<Page>
NOTICE OF GUARANTEED DELIVERY
FOR
TENDER OF ANY AND ALL OUTSTANDING
REGISTERED 11 1/4% SENIOR SUBORDINATED NOTES DUE 2008, SERIES B
AND UNREGISTERED 11 1/4% SENIOR SUBORDINATED NOTES DUE 2008, SERIES C
(THE "EXISTING NOTES")
OF
GREAT LAKES DREDGE & DOCK CORPORATION
As set forth in the Prospectus dated , 2001 (the "Prospectus")
of Great Lakes Dredge & Dock Corporation and in the accompanying Letter of
Transmittal (the "Letter of Transmittal") this Notice of Guaranteed Delivery,
or one substantially equivalent to this form, must be used to accept the
Exchange Offer (as defined below) if (i) certificates for Registered 11 1/4%
Senior Subordinated Notes due 2008, Series B or Unregistered 11 1/4% Senior
Subordinated Notes, Series C (together, the "Existing Notes") of Great Lakes
Dredge & Dock Corporation are not immediately available, (ii) Existing Notes,
the Letter of Transmittal and all other required documents cannot be
delivered to The Bank of New York (the "Exchange Agent") on or prior to 5:00
P.M. New York City time, on the Expiration Date (as defined in the
Prospectus) or (iii) the procedures for delivery by book-entry transfer
cannot be completed on a timely basis. This Notice of Guaranteed Delivery may
be delivered by hand, overnight courier or mail, or transmitted by facsimile
transmission, to the Exchange Agent. See "The Exchange Offer--Procedures for
Tendering Existing Notes" in the Prospectus. In addition, in order to utilize
the guaranteed delivery procedure to tender Existing Notes pursuant to the
Exchange Offer, a completed, signed and dated Letter of Transmittal relating
to the Existing Notes (or facsimile thereof) must also be received by the
Exchange Agent prior to 5:00 P.M. New York City time, on the Expiration Date.
Capitalized terms not defined herein have the meanings assigned to them in
the Prospectus.
The Exchange Agent For The Exchange Offer Is:
THE BANK OF NEW YORK
<Table>
BY REGISTERED OR FACSIMILE BY HAND OR OVERNIGHT
CERTIFIED MAIL: TRANSMISSIONS: DELIVERY:
(Eligible Institutions Only) The Bank of New York
The Bank of New York (212) 815-6339 101 Barclay Street
101 Barclay Street, 7E Corporate Trust
New York, New York 10286 Services Window
Attn: Reorganization Section TO CONFIRM BY TELEPHONE OR FOR Ground Level
INFORMATION CALL: New York, New York 10286
(212) 815-6333 Attn: Reorganization Section
</Table>
DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE OR TRANSMISSION OF THIS NOTICE OF GUARANTEED DELIVERY VIA
FACSIMILE TO A NUMBER OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID
DELIVERY.
THIS NOTICE OF GUARANTEED DELIVERY IS NOT TO BE USED TO GUARANTEE
SIGNATURES. IF SIGNATURE ON A LETTER OF TRANSMITTAL IS REQUIRED TO BE
1
<Page>
GUARANTEED BY AN "ELIGIBLE INSTITUTION" UNDER THE INSTRUCTIONS THERETO, SUCH
SIGNATURE GUARANTEE MUST APPEAR IN THE APPLICABLE SPACE PROVIDED IN THE
SIGNATURE BOX ON THE LETTER OF TRANSMITTAL.
2
<Page>
LADIES AND GENTLEMEN:
The undersigned hereby tenders to Great Lakes Dredge & Dock Corporation, a
Delaware Corporation upon the terms and subject to the conditions set forth in
the Prospectus dated _________, 2001 (as the same may be amended or supplemented
from time to time, the "Prospectus"), and the related Letter of Transmittal
(which together constitute the "Exchange Offer"), receipt of which is hereby
acknowledged, the aggregate principal amount of Existing Notes set forth below
pursuant to the guaranteed delivery procedures set forth in the Prospectus under
the caption "The Exchange Offer--Procedures for Tendering Existing Notes."
________________________________________________________________________________
AGGREGATE PRINCIPAL AMOUNT
________________________________________________________________________________
NAME(S) OF REGISTERED HOLDER(S):
Amount Tendered: $ _____________________________________________________________
Certificate No(s)
if available): _________________________________________________________________
________________________________________________________________________________
(TOTAL PRINCIPAL AMOUNT REPRESENTED BY EXISTING NOTES CERTIFICATE(S)
If Existing Notes will be tendered by book-entry transfer, provide the following
information:
DTC Account Number: ____________________________________________________________
Date: __________________________________________________________________________
________________________________________________________________________________
All authority herein conferred or agreed to be conferred shall survive the death
or incapacity of the undersigned and every obligation of the undersigned
hereunder shall be binding upon the heirs personal representatives, successors
and assigns of the undersigned.
________________________________________________________________________________
PLEASE SIGN HERE
X
___________________________ __________________________________________
X
___________________________ __________________________________________
SIGNATURE(S) OF OWNER(S) DATE
OR AUTHORIZED SIGNATORY
Area Code and Telephone Number: ________________________________________________
Must be signed by the holder(s) of the Existing Notes as their name(s) appear(s)
on certificates for Existing Notes or on a security position listing, or by
person(s) authorized to become registered holder(s)
3
<Page>
by endorsement and documents transmitted with this Notice of Guaranteed
Delivery. If signature is by a trustee, executor, administrator, guardian,
attorney-in-fact, officer or other person acting in a fiduciary or
representative capacity, such person must set forth his or her full title below.
(PLEASE PRINT NAME(S) AND ADDRESS(ES))
Name(s): _______________________________________________________________________
________________________________________________________________________________
________________________________________________________________________________
Capacity: ______________________________________________________________________
Address(es): ___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
4
<Page>
GUARANTEE
(NOT TO BE USED FOR SIGNATURE GUARANTEE)
The undersigned, a firm or other entity identified in Rule 17Ad-15 under
the Securities Exchange Act of 1934, as amended, as an "eligible guarantor
institution," including (as such terms are defined therein): (i) a bank; (ii) a
broker, dealer, municipal securities broker, municipal securities dealer,
government securities broker, government securities dealer; (iii) a credit
union; (v) a national securities exchange, registered securities association or
clearing agency; or (v) a savings association that is a participant in a
Securities Transfer Association recognized program (each of the foregoing being
referred to as an "Eligible Institution"), hereby guarantees to deliver to the
Exchange Agent, at one of its addresses set forth above, either the Existing
Notes tendered hereby in proper form for transfer, or confirmation of the
book-entry transfer of such Existing Notes to the Exchange Agent's account at
The Depository Trust Company ("DTC"), pursuant to the procedures for book- entry
transfer set forth in the Prospectus, in either case together with one or more
properly completed and duly executed Letter(s) or Transmittal (or facsimile
thereof) and any other required documents within five business days after the
date of execution of this Notice of Guaranteed Delivery.
THE UNDERSIGNED ACKNOWLEDGES THAT IT MUST DELIVER THE LETTER(S) OF
TRANSMITTAL AND THE EXISTING NOTES TENDERED HEREBY TO THE EXCHANGE AGENT WITHIN
THE TIME PERIOD SET FORTH ABOVE AND THAT FAILURE TO DO SO COULD RESULT IN A
FINANCIAL LOSS TO THE UNDERSIGNED.
Name of Firm: ________________________ ___________________________________
Authorized Signature
Address: _____________________________ Name ______________________________
Zip Code (Please Type or Print)
Area Code and
Tel. No.: ______________________ Date: ____________________ , 2001
NOTE: DO NOT SEND CERTIFICATES FOR EXISTING NOTES WITH THIS FORM. CERTIFICATES
FOR EXISTING NOTES SHOULD ONLY BE SENT WITH YOUR LETTER OF TRANSMITTAL.
5