The Environmental Protection Authority's decision to grant a marine consent to mine iron ore from the Taranaki seabed is being challenged in court.
Trans-Tasman Resources wants to mine the seabed of the South Taranaki Bight.
The EPA granted permission last August and Kiwis Against Seabed Mining, with Greenpeace, is appealing the decision, alongside six other appellants.
The hearing begins in the High Court at Wellington on Monday morning and will last for four days.
"The outcome of this case will set a precedent for a number of other companies waiting in the wings to mine our seabed, in the South Taranaki Bight and beyond," said KASM chairwoman Cindy Baxter.
KASM and Greenpeace say they are appealing on 12 points of law.
Among these is the issue of what is called "adaptive management" whereby an activity like seabed mining is allowed to go ahead, adapting the conditions on which it occurs along the way.
The environmental groups will also argue the issue of natural justice, the way economic benefits have been calculated, and the role of the so-called precautionary approach.
The EPA set down 109 conditions for the mining operation.