Grand Coulee Third Power Plant Overhaul Update

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Published: Monday, 02 December 2019 20:21

Six years in the making, two of six turbine units being overhauled in Grand Coulee Dam’s Third Power Plant are now back in operation. The second unit came back online in March. Each of the units overhauled has a generating capacity of 805 megawatts.

The six turbines in the Third Power Plant became operational from 1975 – 1980. Other than general maintenance, they’ve been running continuously until each is opened for overhaul. And just like an aging house being remodeled and modernized, engineers and contactors discovered worn-out parts and other issues that dramatically changed the project schedule. Originally, managers envisioned overhaul of all six turbine units by the end of 2017.

To comprehend the size and importance of these turbines, think about one megawatt of electricity being able to serve the needs of about 650 residential homes. That means one of the units overhauled can meet the needs of over 500,000 residential homes and all six units can meet the needs of over 3,000,000 residential homes. Add in the capacity of the 18 generators from Grand Coulee’s Right and Left Powerhouses that received turbine replacements between 2000 and 2010, and Grand Coulee Dam has the generating capacity to meet the needs of over 4.5 million residential homes. Alone, that’s more than all the housing units in Washington State.

While this overhaul is essential to keeping the lights on in the Northwest, the investment is also very significant. The original cost of Third Power Plant construction was about 700 million dollars (in 1980’s dollar value). Overhauling the first two units cost about 100 million dollars.

A third unit was disassembled this spring. Completing the overhaul of this unit will utilize lessons learned from the first two units with work currently scheduled for completion by the end of 2020. Then it’s on to the next three units.