The National Environmental Protection Agency confirmed to Guardian Australia it had approved the BHP Mitsubishi Alliance (BMA) mine extension to dig a further 55m tonnes of coal between now and 2055.

The approval is the agency’s first green light for a coal project since it began operations on 1 July after being created during reforms to national environment laws last year.

An agency spokesperson said the approval came with “strict conditions to protect threatened species and water resources” and would limit clearing of habitat for threatened koalas, ornamental snakes and squatter pigeons.

In its application, BMA said it would likely have to clear 9.7 hectares of endangered koala habitat, 14.2 hectares of vulnerable ornamental snake habitat, 39 hectares of habitat of the vulnerable squatter pigeon and 3.1 hectares of threatened Brigalow woodland.