Tetra Tech Announces Planned Dates for First Quarter 2010 Results and Conference Call

Tetra Tech, Inc. (NASDAQ: TTEK) today announced the planned dates for its first quarter 2010 results and conference call. On Wednesday, January 27, 2010, after market close, Tetra Tech intends to announce its first quarter 2010 results. On Thursday, January 28, 2010, at 8:00 a.m. Pacific Time, Tetra Tech plans to host a conference call to further present and discuss the Company’s financial results and forward outlook.

Investors and other interested parties can access a live audio-visual webcast through a link posted on the Company's website at www.tetratech.com. The webcast will be available for replay through April 28, 2010.

About Tetra Tech (www.tetratech.com)

Tetra Tech is a leading provider of consulting, engineering, program management, construction, and technical services addressing the resource management and infrastructure markets. The Company supports government and commercial clients by providing innovative solutions focused on water, the environment, and energy. With approximately 10,000 employees worldwide, Tetra Tech’s capabilities span the entire project life cycle.

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.