Goodwill and Intangible Assets

9 Months Ended

Sep. 30, 2021

Goodwill And Intangible Assets Disclosure [Abstract]

8. GOODWILL AND INTANGIBLE ASSETS

Amounts related to goodwill are as follows:

	Assessment, Permitting and Response		Measurement and Analysis		Remediation and Reuse		Total
Balance as of December 31, 2020	$	162,156	$	69,054	$	43,457	$	274,667
Goodwill acquired during the period		8,944		12,879		7,747		29,570
Balance as of September 30, 2021	$	171,100	$	81,933	$	51,204	$	304,237

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

September 30, 2021	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	2-15 years	$	189,103	$	67,328	$	121,775
Covenants not to compete	4-5 years		31,623		24,832		6,791
Trade names	1-5 years		19,778		15,107		4,671
Proprietary software	3-5 years		21,595		9,853		11,742
Patent	16 years		17,479		2,219		15,260
Total other intangible assets —net		$	279,578	$	119,339	$	160,239

December 31, 2020	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	7-15 years	$	164,782	$	53,446	$	111,336
Covenants not to compete	4-5 years		29,942		21,469		8,473
Trade names	1-5 years		16,938		12,849		4,089
Proprietary software	3-5 years		21,007		6,132		14,875
Patent	16 years		17,479		1,398		16,081
Total other intangible assets —net		$	250,148	$	95,294	$	154,854

Intangible assets with finite lives are stated at cost, less accumulated amortization and impairment losses, if any. These intangible assets are amortized using the straight-line method over the estimated useful lives of the assets. Amortization expense was $8.9 million and $25.9 million for the three and nine months ended September 30, 2021, respectively, and $7.6 million and $21.0 million for the three and nine months ended September 30, 2020, respectively.

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

December 31,
2021 (remaining)	$	8,463
2022		30,298
2023		24,407
2024		20,623
2025		14,225
2026 and thereafter		62,223
Total	$	160,239