Tetra Tech Awarded $60 Million Federal Aviation Administration Satellite Navigation Assistance Contract

(PASADENA, Calif., Feb. 1, 2006) -- Tetra Tech, Inc. (NASDAQ:TTEK) announced today that it was awarded the rebid to its largest Federal Aviation Administration (FAA) contract, the Global Positioning System Technical Assistance Contract 2 (GPS TAC2). This follow-on contract is worth approximately $60 million over two base years and one option year. Tetra Tech's work helps the FAA capitalize on GPS technology advancements to allow for greater civilian air travel density and to provide greater worldwide accuracy, availability, and integrity of navigation information. Tetra Tech will provide a full range of technical engineering and business support services to help manage the FAA's current and future satellite navigation system needs. Tetra Tech has supported the FAA as the prime contractor for a predecessor to the GPS TAC2 contract for the past seven years. Under the predecessor contract, Tetra Tech provided comprehensive acquisition support services for the world's first satellite navigation system used for civilian aviation. The Wide Area Augmentation System helped improve navigation signal accuracy from 20 meters to as close as 1.5 meters accuracy in both horizontal and vertical dimensions. About Tetra Tech (www.tetratech.com) Tetra Tech is a leading provider of consulting, engineering, and technical services. With over 7,500 associates located in the United States and internationally, the Company supports commercial and government clients in the areas of resource management and infrastructure. Tetra Tech's services include research and development, applied science and technology, engineering design, program management, construction management, and operations and maintenance. Any statements made in this release that are not based on historical fact are forward-looking statements. Any forward-looking statements made in this release represent management's best judgment as to what may occur in the future. However, Tetra Tech's actual outcome and results are not guaranteed and are subject to certain risks, uncertainties, and assumptions ("Future Factors"), and may differ materially from what is expressed. For a description of Future Factors that could cause actual results to differ materially from such forward-looking statements, see the discussion under the section "Risk Factors" included in the Company's Form 10-K and 10-Q filings with the Securities and Exchange Commission. CONTACT: Mike Bieber 626-351-4664

Source: Tetra Tech, Inc.
Date: Feb 1, 2006