This is the Dredge Randolph which helps keep the shipping channel deep enough for barges and other traffic by scouring the bottom and removing objects and sand that have built up over time. A barge rides along with the dredge and accepts the sand which is taken down river to ( I think ) a concrete plant. These shots are all from 2006.
Below: I made a river visit once when the Randolph was being serviced by the tug Sibley. I think it was the front scraper was jammed or the cables were out of alignment. The tug with a crane on the deck came alongside to help.
Above and below the business end of the system that is lowered to the river bed and brings matter to the surface.
Above and below: when one barge is full of sand the Sibley brings an empty one and swaps them out.
Above and below; The Sibley pulls out the loaded barge, turns around, and then heads down the river to (wild guess here) Sibley.