Exhibit 99.1 NEWS RELEASE May 1, 2024 Tetra Tech Reports Record Second Quarter Results and Raises Full Fiscal Year Guidance Pasadena, California. Tetra Tech, Inc. (NASDAQ: TTEK), a leading provider of high-end consulting and engineering services in water, environment and sustainable infrastructure, today announced results for its second quarter ended March 31, 2024. Second Quarter Highlights Recent Key Wins Non-GAAP financial measures which the Company believes provide valuable perspectives on its business ...