EXHIBIT 3.1

                           CERTIFICATE OF AMENDMENT
                                      OF
                         CERTIFICATE OF INCORPORATION
                                      OF
                               TETRA TECH, INC.

      Li-San Hwang and Richard A. Lemmon hereby certify that:

      A.   They are the President and the Secretary, respectively, of Tetra
           Tech, Inc., a Delaware corporation (the "Corporation").

      B.   The Certificate of Incorporation of the Corporation is amended so
           that the first paragraph of Article IV is amended and superseded in
           full by the following paragraph:


                                  "ARTICLE IV


               The total number of shares of stock that the corporation shall
           have authority to issue is twenty-two million (22,000,000),
           consisting of twenty million (20,000,000) shares of common stock, par
           value $.01, and two million (2,000,000) shares of preferred stock,
           par value of $.01. The designation and the powers, preferences and
           rights, and the qualifications, limitations or restrictions thereof
           are as follows:"

     C.    The foregoing Amendment to Certificate of Incorporation of the
           Corporation was duly adopted by a majority of the duly elected
           directors of the Corporation in accordance with the provisions of
           Section 242 of the Delaware General Corporation Law and in accordance
           with their direction was submitted to the stockholders of the
           Corporation.

     D.    Thereafter, pursuant to the resolution of the directors of the
           Corporation, the vote of the stockholders of the Corporation was
           solicited wherein a majority of the outstanding shares of capital
           stock of the Corporation entitled to vote thereon approved the
           foregoing Amendment to the Certificate of Incorporation.

     IN WITNESS WHEREOF, Li-San Hwang and Richard A. Lemmon being the President
and Secretary, respectively, of the Corporation, do hereby certify under penalty
of perjury under the laws of the State of Delaware that the facts hereinabove
stated are truly set forth, and accordingly each of us has hereunto set our
hands this 8th day of May, 1997.

/s/ Li-San Hwang                             /s/ Richard A. Lemmon
- ------------------------                     ----------------------------
Li-San Hwang, President                      Richard A. Lemmon, Secretary