Solid Energy has announced a joint venture with multi-national Downer EDI to run its Stockton Mine in Buller.
The deal replaces a number of smaller agreements with sub-contracting firms.
Solid Energy chief operating officer Barry Bragg says the joint venture with the Australian-headquartered Downer will help develop the mine and keep it running until 2028.
The company is also spending $75 million on heavy mining equipment such as excavators and bulldozers, bringing total investment in the mine this year to $200 million.
Stockton produces coal for the steel industry in countries such as Japan, India and South Africa.