Greenpeace says the impacts of dredging at the site of proposed coal terminals in north Queensland could mirror the issues seen in Gladstone Harbour.
North Queensland Bulk Ports has released a draft report into the effects of dredging at Abbot Point, north of Bowen.
The report says three million cubic metres of dredging will be done over 184 hectares.
Greenpeace spokeswoman Louise Matthiesson says their main concern is the disposal of the dredge spoil.
"It'll only be eight kilometres from Holburn Island National Park, which is part of the Whitsundays," she said.
"With dredging, you always get large sediment plumes, you get muddy water spreading sometimes for kilometres.
"The impacts could go a lot further than the port limits." Ms Matthiesson says chemicals found in the soil at Abbot Point are similar to those in Gladstone Harbour.
"The environmental impact statement shows there is the potential for acid sulphate soils to occur - the sediments in the dredging area are potential acid sulphate soils - so that's a major concern for the local fishing industry," he said.
The ABC has contacted North Queensland Bulk Ports for comment.