April 21, 2005 Great Lakes Dredge & Dock Company Attn: Ms. Deb Wensel 2122 York Road Oak Brook IL 60523 Dear Deb:

Exhibit 10.1

April 21, 2005

Great Lakes Dredge & Dock Company
Attn: Xx. Xxx Xxxxxx
0000 Xxxx Xxxx
Xxx Xxxxx XX 00000

Dear Xxx:

It is our understanding that the Net Worth of Great Lakes Dredge & Dock Corporation and its subsidiaries (GLDD) has dropped below $82.5 million, the minimum Net Worth that GLDD is required to maintain under Section 6.19 of the Third Amended and Restated Underwriting and Continuing Indemnity Agreement.

Travelers Casualty and Surety Company and Travelers Casualty and Surety Company of America (collectively, “Travelers”) hereby agree to waive GLDD’s compliance with the Net Worth requirement for the fiscal quarter ending March 31, 2005.  However, Travelers expressly reserves the right to declare GLDD in default under the Third Amended and Restated Underwriting and Continuing Indemnity Agreement should GLDD fail to increase its Net Worth to $82.5 million for the fiscal quarter ending June 30, 2005, and maintain its Net Worth at that level or higher for any fiscal quarter subsequent to June 30, 2005.

Sincerely,

Travelers Casualty and Surety Company
Travelers Casualty and Surety Company of America

/s/ Xxxxxxx Xxxxxxxx

By: Xxxxxxx Xxxxxxxx

   Assistant Manager

Acknowledged and Agreed to By:

Great Lakes Dredge & Dock Corporation

By:	/s/ Xxxxxxx X. Xxxxxx
Its:	Chief Financial Officer

cc:  Xxxxx Xxxx, Winston & Xxxxxx

1