Wanapum Dam


Sixty-five miles northeast of Yakima, the Wanapum Dam spans the Columbia River.

First constructed in 1959, this remote facility generates 4 million megawatt-hours of hydro-electric energy each year. It all happens in a massive building called the Powerhouse.

  • YEAR 2021
  • SQUARE FEET 80,000


“As long as there’s snow on those mountains, there’ll be wind down the river.” So say the old timers in the Yakima valley.

They aren’t lying. The Wanapum Dam is situated astride the Columbia River as it cuts a wide canyon through the basalt bedrock of Central Washington. Wind systems whip through that valley in great gusts, reaching 100 mph. And there’s no room for error when you’re installing a roof (and tearing one off) within feet of 120,000 volt power lines, suspended in the air seventy five feet above ten huge whirling turbines and the hydro-electric generators that are actively generating power for 40,000 customers.

Since the timeline on this project called for the work to continue over a two-year period, we’d have to plan for another weather extreme too — summer temperatures above 100 degrees in the shade. And there’s no shade to be found when you’re working on an 80,000 square foot roof.

Since there were two roofs on the Powerhouse already — the original roof from 1959 as well as a re-cover from the mid 1980s — our scope called for tearing them both off and removing tens of thousands of pounds of waste — without blocking access to the dam for even a moment, or risking a spill — even in 100 mph winds.


Our first step was the removal of two old roofs. We stripped the structure down to the bare metal decks.

We had a dozen dumpsters to be moved in and out past the turbines and generators without blocking access to the dam, like a well-oiled machine. To preserve access — while always having an empty dumpster where it was needed when we needed it — we choreographed the movements of twenty flatbed trailer loads on semi trucks. Every one of them had to be tied down to prevent pollution of the river should it be hit by a sudden gust of wind.

In tearing off the old roofs, we discovered that some of the sheet metal flashings had been damaged over years of use, and replaced them. Our roofers also noticed some structural damage from years ago, and repaired that.

The discovery that some of the flashing contained asbestos changed our approach, and we were able to safely and legally abate it without risking the functionality of the facility or the health of our people.

With the removal of the two old roofs complete, we were now working in safety harnesses suspended 75 feet above the live generators — using an interior gantry crane, directly beneath the roof. The crane and all our other equipment had to be raised and lowered without coming into contact with the power lines or generators, which remained functional at full capacity.

Extreme summer heat made it necessary for our team to work off-peak hours, avoiding the most intense afternoon sun, and working early mornings and evenings.

On top of the Powerhouse, we added pedestrian coating for access, as well as a viewing platform above the salmon ladder. We also wound up calking joints in the structure to maintain the roof’s water tightness seismically, because the best time to do that work is when the roof is being replaced.

General Contractor: Axiom Division 7


One evening during this successful, 2-year project, we had the privilege of seeing some historical photos of the original crews constructing the first Powerhouse roof.

These folks faced the same extreme conditions we did, but without our modern safety equipment, or our air-conditioned trucks, or our laser guided, automated torch machine. And we thought we had it hard!

Those original roofers left a legacy (and a roof) that stood the test of time, and lasted decades. Ours will too. We’re lucky to be walking in their footsteps.


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