Tetra Tech Selected for $50 Billion Multiple-Award GSA Alliant Information Technology Contract

Business Wire, August 1, 2007

PASADENA, Calif. -- Tetra Tech, Inc. (NASDAQ:TTEK) announced today that it has been selected for the General Services Administration (GSA) Alliant Government-wide Acquisition Contract, a ten-year, multiple-award information technology contract with a $50 billion contract ceiling. GSA selected 29 contractors to share this indefinite delivery/indefinite quantity contract. The contract includes infrastructure, applications, and management services in support of federal agencies' information technology requirements.

"Alliant is expected to be the primary information technology services contract vehicle for civilian agencies and, to a lesser extent, the U.S. Department of Defense over the next ten years," said Tetra Tech CEO Dan Batrack. "With this new contract, Tetra Tech can significantly expand its information management and technology services for the federal government. This is a great new opportunity because Tetra Tech did not hold one of the three primary contracts that Alliant replaces."

Alliant's scope includes all components of an integrated information technology solution, including current and new technologies that may emerge during the lifecycle of the contract as well as information technology systems and services in support of national security systems. The contract supports a broad range of global information technology services and requirements, including infrastructure protection, anti-terrorism efforts, and emerging technologies.

Alliant has a five-year base period and one five-year option. Tetra Tech's Advanced Management Technology, Inc. (AMTI) operating unit was selected for this contract.

About Tetra Tech (www.tetratech.com)

Tetra Tech is a leading provider of consulting, engineering, and technical services. With approximately 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.