Clean Harbors (CLH) 10-Q30 Oct 242024 Q3 Quarterly reportFinancial data

Company Profile

Cover

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2024	Oct. 25, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-34223
Entity Registrant Name	CLEAN HARBORS, INC
Entity Incorporation, State or Country Code	MA
Entity Tax Identification Number	04-2997780
Entity Address, Address Line One	42 Longwater Drive
Entity Address, City or Town	Norwell
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02061-9149
City Area Code	781
Local Phone Number	792-5000
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	CLH
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		53,899,103
Entity Central Index Key	0000822818
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 512,371	$ 444,698
Short-term marketable securities	82,371	106,101
Accounts receivable, net of allowances aggregating $48,570 and $42,209, respectively	1,100,660	983,111
Unbilled accounts receivable	204,308	107,859
Inventories and supplies	376,564	327,511
Prepaid expenses and other current assets	78,204	82,939
Total current assets	2,354,478	2,052,219
Property, plant and equipment, net	2,452,312	2,193,318
Other assets:
Operating lease right-of-use assets	246,061	187,060
Goodwill	1,485,065	1,287,736
Permits and other intangibles, net	708,935	602,797
Other long-term assets	59,159	59,739
Total other assets	2,499,220	2,137,332
Total assets	7,306,010	6,382,869
Current liabilities:
Current portion of long-term debt	15,102	10,000
Accounts payable	504,206	451,806
Deferred revenue	103,291	95,230
Accrued expenses and other current liabilities	398,236	397,157
Current portion of closure, post-closure and remedial liabilities	30,477	26,914
Current portion of operating lease liabilities	70,539	56,430
Total current liabilities	1,121,851	1,037,537
Other liabilities:
Closure and post-closure liabilities, less current portion of $14,203 and $13,556, respectively	105,375	105,044
Remedial liabilities, less current portion of $16,274 and $13,358, respectively	94,384	97,885
Long-term debt, less current portion	2,773,659	2,291,717
Operating lease liabilities, less current portion	179,040	131,743
Deferred tax liabilities	356,150	353,107
Other long-term liabilities	147,241	118,330
Total other liabilities	3,655,849	3,097,826
Commitments and contingent liabilities (See Note 15)
Stockholders’ equity:
Authorized 80,000,000 shares; issued and outstanding 53,898,805 and 53,929,703 shares, respectively	539	539
Additional paid-in capital	438,904	459,728
Accumulated other comprehensive loss	(192,036)	(175,339)
Retained earnings	2,280,903	1,962,578
Total stockholders’ equity	2,528,310	2,247,506
Total liabilities and stockholders’ equity	$ 7,306,010	$ 6,382,869

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Account receivable, allowances aggregating	$ 48,570	$ 42,209
Closure and post-closure liabilities, current portion	14,203	13,556
Remedial liabilities, current portion	$ 16,274	$ 13,358
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)	53,898,805	53,929,703
Common stock, outstanding shares (in shares)	53,898,805	53,929,703

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenues:
Total revenues	$ 1,529,422	$ 1,365,696	$ 4,458,836	$ 4,070,983
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	1,055,599	943,951	3,062,211	2,822,977
Selling, general and administrative expenses	177,846	171,019	557,590	505,154
Accretion of environmental liabilities	3,618	3,388	10,139	10,281
Depreciation and amortization	100,063	92,970	295,632	267,425
Income from operations	192,296	154,368	533,264	465,146
Other (expense) income, net	(1,123)	334	(2,431)	(833)
Loss on early extinguishment of debt	0	0	0	(2,362)
Interest expense, net of interest income of $5,391, $2,877, $13,257, and $7,833, respectively	(35,779)	(29,696)	(100,767)	(80,400)
Income before provision for income taxes	155,394	125,006	430,066	381,551
Provision for income taxes	40,181	33,666	111,741	102,044
Net income	$ 115,213	$ 91,340	$ 318,325	$ 279,507
Earnings per share:
Basic (in dollars per share)	$ 2.14	$ 1.69	$ 5.90	$ 5.17
Diluted (in dollars per share)	$ 2.12	$ 1.68	$ 5.87	$ 5.14
Shares used to compute earnings per share - Basic (in shares)	53,951	54,122	53,936	54,097
Shares used to compute earnings per share - Diluted (in shares)	54,229	54,419	54,229	54,411
Service revenues
Revenues:
Total revenues	$ 1,278,955	$ 1,129,216	$ 3,719,183	$ 3,341,539
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	872,829	765,004	2,539,569	2,288,199
Product revenues
Revenues:
Total revenues	250,467	236,480	739,653	729,444
Cost of revenues: (exclusive of items shown separately below)
Total cost of revenues	$ 182,770	$ 178,947	$ 522,642	$ 534,778

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Interest income	$ 5,391	$ 2,877	$ 13,257	$ 7,833

UNAUDITED CONSOLIDATED STATEM_3

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 115,213	$ 91,340	$ 318,325	$ 279,507
Other comprehensive loss, net of tax:
Unrealized gain on available-for-sale securities	262	93	170	311
Unrealized (loss) gain on fair value of interest rate hedges	(9,361)	7,801	2,406	15,528
Reclassification adjustment for interest rate hedge amounts realized in net income	(3,806)	(3,650)	(11,260)	(12,704)
Reclassification adjustment for settlement of interest rate hedges	0	0	0	(5,905)
Pension adjustments	(10)	6	18	(1)
Foreign currency translation adjustments	5,369	(7,423)	(8,031)	813
Other comprehensive loss, net of tax	(7,546)	(3,173)	(16,697)	(1,958)
Comprehensive income	$ 107,667	$ 88,167	$ 301,628	$ 277,549

UNAUDITED CONSOLIDATED STATEM_4

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net income	$ 318,325	$ 279,507
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	295,632	267,425
Allowance for doubtful accounts	5,674	2,620
Amortization of deferred financing costs and debt discount	4,623	4,036
Accretion of environmental liabilities	10,139	10,281
Changes in environmental liability estimates	4,347	3,258
Deferred income taxes	(418)	(356)
Other expense, net	2,431	833
Stock-based compensation	20,690	14,809
Loss on early extinguishment of debt	0	2,362
Environmental expenditures	(19,679)	(24,064)
Changes in assets and liabilities, net of acquisitions:
Accounts receivable and unbilled accounts receivable	(145,647)	(46,445)
Inventories and supplies	(39,673)	12,691
Other current and long-term assets	(47,826)	(18,190)
Accounts payable	30,004	(40,013)
Other current and long-term liabilities	35,211	(13,062)
Net cash from operating activities	473,833	455,692
Cash flows used in investing activities:
Additions to property, plant and equipment	(369,826)	(311,906)
Proceeds from sale and disposal of fixed assets	6,353	5,129
Acquisitions, net of cash acquired	(474,011)	(119,596)
Proceeds from sale of business	750	750
Additions to intangible assets including costs to obtain or renew permits	(2,545)	(1,507)
Purchases of available-for-sale securities	(73,682)	(104,329)
Proceeds from sale of available-for-sale securities	100,021	84,390
Net cash used in investing activities	(812,940)	(447,069)
Cash flows from (used in) financing activities:
Change in uncashed checks	(5,852)	3,004
Tax payments related to withholdings on vested restricted stock	(11,514)	(10,886)
Repurchases of common stock	(30,215)	(18,000)
Deferred financing costs paid	(8,316)	(6,371)
Payments on finance leases	(23,596)	(11,594)
Principal payments on debt	(11,327)	(621,475)
Proceeds from issuance of debt, net of discount	499,375	500,000
Borrowing from revolving credit facility	0	114,000
Payment on revolving credit facility	0	(114,000)
Net cash from (used in) financing activities	408,555	(165,322)
Effect of exchange rate change on cash	(1,775)	61
Increase (decrease) in cash and cash equivalents	67,673	(156,638)
Cash and cash equivalents, beginning of period	444,698	492,603
Cash and cash equivalents, end of period	512,371	335,965
Cash payments for interest and income taxes:
Interest paid	134,177	100,813
Income taxes paid, net of refunds	100,752	107,328
Non-cash investing activities:
Property, plant and equipment accrued	43,604	29,127
ROU assets obtained in exchange for operating lease liabilities	98,927	61,741
ROU assets obtained in exchange for finance lease liabilities	$ 53,391	$ 26,317

UNAUDITED CONSOLIDATED STATEM_5

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Balance beginning of period (in shares) at Dec. 31, 2022		54,065,000
Balance beginning of period at Dec. 31, 2022	$ 1,922,322	$ 541	$ 504,240	$ (167,181)	$ 1,584,722
Increase (Decrease) in Stockholders' Equity
Net income	72,401				72,401
Other comprehensive income (loss)	(14,346)			(14,346)
Stock-based compensation	6,018		6,018
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		49,000
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(3,351)		(3,351)
Repurchases of common stock (in shares)		(22,000)
Repurchases of common stock	(3,000)		(3,000)
Balance ending of period (in shares) at Mar. 31, 2023		54,092,000
Balance ending of period at Mar. 31, 2023	1,980,044	$ 541	503,907	(181,527)	1,657,123
Balance beginning of period (in shares) at Dec. 31, 2022		54,065,000
Balance beginning of period at Dec. 31, 2022	1,922,322	$ 541	504,240	(167,181)	1,584,722
Increase (Decrease) in Stockholders' Equity
Net income	279,507
Other comprehensive income (loss)	(1,958)
Balance ending of period (in shares) at Sep. 30, 2023		54,103,000
Balance ending of period at Sep. 30, 2023	2,185,794	$ 541	490,163	(169,139)	1,864,229
Balance beginning of period (in shares) at Mar. 31, 2023		54,092,000
Balance beginning of period at Mar. 31, 2023	1,980,044	$ 541	503,907	(181,527)	1,657,123
Increase (Decrease) in Stockholders' Equity
Net income	115,766				115,766
Other comprehensive income (loss)	15,561			15,561
Stock-based compensation	4,500		4,500
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		34,000
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(984)		(984)
Repurchases of common stock (in shares)		(36,000)
Repurchases of common stock	(5,001)		(5,001)
Balance ending of period (in shares) at Jun. 30, 2023		54,090,000
Balance ending of period at Jun. 30, 2023	2,109,886	$ 541	502,422	(165,966)	1,772,889
Increase (Decrease) in Stockholders' Equity
Net income	91,340				91,340
Other comprehensive income (loss)	(3,173)			(3,173)
Stock-based compensation	4,291		4,291
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		71,000
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(6,551)	$ 1	(6,552)
Repurchases of common stock (in shares)		(58,000)
Repurchases of common stock	(9,999)	$ (1)	(9,998)
Balance ending of period (in shares) at Sep. 30, 2023		54,103,000
Balance ending of period at Sep. 30, 2023	$ 2,185,794	$ 541	490,163	(169,139)	1,864,229
Balance beginning of period (in shares) at Dec. 31, 2023	53,929,703	53,930,000
Balance beginning of period at Dec. 31, 2023	$ 2,247,506	$ 539	459,728	(175,339)	1,962,578
Increase (Decrease) in Stockholders' Equity
Net income	69,832				69,832
Other comprehensive income (loss)	(4,287)			(4,287)
Stock-based compensation	6,338		6,338
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		23,000
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(3,052)		(3,052)
Repurchases of common stock (in shares)		(27,000)
Repurchases of common stock	(5,000)		(5,000)
Balance ending of period (in shares) at Mar. 31, 2024		53,926,000
Balance ending of period at Mar. 31, 2024	$ 2,311,337	$ 539	458,014	(179,626)	2,032,410
Balance beginning of period (in shares) at Dec. 31, 2023	53,929,703	53,930,000
Balance beginning of period at Dec. 31, 2023	$ 2,247,506	$ 539	459,728	(175,339)	1,962,578
Increase (Decrease) in Stockholders' Equity
Net income	318,325
Other comprehensive income (loss)	$ (16,697)
Balance ending of period (in shares) at Sep. 30, 2024	53,898,805	53,899,000
Balance ending of period at Sep. 30, 2024	$ 2,528,310	$ 539	438,904	(192,036)	2,280,903
Balance beginning of period (in shares) at Mar. 31, 2024		53,926,000
Balance beginning of period at Mar. 31, 2024	2,311,337	$ 539	458,014	(179,626)	2,032,410
Increase (Decrease) in Stockholders' Equity
Net income	133,280				133,280
Other comprehensive income (loss)	(4,864)			(4,864)
Stock-based compensation	8,515		8,515
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		27,000
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(1,547)		(1,547)
Repurchases of common stock (in shares)		(23,000)
Repurchases of common stock	(5,000)		(5,000)
Balance ending of period (in shares) at Jun. 30, 2024		53,930,000
Balance ending of period at Jun. 30, 2024	2,441,721	$ 539	459,982	(184,490)	2,165,690
Increase (Decrease) in Stockholders' Equity
Net income	115,213				115,213
Other comprehensive income (loss)	(7,546)			(7,546)
Stock-based compensation	5,837		5,837
Issuance of common stock for restricted share vesting, net of employee tax withholdings (in shares)		54,000
Issuance of common stock for restricted share vesting, net of employee tax withholdings	(6,915)	$ 1	(6,916)
Repurchases of common stock (in shares)		(85,000)
Repurchases of common stock	$ (20,000)	$ (1)	(19,999)
Balance ending of period (in shares) at Sep. 30, 2024	53,898,805	53,899,000
Balance ending of period at Sep. 30, 2024	$ 2,528,310	$ 539	$ 438,904	$ (192,036)	$ 2,280,903

UNAUDITED CONSOLIDATED STATEM_6

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (PARENTHETICAL) - $ / shares	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023
Statement of Stockholders' Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01

BASIS OF PRESENTATION

BASIS OF PRESENTATION	9 Months Ended
BASIS OF PRESENTATION	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION The accompanying consolidated interim financial statements are unaudited and include the accounts of Clean Harbors, Inc. and its subsidiaries (collectively, “Clean Harbors” or the “Company”) and have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) and, in the opinion of management, include all adjustments which are of a normal recurring nature and are necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented. Management has made estimates and assumptions affecting the amounts reported in the Company’s consolidated interim financial statements and accompanying footnotes; actual results could differ from those estimates and judgments. The results for interim periods are not necessarily indicative of results for the entire year or any other interim periods. The financial statements presented herein should be read in conjunction with the financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023.

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
SIGNIFICANT ACCOUNTING POLICIES	Sep. 30, 2024
Accounting Policies [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	SIGNIFICANT ACCOUNTING POLICIES The Company’s significant accounting policies are described in Note 2, “Significant Accounting Policies,” in the Company's Annual Report on Form 10-K for the year ended December 31, 2023. Accounting Pronouncements Not Yet Adopted In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-07, S egment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which requires an enhanced disclosure of significant segment expenses on an annual and interim basis. This guidance will be effective for the Company’s annual period beginning January 1, 2024, and for interim periods beginning January 1, 2025. Early adoption is permitted. Upon adoption, the guidance should be applied retrospectively to all prior periods presented in the financial statements. The requirements of this ASU are disclosure related and will not have an impact on the Company’s financial condition, results of operations, or cash flows. The Company is currently evaluating the impact of adopting this ASU on its reportable segment disclosures. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures , which enhances income tax disclosures related to the tax rate reconciliation and income taxes paid. This guidance will be effective for the annual periods beginning the year ended December 31, 2025. Early adoption is permitted. Upon adoption, the guidance can be applied prospectively or retrospectively. The requirements of this ASU are disclosure related and will not have an impact on the Company’s financial condition, results of operations, or cash flows. The Company is currently evaluating the impact of adopting this ASU on its income tax disclosures. In March 2024, the SEC adopted the final rule under SEC Release No. 33-11275, The Enhancement and Standardization of Climate-Related Disclosures for Investors . The rules require disclosure of, among other things: material climate-related risks; activities to mitigate or adapt to such risks; governance and management of such risks; and material Scope 1 and Scope 2 greenhouse gas emissions. Additionally, the rules require disclosure in the notes to the financial statements of the effects of severe weather events and other natural conditions, subject to certain materiality thresholds. The rules will become effective on a phased-in timeline beginning with the year ended December 31, 2025. On April 4, 2024, the SEC voluntarily stayed implementation of the final rule to facilitate the orderly judicial resolution of pending legal challenges to the rule. The Company is currently monitoring the legal challenges and evaluating the final rule to determine its potential impact on the Company’s consolidated financial statements and disclosures.

REVENUES

REVENUES	9 Months Ended
REVENUES	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
REVENUES	REVENUES The Company generates revenues through the following operating segments: Environmental Services and Safety-Kleen Sustainability Solutions (“SKSS”). The Company’s Environmental Services operating segment generally has four sources of revenue and the SKSS 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, collection and transportation, packaging, recycling, treatment and disposal of waste and remediation projects. These services handle hazardous and/or non-hazardous waste, including per- and polyfluoroalkyl substances (“PFAS”). 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 —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, chemical plants, manufacturing facilities, power generation companies 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, environmental remediation, railcar cleaning, manhole/vault clean outs, product recovery and transfer and vacuum services. Additional services include filtration, water treatment services and wetland restoration. Response services for environmental emergencies of any scale range from man-made disasters such as oil spills to natural disasters like 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 SKSS 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 SKSS 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 SKSS 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): Three Months Ended September 30, 2024 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 1,166,660 $ 218,963 $ 96 $ 1,385,719 Canada 120,990 22,713 — 143,703 Total third-party revenues $ 1,287,650 $ 241,676 $ 96 $ 1,529,422 Sources of Revenue Technical Services $ 437,180 $ — $ — $ 437,180 Industrial Services and Other 345,573 — 96 345,669 Field and Emergency Response Services 260,200 — — 260,200 Safety-Kleen Environmental Services 244,697 59,675 — 304,372 Safety-Kleen Oil — 182,001 — 182,001 Total third-party revenues $ 1,287,650 $ 241,676 $ 96 $ 1,529,422 Three Months Ended September 30, 2023 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 1,017,224 $ 206,860 $ 112 $ 1,224,196 Canada 118,055 23,445 — 141,500 Total third-party revenues $ 1,135,279 $ 230,305 $ 112 $ 1,365,696 Sources of Revenue Technical Services $ 403,889 $ — $ — $ 403,889 Industrial Services and Other 350,251 — 112 350,363 Field and Emergency Response Services 155,046 — — 155,046 Safety-Kleen Environmental Services 226,093 59,458 — 285,551 Safety-Kleen Oil — 170,847 — 170,847 Total third-party revenues $ 1,135,279 $ 230,305 $ 112 $ 1,365,696 Nine Months Ended September 30, 2024 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 3,395,446 $ 645,664 $ 297 $ 4,041,407 Canada 350,781 66,648 — 417,429 Total third-party revenues $ 3,746,227 $ 712,312 $ 297 $ 4,458,836 Sources of Revenue Technical Services $ 1,288,339 $ — $ — $ 1,288,339 Industrial Services and Other 1,064,441 — 297 1,064,738 Field and Emergency Response Services 676,562 — — 676,562 Safety-Kleen Environmental Services 716,885 171,117 — 888,002 Safety-Kleen Oil — 541,195 — 541,195 Total third-party revenues $ 3,746,227 $ 712,312 $ 297 $ 4,458,836 Nine Months Ended September 30, 2023 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 3,017,547 $ 641,625 $ 335 $ 3,659,507 Canada 340,196 71,280 — 411,476 Total third-party revenues $ 3,357,743 $ 712,905 $ 335 $ 4,070,983 Sources of Revenue Technical Services $ 1,160,306 $ — $ — $ 1,160,306 Industrial Services and Other 1,086,175 — 335 1,086,510 Field and Emergency Response Services 457,491 — — 457,491 Safety-Kleen Environmental Services 653,771 171,469 — 825,240 Safety-Kleen Oil — 541,436 — 541,436 Total third-party revenues $ 3,357,743 $ 712,905 $ 335 $ 4,070,983 Contract Balances (in thousands) September 30, 2024 December 31, 2023 Receivables $ 1,100,660 $ 983,111 Contract assets (unbilled receivables) 204,308 107,859 Contract liabilities (deferred revenue) 103,291 95,230 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, which 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 are generally fully recognized in the subsequent three-month period.

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	9 Months Ended
BUSINESS COMBINATIONS	Sep. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS 2024 Acquisitions On March 22, 2024, the Company completed its acquisition of Hepaco Blocker, Inc. and its subsidiaries (collectively, “HEPACO”) for an all-cash purchase price of $392.2 million, net of cash acquired. The Company settled working capital balances for this acquisition in the third quarter of 2024 and adjusted the purchase price accordingly. The operations of HEPACO expand the Environmental Services segment’s field services business. 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 March 22, 2024. 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 March 31, 2024 Measurement Period Adjustments At Acquisition Date As Reported September 30, 2024 Accounts receivable, including unbilled receivables $ 68,496 $ 1,777 $ 70,273 Inventories and supplies 1,574 (1,190) 384 Prepaid expenses and other current assets 5,221 (681) 4,540 Property, plant and equipment 45,453 817 46,270 Permits and other intangibles 130,000 500 130,500 Operating lease right-of-use assets 9,385 — 9,385 Other long-term assets 2,660 — 2,660 Accrued expenses and other current liabilities (43,966) (3,012) (46,978) Current portion of operating lease liabilities (2,758) — (2,758) Operating lease liabilities, less current portion (6,627) — (6,627) Deferred tax liabilities (8,916) — (8,916) Closure and post-closure liabilities — (1,025) (1,025) Other long-term liabilities (374) — (374) Total identifiable net assets 200,148 (2,814) 197,334 Goodwill 195,265 (420) 194,845 Total purchase price $ 395,413 $ (3,234) $ 392,179 Other intangible assets acquired include customer relationships and trademarks/tradenames and are anticipated to have estimated useful lives of between seven and 20 years with a weighted average useful life of approximately 19 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 and liabilities assumed, was recorded as goodwill. The goodwill recognized is attributable to the operating synergies, assembled workforce and growth potential that the Company expects to realize from the acquisition. Goodwill generated from the acquisition is not deductible for tax purposes. The operations included in the Company’s financial statements for the period ended September 30, 2024 , and pro forma revenue and earnings amounts on a combined basis as if this acquisition had been completed on January 1, 2023 are immaterial to the unaudited consolidated financial statements of the Company. On March 1, 2024, the Company acquired Noble Oil Services, Inc and its subsidiaries (collectively, “Noble Oil”) for an all-cash purchase price of $68.7 million, net of cash acquired. The Company settled working capital for this acquisition in the second quarter of 2024 and adjusted the purchase price accordingly. The acquisition of Noble Oil expands the SKSS segment’s oil collection operations in the southeastern region of the United States while also adding incremental production from the re-refinery owned and operated by the acquired company. 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 March 1, 2024. 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 March 31, 2024 Measurement Period Adjustments At Acquisition Date As Reported September 30, 2024 Accounts receivable, including unbilled receivables 5,693 158 5,851 Inventories and supplies 6,817 (219) 6,598 Prepaid expenses and other current assets 423 (16) 407 Property, plant and equipment 38,914 8,782 47,696 Permits and other intangibles 20,200 (5,700) 14,500 Operating lease right-of-use assets 3,615 — 3,615 Other long-term assets 92 — 92 Accrued expenses and other current liabilities (8,990) 97 (8,893) Current portion of operating lease liabilities (1,823) — (1,823) Operating lease liabilities, less current portion (1,792) — (1,792) Closure and post-closure liabilities — (820) (820) Total identifiable net assets 63,149 2,282 65,431 Goodwill 5,744 (2,433) 3,311 Total purchase price $ 68,893 $ (151) $ 68,742 Other intangible assets acquired include customer relationships and trademarks/tradenames and are anticipated to have estimated useful lives of between seven . 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 and liabilities assumed, was recorded as goodwill. The goodwill recognized is attributable to the operating synergies and assembled workforce 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 September 30, 2024 , and pro forma revenue and earnings amounts on a combined basis as if this acquisition had been completed on January 1, 2023 are immaterial to the unaudited consolidated financial statements of the Company. 2023 Acquisition On March 31, 2023, the Company acquired Thompson Industrial Services, LLC (“Thompson Industrial”) for an all-cash purchase price of $110.9 million, net of cash acquired. The operations of Thompson Industrial expand the Environmental Services segment’s industrial service operations in the southeastern region of the United States. The Company finalized the purchase accounting for this acquisition in the first quarter of 2024. The allocation of the purchase price was based on estimates of the fair value and assets acquired and liabilities assumed as of March 31, 2023. The following table summarizes the final determination and recognition of assets acquired and liabilities assumed (in thousands): At Acquisition Date As Reported December 31, 2023 Measurement Period Adjustments Final Allocation As Reported September 30, 2024 Accounts receivable, including unbilled receivables $ 25,233 $ (73) $ 25,160 Inventories and supplies 228 — 228 Prepaid expenses and other current assets 1,302 — 1,302 Property, plant and equipment 26,719 — 26,719 Permits and other intangibles 28,900 — 28,900 Operating lease right-of-use assets 4,716 — 4,716 Other long-term assets 72 — 72 Accrued expenses and other current liabilities (10,385) (145) (10,530) Current portion of operating lease liabilities (1,653) — (1,653) Operating lease liabilities, less current portion (3,063) — (3,063) Other long-term liabilities (560) — (560) Total identifiable net assets 71,509 (218) 71,291 Goodwill 39,346 218 39,564 Total purchase price $ 110,855 $ — $ 110,855 Permits and other intangible assets acquired include customer relationships, trademarks/tradenames and non-compete agreements and are anticipated to have estimated useful lives of between five

INVENTORIES AND SUPPLIES

INVENTORIES AND SUPPLIES	9 Months Ended
INVENTORIES AND SUPPLIES	Sep. 30, 2024
Inventory Disclosure [Abstract]
INVENTORIES AND SUPPLIES	INVENTORIES AND SUPPLIES Inventories and supplies consisted of the following (in thousands): September 30, 2024 December 31, 2023 Supplies $ 195,973 $ 177,217 Oil and oil related products 149,814 118,600 Solvent and solutions 12,788 11,795 Other 17,989 19,899 Total inventories and supplies $ 376,564 $ 327,511 Supplies inventories consist primarily of critical spare parts to support the Company’s incinerator and re-refinery operations and other general supplies used in our 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

PROPERTY, PLANT AND EQUIPMENT	9 Months Ended
PROPERTY, PLANT AND EQUIPMENT	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consisted of the following (in thousands): September 30, 2024 December 31, 2023 Land $ 186,984 $ 174,891 Asset retirement costs (non-landfill) 28,935 27,167 Landfill assets 259,233 253,180 Buildings and improvements (1) 649,401 630,525 Vehicles (2) 1,430,325 1,276,567 Equipment (3) 2,453,616 2,388,370 Construction in progress 316,666 213,601 5,325,160 4,964,301 Less - accumulated depreciation and amortization 2,872,848 2,770,983 Total property, plant and equipment, net $ 2,452,312 $ 2,193,318 ________________ (1) Balances inclusive of gross right-of-use (“ROU”) assets classified as finance leases of $8.0 million in both periods. (2) Balances inclusive of gross ROU assets classified as finance leases of $208.7 million and $151.7 million, respectively. (3) Balances inclusive of gross ROU assets classified as finance leases of $9.3 million and $9.2 million, respectively. Depreciation expense, inclusive of landfill and finance lease amortization, was $86.2 million and $254.9 million for the three and nine months ended September 30, 2024, respectively. Depreciation expense, inclusive of landfill and finance lease amortization, was $80.4 million and $229.7 million for the three and nine months ended September 30, 2023, respectively. The Company recorded $3.3 million and $8.6 million of capitalized interest during the three and nine months ended September 30, 2024, respectively. The Compan y recorded $1.7 million and $4.4 million of capitalized interest during the three and nine months ended September 30, 2023, respectively. Capitalized interest in the periods presented is primarily attributable to the construction of a new incinerator in Kimball, Nebraska.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	9 Months Ended
GOODWILL AND OTHER INTANGIBLE ASSETS	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS The changes in goodwill by segment for the nine months ended September 30, 2024 were as follows (in thousands): Environmental Services Safety-Kleen Sustainability Solutions Totals Balance at January 1, 2024 $ 1,112,013 $ 175,723 $ 1,287,736 Increase from current period acquisitions 194,845 3,311 198,156 Measurement period adjustments from prior period acquisitions 218 — 218 Foreign currency translation (745) (300) (1,045) Balance at September 30, 2024 $ 1,306,331 $ 178,734 $ 1,485,065 The Company assesses goodwill on an annual basis as of December 31 or at an interim date when events or changes in the business environment (“triggering events”) would more likely than not reduce the fair value of a reporting unit below its carrying value. During the period ended September 30, 2024, no such triggering events were identified. As of September 30, 2024 and December 31, 2023, the Company’s intangible assets consisted of the following (in thousands): September 30, 2024 December 31, 2023 Cost Accumulated Net Cost Accumulated Net Permits $ 193,201 $ 123,335 $ 69,866 $ 191,747 $ 117,556 $ 74,191 Customer and supplier relationships 697,295 249,215 448,080 604,994 258,879 346,115 Other intangible assets 114,112 43,210 70,902 100,068 37,862 62,206 Total amortizable permits and other intangible assets 1,004,608 415,760 588,848 896,809 414,297 482,512 Trademarks and trade names 120,087 — 120,087 120,285 — 120,285 Total permits and other intangible assets $ 1,124,695 $ 415,760 $ 708,935 $ 1,017,094 $ 414,297 $ 602,797 Amortization expense of permits, customer and supplier relationships and other intangible assets was $13.9 million and $40.7 million in the three and nine months ended September 30, 2024, respectively. Amortization expense of permits, customer and supplier relationships and other intangible assets was $12.5 million and $37.8 million in the three and nine months ended September 30, 2023, respectively. The expected amortization of the net carrying amount of finite-lived intangible assets at September 30, 2024 was as follows (in thousands): Years Ending December 31, Expected Amortization 2024 (three months) $ 13,608 2025 57,103 2026 50,813 2027 48,308 2028 46,836 Thereafter 372,180 $ 588,848

ACCRUED EXPENSES AND OTHER CURR

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	9 Months Ended
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	Sep. 30, 2024
Payables and Accruals [Abstract]
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES	ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, 2024 December 31, 2023 Accrued compensation and benefits $ 117,526 $ 113,236 Accrued insurance 106,906 107,658 Accrued income, real estate, sales and other taxes 60,547 44,752 Accrued interest 14,799 33,857 Accrued other 98,458 97,654 $ 398,236 $ 397,157

CLOSURE AND POST-CLOSURE LIABIL

CLOSURE AND POST-CLOSURE LIABILITIES	9 Months Ended
CLOSURE AND POST-CLOSURE LIABILITIES	Sep. 30, 2024
Asset Retirement Obligation Disclosure [Abstract]
CLOSURE AND POST-CLOSURE LIABILITIES	CLOSURE AND POST-CLOSURE LIABILITIES The changes to closure and post-closure liabilities (also referred to as “asset retirement obligations”) from January 1, 2024 through September 30, 2024 were as follows (in thousands): Landfill Non-Landfill Total Balance at January 1, 2024 $ 59,443 $ 59,157 $ 118,600 Liabilities assumed in acquisitions — 1,845 1,845 New asset retirement obligations 4,093 — 4,093 Accretion 3,915 3,305 7,220 Changes in estimates recorded to consolidated statement of operations (134) (120) (254) Changes in estimates recorded to consolidated balance sheet 46 39 85 Expenditures (8,728) (3,128) (11,856) Currency translation and other (81) (74) (155) Balance at September 30, 2024 $ 58,554 $ 61,024 $ 119,578 In the nine months ended September 30, 2024, there were no significant benefits or charges resulting from changes in estimates for closure and post-closure liabilities.

REMEDIAL LIABILITIES

REMEDIAL LIABILITIES	9 Months Ended
REMEDIAL LIABILITIES	Sep. 30, 2024
Environmental Remediation Obligations [Abstract]
REMEDIAL LIABILITIES	REMEDIAL LIABILITIES The changes to remedial liabilities from January 1, 2024 through September 30, 2024 were as follows (in thousands): Remedial Remedial Remedial Total Balance at January 1, 2024 $ 1,880 $ 60,277 $ 49,086 $ 111,243 Accretion 69 1,719 1,131 2,919 Changes in estimates recorded to consolidated statement of operations 24 614 3,963 4,601 Expenditures (40) (2,944) (4,839) (7,823) Currency translation and other — (11) (271) (282) Balance at September 30, 2024 $ 1,933 $ 59,655 $ 49,070 $ 110,658

FINANCING ARRANGEMENTS

FINANCING ARRANGEMENTS	9 Months Ended
FINANCING ARRANGEMENTS	Sep. 30, 2024
Debt Disclosure [Abstract]
FINANCING ARRANGEMENTS	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: September 30, 2024 December 31, 2023 Secured senior term loans $ 15,102 $ 10,000 Long-Term Debt: Secured senior term loans due October 8, 2028 1,453,571 970,000 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 Unsecured senior notes, at 6.375%, due February 1, 2031 (“2031 Notes”) 500,000 500,000 Long-term debt, at par $ 2,798,571 $ 2,315,000 Unamortized debt issuance costs and discount (24,912) (23,283) Long-term debt, at carrying value $ 2,773,659 $ 2,291,717 Financing Activities The Company’s significant financing arrangements are described in Note 12, “Financing Arrangements,” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 and, other than as noted below, there have been no material changes to the arrangements described therein. On June 28, 2024, the Company and one of the Company’s Canadian subsidiaries (the “Canadian Borrower”) entered into a seventh amended and restated credit agreement (the “Amended Credit Agreement”) with Bank of America, N.A., as administrative agent, and the lenders party to the Amended Credit Agreement. The Amended Credit Agreement amended and restated the sixth amended and restated credit agreement dated October 28, 2020 (the “Prior Credit Agreement”). Under the Amended Credit Agreement, the Company has the right to obtain revolving loans and letters of credit for a combined maximum of up to $550.0 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. The maximum borrowing amount of $600.0 million under the Amended Credit Agreement is increased from $400.0 million under the Prior Credit Agreement. Borrowings by the Company under the Amended Credit Agreement will bear interest at the Company’s option, at either (i) the sum of Term SOFR plus a SOFR Adjustment of 0.1% plus 1.5% per annum, or (ii) the U.S. Base Rate, plus 0.5% per annum, and borrowings by the Canadian Borrower will bear interest, at the Company’s option, at either (i) the sum of Term CORRA plus a Term CORRA adjustment of either 0.29547% or 0.32138% for the one or three month interest period respectively, plus 1.5% per annum, (ii) the Canadian Prime Rate, plus 0.5% per annum, or (iii) the Canadian Base Rate, plus 0.5% per annum, as those terms are defined in the Amended Credit Agreement. Other terms under the Amended Credit Agreement are substantially the same as under the Prior Credit Agreement. Subject to certain customary conditions, the facility will expire on June 28, 2029. The Company had no outstanding loan balance under the Amended Credit Agreement as of the date of the amendment discussed above, September 30, 2024 or December 31, 2023. As of September 30, 2024, the Company had $469.8 million available to borrow under the revolving credit facility and outstanding letters of credit were $130.2 million. On March 22, 2024, the Company and substantially all of the Company’s domestic subsidiaries entered into Incremental Facility Amendment No. 5 to the Company’s existing Credit Agreement, dated as of June 30, 2017 (“Term Loan Agreement”). Incremental Facility Amendment No. 5 provided for the incurrence of additional term loans (the “2024 Incremental Term Loans”) under the Term Loan Agreement in the aggregate principal amount of $500.0 million. Proceeds from the issuance of the 2024 Incremental Term Loans were $491.1 million after debt discount and debt issuance costs, and were used to fund the acquisition of HEPACO, with the excess increasing the Company’s cash balances. The 2024 Incremental Term Loans are in addition to the aggregate of $980.0 million of term loans (the “Existing Term Loans”) which were outstanding prior to the issuance of the 2024 Incremental Term Loans. Both the 2024 Incremental Term Loans and the Existing Term Loans (collectively referred to as the “2028 Term Loans”) will mature on October 8, 2028, and may be prepaid at any time without premium or penalty other than customary breakage costs. The Company’s obligations under the 2028 Term Loans are guaranteed by substantially all of the Company’s domestic restricted subsidiaries and secured by liens on substantially all of the assets of the Company and the guarantors. The 2028 Term Loans bear interest, at the Company’s election, at either of the following rates: (a) the sum of the Term SOFR Rate (as defined in the Term Loan Agreement) plus 0.11448% (the one-month Term SOFR adjustment) plus a 1.75% margin per annum, or (b) the sum of the Base Rate (as defined in the Term Loan Agreement) plus 0.75% margin per annum. The Term SOFR rate is subject to a floor of 0.00% and the Base Rate is subject to a floor of 1.00%. The Company has elected one-month Term SOFR for interest payments on that debt; however, the Term Loan Agreement provides for Term SOFR adjustments for other interest periods. Interest on the 2028 Term Loans is paid monthly with interest payments on the 2024 Incremental Term Loan portion having commenced in April 2024. As of September 30, 2024 and December 31, 2023, the estimated fair value of the Company’s outstanding long-term debt, including the current portion, was $2.8 billion and $2.3 billion, respectively. The Company’s estimates of 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. As of September 30, 2024, after taking into account the interest rate swaps discussed under the “Cash Flow Hedges” heading below, the Company’s variable rate debt consisted of $868.7 million of the 2028 Term Loans. The Company’s interest rate on this variable rate debt as of September 30, 2024 was 7.06%. On October 8, 2024, the Company and substantially all of the Company’s domestic subsidiaries entered into Amendment No. 6 (the “Sixth Amendment”) to the Term Loan Agreement. The Sixth Amendment (i) eliminated the Term SOFR Adjustment (noted above as 0.11448% per annum) and (ii) resets the six month soft call period for a repricing of the 2028 Term Loans. After giving effect to the repricing, the applicable interest rate margins for the 2028 Term Loans are 1.75% for Term SOFR borrowings and 0.75% for base rate borrowings. Under the Sixth Amendment the 2028 Term Loans may be prepaid at any time without premium or penalty other than customary breakage costs or if the Company engages in certain repricing transactions before April 8, 2025, in which event a 1% prepayment premium would be due. Cash Flow Hedges The Company’s strategy to hedge against fluctuations in variable interest rates involves entering into interest rate derivative agreements. The Company has entered into interest rate swap agreements with a notional amount of $600.0 million (“2022 Swaps”) to effectively fix the interest rate on $600.0 million principal of the outstanding existing Term Loans. The fixed rate on these instruments is 1.9645% and the variable rate is linked to the Term SOFR to mirror the variable interest payments for the Term Loans. For the nine months ended September 30, 2024, including the 1.75% interest rate margin and the 0.11448% SOFR adjustment for the Term Loans, the effective annual interest rate of this $600.0 million of principal debt was approximately 3.83%. Following the Sixth Amendment, which eliminated the 0.11448% SOFR adjustment, the effective annual rate on the $600.0 million of principal is approximately 3.71%. Prior to the phase-out of LIBOR as a referenced rate on June 30, 2023, the fixed rate on the 2022 Swaps was 0.931% and the variable rate was linked to LIBOR, to mirror the LIBOR linked variable interest payments for the existing Term Loans. With the then 2.00% interest rate margin for the existing Term Loans, the effective annual interest rate of the $600.0 million of principal debt was 2.931% through June 30, 2023. The 2022 Swaps will expire on September 30, 2027. At the inception of these instruments, the Company designated the 2022 Swaps as cash flow hedges. As of September 30, 2024, the Company recorded a derivative asset with a fair value of $23.3 million related to the 2022 Swaps. The balance of the derivative asset as of December 31, 2023 was $35.5 million. These assets are included in Other long-term assets on the consolidated balance sheets. No ineffectiveness has been identified on the 2022 Swaps and, therefore the change in fair value is 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 unaudited consolidated statement of operations in the same period or periods during which the hedged transactions affect earnings.

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
EARNINGS PER SHARE	Sep. 30, 2024
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE The computation of basic earnings per share (EPS) is based on the weighted-average number of common shares outstanding. The computation of diluted EPS is based on the weighted-average number of common shares outstanding and potential dilutive common shares during the period as determined by using the treasury stock method. The following are computations of basic and diluted earnings per share (in thousands, except per share amounts): Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 Numerator for basic and diluted earnings per share: Net income $ 115,213 $ 91,340 $ 318,325 $ 279,507 Denominator: Weighted-average shares outstanding, basic 53,951 54,122 53,936 54,097 Dilutive impact of equity awards 278 297 293 314 Weighted-average shares outstanding, diluted 54,229 54,419 54,229 54,411 Basic earnings per share: $ 2.14 $ 1.69 $ 5.90 $ 5.17 Diluted earnings per share: $ 2.12 $ 1.68 $ 5.87 $ 5.14 Potentially dilutive shares outstanding include the dilutive effect of unvested restricted stock awards and employee stock purchase plan (“ESPP”) rights (collectively referred to as “equity awards”). Potentially dilutive shares whose effect would have been antidilutive are excluded from the computation of diluted earnings per share. The Company included all outstanding performance awards, restricted stock awards and ESPP rights in the calculation of diluted earnings per share except as shown in the table below (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Antidilutive restricted stock awards 5 7 6 14 Performance stock awards for which performance criteria was not attained at reporting date 160 103 160 103

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE LOSS	9 Months Ended
ACCUMULATED OTHER COMPREHENSIVE LOSS	Sep. 30, 2024
Equity [Abstract]
ACCUMULATED OTHER COMPREHENSIVE LOSS	ACCUMULATED OTHER COMPREHENSIVE LOSS The changes in accumulated other comprehensive loss by component and related tax impacts for the nine months ended September 30, 2024 were as follows (in thousands): Foreign Currency Translation Unrealized (Loss) Gain on Available-For-Sale Securities Unrealized Gain on Fair Value of Interest Rate Hedges Unrealized Loss on Pension Total Balance at January 1, 2024 $ (200,339) $ (4) $ 25,891 $ (887) $ (175,339) Other comprehensive (loss) income before reclassifications (8,031) 215 3,296 18 (4,502) Amounts reclassified out of accumulated other comprehensive loss — — (15,424) — (15,424) Tax (provision) benefit — (45) 3,274 — 3,229 Other comprehensive (loss) income (8,031) 170 (8,854) 18 (16,697) Balance at September 30, 2024 $ (208,370) $ 166 $ 17,037 $ (869) $ (192,036) The amount realiz ed in the unaudited cons olidated statement of operations during the three and nine months ended September 30, 2024 which was reclassified out of accumu lated other co mprehensive loss was as follows (in thousands): Component of Accumulated Other Comprehensive Loss Three Months Ended September 30, 2024 Nine Months Ended September 30, 2024 Location Unrealized Gain on Fair Value of Interest Rate Hedges $ 5,213 $ 15,424 Interest expense, net of interest income

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	9 Months Ended
STOCK-BASED COMPENSATION	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION Total stock-based compensation cost recognized for the three and nine months ended September 30, 2024 was $5.8 million and $20.7 million, respectively. Total stock-based compensation cost recognized for the three and nine months ended September 30, 2023 was $4.3 million and $14.8 million, respectively. The total income tax benefit recognized in the unaudited consolidated statements of operations from stock-based compensation expense for the three and nine months ended September 30, 2024 was $1.0 million and $3.7 million, respectively. The total income tax benefit recognized in the unaudited consolidated statements of operations from stock-based compensation expense for the three and nine months ended September 30, 2023 was $0.7 million and $2.4 million, respectively. Restricted Stock Awards The following table summarizes information about restricted stock awards for the nine months ended September 30, 2024: Restricted Stock Number of Shares Weighted Average Balance at January 1, 2024 414,623 $ 114.02 Granted 144,341 187.87 Vested (130,495) 102.40 Forfeited (21,578) 143.28 Balance at September 30, 2024 406,891 $ 142.39 As of September 30, 2024, there was $43.8 million of total unrecognized compensation cost arising from restricted stock awards. This cost is expected to be recognized over a weighted average period of 2.9 years. The total fair value of restricted stock vested during the three and nine months ended September 30, 2024 was $16.3 million and $27.2 million, respectively. The total fair value of restricted stock vested during the three and nine months ended September 30, 2023 was $16.6 million and $24.6 million, respectively. Performance Stock Awards Performance stock awards are subject to performance criteria established by the Compensation and Human Capital Committee of the Company’s Board of Directors prior to or at the date of grant. The performance stock awards are earned based on achieving certain revenue, Adjusted EBITDA Margin, Return on Invested Capital and Total Recordable Incident Rate targets set forth in the applicable award agreements. Performance stock awards include continued service conditions through vesting. The following table summarizes information about performance stock awards for the nine months ended September 30, 2024: Performance Stock Number of Shares Weighted Average Balance at January 1, 2024 181,284 $ 114.10 Granted 79,738 173.45 Vested (29,358) 100.63 Forfeited (4,800) 148.48 Balance at September 30, 2024 226,864 $ 135.98 As of September 30, 2024, there was $6.8 million of total unrecognized compensation cost arising from performance stock awards achieved or deemed probable of vesting. The total fair value of performance awards vested during the three and nine months ended September 30, 2024 was $2.6 million and $6.3 million. The total fair value of performance awards vested during the three and nine months ended September 30, 2023 was $1.7 million and $9.6 million, respectively. Employee Stock Purchase Plan On May 22, 2024, the Company’s shareholders approved the Clean Harbors Employee Stock Purchase Plan (the “ESPP”). The ESPP provides a means for eligible employees of the Company to authorize after-tax payroll deductions on a voluntary basis to be used for the periodic purchase of the Company's common stock at a 10% discount to its fair market value. The purchase price paid by the employees will be 90% of the lower of the closing price of the Company's common stock on (i) the first trading day of the offering period or (ii) the last trading day of the offering period. A total of 500,000 shares of common stock are reserved for issuance under the ESPP. As of September 30, 2024, no shares have been issued under the plan.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	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 September 30, 2024 and December 31, 2023, the Company had recorded reserves of $32.7 million and $32.4 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 September 30, 2024 and December 31, 2023, the $32.7 million and $32.4 million, respectively, of reserves consisted of (i) $26.1 million and $25.0 million, respectively, related to pending legal or administrative proceedings, including Superfund liabilities, which were included in remedial liabilities on the consolidated balance sheets, and (ii) $6.6 million and $7.4 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 September 30, 2024, the principal legal and administrative proceedings in which the Company was involved, or which had been terminated during 2024, 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 September 30, 2024, there were approximately 71 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 historically has 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 September 30, 2024. From January 1, 2024 to September 30, 2024, 14 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 or the prior owners of certain facilities the Company has since acquired have been identified as potentially responsible parties (“PRPs”) or potential PRPs of indemnification obligations 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 which received waste potentially shipped by the Company or the prior owners of certain facilities the Company has since acquired. Of the 125 third-party sites, 30 are now settled, 13 are currently requiring expenditures on remediation and 82 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 indemnification agreements at a total of 17 sites. These agreements indemnify the Company with respect to any liability at the 17 sites for waste disposed prior to the Company’s acquisition of the former subsidiaries of Waste Management, Inc. and McKesson Corporation 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 September 30, 2024, there was one proceeding for which the Company believed it was possible that the sanctions could equal or exceed $1.0 million. As of December 31, 2023, there were no proceedings for which the Company believed it was possible that the sanctions could equal or exceed $1.0 million. As of the date of these financial statements, 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.

SEGMENT REPORTING

SEGMENT REPORTING	9 Months Ended
SEGMENT REPORTING	Sep. 30, 2024
Segment Reporting [Abstract]
SEGMENT REPORTING	SEGMENT REPORTING Segment reporting is prepared on the same basis that the Company’s chief operating decision maker (“CODM”), which is a committee comprised of the Company’s Co-Chief Executive Officers, 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 revenue 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 three and nine months ended September 30, 2024 and 2023 (in thousands): Three Months Ended Three Months Ended September 30, 2024 September 30, 2023 Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Environmental Services $ 1,287,650 $ 9,537 $ 1,297,187 $ 1,135,279 $ 11,084 $ 1,146,363 Safety-Kleen Sustainability Solutions 241,676 (9,537) 232,139 230,305 (11,084) 219,221 Corporate Items 96 — 96 112 — 112 Total $ 1,529,422 $ — $ 1,529,422 $ 1,365,696 $ — $ 1,365,696 Nine Months Ended Nine Months Ended September 30, 2024 September 30, 2023 Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Environmental Services $ 3,746,227 $ 32,853 $ 3,779,080 $ 3,357,743 $ 31,397 $ 3,389,140 Safety-Kleen Sustainability Solutions 712,312 (32,853) 679,459 712,905 (31,397) 681,508 Corporate Items 297 — 297 335 — 335 Total $ 4,458,836 $ — $ 4,458,836 $ 4,070,983 $ — $ 4,070,983 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): Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 Adjusted EBITDA: Environmental Services $ 332,502 $ 288,982 $ 956,892 $ 822,949 Safety-Kleen Sustainability Solutions 41,226 31,146 122,402 126,024 Corporate Items (71,914) (65,111) (219,569) (191,312) Total 301,814 255,017 859,725 757,661 Reconciliation to Consolidated Statements of Operations: Accretion of environmental liabilities 3,618 3,388 10,139 10,281 Stock-based compensation 5,837 4,291 20,690 14,809 Depreciation and amortization 100,063 92,970 295,632 267,425 Income from operations 192,296 154,368 533,264 465,146 Other expense (income), net 1,123 (334) 2,431 833 Loss on early extinguishment of debt — — — 2,362 Interest expense, net of interest income 35,779 29,696 100,767 80,400 Income before provision for income taxes $ 155,394 $ 125,006 $ 430,066 $ 381,551

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net income	$ 115,213	$ 133,280	$ 69,832	$ 91,340	$ 115,766	$ 72,401	$ 318,325	$ 279,507

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Sep. 30, 2024
Accounting Policies [Abstract]
Accounting pronouncements not yet adopted	Accounting Pronouncements Not Yet Adopted In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-07, S egment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which requires an enhanced disclosure of significant segment expenses on an annual and interim basis. This guidance will be effective for the Company’s annual period beginning January 1, 2024, and for interim periods beginning January 1, 2025. Early adoption is permitted. Upon adoption, the guidance should be applied retrospectively to all prior periods presented in the financial statements. The requirements of this ASU are disclosure related and will not have an impact on the Company’s financial condition, results of operations, or cash flows. The Company is currently evaluating the impact of adopting this ASU on its reportable segment disclosures. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures , which enhances income tax disclosures related to the tax rate reconciliation and income taxes paid. This guidance will be effective for the annual periods beginning the year ended December 31, 2025. Early adoption is permitted. Upon adoption, the guidance can be applied prospectively or retrospectively. The requirements of this ASU are disclosure related and will not have an impact on the Company’s financial condition, results of operations, or cash flows. The Company is currently evaluating the impact of adopting this ASU on its income tax disclosures. In March 2024, the SEC adopted the final rule under SEC Release No. 33-11275, The Enhancement and Standardization of Climate-Related Disclosures for Investors . The rules require disclosure of, among other things: material climate-related risks; activities to mitigate or adapt to such risks; governance and management of such risks; and material Scope 1 and Scope 2 greenhouse gas emissions. Additionally, the rules require disclosure in the notes to the financial statements of the effects of severe weather events and other natural conditions, subject to certain materiality thresholds. The rules will become effective on a phased-in timeline beginning with the year ended December 31, 2025. On April 4, 2024, the SEC voluntarily stayed implementation of the final rule to facilitate the orderly judicial resolution of pending legal challenges to the rule. The Company is currently monitoring the legal challenges and evaluating the final rule to determine its potential impact on the Company’s consolidated financial statements and disclosures.
Revenue recognition	The Company generates revenues through the following operating segments: Environmental Services and Safety-Kleen Sustainability Solutions (“SKSS”). The Company’s Environmental Services operating segment generally has four sources of revenue and the SKSS 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, collection and transportation, packaging, recycling, treatment and disposal of waste and remediation projects. These services handle hazardous and/or non-hazardous waste, including per- and polyfluoroalkyl substances (“PFAS”). 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 —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, chemical plants, manufacturing facilities, power generation companies 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, environmental remediation, railcar cleaning, manhole/vault clean outs, product recovery and transfer and vacuum services. Additional services include filtration, water treatment services and wetland restoration. Response services for environmental emergencies of any scale range from man-made disasters such as oil spills to natural disasters like 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 SKSS 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 SKSS 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 SKSS 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.

REVENUES (Tables)

REVENUES (Tables)	9 Months Ended
REVENUES (Tables)	Sep. 30, 2024
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): Three Months Ended September 30, 2024 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 1,166,660 $ 218,963 $ 96 $ 1,385,719 Canada 120,990 22,713 — 143,703 Total third-party revenues $ 1,287,650 $ 241,676 $ 96 $ 1,529,422 Sources of Revenue Technical Services $ 437,180 $ — $ — $ 437,180 Industrial Services and Other 345,573 — 96 345,669 Field and Emergency Response Services 260,200 — — 260,200 Safety-Kleen Environmental Services 244,697 59,675 — 304,372 Safety-Kleen Oil — 182,001 — 182,001 Total third-party revenues $ 1,287,650 $ 241,676 $ 96 $ 1,529,422 Three Months Ended September 30, 2023 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 1,017,224 $ 206,860 $ 112 $ 1,224,196 Canada 118,055 23,445 — 141,500 Total third-party revenues $ 1,135,279 $ 230,305 $ 112 $ 1,365,696 Sources of Revenue Technical Services $ 403,889 $ — $ — $ 403,889 Industrial Services and Other 350,251 — 112 350,363 Field and Emergency Response Services 155,046 — — 155,046 Safety-Kleen Environmental Services 226,093 59,458 — 285,551 Safety-Kleen Oil — 170,847 — 170,847 Total third-party revenues $ 1,135,279 $ 230,305 $ 112 $ 1,365,696 Nine Months Ended September 30, 2024 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 3,395,446 $ 645,664 $ 297 $ 4,041,407 Canada 350,781 66,648 — 417,429 Total third-party revenues $ 3,746,227 $ 712,312 $ 297 $ 4,458,836 Sources of Revenue Technical Services $ 1,288,339 $ — $ — $ 1,288,339 Industrial Services and Other 1,064,441 — 297 1,064,738 Field and Emergency Response Services 676,562 — — 676,562 Safety-Kleen Environmental Services 716,885 171,117 — 888,002 Safety-Kleen Oil — 541,195 — 541,195 Total third-party revenues $ 3,746,227 $ 712,312 $ 297 $ 4,458,836 Nine Months Ended September 30, 2023 Environmental Services Safety-Kleen Sustainability Solutions Corporate Total Primary Geographical Markets United States $ 3,017,547 $ 641,625 $ 335 $ 3,659,507 Canada 340,196 71,280 — 411,476 Total third-party revenues $ 3,357,743 $ 712,905 $ 335 $ 4,070,983 Sources of Revenue Technical Services $ 1,160,306 $ — $ — $ 1,160,306 Industrial Services and Other 1,086,175 — 335 1,086,510 Field and Emergency Response Services 457,491 — — 457,491 Safety-Kleen Environmental Services 653,771 171,469 — 825,240 Safety-Kleen Oil — 541,436 — 541,436 Total third-party revenues $ 3,357,743 $ 712,905 $ 335 $ 4,070,983
Schedule of Contract Balances	(in thousands) September 30, 2024 December 31, 2023 Receivables $ 1,100,660 $ 983,111 Contract assets (unbilled receivables) 204,308 107,859 Contract liabilities (deferred revenue) 103,291 95,230

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	9 Months Ended
BUSINESS COMBINATIONS (Tables)	Sep. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the preliminary determination and recognition of assets acquired and liabilities assumed (in thousands): At Acquisition Date As Reported March 31, 2024 Measurement Period Adjustments At Acquisition Date As Reported September 30, 2024 Accounts receivable, including unbilled receivables $ 68,496 $ 1,777 $ 70,273 Inventories and supplies 1,574 (1,190) 384 Prepaid expenses and other current assets 5,221 (681) 4,540 Property, plant and equipment 45,453 817 46,270 Permits and other intangibles 130,000 500 130,500 Operating lease right-of-use assets 9,385 — 9,385 Other long-term assets 2,660 — 2,660 Accrued expenses and other current liabilities (43,966) (3,012) (46,978) Current portion of operating lease liabilities (2,758) — (2,758) Operating lease liabilities, less current portion (6,627) — (6,627) Deferred tax liabilities (8,916) — (8,916) Closure and post-closure liabilities — (1,025) (1,025) Other long-term liabilities (374) — (374) Total identifiable net assets 200,148 (2,814) 197,334 Goodwill 195,265 (420) 194,845 Total purchase price $ 395,413 $ (3,234) $ 392,179 At Acquisition Date As Reported March 31, 2024 Measurement Period Adjustments At Acquisition Date As Reported September 30, 2024 Accounts receivable, including unbilled receivables 5,693 158 5,851 Inventories and supplies 6,817 (219) 6,598 Prepaid expenses and other current assets 423 (16) 407 Property, plant and equipment 38,914 8,782 47,696 Permits and other intangibles 20,200 (5,700) 14,500 Operating lease right-of-use assets 3,615 — 3,615 Other long-term assets 92 — 92 Accrued expenses and other current liabilities (8,990) 97 (8,893) Current portion of operating lease liabilities (1,823) — (1,823) Operating lease liabilities, less current portion (1,792) — (1,792) Closure and post-closure liabilities — (820) (820) Total identifiable net assets 63,149 2,282 65,431 Goodwill 5,744 (2,433) 3,311 Total purchase price $ 68,893 $ (151) $ 68,742 At Acquisition Date As Reported December 31, 2023 Measurement Period Adjustments Final Allocation As Reported September 30, 2024 Accounts receivable, including unbilled receivables $ 25,233 $ (73) $ 25,160 Inventories and supplies 228 — 228 Prepaid expenses and other current assets 1,302 — 1,302 Property, plant and equipment 26,719 — 26,719 Permits and other intangibles 28,900 — 28,900 Operating lease right-of-use assets 4,716 — 4,716 Other long-term assets 72 — 72 Accrued expenses and other current liabilities (10,385) (145) (10,530) Current portion of operating lease liabilities (1,653) — (1,653) Operating lease liabilities, less current portion (3,063) — (3,063) Other long-term liabilities (560) — (560) Total identifiable net assets 71,509 (218) 71,291 Goodwill 39,346 218 39,564 Total purchase price $ 110,855 $ — $ 110,855

INVENTORIES AND SUPPLIES (Table

INVENTORIES AND SUPPLIES (Tables)	9 Months Ended
INVENTORIES AND SUPPLIES (Tables)	Sep. 30, 2024
Inventory Disclosure [Abstract]
Schedule of Inventories and Supplies	Inventories and supplies consisted of the following (in thousands): September 30, 2024 December 31, 2023 Supplies $ 195,973 $ 177,217 Oil and oil related products 149,814 118,600 Solvent and solutions 12,788 11,795 Other 17,989 19,899 Total inventories and supplies $ 376,564 $ 327,511

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	9 Months Ended
PROPERTY, PLANT AND EQUIPMENT (Tables)	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property, plant and equipment consisted of the following (in thousands): September 30, 2024 December 31, 2023 Land $ 186,984 $ 174,891 Asset retirement costs (non-landfill) 28,935 27,167 Landfill assets 259,233 253,180 Buildings and improvements (1) 649,401 630,525 Vehicles (2) 1,430,325 1,276,567 Equipment (3) 2,453,616 2,388,370 Construction in progress 316,666 213,601 5,325,160 4,964,301 Less - accumulated depreciation and amortization 2,872,848 2,770,983 Total property, plant and equipment, net $ 2,452,312 $ 2,193,318 ________________ (1) Balances inclusive of gross right-of-use (“ROU”) assets classified as finance leases of $8.0 million in both periods. (2) Balances inclusive of gross ROU assets classified as finance leases of $208.7 million and $151.7 million, respectively. (3) Balances inclusive of gross ROU assets classified as finance leases of $9.3 million and $9.2 million, respectively.

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	9 Months Ended
GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes to Goodwill	The changes in goodwill by segment for the nine months ended September 30, 2024 were as follows (in thousands): Environmental Services Safety-Kleen Sustainability Solutions Totals Balance at January 1, 2024 $ 1,112,013 $ 175,723 $ 1,287,736 Increase from current period acquisitions 194,845 3,311 198,156 Measurement period adjustments from prior period acquisitions 218 — 218 Foreign currency translation (745) (300) (1,045) Balance at September 30, 2024 $ 1,306,331 $ 178,734 $ 1,485,065
Schedule of Finite-Lived Intangible Assets	As of September 30, 2024 and December 31, 2023, the Company’s intangible assets consisted of the following (in thousands): September 30, 2024 December 31, 2023 Cost Accumulated Net Cost Accumulated Net Permits $ 193,201 $ 123,335 $ 69,866 $ 191,747 $ 117,556 $ 74,191 Customer and supplier relationships 697,295 249,215 448,080 604,994 258,879 346,115 Other intangible assets 114,112 43,210 70,902 100,068 37,862 62,206 Total amortizable permits and other intangible assets 1,004,608 415,760 588,848 896,809 414,297 482,512 Trademarks and trade names 120,087 — 120,087 120,285 — 120,285 Total permits and other intangible assets $ 1,124,695 $ 415,760 $ 708,935 $ 1,017,094 $ 414,297 $ 602,797
Summary of Indefinite-Lived Intangible Assets	As of September 30, 2024 and December 31, 2023, the Company’s intangible assets consisted of the following (in thousands): September 30, 2024 December 31, 2023 Cost Accumulated Net Cost Accumulated Net Permits $ 193,201 $ 123,335 $ 69,866 $ 191,747 $ 117,556 $ 74,191 Customer and supplier relationships 697,295 249,215 448,080 604,994 258,879 346,115 Other intangible assets 114,112 43,210 70,902 100,068 37,862 62,206 Total amortizable permits and other intangible assets 1,004,608 415,760 588,848 896,809 414,297 482,512 Trademarks and trade names 120,087 — 120,087 120,285 — 120,285 Total permits and other intangible assets $ 1,124,695 $ 415,760 $ 708,935 $ 1,017,094 $ 414,297 $ 602,797
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 September 30, 2024 was as follows (in thousands): Years Ending December 31, Expected Amortization 2024 (three months) $ 13,608 2025 57,103 2026 50,813 2027 48,308 2028 46,836 Thereafter 372,180 $ 588,848

ACCRUED EXPENSES AND OTHER CU_2

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	9 Months Ended
ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Tables)	Sep. 30, 2024
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses and other current liabilities consisted of the following (in thousands): September 30, 2024 December 31, 2023 Accrued compensation and benefits $ 117,526 $ 113,236 Accrued insurance 106,906 107,658 Accrued income, real estate, sales and other taxes 60,547 44,752 Accrued interest 14,799 33,857 Accrued other 98,458 97,654 $ 398,236 $ 397,157

CLOSURE AND POST-CLOSURE LIAB_2

CLOSURE AND POST-CLOSURE LIABILITIES (Tables)	9 Months Ended
CLOSURE AND POST-CLOSURE LIABILITIES (Tables)	Sep. 30, 2024
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, 2024 through September 30, 2024 were as follows (in thousands): Landfill Non-Landfill Total Balance at January 1, 2024 $ 59,443 $ 59,157 $ 118,600 Liabilities assumed in acquisitions — 1,845 1,845 New asset retirement obligations 4,093 — 4,093 Accretion 3,915 3,305 7,220 Changes in estimates recorded to consolidated statement of operations (134) (120) (254) Changes in estimates recorded to consolidated balance sheet 46 39 85 Expenditures (8,728) (3,128) (11,856) Currency translation and other (81) (74) (155) Balance at September 30, 2024 $ 58,554 $ 61,024 $ 119,578

REMEDIAL LIABILITIES (Tables)

REMEDIAL LIABILITIES (Tables)	9 Months Ended
REMEDIAL LIABILITIES (Tables)	Sep. 30, 2024
Environmental Remediation Obligations [Abstract]
Schedule of Changes to Remedial Liabilities	The changes to remedial liabilities from January 1, 2024 through September 30, 2024 were as follows (in thousands): Remedial Remedial Remedial Total Balance at January 1, 2024 $ 1,880 $ 60,277 $ 49,086 $ 111,243 Accretion 69 1,719 1,131 2,919 Changes in estimates recorded to consolidated statement of operations 24 614 3,963 4,601 Expenditures (40) (2,944) (4,839) (7,823) Currency translation and other — (11) (271) (282) Balance at September 30, 2024 $ 1,933 $ 59,655 $ 49,070 $ 110,658

FINANCING ARRANGEMENTS (Tables)

FINANCING ARRANGEMENTS (Tables)	9 Months Ended
FINANCING ARRANGEMENTS (Tables)	Sep. 30, 2024
Debt Disclosure [Abstract]
Schedule of the Entity's Financial Arrangements	The following table is a summary of the Company’s long-term debt (in thousands): Current Portion of Long-Term Debt: September 30, 2024 December 31, 2023 Secured senior term loans $ 15,102 $ 10,000 Long-Term Debt: Secured senior term loans due October 8, 2028 1,453,571 970,000 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 Unsecured senior notes, at 6.375%, due February 1, 2031 (“2031 Notes”) 500,000 500,000 Long-term debt, at par $ 2,798,571 $ 2,315,000 Unamortized debt issuance costs and discount (24,912) (23,283) Long-term debt, at carrying value $ 2,773,659 $ 2,291,717

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
EARNINGS PER SHARE (Tables)	Sep. 30, 2024
Earnings Per Share [Abstract]
Schedule of Reconciliation of Basic and Diluted Earnings Per Share Computations	The following are computations of basic and diluted earnings per share (in thousands, except per share amounts): Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 Numerator for basic and diluted earnings per share: Net income $ 115,213 $ 91,340 $ 318,325 $ 279,507 Denominator: Weighted-average shares outstanding, basic 53,951 54,122 53,936 54,097 Dilutive impact of equity awards 278 297 293 314 Weighted-average shares outstanding, diluted 54,229 54,419 54,229 54,411 Basic earnings per share: $ 2.14 $ 1.69 $ 5.90 $ 5.17 Diluted earnings per share: $ 2.12 $ 1.68 $ 5.87 $ 5.14
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The Company included all outstanding performance awards, restricted stock awards and ESPP rights in the calculation of diluted earnings per share except as shown in the table below (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Antidilutive restricted stock awards 5 7 6 14 Performance stock awards for which performance criteria was not attained at reporting date 160 103 160 103

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	9 Months Ended
ACCUMULATED OTHER COMPREHENSIVE LOSS (Tables)	Sep. 30, 2024
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Loss	The changes in accumulated other comprehensive loss by component and related tax impacts for the nine months ended September 30, 2024 were as follows (in thousands): Foreign Currency Translation Unrealized (Loss) Gain on Available-For-Sale Securities Unrealized Gain on Fair Value of Interest Rate Hedges Unrealized Loss on Pension Total Balance at January 1, 2024 $ (200,339) $ (4) $ 25,891 $ (887) $ (175,339) Other comprehensive (loss) income before reclassifications (8,031) 215 3,296 18 (4,502) Amounts reclassified out of accumulated other comprehensive loss — — (15,424) — (15,424) Tax (provision) benefit — (45) 3,274 — 3,229 Other comprehensive (loss) income (8,031) 170 (8,854) 18 (16,697) Balance at September 30, 2024 $ (208,370) $ 166 $ 17,037 $ (869) $ (192,036)
Schedule of Reclassification Out of Accumulated Other Comprehensive Loss	The amount realiz ed in the unaudited cons olidated statement of operations during the three and nine months ended September 30, 2024 which was reclassified out of accumu lated other co mprehensive loss was as follows (in thousands): Component of Accumulated Other Comprehensive Loss Three Months Ended September 30, 2024 Nine Months Ended September 30, 2024 Location Unrealized Gain on Fair Value of Interest Rate Hedges $ 5,213 $ 15,424 Interest expense, net of interest income

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	9 Months Ended
STOCK-BASED COMPENSATION (Tables)	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Restricted Stock Awards	The following table summarizes information about restricted stock awards for the nine months ended September 30, 2024: Restricted Stock Number of Shares Weighted Average Balance at January 1, 2024 414,623 $ 114.02 Granted 144,341 187.87 Vested (130,495) 102.40 Forfeited (21,578) 143.28 Balance at September 30, 2024 406,891 $ 142.39
Schedule of Performance Stock Awards	The following table summarizes information about performance stock awards for the nine months ended September 30, 2024: Performance Stock Number of Shares Weighted Average Balance at January 1, 2024 181,284 $ 114.10 Granted 79,738 173.45 Vested (29,358) 100.63 Forfeited (4,800) 148.48 Balance at September 30, 2024 226,864 $ 135.98

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	9 Months Ended
SEGMENT REPORTING (Tables)	Sep. 30, 2024
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 three and nine months ended September 30, 2024 and 2023 (in thousands): Three Months Ended Three Months Ended September 30, 2024 September 30, 2023 Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Environmental Services $ 1,287,650 $ 9,537 $ 1,297,187 $ 1,135,279 $ 11,084 $ 1,146,363 Safety-Kleen Sustainability Solutions 241,676 (9,537) 232,139 230,305 (11,084) 219,221 Corporate Items 96 — 96 112 — 112 Total $ 1,529,422 $ — $ 1,529,422 $ 1,365,696 $ — $ 1,365,696 Nine Months Ended Nine Months Ended September 30, 2024 September 30, 2023 Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Third-Party Revenues Intersegment Revenues (Expenses), net Direct Revenues Environmental Services $ 3,746,227 $ 32,853 $ 3,779,080 $ 3,357,743 $ 31,397 $ 3,389,140 Safety-Kleen Sustainability Solutions 712,312 (32,853) 679,459 712,905 (31,397) 681,508 Corporate Items 297 — 297 335 — 335 Total $ 4,458,836 $ — $ 4,458,836 $ 4,070,983 $ — $ 4,070,983
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): Three Months Ended Nine Months Ended September 30, September 30, 2024 2023 2024 2023 Adjusted EBITDA: Environmental Services $ 332,502 $ 288,982 $ 956,892 $ 822,949 Safety-Kleen Sustainability Solutions 41,226 31,146 122,402 126,024 Corporate Items (71,914) (65,111) (219,569) (191,312) Total 301,814 255,017 859,725 757,661 Reconciliation to Consolidated Statements of Operations: Accretion of environmental liabilities 3,618 3,388 10,139 10,281 Stock-based compensation 5,837 4,291 20,690 14,809 Depreciation and amortization 100,063 92,970 295,632 267,425 Income from operations 192,296 154,368 533,264 465,146 Other expense (income), net 1,123 (334) 2,431 833 Loss on early extinguishment of debt — — — 2,362 Interest expense, net of interest income 35,779 29,696 100,767 80,400 Income before provision for income taxes $ 155,394 $ 125,006 $ 430,066 $ 381,551

REVENUES - Additional Informati

REVENUES - Additional Information (Details)	9 Months Ended
REVENUES - Additional Information (Details)	Sep. 30, 2024 source
Disaggregation of Revenue [Line Items]
Deferred contract cost, recognition period	3 months
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 Re

REVENUES - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,529,422	$ 1,365,696	$ 4,458,836	$ 4,070,983
Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	437,180	403,889	1,288,339	1,160,306
Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	345,669	350,363	1,064,738	1,086,510
Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	260,200	155,046	676,562	457,491
Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	304,372	285,551	888,002	825,240
Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	182,001	170,847	541,195	541,436
United States
Disaggregation of Revenue [Line Items]
Total revenues	1,385,719	1,224,196	4,041,407	3,659,507
Canada
Disaggregation of Revenue [Line Items]
Total revenues	143,703	141,500	417,429	411,476
Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	1,297,187	1,146,363	3,779,080	3,389,140
Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	232,139	219,221	679,459	681,508
Operating Segments \| Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	1,287,650	1,135,279	3,746,227	3,357,743
Operating Segments \| Environmental Services \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	437,180	403,889	1,288,339	1,160,306
Operating Segments \| Environmental Services \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	345,573	350,251	1,064,441	1,086,175
Operating Segments \| Environmental Services \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	260,200	155,046	676,562	457,491
Operating Segments \| Environmental Services \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	244,697	226,093	716,885	653,771
Operating Segments \| Environmental Services \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments \| Environmental Services \| United States
Disaggregation of Revenue [Line Items]
Total revenues	1,166,660	1,017,224	3,395,446	3,017,547
Operating Segments \| Environmental Services \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	120,990	118,055	350,781	340,196
Operating Segments \| Safety-Kleen Sustainability Solutions
Disaggregation of Revenue [Line Items]
Total revenues	241,676	230,305	712,312	712,905
Operating Segments \| Safety-Kleen Sustainability Solutions \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments \| Safety-Kleen Sustainability Solutions \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments \| Safety-Kleen Sustainability Solutions \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments \| Safety-Kleen Sustainability Solutions \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	59,675	59,458	171,117	171,469
Operating Segments \| Safety-Kleen Sustainability Solutions \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	182,001	170,847	541,195	541,436
Operating Segments \| Safety-Kleen Sustainability Solutions \| United States
Disaggregation of Revenue [Line Items]
Total revenues	218,963	206,860	645,664	641,625
Operating Segments \| Safety-Kleen Sustainability Solutions \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	22,713	23,445	66,648	71,280
Corporate
Disaggregation of Revenue [Line Items]
Total revenues	96	112	297	335
Corporate \| Technical Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Industrial Services and Other
Disaggregation of Revenue [Line Items]
Total revenues	96	112	297	335
Corporate \| Field and Emergency Response Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Safety-Kleen Environmental Services
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| Safety-Kleen Oil
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Corporate \| United States
Disaggregation of Revenue [Line Items]
Total revenues	96	112	297	335
Corporate \| Canada
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 0	$ 0	$ 0

REVENUES - Contract Balances (D

REVENUES - Contract Balances (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Receivables	$ 1,100,660	$ 983,111
Contract assets (unbilled receivables)	204,308	107,859
Contract liabilities (deferred revenue)	$ 103,291	$ 95,230

BUSINESS COMBINATIONS - Additio

BUSINESS COMBINATIONS - Additional Information (Details) - USD ($) $ in Millions	Mar. 22, 2024	Mar. 01, 2024	Mar. 31, 2023
HEPACO
Business Acquisition [Line Items]
Purchase price to acquire business	$ 392.2
Weighted average useful life of acquired intangible assets	19 years
HEPACO \| Minimum
Business Acquisition [Line Items]
Intangible asset, estimated useful life	7 years
HEPACO \| Maximum
Business Acquisition [Line Items]
Intangible asset, estimated useful life	20 years
Noble Oil Services , Inc. Acquisition
Business Acquisition [Line Items]
Purchase price to acquire business		$ 68.7
Weighted average useful life of acquired intangible assets		13 years
Noble Oil Services , Inc. Acquisition \| Minimum
Business Acquisition [Line Items]
Intangible asset, estimated useful life		7 years
Noble Oil Services , Inc. Acquisition \| Maximum
Business Acquisition [Line Items]
Intangible asset, estimated useful life		15 years
Thompson Industrial
Business Acquisition [Line Items]
Purchase price to acquire business			$ 110.9
Weighted average useful life of acquired intangible assets			13 years
Thompson Industrial \| Minimum
Business Acquisition [Line Items]
Intangible asset, estimated useful life			5 years
Thompson Industrial \| Maximum
Business Acquisition [Line Items]
Intangible asset, estimated useful life			15 years

BUSINESS COMBINATIONS - Assets

BUSINESS COMBINATIONS - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	6 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Business Acquisition [Line Items]
Goodwill	$ 1,485,065	$ 1,485,065		$ 1,287,736
Measurement Period Adjustments, Goodwill		218
HEPACO
Business Acquisition [Line Items]
Accounts receivable, including unbilled receivables	70,273	70,273	$ 68,496
Inventories and supplies	384	384	1,574
Prepaid expenses and other current assets	4,540	4,540	5,221
Property, plant and equipment	46,270	46,270	45,453
Permits and other intangibles	130,500	130,500	130,000
Operating lease right-of-use assets	9,385	9,385	9,385
Other long-term assets	2,660	2,660	2,660
Accrued expenses and other current liabilities	(46,978)	(46,978)	(43,966)
Current portion of operating lease liabilities	(2,758)	(2,758)	(2,758)
Operating lease liabilities, less current portion	(6,627)	(6,627)	(6,627)
Deferred tax liabilities	(8,916)	(8,916)	(8,916)
Closure and post-closure liabilities	(1,025)	(1,025)
Other long-term liabilities	(374)	(374)	(374)
Total identifiable net assets	197,334	197,334	200,148
Goodwill	194,845	194,845	195,265
Total purchase price	392,179	392,179	395,413
Measurement Period Adjustments, Accounts receivable, including Unbilled receivables	1,777
Measurement Period Adjustments, Inventories and supplies	(1,190)
Measurement Period Adjustments, Prepaid expenses and other current assets	(681)
Measurement Period Adjustments, Property, plant and equipment	817
Measurement Period Adjustments, Permits and other intangibles	500
Measurement Period Adjustments, Accrued expenses and other current liabilities	(3,012)
Measurement Period Adjustments, Closure and post closure liabilities	(1,025)
Measurement Period Adjustments, Total identifiable net assets	(2,814)
Measurement Period Adjustments, Goodwill	(420)
Measurement Period Adjustments, Total purchase price	(3,234)
Noble Oil Services , Inc. Acquisition
Business Acquisition [Line Items]
Accounts receivable, including unbilled receivables	5,851	5,851	5,693
Inventories and supplies	6,598	6,598	6,817
Prepaid expenses and other current assets	407	407	423
Property, plant and equipment	47,696	47,696	38,914
Permits and other intangibles	14,500	14,500	20,200
Operating lease right-of-use assets	3,615	3,615	3,615
Other long-term assets	92	92	92
Accrued expenses and other current liabilities	(8,893)	(8,893)	(8,990)
Current portion of operating lease liabilities	(1,823)	(1,823)	(1,823)
Operating lease liabilities, less current portion	(1,792)	(1,792)	(1,792)
Closure and post-closure liabilities	(820)	(820)
Total identifiable net assets	65,431	65,431	63,149
Goodwill	3,311	3,311	5,744
Total purchase price	68,742	68,742	$ 68,893
Measurement Period Adjustments, Accounts receivable, including Unbilled receivables	158
Measurement Period Adjustments, Inventories and supplies	(219)
Measurement Period Adjustments, Prepaid expenses and other current assets	(16)
Measurement Period Adjustments, Property, plant and equipment	8,782
Measurement Period Adjustments, Permits and other intangibles	(5,700)
Measurement Period Adjustments, Accrued expenses and other current liabilities	97
Measurement Period Adjustments, Closure and post closure liabilities	(820)
Measurement Period Adjustments, Total identifiable net assets	2,282
Measurement Period Adjustments, Goodwill	(2,433)
Measurement Period Adjustments, Total purchase price	(151)
Thompson Industrial
Business Acquisition [Line Items]
Accounts receivable, including unbilled receivables	25,160	25,160		25,233
Inventories and supplies	228	228		228
Prepaid expenses and other current assets	1,302	1,302		1,302
Property, plant and equipment	26,719	26,719		26,719
Permits and other intangibles	28,900	28,900		28,900
Operating lease right-of-use assets	4,716	4,716		4,716
Other long-term assets	72	72		72
Accrued expenses and other current liabilities	(10,530)	(10,530)		(10,385)
Current portion of operating lease liabilities	(1,653)	(1,653)		(1,653)
Operating lease liabilities, less current portion	(3,063)	(3,063)		(3,063)
Other long-term liabilities	(560)	(560)		(560)
Total identifiable net assets	71,291	71,291		71,509
Goodwill	39,564	39,564		39,346
Total purchase price	$ 110,855	110,855		$ 110,855
Measurement Period Adjustments, Accounts receivable, including Unbilled receivables		(73)
Measurement Period Adjustments, Accrued expenses and other current liabilities		(145)
Measurement Period Adjustments, Total identifiable net assets		(218)
Measurement Period Adjustments, Goodwill		218
Measurement Period Adjustments, Total purchase price		$ 0

INVENTORIES AND SUPPLIES (Detai

INVENTORIES AND SUPPLIES (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Inventory [Line Items]
Total inventories and supplies	$ 376,564	$ 327,511
Supplies
Inventory [Line Items]
Total inventories and supplies	195,973	177,217
Oil and oil related products
Inventory [Line Items]
Total inventories and supplies	149,814	118,600
Solvent and solutions
Inventory [Line Items]
Total inventories and supplies	12,788	11,795
Other
Inventory [Line Items]
Total inventories and supplies	$ 17,989	$ 19,899

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,325,160	$ 4,964,301
Less - accumulated depreciation and amortization	2,872,848	2,770,983
Total property, plant and equipment, net	2,452,312	2,193,318
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	186,984	174,891
Asset retirement costs (non-landfill)
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	28,935	27,167
Landfill assets
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	259,233	253,180
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	649,401	630,525
Right-of-Use assets, finance leases	8,000	8,000
Vehicles
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,430,325	1,276,567
Right-of-Use assets, finance leases	208,700	151,700
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,453,616	2,388,370
Right-of-Use assets, finance leases	9,300	9,200
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 316,666	$ 213,601

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Depreciation expense, inclusive of landfill and finance lease amortization	$ 86.2	$ 80.4	$ 254.9	$ 229.7
Interest costs capitalized	$ 3.3	$ 1.7	$ 8.6	$ 4.4

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS - Changes to Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 1,287,736
Increase from current period acquisitions	198,156
Measurement period adjustments from prior period acquisitions	218
Foreign currency translation	(1,045)
Goodwill, ending balance	1,485,065
Environmental Services
Goodwill [Roll Forward]
Goodwill, beginning balance	1,112,013
Increase from current period acquisitions	194,845
Measurement period adjustments from prior period acquisitions	218
Foreign currency translation	(745)
Goodwill, ending balance	1,306,331
Safety-Kleen Sustainability Solutions
Goodwill [Roll Forward]
Goodwill, beginning balance	175,723
Increase from current period acquisitions	3,311
Measurement period adjustments from prior period acquisitions	0
Foreign currency translation	(300)
Goodwill, ending balance	$ 178,734

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS - Finite-lived and Indefinite Lived Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	$ 1,004,608	$ 896,809
Accumulated Amortization	415,760	414,297
Finite-lived intangible assets, net	588,848	482,512
Total permits and other intangible assets, cost	1,124,695	1,017,094
Total permits and other intangible assets, net	708,935	602,797
Trademarks and trade names
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Trademarks and trade names	120,087	120,285
Permits
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	193,201	191,747
Accumulated Amortization	123,335	117,556
Finite-lived intangible assets, net	69,866	74,191
Customer and supplier relationships
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	697,295	604,994
Accumulated Amortization	249,215	258,879
Finite-lived intangible assets, net	448,080	346,115
Other intangible assets
Schedule of Finite-lived and Indefinite-lived Intangible Assets [Line Items]
Finite-lived intangible assets, cost	114,112	100,068
Accumulated Amortization	43,210	37,862
Finite-lived intangible assets, net	$ 70,902	$ 62,206

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of permits and other intangible assets	$ 13.9	$ 12.5	$ 40.7	$ 37.8

GOODWILL AND OTHER INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLE ASSETS - Expected Future Amortization (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
2024 (three months)	$ 13,608
2025	57,103
2026	50,813
2027	48,308
2028	46,836
Thereafter	372,180
Finite-lived intangible assets, net	$ 588,848	$ 482,512

ACCRUED EXPENSES AND OTHER CU_3

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued compensation and benefits	$ 117,526	$ 113,236
Accrued insurance	106,906	107,658
Accrued income, real estate, sales and other taxes	60,547	44,752
Accrued interest	14,799	33,857
Accrued other	98,458	97,654
Total accrued expenses	$ 398,236	$ 397,157

CLOSURE AND POST-CLOSURE LIAB_3

CLOSURE AND POST-CLOSURE LIABILITIES - Changes in Post-Closure Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Changes to post-closure liabilities
Beginning balance	$ 118,600
Liabilities assumed in acquisitions	1,845
New asset retirement obligations	4,093
Accretion	7,220
Changes in estimates recorded to consolidated statement of operations	(254)
Changes in estimates recorded to consolidated balance sheet	85
Expenditures	(11,856)
Currency translation and other	(155)
Ending balance	119,578
Landfill Retirement Liability
Changes to post-closure liabilities
Beginning balance	59,443
Liabilities assumed in acquisitions	0
New asset retirement obligations	4,093
Accretion	3,915
Changes in estimates recorded to consolidated statement of operations	(134)
Changes in estimates recorded to consolidated balance sheet	46
Expenditures	(8,728)
Currency translation and other	(81)
Ending balance	58,554
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Beginning balance	59,157
Liabilities assumed in acquisitions	1,845
New asset retirement obligations	0
Accretion	3,305
Changes in estimates recorded to consolidated statement of operations	(120)
Changes in estimates recorded to consolidated balance sheet	39
Expenditures	(3,128)
Currency translation and other	(74)
Ending balance	$ 61,024

REMEDIAL LIABILITIES - Changes

REMEDIAL LIABILITIES - Changes to Remedial Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 111,243
Accretion	2,919
Changes in estimates recorded to consolidated statement of operations	4,601
Expenditures	(7,823)
Currency translation and other	(282)
Ending balance	110,658
Remedial Liabilities for Landfill Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	1,880
Accretion	69
Changes in estimates recorded to consolidated statement of operations	24
Expenditures	(40)
Currency translation and other	0
Ending balance	1,933
Remedial Liabilities for Inactive Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	60,277
Accretion	1,719
Changes in estimates recorded to consolidated statement of operations	614
Expenditures	(2,944)
Currency translation and other	(11)
Ending balance	59,655
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	49,086
Accretion	1,131
Changes in estimates recorded to consolidated statement of operations	3,963
Expenditures	(4,839)
Currency translation and other	(271)
Ending balance	$ 49,070

REMEDIAL LIABILITIES - Addition

REMEDIAL LIABILITIES - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Remedial liabilities
Increase in reserve estimate	$ 4,601
Remedial Liabilities for Superfund Site
Remedial liabilities
Increase in reserve estimate	$ 2,900

FINANCING ARRANGEMENTS - Schedu

FINANCING ARRANGEMENTS - Schedule of Financing Arrangements (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Current portion of long-term debt	$ 15,102	$ 10,000
Long-term debt, at par	2,798,571	2,315,000
Unamortized debt issuance costs and discount	(24,912)	(23,283)
Long-term debt, at carrying value	2,773,659	2,291,717
Secured debt \| 2028 Term Loans
Debt Instrument [Line Items]
Current portion of long-term debt	15,102	10,000
Long-term debt, at par	1,453,571	970,000
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 percentage)	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 percentage)	5.125%
Unsecured debt \| Unsecured senior notes, at 6.375%, due February 1, 2031 (“2031 Notes”)
Debt Instrument [Line Items]
Long-term debt, at par	$ 500,000	$ 500,000
Interest rate (as a percentage)	6.375%

FINANCING ARRANGEMENTS - Additi

FINANCING ARRANGEMENTS - Additional Information (Details) - USD ($)				9 Months Ended
	Oct. 08, 2024	Jun. 28, 2024	Mar. 22, 2024	Sep. 30, 2024	Sep. 30, 2023	Jun. 27, 2024	Dec. 31, 2023	Jun. 30, 2023
Debt Instrument [Line Items]
Debt fair value				$ 2,800,000,000			$ 2,300,000,000
2022 Swaps
Debt Instrument [Line Items]
Notional amount of interest rate swap agreements				600,000,000
Derivative asset				$ 23,300,000			35,500,000
Secured debt \| 2024 Incremental Term Loans
Debt Instrument [Line Items]
Debt Instrument, face amount			$ 500,000,000
Proceeds from issuance of debt			491,100,000
Secured debt \| Existing Term Loans
Debt Instrument [Line Items]
Debt outstanding			$ 980,000,000
Effective interest rate (as a percent)				3.83%
Secured debt \| Existing Term Loans \| 2022 Swaps
Debt Instrument [Line Items]
Debt Instrument, face amount				$ 600,000,000
Effective interest rate (as a percent)								2.931%
Secured debt \| Existing Term Loans \| 2022 Swaps \| Subsequent Event
Debt Instrument [Line Items]
Effective interest rate (as a percent)	3.71%
Secured debt \| Existing Term Loans \| 2022 Swaps \| From July 1, 2023 through September 30, 2027
Debt Instrument [Line Items]
Derivative, fixed interest rate				1.9645%
Secured debt \| Existing Term Loans \| 2022 Swaps \| Through June 30, 2023
Debt Instrument [Line Items]
Derivative, fixed interest rate								0.931%
Secured debt \| 2028 Term Loans
Debt Instrument [Line Items]
Debt Instrument, prepayment premium percentage, breakage costs or certain repricing transactions	1%
Secured debt \| 2028 Term Loans, Variable Rate
Debt Instrument [Line Items]
Debt outstanding				$ 868,700,000
Effective interest rate (as a percent)				7.06%
Secured debt \| Base Rate \| 2028 Term Loans
Debt Instrument [Line Items]
Debt, interest margin			0.75%
Debt, floor interest rate			1%
Secured debt \| Base Rate \| 2028 Term Loans \| Subsequent Event
Debt Instrument [Line Items]
Debt, interest margin	0.75%
Secured debt \| Term SOFR Adjustment \| 2028 Term Loans
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)			0.11448%	0.11448%
Secured debt \| SOFR \| Existing Term Loans
Debt Instrument [Line Items]
Debt, interest margin					2%
Secured debt \| SOFR \| 2028 Term Loans
Debt Instrument [Line Items]
Debt, interest margin			1.75%	1.75%
Debt, floor interest rate			0%
Secured debt \| SOFR \| 2028 Term Loans \| Subsequent Event
Debt Instrument [Line Items]
Debt, interest margin	1.75%
Revolving credit facility \| Term CORRA Adjustment 1
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.29547%
Revolving credit facility \| Term CORRA Adjustment 2
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.32138%
Revolving credit facility \| Line of Credit
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity		$ 600,000,000				$ 400,000,000
Debt outstanding				$ 0			$ 0
Available to borrow and outstanding letters of credit				469,800,000
Outstanding letters of credit				$ 130,200,000
Revolving credit facility \| Line of Credit \| SOFR Adjustment
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.10%
Revolving credit facility \| Line of Credit \| SOFR Adjustment and Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		1.50%
Revolving credit facility \| Line of Credit \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.50%
Revolving credit facility \| Line of Credit \| Canadian Rate
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)		0.50%
Revolving credit facility \| Line of Credit \| US Borrower
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity		$ 550,000,000
Revolving credit facility \| Line of Credit \| Canadian Subsidiaries
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity		50,000,000
Letter of Credit \| Line of Credit
Debt Instrument [Line Items]
Revolving credit facility maximum borrowing capacity		$ 250,000,000

EARNINGS PER SHARE - Reconcilia

EARNINGS PER SHARE - Reconciliation of Basic and Diluted Earnings Per Share Computations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator for basic and diluted earnings per share:
Net income, basic	$ 115,213	$ 91,340	$ 318,325	$ 279,507
Net income, diluted	$ 115,213	$ 91,340	$ 318,325	$ 279,507
Denominator:
Weighted-average shares outstanding basic (in shares)	53,951	54,122	53,936	54,097
Dilutive impact of equity awards (in shares)	278	297	293	314
Weighted-average shares outstanding, diluted (in shares)	54,229	54,419	54,229	54,411
Basic earnings per share (in dollars per share)	$ 2.14	$ 1.69	$ 5.90	$ 5.17
Diluted earnings per share (in dollars per share)	$ 2.12	$ 1.68	$ 5.87	$ 5.14

EARNINGS PER SHARE - Antidiluti

EARNINGS PER SHARE - Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance stock awards for which performance criteria was not attained at reporting date (in shares)	160	103	160	103
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive restricted stock awards (in shares)	5	7	6	14

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE LOSS - Changes in Accumulated Other Comprehensive Loss by Component (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	$ 2,441,721	$ 2,311,337	$ 2,247,506	$ 2,109,886	$ 1,980,044	$ 1,922,322	$ 2,247,506	$ 1,922,322
Other comprehensive (loss) income before reclassifications							(4,502)
Amounts reclassified out of accumulated other comprehensive loss							(15,424)
Tax (provision) benefit							3,229
Other comprehensive loss, net of tax	(7,546)	(4,864)	(4,287)	(3,173)	15,561	(14,346)	(16,697)	(1,958)
Balance ending of period	2,528,310	2,441,721	2,311,337	2,185,794	2,109,886	1,980,044	2,528,310	2,185,794
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period	(184,490)	(179,626)	(175,339)	(165,966)	(181,527)	(167,181)	(175,339)	(167,181)
Other comprehensive loss, net of tax	(7,546)	(4,864)	(4,287)	(3,173)	15,561	(14,346)
Balance ending of period	(192,036)	$ (184,490)	(179,626)	$ (169,139)	$ (165,966)	$ (181,527)	(192,036)	$ (169,139)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			(200,339)				(200,339)
Other comprehensive (loss) income before reclassifications							(8,031)
Amounts reclassified out of accumulated other comprehensive loss							0
Tax (provision) benefit							0
Other comprehensive loss, net of tax							(8,031)
Balance ending of period	(208,370)						(208,370)
Unrealized (Loss) Gain on Available-For-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			(4)				(4)
Other comprehensive (loss) income before reclassifications							215
Amounts reclassified out of accumulated other comprehensive loss							0
Tax (provision) benefit							(45)
Other comprehensive loss, net of tax							170
Balance ending of period	166						166
Unrealized Gain on Fair Value of Interest Rate Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			25,891				25,891
Other comprehensive (loss) income before reclassifications							3,296
Amounts reclassified out of accumulated other comprehensive loss							(15,424)
Tax (provision) benefit							3,274
Other comprehensive loss, net of tax							(8,854)
Balance ending of period	17,037						17,037
Unrealized Loss on Pension
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning of period			$ (887)				(887)
Other comprehensive (loss) income before reclassifications							18
Amounts reclassified out of accumulated other comprehensive loss							0
Tax (provision) benefit							0
Other comprehensive loss, net of tax							18
Balance ending of period	$ (869)						$ (869)

ACCUMULATED OTHER COMPREHENSI_4

ACCUMULATED OTHER COMPREHENSIVE LOSS - Reclassified Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
Interest Rate Swap
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized Gain on Fair Value of Interest Rate Hedges	$ 5,213	$ 15,424

STOCK-BASED COMPENSATION - Addi

STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-based compensation	$ 5.8	$ 4.3	$ 20.7	$ 14.8
Income tax benefit	$ 1	$ 0.7	$ 3.7	$ 2.4

STOCK-BASED COMPENSATION - Rest

STOCK-BASED COMPENSATION - Restricted Stock Awards (Details) - Restricted stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Number of Shares
Beginning balance (in shares)			414,623
Granted (in shares)			144,341
Vested (in shares)			(130,495)
Forfeited (in shares)			(21,578)
Ending balance (in shares)	406,891		406,891
Weighted Average Grant-Date Fair Value
Beginning of period (in dollars per share)			$ 114.02
Granted (in dollars per share)			187.87
Vested (in dollars per share)			102.40
Forfeited (in dollars per share)			143.28
End of period (in dollars per share)	$ 142.39		$ 142.39
Unrecognized compensation cost	$ 43.8		$ 43.8
Period for recognition (in years)			2 years 10 months 24 days
Fair value of share-based payment awards	$ 16.3	$ 16.6	$ 27.2	$ 24.6

STOCK-BASED COMPENSATION - Perf

STOCK-BASED COMPENSATION - Performance Stock Awards (Details) - Performance stock awards - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Number of Shares
Beginning balance (in shares)			181,284
Granted (in shares)			79,738
Vested (in shares)			(29,358)
Forfeited (in shares)			(4,800)
Ending balance (in shares)	226,864		226,864
Weighted Average Grant-Date Fair Value
Beginning of period (in dollars per share)			$ 114.10
Granted (in dollars per share)			173.45
Vested (in dollars per share)			100.63
Forfeited (in dollars per share)			148.48
End of period (in dollars per share)	$ 135.98		$ 135.98
Unrecognized compensation cost	$ 6.8		$ 6.8
Fair value of share-based payment awards	$ 2.6	$ 1.7	$ 6.3	$ 9.6

STOCK-BASED COMPENSATION - Empl

STOCK-BASED COMPENSATION - Employee Stock Purchase Plan (Details) - Employee Stock - shares shares in Thousands		9 Months Ended
	May 22, 2024	Sep. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP discount percentage from fair market value	10%
ESPP purchase price of common stock, percent of closing price	90%
Shares originally authorized for issuance (in shares)	500
Shares issued under ESPP (in shares)		0

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	9 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Sep. 30, 2024 USD ($) site claim proceeding	Dec. 31, 2023 USD ($) proceeding
Loss Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 32.7	$ 32.4
Product Liability Cases
Loss Contingencies [Line Items]
Number of proceedings as defendant \| proceeding	71
Number of product liability claims settled or dismissed \| claim	14
Legal and Administrative Proceedings
Loss Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 26.1	25
Federal, State, and Provincial Enforcement Actions
Loss Contingencies [Line Items]
Recorded reserves for actual or probable liabilities \| $	$ 6.6	$ 7.4
Number of proceedings as defendant \| proceeding	1	0
Superfund Proceedings
Loss Contingencies [Line Items]
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	13
Number of sites for which environmental remediation expense is not required	82
Number of sites, potential liability exceeds substantial quota	3
Safety-Kleen Sustainability Solutions
Loss Contingencies [Line Items]
Notices received from owners of third party sites seeking indemnification from the company	17

SEGMENT REPORTING - Narrative (

SEGMENT REPORTING - Narrative (Details)	9 Months Ended
SEGMENT REPORTING - Narrative (Details)	Sep. 30, 2024 segment
Segment Reporting [Abstract]
Number of operating segments	2

SEGMENT REPORTING - Reconciliat

SEGMENT REPORTING - Reconciliation of Third Party Revenues to Direct Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total revenues	$ 1,529,422	$ 1,365,696	$ 4,458,836	$ 4,070,983
Environmental Services
Segment Reporting Information [Line Items]
Total revenues	1,297,187	1,146,363	3,779,080	3,389,140
Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	232,139	219,221	679,459	681,508
Operating Segments \| Environmental Services
Segment Reporting Information [Line Items]
Total revenues	1,287,650	1,135,279	3,746,227	3,357,743
Operating Segments \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	241,676	230,305	712,312	712,905
Intersegment Revenues (Expenses), net \| Environmental Services
Segment Reporting Information [Line Items]
Total revenues	9,537	11,084	32,853	31,397
Intersegment Revenues (Expenses), net \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Total revenues	(9,537)	(11,084)	(32,853)	(31,397)
Corporate
Segment Reporting Information [Line Items]
Total revenues	$ 96	$ 112	$ 297	$ 335

SEGMENT REPORTING - Reconcili_2

SEGMENT REPORTING - Reconciliation to Consolidated Statements of Income to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 301,814	$ 255,017	$ 859,725	$ 757,661
Reconciliation to Consolidated Statements of Operations:
Accretion of environmental liabilities	3,618	3,388	10,139	10,281
Stock-based compensation	5,837	4,291	20,690	14,809
Depreciation and amortization	100,063	92,970	295,632	267,425
Income from operations	192,296	154,368	533,264	465,146
Other expense (income), net	1,123	(334)	2,431	833
Loss on early extinguishment of debt	0	0	0	2,362
Interest expense, net of interest income	35,779	29,696	100,767	80,400
Income before provision for income taxes	155,394	125,006	430,066	381,551
Operating Segments \| Environmental Services
Segment Reporting Information [Line Items]
Adjusted EBITDA	332,502	288,982	956,892	822,949
Operating Segments \| Safety-Kleen Sustainability Solutions
Segment Reporting Information [Line Items]
Adjusted EBITDA	41,226	31,146	122,402	126,024
Corporate
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (71,914)	$ (65,111)	$ (219,569)	$ (191,312)