Great Lakes Dredge & Dock Corporation Announces Secondary Equity Offering

Monday, August 10th 2009

Great Lakes Dredge & Dock Corporation announced a 12.5 million share secondary offering of its common stock by certain selling stockholders. The selling stockholders include Madison Dearborn Capital Partners IV, L.P. The offering is being conducted as a public offering pursuant to an effective shelf registration statement under the Securities Act of 1933. Great Lakes will not receive any proceeds from the sale of the shares but will pay the expenses of the offering.

The offering is being made through an underwriting syndicate led by Barclays Capital and BofA Merrill Lynch, as joint book-running managers for the offering. The co-managers of the offering are BB&T Capital Markets and Morgan Joseph & Co. Inc.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be a sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

The offering is being made by means of a prospectus supplement and the accompanying prospectus only. Copies of the prospectus supplement and accompanying prospectus can be obtained from Barclays Capital Inc., c/o Broadridge, Integrated Distribution Services, 1155 Long Island Avenue, Edgewood, NY 11717, Telephone (888) 603-5847 or by email at barclaysprospectus@broadridge.com; or from BofA Merrill Lynch, 4 World Financial Center, New York, NY 10080, Attention: Prospectus Department.