Montrose Environmental (MEG) 10-Q 31 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 28, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Quarterly Report	true
Document Transition Report	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	MEG
Entity Registrant Name	Montrose Environmental Group, Inc.
Entity Central Index Key	0001643615
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		24,955,430
Entity Interactive Data Current	Yes
Entity Current Reporting Status	No
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	1 Park Plaza
Entity Address, Address Line Two	Suite 1000
Entity Address City Or Town	Irvine
Entity Address State Or Province	CA
Entity Address Postal Zip Code	92614
City Area Code	949
Local Phone Number	988-3500
Security12b Title	Common Stock, par value $0.000004 per share
Security Exchange Name	NYSE

UNAUDITED CONDENSED CONSOLIDATE

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and restricted cash	$ 44,814	$ 6,884
Accounts receivable—net	43,255	45,927
Contract assets	22,775	13,605
Prepaid and other current assets	10,194	6,823
Total current assets	121,038	73,239
NON-CURRENT ASSETS:
Property and equipment—net	34,771	27,036
Goodwill	273,096	127,058
Other intangible assets—net	169,274	102,549
Deferred tax asset	1,465
Other assets	3,132	1,956
Compound embedded option	8,605
TOTAL ASSETS	611,381	331,838
CURRENT LIABILITIES:
Accounts payable and other accrued liabilities	30,225	29,585
Accrued payroll and benefits	15,230	11,032
Warrant options	46,978	16,878
Business acquisitions contingent consideration	36,395	8,614
Current portion of long term debt	4,653	7,143
Total current liabilities	133,481	73,252
NON-CURRENT LIABILITIES:
Other non-current liabilities	10,993	379
Deferred tax liabilities—net		3,530
Long-term debt—net of deferred financing fees	198,089	145,046
Total liabilities	356,688	229,307
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS’ DEFICIT:
Additional paid-in-capital	54,405	38,153
Accumulated deficit	(92,428)	(64,404)
Accumulated other comprehensive loss	(93)	(40)
Total stockholders’ deficit	(38,116)	(26,291)
TOTAL LIABILITIES, REDEEMABLE SERIES A-1 PREFERRED STOCK, CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK AND STOCKHOLDERS’ DEFICIT	611,381	331,838
Contingent Put Option
NON-CURRENT LIABILITIES:
Compound embedded option	14,125	7,100
Redeemable Series A-1 Preferred Stock
NON-CURRENT LIABILITIES:
REDEEMABLE SERIES PREFERRED STOCK	139,881	$ 128,822
Convertible And Redeemable Series A-2 Preferred Stock
NON-CURRENT ASSETS:
Compound embedded option	8,600
NON-CURRENT LIABILITIES:
REDEEMABLE SERIES PREFERRED STOCK	$ 152,928

UNAUDITED CONDENSED CONSOLIDA_2

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Common stock, par value	$ 0.000004	$ 0.000004
Common stock, shares authorized	25,000,000	25,000,000
Common stock, shares issued	9,164,746	8,370,107
Common stock, shares outstanding	9,164,746	8,370,107
Redeemable Series A-1 Preferred Stock
Temporary equity, par value	$ 0.0001	$ 0.0001
Temporary equity, shares authorized	12,000	12,000
Temporary equity, shares issued	12,000	12,000
Temporary equity, shares outstanding	12,000	12,000
Temporary equity, aggregate liquidation preference	$ 152,199	$ 141,898
Convertible And Redeemable Series A-2 Preferred Stock
Temporary equity, par value	$ 0.0001	$ 0.0001
Temporary equity, shares authorized	17,500	0
Temporary equity, shares issued	17,500	0
Temporary equity, shares outstanding	17,500	0
Temporary equity, aggregate liquidation preference	$ 181,213	$ 0

UNAUDITED CONDENSED CONSOLIDA_3

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
REVENUES	$ 73,766	$ 57,401	$ 134,797	$ 108,355
COST OF REVENUES (exclusive of depreciation and amortization shown below)	45,889	39,349	90,287	76,444
SELLING, GENERAL AND ADMINISTRATIVE EXPENSE	23,301	11,156	44,232	21,603
RELATED-PARTY EXPENSE		120	119	279
DEPRECIATION AND AMORTIZATION	9,784	6,401	17,344	12,850
(LOSS) INCOME FROM OPERATIONS	(5,208)	375	(17,185)	(2,821)
OTHER EXPENSE
Other income (expense)	21,933	(1,228)	(7,897)	(1,179)
Interest expense—net	(5,260)	(1,181)	(7,853)	(2,460)
Total other expenses—net	16,673	(2,409)	(15,750)	(3,639)
INCOME (LOSS) BEFORE BENEFIT FROM INCOME TAXES	11,465	(2,034)	(32,935)	(6,460)
INCOME TAXES BENEFIT	(1,759)	(1,712)	(4,911)	(896)
NET INCOME (LOSS)	13,224	(322)	(28,024)	(5,564)
EQUITY ADJUSTMENT FROM FOREIGN CURRENCY TRANSLATION	(90)	23	(53)	23
COMPREHENSIVE LOSS	13,134	(299)	(28,077)	(5,541)
ACCRETION OF REDEEMABLE SERIES A-1 PREFERRED STOCK	(5,644)	(4,777)	(11,059)	(9,311)
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON STOCKHOLDERS	$ 7,580	$ (5,099)	$ (39,083)	$ (14,875)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING— BASIC	10,649	8,647	9,718	8,602
NET INCOME (LOSS) PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS— BASIC	$ 0.71	$ (0.59)	$ (4.02)	$ (1.73)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING— DILUTED	19,139	8,647	9,718	8,602
NET INCOME (LOSS) PER SHARE ATTRIBUTABLE TO COMMON STOCKHOLDERS— DILUTED	$ 0.40	$ (0.59)	$ (4.02)	$ (1.73)

UNAUDITED CONDENSED CONSOLIDA_4

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE SERIES A-1 PREFERRED STOCK, CONVERTIBLE AND REDEEMABLE SERIES A-2 PREFERRED STOCK AND STOCKHOLDERS' (DEFICIT) EQUITY - USD ($) $ in Thousands	Total	Redeemable Series A-1 Preferred Stock	Convertible And Redeemable Series A-2 Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Notes Receivable from Stockholders	Accumulated Other Comprehensive (Loss) Income
Beginning balance at Dec. 31, 2018	$ 6,900				$ 47,869	$ (40,847)	$ (122)
Beginning balance, shares at Dec. 31, 2018				8,137,771
Beginning balance at Dec. 31, 2018		$ 109,206
Beginning balance, shares at Dec. 31, 2018		12,000
Net income (loss)	(5,242)					(5,242)
Accretion of the redeemable series A-1 preferred stock to redeemable value	(4,534)				(4,534)
Accretion of the redeemable series A-1 preferred stock to redeemable shares		$ 4,534
Stock-based compensation	1,228				1,228
Common stock issued	6				6
Common stock issued, shares				1,775
Ending balance at Mar. 31, 2019	(1,642)				44,569	(46,089)	(122)
Ending balance, shares at Mar. 31, 2019				8,139,546
Ending balance at Mar. 31, 2019		$ 113,740
Ending balance, shares at Mar. 31, 2019		12,000
Beginning balance at Dec. 31, 2018	6,900				47,869	(40,847)	(122)
Beginning balance, shares at Dec. 31, 2018				8,137,771
Beginning balance at Dec. 31, 2018		$ 109,206
Beginning balance, shares at Dec. 31, 2018		12,000
Net income (loss)	(5,564)
Accumulated other comprehensive loss (income)	23
Ending balance at Jun. 30, 2019	(1,972)				44,538	(46,411)	(122)	$ 23
Ending balance, shares at Jun. 30, 2019				8,278,327
Ending balance at Jun. 30, 2019		$ 118,517
Ending balance, shares at Jun. 30, 2019		12,000
Beginning balance at Mar. 31, 2019	(1,642)				44,569	(46,089)	(122)
Beginning balance, shares at Mar. 31, 2019				8,139,546
Beginning balance at Mar. 31, 2019		$ 113,740
Beginning balance, shares at Mar. 31, 2019		12,000
Net income (loss)	(322)					(322)
Accretion of the redeemable series A-1 preferred stock to redeemable value	(4,777)				(4,777)
Accretion of the redeemable series A-1 preferred stock to redeemable shares		$ 4,777
Stock-based compensation	1,294				1,294
Common stock issued	3,452				3,452
Common stock issued, shares				138,781
Accumulated other comprehensive loss (income)	23							23
Ending balance at Jun. 30, 2019	(1,972)				44,538	(46,411)	$ (122)	23
Ending balance, shares at Jun. 30, 2019				8,278,327
Ending balance at Jun. 30, 2019		$ 118,517
Ending balance, shares at Jun. 30, 2019		12,000
Beginning balance at Dec. 31, 2019	(26,291)				38,153	(64,404)		(40)
Beginning balance, shares at Dec. 31, 2019				8,370,107
Beginning balance at Dec. 31, 2019		$ 128,822
Beginning balance, shares at Dec. 31, 2019		12,000	0
Net income (loss)	(41,248)					(41,248)
Accretion of the redeemable series A-1 preferred stock to redeemable value	(5,415)				(5,415)
Accretion of the redeemable series A-1 preferred stock to redeemable shares		$ 5,415
Stock-based compensation	1,150				1,150
Accumulated other comprehensive loss (income)	37							37
Ending balance at Mar. 31, 2020	(71,767)				33,888	(105,652)		(3)
Ending balance, shares at Mar. 31, 2020				8,370,107
Ending balance at Mar. 31, 2020		$ 134,237
Ending balance, shares at Mar. 31, 2020		12,000
Beginning balance at Dec. 31, 2019	(26,291)				38,153	(64,404)		(40)
Beginning balance, shares at Dec. 31, 2019				8,370,107
Beginning balance at Dec. 31, 2019		$ 128,822
Beginning balance, shares at Dec. 31, 2019		12,000	0
Net income (loss)	(28,024)
Accumulated other comprehensive loss (income)	(53)
Ending balance at Jun. 30, 2020	(38,116)				54,405	(92,428)		(93)
Ending balance, shares at Jun. 30, 2020				9,164,746
Ending balance at Jun. 30, 2020		$ 139,881	$ 152,928
Ending balance, shares at Jun. 30, 2020		12,000	17,500
Beginning balance at Mar. 31, 2020	(71,767)				33,888	(105,652)		(3)
Beginning balance, shares at Mar. 31, 2020				8,370,107
Beginning balance at Mar. 31, 2020		$ 134,237
Beginning balance, shares at Mar. 31, 2020		12,000
Net income (loss)	13,224					13,224
Accretion of the redeemable series A-1 preferred stock to redeemable value	(5,644)				(5,644)
Accretion of the redeemable series A-1 preferred stock to redeemable shares		$ 5,644
Issuance of the convertible and redeemable series A-2 preferred stock			$ 152,928
Issuance of the convertible and redeemable series A-2 preferred stock, shares			17,500
Stock-based compensation	1,140				1,140
Common stock issued	25,021				25,021
Common stock issued, shares				794,639
Accumulated other comprehensive loss (income)	(90)							(90)
Ending balance at Jun. 30, 2020	$ (38,116)				$ 54,405	$ (92,428)		$ (93)
Ending balance, shares at Jun. 30, 2020				9,164,746
Ending balance at Jun. 30, 2020		$ 139,881	$ 152,928
Ending balance, shares at Jun. 30, 2020		12,000	17,500

UNAUDITED CONDENSED CONSOLIDA_5

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
OPERATING ACTIVITIES:
Net Loss	$ 13,224		$ (322)	$ (28,024)	$ (5,564)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Provision for bad debt		$ 6,300		6,263	547	$ 1,246
Depreciation and amortization	9,784		6,401	17,344	12,850
Stock-based compensation expense	1,140		1,294	2,290	2,522
Fair value changes in the contingent put option	(22,602)			7,025
Fair value changes in the compound embedded option	756			756
Fair value changes in the contingent liabilities				3,983	(926)
Deferred income taxes				(4,911)	(896)
Cloud computing costs				(1,346)	(96)
Other				983	1,506
Changes in operating assets and liabilities—net of acquisitions:
Accounts receivable and contract assets				7,427	(5,642)
Prepaid expenses and other current assets				(789)	(91)
Accounts payable and other accrued liabilities				(8,296)	130
Accrued payroll and benefits				1,886	51
Payment of contingent consideration and other assumed purchase price obligations				(6,175)
Net cash (used in) provided by operating activities				(1,584)	4,391
INVESTING ACTIVITIES:
Purchases of property and equipment				(3,160)	(1,179)
Proprietary software development				(155)	(63)
Proceeds from net working capital adjustment related to acquisitions				2,819
Cash paid for acquisitions—net of cash acquired				(173,473)	(26,699)
Net cash used in investing activities				(173,969)	(27,941)
FINANCING ACTIVITIES:
Proceeds from line of credit				104,390	64,628
Payments on line of credit				(176,980)	(40,628)
Proceeds from term loans				175,000
Repayment of term loans				(48,750)
Payment of contingent consideration and other assumed purchase price obligations				(6,005)	(532)
Repayment of capital leases				(1,249)	(821)
Payments on deferred offering costs				(1,462)
Debt issuance cost				(4,866)
Debt extinguishment costs				(351)
Proceeds from issuance of common stock				21	95
Issuance of convertible and redeemable Series A-2 preferred stock and warrant				173,664
Net cash provided by financing activities				213,412	22,742
CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH				37,859	(808)
Foreign exchange impact on cash balance				71	(4)
Beginning of year		$ 6,884		6,884	2,489	2,489
End of period	$ 44,814		$ 1,677	44,814	1,677	$ 6,884
SUPPLEMENTAL DISCLOSURES OF CASH FLOWS INFORMATION:
Cash paid for interest				6,539	2,025
Cash paid for income tax				72	859
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accrued purchases of property and equipment				814	555
Property and equipment purchased under capital leases				1,704	2,136
Accretion of the Redeemable Series A-1 Preferred Stock to redeemable value				11,059	9,311
Acquisitions unpaid contingent liabilities				44,994	5,388
Common stock issued to acquire new businesses				25,000	$ 3,363
Offering costs included in accounts payable and other accrued liabilities				$ 941

Description of the Business and

Description of the Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2020
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 70 offices across the United States, Canada and Australia and over 1,700 employees. Montrose is highly acquisitive and, as of June 30, 2020, had completed 54 acquisitions since its inception. 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. Montrose’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 (“LDAR”) 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 (“O&M”) 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. Initial Public Offering —On July 27, 2020, the Company completed its initial public offering (“IPO”) of common stock, in which it sold 11,500,000 shares, including 1,500,000 shares issued pursuant to the underwriters full exercise on July 24, 2020 of the underwriters’ option to purchase additional shares, at a price to the public of $15.00 per share, resulting in net proceeds to the Company of approximately $161.3 million after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company. The Company’s common stock began trading on the New York Stock Exchange on July 23, 2020. Basis of Presentation —The unaudited condensed consolidated financial statements include the operations of the Company and its wholly-owned subsidiaries. These 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, 2019. 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 condensed consolidated financial statements.

Summary of New Accounting Prono

Summary of New Accounting Pronouncements	6 Months Ended
	Jun. 30, 2020
New Accounting Pronouncements And Changes In Accounting Principles [Abstract]
Summary of New Accounting Pronouncements	2. SUMMARY OF NEW ACCOUNTING PRONOUNCEMENTS Recently Adopted Accounting Pronouncements —The Company qualifies as an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”) and therefore intends to take 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 has elected to use this extended transition period under the JOBS Act. The effective dates shown below reflect the election to use the extended transition period. In June 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2018-07, Compensation—Stock Compensation: Improvements to Nonemployee Share-Based Payment Accounting. Under the revised guidance, the accounting for awards issued to non-employees will be similar to the accounting for employee awards. The new guidance is effective for fiscal years beginning after December 15, 2019. The standard was adopted as of January 1, 2020 and did not have a material impact on the Company’s condensed consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment. The revised guidance eliminates Step 2 of the current goodwill impairment analysis test, which requires hypothetical purchase price allocation to measure goodwill impairment. A goodwill impairment loss will instead be measured at the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of goodwill. The revised guidance was adopted as of January 1, 2020 and did not have a material impact on the Company’s condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted — In August 2020, the FASB issued 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 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, 2023, including interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact of the adoption of the standard on the condensed consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-04 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by the expected transition away from reference rates that are expected to be discontinued, such as LIBOR. ASU 2020-04 was effective upon issuance. The Company may elect to apply the guidance prospectively through December 31, 2022. The Company is evaluating the impact of the standard on its condensed consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and clarifies and amends certain guidance to promote consistent application. ASU 2019-12 is effective for the Company’s annual and interim periods beginning on January 1, 2021, with early adoption permitted. Depending on the amendment, adoption may be applied on a retrospective, modified retrospective or prospective basis. The Company is evaluating the impact of the standard on its condensed consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326). The standard introduces a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses and will apply to trade receivables. The new guidance will be effective for the Company’s annual and interim periods beginning after December 15, 2022. The Company is currently evaluating the impact of the adoption of the standard on the condensed consolidated financial statements. In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842), to improve financial reporting regarding leasing transactions. The ASU primarily affects the accounting by the lessee in that it requires a lessee to recognize lease assets and liabilities, initially measured at the present value of the lease payments, on the balance sheets for those leases classified as operating leases under previous guidance. The new leasing standard is effective for the Company’s annual and interim periods beginning after December 15, 2021. The new leasing standard requires modified retrospective transition. The Company is currently evaluating the impact of the adoption of the updated standard on the condensed consolidated financial statements.

Revenues and Accounts Receivabl

Revenues and Accounts Receivable	6 Months Ended
	Jun. 30, 2020
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 O&M services (on biogas and water treatment facilities), as well as remediation, monitoring and environmental compliance services. Services on the majority of O&M contracts are provided under long-term fixed-fee contracts. The majority of the remediation, monitoring and environmental compliance contracts are fixed price or time-and-materials based. 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 20, Segment Information. 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 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: June 30, 2020 December 31, 2019 Contract assets $ 22,775 $ 13,605 Contract liabilities 7,736 3,314 Contracts assets acquired through business acquisitions amounted to $6.5 million and $0.7 million as of June 30, 2020 and December 31, 2019, respectively. Contract liabilities acquired through business acquisitions amounted to $2.2 million as of December 31, 2019. Contract liabilities acquired through business acquisitions were not material as of June 30, 2020. Revenue recognized during the three and six months ended June 30, 2020, included in the contract liability balance at the beginning of the year was $0.3 million and $1.6 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 six months ended June 30, 2020 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 June 30, 2020 and December 31, 2019, the estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied was approximately $15.3 million and $13.0 million, respectively. As of June 30, 2020, the Company expected to recognize approximately $14.0 million of this amount as revenue within the next year and $1.3 million the year after. Accounts Receivable, Net —Accounts receivable, net as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, 2020 December 31, 2019 Accounts receivable, invoiced $ 50,359 $ 46,643 Accounts receivable, other 1,402 611 Allowance for doubtful accounts (8,506 ) (1,327 ) Accounts receivable—net $ 43,255 $ 45,927 The Company extends non-interest-bearing trade credit to its customers in the ordinary course of business. Accounts receivable are shown on the face of the condensed consolidated statements of financial position, net of an allowance for doubtful accounts. In determining the allowance for doubtful accounts, the Company analyzes the aging of accounts receivable, historical bad debts, customer creditworthiness and current economic trends. Subsequent to December 31, 2019, there was a global outbreak of a new strain of coronavirus, COVID-19. The COVID-19 pandemic has added uncertainty to the collectability of certain receivables, particularly in industries hard hit by the pandemic. As a result, the Company recorded a $6.3 million bad debt reserve during the first quarter of 2020. The bad debt adjustment included a $5.5 million reserve for one customer in the Company’s Remediation and Reuse segment in which management concluded to discontinue select service lines as of March 31, 2020 (Note 20). For all periods presented, no customer accounted for more than 10% of revenue or accounts receivable, net. The allowance for doubtful accounts as of June 30, 2020 and December 31, 2019 consisted of the following: Beginning Balance Bad Debt Expense Charged to Allowance Other (1) Ending Balance Six months ended June 30, 2020 $ 1,327 $ 6,263 $ (122 ) $ 1,038 $ 8,506 Year ended December 31, 2019 453 1,246 (556 ) 184 1,327 (1) This amount consists of additions to the allowance due to business acquisitions.

Prepaid and Other Current Asset

Prepaid and Other Current Assets	6 Months Ended
	Jun. 30, 2020
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 as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, December 31, 2020 2019 Deposits $ 662 $ 605 Prepaid expenses 1,288 1,235 Prepaid insurance 2,539 170 Supplies 2,313 2,368 Offering costs 2,403 1,240 Income tax receivable 989 1,205 Prepaid and other current assets $ 10,194 $ 6,823

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Property and Equipment	5. PROPERTY AND EQUIPMENT Property and equipment are stated at cost or estimated fair value for assets acquired through business combinations. Depreciation and amortization is 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, as of June 30, 2020 and December 31, 2019 consisted of the following: Estimated Useful Life June 30, 2020 December 31, 2019 Lab and test equipment 7 years $ 17,219 $ 14,810 Vehicles 5 years 12,658 11,073 Equipment 3–7 years 30,747 29,922 Furniture and fixtures 7 years 2,798 1,119 Leasehold improvements 7 years 6,633 5,954 Aircraft 10 years 834 — Building 39 years 2,975 — 73,864 62,878 Land 725 — Construction in progress — 796 Less accumulated depreciation (39,818 ) (36,638 ) Total property and equipment—net $ 34,771 $ 27,036 Total depreciation expense included on the condensed consolidated statements of operations was $2.0 million and 4.0 million for the three and six months ended June 30, 2020, respectively. Total depreciation expense included on the condensed consolidated statements of operations was $1.9 million and $3.8 million for the three and six months ended June 30, 2019, respectively.

Business Acquisitions

Business Acquisitions	6 Months Ended
	Jun. 30, 2020
Business Combinations [Abstract]
Business Acquisitions	6. BUSINESS ACQUISITIONS In line with the Company’s strategic growth initiatives, the Company acquired several businesses during the six months ended June 30, 2020 and 2019. The results of each of those acquired businesses are included in the condensed consolidated financial statements beginning on the respective acquisition dates. 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 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) and contingent consideration outstanding from acquisitions are included on the condensed consolidated statements of financial position in accounts payable and other accrued liabilities, other non-current liabilities for long term payables and accounts receivable-net for any working capital deficit receivable balance. These obligations are scheduled to be settled if certain performance thresholds are met. 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. External transaction costs related to business combinations totaled $3.8 million and $1.1 million for the six months ended June 30, 2020 and June 30, 2019, respectively and $2.5 million and $0.9 million for the three months ended June 30, 2020 and June 30, 2019, respectively. These costs are expensed within the selling, general and administrative expense in the accompanying condensed consolidated statements of operations. The cash payment made to acquire The Center for Toxicology and Environmental Health, LLC (“CTEH”) was funded through the issuance of the Convertible and Redeemable Series A-2 Preferred Stock (Note 17) and the common stock portion of the purchase price was funded through the issuance of 791,139 shares of common stock. Cash payments made to acquire businesses during the six months ended June 30, 2019 were funded through the Company’s prior senior secured credit facility (Note 13). Acquisition completed during the Six Months Ended June 30, 2020 The Center for Toxicology and Environmental Health, LLC —In April 2020, the Company completed the acquisition of CTEH by acquiring 100% of its membership interests. CTEH is an environmental consulting company headquartered in Arkansas that specializes in environmental response and toxicology. The transaction qualified as an acquisition of a business and is accounted for as a business combination. Cash Common Stock Other Purchase Price Component Contingent Consideration Current Contingent Consideration Long Term Total Purchase Price CTEH $ 175,000 $ 25,000 $ (2,884 ) $ 34,451 $ 10,543 $ 242,110 The contingent consideration elements of the purchase price of CTEH’s acquisition is 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 first year earnout is to be calculated at twelve times CTEH’s 2020 EBITDA (as defined in the purchase agreement) in excess of $18.3 million, with a maximum first year earn-out payment of $50.0 million. The second year earn-out is to be calculated at ten times CTEH’s 2021 EBITDA in excess of actual 2020 EBITDA (with actual 2020 EBITDA subject to a minimum of $18.3 million and a maximum of $22.5 million), with a maximum second year earn-out payment of $30.0 million. The 2020 earn out was initially payable 100% in common stock, but as a result of the completion of the Company’s IPO (Note 23), 50% of any 2020 earnout payment will be payable in cash and 50% will be payable, at the Company’s election, in cash or shares of common stock. The 2021 earn out, if any, is payable 100% in cash. The current portion of the contingent consideration is recorded in accounts payable and other accrued liabilities. The long term portion of the contingent consideration is recorded in other non-current liabilities. The preliminary purchase price attributable to the acquisition was allocated as follows: Cash $ 1,527 Accounts receivable 17,059 Other current assets 1,265 Current assets 19,851 Property plant and equipment 7,042 Customer relationships 56,000 Trade names 4,200 Covenants not to compete 4,000 Proprietary software 14,700 Goodwill 146,038 Total assets 251,831 Current liabilities 9,721 Total liabilities 9,721 Purchase price $ 242,110 The results of operations of CTEH since the acquisition date have been combined with those of the Company. The Company’s condensed consolidated statement of operations for the three and six months ended June 30, 2020 includes revenue and pre-tax income of $14.6 million and $1.2 million, respectively, related to the CTEH acquisition. CTEH is included in the Company’s Assessment, Permitting and Response segment. The weighted average useful lives for the acquired customer relationships and internal proprietary software for this acquisition are 15 years and 3 years, respectively. The weighted average useful lives for the acquired tradenames, covenants not to compete and external proprietary software for this acquisition is 5 years. Goodwill associated with the CTEH acquisition is deductible for income tax purposes. Acquisitions completed during the Six Months Ended June 30, 2019 Golden Specialty, Inc. — In March 2019, the Company acquired all of the assets and operations of Golden Specialty, Inc. (“Golden”), an air testing laboratory in Texas. Golden expands the Company’s air measurement and analysis capabilities in the Gulf Coast region. Target Emission Services Inc. —In April 2019, the Company acquired 100% of the issued and outstanding capital stock of Target Emission Services, Inc. (“TES”), an emission detection company in Canada. TES expands the Company’s LDAR business, increasing the geographic footprint in Canada and initiating growth into international markets. Target Emission Services USA LP —In April 2019, the Company acquired 100% of the issued and outstanding capital stock of Target Emission Services USA LP (now Target Emission Services USA LLC) (“TESUS”), an emission detection company in the United States. TESUS expands the Company’s LDAR business throughout the United States. Air Water & Soil Laboratories, Inc. —In June 2019, the Company acquired 100% of the issued and outstanding capital stock of Air Water & Soil Laboratories, Inc. (“AWS”), a provider of air, water, and soil testing in the mid-Atlantic region. AWS expands the Company’s air, water, and soil environmental lab services in the East Coast. The following table summarizes the elements of purchase price of the acquisitions completed during the six months ended June 30, 2019: Cash Common Stock Other Purchase Price Components Contingent Consideration Total Purchase Price Golden $ 1,500 $ 477 $ 1,977 TES 2,359 322 25 4,911 7,617 TESUS 18,683 3,041 1,495 — 23,219 AWS 6,020 — 150 — 6,170 $ 28,562 $ 3,363 $ 1,670 $ 5,388 $ 38,983 Contingent consideration elements of the purchase price of these acquisitions are related to earn-outs which are based on the expected achievement of revenue or earnings thresholds by the applicable business as of the date of the acquisition and for which the maximum potential amount to be earned is generally not limited. The purchase price attributable to the acquisitions was allocated as follows: Cash $ 1,863 Accounts receivable 2,670 Other current assets 31 Current assets 4,564 Property and equipment 2,450 Customer relationships 11,823 Trade names 463 Covenants not to compete 1,661 Proprietary software 2,560 Goodwill 17,893 Total assets 41,414 Current liabilities 748 Non- current liabilities 1,683 Total liabilities 2,431 Purchase price $ 38,983 The weighted average useful lives for the acquired customer relationships, trade names, covenants not to compete and proprietary software for these acquisitions are 10 years, 1.5 years, 4 years and 3 years, respectively. For the acquisitions completed during the six months ended June 30, 2019, the results of operations since the acquisition dates have been combined with those of the Company. The Company’s three and six months ended June 30, 2019 condensed consolidated statement of operations includes revenue of $1.6 million and pre-tax income of $0.8 million, respectively, related to these acquisitions. The TES, TESUS and AWS acquisitions are included in the Company’s Measurement and Analysis segment. Goodwill associated with the acquisitions completed during the six months ended June 30, 2019 is not deductible for income tax purposes. Supplemental Unaudited Pro-Forma —The unaudited condensed consolidated financial information summarized in the following table gives effect to the CTEH acquisition and the 2019 acquisitions discussed above assuming they occurred on January 1, 2019. These unaudited consolidated pro forma operating results do not assume any impact from revenue, cost or other operating synergies that are expected 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, 2019, nor does the information purport to reflect results for any future period. Three months ended June 30, 2020 2019 As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) Revenues $ 73,766 $ 31,253 $ 105,019 $ 57,401 $ 59,565 $ 116,966 Net income (loss) 13,224 10,288 23,512 (322 ) 19,971 19,649 Six months ended June 30, 2020 2019 As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) Revenues $ 134,797 $ 31,253 $ 166,050 $ 108,355 $ 88,908 $ 197,263 Net (loss) income (28,024 ) 10,288 (17,736 ) (5,564 ) 25,959 20,395

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	7. GOODWILL AND INTANGIBLE ASSETS Amounts related to goodwill as of June 30, 2020 and December 31, 2019 are as follows: Assessment, Permitting and Response Measurements and Analysis Remediation and Reuse Total Balance as of December 31, 2019 $ 15,173 $ 68,628 $ 43,257 $ 127,058 Goodwill acquired during the period 146,038 — — 146,038 Balance as of June 30, 2020 $ 161,211 $ 68,628 $ 43,257 $ 273,096 Amounts related to finite-lived intangible assets as of June 30, 2020 and December 31, 2019 are as follows: June 30, 2020 Estimated Useful Life Gross Balance Accumulated Amortization Total Intangible Assets—Net Finite lived intangible assets Customer relationships 7–15 years $ 164,782 $ 44,665 $ 120,117 Covenants not to compete 4–5 years 29,832 19,424 10,408 Trade names 1–5 years 16,943 11,518 5,425 Proprietary software 3-5 years 19,561 2,865 16,696 Patent 16 years 17,479 851 16,628 Total other intangible assets—net $ 248,597 $ 79,323 $ 169,274 December 31, 2019 Estimated Useful Life Gross Balance Accumulated Amortization Total Intangible Assets—Net Finite lived intangible assets Customer relationships 7–10 years $ 108,782 $ 36,700 $ 72,082 Covenants not to compete 4–5 years 25,832 17,572 8,260 Trade names 1–5 years 12,738 10,230 2,508 Proprietary software 3 years 3,885 1,359 2,526 Patent 16 years 17,479 306 17,173 Total other intangible assets—net $ 168,716 $ 66,167 $ 102,549 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 $7.8 million and $13.3 million for the three and six months ended June 30, 2020, respectively and $4.5 million and $9.1 million for the three and six months ended June 30, 2019, respectively. Future amortization expense is estimated to be as follows for each of the five following years and thereafter: December 31, 2020 (remaining) $ 15,106 2021 28,043 2022 23,958 2023 20,005 2024 16,929 Thereafter 65,233 $ 169,274

Accounts Payable and Other Accr

Accounts Payable and Other Accrued Liabilities	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Accounts Payable and Other Accrued Liabilities	8. ACCOUNTS PAYABLE AND OTHER ACCRUED LIABILITIES Accounts payable and other accrued liabilities consisted of the following as of June 30, 2020 and December 31, 2019: June 30, 2020 December 31, 2019 Accounts payable $ 12,255 $ 15,034 Accrued expenses 9,931 10,733 Contract liabilities 7,736 3,314 Other current liabilities 303 504 Total accounts payable and other accrued liabilities $ 30,225 $ 29,585

Accrued Payroll and Benefits

Accrued Payroll and Benefits	6 Months Ended
	Jun. 30, 2020
Statement Of Financial Position [Abstract]
Accrued Payroll and Benefits	9. ACCRUED PAYROLL AND BENEFITS Accrued payroll and benefits consisted of the following as of June 30, 2020 and December 31, 2019: June 30, 2020 December 31, 2019 Accrued bonuses $ 3,810 $ 3,449 Accrued paid time off 2,206 2,154 Accrued payroll 7,174 4,470 Accrued other 2,040 959 Total accrued payroll and benefits $ 15,230 $ 11,032

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	10. INCOME TAXES The Company calculates its interim income tax provision in accordance with Accounting Standard Codification Topic 270, Interim Reporting (“ASC 270”), and ASC 740. The Company’s effective tax rate (“ETR”) from continuing operations was (15.3)% and 84.2% for the three months ended June 30, 2020 and June 30, 2019 and 14.9% and 14.0% for the six months ended June 30, 2020 and June 30, 2019, respectively, and the Company recorded income tax benefits of $1.8 million and $1.7 million for the three months ended June 30, 2020 and June 30, 2019, respectively and income tax benefits of $4.9 million and $0.9 million for the six months ended June 30, 2020 and June 30, 2019, respectively. The difference between the ETR and federal statutory rate of 21% is primarily attributable to items recorded for GAAP but permanently disallowed for U.S. federal income tax purposes, state and foreign income tax provisions and Global Intangible Low Taxed Income (“GILTI”). 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 June 30, 2020 and December 31, 2019, the Company expected its net deferred tax assets will more-likely-than-not be realized and did not record a valuation allowance. The Company records uncertain tax positions in accordance with ASC 740, Income Taxes, 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 June 30, 2020. The Company classifies interest and penalties recognized on uncertain tax positions as a component of income tax expense. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“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. Under ASC 740, the effects of new legislation are recognized upon enactment. Accordingly, the effects of the CARES Act have been incorporated into the income tax provision computation for the six months ended June 30, 2020. These provisions did not have a material impact on the income tax provision. The Company anticipates deferring the employer side social security payments for payroll paid for the remainder of 2020 as permitted by the CARES Act.

Warrant Options

Warrant Options	6 Months Ended
	Jun. 30, 2020
Warrants And Rights Note Disclosure [Abstract]
Warrant Options	11. WARRANT OPTIONS In October 2018, in connection with the issuance of the Redeemable Series A-1 Preferred Stock, the Company issued a detachable warrant to acquire 534,240 shares of common stock at a price of $0.01 per share at any given time during a period of ten years beginning on the instrument’s issuance date. The fair value of this warrant was determined to be $16.9 million as of June 30, 2020 and December 31, 2019. The warrant option will be fair valued at each reporting period until exercised. Fair value adjustments recorded in other income (expense) on the condensed consolidated statements were not material for the three and six months ended June 30, 2020, respectively and $1.5 million for the three and six months ended June 30, 2019, respectively. The warrant was In April 2020, in connection with the issuance of the Convertible and Redeemable Series A-2 Preferred Stock, the Company issued a detachable warrant to acquire 1,351,960 shares of common stock at a price of $0.01 per share at any time following the occurrence of a qualifying IPO, a sale of the Company, or a redemption in full of the Series A-1 preferred stock (each, an “Adjustment Event”), with an expiration date of ten years from the instrument’s issuance date. The number of shares underlying the warrant and issuable upon exercise was subject to adjustment based upon the price per share of common stock upon the occurrence of an Adjustment Event (Note 17) to reflect an aggregate value of $30.0 million. The fair value of this warrant was determined to be $30.1 million as of June 30, 2020. The warrant option will be fair valued at each reporting period until exercised. Fair value adjustments recorded in other income (expense) on the condensed consolidated statements were not material for the three months ended June 30, 2020. The warrant was

Contingent Put Option

Contingent Put Option	6 Months Ended
	Jun. 30, 2020
Loss Contingency [Abstract]
Contingent Put Option	12. CONTINGENT PUT OPTION As of June 30, 2019, the Company determined that the fair value of the contingent put option related to the Redeemable Series A-1 Preferred Stock was immaterial as the probability of the feature being exercised was considered remote. As of June 30, 2020 and December 31, 2019, the contingent put option issued in connection with the Redeemable Series A-1 Preferred Stock had a fair value of $14.1 million and $7.1 million, respectively. The change in value of $22.6 million and $7.0 million for the three and six months ended June 30, 2020 was recorded to other income (expense). The contingent put option was redeemed in July 2020 (Note 23).

Debt

Debt	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Debt	13. DEBT Debt as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, December 31, 2020 2019 Term Loan Facility $ 175,000 $ 48,750 Revolving Line of Credit 25,000 97,590 Capital leases 3,899 3,765 Other leases 5 12 Equipment line of credit 3,420 3,124 Less deferred debt issuance costs (4,582 ) (1,052 ) Total debt 202,742 152,189 Less current portion of long term debt (4,653 ) (7,143 ) Long-term debt, less current portion $ 198,089 $ 145,046 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. Revolving Line of Credit and Term Loan Facility — On April 13, 2020, the Company entered into a Unitranche Credit Agreement (the “New Credit Facility”) providing for a new $225.0 million credit facility comprised of a $175.0 million term loan and a $50.0 million revolving credit facility and repaid all amounts outstanding under the prior senior secured credit facility. As a result of the redemption in full of the Company’s Redeemable Series A-1 Preferred Stock in connection with the Company’s IPO, t he facility matures in April 2025 (Note 23). The term loan and the revolver bear interest at LIBOR plus 5.0% with a 1.0% LIBOR floor or the base rate plus 4.0% and LIBOR plus 3.5% or the base rate plus 2.5% , respectively. The revolver is also subject to an unused commitment fee of 0.35%. The Term Loan has quarterly repayments starting on September 30, 2020 of $0.5 million, increasing to $1.1 million on September 30, 2021 and further increasing to $1.6 million on September 30, 2022, with the remaining outstanding principal amount due on the maturity date. The Company has the option to borrow incremental term loans up to an aggregate principal amount of $100.0 million subject to satisfaction of certain conditions, including the borrower’s pro forma compliance with the financial covenants under the New Credit Facility. Immediately after giving effect to the incurrence of any such incremental term loans, the unitranche lenders must collectively hold at least 70% of all pari passu debt of all lenders under the credit facility. The existing lenders are not obligated to participate in any incremental term loan facility. The New 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 to incur indebtedness, prepay or amend other indebtedness, create liens, make certain fundamental changes including mergers or dissolutions, pay dividends and make other payments in respect of capital stock, make certain investments, sell assets, change the Company’s lines of business, enter into transactions with affiliates and other corporate actions. The New Credit Facility also contains financial covenants requiring the Company to remain below a maximum consolidated total leverage ratio of 4.25 times, which steps down to 4.00 times beginning December 31, 2021 and then to 3.75 times beginning December 31, , and a minimum consolidated fixed charge coverage ratio of 1.25 times. The New Credit Facility contains mandatory prepayment features upon a number of events, including with the proceeds of certain asset sales, proceeds from the issuance of any debt and proceeds of the capital contribution amounts contributed to cure a financial covenant default. The New Credit Facility also includes mandatory prepayments of 50.0% of excess cash flow minus voluntary prepayments of the term loan and, solely to the extent accompanied by a permanent reduction in the revolving commitment, the revolver, if the Company’s consolidated total leverage ratio for the year ending December 31, 2020 is greater than or equal to 3.25 times and, for any year thereafter, the amount of any such mandatory prepayment shall be reduced to 25.0% of excess cash flow if the leverage ratio is less than 3.00 times. The weighted average interest rate on the New Credit Facility as of June 30, 2020 was 5.91%. The New Credit Facility contains a number of customary events of default related to, among other things, the non-payment of principal, interest or fees, violations of covenants, inaccuracy of representations or warranties, certain bankruptcy events, default in payment under or the acceleration of other indebtedness and certain change of control events. In the event of a default, subject to varying cure periods and rights for certain events of default, the required lenders may, at their option, declare the commitments to fund the credit facility to be terminated. The Company’s obligations under the 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. Prior Senior Secured Credit Facility —As of December 31, 2019, the Company’s Prior Senior Secured Credit Facility (the “Prior Senior Credit Facility”) consisted of a $50.0 million term loan and a $130.0 million revolving credit facility. Borrowings under the Credit Facility borne interest at either (i) LIBOR plus the applicable margin or (ii) a base rate (equal to the highest of (a) the federal funds rate plus 0.5%, (b) Lender A’s prime rate and (c) Eurodollar Rate, which is based on LIBOR, (using a one-month period plus 1.0%), plus the applicable margin, as the Company elects. The applicable margin means a percentage per annum determined in accordance with the following table as of December 31, 2019: Pricing Tier Consolidated Leverage Ratio Commitment Fee Eurodollar Rate Loans and LIBOR Letter of Credit Fee Daily Floating Rate Loans Rate Loans 1 > 3.75 to 1.0 0.50 % 4.00 % 4.00 % 3.00 % 2 ≤ 3.75 to 1.0 but > 3.00 to 1.0 0.50 3.50 3.50 2.50 3 ≤ 3.00 to 1.0 but > 2.25 to 1.0 0.40 3.00 3.00 2.00 4 < 2.25 to 1.0 0.30 2.50 2.50 1.50 As of December 31, 2019, the Company fell within Pricing Tier 2 and the Company was subject to a fixed charge coverage ratio of greater than 1.25 and a consolidated total leverage ratio of lower than 4.00. The weighted average interest rate on the Prior Senior Credit Facility as of March 31, 2020 was 4.95%. The Prior Senior Secured Credit Facility was repaid in full on April 13, 2020 via proceeds from the issuance of the New Credit Facility. The resulting loss on extinguishment amounted to $1.4 million, of which $0.4 million was related to fees paid and $1.0 related to unamortized debt issuance costs. Total loss on extinguishment is recorded in interest expense-net within the condensed consolidated statement of operations for the three and six months ended June 30, 2020. Equipment Line of Credit —On March 12, 2019, the Company increased its equipment line of credit facility for the purchase of equipment and related freight, installation costs and taxes paid for an additional amount not to exceed $2.0 million. On May 16, 2019, the Company entered into a Canadian equipment line of credit facility for an amount not to exceed $1.0 million Canadian dollars. Interest on the line of credit is determined based on a three-year swap rate at the time of funding. Capital Lease Obligations —The assets and liabilities under capital lease agreements are recorded at the lower of the present value of the minimum lease payments or the fair value of the asset. The assets are being amortized over the shorter of their related lease terms or their estimated useful lives ranging from four to six years. The gross amount of assets under capital leases as of June 30, 2020 and December 31, 2019 was $7.3 million and $6.9 million, respectively. The amortization of assets under capital leases was $0.6 million and $1.1 million for the three and six months ended June 30, 2020, respectively and $0.3 million and $0.6 million for the three and six months ended June 30, 2019, respectively and was included in depreciation and amortization on the condensed consolidated statements of operations June 30, Payments Interest Principal 2021 $ 2,863 $ 397 $ 2,466 2022 2,424 300 2,124 2023 1,872 182 1,690 2024 940 57 883 2025 158 2 156 $ 8,257 $ 938 $ 7,319 The following is a schedule of the aggregate annual maturities of long-term debt presented on the condensed consolidated statement of financial position, based on the terms of the credit facility, capital lease obligations and equipment line of credit as of June 30, 2020: June 30, 2021 $ 4,653 2022 2,130 2023 1,690 2024 883 2025 197,968 Total $ 207,324

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	14. FAIR VALUE OF FINANCIAL INSTRUMENTS As of June 30, 2020 and December 31, 2019, the following financial assets and liabilities are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). June 30, December 31, Level 3 Assets 2020 2019 Compound embedded option $ 8,605 $ — Level 3 Liabilities Contingent consideration payable, current $ 36,395 $ 8,614 Contingent consideration payable, long term 9,117 379 Contingent put option 14,125 7,100 Warrant options 46,978 16,878 Total $ 98,010 $ 32,971 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 for the six months ended June 30, 2020 and June 30, 2019: Level 3 Assets Liabilities Compound Embedded Option Contingent Consideration Current (1) Contingent Consideration Long Term (2) Contingent Put Option Warrant Options Total Balance—at December 31, 2018 $ — $ 2,754 $ — $ — $ 12,818 $ 15,572 Acquisitions — 31 — — — 31 Changes in fair value included in earnings — (926 ) — — 1,549 623 Balance—at June 30, 2019 $ — $ 1,859 $ — $ — $ 14,367 $ 16,226 Balance—at December 31, 2019 $ — $ 8,614 $ 379 $ 7,100 $ 16,878 $ 32,971 Payment of contingent consideration payable — (12,250 ) — — — (12,250 ) Foreign currency translation of contingent consideration payment — (208 ) — — — (208 ) Acquisitions 34,451 10,543 44,994 Series A-2 compound embedded option 9,361 — — — — (9,361 ) Issuance of warrant option — — — — 30,099 30,099 Reclass of long term to short term contingent liabilities — 180 (180 ) — — — Changes in fair value included in earnings (756 ) 5,608 (1,625 ) 7,025 1 11,765 Balance—at June 30, 2020 $ 8,605 $ 36,395 $ 9,117 $ 14,125 $ 46,978 $ 98,010 (1) Current portion of the contingent consideration is recorded in accounts payable and other accrued liabilities. (2) Long term portion of the contingent consideration is recorded in other non-current liabilities. Quantitative Information about Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3): Contingent Consideration Payable —CTEH’s contingent consideration payable fair value was valued using a Monte Carlo simulation analysis in a risk-neutral framework with assumptions for volatility, risk-free rate and dividend yield. 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 earnout thresholds. Compound Embedded Option —The fair value of the compound embedded option associated with the issuance of the Convertible and Redeemable Series A-2 Preferred Stock was estimated using a “with-and-without” method. The “with-and-without” methodology involves valuing the whole instrument on an as-is basis and then valuing the instrument without the embedded derivative feature. The difference between the entire instrument with the embedded derivative feature compared to the instrument without the embedded derivative feature is the fair value of the derivative. The unobservable inputs are based on a 100% probability of an IPO event and IPO date. The considerable quantifiable inputs in the compound embedded option were: (i) the future value of the compound embedded option, (ii) the fair value of the Convertible and Redeemable Series A-2 Preferred Stock, (iii) the present value of the total instrument, as well as the present value of the compound embedded feature plus the fair value of the instrument, and (iv) the risk free, discount rates, conversion date and maximum conversion amounts. Contingent Put Option —The fair value of the contingent put option associated with the issuance of the Redeemable Series A-1 Preferred Stock was estimated using a “with-and-without” method. The “with-and-without” methodology involves valuing the whole instrument on an as-is basis and then valuing the instrument without the individual embedded contingent put option. The difference between the entire instrument with the embedded contingent put option compared to the instrument without the embedded contingent put option is the fair value of the derivative, recorded as the contingent put option liability. The unobservable inputs are based on a 100% probability of an IPO event and IPO date. The considerable quantifiable inputs in the contingent put option liability were: (i) the future value of the put option, (ii) the fair value of the Redeemable Series A-1 Preferred Stock, (iii) the present value of the total instrument, as well as the present value of the contingent put option feature plus the fair value of the instrument, and (iv) the risk free and discount rates. The contingent put option was redeemed in July 2020 (Note 22). Warrant Options —The fair value of the warrant option associated with the issuance of the Redeemable Series A-1 Preferred Stock was calculated based on the Black-Sholes pricing model using the following assumptions: June 30, 2020 2019 Common stock value (per share) $ 31.60 $ 26.90 Expected volatility 43.64 % 49.17 % Risk-free interest rate 0.66 % 2.00 % Expected life (years) 10 10 The fair value of the warrant option associated with the issuance of the Convertible and Redeemable Series A-2 Preferred Stock was calculated based on a Monte Carlo simulation analysis with assumptions for (i) stock price, (ii) volatility based on the median historical volatility of publicly listed comparable companies’ stock price returns, (iii) risk-free rates based on U.S. treasury yields and (iv) dividend yield. The method used to price these liabilities is considered Level 3 due to the subjective nature of the unobservable inputs (common stock value and expected volatility) used to determine the fair value.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. COMMITMENTS AND CONTINGENCIES Operating Leases —The Company leases office facilities over various terms expiring through 2028. Certain of these operating leases contain rent escalation clauses. The Company also has office equipment leases that expire through 2025 June 30, Rent Office Equipment Total 2021 $ 6,095 $ 344 $ 6,439 2022 4,846 311 5,157 2023 3,513 201 3,714 2024 2,030 62 2,092 2025 and thereafter 1,573 3 1,576 $ 18,057 $ 921 $ 18,978 Total rent expense under operating leases was $2.1 and $4.2 for the three and six months ended June 30, 2020, respectively, and $1.8 and $3.6 for the three and six months ended June 30, 2019, respectively Other Commitments —The Company has commitments under the New Credit Facility, its equipment line of credit and its capital lease obligations (Note 14). Contingencies —The Company is subject to purchase price contingencies related to earn-outs associated with certain acquisitions (Note 6). 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 condensed consolidated results of operations, financial position or cash flows of the Company.

Redeemable Series A-1 Preferred

Redeemable Series A-1 Preferred Stock	6 Months Ended
	Jun. 30, 2020
Temporary Equity Disclosure [Abstract]
Redeemable Series A-1 Preferred Stock	16. REDEEMABLE SERIES A-1 PREFERRED STOCK On October 19, 2018, the Company issued 12,000 shares of Redeemable Series A-1 Preferred Stock with a par value of $0.0001 per share and a detachable warrant to purchase 534,240 shares of the Company’s common stock. Each preferred share was issued as part of a unit, which consisted of one share of the Redeemable Series A-1 Preferred Stock at $0.01 million per share. On April 13, 2020, the Company amended and restated the certificate of designation of the Company’s Redeemable Series A-1 Preferred Stock. The most significant changes in the amendment included (i) the Redeemable Series A-1 Preferred Stock became pari passu with the Convertible and Redeemable Series A-2 Preferred Stock (Note 17), (ii) the maturity was extended to October 2024; (iii) the Company may use up to $50.0 million of indebtedness or cash on hand to redeem the Redeemable Series A-1 Preferred Stock, and (iv) upon an IPO, up to 50.0% of accumulated dividends may be paid in shares of common shares and (v) the Company may elect to reduce the three year make whole penalty to a two year make whole penalty if the warrant issued in connection with the issuance of the Redeemable Series A-1 Preferred Stock is redeemed in full at a share price of no less than $31.60. Following a partial redemption of outstanding Redeemable Series A-1 Preferred Stock, the dividend rate of the remaining Redeemable Series A-1 Preferred Stock would be reduced proportionally (between 15.0% and 9.0%) in relation to the proportion of Redeemable Series A-1 Preferred Stock redeemed, with the rate increasing by an additional 1.0% for dividends that are accrued versus paid in cash. Based on a qualitative assessment performed by the Company, the Redeemable Series A-1 Preferred Stock amendments did not represent a significant long-term change to the original terms of the instrument and, therefore, there was no change in the accounting of the instrument. The Redeemable Series A-1 Preferred Stock contains restrictive covenants. As of June 30, 2020 and December 31, 2019, the Company was subject to a consolidated total leverage ratio (including the outstanding principal and accrued dividend on the Redeemable Series A-1 Preferred Stock) limit of less than 10.0 times as of the end of any fiscal quarter ending until maturity. The Company was in compliance with the covenants as of June 30, 2020 and December 31, 2019. The Redeemable Series A-1 Preferred Stock has a liquidation preference of $0.01 million per share. The Redeemable Series A-1 Preferred Stock accrues dividends quarterly at an annual rate of 15.0% with respect to any dividends paid in cash and at an annual rate of 14.2% with respect to dividends that are accrued. In the case of a redemption upon the occurrence of an IPO, the holder is guaranteed a minimum of two years of dividends or in the event of an optional redemption event other than in connection with an IPO, the holder is guaranteed a minimum of three years of dividends. Total accrued and unpaid dividends as of June 30, 2020 and December 31, 2019 were $32.2 million and $21.9 million, respectively. The total accreted amount as of June 30, 2020 was $34.3 million. At issuance the Company determined that the detachable warrant and the contingent put option were required to be accounted for separately (Notes 11 and 12). The Redeemable Series A-1 Preferred Stock, including the guaranteed minimum dividend, was fully redeemed on July 27, 2020 (Note 23).

Convertible and Redeemable Seri

Convertible and Redeemable Series A-2 Preferred Stock	6 Months Ended
	Jun. 30, 2020
Temporary Equity Disclosure [Abstract]
Convertible and Redeemable Series A-2 Preferred Stock	17. 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. Each share of Convertible and Redeemable Series A-2 Preferred Stock accrues dividends at the rate of 15.0% per annum, with respect to dividends that are paid in cash, and 14.2% per annum, with respect to dividends that are accrued. The Convertible and Redeemable Series A-2 Preferred Stock contains restrictive covenants that include: (i) maximum 4.0 times debt incurrence test and (ii) 10.0 times total leverage cap (inclusive of the outstanding balance on the Convertible and Redeemable Series A-2 Preferred Stock). The Company may, at its option on any one or more dates, redeem all or a minimum portion (the lesser of (i) $50.0 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. In the event the Company redeemed all or a portion of the Convertible and Redeemable Series A-2 Preferred Stock prior to the three year anniversary of the issuance date, such redemption amount shall include principal, accrued but unpaid interest and a make whole payment such that the aggregate redemption amount reflects three years of dividends. On the occurrence of (i)(x) before a private offering which results in a redemption in full of the Redeemable Series A-1 Preferred Stock, the four-and-a-half-year anniversary of the closing date or (y) after a private offering which results in a redemption in full of the Redeemable Series A-1 Preferred Stock, the five-year anniversary of the closing date, (ii) a change of control, (iii) a sale of the Company, (iv) a non-qualifying IPO, (v) any recapitalization of the Company (other than a redemption of the Redeemable Series A-1 Preferred Stock) or (vi) an event of noncompliance, as defined in the Series A-2 certificate of designation (each, a “mandatory redemption event”), the Company shall, at the option of the holders of a majority of the Convertible and Redeemable Series A-2 Preferred Stock, redeem all shares of the Convertible and Redeemable Series A-2 Preferred Stock, for cash, at a price per share of Convertible and Redeemable Series A-2 Preferred Stock equal to the applicable redemption price on such mandatory redemption date. Upon a qualifying IPO, following which the Redeemable Series A-1 Preferred Stock is fully redeemed, the Convertible and Redeemable Series A-2 Preferred Stock terms automatically update to the following: (i) no mandatory redemption, (ii) no principal cash repayment obligation other than in the event of certain defined liquidation events, (iii) only redeemable at the Company’s option, (iv) the instrument becomes 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 principal of the Convertible and Redeemable Series A-2 Preferred Stock and any accrued but unpaid dividends added to such principal of any shares of Convertible and Redeemable Series A-2 Preferred Stock converted in year 5) during year 6), (v) the dividend rate steps down to 9.0% per year with required quarterly cash payments, (vi) the debt incurrence test ratio increases to 4.5 times (unless the Redeemable Series A-1 Preferred Stock is partially repaid with debt but only for so long as such debt remains unpaid) and (vii) removal of the total leverage cap covenant. The Company’s IPO in July 2020 constituted a qualifying IPO for purposes of the terms of the Convertible and Redeemable Series A-2 Preferred Stock (Note 23). 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 principal plus three years of dividends accrued or accruable thereon. Following a private offering, following which the Redeemable Series A-1 Preferred Stock is fully redeemed, the Convertible and Redeemable Series A-2 Preferred Stock terms automatically update to the following (i) mandatory redemption date extended to 5 years from date of issuance, (ii) the dividend rate steps down to 9.0% per year (payable in cash only) with quarterly cash payments required and (iii) the total leverage cap covenant is removed and (iv) the debt incurrence test ratio increases to 4.5 times (unless the Redeemable Series A-1 Preferred Stock is partially repaid with debt but only for so long as such debt remains unpaid). Following a partial redemption of outstanding Redeemable Series A-1 Preferred Stock, the dividend rate of the Convertible and Redeemable Series A-2 Preferred Stock is reduced proportionally (between 15.0% and 9.0%) in relation to the proportion of the Redeemable Series A-1 Preferred Stock redeemed, with the rate increasing by an additional 1.0% for dividends are accrued versus paid in cash. Following the completion of the Company’s initial public offering and redemption of the Series A-1 preferred stock on July 27, 2020, the Series A-2 preferred stock dividend rate changed to 9.0% per annum, with such dividends accruing daily and compounding quarterly (Note 23). The Company classified the Convertible and Redeemable Series A-2 Preferred Stock as mezzanine equity since the instrument does not meet the definition of a liability pursuant to “ASC 480- Distinguishing Liabilities from Equity” and the instrument is redeemable upon the occurrence of an event that is not solely within the control of the Company. Given that the Company has determined that the instrument is not probable of becoming redeemable (it is only redeemable upon liquidation/ or a change of control), subsequent adjustment of the carrying value of the instrument is not necessary. 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. These embedded features consist 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 common shares beginning on the fourth-year anniversary of the issuance date. As of June 30, 2020, these embedded features had a net fair value of $8.6 million. The change in value of $0.8 million for the three and six months ended June 30, 2020 was recorded to other income (expense). The contingent dividend rate feature and the conversion option are bundled together as a single, compound embedded derivative, as an asset or a liability. At issuance, the Company determined that Convertible and Redeemable Series A-2 Preferred Stock and the detachable warrant, was also required to be accounted for separately (Notes 11).

Stockholder's Deficit

Stockholder's Deficit	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders' Deficit	18. STOCKHOLDERS’ DEFICIT Authorized Capital Stock— The Company was authorized to issue 25,000,000 shares of common stock, with a par value of $0.000004 per share as of June 30, 2020 and December 31, 2019. 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. There were no changes related to these warrants during the three and six months ended June 30, 2020 and June 30, 2019. Common Stock Issuances and Repurchases —During the three and six months ended June 30, 2020, the Company issued 791,139 shares of common stock with an average price per share of $31.60, in connection with the CTEH business acquisition and issued 3,500 shares at an average price per share of $6.03, in connection with the exercise of certain employee stock options. During the three months ended June 30, 2019, the Company issued 125,031 shares of common stock with an average price per share of $26.90, in connection with the TES and TESUS business acquisition and 13,750 shares of common stock with an average price per share of $7.38, in connection with the exercise of certain employee stock options. During the six months ended June 30, 2019, the Company issued 125,031 shares of common stock with an average price per share of $26.90, in connection with the TES and TESUS business acquisition and 15,000 shares of common stock with an average price per share of $6.71, in connection with the exercise of certain employee stock options. 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 June 30, 2020 and June 30, 2019, there was $6.5 million and $6.8 million, respectively, of total unrecognized stock compensation expense related to unvested options and restricted stock granted under the Plans. Such unrecognized expense is expected to be recognized over the next two years. The following number of shares were authorized to be issued and available for grant as of June 30, 2020 and June 30, 2019: June 30, 2020 2017 Plan 2013 Plan Shares authorized to be issued 1,066,160 2,050,244 Shares available for grant 20,817 — June 30, 2019 2017 Plan 2013 Plan Shares authorized to be issued 981,800 2,074,604 Shares available for grant 201,183 — Total stock compensation expense for the Plans was as follows: Three Months Ended June 30, 2020 2019 2017 plan 2013 plan 2017 plan 2013 plan Options Restricted Stock Options Total Options Restricted Stock Options Total Cost of revenue $ 342 $ — $ 61 $ 403 $ 205 $ — $ 147 $ 352 Selling, general and administrative expense 299 370 68 737 145 110 687 942 $ 641 $ 370 $ 129 $ 1,140 $ 350 $ 110 $ 834 $ 1,294 Six Months Ended June 30, 2020 2019 2017 plan 2013 plan 2017 plan 2013 plan Options Restricted Stock Options Total Options Restricted Stock Options Total Cost of revenue $ 697 $ — $ 131 $ 828 $ 345 $ — $ 293 $ 638 Selling, general and administrative expense 586 740 136 1,462 272 212 1,400 1,884 $ 1,283 $ 740 $ 267 $ 2,290 $ 617 $ 212 $ 1,693 $ 2,522 Montrose Amended & Restated 2017 Stock Incentive Plan Restricted Stock —During the six months ended June 30, 2020 and June 30, 2019, the Company issued 33,229 and 30,000 shares of restricted stock with a fair market value of $31.60 and $24.00 per share, respectively, to certain 2017 Plan participants as Director’s compensation. These shares of restricted stock granted in the six months ended June 30, 2020 vest one year from the date of grant and the shares of restricted stock granted during the six months ended June 30, 2019 vest over three years, 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. No restricted shares vested and were released as unrestricted shares of common stock during the six months ended June 30, 2020 and June 30, 2019. There were an aggregate of 273,122 and 242,025 restricted shares outstanding as of June 30, 2020 and June 30, 2019, respectively. There were no forfeitures, cancellations or expirations of restricted shares during the six and three months ended June 30, 2020 and June 30, 2019. 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 period. The following summarizes the options activity of the 2017 Plan for the six months ended June 30, 2020 and June 30, 2019: 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 at December 31, 2018 257,762 $ 20 $ 10 — $ 1,151 Granted 308,990 24 13 Forfeitured/cancelled (14,800 ) 24 Outstanding at June 30, 2019 551,952 23 12 — 2,136 Outstanding at December 31, 2019 617,852 24 12 7.82 4,696 Granted 160,712 32 12 Forfeitured/cancelled (5,500 ) 20 Outstanding at June 30, 2020 773,064 26 12 8.03 4,651 Options vested and expected to vest 773,064 $ 26 8.57 $ 4,651 The following weighted-average assumptions were used in the Black-Sholes option-pricing model calculation for the six months ended June 30, 2020 and June 30, 2019: June 30, 2020 June 30, 2019 Common stock value (per share) $ 31.60 $ 26.90 Expected volatility 45.26 % 48.42 % Risk-free interest rate 0.49 % 2.19 % Expected life (years) 7 7 Forfeiture rate None None Dividend rate None None Montrose Amended & Restated 2013 Stock Option Plan —The following summarizes the activity of the 2013 Plan for the six months ended June 30, 2020 and June 30, 2019: 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 at December 31, 2018 1,900,404 $ 6 $ 1 7.30 33,290 Forfeitured/ cancelled (12,600 ) 14 Expired (4,475 ) 8 Exercised (11,385 ) 5 283 Outstanding at June 30, 2019 1,871,944 6 1 6.87 38,235 Outstanding at December 31, 2019 1,855,469 6 1 6.40 46,617 Forfeitured/ cancelled (1,250 ) 6 Expired (8,550 ) 6 Exercised (3,500 ) 6 89 Outstanding at June 30, 2020 1,842,169 6 1 5.91 46,276 Options vested and expected to vest 1,842,169 6 5.43 46,276 Total shares outstanding from exercised options were 205,100 shares and 201,600 shares as of June 30, 2020 and December 31, 2019. Common Stock Reserved for Future Issuances —At June 30, 2020 and June 30, 2019, the Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following: June 30, 2020 December 31, 2019 Warrants 2,002,550 650,590 Montrose 2013 Stock Incentive Plan 2,050,244 2,058,619 Montrose 2017 Stock Incentive Plan 1,066,160 997,785 Common stock reserved for future issuance 5,118,954 3,706,994

Net Income (Loss) Per Share

Net Income (Loss) Per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income (Loss) per Share	19. NET INCOME (LOSS) PER SHARE Basic net income (loss) per share is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during each period. Diluted net income (loss) per share is computed by dividing net income (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. Shares issuable in connection with the warrant options (Note 11) are considered outstanding common shares for purposes of calculating net income (loss) per share since they do not contain any conditions that must be satisfied for the holder to exercise the warrant. Potentially dilutive shares are comprised of restricted stock and shares of common stock underlying stock options outstanding under the Plans and warrants (other than warrant options) to purchase common stock. The following table summarizes the computation of basic and diluted net income (loss) per share attributable to common stockholders of the Company for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, Six Months Ended June 30, In thousands, except for net loss per share 2020 2019 2020 2019 Net income (loss) $ 13,224 $ (322 ) $ (28,024 ) $ (5,564 ) Accretion of redeemable preferred stock (5,644 ) (4,777 ) (11,059 ) (9,311 ) Net income (loss) attributable to common stockholders - basic and diluted 7,580 (5,099 ) (39,083 ) (14,875 ) Weighted-average common shares outstanding - basic 10,649 8,647 9,718 8,602 Net income (loss) per share attributable to common stockholders - basic $ 0.71 $ (0.59 ) $ (4.02 ) $ (1.73 ) Weighted-average common shares outstanding - diluted 19,139 8,647 9,718 8,602 Net income (loss) per share attributable to common stockholders - diluted $ 0.40 $ (0.59 ) $ (4.02 ) $ (1.73 ) 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 for the periods where a net loss was recorded: June 30, 2020 2019 Stock options 2,685,439 1,960,887 Restricted stock 24,362 168,001 Warrants 116,350 116,350

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Segment Information	20. 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 for the three and six months ended June 30, 2020 and June 30, 2019 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Segment Segment Segment Segment Segment Adjusted Segment Adjusted Segment Adjusted Segment Adjusted Revenues EBITDA Revenues EBITDA Revenues EBITDA Revenues EBITDA Assessment, Permitting and Response $ 18,631 $ 4,989 $ 5,028 $ 2,002 $ 23,161 $ 6,431 $ 9,603 $ 3,996 Measurement and Analysis 37,036 11,615 34,617 7,979 73,476 19,176 62,948 12,112 Remediation and Reuse 18,099 2,375 17,756 2,399 38,160 4,481 35,804 4,875 Total Operating Segments 73,766 18,979 57,401 12,380 134,797 30,088 108,355 20,983 Corporate and Other (5,084 ) (3,842 ) (10,640 ) (7,373 ) Total $ 73,766 $ 13,895 $ 57,401 $ 8,538 $ 134,797 $ 19,448 $ 108,355 $ 13,610 Presented below is a reconciliation of the Company’s segment measure to income (loss) before benefit from income taxes for the three and six months ended June 30, 2020 and June 30, 2019: For the Three Months Ended June 30, For the Six Months Ended June 30, 2020 2019 2020 2019 Total $ 13,895 $ 8,538 $ 19,448 $ 13,610 Interest Expense, net (5,260 ) (1,181 ) (7,853 ) (2,460 ) Income tax benefit 1,759 1,712 4,911 896 Depreciation and Amortization (9,784 ) (6,401 ) (17,344 ) (12,850 ) Stock-based compensation (1,140 ) (1,294 ) (2,290 ) (2,522 ) Start-up losses and investment in new services (296 ) (143 ) (675 ) (457 ) Acquisition costs (2,454 ) (857 ) (3,761 ) (1,072 ) Fair value changes in contingent put option 22,602 — (7,025 ) — Fair value changes in warrant options (4 ) (1,549 ) (2 ) (1,549 ) Fair value changes in compound embedded option (756 ) — (756 ) — Fair value changes in contingent liabilities (3,983 ) 926 (3,983 ) 926 Short term purchase accounting fair value adjustment to deferred revenue — — (243 ) — IPO preparation costs — (73 ) (531 ) (86 ) Discontinued services (i) (1,078 ) — (7,496 ) — Other expenses — — (147 ) — Expenses related to financing transactions (277 ) — (277 ) — Net Income (Loss) $ 13,224 $ (322 ) $ (28,024 ) $ (5,564 ) (i)

Related-Party Transactions

Related-Party Transactions	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Related-Party Transactions	21. RELATED-PARTY TRANSACTIONS The Company engages a related party to provide Quality of Earnings reports on acquisition targets. The Company paid this related party approximately $0.1 $0.1 million during both the three and six months ended June 30, 2019

Defined Contribution Plan

Defined Contribution Plan	6 Months Ended
	Jun. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan	22. DEFINED CONTRIBUTION PLAN On January 1, 2014, the Company established the Montrose Environmental Group 401(k) Savings Plan. As of June 30, 2020 and December 31, 2019, 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. Up 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. Subsequent to May 22, 2020, the Company temporarily ceased making employer contributions. Employer contributions for the three and six months ended June 30, 2020 were $0.4 1.2 $0.7 million and $1.3 million for the three and six months ended June 30, 2019, respectively,

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	23. SUBSEQUENT EVENTS On July 14, 2020, the Company amended and restated its certificate of incorporation to, among other things, increase the number of shares of common stock the Company is authorized to issue to 190,000,000. On July 27, 2020, the Company completed its IPO. In the IPO, the Company issued and sold 11,500,000 shares of common stock, including 1,500,000 shares issued pursuant to the underwriters full exercise on July 24, 2020 of their option to purchase additional shares, at a price to the public of $15.00 per share, resulting in net proceeds to the Company of approximately $161.3 million after deducting underwriting discounts and commissions and offering expenses of approximately $9.8 million payable by the Company. All shares issued and sold were registered pursuant to a registration statement on Form S-1 (File No. 333-239542 The Company used $131.8 million of proceeds and 1,786,739 shares of common stock to redeem in full all outstanding shares of the Company’s Redeemable Series A-1 Preferred Stock. As a result of the $15.00 per share public offering price in the IPO, the warrant issued in connection with the issuance of the Convertible and Redeemable Series A-2 Preferred Stock was adjusted pursuant to its terms and, upon closing of the IPO, represented a warrant to purchase 1,999,999 shares of common stock (an increase of 648,039 shares). On July 30, 2020, the holders of the warrants issued in connection with the Redeemable Series A-1 and Convertible and Redeemable Series A-2 Preferred Stock, fully exercised the warrants, and paid the Company in cash the aggregate exercise price of $0.03 million in cash in return for 2,534,239 shares of common stock.

Description of the Business a_2

Description of the Business and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2020
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 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, 2019. 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 condensed consolidated financial statements.
Recently Adopted Accounting Pronouncements /Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Adopted Accounting Pronouncements —The Company qualifies as an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”) and therefore intends to take 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 has elected to use this extended transition period under the JOBS Act. The effective dates shown below reflect the election to use the extended transition period. In June 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) 2018-07, Compensation—Stock Compensation: Improvements to Nonemployee Share-Based Payment Accounting. Under the revised guidance, the accounting for awards issued to non-employees will be similar to the accounting for employee awards. The new guidance is effective for fiscal years beginning after December 15, 2019. The standard was adopted as of January 1, 2020 and did not have a material impact on the Company’s condensed consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Accounting for Goodwill Impairment. The revised guidance eliminates Step 2 of the current goodwill impairment analysis test, which requires hypothetical purchase price allocation to measure goodwill impairment. A goodwill impairment loss will instead be measured at the amount by which a reporting unit’s carrying amount exceeds its fair value, not to exceed the carrying amount of goodwill. The revised guidance was adopted as of January 1, 2020 and did not have a material impact on the Company’s condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted — In August 2020, the FASB issued 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 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, 2023, including interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact of the adoption of the standard on the condensed consolidated financial statements. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting. ASU 2020-04 provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by the expected transition away from reference rates that are expected to be discontinued, such as LIBOR. ASU 2020-04 was effective upon issuance. The Company may elect to apply the guidance prospectively through December 31, 2022. The Company is evaluating the impact of the standard on its condensed consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and clarifies and amends certain guidance to promote consistent application. ASU 2019-12 is effective for the Company’s annual and interim periods beginning on January 1, 2021, with early adoption permitted. Depending on the amendment, adoption may be applied on a retrospective, modified retrospective or prospective basis. The Company is evaluating the impact of the standard on its condensed consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326). The standard introduces a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses and will apply to trade receivables. The new guidance will be effective for the Company’s annual and interim periods beginning after December 15, 2022. The Company is currently evaluating the impact of the adoption of the standard on the condensed consolidated financial statements. In February 2016, the FASB issued ASU 2016-2, Leases (Topic 842), to improve financial reporting regarding leasing transactions. The ASU primarily affects the accounting by the lessee in that it requires a lessee to recognize lease assets and liabilities, initially measured at the present value of the lease payments, on the balance sheets for those leases classified as operating leases under previous guidance. The new leasing standard is effective for the Company’s annual and interim periods beginning after December 15, 2021. The new leasing standard requires modified retrospective transition. The Company is currently evaluating the impact of the adoption of the updated standard on the condensed consolidated financial statements.

Revenues and Accounts Receiva_2

Revenues and Accounts Receivable (Tables)	6 Months Ended
	Jun. 30, 2020
Revenues And Accounts Receivable [Abstract]
Schedule of Contract Balances	The following table presents the Company’s contract balances: June 30, 2020 December 31, 2019 Contract assets $ 22,775 $ 13,605 Contract liabilities 7,736 3,314
Schedule of Accounts Receivable, Net	Accounts receivable, net as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, 2020 December 31, 2019 Accounts receivable, invoiced $ 50,359 $ 46,643 Accounts receivable, other 1,402 611 Allowance for doubtful accounts (8,506 ) (1,327 ) Accounts receivable—net $ 43,255 $ 45,927
Schedule of Allowance for Doubtful Accounts	The allowance for doubtful accounts as of June 30, 2020 and December 31, 2019 consisted of the following: Beginning Balance Bad Debt Expense Charged to Allowance Other (1) Ending Balance Six months ended June 30, 2020 $ 1,327 $ 6,263 $ (122 ) $ 1,038 $ 8,506 Year ended December 31, 2019 453 1,246 (556 ) 184 1,327 (1) This amount consists of additions to the allowance due to business acquisitions.

Prepaid and Other Current Ass_2

Prepaid and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Schedule of Prepaid and Other Current Assets	Prepaid and other current assets as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, December 31, 2020 2019 Deposits $ 662 $ 605 Prepaid expenses 1,288 1,235 Prepaid insurance 2,539 170 Supplies 2,313 2,368 Offering costs 2,403 1,240 Income tax receivable 989 1,205 Prepaid and other current assets $ 10,194 $ 6,823

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Property and Equipment, Net	Property and equipment, net, as of June 30, 2020 and December 31, 2019 consisted of the following: Estimated Useful Life June 30, 2020 December 31, 2019 Lab and test equipment 7 years $ 17,219 $ 14,810 Vehicles 5 years 12,658 11,073 Equipment 3–7 years 30,747 29,922 Furniture and fixtures 7 years 2,798 1,119 Leasehold improvements 7 years 6,633 5,954 Aircraft 10 years 834 — Building 39 years 2,975 — 73,864 62,878 Land 725 — Construction in progress — 796 Less accumulated depreciation (39,818 ) (36,638 ) Total property and equipment—net $ 34,771 $ 27,036

Business Acquisitions (Tables)

Business Acquisitions (Tables)	6 Months Ended
	Jun. 30, 2020
Business Acquisition [Line Items]
Summary of Elements of Purchase Price of Acquisitions	The following table summarizes the elements of purchase price of the acquisitions completed during the six months ended June 30, 2019: Cash Common Stock Other Purchase Price Components Contingent Consideration Total Purchase Price Golden $ 1,500 $ 477 $ 1,977 TES 2,359 322 25 4,911 7,617 TESUS 18,683 3,041 1,495 — 23,219 AWS 6,020 — 150 — 6,170 $ 28,562 $ 3,363 $ 1,670 $ 5,388 $ 38,983
Summary of Purchase Price Attributable to Acquisitions	The purchase price attributable to the acquisitions was allocated as follows: Cash $ 1,863 Accounts receivable 2,670 Other current assets 31 Current assets 4,564 Property and equipment 2,450 Customer relationships 11,823 Trade names 463 Covenants not to compete 1,661 Proprietary software 2,560 Goodwill 17,893 Total assets 41,414 Current liabilities 748 Non- current liabilities 1,683 Total liabilities 2,431 Purchase price $ 38,983
Summary of Supplemental Unaudited Pro-Forma Information	The unaudited condensed consolidated financial information summarized in the following table gives effect to the CTEH acquisition and the 2019 acquisitions discussed above assuming they occurred on January 1, 2019. These unaudited consolidated pro forma operating results do not assume any impact from revenue, cost or other operating synergies that are expected 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, 2019, nor does the information purport to reflect results for any future period. Three months ended June 30, 2020 2019 As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) Revenues $ 73,766 $ 31,253 $ 105,019 $ 57,401 $ 59,565 $ 116,966 Net income (loss) 13,224 10,288 23,512 (322 ) 19,971 19,649 Six months ended June 30, 2020 2019 As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) As reported Acquisitions Pro-Forma (Unaudited) Consolidated Pro-Forma (Unaudited) Revenues $ 134,797 $ 31,253 $ 166,050 $ 108,355 $ 88,908 $ 197,263 Net (loss) income (28,024 ) 10,288 (17,736 ) (5,564 ) 25,959 20,395
CTEH
Business Acquisition [Line Items]
Summary of Elements of Purchase Price of Acquisitions	The following table summarizes the elements of the purchase price of CTEH: Cash Common Stock Other Purchase Price Component Contingent Consideration Current Contingent Consideration Long Term Total Purchase Price CTEH $ 175,000 $ 25,000 $ (2,884 ) $ 34,451 $ 10,543 $ 242,110
Summary of Purchase Price Attributable to Acquisitions	The preliminary purchase price attributable to the acquisition was allocated as follows: Cash $ 1,527 Accounts receivable 17,059 Other current assets 1,265 Current assets 19,851 Property plant and equipment 7,042 Customer relationships 56,000 Trade names 4,200 Covenants not to compete 4,000 Proprietary software 14,700 Goodwill 146,038 Total assets 251,831 Current liabilities 9,721 Total liabilities 9,721 Purchase price $ 242,110

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Schedule of Amounts Related to Goodwill	Amounts related to goodwill as of June 30, 2020 and December 31, 2019 are as follows: Assessment, Permitting and Response Measurements and Analysis Remediation and Reuse Total Balance as of December 31, 2019 $ 15,173 $ 68,628 $ 43,257 $ 127,058 Goodwill acquired during the period 146,038 — — 146,038 Balance as of June 30, 2020 $ 161,211 $ 68,628 $ 43,257 $ 273,096
Schedule of Amounts Related to Finite-Lived Intangible Assets	Amounts related to finite-lived intangible assets as of June 30, 2020 and December 31, 2019 are as follows: June 30, 2020 Estimated Useful Life Gross Balance Accumulated Amortization Total Intangible Assets—Net Finite lived intangible assets Customer relationships 7–15 years $ 164,782 $ 44,665 $ 120,117 Covenants not to compete 4–5 years 29,832 19,424 10,408 Trade names 1–5 years 16,943 11,518 5,425 Proprietary software 3-5 years 19,561 2,865 16,696 Patent 16 years 17,479 851 16,628 Total other intangible assets—net $ 248,597 $ 79,323 $ 169,274 December 31, 2019 Estimated Useful Life Gross Balance Accumulated Amortization Total Intangible Assets—Net Finite lived intangible assets Customer relationships 7–10 years $ 108,782 $ 36,700 $ 72,082 Covenants not to compete 4–5 years 25,832 17,572 8,260 Trade names 1–5 years 12,738 10,230 2,508 Proprietary software 3 years 3,885 1,359 2,526 Patent 16 years 17,479 306 17,173 Total other intangible assets—net $ 168,716 $ 66,167 $ 102,549
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, 2020 (remaining) $ 15,106 2021 28,043 2022 23,958 2023 20,005 2024 16,929 Thereafter 65,233 $ 169,274

Accounts Payable and Other Ac_2

Accounts Payable and Other Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Summary of Accounts Payable and Other Accrued Liabilities	Accounts payable and other accrued liabilities consisted of the following as of June 30, 2020 and December 31, 2019: June 30, 2020 December 31, 2019 Accounts payable $ 12,255 $ 15,034 Accrued expenses 9,931 10,733 Contract liabilities 7,736 3,314 Other current liabilities 303 504 Total accounts payable and other accrued liabilities $ 30,225 $ 29,585

Accrued Payroll and Benefits (T

Accrued Payroll and Benefits (Tables)	6 Months Ended
	Jun. 30, 2020
Statement Of Financial Position [Abstract]
Schedule of Accrued Payroll and Benefits	Accrued payroll and benefits consisted of the following as of June 30, 2020 and December 31, 2019: June 30, 2020 December 31, 2019 Accrued bonuses $ 3,810 $ 3,449 Accrued paid time off 2,206 2,154 Accrued payroll 7,174 4,470 Accrued other 2,040 959 Total accrued payroll and benefits $ 15,230 $ 11,032

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Debt	Debt as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, December 31, 2020 2019 Term Loan Facility $ 175,000 $ 48,750 Revolving Line of Credit 25,000 97,590 Capital leases 3,899 3,765 Other leases 5 12 Equipment line of credit 3,420 3,124 Less deferred debt issuance costs (4,582 ) (1,052 ) Total debt 202,742 152,189 Less current portion of long term debt (4,653 ) (7,143 ) Long-term debt, less current portion $ 198,089 $ 145,046
Schedule of Applicable Percentages	The applicable margin means a percentage per annum determined in accordance with the following table as of December 31, 2019: Pricing Tier Consolidated Leverage Ratio Commitment Fee Eurodollar Rate Loans and LIBOR Letter of Credit Fee Daily Floating Rate Loans Rate Loans 1 > 3.75 to 1.0 0.50 % 4.00 % 4.00 % 3.00 % 2 ≤ 3.75 to 1.0 but > 3.00 to 1.0 0.50 3.50 3.50 2.50 3 ≤ 3.00 to 1.0 but > 2.25 to 1.0 0.40 3.00 3.00 2.00 4 < 2.25 to 1.0 0.30 2.50 2.50 1.50
Schedule of Capital Leases Mature by 2025	All capital leases (including those purchased through the Company’s equipment line of credit) mature by 2025 as follows: June 30, Payments Interest Principal 2021 $ 2,863 $ 397 $ 2,466 2022 2,424 300 2,124 2023 1,872 182 1,690 2024 940 57 883 2025 158 2 156 $ 8,257 $ 938 $ 7,319
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 condensed consolidated statement of financial position, based on the terms of the credit facility, capital lease obligations and equipment line of credit as of June 30, 2020: June 30, 2021 $ 4,653 2022 2,130 2023 1,690 2024 883 2025 197,968 Total $ 207,324

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	As of June 30, 2020 and December 31, 2019, the following financial assets and liabilities are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). June 30, December 31, Level 3 Assets 2020 2019 Compound embedded option $ 8,605 $ — Level 3 Liabilities Contingent consideration payable, current $ 36,395 $ 8,614 Contingent consideration payable, long term 9,117 379 Contingent put option 14,125 7,100 Warrant options 46,978 16,878 Total $ 98,010 $ 32,971
Summary of Financial Instruments Measured at Fair Value on Recurring Basis	The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis for the six months ended June 30, 2020 and June 30, 2019: Level 3 Assets Liabilities Compound Embedded Option Contingent Consideration Current (1) Contingent Consideration Long Term (2) Contingent Put Option Warrant Options Total Balance—at December 31, 2018 $ — $ 2,754 $ — $ — $ 12,818 $ 15,572 Acquisitions — 31 — — — 31 Changes in fair value included in earnings — (926 ) — — 1,549 623 Balance—at June 30, 2019 $ — $ 1,859 $ — $ — $ 14,367 $ 16,226 Balance—at December 31, 2019 $ — $ 8,614 $ 379 $ 7,100 $ 16,878 $ 32,971 Payment of contingent consideration payable — (12,250 ) — — — (12,250 ) Foreign currency translation of contingent consideration payment — (208 ) — — — (208 ) Acquisitions 34,451 10,543 44,994 Series A-2 compound embedded option 9,361 — — — — (9,361 ) Issuance of warrant option — — — — 30,099 30,099 Reclass of long term to short term contingent liabilities — 180 (180 ) — — — Changes in fair value included in earnings (756 ) 5,608 (1,625 ) 7,025 1 11,765 Balance—at June 30, 2020 $ 8,605 $ 36,395 $ 9,117 $ 14,125 $ 46,978 $ 98,010 (1) Current portion of the contingent consideration is recorded in accounts payable and other accrued liabilities. (2) Long term portion of the contingent consideration is recorded in other non-current liabilities.
Summary of Fair Value of Warrant Options Associated with Issuance of Redeemable Series A-1 Preferred Stock	The fair value of the warrant option associated with the issuance of the Redeemable Series A-1 Preferred Stock was calculated based on the Black-Sholes pricing model using the following assumptions: June 30, 2020 2019 Common stock value (per share) $ 31.60 $ 26.90 Expected volatility 43.64 % 49.17 % Risk-free interest rate 0.66 % 2.00 % Expected life (years) 10 10

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments under Leases	The following is a schedule of the future minimum lease payments by year under the leases as of June 30, 2020: June 30, Rent Office Equipment Total 2021 $ 6,095 $ 344 $ 6,439 2022 4,846 311 5,157 2023 3,513 201 3,714 2024 2,030 62 2,092 2025 and thereafter 1,573 3 1,576 $ 18,057 $ 921 $ 18,978

Stockholder's Deficit (Tables)

Stockholder's Deficit (Tables)	6 Months Ended
	Jun. 30, 2020
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 as of June 30, 2020 and June 30, 2019: June 30, 2020 2017 Plan 2013 Plan Shares authorized to be issued 1,066,160 2,050,244 Shares available for grant 20,817 — June 30, 2019 2017 Plan 2013 Plan Shares authorized to be issued 981,800 2,074,604 Shares available for grant 201,183 —
Schedule of Stock Compensation Expense	Total stock compensation expense for the Plans was as follows: Three Months Ended June 30, 2020 2019 2017 plan 2013 plan 2017 plan 2013 plan Options Restricted Stock Options Total Options Restricted Stock Options Total Cost of revenue $ 342 $ — $ 61 $ 403 $ 205 $ — $ 147 $ 352 Selling, general and administrative expense 299 370 68 737 145 110 687 942 $ 641 $ 370 $ 129 $ 1,140 $ 350 $ 110 $ 834 $ 1,294 Six Months Ended June 30, 2020 2019 2017 plan 2013 plan 2017 plan 2013 plan Options Restricted Stock Options Total Options Restricted Stock Options Total Cost of revenue $ 697 $ — $ 131 $ 828 $ 345 $ — $ 293 $ 638 Selling, general and administrative expense 586 740 136 1,462 272 212 1,400 1,884 $ 1,283 $ 740 $ 267 $ 2,290 $ 617 $ 212 $ 1,693 $ 2,522
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 for the six months ended June 30, 2020 and June 30, 2019: June 30, 2020 June 30, 2019 Common stock value (per share) $ 31.60 $ 26.90 Expected volatility 45.26 % 48.42 % Risk-free interest rate 0.49 % 2.19 % Expected life (years) 7 7 Forfeiture rate None None Dividend rate None None
Schedule of Common Stock Reserved for Future Issuance	Common Stock Reserved for Future Issuances —At June 30, 2020 and June 30, 2019, the Company has reserved certain stock of its authorized but unissued common stock for possible future issuance in connection with the following: June 30, 2020 December 31, 2019 Warrants 2,002,550 650,590 Montrose 2013 Stock Incentive Plan 2,050,244 2,058,619 Montrose 2017 Stock Incentive Plan 1,066,160 997,785 Common stock reserved for future issuance 5,118,954 3,706,994
Montrose Amended & Restated 2017 Stock Incentive Plan
Summary of Stock Option Activity	The following summarizes the options activity of the 2017 Plan for the six months ended June 30, 2020 and June 30, 2019: 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 at December 31, 2018 257,762 $ 20 $ 10 — $ 1,151 Granted 308,990 24 13 Forfeitured/cancelled (14,800 ) 24 Outstanding at June 30, 2019 551,952 23 12 — 2,136 Outstanding at December 31, 2019 617,852 24 12 7.82 4,696 Granted 160,712 32 12 Forfeitured/cancelled (5,500 ) 20 Outstanding at June 30, 2020 773,064 26 12 8.03 4,651 Options vested and expected to vest 773,064 $ 26 8.57 $ 4,651
Montrose Amended and Restated 2013 Stock Option Plan
Summary of Stock Option Activity	Montrose Amended & Restated 2013 Stock Option Plan —The following summarizes the activity of the 2013 Plan for the six months ended June 30, 2020 and June 30, 2019: 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 at December 31, 2018 1,900,404 $ 6 $ 1 7.30 33,290 Forfeitured/ cancelled (12,600 ) 14 Expired (4,475 ) 8 Exercised (11,385 ) 5 283 Outstanding at June 30, 2019 1,871,944 6 1 6.87 38,235 Outstanding at December 31, 2019 1,855,469 6 1 6.40 46,617 Forfeitured/ cancelled (1,250 ) 6 Expired (8,550 ) 6 Exercised (3,500 ) 6 89 Outstanding at June 30, 2020 1,842,169 6 1 5.91 46,276 Options vested and expected to vest 1,842,169 6 5.43 46,276

Net Income (Loss) Per Share (Ta

Net Income (Loss) Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
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 income (loss) per share attributable to common stockholders of the Company for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, Six Months Ended June 30, In thousands, except for net loss per share 2020 2019 2020 2019 Net income (loss) $ 13,224 $ (322 ) $ (28,024 ) $ (5,564 ) Accretion of redeemable preferred stock (5,644 ) (4,777 ) (11,059 ) (9,311 ) Net income (loss) attributable to common stockholders - basic and diluted 7,580 (5,099 ) (39,083 ) (14,875 ) Weighted-average common shares outstanding - basic 10,649 8,647 9,718 8,602 Net income (loss) per share attributable to common stockholders - basic $ 0.71 $ (0.59 ) $ (4.02 ) $ (1.73 ) Weighted-average common shares outstanding - diluted 19,139 8,647 9,718 8,602 Net income (loss) per share attributable to common stockholders - diluted $ 0.40 $ (0.59 ) $ (4.02 ) $ (1.73 )
Equity Shares Excluded from Calculation of Diluted Net 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 for the periods where a net loss was recorded: June 30, 2020 2019 Stock options 2,685,439 1,960,887 Restricted stock 24,362 168,001 Warrants 116,350 116,350

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Components of Segment Revenues and Adjusted EBITDA	Segment revenues and Adjusted EBITDA for the three and six months ended June 30, 2020 and June 30, 2019 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Segment Segment Segment Segment Segment Adjusted Segment Adjusted Segment Adjusted Segment Adjusted Revenues EBITDA Revenues EBITDA Revenues EBITDA Revenues EBITDA Assessment, Permitting and Response $ 18,631 $ 4,989 $ 5,028 $ 2,002 $ 23,161 $ 6,431 $ 9,603 $ 3,996 Measurement and Analysis 37,036 11,615 34,617 7,979 73,476 19,176 62,948 12,112 Remediation and Reuse 18,099 2,375 17,756 2,399 38,160 4,481 35,804 4,875 Total Operating Segments 73,766 18,979 57,401 12,380 134,797 30,088 108,355 20,983 Corporate and Other (5,084 ) (3,842 ) (10,640 ) (7,373 ) Total $ 73,766 $ 13,895 $ 57,401 $ 8,538 $ 134,797 $ 19,448 $ 108,355 $ 13,610
Reconciliation of Segment Measure to Income (Loss) Before Benefit from Income Taxes	Presented below is a reconciliation of the Company’s segment measure to income (loss) before benefit from income taxes for the three and six months ended June 30, 2020 and June 30, 2019: For the Three Months Ended June 30, For the Six Months Ended June 30, 2020 2019 2020 2019 Total $ 13,895 $ 8,538 $ 19,448 $ 13,610 Interest Expense, net (5,260 ) (1,181 ) (7,853 ) (2,460 ) Income tax benefit 1,759 1,712 4,911 896 Depreciation and Amortization (9,784 ) (6,401 ) (17,344 ) (12,850 ) Stock-based compensation (1,140 ) (1,294 ) (2,290 ) (2,522 ) Start-up losses and investment in new services (296 ) (143 ) (675 ) (457 ) Acquisition costs (2,454 ) (857 ) (3,761 ) (1,072 ) Fair value changes in contingent put option 22,602 — (7,025 ) — Fair value changes in warrant options (4 ) (1,549 ) (2 ) (1,549 ) Fair value changes in compound embedded option (756 ) — (756 ) — Fair value changes in contingent liabilities (3,983 ) 926 (3,983 ) 926 Short term purchase accounting fair value adjustment to deferred revenue — — (243 ) — IPO preparation costs — (73 ) (531 ) (86 ) Discontinued services (i) (1,078 ) — (7,496 ) — Other expenses — — (147 ) — Expenses related to financing transactions (277 ) — (277 ) — Net Income (Loss) $ 13,224 $ (322 ) $ (28,024 ) $ (5,564 ) (i)

Description of the Business a_3

Description of the Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	Jul. 27, 2020USD ($)$ / sharesshares	Jun. 30, 2020USD ($)EmployeeOfficeAcquisition$ / shares	Jun. 30, 2019USD ($)$ / shares
Description Of Business And Basis Of Presentation [Line Items]
Entity formation, month and year		2013-11
Number of offices in which entity operates | Office		70
Entity number of employees | Employee		1,700
Number of acquisitions completed | Acquisition		54
Share price | $ / shares		$ 31.60	$ 26.90
Net proceeds from sale of common stock | $		$ 21	$ 95
Subsequent Event
Description Of Business And Basis Of Presentation [Line Items]
Common stock shares sold under IPO	1,786,739
Subsequent Event | IPO
Description Of Business And Basis Of Presentation [Line Items]
Common stock shares sold under IPO	11,500,000
Share price | $ / shares	$ 15
Net proceeds from sale of common stock | $	$ 161,300
Subsequent Event | Underwriters
Description Of Business And Basis Of Presentation [Line Items]
Common stock shares sold under IPO	1,500,000

Summary of New Accounting Pro_2

Summary of New Accounting Pronouncements - Additional Information (Details)	Jun. 30, 2020
Accounting Standards Update 2018-07
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. 1, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
Accounting Standards Update 2017-04
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. 1, 2020
Change in accounting principle, accounting standards update, immaterial effect	true

Revenues and Accounts Receiva_3

Revenues and Accounts Receivable - Schedule of Contract Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Revenues And Accounts Receivable [Abstract]
Contract assets	$ 22,775	$ 13,605
Contract liabilities	$ 7,736	$ 3,314

Revenues and Accounts Receiva_4

Revenues and Accounts Receivable - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Contracts assets acquired through business acquisitions	$ 6,500,000		$ 6,500,000		$ 700,000
Contract liabilities acquired through business acquisitions	0		0		2,200,000
Contract with customer, liability, revenue recognized	300,000		1,600,000
Revenue remaining performance obligations	$ 15,300,000		15,300,000		13,000,000
Provision for bad debt		$ 6,300,000	6,263,000	$ 547,000	$ 1,246,000
Remediation and Reuse Segment
Accounts Notes And Loans Receivable [Line Items]
Provision for bad debt			$ 5,500,000
Customer Concentration Risk | Accounts Receivable | Minimum
Accounts Notes And Loans Receivable [Line Items]
Concentration Risk Percentage			10.00%

Revenues and Accounts Receiva_5

Revenues and Accounts Receivable - Additional Information (Details1) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligations	$ 15.3	$ 13
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-07-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligations	$ 14
Revenue remaining performance obligations, satisfaction period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Revenue remaining performance obligations	$ 1.3
Revenue remaining performance obligations, satisfaction period

Revenues and Accounts Receiva_6

Revenues and Accounts Receivable - Schedule of Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues And Accounts Receivable [Abstract]
Accounts receivable, invoiced	$ 50,359	$ 46,643
Accounts receivable, other	1,402	611
Allowance for doubtful accounts	(8,506)	(1,327)	$ (453)
Accounts receivable—net	$ 43,255	$ 45,927

Revenues and Accounts Receiva_7

Revenues and Accounts Receivable - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenues And Accounts Receivable [Abstract]
Beginning Balance	$ 1,327	$ 1,327	$ 453	$ 453
Bad Debt Expense	$ 6,300	6,263	$ 547	1,246
Charged to Allowance		(122)		(556)
Other		1,038		184
Ending Balance		$ 8,506		$ 1,327

Prepaid and Other Current Ass_3

Prepaid and Other Current Assets - Schedule of Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Prepaid Expense and Other Assets, Current [Abstract]
Deposits	$ 662	$ 605
Prepaid expenses	1,288	1,235
Prepaid insurance	2,539	170
Supplies	2,313	2,368
Offering costs	2,403	1,240
Income tax receivable	989	1,205
Prepaid and other current assets	$ 10,194	$ 6,823

Property and Equipment - Proper

Property and Equipment - Property and Equipment, Net (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 73,864	$ 62,878
Less accumulated depreciation	(39,818)	(36,638)
Total property and equipment—net	$ 34,771	27,036
Lab and Test Equipment
Property Plant And Equipment [Line Items]
Estimated Useful Life	7 years
Property and equipment, gross	$ 17,219	14,810
Vehicles
Property Plant And Equipment [Line Items]
Estimated Useful Life	5 years
Property and equipment, gross	$ 12,658	11,073
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 30,747	29,922
Equipment | Minimum
Property Plant And Equipment [Line Items]
Estimated Useful Life	3 years
Equipment | Maximum [Member]
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	$ 2,798	1,119
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated Useful Life	7 years
Property and equipment, gross	$ 6,633	5,954
Aircraft
Property Plant And Equipment [Line Items]
Estimated Useful Life	10 years
Property and equipment, gross	$ 834
Building
Property Plant And Equipment [Line Items]
Estimated Useful Life	39 years
Property and equipment, gross	$ 2,975
Land
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 725
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 796

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 2	$ 1.9	$ 4	$ 3.8

Business Acquisitions - Additio

Business Acquisitions - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Apr. 30, 2019
Business Acquisition [Line Items]
External transaction costs related to business combinations		$ 2,454,000	$ 857,000	$ 3,761,000	$ 1,072,000
Revenue			1,600,000		1,600,000
Pre-tax income (loss)			$ 800,000		$ 800,000
Customer Relationships
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets					10 years
Trade Names
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets					1 year 6 months
Covenants Not to Compete
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets					4 years
Proprietary Software
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets					3 years
CTEH
Business Acquisition [Line Items]
Number of common stock shares issued in connection with business acquisition		791,139		791,139
Percentage of interests acquired	100.00%
Revenue		$ 14,600,000		$ 14,600,000
Pre-tax income (loss)		$ 1,200,000		$ 1,200,000
CTEH | External Proprietary Software
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
CTEH | Customer Relationships
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	15 years
CTEH | Trade Names
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
CTEH | Covenants Not to Compete
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	5 years
CTEH | Proprietary Software
Business Acquisition [Line Items]
Weighted average useful lives for acquired intangible assets	3 years
CTEH | 2020 Earn Out
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, basis for amount				The first year earnout is to be calculated at twelve times CTEH’s 2020 EBITDA (as defined in the purchase agreement) in excess of $18.3 million, with a maximum first year earn-out payment of $50.0 million.
Business combination, contingent consideration arrangements, description				The 2020 earn out was initially payable 100% in common stock, but as a result of the completion of the Company’s IPO (Note 23), 50% of any 2020 earnout payment will be payable in cash and 50% will be payable, at the Company’s election, in cash or shares of common stock.
Business combination, minimum EBITDA for contingent consideration arrangements	$ 18,300,000
Business combination, earn-out payment, maximum	$ 50,000,000
Percentage of earn out payable in common stock	100.00%
Percentage of earn out payable in cash, as result of completing of IPO	50.00%
Percentage of earn out payable in cash or shares, as a result of completion of IPO, at company's election	50.00%
CTEH | 2021 Earn Out
Business Acquisition [Line Items]
Business combination, contingent consideration arrangements, basis for amount				The second year earn-out is to be calculated at ten times CTEH’s 2021 EBITDA in excess of actual 2020 EBITDA (with actual 2020 EBITDA subject to a minimum of $18.3 million and a maximum of $22.5 million), with a maximum second year earn-out payment of $30.0 million.
Business combination, contingent consideration arrangements, description				The 2021 earn out, if any, is payable 100% in cash. The current portion of the contingent consideration is recorded in accounts payable and other accrued liabilities. The long term portion of the contingent consideration is recorded in other non-current liabilities.
Business combination, earn-out payment, maximum	$ 30,000,000
Percentage of earn out payable in cash	100.00%
CTEH | Minimum | 2020 Earn Out
Business Acquisition [Line Items]
Business combination, actual EBITDA	$ 18,300,000
CTEH | Maximum [Member] | 2020 Earn Out
Business Acquisition [Line Items]
Business combination, actual EBITDA	$ 22,500,000
CTEH | Convertible And Redeemable Series A-2 Preferred Stock
Business Acquisition [Line Items]
Number of common stock shares issued in connection with business acquisition					791,139
TES
Business Acquisition [Line Items]
Percentage of interests acquired						100.00%
TESUS
Business Acquisition [Line Items]
Percentage of interests acquired						100.00%
AWS
Business Acquisition [Line Items]
Percentage of interests acquired			100.00%		100.00%

Business Acquisitions - Summary

Business Acquisitions - Summary of Elements of Purchase Price of Acquisitions (Details) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Apr. 30, 2020	Jun. 30, 2019
Business Acquisition [Line Items]
Cash		$ 28,562
Common Stock		3,363
Other Purchase Price Components		1,670
Contingent Consideration		5,388
Total Purchase Price		38,983
CTEH
Business Acquisition [Line Items]
Cash	$ 175,000
Common Stock	25,000
Other Purchase Price Component	(2,884)
Contingent Consideration Current	34,451
Contingent Consideration Long Term	10,543
Total Purchase Price	$ 242,110
Golden
Business Acquisition [Line Items]
Cash		1,500
Contingent Consideration		477
Total Purchase Price		1,977
TES
Business Acquisition [Line Items]
Cash		2,359
Common Stock		322
Other Purchase Price Components		25
Contingent Consideration		4,911
Total Purchase Price		7,617
TESUS
Business Acquisition [Line Items]
Cash		18,683
Common Stock		3,041
Other Purchase Price Components		1,495
Total Purchase Price		23,219
AWS
Business Acquisition [Line Items]
Cash		6,020
Other Purchase Price Components		150
Total Purchase Price		$ 6,170

Business Acquisitions - Summa_2

Business Acquisitions - Summary of Purchase Price Attributable to Acquisitions (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Apr. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Cash				$ 1,863
Accounts receivable				2,670
Other current assets				31
Current assets				4,564
Property plant and equipment				2,450
Goodwill	$ 273,096		$ 127,058	17,893
Total assets				41,414
Current liabilities				748
Total liabilities				2,431
Purchase price				38,983
Non- current liabilities				1,683
Customer Relationships
Business Acquisition [Line Items]
Intangible assets				11,823
Trade Names
Business Acquisition [Line Items]
Intangible assets				463
Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets				1,661
Proprietary Software
Business Acquisition [Line Items]
Intangible assets				$ 2,560
CTEH
Business Acquisition [Line Items]
Cash		$ 1,527
Accounts receivable		17,059
Other current assets		1,265
Current assets		19,851
Property plant and equipment		7,042
Goodwill		146,038
Total assets		251,831
Current liabilities		9,721
Total liabilities		9,721
Purchase price		242,110
CTEH | Customer Relationships
Business Acquisition [Line Items]
Intangible assets		56,000
CTEH | Trade Names
Business Acquisition [Line Items]
Intangible assets		4,200
CTEH | Covenants Not to Compete
Business Acquisition [Line Items]
Intangible assets		4,000
CTEH | Proprietary Software
Business Acquisition [Line Items]
Intangible assets		$ 14,700

Business Acquisitions - Summa_3

Business Acquisitions - Summary of Supplemental Unaudited Pro-Forma Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Business Acquisition [Line Items]
Revenues	$ 73,766	$ 57,401	$ 134,797	$ 108,355
Net income (loss)	13,224	(322)	(28,024)	(5,564)
Acquisition Proforma
Business Acquisition [Line Items]
Revenues	31,253	59,565	31,253	88,908
Net income (loss)	10,288	19,971	10,288	25,959
Consolidated Proforma
Business Acquisition [Line Items]
Revenues	105,019	116,966	166,050	197,263
Net income (loss)	$ 23,512	$ 19,649	$ (17,736)	$ 20,395

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Schedule of Amounts Related to Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Goodwill [Line Items]
Balance	$ 127,058
Goodwill acquired during the period	146,038
Balance	273,096
Assessment, Permitting and Response
Goodwill [Line Items]
Balance	15,173
Goodwill acquired during the period	146,038
Balance	161,211
Measurement and Analysis
Goodwill [Line Items]
Balance	68,628
Balance	68,628
Remediation and Reuse Segment
Goodwill [Line Items]
Balance	43,257
Balance	$ 43,257

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Amounts Related to Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Gross Balance	$ 248,597	$ 168,716
Accumulated Amortization	79,323	66,167
Total Intangible Assets—Net	169,274	102,549
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Gross Balance	164,782	108,782
Accumulated Amortization	44,665	36,700
Total Intangible Assets—Net	$ 120,117	$ 72,082
Customer Relationships | Minimum
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	7 years	7 years
Customer Relationships | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	15 years	10 years
Covenants Not to Compete
Finite Lived Intangible Assets [Line Items]
Gross Balance	$ 29,832	$ 25,832
Accumulated Amortization	19,424	17,572
Total Intangible Assets—Net	$ 10,408	$ 8,260
Covenants Not to Compete | Minimum
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	4 years	4 years
Covenants Not to Compete | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Trade Names
Finite Lived Intangible Assets [Line Items]
Gross Balance	$ 16,943	$ 12,738
Accumulated Amortization	11,518	10,230
Total Intangible Assets—Net	$ 5,425	$ 2,508
Trade Names | Minimum
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	1 year	1 year
Trade Names | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years	5 years
Proprietary Software
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life		3 years
Gross Balance	$ 19,561	$ 3,885
Accumulated Amortization	2,865	1,359
Total Intangible Assets—Net	$ 16,696	$ 2,526
Proprietary Software | Minimum
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	3 years
Proprietary Software | Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	5 years
Patent
Finite Lived Intangible Assets [Line Items]
Estimated Useful Life	16 years	16 years
Gross Balance	$ 17,479	$ 17,479
Accumulated Amortization	851	306
Total Intangible Assets—Net	$ 16,628	$ 17,173

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense	$ 7.8	$ 4.5	$ 13.3	$ 9.1

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Schedule of Future Amortization Expense (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
2020 (remaining)	$ 15,106
2021	28,043
2022	23,958
2023	20,005
2024	16,929
Thereafter	65,233
Total Intangible Assets—Net	$ 169,274	$ 102,549

Accounts Payable and Other Ac_3

Accounts Payable and Other Accrued Liabilities - Summary of Accounts Payable and Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accounts payable	$ 12,255	$ 15,034
Accrued expenses	9,931	10,733
Contract liabilities	7,736	3,314
Other current liabilities	303	504
Total accounts payable and other accrued liabilities	$ 30,225	$ 29,585

Accrued Payroll and Benefits -

Accrued Payroll and Benefits - Schedule of Accrued Payroll and Benefits (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Accrued bonuses	$ 3,810	$ 3,449
Accrued paid time off	2,206	2,154
Accrued payroll	7,174	4,470
Accrued other	2,040	959
Total accrued payroll and benefits	$ 15,230	$ 11,032

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Annual effective tax rate ("ETR") from continuing operations	(15.30%)	84.20%	14.90%	14.00%
Federal statutory rate			21.00%
Income tax benefits	$ 1,759,000	$ 1,712,000	$ 4,911,000	$ 896,000
Net deferred tax assets, valuation allowance	0		0		$ 0
Uncertain tax positions	$ 0		$ 0

Warrant Options - Additional In

Warrant Options - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Apr. 30, 2020	Apr. 13, 2020	Dec. 31, 2019	Oct. 31, 2018	Oct. 19, 2018
Class Of Warrant Or Right [Line Items]
Period between issuance and expiration of outstanding warrant					10 years
Redeemable Series A-1 Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants to purchase common stock							534,240	534,240
Warrant exercise price per share							$ 0.01
Period between issuance and expiration of outstanding warrant							10 years
Fair value of warrants		$ 16.9				$ 16.9
Warrants exercised in full for cash, date		Jul. 30, 2020
Redeemable Series A-1 Preferred Stock | Other Income (Expense)
Class Of Warrant Or Right [Line Items]
Fair value adjustment of warrants	$ 1.5		$ 1.5
Redeemable Series A-2 Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants to purchase common stock				1,351,960
Warrant exercise price per share				$ 0.01
Period between issuance and expiration of outstanding warrant				10 years
Fair value of warrants		$ 30.1
Warrants exercised in full for cash, date		Jul. 30, 2020
Aggregate value to determine number of shares underlying the warrant and issuable upon exercise of warrants		$ 30

Contingent Put Option - Additio

Contingent Put Option - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Fair value changes in the contingent put option	$ (22,602)	$ 7,025
Redeemable Series A-1 Preferred Stock
Fair value changes in the contingent put option		14,100	$ 7,100
Changes in fair value	$ 22,600	$ 7,000

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Apr. 13, 2020	Dec. 31, 2019
Line Of Credit Facility [Line Items]
Total debt		$ 225,000
Capital leases	$ 3,899		$ 3,765
Other leases	5		12
Less deferred debt issuance costs	(4,582)		(1,052)
Total debt	202,742		152,189
Less current portion of long term debt	(4,653)		(7,143)
Long-term debt, less current portion	198,089		145,046
Term Loan Facility
Line Of Credit Facility [Line Items]
Total debt	175,000	175,000	48,750
Revolving Line of Credit
Line Of Credit Facility [Line Items]
Total debt	25,000	$ 50,000	97,590
Equipment Line Of Credit
Line Of Credit Facility [Line Items]
Total debt	$ 3,420		$ 3,124

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($)

Sep. 30, 2022

Sep. 30, 2021

Sep. 30, 2020

Apr. 13, 2020

Jun. 30, 2020

Jun. 30, 2019

Jun. 30, 2020

Jun. 30, 2019

Dec. 31, 2019

Dec. 31, 2022

Dec. 31, 2021

Mar. 31, 2020

May 16, 2019

Mar. 12, 2019

Line Of Credit Facility [Line Items]

Line of credit

$ 225,000,000

Line of credit facility maturity date

Apr. 30, 2025

Debt instrument, repayments term

quarterly

Maximum consolidated leverage ratio

425.00%

425.00%

400.00%

Minimum consolidated fixed charge coverage ratio

125.00%

125.00%

Weighted average interest rate

5.91%

5.91%

Capital Lease Obligations

Line Of Credit Facility [Line Items]

Capital leased assets, gross

$ 7,300,000

$ 7,300,000

$ 6,900,000

Capital leases, income statement, amortization expense

600,000

$ 300,000

$ 1,100,000

$ 600,000

Minimum | Capital Lease Obligations

Line Of Credit Facility [Line Items]

Capital lease asset estimated useful lives

4 years

Maximum [Member] | Capital Lease Obligations

Line Of Credit Facility [Line Items]

Capital lease asset estimated useful lives

6 years

Forecast

Line Of Credit Facility [Line Items]

Debt instrument, repayments

$ 1,600,000

$ 1,100,000

$ 500,000

Maximum consolidated leverage ratio

375.00%

400.00%

Incremental Term Loans

Line Of Credit Facility [Line Items]

Line of credit facility, maximum borrowing capacity

$ 100,000,000

Incremental Term Loans | Minimum

Line Of Credit Facility [Line Items]

Percentage of pari passu debt of all lenders to be held by unitranche lenders

70.00%

Leverage Ratio Greater Than Equal to 3.25

Line Of Credit Facility [Line Items]

Percentage of prepayment on excess cash flow less voluntary prepayments of term loan

50.00%

Consolidated fixed leverage ratio

3.25%

Leverage Ratio Less Than 3.00

Line Of Credit Facility [Line Items]

Percentage of prepayment on excess cash flow less voluntary prepayments of term loan

25.00%

Consolidated fixed leverage ratio

3.00%

Prior Senior Secured Credit Facility

Line Of Credit Facility [Line Items]

Weighted average interest rate

4.95%

Loss on extinguishment

$ 1,400,000

Debt fee paid

400,000

Unamortized debt issuance costs

1,000,000

Equipment Line Of Credit

Line Of Credit Facility [Line Items]

Line of credit facility, maximum borrowing capacity

$ 2,000,000

Canadian Equipment Line Of Credit

Line Of Credit Facility [Line Items]

Line of credit facility, maximum borrowing capacity

$ 1,000,000

LIBOR Plus | Prior Senior Secured Credit Facility

Line Of Credit Facility [Line Items]

Interest rate

1.00%

Federal Funds Rate Plus | Prior Senior Secured Credit Facility

Line Of Credit Facility [Line Items]

Interest rate

0.50%

Term Loan Facility

Line Of Credit Facility [Line Items]

Line of credit

$ 175,000,000

175,000,000

$ 175,000,000

$ 48,750,000

Term Loan Facility | Prior Senior Secured Credit Facility

Line Of Credit Facility [Line Items]

Line of credit

50,000,000

Term Loan Facility | LIBOR Plus

Line Of Credit Facility [Line Items]

Interest rate

5.00%

Term Loan Facility | Base Rate Plus

Line Of Credit Facility [Line Items]

Interest rate

4.00%

Term Loan Facility | LIBOR Floor

Line Of Credit Facility [Line Items]

Interest rate

1.00%

Revolving Line of Credit

Line Of Credit Facility [Line Items]

Line of credit

$ 50,000,000

$ 25,000,000

$ 25,000,000

97,590,000

Line of credit facility unused commitment fee

0.35%

Revolving Line of Credit | Prior Senior Secured Credit Facility

Line Of Credit Facility [Line Items]

Line of credit

$ 130,000,000

Revolving Line of Credit | LIBOR Plus

Line Of Credit Facility [Line Items]

Interest rate

3.50%

Revolving Line of Credit | Base Rate Plus

Line Of Credit Facility [Line Items]

Interest rate

2.50%

Debt - Schedule of Applicable P

Debt - Schedule of Applicable Percentages (Details) - Prior Senior Secured Credit Facility	12 Months Ended
	Dec. 31, 2019
Pricing Tier 1
Line Of Credit Facility [Line Items]
Commitment Fee	0.50%
Pricing Tier 1 | Minimum
Line Of Credit Facility [Line Items]
Consolidated Leverage Ratio	375.00%
Pricing Tier 1 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee
Line Of Credit Facility [Line Items]
Interest rate	4.00%
Pricing Tier 1 | Daily Floating Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	4.00%
Pricing Tier 1 | Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	3.00%
Pricing Tier 2
Line Of Credit Facility [Line Items]
Commitment Fee	0.50%
Pricing Tier 2 | Maximum [Member]
Line Of Credit Facility [Line Items]
Consolidated Leverage Ratio	375.00%
Pricing Tier 2 | Minimum
Line Of Credit Facility [Line Items]
Consolidated Leverage Ratio	300.00%
Pricing Tier 2 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee
Line Of Credit Facility [Line Items]
Interest rate	3.50%
Pricing Tier 2 | Daily Floating Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	3.50%
Pricing Tier 2 | Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	2.50%
Pricing Tier 3
Line Of Credit Facility [Line Items]
Commitment Fee	0.40%
Pricing Tier 3 | Maximum [Member]
Line Of Credit Facility [Line Items]
Consolidated Leverage Ratio	300.00%
Pricing Tier 3 | Minimum
Line Of Credit Facility [Line Items]
Consolidated Leverage Ratio	225.00%
Pricing Tier 3 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee
Line Of Credit Facility [Line Items]
Interest rate	3.00%
Pricing Tier 3 | Daily Floating Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	3.00%
Pricing Tier 3 | Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	2.00%
Pricing Tier 4
Line Of Credit Facility [Line Items]
Commitment Fee	0.30%
Pricing Tier 4 | Maximum [Member]
Line Of Credit Facility [Line Items]
Consolidated Leverage Ratio	225.00%
Pricing Tier 4 | Eurodollar Rate Loans and LIBOR Letter of Credit Fee
Line Of Credit Facility [Line Items]
Interest rate	2.50%
Pricing Tier 4 | Daily Floating Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	2.50%
Pricing Tier 4 | Rate Loans
Line Of Credit Facility [Line Items]
Interest rate	1.50%

Debt - Schedule of Capital Leas

Debt - Schedule of Capital Leases Mature by 2025 (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Line Of Credit Facility [Line Items]
Payments	$ 8,257
Interest	938
Principal	7,319
2021
Line Of Credit Facility [Line Items]
Payments	2,863
Interest	397
Principal	2,466
2022
Line Of Credit Facility [Line Items]
Payments	2,424
Interest	300
Principal	2,124
2023
Line Of Credit Facility [Line Items]
Payments	1,872
Interest	182
Principal	1,690
2024
Line Of Credit Facility [Line Items]
Payments	940
Interest	57
Principal	883
2025
Line Of Credit Facility [Line Items]
Payments	158
Interest	2
Principal	$ 156

Debt - Schedule of Aggregate An

Debt - Schedule of Aggregate Annual Maturities of Long-Term Debt (Details) $ in Thousands	Jun. 30, 2020USD ($)
Debt Disclosure [Abstract]
2021	$ 4,653
2022	2,130
2023	1,690
2024	883
2025	197,968
Total	$ 207,324

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - Level 3 - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	$ 98,010	$ 32,971	$ 16,226	$ 15,572
Compound Embedded Option
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Assets	8,605
Contingent Consideration Payable, Current
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	36,395	8,614	1,859	2,754
Contingent Consideration Payable, Long Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	9,117	379
Warrant Options
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	46,978	16,878	$ 14,367	$ 12,818
Contingent Put Option
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Level 3 Liabilities	$ 14,125	$ 7,100

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - Level 3 - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Total
Beginning balance	$ 32,971	$ 15,572
Payment of contingent consideration payable	(12,250)
Foreign currency translation of contingent consideration payment	(208)
Acquisitions	44,994	31
Series A-2 compound embedded option	(9,361)
Issuance of warrant option	30,099
Changes in fair value included in earnings	11,765	623
Ending balance	98,010	16,226
Contingent Put Option
Level 3 Liabilities
Beginning balance	7,100
Changes in fair value included in earnings	7,025
Ending balance	14,125
Contingent Consideration Current
Level 3 Liabilities
Beginning balance	8,614	2,754
Payment of contingent consideration payable	(12,250)
Foreign currency translation of contingent consideration payment	(208)
Acquisitions	34,451	31
Reclass of long term to short term contingent liabilities	180
Changes in fair value included in earnings	5,608	(926)
Ending balance	36,395	1,859
Contingent Consideration Long Term
Level 3 Liabilities
Beginning balance	379
Acquisitions	10,543
Reclass of long term to short term contingent liabilities	(180)
Changes in fair value included in earnings	(1,625)
Ending balance	9,117
Warrant Options
Level 3 Liabilities
Beginning balance	16,878	12,818
Issuance of warrant option	30,099
Changes in fair value included in earnings	1	1,549
Ending balance	46,978	$ 14,367
Compound Embedded Option
Level 3 Assets
Series A-2 compound embedded option	9,361
Changes in fair value included in earnings	(756)
Ending balance	$ 8,605

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Summary of Fair Value of Warrant Options Associated with Issuance of Redeemable Series A-1 Preferred Stock (Details)	Jun. 30, 2020	Apr. 13, 2020	Jun. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used in calculating fair value of the warrant option		10 years
Common Stock Value (per Share)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used in calculating fair value of the warrant option	31.60		26.90
Expected Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used in calculating fair value of the warrant option	0.4364		0.4917
Risk-free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used in calculating fair value of the warrant option	0.0066		0.0200
Expected Life (Years)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used in calculating fair value of the warrant option	10 years		10 years

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments And Contingencies [Line Items]
Lessee operating lease, expiration year			2028
Rent expense	$ 2.1	$ 1.8	$ 4.2	$ 3.6
Office Equipment
Commitments And Contingencies [Line Items]
Lessee operating lease, expiration year			2025

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Leases (Details) $ in Thousands	Jun. 30, 2020USD ($)
Commitments And Contingencies [Line Items]
2021	$ 6,439
2022	5,157
2023	3,714
2024	2,092
2025 and thereafter	1,576
Total	18,978
Rent
Commitments And Contingencies [Line Items]
2021	6,095
2022	4,846
2023	3,513
2024	2,030
2025 and thereafter	1,573
Total	18,057
Office Equipment
Commitments And Contingencies [Line Items]
2021	344
2022	311
2023	201
2024	62
2025 and thereafter	3
Total	$ 921

Redeemable Series A-1 Preferr_2

Redeemable Series A-1 Preferred Stock - Additional Information (Details) - USD ($)	Apr. 13, 2020	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Oct. 31, 2018	Oct. 19, 2018
Temporary Equity [Line Items]
Share price		$ 31.60		$ 26.90
Percentage of dividends paid in cash	14.20%
Redeemable Series A-1 Preferred Stock
Temporary Equity [Line Items]
Temporary equity, shares issued		12,000	12,000			12,000
Temporary equity, par value per share		$ 0.0001	$ 0.0001			$ 0.0001
Warrants to purchase common stock					534,240	534,240
Temporary equity, liquidation preference per share		$ 10,000				$ 10,000
Temporary equity, maturity month and year	2024-10
Temporary equity, penalty term	3 years
Temporary equity, penalty term upon full exercise of warrant	2 years
Percentage of increase in accrued dividend	1.00%
Temporary equity, covenant description		The Redeemable Series A-1 Preferred Stock contains restrictive covenants. As of June 30, 2020 and December 31, 2019, the Company was subject to a consolidated total leverage ratio (including the outstanding principal and accrued dividend on the Redeemable Series A-1 Preferred Stock) limit of less than 10.0 times as of the end of any fiscal quarter ending until maturity. The Company was in compliance with the covenants as of June 30, 2020 and December 31, 2019.
Percentage of dividends paid in cash		15.00%
Percentage of dividends accrued		14.20%
Minimum guaranteed dividends upon optional redemption event other than in connection with IPO		3 years
Accrued and unpaid dividends		$ 32,200,000	$ 21,900,000
Temporary equity, accretion value		$ 34,300,000
Redeemable Series A-1 Preferred Stock | IPO
Temporary Equity [Line Items]
Minimum guaranteed dividends on redemption		2 years
Redeemable Series A-1 Preferred Stock | Maximum [Member]
Temporary Equity [Line Items]
Temporary equity, aggregate amount of redemption requirement	$ 50,000,000
Percentage of accumulated dividends payable in common stock upon IPO	50.00%
Share price	$ 31.60
Percentage of dividend payable in cash	15.00%
Redeemable Series A-1 Preferred Stock | Minimum
Temporary Equity [Line Items]
Percentage of dividend payable in cash	9.00%

Convertible and Redeemable Se_2

Convertible and Redeemable Series A-2 Preferred Stock - Additional Information (Details) - USD ($)	Jul. 27, 2020	Apr. 13, 2020	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Oct. 31, 2018	Oct. 19, 2018
Temporary Equity [Line Items]
Period between issuance and expiration of outstanding warrant		10 years
Proceeds from the Series A-2 and Warrant		$ 175,000,000
Percentage of dividends accrued		14.20%
Compound embedded derivative, fair value net			$ 8,605,000	$ 8,605,000
Convertible And Redeemable Series A-2 Preferred Stock
Temporary Equity [Line Items]
Temporary equity, shares issued		17,500	17,500	17,500	0
Temporary equity, par value per share		$ 0.0001	$ 0.0001	$ 0.0001	$ 0.0001
Debt fee paid		$ 1,300,000
Percentage of dividends accrued		15.00%
Temporary equity, covenant description				The Convertible and Redeemable Series A-2 Preferred Stock contains restrictive covenants that include: (i) maximum 4.0 times debt incurrence test and (ii) 10.0 times total leverage cap (inclusive of the outstanding balance on the Convertible and Redeemable Series A-2 Preferred Stock).
Maximum number of times debt incurrence test		4
Number of times total leverage cap		10
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) $50.0 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. In the event the Company redeemed all or a portion of the Convertible and Redeemable Series A-2 Preferred Stock prior to the three year anniversary of the issuance date, such redemption amount shall include principal, accrued but unpaid interest and a make whole payment such that the aggregate redemption amount reflects three years of dividends.
Aggregate stated value of stock redeemed			$ 50,000,000	$ 50,000,000
Percentage of discount on common stock market price				15.00%
Percentage of dividend rate steps downs per year				9.00%
Number of times increase in debt incurrence test ratio				4.5
Percentage of increase in accrued dividend			1.00%	1.00%
Aggregate liquidation preference			$ 181,213,000	$ 181,213,000	$ 0
Compound embedded derivative, fair value net			8,600,000	8,600,000
Convertible And Redeemable Series A-2 Preferred Stock | Other Income (Expense)
Temporary Equity [Line Items]
Compound embedded derivative, change in value			$ 800,000	$ 800,000
Convertible And Redeemable Series A-2 Preferred Stock | Maximum [Member]
Temporary Equity [Line Items]
Percentage of dividend payable in cash			15.00%	15.00%
Convertible And Redeemable Series A-2 Preferred Stock | Minimum
Temporary Equity [Line Items]
Percentage of dividend payable in cash			9.00%	9.00%
Convertible And Redeemable Series A-2 Preferred Stock | Subsequent Event
Temporary Equity [Line Items]
Percentage of dividends accrued	9.00%
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			$ 60,000,000	$ 60,000,000
Convertible And Redeemable Series A-2 Preferred Stock | Year 5
Temporary Equity [Line Items]
Temporary equity convertible into common stock			60,000,000	60,000,000
Convertible And Redeemable Series A-2 Preferred Stock | Year 6
Temporary Equity [Line Items]
Temporary equity convertible into common stock			$ 120,000,000	$ 120,000,000
Convertible And Redeemable Series A-2 Preferred Stock | Private Offering
Temporary Equity [Line Items]
Percentage of dividend rate steps downs per year				9.00%
Number of times increase in debt incurrence test ratio				4.5
Mandatory redemption date extended from date of issuance				5 years
Redeemable Series A-1 Preferred Stock
Temporary Equity [Line Items]
Temporary equity, shares issued			12,000	12,000	12,000		12,000
Temporary equity, par value per share			$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001
Period between issuance and expiration of outstanding warrant						10 years
Percentage of dividends accrued				15.00%
Temporary equity, covenant description				The Redeemable Series A-1 Preferred Stock contains restrictive covenants. As of June 30, 2020 and December 31, 2019, the Company was subject to a consolidated total leverage ratio (including the outstanding principal and accrued dividend on the Redeemable Series A-1 Preferred Stock) limit of less than 10.0 times as of the end of any fiscal quarter ending until maturity. The Company was in compliance with the covenants as of June 30, 2020 and December 31, 2019.
Temporary equity description				On the occurrence of (i)(x) before a private offering which results in a redemption in full of the Redeemable Series A-1 Preferred Stock, the four-and-a-half-year anniversary of the closing date or (y) after a private offering which results in a redemption in full of the Redeemable Series A-1 Preferred Stock, the five-year anniversary of the closing date, (ii) a change of control, (iii) a sale of the Company, (iv) a non-qualifying IPO, (v) any recapitalization of the Company (other than a redemption of the Redeemable Series A-1 Preferred Stock) or (vi) an event of noncompliance, as defined in the Series A-2 certificate of designation (each, a “mandatory redemption event”), the Company shall, at the option of the holders of a majority of the Convertible and Redeemable Series A-2 Preferred Stock, redeem all shares of the Convertible and Redeemable Series A-2 Preferred Stock, for cash, at a price per share of Convertible and Redeemable Series A-2 Preferred Stock equal to the applicable redemption price on such mandatory redemption date.
Percentage of increase in accrued dividend		1.00%
Aggregate liquidation preference			$ 152,199,000	$ 152,199,000	$ 141,898,000
Redeemable Series A-1 Preferred Stock | Maximum [Member]
Temporary Equity [Line Items]
Aggregate stated value of stock redeemed		$ 50,000,000
Percentage of dividend payable in cash		15.00%
Redeemable Series A-1 Preferred Stock | Minimum
Temporary Equity [Line Items]
Percentage of dividend payable in cash		9.00%
Redeemable Series A-1 Preferred Stock | Before Private Offering
Temporary Equity [Line Items]
Temporary equity redemption period				4 years 6 months
Redeemable Series A-1 Preferred Stock | After Private Offering
Temporary Equity [Line Items]
Temporary equity redemption period				5 years

Stockholders' Deficit - Additio

Stockholders' Deficit - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	May 31, 2015
Class Of Stock [Line Items]
Common stock, shares authorized	25,000,000		25,000,000		25,000,000
Common stock, par value	$ 0.000004		$ 0.000004		$ 0.000004
Shares issued average price per share	$ 31.60	$ 26.90	$ 31.60	$ 26.90
Total unrecognized stock compensation expense related to unvested options and restricted stock granted under the Plans	$ 6.5	$ 6.8	$ 6.5	$ 6.8
Unrecognized expense expected to be recognized period			2 years
Montrose Amended & Restated 2017 Stock Incentive Plan
Class Of Stock [Line Items]
Number of restricted stock shares issued			33,229	30,000
Montrose Amended & Restated 2017 Stock Incentive Plan | Restricted Stock
Class Of Stock [Line Items]
Restricted stock fair value market price per share			$ 31.60	$ 24
Shares of vested over period			1 year	3 years
Restricted shares became fully vested and released as common stock			0	0
Restricted shares outstanding	273,122	242,025	273,122	242,025
Forfeitures, cancellations or expirations of restricted shares	0	0	0	0
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
Montrose Amended and Restated 2013 Stock Option Plan
Class Of Stock [Line Items]
Shares outstanding from exercised options	205,100		205,100		201,600
CTEH
Class Of Stock [Line Items]
Number of common stock shares issued in connection with business acquisition	791,139		791,139
Shares issued average price per share	$ 31.60		$ 31.60
TES and TESUS
Class Of Stock [Line Items]
Number of common stock shares issued in connection with business acquisition		125,031		125,031
Shares issued average price per share		$ 26.90		$ 26.90
Private Offering
Class Of Stock [Line Items]
Warrants to purchase common stock						116,350
Warrant exercise price per share						$ 17.19
Employee Stock
Class Of Stock [Line Items]
Number of common stock shares issued in connection with exercise of certain options	3,500	13,750	3,500	15,000
Shares issued average exercise price per share	$ 6.03	$ 7.38	$ 6.03	$ 6.71

Stockholders' Deficit - Summary

Stockholders' Deficit - Summary of Number of Shares Authorized to be Issued and Available for Grant (Details) - shares	Jun. 30, 2020	Jun. 30, 2019
2017 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized to be issued	1,066,160	981,800
Shares available for grant	20,817	201,183
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized to be issued	2,050,244	2,074,604

Stockholders' Deficit - Schedul

Stockholders' Deficit - Schedule of Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	$ 1,140		$ 2,290	$ 2,522
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense		$ 1,294
2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	641	350	1,283	617
2017 Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	370	110	740	212
2013 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	129	834	267	1,693
Cost of Revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	403		828	638
Cost of Revenue | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense		352
Cost of Revenue | 2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	342	205	697	345
Cost of Revenue | 2013 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	61	147	131	293
Selling, General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	737		1,462	1,884
Selling, General and Administrative Expense | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense		942
Selling, General and Administrative Expense | 2017 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	299	145	586	272
Selling, General and Administrative Expense | 2017 Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	370	110	740	212
Selling, General and Administrative Expense | 2013 Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock compensation expense	$ 68	$ 687	$ 136	$ 1,400

Stockholders Deficit - Summary

Stockholders Deficit - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Montrose Amended & Restated 2017 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price per Share Beginning Balance	$ 24	$ 20	$ 20
Weighted-Average Exercise Price per Share Granted	32	24
Weighted-Average Exercise Price per Share Forfeitured/cancelled	20	24
Weighted-Average Exercise Price per Share Ending Balance	26	23	24	$ 20
Weighted-Average Exercise Price per Share Options vested and expected to vest	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 Beginning Balance	12	10	10
Weighted Average Grant Date Fair Value per Share Granted	12	13
Weighted Average Grant Date Fair Value per Share Ending Balance	$ 12	$ 12	$ 12	$ 10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contract Life (in Years) Outstanding	8 years 10 days		7 years 9 months 25 days
Weighted Average Remaining Contract Life (in Years) Options vested and expected to vest	8 years 6 months 25 days
Aggregate Intrinsic Value of In-The-Money Options Outstanding	$ 4,696	$ 1,151	$ 1,151
Aggregate Intrinsic Value of In-The-Money Options Outstanding	4,651	$ 2,136	$ 4,696	$ 1,151
Aggregate Intrinsic Value of In-The-Money Options vested and expected to vest	$ 4,651
Montrose Amended & Restated 2017 Stock Incentive Plan | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options to Purchase Common Stock Outstanding Beginning Balance	617,852	257,762	257,762
Options to Purchase Common Stock Granted	160,712	308,990
Options to Purchase Common Stock Forfeitured/cancelled	(5,500)	(14,800)
Options to Purchase Common Stock Outstanding Ending Balance	773,064	551,952	617,852	257,762
Options to Purchase Common Stock Options vested and expected to vest	773,064
Montrose Amended and Restated 2013 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-Average Exercise Price per Share Beginning Balance	$ 6	$ 6	$ 6
Weighted-Average Exercise Price per Share Forfeitured/cancelled	6	14
Weighted-Average Exercise Price per Share Expired	6	8
Weighted-Average Exercise Price per Share Exercised	6	5
Weighted-Average Exercise Price per Share Ending Balance	6	6	6	$ 6
Weighted-Average Exercise Price per Share Options vested and expected to vest	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 Beginning Balance	1	1	1
Weighted Average Grant Date Fair Value per Share Ending Balance	$ 1	$ 1	$ 1	$ 1
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contract Life (in Years) Outstanding	5 years 10 months 28 days	6 years 10 months 13 days	6 years 4 months 24 days	7 years 3 months 18 days
Weighted Average Remaining Contract Life (in Years) Options vested and expected to vest	5 years 5 months 4 days
Aggregate Intrinsic Value of In-The-Money Options Outstanding	$ 46,617	$ 33,290	$ 33,290
Aggregate Intrinsic Value of In-The-Money Options Exercised	89	283
Aggregate Intrinsic Value of In-The-Money Options Outstanding	46,276	$ 38,235	$ 46,617	$ 33,290
Aggregate Intrinsic Value of In-The-Money Options vested and expected to vest	$ 46,276
Montrose Amended and Restated 2013 Stock Option Plan | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options to Purchase Common Stock Outstanding Beginning Balance	1,855,469	1,900,404	1,900,404
Options to Purchase Common Stock Forfeitured/cancelled	(1,250)	(12,600)
Options to Purchase Common Stock Expired	(8,550)	(4,475)
Options to Purchase Common Stock Exercised	(3,500)	(11,385)
Options to Purchase Common Stock Outstanding Ending Balance	1,842,169	1,871,944	1,855,469	1,900,404
Options to Purchase Common Stock Options vested and expected to vest	1,842,169

Stockholders Deficit - Summar_2

Stockholders Deficit - Summary of Weighted Average Assumptions Used in Black-Sholes Option-pricing Model (Details) - $ / shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Common stock value (per share)	$ 31.60	$ 26.90
Expected volatility	45.26%	48.42%
Risk-free interest rate	0.49%	2.19%
Expected life (years)	7 years	7 years
Forfeiture rate	0.00%	0.00%
Dividend rate	0.00%	0.00%

Stockholders' Deficit - Sched_2

Stockholders' Deficit - Schedule of Common Stock Reserved for Future Issuance (Details) - shares	Jun. 30, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	5,118,954	3,706,994
Warrants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	2,002,550	650,590
Montrose 2013 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	2,050,244	2,058,619
Montrose 2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,066,160	997,785

Net Income (Loss) Per Share - C

Net Income (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				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ 13,224	$ (41,248)	$ (322)	$ (5,242)	$ (28,024)	$ (5,564)
Accretion of redeemable preferred stock	(5,644)		(4,777)		(11,059)	(9,311)
Net income (loss) attributable to common stockholders - basic and diluted	$ 7,580		$ (5,099)		$ (39,083)	$ (14,875)
Weighted-average common shares outstanding - basic	10,649		8,647		9,718	8,602
Net income (loss) per share attributable to common stockholders - basic	$ 0.71		$ (0.59)		$ (4.02)	$ (1.73)
Weighted-average common shares outstanding - diluted	19,139		8,647		9,718	8,602
Net income (loss) per share attributable to common stockholders - diluted	$ 0.40		$ (0.59)		$ (4.02)	$ (1.73)

Net Income (Loss) Per Share - E

Net Income (Loss) Per Share - Equity Shares Excluded from Calculation of Diluted Net Loss per Share Attributable to Common Stockholders (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of loss per share amount	2,685,439	1,960,887
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of loss per share amount	24,362	168,001
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of loss per share amount	116,350	116,350

Segment Information - Additiona

Segment Information - Additional Information (Details)	6 Months Ended
	Jun. 30, 2020Segment
Segment Reporting [Abstract]
Number of operating segments	3
Number of reportable segments	3

Segment Information - Component

Segment Information - Components of Segment Revenues and Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Segment Revenues	$ 73,766	$ 57,401	$ 134,797	$ 108,355
Segment Adjusted EBITDA	13,895	8,538	19,448	13,610
Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	73,766	57,401	134,797	108,355
Segment Adjusted EBITDA	18,979	12,380	30,088	20,983
Assessment, Permitting and Response | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	18,631	5,028	23,161	9,603
Segment Adjusted EBITDA	4,989	2,002	6,431	3,996
Measurement and Analysis | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	37,036	34,617	73,476	62,948
Segment Adjusted EBITDA	11,615	7,979	19,176	12,112
Remediation and Reuse | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	18,099	17,756	38,160	35,804
Segment Adjusted EBITDA	2,375	2,399	4,481	4,875
Corporate and Other
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	$ (5,084)	$ (3,842)	$ (10,640)	$ (7,373)

Segment Information - Reconcili

Segment Information - Reconciliation of Segment Measure to Income (Loss) Before Benefit from Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting [Abstract]
Total	$ 13,895	$ 8,538	$ 19,448	$ 13,610
Interest Expense, net	(5,260)	(1,181)	(7,853)	(2,460)
Income tax benefit	1,759	1,712	4,911	896
Depreciation and Amortization	(9,784)	(6,401)	(17,344)	(12,850)
Stock-based compensation	(1,140)	(1,294)	(2,290)	(2,522)
Start-up losses and investment in new services	(296)	(143)	(675)	(457)
Acquisition costs	(2,454)	(857)	(3,761)	(1,072)
Fair value changes in contingent put option	22,602		(7,025)
Fair value changes in warrant options	(4)	(1,549)	(2)	(1,549)
Fair value changes in compound embedded option	(756)		(756)
Fair value changes in contingent liabilities	(3,983)	926	(3,983)	926
Short term purchase accounting fair value adjustment to deferred revenue			(243)
IPO preparation costs		(73)	(531)	(86)
Discontinued services	(1,078)		(7,496)
Other expenses			(147)
Expenses related to financing transactions	(277)		(277)
Net Income (Loss)	$ 13,224	$ (322)	$ (28,024)	$ (5,564)

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Related Party Transaction [Line Items]
Payment to related party		$ 120,000	$ 119,000	$ 279,000
Amount due to related party	$ 0		0
Acquisition Targets
Related Party Transaction [Line Items]
Payment to related party	$ 0	$ 100,000	$ 100,000	$ 100,000

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		5 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	May 22, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
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	$ 0.4	$ 0.7		$ 1.2	$ 1.3
Minimum
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan participant's compensation percent			3.00%
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan participant's compensation percent			4.00%

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 27, 2020	Jun. 30, 2020	Jun. 30, 2019	Jul. 30, 2020	Jul. 14, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Common stock, authorized		25,000,000				25,000,000
Share price		$ 31.60	$ 26.90
Net proceeds from sale of common stock		$ 21	$ 95
Payment of underwriting discounts and commissions and offering expenses		$ 1,462
Subsequent Event
Subsequent Event [Line Items]
Common stock, authorized					190,000,000
Common stock shares sold under IPO	1,786,739
Warrants to purchase common stock				2,534,239
Warrant exercise price per share				$ 30,000
Payments for repurchase of redeemable preferred stock in cash	$ 131,800
Subsequent Event | Convertible And Redeemable Series A-2 Preferred Stock
Subsequent Event [Line Items]
Share price	$ 15
Warrants to purchase common stock	1,999,999
Increase of shares	648,039
Subsequent Event | IPO
Subsequent Event [Line Items]
Common stock shares sold under IPO	11,500,000
Share price	$ 15
Net proceeds from sale of common stock	$ 161,300
Payment of underwriting discounts and commissions and offering expenses	$ 9,800
Subsequent Event | Underwriters
Subsequent Event [Line Items]
Common stock shares sold under IPO	1,500,000