Segment Information - Operating Segment Results (Details) $ in Thousands	3 Months Ended						4 Months Ended		12 Months Ended
	Sep. 07, 2019 USD ($)	Jun. 15, 2019 USD ($)	Mar. 23, 2019 USD ($)	Sep. 08, 2018 USD ($)	Jun. 16, 2018 USD ($)	Mar. 24, 2018 USD ($)	Dec. 28, 2019 USD ($)	Dec. 29, 2018 USD ($)	Dec. 28, 2019 USD ($) segment	Dec. 29, 2018 USD ($)	Dec. 30, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment									2
Revenues
Revenues	$ 104,841	$ 105,000	$ 95,772	$ 99,674	$ 100,303	$ 83,147	$ 138,814	$ 127,059	$ 444,427	$ 410,183	$ 365,957
Rental income	5,657	5,762	3,548	0	0	0	7,696	0	22,663
Operating expenses
Operating costs	80,117	78,849	82,483	76,045	76,272	68,386	108,154	102,462	349,603	323,165	276,102
Operating depreciation and amortization									14,424	12,907	14,302
Profit before corporate selling, general, and administrative expenses									80,400	74,111	75,553
Selling, general, and administrative expenses	11,241	11,042	12,396	10,641	11,522	11,022	15,545	14,529	50,224	47,714	47,401
Depreciation and amortization from SG&A									3,825	3,250	3,665
Total selling, general, and administrative expenses									54,049	50,964	51,066
Other expense (income) - net	1,021	1,514	(58)	253	341	389	11,013	623	13,490	1,606	(10,940)
Operating income	8,482	9,534	(3,185)	8,959	8,509	(293)	(1,970)	4,366	12,861	21,541	35,427
Interest expense - net	180	219	230	256	240	245	240	310	869	1,052	1,094
Income before income taxes									11,992	20,489	34,333
Corporate and Eliminations
Revenues
Revenues									0	0	0
Rental income									0
Operating expenses
Operating costs									0	0	0
Operating depreciation and amortization									0	0	0
Profit before corporate selling, general, and administrative expenses									0	0	0
Selling, general, and administrative expenses									50,224	47,714	47,401
Depreciation and amortization from SG&A									3,825	3,250	3,665
Total selling, general, and administrative expenses									54,049	50,964	51,066
Other expense (income) - net									13,490	1,606	(10,940)
Interest expense - net									869	1,052	1,094
Environmental Services
Revenues
Revenues									302,543	271,131
Rental income									22,408
Environmental Services | Operating segments
Revenues
Revenues									302,543	271,131	238,055
Rental income									22,408
Operating expenses
Operating costs									219,040	194,959	163,633
Operating depreciation and amortization									7,768	6,766	7,526
Profit before corporate selling, general, and administrative expenses									75,735	69,406	66,896
Oil Business
Revenues
Revenues									141,884	139,052
Rental income									255
Oil Business | Operating segments
Revenues
Revenues									141,884	139,052	127,902
Rental income									255
Operating expenses
Operating costs									130,563	128,206	112,469
Operating depreciation and amortization									6,656	6,141	6,776
Profit before corporate selling, general, and administrative expenses									4,665	4,705	8,657
Service revenues
Revenues
Revenues	57,220	57,936	56,366	58,054	60,014	54,137	78,969	78,057	250,491	250,262	233,999
Service revenues | Corporate and Eliminations
Revenues
Revenues									0	0	0
Service revenues | Environmental Services | Operating segments
Revenues
Revenues									236,530	237,806	212,883
Service revenues | Oil Business | Operating segments
Revenues
Revenues									13,961	12,456	21,116
Product revenues
Revenues
Revenues	$ 41,964	$ 41,302	$ 35,858	$ 41,620	$ 40,289	$ 29,010	$ 52,149	$ 49,002	171,273	159,921	131,958
Product revenues | Corporate and Eliminations
Revenues
Revenues									0	0	0
Product revenues | Environmental Services | Operating segments
Revenues
Revenues									43,605	33,325	25,172
Product revenues | Oil Business | Operating segments
Revenues
Revenues									$ 127,668	$ 126,596	$ 106,786