Editor’s Note: This is the first in a series of news commentaries on the Bonneville Dam safety reclassification. In this edition, the author will explain the basis of the reclassification, with future articles addressing specific aspects influencing the reclassification and evaluation.
PORTLAND, Ore. -- “Bonneville Dam is really complicated.”
That is the single most accurate description I heard while working on this article.
As a journalist, my inclination is to apply bombastic literary effects whenever possible. And by all accounts, this historic and massive piece of Pacific Northwest infrastructure beckons it: colossal statistics, fantastical personification opportunities, and, of course, a harrowing historical account or two. And trust me, those do exist.
But all the interviews, document deciphering, and a shocking sum of research led to the same result: Bonneville Dam is just really complicated.
So, when the media desk team here at the Portland District, U.S. Army Corps of Engineers (USACE), heard that the dam underwent a safety reclassification, we knew it was big. (The story, not the dam. Although the dam itself is truly massive, stretching2,690 feet long and standing 171 feet high from its foundation.)
What we didn’t know was that the terms “safety” and “reclassification,” when applied to Bonneville, assume the same intricate essence as the dam itself.
But there’s a great deal of current context that doesn’t add up without a bit of Bonneville’s background.
Bonneville is the Snoop Dogg of infrastructure. Yea, I said it. This epic edifice has continued diversifying its portfolio, embracing technological changes, and shifting its brand to stay relevant to the region it serves.
When Bonneville was put into operation in 1938, it had only two main turbine generating units. And its primary missions were navigation, hydropower, and fish passage.
The onset of World War II enlisted Bonneville in the fight. With an increased demand for power to fabricate material for the war effort, the powerhouse was expanded. Eight more main generating units were installed, bringing the total number of units to10.
The spillway was modified in the 1970s to allow The Dalles and John Day dams, located about an hour upstream, to operate as peaking power plants, facilities designed to ramp up electricity production quickly during hours of maximum demand. But even with these upgrades, the regional power demand kept increasing.
Bonneville responded with a second powerhouse, constructedin 1983, which added eight moremaingenerating units.This brought the dam to its current total of 18 generating units.
And while the Pacific Northwest introduced grunge into the music scene in the '90s, Bonneville began providing better control for fish passage. (The two are not authoritatively related in any official context, but it seems like a very Gen X thing in which to take part.)
Finally, in 1992, a second navigation lock was added. This vastly improved river navigation and massively helped the economy of the Pacific Northwest.
Verdict rendered: Seamlessly cooler with age.
Now you have the background on our protagonist, what about this safety reclassification? That’s a great question, which you were completely set up to ask! Here’s the deal.
In 2024, our dam safety team checked the Bonneville Dam to see how safe it is. They found out that the dam is actually safer than they once thought. However, they also learned that big earthquakes are the main factor to consider when talking about safety and risk.
A large earthquake could damage the dam and devastate the power grid that brings electricity to the region. If the power goes out, the dam may not be able to provide the electricity it needs to function; and if that happens, water might rise too high and flow over the top of the dam. This is referred to as, appropriately, overtopping.
Wait. Don’t crash out.
Fight the instinct to go all Debbie (or Daniel) Downer about the dam. When engineers talk about 'overtopping' in this specific scenario, they refer toa very rare, extreme chain of events where water temporarily rise sand flows over the top of some of the structures.
Because Bonneville Dam is a straight beast, it’s built to handle massive flows. But, as I channel my inner Neil deGrasse Tyson (we all have one), we live in world of infinite possibilities. So, while we don’t expect all the concrete structures to fail, we could expect some localized failures and breaches.
Under a worst-case scenario, a structural failure might originate through the gate repair pit structure. This is a specialized engineering structure used by maintenance crews to inspect and repair the massive steel gates that control water flow.
According to really smart people we have here at USACE, like Portland District Dam Safety Program Manager Matt Chase, “Bonneville Dam is working well and is operating safely today.
“The new understanding of the dam’s safety and risk just helps us know what to fix for the future. Our most important job is keeping people safe while fulfilling the dam’s intended purposes.”
If you’re not freaking out, that’s good. But let’s go down this rabbit hole a bit more.
When I asked Bonneville Dam Issue Evaluation Study Project Manager Ross Foster to help stoke the fires of my perpetual anxiety with his worst-case scenario, I learned it wasn’t the cinematic destruction scene I feared.
You: What’s an Issue Evaluation Study (IES)?
Me: Ah, yes. *clears throat* An IES is basically a high-tech safety check-up. Its job is to find out exactly what the safety problem is, decide if the dam is still worth investing taxpayer money into, and figure out how quickly it needs to be fixed compared to all the other dams across the country
“It gets pretty technical quickly, but uncontrolled release of water is what we are worried about,” said Foster. “That [uncontrolled release] could manifest by a breach or overtopping event, and anticipated repairs would be financially costly, but also take time to implement.
“While those repairs are in progress, our missions would be impacted in a meaningful way. Power production would be reduced or halted, navigation would be reduced or halted, recreation would be stopped, fish passage would be reduced or halted, and other typical consequences you might think of when you hear ‘dam breach’.”
He said: Other typical consequences you might think of when you hear ‘dam breach.’
Time for this stress cadet to report for duty! What could happen to areas downstream versus upstream from the dam?
The concerns related to the threat of overtopping are mostly economic and environmental. But what are the specific consequences?
The water, not unlike a college student picking out electives, chooses the path of least resistance.
“We’ve mapped out where the water pathways will go,” Foster answered. “As you can imagine, the lower-elevation locations at the dam will overtop first. We have plans to intervene and sandbag as much as possible to fend off an overtopping event.”
My apologies to any other veterans who just relived one of the most tedious, exhausting, and soul-crushing details in the military: filling sandbags. I salute you.
But in the event gravity and topography are too much for mediating measures, Foster said the bulk of the water would flow across Bradford Island. With that, the associated erosion of that land would require restoration, which makes the primary consequences of temporary overtopping localized, operational, economic, and environmental.
But it’s important to explain Bradford Island a bit more, as it’s the geographical heart of the Bonneville Dam complex.
Sitting right in the middle of the Columbia River, the island physically divides the massive spillway from the original powerhouse. And it’s not some barren piece of land. It’s home to the project’s visitor center, major fish ladders, and critical operational infrastructure. So, when experts warn about floodwaters overtopping and eroding Bradford Island, they're highlighting a direct threat to this central hub. Severe erosion here wouldn't just wash away dirt. It would devastate vital public, environmental, and operational systems that keep the dam and the river functioning.
(Remember, this is all regarding the earthquake scenario we talked about in the So, what’s shakin’? part of this article. Keep that in mind.)
Chase added, “Downstream flooding is not expected to exceed downstream levees for this earthquake scenario.
However, low-lying areas, houseboats, and recreators downstream of the dam could be affected since they are in or near the river or close to the shore.”
And upstream of Bonneville? As the reservoir rises, localized flooding could occur at communities like Stevenson, Hood River, and The Dalles. Upstream folks have time as an advantage: Water levels would be expected to rise slowly enough to allow the opportunity for warnings and evacuation.
And while we’re talking about people, it’s important to point out the following: while we noted that the concerns are mostly economic and environmental, we can never assume that there is no life-safety risk. Even if dam breach is very unlikely, many dams pose a risk to people living upstream and downstream.
Those who live or work near dams can benefit from visiting the Portland District dam safety page as well as the National Inventory of Dams.
The worst-case scenario I was so ready to write about—and, admit it, what readers really want to know—is this: regional economic and environmental disruption.
Overtopping could temporarily shut down the navigation locks, thus paralyzing river barge traffic; halt or drastically decrease hydropower production; and disrupt the critical fish passage systems for salmon up and down the Columbia River.
A major element to also consider is the electrical and mechanical services throughout the Bonneville site, like bridges, cranes, and hoists.
Recovering the dam’s power-generating capabilities after a major earthquake would be extraordinarily difficult and expensive.
So, if an earthquake triggers an overtopping at the Bonneville Dam, the real threat to our communities isn't a wall of water; it’s the breakdown of the critical power, transit, and environmental systems people rely on every single day.
USACE runs a robust dam safety program. And districts, like Portland, continually look at all their dams. Safety teams scrutinize hazards like earthquakes and floods, while reviewing how well the dam is built, how it’s working, and what could happen if something goes wrong.
They use a https://www.google.com/search?q=Dam+Safety+Action+Classification&ved=2ahUKEwi6zYzQ3bGSAxURklYBHQXqDgoQgK4QegQIARAB(DSAC) system. The DSAC is a tool that provides consistency in risk characterization, communication, and risk management. And while the DSAC doesn’t go into the specific characteristics of risk, it helps keep everyone on the same page regarding priority.
Often, especially when talking with the public, USACE employees use the terms “very low, low, moderate, high, or very high” when speaking about risk.
For example, a DSAC rating of high would elicit greater urgency than a dam rated low.
Bonneville Dam was originally rated as being high risk.
But USACE, with our commitment to safety, conducts more detailed studies on all high-risk dams to better understand that risk. So, Portland District did an in-depth checkup: the IES.
The results of the IES indicated the dam safety risk is less than originally understood. Bonneville is considered a moderate risk dam.
But again, Bonneville Dam is really complicated.
While the risk is less than originally thought, the IES gave us a better understanding of the economic and environmental risk mentioned earlier. And due to the potential economic and environmental impact, the agency feels this necessitates action.
The Portland District is currently navigating through answers for ways to reduce environmental and economic risks and improve reliability, in the fastest and most fiscally responsible manner.
“We are looking to minimize costs and maximize benefits by combining two studies to ensure a wholistic look at this complex and integrated structure,” said Marie Adams, Portland District project manager.
To operate expeditiously while still accurately, USACE uses state-of-the art geological data to assess earthquake risk. This includes general information from U.S. Geological Survey, as well as studies that look at the ground around a specific dam to find out how much earthquake-induced shaking a dam could experience and handle.
According to Chase, “We’re taking action now to prevent the possible localized damages, protect our regional economy, and ensure the dam can quickly recover to provide power, and protect the environment after a major earthquake.”
There are two things that I recollect immediately from high school. First, mitochondria are the powerhouse of the cell. Second, Maslow’s hierarchy of needs, with self-actualization being the pinnacle. (If you’re wondering, the Pythagorean Theorem came in a distant third.)
That said, we can apply that idea of self-actualization to the Bonneville Dam – stay with me here.
It’s not a stretch to admit that, historically, massive federal infrastructure projects can get bogged down in years of reviews. Similarly, an engineering team cannot focus on its ultimate purpose (building world-class infrastructure) if it is trapped in the "survival mode" of navigating endless bureaucratic red tape, redundant forms, and administrative delays.
Portland District’s goal with the work at Bonneville aligns directly with the administration’s focus on building infrastructure, not generating paperwork. The district is actively looking for every opportunity to get to the construction phase as quickly as possible. And while upgrading an active hydroelectric dam is incredibly complex, the team is aggressively pushing the timeline forward.
“I can tell you this, our directive is to move with urgency.” said Adams. “We want to spend our time and resources putting steel and concrete into the dam, not paper into a filing cabinet.”
Bonneville Dam has stood as a proud symbol of American engineering since 1938. By upgrading this historic facility to meet the geological realities of tomorrow, USACE is ensuring it will safely power our homes, support our economy, and protect the Columbia River for generations to come.
At the time of this article’s publication, the evaluation project is gearing up to begin. As this story unfolds, the Portland District will continue to publish the articles that keep our readers in the know.