Clive Palmer's plan to develop a coal mine 10 kilometres from the Great Barrier Reef marine park is too risky to proceed, Queensland's environment department has found.

Environmental campaigners are celebrating after the department found the former federal MP's Central Queensland Coal posed unacceptable risks, including to water quality in the marine park.

But the mine's future is far from sealed. The final decision rests with federal Environment Minister Sussan Ley, who has 30 business days to make a decision or seek more information.

Mr Palmer's proposed mine site is on a coastal flood plain, about 130km northwest of Rockhampton and 25km northwest of Marlborough.

It's close to two significant creeks that join 2.3km downstream of the proposed mine and become the Styx River, which flows into Broad Sound, within the Great Barrier Reef World Heritage area.

On Wednesday, the department released its assessment of the mine's environmental impact statement, which found the risks were simply too great.

"The project presents a number of significant risks, due to its location, particularly its proximity to important environmental values, including the Great Barrier Reef Marine Park and World Heritage Area," the assessment said.