Segment Information - Components of Segment Revenues and Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Segment Revenues	$ 136,224	$ 73,766	$ 270,041	$ 134,797
Segment Adjusted EBITDA	20,963	13,895	37,762	19,448
Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	136,224	73,766	270,041	134,797
Segment Adjusted EBITDA	28,656	18,979	51,801	30,088
Assessment, Permitting and Response | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	70,705	18,631	145,967	23,161
Segment Adjusted EBITDA	14,856	4,989	30,660	6,431
Measurement and Analysis | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	39,117	37,036	72,557	73,476
Segment Adjusted EBITDA	9,491	11,615	14,351	19,176
Remediation and Reuse | Operating Segments
Segment Reporting Information [Line Items]
Segment Revenues	26,402	18,099	51,517	38,160
Segment Adjusted EBITDA	4,309	2,375	6,790	4,481
Corporate and Other
Segment Reporting Information [Line Items]
Segment Adjusted EBITDA	$ (7,693)	$ (5,084)	$ (14,039)	$ (10,640)