0000822818-23-000015 | 10-K | XBRL Viewer

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2022
Audit Information [Abstract]
Auditor Location	Boston, Massachusetts
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 492,603	$ 452,575
Short-term marketable securities	62,033	81,724
Accounts receivable, net of allowances aggregating $45,253 and $40,140, respectively	964,603	792,734
Unbilled accounts receivable	107,010	94,963
Inventories and supplies	324,994	250,692
Prepaid expenses and other current assets	82,518	68,483
Total current assets	2,033,761	1,741,171
Property, plant and equipment, net	1,980,302	1,863,175
Other assets:
Operating lease right-of-use assets	166,181	161,797
Goodwill	1,246,878	1,227,042
Permits and other intangibles, net	620,782	644,912
Other	81,803	15,602
Total other assets	2,115,644	2,049,353
Total assets	6,129,707	5,653,699
Current liabilities:
Current portion of long-term debt	10,000	17,535
Accounts payable	446,629	359,866
Deferred revenue	94,094	83,749
Accrued expenses and other current liabilities	396,716	391,414
Current portion of closure, post-closure and remedial liabilities	23,123	25,136
Current portion of operating lease liabilities	49,532	47,614
Total current liabilities	1,020,094	925,314
Other liabilities:
Closure and post-closure liabilities, less current portion of $13,205 and $12,015, respectively	105,596	87,088
Remedial liabilities, less current portion of $9,918 and $13,121, respectively	106,372	98,752
Long-term debt, less current portion	2,414,828	2,517,024
Operating lease liabilities, less current portion	119,259	117,991
Deferred tax liabilities	350,389	314,853
Other long-term liabilities	90,847	78,790
Total other liabilities	3,187,291	3,214,498
Commitments and contingent liabilities (See Note 18)
Stockholders' equity:
Common stock	541	544
Additional paid-in capital	504,240	536,377
Accumulated other comprehensive loss	(167,181)	(196,012)
Accumulated earnings	1,584,722	1,172,978
Total stockholders' equity	1,922,322	1,513,887
Total liabilities and stockholders' equity	$ 6,129,707	$ 5,653,699

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 45,253	$ 40,140
Closure and post-closure liabilities, current portion	13,205	12,015
Remedial liabilities, current portion	$ 9,918	$ 13,121
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	80,000,000	80,000,000
Common stock, issued shares (in shares)	54,064,797	54,419,321
Common stock, outstanding shares (in shares)	54,064,797	54,419,321

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Total revenues	$ 5,166,605	$ 3,805,566	$ 3,144,097
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	3,543,930	2,609,837	2,137,751
Selling, general and administrative expenses	627,391	537,962	451,044
Accretion of environmental liabilities	12,943	11,745	11,051
Depreciation and amortization	347,594	298,135	292,915
Income from operations	634,747	347,887	251,336
Other income (expense), net	2,472	(515)	(290)
Loss on early extinguishment of debt	(422)	0	0
Gain (loss) on sale of businesses	8,864	0	(3,376)
Interest expense, net of interest income of $4,607, $2,218 and $3,462, respectively	(107,663)	(77,657)	(73,120)
Income from operations before provision for income taxes	537,998	269,715	174,550
Provision for income taxes	126,254	66,468	39,713
Net income	$ 411,744	$ 203,247	$ 134,837
Earnings per share:
Basic (in dollars per share)	$ 7.59	$ 3.73	$ 2.43
Diluted (in dollars per share)	$ 7.56	$ 3.71	$ 2.42
Shares used to compute earnings per share — Basic (in shares)	54,223	54,514	55,479
Shares used to compute earnings per share — Diluted (in shares)	54,487	54,761	55,690
Service revenues
Revenues:
Total revenues	$ 4,133,184	$ 3,048,019	$ 2,724,584
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	2,892,726	2,105,043	1,786,718
Product revenues
Revenues:
Total revenues	1,033,421	757,547	419,513
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 651,204	$ 504,794	$ 351,033

CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Interest income	$ 4,607	$ 2,218	$ 3,462

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 411,744	$ 203,247	$ 134,837
Other comprehensive income (loss), net of tax:
Unrealized loss on available-for-sale securities	(413)	(285)	(8)
Unrealized gain (loss) on fair value of interest rate hedge	61,124	6,235	(20,970)
Reclassification adjustment for interest rate hedge amounts realized in net income	(683)	10,011	8,180
Unfunded pension liability	318	1,094	(189)
Foreign currency translation adjustments	(31,515)	(1,590)	11,561
Other comprehensive income (loss), net of tax	28,831	15,465	(1,426)
Comprehensive income	$ 440,575	$ 218,712	$ 133,411

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 411,744	$ 203,247	$ 134,837
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	347,594	298,135	292,915
Allowance for doubtful accounts	7,783	8,018	10,133
Amortization of deferred financing costs and debt discount	6,301	4,245	3,666
Accretion of environmental liabilities	12,943	11,745	11,051
Changes in environmental liability estimates	8,272	2,979	10,698
Deferred income taxes	17,549	1,482	(9,748)
Other (income) expense, net	(2,472)	515	290
Stock-based compensation	26,844	18,839	18,502
(Gain) loss on sale of businesses	(8,864)	0	3,376
Loss on early extinguishment of debt	422	0	0
Environmental expenditures	(13,946)	(15,506)	(12,401)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(201,087)	(96,551)	22,422
Inventories and supplies	(74,547)	(31,689)	(7,933)
Other current and non-current assets	(17,303)	9,268	(12,602)
Accounts payable	74,460	108,398	(80,328)
Other current and long-term liabilities	30,521	22,872	45,719
Net cash from operating activities	626,214	545,997	430,597
Cash flows used in investing activities:
Additions to property, plant and equipment	(345,056)	(241,856)	(196,256)
Proceeds from sale and disposal of fixed assets	8,779	22,156	9,623
Acquisitions, net of cash acquired	(86,278)	(1,253,232)	(8,839)
Additions to intangible assets including costs to obtain or renew permits	(1,966)	(3,848)	(2,029)
Purchases of available-for-sale securities	(49,845)	(129,234)	(70,891)
Proceeds from sale of available-for-sale securities	68,611	98,412	61,220
Proceeds from sale of businesses, net of transactional costs	16,811	0	7,712
Net cash used in investing activities	(388,944)	(1,507,602)	(199,460)
Cash flows (used in) from financing activities:
Change in uncashed checks	552	(1,806)	5,404
Tax payments related to withholdings on vested restricted stock	(8,801)	(10,805)	(5,331)
Repurchases of common stock	(50,183)	(54,410)	(74,844)
Deferred financing costs paid	(410)	(13,737)	(2,171)
Payments on finance leases	(12,821)	(8,458)	(4,469)
Principal payments on debt	(115,652)	(7,535)	(7,535)
Proceeds from issuance of debt, net of discount	0	995,000	0
Borrowings from revolving credit facility	0	0	150,000
Payments on revolving credit facility	0	0	(150,000)
Net cash (used in) from financing activities	(187,315)	898,249	(88,946)
Effect of exchange rate change on cash	(9,927)	(3,170)	4,919
Increase (decrease) in cash and cash equivalents	40,028	(66,526)	147,110
Cash and cash equivalents, beginning of year	452,575	519,101	371,991
Cash and cash equivalents, end of year	492,603	452,575	519,101
Cash payments for interest and income taxes:
Interest paid	105,643	73,440	72,535
Income taxes paid, net of refunds	78,526	65,192	53,123
Non-cash investing activities:
Property, plant and equipment accrued	30,950	19,264	3,536
Remedial liability assumed in acquisition of property, plant and equipment	$ 8,092	$ 0	$ 0

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings
Beginning balance (in shares) at Dec. 31, 2019		55,798
Beginning balance at Dec. 31, 2019	$ 1,269,813	$ 558	$ 644,412	$ (210,051)	$ 834,894
Increase (Decrease) in Stockholders' Equity
Net income	134,837				134,837
Other comprehensive income (loss)	(1,426)			(1,426)
Stock-based compensation	18,502		18,502
Issuance of common stock for restricted share vesting, net of employee tax withholding (in shares)		179
Issuance of common stock for restricted share vesting, net of employee tax withholdings	$ (5,331)	$ 2	(5,333)
Repurchases of common stock (in shares)	(1,200)	(1,204)
Repurchases of common stock	$ (74,844)	$ (12)	(74,832)
Ending balance (in shares) at Dec. 31, 2020		54,773
Ending balance at Dec. 31, 2020	1,341,551	$ 548	582,749	(211,477)	969,731
Increase (Decrease) in Stockholders' Equity
Net income	203,247				203,247
Other comprehensive income (loss)	15,465			15,465
Stock-based compensation	18,839		18,839
Issuance of common stock for restricted share vesting, net of employee tax withholding (in shares)		235
Issuance of common stock for restricted share vesting, net of employee tax withholdings	$ (10,805)	$ 2	(10,807)
Repurchases of common stock (in shares)	(600)	(589)
Repurchases of common stock	$ (54,410)	$ (6)	(54,404)
Ending balance (in shares) at Dec. 31, 2021		54,419
Ending balance at Dec. 31, 2021	1,513,887	$ 544	536,377	(196,012)	1,172,978
Increase (Decrease) in Stockholders' Equity
Net income	411,744				411,744
Other comprehensive income (loss)	28,831			28,831
Stock-based compensation	26,844		26,844
Issuance of common stock for restricted share vesting, net of employee tax withholding (in shares)		183
Issuance of common stock for restricted share vesting, net of employee tax withholdings	$ (8,801)	$ 2	(8,803)
Repurchases of common stock (in shares)	(500)	(537)
Repurchases of common stock	$ (50,183)	$ (5)	(50,178)
Ending balance (in shares) at Dec. 31, 2022		54,065
Ending balance at Dec. 31, 2022	$ 1,922,322	$ 541	$ 504,240	$ (167,181)	$ 1,584,722

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (PARENTHETICAL) - $ / shares	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Stockholders' Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01

OPERATIONS	12 Months Ended
OPERATIONS	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OPERATIONS	OPERATIONSClean Harbors, Inc., through its subsidiaries (collectively, the "Company"), is a leading provider of sustainable environmental and industrial services throughout North America. The Company is also the largest re-refiner and recycler of used oil and the premier provider of parts cleaning and related environmental services to commercial, industrial and automotive customers in North America.

SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

SIGNIFICANT ACCOUNTING POLICIES

The accompanying consolidated financial statements of the Company reflect the application of certain significant accounting policies as described below:

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of Clean Harbors, Inc. and its majority-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions, which are evaluated on an ongoing basis, that affect the amounts reported in the Company's consolidated financial statements and accompanying notes. Management bases its estimates on historical experience and on various other assumptions it believes to be reasonable at the time under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and disclosure, if any, of contingent assets and liabilities and reported amounts of revenues and expenses. Actual results could differ from those estimates and judgments.

Cash, Cash Equivalents, Marketable Securities and Uncashed Checks

Cash consists primarily of cash on deposit and money market accounts. The Company, through its wholly-owned captive insurance subsidiary, invests in marketable securities. Marketable securities with maturities of three months or less from the date of purchase are classified as cash equivalents. As of December 31, 2022 and 2021, the Company had total marketable securities as follows (in thousands):


	December 31, 2022		December 31, 2021
Commercial paper	$	5,035	$	—
U.S. Treasury securities	28,973		—
Total cash equivalents	34,008		—

U.S. Treasury securities	—		901
Municipal bonds	1,930		1,978
Commercial paper	24,075		21,160
Corporate notes and bonds	36,028		57,685
Total marketable securities	62,033		81,724
Total	$	96,041	$	81,724

Realized gains and losses on sales of available-for-sale marketable securities in the years presented were immaterial. The majority of the marketable securities have a remaining maturity of less than one year and fair value approximates cost.

The Company's cash management program with its revolving credit lender allows for the maintenance of a zero balance in the U.S. bank disbursement accounts that are used to issue vendor and payroll checks. When checks are presented to the bank for payment, cash deposits in amounts sufficient to fund the checks are made, at the Company's discretion, either from funds provided by other accounts or under the terms of the Company's revolving credit facility. Checks that have been written to vendors or employees but have not yet been presented for payment at the Company's bank are classified as uncashed checks as

part of accounts payable and changes in the balance are reported as a financing activity in the consolidated statements of cash flows.

Allowance for Doubtful Accounts and Revenue Allowance

On a regular basis, the Company evaluates its accounts receivable and establishes the allowance for doubtful accounts based on an evaluation of certain criteria and evidence of collection uncertainty including historical collection trends, reasonable expectations of future collections, current economic trends and changes in customer payment patterns. Past-due receivable balances are written off when the Company's collection efforts have been deemed unsuccessful in collecting the outstanding balance due.

Due to the nature of the Company's businesses and the invoices that result from the services provided, customers may withhold payments and attempt to renegotiate amounts invoiced. In addition, for some of the services provided, the Company's invoices are based on quotes that, in limited instances can result in adjustments to revenue subsequent to billing. Based on industry knowledge and historical trends, the Company records a revenue allowance in anticipation of these expected adjustments. This practice causes the volume of activity flowing through the revenue allowance during the year to be higher than the balance at the end of the year. The revenue allowance is intended to cover the net amount of revenue adjustments that may need to be credited to customers' accounts in future periods. Management determines the appropriate total revenue allowance by evaluating the following factors on an invoice-by-invoice basis as well as on a consolidated level: trends in adjustments to previously billed amounts, existing economic conditions, communications with customers and other information as deemed applicable. Revenue allowance estimates can differ from the actual adjustments, but historically the revenue allowance has been sufficient to cover the net amount of the reserve adjustments issued in subsequent reporting periods.

The following table reflects the activity in the allowance for doubtful accounts and revenue allowance (in thousands):


	Allowance for Doubtful Accounts						Revenue Allowance
	2022		2021		2020		2022		2021		2020
Balance at January 1,	$	24,136	$	24,634	$	22,493	$	16,004	$	20,115	$	16,218
Additions charged to earnings	7,783		8,018		10,133		54,836		34,319		45,784
Deductions from reserves, net of recoveries	(7,260)		(8,516)		(7,992)		(50,246)		(38,430)		(41,887)
Balance at December 31,	$	24,659	$	24,136	$	24,634	$	20,594	$	16,004	$	20,115

Credit Concentration

Concentration of credit risks in accounts receivable is limited due to the large number of customers comprising the Company's customer base throughout North America. The Company maintains policies over credit extension that include credit evaluations, credit limits and collection monitoring procedures on a customer-by-customer basis. However, the Company generally does not require collateral before services are performed. No individual customer accounted for more than 10% of accounts receivable or more than 10% of total direct revenues in the periods presented.

Inventories and Supplies

Inventories are stated at the lower of cost or market. The cost of oil and oil products as well as the cost of supplies and drums, solvent and solution and other inventories is principally determined on a first-in, first-out ("FIFO") basis. The Company continually reviews its inventories for obsolete or unsalable items and adjusts its carrying value to reflect estimated realizable values.

Property, Plant and Equipment, net (excluding landfill assets and finance lease right-of-use assets)

Property, plant and equipment, net is stated at cost less accumulated depreciation. Expenditures for major renewals and improvements which extend the life or usefulness of the asset are capitalized. Items of an ordinary repair or maintenance nature are charged directly to operating expense as incurred. During the construction and development period of an asset, the costs incurred, including interest expense, are classified as construction-in-progress. When the asset is ready for its intended use, the asset is reclassified to an appropriate asset classification and depreciation or amortization commences. The Company

depreciates and amortizes the capitalized cost of these assets, using the straight-line method as follows:


Asset Classification						Estimated Useful Life
Buildings and building improvements
Buildings						20-42 years
Leasehold and building improvements						2-45 years
Camp and lodging equipment						8-15 years
Vehicles						2-15 years
Equipment
Capitalized software and computer equipment						3-5 years
Containers and railcars						8-16 years
All other equipment						4-30 years
Furniture and fixtures						5-8 years

Gains and losses on the sale of property, plant and equipment are included in Other income (expense), net. Fully depreciated assets are retained in property, plant and equipment and accumulated depreciation until they are removed from service.

The Company tests asset groups for impairment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. An impairment in the carrying value of long-lived assets is recognized if the expected future undiscounted cash flows derived from the assets, or group of assets, are less than their carrying value. The Company did not record any impairment charges related to long-lived assets in the periods presented.

Business Combinations

In accordance with the acquisition method of accounting, the purchase price paid for an acquisition is allocated to the assets and liabilities acquired based upon their estimated fair values as of the acquisition date, with the excess of the purchase price over the net assets acquired recorded as goodwill. As required, a preliminary fair value is determined once a business is acquired, with the final determination of the fair value being completed no later than one year from the date of acquisition.

Goodwill

Goodwill is comprised of the purchase price of business acquisitions in excess of the fair value of the net assets acquired. Goodwill is reviewed for impairment annually as of December 31 or when events or changes in the business environment indicate the carrying value of a reporting unit may exceed its fair value. This review is performed by comparing the fair value of each reporting unit to its carrying value, including goodwill. If the fair value is less than the carrying amount, a loss is recorded for the excess of the carrying value over the fair value up to the carrying amount of goodwill.

The Company determines its reporting units by identifying the components of each operating segment. As of December 31, 2022, the Company had three reporting units consisting of, Environmental Sales and Service, Environmental Facilities and Safety-Kleen Sustainability Solutions. See Note 8, "Goodwill and Other Intangible Assets," for additional information related to the Company's goodwill impairment tests.

Permits and Other Intangibles

Costs related to acquiring licenses, permits and intangible assets, such as legal fees, site surveys, engineering costs and other expenditures are capitalized. Other intangible assets consist primarily of customer and supplier relationships, trademarks and trade names and developed technology.

Permits relating to landfills are amortized on a units-of-consumption basis. All other permits are amortized over periods ranging from five to 30 years on a straight-line basis. Finite-lived other intangible assets are amortized on a straight-line basis over their respective useful lives, which range from two to 25 years.

All finite-lived intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value may not be recoverable. When such factors and circumstances exist, management compares the projected undiscounted future cash flows associated with the related asset or group of assets to the carrying amount. The impairment loss, if any, is measured as the excess of the carrying amount over the fair value of the asset or group of assets.

Indefinite-lived intangible assets are not amortized but are reviewed for impairment annually as of December 31, or when events or changes in the business environment indicate that the carrying value may be impaired. If the fair value of the asset is less than the carrying amount, the impairment loss is measured as the excess of the carrying value of the asset over its fair value.

Landfill Accounting

The Company amortizes landfill improvements and certain landfill-related permits over the estimated useful lives. The units-of-consumption method is used to amortize land, landfill cell construction, asset retirement costs and remaining landfill cells and sites. The Company also utilizes the units-of-consumption method to record closure and post-closure obligations for landfill cells and sites. Under the units-of-consumption method, the Company includes future estimated construction and asset retirement costs, as well as costs incurred to date, in the amortization base of the landfill assets. Additionally, where appropriate, as described below, the Company includes probable expansion airspace that has yet to be permitted in the calculation of the total remaining useful life of the landfill. If it is determined that expansion capacity should no longer be considered in calculating the recoverability of a landfill asset, the Company may be required to recognize an asset impairment or incur significantly higher amortization expense. If at any time the Company makes the decision to abandon the expansion effort, the capitalized costs related to the expansion effort are expensed immediately.

Landfill assets—Landfill assets include the costs of landfill site acquisition, permits and cell construction incurred to date. These amounts are recorded at cost, which includes capitalized interest as applicable. Landfill assets, net of amortization, are combined with management's estimate of the costs required to complete construction of the landfill to determine the amount to be amortized over the remaining estimated useful economic life of a site. Amortization of landfill assets is recorded on a units-of-consumption basis, such that the landfill assets should be completely amortized at the date the landfill ceases accepting waste. Amortization totaled $16.2 million, $13.7 million and $10.9 million for the years ended December 31, 2022, 2021 and 2020, respectively. Changes in the determination of when the landfill will cease accepting waste, either through a business decision by the Company, determination that expansion capacity should no longer be considered probable or changes in estimates on annual airspace consumption, will impact the amortization expense of the landfill assets. Changes in estimated costs to complete construction are applied prospectively to the amortization rate.

Landfill capacity—Landfill capacity, which is the basis for the amortization of landfill assets and for the accrual of final closure and post-closure obligations, represents total permitted airspace plus unpermitted airspace that management believes is highly probable of ultimately being permitted. As of December 31, 2022, there were no unpermitted expansions included in the Company's landfill accounting model. If actual expansion airspace is significantly different from management's estimate of expansion airspace, the amortization rates used for the units-of-consumption method would change, therefore impacting the Company's profitability.

As of December 31, 2022, the Company had nine active landfill sites including the Company's two non-commercial landfills. It is anticipated that the non-commercial landfill at the Deer Park, Texas incineration facility will reach its permitted capacity early in 2023 at which point the Company will commence closure activities. This landfill has been excluded from the table below which includes the estimated remaining lives (based on anticipated waste volumes and remaining highly probable airspace) for the remaining eight landfills, as follows:


Facility Name	Location	Remaining Lives (Years)	Permitted Remaining Highly Probable Airspace (cubic yards) (in thousands)
Buttonwillow	California	20	5,197
Deer Trail	Colorado	23	1,488
Grassy Mountain	Utah	39	4,454
Kimball	Nebraska	5	116
Lambton	Ontario, Canada	47	4,443
Lone Mountain	Oklahoma	16	3,412
Ryley	Alberta, Canada	37	5,851
Sawyer	North Dakota	83	3,309
			28,270

At December 31, 2022 and 2021, the Company had no cubic yards of permitted, but not highly probable, airspace.

The following table presents the remaining highly probable airspace from January 1, 2021 through December 31, 2022 (in thousands of cubic yards):


	2022	2021
Remaining capacity, beginning of year	23,784	24,716
Changes in highly probable airspace, net	5,579	—
Consumed	(1,093)	(932)
Remaining capacity, end of year	28,270	23,784

In the year ended December 31, 2022, the Company received a permit for the expansion of its Ryley landfill in Alberta, Canada. In the year ended December 31, 2021, the Company had no changes in highly probable airspace.

Amortization of cell construction costs and accrual of cell closure obligations—Landfills are typically comprised of a number of cells, which are constructed within a defined acreage (or footprint). The cells are typically discrete units, which require both separate construction and separate capping and closure procedures. Cell construction costs are the costs required to excavate and construct the landfill cell. These costs are typically amortized on a units-of-consumption basis, such that they are completely amortized when the specific cell ceases accepting waste. In some instances, the Company has landfills that are engineered and constructed as "progressive trenches." In progressive trench landfills, a number of contiguous cells form a progressive trench. In those instances, the Company amortizes cell construction costs over the airspace within the entire trench, such that the cell construction costs will be fully amortized at the end of the trench useful life.

The design and construction of a landfill does not create a landfill asset retirement obligation. Rather, the asset retirement obligation for cell closure (the cost associated with capping each cell) is incurred in relatively small increments as waste is placed in the landfill. Therefore, the cost required to construct the cell cap is capitalized as an asset retirement cost and a liability of an equal amount is established, based on the discounted cash flow associated with each capping event, as airspace is consumed. Spending for cell capping is reflected as environmental expenditures within operating activities in the consolidated statements of cash flows.

Landfill final closure and post-closure liabilities —The balance of landfill final closure and post-closure liabilities at December 31, 2022 and 2021 was $62.3 million and $53.4 million, respectively. The Company has material financial commitments for the costs associated with requirements of the Environmental Protection Agency ("EPA") and the comparable regulatory agency in Canada for landfill final closure and post-closure activities. The Company develops estimates for the cost of these activities based on an evaluation of site-specific facts and circumstances, including the Company's interpretation of current regulatory requirements and proposed regulatory changes. Such estimates may change in the future due to various circumstances including, but not limited to, permit modifications, changes in legislation or regulations, technological changes and results of environmental studies.

Final closure costs are the costs incurred after the site ceases to accept waste, but before the landfill is certified as closed by the applicable state regulatory agency. These costs generally include the costs required to cap the final cell of the landfill (if not included in cell closure), the costs required to dismantle certain structures for landfills and other landfill improvements, and regulation-mandated groundwater monitoring and leachate management. Post-closure costs involve the maintenance and monitoring of a landfill site that has been certified closed by the applicable regulatory agency. These costs generally include groundwater monitoring and leachate management. Regulatory post-closure periods are generally 30 years after landfill closure. Final closure and post-closure obligations are accrued on a units-of-consumption basis, such that the present value of the final closure and post-closure obligations are fully accrued at the date the landfill ceases accepting waste.

Cell closure, final closure and post-closure costs (also referred to as "asset retirement obligations") are calculated by estimating the total obligation in current dollars, adjusted for future inflation estimates and discounted at the Company's credit-adjusted risk-free interest rate (5.37% and 4.84% during 2022 and 2021, respectively).

Non-Landfill Closure and Post-Closure Liabilities

The balance of non-landfill closure and post-closure liabilities at December 31, 2022 and 2021 was $56.6 million and $45.7 million, respectively. Non-landfill closure and post-closure obligations arise when the Company commences non-landfill facility operations and include costs required to dismantle and decontaminate certain structures and other costs incurred during the closure process. Post-closure costs, if required, include associated maintenance and monitoring costs as required by the closure permit. Post-closure periods are performance-based and are not typically specified in terms of years in the closure permit, but generally range from 10 to 30 years or more.

The Company records its non-landfill closure and post-closure liability by: (i) estimating the current cost of closing a non-landfill facility and the post-closure care of that facility, if required, based upon the closure plan that the Company is required to follow under its operating permit, or in the event the facility operates with a permit that does not contain a closure plan, based upon legally enforceable closure commitments made by the Company to various government agencies; (ii) estimates as to when future operations may cease; (iii) cost estimates of closing the non-landfill facility using the inflation rate to the time of closing; and (iv) discounting the future value back to the present using the credit-adjusted risk-free interest rate.

The estimates for non-landfill closure and post-closure liabilities are inherently uncertain due to the possibility that permit and regulatory requirements will change in the future, impacting the estimation of total costs and the timing of the expenditures. Management reviews non-landfill closure and post-closure liabilities for changes to key assumptions that would impact the amount of the recorded liabilities. Changes that would prompt management to revise a liability estimate include changes in legal requirements that impact the Company's expected closure plan or scope of work, in the market price of a significant cost item, in the estimate as to when future operations at a location might cease or in the expected timing of the costs. Changes in estimates for non-landfill closure and post-closure events immediately impact the liability and the value of the corresponding asset. If a change is made to a fully-amortized asset, the adjustment is charged immediately to expense. When a change in estimate relates to an asset that has not been fully amortized, the adjustment to the asset is recognized in income prospectively as a component of amortization. Historically, changes to non-landfill closure and post-closure estimates have not been material.

Remedial Liabilities

The balance of remedial liabilities at December 31, 2022 and 2021 was $116.3 million and $111.9 million, respectively. Remedial liabilities, including Superfund liabilities, include the costs of removal or containment of contaminated material, treatment of potentially contaminated groundwater and maintenance and monitoring costs necessary to comply with regulatory requirements. Most of the Company's remedial liabilities relate to the active and inactive hazardous waste treatment and disposal facilities which the Company acquired and Superfund sites owned by third-parties for which the Company, or the prior owners of certain of the Company's facilities for which the Company may have certain indemnification obligations, have been identified as potentially responsible parties ("PRPs") or potential PRPs. The Company's estimate of remedial liabilities involves an analysis of such factors as: (i) the nature and extent of environmental contamination (if any); (ii) the terms of applicable permits and agreements with regulatory authorities as to cleanup procedures and whether modifications to such permits and agreements will likely need to be negotiated; (iii) the cost of performing anticipated cleanup activities based upon current technology; and (iv) in the case of Superfund and other sites where other parties will also be responsible for a portion of the cleanup costs, the likely allocation of such costs and the ability of such other parties to pay their share. The measurement of remedial liabilities is reviewed at least quarterly and changes in estimates are recognized in the consolidated statements of operations when identified.

Where the Company concludes that it is probable that a liability has been incurred and an amount can be estimated, a liability is recognized. Remedial liabilities are inherently difficult to estimate. Estimating remedial liabilities requires that the existing environmental contamination be understood. There are risks that the actual quantities of contaminants differ from the results of the site investigation, and that contaminants exist that have not been previously identified. In addition, the amount of remedial liabilities recorded is dependent on the remedial method selected. There is a risk that funds will be expended on a remedial solution that is not successful, which could result in the Company incurring the incremental costs of an alternative solution. Such estimates, which are subject to change, are subsequently revised if and when additional or new information becomes available.

Remedial liabilities are discounted when the timing of the payments is determinable and the amounts are estimable. In the case of remedial liabilities assumed in connection with acquisitions, acquired liabilities are recorded at fair value as of the dates of the acquisitions calculated by inflating costs in current dollars using an estimate of future inflation rates as of the respective acquisition dates until the expected time of payment, and then discounting the amount of the payments to their present value using a risk-free discount rate as of the acquisition dates. Discount rates used in the present value determination of the Company's remedial liabilities range from 1.37% to 4.90%.

Self-Insurance Liabilities

The Company self-insures a significant portion of expected losses related to workers' compensation, employee medical, comprehensive general liability and vehicle liability. Liabilities associated with these losses are recorded based on the Company's estimates of the ultimate cost to settle incurred claims. These recorded liabilities are estimated based on independent

actuarial estimates and judgments which consider the frequency and settlement amount of historical claims data and are discounted to present value using a risk-free interest rate.

Revenue Recognition

The Company recognizes revenue when control of the promised goods or services is transferred to the Company's customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. The majority of the Company’s revenues are for services, which are recognized based on time and materials incurred at contractually agreed-upon rates. Product revenues are recognized when the products are delivered and control transfers to the customer. The Company’s payment terms vary by the type of customers and the products or services offered. The periods between invoicing and when payments are due are not significant. Amounts billed to customers related to shipping and handling are classified as revenue, and the Company's shipping and handling costs are included in costs of revenues. In the course of operations, the Company collects sales tax and other excise taxes from its customers and recognizes a current liability, which is then relieved when the taxes are remitted to the appropriate government authorities. The Company excludes sales and other excise taxes that it collects from customers from its revenues.

Foreign Currency

The Company has international operations in Canada and administrative support services located in India. The functional currencies of foreign operations are the local currency and therefore assets and liabilities of those foreign operations are translated to U.S. Dollars 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 foreign subsidiaries into U.S. Dollars are included in stockholders' equity as a component of accumulated other comprehensive loss. Gains and losses from transactions not denominated in the functional currency of an entity are recognized in the consolidated statements of operations. Recorded balances that are denominated in a currency other than the functional currency are remeasured to the functional currency using the exchange rate at the balance sheet date and gains or losses are recorded in the consolidated statements of operations.

Defined Contribution Plan

The Company has defined contribution plans under which eligible employees may contribute up to the maximum amount as provided by law. The Company matches a portion of these employee contributions and contributed $25.3 million, $20.5 million and $18.6 million in 2022, 2021 and 2020 respectively.

Advertising Expense

Advertising costs are expensed as incurred. Advertising expense was $9.4 million in 2022, $6.0 million in 2021 and $9.0 million in 2020.

Stock-Based Compensation

Stock-based compensation cost is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which generally represents the vesting period. In addition, the Company issues awards with performance targets established prior to or at the grant date. The expense for these awards is recognized over the requisite service period when management believes it is probable those performance targets will be achieved. The fair value of the Company's grants are based on the closing price of the Company's common stock on the respective dates of grant. Forfeitures are recognized as they occur. Stock-based compensation is recognized in selling, general and administrative expense.

Interest Rate Derivatives

The Company enters into interest rate derivative agreements as part of the overall strategy to hedge against fluctuations in variable interest rates. These interest rate derivatives swap a variable interest rate for a fixed interest rate and have been designated as cash flow hedges. The Company assesses the hedge’s effectiveness at the inception of the hedge and at regular intervals throughout the life of the derivative. To the extent that the interest rate swap is highly effective, changes in fair value are recorded in stockholders’ equity as a component of accumulated other comprehensive loss. Amounts are reclassified from accumulated other comprehensive loss into interest expense on the consolidated statement of operations in the same period or periods during which the hedged transactions affect earnings. Although it was determined that the interest rate swaps will be a highly effective hedge, any portion of the interest rate swaps subsequently determined to be ineffective will be recognized in earnings. Further, if it becomes probable that a forecasted transaction designated as the hedged item will not occur, any gain or loss deferred is recognized in interest expense at that time.

The fair value of the interest rate swaps is calculated using discounted cash flow valuation methodologies based upon the one-month variable rate yield curves that are observable at commonly quoted intervals for the full term of the interest rate swaps and as such is considered a Level 2 measure according to the fair value hierarchy. The Company recognizes the fair value of the derivative instruments by counterparty as either a net asset, included in Other assets, or net liability, included in Accrued expenses and other current liabilities, on the consolidated balance sheets.

Income Taxes

Current income tax expense approximates cash to be paid or refunded for taxes for the applicable period. Deferred tax expense or benefit is the result of changes between deferred tax assets and liabilities. Deferred tax assets and liabilities are determined based upon the temporary differences between the financial statement basis and tax basis of assets and liabilities as well as from net operating loss and tax credit carryforwards as measured by the enacted tax rates which will be in effect when these differences reverse. The effect of a change in tax rates on deferred tax assets and liabilities is generally recognized in income in the period that includes the enactment date. The Company evaluates the recoverability of future tax deductions and credits and a valuation allowance is established by tax jurisdiction when, based on an evaluation of both positive and negative objective verifiable evidence, it is more likely than not that some portion or all of deferred tax assets will not be realized.

The Company recognizes and measures a tax benefit from uncertain tax positions when it is more likely than not that the tax position will be sustained upon examination by the taxing authorities, based on the technical merits of the position. The Company recognizes a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. The Company adjusts these liabilities when its judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the current estimate or future recognition of an unrecognized benefit. These differences will be reflected as increases or decreases to income tax expense in the period in which they are determined. Liabilities for unrecognized tax benefits are included within other long-term liabilities in the consolidated balance sheets.

The Company recognizes interest and penalties related to unrecognized tax benefits within the provision for income taxes line in the consolidated statements of operations. Accrued interest and penalties are included within the other long-term liabilities line in the consolidated balance sheets.

Earnings per Share ("EPS")

Basic EPS is calculated by dividing net income by the weighted average number of common shares outstanding during the period. Diluted EPS gives effect to all potentially dilutive common shares that were outstanding during the period.

Leases

The Company’s leases predominately relate to real estate, equipment, such as vehicles and industrial equipment utilized in operations, and rail cars utilized in connection with the Company’s transportation needs. Contracts are reviewed at inception to determine if the arrangement is a lease and, if so, whether it is an operating or finance lease. For all of its leases, the Company has elected not to separate lease and nonlease components, such as common area maintenance.

The Company generally enters into long-term real estate leases with three to ten-year terms and long-term non-real estate leases with two to eight-year terms. In the normal course of business, the Company also enters into short-term leases having terms of less than one year. These leases are generally equipment leases entered into for short periods of time (e.g. daily, weekly or monthly) to satisfy immediate and/or short-term operational needs of the business which can arise based upon the nature of particular services performed or seasonality factors. The Company has elected not to recognize right-of-use ("ROU")

assets and lease liabilities for these short-term leases. Operating and finance leases with terms exceeding one year are recognized as ROU assets and lease liabilities and measured based on the present value of the future lease payments over the lease term at commencement date.

Certain of the Company's real estate leases contain escalating future lease payments. Escalating lease payments that are based upon explicit amounts contained in the lease or an index (e.g., consumer price index) are included in the Company's determination of future lease payments to determine the ROU asset and lease liability recognized at the commencement date. Any differences in the future lease payments from initial recognition are not anticipated to be material and will be recorded as variable lease cost in the period incurred. The variable lease cost will also include the Company’s portion of property tax, utilities and common area maintenance. A significant portion of the Company’s real estate lease agreements include renewal periods at the Company’s option. The Company includes these renewal periods in the lease term only when renewal is reasonably certain based upon facts and circumstances specific to the lease and known by the Company. Certain of the equipment and rail car leases transfer ownership upon the conclusion of the lease term and as such, are classified as finance leases. Leases containing purchase options are classified as finance leases only when it is reasonably certain that the Company will execute such options.

The Company uses its incremental borrowing rate on collateralized debt based on the information available at the lease commencement date in determining the present value of future lease payments as the implicit rate is typically not readily determinable.

For operating leases, lease cost is recognized on a straight-line basis over the lease term and is included in cost of revenues or selling, general and administrative expenses depending on the use of the asset. For finance leases, ROU assets are amortized on a straight-line basis and interest expense is recognized based on the incremental borrowing rate. Amortization and interest expense for finance leases are included in depreciation and amortization and interest expense, net of interest income, respectively.

REVENUES

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

REVENUES

The Company generates revenues through the following operating segments: Environmental Services and Safety-Kleen Sustainability Solutions. The Company's Environmental Services operating segment generally has four sources of revenue and the Safety-Kleen Sustainability Solutions operating segment has two sources of revenue. The Company disaggregates third-party revenues by geographic location and source of revenue as management believes these categories depict how revenue and cash flows are affected by economic factors. The Company's significant sources of revenue include:

Technical Services—Technical Services contribute to the revenues of the Environmental Services operating segment. Revenues for these services are generated from fees charged for waste material management and disposal services including onsite environmental management services, large remediation projects, collection and transportation, packaging, recycling, treatment and disposal of waste. Revenue is primarily generated by short-term projects, most of which are governed by master service agreements that are long-term in nature. These master service agreements are typically entered into with the Company's larger customers and outline the pricing and legal frameworks for such arrangements. Services are provided based on purchase orders or agreements with the customer and include prices based upon units of volume of waste, material and personnel costs as well as transportation and other fees. Collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred as a basis for measuring the satisfaction of the performance obligation. Revenues for treatment and disposal of waste are recognized upon completion of treatment, final disposition in a landfill or incinerator, or when the waste is shipped to a third-party for processing and disposal. The Company periodically enters into bundled arrangements for the collection and transportation and disposal of waste. For such arrangements, transportation and disposal are considered distinct performance obligations and the Company allocates revenue to each based on the relative standalone selling price (i.e., the estimated price that a customer would pay for the services on a standalone basis). Revenues and the related costs from waste that is not yet completely processed and disposed of are deferred. The deferred revenues and costs are recognized when the services are completed. The period between collection and transportation and the final processing and disposal ranges depending on the location of the customer, but generally is measured in days.

Industrial Services and Other—Industrial Services contribute to the revenues of the Environmental Services operating segment. These revenues are primarily generated from industrial and specialty services provided to refineries, mines, upgraders, chemical plants, pulp and paper mills, manufacturing facilities, power generation facilities and other industrial customers throughout North America. Services include in-plant cleaning and maintenance services, plant outage and turnaround services,

specialty cleaning services including chemical cleaning, pigging and high and ultra-high pressure water cleaning, leak detection and repair, daylighting, production services and upstream energy services. 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. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred.

Field and Emergency Response Services—Field and Emergency Response Services contribute to the revenues of the Environmental Services operating segment. Field Services revenues are generated from cleanup services at customer sites, including those managed by municipalities and utility providers, or other locations on a scheduled or emergency response basis. Services include confined space entry for tank cleaning, site decontamination, remediation, railcar cleaning, manhole/vault clean outs, product recovery and transfer and vacuum services. Additional services include filtration and water treatment services. Response services for environmental emergencies of any scale range from man-made disasters such as oil spills to natural disasters such as hurricanes. Emergency response services also include spill cleanup on land and water, as well as contagion disinfection, decontamination and disposal services. Field and emergency response services are provided based on purchase orders or agreements with customers and include prices generally based upon daily, hourly or job rates for equipment, materials and personnel. The Company recognizes revenue for these services over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The Company uses the input method to recognize revenue over time, based on time and materials incurred. The duration of such services can be over a number of hours, several days or even months for larger scale projects.

Safety-Kleen Environmental Services—Safety-Kleen Environmental Services revenues contribute both to the Environmental Services operating segment and the Safety-Kleen Sustainability Solutions operating segment depending upon the nature of such revenues and operating responsibilities relative to executing the revenue contracts. Revenues from providing containerized waste handling and disposal services, parts washer services and vacuum services, referred to collectively as the Safety-Kleen branches' core service offerings, contribute to the revenues of the Environmental Services operating segment. In addition, sales of packaged blended oil products and other complementary product sales contribute to the revenues of the Environmental Services operating segment. Revenues generated from waste oil, anti-freeze and oil filter collection services, sales of bulk blended oil products and sales of bulk automotive fluids contribute to the Safety-Kleen Sustainability Solutions operating segment.

Generally, the revenue from services is recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. The duration of such services can be over a number of hours or several days. The Company uses the input method to recognize revenue over time, based on time and materials incurred. Product revenue is recognized upon the transfer of control whereby control transfers when the products are delivered to the customer. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of waste. Related collection and transportation revenues are recognized over time, as the customer receives and consumes the benefits of the services as they are being performed and the Company has a right to payment for performance completed to date. Parts washer services include customer use of the Company's parts washer equipment, cleaning and maintenance of the parts washer equipment and removal and replacement of used cleaning fluids. Parts washer services are considered a single performance obligation due to the highly integrated and interdependent nature of the arrangement. Revenue from parts washer services is recognized over the service interval as the customer receives the benefit of the services.

Safety-Kleen Oil—Safety-Kleen Oil related sales contribute to the revenues of the Safety-Kleen Sustainability Solutions segment. These revenues are generated from sales of high-quality base and blended lubricating oils to third-party distributors, government agencies, fleets, railroads and industrial customers. The business also sells recycled fuel oil to asphalt plants, industrial plants and pulp and paper companies. The used oil is also processed into vacuum gas oil which can be further re-refined into lubricant base oils or sold directly into the marine diesel oil fuel market. Revenue for oil products is recognized at a point in time, upon the transfer of control. Control transfers when the products are delivered to the customer.

The following tables present the Company's third-party revenue disaggregated by source of revenue and geography (in thousands):


	For the year ended December 31, 2022
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	3,675,880	$	899,780	$	507	$	4,576,167
Canada	469,093		121,345		—		590,438
Total third-party revenues	$	4,144,973	$	1,021,125	$	507	$	5,166,605

Sources of Revenue
Technical Services	$	1,495,264	$	—	$	—	$	1,495,264
Industrial Services and Other	1,311,072		—		507		1,311,579
Field and Emergency Response Services	575,300		—		—		575,300
Safety-Kleen Environmental Services	763,337		199,360		—		962,697
Safety-Kleen Oil	—		821,765		—		821,765
Total third-party revenues	$	4,144,973	$	1,021,125	$	507	$	5,166,605


	For the year ended December 31, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	2,631,112	$	693,542	$	299	$	3,324,953
Canada	394,795		85,818		—		480,613
Total third-party revenues	$	3,025,907	$	779,360	$	299	$	3,805,566

Sources of Revenue
Technical Services	$	1,209,624	$	—	$	—	$	1,209,624
Industrial Services and Other	705,999		—		299		706,298
Field and Emergency Response Services	466,380		—		—		466,380
Safety-Kleen Environmental Services	643,904		161,587		—		805,491
Safety-Kleen Oil	—		617,773		—		617,773
Total third-party revenues	$	3,025,907	$	779,360	$	299	$	3,805,566


	For the year ended December 31, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	2,287,796	$	452,435	$	(674)	$	2,739,557
Canada	349,845		53,731		964		404,540
Total third-party revenues	$	2,637,641	$	506,166	$	290	$	3,144,097

Sources of Revenue
Technical Services	$	1,062,714	$	—	$	—	$	1,062,714
Industrial Services and Other	480,331		—		290		480,621
Field and Emergency Response Services	461,036		—		—		461,036
Safety-Kleen Environmental Services	633,560		175,676		—		809,236
Safety-Kleen Oil	—		330,490		—		330,490
Total third-party revenues	$	2,637,641	$	506,166	$	290	$	3,144,097

Contract Balances


(in thousands)	December 31, 2022		December 31, 2021
Receivables	$	964,603	$	792,734
Contract assets (unbilled receivables)	107,010		94,963
Contract liabilities (deferred revenue)	94,094		83,749

The timing of revenue recognition, billings and cash collections results in billed accounts receivable, unbilled receivables (contract assets) and customer advances and deposits or deferred revenue (contract liabilities) on the consolidated balance sheet. Generally, billing occurs subsequent to revenue recognition, as a right to payment is not just subject to passage of time, resulting in contract assets. Contract assets are generally classified as current. The Company sometimes receives advances or deposits from its customers before revenue is recognized, resulting in contract liabilities. These assets and liabilities are reported on the consolidated balance sheet on a contract-by-contract basis at the end of each reporting period. The contract liability balances at the beginning of each period presented were generally fully recognized in the subsequent three-month period.

Variable Consideration

The nature of the Company's contracts give rise to certain types of variable consideration, including in limited cases volume discounts. Accordingly, management establishes a revenue allowance to cover the estimated amounts of revenue that may need to be credited to customers' accounts in future periods. The Company estimates the amount of variable consideration to include in the estimated transaction price based on historical experience, anticipated performance and management's best judgment at the time and to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. There have been no material changes in estimates of variable consideration in the periods presented.

Contract Costs

Contract costs include direct and incremental costs to obtain or fulfill a contract. Parts washer costs include costs of solvent, commissions paid relating to revenue generated from parts washer services, and transportation costs associated with transferring the product picked up from the services as it is returned to the Company’s facilities or a third-party site. Costs related to the treatment of waste include costs for waste receiving, drum movement and storage, waste consolidation and transportation between facilities.

The Company’s contract costs that are subject to capitalization are comprised of costs associated with parts washer services and costs associated with the treatment and disposal of waste. As of December 31, 2022 and 2021, the Company's deferred contract costs totaled $29.7 million and $26.4 million, respectively. Deferred parts washer costs are recognized over the service interval as the customer receives the benefit of the services, and deferred costs related to treatment and disposal of waste are recognized when the corresponding waste is disposed. Deferred costs are included within total current assets in the

Company’s consolidated balance sheets. The deferred contract cost balances at the beginning of each period presented were fully recognized in cost of revenue in the subsequent three-month period.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI https://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126920106&loc=SL49130554-203045

+ Details

BUSINESS COMBINATIONS

12 Months Ended

Dec. 31, 2022

Business Combination and Asset Acquisition [Abstract]

BUSINESS COMBINATIONS

Proposed 2023 Acquisition

On February 9, 2023, the Company signed a purchase agreement to acquire a privately-owned company for an all cash purchase price of approximately $100.0 million, subject to customary closing adjustments. The Company intends to fund this acquisition with available cash. Once acquired, the operations of the acquired company will expand the Environmental Services segment's industrial service operations in the southeastern region of the United States. The acquisition is expected to close in early 2023.

2022 Acquisitions

On June 17, 2022, the Company acquired a privately-owned company for an all-cash purchase price of approximately $78.9 million, net of cash acquired. The operations of the newly acquired company expand the Safety-Kleen Sustainability Solutions segment's waste oil collection capabilities and re-refining business throughout the southeast region of the United States, including the addition of a re-refinery in Georgia.

The preliminary allocation of the purchase price is provisional and was based on estimates of the fair value of assets acquired and liabilities assumed as of June 17, 2022. The Company continues to obtain information to complete the valuation of these balances and the associated income tax accounting. Measurement period adjustments will reflect new information obtained about facts and circumstances that existed as of the acquisition date. The following table summarizes the preliminary determination and recognition of assets acquired and liabilities assumed (in thousands):


	At Acquisition Date As Reported December 31, 2022
Accounts receivable	$	1,111
Inventories and supplies	5,816
Prepaid expenses and other current assets	144
Property, plant and equipment	19,605
Permits and other intangibles	23,500
Operating lease right-of-use assets	585
Other non-current assets	13
Current liabilities	(3,271)
Current portion of operating lease liabilities	(186)
Operating lease liabilities, less current portion	(399)

Other long-term liabilities	(55)
Total identifiable net assets	46,863
Goodwill	32,015
Total purchase price	$	78,878

Permits and other intangible assets acquired include supplier relationships, permits, customer relationships and trademarks/tradenames and are anticipated to have estimated useful lives of between five and 20 years with a weighted average useful life of approximately 18 years. The excess of the total purchase price, which includes the aggregate cash consideration paid in excess of the fair value of the tangible and intangible assets acquired, was recorded as goodwill. The goodwill recognized is

attributable to the expected operating synergies, assembled workforce and growth potential that the Company expects to realize from the acquisition. Goodwill generated from the acquisition is deductible for tax purposes.

The operations included in the Company's financial statements for the period ended December 31, 2022 and pro forma revenue and earnings amounts on a combined basis as if this acquisition had been completed on January 1, 2021 are immaterial to the consolidated financial statements of the Company.

On December 9, 2022, the Company acquired a privately-owned business for $12.4 million cash consideration, subject to the settlement of working capital. The acquired company expands the Safety-Kleen Sustainability Solutions segment's oil collection operations in the southeast United States. In connection with this acquisition, goodwill of $2.5 million was recognized. The results of operations for the acquired business were not material in 2022.

HydroChemPSC

On October 8, 2021, the Company completed its acquisition of LJ Energy Services Intermediate Holding Corp. and its subsidiaries (collectively, “HydroChemPSC”), a privately owned company, for an all-cash purchase price of approximately $1.23 billion. HydroChemPSC is a leading U.S. provider of industrial cleaning, specialty maintenance and utilities services. These operations enhance and have been fully integrated into the Company's Environmental Services segment. In the first quarter of 2022, the Company received $5.0 million after finalizing the acquisition date working capital balances, which decreased the overall purchase price.

The Company finalized the purchase accounting for the acquisition of HydroChemPSC in the third quarter of 2022. The allocation of the purchase price was based on estimates of the fair value of assets acquired and liabilities assumed as of October 8, 2021. The following table summarizes the final determination and recognition of assets acquired and liabilities assumed (in thousands):


	At Acquisition Date As Reported December 31, 2021		Measurement Period Adjustments		Final Allocation at Acquisition Date As Reported December 31, 2022
Accounts receivable, including unbilled receivables	$	131,924	$	(408)	$	131,516
Inventories and supplies	3,162		—		3,162
Prepaid expenses and other current assets	16,016		275		16,291
Property, plant and equipment	313,540		857		314,397
Other intangibles	289,000		—		289,000
Operating lease right-of-use assets	34,347		68		34,415
Other non-current assets	1,045		(83)		962
Current liabilities	(115,704)		(3,150)		(118,854)
Current portion of operating lease liabilities	(11,659)		382		(11,277)
Operating lease liabilities, less current portion	(26,128)		(216)		(26,344)
Deferred tax liabilities	(85,908)		5,522		(80,386)
Other long-term liabilities	(2,685)		(1,485)		(4,170)
Total identifiable net assets	546,950		1,762		548,712
Goodwill (i)	683,463		(6,762)		676,701
Total purchase price	$	1,230,413	$	(5,000)	$	1,225,413

_____________

(i) Goodwill represents the excess of the fair value of the net assets acquired over the purchase price. Goodwill of $676.7 million was assigned to the Environmental Sales and Service reporting unit and is attributable to the future economic benefits arising from the acquired operations, synergies and the acquired workforce of HydroChemPSC. None of the goodwill related to this acquisition will be deductible for tax purposes.

Unaudited Pro Forma Financial Information

The following table presents unaudited pro forma combined summary financial information for the years ended December 31, 2021 and December 31, 2020, respectively, and assumes the acquisition of HydroChemPSC occurred on January 1, 2020 (in thousands):


	2021		2020
Pro forma combined revenues	$	4,380,724	$	3,859,430
Pro forma combined net income	229,807		149,219

The pro forma results do not include any costs incurred directly attributable to the acquisition of HydroChemPSC. The pro forma results do reflect impacts resulting from the issuance of $1.0 billion senior secured term loans issued in connection with the acquisition assuming interest rates in effect at the time of the acquisition.

This pro forma financial information is not necessarily indicative of the Company's consolidated operating results that would have been reported had the transactions been completed as described herein, nor is such information necessarily indicative of the Company's consolidated results for any future period. Interest expense used in calculating the pro forma net income in both periods did not contemplate the interest rate swap that the Company put in place in early 2022. See Note 12, "Financing Arrangements."

Other 2021 Acquisition Activity

On March 27, 2021, the Company acquired a privately-owned business for $22.8 million cash consideration. The acquired company increases the Safety-Kleen Sustainability Solutions segment's network within the south central United States. In connection with this acquisition, a goodwill amount of $16.3 million was recognized. The results of operations for this acquired business were not material in 2021.

On June 29, 2021, the Company signed a definitive agreement with Vertex Energy, Inc. ("Vertex") to acquire certain assets related to Vertex's used motor oil collection and re-refinery business in an all-cash transaction for $140.0 million, subject to working capital and other adjustments. On January 25, 2022, Vertex and the Company mutually agreed to terminate the planned acquisition. In connection with the termination, in early 2022, Vertex paid Clean Harbors a breakup fee of $3.0 million pursuant to the agreement.

2020 Acquisition

On April 17, 2020, the Company acquired a privately-owned business for $8.8 million cash consideration. The acquired company expands the Safety-Kleen Sustainability Solutions segment's oil re-refining operations to the northeast United States. In connection with this acquisition, goodwill of $1.4 million was recognized. The results of operations of this acquired business were not material in 2020.

DISPOSITION OF BUSINESS	12 Months Ended
DISPOSITION OF BUSINESS	Dec. 31, 2022
Discontinued Operations and Disposal Groups [Abstract]
DISPOSITION OF BUSINESS	DISPOSITION OF BUSINESSOn June 30, 2022, the Company completed the sale of a line of business as part of its continuous focus on divesting certain non-core operations. The divested line of business was previously included within the Environmental Sales and Service reporting unit of the Environmental Services segment. The Company determined that the disposition did not constitute a strategic shift and that the impact on the Company's overall operations and financial results will not be material. Accordingly, the operations associated with the disposal are not reported in discontinued operations. The final purchase price for the line of business was $18.8 million, after settling working capital. The gain on sale of $8.9 million, after accounting for the assets sold, liabilities transferred upon sale and transaction costs, is included in gain on sale of business in the Company’s consolidated statement of operations for the year ended December 31, 2022.

INVENTORIES AND SUPPLIES

12 Months Ended

Dec. 31, 2022

Inventory Disclosure [Abstract]

INVENTORIES AND SUPPLIES

Inventories and supplies consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Oil and oil related products	$	151,519	$	101,965
Supplies	143,743		126,602
Solvent and solutions	11,994		8,099
Other	17,738		14,026
Total inventories and supplies	$	324,994	$	250,692

The balance of oil and oil related products has increased due to higher volumes of base oil on hand at December 31, 2022 when compared with December 31, 2021 and overall price increases for the oil inventory and additives. Supplies inventories consist primarily of critical spare parts to support the Company's incinerator and re-refinery operations and other general supplies used in normal day-to-day operations. Other inventories consist primarily of parts washer components, cleaning fluids, absorbents and automotive fluids, such as windshield washer fluid and antifreeze.

PROPERTY, PLANT, AND EQUIPMENT

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

PROPERTY, PLANT, AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT

Property, plant and equipment consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Land	$	172,579	$	165,010
Asset retirement costs (non-landfill)	22,001		19,105
Landfill assets	232,872		205,873
Buildings and improvements (1)	584,916		551,795
Camp equipment	116,976		127,680
Vehicles (2)	1,112,188		912,836
Equipment (3)	2,078,088		2,092,395
Furniture and fixtures	6,481		6,444
Construction in progress	140,328		60,447
	4,466,429		4,141,585
Less - accumulated depreciation and amortization	2,486,127		2,278,410
Total property, plant and equipment, net	$	1,980,302	$	1,863,175

___________________________________

(1) Balances inclusive of gross ROU assets classified as finance leases of $8.0 million and $8.9 million, respectively.

(2) Balances inclusive of gross ROU assets classified as finance leases of $106.7 million and $77.7 million, respectively.

(3) Balances inclusive of gross ROU assets classified as finance leases of $9.2 million and $9.3 million, respectively.

Depreciation expense, inclusive of landfill and finance lease amortization was $297.4 million, $263.4 million and $257.1 million for the years ended December 31, 2022, 2021 and 2020, respectively. The Company recorded $3.4 million of capitalized interest in 2022, mainly attributable to the construction of a new incinerator in Kimball, Nebraska. Capitalized interest in 2021 and 2020 was negligible.

GOODWILL AND OTHER INTANGIBLE ASSETS

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

GOODWILL AND OTHER INTANGIBLE ASSETS

The changes in goodwill for the years ended December 31, 2022 and 2021 were as follows (in thousands):


	Environmental Services		Safety-Kleen Sustainability Solutions		Totals
Balance at January 1, 2021	$	401,918	$	125,105	$	527,023
Increase from current period acquisitions	683,463		16,349		699,812



Foreign currency translation	153		54		207
Balance at December 31, 2021	$	1,085,534	$	141,508	$	1,227,042
Increase from current period acquisitions	—		34,510		34,510
Measurement period adjustments from prior period acquisition	(6,762)		—		(6,762)
Decrease from disposition of business	(4,412)		—		(4,412)
Foreign currency translation	(2,514)		(986)		(3,500)
Balance at December 31, 2022	$	1,071,846	$	175,032	$	1,246,878

The Company regularly assesses goodwill for impairment when it is more likely than not that events or changes in the business environment ("triggering events") would reduce the fair value of a reporting unit below its carrying value. The Company did not identify any triggering events in the years presented.

Goodwill impairment is also tested annually. The Company conducted its annual impairment test of goodwill as of December 31, 2022 and determined that no adjustment to the carrying value of goodwill for any reporting unit was then necessary because the fair values of the reporting units exceeded their respective carrying values. The fair value of all reporting units was determined using an income approach based upon estimates of future discounted cash flows. The resulting estimates of fair value were validated through the consideration of other factors such as the fair value of comparable companies to the reporting units and a reconciliation of the sum of all estimated fair values of the reporting units to the Company’s overall market capitalization. In all cases, the estimated fair values of the reporting units significantly exceeded the respective carrying values.

Significant judgments and unobservable inputs, categorized as Level 3 in the fair value hierarchy, are inherent in the impairment tests performed and include assumptions about the amount and timing of expected future cash flows, growth rates, and the determination of appropriate discount rates. Level 3 inputs are unobservable inputs for the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date. The Company believes that the assumptions used in its impairment tests are reasonable, but variations in any of the assumptions may result in different measurements of fair values.

The impacts of any adverse business and market conditions which may impact the overall performance of the Company's reporting units will continue to be monitored. If the Company's reporting units do not achieve the financial performance that the Company expects, or if there is a significant prolonged change in demand for the Company's products and services, it is possible that goodwill impairment charges may result. Therefore, there can be no assurance that future events will not result in an impairment of goodwill.

As of December 31, 2022 and 2021, the Company's finite-lived and indefinite-lived intangible assets consisted of the following (in thousands):


	December 31, 2022						December 31, 2021
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	188,373	$	109,036	$	79,337	$	187,519	$	102,408	$	85,111
Customer and supplier relationships	583,709		229,368		354,341		576,474		214,776		361,698
Other intangible assets	89,388		24,818		64,570		94,271		19,359		74,912
Total amortizable permits and other intangible assets	861,470		363,222		498,248		858,264		336,543		521,721
Trademarks and trade names	122,534		—		122,534		123,191		—		123,191
Total permits and other intangible assets	$	984,004	$	363,222	$	620,782	$	981,455	$	336,543	$	644,912

The Company regularly monitors and assesses whether events or changes in circumstances relative to the Company's business might indicate that future cash flows attributable to the Company's asset groups may not be sufficient to recover the current value of those assets. During the periods presented, there were no events or changes in circumstances which would indicate that the carrying values of the Company's asset groups would not be recoverable and thus no impairment charge was recorded related to the Company's long-lived assets. If expectations of future cash flows were to decrease in the future as a result of worse than expected or prolonged periods of depressed activity, future impairments may become evident.

Amortization expense of permits, customer and supplier relationships and other intangible assets for the years ended December 31, 2022, 2021 and 2020 were $50.2 million, $34.7 million and $35.8 million, respectively. The Company wrote-off fully amortized intangible assets with a cost of $19.1 million during the year ended December 31, 2022.

The expected amortization of the net carrying amount of finite-lived intangible assets at December 31, 2022 is as follows (in thousands):


Years ending December 31,	Expected Amortization
2023	$	46,030
2024	41,814
2025	39,828
2026	37,943
2027	35,869
Thereafter	296,764
	$	498,248

ACCRUED EXPENSES

12 Months Ended

Dec. 31, 2022

Payables and Accruals [Abstract]

ACCRUED EXPENSES

Accrued expenses consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Accrued insurance	$	92,909	$	102,853
Accrued interest	20,033		19,785
Accrued compensation and benefits	123,226		133,604
Accrued income, real estate, sales and other taxes	61,442		29,954
Interest rate swap liability	—		17,383
Accrued other	99,106		87,835
	$	396,716	$	391,414

As of December 31, 2022 and 2021, accrued insurance included employee medical insurance costs of $16.4 million and $18.6 million, respectively, and accruals for losses under workers' compensation, comprehensive general liability and vehicle liability self-insurance programs of $74.9 million and $82.8 million, respectively. The increase in accrued income, real estate, sales and other taxes is due to the timing and amount of estimated payments of foreign income tax liabilities. The change in the

fair value of the interest rate swap liability from December 31, 2021 is mainly due to the passage of time and changes in future interest rate expectations. As of December 31, 2022, the interest rate swap derivatives are in an asset position and therefore, are included within Other Assets on the consolidated balance sheet. For additional information relating to the interest rate swaps, see Note 12, "Financing Arrangements."

CLOSURE AND POST-CLOSURE LIABILITIES

12 Months Ended

Dec. 31, 2022

Asset Retirement Obligation Disclosure [Abstract]

CLOSURE AND POST-CLOSURE LIABILITIES

The changes to closure and post-closure liabilities (also referred to as "asset retirement obligations") from January 1, 2021 through December 31, 2022 were as follows (in thousands):


	Landfill Retirement Liability		Non-Landfill Retirement Liability		Total
Balance at January 1, 2021	$	48,412	$	39,514	$	87,926
Liabilities assumed in acquisitions	—		1,446		1,446
New asset retirement obligations	2,443		—		2,443
Accretion	3,655		3,702		7,357
Changes in estimates recorded to consolidated statement of operations	2,287		396		2,683
Changes in estimates recorded to consolidated balance sheet	2,297		1,415		3,712
Expenditures	(5,818)		(784)		(6,602)
Currency translation and other	149		(11)		138
Balance at December 31, 2021	53,425		45,678		99,103
Liabilities assumed in acquisitions	—		55		55
Measurement period adjustments from prior period acquisitions	—		1,148		1,148
New asset retirement obligations	3,743		—		3,743
Accretion	4,605		4,147		8,752
Changes in estimates recorded to consolidated statement of operations	1,063		5,712		6,775
Changes in estimates recorded to consolidated balance sheet	3,219		1,742		4,961
Expenditures	(3,373)		(1,778)		(5,151)
Currency translation and other	(431)		(154)		(585)
Balance at December 31, 2022	$	62,251	$	56,550	$	118,801

The Company is in the process of closing two of its commercial landfill sites. The Altair landfill reached its permitted capacity in 2020 and the Westmorland landfill was closed due to the costs of obtaining and maintaining permits and operating the landfill. The changes in estimates recorded to the consolidated statement of operations includes $0.6 million and $2.3 million in 2022 and 2021, respectively, related to the closure of these two commercial landfills. The remainder of the change in estimate recorded to the consolidated statement of operations in 2022 was predominately the result of updated cost estimates for the planned closure of two non-landfill locations expected to commence in 2023.

Anticipated payments (based on current estimated costs and anticipated timing of necessary regulatory approvals to commence work on closure and post-closure activities) for each of the next five years and thereafter are as follows (in thousands):


Years ending December 31,
2023	$	14,414
2024	14,733
2025	12,808
2026	8,369
2027	7,420
Thereafter	290,366
Undiscounted closure and post-closure liabilities	348,110
Less: Discount at credit-adjusted risk-free rate	(153,062)
Less: Undiscounted estimated closure and post-closure liabilities relating to airspace not yet consumed	(76,247)
Present value of closure and post-closure liabilities	$	118,801

REMEDIAL LIABILITIES

12 Months Ended

Dec. 31, 2022

Environmental Remediation Obligations [Abstract]

REMEDIAL LIABILITIES

The changes to remedial liabilities from January 1, 2021 through December 31, 2022 were as follows (in thousands):


	Remedial Liabilities for Landfill Sites		Remedial Liabilities for Inactive Sites		Remedial Liabilities (Including Superfund) for Non-Landfill Operations		Total
Balance at January 1, 2021	$	1,865	$	63,060	$	49,888	$	114,813
Liabilities assumed in acquisitions	—		—		1,216		1,216
Accretion	90		2,614		1,684		4,388
Changes in estimates recorded to consolidated statement of operations	(126)		(178)		600		296
Expenditures	(49)		(4,889)		(3,966)		(8,904)
Currency translation and other	—		(820)		884		64
Balance at December 31, 2021	1,780		59,787		50,306		111,873
Liabilities assumed in acquisition of real estate	—		—		8,092		8,092
Measurement period adjustments from prior period acquisition	—		—		338		338
Accretion	86		2,498		1,607		4,191
Changes in estimates recorded to consolidated statement of operations	8		877		612		1,497
Expenditures	(50)		(3,370)		(5,375)		(8,795)
Currency translation and other	—		(43)		(863)		(906)
Balance at December 31, 2022	$	1,824	$	59,749	$	54,717	$	116,290

In 2022, there were no significant charges or benefits resulting from changes in estimates for remedial liabilities. The $8.1 million liability assumed in acquisition relates to real estate that the Company acquired in 2022. In purchasing the property, the Company assumed a known associated remedial liability, which was contemplated in the purchase price.

Anticipated payments at December 31, 2022 (based on current estimated costs and anticipated timing of necessary regulatory approvals to commence work on remedial activities) for each of the next five years and thereafter were as follows (in thousands):


Years ending December 31,
2023	$	10,793
2024	20,912
2025	12,065
2026	7,581
2027	6,390
Thereafter	76,416
Undiscounted remedial liabilities	134,157
Less: Discount at risk free rates	(17,867)
Total remedial liabilities	$	116,290

The following table presents the Company's estimated remedial liabilities and reasonably possible additional liabilities as of December 31, 2022 disaggregated by facility/site type (in thousands, except percentages):


Type of Facility or Site	Remedial Liabilities		% of Total		Reasonably Possible Additional Liabilities (1)
Inactive facilities not used in active conduct of the Company's business, most of which were assumed through prior period acquisitions (25 facilities)	$	59,759	51.4	%	$	10,295
Facilities now used in active conduct of the Company's business (45 facilities)	47,951		41.2		11,189
Superfund sites (16 sites)	8,580		7.4		1,288
Total	$	116,290	100.0	%	$	22,772

___________________________________

(1)Amounts represent the high end of the range of management's best estimate of the reasonably possible additional liabilities.

The following table presents the Company's estimated remedial liabilities and reasonably possible additional liabilities as of December 31, 2022 disaggregated by facilities/sites which represent at least 5% of the total and with all other facilities/ sites combined (in thousands, except percentages):


Location	Type of Facility or Site	Remedial Liabilities(1)		% of Total		Reasonably Possible Additional Liabilities(2)
Baton Rouge, LA	Closed incinerator and landfill	$	26,604	22.9	%	$	4,547
Bridgeport, NJ	Closed incinerator	18,089		15.6		3,364
Linden, NJ	Operating solvent recycling center	14,479		12.5		3,352
Mercier, Quebec	Idled incinerator	10,996		9.5		1,659
Various	All other incinerators, landfills, wastewater treatment facilities and service centers (66 facilities)	37,542		32.1		8,562
Various	Superfund sites (each representing less than 5% of total liabilities) (16 sites)	8,580		7.4		1,288
Total		$	116,290	100.0	%	$	22,772

_________________________________

(1)$24.1 million of the $116.3 million remedial liabilities include estimates related to the legal and administrative proceedings discussed in Note 18, "Commitments and Contingencies."

(2)Amounts represent the high end of the range of management's best estimate of the reasonably possible additional liabilities.

Revisions to remediation reserve requirements may result in upward or downward adjustments to income from operations in any given period. The Company believes that its extensive experience in the environmental services business, as well as its involvement with a large number of sites, provides a reasonable basis for estimating its aggregate liability. It is possible, however, that future changes in available technology, regulatory or enforcement developments, the results of environmental studies or other factors could necessitate the recording of additional liabilities or the revision of currently recorded liabilities that could be material. Since the Company's satisfaction of the liabilities will occur over many years, the Company cannot reasonably predict the nature or extent of possible future events or the impact that those events, if any, might have on the current estimates of remedial liabilities.

- Definition

The entire disclosure for environmental loss contingencies, such as presence of hazardous waste, relevant information from reports issued by regulators, and estimated costs to achieve compliance with regulatory requirements. This element may be used for all of an entity's disclosures about environmental loss contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (d)(5)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 55
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=6571209&loc=d3e13644-110860

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 55
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=6571209&loc=d3e13718-110860

Reference 4: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13328-110859

Reference 5: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 6: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (d)(4)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 55
-Paragraph 16
-URI https://asc.fasb.org/extlink&oid=6571209&loc=d3e13703-110860

Reference 8: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (d)(3)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 9: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13319-110859

Reference 10: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-URI https://asc.fasb.org/subtopic&trid=2175709

Reference 12: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (d)(2)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 13: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 10
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859

Reference 14: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=6393242&loc=d3e13283-110859

+ Details

FINANCING ARRANGEMENTS

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

FINANCING ARRANGEMENTS

Long-term Debt

The following table is a summary of the Company's long-term debt (in thousands):


Current Portion of Long-Term Debt:	December 31, 2022		December 31, 2021
Secured senior term loans	$	10,000	$	17,535


Long-Term Debt:
Secured senior term loans due June 30, 2024 ("2024 Term Loans")	$	613,975	$	712,091
Secured senior term loans due October 8, 2028 ("2028 Term Loans")	980,000		990,000
Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")	545,000		545,000
Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")	300,000		300,000
Long-term debt, at par	2,438,975		2,547,091
Unamortized debt issuance costs and discount, net	(24,147)		(30,067)
Long-term debt, at carrying value	$	2,414,828	$	2,517,024

Secured Senior Term Loans.

As of December 31, 2022, the Company had two series of secured senior term loans ("Term Loans") outstanding under Incremental Facility Amendment No. 2, dated October 8, 2021, to the Company's existing Credit Agreement, dated June 30, 2017 ("the Term Loan Agreement").

The 2028 Term Loans had an aggregate principal amount outstanding of $990.0 million as of December 31, 2022. Under the Term Loan Agreement, the 2028 Term Loans bear interest, at the Company’s election, at either of the following rates: (a) the sum of the Eurodollar Rate (as defined in the Term Loan Agreement) plus 2.00%, or (b) the sum of the Base Rate (as defined in the Term Loan Agreement) plus 1.00%, with the Eurodollar Rate being subject to a floor of 0.00% and the Base Rate being subject to a floor of 1.00%. The 2024 Term Loans had an aggregate principal amount outstanding of $614.0 million as of December 31, 2022. Under the Term Loan Agreement, the 2024 Term Loans bore interest, at the Company’s election, at either of the following rates: (a) the sum of the Eurodollar Rate (as defined in the Term Loan Agreement) plus 1.75%, or (b) the sum of the Base Rate (as defined in the Term Loan Agreement) plus 1.00%, with the Eurodollar Rate being subject to a floor of 0.00% and the Based Rate being subject to a floor of 1.00%. Interest on the Term Loans are paid monthly. The Term Loans are prepayable at any time without premium or penalty, other than customary breakage costs with respect to Eurodollar based loans.

The Company’s obligations under the Term Loan Agreement with respect to both the 2024 Term Loans and the 2028 Term Loans are guaranteed by all of the Company’s domestic restricted subsidiaries and secured by liens on substantially all of the assets of the Company and the guarantors.

On November 21, 2022, the Company repaid $100.0 million principal amount of the then outstanding 2024 Term Loans with available cash. In connection with this transaction, the Company recorded a loss on early extinguishment of debt of $0.4 million during the year ended December 31, 2022 related to the write-off of unamortized debt issuance costs for the settled debt. On January 24, 2023, the remaining $614.0 million principal amount of the 2024 Term Loans was repaid using net proceeds from the issuance of $500.0 million of unsecured senior notes due on February 1, 2031 as described below, a

$114.0 million loan under the Company's Revolving Credit Facility and available cash. In connection with the repayment, the Company will recognize a loss on early extinguishment of debt of approximately $2.4 million in 2023.

Unsecured Senior Notes.

On July 2, 2019, the Company completed a private placement of $545.0 million aggregate principal amount of 2027 Notes and $300.0 million aggregate principal amount of 2029 Notes. The 2027 Notes will mature on July 15, 2027, and the 2029 Notes will mature on July 15, 2029. Interest payments on the 2027 Notes and 2029 Notes are paid semiannually on January 15 and July 15.

On January 24, 2023, the Company completed a private placement of $500.0 million aggregate principal amount of unsecured senior notes which mature on February 1, 2031 (the "2031 Notes" and, together with the 2027 and 2029 Notes, the "Notes"). The interest rate on the 2031 Notes is fixed at 6.375% and is paid semiannually on February 1 and August 1 of each year commencing on August 1, 2023.

The tables below depict the redemption prices (expressed as percentages of the principal amount) of the Notes if redeemed during the twelve-month period commencing on the dates below, plus accrued and unpaid interest, if any, to but not including the date of redemption.

2027 Notes


Year	Percentage
July 15, 2022	102.438	%
July 15, 2023	101.219	%
July 15, 2024 and thereafter	100.000	%

2029 Notes


Year	Percentage
July 15, 2024	102.563	%
July 15, 2025	101.281	%
July 15, 2026 and thereafter	100.000	%

2031 Notes


Year	Percentage
February 1, 2026	103.188	%
February 1, 2027	101.594	%
February 1, 2028 and thereafter	100.000	%

The Company may also redeem all or any portion of the 2029 Notes prior to July 15, 2024 or the 2031 Notes prior to February 1, 2026, at a redemption price equal to 100% of the principal amount redeemed plus a make whole premium as of the date of redemption including accrued and unpaid interest, if any, up to but not including the date of redemption.

Additionally, subject to certain limitations, prior to February 1, 2026, the Company may use net cash proceeds of one or more equity offerings to redeem up to 40% in aggregate principal of the 2031 Notes at a redemption price equal to 106.375% of the principal amount thereof plus accrued and unpaid interest thereon, if any, up to but not including the date of redemption.

The Notes and the related indentures contain various customary non-financial covenants and are guaranteed by substantially all of the Company’s current and future domestic subsidiaries. The Notes are effectively subordinated to the Company's Term Loans, revolving credit facility and finance lease obligations to the extent of the value of the assets securing such secured indebtedness. The Notes are also effectively subordinated to all indebtedness and other liabilities of the Company's subsidiaries that are not guarantors of the Notes.

As of December 31, 2022 and 2021, the estimated fair value of the Company’s outstanding long-term debt, including the current portion, was $2.4 billion and $2.6 billion, respectively. The Company’s estimates of the fair value of its long-term debt, including the current portion, are based on quoted market prices or other available market data which are considered Level 2 measures according to the fair value hierarchy. Level 2 utilizes quoted market prices in markets that are not active, broker or dealer quotation, or alternative pricing sources with reasonable levels of price transparency for similar assets and liabilities.

Revolving Credit Facility. On October 28, 2020, the Company and one of the Company's subsidiaries (the "Canadian Borrower") entered into an amended and restated credit agreement for the Company's revolving credit facility with Bank of America, N.A. (“BofA”), as agent for the lenders under the facility (the "Agent"). Under the amended and restated facility, the Company has the right to obtain revolving loans and letters of credit for a combined maximum of up to $350.0 million (with a sub-limit of $250.0 million for letters of credit) and the Canadian Borrower has the right to obtain revolving loans and letters of credit for a combined maximum of up to $50.0 million. Availability under the U.S. line is subject to a borrowing base primarily comprised of 85% of the eligible accounts receivable of the Company and its U.S. subsidiaries plus 100% of cash deposited in a controlled account with the Agent, and availability under the Canadian line is subject to a borrowing base primarily comprised of 85% of the eligible accounts receivable of the Company’s Canadian subsidiaries plus 100% of cash deposited in a controlled account with the Agent’s Canadian affiliate. Subject to certain conditions, the revolving credit facility will expire on October 28, 2025.

Borrowings under the revolving credit facility bear interest at a rate of, at the Company’s option, either (i) LIBOR plus an applicable margin ranging from 1.50% to 1.75% per annum based primarily on the level of the Company’s average liquidity for the most recent 30 day period or (ii) BofA’s base rate plus an applicable margin ranging from 0.50% to 0.75% per annum based primarily on such average liquidity. There is also an unused line fee, calculated on the then unused portion of the lenders’ $400.0 million maximum commitments, ranging from 0.25% to 0.375% per annum of the unused commitment. For outstanding letters of credit, the Company pays to the lenders a fee equal to the then applicable LIBOR margin described above, and to the issuing banks a standard fronting fee and customary fees and charges in connection with all amendments, extensions, draws and other actions with respect to letters of credit. In the event that LIBOR ceases to be available during the term of the revolving credit facility, the amended and restated credit agreement provides procedures to determine a LIBOR successor rate.

Letters of credit issued under the revolving credit facility are utilized primarily as security for the Company's insurance program that includes casualty and financial assurance.

The Company’s obligations under the revolving credit facility (including revolving loans and reimbursement obligations for outstanding letters of credit) are guaranteed by substantially all of the Company’s U.S. subsidiaries and secured by a first lien on the Company’s and its U.S. subsidiaries’ accounts receivable. The Canadian Borrower’s obligations under the facility are guaranteed by substantially all of the Company’s Canadian subsidiaries and secured by a first lien on the accounts receivable of the Canadian subsidiaries.

The revolving credit facility had no outstanding loan balances at December 31, 2022 and 2021 and had availability of $288.6 million and outstanding letters of credit of $111.4 million at December 31, 2022. As noted above, on January 24, 2023, the Company borrowed $114.0 million under the revolving credit facility. Proceeds from this borrowing were used toward the repayment of the 2024 Term Loans.

Cash Flow Hedges

Although the interest rates on the Term Loans are variable, as of December 31, 2022, the Company effectively fixed the interest rate on $350.0 million principal of the outstanding 2024 Term Loans by entering into interest rate swap agreements in 2018 with a notional amount of $350.0 million ("2018 Swaps"). Under the terms of the 2018 Swaps' agreements, the Company receives interest based on the one-month LIBOR index and pays interest at a weighted average rate of approximately 2.92%, which together with the 1.75% interest rate margin for Eurocurrency borrowings on the 2024 Term Loans, results in an effective annual interest rate of approximately 4.67%.

In January 2022, the Company entered into interest rate swap agreements ("2022 Swaps") with a notional amount of $600.0 million to effectively fix the interest rate on $600.0 million principal of the outstanding 2028 Term Loans. Under the terms of the 2022 Swaps' agreements, the Company will receive interest based upon the variable rates on the 2028 Term Loans and pay a fixed amount of interest. The fixed rate on these instruments is 0.931% through June 30, 2023 which, together with the 2.00% interest rate margin for Eurodollar borrowings on the 2028 Term Loans, results in an effective annual interest rate of approximately 2.931%. The fixed rate on these instruments increases to 1.9645% from July 1, 2023 through September 30, 2027 to both mirror the current 2028 Term Loans variable interest payments and the successor rate upon the eventual sunsetting of the LIBOR rate.

The Company has designated both the 2018 Swaps and the 2022 Swaps (collectively referred to as the “Swaps”) as cash flow hedges. As of December 31, 2022 the Company recorded a derivative asset with a fair value of $60.6 million. As of December 31, 2021, the Company recorded a derivative liability of $17.4 million. No ineffectiveness has been recognized on the Swaps in 2022, 2021 or 2020.

On January 24, 2023, concurrently with the repayment of the 2024 Term Loans, the Company received a cash payment of $8.7 million from the counterparties to settle the 2018 Swaps. The Company also reclassified the amounts previously deferred in accumulated other comprehensive loss and recognized an $8.7 million gain in interest expense.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI https://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1E
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

INCOME TAXES

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

INCOME TAXES

The domestic and foreign components of income before provision for income taxes were as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Domestic	$	406,206	$	223,438	$	168,117
Foreign	131,792		46,277		6,433
Total	$	537,998	$	269,715	$	174,550

The provision for income taxes consisted of the following (in thousands, except percentages):


	For the years ended December 31,
	2022		2021		2020
Current:
Federal	$	52,237	$	42,480	$	33,327
State	26,980		18,126		14,575
Foreign	29,488		4,380		1,559
	108,705		64,986		49,461
Deferred
Federal	32,199		2,275		(965)
State	(2,432)		(4,777)		(2,506)
Foreign	(12,218)		3,984		(6,277)
	17,549		1,482		(9,748)
Provision for income taxes	$	126,254	$	66,468	$	39,713

Effective tax rate	23.5%		24.6%		22.8%

The Company's effective income tax rate varied from the amount computed using the statutory federal income tax rate of 21% as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Tax expense at U.S. statutory rate	$	112,980	$	56,640	$	36,655
State income taxes, net of federal benefit	19,831		12,101		9,837
Foreign rate differential	6,196		1,922		1,256
Valuation allowance	(18,769)		(9,139)		(11,339)
Uncertain tax position interest and penalties	(2,454)		263		(712)
Tax credits expired	2,768		2,530		2,039
Non-deductible compensation	2,754		2,326		1,406
Other	2,948		(175)		571
Provision for income taxes	$	126,254	$	66,468	$	39,713

The valuation allowance benefits recognized in 2022 were the result of cumulative profitable earnings at certain Canadian entities with historic operating losses. The 2022 earnings were sufficient to utilize substantially all of the net operating losses, and as of December 31, 2022, the Company released any remaining valuation allowances associated with these entities, which were nominal.

The valuation allowance benefits recognized in 2021 and 2020 were predominately related to taxable earnings in certain Canadian entities that benefited from amounts received under the Canada Emergency Wage Subsidiary. In addition, foreign tax credits that expired in the periods presented had full valuation allowances which were also written off, contributing to the

valuation allowance benefits in the table above. The foreign tax credit expirations and associated valuation allowance write-offs had no net impact to the provision for income taxes in any year.

The components of the total net deferred tax assets and liabilities as of December 31, 2022 and 2021 were as follows (in thousands):


	2022		2021
Deferred tax assets:

Provision for doubtful accounts	$	11,544	$	10,188
Closure, post-closure and remedial liabilities	31,837		28,206
Operating lease liabilities	42,255		42,218
Accrued expenses	19,311		20,455
Accrued compensation and benefits	20,171		24,504
Net operating loss carryforwards(1)	41,585		68,381
Tax credit carryforwards(2)	8,903		12,368
Interest rate swap liability	—		5,215
Stock-based compensation	3,988		2,705
Other	7,487		5,635
Total deferred tax assets	187,081		219,875
Deferred tax liabilities:
Property, plant and equipment	(281,131)		(273,883)
Operating lease right-of-use assets	(41,939)		(41,260)
Interest rate swap asset	(17,587)		—
Permits and other intangible assets	(132,681)		(138,241)
Prepaid expenses	(12,088)		(10,212)
Total deferred tax liabilities	(485,426)		(463,596)
Total net deferred tax liability before valuation allowance	(298,345)		(243,721)
Less valuation allowance	(42,509)		(69,806)
Net deferred tax liabilities	$	(340,854)	$	(313,527)

___________________________________

(1)As of December 31, 2022, the net operating loss carryforwards included (i) state net operating loss carryforwards of $231.4 million which will begin to expire in 2023, (ii) federal net operating loss carryforwards of $34.8 million which will begin to expire in 2024 and (iii) foreign net operating loss carryforwards of $85.6 million which will begin to expire in 2023.

(2)As of December 31, 2022, the foreign tax credit carryforwards of $7.7 million will expire between 2023 and 2024.

The Company previously recognized the U.S. federal income taxes related to the operations in Canada and has not accrued for any remaining undistributed foreign earnings. These amounts continue to be indefinitely reinvested. The amount of tax associated with those unrepatriated earnings is not expected to be material.

A valuation allowance is required to be established when, based on an evaluation of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. The components of the total valuation allowance as of December 31, 2022 and 2021 were as follows (in thousands):


	2022		2021
Allowance related to:
Foreign tax credits	7,666		11,047
Federal net operating losses	3,783		3,788
State net operating loss carryforwards	9,928		12,053
Foreign net operating loss carryforwards	15,488		26,697
Deferred tax assets of a Canadian subsidiary	5,339		10,701
Realized and unrealized capital losses	305		5,520
Total valuation allowance	$	42,509	$	69,806

The Company files U.S. federal income tax returns as well as income tax returns in various states and foreign jurisdictions. The Company may be subject to examination by the Internal Revenue Service for calendar years 2017 through 2021. The Company may be subject to examination by Canadian federal and provincial authorities for calendar years 2015 through 2021 and by state and local revenue authorities for calendar years 2016 through 2021. The Company has ongoing U.S., state and local jurisdictional audits, as well as Canadian federal and provincial audits, all of which the Company believes will not result in material liabilities. The Company has not identified any material uncertain positions in the periods presented.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

EARNINGS PER SHARE

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

EARNINGS PER SHARE

The following are computations of basic and diluted earnings per share (in thousands, except for per share amounts):


	For the years ended December 31,
	2022		2021		2020
Numerator for basic and diluted earnings per share:
Net income	$	411,744	$	203,247	$	134,837
Denominator:
Weighted basic shares outstanding	54,223		54,514		55,479
Dilutive effect of equity-based compensation awards	264		247		211
Weighted dilutive shares outstanding	54,487		54,761		55,690

Basic earnings per share	$	7.59	$	3.73	$	2.43
Diluted earnings per share	$	7.56	$	3.71	$	2.42

For the year ended December 31, 2022, all then outstanding performance stock awards and restricted stock awards were included in the calculation of diluted earnings per share except for 10,250 of restricted stock awards which were excluded as their inclusion would have had an antidilutive effect. For the years ended 2021 and 2020, all the outstanding performance stock awards and restricted stock awards were included in the calculation of diluted earnings per share except for 14,237 and 53,667, respectively, of performance stock awards for which the performance criteria were not yet attained at the reporting dates and 67,981 and 8,878, respectively, of restricted stock awards which were excluded as their inclusion would have had an antidilutive effect.

STOCKHOLDERS' EQUITY	12 Months Ended
STOCKHOLDERS' EQUITY	Dec. 31, 2022
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITYThe Company's board of directors has authorized the repurchase of up to $600.0 million of the Company's common stock. The repurchase program authorizes the Company to purchase the Company's common stock on the open market or in privately negotiated transactions periodically in a manner that complies with applicable U.S. securities laws. The number of shares purchased and the timing of the purchases have depended and will depend on a number of factors including share price, cash required for future business plans, trading volume and other conditions. The Company has no obligation to repurchase stock under this program and may suspend or terminate the repurchase program at any time. During the years ended December 31, 2022, 2021 and 2020, the Company repurchased and retired a total of 0.5 million, 0.6 million and 1.2 million shares, respectively, of the Company's common stock for total costs of $50.2 million, $54.4 million and $74.8 million, respectively. As of December 31, 2022, an additional $105.3 million remained available to repurchase shares under this program.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI https://asc.fasb.org/topic&trid=2208762

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 14
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496171-112644

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 18
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496189-112644

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496180-112644

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (i)
-URI https://asc.fasb.org/extlink&oid=126973232&loc=SL123496158-112644

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126731327&loc=SL126733271-114008

+ Details

ACCUMULATED OTHER COMPREHENSIVE LOSS

12 Months Ended

Dec. 31, 2022

Equity [Abstract]

ACCUMULATED OTHER COMPREHENSIVE LOSS

The changes in accumulated other comprehensive loss by component and related tax impacts for the years ended December 31, 2022, 2021 and 2020 were as follows (in thousands):


	Foreign Currency Translation Adjustments		Unrealized Gain (Loss) on Available-For-Sale Securities		Unrealized (Loss) Gain on Fair Value of Interest Rate Hedges		Unrealized Loss on Unfunded Pension Liability		Total
Balance at January 1, 2020	$	(187,795)	$	143	$	(20,839)	$	(1,560)	$	(210,051)
Other comprehensive income (loss) before reclassifications	10,212		(10)		(20,970)		(255)		(11,023)
Amounts reclassified out of accumulated other comprehensive loss	—		—		8,180		—		8,180
Tax benefit	1,349		2		—		66		1,417
Other comprehensive income (loss)	11,561		(8)		(12,790)		(189)		(1,426)
Balance at December 31, 2020	(176,234)		135		(33,629)		(1,749)		(211,477)
Other comprehensive (loss) income before reclassifications	(1,590)		(361)		6,235		1,411		5,695
Amounts reclassified out of accumulated other comprehensive loss	—		—		10,011		—		10,011
Tax benefit (provision)	—		76		—		(317)		(241)
Other comprehensive (loss) income	(1,590)		(285)		16,246		1,094		15,465
Balance at December 31, 2021	(177,824)		(150)		(17,383)		(655)		(196,012)
Other comprehensive (loss) income before reclassifications	(31,515)		(523)		78,711		415		47,088
Amounts reclassified out of accumulated other comprehensive loss	—		—		(683)		—		(683)
Tax benefit (provision)	—		110		(17,587)		(97)		(17,574)
Other comprehensive (loss) income	(31,515)		(413)		60,441		318		28,831
Balance at December 31, 2022	$	(209,339)	$	(563)	$	43,058	$	(337)	$	(167,181)

The amounts realized in the consolidated statements of operations during the years ended December 31, 2022, 2021 and 2020 which were reclassified out of accumulated other comprehensive loss were as follows (in thousands):


	For the years ended December 31,
Other Comprehensive Loss Component	2022	2021	2020	Location

Unrealized (Loss) Gain on Fair Value of Interest Rate Hedges	683	(10,011)	(8,180)	Interest expense, net of interest income

In the first quarter of 2023, the Company reclassified an unrealized gain of $8.7 million out of unrealized (loss) gain on fair value of interest rate hedges into interest expense in connection with the discontinuance of the 2018 Swap. For more information on this transaction, see Note 12, "Financing Arrangements."

STOCK-BASED COMPENSATION

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION

Stock-Based Compensation

In 2020, the Company's shareholders approved the Clean Harbors, Inc. 2020 Stock Incentive Plan (the "2020 Plan"). The 2020 Plan provides for future awards of up to 2.5 million shares of the Company’s common stock (subject to certain anti-dilution adjustments) in the form of stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards. The 2020 Plan is administered by the Compensation Committee of the Company’s Board of Directors.

The Company grants restricted stock awards and performance stock awards. The restricted stock awards generally vest over three to five years subject to continued employment. The performance stock awards vest depending on the satisfaction of certain performance conditions typically based on revenue, Adjusted EBITDA, Adjusted EBITDA margin, Adjusted free cash

flow, return on invested capital and a measure of workplace safety. In addition, performance stock awards include continued service conditions subsequent to the attainment of any performance conditions.

Total stock-based compensation expense for the years ended December 31, 2022, 2021 and 2020 was $26.8 million, $18.8 million and $18.5 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense was $5.0 million, $3.5 million and $4.2 million for the years ended December 31, 2022, 2021 and 2020, respectively.

Restricted Stock Awards

The following table summarizes information about restricted stock awards for the year ended December 31, 2022:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2022	452,197	$	76.88
Granted	165,149	94.88
Vested	(167,086)	74.37
Forfeited	(23,118)	80.17
Balance at December 31, 2022	427,142	$	84.64

As of December 31, 2022, there was $25.6 million of total unrecognized compensation cost arising from restricted stock awards. This cost is expected to be recognized over a weighted average period of 2.5 years. The total fair value of restricted stock vested during 2022, 2021 and 2020 was $16.4 million, $17.7 million and $13.3 million, respectively.

Performance Stock Awards

The following table summarizes information about performance stock awards for the year ended December 31, 2022:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2022	169,757	$	85.56
Granted	156,687	92.60
Vested	(100,892)	83.51
Forfeited	(11,873)	86.87
Balance at December 31, 2022	213,679	$	91.62

As of December 31, 2022, there was $9.3 million of total unrecognized compensation cost arising from performance stock awards whereby the performance conditions either had been or were probable of being met. The total fair value of performance awards vested during 2022, 2021 and 2020 was $11.1 million, $15.0 million and $3.5 million, respectively.

COMMITMENTS AND CONTINGENCIES

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

The Company and its subsidiaries are subject to legal proceedings and claims arising in the ordinary course of business. Actions filed against the Company arise from commercial and employment-related claims including alleged class actions related to sales practices and wage and hour claims. The plaintiffs in these actions may be seeking damages or injunctive relief or both. These actions are in various jurisdictions and stages of proceedings, and some are covered in part by insurance. In addition, the Company’s waste management services operations are regulated by federal, state, provincial and local laws enacted to regulate discharge of materials into the environment, remediation of contaminated soil and groundwater or otherwise protect the environment. This ongoing regulation results in the Company frequently becoming a party to legal or administrative proceedings involving all levels of government authorities and other interested parties. The issues involved in such proceedings generally relate to alleged violations of existing permits and licenses or alleged responsibility under federal or state Superfund laws to remediate contamination at properties owned either by the Company or by other parties (“third-party sites”) to which either the Company or the prior owners of certain of the Company’s facilities shipped waste.

At December 31, 2022 and 2021, the Company had recorded reserves of $37.1 million and $36.1 million, respectively, for actual or probable liabilities related to the legal and administrative proceedings in which the Company was then involved, the principal of which are described below. As of December 31, 2022 and 2021, the $37.1 million and $36.1 million, respectively,

of reserves consisted of (i) $24.1 million in both periods, related to pending legal or administrative proceedings, including Superfund liabilities, which were included in remedial liabilities on the consolidated balance sheets, and (ii) $13.0 million and $12.0 million, respectively, primarily related to federal, state and provincial enforcement actions, which were included in accrued expenses on the consolidated balance sheets.

In management's opinion, it is not reasonably possible that the potential liability beyond what has been recorded, if any, that may result from these actions, either individually or collectively, will have a material effect on the Company's financial position, results of operations or cash flows. The Company periodically adjusts the aggregate amount of these reserves when actual or probable liabilities are paid or otherwise discharged, new claims arise, or additional relevant information about existing or probable claims becomes available.

Legal or Administrative Proceedings

As of December 31, 2022, the principal legal and administrative proceedings in which the Company was involved, or which had been terminated during 2022, mainly relate to Safety-Kleen product liability cases and Superfund proceedings.

Safety-Kleen Product Liability Cases: Safety-Kleen, Inc. ("Safety-Kleen"), which is a legal entity acquired by the Company in 2012, has been named as a defendant in certain product liability cases that are currently pending in various courts and jurisdictions throughout the United States. As of December 31, 2022, there were approximately 54 proceedings (excluding cases which have been settled but not formally dismissed) wherein persons claim personal injury resulting from the use of Safety-Kleen's parts cleaning equipment or cleaning products. These proceedings typically involve allegations that the solvent used in Safety-Kleen's parts cleaning equipment contains contaminants and/or that Safety-Kleen's recycling process does not effectively remove the contaminants that become entrained in the solvent during their use. In addition, certain claimants assert that Safety-Kleen failed to warn adequately the product user of potential risks, including a historic failure to warn that solvent contains trace amounts of toxic or hazardous substances such as benzene.

The Company maintains insurance that it believes will provide coverage for these product liability claims (over amounts accrued for self-insured retentions and deductibles in certain limited cases), except for punitive damages to the extent not insurable under state law or excluded from insurance coverage. The Company also believes that these claims lack merit and has historically vigorously defended, and intends to continue to vigorously defend, itself and the safety of its products against all of these claims. Such matters are subject to many uncertainties and outcomes are not predictable with assurance. Consequently, the Company is unable to ascertain the ultimate aggregate amount of monetary liability or financial impact with respect to these matters as of December 31, 2022. From January 1, 2022 to December 31, 2022, 20 product liability claims were settled or dismissed. Due to the nature of these claims and the related insurance, the Company did not incur any expense as insurance provided coverage in full for all such claims. Safety-Kleen may be named in similar, additional lawsuits in the future, including claims for which insurance coverage may not be available.

Superfund Proceedings: The Company has been notified that either the Company (which, since December 28, 2012, has included Safety-Kleen) or the prior owners of certain of the Company's facilities for which the Company may have certain indemnification obligations have been identified as PRPs or potential PRPs in connection with 131 sites which are subject to or are proposed to become subject to proceedings under federal or state Superfund laws. Of the 131 Superfund related sites, six involve facilities that are now owned or leased by the Company and 125 involve third-party sites to which either the Company or the prior owners of certain of the Company’s facilities shipped waste. Of the 125 third-party sites, 30 are now settled, 16 are currently requiring expenditures on remediation and 79 are not currently requiring expenditures on remediation.

In connection with each site, the Company has estimated the extent, if any, to which it may be subject, either directly or as a result of any indemnification obligations, for cleanup and remediation costs, related legal and consulting costs associated with PRP investigations, settlements, and related legal and administrative proceedings. The amount of such actual and potential liability is inherently difficult to estimate because of, among other relevant factors, uncertainties as to the legal liability (if any) of the Company or the prior owners of certain of the Company's facilities to contribute a portion of the cleanup costs, the assumptions that must be made in calculating the estimated cost and timing of remediation, the identification of other PRPs and their respective capability and obligation to contribute to remediation efforts, and the existence and legal standing of indemnification agreements (if any) with prior owners, which may either benefit the Company or subject the Company to potential indemnification obligations. The Company believes its potential monetary liability could exceed $1.0 million at three of the 131 Superfund related sites.

Of the 125 third-party sites at which the Company has been notified it is a PRP or potential PRP or may have indemnification obligations, the Company has an indemnification agreements at a total of 17 sites. These agreements indemnify the Company (which now includes Safety-Kleen) with respect to any liability at the 17 sites for waste disposed prior to the

Company's (or Safety-Kleen's) acquisition of the former subsidiaries of Waste Management and McKesson which had shipped waste to those sites. Accordingly, the indemnifying parties are paying all costs of defending those subsidiaries in those 17 cases, including legal fees and settlement costs. However, there can be no guarantee that the Company's ultimate liabilities for those sites will not exceed the amount recorded or that indemnities applicable to any of these sites will be available to pay all or a portion of related costs. Except for those indemnification agreements discussed, the Company does not have an indemnity agreement with respect to any of the 125 third-party sites discussed above.

Federal, State and Provincial Enforcement Actions

From time to time, the Company pays fines or penalties in regulatory proceedings relating primarily to waste treatment, storage or disposal facilities. As of December 31, 2022, there was one proceeding for which the Company believes it is possible that the sanctions could equal or exceed $1.0 million. The Company believes that the fines or other penalties in this or any of the other regulatory proceedings will, individually or in the aggregate, not have a material effect on its financial condition, results of operations or cash flows.

Self-Insurance Liabilities

Under the Company's insurance programs, coverage is obtained for catastrophic exposures, as well as those risks required to be insured by law or contract. The Company's policy is to retain a significant portion of certain expected losses related to workers' compensation, employee medical, comprehensive general liability and vehicle liability. A portion of these self-insured liabilities are managed through its wholly-owned captive insurance subsidiary.

Provisions for losses expected under these programs are recorded based upon the Company's estimates of the aggregate liability for claims. The current deductible per participant per year for the employee medical insurance policy is $0.9 million. The current deductible per occurrence for workers' compensation is $1.0 million, general liability is $2.0 million and vehicle liability is $2.0 million. The retention per claim for the environmental impairment policy is $1.0 million. At December 31, 2022 and 2021, the Company had accrued $74.9 million and $82.8 million, respectively, for its self-insurance liabilities (exclusive of employee medical insurance) using a risk-free discount rate of 4.36% and 0.97%, respectively.

Anticipated payments for contingencies related to workers' compensation, comprehensive general liability and vehicle liability related claims at December 31, 2022 for each of the next five years and thereafter were as follows (in thousands):


Years ending December 31,
2023	$	26,736
2024	16,317
2025	12,172
2026	8,170
2027	6,318
Thereafter	10,631
Undiscounted self-insurance liabilities	80,344
Less: Discount	(5,452)
Total self-insurance liabilities (included in accrued expenses)	$	74,892

LEASES

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

LEASES

The Company’s lease portfolio is predominately operating leases for real estate, vehicles and industrial equipment utilized in operations and rail cars. The Company presents operating lease balances separately on the consolidated balance sheets. The Company's finance leases relate to equipment, rail cars and certain real estate. The following table presents the Company's finance lease balances and their classification on the consolidated balance sheets (in thousands):


Finance Lease Balances (Classification)	December 31, 2022		December 31, 2021
ROU assets (Property, plant and equipment, net)	$	96,207	$	81,267
Current portion of lease liabilities (Accrued expenses)	12,767		10,893
Long-term portion of lease liabilities (Other long-term liabilities)	86,390		72,051

The Company’s lease expense was as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Operating lease cost	$	59,041	$	50,264	$	53,194

Finance lease cost:
Amortization of ROU assets	13,239		9,504		4,966
Interest on lease liabilities	3,011		2,544		1,523
Total finance lease cost	16,250		12,048		6,489

Short-term lease cost	158,736		102,913		70,692
Variable lease cost	4,353		3,546		3,691
Total lease cost	$	238,380	$	168,771	$	134,066

Other information related to leases was as follows:


Weighted Average Remaining Lease Term (years)	December 31, 2022		December 31, 2021
Operating leases	4.2		4.4
Finance leases	7.5		8.1

Weighted Average Discount Rate	December 31, 2022		December 31, 2021
Operating leases	4.08	%	4.35	%
Finance leases	3.53	%	3.65	%


	For the years ended December 31,
Supplemental Cash Flow Related Disclosures (in thousands)	2022		2021		2020
Cash paid for amounts related to lease liabilities:
Operating cash flows from operating leases	$	61,014	$	50,963	$	53,498
Operating cash flows from finance leases	3,011		2,544		1,523
Financing cash flows from finance leases	12,821		8,458		4,469
ROU assets obtained in exchange for operating lease liabilities	58,230		55,556		34,358
ROU assets obtained in exchange for finance lease liabilities	29,205		30,476		32,526

At December 31, 2022, the Company's future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands):


Years ending December 31,	December 31, 2022
	Operating Leases		Finance Leases
2023	$	57,757	$	17,085
2024	45,478		16,423
2025	32,739		15,748
2026	23,791		15,761
2027	14,635		15,748
Thereafter	11,564		33,950
Total future lease payments	185,964		114,715
Amount representing interest	(17,173)		(15,558)
Total lease liabilities	$	168,791	$	99,157

At December 31, 2022, none of the Company's executed leases that had not yet commenced will create significant rights or obligations in the future and sublease transactions are not material. Additionally, the Company does not have any related party leases, and there were no restrictions or covenants imposed by its leases.

LEASES


Finance Lease Balances (Classification)	December 31, 2022		December 31, 2021
ROU assets (Property, plant and equipment, net)	$	96,207	$	81,267
Current portion of lease liabilities (Accrued expenses)	12,767		10,893
Long-term portion of lease liabilities (Other long-term liabilities)	86,390		72,051

The Company’s lease expense was as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Operating lease cost	$	59,041	$	50,264	$	53,194

Finance lease cost:
Amortization of ROU assets	13,239		9,504		4,966
Interest on lease liabilities	3,011		2,544		1,523
Total finance lease cost	16,250		12,048		6,489

Short-term lease cost	158,736		102,913		70,692
Variable lease cost	4,353		3,546		3,691
Total lease cost	$	238,380	$	168,771	$	134,066

Other information related to leases was as follows:


Weighted Average Remaining Lease Term (years)	December 31, 2022		December 31, 2021
Operating leases	4.2		4.4
Finance leases	7.5		8.1

Weighted Average Discount Rate	December 31, 2022		December 31, 2021
Operating leases	4.08	%	4.35	%
Finance leases	3.53	%	3.65	%


	For the years ended December 31,
Supplemental Cash Flow Related Disclosures (in thousands)	2022		2021		2020
Cash paid for amounts related to lease liabilities:
Operating cash flows from operating leases	$	61,014	$	50,963	$	53,498
Operating cash flows from finance leases	3,011		2,544		1,523
Financing cash flows from finance leases	12,821		8,458		4,469
ROU assets obtained in exchange for operating lease liabilities	58,230		55,556		34,358
ROU assets obtained in exchange for finance lease liabilities	29,205		30,476		32,526

At December 31, 2022, the Company's future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands):


Years ending December 31,	December 31, 2022
	Operating Leases		Finance Leases
2023	$	57,757	$	17,085
2024	45,478		16,423
2025	32,739		15,748
2026	23,791		15,761
2027	14,635		15,748
Thereafter	11,564		33,950
Total future lease payments	185,964		114,715
Amount representing interest	(17,173)		(15,558)
Total lease liabilities	$	168,791	$	99,157

SEGMENT REPORTING

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

SEGMENT REPORTING

Segment reporting is prepared on the same basis that the Company's chief executive officer, who is the Company's chief operating decision maker, manages the business, makes operating decisions and assesses performance. The Company is managed and reports as two operating segments; (i) the Environmental Services segment and (ii) the Safety-Kleen Sustainability Solutions segment.

Third-party revenue is revenue billed to outside customers by a particular segment. Direct revenues is revenue allocated to the segment providing the product or service. Intersegment revenues represent the sharing of third-party revenues among the segments based on products and services provided by each segment as if the products and services were sold directly to the third-party. The intersegment revenues are shown net. The operations not managed through the Company’s operating segments described above are recorded as “Corporate Items.”

The following tables reconcile third-party revenues to direct revenues for the years ended December 31, 2022, 2021 and 2020 (in thousands):


	For the year ended December 31, 2022
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate Items		Totals
Third-party revenues	$	4,144,973	$	1,021,125	$	507	$	5,166,605
Intersegment revenues (expense), net	26,733		(26,733)		—		—
Direct revenues	$	4,171,706	$	994,392	$	507	$	5,166,605


	For the year ended December 31, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate Items		Totals
Third-party revenues	$	3,025,907	$	779,360	$	299	$	3,805,566
Intersegment revenues (expense), net	6,547		(6,547)		—		—
Direct revenues	$	3,032,454	$	772,813	$	299	$	3,805,566


	For the year ended December 31, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate Items		Totals
Third-party revenues	$	2,637,641	$	506,166	$	290	$	3,144,097
Intersegment revenues (expense), net	(1,740)		1,740		—		—
Direct revenues	$	2,635,901	$	507,906	$	290	$	3,144,097

The primary financial measure by which the Company evaluates the performance of its segments is Adjusted EBITDA, which consists of net income plus accretion of environmental liabilities, stock-based compensation, depreciation and amortization, net interest expense, loss on early extinguishment of debt and provision for income taxes and excludes other gains, losses and non-cash charges not deemed representative of fundamental segment results and other expense (income), net. Transactions between the segments are accounted for at the Company’s best estimate based on similar transactions with outside customers.

The following table presents Adjusted EBITDA information used by management by reported segment (in thousands):


	For the years ended December 31,
	2022		2021		2020
Adjusted EBITDA:
Environmental Services	$	953,053	$	659,718	$	665,918
Safety-Kleen Sustainability Solutions	306,327		227,354		83,214
Corporate Items	(237,252)		(210,466)		(175,328)
Total	1,022,128		676,606		573,804
Reconciliation to Consolidated Statements of Operations:

Accretion of environmental liabilities	12,943		11,745		11,051
Stock-based compensation	26,844		18,839		18,502
Depreciation and amortization	347,594		298,135		292,915

Income from operations	634,747		347,887		251,336
Other (income) expense, net	(2,472)		515		290
Loss on early extinguishment of debt	422		—		—
(Gain) loss on sale of businesses	(8,864)		—		3,376
Interest expense, net of interest income	107,663		77,657		73,120
Income from operations before provision for income taxes	$	537,998	$	269,715	$	174,550

The following table presents assets by reported segment and in the aggregate (in thousands):


	December 31, 2022		December 31, 2021
Property, plant and equipment, net
Environmental Services	$	1,467,641	$	1,374,913
Safety-Kleen Sustainability Solutions	398,660		373,721
Corporate Items	114,001		114,541
Total property, plant and equipment, net	$	1,980,302	$	1,863,175

Goodwill and Permits and other intangibles, net
Environmental Services
Goodwill	$	1,071,846	$	1,085,534
Permits and other intangibles, net	462,050		498,739
Total Environmental Services	1,533,896		1,584,273

Safety-Kleen Sustainability Solutions
Goodwill	$	175,032	$	141,508
Permits and other intangibles, net	158,732		146,173
Total Safety-Kleen Sustainability Solutions	333,764		287,681

Total	$	1,867,660	$	1,871,954

Geographic Information

As of December 31, 2022 and 2021, the Company had property, plant and equipment, net of depreciation and amortization and permits and other intangible assets, net of amortization in the following geographic locations (in thousands):


	December 31, 2022				December 31, 2021
	Total		% of Total		Total		% of Total
Property, plant and equipment, net
United States	$	1,765,291	89.1	%	$	1,610,402	86.4	%
Canada and other foreign	215,011		10.9		252,773		13.6
Total property, plant and equipment, net	$	1,980,302	100.0	%	$	1,863,175	100.0	%

Permits and other intangibles, net
United States	$	585,887	94.4	%	$	604,076	93.7	%
Canada and other foreign	34,895		5.6		40,836		6.3
Total permits and other intangibles, net	$	620,782	100.0	%	$	644,912	100.0	%

The following table presents the total assets by geographical area (in thousands):


	December 31, 2022		December 31, 2021
United States	$	5,595,255	$	5,077,585
Canada and other foreign	534,452		576,114

Total	$	6,129,707	$	5,653,699

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8721-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9031-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9038-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e9054-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 15
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI https://asc.fasb.org/topic&trid=2134510

+ Details

SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Principles of Consolidation

Principles of ConsolidationThe accompanying consolidated financial statements include the accounts of Clean Harbors, Inc. and its majority-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

Cash, Cash Equivalents, Marketable Securities and Uncashed Checks

Cash, Cash Equivalents, Marketable Securities and Uncashed ChecksCash consists primarily of cash on deposit and money market accounts. The Company, through its wholly-owned captive insurance subsidiary, invests in marketable securities. Marketable securities with maturities of three months or less from the date of purchase are classified as cash equivalents.

Cash, Cash Equivalents, Marketable Securities and Uncashed Checks

part of accounts payable and changes in the balance are reported as a financing activity in the consolidated statements of cash flows.

Allowances for Doubtful Accounts

Allowance for Doubtful Accounts and Revenue Allowance

Revenue Allowance

Allowance for Doubtful Accounts and Revenue Allowance

Credit Concentration

Inventories and Supplies

Property, Plant and Equipment, net (excluding landfill assets and finance lease right-of-use assets)

depreciates and amortizes the capitalized cost of these assets, using the straight-line method as follows:


Asset Classification						Estimated Useful Life
Buildings and building improvements
Buildings						20-42 years
Leasehold and building improvements						2-45 years
Camp and lodging equipment						8-15 years
Vehicles						2-15 years
Equipment
Capitalized software and computer equipment						3-5 years
Containers and railcars						8-16 years
All other equipment						4-30 years
Furniture and fixtures						5-8 years

Business Combinations

Business Combinations In accordance with the acquisition method of accounting, the purchase price paid for an acquisition is allocated to the assets and liabilities acquired based upon their estimated fair values as of the acquisition date, with the excess of the purchase price over the net assets acquired recorded as goodwill. As required, a preliminary fair value is determined once a business is acquired, with the final determination of the fair value being completed no later than one year from the date of acquisition.

Goodwill

Permits and Other Intangibles

Landfill Accounting


Facility Name	Location	Remaining Lives (Years)	Permitted Remaining Highly Probable Airspace (cubic yards) (in thousands)
Buttonwillow	California	20	5,197
Deer Trail	Colorado	23	1,488
Grassy Mountain	Utah	39	4,454
Kimball	Nebraska	5	116
Lambton	Ontario, Canada	47	4,443
Lone Mountain	Oklahoma	16	3,412
Ryley	Alberta, Canada	37	5,851
Sawyer	North Dakota	83	3,309
			28,270

At December 31, 2022 and 2021, the Company had no cubic yards of permitted, but not highly probable, airspace.

The following table presents the remaining highly probable airspace from January 1, 2021 through December 31, 2022 (in thousands of cubic yards):


	2022	2021
Remaining capacity, beginning of year	23,784	24,716
Changes in highly probable airspace, net	5,579	—
Consumed	(1,093)	(932)
Remaining capacity, end of year	28,270	23,784

Non-Landfill Closure and Post-Closure Liabilities

Remedial Liabilities

Self Insurance Liabilities

Self-Insurance Liabilities

actuarial estimates and judgments which consider the frequency and settlement amount of historical claims data and are discounted to present value using a risk-free interest rate.

Revenue recognition

Revenue Recognition

Foreign Currency

Defined Contribution Plan

Defined Contribution PlanThe Company has defined contribution plans under which eligible employees may contribute up to the maximum amount as provided by law.

Advertising Expense

Advertising ExpenseAdvertising costs are expensed as incurred.

Stock-Based Compensation

Interest Rate Derivatives

Income Taxes

Earnings per Share ("EPS")

Leases

SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2022

Accounting Policies [Abstract]

Schedule of Marketable Securities

As of December 31, 2022 and 2021, the Company had total marketable securities as follows (in thousands):


	December 31, 2022		December 31, 2021
Commercial paper	$	5,035	$	—
U.S. Treasury securities	28,973		—
Total cash equivalents	34,008		—

U.S. Treasury securities	—		901
Municipal bonds	1,930		1,978
Commercial paper	24,075		21,160
Corporate notes and bonds	36,028		57,685
Total marketable securities	62,033		81,724
Total	$	96,041	$	81,724

Schedule of Activity in Allowance for Doubtful Accounts

The following table reflects the activity in the allowance for doubtful accounts and revenue allowance (in thousands):


	Allowance for Doubtful Accounts						Revenue Allowance
	2022		2021		2020		2022		2021		2020
Balance at January 1,	$	24,136	$	24,634	$	22,493	$	16,004	$	20,115	$	16,218
Additions charged to earnings	7,783		8,018		10,133		54,836		34,319		45,784
Deductions from reserves, net of recoveries	(7,260)		(8,516)		(7,992)		(50,246)		(38,430)		(41,887)
Balance at December 31,	$	24,659	$	24,136	$	24,634	$	20,594	$	16,004	$	20,115

Schedule of Activity in Revenue Allowance

The following table reflects the activity in the allowance for doubtful accounts and revenue allowance (in thousands):


	Allowance for Doubtful Accounts						Revenue Allowance
	2022		2021		2020		2022		2021		2020
Balance at January 1,	$	24,136	$	24,634	$	22,493	$	16,004	$	20,115	$	16,218
Additions charged to earnings	7,783		8,018		10,133		54,836		34,319		45,784
Deductions from reserves, net of recoveries	(7,260)		(8,516)		(7,992)		(50,246)		(38,430)		(41,887)
Balance at December 31,	$	24,659	$	24,136	$	24,634	$	20,594	$	16,004	$	20,115

Schedule of Asset Classification and Estimated Useful Life

The Company

depreciates and amortizes the capitalized cost of these assets, using the straight-line method as follows:


Asset Classification						Estimated Useful Life
Buildings and building improvements
Buildings						20-42 years
Leasehold and building improvements						2-45 years
Camp and lodging equipment						8-15 years
Vehicles						2-15 years
Equipment
Capitalized software and computer equipment						3-5 years
Containers and railcars						8-16 years
All other equipment						4-30 years
Furniture and fixtures						5-8 years

Property, plant and equipment consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Land	$	172,579	$	165,010
Asset retirement costs (non-landfill)	22,001		19,105
Landfill assets	232,872		205,873
Buildings and improvements (1)	584,916		551,795
Camp equipment	116,976		127,680
Vehicles (2)	1,112,188		912,836
Equipment (3)	2,078,088		2,092,395
Furniture and fixtures	6,481		6,444
Construction in progress	140,328		60,447
	4,466,429		4,141,585
Less - accumulated depreciation and amortization	2,486,127		2,278,410
Total property, plant and equipment, net	$	1,980,302	$	1,863,175

___________________________________

(1) Balances inclusive of gross ROU assets classified as finance leases of $8.0 million and $8.9 million, respectively.

(2) Balances inclusive of gross ROU assets classified as finance leases of $106.7 million and $77.7 million, respectively.

(3) Balances inclusive of gross ROU assets classified as finance leases of $9.2 million and $9.3 million, respectively.

Schedule of Active Landfill Sites


Facility Name	Location	Remaining Lives (Years)	Permitted Remaining Highly Probable Airspace (cubic yards) (in thousands)
Buttonwillow	California	20	5,197
Deer Trail	Colorado	23	1,488
Grassy Mountain	Utah	39	4,454
Kimball	Nebraska	5	116
Lambton	Ontario, Canada	47	4,443
Lone Mountain	Oklahoma	16	3,412
Ryley	Alberta, Canada	37	5,851
Sawyer	North Dakota	83	3,309
			28,270

Schedule of Remaining Highly Probable Airspace

The following table presents the remaining highly probable airspace from January 1, 2021 through December 31, 2022 (in thousands of cubic yards):


	2022	2021
Remaining capacity, beginning of year	23,784	24,716
Changes in highly probable airspace, net	5,579	—
Consumed	(1,093)	(932)
Remaining capacity, end of year	28,270	23,784

REVENUES (Tables)

12 Months Ended

Dec. 31, 2022

Revenue from Contract with Customer [Abstract]

Schedule of Disaggregation of Revenue

The following tables present the Company's third-party revenue disaggregated by source of revenue and geography (in thousands):


	For the year ended December 31, 2022
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	3,675,880	$	899,780	$	507	$	4,576,167
Canada	469,093		121,345		—		590,438
Total third-party revenues	$	4,144,973	$	1,021,125	$	507	$	5,166,605

Sources of Revenue
Technical Services	$	1,495,264	$	—	$	—	$	1,495,264
Industrial Services and Other	1,311,072		—		507		1,311,579
Field and Emergency Response Services	575,300		—		—		575,300
Safety-Kleen Environmental Services	763,337		199,360		—		962,697
Safety-Kleen Oil	—		821,765		—		821,765
Total third-party revenues	$	4,144,973	$	1,021,125	$	507	$	5,166,605


	For the year ended December 31, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	2,631,112	$	693,542	$	299	$	3,324,953
Canada	394,795		85,818		—		480,613
Total third-party revenues	$	3,025,907	$	779,360	$	299	$	3,805,566

Sources of Revenue
Technical Services	$	1,209,624	$	—	$	—	$	1,209,624
Industrial Services and Other	705,999		—		299		706,298
Field and Emergency Response Services	466,380		—		—		466,380
Safety-Kleen Environmental Services	643,904		161,587		—		805,491
Safety-Kleen Oil	—		617,773		—		617,773
Total third-party revenues	$	3,025,907	$	779,360	$	299	$	3,805,566


	For the year ended December 31, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate		Total
Primary Geographical Markets
United States	$	2,287,796	$	452,435	$	(674)	$	2,739,557
Canada	349,845		53,731		964		404,540
Total third-party revenues	$	2,637,641	$	506,166	$	290	$	3,144,097

Sources of Revenue
Technical Services	$	1,062,714	$	—	$	—	$	1,062,714
Industrial Services and Other	480,331		—		290		480,621
Field and Emergency Response Services	461,036		—		—		461,036
Safety-Kleen Environmental Services	633,560		175,676		—		809,236
Safety-Kleen Oil	—		330,490		—		330,490
Total third-party revenues	$	2,637,641	$	506,166	$	290	$	3,144,097

Schedule of Contract Balances

Contract Balances


(in thousands)	December 31, 2022		December 31, 2021
Receivables	$	964,603	$	792,734
Contract assets (unbilled receivables)	107,010		94,963
Contract liabilities (deferred revenue)	94,094		83,749

BUSINESS COMBINATIONS (Tables)

12 Months Ended

Dec. 31, 2022

Business Combination and Asset Acquisition [Abstract]

Schedule of Allocation of Purchase Price

The following table summarizes the preliminary determination and recognition of assets acquired and liabilities assumed (in thousands):


	At Acquisition Date As Reported December 31, 2022
Accounts receivable	$	1,111
Inventories and supplies	5,816
Prepaid expenses and other current assets	144
Property, plant and equipment	19,605
Permits and other intangibles	23,500
Operating lease right-of-use assets	585
Other non-current assets	13
Current liabilities	(3,271)
Current portion of operating lease liabilities	(186)
Operating lease liabilities, less current portion	(399)

Other long-term liabilities	(55)
Total identifiable net assets	46,863
Goodwill	32,015
Total purchase price	$	78,878

The following table summarizes the final determination and recognition of assets acquired and liabilities assumed (in thousands):


	At Acquisition Date As Reported December 31, 2021		Measurement Period Adjustments		Final Allocation at Acquisition Date As Reported December 31, 2022
Accounts receivable, including unbilled receivables	$	131,924	$	(408)	$	131,516
Inventories and supplies	3,162		—		3,162
Prepaid expenses and other current assets	16,016		275		16,291
Property, plant and equipment	313,540		857		314,397
Other intangibles	289,000		—		289,000
Operating lease right-of-use assets	34,347		68		34,415
Other non-current assets	1,045		(83)		962
Current liabilities	(115,704)		(3,150)		(118,854)
Current portion of operating lease liabilities	(11,659)		382		(11,277)
Operating lease liabilities, less current portion	(26,128)		(216)		(26,344)
Deferred tax liabilities	(85,908)		5,522		(80,386)
Other long-term liabilities	(2,685)		(1,485)		(4,170)
Total identifiable net assets	546,950		1,762		548,712
Goodwill (i)	683,463		(6,762)		676,701
Total purchase price	$	1,230,413	$	(5,000)	$	1,225,413

_____________

Business Acquisition, Pro Forma Information


	2021		2020
Pro forma combined revenues	$	4,380,724	$	3,859,430
Pro forma combined net income	229,807		149,219

INVENTORIES AND SUPPLIES (Tables)

12 Months Ended

Dec. 31, 2022

Inventory Disclosure [Abstract]

Schedule of Inventories

Inventories and supplies consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Oil and oil related products	$	151,519	$	101,965
Supplies	143,743		126,602
Solvent and solutions	11,994		8,099
Other	17,738		14,026
Total inventories and supplies	$	324,994	$	250,692

PROPERTY, PLANT, AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2022

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

The Company

depreciates and amortizes the capitalized cost of these assets, using the straight-line method as follows:


Asset Classification						Estimated Useful Life
Buildings and building improvements
Buildings						20-42 years
Leasehold and building improvements						2-45 years
Camp and lodging equipment						8-15 years
Vehicles						2-15 years
Equipment
Capitalized software and computer equipment						3-5 years
Containers and railcars						8-16 years
All other equipment						4-30 years
Furniture and fixtures						5-8 years

Property, plant and equipment consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Land	$	172,579	$	165,010
Asset retirement costs (non-landfill)	22,001		19,105
Landfill assets	232,872		205,873
Buildings and improvements (1)	584,916		551,795
Camp equipment	116,976		127,680
Vehicles (2)	1,112,188		912,836
Equipment (3)	2,078,088		2,092,395
Furniture and fixtures	6,481		6,444
Construction in progress	140,328		60,447
	4,466,429		4,141,585
Less - accumulated depreciation and amortization	2,486,127		2,278,410
Total property, plant and equipment, net	$	1,980,302	$	1,863,175

___________________________________

(1) Balances inclusive of gross ROU assets classified as finance leases of $8.0 million and $8.9 million, respectively.

(2) Balances inclusive of gross ROU assets classified as finance leases of $106.7 million and $77.7 million, respectively.

(3) Balances inclusive of gross ROU assets classified as finance leases of $9.2 million and $9.3 million, respectively.

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes to Goodwill

The changes in goodwill for the years ended December 31, 2022 and 2021 were as follows (in thousands):


	Environmental Services		Safety-Kleen Sustainability Solutions		Totals
Balance at January 1, 2021	$	401,918	$	125,105	$	527,023
Increase from current period acquisitions	683,463		16,349		699,812



Foreign currency translation	153		54		207
Balance at December 31, 2021	$	1,085,534	$	141,508	$	1,227,042
Increase from current period acquisitions	—		34,510		34,510
Measurement period adjustments from prior period acquisition	(6,762)		—		(6,762)
Decrease from disposition of business	(4,412)		—		(4,412)
Foreign currency translation	(2,514)		(986)		(3,500)
Balance at December 31, 2022	$	1,071,846	$	175,032	$	1,246,878

Schedule of Finite-Lived Intangible Assets by Major Class

As of December 31, 2022 and 2021, the Company's finite-lived and indefinite-lived intangible assets consisted of the following (in thousands):


	December 31, 2022						December 31, 2021
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	188,373	$	109,036	$	79,337	$	187,519	$	102,408	$	85,111
Customer and supplier relationships	583,709		229,368		354,341		576,474		214,776		361,698
Other intangible assets	89,388		24,818		64,570		94,271		19,359		74,912
Total amortizable permits and other intangible assets	861,470		363,222		498,248		858,264		336,543		521,721
Trademarks and trade names	122,534		—		122,534		123,191		—		123,191
Total permits and other intangible assets	$	984,004	$	363,222	$	620,782	$	981,455	$	336,543	$	644,912

Schedule of Indefinite-Lived Intangible Assets

As of December 31, 2022 and 2021, the Company's finite-lived and indefinite-lived intangible assets consisted of the following (in thousands):


	December 31, 2022						December 31, 2021
	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
Permits	$	188,373	$	109,036	$	79,337	$	187,519	$	102,408	$	85,111
Customer and supplier relationships	583,709		229,368		354,341		576,474		214,776		361,698
Other intangible assets	89,388		24,818		64,570		94,271		19,359		74,912
Total amortizable permits and other intangible assets	861,470		363,222		498,248		858,264		336,543		521,721
Trademarks and trade names	122,534		—		122,534		123,191		—		123,191
Total permits and other intangible assets	$	984,004	$	363,222	$	620,782	$	981,455	$	336,543	$	644,912

Schedule of Expected Amortization for the Net Carrying Amount of Finite Lived Intangible Assets

The expected amortization of the net carrying amount of finite-lived intangible assets at December 31, 2022 is as follows (in thousands):


Years ending December 31,	Expected Amortization
2023	$	46,030
2024	41,814
2025	39,828
2026	37,943
2027	35,869
Thereafter	296,764
	$	498,248

- Definition

Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=121556970&loc=SL108378252-109267

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13854-109267

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 55
-Paragraph 24
-URI https://asc.fasb.org/extlink&oid=122137925&loc=d3e14258-109268

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

ACCRUED EXPENSES (Tables)

12 Months Ended

Dec. 31, 2022

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31, 2022		December 31, 2021
Accrued insurance	$	92,909	$	102,853
Accrued interest	20,033		19,785
Accrued compensation and benefits	123,226		133,604
Accrued income, real estate, sales and other taxes	61,442		29,954
Interest rate swap liability	—		17,383
Accrued other	99,106		87,835
	$	396,716	$	391,414

CLOSURE AND POST-CLOSURE LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2022

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Closure and Post-Closure Liabilities

The changes to closure and post-closure liabilities (also referred to as "asset retirement obligations") from January 1, 2021 through December 31, 2022 were as follows (in thousands):


	Landfill Retirement Liability		Non-Landfill Retirement Liability		Total
Balance at January 1, 2021	$	48,412	$	39,514	$	87,926
Liabilities assumed in acquisitions	—		1,446		1,446
New asset retirement obligations	2,443		—		2,443
Accretion	3,655		3,702		7,357
Changes in estimates recorded to consolidated statement of operations	2,287		396		2,683
Changes in estimates recorded to consolidated balance sheet	2,297		1,415		3,712
Expenditures	(5,818)		(784)		(6,602)
Currency translation and other	149		(11)		138
Balance at December 31, 2021	53,425		45,678		99,103
Liabilities assumed in acquisitions	—		55		55
Measurement period adjustments from prior period acquisitions	—		1,148		1,148
New asset retirement obligations	3,743		—		3,743
Accretion	4,605		4,147		8,752
Changes in estimates recorded to consolidated statement of operations	1,063		5,712		6,775
Changes in estimates recorded to consolidated balance sheet	3,219		1,742		4,961
Expenditures	(3,373)		(1,778)		(5,151)
Currency translation and other	(431)		(154)		(585)
Balance at December 31, 2022	$	62,251	$	56,550	$	118,801

Schedule of Expected Payments Related to Asset Retirement Obligations


Years ending December 31,
2023	$	14,414
2024	14,733
2025	12,808
2026	8,369
2027	7,420
Thereafter	290,366
Undiscounted closure and post-closure liabilities	348,110
Less: Discount at credit-adjusted risk-free rate	(153,062)
Less: Undiscounted estimated closure and post-closure liabilities relating to airspace not yet consumed	(76,247)
Present value of closure and post-closure liabilities	$	118,801

REMEDIAL LIABILITIES (Tables)

12 Months Ended

Dec. 31, 2022

Environmental Remediation Obligations [Abstract]

Schedule of Changes to Remedial Liabilities

The changes to remedial liabilities from January 1, 2021 through December 31, 2022 were as follows (in thousands):


	Remedial Liabilities for Landfill Sites		Remedial Liabilities for Inactive Sites		Remedial Liabilities (Including Superfund) for Non-Landfill Operations		Total
Balance at January 1, 2021	$	1,865	$	63,060	$	49,888	$	114,813
Liabilities assumed in acquisitions	—		—		1,216		1,216
Accretion	90		2,614		1,684		4,388
Changes in estimates recorded to consolidated statement of operations	(126)		(178)		600		296
Expenditures	(49)		(4,889)		(3,966)		(8,904)
Currency translation and other	—		(820)		884		64
Balance at December 31, 2021	1,780		59,787		50,306		111,873
Liabilities assumed in acquisition of real estate	—		—		8,092		8,092
Measurement period adjustments from prior period acquisition	—		—		338		338
Accretion	86		2,498		1,607		4,191
Changes in estimates recorded to consolidated statement of operations	8		877		612		1,497
Expenditures	(50)		(3,370)		(5,375)		(8,795)
Currency translation and other	—		(43)		(863)		(906)
Balance at December 31, 2022	$	1,824	$	59,749	$	54,717	$	116,290

Schedule of Remedial Liabilities Anticipated Payments for Each of the Next Five Years


Years ending December 31,
2023	$	10,793
2024	20,912
2025	12,065
2026	7,581
2027	6,390
Thereafter	76,416
Undiscounted remedial liabilities	134,157
Less: Discount at risk free rates	(17,867)
Total remedial liabilities	$	116,290

Schedule of Environmental Exit Costs by Cost


Type of Facility or Site	Remedial Liabilities		% of Total		Reasonably Possible Additional Liabilities (1)
Inactive facilities not used in active conduct of the Company's business, most of which were assumed through prior period acquisitions (25 facilities)	$	59,759	51.4	%	$	10,295
Facilities now used in active conduct of the Company's business (45 facilities)	47,951		41.2		11,189
Superfund sites (16 sites)	8,580		7.4		1,288
Total	$	116,290	100.0	%	$	22,772

___________________________________

(1)Amounts represent the high end of the range of management's best estimate of the reasonably possible additional liabilities.


Location	Type of Facility or Site	Remedial Liabilities(1)		% of Total		Reasonably Possible Additional Liabilities(2)
Baton Rouge, LA	Closed incinerator and landfill	$	26,604	22.9	%	$	4,547
Bridgeport, NJ	Closed incinerator	18,089		15.6		3,364
Linden, NJ	Operating solvent recycling center	14,479		12.5		3,352
Mercier, Quebec	Idled incinerator	10,996		9.5		1,659
Various	All other incinerators, landfills, wastewater treatment facilities and service centers (66 facilities)	37,542		32.1		8,562
Various	Superfund sites (each representing less than 5% of total liabilities) (16 sites)	8,580		7.4		1,288
Total		$	116,290	100.0	%	$	22,772

_________________________________

(1)$24.1 million of the $116.3 million remedial liabilities include estimates related to the legal and administrative proceedings discussed in Note 18, "Commitments and Contingencies."

(2)Amounts represent the high end of the range of management's best estimate of the reasonably possible additional liabilities.

FINANCING ARRANGEMENTS (Tables)

12 Months Ended

Dec. 31, 2022

Debt Disclosure [Abstract]

Schedule of Long-term Debt

The following table is a summary of the Company's long-term debt (in thousands):


Current Portion of Long-Term Debt:	December 31, 2022		December 31, 2021
Secured senior term loans	$	10,000	$	17,535


Long-Term Debt:
Secured senior term loans due June 30, 2024 ("2024 Term Loans")	$	613,975	$	712,091
Secured senior term loans due October 8, 2028 ("2028 Term Loans")	980,000		990,000
Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")	545,000		545,000
Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")	300,000		300,000
Long-term debt, at par	2,438,975		2,547,091
Unamortized debt issuance costs and discount, net	(24,147)		(30,067)
Long-term debt, at carrying value	$	2,414,828	$	2,517,024

Schedule of Redemption Prices

2027 Notes


Year	Percentage
July 15, 2022	102.438	%
July 15, 2023	101.219	%
July 15, 2024 and thereafter	100.000	%

2029 Notes


Year	Percentage
July 15, 2024	102.563	%
July 15, 2025	101.281	%
July 15, 2026 and thereafter	100.000	%

2031 Notes


Year	Percentage
February 1, 2026	103.188	%
February 1, 2027	101.594	%
February 1, 2028 and thereafter	100.000	%

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28541-108399

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21506-112644

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69B
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69E
-URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495743-112612

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21521-112644

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21538-112644

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

Reference 11: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21475-112644

+ Details

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2022

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign

The domestic and foreign components of income before provision for income taxes were as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Domestic	$	406,206	$	223,438	$	168,117
Foreign	131,792		46,277		6,433
Total	$	537,998	$	269,715	$	174,550

Schedule of Components of Provision for Income Taxes

The provision for income taxes consisted of the following (in thousands, except percentages):


	For the years ended December 31,
	2022		2021		2020
Current:
Federal	$	52,237	$	42,480	$	33,327
State	26,980		18,126		14,575
Foreign	29,488		4,380		1,559
	108,705		64,986		49,461
Deferred
Federal	32,199		2,275		(965)
State	(2,432)		(4,777)		(2,506)
Foreign	(12,218)		3,984		(6,277)
	17,549		1,482		(9,748)
Provision for income taxes	$	126,254	$	66,468	$	39,713

Effective tax rate	23.5%		24.6%		22.8%

Schedule of Effective Income Tax Rate Reconciliation

The Company's effective income tax rate varied from the amount computed using the statutory federal income tax rate of 21% as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Tax expense at U.S. statutory rate	$	112,980	$	56,640	$	36,655
State income taxes, net of federal benefit	19,831		12,101		9,837
Foreign rate differential	6,196		1,922		1,256
Valuation allowance	(18,769)		(9,139)		(11,339)
Uncertain tax position interest and penalties	(2,454)		263		(712)
Tax credits expired	2,768		2,530		2,039
Non-deductible compensation	2,754		2,326		1,406
Other	2,948		(175)		571
Provision for income taxes	$	126,254	$	66,468	$	39,713

Schedule of Deferred Tax Assets and Liabilities

The components of the total net deferred tax assets and liabilities as of December 31, 2022 and 2021 were as follows (in thousands):


	2022		2021
Deferred tax assets:

Provision for doubtful accounts	$	11,544	$	10,188
Closure, post-closure and remedial liabilities	31,837		28,206
Operating lease liabilities	42,255		42,218
Accrued expenses	19,311		20,455
Accrued compensation and benefits	20,171		24,504
Net operating loss carryforwards(1)	41,585		68,381
Tax credit carryforwards(2)	8,903		12,368
Interest rate swap liability	—		5,215
Stock-based compensation	3,988		2,705
Other	7,487		5,635
Total deferred tax assets	187,081		219,875
Deferred tax liabilities:
Property, plant and equipment	(281,131)		(273,883)
Operating lease right-of-use assets	(41,939)		(41,260)
Interest rate swap asset	(17,587)		—
Permits and other intangible assets	(132,681)		(138,241)
Prepaid expenses	(12,088)		(10,212)
Total deferred tax liabilities	(485,426)		(463,596)
Total net deferred tax liability before valuation allowance	(298,345)		(243,721)
Less valuation allowance	(42,509)		(69,806)
Net deferred tax liabilities	$	(340,854)	$	(313,527)

___________________________________

(2)As of December 31, 2022, the foreign tax credit carryforwards of $7.7 million will expire between 2023 and 2024.

Schedule of Valuation Allowance

The components of the total valuation allowance as of December 31, 2022 and 2021 were as follows (in thousands):


	2022		2021
Allowance related to:
Foreign tax credits	7,666		11,047
Federal net operating losses	3,783		3,788
State net operating loss carryforwards	9,928		12,053
Foreign net operating loss carryforwards	15,488		26,697
Deferred tax assets of a Canadian subsidiary	5,339		10,701
Realized and unrealized capital losses	305		5,520
Total valuation allowance	$	42,509	$	69,806

EARNINGS PER SHARE (Tables)

12 Months Ended

Dec. 31, 2022

Earnings Per Share [Abstract]

Reconciliation of Basic and Diluted Earnings Per Share Computations

The following are computations of basic and diluted earnings per share (in thousands, except for per share amounts):


	For the years ended December 31,
	2022		2021		2020
Numerator for basic and diluted earnings per share:
Net income	$	411,744	$	203,247	$	134,837
Denominator:
Weighted basic shares outstanding	54,223		54,514		55,479
Dilutive effect of equity-based compensation awards	264		247		211
Weighted dilutive shares outstanding	54,487		54,761		55,690

Basic earnings per share	$	7.59	$	3.73	$	2.43
Diluted earnings per share	$	7.56	$	3.71	$	2.42

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)

12 Months Ended

Dec. 31, 2022

Equity [Abstract]

Schedule of Reclassification of Accumulated Other Comprehensive Income (Loss)

The changes in accumulated other comprehensive loss by component and related tax impacts for the years ended December 31, 2022, 2021 and 2020 were as follows (in thousands):


	Foreign Currency Translation Adjustments		Unrealized Gain (Loss) on Available-For-Sale Securities		Unrealized (Loss) Gain on Fair Value of Interest Rate Hedges		Unrealized Loss on Unfunded Pension Liability		Total
Balance at January 1, 2020	$	(187,795)	$	143	$	(20,839)	$	(1,560)	$	(210,051)
Other comprehensive income (loss) before reclassifications	10,212		(10)		(20,970)		(255)		(11,023)
Amounts reclassified out of accumulated other comprehensive loss	—		—		8,180		—		8,180
Tax benefit	1,349		2		—		66		1,417
Other comprehensive income (loss)	11,561		(8)		(12,790)		(189)		(1,426)
Balance at December 31, 2020	(176,234)		135		(33,629)		(1,749)		(211,477)
Other comprehensive (loss) income before reclassifications	(1,590)		(361)		6,235		1,411		5,695
Amounts reclassified out of accumulated other comprehensive loss	—		—		10,011		—		10,011
Tax benefit (provision)	—		76		—		(317)		(241)
Other comprehensive (loss) income	(1,590)		(285)		16,246		1,094		15,465
Balance at December 31, 2021	(177,824)		(150)		(17,383)		(655)		(196,012)
Other comprehensive (loss) income before reclassifications	(31,515)		(523)		78,711		415		47,088
Amounts reclassified out of accumulated other comprehensive loss	—		—		(683)		—		(683)
Tax benefit (provision)	—		110		(17,587)		(97)		(17,574)
Other comprehensive (loss) income	(31,515)		(413)		60,441		318		28,831
Balance at December 31, 2022	$	(209,339)	$	(563)	$	43,058	$	(337)	$	(167,181)

Schedule of Reclassification out of Accumulated Other Comprehensive Income


	For the years ended December 31,
Other Comprehensive Loss Component	2022	2021	2020	Location

Unrealized (Loss) Gain on Fair Value of Interest Rate Hedges	683	(10,011)	(8,180)	Interest expense, net of interest income

STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Restricted Stock

The following table summarizes information about restricted stock awards for the year ended December 31, 2022:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2022	452,197	$	76.88
Granted	165,149	94.88
Vested	(167,086)	74.37
Forfeited	(23,118)	80.17
Balance at December 31, 2022	427,142	$	84.64

Schedule of Performance Stock Awards

The following table summarizes information about performance stock awards for the year ended December 31, 2022:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2022	169,757	$	85.56
Granted	156,687	92.60
Vested	(100,892)	83.51
Forfeited	(11,873)	86.87
Balance at December 31, 2022	213,679	$	91.62

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2022

Commitments and Contingencies Disclosure [Abstract]

Schedule of Self-Insurance Liabilities Anticipated Payments


Years ending December 31,
2023	$	26,736
2024	16,317
2025	12,172
2026	8,170
2027	6,318
Thereafter	10,631
Undiscounted self-insurance liabilities	80,344
Less: Discount	(5,452)
Total self-insurance liabilities (included in accrued expenses)	$	74,892

LEASES (Tables)

12 Months Ended

Dec. 31, 2022

Leases [Abstract]

Schedule of Supplemental Lease Balance Sheet Information

The following table presents the Company's finance lease balances and their classification on the consolidated balance sheets (in thousands):


Finance Lease Balances (Classification)	December 31, 2022		December 31, 2021
ROU assets (Property, plant and equipment, net)	$	96,207	$	81,267
Current portion of lease liabilities (Accrued expenses)	12,767		10,893
Long-term portion of lease liabilities (Other long-term liabilities)	86,390		72,051

Schedule of Lease Expense and Other Information

The Company’s lease expense was as follows (in thousands):


	For the years ended December 31,
	2022		2021		2020
Operating lease cost	$	59,041	$	50,264	$	53,194

Finance lease cost:
Amortization of ROU assets	13,239		9,504		4,966
Interest on lease liabilities	3,011		2,544		1,523
Total finance lease cost	16,250		12,048		6,489

Short-term lease cost	158,736		102,913		70,692
Variable lease cost	4,353		3,546		3,691
Total lease cost	$	238,380	$	168,771	$	134,066

Other information related to leases was as follows:


Weighted Average Remaining Lease Term (years)	December 31, 2022		December 31, 2021
Operating leases	4.2		4.4
Finance leases	7.5		8.1

Weighted Average Discount Rate	December 31, 2022		December 31, 2021
Operating leases	4.08	%	4.35	%
Finance leases	3.53	%	3.65	%


	For the years ended December 31,
Supplemental Cash Flow Related Disclosures (in thousands)	2022		2021		2020
Cash paid for amounts related to lease liabilities:
Operating cash flows from operating leases	$	61,014	$	50,963	$	53,498
Operating cash flows from finance leases	3,011		2,544		1,523
Financing cash flows from finance leases	12,821		8,458		4,469
ROU assets obtained in exchange for operating lease liabilities	58,230		55,556		34,358
ROU assets obtained in exchange for finance lease liabilities	29,205		30,476		32,526

Schedule of Operating Lease Maturity

At December 31, 2022, the Company's future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands):


Years ending December 31,	December 31, 2022
	Operating Leases		Finance Leases
2023	$	57,757	$	17,085
2024	45,478		16,423
2025	32,739		15,748
2026	23,791		15,761
2027	14,635		15,748
Thereafter	11,564		33,950
Total future lease payments	185,964		114,715
Amount representing interest	(17,173)		(15,558)
Total lease liabilities	$	168,791	$	99,157

Schedule of Finance Lease Maturity

At December 31, 2022, the Company's future lease payments under non-cancelable leases that have lease terms in excess of one year were as follows (in thousands):


Years ending December 31,	December 31, 2022
	Operating Leases		Finance Leases
2023	$	57,757	$	17,085
2024	45,478		16,423
2025	32,739		15,748
2026	23,791		15,761
2027	14,635		15,748
Thereafter	11,564		33,950
Total future lease payments	185,964		114,715
Amount representing interest	(17,173)		(15,558)
Total lease liabilities	$	168,791	$	99,157

SEGMENT REPORTING (Tables)

12 Months Ended

Dec. 31, 2022

Segment Reporting [Abstract]

Schedule of Reconciliation of Third Party Revenues to Direct Revenues

The following tables reconcile third-party revenues to direct revenues for the years ended December 31, 2022, 2021 and 2020 (in thousands):


	For the year ended December 31, 2022
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate Items		Totals
Third-party revenues	$	4,144,973	$	1,021,125	$	507	$	5,166,605
Intersegment revenues (expense), net	26,733		(26,733)		—		—
Direct revenues	$	4,171,706	$	994,392	$	507	$	5,166,605


	For the year ended December 31, 2021
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate Items		Totals
Third-party revenues	$	3,025,907	$	779,360	$	299	$	3,805,566
Intersegment revenues (expense), net	6,547		(6,547)		—		—
Direct revenues	$	3,032,454	$	772,813	$	299	$	3,805,566


	For the year ended December 31, 2020
	Environmental Services		Safety-Kleen Sustainability Solutions		Corporate Items		Totals
Third-party revenues	$	2,637,641	$	506,166	$	290	$	3,144,097
Intersegment revenues (expense), net	(1,740)		1,740		—		—
Direct revenues	$	2,635,901	$	507,906	$	290	$	3,144,097

Schedule of Reconciliation to Consolidated Statements of Income to Adjusted EBITDA

The following table presents Adjusted EBITDA information used by management by reported segment (in thousands):


	For the years ended December 31,
	2022		2021		2020
Adjusted EBITDA:
Environmental Services	$	953,053	$	659,718	$	665,918
Safety-Kleen Sustainability Solutions	306,327		227,354		83,214
Corporate Items	(237,252)		(210,466)		(175,328)
Total	1,022,128		676,606		573,804
Reconciliation to Consolidated Statements of Operations:

Accretion of environmental liabilities	12,943		11,745		11,051
Stock-based compensation	26,844		18,839		18,502
Depreciation and amortization	347,594		298,135		292,915

Income from operations	634,747		347,887		251,336
Other (income) expense, net	(2,472)		515		290
Loss on early extinguishment of debt	422		—		—
(Gain) loss on sale of businesses	(8,864)		—		3,376
Interest expense, net of interest income	107,663		77,657		73,120
Income from operations before provision for income taxes	$	537,998	$	269,715	$	174,550

Schedule of Segment Reporting Information, by Segment

The following table presents assets by reported segment and in the aggregate (in thousands):


	December 31, 2022		December 31, 2021
Property, plant and equipment, net
Environmental Services	$	1,467,641	$	1,374,913
Safety-Kleen Sustainability Solutions	398,660		373,721
Corporate Items	114,001		114,541
Total property, plant and equipment, net	$	1,980,302	$	1,863,175

Goodwill and Permits and other intangibles, net
Environmental Services
Goodwill	$	1,071,846	$	1,085,534
Permits and other intangibles, net	462,050		498,739
Total Environmental Services	1,533,896		1,584,273

Safety-Kleen Sustainability Solutions
Goodwill	$	175,032	$	141,508
Permits and other intangibles, net	158,732		146,173
Total Safety-Kleen Sustainability Solutions	333,764		287,681

Total	$	1,867,660	$	1,871,954

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas


	December 31, 2022				December 31, 2021
	Total		% of Total		Total		% of Total
Property, plant and equipment, net
United States	$	1,765,291	89.1	%	$	1,610,402	86.4	%
Canada and other foreign	215,011		10.9		252,773		13.6
Total property, plant and equipment, net	$	1,980,302	100.0	%	$	1,863,175	100.0	%

Permits and other intangibles, net
United States	$	585,887	94.4	%	$	604,076	93.7	%
Canada and other foreign	34,895		5.6		40,836		6.3
Total permits and other intangibles, net	$	620,782	100.0	%	$	644,912	100.0	%

Schedule of Long-lived Assets by Geographic Areas

The following table presents the total assets by geographical area (in thousands):


	December 31, 2022		December 31, 2021
United States	$	5,595,255	$	5,077,585
Canada and other foreign	534,452		576,114

Total	$	6,129,707	$	5,653,699

SIGNIFICANT ACCOUNTING POLICIES - Cash, Cash Equivalents and Uncashed Checks (Details)	Dec. 31, 2022 USD ($)
Accounting Policies [Abstract]
Bank disbursement account balance	$ 0

SIGNIFICANT ACCOUNTING POLICIES - Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Total cash equivalents	$ 34,008	$ 0
Total marketable securities	62,033	81,724
Total	96,041	81,724
Commercial paper
Marketable Securities [Line Items]
Total marketable securities	24,075	21,160
U.S. Treasury securities
Marketable Securities [Line Items]
Total marketable securities	0	901
Municipal bonds
Marketable Securities [Line Items]
Total marketable securities	1,930	1,978
Corporate notes and bonds
Marketable Securities [Line Items]
Total marketable securities	36,028	57,685
Commercial paper
Marketable Securities [Line Items]
Total cash equivalents	5,035	0
U.S. Treasury securities
Marketable Securities [Line Items]
Total cash equivalents	$ 28,973	$ 0

SIGNIFICANT ACCOUNTING POLICIES - Allowances for Doubtful Accounts And Revenue Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1,	$ 24,136	$ 24,634	$ 22,493
Additions charged to earnings	7,783	8,018	10,133
Deductions from reserves, net of recoveries	(7,260)	(8,516)	(7,992)
Balance at December 31,	24,659	24,136	24,634
Revenue Allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1,	16,004	20,115	16,218
Additions charged to earnings	54,836	34,319	45,784
Deductions from reserves, net of recoveries	(50,246)	(38,430)	(41,887)
Balance at December 31,	$ 20,594	$ 16,004	$ 20,115

SIGNIFICANT ACCOUNTING POLICIES - Property, Plant and Equipment, net (Details)	12 Months Ended
	Dec. 31, 2022
Minimum \| Buildings
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	20 years
Minimum \| Leasehold and building improvements
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	2 years
Minimum \| Camp and lodging equipment
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	8 years
Minimum \| Vehicles
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	2 years
Minimum \| Capitalized software and computer equipment
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	3 years
Minimum \| Containers and railcars
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	8 years
Minimum \| All other equipment
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	4 years
Minimum \| Furniture and fixtures
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	5 years
Maximum \| Buildings
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	42 years
Maximum \| Leasehold and building improvements
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	45 years
Maximum \| Camp and lodging equipment
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	15 years
Maximum \| Vehicles
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	15 years
Maximum \| Capitalized software and computer equipment
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	5 years
Maximum \| Containers and railcars
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	16 years
Maximum \| All other equipment
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	30 years
Maximum \| Furniture and fixtures
Property, Plant and Equipment [Line Items]
Weighted average remaining useful life (in years)	8 years

SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details)	12 Months Ended
SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details)	Dec. 31, 2022 reportingUnit
Accounting Policies [Abstract]
Number of reporting units	3

SIGNIFICANT ACCOUNTING POLICIES - Permits and Other Intangibles (Details)	12 Months Ended
	Dec. 31, 2022
Minimum \| Permits
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life (in years)	5 years
Minimum \| Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life (in years)	2 years
Maximum \| Permits
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life (in years)	30 years
Maximum \| Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life (in years)	25 years

SIGNIFICANT ACCOUNTING POLICIES - Landfill Accounting (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) cubic_yard landfill_site	Dec. 31, 2021 USD ($) cubic_yard	Dec. 31, 2020 USD ($) cubic_yard
Property, Plant and Equipment [Line Items]
Landfill sites \| landfill_site	9
Permitted, but not highly probable airspace (cubic yards)	0	0
Remaining Airspace Capacity [Roll Forward]
Remaining capacity, beginning of period (cubic yards)	23,784,000	24,716,000
Changes in highly probable airspace, net (cubic yards)	5,579,000	0
Consumed (cubic yards)	(1,093,000)	(932,000)
Remaining capacity, end of period (cubic yards)	28,270,000	23,784,000	24,716,000
Landfill final closure and post-closure liabilities \| $	$ 62.3	$ 53.4
Regulatory post-closure period for landfill (in years)	30 years
Asset retirement obligations, risk free rate (as a percent)	5.37%	4.84%
Non-landfill closure and post-closure liabilities \| $	$ 56.6	$ 45.7
Minimum
Remaining Airspace Capacity [Roll Forward]
Non-landfill closure and post-closure liabilities, period (in years)	10 years
Maximum
Remaining Airspace Capacity [Roll Forward]
Non-landfill closure and post-closure liabilities, period (in years)	30 years
Buttonwillow \| California
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	20 years
Deer Trail \| Colorado
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	23 years
Grassy Mountain \| Utah
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	39 years
Kimball \| Nebraska
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	5 years
Lambton \| Ontario, Canada
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	47 years
Lone Mountain \| Oklahoma
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	16 years
Ryley \| Alberta, Canada
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	37 years
Sawyer \| North Dakota
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	83 years
Landfill assets
Property, Plant and Equipment [Line Items]
Amortization \| $	$ 16.2	$ 13.7	$ 10.9
Non-commercial landfills
Property, Plant and Equipment [Line Items]
Landfill sites \| landfill_site	2
Permitted
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	28,270,000
Permitted \| Buttonwillow \| California
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	5,197,000
Permitted \| Deer Trail \| Colorado
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	1,488,000
Permitted \| Grassy Mountain \| Utah
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	4,454,000
Permitted \| Kimball \| Nebraska
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	116,000
Permitted \| Lambton \| Ontario, Canada
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	4,443,000
Permitted \| Lone Mountain \| Oklahoma
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	3,412,000
Permitted \| Ryley \| Alberta, Canada
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	5,851,000
Permitted \| Sawyer \| North Dakota
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	3,309,000

SIGNIFICANT ACCOUNTING POLICIES - Remedial Liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) site	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Regulatory Liabilities [Line Items]
Accrual for environmental loss contingencies \| $	$ 116,290	$ 111,873	$ 114,813
Minimum
Regulatory Liabilities [Line Items]
Remedial liabilities at acquisition, risk-free interest rate (as a percent)	1.37%
Maximum
Regulatory Liabilities [Line Items]
Remedial liabilities at acquisition, risk-free interest rate (as a percent)	4.90%
Superfund Proceedings
Regulatory Liabilities [Line Items]
Superfund sites \| site	131

SIGNIFICANT ACCOUNTING POLICIES - Defined Contribution Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Employer discretionary contribution	$ 25.3	$ 20.5	$ 18.6

SIGNIFICANT ACCOUNTING POLICIES - Advertising Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Advertising expense	$ 9.4	$ 6.0	$ 9.0

SIGNIFICANT ACCOUNTING POLICIES - Leases (Details)	Dec. 31, 2022
Real Estate \| Minimum
Property, Plant and Equipment [Line Items]
Lessee term	3 years
Real Estate \| Maximum
Property, Plant and Equipment [Line Items]
Lessee term	10 years
Non-Real Estate \| Minimum
Property, Plant and Equipment [Line Items]
Lessee term	2 years
Non-Real Estate \| Maximum
Property, Plant and Equipment [Line Items]
Lessee term	8 years

REVENUES - Narrative (Details) $ in Millions	12 Months Ended
REVENUES - Narrative (Details) $ in Millions	Dec. 31, 2022 USD ($) source	Dec. 31, 2021 USD ($)
Disaggregation of Revenue [Line Items]
Deferred contract cost, recognition period	3 months
Deferred contracts costs \| $	$ 29.7	$ 26.4
Environmental Services
Disaggregation of Revenue [Line Items]
Number of revenue sources	4
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Number of revenue sources	2

REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 5,166,605	$ 3,805,566	$ 3,144,097
Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	1,495,264	1,209,624	1,062,714
Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	1,311,579	706,298	480,621
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	575,300	466,380	461,036
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	962,697	805,491	809,236
Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	821,765	617,773	330,490
United States
Disaggregation of Revenue [Line Items]
Total revenues	4,576,167	3,324,953	2,739,557
Canada
Disaggregation of Revenue [Line Items]
Total revenues	590,438	480,613	404,540
Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	4,171,706	3,032,454	2,635,901
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	994,392	772,813	507,906
Operating segments \| Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	4,144,973	3,025,907	2,637,641
Operating segments \| Environmental Services \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	1,495,264	1,209,624	1,062,714
Operating segments \| Environmental Services \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	1,311,072	705,999	480,331
Operating segments \| Environmental Services \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	575,300	466,380	461,036
Operating segments \| Environmental Services \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	763,337	643,904	633,560
Operating segments \| Environmental Services \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Operating segments \| Environmental Services \| United States
Disaggregation of Revenue [Line Items]
Total revenues	3,675,880	2,631,112	2,287,796
Operating segments \| Environmental Services \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	469,093	394,795	349,845
Operating segments \| Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	1,021,125	779,360	506,166
Operating segments \| Safety-Kleen Sustainability Solutions \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Operating segments \| Safety-Kleen Sustainability Solutions \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Operating segments \| Safety-Kleen Sustainability Solutions \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Operating segments \| Safety-Kleen Sustainability Solutions \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	199,360	161,587	175,676
Operating segments \| Safety-Kleen Sustainability Solutions \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	821,765	617,773	330,490
Operating segments \| Safety-Kleen Sustainability Solutions \| United States
Disaggregation of Revenue [Line Items]
Total revenues	899,780	693,542	452,435
Operating segments \| Safety-Kleen Sustainability Solutions \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	121,345	85,818	53,731
Corporate, non-segment
Disaggregation of Revenue [Line Items]
Total revenues	507	299	290
Corporate, non-segment \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Corporate, non-segment \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	507	299	290
Corporate, non-segment \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Corporate, non-segment \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Corporate, non-segment \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Corporate, non-segment \| United States
Disaggregation of Revenue [Line Items]
Total revenues	507	299	(674)
Corporate, non-segment \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 964

REVENUES - Contract Balances (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Receivables	$ 964,603	$ 792,734
Contract assets (unbilled receivables)	107,010	94,963
Contract liabilities (deferred revenue)	$ 94,094	$ 83,749

BUSINESS COMBINATIONS - Proposed 2023 Acquisition (Details) $ in Millions	Feb. 09, 2023 USD ($)
February 9, 2023 Acquisition \| Subsequent Event
Business Acquisition [Line Items]
Purchase price to acquire business	$ 100.0

BUSINESS COMBINATIONS - 2022 Acquisitions (Details) - USD ($) $ in Thousands	Dec. 09, 2022	Jun. 17, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill			$ 1,246,878	$ 1,227,042	$ 527,023
June 17, 2022 Acquisition
Business Acquisition [Line Items]
Purchase price to acquire business		$ 78,900
Weighted average useful life of acquired intangible assets (in years)		18 years
Goodwill			$ 32,015
June 17, 2022 Acquisition \| Minimum
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life (in years)		5 years
June 17, 2022 Acquisition \| Maximum
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life (in years)		20 years
December 9, 2022 Acquisition
Business Acquisition [Line Items]
Purchase price to acquire business	$ 12,400
Goodwill	$ 2,500

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References + Details

BUSINESS COMBINATIONS - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended	15 Months Ended
	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Oct. 08, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill		$ 1,246,878	$ 1,246,878	$ 1,227,042		$ 527,023
Measurement Period Adjustments, Goodwill		(6,762)
June 17, 2022 Acquisition
Business Acquisition [Line Items]
Accounts receivable, including unbilled receivables		1,111	1,111
Inventories and supplies		5,816	5,816
Prepaid expenses and other current assets		144	144
Property, plant and equipment		19,605	19,605
Other intangibles		23,500	23,500
Operating lease right-of-use assets		585	585
Other non-current assets		13	13
Current liabilities		(3,271)	(3,271)
Current portion of operating lease liabilities		(186)	(186)
Operating lease liabilities, less current portion		(399)	(399)
Other long-term liabilities		(55)	(55)
Total identifiable net assets		46,863	46,863
Goodwill		32,015	32,015
Total purchase price		78,878	78,878
HydroChemPSC
Business Acquisition [Line Items]
Accounts receivable, including unbilled receivables		131,516	131,516		$ 131,924
Inventories and supplies		3,162	3,162		3,162
Prepaid expenses and other current assets		16,291	16,291		16,016
Property, plant and equipment		314,397	314,397		313,540
Other intangibles		289,000	289,000		289,000
Operating lease right-of-use assets		34,415	34,415		34,347
Other non-current assets		962	962		1,045
Current liabilities		(118,854)	(118,854)		(115,704)
Current portion of operating lease liabilities		(11,277)	(11,277)		(11,659)
Operating lease liabilities, less current portion		(26,344)	(26,344)		(26,128)
Deferred tax liabilities		(80,386)	(80,386)		(85,908)
Other long-term liabilities		(4,170)	(4,170)		(2,685)
Total identifiable net assets		548,712	548,712		546,950
Goodwill		676,701	676,701		683,463
Total purchase price		$ 1,225,413	1,225,413		1,230,413
Measurement Period Adjustments, Accounts receivable, including unbilled receivables			(408)
Measurement Period Adjustments, Inventory			0
Measurement Period Adjustments, Prepaid expenses and other current assets			275
Measurement Period Adjustments, Property, plant and equipment			857
Measurement Period Adjustments, Permits and other intangibles			0
Measurement Period Adjustments, Operating lease right-of-use assets			68
Measurement Period Adjustments, Other non-current assets			(83)
Measurement Period Adjustments, Current liabilities			(3,150)
Measurement Period Adjustments, Current portion of operating lease liabilities			382
Measurement Period Adjustments, Operating lease liabilities, less current portion			(216)
Measurement Period Adjustments, Deferred tax liabilities			5,522
Measurement Period Adjustments, Other long-term liabilities			(1,485)
Measurement Period Adjustments, Total identifiable net assets			1,762
Measurement Period Adjustments, Goodwill			(6,762)
Measurement Period Adjustments, Total purchase price	$ (5,000)		$ (5,000)
HydroChemPSC \| Environmental sales & service reporting unit
Business Acquisition [Line Items]
Goodwill					$ 676,700

BUSINESS COMBINATIONS - HydroChemPSC (Details) - HydroChemPSC - USD ($)		3 Months Ended	15 Months Ended
	Oct. 08, 2021	Mar. 31, 2022	Dec. 31, 2022
Business Acquisition [Line Items]
Purchase price to acquire business	$ 1,230,000,000
Purchase price adjustment		$ 5,000,000	$ 5,000,000
Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| Secured debt
Business Acquisition [Line Items]
Aggregate principal amount	$ 1,000,000,000

BUSINESS COMBINATIONS - Unaudited Pro Forma Financial Information (Details) - HydroChemPSC - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Pro forma combined revenues	$ 4,380,724	$ 3,859,430
Pro forma combined net income	$ 229,807	$ 149,219

BUSINESS COMBINATIONS - Other 2021 Acquisition Activity (Details) - USD ($) $ in Thousands	Jan. 25, 2022	Jun. 29, 2021	Mar. 27, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill				$ 1,246,878	$ 1,227,042	$ 527,023
March 27, 2021 Acquisition
Business Acquisition [Line Items]
Purchase price to acquire business			$ 22,800
Goodwill			$ 16,300
Vertex Energy, Inc.
Business Acquisition [Line Items]
Consideration to acquire assets		$ 140,000
Payment for acquisition termination fee	$ 3,000

- Definition

+ References + Details

BUSINESS COMBINATIONS - 2020 Acquisition (Details) - USD ($) $ in Thousands	Apr. 17, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill		$ 1,246,878	$ 1,227,042	$ 527,023
2020 Acquisitions
Business Acquisition [Line Items]
Purchase price to acquire business	$ 8,800
Goodwill	$ 1,400

- Definition

+ References + Details

DISPOSITION OF BUSINESS (Details) - USD ($) $ in Thousands		12 Months Ended
DISPOSITION OF BUSINESS (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on sale of businesses		$ 8,864	$ 0	$ (3,376)
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| June 30, 2022 Disposition
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from disposition of business	$ 18,800
Gain (loss) on sale of businesses	$ 8,900

INVENTORIES AND SUPPLIES (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Inventory [Line Items]
Inventories and supplies	$ 324,994	$ 250,692
Oil and oil related products
Inventory [Line Items]
Inventories and supplies	151,519	101,965
Supplies
Inventory [Line Items]
Inventories and supplies	143,743	126,602
Solvent and solutions
Inventory [Line Items]
Inventories and supplies	11,994	8,099
Other
Inventory [Line Items]
Inventories and supplies	$ 17,738	$ 14,026

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 4,466,429	$ 4,141,585
Less - accumulated depreciation and amortization	2,486,127	2,278,410
Total property, plant and equipment, net	1,980,302	1,863,175
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	172,579	165,010
Asset retirement costs (non-landfill)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	22,001	19,105
Landfill assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	232,872	205,873
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	584,916	551,795
Right-of-use assets, finance leases	8,000	8,900
Camp equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	116,976	127,680
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,112,188	912,836
Right-of-use assets, finance leases	106,700	77,700
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,078,088	2,092,395
Right-of-use assets, finance leases	9,200	9,300
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,481	6,444
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 140,328	$ 60,447

PROPERTY, PLANT AND EQUIPMENT (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation inclusive of amortization	$ 297.4	$ 263.4	$ 257.1
Interest costs capitalized	$ 3.4

GOODWILL AND OTHER INTANGIBLE ASSETS - Changes to Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 1,227,042	$ 527,023
Increase from current period acquisitions	34,510	699,812
Measurement period adjustments from prior period acquisitions	(6,762)
Decrease from disposition of business	(4,412)
Foreign currency translation	(3,500)	207
Goodwill, end of period	1,246,878	1,227,042
Environmental Services
Goodwill [Roll Forward]
Goodwill, beginning of period	1,085,534	401,918
Increase from current period acquisitions	0	683,463
Measurement period adjustments from prior period acquisitions	(6,762)
Decrease from disposition of business	(4,412)
Foreign currency translation	(2,514)	153
Goodwill, end of period	1,071,846	1,085,534
Safety-Kleen Sustainability Solutions
Goodwill [Roll Forward]
Goodwill, beginning of period	141,508	125,105
Increase from current period acquisitions	34,510	16,349
Measurement period adjustments from prior period acquisitions	0
Decrease from disposition of business	0
Foreign currency translation	(986)	54
Goodwill, end of period	$ 175,032	$ 141,508

- Definition

+ References + Details

GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense of permits and other intangible assets	$ 50.2	$ 34.7	$ 35.8
Costs of intangible assets written-off	$ 19.1

GOODWILL AND OTHER INTANGIBLE ASSETS - Finite-lived and Indefinite Lived Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Finite-lived intangible assets
Finite-lived intangible assets, cost	$ 861,470	$ 858,264
Accumulated Amortization	363,222	336,543
Finite-lived intangible assets, net	498,248	521,721
Total permits and other intangible assets, cost	984,004	981,455
Total permits and other intangible assets, net	620,782	644,912
Trademarks and trade names
Finite-lived intangible assets
Trademarks and trade names	122,534	123,191
Permits
Finite-lived intangible assets
Finite-lived intangible assets, cost	188,373	187,519
Accumulated Amortization	109,036	102,408
Finite-lived intangible assets, net	79,337	85,111
Customer and supplier relationships
Finite-lived intangible assets
Finite-lived intangible assets, cost	583,709	576,474
Accumulated Amortization	229,368	214,776
Finite-lived intangible assets, net	354,341	361,698
Other intangible assets
Finite-lived intangible assets
Finite-lived intangible assets, cost	89,388	94,271
Accumulated Amortization	24,818	19,359
Finite-lived intangible assets, net	$ 64,570	$ 74,912

GOODWILL AND OTHER INTANGIBLE ASSETS - Expected Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Expected amortization
2023	$ 46,030
2024	41,814
2025	39,828
2026	37,943
2027	35,869
Thereafter	296,764
Finite-lived intangible assets, net	$ 498,248	$ 521,721

ACCRUED EXPENSES - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued insurance	$ 92,909	$ 102,853
Accrued interest	20,033	19,785
Accrued compensation and benefits	123,226	133,604
Accrued income, real estate, sales and other taxes	61,442	29,954
Interest rate swap liability	0	17,383
Accrued other	99,106	87,835
Total accrued expenses	$ 396,716	$ 391,414

ACCRUED EXPENSES - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accrued insurance, employee medical insurance costs	$ 16.4	$ 18.6
Accrual loss for workers' compensation, comprehensive general liability and vehicle liability self-insurance programs	$ 74.9	$ 82.8

CLOSURE AND POST-CLOSURE LIABILITIES - Changes in Post-Closure Liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) landfill_site	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) landfill_site
Changes to post-closure liabilities
Balance at the beginning of the period	$ 99,103	$ 87,926
Liabilities assumed in acquisitions	55	1,446
Measurement period adjustments from prior period acquisitions	1,148
New asset retirement obligations	3,743	2,443
Accretion	8,752	7,357
Changes in estimates recorded to consolidated statement of operations	6,775	2,683
Changes in estimates recorded to consolidated balance sheet	4,961	3,712
Expenditures	(5,151)	(6,602)
Currency translation and other	(585)	138
Balance at the end of the period	118,801	99,103	$ 87,926
Number of landfill sites closed during period \| landfill_site			2
Changes in estimates recorded to the consolidated statement of operations, related to facility closure	$ 600	2,300
Number of non-landfill site closure expected \| landfill_site	2
Landfill Retirement Liability
Changes to post-closure liabilities
Balance at the beginning of the period	$ 53,425	48,412
Liabilities assumed in acquisitions	0	0
Measurement period adjustments from prior period acquisitions	0
New asset retirement obligations	3,743	2,443
Accretion	4,605	3,655
Changes in estimates recorded to consolidated statement of operations	1,063	2,287
Changes in estimates recorded to consolidated balance sheet	3,219	2,297
Expenditures	(3,373)	(5,818)
Currency translation and other	(431)	149
Balance at the end of the period	62,251	53,425	$ 48,412
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Balance at the beginning of the period	45,678	39,514
Liabilities assumed in acquisitions	55	1,446
Measurement period adjustments from prior period acquisitions	1,148
New asset retirement obligations	0	0
Accretion	4,147	3,702
Changes in estimates recorded to consolidated statement of operations	5,712	396
Changes in estimates recorded to consolidated balance sheet	1,742	1,415
Expenditures	(1,778)	(784)
Currency translation and other	(154)	(11)
Balance at the end of the period	$ 56,550	$ 45,678	$ 39,514

CLOSURE AND POST-CLOSURE LIABILITIES - Anticipated Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Environmental Property Sale, Disposal or Abandonment Costs
2023	$ 14,414
2024	14,733
2025	12,808
2026	8,369
2027	7,420
Thereafter	290,366
Undiscounted closure and post-closure liabilities	348,110
Less: Discount at credit-adjusted risk-free rate	(153,062)
Less: Undiscounted estimated closure and post-closure liabilities relating to airspace not yet consumed	(76,247)
Present value of closure and post-closure liabilities	$ 118,801	$ 99,103	$ 87,926

REMEDIAL LIABILITIES - Changes in Remedial Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Changes to remedial liabilities
Balance at the beginning of the period	$ 111,873	$ 114,813
Liabilities assumed in acquisitions		1,216
Accretion	4,191	4,388
Changes in estimates recorded to consolidated statement of operations	1,497	296
Expenditures	(8,795)	(8,904)
Currency translation and other	(906)	64
Liabilities assumed in acquisition of real estate	8,092
Measurement period adjustments from prior period acquisition	338
Balance at the end of the period	116,290	111,873
Remedial Liabilities for Landfill Sites
Changes to remedial liabilities
Balance at the beginning of the period	1,780	1,865
Liabilities assumed in acquisitions		0
Accretion	86	90
Changes in estimates recorded to consolidated statement of operations	8	(126)
Expenditures	(50)	(49)
Currency translation and other	0	0
Liabilities assumed in acquisition of real estate	0
Measurement period adjustments from prior period acquisition	0
Balance at the end of the period	1,824	1,780
Remedial Liabilities for Inactive Sites
Changes to remedial liabilities
Balance at the beginning of the period	59,787	63,060
Liabilities assumed in acquisitions		0
Accretion	2,498	2,614
Changes in estimates recorded to consolidated statement of operations	877	(178)
Expenditures	(3,370)	(4,889)
Currency translation and other	(43)	(820)
Liabilities assumed in acquisition of real estate	0
Measurement period adjustments from prior period acquisition	0
Balance at the end of the period	59,749	59,787
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Changes to remedial liabilities
Balance at the beginning of the period	50,306	49,888
Liabilities assumed in acquisitions		1,216
Accretion	1,607	1,684
Changes in estimates recorded to consolidated statement of operations	612	600
Expenditures	(5,375)	(3,966)
Currency translation and other	(863)	884
Liabilities assumed in acquisition of real estate	8,092
Measurement period adjustments from prior period acquisition	338
Balance at the end of the period	$ 54,717	$ 50,306

REMEDIAL LIABILITIES - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Site Contingency [Line Items]
Liabilities assumed in acquisition of real estate	$ 8,092
Accrual for environmental loss contingencies	5.00%
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration]	Remedial liabilities, less current portion of $9,918 and $13,121, respectively
Remedial Liabilities for Inactive Sites
Site Contingency [Line Items]
Liabilities assumed in acquisition of real estate	$ 0

REMEDIAL LIABILITIES - Anticipated Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accrual for Environmental Loss Contingencies, Net [Abstract]
2023	$ 10,793
2024	20,912
2025	12,065
2026	7,581
2027	6,390
Thereafter	76,416
Undiscounted remedial liabilities	134,157
Less: Discount at risk free rates	$ (17,867)
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]	Remedial liabilities, less current portion of $9,918 and $13,121, respectively
Total remedial liabilities	$ 116,290	$ 111,873	$ 114,813

REMEDIAL LIABILITIES - Estimates (Details) $ in Thousands	12 Months Ended
REMEDIAL LIABILITIES - Estimates (Details) $ in Thousands	Dec. 31, 2022 USD ($) facility	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 116,290	$ 111,873	$ 114,813
% of Total	100.00%
Reasonably possible additional liabilities	$ 22,772
Loss contingency accrual	37,100	36,100
Total remedial liabilities	116,290	111,873	$ 114,813
Legal and Administrative Proceedings
Site Contingency [Line Items]
Loss contingency accrual	24,100	$ 24,100
Inactive facilities not used in active conduct of the Company's business, most of which were assumed through prior period acquisitions (25 facilities)
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 59,759
% of Total	51.40%
Reasonably possible additional liabilities	$ 10,295
Number of facility by type \| facility	25
Total remedial liabilities	$ 59,759
Facilities now used in active conduct of the Company's business (45 facilities)
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 47,951
% of Total	41.20%
Reasonably possible additional liabilities	$ 11,189
Number of facility by type \| facility	45
Total remedial liabilities	$ 47,951
Superfund sites
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 8,580
% of Total	7.40%
Reasonably possible additional liabilities	$ 1,288
Number of facility by type \| facility	16
Total remedial liabilities	$ 8,580
Superfund sites \| Various
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 8,580
% of Total	7.40%
Reasonably possible additional liabilities	$ 1,288
Number of facility by type \| facility	16
Total remedial liabilities	$ 8,580
Closed incinerator and landfill \| Baton Rouge, LA
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 26,604
% of Total	22.90%
Reasonably possible additional liabilities	$ 4,547
Total remedial liabilities	26,604
Closed incinerator \| Bridgeport, NJ
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 18,089
% of Total	15.60%
Reasonably possible additional liabilities	$ 3,364
Total remedial liabilities	18,089
Operating solvent recycling center \| Linden, NJ
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 14,479
% of Total	12.50%
Reasonably possible additional liabilities	$ 3,352
Total remedial liabilities	14,479
Idled incinerator \| Mercier, Quebec
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 10,996
% of Total	9.50%
Reasonably possible additional liabilities	$ 1,659
Total remedial liabilities	10,996
All other incinerators, landfills, wastewater treatment facilities and service centers (66 facilities) \| Various
Site Contingency [Line Items]
Accrual for environmental loss contingencies	$ 37,542
% of Total	32.10%
Reasonably possible additional liabilities	$ 8,562
Number of facility by type \| facility	66
Total remedial liabilities	$ 37,542

FINANCING ARRANGEMENTS - Summary of Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Current portion of long-term debt	$ 10,000	$ 17,535
Long-term debt, at par	2,438,975	2,547,091
Unamortized debt issuance costs and discount, net	(24,147)	(30,067)
Long-term debt, at carrying value	2,414,828	2,517,024
Secured debt \| Secured senior term loans
Debt Instrument [Line Items]
Current portion of long-term debt	10,000	17,535
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans")
Debt Instrument [Line Items]
Long-term debt, at par	613,975	712,091
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans")
Debt Instrument [Line Items]
Long-term debt, at par	980,000	990,000
Unsecured debt \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument [Line Items]
Long-term debt, at par	$ 545,000	545,000
Interest rate (as a percent)	4.875%
Unsecured debt \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument [Line Items]
Long-term debt, at par	$ 300,000	$ 300,000
Interest rate (as a percent)	5.125%

FINANCING ARRANGEMENTS - Narrative (Details)					1 Months Ended	12 Months Ended
FINANCING ARRANGEMENTS - Narrative (Details)	Jan. 24, 2023 USD ($)	Nov. 21, 2022 USD ($)	Oct. 08, 2021	Oct. 28, 2020 USD ($)	Jan. 31, 2022 USD ($)	Dec. 31, 2022 USD ($) termLoan	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jul. 02, 2019 USD ($)
Financing arrangements
Loss on early extinguishment of debt						$ 422,000	$ 0	$ 0
Debt redemption period						12 months
Fair value of long-term obligations, including current portion						$ 2,400,000,000	2,600,000,000
Revolving credit facility, available borrowing capacity						288,600,000
Letters of credit outstanding, amount						111,400,000
Borrowings from revolving credit facility						0	0	150,000,000
2018 Swaps
Financing arrangements
Derivative notional amount						350,000,000
Interest rate swap
Financing arrangements
Derivative asset						60,600,000
Derivative liability							17,400,000
Reclassification of gain from accumulated other comprehensive loss to interest expense						$ 683,000	(10,011,000)	$ (8,180,000)
Subsequent Event \| 2018 Swaps
Financing arrangements
Reclassification of gain from accumulated other comprehensive loss to interest expense	$ 8,700,000
Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| 2022 Swaps
Financing arrangements
Derivative notional amount					$ 600,000,000
Secured debt \| Secured senior term loans
Financing arrangements
Number of secured senior term loans outstanding \| termLoan						2
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans")
Financing arrangements
Debt outstanding						$ 990,000,000
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| 2022 Swaps
Financing arrangements
Debt outstanding					$ 600,000,000
Effective interest rate (as a percent)						2.931%
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| 2022 Swaps \| Through June 30, 2023
Financing arrangements
Derivative, fixed interest rate					0.931%
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| 2022 Swaps \| From July 1, 2023 through September 30, 2027
Financing arrangements
Derivative, fixed interest rate					1.9645%
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| Eurodollar
Financing arrangements
Basis spread on variable rate (as a percent)			2.00%		2.00%
Debt, floor interest rate			0.00%
Secured debt \| Secured senior term loans due October 8, 2028 ("2028 Term Loans") \| Base rate
Financing arrangements
Basis spread on variable rate (as a percent)			1.00%
Debt, floor interest rate			1.00%
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans")
Financing arrangements
Debt outstanding						$ 614,000,000
Repayments of debt		$ 100,000,000
Loss on early extinguishment of debt						400,000
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans") \| 2018 Swaps
Financing arrangements
Debt outstanding						$ 350,000,000
Debt, weighted average interest rate						2.92%
Effective interest rate (as a percent)						4.67%
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans") \| Subsequent Event
Financing arrangements
Repayments of debt	614,000,000
Loss on early extinguishment of debt	2,400,000
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans") \| Eurodollar
Financing arrangements
Basis spread on variable rate (as a percent)			1.75%			1.75%
Debt, floor interest rate			0.00%
Secured debt \| Secured senior term loans due June 30, 2024 ("2024 Term Loans") \| Base rate
Financing arrangements
Basis spread on variable rate (as a percent)			1.00%
Debt, floor interest rate			1.00%
Unsecured debt
Financing arrangements
Redemption percentage of principal amount						100.00%
Unsecured debt \| Unsecured senior notes at 6.375% due at 2031
Financing arrangements
Redemption percentage of principal amount						106.375%
Debt instrument, redemption price, percentage of principal amount redeemed						40.00%
Unsecured debt \| Unsecured senior notes at 6.375% due at 2031 \| Subsequent Event
Financing arrangements
Net proceeds from the company’s issuance	500,000,000
Aggregate principal amount	$ 500,000,000
Interest rate (as a percent)	6.375%
Unsecured debt \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Financing arrangements
Aggregate principal amount									$ 545,000,000
Interest rate (as a percent)						4.875%
Unsecured debt \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Financing arrangements
Aggregate principal amount									$ 300,000,000
Interest rate (as a percent)						5.125%
LIne of credit
Financing arrangements
Credit facility, maximum borrowing capacity						$ 400,000,000
Period for measurement of average liquidity (in days)						30 days
LIne of credit \| Minimum
Financing arrangements
Commitment fee (as a percent)						0.25%
LIne of credit \| Maximum
Financing arrangements
Commitment fee (as a percent)						0.375%
LIne of credit \| Parent and Domestic Subsidiaries
Financing arrangements
Credit available subject to percentage of accounts receivable (as a percent)				85.00%
Credit available subject to percentage of cash deposited (as a percent)				100.00%
LIne of credit \| Canadian Subsidiaries
Financing arrangements
Credit available subject to percentage of accounts receivable (as a percent)				85.00%
Credit available subject to percentage of cash deposited (as a percent)				100.00%
LIne of credit \| Revolving credit facility
Financing arrangements
Debt outstanding						$ 0	$ 0
LIne of credit \| Revolving credit facility \| Parent and Domestic Subsidiaries
Financing arrangements
Credit facility, maximum borrowing capacity				$ 350,000,000
LIne of credit \| Revolving credit facility \| Canadian Subsidiaries
Financing arrangements
Credit facility, maximum borrowing capacity				50,000,000
LIne of credit \| Letters of credit \| Parent and Domestic Subsidiaries
Financing arrangements
Credit facility, maximum borrowing capacity				$ 250,000,000
LIne of credit \| Subsequent Event \| Revolving credit facility
Financing arrangements
Net proceeds from the company’s issuance	$ 114,000,000
Borrowings from revolving credit facility	$ 114,000,000
LIne of credit \| Base rate \| Minimum
Financing arrangements
Basis spread on variable rate (as a percent)						0.50%
LIne of credit \| Base rate \| Maximum
Financing arrangements
Basis spread on variable rate (as a percent)						0.75%
LIne of credit \| LIBOR \| Minimum
Financing arrangements
Basis spread on variable rate (as a percent)						1.50%
LIne of credit \| LIBOR \| Maximum
Financing arrangements
Basis spread on variable rate (as a percent)						1.75%

FINANCING ARRANGEMENTS - Summary of Redemption Prices (Details) - Unsecured debt	12 Months Ended
	Dec. 31, 2022
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	100.00%
Unsecured senior notes at 6.375% due at 2031
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	106.375%
Debt Instrument, Redemption, Period One \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	102.438%
Debt Instrument, Redemption, Period One \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	102.563%
Debt Instrument, Redemption, Period One \| Unsecured senior notes at 6.375% due at 2031
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	103.188%
Debt Instrument, Redemption, Period Two \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	101.219%
Debt Instrument, Redemption, Period Two \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	101.281%
Debt Instrument, Redemption, Period Two \| Unsecured senior notes at 6.375% due at 2031
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	101.594%
Debt Instrument, Redemption, Period Three \| Unsecured senior notes, at 4.875%, due July 15, 2027 ("2027 Notes")
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	100.00%
Debt Instrument, Redemption, Period Three \| Unsecured senior notes, at 5.125%, due July 15, 2029 ("2029 Notes")
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	100.00%
Debt Instrument, Redemption, Period Three \| Unsecured senior notes at 6.375% due at 2031
Debt Instrument, Redemption [Line Items]
Redemption percentage of principal amount	100.00%

INCOME TAXES - Provision for Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
Domestic	$ 406,206	$ 223,438	$ 168,117
Foreign	131,792	46,277	6,433
Income from operations before provision for income taxes	537,998	269,715	174,550
Current:
Federal	52,237	42,480	33,327
State	26,980	18,126	14,575
Foreign	29,488	4,380	1,559
Current income taxes	108,705	64,986	49,461
Deferred
Federal	32,199	2,275	(965)
State	(2,432)	(4,777)	(2,506)
Foreign	(12,218)	3,984	(6,277)
Deferred income taxes	17,549	1,482	(9,748)
Provision for income taxes	$ 126,254	$ 66,468	$ 39,713
Effective tax rate	23.50%	24.60%	22.80%
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Tax expense at U.S. statutory rate	$ 112,980	$ 56,640	$ 36,655
State income taxes, net of federal benefit	19,831	12,101	9,837
Foreign rate differential	6,196	1,922	1,256
Valuation allowance	(18,769)	(9,139)	(11,339)
Uncertain tax position interest and penalties	(2,454)	263	(712)
Tax credits expired	2,768	2,530	2,039
Non-deductible compensation	2,754	2,326	1,406
Other	2,948	(175)	571
Provision for income taxes	$ 126,254	$ 66,468	$ 39,713

INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Provision for doubtful accounts	$ 11,544	$ 10,188
Closure, post-closure and remedial liabilities	31,837	28,206
Operating lease liabilities	42,255	42,218
Accrued expenses	19,311	20,455
Accrued compensation and benefits	20,171	24,504
Net operating loss carryforwards	41,585	68,381
Tax credit carryforwards	8,903	12,368
Interest rate swap liability	0	5,215
Stock-based compensation	3,988	2,705
Other	7,487	5,635
Total deferred tax assets	187,081	219,875
Deferred tax liabilities:
Property, plant and equipment	(281,131)	(273,883)
Operating lease right-of-use assets	(41,939)	(41,260)
Interest rate swap asset	(17,587)	0
Permits and other intangible assets	(132,681)	(138,241)
Prepaid expenses	(12,088)	(10,212)
Total deferred tax liabilities	(485,426)	(463,596)
Total net deferred tax liability before valuation allowance	(298,345)	(243,721)
Less valuation allowance	(42,509)	(69,806)
Net deferred tax liabilities	(340,854)	$ (313,527)
State net operating loss carryforwards, begin to expire in 2023	231,400
Federal operating loss carryforwards, begin to expire in 2024	34,800
Foreign net operating loss carryforwards, begin to expire in 2023	85,600
Foreign tax credit carryforwards, begin to expire between 2023 and 2024	$ 7,700

INCOME TAXES - Valuation Allowance (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Foreign tax credits	$ 7,666	$ 11,047
Federal net operating losses	3,783	3,788
State net operating loss carryforwards	9,928	12,053
Foreign net operating loss carryforwards	15,488	26,697
Deferred tax assets of a Canadian subsidiary	5,339	10,701
Realized and unrealized capital losses	305	5,520
Total valuation allowance	$ 42,509	$ 69,806

EARNINGS PER SHARE - Reconciliation of Basic and Diluted Earnings Per Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator for basic and diluted earnings per share:
Net income, basic	$ 411,744	$ 203,247	$ 134,837
Net income, diluted	$ 411,744	$ 203,247	$ 134,837
Denominator:
Weighted basic shares outstanding (in shares)	54,223	54,514	55,479
Dilutive effect of equity-based compensation awards (in shares)	264	247	211
Weighted dilutive shares outstanding (in shares)	54,487	54,761	55,690
Basic earnings per share (in dollars per share)	$ 7.59	$ 3.73	$ 2.43
Diluted earnings per share (in dollars per share)	$ 7.56	$ 3.71	$ 2.42

- Definition

The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1252-109256

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1337-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(20))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 14: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-03(13))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868656-224227

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

+ Details

- Definition

The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1337-109256

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126732423&loc=SL123482106-238011

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-03(13))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868656-224227

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1252-109256

Reference 13: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1448-109256

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI https://asc.fasb.org/extlink&oid=126958026&loc=d3e1377-109256

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126958026&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

+ References + Details

EARNINGS PER SHARE - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of performance stock awards that performance criteria not attained (in shares)		14,237	53,667
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	10,250	67,981	8,878

STOCKHOLDERS' EQUITY (Details) - USD ($) $ in Thousands, shares in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Stock repurchase program, authorized amount	$ 600,000
Repurchase of common stock (in shares)	0.5	0.6	1.2
Repurchases of common stock	$ 50,183	$ 54,410	$ 74,844
Stock repurchase program, remaining authorized repurchase amount	$ 105,300

ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Increase (Decrease) in Equity
Beginning balance	$ 1,513,887	$ 1,341,551	$ 1,269,813
Other comprehensive (loss) income before reclassifications	47,088	5,695	(11,023)
Amounts reclassified out of accumulated other comprehensive loss	(683)	10,011	8,180
Tax benefit (provision)	(17,574)	(241)	1,417
Other comprehensive income (loss), net of tax	28,831	15,465	(1,426)
Ending balance	1,922,322	1,513,887	1,341,551
Foreign Currency Translation Adjustments
Increase (Decrease) in Equity
Beginning balance	(177,824)	(176,234)	(187,795)
Other comprehensive (loss) income before reclassifications	(31,515)	(1,590)	10,212
Amounts reclassified out of accumulated other comprehensive loss	0	0	0
Tax benefit (provision)	0	0	1,349
Other comprehensive income (loss), net of tax	(31,515)	(1,590)	11,561
Ending balance	(209,339)	(177,824)	(176,234)
Unrealized Gain (Loss) on Available-For-Sale Securities
Increase (Decrease) in Equity
Beginning balance	(150)	135	143
Other comprehensive (loss) income before reclassifications	(523)	(361)	(10)
Amounts reclassified out of accumulated other comprehensive loss	0	0	0
Tax benefit (provision)	110	76	2
Other comprehensive income (loss), net of tax	(413)	(285)	(8)
Ending balance	(563)	(150)	135
Unrealized (Loss) Gain on Fair Value of Interest Rate Hedges
Increase (Decrease) in Equity
Beginning balance	(17,383)	(33,629)	(20,839)
Other comprehensive (loss) income before reclassifications	78,711	6,235	(20,970)
Amounts reclassified out of accumulated other comprehensive loss	(683)	10,011	8,180
Tax benefit (provision)	(17,587)	0	0
Other comprehensive income (loss), net of tax	60,441	16,246	(12,790)
Ending balance	43,058	(17,383)	(33,629)
Unrealized Loss on Unfunded Pension Liability
Increase (Decrease) in Equity
Beginning balance	(655)	(1,749)	(1,560)
Other comprehensive (loss) income before reclassifications	415	1,411	(255)
Amounts reclassified out of accumulated other comprehensive loss	0	0	0
Tax benefit (provision)	(97)	(317)	66
Other comprehensive income (loss), net of tax	318	1,094	(189)
Ending balance	(337)	(655)	(1,749)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Equity
Beginning balance	(196,012)	(211,477)	(210,051)
Other comprehensive income (loss), net of tax	28,831	15,465	(1,426)
Ending balance	$ (167,181)	$ (196,012)	$ (211,477)

ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Interest rate swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized (Loss) Gain on Fair Value of Interest Rate Hedges	$ 683	$ (10,011)	$ (8,180)

STOCK-BASED COMPENSATION - Stock-Based Compensation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 26.8	$ 18.8	$ 18.5
Total income tax benefit from stock-based compensation	$ 5.0	$ 3.5	$ 4.2
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	5 years
2020 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			2,500,000

STOCK-BASED COMPENSATION - Restricted Stock Awards (Details) - Restricted Stock - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Number of Shares
Unvested, beginning of period (in shares)	452,197
Granted (in shares)	165,149
Vested (in shares)	(167,086)
Forfeited (in shares)	(23,118)
Unvested, end of period (in shares)	427,142	452,197
Weighted Average Grant-Date Fair Value
Unvested, beginning of period (in dollars per share)	$ 76.88
Granted (in dollars per share)	94.88
Vested (in dollars per share)	74.37
Forfeited (in dollars per share)	80.17
Unvested, end of period (in dollars per share)	$ 84.64	$ 76.88
Total unrecognized compensation cost	$ 25.6
Expected to be recognized over a weighted average period	2 years 6 months
Fair value of awards vested in period	$ 16.4	$ 17.7	$ 13.3

STOCK-BASED COMPENSATION - Performance Stock Awards (Details) - Performance Stock Awards - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Number of Shares
Unvested, beginning of period (in shares)	169,757
Granted (in shares)	156,687
Vested (in shares)	(100,892)
Forfeited (in shares)	(11,873)
Unvested, end of period (in shares)	213,679	169,757
Weighted Average Grant-Date Fair Value
Unvested, beginning of period (in dollars per share)	$ 85.56
Granted (in dollars per share)	92.60
Vested (in dollars per share)	83.51
Forfeited (in dollars per share)	86.87
Unvested, end of period (in dollars per share)	$ 91.62	$ 85.56
Total unrecognized compensation cost	$ 9.3
Fair value of awards vested in period	$ 11.1	$ 15.0	$ 3.5

COMMITMENTS AND CONTINGENCIES - Legal and Administrative Proceedings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) proceeding claim	Dec. 31, 2021 USD ($)
Legal and Administrative Proceedings
Loss contingency accrual	$ 37.1	$ 36.1
Product Liability Cases
Legal and Administrative Proceedings
Number of proceedings \| proceeding	54
Loss contingency, claims settled and dismissed, claims \| claim	20
Legal and Administrative Proceedings
Legal and Administrative Proceedings
Loss contingency accrual	$ 24.1	24.1
Federal, State, and Provincial Enforcement Actions
Legal and Administrative Proceedings
Loss contingency accrual	$ 13.0	$ 12.0
Number of proceedings \| proceeding	1

COMMITMENTS AND CONTINGENCIES - Superfund Proceedings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) site
Superfund Proceedings
Superfund Proceedings
Number of sites subject to proceedings under federal or state superfund laws	131
Number of sites owned by the entity subject to proceedings under federal or state superfund laws	6
Number of sites owned by third parties subject to proceedings under federal or state superfund laws	125
Number of sites for which environmental remediation expense is settled	30
Third party sites requiring expenditure on remediation	16
Number of sites for which environmental remediation expense is not required	79
Loss contingency, liability limit amount \| $	$ 1.0
Number of sites which potential liability could exceed $1.0 million	3
Safety-Kleen Sustainability Solutions
Superfund Proceedings
Notices received from owners of third party sites seeking indemnification from the company	17

COMMITMENTS AND CONTINGENCIES - Federal, State and Provincial Enforcement Actions (Details) - Federal, State, and Provincial Enforcement Actions $ in Millions	Dec. 31, 2022 USD ($) proceeding
Federal and State Enforcement Actions
Number of proceedings \| proceeding	1
Loss contingency, liability limit amount \| $	$ 1.0

COMMITMENTS AND CONTINGENCIES - Self Insurance Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Product Liability Contingency [Line Items]
Retention for environmental impairment	$ 1,000
Self-insurance liabilities	$ 74,900	$ 82,800
Weighted average risk free discount rate for self insurance liabilities	4.36%	0.97%
Self Insurance Losses Expected [Abstract]
2023	$ 26,736
2024	16,317
2025	12,172
2026	8,170
2027	6,318
Thereafter	10,631
Undiscounted self-insurance liabilities	80,344
Less: Discount	(5,452)
Total self-insurance liabilities (included in accrued expenses)	74,892
Minimum
Product Liability Contingency [Line Items]
Deductible medical insurance policy	900
Safety-Kleen Sustainability Solutions
Product Liability Contingency [Line Items]
Deductible per occurrence for workers compensation	1,000
Deductible per occurrence for general liability	2,000
Deductible per occurrence for vehicle liability	$ 2,000

LEASES - Supplemental Finance Lease Balance Sheet information (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
ROU assets:
Finance lease (included in property, plant and equipment, net)	$ 96,207	$ 81,267
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, plant and equipment, net	Property, plant and equipment, net
Current portion of lease liabilities:
Finance lease (included in accrued expenses)	$ 12,767	$ 10,893
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Long-term portion of lease liabilities:
Finance lease (included in deferred taxes, unrecognized tax benefits and other long-term liabilities)	$ 86,390	$ 72,051
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities

LEASES - Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
LEASES - Lease Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease cost	$ 59,041	$ 50,264	$ 53,194
Finance lease cost:
Amortization of ROU assets	13,239	9,504	4,966
Interest on lease liabilities	3,011	2,544	1,523
Total finance lease cost	16,250	12,048	6,489
Short-term lease cost	158,736	102,913	70,692
Variable lease cost	4,353	3,546	3,691
Total lease cost	$ 238,380	$ 168,771	$ 134,066

LEASES - Other Information related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Weighted Average Remaining Lease Term (years)
Operating lease (in years)	4 years 2 months 12 days	4 years 4 months 24 days
Finance lease (in years)	7 years 6 months	8 years 1 month 6 days
Weighted Average Discount Rate
Operating lease (as a percentage)	4.08%	4.35%
Finance lease (as a percentage)	3.53%	3.65%
Cash paid for amounts related to lease liabilities:
Operating cash flows from operating leases	$ 61,014	$ 50,963	$ 53,498
Operating cash flows from finance leases	3,011	2,544	1,523
Financing cash flows from finance leases	12,821	8,458	4,469
ROU assets obtained in exchange for operating lease liabilities	58,230	55,556	34,358
ROU assets obtained in exchange for finance lease liabilities	$ 29,205	$ 30,476	$ 32,526

LEASES - Schedule of Future Lease Payments (Details) $ in Thousands	Dec. 31, 2022 USD ($)
Operating Leases
2023	$ 57,757
2024	45,478
2025	32,739
2026	23,791
2027	14,635
Thereafter	11,564
Total future lease payments	185,964
Amount representing interest	(17,173)
Total lease liabilities	168,791
Finance Leases
2023	17,085
2024	16,423
2025	15,748
2026	15,761
2027	15,748
Thereafter	33,950
Total future lease payments	114,715
Amount representing interest	(15,558)
Total lease liabilities	$ 99,157

Segment Reporting - Narrative (Details)	12 Months Ended
Segment Reporting - Narrative (Details)	Dec. 31, 2022 segment
Segment Reporting [Abstract]
Number of operating segments	2

SEGMENT REPORTING - Segment Information, Revenues, EBITA, and Reconciliation to the Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 5,166,605	$ 3,805,566	$ 3,144,097
Adjusted EBITDA	1,022,128	676,606	573,804
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	12,943	11,745	11,051
Stock-based compensation	26,844	18,839	18,502
Depreciation and amortization	347,594	298,135	292,915
Income from operations	634,747	347,887	251,336
Other (income) expense, net	(2,472)	515	290
Loss on early extinguishment of debt	422	0	0
(Gain) loss on sale of businesses	(8,864)	0	3,376
Interest expense, net of interest income	107,663	77,657	73,120
Income from operations before provision for income taxes	537,998	269,715	174,550
Property, plant and equipment, net	1,980,302	1,863,175
Goodwill	1,246,878	1,227,042	527,023
Permits and other intangibles, net	620,782	644,912
Permits and other intangibles, net	1,867,660	1,871,954
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	4,171,706	3,032,454	2,635,901
Reconciliation to Consolidated Statements of Operations:
Goodwill	1,071,846	1,085,534	401,918
Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	994,392	772,813	507,906
Reconciliation to Consolidated Statements of Operations:
Goodwill	175,032	141,508	125,105
Operating segments \| Environmental Services
Segment Reporting Information [Line Items]
Total revenues	4,144,973	3,025,907	2,637,641
Adjusted EBITDA	953,053	659,718	665,918
Reconciliation to Consolidated Statements of Operations:
Property, plant and equipment, net	1,467,641	1,374,913
Goodwill	1,071,846	1,085,534
Permits and other intangibles, net	462,050	498,739
Permits and other intangibles, net	1,533,896	1,584,273
Operating segments \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	1,021,125	779,360	506,166
Adjusted EBITDA	306,327	227,354	83,214
Reconciliation to Consolidated Statements of Operations:
Property, plant and equipment, net	398,660	373,721
Goodwill	175,032	141,508
Permits and other intangibles, net	158,732	146,173
Permits and other intangibles, net	333,764	287,681
Intersegment revenues (expense), net \| Environmental Services
Segment Reporting Information [Line Items]
Total revenues	26,733	6,547	(1,740)
Intersegment revenues (expense), net \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	(26,733)	(6,547)	1,740
Corporate Items
Segment Reporting Information [Line Items]
Total revenues	507	299	290
Adjusted EBITDA	(237,252)	(210,466)	(175,328)
Reconciliation to Consolidated Statements of Operations:
Property, plant and equipment, net	114,001	114,541
Operating segments and corporate non segment
Segment Reporting Information [Line Items]
Total revenues	$ 507	$ 299	$ 290

SEGMENT REPORTING - Assets by Geographical Area (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,980,302	$ 1,863,175
Percent of property, plant and equipment, net	100.00%	100.00%
Permits and other intangibles, net	$ 620,782	$ 644,912
Percent of permits and other intangibles, net	100.00%	100.00%
Assets	$ 6,129,707	$ 5,653,699
United States
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 1,765,291	$ 1,610,402
Percent of property, plant and equipment, net	89.10%	86.40%
Permits and other intangibles, net	$ 585,887	$ 604,076
Percent of permits and other intangibles, net	94.40%	93.70%
Assets	$ 5,595,255	$ 5,077,585
Canada and other foreign
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 215,011	$ 252,773
Percent of property, plant and equipment, net	10.90%	13.60%
Permits and other intangibles, net	$ 34,895	$ 40,836
Percent of permits and other intangibles, net	5.60%	6.30%
Assets	$ 534,452	$ 576,114

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124433192&loc=SL2890621-112765

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 14: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442526-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (bb)
-URI https://asc.fasb.org/extlink&oid=123419778&loc=d3e5710-111685

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=116870748&loc=SL6758485-165988

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI https://asc.fasb.org/extlink&oid=126975872&loc=SL124442552-122756

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(18))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

+ Details