Tetra Tech (TTEK) 10-Q 4 Aug 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Jun. 29, 2014	Jul. 28, 2014
Document and Entity Information	'	'
Entity Registrant Name	'TETRA TECH INC	'
Entity Central Index Key	'0000831641	'
Document Type	'10-Q	'
Document Period End Date	29-Jun-14	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--09-28	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	64,243,795
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jun. 29, 2014	Sep. 29, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$188,872	$129,305
Accounts receivable - net	674,447	660,847
Prepaid expenses and other current assets	49,939	61,446
Income taxes receivable	17,570	20,044
Total current assets	930,828	871,642
Property and equipment - net	78,208	88,026
Investments in and advances to unconsolidated joint ventures	1,938	2,198
Goodwill	722,583	722,792
Intangible assets - net	66,115	86,929
Other long-term assets	24,548	27,505
Total assets	1,824,220	1,799,092
Current liabilities:	'	'
Accounts payable	173,024	142,813
Accrued compensation	115,730	114,810
Billings in excess of costs on uncompleted contracts	79,160	79,507
Deferred income taxes	25,120	18,170
Current portion of long-term debt	8,441	4,311
Estimated contingent earn-out liabilities	8,673	23,281
Other current liabilities	68,031	100,241
Total current liabilities	478,179	483,133
Deferred income taxes	26,480	30,525
Long-term debt	195,501	203,438
Long-term estimated contingent earn-out liabilities	22,830	58,508
Other long-term liabilities	35,069	24,685
Commitments and contingencies	'	'
Equity:	'	'
Preferred stock - Authorized, 2,000 shares of $0.01 par value; no shares issued and outstanding at June 29, 2014, and September 29, 2013	'	'
Common stock - Authorized, 150,000 shares of $0.01 par value; issued and outstanding, 64,348 and 64,134 shares at June 29, 2014, and September 29, 2013, respectively	643	641
Additional paid-in capital	447,864	443,099
Accumulated other comprehensive (loss) income	-16,588	1,858
Retained earnings	633,339	552,165
Tetra Tech stockholders' equity	1,065,258	997,763
Noncontrolling interests	903	1,040
Total equity	1,066,161	998,803
Total liabilities and equity	$1,824,220	$1,799,092

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 29, 2014	Sep. 29, 2013
In Thousands, except Per Share data, unless otherwise specified
Condensed Consolidated Balance Sheets	'	'
Preferred stock, Authorized shares	2,000	2,000
Preferred stock, par value (in dollars per share)	$0.01	$0.01
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, Authorized shares	150,000	150,000
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares issued	64,348	64,134
Common stock, shares outstanding	64,348	64,134

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013
Condensed Consolidated Statements of Operations	'	'	'	'
Revenue	$629,502	$614,835	$1,861,635	$1,915,379
Subcontractor costs	-170,746	-139,693	-463,904	-422,092
Other costs of revenue	-381,319	-469,398	-1,164,761	-1,314,219
Selling, general and administrative expense	-47,175	-56,744	-138,778	-151,539
Contingent consideration - fair value adjustments	8,905	7,716	34,878	8,662
Impairment of goodwill	'	-56,600	'	-56,600
Operating income (loss)	39,167	-99,884	129,070	-20,409
Interest expense	-2,454	-2,010	-7,373	-5,330
Income (loss) before income tax (expense) benefit	36,713	-101,894	121,697	-25,739
Income tax (expense) benefit	-10,002	23,779	-35,751	-1,108
Net income (loss) including noncontrolling interests	26,711	-78,115	85,946	-26,847
Net income attributable to noncontrolling interests	-54	-270	-266	-495
Net income (loss) attributable to Tetra Tech	$26,657	($78,385)	$85,680	($27,342)
Net income (loss) per share attributable to Tetra Tech:	'	'	'	'
Basic (in dollars per share)	$0.41	($1.21)	$1.32	($0.42)
Diluted (in dollars per share)	$0.41	($1.21)	$1.31	($0.42)
Weighted-average common shares outstanding:	'	'	'	'
Basic (in shares)	64,566	64,832	64,683	64,554
Diluted (in shares)	65,302	64,832	65,493	64,554
Cash dividends paid per share	$0.07	'	$0.07	'

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income (Loss) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013
Condensed Consolidated Statements of Comprehensive Income	'	'	'	'
Net income (loss) including noncontrolling interests	$26,711	($78,115)	$85,946	($26,847)
Other comprehensive income (loss):	'	'	'	'
Foreign currency translation adjustments, net of tax	19,177	-22,430	-18,642	-40,197
(Loss) gain on cash flow hedge valuations, net of tax	-645	'	-206	93
Other comprehensive income (loss)	18,532	-22,430	-18,848	-40,104
Comprehensive income (loss) including noncontrolling interests	45,243	-100,545	67,098	-66,951
Net income attributable to noncontrolling interests	-54	-270	-266	-495
Foreign currency translation adjustments attributable to noncontrolling interests, net of tax	330	33	403	66
Comprehensive income (loss) attributable to noncontrolling interests	276	-237	137	-429
Comprehensive income (loss) attributable to Tetra Tech	$45,519	($100,782)	$67,235	($67,380)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013
Cash flows from operating activities:	'	'
Net income (loss) including noncontrolling interests	$85,946	($26,847)
Adjustments to reconcile net income (loss) to net cash from operating activities:	'	'
Depreciation and amortization	42,147	47,148
Loss on settlement of foreign currency forward contract	'	270
Equity in earnings of unconsolidated joint ventures	-1,929	-2,495
Distributions of earnings from unconsolidated joint ventures	2,145	2,868
Stock-based compensation	8,329	7,628
Excess tax benefits from stock-based compensation	-692	-875
Deferred income taxes	2,040	-27,005
Provision for doubtful accounts	384	12,125
Fair value adjustments to contingent consideration	-34,878	-8,662
Loss (gain) on disposal of property and equipment	66	-142
Lease termination costs and related asset impairment	'	6,463
Impairment of goodwill	'	56,600
Changes in operating assets and liabilities, net of effects of business acquisitions:	'	'
Accounts receivable	-9,166	117,687
Prepaid expenses and other assets	-3,738	7,435
Accounts payable	28,944	-43,911
Accrued compensation	817	-12,458
Billings in excess of costs on uncompleted contracts	-351	-10,986
Other liabilities	-16,437	5,569
Income taxes receivable/payable	10,670	-15,144
Net cash provided by operating activities	114,297	115,268
Cash flows from investing activities:	'	'
Capital expenditures	-14,879	-20,533
Payments for business acquisitions, net of cash acquired	-10,695	-168,660
Payment in settlement of foreign currency forward contract	'	-4,177
Receipt in settlement of foreign currency forward contract	'	3,907
Changes in restricted cash	'	470
Payment received on note for sale of operation	3,900	'
Proceeds from sale of property and equipment	3,740	1,763
Net cash used in investing activities	-17,934	-187,230
Cash flows from financing activities:	'	'
Payments on long-term debt	-3,641	-167,185
Proceeds from borrowings	'	296,098
Payments of earn-out liabilities	-18,662	-24,015
Payment of debt issuance cost	'	-1,938
Net change in overdrafts	-915	291
Excess tax benefits from stock-based compensation	692	875
Repurchases of common stock	-26,088	-4,147
Dividends paid	-4,506	'
Net proceeds from exercise of stock options	18,310	15,697
Net cash (used in) provided by financing activities	-34,810	115,676
Effect of foreign exchange rate changes on cash	-1,986	-2,227
Net increase in cash and cash equivalents	59,567	41,487
Cash and cash equivalents at beginning of period	129,305	104,848
Cash and cash equivalents at end of period	188,872	146,335
Cash paid during the period for:	'	'
Interest	6,181	3,801
Income taxes, net of refunds of $12,122 and $4,646	$22,109	$34,913

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Cash Flows (Parenthetical) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013
Condensed Consolidated Statements of Cash Flows	'	'
Income taxes, refunds received	$12,122	$4,646

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Jun. 29, 2014
Basis of Presentation	'
Basis of Presentation	'
	1.Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements and related notes of Tetra Tech, Inc. (“we,” “us” or “our”) have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X.  They do not include all of the information and footnotes required by GAAP for complete financial statements and, therefore, should be read in conjunction with the audited consolidated financial statements and related notes contained in our Annual Report on Form 10-K for the fiscal year ended September 29, 2013.
	These financial statements reflect all normal recurring adjustments that are considered necessary for the fair statement of our financial position, results of operations and cash flows for the interim periods presented.  The results of operations and cash flows for any interim period are not necessarily indicative of results for the full year or for future years.  Certain immaterial reclassifications were made to the prior year to conform to current year presentation.

Accounts_Receivable_Net_and_Re

Accounts Receivable - Net and Revenue Recognition	9 Months Ended
	Jun. 29, 2014
Accounts Receivable - Net and Revenue Recognition	'
Accounts Receivable - Net and Revenue Recognition	'
	2.Accounts Receivable – Net and Revenue Recognition
	Net accounts receivable and billings in excess of costs on uncompleted contracts consisted of the following:
		June 29,		September 29,
		2014		2013
		(in thousands)
	Billed	$	307,905	$	375,149
	Unbilled	381,429		306,969
	Contract retentions	25,885		23,353
	Total accounts receivable – gross	715,219		705,471
	Allowance for doubtful accounts	-40,772		-44,624
	Total accounts receivable – net	$	674,447	$	660,847
	Billings in excess of costs on uncompleted contracts	$	79,160	$	79,507
	Billed accounts receivable represent amounts billed to clients that have not been collected.  Unbilled accounts receivable represent revenue recognized but not yet billed pursuant to contract terms or billed after the period end date.  Most of our unbilled receivables at June 29, 2014 are expected to be billed and collected within 12 months.  Contract retentions represent amounts withheld by clients until certain conditions are met or the project is completed, which may be several months or years.  The allowance for doubtful accounts represents amounts that may become uncollectible or unrealizable in the future.  We determine an estimated allowance for uncollectible accounts based on management’s consideration of trends in the actual and forecasted credit quality of our clients, including delinquency and payment history; type of client, such as a government agency or a commercial sector client; and general economic and particular industry conditions that may affect a client’s ability to pay.  Billings in excess of costs on uncompleted contracts represent the amount of cash collected from clients and billings to clients on contracts in advance of revenue recognized.  The majority of billings in excess of costs on uncompleted contracts, excluding those related to claims, will be earned within 12 months.
	Once contract performance is underway, we may experience changes in conditions, client requirements, specifications, designs, materials and expectations regarding the period of performance. Such changes result in “change orders” and may be initiated by us or by our clients. In many cases, agreement with the client as to the terms of change orders is reached prior to work commencing; however, sometimes circumstances require that work progresses without obtaining a definitive client agreement. Unapproved change orders constitute claims in excess of agreed contract prices that we seek to collect from our clients (or other third parties) for delays, errors in specifications and designs, contract terminations, or other causes of unanticipated additional costs. Revenue on claims is recognized when contract costs related to claims have been incurred and when their addition to contract value can be reliably estimated. This can lead to a situation in which costs are recognized in one period and revenue is recognized in a subsequent period such as when client agreement is obtained or a claims resolution occurs.
	Total accounts receivable at June 29, 2014 and September 29, 2013 include approximately $86 million and $41 million, respectively, related to claims, including requests for equitable adjustment, on contracts that provide for price redetermination.  The increase from the end of fiscal 2013 includes the impact of changes in scope on an oil and gas project in Western Canada in fiscal 2014 that is currently in negotiation with the client.  The remainder of the increase in claims primarily related to revenue recognized as progress continued on projects with claims that were in process at the end of fiscal 2013.  We regularly evaluate all claim amounts and record appropriate adjustments to operating earnings when it is probable that the claim will result in a different contract value than the amount previously estimated.  As a result of this assessment, we recognized revenue and an increase to operating income of $3.4 million for the second quarter and first nine months of fiscal 2014.  We recognized net losses of approximately $17 million and $17 million related to the evaluation of collectability of claims during the third quarter and first nine months of fiscal 2013, respectively.
	Billed accounts receivable related to U.S. federal government contracts were $59.5 million and $50.5 million at June 29, 2014 and September 29, 2013, respectively.  U.S. federal government unbilled receivables, net of progress payments, were $81.0 million and $79.3 million at June 29, 2014 and September 29, 2013, respectively.  Other than the U.S. federal government, no single client accounted for more than 10% of our accounts receivable at June 29, 2014 and September 29, 2013.
	We recognize revenue for most of our contracts using the percentage-of-completion method, primarily utilizing the cost-to-cost approach to estimate the progress towards completion in order to determine the amount of revenue and profit to recognize. Revenue and cost estimates for each significant contract are reviewed and reassessed quarterly. Changes in those estimates could result in recognition of cumulative catch-up adjustments to the contract’s inception-to-date revenue, costs and profit in the period in which such changes are made. As a result, we recognized the net unfavorable operating income adjustments of $5.0 million and $10.3 million during the third quarter and the first nine months of fiscal 2014, respectively. No material operating income adjustments were recognized during the three and nine months ended June 30, 2013 due to updated cost to complete estimates. Changes in revenue and cost estimates could also result in a projected loss that would be recorded immediately in earnings. As of June 29, 2014 and September 29, 2013, we recorded a liability for anticipated losses of $10.4 million and $13.3 million, respectively. The estimated cost to complete the related contracts as of June 29, 2014 was $37.2 million.

Mergers_and_Acquisitions

Mergers and Acquisitions	9 Months Ended
	Jun. 29, 2014
Mergers and Acquisitions	'
Mergers and Acquisitions	'
	3.Mergers and Acquisitions
	In the second quarter of fiscal 2013, we acquired American Environmental Group, Ltd. (“AEG”), headquartered in Richfield, Ohio. AEG provides environmental, design, construction and maintenance services primarily to solid and hazardous waste, environmental, energy and utility clients. Also in the second quarter of fiscal 2013, we acquired Parkland Pipeline Contractors Ltd., Parkland Pipeline Equipment Ltd., Park L Projects Ltd. and Parkland Projects Ltd. (collectively, “Parkland”), headquartered in Alberta, Canada. Parkland serves the oil and gas industry in Western Canada, and specializes in the technical support, engineering support and construction of pipelines and oilfield facilities. AEG and Parkland are both included in our Remediation and Construction Management (“RCM”) segment. We also made other acquisitions that enhanced our service offerings and expanded our geographic presence in our Engineering and Consulting Services (“ECS”) and Technical Support Services (“TSS”) segments during fiscal 2013. The aggregate fair value of the purchase prices for fiscal 2013 acquisitions was $248.9 million. Of this amount, $171.6 million was paid to the sellers, $2.0 million was recorded as liabilities in accordance with the purchase agreements, and $75.3 million was the estimated fair value of contingent earn-out obligations as of the respective acquisition dates, with an aggregate maximum of $86.7 million upon the achievement of specified financial objectives. In the first quarter of fiscal 2014, we acquired a company that enhanced our service offerings in our ECS segment.
	Goodwill additions resulting from the above business combinations are primarily attributable to the existing workforce of the acquired companies and the synergies expected to arise after the acquisitions.  Specifically, the goodwill additions related to the fiscal 2013 acquisitions primarily represent the value of workforces with distinct expertise in the solid and hazardous waste, and oil and gas markets.  In addition, these acquired capabilities, when combined with our existing global consulting and engineering business, result in opportunities that allow us to provide services under contracts that could not have been pursued individually by either us or the acquired companies.  The results of these acquisitions were included in the consolidated financial statements from their respective closing dates.  The purchase price allocations related to acquisitions completed during the fourth quarter of fiscal 2013 and the first quarter of fiscal 2014 are preliminary, and subject to adjustment, based on the valuation and final determination of net assets acquired.  We do not believe that any such adjustment will have a material effect on our consolidated results of operations.  None of the acquisitions were considered material, individually or in the aggregate, to our condensed consolidated financial statements.  As a result, no pro forma information has been provided for the respective periods.
	Most of our acquisition agreements include contingent earn-out agreements, which are generally based on the achievement of future operating income thresholds.  The contingent earn-out arrangements are based on our valuations of the acquired companies, and reduce the risk of overpaying for acquisitions if the projected financial results are not achieved. The fair values of any earn-out arrangements are included as part of the purchase price of the acquired companies on their respective acquisition dates.  For each transaction, we estimate the fair value of contingent earn-out payments as part of the initial purchase price and record the estimated fair value of contingent consideration as a liability in “Estimated contingent earn-out liabilities” and “Long-term estimated contingent earn-out liabilities” on the condensed consolidated balance sheets.  We consider several factors when determining that contingent earn-out liabilities are part of the purchase price, including the following:  (1) the valuation of our acquisitions is not supported solely by the initial consideration paid, and the contingent earn-out formula is a critical and material component of the valuation approach to determining the purchase price; and (2) the former owners of acquired companies that remain as key employees receive compensation other than contingent earn-out payments at a reasonable level compared with the compensation of our other key employees.  The contingent earn-out payments are not affected by employment termination.
	We measure our contingent earn-out liabilities at fair value on a recurring basis using significant unobservable inputs classified within Level 3 of the fair value hierarchy (as described in “Critical Accounting Policies and Estimates” in our Annual Report on Form 10-K for the fiscal year ended September 29, 2013).  We use a probability-weighted discounted income approach as a valuation technique to convert future estimated cash flows to a single present value amount.  The significant unobservable inputs used in the fair value measurements are operating income projections over the earn-out period (generally two or three years), and the probability outcome percentages we assign to each scenario.  Significant increases or decreases to either of these inputs in isolation would result in a significantly higher or lower liability with a higher liability capped by the contractual maximum of the contingent earn-out obligation.  Ultimately, the liability will be equivalent to the amount paid, and the difference between the fair value estimate and amount paid will be recorded in earnings.  The amount paid that is less than or equal to the contingent earn-out liability on the acquisition date is reflected as cash used in financing activities in our condensed consolidated statements of cash flows.  Any amount paid in excess of the contingent earn-out liability on the acquisition date is reflected as cash used in operating activities.
	We review and re-assess the estimated fair value of contingent consideration on a quarterly basis, and the updated fair value could differ materially from the initial estimates.  Changes in the estimated fair value of our contingent earn-out liabilities related to the time component of the present value calculation are reported in interest expense.  Adjustments to the estimated fair value related to changes in all other unobservable inputs are reported in operating income.  During the three and nine months ended June 29, 2014, we recorded net decreases in our contingent earn-out liabilities and reported related net gains in operating income of $8.9 million and $34.9 million, respectively, compared with net gains of $7.7 million and $8.7 million, respectively, in the same periods last year.  The fiscal 2014 gains primarily resulted from updated valuations of the contingent consideration liability for AEG in the third quarter and Parkland in the second quarter.  Adverse weather conditions during the second and third quarter of fiscal 2014 hindered AEG’s ability to complete construction field work.  We recognized a net unfavorable operating income adjustment for Parkland related to a single project during the second quarter of fiscal 2014.  As a result, we lowered our income projections over the remaining earn-out periods and recorded corresponding reductions of the earn-out liabilities for AEG and Parkland.  We also determined that these lower income projections were the result of temporary events, and would not negatively impact AEG and Parkland’s longer-term performance or result in goodwill impairment.  However, if our income projections for AEG and Parkland were to decline further, this could result in the impairment of a portion of the combined related goodwill balance of approximately $139 million.  In this event, we would also likely have gains in our operating income up to a maximum of the remaining related contingent consideration liabilities.  Conversely, if AEG or Parkland’s performance increases beyond our projections, we could incur future losses in operating income if the resulting contingent consideration earned exceeds the current recorded liability.
	At June 29, 2014, there was a total maximum of $68.3 million of outstanding contingent consideration related to completed acquisitions.  Of this amount, $31.5 million was estimated as the fair value and accrued on our condensed consolidated balance sheets.  For the nine months ended June 29, 2014, we made $20.6 million of earn-out payments to former owners.  Of this amount, we reported $18.7 million as cash used in financing activities and $1.9 million as cash used in operating activities.  For the nine months ended June 30, 2013, we made $24.4 million of earn-out payments to former owners.  Of this amount, we reported $24.0 million as cash used in financing activities and $0.4 million as cash used in operating activities.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	9 Months Ended
	Jun. 29, 2014
Goodwill and Intangible Assets	'
Goodwill and Intangible Assets	'
	4.Goodwill and Intangible Assets
	The following table summarizes the changes in the carrying value of goodwill:
		ECS			TSS			RCM			Total
		(in thousands)
	Balance at September 29, 2013	$	353,608		$	177,579		$	191,605		$	722,792
	Goodwill additions	11,472			–			–			11,472
	Foreign exchange impact	-8,725			51			-3,482			-12,156
	Goodwill adjustments	–			161			314			475
	Balance at June 29, 2014	$	356,355		$	177,791		$	188,437		$	722,583
	Goodwill additions are attributable to an acquisition completed in the first quarter of fiscal 2014.  Substantially all of the goodwill additions are not deductible for income tax purposes.  The foreign exchange impact relates to our foreign subsidiaries with functional currencies that are different than our reporting currency.  The gross amounts of goodwill for ECS were $413.9 million and $411.1 million at June 29, 2014 and September 29, 2013, respectively, excluding $57.5 million of accumulated impairment.
	We test our goodwill for impairment on an annual basis, and more frequently when an event occurs or circumstances indicate that the carrying value of the asset may not be recoverable. We perform our annual goodwill impairment review at the beginning of our fiscal fourth quarter. Our last annual review at July 1, 2013, indicated that we had no impairment of goodwill, and all of our reporting units had estimated fair values that were in excess of their carrying values, including goodwill. During this review we identified three operating units (with goodwill totaling $214.0 million as of June 29, 2014) in the ECS segment and two recently acquired reporting units (with goodwill totaling $138.7 million as of June 29, 2014) in the RCM segment with fair values in excess of their carrying values of less than 20%. The goodwill related to the three reporting units in the ECS segment was adjusted to fair value in the third quarter of fiscal 2013, and a $56.6 million impairment charge was recorded. The two reporting units in the RCM segment were acquired at fair value in the second quarter of fiscal 2013. In addition, we regularly evaluate whether events and circumstances have occurred that may indicate a potential change in recoverability of goodwill. Based on these assessments as of June 29, 2014, we also determined that all of our reporting units had estimated fair values in excess of their carrying values, including goodwill as of June 29, 2014. However, four of the five aforementioned reporting units had fair value in excess of carrying value of less than 20%. Although we believe that our estimates of fair value for these reporting units are reasonable, if the financial performance for these reporting units falls significantly below our expectations or market prices for similar businesses decline, the goodwill for these reporting units could become impaired.
	The gross amount and accumulated amortization of our acquired identifiable intangible assets with finite useful lives included in “Intangible assets - net” on the condensed consolidated balance sheets, were as follows:
		June 29, 2014								September 29, 2013
		Weighted-		Gross			Accumulated			Gross			Accumulated
		Average		Amount			Amortization			Amount			Amortization
		Remaining Life
		(in Years)
		($ in thousands)
	Non-compete agreements	2.3		$	2,150		$	-1,456		$	6,160		$	-5,247
	Client relations	4		121,612			-58,214			128,839			-49,189
	Backlog	0.4		1,459			-927			68,968			-64,675
	Technology and trade names	2.3		3,300			-1,809			4,204			-2,131
	Total			$	128,521		$	-62,406		$	208,171		$	-121,242
	The gross amount and accumulated amortization for acquired identifiable intangible assets decreased due to the full amortization of assets in fiscal 2014.  The fiscal 2014 acquisition added $2.2 million of identifiable intangible assets.  Amortization expense for the identifiable intangible assets for the three and nine months ended June 29, 2014 was $6.1 million and $21.4 million, respectively, compared to $9.6 million and $24.2 million for the prior-year periods.  Estimated amortization expense for the remainder of fiscal 2014 and succeeding years is as follows:
		Amount
		(in thousands)
	2014	$	5,988
	2015	19,688
	2016	15,742
	2017	13,426
	2018	6,312
	Beyond	4,959
	Total	$	66,115

Property_and_Equipment

Property and Equipment	9 Months Ended
	Jun. 29, 2014
Property and Equipment	'
Property and Equipment	'
	5.Property and Equipment
	Property and equipment consisted of the following:
		June 29,		September 29,
		2014		2013
		(in thousands)
	Land and buildings	$	5,429	$	5,565
	Equipment, furniture and fixtures	211,264		210,172
	Leasehold improvements	25,823		26,429
	Total property and equipment	242,516		242,166
	Accumulated depreciation	-164,308		-154,140
	Property and equipment, net	$	78,208	$	88,026
	The depreciation expense related to property and equipment, including assets under capital leases, was $6.5 million and $20.2 million for the three and nine months ended June 29, 2014, respectively, compared to $8.1 million and $22.4 million for the prior-year periods.

Stock_Repurchase_and_Dividends

Stock Repurchase and Dividends	9 Months Ended
	Jun. 29, 2014
Stock Repurchase and Dividends	'
Stock Repurchase and Dividends	'
	6.Stock Repurchase and Dividends
	In June 2013, our Board of Directors authorized a stock repurchase program (the “Stock Repurchase Program”) under which we may currently repurchase up to $100 million of our common stock.  Stock repurchases may be made on the open market or in privately negotiated transactions with third parties.  From the inception of the Stock Repurchase Program through June 29, 2014, we repurchased through open market purchases a total of 1.8 million shares at an average price of $25.50 per share, for a total cost of $46.6 million.
	On April 28, 2014, the Board of Directors declared a quarterly cash dividend of $0.07 per share payable on June 4, 2014 to stockholders of record as of the close of business on May 16, 2014.  We paid $4.5 million of cash dividends for the three months ended June 29, 2014.
	Subsequent Events.  On July 28, 2014, the Board of Directors declared a quarterly cash dividend of $0.07 per share payable on September 5, 2014 to stockholders of record as of the close of business on August 15, 2014.  Further, on July 28, 2014, the Board of Directors amended the Stock Repurchase Program to authorize the repurchase of the remaining amount in the $100 million Stock Repurchase Program in open market purchases through September 2014 without regard to pricing parameters.

Stockholders_Equity_and_Stock_

Stockholders' Equity and Stock Compensation Plans	9 Months Ended
	Jun. 29, 2014
Stockholders' Equity and Stock Compensation Plans	'
Stockholders' Equity and Stock Compensation Plans	'
	7.Stockholders’ Equity and Stock Compensation Plans
	We recognize the fair value of our stock-based compensation awards as compensation expense on a straight-line basis over the requisite service period in which the award vests. Stock-based compensation expense for the three and nine months ended June 29, 2014 was $2.8 million and $8.3 million, respectively, compared to $2.8 million and $7.6 million for the same periods last year. The majority of these amounts was included in “Selling, general and administrative (“SG&A”) expenses” in our condensed consolidated statements of operations. In the three months ended June 29, 2014, no stock options were granted. For the nine months ended June 29, 2014, we granted 354,238 stock options with exercise prices of $28.58 - $28.68 per share and an estimated weighted-average fair value of $9.36 per share. In addition, we awarded 117,067 shares of restricted stock to our non-employee directors and executive officers at the fair value of $28.58 per share on the award date. All of these shares are performance-based and vest, if at all, over a three-year period. The number of shares that ultimately vest is based on the growth in our diluted earnings per share. Additionally, we awarded 224,743 restricted stock units (“RSUs”) to our non-employee directors, executive officers and employees at the weighted-average fair value of $28.58 per share on the award date. All of the executive officer and employee RSUs have time-based vesting over a four-year period, and the non-employee director RSUs vest after one year.

Earnings_Per_Share_EPS

Earnings Per Share (''EPS'')	9 Months Ended
	Jun. 29, 2014
Earnings Per Share (''EPS'')	'
Earnings Per Share (''EPS'')	'
	8.Earnings Per Share (“EPS”)
	Basic EPS is computed by dividing net income available to common stockholders by the weighted-average number of common shares outstanding, less unvested restricted stock for the period.  Diluted EPS is computed by dividing net income by the weighted-average number of common shares outstanding and dilutive potential common shares for the period.  Potential common shares include the weighted-average dilutive effects of outstanding stock options and unvested restricted stock using the treasury stock method.
	The following table sets forth the number of weighted-average shares used to compute basic and diluted EPS:
		Three Months Ended				Nine Months Ended
		June 29,		June 30,		June 29,		June 30,
		2014		2013		2014		2013
		(in thousands, except per share data)
	Net income (loss) attributable to Tetra Tech	$	26,657	$	-78,385	$	85,680	$	-27,342
	Weighted-average common shares outstanding – basic	64,566		64,832		64,683		64,554
	Effect of dilutive stock options and unvested restricted stock	736		–		810		–
	Weighted-average common stock outstanding – diluted	65,302		64,832		65,493		64,554
	Earnings (loss) per share attributable to Tetra Tech:
	Basic	$	0.41	$	-1.21	$	1.32	$	-0.42
	Diluted	$	0.41	$	-1.21	$	1.31	$	-0.42
	For the three and nine months ended June 29, 2014, 0.7 million and no options were excluded from the calculation of dilutive potential common shares, respectively.  These options were not included in the computation of dilutive potential common shares because the assumed proceeds per share exceeded the average market price per share during the period.  Therefore, their inclusion would have been anti-dilutive.  The computation of diluted loss per share for the three and nine months ended June 30, 2013 excluded 0.7 million and 0.8 million of potential common shares due to their anti-dilutive effect.

Income_Taxes

Income Taxes	9 Months Ended
	Jun. 29, 2014
Income Taxes	'
Income Taxes	'
	9.Income Taxes
	The effective tax rates for the first nine months of fiscal 2014 and 2013 were 29.4% and (4.3%), respectively. The fiscal 2014 effective rate reflects $26.2 million of gains related to the updated valuation of contingent consideration liabilities that were not taxable. The negative effective tax rate of 4.3% resulted primarily from the approximately $35 million goodwill impairment charge taken during the third quarter of fiscal 2013 that was not deductible for tax purposes. At June 29, 2014, undistributed earnings of our foreign subsidiaries, primarily in Canada, in the amount of approximately $43.3 million, are expected to be permanently reinvested. Accordingly, no provision for U.S. income taxes or foreign withholding taxes has been made. Upon distribution of those earnings, we would be subject to U.S. income taxes and foreign withholding taxes. Determination of the amount of unrecognized deferred U.S. income tax liability is not practicable; however, the potential foreign tax credit associated with the deferred income would be available to partially reduce the resulting U.S. tax liabilities.
	We review the realizability of deferred tax assets on a quarterly basis by assessing the need for a valuation allowance.  As of June 29, 2014, we performed our assessment of net deferred tax assets.  Significant management judgment is required to determine the provision for income taxes and, in particular, any valuation allowance recorded against our deferred tax assets.  Applying the applicable accounting guidance requires an assessment of all available evidence, both positive and negative, regarding the realizability of the net deferred tax assets.  Based upon recent results, we concluded that a cumulative loss in recent years exists in certain foreign jurisdictions.  We have historically relied on the following factors in our assessment of the realizability of our net deferred tax assets:
		·	taxable income in prior carryback years as permitted under the tax law;
		·	future reversals of existing taxable temporary differences;
		·	consideration of available tax planning strategies and actions that could be implemented, if necessary; and
		·	estimates of future taxable income from our operations.
	We considered these factors in our estimate of the reversal pattern of deferred tax assets, using assumptions that we believe are reasonable and consistent with operating results.  However, as a result of projected cumulative pre-tax losses in these certain foreign jurisdictions for the 36 months ending September 28, 2014, we concluded that our estimates of future taxable income and certain tax planning strategies did not constitute sufficient positive evidence to assert that it is more likely than not that certain deferred tax assets would be realizable before expiration.  Although we project earnings in the related business beyond 2014, we did not rely on these projections when assessing the realizability of our deferred tax assets.  Based on our assessment, we concluded that it is more likely than not that the assets will be realized except for the assets related to loss carry-forwards in foreign jurisdictions for which a valuation allowance of $8.8 million had been provided in previous years.
	In the third quarter of fiscal 2014, we received notification from the Internal Revenue Service that our appeals settlement in connection with three issues, research and experimentation tax credit (“R&E credit”), domestic production activities deduction, and meals and entertainment expenses, was approved for fiscal years 2005 through 2007.  The settlement of these issues, including interest, resulted in a cash refund of $6.3 million, which was received in the third quarter of fiscal 2014.  The settlement did not have a material impact on our financial statements as the amount received was consistent with the amount previously recognized in the financial statements.
	During the second quarter of fiscal 2013, the American Taxpayer Relief Act of 2012 was signed into law. This law retroactively extended the federal R&E credits for amounts incurred from January 1, 2012 through December 31, 2013. Our effective tax rate for the first quarter of fiscal 2014 includes a tax benefit from R&E credits attributable to the first three months of fiscal 2014. Should the R&E credits provision be retroactively extended during fiscal 2014, additional benefits will be reflected in our effective tax rate during the quarter reporting period of enactment.

Reportable_Segments

Reportable Segments	9 Months Ended
	Jun. 29, 2014
Reportable Segments	'
Reportable Segments	'
	10.Reportable Segments
	Our reportable segments are as follows:
	ECS:  provides front-end science, consulting engineering and project management services in the areas of surface water management, water infrastructure, solid waste management, mining, geotechnical sciences, arctic engineering, industrial processes and oil sands, transportation and information technology.
	TSS:  provides management consulting and engineering services and strategic direction in the areas of environmental assessments/hazardous waste management, climate change, international development, international reconstruction and stabilization, energy, oil and gas, technical government consulting, and building and facilities.
	RCM:  provides full-service support, including construction and construction management, to all of our client sectors, including the U.S. federal government in the United States and internationally, and commercial clients worldwide, in the areas of environmental remediation, infrastructure development, solid waste management, energy, and oil and gas.
	Management evaluates the performance of these reportable segments based upon their respective segment operating income before the effect of amortization expense related to acquisitions and other unallocated corporate expenses.  We account for inter-segment sales and transfers as if the sales and transfers were to third parties; that is, by applying a negotiated fee onto the costs of the services performed.  All significant intercompany balances and transactions are eliminated in consolidation.
	The following tables set forth summarized financial information regarding our reportable segments:
	Reportable Segments
			Three Months Ended				Nine Months Ended
			June 29,		June 30,		June 29,		June 30,
			2014		2013		2014		2013
			(in thousands)
	Revenue
	ECS		$	246,977	$	251,239	$	707,952	$	788,600
	TSS		236,056		221,198		674,042		687,230
	RCM		171,518		162,560		549,949		499,491
	Elimination of inter-segment revenue		-25,049		-20,162		-70,308		-59,942
	Total revenue		$	629,502	$	614,835	$	1,861,635	$	1,915,379
	Operating Income (loss)
	ECS		$	18,351	$	-7,700	$	50,322	$	22,793
	TSS		22,867		5,118		68,971		49,723
	RCM		-2,194		-35,285		836		-14,109
	Corporate (1)		143		-62,017		8,941		-78,816
	Total operating income (loss)		$	39,167	$	-99,884	$	129,070	$	-20,409
	Depreciation
	ECS		$	1,737	$	2,941	$	5,950	$	8,154
	TSS		577		723		1,746		2,198
	RCM		3,300		3,700		10,134		9,735
	Corporate		840		726		2,330		2,333
	Total depreciation		$	6,454	$	8,090	$	20,160	$	22,420
		-1		Includes goodwill impairment charge, amortization of intangibles, other costs and other income not allocable to segments. The goodwill impairment charge of $56.6 million for the three and nine-month periods of fiscal 2013 was recorded at Corporate.  The intangible asset amortization expense for the three and nine-month periods of fiscal 2014 was $6.1 million and $21.4 million, respectively, compared to $9.6 million and $24.2 million for the same periods last year.
			June 29,		September 29,
			2014		2013
			(in thousands)
	Total Assets
	ECS		$	931,810	$	912,996
	TSS		742,047		673,864
	RCM		432,203		435,053
	Corporate (1)		-281,840		-222,821
	Total assets		$	1,824,220	$	1,799,092
		-1		Corporate assets consist of intercompany eliminations and assets not allocated to segments including goodwill, intangible assets, deferred income taxes and certain other assets.
	Major Clients
	Other than the U.S. federal government, no single client accounted for more than 10% of our revenue.  All of our segments generated revenue from all client sectors.
	The following table represents our revenue by client sector:
			Three Months Ended				Nine Months Ended
			June 29,		June 30,		June 29,		June 30,
			2014		2013		2014		2013
			(in thousands)
	Client Sector
	International (1)		$	141,553	$	158,579	$	487,056	$	522,921
	U.S. commercial		183,757		167,280		517,907		488,722
	U.S. federal government (2)		202,905		187,983		576,431		621,677
	U.S. state and local government		101,287		100,993		280,241		282,059
	Total		$	629,502	$	614,835	$	1,861,635	$	1,915,379
		-1		Includes revenue generated from foreign operations, primarily in Canada, and revenue generated from non-U.S. clients.
		-2		Includes revenue generated under U.S. federal government contracts performed outside the United States.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Jun. 29, 2014
Fair Value Measurements	'
Fair Value Measurements	'
	11.Fair Value Measurements
	The fair value of long-term debt was determined using the present value of future cash flows based on the borrowing rates currently available for debt with similar terms and maturities (Level 2 measurement, as described in “Critical Accounting Policies and Estimates” in our Annual Report on Form 10-K for the fiscal year ended September 29, 2013).  The carrying value of our long-term debt approximated fair value at June 29, 2014 and September 29, 2013.  As of June 29, 2014, we had outstanding borrowings of $202.4 million under our amended credit agreement to fund our business acquisitions, working capital needs and contingent earn-outs.

Joint_Ventures

Joint Ventures	9 Months Ended
	Jun. 29, 2014
Joint Ventures	'
Joint Ventures	'
	12.Joint Ventures
	Consolidated Joint Ventures
	The aggregate revenue of our consolidated joint ventures for the three and nine months ended June 29, 2014 was $3.1 million and $9.3 million, respectively, compared to $2.8 million and $9.8 million for the same periods last year.  The assets and liabilities of these consolidated joint ventures were immaterial at June 29, 2014 and September 29, 2013.  These assets are restricted for use only by those joint ventures and are not available for our general operations.  Cash and cash equivalents maintained by the consolidated joint ventures at June 29, 2014 and September 29, 2013 were $0.9 million and $1.2 million, respectively.
	Unconsolidated Joint Ventures
	We account for our unconsolidated joint ventures using the equity method of accounting.  Under this method, we recognize our proportionate share of the net earnings of these joint ventures within “Other costs of revenue” in our condensed consolidated statements of operations.  For the three and nine months ended June 29, 2014, we reported $0.4 million and $1.9 million of equity in earnings of unconsolidated joint ventures, respectively, compared to $0.6 million and $2.5 million for the same periods last year.  Our maximum exposure to loss as a result of our investments in unconsolidated joint ventures is typically limited to the aggregate of the carrying value of the investment.  Future funding commitments for our unconsolidated joint ventures are immaterial.  The unconsolidated joint ventures are, individually and in aggregate, immaterial to our consolidated financial statements.
	The aggregate carrying values of the assets and liabilities of the unconsolidated joint ventures were $22.1 million and $20.2 million, respectively, at June 29, 2014, and $24.0 million and $21.8 million, respectively, at September 29, 2013.

Derivative_Financial_Instrumen

Derivative Financial Instruments	9 Months Ended
	Jun. 29, 2014
Derivative Financial Instruments	'
Derivative Financial Instruments	'
	13.Derivative Financial Instruments
	We use certain interest rate derivative contracts to hedge interest rate exposures on our variable rate debt. We have also entered into foreign currency derivative contracts with financial institutions to reduce the risk that cash flows and earnings will be adversely affected by foreign currency exchange rate fluctuations.  Our hedging program is not designated for trading or speculative purposes.
	We recognize derivative instruments as either assets or liabilities on the accompanying condensed consolidated balance sheets at fair value.  We record changes in the fair value (i.e., gains or losses) of the derivatives that have been designated as accounting hedges in our condensed consolidated balance sheets as accumulated other comprehensive income.
	In fiscal 2013, we entered into three interest rate swap agreements that we designated as cash flow hedges to fix the variable interest rates on a portion of borrowings under our term loan facility.  In the first quarter of fiscal 2014, we entered into two additional interest rate swap agreements that we designated as cash flow hedges to fix the variable interest rates on the balance of the term loan facility.  At June 29, 2014, the effective portion of our interest rate swap agreements designated as cash flow hedges before tax effect was immaterial, all of which we expect to reclassify from accumulated other comprehensive income to interest expense within the next 12 months.
	As of June 29, 2014, the total notional principal amount of our outstanding interest rate swap agreements with expiration date of May 2018 was $205.0 million and the weighted average fixed rate was 1.32%.
	The fair values of our outstanding derivatives designated as hedging instruments are as follows:
		Balance Sheet Location	June 29,		September 29,
			2014		2013
			(in thousands)
	Interest rate swap agreements	Other current liabilities	$	1,284	$	987
	The impact of the effective portions of derivative instruments in cash flow hedging relationships on income and other comprehensive income from our interest rate swap agreements was immaterial for the three and nine-month periods of fiscal 2014 and 2013.  Additionally, there were no ineffective portions of derivative instruments.  Accordingly, no amounts were excluded from effectiveness testing for our interest rate swap agreements.  We had no derivative instruments that were not designated as hedging instruments for fiscal 2013 and the first nine months of fiscal 2014.

Reclassifications_Out_of_Accum

Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Jun. 29, 2014
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	'
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	'
	14.Reclassifications Out of Accumulated Other Comprehensive Income (Loss)
	The accumulated balances and reporting period activities for the three and nine months ended June 29, 2014 and September 29, 2013 related to reclassifications out of accumulated other comprehensive income (loss) are summarized as follows:
			Three Months Ended
			Foreign		Loss on		Accumulated
			Currency		Derivative		Other
			Translation		Instruments		Comprehensive
			Adjustments				Income (Loss)
			(in thousands)
	Balances at March 31, 2013		$	13,377	$	–	$	13,377
	Other comprehensive loss before reclassifications		-22,398		–		-22,398
	Net current-period other comprehensive loss		-22,398		–		-22,398
	Balances at June 30, 2013		$	-9,021	$	–	$	-9,021
	Balances at March 30, 2014		$	-35,406	$	-43	$	-35,449
	Other comprehensive income (loss) before reclassifications		19,507		-41		19,466
	Amounts reclassified from accumulated other comprehensive income
	Interest rate contacts, net of tax (1)		–		-605		-605
	Net current-period other comprehensive income (loss)		19,507		-646		18,861
	Balances at June 29, 2014		$	-15,899	$	-689	$	-16,588
		-1		This accumulated other comprehensive component is reclassified in “Interest expense” in our condensed consolidated statements of operations.  See Note 13, “Derivative Financial Instruments”, for more information.
			Nine Months Ended
			Foreign		Loss on		Accumulated
			Currency		Derivative		Other
			Translation		Instruments		Comprehensive
			Adjustments				Income (Loss)
			(in thousands)
	Balances at September 30, 2012		$	31,110	$	-93	$	31,017
	Other comprehensive (loss) income before reclassifications		-40,131		257		-39,874
	Amounts reclassified from accumulated other comprehensive income
	Foreign exchange contracts, net of tax (1)		–		-164		-164
	Net current-period other comprehensive (loss) income		-40,131		93		-40,038
	Balances at June 30, 2013		$	-9,021	$	–	$	-9,021
	Balances at September 29, 2013		$	2,340	$	-482	$	1,858
	Other comprehensive (loss) income before reclassifications		-18,239		1,481		-16,758
	Amounts reclassified from accumulated other comprehensive income
	Interest rate contracts, net of tax (2)		–		-1,688		-1,688
	Net current-period other comprehensive income loss		-18,239		-207		-18,446
	Balances at June 29, 2014		$	-15,899	$	-689	$	-16,588
		-1		This accumulated other comprehensive component is reclassified in “Interest expense” and foreign exchange expense in “Selling, general and administrative expenses” in our condensed consolidated statements of operations.  See Note 13, “Derivative Financial Instruments”, for more information.
		-2		This accumulated other comprehensive component is reclassified in “Interest expense” in our condensed consolidated statements of operations.  See Note 13, “Derivative Financial Instruments”, for more information.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Jun. 29, 2014
Commitments and Contingencies	'
Commitments and Contingencies	'
	15.Commitments and Contingencies
	We are subject to certain claims and lawsuits typically filed against the engineering, consulting and construction profession, alleging primarily professional errors or omissions.  We carry professional liability insurance, subject to certain deductibles and policy limits, against such claims.  However, in some actions, parties are seeking damages that exceed our insurance coverage or for which we are not insured.  While management does not believe that the resolution of these claims will have a material adverse effect, individually or in aggregate, on our financial position, results of operations or cash flows, management acknowledges the uncertainty surrounding the ultimate resolution of these matters.
	We acquired BPR Inc. (“BPR”), a Quebec-based engineering firm on October 4, 2010.  Subsequently, we have been informed of the following with respect to pre-acquisition activities at BPR:
	On April 17, 2012, authorities in the province of Quebec, Canada charged two employees of BPR Triax, a subsidiary of BPR, and BPR Triax, under the Canadian Criminal Code with allegations of corruption.  Discovery procedures associated with the charges are currently ongoing, and the legal process is expected to continue through September 2014.  We have conducted an internal investigation concerning this matter and, based on the results of our investigation, we believe these allegations are limited to activities at BPR Triax prior to our acquisition of BPR.
	During late March 2013, the then-president of BPR gave testimony to the Charbonneau Commission, which is investigating possible corruption in the engineering industry in Quebec.  He stated that, during 2007 and 2008, he and other former BPR shareholders paid personal funds to a political party official in exchange for the award of five government contracts.  Further, prior to the testimony, we were not aware of the misconduct.  We have accepted the resignation of BPR’s former president, and are evaluating the impact of these pre-acquisition actions on our business and results of operations.
	During March 2013, following the resignation of BPR’s former president, we learned that criminal charges had been filed against BPR and its former president in France.  The charges relate to allegations that, in 2009, a BPR subsidiary had hired an employee of another firm to be CEO of that BPR subsidiary as a part of a corrupt scheme that allegedly damaged, among others, the employee’s former employer.  The hearing on this matter was held on May 9, 2014.  On June 12, 2014, the Court dismissed all charges against all defendants.  The Public Prosecutor did not file an appeal, and the Court’s decision is therefore final.
	On April 19, 2013, a class action proceeding was filed in Montreal in which BPR, BPR’s former president, and other Quebec-based engineering firms and individuals are named as defendants.  The plaintiff class includes all individuals and entities that have paid real estate or municipal taxes to the city of Montreal.  The allegations include participation in collusion to share contracts awarded by the City of Montreal, conspiracy to reduce competition and fix prices, payment of bribes to officials, making illegal political contributions, and bid rigging.  A class certification hearing was held in March 2014, and on May 7, 2014, the court dismissed the action.  On June 5, 2014, the plaintiff filed an appeal, and the defendants are preparing their motion to dismiss.
	The financial impact to us of the matters discussed above is unknown at this time.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	9 Months Ended
	Jun. 29, 2014
Recent Accounting Pronouncements	'
Recent Accounting Pronouncements	'
	16.Recent Accounting Pronouncements
	In December 2011, the Financial Accounting Standards Board (“FASB”) issued new guidance to enhance disclosures about financial instruments and derivative instruments that are either offset on the statement of financial position or subject to an enforceable master netting arrangement or similar agreement, irrespective of whether they are offset on the statement of financial position.  We are required to provide both net and gross information for these assets and liabilities in order to facilitate comparability between financial statements prepared on the basis of U.S. GAAP and financial statements prepared on the basis of International Financial Reporting Standards.  This guidance became effective for us in the first quarter of fiscal 2014 on a retrospective basis.  The adoption of this guidance had no impact on our consolidated financial statements.
	In February 2013, the FASB issued an update to the reporting of reclassifications out of accumulated other comprehensive income.  We are required to disclose additional information about changes in and significant items reclassified out of accumulated other comprehensive income. The guidance became effective for us in the first quarter of fiscal 2014.  The adoption of this guidance did not have an impact on our consolidated financial statements.
	In July 2013, the FASB issued an update on an inclusion of the Fed Funds Effective Swap as a benchmark interest rate (Overnight Interest Swap Rate) for hedge accounting purposes.  This guidance permits the Fed Funds Effective Swap Rate to be used as a U.S. benchmark interest rate for hedge accounting purposes under U.S. GAAP.  This guidance became effective prospectively for qualifying new or redesigned hedging relationships entered into on or after July 17, 2013.  The adoption of this guidance did not have a material impact on our consolidated financial statements.
	In July 2013, the FASB issued an update on the financial statement presentation of unrecognized tax benefits.  We are required to present a liability related to an unrecognized tax benefit as a reduction of a deferred tax asset for a net operating loss carryforward, a similar tax loss or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed.  This guidance will be effective for us in the first quarter of fiscal 2015.  We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.
	In April 2014, the FASB issued guidance that changes the threshold for reporting discontinued operations and adds new disclosures. The new guidance defines a discontinued operation as a disposal of a component or group of components that is disposed of or is classified as held for sale and “represents a strategic shift that has (or will have) a major effect on our operations and financial results.” For disposals of individually significant components that do not qualify as discontinued operations, we must disclose pre-tax earnings of the disposed component. This guidance is effective for us prospectively in the first quarter of fiscal 2016.  Early adoption is permitted, but only for disposals (or classifications as held for sale) that have not been reported in financial statements previously issued or available for issuance. We do not expect the adoption of this guidance to have a material impact on our consolidated financial statements.
	In May 2014, the FASB issued an accounting standard which will supersede existing revenue recognition guidance under current U.S. GAAP. The new standard is a comprehensive new revenue recognition model that requires a company to recognize revenue to depict the transfer of goods or services to a customer at an amount that reflects the consideration it expects to receive in exchange for those goods or services. The accounting standard is effective for us in the first quarter of fiscal year 2018. Companies may use either a full retrospective or a modified retrospective approach to adopt this standard and management is currently evaluating which transition approach to use. We are currently in the process of assessing what impact this new standard may have on our condensed consolidated financial statements.

Accounts_Receivable_Net_and_Re1

Accounts Receivable - Net and Revenue Recognition (Tables)	9 Months Ended
	Jun. 29, 2014
Accounts Receivable - Net and Revenue Recognition	'
Net accounts receivable and billings in excess of costs on uncompleted contracts	'
		June 29,		September 29,
		2014		2013
		(in thousands)
	Billed	$	307,905	$	375,149
	Unbilled	381,429		306,969
	Contract retentions	25,885		23,353
	Total accounts receivable – gross	715,219		705,471
	Allowance for doubtful accounts	-40,772		-44,624
	Total accounts receivable – net	$	674,447	$	660,847
	Billings in excess of costs on uncompleted contracts	$	79,160	$	79,507

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Jun. 29, 2014
Goodwill and Intangible Assets	'
Summary of changes in the carrying value of goodwill	'
		ECS			TSS			RCM			Total
		(in thousands)
	Balance at September 29, 2013	$	353,608		$	177,579		$	191,605		$	722,792
	Goodwill additions	11,472			–			–			11,472
	Foreign exchange impact	-8,725			51			-3,482			-12,156
	Goodwill adjustments	–			161			314			475
	Balance at June 29, 2014	$	356,355		$	177,791		$	188,437		$	722,583
Summary of acquired identifiable intangible assets with finite useful lives	'
		June 29, 2014								September 29, 2013
		Weighted-		Gross			Accumulated			Gross			Accumulated
		Average		Amount			Amortization			Amount			Amortization
		Remaining Life
		(in Years)
		($ in thousands)
	Non-compete agreements	2.3		$	2,150		$	-1,456		$	6,160		$	-5,247
	Client relations	4		121,612			-58,214			128,839			-49,189
	Backlog	0.4		1,459			-927			68,968			-64,675
	Technology and trade names	2.3		3,300			-1,809			4,204			-2,131
	Total			$	128,521		$	-62,406		$	208,171		$	-121,242
Estimated amortization expense for the succeeding five years and beyond	'
		Amount
		(in thousands)
	2014	$	5,988
	2015	19,688
	2016	15,742
	2017	13,426
	2018	6,312
	Beyond	4,959
	Total	$	66,115

Property_and_Equipment_Tables

Property and Equipment (Tables)	9 Months Ended
	Jun. 29, 2014
Property and Equipment	'
Schedule of components of property and equipment	'
		June 29,		September 29,
		2014		2013
		(in thousands)
	Land and buildings	$	5,429	$	5,565
	Equipment, furniture and fixtures	211,264		210,172
	Leasehold improvements	25,823		26,429
	Total property and equipment	242,516		242,166
	Accumulated depreciation	-164,308		-154,140
	Property and equipment, net	$	78,208	$	88,026

Earnings_Per_Share_EPS_Tables

Earnings Per Share (''EPS'') (Tables)	9 Months Ended
	Jun. 29, 2014
Earnings Per Share (''EPS'')	'
Schedule of number of weighted-average shares used to compute basic and diluted EPS	'
		Three Months Ended				Nine Months Ended
		June 29,		June 30,		June 29,		June 30,
		2014		2013		2014		2013
		(in thousands, except per share data)
	Net income (loss) attributable to Tetra Tech	$	26,657	$	-78,385	$	85,680	$	-27,342
	Weighted-average common shares outstanding – basic	64,566		64,832		64,683		64,554
	Effect of dilutive stock options and unvested restricted stock	736		–		810		–
	Weighted-average common stock outstanding – diluted	65,302		64,832		65,493		64,554
	Earnings (loss) per share attributable to Tetra Tech:
	Basic	$	0.41	$	-1.21	$	1.32	$	-0.42
	Diluted	$	0.41	$	-1.21	$	1.31	$	-0.42

Reportable_Segments_Tables

Reportable Segments (Tables)	9 Months Ended
	Jun. 29, 2014
Reportable Segments	'
Summarized financial information of reportable segments	'
	Reportable Segments
			Three Months Ended				Nine Months Ended
			June 29,		June 30,		June 29,		June 30,
			2014		2013		2014		2013
			(in thousands)
	Revenue
	ECS		$	246,977	$	251,239	$	707,952	$	788,600
	TSS		236,056		221,198		674,042		687,230
	RCM		171,518		162,560		549,949		499,491
	Elimination of inter-segment revenue		-25,049		-20,162		-70,308		-59,942
	Total revenue		$	629,502	$	614,835	$	1,861,635	$	1,915,379
	Operating Income (loss)
	ECS		$	18,351	$	-7,700	$	50,322	$	22,793
	TSS		22,867		5,118		68,971		49,723
	RCM		-2,194		-35,285		836		-14,109
	Corporate (1)		143		-62,017		8,941		-78,816
	Total operating income (loss)		$	39,167	$	-99,884	$	129,070	$	-20,409
	Depreciation
	ECS		$	1,737	$	2,941	$	5,950	$	8,154
	TSS		577		723		1,746		2,198
	RCM		3,300		3,700		10,134		9,735
	Corporate		840		726		2,330		2,333
	Total depreciation		$	6,454	$	8,090	$	20,160	$	22,420
		-1		Includes goodwill impairment charge, amortization of intangibles, other costs and other income not allocable to segments. The goodwill impairment charge of $56.6 million for the three and nine-month periods of fiscal 2013 was recorded at Corporate.  The intangible asset amortization expense for the three and nine-month periods of fiscal 2014 was $6.1 million and $21.4 million, respectively, compared to $9.6 million and $24.2 million for the same periods last year.
			June 29,		September 29,
			2014		2013
			(in thousands)
	Total Assets
	ECS		$	931,810	$	912,996
	TSS		742,047		673,864
	RCM		432,203		435,053
	Corporate (1)		-281,840		-222,821
	Total assets		$	1,824,220	$	1,799,092
		-1		Corporate assets consist of intercompany eliminations and assets not allocated to segments including goodwill, intangible assets, deferred income taxes and certain other assets.
Summary of revenue by client sector	'
			Three Months Ended				Nine Months Ended
			June 29,		June 30,		June 29,		June 30,
			2014		2013		2014		2013
			(in thousands)
	Client Sector
	International (1)		$	141,553	$	158,579	$	487,056	$	522,921
	U.S. commercial		183,757		167,280		517,907		488,722
	U.S. federal government (2)		202,905		187,983		576,431		621,677
	U.S. state and local government		101,287		100,993		280,241		282,059
	Total		$	629,502	$	614,835	$	1,861,635	$	1,915,379
		-1		Includes revenue generated from foreign operations, primarily in Canada, and revenue generated from non-U.S. clients.
		-2		Includes revenue generated under U.S. federal government contracts performed outside the United States.

Derivative_Financial_Instrumen1

Derivative Financial Instruments (Tables)	9 Months Ended
	Jun. 29, 2014
Derivative Financial Instruments	'
Schedule of fair values of the entity's outstanding derivatives designated as hedging instruments	'
		Balance Sheet Location	June 29,		September 29,
			2014		2013
			(in thousands)
	Interest rate swap agreements	Other current liabilities	$	1,284	$	987

Reclassifications_Out_of_Accum1

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Jun. 29, 2014
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	'
Summary of reclassifications out of accumulated other comprehensive income (loss)	'
			Three Months Ended
			Foreign		Loss on		Accumulated
			Currency		Derivative		Other
			Translation		Instruments		Comprehensive
			Adjustments				Income (Loss)
			(in thousands)
	Balances at March 31, 2013		$	13,377	$	–	$	13,377
	Other comprehensive loss before reclassifications		-22,398		–		-22,398
	Net current-period other comprehensive loss		-22,398		–		-22,398
	Balances at June 30, 2013		$	-9,021	$	–	$	-9,021
	Balances at March 30, 2014		$	-35,406	$	-43	$	-35,449
	Other comprehensive income (loss) before reclassifications		19,507		-41		19,466
	Amounts reclassified from accumulated other comprehensive income
	Interest rate contacts, net of tax (1)		–		-605		-605
	Net current-period other comprehensive income (loss)		19,507		-646		18,861
	Balances at June 29, 2014		$	-15,899	$	-689	$	-16,588
		-1		This accumulated other comprehensive component is reclassified in “Interest expense” in our condensed consolidated statements of operations.  See Note 13, “Derivative Financial Instruments”, for more information.
			Nine Months Ended
			Foreign		Loss on		Accumulated
			Currency		Derivative		Other
			Translation		Instruments		Comprehensive
			Adjustments				Income (Loss)
			(in thousands)
	Balances at September 30, 2012		$	31,110	$	-93	$	31,017
	Other comprehensive (loss) income before reclassifications		-40,131		257		-39,874
	Amounts reclassified from accumulated other comprehensive income
	Foreign exchange contracts, net of tax (1)		–		-164		-164
	Net current-period other comprehensive (loss) income		-40,131		93		-40,038
	Balances at June 30, 2013		$	-9,021	$	–	$	-9,021
	Balances at September 29, 2013		$	2,340	$	-482	$	1,858
	Other comprehensive (loss) income before reclassifications		-18,239		1,481		-16,758
	Amounts reclassified from accumulated other comprehensive income
	Interest rate contracts, net of tax (2)		–		-1,688		-1,688
	Net current-period other comprehensive income loss		-18,239		-207		-18,446
	Balances at June 29, 2014		$	-15,899	$	-689	$	-16,588
		-1		This accumulated other comprehensive component is reclassified in “Interest expense” and foreign exchange expense in “Selling, general and administrative expenses” in our condensed consolidated statements of operations.  See Note 13, “Derivative Financial Instruments”, for more information.
		-2		This accumulated other comprehensive component is reclassified in “Interest expense” in our condensed consolidated statements of operations.  See Note 13, “Derivative Financial Instruments”, for more information.

Accounts_Receivable_Net_and_Re2

Accounts Receivable - Net and Revenue Recognition (Details) (USD $)	3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 29, 2014	Mar. 30, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Sep. 29, 2013
Accounts Receivable - Net and Revenue Recognition	'	'	'	'	'	'
Billed	$307,905,000	'	'	$307,905,000	'	$375,149,000
Unbilled	381,429,000	'	'	381,429,000	'	306,969,000
Contract retentions	25,885,000	'	'	25,885,000	'	23,353,000
Total accounts receivable - gross	715,219,000	'	'	715,219,000	'	705,471,000
Allowance for doubtful accounts	-40,772,000	'	'	-40,772,000	'	-44,624,000
Total accounts receivable - net	674,447,000	'	'	674,447,000	'	660,847,000
Billings in excess of costs on uncompleted contracts	79,160,000	'	'	79,160,000	'	79,507,000
Period for billing and collecting unbilled receivables	'	'	'	'12 months	'	'
Period for earning majority of billings in excess of costs	'	'	'	'12 months	'	'
Total accounts receivable related to claims and requests for equitable adjustment on contracts	86,000,000	'	'	86,000,000	'	41,000,000
Revenue recognized related to the evaluation of claim amounts	'	3,400,000	'	3,400,000	'	'
Increase in operating income related to the evaluation of claim amounts	'	3,400,000	'	3,400,000	'	'
Billed accounts receivable related to U.S. federal government contracts	59,500,000	'	'	59,500,000	'	50,500,000
U.S. federal government unbilled receivables, net of progress payments	81,000,000	'	'	81,000,000	'	79,300,000
Threshold percentage for disclosure of accounts receivable from a single client	'	'	'	10.00%	'	10.00%
Revenue Recognition and Contract Costs	'	'	'	'	'	'
Net unfavorable operating income adjustments	5,000,000	'	'	10,300,000	'	'
Liability for anticipated losses	10,400,000	'	'	10,400,000	'	13,300,000
Estimated cost to complete the related contracts	37,200,000	'	'	37,200,000	'	'
Account receivable major customer	'	'	'	'	'	'
Loss on uncollectible accounts receivable related to claims	'	'	$17,000,000	'	$17,000,000	'
Accounts Receivable [Member]	'	'	'	'	'	'
Account receivable major customer	'	'	'	'	'	'
Number of clients exceeding threshold	'	'	'	0	'	0

Mergers_and_Acquisitions_Detai

Mergers and Acquisitions (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended		12 Months Ended
	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Sep. 29, 2013	Jun. 29, 2014	Jun. 29, 2014	Sep. 29, 2013	Jun. 29, 2014
						Maximum [Member]	Minimum [Member]	Parkland and Other Acquisitions 2013 [Member]	Parkland Acquisitions [Member]
Business acquisition	'	'	'	'	'	'	'	'	'
Aggregate fair value of purchase prices	'	'	'	'	'	'	'	$248,900,000	'
Cash paid to the sellers	'	'	'	'	'	'	'	171,600,000	'
Amount recorded as liabilities in accordance with the purchase agreements	'	'	'	'	'	'	'	2,000,000	'
Estimated fair value of contingent earn-out obligations	31,500,000	'	31,500,000	'	'	'	'	75,300,000	'
Aggregate maximum of contingent consideration	68,300,000	'	68,300,000	'	'	'	'	86,700,000	'
Earn out period for operating income projection	'	'	'	'	'	'3 years	'2 years	'	'
Net decreases in our contingent earn-out liabilities	8,900,000	7,700,000	34,900,000	8,700,000	'	'	'	'	'
Net gains on fair value adjustment in operating income	8,900,000	7,700,000	34,900,000	8,700,000	'	'	'	'	'
Goodwill balance	722,583,000	'	722,583,000	'	722,792,000	'	'	'	139,000,000
Earn-outs paid to former owners	'	'	20,600,000	24,400,000	'	'	'	'	'
Reported as cash used in financing activities	'	'	18,700,000	24,000,000	'	'	'	'	'
Reported as cash used in operating activities	'	'	$1,900,000	$400,000	'	'	'	'	'

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

9 Months Ended

6 Months Ended

9 Months Ended

Jun. 30, 2013

Jun. 29, 2014

Jun. 30, 2013

Jun. 29, 2014

Jun. 30, 2013

Jun. 29, 2014

Sep. 29, 2013

Jun. 29, 2014

Jun. 29, 2014

Mar. 31, 2013

Jun. 29, 2014

Jun. 29, 2014

item

Maximum [Member]

Engineering and Consulting Services [Member]

Engineering and Consulting Services [Member]

Engineering and Consulting Services [Member]

Engineering and Consulting Services [Member]

Technical Support Services [Member]

Remediation and Construction Management [Member]

Remediation and Construction Management [Member]

Remediation and Construction Management [Member]

item

Maximum [Member]

item

item

Maximum [Member]

Goodwill

'

'

'

'

'

'

'

'

'

'

'

'

Balance at beginning of the period

'

$722,792,000

'

'

'

$353,608,000

'

'

$177,579,000

'

$191,605,000

'

Goodwill additions

'

11,472,000

'

'

'

11,472,000

'

'

'

'

'

'

Foreign exchange impact

'

-12,156,000

'

'

'

-8,725,000

'

'

51,000

'

-3,482,000

'

Goodwill adjustments

'

475,000

'

'

'

'

'

'

161,000

'

314,000

'

Balance at end of the period

'

722,583,000

'

'

'

356,355,000

'

'

177,791,000

'

188,437,000

'

Gross amounts of goodwill

'

'

'

'

'

413,900,000

411,100,000

'

'

'

'

'

Accumulated impairment

'

'

'

'

'

57,500,000

57,500,000

'

'

'

'

'

Impairment of goodwill

56,600,000

'

56,600,000

'

56,600,000

'

'

'

'

'

'

'

Number of reporting units having fair value in excess of carrying value of less than 20%.

'

4

'

'

'

3

'

'

'

'

2

'

Goodwill

'

722,583,000

'

'

'

356,355,000

'

'

177,791,000

'

188,437,000

'

Represents the goodwill determined to have fair value in excess of carrying value of less than 20%

'

'

'

'

'

$214,000,000

'

'

'

'

$138,700,000

'

Number of reporting units recently acquired

'

'

'

'

'

'

'

'

'

2

'

'

Percentage of excess of fair value over carrying value

'

'

'

20.00%

'

'

'

20.00%

'

'

'

20.00%

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets (Details 2) (USD $)	3 Months Ended		9 Months Ended
	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Sep. 29, 2013
Finite-lived intangible assets	'	'	'	'	'
Gross Amount	$128,521,000	'	$128,521,000	'	$208,171,000
Accumulated Amortization	-62,406,000	'	-62,406,000	'	-121,242,000
Identifiable intangible assets added on acquisition	'	'	2,200,000	'	'
Amortization expense for identifiable intangible assets	6,100,000	9,600,000	21,400,000	24,200,000	'
Estimated amortization expense	'	'	'	'	'
2014	5,988,000	'	5,988,000	'	'
2015	19,688,000	'	19,688,000	'	'
2016	15,742,000	'	15,742,000	'	'
2017	13,426,000	'	13,426,000	'	'
2018	6,312,000	'	6,312,000	'	'
Beyond	4,959,000	'	4,959,000	'	'
Total	66,115,000	'	66,115,000	'	'
Noncompete Agreements [Member]	'	'	'	'	'
Finite-lived intangible assets	'	'	'	'	'
Weighted-Average Remaining Life	'	'	'2 years 3 months 18 days	'	'
Gross Amount	2,150,000	'	2,150,000	'	6,160,000
Accumulated Amortization	-1,456,000	'	-1,456,000	'	-5,247,000
Customer Relationships [Member]	'	'	'	'	'
Finite-lived intangible assets	'	'	'	'	'
Weighted-Average Remaining Life	'	'	'4 years	'	'
Gross Amount	121,612,000	'	121,612,000	'	128,839,000
Accumulated Amortization	-58,214,000	'	-58,214,000	'	-49,189,000
Order or Production Backlog [Member]	'	'	'	'	'
Finite-lived intangible assets	'	'	'	'	'
Weighted-Average Remaining Life	'	'	'4 months 24 days	'	'
Gross Amount	1,459,000	'	1,459,000	'	68,968,000
Accumulated Amortization	-927,000	'	-927,000	'	-64,675,000
Technology and Trade Names [Member]	'	'	'	'	'
Finite-lived intangible assets	'	'	'	'	'
Weighted-Average Remaining Life	'	'	'2 years 3 months 18 days	'	'
Gross Amount	3,300,000	'	3,300,000	'	4,204,000
Accumulated Amortization	($1,809,000)	'	($1,809,000)	'	($2,131,000)

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Sep. 29, 2013
Property and Equipment	'	'	'	'	'
Property and equipment at cost, gross	$242,516	'	$242,516	'	$242,166
Accumulated depreciation	-164,308	'	-164,308	'	-154,140
Property and equipment, net	78,208	'	78,208	'	88,026
Depreciation expense related to property and equipment, including assets under capital leases	6,454	8,090	20,160	22,420	'
Land and Building [Member]	'	'	'	'	'
Property and Equipment	'	'	'	'	'
Property and equipment at cost, gross	5,429	'	5,429	'	5,565
Equipment, Furniture and Fixtures [Member]	'	'	'	'	'
Property and Equipment	'	'	'	'	'
Property and equipment at cost, gross	211,264	'	211,264	'	210,172
Leasehold Improvements [Member]	'	'	'	'	'
Property and Equipment	'	'	'	'	'
Property and equipment at cost, gross	$25,823	'	$25,823	'	$26,429

Stock_Repurchase_and_Dividends1

Stock Repurchase and Dividends (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended	13 Months Ended	0 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Apr. 28, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 29, 2014	Jun. 29, 2014	Jul. 28, 2014
						Subsequent Event [Member]
Stock Repurchase and Dividends	'	'	'	'	'	'
Maximum repurchase amount under stock repurchase program	'	$100,000,000	'	'	'	'
Shares repurchased through open market purchases	'	'	'	'	1.8	'
Average price of shares repurchased (in dollars per share)	'	'	'	'	$25.50	'
Cost of shares repurchased	'	'	'	'	46,600,000	'
Payments of Ordinary Dividends	'	'	$4,500,000	$4,506,000	'	'
Subsequent Event	'	'	'	'	'	'
Quarterly cash dividend declared (in dollars per share)	$0.07	'	'	'	'	$0.07

Stockholders_Equity_and_Stock_1

Stockholders' Equity and Stock Compensation Plans (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Share data, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013
Stockholders' Equity and Stock Compensation Plans	'	'	'	'
Stock-based compensation expense	$2.80	$2.80	$8.30	$7.60
Options granted (in shares)	0	'	354,238	'
Restricted stock award	'	'	'	'
Weighted-average fair value of stock options granted (in dollars per share)	'	'	$9.36	'
Minimum [Member]	'	'	'	'
Restricted stock award	'	'	'	'
Exercise price of stock options granted (in dollars per share)	'	'	$28.58	'
Maximum [Member]	'	'	'	'
Restricted stock award	'	'	'	'
Exercise price of stock options granted (in dollars per share)	'	'	$28.68	'
Executive Officer and Employees [Member]	'	'	'	'
Restricted stock award	'	'	'	'
Vesting period	'	'	'4 years	'
Director [Member]	'	'	'	'
Restricted stock award	'	'	'	'
Vesting period	'	'	'1 year	'
Restricted Stock Performance Based Award [Member] | Director and Executive Officer [Member]	'	'	'	'
Restricted stock award	'	'	'	'
Granted (in shares)	'	'	117,067	'
Granted, fair value (in dollars per share)	'	'	$28.58	'
Vesting period	'	'	'3 years	'
Restricted Stock Time Based Award [Member] | Director Executive Officer and Employees [Member]	'	'	'	'
Restricted stock award	'	'	'	'
Granted (in shares)	'	'	224,743	'
Granted, fair value (in dollars per share)	'	'	$28.58	'

Earnings_Per_Share_EPS_Details

Earnings Per Share (''EPS'') (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013
Number of weighted-average shares used to compute basic and diluted EPS:	'	'	'	'
Net income (loss) attributable to Tetra Tech	$26,657	($78,385)	$85,680	($27,342)
Weighted-average common shares outstanding - basic	64,566,000	64,832,000	64,683,000	64,554,000
Effect of dilutive stock options and unvested restricted stock	736,000	'	810,000	'
Weighted-average common stock outstanding - diluted	65,302,000	64,832,000	65,493,000	64,554,000
Earnings (loss) per share attributable to Tetra Tech:	'	'	'	'
Basic (in dollars per share)	$0.41	($1.21)	$1.32	($0.42)
Diluted (in dollars per share)	$0.41	($1.21)	$1.31	($0.42)
Employee and Directors Stock Options [Member]	'	'	'	'
Antidilutive securities	'	'	'	'
Securities excluded from the calculation of dilutive potential common shares	700,000	'	0	'
Potential Common Shares [Member]	'	'	'	'
Antidilutive securities	'	'	'	'
Securities excluded from the calculation of dilutive potential common shares	'	700,000	'	800,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	0 Months Ended	3 Months Ended	9 Months Ended
In Millions, unless otherwise specified	Sep. 28, 2014	Jun. 29, 2014	Jun. 29, 2014	Jun. 30, 2013
		item
Income Taxes	'	'	'	'
Effective tax rate (as a percent)	'	'	29.40%	-4.30%
Gain related to updated valuation of contingent consideration liabilities	'	'	$26.20	'
Goodwill impairment charge, not deductible for tax purposes	'	'	'	35
Undistributed earnings of foreign subsidiaries	'	43.3	43.3	'
Loss carry-forwards in foreign jurisdictions, valuation allowance	'	8.8	8.8	'
Represents the period of projected cumulative pre-tax losses in certain foreign jurisdictions	'36 months	'	'	'
Number of issues under examination by the IRS	'	3	'	'
Income tax cash refund, including interest related to settlement	'	$6.30	$6.30	'

Reportable_Segments_Details

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

Reportable_Segments_Details_2

Reportable Segments (Details 2) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013
Revenue by client sector	'	'	'	'
Threshold percentage for disclosure of revenue from a single client	'	'	10.00%	'
Revenue	$629,502	$614,835	$1,861,635	$1,915,379
Sales Revenue, Services, Net [Member]	'	'	'	'
Revenue by client sector	'	'	'	'
Number of clients exceeding threshold	'	'	0	'
International [Member]	'	'	'	'
Revenue by client sector	'	'	'	'
Revenue	141,553	158,579	487,056	522,921
Commercial [Member]	'	'	'	'
Revenue by client sector	'	'	'	'
Revenue	183,757	167,280	517,907	488,722
Federal Government [Member]	'	'	'	'
Revenue by client sector	'	'	'	'
Revenue	202,905	187,983	576,431	621,677
State and Local Government [Member]	'	'	'	'
Revenue by client sector	'	'	'	'
Revenue	$101,287	$100,993	$280,241	$282,059

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Jun. 29, 2014
In Millions, unless otherwise specified
Fair Value Measurements	'
Outstanding borrowing under the amended credit agreement	$202.40

Joint_Ventures_Details

Joint Ventures (Details) (USD $)	3 Months Ended		9 Months Ended
	Jun. 29, 2014	Jun. 30, 2013	Jun. 29, 2014	Jun. 30, 2013	Sep. 29, 2013
Aggregate revenue of consolidated joint ventures	$629,502,000	$614,835,000	$1,861,635,000	$1,915,379,000	'
Unconsolidated Joint Ventures	'	'	'	'	'
Equity in earnings from unconsolidated joint ventures	400,000	600,000	1,929,000	2,495,000	'
Carrying value of assets of unconsolidated joint ventures	22,100,000	'	22,100,000	'	24,000,000
Carrying value of liabilities of unconsolidated joint ventures	20,200,000	'	20,200,000	'	21,800,000
Consolidated Joint Ventures [Member]	'	'	'	'	'
Aggregate revenue of consolidated joint ventures	3,100,000	2,800,000	9,300,000	9,800,000	'
Restricted cash and cash equivalents of consolidated joint ventures	$900,000	'	$900,000	'	$1,200,000

Derivative_Financial_Instrumen2

Derivative Financial Instruments (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Dec. 29, 2013	Jun. 29, 2014	Sep. 29, 2013
	item		item
Not Designated as Hedging Instrument [Member]	'	'	'
Derivative financial instruments	'	'	'
Number of derivative instruments	'	0	0
Interest Rate Swap [Member]	'	'	'
Derivative financial instruments	'	'	'
Notional Amount	'	205	'
Weighted average fixed rate	'	1.32%	'
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]	'	'	'
Derivative financial instruments	'	'	'
Amounts excluded from effectiveness testing	'	0	'
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]	'	'	'
Derivative financial instruments	'	'	'
Number of derivative agreements	2	'	3
Period of reclassification from accumulated other comprehensive income to interest expense	'	'12 months	'

Derivative_Financial_Instrumen3

Derivative Financial Instruments (Details 2) (Interest Rate Swap [Member], Designated as Hedging Instrument [Member], Cash Flow Hedging [Member], Other Current Liabilities [Member], USD $)	Jun. 29, 2014	Sep. 29, 2013
In Thousands, unless otherwise specified
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Current Liabilities [Member]	'	'
Derivative financial instruments	'	'
Derivative liabilities, Fair Value of Derivative Instruments	$1,284	$987

Reclassifications_Out_of_Accum2

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) (USD $)

Jun. 29, 2014

Sep. 29, 2013

Jun. 29, 2014

Jun. 30, 2013

Jun. 29, 2014

Jun. 30, 2013

Jun. 30, 2013

Jun. 29, 2014

Jun. 29, 2014

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 29, 2014

Jun. 29, 2014

Jun. 29, 2014

Jun. 30, 2013

Jun. 29, 2014

Jun. 30, 2013

Jun. 30, 2013

Jun. 30, 2013

Jun. 29, 2014

Jun. 29, 2014

In Thousands, unless otherwise specified

Accumulated Translation Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Foreign Exchange Contract [Member]

Foreign Exchange Contract [Member]

Foreign Exchange Contract [Member]

Interest Rate Contract [Member]

Interest Rate Contract [Member]

Foreign Exchange Contract [Member]

Foreign Exchange Contract [Member]

Interest Rate Contract [Member]

Interest Rate Contract [Member]

Reclassifications out of accumulated other comprehensive income (loss)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Balances at the beginning of the period

($16,588)

$1,858

($35,406)

$13,377

$2,340

$31,110

'

($43)

($482)

($93)

'

'

'

'

($35,449)

$13,377

$1,858

$31,017

'

'

'

'

Other comprehensive income (loss) before reclassifications

'

'

19,507

-22,398

-18,239

-40,131

'

-41

1,481

257

'

'

'

'

19,466

-22,398

-16,758

-39,874

'

'

'

'

Amounts reclassified from accumulated other comprehensive income

'

'

'

'

'

'

0

'

'

'

0

-164

-605

-1,688

'

'

'

'

0

-164

-605

-1,688

Net current-period other comprehensive income (loss)

'

'

19,507

-22,398

-18,239

-40,131

'

-646

-207

93

'

'

'

'

18,861

-22,398

-18,446

-40,038

'

'

'

'

Balances at the end of the period

($16,588)

$1,858

($15,899)

($9,021)

($15,899)

($9,021)

'

($689)

($689)

'

'

'

'

'

($16,588)

($9,021)

($16,588)

($9,021)

'

'

'

'

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (Subsidiary of Common Parent [Member])	Mar. 31, 2013	Apr. 17, 2012
	item	item
Subsidiary of Common Parent [Member]	'	'
Loss contingencies	'	'
Number of employees of BPR Triax charged with allegations of corruption	'	2
Number of government contracts cited in testimony	5	'