GOODWILL AND INTANGIBLE ASSETS (Details) (USD $)	12 Months Ended
	Jul. 28, 2012	Jul. 30, 2011	Jul. 31, 2010
Goodwill, Net [Abstract]
Gross carrying amount	$ 370,616,000	$ 370,616,000	$ 353,618,000
Accumulated Impairment Loss	(195,767,000)	(195,767,000)	(195,767,000)
Net Carrying amount	174,849,000	174,849,000	157,851,000
Goodwill, Impairment Loss	0	0
Goodwill, Acquisitions		16,998,000
Amortization expense for finite-lived intangible assets	6,500,000	6,800,000	6,400,000
UtiliQuest trade name, carrying amount	4,700,000	4,700,000
Gross Intangible Assets	96,855,000	96,855,000
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets, Net	49,773,000	56,279,000
Cash flow period (in years)	7Y	7Y	7Y
Discount rate (in hundredths)	13.00%	13.50%	15.00%
Goodwill, Impairment Loss	0	0
Future Amortization Expense [Abstract]
Amortization expense 2013	6,364,000
Amortization expense 2014	6,125,000
Amortization expense 2015	6,006,000
Amortization expense 2016	5,625,000
Amortization expense 2017	4,826,000
Amortization thereafter	16,128,000
GOODWILL	174,849,000	174,849,000	157,851,000
Minimum [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Terminal growth rate (in hundredths)	1.50%	1.50%	1.00%
Maximum [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Terminal growth rate (in hundredths)	3.00%	3.00%	3.00%
UtiliQuest [Member]
Goodwill, Net [Abstract]
Net Carrying amount	35,600,000
Future Amortization Expense [Abstract]
GOODWILL	35,600,000
Margin of excess of fair value over carrying value (in hundredths)	30.00%
Customer Relationships [Member]
Goodwill, Net [Abstract]
Weighted Average Remaining Useful lives	9 years 4 months 24 days
Finite-Lived Intangible Assets, Net [Abstract]
Carrying amount	89,145,000	89,145,000
Accumulated amortization	45,852,000	39,601,000
Trade Names [Member]
Goodwill, Net [Abstract]
Weighted Average Remaining Useful lives	8 years 2 months 12 days
Finite-Lived Intangible Assets, Net [Abstract]
Carrying amount	2,860,000	2,860,000
Accumulated amortization	1,182,000	957,000
Noncompete Agreements [Member]
Goodwill, Net [Abstract]
Weighted Average Remaining Useful lives	3 years 4 months 24 days
Finite-Lived Intangible Assets, Net [Abstract]
Carrying amount	150,000	150,000
Accumulated amortization	$ 48,000	$ 18,000