Tetra Tech Expands Water Programs with Over $17 Million in New Contracts at EPA.

Business Editors

PASADENA, Calif.--(BUSINESS WIRE)--April 13, 2004

Tetra Tech, Inc. (Nasdaq:TTEK) announced today that it was awarded over $17 million in new contracts from the U.S. EPA Office of Water. These three contracts support development of water quality standards and

Under a five-year $12.2 million contract, Tetra Tech will support the EPA Office of Water to assess and manage risks associated with toxic bioaccumulation of contaminants in surface waters. Tetra Tech will provide a broad range of technical support, including EPA guidance support, scientific methods development, and national assessment of the extent and severity of watershed contamination.

Additionally, under a five-year $3.3 million contract, Tetra Tech will support the EPA Office of Water to develop, revise, and implement ecological criteria for the protection of water quality on a national, state, and site-specific basis. This includes conducting the National Wadeable Streams Assessment under a congressionally mandated initiative to the EPA.

Tetra Tech was also awarded a one-year $1.8 million contract extension to a separate EPA contract to provide technical services for EPA's nationwide animal feeding operations (AFOs), permitting initiatives under the National Pollutant Discharge Elimination System (NPDES) program.

Li-San Hwang, Tetra Tech's CEO, commented, "Tetra Tech has been supporting national clean water programs through the EPA Office of Water for over 20 years. We are pleased to be expanding our technical support to this customer through these latest contracts and look forward to our continued relationship."

About the EPA Office of Water (www.epa.gov/ow)

The EPA Office of Water is responsible for supporting improvement to the condition of the nation's water resources, and ensuring that waterbodies are safe for the benefit of human health and the environment.

About Tetra Tech (www.tetratech.com)

Tetra Tech is a leading provider of consulting, engineering, and technical services. With over 9,000 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, 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.