The company that hopes to mine ironsand from the South Taranaki seabed will use a remote-controlled crawler on the sea floor rather than a suction dredge above.

Trans-Tasman Resources chief executive Tim Crossley said the change was made for economic and environmental reasons, and would leave a smaller footprint. The company plans to apply to the Environmental Protection Agency for consent next month and said it would release environmental information it has commissioned next week.

The area to be mined is 22 to 35km from the coast near Patea, in 20m of water.

It consists of 66sq km of seabed and an estimated 50 million tonnes of sand would be processed each year, with 5 million tonnes of iron ore extracted and shipped to Asia. Work could begin by 2016.