Great Barrier Island residents are going to court to stop a company being allowed to dump millions of cubic metres of Auckland's sediment off its coast.

In February the Environmental Protection Authority granted Coastal Resources Limited (CRL) a 35-year consent to increase the sediment it dumps off the island from 50,000 to 250,000 cubic metres annually.

The sediment would come from Auckland City infrastructure spoils, marinas in Auckland and Waikato, Ports of Auckland dredgings and a proposed America's Cup village at Hobsonville Pt.

Two separate appeals had been lodged in the High Court, by the Society for the Protection of Aotea Community and Ecology, and island resident Kelly Klink, on behalf of her iwi Ngāti Rehua-Ngātiwai ki Aotea.

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Klink said the proposed activity would have an "irreversible impact on our moana".

She said the decision-making process was flawed, there had not been adequate consultation, and was a breach of the Treaty of Waitangi.

"There have been no hui on the island to tell us anything about any potential impacts. That needs to happen before anything else. They are increasing it five times. I think the safest option is to put it on land."

The island of roughly 1000 people was unified in its opposition, she said.

"It is disgusting. It is going straight into wahi tapu (sacred places). Our tupuna spilt blood protecting those fishing grounds, and now they could be destroyed.

"People rely on the sea for food, and for work. There is no supermarket here."

The EPA had received 76 submissions about the application, with the majority opposed.

The dump site covered about 7 sq km and was about 25km east of Great Barrier Island and 22km north of Cuvier Island, a culturally significant site for founding tribes of the Te Arawa canoe.

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Dredged material was first dumped at the site in 2010, in a test under Maritime New Zealand.

The initial application in 2009 was also challenged by iwi, who were concerned about potential impacts on marine life and the potential for marinas up and down the east coast to use the site.

Since then, between 100 and 130 barge loads had been dumped each year from dredgings at the Pine Harbour, Half Moon Bay, Sandspit, Hobsonville, Hobsonville Pt and Whitianga marinas.

The Auckland Conservation Board, one of about 70 submitters against the application, was yet to decide if it would support the appeals.

Board member Dr Andrew Jeffs, Professor of Marine Science at the University of Auckland, said they were "dismayed" at the initial decision to grant the application.

"We feel like our concerns were just ignored."

They had major concerns about the increased vessel movements corresponding with the increased amount to be dredged.

The noise of marine vessels could affect feeding and breeding of marine mammals, displace them and mess up their social arrangements.

"They are very acoustic animals and the increase in vessel movement could have a major impact on their habitat.

"The Hauraki Gulf is an exceptional marine habitat, internationally significant, and has a very large number of marine species."

Internationally there was a very strong movement to implement stronger constraints where there could be impacts on marine mammals, Jeffs said.

"But the applicant made no reference to underwater sound concerns, and the commissioners just dismissed that. It would be like building an airport, and not providing any information about how loud the planes would be."

Alternatives were to place the sediment on land, or to use vessels with appropriate noise limits, Jeffs said.

EPA general manager climate, land and oceans Siobhan Quayle said Klink had not made a submission against the application nor appeared at the hearing.

The EPA publicly notified the application on July 30 last year, and notified a number of iwi authorities, customary marine titles, and protected customary rights groups, including the trust, which was separate to the iwi Klink was representing.

Ngāti Rehua-Ngātiwai ki Aotea Trust made a submission on the application, and representatives appeared at the hearing in Auckland to give evidence. Their information was provided and taken into account in the decision, Quayle said.

Staff had also visited Great Barrier Island and engaged with the Great Barrier Local Board on the application, Quayle said.

CRL has been approached for comment.