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                                                                   EXHIBIT 10.18


                       FIFTH AMENDMENT TO CREDIT AGREEMENT

THIS FIFTH AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is entered into as
of April 27, 2001, by and between THE KEITH COMPANIES, INC., a California
corporation, HEA ACQUISTION, INC., a California corporation, (individually and
collectively "Borrower"), and WELLS FARGO BANK, NATIONAL ASSOCIATION ("Bank").

                                    RECITALS

WHEREAS, Borrower is currently indebted to Bank pursuant to the terms and
conditions of that certain Credit Agreement between Borrower and Bank dated as
of September 1, 1999, as amended from time to time ("Credit Agreement").

WHEREAS, Bank and Borrower have agreed to certain changes in the terms and
conditions set forth in the Credit Agreement and have agreed to amend the Credit
Agreement to reflect said changes.

NOW, THEREFORE, for valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the parties hereto agree that the Credit Agreement
shall be amended as follows:

     1. Section 6.1.(h) is hereby deleted in its entirety, and the following
substituted therefor:

           "(h) Aram Keith shall not for any reason own less than an
           aggregate of eighteen percent (18%) of the common stock of
           Borrower."

     2. Except as specifically provided herein, all terms and conditions of the
Credit Agreement remain in full force and effect, without waiver or
modification. All terms defined in the Credit Agreement shall have the same
meaning when used in this- Amendment. This Amendment and the Credit Agreement
shall be read together, as one document.

     3. Borrower hereby remakes all representations and warranties contained in
the Credit Agreement and reaffirms all covenants set forth therein. Borrower
further certifies that as of the date of this Amendment there exists no Event of
Default as defined in the Credit Agreement, nor any condition, act or event
which with the giving of notice or the passage of time or both would constitute
any such Event of Default.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed
as of the day and year first written above.


WELLS FARGO BANK,


THE KEITH COMPANIES, INC.                         NATIONAL ASSOCIATION

By: /s/ Gary Campanaro                            By: /s/ Stephanie Juneau
    --------------------------------                  --------------------------
Title:  CFO                                       Title:  Vice President


HEA ACQUISITION, INC.

By: /s/ Gary Campanaro
    -------------------------------
Title:  CFO