Reportable Segments (Details) (USD $)	3 Months Ended		9 Months Ended
	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Sep. 29, 2013
Financial information concerning reportable segments
Revenue	$ 629,502,000	$ 614,835,000	$ 1,861,635,000	$ 1,915,379,000
Operating Income (loss)	39,167,000	(99,884,000)	129,070,000	(20,409,000)
Depreciation	6,454,000	8,090,000	20,160,000	22,420,000
Impairment of goodwill		56,600,000		56,600,000
Amortization expense for intangible assets	6,100,000	9,600,000	21,400,000	24,200,000
Total assets	1,824,220,000		1,824,220,000		1,799,092,000
Intersegment Eliminations [Member]
Financial information concerning reportable segments
Revenue	(25,049,000)	(20,162,000)	(70,308,000)	(59,942,000)
Corporate, Non-Segment [Member]
Financial information concerning reportable segments
Operating Income (loss)	143,000	(62,017,000)	8,941,000	(78,816,000)
Depreciation	840,000	726,000	2,330,000	2,333,000
Amortization expense for intangible assets	6,100,000	9,600,000	21,400,000	24,200,000
Corporate Non Segment Intersegment Elimination [Member]
Financial information concerning reportable segments
Total assets	(281,840,000)		(281,840,000)		(222,821,000)
Engineering and Consulting Services [Member]
Financial information concerning reportable segments
Impairment of goodwill		56,600,000
Engineering and Consulting Services [Member] | Operating Segments [Member]
Financial information concerning reportable segments
Revenue	246,977,000	251,239,000	707,952,000	788,600,000
Operating Income (loss)	18,351,000	(7,700,000)	50,322,000	22,793,000
Depreciation	1,737,000	2,941,000	5,950,000	8,154,000
Total assets	931,810,000		931,810,000		912,996,000
Technical Support Services [Member] | Operating Segments [Member]
Financial information concerning reportable segments
Revenue	236,056,000	221,198,000	674,042,000	687,230,000
Operating Income (loss)	22,867,000	5,118,000	68,971,000	49,723,000
Depreciation	577,000	723,000	1,746,000	2,198,000
Total assets	742,047,000		742,047,000		673,864,000
Remediation and Construction Management [Member] | Operating Segments [Member]
Financial information concerning reportable segments
Revenue	171,518,000	162,560,000	549,949,000	499,491,000
Operating Income (loss)	(2,194,000)	(35,285,000)	836,000	(14,109,000)
Depreciation	3,300,000	3,700,000	10,134,000	9,735,000
Total assets	$ 432,203,000		$ 432,203,000		$ 435,053,000