The work began this week and Contact communications adviser Louise Griffin said it should be completed by the end of July.
"This work is a requirement of the resource consents granted to Contact by the Otago Regional Council and the Environment Court in 2007 for our Clutha River operations," Miss Griffin said.
The project involves excavating and removing about 50,000cu m of sediment from the river bed between the Shaky Bridge and the confluence of the Clutha and Manuherikia Rivers, just downstream from the Alexandra bridge.
The sediment would be placed on to the Linger and Die area near the river and on a paddock near the Shaky Bridge cafe.
Those sites would be covered with topsoil and sown with grass, Miss Griffin said.
During the work, a temporary fence might be placed around part of the works area to ensure public safety while heavy machinery was in operation.
Under the terms of its consent, Contact was required to mitigate effects of flooding that might arise because of its hydro dams at Roxburgh and Clyde.
The first section of the work involves removing sediment up to 2m deep from the terraces and beaches beside the river channel, between the Shaky and Alexandra bridges and deepening that stretch of river by up to 1m.
Contact Energy generation manager Graham Quinn said the second stage of the work involved excavating a similar amount of gravel from the river downstream of the Galloway bridge for a distance of about 2.5km.
That work might not be carried out until next year, he said.
