Exhibit 99.1 NEWS RELEASE May 1, 2024 Tetra Tech Reports Record Second Quarter Results and Raises Full Fiscal Year Guidance · Record Revenue $1.25 billion and Record Net Revenue $1.05 billion · Record Q2 EBITDA $135 million, up 28% Y/Y · Record Q2 EPS of $1.42, up 34% Y/Y · Increasing Fiscal Year 2024 Net Revenue and EPS full year guidance Pasadena, California. Tetra Tech, Inc. (NASDAQ: TTEK), a leading provider of high-end consulting and engineering services in water, environment and sustainable infrastruc ...