Casella Waste Systems (CWST) 10-Q 29 Oct 21 2021 Q3 Quarterly report Financial data

COVER

COVER - shares	9 Months Ended
	Sep. 30, 2021	Oct. 15, 2021
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
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	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		50,409,773
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Cash and cash equivalents	$ 46,481	$ 154,342
Accounts receivable, net of allowance for credit losses of $3,057 and $2,333, respectively	90,500	74,198
Refundable income taxes	0	229
Prepaid expenses	16,806	9,289
Inventory	9,797	7,868
Other current assets	3,575	1,328
Total current assets	167,159	247,254
Property, plant and equipment, net of accumulated depreciation and amortization of $952,032 and $900,882, respectively	617,348	510,512
Operating lease right-of-use assets	96,712	95,310
Goodwill	227,929	194,901
Intangible assets, net	92,908	58,324
Restricted assets	1,948	1,848
Cost method investments	11,264	11,264
Deferred income taxes	46,777	61,163
Other non-current assets	18,352	13,322
Total assets	1,280,397	1,193,898
CURRENT LIABILITIES:
Current maturities of debt	16,751	9,240
Current operating lease liabilities	7,128	8,547
Accounts payable	69,516	49,198
Accrued payroll and related expenses	19,793	17,282
Accrued interest	1,960	2,126
Contract liabilities	3,422	2,685
Current accrued capping, closure and post-closure costs	17,848	10,268
Other accrued liabilities	41,951	31,862
Total current liabilities	178,369	131,208
Debt, less current portion	534,752	530,411
Operating lease liabilities, less current portion	59,001	60,979
Accrued capping, closure and post-closure costs, less current portion	68,425	72,265
Deferred income taxes	879	912
Other long-term liabilities	31,020	35,981
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
Additional paid-in capital	648,611	639,247
Accumulated deficit	(234,144)	(266,099)
Accumulated other comprehensive loss, net of tax	(7,030)	(11,517)
Total stockholders' equity	407,951	362,142
Total liabilities and stockholders' equity	1,280,397	1,193,898
Class A Common Stock
STOCKHOLDERS' EQUITY:
Common stock	504	501
Class B Common Stock
STOCKHOLDERS' EQUITY:
Common stock	$ 10	$ 10

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)vote$ / sharesshares	Dec. 31, 2020USD ($)vote$ / sharesshares
Accounts receivable - trade, allowance for credit losses | $	$ 3,057	$ 2,333
Accumulated depreciation and amortization | $	$ 952,032	$ 900,882
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)	50,410,000	50,101,000
Common stock, shares outstanding (in shares)	50,410,000	50,101,000
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

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Revenues	$ 241,969	$ 202,667	$ 647,375	$ 574,344
Operating expenses:
Cost of operations	153,892	130,406	419,583	382,386
General and administration	30,993	25,014	87,336	74,240
Depreciation and amortization	27,491	23,799	74,510	67,281
Expense from acquisition activities	1,904	173	3,950	1,533
Southbridge Landfill closure charge	302	2,642	653	3,815
Total operating expenses	214,582	182,034	586,032	529,255
Operating income	27,387	20,633	61,343	45,089
Other expense (income):
Interest income	(61)	(107)	(191)	(203)
Interest expense	5,164	5,406	15,928	16,869
Other income	(178)	(157)	(825)	(606)
Other expense, net	4,925	5,142	14,912	16,060
Income before income taxes	22,462	15,491	46,431	29,029
Provision for income taxes	6,601	374	14,476	840
Net income	$ 15,861	$ 15,117	$ 31,955	$ 28,189
Basic earnings per share attributable to common stockholders:
Weighted average common shares outstanding, basic (in shares)	51,389	48,370	51,312	48,241
Basic earnings per common share (in dollars per share)	$ 0.31	$ 0.31	$ 0.62	$ 0.58
Diluted earnings per share attributable to common stockholders:
Weighted average common shares outstanding, diluted (in shares)	51,586	48,619	51,506	48,481
Diluted earnings per common share (in dollars per share)	$ 0.31	$ 0.31	$ 0.62	$ 0.58

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 15,861	$ 15,117	$ 31,955	$ 28,189
Hedging activity:
Interest rate swap settlements	(1,205)	(1,141)	(3,551)	(2,492)
Interest rate swap amounts reclassified into interest expense	1,204	1,156	3,551	2,513
Unrealized gain (loss) resulting from changes in fair value of derivative instruments	1,215	145	5,866	(8,731)
Other comprehensive income (loss), before tax	1,214	160	5,866	(8,710)
Income tax provision (benefit) related to items of other comprehensive income (loss)	322	0	1,379	(112)
Other comprehensive income (loss), net of tax	892	160	4,487	(8,598)
Comprehensive income	$ 16,753	$ 15,277	$ 36,442	$ 19,591

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Cumulative effect of new accounting principle	Additional Paid-In Capital	Accumulated Deficit	Accumulated DeficitCumulative effect of new accounting principle	Accumulated other comprehensive 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, 2019	$ 122,753	$ (189)	$ 485,332	$ (357,016)	$ (189)	$ (6,041)		$ 468		$ 10
Beginning balance (in shares) at Dec. 31, 2019								46,803,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	100		95					$ 5
Issuance of Class A common stock (in shares)								517,000
Stock-based compensation	1,562		1,562
Net income (loss)	959			959
Hedging activity	(7,189)					(7,189)
Ending balance at Mar. 31, 2020	117,996		486,989	(356,246)		(13,230)		$ 473		$ 10
Ending balance (in shares) at Mar. 31, 2020								47,320,000		988,000
Beginning balance at Dec. 31, 2019	122,753	$ (189)	485,332	(357,016)	$ (189)	(6,041)		$ 468		$ 10
Beginning balance (in shares) at Dec. 31, 2019								46,803,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	28,189
Hedging activity	(8,598)
Ending balance at Sep. 30, 2020	147,987		491,158	(329,016)		(14,639)		$ 474		$ 10
Ending balance (in shares) at Sep. 30, 2020							47,384,000	47,384,000	988,000	988,000
Beginning balance at Mar. 31, 2020	117,996		486,989	(356,246)		(13,230)		$ 473		$ 10
Beginning balance (in shares) at Mar. 31, 2020								47,320,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock - acquisition	0		(1)					$ 1
Issuance of Class A common stock - acquisition (in shares)								36,000
Issuances of Class A common stock	387		387
Issuance of Class A common stock (in shares)								26,000
Stock-based compensation	1,818		1,818
Net income (loss)	12,113			12,113
Hedging activity	(1,569)					(1,569)
Ending balance at Jun. 30, 2020	130,745		489,193	(344,133)		(14,799)		$ 474		$ 10
Ending balance (in shares) at Jun. 30, 2020								47,382,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock (in shares)								2,000
Stock-based compensation	1,965		1,965
Net income (loss)	15,117			15,117
Hedging activity	160					160
Ending balance at Sep. 30, 2020	147,987		491,158	(329,016)		(14,639)		$ 474		$ 10
Ending balance (in shares) at Sep. 30, 2020							47,384,000	47,384,000	988,000	988,000
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	50,101,000	988,000	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		988,000
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	50,101,000	988,000	988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	31,955
Hedging activity	4,487
Ending balance at Sep. 30, 2021	407,951		648,611	(234,144)		(7,030)		$ 504		$ 10
Ending balance (in shares) at Sep. 30, 2021							50,410,000	50,410,000	988,000	988,000
Beginning balance at Mar. 31, 2021	373,336		642,297	(261,788)		(7,687)		$ 504		$ 10
Beginning balance (in shares) at Mar. 31, 2021								50,374,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	492		492
Issuance of Class A common stock (in shares)								24,000
Stock-based compensation	3,116		3,116
Net income (loss)	11,783			11,783
Hedging activity	(235)					(235)
Ending balance at Jun. 30, 2021	388,492		645,905	(250,005)		(7,922)		$ 504		$ 10
Ending balance (in shares) at Jun. 30, 2021								50,398,000		988,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances of Class A common stock	51		51
Issuance of Class A common stock (in shares)								12,000
Stock-based compensation	2,655		2,655
Net income (loss)	15,861			15,861
Hedging activity	892					892
Ending balance at Sep. 30, 2021	$ 407,951		$ 648,611	$ (234,144)		$ (7,030)		$ 504		$ 10
Ending balance (in shares) at Sep. 30, 2021							50,410,000	50,410,000	988,000	988,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash Flows from Operating Activities:
Net income	$ 31,955	$ 28,189
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	74,510	67,281
Interest accretion on landfill and environmental remediation liabilities	5,915	5,324
Amortization of debt issuance costs	1,716	1,597
Stock-based compensation	8,712	5,345
Operating lease right-of-use assets expense	9,981	12,347
(Gain) loss on sale of property and equipment	(1)	254
Southbridge Landfill non-cash closure charge	112	2,077
Non-cash expense from acquisition activities	532	549
Deferred income taxes	12,974	1,514
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(10,943)	6,400
Landfill operating lease contract expenditures	(3,646)	(3,386)
Accounts payable	20,318	(8,585)
Prepaid expenses, inventories and other assets	(14,391)	(2,908)
Accrued expenses, contract liabilities and other liabilities	(3,655)	(4,083)
Net cash provided by operating activities	134,089	111,915
Cash Flows from Investing Activities:
Acquisitions, net of cash acquired	(153,112)	(25,379)
Additions to property, plant and equipment	(81,577)	(77,271)
Proceeds from sale of property and equipment	593	430
Net cash used in investing activities	(234,096)	(102,220)
Cash Flows from Financing Activities:
Proceeds from debt borrowings	500	154,400
Principal payments on debt	(8,517)	(145,008)
Payments of debt issuance costs	0	(1,531)
Proceeds from the exercise of share based awards	163	100
Net cash (used in) provided by financing activities	(7,854)	7,961
Net (decrease) increase in cash and cash equivalents	(107,861)	17,656
Cash and cash equivalents, beginning of period	154,342	3,471
Cash and cash equivalents, end of period	46,481	21,127
Supplemental Disclosure of Cash Flow Information:
Cash interest payments	14,378	15,239
Cash income tax payments	597	(1,650)
Non-current assets obtained through long-term financing obligations	18,153	16,937
Right-of-use assets obtained in exchange for operating lease liabilities	$ 3,566	$ 3,289

BASIS OF PRESENTATION

BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 2021
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 that provides collection, transfer, disposal, landfill, landfill gas-to-energy, recycling and organics services in the northeastern United States. We market recyclable metals, aluminum, plastics, paper, and corrugated cardboard, which have been processed at our recycling facilities or purchased from third-parties. 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 includes our larger-scale recycling and commodity brokerage operations along with our organics services and large scale commercial and industrial services. 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 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 ("fiscal year 2020"), which was filed with the SEC on February 19, 2021. 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 and nine months ended September 30, 2021 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 2020. Recent Events The global outbreak of the novel coronavirus ("COVID-19") pandemic has caused economic disruption across our geographic footprint and has adversely affected our business. The COVID-19 pandemic negatively impacted our revenues starting at the end of the three months ended March 31, 2020, as many small business and construction collection customers required service level changes and volumes into our landfills declined due to lower economic activity. Demand for services has improved as local economies have reopened as allowed by State Governments and our collection and disposal volumes, as well as overall operations, have been less impacted by the effects of the COVID-19 pandemic in the three and nine months ended September 30, 2021. The COVID-19 pandemic has negatively impacted and may continue to impact our business in other ways, as we have experienced increased costs as a result of the COVID-19 pandemic, including, but not limited to, higher costs associated with providing a safe working environment for our employees (such as increased costs associated with the protection of our employees, including costs for additional safety equipment, hygiene products and enhanced facility cleaning), employee impacts from illness, supporting a remote administrative workforce, community response measures, the inability of customers to continue to pay for services, and temporary facility closures of our customers. Furthermore, residual macroeconomic effects associated with the pandemic have negatively impacted the global supply chain, labor markets and distribution networks leading to heightened inflation across labor, select services and goods, and capital investments. As of the date of this filing, we are unable to determine or predict the full extent of any possible continuing impact that the COVID-19 pandemic will have on our business, results of operations, liquidity and capital resources. Future developments, such as the possibility of continuing spread of COVID-19 across our geographic footprint, the administration rates and effectiveness of vaccinations, the severity and containment of certain COVID-19 variants along with the pace and extent to which the States in which we operate continue to facilitate a return to normal economic and operation conditions, are uncertain and cannot be predicted at this time. Subsequent Events We have evaluated subsequent events or transactions that have occurred after the consolidated balance sheet date of September 30, 2021 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	9 Months Ended
	Sep. 30, 2021
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 we adopted and deemed to have a material impact on our consolidated financial statements, or a possible material impact in the future, based on current account balances and activity follows: Standard Description Effect on the Financial Statements or Other Accounting standards adopted effective January 1, 2021 ASU No. 2019-12: Income Taxes (Topic 740) Reduces the complexity over accounting for income taxes by removing certain exceptions and amending guidance to improve consistent application of accounting over income taxes. This guidance did not have a material impact on our consolidated financial statements and related disclosures upon adoption, but may in the future. This guidance was effective January 1, 2021. A table providing a brief description of recent ASUs to the ASC issued by the 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, which extend past the fiscal year ended December 31, 2021. We are currently assessing the provisions of this guidance as LIBOR is still in place and do not expect that its adoption 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.

REVENUE RECOGNITION

REVENUE RECOGNITION	9 Months Ended
	Sep. 30, 2021
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, landfill, landfill gas-to-energy, processing, transfer and recycling services in the northeastern United States. Effective January 1, 2021, we reorganized the Resource Solutions operating segment, which includes our larger-scale recycling and commodity brokerage operations along with our organics services and large scale commercial and industrial services, from our historical lines-of-service of recycling, organics and customer solutions into two lines-of-service: processing and non-processing. Processing services consist of the receipt of recycled, sludge or other organic materials at one of our materials recovery, processing or disposal facilities, where it is then sorted, mixed and/or processed, and then disposed of or sold. 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; overall resource management services providing a wide range of environmental services and zero waste solutions to large and complex organizations; and traditional collection, disposal and recycling services provided to large account multi-site customers. In brokerage arrangements, we act as an agent that facilitates the sale of recyclable materials between an inbound customer and an outbound customer. Revenues from the brokerage of recycled materials are recognized on a net basis at the time of shipment. In general, these fees are variable in nature. Classification of revenues by service line reported in the three and nine months ended September 30, 2020 has been reclassified to conform with the presentation for the three and nine months ended September 30, 2021. The following tables set forth revenues disaggregated by service line and timing of revenue recognition by operating segment for each of the three and nine months ended September 30, 2021 and 2020: Three Months Ended September 30, 2021 Eastern Western Resource Solutions Total Revenues Collection $ 48,951 $ 69,921 $ — $ 118,872 Landfill 6,622 18,201 — 24,823 Transfer 16,948 10,375 — 27,323 Transportation 54 3,393 — 3,447 Landfill gas-to-energy 269 984 — 1,253 Processing 2,310 649 27,418 30,377 Non-processing — — 35,874 35,874 Total revenues $ 75,154 $ 103,523 $ 63,292 $ 241,969 Transferred at a point-in-time $ 43 $ 296 $ 19,927 $ 20,266 Transferred over time 75,111 103,227 43,365 221,703 Total revenues $ 75,154 $ 103,523 $ 63,292 $ 241,969 Three Months Ended September 30, 2020 Eastern Western Resource Solutions Total Revenues Collection $ 38,659 $ 63,611 $ — $ 102,270 Landfill 5,694 17,880 — 23,574 Transfer 11,861 9,756 — 21,617 Transportation 61 2,348 — 2,409 Landfill gas-to-energy 210 777 — 987 Processing 1,838 356 15,701 17,895 Non-processing — — 33,915 33,915 Total revenues $ 58,323 $ 94,728 $ 49,616 $ 202,667 Transferred at a point-in-time $ 52 $ 347 $ 7,736 $ 8,135 Transferred over time 58,271 94,381 41,880 194,532 Total revenues $ 58,323 $ 94,728 $ 49,616 $ 202,667 Nine Months Ended September 30, 2021 Eastern Western Resource Solutions Total Revenues Collection $ 124,389 $ 199,278 $ — $ 323,667 Landfill 18,143 48,336 — 66,479 Transfer 39,847 27,498 — 67,345 Transportation 148 8,646 — 8,794 Landfill gas-to-energy 784 2,873 — 3,657 Processing 5,246 1,508 65,721 72,475 Non-processing — — 104,958 104,958 Total revenues $ 188,557 $ 288,139 $ 170,679 $ 647,375 Transferred at a point-in-time $ 125 $ 1,284 $ 44,964 $ 46,373 Transferred over time 188,432 286,855 125,715 601,002 Total revenues $ 188,557 $ 288,139 $ 170,679 $ 647,375 Nine Months Ended September 30, 2020 Eastern Western Resource Solutions Total Revenues Collection $ 110,059 $ 180,778 $ — $ 290,837 Landfill 13,807 49,409 — 63,216 Transfer 32,695 25,429 — 58,124 Transportation 159 8,472 — 8,631 Landfill gas-to-energy 793 2,138 — 2,931 Processing 4,290 992 45,724 51,006 Non-processing — — 99,599 99,599 Total revenues $ 161,803 $ 267,218 $ 145,323 $ 574,344 Transferred at a point-in-time $ 177 $ 949 $ 20,428 $ 21,554 Transferred over time 161,626 266,269 124,895 552,790 Total revenues $ 161,803 $ 267,218 $ 145,323 $ 574,344 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 $4,341 and $8,440 in the three and nine months ended September 30, 2021, respectively, and $1,018 and $3,555 in the three and nine months ended September 30, 2020, respectively. 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 and nine months ended September 30, 2021 or September 30, 2020 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 $91,469 and $74,162 as of September 30, 2021 and December 31, 2020, 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 $3,422 and $2,685 as of September 30, 2021 and December 31, 2020, 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, 2020 and December 31, 2019 was recognized as revenue during the nine months ended September 30, 2021 and September 30, 2020, respectively, when the services were performed.

BUSINESS COMBINATIONS

BUSINESS COMBINATIONS	9 Months Ended
	Sep. 30, 2021
Business Combination and Asset Acquisition [Abstract]
BUSINESS COMBINATIONS	BUSINESS COMBINATIONSIn the nine months ended September 30, 2021, we acquired the following businesses: a residential, commercial and roll-off collection business in eastern Connecticut that operates a rail-served construction and demolition processing and waste transfer facility, a waste transfer station, a single-stream recycling facility, and several other recycling operations whose assets and liabilities are allocated between our Eastern region and Resource Solutions operating segments; a solid-waste collection business that operates a waste transfer station, a septic and portable toilet business, and a tuck-in solid-waste collection business in our Eastern region; and a waste composting and food-scrap hauling business, a solid-waste collection business that operates a waste transfer station, and two tuck-in solid-waste collection businesses in our Western region. In the nine months ended September 30, 2020, we acquired six businesses: five tuck-in solid-waste collection businesses in our Western region and one recycling operation in our Resource Solutions operating segment. The operating results of the acquired 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. Acquired intangible assets other than goodwill that are subject to amortization include client lists, trade names, and non-compete covenants. Such assets are amortized over a four-year to ten-year period from the date of acquisition. All amounts recorded to goodwill, except goodwill related to certain acquisitions, are expected to be deductible for tax purposes. A summary of the purchase price paid and the purchase price allocation for these acquisitions follows: Nine Months Ended 2021 2020 Purchase Price: Cash used in acquisitions, net of cash acquired $ 150,364 $ 23,062 Contingent consideration 3,000 — Holdbacks 1,865 3,387 Total 155,229 26,449 Allocated as follows: Current assets 7,260 227 Operating lease right-of-use assets 6,500 — Land 803 895 Finance lease right-of-use-assets 31,467 — Buildings and improvements 8,468 1,908 Equipment 42,458 10,006 Intangible assets 41,759 7,159 Other liabilities, net (5,120) (306) Finance leases (11,367) — Fair value of assets acquired and liabilities assumed 122,228 19,889 Excess purchase price allocated to goodwill $ 33,001 $ 6,560 Certain purchase price allocations are preliminary and are based on information existing at the acquisition dates or upon closing the transaction. This includes purchase price allocations associated with the accounting for three acquisitions, acquired during the three months ended September 30, 2021, that have not yet been completed because we have not finalized the valuations of certain tangible and intangible assets, as well as the contingent consideration. Accordingly, these 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, 2020 is as follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Revenues $ 248,981 $ 225,580 $ 696,391 $ 646,004 Operating income $ 26,996 $ 20,100 $ 59,526 $ 43,660 Net income $ 14,996 $ 12,976 $ 26,542 $ 21,845 Basic earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,389 48,370 51,312 48,241 Basic earnings per common share $ 0.29 $ 0.27 $ 0.52 $ 0.45 Diluted earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,586 48,619 51,506 48,481 Diluted earnings per common share $ 0.29 $ 0.27 $ 0.52 $ 0.45 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, 2020 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	9 Months Ended
	Sep. 30, 2021
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 September 30, Eastern region $ 30,873 $ 18,984 $ 49,857 Western region 149,984 10,156 160,140 Resource solutions 14,044 3,888 17,932 Total $ 194,901 $ 33,028 $ 227,929 Summaries of intangible assets by type follows: Covenants Client Lists Trade Names Total Balance, September 30, 2021 Intangible assets $ 29,514 $ 109,676 $ 8,350 $ 147,540 Less accumulated amortization (21,752) (32,298) (582) (54,632) $ 7,762 $ 77,378 $ 7,768 $ 92,908 Covenants Client Lists Total Balance, December 31, 2020 Intangible assets $ 26,971 $ 78,809 $ 105,780 Less accumulated amortization (20,547) (26,909) (47,456) $ 6,424 $ 51,900 $ 58,324 Intangible amortization expense was $3,133 and $7,175 during the three and nine months ended September 30, 2021, respectively, and $2,265 and $6,580 during the three and nine months ended September 30, 2020, respectively. A summary of intangible amortization expense estimated for the five fiscal years following fiscal year 2020 and thereafter follows: Estimated Future Amortization Expense as of September 30, 2021 Fiscal year ending December 31, 2021 $ 3,694 Fiscal year ending December 31, 2022 $ 14,007 Fiscal year ending December 31, 2023 $ 12,970 Fiscal year ending December 31, 2024 $ 12,634 Fiscal year ending December 31, 2025 $ 11,945 Thereafter $ 37,658

ACCRUED FINAL CAPPING, CLOSURE

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE	9 Months Ended
	Sep. 30, 2021
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: Nine Months Ended 2021 2020 Beginning balance $ 82,533 $ 71,927 Obligations incurred 3,638 2,820 Revision in estimates (1) — 152 Accretion expense 5,496 4,826 Obligations settled (2) (5,394) (2,706) Ending balance $ 86,273 $ 77,019 (1) Relates to changes in estimated costs and timing of final capping, closure and post-closure activities at the Town of Southbridge, Massachusetts landfill. See Note 8, Commitments and Contingencies and Note 11, Other Items and Charges for further discussion. (2) May include amounts that are being processed through accounts payable as a part of our disbursements cycle.

DEBT

DEBT	9 Months Ended
	Sep. 30, 2021
Debt And Derivatives Disclosure [Abstract]
DEBT	DEBT A summary of debt is as follows: September 30, December 31, Senior Secured Credit Facility: Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.50% $ — $ — Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.50% 347,375 350,000 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 3.6% 44,804 31,486 Notes payable maturing through June 2027; bearing interest at a weighted average of 3.4% 4,377 4,933 Principal amount of debt 558,556 548,419 Less—unamortized debt issuance costs (1) 7,053 8,768 Debt less unamortized debt issuance costs 551,503 539,651 Less—current maturities of debt 16,751 9,240 $ 534,752 $ 530,411 (1) A summary of unamortized debt issuance costs by debt instrument follows: September 30, December 31, Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility") $ 2,609 $ 3,839 New York Bonds 2014R-1 950 1,000 New York Bonds 2014R-2 283 329 New York Bonds 2020 1,328 1,461 FAME Bonds 2005R-3 283 347 FAME Bonds 2015R-1 430 482 FAME Bonds 2015R-2 287 343 Vermont Bonds 446 487 New Hampshire Bonds 437 480 $ 7,053 $ 8,768 Credit Facility As of September 30, 2021, we are party to a credit agreement ("Credit Agreement"), which provides for a $350,000 aggregate principal amount Term Loan Facility and a $200,000 Revolving Credit Facility. 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 May 2023 and bears interest at a rate of LIBOR plus 1.50% per annum, which will be reduced to a rate of LIBOR plus as low as 1.25% upon us reaching a consolidated net leverage ratio of less than 2.25x. 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 September 30, 2021, further advances were available under the Credit Facility in the amount of $172,030. The available amount is net of outstanding irrevocable letters of credit totaling $27,970, and as of September 30, 2021 no amount had been drawn. The Credit Agreement requires us to maintain a minimum interest coverage ratio and a maximum consolidated net leverage ratio, to be measured at the end of each fiscal quarter. As of September 30, 2021, we were in compliance with the covenants contained in the Credit Agreement. In addition to these financial covenants, the Credit Agreement also contains a number of important customary affirmative and negative covenants which restrict, among other things, our ability to sell assets, incur additional debt, create liens, make investments, and pay dividends. We do not believe that these restrictions impact our ability to meet future liquidity needs. 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 loss 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 September 30, 2021 and December 31, 2020, our active interest rate derivative agreements had total notional amounts of $195,000 and $190,000, respectively. According to the terms of the agreements, we receive interest based on the 1-month LIBOR index and pay interest at a weighted average rate of approximately 2.51% as of September 30, 2021. The agreements mature between February 2022 and December 2026. As of September 30, 2021 and December 31, 2020, we had forward starting interest rate derivative agreements with total notional amounts of $85,000 and $125,000, respectively. According to the terms of the agreements, we 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 1.55%. The agreements mature between February 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 September 30, December 31, Interest rate swaps Other non-current assets $ 228 $ — Interest rate swaps Other accrued liabilities $ 4,612 $ 4,774 Interest rate swaps Other long-term liabilities 2,992 8,463 $ 7,604 $ 13,237 Interest rate swaps Accumulated other comprehensive loss, net of tax $ (7,568) $ (13,434) Interest rate swaps - tax effect Accumulated other comprehensive loss, net of tax 538 1,917 $ (7,030) $ (11,517) A summary of the amount of expense on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive loss into earnings follows: Three Months Ended Nine Months Ended Statement of Operations Location 2021 2020 2021 2020 Interest expense $ 1,204 $ 1,156 $ 3,551 $ 2,513

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES 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. In accordance with FASB ASC 450 - Contingencies, we accrue for legal proceedings, inclusive of legal costs, when losses become probable and reasonably estimable. 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. Legal Proceedings North Country Environmental Services vs. New Hampshire Citizens Group On or about March 8, 2018, NELC and the Conservation Law Foundation ("CLF") (the "NH Citizen Groups") delivered correspondence to our subsidiary, North Country Environmental Services, Inc. ("NCES"), and us, providing notice of the NH Citizen Groups' intent to sue NCES and us for violations of the CWA in conjunction with NCES's operation of its landfill in Bethlehem, New Hampshire ("NCES Landfill"). On May 14, 2018, the NH Citizen Groups filed a lawsuit against NCES and us in the United States District Court for the District of New Hampshire (the “New Hampshire Court”) alleging violations of the CWA, arguing that ground water discharging into the Ammonoosuc River is a "point source" under the CWA (the "New Hampshire Litigation"). The New Hampshire Litigation seeks remediation and fines under the CWA and an order requiring NCES to seek a Federal National Pollutant Discharge Elimination System permit for the operation of the NCES Landfill. On June 15, 2018, we and NCES filed a Motion to Dismiss the New Hampshire Litigation. On July 13, 2018, the NH Citizen Groups filed objections to our Motion to Dismiss. On July 27, 2018, we filed a reply in support of our Motion to Dismiss. On September 25, 2018, the New Hampshire Court denied our Motion to Dismiss. In March of 2019, we filed a motion in the New Hampshire Litigation asking for a stay of this litigation until certain appeals from discordant federal circuit courts were heard by the Supreme Court of the United States (“SCOTUS”), in the case identified as “County of Maui v. Hawaii Wildlife Fund (“MAUI”)". Our motion for a stay was granted in the New Hampshire Litigation, and SCOTUS heard the case in 2019 and issued a ruling on April 23, 2020. SCOTUS remanded the case to the U.S. Court of Appeals for the Ninth Circuit in San Francisco (the “Circuit Court”) ruling that the Circuit Court’s standard as to whether ground water impacts to navigable waters is too broad. We do not believe that the MAUI decision resolves the issues presented in the New Hampshire Litigation, and until the Circuit Court rules in the remanded MAUI case, we intend to continue to vigorously defend against the New Hampshire Litigation, which we believe is without merit. The NH Citizens Groups filed a motion with the New Hampshire Court on July 15, 2020 to amend their complaint based on MAUI. The New Hampshire Court granted the NH Citizen Groups' motion on September 2, 2020 and encouraged the parties to file motions for summary judgment. We filed our Motion for Summary Judgment on November 20, 2020 and the NH Citizens Groups filed a Motion for Summary Judgment on February 19, 2021. A hearing on motions for summary judgment was held on May 14, 2021. On May 24, 2021 the NH Citizens Group submitted a post-hearing filing requesting that the New Hampshire Court consider purported supplemental material facts discovered after the hearing, and to provide a response to questions posed by the Court at the hearing, in response to which we filed a Motion to Strike on June 2, 2021. The NH Citizens Group filed an Objection to the Motion to Strike on June 8, 2021. We filed a response on June 25, 2021. On August 11, 2021, the New Hampshire Court denied the parties’ Motions for Summary Judgment and denied as moot the NH Citizens Groups’ request that the Court consider purported supplemental material facts and NCES’s Motion to Strike. We filed a Motion for Partial Reconsideration on September 7, 2021, and on September 22, 2021 we filed a Motion to Temporarily Suspend the Procedural Schedule (assented to by the NH Citizens Groups) to allow the parties the opportunity to engage in settlement negotiations, which was granted by the New Hampshire Court on October 5, 2021. North Country Environmental Services Expansion Permit On October 9, 2020, NCES received a Type I-A Permit Modification for Expansion in the Stage VI area of the NCES Landfill (the “Permit”). On November 9, 2020, CLF filed an appeal of the Permit to the New Hampshire Waste Management Council (the “Council”) on the grounds it failed to meet the public benefit criteria. On January 19, 2021, CLF filed a Complaint for Injunctive Relief with the Grafton Superior Court to enjoin NCES from accepting waste pursuant to the new Permit until such a time as CLF has exhausted its appeal rights. A hearing on the Complaint for Injunctive Relief was held on March 10, 2021; the Grafton Superior Court denied the motion on May 14, 2021. CLF did not appeal this decision. The Council denied NCES’s Motion to Dismiss CLF’s appeal for lack of standing by Order dated March 17, 2021. NCES filed a Motion to Reconsider on March 26, 2021, which was denied by the Council on May 11, 2021. A prehearing conference was held and a schedule for the case was established on June 8, 2021. NCES filed a Motion to Dismiss on the merits of the appeal on June 30, 2021, and will continue to vigorously defend against this litigation pending the Council’s ruling. On July 16, 2021, CLF filed its objection to the Motion to Dismiss, and NCES filed its reply on July 26, 2021. The Council issued an Order on September 3, 2021 granting NCES’s Motion to Dismiss, in part. CLF filed a Motion for Reconsideration on September 23, 2021, and NCES filed its objection on September 28, 2021 and CLF filed a reply on September 30, 2021. A hearing on the merits is expected to take place in February 2022. Hakes Landfill Litigation On or about December 19, 2019, the New York State Department of Environmental Conservation (“Department”) issued certain permits to us to expand the landfill owned and operated by Hakes C&D Disposal Inc. in the Town of Campbell, Steuben County, New York (“Hakes Landfill”). The permits authorize approximately five years of expansion capacity at the Hakes Landfill. The authorizations issued by the Department followed approvals issued by the Town of Campbell Planning Board (“Planning Board”) in January 2019, and the Town Board of the Town of Campbell (“Town Board”) in March 2019, granting site plan review and a zoning change for the project. Litigation was commenced by the Sierra Club, several other non-governmental organizations, and several individuals (“the Petitioners”), challenging the approvals issued by the Department, the Planning Board and the Town Board in New York State Supreme Court, Steuben County (the “Hakes Litigation”). The challenge was based upon allegations that the agencies issuing these approvals did not follow the requirements of Article 8 of the Environmental Conservation Law of the State of New York, the State Environmental Quality Review Act, by failing to address certain radioactivity issues alleged by Petitioners to be associated with certain drilling wastes authorized for disposal at the Hakes Landfill. The Department opposed the Hakes Litigation on procedural grounds. We and the Town of Campbell opposed the Hakes Litigation on the merits, and on July 31, 2020, the Court dismissed the Hakes Litigation on the merits. The Petitioners filed a notice of appeal. The time to appeal expired on February 10, 2021, and the attorney for the Petitioners confirmed that they are not pursuing the appeal. Accordingly, all approvals issued for the expansion project are now final and binding. Ontario County, New York Class Action Litigation On or about September 17, 2019, Richard Vandemortel and Deb Vandemortel ("Named Plaintiffs") filed a class action complaint against us in Ontario County Supreme Court (the "New York Court") on behalf of similarly situated citizens ("Class Members") in Ontario County, New York (the "New York Litigation"). The New York Litigation alleges that over one thousand (1,000) citizens constitute the putative class in the New York Litigation, and it seeks damages for diminution of property values and infringement of the putative class’ rights to live without interference to their daily lives due to odors emanating from the Subtitle D landfill located in Seneca, New York, which is operated by us pursuant to a long-term Operation, Maintenance and Lease Agreement with Ontario County. The New York Litigation was served on us on October 14, 2019, and the parties commenced settlement negotiations in early 2020. On December 1, 2020, the parties entered into a settlement agreement (the "Settlement Agreement") and thereafter the Named Plaintiffs and Class Members' counsel ("Counsel") moved the New York Court for entry of the Order on Notice/Preliminary Approvals. A settlement fairness hearing was held on July 7, 2021, and the judge issued an Order and Final Judgment that was filed on July 8, 2021. The settlement includes a $750 payment to a Qualified Settlement Fund for the benefit of Counsel and one-time lump sum payments to the Named Plaintiffs and Class Members who opt into the Settlement Agreement. We also committed $900 in expenses and capital improvements for remediation measures to be completed by December 31, 2022. Conservation Law Foundation, Inc. v Robert R. Scott, Commissioner, New Hampshire Department of Environmental Services On or about February 11, 2021, the CLF filed a complaint against Robert R. Scott, Commissioner of the New Hampshire Department of Environmental Services (“DES”), in the Merrimac County Superior Court. The complaint alleges that DES has failed to comply with the duty to establish and update a solid waste plan for the State of New Hampshire, and the duty to rely on that solid waste plan in determining whether to grant permits for proposed waste disposal facilities, and seeks a declaratory judgment that DES is violating statutory solid waste planning and regulatory requirements; a writ of mandamus ordering DES to achieve compliance with the statutory solid waste plan requirement; and an order enjoining DES from reviewing, and issuing decisions on, permit applications for new or expanded waste facilities, including a landfill under development by us in Dalton, New Hampshire, as well as any further review and decision-making required for permits it has already granted, including our NCES Landfill, until it has a legally valid state solid waste plan. On or about February 16, 2021, our subsidiary, Granite State Landfill, LLC, filed a Motion to Intervene in the action, which was granted by the Merrimac County Superior Court on February 17, 2021. A hearing on CLF's request for preliminary injunctive relief and the parties' motions to dismiss was held April 9, 2021. The Court issued a decision on May 14, 2021 granting the defendants’ Motions to Dismiss. CLF filed a Motion for Reconsideration which was denied by the Court on July 13, 2021. Environmental Remediation Liability 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. The following matters represent our material outstanding claims. Southbridge Recycling & Disposal Park, Inc. In October 2015, our Southbridge Recycling and Disposal Park, Inc. (“SRD”) subsidiary reported to the Massachusetts Department of Environmental Protection (“MADEP”) results of analysis of samples collected pursuant to our existing permit from private drinking water wells located near the Town of Southbridge, Massachusetts (“Town”) Landfill (“Southbridge Landfill”), which was operated by SRD and later closed in November 2018 when Southbridge Landfill reached its final capacity. Those results indicated the presence of contaminants above the levels triggering notice and response obligations under MADEP regulations. In response to those results, we carried out an Immediate Response Action pursuant to Massachusetts General Law Chapter 21E (the "Charlton 21E Obligations"). Further, we implemented a plan to analyze and better understand the groundwater near the Southbridge Landfill and we investigated with the objective of identifying the source or sources of the elevated levels of contamination measured in the well samples. We entered into an Administrative Consent Order on April 26, 2017 (the “ACO”), with MADEP, the Town, and the Town of Charlton, committing us to equally share the costs with MADEP, of up to $10,000 ($5,000 each) for the Town to install a municipal waterline in the Town of Charlton ("Waterline"). Upon satisfactory completion of that Waterline, and other matters covered by the ACO, we and the Town will be released by MADEP from any future responsibilities for the Charlton 21E Obligations. We also entered into an agreement with the Town on April 28, 2017 entitled the “21E Settlement and Water System Construction Funding Agreement” (the “Waterline Agreement”), wherein we and the Town released each other from claims arising from the Charlton 21E Obligations. Pursuant to the Waterline Agreement, the Town issued a twenty (20) year bond for our portion of the Waterline costs in the amount of $4,089. We have agreed to reimburse the Town for periodic payments under such bond. Construction of the Waterline is complete and homeowners are relying on municipal water supply. Bond reimbursement to the Town commenced in the quarter ended June 30, 2020. We have recorded an environmental remediation liability related to our obligation associated with installation of the Waterline in other accrued liabilities and other long-term liabilities. 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 of 2.6%. Our expenditures could be significantly higher if costs exceed estimates. A summary of the changes to the environmental remediation liability associated with the Southbridge Landfill follows: Nine Months Ended 2021 2020 Beginning balance $ 4,261 $ 4,596 Accretion expense 82 90 Obligations incurred — 28 Revision in estimates (1) — (188) Obligations settled (2) (281) (293) Ending balance $ 4,062 $ 4,233 (1) The revision in estimates is associated with the completion of the environmental remediation at the site. See Note 11, Other Items and Charges to our consolidated financial statements for further discussion. (2) May include amounts that are being processed through accounts payable as a part of our disbursements cycle. The costs and liabilities we may be required to incur in connection with the foregoing Southbridge Landfill matters could be material to our results of operations, our cash flows and our financial condition. Potsdam Environmental Remediation Liability On December 20, 2000, the State of New York Department of Environmental Conservation (“DEC”) issued an Order on Consent (“Order”) which named Waste-Stream, Inc. (“WSI”), our subsidiary, General Motors Corporation and Niagara Mohawk Power Corporation (“NiMo”) as Respondents. The Order required that the Respondents undertake certain work on a 25-acre scrap yard and solid waste transfer station owned by WSI in Potsdam, New York, including the preparation of a Remedial Investigation and Feasibility Study (“Study”). A draft of the Study was submitted to the DEC in January 2009 (followed by a final report in May 2009). The Study estimated that the undiscounted costs associated with implementing the preferred remedies would be approximately $10,219. On February 28, 2011, the DEC issued a Proposed Remedial Action Plan for the site and accepted public comments on the proposed remedy through March 29, 2011. We submitted comments to the DEC on this matter. In April 2011, the DEC issued the final Record of Decision (“ROD”) for the site. The ROD was subsequently rescinded by the DEC for failure to respond to all submitted comments. The preliminary ROD, however, estimated that the present cost associated with implementing the preferred remedies would be approximately $12,130. The DEC issued the final ROD in June 2011 with proposed remedies consistent with its earlier ROD. An Order on Consent and Administrative Settlement naming WSI and NiMo as Respondents was executed by the Respondents and DEC with an effective date of October 25, 2013. On January 29, 2016, a Cost-Sharing Agreement was executed between WSI, NiMo, Alcoa Inc. (“Alcoa”) and Reynolds Metal Company (“Reynolds”) whereby Alcoa and Reynolds elected to voluntarily participate in the onsite remediation activities at a combined 15% participant share. The majority of the remediation work has been completed as of September 30, 2021. WSI is jointly and severally liable with NiMo, Alcoa and Reynolds for the total cost to remediate.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	9 Months Ended
	Sep. 30, 2021
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 September 30, 2021, there were 932 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, 2020 90 $ 8.91 Granted 8 $ 68.78 Exercised (19) $ 8.36 Forfeited — $ — Outstanding, September 30, 2021 79 $ 15.41 4.6 $ 4,779 Exercisable, September 30, 2021 71 $ 9.06 4.0 $ 4,719 Stock-based compensation expense related to stock options was $11 and $11 during the three and nine months ended September 30, 2021, respectively. We did not record any stock-based compensation expense for stock options during the three and nine months ended and September 30, 2020. As of September 30, 2021, we had $188 of unrecognized stock-based compensation expense related to outstanding stock options to be recognized over a weighted average period of 2.8 years. During the three and nine months ended September 30, 2021, the aggregate intrinsic value of stock options exercised was $733 and $1,181, respectively. 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, 2020 307 $ 41.55 Granted 108 $ 67.65 Class A Common Stock Vested (82) $ 35.44 Forfeited (8) $ 51.22 Outstanding, September 30, 2021 325 $ 51.56 1.8 $ 24,647 Unvested, September 30, 2021 590 $ 51.26 1.5 $ 44,796 (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 265 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 $2,576 and $8,505 during the three and nine months ended September 30, 2021, respectively, as compared to $1,898 and $5,175 during the three and nine months ended September 30, 2020, respectively. During the three and nine months ended September 30, 2021, the total fair value of other stock awards vested was $71 and $5,364, respectively. As of September 30, 2021, total unrecognized stock-based compensation expense related to outstanding restricted stock was $96, which will be recognized over a weighted average period of 2.1 years. As of September 30, 2021, total unrecognized stock-based compensation expense related to outstanding restricted stock units was $4,931, which will be recognized over a weighted average period of 1.9 years. As of September 30, 2021, total expected unrecognized stock-based compensation expense related to outstanding performance stock units was $8,137 to be recognized over a weighted average period of 1.8 years. We also recorded $67 and $196 of stock-based compensation expense related to our Amended and Restated 1997 Employee Stock Purchase Plan during the three and nine months ended September 30, 2021, respectively, as compared to $67 and $171 during the three and nine months ended September 30, 2020, respectively. Accumulated Other Comprehensive Loss, Net of Tax A summary of the changes in the balances of each component of accumulated other comprehensive loss, net of tax follows: Interest Rate Swaps Balance, December 31, 2020 $ (11,517) Other comprehensive income before reclassifications 2,315 Amounts reclassified from accumulated other comprehensive loss 3,551 Income tax provision related to items of other comprehensive income (1,379) Net current-period other comprehensive income 4,487 Balance, September 30, 2021 $ (7,030) A summary of reclassifications out of accumulated other comprehensive loss, net of tax follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Details About Accumulated Other Comprehensive Loss Components Amounts Reclassified Out of Accumulated Other Comprehensive Loss Affected Line Item in the Consolidated Interest rate swaps $ 1,204 $ 1,156 $ 3,551 $ 2,513 Interest expense (1,204) (1,156) (3,551) (2,513) Income before income taxes (496) — (765) 112 Provision for income taxes $ (708) $ (1,156) $ (2,786) $ (2,625) Net income

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2021
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 Nine Months Ended 2021 2020 2021 2020 Numerator: Net income $ 15,861 $ 15,117 $ 31,955 $ 28,189 Denominators: Number of shares outstanding, end of period: Class A common stock 50,410 47,384 50,410 47,384 Class B common stock 988 988 988 988 Unvested restricted stock (2) (2) (2) (2) Effect of weighted average shares outstanding (7) — (84) (129) Basic weighted average common shares outstanding 51,389 48,370 51,312 48,241 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards 197 249 194 240 Diluted weighted average common shares outstanding 51,586 48,619 51,506 48,481 Anti-dilutive potentially issuable shares 12 — 12 1

OTHER ITEMS AND CHARGES

OTHER ITEMS AND CHARGES	9 Months Ended
	Sep. 30, 2021
Unusual or Infrequent Items, or Both [Abstract]
OTHER ITEMS AND CHARGES	OTHER ITEMS AND CHARGES Expense from Acquisition Activities In the three and nine months ended September 30, 2021, we recorded charges of $1,904 and $3,950, respectively, and in the three and nine months ended September 30, 2020 we recorded charges of $173 and $1,533, respectively, comprised primarily of legal, consulting and other similar costs associated with the acquisition and integration of acquired businesses or select development projects. Southbridge Landfill Closure Charge In 2017, we initiated the plan to cease operations of the Southbridge Landfill and later closed it in November 2018 when Southbridge Landfill reached its final capacity .

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2021
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 swaps, trade payables and long-term 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 swaps 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. 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 September 30, 2021 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 1,948 $ — $ — Interest rate swaps — 228 — $ 1,948 $ 228 $ — Liabilities: Interest rate swaps $ — $ 7,604 $ — Fair Value Measurement at December 31, 2020 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 1,848 $ — $ — Liabilities: Interest rate swaps $ — $ 13,237 $ — Fair Value of Debt As of September 30, 2021, 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 $177,501 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 September 30, 2021, the carrying value of our Term Loan Facility was $347,375 and the carrying value of our Revolving Credit Facility was $0. 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	9 Months Ended
	Sep. 30, 2021
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. Effective January 1, 2021, we reorganized the Resource Solutions operating segment, which includes our larger-scale recycling and commodity brokerage operations along with our organics services and large scale commercial and industrial services, from our historical lines-of-service of recycling, organics and customer solutions into 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; overall resource management services providing a wide range of environmental services and zero waste solutions to large and complex organizations; and traditional collection, disposal and recycling services provided to large account multi-site customers. Revenues classification by service line reported in the three and nine months ended September 30, 2020 has been reclassified to conform with the presentation for the three and nine months ended September 30, 2021. Legal, tax, information technology, human resources, certain finance and accounting and other administrative functions are included in our Corporate Entities segment. Three Months Ended September 30, 2021 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 75,154 $ 18,768 $ 9,407 $ 5,374 $ 352,067 Western 103,523 35,523 15,710 15,805 673,608 Resource solutions 63,292 156 1,903 6,679 126,529 Corporate entities — — 471 (471) 128,193 Eliminations — (54,447) — — — $ 241,969 $ — $ 27,491 $ 27,387 $ 1,280,397 Three Months Ended September 30, 2020 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 58,323 $ 14,261 $ 6,659 $ 3,683 $ 215,639 Western 94,728 31,692 15,000 15,344 635,153 Resource solutions 49,616 2,806 1,544 2,204 89,870 Corporate entities — — 596 (598) 53,593 Eliminations — (48,759) — — — $ 202,667 $ — $ 23,799 $ 20,633 $ 994,255 Nine Months Ended September 30, 2021 Segment Outside Inter-company Depreciation and Operating Total assets Eastern $ 188,557 $ 47,322 $ 23,342 $ 11,401 $ 352,067 Western 288,139 97,771 44,838 38,462 673,608 Resource solutions 170,679 3,337 5,020 12,792 126,529 Corporate entities — — 1,310 (1,312) 128,193 Eliminations — (148,430) — — — $ 647,375 $ — $ 74,510 $ 61,343 $ 1,280,397 Nine Months Ended September 30, 2020 Segment Outside Inter-company Depreciation and Operating Total assets Eastern $ 161,803 $ 39,936 $ 18,956 $ 9,023 $ 215,639 Western 267,218 86,259 41,847 32,849 635,153 Resource solutions 145,323 8,147 4,692 5,008 89,870 Corporate entities — — 1,786 (1,791) 53,593 Eliminations — (134,342) — — — $ 574,344 $ — $ 67,281 $ 45,089 $ 994,255 A summary of our revenues attributable to services provided follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Collection $ 118,872 $ 102,270 $ 323,667 $ 290,837 Disposal 55,593 47,600 142,618 129,971 Power generation 1,253 987 3,657 2,931 Processing 2,959 2,194 6,754 5,282 Solid waste operations 178,677 153,051 476,696 429,021 Processing 27,418 15,701 65,721 45,724 Non-processing 35,874 33,915 104,958 99,599 Resource solutions operations 63,292 49,616 170,679 145,323 Total revenues $ 241,969 $ 202,667 $ 647,375 $ 574,344

ACCOUNTING CHANGES (Policies)

ACCOUNTING CHANGES (Policies)	9 Months Ended
	Sep. 30, 2021
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 that provides collection, transfer, disposal, landfill, landfill gas-to-energy, recycling and organics services in the northeastern United States. We market recyclable metals, aluminum, plastics, paper, and corrugated cardboard, which have been processed at our recycling facilities or purchased from third-parties. 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 includes our larger-scale recycling and commodity brokerage operations along with our organics services and large scale commercial and industrial services. 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 of our Annual Report on Form 10-K for the fiscal year ended December 31, 2020 ("fiscal year 2020"), which was filed with the SEC on February 19, 2021.
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 and nine months ended September 30, 2021 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 September 30, 2021 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	Standard Description Effect on the Financial Statements or Other Accounting standards adopted effective January 1, 2021 ASU No. 2019-12: Income Taxes (Topic 740) Reduces the complexity over accounting for income taxes by removing certain exceptions and amending guidance to improve consistent application of accounting over income taxes. This guidance did not have a material impact on our consolidated financial statements and related disclosures upon adoption, but may in the future. This guidance was effective January 1, 2021. A table providing a brief description of recent ASUs to the ASC issued by the 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, which extend past the fiscal year ended December 31, 2021. We are currently assessing the provisions of this guidance as LIBOR is still in place and do not expect that its adoption 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.
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.
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. Effective January 1, 2021, we reorganized the Resource Solutions operating segment, which includes our larger-scale recycling and commodity brokerage operations along with our organics services and large scale commercial and industrial services, from our historical lines-of-service of recycling, organics and customer solutions into 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; overall resource management services providing a wide range of environmental services and zero waste solutions to large and complex organizations; and traditional collection, disposal and recycling services provided to large account multi-site customers. Revenues classification by service line reported in the three and nine months ended September 30, 2020 has been reclassified to conform with the presentation for the three and nine months ended September 30, 2021. Legal, tax, information technology, human resources, certain finance and accounting and other administrative functions are included in our Corporate Entities segment.

ACCOUNTING CHANGES (Tables)

ACCOUNTING CHANGES (Tables)	9 Months Ended
	Sep. 30, 2021
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 we adopted and deemed to have a material impact on our consolidated financial statements, or a possible material impact in the future, based on current account balances and activity follows: Standard Description Effect on the Financial Statements or Other Accounting standards adopted effective January 1, 2021 ASU No. 2019-12: Income Taxes (Topic 740) Reduces the complexity over accounting for income taxes by removing certain exceptions and amending guidance to improve consistent application of accounting over income taxes. This guidance did not have a material impact on our consolidated financial statements and related disclosures upon adoption, but may in the future. This guidance was effective January 1, 2021. A table providing a brief description of recent ASUs to the ASC issued by the 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, which extend past the fiscal year ended December 31, 2021. We are currently assessing the provisions of this guidance as LIBOR is still in place and do not expect that its adoption 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.

REVENUE RECOGNITION (Tables)

REVENUE RECOGNITION (Tables)	9 Months Ended
	Sep. 30, 2021
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 and nine months ended September 30, 2021 and 2020: Three Months Ended September 30, 2021 Eastern Western Resource Solutions Total Revenues Collection $ 48,951 $ 69,921 $ — $ 118,872 Landfill 6,622 18,201 — 24,823 Transfer 16,948 10,375 — 27,323 Transportation 54 3,393 — 3,447 Landfill gas-to-energy 269 984 — 1,253 Processing 2,310 649 27,418 30,377 Non-processing — — 35,874 35,874 Total revenues $ 75,154 $ 103,523 $ 63,292 $ 241,969 Transferred at a point-in-time $ 43 $ 296 $ 19,927 $ 20,266 Transferred over time 75,111 103,227 43,365 221,703 Total revenues $ 75,154 $ 103,523 $ 63,292 $ 241,969 Three Months Ended September 30, 2020 Eastern Western Resource Solutions Total Revenues Collection $ 38,659 $ 63,611 $ — $ 102,270 Landfill 5,694 17,880 — 23,574 Transfer 11,861 9,756 — 21,617 Transportation 61 2,348 — 2,409 Landfill gas-to-energy 210 777 — 987 Processing 1,838 356 15,701 17,895 Non-processing — — 33,915 33,915 Total revenues $ 58,323 $ 94,728 $ 49,616 $ 202,667 Transferred at a point-in-time $ 52 $ 347 $ 7,736 $ 8,135 Transferred over time 58,271 94,381 41,880 194,532 Total revenues $ 58,323 $ 94,728 $ 49,616 $ 202,667 Nine Months Ended September 30, 2021 Eastern Western Resource Solutions Total Revenues Collection $ 124,389 $ 199,278 $ — $ 323,667 Landfill 18,143 48,336 — 66,479 Transfer 39,847 27,498 — 67,345 Transportation 148 8,646 — 8,794 Landfill gas-to-energy 784 2,873 — 3,657 Processing 5,246 1,508 65,721 72,475 Non-processing — — 104,958 104,958 Total revenues $ 188,557 $ 288,139 $ 170,679 $ 647,375 Transferred at a point-in-time $ 125 $ 1,284 $ 44,964 $ 46,373 Transferred over time 188,432 286,855 125,715 601,002 Total revenues $ 188,557 $ 288,139 $ 170,679 $ 647,375 Nine Months Ended September 30, 2020 Eastern Western Resource Solutions Total Revenues Collection $ 110,059 $ 180,778 $ — $ 290,837 Landfill 13,807 49,409 — 63,216 Transfer 32,695 25,429 — 58,124 Transportation 159 8,472 — 8,631 Landfill gas-to-energy 793 2,138 — 2,931 Processing 4,290 992 45,724 51,006 Non-processing — — 99,599 99,599 Total revenues $ 161,803 $ 267,218 $ 145,323 $ 574,344 Transferred at a point-in-time $ 177 $ 949 $ 20,428 $ 21,554 Transferred over time 161,626 266,269 124,895 552,790 Total revenues $ 161,803 $ 267,218 $ 145,323 $ 574,344

BUSINESS COMBINATIONS (Tables)

BUSINESS COMBINATIONS (Tables)	9 Months Ended
	Sep. 30, 2021
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 these acquisitions follows: Nine Months Ended 2021 2020 Purchase Price: Cash used in acquisitions, net of cash acquired $ 150,364 $ 23,062 Contingent consideration 3,000 — Holdbacks 1,865 3,387 Total 155,229 26,449 Allocated as follows: Current assets 7,260 227 Operating lease right-of-use assets 6,500 — Land 803 895 Finance lease right-of-use-assets 31,467 — Buildings and improvements 8,468 1,908 Equipment 42,458 10,006 Intangible assets 41,759 7,159 Other liabilities, net (5,120) (306) Finance leases (11,367) — Fair value of assets acquired and liabilities assumed 122,228 19,889 Excess purchase price allocated to goodwill $ 33,001 $ 6,560
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, 2020 is as follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Revenues $ 248,981 $ 225,580 $ 696,391 $ 646,004 Operating income $ 26,996 $ 20,100 $ 59,526 $ 43,660 Net income $ 14,996 $ 12,976 $ 26,542 $ 21,845 Basic earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,389 48,370 51,312 48,241 Basic earnings per common share $ 0.29 $ 0.27 $ 0.52 $ 0.45 Diluted earnings per share attributable to common stockholders: Weighted average common shares outstanding 51,586 48,619 51,506 48,481 Diluted earnings per common share $ 0.29 $ 0.27 $ 0.52 $ 0.45

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2021
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 September 30, Eastern region $ 30,873 $ 18,984 $ 49,857 Western region 149,984 10,156 160,140 Resource solutions 14,044 3,888 17,932 Total $ 194,901 $ 33,028 $ 227,929
Summary of Intangible Assets by Type	Summaries of intangible assets by type follows: Covenants Client Lists Trade Names Total Balance, September 30, 2021 Intangible assets $ 29,514 $ 109,676 $ 8,350 $ 147,540 Less accumulated amortization (21,752) (32,298) (582) (54,632) $ 7,762 $ 77,378 $ 7,768 $ 92,908 Covenants Client Lists Total Balance, December 31, 2020 Intangible assets $ 26,971 $ 78,809 $ 105,780 Less accumulated amortization (20,547) (26,909) (47,456) $ 6,424 $ 51,900 $ 58,324
Summary of Intangible Amortization Expense Estimated	A summary of intangible amortization expense estimated for the five fiscal years following fiscal year 2020 and thereafter follows: Estimated Future Amortization Expense as of September 30, 2021 Fiscal year ending December 31, 2021 $ 3,694 Fiscal year ending December 31, 2022 $ 14,007 Fiscal year ending December 31, 2023 $ 12,970 Fiscal year ending December 31, 2024 $ 12,634 Fiscal year ending December 31, 2025 $ 11,945 Thereafter $ 37,658

ACCRUED FINAL CAPPING, CLOSUR_2

ACCRUED FINAL CAPPING, CLOSURE AND POST CLOSURE (Tables)	9 Months Ended
	Sep. 30, 2021
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: Nine Months Ended 2021 2020 Beginning balance $ 82,533 $ 71,927 Obligations incurred 3,638 2,820 Revision in estimates (1) — 152 Accretion expense 5,496 4,826 Obligations settled (2) (5,394) (2,706) Ending balance $ 86,273 $ 77,019 (1) Relates to changes in estimated costs and timing of final capping, closure and post-closure activities at the Town of Southbridge, Massachusetts landfill. See Note 8, Commitments and Contingencies and Note 11, Other Items and Charges for further discussion. (2) May include amounts that are being processed through accounts payable as a part of our disbursements cycle.

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2021
Debt And Derivatives Disclosure [Abstract]
Summary of Debt	A summary of debt is as follows: September 30, December 31, Senior Secured Credit Facility: Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.50% $ — $ — Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.50% 347,375 350,000 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 3.6% 44,804 31,486 Notes payable maturing through June 2027; bearing interest at a weighted average of 3.4% 4,377 4,933 Principal amount of debt 558,556 548,419 Less—unamortized debt issuance costs (1) 7,053 8,768 Debt less unamortized debt issuance costs 551,503 539,651 Less—current maturities of debt 16,751 9,240 $ 534,752 $ 530,411 (1) A summary of unamortized debt issuance costs by debt instrument follows: September 30, December 31, Revolving Credit Facility and Term Loan Facility (collectively, the "Credit Facility") $ 2,609 $ 3,839 New York Bonds 2014R-1 950 1,000 New York Bonds 2014R-2 283 329 New York Bonds 2020 1,328 1,461 FAME Bonds 2005R-3 283 347 FAME Bonds 2015R-1 430 482 FAME Bonds 2015R-2 287 343 Vermont Bonds 446 487 New Hampshire Bonds 437 480 $ 7,053 $ 8,768
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 September 30, December 31, Interest rate swaps Other non-current assets $ 228 $ — Interest rate swaps Other accrued liabilities $ 4,612 $ 4,774 Interest rate swaps Other long-term liabilities 2,992 8,463 $ 7,604 $ 13,237 Interest rate swaps Accumulated other comprehensive loss, net of tax $ (7,568) $ (13,434) Interest rate swaps - tax effect Accumulated other comprehensive loss, net of tax 538 1,917 $ (7,030) $ (11,517) A summary of the amount of expense on cash flow hedging relationships related to interest rate swaps reclassified from accumulated other comprehensive loss into earnings follows: Three Months Ended Nine Months Ended Statement of Operations Location 2021 2020 2021 2020 Interest expense $ 1,204 $ 1,156 $ 3,551 $ 2,513

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Summary of Environmental Liability	A summary of the changes to the environmental remediation liability associated with the Southbridge Landfill follows: Nine Months Ended 2021 2020 Beginning balance $ 4,261 $ 4,596 Accretion expense 82 90 Obligations incurred — 28 Revision in estimates (1) — (188) Obligations settled (2) (281) (293) Ending balance $ 4,062 $ 4,233 (1) The revision in estimates is associated with the completion of the environmental remediation at the site. See Note 11, Other Items and Charges to our consolidated financial statements for further discussion. (2) May include amounts that are being processed through accounts payable as a part of our disbursements cycle.

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	9 Months Ended
	Sep. 30, 2021
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, 2020 90 $ 8.91 Granted 8 $ 68.78 Exercised (19) $ 8.36 Forfeited — $ — Outstanding, September 30, 2021 79 $ 15.41 4.6 $ 4,779 Exercisable, September 30, 2021 71 $ 9.06 4.0 $ 4,719
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, 2020 307 $ 41.55 Granted 108 $ 67.65 Class A Common Stock Vested (82) $ 35.44 Forfeited (8) $ 51.22 Outstanding, September 30, 2021 325 $ 51.56 1.8 $ 24,647 Unvested, September 30, 2021 590 $ 51.26 1.5 $ 44,796 (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 265 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 loss, net of tax follows: Interest Rate Swaps Balance, December 31, 2020 $ (11,517) Other comprehensive income before reclassifications 2,315 Amounts reclassified from accumulated other comprehensive loss 3,551 Income tax provision related to items of other comprehensive income (1,379) Net current-period other comprehensive income 4,487 Balance, September 30, 2021 $ (7,030)
Summary of Reclassifications Out of Accumulated Other Comprehensive Loss	A summary of reclassifications out of accumulated other comprehensive loss, net of tax follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Details About Accumulated Other Comprehensive Loss Components Amounts Reclassified Out of Accumulated Other Comprehensive Loss Affected Line Item in the Consolidated Interest rate swaps $ 1,204 $ 1,156 $ 3,551 $ 2,513 Interest expense (1,204) (1,156) (3,551) (2,513) Income before income taxes (496) — (765) 112 Provision for income taxes $ (708) $ (1,156) $ (2,786) $ (2,625) Net income

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2021
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 Nine Months Ended 2021 2020 2021 2020 Numerator: Net income $ 15,861 $ 15,117 $ 31,955 $ 28,189 Denominators: Number of shares outstanding, end of period: Class A common stock 50,410 47,384 50,410 47,384 Class B common stock 988 988 988 988 Unvested restricted stock (2) (2) (2) (2) Effect of weighted average shares outstanding (7) — (84) (129) Basic weighted average common shares outstanding 51,389 48,370 51,312 48,241 Impact of potentially dilutive securities: Dilutive effect of stock options and other stock awards 197 249 194 240 Diluted weighted average common shares outstanding 51,586 48,619 51,506 48,481 Anti-dilutive potentially issuable shares 12 — 12 1

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2021
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 September 30, 2021 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 1,948 $ — $ — Interest rate swaps — 228 — $ 1,948 $ 228 $ — Liabilities: Interest rate swaps $ — $ 7,604 $ — Fair Value Measurement at December 31, 2020 Using: Quoted Prices in Significant Other Significant Assets: Restricted investment securities - landfill closure $ 1,848 $ — $ — Liabilities: Interest rate swaps $ — $ 13,237 $ —

SEGMENT REPORTING (Tables)

SEGMENT REPORTING (Tables)	9 Months Ended
	Sep. 30, 2021
Segment Reporting [Abstract]
Summary of Segment Reporting Information by Segment	Three Months Ended September 30, 2021 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 75,154 $ 18,768 $ 9,407 $ 5,374 $ 352,067 Western 103,523 35,523 15,710 15,805 673,608 Resource solutions 63,292 156 1,903 6,679 126,529 Corporate entities — — 471 (471) 128,193 Eliminations — (54,447) — — — $ 241,969 $ — $ 27,491 $ 27,387 $ 1,280,397 Three Months Ended September 30, 2020 Segment Outside Inter-company Depreciation and Operating Total Eastern $ 58,323 $ 14,261 $ 6,659 $ 3,683 $ 215,639 Western 94,728 31,692 15,000 15,344 635,153 Resource solutions 49,616 2,806 1,544 2,204 89,870 Corporate entities — — 596 (598) 53,593 Eliminations — (48,759) — — — $ 202,667 $ — $ 23,799 $ 20,633 $ 994,255 Nine Months Ended September 30, 2021 Segment Outside Inter-company Depreciation and Operating Total assets Eastern $ 188,557 $ 47,322 $ 23,342 $ 11,401 $ 352,067 Western 288,139 97,771 44,838 38,462 673,608 Resource solutions 170,679 3,337 5,020 12,792 126,529 Corporate entities — — 1,310 (1,312) 128,193 Eliminations — (148,430) — — — $ 647,375 $ — $ 74,510 $ 61,343 $ 1,280,397 Nine Months Ended September 30, 2020 Segment Outside Inter-company Depreciation and Operating Total assets Eastern $ 161,803 $ 39,936 $ 18,956 $ 9,023 $ 215,639 Western 267,218 86,259 41,847 32,849 635,153 Resource solutions 145,323 8,147 4,692 5,008 89,870 Corporate entities — — 1,786 (1,791) 53,593 Eliminations — (134,342) — — — $ 574,344 $ — $ 67,281 $ 45,089 $ 994,255
Summary of Revenue Attributable to Services	A summary of our revenues attributable to services provided follows: Three Months Ended Nine Months Ended 2021 2020 2021 2020 Collection $ 118,872 $ 102,270 $ 323,667 $ 290,837 Disposal 55,593 47,600 142,618 129,971 Power generation 1,253 987 3,657 2,931 Processing 2,959 2,194 6,754 5,282 Solid waste operations 178,677 153,051 476,696 429,021 Processing 27,418 15,701 65,721 45,724 Non-processing 35,874 33,915 104,958 99,599 Resource solutions operations 63,292 49,616 170,679 145,323 Total revenues $ 241,969 $ 202,667 $ 647,375 $ 574,344

BASIS OF PRESENTATION (Details)

BASIS OF PRESENTATION (Details)	9 Months Ended
	Sep. 30, 2021regionalOperatingSegment
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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 241,969	$ 202,667	$ 647,375	$ 574,344
Collection
Disaggregation of Revenue [Line Items]
Total revenues	118,872	102,270	323,667	290,837
Landfill
Disaggregation of Revenue [Line Items]
Total revenues	24,823	23,574	66,479	63,216
Transfer
Disaggregation of Revenue [Line Items]
Total revenues	27,323	21,617	67,345	58,124
Transportation
Disaggregation of Revenue [Line Items]
Total revenues	3,447	2,409	8,794	8,631
Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	1,253	987	3,657	2,931
Processing
Disaggregation of Revenue [Line Items]
Total revenues	30,377	17,895	72,475	51,006
Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	35,874	33,915	104,958	99,599
Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	20,266	8,135	46,373	21,554
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	221,703	194,532	601,002	552,790
Eastern
Disaggregation of Revenue [Line Items]
Total revenues	75,154	58,323	188,557	161,803
Eastern | Collection
Disaggregation of Revenue [Line Items]
Total revenues	48,951	38,659	124,389	110,059
Eastern | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	6,622	5,694	18,143	13,807
Eastern | Transfer
Disaggregation of Revenue [Line Items]
Total revenues	16,948	11,861	39,847	32,695
Eastern | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	54	61	148	159
Eastern | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	269	210	784	793
Eastern | Processing
Disaggregation of Revenue [Line Items]
Total revenues	2,310	1,838	5,246	4,290
Eastern | Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Eastern | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	43	52	125	177
Eastern | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	75,111	58,271	188,432	161,626
Western
Disaggregation of Revenue [Line Items]
Total revenues	103,523	94,728	288,139	267,218
Western | Collection
Disaggregation of Revenue [Line Items]
Total revenues	69,921	63,611	199,278	180,778
Western | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	18,201	17,880	48,336	49,409
Western | Transfer
Disaggregation of Revenue [Line Items]
Total revenues	10,375	9,756	27,498	25,429
Western | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	3,393	2,348	8,646	8,472
Western | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	984	777	2,873	2,138
Western | Processing
Disaggregation of Revenue [Line Items]
Total revenues	649	356	1,508	992
Western | Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Western | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	296	347	1,284	949
Western | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	103,227	94,381	286,855	266,269
Resource solutions
Disaggregation of Revenue [Line Items]
Total revenues	63,292	49,616	170,679	145,323
Resource solutions | Collection
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Resource solutions | Landfill
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Resource solutions | Transfer
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Resource solutions | Transportation
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Resource solutions | Landfill gas-to-energy
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Resource solutions | Processing
Disaggregation of Revenue [Line Items]
Total revenues	27,418	15,701	65,721	45,724
Resource solutions | Non-processing
Disaggregation of Revenue [Line Items]
Total revenues	35,874	33,915	104,958	99,599
Resource solutions | Transferred at a point-in-time
Disaggregation of Revenue [Line Items]
Total revenues	19,927	7,736	44,964	20,428
Resource solutions | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	$ 43,365	$ 41,880	$ 125,715	$ 124,895

REVENUE RECOGNITION - Narrative

REVENUE RECOGNITION - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rebates	$ (241,969,000)	$ (202,667,000)	$ (647,375,000)	$ (574,344,000)
Revenue recognized fro performance obligation satisfied in previous period	0	0	0	0
Gross receivables from contracts	91,469,000		91,469,000		$ 74,162,000
Contract liabilities	3,422,000		3,422,000		$ 2,685,000
Rebate for Recycled or Returned Organic Materials
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Rebates	$ 4,341,000	$ 1,018,000	$ 8,440,000	$ 3,555,000

BUSINESS COMBINATIONS - Narrati

BUSINESS COMBINATIONS - Narrative (Details) - business	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Number of businesses acquired		6
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	2	5
Resource solutions | Recycling Operation
Business Acquisition [Line Items]
Number of businesses acquired		1

BUSINESS COMBINATIONS - Summary

BUSINESS COMBINATIONS - Summary of Purchase Price Paid for Acquisitions (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Purchase Price:
Cash used in acquisitions, net of cash acquired	$ 153,112	$ 25,379
Allocated as follows:
Excess purchase price allocated to goodwill	227,929		$ 194,901
Waste Collection Acquisitions
Purchase Price:
Cash used in acquisitions, net of cash acquired	150,364	23,062
Contingent consideration	3,000	0
Holdbacks	1,865	3,387
Total	155,229	26,449
Allocated as follows:
Current assets	7,260	227
Operating lease right-of-use assets	6,500	0
Land	803	895
Finance lease right-of-use-assets	31,467	0
Buildings and improvements	8,468	1,908
Equipment	42,458	10,006
Intangible assets	41,759	7,159
Other liabilities, net	(5,120)	(306)
Finance leases	(11,367)	0
Fair value of assets acquired and liabilities assumed	122,228	19,889
Excess purchase price allocated to goodwill	$ 33,001	$ 6,560

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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Business Combination and Asset Acquisition [Abstract]
Revenues	$ 248,981	$ 225,580	$ 696,391	$ 646,004
Operating income	26,996	20,100	59,526	43,660
Net income	$ 14,996	$ 12,976	$ 26,542	$ 21,845
Weighted average common shares outstanding, basic (in shares)	51,389	48,370	51,312	48,241
Basic earnings per common share (in dollars per share)	$ 0.29	$ 0.27	$ 0.52	$ 0.45
Weighted average common shares outstanding, diluted (in shares)	51,586	48,619	51,506	48,481
Diluted earnings per common share (in dollars per share)	$ 0.29	$ 0.27	$ 0.52	$ 0.45

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Summary of Goodwill Activity (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 194,901
Acquisitions	33,028
Goodwill, ending balance	227,929
Eastern
Goodwill [Roll Forward]
Goodwill, beginning balance	30,873
Acquisitions	18,984
Goodwill, ending balance	49,857
Western
Goodwill [Roll Forward]
Goodwill, beginning balance	149,984
Acquisitions	10,156
Goodwill, ending balance	160,140
Resource solutions
Goodwill [Roll Forward]
Goodwill, beginning balance	14,044
Acquisitions	3,888
Goodwill, ending balance	$ 17,932

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Assets by Type (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 147,540	$ 105,780
Less accumulated amortization	(54,632)	(47,456)
Intangible assets, net	92,908	58,324
Covenants Not-to-Compete
Finite-Lived Intangible Assets [Line Items]
Intangible assets	29,514	26,971
Less accumulated amortization	(21,752)	(20,547)
Intangible assets, net	7,762	6,424
Client Lists
Finite-Lived Intangible Assets [Line Items]
Intangible assets	109,676	78,809
Less accumulated amortization	(32,298)	(26,909)
Intangible assets, net	77,378	$ 51,900
Trade Names
Finite-Lived Intangible Assets [Line Items]
Intangible assets	8,350
Less accumulated amortization	(582)
Intangible assets, net	$ 7,768

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Narrative (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible amortization expense	$ 3,133	$ 2,265	$ 7,175	$ 6,580

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Summary of Intangible Amortization Expense Estimated (Detail) $ in Thousands	Sep. 30, 2021USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Fiscal year ending December 31, 2021	$ 3,694
Fiscal year ending December 31, 2022	14,007
Fiscal year ending December 31, 2023	12,970
Fiscal year ending December 31, 2024	12,634
Fiscal year ending December 31, 2025	11,945
Thereafter	$ 37,658

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	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning balance	$ 82,533	$ 71,927
Obligations incurred	3,638	2,820
Revision in estimates	0	152
Accretion expense	5,496	4,826
Obligations settled	(5,394)	(2,706)
Ending balance	$ 86,273	$ 77,019

DEBT - Summary of Debt (Details

DEBT - Summary of Debt (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Weighted-average discount rate - finance leases	3.60%
Finance leases maturing through December 2107; bearing interest at a weighted average of 3.6%	$ 44,804	$ 31,486
Principal amount of debt	558,556	548,419
Less - unamortized debt issuance costs	7,053	8,768
Debt less unamortized debt issuance costs	551,503	539,651
Less—current maturities of debt	16,751	9,240
Debt, less current portion	534,752	530,411
Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.50%
Debt Instrument [Line Items]
Principal amount of debt	$ 0	0
Revolving line of credit facility ("Revolving Credit Facility") due May 2023; bearing interest at LIBOR plus 1.50% | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Secured Debt | Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.50%
Debt Instrument [Line Items]
Principal amount of debt	$ 347,375	350,000
Secured Debt | Term loan A facility ("Term Loan Facility") due May 2023; bearing interest at LIBOR plus 1.50% | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
Credit Facility
Debt Instrument [Line Items]
Less - unamortized debt issuance costs	$ 2,609	3,839
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	$ 950	1,000
Unsecured Debt | New York State Environmental Facilities Corporation Solid Waste Disposal Revenue Bonds Series 2014R-2 ("New York Bonds 2014R-2") due December 2044 - fixed rate interest period 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	$ 283	329
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	$ 1,328	1,461
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	$ 283	347
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	$ 430	482
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	$ 287	343
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	$ 446	487
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	$ 437	480
Notes payable maturing through June 2027; bearing interest at a weighted average of 3.4%
Debt Instrument [Line Items]
Weighted average interest rate	3.40%
Principal amount of debt	$ 4,377	$ 4,933

DEBT - Credit Facility Narrativ

DEBT - Credit Facility Narrative (Details)	9 Months Ended
	Sep. 30, 2021USD ($)
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	$ 172,030,000
Line of Credit | LIBOR | Maximum
Debt Instrument [Line Items]
Floor interest rate received (as a percent)	1.50%
Line of Credit | LIBOR | Minimum
Debt Instrument [Line Items]
Floor interest rate received (as a percent)	1.25%
Secured Debt | Term Loan Facility | Line of Credit
Debt Instrument [Line Items]
Aggregate principal amount	$ 350,000,000
Revolving Credit Facility | Revolving Credit Facility Due 2023 | Line of Credit
Debt Instrument [Line Items]
Credit facility maximum	200,000,000
Letters of credit outstanding	$ 27,970,000

DEBT - Cash Flow Hedges Narrati

DEBT - Cash Flow Hedges Narrative (Details) - Cash Flow Hedging - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Interest Rate Derivative
Debt Instrument [Line Items]
Notional amount	$ 195,000,000	$ 190,000,000
Weighted average percentage rate paid (as a percent)	2.51%
Forward Starting Interest Rate Derivative
Debt Instrument [Line Items]
Notional amount	$ 85,000,000	$ 125,000,000
Weighted average percentage rate paid (as a percent)	1.55%
Floor interest rate (as a percent)	0.00%

DEBT - Summary of Cash Flow Hed

DEBT - Summary of Cash Flow Hedges (Details) - Designated as Hedging Instrument - Interest rate swaps - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross liability	$ 7,604	$ 13,237
Other non-current assets
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross asset	228	0
Other accrued liabilities
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross liability	4,612	4,774
Other long-term liabilities
Derivatives, Fair Value [Line Items]
Cash flow hedge derivatives, gross liability	2,992	8,463
Accumulated other comprehensive loss, net of tax
Derivatives, Fair Value [Line Items]
Accumulated other comprehensive loss, interest rate swaps	(7,568)	(13,434)
Accumulated other comprehensive loss, interest rate swaps, tax provision	538	1,917
Accumulated other comprehensive loss, net of tax	$ (7,030)	$ (11,517)

DEBT - Schedule of Loss On Cash

DEBT - Schedule of Loss On Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ 1,204	$ 1,156	$ 3,551	$ 2,513
Interest rate swaps | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Other comprehensive loss, reclassification adjustment from AOCI	$ 1,204	$ 1,156	$ 3,551	$ 2,513

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Detail) plantiff in Thousands, $ in Thousands

Dec. 01, 2020USD ($)

Sep. 17, 2019plantiff

Apr. 28, 2017USD ($)

Sep. 30, 2020USD ($)

Sep. 30, 2020USD ($)

Sep. 30, 2021USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Apr. 26, 2017USD ($)

Jan. 29, 2016

Apr. 30, 2011USD ($)

May 31, 2009USD ($)

Dec. 20, 2000a

Southbridge Landfill

Loss Contingencies [Line Items]

Loss contingency, settlement awarded

$ 2,000

$ 2,000

Risk free interest (as a percent)

2.60%

Environmental remediation liability

$ 4,233

$ 4,233

$ 4,062

$ 4,261

$ 4,596

Potsdam Environmental Remediation

Loss Contingencies [Line Items]

Risk free interest (as a percent)

1.90%

Scrap yard and solid waste transfer station (in acres) | a

25

Undiscounted costs preferred remedies

$ 12,130

$ 10,219

Remediation activities, participant share (as a percent)

15.00%

Environmental remediation liability

$ 939

$ 939

21E Settlement and Water System Construction Funding Agreement | Bonds

Loss Contingencies [Line Items]

Bond period

20 years

21E Settlement and Water System Construction Funding Agreement | Bonds | Maximum

Loss Contingencies [Line Items]

Anticipated cost

$ 4,089

Notice of Intent to Sue under the Resource Conservation and Recovery Act

Loss Contingencies [Line Items]

Estimate of possible loss

$ 5,000

Notice of Intent to Sue under the Resource Conservation and Recovery Act | MADEP and Casella Waste Systems

Loss Contingencies [Line Items]

Estimate of possible loss

$ 10,000

Ontario County, New York Class Action Litigation

Loss Contingencies [Line Items]

Number of citizens seeking damages | plantiff

1

Loss contingency, settlement awarded

$ 750

Estimate of possible loss

$ 900

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Environmental Remediation Liability (Details) - Southbridge Landfill - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 4,261	$ 4,596
Accretion expense	82	90
Obligations incurred	0	28
Revision in estimates	0	(188)
Obligations settled	(281)	(293)
Ending balance	$ 4,062	$ 4,233

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Limited Partners' Capital Account [Line Items]
Fair value of stock awards vested	$ 71,000		$ 5,364,000
Unrecognized stock-based compensation, weighted average period (in years)			2 years 9 months 18 days
Stock Options
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	11,000	$ 0	$ 11,000	$ 0
Unrecognized stock-based compensation expense, stock options	188,000		188,000
Aggregate intrinsic value of options exercised	733,000		1,181,000
Restricted Stock, Restricted Stock Units And Performance Stock Units
Limited Partners' Capital Account [Line Items]
Stock-based compensation expense	2,576,000	1,898,000	8,505,000	5,175,000
Restricted Stock
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	96,000		$ 96,000
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	4,931,000		$ 4,931,000
Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation expense	8,137,000		$ 8,137,000
Weighted average | Restricted Stock
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period (in years)			2 years 1 month 6 days
Weighted average | Restricted Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period (in years)			1 year 10 months 24 days
Weighted average | Performance Stock Unit
Limited Partners' Capital Account [Line Items]
Unrecognized stock-based compensation, weighted average period (in years)			1 year 9 months 18 days
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	$ 67,000	$ 67,000	$ 196,000	$ 171,000
Class A Common Stock | 2016 Plan
Limited Partners' Capital Account [Line Items]
Common stock, authorized shares (in shares)	2,250,000		2,250,000
Number of shares available for future grant (in shares)	932,000		932,000
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	9 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares
Stock Options
Beginning balance, outstanding (in shares) | shares	90
Granted (in shares) | shares	8
Exercised (in shares) | shares	(19)
Forfeited (in shares) | shares	0
Ending balance, outstanding (in shares) | shares	79
Exercisable at end of period (in shares) | shares	71
Weighted Average Exercise Price
Beginning balance, outstanding (in dollars per share) | $ / shares	$ 8.91
Granted (in dollars per share) | $ / shares	68.78
Exercised (in dollars per share) | $ / shares	8.36
Forfeited (in dollars per share) | $ / shares	0
Ending balance, outstanding (in dollars per share) | $ / shares	15.41
Exercisable at end of period (in dollars per share) | $ / shares	$ 9.06
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Outstanding contractual term (in years)	4 years 7 months 6 days
Exercisable contractual term (in years)	4 years
Outstanding aggregate intrinsic value | $	$ 4,779
Exercisable aggregate intrinsic value | $	$ 4,719

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	9 Months Ended
	Sep. 30, 2021USD ($)$ / 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)	307
Granted (in shares)	108
Forfeited (in shares)	(8)
Outstanding, end of period (in shares)	325
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 41.55
Granted (in dollars per share) | $ / shares	67.65
Forfeited (in dollars per share) | $ / shares	51.22
Outstanding at end of period (in dollars per share) | $ / shares	$ 51.56
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term (in years)	1 year 9 months 18 days
Aggregate intrinsic value | $	$ 24,647
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)	(82)
Weighted Average Grant Date Fair Value
Class A Common Stock Vested (in dollars per share) | $ / shares	$ 35.44
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)	265
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)	590
Weighted Average Grant Date Fair Value
Outstanding at end of period (in dollars per share) | $ / shares	$ 51.26
Weighted Average Remaining Contractual Term (years) and Aggregate Intrinsic Value
Contractual term (in years)	1 year 6 months
Aggregate intrinsic value | $	$ 44,796

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						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 388,492	$ 373,336	$ 362,142	$ 130,745	$ 117,996	$ 122,753	$ 362,142	$ 122,753
Other comprehensive income (loss), net of tax	892	(235)	3,830	160	(1,569)	(7,189)	4,487	(8,598)
Ending balance	407,951	$ 388,492	373,336	$ 147,987	$ 130,745	$ 117,996	407,951	$ 147,987
Accumulated Gain (Loss), Cash Flow Hedge
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			$ (11,517)				(11,517)
Other comprehensive income							2,315
Amounts reclassified from accumulated other comprehensive loss							3,551
Income tax provision related to items of other comprehensive income							(1,379)
Other comprehensive income (loss), net of tax							4,487
Ending balance	$ (7,030)						$ (7,030)

STOCKHOLDERS' EQUITY - Summar_4

STOCKHOLDERS' EQUITY - Summary of Reclassifications Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 5,164			$ 5,406			$ 15,928	$ 16,869
Income before income taxes	22,462			15,491			46,431	29,029
Provision for income taxes	6,601			374			14,476	840
Net income	15,861	$ 11,783	$ 4,311	15,117	$ 12,113	$ 959	31,955	28,189
Accumulated Gain (Loss), Cash Flow Hedge | Amounts Reclassified Out of Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(1,204)			(1,156)			(3,551)	(2,513)
Provision for income taxes	(496)			0			(765)	112
Net income	(708)			(1,156)			(2,786)	(2,625)
Interest rate swaps | Accumulated Gain (Loss), Cash Flow Hedge | Amounts Reclassified Out of Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense	$ 1,204			$ 1,156			$ 3,551	$ 2,513

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Numerator:
Net income	$ 15,861	$ 15,117	$ 31,955	$ 28,189
Denominators:
Unvested restricted stock (in shares)	(2,000)	(2,000)	(2,000)	(2,000)
Effect of weighted average shares outstanding (in shares)	(7,000)	0	(84,000)	(129,000)
Weighted average common shares outstanding, basic (in shares)	51,389,000	48,370,000	51,312,000	48,241,000
Impact of potentially dilutive securities:
Dilutive effect of stock options and other stock awards (in shares)	197,000	249,000	194,000	240,000
Weighted average common shares outstanding, diluted	51,586,000	48,619,000	51,506,000	48,481,000
Anti-dilutive potentially issuable shares (in shares)	12,000	0	12,000	1,000
Class A Common Stock
Denominators:
Common stock, shares outstanding (in shares)	50,410,000	47,384,000	50,410,000	47,384,000	50,101,000
Class B Common Stock
Denominators:
Common stock, shares outstanding (in shares)	988,000	988,000	988,000	988,000	988,000

OTHER ITEMS AND CHARGES (Detail

OTHER ITEMS AND CHARGES (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Site Contingency [Line Items]
Expense from acquisition activities	$ 1,904	$ 173	$ 3,950	$ 1,533
Southbridge Landfill closure charge	302	2,642	653	3,815
Southbridge Landfill
Site Contingency [Line Items]
Southbridge Landfill closure charge	$ 302	2,642	$ 653	3,815
Legal and other costs		642		1,851
Loss contingency, settlement awarded		$ 2,000		2,000
Amortization				152
Recovery credited to environmental remediation expense				$ (188)

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS - Recurring Fair Value Measurements (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Restricted investment securities - landfill closure	$ 1,948	$ 1,848
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Interest rate swaps	0
Total assets	1,948
Liabilities:
Interest rate swaps	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Landfill
Assets:
Restricted investment securities - landfill closure	1,948	1,848
Recurring | Significant Other Observable Inputs (Level 2)
Assets:
Interest rate swaps	228
Total assets	228
Liabilities:
Interest rate swaps	7,604	13,237
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
Total assets	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 ($)	Sep. 30, 2021	Dec. 31, 2020
Term Loan Facility | Secured Debt
Debt Instrument [Line Items]
Principal amount of debt	$ 347,375,000	$ 350,000,000
Fair Value | Fixed Rate Bonds
Debt Instrument [Line Items]
Fixed rate debt	177,501,000
Carrying Value
Debt Instrument [Line Items]
Revolving credit facility	0
Carrying Value | Fixed Rate Bonds
Debt Instrument [Line Items]
Fixed rate debt	$ 162,000,000

SEGMENT REPORTING - Summary of

SEGMENT REPORTING - Summary of Financial Information by Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 241,969	$ 202,667	$ 647,375	$ 574,344
Depreciation and amortization	27,491	23,799	74,510	67,281
Operating income (loss)	27,387	20,633	61,343	45,089
Total assets	1,280,397	994,255	1,280,397	994,255	$ 1,193,898
Operating | Eastern
Segment Reporting Information [Line Items]
Revenues	75,154	58,323	188,557	161,803
Depreciation and amortization	9,407	6,659	23,342	18,956
Operating income (loss)	5,374	3,683	11,401	9,023
Total assets	352,067	215,639	352,067	215,639
Operating | Western
Segment Reporting Information [Line Items]
Revenues	103,523	94,728	288,139	267,218
Depreciation and amortization	15,710	15,000	44,838	41,847
Operating income (loss)	15,805	15,344	38,462	32,849
Total assets	673,608	635,153	673,608	635,153
Operating | Resource solutions
Segment Reporting Information [Line Items]
Revenues	63,292	49,616	170,679	145,323
Depreciation and amortization	1,903	1,544	5,020	4,692
Operating income (loss)	6,679	2,204	12,792	5,008
Total assets	126,529	89,870	126,529	89,870
Corporate entities
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Depreciation and amortization	471	596	1,310	1,786
Operating income (loss)	(471)	(598)	(1,312)	(1,791)
Total assets	128,193	53,593	128,193	53,593
Inter-company revenues
Segment Reporting Information [Line Items]
Revenues	(54,447)	(48,759)	(148,430)	(134,342)
Inter-company revenues | Eastern
Segment Reporting Information [Line Items]
Revenues	(18,768)	(14,261)	(47,322)	(39,936)
Inter-company revenues | Western
Segment Reporting Information [Line Items]
Revenues	(35,523)	(31,692)	(97,771)	(86,259)
Inter-company revenues | Resource solutions
Segment Reporting Information [Line Items]
Revenues	$ (156)	$ (2,806)	$ (3,337)	$ (8,147)

SEGMENT REPORTING - Summary o_2

SEGMENT REPORTING - Summary of Revenues Attributable to Services Provided by Company (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue from External Customer [Line Items]
Revenues	$ 241,969	$ 202,667	$ 647,375	$ 574,344
Solid waste operations
Revenue from External Customer [Line Items]
Revenues	178,677	153,051	476,696	429,021
Collection
Revenue from External Customer [Line Items]
Revenues	118,872	102,270	323,667	290,837
Disposal
Revenue from External Customer [Line Items]
Revenues	55,593	47,600	142,618	129,971
Power generation
Revenue from External Customer [Line Items]
Revenues	1,253	987	3,657	2,931
Processing
Revenue from External Customer [Line Items]
Revenues	2,959	2,194	6,754	5,282
Resource solutions operations
Revenue from External Customer [Line Items]
Revenues	63,292	49,616	170,679	145,323
Processing
Revenue from External Customer [Line Items]
Revenues	27,418	15,701	65,721	45,724
Non-processing
Revenue from External Customer [Line Items]
Revenues	$ 35,874	$ 33,915	$ 104,958	$ 99,599

Uncategorized Items - cwst-2021

Label	Element	Value
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-13 [Member]