EXHIBIT 23 INDEPENDENT AUDITORS' CONSENT We consent to the incorporation by reference in Registration Statement Nos. 33- 46240, 33-47533, 33-80606 and 33-94706 of Tetra Tech, Inc. on Form S-8 and 333-2766 of Tetra Tech, Inc. on Form S-3 of our reports dated November 12, 1996, appearing in, and incorporated by reference in, this Annual Report on Form 10-K for the year ended September 29, 1996. Los Angeles, California December 26, 1996