| ARD OF VERMONT, INC. (F17000001520) | Dire |
| ARDAMAN & ASSOCIATES, INC. (L40551) | VPD |
| DIGITAL SYSTEMS X, LLC (M25000013771) | MGR |
| INDUS CORPORATION (F05000000461) | Dire |
| MCNAMEE,PORTER & SEELEY, INC. (F97000002260) | VS |
| TETRA TECH RMC, INC. (F01000000440) | VSD |
| THE THOMAS GROUP OF COMPANIES, INC. (F08000002641) | VS |
| CORNERSTONE ENVIRONMENTAL GROUP, LLC (M06000005592) | VP |
| GLUMAC ENGINEERING INC. (F17000002823) | Dire |
| TETRA TECH CONSTRUCTION SERVICES, INC. (F08000004083) | VSD |
| TETRA TECH EM INC. (F93000005133) | Secretary |
| TETRA TECH ES, INC. (F04000006542) | Dire |
| TETRA TECH MA, INC. (F12000002112) | SD |
| TETRA TECH MM, INC. (F00000003483) | VSD |
| TETRA TECH TESORO, INC. (F10000002622) | Dire |
| THE INTEGRATION GROUP OF AMERICAS, INC. (F24000002362) | Dire |
| AAI ACQUISITION CORPORATION (P02000066075) | VS |
| COSENTINI ASSOCIATES, INC. (F99000006494) | VP |
| EGLOBAL TECH INC. (F20000003065) | Dire |
| HAI AQUISITION CORPORATION (P02000024884) | VS |
| HARTMAN & ASSOCIATES, INC. (L81775) | VPSD |
| ROONEY ENGINEERING, INC. (F09000004095) | Dire |
| TETRA TECH EC, INC. (F03000000854) | VP |
| TETRA TECH EXECUTIVE SERVICES, INC. (F07000005234) | Dire |
| TETRA TECH, INC. (P19034) | Seni |
| WHALEN & COMPANY, INC. (F99000000834) | SD |
| ADVANCED MANAGEMENT TECHNOLOGY, INC. (F04000001577) | VP |
| AMYX, INC. (F22000006996) | Dire |
| BRIDGENET INTERNATIONAL INC. (F23000002727) | Dire |
| CLANCY ENVIRONMENTAL CONSULTANTS, INC. (F10000001207) | SD |
| LC OF ILLINOIS, INC. (F00000000166) | VS |
| MAXIM TECHNOLOGIES OF TEXAS, INC. (F00000004147) | VPS |
| RPS GROUP, INCORPORATED (FL) (F18000005067) | VICE |
| SCIENCES INTERNATIONAL, INC. (F01000005207) | VSD |
| TETRA TECH EMC, INC. (F00000006557) | Secretary |
| TETRA TECH NUS, INC. (F98000000207) | Secretary |
| TETRA TECH/KCM, INC. (F00000001856) | VS |
| AMERICAN ENVIRONMENTAL GROUP, LTD., LLC (M02000001128) | Vice |
| GEOTRANS, INC. (P27609) | VASD |
| TETRA TECH CONSTRUCTION, INC. (F07000003839) | SD |
| TETRA TECH TECHNICAL SERVICES, INC. (F99000001988) | Dire |
| WESTERN UTILITY CONTRACTORS, INC. (F05000005818) | VPS |
| WILLIAMS, HATFIELD & STONER, INC. (215248) | VS |
