Solid Energy is applying for consent to develop an opencast coal mine north of Westport.
If successful the company plans to start in early 2015, and the new site would produce 500,000 tonnes of coal per year.
The company has applied to Buller District Council and West Coast Regional Council for consent to develop the Mount William North block on the Stockton plateau in 2015.
Solid Energy says Stockton already produces up to two million tonnes of high value coal each year for export, and the new area would contribute another 500,000 tonnes per year for a decade and extend the mine's life.
Buller Mayor Pat McManus says the development means job security for the 1000 employees at Stockton mine.
