X0508 4 2025-11-18 0 0000831641 TETRA TECH INC TTEK 0001721930 Argus Roger R 3475 EAST FOOTHILL BOULEVARD PASADENA CA 91107 0 1 0 0 President 0 COMMON STOCK 2025-11-18 4 M 0 2055 0 A 27747 D COMMON STOCK 2025-11-18 4 M 0 2535 0 A 30282 D COMMON STOCK 2025-11-18 4 F 0 2533 35.69 D 27749 D COMMON STOCK 2025-11-18 4 A 0 21902 0 A 49651 D COMMON STOCK 2025-11-18 4 F 0 12086 35.69 D 37565 D RESTRICTED STOCK UNITS (RIGHT TO RECEIVE) 2025-11-18 4 M 0 2055 0 D 2022-11-18 COMMON STOCK 2055 0 D RESTRICTED STOCK UNITS (RIGHT TO RECEIVE) 2025-11-18 4 M 0 2535 0 D 2023-11-18 COMMON STOCK 2535 2535 D Amount of securities beneficially owned was updated to reflect that 149 shares of common stock were acquired by the Reporting Person on December 15, 2024, pursuant to the Tetra Tech, Inc. Employee Stock Purchase Plan (ESPP). Represents the shares withheld to pay the related tax liability of the restricted stock units (RSUs) that vested on November 18, 2025. Shares acquired pursuant to vesting of performance stock units earned under 2018 Equity Incentive Plan. Represents the shares withheld to pay the related tax liability of performance stock units that vested on November 18, 2025. Represents an award of restricted stock units (RSUs), each unit of which represents a contingent right to receive one share of Tetra Tech common stock. The RSUs become vested as to 25% of the shares on November 18, 2022, and 25% annually, thereafter, until fully vested. The RSUs are exercisable at the time of vesting and do not have a set expiration date. The RSUs become vested as to 25% of the shares on November 18, 2023, and 25% annually, thereafter, until fully vested. /s/ Preston Hopson, Attorney-in-fact for Roger R. Argus 2025-11-20