The owner of an earthquake-damaged private dam in Marlborough could face a repair bill of tens of thousands of dollars.
Contractors are digging two trenches to drain the Haldon Dam, upstream from Seddon, at the Marlborough District Council's direction.
Concerns were raised about the dam's stability following Friday's big earthquake.
The council has warned of shallow flooding to downstream properties if the wall breaks.
Council assets manager Mark Wheeler says there will be legal issues and insurance companies will be called in but who ultimately pays is yet to be decided.
Mr Wheeler says owners of private dams are responsible for their maintenance and the cost of this work is likely to be in the tens of thousands of dollars.