Major modernization work underway at Rock Island Dam

ROCK ISLAND — A 180-foot crane floating on a barge near Rock Island Dam is the most visible sign of a series of major modernization projects underway at the nearly century-old hydroelectric facility.

Chelan PUD has hired Kuney-Brennan Joint Venture, a partnership between J.F. Brennan Company and Kuney Construction, to rehabilitate portions of the dam and modernize major spillway components over the next several years.

Rock Island Dam began operating in 1933 as the first hydroelectric project to span the main stem of the Columbia River. Chelan PUD purchased the project from Puget Power in 1956 and completed its second powerhouse in 1979.

One of the first major projects will strengthen and reinforce part of the dam's drop-gate structure, which supplies water to the lower portion of the fish ladder.

Much of the work will take place underwater, where specialized commercial divers will install new concrete. The crane, visible from Highway 28, will lift equipment including 45-foot concrete forms and reinforcement mats and help relocate water, communications and power utilities to make room for the rehabilitation work.

The drop-gate rehabilitation is estimated to cost $50 million and is expected to be completed by July 2027.

Work is also moving forward on modernization of Rock Island Dam's spillway system. The dam has 31 spill bays installed at different points in its history, and many of the steel gates and hoists are now due for replacement.

The gates allow water to pass through the dam to manage Columbia River flows and support juvenile fish passage during the spring.

Kuney-Brennan and lead engineer Tetra Tech are designing replacement spillway gates and hoists intended to improve reliability and response times while making the equipment safer and more efficient for crews to operate. Thirty-percent designs are expected in 2027, with installation of the new system planned over the following several years.

The work comes as Chelan PUD also tackles modernization projects inside both of Rock Island Dam's powerhouses.

Powerhouse 2 contains eight horizontal bulb turbine generators installed between 1974 and 1979, the only generating units of their type on the Columbia River. Designed for a 40-year operating life, the units will be taken out of service one at a time over the next decade and rebuilt with new or refurbished components.

The first unit is being used to test what the PUD says is the nation's largest air-filled hub design. Chelan PUD and contractor GE Vernova are currently reassembling the unit, with a return to service anticipated in 2027.

The air-filled design is intended to reduce the risk of oil leaks, avoiding shutdowns while reducing the potential for oil to enter the Columbia River.

Meanwhile, crews are nearing the end of a 20-year modernization project at Powerhouse 1, rebuilding its 10 generating units for greater efficiency, improved fish passage and another 40 years of operating life.

Early results show efficiency gains of nearly 10%, according to the PUD. The rebuilt units collectively generate about 18 additional megawatts using the same amount of water, roughly equivalent to adding another generating unit to the powerhouse.

Taken together, the projects represent a transition already underway at Rock Island Dam: extending the operating life of infrastructure built across different eras while updating the systems that allow the dam to generate power, manage river flows and support fish passage. The work now visible from Highway 28 is expected to continue in various forms for years.

Andrew Simpson: 509-433-7626 or andrew@ward.media