The final results of all that investigation are expected in April.
The company expects the Government to treat its proposal to mine the South Taranaki seabed as a project of national significance.
As such, its mining permit is likely to be granted after a board of inquiry process rather than the usual regional council resource consent.
The board of inquiry would take nine months, chairman Bill Bisset said, and be finished about April next year.
After that comes a crunch time for the company - to decide whether to invest a further $600 million to $700 million in the ships and other infrastructure needed to begin mining.
The earliest mining could start is the middle of the following year.
The initial target area is about 15km off the coast between Hawera and Patea, near the Kupe Platform.
It would barely be visible from shore.
All production would happen offshore, with a dredge sucking up sand, a ship separating out iron-rich particles magnetically and those transferred to another ship to take them to the Asian buyers.
The remaining sand would be returned to the sea floor.
Mr Bisset said benefits to local people could include jobs - up to 450 of them - and providing supplies.
Wanganui's port had already benefited because it has been the main base for Trans-Tasman's contracted research vessels.
"It's too early to tell how the port might be used [later].
"We might be able to help in the refreshing of it. It's on our radar screen," chief executive Tim Crossley said.
The company could end up getting $600 million to $1 billion a year for the iron ore, and Mr Bisset said at least 50 per cent of that would stay in New Zealand - as wages, taxes, royalties and payments for supplies.
Fishermen, surfers and environmentalists have all expressed concern about the mining proposal.