s variable-rate term loan was estimated to be $442.3 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 at December 31, 2021 and 2020 consisted of the following: 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) $ 1,695 $ 255 $ — $ 1,950 Money market funds (2) 1,886 — — 1,886 Interest rate swap agreement (3) — 5,022 — 5,022 Total $ 3,581 $ 5,277 $ — $ 8,858 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 have short-term 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-year and end-of-year 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 and October 2014 that effectively converts a portion of our variable-rate debt to a fixed interest rate. In connection with our entry into the March 2020 interest rate swap, we terminated the October 2014 interest rate swap prior to its scheduled maturity date of June 2021. The March 2020 interest rate 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 October 2014 interest rate swap was also designated as a highly effective cash flow hedge. The March 2020 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 agreements are included in Other assets and Other long-term liabilities in the Company’s consolidated balance sheets as of December 31, 2021 and 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 prior to the 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 December 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. Changes in Level 3 liabilities measured at fair value for the years ended December 31, 2021 and 2020 are as follows: $s in thousands 2021 2020 Contingent consideration, beginning of year $ 2,173 $ 8,283 Change in fair value of contingent consideration 282 (3,682) Contingent consideration paid (2,553) (2,517) Foreign currency translation 98 89 Contingent consideration, end of year $ — $ 2,173

CONCENTRATIONS AND CREDIT RISK

CONCENTRATIONS AND CREDIT RISK	12 Months Ended
CONCENTRATIONS AND CREDIT RISK	Dec. 31, 2021
CONCENTRATIONS AND CREDIT RISK
CONCENTRATIONS AND CREDIT RISK	NOTE 9. CONCENTRATIONS AND CREDIT RISK Major Customers No customer accounted for more than 10% of total revenue for the years ended December 31, 2021, 2020 or 2019. No customer accounted for more than 10% of total receivables as of December 31, 2021 or 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 December 31, 2021, the Company did not have any trade receivables that are eligible for submission to the OSLTF for reimbursement. Labor Concentrations As of December 31, 2021, approximately 500, or approximately 13%, of our employees were covered by collective bargaining agreements with various labor unions. Approximately 40% of these employees are covered by collective bargaining agreements that expired and are in negotiation as of December 31, 2021, or expire within one year of December 31, 2021.

RECEIVABLES

RECEIVABLES	12 Months Ended
RECEIVABLES	Dec. 31, 2021
RECEIVABLES
RECEIVABLES	NOTE 10. RECEIVABLES Receivables as of December 31, 2021 and 2020 consisted of the following: $s in thousands 2021 2020 Trade $ 183,747 $ 186,502 Unbilled revenue 62,029 52,858 Other 7,421 5,554 Total receivables 253,197 244,914 Allowance for credit losses (3,043) (2,936) Receivables, net $ 250,154 $ 241,978 The allowance for credit losses is a provision for uncollectible accounts receivable and unbilled receivables. The allowance is evaluated and adjusted to reflect our expected credit losses based on collection history and an analysis of the accounts receivables aging. The allowance is decreased by accounts receivable as they are written off. The allowance is adjusted periodically to reflect actual experience. The change in the allowance during 2021, 2020 and 2019 was as follows: Charged Balance at (Credited) to Recoveries Beginning of Costs and (Deductions/ Balance at $s in thousands Period Expenses Write-offs) Adjustments End of Period Year ended December 31, 2021 $ 2,936 $ 1,179 $ (1,075) $ 3 $ 3,043 Year ended December 31, 2020 $ 3,010 $ (412) $ 296 $ 42 $ 2,936 Year ended December 31, 2019 $ 2,998 $ 226 $ (439) $ 225 $ 3,010

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	12 Months Ended
PROPERTY AND EQUIPMENT	Dec. 31, 2021
PROPERTY AND EQUIPMENT
PROPERTY AND EQUIPMENT	NOTE 11. PROPERTY AND EQUIPMENT Property and equipment as of December 31, 2021 and 2020 consisted of the following: $s in thousands 2021 2020 Cell development costs $ 203,217 $ 186,170 Land and improvements 74,298 65,953 Buildings and improvements 138,659 128,206 Railcars 17,299 17,299 Vehicles, vessels and other equipment 350,950 331,167 Construction in progress 54,609 44,840 Total property and equipment 839,032 773,635 Accumulated depreciation and amortization (382,648) (316,998) Property and equipment, net $ 456,384 $ 456,637 Depreciation and amortization expense was $70.8 million, $66.6 million and $41.4 million for the years ended December 31, 2021, 2020 and 2019, respectively.

LEASES

LEASES	12 Months Ended
LEASES	Dec. 31, 2021
LEASES
LEASES	NOTE 12. 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 to include one lease up 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 as of December 31, 2021 and 2020 consisted of the following: $s in thousands 2021 2020 Assets: Operating right-of-use assets (1) $ 43,607 $ 51,474 Finance right-of-use assets (2) 17,290 21,209 Total $ 60,897 $ 72,683 Liabilities: Current: Operating (3) $ 15,799 $ 17,048 Finance (4) 4,969 4,462 Long-term: Operating (5) 28,477 35,069 Finance (6) 12,108 17,501 Total $ 61,353 $ 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 $13.3 million and $8.0 million as of December 31, 2021 and 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: Year Ended December 31, $s in thousands 2021 2020 Operating lease cost (1) $ 19,950 $ 20,880 Finance lease cost: Amortization of leased assets (2) 5,249 5,312 Interest on lease liabilities (3) 1,012 1,221 Total $ 26,211 $ 27,413 (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: Year Ended December 31, $s in thousands 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 19,687 $ 20,297 Operating cash flows from finance leases $ 1,012 $ 1,221 Financing cash flows from finance leases $ 4,885 $ 4,659 Non-cash investing and financing activities: Right-of-use assets obtained in exchange for new operating lease liabilities $ 10,010 $ 13,576 Right-of-use assets obtained in exchange for new finance lease liabilities $ — $ 6,197 Other information related to our leases as of December 31, 2021 and 2020 is as follows: 2021 2020 Weighted-average remaining lease term (years): Operating leases 3.7 4.1 Finance leases 3.2 4.0 Weighted-average discount rate: Operating leases 3.59 % 3.69 % Finance leases 5.85 % 5.86 % The Company’s maturity analysis of its lease liabilities as of December 31, 2021 is as follows: Operating Finance $s in thousands Leases Leases Total 2022 $ 17,091 $ 5,694 $ 22,785 2023 13,617 5,668 19,285 2024 8,510 3,929 12,439 2025 3,366 3,565 6,931 2026 1,557 953 2,510 Thereafter 3,356 264 3,620 Total $ 47,497 $ 20,073 $ 67,570 Less: Interest 3,221 2,996 6,217 Present value of lease liabilities $ 44,276 $ 17,077 $ 61,353

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	12 Months Ended
GOODWILL AND INTANGIBLE ASSETS	Dec. 31, 2021
GOODWILL AND INTANGIBLE ASSETS
GOODWILL AND INTANGIBLE ASSETS	NOTE 13. GOODWILL AND INTANGIBLE ASSETS Changes in goodwill for the years ended December 31, 2021 and 2020 were as follows: Waste Solutions Field Services Energy Waste Accumulated Accumulated Accumulated $s in thousands Gross Impairment Gross Impairment Gross Impairment Total Balance at December 31, 2019 $ 166,415 $ (6,870) $ 298,579 $ — $ 308,856 $ — $ 766,980 Impairment charges — — — (19,900) — (363,900) (383,800) NRC Merger purchase price allocation adjustment — — (61,735) — 90,647 — 28,912 Impact Environmental acquisition — — 300 — — — 300 Foreign currency translation 448 — 197 — — — 645 Balance at December 31, 2020 $ 166,863 $ (6,870) $ 237,341 $ (19,900) $ 399,503 $ (363,900) $ 413,037 Foreign currency translation 62 — 27 — — — 89 Balance at December 31, 2021 $ 166,925 $ (6,870) $ 237,368 $ (19,900) $ 399,503 $ (363,900) $ 413,126 We assess goodwill for impairment during the fourth quarter as of October 1 of each year, and also if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The assessment consists of comparing the fair value of the reporting unit to the carrying value of the net assets assigned to the reporting unit, including goodwill. Fair values are generally determined by an income approach, discounting projected future cash flows based on our expectations of the current and future operating environment, using a market approach, applying a multiple of earnings based on guideline for publicly traded companies, or a combination thereof. Estimating future cash flows requires significant judgment about factors such as general economic conditions and projected growth rates, and our estimates often vary from the cash flows eventually realized. The rates used to discount projected future cash flows reflect a weighted average cost of capital based on our industry, capital structure and risk premiums including those reflected in the current market capitalization. In the event the fair value of a reporting unit exceeds its carrying amount, goodwill of the reporting unit is considered not impaired. If the carrying amount of a reporting unit exceeds its fair value, goodwill of the reporting unit is considered impaired, and an impairment charge would be recognized during the period in which the determination has been made for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized will not exceed the total amount of goodwill allocated to that reporting unit. Assessing impairment inherently involves management judgments as to the assumptions used to calculate fair value of the reporting units and the impact of market conditions on those assumptions. The key inputs that management uses in its assumptions to estimate the fair value of our reporting units under the income-based approach are as follows: ● Projected cash flows of the reporting unit, with consideration given to projected revenues, operating margins and the levels of capital investment required to generate the corresponding revenues; and ● Weighted average cost of capital (“WACC”), the risk-adjusted rate used to discount the projected cash flows. To develop the projected cash flows of our reporting units, management considers factors that may impact the revenue streams within each reporting unit. These factors include, but are not limited to, economic conditions on both a global scale and specifically in the regions in which the reporting units operate, customer relationships, strategic plans and opportunities, required returns on invested capital and competition from other service providers. With regard to operating margins, management considers its historical reporting unit operating margins on the revenue streams within each reporting unit, adjusting historical margins for the projected impact of current market trends on both fixed and variable costs. Expected future after-tax operating cash flows of each reporting unit are discounted to a present value using a risk-adjusted discount rate. Estimates of future cash flows require management to make significant assumptions regarding future operating performance including the projected mix of revenue streams within each reporting unit, projected operating margins, the amount and timing of capital investments and the overall probability of achieving the projected cash flows, as well as future economic conditions, which may result in actual future cash flows that are different than management’s estimates. The discount rate, which is intended to reflect the risks inherent in future cash flow projections, used in estimating the present value of future cash flows, is based on estimates of the WACC of market participants relative to the reporting units. Financial and credit market volatility can directly impact certain inputs and assumptions used to develop the WACC. The result of the annual assessment of goodwill undertaken in the fourth quarter of 2021 indicated that the fair value of each of our reporting units was in excess of its respective carrying value. In connection with our financial review and forecasting procedures performed during the first quarter of 2020, management determined that the projected future cash flows of our Energy Waste (“EW”) reporting unit and our International reporting unit (described below) indicated that the fair value of such reporting units may be below their respective carrying amounts. Accordingly, we performed an interim assessment of each reporting unit’s fair value as of March 31, 2020 (the “Interim Assessment”). Based on the results of the Interim Assessment, we recognized goodwill impairment charges of $283.6 million related to our EW reporting unit and $16.7 million related to our International reporting unit in the first quarter of 2020. During the fourth quarter of 2020, the Company finalized the purchase price allocation related to the NRC Merger. The finalization of fair value estimates during the fourth quarter of 2020, and resulting final determination of goodwill by reporting unit, resulted in an increase in the amount of goodwill assigned to the EW reporting unit and a decrease in the amount of goodwill assigned to the International reporting unit. $80.3 million of additional goodwill assigned to the EW reporting unit was immediately impaired in the fourth quarter of 2020 based on the fair value of the reporting unit determined in the Interim Assessment. The decrease in goodwill assigned to the International reporting unit resulted in the reversal in the fourth quarter of 2020 of $11.2 million of International reporting unit goodwill impairment charges recorded in the first quarter of 2020. Our EW reporting unit, the sole component of our Energy Waste segment, provides energy-related services including solid and liquid waste treatment and disposal, equipment cleaning and maintenance, specialty equipment rental, spill containment and site remediation for a full complement of oil and gas waste streams, predominately to upstream energy customers currently concentrated in the Eagle Ford and Permian Basins in Texas. Our International reporting unit, a component of our Field Services segment, provides industrial and emergency response services to the offshore oil and gas sector in the North Sea and land-based industries across the EMEA region. Both our EW and International reporting units are dependent on energy-related exploration and production investments and expenditures by our energy industry customers. Lower crude oil prices and the volatility of such prices affect the level of investment as it impacts the ability of energy companies to access capital on economically advantageous terms or at all. In addition, energy companies decrease investments when the projected profits are inadequate or uncertain due to lower crude oil prices or volatility in crude oil prices. Such reductions in capital spending negatively impact energy waste generation and therefore the demand for our services. The principal factors contributing to the goodwill impairment charges for both the EW and International reporting units related to historically-low energy commodity prices reducing anticipated energy-related exploration and production investments and expenditures by our energy industry customers, which negatively impacted each reporting unit’s prospective cash flows and each reporting unit's estimated fair value. A longer-than-expected recovery in crude oil pricing and energy-related exploration and production investments became evident during the first quarter of 2020 as we assessed the projected impact of the COVID-19 pandemic and foreign oil production increases on the global demand for oil and updated the long-term projections for each reporting unit which, as a result, decreased each reporting unit’s anticipated future cash flows as compared to those estimated previously. Consistent with our annual impairment testing methodology, we utilized a weighted average of (1) an income approach and (2) a market approach to determine the fair value of each of the reporting units for the Interim Assessment. The income approach is based on the estimated present value of future cash flows for each reporting unit. The market approach is based on assumptions about how market data relates to each reporting unit. The rapid and sustained decline in the energy markets served by our EW and International reporting units, exacerbated by the uncertainty surrounding the impact of the COVID-19 pandemic and foreign oil production increases, has inherently increased the risk associated with the future cash flows of these reporting units. Accordingly, when performing the Interim Assessment, we increased the discount rates and decreased the projected capital investment for each reporting unit compared to the assumptions used in the initial fair value assessment in connection with the NRC Merger on November 1, 2019. We also considered the estimated fair value of our EW and International reporting units under a market-based approach by applying industry-comparable multiples of revenues and operating earnings to reporting unit revenues and operating earnings. The lack of a broad base of publicly available market data specific to the industry in which we operate, combined with the general market volatility attributable to the COVID-19 pandemic, results in a wide range of currently observable market multiples. Accordingly, we applied less weight to the estimated fair value of our reporting units calculated under the market-based approach (10%) compared to the income approach (90%) described above. The result of the annual assessment of goodwill undertaken in the fourth quarter of 2020 indicated that the fair value of each of our reporting units was in excess of its respective carrying value, with the exception of our Field Services reporting unit. Our Field Services reporting unit, a component of our Field Services segment, offers specialty field services and total waste management solutions to commercial and industrial facilities and to government entities through our 10-day transfer facilities and at customer sites. Consistent with prior assessments, we utilized a weighted average of (1) an income approach and (2) a market approach to determine the fair value of each of the Field Services reporting unit. The income approach is based on the estimated present value of future cash flows for the reporting unit. The market approach is based on assumptions about how market data relates to the reporting unit. The estimated fair value of the Field Services reporting unit was then compared to the reporting unit’s carrying amount as of October 1, 2020. Based on the results of that comparison, the carrying amount of the Field Services reporting unit exceeded the estimated fair value of the reporting unit by $14.4 million and, as a result, we recognized a corresponding goodwill impairment charge in the fourth quarter of 2020. The factors contributing to the $14.4 million goodwill impairment charge principally related to an increase in the risk-adjusted rate used to discount the projected cash flows of the reporting unit as a result of the decline in our share price since the last annual assessment as well as a slower than expected recovery to cash flow levels forecasted prior to the COVID-19 pandemic, which negatively impacted the reporting unit’s prospective financial information in its discounted cash flow model and the reporting unit’s estimated fair value as compared to previous estimates. Intangible assets as of December 31, 2021 and 2020 consisted of the following: 2021 2020 Accumulated Accumulated $s in thousands Cost Amortization Net Cost Amortization Net Amortizing intangible assets: Permits, licenses and lease $ 174,959 $ (27,170) $ 147,789 $ 174,885 $ (23,005) $ 151,880 Customer relationships 340,065 (87,952) 252,113 340,032 (61,778) 278,254 Technology - formulae and processes 7,166 (2,531) 4,635 7,142 (2,293) 4,849 Customer backlog 3,652 (2,752) 900 3,652 (2,387) 1,265 Tradename 10,390 (10,390) — 10,390 (8,015) 2,375 Developed software 2,903 (2,475) 428 2,902 (2,182) 720 Non-compete agreements 5,573 (5,211) 362 5,571 (4,318) 1,253 Internet domain and website 536 (213) 323 536 (184) 352 Database 390 (235) 155 389 (214) 175 Total amortizing intangible assets 545,634 (138,929) 406,705 545,499 (104,376) 441,123 Non-amortizing intangible assets: Permits and licenses 82,734 — 82,734 82,732 — 82,732 Tradename 134 — 134 133 — 133 Total intangible assets $ 628,502 $ (138,929) $ 489,573 $ 628,364 $ (104,376) $ 523,988 We review non-amortizing intangible assets for impairment during the fourth quarter as of October 1 of each year. Fair value is generally determined by considering an internally developed discounted projected cash flow analysis. Estimating future cash flows requires significant judgment about factors such as general economic conditions and projected growth rates, and our estimates often vary from the cash flows eventually realized. If the fair value of an asset is determined to be less than the carrying amount of the intangible asset, an impairment in the amount of the difference is recorded in the period in which the annual assessment occurs. The results of the annual assessment of non-amortizing intangible assets undertaken in the fourth quarter of 2021 indicated no impairment charges were required. The results of the annual assessment of non-amortizing intangible assets undertaken in the fourth quarter of 2020 indicated no impairment charges were required, with the exception of certain non-amortizing permit intangibles within our Field Services segment. Our Field Services segment provides government-mandated, commercial standby oil spill compliance solutions to companies that store, transport, produce or handle petroleum and certain nonpetroleum oils on or near U.S. waters. A company’s ability to provide these standby services is subject to significant regulatory certification requirements and other high barriers to entry. As such, the Company assigned $57.1 million of fair value to non-amortizing standby services permit intangible assets upon finalization of the purchase accounting allocation related to the NRC Merger. In performing the annual indefinite-lived intangible assets impairment tests, the estimated fair value of the standby services permits was determined under an income approach using discounted projected future cash flows associated with the permits and then compared to the $57.1 million carrying amount of the permits as of October 1, 2020. Based on the results of that evaluation, the carrying amount of the permits exceeded the estimated fair value of the permits and, as a result, we recognized a $21.1 million impairment charge in the fourth quarter of 2020. The factors contributing to the impairment charge principally related to a less favorable outlook on the potential for both significant oil spill events and growth opportunities, which negatively impacted the discounted projected cash flows associated with the standby services permits and their estimated fair value as compared to previous estimates. On November 1, 2019, the Company completed the NRC Merger and recorded $577.4 million of goodwill, $252.1 million of amortizing intangible assets (consisting primarily of customer relationships) and $57.4 million of non-amortizing intangible assets (consisting of permits and licenses) as a result of the acquisition. See Note 5 for additional information. 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 5 for additional information. On August 1, 2019, the Company acquired US Ecology Sarnia and recorded $7.7 million of goodwill and $6.2 million of amortizing intangible assets (consisting primarily of customer relationships) as a result of the acquisition. See Note 5 for additional information. Amortization expense relating to intangible assets was $34.6 million, $37.3 million and $15.5 million for the years ended December 31, 2021, 2020 and 2019, respectively. Foreign intangible asset carrying amounts are affected by foreign currency translation. Future amortization expense of amortizing intangible assets is expected to be as follows: Expected $s in thousands Amortization 2022 $ 31,403 2023 31,216 2024 30,830 2025 30,586 2026 29,767 Thereafter 252,903 $ 406,705

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
EMPLOYEE BENEFIT PLANS	Dec. 31, 2021
EMPLOYEE BENEFIT PLANS
EMPLOYEE BENEFIT PLANS	NOTE 14. EMPLOYEE BENEFIT PLANS Defined Contribution Plans We maintain the US Ecology, Inc., 401(k) Savings and Retirement Plan (“the Plan”) for employees who voluntarily contribute a portion of their compensation, thereby deferring income for federal income tax purposes. Participants may contribute a percentage of salary up to the IRS limitations. The Company contributes a matching contribution equal to 55% of participant contributions up to 6% of eligible compensation. The Company contributed matching contributions to the Plan of $6.4 million, $3.3 million and $3.0 million in 2021, 2020 and 2019, respectively. The Company maintained 401(k) savings and retirement plans (“the NRC Plans”) for the employees that joined the Company through the NRC Merger, until the NRC Plans were merged into the Plan on January 1, 2021. The Company contributed matching contributions to the NRC Plans of $2.3 million and $325,000 in 2020 and 2019, respectively. We also maintain the Stablex Canada Inc. Simplified Pension Plan (“the SPP”). This defined contribution plan covers substantially all of our non-union employees at our Blainville, Québec facility in Canada. Employees represented by the Unifor Section Local 171 receive Company contributions to the Regime de Retraite Par Financement Salarial pension plan and employees at our other Canadian facilities receive contributions to separate defined contribution plans. The Company contributes 5% to 9.5% of eligible compensation to these plans. The Company contributed $858,000, $782,000 and $719,000 in aggregate to these plans in 2021, 2020 and 2019, respectively. Multi-Employer Defined Benefit Pension Plans Certain of the Company’s wholly-owned subsidiaries participate in a total of four multi-employer defined benefit pension plans under the terms of collective bargaining agreements covering most of the subsidiaries’ union employees. Contributions are determined in accordance with the provisions of negotiated labor contracts and are generally based on stipulated rates per hours worked. Benefits under these plans are generally based on compensation levels and years of service. The financial risks of participating in multi-employer plans are different from single employer defined benefit pension plans in the following respects: ● Assets contributed to the multi-employer plan by one employer may be used to provide benefits to employees of other participating employers. ● If a participating employer discontinues contributions to a plan, the unfunded obligations of the plan may be borne by the remaining participating employers. ● If a participating employer chooses to stop participating in a plan, a withdrawal liability may be created based on the unfunded vested benefits for all employees in the plan. Information regarding significant multi-employer pension benefit plans in which the Company participates is shown in the following table: Pension Protection Act Certified Plan Employer Plan Zone Status Name of Plan ID Number Number 2021 2020 Operating Engineers Local 324 Pension Fund 38-1900637 001 Red Red The Company contributed $1.1 million and $1.0 million to the Operating Engineers Local 324 Pension Fund (the “Local 324 Plan”) in 2021 and 2020, respectively. The Company also contributed $157,000 and $205,000 to other multi-employer plans in 2021 and 2020, respectively, which are excluded from the table above as they are not individually significant. Based on information as of April 30, 2021 and 2020, the year end of the Local 324 Plan, the Company’s contributions made to the Local 324 Plan represented less than 5% of total contributions received by the Local 324 Plan during the 2021 and 2020 plan years. The certified zone status in the table above is defined by the Department of Labor and the Pension Protection Act of 2006 and represents the level at which the plan is funded. Plans in the red zone are less than 65% funded; plans in the yellow zone are less than 80% funded; and plans in the green zone are at least 80% funded. The certified zone status is as of the Local 324 Plan’s year-end of April 30, 2021 and 2020.

CLOSURE AND POST-CLOSURE OBLIGA

CLOSURE AND POST-CLOSURE OBLIGATIONS	12 Months Ended
CLOSURE AND POST-CLOSURE OBLIGATIONS	Dec. 31, 2021
CLOSURE AND POST-CLOSURE OBLIGATIONS
CLOSURE AND POST-CLOSURE OBLIGATIONS	NOTE 15. 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. We do not presently bear significant financial responsibility for closure and/or post-closure care of the disposal facilities located on state-owned land at our Beatty, Nevada site, provincial-owned land in Blainville, Québec; or state-leased federal land on the Department of Energy Hanford Reservation near Richland, Washington. The states of Nevada and Washington and the province of Québec collect fees from us based on the waste received on a quarterly or annual basis. Such fees are deposited in dedicated, government-controlled funds to cover the future costs of closure and post-closure care and maintenance. Such fees are periodically reviewed for adequacy by the governmental authorities. We maintain a surety bond for closure costs associated with the Stablex facility. Our lease agreement with the province of Québec requires that the surety bond be maintained for 25 years after the lease expires. We also maintain surety bonds for closure costs associated with our energy waste landfills in Texas. Under the terms of our waste disposal permits for these landfills, financial security must be provided to the Railroad Commission of Texas in an amount necessary to close the facility. At December 31, 2021 we had $13.3 million in commercial surety bonds dedicated for closure obligations at our operating and non-operating disposal facilities. In accounting for closure and post-closure obligations, which represent our asset retirement obligations, we recognize a liability as part of the fair value of future asset retirement obligations and an associated asset as part of the carrying amount of the underlying asset. This obligation is valued based on our best estimates of current costs and current estimated closure and post-closure costs taking into account current technology, material and service costs, laws and regulations. These cost estimates are increased by an estimated inflation rate, estimated to be 2.6% at December 31, 2021. Inflated current costs are then discounted using our credit-adjusted risk-free interest rate, which approximates our incremental borrowing rate, in effect at the time the obligation is established or when there are upward revisions to our estimated closure and post-closure costs. Our weighted-average credit-adjusted risk-free interest rate at December 31, 2021 approximated 5.3%. Changes to reported closure and post-closure obligations for the years ended December 31, 2021 and 2020, were as follows: $s in thousands 2021 2020 Closure and post-closure obligations, beginning of year $ 95,869 $ 86,383 NRC Merger purchase price allocation adjustment — 1,782 Accretion expense 5,363 4,000 Payments (3,054) (1,750) Adjustments 732 5,422 Foreign currency translation 10 32 Closure and post-closure obligations, end of year 98,920 95,869 Less current portion (5,771) (6,471) Long-term portion $ 93,149 $ 89,398 Adjustment to the obligations represents changes in the expected timing or amount of cash expenditures based upon actual and estimated cash expenditures. The adjustments in 2021 were primarily attributable to a $584,000 increase in closure and post-closure obligations at our Belleville, Michigan operating facility due to an increase in estimated closure costs. The adjustments in 2020 were primarily attributable to a $5.4 million increase in closure and post-closure obligations at our Robstown, Texas operating facility due to placing a new landfill cell into service in the fourth quarter of 2020. Changes in the reported closure and post-closure asset, recorded as a component of Property and equipment, net, in the consolidated balance sheets, for the years ended December 31, 2021 and 2020 were as follows: $s in thousands 2021 2020 Net closure and post-closure asset, beginning of year $ 26,532 $ 22,884 NRC Merger purchase price allocation adjustment — (389) Additions or adjustments to closure and post-closure asset 732 5,422 Amortization of closure and post-closure asset (1,614) (1,407) Foreign currency translation 12 22 Net closure and post-closure asset, end of year $ 25,662 $ 26,532

DEBT

DEBT	12 Months Ended
DEBT	Dec. 31, 2021
DEBT
DEBT	NOTE 16. DEBT Long-term debt consisted of the following: December 31, $s in thousands 2021 2020 Revolving credit facility $ 303,000 $ 347,000 Term loan 441,000 445,500 Unamortized term loan discount and debt issuance costs (5,516) (6,657) Total debt 738,484 785,843 Current portion of long-term debt (3,359) (3,359) Long-term debt $ 735,125 $ 782,484 Future maturities of long-term debt, excluding unamortized discount and debt issuance costs, as of December 31, 2021 consisted of the following: $s in thousands Maturities 2022 $ 4,500 2023 4,500 2024 4,500 2025 4,500 2026 726,000 Thereafter — $ 744,000 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 EBITDA (as defined in the Credit Agreement) 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 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 year ended December 31, 2021, the effective interest rate on the term loan, including the impact of the amortization of debt issuance costs, was 2.86%. 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 Consolidated 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 year ended December 31, 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 4.00%. 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 December 31, 2021, there were $303.0 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 December 31, 2021, there were no borrowings outstanding subject to the Sweep Arrangement. As of December 31, 2021, the availability under the Revolving Credit Facility was $71.2 million, subject to our leverage covenant limitation, with $12.2 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 as 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 December 31, 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 $440.0 million, or approximately 59%, of the Revolving Credit Facility and term loan borrowings outstanding as of December 31, 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. The fair value of the interest rate swap as of December 31, 2021 is an asset of $5.0 million which is included in Other assets with the offset to Accumulated other comprehensive loss on the Company’s consolidated balance sheet. During the years ended December 31, 2021, 2020 and 2019, the Company recognized $3.7 million of losses, $3.3 million of losses and $170,000 of gains, respectively, related to settlements of the interest rate swaps which were recorded as Interest expense on the Company’s consolidated statements of operations.

INCOME TAXES

INCOME TAXES	12 Months Ended
INCOME TAXES	Dec. 31, 2021
INCOME TAXES
INCOME TAXES	NOTE 17. INCOME TAXES The domestic and foreign components of income (loss) before income taxes consisted of the following: $s in thousands 2021 2020 2019 Domestic $ (10,567) $ (403,492) $ 30,706 Foreign 20,669 9,891 19,093 Income (loss) before income taxes $ 10,102 $ (393,601) $ 49,799 The components of the income tax expense (benefit) consisted of the following: $s in thousands 2021 2020 2019 Current: U.S. Federal $ (1,534) $ (9,905) $ 3,120 State 68 3,062 1,547 Foreign 6,948 6,768 5,426 Total current 5,482 (75) 10,093 Deferred: U.S. Federal (509) 1,384 5,977 State 503 (2,859) 714 Foreign (711) (2,692) (125) Total deferred (717) (4,167) 6,566 Income tax expense (benefit) $ 4,765 $ (4,242) $ 16,659 A reconciliation between the statutory federal income tax rate and the effective income tax rate is as follows: 2021 2020 2019 Taxes computed at federal statutory rate 21.0 % 21.0 % 21.0 % Goodwill impairment charges — (20.4) — State income taxes (net of federal income tax benefit) 9.8 0.3 5.7 Share-based compensation 4.6 (0.1) (0.4) Research and development credits (4.4) 0.1 (0.8) Non-deductible transaction costs 1.6 — 3.4 Global intangible low taxed income — — 1.1 Foreign rate differential 11.0 (0.3) 2.5 Net operating loss reduction — (1.7) — Change in unrecognized tax benefits — 1.7 — State deferred rate differential — (0.1) (1.6) State credits (5.1) — — Assumed contingent liability 3.1 — — Non-deductible executive compensation 1.5 — — Non-deductible foreign expenses 4.3 — — Non-deductible political contributions 1.3 — — Net operating loss carryback rate differential (4.6) — — Other 3.1 0.6 2.6 47.2 % 1.1 % 33.5 % The components of the total net deferred tax assets and liabilities as of December 31, 2021 and 2020 consisted of the following: $s in thousands 2021 2020 Deferred tax assets: Net operating losses $ 16,963 $ 18,751 Operating leases 10,980 12,875 Foreign tax credit and capital loss carry forwards 5,579 4,928 Accruals, allowances and other 4,963 8,691 Environmental compliance and other site related costs 10,833 10,909 Unrealized foreign exchange gains 819 790 Total deferred tax assets 50,137 56,944 Less: valuation allowance (4,164) (4,207) Net deferred tax assets 45,973 52,737 Deferred tax liabilities: Property and equipment (50,601) (53,838) Intangible assets (106,504) (107,109) Operating leases (10,980) (12,875) Other (1,370) 102 Total deferred tax liabilities (169,455) (173,720) Net deferred tax liability $ (123,482) $ (120,983) All deferred tax assets and liabilities are recorded in Deferred income taxes, net on the consolidated balance sheets as of December 31, 2021 and 2020. Utilization of the Company’s net operating loss carryforwards are subject to an annual limitation due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. Such an annual limitation could result in the expiration or elimination of the net operating loss carryforwards before utilization. Management believes that the limitation will not limit utilization of the carryforwards prior to their expiration based on the historic profitability of the Company and certain favorable adjustments available to the annual limitation calculations. As of December 31, 2021, we had approximately $58.5 million, $7.2 million, and $52.2 million of federal, foreign, and state and local net operating losses (“NOLs”), respectively. A portion of the federal NOLs begin to expire in 2029 and the remaining federal NOLs have no expiration date. Approximately $26.4 million of the US Federal NOLs are indefinite lived and the remainder expire between 2029 and 2037. Foreign NOLs are indefinite lived and therefore have no expiration date. State and local NOLs expire between 2022 and 2041. We have historically recorded a valuation allowance for certain deferred tax assets due to uncertainties regarding future operating results and limitations on utilization of state and local NOLs for tax purposes. At December 31, 2021 and 2020, we maintained a valuation allowance of approximately $37,000 and $79,000, respectively, for state and local NOLs that are not expected to be utilizable prior to expiration. The valuation allowance as of December 31, 2021 and 2020 was primarily related to foreign tax credit that, in the judgment of management, was not more likely than not to be realized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets depends on the generation of future taxable income during the periods in which those temporary differences are deductible. Management considers the scheduled reversal of deferred tax liabilities (including the impact of available carryback and carryforward periods), projected taxable income, and tax-planning strategies in making this assessment. The net valuation allowance decreased $42,000 for the year ended December 31, 2021 compared to December 31, 2020. Changes to unrecognized tax benefits for the years ended December 31, 2021, 2020 and 2019, were as follows: $s in thousands 2021 2020 2019 Unrecognized tax benefits, beginning of year $ 239 $ 8,335 $ 555 Gross increases - tax positions in prior period 9 — 8,088 Gross decreases - tax positions in prior period — (8,091) (9) Gross increases - tax positions in current period 58 50 52 Settlements — — (284) Lapse of statute of limitations (50) (55) (67) Unrecognized tax benefits, end of year $ 256 $ 239 $ 8,335 As of December 31, 2021, the total amount of unrecognized tax benefits was $256,000, of which $237,000, if recognized, would favorably impact our future earnings. The $8.1 million decrease in prior period tax positions in 2020 related to the acquired NRC net operating losses that were recorded as a reduction to our net operating losses deferred tax asset in 2019 for which an election to treat them as expired was made during 2020. 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 as of December 31, 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 is subject to examination by the IRS for tax years 2018 through 2021. The 2017 through 2021 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. The tax years 2017 through 2021 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.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Dec. 31, 2021
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	NOTE 18. 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” or the “MDL”). The claims against National Response Corporation, and other “Dispersant Defendants,” were brought by workers and others who alleged injury arising from post-explosion clean–up efforts, including particularly the use of certain chemical dispersants. In January 2013, the Court approved a Medical Benefits Class Action Settlement, which, among other things, provided for a “class wide” settlement as well as a release of claims against Dispersant Defendants, including National Response Corporation. Further, National Response Corporation successfully moved the court to dismiss all claims against it based on derivative immunity, as it was acting at the direction of the U.S. Government. In early 2018, BP began asserting an alleged contractual right of indemnity against National Response Corporation and others in post-settlement lawsuits brought by persons who had either chosen not to participate in the class-wide agreement or whose injuries were allegedly manifest after the period covered by the claim submission process. The Company advised BP that it considers the attempt to bring National Response Corporation back into previously settled litigation to be improper and moved for a declaratory judgment that it owes no indemnity or contribution to BP, raising various arguments, including BP’s own actions and conduct over the preceding nine years with respect to these claims (including its failure to seek indemnity) and the resultant prejudice to National Response Corporation, BP’s waiver of any indemnity, and the court’s prior finding that National Response Corporation is entitled to derivative immunity. In response, BP asserted counterclaims against National Response Corporation for a declaratory judgment that National Response Corporation must indemnify BP under certain circumstances and for unjust enrichment. National Response Corporation successfully moved to dismiss the unjust enrichment claim. The parties filed simultaneous judgment on the pleadings briefs in February 2020, and all oppositions were filed on March 16, 2020. On May 4, 2020, the court found in favor of National Response Corporation, and held that the Company is not liable to BP or any back end litigation plaintiffs for any damages related to the Deepwater Horizon oil spill. BP timely appealed the ruling on June 11, 2020. On January 19, 2022, the U.S. Court of Appeals for the Fifth Circuit held with respect to NRC that the district court erred in stating that BP was not entitled to indemnity from NRC under any circumstances but remanded to the district court for a claim-specific factual inquiry. The Court made clear that indemnity was only possible in the event of gross negligence or willful misconduct by NRC in cases where the claims in question were not otherwise lost under Texas law. The Company is currently unable to estimate the range of possible losses associated with this proceeding, although the Company believes that the opinion of the Court of Appeals positions it well on remand. Additionally, the Company believes that if it were deemed to have liability arising out of or related to BP’s indemnity claims, such liability would be covered by an indemnity by SEACOR Holdings Inc., the former owner of National Response Corporation, in favor of National Response Corporation and its affiliates. On November 17, 2018, an explosion occurred at our Grand View, Idaho facility. 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, as of December 31, 2021 we were not 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.

EQUITY

EQUITY	12 Months Ended
EQUITY	Dec. 31, 2021
EQUITY
EQUITY	NOTE 19. EQUITY Equity-Based Purchase Consideration Pursuant to the NRC Merger Agreement, on November 1, 2019 the Company paid $626.5 million of the purchase price in equity-based consideration comprising 9,337,949 newly-issued shares of US Ecology common stock, 3,772,753 replacement warrants, 118,239 replacement restricted stock units and 29,400 replacement stock options. 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. The Company repurchased 397,600 shares of common stock in an aggregate amount of $17.3 million under the repurchase program during the year ended December 31, 2020. 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 December 31, 2021, 2,088,750 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 Stock Units (PSUs) We have PSU awards outstanding under the Omnibus Plan. Each PSU represents the right to receive, on the settlement date, one share of the Company’s common stock. The total number of 2019 PSUs each participant is eligible to earn ranges from 0% to 300% of the target number of PSUs granted in 2019. The actual number of 2019 PSUs that will vest and be settled in shares is determined based on achievement of certain Company financial performance metrics and total stockholder return relative to a set of peer companies, over a three-year performance period. Compensation expense is recorded over the awards’ three-year vesting period. On January 24, 2020, the Company granted 5,358 PSUs to certain employees. Each January 2020 PSU represents the right to receive, on the settlement date, one share of the Company’s common stock. The actual number of January 2020 PSUs that will vest and be settled in shares is determined based on the achievement of certain milestones. The fair value of the January 2020 PSUs estimated on the grant date was $54.55 per unit. Compensation expense is recorded over the awards’ milestone measurement period. On July 16, 2020, the Company granted 51,922 PSUs to certain employees. Each July 2020 PSU represents the right to receive, on the settlement date, one share of the Company’s common stock. The total number of July 2020 PSUs each participant is eligible to earn ranges from 0% to 200% of the target number of PSUs granted. The actual number of July 2020 PSUs that will vest and be settled in shares is determined at the end of a 2.5-year performance period beginning July 1, 2020, based on the Company’s total shareholder return relative to a set of peer companies. Compensation expense is recorded over the awards’ 2.5-year vesting period. The Company did not grant any PSUs in 2021. A summary of our PSU activity is as follows: Weighted Average Grant Date Units Fair Value Outstanding as of December 31, 2020 86,070 $ 49.45 Vested (31,211) 60.62 Cancelled, expired or forfeited (1,474) 54.55 Outstanding as of December 31, 2021 53,385 $ 42.79 The fair value of PSUs granted on July, 16, 2020 and March 1, 2019 was estimated as of the date of grant using a Monte Carlo simulation model. The grant date fair value of PSUs granted on July 16, 2020 and March 1, 2019 was $42.47 and $58.20 per unit, respectively. Assumptions used in the Monte Carlo simulation to calculate the fair value of the PSUs granted are as follows: 2020 2019 Stock price on grant date $ 32.89 $ 58.40 Expected term 2.5 years 3.0 years Expected volatility 40.6 % 30.0 % Risk-free interest rate 0.2 % 2.5 % Expected dividend yield — % 1.1 % During 2021, 31,211 PSUs vested and PSU holders earned zero shares of the Company’s common stock. Stock Options We have stock option awards outstanding under the 2008 Stock Option Plan and the Omnibus Plan. Stock options expire ten years from the date of grant and generally vest over a period of three years from the date of grant. Vesting requirements for non-employee directors are contingent on attending a minimum of 75% of regularly scheduled board meetings during the year. Upon the exercise of stock options, common stock is issued from treasury stock or, when depleted, from new stock issuances. A summary of our stock option activity is as follows: Weighted Weighted Average Average Aggregate Remaining Exercise Intrinsic Contractual Shares Price Value Term (Years) Outstanding as of December 31, 2020 357,033 $ 49.93 Granted 205,800 35.30 Cancelled, expired or forfeited (16,239) 44.38 Outstanding as of December 31, 2021 546,594 $ 44.59 $ — 6.9 Exercisable as of December 31, 2021 283,329 $ 48.52 $ — 5.3 The weighted average grant date fair value of all stock options granted during 2021, 2020 and 2019 was $9.90, $12.30 and $14.26 per share, respectively. The total intrinsic value of stock options exercised during 2020 and 2019 was $100,000 and $152,000, respectively. No The fair value of each stock option is estimated as of the date of grant using the Black-Scholes option-pricing model. Expected volatility is estimated based on an average of actual historical volatility and implied volatility corresponding to the stock option’s estimated expected term. We believe this approach to determine volatility is representative of future stock volatility. The expected term of a stock option is estimated based on analysis of stock options already exercised and foreseeable trends or changes in behavior. The risk-free interest rates are based on the U.S. Treasury securities maturities as of each applicable grant date. The dividend yield is based on analysis of actual historical dividend yield. The significant weighted-average assumptions relating to the valuation of option grants are as follows: 2021 2020 2019 Expected life 3.8 years 4.0 years 2.7 years Expected volatility 38 % 30 % 30 % Risk-free interest rate 0.2 % 1.4 % 2.1 % Expected dividend yield 0.5 % 1.2 % 1.2 % Restricted Stock We have restricted stock awards outstanding under the Omnibus Plan. Generally, restricted stock awards vest annually over a three-year period. Vesting of restricted stock awards to non-employee directors is contingent on the non-employee director attending a minimum of 75% of regularly scheduled board meetings and 75% of the meetings of each committee of which the non‐employee director is a member during the year. Upon the vesting of restricted stock awards, common stock is issued from treasury stock or, when depleted, from new stock issuances. A summary of our restricted stock activity is as follows: Weighted Average Grant Date Shares Fair Value Outstanding as of December 31, 2020 72,766 $ 51.47 Granted 84,800 36.49 Vested (47,002) 47.08 Outstanding as of December 31, 2021 110,564 $ 41.85 The total fair value of restricted stock vested during 2021, 2020 and 2019 was $1.8 million, $2.3 million and $2.5 million, respectively. Restricted Stock Units We have restricted stock unit awards outstanding under the Omnibus Plan. Each restricted stock unit represents the right to receive, on the settlement date, one share of the Company’s common stock. Generally, restricted stock unit awards vest annually over a three-year period. Upon the vesting of restricted stock unit awards, common stock is issued from treasury stock or, when depleted, from new stock issuances. A summary of our restricted stock unit activity is as follows: Weighted Average Grant Date Units Fair Value Outstanding as of December 31, 2020 147,243 $ 39.92 Granted 62,759 39.33 Vested (64,597) 44.75 Cancelled, expired or forfeited (18,856) 42.51 Outstanding as of December 31, 2021 126,549 $ 36.78 The total fair value of restricted stock units vested during 2021, 2020 and 2019 was $2.6 million, $3.0 million and $4.8 million, respectively. Treasury Stock During 2021, the Company repurchased 12,788 shares of the Company’s common stock in connection with the net share settlement of employee withholding taxes due on vested equity awards at an average cost of $36.33 per share and issued 128,714 shares of common stock from our treasury stock in connection with employee equity awards at an average cost of $43.93 per share. During 2020, the Company repurchased 17,169 shares of the Company’s common stock in connection with the net share settlement of employee withholding taxes due on vested equity awards at an average cost of $57.91 per share, repurchased 397,600 shares of the Company’s common stock under our stock repurchase program at an average cost of $43.61 per share and issued 56,381 shares of common stock from our treasury stock in connection with employee equity awards at an average cost of $44.20 per share. Share-Based Compensation Expense All share-based compensation is measured at the grant date based on the fair value of the award, and is recognized as an expense in earnings over the requisite service period. The components of pre-tax share-based compensation expense (primarily included in Selling, general and administrative expenses in our consolidated statements of operations) and related tax benefits were as follows: $s in thousands 2021 2020 2019 Share-based compensation from: Stock options $ 1,201 $ 725 $ 575 Restricted stock 2,719 2,032 1,662 Restricted stock units (1) 2,758 3,810 6,193 Performance stock units (2) 1,211 1,266 831 Total share-based compensation 7,889 7,833 9,261 Income tax benefit (1,162) (2,115) (3,098) Share-based compensation, net of tax $ 6,727 $ 5,718 $ 6,163 (1) Share-based compensation from restricted stock units for the years ended December 31, 2020 and 2019 includes $605,000 and $3.7 million, respectively, of compensation expense related to the accelerated vesting of restricted stock unit awards upon the termination of former employees of NRC subsequent to the NRC Merger in accordance with change-in-control provisions of their respective employment agreements. Share-based compensation from restricted stock units for the year ended December 31, 2021 and 2020 also includes $434,000 and $405,000, respectively, of compensation expense related restricted stock unit awards granted to certain employees identified as critical to the successful integration of NRC. Share-based compensation from these awards is attributable entirely to the NRC Merger therefore the Company has classified this portion of share-based compensation expense as business development and integration expenses within Selling, general and administrative expenses in our consolidated statements of operations. (2) Share-based compensation from performance stock units for the year ended December 31, 2021 includes a benefit of $23,000 to compensation expense related to the expiration of milestone-based performance stock unit awards granted to certain employees identified as critical to the successful integration of NRC. Share-based compensation from performance stock units for the year ended December 31, 2020 includes $173,000 of compensation expense related to achievement of milestone-based performance stock unit awards granted to certain employees identified as critical to the successful integration of NRC. Share-based compensation from these awards is attributable entirely to the NRC Merger therefore the Company has classified this portion of share-based compensation expense as business development and integration expenses within Selling, general and administrative expenses in our consolidated statements of operations. The tax benefits from stock options exercised during 2020 and 2019 were $113,000 and $321,000, respectively. No Unrecognized Share-Based Compensation Expense As of December 31, 2021, there was $7.6 million of unrecognized compensation expense related to unvested share-based awards granted under our share-based award plans. The expense is expected to be recognized over a weighted average remaining vesting period of approximately one year. Warrants At December 31, 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

EARNINGS (LOSS) PER SHARE

EARNINGS (LOSS) PER SHARE	12 Months Ended
EARNINGS (LOSS) PER SHARE	Dec. 31, 2021
EARNINGS (LOSS) PER SHARE
EARNINGS (LOSS) PER SHARE	NOTE 20. EARNINGS (LOSS) PER SHARE 2021 2020 2019 $s and shares in thousands, except per share amounts Basic Diluted Basic Diluted Basic Diluted Net income (loss) $ 5,337 $ 5,337 $ (389,359) $ (389,359) $ 33,140 $ 33,140 Weighted average basic shares outstanding 31,138 31,138 31,126 31,126 23,521 23,521 Dilutive effect of share-based awards and warrants 235 — 228 Weighted average diluted shares outstanding 31,373 31,126 23,749 Earnings (loss) per share $ 0.17 $ 0.17 $ (12.51) $ (12.51) $ 1.41 $ 1.40 Anti-dilutive shares excluded from calculation 4,359 4,213 90

SEGMENT REPORTING

SEGMENT REPORTING	12 Months Ended
SEGMENT REPORTING	Dec. 31, 2021
OPERATING SEGMENTS
OPERATING SEGMENTS	NOTE 21. SEGMENT REPORTING 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”). All periods presented below have been recast to reflect these changes. Under our new structure our operations are 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. 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 Annual Report on Form 10-K, all periods presented have been recast to reflect these changes. Summarized financial information of our reportable segments for the years ended December 31, 2021, 2020 and 2019 is as follows: 2021 Waste Field Energy $s in thousands Solutions Services Waste Corporate Total Revenue $ 451,249 $ 500,187 $ 36,565 $ — $ 988,001 Depreciation, amortization and accretion $ 43,746 $ 44,368 $ 19,520 $ 3,142 $ 110,776 Capital expenditures $ 45,602 $ 15,393 $ 4,923 $ 2,748 $ 68,666 Total assets $ 796,645 $ 733,086 $ 216,292 $ 59,375 $ 1,805,398 2020 Waste Field Energy $s in thousands Solutions Services Waste Corporate Total Revenue $ 425,413 $ 473,754 $ 34,687 $ — $ 933,854 Depreciation, amortization and accretion $ 41,540 $ 43,465 $ 19,814 $ 3,086 $ 107,905 Capital expenditures $ 31,027 $ 16,149 $ 6,189 $ 4,034 $ 57,399 Total assets $ 773,448 $ 762,854 $ 231,475 $ 63,506 $ 1,831,283 2019 Waste Field Energy $s in thousands Solutions Services Waste Corporate Total Revenue $ 440,547 $ 232,402 $ 12,560 $ — $ 685,509 Depreciation, amortization and accretion $ 41,133 $ 15,007 $ 3,402 $ 1,760 $ 61,302 Capital expenditures $ 46,202 $ 5,986 $ 1,391 $ 4,521 $ 58,100 Total assets $ 755,566 $ 865,540 $ 534,738 $ 75,400 $ 2,231,244 Management uses Adjusted EBITDA as a financial measure to assess segment performance. Adjusted EBITDA is defined as net income (loss) 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 property and equipment impairment charges, non-cash goodwill and intangible asset impairment charges, gain on property insurance recoveries, 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 (loss), 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 for the years ended December 31, 2021, 2020 and 2019 is as follows: $s in thousands 2021 2020 2019 Net income (loss) $ 5,337 $ (389,359) $ 33,140 Income tax expense (benefit) 4,765 (4,242) 16,659 Interest expense 28,966 32,595 19,239 Interest income (1,417) (258) (605) Foreign currency loss 171 1,134 733 Other income (4,476) (788) (455) Property and equipment impairment charges — — 25 Goodwill and intangible asset impairment charges — 404,900 — Depreciation and amortization of plant and equipment 70,799 66,561 41,423 Amortization of intangible assets 34,614 37,344 15,491 Share-based compensation 7,478 6,651 5,544 Accretion and non-cash adjustment of closure & post-closure liabilities 5,363 4,000 4,388 Gain on property insurance recoveries — — (12,366) Business development and integration expenses 3,274 11,621 26,150 Adjusted EBITDA $ 154,874 $ 170,159 $ 149,366 Adjusted EBITDA, by reportable segment, for the years ended December 31, 2021, 2020 and 2019 is as follows: $s in thousands 2021 2020 2019 Waste Solutions $ 170,953 $ 176,702 $ 184,133 Field Services 70,578 81,770 26,707 Energy Waste 11,321 4,982 3,626 Corporate (97,978) (93,295) (65,100) Total $ 154,874 $ 170,159 $ 149,366 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 as of December 31, 2021 and 2020 are as follows: $s in thousands 2021 2020 United States $ 855,200 $ 882,639 Canada 65,437 68,623 EMEA 15,604 18,042 Other (1) 9,716 11,321 Total long-lived assets, net $ 945,957 $ 980,625 (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2021
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	NOTE 22. SUBSEQUENT EVENTS On February 8, 2022, we entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Republic Services, Inc., a Delaware corporation (“Republic”), and Bronco Acquisition Corp., a Delaware corporation and a wholly-owned subsidiary of Republic (“Merger Sub”). The Merger Agreement provides that, upon the terms and subject to the conditions set forth in the Merger Agreement, Merger Sub will merge with and into the Company (the “Merger”), with the Company continuing as the surviving corporation and as a wholly-owned subsidiary of Republic. At the effective time of the Merger, each share of our common stock issued and outstanding immediately prior to the effective time (other than shares of our common stock owned by Republic or the Company (as treasury stock or otherwise) or any of their respective direct or indirect wholly-owned subsidiaries as of immediately prior to the effective time or for which appraisal rights have been demanded properly in accordance with Section 262 of the General Corporation Law of the State of Delaware), will be converted into the right to receive $48.00 per share in cash, without interest. The consummation of the Merger is subject to certain conditions, including (i) the affirmative vote of the holders of a majority of the outstanding shares of our common stock, (ii) (a) the expiration or termination of any waiting period (or any extension thereof) under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and the rules and regulations promulgated thereunder, (b) receipt of other required regulatory approvals, and (iii) the absence of any law or order restraining, enjoining or otherwise prohibiting the Merger. Each of Republic’s, Merger Sub’s, and our obligation to consummate the Merger is also subject to additional customary conditions, including (x) subject to specific standards, the accuracy of the representations and warranties of the other party, and (y) performance in all material respects by the other party of its obligations under the Merger Agreement. The Merger Agreement also includes customary termination provisions for both the Company and Republic and provides that, in connection with the termination of the Merger Agreement, under specified circumstances, we will be required to pay Republic a termination fee of $46.3 million, including if (i) Republic terminates the Merger Agreement because the Board changes its recommendation regarding the Merger Agreement, (ii) the Company terminates the Merger Agreement prior to the receipt of the Company stockholder approval to enter into an acquisition agreement with a third-party with respect to a superior proposal or (iii) Republic or the Company terminates the Merger Agreement in certain circumstances and, in any such case, prior to such termination, a takeover proposal by a third-party shall have been publicly disclosed and not publicly withdrawn and within 12 months following the date of termination, the Company shall have entered into an alternative transaction agreement (whether or not relating to a takeover proposal made, communication or publicly disclosed prior to the termination of the Merger Agreement). The Merger Agreement also provides that if the Merger Agreement is terminated because (i) of the issuance of a nonappealable court order or legal restraint prohibiting the transaction for antitrust reasons or (ii) the transactions have not been consummated by August 8, 2023, and at such time, antitrust approval for the transaction has not been obtained but the other conditions to Closing have been satisfied, then Republic will be required to reimburse the Company for 50% of its reasonable and documented out-of-pocket expenses incurred in connection with the Merger up to $5.0 million (i.e., Republic’s reimbursement shall not exceed $2.5 million). The foregoing description of the Merger Agreement is a summary only and is qualified in its entirety by reference to the complete text of the Merger Agreement filed herewith as Exhibit 2.1.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Principles of Consolidation	Principles of Consolidation The accompanying financial statements are prepared on a consolidated basis. All inter-company balances and transactions have been eliminated in consolidation. Our year-end is December 31.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist primarily of cash on deposit, money market accounts or short-term investments with original maturities of 90 days or less at the date of acquisition. Cash and cash equivalents totaled $67.5 million and $73.8 million at December 31, 2021 and 2020, respectively. At December 31, 2021 and 2020, we had $54.4 million and $59.3 million, respectively, of cash at our operations outside the United States.
Receivables	Receivables Our receivables include invoiced and unbilled amounts where the Company has an unconditional right to payment. Receivables are stated at an amount management expects to collect. Based on management’s assessment of the credit history of the customers having outstanding balances and factoring in current economic conditions, management has concluded that potential unidentified losses on balances outstanding at year-end will not be material. Unbilled receivables are recorded for work performed under contracts that have not yet been invoiced to customers and arise due to the timing of billings. Substantially all unbilled receivables at December 31, 2021, were billed in the following month.
Restricted Cash and Investments	Restricted Cash and Investments Restricted cash and investments of $1.6 million and $5.6 million at December 31, 2021 and 2020, respectively, represent funds held in third-party managed trust accounts as collateral for our financial assurance obligations for post-closure activities at our non-operating facilities and other restricted funds related to deferred compensation plans. These funds are primarily invested in money market accounts.
Revenue Recognition	Revenue Recognition Revenues are recognized when control of the promised services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those services. We recognize revenue from three primary sources: (1) waste treatment, recycling and disposal services, (2) field and industrial waste management services, and (3) waste transportation services. Our waste treatment and disposal customers are legally obligated to properly treat and dispose of their waste in accordance with local, state, and federal laws and regulations. As our customers do not possess the resources to properly treat and dispose of their waste independently, they contract with the Company to perform these services. Waste treatment, recycling, and disposal revenue results primarily from fixed fees charged to customers for treatment and/or disposal or recycling of specified wastes. Waste treatment, recycling, and disposal revenue is generally charged on a per-ton or per-yard basis based on contracted prices and is recognized over time as the services are performed. Our treatment and disposal services are generally performed as the waste is received and considered complete upon final disposal. Field and industrial waste management services revenue results primarily from specialty onsite services such as high-pressure cleaning, tank cleaning, decontamination, remediation, transportation, spill cleanup and emergency response at refineries, chemical plants, steel and automotive plants, and other government, commercial and industrial facilities. We also provide hazardous waste packaging and collection services and total waste management solutions at customer sites and through our 10-day transfer facilities. These services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. Generally, the pricing in these types of contracts is fixed, but the quantity of services to be provided during the contract term is variable and revenues are recognized over the term of the agreements or as services are performed. As we have a right to consideration from our customers in an amount that corresponds directly with the value to the customer of the Company’s performance completed to date, we have applied the practical expedient to recognize revenue in the amount to which we have the right to invoice. Additionally, we have customers that pay annual retainer fees, primarily for our standby services, under long-term or evergreen contracts. Such retainer fees are recognized over time as the services are performed and it is probable that a significant reversal in the amount of cumulative revenue recognized on the contracts will not occur. Transportation and logistics revenue results from delivering customer waste to a disposal facility for treatment and/or disposal or recycling. Transportation services are generally not provided on a stand-alone basis and instead are bundled with other Company services. However, in some instances we provide transportation and logistics services for shipment of waste from cleanup sites to disposal facilities operated by other companies. For such arrangements, we allocate revenue to each performance obligation based on its relative standalone selling price. We generally determine standalone selling prices based on the prices charged to customer or using expected cost-plus margin. Transportation revenue is recognized over time as the waste is transported. Taxes and fees collected from customers concurrent with revenue-producing transactions to be remitted to governmental authorities are excluded from revenue. Our Richland, Washington disposal facility is regulated by the Washington Utilities and Transportation Commission (“WUTC”), which approves our rates for disposal of low-level radioactive waste (“LLRW”). Annual revenue levels are established based on a rate agreement with the WUTC at amounts sufficient to cover the costs of operation, including facility maintenance, equipment replacement and related costs, and provide us with a reasonable profit. Per-unit rates charged to LLRW customers during the year are based on our evaluation of disposal volume and radioactivity projections submitted to us by waste generators. Our proposed rates are then reviewed and approved by the WUTC. If annual revenue exceeds the approved levels set by the WUTC, we are required to refund excess collections to facility users on a pro-rata basis. Refundable excess collections, if any, are recorded in Accrued liabilities in the consolidated balance sheets. The current rate agreement with the WUTC was extended in 2019 and is effective until December 31, 2025.
Deferred Revenue	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, and is recognized when these services are performed. During the year ended December 31, 2021 and 2020, we recognized $15.1 million and $14.7 million of revenue that was included in the deferred revenue balance at the beginning of each year, respectively.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost and depreciated on the straight-line method over estimated useful lives. Replacements and major repairs of property and equipment are capitalized and retirements are made when assets are disposed of or when the useful life has been exhausted. Minor components and parts are expensed as incurred. Repair and maintenance expenses were $29.5 million, $26.9 million and $20.5 million for the years ended December 31, 2021, 2020 and 2019, respectively. We assume no salvage value for our depreciable fixed assets. The estimated useful lives for significant property and equipment categories are as follows: Useful Lives Vehicles, vessels and other equipment 3 to 10 years Disposal facility and equipment 3 to 20 years Buildings and improvements 5 to 40 years Railcars 40 years
Disposal Cell Accounting	Disposal Cell Accounting Qualified disposal cell development costs such as personnel and equipment costs incurred to construct new disposal cells are recorded and capitalized at cost. Capitalized cell development costs, net of recorded amortization, are added to estimated future costs of the permitted disposal cell to be incurred over the remaining construction of the cell, to determine the amount to be amortized over the remaining estimated cell life. Estimates of future costs are developed using input from independent engineers and internal technical and accounting managers. We review these estimates at least annually. Amortization is recorded on a unit of consumption basis, typically applying cost as a rate per cubic yard disposed. Disposal facility costs are expected to be fully amortized upon final closure of the facility, as no salvage value applies. Costs associated with ongoing disposal operations are charged to expense as incurred. We have material financial commitments for closure and post-closure obligations for certain facilities we own or operate. We estimate future cost requirements for closure and post-closure monitoring based on RCRA and conforming state requirements and facility permits. RCRA requires that companies provide the responsible regulatory agency acceptable financial assurance for closure work and subsequent post-closure monitoring of each facility for 30 years following closure. Estimates for final closure and post-closure costs are developed using input from our technical and accounting managers as well as independent engineers and are reviewed by management at least annually. These estimates involve projections of costs that will be incurred after the disposal facility ceases operations, through the required post-closure care period. The present value of the estimated closure and post-closure costs are accreted using the interest method of allocation to direct costs in our consolidated statements of operations so that 100% of the future cost has been incurred at the time of payment.
Business Combinations	Business Combinations We account for business combinations under the acquisition method of accounting. The cost of an acquired company is assigned to the tangible and identifiable intangible assets purchased and the liabilities assumed on the basis of their fair values at the date of acquisition. Any excess of purchase price over the fair value of net tangible and intangible assets acquired is assigned to goodwill. The transaction costs associated with business combinations are expensed as they are incurred.
Goodwill	Goodwill Goodwill represents the excess of the fair value of the consideration transferred over the fair value of the underlying identifiable assets and liabilities acquired. Goodwill is not amortized, but instead is assessed for impairment annually in the fourth quarter as of October 1 and also if an event occurs or circumstances change that may indicate a possible impairment. In the event that we determine that the value of goodwill has become impaired, we will incur an accounting charge for the amount of impairment during the period in which the determination has been made. See Note 3 for additional information related to the use of estimates in the Company’s goodwill impairment tests and Note 13 for additional information related to our annual assessment of goodwill.
Intangible Assets	Intangible Assets Intangible assets are stated at the fair value assigned in a business combination net of amortization. We amortize our amortizing intangible assets using the straight-line method over their estimated economic lives ranging from 1 to 60 years. We review intangible assets with indefinite useful lives for impairment during the fourth quarter as of October 1 of each year. We also review both non-amortizing and amortizing intangible assets for impairment whenever events or changes in circumstances indicate that the carrying value of an intangible asset may not be recoverable. See Note 3 for additional information related to the use of estimates in the Company’s intangible assets impairment tests and Note 13 for additional information related to our annual assessment of non-amortizing intangible assets. Our acquired permits and licenses generally have renewal terms of approximately 5-10 years. We have a history of renewing these permits and licenses as demonstrated by the fact that each of the sites’ treatment permits and licenses have been renewed regularly since the facility began operations. We intend to continue to renew our permits and licenses as they come up for renewal for the foreseeable future. Costs incurred to renew or extend the term of our permits and licenses are recorded in Selling, general and administrative expenses in our consolidated statements of operations.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist primarily of property and equipment facility development costs and amortizing intangible assets. The recoverability of long-lived assets is evaluated periodically through analysis of operating results and consideration of other significant events or changes in the business environment. If an operating unit had indications of possible impairment, we would evaluate whether impairment exists on the basis of undiscounted expected future cash flows from operations over the remaining amortization period. If an impairment loss were to exist, the carrying amount of the related long-lived assets would be reduced to their estimated fair value. We did not observe any events or changes in circumstances in 2021 that indicated the carrying value of our long-lived assets may not be recoverable.
Share-Based Payments	Share-Based Payments The Company has elected to account for forfeitures of share-based awards as they occur, rather than estimate expected forfeitures. See Note 19 for additional information related to our accounting policies for share-based payments.
Debt Issuance Costs & Debt Discount	Debt Issuance Costs & Debt Discount Debt issuance costs and debt discount are amortized over the scheduled maturity of the underlying debt instrument. Amortization of debt issuance costs and debt discount is included as a component of interest expense in the consolidated statements of operations. Unamortized debt discount and debt issuance costs associated with our term loan were $5.5 million and $6.7 million at December 31, 2021 and 2020, respectively, and have been recorded as a reduction of the Current portion of long-term debt and Long-term debt in the consolidated balance sheets. Unamortized debt issuance costs associated with our Revolving Credit Facility were $4.8 million and $5.3 million at December 31, 2021 and 2020, respectively, and have been recorded in Prepaid expenses and other current assets and Other assets in the consolidated balance sheets.
Derivative Instruments	Derivative Instruments 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. Changes in the fair value of the interest rate swap are recorded as a component of accumulated other comprehensive income within stockholders’ equity, and are recognized in interest expense in the period in which the payment is settled, or for terminated swap agreements, amortized to interest expense over the period from termination to original maturity. The interest rate swap has an effective date of March 31, 2020 in an initial notional amount of $500.0 million. The Company does not hold or issue derivative financial instruments for trading or speculative purposes.
Foreign Currency	Foreign Currency The assets, liabilities and results of operations of certain of our foreign subsidiaries are measured using their functional currency which is the currency of the primary foreign economic environment in which they operate. Assets and liabilities are translated to U.S. dollars (“USD”) at the exchange rate in effect at the balance sheet date and revenue and expenses at the average exchange rate for the period. Gains and losses from the translation of the consolidated financial statements of our foreign subsidiaries into USD are included in stockholders’ equity as a component of Accumulated other comprehensive loss. Gains and losses resulting from foreign currency transactions are recognized in the consolidated statements of operations. Recorded balances that are denominated in a currency other than the functional currency are re-measured to the functional currency using the exchange rate at the balance sheet date and gains or losses are recorded in the statements of operations.
Income Taxes	Income Taxes We account for income taxes using an asset and liability method, which requires the recognition of taxes payable or refundable for the current year and deferred tax assets and liabilities for the expected future tax consequences of temporary differences that currently exist between the tax basis and the financial reporting basis of our taxable subsidiaries’ assets and liabilities using the enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in operations in the period that includes the enactment date. The measurement of deferred tax assets is reduced, if necessary, by the amount of any tax benefits that, based on available evidence, are not expected to be realized. The unrecognized tax benefits that are not expected to result in payment or receipt of cash within one year are classified as “Other long-term liabilities” in the Consolidated Balance Sheets. We regularly assess the need for a valuation allowance against our deferred tax assets. In making that assessment, we consider both positive and negative evidence related to the likelihood of realization of the deferred tax assets on a jurisdictional basis to determine, based on the weight of available evidence, whether it is more-likely-than-not that some or all of the deferred tax assets will not be realized. Examples of positive and negative evidence include future growth, forecasted earnings, future taxable income, the mix of earnings in the jurisdictions in which we operate, historical earnings, taxable income in prior years, if carryback is permitted under the law and prudent, and feasible tax planning strategies. In the event we were to determine that we would not be able to realize all or part of our net deferred tax assets in the future, an adjustment to the deferred tax assets valuation allowance would be charged to earnings in the period in which we make such a determination, or goodwill would be adjusted at our final determination of the valuation allowance related to an acquisition within the measurement period. If we later determine that it is more-likely-than-not that the net deferred tax assets would be realized, we would reverse the applicable portion of the previously-provided valuation allowance as an adjustment to earnings at such time. We account for unrecognized tax benefits using a more-likely-than-not threshold for financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. We establish reserves for tax-related uncertainties based on estimates of whether, and the extent to which, additional taxes will be due. We record an income tax liability, if any, for the difference between the benefit recognized and measured and the tax position taken or expected to be taken on our tax returns. We recognize interest assessed by taxing authorities or interest associated with uncertain tax positions as a component of interest expense. We recognize any penalties assessed by taxing authorities or penalties associated with uncertain tax positions as a component of selling, general and administrative expenses. Our income tax expense, deferred tax assets and deferred tax liabilities, and liabilities for uncertain tax benefits reflect management’s best estimate of current and future taxes to be paid. We are subject to income taxes in the United States and numerous foreign jurisdictions. Significant judgments and estimates are required in the determination of the consolidated income tax expense. See Note 17 for additional information regarding income taxes.
Insurance	Insurance Accrued costs for our self-insured healthcare coverage were $3.4 million and $3.3 million at December 31, 2021 and 2020, respectively.
Earnings (Loss) Per Share	Earnings (Loss) Per Share Basic earnings per share is calculated based on the weighted-average number of outstanding common shares during the applicable period. Diluted earnings per share is based on the weighted-average number of outstanding common shares plus the weighted-average number of potential outstanding common shares. Potential common shares that would increase earnings per share or decrease loss per share are anti-dilutive and are excluded from earnings per share computations. Earnings per share is computed separately for each period presented.
Treasury Stock	Treasury Stock Shares of common stock repurchased by us are recorded at cost as treasury stock and result in a reduction of stockholders’ equity in our consolidated balance sheets. Treasury shares are reissued using the weighted average cost method for determining the cost of the shares reissued. The difference between the cost of the shares reissued and the issuance price is added or deducted from additional paid-in capital.
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.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	Dec. 31, 2021
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Schedule of property and equipment	Useful Lives Vehicles, vessels and other equipment 3 to 10 years Disposal facility and equipment 3 to 20 years Buildings and improvements 5 to 40 years Railcars 40 years

REVENUES (Tables)

REVENUES (Tables)	12 Months Ended
REVENUES (Tables)	Dec. 31, 2021
REVENUES
Schedule of disaggregation of revenues	2021 Waste Field Energy $s in thousands Solutions Services Waste Total Treatment & Disposal Revenue (1) $ 372,204 $ 50,327 $ 20,997 $ 443,528 Services Revenue: Transportation and Logistics (2) 79,045 29,096 8,978 117,119 Industrial Services (3) — 121,357 2,814 124,171 Small Quantity Generation (4) — 55,158 — 55,158 Total Waste Management (5) — 39,949 — 39,949 Remediation (6) — 48,224 — 48,224 Emergency Response (7) — 138,425 18 138,443 Other (8) — 17,651 3,758 21,409 Revenue $ 451,249 $ 500,187 $ 36,565 $ 988,001 2020 Waste Field Energy $s in thousands Solutions Services Waste Total Treatment & Disposal Revenue (1) $ 354,055 $ 47,781 $ 18,884 $ 420,720 Services Revenue: Transportation and Logistics (2) 71,358 34,218 7,184 112,760 Industrial Services (3) — 118,584 4,178 122,762 Small Quantity Generation (4) — 48,049 — 48,049 Total Waste Management (5) — 35,401 — 35,401 Remediation (6) — 30,225 — 30,225 Emergency Response (7) — 140,253 — 140,253 Other (8) — 19,243 4,441 23,684 Revenue $ 425,413 $ 473,754 $ 34,687 $ 933,854 2019 Waste Field Energy $s in thousands Solutions Services Waste Total Treatment & Disposal Revenue (1) $ 359,847 $ 18,523 $ 6,039 $ 384,409 Services Revenue: Transportation and Logistics (2) 80,700 40,670 2,877 124,247 Industrial Services (3) — 38,861 1,200 40,061 Small Quantity Generation (4) — 37,471 — 37,471 Total Waste Management (5) — 33,794 — 33,794 Remediation (6) — 13,307 — 13,307 Emergency Response (7) — 41,088 — 41,088 Other (8) — 8,688 2,444 11,132 Revenue $ 440,547 $ 232,402 $ 12,560 $ 685,509 (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 years ended December 31, 2021, 2020 and 2019, 24% , 27% and 22% , respectively, of our treatment and disposal revenue was derived from Event Business projects. Base Business revenue accounted for 76% , 73% and 78% of our treatment and disposal revenue for the years ended December 31, 2021, 2020 and 2019, 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-then-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 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 EMEA region. The following table presents our revenue disaggregated by our reportable segments and geographic location where the underlying services were performed: 2021 Waste Field Energy $s in thousands Solutions Services Waste Total United States $ 374,414 $ 450,276 $ 36,565 $ 861,255 Canada 76,835 3,785 — 80,620 EMEA — 41,218 — 41,218 Other (1) — 4,908 — 4,908 Total revenue $ 451,249 $ 500,187 $ 36,565 $ 988,001 2020 Waste Field Energy $s in thousands Solutions Services Waste Total United States $ 355,226 $ 445,405 $ 34,687 $ 835,318 Canada 70,187 3,064 — 73,251 EMEA — 19,947 — 19,947 Other (1) — 5,338 — 5,338 Total revenue $ 425,413 $ 473,754 $ 34,687 $ 933,854 2019 Waste Field Energy $s in thousands Solutions Services Waste Total United States $ 354,625 $ 221,942 $ 12,560 $ 589,127 Canada 85,922 2,577 — 88,499 EMEA — 5,079 — 5,079 Other (1) — 2,804 — 2,804 Total revenue $ 440,547 $ 232,402 $ 12,560 $ 685,509 (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions.

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	12 Months Ended
BUSINESS COMBINATIONS (Tables)	Dec. 31, 2021
Summary of total merger consideration	November 1, $s in thousands 2019 Fair value of US Ecology common stock issued (1) $ 581,101 Fair value of replacement warrants issued (2) 44,858 Fair value of replacement restricted stock units issued (3) 141 Fair value of replacement stock options (4) 360 Repayment of NRC’s term loan and revolving credit facility 398,373 Total merger consideration $ 1,024,833 (1) The fair value of US Ecology common stock issued was calculated based on 9,337,949 shares of US Ecology common stock multiplied by the closing price of US Ecology common stock of $62.23 per share on October 31, 2019, the day immediately preceding the closing of the NRC Merger. (2) The fair value of replacement warrants issued was calculated based on 3,772,753 replacement warrants multiplied by the fair value per warrant of $11.89 . The fair value per warrant was based on the closing price of the replaced NRC warrants (NYSE: NRCG.WS) of $2.33 on October 31, 2019, the day immediately preceding the closing of the NRC Merger, divided by the exchange ratio of 0.196 pursuant to the NRC Merger Agreement. (3) The fair value of replacement restricted stock units issued was calculated based on 118,239 replacement restricted stock units multiplied by the closing price of US Ecology common stock of $62.23 per share on October 31, 2019, the day immediately preceding the closing of the NRC Merger, further multiplied by the ratio of the precombination service period to the remaining vesting period, or approximately 1.9% . (4) The fair value of replacement stock options issued was calculated based on 29,400 replacement stock options multiplied by the fair value per option of $12.26 . The fair value per option was calculated using the Black-Scholes option pricing model, with the following weighted-average assumptions: strike price of $52.30 per option, dividend yield of 1.2% ; expected volatility of 28.9% ; average risk-free interest rate of 1.5% ; and an expected term of 1 year. The replacement stock options became fully vested at the merger date therefore the entire fair value is considered merger consideration.
Schedule of preliminary fair value of identifiable intangible assets related to the acquisition of NRCG	2021 2020 Accumulated Accumulated $s in thousands Cost Amortization Net Cost Amortization Net Amortizing intangible assets: Permits, licenses and lease $ 174,959 $ (27,170) $ 147,789 $ 174,885 $ (23,005) $ 151,880 Customer relationships 340,065 (87,952) 252,113 340,032 (61,778) 278,254 Technology - formulae and processes 7,166 (2,531) 4,635 7,142 (2,293) 4,849 Customer backlog 3,652 (2,752) 900 3,652 (2,387) 1,265 Tradename 10,390 (10,390) — 10,390 (8,015) 2,375 Developed software 2,903 (2,475) 428 2,902 (2,182) 720 Non-compete agreements 5,573 (5,211) 362 5,571 (4,318) 1,253 Internet domain and website 536 (213) 323 536 (184) 352 Database 390 (235) 155 389 (214) 175 Total amortizing intangible assets 545,634 (138,929) 406,705 545,499 (104,376) 441,123 Non-amortizing intangible assets: Permits and licenses 82,734 — 82,734 82,732 — 82,732 Tradename 134 — 134 133 — 133 Total intangible assets $ 628,502 $ (138,929) $ 489,573 $ 628,364 $ (104,376) $ 523,988
Schedule of unaudited pro forma financial information	(unaudited) $s in thousands 2019 Pro forma combined: Revenue $ 1,048,745 Net income (loss) $ 11,775
NRC
Summary of preliminary fair value estimates of assets acquired and liabilities assumed	Purchase Price $s in thousands Allocation Current assets $ 130,110 Property and equipment 170,208 Identifiable intangible assets 309,500 Other assets 41,687 Current liabilities (89,733) Deferred income tax liabilities (54,974) Other liabilities (59,363) Total identifiable net assets 447,435 Goodwill 577,398 Total purchase price $ 1,024,833
Schedule of preliminary fair value of identifiable intangible assets related to the acquisition of NRCG	Average Amortization $s in thousands Fair Value Period (Years) Amortizing intangible assets: Customer relationships - noncontractual $ 199,600 14 Customer relationships - contractual 34,400 7 Permits and licenses 8,700 16 Tradenames 6,100 2 Non-compete agreements 3,300 2 Total identified amortizing intangible assets 252,100 Non-amortizing intangible assets: Permits and licenses 57,400 n/a Total identified intangible assets $ 309,500

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	Dec. 31, 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, 2019 $ (10,925) $ (929) $ (11,854) Other comprehensive income (loss) before reclassifications, net of tax 3,055 (8,494) (5,439) Amounts reclassified out of AOCI, net of tax (1) — 2,635 2,635 Other comprehensive income (loss), net 3,055 (5,859) (2,804) Balance at December 31, 2020 $ (7,870) $ (6,788) $ (14,658) Other comprehensive (loss) income before reclassifications, net of tax (1,505) 9,010 7,505 Amounts reclassified out of AOCI, net of tax (2) — 2,959 2,959 Other comprehensive (loss) income, net (1,505) 11,969 10,464 Balance at December 31, 2021 $ (9,375) $ 5,181 $ (4,194) (1) Before-tax reclassifications of $3.3 million ( $2.6 million, after-tax) for the year ended December 31, 2020 were included in Interest expense in the Company’s consolidated statements of operations. Amount relates 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. (2) Before-tax reclassifications of $3.7 million ( $3.0 million, after-tax) for the year ended December 31, 2021 were included in Interest expense in the Company’s consolidated statements of operations. Amount relates 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 recognized as interest expense over the next 12 months total approximately $2.8 million ( $2.2 million after tax).

DISCLOSURE OF SUPPLEMENTAL CA_2

DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	12 Months Ended
DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION (Tables)	Dec. 31, 2021
DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION
Schedule of disclosure of supplemental cash flow information	For the Year Ended December 31, $s in thousands 2021 2020 2019 Income taxes and interest paid: Income taxes paid, net of receipts $ 1,951 $ 7,774 $ 14,777 Interest paid 25,771 28,433 17,204 Non-cash investing and financing activities: Fair value of equity issued for acquisition of NRC $ — $ — $ 626,460 Adjustments to closure/post-closure retirement asset 732 5,422 (221) Capital expenditures in accounts payable 7,702 4,712 2,882 Acquisition of equipment with financing arrangements — 6,197 2,481 Restricted common stock and common stock issuances from treasury shares 5,654 2,491 514

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
FAIR VALUE MEASUREMENTS (Tables)	Dec. 31, 2021
FAIR VALUE MEASUREMENTS
Schedule of assets and liabilities measured at fair value on a recurring basis	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) $ 1,695 $ 255 $ — $ 1,950 Money market funds (2) 1,886 — — 1,886 Interest rate swap agreement (3) — 5,022 — 5,022 Total $ 3,581 $ 5,277 $ — $ 8,858 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 have short-term 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-year and end-of-year 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 and October 2014 that effectively converts a portion of our variable-rate debt to a fixed interest rate. In connection with our entry into the March 2020 interest rate swap, we terminated the October 2014 interest rate swap prior to its scheduled maturity date of June 2021. The March 2020 interest rate 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 October 2014 interest rate swap was also designated as a highly effective cash flow hedge. The March 2020 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 agreements are included in Other assets and Other long-term liabilities in the Company’s consolidated balance sheets as of December 31, 2021 and 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 prior to the 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 December 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	$s in thousands 2021 2020 Contingent consideration, beginning of year $ 2,173 $ 8,283 Change in fair value of contingent consideration 282 (3,682) Contingent consideration paid (2,553) (2,517) Foreign currency translation 98 89 Contingent consideration, end of year $ — $ 2,173

RECEIVABLES (Tables)

RECEIVABLES (Tables)	12 Months Ended
RECEIVABLES (Tables)	Dec. 31, 2021
RECEIVABLES
Schedule of receivables	$s in thousands 2021 2020 Trade $ 183,747 $ 186,502 Unbilled revenue 62,029 52,858 Other 7,421 5,554 Total receivables 253,197 244,914 Allowance for credit losses (3,043) (2,936) Receivables, net $ 250,154 $ 241,978
Schedule of change in the allowance for doubtful accounts receivable	Charged Balance at (Credited) to Recoveries Beginning of Costs and (Deductions/ Balance at $s in thousands Period Expenses Write-offs) Adjustments End of Period Year ended December 31, 2021 $ 2,936 $ 1,179 $ (1,075) $ 3 $ 3,043 Year ended December 31, 2020 $ 3,010 $ (412) $ 296 $ 42 $ 2,936 Year ended December 31, 2019 $ 2,998 $ 226 $ (439) $ 225 $ 3,010

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	12 Months Ended
PROPERTY AND EQUIPMENT (Tables)	Dec. 31, 2021
PROPERTY AND EQUIPMENT
Schedule of property and equipment	$s in thousands 2021 2020 Cell development costs $ 203,217 $ 186,170 Land and improvements 74,298 65,953 Buildings and improvements 138,659 128,206 Railcars 17,299 17,299 Vehicles, vessels and other equipment 350,950 331,167 Construction in progress 54,609 44,840 Total property and equipment 839,032 773,635 Accumulated depreciation and amortization (382,648) (316,998) Property and equipment, net $ 456,384 $ 456,637

LEASES (Tables)

LEASES (Tables)	12 Months Ended
LEASES (Tables)	Dec. 31, 2021
LEASES
Summary of leased assets and liabilities	$s in thousands 2021 2020 Assets: Operating right-of-use assets (1) $ 43,607 $ 51,474 Finance right-of-use assets (2) 17,290 21,209 Total $ 60,897 $ 72,683 Liabilities: Current: Operating (3) $ 15,799 $ 17,048 Finance (4) 4,969 4,462 Long-term: Operating (5) 28,477 35,069 Finance (6) 12,108 17,501 Total $ 61,353 $ 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 $13.3 million and $8.0 million as of December 31, 2021 and 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	Year Ended December 31, $s in thousands 2021 2020 Operating lease cost (1) $ 19,950 $ 20,880 Finance lease cost: Amortization of leased assets (2) 5,249 5,312 Interest on lease liabilities (3) 1,012 1,221 Total $ 26,211 $ 27,413 (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	Year Ended December 31, $s in thousands 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 19,687 $ 20,297 Operating cash flows from finance leases $ 1,012 $ 1,221 Financing cash flows from finance leases $ 4,885 $ 4,659 Non-cash investing and financing activities: Right-of-use assets obtained in exchange for new operating lease liabilities $ 10,010 $ 13,576 Right-of-use assets obtained in exchange for new finance lease liabilities $ — $ 6,197
Summary of weighted-average remaining lease term and discount rate	2021 2020 Weighted-average remaining lease term (years): Operating leases 3.7 4.1 Finance leases 3.2 4.0 Weighted-average discount rate: Operating leases 3.59 % 3.69 % Finance leases 5.85 % 5.86 %
Summary of future maturity of lease liability and its present value	Operating Finance $s in thousands Leases Leases Total 2022 $ 17,091 $ 5,694 $ 22,785 2023 13,617 5,668 19,285 2024 8,510 3,929 12,439 2025 3,366 3,565 6,931 2026 1,557 953 2,510 Thereafter 3,356 264 3,620 Total $ 47,497 $ 20,073 $ 67,570 Less: Interest 3,221 2,996 6,217 Present value of lease liabilities $ 44,276 $ 17,077 $ 61,353

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
GOODWILL AND INTANGIBLE ASSETS (Tables)	Dec. 31, 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, 2019 $ 166,415 $ (6,870) $ 298,579 $ — $ 308,856 $ — $ 766,980 Impairment charges — — — (19,900) — (363,900) (383,800) NRC Merger purchase price allocation adjustment — — (61,735) — 90,647 — 28,912 Impact Environmental acquisition — — 300 — — — 300 Foreign currency translation 448 — 197 — — — 645 Balance at December 31, 2020 $ 166,863 $ (6,870) $ 237,341 $ (19,900) $ 399,503 $ (363,900) $ 413,037 Foreign currency translation 62 — 27 — — — 89 Balance at December 31, 2021 $ 166,925 $ (6,870) $ 237,368 $ (19,900) $ 399,503 $ (363,900) $ 413,126
Schedule of intangible assets, net	2021 2020 Accumulated Accumulated $s in thousands Cost Amortization Net Cost Amortization Net Amortizing intangible assets: Permits, licenses and lease $ 174,959 $ (27,170) $ 147,789 $ 174,885 $ (23,005) $ 151,880 Customer relationships 340,065 (87,952) 252,113 340,032 (61,778) 278,254 Technology - formulae and processes 7,166 (2,531) 4,635 7,142 (2,293) 4,849 Customer backlog 3,652 (2,752) 900 3,652 (2,387) 1,265 Tradename 10,390 (10,390) — 10,390 (8,015) 2,375 Developed software 2,903 (2,475) 428 2,902 (2,182) 720 Non-compete agreements 5,573 (5,211) 362 5,571 (4,318) 1,253 Internet domain and website 536 (213) 323 536 (184) 352 Database 390 (235) 155 389 (214) 175 Total amortizing intangible assets 545,634 (138,929) 406,705 545,499 (104,376) 441,123 Non-amortizing intangible assets: Permits and licenses 82,734 — 82,734 82,732 — 82,732 Tradename 134 — 134 133 — 133 Total intangible assets $ 628,502 $ (138,929) $ 489,573 $ 628,364 $ (104,376) $ 523,988
Schedule of future amortization expense of amortizing intangible assets	Expected $s in thousands Amortization 2022 $ 31,403 2023 31,216 2024 30,830 2025 30,586 2026 29,767 Thereafter 252,903 $ 406,705

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
EMPLOYEE BENEFIT PLANS (Tables)	Dec. 31, 2021
EMPLOYEE BENEFIT PLANS
Schedule of information regarding significant multi-employer pension benefit plans	Pension Protection Act Certified Plan Employer Plan Zone Status Name of Plan ID Number Number 2021 2020 Operating Engineers Local 324 Pension Fund 38-1900637 001 Red Red

CLOSURE AND POST-CLOSURE OBLI_2

CLOSURE AND POST-CLOSURE OBLIGATIONS (Tables)	12 Months Ended
CLOSURE AND POST-CLOSURE OBLIGATIONS (Tables)	Dec. 31, 2021
CLOSURE AND POST-CLOSURE OBLIGATIONS
Schedule of changes to reported closure and post closure obligations	$s in thousands 2021 2020 Closure and post-closure obligations, beginning of year $ 95,869 $ 86,383 NRC Merger purchase price allocation adjustment — 1,782 Accretion expense 5,363 4,000 Payments (3,054) (1,750) Adjustments 732 5,422 Foreign currency translation 10 32 Closure and post-closure obligations, end of year 98,920 95,869 Less current portion (5,771) (6,471) Long-term portion $ 93,149 $ 89,398
Schedule of changes in the reported closure and post-closure asset recorded as a component of Property and equipment, net	$s in thousands 2021 2020 Net closure and post-closure asset, beginning of year $ 26,532 $ 22,884 NRC Merger purchase price allocation adjustment — (389) Additions or adjustments to closure and post-closure asset 732 5,422 Amortization of closure and post-closure asset (1,614) (1,407) Foreign currency translation 12 22 Net closure and post-closure asset, end of year $ 25,662 $ 26,532

DEBT (Tables)

DEBT (Tables)	12 Months Ended
DEBT (Tables)	Dec. 31, 2021
DEBT
Schedule of long-term debt	December 31, $s in thousands 2021 2020 Revolving credit facility $ 303,000 $ 347,000 Term loan 441,000 445,500 Unamortized term loan discount and debt issuance costs (5,516) (6,657) Total debt 738,484 785,843 Current portion of long-term debt (3,359) (3,359) Long-term debt $ 735,125 $ 782,484
Schedule of future maturities of long-term debt, excluding the unamortized discount and debt issuance costs	$s in thousands Maturities 2022 $ 4,500 2023 4,500 2024 4,500 2025 4,500 2026 726,000 Thereafter — $ 744,000
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%

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
INCOME TAXES (Tables)	Dec. 31, 2021
INCOME TAXES
Schedule of domestic and foreign components of income (loss) before income taxes	$s in thousands 2021 2020 2019 Domestic $ (10,567) $ (403,492) $ 30,706 Foreign 20,669 9,891 19,093 Income (loss) before income taxes $ 10,102 $ (393,601) $ 49,799
Schedule of components of the income tax expense (benefit)	$s in thousands 2021 2020 2019 Current: U.S. Federal $ (1,534) $ (9,905) $ 3,120 State 68 3,062 1,547 Foreign 6,948 6,768 5,426 Total current 5,482 (75) 10,093 Deferred: U.S. Federal (509) 1,384 5,977 State 503 (2,859) 714 Foreign (711) (2,692) (125) Total deferred (717) (4,167) 6,566 Income tax expense (benefit) $ 4,765 $ (4,242) $ 16,659
Schedule of reconciliation between the effective income tax rate and the applicable statutory federal and state income tax rate	2021 2020 2019 Taxes computed at federal statutory rate 21.0 % 21.0 % 21.0 % Goodwill impairment charges — (20.4) — State income taxes (net of federal income tax benefit) 9.8 0.3 5.7 Share-based compensation 4.6 (0.1) (0.4) Research and development credits (4.4) 0.1 (0.8) Non-deductible transaction costs 1.6 — 3.4 Global intangible low taxed income — — 1.1 Foreign rate differential 11.0 (0.3) 2.5 Net operating loss reduction — (1.7) — Change in unrecognized tax benefits — 1.7 — State deferred rate differential — (0.1) (1.6) State credits (5.1) — — Assumed contingent liability 3.1 — — Non-deductible executive compensation 1.5 — — Non-deductible foreign expenses 4.3 — — Non-deductible political contributions 1.3 — — Net operating loss carryback rate differential (4.6) — — Other 3.1 0.6 2.6 47.2 % 1.1 % 33.5 %
Schedule of components of the total net deferred tax assets and liabilities	$s in thousands 2021 2020 Deferred tax assets: Net operating losses $ 16,963 $ 18,751 Operating leases 10,980 12,875 Foreign tax credit and capital loss carry forwards 5,579 4,928 Accruals, allowances and other 4,963 8,691 Environmental compliance and other site related costs 10,833 10,909 Unrealized foreign exchange gains 819 790 Total deferred tax assets 50,137 56,944 Less: valuation allowance (4,164) (4,207) Net deferred tax assets 45,973 52,737 Deferred tax liabilities: Property and equipment (50,601) (53,838) Intangible assets (106,504) (107,109) Operating leases (10,980) (12,875) Other (1,370) 102 Total deferred tax liabilities (169,455) (173,720) Net deferred tax liability $ (123,482) $ (120,983)
Schedule of changes to unrecognized tax benefits	$s in thousands 2021 2020 2019 Unrecognized tax benefits, beginning of year $ 239 $ 8,335 $ 555 Gross increases - tax positions in prior period 9 — 8,088 Gross decreases - tax positions in prior period — (8,091) (9) Gross increases - tax positions in current period 58 50 52 Settlements — — (284) Lapse of statute of limitations (50) (55) (67) Unrecognized tax benefits, end of year $ 256 $ 239 $ 8,335

EQUITY (Tables)

EQUITY (Tables)	12 Months Ended
EQUITY (Tables)	Dec. 31, 2021
Summary of stock option activity	Weighted Weighted Average Average Aggregate Remaining Exercise Intrinsic Contractual Shares Price Value Term (Years) Outstanding as of December 31, 2020 357,033 $ 49.93 Granted 205,800 35.30 Cancelled, expired or forfeited (16,239) 44.38 Outstanding as of December 31, 2021 546,594 $ 44.59 $ — 6.9 Exercisable as of December 31, 2021 283,329 $ 48.52 $ — 5.3
Schedule of significant weighted-average assumptions relating to the valuation of option grants	2021 2020 2019 Expected life 3.8 years 4.0 years 2.7 years Expected volatility 38 % 30 % 30 % Risk-free interest rate 0.2 % 1.4 % 2.1 % Expected dividend yield 0.5 % 1.2 % 1.2 %
Schedule of components of pre-tax share-based compensation expense (primarily included in Selling, general and administrative expenses in our consolidated statements of operations) and related tax benefits	$s in thousands 2021 2020 2019 Share-based compensation from: Stock options $ 1,201 $ 725 $ 575 Restricted stock 2,719 2,032 1,662 Restricted stock units (1) 2,758 3,810 6,193 Performance stock units (2) 1,211 1,266 831 Total share-based compensation 7,889 7,833 9,261 Income tax benefit (1,162) (2,115) (3,098) Share-based compensation, net of tax $ 6,727 $ 5,718 $ 6,163 (1) Share-based compensation from restricted stock units for the years ended December 31, 2020 and 2019 includes $605,000 and $3.7 million, respectively, of compensation expense related to the accelerated vesting of restricted stock unit awards upon the termination of former employees of NRC subsequent to the NRC Merger in accordance with change-in-control provisions of their respective employment agreements. Share-based compensation from restricted stock units for the year ended December 31, 2021 and 2020 also includes $434,000 and $405,000, respectively, of compensation expense related restricted stock unit awards granted to certain employees identified as critical to the successful integration of NRC. Share-based compensation from these awards is attributable entirely to the NRC Merger therefore the Company has classified this portion of share-based compensation expense as business development and integration expenses within Selling, general and administrative expenses in our consolidated statements of operations. (2) Share-based compensation from performance stock units for the year ended December 31, 2021 includes a benefit of $23,000 to compensation expense related to the expiration of milestone-based performance stock unit awards granted to certain employees identified as critical to the successful integration of NRC. Share-based compensation from performance stock units for the year ended December 31, 2020 includes $173,000 of compensation expense related to achievement of milestone-based performance stock unit awards granted to certain employees identified as critical to the successful integration of NRC. Share-based compensation from these awards is attributable entirely to the NRC Merger therefore the Company has classified this portion of share-based compensation expense as business development and integration expenses within Selling, general and administrative expenses in our consolidated statements of operations.
PSUs
Schedule of assumptions for determining the fair value for PSU awards using Monte Carlo simulation models	2020 2019 Stock price on grant date $ 32.89 $ 58.40 Expected term 2.5 years 3.0 years Expected volatility 40.6 % 30.0 % Risk-free interest rate 0.2 % 2.5 % Expected dividend yield — % 1.1 %
Summary of PSU, restricted stock and RSU activity	Weighted Average Grant Date Units Fair Value Outstanding as of December 31, 2020 86,070 $ 49.45 Vested (31,211) 60.62 Cancelled, expired or forfeited (1,474) 54.55 Outstanding as of December 31, 2021 53,385 $ 42.79
Restricted stock
Summary of PSU, restricted stock and RSU activity	Weighted Average Grant Date Shares Fair Value Outstanding as of December 31, 2020 72,766 $ 51.47 Granted 84,800 36.49 Vested (47,002) 47.08 Outstanding as of December 31, 2021 110,564 $ 41.85
RSUs
Summary of PSU, restricted stock and RSU activity	Weighted Average Grant Date Units Fair Value Outstanding as of December 31, 2020 147,243 $ 39.92 Granted 62,759 39.33 Vested (64,597) 44.75 Cancelled, expired or forfeited (18,856) 42.51 Outstanding as of December 31, 2021 126,549 $ 36.78

EARNINGS (L0SS) PER SHARE (Tabl

EARNINGS (L0SS) PER SHARE (Tables)	12 Months Ended
EARNINGS (L0SS) PER SHARE (Tables)	Dec. 31, 2021
EARNINGS (LOSS) PER SHARE
Schedule of earnings (loss) per share	2021 2020 2019 $s and shares in thousands, except per share amounts Basic Diluted Basic Diluted Basic Diluted Net income (loss) $ 5,337 $ 5,337 $ (389,359) $ (389,359) $ 33,140 $ 33,140 Weighted average basic shares outstanding 31,138 31,138 31,126 31,126 23,521 23,521 Dilutive effect of share-based awards and warrants 235 — 228 Weighted average diluted shares outstanding 31,373 31,126 23,749 Earnings (loss) per share $ 0.17 $ 0.17 $ (12.51) $ (12.51) $ 1.41 $ 1.40 Anti-dilutive shares excluded from calculation 4,359 4,213 90

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	12 Months Ended
SEGMENT REPORTING (Tables)	Dec. 31, 2021
OPERATING SEGMENTS
Summary of financial information of our reportable segments	2021 Waste Field Energy $s in thousands Solutions Services Waste Corporate Total Revenue $ 451,249 $ 500,187 $ 36,565 $ — $ 988,001 Depreciation, amortization and accretion $ 43,746 $ 44,368 $ 19,520 $ 3,142 $ 110,776 Capital expenditures $ 45,602 $ 15,393 $ 4,923 $ 2,748 $ 68,666 Total assets $ 796,645 $ 733,086 $ 216,292 $ 59,375 $ 1,805,398 2020 Waste Field Energy $s in thousands Solutions Services Waste Corporate Total Revenue $ 425,413 $ 473,754 $ 34,687 $ — $ 933,854 Depreciation, amortization and accretion $ 41,540 $ 43,465 $ 19,814 $ 3,086 $ 107,905 Capital expenditures $ 31,027 $ 16,149 $ 6,189 $ 4,034 $ 57,399 Total assets $ 773,448 $ 762,854 $ 231,475 $ 63,506 $ 1,831,283 2019 Waste Field Energy $s in thousands Solutions Services Waste Corporate Total Revenue $ 440,547 $ 232,402 $ 12,560 $ — $ 685,509 Depreciation, amortization and accretion $ 41,133 $ 15,007 $ 3,402 $ 1,760 $ 61,302 Capital expenditures $ 46,202 $ 5,986 $ 1,391 $ 4,521 $ 58,100 Total assets $ 755,566 $ 865,540 $ 534,738 $ 75,400 $ 2,231,244
Reconciliation of Net income (loss) to Adjusted EBITDA and adjusted EBITDA by operating segment	$s in thousands 2021 2020 2019 Net income (loss) $ 5,337 $ (389,359) $ 33,140 Income tax expense (benefit) 4,765 (4,242) 16,659 Interest expense 28,966 32,595 19,239 Interest income (1,417) (258) (605) Foreign currency loss 171 1,134 733 Other income (4,476) (788) (455) Property and equipment impairment charges — — 25 Goodwill and intangible asset impairment charges — 404,900 — Depreciation and amortization of plant and equipment 70,799 66,561 41,423 Amortization of intangible assets 34,614 37,344 15,491 Share-based compensation 7,478 6,651 5,544 Accretion and non-cash adjustment of closure & post-closure liabilities 5,363 4,000 4,388 Gain on property insurance recoveries — — (12,366) Business development and integration expenses 3,274 11,621 26,150 Adjusted EBITDA $ 154,874 $ 170,159 $ 149,366 $s in thousands 2021 2020 2019 Waste Solutions $ 170,953 $ 176,702 $ 184,133 Field Services 70,578 81,770 26,707 Energy Waste 11,321 4,982 3,626 Corporate (97,978) (93,295) (65,100) Total $ 154,874 $ 170,159 $ 149,366
Schedule of long-lived assets by geographic location	$s in thousands 2021 2020 United States $ 855,200 $ 882,639 Canada 65,437 68,623 EMEA 15,604 18,042 Other (1) 9,716 11,321 Total long-lived assets, net $ 945,957 $ 980,625 (1) Includes Mexico, Asia Pacific, and Latin America and Caribbean geographical regions.

DESCRIPTION OF BUSINESS (Detail

DESCRIPTION OF BUSINESS (Details)	12 Months Ended
DESCRIPTION OF BUSINESS (Details)	Dec. 31, 2021segment
GENERAL
Number of Reportable Segments	3

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents
Cash and Cash Equivalents, at Carrying Value	$ 67,487	$ 73,848	$ 41,281	$ 31,969
Non-US Operations
Cash and Cash Equivalents
Cash	$ 54,400	$ 59,300

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Restricted Cash and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Restricted Cash and Investments
Restricted cash and investments	$ 1,567	$ 5,598

SUMMARY OF SIGNIFICANT ACCOUN_6

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Deferred Revenue (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)item	Dec. 31, 2020USD ($)
Revenue Recognition
Number of primary sources for revenue recognition \| item	3
Deferred revenue recognized in revenue \| $	$ 15.1	$ 14.7

SUMMARY OF SIGNIFICANT ACCOUN_7

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property and Equipment
Repair and maintenance expenses	$ 29.5	$ 26.9	$ 20.5
Salvage value for the depreciable fixed assets	$ 0
Vehicles, vessels and other equipment \| Minimum
Property and Equipment
Useful Lives	3 years
Vehicles, vessels and other equipment \| Maximum
Property and Equipment
Useful Lives	10 years
Disposal facility and equipment \| Minimum
Property and Equipment
Useful Lives	3 years
Disposal facility and equipment \| Maximum
Property and Equipment
Useful Lives	20 years
Buildings and improvements \| Minimum
Property and Equipment
Useful Lives	5 years
Buildings and improvements \| Maximum
Property and Equipment
Useful Lives	40 years
Railcars
Property and Equipment
Useful Lives	40 years

SUMMARY OF SIGNIFICANT ACCOUN_8

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disposal Cell Accounting (Details)	12 Months Ended
	Dec. 31, 2021
Disposal Cell Accounting
Period of acceptable financial assurance for closure and post-closure monitoring of each facility as per RCRA requirements	30 years

SUMMARY OF SIGNIFICANT ACCOUN_9

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Intangible Assets (Details)	12 Months Ended
	Dec. 31, 2021
Minimum
Intangible Assets
Estimated economic lives	1 year
Maximum
Intangible Assets
Estimated economic lives	60 years
Permits and license \| Minimum
Intangible Assets
Renewal terms of acquired intangible assets	5 years
Permits and license \| Maximum
Intangible Assets
Renewal terms of acquired intangible assets	10 years

SUMMARY OF SIGNIFICANT ACCOU_10

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Debt Issuance Costs & Debt Discount (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Issuance Costs & Debt Discount
Unamortized discount and debt issuance costs	$ 5,516	$ 6,657
Term Loan
Debt Issuance Costs & Debt Discount
Unamortized discount and debt issuance costs	5,500	6,700
Revolving Line of Credit
Debt Issuance Costs & Debt Discount
Unamortized debt issuance costs	$ 4,800	$ 5,300

SUMMARY OF SIGNIFICANT ACCOU_11

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Derivative Instruments (Details) $ in Millions	Mar. 31, 2020USD ($)
Derivative Instruments
Initial notional amount	$ 500

SUMMARY OF SIGNIFICANT ACCOU_12

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Insurance (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Insurance
Accrued costs for self-insured health care coverage	$ 3.4	$ 3.3

REVENUES (Details)

REVENUES (Details) $ in Thousands	12 Months Ended
REVENUES (Details) $ in Thousands	Dec. 31, 2021USD ($)segment	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Disaggregation of revenue
Number of reportable segments \| segment	3
Revenue	$ 988,001	$ 933,854	$ 685,509
Treatment and disposal
Disaggregation of revenue
Revenue	443,528	420,720	384,409
Transportation and Logistics
Disaggregation of revenue
Revenue	117,119	112,760	124,247
Industrial Services
Disaggregation of revenue
Revenue	124,171	122,762	40,061
Small Quantity Generation
Disaggregation of revenue
Revenue	55,158	48,049	37,471
Total Waste Management
Disaggregation of revenue
Revenue	39,949	35,401	33,794
Remediation
Disaggregation of revenue
Revenue	48,224	30,225	13,307
Emergency Response
Disaggregation of revenue
Revenue	138,443	140,253	41,088
Other Services
Disaggregation of revenue
Revenue	21,409	23,684	11,132
Operating Segment
Disaggregation of revenue
Revenue	988,001	933,854	685,509
Operating Segment \| Environmental Services
Disaggregation of revenue
Revenue	451,249	425,413	440,547
Operating Segment \| Field & Industrial Services
Disaggregation of revenue
Revenue	500,187	473,754	232,402
Operating Segment \| Energy Waste
Disaggregation of revenue
Revenue	36,565	34,687	12,560
Operating Segment \| Treatment and disposal \| Environmental Services
Disaggregation of revenue
Revenue	372,204	354,055	359,847
Operating Segment \| Treatment and disposal \| Field & Industrial Services
Disaggregation of revenue
Revenue	50,327	47,781	18,523
Operating Segment \| Treatment and disposal \| Energy Waste
Disaggregation of revenue
Revenue	20,997	18,884	6,039
Operating Segment \| Transportation and Logistics \| Environmental Services
Disaggregation of revenue
Revenue	79,045	71,358	80,700
Operating Segment \| Transportation and Logistics \| Field & Industrial Services
Disaggregation of revenue
Revenue	29,096	34,218	40,670
Operating Segment \| Transportation and Logistics \| Energy Waste
Disaggregation of revenue
Revenue	8,978	7,184	2,877
Operating Segment \| Industrial Services \| Field & Industrial Services
Disaggregation of revenue
Revenue	121,357	118,584	38,861
Operating Segment \| Industrial Services \| Energy Waste
Disaggregation of revenue
Revenue	2,814	4,178	1,200
Operating Segment \| Small Quantity Generation \| Field & Industrial Services
Disaggregation of revenue
Revenue	55,158	48,049	37,471
Operating Segment \| Total Waste Management \| Field & Industrial Services
Disaggregation of revenue
Revenue	39,949	35,401	33,794
Operating Segment \| Remediation \| Field & Industrial Services
Disaggregation of revenue
Revenue	48,224	30,225	13,307
Operating Segment \| Emergency Response \| Field & Industrial Services
Disaggregation of revenue
Revenue	138,425	140,253	41,088
Operating Segment \| Emergency Response \| Energy Waste
Disaggregation of revenue
Revenue	18
Operating Segment \| Other Services \| Field & Industrial Services
Disaggregation of revenue
Revenue	17,651	19,243	8,688
Operating Segment \| Other Services \| Energy Waste
Disaggregation of revenue
Revenue	$ 3,758	$ 4,441	$ 2,444

REVENUES - Treatment and Dispos

REVENUES - Treatment and Disposal Revenue (Details) - T	12 Months Ended
REVENUES - Treatment and Disposal Revenue (Details) - T	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Small Quantity Generation \| Minimum
Disaggregation of revenue
Revenue Contract Term	1 year
Total Waste Management \| Minimum
Disaggregation of revenue
Revenue Contract Term	1 year
Remediation \| Minimum
Disaggregation of revenue
Revenue Contract Term	1 year
Event Business \| Treatment and disposal
Disaggregation of revenue
Threshold Tons of Non-recurring projects	1,000
Revenue (in percent)	24.00%	27.00%	22.00%
Base Business \| Treatment and disposal
Disaggregation of revenue
Revenue (in percent)	76.00%	73.00%	78.00%

REVENUES - Geography (Details)

REVENUES - Geography (Details) - USD ($) $ in Thousands	12 Months Ended
REVENUES - Geography (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of revenue
Revenue	$ 988,001	$ 933,854	$ 685,509
Operating Segment
Disaggregation of revenue
Revenue	988,001	933,854	685,509
Operating Segment \| United States
Disaggregation of revenue
Revenue	861,255	835,318	589,127
Operating Segment \| Canada
Disaggregation of revenue
Revenue	80,620	73,251	88,499
Operating Segment \| EMEA
Disaggregation of revenue
Revenue	41,218	19,947	5,079
Operating Segment \| Other
Disaggregation of revenue
Revenue	4,908	5,338	2,804
Operating Segment \| Environmental Services
Disaggregation of revenue
Revenue	451,249	425,413	440,547
Operating Segment \| Environmental Services \| United States
Disaggregation of revenue
Revenue	374,414	355,226	354,625
Operating Segment \| Environmental Services \| Canada
Disaggregation of revenue
Revenue	76,835	70,187	85,922
Operating Segment \| Field & Industrial Services
Disaggregation of revenue
Revenue	500,187	473,754	232,402
Operating Segment \| Field & Industrial Services \| United States
Disaggregation of revenue
Revenue	450,276	445,405	221,942
Operating Segment \| Field & Industrial Services \| Canada
Disaggregation of revenue
Revenue	3,785	3,064	2,577
Operating Segment \| Field & Industrial Services \| EMEA
Disaggregation of revenue
Revenue	41,218	19,947	5,079
Operating Segment \| Field & Industrial Services \| Other
Disaggregation of revenue
Revenue	4,908	5,338	2,804
Operating Segment \| Energy Waste
Disaggregation of revenue
Revenue	36,565	34,687	12,560
Operating Segment \| Energy Waste \| United States
Disaggregation of revenue
Revenue	$ 36,565	$ 34,687	$ 12,560

REVENUES - Practical Expedients

REVENUES - Practical Expedients (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
REVENUES
Contract with Customer, Liability, Revenue Recognized	$ 15.1	$ 14.7
Revenue, Practical Expedient, Financing Component	true
Revenue, Practical Expedient, Initial Application and Transition, Nonrestatement of Modified Contract	true

BUSINESS COMBINATIONS - Merger

BUSINESS COMBINATIONS - Merger consideration (Details) $ / shares in Units, $ in Thousands	Nov. 01, 2019USD ($)$ / sharesYshares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Oct. 31, 2019$ / shares
Business Acquisition [Line Items]
Proceeds from term loan		$ 90,000	$ 491,875
NRC
Business Acquisition [Line Items]
Fair value of US Ecology common stock issued			$ 626,460
Repayment of NRC's term loan and revolving credit facility	$ 398,373
Total merger consideration	1,024,833
Proceeds from term loan	$ 450,000
Term of long term debt	7 years
NRC \| Common Stock
Business Acquisition [Line Items]
Fair value of US Ecology common stock issued	$ 581,101
Shares Issued \| shares	9,337,949
Closing share price \| $ / shares				$ 62.23
NRC \| Warrants
Business Acquisition [Line Items]
Fair value of replacement warrants issued	$ 44,858
Shares Issued \| shares	3,772,753
Fair value per warrant \| $ / shares	$ 11.89
Closing share price \| $ / shares				$ 2.33
Exchange ratio	0.196
NRC \| RSUs
Business Acquisition [Line Items]
Fair value of replacement RSUs issued	$ 141
Shares Issued \| shares	118,239
Ratio of precombination service period to vesting period	1.90%
NRC \| Stock options
Business Acquisition [Line Items]
Fair value of replacement stock options	$ 360
Shares Issued \| shares	29,400
Fair value per option \| $ / shares	$ 12.26
Strike price \| $ / shares	$ 52.30
NRC \| Stock options \| Dividend yield
Business Acquisition [Line Items]
Fair value of option	1.2
NRC \| Stock options \| Expected volatility
Business Acquisition [Line Items]
Fair value of option	28.9
NRC \| Stock options \| Risk free rate
Business Acquisition [Line Items]
Fair value of option \| $ / shares	1.5
NRC \| Stock options \| Expected term
Business Acquisition [Line Items]
Fair value of option \| Y	1

BUSINESS COMBINATIONS - Prelimi

BUSINESS COMBINATIONS - Preliminary fair value estimates of assets acquired and liabilities assumed recognized (Details) $ in Thousands, $ in Millions	Oct. 31, 2020USD ($)	Jan. 28, 2020USD ($)	Aug. 01, 2019USD ($)	Aug. 01, 2019CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Nov. 01, 2019USD ($)
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill					$ 413,037	$ 413,126	$ 413,037	$ 766,980
Depreciation and amortization of plant and equipment						70,799	66,561	41,423
Amortization of intangibles assets						34,614	37,344	15,491
Environmental Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill					166,863	166,925	166,863	166,415
Field & Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill					237,341	237,368	237,341	$ 298,579
Goodwill impairment charges					$ 14,400
NRC
Consideration paid and the fair value of assets acquired and liabilities assumed
Current assets	$ 130,110
Property and equipment	170,208
Identifiable intangible assets	309,500
Other assets	41,687
Current liabilities	(89,733)
Deferred income tax liabilities	(54,974)
Other liabilities	(59,363)
Total identifiable net assets	447,435
Goodwill	577,398					$ 577,400			$ 577,400
Total purchase price	$ 1,024,833
Goodwill expected to be deductible for income tax purposes									33,300
Goodwill impairment charges							383,800
Adjustments
Goodwill - adjustment							28,912
NRC \| Environmental Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill									399,500
NRC \| Field & Industrial Services
Consideration paid and the fair value of assets acquired and liabilities assumed
Goodwill									$ 177,900
Goodwill impairment charges							19,900
Adjustments
Goodwill - adjustment							$ (61,735)
US Ecology Sarnia
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets			$ 6,200
Goodwill			7,700
Total purchase price			$ 17,900	$ 23.5
Impact Environmental Services Inc
Consideration paid and the fair value of assets acquired and liabilities assumed
Identifiable intangible assets		$ 900
Goodwill		300
Total purchase price		$ 3,300

BUSINESS COMBINATIONS - Preli_2

BUSINESS COMBINATIONS - Preliminary fair value of identifiable intangible assets (Details) - NRC - USD ($) $ in Thousands	Nov. 01, 2019	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total identified intangible assets	$ 252,100
Non-amortizing intangible assets		$ 57,100
Total identified intangible assets	309,500
Customer relationships - noncontractual
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total identified intangible assets	$ 199,600
Average Amortization Period	14 years
Customer relationships - contractual
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total identified intangible assets	$ 34,400
Average Amortization Period	7 years
Permits and licenses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total identified intangible assets	$ 8,700
Average Amortization Period	16 years
Tradename
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total identified intangible assets	$ 6,100
Average Amortization Period	2 years
Non-compete agreements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total identified intangible assets	$ 3,300
Average Amortization Period	2 years
Permits and license
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-amortizing intangible assets	$ 57,400

BUSINESS COMBINATIONS - Pro for

BUSINESS COMBINATIONS - Pro forma information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Additional information
Business development and integration expenses	$ 3,274	$ 11,621	$ 26,150
NRC
Pro forma combined:
Revenue			1,048,745
Net income (loss)			11,775
Additional information
Revenue since acquisition included in consolidated statements of operations			70,200
Operating loss since acquisition included in consolidated statements of operations			9,100
Business development and integration expenses	$ 2,400	$ 11,500	$ 24,400

BUSINESS COMBINATIONS - Additio

BUSINESS COMBINATIONS - Additional Information (Details) $ in Thousands, $ in Millions	Oct. 31, 2020USD ($)	Jan. 28, 2020USD ($)	Aug. 01, 2019USD ($)	Aug. 01, 2019CAD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Nov. 01, 2019USD ($)
Acquisition
Goodwill					$ 413,126	$ 413,037	$ 766,980
Field & Industrial Services
Acquisition
Goodwill					237,368	237,341	298,579
Environmental Services
Acquisition
Goodwill					166,925	$ 166,863	$ 166,415
NRC
Acquisition
Acquisition price	$ 1,024,833
Goodwill	577,398				$ 577,400			$ 577,400
Identifiable intangible assets	309,500
Property and equipment	$ 170,208
NRC \| Field & Industrial Services
Acquisition
Goodwill								177,900
NRC \| Environmental Services
Acquisition
Goodwill								$ 399,500
US Ecology Sarnia
Acquisition
Percentage of outstanding shares acquired			100.00%
Acquisition price			$ 17,900	$ 23.5
Goodwill			7,700
Identifiable intangible assets			$ 6,200
Weighted average amortization period			14 years	14 years
ES&H Dallas
Acquisition
Goodwill			$ 7,700
Impact Environmental Services Inc
Acquisition
Acquisition price		$ 3,300
Goodwill		300
Identifiable intangible assets		$ 900
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 INCOME (LOSS) - Changes in AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accumulated other comprehensive income (loss)
Beginning balances	$ 601,931	$ 1,011,380	$ 359,217
Other comprehensive income (loss), net	10,464	(2,804)	1,937
Ending balances	624,324	601,931	1,011,380
Foreign Currency Translation
Accumulated other comprehensive income (loss)
Beginning balances	(7,870)	(10,925)
Other comprehensive income (loss) before reclassifications, net of tax	(1,505)	3,055
Other comprehensive income (loss), net	(1,505)	3,055
Ending balances	(9,375)	(7,870)	(10,925)
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	9,010	(8,494)
Amounts reclassified out of AOCI, net of tax	2,959	2,635
Other comprehensive income (loss), net	11,969	(5,859)
Ending balances	5,181	(6,788)	(929)
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss)
Beginning balances	(14,658)	(11,854)	(13,791)
Other comprehensive income (loss) before reclassifications, net of tax	7,505	(5,439)
Amounts reclassified out of AOCI, net of tax	2,959	2,635
Other comprehensive income (loss), net	10,464	(2,804)	1,937
Ending balances	$ (4,194)	$ (14,658)	$ (11,854)

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) -Reclassifications Line Items (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reclassification adjustments
Interest expense	$ 28,966	$ 32,595	$ 19,239
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	2,800
Amounts in AOCI expected to be recognized over the next 12 months, net of taxes	2,200
Unrealized Gain (Loss) on Interest Rate Hedge \| Interest rate swap agreement \| Reclassification out of accumulated other comprehensive income
Reclassification adjustments
Interest expense	3,700	3,300
Interest expense, net of tax	$ 3,000	$ 2,600

DISCLOSURE OF SUPPLEMENTAL CA_3

DISCLOSURE OF SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income taxes and interest paid:
Income taxes paid, net of receipts	$ 1,951	$ 7,774	$ 14,777
Interest paid	25,771	28,433	17,204
Non-cash investing and financing activities:
Adjustments to closure/post-closure retirement asset	732	5,422	(221)
Capital expenditures in accounts payable	7,702	4,712	2,882
Acquisition of equipment with financing arrangements		6,197	2,481
Restricted stock issued from treasury shares	$ 5,654	$ 2,491	514
NRC
Non-cash investing and financing activities:
Fair value of equity issued for acquisition of NRC			$ 626,460

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	1 Months Ended
FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Sep. 30, 2019
Assets measured at fair value on a recurring basis
Initial notional amount				$ 500,000
Equity securities without readily determinable fair value
Variable rate		$ 442,300
Interest rate swap agreement
Assets measured at fair value on a recurring basis
Initial notional amount				$ 440,000
Preferred Stock
Equity securities without readily determinable fair value
Investment in privately held company	$ 712,000		$ 7,900		$ 7,900
Fair value change	3,500
Gain on investment	$ 3,500
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		8,858	5,660
Liabilities fair value disclosure			11,917
Recurring \| Interest rate swap agreement
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure			9,744
Recurring \| Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure		1,950	4,341
Recurring \| Money market funds
Assets measured at fair value on a recurring basis
Assets fair value disclosure		1,886	1,319
Recurring \| Money market funds \| Interest rate swap agreement
Assets measured at fair value on a recurring basis
Assets fair value disclosure		5,022
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		3,581	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		1,695	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		1,886	1,319
Recurring \| Other Observable Inputs (Level 2)
Assets measured at fair value on a recurring basis
Assets fair value disclosure		5,277	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
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		255	1,427
Recurring \| Other Observable Inputs (Level 2) \| Money market funds \| Interest rate swap agreement
Assets measured at fair value on a recurring basis
Assets fair value disclosure		$ 5,022
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 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, beginning of period	$ 2,173	$ 8,283
Change in fair value of contingent consideration	282	(3,682)
Contingent consideration paid	(2,553)	(2,517)
Foreign currency translation	$ 98	89
Contingent consideration, end of period		$ 2,173

CONCENTRATIONS AND CREDIT RISK

CONCENTRATIONS AND CREDIT RISK (Details)	12 Months Ended
CONCENTRATIONS AND CREDIT RISK (Details)	Dec. 31, 2021employee
Workforce Subject to Collective Bargaining Arrangements
CONCENTRATIONS AND CREDIT RISK
Number of employees covered under collective bargaining agreements	500
Workforce Subject to Collective Bargaining Arrangements \| Non-unionized employees
CONCENTRATIONS AND CREDIT RISK
Concentration of risk (as a percent)	13.00%
Workforce Subject to Collective Bargaining Arrangements That Expired and are in Negotiation or Expiring within One Year \| Non-unionized employees
CONCENTRATIONS AND CREDIT RISK
Concentration of risk (as a percent)	40.00%

RECEIVABLES (Details)

RECEIVABLES (Details) - USD ($) $ in Thousands	12 Months Ended
RECEIVABLES (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
RECEIVABLES
Trade	$ 183,747	$ 186,502
Unbilled revenue	62,029	52,858
Other	7,421	5,554
Total receivables	253,197	244,914
Allowance for credit losses	(3,043)	(2,936)	$ (3,010)
Receivables, net	250,154	241,978
Change in the allowance for doubtful accounts receivable
Balance at Beginning of Period	2,936	3,010	2,998
Charged (Credited) to Costs and Expenses	1,179	(412)	226
Recoveries (Deductions/Write-offs)	(1,075)		(439)
Recoveries		296
Adjustments	3	42	225
Balance at End of Period	$ 3,043	$ 2,936	$ 3,010

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
PROPERTY AND EQUIPMENT
Total property and equipment	$ 839,032	$ 773,635
Accumulated depreciation and amortization	(382,648)	(316,998)
Property and equipment, net	456,384	456,637
Depreciation and amortization of plant and equipment	70,799	66,561	$ 41,423
Cell development costs
PROPERTY AND EQUIPMENT
Total property and equipment	203,217	186,170
Land and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	74,298	65,953
Buildings and improvements
PROPERTY AND EQUIPMENT
Total property and equipment	138,659	128,206
Railcars
PROPERTY AND EQUIPMENT
Total property and equipment	17,299	17,299
Vehicles, vessels and other equipment
PROPERTY AND EQUIPMENT
Total property and equipment	350,950	331,167
Construction in progress
PROPERTY AND EQUIPMENT
Total property and equipment	$ 54,609	$ 44,840

LEASES (Details)

LEASES (Details)	12 Months Ended
LEASES (Details)	Dec. 31, 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	Dec. 31, 2021	Dec. 31, 2020
Assets:
Operating lease assets	$ 43,607	$ 51,474
Finance right-of-use lease assets	17,290	21,209
Total	60,897	72,683
Finance leased assets - accumulated amortization	13,300	8,000
Liabilities:
Operating lease, current	15,799	17,048
Finance lease, current	$ 4,969	$ 4,462
Finance Lease, Liability, Current	Accrued liabilities	Accrued liabilities
Long-term operating lease liabilities	$ 28,477	$ 35,069
Finance lease, long term	$ 12,108	$ 17,501
Finance Lease, Liability, Noncurrent	Other long-term liabilities	Other long-term liabilities
Total	$ 61,353	$ 74,080

LEASES - Lease cost (Details)

LEASES - Lease cost (Details) - USD ($) $ in Thousands	12 Months Ended
LEASES - Lease cost (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Lease cost
Operating lease cost	$ 19,950	$ 20,880
Amortization of leased assets	5,249	5,312
Interest on lease liabilities	1,012	1,221
Total	$ 26,211	$ 27,413

LEASES - Supplemental Cash Flow

LEASES - Supplemental Cash Flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
LEASES
Operating cash flows from operating leases	$ 19,687	$ 20,297
Operating cash flows from finance leases	1,012	1,221
Financing cash flows from finance leases	4,885	4,659
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 10,010	13,576
Right-of-use assets obtained in exchange for new finance lease liabilities		$ 6,197

LEASES - Weighted-average remai

LEASES - Weighted-average remaining lease term and discount rate (Details)	Dec. 31, 2021	Dec. 31, 2020
LEASES
Weighted-average remaining lease term, operating leases	3 years 8 months 12 days	4 years 1 month 6 days
Weighted-average remaining lease term, finance leases	3 years 2 months 12 days	4 years
Weighted-average discount rate, operating leases	3.59%	3.69%
Weighted-average discount rate, finance leases	5.85%	5.86%

LEASES - Maturity analysis of o

LEASES - Maturity analysis of operating and finance lease liabilities (Details) $ in Thousands	Dec. 31, 2021USD ($)
Operating Leases
2022	$ 17,091
2023	13,617
2024	8,510
2025	3,366
2026	1,557
Thereafter	3,356
Total	47,497
Less: Interest	3,221
Present Value of Lease Liabilities	44,276
Finance Leases
2022	5,694
2023	5,668
2024	3,929
2025	3,565
2026	953
Thereafter	264
Total	20,073
Less: Interest	2,996
Present Value of Lease Liabilities	17,077
Operating And Finance Leases
2022	22,785
2023	19,285
2024	12,439
2025	6,931
2026	2,510
Thereafter	3,620
Total	67,570
Less: Interest	6,217
Present Value of Lease Liabilities	$ 61,353

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Oct. 01, 2020	Nov. 01, 2019
Changes in goodwill
Balance at the beginning of the period			$ 766,980	$ 413,037	$ 766,980
Foreign currency translation				89	645
Balance at the end of the period	$ 413,126	$ 413,037		413,126	413,037
Impairment charges of finite-lived assets		0
Permits and license
Changes in goodwill
Non-amortizing intangible assets						$ 57,100
Impairment charges of finite-lived assets	0	21,100
NRC
Changes in goodwill
Impairment charges					(383,800)
NRC Merger purchase price allocation adjustment					28,912
Balance at the end of the period	577,400			577,400
Non-amortizing intangible assets	57,100			57,100
Total identified intangible assets							$ 252,100
Accumulated Impairment
NRC Merger purchase price allocation adjustment					28,912
NRC \| Permits and license
Changes in goodwill
Non-amortizing intangible assets							$ 57,400
Impact Environmental Services Inc
Changes in goodwill
Acquisition					300
EW
Changes in goodwill
Impairment charges			(283,600)
Accumulated Impairment
Goodwill, Period Increase (Decrease)		80,300
International reporting unit
Changes in goodwill
Impairment charges			(16,700)
Accumulated Impairment
Reversal of impairment charges		11,200
Environmental Services
Changes in goodwill
Balance at the beginning of the period			166,415	166,863	166,415
Foreign currency translation				62	448
Balance at the end of the period	166,925	166,863		166,925	166,863
Accumulated Impairment
Accumulated impairment at the beginning			(6,870)	(6,870)	(6,870)
Accumulated impairment at the ending	(6,870)	(6,870)		(6,870)	(6,870)
Energy Waste
Changes in goodwill
Balance at the beginning of the period			308,856	399,503	308,856
Balance at the end of the period	399,503	399,503		399,503	399,503
Accumulated Impairment
Accumulated impairment at the beginning				(363,900)
Accumulated impairment at the ending	(363,900)	(363,900)		(363,900)	(363,900)
Energy Waste \| NRC
Changes in goodwill
Impairment charges					(363,900)
NRC Merger purchase price allocation adjustment					90,647
Accumulated Impairment
NRC Merger purchase price allocation adjustment					90,647
Field & Industrial Services
Changes in goodwill
Balance at the beginning of the period			$ 298,579	237,341	298,579
Impairment charges		(14,400)
Foreign currency translation				27	197
Balance at the end of the period	237,368	237,341		237,368	237,341
Accumulated Impairment
Accumulated impairment at the beginning				(19,900)
Accumulated impairment at the ending	$ (19,900)	$ (19,900)		$ (19,900)	(19,900)
Carrying value greater than fair value						$ 14,400
Field & Industrial Services \| NRC
Changes in goodwill
Impairment charges					(19,900)
NRC Merger purchase price allocation adjustment					(61,735)
Accumulated Impairment
NRC Merger purchase price allocation adjustment					(61,735)
Field & Industrial Services \| Impact Environmental Services Inc
Changes in goodwill
Acquisition					$ 300

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill
Goodwill	$ 413,037		$ 413,126	$ 413,037	$ 766,980
Foreign currency translation			$ 89	$ 645
Impairment charges of finite-lived assets	$ 0
EW
Goodwill
Impairment charges		$ 283,600
International reporting unit
Goodwill
Impairment charges		$ 16,700

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Impairment (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets
Goodwill	$ 413,126	$ 413,037	$ 766,980

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Oct. 31, 2020	Jan. 28, 2020	Nov. 01, 2019	Aug. 01, 2019
Intangible Assets
Amortizing intangible assets, Cost	$ 545,634	$ 545,499
Accumulated amortization	(138,929)	(104,376)
Amortizing intangible assets, Net	406,705	441,123
Total intangible assets, cost	628,502	628,364
Total intangible assets, net	489,573	523,988
Goodwill	413,126	413,037	$ 766,980
Amortization of intangible assets	34,614	37,344	15,491
Permits and license
Intangible Assets
Non-amortizing intangible assets	82,734	82,732
Tradename
Intangible Assets
Non-amortizing intangible assets	134	133
Permits, licenses and lease
Intangible Assets
Amortizing intangible assets, Cost	174,959	174,885
Accumulated amortization	(27,170)	(23,005)
Amortizing intangible assets, Net	147,789	151,880
Customer relationships
Intangible Assets
Amortizing intangible assets, Cost	340,065	340,032
Accumulated amortization	(87,952)	(61,778)
Amortizing intangible assets, Net	252,113	278,254
Technology - Formulae and processes
Intangible Assets
Amortizing intangible assets, Cost	7,166	7,142
Accumulated amortization	(2,531)	(2,293)
Amortizing intangible assets, Net	4,635	4,849
Customer backlog
Intangible Assets
Amortizing intangible assets, Cost	3,652	3,652
Accumulated amortization	(2,752)	(2,387)
Amortizing intangible assets, Net	900	1,265
Tradename
Intangible Assets
Amortizing intangible assets, Cost	10,390	10,390
Accumulated amortization	(10,390)	(8,015)
Amortizing intangible assets, Net		2,375
Developed software
Intangible Assets
Amortizing intangible assets, Cost	2,903	2,902
Accumulated amortization	(2,475)	(2,182)
Amortizing intangible assets, Net	428	720
Non-compete agreements
Intangible Assets
Amortizing intangible assets, Cost	5,573	5,571
Accumulated amortization	(5,211)	(4,318)
Amortizing intangible assets, Net	362	1,253
Internet domain and website
Intangible Assets
Amortizing intangible assets, Cost	536	536
Accumulated amortization	(213)	(184)
Amortizing intangible assets, Net	323	352
Database
Intangible Assets
Amortizing intangible assets, Cost	390	389
Accumulated amortization	(235)	(214)
Amortizing intangible assets, Net	155	175
Impact Environmental Services Inc
Intangible Assets
Amortizing intangible assets, Cost					$ 900
Goodwill					$ 300
ES&H Dallas
Intangible Assets
Goodwill							$ 7,700
US Ecology Sarnia
Intangible Assets
Goodwill							$ 7,700
NRC
Intangible Assets
Goodwill	577,400			$ 577,398		$ 577,400
Field & Industrial Services
Intangible Assets
Goodwill	$ 237,368	$ 237,341	$ 298,579
Field & Industrial Services \| NRC
Intangible Assets
Goodwill						$ 177,900

GOODWILL AND INTANGIBLE ASSET_6

GOODWILL AND INTANGIBLE ASSETS - Future amortization expense (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Expected future amortization expense of amortizing intangible assets
2022	$ 31,403
2023	31,216
2024	30,830
2025	30,586
2026	29,767
Thereafter	252,903
Amortizing intangible assets, Net	$ 406,705	$ 441,123

EMPLOYEE BENEFIT PLANS (Details

EMPLOYEE BENEFIT PLANS (Details)	12 Months Ended
EMPLOYEE BENEFIT PLANS (Details)	Dec. 31, 2021USD ($)plan	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Defined contribution plans
Individually insignificant contributions made	$ 157,000	$ 205,000
The Plan
Defined contribution plans
Entity's matching contribution (as a percent)	55.00%
Company's contribution as a percentage of eligible compensation	6.00%
Entity's matching contributions to the Plan	$ 6,400,000	3,300,000	$ 3,000,000
The NRC Plans
Defined contribution plans
Entity's matching contributions to the Plan		2,300,000	325,000
Multi-employer Defined Benefit Pension Plans
Defined contribution plans
Number of multi-employer plans \| plan	4
Operating Engineers Local 324 Pension Plan
Defined contribution plans
Significant contribution made	$ 1,100,000	1,000,000
Communications, Energy and Paperworkers Union of Canada \| Minimum
Defined contribution plans
Company's contribution as a percentage of eligible compensation	5.00%
Communications, Energy and Paperworkers Union of Canada \| Maximum
Defined contribution plans
Company's contribution as a percentage of eligible compensation	9.50%
Non-unionized employees \| The SPP
Defined contribution plans
Entity's matching contributions to the Plan	$ 858,000	$ 782,000	$ 719,000

CLOSURE AND POST-CLOSURE OBLI_3

CLOSURE AND POST-CLOSURE OBLIGATIONS (Details) - Surety bond $ in Millions	12 Months Ended
	Dec. 31, 2021USD ($)
Closure obligations
Period for which the guarantee obligation is required to be maintained	25 years
Carrying value of Commercial bonds dedicated for closure obligations	$ 13.3

CLOSURE AND POST-CLOSURE OBLI_4

CLOSURE AND POST-CLOSURE OBLIGATIONS - FAIR VALUE ASSUMPTIONS (Details) - Asset retirement obligations	12 Months Ended
	Dec. 31, 2021
Fair value of future asset retirement obligations
Estimated inflation rate (as a percent)	2.60%
Risk free rate \| Weighted-average
Fair value of future asset retirement obligations
Measurement input	5.3

CLOSURE AND POST-CLOSURE OBLI_5

CLOSURE AND POST-CLOSURE OBLIGATIONS - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Changes to reported closure and post-closure obligations
Closure and post-closure obligations, beginning of year	$ 95,869	$ 86,383
NRC Merger purchase price allocation adjustment		1,782
Accretion expense	5,363	4,000	$ 4,388
Payments	(3,054)	(1,750)
Adjustments	732	5,422
Foreign currency translation	10	32
Closure and post-closure obligations, end of year	98,920	95,869	$ 86,383
Less current portion	(5,771)	(6,471)
Long-term portion	93,149	89,398
Additions or adjustments to closure and post-closure asset	732	5,422
Belleville, Michigan
Changes to reported closure and post-closure obligations
Additions or adjustments to closure and post-closure asset	$ 584
Robstown Texas Operating Facility
Changes to reported closure and post-closure obligations
Additions or adjustments to closure and post-closure asset		$ 5,400

CLOSURE AND POST-CLOSURE OBLI_6

CLOSURE AND POST-CLOSURE OBLIGATIONS - CHANGES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Changes in the reported closure and post-closure asset, recorded as a component of Property and equipment, net
Net closure and post-closure asset, beginning of year	$ 26,532	$ 22,884
NRC Merger purchase price allocation adjustment		(389)
Additions or adjustments to closure and post-closure asset	732	5,422
Amortization of closure and post-closure asset	(1,614)	(1,407)
Foreign currency translation	12	22
Net closure and post-closure asset, end of year	$ 25,662	$ 26,532

DEBT - Schedule (Details)

DEBT - Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Aug. 06, 2019
Long-term debt
Loan amount	$ 744,000
Unamortized term loan discount and debt issuance costs	(5,516)	$ (6,657)
Total debt	738,484	785,843
Current portion of long-term debt	(3,359)	(3,359)
Long-term debt	735,125	782,484
Credit agreement
Long-term debt
Loan amount	303,000	347,000
Term Loan
Long-term debt
Loan amount	441,000	445,500	$ 400,000
Unamortized term loan discount and debt issuance costs	$ (5,500)	$ (6,700)

DEBT - Future Maturities (Detai

DEBT - Future Maturities (Details) $ in Thousands	Dec. 31, 2021USD ($)
Future maturities of long-term debt, excluding unamortized net discount
2022	$ 4,500
2023	4,500
2024	4,500
2025	4,500
2026	726,000
Total	$ 744,000

DEBT - Paragraph (Details)

DEBT - Paragraph (Details) $ in Thousands	Jun. 29, 2021	Jun. 26, 2020	Nov. 01, 2019USD ($)	Aug. 06, 2019USD ($)	Apr. 18, 2017USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
DEBT
Loan amount							$ 744,000
Notional amount						$ 500,000
Interest rate swap agreement
DEBT
Notional amount						$ 440,000
Percentage of outstanding debt						59.00%
Net loss related to terminated swap						$ 1,800
Fair value of the interest rate swap							5,000
Gain (loss) on settlements of the interest rate swaps							(3,700)	$ (3,300)	$ 170
Sweep Arrangements
DEBT
Advances outstanding							$ 0
Credit agreement
DEBT
Maximum borrowing capacity					$ 500,000
Contractual term					5 years
Accordion feature			$ 250,000
Effective interest rate (as a percent)							4.00%
Loan amount							$ 303,000	347,000
Availability for borrowings under line of credit							$ 71,200
Voting equity interest in foreign subsidiaries pledged as security (as a percent)					100.00%
Non-voting equity interest in foreign subsidiaries pledged as security (as a percent)					65.00%
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							$ 12,200
Credit Agreement, Swingline Loans
DEBT
Maximum borrowing capacity			$ 40,000
Credit Agreement, Swingline Loans \| Sweep Arrangements
DEBT
Maximum borrowing capacity							40,000
Term Loan
DEBT
Maximum borrowing capacity			$ 450,000
Contractual term			7 years
Loan amount				$ 400,000			$ 441,000	$ 445,500
Increase in capacity			$ 50,000
Required annual principal repayment (as a percent)			1.00%
Stated interest rate							2.86%
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	Dec. 31, 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
DEBT
Minimum consolidated senior secured leverage ratio	4.50
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

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
INCOME TAXES (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Domestic and foreign components of Income (loss) before income taxes
Domestic	$ (10,567)	$ (403,492)	$ 30,706
Foreign	20,669	9,891	19,093
Income (loss) before income taxes	10,102	(393,601)	49,799
Current:
U.S. Federal	(1,534)	(9,905)	3,120
State	68	3,062	1,547
Foreign	6,948	6,768	5,426
Total current	5,482	(75)	10,093
Deferred:
U.S. Federal	(509)	1,384	5,977
State	503	(2,859)	714
Foreign	(711)	(2,692)	(125)
Total deferred	(717)	(4,167)	6,566
Income tax expense (benefit)	$ 4,765	$ (4,242)	$ 16,659
Reconciliation between the effective income tax rate and the applicable statutory federal and state income tax rate
Taxes computed at federal statutory rate	21.00%	21.00%	21.00%
Goodwill impairment charges		(20.40%)
State income taxes (net of federal income tax benefit)	9.80%	0.30%	5.70%
Share-based compensation	4.60%	(0.10%)	(0.40%)
Research and development credits	(4.40%)	0.10%	(0.80%)
Non-deductible transaction costs	1.60%		3.40%
Global intangible low taxed income			1.10%
Foreign rate differential	11.00%	(0.30%)	2.50%
Net operating loss reduction		(1.70%)
Unrecognized tax benefit reduction		1.70%
State deferred rate differential		(0.10%)	(1.60%)
State credits	(5.10%)
Assumed contingent liability	3.10%
Non-deductible executive compensation	1.50%
Non-deductible foreign expenses	4.30%
Non-deductible political contributions	1.30%
Net operating loss carryback rate differential	(4.60%)
Other	3.10%	0.60%	2.60%
Total (as a percent)	47.20%	1.10%	33.50%

INCOME TAXES - DEFERRED TAX ASS

INCOME TAXES - DEFERRED TAX ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating losses	$ 16,963	$ 18,751
Operating leases	10,980	12,875
Foreign tax credit and capital loss carry forwards	5,579	4,928
Accruals, allowances and other	4,963	8,691
Environmental compliance and other site related costs	10,833	10,909
Unrealized foreign exchange gains	819	790
Total deferred tax assets	50,137	56,944
Less: valuation allowance	(4,164)	(4,207)
Net deferred tax assets	45,973	52,737
Deferred tax liabilities:
Property and equipment	(50,601)	(53,838)
Intangible assets	(106,504)	(107,109)
Operating leases	(10,980)	(12,875)
Other	(1,370)	102
Total deferred tax liabilities	(169,455)	(173,720)
Net deferred tax liability	(123,482)	(120,983)
Valuation allowance decreased	(42)
Foreign
Deferred tax liabilities:
Operating loss carryforwards	7,200
State
Deferred tax liabilities:
Operating loss carryforwards	52,200
Valuation allowance for certain deferred tax assets	37	$ 79
Federal
Deferred tax liabilities:
Operating loss carryforwards	58,500
Indefinite lived net operating losses	$ 26,400

INCOME TAXES - DOMESTIC AND FOR

INCOME TAXES - DOMESTIC AND FOREIGN COMPONENTS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Changes to unrecognized tax benefits (excluding related penalties and interest)
Unrecognized tax benefits, beginning of year	$ 239,000	$ 8,335,000	$ 555,000
Gross increases - tax positions in prior period	9,000		8,088,000
Gross decreases - tax positions in prior period		(8,091,000)	(9,000)
Gross increases - tax positions in current period	58,000	50,000	52,000
Settlements			(284,000)
Lapse of statute of limitations	(50,000)	(55,000)	(67,000)
Unrecognized tax benefits, end of year	256,000	$ 239,000	$ 8,335,000
Unrecognized tax benefits, if recognized, would favorably impact future earnings	237,000
Penalties accrued on unrecognized tax benefits	0
NRC
Changes to unrecognized tax benefits (excluding related penalties and interest)
Change in net operating losses deferred tax asset	$ 8,100,000

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Litigation and Regulatory Proceedings (Details)	Jan. 10, 2020USD ($)
Occupational Safety and Health Review Commission
Litigation and Regulatory Proceedings
Settlement	$ 50,000

EQUITY - Equity Based Purchase

EQUITY - Equity Based Purchase Consideration (Details) - NRC $ in Millions	Nov. 01, 2019USD ($)shares
Business Acquisition [Line Items]
Purchase price in equity-based consideration \| $	$ 626.5
Common Stock
Business Acquisition [Line Items]
Shares Issued	9,337,949
Warrants
Business Acquisition [Line Items]
Shares Issued	3,772,753
RSUs
Business Acquisition [Line Items]
Shares Issued	118,239
Stock options
Business Acquisition [Line Items]
Shares Issued	29,400

EQUITY - Stock Repurchase Progr

EQUITY - Stock Repurchase Program (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Repurchase of Common Stock
Repurchase of common stock (in shares)	12,788
Common stock repurchase program
Repurchase of Common Stock
Repurchase of common stock (in shares)		397,600
Repurchase of common stock value		$ 17.3

EQUITY - Omnibus Incentive Plan

EQUITY - Omnibus Incentive Plan (Details) - Omnibus Plan - shares	Dec. 31, 2021	May 27, 2015
Stock-Based Compensation Plans
Number of shares authorized for grant		3,272,000
Number of shares available for future grant	2,088,750
Number of shares outstanding	0

EQUITY - PSUs, Restricted Stock

EQUITY - PSUs, Restricted Stock and RSU (Details) - USD ($)	Jul. 16, 2020	Jan. 24, 2020	Mar. 01, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-Based Compensation Plans
Number of common stock shares each RSUs represents (in shares)				1
Assumptions used in Monte Carlo simulation
Common stock, shares issued				31,512,000	31,512,000
PSUs
Stock-Based Compensation Plans
Number of common shares each PSU represents (in shares)	1	1		1
Vesting period	2 years 6 months			3 years
Shares
Outstanding at the beginning of the year (in shares)				86,070
Granted (in shares)	51,922	5,358
Vested (in shares)				(31,211)
Cancelled, expired or forfeited (in shares)				(1,474)
Outstanding at the end of the year (in shares)				53,385	86,070
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)				$ 49.45
Granted (in dollars per share)		$ 54.55
Vested (in dollars per share)				60.62
Cancelled, expired or forfeited (in dollars per share)				54.55
Outstanding at the end of the period (in dollars per share)				$ 42.79	$ 49.45
Additional disclosures
Total fair value of restricted stock vested	$ 42.47		$ 58.20
Assumptions used in Monte Carlo simulation
Stock price on grant date					$ 32.89	$ 58.40
Expected term (years)					2 years 6 months	3 years
Expected volatility (as a percent)					40.60%	30.00%
Risk-free interest rate (as a percent)					0.20%	2.50%
Expected dividend yield (as a percent)						1.10%
Common stock, shares issued				0
PSUs \| Minimum
Stock-Based Compensation Plans
Percentage payout rate	0.00%					0.00%
PSUs \| Maximum
Stock-Based Compensation Plans
Percentage payout rate	200.00%					300.00%
Restricted stock
Stock-Based Compensation Plans
Vesting period				3 years
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	72,766
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	$ 51.47
Additional disclosures
Total fair value of restricted stock vested				$ 1,800,000	$ 2,300,000	$ 2,500,000
RSUs
Stock-Based Compensation Plans
Vesting period				3 years
Shares
Outstanding at the beginning of the year (in shares)					147,243
Granted (in shares)				62,759
Vested (in shares)				(64,597)
Cancelled, expired or forfeited (in shares)				(18,856)
Outstanding at the end of the year (in shares)				126,549		147,243
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)				44.75
Cancelled, expired or forfeited (in dollars per share)				42.51
Outstanding at the end of the period (in dollars per share)				$ 36.78		$ 39.92
Additional disclosures
Total fair value of restricted stock vested				$ 2,600,000	$ 3,000,000	$ 4,800,000
Stock options
Stock-Based Compensation Plans
Vesting period				3 years
Additional disclosures
Weighted average grant date fair value (in dollars per share)				$ 9.90	$ 12.30	$ 14.26
Assumptions used in Monte Carlo simulation
Expected term (years)				3 years 9 months 18 days	4 years	2 years 8 months 12 days
Expected volatility (as a percent)				38.00%	30.00%	30.00%
Risk-free interest rate (as a percent)				0.20%	1.40%	2.10%
Expected dividend yield (as a percent)				0.50%	1.20%	1.20%
Stock options \| Minimum \| Non-employee directors
Stock-Based Compensation Plans
Vesting requirement condition, percentage of attendance in regularly scheduled board meetings				75.00%
Director Plan \| Restricted stock \| Minimum \| Non-employee directors
Stock-Based Compensation Plans
Vesting requirement condition, percentage of attendance in regularly scheduled board meetings				75.00%
Vesting requirement condition, percentage of attendance in regularly scheduled committee meetings that they are a member of				75.00%

EQUITY - Stock Options (Details

EQUITY - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Remaining Contractual Term (Years)
Outstanding at the end of the year	6 years 10 months 24 days
Exercisable at the end of the year	5 years 3 months 18 days
Stock options
Stock-Based Compensation Plans
Expiration term	10 years
Shares
Outstanding at the beginning of the period (in shares)	357,033
Granted (in shares)	205,800
Exercised (in shares)	0
Cancelled, expired or forfeited (in shares)	(16,239)
Outstanding at the end of the period (in shares)	546,594	357,033
Exercisable at the end of the period (in shares)	283,329
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 49.93
Granted (in dollars per share)	35.30
Cancelled, expired or forfeited (in dollars per share)	44.38
Outstanding at the end of the period (in dollars per share)	44.59	$ 49.93
Exercisable at the end of the period (in dollars per share)	48.52
Additional disclosures
Weighted average grant date fair value (in dollars per share)	$ 9.90	$ 12.30	$ 14.26
Intrinsic value of stock options exercised		$ 100	$ 152
Minimum \| Stock options \| Non-employee directors
Stock-Based Compensation Plans
Vesting requirement condition, percentage of attendance in regularly scheduled board meetings	75.00%

EQUITY - Treasury Stock (Detail

EQUITY - Treasury Stock (Details) - $ / shares	12 Months Ended
EQUITY - Treasury Stock (Details) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Treasury Stock
Repurchase of common stock (in shares)	12,788
Average cost of repurchase (in dollars per share)	$ 36.33
Share repurchase program related to net share settlement
Treasury Stock
Repurchase of common stock (in shares)		17,169
Average cost of repurchase (in dollars per share)		$ 57.91
Common stock repurchase program
Treasury Stock
Repurchase of common stock (in shares)		397,600
Average cost of repurchase (in dollars per share)		$ 43.61
Restricted stock \| Omnibus Plan
Treasury Stock
Issuance of restricted stock from treasury stock (in shares)	128,714	56,381
Average cost (in dollars per share)	$ 43.93	$ 44.20

EQUITY - Share-based Compensati

EQUITY - Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-Based Compensation Expense
Total share-based compensation	$ 7,889	$ 7,833	$ 9,261
Income tax benefit	(1,162)	(2,115)	(3,098)
Share-based compensation, net of tax	6,727	5,718	6,163
Tax benefits from stock options exercised		113	321
Unrecognized Share-Based Compensation Expense
Unrecognized compensation expense related to unvested share-based awards granted	$ 7,600
Weighted average remaining vesting period over which expense is expected to be recognized	1 year
Stock options
Share-Based Compensation Expense
Total share-based compensation	$ 1,201	725	575
Restricted stock
Share-Based Compensation Expense
Total share-based compensation	2,719	2,032	1,662
Restricted stock \| Employee
Share-Based Compensation Expense
Total share-based compensation	434	405
RSUs
Share-Based Compensation Expense
Total share-based compensation	2,758	3,810	6,193
Share-based Payment Arrangement, Accelerated Cost	605	3,700
PSUs
Share-Based Compensation Expense
Total share-based compensation	1,211	1,266	$ 831
PSUs \| Employee
Share-Based Compensation Expense
Total share-based compensation	$ 23	$ 173

EQUITY - Warrants (Details)

EQUITY - Warrants (Details)	12 Months Ended
EQUITY - Warrants (Details)	Dec. 31, 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

EARNINGS (LOSS) PER SHARE (Deta

EARNINGS (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
EARNINGS (LOSS) PER SHARE
Net income (loss)	$ 5,337	$ (389,359)	$ 33,140
Basic
Weighted average basic shares outstanding	31,138	31,126	23,521
Earnings (loss) per share (in dollars per share)	$ 0.17	$ (12.51)	$ 1.41
Diluted
Net income (loss), diluted	$ 5,337	$ (389,359)	$ 33,140
Dilutive effect of share-based awards and warrants (in shares)	235		228
Weighted average diluted shares outstanding	31,373	31,126	23,749
Earnings (loss) per share (in dollars per share)	$ 0.17	$ (12.51)	$ 1.40
Anti-dilutive shares excluded from calculation	4,359	4,213	90

SEGMENT REPORTING - Summarized

SEGMENT REPORTING - Summarized Financial Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)segment	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
OPERATING SEGMENTS
Number of reportable segments \| segment	3
Revenue	$ 988,001	$ 933,854	$ 685,509
Depreciation, amortization and accretion	110,776	107,905	61,302
Capital expenditures	68,666	57,399	58,100
Total assets	1,805,398	1,831,283	2,231,244
Operating Segment
OPERATING SEGMENTS
Revenue	988,001	933,854	685,509
Corporate
OPERATING SEGMENTS
Depreciation, amortization and accretion	3,142	3,086	1,760
Capital expenditures	2,748	4,034	4,521
Total assets	59,375	63,506	75,400
Environmental Services \| Operating Segment
OPERATING SEGMENTS
Revenue	451,249	425,413	440,547
Depreciation, amortization and accretion	43,746	41,540	41,133
Capital expenditures	45,602	31,027	46,202
Total assets	796,645	773,448	755,566
Field & Industrial Services \| Operating Segment
OPERATING SEGMENTS
Revenue	500,187	473,754	232,402
Depreciation, amortization and accretion	44,368	43,465	15,007
Capital expenditures	15,393	16,149	5,986
Total assets	733,086	762,854	865,540
Energy Waste \| Operating Segment
OPERATING SEGMENTS
Revenue	36,565	34,687	12,560
Depreciation, amortization and accretion	19,520	19,814	3,402
Capital expenditures	4,923	6,189	1,391
Total assets	$ 216,292	$ 231,475	$ 534,738

SEGMENT REPORTING - Reconciliat

SEGMENT REPORTING - Reconciliation of EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Net Income to Adjusted EBITDA
Net income (loss)		$ 5,337	$ (389,359)	$ 33,140
Income tax expense (benefit)		4,765	(4,242)	16,659
Interest expense		28,966	32,595	19,239
Interest income		(1,417)	(258)	(605)
Foreign currency loss		171	1,134	733
Other income		(4,476)	(788)	(455)
Property and equipment impairment charges				25
Goodwill impairment charges			404,900
Depreciation and amortization of plant and equipment		70,799	66,561	41,423
Amortization of intangibles assets		34,614	37,344	15,491
Share-based compensation		7,478	6,651	5,544
Accretion and non-cash adjustment of closure & post-closure liabilities		5,363	4,000	4,388
Gain on property insurance recoveries				(12,366)
Business development and integration expenses		3,274	11,621	26,150
Adjusted EBITDA		154,874	170,159	149,366
Field & Industrial Services
Reconciliation of Net Income to Adjusted EBITDA
Goodwill impairment charges	$ 14,400
Operating Segment \| Environmental Services
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA		170,953	176,702	184,133
Operating Segment \| Field & Industrial Services
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA		70,578	81,770	26,707
Operating Segment \| Energy Waste
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA		11,321	4,982	3,626
Corporate
Reconciliation of Net Income to Adjusted EBITDA
Adjusted EBITDA		$ (97,978)	$ (93,295)	$ (65,100)

SEGMENT REPORTING - Revenue and

SEGMENT REPORTING - Revenue and Long-lived Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	$ 945,957	$ 980,625
United States
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	855,200	882,639
Canada
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	65,437	68,623
EMEA
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	15,604	18,042
Other
Revenue and Long-Lived Assets Outside of the United States
Total long- lived assets	$ 9,716	$ 11,321

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - Subsequent event - Republic - US Ecology $ / shares in Units, $ in Millions	Feb. 08, 2022USD ($)$ / shares
Subsequent events
Price per share to be paid \| $ / shares	$ 48
Termination fee due to the acquiring company required by the merger agreement, under specified circumstances	$ 46.3
Percentage on out-of -pocket merger costs incurred by US Ecology used to calculate the termination fee due to them, per the merger agreement	0.50
Maximum amount of out-of-pocket merger expenses incurred by US Ecology that the termination fee will be calculated on, per the merger agreement	$ 5
Maximum amount of termination fee due to US Ecology, per the merger agreement	$ 2.5