Segment Information - Components of Segment Revenues and Adjusted EBITDA (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Segment Revenues	$ 108,741	$ 84,705	$ 73,766	$ 61,031	$ 67,876	$ 57,623	$ 57,401	$ 50,954	$ 328,243	$ 233,854	$ 188,805
Segment Adjusted EBITDA									54,476	31,495	21,817
Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues									328,243	233,854	188,805
Segment Adjusted EBITDA									72,532	45,136	33,518
Assessment, Permitting and Response | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues									98,521	21,071	3,663
Segment Adjusted EBITDA									24,208	7,572	1,339
Measurement and Analysis | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues									151,557	135,531	117,373
Segment Adjusted EBITDA									39,386	27,828	20,779
Remediation and Reuse | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues									78,165	77,252	67,769
Segment Adjusted EBITDA									8,938	9,736	11,400
Corporate and Other
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA									$ (18,056)	$ (13,641)	$ (11,701)