Queensland authorities say there is no evidence the release of stormwater from Abbot Point Coal Terminal caused widespread contamination of the nearby Caley Valley Wetlands.

Adani's coal terminal gained extra privileges for managing water on the site during Tropical Cyclone Debbie in March, but received a fine after it released water with sediment levels eight times higher than was permitted.

Satellite imagery from the spill appeared to show material had reached right up to the wetlands, located near Mackay, triggering an Environment Department investigation.

That review has now been completed, and found a coal concentration of 10 per cent in sediment where water was discharged from the facility.

But the experts say that concentration was down to a “minor” level of 1 to 2 per cent further away from that point.

There was no evidence of widespread contamination and little visual evidence of fine coal particles across the wetlands, the investigators say.

“The appearance of water bodies in remotely sensed imagery can be affected by several factors, including the depth and clarity of the water, the angle of the sun and the sensor when the image is captured,” the department said in a statement.

Additional monitoring will be conducted, while the Abbot Point terminal has been ordered to prepare an environmental evaluation.

Queensland Conservation Council's Tim Seelig said that because of nature of the substances in the spill, it is far too early to say there was no evidence of contamination.

“We do know that sediment in sections of the wetlands contains 10 per cent coal pollutant,” he told reporters.

“That is vastly more than we would expect to occur naturally … Adani should be held responsible and fined.”