The Hawkes Bay Regional Council says they have been told work to fix a dam discharging silt into the Wairau River will begin tomorrow.
The dam, owned by the Eastland Group, has been discharging sediment since last November after a floodgate was damaged during a storm.
The council's group manager of resource management, Iain Maxwell, said it would take about three weeks to fix.
He said the silt would have to be cleared from under the gate and a second structure would have to be built downstream.
Mr Maxwell said a decision on whether to prosecute Eastland Group would be made once an investigation was completed.