But environmental group Kiwis Against Seabed Mining (KASM), which is delivering its closing submission tomorrow, held hopes the Environmental Protection Authority-appointed committee would refuse the consent.
KASM chairman Phil McCabe cited a recent EPA staff report, which highlighted shortcomings with TTR's evidence - particularly expected adverse effects on the mining site's benthic habitat.
"The EPA staff themselves have validated the position we have held from day one: that the company doesn't know enough what's in the environment to start with, let alone the impact, and therefore we can neither predict - nor monitor - the environmental effects," he said.
"The staff report shows that mining 50 million tonnes of seabed a year for 20 years is a very complex proposition and that Trans Tasman Resources, after two months of hearings, have not been able to prove that they can do it in an environmentally safe way."
He claimed the company was "asking the EPA to grant them a license to find out".
"That's why so many people from so many sectors of society are concerned and have opposed this application."
New Zealand's seafood industry has also raised concern over the effects of the proposed mining.
"The potential damage from this seabed mining proposal should be of grave concern to any kiwi that values the marine ecosystem; including recreational and customary fishers and anyone else who finds intrinsic value in a functional marine ecosystem," Fisheries Inshore New Zealand chief executive Dr Jeremy Helson said.
"The marine environment is complex and marine life in it can be disrupted by even small changes."
The applicants have submitted otherwise, stating that no rare or vulnerable ecosystems or habitats of threatened species had been identified as being potentially affected.
This was supported by consultants SKM in a peer review report noting the project area and adjacent habitats was not known to provide habitat for any threatened species of benthic fauna, nor contain threatened marine mammals.
The Ministry of Primary Industries has also submitted that effects on fishing would be "negligible or non-existent".
The mining would be done by remote-controlled 12m-long, 350-tonne "crawler" machines, travelling along the seafloor pumping sand to a processing ship above.
Once iron ore particles were separated magnetically, the sand would be deposited on areas already worked over.
Any life on the seafloor, such as tubeworms, would be destroyed as the mining progressed 300sqm block by block, but the company believed the areas would soon be repopulated.
The company proposes to extract up to 50 million tonnes of sediment per year and process it aboard an integrated mining vessel, with around five million tonnes of iron ore concentrate to be exported per year.
TTR had spent more than $50 million on the project, and estimated that the project would generate an extra $147 million in exports for New Zealand.
The remaining sediment would be re-deposited on the seafloor in a "controlled manner", usually backfilling previous mined areas, which will be typically five metres deep.
Read a summary of the main concerns around the proposal here.
