Exhibit 23.1 INDEPENDENT AUDITORS' CONSENT We consent to the incorporation by reference in Registration Statement Nos. 33- 46240, 33-47533, 33-80606, and 33-94706 on Form S-8 and Registration Statement No. 333-26199 on Form S-3 of Tetra Tech, Inc. of our report dated August 8, 1997 appearing in this Form 8-K/A. DELOITTE & TOUCHE LLP Los Angeles, California August 21, 1997