The Environmental Protection Authority is seeking public submissions on a company's application to extract iron sand in the South Taranaki Bight.
Trans-Tasman Resources lodged an application with the authority in August for a marine consent to mine almost 66sq/km of seabed off the coast.
A similar application by Trans-Tasman Resources was turned down in 2014 after a lengthy hearing by the authority, which expressed concern about potential environmental effects and the impact on fishing and iwi interests.
Trans-Tasman Resources wants to extract and process up to 50 million tonnes of seabed material and export up to 5m tonnes of iron ore annually for up to 35 years.
The company wants to mine an area of seabed 22 to 36km offshore.