Some residents of the Wairau Valley in Marlborough are concerned that a planned hydroelectric scheme wouldn't be able to withstand a major earthquake.
The Environment Court has given the go-ahead to Trustpower's $275m Wairau Hydro project, which will divert 60% of the Wairau river's water along a canal system.
Ron Tannock, of the Save the Wairau campaign, says he's worried that the 46 kilometres of canals will cross the Wairau fault 11 times.
Mr Tannock says in some places the canals will sit 30 metres above the valley, and in the event of an earthquake water could spill over.
Trustpower says the fault line is a known risk and it will cut no corners in making the project earthquake-safe.