DESERT AIRE — Construction has begun on a $27.4 million project at Priest Rapids Dam that will enable young, outbound salmon to more safely bypass the dam without passing through the turbines or tumbling past in conventional spill.

The project will transform three of the dam’s 22 spill gates into fish water slides. It’s on schedule to be finished by April 2014.

The slides allow the fish to spill through the gates at water volumes of 27 thousand cubic feet per second, far less than the usual 110 cubic feet per second that passes through a conventional gate, PUD spokesman Thomas Stredwick said.

The lower volume gives the fish a smoother ride down and creates less turbulence on the downriver side of the dam. Churning water causes a dissolved-gas buildup that can be harmful to fish.

Priest Rapids’ spill gates operate by allowing water to spill from below the open gate.

The three redesigned gates will spill water over the top, creating three watery chutes into the river, Stredwick said. The chutes will be operational during the salmon’s outward migration from April to August.

The project will help the utility meet or surpass its federally mandated 95-percent fish-survival rate past the dam.

The PUD has two cameras accessible from its website that show different views of the construction. To view them, visit www.gcpud.org and do a search for “Priest Rapids bypass.”

Christine Pratt: 665-1173

pratt@wenatcheeworld.com