Final days of Trans Tasman Resources hearing underway

The hearing marks the second time TTR has sought permission to extract 50 million tonnes of seabed material a year.

The final days of the hearing to determine whether Trans Tasman Resources gets a green light to mine iron sands from the ocean floor in New Zealand's Exclusive Economic Zone kicked off in Wellington.

The hearing marks the second time TTR has sought permission to extract 50 million tonnes of seabed material a year to export up to 5 million tonnes of iron sand per year after it was turned down in 2014 when a committee appointed by the Environmental Protect Authority ruled the environmental impacts of the proposal were too difficult to gauge on the evidence available.

The current hearing - which began in mid-February - was extended to May 31 when the decision-making committee requested additional information around the so-called "plume" and noise resulting from the project and gave those opposed to the project time to respond to the new information.

The sand is mined using a very slow moving crawler which creeps along the seafloor "vacuuming" up sand and seawater and pumping it to a vessel. The iron ore is magnetically separated and the de-ored sand, about 90 percent of the total, is immediately re-deposited. According to TTR, the vast majority of the redeposited sand will settle back on the seabed and effectively fill areas previously dredged by the crawler. However, the process will form a "plume" in the water column, which will drift depending on tides, ocean currents and general weather conditions in an often turbulent part of the Tasman Sea.

TTR has provided extensive additional information to the committee, including "worst case" sediment plume modelling and at today's hearing, Darran Humpheson, a specialist acoustic consultant for TTR, presented his assessment of underwater noise from the planned project. Among other things, he said most of the noise that will be produced by TTR is low frequency and that large container vessels operating in nearby waters would produce more noise.

Several more experts are due to testify Monday and Wednesday and the involved parties will offer closing comments on Thursday, according to the hearing schedule.