Casella Waste Systems (CWST) 10-Q 26 Apr 24 2024 Q1 Quarterly report Financial data

COVER

COVER - shares	3 Months Ended
	Mar. 31, 2024	Apr. 15, 2024
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	000-23211
Entity Registrant Name	CASELLA WASTE SYSTEMS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	03-0338873
Entity Address, Address Line One	25 Greens Hill Lane,
Entity Address, City or Town	Rutland,
Entity Address, State or Province	VT
Entity Address, Postal Zip Code	05701
City Area Code	802
Local Phone Number	775-0325
Title of 12(b) Security	Class A common stock, $0.01 par value per share
Trading Symbol	CWST
Security Exchange Name	NASDAQ
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 Central Index Key	0000911177
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		57,120,029
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
CURRENT ASSETS:
Cash and cash equivalents	$ 189,457	$ 220,912
Accounts receivable, net of allowance for credit losses of $3,881 and $4,066, respectively	146,795	157,324
Refundable income taxes	4,108	3,089
Prepaid expenses	14,975	17,223
Inventory	18,537	17,859
Other current assets	11,530	9,918
Total current assets	385,402	426,325
Property and equipment, net of accumulated depreciation and amortization of $1,196,561 and $1,167,541, respectively	978,622	980,553
Operating lease right-of-use assets	99,679	100,844
Goodwill	736,513	735,670
Intangible assets, net	228,865	241,429
Restricted assets	2,281	2,203
Cost method investments	10,967	10,967
Deferred income taxes	11,018	11,224
Other non-current assets	23,907	26,255
Total assets	2,477,254	2,535,470
CURRENT LIABILITIES:
Current maturities of debt	63,368	35,781
Current operating lease liabilities	8,825	9,039
Accounts payable	79,989	116,794
Accrued payroll and related expenses	12,126	22,657
Accrued interest	3,527	3,886
Contract liabilities	29,715	31,472
Current accrued final capping, closure and post-closure costs	10,140	10,773
Other accrued liabilities	36,431	48,456
Total current liabilities	244,121	278,858
Debt, less current portion	980,878	1,007,662
Operating lease liabilities, less current portion	66,630	66,074
Accrued final capping, closure and post-closure costs, less current portion	127,184	123,131
Deferred income taxes	908	627
Other long-term liabilities	31,609	37,327
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
Additional paid-in capital	1,170,946	1,168,812
Accumulated deficit	(150,638)	(146,521)
Accumulated other comprehensive income (loss), net of tax	5,035	(1,080)
Total stockholders' equity	1,025,924	1,021,791
Total liabilities and stockholders' equity	2,477,254	2,535,470
Class A Common Stock
STOCKHOLDERS' EQUITY:
Common stock	571	570
Class B Common Stock
STOCKHOLDERS' EQUITY:
Common stock	$ 10	$ 10

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($) vote $ / shares shares	Dec. 31, 2023 USD ($) vote $ / shares shares
Accounts receivable - trade, allowance for credit losses | $	$ 3,881	$ 4,066
Accumulated depreciation and amortization | $	$ 1,196,561	$ 1,167,541
Class A Common Stock
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	57,120,000	57,007,000
Common stock, shares outstanding (in shares)	57,120,000	57,007,000
Class B Common Stock
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000,000	1,000,000
Common stock, shares issued (in shares)	988,000	988,000
Common stock, shares outstanding (in shares)	988,000	988,000
Votes per share held (in votes) | vote	10	10

UNAUDITED CONSOLIDATED STATEMEN

UNAUDITED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Revenues	$ 341,008	$ 262,595
Operating expenses:
Cost of operations	230,792	180,243
General and administration	44,334	35,679
Depreciation and amortization	54,037	33,435
Expense from acquisition activities	5,010	2,863
Southbridge Landfill closure charge	0	110
Total operating expenses	334,173	252,330
Operating income	6,835	10,265
Other expense (income):
Interest income	(2,812)	(684)
Interest expense	15,882	6,959
Other income	(352)	(349)
Other expense, net	12,718	5,926
(Loss) income before income taxes	(5,883)	4,339
(Benefit) provision for income taxes	(1,766)	791
Net (loss) income	$ (4,117)	$ 3,548
Basic earnings (loss) per share attributable to common stockholders:
Weighted average common shares outstanding, basic (in shares)	58,030	51,770
Basic (loss) earnings per common share (in dollars per share)	$ (0.07)	$ 0.07
Diluted earnings (loss) per share attributable to common stockholders:
Weighted average common shares outstanding, diluted (in shares)	58,030	51,869
Diluted (loss) earnings per common share (in dollars per share)	$ (0.07)	$ 0.07

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (4,117)	$ 3,548
Hedging activity:
Interest rate swap settlements	2,315	1,055
Interest rate swap income reclassified into interest expense	(2,330)	(1,106)
Unrealized gain (loss) resulting from changes in fair value of derivative instruments	8,438	(2,391)
Other comprehensive income (loss), before tax	8,423	(2,442)
Income tax provision (benefit) related to items of other comprehensive income (loss)	2,308	(673)
Other comprehensive income (loss), net of tax	6,115	(1,769)
Comprehensive income	$ 1,998	$ 1,779

UNAUDITED CONSOLIDATED STATEM_3

UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
Beginning balance at Dec. 31, 2022	$ 497,900	$ 661,761	$ (171,920)	$ 7,542		$ 507		$ 10
Beginning balance (in shares) at Dec. 31, 2022						50,704,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	0	(2)				$ 2
Issuance of Class A common stock (in shares)						194,000
Stock-based compensation	1,976	1,976
Net loss	3,548		3,548
Other comprehensive income (loss), hedging activity	(1,769)			(1,769)
Ending balance at Mar. 31, 2023	501,655	663,735	(168,372)	5,773		$ 509		$ 10
Ending balance (in shares) at Mar. 31, 2023					50,898,000	50,898,000	988,000	988,000
Beginning balance at Dec. 31, 2023	1,021,791	1,168,812	(146,521)	(1,080)		$ 570		$ 10
Beginning balance (in shares) at Dec. 31, 2023					57,007,000	57,007,000	988,000	988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	0	(1)				$ 1
Issuance of Class A common stock (in shares)						113,000
Stock-based compensation	2,135	2,135
Net loss	(4,117)		(4,117)
Other comprehensive income (loss), hedging activity	6,115			6,115
Ending balance at Mar. 31, 2024	$ 1,025,924	$ 1,170,946	$ (150,638)	$ 5,035		$ 571		$ 10
Ending balance (in shares) at Mar. 31, 2024					57,120,000	57,120,000	988,000	988,000

UNAUDITED CONSOLIDATED STATEM_4

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash Flows from Operating Activities:
Net (loss) income	$ (4,117)	$ 3,548
Adjustment to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	54,037	33,435
Interest accretion on landfill and environmental remediation liabilities	2,937	2,510
Amortization of debt issuance costs	741	502
Stock-based compensation	2,135	1,976
Operating lease right-of-use assets expense	4,070	3,328
Disposition of assets, other items and charges, net	320	1,315
Deferred income taxes	(2,425)	86
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	10,529	5,694
Accounts payable	(36,505)	(7,563)
Prepaid expenses, inventories and other assets	3,739	1,701
Accrued expenses, contract liabilities and other liabilities	(27,782)	(30,453)
Net cash provided by operating activities	7,679	16,079
Cash Flows from Investing Activities:
Acquisitions, net of cash acquired	(294)	(263)
Additions to property and equipment	(30,251)	(17,879)
Proceeds from sale of property and equipment	488	415
Net cash used in investing activities	(30,057)	(17,727)
Cash Flows from Financing Activities:
Proceeds from debt borrowings	875	0
Principal payments on debt	(9,952)	(8,996)
Payments of debt issuance costs	0	(282)
Net cash used in financing activities	(9,077)	(9,278)
Net decrease in cash and cash equivalents	(31,455)	(10,926)
Cash and cash equivalents, beginning of period	220,912	71,152
Cash and cash equivalents, end of period	189,457	60,226
Cash paid during the period for:
Cash interest payments	15,500	5,873
Cash income tax payments	1,681	4,807
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Right-of-use assets obtained in exchange for financing lease obligations	9,139	1,634
Right-of-use assets obtained in exchange for operating lease obligations	$ 1,613	$ 5,682

BASIS OF PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION Casella Waste Systems, Inc. (“Parent”) and its subsidiaries (collectively, “we”, “us” or “our”), is a regional, vertically integrated solid waste services company. We provide resource management expertise and services to residential, commercial, municipal, institutional and industrial customers, primarily in the areas of solid waste collection and disposal, transfer, recycling and organics services. We provide integrated solid waste services in nine states: Vermont, New Hampshire, New York, Massachusetts, Connecticut, Maine, Pennsylvania, Delaware and Maryland, with our headquarters located in Rutland, Vermont. We manage our solid waste operations on a geographic basis through regional operating segments, the Eastern, Western and Mid-Atlantic regions, each of which provides a comprehensive range of non-hazardous solid waste services. We manage our resource renewal operations through the Resource Solutions operating segment, which leverages our core competencies in materials processing, industrial recycling, organics and resource management service offerings to deliver a comprehensive solution for our larger commercial, municipal, institutional and industrial customers that have more diverse waste and recycling needs. Legal, tax, information technology, human resources, certain finance and accounting and other administrative functions are included in our Corporate Entities segment. The accompanying unaudited consolidated financial statements, which include the accounts of the Parent and our wholly-owned subsidiaries, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). All significant intercompany accounts and transactions are eliminated in consolidation. Investments in entities in which we do not have a controlling financial interest are accounted for under either the equity method or the cost method of accounting, as appropriate. Our significant accounting policies are more fully discussed in Item 8. “ Financial Statements and Supplementary Data ” of our Annual Report on Form 10-K for the fiscal year ended December 31, 2023 (“fiscal year 2023”), which was filed with the SEC on February 16, 2024 (“2023 Form 10-K”). Preparation of our consolidated financial statements in accordance with GAAP requires management to make certain estimates and assumptions. These estimates and assumptions affect the accounting for and recognition and disclosure of assets, liabilities, equity, revenues and expenses. We must make these estimates and assumptions because certain information that we use is dependent on future events, cannot be calculated with a high degree of precision given the available data, or simply cannot be readily calculated. In the opinion of management, these consolidated financial statements include all adjustments, including normal recurring and nonrecurring adjustments, as applicable, necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. The results for the three months ended March 31, 2024 may not be indicative of the results for any other interim period or the entire fiscal year. The consolidated financial statements presented herein should be read in conjunction with our audited consolidated financial statements included in our 2023 Form 10-K. Subsequent Events We have evaluated subsequent events or transactions that have occurred after the consolidated balance sheet date of March 31, 2024 through the date of filing of the consolidated financial statements with the SEC on this Quarterly Report on Form 10-Q and determined that there have been no material events that have occurred that would require recognition or adjustments to our disclosures in our consolidated financial statements.

ACCOUNTING CHANGES

ACCOUNTING CHANGES	3 Months Ended
	Mar. 31, 2024
Accounting Changes and Error Corrections [Abstract]
ACCOUNTING CHANGES	ACCOUNTING CHANGES The following table provides a brief description of recent Accounting Standards Updates (“ASU”) to the Accounting Standards Codification (“ASC”) issued by the Financial Accounting Standards Board (“FASB”) and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity: Standard Description Effect on the Financial Statements or Other Accounting standards issued pending adoption ASU No. 2023-07: Improvements to Reportable Segment Disclosures (Topic 280) Requires entities to provide additional disclosure related to the chief operating decision maker (“CODM”) and reportable operating segments, including providing more detailed information about reportable operating segment's significant expenses and how that information is used by the CODM. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements, however, the adoption of this guidance will have an impact on reportable operating segment disclosures within the accompanying notes to our consolidated financial statements. This guidance does not change how we identify our operating segments, aggregate them or apply quantitative thresholds to determine our reportable segments. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. ASU No. 2023-09: Improvements to Income Tax Disclosures (Topic 740) Requires entities to provide additional disclosure related to the transparency and decision usefulness of income tax disclosures, including additional disclosure around the rate reconciliation and income taxes paid. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements, however, the adoption of this guidance will have an impact on income tax disclosures within the accompanying notes to our consolidated financial statements. This guidance is effective for fiscal years beginning after December 15, 2024, with early adoption permitted.

REVENUE RECOGNITION

REVENUE RECOGNITION	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION Revenues associated with our solid waste operations are derived mainly from solid waste collection and disposal services, including landfill, transfer station and transportation services, landfill gas-to-energy services and processing services. Revenues associated with our resource renewal operations are derived from processing services and non-processing services, which we refer to as our National Accounts business. The following tables set forth revenues disaggregated by service line and timing of revenue recognition by operating segment for each of the three months ended March 31, 2024 and 2023: Three Months Ended March 31, 2024 Eastern Western Mid-Atlantic Resource Solutions Total Revenues Collection $ 70,260 $ 99,870 $ 41,230 $ — $ 211,360 Landfill 6,612 12,938 — — 19,550 Transfer station 14,129 11,971 374 — 26,474 Transportation 1,276 2,839 — — 4,115 Landfill gas-to-energy 458 2,051 — — 2,509 Processing 1,269 660 — 29,762 31,691 National Accounts — — — 45,309 45,309 Total revenues $ 94,004 $ 130,329 $ 41,604 $ 75,071 $ 341,008 Transferred at a point-in-time $ 122 $ 618 $ — $ 12,552 $ 13,292 Transferred over time 93,882 129,711 41,604 62,519 327,716 Total revenues $ 94,004 $ 130,329 $ 41,604 $ 75,071 $ 341,008 Three Months Ended March 31, 2023 Eastern Western Mid-Atlantic (1) Resource Solutions Total Revenues Collection $ 61,108 $ 78,869 $ — $ — $ 139,977 Landfill 6,301 16,460 — — 22,761 Transfer station 13,981 9,961 — — 23,942 Transportation 1,183 3,580 — — 4,763 Landfill gas-to-energy 213 1,711 — — 1,924 Processing 1,123 453 — 22,806 24,382 National Accounts — — — 44,846 44,846 Total revenues $ 83,909 $ 111,034 $ — $ 67,652 $ 262,595 Transferred at a point-in-time $ 119 $ 731 $ — $ 6,438 $ 7,288 Transferred over time 83,790 110,303 — 61,214 255,307 Total revenues $ 83,909 $ 111,034 $ — $ 67,652 $ 262,595 (1) Operations under the Mid-Atlantic region commenced July 1, 2023. Payments to customers that are not in exchange for a distinct good or service are recorded as a reduction of revenues. Rebates to certain customers associated with payments for recycled or organic materials that are received and subsequently processed and sold to other third-parties amounted to $7,115 in the three months ended March 31, 2024 and $6,629 in the three months ended March 31, 2023. Rebates are generally recorded as a reduction of revenues upon the sale of such materials, or upon receipt of the recycled materials at our facilities. We did not record revenues in the three months ended March 31, 2024 or March 31, 2023 from performance obligations satisfied in previous periods. Contract receivables, which are included in accounts receivable, net in our consolidated balance sheets are recorded when billed or when related revenue is earned, if earlier, and represent claims against third-parties that will be settled in cash. Accounts receivable, net includes receivables from contracts of $147,635 and $158,931 as of March 31, 2024 and December 31, 2023, respectively. Certain customers are billed in advance and, accordingly, recognition of the related revenues for which payment has been received is deferred as a contract liability until the services are provided and control transferred to the customer. We recognized contract liabilities of $29,715 and $31,472 as of March 31, 2024 and December 31, 2023, respectively. Due to the short term nature of advanced billings, substantially all of the deferred revenue recognized as a contract liability as of December 31, 2023 and December 31, 2022 was recognized as revenue during the three months ended March 31, 2024 and March 31, 2023, respectively, when the services were performed.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS A summary of the activity and balances related to goodwill by operating segment is as follows: December 31, Measurement Period Adjustments March 31, Eastern $ 73,893 $ — $ 73,893 Western 285,056 762 285,818 Mid-Atlantic 332,247 (107) 332,140 Resource Solutions 44,474 188 44,662 $ 735,670 $ 843 $ 736,513 Summaries of intangible assets by type follows: Covenants Customer Relationships Trade Names Total Balance, March 31, 2024 Intangible assets $ 61,573 $ 272,571 $ 13,325 $ 347,469 Less accumulated amortization (29,569) (80,514) (8,521) (118,604) $ 32,004 $ 192,057 $ 4,804 $ 228,865 Covenants Customer Relationships Trade Names Total Balance, December 31, 2023 Intangible assets $ 61,573 $ 272,571 $ 13,325 $ 347,469 Less accumulated amortization (26,645) (72,227) (7,168) (106,040) $ 34,928 $ 200,344 $ 6,157 $ 241,429 Intangible amortization expense was $12,564 during the three months ended March 31, 2024, and $4,071 during the three months ended March 31, 2023. A summary of intangible amortization expense estimated for each of the next five fiscal years following fiscal year 2023 and thereafter is estimated as follows: Estimated Future Amortization Expense as of March 31, 2024 Fiscal year ending December 31, 2024 $ 35,421 Fiscal year ending December 31, 2025 $ 43,593 Fiscal year ending December 31, 2026 $ 38,720 Fiscal year ending December 31, 2027 $ 34,129 Fiscal year ending December 31, 2028 $ 29,077 Thereafter $ 47,925

ACCRUED FINAL CAPPING, CLOSURE

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	3 Months Ended
	Mar. 31, 2024
Asset Retirement Obligation Disclosure [Abstract]
ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE Accrued final capping, closure and post-closure costs include the current and non-current portion of costs associated with obligations for final capping, closure and post-closure of our landfills. We estimate our future final capping, closure and post-closure costs in order to determine the final capping, closure and post-closure expense per ton of waste placed into each landfill. The anticipated time frame for paying these costs varies based on the remaining useful life of each landfill as well as the duration of the post-closure monitoring period. A summary of the changes to accrued final capping, closure and post-closure liabilities follows: Three Months Ended 2024 2023 Beginning balance $ 133,904 $ 113,678 Obligations incurred 1,549 1,247 Accretion expense 2,869 2,410 Obligations settled (1) (998) (1,179) Ending balance $ 137,324 $ 116,156 (1) May include amounts that are being processed through accounts payable as a part of our disbursements cycle.

DEBT

DEBT	3 Months Ended
	Mar. 31, 2024
Debt And Derivatives Disclosure [Abstract]
DEBT	DEBT A summary of debt is as follows: March 31, December 31, Senior Secured Credit Facility: Term loan A facility (“Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.054% as of March 31, 2024 $ 349,125 $ 350,000 Term loan A facility (“2023 Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.552% as of March 31, 2024 413,875 419,250 Revolving credit facility (“Revolving Credit Facility”) due December 2026; bearing interest at term secured overnight financing rate (“Term SOFR”) plus 1.725% — — Tax-Exempt Bonds: New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014 (“New York Bonds 2014R-1”) due December 2044 - fixed rate interest period bearing interest at 2.875% through December 2029 25,000 25,000 New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 (“New York Bonds 2014R-2”) due December 2044 - fixed rate interest period bearing interest at 3.125% through May 2026 15,000 15,000 New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2020 (“New York Bonds 2020”) due September 2050 - fixed rate interest period bearing interest at 2.750% through September 2025 40,000 40,000 New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2020R-2 (“New York Bonds 2020R-2”) due September 2050 - fixed rate interest period bearing interest at 5.125% through September 2030 35,000 35,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 (“FAME Bonds 2005R-3”) due January 2025 - fixed rate interest period bearing interest at 5.25% through January 2025 25,000 25,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-1 (“FAME Bonds 2015R-1”) due August 2035 - fixed rate interest period bearing interest at 5.125% through July 2025 15,000 15,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2 (“FAME Bonds 2015R-2”) due August 2035 - fixed rate interest period bearing interest at 4.375% through July 2025 15,000 15,000 Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 (“Vermont Bonds 2013”) due April 2036 - fixed rate interest period bearing interest at 4.625% through April 2028 16,000 16,000 Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2022A-1 (“Vermont Bonds 2022A-1”) due June 2052 - fixed rate interest period bearing interest at 5.00% through May 2027 35,000 35,000 Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 (“New Hampshire Bonds”) due April 2029 - fixed rate interest period bearing interest at 2.95% through April 2029 11,000 11,000 Other: Finance leases 59,460 53,066 Notes payable maturing through March 2025; bearing interest up to 8.1% 146 230 Principal amount of debt 1,054,606 1,054,546 Less—unamortized debt issuance costs 10,360 11,103 Debt less unamortized debt issuance costs 1,044,246 1,043,443 Less—current maturities of debt 63,368 35,781 $ 980,878 $ 1,007,662 Cash Flow Hedges Our strategy to reduce exposure to interest rate risk involves entering into interest rate derivative agreements to hedge against adverse movements in interest rates related to the variable rate portion of our long-term debt. We have designated these derivative instruments as highly effective cash flow hedges, and therefore the change in their fair value is recorded in stockholders’ equity as a component of accumulated other comprehensive income (loss), net of tax and included in interest expense at the same time as interest expense is affected by the hedged transactions. Differences paid or received over the life of the agreements are recorded as additions to or reductions of interest expense on the underlying debt and included in cash flows from operating activities. As of both March 31, 2024 and December 31, 2023, we had $515,000 notional amount of active interest rate derivative agreements outstanding. These agreements mature between February 2026 and June 2028 and provide that we receive interest based on Term SOFR, restricted by a 0.0% floor, and pay interest at a weighted average rate of approximately 3.6%. A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheets follows: Fair Value Balance Sheet Location March 31, December 31, Interest rate swaps Other current assets $ 7,196 $ 5,951 Interest rate swaps Other non-current assets 5,261 4,413 $ 12,457 $ 10,364 Interest rate swaps Other long-term liabilities $ 5,433 $ 11,762 Interest rate swaps Accumulated other comprehensive income (loss), net of tax $ 7,024 $ (1,398) Interest rate swaps - tax effect Accumulated other comprehensive income (loss), net of tax (1,989) 318 $ 5,035 $ (1,080)

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal Proceedings In the ordinary course of our business and as the result of the extensive governmental regulation of the solid waste industry, we are subject to various judicial and administrative proceedings involving state and local agencies. In these proceedings, an agency may seek to impose fines or to revoke or deny renewal of an operating permit held by us. From time to time, we may also be subject to actions brought by special interest or other groups, adjacent landowners or residents in connection with the permitting and licensing of landfills and transfer stations, or allegations of environmental damage or violations of the permits and licenses pursuant to which we operate. In addition, we may be named defendants in various claims and suits pending for alleged damages to persons and property, alleged violations of certain laws and alleged liabilities arising out of matters occurring during the ordinary operation of a waste management business. The plaintiffs in some actions seek unspecified damages or injunctive relief, or both. These actions fall within various procedural stages at any point in time, and some are covered in part by insurance. In accordance with FASB ASC 450 - Contingencies, we accrue for legal proceedings, inclusive of legal costs, when losses become probable and reasonably estimable. We have recorded an aggregate accrual of $23 relating to our outstanding legal proceedings as of March 31, 2024. As of the end of each applicable reporting period, we review each of our legal proceedings to determine whether it is probable, reasonably possible or remote that a liability has been incurred and, if it is at least reasonably possible, whether a range of loss can be reasonably estimated under the provisions of FASB ASC 450-20. In instances where we determine that a loss is probable and we can reasonably estimate a range of loss we may incur with respect to such a matter, we record an accrual for the amount within the range that constitutes our best estimate of the possible loss. If we are able to reasonably estimate a range, but no amount within the range appears to be a better estimate than any other, we record an accrual in the amount that is the low end of such range. When a loss is reasonably possible, but not probable, we will not record an accrual, but we will disclose our estimate of the possible range of loss where such estimate can be made in accordance with FASB ASC 450-20. We disclose outstanding matters that we believe could have a material adverse effect on our financial condition, results of operations or cash flows. North Country Environmental Services Expansion Permit The permit for expansion of the Bethlehem, New Hampshire landfill of our subsidiary, North Country Environmental Services, Inc. (“NCES”), known as “Stage VI”, issued in October 2020 (“Permit”), was appealed by the Conservation Law Foundation (“CLF”) to the New Hampshire Waste Management Council (“Council”) on November 9, 2020 on the grounds it failed to meet the public benefit criteria. Following a hearing on the merits during which the Council found that the New Hampshire Department of Environmental Services (“DES”) had reasonably measured and acted lawfully in determining a capacity need for Stage VI, the hearing officer presiding over the proceedings issued an Order on May 11, 2022, without further hearing, determining instead that DES had acted unlawfully in reaching these conclusions (“Hearing Officer’s Order”), and remanded the Permit to DES on this determination. On December 5, 2022, DES and NCES both separately sought review of the Hearing Officer’s Order on appeal to the New Hampshire Supreme Court (“Supreme Court”). The parties presented oral arguments to the Supreme Court on October 3, 2023. On December 28, 2023, the Supreme Court issued a decision reversing the Hearing Officer's Order and held that the Stage VI Permit was lawfully issued by DES, fully resolving this matter and upholding the Stage VI Permit. On December 14, 2022, NCES filed an action in Merrimack Superior Court (“Superior Court”) seeking to invalidate the Hearing Officer’s Order as having been adopted in violation of New Hampshire’s statute governing access to public records and meetings in that the Council did not hold a public meeting to deliberate on the Hearing Officer’s Order. The Superior Court dismissed that proceeding by Order dated April 6, 2023, and NCES appealed that decision to the Supreme Court on April 18, 2023. NCES’s brief on appeal was filed with the Supreme Court on August 11, 2023. On September 26, 2023, CLF filed a Motion to Intervene as well as a memorandum of law asking the Supreme Court to uphold the Superior Court’s dismissal, to which NCES filed an Objection in response on October 23, 2023. The Council filed its brief on October 25, 2023. On November 9, 2023, the Supreme Court issued an Order denying CLF’s Motion to Intervene but treating CLF’s memorandum of law as an amicus brief. NCES filed a reply brief on November 14, 2023. On January 18, 2024, the Supreme Court issued an Order setting a deadline of February 2, 2024 for the parties to submit memoranda addressing the mootness of this appeal in light of the Supreme Court’s December 28, 2023 Order reversing the Hearing Officer’s Order and upholding the Stage VI Permit. NCES subsequently filed a Motion for Vacatur of the Superior Court’s April 6, 2023 Order and a Memorandum in Response to the Supreme Court's February 2, 2024 Order on January 23, 2024. On March 18, 2024, the Supreme Court issued an order finding the appeal to be moot and vacating the Superior Court’s April 6, 2023 Order, resolving this matter. On September 20, 2022, NCES, which has since withdrawn as a party, and our subsidiary, Granite State Landfill, LLC (“GSL”), filed a Petition for Declaratory Judgment (“Petition”) in the Superior Court asking the Superior Court for a determination of the meaning and constitutionality of New Hampshire’s public benefit requirement, the same statute at issue in the Hearing Officer’s Order. CLF was granted intervention in the Petition proceeding on June 8, 2023. On December 19, 2023, GSL filed a Motion To Stay pending the outcome of the Supreme Court’s consideration of the Stage VI Permit appeal. The Stage VI Permit appeal was decided and upheld by Order of December 28, 2023 as discussed above. As NCES prevailed in the Stage VI Permit appeal, GSL and NCES voluntarily non-suited the Petition on January 2, 2024, resolving this matter. On April 12, 2023, DES issued approval of construction plans for Stage VI, Phase II to NCES (“DES Approval”). CLF appealed the DES Approval to the Council on May 11, 2023, on the grounds that it failed to meet the public benefit criteria, and that the DES Approval conflicts with the Hearing Officer’s May 11, 2022 Order determining that DES had acted unlawfully in issuing the Permit, and requested expedited review. The Council has denied CLF's request for expedited review. CLF withdrew its appeal by notice to the Council on February 7, 2024. In light of CLF's withdrawal of appeal, this matter is fully resolved. Environmental Remediation Liabilities We are subject to liability for environmental damage, including personal injury and property damage, that our solid waste, recycling and power generation facilities may cause to neighboring property owners, particularly as the result of the contamination of drinking water sources or soil, possibly including damage resulting from conditions that existed before we acquired the facilities. We may also be subject to liability for similar claims arising from off-site environmental contamination caused by pollutants or hazardous substances if we or our predecessors arrange or arranged to transport, treat or dispose of those materials. We accrue for costs associated with environmental remediation obligations when such costs become both probable and reasonably estimable. Determining the method and ultimate cost of remediation requires that a number of assumptions be made. There can sometimes be a range of reasonable estimates of the costs associated with remediation of a site. In these cases, we use the amount within the range that constitutes our best estimate. In the early stages of the remediation process, particular components of the overall liability may not be reasonably estimable; in this instance we use the components of the liability that can be reasonably estimated as a surrogate for the liability. It is reasonably possible that we will need to adjust the liabilities recorded for remediation to reflect the effects of new or additional information, to the extent such information impacts the costs, timing or duration of the required actions. Future changes in our estimates of the cost, timing or duration of the required actions could have a material adverse effect on our consolidated financial position, results of operations and cash flows. We disclose outstanding environmental remediation matters that remain unsettled or are settled in the reporting period that we believe could have a material adverse effect on our financial condition, results of operations or cash flows. We inflate the estimated costs in current dollars to the expected time of payment and discount the total cost to present value using a risk-free interest rate. The risk-free interest rates associated with our environmental remediation liabilities as of March 31, 2024 range between 1.5% and 7.1%. A summary of the changes to the aggregate environmental remediation liabilities for the three months ended March 31, 2024 and 2023 follows: Three Months Ended 2024 2023 Beginning balance $ 5,889 $ 6,335 Accretion expense 24 26 Obligations settled (1) (32) (18) Ending balance 5,881 6,343 Less: current portion 1,631 1,131 Long-term portion $ 4,250 $ 5,212 (1) May include amounts that are being processed through accounts payable as a part of our disbursement cycle.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY Stock Based Compensation Shares Available For Issuance In the fiscal year ended December 31, 2016, we adopted the 2016 Incentive Plan (“2016 Plan”). Under the 2016 Plan, we may grant awards up to an aggregate amount of shares equal to the sum of: (i) 2,250 shares of Class A common stock (subject to adjustment in the event of stock splits and other similar events), plus (ii) such additional number of shares of Class A common stock (up to 2,723 shares) as is equal to the sum of the number of shares of Class A common stock that remained available for grant under the 2006 Stock Incentive Plan (“2006 Plan”) immediately prior to the expiration of the 2006 Plan and the number of shares of Class A common stock subject to awards granted under the 2006 Plan that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by us. As of March 31, 2024, there were 456 Class A common stock equivalents available for future grant under the 2016 Plan. Stock Options Stock options are granted at a price equal to the prevailing fair value of our Class A common stock at the date of grant. Generally, stock options granted have a term not to exceed ten years and vest over a one-year to five-year period from the date of grant. The fair value of each stock option granted is estimated using a Black-Scholes option-pricing model, which requires extensive use of accounting judgment and financial estimation, including estimates of the expected term stock option holders will retain their vested stock options before exercising them and the estimated volatility of our Class A common stock price over the expected term. A summary of stock option activity follows: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding, December 31, 2023 129 $ 66.03 Granted — $ — Exercised — $ — Forfeited — $ — Outstanding, March 31, 2024 129 $ 66.03 7.2 $ 4,231 Exercisable, March 31, 2024 49 $ 40.60 4.9 $ 2,828 Stock-based compensation expense related to stock options was $151 during the three months ended March 31, 2024, as compared to $123 during the three months ended March 31, 2023. As of March 31, 2024, we had $1,957 of unrecognized stock-based compensation expense related to outstanding stock options to be recognized over a weighted average period of 3.6 years. During the three months ended March 31, 2024, the aggregate intrinsic value of stock options exercised was zero dollars. Other Stock Awards Restricted stock awards, restricted stock units and performance stock units, with the exception of market-based performance stock units, are granted at a price equal to the fair value of our Class A common stock at the date of grant. The fair value of each market-based performance stock unit is estimated using a Monte Carlo pricing model, which requires extensive use of accounting judgment and financial estimation, including the estimated share price appreciation plus, if applicable, the value of dividends of our Class A common stock as compared to the Russell 2000 Index over the requisite service period. Typically, restricted stock awards granted to non-employee directors vest incrementally over a three-year period beginning on the first anniversary of the date of grant. Restricted stock units granted to non-employee directors vest in full on the first anniversary of the grant date. Restricted stock units granted to employees vest incrementally over an identified service period, typically three years, beginning on the grant date based on continued employment. Performance stock units granted to employees, including market-based performance stock units, vest at a future date following the grant date and are based on the attainment of performance targets and market achievements, as applicable. A summary of restricted stock award, restricted stock unit and performance stock unit activity follows: Restricted Stock Awards, Restricted Stock Units, and Performance Stock Units (1) Weighted Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding, December 31, 2023 181 $ 84.82 Granted 93 $ 99.70 Class A Common Stock Vested (34) $ 76.16 Forfeited (1) $ 77.94 Outstanding, March 31, 2024 239 $ 91.82 2.4 $ 23,649 Unvested, March 31, 2024 414 $ 93.99 2.2 $ 40,908 (1) Performance stock unit grants, including market-based performance stock units, are included at the 100% attainment level. Attainment of the maximum performance targets and market achievements would result in the issuance of an additional 175 shares of Class A common stock currently included in unvested. Stock-based compensation expense related to restricted stock awards, restricted stock units and performance stock units was $1,875 during the three months ended March 31, 2024, as compared to $1,762 during the three months ended March 31, 2023. During the three months ended March 31, 2024, the total fair value of other stock awards vested was $3,165. As of March 31, 2024, total unrecognized stock-based compensation expense related to outstanding restricted stock awards was $3, which will be recognized over a weighted average period of 0.2 years. As of March 31, 2024, total unrecognized stock-based compensation expense related to outstanding restricted stock units was $8,417, which will be recognized over a weighted average period of 2.6 years. As of March 31, 2024, total expected unrecognized stock-based compensation expense related to outstanding performance stock units was $8,626, which will be recognized over a weighted average period of 2.2 years. The weighted average fair value of market-based performance stock units granted during the three months ended March 31, 2024 was $105.35 per award, which was calculated using a Monte Carlo pricing model assuming a risk-free interest rate of 4.31% and an expected volatility of 25.3% assuming no expected dividend yield. Risk-free interest rate is based on the U.S. Treasury yield curve for the expected service period of the award. Expected volatility is calculated using the daily volatility of our Class A common stock over the expected service period of the award. The Monte Carlo pricing model requires extensive use of accounting judgment and financial estimation. Application of alternative assumptions could produce significantly different estimates of the fair value of stock-based compensation and consequently, the related amounts recognized in the consolidated statements of operations. We also recorded $109 of stock-based compensation expense related to the Second Amended and Restated 1997 Employee Stock Purchase Plan during the three months ended March 31, 2024, as compared to $90 during the three months ended March 31, 2023. Accumulated Other Comprehensive Income (Loss), Net of Tax A summary of the changes in the balances of each component of accumulated other comprehensive income (loss), net of tax follows: Interest Rate Swaps Balance, December 31, 2023 $ (1,080) Other comprehensive income before reclassifications 10,753 Income reclassified from accumulated other comprehensive income (loss) into interest expense (2,330) Income tax provision related to items of other comprehensive income (2,308) Other comprehensive income, net of tax 6,115 Balance, March 31, 2024 $ 5,035 A summary of reclassifications out of accumulated other comprehensive income (loss), net of tax into earnings follows: Three Months Ended 2024 2023 Accumulated Other Comprehensive Income (Loss), Net of Tax Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss), Net of Tax Affected Line Item in the Consolidated Interest rate swaps $ (2,330) $ (1,106) Interest expense 2,330 1,106 (Loss) income before income taxes 642 303 (Benefit) provision for income taxes $ 1,688 $ 803 Net (loss) income

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per share is computed by dividing net (loss) income by the weighted average number of common shares outstanding during the period. Diluted earnings per share is calculated based on the combined weighted average number of common shares and potentially dilutive shares, which include the assumed exercise of employee stock options, unvested restricted stock awards, unvested restricted stock units and unvested performance stock units, including market-based performance units based on the expected achievement of performance targets. In computing diluted earnings per share, we utilize the treasury stock method. A summary of the numerator and denominators used in the computation of earnings per share follows: Three Months Ended 2024 2023 Numerator: Net (loss) income $ (4,117) $ 3,548 Denominators: Number of shares outstanding, end of period: Class A common stock 57,120 50,898 Class B common stock 988 988 Unvested restricted stock — (1) Effect of weighted average shares outstanding (78) (115) Basic weighted average common shares outstanding 58,030 51,770 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards — 99 Diluted weighted average common shares outstanding 58,030 51,869 Anti-dilutive potentially issuable shares 379 126

OTHER ITEMS AND CHARGES

OTHER ITEMS AND CHARGES	3 Months Ended
	Mar. 31, 2024
Unusual or Infrequent Items, or Both [Abstract]
OTHER ITEMS AND CHARGES	OTHER ITEMS AND CHARGES Expense from Acquisition Activities In the three months ended March 31, 2024, and 2023, we recorded charges of $5,010 and $2,863, respectively, comprised primarily of legal, consulting and other similar costs associated with the due diligence, acquisition and integration of acquired businesses, including expenses related to the development of our Mid-Atlantic region, in the three months ended March 31, 2024.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS Leases In the fiscal year ended April 30, 1994, we entered into two leases for facilities with a partnership of which John Casella, our Chairman and Chief Executive Officer, and Douglas Casella, a member of our Board of Directors, are the general partners. In the three months ended March 31, 2024, we extended one of these leases through February 2039. The terms of the lease agreement require a monthly payment of approximately $17, subject to a fixed annual escalation.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	FAIR VALUE OF FINANCIAL INSTRUMENTS We use a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. These tiers include: Level 1, defined as quoted market prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; and Level 3, defined as unobservable inputs that are not corroborated by market data. We use valuation techniques that maximize the use of market prices and observable inputs and minimize the use of unobservable inputs. In measuring the fair value of our financial assets and liabilities, we rely on market data or assumptions that we believe market participants would use in pricing an asset or a liability. Assets and Liabilities Accounted for at Fair Value Our financial instruments include cash and cash equivalents, accounts receivable, restricted investment securities held in trust on deposit with various banks as collateral for our obligations relative to our landfill final capping, closure and post-closure costs, interest rate derivatives, trade payables and debt. The carrying values of cash and cash equivalents, accounts receivable and trade payables approximate their respective fair values due to their short-term nature. The fair value of restricted investment securities held in trust, which are valued using quoted market prices, are included as restricted assets in the Level 1 tier below. The fair value of the interest rate derivatives included in the Level 2 tier below is calculated using discounted cash flow valuation methodologies based upon Term SOFR yield curves that are observable at commonly quoted intervals for the full term of the swaps. We recognize all derivatives accounted for on the balance sheet at fair value. Recurring Fair Value Measurements Summaries of our financial assets and liabilities that are measured at fair value on a recurring basis follow: Fair Value Measurement at March 31, 2024 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 2,281 $ — $ — Interest rate swaps — 12,457 — $ 2,281 $ 12,457 $ — Liabilities: Interest rate swaps $ — $ 5,433 $ — Fair Value Measurement at December 31, 2023 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 2,203 $ — $ — Interest rate swaps — 10,364 — $ 2,203 $ 10,364 $ — Liabilities: Interest rate swaps $ — $ 11,762 $ — Fair Value of Debt As of March 31, 2024, the fair value of our fixed rate debt, including our FAME Bonds 2005R-3, FAME Bonds 2015R-1, FAME Bonds 2015R-2, Vermont Bonds 2013, Vermont Bonds 2022A-1, New York Bonds 2014R-1, New York Bonds 2014R-2, New York Bonds 2020, New York Bonds 2020R-2 and New Hampshire Bonds (collectively, the “Industrial Revenue Bonds”) was approximately $228,571 and the carrying value was $232,000. The fair value of the Industrial Revenue Bonds is considered to be Level 2 within the fair value hierarchy as the fair value is determined using market approach pricing provided by a third-party that utilizes pricing models and pricing systems, mathematical tools and judgment to determine the evaluated price for the security based on the market information of each of the bonds or securities with similar characteristics. As of March 31, 2024, the carrying values of our Term Loan Facility and 2023 Term Loan Facility were $349,125 and $413,875, respectively, and the carrying value of our Revolving Credit Facility was zero dollars. Their fair values are based on current borrowing rates for similar types of borrowing arrangements, or Level 2 inputs, and approximate their carrying values.

SEGMENT REPORTING

SEGMENT REPORTING	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
SEGMENT REPORTING	SEGMENT REPORTING We report selected information about our reportable operating segments in a manner consistent with that used for internal management reporting. We classify our solid waste operations on a geographic basis through regional operating segments, our Eastern, Western and Mid-Atlantic regions. Revenues associated with our solid waste operations are derived mainly from solid waste collection and disposal services, including landfill, transfer station and transportation services, landfill gas-to-energy services, and processing services in the eastern United States. Our Resource Solutions operating segment leverages our core competencies in materials processing, industrial recycling, organics and resource management service offerings to deliver a comprehensive solution for our larger commercial, municipal, institutional and industrial customers that have more diverse waste and recycling needs. Revenues associated with our Resource Solutions operations are comprised of processing services and non-processing services, which we refer to as our National Accounts business. Revenues from processing services are derived from customers in the form of processing fees, tipping fees, commodity sales, and organic material sales. Revenues from our National Accounts business are derived from brokerage services and overall resource management services providing a wide range of environmental services and resource management solutions to large and complex organizations, as well as traditional collection, disposal and recycling services provided to large account multi-site customers. Legal, tax, information technology, human resources, certain finance and accounting and other administrative functions are included in our Corporate Entities segment, which is not a reportable operating segment. Corporate Entities results reflect those costs not allocated to our reportable operating segments. Three Months Ended March 31, 2024 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 94,004 $ 22,488 $ 13,468 $ 3,622 $ 429,198 Western 130,329 46,436 24,475 8,784 990,745 Mid-Atlantic 41,604 213 10,324 (4,799) 541,979 Resource Solutions 75,071 3,123 4,794 1,393 249,930 Corporate Entities — — 976 (2,165) 265,402 Eliminations — (72,260) — — — $ 341,008 $ — $ 54,037 $ 6,835 $ 2,477,254 Three Months Ended March 31, 2023 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 83,909 $ 19,369 $ 11,903 $ 2,139 $ 364,872 Western 111,034 36,559 17,665 12,426 744,084 Mid-Atlantic (1) — — — — — Resource Solutions 67,652 3,487 3,076 (1,943) 195,028 Corporate Entities — — 791 (2,357) 115,906 Eliminations — (59,415) — — — $ 262,595 $ — $ 33,435 $ 10,265 $ 1,419,890 (1) Operations under the Mid-Atlantic region commenced July 1, 2023. A summary of our revenues attributable to services provided follows: Three Months Ended 2024 2023 Collection $ 211,360 $ 139,977 Disposal 50,139 51,466 Landfill gas-to-energy 2,509 1,924 Processing 1,929 1,576 Solid waste operations 265,937 194,943 Processing 29,762 22,806 National Accounts 45,309 44,846 Resource Solutions operations 75,071 67,652 Total revenues $ 341,008 $ 262,595

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net (loss) income	$ (4,117)	$ 3,548

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 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

ACCOUNTING CHANGES (Policies)

ACCOUNTING CHANGES (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Changes and Error Corrections [Abstract]
Basis of Accounting	Casella Waste Systems, Inc. (“Parent”) and its subsidiaries (collectively, “we”, “us” or “our”), is a regional, vertically integrated solid waste services company. We provide resource management expertise and services to residential, commercial, municipal, institutional and industrial customers, primarily in the areas of solid waste collection and disposal, transfer, recycling and organics services. We provide integrated solid waste services in nine states: Vermont, New Hampshire, New York, Massachusetts, Connecticut, Maine, Pennsylvania, Delaware and Maryland, with our headquarters located in Rutland, Vermont. We manage our solid waste operations on a geographic basis through regional operating segments, the Eastern, Western and Mid-Atlantic regions, each of which provides a comprehensive range of non-hazardous solid waste services. We manage our resource renewal operations through the Resource Solutions operating segment, which leverages our core competencies in materials processing, industrial recycling, organics and resource management service offerings to deliver a comprehensive solution for our larger commercial, municipal, institutional and industrial customers that have more diverse waste and recycling needs. Legal, tax, information technology, human resources, certain finance and accounting and other administrative functions are included in our Corporate Entities segment. The accompanying unaudited consolidated financial statements, which include the accounts of the Parent and our wholly-owned subsidiaries, have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). All significant intercompany accounts and transactions are eliminated in consolidation. Investments in entities in which we do not have a controlling financial interest are accounted for under either the equity method or the cost method of accounting, as appropriate. Our significant accounting policies are more fully discussed in Item 8. “ Financial Statements and Supplementary Data ” of our Annual Report on Form 10-K for the fiscal year ended December 31, 2023 (“fiscal year 2023”), which was filed with the SEC on February 16, 2024 (“2023 Form 10-K”).
Use of Estimates	Preparation of our consolidated financial statements in accordance with GAAP requires management to make certain estimates and assumptions. These estimates and assumptions affect the accounting for and recognition and disclosure of assets, liabilities, equity, revenues and expenses. We must make these estimates and assumptions because certain information that we use is dependent on future events, cannot be calculated with a high degree of precision given the available data, or simply cannot be readily calculated. In the opinion of management, these consolidated financial statements include all adjustments, including normal recurring and nonrecurring adjustments, as applicable, necessary for a fair statement of the financial position, results of operations and cash flows for the periods presented. The results for the three months ended March 31, 2024 may not be indicative of the results for any other interim period or the entire fiscal year.
Subsequent Events	We have evaluated subsequent events or transactions that have occurred after the consolidated balance sheet date of March 31, 2024 through the date of filing of the consolidated financial statements with the SEC on this Quarterly Report on Form 10-Q and determined that there have been no material events that have occurred that would require recognition or adjustments to our disclosures in our consolidated financial statements.
Accounting Standards Adopted and Pending Adoption	The following table provides a brief description of recent Accounting Standards Updates (“ASU”) to the Accounting Standards Codification (“ASC”) issued by the Financial Accounting Standards Board (“FASB”) and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity: Standard Description Effect on the Financial Statements or Other Accounting standards issued pending adoption ASU No. 2023-07: Improvements to Reportable Segment Disclosures (Topic 280) Requires entities to provide additional disclosure related to the chief operating decision maker (“CODM”) and reportable operating segments, including providing more detailed information about reportable operating segment's significant expenses and how that information is used by the CODM. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements, however, the adoption of this guidance will have an impact on reportable operating segment disclosures within the accompanying notes to our consolidated financial statements. This guidance does not change how we identify our operating segments, aggregate them or apply quantitative thresholds to determine our reportable segments. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. ASU No. 2023-09: Improvements to Income Tax Disclosures (Topic 740) Requires entities to provide additional disclosure related to the transparency and decision usefulness of income tax disclosures, including additional disclosure around the rate reconciliation and income taxes paid. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements, however, the adoption of this guidance will have an impact on income tax disclosures within the accompanying notes to our consolidated financial statements. This guidance is effective for fiscal years beginning after December 15, 2024, with early adoption permitted.
Accrued Final Capping, Closure and Post Closure	Accrued final capping, closure and post-closure costs include the current and non-current portion of costs associated with obligations for final capping, closure and post-closure of our landfills. We estimate our future final capping, closure and post-closure costs in order to determine the final capping, closure and post-closure expense per ton of waste placed into each landfill. The anticipated time frame for paying these costs varies based on the remaining useful life of each landfill as well as the duration of the post-closure monitoring period.
Fair Value of Financial Instruments	We use a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. These tiers include: Level 1, defined as quoted market prices in active markets for identical assets or liabilities; Level 2, defined as inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; and Level 3, defined as unobservable inputs that are not corroborated by market data. We use valuation techniques that maximize the use of market prices and observable inputs and minimize the use of unobservable inputs. In measuring the fair value of our financial assets and liabilities, we rely on market data or assumptions that we believe market participants would use in pricing an asset or a liability. Assets and Liabilities Accounted for at Fair Value Our financial instruments include cash and cash equivalents, accounts receivable, restricted investment securities held in trust on deposit with various banks as collateral for our obligations relative to our landfill final capping, closure and post-closure costs, interest rate derivatives, trade payables and debt. The carrying values of cash and cash equivalents, accounts receivable and trade payables approximate their respective fair values due to their short-term nature. The fair value of restricted investment securities held in trust, which are valued using quoted market prices, are included as restricted assets in the Level 1 tier below. The fair value of the interest rate derivatives included in the Level 2 tier below is calculated using discounted cash flow valuation methodologies based upon Term SOFR yield curves that are observable at commonly quoted intervals for the full term of the swaps. We recognize all derivatives accounted for on the balance sheet at fair value.
Segment Reporting	We report selected information about our reportable operating segments in a manner consistent with that used for internal management reporting. We classify our solid waste operations on a geographic basis through regional operating segments, our Eastern, Western and Mid-Atlantic regions. Revenues associated with our solid waste operations are derived mainly from solid waste collection and disposal services, including landfill, transfer station and transportation services, landfill gas-to-energy services, and processing services in the eastern United States. Our Resource Solutions operating segment leverages our core competencies in materials processing, industrial recycling, organics and resource management service offerings to deliver a comprehensive solution for our larger commercial, municipal, institutional and industrial customers that have more diverse waste and recycling needs. Revenues associated with our Resource Solutions operations are comprised of processing services and non-processing services, which we refer to as our National Accounts business. Revenues from processing services are derived from customers in the form of processing fees, tipping fees, commodity sales, and organic material sales. Revenues from our National Accounts business are derived from brokerage services and overall resource management services providing a wide range of environmental services and resource management solutions to large and complex organizations, as well as traditional collection, disposal and recycling services provided to large account multi-site customers. Legal, tax, information technology, human resources, certain finance and accounting and other administrative functions are included in our Corporate Entities segment, which is not a reportable operating segment. Corporate Entities results reflect those costs not allocated to our reportable operating segments.

ACCOUNTING CHANGES (Tables)

ACCOUNTING CHANGES (Tables)	3 Months Ended
	Mar. 31, 2024
Accounting Changes and Error Corrections [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following table provides a brief description of recent Accounting Standards Updates (“ASU”) to the Accounting Standards Codification (“ASC”) issued by the Financial Accounting Standards Board (“FASB”) and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity: Standard Description Effect on the Financial Statements or Other Accounting standards issued pending adoption ASU No. 2023-07: Improvements to Reportable Segment Disclosures (Topic 280) Requires entities to provide additional disclosure related to the chief operating decision maker (“CODM”) and reportable operating segments, including providing more detailed information about reportable operating segment's significant expenses and how that information is used by the CODM. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements, however, the adoption of this guidance will have an impact on reportable operating segment disclosures within the accompanying notes to our consolidated financial statements. This guidance does not change how we identify our operating segments, aggregate them or apply quantitative thresholds to determine our reportable segments. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. ASU No. 2023-09: Improvements to Income Tax Disclosures (Topic 740) Requires entities to provide additional disclosure related to the transparency and decision usefulness of income tax disclosures, including additional disclosure around the rate reconciliation and income taxes paid. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements, however, the adoption of this guidance will have an impact on income tax disclosures within the accompanying notes to our consolidated financial statements. This guidance is effective for fiscal years beginning after December 15, 2024, with early adoption permitted.

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following tables set forth revenues disaggregated by service line and timing of revenue recognition by operating segment for each of the three months ended March 31, 2024 and 2023: Three Months Ended March 31, 2024 Eastern Western Mid-Atlantic Resource Solutions Total Revenues Collection $ 70,260 $ 99,870 $ 41,230 $ — $ 211,360 Landfill 6,612 12,938 — — 19,550 Transfer station 14,129 11,971 374 — 26,474 Transportation 1,276 2,839 — — 4,115 Landfill gas-to-energy 458 2,051 — — 2,509 Processing 1,269 660 — 29,762 31,691 National Accounts — — — 45,309 45,309 Total revenues $ 94,004 $ 130,329 $ 41,604 $ 75,071 $ 341,008 Transferred at a point-in-time $ 122 $ 618 $ — $ 12,552 $ 13,292 Transferred over time 93,882 129,711 41,604 62,519 327,716 Total revenues $ 94,004 $ 130,329 $ 41,604 $ 75,071 $ 341,008 Three Months Ended March 31, 2023 Eastern Western Mid-Atlantic (1) Resource Solutions Total Revenues Collection $ 61,108 $ 78,869 $ — $ — $ 139,977 Landfill 6,301 16,460 — — 22,761 Transfer station 13,981 9,961 — — 23,942 Transportation 1,183 3,580 — — 4,763 Landfill gas-to-energy 213 1,711 — — 1,924 Processing 1,123 453 — 22,806 24,382 National Accounts — — — 44,846 44,846 Total revenues $ 83,909 $ 111,034 $ — $ 67,652 $ 262,595 Transferred at a point-in-time $ 119 $ 731 $ — $ 6,438 $ 7,288 Transferred over time 83,790 110,303 — 61,214 255,307 Total revenues $ 83,909 $ 111,034 $ — $ 67,652 $ 262,595 (1) Operations under the Mid-Atlantic region commenced July 1, 2023.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill Activity	A summary of the activity and balances related to goodwill by operating segment is as follows: December 31, Measurement Period Adjustments March 31, Eastern $ 73,893 $ — $ 73,893 Western 285,056 762 285,818 Mid-Atlantic 332,247 (107) 332,140 Resource Solutions 44,474 188 44,662 $ 735,670 $ 843 $ 736,513
Schedule of Intangible Assets by Type	Summaries of intangible assets by type follows: Covenants Customer Relationships Trade Names Total Balance, March 31, 2024 Intangible assets $ 61,573 $ 272,571 $ 13,325 $ 347,469 Less accumulated amortization (29,569) (80,514) (8,521) (118,604) $ 32,004 $ 192,057 $ 4,804 $ 228,865 Covenants Customer Relationships Trade Names Total Balance, December 31, 2023 Intangible assets $ 61,573 $ 272,571 $ 13,325 $ 347,469 Less accumulated amortization (26,645) (72,227) (7,168) (106,040) $ 34,928 $ 200,344 $ 6,157 $ 241,429
Schedule of Intangible Amortization Expense Estimated	A summary of intangible amortization expense estimated for each of the next five fiscal years following fiscal year 2023 and thereafter is estimated as follows: Estimated Future Amortization Expense as of March 31, 2024 Fiscal year ending December 31, 2024 $ 35,421 Fiscal year ending December 31, 2025 $ 43,593 Fiscal year ending December 31, 2026 $ 38,720 Fiscal year ending December 31, 2027 $ 34,129 Fiscal year ending December 31, 2028 $ 29,077 Thereafter $ 47,925

ACCRUED FINAL CAPPING, CLOSUR_2

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE (Tables)	3 Months Ended
	Mar. 31, 2024
Asset Retirement Obligation Disclosure [Abstract]
Schedule of Changes to Accrued Capping, Closure and Post-Closure Liabilities	A summary of the changes to accrued final capping, closure and post-closure liabilities follows: Three Months Ended 2024 2023 Beginning balance $ 133,904 $ 113,678 Obligations incurred 1,549 1,247 Accretion expense 2,869 2,410 Obligations settled (1) (998) (1,179) Ending balance $ 137,324 $ 116,156 (1) May include amounts that are being processed through accounts payable as a part of our disbursements cycle.

DEBT (Tables)

DEBT (Tables)	3 Months Ended
	Mar. 31, 2024
Debt And Derivatives Disclosure [Abstract]
Schedule of Debt	A summary of debt is as follows: March 31, December 31, Senior Secured Credit Facility: Term loan A facility (“Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.054% as of March 31, 2024 $ 349,125 $ 350,000 Term loan A facility (“2023 Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.552% as of March 31, 2024 413,875 419,250 Revolving credit facility (“Revolving Credit Facility”) due December 2026; bearing interest at term secured overnight financing rate (“Term SOFR”) plus 1.725% — — Tax-Exempt Bonds: New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014 (“New York Bonds 2014R-1”) due December 2044 - fixed rate interest period bearing interest at 2.875% through December 2029 25,000 25,000 New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 (“New York Bonds 2014R-2”) due December 2044 - fixed rate interest period bearing interest at 3.125% through May 2026 15,000 15,000 New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2020 (“New York Bonds 2020”) due September 2050 - fixed rate interest period bearing interest at 2.750% through September 2025 40,000 40,000 New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2020R-2 (“New York Bonds 2020R-2”) due September 2050 - fixed rate interest period bearing interest at 5.125% through September 2030 35,000 35,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 (“FAME Bonds 2005R-3”) due January 2025 - fixed rate interest period bearing interest at 5.25% through January 2025 25,000 25,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-1 (“FAME Bonds 2015R-1”) due August 2035 - fixed rate interest period bearing interest at 5.125% through July 2025 15,000 15,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2 (“FAME Bonds 2015R-2”) due August 2035 - fixed rate interest period bearing interest at 4.375% through July 2025 15,000 15,000 Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 (“Vermont Bonds 2013”) due April 2036 - fixed rate interest period bearing interest at 4.625% through April 2028 16,000 16,000 Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2022A-1 (“Vermont Bonds 2022A-1”) due June 2052 - fixed rate interest period bearing interest at 5.00% through May 2027 35,000 35,000 Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 (“New Hampshire Bonds”) due April 2029 - fixed rate interest period bearing interest at 2.95% through April 2029 11,000 11,000 Other: Finance leases 59,460 53,066 Notes payable maturing through March 2025; bearing interest up to 8.1% 146 230 Principal amount of debt 1,054,606 1,054,546 Less—unamortized debt issuance costs 10,360 11,103 Debt less unamortized debt issuance costs 1,044,246 1,043,443 Less—current maturities of debt 63,368 35,781 $ 980,878 $ 1,007,662
Schedule of Cash Flow Hedges	A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheets follows: Fair Value Balance Sheet Location March 31, December 31, Interest rate swaps Other current assets $ 7,196 $ 5,951 Interest rate swaps Other non-current assets 5,261 4,413 $ 12,457 $ 10,364 Interest rate swaps Other long-term liabilities $ 5,433 $ 11,762 Interest rate swaps Accumulated other comprehensive income (loss), net of tax $ 7,024 $ (1,398) Interest rate swaps - tax effect Accumulated other comprehensive income (loss), net of tax (1,989) 318 $ 5,035 $ (1,080)

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Schedule of Environmental Liability	A summary of the changes to the aggregate environmental remediation liabilities for the three months ended March 31, 2024 and 2023 follows: Three Months Ended 2024 2023 Beginning balance $ 5,889 $ 6,335 Accretion expense 24 26 Obligations settled (1) (32) (18) Ending balance 5,881 6,343 Less: current portion 1,631 1,131 Long-term portion $ 4,250 $ 5,212 (1) May include amounts that are being processed through accounts payable as a part of our disbursement cycle.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Schedule of Stock Option Activity	A summary of stock option activity follows: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding, December 31, 2023 129 $ 66.03 Granted — $ — Exercised — $ — Forfeited — $ — Outstanding, March 31, 2024 129 $ 66.03 7.2 $ 4,231 Exercisable, March 31, 2024 49 $ 40.60 4.9 $ 2,828
Schedule of Restricted Stock, Restricted Stock Unit and Performance Stock Unit Activity	A summary of restricted stock award, restricted stock unit and performance stock unit activity follows: Restricted Stock Awards, Restricted Stock Units, and Performance Stock Units (1) Weighted Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding, December 31, 2023 181 $ 84.82 Granted 93 $ 99.70 Class A Common Stock Vested (34) $ 76.16 Forfeited (1) $ 77.94 Outstanding, March 31, 2024 239 $ 91.82 2.4 $ 23,649 Unvested, March 31, 2024 414 $ 93.99 2.2 $ 40,908 (1) Performance stock unit grants, including market-based performance stock units, are included at the 100% attainment level. Attainment of the maximum performance targets and market achievements would result in the issuance of an additional 175 shares of Class A common stock currently included in unvested.
Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Loss	A summary of the changes in the balances of each component of accumulated other comprehensive income (loss), net of tax follows: Interest Rate Swaps Balance, December 31, 2023 $ (1,080) Other comprehensive income before reclassifications 10,753 Income reclassified from accumulated other comprehensive income (loss) into interest expense (2,330) Income tax provision related to items of other comprehensive income (2,308) Other comprehensive income, net of tax 6,115 Balance, March 31, 2024 $ 5,035
Schedule of Reclassifications Out of Accumulated Other Comprehensive Loss	A summary of reclassifications out of accumulated other comprehensive income (loss), net of tax into earnings follows: Three Months Ended 2024 2023 Accumulated Other Comprehensive Income (Loss), Net of Tax Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss), Net of Tax Affected Line Item in the Consolidated Interest rate swaps $ (2,330) $ (1,106) Interest expense 2,330 1,106 (Loss) income before income taxes 642 303 (Benefit) provision for income taxes $ 1,688 $ 803 Net (loss) income

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Earnings per Share Computation	A summary of the numerator and denominators used in the computation of earnings per share follows: Three Months Ended 2024 2023 Numerator: Net (loss) income $ (4,117) $ 3,548 Denominators: Number of shares outstanding, end of period: Class A common stock 57,120 50,898 Class B common stock 988 988 Unvested restricted stock — (1) Effect of weighted average shares outstanding (78) (115) Basic weighted average common shares outstanding 58,030 51,770 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards — 99 Diluted weighted average common shares outstanding 58,030 51,869 Anti-dilutive potentially issuable shares 379 126

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value	Summaries of our financial assets and liabilities that are measured at fair value on a recurring basis follow: Fair Value Measurement at March 31, 2024 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 2,281 $ — $ — Interest rate swaps — 12,457 — $ 2,281 $ 12,457 $ — Liabilities: Interest rate swaps $ — $ 5,433 $ — Fair Value Measurement at December 31, 2023 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 2,203 $ — $ — Interest rate swaps — 10,364 — $ 2,203 $ 10,364 $ — Liabilities: Interest rate swaps $ — $ 11,762 $ —

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information by Segment	Three Months Ended March 31, 2024 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 94,004 $ 22,488 $ 13,468 $ 3,622 $ 429,198 Western 130,329 46,436 24,475 8,784 990,745 Mid-Atlantic 41,604 213 10,324 (4,799) 541,979 Resource Solutions 75,071 3,123 4,794 1,393 249,930 Corporate Entities — — 976 (2,165) 265,402 Eliminations — (72,260) — — — $ 341,008 $ — $ 54,037 $ 6,835 $ 2,477,254 Three Months Ended March 31, 2023 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 83,909 $ 19,369 $ 11,903 $ 2,139 $ 364,872 Western 111,034 36,559 17,665 12,426 744,084 Mid-Atlantic (1) — — — — — Resource Solutions 67,652 3,487 3,076 (1,943) 195,028 Corporate Entities — — 791 (2,357) 115,906 Eliminations — (59,415) — — — $ 262,595 $ — $ 33,435 $ 10,265 $ 1,419,890 (1) Operations under the Mid-Atlantic region commenced July 1, 2023.
Schedule of Revenue Attributable to Services	A summary of our revenues attributable to services provided follows: Three Months Ended 2024 2023 Collection $ 211,360 $ 139,977 Disposal 50,139 51,466 Landfill gas-to-energy 2,509 1,924 Processing 1,929 1,576 Solid waste operations 265,937 194,943 Processing 29,762 22,806 National Accounts 45,309 44,846 Resource Solutions operations 75,071 67,652 Total revenues $ 341,008 $ 262,595

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details)	Mar. 31, 2024 state
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of states in which entity operates	9

REVENUE RECOGNITION - Disaggreg

REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 341,008	$ 262,595
Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	13,292	7,288
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	327,716	255,307
Collection
Disaggregation of Revenue [Line Items]
Total revenues	211,360	139,977
Landfill
Disaggregation of Revenue [Line Items]
Total revenues	19,550	22,761
Transfer station
Disaggregation of Revenue [Line Items]
Total revenues	26,474	23,942
Transportation
Disaggregation of Revenue [Line Items]
Total revenues	4,115	4,763
Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	2,509	1,924
Processing
Disaggregation of Revenue [Line Items]
Total revenues	31,691	24,382
National Accounts
Disaggregation of Revenue [Line Items]
Total revenues	45,309	44,846
Eastern
Disaggregation of Revenue [Line Items]
Total revenues	94,004	83,909
Eastern | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	122	119
Eastern | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	93,882	83,790
Eastern | Collection
Disaggregation of Revenue [Line Items]
Total revenues	70,260	61,108
Eastern | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	6,612	6,301
Eastern | Transfer station
Disaggregation of Revenue [Line Items]
Total revenues	14,129	13,981
Eastern | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	1,276	1,183
Eastern | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	458	213
Eastern | Processing
Disaggregation of Revenue [Line Items]
Total revenues	1,269	1,123
Eastern | National Accounts
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Western
Disaggregation of Revenue [Line Items]
Total revenues	130,329	111,034
Western | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	618	731
Western | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	129,711	110,303
Western | Collection
Disaggregation of Revenue [Line Items]
Total revenues	99,870	78,869
Western | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	12,938	16,460
Western | Transfer station
Disaggregation of Revenue [Line Items]
Total revenues	11,971	9,961
Western | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	2,839	3,580
Western | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	2,051	1,711
Western | Processing
Disaggregation of Revenue [Line Items]
Total revenues	660	453
Western | National Accounts
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Mid-Atlantic
Disaggregation of Revenue [Line Items]
Total revenues	41,604	0
Mid-Atlantic | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Mid-Atlantic | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	41,604	0
Mid-Atlantic | Collection
Disaggregation of Revenue [Line Items]
Total revenues	41,230	0
Mid-Atlantic | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Mid-Atlantic | Transfer station
Disaggregation of Revenue [Line Items]
Total revenues	374	0
Mid-Atlantic | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Mid-Atlantic | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Mid-Atlantic | Processing
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Mid-Atlantic | National Accounts
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Resource Solutions
Disaggregation of Revenue [Line Items]
Total revenues	75,071	67,652
Resource Solutions | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	12,552	6,438
Resource Solutions | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	62,519	61,214
Resource Solutions | Collection
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Resource Solutions | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Resource Solutions | Transfer station
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Resource Solutions | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Resource Solutions | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Resource Solutions | Processing
Disaggregation of Revenue [Line Items]
Total revenues	29,762	22,806
Resource Solutions | National Accounts
Disaggregation of Revenue [Line Items]
Total revenues	$ 45,309	$ 44,846

REVENUE RECOGNITION - Narrative

REVENUE RECOGNITION - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Rebates	$ (341,008,000)	$ (262,595,000)
Revenue recognized fro performance obligation satisfied in previous period	0	0
Gross receivables from contracts	147,635,000		$ 158,931,000
Contract liabilities	29,715,000		$ 31,472,000
Rebate for Recycled or Returned Organic Materials
Disaggregation of Revenue [Line Items]
Rebates	$ 7,115,000	$ 6,629,000

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Summary of Goodwill Activity (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 735,670
Measurement Period Adjustments	843
Goodwill, ending balance	736,513
Eastern
Goodwill [Roll Forward]
Goodwill, beginning balance	73,893
Measurement Period Adjustments	0
Goodwill, ending balance	73,893
Western
Goodwill [Roll Forward]
Goodwill, beginning balance	285,056
Measurement Period Adjustments	762
Goodwill, ending balance	285,818
Mid-Atlantic
Goodwill [Roll Forward]
Goodwill, beginning balance	332,247
Measurement Period Adjustments	(107)
Goodwill, ending balance	332,140
Resource Solutions
Goodwill [Roll Forward]
Goodwill, beginning balance	44,474
Measurement Period Adjustments	188
Goodwill, ending balance	$ 44,662

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets by Type (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 347,469	$ 347,469
Less accumulated amortization	(118,604)	(106,040)
Intangible assets, net	228,865	241,429
Covenants Not-to-Compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets	61,573	61,573
Less accumulated amortization	(29,569)	(26,645)
Intangible assets, net	32,004	34,928
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets	272,571	272,571
Less accumulated amortization	(80,514)	(72,227)
Intangible assets, net	192,057	200,344
Trade Names
Finite-Lived Intangible Assets [Line Items]
Intangible assets	13,325	13,325
Less accumulated amortization	(8,521)	(7,168)
Intangible assets, net	$ 4,804	$ 6,157

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible amortization expense	$ 12,564	$ 4,071

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Amortization Expense Estimated (Detail) $ in Thousands	Mar. 31, 2024 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Fiscal year ending December 31, 2024	$ 35,421
Fiscal year ending December 31, 2025	43,593
Fiscal year ending December 31, 2026	38,720
Fiscal year ending December 31, 2027	34,129
Fiscal year ending December 31, 2028	29,077
Thereafter	$ 47,925

ACCRUED FINAL CAPPING, CLOSUR_3

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE - Summary of Changes to Accrued Capping, Closure and Post-Closure Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 133,904	$ 113,678
Obligations incurred	1,549	1,247
Accretion expense	2,869	2,410
Obligations settled	(998)	(1,179)
Ending balance	$ 137,324	$ 116,156

DEBT - Summary of Debt (Details

DEBT - Summary of Debt (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Weighted-average discount rate - finance leases	4.30%
Finance leases maturing through December 2107; bearing interest at a weighted average of 4.3%	$ 59,460	$ 53,066
Principal amount of debt	1,054,606	1,054,546
Less—unamortized debt issuance costs	10,360	11,103
Debt less unamortized debt issuance costs	1,044,246	1,043,443
Less—current maturities of debt	63,368	35,781
Debt, less current portion	$ 980,878	$ 1,007,662
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Debt, less current portion	Debt, less current portion
Secured Debt | Term loan A facility (“Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.054% as of March 31, 2024
Debt Instrument [Line Items]
Stated interest rate	7.054%
Principal amount of debt	$ 349,125	$ 350,000
Secured Debt | Term loan A facility (“2023 Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.552% as of March 31, 2024
Debt Instrument [Line Items]
Stated interest rate	7.552%
Principal amount of debt	$ 413,875	419,250
Line of Credit | Revolving credit facility (“Revolving Credit Facility”) due December 2026; bearing interest at term secured overnight financing rate (“Term SOFR”) plus 1.725%
Debt Instrument [Line Items]
Principal amount of debt	$ 0	0
Line of Credit | Revolving credit facility (“Revolving Credit Facility”) due December 2026; bearing interest at term secured overnight financing rate (“Term SOFR”) plus 1.725% | SOFR
Debt Instrument [Line Items]
Variable rate margin	1.725%
Unsecured Debt | New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014 (“New York Bonds 2014R-1”) due December 2044 - fixed rate interest period bearing interest at 2.875% through December 2029
Debt Instrument [Line Items]
Stated interest rate	2.875%
Principal amount of debt	$ 25,000	25,000
Unsecured Debt | New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 (“New York Bonds 2014R-2”) due December 2044 - fixed rate interest period bearing interest at 3.125% through May 2026
Debt Instrument [Line Items]
Stated interest rate	3.125%
Principal amount of debt	$ 15,000	15,000
Unsecured Debt | New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2020 (“New York Bonds 2020”) due September 2050 - fixed rate interest period bearing interest at 2.750% through September 2025
Debt Instrument [Line Items]
Stated interest rate	2.75%
Principal amount of debt	$ 40,000	40,000
Unsecured Debt | New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2020R-2 (“New York Bonds 2020R-2”) due September 2050 - fixed rate interest period bearing interest at 5.125% through September 2030
Debt Instrument [Line Items]
Stated interest rate	5.125%
Principal amount of debt	$ 35,000	35,000
Unsecured Debt | Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 (“FAME Bonds 2005R-3”) due January 2025 - fixed rate interest period bearing interest at 5.25% through January 2025
Debt Instrument [Line Items]
Stated interest rate	5.25%
Principal amount of debt	$ 25,000	25,000
Unsecured Debt | Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-1 (“FAME Bonds 2015R-1”) due August 2035 - fixed rate interest period bearing interest at 5.125% through July 2025
Debt Instrument [Line Items]
Stated interest rate	5.125%
Principal amount of debt	$ 15,000	15,000
Unsecured Debt | Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2015R-2 (“FAME Bonds 2015R-2”) due August 2035 - fixed rate interest period bearing interest at 4.375% through July 2025
Debt Instrument [Line Items]
Stated interest rate	4.375%
Principal amount of debt	$ 15,000	15,000
Unsecured Debt | Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 (“Vermont Bonds 2013”) due April 2036 - fixed rate interest period bearing interest at 4.625% through April 2028
Debt Instrument [Line Items]
Stated interest rate	4.625%
Principal amount of debt	$ 16,000	16,000
Unsecured Debt | Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2022A-1 (“Vermont Bonds 2022A-1”) due June 2052 - fixed rate interest period bearing interest at 5.00% through May 2027
Debt Instrument [Line Items]
Stated interest rate	5%
Principal amount of debt	$ 35,000	35,000
Unsecured Debt | Business Finance Authority of the State of New Hampshire Solid Waste Disposal Revenue Bonds Series 2013 (“New Hampshire Bonds”) due April 2029 - fixed rate interest period bearing interest at 2.95% through April 2029
Debt Instrument [Line Items]
Stated interest rate	2.95%
Principal amount of debt	$ 11,000	11,000
Notes payable maturing through March 2025; bearing interest up to 8.1%
Debt Instrument [Line Items]
Stated interest rate	8.10%
Principal amount of debt	$ 146	$ 230

DEBT - Narrative (Details)

DEBT - Narrative (Details) - Interest Rate Contract - Cash Flow Hedging - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Notional amount	$ 515,000	$ 515,000
Floor interest rate (as a percent)	0%
Weighted average percentage rate paid (as a percent)	3.60%

DEBT - Summary of Cash Flow Hed

DEBT - Summary of Cash Flow Hedges (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive income (loss), net of tax	$ 5,035	$ (1,080)
Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	12,457	10,364
Designated as Hedging Instrument | Interest rate swaps | Accumulated gain (loss), cash flow hedge
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive income (loss), before tax	7,024	(1,398)
Accumulated other comprehensive income (loss), tax	(1,989)	318
Accumulated other comprehensive income (loss), net of tax	5,035	(1,080)
Other current assets | Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	7,196	5,951
Other non-current assets | Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	5,261	4,413
Other long-term liabilities | Designated as Hedging Instrument | Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross liability	$ 5,433	$ 11,762

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Detail) $ in Thousands	Mar. 31, 2024 USD ($)
Loss Contingencies [Line Items]
Loss contingency accrual	$ 23
Minimum
Loss Contingencies [Line Items]
Risk free interest	1.50%
Maximum
Loss Contingencies [Line Items]
Risk free interest	7.10%

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Environmental Remediation Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 5,889	$ 6,335
Obligations incurred	24	26
Obligations settled	(32)	(18)
Ending balance	5,881	6,343
Less: current portion	1,631	1,131
Long-term portion	$ 4,250	$ 5,212

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	3 years 7 months 6 days
Fair value of stock awards vested	$ 3,165
Stock Options
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	151	$ 123
Unrecognized stock-based compensation expense, stock options	1,957
Aggregate intrinsic value of options exercised	0
Restricted Stock Awards, Restricted Stock Units And Performance Stock Units
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	1,875	1,762
Restricted Stock
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 3
Restricted Stock | Non Employee Director
Limited Partners' Capital Account [Line Items]
Award vesting period	3 years
Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 8,417
Restricted Stock Unit | Non Employee Director
Limited Partners' Capital Account [Line Items]
Award service period	3 years
Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 8,626
Market-based Performance Stock Units
Limited Partners' Capital Account [Line Items]
Weighted average fair value of market-based performance (in dollars per share)	$ 105.35
Risk-free interest rate	4.31%
Expected volatility	25.30%
Weighted average | Restricted Stock
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	2 months 12 days
Weighted average | Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	2 years 7 months 6 days
Weighted average | Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	2 years 2 months 12 days
2016 Plan
Limited Partners' Capital Account [Line Items]
Expiration period	10 years
2016 Plan | Minimum
Limited Partners' Capital Account [Line Items]
Award vesting period	1 year
2016 Plan | Maximum
Limited Partners' Capital Account [Line Items]
Award vesting period	5 years
Amended and Restated 1997 Employee Stock Purchase Plan
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	$ 109	$ 90
Class A Common Stock | 2016 Plan
Limited Partners' Capital Account [Line Items]
Common stock, authorized shares (in shares)	2,250,000
Number of shares available for future grant (in shares)	456,000
Class A Common Stock | 2006 Incentive Plan
Limited Partners' Capital Account [Line Items]
Common stock, additional authorized shares (in shares)	2,723,000

STOCKHOLDERS' EQUITY - Summary

STOCKHOLDERS' EQUITY - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) $ / shares shares
Stock Options
Beginning balance, outstanding (in shares) | shares	129
Granted (in shares) | shares	0
Exercised (in shares) | shares	0
Forfeited (in shares) | shares	0
Ending balance, outstanding (in shares) | shares	129
Exercisable at end of period (in shares) | shares	49
Weighted Average Exercise Price
Beginning balance, outstanding (in dollars per share) | $ / shares	$ 66.03
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	0
Forfeited (in dollars per share) | $ / shares	0
Ending balance, outstanding (in dollars per share) | $ / shares	66.03
Exercisable at end of period (in dollars per share) | $ / shares	$ 40.60
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Outstanding contractual term	7 years 2 months 12 days
Exercisable contractual term	4 years 10 months 24 days
Outstanding aggregate intrinsic value | $	$ 4,231
Exercisable aggregate intrinsic value | $	$ 2,828

STOCKHOLDERS' EQUITY - Summar_2

STOCKHOLDERS' EQUITY - Summary of Restricted Stock Awards, Restricted Stock Unit and Performance-based Stock Unit Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) $ / shares shares
Performance Stock Unit
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Percentage of attainment level (as a percent)	100%
Performance Stock Unit | Class A Common Stock
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Number of additional shares (in shares)	175
Restricted Stock Awards, Restricted Stock Units And Performance Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding, beginning of period (in shares)	181
Granted (in shares)	93
Forfeited (in shares)	(1)
Outstanding, end of period (in shares)	239
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 84.82
Granted (in dollars per share) | $ / shares	99.70
Forfeited (in dollars per share) | $ / shares	77.94
Outstanding at end of period (in dollars per share) | $ / shares	$ 91.82
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term (in years)	2 years 4 months 24 days
Aggregate intrinsic value | $	$ 23,649
Restricted Stock Awards, Restricted Stock Units And Performance Stock Units | Class A Common Stock
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Class A Common Stock Vested (in shares)	(34)
Weighted Average Grant Date Fair Value
Class A Common Stock Vested (in dollars per share) | $ / shares	$ 76.16
Unvested | Restricted Stock Awards, Restricted Stock Units And Performance Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding, end of period (in shares)	414
Weighted Average Grant Date Fair Value
Outstanding at end of period (in dollars per share) | $ / shares	$ 93.99
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term (in years)	2 years 2 months 12 days
Aggregate intrinsic value | $	$ 40,908

STOCKHOLDERS' EQUITY - Summar_3

STOCKHOLDERS' EQUITY - Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 1,021,791	$ 497,900
Other comprehensive income (loss), net of tax	6,115	(1,769)
Ending balance	1,025,924	$ 501,655
Accumulated gain (loss), cash flow hedge
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,080)
Other comprehensive income before reclassifications	10,753
Income reclassified from accumulated other comprehensive income (loss) into interest expense	(2,330)
Income tax provision related to items of other comprehensive income	(2,308)
Other comprehensive income (loss), net of tax	6,115
Ending balance	$ 5,035

STOCKHOLDERS' EQUITY - Summar_4

STOCKHOLDERS' EQUITY - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 15,882	$ 6,959
(Loss) income before income taxes	(5,883)	4,339
(Benefit) provision for income taxes	(1,766)	791
Net (loss) income	(4,117)	3,548
Accumulated gain (loss), cash flow hedge | Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss), Net of Tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
(Loss) income before income taxes	2,330	1,106
(Benefit) provision for income taxes	642	303
Net (loss) income	1,688	803
Interest rate swaps | Accumulated gain (loss), cash flow hedge | Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss), Net of Tax
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ (2,330)	$ (1,106)

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Numerator:
Net (loss) income	$ (4,117)	$ 3,548
Denominators:
Unvested restricted stock (in shares)	0	(1,000)
Effect of weighted average shares outstanding (in shares)	(78,000)	(115,000)
Basic weighted average common shares outstanding (in shares)	58,030,000	51,770,000
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards (in shares)	0	99,000
Diluted weighted average common shares outstanding (in shares)	58,030,000	51,869,000
Anti-dilutive potentially issuable shares (in shares)	379,000	126,000
Class A Common Stock
Denominators:
Common stock, shares outstanding (in shares)	57,120,000	50,898,000	57,007,000
Class B Common Stock
Denominators:
Common stock, shares outstanding (in shares)	988,000	988,000	988,000

OTHER ITEMS AND CHARGES (Detail

OTHER ITEMS AND CHARGES (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Unusual or Infrequent Items, or Both [Abstract]
Expense from acquisition activities	$ 5,010	$ 2,863

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($)	Apr. 30, 1994 lease
Related Party Transaction [Line Items]
Number of leases | lease		2
Related Party
Related Party Transaction [Line Items]
Leases monthly payments | $	$ 17

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring Fair Value Measurements (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Assets:
Restricted investment securities - landfill closure	$ 2,281	$ 2,203
Liabilities:
Derivative Asset, Statement Of Financial Position Extensible Enumeration, Not Disclosed Flag	Interest rate swaps	Interest rate swaps
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate swaps	$ 0	$ 0
Total assets	2,281	2,203
Liabilities:
Interest rate swaps	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Landfill
Assets:
Restricted investment securities - landfill closure	2,281	2,203
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate swaps	12,457	10,364
Total assets	12,457	10,364
Liabilities:
Interest rate swaps	5,433	11,762
Recurring | Significant Other Observable Inputs (Level 2) | Landfill
Assets:
Restricted investment securities - landfill closure	0	0
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Interest rate swaps	0	0
Total assets	0	0
Liabilities:
Interest rate swaps	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Landfill
Assets:
Restricted investment securities - landfill closure	$ 0	$ 0

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS - Narrative (Detail) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Term loan A facility (“Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.054% as of March 31, 2024 | Secured Debt
Debt Instrument [Line Items]
Principal amount of debt	$ 349,125,000	$ 350,000,000
Term loan A facility (“2023 Term Loan Facility”) payable quarterly with balance due December 2026; bearing interest at 7.552% as of March 31, 2024 | Secured Debt
Debt Instrument [Line Items]
Principal amount of debt	413,875,000	$ 419,250,000
Fair Value | Fixed Rate Bonds
Debt Instrument [Line Items]
Fixed rate debt	228,571,000
Carrying Value
Debt Instrument [Line Items]
Revolving credit facility	0
Carrying Value | Fixed Rate Bonds
Debt Instrument [Line Items]
Fixed rate debt	$ 232,000,000

SEGMENT REPORTING - Summary of

SEGMENT REPORTING - Summary of Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Revenues	$ 341,008	$ 262,595
Depreciation and amortization	54,037	33,435
Operating income (loss)	6,835	10,265
Total assets	2,477,254	1,419,890	$ 2,535,470
Operating | Eastern
Segment Reporting Information [Line Items]
Revenues	94,004	83,909
Depreciation and amortization	13,468	11,903
Operating income (loss)	3,622	2,139
Total assets	429,198	364,872
Operating | Western
Segment Reporting Information [Line Items]
Revenues	130,329	111,034
Depreciation and amortization	24,475	17,665
Operating income (loss)	8,784	12,426
Total assets	990,745	744,084
Operating | Mid-Atlantic
Segment Reporting Information [Line Items]
Revenues	41,604	0
Depreciation and amortization	10,324	0
Operating income (loss)	(4,799)	0
Total assets	541,979	0
Operating | Resource Solutions
Segment Reporting Information [Line Items]
Revenues	75,071	67,652
Depreciation and amortization	4,794	3,076
Operating income (loss)	1,393	(1,943)
Total assets	249,930	195,028
Corporate Entities
Segment Reporting Information [Line Items]
Revenues	0	0
Depreciation and amortization	976	791
Operating income (loss)	(2,165)	(2,357)
Total assets	265,402	115,906
Inter-company revenues
Segment Reporting Information [Line Items]
Revenues	(72,260)	(59,415)
Inter-company revenues | Eastern
Segment Reporting Information [Line Items]
Revenues	(22,488)	(19,369)
Inter-company revenues | Western
Segment Reporting Information [Line Items]
Revenues	(46,436)	(36,559)
Inter-company revenues | Mid-Atlantic
Segment Reporting Information [Line Items]
Revenues	(213)	0
Inter-company revenues | Resource Solutions
Segment Reporting Information [Line Items]
Revenues	$ (3,123)	$ (3,487)

SEGMENT REPORTING - Summary o_2

SEGMENT REPORTING - Summary of Revenues Attributable to Services Provided by Company (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenue from External Customer [Line Items]
Revenues	$ 341,008	$ 262,595
Solid waste operations
Revenue from External Customer [Line Items]
Revenues	265,937	194,943
Collection
Revenue from External Customer [Line Items]
Revenues	211,360	139,977
Disposal
Revenue from External Customer [Line Items]
Revenues	50,139	51,466
Landfill gas-to-energy
Revenue from External Customer [Line Items]
Revenues	2,509	1,924
Processing
Revenue from External Customer [Line Items]
Revenues	1,929	1,576
Resource Solutions operations
Revenue from External Customer [Line Items]
Revenues	75,071	67,652
Processing
Revenue from External Customer [Line Items]
Revenues	29,762	22,806
National Accounts
Revenue from External Customer [Line Items]
Revenues	$ 45,309	$ 44,846