Goodwill and Intangible Assets

9 Months Ended

Sep. 30, 2020

Goodwill And Intangible Assets Disclosure [Abstract]

7. GOODWILL AND INTANGIBLE ASSETS

Amounts related to goodwill as of September 30, 2020 and December 31, 2019 are as follows:

	Assessment, Permitting and Response		Measurement 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		146,625		426		200		147,251
Balance as of September 30, 2020	$	161,798	$	69,054	$	43,457	$	274,309

Amounts related to finite-lived intangible assets as of September 30, 2020 and December 31, 2019 are as follows:

September 30, 2020	Estimated Useful Life	Gross Balance		Accumulated Amortization		Total Intangible Assets—Net
Finite lived intangible assets
Customer relationships	7–15 years	$	164,782	$	49,068	$	115,714
Covenants not to compete	4–5 years		29,942		20,444		9,498
Trade names	1–5 years		16,938		12,196		4,742
Proprietary software	3-5 years		20,808		4,915		15,893
Patent	16 years		17,479		1,125		16,354
Total other intangible assets—net		$	249,949	$	87,748	$	162,201

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 $7.6 million and $21.0 million for the three and nine months ended September 30, 2020, respectively and $5.3 million and $14.4 million for the three and nine months ended September 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)	$	7,543
2021		28,140
2022		24,053
2023		20,073
2024		16,951
Thereafter		65,441
	$	162,201