Grand Coulee Dam Third Power Plant Overhaul, Coulee Dam

The three biggest generators in Grand Coulee Dam’s Third Power Plant are rated at 805 megawatts each, and their rotors weigh 1,480 tons apiece. When the Bureau of Reclamation hired Andritz Hydro Corp. in 2011 to overhaul them, the machines had been running since the mid-1970s and their mechanical components had never been replaced.

The Grand Coulee Third Power Plant overhaul was supposed to be a refurbishment. It turned into something closer to a rebuild, and what crews found inside those units now shapes the next contract at the same powerhouse.

Project Scope

Reclamation awarded the $102 million contract to Andritz Hydro Corp. of Charlotte, N.C., on May 12, 2011. Work started in March 2013, one unit at a time, with each outage planned at 17 months so the rest of the plant could keep generating. The units, G22 through G24, each turn a Francis runner 32.5 feet in diameter and weighing 430 tons at 200 rpm, according to Andritz.

Teardown changed the plan. Reclamation found major wear on wicket gates, shaft assemblies, the thrust bearing, rotors, outer head covers and embedded components, and the job shifted from overhaul toward modernization. The agency says those problems stretched the contract four years past its original schedule. G24 returned to service in April 2016, G23 in March 2019 and G22 on September 30, 2021. Andritz says two of the units still finished ahead of schedule and earned early-completion bonuses.

The Bonneville Power Administration paid for the work out of power revenues rather than federal appropriations, a point Interior made when the contract was awarded.

Why It Matters

Grand Coulee is the largest power producer in the United States, a 6,809 MW complex on the Columbia River about 90 miles west of Spokane. Pulling an 805 MW unit for a year and a half isn’t a maintenance ticket. It’s a grid-planning event.

The next phase is bigger in unit count. G19 through G21, rated at 615 MVA each and also in service since the mid-1970s, are slated for modernization beginning in 2026. Reclamation’s environmental assessment gives the contractor a design-build option to replace up to every component of each unit if needed, and the agency is studying an uprate to 790 MVA per unit. Elsewhere at the dam, Andritz’s automation contract for the 12 units of the John W. Keys III Pump-Generating Plant was scheduled to reach final completion in March 2026.

The G22 to G24 job showed what 40-year-old hydro machinery looks like once it’s opened. The G19 to G21 procurement was written with that lesson built in.

Project Team & Details