Tetra Tech (TTEK) 10-Q 2 Feb 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Dec. 28, 2014	Jan. 26, 2015
Document and Entity Information
Entity Registrant Name	TETRA TECH INC
Entity Central Index Key	831641
Document Type	10-Q
Document Period End Date	28-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-18
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		61,661,071
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Dec. 28, 2014	Sep. 28, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$98,890	$122,379
Accounts receivable - net	667,425	701,892
Prepaid expenses and other current assets	53,040	52,256
Income taxes receivable	25,338	22,076
Total current assets	844,693	898,603
Property and equipment - net	70,661	73,864
Investments in and advances to unconsolidated joint ventures	1,936	2,140
Goodwill	698,833	714,190
Intangible assets - net	55,889	63,095
Other long-term assets	24,124	24,512
Total assets	1,696,136	1,776,404
Current liabilities:
Accounts payable	116,571	175,952
Accrued compensation	96,838	110,186
Billings in excess of costs on uncompleted contracts	106,882	103,343
Deferred income taxes	19,916	20,387
Current portion of long-term debt	10,907	10,989
Estimated contingent earn-out liabilities	6,786	3,568
Other current liabilities	78,467	79,436
Total current liabilities	436,367	503,861
Deferred income taxes	33,483	28,786
Long-term debt	190,116	192,842
Long-term estimated contingent earn-out liabilities		3,462
Other long-term liabilities	39,122	34,397
Commitments and contingencies
Equity:
Preferred stock - Authorized, 2,000 shares of $0.01 par value; no shares issued and outstanding at December 28, 2014, and September 28, 2014
Common stock - Authorized, 150,000 shares of $0.01 par value; issued and outstanding, 62,169 and 62,591 shares at December 28, 2014, and September 28, 2014, respectively	622	626
Additional paid-in capital	390,214	402,516
Accumulated other comprehensive loss	-67,587	-42,538
Retained earnings	672,677	651,475
Tetra Tech stockholders' equity	995,926	1,012,079
Noncontrolling interests	1,122	977
Total equity	997,048	1,013,056
Total liabilities and equity	$1,696,136	$1,776,404

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 28, 2014	Sep. 28, 2014
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	62,169	62,591
Common stock, shares outstanding	62,169	62,591

Condensed_Consolidated_Stateme

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

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013
Consolidated Statements of Comprehensive Income
Net income including noncontrolling interests	$25,646	$27,327
Other comprehensive income, net of tax
Foreign currency translation adjustments	-24,510	-22,135
(Loss) gain on cash flow hedge valuations, net of tax	-480	826
Other comprehensive loss, net of tax	-24,990	-21,309
Comprehensive income including noncontrolling interests	656	6,018
Net income attributable to noncontrolling interests	-71	-12
Foreign currency translation adjustments	-59	38
Comprehensive (income) loss attributable to noncontrolling interests	-130	26
Comprehensive income attributable to Tetra Tech	$526	$6,044

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013
Cash flows from operating activities:
Net income including noncontrolling interests	$25,646	$27,327
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	12,992	15,914
Equity in earnings of unconsolidated joint ventures	-650	-650
Distributions of earnings from unconsolidated joint ventures	810	364
Stock-based compensation	2,840	2,339
Excess tax benefits from stock-based compensation	-142	-213
Deferred income taxes	4,846	557
Provision for doubtful accounts	-1,150	3,069
Fair value adjustments to contingent consideration		-4,630
Foreign exchange loss (gain)	120	-91
(Gain) loss on disposal of property and equipment	-51	1,035
Changes in operating assets and liabilities, net of effects of business acquisitions:
Accounts receivable	35,617	19,237
Prepaid expenses and other assets	769	-3,928
Accounts payable	-59,382	-6,186
Accrued compensation	-13,348	-13,646
Billings in excess of costs on uncompleted contracts	3,539	12,671
Other liabilities	-6,276	-7,790
Income taxes receivable/payable	-726	-3,660
Net cash provided by operating activities	5,454	41,719
Cash flows from investing activities:
Capital expenditures	-7,137	-6,602
Payments for business acquisitions, net of cash acquired		-10,678
Payment received on note for sale of operation		3,900
Proceeds from sale of property and equipment	5,216	1,926
Net cash used in investing activities	-1,921	-11,454
Cash flows from financing activities:
Payments on long-term debt	-15,926	-233
Proceeds from borrowings	13,493
Payments of earn-out liabilities		-1,589
Net change in overdrafts		-915
Excess tax benefits from stock-based compensation	142	213
Repurchases of common stock	-20,167
Dividend paid	-4,372
Net proceeds from issuance of common stock	1,521	6,327
Net cash (used in) provided by financing activities	-25,309	3,803
Effect of foreign exchange rate changes on cash	-1,713	-2,577
Net (decrease) increase in cash and cash equivalents	-23,489	31,491
Cash and cash equivalents at beginning of year	122,379	129,305
Cash and cash equivalents at end of year	98,890	160,796
Cash paid during the year for:
Interest	1,867	2,251
Income taxes, net of refunds received of $0.4 million and $0.8 million	$4,700	$16,158

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Cash Flows (Parenthetical) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013
Condensed Consolidated Statements of Cash Flows
Income taxes, refunds received	$0.40	$0.80

Basis_of_Presentation

Basis of Presentation	3 Months Ended
	Dec. 28, 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 28, 2014.
	These financial statements reflect all normal recurring adjustments that are considered necessary for a 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.
	Beginning in the first quarter of fiscal 2015, we reorganized our core operations to better align them with our markets, resulting in two renamed reportable segments.  We now report our water resources, water and wastewater treatment, environment, and infrastructure engineering activities in the Water, Environment and Infrastructure (“WEI”) reportable segment.  Our Resource Management and Energy (“RME”) reportable segment includes our oil and gas, energy, mining, waste management, remediation, utilities, and international development services.  We report the results of the wind-down of our non-core construction activities in the Remediation and Construction Management (“RCM”) reportable segment.  Prior year amounts for reportable segments have been revised to conform to the current-year presentation.

Accounts_Receivable_Net

Accounts Receivable - Net	3 Months Ended
	Dec. 28, 2014
Accounts Receivable - Net
Accounts Receivable - Net
	2.Accounts Receivable – Net
	Net accounts receivable and billings in excess of costs on uncompleted contracts consisted of the following:
		December 28,		September 28,
		2014		2014
		(in thousands)
	Billed	$	337,791	$	351,693
	Unbilled	342,336		363,050
	Contract retentions	23,621		26,929
	Total accounts receivable – gross	703,748		741,672
	Allowance for doubtful accounts	-36,323		-39,780
	Total accounts receivable – net	$	667,425	$	701,892
	Billings in excess of costs on uncompleted contracts	$	106,882	$	103,343
	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 December 28, 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 December 28, 2014 and September 28, 2014 included approximately $78 million and $79 million, respectively, related to claims, including requests for equitable adjustment, on contracts that provide for price redetermination.  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 $3.2 million in the first quarter of fiscal 2015 related to the settlement of claims with a federal government client.
	Billed accounts receivable related to U.S. federal government contracts were $69.1 million and $57.4 million at December 28, 2014 and September 28, 2014, respectively.  U.S. federal government unbilled receivables were $67.8 million and $73.2 million at December 28, 2014 and September 28, 2014, respectively.  Other than the U.S. federal government, no single client accounted for more than 10% of our accounts receivable at December 28, 2014 and September 28, 2014.
	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. 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 net unfavorable operating income adjustments of $2.4 million during the first quarter of fiscal 2015 compared to $1.2 million in last year’s first quarter.  Changes in revenue and cost estimates could also result in a projected loss that would be recorded immediately in earnings.  As of December 28, 2014 and September 28, 2014, we recorded a liability for anticipated losses of $16.8 million and $18.6 million, respectively.  The estimated cost to complete the related contracts as of December 28, 2014 was $99.1 million.

Mergers_and_Acquisitions

Mergers and Acquisitions	3 Months Ended
	Dec. 28, 2014
Mergers and Acquisitions
Mergers and Acquisitions
	3.Mergers and Acquisitions
	We made no acquisitions in the first quarter of fiscal 2015.  In fiscal 2014, we made immaterial acquisitions that enhanced our service offerings and expanded our geographic presence in our WEI and RME reportable segments.
	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 2014 acquisitions primarily represent the value of workforces with distinct expertise in the oil and gas and disaster preparedness 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.  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 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 28, 2014).  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 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 first quarter of fiscal 2014, we recorded net decreases in our contingent earn-out liabilities and reported related net gains in operating income of $4.6 million.  The fiscal 2014 gains primarily resulted from updated valuations of the contingent consideration liability associated with our fiscal 2013 acquisition of Parkland Pipeline (“Parkland”).  Parkland serves the oil and gas industry in Western Canada.  Subsequent to the acquisition date, we lowered our income projections over the remaining earn-out periods and recorded corresponding reductions of the earn-out liabilities for Parkland.  We also determined that these lower income projections were the result of temporary events, and would not negatively impact Parkland’s longer-term performance or result in goodwill impairment.  We recorded no gains or losses related to changes in the estimated fair value of our contingent earn-out liabilities in the first quarter of fiscal 2015.
	At December 28, 2014, there was a total maximum of $44.7 million of outstanding contingent consideration related to acquisitions.  Of this amount, $6.8 million was estimated as the fair value and accrued on our condensed consolidated balance sheet. In the first quarter of fiscal 2015, we made no earn-out payments.  In the first quarter of fiscal 2014, we made $1.6 million of earn-out payments to former owners and reported them as cash used in financing activities.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	3 Months Ended
	Dec. 28, 2014
Goodwill and Intangible Assets
Goodwill and Intangible Assets
	4.Goodwill and Intangible Assets
	Effective September 29, 2014, we reorganized our core operations to better align them with our markets, resulting in two renamed reportable segments.  We now report our water resources, water and wastewater treatment, environment, and infrastructure engineering activities in the WEI reportable segment.  Our RME reportable segment includes our oil and gas, energy, mining, waste management, remediation, utilities, and international development services.  We report the results of the wind-down of our non-core construction activities in the RCM reportable segment.  Prior year amounts for reportable segments have been revised to conform to the current-year presentation.
	The following table summarizes the changes in the carrying value of goodwill:
		WEI			RME			RCM			Total
		(in thousands)
	Balance at September 28, 2014	$	238,086		$	476,104		$	–		$	714,190
	Goodwill additions	–			–			–			–
	Foreign exchange impact	-5,452			-9,905			–			-15,357
	Balance at December 28, 2014	$	232,634		$	466,199		$	–		$	698,833
	We perform our annual goodwill impairment review at the beginning of our fiscal fourth quarter.  Our most recent review at June 30, 2014 (i.e. the first day of our fourth quarter in fiscal 2014), 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.
	The reorganization of our core operations, described further in Note 10, “Reportable Segments”, also impacted the definition of our reporting units used for goodwill impairment testing.  As a result, as of September 29, 2014, we performed impairment testing for goodwill under our new segment structure and determined that the estimated fair value of each reporting unit exceeded its corresponding carrying amount including recorded goodwill, and, as such, no impairment existed as of September 29, 2014.  However, our Global Mining Practice (“GMP”) reporting unit had an estimated fair value that exceeded its carrying value by less than 20%.  As of December 28, 2014, the goodwill amount for GMP was $65.6 million.  Although we believe that our estimate of fair value for GMP is reasonable, if GMP’s financial performance falls significantly below our expectations or market prices for similar businesses decline, the goodwill for GMP could become impaired.
	Foreign exchange impact relates to our foreign subsidiaries with functional currencies that are different than our reporting currency.  The gross amounts of goodwill for WEI were $263.7 million and $269.2 million at December 28, 2014 and September 28, 2014, respectively, excluding $31.1 million of accumulated impairment.  The gross amounts of goodwill for RME were $492.6 million and $502.5 million at December 28, 2014 and September 28, 2014, respectively, excluding $26.4 million of accumulated impairment.
	The gross amount and accumulated amortization of our acquired identifiable intangible assets with finite useful lives included in “Intangible assets - net” on the condensed consolidated balance sheets, were as follows:
		December 28, 2014								September 28, 2014
		Weighted-		Gross			Accumulated			Gross			Accumulated
		Average		Amount			Amortization			Amount			Amortization
		Remaining Life
		(in Years)
		($ in thousands)
	Non-compete agreements	1.9		$	1,033		$	-562		$	1,086		$	-524
	Client relations	3.6		119,098			-64,742			122,198			-61,117
	Backlog	0.1		1,209			-1,174			1,283			-1,072
	Technology and trade names	1.9		2,815			-1,788			2,917			-1,676
	Total			$	124,155		$	-68,266		$	127,484		$	-64,389
	Foreign currency translation adjustments reduced net identifiable intangible assets by $1.3 million in the first quarter of fiscal 2015.  Amortization expense for the identifiable intangible assets for the first quarters of fiscal 2015 and 2014 was $5.9 million and $8.6 million, respectively.  Estimated amortization expense for the remainder of fiscal 2015 and succeeding years is as follows:
		Amount
		(in thousands)
	2015	$	14,327
	2016	16,713
	2017	13,987
	2018	5,968
	2019	2,887
	Beyond	2,007
	Total	$	55,889

Property_and_Equipment

Property and Equipment	3 Months Ended
	Dec. 28, 2014
Property and Equipment
Property and Equipment
	5.Property and Equipment
	Property and equipment consisted of the following:
		December 28,		September 28,
		2014		2014
		(in thousands)
	Land and buildings	$	4,029	$	4,029
	Equipment, furniture and fixtures	189,955		204,298
	Leasehold improvements	24,050		24,478
	Total property and equipment	218,034		232,805
	Accumulated depreciation	-147,373		-158,941
	Property and equipment, net	$	70,661	$	73,864
	The depreciation expense related to property and equipment, including assets under capital leases, was $6.9 million and $7.1 million for the first quarters of fiscal 2015 and 2014, respectively.

Stock_Repurchase_and_Dividends

Stock Repurchase and Dividends	3 Months Ended
	Dec. 28, 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 under which we could repurchase up to $100 million of our common stock.  Stock repurchases could be made on the open market or in privately negotiated transactions with third parties.  From the inception of this program through September 28, 2014, we repurchased through open market purchases a total of 3.9 million shares at an average price of $25.59 per share, for a total cost of $100 million.
	On November 10, 2014, the Board of Directors authorized a new stock repurchase program under which we may repurchase up to $200 million of our common stock over the next two years.  In the first quarter of fiscal 2015, we repurchased through open market purchases a total of 760,926 shares at an average price of $26.50, for a total cost of $20.2 million under this new repurchase program.
	On November 10, 2014, the Board of Directors declared a quarterly cash dividend of $0.07 per share to shareholders of record as of the close of business on November 26, 2014.  The total dividend of $4.4 million was paid on December 14, 2014.
	Subsequent Event.  On January 26, 2015, the Board of Directors declared a quarterly cash dividend of $0.07 per share payable on February 26, 2015 to stockholders of record as of the close of business on February 11, 2015.

Stockholders_Equity_and_Stock_

Stockholders' Equity and Stock Compensation Plans	3 Months Ended
	Dec. 28, 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 first quarters of fiscal 2015 and 2014 was $2.8 million and $2.3 million, respectively.  The majority of these amounts were included in “Selling, general and administrative (“SG&A”) expenses” in our condensed consolidated statements of income.  In the first quarter of fiscal 2015, we granted 266,420 stock options with an exercise price of $27.26 per share and an estimated weighted-average fair value of $8.20 per share.  In addition, we awarded 155,265 performance shares units (“PSUs”) to our non-employee directors and executive officers at the fair value of $27.26 per share on the award date.  All of the PSUs are performance-based and vest, if at all, after the conclusion of the three-year performance period.  The number of PSUs that ultimately vest is based 50% on the growth in our diluted earnings per share and 50% on our total shareholder return over the vesting period.  Additionally, we awarded 239,247 restricted stock units (“RSUs”) to our non-employee directors, executive officers and employees at the fair value of $27.26 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")	3 Months Ended
	Dec. 28, 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
		December 28,		December 29,
		2014		2013
		(in thousands, except per share data)
	Net income attributable to Tetra Tech	$	25,575	$	27,315
	Weighted-average common shares outstanding - basic	62,452		64,227
	Effect of dilutive stock options and unvested restricted stock	660		821
	Weighted-average common stock outstanding - diluted	63,112		65,048
	Earnings per share attributable to Tetra Tech:
	Basic	$	0.41	$	0.43
	Diluted	$	0.41	$	0.42
	For the first quarters of fiscal 2015 and 2014, 0.8 million and 0.4 million options, respectively, were excluded from the calculation 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.

Income_Taxes

Income Taxes	3 Months Ended
	Dec. 28, 2014
Income Taxes
Income Taxes
	9.Income Taxes
	The effective tax rates for the first quarters of fiscal 2015 and 2014 were 26.4% and 33.8%, respectively.  During the first quarter of fiscal 2015, the Tax Increase Prevention Act of 2014 was signed into law.  This law retroactively extended the federal research and experimentation credits (“R&E credits”) for amounts incurred from January 1, 2014 through December 31, 2014.  Our income tax expense for the first quarter of fiscal 2015 includes a tax benefit of $1.2 million attributable to operating income during the last nine months of fiscal 2014, primarily related to the retroactive recognition of these tax credits.
	At December 28, 2014, approximately $53 million of undistributed earnings of our foreign subsidiaries, primarily in Canada, 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 December 28, 2014, we performed our assessment of net deferred tax assets.  Significant management judgment is required in determining 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 27, 2015, 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.  Based on our assessment, we have 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 $7.3 million has been provided in prior years.

Reportable_Segments

Reportable Segments	3 Months Ended
	Dec. 28, 2014
Reportable Segments
Reportable Segments
	10.Reportable Segments
	Beginning in the first quarter of fiscal 2015, we reorganized our core operations to better align them with our markets, resulting in two renamed reportable segments.  We now report our water resources, water and wastewater treatment, environment, and infrastructure engineering activities in the WEI reportable segment.  Our RME reportable segment includes our oil and gas, energy, mining, waste management, remediation, utilities, and international development services.  We report the results of the wind-down of our non-core construction activities in the RCM reportable segment.  Prior year amounts for reportable segments have been revised to conform to the current-year presentation.
	Our reportable segments are as follows:
	WEI:  WEI provides consulting and engineering services worldwide for a broad range of water and infrastructure-related needs in both developed and emerging economies.  WEI supports both public and private clients including federal, state/provincial, and local governments, and global and local commercial and industrial clients.  The primary markets for WEI’s services include water management, environmental restoration, government consulting, and a broad range of civil infrastructure requirements for facilities, transportation, and regional and local development.  WEI’s services span from early data collection and monitoring, to data analysis and information technology, to science and engineering applied research, to engineering design, to construction management and operations and maintenance.
	RME:  RME provides consulting and engineering services worldwide for a broad range of resource management and energy needs.  RME supports both private and public clients, including global industrial and commercial clients, U.S. federal agencies in large scale remediation, and major international development agencies.  The primary markets for RME’s services include oil and gas, energy, mining, remediation, utilities, waste management, and international development.  RME’s services span from early data collection and monitoring, to data analysis and information technology, to science and engineering applied research, to engineering design, to construction management and operations and maintenance.  RME supports engineering, procurement and construction management (“EPCM”) for full service implementation of commercial projects, especially for oil and gas, industrial, and mining customers.
	RCM:  We report the results of the wind-down of our non-core construction activities in the RCM reportable segment.  We plan to complete all remaining work performed in this segment primarily in fiscal 2015.
	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
		December 28,		December 29,
		2014		2013
		(in thousands)
	Revenue
	WEI	$	233,668	$	229,330
	RME	331,673		359,263
	RCM	34,430		82,082
	Elimination of inter-segment revenue	-18,715		-24,827
	Total revenue	$	581,056	$	645,848
	Operating Income (Loss)
	WEI	$	21,832	$	22,225
	RME	25,720		33,260
	RCM	-3,420		-4,131
	Corporate (1)	-7,520		-7,636
	Total operating income	$	36,612	$	43,718
	Depreciation
	WEI	$	1,232	$	1,414
	RME	3,679		4,163
	RCM	660		798
	Corporate	1,293		754
	Total depreciation	$	6,864	$	7,129
	(1)Includes amortization of intangibles, other costs, and other income not allocable to our reportable segments.
		December 28,		September 28,
		2014		2014
		(in thousands)
	Total Assets
	WEI	$	267,615	$	302,877
	RME	421,493		442,911
	RCM	112,026		100,996
	Corporate (1)	895,002		929,620
	Total assets	$	1,696,136	$	1,776,404
	(1)Corporate assets consist of intercompany eliminations and assets not allocated to our reportable 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
		December 28,		December 29,
		2014		2013
		(in thousands)
	Client Sector
	International (1)	$	147,061	$	163,933
	U.S. commercial	175,183		186,296
	U.S. federal government (2)	184,186		195,184
	U.S. state and local government	74,626		100,435
	Total	$	581,056	$	645,848
	(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	3 Months Ended
	Dec. 28, 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 28, 2014).  The carrying value of our long-term debt approximated fair value at December 28, 2014 and September 28, 2014.  As of December 28, 2014 we had borrowings of $199.9 million outstanding under our amended credit agreement, which were used to fund our business acquisitions, working capital needs, and contingent earn-outs.

Joint_Ventures

Joint Ventures	3 Months Ended
	Dec. 28, 2014
Joint Ventures
Joint Ventures
	12.Joint Ventures
	Consolidated Joint Ventures
	The aggregate revenue of our consolidated joint ventures was $2.2 million and $2.6 million for the first quarters of fiscal 2015 and 2014, respectively.  The assets and liabilities of these consolidated joint ventures were immaterial at December 28, 2014 and September 28, 2014.  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 December 28, 2014 and September 28, 2014 were $1.7 million and $1.4 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 income.  For both the first quarter of fiscal 2015 and 2014, we reported $0.7 million of equity in earnings of unconsolidated joint ventures.  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 the aggregate, immaterial to our condensed consolidated financial statements.
	The aggregate carrying values of the assets and liabilities of the unconsolidated joint ventures were $20.3 million and $18.4 million, respectively, at December 28, 2014, and $20.1 million and $18.0 million, respectively, at September 28, 2014.

Derivative_Financial_Instrumen

Derivative Financial Instruments	3 Months Ended
	Dec. 28, 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 enter 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 (Level 2 measurement, as discribed in “Critical Accounting Policies and Estimates” in our Annual Report on Form 10-K for the fiscal year ended September 28, 2014).  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 (loss).
	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 interest rate swap agreements that we designated as cash flow hedges to fix the variable interest rates on the borrowings under the term loan facility.  At December 28, 2014, the effective portion of our interest rate swap agreements designated as cash flow hedges before tax effect was $0.3 million, all of which we expect to be reclassified from accumulated other comprehensive income to interest expense within the next 12 months.
	As of December 28, 2014, the total notional principal amount of our outstanding interest rate swap agreements which expire in May 2018 was $199.9 million and the weighted average fixed interest rate was 1.32%.
	The fair values of our outstanding derivatives designated as hedging instruments were as follows:
		Balance Sheet Location	December 28,		September 28,
			2014		2014
			(in thousands)
	Interest rate swap agreements	Other current liabilities	$	523	$	45
	The impact of the effective portions of derivative instruments in cash flow hedging relationships on income and other comprehensive income from our foreign currency forward contracts and interest rate swap agreements was immaterial for the first three months of fiscal 2015 and the fiscal year ended September 28, 2014.  Additionally, there were no ineffective portions of derivative instruments.  Accordingly, no amounts were excluded from effectiveness testing for our foreign currency forward contracts and interest rate swap agreements.  We had no derivative instruments that were not designated as hedging instruments for fiscal 2014 and the first quarter of fiscal 2015.

Reclassifications_Out_of_Accum

Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Dec. 28, 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 months ended December 28, 2014 and December 29, 2013 related to reclassifications out of accumulated other comprehensive income (loss) are summarized as follows:
		Foreign		Loss on		Accumulated
		Currency		Derivative		Other
		Translation		Instruments		Comprehensive
		Adjustments				Income (Loss)
		(in thousands)
	Balances at September 29, 2013	$	2,340	$	-482	$	1,858
	Other comprehensive income (loss) before reclassifications	-22,096		308		-21,788
	Reclassification adjustment of prior derivative settlement, net of tax	–		517		517
	Net current-period other comprehensive income (loss)	-22,096		825		-21,271
	Balances at December 29, 2013	$	-19,756	$	343	$	-19,413
	Balances at September 28, 2014	$	-43,085	$	547	$	-42,538
	Other comprehensive income (loss) before reclassifications	-24,569		111		-24,458
	Reclassification adjustment of prior derivative settlement, net of tax	–		-591		-591
	Net current-period other comprehensive income (loss)	-24,569		-480		-25,049
	Balances at December 28, 2014	$	-67,654	$	67	$	-67,587

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 28, 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 former 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 into 2016.  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.
	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 then filed a motion to dismiss.  On November 3, 2014, the court dismissed the plaintiff’s appeal.  The plaintiff has filed an appeal with the Supreme Court of Canada.
	The financial impact to us of the matters discussed above is unknown at this time.

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	3 Months Ended
	Dec. 28, 2014
Recent Accounting Pronouncements
Recent Accounting Pronouncements
	16.Recent Accounting Pronouncements
	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.  The guidance became effective for us in the first quarter of fiscal 2015.  The adoption of this guidance did not 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 that 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.
	In August 2014, the FASB issued an amendment to the accounting guidance related to the evaluation of an entity to continue as a going concern.  The amendment establishes management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern in connection with preparing financial statements for each annual and interim reporting period.  The update also gives guidance to determine whether to disclose information about relevant conditions and events when there is substantial doubt about an entity’s ability to continue as a going concern.  This guidance is effective for us in the first quarter of fiscal 2017.  We do not expect the adoption of this guidance to have an impact on our condensed consolidated financial statements.
	In January 2015, the FASB issued an amendment to the accounting guidance related to the income statement presentation of extraordinary and unusual items.  The amendment eliminates from U.S. GAAP the concept of extraordinary items.  This guidance is effective for us in the first quarter of fiscal 2017.  We do not expect the adoption of this guidance to have an impact on our condensed consolidated financial statements.

Accounts_Receivable_Net_Tables

Accounts Receivable - Net (Tables)	3 Months Ended
	Dec. 28, 2014
Accounts Receivable - Net
Net accounts receivable and billings in excess of costs on uncompleted contracts
		December 28,		September 28,
		2014		2014
		(in thousands)
	Billed	$	337,791	$	351,693
	Unbilled	342,336		363,050
	Contract retentions	23,621		26,929
	Total accounts receivable – gross	703,748		741,672
	Allowance for doubtful accounts	-36,323		-39,780
	Total accounts receivable – net	$	667,425	$	701,892
	Billings in excess of costs on uncompleted contracts	$	106,882	$	103,343

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Dec. 28, 2014
Goodwill and Intangible Assets
Summary of changes in the carrying value of goodwill
		WEI			RME			RCM			Total
		(in thousands)
	Balance at September 28, 2014	$	238,086		$	476,104		$	–		$	714,190
	Goodwill additions	–			–			–			–
	Foreign exchange impact	-5,452			-9,905			–			-15,357
	Balance at December 28, 2014	$	232,634		$	466,199		$	–		$	698,833
Summary of acquired identifiable intangible assets with finite useful lives
		December 28, 2014								September 28, 2014
		Weighted-		Gross			Accumulated			Gross			Accumulated
		Average		Amount			Amortization			Amount			Amortization
		Remaining Life
		(in Years)
		($ in thousands)
	Non-compete agreements	1.9		$	1,033		$	-562		$	1,086		$	-524
	Client relations	3.6		119,098			-64,742			122,198			-61,117
	Backlog	0.1		1,209			-1,174			1,283			-1,072
	Technology and trade names	1.9		2,815			-1,788			2,917			-1,676
	Total			$	124,155		$	-68,266		$	127,484		$	-64,389
Estimated amortization expense for the succeeding five years and beyond
		Amount
		(in thousands)
	2015	$	14,327
	2016	16,713
	2017	13,987
	2018	5,968
	2019	2,887
	Beyond	2,007
	Total	$	55,889

Property_and_Equipment_Tables

Property and Equipment (Tables)	3 Months Ended
	Dec. 28, 2014
Property and Equipment
Schedule of components of property and equipment
		December 28,		September 28,
		2014		2014
		(in thousands)
	Land and buildings	$	4,029	$	4,029
	Equipment, furniture and fixtures	189,955		204,298
	Leasehold improvements	24,050		24,478
	Total property and equipment	218,034		232,805
	Accumulated depreciation	-147,373		-158,941
	Property and equipment, net	$	70,661	$	73,864

Earnings_Per_Share_EPS_Tables

Earnings Per Share ("EPS") (Tables)	3 Months Ended
	Dec. 28, 2014
Earnings Per Share ("EPS")
Schedule of number of weighted-average shares used to compute basic and diluted EPS
		Three Months Ended
		December 28,		December 29,
		2014		2013
		(in thousands, except per share data)
	Net income attributable to Tetra Tech	$	25,575	$	27,315
	Weighted-average common shares outstanding - basic	62,452		64,227
	Effect of dilutive stock options and unvested restricted stock	660		821
	Weighted-average common stock outstanding - diluted	63,112		65,048
	Earnings per share attributable to Tetra Tech:
	Basic	$	0.41	$	0.43
	Diluted	$	0.41	$	0.42

Reportable_Segments_Tables

Reportable Segments (Tables)	3 Months Ended
	Dec. 28, 2014
Reportable Segments
Summarized financial information of reportable segments
		Three Months Ended
		December 28,		December 29,
		2014		2013
		(in thousands)
	Revenue
	WEI	$	233,668	$	229,330
	RME	331,673		359,263
	RCM	34,430		82,082
	Elimination of inter-segment revenue	-18,715		-24,827
	Total revenue	$	581,056	$	645,848
	Operating Income (Loss)
	WEI	$	21,832	$	22,225
	RME	25,720		33,260
	RCM	-3,420		-4,131
	Corporate (1)	-7,520		-7,636
	Total operating income	$	36,612	$	43,718
	Depreciation
	WEI	$	1,232	$	1,414
	RME	3,679		4,163
	RCM	660		798
	Corporate	1,293		754
	Total depreciation	$	6,864	$	7,129
	(1)Includes amortization of intangibles, other costs, and other income not allocable to our reportable segments.
		December 28,		September 28,
		2014		2014
		(in thousands)
	Total Assets
	WEI	$	267,615	$	302,877
	RME	421,493		442,911
	RCM	112,026		100,996
	Corporate (1)	895,002		929,620
	Total assets	$	1,696,136	$	1,776,404
	(1)Corporate assets consist of intercompany eliminations and assets not allocated to our reportable segments including goodwill, intangible assets, deferred income taxes and certain other assets.
Summary of revenue by client sector
		Three Months Ended
		December 28,		December 29,
		2014		2013
		(in thousands)
	Client Sector
	International (1)	$	147,061	$	163,933
	U.S. commercial	175,183		186,296
	U.S. federal government (2)	184,186		195,184
	U.S. state and local government	74,626		100,435
	Total	$	581,056	$	645,848
	(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)	3 Months Ended
	Dec. 28, 2014
Derivative Financial Instruments
Schedule of fair values of the entity's outstanding derivatives designated as hedging instruments
		Balance Sheet Location	December 28,		September 28,
			2014		2014
			(in thousands)
	Interest rate swap agreements	Other current liabilities	$	523	$	45

Reclassifications_Out_of_Accum1

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Dec. 28, 2014
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)
Summary of reclassifications out of accumulated other comprehensive income (loss)
		Foreign		Loss on		Accumulated
		Currency		Derivative		Other
		Translation		Instruments		Comprehensive
		Adjustments				Income (Loss)
		(in thousands)
	Balances at September 29, 2013	$	2,340	$	-482	$	1,858
	Other comprehensive income (loss) before reclassifications	-22,096		308		-21,788
	Reclassification adjustment of prior derivative settlement, net of tax	–		517		517
	Net current-period other comprehensive income (loss)	-22,096		825		-21,271
	Balances at December 29, 2013	$	-19,756	$	343	$	-19,413
	Balances at September 28, 2014	$	-43,085	$	547	$	-42,538
	Other comprehensive income (loss) before reclassifications	-24,569		111		-24,458
	Reclassification adjustment of prior derivative settlement, net of tax	–		-591		-591
	Net current-period other comprehensive income (loss)	-24,569		-480		-25,049
	Balances at December 28, 2014	$	-67,654	$	67	$	-67,587

Basis_of_Presentation_Details

Basis of Presentation (Details)	3 Months Ended
	Dec. 28, 2014
	item
Basis of Presentation
Number Of Renamed Reportable Segments	2

Accounts_Receivable_Net_Detail

Accounts Receivable - Net (Details) (USD $)	3 Months Ended
	Dec. 28, 2014	Sep. 28, 2014	Dec. 29, 2013
Accounts Receivable - Net
Billed	$337,791,000	$351,693,000
Unbilled	342,336,000	363,050,000
Contract retentions	23,621,000	26,929,000
Total accounts receivable - gross	703,748,000	741,672,000
Allowance for doubtful accounts	-36,323,000	-39,780,000
Total accounts receivable - net	667,425,000	701,892,000
Billings in excess of costs on uncompleted contracts	106,882,000	103,343,000
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	78,000,000	79,000,000
Revenue recognized related to the evaluation of claim amounts	3,200,000
Increase in operating income related to the evaluation of claim amounts	3,200,000
Billed accounts receivable related to U.S. federal government contracts	69,100,000	57,400,000
U.S. federal government unbilled receivables	67,800,000	73,200,000
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	2,400,000		1,200,000
Liability for anticipated losses	16,800,000	18,600,000
Estimated cost to complete the related contracts	$99,100,000
Accounts Receivable
Account receivable major customer
Number of clients exceeding threshold	0	0

Mergers_and_Acquisitions_Detai

Mergers and Acquisitions (Details) (USD $)	3 Months Ended
	Dec. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
	item
Business acquisition
Number of acquisitions	0
Estimated fair value of contingent earn-out obligations	$6,800,000
Aggregate maximum of contingent consideration	44,700,000
Net decreases in our contingent earn-out liabilities	0	4,600,000
Net gains on fair value adjustment in operating income		4,600,000
Goodwill balance	698,833,000		714,190,000
Earn-outs paid to former owners reported as cash used in financing activities	$0	$1,600,000
Maximum
Business acquisition
Earn out period for operating income projection	3 years
Minimum
Business acquisition
Earn out period for operating income projection	2 years

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets (Details) (USD $)	3 Months Ended
	Dec. 28, 2014	Sep. 28, 2014
Goodwill information
Number Of Renamed Reportable Segments	2
Goodwill	$698,833,000
Goodwill
Balance at beginning of the period	714,190,000
Foreign exchange impact	-15,357,000
Balance at end of the period	698,833,000
Impairment of goodwill	0
GMP
Goodwill information
Goodwill	65,600,000
Goodwill
Balance at end of the period	65,600,000
WEI
Goodwill information
Goodwill	232,634,000
Goodwill
Balance at beginning of the period	238,086,000
Foreign exchange impact	-5,452,000
Balance at end of the period	232,634,000
Gross amounts of goodwill	263,700,000	269,200,000
Accumulated impairment	31,100,000	31,100,000
RME
Goodwill information
Goodwill	466,199,000
Goodwill
Balance at beginning of the period	476,104,000
Foreign exchange impact	-9,905,000
Balance at end of the period	466,199,000
Gross amounts of goodwill	492,600,000	502,500,000
Accumulated impairment	$26,400,000	$26,400,000

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets (Details 2) (USD $)	3 Months Ended
	Dec. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
Finite-lived intangible assets
Gross Amount	$124,155,000		$127,484,000
Accumulated Amortization	-68,266,000		-64,389,000
Foreign currency translation adjustments	1,300,000
Amortization expense for identifiable intangible assets	5,900,000	8,600,000
Estimated amortization expense
2015	14,327,000
2016	16,713,000
2017	13,987,000
2018	5,968,000
2019	2,887,000
Beyond	2,007,000
Total	55,889,000
Non-compete agreements
Finite-lived intangible assets
Weighted-Average Remaining Life	1 year 10 months 24 days
Gross Amount	1,033,000		1,086,000
Accumulated Amortization	-562,000		-524,000
Client relations
Finite-lived intangible assets
Weighted-Average Remaining Life	3 years 7 months 6 days
Gross Amount	119,098,000		122,198,000
Accumulated Amortization	-64,742,000		-61,117,000
Backlog
Finite-lived intangible assets
Weighted-Average Remaining Life	1 month 6 days
Gross Amount	1,209,000		1,283,000
Accumulated Amortization	-1,174,000		-1,072,000
Technology and trade names
Finite-lived intangible assets
Weighted-Average Remaining Life	1 year 10 months 24 days
Gross Amount	2,815,000		2,917,000
Accumulated Amortization	($1,788,000)		($1,676,000)

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
Property and Equipment
Property and equipment at cost, gross	$218,034		$232,805
Accumulated depreciation	-147,373		-158,941
Property and equipment, net	70,661		73,864
Depreciation expense related to property and equipment, including assets under capital leases	6,864	7,129
Land and buildings
Property and Equipment
Property and equipment at cost, gross	4,029		4,029
Equipment, furniture and fixtures
Property and Equipment
Property and equipment at cost, gross	189,955		204,298
Leasehold improvements
Property and Equipment
Property and equipment at cost, gross	$24,050		$24,478

Stock_Repurchase_and_Dividends1

Stock Repurchase and Dividends (Details) (USD $)	0 Months Ended		3 Months Ended	16 Months Ended	0 Months Ended
	Dec. 14, 2014	Nov. 10, 2014	Dec. 28, 2014	Sep. 28, 2014	Jan. 26, 2015	Jun. 30, 2013
Maximum repurchase amount under stock repurchase program		$200,000,000				$100,000,000
Shares repurchased through open market purchases			760,926	3,900,000
Average price of shares repurchased (in dollars per share)			$26.50	$25.59
Cost of shares repurchased			20,200,000	100,000,000
Payment of ordinary dividends	$4,400,000		$4,372,000
Quarterly cash dividend declared (in dollars per share)		$0.07
Cash dividends paid per share			$0.07
Period of stock repurchase program		2 years
Subsequent Event
Quarterly cash dividend declared (in dollars per share)					$0.07

Stockholders_Equity_and_Stock_1

Stockholders' Equity and Stock Compensation Plans (Details) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013
Stockholders' Equity and Stock Compensation Plans
Stock-based compensation expense	$2.80	$2.30
Options granted (in shares)	266,420
Restricted stock award
Exercise price of stock options granted (in dollars per share)	$27.26
Weighted-average fair value of stock options granted (in dollars per share)	$8.20
Non-employee executive officers and employees
Restricted stock award
Vesting period	4 years
Non-employee director
Restricted stock award
Vesting period	1 year
Performance-based restricted stock
Restricted stock award
Percentage of shares that ultimately vest depending on fiscal year earnings per share growth rates	50.00%
Percentage of shares that ultimately vest depending on fiscal year shareholder vesting period	50.00%
Performance-based restricted stock | Non-employee directors and executive officers
Restricted stock award
Granted (in shares)	155,265
Granted, fair value (in dollars per share)	$27.26
Vesting period	3 years
Time-based restricted stock | Non-employee directors, executive officers and employees
Restricted stock award
Granted (in shares)	239,247
Granted, fair value (in dollars per share)	$27.26

Earnings_Per_Share_EPS_Details

Earnings Per Share (''EPS'') (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013
Number of weighted-average shares used to compute basic and diluted EPS:
Net income attributable to Tetra Tech	$25,575	$27,315
Weighted-average common shares outstanding - basic	62,452,000	64,227,000
Effect of diluted stock options and unvested restricted stock	660,000	821,000
Weighted-average common stock outstanding - diluted	63,112,000	65,048,000
Earnings per share attributable to Tetra Tech:
Basic	$0.41	$0.43
Diluted	$0.41	$0.42
Stock options
Antidilutive securities
Securities excluded from the calculation of dilutive potential common shares	800,000	400,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013	Sep. 27, 2015
Income Taxes
Effective tax rate (as a percent)	26.40%	33.80%
Undistributed earnings of foreign subsidiaries	$53
Loss carry-forwards in foreign jurisdictions, valuation allowance	7.3
Represents the period of projected cumulative pre-tax losses in certain foreign jurisdictions			36 months
R&E credits	$1.20

Reportable_Segments_Details

Reportable Segments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
	item
Financial information concerning reportable segments
Number of renamed reportable segments	2
Revenue	$581,056	$645,848
Operating income (loss)	36,612	43,718
Depreciation	6,864	7,129
Total assets	1,696,136		1,776,404
Inter-segment elimination
Financial information concerning reportable segments
Revenue	-18,715	-24,827
Corporate
Financial information concerning reportable segments
Operating income (loss)	-7,520	-7,636
Depreciation	1,293	754
Corporate
Financial information concerning reportable segments
Total assets	895,002		929,620
WEI | Operating segment
Financial information concerning reportable segments
Revenue	233,668	229,330
Operating income (loss)	21,832	22,225
Depreciation	1,232	1,414
Total assets	267,615		302,877
RME | Operating segment
Financial information concerning reportable segments
Revenue	331,673	359,263
Operating income (loss)	25,720	33,260
Depreciation	3,679	4,163
Total assets	421,493		442,911
RCM | Operating segment
Financial information concerning reportable segments
Revenue	34,430	82,082
Operating income (loss)	-3,420	-4,131
Depreciation	660	798
Total assets	$112,026		$100,996

Reportable_Segments_Details_2

Reportable Segments (Details 2) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013
Revenue by client sector
Threshold percentage for disclosure of revenue from a single client	10.00%
Revenue	$581,056	$645,848
Revenue
Revenue by client sector
Number of clients exceeding threshold	0
International
Revenue by client sector
Revenue	147,061	163,933
U.S. commercial
Revenue by client sector
Revenue	175,183	186,296
U.S. federal government
Revenue by client sector
Revenue	184,186	195,184
U.S. state and local government
Revenue by client sector
Revenue	$74,626	$100,435

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	Dec. 28, 2014
In Millions, unless otherwise specified
Fair Value Measurements
Outstanding borrowings under the amended credit agreement	$199.90

Joint_Ventures_Details

Joint Ventures (Details) (USD $)	3 Months Ended
	Dec. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
Aggregate revenue of consolidated joint ventures	$581,056,000	$645,848,000
Unconsolidated Joint Ventures
Equity in earnings from unconsolidated joint ventures	650,000	650,000
Carrying value of assets of unconsolidated joint ventures	20,300,000		20,100,000
Carrying value of liabilities of unconsolidated joint ventures	18,400,000		18,000,000
Consolidated Joint Ventures
Aggregate revenue of consolidated joint ventures	2,200,000	2,600,000
Cash and cash equivalents of consolidated joint ventures	$1,700,000		$1,400,000

Derivative_Financial_Instrumen2

Derivative Financial Instruments (Details) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Dec. 28, 2014	Sep. 28, 2014	Dec. 29, 2013	Sep. 29, 2013
			item	item
Derivative financial instruments
Notional Amount	$199.90
Weighted average fixed rate	1.32%
Not designated as hedging instruments
Derivative financial instruments
Number of derivative instruments	0		0
Interest rate swap agreements | Derivatives designated as hedging instruments
Derivative financial instruments
Amounts excluded from effectiveness testing	0	0
Interest rate swap agreements | Designated as cash flow hedges | Derivatives designated as hedging instruments
Derivative financial instruments
Number of derivative agreements			2	3
Amount of effective portion of derivatives before tax effect	$0.30
Period of reclassification from accumulated other comprehensive income to interest expense	12 months

Derivative_Financial_Instrumen3

Derivative Financial Instruments (Details 2) (Interest rate swap agreements, Derivatives designated as hedging instruments, Designated as cash flow hedges, Other current liabilities, USD $)	Dec. 28, 2014	Sep. 28, 2014
In Thousands, unless otherwise specified
Interest rate swap agreements | Derivatives designated as hedging instruments | Designated as cash flow hedges | Other current liabilities
Derivative financial instruments
Derivative liabilities, Fair Value of Derivative Instruments	$523	$45

Reclassifications_Out_of_Accum2

Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Dec. 28, 2014	Dec. 29, 2013	Sep. 28, 2014
Reclassifications out of accumulated other comprehensive income (loss)
Balances at the beginning of the period			($42,538)
Balances at the end of the period	-67,587		-42,538
Foreign Currency Translation Adjustments
Reclassifications out of accumulated other comprehensive income (loss)
Balances at the beginning of the period	-43,085	2,340
Other comprehensive income (loss) before reclassifications	-24,569	-22,096
Net current-period other comprehensive (loss) income	-24,569	-22,096
Balances at the end of the period	-67,654	-19,756
Loss on Derivative Instruments
Reclassifications out of accumulated other comprehensive income (loss)
Balances at the beginning of the period	547	-482
Other comprehensive income (loss) before reclassifications	111	308
Net current-period other comprehensive (loss) income	-480	825
Balances at the end of the period	67	343
Loss on Derivative Instruments | Foreign exchange contracts
Reclassifications out of accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income	-591	517
Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income (loss)
Balances at the beginning of the period	-42,538	1,858
Other comprehensive income (loss) before reclassifications	-24,458	-21,788
Net current-period other comprehensive (loss) income	-25,049	-21,271
Balances at the end of the period	-67,587	-19,413
Accumulated Other Comprehensive Income | Foreign exchange contracts
Reclassifications out of accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income	($591)	$517

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (BPR Triax)	Apr. 17, 2012
	item
BPR Triax
Loss contingencies
Number of former employees of BPR Triax charged with allegations of corruption	2