Coal miner Bathurst Resources is defending its plans to expand its Canterbury Coal Mine into another 18 hectares of forest, farms, and wetland.
The 38-ha mine at Coalgate, near Darfield, supplies 95,000 tonnes of low sulphur coal annually to regional customers, including dairy factories.
Environmental groups feared for fragile eco-systems - including aquatic life in nearby waterways - if it gained the resource consents needed to expand.
Forest and Bird's Canterbury and Westland manager Nicky Snoyink was among several lobbyists opposing the plan.
Snoyink said aquatic species in Selwyn District's waterways were already under enough strain.
But Bathurst Resources chief executive Richard Tacon rejected that and said the mine's "active footprint" would not change significantly.
Older workings at the mine would be rehabilitated.
Bathurst Resources also said the mine provided Canterbury customers with relatively clean-burning coal.
Climate action group Extinction Rebellion said members might occupy the mine if it was allowed to expand.
A spokesperson, Siana Fitzjohn, said it would be wrong to let the coal industry grow during the climate emergency.