X0306 4 2022-03-14 0 0001372020 Great Lakes Dredge & Dock CORP GLDD 0001455941 Petterson Lasse C/O GREAT LAKES DREDGE & DOCK CORP., 9811 KATY FREEWAY, SUITE 1200 HOUSTON TX 77024 1 1 0 0 CEO & President Common Stock 2022-03-14 4 A 0 22353 A 885552 D Common Stock 2022-03-14 4 A 0 12854 A 898406 D Common Stock 2022-03-14 4 F 0 35689 14.66 D 864380.34 D Represents shares awarded pursuant to satisfaction of performance conditions per the terms of Mr. Petterson's performance-based restricted stock units granted on March 12, 2020. Represents shares awarded pursuant to satisfaction of performance conditions per the terms of Mr. Petterson's performance-based restricted stock units granted on March 13, 2019. The filing adds 1,663.34 shares of Common Stock acquired under the Company's Employee Stock Purchase Program. /s/Vivienne R. Schiffer, by Power of Attorney 2022-03-16