10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 10-Q

(Mark One)

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2022

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission File Number: 001-39394

Montrose Environmental Group, Inc.

(Exact Name of Registrant as Specified in its Charter)

Delaware	46-4195044
( State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)
5120 Northshore Drive, North Little Rock, Arkansas	72118
(Address of principal executive offices)	(Zip Code)

Registrant’s telephone number, including area code: (501) 900-6400

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, par value $0.000004 per share	MEG	The New York Stock Exchange

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer	☒	Accelerated filer	☐
Non-accelerated filer	☐	Smaller reporting company	☐
Emerging growth company	☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

As of November 3, 2022, the registrant had 29,711,566 shares of common stock, $0.000004 par value per share, outstanding.

Table of Contents

		Page
PART I.	FINANCIAL INFORMATION
Item 1.	Financial Statements	1
	Unaudited Condensed Consolidated Statements of Financial Position	1
	Unaudited Condensed Consolidated Statements of Operations and Comprehensive Loss	2
	Unaudited Condensed Consolidated Statements of Convertible and Redeemable Series A-2 Preferred Stock and Stockholders’ Equity	3
	Unaudited Condensed Consolidated Statements of Cash Flows	4
	Notes to Unaudited Condensed Consolidated Financial Statements	5
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	33
Item 3.	Quantitative and Qualitative Disclosures About Market Risk	47
Item 4.	Controls and Procedures	47
PART II.	OTHER INFORMATION
Item 1.	Legal Proceedings	49
Item 1A.	Risk Factors	49
Item 2.	Unregistered Sales of Equity Securities and Use of Proceeds	49
Item 3.	Defaults Upon Senior Securities	49
Item 4.	Mine Safety Disclosures	49
Item 5.	Other Information	49
Item 6.	Exhibits	50
Signatures		51

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PART I—FINANCIAL INFORMATION

Item 1. Financial Statements.

MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION

(In thousands, except share data)

	September 30,			December 31,
	2022			2021
ASSETS
CURRENT ASSETS:
Cash and restricted cash	$	93,566		$	146,741
Accounts receivable—net		80,927			98,513
Contract assets		60,444			40,139
Prepaid and other current assets		10,890			8,465
Total current assets		245,827			293,858
NON-CURRENT ASSETS:
Property and equipment—net		33,581			31,521
Operating lease right-of-use asset—net		28,453			23,532
Finance lease right-of-use asset—net		9,869			8,944
Goodwill		318,413			311,944
Other intangible assets—net		146,268			160,997
Other assets		6,694			2,298
TOTAL ASSETS	$	789,105		$	833,094
LIABILITIES, CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK AND    STOCKHOLDERS’ EQUITY
CURRENT LIABILITIES:
Accounts payable and other accrued liabilities	$	58,316		$	68,936
Accrued payroll and benefits		20,477			25,971
Business acquisitions contingent consideration, current		3,967			31,450
Current portion of operating lease liabilities		8,130			6,888
Current portion of finance lease liabilities		3,763			3,512
Current portion of long-term debt		8,750			10,938
Total current liabilities		103,403			147,695
NON-CURRENT LIABILITIES:
Business acquisitions contingent consideration, long-term		2,810			4,350
Other non-current liabilities		22			100
Deferred tax liabilities—net		5,766			4,006
Conversion option		24,730			23,081
Operating lease liability—net of current portion		20,841			16,859
Finance lease liability—net of current portion		6,562			5,756
Long-term debt—net of deferred financing fees		155,645			161,818
Total liabilities		319,779			363,665
COMMITMENTS AND CONTINGENCIES
CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK $0.0001    PAR VALUE—
Authorized, issued and outstanding shares: 17,500 at September 30, 2022 and    December 31, 2021; aggregate liquidation preference of $182.2 million at September 30, 2022 and    December 31, 2021		152,928			152,928
STOCKHOLDERS’ EQUITY:
Common stock, $0.000004 par value; authorized shares: 190,000,000 at    September 30, 2022 and December 31, 2021; issued and outstanding shares: 29,707,503 and    29,619,921 at September 30, 2022 and December 31, 2021, respectively		—			—
Additional paid-in-capital		485,030			464,143
Accumulated deficit		(168,685	)		(147,678	)
Accumulated other comprehensive income		53			36
Total stockholders’ equity		316,398			316,501
TOTAL LIABILITIES, CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK    AND STOCKHOLDERS’ EQUITY	$	789,105		$	833,094

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

1

MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND

COMPREHENSIVE (LOSS) INCOME

(In thousands, except per share data)

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2022			2021			2022			2021
REVENUES	$	130,312		$	132,578		$	404,902		$	402,619
COST OF REVENUES (exclusive of depreciation and    amortization shown below)		82,234			85,242			261,049			272,662
SELLING, GENERAL AND ADMINISTRATIVE EXPENSE		42,857			30,499			131,120			82,865
FAIR VALUE CHANGES IN BUSINESS ACQUISITION    CONTINGENCIES		59			—			(3,472	)		24,035
DEPRECIATION AND AMORTIZATION		11,504			11,471			35,928			33,145
(LOSS) INCOME FROM OPERATIONS		(6,342	)		5,366			(19,723	)		(10,088	)
OTHER INCOME (EXPENSE)
Other income (expense)		1,814			(516	)		4,618			(1,909	)
Interest expense—net		(1,400	)		(1,722	)		(4,010	)		(11,208	)
Total other income (expense)—net		414			(2,238	)		608			(13,117	)
(LOSS) INCOME BEFORE (BENEFIT) EXPENSE FROM    INCOME TAXES		(5,928	)		3,128			(19,115	)		(23,205	)
INCOME TAX (BENEFIT) EXPENSE		(208	)		902			1,892			648
NET (LOSS) INCOME	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)
EQUITY ADJUSTMENT FROM FOREIGN    CURRENCY TRANSLATION		20			(74	)		17			(17	)
COMPREHENSIVE (LOSS) INCOME		(5,700	)		2,152			(20,990	)		(23,870	)
CONVERTIBLE AND REDEEMABLE SERIES A-2    PREFERRED STOCK DIVIDEND		(4,100	)		(4,100	)		(12,300	)		(12,300	)
NET LOSS ATTRIBUTABLE TO    COMMON STOCKHOLDERS		(9,820	)		(1,874	)		(33,307	)		(36,153	)
WEIGHTED AVERAGE COMMON SHARES    OUTSTANDING— BASIC AND DILUTED		29,691			26,220			29,677			25,798
NET LOSS PER SHARE ATTRIBUTABLE TO    COMMON STOCKHOLDERS— BASIC AND DILUTED	$	(0.33	)	$	(0.07	)	$	(1.12	)	$	(1.40	)

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

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MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK AND STOCKHOLDERS’ EQUITY

(In thousands, except share data)

															Accumulated
															Other
	Convertible and Redeemable														Comprehensive			Total
	Series A-2 Preferred Stock				Common Stock				Additional			Accumulated			Income			Stockholders'
	Shares		Amount		Shares		Amount		Paid-In Capital			Deficit			(Loss)			Equity
BALANCE—December 31, 2020		17,500	$	152,928		24,932,527	$	—	$	259,427		$	(122,353	)	$	71		$	137,145
Net loss		—		—		—		—		—			(12,931	)		—			(12,931	)
Stock-based compensation		—		—		—		—		1,805			—			—			1,805
Dividend payment to the Series A-2    preferred shareholders		—		—		—		—		(4,100	)		—			—			(4,100	)
Common stock issued		—		—		506,330		—		4,456			—			—			4,456
Accumulated other comprehensive income		—		—		—		—		—			—			29			29
BALANCE—March 31, 2021		17,500	$	152,928		25,438,857	$	—	$	261,588		$	(135,284	)	$	100		$	126,404
Net loss		—		—		—		—		—			(13,148	)		—			(13,148	)
Stock-based compensation		—		—		—		—		2,417			—			—			2,417
Dividend payment to the Series A-2    preferred shareholders		—		—		—		—		(4,100	)		—			—			(4,100	)
Common stock issued		—		—		669,331		—		27,460			—			—			27,460
Accumulated other comprehensive income		—		—		—		—		—			—			28			28
BALANCE—June 30, 2021		17,500	$	152,928		26,108,188	$	—	$	287,365		$	(148,432	)	$	128		$	139,061
Net loss		—		—		—		—					2,226			—			2,226
Stock-based compensation		—		—		—		—		2,365			—			—			2,365
Dividend payment to the Series A-2    preferred shareholders		—		—		—		—		(4,100	)		—			—			(4,100	)
Common stock issued		—		—		417,656		—		6,220			—			—			6,220
Accumulated other comprehensive income		—		—		—		—		—			—			(74	)		(74	)
BALANCE—September 30, 2021		17,500		152,928		26,525,844		—		291,850			(146,206	)		54			145,698
BALANCE—December 31, 2021		17,500	$	152,928		29,619,921	$	—	$	464,143		$	(147,678	)	$	36		$	316,501
Net loss		—		—		—		—		—			(7,536	)		—			(7,536	)
Stock-based compensation		—		—		—		—		10,425			—			—			10,425
Dividend payment to the Series A-2    preferred shareholders		—		—		—		—		(4,100	)		—			—			(4,100	)
Common stock issued		—		—		55,896		—		429			—			—			429
Accumulated other comprehensive income		—		—		—		—		—			—			45			45
BALANCE—March 31, 2022		17,500	$	152,928		29,675,817	$	—	$	470,897		$	(155,214	)	$	81		$	315,764
Net loss		—		—		—		—		—			(7,751	)		—			(7,751	)
Stock-based compensation		—		—		—		—		10,932			—			—			10,932
Dividend payment to the Series A-2    preferred shareholders		—		—		—		—		(4,100	)		—			—			(4,100	)
Common stock issued		—		—		3,575		—		54			—			—			54
Accumulated other comprehensive loss		—		—		—		—		—			—			(48	)		(48	)
BALANCE—June 30, 2022		17,500	$	152,928		29,679,392	$	—	$	477,783		$	(162,965	)	$	33		$	314,851
Net loss		—		—		—		—		—			(5,720	)		—			(5,720	)
Stock-based compensation		—		—		—		—		11,018			—			—			11,018
Dividend payment to the Series A-2    preferred shareholders		—		—		—		—		(4,100	)		—			—			(4,100	)
Common stock issued		—		—		28,111		—		329			—			—			329
Accumulated other comprehensive income		—		—		—		—		—			—			20			20
BALANCE—September 30, 2022		17,500	$	152,928		29,707,503	$	—	$	485,030		$	(168,685	)	$	53		$	316,398

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

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MONTROSE ENVIRONMENTAL GROUP, INC.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands)

	Nine Months Ended September 30,
	2022			2021
OPERATING ACTIVITIES:
Net loss	$	(21,007	)	$	(23,853	)
Adjustments to reconcile net loss to net cash used in operating activities:
(Recovery) provision for bad debt		(821	)		803
Depreciation and amortization		35,928			33,145
Amortization of right-of-use asset		6,934			5,947
Stock-based compensation expense		32,375			6,587
Fair value changes in financial instruments		(4,664	)		1,651
Fair value changes in business acquisition contingencies		(3,472	)		24,035
Deferred income taxes		1,892			232
Debt extinguishment costs		—			4,052
Other		460			68
Changes in operating assets and liabilities—net of acquisitions:
Accounts receivable and contract assets		7,301			(12,503	)
Prepaid expenses and other current assets		(1,364	)		(1,781	)
Accounts payable and other accrued liabilities		(12,943	)		(3,422	)
Accrued payroll and benefits		(6,363	)		61
Payment of contingent consideration		(19,457	)		(15,549	)
Change in operating leases		(6,634	)		(5,765	)
Net cash provided by operating activities		8,165			13,708
INVESTING ACTIVITIES:
Purchases of property and equipment		(5,414	)		(5,405	)
Proceeds received from corporate owned insurance		277			—
Proprietary software development and other software costs		(397	)		(241	)
Purchase price true ups		(439	)		(8,562	)
Cash paid for acquisitions—net of cash acquired		(21,342	)		(36,480	)
Net cash used in investing activities		(27,315	)		(50,688	)
FINANCING ACTIVITIES:
Proceeds from line of credit		—			109,000
Payments on line of credit		—			(72,000	)
Proceeds from term loans		—			175,000
Repayment of term loan		(8,751	)		(173,905	)
Payment of contingent consideration		(10,722	)		(9,605	)
Repayment of finance leases		(2,906	)		(1,884	)
Debt issuance costs		—			(2,590	)
Proceeds from issuance of common stock for exercised stock options		812			6,032
Dividend payment to the Series A-2 shareholders		(12,300	)		(12,300	)
Payments of deferred offering costs		(183	)		—
Net cash (used in) provided by financing activities		(34,050	)		17,748
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH		(53,200	)		(19,232	)
Foreign exchange impact on cash balance		25			357
CASH, CASH EQUIVALENTS AND RESTRICTED CASH:
Beginning of year		146,741			34,881
End of period	$	93,566		$	16,006
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION:
Cash paid for interest	$	4,852		$	4,649
Cash paid for income tax	$	587		$	958
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accrued purchases of property and equipment	$	881		$	1,171
Property and equipment purchased under finance leases	$	3,939		$	1,766
Common stock issued to acquire new businesses	$	—		$	6,020
Acquisitions unpaid contingent consideration	$	6,777		$	35,352
Offering costs included in accounts payable and other accrued liabilities	$	—		$	389
Acquisitions contingent consideration paid in shares	$	—		$	26,084

The accompanying notes are an integral part of these unaudited condensed consolidated financial statements.

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MONTROSE ENVIRONMENTAL GROUP, INC.

NOTES TO UNAUDITED CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(In thousands, except where otherwise indicated)

1. DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION

Description of the Business—Montrose Environmental Group, Inc. (“Montrose” or the “Company”) is a corporation formed on November 2013, under the laws of the State of Delaware. The Company has approximately 80 offices across the United States, Canada and Australia and approximately 2,800 employees as of September 30, 2022.

Montrose is an environmental services company serving the recurring environmental needs of a diverse client base, including Fortune 500 companies and federal, state and local governments through the following three segments:

Assessment, Permitting and Response—Through its Assessment, Permitting and Response segment, Montrose provides scientific advisory and consulting services to support environmental assessments, environmental emergency response, and environmental audits and permits for current operations, facility upgrades, new projects, decommissioning projects and development projects. The Company’s technical advisory and consulting offerings include regulatory compliance support and planning, environmental, ecosystem and toxicological assessments and support during responses to environmental disruption. Montrose helps clients navigate regulations at the local, state, provincial and federal levels.

Measurement and Analysis—Through its Measurement and Analysis segment, Montrose’s teams test and analyze air, water and soil to determine concentrations of contaminants, as well as the toxicological impact of contaminants on flora, fauna and human health. Montrose’s offerings include source and ambient air testing and monitoring, leak detection and repair and advanced analytical laboratory services such as air, storm water, wastewater and drinking water analysis.

Remediation and Reuse—Through its Remediation and Reuse segment, Montrose provides clients with engineering, design, implementation and operations and maintenance services, primarily to treat contaminated water, remove contaminants from soil or create biogas from waste. The Company does not own the properties or facilities at which it implements these projects or the underlying liabilities, nor does it own material amounts of the equipment used in projects; instead, the Company assists clients in designing solutions, managing projects and mitigating their environmental risks and liabilities at their locations.

Basis of Presentation—The unaudited condensed consolidated financial statements include the operations of the Company and its wholly-owned subsidiaries. These unaudited condensed consolidated financial statements are presented in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) and have been prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) that permit reduced disclosure for interim periods. The unaudited condensed consolidated financial statements include all accounts of the Company and, in the opinion of management, include all recurring adjustments and normal accruals necessary for a fair statement of the Company’s financial position, results of operations and cash flows for the dates and periods presented. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2021. Results for interim periods are not necessarily indicative of the results to be expected during the remainder of the current year or for any future period. All intercompany transactions, accounts and profits, have been eliminated in the unaudited condensed consolidated financial statements.

Subsequent Events— The Company has evaluated subsequent events through the filing of this Quarterly Report on Form 10-Q, and determined that there have been no events that have occurred that would require adjustments to our disclosures in the unaudited condensed consolidated financial statements.

2. SUMMARY OF NEW ACCOUNTING PRONOUNCEMENTS

Recently Adopted Accounting Pronouncements—Through the end of the year ended December 31, 2021, the Company qualified as an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”) and therefore has historically taken advantage of certain exemptions from various public company reporting requirements, including delaying adoption of new or revised accounting standards until those standards apply to private companies. The Company elected to use this extended transition period under the JOBS Act. The adoption dates discussed below are based on the Company no longer qualifying as an emerging growth company.

In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standard Update ("ASU") 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity

5

(Subtopic 815-40)—Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The ASU simplifies accounting for convertible instruments by removing major separation models required under current U.S. GAAP. Consequently, more convertible debt instruments will be reported as a single liability instrument with no separate accounting for embedded conversion features. The ASU removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception, which will permit more equity contracts to qualify for the exception. The ASU also simplifies the diluted net income per share calculation in certain areas. The new guidance is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years, and early adoption is permitted. The new guidance was adopted as of January 1, 2022 and did not have a material impact on the Company’s consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted—In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. Under the new guidance (ASC 805-20-30-28), the acquirer should determine what contract assets and/or contract liabilities it would have recorded under ASC 606 (the revenue guidance) as of the acquisition date, as if the acquirer had entered into the original contract at the same date and on the same terms as the acquiree. The new guidance is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is currently evaluating the impact of the adoption of the standard on the consolidated financial statements, but does not expect adoption to have a material impact on its consolidated financial statements. The future impact of this new guidance will be primarily a function of the facts and circumstances specific to any acquisitions consummated after adoption and therefore cannot be predicted prior to or at the time of adoption.

3. REVENUES AND ACCOUNTS RECEIVABLE

The Company’s main revenue sources derive from the following revenue streams:

Assessment, Permitting and Response Revenues—Assessment, Permitting and Response revenues are generated from multidisciplinary environmental consulting services. The majority of the contracts are fixed-price or time and material based.

Measurement and Analysis Revenues—Measurement and Analysis revenues are generated from emissions sampling, testing and reporting services, leak detection services, ambient air monitoring services and laboratory testing services. The majority of the contracts are fixed-price or time-and-materials based.

Remediation and Reuse Revenues—Remediation and Reuse revenues are generated from engineering, design, implementation and operating and maintenance (“O&M”) services primarily to treat contaminated water, remove contaminants from soil or create biogas from waste. Engineering, design and implementation contracts are predominantly fixed-fee and time-and-materials based. Services on the majority of O&M contracts are provided under long-term fixed-fee contracts.

Disaggregation of Revenue—The Company disaggregates revenue by its operating segments. The Company believes disaggregating revenue into these categories achieves the disclosure objectives to depict how the nature, amount, and uncertainty of revenue and cash flows are affected by economic factors. Disaggregated revenue disclosures are provided in Note 18.

Contract Balances—The Company presents contract balances for unbilled receivables (contract assets), as well as customer advances, deposits and deferred revenue (contract liabilities) within contract assets and accounts payable and accrued expenses, respectively, on the unaudited condensed consolidated statements of financial position. Amounts are generally billed at periodic intervals (e.g. weekly, bi-weekly or monthly) as work progresses in accordance with agreed-upon contractual terms. The Company utilizes the practical expedient to not adjust the promised amount of consideration for the effects of a significant financing component as the period between when the Company transfers services to a customer and when the customer pays for those services is one year or less. Amounts recorded as unbilled receivables are generally for services the Company is not entitled to bill based on the passage of time. Under certain contracts, billing occurs subsequent to revenue recognition, resulting in contract assets. The Company sometimes receives advances or deposits from customers before revenue is recognized, resulting in contract liabilities.

The following table presents the Company’s contract balances:

	September 30,		December 31,
	2022		2021
Contract assets	$	60,444	$	40,139
Contract liabilities		23,270		27,907

Contract assets acquired through business acquisitions amounted to $1.3 million and $0.5 million as of September 30, 2022 and December 31, 2021, respectively. Contract liabilities acquired through business acquisitions amounted to zero and $ 0.5 million as of

6

September 30, 2022 and December 31, 2021, respectively. Revenue recognized during the three and nine months ended September 30, 2022, included in the contract liabilities balance at the beginning of the year was $10.3 million and $23.6 million, respectively. The revenue recognized from the contract liabilities consisted of the Company satisfying performance obligations during the normal course of business.

The amount of revenue recognized from changes in the transaction price associated with performance obligations satisfied in prior periods during the three and nine months ended September 30, 2022 was not material.

Remaining Unsatisfied Performance Obligations—Remaining unsatisfied performance obligations represent the total dollar value of work to be performed on contracts awarded and in progress. The amount of remaining unsatisfied performance obligations increases with new contracts or additions to existing contracts and decreases as revenue is recognized on existing contracts. Contracts are included in the amount of remaining unsatisfied performance obligations when an enforceable agreement has been reached. As of September 30, 2022 and December 31, 2021, the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied was approximately $92.0 million and $108.7 million, respectively. As of September 30, 2022, the Company expected to recognize approximately $67.8 million of this amount as revenue within a year and $24.2 million the year after.

Accounts Receivable, Net—The Company extends non-interest-bearing trade credit to its customers in the ordinary course of business. Accounts receivable, net consisted of the following:

	September 30, 2022			December 31, 2021
Accounts receivable, invoiced	$	82,649		$	101,709
Accounts receivable, other		544			1,385
Allowance for doubtful accounts		(2,266	)		(4,581	)
Accounts receivable—net	$	80,927		$	98,513

As of September 30, 2022, the Company did not have any customers that exceeded 10.0% of its gross accounts receivable. As of December 31, 2021, the Company had one customer who accounted for 23.1% of its gross accounts receivable. For the three and nine months ended September 30, 2022, the Company had one customer who accounted for 11.1% and 14.8% of revenue, respectively. During the three months ended September 30, 2021, the Company did not have any customers that exceeded 10.0% of revenue. During the nine months ended September 30, 2021, the Company had three customers who accounted for 12.1%, 11.4% and 10.7% of revenue. The Company performs ongoing credit evaluations and based on past collection experience, the Company believes that the receivable balances from these largest customers do not represent a significant credit risk.

Accounts receivable are shown on the face of the consolidated statements of financial position, net of an allowance for doubtful accounts. The allowance for doubtful accounts is established at the origination of an account in accordance with ASU 2016-13, Financial Instruments—Credit Losses (Topic 326). ASC 326 requires the Company to estimate the lifetime expected credit losses on such instruments and to record an allowance to offset the receivables. In determining the allowance for doubtful accounts, the Company analyzes the aging of accounts receivable, historical bad debts, customer creditworthiness and current economic trends. The allowance for doubtful accounts consisted of the following:

	Beginning Balance		Bad Debt (Recovery) Expense			Charged to Allowance			Other(1)		Ending Balance
Nine months ended September 30, 2022	$	4,581	$	(821	)	$	(1,621	)	$	127	$	2,266
Year ended December 31, 2021		4,265		1,135			(1,548	)		729		4,581

____________________

(1)This amount consists of additions to the allowance due to business acquisitions.

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4. PREPAID AND OTHER CURRENT ASSETS

Prepaid and other current assets consisted of the following:

	September 30,		December 31,
	2022		2021
Deposits	$	1,402	$	843
Prepaid expenses		4,708		4,675
Supplies		3,686		2,439
Income tax receivable		1,094		508
Prepaid and other current assets	$	10,890	$	8,465

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5. PROPERTY AND EQUIPMENT, NET

Property and equipment are stated at cost or estimated fair value for assets acquired through business combinations. Depreciation and amortization are provided using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term, including options that are deemed to be reasonably assured, or the estimated useful life of the improvement.

Property and equipment, net, consisted of the following:

	Estimated	September 30,			December 31,
	Useful Life	2022			2021
Lab and test equipment	7 years	$	19,975		$	18,581
Vehicles	5 years		5,642			5,414
Equipment	3-7 years		38,446			35,148
Furniture and fixtures	7 years		2,895			2,844
Leasehold improvements	7 years		8,535			7,268
Aircraft	10 years		931			931
Building	39 years		2,975			2,975
			79,399			73,161
Land			725			725
Construction in progress			2,566			2,342
Less accumulated depreciation			(49,109	)		(44,707	)
Total property and equipment—    net		$	33,581		$	31,521

Total depreciation expense included in the unaudited condensed consolidated statements of operations was $1.7 million and $5.3 million for the three and nine months ended September 30, 2022, respectively, and $1.8 million and $4.8 million for the three and nine months ended September 30, 2021, respectively.

6. LEASES

In June 2021, with an effective adoption date of January 1, 2021, the Company adopted ASU 2016-02 using the modified retrospective approach, which permits application of this guidance at the beginning of the period of adoption.

Leases are classified as either finance leases or operating leases based on criteria in ASC 842. The Company has finance leases for its vehicle and equipment leases and operating leases for its real estate space and office equipment leases. The Company’s operating and finance leases generally have original lease terms between 1 year and 15 years, and in some instances include one or more options to renew. The Company includes options to extend the lease term if the options are reasonably certain of being exercised. The Company currently considers some of its renewal options to be reasonably certain to be exercised. Some leases also include early termination options, which can be exercised under specific conditions. The Company does not have material residual value guarantees or restrictive covenants associated with its leases.

Finance and operating lease assets represent the right to use an underlying asset for the lease term, and finance and operating lease liabilities represent the obligation to make lease payments arising from the lease.

The Company calculates the present value of its finance and operating leases using an estimated incremental borrowing rate (“IBR”), which requires judgment. For real estate operating leases, the Company estimates the IBR based on prevailing market rates for collateralized debt in a similar economic environment with similar payment terms and maturity dates commensurate with the terms of the lease. For all other leases, the Company estimates the IBR based on the stated interest rate on the contract. Since many of the inputs used to calculate the rate implicit in the leases are not readily determinable from the lessee’s perspective, the Company will not use the implicit interest rate.

Certain leases contain variable payments, these payments are expensed as incurred and not included in the Company’s operating lease right-of-use assets and operating lease liabilities. These amounts primarily include payments for maintenance, utilities, taxes, and insurance and are excluded from the present value of the Company’s lease obligations.

Effective January 1, 2021, the Company recognized operating lease right-of-use assets, current operating lease liabilities and operating lease liabilities, net of current portion of $24.6 million, $7.3 million and $17.3 million, respectively. The Company also

9

recognized finance lease right-of-use assets, current finance lease liabilities and finance lease liabilities, net of current portion of $7.2 million, $2.9 million and $4.6 million, respectively.

The Company does not record operating lease right-of-use assets or operating lease liabilities for leases with an initial term of 12 months or less. The Company also combines lease and non-lease components on all new or modified operating leases into a single lease component for all classes of assets.

The components of lease expense were as follows:

		For the Three Months Ended September 30,
	Statement of Operations Location	2022		2021
Operating lease cost
Lease cost	Selling, general and administrative expense	$	2,542	$	2,203
Variable lease cost	Selling, general and administrative expense		354		120
Total operating lease cost			2,896		2,323
Finance lease cost
Amortization of right of use assets	Depreciation and amortization		1,075		825
Interest on lease liabilities	Interest expense—net		116		97
Total finance lease cost			1,191		922
Total lease cost		$	4,087	$	3,245
		For the Nine Months Ended September 30,
	Statement of Operations Location	2022		2021
Operating lease cost
Lease cost	Selling, general and administrative expense	$	7,472	$	6,398
Variable lease cost	Selling, general and administrative expense		911		329
Total operating lease cost			8,383		6,727
Finance lease cost
Amortization of right of use assets	Depreciation and amortization		3,026		2,391
Interest on lease liabilities	Interest expense—net		335		300
Total finance lease cost			3,361		2,691
Total lease cost		$	11,744	$	9,418

Supplemental cash flows information related to leases was as follows:

	For the Nine Months Ended September 30,
	2022		2021
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used in operating leases	$	7,171	$	6,273
Operating cash flows used in finance leases		335		300
Financing cash flows used in finance leases		2,906		2,367
Lease liabilities arising from new ROU assets
Operating leases		11,786		5,078
Finance leases		3,939		2,719

Weighted average remaining lease terms and weighted average discount rates were:

	September 30, 2022
	Operating Leases			Finance Leases
Weighted average remaining lease term (years)	4.56				3.32
Weighted average discount rate	2.58%			5.27%
	September 30, 2021
	Operating Leases			Finance Leases
Weighted average remaining lease term (years)	5.22				2.80
Weighted average discount rate		2.62	%		4.95	%

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The following is a schedule by year of the maturities of lease liabilities with original terms in excess of one year:

	Operating Leases			Finance Leases
Remainder of 2022	$	2,447		$	1,181
2023		8,295			3,871
2024		6,595			2,781
2025		4,680			1,881
2026 and thereafter		8,733			1,570
Total undiscounted future minimum lease payments		30,750			11,284
Less imputed interest		(1,779	)		(959	)
Total discounted future minimum lease payments	$	28,971		$	10,325

7. BUSINESS ACQUISITIONS

In line with the Company’s strategic growth initiatives, the Company acquired certain businesses during the nine months ended September 30, 2022 and during the year ended December 31, 2021. The results of each of those acquired businesses are included in the unaudited condensed consolidated financial statements beginning on the acquisition date. Each transaction qualified as an acquisition of a business and was accounted for as a business combination. All acquisitions resulted in the recognition of goodwill. The Company paid these premiums resulting in such goodwill for a number of reasons, including expected synergies from combining operations of the acquiree and the Company while also growing the Company’s customer base, acquiring assembled workforces, expanding its presence in certain markets and expanding and advancing its product and service offerings. The Company recorded the assets acquired and liabilities assumed at their acquisition date fair value, with the difference between the fair value of the net assets acquired and the acquisition consideration reflected as goodwill.

The identifiable intangible assets for significant acquisitions are valued using the excess earnings method discounted cash flow approach for customer relationships, the relief from royalty method for trade names, the patent and external proprietary software, the “with and without” method for covenants not to compete and the replacement cost method for the internal proprietary software by incorporating Level 3 inputs as described under the fair value hierarchy of ASC 820. These unobservable inputs reflect the Company’s own assumptions about which assumptions market participants would use in pricing an asset on a non-recurring basis. These assets will be amortized over their respective estimated useful lives.

Other purchase price obligations (primarily deferred purchase price liabilities and target working capital liabilities or receivables) are included on the unaudited condensed consolidated statements of financial position in accounts payable and other accrued liabilities, other non-current liabilities or accounts receivable-net in the case of working capital deficits. Contingent consideration outstanding from acquisitions are included on the unaudited condensed consolidated statements of financial position in business acquisition contingent consideration, current or in business acquisitions contingent consideration, long-term. The contingent consideration elements of the purchase price of the acquisitions are related to earn-outs which are based on the expected achievement of revenue or earnings thresholds as of the date of the acquisition and for which the maximum potential amount is limited.

The Company considers several factors when determining whether or not contingent consideration liabilities are part of the purchase price, including the following: (i) the valuation of its acquisitions is not supported solely by the initial consideration paid, (ii) the former stockholders of acquired companies that remain as key employees receive compensation other than contingent consideration payments at a reasonable level compared with the compensation of the Company’s other key employees and (iii) contingent consideration payments are not affected by employment termination. The Company reviews and assesses the estimated fair value of contingent consideration at each reporting period.

The Company may be required to make up to $8.5 million in aggregate earn-out payments between the years 2023 and 2026 in connection with certain of its business acquisitions, up to $3.0 million of which may be paid in cash.

Transaction costs related to business combinations totaled $0.4 million and $1.4 million for the three and nine months ended September 30, 2022, respectively, and $0.9 million and $1.7 million for the three and nine months ended September 30, 2021, respectively. These costs are expensed within selling, general and administrative expense in the accompanying unaudited condensed consolidated statements of operations.

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Acquisitions Completed During the Nine Months Ended September 30, 2022

Environmental Standards, Inc. (“EnvStd”)—In January 2022, the Company completed the acquisition of Environmental Standards, Inc. by acquiring 100.0% of its common stock. EnvStd is a provider of environmental consulting services. EnvStd is based in Valley Forge, PA with satellite locations nationwide. The upfront cash payment made to acquire EnvStd was funded through cash on hand.

Industrial Automation Group, Inc. (“IAG”)—In January 2022, the Company completed the acquisition of Industrial Automation Group, Inc. by acquiring certain of its employees and a covenant not to compete. The upfront cash payment made to acquire IAG was funded through cash on hand. IAG is based in Atlanta, GA.

TriAD Environmental Consultants, Inc. (“TriAD”)—In August 2022, the Company completed the acquisition of TriAD Environmental Consultants, Inc. by acquiring 100.0% of its common stock. TriAD is a provider of environmental consulting services. TriAD is based in Nashville, TN. The upfront cash payment made to acquire TriAD was funded through cash on hand.

AirKinetics, Inc. (“AirKinetics”)—In September 2022, the Company completed the acquisition of AirKinetics, Inc. by acquiring 100.0% of its common stock. AirKinetics is a provider of emissions testing services. AirKinetics is based in Anaheim, CA. The upfront cash payment made to acquire AirKinetics was funded through cash on hand.

The following table summarizes the elements of the purchase price of the acquisitions completed during the nine months ended September 30, 2022:

	Cash		Common Stock		Other Purchase Price Components Current		Contingent Consideration Current		Contingent Consideration Long Term		Total Purchase Price
EnvStd	$	14,473	$	—	$	521	$	1,166	$	—	$	16,160
All other 2022 acquisitions		7,650		—		472		50		—		8,172
Total	$	22,123	$	—	$	993	$	1,216	$	—	$	24,332

The other purchase price components of the EnvStd purchase price consist of a surplus working capital amount, which will be finalized in the fourth quarter of 2022 and a seller make-whole for taxes related to a 338(h)(10) election. The other purchase price components of all the other acquisitions purchase price mainly consist of surplus/deficit working capital amounts.

The preliminary purchase price attributable to the acquisitions was allocated as follows:

	EnvStd		All Other 2022 Acquisitions		Total
Cash	$	295	$	486	$	781
Accounts receivable and contract assets		5,200		1,846		7,046
Other current assets		456		19		475
Current assets		5,951		2,351		8,302
Property and equipment		168		11		179
Operating lease right-of-use asset—net		2,895		215		3,110
Customer relationships		5,807		2,714		8,521
Trade names		1,010		251		1,261
Covenants not to compete		269		394		663
Goodwill		4,107		2,965		7,072
Total assets		20,207		8,901		29,108
Current liabilities		1,719		619		2,338
Operating lease liability—net of    current portion		2,328		110		2,438
Total liabilities		4,047		729		4,776
Purchase price	$	16,160	$	8,172	$	24,332

The weighted average useful lives for the acquired companies’ identifiable intangible assets are as follows:

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	Customer Relationships	Tradenames	Covenants Not to Compete
EnvStd	7	2	5
All other 2022 acquisitions	7	2	5

Goodwill associated with the EnvStd and IAG acquisitions are deductible for income tax purposes.

For the acquisitions completed during the nine months ended September 30, 2022, the results of operations since the acquisition dates have been combined with those of the Company. The Company’s unaudited condensed consolidated statement of operations for the three and nine months ended September 30, 2022 includes revenue of $5.6 million and $13.2 million, respectively, and pre-tax income of $1.0 million and $1.7 million, respectively, related to these acquisitions. EnvStd is included in the Company’s Assessment, Permitting and Response segment, IAG and TriAD are included in the Remediation and Reuse segment and AirKinetics is included in the Measurement and Analysis segment.

13

Acquisitions Completed During the Year Ended December 31, 2021

MSE Group, LLC (“MSE”)—In January 2021, the Company completed the acquisition of MSE Group, LLC by acquiring 100.0% of its membership interests. MSE is a provider of environmental assessment, permitting and remediation services primarily to the U.S. federal government. MSE is based in Orlando, FL with additional offices in Tampa, Orlando, Jacksonville, San Antonio, TX, and Wilmington, NC, and satellite locations nationwide. The upfront cash payment made to acquire MSE was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 71,740 shares of common stock.

Vista Analytical Laboratory, Inc. (“Vista”)—In June 2021, the Company completed the acquisition of Vista Analytical Laboratory, Inc. (“Vista”) by acquiring 100.0% of its common stock. Vista provides specialty analytical services related to Per- and polyfluoroalkyl substances (“PFAS”) and other semi-volatile organic compounds. Vista is based in Dorado Hills, CA. The upfront cash payment made to acquire Vista was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 9,322 shares of common stock.

Environmental Intelligence, LLC (“EI”) —In July 2021, the Company completed the acquisition of Environmental Intelligence, LLC (“EI”) by acquiring 100.0% of its membership interests. EI provides environmental consulting services and is recognized for its innovative work in wildlife mitigation and biological assessments. EI is based in Laguna Beach, CA and enhances Montrose’s ecological planning and service capabilities in California and the US West Coast. The upfront cash payment made to acquire EI was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 43,100 shares of common stock.

SensibleIoT, LLC (“Sensible”) —In August, 2021, the Company completed the business acquisition of SensibleIoT, LLC (“Sensible”) by acquiring 100.0% of its membership interests. Sensible is a technology platform that connects sensors and sources of environment data to a central, proprietary database that enables real-time client interaction. Sensible provides Montrose with an advanced ability to integrate environmental services and enhance environmental data analytics for clients. The upfront cash payment made to acquire Sensible was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 19,638 shares of common stock.

Environmental Chemistry, Inc. (“ECI”) —In October 2021, the Company completed the business acquisition of Environmental Chemistry, Inc. (“ECI”) by acquiring 100.0% of its common stock. ECI provides a full suite of environmental laboratory analytical services to industrial, governmental, and engineering/consulting clients. Combined with the Company’s existing Houston, TX laboratory, ECI (located also in Houston, TX) will enable Montrose to provide air, water and soil analytical services in the gulf coast region. The upfront cash payment made to acquire ECI was funded through cash on hand.

Horizon Water and Environment, LLC (“Horizon”)— In November 2021, the Company completed the business acquisition of Horizon Water and Environment, LLC (“Horizon”) by acquiring 100.0% of its membership interests. Horizon is an environmental consulting firm specializing in planning, watershed science, and environmental compliance for water and natural resource projects. The upfront cash payment made to acquire Horizon was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 34,921 shares of common stock.

The following table summarizes the elements of the purchase price of the acquisitions completed during the year ended December 31, 2021:

	Cash		Common Stock		Other Purchase Price Components Current			Contingent Consideration Current		Contingent Consideration Long Term		Total Purchase Price
MSE	$	9,082	$	2,271	$	10,701		$	1,551	$	253	$	23,858
EI		20,721		2,274		(63	)		—		—		22,932
All other 2021 acquisitions		29,683		3,775		1,228			1,250		4,350		40,286
Total	$	59,486	$	8,320	$	11,866		$	2,801	$	4,603	$	87,076

The other purchase price components of the MSE purchase price consist of a surplus working capital amount on the date of close, a seller make-whole for taxes related to a 338(h)(10) election, an integration payment liability and a purchase price true up related to MSE’s financial performance in the fourth quarter of 2020. The other purchase price components of the EI purchase price consist of a surplus working capital amount on the date of close. The other purchase price components of all the other acquisitions purchase price mainly consist of surplus/deficit working capital amounts and 338(h)(10) election liabilities.

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The purchase price attributable to the acquisitions was allocated as follows:

	MSE		EI		All other 2021 acquisitions		Total
Cash	$	2,810	$	250	$	693	$	3,753
Accounts receivable		2,980		4,675		4,133		11,788
Other current assets		31		84		289		404
Current assets		5,821		5,009		5,115		15,945
Property and equipment		513		32		1,168		1,713
Operating lease right-of-use asset—net		740		106		2,233		3,079
Customer relationships		8,720		10,073		12,830		31,623
Trade names		521		996		1,958		3,475
Covenants not to compete		922		511		1,248		2,681
Acquired Technology		—		—		321		321
Goodwill		8,176		8,960		19,569		36,705
Total assets		25,413		25,687		44,442		95,542
Current liabilities		1,007		2,719		2,351		6,077
Operating lease liability—net of    current portion		548		36		1,805		2,389
Total liabilities		1,555		2,755		4,156		8,466
Purchase price	$	23,858	$	22,932	$	40,286	$	87,076

The weighted average useful lives for the acquired companies’ identifiable intangible assets are as follows:

	Customer Relationships	Tradenames	Covenants Not to Compete	Developed Technology
MSE	2-7	2	5	n/a
EI	10	5	5	n/a
All other 2021 acquisitions	10	n/a-3	n/a-5	n/a-5

Goodwill associated with all of these acquisitions is deductible for income tax purposes.

For the acquisitions completed during the year ended December 31, 2021, the results of operations since the acquisition dates have been combined with those of the Company. The Company’s unaudited condensed consolidated statement of operations for the three and nine months ended September 30, 2021 includes revenue of $11.9 million and $19.7 million, respectively, and pre-tax (loss) of $(0.2) million and zero, respectively, related to the acquisitions completed prior to September 30, 2021. MSE is included in the Company’s Remediation and Reuse segment, Vista, Sensible and ECI are included in the Company’s Measurement and Analysis segment and EI and Horizon are included in the Company's Assessment, Permitting and Response segment.

Supplemental Unaudited Pro-Forma—The unaudited condensed consolidated financial information summarized in the following table gives effect to the 2022 and the 2021 acquisitions discussed above assuming they occurred on January 1, 2021. These unaudited consolidated pro forma operating results do not assume any impact from revenue, cost or other operating synergies that are expected or may have been realized as a result of the acquisitions. These unaudited consolidated pro forma operating results are presented for illustrative purposes only and are not indicative of the operating results that would have been achieved had the acquisitions occurred on January 1, 2021, nor does the information purport to reflect results for any future period.

	For the Three Months Ended September 30,
	2022								2021
	(Unaudited)
	As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma			As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma
Revenues	$	130,312		$	1,202	$	131,514		$	132,578		$	9,457	$	142,035
Net (loss) income		(5,720	)		290		(5,430	)		2,226			1,479		3,705
	For the Nine Months Ended September 30,
	2022								2021
	(Unaudited)
	As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma			As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma
Revenues	$	404,902		$	6,422	$	411,324		$	402,619		$	39,819	$	442,438
Net (loss) income		(21,007	)		832		(20,175	)		(23,853	)		6,848		(17,005	)

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8. GOODWILL AND INTANGIBLE ASSETS

Amounts related to goodwill are as follows:

	Assessment, Permitting and Response			Measurement and Analysis		Remediation and Reuse		Total
Balance as of December 31, 2021	$	176,541		$	83,770	$	51,633	$	311,944
Goodwill acquired during the period		4,764			2,158		150		7,072
Acquisitions measurement period adjustments		(899	)		296		—		(603	)
Balance as of September 30, 2022	$	180,406		$	86,224	$	51,783	$	318,413

Amounts related to finite-lived intangible assets are as follows:

September 30, 2022	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	204,926	$	90,572	$	114,354
Covenants not to compete	4-5 years		33,286		27,523		5,763
Trade names	1-5 years		21,673		17,442		4,231
Proprietary software	3-5 years		22,469		14,719		7,750
Patent	16 years		17,479		3,309		14,170
Total other intangible assets    —net		$	299,833	$	153,565	$	146,268

December 31, 2021	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	196,323	$	74,010	$	122,313
Covenants not to compete	4-5 years		32,622		25,113		7,509
Trade names	1-5 years		20,403		15,139		5,264
Proprietary software	3-5 years		22,077		11,155		10,922
Patent	16 years		17,479		2,490		14,989
Total other intangible assets    —net		$	288,904	$	127,907	$	160,997

Intangible assets with finite lives are stated at cost, less accumulated amortization and impairment losses, if any. These intangible assets are amortized using the straight-line method over the estimated useful lives of the assets. Amortization expense was $8.7 million and $27.6 million for the three and nine months ended September 30, 2022, respectively, and $8.9 million and $25.9 million for the three and nine months ended September 30, 2021, respectively.

Future amortization expense is estimated to be as follows for each of the five following years and thereafter:

December 31,
2022 (remaining)		8,135
2023		28,163
2024		23,588
2025		16,897
2026 and thereafter		69,485
Total	$	146,268

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9. ACCOUNTS PAYABLE AND OTHER ACCRUED LIABILITIES

Accounts payable and other accrued liabilities consisted of the following:

	September 30,		December 31,
	2022		2021
Accounts payable	$	19,023	$	24,167
Accrued expenses		12,312		14,906
Other business acquisitions purchase    price obligations		505		502
Contract liabilities		23,270		27,907
Other current liabilities		3,206		1,454
Total accounts payable and    other accrued liabilities	$	58,316	$	68,936

10. ACCRUED PAYROLL AND BENEFITS

Accrued payroll and benefits consisted of the following:

	September 30,		December 31,
	2022		2021
Accrued bonuses	$	7,036	$	13,438
Accrued paid time off		1,309		1,144
Accrued payroll		7,749		6,547
Accrued other		4,383		4,842
Total accrued payroll and benefits	$	20,477	$	25,971

11. INCOME TAXES

The Company calculates its interim income tax provision in accordance with ASC Topic 270, Interim Reporting (“ASC 270”), and ASC 740. The Company’s effective tax rate (“ETR”) from continuing operations was 3.5% and (9.9)% for the three and nine months ended September 30, 2022, respectively, and 28.8% and (2.8)% for the three and nine months ended September 30, 2021, respectively. Income tax (benefit) expense recorded by the Company during the three and nine months ended September 30, 2022 was $(0.2) million and $1.9 million, respectively. The income tax expense recorded by the Company during the three and nine months ended September 30, 2021 was $0.9 million and $0.6 million, respectively. The difference between the ETR and federal statutory rate of 21.0% is primarily attributable to items recorded for U.S. GAAP but permanently disallowed for U.S. federal income tax purposes, recognition of a U.S. federal and state valuation allowance and state and foreign income tax provisions.

A valuation allowance is recorded when it is more-likely-than-not some of the Company’s deferred tax assets may not be realized. Significant judgment is applied when assessing the need for a valuation allowance and the Company considers future taxable income, reversals of existing deferred tax assets and liabilities and ongoing prudent and feasible tax planning strategies, in making such assessment. As of September 30, 2022, the Company’s U.S. federal, state and various foreign net deferred tax assets are not more-likely-than-not to be realized and a full valuation allowance is maintained.

The Company records uncertain tax positions in accordance with ASC 740, on the basis of a two-step process in which (i) the Company determines whether it is more likely than not a tax position will be sustained on the basis of the technical merits of such position and (ii) for those tax positions meeting the more-likely-than-not recognition threshold, the Company would recognize the largest amount of tax benefit that is more than 50.0% likely to be realized upon ultimate settlement with the related tax authority. The Company has determined it has no uncertain tax positions as of September 30, 2022. The Company classifies interest and penalties recognized on uncertain tax positions as a component of income tax expense.

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12. DEBT

Debt consisted of the following:

	September 30,			December 31,
	2022			2021
Term loan facility	$	166,250		$	175,000
Revolving line of credit		—			—
Less deferred debt issuance costs		(1,855	)		(2,244	)
Total debt		164,395			172,756
Less current portion of long-term debt		(8,750	)		(10,938	)
Long-term debt, less current portion	$	155,645		$	161,818

Deferred Financing Costs—Costs relating to debt issuance have been deferred and are presented as discounted against the underlying debt instrument. These costs are amortized to interest expense over the terms of the underlying debt instruments.

2021 Credit Facility—On April 27, 2021, the Company entered into a Senior Secured Credit Agreement providing for a $300.0 million credit facility comprised of a $175.0 million term loan and a $125.0 million revolving line of credit (the “2021 Credit Facility”), and used a portion of the proceeds from the 2021 Credit Facility to repay all amounts outstanding under the 2020 Credit Facility (as defined below). The 2021 revolving credit facility includes a $20.0 million sublimit for the issuance of letters of credit. Subject to certain exceptions, all amounts under the 2021 Credit Facility will become due on April 27, 2026. The Company has the option to borrow incremental term loans or request an increase in the aggregate commitments under the revolving credit facility up to an aggregate amount of $150.0 million subject to the satisfaction of certain conditions.

The 2021 Credit Facility term loan must be repaid in quarterly installments and shall amortize at the following future quarterly rates:

Date	Quarterly Installment Rate
December 31, 2022	1.25%
March 31, 2023	1.25%
June 30, 2023	1.25%
September 30, 2023	1.25%
December 31, 2023	1.88%
March 31, 2024	1.88%
June 30, 2024	1.88%
September 30, 2024	1.88%
December 31, 2024	1.88%
March 31, 2025	1.88%
June 30, 2025	1.88%
September 30, 2025	1.88%
December 31, 2025	2.50%
March 31, 2026	2.50%
April 27, 2026	Remaining balance

Repayments of quarterly installments were scheduled to begin with the quarter ended December 31, 2021. The first quarterly installment repayment, amounting to $2.2 million, was billed and charged by the lenders in January 2022. Exclusive of the payment made in respect of the quarter ended December 31, 2021, the three quarterly installment repayments for the nine months ended September 30, 2022 amounted to $6.6 million.

The 2021 Credit Facility term loan and the revolver bear interest subject to the Company’s leverage ratio and LIBOR as follows:

Pricing Tier	Consolidated Leverage Ratio	Senior Credit Facilities LIBOR			Senior Credit Facilities Base Rate			Commitment Fee			Letter of Credit Fee
1	≥ 3.75x to 1.0		2.50	%		1.50	%		0.25	%		2.50	%
2	< 3.75x to 1.0 but ≥ 3.25 to 1.0		2.25			1.25			0.23			2.25
3	<3.25x to 1.0 but ≥ 2.50 to 1.0		2.00			1.00			0.20			2.00
4	<2.50x to 1.0 but ≥ 1.75 to 1.0		1.75			0.75			0.15			1.75
5	<1.75x to 1.0		1.50			0.50		0.15				1.50

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On January 27, 2022, the Company entered into an interest rate swap transaction fixing the floating component of the interest rate on $100.0 million of borrowings to 1.39% until January 27, 2025. Additionally, effective September 1, 2022, the Company received an interest rate reduction of 0.05% under the 2021 Credit Facility based on the Company’s achievement of certain sustainability and environmental, social and governance related objectives as provided for in the 2021 Credit Facility.

The 2021 Credit Facility includes a number of covenants imposing certain restrictions on the Company’s business, including, among other things, restrictions on the Company’s ability, subject to certain exceptions and baskets, to incur indebtedness, incur liens on its assets, agree to any additional negative pledges, pay dividends or repurchase stock, limit the ability of its subsidiaries to pay dividends or distribute assets, make investments, enter into any transaction of merger or consolidation, liquidate, wind-up or dissolve, or convey any part of its business, assets or property, or acquire the business, property or assets of another person, enter into sale and leaseback transactions, enter into certain transactions with affiliates, engage in any material line of business substantially different from those engaged on the closing date, modify the terms of indebtedness subordinated to the loans incurred under the 2021 Credit Facility and modify the terms of its organizational documents. The 2021 Credit Facility also includes financial covenants requiring the Company to remain below a maximum total net leverage ratio of 4.25 times, which steps down to 4.00 times beginning with the fiscal quarter ending December 31, 2022 through and including the fiscal quarter ending September 30, 2023 and then to 3.75 times beginning with the fiscal quarter ending December 31, 2023, and a minimum fixed charge coverage ratio of 1.25 times. As of September 30, 2022, the Company’s consolidated total leverage ratio (as defined in the 2021 Credit Facility) was 1.2 times and the Company was in compliance with all covenants under the 2021 Credit Facility.

The 2021 Credit Facility requires customary mandatory prepayments of the term loan and revolver and cash collateralization of letters of credit, subject to customary exceptions, including 100.0% of the proceeds of debt not permitted by the 2021 Credit Facility, 100.0% of the proceeds of certain dispositions, subject to customary reinvestment rights, where applicable, and 100.0% of insurance or condemnation proceeds, subject to customary reinvestment rights, where applicable. The 2021 Credit Facility also includes customary events of default and related acceleration and termination rights.

The weighted average interest rate on the 2021 Credit Facility for the nine months ended September 30, 2022 was 2.9%.

The Company’s obligations under the 2021 Credit Facility are guaranteed by certain of the Company’s existing and future direct and indirect subsidiaries, and such obligations are secured by substantially all of the Company’s assets, including the capital stock or other equity interests in those subsidiaries.

2020 Credit Facility—On April 13, 2020, the Company entered into a Unitranche Credit Agreement (the “2020 Credit Facility”) providing for a $225.0 million credit facility comprised of a $175.0 million term loan and a $50.0 million revolving credit facility. The 2020 Credit facility was repaid in full in in April 2021. The resulting loss on extinguishment upon repayment of the 2020 Credit Facility in April 2021, amounted to $4.1 million, of which $1.0 million was related to fees paid and $3.1 related to unamortized debt issuance costs. Total loss on extinguishment is recorded in interest expense, net within the unaudited condensed consolidated statement of operations for the nine months ended September 30, 2021.

Equipment Line of Credit—In the first quarter of 2022, the Company entered into a new $10.0 million equipment leasing facility for the purchase of equipment and related freight, installation costs and taxes paid. Any unused capacity on this equipment leasing facility expires on December 30, 2022. Interest on the line of credit is determined based on a three-year swap rate at the time of funding. Equipment leased through this line of credit meets the finance lease criteria as per ASC 842 and accordingly is accounted for as finance lease right-of-use assets and a finance lease liabilities (Note 6).

The following is a schedule of the aggregate annual maturities of long-term debt presented on the unaudited condensed consolidated statement of financial position, based on the terms of the 2021 Credit Facility:

September 30,
2023	$	8,750
2024		13,125
2025		13,125
2026		131,250
Total	$	166,250

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13. FAIR VALUE OF FINANCIAL INSTRUMENTS

The following financial instruments are measured at fair value on a recurring basis using significant unobservable inputs (Level 3):

	September 30,		December 31,
	2022		2021
Interest rate swap	$	6,313	$	—
Total assets	$	6,313	$	—
Business acquisitions contingent consideration,    current	$	3,967	$	31,450
Business acquisitions contingent consideration,    long-term		2,810		4,350
Conversion option		24,730		23,081
Total liabilities	$	31,507	$	58,881

The estimated fair value amounts shown above are not necessarily indicative of the amounts that the Company would realize upon disposition, nor do they indicate the Company’s intent or ability to dispose of the financial instrument.

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis:

	Interest Rate Swap		Total Assets		Business Acquisitions Contingent Consideration, Current			Business Acquisitions Contingent Consideration, Long-term			Conversion    Option		Total Liabilities
Balance—at January 1, 2021	$	—	$	—	$	49,902		$	4,565		$	20,886	$	75,353
Acquisitions		—		—		1,000			6,004			—		7,004
Changes in fair value included in earnings		—		—		13,774			10,261			1,651		25,686
Payment of contingent consideration        payable		—		—		(50,154	)		—			—		(50,154	)
Reclass of long term to short term       contingent liabilities		—		—		16,630			(16,630	)		—		—
Balance—at September 30, 2021	$	—	$	—	$	31,152		$	4,200		$	22,537	$	57,889
Balance—at January 1, 2022	$	—		—	$	31,450		$	4,350		$	23,081	$	58,881
Acquisitions		—		—		—			1,216			—		1,216
Changes in fair value included in earnings		6,313		6,313		330			(390	)		1,649		1,589
Payment of contingent consideration        payable		—		—		(30,179	)		—			—		(30,179	)
Reclass of long term to short term       contingent liabilities		—		—		2,366			(2,366	)		—		—
Balance—at September 30, 2022	$	6,313	$	6,313	$	3,967		$	2,810		$	24,730	$	31,507

Quantitative Information about Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3):

Interest Rate Swap—The interest rate swap fair value is estimated based on a mid-market price for the swap as of the close of business of the reporting period. The fair value is prepared by discounting future cash flows of the swap to arrive at a current value of the swap. Forward curves and volatility levels inputs are determined on the basis of observable market inputs when available and on the basis of estimates when observable market inputs are not available. The Company does not apply hedge accounting but instead recognizes the instrument at fair value on the unaudited condensed consolidated statement of financial position within other assets, with changes in fair value recognized in earnings in each reporting period. The change in fair value of $2.3 million and $6.3 million for the three and nine months ended September 30, 2022, respectively was recognized as a component of other expense on the Company's unaudited condensed consolidated statements of operations.

Business Acquisitions Contingent Consideration—The fair value of the contingent consideration payable associated with the acquisition of CTEH, MSE and Sensible was determined using a Monte Carlo simulation of earnings in a risk-neutral Geometric Brownian Motion framework. The fair value of the contingent consideration payable associated with the acquisition of EnvStd was determined using a Probabilistic (Scenario Based) method. The fair values of the contingent consideration payables for the other acquisitions were calculated based on expected target achievement amounts, which are measured quarterly and then subsequently

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adjusted to actuals at the target measurement date. The method used to price these liabilities is considered level 3 due to the subjective nature of the unobservable inputs used to determine the fair value. The input is the expected achievement of earn-out thresholds.

Conversion Option—Upon the Company’s initial public offering ("IPO"), the fair value of the conversion option associated with the issuance of the Convertible and Redeemable Series A-2 Preferred Stock (Note 15) was estimated using a “with-and-without” method. The “with-and-without” methodology considers the value of the security on an as-is basis and then without the embedded conversion premium. The difference between the two scenarios is the implied fair value of the embedded derivative. The unobservable input is the required rate of return on the Series A-2. The considerable quantifiable inputs in the valuation relate to the timing of conversions or redemptions.

14. COMMITMENTS AND CONTINGENCIES

Leases—The Company leases office facilities over various terms expiring through 2031. Certain of these operating leases contain rent escalation clauses. The Company also has office equipment leases that expire through 2027 (Note 6 and 12).

Other Commitments—The Company has commitments under the 2021 Credit Facility, its equipment line of credit and its lease obligations (Note 6 and 12).

Contingencies—The Company is subject to purchase price contingencies related to earn-outs associated with certain acquisitions (Note 7 and 13).

Legal—In the normal course of business, the Company is at times subject to pending and threatened legal actions. In management’s opinion, any potential loss resulting from the resolution of these matters is not expected to have a material effect on the unaudited condensed consolidated results of operations, financial position or cash flows of the Company.

15. CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK

On April 13, 2020, the Company entered into an agreement to issue 17,500 shares of the Convertible and Redeemable Series A-2 Preferred Stock with a par value of $0.0001 per share and a detachable warrant to purchase shares of the Company’s common stock with a 10-year life, in exchange for gross proceeds of $175.0 million, net of $1.3 million debt issuance costs. Before the Company’s IPO, each share of Convertible and Redeemable Series A-2 Preferred Stock accrued dividends at the rate of 15.0% per annum, with respect to dividends that were paid in cash, and 14.2% per annum, with respect to dividends that were accrued. The Company paid dividends on shares of the Convertible and Redeemable Series A-2 Preferred Stock of $4.1 million during both the three months ended September 30, 2022 and September 30, 2021, and $12.3 million during both the nine months ended September 30, 2022 and September 30, 2021.

At issuance, the Company determined that the Convertible and Redeemable Series A-2 Preferred Stock and the detachable warrant, were required to be accounted for separately.

Upon the Company’s IPO, the Convertible and Redeemable Series A-2 Preferred Stock terms automatically updated to the following: (i) no mandatory redemption, (ii) no stated value cash repayment obligation other than in the event of certain defined liquidation events, (iii) only redeemable at the Company’s option, (iv) the instrument became convertible into common stock beginning on the four year anniversary of issuance at a 15.0% discount to the common stock market price (with a limit of $60.0 million in stated value of Convertible and Redeemable Series A-2 Preferred Stock eligible to be converted in any 60-day period prior to the seventh anniversary of issuance and the amount of stated value of the Convertible and Redeemable Series A-2 Preferred Stock eligible for conversion limited to $60.0 million during year 5 and $120.0 million (which includes the aggregate amount of the stated value of the Convertible and Redeemable Series A-2 Preferred Stock and any accrued but unpaid dividends added to such stated value of any shares of Convertible and Redeemable Series A-2 Preferred Stock converted in year 5) during year 6), (v) the dividend rate stepped down to 9.0% per year with required quarterly cash payments, (vi) in an event of noncompliance, the dividend rate shall increase to 12.0% per annum for the first 90-day period from and including the date the noncompliance event occurred, and thereafter shall increase to 14.0% per annum, (vii) the debt incurrence test ratio increased to 4.5 times, (viii) the total leverage cap covenant was removed, and (ix) minimum repayment amount dropped down from $50.0 million to $25.0 million.

The Company may, at its option on any one or more dates, redeem all or a minimum portion (the lesser of (i) $25.0 million in aggregate stated value of the Convertible and Redeemable Series A-2 Preferred Stock and (ii) all of the Convertible and Redeemable Series A-2 Preferred Stock then outstanding) of the outstanding Convertible and Redeemable Series A-2 Preferred Stock in cash.

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With respect to any redemption of any share of the Convertible and Redeemable Series A-2 Preferred Stock prior to the third-year anniversary, the Company is subject to a make whole penalty in which the holders of the Convertible and Redeemable Series A-2 Preferred Stock are guaranteed a minimum repayment equal to outstanding redeemed stated value plus three years of dividends accrued or accruable thereon.

The Convertible and Redeemable Series A-2 Preferred Stock does not meet the definition of a liability pursuant to “ASC 480- Distinguishing Liabilities from Equity.” However, as (i) the instrument is redeemable upon a change of control as defined in the certificate of designations governing the terms of the Convertible and Redeemable Series A-2 Preferred Stock, and (ii) the Company cannot assert it would have sufficient authorized and unissued shares of common stock to settle all future conversion requests due to the variable conversion terms, the instrument is redeemable upon the occurrence of events that are not solely within the control of the Company, and therefore the Company classifies the Convertible and Redeemable Series A-2 Preferred Stock as mezzanine equity. Subsequent adjustment of the carrying value of the instrument is required if the instrument is probable of becoming redeemable. As of September 30, 2022, the Company has determined that a change of control is not probable. Additionally, as of September 30, 2022, the Company has determined that it is not probable that there will be a future conversion request that the Company is unable to settle with authorized and issued shares based on the Company’s current stock price and available shares as well as the Company’s monitoring efforts to ensure there are a sufficient number of shares available to settle any conversion request. Therefore, as of September 30, 2022, the Company has determined that the instrument is not probable of becoming redeemable, and does not believe subsequent adjustment of the carrying value of the instrument will be necessary. The Convertible and Redeemable Series A-2 Preferred Stock had an aggregate liquidation preference of $182.2 million as of September 30, 2022 and December 31, 2021.

The Convertible and Redeemable Series A-2 Preferred Stock contains embedded features that are required to be bifurcated and are subject to separate accounting treatment from the instrument itself. At issuance, these embedded features consisted of (i) a contingent dividend feature associated with the decrease in the dividend rate upon an IPO and (ii) a conversion option of the preferred shares to shares of common stock beginning on the fourth-year anniversary of the issuance date. Upon the Company’s IPO, the embedded derivative only consisted of the conversion option. As of September 30, 2022 and December 31, 2021, this conversion embedded feature had a net fair value of $24.7 million and $23.1 million, respectively. The change in value of $0.5 million and $1.6 million for the three and nine months ended September 30, 2022, respectively, was recorded to other expense.

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16. STOCKHOLDERS’ EQUITY

Authorized Capital Stock—The Company was authorized to issue 190,000,000 shares of common stock, with a par value of $0.000004 per share as of September 30, 2022 and December 31, 2021.

Warrants—In May 2015, the Company issued warrants to acquire 116,350 shares of Common Stock at a price of approximately $17.19 per share to the placement agent as consideration for backstopping the financing completed in May 2015. These warrants were exercised in full as a cashless transaction during the first quarter of 2021. As a result of this cashless transaction, the resulting number of shares issued was 67,713 shares.

Common Stock Issuances—The Company issued the following shares of common stock:

	Three Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Total (in thousands)		Shares		Average Price per Share		Total (in thousands)
Acquisitions		—	$	—	$	—		62,738	$	52.18	$	3,274
Exercise of options		28,111		11.70		329		354,918		8.30		2,946
Total		28,111	$	11.70	$	329		417,656	$	14.89	$	6,220
	Nine Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Total (in thousands)		Shares		Average Price per Share		Total (in thousands)
Acquisitions		—	$	—	$	—		143,800	$	41.86	$	6,020
Exercise of warrants (1)		—		—		—		67,713		17.19		—
Exercise of options		62,293		13.04		812		779,068		7.74		6,032
Restricted shares, net (1)		25,289		66.58		—		38,929		31.31		—
Payment of earn-out liability		—		—		—		539,607		46.33		25,000
Payment of purchase price    true up		—		—		—		24,200		44.81		1,084
Total		87,582	$	28.50	$	812		1,593,317	$	25.43	$	38,136

(1) Represents the non-cash release of common shares due to the exercise of warrants and the vesting of restricted stock.

Employee Equity Incentive Plans—The Company has two plans under which stock-based awards have been issued: (i) the Montrose Amended & Restated 2017 Stock Incentive Plan (“2017 Plan”) and (ii) the Montrose Amended & Restated 2013 Stock Option Plan (“2013 Plan”) (collectively the “Plans”).

As of September 30, 2022, and September 30, 2021, there was $152.5 million and $15.0 million, respectively, of total unrecognized stock compensation expense related to unvested options, restricted stock and stock appreciation rights granted under the Plans. Such unrecognized expense is expected to be recognized over a weighted-average four year period. The following number of shares were authorized to be issued and available for grant:

	September 30, 2022
	2017 Plan		2013 Plan		Total
Shares authorized to be issued		5,140,112		2,037,019		7,177,131
Shares available for grant(1)		364,949		—		364,949
	September 30, 2021
	2017 Plan		2013 Plan		Total
Shares authorized to be issued		3,944,750		2,047,269		5,992,019
Shares available for grant		1,593,287		—		1,593,287

(1) In January 2022 the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued

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under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. Shares available for grant exclude awards of stock appreciation rights approved in December 2021 that are subject to vesting based on the achievement of certain market conditions, which have not yet been, and may not be, achieved. See footnote 1 to the table in Common Stock Reserved for Future Issuance below for additional information regarding the December 2021 grant.

Total stock compensation expense for the Plans was as follows:

	Three Months Ended September 30,
	2022										2021
	2017 plan						2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		SARs		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	404	$	—	$	—	$	—	$	404	$	282	$	—	$	—	$	282
Selling, general and    administrative expense		2,216		6,083		2,315		—		10,614		1,844		237		2		2,083
Total	$	2,620	$	6,083	$	2,315	$	—	$	11,018	$	2,126	$	237	$	2	$	2,365
	Nine Months Ended September 30,
	2022										2021
	2017 plan						2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		SARs		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	1,069	$	—	$	—	$	—	$	1,069	$	1,178	$	—	$	10	$	1,188
Selling, general and    administrative expense		6,449		17,892		6,965		—		31,306		4,638		749		11		5,399
Total	$	7,518	$	17,892	$	6,965	$	—	$	32,375	$	5,816	$	749	$	21	$	6,587

Montrose Amended & Restated 2017 Stock Incentive Plan

Restricted Stock Awards and Restricted Stock Units—The Company issues restricted stock awards ("RSAs") to certain 2017 Plan participants as Director’s compensation. There were zero RSAs granted during both the three months ended September 30, 2022 and September 30, 2021, respectively. There were 10,920 and 19,066 RSAs granted during the nine months ended September 30, 2022 and September 30, 2021, respectively. These RSAs vest one year from the date of grant, or, in each case, in full upon a change in control, subject to the participant’s continued service as a Director throughout such date, or upon retirement. Members of the Board of Directors that receive stock-based compensation are treated as employees for accounting purposes.

During the year ended December 31, 2021, the Board of Directors approved the grant of 1,671,391 restricted stock units (“RSUs”) to certain executives and selected employees of the Company under the 2017 Plan. These RSUs represent the right to receive one share of the Company’s common stock upon vesting. These incentives were designed by the Board, in coordination with the Company’s compensation advisors, to (i) retain selected employees of the Company for a minimum of 5 years, (ii) reward selected employees for the Company’s significant outperformance and stockholder value creation in 2021, and (iii) provide incentives to selected employees of the Company to accelerate value creation for stockholders and other stakeholders over the next five-year period. With respect to 1,355,182 RSUs, 50.0% will vest on each of the 4th and 5th anniversaries of the date of grant, subject to continued service through each such date. With respect to the remaining 316,209 RSUs (“The Performance-Vested RSUs”), 50.0% will vest on each of the 4th and 5th anniversaries of the date of grant, subject to continued service through each such date and further subject to Company achieving $90.0 million in adjusted EBITDA (as reported) for any trailing twelve-month period from and after December 31, 2022. If the Performance Criteria is not met prior to the 4th anniversary of the date of grant, none of the Performance-Vested RSUs will vest at such time, and if the Performance Criteria is subsequently met prior to the 5th anniversary of the date of grant, all of the Performance-Vested RSUs will vest at such time, subject to continued service through such date. If the Performance Criteria is not met by the 5th anniversary of the date of grant, all of the Performance-Vested RSUs will be forfeited.

During 2021 and 2022, the Board of Directors approved the creation of certain supplemental incentive plans (“SI Plans”) for selected employees to reward exceptional performance. These SI Plans provide supplemental bonus opportunities payable in RSUs under the 2017 Plan upon meeting certain financial performance targets. There were 95,404 RSUs issued under these SI Plans during the nine months ended September 30, 2022 and zero RSUs issued under these SI plans during the nine months ended September 30, 2021. These RSUs vest four years from the date of grant, subject to continued service through such date.

During 2021, the Board approved and reserved for future issuance an aggregate of 135,517 RSUs (the “Future RSU Pool”) to be granted under the 2017 Plan to certain of its executives and selected employees. Final determination and allocation of the awards

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under the Future RSU Pool will be determined on December 16, 2025 based on individual performance and continued service through such date. Any RSUs granted under the Future RSU Pool will vest on December 16, 2026, subject to continued service through such date.

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RSA and RSU activity was as follows:

	Nine Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Fair Value (in thousands)		Shares		Average Price per Share		Fair Value (in thousands)
Awards granted		106,324	$	46.82	$	4,978		19,066	$	36.99	$	705

There were no awards granted during the three months ended September 30, 2022 and September 30, 2021. There were an aggregate of zero and 25,289 shares underlying RSAs and RSUs that became fully vested and were released as unrestricted shares of common stock during the three and nine months ended September 30, 2022, respectively. During the three and nine months ended September 30, 2021, there were an aggregate of zero and 38,929 shares underlying RSAs that became fully vested and were released as unrestricted shares of common stock, respectively. There was an aggregate of 2,064,197 and 286,239 shares underlying outstanding RSA and RSU awards as of September 30, 2022 and September 30, 2021, respectively. There were no forfeitures of RSAs or RSUs during the three and nine months ended September 30, 2022 and September 30, 2021.

Stock Appreciation Rights— During the year ended December 31, 2021, the Board of Directors approved the grant of 3,000,000 units of stock appreciation rights (“SARs”) to certain executives and selected employees under the 2017 Plan. These SARs represent the right to receive, upon exercise, a payment equal to the excess of (a) the fair market value of one share of the Company’s common stock, over (b) an exercise price of $66.79, payable, at the Company’s election, in cash or shares of common stock. These SARs vest on the 5th anniversary of the date of grant based on achievement of performance hurdles over a five year period, subject to continued service on the vesting date. The performance hurdles shall be deemed achieved if the average trading price per share of the Company’s common stock equals or exceeds the following stock prices:

SARs Stock Price Performance Hurdle		Portion of SARs Subject to Performance Hurdle
$	133.58	1/3
$	166.98	1/3
$	200.37	1/3

The performance hurdles shall be deemed achieved if the average trading price per share of the Company’s common stock equals or exceeds the applicable stock price performance hurdle set forth above for the trading days falling in a consecutive 20-day period prior to the vesting date. The SARs expire 10 years after the grant date. The fair value of these SARs at the grant date was $46.0 million. The weighted average remaining contract life of these SARs as of September 30, 2022 was 9.21 years.

Options—Options issued to all optionees under the 2017 Plan vest over four years from the date of issuance (or earlier vesting start date, as determined by the Board of Directors) as follows: one half on the second anniversary of date of grant and the remaining half on the fourth anniversary of the date of grant, with the exception of certain annual grants to certain executive officers, which vest annually over a 3-year and 1-year period. The following summarizes the options activity of the 2017 Plan:

	Options to Purchase Common Stock			Weighted- Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The- Money Options (in Thousands)
Outstanding as of January 1, 2021		1,840,229		$	23	$	12		9.09	$	15,598
Granted		264,470			40		22		—		—
Forfeited/ cancelled		(29,025	)		28		—		—		—
Expired		(1,250	)		18		—		—		—
Exercised		(66,875	)		22		—		—		2,078
Outstanding as of September 30, 2021		2,007,549			25		14		8.53		73,724
Outstanding as of January 1, 2022		2,036,729		$	26	$	14		8.30	$	91,030
Granted		664,784			44		16		—		—
Forfeited/ cancelled		(60,167	)		36		—		—		—
Exercised		(26,258	)		22		—		—		671
Outstanding as of September 30, 2022		2,615,088		$	30	$	15		8.04	$	18,784
Exercisable at September 30, 2022		1,010,302			26		—		7.48		9,966

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The following weighted-average assumptions were used in the Black-Sholes option-pricing model calculation:

	September 30,			September 30,
	2022			2021
Common stock value (per share)	$	43.72		$	39.83
Expected volatility		33.45			58.34
Risk-free interest rate		1.94	%		0.77	%
Expected life (years)		6.45			6.32
Forfeiture rate	None			None
Dividend rate	None			None

Montrose Amended & Restated 2013 Stock Option Plan—The following summarizes the activity of the 2013 Plan:

	Options to Purchase Common Stock			Weighted- Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The- Money Options (in Thousands)
Outstanding as of January 1, 2021		1,787,869		$	6	$	1		5.40	$	43,867
Expired		(625	)		6		—		—		—
Exercised		(710,568	)		6		—		—		33,480
Outstanding as of September 30, 2021		1,076,676			6		2		4.65		59,532
Outstanding as of January 1, 2022		897,674		$	6	$	2		4.37	$	57,529
Expired		(125	)		6		—		—		—
Exercised		(36,035	)		6		—		—		1,425
Outstanding as of September 30, 2022		861,514		$	6	$	2		3.61	$	23,448
Exercisable at September 30, 2022		861,514			6		—		3.61		23,448

Total shares outstanding from exercised options were 1,271,383 shares and 1,028,268 shares as of September 30, 2022 and September 30, 2021, respectively.

Common Stock Reserved for Future Issuances—The Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following:

	September 30,
	2022		2021
Montrose 2013 Stock Incentive Plan		861,514		2,047,269
Montrose 2017 Stock Incentive Plan(1)		7,757,995		3,944,750
Total		8,619,509		5,992,019

(1) In January 2022, the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. The Company expects to have sufficient shares available under the 2017 Plan to satisfy the future settlement of outstanding awards. Shares reserved for future issuance include 3,000,000 shares underlying the 3,000,000 performance SARs granted in December 2021 that are subject to vesting based on the achievement of certain market conditions. Assuming achievement at the highest price performance hurdle, approximately 2,000,000 shares of common stock would be issued upon vesting of these performance SARs. To date, none of the market conditions have been achieved.

17. NET LOSS PER SHARE

Basic net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during each period. The Convertible and Redeemable Series A-2 Preferred Stock is considered a participating security during the applicable period. Net losses are not allocated to the Convertible and Redeemable Series A-2 stockholders, as they were not contractually obligated to share in the Company’s losses.

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Diluted net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of common and dilutive common equivalent shares outstanding for the period using the treasury-stock method or the as-converted method. Potentially dilutive shares are comprised of RSAs, RSUs, SARs and shares of common stock underlying stock options outstanding under the Plans. During the three and nine months ended September 30, 2022 and September 30, 2021, there is no difference in the number of shares used to calculate basic and diluted shares outstanding during the applicable period due to the Company’s net loss attributable to common stockholders and potentially dilutive shares being anti-dilutive.

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(In thousands, except for net loss per share)	2022			2021			2022			2021
Net (loss) income	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)
Convertible and redeemable series A-2 preferred    stock dividend		(4,100	)		(4,100	)		(12,300	)		(12,300	)
Net loss attributable to common stockholders    –basic and diluted		(9,820	)		(1,874	)		(33,307	)		(36,153	)
Weighted-average common shares outstanding –    basic and diluted		29,691			26,220			29,677			25,798
Net loss per share attributable to common    stockholders –basic and diluted	$	(0.33	)	$	(0.07	)	$	(1.12	)	$	(1.40	)

The following equity shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive:

	September 30,
	2022		2021
Stock options		3,476,602		1,686,688
Restricted stock		1,777,958		28,623
SARs		3,000,000		—

18. SEGMENT INFORMATION

The Company has three operating and reportable segments: Assessment, Permitting and Response, Measurement and Analysis and Remediation and Reuse. These segments are monitored separately by management for performance against budget and prior year and are consistent with internal financial reporting. The Company’s operating segments are organized based upon primary services provided, the nature of the production process, their type of customers, methods used to distribute the products and the nature of the regulatory environment.

Segment Adjusted EBITDA is the primary measure of operating performance for all three operating segments. Segment Adjusted EBITDA is the calculated Company’s Earnings before Interest, Tax, Depreciation and Amortization (“EBITDA”), adjusted to exclude certain transactions such as stock-based compensation, acquisition costs and fair value changes in financial instruments, amongst others. The Chief Operating Decision Maker (“CODM”) does not review segment assets as a measure of segment performance.

Corporate and Other includes costs associated with general corporate overhead (including executive, legal, finance, safety, human resources, marketing and IT related costs) that are not directly related to supporting operations. Overhead costs that are directly related to supporting operations (such as insurance, software, licenses, shared services and payroll processing costs) are allocated to the operating segments on a basis that reasonably approximates an estimate of the use of these services.

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Segment revenues and Adjusted EBITDA consisted of the following:

	Three Months Ended September 30,
	2022					2021
			Segment					Segment
	Segment		Adjusted			Segment		Adjusted
	Revenues		EBITDA			Revenues		EBITDA
Assessment, Permitting and Response	$	46,414	$	9,820		$	63,412	$	15,719
Measurement and Analysis		43,754		8,483			38,752		8,283
Remediation and Reuse		40,144		7,010			30,414		5,472
Total Operating Segments		130,312		25,313			132,578		29,474
Corporate and Other		—		(6,940	)		—		(7,987	)
Total	$	130,312	$	18,373		$	132,578	$	21,487
	Nine Months Ended September 30,
	2022					2021
			Segment					Segment
	Segment		Adjusted			Segment		Adjusted
	Revenues		EBITDA			Revenues		EBITDA
Assessment, Permitting and Response	$	142,051	$	30,252		$	209,379	$	46,379
Measurement and Analysis		125,739		21,852			111,309		22,634
Remediation and Reuse		137,112		22,059			81,931		12,262
Total Operating Segments		404,902		74,163			402,619		81,275
Corporate and Other		—		(22,826	)		—		(22,026	)
Total	$	404,902	$	51,337		$	402,619	$	59,249

Presented below is a reconciliation of the Company’s segment measure to net loss:

	For the Three Months Ended September 30,						For the Nine Months Ended September 30,
	2022			2021			2022			2021
Total	$	18,373		$	21,487		$	51,337		$	59,249
Interest expense, net		(1,400	)		(1,722	)		(4,010	)		(11,208	)
Income tax benefit (expense)		208			(902	)		(1,892	)		(648	)
Depreciation and amortization		(11,504	)		(11,471	)		(35,928	)		(33,145	)
Stock-based compensation		(11,018	)		(2,365	)		(32,375	)		(6,587	)
Start-up losses and investment in new services		(1,278	)		(1,186	)		(2,949	)		(3,276	)
Acquisition costs		(368	)		(913	)		(1,354	)		(1,656	)
Fair value changes in financial instruments		1,808			(531	)		4,664			(1,651	)
Fair value changes in business acquisition    contingencies		(59	)		—			3,472			(24,035	)
Expenses related to financing transactions		—			—			(7	)		(50	)
Other losses or expenses (1)		(482	)		(171	)		(1,965	)		(846	)
Net (loss) income	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)

(1) In 2022, amounts include costs associated with the closing of a lab and severance costs related to a restructuring within our soil remediation business. In 2021, amounts include non-operational charges incurred due to the remeasurement of finance leases as a result of the adoption of ASC 842 and costs related to the implementation of a new ERP.

19. RELATED-PARTY TRANSACTIONS

The Company did not have any related party transactions during the three and nine months ended September 30, 2022 and September 30, 2021.

20. DEFINED CONTRIBUTION PLAN

On January 1, 2014, the Company established the Montrose Environmental Group 401(k) Savings Plan (the “401(k) Savings Plan”). As of September 30, 2022, and December 31, 2021, plan participants may defer up to 85.0% of their eligible wages for the year, up to the Internal Revenue Service dollar limit and catch-up contribution allowed by law. Prior to May 22, 2020, the Company provided employer matching contributions equal to 100.0% of the first 3.0% of the participant’s compensation and 50.0% of the

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participant’s elective deferrals that exceed 3.0% but do not exceed 4.0% of the participant’s compensation. Beginning on May 22, 2020, the Company temporarily ceased making employer contributions. Employer contributions were reinstated beginning on April 23, 2021. Employer contributions under the 401(k) Savings Plan were $1.2 million and $4.6 million for the three and nine months ended September 30, 2022, respectively, and $0.8 million and $1.6 million for the three and nine months ended September 30, 2021, and are included within selling, general, and administrative expense on the unaudited condensed consolidated statements of operations.

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FORWARD-LOOKING STATEMENTS

This Quarterly Report on Form 10-Q contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. These forward-looking statements relate to matters such as our industry, business strategy, goals and expectations concerning our market position, future operations, margins, profitability, capital expenditures, liquidity, capital resources and other financial and operating information. We use words such as “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “future,” “intend,” “may,” “plan,” “position,” “potential,” “predict,” “project,” “seek,” “should,” “target,” “will” and similar terms and phrases to identify forward-looking statements in this filing. All of our forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially from those that we are expecting, including:

•our limited operating history;

•our history of losses and ability to achieve profitability;

•general global economic, business and other conditions, including inflation, the cyclical nature of our industry and the significant fluctuations in events that impact our business;

•the impact of the COVID-19 pandemic on our business operations and on local, national and global economies;

•the parts of our business that depend on difficult to predict natural or manmade events and the fluctuations in our revenue and customer concentration as a result thereof;

•the highly competitive nature of our business;

•our ability to execute on our acquisition strategy and successfully integrate and realize benefits of our acquisitions;

•our ability to promote and develop our brands;

•our ability to maintain and expand our client base;

•our ability to maintain necessary accreditations and other authorizations in varying jurisdictions;

•significant environmental governmental regulation;

•our ability to attract and retain qualified managerial and skilled technical personnel;

•safety-related issues;

•allegations regarding compliance with professional standards, duties and statutory obligations and our ability to provide accurate results;

•the lack of formal long-term agreements with many of our clients;

•our ability to adapt to changing technology, industry standards or regulatory requirements;

•government clients and contracts;

•our ability to maintain our prices and manage costs;

•our ability to protect our intellectual property or claims that we infringe on the intellectual property rights of others;

•laws and regulations regarding handling of confidential information;

•any failure in or breach of our networks and systems or other forms of cyber-attack;

•our international operations;

•product related risks;

•environmental regulations and liabilities; and

•additional factors discussed in our filings with the Securities and Exchange Commission, or the SEC.

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The forward-looking statements in this Quarterly Report on Form 10-Q are based on historical performance and management’s current plans, estimates and expectations in light of information currently available to us and are subject to uncertainty and changes in circumstances. There can be no assurance that future developments affecting us will be those that we have anticipated. Actual results or outcomes may differ materially from these expectations due to changes in global, regional or local political, economic, business, competitive, market, regulatory and other factors, many of which are beyond our control, as well as the other factors described in Item 1A. “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2021 filed with the SEC on March 1, 2022, or the 2021 Form 10-K. Further, many of these factors are, and may continue to be, amplified by the COVID-19 pandemic.

Additional factors or events that could cause our actual results or outcomes to differ may also emerge from time to time, and it is not possible for us to predict all of them. In addition, historical, current and forward-looking sustainability-related statements may be based on standards for measuring progress that are still developing, internal controls and processes that continue to evolve, and assumptions that are subject to change in the future. Should one or more of these risks or uncertainties materialize, or should any of our assumptions prove to be incorrect, our actual results or outcomes may vary in material respects from what we may have expressed or implied by any forward-looking statement and, therefore, you should not regard any forward-looking statement as a representation or warranty by us or any other person that we will successfully achieve the expectation, plan or objective expressed in such forward-looking statement in any specified time frame, or at all. We caution that you should not place undue reliance on any of our forward-looking statements. Any forward-looking statement made by us speaks only as of the date on which we make it. We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by applicable securities laws.

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Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our historical audited and unaudited consolidated financial statements and related notes and other information included elsewhere in this filing and our other filings with the SEC, including our unaudited condensed consolidated financial statements and the accompanying notes as of and for the three and nine months ended September 30, 2022 and September 30, 2021 included in Part I, Item 1. “Financial Statements” in this Quarterly Report on Form 10-Q. This discussion contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from such forward-looking statements. Factors that could cause or contribute to those differences include, but are not limited to, those identified below and those discussed in the section entitled “Forward-Looking Statements”, and elsewhere in this filing and our other filings with the SEC, including in Item 1A. Risk Factors in the 2021 Form 10-K.

Overview

Since our inception in 2012, our mission has been to help clients and communities meet their environmental goals and needs. According to data derived from a 2021 Environmental Industry Study prepared by Environmental Business International, Inc., or EBI, which we commissioned, the global environmental industry is estimated to be approximately $1.3 trillion, with $428.0 billion concentrated in the United States.

Our Segments

We provide environmental services to our clients through three business segments—Assessment, Permitting and Response, Measurement and Analysis and Remediation and Reuse. For more information on each of our operating segments, see Item 1. “Business” in the 2021 Form 10-K.

Assessment, Permitting and Response

Through our Assessment, Permitting and Response segment, we provide scientific advisory and consulting services to support environmental assessments, environmental emergency response, and environmental audits and permits for current operations, facility upgrades, new projects, decommissioning projects and development projects. Our technical advisory and consulting offerings include regulatory compliance support and planning, environmental, ecosystem and toxicological assessments and support during responses to environmental disruption. We help clients navigate regulations at the local, state, provincial and federal levels. In addition to environmental toxicology, and given our expertise in helping businesses plan for and respond to disruptions, our scientists and response teams have helped clients navigate their preparation for and response to the COVID-19 pandemic.

Measurement and Analysis

Through our Measurement and Analysis segment, our highly credentialed teams test and analyze air, water and soil to determine concentrations of contaminants, as well as the toxicological impact of contaminants on flora, fauna and human health. Our offerings include source and ambient air testing and monitoring, leak detection and advanced analytical laboratory services such as air, storm water, wastewater and drinking water analysis.

Remediation and Reuse

Through our Remediation and Reuse segment, we provide clients with engineering, design, implementation and operations and maintenance services, primarily to treat contaminated water, remove contaminants from soil or create biogas from waste. We do not own the properties or facilities at which we implement these projects or the underlying liabilities, nor do we own material amounts of the equipment used in projects; instead, we assist our clients in designing solutions, managing projects and mitigating their environmental risks and liabilities.

These operating segments have been structured and organized to align with how we view and manage the business with the full lifecycle of our clients’ targeted environmental concerns and needs in mind. Within each segment, we cover similar service offerings, regulatory frameworks, internal operating structures and client types. Corporate activities not directly related to segment performance, including general corporate expenses, interest and taxes, are reported separately.

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COVID-19

To date, COVID-19 related adverse impacts such as temporarily delayed project start dates, particularly within our Remediation and Reuse segment, exiting certain service lines and employee quarantines have not had a material adverse effect on our reported results. On the other hand, we have seen benefits from COVID-19 given client demand for CTEH’s toxicology and response services, which represented a meaningful, although expectedly declining, revenue stream in the three and nine months ended September 30, 2022 and September 30, 2021, and that, once the pandemic subsides, we may not be able to replace in future periods. Although many parts of our business saw some impact from COVID-19, in the aggregate, our overall business benefitted from COVID-19 during the three and nine months ended September 30, 2022 and September 30, 2021, primarily as a result of COVID-19 response work performed by CTEH. For additional information regarding the historical impacts of COVID-19 on our business, see Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations in the 2021 Form 10-K.

COVID-19 has had an impact on our historical seasonality trends. We have not experienced a significant slowdown in cash collections, and as a result cash flow from operations has not been materially adversely impacted.

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act, or the CARES Act, was enacted. The CARES Act includes several significant provisions for corporations, including those pertaining to net operating losses, interest deductions and payroll tax benefits. We utilized certain of these provisions in 2020, including the deferral of the employer side social security payments for payroll for the eligible portion of the year. In total, we deferred approximately $5.0 million of 2020 payments to 2021 and 2022, of which $2.5 million was repaid in December 2021 and we expect to pay the remaining $2.5 million in the fourth quarter of 2022.

It is difficult to predict the future impact COVID-19 may have on our business, results of operations, financial position, or cash flows. The extent to which we may be impacted will depend largely on future and rapidly evolving developments, including new information on the severity of new strains, the roll-out and long-term efficacy of vaccines, and actions by various government authorities to contain the pandemic and mitigate its impact. We intend to closely monitor the impact of COVID-19 on our business and will respond as we believe is appropriate.

Key Factors that Affect Our Business and Our Results

Our operating results and financial performance are influenced by a variety of internal and external trends and other factors. Some of the more important factors are discussed briefly below.

Acquisitions

We have been, and expect to continue to be, an acquisitive company. Acquisitions have expanded our environmental service capabilities across all three segments, our access to technology, as well as our geographic reach in the United States, Canada and Australia. The table below sets forth the number of acquisitions completed, revenues generated by and the percentage of total revenues attributable to those acquisitions completed during the three and nine months ended September 30, 2022 and September 30, 2021:

	Three Months Ended September 30,						Nine Months Ended September 30,
(Revenues in thousands)	2022			2021			2022			2021
Acquisitions completed		2		2				4		4
Revenues attributable to    acquisitions in the period		908		$	5,803		$	13,193		$	19,720
Percentage of revenues		0.7	%		4.4	%		3.3	%		4.9	%

Revenues from acquired companies exclude intercompany revenues from revenue synergies realized between business lines within operating segments, as these are eliminated at the consolidated segment and Company level. We expect our revenue growth to continue to be driven in significant part by acquisitions.

As a result of our acquisitions, goodwill and other intangible assets represent a significant proportion of our total assets, and amortization of intangible assets has historically been a significant expense. Our historical financial statements also include other acquisition-related costs, including costs relating to external legal support, diligence and valuation services and other transaction and integration-related matters. In addition, in any year gains and losses from changes in the fair value of business acquisition contingencies such as earn outs could be significant. The amount of each for the three and nine months ended September 30, 2022 and September 30, 2021, was:

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	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2022		2021		2022			2021
Amortization expense	$	8,668	$	8,936	$	27,579		$	25,938
Acquisition-related costs		368		913		1,354			1,656
Fair value changes in business    acquisition contingencies		59		—		(3,472	)		24,035

We expect that amortization of identifiable intangible assets and other acquisition-related costs, assuming we continue to acquire, will continue to be significant.

Additionally, we made earn-out payments of $30.0 million and $50.0 million in March 2022 and April 2021, respectively, in connection with our CTEH acquisition. $25.0 million of the 2021 CTEH earn-out payment was made in the form of shares of our common stock. In connection with our Vista, Sensible, ECI and EnvStd acquisitions, we may make up to $8.5 million in aggregate earn-out payments between the years 2023 and 2026, up to $3.0 million of which may be paid in cash. See Note 7 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Organic Growth

We define organic growth as the change in revenues excluding revenues from acquisitions for the first twelve months following the date of acquisition and excluding revenues from businesses disposed of or discontinued. As a result of the significance of CTEH to Montrose and the potential annual volatility in CTEH’s revenues due to the emergency response aspect of their business, we also disclose organic growth without the annual organic revenue growth of CTEH. We expect to continue to disclose organic revenue growth with and without CTEH. Management uses organic growth as one of the means by which it assesses our results of operations. Organic growth is not, however, a measure of revenue growth calculated in accordance with U.S. generally accepted accounting principles, or GAAP, and should be considered in conjunction with revenue growth calculated in accordance with GAAP. We have grown organically and expect to continue to do so.

Discontinued Service Lines

Periodically, or when circumstances warrant, we evaluate the performance of our business services to ensure that performance and outlook are consistent with expectations. During the second quarter of 2022, as part of this evaluation, we determined to exit all legacy water treatment and biogas operations and maintenance contracts, collectively, the Discontinued O&M Contracts. The decision to exit these contracts was reached after a careful consideration of the risks and rewards associated with them. The work associated with these contracts is non-specialized and commoditized, and it was determined that the risk of facility failure taken on by the Company as the O&M contractor, no longer justified the low margins in these contracts. As a part of exiting these contracts, a process that is expected to be completed by the end of 2022, we have eliminated the positions associated with the workstreams. Revenue from our water treatment and biogas operations and maintenance contracts, which are included in the results of our Remediation and Reuse segment, were $0.7 million and $2.9 million in the three months ended September 30, 2022 and September 30, 2021, respectively, and $3.1 million and $9.7 million in the nine months ended September 30, 2022 and September 30, 2021, respectively. This decision does not impact the Company’s specialized PFAS water treatment operations and maintenance contracts.

Revenue Mix

Our segments generate different levels of profitability and, accordingly, shifts in the mix of revenues between segments can impact our consolidated reported net income, net loss margin, Adjusted EBITDA and Adjusted EBITDA margin from quarter to quarter and year to year. Inter-company revenues between business lines within segments have been eliminated. See Note 18 to our unaudited condensed consolidated financial statements included in Part 1, Item 1 “Financial Statements.”

Financing Costs

Financing costs, relating primarily to interest expense on our debt, continue to be a significant component of our results of operations. We incurred interest expense of $1.4 million and $4.0 million during the three and nine months ended September 30, 2022, respectively, and $1.7 million and $11.2 million during the three and nine months ended September 30, 2021.

On April 27, 2021, we entered into the 2021 Credit Facility and repaid all amounts outstanding under the prior Credit Facility. The 2021 Credit Facility consists of a $175.0 million term loan and a $125.0 million revolving credit facility. The interest rate on the 2021 Credit Facility varies depending on leverage, with a minimum of LIBOR plus 1.5% and a maximum of LIBOR plus 2.5%. We incurred debt extinguishment costs of $4.1 million in connection with this refinancing.

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Furthermore, effective January 27, 2022, we entered into an interest rate swap transaction fixing the floating component of the interest rate on $100.0 million of borrowings to 1.39% until January 27, 2025.

We expect interest expense to remain a significant cost as we continue to leverage our credit facility to support our operations and future acquisitions.

See Note 12 to our unaudited condensed consolidated financial statements included in Part 1, Item 1 “Financial Statements” and “Liquidity and Capital Resources.”

Corporate and Operational Infrastructure Investments

Our historical operating results reflect the impact of our ongoing investments in our corporate infrastructure to support our growth. We have made and expect to continue to make investments in our business platform that we believe have laid the foundation for continued growth. Investments in logistics, quality, risk management, sales and marketing, safety, human resources, research and development, finance and information technology and other areas enable us to support continued growth. These investments should allow us to improve our margins over time.

Seasonality

Due to the field-based nature of certain of our services, weather patterns generally impact our field-based teams’ ability to operate in the winter months. As a result, our operating results in our Measurement and Analysis segment experience some quarterly variability with generally lower revenues and lower earnings in the first and fourth quarters and higher overall revenues and earnings in the second and third quarters. As we continue to grow and expand into new geographies and service lines, quarterly variability in our Measurement and Analysis segment may deviate from historical trends.

Earnings Volatility

In addition to the impact of seasonality on earnings, the acquisition of CTEH exposes us to potentially significant revenue and earnings fluctuations tied both to the timing of large environmental emergency response projects following an incident or natural disaster, and more recently, the benefit from COVID related work. The benefit from COVID related work began in the third quarter of 2020, peaked in the first quarter of 2021 and has declined each subsequent quarter, although demand has continued through September 30, 2022. Demand for COVID-19 related or environmental emergency response services provided by CTEH remains difficult to predict and as a result, we may have experienced revenues and earnings in both the nine months ended September 30, 2022 and in fiscal year 2021 that are not indicative of future results, making those periods particularly difficult comparisons for future periods. We do however expect that a portion of expectedly declining COVID-19 response revenues will be offset by other CTEH service line revenues such as environmental emergency responses as internal resources are freed up from the COVID-19 response work. Earnings volatility is also driven by the timing of large projects, particularly in our Remediation and Reuse segment, and the impact of acquisitions. As a result of these factors, and because demand for environmental services is not driven by specific or predictable patterns in one or more fiscal quarters, our business is better assessed based on yearly results.

Cybersecurity Breach

As previously disclosed, on June 11, 2022 we were the target of an organized ransomware attack on our IT systems that led to the temporary disruption of our regular operations. The most affected portion of the business was our Enthalpy lab network. Upon discovery of the attack, we immediately began restoration and remediation efforts. By June 30, 2022, we had substantially restored our operations. The Company's financial systems are cloud based and were not affected. We engaged third party experts, including cyber legal counsel and a cybersecurity firm, to perform a fulsome forensic investigation of this attack and we promptly notified federal law enforcement. Based on the results of the investigation, we do not believe there has been any misuse of confidential or sensitive client data, have made notifications to clients, and have proactively addressed client concerns regarding our security environment. Furthermore, we have identified a limited number of individuals whose personally identifiable information may have been accessed from our systems and have made appropriate notifications to such individuals and required regulators. The Company has insurance coverage, subject to a $0.3 million deductible, against recovery costs and business interruption resulting from cyber-attacks and is in the process of preparing and submitting claims. We believe that the impact on revenues and income before tax in the quarters ended June 30, 2022 and September 30, 2022 was approximately $1.0 million and $0.5 million, respectively, with the third quarter impact limited to July 2022.

 

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Results of Operations

Three Months Ended September 30, 2022 Compared to the Three Months Ended September 30, 2021

	Three Months Ended September 30,
(in thousands, except per share and percentage data)	2022			2021
Statements of operations data:
Revenues	$	130,312		$	132,578
Cost of revenues (exclusive of depreciation and amortization)		82,234			85,242
Selling, general and administrative expense		42,857			30,499
Fair value changes in business acquisition contingencies		59			—
Depreciation and amortization		11,504			11,471
(Loss) income from operations	$	(6,342	)	$	5,366
Other income (expense)		1,814			(516	)
Interest expense, net		(1,400	)		(1,722	)
(Loss) income before income taxes		(5,928	)		3,128
Income tax (benefit) expense		(208	)		902
Net (loss) income	$	(5,720	)	$	2,226
Series A-2 dividend payment		(4,100	)		(4,100	)
Net loss attributable to common stockholders	$	(9,820	)	$	(1,874	)
Weighted average number of shares — basic and diluted		29,691			26,220
Loss per share — basic and diluted	$	(0.33	)	$	(0.07	)

Revenues

For the three months ended September 30, 2022, we had revenues of $130.3 million, a decrease of $2.3 million, or (1.7)% over the three months ended September 30, 2021. The period over period decrease in revenues was driven by expected and significantly lower revenue from CTEH driven by lower demand for COVID-19 related services, and exiting the Discontinued O&M Contracts. These decreases were partially offset by organic growth in our Measurement and Analysis and Remediation and Reuse segments, and acquisitions completed in and subsequent to the quarter ended September 30, 2021, which contributed revenues of $7.5 million. Revenue from CTEH was $26.2 million in the three months ended September 30, 2022 compared to $53.1 million in the three months ended September 30, 2021. Total revenue from COVID-19 related services was $13.8 million and $44.9 million in the three months ended September 30, 2022 and September 30, 2021, respectively. Discontinued O&M Contracts generated revenues of $0.7 million and $2.9 million in the three months ended September 30, 2022 and September 30, 2021, respectively. Revenue by segment and as a percentage of total revenues was as follows:

	Three Months Ended September 30,
	2022					2021
(Revenues in thousands)	Revenues		% of Total Revenues			Revenues		% of Total Revenues
Assessment, Permitting and    Response	$	46,414		35.6	%	$	63,412		47.8	%
Measurement and Analysis		43,754		33.6			38,752		29.2
Remediation and Reuse		40,144		30.8			30,414		22.9
	$	130,312				$	132,578

See “—Segment Results of Operations” below.

Cost of Revenues

Cost of revenues consists of all direct costs required to provide services, including fixed and variable direct labor costs, equipment rental and other outside services, field and lab supplies, vehicle costs and travel-related expenses. Variable costs of revenues generally follow the same trends as revenue, while fixed costs tend to change primarily as a result of acquisitions.

For the three months ended September 30, 2022, cost of revenues was $82.2 million or 63.1% of revenues, and was comprised of direct labor of $38.0 million, outside services (including contracted labor, laboratory, shipping and freight and other outside services) of $22.4 million, field supplies, testing supplies and equipment costs of $15.0 million, project-related travel expenses of $4.5 million and other direct costs of $2.3 million.

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For the three months ended September 30, 2021, cost of revenues was $85.2 million or 64.3% of revenues, and was comprised of direct labor of $37.0 million, outside services (including contracted labor, laboratory, shipping and freight and other outside services) of $32.3 million, field supplies, testing supplies and equipment costs of $9.7 million, project-related travel expenses of $4.0 million and other direct costs of $2.2 million.

For the three months ended September 30, 2022, cost of revenues as a percentage of revenue decreased 1.2% from the three months ended September 30, 2021, as a result of significantly lower outside service costs in 2022 when compared to 2021 driven primarily by a decrease in external lab expenses needed to support CTEH’s COVID-19 response work during 2022, partially offset by higher equipment costs primarily to support higher water treatment and biogas revenues.

Selling, General and Administrative Expense

Selling, general and administrative expense consists of general corporate overhead, including executive, legal, finance, safety, risk management, human resource, marketing and information technology related costs, as well as indirect operational costs of labor, rent, insurance and stock-based compensation.

For the three months ended September 30, 2022, selling, general and administrative expense was $42.9 million, an increase of $12.4 million or 40.5% versus the three months ended September 30, 2021. This increase was primarily driven by $8.5 million related to an increase in stock compensation expense, $2.1 million from selling, general and administrative expense pertaining to companies we acquired subsequent to the third quarter of 2021, $1.1 million related to the higher labor and medical benefit costs, primarily reflecting inflationary increases, an increase in headcount to support growth in our PFAS water treatment business, and higher travel expenses. See Part I, Item 3. “Quantitative and Qualitative Disclosures About Market Risk” for additional information regarding the impact of inflation on our business.

For the three months ended September 30, 2022, selling, general and administrative expense was comprised of indirect labor of $19.6 million, stock-based compensation of $10.6 million, facilities costs of $4.5 million, and other costs (including software, travel, insurance, legal, consulting, audit services, bad debt and acquisition-related costs) of $8.2 million.

For the three months ended September 30, 2021, selling, general and administrative expense was comprised of indirect labor of $16.0 million, facilities costs of $3.7 million, stock-based compensation of $2.1 million, and other costs (including software, travel, insurance, legal, consulting, audit services, bad debt and acquisition-related costs) of $8.7 million.

Fair Value Changes in Business Acquisition Contingencies

For the three months ended September 30, 2022, fair value changes in business acquisition contingencies resulted in a loss of $0.1 million versus zero for the three months ended September 30, 2021. The change in value in the three months ended September 30, 2022, was attributable to a $0.4 million expense related to fair value changes in business acquisition contingencies and a $0.3 million gain related to acquisitions' 338(h)(10) elections make-whole tax accruals. See “—Key Factors that Affect Our Business and Our Results—Acquisitions” and Notes 7 and 13 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Depreciation and Amortization

Depreciation and amortization expense for the three months ended September 30, 2022, was $11.5 million and was comprised of amortization of finite lived intangibles of $8.7 million, arising as a result of our acquisition activity, depreciation of property and equipment of $1.7 million and finance leases right-of-use asset amortization of $1.1 million.

Depreciation and amortization expense for the three months ended September 30, 2021, was $11.5 million and was comprised of amortization of finite lived intangibles of $8.9 million, arising as a result of our acquisition activity, depreciation of property and equipment of $1.8 million and finance leases right-of-use asset amortization of $0.8 million.

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See Notes 5 and 6 to our unaudited condensed consolidated financial statements included in Part 1, Item 1. “Financial Statements.”

Other Income (Expense)

Other income for the three months ended September 30, 2022 of $1.8 million was driven by the fair value adjustment on our interest rate swap of $2.3 million, which was partially offset by an expense of $0.5 million related to the fair value adjustment of the Series A-2 preferred stock conversion option. Other expense of $(0.5) million for the three months ended September 30, 2021 was driven by fair value adjustments related to the Series A-2 preferred stock conversion option. See Notes 12 and 15 to our unaudited condensed consolidated financial statements included in Part 1, Item 1. “Financial Statements.”

Interest Expense, Net

Interest expense, net incurred in the three months ended September 30, 2022, was $1.4 million, compared to $1.7 million for the three months ended September 30, 2021. The decrease in interest expense was driven by lower outstanding debt balances during the three months ended September 30, 2022 when compared to the three months ended September 30, 2021. See “—Key Factors that Affect Our Business and Our Results—Financing Costs” and Note 12 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Income Tax (Benefit) Expense

Income tax benefit was $(0.2) million during the three months ended September 30, 2022. Income tax expense was $0.9 million for the three months ended September 30, 2021.

Nine Months Ended September 30, 2022 Compared to the Nine Months Ended September 30, 2021

	Nine months ended September 30,
(in thousands, except per share and percentage data)	2022			2021
Statements of operations data:
Revenues	$	404,902		$	402,619
Cost of revenues (exclusive of depreciation and amortization)		261,049			272,662
Selling, general and administrative expense		131,120			82,865
Fair value changes in business acquisition contingencies		(3,472	)		24,035
Depreciation and amortization		35,928			33,145
Loss from operations	$	(19,723	)	$	(10,088	)
Other income (expense)		4,618			(1,909	)
Interest expense, net		(4,010	)		(11,208	)
Loss before income taxes		(19,115	)		(23,205	)
Income tax expense		1,892			648
Net loss	$	(21,007	)	$	(23,853	)
Series A-2 dividend payment		(12,300	)		(12,300	)
Net loss attributable to common stockholders	$	(33,307	)	$	(36,153	)
Weighted average number of shares— basic and diluted		29,677			25,798
Loss per share— basic and diluted	$	(1.12	)	$	(1.40	)

Revenues

For the nine months ended September 30, 2022, we had revenues of $404.9 million, an increase of $2.3 million, or 0.6% over the nine months ended September 30, 2021. The period over period increase in revenues was driven by organic growth in our Measurement and Analysis and Remediation and Reuse segments, and acquisitions completed in and subsequent to the quarter ended September 30, 2021, which contributed revenues of $19.9 million. These increases were partially offset by expected significantly lower revenues from CTEH, primarily from lower COVID-19 related services, and the exiting of Discontinued O&M Contracts. Revenue from CTEH was $88.2 million in the nine months ended September 30, 2022 compared to $189.6 million in the nine months ended September 30, 2021. Total revenue from COVID-19 related services was $55.4 million and $158.8 million in the nine months ended September 30, 2022 and September 30, 2021, respectively. Discontinued O&M Contracts generated revenues of $3.1 million and $9.7 million in the nine months ended September 30, 2022 and September 30, 2021, respectively. Revenue by segment and as a percentage of total revenues was as follows:

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	Nine Months Ended September 30,
	2022					2021
(revenue in thousands)	Revenues		% of Total Revenues			Revenues		% of Total Revenues
Assessment, Permitting and    Response	$	142,051		35.1	%	$	209,379		52.0	%
Measurement and Analysis		125,739		31.1			111,309		27.6
Remediation and Reuse		137,112		33.9			81,931		20.3
	$	404,902				$	402,619

See “—Segment Results of Operations” below.

Cost of Revenues

For the nine months ended September 30, 2022, cost of revenues was $261.0 million or 64.5% of revenues, and was comprised of direct labor of $114.0 million, outside services (including contracted labor, laboratory, shipping and freight and other outside services) of $64.2 million, field supplies, testing supplies and equipment costs of $58.1 million, project-related travel expenses of $13.9 million and other direct costs of $10.8 million.

For the nine months ended September 30, 2021, cost of revenues was $272.7 million or 67.7% of revenues, and was comprised of direct labor of $109.3 million, outside services (including contracted labor, laboratory, shipping and freight and other outside services) of $115.2 million, field supplies, testing supplies and equipment costs of $27.9 million, project-related travel expenses of $12.8 million and other direct costs of $7.4 million.

For the nine months ended September 30, 2022, cost of revenues as a percentage of revenue decreased 3.2% from the nine months ended September 30, 2021, as a result of significantly lower outside service costs in 2022 when compared to 2021 driven primarily by a decrease in external lab expenses needed to support CTEH’s COVID-19 response work during 2022, partially offset by higher equipment costs primarily to support higher water treatment and biogas revenues.

Selling, General and Administrative Expense

For the nine months ended September 30, 2022, selling, general and administrative expense was $131.1 million, an increase of $48.2 million or 58.2% versus the nine months ended September 30, 2021. This increase was primarily driven by $25.9 million related to an increase in stock compensation expense, $5.6 million from selling, general and administrative expense pertaining to companies we acquired subsequent to the third quarter of 2021, $9.0 million related to the higher labor and medical benefit costs, primarily reflecting inflationary increases, an increase in headcount to support growth in our PFAS water treatment business, and investments in corporate infrastructure (primarily administrative, marketing, finance, IT, legal and human resources) and $3.0 million was from an increase in the defined contribution plan employer contributions following the reinstatement of employer matching during the second quarter of 2021, as well as higher travel expenses. See Part I, Item 3. “Quantitative and Qualitative Disclosures About Market Risk” for additional information regarding the impact of inflation on our business.

For the nine months ended September 30, 2022, selling, general and administrative expense was comprised of indirect labor of $60.8 million, stock-based compensation of $31.3 million, facilities costs of $13.2 million, acquisition-related costs of $1.4 million, a bad debt credit of $0.8 million, and other costs (including software, travel, insurance, legal, consulting and audit services) of $25.2 million.

For the nine months ended September 30, 2021, selling, general and administrative expense was comprised of indirect labor of $43.2 million, facilities costs of $10.7 million, stock-based compensation of $5.4 million, acquisition-related costs of $1.7 million, bad debt expense of $0.8 million, and other costs (including software, travel, insurance, legal, consulting and audit services) of $20.7 million.

Fair Value Changes in Business Acquisition Contingencies

For the nine months ended September 30, 2022, fair value changes in business acquisition contingencies resulted in a gain of $3.5 million versus an expense of $24.0 million for the nine months ended September 30, 2021. The majority of the change in value in the nine months ended September 30, 2022, was attributable to a $3.4 million gain related to acquisitions' 338(h)(10) elections make-whole tax accruals. The majority of the change in value in the nine months ended September 30, 2021 period was attributable to the

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CTEH earn-outs. See “—Key Factors that Affect Our Business and Our Results —Acquisitions” and Notes 7 and 13 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Depreciation and Amortization

Depreciation and amortization expense for the nine months ended September 30, 2022, was $35.9 million and was comprised of amortization of finite lived intangibles of $27.6 million, arising as a result of our acquisition activity, depreciation of property and equipment of $5.3 million and finance leases right-of-use asset amortization of $3.0 million.

Depreciation and amortization expense for the nine months ended September 30, 2021, was $33.1 million and was comprised of amortization of finite lived intangibles of $25.9 million, arising as a result of our acquisition activity, depreciation of property and equipment of $4.8 million and finance leases right-of-use asset amortization of $2.4 million.

The increase in amortization, depreciation of property and equipment and the amortization of finance leases right-of-use asset for the nine months ended September 30, 2022 versus the nine months ended September 30, 2021, was primarily a result of acquisitions. See Notes 5 and 6 to our unaudited condensed consolidated financial statements included in Part 1, Item 1. “Financial Statements.”

Other Income (Expense)

Other income for the nine months ended September 30, 2022 of $4.6 million was driven by a gain related to the fair value adjustment on our interest rate swap of $6.3 million which was partially offset by an expense of $1.6 million related to the fair value adjustment of the Series A-2 preferred stock conversion option. Other expense of $(1.9) million for the nine months ended September 30, 2021 was driven by fair value adjustments related to the Series A-2 preferred stock conversion option. See Notes 12 and 15 to our unaudited condensed consolidated financial statements included in Part 1, Item 1. “Financial Statements.”

Interest Expense, Net

Interest expense, net incurred in the nine months ended September 30, 2022, was $4.0 million, compared to $11.2 million for the nine months ended September 30, 2021. The decrease in interest expense was driven by lower outstanding debt balances during the nine months ended September 30, 2022 when compared to the nine months ended September 30, 2021, as well as the $4.1 million loss on extinguishment of debt realized in the nine months ended September 30, 2021 in connection with the repayment in full of the 2020 credit facility. See “—Key Factors that Affect Our Business and Our Results—Financing Costs” and Note 12 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Income Tax Expense

Income tax expense was $1.9 million and $0.6 million during the nine months ended September 30, 2022 and nine months ended September 30, 2021, respectively.

Segment Results of Operations

Three Months Ended September 30, 2022 Compared to the Three Months Ended September 30, 2021

	Three Months Ended September 30,
	2022								2021
(in thousands)	Segment Revenues		Segment Adjusted EBITDA (1)			Segment Adjusted EBITDA Margin(2)			Segment Revenues		Segment Adjusted EBITDA(1)			Segment Adjusted EBITDA Margin(2)
Assessment, Permitting and Response	$	46,414	$	9,820			21.2	%	$	63,412	$	15,719			24.8	%
Measurement and Analysis		43,754		8,483			19.4			38,752		8,283			21.4
Remediation and Reuse		40,144		7,010			17.5			30,414		5,472			18.0
Total Operating Segments	$	130,312	$	25,313			19.4	%	$	132,578	$	29,474			22.2	%
Corporate and Other		—		(6,940	)	n/a				—		(7,987	)	n/a

(1)For purposes of evaluating segment profit, the Company’s chief operating decision maker reviews Segment Adjusted EBITDA as a basis for making the decisions to allocate resources and assess performance. See Note 18 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

(2)Represents Segment Adjusted EBITDA as a percentage of segment revenues.

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Revenues

Assessment, Permitting and Response segment revenues for the three months ended September 30, 2022 were $46.4 million, compared to $63.4 million for the three months ended September 30, 2021. The decrease was driven by expected significantly lower CTEH revenues in the three months ended September 30, 2022 when compared to the three months ended September 30, 2021, as a result of lower revenue from COVID-19 related services, partially offset by organic growth, excluding CTEH, and revenues of $6.4 million from acquisitions completed subsequent to the quarter ended September 30, 2021. CTEH revenues were $26.2 million in the three months ended September 30, 2022 compared to $53.1 million in the three months ended September 30, 2021. Total revenue from COVID-19 related services was $13.8 million and $44.9 million in the three months ended September 30, 2022 and September 30, 2021, respectively.

Measurement and Analysis segment revenues for the three months ended September 30, 2022 were $43.8 million, an increase of $5.0 million or 12.9% compared to revenues for the three months ended September 30, 2021 of $38.8 million. The increase was driven primarily by organic growth, as well as by revenues of $0.6 million from acquisitions completed subsequent to the quarter ended September 30, 2021.

Remediation and Reuse segment revenues for the three months ended September 30, 2022 were $40.1 million, an increase of $9.7 million or 32.0% compared to revenues for the three months ended September 30, 2021 of $30.4 million. The increase was driven by organic growth, driven by increases in demand for our water treatment technology (PFAS removal) and waste-to-resources (agricultural waste to biogas) services, partially offset by the exiting of Discontinued O&M Contracts, which generated revenues of $0.7 million and $2.9 million in the three months ended September 30, 2022 and September 30, 2021, respectively.

Segment Adjusted EBITDA

Assessment, Permitting and Response Segment Adjusted EBITDA was $9.8 million for the three months ended September 30, 2022, compared to $15.7 million for the three months ended September 30, 2021. For the three months ended September 30, 2022 and September 30, 2021, Segment Adjusted EBITDA margin was 21.2% and 24.8%, respectively. The decrease in Segment Adjusted EBITDA was a result of a decrease in CTEH COVID-19 related revenues during the three months ended September 30, 2022 when compared to the three months ended September 30, 2021. The decrease in Segment Adjusted EBITDA margin was primarily as a result of the acquisitions of Environmental Intelligence, Horizon and Environmental Standards, which typically operate at lower margins.

Measurement and Analysis Segment Adjusted EBITDA for the three months ended September 30, 2022 was $8.5 million, an increase of $0.2 million compared to Segment Adjusted EBITDA for the three months ended September 30, 2021 of $8.3 million. For the three months ended September 30, 2022 and September 30, 2021 Segment Adjusted EBITDA margin was 19.4% and 21.4%, respectively. The increase in Segment Adjusted EBITDA was due to higher revenues, whereas the decrease in Segment Adjusted EBITDA margin was a result of the timing of projects in some of our specialty labs, and to a lesser degree, the impact of the cyber-attack in June 2022, which temporarily disrupted certain of our labs’ ability to operate in July 2022, partially offset by favorable business mix.

Remediation and Reuse Segment Adjusted EBITDA for the three months ended September 30, 2022 was $7.0 million, an increase of $1.5 million compared to Segment Adjusted EBITDA for the three months ended September 30, 2021 of $5.5 million. For the three months ended September 30, 2022 and September 30, 2021 Segment Adjusted EBITDA margin was 17.5% and 18.0%, respectively. The increase in Segment Adjusted EBITDA was a result of significantly higher revenues. The slight decrease in Segment Adjusted EBITDA margin was primarily a result of business mix and our continued investments in operating infrastructure in our biogas and water treatment technology businesses, which temporarily impact margins.

Corporate and other costs were $6.9 million for the three months ended September 30, 2022 compared to $8.0 million for the three months ended September 30, 2021. The cost decrease was primarily driven by a bad debt credit of $0.6 million in the three months ended September 30, 2022. Corporate and other costs were 5.3% and 6.0% of revenues for the three months ended September 30, 2022 and September 30, 2021, respectively.

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Nine Months Ended September 30, 2022 Compared to the Nine Months Ended September 30, 2021

	Nine Months Ended September 30,
	2022								2021
(in thousands)	Segment Revenues		Segment Adjusted EBITDA(1)			Segment Adjusted EBITDA Margin(2)			Segment Revenues		Segment Adjusted EBITDA(1)			Segment Adjusted EBITDA Margin(2)
Assessment, Permitting and Response	$	142,051	$	30,252			21.3	%	$	209,379	$	46,379			22.2	%
Measurement and Analysis		125,739		21,852			17.4			111,309		22,634			20.3
Remediation and Reuse		137,112		22,059			16.1			81,931		12,262			15.0
Total Operating Segments	$	404,902	$	74,163			18.3	%	$	402,619	$	81,275			20.2	%
Corporate and Other				(22,826	)	n/a						(22,026	)	n/a

_______________________________

(1)For purposes of evaluating segment profit, the Company’s chief operating decision maker reviews Segment Adjusted EBITDA as a basis for making the decisions to allocate resources and assess performance. See Note 18 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

(2)Represents Segment Adjusted EBITDA as a percentage of segment revenues.

Revenues

Assessment, Permitting and Response segment revenues for the nine months ended September 30, 2022 were $142.1 million, compared to $209.4 million for the nine months ended September 30, 2021. The decrease was driven by expected significantly lower CTEH revenues in the first nine months of 2022 when compared to the first nine months of 2021, as a result of lower revenue from COVID-19 related services, partially offset by revenues of $17.4 million from acquisitions completed subsequent to the quarter ended September 30, 2021. CTEH revenues were $88.2 million in the nine months ended September 30, 2022 compared to $189.6 million in the nine months ended September 30, 2021. Total revenue from COVID-19 related services was $55.4 million and $158.8 million in the nine months ended September 30, 2022 and September 30, 2021, respectively.

Measurement and Analysis segment revenues for the nine months ended September 30, 2022 were $125.7 million, an increase of $14.4 million or 13.0% compared to revenues for the nine months ended September 30, 2021 of $111.3 million. The increase was driven primarily by organic growth, as well as by revenues of $2.0 million from acquisitions completed subsequent to the quarter ended September 30, 2021.

Remediation and Reuse segment revenues for the nine months ended September 30, 2022 were $137.1 million, an increase of $55.2 million or 67.4% compared to revenues for the nine months ended September 30, 2021 of $81.9 million. The increase was driven primarily by organic growth related to increases in demand for our water treatment technology (PFAS removal) and waste-to-resources (agricultural waste to biogas) services.

Segment Adjusted EBITDA

Assessment, Permitting and Response Segment Adjusted EBITDA was $30.3 million for the nine months ended September 30, 2022, compared to $46.4 million for the nine months ended September 30, 2021. For the nine months ended September 30, 2022 and September 30, 2021, Segment Adjusted EBITDA margin was 21.3% and 22.2%, respectively. The decrease in Segment Adjusted EBITDA was a result of an expected decrease in CTEH COVID-19 related revenues during the nine months ended September 30, 2022 when compared to the nine months ended September 30, 2021. The decrease in Segment Adjusted EBITDA margin was a result of business mix and the acquisitions of Environmental Intelligence, Horizon and Environmental Standards, which operate at lower margins, partially offset by higher CTEH margins, as a result of lower COVID-related work as a percentage of CTEH revenues in the current year versus the prior year.

Measurement and Analysis Segment Adjusted EBITDA for the nine months ended September 30, 2022 was $21.9 million, a decrease of $0.7 million compared to Segment Adjusted EBITDA for the nine months ended September 30, 2021 of $22.6 million. For the nine months ended September 30, 2022 and September 30, 2021, Segment Adjusted EBITDA margin was 17.4% and 20.3%, respectively. The decrease in both Segment Adjusted EBITDA and Segment Adjusted EBITDA margin was a result of business mix, the timing of projects in some of our specialty labs, the impact of the cyber-attack in June 2022, which temporarily disrupted certain of our labs’ ability to operate and higher variable cost increases (including travel, laboratory and field supplies).

Remediation and Reuse Segment Adjusted EBITDA for the nine months ended September 30, 2022 was $22.1 million, an increase of $9.8 million compared to Segment Adjusted EBITDA for the nine months ended September 30, 2021 of $12.3 million. For the nine months ended September 30, 2022 and September 30, 2021, Segment Adjusted EBITDA margin was 16.1% and 15.0%,

43

respectively. The increase in both Segment Adjusted EBITDA and Segment Adjusted EBITDA margin was a result of significantly higher revenues and business mix, partially offset by our continued investments in operating infrastructure in this segment that temporarily impact margins.

Corporate and other costs were $22.8 million for the nine months ended September 30, 2022 compared to $22.0 million for the nine months ended September 30, 2021. Corporate and other costs were 5.6% and 5.5% of revenues for the nine months ended September 30, 2022 and September 30, 2021, respectively.

Liquidity and Capital Resources

Liquidity describes the ability of a company to generate sufficient cash flows to meet the cash requirements of its business operations, including working capital needs, debt service, acquisitions, other commitments and contractual obligations. We consider liquidity in terms of cash flows from operations and other sources, including availability under our credit facility, and their sufficiency to fund our operating and investing activities.

Our principal sources of liquidity have been cash generated by operating activities, borrowings under our credit facilities, other borrowing arrangements, and proceeds from the issuance of common and preferred stock. Historically, we have financed our operations and acquisitions from a combination of cash generated from operations, periodic borrowings under senior secured credit facilities, other prior secured and unsecured borrowings and proceeds from the issuance of common and preferred stock. Our primary cash needs are for day to day operations, to fund working capital requirements, to fund our acquisition strategy, to pay interest and principal on our indebtedness and dividends on our Series A-2 preferred stock, and to make capital expenditures. Additionally, in connection with certain acquisitions, we agree to earn-out provisions and other purchase price adjustments that may require future payments. For example, the CTEH acquisition agreement included an earn-out provision that provided for the payment of contingent consideration based on CTEH’s 2021 results in an aggregate amount not to exceed $30.0 million, with the earn-out payment equal to a specified multiple of CTEH’s EBITDA for 2021 in excess of a specified target. CTEH fully achieved the target in 2021 and the $30.0 million payment was paid in cash in the first quarter of 2022. We may also be required to make up to $3.0 million in aggregate earn-out payments during the year 2023 in connection with certain of our business acquisitions. See Note 7 to our unaudited condensed consolidated financial statements included in Part 1, Item 1. “Financial Statements.”

We expect to continue to fund our liquidity requirements, including any cash earn-out payments that may be required in connection with acquisitions, through cash generated from operations and borrowings under our credit facility. We believe these sources will be sufficient to fund our cash needs for the short- and long-term. See “—COVID-19” above for a discussion of the impact of the pandemic on our liquidity.

Cash Flows

The following table summarizes our cash flows for the periods presented:

	Nine Months Ended September 30,
(in thousands)	2022			2021
Consolidated Statement of Cash Flows Data:
Net cash provided by operating activities	$	8,165		$	13,708
Net cash used in investing activities		(27,315	)		(50,688	)
Net cash (used in) provided by financing activities		(34,050	)		17,748
Change in cash, cash equivalents and restricted cash	$	(53,200	)	$	(19,232	)

Operating Activities

Cash flows from operating activities can fluctuate from period-to-period as earnings, working capital needs and the timing of payments for contingent consideration, taxes, bonus payments and other operating items impact reported cash flows.

For the nine months ended September 30, 2022, net cash provided by operating activities was $8.2 million compared to net cash provided by operating activities of $13.7 million for the nine months ended September 30, 2021. Cash provided by operations includes payment of contingent consideration of $19.5 million and $15.5 million in the nine months ended September 30, 2022 and September 30, 2021, respectively. Excluding payment of contingent consideration, cash provided by operating activities was $27.7 million for the nine months ended September 30, 2022, compared to cash provided by operating activities of $29.2 million in the prior year, a decrease of $1.5 million. The period-over-period decrease, excluding the impact of contingent consideration, was primarily due

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to lower earnings before non-cash items of $6.0 million, partially offset by an increase in working capital in the current year of $13.4 million versus an increase in working capital in the prior year of $17.6 million.

Working capital increased by $13.4 million in the nine months ended September 30, 2022, primarily due to a decrease in accounts payable and other accrued liabilities of $12.9 million, (as a result of the timing of vendor payments and lower contract liabilities due to the timing of project completion), a decrease in accrued payroll and benefits of $6.4 million, and an increase in prepaid expenses and other current assets of $1.4 million, partially offset by a decrease in accounts receivable and contract assets of $7.3 million. The increase in working capital of $17.6 million in the nine months ended September 30, 2021, was driven by an increase in accounts receivable and contract assets of $12.5 million (as a result of significantly higher revenues in the three months ended September 30, 2021 when compared to the three months ended December 31, 2020), a decrease in accounts payable and other accrued liabilities of $3.4 million and an increase in prepaid expenses and other current assets of $1.8 million.

Investing Activities

For the nine months ended September 30, 2022, net cash used in investing activities was $27.3 million, primarily driven by cash paid for the acquisitions of EnvStd, IAG, Triad and AirKinetics net of cash acquired, of $21.3 million, as well as purchases of property and equipment for cash consideration of $5.4 million and payment of assumed purchase price obligations of $0.4 million.

For the nine months ended September 30, 2021, net cash used in investing activities was $50.7 million, primarily driven by cash paid for the acquisitions of MSE, Vista, EI and Sensible, net of cash acquired, of $36.5 million, as well as payment of assumed purchase price obligations of $8.6 million, and purchases of property and equipment for cash consideration of $5.4 million.

Financing Activities

For the nine months ended September 30, 2022, net cash used in financing activities was $34.1 million. Cash used in financing activities was driven by the payment of the quarterly dividends on the Series A-2 preferred stock of $12.3 million, the payment of acquisition-related contingent consideration of $10.7 million, term loan amortization payments of $8.8 million related to our 2021 Credit Facility, and the repayment of finance leases of $2.9 million, partially offset by proceeds received from the exercise of stock options of $0.8 million.

For the nine months ended September 30, 2021, net cash provided in financing activities was $17.7 million. Cash provided by financing activities was driven by borrowings under the 2021 Credit Facility, consisting of $175.0 million under the term loan and $37.0 million under the revolver, and proceeds received from the exercise of stock options of $6.0 million, partially offset by the use of proceeds from the 2021 Credit Facility to repay the $213.4 million outstanding under the 2020 Credit Facility, the payment of the quarterly dividend on the Series A-2 preferred stock of $12.3 million, the payment of acquisition-related contingent consideration of $9.6 million, and the repayment of finance leases of $1.9 million.

Credit Facilities

2021 Credit Facility

On April 27, 2021, we entered into a Senior Secured Credit Agreement, or the 2021 Credit Facility, providing for a $300.0 million credit facility comprised of a $175.0 million term loan and a $125.0 million revolving credit facility, and used a portion of the proceeds to repay all amounts outstanding under the 2020 Credit Facility. The 2021 revolving credit facility includes a $20.0 million sublimit for the issuance of letters of credit. Subject to certain exceptions, all amounts under the 2021 Credit Facility will become due on April 27, 2026. We have the option to borrow incremental term loans or request an increase in the aggregate commitments under the revolving credit facility up to an aggregate amount of $150.0 million subject to the satisfaction of certain conditions.

The 2021 Credit Facility term loan must be repaid in quarterly installments. See Note 12 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

The 2021 Credit Facility term loan and the revolver bear interest subject to the Company’s leverage ratio and LIBOR as follows:

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Pricing Tier	Consolidated Leverage Ratio	Senior Credit Facilities LIBOR			Senior Credit Facilities Base Rate			Commitment Fee			Letter of Credit Fee
1	≥ 3.75x to 1.0		2.50	%		1.50	%		0.25	%		2.50	%
2	< 3.75x to 1.0 but ≥ 3.25 to 1.0		2.25			1.25			0.23			2.25
3	<3.25x to 1.0 but ≥ 2.50 to 1.0		2.00			1.00			0.20			2.00
4	<2.50x to 1.0 but ≥ 1.75 to 1.0		1.75			0.75			0.15			1.75
5	<1.75x to 1.0		1.50			0.50		0.15				1.50

On January 27, 2022, the Company entered into an interest rate swap transaction fixing the floating component of the interest rate on $100.0 million of borrowings to 1.39% until January 27, 2025. Additionally, effective September 1, 2022, the Company received an interest rate reduction of 0.05% under the 2021 Credit Facility based on the Company’s achievement of certain sustainability and environmental, social and governance related objectives as provided for in the 2021 Credit Facility.

Our obligations under the 2021 Credit Facility are guaranteed by certain of our existing and future direct and indirect subsidiaries, and such obligations are secured by substantially all of our assets. The 2021 Credit Facility includes a number of covenants imposing certain restrictions on our business, including, among other things, restrictions on our ability to incur indebtedness, prepay or amend other indebtedness, create liens, make certain fundamental changes including mergers or dissolutions, pay dividends and repurchase or make other payments in respect of capital stock, make certain investments, sell assets, change our lines of business, enter into transactions with affiliates and other corporate actions. The 2021 Credit Facility also includes financial covenants requiring us to remain below a maximum total net leverage ratio of 4.25 times, which steps down to 4.00 times beginning with the quarter ending December 31, 2022 through and including the quarter ending September 30, 2023 and then to 3.75 times beginning with the quarter ending December 31, 2023 (provided that, subject to certain requirements, the maximum net leverage ratio may be increased by 0.50:1.00, not to exceed 4.25:1.00, for a period of four consecutive fiscal quarters in connection with certain permitted acquisitions), and a minimum fixed charge coverage ratio of 1.25 times. As of September 30, 2022, the Company’s consolidated total leverage ratio (as defined in the 2021 Credit Facility) was 1.2 times. The calculation of the Company’s consolidated total leverage ratio under the 2021 Credit Facility is consistent with the calculation of the consolidated total leverage ratio under the 2020 Credit Facility.

The weighted average interest rate on the 2021 Credit Facility for the nine months ended September 30, 2022 was 2.9%. We were in compliance with all applicable covenants under the 2021 Credit Facility for the nine months ended September 30, 2022.

The 2021 Credit Facility contains a mandatory prepayment feature upon a number of events, including with the proceeds of certain asset sales and proceeds from the issuance of any debt.

See Note 12 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

2020 Credit Facility

On April 13, 2020, we entered into a Unitranche Credit Agreement, or the 2020 Credit Facility, providing for a $225.0 million credit facility comprised of a $175.0 million term loan and a $50.0 million revolving credit facility. The 2020 Credit facility was repaid in full in April 2021. The resulting loss on extinguishment upon repayment of the 2020 Credit Facility in April 2021, amounted to $4.1 million, of which $1.0 million was related to fees paid and $3.1 related to unamortized debt issuance costs. Total loss on extinguishment is recorded in interest expense-net within the unaudited condensed consolidated statement of operations for the nine months ended September 30, 2021.

See Note 12 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Series A-2 Preferred Stock

On April 13, 2020, we issued 17,500 shares of the Series A-2 preferred stock with a par value of $0.0001 per share and a warrant to purchase common stock, in exchange for $175.0 million. Prior to the completion of the IPO, each share of Series A-2 preferred stock accrued dividends at the rate of 15.0% per annum with respect to dividends that were paid in cash, and 14.2% per annum, with respect to dividends that accrued and compounded, resulting in an annual dividend rate of 15.0%. Following the completion of the IPO, the Series A-2 preferred stock does not mature or have a cash repayment obligation; however, it is redeemable at our option. The Series A-2 preferred stock becomes convertible into our common stock beginning on the four-year anniversary of the Series A-2 preferred stock issuance. Upon the four-year anniversary of the issuance, holders of Series A-2 preferred stock may convert up to $60.0 million of such shares into our common stock at a conversion rate discounted to 85.0% of the volume weighted average trading value, with the permitted amount of Series A-2 preferred stock to be converted increasing at each subsequent

46

anniversary of the issuance until the sixth anniversary, after which all of the Series A-2 preferred stock may be converted at the holder’s option. Following the completion of the IPO on July 27, 2020, the Series A-2 preferred stock dividend rate changed to 9.0% per annum with required quarterly cash payments. If permitted under our existing debt facilities, we must pay the Series A-2 preferred stock dividend in cash each quarter.

With respect to any redemption of any share of the Series A-2 preferred stock prior to April 13, 2023, we are subject to a make whole penalty in which the holder is guaranteed at least three years of dividend payments on the redeemed amount.

See Note 15 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Critical Accounting Policies and Estimates

Our 2021 Form 10-K includes a summary of the critical accounting policies and estimates we believe are the most important to aid in understanding our financial results. There have been no material changes to those critical accounting policies and estimates as disclosed therein, other than as described in Note 2 to our unaudited condensed consolidated financial statements included in Part I, Item 1. “Financial Statements.”

Item 3. Quantitative and Qualitative Disclosures About Market Risk.

Interest Rate Risk

We have market risk exposure arising from changes in interest rates on our credit facility, which bears interest at rates that are benchmarked subject to the Company’s leverage ratio and LIBOR. Based on our overall interest rate exposure to variable rate debt outstanding as of September 30, 2022, which factors in our interest rate swap on $100.0 million of debt, a 1.0% increase or decrease in interest rates on the term loan and revolver would increase annual income (loss) before income taxes by approximately $0.7 million.

Inflation Risk

We have experienced higher labor and significantly higher travel and other direct costs in the current year as a result of inflation, particularly in our Measurement and Analysis and Remediation and Reuse segments. We believe we have successfully raised prices in businesses with short term contracts to offset these inflationary effects. We also have and are continuing to raise prices on medium term (one to four quarter) contracts as these contracts are renewed or new contracts are won, but the timing of these price increases has lagged behind our cost increases due to the longer term nature of these contracts. We expect to continue to raise prices if direct costs continue to increase in the last quarter of 2022 and beyond. Although inflation has increased our Selling, general and administrative expense, impacting margins and segment Adjusted EBITDA, in the year-to-date period, we do not believe over a longer period of time that inflation will have a material effect on our business, financial condition or results of operations. If our costs were to become subject to additional and unanticipated significant sustained inflationary pressures, we may not be able to fully offset such higher costs through price increases. Our inability or failure to do so could adversely affect our business, financial condition and results of operations.

Item 4. Controls and Procedures.

Evaluation of Disclosure Controls and Procedures

As required by Rule 13a-15(b) under the Exchange Act, our management, including our Chief Executive Officer and Chief Financial Officer, carried out an evaluation of the effectiveness of the design and operation of our disclosure controls and procedures (as defined in Rule 13a-15(e) under the Exchange Act), as of September 30, 2022, the end of the period covered by this Quarterly Report on Form 10-Q. Based on the foregoing, our Chief Executive Officer and Chief Financial Officer concluded that, as of September 30, 2022, the end of the period covered by this Quarterly Report on Form 10-Q, our disclosure controls and procedures were effective at the reasonable assurance level.

Internal Control Over Financial Reporting

There were no changes in our internal control over financial reporting (as defined in Rule 13a-15(f) under the Exchange Act) that occurred during the quarter ended September 30, 2022, that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

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Limitations on Effectiveness of Controls

Our management, including our Chief Executive Officer and Chief Financial Officer, does not expect that our disclosure controls and procedures or our system of internal control over financial reporting will prevent or detect all errors and all fraud. A control system, no matter how well designed or operated, can provide only reasonable, but not absolute, assurance that the objectives of the system of internal control are met. The design of our control system reflects the fact that there are resource constraints, and that the benefits of such control system must be considered relative to their costs. Further, because of the inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that all control failures and instances of fraud, if any, within the Company have been detected. These inherent limitations include the realities that judgments in decision-making can be faulty and that breakdowns can occur because of simple error or mistake. Additionally, controls can be circumvented by the intentional acts of individuals, by collusion of two or more people, or by management override of the controls. The design of any system of controls is also based in part on certain assumptions about the likelihood of future events, and there can be no assurance that the design of any particular control will always succeed in achieving its objective under all potential future conditions.

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PART II—OTHER INFORMATION

Item 1. Legal Proceedings.

From time to time, we are subject to various legal proceedings that arise in the normal course of our business activities, including those involving labor and employment, anti-discrimination, commercial disputes and other matters. We are not a party to any litigation the outcome of which, if determined adversely to us, would individually or in the aggregate be reasonably expected to have a material adverse effect on our results of operations or financial position. Regardless of outcome, litigation can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors.

Item 1A. Risk Factors.

There have been no material changes to our risk factors from the risk factors disclosed in our 2021 Form 10-K. The risks described in our 2021 Form 10-K, in addition to the other information set forth in this Quarterly Report on Form 10-Q, are not the only risks facing we face. Additional risks and uncertainties not currently known to us or that we currently deem to be immaterial also may materially adversely affect our business, financial condition and/or operating results.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds.

None.

Item 3. Defaults Upon Senior Securities.

None.

Item 4. Mine Safety Disclosures.

Not applicable.

Item 5. Other Information.

None.

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Item 6. Exhibits.

Exhibit Number	Description
31.1*	Certification of Principal Executive Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
31.2*	Certification of Principal Financial Officer Pursuant to Rules 13a-14(a) and 15d-14(a) under the Securities Exchange Act of 1934, as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
32.1**	Certification of Principal Executive Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
32.2**	Certification of Principal Financial Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
101.INS*	Inline XBRL Instance Document
101.SCH*	Inline XBRL Taxonomy Extension Schema Document
101.CAL*	Inline XBRL Taxonomy Extension Calculation Linkbase Document
101.DEF*	Inline XBRL Taxonomy Extension Definition Linkbase Document
101.LAB*	Inline XBRL Taxonomy Extension Label Linkbase Document
101.PRE*	Inline XBRL Taxonomy Extension Presentation Linkbase Document
104*	Cover Page Interactive Data File – The cover page from the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2022 is formatted in Inline XBRL (included as Exhibit 101)

* Filed herewith.

** Exhibit is furnished and shall not be deemed “filed” for purposes of Section 18 of the Exchange Act, or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act, or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.

50

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	Montrose Environmental Group, Inc.
Date: November 9, 2022	By:	/s/ Allan Dicks
		Allan Dicks
		Chief Financial Officer

51

EX-31.1

Exhibit 31.1

CERTIFICATION PURSUANT TO

RULES 13a-14(a) AND 15d-14(a) UNDER THE SECURITIES EXCHANGE ACT OF 1934,

AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Vijay Manthripragada, certify that:

1.I have reviewed this Quarterly Report on Form 10-Q of Montrose Environmental Group, Inc.;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5.The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: November 9, 2022	By:	/s/ Vijay Manthripragada
		Vijay Manthripragada
		Chief Executive Officer (Principal Executive Officer)

EX-31.2

Exhibit 31.2

CERTIFICATION PURSUANT TO

RULES 13a-14(a) AND 15d-14(a) UNDER THE SECURITIES EXCHANGE ACT OF 1934,

AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Allan Dicks, certify that:

1.I have reviewed this Quarterly Report on Form 10-Q of Montrose Environmental Group, Inc.;

2.Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a)Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b)Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c)Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d)Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5.The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a)All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b)Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: November 9, 2022	By:	/s/ Allan Dicks
		Allan Dicks
		Chief Financial Officer (Principal Financial Officer)

EX-32.1

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Montrose Environmental Group, Inc. (the “Company”) on Form 10-Q for the quarter ended September 30, 2022 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Vijay Manthripragada, Chief Executive Officer of the Company, certify pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

(1)The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: November 9, 2022	By:	/s/ Vijay Manthripragada
		Vijay Manthripragada
		Chief Executive Officer (Principal Executive Officer)

A signed original of this written statement required by Section 906 has been provided to Montrose Environmental Group, Inc. and will be retained by Montrose Environmental Group, Inc. and furnished to the Securities and Exchange Commission or its staff upon request.

EX-32.2

Exhibit 32.2

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Montrose Environmental Group, Inc. (the “Company”) on Form 10-Q for the quarter ended September 30, 2022 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Allan Dicks, Chief Financial Officer of the Company, certify pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

(1)The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2)The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Date: November 9, 2022	By:	/s/ Allan Dicks
		Allan Dicks
		Chief Financial Officer (Principal Financial Officer)

A signed original of this written statement required by Section 906 has been provided to Montrose Environmental Group, Inc. and will be retained by Montrose Environmental Group, Inc. and furnished to the Securities and Exchange Commission or its staff upon request.

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Entity Common Stock, Shares Outstanding		29,711,566
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-39394
Entity Tax Identification Number	46-4195044
Entity Incorporation State Country Code	DE
Entity Address Address Line1	5120 Northshore Drive
Entity Address City Or Town	North Little Rock
Entity Address State Or Province	AR
Entity Address Postal Zip Code	72118
City Area Code	501
Local Phone Number	900-6400
Security12b Title	Common Stock, par value $0.000004 per share
Security Exchange Name	NYSE

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UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
CURRENT ASSETS:
Cash and restricted cash	$ 93,566	$ 146,741
Accounts receivable—net	80,927	98,513
Contract assets	60,444	40,139
Prepaid and other current assets	10,890	8,465
Total current assets	245,827	293,858
NON-CURRENT ASSETS:
Property and equipment—net	33,581	31,521
Operating lease right-of-use asset—net	28,453	23,532
Finance lease right-of-use asset—net	9,869	8,944
Goodwill	318,413	311,944
Other intangible assets—net	146,268	160,997
Other assets	6,694	2,298
TOTAL ASSETS	789,105	833,094
CURRENT LIABILITIES:
Accounts payable and other accrued liabilities	58,316	68,936
Accrued payroll and benefits	20,477	25,971
Business acquisitions contingent consideration, current	3,967	31,450
Current portion of operating lease liabilities	8,130	6,888
Current portion of finance lease liabilities	3,763	3,512
Current portion of long-term debt	8,750	10,938
Total current liabilities	103,403	147,695
NON-CURRENT LIABILITIES:
Business acquisitions contingent consideration, long-term	2,810	4,350
Other non-current liabilities	22	100
Deferred tax liabilities—net	5,766	4,006
Conversion option	24,730	23,081
Operating lease liability—net of current portion	20,841	16,859
Finance lease liability—net of current portion	6,562	5,756
Long-term debt—net of deferred financing fees	155,645	161,818
Total liabilities	319,779	363,665
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS’ EQUITY:
Additional paid-in-capital	485,030	464,143
Accumulated deficit	(168,685)	(147,678)
Accumulated other comprehensive income	53	36
Total stockholders’ equity	316,398	316,501
TOTAL LIABILITIES, CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK AND STOCKHOLDERS’ EQUITY	789,105	833,094
Convertible And Redeemable Series A-2 Preferred Stock
NON-CURRENT LIABILITIES:
REDEEMABLE SERIES PREFERRED STOCK	$ 152,928	$ 152,928

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UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Common stock, par value	$ 0.000004	$ 0.000004
Common stock, shares authorized	190,000,000	190,000,000
Common stock, shares issued	29,707,503	29,619,921
Common stock, shares outstanding	29,707,503	29,619,921
Convertible And Redeemable Series A-2 Preferred Stock
Temporary equity, par value	$ 0.0001	$ 0.0001
Temporary equity, shares authorized	17,500	17,500
Temporary equity, shares issued	17,500	17,500
Temporary equity, shares outstanding	17,500	17,500
Temporary equity, aggregate liquidation preference	$ 182.2	$ 182.2

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UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE (LOSS) INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
REVENUES	$ 130,312	$ 132,578	$ 404,902	$ 402,619
COST OF REVENUES (exclusive of depreciation and amortization shown below)	82,234	85,242	261,049	272,662
SELLING, GENERAL AND ADMINISTRATIVE EXPENSE	42,857	30,499	131,120	82,865
FAIR VALUE CHANGES IN BUSINESS ACQUISITIONS CONTINGENCIES	59	0	(3,472)	24,035
DEPRECIATION AND AMORTIZATION	11,504	11,471	35,928	33,145
(LOSS) INCOME FROM OPERATIONS	(6,342)	5,366	(19,723)	(10,088)
OTHER INCOME (EXPENSE)
Other income (expense)	1,814	(516)	4,618	(1,909)
Interest expense—net	(1,400)	(1,722)	(4,010)	(11,208)
Total other income (expense) - net	414	(2,238)	608	(13,117)
(LOSS) INCOME BEFORE (BENEFIT) EXPENSE FROM INCOME TAXES	(5,928)	3,128	(19,115)	(23,205)
INCOME TAX (BENEFIT) EXPENSE	(208)	902	1,892	648
NET (LOSS) INCOME	(5,720)	2,226	(21,007)	(23,853)
EQUITY ADJUSTMENT FROM FOREIGN CURRENCY TRANSLATION	20	(74)	17	(17)
COMPREHENSIVE (LOSS) INCOME	(5,700)	2,152	(20,990)	(23,870)
CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK DIVIDEND	(4,100)	(4,100)	(12,300)	(12,300)
NET LOSS ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ (9,820)	$ (1,874)	$ (33,307)	$ (36,153)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING - BASIC	29,691	26,220	29,677	25,798
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING - DILUTED	29,691	26,220	29,677	25,798
NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS - BASIC	$ (0.33)	$ (0.07)	$ (1.12)	$ (1.40)
NET LOSS PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS - DILUTED	$ (0.33)	$ (0.07)	$ (1.12)	$ (1.40)

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UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Convertible And Redeemable Series A-2 Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2020	$ 137,145			$ 259,427	$ (122,353)	$ 71
Beginning balance, shares at Dec. 31, 2020			24,932,527
Beginning balance at Dec. 31, 2020		$ 152,928
Beginning balance, shares at Dec. 31, 2020		17,500
Net loss	(12,931)				(12,931)
Stock-based compensation	1,805			1,805
Dividend payment to the Series A-2 preferred shareholders	(4,100)			(4,100)
Common stock issued	4,456			4,456
Common stock issued, shares			506,330
Accumulated other comprehensive income (loss)	29					29
Ending balance at Mar. 31, 2021	126,404			261,588	(135,284)	100
Ending balance, shares at Mar. 31, 2021		17,500
Ending balance at Mar. 31, 2021		$ 152,928
Ending balance, shares at Mar. 31, 2021			25,438,857
Beginning balance at Dec. 31, 2020	137,145			259,427	(122,353)	71
Beginning balance, shares at Dec. 31, 2020			24,932,527
Beginning balance at Dec. 31, 2020		$ 152,928
Beginning balance, shares at Dec. 31, 2020		17,500
Net loss	$ (23,853)
Dividend payment to the Series A-2 preferred shareholders		$ (12,300)
Common stock issued, shares	1,593,317
Ending balance at Sep. 30, 2021	$ 145,698			291,850	(146,206)	54
Ending balance, shares at Sep. 30, 2021		17,500
Ending balance at Sep. 30, 2021		$ 152,928
Ending balance, shares at Sep. 30, 2021			26,525,844
Beginning balance at Mar. 31, 2021	126,404			261,588	(135,284)	100
Beginning balance, shares at Mar. 31, 2021			25,438,857
Beginning balance at Mar. 31, 2021		$ 152,928
Beginning balance, shares at Mar. 31, 2021		17,500
Net loss	(13,148)				(13,148)
Stock-based compensation	2,417			2,417
Dividend payment to the Series A-2 preferred shareholders	(4,100)			(4,100)
Common stock issued	27,460			27,460
Common stock issued, shares			669,331
Accumulated other comprehensive income (loss)	28					28
Ending balance at Jun. 30, 2021	139,061			287,365	(148,432)	128
Ending balance, shares at Jun. 30, 2021		17,500
Ending balance at Jun. 30, 2021		$ 152,928
Ending balance, shares at Jun. 30, 2021			26,108,188
Net loss	2,226				2,226
Stock-based compensation	2,365			2,365
Dividend payment to the Series A-2 preferred shareholders	(4,100)	$ (4,100)		(4,100)
Common stock issued	$ 6,220			6,220
Common stock issued, shares	417,656		417,656
Accumulated other comprehensive income (loss)	$ (74)					(74)
Ending balance at Sep. 30, 2021	145,698			291,850	(146,206)	54
Ending balance, shares at Sep. 30, 2021		17,500
Ending balance at Sep. 30, 2021		$ 152,928
Ending balance, shares at Sep. 30, 2021			26,525,844
Beginning balance at Dec. 31, 2021	316,501			464,143	(147,678)	36
Beginning balance, shares at Dec. 31, 2021			29,619,921
Beginning balance at Dec. 31, 2021		$ 152,928
Beginning balance, shares at Dec. 31, 2021		17,500
Net loss	(7,536)				(7,536)
Stock-based compensation	10,425			10,425
Dividend payment to the Series A-2 preferred shareholders	(4,100)			(4,100)
Common stock issued	429			429
Common stock issued, shares			55,896
Accumulated other comprehensive income (loss)	45					45
Ending balance at Mar. 31, 2022	315,764			470,897	(155,214)	81
Ending balance, shares at Mar. 31, 2022		17,500
Ending balance at Mar. 31, 2022		$ 152,928
Ending balance, shares at Mar. 31, 2022			29,675,817
Beginning balance at Dec. 31, 2021	316,501			464,143	(147,678)	36
Beginning balance, shares at Dec. 31, 2021			29,619,921
Beginning balance at Dec. 31, 2021		$ 152,928
Beginning balance, shares at Dec. 31, 2021		17,500
Net loss	$ (21,007)
Dividend payment to the Series A-2 preferred shareholders		$ (12,300)
Common stock issued, shares	87,582
Ending balance at Sep. 30, 2022	$ 316,398			485,030	(168,685)	53
Ending balance, shares at Sep. 30, 2022		17,500
Ending balance at Sep. 30, 2022		$ 152,928
Ending balance, shares at Sep. 30, 2022			29,707,503
Beginning balance at Mar. 31, 2022	315,764			470,897	(155,214)	81
Beginning balance, shares at Mar. 31, 2022			29,675,817
Beginning balance at Mar. 31, 2022		$ 152,928
Beginning balance, shares at Mar. 31, 2022		17,500
Net loss	(7,751)				(7,751)
Stock-based compensation	10,932			10,932
Dividend payment to the Series A-2 preferred shareholders	(4,100)			(4,100)
Common stock issued	54			54
Common stock issued, shares			3,575
Accumulated other comprehensive income (loss)	(48)					(48)
Ending balance at Jun. 30, 2022	314,851			477,783	(162,965)	33
Ending balance, shares at Jun. 30, 2022		17,500
Ending balance at Jun. 30, 2022		$ 152,928
Ending balance, shares at Jun. 30, 2022			29,679,392
Net loss	(5,720)				(5,720)
Stock-based compensation	11,018			11,018
Dividend payment to the Series A-2 preferred shareholders	(4,100)	$ (4,100)		(4,100)
Common stock issued	$ 329			329
Common stock issued, shares	28,111		28,111
Accumulated other comprehensive income (loss)	$ 20					20
Ending balance at Sep. 30, 2022	$ 316,398			$ 485,030	$ (168,685)	$ 53
Ending balance, shares at Sep. 30, 2022		17,500
Ending balance at Sep. 30, 2022		$ 152,928
Ending balance, shares at Sep. 30, 2022			29,707,503

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UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
OPERATING ACTIVITIES:
Net loss	$ (5,720)	$ 2,226	$ (21,007)	$ (23,853)
Adjustments to reconcile net loss to net cash used in operating activities:
(Recovery) Provision for bad debt			(821)	803	$ 1,135
Depreciation and amortization	11,504	11,471	35,928	33,145
Amortization of right-of-use asset			6,934	5,947
Stock-based compensation expense	11,018	2,365	32,375	6,587
Fair value changes in financial instruments			(4,664)	1,651
Fair value changes in business acquisitions contingencies	59	0	(3,472)	24,035
Deferred income taxes			1,892	232
Debt extinguishment costs				4,052
Other			460	68
Changes in operating assets and liabilities—net of acquisitions:
Accounts receivable and contract assets			7,301	(12,503)
Prepaid expenses and other current assets			(1,364)	(1,781)
Accounts payable and other accrued liabilities			(12,943)	(3,422)
Accrued payroll and benefits			(6,363)	61
Payment of contingent consideration			(19,457)	(15,549)
Change in operating leases			(6,634)	(5,765)
Net cash (used in) provided by operating activities			8,165	13,708
INVESTING ACTIVITIES:
Purchases of property and equipment			(5,414)	(5,405)
Proceeds received from corporate owned insurance			277
Proprietary software development and other software costs			(397)	(241)
Purchase price true ups			(439)	(8,562)
Cash paid for acquisitions—net of cash acquired			(21,342)	(36,480)
Net cash used in investing activities			(27,315)	(50,688)
FINANCING ACTIVITIES:
Proceeds from line of credit				109,000
Payments on line of credit				(72,000)
Proceeds from term loans				175,000
Repayment of term loan			(8,751)	(173,905)
Payment of contingent consideration			(10,722)	(9,605)
Repayment of finance leases			(2,906)	(1,884)
Debt issuance costs				(2,590)
Proceeds from issuance of common stock for exercised stock options			812	6,032
Dividend payment to the Series A-2 shareholders			(12,300)	(12,300)
Payments of deferred offering costs			(183)
Net cash (used in) provided by financing activities			(34,050)	17,748
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH			(53,200)	(19,232)
Foreign exchange impact on cash balance			25	357
Beginning of year			146,741	34,881	34,881
End of period	$ 93,566	$ 16,006	93,566	16,006	$ 146,741
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION:
Cash paid for interest			4,852	4,649
Cash paid for income tax			587	958
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accrued purchases of property and equipment			881	1,171
Property and equipment purchased under finance leases			3,939	1,766
Common stock issued to acquire new businesses				6,020
Acquisitions unpaid contingent consideration			$ 6,777	35,352
Offering costs included in accounts payable and other accrued liabilities				389
Acquisitions contingent consideration paid in shares				$ 26,084

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Description of the Business and Basis of Presentation

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of the Business and Basis of Presentation

1. DESCRIPTION OF THE BUSINESS AND BASIS OF PRESENTATION

Description of the Business—Montrose Environmental Group, Inc. (“Montrose” or the “Company”) is a corporation formed on November 2013, under the laws of the State of Delaware. The Company has approximately 80 offices across the United States, Canada and Australia and approximately 2,800 employees as of September 30, 2022.

Montrose is an environmental services company serving the recurring environmental needs of a diverse client base, including Fortune 500 companies and federal, state and local governments through the following three segments:

Assessment, Permitting and Response—Through its Assessment, Permitting and Response segment, Montrose provides scientific advisory and consulting services to support environmental assessments, environmental emergency response, and environmental audits and permits for current operations, facility upgrades, new projects, decommissioning projects and development projects. The Company’s technical advisory and consulting offerings include regulatory compliance support and planning, environmental, ecosystem and toxicological assessments and support during responses to environmental disruption. Montrose helps clients navigate regulations at the local, state, provincial and federal levels.

Measurement and Analysis—Through its Measurement and Analysis segment, Montrose’s teams test and analyze air, water and soil to determine concentrations of contaminants, as well as the toxicological impact of contaminants on flora, fauna and human health. Montrose’s offerings include source and ambient air testing and monitoring, leak detection and repair and advanced analytical laboratory services such as air, storm water, wastewater and drinking water analysis.

Remediation and Reuse—Through its Remediation and Reuse segment, Montrose provides clients with engineering, design, implementation and operations and maintenance services, primarily to treat contaminated water, remove contaminants from soil or create biogas from waste. The Company does not own the properties or facilities at which it implements these projects or the underlying liabilities, nor does it own material amounts of the equipment used in projects; instead, the Company assists clients in designing solutions, managing projects and mitigating their environmental risks and liabilities at their locations.

Basis of Presentation—The unaudited condensed consolidated financial statements include the operations of the Company and its wholly-owned subsidiaries. These unaudited condensed consolidated financial statements are presented in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) and have been prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) that permit reduced disclosure for interim periods. The unaudited condensed consolidated financial statements include all accounts of the Company and, in the opinion of management, include all recurring adjustments and normal accruals necessary for a fair statement of the Company’s financial position, results of operations and cash flows for the dates and periods presented. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2021. Results for interim periods are not necessarily indicative of the results to be expected during the remainder of the current year or for any future period. All intercompany transactions, accounts and profits, have been eliminated in the unaudited condensed consolidated financial statements.

Subsequent Events— The Company has evaluated subsequent events through the filing of this Quarterly Report on Form 10-Q, and determined that there have been no events that have occurred that would require adjustments to our disclosures in the unaudited condensed consolidated financial statements.

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Summary of New Accounting Pronouncements

9 Months Ended

Sep. 30, 2022

Accounting Standards Update and Change in Accounting Principle [Abstract]

Summary of New Accounting Pronouncements

2. SUMMARY OF NEW ACCOUNTING PRONOUNCEMENTS

Recently Adopted Accounting Pronouncements—Through the end of the year ended December 31, 2021, the Company qualified as an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”) and therefore has historically taken advantage of certain exemptions from various public company reporting requirements, including delaying adoption of new or revised accounting standards until those standards apply to private companies. The Company elected to use this extended transition period under the JOBS Act. The adoption dates discussed below are based on the Company no longer qualifying as an emerging growth company.

In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standard Update ("ASU") 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity

(Subtopic 815-40)—Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The ASU simplifies accounting for convertible instruments by removing major separation models required under current U.S. GAAP. Consequently, more convertible debt instruments will be reported as a single liability instrument with no separate accounting for embedded conversion features. The ASU removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception, which will permit more equity contracts to qualify for the exception. The ASU also simplifies the diluted net income per share calculation in certain areas. The new guidance is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years, and early adoption is permitted. The new guidance was adopted as of January 1, 2022 and did not have a material impact on the Company’s consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted—In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. Under the new guidance (ASC 805-20-30-28), the acquirer should determine what contract assets and/or contract liabilities it would have recorded under ASC 606 (the revenue guidance) as of the acquisition date, as if the acquirer had entered into the original contract at the same date and on the same terms as the acquiree. The new guidance is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is currently evaluating the impact of the adoption of the standard on the consolidated financial statements, but does not expect adoption to have a material impact on its consolidated financial statements. The future impact of this new guidance will be primarily a function of the facts and circumstances specific to any acquisitions consummated after adoption and therefore cannot be predicted prior to or at the time of adoption.

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Revenues and Accounts Receivable

9 Months Ended

Sep. 30, 2022

Revenues And Accounts Receivable [Abstract]

Revenues and Accounts Receivable

3. REVENUES AND ACCOUNTS RECEIVABLE

The Company’s main revenue sources derive from the following revenue streams:

Assessment, Permitting and Response Revenues—Assessment, Permitting and Response revenues are generated from multidisciplinary environmental consulting services. The majority of the contracts are fixed-price or time and material based.

Measurement and Analysis Revenues—Measurement and Analysis revenues are generated from emissions sampling, testing and reporting services, leak detection services, ambient air monitoring services and laboratory testing services. The majority of the contracts are fixed-price or time-and-materials based.

Remediation and Reuse Revenues—Remediation and Reuse revenues are generated from engineering, design, implementation and operating and maintenance (“O&M”) services primarily to treat contaminated water, remove contaminants from soil or create biogas from waste. Engineering, design and implementation contracts are predominantly fixed-fee and time-and-materials based. Services on the majority of O&M contracts are provided under long-term fixed-fee contracts.

Disaggregation of Revenue—The Company disaggregates revenue by its operating segments. The Company believes disaggregating revenue into these categories achieves the disclosure objectives to depict how the nature, amount, and uncertainty of revenue and cash flows are affected by economic factors. Disaggregated revenue disclosures are provided in Note 18.

Contract Balances—The Company presents contract balances for unbilled receivables (contract assets), as well as customer advances, deposits and deferred revenue (contract liabilities) within contract assets and accounts payable and accrued expenses, respectively, on the unaudited condensed consolidated statements of financial position. Amounts are generally billed at periodic intervals (e.g. weekly, bi-weekly or monthly) as work progresses in accordance with agreed-upon contractual terms. The Company utilizes the practical expedient to not adjust the promised amount of consideration for the effects of a significant financing component as the period between when the Company transfers services to a customer and when the customer pays for those services is one year or less. Amounts recorded as unbilled receivables are generally for services the Company is not entitled to bill based on the passage of time. Under certain contracts, billing occurs subsequent to revenue recognition, resulting in contract assets. The Company sometimes receives advances or deposits from customers before revenue is recognized, resulting in contract liabilities.

The following table presents the Company’s contract balances:

	September 30,		December 31,
	2022		2021
Contract assets	$	60,444	$	40,139
Contract liabilities		23,270		27,907

Contract assets acquired through business acquisitions amounted to $1.3 million and $0.5 million as of September 30, 2022 and December 31, 2021, respectively. Contract liabilities acquired through business acquisitions amounted to zero and $ 0.5 million as of

September 30, 2022 and December 31, 2021, respectively. Revenue recognized during the three and nine months ended September 30, 2022, included in the contract liabilities balance at the beginning of the year was $10.3 million and $23.6 million, respectively. The revenue recognized from the contract liabilities consisted of the Company satisfying performance obligations during the normal course of business.

The amount of revenue recognized from changes in the transaction price associated with performance obligations satisfied in prior periods during the three and nine months ended September 30, 2022 was not material.

Remaining Unsatisfied Performance Obligations—Remaining unsatisfied performance obligations represent the total dollar value of work to be performed on contracts awarded and in progress. The amount of remaining unsatisfied performance obligations increases with new contracts or additions to existing contracts and decreases as revenue is recognized on existing contracts. Contracts are included in the amount of remaining unsatisfied performance obligations when an enforceable agreement has been reached. As of September 30, 2022 and December 31, 2021, the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied was approximately $92.0 million and $108.7 million, respectively. As of September 30, 2022, the Company expected to recognize approximately $67.8 million of this amount as revenue within a year and $24.2 million the year after.

Accounts Receivable, Net—The Company extends non-interest-bearing trade credit to its customers in the ordinary course of business. Accounts receivable, net consisted of the following:

	September 30, 2022			December 31, 2021
Accounts receivable, invoiced	$	82,649		$	101,709
Accounts receivable, other		544			1,385
Allowance for doubtful accounts		(2,266	)		(4,581	)
Accounts receivable—net	$	80,927		$	98,513

As of September 30, 2022, the Company did not have any customers that exceeded 10.0% of its gross accounts receivable. As of December 31, 2021, the Company had one customer who accounted for 23.1% of its gross accounts receivable. For the three and nine months ended September 30, 2022, the Company had one customer who accounted for 11.1% and 14.8% of revenue, respectively. During the three months ended September 30, 2021, the Company did not have any customers that exceeded 10.0% of revenue. During the nine months ended September 30, 2021, the Company had three customers who accounted for 12.1%, 11.4% and 10.7% of revenue. The Company performs ongoing credit evaluations and based on past collection experience, the Company believes that the receivable balances from these largest customers do not represent a significant credit risk.

Accounts receivable are shown on the face of the consolidated statements of financial position, net of an allowance for doubtful accounts. The allowance for doubtful accounts is established at the origination of an account in accordance with ASU 2016-13, Financial Instruments—Credit Losses (Topic 326). ASC 326 requires the Company to estimate the lifetime expected credit losses on such instruments and to record an allowance to offset the receivables. In determining the allowance for doubtful accounts, the Company analyzes the aging of accounts receivable, historical bad debts, customer creditworthiness and current economic trends. The allowance for doubtful accounts consisted of the following:

	Beginning Balance		Bad Debt (Recovery) Expense			Charged to Allowance			Other(1)		Ending Balance
Nine months ended September 30, 2022	$	4,581	$	(821	)	$	(1,621	)	$	127	$	2,266
Year ended December 31, 2021		4,265		1,135			(1,548	)		729		4,581

____________________

(1)This amount consists of additions to the allowance due to business acquisitions.

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Prepaid and Other Current Assets

9 Months Ended

Sep. 30, 2022

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid and Other Current Assets

4. PREPAID AND OTHER CURRENT ASSETS

Prepaid and other current assets consisted of the following:

	September 30,		December 31,
	2022		2021
Deposits	$	1,402	$	843
Prepaid expenses		4,708		4,675
Supplies		3,686		2,439
Income tax receivable		1,094		508
Prepaid and other current assets	$	10,890	$	8,465

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Property and Equipment, Net

9 Months Ended

Sep. 30, 2022

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

5. PROPERTY AND EQUIPMENT, NET

Property and equipment are stated at cost or estimated fair value for assets acquired through business combinations. Depreciation and amortization are provided using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the remaining lease term, including options that are deemed to be reasonably assured, or the estimated useful life of the improvement.

Property and equipment, net, consisted of the following:

	Estimated	September 30,			December 31,
	Useful Life	2022			2021
Lab and test equipment	7 years	$	19,975		$	18,581
Vehicles	5 years		5,642			5,414
Equipment	3-7 years		38,446			35,148
Furniture and fixtures	7 years		2,895			2,844
Leasehold improvements	7 years		8,535			7,268
Aircraft	10 years		931			931
Building	39 years		2,975			2,975
			79,399			73,161
Land			725			725
Construction in progress			2,566			2,342
Less accumulated depreciation			(49,109	)		(44,707	)
Total property and equipment—    net		$	33,581		$	31,521

Total depreciation expense included in the unaudited condensed consolidated statements of operations was $1.7 million and $5.3 million for the three and nine months ended September 30, 2022, respectively, and $1.8 million and $4.8 million for the three and nine months ended September 30, 2021, respectively.

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Leases

9 Months Ended

Sep. 30, 2022

Leases [Abstract]

Leases

6. LEASES

In June 2021, with an effective adoption date of January 1, 2021, the Company adopted ASU 2016-02 using the modified retrospective approach, which permits application of this guidance at the beginning of the period of adoption.

Leases are classified as either finance leases or operating leases based on criteria in ASC 842. The Company has finance leases for its vehicle and equipment leases and operating leases for its real estate space and office equipment leases. The Company’s operating and finance leases generally have original lease terms between 1 year and 15 years, and in some instances include one or more options to renew. The Company includes options to extend the lease term if the options are reasonably certain of being exercised. The Company currently considers some of its renewal options to be reasonably certain to be exercised. Some leases also include early termination options, which can be exercised under specific conditions. The Company does not have material residual value guarantees or restrictive covenants associated with its leases.

Finance and operating lease assets represent the right to use an underlying asset for the lease term, and finance and operating lease liabilities represent the obligation to make lease payments arising from the lease.

The Company calculates the present value of its finance and operating leases using an estimated incremental borrowing rate (“IBR”), which requires judgment. For real estate operating leases, the Company estimates the IBR based on prevailing market rates for collateralized debt in a similar economic environment with similar payment terms and maturity dates commensurate with the terms of the lease. For all other leases, the Company estimates the IBR based on the stated interest rate on the contract. Since many of the inputs used to calculate the rate implicit in the leases are not readily determinable from the lessee’s perspective, the Company will not use the implicit interest rate.

Certain leases contain variable payments, these payments are expensed as incurred and not included in the Company’s operating lease right-of-use assets and operating lease liabilities. These amounts primarily include payments for maintenance, utilities, taxes, and insurance and are excluded from the present value of the Company’s lease obligations.

Effective January 1, 2021, the Company recognized operating lease right-of-use assets, current operating lease liabilities and operating lease liabilities, net of current portion of $24.6 million, $7.3 million and $17.3 million, respectively. The Company also

recognized finance lease right-of-use assets, current finance lease liabilities and finance lease liabilities, net of current portion of $7.2 million, $2.9 million and $4.6 million, respectively.

The Company does not record operating lease right-of-use assets or operating lease liabilities for leases with an initial term of 12 months or less. The Company also combines lease and non-lease components on all new or modified operating leases into a single lease component for all classes of assets.

The components of lease expense were as follows:

		For the Three Months Ended September 30,
	Statement of Operations Location	2022		2021
Operating lease cost
Lease cost	Selling, general and administrative expense	$	2,542	$	2,203
Variable lease cost	Selling, general and administrative expense		354		120
Total operating lease cost			2,896		2,323
Finance lease cost
Amortization of right of use assets	Depreciation and amortization		1,075		825
Interest on lease liabilities	Interest expense—net		116		97
Total finance lease cost			1,191		922
Total lease cost		$	4,087	$	3,245
		For the Nine Months Ended September 30,
	Statement of Operations Location	2022		2021
Operating lease cost
Lease cost	Selling, general and administrative expense	$	7,472	$	6,398
Variable lease cost	Selling, general and administrative expense		911		329
Total operating lease cost			8,383		6,727
Finance lease cost
Amortization of right of use assets	Depreciation and amortization		3,026		2,391
Interest on lease liabilities	Interest expense—net		335		300
Total finance lease cost			3,361		2,691
Total lease cost		$	11,744	$	9,418

Supplemental cash flows information related to leases was as follows:

	For the Nine Months Ended September 30,
	2022		2021
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used in operating leases	$	7,171	$	6,273
Operating cash flows used in finance leases		335		300
Financing cash flows used in finance leases		2,906		2,367
Lease liabilities arising from new ROU assets
Operating leases		11,786		5,078
Finance leases		3,939		2,719

Weighted average remaining lease terms and weighted average discount rates were:

	September 30, 2022
	Operating Leases			Finance Leases
Weighted average remaining lease term (years)	4.56				3.32
Weighted average discount rate	2.58%			5.27%
	September 30, 2021
	Operating Leases			Finance Leases
Weighted average remaining lease term (years)	5.22				2.80
Weighted average discount rate		2.62	%		4.95	%

The following is a schedule by year of the maturities of lease liabilities with original terms in excess of one year:

	Operating Leases			Finance Leases
Remainder of 2022	$	2,447		$	1,181
2023		8,295			3,871
2024		6,595			2,781
2025		4,680			1,881
2026 and thereafter		8,733			1,570
Total undiscounted future minimum lease payments		30,750			11,284
Less imputed interest		(1,779	)		(959	)
Total discounted future minimum lease payments	$	28,971		$	10,325

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Business Acquisitions

9 Months Ended

Sep. 30, 2022

Business Combinations [Abstract]

Business Acquisitions

7. BUSINESS ACQUISITIONS

In line with the Company’s strategic growth initiatives, the Company acquired certain businesses during the nine months ended September 30, 2022 and during the year ended December 31, 2021. The results of each of those acquired businesses are included in the unaudited condensed consolidated financial statements beginning on the acquisition date. Each transaction qualified as an acquisition of a business and was accounted for as a business combination. All acquisitions resulted in the recognition of goodwill. The Company paid these premiums resulting in such goodwill for a number of reasons, including expected synergies from combining operations of the acquiree and the Company while also growing the Company’s customer base, acquiring assembled workforces, expanding its presence in certain markets and expanding and advancing its product and service offerings. The Company recorded the assets acquired and liabilities assumed at their acquisition date fair value, with the difference between the fair value of the net assets acquired and the acquisition consideration reflected as goodwill.

The identifiable intangible assets for significant acquisitions are valued using the excess earnings method discounted cash flow approach for customer relationships, the relief from royalty method for trade names, the patent and external proprietary software, the “with and without” method for covenants not to compete and the replacement cost method for the internal proprietary software by incorporating Level 3 inputs as described under the fair value hierarchy of ASC 820. These unobservable inputs reflect the Company’s own assumptions about which assumptions market participants would use in pricing an asset on a non-recurring basis. These assets will be amortized over their respective estimated useful lives.

Other purchase price obligations (primarily deferred purchase price liabilities and target working capital liabilities or receivables) are included on the unaudited condensed consolidated statements of financial position in accounts payable and other accrued liabilities, other non-current liabilities or accounts receivable-net in the case of working capital deficits. Contingent consideration outstanding from acquisitions are included on the unaudited condensed consolidated statements of financial position in business acquisition contingent consideration, current or in business acquisitions contingent consideration, long-term. The contingent consideration elements of the purchase price of the acquisitions are related to earn-outs which are based on the expected achievement of revenue or earnings thresholds as of the date of the acquisition and for which the maximum potential amount is limited.

The Company considers several factors when determining whether or not contingent consideration liabilities are part of the purchase price, including the following: (i) the valuation of its acquisitions is not supported solely by the initial consideration paid, (ii) the former stockholders of acquired companies that remain as key employees receive compensation other than contingent consideration payments at a reasonable level compared with the compensation of the Company’s other key employees and (iii) contingent consideration payments are not affected by employment termination. The Company reviews and assesses the estimated fair value of contingent consideration at each reporting period.

The Company may be required to make up to $8.5 million in aggregate earn-out payments between the years 2023 and 2026 in connection with certain of its business acquisitions, up to $3.0 million of which may be paid in cash.

Transaction costs related to business combinations totaled $0.4 million and $1.4 million for the three and nine months ended September 30, 2022, respectively, and $0.9 million and $1.7 million for the three and nine months ended September 30, 2021, respectively. These costs are expensed within selling, general and administrative expense in the accompanying unaudited condensed consolidated statements of operations.

Acquisitions Completed During the Nine Months Ended September 30, 2022

Environmental Standards, Inc. (“EnvStd”)—In January 2022, the Company completed the acquisition of Environmental Standards, Inc. by acquiring 100.0% of its common stock. EnvStd is a provider of environmental consulting services. EnvStd is based in Valley Forge, PA with satellite locations nationwide. The upfront cash payment made to acquire EnvStd was funded through cash on hand.

Industrial Automation Group, Inc. (“IAG”)—In January 2022, the Company completed the acquisition of Industrial Automation Group, Inc. by acquiring certain of its employees and a covenant not to compete. The upfront cash payment made to acquire IAG was funded through cash on hand. IAG is based in Atlanta, GA.

TriAD Environmental Consultants, Inc. (“TriAD”)—In August 2022, the Company completed the acquisition of TriAD Environmental Consultants, Inc. by acquiring 100.0% of its common stock. TriAD is a provider of environmental consulting services. TriAD is based in Nashville, TN. The upfront cash payment made to acquire TriAD was funded through cash on hand.

AirKinetics, Inc. (“AirKinetics”)—In September 2022, the Company completed the acquisition of AirKinetics, Inc. by acquiring 100.0% of its common stock. AirKinetics is a provider of emissions testing services. AirKinetics is based in Anaheim, CA. The upfront cash payment made to acquire AirKinetics was funded through cash on hand.

The following table summarizes the elements of the purchase price of the acquisitions completed during the nine months ended September 30, 2022:

	Cash		Common Stock		Other Purchase Price Components Current		Contingent Consideration Current		Contingent Consideration Long Term		Total Purchase Price
EnvStd	$	14,473	$	—	$	521	$	1,166	$	—	$	16,160
All other 2022 acquisitions		7,650		—		472		50		—		8,172
Total	$	22,123	$	—	$	993	$	1,216	$	—	$	24,332

The other purchase price components of the EnvStd purchase price consist of a surplus working capital amount, which will be finalized in the fourth quarter of 2022 and a seller make-whole for taxes related to a 338(h)(10) election. The other purchase price components of all the other acquisitions purchase price mainly consist of surplus/deficit working capital amounts.

The preliminary purchase price attributable to the acquisitions was allocated as follows:

	EnvStd		All Other 2022 Acquisitions		Total
Cash	$	295	$	486	$	781
Accounts receivable and contract assets		5,200		1,846		7,046
Other current assets		456		19		475
Current assets		5,951		2,351		8,302
Property and equipment		168		11		179
Operating lease right-of-use asset—net		2,895		215		3,110
Customer relationships		5,807		2,714		8,521
Trade names		1,010		251		1,261
Covenants not to compete		269		394		663
Goodwill		4,107		2,965		7,072
Total assets		20,207		8,901		29,108
Current liabilities		1,719		619		2,338
Operating lease liability—net of    current portion		2,328		110		2,438
Total liabilities		4,047		729		4,776
Purchase price	$	16,160	$	8,172	$	24,332

The weighted average useful lives for the acquired companies’ identifiable intangible assets are as follows:

	Customer Relationships	Tradenames	Covenants Not to Compete
EnvStd	7	2	5
All other 2022 acquisitions	7	2	5

Goodwill associated with the EnvStd and IAG acquisitions are deductible for income tax purposes.

For the acquisitions completed during the nine months ended September 30, 2022, the results of operations since the acquisition dates have been combined with those of the Company. The Company’s unaudited condensed consolidated statement of operations for the three and nine months ended September 30, 2022 includes revenue of $5.6 million and $13.2 million, respectively, and pre-tax income of $1.0 million and $1.7 million, respectively, related to these acquisitions. EnvStd is included in the Company’s Assessment, Permitting and Response segment, IAG and TriAD are included in the Remediation and Reuse segment and AirKinetics is included in the Measurement and Analysis segment.

Acquisitions Completed During the Year Ended December 31, 2021

MSE Group, LLC (“MSE”)—In January 2021, the Company completed the acquisition of MSE Group, LLC by acquiring 100.0% of its membership interests. MSE is a provider of environmental assessment, permitting and remediation services primarily to the U.S. federal government. MSE is based in Orlando, FL with additional offices in Tampa, Orlando, Jacksonville, San Antonio, TX, and Wilmington, NC, and satellite locations nationwide. The upfront cash payment made to acquire MSE was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 71,740 shares of common stock.

Vista Analytical Laboratory, Inc. (“Vista”)—In June 2021, the Company completed the acquisition of Vista Analytical Laboratory, Inc. (“Vista”) by acquiring 100.0% of its common stock. Vista provides specialty analytical services related to Per- and polyfluoroalkyl substances (“PFAS”) and other semi-volatile organic compounds. Vista is based in Dorado Hills, CA. The upfront cash payment made to acquire Vista was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 9,322 shares of common stock.

Environmental Intelligence, LLC (“EI”) —In July 2021, the Company completed the acquisition of Environmental Intelligence, LLC (“EI”) by acquiring 100.0% of its membership interests. EI provides environmental consulting services and is recognized for its innovative work in wildlife mitigation and biological assessments. EI is based in Laguna Beach, CA and enhances Montrose’s ecological planning and service capabilities in California and the US West Coast. The upfront cash payment made to acquire EI was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 43,100 shares of common stock.

SensibleIoT, LLC (“Sensible”) —In August, 2021, the Company completed the business acquisition of SensibleIoT, LLC (“Sensible”) by acquiring 100.0% of its membership interests. Sensible is a technology platform that connects sensors and sources of environment data to a central, proprietary database that enables real-time client interaction. Sensible provides Montrose with an advanced ability to integrate environmental services and enhance environmental data analytics for clients. The upfront cash payment made to acquire Sensible was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 19,638 shares of common stock.

Environmental Chemistry, Inc. (“ECI”) —In October 2021, the Company completed the business acquisition of Environmental Chemistry, Inc. (“ECI”) by acquiring 100.0% of its common stock. ECI provides a full suite of environmental laboratory analytical services to industrial, governmental, and engineering/consulting clients. Combined with the Company’s existing Houston, TX laboratory, ECI (located also in Houston, TX) will enable Montrose to provide air, water and soil analytical services in the gulf coast region. The upfront cash payment made to acquire ECI was funded through cash on hand.

Horizon Water and Environment, LLC (“Horizon”)— In November 2021, the Company completed the business acquisition of Horizon Water and Environment, LLC (“Horizon”) by acquiring 100.0% of its membership interests. Horizon is an environmental consulting firm specializing in planning, watershed science, and environmental compliance for water and natural resource projects. The upfront cash payment made to acquire Horizon was funded through cash on hand and the common stock portion of the purchase price was funded through the issuance of 34,921 shares of common stock.

The following table summarizes the elements of the purchase price of the acquisitions completed during the year ended December 31, 2021:

	Cash		Common Stock		Other Purchase Price Components Current			Contingent Consideration Current		Contingent Consideration Long Term		Total Purchase Price
MSE	$	9,082	$	2,271	$	10,701		$	1,551	$	253	$	23,858
EI		20,721		2,274		(63	)		—		—		22,932
All other 2021 acquisitions		29,683		3,775		1,228			1,250		4,350		40,286
Total	$	59,486	$	8,320	$	11,866		$	2,801	$	4,603	$	87,076

The other purchase price components of the MSE purchase price consist of a surplus working capital amount on the date of close, a seller make-whole for taxes related to a 338(h)(10) election, an integration payment liability and a purchase price true up related to MSE’s financial performance in the fourth quarter of 2020. The other purchase price components of the EI purchase price consist of a surplus working capital amount on the date of close. The other purchase price components of all the other acquisitions purchase price mainly consist of surplus/deficit working capital amounts and 338(h)(10) election liabilities.

The purchase price attributable to the acquisitions was allocated as follows:

	MSE		EI		All other 2021 acquisitions		Total
Cash	$	2,810	$	250	$	693	$	3,753
Accounts receivable		2,980		4,675		4,133		11,788
Other current assets		31		84		289		404
Current assets		5,821		5,009		5,115		15,945
Property and equipment		513		32		1,168		1,713
Operating lease right-of-use asset—net		740		106		2,233		3,079
Customer relationships		8,720		10,073		12,830		31,623
Trade names		521		996		1,958		3,475
Covenants not to compete		922		511		1,248		2,681
Acquired Technology		—		—		321		321
Goodwill		8,176		8,960		19,569		36,705
Total assets		25,413		25,687		44,442		95,542
Current liabilities		1,007		2,719		2,351		6,077
Operating lease liability—net of    current portion		548		36		1,805		2,389
Total liabilities		1,555		2,755		4,156		8,466
Purchase price	$	23,858	$	22,932	$	40,286	$	87,076

The weighted average useful lives for the acquired companies’ identifiable intangible assets are as follows:

	Customer Relationships	Tradenames	Covenants Not to Compete	Developed Technology
MSE	2-7	2	5	n/a
EI	10	5	5	n/a
All other 2021 acquisitions	10	n/a-3	n/a-5	n/a-5

Goodwill associated with all of these acquisitions is deductible for income tax purposes.

For the acquisitions completed during the year ended December 31, 2021, the results of operations since the acquisition dates have been combined with those of the Company. The Company’s unaudited condensed consolidated statement of operations for the three and nine months ended September 30, 2021 includes revenue of $11.9 million and $19.7 million, respectively, and pre-tax (loss) of $(0.2) million and zero, respectively, related to the acquisitions completed prior to September 30, 2021. MSE is included in the Company’s Remediation and Reuse segment, Vista, Sensible and ECI are included in the Company’s Measurement and Analysis segment and EI and Horizon are included in the Company's Assessment, Permitting and Response segment.

Supplemental Unaudited Pro-Forma—The unaudited condensed consolidated financial information summarized in the following table gives effect to the 2022 and the 2021 acquisitions discussed above assuming they occurred on January 1, 2021. These unaudited consolidated pro forma operating results do not assume any impact from revenue, cost or other operating synergies that are expected or may have been realized as a result of the acquisitions. These unaudited consolidated pro forma operating results are presented for illustrative purposes only and are not indicative of the operating results that would have been achieved had the acquisitions occurred on January 1, 2021, nor does the information purport to reflect results for any future period.

	For the Three Months Ended September 30,
	2022								2021
	(Unaudited)
	As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma			As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma
Revenues	$	130,312		$	1,202	$	131,514		$	132,578		$	9,457	$	142,035
Net (loss) income		(5,720	)		290		(5,430	)		2,226			1,479		3,705
	For the Nine Months Ended September 30,
	2022								2021
	(Unaudited)
	As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma			As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma
Revenues	$	404,902		$	6,422	$	411,324		$	402,619		$	39,819	$	442,438
Net (loss) income		(21,007	)		832		(20,175	)		(23,853	)		6,848		(17,005	)

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Goodwill and Intangible Assets

9 Months Ended

Sep. 30, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

8. GOODWILL AND INTANGIBLE ASSETS

Amounts related to goodwill are as follows:

	Assessment, Permitting and Response			Measurement and Analysis		Remediation and Reuse		Total
Balance as of December 31, 2021	$	176,541		$	83,770	$	51,633	$	311,944
Goodwill acquired during the period		4,764			2,158		150		7,072
Acquisitions measurement period adjustments		(899	)		296		—		(603	)
Balance as of September 30, 2022	$	180,406		$	86,224	$	51,783	$	318,413

Amounts related to finite-lived intangible assets are as follows:

September 30, 2022	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	204,926	$	90,572	$	114,354
Covenants not to compete	4-5 years		33,286		27,523		5,763
Trade names	1-5 years		21,673		17,442		4,231
Proprietary software	3-5 years		22,469		14,719		7,750
Patent	16 years		17,479		3,309		14,170
Total other intangible assets    —net		$	299,833	$	153,565	$	146,268

December 31, 2021	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	196,323	$	74,010	$	122,313
Covenants not to compete	4-5 years		32,622		25,113		7,509
Trade names	1-5 years		20,403		15,139		5,264
Proprietary software	3-5 years		22,077		11,155		10,922
Patent	16 years		17,479		2,490		14,989
Total other intangible assets    —net		$	288,904	$	127,907	$	160,997

Intangible assets with finite lives are stated at cost, less accumulated amortization and impairment losses, if any. These intangible assets are amortized using the straight-line method over the estimated useful lives of the assets. Amortization expense was $8.7 million and $27.6 million for the three and nine months ended September 30, 2022, respectively, and $8.9 million and $25.9 million for the three and nine months ended September 30, 2021, respectively.

Future amortization expense is estimated to be as follows for each of the five following years and thereafter:

December 31,
2022 (remaining)		8,135
2023		28,163
2024		23,588
2025		16,897
2026 and thereafter		69,485
Total	$	146,268

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Accounts Payable and Other Accrued Liabilities

9 Months Ended

Sep. 30, 2022

Payables and Accruals [Abstract]

Accounts Payable and Other Accrued Liabilities

9. ACCOUNTS PAYABLE AND OTHER ACCRUED LIABILITIES

Accounts payable and other accrued liabilities consisted of the following:

	September 30,		December 31,
	2022		2021
Accounts payable	$	19,023	$	24,167
Accrued expenses		12,312		14,906
Other business acquisitions purchase    price obligations		505		502
Contract liabilities		23,270		27,907
Other current liabilities		3,206		1,454
Total accounts payable and    other accrued liabilities	$	58,316	$	68,936

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Accrued Payroll and Benefits

9 Months Ended

Sep. 30, 2022

Statement of Financial Position [Abstract]

Accrued Payroll and Benefits

10. ACCRUED PAYROLL AND BENEFITS

Accrued payroll and benefits consisted of the following:

	September 30,		December 31,
	2022		2021
Accrued bonuses	$	7,036	$	13,438
Accrued paid time off		1,309		1,144
Accrued payroll		7,749		6,547
Accrued other		4,383		4,842
Total accrued payroll and benefits	$	20,477	$	25,971

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Income Taxes

9 Months Ended

Sep. 30, 2022

Income Tax Disclosure [Abstract]

Income Taxes

11. INCOME TAXES

The Company calculates its interim income tax provision in accordance with ASC Topic 270, Interim Reporting (“ASC 270”), and ASC 740. The Company’s effective tax rate (“ETR”) from continuing operations was 3.5% and (9.9)% for the three and nine months ended September 30, 2022, respectively, and 28.8% and (2.8)% for the three and nine months ended September 30, 2021, respectively. Income tax (benefit) expense recorded by the Company during the three and nine months ended September 30, 2022 was $(0.2) million and $1.9 million, respectively. The income tax expense recorded by the Company during the three and nine months ended September 30, 2021 was $0.9 million and $0.6 million, respectively. The difference between the ETR and federal statutory rate of 21.0% is primarily attributable to items recorded for U.S. GAAP but permanently disallowed for U.S. federal income tax purposes, recognition of a U.S. federal and state valuation allowance and state and foreign income tax provisions.

A valuation allowance is recorded when it is more-likely-than-not some of the Company’s deferred tax assets may not be realized. Significant judgment is applied when assessing the need for a valuation allowance and the Company considers future taxable income, reversals of existing deferred tax assets and liabilities and ongoing prudent and feasible tax planning strategies, in making such assessment. As of September 30, 2022, the Company’s U.S. federal, state and various foreign net deferred tax assets are not more-likely-than-not to be realized and a full valuation allowance is maintained.

The Company records uncertain tax positions in accordance with ASC 740, on the basis of a two-step process in which (i) the Company determines whether it is more likely than not a tax position will be sustained on the basis of the technical merits of such position and (ii) for those tax positions meeting the more-likely-than-not recognition threshold, the Company would recognize the largest amount of tax benefit that is more than 50.0% likely to be realized upon ultimate settlement with the related tax authority. The Company has determined it has no uncertain tax positions as of September 30, 2022. The Company classifies interest and penalties recognized on uncertain tax positions as a component of income tax expense.

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Debt

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

Debt

12. DEBT

Debt consisted of the following:

	September 30,			December 31,
	2022			2021
Term loan facility	$	166,250		$	175,000
Revolving line of credit		—			—
Less deferred debt issuance costs		(1,855	)		(2,244	)
Total debt		164,395			172,756
Less current portion of long-term debt		(8,750	)		(10,938	)
Long-term debt, less current portion	$	155,645		$	161,818

Deferred Financing Costs—Costs relating to debt issuance have been deferred and are presented as discounted against the underlying debt instrument. These costs are amortized to interest expense over the terms of the underlying debt instruments.

2021 Credit Facility—On April 27, 2021, the Company entered into a Senior Secured Credit Agreement providing for a $300.0 million credit facility comprised of a $175.0 million term loan and a $125.0 million revolving line of credit (the “2021 Credit Facility”), and used a portion of the proceeds from the 2021 Credit Facility to repay all amounts outstanding under the 2020 Credit Facility (as defined below). The 2021 revolving credit facility includes a $20.0 million sublimit for the issuance of letters of credit. Subject to certain exceptions, all amounts under the 2021 Credit Facility will become due on April 27, 2026. The Company has the option to borrow incremental term loans or request an increase in the aggregate commitments under the revolving credit facility up to an aggregate amount of $150.0 million subject to the satisfaction of certain conditions.

The 2021 Credit Facility term loan must be repaid in quarterly installments and shall amortize at the following future quarterly rates:

Date	Quarterly Installment Rate
December 31, 2022	1.25%
March 31, 2023	1.25%
June 30, 2023	1.25%
September 30, 2023	1.25%
December 31, 2023	1.88%
March 31, 2024	1.88%
June 30, 2024	1.88%
September 30, 2024	1.88%
December 31, 2024	1.88%
March 31, 2025	1.88%
June 30, 2025	1.88%
September 30, 2025	1.88%
December 31, 2025	2.50%
March 31, 2026	2.50%
April 27, 2026	Remaining balance

Repayments of quarterly installments were scheduled to begin with the quarter ended December 31, 2021. The first quarterly installment repayment, amounting to $2.2 million, was billed and charged by the lenders in January 2022. Exclusive of the payment made in respect of the quarter ended December 31, 2021, the three quarterly installment repayments for the nine months ended September 30, 2022 amounted to $6.6 million.

The 2021 Credit Facility term loan and the revolver bear interest subject to the Company’s leverage ratio and LIBOR as follows:

Pricing Tier	Consolidated Leverage Ratio	Senior Credit Facilities LIBOR			Senior Credit Facilities Base Rate			Commitment Fee			Letter of Credit Fee
1	≥ 3.75x to 1.0		2.50	%		1.50	%		0.25	%		2.50	%
2	< 3.75x to 1.0 but ≥ 3.25 to 1.0		2.25			1.25			0.23			2.25
3	<3.25x to 1.0 but ≥ 2.50 to 1.0		2.00			1.00			0.20			2.00
4	<2.50x to 1.0 but ≥ 1.75 to 1.0		1.75			0.75			0.15			1.75
5	<1.75x to 1.0		1.50			0.50		0.15				1.50

On January 27, 2022, the Company entered into an interest rate swap transaction fixing the floating component of the interest rate on $100.0 million of borrowings to 1.39% until January 27, 2025. Additionally, effective September 1, 2022, the Company received an interest rate reduction of 0.05% under the 2021 Credit Facility based on the Company’s achievement of certain sustainability and environmental, social and governance related objectives as provided for in the 2021 Credit Facility.

The 2021 Credit Facility includes a number of covenants imposing certain restrictions on the Company’s business, including, among other things, restrictions on the Company’s ability, subject to certain exceptions and baskets, to incur indebtedness, incur liens on its assets, agree to any additional negative pledges, pay dividends or repurchase stock, limit the ability of its subsidiaries to pay dividends or distribute assets, make investments, enter into any transaction of merger or consolidation, liquidate, wind-up or dissolve, or convey any part of its business, assets or property, or acquire the business, property or assets of another person, enter into sale and leaseback transactions, enter into certain transactions with affiliates, engage in any material line of business substantially different from those engaged on the closing date, modify the terms of indebtedness subordinated to the loans incurred under the 2021 Credit Facility and modify the terms of its organizational documents. The 2021 Credit Facility also includes financial covenants requiring the Company to remain below a maximum total net leverage ratio of 4.25 times, which steps down to 4.00 times beginning with the fiscal quarter ending December 31, 2022 through and including the fiscal quarter ending September 30, 2023 and then to 3.75 times beginning with the fiscal quarter ending December 31, 2023, and a minimum fixed charge coverage ratio of 1.25 times. As of September 30, 2022, the Company’s consolidated total leverage ratio (as defined in the 2021 Credit Facility) was 1.2 times and the Company was in compliance with all covenants under the 2021 Credit Facility.

The 2021 Credit Facility requires customary mandatory prepayments of the term loan and revolver and cash collateralization of letters of credit, subject to customary exceptions, including 100.0% of the proceeds of debt not permitted by the 2021 Credit Facility, 100.0% of the proceeds of certain dispositions, subject to customary reinvestment rights, where applicable, and 100.0% of insurance or condemnation proceeds, subject to customary reinvestment rights, where applicable. The 2021 Credit Facility also includes customary events of default and related acceleration and termination rights.

The weighted average interest rate on the 2021 Credit Facility for the nine months ended September 30, 2022 was 2.9%.

The Company’s obligations under the 2021 Credit Facility are guaranteed by certain of the Company’s existing and future direct and indirect subsidiaries, and such obligations are secured by substantially all of the Company’s assets, including the capital stock or other equity interests in those subsidiaries.

2020 Credit Facility—On April 13, 2020, the Company entered into a Unitranche Credit Agreement (the “2020 Credit Facility”) providing for a $225.0 million credit facility comprised of a $175.0 million term loan and a $50.0 million revolving credit facility. The 2020 Credit facility was repaid in full in in April 2021. The resulting loss on extinguishment upon repayment of the 2020 Credit Facility in April 2021, amounted to $4.1 million, of which $1.0 million was related to fees paid and $3.1 related to unamortized debt issuance costs. Total loss on extinguishment is recorded in interest expense, net within the unaudited condensed consolidated statement of operations for the nine months ended September 30, 2021.

Equipment Line of Credit—In the first quarter of 2022, the Company entered into a new $10.0 million equipment leasing facility for the purchase of equipment and related freight, installation costs and taxes paid. Any unused capacity on this equipment leasing facility expires on December 30, 2022. Interest on the line of credit is determined based on a three-year swap rate at the time of funding. Equipment leased through this line of credit meets the finance lease criteria as per ASC 842 and accordingly is accounted for as finance lease right-of-use assets and a finance lease liabilities (Note 6).

The following is a schedule of the aggregate annual maturities of long-term debt presented on the unaudited condensed consolidated statement of financial position, based on the terms of the 2021 Credit Facility:

September 30,
2023	$	8,750
2024		13,125
2025		13,125
2026		131,250
Total	$	166,250

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Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

13. FAIR VALUE OF FINANCIAL INSTRUMENTS

The following financial instruments are measured at fair value on a recurring basis using significant unobservable inputs (Level 3):

	September 30,		December 31,
	2022		2021
Interest rate swap	$	6,313	$	—
Total assets	$	6,313	$	—
Business acquisitions contingent consideration,    current	$	3,967	$	31,450
Business acquisitions contingent consideration,    long-term		2,810		4,350
Conversion option		24,730		23,081
Total liabilities	$	31,507	$	58,881

The estimated fair value amounts shown above are not necessarily indicative of the amounts that the Company would realize upon disposition, nor do they indicate the Company’s intent or ability to dispose of the financial instrument.

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis:

	Interest Rate Swap		Total Assets		Business Acquisitions Contingent Consideration, Current			Business Acquisitions Contingent Consideration, Long-term			Conversion    Option		Total Liabilities
Balance—at January 1, 2021	$	—	$	—	$	49,902		$	4,565		$	20,886	$	75,353
Acquisitions		—		—		1,000			6,004			—		7,004
Changes in fair value included in earnings		—		—		13,774			10,261			1,651		25,686
Payment of contingent consideration        payable		—		—		(50,154	)		—			—		(50,154	)
Reclass of long term to short term       contingent liabilities		—		—		16,630			(16,630	)		—		—
Balance—at September 30, 2021	$	—	$	—	$	31,152		$	4,200		$	22,537	$	57,889
Balance—at January 1, 2022	$	—		—	$	31,450		$	4,350		$	23,081	$	58,881
Acquisitions		—		—		—			1,216			—		1,216
Changes in fair value included in earnings		6,313		6,313		330			(390	)		1,649		1,589
Payment of contingent consideration        payable		—		—		(30,179	)		—			—		(30,179	)
Reclass of long term to short term       contingent liabilities		—		—		2,366			(2,366	)		—		—
Balance—at September 30, 2022	$	6,313	$	6,313	$	3,967		$	2,810		$	24,730	$	31,507

Quantitative Information about Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3):

Interest Rate Swap—The interest rate swap fair value is estimated based on a mid-market price for the swap as of the close of business of the reporting period. The fair value is prepared by discounting future cash flows of the swap to arrive at a current value of the swap. Forward curves and volatility levels inputs are determined on the basis of observable market inputs when available and on the basis of estimates when observable market inputs are not available. The Company does not apply hedge accounting but instead recognizes the instrument at fair value on the unaudited condensed consolidated statement of financial position within other assets, with changes in fair value recognized in earnings in each reporting period. The change in fair value of $2.3 million and $6.3 million for the three and nine months ended September 30, 2022, respectively was recognized as a component of other expense on the Company's unaudited condensed consolidated statements of operations.

Business Acquisitions Contingent Consideration—The fair value of the contingent consideration payable associated with the acquisition of CTEH, MSE and Sensible was determined using a Monte Carlo simulation of earnings in a risk-neutral Geometric Brownian Motion framework. The fair value of the contingent consideration payable associated with the acquisition of EnvStd was determined using a Probabilistic (Scenario Based) method. The fair values of the contingent consideration payables for the other acquisitions were calculated based on expected target achievement amounts, which are measured quarterly and then subsequently

adjusted to actuals at the target measurement date. The method used to price these liabilities is considered level 3 due to the subjective nature of the unobservable inputs used to determine the fair value. The input is the expected achievement of earn-out thresholds.

Conversion Option—Upon the Company’s initial public offering ("IPO"), the fair value of the conversion option associated with the issuance of the Convertible and Redeemable Series A-2 Preferred Stock (Note 15) was estimated using a “with-and-without” method. The “with-and-without” methodology considers the value of the security on an as-is basis and then without the embedded conversion premium. The difference between the two scenarios is the implied fair value of the embedded derivative. The unobservable input is the required rate of return on the Series A-2. The considerable quantifiable inputs in the valuation relate to the timing of conversions or redemptions.

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Commitments and Contingencies

9 Months Ended

Sep. 30, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

14. COMMITMENTS AND CONTINGENCIES

Leases—The Company leases office facilities over various terms expiring through 2031. Certain of these operating leases contain rent escalation clauses. The Company also has office equipment leases that expire through 2027 (Note 6 and 12).

Other Commitments—The Company has commitments under the 2021 Credit Facility, its equipment line of credit and its lease obligations (Note 6 and 12).

Contingencies—The Company is subject to purchase price contingencies related to earn-outs associated with certain acquisitions (Note 7 and 13).

Legal—In the normal course of business, the Company is at times subject to pending and threatened legal actions. In management’s opinion, any potential loss resulting from the resolution of these matters is not expected to have a material effect on the unaudited condensed consolidated results of operations, financial position or cash flows of the Company.

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Convertible and Redeemable Series A-2 Preferred Stock

9 Months Ended

Sep. 30, 2022

Temporary Equity Disclosure [Abstract]

Convertible and Redeemable Series A-2 Preferred Stock

15. CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK

On April 13, 2020, the Company entered into an agreement to issue 17,500 shares of the Convertible and Redeemable Series A-2 Preferred Stock with a par value of $0.0001 per share and a detachable warrant to purchase shares of the Company’s common stock with a 10-year life, in exchange for gross proceeds of $175.0 million, net of $1.3 million debt issuance costs. Before the Company’s IPO, each share of Convertible and Redeemable Series A-2 Preferred Stock accrued dividends at the rate of 15.0% per annum, with respect to dividends that were paid in cash, and 14.2% per annum, with respect to dividends that were accrued. The Company paid dividends on shares of the Convertible and Redeemable Series A-2 Preferred Stock of $4.1 million during both the three months ended September 30, 2022 and September 30, 2021, and $12.3 million during both the nine months ended September 30, 2022 and September 30, 2021.

At issuance, the Company determined that the Convertible and Redeemable Series A-2 Preferred Stock and the detachable warrant, were required to be accounted for separately.

Upon the Company’s IPO, the Convertible and Redeemable Series A-2 Preferred Stock terms automatically updated to the following: (i) no mandatory redemption, (ii) no stated value cash repayment obligation other than in the event of certain defined liquidation events, (iii) only redeemable at the Company’s option, (iv) the instrument became convertible into common stock beginning on the four year anniversary of issuance at a 15.0% discount to the common stock market price (with a limit of $60.0 million in stated value of Convertible and Redeemable Series A-2 Preferred Stock eligible to be converted in any 60-day period prior to the seventh anniversary of issuance and the amount of stated value of the Convertible and Redeemable Series A-2 Preferred Stock eligible for conversion limited to $60.0 million during year 5 and $120.0 million (which includes the aggregate amount of the stated value of the Convertible and Redeemable Series A-2 Preferred Stock and any accrued but unpaid dividends added to such stated value of any shares of Convertible and Redeemable Series A-2 Preferred Stock converted in year 5) during year 6), (v) the dividend rate stepped down to 9.0% per year with required quarterly cash payments, (vi) in an event of noncompliance, the dividend rate shall increase to 12.0% per annum for the first 90-day period from and including the date the noncompliance event occurred, and thereafter shall increase to 14.0% per annum, (vii) the debt incurrence test ratio increased to 4.5 times, (viii) the total leverage cap covenant was removed, and (ix) minimum repayment amount dropped down from $50.0 million to $25.0 million.

The Company may, at its option on any one or more dates, redeem all or a minimum portion (the lesser of (i) $25.0 million in aggregate stated value of the Convertible and Redeemable Series A-2 Preferred Stock and (ii) all of the Convertible and Redeemable Series A-2 Preferred Stock then outstanding) of the outstanding Convertible and Redeemable Series A-2 Preferred Stock in cash.

With respect to any redemption of any share of the Convertible and Redeemable Series A-2 Preferred Stock prior to the third-year anniversary, the Company is subject to a make whole penalty in which the holders of the Convertible and Redeemable Series A-2 Preferred Stock are guaranteed a minimum repayment equal to outstanding redeemed stated value plus three years of dividends accrued or accruable thereon.

The Convertible and Redeemable Series A-2 Preferred Stock does not meet the definition of a liability pursuant to “ASC 480- Distinguishing Liabilities from Equity.” However, as (i) the instrument is redeemable upon a change of control as defined in the certificate of designations governing the terms of the Convertible and Redeemable Series A-2 Preferred Stock, and (ii) the Company cannot assert it would have sufficient authorized and unissued shares of common stock to settle all future conversion requests due to the variable conversion terms, the instrument is redeemable upon the occurrence of events that are not solely within the control of the Company, and therefore the Company classifies the Convertible and Redeemable Series A-2 Preferred Stock as mezzanine equity. Subsequent adjustment of the carrying value of the instrument is required if the instrument is probable of becoming redeemable. As of September 30, 2022, the Company has determined that a change of control is not probable. Additionally, as of September 30, 2022, the Company has determined that it is not probable that there will be a future conversion request that the Company is unable to settle with authorized and issued shares based on the Company’s current stock price and available shares as well as the Company’s monitoring efforts to ensure there are a sufficient number of shares available to settle any conversion request. Therefore, as of September 30, 2022, the Company has determined that the instrument is not probable of becoming redeemable, and does not believe subsequent adjustment of the carrying value of the instrument will be necessary. The Convertible and Redeemable Series A-2 Preferred Stock had an aggregate liquidation preference of $182.2 million as of September 30, 2022 and December 31, 2021.

The Convertible and Redeemable Series A-2 Preferred Stock contains embedded features that are required to be bifurcated and are subject to separate accounting treatment from the instrument itself. At issuance, these embedded features consisted of (i) a contingent dividend feature associated with the decrease in the dividend rate upon an IPO and (ii) a conversion option of the preferred shares to shares of common stock beginning on the fourth-year anniversary of the issuance date. Upon the Company’s IPO, the embedded derivative only consisted of the conversion option. As of September 30, 2022 and December 31, 2021, this conversion embedded feature had a net fair value of $24.7 million and $23.1 million, respectively. The change in value of $0.5 million and $1.6 million for the three and nine months ended September 30, 2022, respectively, was recorded to other expense.

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Stockholder's Equity

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Stockholders' Equity

16. STOCKHOLDERS’ EQUITY

Authorized Capital Stock—The Company was authorized to issue 190,000,000 shares of common stock, with a par value of $0.000004 per share as of September 30, 2022 and December 31, 2021.

Warrants—In May 2015, the Company issued warrants to acquire 116,350 shares of Common Stock at a price of approximately $17.19 per share to the placement agent as consideration for backstopping the financing completed in May 2015. These warrants were exercised in full as a cashless transaction during the first quarter of 2021. As a result of this cashless transaction, the resulting number of shares issued was 67,713 shares.

Common Stock Issuances—The Company issued the following shares of common stock:

	Three Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Total (in thousands)		Shares		Average Price per Share		Total (in thousands)
Acquisitions		—	$	—	$	—		62,738	$	52.18	$	3,274
Exercise of options		28,111		11.70		329		354,918		8.30		2,946
Total		28,111	$	11.70	$	329		417,656	$	14.89	$	6,220
	Nine Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Total (in thousands)		Shares		Average Price per Share		Total (in thousands)
Acquisitions		—	$	—	$	—		143,800	$	41.86	$	6,020
Exercise of warrants (1)		—		—		—		67,713		17.19		—
Exercise of options		62,293		13.04		812		779,068		7.74		6,032
Restricted shares, net (1)		25,289		66.58		—		38,929		31.31		—
Payment of earn-out liability		—		—		—		539,607		46.33		25,000
Payment of purchase price    true up		—		—		—		24,200		44.81		1,084
Total		87,582	$	28.50	$	812		1,593,317	$	25.43	$	38,136

(1) Represents the non-cash release of common shares due to the exercise of warrants and the vesting of restricted stock.

Employee Equity Incentive Plans—The Company has two plans under which stock-based awards have been issued: (i) the Montrose Amended & Restated 2017 Stock Incentive Plan (“2017 Plan”) and (ii) the Montrose Amended & Restated 2013 Stock Option Plan (“2013 Plan”) (collectively the “Plans”).

As of September 30, 2022, and September 30, 2021, there was $152.5 million and $15.0 million, respectively, of total unrecognized stock compensation expense related to unvested options, restricted stock and stock appreciation rights granted under the Plans. Such unrecognized expense is expected to be recognized over a weighted-average four year period. The following number of shares were authorized to be issued and available for grant:

	September 30, 2022
	2017 Plan		2013 Plan		Total
Shares authorized to be issued		5,140,112		2,037,019		7,177,131
Shares available for grant(1)		364,949		—		364,949
	September 30, 2021
	2017 Plan		2013 Plan		Total
Shares authorized to be issued		3,944,750		2,047,269		5,992,019
Shares available for grant		1,593,287		—		1,593,287

(1) In January 2022 the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued

under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. Shares available for grant exclude awards of stock appreciation rights approved in December 2021 that are subject to vesting based on the achievement of certain market conditions, which have not yet been, and may not be, achieved. See footnote 1 to the table in Common Stock Reserved for Future Issuance below for additional information regarding the December 2021 grant.

Total stock compensation expense for the Plans was as follows:

	Three Months Ended September 30,
	2022										2021
	2017 plan						2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		SARs		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	404	$	—	$	—	$	—	$	404	$	282	$	—	$	—	$	282
Selling, general and    administrative expense		2,216		6,083		2,315		—		10,614		1,844		237		2		2,083
Total	$	2,620	$	6,083	$	2,315	$	—	$	11,018	$	2,126	$	237	$	2	$	2,365
	Nine Months Ended September 30,
	2022										2021
	2017 plan						2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		SARs		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	1,069	$	—	$	—	$	—	$	1,069	$	1,178	$	—	$	10	$	1,188
Selling, general and    administrative expense		6,449		17,892		6,965		—		31,306		4,638		749		11		5,399
Total	$	7,518	$	17,892	$	6,965	$	—	$	32,375	$	5,816	$	749	$	21	$	6,587

Montrose Amended & Restated 2017 Stock Incentive Plan

Restricted Stock Awards and Restricted Stock Units—The Company issues restricted stock awards ("RSAs") to certain 2017 Plan participants as Director’s compensation. There were zero RSAs granted during both the three months ended September 30, 2022 and September 30, 2021, respectively. There were 10,920 and 19,066 RSAs granted during the nine months ended September 30, 2022 and September 30, 2021, respectively. These RSAs vest one year from the date of grant, or, in each case, in full upon a change in control, subject to the participant’s continued service as a Director throughout such date, or upon retirement. Members of the Board of Directors that receive stock-based compensation are treated as employees for accounting purposes.

During the year ended December 31, 2021, the Board of Directors approved the grant of 1,671,391 restricted stock units (“RSUs”) to certain executives and selected employees of the Company under the 2017 Plan. These RSUs represent the right to receive one share of the Company’s common stock upon vesting. These incentives were designed by the Board, in coordination with the Company’s compensation advisors, to (i) retain selected employees of the Company for a minimum of 5 years, (ii) reward selected employees for the Company’s significant outperformance and stockholder value creation in 2021, and (iii) provide incentives to selected employees of the Company to accelerate value creation for stockholders and other stakeholders over the next five-year period. With respect to 1,355,182 RSUs, 50.0% will vest on each of the 4th and 5th anniversaries of the date of grant, subject to continued service through each such date. With respect to the remaining 316,209 RSUs (“The Performance-Vested RSUs”), 50.0% will vest on each of the 4th and 5th anniversaries of the date of grant, subject to continued service through each such date and further subject to Company achieving $90.0 million in adjusted EBITDA (as reported) for any trailing twelve-month period from and after December 31, 2022. If the Performance Criteria is not met prior to the 4th anniversary of the date of grant, none of the Performance-Vested RSUs will vest at such time, and if the Performance Criteria is subsequently met prior to the 5th anniversary of the date of grant, all of the Performance-Vested RSUs will vest at such time, subject to continued service through such date. If the Performance Criteria is not met by the 5th anniversary of the date of grant, all of the Performance-Vested RSUs will be forfeited.

During 2021 and 2022, the Board of Directors approved the creation of certain supplemental incentive plans (“SI Plans”) for selected employees to reward exceptional performance. These SI Plans provide supplemental bonus opportunities payable in RSUs under the 2017 Plan upon meeting certain financial performance targets. There were 95,404 RSUs issued under these SI Plans during the nine months ended September 30, 2022 and zero RSUs issued under these SI plans during the nine months ended September 30, 2021. These RSUs vest four years from the date of grant, subject to continued service through such date.

During 2021, the Board approved and reserved for future issuance an aggregate of 135,517 RSUs (the “Future RSU Pool”) to be granted under the 2017 Plan to certain of its executives and selected employees. Final determination and allocation of the awards

under the Future RSU Pool will be determined on December 16, 2025 based on individual performance and continued service through such date. Any RSUs granted under the Future RSU Pool will vest on December 16, 2026, subject to continued service through such date.

RSA and RSU activity was as follows:

	Nine Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Fair Value (in thousands)		Shares		Average Price per Share		Fair Value (in thousands)
Awards granted		106,324	$	46.82	$	4,978		19,066	$	36.99	$	705

There were no awards granted during the three months ended September 30, 2022 and September 30, 2021. There were an aggregate of zero and 25,289 shares underlying RSAs and RSUs that became fully vested and were released as unrestricted shares of common stock during the three and nine months ended September 30, 2022, respectively. During the three and nine months ended September 30, 2021, there were an aggregate of zero and 38,929 shares underlying RSAs that became fully vested and were released as unrestricted shares of common stock, respectively. There was an aggregate of 2,064,197 and 286,239 shares underlying outstanding RSA and RSU awards as of September 30, 2022 and September 30, 2021, respectively. There were no forfeitures of RSAs or RSUs during the three and nine months ended September 30, 2022 and September 30, 2021.

Stock Appreciation Rights— During the year ended December 31, 2021, the Board of Directors approved the grant of 3,000,000 units of stock appreciation rights (“SARs”) to certain executives and selected employees under the 2017 Plan. These SARs represent the right to receive, upon exercise, a payment equal to the excess of (a) the fair market value of one share of the Company’s common stock, over (b) an exercise price of $66.79, payable, at the Company’s election, in cash or shares of common stock. These SARs vest on the 5th anniversary of the date of grant based on achievement of performance hurdles over a five year period, subject to continued service on the vesting date. The performance hurdles shall be deemed achieved if the average trading price per share of the Company’s common stock equals or exceeds the following stock prices:

SARs Stock Price Performance Hurdle		Portion of SARs Subject to Performance Hurdle
$	133.58	1/3
$	166.98	1/3
$	200.37	1/3

The performance hurdles shall be deemed achieved if the average trading price per share of the Company’s common stock equals or exceeds the applicable stock price performance hurdle set forth above for the trading days falling in a consecutive 20-day period prior to the vesting date. The SARs expire 10 years after the grant date. The fair value of these SARs at the grant date was $46.0 million. The weighted average remaining contract life of these SARs as of September 30, 2022 was 9.21 years.

Options—Options issued to all optionees under the 2017 Plan vest over four years from the date of issuance (or earlier vesting start date, as determined by the Board of Directors) as follows: one half on the second anniversary of date of grant and the remaining half on the fourth anniversary of the date of grant, with the exception of certain annual grants to certain executive officers, which vest annually over a 3-year and 1-year period. The following summarizes the options activity of the 2017 Plan:

	Options to Purchase Common Stock			Weighted- Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The- Money Options (in Thousands)
Outstanding as of January 1, 2021		1,840,229		$	23	$	12		9.09	$	15,598
Granted		264,470			40		22		—		—
Forfeited/ cancelled		(29,025	)		28		—		—		—
Expired		(1,250	)		18		—		—		—
Exercised		(66,875	)		22		—		—		2,078
Outstanding as of September 30, 2021		2,007,549			25		14		8.53		73,724
Outstanding as of January 1, 2022		2,036,729		$	26	$	14		8.30	$	91,030
Granted		664,784			44		16		—		—
Forfeited/ cancelled		(60,167	)		36		—		—		—
Exercised		(26,258	)		22		—		—		671
Outstanding as of September 30, 2022		2,615,088		$	30	$	15		8.04	$	18,784
Exercisable at September 30, 2022		1,010,302			26		—		7.48		9,966

The following weighted-average assumptions were used in the Black-Sholes option-pricing model calculation:

	September 30,			September 30,
	2022			2021
Common stock value (per share)	$	43.72		$	39.83
Expected volatility		33.45			58.34
Risk-free interest rate		1.94	%		0.77	%
Expected life (years)		6.45			6.32
Forfeiture rate	None			None
Dividend rate	None			None

Montrose Amended & Restated 2013 Stock Option Plan—The following summarizes the activity of the 2013 Plan:

	Options to Purchase Common Stock			Weighted- Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The- Money Options (in Thousands)
Outstanding as of January 1, 2021		1,787,869		$	6	$	1		5.40	$	43,867
Expired		(625	)		6		—		—		—
Exercised		(710,568	)		6		—		—		33,480
Outstanding as of September 30, 2021		1,076,676			6		2		4.65		59,532
Outstanding as of January 1, 2022		897,674		$	6	$	2		4.37	$	57,529
Expired		(125	)		6		—		—		—
Exercised		(36,035	)		6		—		—		1,425
Outstanding as of September 30, 2022		861,514		$	6	$	2		3.61	$	23,448
Exercisable at September 30, 2022		861,514			6		—		3.61		23,448

Total shares outstanding from exercised options were 1,271,383 shares and 1,028,268 shares as of September 30, 2022 and September 30, 2021, respectively.

Common Stock Reserved for Future Issuances—The Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following:

	September 30,
	2022		2021
Montrose 2013 Stock Incentive Plan		861,514		2,047,269
Montrose 2017 Stock Incentive Plan(1)		7,757,995		3,944,750
Total		8,619,509		5,992,019

(1) In January 2022, the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. The Company expects to have sufficient shares available under the 2017 Plan to satisfy the future settlement of outstanding awards. Shares reserved for future issuance include 3,000,000 shares underlying the 3,000,000 performance SARs granted in December 2021 that are subject to vesting based on the achievement of certain market conditions. Assuming achievement at the highest price performance hurdle, approximately 2,000,000 shares of common stock would be issued upon vesting of these performance SARs. To date, none of the market conditions have been achieved.

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Net Loss Per Share

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Net Loss Per Share

17. NET LOSS PER SHARE

Basic net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during each period. The Convertible and Redeemable Series A-2 Preferred Stock is considered a participating security during the applicable period. Net losses are not allocated to the Convertible and Redeemable Series A-2 stockholders, as they were not contractually obligated to share in the Company’s losses.

Diluted net loss per share is computed by dividing net loss attributable to common stockholders by the weighted average number of common and dilutive common equivalent shares outstanding for the period using the treasury-stock method or the as-converted method. Potentially dilutive shares are comprised of RSAs, RSUs, SARs and shares of common stock underlying stock options outstanding under the Plans. During the three and nine months ended September 30, 2022 and September 30, 2021, there is no difference in the number of shares used to calculate basic and diluted shares outstanding during the applicable period due to the Company’s net loss attributable to common stockholders and potentially dilutive shares being anti-dilutive.

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(In thousands, except for net loss per share)	2022			2021			2022			2021
Net (loss) income	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)
Convertible and redeemable series A-2 preferred    stock dividend		(4,100	)		(4,100	)		(12,300	)		(12,300	)
Net loss attributable to common stockholders    –basic and diluted		(9,820	)		(1,874	)		(33,307	)		(36,153	)
Weighted-average common shares outstanding –    basic and diluted		29,691			26,220			29,677			25,798
Net loss per share attributable to common    stockholders –basic and diluted	$	(0.33	)	$	(0.07	)	$	(1.12	)	$	(1.40	)

The following equity shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive:

	September 30,
	2022		2021
Stock options		3,476,602		1,686,688
Restricted stock		1,777,958		28,623
SARs		3,000,000		—

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Segment Information

9 Months Ended

Sep. 30, 2022

Segment Reporting [Abstract]

Segment Information

18. SEGMENT INFORMATION

The Company has three operating and reportable segments: Assessment, Permitting and Response, Measurement and Analysis and Remediation and Reuse. These segments are monitored separately by management for performance against budget and prior year and are consistent with internal financial reporting. The Company’s operating segments are organized based upon primary services provided, the nature of the production process, their type of customers, methods used to distribute the products and the nature of the regulatory environment.

Segment Adjusted EBITDA is the primary measure of operating performance for all three operating segments. Segment Adjusted EBITDA is the calculated Company’s Earnings before Interest, Tax, Depreciation and Amortization (“EBITDA”), adjusted to exclude certain transactions such as stock-based compensation, acquisition costs and fair value changes in financial instruments, amongst others. The Chief Operating Decision Maker (“CODM”) does not review segment assets as a measure of segment performance.

Corporate and Other includes costs associated with general corporate overhead (including executive, legal, finance, safety, human resources, marketing and IT related costs) that are not directly related to supporting operations. Overhead costs that are directly related to supporting operations (such as insurance, software, licenses, shared services and payroll processing costs) are allocated to the operating segments on a basis that reasonably approximates an estimate of the use of these services.

Segment revenues and Adjusted EBITDA consisted of the following:

	Three Months Ended September 30,
	2022					2021
			Segment					Segment
	Segment		Adjusted			Segment		Adjusted
	Revenues		EBITDA			Revenues		EBITDA
Assessment, Permitting and Response	$	46,414	$	9,820		$	63,412	$	15,719
Measurement and Analysis		43,754		8,483			38,752		8,283
Remediation and Reuse		40,144		7,010			30,414		5,472
Total Operating Segments		130,312		25,313			132,578		29,474
Corporate and Other		—		(6,940	)		—		(7,987	)
Total	$	130,312	$	18,373		$	132,578	$	21,487
	Nine Months Ended September 30,
	2022					2021
			Segment					Segment
	Segment		Adjusted			Segment		Adjusted
	Revenues		EBITDA			Revenues		EBITDA
Assessment, Permitting and Response	$	142,051	$	30,252		$	209,379	$	46,379
Measurement and Analysis		125,739		21,852			111,309		22,634
Remediation and Reuse		137,112		22,059			81,931		12,262
Total Operating Segments		404,902		74,163			402,619		81,275
Corporate and Other		—		(22,826	)		—		(22,026	)
Total	$	404,902	$	51,337		$	402,619	$	59,249

Presented below is a reconciliation of the Company’s segment measure to net loss:

	For the Three Months Ended September 30,						For the Nine Months Ended September 30,
	2022			2021			2022			2021
Total	$	18,373		$	21,487		$	51,337		$	59,249
Interest expense, net		(1,400	)		(1,722	)		(4,010	)		(11,208	)
Income tax benefit (expense)		208			(902	)		(1,892	)		(648	)
Depreciation and amortization		(11,504	)		(11,471	)		(35,928	)		(33,145	)
Stock-based compensation		(11,018	)		(2,365	)		(32,375	)		(6,587	)
Start-up losses and investment in new services		(1,278	)		(1,186	)		(2,949	)		(3,276	)
Acquisition costs		(368	)		(913	)		(1,354	)		(1,656	)
Fair value changes in financial instruments		1,808			(531	)		4,664			(1,651	)
Fair value changes in business acquisition    contingencies		(59	)		—			3,472			(24,035	)
Expenses related to financing transactions		—			—			(7	)		(50	)
Other losses or expenses (1)		(482	)		(171	)		(1,965	)		(846	)
Net (loss) income	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)

(1) In 2022, amounts include costs associated with the closing of a lab and severance costs related to a restructuring within our soil remediation business. In 2021, amounts include non-operational charges incurred due to the remeasurement of finance leases as a result of the adoption of ASC 842 and costs related to the implementation of a new ERP.

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Related-Party Transactions

9 Months Ended

Sep. 30, 2022

Related Party Transactions [Abstract]

Related-Party Transactions

19. RELATED-PARTY TRANSACTIONS

The Company did not have any related party transactions during the three and nine months ended September 30, 2022 and September 30, 2021.

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Defined Contribution Plan

9 Months Ended

Sep. 30, 2022

Retirement Benefits [Abstract]

Defined Contribution Plan

20. DEFINED CONTRIBUTION PLAN

On January 1, 2014, the Company established the Montrose Environmental Group 401(k) Savings Plan (the “401(k) Savings Plan”). As of September 30, 2022, and December 31, 2021, plan participants may defer up to 85.0% of their eligible wages for the year, up to the Internal Revenue Service dollar limit and catch-up contribution allowed by law. Prior to May 22, 2020, the Company provided employer matching contributions equal to 100.0% of the first 3.0% of the participant’s compensation and 50.0% of the

participant’s elective deferrals that exceed 3.0% but do not exceed 4.0% of the participant’s compensation. Beginning on May 22, 2020, the Company temporarily ceased making employer contributions. Employer contributions were reinstated beginning on April 23, 2021. Employer contributions under the 401(k) Savings Plan were $1.2 million and $4.6 million for the three and nine months ended September 30, 2022, respectively, and $0.8 million and $1.6 million for the three and nine months ended September 30, 2021, and are included within selling, general, and administrative expense on the unaudited condensed consolidated statements of operations.

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Description of the Business and Basis of Presentation (Policies)

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Presentation

Basis of Presentation—The unaudited condensed consolidated financial statements include the operations of the Company and its wholly-owned subsidiaries. These unaudited condensed consolidated financial statements are presented in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) and have been prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) that permit reduced disclosure for interim periods. The unaudited condensed consolidated financial statements include all accounts of the Company and, in the opinion of management, include all recurring adjustments and normal accruals necessary for a fair statement of the Company’s financial position, results of operations and cash flows for the dates and periods presented. These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2021. Results for interim periods are not necessarily indicative of the results to be expected during the remainder of the current year or for any future period. All intercompany transactions, accounts and profits, have been eliminated in the unaudited condensed consolidated financial statements.

Recently Adopted Accounting Pronouncements /Recently Issued Accounting Pronouncements Not Yet Adopted

Recently Adopted Accounting Pronouncements—Through the end of the year ended December 31, 2021, the Company qualified as an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”) and therefore has historically taken advantage of certain exemptions from various public company reporting requirements, including delaying adoption of new or revised accounting standards until those standards apply to private companies. The Company elected to use this extended transition period under the JOBS Act. The adoption dates discussed below are based on the Company no longer qualifying as an emerging growth company.

In August 2020, the Financial Accounting Standards Board ("FASB") issued Accounting Standard Update ("ASU") 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity

(Subtopic 815-40)—Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity. The ASU simplifies accounting for convertible instruments by removing major separation models required under current U.S. GAAP. Consequently, more convertible debt instruments will be reported as a single liability instrument with no separate accounting for embedded conversion features. The ASU removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception, which will permit more equity contracts to qualify for the exception. The ASU also simplifies the diluted net income per share calculation in certain areas. The new guidance is effective for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years, and early adoption is permitted. The new guidance was adopted as of January 1, 2022 and did not have a material impact on the Company’s consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted—In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customers. Under the new guidance (ASC 805-20-30-28), the acquirer should determine what contract assets and/or contract liabilities it would have recorded under ASC 606 (the revenue guidance) as of the acquisition date, as if the acquirer had entered into the original contract at the same date and on the same terms as the acquiree. The new guidance is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is currently evaluating the impact of the adoption of the standard on the consolidated financial statements, but does not expect adoption to have a material impact on its consolidated financial statements. The future impact of this new guidance will be primarily a function of the facts and circumstances specific to any acquisitions consummated after adoption and therefore cannot be predicted prior to or at the time of adoption.

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Revenues and Accounts Receivable (Tables)

9 Months Ended

Sep. 30, 2022

Revenues And Accounts Receivable [Abstract]

Schedule of Contract Balances

The following table presents the Company’s contract balances:

	September 30,		December 31,
	2022		2021
Contract assets	$	60,444	$	40,139
Contract liabilities		23,270		27,907

Schedule of Accounts Receivable, Net

Accounts Receivable, NetAccounts receivable, net consisted of the following:

	September 30, 2022			December 31, 2021
Accounts receivable, invoiced	$	82,649		$	101,709
Accounts receivable, other		544			1,385
Allowance for doubtful accounts		(2,266	)		(4,581	)
Accounts receivable—net	$	80,927		$	98,513

Schedule of Allowance for Doubtful Accounts

The allowance for doubtful accounts consisted of the following:

	Beginning Balance		Bad Debt (Recovery) Expense			Charged to Allowance			Other(1)		Ending Balance
Nine months ended September 30, 2022	$	4,581	$	(821	)	$	(1,621	)	$	127	$	2,266
Year ended December 31, 2021		4,265		1,135			(1,548	)		729		4,581

____________________

(1)This amount consists of additions to the allowance due to business acquisitions.

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Prepaid and Other Current Assets (Tables)

9 Months Ended

Sep. 30, 2022

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Prepaid and Other Current Assets

Prepaid and other current assets consisted of the following:

	September 30,		December 31,
	2022		2021
Deposits	$	1,402	$	843
Prepaid expenses		4,708		4,675
Supplies		3,686		2,439
Income tax receivable		1,094		508
Prepaid and other current assets	$	10,890	$	8,465

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Property and Equipment, Net (Tables)

9 Months Ended

Sep. 30, 2022

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net, consisted of the following:

	Estimated	September 30,			December 31,
	Useful Life	2022			2021
Lab and test equipment	7 years	$	19,975		$	18,581
Vehicles	5 years		5,642			5,414
Equipment	3-7 years		38,446			35,148
Furniture and fixtures	7 years		2,895			2,844
Leasehold improvements	7 years		8,535			7,268
Aircraft	10 years		931			931
Building	39 years		2,975			2,975
			79,399			73,161
Land			725			725
Construction in progress			2,566			2,342
Less accumulated depreciation			(49,109	)		(44,707	)
Total property and equipment—    net		$	33,581		$	31,521

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Leases (Tables)

9 Months Ended

Sep. 30, 2022

Leases [Abstract]

Summary of Components of Lease Expense

The components of lease expense were as follows:

		For the Three Months Ended September 30,
	Statement of Operations Location	2022		2021
Operating lease cost
Lease cost	Selling, general and administrative expense	$	2,542	$	2,203
Variable lease cost	Selling, general and administrative expense		354		120
Total operating lease cost			2,896		2,323
Finance lease cost
Amortization of right of use assets	Depreciation and amortization		1,075		825
Interest on lease liabilities	Interest expense—net		116		97
Total finance lease cost			1,191		922
Total lease cost		$	4,087	$	3,245
		For the Nine Months Ended September 30,
	Statement of Operations Location	2022		2021
Operating lease cost
Lease cost	Selling, general and administrative expense	$	7,472	$	6,398
Variable lease cost	Selling, general and administrative expense		911		329
Total operating lease cost			8,383		6,727
Finance lease cost
Amortization of right of use assets	Depreciation and amortization		3,026		2,391
Interest on lease liabilities	Interest expense—net		335		300
Total finance lease cost			3,361		2,691
Total lease cost		$	11,744	$	9,418

Summary of Supplemental Cash Flow Information Related To Leases

Supplemental cash flows information related to leases was as follows:

	For the Nine Months Ended September 30,
	2022		2021
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used in operating leases	$	7,171	$	6,273
Operating cash flows used in finance leases		335		300
Financing cash flows used in finance leases		2,906		2,367
Lease liabilities arising from new ROU assets
Operating leases		11,786		5,078
Finance leases		3,939		2,719

Summary of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates

Weighted average remaining lease terms and weighted average discount rates were:

	September 30, 2022
	Operating Leases			Finance Leases
Weighted average remaining lease term (years)	4.56				3.32
Weighted average discount rate	2.58%			5.27%
	September 30, 2021
	Operating Leases			Finance Leases
Weighted average remaining lease term (years)	5.22				2.80
Weighted average discount rate		2.62	%		4.95	%

Schedule of Maturities of Lease Liabilities

The following is a schedule by year of the maturities of lease liabilities with original terms in excess of one year:

	Operating Leases			Finance Leases
Remainder of 2022	$	2,447		$	1,181
2023		8,295			3,871
2024		6,595			2,781
2025		4,680			1,881
2026 and thereafter		8,733			1,570
Total undiscounted future minimum lease payments		30,750			11,284
Less imputed interest		(1,779	)		(959	)
Total discounted future minimum lease payments	$	28,971		$	10,325

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Business Acquisitions (Tables)

9 Months Ended

Sep. 30, 2022

Business Acquisition [Line Items]

Summary of Supplemental Unaudited Pro-Forma Information

The unaudited condensed consolidated financial information summarized in the following table gives effect to the 2022 and the 2021 acquisitions discussed above assuming they occurred on January 1, 2021. These unaudited consolidated pro forma operating results do not assume any impact from revenue, cost or other operating synergies that are expected or may have been realized as a result of the acquisitions. These unaudited consolidated pro forma operating results are presented for illustrative purposes only and are not indicative of the operating results that would have been achieved had the acquisitions occurred on January 1, 2021, nor does the information purport to reflect results for any future period.

	For the Three Months Ended September 30,
	2022								2021
	(Unaudited)
	As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma			As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma
Revenues	$	130,312		$	1,202	$	131,514		$	132,578		$	9,457	$	142,035
Net (loss) income		(5,720	)		290		(5,430	)		2,226			1,479		3,705
	For the Nine Months Ended September 30,
	2022								2021
	(Unaudited)
	As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma			As reported			Acquisitions Pro-Forma		Consolidated Pro-Forma
Revenues	$	404,902		$	6,422	$	411,324		$	402,619		$	39,819	$	442,438
Net (loss) income		(21,007	)		832		(20,175	)		(23,853	)		6,848		(17,005	)

EnvStd, IAG, TriAD and AirKinetics

Business Acquisition [Line Items]

Summary of Elements of Purchase Price of Acquisitions

The following table summarizes the elements of the purchase price of the acquisitions completed during the nine months ended September 30, 2022:

	Cash		Common Stock		Other Purchase Price Components Current		Contingent Consideration Current		Contingent Consideration Long Term		Total Purchase Price
EnvStd	$	14,473	$	—	$	521	$	1,166	$	—	$	16,160
All other 2022 acquisitions		7,650		—		472		50		—		8,172
Total	$	22,123	$	—	$	993	$	1,216	$	—	$	24,332

Summary of Purchase Price Attributable to Acquisitions

The preliminary purchase price attributable to the acquisitions was allocated as follows:

	EnvStd		All Other 2022 Acquisitions		Total
Cash	$	295	$	486	$	781
Accounts receivable and contract assets		5,200		1,846		7,046
Other current assets		456		19		475
Current assets		5,951		2,351		8,302
Property and equipment		168		11		179
Operating lease right-of-use asset—net		2,895		215		3,110
Customer relationships		5,807		2,714		8,521
Trade names		1,010		251		1,261
Covenants not to compete		269		394		663
Goodwill		4,107		2,965		7,072
Total assets		20,207		8,901		29,108
Current liabilities		1,719		619		2,338
Operating lease liability—net of    current portion		2,328		110		2,438
Total liabilities		4,047		729		4,776
Purchase price	$	16,160	$	8,172	$	24,332

Weighted Average Useful Lives for Acquired Identifiable Intangible Assets

The weighted average useful lives for the acquired companies’ identifiable intangible assets are as follows:

	Customer Relationships	Tradenames	Covenants Not to Compete
EnvStd	7	2	5
All other 2022 acquisitions	7	2	5

MSE Group, Vista, EI, Sensible, ECI, Horizon

Business Acquisition [Line Items]

Summary of Elements of Purchase Price of Acquisitions

The following table summarizes the elements of the purchase price of the acquisitions completed during the year ended December 31, 2021:

	Cash		Common Stock		Other Purchase Price Components Current			Contingent Consideration Current		Contingent Consideration Long Term		Total Purchase Price
MSE	$	9,082	$	2,271	$	10,701		$	1,551	$	253	$	23,858
EI		20,721		2,274		(63	)		—		—		22,932
All other 2021 acquisitions		29,683		3,775		1,228			1,250		4,350		40,286
Total	$	59,486	$	8,320	$	11,866		$	2,801	$	4,603	$	87,076

Summary of Purchase Price Attributable to Acquisitions

The purchase price attributable to the acquisitions was allocated as follows:

	MSE		EI		All other 2021 acquisitions		Total
Cash	$	2,810	$	250	$	693	$	3,753
Accounts receivable		2,980		4,675		4,133		11,788
Other current assets		31		84		289		404
Current assets		5,821		5,009		5,115		15,945
Property and equipment		513		32		1,168		1,713
Operating lease right-of-use asset—net		740		106		2,233		3,079
Customer relationships		8,720		10,073		12,830		31,623
Trade names		521		996		1,958		3,475
Covenants not to compete		922		511		1,248		2,681
Acquired Technology		—		—		321		321
Goodwill		8,176		8,960		19,569		36,705
Total assets		25,413		25,687		44,442		95,542
Current liabilities		1,007		2,719		2,351		6,077
Operating lease liability—net of    current portion		548		36		1,805		2,389
Total liabilities		1,555		2,755		4,156		8,466
Purchase price	$	23,858	$	22,932	$	40,286	$	87,076

Weighted Average Useful Lives for Acquired Identifiable Intangible Assets

The weighted average useful lives for the acquired companies’ identifiable intangible assets are as follows:

	Customer Relationships	Tradenames	Covenants Not to Compete	Developed Technology
MSE	2-7	2	5	n/a
EI	10	5	5	n/a
All other 2021 acquisitions	10	n/a-3	n/a-5	n/a-5

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Goodwill and Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2022

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Amounts Related to Goodwill

Amounts related to goodwill are as follows:

	Assessment, Permitting and Response			Measurement and Analysis		Remediation and Reuse		Total
Balance as of December 31, 2021	$	176,541		$	83,770	$	51,633	$	311,944
Goodwill acquired during the period		4,764			2,158		150		7,072
Acquisitions measurement period adjustments		(899	)		296		—		(603	)
Balance as of September 30, 2022	$	180,406		$	86,224	$	51,783	$	318,413

Schedule of Amounts Related to Finite-Lived Intangible Assets

Amounts related to finite-lived intangible assets are as follows:

September 30, 2022	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	204,926	$	90,572	$	114,354
Covenants not to compete	4-5 years		33,286		27,523		5,763
Trade names	1-5 years		21,673		17,442		4,231
Proprietary software	3-5 years		22,469		14,719		7,750
Patent	16 years		17,479		3,309		14,170
Total other intangible assets    —net		$	299,833	$	153,565	$	146,268

December 31, 2021	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	196,323	$	74,010	$	122,313
Covenants not to compete	4-5 years		32,622		25,113		7,509
Trade names	1-5 years		20,403		15,139		5,264
Proprietary software	3-5 years		22,077		11,155		10,922
Patent	16 years		17,479		2,490		14,989
Total other intangible assets    —net		$	288,904	$	127,907	$	160,997

Schedule of Future Amortization Expense

Future amortization expense is estimated to be as follows for each of the five following years and thereafter:

December 31,
2022 (remaining)		8,135
2023		28,163
2024		23,588
2025		16,897
2026 and thereafter		69,485
Total	$	146,268

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Accounts Payable and Other Accrued Liabilities (Tables)

9 Months Ended

Sep. 30, 2022

Payables and Accruals [Abstract]

Summary of Accounts Payable and Other Accrued Liabilities

Accounts payable and other accrued liabilities consisted of the following:

	September 30,		December 31,
	2022		2021
Accounts payable	$	19,023	$	24,167
Accrued expenses		12,312		14,906
Other business acquisitions purchase    price obligations		505		502
Contract liabilities		23,270		27,907
Other current liabilities		3,206		1,454
Total accounts payable and    other accrued liabilities	$	58,316	$	68,936

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Accrued Payroll and Benefits (Tables)

9 Months Ended

Sep. 30, 2022

Statement of Financial Position [Abstract]

Schedule of Accrued Payroll and Benefits

Accrued payroll and benefits consisted of the following:

	September 30,		December 31,
	2022		2021
Accrued bonuses	$	7,036	$	13,438
Accrued paid time off		1,309		1,144
Accrued payroll		7,749		6,547
Accrued other		4,383		4,842
Total accrued payroll and benefits	$	20,477	$	25,971

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Debt (Tables)

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

Schedule of Debt

Debt consisted of the following:

	September 30,			December 31,
	2022			2021
Term loan facility	$	166,250		$	175,000
Revolving line of credit		—			—
Less deferred debt issuance costs		(1,855	)		(2,244	)
Total debt		164,395			172,756
Less current portion of long-term debt		(8,750	)		(10,938	)
Long-term debt, less current portion	$	155,645		$	161,818

Summary of Term Loan Amortization

The 2021 Credit Facility term loan must be repaid in quarterly installments and shall amortize at the following future quarterly rates:

Date	Quarterly Installment Rate
December 31, 2022	1.25%
March 31, 2023	1.25%
June 30, 2023	1.25%
September 30, 2023	1.25%
December 31, 2023	1.88%
March 31, 2024	1.88%
June 30, 2024	1.88%
September 30, 2024	1.88%
December 31, 2024	1.88%
March 31, 2025	1.88%
June 30, 2025	1.88%
September 30, 2025	1.88%
December 31, 2025	2.50%
March 31, 2026	2.50%
April 27, 2026	Remaining balance

Summary of 2021 Credit Facility Interest Rate Subject to Leverage Ratio and LIBOR

The 2021 Credit Facility term loan and the revolver bear interest subject to the Company’s leverage ratio and LIBOR as follows:

Pricing Tier	Consolidated Leverage Ratio	Senior Credit Facilities LIBOR			Senior Credit Facilities Base Rate			Commitment Fee			Letter of Credit Fee
1	≥ 3.75x to 1.0		2.50	%		1.50	%		0.25	%		2.50	%
2	< 3.75x to 1.0 but ≥ 3.25 to 1.0		2.25			1.25			0.23			2.25
3	<3.25x to 1.0 but ≥ 2.50 to 1.0		2.00			1.00			0.20			2.00
4	<2.50x to 1.0 but ≥ 1.75 to 1.0		1.75			0.75			0.15			1.75
5	<1.75x to 1.0		1.50			0.50		0.15				1.50

Schedule of Aggregate Annual Maturities of Long-Term Debt

The following is a schedule of the aggregate annual maturities of long-term debt presented on the unaudited condensed consolidated statement of financial position, based on the terms of the 2021 Credit Facility:

September 30,
2023	$	8,750
2024		13,125
2025		13,125
2026		131,250
Total	$	166,250

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Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Summary of Financial Instruments Measured at Fair Value on Recurring Basis

The following financial instruments are measured at fair value on a recurring basis using significant unobservable inputs (Level 3):

	September 30,		December 31,
	2022		2021
Interest rate swap	$	6,313	$	—
Total assets	$	6,313	$	—
Business acquisitions contingent consideration,    current	$	3,967	$	31,450
Business acquisitions contingent consideration,    long-term		2,810		4,350
Conversion option		24,730		23,081
Total liabilities	$	31,507	$	58,881

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis:

	Interest Rate Swap		Total Assets		Business Acquisitions Contingent Consideration, Current			Business Acquisitions Contingent Consideration, Long-term			Conversion    Option		Total Liabilities
Balance—at January 1, 2021	$	—	$	—	$	49,902		$	4,565		$	20,886	$	75,353
Acquisitions		—		—		1,000			6,004			—		7,004
Changes in fair value included in earnings		—		—		13,774			10,261			1,651		25,686
Payment of contingent consideration        payable		—		—		(50,154	)		—			—		(50,154	)
Reclass of long term to short term       contingent liabilities		—		—		16,630			(16,630	)		—		—
Balance—at September 30, 2021	$	—	$	—	$	31,152		$	4,200		$	22,537	$	57,889
Balance—at January 1, 2022	$	—		—	$	31,450		$	4,350		$	23,081	$	58,881
Acquisitions		—		—		—			1,216			—		1,216
Changes in fair value included in earnings		6,313		6,313		330			(390	)		1,649		1,589
Payment of contingent consideration        payable		—		—		(30,179	)		—			—		(30,179	)
Reclass of long term to short term       contingent liabilities		—		—		2,366			(2,366	)		—		—
Balance—at September 30, 2022	$	6,313	$	6,313	$	3,967		$	2,810		$	24,730	$	31,507

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Stockholder's Equity (Tables)

9 Months Ended

Sep. 30, 2022

Summary of Issued Shares of Common Stock

The Company issued the following shares of common stock:

	Three Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Total (in thousands)		Shares		Average Price per Share		Total (in thousands)
Acquisitions		—	$	—	$	—		62,738	$	52.18	$	3,274
Exercise of options		28,111		11.70		329		354,918		8.30		2,946
Total		28,111	$	11.70	$	329		417,656	$	14.89	$	6,220
	Nine Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Total (in thousands)		Shares		Average Price per Share		Total (in thousands)
Acquisitions		—	$	—	$	—		143,800	$	41.86	$	6,020
Exercise of warrants (1)		—		—		—		67,713		17.19		—
Exercise of options		62,293		13.04		812		779,068		7.74		6,032
Restricted shares, net (1)		25,289		66.58		—		38,929		31.31		—
Payment of earn-out liability		—		—		—		539,607		46.33		25,000
Payment of purchase price    true up		—		—		—		24,200		44.81		1,084
Total		87,582	$	28.50	$	812		1,593,317	$	25.43	$	38,136

(1) Represents the non-cash release of common shares due to the exercise of warrants and the vesting of restricted stock.

Schedule of Share Authorized to be Issue and Available for Grant

The following number of shares were authorized to be issued and available for grant:

	September 30, 2022
	2017 Plan		2013 Plan		Total
Shares authorized to be issued		5,140,112		2,037,019		7,177,131
Shares available for grant(1)		364,949		—		364,949
	September 30, 2021
	2017 Plan		2013 Plan		Total
Shares authorized to be issued		3,944,750		2,047,269		5,992,019
Shares available for grant		1,593,287		—		1,593,287

(1) In January 2022 the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued

under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. Shares available for grant exclude awards of stock appreciation rights approved in December 2021 that are subject to vesting based on the achievement of certain market conditions, which have not yet been, and may not be, achieved. See footnote 1 to the table in Common Stock Reserved for Future Issuance below for additional information regarding the December 2021 grant.

Schedule of Stock Compensation Expense

Total stock compensation expense for the Plans was as follows:

	Three Months Ended September 30,
	2022										2021
	2017 plan						2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		SARs		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	404	$	—	$	—	$	—	$	404	$	282	$	—	$	—	$	282
Selling, general and    administrative expense		2,216		6,083		2,315		—		10,614		1,844		237		2		2,083
Total	$	2,620	$	6,083	$	2,315	$	—	$	11,018	$	2,126	$	237	$	2	$	2,365
	Nine Months Ended September 30,
	2022										2021
	2017 plan						2013 plan				2017 plan				2013 plan
	Options		Restricted Stock		SARs		Options		Total		Options		Restricted Stock		Options		Total
Cost of revenue	$	1,069	$	—	$	—	$	—	$	1,069	$	1,178	$	—	$	10	$	1,188
Selling, general and    administrative expense		6,449		17,892		6,965		—		31,306		4,638		749		11		5,399
Total	$	7,518	$	17,892	$	6,965	$	—	$	32,375	$	5,816	$	749	$	21	$	6,587

Summary of Performance Hurdles

The performance hurdles shall be deemed achieved if the average trading price per share of the Company’s common stock equals or exceeds the following stock prices:

SARs Stock Price Performance Hurdle		Portion of SARs Subject to Performance Hurdle
$	133.58	1/3
$	166.98	1/3
$	200.37	1/3

Summary of Weighted Average Assumptions Used in Black-Sholes Option-pricing Model

The following weighted-average assumptions were used in the Black-Sholes option-pricing model calculation:

	September 30,			September 30,
	2022			2021
Common stock value (per share)	$	43.72		$	39.83
Expected volatility		33.45			58.34
Risk-free interest rate		1.94	%		0.77	%
Expected life (years)		6.45			6.32
Forfeiture rate	None			None
Dividend rate	None			None

Schedule of Common Stock Reserved for Future Issuance

The Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following:

	September 30,
	2022		2021
Montrose 2013 Stock Incentive Plan		861,514		2,047,269
Montrose 2017 Stock Incentive Plan(1)		7,757,995		3,944,750
Total		8,619,509		5,992,019

(1) In January 2022, the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. The Company expects to have sufficient shares available under the 2017 Plan to satisfy the future settlement of outstanding awards. Shares reserved for future issuance include 3,000,000 shares underlying the 3,000,000 performance SARs granted in December 2021 that are subject to vesting based on the achievement of certain market conditions. Assuming achievement at the highest price performance hurdle, approximately 2,000,000 shares of common stock would be issued upon vesting of these performance SARs. To date, none of the market conditions have been achieved.

Montrose Amended & Restated 2017 Stock Incentive Plan

Schedule of Restricted Stock Activity

RSA and RSU activity was as follows:

	Nine Months Ended September 30,
	2022						2021
	Shares		Average Price per Share		Fair Value (in thousands)		Shares		Average Price per Share		Fair Value (in thousands)
Awards granted		106,324	$	46.82	$	4,978		19,066	$	36.99	$	705

Summary of Stock Option Activity

The following summarizes the options activity of the 2017 Plan:

	Options to Purchase Common Stock			Weighted- Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The- Money Options (in Thousands)
Outstanding as of January 1, 2021		1,840,229		$	23	$	12		9.09	$	15,598
Granted		264,470			40		22		—		—
Forfeited/ cancelled		(29,025	)		28		—		—		—
Expired		(1,250	)		18		—		—		—
Exercised		(66,875	)		22		—		—		2,078
Outstanding as of September 30, 2021		2,007,549			25		14		8.53		73,724
Outstanding as of January 1, 2022		2,036,729		$	26	$	14		8.30	$	91,030
Granted		664,784			44		16		—		—
Forfeited/ cancelled		(60,167	)		36		—		—		—
Exercised		(26,258	)		22		—		—		671
Outstanding as of September 30, 2022		2,615,088		$	30	$	15		8.04	$	18,784
Exercisable at September 30, 2022		1,010,302			26		—		7.48		9,966

Montrose Amended and Restated 2013 Stock Option Plan

Summary of Stock Option Activity

The following summarizes the activity of the 2013 Plan:

	Options to Purchase Common Stock			Weighted- Average Exercise Price per Share		Weighted Average Grant Date Fair Value per Share		Weighted Average Remaining Contract Life (in Years)		Aggregate Intrinsic Value of In-The- Money Options (in Thousands)
Outstanding as of January 1, 2021		1,787,869		$	6	$	1		5.40	$	43,867
Expired		(625	)		6		—		—		—
Exercised		(710,568	)		6		—		—		33,480
Outstanding as of September 30, 2021		1,076,676			6		2		4.65		59,532
Outstanding as of January 1, 2022		897,674		$	6	$	2		4.37	$	57,529
Expired		(125	)		6		—		—		—
Exercised		(36,035	)		6		—		—		1,425
Outstanding as of September 30, 2022		861,514		$	6	$	2		3.61	$	23,448
Exercisable at September 30, 2022		861,514			6		—		3.61		23,448

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Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders

The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(In thousands, except for net loss per share)	2022			2021			2022			2021
Net (loss) income	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)
Convertible and redeemable series A-2 preferred    stock dividend		(4,100	)		(4,100	)		(12,300	)		(12,300	)
Net loss attributable to common stockholders    –basic and diluted		(9,820	)		(1,874	)		(33,307	)		(36,153	)
Weighted-average common shares outstanding –    basic and diluted		29,691			26,220			29,677			25,798
Net loss per share attributable to common    stockholders –basic and diluted	$	(0.33	)	$	(0.07	)	$	(1.12	)	$	(1.40	)

Equity Shares Excluded from Calculation of Diluted Loss Per Share Attributable to Common Stockholders

The following equity shares were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive:

	September 30,
	2022		2021
Stock options		3,476,602		1,686,688
Restricted stock		1,777,958		28,623
SARs		3,000,000		—

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Segment Information (Tables)

9 Months Ended

Sep. 30, 2022

Segment Reporting [Abstract]

Components of Segment Revenues and Adjusted EBITDA

Segment revenues and Adjusted EBITDA consisted of the following:

	Three Months Ended September 30,
	2022					2021
			Segment					Segment
	Segment		Adjusted			Segment		Adjusted
	Revenues		EBITDA			Revenues		EBITDA
Assessment, Permitting and Response	$	46,414	$	9,820		$	63,412	$	15,719
Measurement and Analysis		43,754		8,483			38,752		8,283
Remediation and Reuse		40,144		7,010			30,414		5,472
Total Operating Segments		130,312		25,313			132,578		29,474
Corporate and Other		—		(6,940	)		—		(7,987	)
Total	$	130,312	$	18,373		$	132,578	$	21,487
	Nine Months Ended September 30,
	2022					2021
			Segment					Segment
	Segment		Adjusted			Segment		Adjusted
	Revenues		EBITDA			Revenues		EBITDA
Assessment, Permitting and Response	$	142,051	$	30,252		$	209,379	$	46,379
Measurement and Analysis		125,739		21,852			111,309		22,634
Remediation and Reuse		137,112		22,059			81,931		12,262
Total Operating Segments		404,902		74,163			402,619		81,275
Corporate and Other		—		(22,826	)		—		(22,026	)
Total	$	404,902	$	51,337		$	402,619	$	59,249

Reconciliation of Segment Measure to Net Loss

Presented below is a reconciliation of the Company’s segment measure to net loss:

	For the Three Months Ended September 30,						For the Nine Months Ended September 30,
	2022			2021			2022			2021
Total	$	18,373		$	21,487		$	51,337		$	59,249
Interest expense, net		(1,400	)		(1,722	)		(4,010	)		(11,208	)
Income tax benefit (expense)		208			(902	)		(1,892	)		(648	)
Depreciation and amortization		(11,504	)		(11,471	)		(35,928	)		(33,145	)
Stock-based compensation		(11,018	)		(2,365	)		(32,375	)		(6,587	)
Start-up losses and investment in new services		(1,278	)		(1,186	)		(2,949	)		(3,276	)
Acquisition costs		(368	)		(913	)		(1,354	)		(1,656	)
Fair value changes in financial instruments		1,808			(531	)		4,664			(1,651	)
Fair value changes in business acquisition    contingencies		(59	)		—			3,472			(24,035	)
Expenses related to financing transactions		—			—			(7	)		(50	)
Other losses or expenses (1)		(482	)		(171	)		(1,965	)		(846	)
Net (loss) income	$	(5,720	)	$	2,226		$	(21,007	)	$	(23,853	)

(1) In 2022, amounts include costs associated with the closing of a lab and severance costs related to a restructuring within our soil remediation business. In 2021, amounts include non-operational charges incurred due to the remeasurement of finance leases as a result of the adoption of ASC 842 and costs related to the implementation of a new ERP.

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Description of the Business and Basis of Presentation - Additional Information (Details)	9 Months Ended
	Sep. 30, 2022 Employee Segment Office
Description Of Business And Basis Of Presentation [Line Items]
Entity formation, month and year	2013-11
Number of offices in which entity operates | Office	80
Entity number of employees | Employee	2,800
Number of operating segments | Segment	3

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Summary of New Accounting Pronouncements - Additional Information (Details) - Accounting Standards Update 2020-06	Sep. 30, 2022
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2022
Change in accounting principle, accounting standards update, immaterial effect	true

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Revenues and Accounts Receivable - Schedule of Contract Balances (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Revenues And Accounts Receivable [Abstract]
Contract assets	$ 60,444	$ 40,139
Contract liabilities	$ 23,270	$ 27,907

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Revenues and Accounts Receivable - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) Customer	Sep. 30, 2021 Customer	Sep. 30, 2022 USD ($) Customer	Sep. 30, 2021 Customer	Dec. 31, 2021 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Contracts assets acquired through business acquisitions			$ 1.3		$ 0.5
Contract liabilities acquired through business acquisitions			0.0		0.5
Contract with customer liabilities, revenue recognized	$ 10.3		23.6
Revenue remaining performance obligations	$ 92.0		$ 92.0		$ 108.7
Customer Concentration Risk | Accounts Receivable | Customer One
Accounts Notes And Loans Receivable [Line Items]
Concentration risk percentage					23.10%
Customer Concentration Risk | Accounts Receivable | Significant Customer
Accounts Notes And Loans Receivable [Line Items]
Concentration risk percentage			10.00%
Number of customers | Customer			0
Customer Concentration Risk | Revenue | Customer One
Accounts Notes And Loans Receivable [Line Items]
Concentration risk percentage		12.10%
Customer Concentration Risk | Revenue | Significant Customer
Accounts Notes And Loans Receivable [Line Items]
Concentration risk percentage	11.10%		14.80%	10.00%
Number of customers | Customer	1	0	1	3
Customer Concentration Risk | Revenue | Customer Two
Accounts Notes And Loans Receivable [Line Items]
Concentration risk percentage		11.40%
Customer Concentration Risk | Revenue | Customer Three
Accounts Notes And Loans Receivable [Line Items]
Concentration risk percentage		10.70%

XML

Revenues and Accounts Receivable - Additional Information (Details1) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligations	$ 92.0	$ 108.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligations	$ 67.8
Revenue remaining performance obligations, satisfaction period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligations	$ 24.2
Revenue remaining performance obligations, satisfaction period

XML

Revenues and Accounts Receivable - Schedule of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues And Accounts Receivable [Abstract]
Accounts receivable, invoiced	$ 82,649	$ 101,709
Accounts receivable, other	544	1,385
Allowance for doubtful accounts	(2,266)	(4,581)	$ (4,265)
Accounts receivable—net	$ 80,927	$ 98,513

XML

Revenues and Accounts Receivable - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Revenues And Accounts Receivable [Abstract]
Beginning Balance		$ 4,581	$ 4,265	$ 4,265
Bad Debt (Recovery) Expense		(821)	$ 803	1,135
Charged to Allowance		(1,621)		(1,548)
Other	[1]	127		729
Ending Balance		$ 2,266		$ 4,581

[1] This amount consists of additions to the allowance due to business acquisitions.

XML

Prepaid and Other Current Assets - Schedule of Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deposits	$ 1,402	$ 843
Prepaid expenses	4,708	4,675
Supplies	3,686	2,439
Income tax receivable	1,094	508
Prepaid and other current assets	$ 10,890	$ 8,465

XML

Property and Equipment, Net - Property and Equipment, Net (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 79,399	$ 73,161
Less accumulated depreciation	(49,109)	(44,707)
Total property and equipment— net	$ 33,581	31,521
Lab and test equipment
Property Plant And Equipment [Line Items]
Estimated Useful Life	7 years
Property and equipment, gross	$ 19,975	18,581
Vehicles
Property Plant And Equipment [Line Items]
Estimated Useful Life	5 years
Property and equipment, gross	$ 5,642	5,414
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 38,446	35,148
Equipment | Minimum
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Equipment | Maximum
Property Plant And Equipment [Line Items]
Estimated Useful Life	7 years
Furniture and fixtures
Property Plant And Equipment [Line Items]
Estimated Useful Life	7 years
Property and equipment, gross	$ 2,895	2,844
Leasehold improvements
Property Plant And Equipment [Line Items]
Estimated Useful Life	7 years
Property and equipment, gross	$ 8,535	7,268
Aircraft
Property Plant And Equipment [Line Items]
Estimated Useful Life	10 years
Property and equipment, gross	$ 931	931
Building
Property Plant And Equipment [Line Items]
Estimated Useful Life	39 years
Property and equipment, gross	$ 2,975	2,975
Land
Property Plant And Equipment [Line Items]
Property and equipment, gross	725	725
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,566	$ 2,342

XML

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Property Plant And Equipment [Line Items]
Depreciation expense	$ 1.7	$ 1.8	$ 5.3	$ 4.8

XML

Leases - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021	Jan. 01, 2021
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	$ 28,453	$ 23,532	$ 24,600
Current operating lease liabilities	8,130	6,888	7,300
Operating lease liabilities, net of current portion	20,841	16,859	17,300
Finance lease right-of-use assets	9,869	8,944	7,200
Current finance lease liabilities	3,763	3,512	2,900
Finance lease liabilities, net of current portion	$ 6,562	$ 5,756	$ 4,600
Minimum
Lessee Lease Description [Line Items]
Lessee operating and finance lease term	1 year
Maximum
Lessee Lease Description [Line Items]
Lessee operating and finance lease term	15 years

XML

Leases - Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Lessee Lease Description [Line Items]
Total operating lease cost	$ 2,896	$ 2,323	$ 8,383	$ 6,727
Total finance lease cost	1,191	922	3,361	2,691
Total lease cost	4,087	3,245	11,744	9,418
Selling, General and Administrative Expenses
Lessee Lease Description [Line Items]
Lease cost	2,542	2,203	7,472	6,398
Variable lease cost	354	120	911	329
Depreciation and Amortization
Lessee Lease Description [Line Items]
Amortization of right of use assets	1,075	825	3,026	2,391
Interest Expense, Net
Lessee Lease Description [Line Items]
Interest on lease liabilities	$ 116	$ 97	$ 335	$ 300

XML

Leases - Summary of Supplemental Cash Flow Information Related To Leases (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Operating cash flows used in operating leases	$ 7,171	$ 6,273
Operating cash flows used in finance leases	335	300
Financing cash flows used in finance leases	2,906	2,367
Operating leases	11,786	5,078
Finance leases	$ 3,939	$ 2,719

XML

Leases - Summary of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates (Details)	Sep. 30, 2022	Sep. 30, 2021
Leases [Abstract]
Weighted average remaining lease term, Operating Leases	4 years 6 months 21 days	5 years 2 months 19 days
Weighted average remaining lease term, Finance Leases	3 years 3 months 25 days	2 years 9 months 18 days
Weighted average discount rate, Operating Leases	2.58%	2.62%
Weighted average discount rate, Finance Leases	5.27%	4.95%

XML

Leases - Summary of Maturities of Lease Liabilities (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Leases [Abstract]
Operating Leases, Remainder of 2022	$ 2,447
Operating Leases, 2023	8,295
Operating Leases, 2024	6,595
Operating Leases, 2025	4,680
Operating Leases, 2026 and thereafter	8,733
Operating Leases, Total undiscounted future minimum lease payments	30,750
Operating Leases, Less imputed interest	(1,779)
Operating Leases, Total discounted future minimum lease payments	28,971
Finance Leases, Remainder of 2022	1,181
Finance Leases, 2023	3,871
Finance Leases, 2024	2,781
Finance Leases, 2025	1,881
Finance Leases, 2026 and thereafter	1,570
Finance Leases, Total undiscounted future minimum lease payments	11,284
Finance Leases, Less imputed interest	(959)
Finance Leases, Total discounted future minimum lease payments	$ 10,325

XML

Business Acquisitions - Additional Information (Details) - USD ($)	1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 30, 2021	Aug. 31, 2021	Jul. 31, 2021	Jun. 30, 2021	Jan. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Aug. 31, 2022	Jan. 31, 2022	Oct. 31, 2021
Business Acquisition [Line Items]
Transaction costs related to business combinations						$ 368,000	$ 913,000	$ 1,354,000	$ 1,656,000
Number of common stock shares issued in connection with business acquisition							62,738		143,800
Business combination, paid in cash								22,123,000		$ 59,486,000
EnvStd
Business Acquisition [Line Items]
Percentage of interests acquired												100.00%
Business combination, paid in cash								$ 14,473,000
TriAD
Business Acquisition [Line Items]
Percentage of interests acquired											100.00%
AirKinetics
Business Acquisition [Line Items]
Percentage of interests acquired						100.00%		100.00%
MSE Group
Business Acquisition [Line Items]
Percentage of interests acquired					100.00%
Number of common stock shares issued in connection with business acquisition					71,740
Vista
Business Acquisition [Line Items]
Percentage of interests acquired				100.00%
Number of common stock shares issued in connection with business acquisition				9,322
EI
Business Acquisition [Line Items]
Percentage of interests acquired			100.00%
Number of common stock shares issued in connection with business acquisition			43,100
Business combination, paid in cash										$ 20,721,000
Sensible
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Number of common stock shares issued in connection with business acquisition		19,638
ECI
Business Acquisition [Line Items]
Percentage of interests acquired													100.00%
Horizon
Business Acquisition [Line Items]
Percentage of interests acquired	100.00%
Number of common stock shares issued in connection with business acquisition	34,921
MSE Group, EI, Vista and Sensible
Business Acquisition [Line Items]
Revenue							$ 11,900,000		$ 19,700,000
Pre-tax income (loss)							$ (200,000)		$ 0
EnvStd and IAG | 2026 Earn Out
Business Acquisition [Line Items]
Business combination, earn-out payment, maximum						$ 8,500,000		$ 8,500,000
Business combination, paid in cash								3,000,000.0
EnvStd, IAG, TriAD and AirKinetics
Business Acquisition [Line Items]
Revenue						5,600,000		13,200,000
Pre-tax income (loss)						$ 1,000,000.0		$ 1,700,000

XML

Business Acquisitions - Summary of Elements of Purchase Price of Acquisitions (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Cash	$ 22,123	$ 59,486
Common Stock		8,320
Other Purchase Price Components Current	993	11,866
Contingent Consideration Current	1,216	2,801
Contingent Consideration Long Term		4,603
Total Purchase Price	24,332	87,076
EnvStd
Business Acquisition [Line Items]
Cash	14,473
Other Purchase Price Components Current	521
Contingent Consideration Current	1,166
Total Purchase Price	16,160
All Other 2022 Acquisitions
Business Acquisition [Line Items]
Cash	7,650
Other Purchase Price Components Current	472
Contingent Consideration Current	50
Total Purchase Price	$ 8,172
MSE Group
Business Acquisition [Line Items]
Cash		9,082
Common Stock		2,271
Other Purchase Price Components Current		10,701
Contingent Consideration Current		1,551
Contingent Consideration Long Term		253
Total Purchase Price		23,858
EI
Business Acquisition [Line Items]
Cash		20,721
Common Stock		2,274
Other Purchase Price Components Current		(63)
Total Purchase Price		22,932
All Other 2021 Acquisitions
Business Acquisition [Line Items]
Cash		29,683
Common Stock		3,775
Other Purchase Price Components Current		1,228
Contingent Consideration Current		1,250
Contingent Consideration Long Term		4,350
Total Purchase Price		$ 40,286

XML

Business Acquisitions - Summary of Purchase Price Attributable to Acquisitions (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Cash	$ 781	$ 3,753
Accounts receivable and contract assets	7,046
Accounts receivable		11,788
Other current assets	475	404
Current assets	8,302	15,945
Property and equipment	179	1,713
Operating lease right-of-use asset-net	3,110	3,079
Goodwill	7,072	36,705
Total assets	29,108	95,542
Current liabilities	2,338	6,077
Operating lease liability-net of current portion	2,438	2,389
Total liabilities	4,776	8,466
Purchase price	24,332	87,076
EnvStd
Business Acquisition [Line Items]
Cash	295
Accounts receivable and contract assets	5,200
Other current assets	456
Current assets	5,951
Property and equipment	168
Operating lease right-of-use asset-net	2,895
Goodwill	4,107
Total assets	20,207
Current liabilities	1,719
Operating lease liability-net of current portion	2,328
Total liabilities	4,047
Purchase price	16,160
All Other 2022 Acquisitions
Business Acquisition [Line Items]
Cash	486
Accounts receivable and contract assets	1,846
Other current assets	19
Current assets	2,351
Property and equipment	11
Operating lease right-of-use asset-net	215
Goodwill	2,965
Total assets	8,901
Current liabilities	619
Operating lease liability-net of current portion	110
Total liabilities	729
Purchase price	8,172
MSE Group
Business Acquisition [Line Items]
Cash		2,810
Accounts receivable		2,980
Other current assets		31
Current assets		5,821
Property and equipment		513
Operating lease right-of-use asset-net		740
Goodwill		8,176
Total assets		25,413
Current liabilities		1,007
Operating lease liability-net of current portion		548
Total liabilities		1,555
Purchase price		23,858
EI
Business Acquisition [Line Items]
Cash		250
Accounts receivable		4,675
Other current assets		84
Current assets		5,009
Property and equipment		32
Operating lease right-of-use asset-net		106
Goodwill		8,960
Total assets		25,687
Current liabilities		2,719
Operating lease liability-net of current portion		36
Total liabilities		2,755
Purchase price		22,932
Other Acquisitions
Business Acquisition [Line Items]
Cash		693
Accounts receivable		4,133
Other current assets		289
Current assets		5,115
Property and equipment		1,168
Operating lease right-of-use asset-net		2,233
Goodwill		19,569
Total assets		44,442
Current liabilities		2,351
Operating lease liability-net of current portion		1,805
Total liabilities		4,156
Purchase price		40,286
Customer Relationships
Business Acquisition [Line Items]
Intangible assets	8,521	31,623
Customer Relationships | EnvStd
Business Acquisition [Line Items]
Intangible assets	5,807
Customer Relationships | All Other 2022 Acquisitions
Business Acquisition [Line Items]
Intangible assets	2,714
Customer Relationships | MSE Group
Business Acquisition [Line Items]
Intangible assets		8,720
Customer Relationships | EI
Business Acquisition [Line Items]
Intangible assets		10,073
Customer Relationships | Other Acquisitions
Business Acquisition [Line Items]
Intangible assets		12,830
Trade Names
Business Acquisition [Line Items]
Intangible assets	1,261	3,475
Trade Names | EnvStd
Business Acquisition [Line Items]
Intangible assets	1,010
Trade Names | All Other 2022 Acquisitions
Business Acquisition [Line Items]
Intangible assets	251
Trade Names | MSE Group
Business Acquisition [Line Items]
Intangible assets		521
Trade Names | EI
Business Acquisition [Line Items]
Intangible assets		996
Trade Names | Other Acquisitions
Business Acquisition [Line Items]
Intangible assets		1,958
Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets	663	2,681
Covenants Not to Compete | EnvStd
Business Acquisition [Line Items]
Intangible assets	269
Covenants Not to Compete | All Other 2022 Acquisitions
Business Acquisition [Line Items]
Intangible assets	$ 394
Covenants Not to Compete | MSE Group
Business Acquisition [Line Items]
Intangible assets		922
Covenants Not to Compete | EI
Business Acquisition [Line Items]
Intangible assets		511
Covenants Not to Compete | Other Acquisitions
Business Acquisition [Line Items]
Intangible assets		1,248
Acquired Technology
Business Acquisition [Line Items]
Intangible assets		321
Acquired Technology | Other Acquisitions
Business Acquisition [Line Items]
Intangible assets		$ 321

XML

Business Acquisitions - Weighted Average Useful Lives for Acquired Identifiable Intangible Assets (Details)	9 Months Ended
	Sep. 30, 2022
Customer Relationships | EnvStd
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	7 years
Customer Relationships | MSE Group | Minimum
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	2 years
Customer Relationships | MSE Group | Maximum
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	7 years
Customer Relationships | EI
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	10 years
Customer Relationships | All Other 2021 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	10 years
Customer Relationships | All Other 2022 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	7 years
Trade Names | EnvStd
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	2 years
Trade Names | MSE Group
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	2 years
Trade Names | EI
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
Trade Names | All Other 2021 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	3 years
Trade Names | All Other 2022 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	2 years
Covenants Not to Compete | EnvStd
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
Covenants Not to Compete | MSE Group
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
Covenants Not to Compete | EI
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
Covenants Not to Compete | All Other 2021 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
Covenants Not to Compete | All Other 2022 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
Developed Technology | All Other 2021 Acquisitions
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years

XML

Business Acquisitions - Summary of Supplemental Unaudited Pro-Forma Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Business Acquisition [Line Items]
Revenues	$ 130,312	$ 132,578	$ 404,902	$ 402,619
Net (loss) income	(5,720)	2,226	(21,007)	(23,853)
Acquisition Proforma
Business Acquisition [Line Items]
Revenues	1,202	9,457	6,422	39,819
Net (loss) income	290	1,479	832	6,848
Consolidated Proforma
Business Acquisition [Line Items]
Revenues	131,514	142,035	411,324	442,438
Net (loss) income	$ (5,430)	$ 3,705	$ (20,175)	$ (17,005)

XML

Goodwill and Intangible Assets - Schedule of Amounts Related to Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($)
Goodwill [Line Items]
Beginning balance	$ 311,944
Goodwill acquired during the period	7,072
Acquisitions measurement period adjustments	(603)
Ending balance	318,413
Assessment, Permitting and Response
Goodwill [Line Items]
Beginning balance	176,541
Goodwill acquired during the period	4,764
Acquisitions measurement period adjustments	(899)
Ending balance	180,406
Measurement and Analysis
Goodwill [Line Items]
Beginning balance	83,770
Goodwill acquired during the period	2,158
Acquisitions measurement period adjustments	296
Ending balance	86,224
Remediation and Reuse Segment
Goodwill [Line Items]
Beginning balance	51,633
Goodwill acquired during the period	150
Ending balance	$ 51,783

XML

Goodwill and Intangible Assets - Schedule of Amounts Related to Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 299,833	$ 288,904
Accumulated Amortization	153,565	127,907
Total Intangible Assets—Net	146,268	160,997
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Balance	204,926	196,323
Accumulated Amortization	90,572	74,010
Total Intangible Assets—Net	$ 114,354	$ 122,313
Customer Relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	2 years	2 years
Customer Relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	15 years	15 years
Covenants Not to Compete
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 33,286	$ 32,622
Accumulated Amortization	27,523	25,113
Total Intangible Assets—Net	$ 5,763	$ 7,509
Covenants Not to Compete | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	4 years	4 years
Covenants Not to Compete | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 21,673	$ 20,403
Accumulated Amortization	17,442	15,139
Total Intangible Assets—Net	$ 4,231	$ 5,264
Trade Names | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	1 year	1 year
Trade Names | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Proprietary Software
Finite-Lived Intangible Assets [Line Items]
Gross Balance	$ 22,469	$ 22,077
Accumulated Amortization	14,719	11,155
Total Intangible Assets—Net	$ 7,750	$ 10,922
Proprietary Software | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years	3 years
Proprietary Software | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Patent
Finite-Lived Intangible Assets [Line Items]
Estimated Useful Life	16 years	16 years
Gross Balance	$ 17,479	$ 17,479
Accumulated Amortization	3,309	2,490
Total Intangible Assets—Net	$ 14,170	$ 14,989

XML

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 8.7	$ 8.9	$ 27.6	$ 25.9

XML

Goodwill and Intangible Assets - Schedule of Future Amortization Expense (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
2022 (remaining)	$ 8,135
2023	28,163
2024	23,588
2025	16,897
2026 and thereafter	69,485
Total Intangible Assets—Net	$ 146,268	$ 160,997

XML

Accounts Payable and Other Accrued Liabilities - Summary of Accounts Payable and Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Accounts payable	$ 19,023	$ 24,167
Accrued expenses	12,312	14,906
Other business acquisitions purchase price obligations	505	502
Contract liabilities	23,270	27,907
Other current liabilities	3,206	1,454
Total accounts payable and other accrued liabilities	$ 58,316	$ 68,936

XML

Accrued Payroll and Benefits - Schedule of Accrued Payroll and Benefits (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Accrued bonuses	$ 7,036	$ 13,438
Accrued paid time off	1,309	1,144
Accrued payroll	7,749	6,547
Accrued other	4,383	4,842
Total accrued payroll and benefits	$ 20,477	$ 25,971

XML

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Annual effective tax rate ("ETR") from continuing operations	3.50%	28.80%	(9.90%)	(2.80%)
Federal statutory rate			21.00%
Uncertain tax positions	$ 0		$ 0
Income tax (benefit) expense	$ (208,000)	$ 902,000	$ 1,892,000	$ 648,000

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Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Line Of Credit Facility [Line Items]
Less deferred debt issuance costs	$ (1,855)	$ (2,244)
Total debt	164,395	172,756
Less current portion of long-term debt	(8,750)	(10,938)
Long-term debt, less current portion	155,645	161,818
Term Loan Facility
Line Of Credit Facility [Line Items]
Total debt	$ 166,250	$ 175,000

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Debt - Additional Information (Details) - USD ($)					1 Months Ended	9 Months Ended
	Jan. 27, 2022	Jan. 26, 2022	Apr. 30, 2021	Apr. 27, 2021	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2022	Dec. 31, 2021	Apr. 13, 2020
Line Of Credit Facility [Line Items]
Loss on extinguishment							$ (4,052,000)
Floating Component | Interest Rate Swap
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000.0
Credit facility maturity date	Jan. 27, 2025
Interest rate	1.39%
2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				$ 300,000,000.0
Credit facility maturity date				Apr. 27, 2026
Percentage of interest rate reduction					0.05%
Maximum net leverage ratio				425.00%
Maximum net leverage ratio year two				400.00%
Maximum net leverage ratio year three				375.00%
Minimum fixed charge coverage ratio				125.00%
Consolidated total leverage ratio						120.00%
Percentage of proceeds of debt, subject to customary exceptions						100.00%
Percentage of proceeds of certain dispositions, subject to customary reinvestment rights						100.00%
Percentage of proceeds of insurance or condemnation, subject to customary reinvestment rights						100.00%
Weighted average interest rate					2.90%	2.90%
Incremental Term Loans
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				$ 150,000,000.0
2020 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit										$ 225,000,000.0
Loss on extinguishment			$ 4,100,000
Debt fee paid			1,000,000.0
Unamortized debt issuance costs			$ 3,100,000
Equipment Line Of Credit
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity								$ 10,000,000.0
Credit facility maturity date						Dec. 30, 2022
Term Loan Facility
Line Of Credit Facility [Line Items]
Line of credit					$ 166,250,000	$ 166,250,000			$ 175,000,000
Term Loan Facility | 2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				175,000,000.0
Installment repayment amount		$ 2,200,000				$ 6,600,000
Term Loan Facility | 2020 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit										175,000,000.0
Revolving Line of Credit | 2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				125,000,000.0
Revolving Line of Credit | 2020 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit										$ 50,000,000.0
Revolving Line of Credit | Letter of Credit | 2021 Credit Facility
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity				$ 20,000,000.0

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Debt - Summary of Term Loan Amortization (Details) - 2021 Credit Facility - Term Loan Facility	9 Months Ended
	Sep. 30, 2022
Subsequent Event [Line Items]
Debt instrument, quarterly installment rate, December 31, 2022	1.25%
Debt instrument, quarterly installment rate, March 31, 2023	1.25%
Debt instrument, quarterly installment rate, June 30, 2023	1.25%
Debt instrument, quarterly installment rate, September 30, 2023	1.25%
Debt instrument, quarterly installment rate, December 31, 2023	1.88%
Debt instrument, quarterly installment rate, March 31, 2024	1.88%
Debt instrument, quarterly installment rate, June 30, 2024	1.88%
Debt instrument, quarterly installment rate, September 30, 2024	1.88%
Debt instrument, quarterly installment rate, December 31, 2024	1.88%
Debt instrument, quarterly installment rate, March 31, 2025	1.88%
Debt instrument, quarterly installment rate, June 30, 2025	1.88%
Debt instrument, quarterly installment rate, September 30, 2025	1.88%
Debt instrument, quarterly installment rate, December 31, 2025	2.50%
Debt instrument, quarterly installment rate, March 31, 2026	2.50%
Debt instrument, quarterly installment rate, April 27, 2026	Remaining balance

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Debt - Summary of 2021 Credit Facility Interest Rate Subject to Leverage Ratio and LIBOR (Details) - 2021 Credit Facility	Apr. 27, 2021
Pricing Tier1
Subsequent Event [Line Items]
Commitment Fee	0.25%
Letter of Credit Fee	2.50%
Pricing Tier1 | Minimum
Subsequent Event [Line Items]
Net Leverage Ratio	375.00%
Pricing Tier1 | LIBOR Plus
Subsequent Event [Line Items]
Interest rate	2.50%
Pricing Tier1 | Base Rate Plus
Subsequent Event [Line Items]
Interest rate	1.50%
Pricing Tier2
Subsequent Event [Line Items]
Commitment Fee	0.23%
Letter of Credit Fee	2.25%
Pricing Tier2 | Maximum
Subsequent Event [Line Items]
Net Leverage Ratio	375.00%
Pricing Tier2 | Minimum
Subsequent Event [Line Items]
Net Leverage Ratio	325.00%
Pricing Tier2 | LIBOR Plus
Subsequent Event [Line Items]
Interest rate	2.25%
Pricing Tier2 | Base Rate Plus
Subsequent Event [Line Items]
Interest rate	1.25%
Pricing Tier3
Subsequent Event [Line Items]
Commitment Fee	0.20%
Letter of Credit Fee	2.00%
Pricing Tier3 | Maximum
Subsequent Event [Line Items]
Net Leverage Ratio	325.00%
Pricing Tier3 | Minimum
Subsequent Event [Line Items]
Net Leverage Ratio	250.00%
Pricing Tier3 | LIBOR Plus
Subsequent Event [Line Items]
Interest rate	2.00%
Pricing Tier3 | Base Rate Plus
Subsequent Event [Line Items]
Interest rate	1.00%
Pricing Tier4
Subsequent Event [Line Items]
Commitment Fee	0.15%
Letter of Credit Fee	1.75%
Pricing Tier4 | Maximum
Subsequent Event [Line Items]
Net Leverage Ratio	250.00%
Pricing Tier4 | Minimum
Subsequent Event [Line Items]
Net Leverage Ratio	175.00%
Pricing Tier4 | LIBOR Plus
Subsequent Event [Line Items]
Interest rate	1.75%
Pricing Tier4 | Base Rate Plus
Subsequent Event [Line Items]
Interest rate	0.75%
Pricing Tier5
Subsequent Event [Line Items]
Commitment Fee	0.15%
Letter of Credit Fee	1.50%
Pricing Tier5 | Maximum
Subsequent Event [Line Items]
Net Leverage Ratio	175.00%
Pricing Tier5 | LIBOR Plus
Subsequent Event [Line Items]
Interest rate	1.50%
Pricing Tier5 | Base Rate Plus
Subsequent Event [Line Items]
Interest rate	0.50%

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Debt - Schedule of Aggregate Annual Maturities of Long-Term Debt (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Debt Disclosure [Abstract]
2023	$ 8,750
2024	13,125
2025	13,125
2026	131,250
Total	$ 166,250

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Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs (Level 3) (Details) - Fair Value, Recurring - Level 3 - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	$ 31,507	$ 58,881	$ 57,889	$ 75,353
Level 3 Assets	6,313
Business Acquisitions Contingent Consideration, Current
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	3,967	31,450	31,152	49,902
Business Acquisitions Contingent Consideration, Long-Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	2,810	4,350	4,200	4,565
Conversion Option
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	24,730	$ 23,081	$ 22,537	$ 20,886
Interest Rate Swap
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Assets	$ 6,313

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Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022	Sep. 30, 2021
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance		$ 58,881	$ 75,353
Acquisitions		1,216	7,004
Changes in fair value included in earnings		1,589	25,686
Asset value, Changes in fair value included in earnings		6,313
Payment of contingent consideration payable		(30,179)	(50,154)
Ending balance	$ 31,507	31,507	57,889
Total Assets, Ending balance	6,313	6,313
Level 3 | Business Acquisitions Contingent Consideration, Current
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance		31,450	49,902
Acquisitions			1,000
Changes in fair value included in earnings		330	13,774
Payment of contingent consideration payable		(30,179)	(50,154)
Reclass of long term to short term contingent liabilities		2,366	16,630
Ending balance	3,967	3,967	31,152
Level 3 | Business Acquisitions Contingent Consideration, Long-Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance		4,350	4,565
Acquisitions		1,216	6,004
Changes in fair value included in earnings		(390)	10,261
Reclass of long term to short term contingent liabilities		(2,366)	(16,630)
Ending balance	2,810	2,810	4,200
Level 3 | Conversion Option
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance		23,081	20,886
Changes in fair value included in earnings		1,649	1,651
Ending balance	24,730	24,730	$ 22,537
Interest Rate Swap
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset value, Changes in fair value included in earnings	2,300	6,300
Interest Rate Swap | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset value, Changes in fair value included in earnings		6,313
Total Assets, Ending balance	$ 6,313	$ 6,313

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Fair Value of Financial Instruments - Additional Information (Details) - Fair Value, Recurring - Interest Rate Swap - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Line Items]
Change in fair value recognized	$ 2.3	$ 6.3
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)

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Convertible and Redeemable Series A-2 Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended						9 Months Ended
	Apr. 13, 2020	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Temporary Equity [Line Items]
Period between issuance and expiration of outstanding warrant	10 years
Proceeds from the Series A-2 and Warrant	$ 175,000
Percentage of dividends paid in cash	14.20%
Preferred stock, dividends paid		$ 4,100	$ 4,100	$ 4,100	$ 4,100	$ 4,100	$ 4,100
Compound embedded derivative, change in value								$ 4,664	$ (1,651)
Convertible And Redeemable Series A-2 Preferred Stock
Temporary Equity [Line Items]
Number of shares issued	17,500	17,500						17,500		17,500
Par value per share	$ 0.0001	$ 0.0001						$ 0.0001		$ 0.0001
Debt issuance costs, net	$ 1,300
Percentage of dividends paid in cash	15.00%
Preferred stock, dividends paid		$ 4,100			$ 4,100			$ 12,300	$ 12,300
Percentage of discount on common stock market price								15.00%
Percentage of dividend rate steps downs per year								9.00%
Percentage of dividend rate increase per annum in the event of noncompliance								12.00%
Number of days dividend increase rate applicable noncompliance event occurred								90 days
Percentage of dividend rate increase per annum upon noncompliance occurred and thereafter								14.00%
Number of times increase in debt incurrence test ratio								4.5
Minimum repayment amount								$ 50,000
Minimum repayment amount drop down								$ 25,000
Temporary equity description								The Company may, at its option on any one or more dates, redeem all or a minimum portion (the lesser of (i) $25.0 million in aggregate stated value of the Convertible and Redeemable Series A-2 Preferred Stock and (ii) all of the Convertible and Redeemable Series A-2 Preferred Stock then outstanding) of the outstanding Convertible and Redeemable Series A-2 Preferred Stock in cash.With respect to any redemption of any share of the Convertible and Redeemable Series A-2 Preferred Stock prior to the third-year anniversary, the Company is subject to a make whole penalty in which the holders of the Convertible and Redeemable Series A-2 Preferred Stock are guaranteed a minimum repayment equal to outstanding redeemed stated value plus three years of dividends accrued or accruable thereon.
Aggregate stated value of stock redeemed		25,000						$ 25,000
Aggregate liquidation preference		182,200						182,200		$ 182,200
Compound embedded derivative, fair value net		24,700						24,700		$ 23,100
Convertible And Redeemable Series A-2 Preferred Stock | Other Expense
Temporary Equity [Line Items]
Compound embedded derivative, change in value		500						1,600
Convertible And Redeemable Series A-2 Preferred Stock | 60-Day Period Prior to Seventh Anniversary
Temporary Equity [Line Items]
Temporary equity convertible into common stock		60,000						60,000
Convertible And Redeemable Series A-2 Preferred Stock | Year 5
Temporary Equity [Line Items]
Temporary equity convertible into common stock		60,000						60,000
Convertible And Redeemable Series A-2 Preferred Stock | Year 6
Temporary Equity [Line Items]
Temporary equity convertible into common stock		$ 120,000						$ 120,000

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Stockholder's Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended			12 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021		Dec. 31, 2021	Jan. 31, 2021	May 31, 2015
Class Of Stock [Line Items]
Common stock, shares authorized		190,000,000		190,000,000			190,000,000
Common stock, par value		$ 0.000004		$ 0.000004			$ 0.000004
Stock issued on exercise of warrants				67,713	67,713	[1]
Total unrecognized stock compensation expense related to unvested options and restricted stock granted under the Plans		$ 152,500	$ 15,000	$ 152,500	$ 15,000
Unrecognized expense expected to be recognized period				4 years
Restricted shares became fully vested and released as common stock		0	0	25,289	38,929
Shares, granted	[1]			25,289	38,929
Stock compensation expense		$ 11,018	$ 2,365	$ 32,375	$ 6,587
Shares reserved for future issuance		8,619,509	5,992,019	8,619,509	5,992,019
Restricted shares outstanding		2,064,197	286,239	2,064,197	286,239
Shares of vested over period		1 year	1 year	1 year	1 year
Shares RSAs granted		0	0
Supplemental Incentive Plans
Class Of Stock [Line Items]
Shares, granted				95,404	0
Montrose Amended & Restated 2017 Stock Incentive Plan
Class Of Stock [Line Items]
Shares, granted							1,671,391
Share based, description							These RSUs represent the right to receive one share of the Company’s common stock upon vesting. These incentives were designed by the Board, in coordination with the Company’s compensation advisors, to (i) retain selected employees of the Company for a minimum of 5 years, (ii) reward selected employees for the Company’s significant outperformance and stockholder value creation in 2021, and (iii) provide incentives to selected employees of the Company to accelerate value creation for stockholders and other stakeholders over the next five-year period
Stock compensation expense							$ 90,000
Shares reserved for future issuance		7,757,995	3,944,750	7,757,995	3,944,750		135,517	1,185,112
Restricted shares forfeited		0	0	0	0
Shares of vested over period							5 years
Montrose Amended & Restated 2017 Stock Incentive Plan | Restricted Stock
Class Of Stock [Line Items]
Shares RSAs granted		0	0	10,920	19,066
Montrose Amended & Restated 2017 Stock Incentive Plan | Stock Options | Board of Directors
Class Of Stock [Line Items]
Shares of vested over period				4 years
Montrose Amended & Restated 2017 Stock Incentive Plan | Stock Options | Executive Officers
Class Of Stock [Line Items]
Shares of vested over period				3 years
Vesting frequency of period				1 year
Montrose Amended & Restated 2017 Stock Incentive Plan | Stock Options | Second Anniversary | Board of Directors
Class Of Stock [Line Items]
Shares, vesting rights, percentage				50.00%
Montrose Amended & Restated 2017 Stock Incentive Plan | Stock Options | Fourth Anniversary | Board of Directors
Class Of Stock [Line Items]
Shares, vesting rights, percentage				50.00%
Montrose Amended & Restated 2017 Stock Incentive Plan | Performance-Vested RSUs
Class Of Stock [Line Items]
Shares, granted							316,209
Shares, vesting rights, percentage							50.00%
Montrose Amended & Restated 2017 Stock Incentive Plan | RSUs
Class Of Stock [Line Items]
Shares, granted							1,355,182
Shares, vesting rights, percentage							50.00%
Montrose Amended and Restated 2013 Stock Option Plan
Class Of Stock [Line Items]
Shares outstanding from exercised options		1,271,383	1,028,268	1,271,383	1,028,268
Two Thousand Seventeen Plan | Restricted Stock
Class Of Stock [Line Items]
Stock compensation expense			$ 237	$ 17,892	$ 749
Two Thousand Seventeen Plan | Stock Options
Class Of Stock [Line Items]
Stock compensation expense		$ 2,620	$ 2,126	7,518	$ 5,816
Two Thousand Seventeen Plan | Stock Appreciation Rights (SARs)
Class Of Stock [Line Items]
Shares, granted							3,000,000
Stock compensation expense		$ 2,315		$ 6,965
Exercise price							$ 66.79
Shares of vested over period							5 years
Remaining contractual terms				10 years
Weighted average remaining contract life				9 years 2 months 15 days
Fair value vested in period				$ 46,000
Private Offering
Class Of Stock [Line Items]
Warrants to purchase common stock									116,350
Warrant exercise price per share									$ 17.19

[1] Represents the non-cash release of common shares due to the exercise of warrants and the vesting of restricted stock.

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Stockholder's Equity - Summary of Issued Shares of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Equity [Abstract]
Acquisitions, Shares			62,738		143,800
Exercise of warrants options, Shares				67,713	67,713	[1]
Exercise of options, Shares		28,111	354,918	62,293	779,068
Restricted shares, net, Shares	[1]			25,289	38,929
Payment of earn-out liability, Shares					539,607
Payment of purchase price true up, Shares					24,200
Total, Shares		28,111	417,656	87,582	1,593,317
Acquisitions, Average Price per Share			$ 52.18		$ 41.86
Exercise of warrants options, Average Price per Share	[1]				17.19
Exercise of options, Average Price per Share		$ 11.70	8.30	$ 13.04	7.74
Restricted shares, net, Average Price per Share	[1]			66.58	31.31
Payment of earn-out liability, Average Price per share					46.33
Payment of purchase price true up, Average Price per share					44.81
Total, Average Price per Share		$ 11.70	$ 14.89	$ 28.50	$ 25.43
Acquisitions, Total			$ 3,274		$ 6,020
Exercise of options, Total		$ 329	2,946	$ 812	6,032
Payment of earn-out liability, Total					25,000
Payment of purchase price true up, Total					1,084
Total		$ 329	$ 6,220	$ 812	$ 38,136

[1] Represents the non-cash release of common shares due to the exercise of warrants and the vesting of restricted stock.

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Stockholder's Equity - Summary of Number of Shares Authorized to be Issued and Available for Grant (Details) - shares	Sep. 30, 2022		Jan. 31, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized to be issued	7,177,131			5,992,019
Shares available for grant	364,949	[1]		1,593,287
2017 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized to be issued	5,140,112			3,944,750
Shares available for grant	364,949	[1]	1,185,112	1,593,287
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized to be issued	2,037,019			2,047,269

[1] In January 2022 the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. Shares available for grant exclude awards of stock appreciation rights approved in December 2021 that are subject to vesting based on the achievement of certain market conditions, which have not yet been, and may not be, achieved. See footnote 1 to the table in Common Stock Reserved for Future Issuance below for additional information regarding the December 2021 grant.

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Stockholders' Equity - Summary of Number of Shares Authorized to be Issued and Available for Grant (Parenthetical) (Details) - shares	Sep. 30, 2022	[1]	Jan. 31, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant	364,949			1,593,287
Two Thousand Seventeen Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant	364,949		1,185,112	1,593,287

[1] In January 2022 the Board of Directors ratified the addition of 1,185,112 shares of common stock to the number of shares available for issuance under the 2017 Plan pursuant to the annual increase provision of such plan. Unless the Board of Directors determines otherwise, additional annual increases will be effective on each January 1, through January 1, 2027. The 2017 Plan permits the company to settle awards, if and when vested, in cash at its discretion. Pursuant to the terms of the 2017 Plan, the number of shares authorized for issuance thereunder will only be reduced with respect to shares of common stock actually issued upon exercise or settlement of an award. Shares of common stock subject to awards that have been canceled, expired, forfeited or otherwise not issued under an award and shares of common stock subject to awards settled in cash do not count as shares of common stock issued under the 2017 Plan. Shares available for grant exclude awards of stock appreciation rights approved in December 2021 that are subject to vesting based on the achievement of certain market conditions, which have not yet been, and may not be, achieved. See footnote 1 to the table in Common Stock Reserved for Future Issuance below for additional information regarding the December 2021 grant.

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Stockholder's Equity - Schedule of Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	$ 11,018	$ 2,365	$ 32,375	$ 6,587
2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	2,620	2,126	7,518	5,816
2017 Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense		237	17,892	749
2017 Plan | Stock Appreciation Rights (SARs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	2,315		6,965
2013 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense		2		21
Cost of Revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	404	282	1,069	1,188
Cost of Revenue | 2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	404	282	1,069	1,178
Cost of Revenue | 2013 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense				10
Selling, General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	10,614	2,083	31,306	5,399
Selling, General and Administrative Expenses | 2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	2,216	1,844	6,449	4,638
Selling, General and Administrative Expenses | 2017 Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	6,083	237	17,892	749
Selling, General and Administrative Expenses | 2017 Plan | Stock Appreciation Rights (SARs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	$ 2,315		$ 6,965
Selling, General and Administrative Expenses | 2013 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense		$ 2		$ 11

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Stockholder's Equity - Schedule of Restricted Stock Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares		0	0
Average Price per Share	[1]			$ 66.58	$ 31.31
Montrose Amended & Restated 2017 Stock Incentive Plan | Restricted stock units awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares				106,324	19,066
Average Price per Share				$ 46.82	$ 36.99
Fair Value				$ 4,978	$ 705

[1] Represents the non-cash release of common shares due to the exercise of warrants and the vesting of restricted stock.

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Stockholders' Equity - Summary of Performance Hurdles (Details)	9 Months Ended
	Sep. 30, 2022 $ / shares
SAR Stock Price Performance Hurdle One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
SARs Stock Price Performance Hurdle	$ 133.58
Portion of SARs Subject to Performance Hurdle	0.33%
SAR Stock Price Performance Hurdle Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
SARs Stock Price Performance Hurdle	$ 166.98
Portion of SARs Subject to Performance Hurdle	0.33%
SAR Stock Price Performance Hurdle Three
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
SARs Stock Price Performance Hurdle	$ 200.37
Portion of SARs Subject to Performance Hurdle	0.33%

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Stockholder's Equity - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Exercise of options, Shares	(28,111)	(354,918)	(62,293)	(779,068)
Montrose Amended & Restated 2017 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options to Purchase Common Stock Outstanding Beginning Balance			2,036,729	1,840,229	1,840,229
Options to Purchase Common Stock Granted			664,784	264,470
Options to Purchase Common Stock Forfeited/cancelled			(60,167)	(29,025)
Options to Purchase Common Stock Expired				(1,250)
Exercise of options, Shares			(26,258)	(66,875)
Options to Purchase Common Stock Outstanding Ending Balance	2,615,088	2,007,549	2,615,088	2,007,549	2,036,729	1,840,229
Options to Purchase Common Stock Exercisable	1,010,302		1,010,302
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price per Share Outstanding Beginning Balance			$ 26	$ 23	$ 23
Weighted-Average Exercise Price per Share Granted			44	40
Weighted-Average Exercise Price per Share Forfeited/cancelled			36	28
Weighted-Average Exercise Price per Share Expired				18
Weighted-Average Exercise Price per Share Exercised			22	22
Weighted-Average Exercise Price per Share Outstanding Ending Balance	$ 30	$ 25	30	25	26	$ 23
Weighted-Average Exercise Price per Share Exercisable	26		26
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value per Share Outstanding Beginning Balance			14	12	12
Weighted Average Grant Date Fair Value per Share Granted			16	22
Weighted Average Grant Date Fair Value per Share Ending Balance	$ 15	$ 14	$ 15	$ 14	$ 14	$ 12
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contract Life (in Years) Outstanding			8 years 14 days	8 years 6 months 10 days	8 years 3 months 18 days	9 years 1 month 2 days
Weighted Average Remaining Contract Life (in Years) Exercisable			7 years 5 months 23 days
Aggregate Intrinsic Value of In-The-Money Options Outstanding	$ 18,784	$ 73,724	$ 18,784	$ 73,724	$ 91,030	$ 15,598
Aggregate Intrinsic Value of In-The-Money Options Exercised			671	$ 2,078
Aggregate Intrinsic Value of In-The-Money Options Exercisable	$ 9,966		$ 9,966
Montrose Amended and Restated 2013 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options to Purchase Common Stock Outstanding Beginning Balance			897,674	1,787,869	1,787,869
Options to Purchase Common Stock Expired			(125)	(625)
Exercise of options, Shares			(36,035)	(710,568)
Options to Purchase Common Stock Outstanding Ending Balance	861,514	1,076,676	861,514	1,076,676	897,674	1,787,869
Options to Purchase Common Stock Exercisable	861,514		861,514
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price per Share Outstanding Beginning Balance			$ 6	$ 6	$ 6
Weighted-Average Exercise Price per Share Expired			6	6
Weighted-Average Exercise Price per Share Exercised			6	6
Weighted-Average Exercise Price per Share Outstanding Ending Balance	$ 6	$ 6	6	6	6	$ 6
Weighted-Average Exercise Price per Share Exercisable	6		6
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value per Share Outstanding Beginning Balance			2	1	1
Weighted Average Grant Date Fair Value per Share Ending Balance	$ 2	$ 2	$ 2	$ 2	$ 2	$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contract Life (in Years) Outstanding			3 years 7 months 9 days	4 years 7 months 24 days	4 years 4 months 13 days	5 years 4 months 24 days
Weighted Average Remaining Contract Life (in Years) Exercisable			3 years 7 months 9 days
Aggregate Intrinsic Value of In-The-Money Options Outstanding	$ 23,448	$ 59,532	$ 23,448	$ 59,532	$ 57,529	$ 43,867
Aggregate Intrinsic Value of In-The-Money Options Exercised			1,425	$ 33,480
Aggregate Intrinsic Value of In-The-Money Options Exercisable	$ 23,448		$ 23,448

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Stockholder's Equity - Summary of Weighted Average Assumptions Used in Black-Sholes Option-pricing Model (Details) - $ / shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock value (per share)	$ 43.72	$ 39.83
Expected volatility	33.45%	58.34%
Risk-free interest rate	1.94%	0.77%
Expected life (years)	6 years 5 months 12 days	6 years 3 months 25 days
Forfeiture rate	0.00%	0.00%
Dividend rate	0.00%	0.00%

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Stockholder's Equity - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jan. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	8,619,509		5,992,019
Montrose 2013 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	861,514		2,047,269
Montrose 2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	7,757,995	135,517	3,944,750	1,185,112

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Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance (Parenthetical) (Details) - shares	1 Months Ended
	Jan. 31, 2021	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		8,619,509		5,992,019
Montrose 2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,185,112	7,757,995	135,517	3,944,750
Stock Appreciation Rights Units Grant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	3,000,000		3,000,000
Common stock issued upon vesting of performance SARs	2,000,000

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Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net loss	$ (5,720)	$ (7,751)	$ (7,536)	$ 2,226	$ (13,148)	$ (12,931)	$ (21,007)	$ (23,853)
Convertible and redeemable series A-2 preferred stock dividend	(4,100)			(4,100)			(12,300)	(12,300)
Net loss attributable to common stockholders -basic and diluted	$ (9,820)			$ (1,874)			$ (33,307)	$ (36,153)
Weighted-average common shares outstanding basic	29,691			26,220			29,677	25,798
Weighted Average Number of Shares Outstanding, Diluted	29,691			26,220			29,677	25,798
Net loss per share attributable to common stockholders basic	$ (0.33)			$ (0.07)			$ (1.12)	$ (1.40)
Net loss per share attributable to common stockholder diluted	$ (0.33)			$ (0.07)			$ (1.12)	$ (1.40)

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Net Loss Per Share - Equity Shares Excluded from Calculation of Diluted Loss Per Share Attributable to Common Stockholders (Details) - shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of loss per share amount	3,476,602	1,686,688
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of loss per share amount	1,777,958	28,623
Stock Appreciation Rights (SARs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of loss per share amount	3,000,000

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Segment Information - Additional Information (Details)	9 Months Ended
	Sep. 30, 2022 Segment
Segment Reporting [Abstract]
Number of operating segments	3
Number of reportable segments	3

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Segment Information - Components of Segment Revenues and Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Segment Revenues	$ 130,312	$ 132,578	$ 404,902	$ 402,619
Segment Adjusted EBITDA	18,373	21,487	51,337	59,249
Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	130,312	132,578	404,902	402,619
Segment Adjusted EBITDA	25,313	29,474	74,163	81,275
Assessment, Permitting and Response | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	46,414	63,412	142,051	209,379
Segment Adjusted EBITDA	9,820	15,719	30,252	46,379
Measurement and Analysis | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	43,754	38,752	125,739	111,309
Segment Adjusted EBITDA	8,483	8,283	21,852	22,634
Remediation and Reuse | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	40,144	30,414	137,112	81,931
Segment Adjusted EBITDA	7,010	5,472	22,059	12,262
Corporate and Other
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	$ (6,940)	$ (7,987)	$ (22,826)	$ (22,026)

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Segment Information - Reconciliation of Segment Measure to Net Loss (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting [Abstract]
Total		$ 18,373	$ 21,487	$ 51,337	$ 59,249
Interest expense, net		(1,400)	(1,722)	(4,010)	(11,208)
Income tax benefit (expense)		208	(902)	(1,892)	(648)
Depreciation and amortization		(11,504)	(11,471)	(35,928)	(33,145)
Stock-based compensation		(11,018)	(2,365)	(32,375)	(6,587)
Start-up losses and investment in new services		(1,278)	(1,186)	(2,949)	(3,276)
Acquisition costs		(368)	(913)	(1,354)	(1,656)
Fair value changes in financial instruments		1,808	(531)	4,664	(1,651)
Fair value changes in business acquisitions contingencies		(59)		3,472	(24,035)
Expenses related to financing transactions				(7)	(50)
Other losses or expenses	[1]	(482)	(171)	(1,965)	(846)
Net loss		$ (5,720)	$ 2,226	$ (21,007)	$ (23,853)

[1] In 2022, amounts include costs associated with the closing of a lab and severance costs related to a restructuring within our soil remediation business. In 2021, amounts include non-operational charges incurred due to the remeasurement of finance leases as a result of the adoption of ASC 842 and costs related to the implementation of a new ERP.

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Related-Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Related Party Transactions [Abstract]
Related party transaction amount	$ 0	$ 0	$ 0	$ 0

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Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		5 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	May 22, 2020	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, description				401(k) Savings Plan
Defined contribution plan, maximum annual contributions per employee, percent				85.00%		85.00%
Defined contribution plan, employer matching contribution, percent of match			100.00%
Defined contribution plan participant's compensation percent			3.00%
Defined contribution plan percentage of participant's elective deferrals			50.00%
Selling, General and Administrative Expenses
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer discretionary contribution amount	$ 1.2	$ 0.8		$ 4.6	$ 1.6
Minimum
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan participant's compensation percent			3.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan participant's compensation percent			4.00%