Hopes silt to stop next week

As well as the sediment flowing from the dam there is a large amount of silt behind it. Photo / Peter Scott

Hawke's Bay Regional Council is hopeful the discharge of sediment from the Waihi Dam into the Waiau River will cease by the end of next week.

Regional council staff met with Eastland Group staff and contractors yesterday to discuss a forward plan to resolve the issues with the dam.

Regional council group manager resource management Iain Maxwell said Eastland Group had indicated it would have its plan to solve the issue to council by tomorrow.

Mr Maxwell said Eastland Group's plans were expected to focus on the immediate priority of closing the open sluice gate, and he was hopeful this would be done by the end of next week.

"I am very pleased the Eastland Group is acting with real urgency on this issue and aim to have the damaged sluice gate closed as soon as practicable."

The next issue needing to be resolved was the amount of sediment above the dam, and the two other sluice gates which were unable to open because of the silt backlog. At a meeting last week it was estimated this sediment went as far as 900m back from the dam. Mr Maxwell said the council had also engaged specialist dam engineering company, DamWatch, to provide advice on the options Eastland Group was proposing.

In the interim, Eastland Group had created a mitigating structure below the dam to trap as much sediment as it could before it hit the Waiau River. Mr Maxwell said the gabion baskets were performing as hoped, and preventing a portion of the sediment released from the dam from entering the Waiau River.

The dam has been discharging silt into the Waiau River since before Christmas after a sluice gate was damaged in a storm in September. The council issued an abatement notice on Christmas Eve and reissued it on January 6 requiring the gate to be closed, but the damage is preventing it being fully closed. This abatement notice was still being enforced.