Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Dec. 28, 2014	Dec. 29, 2013
Condensed Consolidated Statements of Income
Revenue	$ 581,056us-gaap_SalesRevenueServicesNet	$ 645,848us-gaap_SalesRevenueServicesNet
Subcontractor costs	(143,976)ttek_SubcontractorCosts	(162,857)ttek_SubcontractorCosts
Other costs of revenue	(358,281)us-gaap_OtherCostOfOperatingRevenue	(396,528)us-gaap_OtherCostOfOperatingRevenue
Selling, general and administrative expenses	(42,187)	(47,375)
Contingent consideration - fair value adjustments		4,630
Operating income	36,612us-gaap_OperatingIncomeLoss	43,718us-gaap_OperatingIncomeLoss
Interest expense	(1,790)us-gaap_InterestExpense	(2,424)us-gaap_InterestExpense
Income before income tax expense	34,822	41,294
Income tax expense	(9,176)us-gaap_IncomeTaxExpenseBenefit	(13,967)us-gaap_IncomeTaxExpenseBenefit
Net income including noncontrolling interests	25,646us-gaap_ProfitLoss	27,327us-gaap_ProfitLoss
Net income attributable to noncontrolling interests	(71)	(12)
Net income attributable to Tetra Tech	$ 25,575	$ 27,315
Earnings per share attributable to Tetra Tech:
Basic	$ 0.41us-gaap_EarningsPerShareBasic	$ 0.43us-gaap_EarningsPerShareBasic
Diluted	$ 0.41us-gaap_EarningsPerShareDiluted	$ 0.42us-gaap_EarningsPerShareDiluted
Weighted-average common shares outstanding:
Basic	62,452	64,227
Diluted	63,112	65,048
Cash dividends paid per share	$ 0.07

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Other costs incurred during the reporting period related to other revenue generating activities.

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