If dredge spoil from Queensland’s Abbot Point expansion is dumped onshore, rather than at sea, the project needs to be planned carefully, an expert warns.

An Australian water expert says dumping dredge spoil onshore rather than in the Great Barrier Reef Marine Park is less damaging but still a risky option.

The Commonwealth is considering a plan by the Queensland government that involves seabed being dredged as part of the Abbot Point coal port expansion and used to reclaim land.

The new disposal plan would replace an already approved option that involves dumping the three million cubic metres of spoil in the marine park.

Richard Bush, a professor of water research at Southern Cross University, says there can be long-term consequences if onshore dredge disposal is not done properly.

“If you don’t have the right, precise, technical plans in place, you virtually don’t get a second chance in some cases,” he told AAP.

“If you get it wrong, you can end up with a huge legacy issue that is very difficult to turn around.”

However, Prof Bush said, if the right checks and balances were in place, there were good prospects of a positive outcome at Abbot Point.

One of the main concerns is containing the large amounts of acid sulfate that will form when the spoil is brought to the surface and mixes with oxygen.

This mineral, as well as aluminium and iron, could potentially have devastating effects on marine life, possibly even hundreds of kilometres from the site, if it leaches into the soil or water.

“Once you get into the league of managing millions of cubic metres of the material, it’s difficult to homogenise and treat the acidity,” Prof Bush said.

He warned that research had shown some onshore dredge dump sites in Western Australia were extremely acidic and had led to the destruction of marine life.

Prof Bush is confident the state government, who he describes as a leader in dealing with the material, has the expertise to explore the issues, but warns the task should not be rushed.

Asked whether the proposed March deadline to begin dredging was too soon, he said: “Basically, you’d want to hit the ground running now.”

He said there was “no question” depositing dredged material onshore rather than at sea was less damaging to the environment.

Premier Campbell Newman has described the onshore disposal plan as a “win-win” for jobs and the environment.