Casella Waste Systems (CWST) 10-Q29 Apr 222022 Q1 Quarterly reportFinancial data

Company Profile

COVER

COVER - shares	3 Months Ended
COVER - shares	Mar. 31, 2022	Apr. 15, 2022
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
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	2022
Document Fiscal Period Focus	Q1
Amendment Flag	false
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		50,650,518
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, 2022	Dec. 31, 2021
CURRENT ASSETS:
Cash and cash equivalents	$ 12,594	$ 33,809
Accounts receivable, net of allowance for credit losses of $2,812 and $3,276, respectively	93,244	86,979
Prepaid expenses	13,840	12,766
Inventory	11,770	9,729
Other current assets	2,537	3,196
Total current assets	133,985	146,479
Property, plant and equipment, net of accumulated depreciation and amortization of $997,459 and $973,094, respectively	646,691	644,604
Operating lease right-of-use assets	93,961	93,799
Goodwill	258,414	232,860
Intangible assets, net	100,864	93,723
Restricted assets	1,985	2,122
Cost method investments	11,264	11,264
Deferred income taxes	41,237	43,957
Other non-current assets	18,570	14,772
Total assets	1,306,971	1,283,580
CURRENT LIABILITIES:
Current maturities of debt	9,873	9,901
Current operating lease liabilities	7,125	7,307
Accounts payable	65,244	63,086
Accrued payroll and related expenses	10,139	22,210
Accrued interest	1,949	2,042
Contract liabilities	5,500	3,404
Current accrued capping, closure and post-closure costs	8,250	7,915
Other accrued liabilities	35,467	36,328
Total current liabilities	143,547	152,193
Debt, less current portion	560,594	542,503
Operating lease liabilities, less current portion	58,262	56,375
Accrued capping, closure and post-closure costs, less current portion	80,577	78,999
Deferred income taxes	885	868
Other long-term liabilities	28,056	30,185
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
Additional paid-in capital	654,303	652,045
Accumulated deficit	(220,809)	(224,999)
Accumulated other comprehensive income (loss), net of tax	1,040	(5,103)
Total stockholders' equity	435,050	422,457
Total liabilities and stockholders' equity	1,306,971	1,283,580
Class A Common Stock
STOCKHOLDERS' EQUITY:
Common stock	506	504
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
CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	Mar. 31, 2022USD ($)vote$ / sharesshares	Dec. 31, 2021USD ($)vote$ / sharesshares
Accounts receivable - trade, allowance for credit losses \| $	$ 2,812	$ 3,276
Accumulated depreciation and amortization \| $	$ 997,459	$ 973,094
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)	50,650,000	50,423,000
Common stock, shares outstanding (in shares)	50,650,000	50,423,000
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, 2022	Mar. 31, 2021
Income Statement [Abstract]
Revenues	$ 234,027	$ 189,532
Operating expenses:
Cost of operations	162,455	127,139
General and administration	29,793	27,131
Depreciation and amortization	29,428	22,682
Expense from acquisition activities	2,043	414
Southbridge Landfill closure charge	140	157
Total operating expenses	223,859	177,523
Operating income	10,168	12,009
Other expense (income):
Interest income	(40)	(64)
Interest expense	5,204	5,468
Other income	(144)	(138)
Other expense, net	5,020	5,266
Income before income taxes	5,148	6,743
Provision for income taxes	958	2,432
Net income	$ 4,190	$ 4,311
Basic earnings per share attributable to common stockholders:
Weighted average common shares outstanding, basic (in shares)	51,490	51,179
Basic earnings per common share (in dollars per share)	$ 0.08	$ 0.08
Diluted earnings per share attributable to common stockholders:
Weighted average common shares outstanding, diluted (in shares)	51,657	51,387
Diluted earnings per common share (in dollars per share)	$ 0.08	$ 0.08

UNAUDITED CONSOLIDATED STATEM_2

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 4,190	$ 4,311
Hedging activity:
Interest rate swap settlements	(1,163)	(1,160)
Interest rate swap amounts reclassified into interest expense	1,128	1,145
Unrealized gain resulting from changes in fair value of derivative instruments	8,381	4,987
Other comprehensive income, before tax	8,346	4,972
Income tax provision related to items of other comprehensive income	2,203	1,142
Other comprehensive income, net of tax	6,143	3,830
Comprehensive income	$ 10,333	$ 8,141

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), net of tax	Class A Common Stock	Class A Common StockCommon Stock	Class B Common Stock	Class B Common StockCommon Stock
Beginning balance at Dec. 31, 2020	$ 362,142	$ 639,247	$ (266,099)	$ (11,517)		$ 501		$ 10
Beginning balance (in shares) at Dec. 31, 2020						50,101,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	112	109				$ 3
Issuance of Class A common stock (in shares)						273,000
Stock-based compensation	2,941	2,941
Net income (loss)	4,311		4,311
Hedging activity	3,830			3,830
Ending balance at Mar. 31, 2021	373,336	642,297	(261,788)	(7,687)		$ 504		$ 10
Ending balance (in shares) at Mar. 31, 2021					50,374,000	50,374,000	988,000	988,000
Beginning balance at Dec. 31, 2021	422,457	652,045	(224,999)	(5,103)		$ 504		$ 10
Beginning balance (in shares) at Dec. 31, 2021					50,423,000	50,423,000	988,000	988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	19	17				$ 2
Issuance of Class A common stock (in shares)						227,000
Stock-based compensation	2,241	2,241
Net income (loss)	4,190		4,190
Hedging activity	6,143			6,143
Ending balance at Mar. 31, 2022	$ 435,050	$ 654,303	$ (220,809)	$ 1,040		$ 506		$ 10
Ending balance (in shares) at Mar. 31, 2022					50,650,000	50,650,000	988,000	988,000

UNAUDITED CONSOLIDATED STATEM_4

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash Flows from Operating Activities:
Net income	$ 4,190	$ 4,311
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	29,428	22,682
Interest accretion on landfill and environmental remediation liabilities	1,966	1,957
Amortization of debt issuance costs	457	572
Stock-based compensation	2,241	2,941
Operating lease right-of-use assets expense	3,162	3,015
Gain on sale of property and equipment	(77)	(24)
Non-cash expense from acquisition activities	937	146
Deferred income taxes	534	2,300
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	402	7,872
Landfill operating lease contract expenditures	0	(160)
Accounts payable	2,116	1,349
Prepaid expenses, inventories and other assets	(1,060)	(2,077)
Accrued expenses, contract liabilities and other liabilities	(19,582)	(12,737)
Net cash provided by operating activities	24,714	32,147
Cash Flows from Investing Activities:
Acquisitions, net of cash acquired	(49,757)	(4,568)
Additions to property, plant and equipment	(12,910)	(26,832)
Proceeds from sale of property and equipment	145	123
Net cash used in investing activities	(62,522)	(31,277)
Cash Flows from Financing Activities:
Proceeds from debt borrowings	25,600	0
Principal payments on debt	(9,014)	(2,769)
Payments of debt issuance costs	(12)	0
Proceeds from the exercise of share based awards	19	112
Net cash provided by (used in) financing activities	16,593	(2,657)
Net decrease in cash and cash equivalents	(21,215)	(1,787)
Cash and cash equivalents, beginning of period	33,809	154,342
Cash and cash equivalents, end of period	12,594	152,555
Supplemental Disclosure of Cash Flow Information:
Cash interest payments	4,840	5,020
Cash income tax payments	221	238
Non-current assets obtained through long-term financing obligations	1,032	4,569
Right-of-use assets obtained in exchange for operating lease liabilities	$ 2,710	$ 512

BASIS OF PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
BASIS OF PRESENTATION	Mar. 31, 2022
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 seven states: Vermont, New Hampshire, New York, Massachusetts, Connecticut, Maine and Pennsylvania, with our headquarters located in Rutland, Vermont. We manage our solid waste operations on a geographic basis through two regional operating segments, the Eastern and Western regions, each of which provides a full range of 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, 2021 ("fiscal year 2021"), which was filed with the SEC on February 18, 2022. 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, which include normal recurring and nonrecurring adjustments, necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented. The results for the three months ended March 31, 2022 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 Annual Report on Form 10-K for fiscal year 2021. Subsequent Events We have evaluated subsequent events or transactions that have occurred after the consolidated balance sheet date of March 31, 2022 through the date of filing of the consolidated financial statements with the SEC on this Quarterly Report on Form 10-Q. We have determined that there are no subsequent events that require disclosure in this Quarterly Report on Form 10-Q.

ACCOUNTING CHANGES

ACCOUNTING CHANGES	3 Months Ended
ACCOUNTING CHANGES	Mar. 31, 2022
Accounting Changes and Error Corrections [Abstract]
ACCOUNTING CHANGES	ACCOUNTING CHANGES A table providing a brief description of recent Accounting Standards Updates ("ASUs") to the Accounting Standards Codification ("ASC") issued by the Financial Accounting Standards Board (“FASB”) that are pending adoption and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity follows: Standard Description Effect on the Financial Statements or Other Accounting standards issued pending adoption ASU No. 2020-04: Reference Rate Reform (Topic 848), as amended through January 2021 Provides temporary optional guidance to ease the potential burden in applying GAAP to contract modifications and hedging relationships that reference London Inter-Bank Offered Rate ("LIBOR") or another reference rate expected to be discontinued, subject to meeting certain criteria. We currently have interest rate derivative agreements with hedging relationships that reference LIBOR. This guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. We are currently assessing the provisions of this guidance, and reviewing and updating our existing contracts, as applicable, for transition or fallback language that specifies how a replacement rate for LIBOR will be identified. We are also no longer using LIBOR as a reference rate for any new contracts. We do not expect that the adoption of this guidance will have a material impact on our consolidated financial statements and related disclosures. This guidance will be in effect from March 12, 2020 through December 31, 2022. See Note 7, Debt for further disclosure over our interest rate derivative agreements and debt instruments that reference LIBOR. ASU No. 2021-08: Accounting for Contract Assets and Contract Liabilities from Contracts with Customers (Topic 805) Requires entities to apply ASC 606 to recognize and measure contract assets and contract liabilities in a business combination. This guidance improves comparability after the business combination by providing consistent recognition and measurement guidance for revenue contracts with customers acquired in a business combination and revenue contracts with customers not acquired in a business combination. We have made in the past, and we may make in the future, acquisitions to densify existing operations, expand service areas, and grow services for our customers, and these acquisitions may include contract assets or contract liabilities. We do not expect that the adoption of this guidance will have a material impact on our consolidated financial statements and related disclosures. This guidance is effective January 1, 2023 with early adoption permitted.

REVENUE RECOGNITION

REVENUE RECOGNITION	3 Months Ended
REVENUE RECOGNITION	Mar. 31, 2022
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 services are derived from processing and non-processing services. 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, 2022 and 2021: Three Months Ended March 31, 2022 Eastern Western Resource Solutions Total Revenues Collection $ 51,497 $ 68,034 $ — $ 119,531 Landfill 5,376 14,190 — 19,566 Transfer 11,613 7,844 — 19,457 Transportation 1,472 2,658 — 4,130 Landfill gas-to-energy 274 2,380 — 2,654 Processing 1,087 733 27,395 29,215 Non-processing — — 39,474 39,474 Total revenues $ 71,319 $ 95,839 $ 66,869 $ 234,027 Transferred at a point-in-time $ 120 $ 511 $ 15,086 $ 15,717 Transferred over time 71,199 95,328 51,783 218,310 Total revenues $ 71,319 $ 95,839 $ 66,869 $ 234,027 Three Months Ended March 31, 2021 Eastern Western Resource Solutions Total Revenues Collection $ 36,076 $ 61,393 $ — $ 97,469 Landfill 5,403 13,619 — 19,022 Transfer 9,424 7,146 — 16,570 Transportation 48 2,213 — 2,261 Landfill gas-to-energy 268 1,035 — 1,303 Processing 1,126 358 17,272 18,756 Non-processing — — 34,151 34,151 Total revenues $ 52,345 $ 85,764 $ 51,423 $ 189,532 Transferred at a point-in-time $ 44 $ 501 $ 10,092 $ 10,637 Transferred over time 52,301 85,263 41,331 178,895 Total revenues $ 52,345 $ 85,764 $ 51,423 $ 189,532 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 $3,794 in the three months ended March 31, 2022 and $1,568 in the three months ended March 31, 2021. 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 any revenues in the three months ended March 31, 2022 or March 31, 2021 from performance obligations satisfied in previous periods. Contract receivables, which are included in Accounts receivable, net 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 gross receivables from contracts of $94,967 and $89,232 as of March 31, 2022 and December 31, 2021, respectively. Certain customers are billed in advance and, accordingly, recognition of the related revenues is deferred as a contract liability until the services are provided and control transferred to the customer. We recognized contract liabilities of $5,500 and $3,404 as of March 31, 2022 and December 31, 2021, 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, 2021 and December 31, 2020 was recognized as revenue during the three months ended March 31, 2022 and March 31, 2021, respectively, when the services were performed.

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	3 Months Ended
BUSINESS COMBINATIONS	Mar. 31, 2022
Business Combination and Asset Acquisition [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONS In the three months ended March 31, 2022, we acquired the following businesses: a full service solid-waste collection, recycling and hauling business in our Resource Solutions operating segment; three tuck-in solid waste collection businesses in our Western region; a portable toilets business in our Eastern region; and a scrap metal collection business whose assets are allocated between our Eastern region and Resource Solutions operating segments. In the three months ended March 31, 2021, we acquired one tuck-in solid waste collection business in our Western region. The operating results of these businesses are included in the accompanying unaudited consolidated statements of operations from each date of acquisition, and the purchase price has been allocated to the net assets acquired based on fair values at each date of acquisition, with the residual amounts recorded as goodwill. Purchase price allocations are based on information existing at the acquisition dates or upon closing the transactions, including contingent consideration. Acquired intangible assets other than goodwill that are subject to amortization include customer relationships, trade names and covenants not-to-compete. Such assets are amortized over a four-year to ten-year period from the date of acquisition. All amounts recorded to goodwill are expected to be deductible for tax purposes. A summary of the purchase price paid and the purchase price allocation for acquisitions follows: Three Months Ended 2022 2021 Purchase Price: Cash used in acquisitions, net of cash acquired $ 49,747 $ 3,465 Holdbacks 3,707 385 Total consideration 53,454 3,850 Allocated as follows: Current assets 7,584 — Property, plant and equipment: Land 1,940 — Buildings and improvements 5,078 — Equipment 6,655 1,254 Operating lease right-of-use assets 405 — Intangible assets: Covenants not-to-compete 1,343 331 Customer relationships 9,637 954 Current liabilities (3,573) (76) Operating lease liabilities, less current portion (282) — Fair value of assets acquired and liabilities assumed 28,787 2,463 Excess purchase price allocated to goodwill $ 24,667 $ 1,387 Certain purchase price allocations are preliminary and are based on information existing at the acquisition dates or upon closing the transaction. Accordingly, the purchase price allocations are subject to change. Unaudited pro forma combined information that shows our operational results as though each acquisition completed since the beginning of the prior fiscal year had occurred as of January 1, 2021 is as follows: Three Months Ended 2022 2021 Revenues $ 238,836 $ 218,841 Operating income $ 10,834 $ 12,615 Net income $ 4,303 $ 2,571 Basic earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,490 51,179 Basic earnings per common share $ 0.08 $ 0.05 Diluted earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,657 51,387 Diluted earnings per common share $ 0.08 $ 0.05 The unaudited pro forma results set forth in the table above have been prepared for comparative purposes only and are not necessarily indicative of the actual results of operations had the acquisitions occurred as of January 1, 2021 or of the results of our future operations. Furthermore, the unaudited pro forma results do not give effect to all cost savings or incremental costs that may occur as a result of the integration and consolidation of the completed acquisitions.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	3 Months Ended
GOODWILL AND INTANGIBLE ASSETS	Mar. 31, 2022
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 reporting segment is as follows: December 31, Acquisitions March 31, Eastern region $ 52,072 $ 330 $ 52,402 Western region 163,728 3,906 167,634 Resource solutions 17,060 21,318 38,378 Total $ 232,860 $ 25,554 $ 258,414 Summaries of intangible assets by type follows: Covenants Customer Relationships Trade Names Total Balance, March 31, 2022 Intangible assets $ 30,120 $ 124,592 $ 8,350 $ 163,062 Less accumulated amortization (22,614) (37,322) (2,262) (62,198) $ 7,506 $ 87,270 $ 6,088 $ 100,864 Covenants Customer Relationships Trade Names Total Balance, December 31, 2021 Intangible assets $ 28,777 $ 115,005 $ 8,350 $ 152,132 Less accumulated amortization (22,148) (34,809) (1,452) (58,409) $ 6,629 $ 80,196 $ 6,898 $ 93,723 Intangible amortization expense was $3,789 during the three months ended March 31, 2022 and $2,028 during the three months ended March 31, 2021. A summary of intangible amortization expense estimated for the five fiscal years following fiscal year 2021 and thereafter follows: Estimated Future Amortization Expense as of March 31, 2022 Fiscal year ending December 31, 2022 $ 12,404 Fiscal year ending December 31, 2023 $ 15,574 Fiscal year ending December 31, 2024 $ 14,855 Fiscal year ending December 31, 2025 $ 13,736 Fiscal year ending December 31, 2026 $ 12,102 Thereafter $ 32,193

ACCRUED FINAL CAPPING, CLOSURE

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	3 Months Ended
ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	Mar. 31, 2022
Asset Retirement Obligation Disclosure [Abstract]
ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSUREAccrued 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 2022 2021 Beginning balance $ 86,914 $ 82,533 Obligations incurred 966 1,038 Accretion expense 1,873 1,811 Obligations settled (1) (926) (357) Ending balance $ 88,827 $ 85,025 (1) May include amounts that are being processed through accounts payable as a part of our disbursements cycle.

DEBT

DEBT	3 Months Ended
DEBT	Mar. 31, 2022
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") due December 2026; bearing interest at LIBOR plus 1.375% 350,000 350,000 Revolving Credit Facility due December 2026 ("Revolving Credit Facility"); bearing interest at LIBOR plus 1.375% 19,000 — 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 through 2029; bearing interest at 2.875% 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 through 2026; bearing interest at 3.125% 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 through 2025; bearing interest at 2.750% 40,000 40,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 ("FAME Bonds 2005R-3") due January 2025 - fixed rate interest period through 2025; bearing interest at 5.25% 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 through 2025; bearing interest at 5.125% 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 through 2025; bearing interest at 4.375% 15,000 15,000 Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 ("Vermont Bonds") due April 2036 - fixed rate interest period through 2028; bearing interest at 4.625% 16,000 16,000 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 through 2029; bearing interest at 2.95% 11,000 11,000 Other: Finance leases maturing through December 2107; bearing interest at a weighted average of 3.5% 44,783 45,724 Notes payable maturing through June 2027; bearing interest at a weighted average of 3.1% 4,405 4,846 Principal amount of debt 580,188 562,570 Less—unamortized debt issuance costs (1) 9,721 10,166 Debt less unamortized debt issuance costs 570,467 552,404 Less—current maturities of debt 9,873 9,901 $ 560,594 $ 542,503 (1) A summary of unamortized debt issuance costs by debt instrument follows: March 31, December 31, Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility") $ 5,601 $ 5,884 New York Bonds 2014R-1 916 933 New York Bonds 2014R-2 249 268 New York Bonds 2020 1,239 1,283 FAME Bonds 2005R-3 240 262 FAME Bonds 2015R-1 396 413 FAME Bonds 2015R-2 253 268 Vermont Bonds 419 433 New Hampshire Bonds 408 422 $ 9,721 $ 10,166 Credit Facility As of March 31, 2022, we are party to an amended and restated credit agreement ("Credit Agreement"), which provides for a $350,000 aggregate principal amount Term Loan Facility and a $300,000 Revolving Credit Facility, with a $75,000 sublimit for letters of credit. We have the right to request, at our discretion, an increase in the amount of loans under the Credit Facility by an aggregate amount of $125,000, subject to the terms and conditions set forth in the Credit Agreement. The Credit Facility has a 5-year term that matures in December 2026 and bears interest at a rate of LIBOR plus 1.375% per annum, which will be reduced to a rate of LIBOR plus as low as 1.125% upon us reaching a consolidated net leverage ratio of less than 2.25x. The Credit Facility contains customary benchmark replacement provisions pursuant to which, upon certain triggering events, the LIBOR benchmark used to calculate the LIBOR rate will be replaced with a secured overnight financing rate, as adjusted, on the terms and conditions in the Credit Facility. The Credit Facility is guaranteed jointly and severally, fully and unconditionally by all of our significant wholly-owned subsidiaries and secured by substantially all of our assets. As of March 31, 2022, further advances were available under the Credit Facility in the amount of $252,805. The available amount is net of outstanding irrevocable letters of credit totaling $28,195, and as of March 31, 2022 no amount had been drawn. 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 fair value is recorded in our 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, 2022 and December 31, 2021, our active interest rate derivative agreements had total notional amounts of $195,000. According to the terms of the agreements, we receive interest based on the 1-month LIBOR index, in some instances restricted by a 0.0% floor, and pay interest at a weighted average rate of approximately 2.48%. The agreements mature between June 2022 and February 2027. Additionally, as of March 31, 2022 and December 31, 2021, we have forward starting interest rate derivative agreements with total notional amounts of $60,000 and $85,000, respectively, after considering any forward starting interest rate derivative agreements that have become effective in the current period. According to the terms of the agreements, we will receive interest based on the 1-month LIBOR index, restricted by a 0.0% floor, and will pay interest at a weighted average rate of approximately 1.44%. The agreements mature between June 2027 and May 2028. A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows: Fair Value Balance Sheet Location March 31, December 31, Interest rate swaps Other current assets $ 785 $ — Interest rate swaps Other non-current assets 4,084 424 $ 4,869 $ 424 Interest rate swaps Other accrued liabilities $ 1,270 $ 3,796 Interest rate swaps Other long-term liabilities — 1,380 $ 1,270 $ 5,176 Interest rate swaps Accumulated other comprehensive income (loss), net of tax $ 3,412 $ (4,935) Interest rate swaps - tax effect Accumulated other comprehensive income (loss), net of tax (2,372) (168) $ 1,040 $ (5,103) A summary of the amount of expense on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income (loss), net of tax into earnings follows: Three Months Ended Statement of Operations Location 2022 2021 Interest expense $ 1,128 $ 1,145

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Legal Proceedings In the ordinary course of our business and as a 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 $1,241 relating to our outstanding legal proceedings as of March 31, 2022. 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 On October 9, 2020, our subsidiary, North Country Environmental Services, Inc. ("NCES"), received a Type I-A Permit Modification (the "Permit") for Expansion in the Stage VI area of the NCES landfill located in Bethlehem, New Hampshire. On 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 a 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 weighted average risk-free interest rate associated with our environmental remediation liabilities as of March 31, 2022 ranges between 1.5% and 2.6%. A summary of the changes to the aggregate environmental remediation liabilities for the three months ended March 31, 2022 and 2021 follows: Three Months Ended 2022 2021 Beginning balance $ 5,887 $ 5,200 Accretion expense 26 28 Obligations settled (1) (49) — Ending balance 5,864 5,228 Less: current portion 304 376 Long-term portion $ 5,560 $ 4,852 (1) May include amounts paid and amounts that are being processed through accounts payable as a part of our disbursement cycle.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
STOCKHOLDERS' EQUITY	Mar. 31, 2022
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, 2022, there were 811 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 four-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, 2021 77 $ 15.68 Granted — $ — Exercised (4) $ 4.85 Forfeited — $ — Outstanding, March 31, 2022 73 $ 16.28 4.3 $ 5,207 Exercisable, March 31, 2022 65 $ 9.45 3.6 $ 5,048 Stock-based compensation expense related to stock options was $16 during the three months ended March 31, 2022. We did not record any stock-based compensation expense for stock options during the three months ended March 31, 2021. As of March 31, 2022, we had $155 of unrecognized stock-based compensation expense related to outstanding stock options to be recognized over a weighted average period of 2.3 years. During the three months ended March 31, 2022, the aggregate intrinsic value of stock options exercised was $311. 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. Generally, 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 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, restricted stock unit and performance stock unit activity follows: Restricted Stock, Restricted Stock Units, and Performance Stock Units (1) Weighted Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding, December 31, 2021 249 $ 55.40 Granted 70 $ 97.77 Class A Common Stock Vested (51) $ 45.42 Forfeited (1) $ 57.55 Outstanding, March 31, 2022 267 $ 68.41 2.1 $ 23,374 Unvested, March 31, 2022 487 $ 68.66 1.8 $ 42,694 (1) Market-based performance stock unit grants are included at the 100% attainment level. Attainment of the maximum performance targets and market achievements would result in the issuance of an additional 221 shares of Class A common stock currently included in unvested. Stock-based compensation expense related to restricted stock, restricted stock units and performance stock units was $2,151 during the three months ended March 31, 2022, as compared to $2,884 during the three months ended March 31, 2021. During the three months ended March 31, 2022, the total fair value of other stock awards vested was $4,545. As of March 31, 2022, total unrecognized stock-based compensation expense related to outstanding restricted stock was $71, which will be recognized over a weighted average period of 1.7 years. As of March 31, 2022, total unrecognized stock-based compensation expense related to outstanding restricted stock units was $6,015, which will be recognized over a weighted average period of 2.2 years. As of March 31, 2022, total expected unrecognized stock-based compensation expense related to outstanding performance stock units was $9,779 to be recognized over a weighted average period of 2.0 years. We also recorded $73 of stock-based compensation expense related to our Amended and Restated 1997 Employee Stock Purchase Plan during the three months ended March 31, 2022, as compared to $57 during the three months ended March 31, 2021. 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, 2021 $ (5,103) Other comprehensive income before reclassifications 7,218 Amounts reclassified from accumulated other comprehensive income (loss) 1,128 Income tax provision related to items of other comprehensive income (2,203) Net current-period other comprehensive income 6,143 Balance, March 31, 2022 $ 1,040 A summary of reclassifications out of accumulated other comprehensive income (loss), net of tax follows: Three Months Ended 2022 2021 Details About Accumulated Other Comprehensive Income (Loss), Net of Tax Components Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss), Net of Tax Affected Line Item in the Consolidated Interest rate swaps $ 1,128 $ 1,145 Interest expense (1,128) (1,145) Income before income taxes (190) (127) Provision for income taxes $ (938) $ (1,018) Net income

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
EARNINGS PER SHARE	Mar. 31, 2022
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHAREBasic earnings per share is computed by dividing net 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 2022 2021 Numerator: Net income $ 4,190 $ 4,311 Denominators: Number of shares outstanding, end of period: Class A common stock 50,650 50,374 Class B common stock 988 988 Unvested restricted stock (2) (2) Effect of weighted average shares outstanding (146) (181) Basic weighted average common shares outstanding 51,490 51,179 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards 167 208 Diluted weighted average common shares outstanding 51,657 51,387 Anti-dilutive potentially issuable shares 78 88

OTHER ITEMS AND CHARGES

OTHER ITEMS AND CHARGES	3 Months Ended
OTHER ITEMS AND CHARGES	Mar. 31, 2022
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, 2022 and 2021, we recorded charges of $2,043 and $414, respectively, comprised primarily of legal, consulting and other similar costs associated with the acquisition and integration of acquired businesses or select development projects.

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	3 Months Ended
FAIR VALUE OF FINANCIAL INSTRUMENTS	Mar. 31, 2022
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, contingent consideration related to acquisitions, 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 the one-month LIBOR 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, 2022 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 1,985 $ — $ — Interest rate swaps — 4,869 — $ 1,985 $ 4,869 $ — Liabilities: Interest rate swaps $ — $ 1,270 $ — Fair Value Measurement at December 31, 2021 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 2,122 $ — $ — Interest rate swaps — 424 — $ 2,122 $ 424 $ — Liabilities: Interest rate swaps $ — $ 5,176 $ — Fair Value of Debt As of March 31, 2022, the fair value of our fixed rate debt, including our FAME Bonds 2005R-3, FAME Bonds 2015R-1, FAME Bonds 2015R-2, Vermont Bonds, New York Bonds 2014R-1, New York Bonds 2014R-2, New York Bonds 2020 and New Hampshire Bonds was approximately $165,864 and the carrying value was $162,000. The fair value of the FAME Bonds 2005R-3, the FAME Bonds 2015R-1, the FAME Bonds 2015R-2, the Vermont Bonds, the New York Bonds 2014R-1, the New York Bonds 2014R-2, New York Bonds 2020 and the New Hampshire 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, 2022, the carrying value of our Term Loan Facility was $350,000 and the carrying value of our Revolving Credit Facility was $19,000. 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
SEGMENT REPORTING	Mar. 31, 2022
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 Western and Eastern regions. Revenues associated with our solid waste operations are derived mainly from solid waste collection, transfer, transportation and disposal, landfill gas-to-energy, processing, and recycling services in the northeastern 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 derived from two lines-of-service: processing and non-processing. Revenues from processing services are derived from municipalities and customers in the form of processing fees, tipping fees, commodity sales, and organic material sales. Revenues from non-processing services are derived from brokerage services and overall resource management services providing a wide range of environmental services and zero waste 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, 2022 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 71,319 $ 16,668 $ 11,450 $ (2,229) $ 355,371 Western 95,839 32,493 14,659 9,263 684,969 Resource solutions 66,869 778 2,762 3,691 176,128 Corporate entities — — 557 (557) 90,503 Eliminations — (49,939) — — — $ 234,027 $ — $ 29,428 $ 10,168 $ 1,306,971 Three Months Ended March 31, 2021 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 52,345 $ 12,426 $ 6,622 $ 2,245 $ 221,200 Western 85,764 28,682 14,039 7,756 646,381 Resource solutions 51,423 1,903 1,568 2,462 88,759 Corporate entities — — 453 (454) 237,906 Eliminations — (43,011) — — — $ 189,532 $ — $ 22,682 $ 12,009 $ 1,194,246 A summary of our revenues attributable to services provided follows: Three Months Ended 2022 2021 Collection $ 119,531 $ 97,469 Disposal 43,153 37,853 Power generation 2,654 1,303 Processing 1,820 1,484 Solid waste operations 167,158 138,109 Processing 27,395 17,272 Non-processing 39,474 34,151 Resource solutions operations 66,869 51,423 Total revenues $ 234,027 $ 189,532

ACCOUNTING CHANGES (Policies)

ACCOUNTING CHANGES (Policies)	3 Months Ended
ACCOUNTING CHANGES (Policies)	Mar. 31, 2022
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 seven states: Vermont, New Hampshire, New York, Massachusetts, Connecticut, Maine and Pennsylvania, with our headquarters located in Rutland, Vermont. We manage our solid waste operations on a geographic basis through two regional operating segments, the Eastern and Western regions, each of which provides a full range of 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, 2021 ("fiscal year 2021"), which was filed with the SEC on February 18, 2022.
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, which include normal recurring and nonrecurring adjustments, necessary for a fair presentation of the financial position, results of operations and cash flows for the periods presented. The results for the three months ended March 31, 2022 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, 2022 through the date of filing of the consolidated financial statements with the SEC on this Quarterly Report on Form 10-Q. We have determined that there are no subsequent events that require disclosure in this Quarterly Report on Form 10-Q.
Accounting Standards Adopted and Pending Adoption	A table providing a brief description of recent Accounting Standards Updates ("ASUs") to the Accounting Standards Codification ("ASC") issued by the Financial Accounting Standards Board (“FASB”) that are pending adoption and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity follows: Standard Description Effect on the Financial Statements or Other Accounting standards issued pending adoption ASU No. 2020-04: Reference Rate Reform (Topic 848), as amended through January 2021 Provides temporary optional guidance to ease the potential burden in applying GAAP to contract modifications and hedging relationships that reference London Inter-Bank Offered Rate ("LIBOR") or another reference rate expected to be discontinued, subject to meeting certain criteria. We currently have interest rate derivative agreements with hedging relationships that reference LIBOR. This guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. We are currently assessing the provisions of this guidance, and reviewing and updating our existing contracts, as applicable, for transition or fallback language that specifies how a replacement rate for LIBOR will be identified. We are also no longer using LIBOR as a reference rate for any new contracts. We do not expect that the adoption of this guidance will have a material impact on our consolidated financial statements and related disclosures. This guidance will be in effect from March 12, 2020 through December 31, 2022. See Note 7, Debt for further disclosure over our interest rate derivative agreements and debt instruments that reference LIBOR. ASU No. 2021-08: Accounting for Contract Assets and Contract Liabilities from Contracts with Customers (Topic 805) Requires entities to apply ASC 606 to recognize and measure contract assets and contract liabilities in a business combination. This guidance improves comparability after the business combination by providing consistent recognition and measurement guidance for revenue contracts with customers acquired in a business combination and revenue contracts with customers not acquired in a business combination. We have made in the past, and we may make in the future, acquisitions to densify existing operations, expand service areas, and grow services for our customers, and these acquisitions may include contract assets or contract liabilities. We do not expect that the adoption of this guidance will have a material impact on our consolidated financial statements and related disclosures. This guidance is effective January 1, 2023 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
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 Western and Eastern regions. Revenues associated with our solid waste operations are derived mainly from solid waste collection, transfer, transportation and disposal, landfill gas-to-energy, processing, and recycling services in the northeastern 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 derived from two lines-of-service: processing and non-processing. Revenues from processing services are derived from municipalities and customers in the form of processing fees, tipping fees, commodity sales, and organic material sales. Revenues from non-processing services are derived from brokerage services and overall resource management services providing a wide range of environmental services and zero waste 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
ACCOUNTING CHANGES (Tables)	Mar. 31, 2022
Accounting Changes and Error Corrections [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	A table providing a brief description of recent Accounting Standards Updates ("ASUs") to the Accounting Standards Codification ("ASC") issued by the Financial Accounting Standards Board (“FASB”) that are pending adoption and deemed to have a possible material impact on our consolidated financial statements based on current account balances and activity follows: Standard Description Effect on the Financial Statements or Other Accounting standards issued pending adoption ASU No. 2020-04: Reference Rate Reform (Topic 848), as amended through January 2021 Provides temporary optional guidance to ease the potential burden in applying GAAP to contract modifications and hedging relationships that reference London Inter-Bank Offered Rate ("LIBOR") or another reference rate expected to be discontinued, subject to meeting certain criteria. We currently have interest rate derivative agreements with hedging relationships that reference LIBOR. This guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform if certain criteria are met. We are currently assessing the provisions of this guidance, and reviewing and updating our existing contracts, as applicable, for transition or fallback language that specifies how a replacement rate for LIBOR will be identified. We are also no longer using LIBOR as a reference rate for any new contracts. We do not expect that the adoption of this guidance will have a material impact on our consolidated financial statements and related disclosures. This guidance will be in effect from March 12, 2020 through December 31, 2022. See Note 7, Debt for further disclosure over our interest rate derivative agreements and debt instruments that reference LIBOR. ASU No. 2021-08: Accounting for Contract Assets and Contract Liabilities from Contracts with Customers (Topic 805) Requires entities to apply ASC 606 to recognize and measure contract assets and contract liabilities in a business combination. This guidance improves comparability after the business combination by providing consistent recognition and measurement guidance for revenue contracts with customers acquired in a business combination and revenue contracts with customers not acquired in a business combination. We have made in the past, and we may make in the future, acquisitions to densify existing operations, expand service areas, and grow services for our customers, and these acquisitions may include contract assets or contract liabilities. We do not expect that the adoption of this guidance will have a material impact on our consolidated financial statements and related disclosures. This guidance is effective January 1, 2023 with early adoption permitted.

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	3 Months Ended
REVENUE RECOGNITION (Tables)	Mar. 31, 2022
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, 2022 and 2021: Three Months Ended March 31, 2022 Eastern Western Resource Solutions Total Revenues Collection $ 51,497 $ 68,034 $ — $ 119,531 Landfill 5,376 14,190 — 19,566 Transfer 11,613 7,844 — 19,457 Transportation 1,472 2,658 — 4,130 Landfill gas-to-energy 274 2,380 — 2,654 Processing 1,087 733 27,395 29,215 Non-processing — — 39,474 39,474 Total revenues $ 71,319 $ 95,839 $ 66,869 $ 234,027 Transferred at a point-in-time $ 120 $ 511 $ 15,086 $ 15,717 Transferred over time 71,199 95,328 51,783 218,310 Total revenues $ 71,319 $ 95,839 $ 66,869 $ 234,027 Three Months Ended March 31, 2021 Eastern Western Resource Solutions Total Revenues Collection $ 36,076 $ 61,393 $ — $ 97,469 Landfill 5,403 13,619 — 19,022 Transfer 9,424 7,146 — 16,570 Transportation 48 2,213 — 2,261 Landfill gas-to-energy 268 1,035 — 1,303 Processing 1,126 358 17,272 18,756 Non-processing — — 34,151 34,151 Total revenues $ 52,345 $ 85,764 $ 51,423 $ 189,532 Transferred at a point-in-time $ 44 $ 501 $ 10,092 $ 10,637 Transferred over time 52,301 85,263 41,331 178,895 Total revenues $ 52,345 $ 85,764 $ 51,423 $ 189,532

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	3 Months Ended
BUSINESS COMBINATIONS (Tables)	Mar. 31, 2022
Business Combination and Asset Acquisition [Abstract]
Summary of Purchase Price Paid for Acquisitions	A summary of the purchase price paid and the purchase price allocation for acquisitions follows: Three Months Ended 2022 2021 Purchase Price: Cash used in acquisitions, net of cash acquired $ 49,747 $ 3,465 Holdbacks 3,707 385 Total consideration 53,454 3,850 Allocated as follows: Current assets 7,584 — Property, plant and equipment: Land 1,940 — Buildings and improvements 5,078 — Equipment 6,655 1,254 Operating lease right-of-use assets 405 — Intangible assets: Covenants not-to-compete 1,343 331 Customer relationships 9,637 954 Current liabilities (3,573) (76) Operating lease liabilities, less current portion (282) — Fair value of assets acquired and liabilities assumed 28,787 2,463 Excess purchase price allocated to goodwill $ 24,667 $ 1,387
Schedule of Unaudited Pro forma Combined Information	Unaudited pro forma combined information that shows our operational results as though each acquisition completed since the beginning of the prior fiscal year had occurred as of January 1, 2021 is as follows: Three Months Ended 2022 2021 Revenues $ 238,836 $ 218,841 Operating income $ 10,834 $ 12,615 Net income $ 4,303 $ 2,571 Basic earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,490 51,179 Basic earnings per common share $ 0.08 $ 0.05 Diluted earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,657 51,387 Diluted earnings per common share $ 0.08 $ 0.05

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	3 Months Ended
GOODWILL AND INTANGIBLE ASSETS (Tables)	Mar. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of Goodwill Activity	A summary of the activity and balances related to goodwill by reporting segment is as follows: December 31, Acquisitions March 31, Eastern region $ 52,072 $ 330 $ 52,402 Western region 163,728 3,906 167,634 Resource solutions 17,060 21,318 38,378 Total $ 232,860 $ 25,554 $ 258,414
Summary of Intangible Assets by Type	Summaries of intangible assets by type follows: Covenants Customer Relationships Trade Names Total Balance, March 31, 2022 Intangible assets $ 30,120 $ 124,592 $ 8,350 $ 163,062 Less accumulated amortization (22,614) (37,322) (2,262) (62,198) $ 7,506 $ 87,270 $ 6,088 $ 100,864 Covenants Customer Relationships Trade Names Total Balance, December 31, 2021 Intangible assets $ 28,777 $ 115,005 $ 8,350 $ 152,132 Less accumulated amortization (22,148) (34,809) (1,452) (58,409) $ 6,629 $ 80,196 $ 6,898 $ 93,723
Summary of Intangible Amortization Expense Estimated	A summary of intangible amortization expense estimated for the five fiscal years following fiscal year 2021 and thereafter follows: Estimated Future Amortization Expense as of March 31, 2022 Fiscal year ending December 31, 2022 $ 12,404 Fiscal year ending December 31, 2023 $ 15,574 Fiscal year ending December 31, 2024 $ 14,855 Fiscal year ending December 31, 2025 $ 13,736 Fiscal year ending December 31, 2026 $ 12,102 Thereafter $ 32,193

ACCRUED FINAL CAPPING, CLOSUR_2

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE (Tables)	3 Months Ended
ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE (Tables)	Mar. 31, 2022
Asset Retirement Obligation Disclosure [Abstract]
Summary 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 2022 2021 Beginning balance $ 86,914 $ 82,533 Obligations incurred 966 1,038 Accretion expense 1,873 1,811 Obligations settled (1) (926) (357) Ending balance $ 88,827 $ 85,025 (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
DEBT (Tables)	Mar. 31, 2022
Debt And Derivatives Disclosure [Abstract]
Summary of Debt	A summary of debt is as follows: March 31, December 31, Senior Secured Credit Facility: Term loan A facility ("Term Loan Facility") due December 2026; bearing interest at LIBOR plus 1.375% 350,000 350,000 Revolving Credit Facility due December 2026 ("Revolving Credit Facility"); bearing interest at LIBOR plus 1.375% 19,000 — 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 through 2029; bearing interest at 2.875% 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 through 2026; bearing interest at 3.125% 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 through 2025; bearing interest at 2.750% 40,000 40,000 Finance Authority of Maine Solid Waste Disposal Revenue Bonds Series 2005R-3 ("FAME Bonds 2005R-3") due January 2025 - fixed rate interest period through 2025; bearing interest at 5.25% 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 through 2025; bearing interest at 5.125% 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 through 2025; bearing interest at 4.375% 15,000 15,000 Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 ("Vermont Bonds") due April 2036 - fixed rate interest period through 2028; bearing interest at 4.625% 16,000 16,000 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 through 2029; bearing interest at 2.95% 11,000 11,000 Other: Finance leases maturing through December 2107; bearing interest at a weighted average of 3.5% 44,783 45,724 Notes payable maturing through June 2027; bearing interest at a weighted average of 3.1% 4,405 4,846 Principal amount of debt 580,188 562,570 Less—unamortized debt issuance costs (1) 9,721 10,166 Debt less unamortized debt issuance costs 570,467 552,404 Less—current maturities of debt 9,873 9,901 $ 560,594 $ 542,503 (1) A summary of unamortized debt issuance costs by debt instrument follows: March 31, December 31, Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility") $ 5,601 $ 5,884 New York Bonds 2014R-1 916 933 New York Bonds 2014R-2 249 268 New York Bonds 2020 1,239 1,283 FAME Bonds 2005R-3 240 262 FAME Bonds 2015R-1 396 413 FAME Bonds 2015R-2 253 268 Vermont Bonds 419 433 New Hampshire Bonds 408 422 $ 9,721 $ 10,166
Summary of Cash Flow Hedges	A summary of the effect of cash flow hedges related to derivative instruments on the consolidated balance sheet follows: Fair Value Balance Sheet Location March 31, December 31, Interest rate swaps Other current assets $ 785 $ — Interest rate swaps Other non-current assets 4,084 424 $ 4,869 $ 424 Interest rate swaps Other accrued liabilities $ 1,270 $ 3,796 Interest rate swaps Other long-term liabilities — 1,380 $ 1,270 $ 5,176 Interest rate swaps Accumulated other comprehensive income (loss), net of tax $ 3,412 $ (4,935) Interest rate swaps - tax effect Accumulated other comprehensive income (loss), net of tax (2,372) (168) $ 1,040 $ (5,103) A summary of the amount of expense on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive income (loss), net of tax into earnings follows: Three Months Ended Statement of Operations Location 2022 2021 Interest expense $ 1,128 $ 1,145

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	3 Months Ended
COMMITMENTS AND CONTINGENCIES (Tables)	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Summary of Environmental Liability	A summary of the changes to the aggregate environmental remediation liabilities for the three months ended March 31, 2022 and 2021 follows: Three Months Ended 2022 2021 Beginning balance $ 5,887 $ 5,200 Accretion expense 26 28 Obligations settled (1) (49) — Ending balance 5,864 5,228 Less: current portion 304 376 Long-term portion $ 5,560 $ 4,852 (1) May include amounts paid and amounts that are being processed through accounts payable as a part of our disbursement cycle.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
STOCKHOLDERS' EQUITY (Tables)	Mar. 31, 2022
Equity [Abstract]
Summary 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, 2021 77 $ 15.68 Granted — $ — Exercised (4) $ 4.85 Forfeited — $ — Outstanding, March 31, 2022 73 $ 16.28 4.3 $ 5,207 Exercisable, March 31, 2022 65 $ 9.45 3.6 $ 5,048
Summary of Restricted Stock, Restricted Stock Unit and Performance Stock Unit Activity	A summary of restricted stock, restricted stock unit and performance stock unit activity follows: Restricted Stock, Restricted Stock Units, and Performance Stock Units (1) Weighted Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding, December 31, 2021 249 $ 55.40 Granted 70 $ 97.77 Class A Common Stock Vested (51) $ 45.42 Forfeited (1) $ 57.55 Outstanding, March 31, 2022 267 $ 68.41 2.1 $ 23,374 Unvested, March 31, 2022 487 $ 68.66 1.8 $ 42,694 (1) Market-based performance stock unit grants are included at the 100% attainment level. Attainment of the maximum performance targets and market achievements would result in the issuance of an additional 221 shares of Class A common stock currently included in unvested.
Summary 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, 2021 $ (5,103) Other comprehensive income before reclassifications 7,218 Amounts reclassified from accumulated other comprehensive income (loss) 1,128 Income tax provision related to items of other comprehensive income (2,203) Net current-period other comprehensive income 6,143 Balance, March 31, 2022 $ 1,040
Summary of Reclassifications Out of Accumulated Other Comprehensive Loss	A summary of reclassifications out of accumulated other comprehensive income (loss), net of tax follows: Three Months Ended 2022 2021 Details About Accumulated Other Comprehensive Income (Loss), Net of Tax Components Amounts Reclassified Out of Accumulated Other Comprehensive Income (Loss), Net of Tax Affected Line Item in the Consolidated Interest rate swaps $ 1,128 $ 1,145 Interest expense (1,128) (1,145) Income before income taxes (190) (127) Provision for income taxes $ (938) $ (1,018) Net income

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
EARNINGS PER SHARE (Tables)	Mar. 31, 2022
Earnings Per Share [Abstract]
Summary of Earnings per Share Computation	A summary of the numerator and denominators used in the computation of earnings per share follows: Three Months Ended 2022 2021 Numerator: Net income $ 4,190 $ 4,311 Denominators: Number of shares outstanding, end of period: Class A common stock 50,650 50,374 Class B common stock 988 988 Unvested restricted stock (2) (2) Effect of weighted average shares outstanding (146) (181) Basic weighted average common shares outstanding 51,490 51,179 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards 167 208 Diluted weighted average common shares outstanding 51,657 51,387 Anti-dilutive potentially issuable shares 78 88

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	3 Months Ended
FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Summary 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, 2022 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 1,985 $ — $ — Interest rate swaps — 4,869 — $ 1,985 $ 4,869 $ — Liabilities: Interest rate swaps $ — $ 1,270 $ — Fair Value Measurement at December 31, 2021 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 2,122 $ — $ — Interest rate swaps — 424 — $ 2,122 $ 424 $ — Liabilities: Interest rate swaps $ — $ 5,176 $ —

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	3 Months Ended
SEGMENT REPORTING (Tables)	Mar. 31, 2022
Segment Reporting [Abstract]
Summary of Segment Reporting Information by Segment	Three Months Ended March 31, 2022 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 71,319 $ 16,668 $ 11,450 $ (2,229) $ 355,371 Western 95,839 32,493 14,659 9,263 684,969 Resource solutions 66,869 778 2,762 3,691 176,128 Corporate entities — — 557 (557) 90,503 Eliminations — (49,939) — — — $ 234,027 $ — $ 29,428 $ 10,168 $ 1,306,971 Three Months Ended March 31, 2021 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 52,345 $ 12,426 $ 6,622 $ 2,245 $ 221,200 Western 85,764 28,682 14,039 7,756 646,381 Resource solutions 51,423 1,903 1,568 2,462 88,759 Corporate entities — — 453 (454) 237,906 Eliminations — (43,011) — — — $ 189,532 $ — $ 22,682 $ 12,009 $ 1,194,246
Summary of Revenue Attributable to Services	A summary of our revenues attributable to services provided follows: Three Months Ended 2022 2021 Collection $ 119,531 $ 97,469 Disposal 43,153 37,853 Power generation 2,654 1,303 Processing 1,820 1,484 Solid waste operations 167,158 138,109 Processing 27,395 17,272 Non-processing 39,474 34,151 Resource solutions operations 66,869 51,423 Total revenues $ 234,027 $ 189,532

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details)	3 Months Ended
BASIS OF PRESENTATION (Details)	Mar. 31, 2022regionalOperatingSegment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of regional operating segments	2

REVENUE RECOGNITION - Disaggreg

REVENUE RECOGNITION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 234,027	$ 189,532
Collection
Disaggregation of Revenue [Line Items]
Total revenues	119,531	97,469
Landfill
Disaggregation of Revenue [Line Items]
Total revenues	19,566	19,022
Transfer
Disaggregation of Revenue [Line Items]
Total revenues	19,457	16,570
Transportation
Disaggregation of Revenue [Line Items]
Total revenues	4,130	2,261
Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	2,654	1,303
Processing
Disaggregation of Revenue [Line Items]
Total revenues	29,215	18,756
Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	39,474	34,151
Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	15,717	10,637
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	218,310	178,895
Eastern
Disaggregation of Revenue [Line Items]
Total revenues	71,319	52,345
Eastern \| Collection
Disaggregation of Revenue [Line Items]
Total revenues	51,497	36,076
Eastern \| Landfill
Disaggregation of Revenue [Line Items]
Total revenues	5,376	5,403
Eastern \| Transfer
Disaggregation of Revenue [Line Items]
Total revenues	11,613	9,424
Eastern \| Transportation
Disaggregation of Revenue [Line Items]
Total revenues	1,472	48
Eastern \| Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	274	268
Eastern \| Processing
Disaggregation of Revenue [Line Items]
Total revenues	1,087	1,126
Eastern \| Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Eastern \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	120	44
Eastern \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	71,199	52,301
Western
Disaggregation of Revenue [Line Items]
Total revenues	95,839	85,764
Western \| Collection
Disaggregation of Revenue [Line Items]
Total revenues	68,034	61,393
Western \| Landfill
Disaggregation of Revenue [Line Items]
Total revenues	14,190	13,619
Western \| Transfer
Disaggregation of Revenue [Line Items]
Total revenues	7,844	7,146
Western \| Transportation
Disaggregation of Revenue [Line Items]
Total revenues	2,658	2,213
Western \| Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	2,380	1,035
Western \| Processing
Disaggregation of Revenue [Line Items]
Total revenues	733	358
Western \| Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Western \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	511	501
Western \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	95,328	85,263
Resource solutions
Disaggregation of Revenue [Line Items]
Total revenues	66,869	51,423
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
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	27,395	17,272
Resource solutions \| Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	39,474	34,151
Resource solutions \| Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	15,086	10,092
Resource solutions \| Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	$ 51,783	$ 41,331

REVENUE RECOGNITION - Narrative

REVENUE RECOGNITION - Narrative (Details) - USD ($)	3 Months Ended
REVENUE RECOGNITION - Narrative (Details) - USD ($)	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rebates	$ (234,027,000)	$ (189,532,000)
Revenue recognized fro performance obligation satisfied in previous period	0	0
Gross receivables from contracts	94,967,000		$ 89,232,000
Contract liabilities	5,500,000		$ 3,404,000
Rebate for Recycled or Returned Organic Materials
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rebates	$ 3,794,000	$ 1,568,000

BUSINESS COMBINATIONS - Narrati

BUSINESS COMBINATIONS - Narrative (Details) - business	3 Months Ended
BUSINESS COMBINATIONS - Narrative (Details) - business	Mar. 31, 2022	Mar. 31, 2021
Minimum
Business Acquisition [Line Items]
Useful life of finite lived intangible assets	4 years
Maximum
Business Acquisition [Line Items]
Useful life of finite lived intangible assets	10 years
Western \| Tuck-in Solid Waste Collection Business
Business Acquisition [Line Items]
Number of businesses acquired	3	1

BUSINESS COMBINATIONS - Summary

BUSINESS COMBINATIONS - Summary of Purchase Price Paid for Acquisitions (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Purchase Price:
Cash used in acquisitions, net of cash acquired	$ 49,757	$ 4,568
Allocated as follows:
Excess purchase price allocated to goodwill	258,414		$ 232,860
Waste Collection Acquisitions
Purchase Price:
Cash used in acquisitions, net of cash acquired	49,747	3,465
Holdbacks	3,707	385
Total consideration	53,454	3,850
Allocated as follows:
Current assets	7,584	0
Land	1,940	0
Buildings and improvements	5,078	0
Equipment	6,655	1,254
Operating lease right-of-use assets	405	0
Current liabilities	(3,573)	(76)
Operating lease liabilities, less current portion	(282)	0
Fair value of assets acquired and liabilities assumed	28,787	2,463
Excess purchase price allocated to goodwill	24,667	1,387
Waste Collection Acquisitions \| Covenants not-to-compete
Allocated as follows:
Intangible assets:	1,343	331
Waste Collection Acquisitions \| Customer Relationships
Allocated as follows:
Intangible assets:	$ 9,637	$ 954

BUSINESS COMBINATIONS - Schedul

BUSINESS COMBINATIONS - Schedule of Unaudited Pro forma Combined Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Business Combination and Asset Acquisition [Abstract]
Revenues	$ 238,836	$ 218,841
Operating income	10,834	12,615
Net income	$ 4,303	$ 2,571
Weighted average common shares outstanding, basic (in shares)	51,490	51,179
Basic earnings per common share (in dollars per share)	$ 0.08	$ 0.05
Weighted average common shares outstanding, diluted (in shares)	51,657	51,387
Diluted earnings per common share (in dollars per share)	$ 0.08	$ 0.05

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Summary of Goodwill Activity (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 232,860
Acquisitions	25,554
Goodwill, ending balance	258,414
Eastern
Goodwill [Roll Forward]
Goodwill, beginning balance	52,072
Acquisitions	330
Goodwill, ending balance	52,402
Western
Goodwill [Roll Forward]
Goodwill, beginning balance	163,728
Acquisitions	3,906
Goodwill, ending balance	167,634
Resource solutions
Goodwill [Roll Forward]
Goodwill, beginning balance	17,060
Acquisitions	21,318
Goodwill, ending balance	$ 38,378

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets by Type (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 163,062	$ 152,132
Less accumulated amortization	(62,198)	(58,409)
Intangible assets, net	100,864	93,723
Covenants not-to-compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets	30,120	28,777
Less accumulated amortization	(22,614)	(22,148)
Intangible assets, net	7,506	6,629
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets	124,592	115,005
Less accumulated amortization	(37,322)	(34,809)
Intangible assets, net	87,270	80,196
Trade Names
Finite-Lived Intangible Assets [Line Items]
Intangible assets	8,350	8,350
Less accumulated amortization	(2,262)	(1,452)
Intangible assets, net	$ 6,088	$ 6,898

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible amortization expense	$ 3,789	$ 2,028

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Amortization Expense Estimated (Detail) $ in Thousands	Mar. 31, 2022USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Fiscal year ending December 31, 2022	$ 12,404
Fiscal year ending December 31, 2023	15,574
Fiscal year ending December 31, 2024	14,855
Fiscal year ending December 31, 2025	13,736
Fiscal year ending December 31, 2026	12,102
Thereafter	$ 32,193

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, 2022	Mar. 31, 2021
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 86,914	$ 82,533
Obligations incurred	966	1,038
Accretion expense	1,873	1,811
Obligations settled	(926)	(357)
Ending balance	$ 88,827	$ 85,025

DEBT - Summary of Debt (Details

DEBT - Summary of Debt (Details) - USD ($) $ in Thousands	3 Months Ended
DEBT - Summary of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Weighted-average discount rate - finance leases	3.50%
Finance leases maturing through December 2107; bearing interest at a weighted average of 3.5%	$ 44,783	$ 45,724
Principal amount of debt	580,188	562,570
Less - unamortized debt issuance costs	9,721	10,166
Debt less unamortized debt issuance costs	570,467	552,404
Less—current maturities of debt	9,873	9,901
Debt, less current portion	560,594	542,503
Secured Debt \| Term loan A facility ("Term Loan Facility") due December 2026; bearing interest at LIBOR plus 1.375%
Debt Instrument [Line Items]
Principal amount of debt	$ 350,000	350,000
Secured Debt \| Term loan A facility ("Term Loan Facility") due December 2026; bearing interest at LIBOR plus 1.375% \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.375%
Line of Credit \| Revolving Credit Facility due December 2026 ("Revolving Credit Facility"); bearing interest at LIBOR plus 1.375%
Debt Instrument [Line Items]
Principal amount of debt	$ 19,000	0
Line of Credit \| Revolving Credit Facility due December 2026 ("Revolving Credit Facility"); bearing interest at LIBOR plus 1.375% \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.375%
Credit Facility \| Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility")
Debt Instrument [Line Items]
Less - unamortized debt issuance costs	$ 5,601	5,884
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 through 2029; bearing interest at 2.875%
Debt Instrument [Line Items]
Stated interest rate	2.875%
Principal amount of debt	$ 25,000	25,000
Less - unamortized debt issuance costs	$ 916	933
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 through 2026; bearing interest at 3.125%
Debt Instrument [Line Items]
Stated interest rate	3.125%
Principal amount of debt	$ 15,000	15,000
Less - unamortized debt issuance costs	$ 249	268
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 through 2025; bearing interest at 2.750%
Debt Instrument [Line Items]
Stated interest rate	2.75%
Principal amount of debt	$ 40,000	40,000
Less - unamortized debt issuance costs	$ 1,239	1,283
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 through 2025; bearing interest at 5.25%
Debt Instrument [Line Items]
Stated interest rate	5.25%
Principal amount of debt	$ 25,000	25,000
Less - unamortized debt issuance costs	$ 240	262
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 through 2025; bearing interest at 5.125%
Debt Instrument [Line Items]
Stated interest rate	5.125%
Principal amount of debt	$ 15,000	15,000
Less - unamortized debt issuance costs	$ 396	413
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 through 2025; bearing interest at 4.375%
Debt Instrument [Line Items]
Stated interest rate	4.375%
Principal amount of debt	$ 15,000	15,000
Less - unamortized debt issuance costs	$ 253	268
Unsecured Debt \| Vermont Economic Development Authority Solid Waste Disposal Long-Term Revenue Bonds Series 2013 ("Vermont Bonds") due April 2036 - fixed rate interest period through 2028; bearing interest at 4.625%
Debt Instrument [Line Items]
Stated interest rate	4.625%
Principal amount of debt	$ 16,000	16,000
Less - unamortized debt issuance costs	$ 419	433
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 through 2029; bearing interest at 2.95%
Debt Instrument [Line Items]
Stated interest rate	2.95%
Principal amount of debt	$ 11,000	11,000
Less - unamortized debt issuance costs	$ 408	422
Notes payable maturing through June 2027; bearing interest at a weighted average of 3.1%
Debt Instrument [Line Items]
Weighted average interest rate	3.10%
Principal amount of debt	$ 4,405	$ 4,846

DEBT - Credit Facility Narrativ

DEBT - Credit Facility Narrative (Details)	3 Months Ended
DEBT - Credit Facility Narrative (Details)	Mar. 31, 2022USD ($)
Debt Instrument [Line Items]
Additional borrowing capacity	$ 125,000,000
Line of Credit
Debt Instrument [Line Items]
Debt instrument, term (in years)	5 years
Net leverage ratio	2.25
Line of credit facility, remaining borrowing capacity	$ 252,805,000
Line of Credit \| LIBOR \| Maximum
Debt Instrument [Line Items]
Floor interest rate received	1.375%
Line of Credit \| LIBOR \| Minimum
Debt Instrument [Line Items]
Floor interest rate received	1.125%
Secured Debt \| Term loan A facility ("Term Loan Facility") due December 2026; bearing interest at LIBOR plus 1.375%
Debt Instrument [Line Items]
Aggregate principal amount	$ 350,000,000
Revolving Credit Facility \| Revolving Credit Facility due December 2026 ("Revolving Credit Facility"); bearing interest at LIBOR plus 1.375% \| Line of Credit
Debt Instrument [Line Items]
Credit facility maximum	300,000,000
Letters of credit outstanding	28,195,000
Revolving Credit Facility \| Revolving Credit Facility due December 2026 ("Revolving Credit Facility"); bearing interest at LIBOR plus 1.375% \| Letter of Credit
Debt Instrument [Line Items]
Letters of credit sublimit	$ 75,000,000

DEBT - Cash Flow Hedges Narrati

DEBT - Cash Flow Hedges Narrative (Details) - Cash Flow Hedging - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Interest Rate Derivative
Debt Instrument [Line Items]
Notional amount	$ 195,000,000	$ 195,000,000
Floor interest rate	0.00%
Weighted average percentage rate paid	2.48%
Forward Starting Interest Rate Derivative
Debt Instrument [Line Items]
Notional amount	$ 60,000,000	$ 85,000,000
Floor interest rate	0.00%
Weighted average percentage rate paid	1.44%

DEBT - Summary of Cash Flow Hed

DEBT - Summary of Cash Flow Hedges (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive income (loss), net of tax	$ 1,040	$ (5,103)
Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	4,869	424
Cash flow hedge derivatives, gross liability	1,270	5,176
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	3,412	(4,935)
Accumulated other comprehensive income (loss), tax	(2,372)	(168)
Accumulated other comprehensive income (loss), net of tax	1,040	(5,103)
Other current assets \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	785	0
Other non-current assets \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	4,084	424
Other accrued liabilities \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross liability	1,270	3,796
Other long-term liabilities \| Designated as Hedging Instrument \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross liability	$ 0	$ 1,380

DEBT - Schedule of Loss On Cash

DEBT - Schedule of Loss On Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ 1,128	$ 1,145
Interest rate swaps \| Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ 1,128	$ 1,145

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Detail) $ in Thousands	Mar. 31, 2022USD ($)
Loss Contingencies [Line Items]
Loss contingency accrual	$ 1,241
Maximum
Loss Contingencies [Line Items]
Risk free interest	2.60%
Minimum
Loss Contingencies [Line Items]
Risk free interest	1.50%

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Environmental Remediation Liability (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 5,887	$ 5,200
Accretion expense	26	28
Obligations settled	(49)	0
Ending balance	5,864	5,228
Accrual for environmental loss contingencies	5,864	5,228
Less: current portion	304	376
Long-term portion	$ 5,560	$ 4,852

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Detail) - USD ($)	3 Months Ended
STOCKHOLDERS' EQUITY - Narrative (Detail) - USD ($)	Mar. 31, 2022	Mar. 31, 2021
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	2 years 3 months 18 days
Fair value of stock awards vested	$ 4,545,000
Stock Options
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	16,000	$ 0
Unrecognized stock-based compensation expense, stock options	155,000
Aggregate intrinsic value of options exercised	311,000
Restricted Stock, Restricted Stock Units And Performance Stock Units
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	2,151,000	2,884,000
Restricted Stock
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 71,000
Restricted Stock \| Non Employee Director
Limited Partners' Capital Account [Line Items]
Options, vesting period (in years)	3 years
Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 6,015,000
Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	$ 9,779,000
Weighted average \| Restricted Stock
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	1 year 8 months 12 days
Weighted average \| Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	2 years 2 months 12 days
Weighted average \| Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period	2 years
2016 Plan
Limited Partners' Capital Account [Line Items]
Options granted, term (in years)	10 years
2016 Plan \| Minimum
Limited Partners' Capital Account [Line Items]
Options, vesting period (in years)	1 year
2016 Plan \| Maximum
Limited Partners' Capital Account [Line Items]
Options, vesting period (in years)	4 years
Amended and Restated 1997 Employee Stock Purchase Plan
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	$ 73,000	$ 57,000
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)	811,000
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, 2022USD ($)$ / sharesshares
Stock Options
Beginning balance, outstanding (in shares) \| shares	77
Granted (in shares) \| shares	0
Exercised (in shares) \| shares	(4)
Forfeited (in shares) \| shares	0
Ending balance, outstanding (in shares) \| shares	73
Exercisable at end of period (in shares) \| shares	65
Weighted Average Exercise Price
Beginning balance, outstanding (in dollars per share) \| $ / shares	$ 15.68
Granted (in dollars per share) \| $ / shares	0
Exercised (in dollars per share) \| $ / shares	4.85
Forfeited (in dollars per share) \| $ / shares	0
Ending balance, outstanding (in dollars per share) \| $ / shares	16.28
Exercisable at end of period (in dollars per share) \| $ / shares	$ 9.45
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Outstanding contractual term	4 years 3 months 18 days
Exercisable contractual term	3 years 7 months 6 days
Outstanding aggregate intrinsic value \| $	$ 5,207
Exercisable aggregate intrinsic value \| $	$ 5,048

STOCKHOLDERS' EQUITY - Summar_2

STOCKHOLDERS' EQUITY - Summary of Restricted Stock, Restricted Stock Unit and Performance-based Stock Unit Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)$ / sharesshares
Restricted Stock, Restricted Stock Units And Performance Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding, beginning of period (in shares)	249
Granted (in shares)	70
Forfeited (in shares)	(1)
Outstanding, end of period (in shares)	267
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) \| $ / shares	$ 55.40
Granted (in dollars per share) \| $ / shares	97.77
Forfeited (in dollars per share) \| $ / shares	57.55
Outstanding at end of period (in dollars per share) \| $ / shares	$ 68.41
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term (in years)	2 years 1 month 6 days
Aggregate intrinsic value \| $	$ 23,374
Restricted Stock, Restricted Stock Units And Performance Stock Units \| Class A Common Stock
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Vested (in shares)	(51)
Weighted Average Grant Date Fair Value
Class A Common Stock Vested (in dollars per share) \| $ / shares	$ 45.42
Performance Stock Unit
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Percentage of attainment level (as a percent)	100.00%
Performance Stock Unit \| Class A Common Stock
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Number of additional shares (in shares)	221
Unvested \| Restricted Stock, Restricted Stock Units And Performance Stock Units
Restricted Stock, Restricted Stock Units, and Performance Stock Units
Outstanding, end of period (in shares)	487
Weighted Average Grant Date Fair Value
Outstanding at end of period (in dollars per share) \| $ / shares	$ 68.66
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term (in years)	1 year 9 months 18 days
Aggregate intrinsic value \| $	$ 42,694

STOCKHOLDERS' EQUITY - Summar_3

STOCKHOLDERS' EQUITY - Summary of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 422,457	$ 362,142
Other comprehensive income, net of tax	6,143	3,830
Ending balance	435,050	$ 373,336
Accumulated Gain (Loss), Cash Flow Hedge
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(5,103)
Other comprehensive income	7,218
Amounts reclassified from accumulated other comprehensive income (loss)	1,128
Income tax provision related to items of other comprehensive income	(2,203)
Other comprehensive income, net of tax	6,143
Ending balance	$ 1,040

STOCKHOLDERS' EQUITY - Summar_4

STOCKHOLDERS' EQUITY - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 5,204	$ 5,468
Income before income taxes	5,148	6,743
Provision for income taxes	958	2,432
Net income	4,190	4,311
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]
Income before income taxes	(1,128)	(1,145)
Provision for income taxes	(190)	(127)
Net income	(938)	(1,018)
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	$ 1,128	$ 1,145

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ in Thousands	3 Months Ended
EARNINGS PER SHARE (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Numerator:
Net income	$ 4,190	$ 4,311
Denominators:
Unvested restricted stock (in shares)	(2,000)	(2,000)
Effect of weighted average shares outstanding (in shares)	(146,000)	(181,000)
Weighted average common shares outstanding, basic (in shares)	51,490,000	51,179,000
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards (in shares)	167,000	208,000
Weighted average common shares outstanding, diluted	51,657,000	51,387,000
Anti-dilutive potentially issuable shares (in shares)	78,000	88,000
Class A Common Stock
Denominators:
Common stock, shares outstanding (in shares)	50,650,000	50,374,000	50,423,000
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
OTHER ITEMS AND CHARGES (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Mar. 31, 2021
Unusual or Infrequent Items, or Both [Abstract]
Expense from acquisition activities	$ 2,043	$ 414

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring Fair Value Measurements (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets:
Restricted investment securities - landfill closure	$ 1,985	$ 2,122
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate swaps	0	0
Total assets	1,985	2,122
Liabilities:
Interest rate swaps	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Landfill
Assets:
Restricted investment securities - landfill closure	1,985	2,122
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Interest rate swaps	4,869	424
Total assets	4,869	424
Liabilities:
Interest rate swaps	1,270	5,176
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 - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Term loan A facility ("Term Loan Facility") due December 2026; bearing interest at LIBOR plus 1.375% \| Secured Debt
Debt Instrument [Line Items]
Principal amount of debt	$ 350,000	$ 350,000
Fair Value \| Fixed Rate Bonds
Debt Instrument [Line Items]
Fixed rate debt	165,864
Carrying Value
Debt Instrument [Line Items]
Revolving credit facility	19,000
Carrying Value \| Fixed Rate Bonds
Debt Instrument [Line Items]
Fixed rate debt	$ 162,000

SEGMENT REPORTING - Summary of

SEGMENT REPORTING - Summary of Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues	$ 234,027	$ 189,532
Depreciation and amortization	29,428	22,682
Operating income (loss)	10,168	12,009
Total assets	1,306,971	1,194,246	$ 1,283,580
Operating \| Eastern
Segment Reporting Information [Line Items]
Revenues	71,319	52,345
Depreciation and amortization	11,450	6,622
Operating income (loss)	(2,229)	2,245
Total assets	355,371	221,200
Operating \| Western
Segment Reporting Information [Line Items]
Revenues	95,839	85,764
Depreciation and amortization	14,659	14,039
Operating income (loss)	9,263	7,756
Total assets	684,969	646,381
Operating \| Resource solutions
Segment Reporting Information [Line Items]
Revenues	66,869	51,423
Depreciation and amortization	2,762	1,568
Operating income (loss)	3,691	2,462
Total assets	176,128	88,759
Corporate entities
Segment Reporting Information [Line Items]
Revenues	0	0
Depreciation and amortization	557	453
Operating income (loss)	(557)	(454)
Total assets	90,503	237,906
Inter-company revenues
Segment Reporting Information [Line Items]
Revenues	(49,939)	(43,011)
Inter-company revenues \| Eastern
Segment Reporting Information [Line Items]
Revenues	(16,668)	(12,426)
Inter-company revenues \| Western
Segment Reporting Information [Line Items]
Revenues	(32,493)	(28,682)
Inter-company revenues \| Resource solutions
Segment Reporting Information [Line Items]
Revenues	$ (778)	$ (1,903)

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, 2022	Mar. 31, 2021
Revenue from External Customer [Line Items]
Revenues	$ 234,027	$ 189,532
Solid waste operations
Revenue from External Customer [Line Items]
Revenues	167,158	138,109
Collection
Revenue from External Customer [Line Items]
Revenues	119,531	97,469
Disposal
Revenue from External Customer [Line Items]
Revenues	43,153	37,853
Power generation
Revenue from External Customer [Line Items]
Revenues	2,654	1,303
Processing
Revenue from External Customer [Line Items]
Revenues	1,820	1,484
Resource solutions operations
Revenue from External Customer [Line Items]
Revenues	66,869	51,423
Processing
Revenue from External Customer [Line Items]
Revenues	27,395	17,272
Non-processing
Revenue from External Customer [Line Items]
Revenues	$ 39,474	$ 34,151