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EXECUTION COPY

AMENDMENT NO. 2

TO

CREDIT AGREEMENT

    THIS AMENDMENT NO. 2 TO CREDIT AGREEMENT ("Agreement") is being executed and
delivered as of October 23, 2000, by and among Great Lakes Dredge & Dock
Corporation, a Delaware corporation (the "Borrower"), the other "Loan Parties"
from time to time party to the Credit Agreement referred to and defined below
(collectively, the "Loan Parties"), the financial institutions from time to time
party to such Credit Agreement referred to and defined below (collectively, the
"Lenders") and Bank of America, N.A. (as successor to Bank of America National
Trust and Savings Association), as representative of the Lenders (in such
capacity, the "Administrative Agent"). Undefined Capitalized terms used herein
shall have the meanings ascribed to such terms in such Credit Agreement.

W I T N E S S E T H:

    WHEREAS, the Borrower, the other Loan Parties, the Lenders, the
Administrative Agent and Bank of America, N.A. (as successor to Bank of America
National Trust and Savings Association), in its separate capacity as "Issuing
Bank", have entered into that certain Credit Agreement dated as of August 19,
1998, as heretofore amended (the "Credit Agreement"), pursuant to which, among
other things, the Lenders have agreed to provide, subject to the terms and
conditions contained therein, certain loans and other financial accommodations
to the Borrower;

    WHEREAS, the Borrower has requested that the Lenders agree to permit the
Borrower to make or incur Capital Expenditures and Permitted Business
Acquisitions during Fiscal Year 2000 in an aggregate amount which is greater
than that currently permitted under the terms of the Credit Agreement; and

    WHEREAS, subject to the terms and conditions of this Agreement, the Lenders
have agreed to amend the Credit Agreement to permit such Capital Expenditures
and Permitted Business Acquisitions;

    NOW, THEREFORE, in consideration of the foregoing premises, the terms and
conditions stated herein and other valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by the Borrower, the other Loan
Parties, the Lenders and the Administrative Agent, such parties hereby agree as
follows:

    1.  Amendment to Credit Agreement. Subject to the satisfaction of each of
the conditions set forth in Paragraph 2 of this Agreement, the Credit Agreement
is amended to add the reference "(x)" to the beginning of the existing provision
which follows the language "provided, further, however" in Section 6.3(a)
thereof and to add the following provision to the end of such Section 6.3(a):,

(y) the Borrower and its Subsidiaries may make and incur Capital Expenditures
and Permitted Business Acquisitions in an aggregate amount not exceeding
$14,000,000 during Fiscal Year 2000 and (z) the amount of permitted Capital
Expenditures and Permitted Business Acquisitions for Fiscal Year 2001 may not be
increased pursuant to the first proviso of this section.

    2.  Effectiveness of this Agreement; Conditions Precedent. The provisions of
Paragraph 1 of this Agreement shall be deemed to have become effective as of the
date of this Agreement, but such effectiveness shall be expressly conditioned
upon the Administrative Agent's receipt of originally-executed counterparts of
this Agreement executed by duly authorized officers of the Borrower, the other
Loan Parties and the Majority Lenders.

    3.  Representations and Warranties.

    (a) The Borrower and each other Loan Party hereby represents and warrants
that this Agreement, and the Credit Agreement as amended by this Agreement,
constitute legal, valid and binding

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obligations of the Borrower and the other Loan Parties enforceable against the
Borrower and the other Loan Parties in accordance with their terms.

    (b) The Borrower and each other Loan Party hereby represents and warrants
that its execution, delivery and performance of this Agreement, and its
performance of the Credit Agreement as amended by this Agreement, have been duly
authorized by all proper corporate action, do not violate any provision of its
articles or certificate of incorporation or bylaws, will not violate any law,
regulation, court order or writ applicable to it, and will not require the
approval or consent of any governmental agency, or of any other third party
under the terms of any contract or agreement to which it or any of its
Affiliates is bound (which has not been previously obtained), including without
limitation, the Note Indenture and the Reliance Agreement.

    (c) The Borrower and each other Loan Party hereby represents and warrants
that, both before and after giving effect to the provisions of this Agreement,
(i) no Default or Event of Default has occurred and is continuing or will have
occurred and be continuing and (ii) all of the representations and warranties of
the Borrower and each other Loan Party contained in the Credit Agreement and in
each other Loan Document (other than representations and warranties which, in
accordance with their express terms, are made only as of an earlier specified
date) are, and will be, true and correct as of the date of its execution and
delivery hereof or thereof in all material respects as though made on and as of
such date.

    4.  Reaffirmation, Ratification and Acknowledgment. The Borrower and each
other Loan Party hereby (a) ratifies and reaffirms all of its payment and
performance obligations, contingent or otherwise, and each grant of security
interests and liens in favor of the Administrative Agent, under each Loan
Document to which it is a party, (b) agrees and acknowledges that such
ratification and reaffirmation is not a condition to the continued effectiveness
of such Loan Documents and (c) agrees that neither such ratification and
reaffirmation, nor the Administrative Agent's, or any Lender's solicitation of
such ratification and reaffirmation, constitutes a course of dealing giving rise
to any obligation or condition requiring a similar or any other ratification or
reaffirmation from the Borrower or such other Loan Parties with respect to any
subsequent modifications to the Credit Agreement or the other Loan Documents. As
modified hereby, the Credit Agreement is in all respects ratified and confirmed,
and the Credit Agreement as so modified by this Amendment shall be read, taken
and so construed as one and the same instrument. Each of the Loan Documents
shall remain in full force and effect and are hereby ratified and confirmed.
Neither the execution, delivery nor effectiveness of this Agreement shall
operate as a waiver of any right, power or remedy of the Administrative Agent or
the Lenders, or of any Default or Event of Default (whether or not known to the
Administrative Agent or the Lenders), under any of the Loan Documents. This
Agreement shall constitute Loan Documents for purposes of the Credit Agreement.

    5.  Governing Law. This Agreement shall be governed by and construed in
accordance with the laws and decisions of the State of Illinois (including
S.H.A. 735 ILCS 105/5-1, et. seq., but without giving effect to any other
conflicts of law provisions).

    6.  Administrative Agent's Expenses. The Borrower hereby agrees to promptly
reimburse the Administrative Agent for all of the reasonable out-of-pocket
expenses, including, without limitation, attorneys' and paralegals' fees, it has
heretofore or hereafter incurred or incurs in connection with the preparation,
negotiation and execution of this Agreement and the other documents, agreements
and instruments contemplated hereby.

    7.  Counterparts. This Agreement may be executed in counterparts, each of
which shall be an original and all of which together shall constitute one and
the same agreement among the parties.

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    IN WITNESS WHEREOF, this Agreement has been duly executed as of the day and
year first above written.

    GREAT LAKES DREDGE & DOCK
CORPORATION
 
 
By:
/s/ DEBORAH A. WENSEL   

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    Name: Deborah A. Wensel

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    Title: Vice President and CFO

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GREAT LAKES DREDGE & DOCK COMPANY
 
 
By:
/s/ DEBORAH A. WENSEL   

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    Name: Deborah A. Wensel

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    Title: Vice President and CFO

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DAWSON MARINE SERVICES COMPANY
(formerly, Dawson Dredging Company)
 
 
By:
/s/ DEBORAH A. WENSEL   

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    Name: Deborah A. Wensel

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    Title: Vice President and CFO

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FIFTY-THREE DREDGING CORPORATION
 
 
By:
/s/ PAUL DINQUEL   

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    Name: Paul Dinquel

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    Title: Vice President

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GATES CONSTRUCTION CORP.
 
 
By:
/s/ DEBORAH A. WENSEL   

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    Name: Deborah A. Wensel

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    Title: Vice President and CFO

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BANK OF AMERICA, N.A. (as successor to Bank of America National Trust and
Savings Association), as Administrative Agent
 
 
By:
/s/ KRISTINE D. HYDE   

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    Name: Kristine D. Hyde

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    Title: Vice President

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BANK OF AMERICA, N.A. (as successor to Bank of America National Trust and
Savings Association), as a Lender
 
 
By:
/s/ JENNIFER L. GERDES   

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    Name: Jennifer L. Gerdes

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    Title: Vice President

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BANK OF MONTREAL, CHICAGO BRANCH, as a Lender
 
 
By:
/s/ BRUCE A. PIETKA   

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    Name: Bruce A. Pietka

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    Title: Director

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FLEET BANK, N.A., as Lender
 
 
By:

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    Name:

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    Title:

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LASALLE BANK, N.A., as a Lender
 
 
By:
/s/ DREW E. BURLAK   

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    Name: Drew E. Burlak

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    Title: AVP

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COMERICA BANK—DETROIT, as a Lender
 
 
By:
/s/ ALAN S. CARLYLE   

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    Name: Alan S. Carlyle

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    Title: Officer

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SUMMIT BANK, as a Lender
 
 
By:
/s/ BONNIE GERSHON   

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    Name: Bonnie Gershon

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    Title: Vice President

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THE NORTHERN TRUST COMPANY, as a Lender
 
 
By:
/s/ ROBIN BRODY   

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    Name: Robin Brody

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    Title: Vice President

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    FLEET NATIONAL BANK, Successor by merger to Fleet Bank, N.A.
 
 
By:
/s/ SCOTT VANDERWALL   

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Scott Vanderwall
Vice President

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