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EXHIBIT 5
RIORDAN & MCKINZIE
A PROFESSIONAL LAW CORPORATION
300 S. GRAND AVENUE, 29TH FLOOR
LOS ANGELES, CALIFORNIA 90071-3155
August 15, 2000
21-088-001
Tetra Tech, Inc.
670 N. Rosemead Boulevard
Pasadena, California 91107-2190
Ladies and Gentlemen:
We have acted as counsel to Tetra Tech, Inc., a Delaware
corporation (the "Company"), in connection with the registration under the
Securities Act of 1933, as amended (the "1933 Act"), of 402,680 authorized
and previously issued shares of the Common Stock (the "Shares"), $.01 par
value per share, of the Company to be sold by certain selling stockholders.
This opinion is delivered to you in accordance with the requirements of Item
601(b)(5) of Regulation S-K under the 1933 Act in connection with the
Registration Statement on Form S-3, including all pre-effective and
post-effective amendments thereto (the "Registration Statement"), for the
aforementioned sale, filed with the Securities and Exchange Commission (the
"Commission") under the 1933 Act.
In rendering the opinion set forth herein, we have made
such investigations of fact and law, and examined such documents and
instruments, or copies thereof established to our satisfaction to be true and
correct copies thereof, as we have deemed necessary under the circumstances.
Based upon the foregoing and such other examination of law
and fact as we have deemed necessary, and in reliance thereon, we are of the
opinion that, the Shares are duly authorized, validly issued, fully paid and
non-assessable.
We hereby consent to the filing of this opinion as an
exhibit to the Registration Statement and to the reference to this firm under
the caption "Legal Matters" in the Prospectus which is a part of the
Registration Statement. In giving such consent, we do not thereby admit that
we are in the category of persons whose consent is required under Section 7
of the 1933 Act or the rules and regulations of the Commission thereunder.
Very truly yours,
/s/ Riordan & McKinzie
