Chelan County Public Utility District (PUD) operates the Rock Island Hydroelectric Project on the Columbia River approximately 14 miles downstream of Wenatchee, WA. The project has two powerhouses, a gated spillway, and three fish passages.

Brennan was contracted to perform concrete overlays in the draft tube of Unit B-8 in Powerhouse #1 to increase the efficiency of the hydro turbine and reduce future cavitation. At the same time, the client took advantage of this outage to perform rehabilitation and upgrades to the hydro unit and generator.

Accessing A Draft Tube 100 Feet Below the Surface

To access our work area, the Chelan County PUD installed upstream and downstream bulkheads to dewater the draft tube, removing the entire hydro turbine to assist in other planned rehabilitation. Dewatering pumps lowered the water level to approximately 3 feet, and the rest was up to us.