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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

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FORM 10-Q/A
(Amendment No. 1)

(Mark One)

/x/	QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended April 1, 2001

OR

/ /	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                to               

Commission File Number 0-19655

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TETRA TECH, INC.
(Exact name of registrant as specified in its charter)

(626) 351-4664
(Registrant's telephone number, including area code)

Not Applicable
(Former name, former address and former fiscal year, if changed since last report)

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    Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter periods that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes /x/  No / /

    As of May 11, 2001, the total number of outstanding shares of the Registrant's common stock was 40,656,537.

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    The undersigned Registrant hereby amends the following item of its Quarterly Report on Form 10-Q for the quarter ended April 1, 2001, as set forth below:

PART I. FINANCIAL INFORMATION
Tetra Tech, Inc.
Condensed Consolidated Balance Sheets

Item 1.

In thousands, except share data				April 1, 2001			October 1, 2000
				(Unaudited)
ASSETS
CURRENT ASSETS:
	Cash and cash equivalents			$	12,411		$	7,557
	Accounts receivable—net				152,449			153,527
	Unbilled receivables—net				125,209			122,102
	Prepaid expenses and other current assets				18,904			11,203
	Deferred income taxes				2,551			2,551
		Total Current Assets			311,524			296,940
PROPERTY AND EQUIPMENT:
	Equipment, furniture and fixtures				65,210			59,361
	Leasehold improvements				5,299			4,182
		Total			70,509			63,543
	Accumulated depreciation and amortization				(32,988	)		(28,331	)
PROPERTY AND EQUIPMENT—NET					37,521			35,212
INTANGIBLE ASSETS—NET					210,157			190,452
OTHER ASSETS					4,162			3,434
TOTAL ASSETS				$	563,364		$	526,038
LIABILITIES AND STOCKHOLDERS' EQUITY
CURRENT LIABILITIES:
	Accounts payable			$	40,495		$	50,304
	Accrued compensation				25,166			25,705
	Billings in excess of costs on uncompleted contracts				10,842			15,947
	Other current liabilities				17,315			17,523
	Current portion of long-term obligations				28,000			26,000
	Income taxes payable				7,472			7,120
		Total Current Liabilities			129,290			142,599
LONG-TERM OBLIGATIONS					102,242			85,532
COMMITMENTS AND CONTINGENCIES
STOCKHOLDERS' EQUITY:
	Preferred stock—authorized, 2,000,000 shares of $.01 par value; issued and outstanding 0 shares at April 1, 2001 and October 1, 2000				—			—
	Exchangeable stock of a subsidiary				13,804			13,887
	Common stock—authorized, 85,000,000 shares of $.01 par value; issued and outstanding 40,579,267 and 39,830,633 shares at April 1, 2001 and October 1, 2000, respectively				406			398
	Additional paid-in capital				164,838			150,391
	Accumulated other comprehensive loss				(1,195	)		(844	)
	Retained earnings				153,979			134,075
TOTAL STOCKHOLDERS' EQUITY					331,832			297,907
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY				$	563,364		$	526,038

See accompanying Notes to Condensed Consolidated Financial Statements.

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Tetra Tech, Inc.
Condensed Consolidated Statements of Income
(Unaudited)

				Three Months Ended						Six Months Ended
In thousands, except per share data				April 1, 2001			April 2, 2000			April 1, 2001			April 2, 2000
Gross Revenue				$	234,315		$	177,581		$	463,645		$	347,822
	Subcontractor costs				54,657			38,735			116,849			79,805
Net Revenue					179,658			138,846			346,796			268,017
Cost of Net Revenue					138,254			109,562			266,659			209,979
Gross Profit					41,404			29,284			80,137			58,038
Selling, General and Administrative Expenses					18,868			11,999			37,427			24,551
Amortization of Intangibles					2,175			1,305			4,199			2,773
Income from Operations					20,361			15,980			38,511			30,714
Interest Expense					2,308			1,507			4,463			2,791
Interest Income					108			34			269			89
Income Before Income Tax Expense					18,161			14,507			34,317			28,012
Income Tax Expense					7,627			6,383			14,413			12,325
Net Income				$	10,534		$	8,124		$	19,904		$	15,687
Basic Earnings Per Share				$	0.26		$	0.21		$	0.50		$	0.41
Diluted Earnings Per Share				$	0.25		$	0.20		$	0.46		$	0.38
Weighted Average Common Shares Outstanding:
		Basic			40,363			38,550			40,189			38,501
		Diluted			42,804			41,140			42,944			40,779

See accompanying Notes to Condensed Consolidated Financial Statements.

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Tetra Tech, Inc.
Condensed Consolidated Statements of Cash Flow
(Unaudited)

				Six Months Ended
In thousands				April 1, 2001			April 2, 2000
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income				$	19,904		$	15,687
Adjustments to reconcile net income to net cash provided by (used in) operating
activities:
	Depreciation and amortization				8,956			7,377
	Provision for losses on receivables				1,434			(959	)
Changes in operating assets and liabilities, net of effects of acquisitions:
	Accounts receivable				3,250			(11,158	)
	Unbilled receivables				1,240			(6,489	)
	Prepaid expenses and other assets				(7,431	)		(4,555	)
	Accounts payable				(12,074	)		(7,573	)
	Accrued compensation				(2,405	)		496
	Billings in excess of costs on uncompleted contracts				(5,418	)		(181	)
	Other current liabilities				(2,243	)		(1,096	)
	Income taxes payable				(562	)		(7,392	)
		Net Cash Provided By (Used In) Operating Activities			4,651			(15,843	)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures					(4,439	)		(7,015	)
Payments for business acquisitions, net of cash acquired					(11,372	)		(2,089	)
		Net Cash Used In Investing Activities			(15,811	)		(9,104	)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments on long-term obligations					(39,216	)		(28,196	)
Proceeds from issuance of long-term obligations					53,500			63,000
Net proceeds from issuance of common stock					2,081			1,671
		Net Cash Provided By Financing Activities			16,365			36,475
EFFECT OF RATE CHANGES ON CASH					(351	)		926
NET INCREASE IN CASH AND CASH EQUIVALENTS					4,854			12,454
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD					7,557			8,189
CASH AND CASH EQUIVALENTS AT END OF PERIOD				$	12,411		$	20,643
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for:
	Interest			$	4,240		$	2,527
	Income taxes			$	14,061		$	19,718

See accompanying Notes to Condensed Consolidated Financial Statements.
(Continued)

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					Six Months Ended
In thousands					April 1, 2001			April 2, 2000
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING
ACTIVITIES:
	In March 2001, the Company purchased all of the capital stock of Williams, Hatfield & Stoner, Inc. (WHS). In conjunction with this acquisition, liabilities were assumed as follows:
		Fair value of assets acquired			$	10,725
		Cash paid				(6,234	)
		Issuance of common stock				(2,500	)
		Other acquisition costs				(50	)
			Liabilities assumed		$	1,941
	In March 2001, the Company purchased all of the capital stock of Wahco Construction, Inc. In conjunction with this acquisition, liabilities were assumed as follows:
		Fair value of assets acquired			$	4,567
		Cash paid				(400	)
		Issuance of common stock				(950	)
		Purchase price payable				(200	)
		Other acquisition costs				(65	)
			Liabilities assumed		$	2,952
	In December 2000, the Company purchased all of the capital stock of Rocky Mountain Consultants, Inc. In conjunction with this acquisition, liabilities were assumed as follows:
		Fair value of assets acquired			$	22,112
		Cash paid				(6,524	)
		Issuance of common stock				(8,700	)
		Other acquisition costs				(70	)
			Liabilities assumed		$	6,818
	In March 2000, concurrent with Tetra Tech Engineers, P.C.'s acquisition of certain assets of Edward A. Sears Associates, the Company's s subsidiary, Cosentini Associates, Inc., acquired certain non-licensed assets of Edward A. Sears Associates from Tetra Tech Engineers, P.C. In conjunction with this acquisition, liabilities were assumed as follows:
		Fair value of assets acquired						$	505
		Cash paid							(350	)
		Other acquisition costs							(80	)
			Liabilities assumed					$	75
	In October 1999, the Company purchased all of the capital stock of LC of Illinois, Inc. and HFC Technologies, Inc. In conjunction with these acquisitions, liabilities were assumed as follows:
		Fair value of assets acquired						$	2,606
		Cash paid							(1,513	)
		Other acquisition costs							(80	)
			Liabilities assumed					$	1,013

See accompanying Notes to Condensed Consolidated Financial Statements.
(Concluded)

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TETRA TECH, INC.
NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

1. Basis of Presentation

    The accompanying condensed consolidated balance sheet as of April 1, 2001, the condensed consolidated statements of income for the three-month and six-month periods ended April 1, 2001 and April 2, 2000 and the condensed consolidated statements of cash flows for the six months ended April 1, 2001 and April 2, 2000 are unaudited, and in the opinion of management include all adjustments, consisting of only normal and recurring adjustments, necessary for a fair presentation of the financial position and the results of operations for the periods presented.

    The condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the fiscal year ended October 1, 2000.

    The results of operations for the three and six months ended April 1, 2001 are not necessarily indicative of the results to be expected for the fiscal year ending September 30, 2001.

2.  Accounting Pronouncements

    In June 1998, the Financial Accounting Standards Board issued Statement of Financial Accounting Standards (SFAS) No. 133, Accounting for Derivative Instruments and Hedging Activities, which was amended by SFAS No. 138, Accounting for Certain Derivative Instruments and Certain Hedging Activities. These Statements required derivatives to be measured at fair value and to be recorded as assets or liabilities on the balance sheet. The accounting for gains or losses resulting from changes in the fair values of those derivatives would be dependent upon the use of the derivative and whether it qualifies for hedge accounting. These Statements became effective for all fiscal quarters of fiscal years beginning after June 15, 2000. The Company adopted these Statements in the first quarter of fiscal year 2001 and the adoption of SFAS No. 133 and SFAS No. 138 has had no material impact on the Company's results of operations or financial position.

    In December 1999, the Securities and Exchange Commission issued Staff Accounting Bulletin (SAB) No. 101, Revenue Recognition, which outlines the basic criteria that must be met to recognize revenue and provides guidance for disclosures related to revenue recognition policies. SAB No. 101 requires companies to report any changes in revenue recognition as a cumulative change in accounting principle at the time of implementation in accordance with Accounting Principles Board Opinion No. 20, Accounting Changes. SAB No. 101, as amended, is effective no later than the fourth quarter of fiscal years beginning after December 15, 1999. The Company will adopt SAB No. 101 in the fourth quarter of fiscal year 2001. The Company believes its existing revenue recognition policies and procedures are in compliance with SAB No. 101, and that the adoption of SAB No. 101 will have no material impact on the Company's results of operations or financial position.

3.  Earnings Per Share

    Basic EPS excludes dilution and is computed by dividing net income available to common stockholders by the weighted average number of common shares outstanding 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. The Company includes as potential common shares the weighted average number shares of exchangeable stock of a subsidiary and the weighted average dilutive effects of outstanding stock options. The exchangeable stock of a subsidiary is non-voting and is exchangeable on a one to one basis, as adjusted for stock splits and stock dividends subsequent to the

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original issuance, for the Company's common stock. The following table sets forth the computation of basic and diluted earnings per share:

4.  Cash and Cash Equivalents

    The Company considers all highly liquid investments purchased with a maturity of three months or less to be cash equivalents. Cash and cash equivalents totaled $12.4 million and $7.6 million at April 1, 2001 and October 1, 2001, respectively.

5.  Mergers and Acquisitions

    On October 25, 1999, the Company acquired 100% of the capital stock of LC of Illinois, Inc. and HFC Technologies, Inc. (collectively, LCI), a provider of engineering and network infrastructure services for cable television and fiber optic telephone networks including design, construction and maintenance capabilities for communications and information transport systems. The purchase was valued at approximately $1.6 million and consisted of cash.

    On March 30, 2000, Tetra Tech Engineers, P.C. acquired certain assets of Edward A. Sears Associates (ESA), a provider of engineering services to hospitals in New York. Concurrent with this transaction, the Company's subsidiary, Cosentini Associates, Inc., acquired certain non-licensed assets of ESA from Tetra Tech Engineers, P.C. The purchase was valued at approximately $0.4 million and consisted of cash.

    On April 3, 2000, the Company acquired 100% of the capital stock of eXpert Wireless Solutions, Inc. (EWS), a provider of radio-frequency engineering and consulting services to the wireless communications industry. The purchase was valued at approximately $18.8 million and consisted of cash (of which $500,000 is dependent on operational performance) and 407,877 shares of Company common stock. Additionally, concurrently with the acquisition, EWS distributed to its former shareholders accounts receivable valued at approximately $1.8 million.

    On May 3, 2000, the Company, through its majority-owned subsidiary, Tetra Tech Canada Ltd., acquired 100% of the capital stock of 1261248 Ontario, Inc., which does business as Engineered Communications (ENG), a provider of engineering and network services for the wired communications

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industry in Ontario, Canada. The purchase was valued at approximately $1.5 million and consisted of cash and 33,606 shares of exchangeable stock of the Company's majority-owned subsidiary.

    On May 17, 2000, the Company acquired 100% of the capital stock of FHC, Inc. (FHC), a provider of engineering consulting services primarily to the state and local governments in Oklahoma. The purchase was valued at approximately $5.2 million and consisted of cash and 56,334 shares of Company common stock.

    On May 24, 2000, the Company acquired 100% of the capital stock of Rizzo Associates, Inc. (RAI), a provider of engineering consulting services to state and local governments and commercial clients in the upper Northeast region of the U.S. This purchase was valued at approximately $10.3 million and consisted of cash and 112,436 shares of Company common stock.

    On June 16, 2000, the Company acquired 100% of the capital stock of Drake Contractors, Inc. (DCI), a provider of infrastructure installation and maintenance services primarily in Colorado. The purchase was valued at approximately $5.5 million and consisted of cash (of which $1.0 million is contingent on operational performance). Additionally, concurrent with the acquisition, DCI distributed to its former shareholders accounts receivable valued at approximately $2.1 million.

    On July 5, 2000, the Company, through its majority-owned subsidiary, Tetra Tech Canada Ltd., acquired 100% of the capital stock of Wm. Bethlehem Trenching Ltd. (BTL), a provider of infrastructure installation and maintenance services primarily in Ontario, Canada. The purchase was valued at approximately $0.3 million and consisted of cash.

    On December 21, 2000, the Company acquired 100% of the capital stock of Rocky Mountain Consultants, Inc. (RMC), a provider of water-related engineering and facility development services to state and local governments and private clients primarily in the western and midwestern United States. The purchase was valued at approximately $15.3 million and consisted of cash and 296,667 shares of Company common stock.

    On March 2, 2001, the Company acquired 100% of the capital stock of Wahco Construction, Inc. (WCI), a provider of network and field services to the utility and communications industry primarily in the northwestern United States. The purchase was valued at approximately $1.6 million and consisted of cash and 51,982 shares of Company common stock and is subject to a purchase price and purchase allocation adjustment based upon the final determination of WCI's net asset value as of March 2, 2001.

    On March 29, 2001, the Company acquired 100% of the capital stock of Williams, Hatfield & Stoner, Inc. (WHS), a provider of civil engineering, planning and environmental services primarily in the southeastern United States. The purchase was valued at approximately $8.8 million and consisted of cash and 127,547 shares of Company common stock and is subject to a purchase price and purchase allocation adjustment based upon the final determination of WHS's net asset value as of March 29, 2001.

    All of the acquisitions above have been accounted for as purchases and, accordingly, the purchase prices of the businesses acquired have been allocated to the assets and liabilities acquired based upon their fair values. The excess of the purchase cost of the acquisitions over the fair value of the net assets acquired was recorded as goodwill and is included in Intangible Assets—Net in the accompanying condensed consolidated balance sheets. Prior to fiscal 2001, the Company valued stock exchanged in acquisitions based on extended restriction periods, high volatility in the trading price of the Company's common stock and other economic factors specific to the Company's circumstances at the time of acquisition. During the first three quarters of fiscal 2000, stock exchanged in acquisitions was discounted by 15%. During fiscal 2001, the stock exchanged in acquisitions was not discounted. The results of operations of each of the companies acquired have been included in the Company's financial statements from the effective acquisition dates.

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6.  Accounts Receivable

    Accounts receivable are presented net of a valuation allowance to provide for doubtful accounts and for the potential disallowance of billed and unbilled costs. The allowance for doubtful accounts as of April 1, 2001 and October 1, 2000 was $6.5 million and $5.5 million, respectively. The allowance for disallowed costs as of both April 1, 2001 and October 1, 2000 was $1.6 million. Disallowance of billed and unbilled costs is primarily associated with contracts with the Federal government which contain clauses that subject contractors to several levels of audit. The Company establishes reserves on those contract receivables where collectibility is not assured. Management believes that resolution of these matters will not have a material adverse impact on the Company's financial position or results of operations.

7.  Unaudited Pro Forma Operating Results

    The table below presents summarized unaudited pro forma operating results assuming that the Company had acquired EWS, FHC, RAI and RMC on October 4, 1999. The effect of unaudited pro forma results of LCI, ENG, ESA, DCI, BTL, WCI and WHS, had they been acquired on October 4, 1999 is not material. These amounts are based on historical results and assumptions and estimates which the Company believes to be reasonable. The pro forma results do not reflect anticipated cost savings and do not necessarily represent results which would have occurred if these acquisitions had actually taken place on October 4, 1999.

			Pro Forma Six Months Ended
			April 1, 2001			April 2, 2000
Gross revenue			$	465,515,000		$	380,225,000
Income from operations				38,834,000			33,323,000
Net income				20,044,000			16,159,000
Basic earnings per share			$	0.50		$	0.42
Diluted earnings per share			$	0.47		$	0.39
Weighted average shares outstanding:
	Basic			40,239,000			38,938,000
	Diluted			42,994,000			41,216,000

8.  Operating Segments

    The Company's management has organized its operations into three operating segments: Resource Management, Infrastructure, and Communications. The Resource Management operating segment provides specialized environmental engineering and consulting services primarily relating to water quality and water availability to both public and private organizations. The Infrastructure operating segment provides engineering services to provide additional development, as well as upgrading and replacement of existing infrastructure to both public and private organizations. The Communications operating segment provides a comprehensive set of services including engineering, consulting and field services to telecommunications companies, wireless service providers and cable operators. Management has established these operating segments based upon the services provided, the different marketing strategies, and the specialized needs of the clients. The Company accounts 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 cost of the services performed. Management evaluates the performance of these operating segments based upon their respective income from operations before the effect of any acquisition related amortization.

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    The following tables set forth (in thousands) summarized financial information on the Company's reportable segments:

Reportable Segments:

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Reconciliations:

Major Clients

    The Company's net revenue attributable to the U.S. government was approximately $44.4 million and $41.9 million for the three months ended April 1, 2001 and April 2, 2000, respectively. Net revenue attributable to the U.S. government was approximately $85.6 million and $81.0 million for the six months ended April 1, 2001 and April 2, 2000, respectively. Both the Resource Management and Infrastructure operating segments report revenue from the U.S. government.

9.  Comprehensive Income

    Comprehensive income is the change in equity of a business enterprise during a period from transactions and other events and circumstances from non owner sources. These sources include net income and other revenues, expenses, gains and losses incurred. The Company includes as other

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comprehensive income translation gains and losses from subsidiaries with functional currencies different than that of the Company. Comprehensive income was approximately $10.2 million and $8.6 million for the three months ended April 1, 2001 and April 2, 2000, respectively. For the six months ended April 1, 2001 and April 2, 2000, comprehensive income was $19.5 million and $16.6 million, respectively. For the three and six months ended April 1, 2001, the Company realized net translation losses of $0.3 million and $0.4 million, respectively. For the three and six months ended April 2, 2000, the Company incurred net translation losses of $0.5 million and $0.9 million, respectively.

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SIGNATURES

    Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		TETRA TECH, INC.
Dated: May 18, 2001		By:	/s/ JAMES M. JASKA    James M. Jaska Executive Vice President, Chief Financial Officer and Treasurer (Principal Financial and Accounting Officer)

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PART I. FINANCIAL INFORMATION Tetra Tech, Inc. Condensed Consolidated Balance Sheets
Tetra Tech, Inc. Condensed Consolidated Statements of Income (Unaudited)
Tetra Tech, Inc. Condensed Consolidated Statements of Cash Flow (Unaudited)
TETRA TECH, INC. NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
SIGNATURES