Modernization Work Takes Shape at Rock Island Dam

PUD begins 11-month, $50 million improvement project

information released

Here’s something you don’t see every day: A 180-foot-tall crane floating on a barge near Rock Island Dam. That’s about as tall as the driving deck of the George Sellar Bridge is above the Columbia River.

That will be the view from Highway 28 as a series of modernization projects at Rock Island Dam ramp up this month. Chelan PUD hired the contractor Kuney-Brennan Joint Venture, a partnership between J.F. Brennan Company and Kuney Construction, to rehabilitate parts of the dam and modernize major spillway components over the next few years. The rehabilitation will help maintain the facility’s safety, efficiency, and long-term reliability.

Built like a rock

In 1933, Rock Island Dam became the first hydroelectric project to span the main stem of the Columbia River. Chelan PUD purchased the dam from Puget Power in 1956 and finished construction of a second powerhouse in 1979.

Over the next few months, crews will strengthen and reinforce part of the drop gate structure, which provides water to the lower part of the fish ladder. Most of this work will occur underwater, where a specialized commercial dive team will install new concrete.

That’s when you’ll see a huge crane on a barge. The crane will lift heavy equipment, such as 45-foot concrete forms and reinforcement mats. The crane will also help relocate utilities – water, communication and power conduit – to make way for the drop gate rehabilitation.

Rehab will cost an estimated $50 million and is expected to conclude by July 2027.

Spillway modernization

Rock Island Dam’s 31 spill bays were installed at different times throughout the dam’s history, and many spillway gates and hoists are due for replacement. The massive steel gates allow water through the dam to manage river flows and support juvenile fish passage in spring.

Kuney-Brennan JV and their lead engineer Tetra Tech are designing new spillway gates and hoists that will improve reliability, response time and are safer and more efficient for crews to operate. The team is planning to develop 30% designs by 2027. The new system is scheduled to be installed over the next couple of years.

Innovations inside the dam

When Chelan PUD built Rock Island Powerhouse 2 between 1974 and 1979, it installed eight horizontal bulb turbine generators. To this day, they are the only bulb units on the Columbia River.

The units were designed for a 40-year operating life, which means they’re due for modernization. Over the next decade, units will be taken out of service, disassembled, and reassembled with new or refurbished components.

The first unit will be the most challenging as Chelan PUD and contractor GE Vernova test the nation’s largest air-filled hub design. The unit is currently being reassembled, and it is anticipated to be back in operation in 2027.

The purpose of developing an air-filled hub is to reduce the risk of oil leaks, avoiding costly shutdowns, and keeping the river cleaner for everyone. Two turbines with a new water-filled hub design were commissioned last year at Rocky Reach Dam.

Renovations are also underway at Powerhouse 1, where crews are finishing a 20-year modernization project. The modernization project rebuilds 10 generating units in a way that’s more efficient, fish-friendly and will last another 40 years.

Some early findings show that the renovations on Powerhouse 1 have resulted in nearly 10% efficiency gains, meaning the units generate about 18 more megawatts of electricity with the same amount of water. That’s roughly the equivalent of one additional generating unit.