Protesters are gearing up for an indefinite occupation of a new opencast coal mine on the West Coast.

A High Court decision last month cleared the last hurdle for the Happy Valley mine near Westport, rejecting Forest and Bird's appeal against an Environment Court ruling in favour of mining.

The Save Happy Valley Coalition plans to occupy an area of the proposed mine indefinitely from this weekend.

Coalition spokeswoman Frances Mountier said volunteers had offered to occupy the mine site and to provide food and donations.

Ms Mountier said the occupation would start on Saturday.

"It's an indefinite occupation to raise awareness and to stall Solid Energy and put pressure on the Labour Government to step in and stop Solid Energy mining this awesome valley," she said.

Protesters planned to camp in 24 hectares of tussock wetland that would eventually become the mine's northern opencast pit.

Ms Mountier said the area was the "best remaining example of wetland in the country" and the coalition was determined to stop it being mined by occupying the land and continuing protest action.

"It's a sad thing that the court process failed to protect such a pristine area and kiwi and other species, and failed to stop more coal extraction," she said.

The mine site is in an area known as the habitat for endangered species, such as the great spotted kiwi and the giant carnivorous snail powelliphanta patrickensis.

Ms Mountier said Cypress coal was destined for export "but regardless of where that coal is going, it's going to release 12 million tonnes of carbon dioxide [from burning] which is going to contribute to climate change".

"That's another reason why the Labour Government should stick to its stated commitments to help curb climate change," Ms Mountier said.