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The Great Barrier Reef Marine Park Authority would prefer if dredge spoil wasn’t dumped within park boundaries, but says it doesn’t have the power to enforce its view.

However, the authority has assured the dumping of three million cubic metres of spoil in the park won’t harm the world icon.

GBRMPA chairman Russell Reichelt says its preference was for the spoil, from the Abbot Point port expansion, to be dumped on land.

Essentially that wasn’t a decision for the marine park authority in the legal no-go sense.

“Absolutely. It’s part of our national guidelines,” he told ABC Radio.

The GBRMPA last week approved North Queensland Bulk Port’s application to dump up to three million cubic metres of sludge in the marine park, after the federal environment minister gave the project the green light.

Dr Reichelt says the authority failed to persuade NQBP to dump the dredge inland and it can’t legally force it to.

“Essentially that wasn’t a decision for the marine park authority in the legal no-go sense,” he said.

However, he said land dumping was difficult given the port was surrounded by valuable wetland and bird habitats.

But the authority was satisfied with the offshore dumping plan.

“We determined that action wouldn’t harm the Barrier Reef if it was done in a certain way and that’s something that’s critically important,” Dr Reichelt said.

The approved dumping site is about 25km east-northeast of the port and about 20km from the nearest reef.

The spoil, about 70 per cent sand and 30 per cent silt and clay, would become part of the moving billion of tonnes of natural sediment in the ocean within a year of disposal, Dr Reichelt said.

He said detailed scientific studies determined the dumping would have no adverse impacts on the reef.

Dr Reichelt also said the authority would man the port at all times to ensure all conditions were met.