By Christopher Gaylord, Army Corps of Engineers, Portland District
Dam safety can be a gloomy business at times. In order to protect a dam, engineers must first brainstorm all the different ways the structure could possibly fail. It’s a strategy of predicting and preparing for the worst.
But not a whole lot about the wildfires that devastated parts of Oregon’s Willamette Valley last month was predictable—even in the highly calculated world of dam safety.
In a matter of days, fires that started out small had ravaged nearly 400,000 acres east of Salem and almost 200,000 acres east of Eugene, about an hour to the south. Together, the blazes closed in on the 13-dam system the U.S. Army Corps of Engineers’ Portland District operates for flood risk management, power generation, water quality improvement, irrigation, fish and wildlife habitat, and recreation for the Willamette River and many of its tributaries.
By the time Labor Day weekend arrived, a relatively small lightning-caused fire had been smoldering away for three weeks in a remote wilderness area too treacherous and overgrown for firefighters to safely access by foot. Referred to as the Beachie Creek Fire, it occupied a few hundred acres about an hour east of Salem. At the same time, a separate fire, the Lionshead Fire, burned to the southeast.
Tim Ernster, operations and maintenance manager for Portland District’s North Willamette Valley projects, wasn’t overly worried. Neither fire posed a serious threat to any Corps projects. The Beachie Creek Fire burned about 10 miles to the northwest of the district’s Detroit Dam but was mostly unremarkable.
In Ernster’s mind, any impacts to Detroit would happen on the off chance. Just in case, he and operators at the project talked through procedures to put Detroit and its downstream reregulation dam, Big Cliff, into a safe configuration—essentially an autopilot state—in case the dams had to be abandoned. But that didn’t seem likely.
Then, on the evening of Sept. 7, the winds came. Forest officials described the situation as a “hurricane hitting a wildfire”: extremely dry gales of 50 to 75 miles per hour crossing paths with multiple fires burning throughout the Pacific Northwest—conditions that occur only a few times a century.
In Ernster’s words, “all went to hell.”
The gusts put the fires into overdrive, and the blazes spread throughout the North Santiam Canyon, speeding mostly westward. Wind knocked out power lines, which ignited more than a dozen spot fires. The spot fires kicked up and joined one another as they raced through the canyon, eventually feeding the Beachie Creek Fire. Before long, the Beachie Creek and Lionshead fires merged.
“You’re talking about a change that occurred within a couple of hours—fire travelling more than 10 miles,” says Dustin Bengtson, Portland District’s Willamette Valley deputy operations project manager. “It happened that quickly.”
The off-chance scenario Ernster and his team had discussed became a reality. Mike Pomeroy, the operator on shift at the time, put the Detroit powerplant into safe condition. But by the time Pomeroy was ready to leave, the fires had arrived—and trapped him there. Then, Ernster and others lost all communication with Pomeroy.
Pomeroy would secure the dam for more than 30 hours before anyone could reach him.
Meanwhile, an hour to the south, a new fire started in the McKenzie River Valley, where Portland District manages Cougar and Blue River dams, separate flood risk management projects about 10 miles apart.
At some point in the evening, downed powerlines took Cougar Dam’s hydropower turbines offline. Roving operators made it to the project, which is operated remotely from a primary control center an hour southwest, put the plant into a safe configuration, and left before things got too bad.
“Everything worked like it was supposed to”
Bengtson refers to what happened in the Willamette Valley as “burn-over” events. Fire surrounded and encroached on four dams—Detroit, Big Cliff, Cougar and Blue River—and their associated fish facilities. The fir trees along the hillsides around the projects, some of which look like burned matchsticks, are evidence of the destruction.
Surprisingly, however, the four projects sustained no serious damages.
Some of the gauges the Corps uses to measure outflows and monitor reservoir elevations at the projects were destroyed, according to Dam Safety Program Manager Ross Hiner. Signs were melted to resemble twisted bits of tinfoil. A storage facility was lapped by flames, and a truck’s headlights and grill melted. A Corps-built fish facility upstream of Detroit was touched. Some communication boxes burned.
But dams are designed to endure.
“There’s a lot of resiliency built into the dams, in their design and in their operation and maintenance, to ensure that they’re capable of withstanding what Mother Nature might subject them to,” says Hiner.
Hiner refers partly to the redundant systems in place to protect a dam. Getting electricity through a diesel generator versus a turbine (or vice versa) is one example.
Some turbine units went offline briefly, transmission lines failed under the weight of fallen trees, and ash and debris occasionally clogged generator filters. But Ernster sees success in how the projects performed.
“Everything worked like it was supposed to,” says Ernster.
No significant flow deviations. No impacts to communities downstream. No fish lost.
According to Bengtson, that credit goes to a well-oiled engineering, construction and maintenance program at the district—especially important in the Willamette River Basin, where many Corps dams rely on automation and remote operation.
“Operators’ decisions are critical to the safe functioning of the plant, but everything they can do is a function of solid design, construction and maintenance activities,” says Bengtson. “Everything has to be well thought through, well-built, and well-maintained for an operator to be successful when it all really hits the fan.”
The dams emerged from the fires relatively unscathed. According to Bengtson, the district’s infrastructure is “pretty much all ready to go.”
It’s the landscape that bore most of the devastation.
Vegetation helps stabilize slopes by holding soil together and reduces runoff after heavy rain events by taking up some of the water. But the fires burned a considerable amount of it away in the two impacted river basins.
Add to this a diminished ability of scorched soil to soak up rainwater and increased potential for landslides and falling debris, and the district’s two immediate priorities come into focus: Provide safe access to the dam sites and protect communities downstream from flooding.
Teams are ramping up assessments with partner agencies, like the Forest Service, to better understand these risks as the flood season looms.
“We’ll be monitoring smaller rainfall events more closely than we have in the past,” says Hiner, adding that the district will also work quickly to ensure operators can get to the area’s remote projects safely if needed—something Bengtson says will likely be a constant focus all winter long.
They’re issues that will probably remain with the district for some time, according to Paul Sclafani, Portland District’s Floodplain Management Services Program manager.
“The road to recovery is going to take several years,” he says.
“We’re going to learn a lot from this”
Wildfire has threatened the Willamette Valley before. This time was different. The fires in the valley spread faster and grew more than most expected. They destroyed thousands of structures and killed at least five people. Across Oregon, more than 40,000 evacuated their homes. Half a million were under some level of evacuation alert. And the state experienced, by many accounts, its worst wildfire year in recorded history.
“We’ve been in and around wildfire on a number of occasions, but never anything like it was in those two days,” says Bengtson, who has worked for the Corps’ Willamette Valley project since 1993.
Hiner backs that up with historical data.
“There have been wildfires in the watersheds and adjacent to our reservoirs and dams in the past, but nowhere near—at least in the history of the dams—this magnitude,” he says. “The amount of acres burned is pretty remarkable when you look at historical fires in the past 50 to 60 years.”
Like with most unprecedented events, the experience has imparted some key lessons. In previous years, dam safety at Portland District hasn’t focused a lot of attention on wildfires—at least, not as far as seeing fire as a probable cause for a dam’s failure.
That’s likely to change.
“It’s just another potential scenario that we’ll have to consider in a little more detail than we have in the past,” says Hiner. “This experience will help us brainstorm different scenarios that we might want to think about when we do risk assessments.”
“We’re going to learn a lot from this. Things we’ve speculated on before, but we have some practical experience now that will maybe take us in a different direction in terms of our contingency planning.”
— CBB, Sept. 24, 2020, LABOR DAY WILDFIRES: DAM OPERATOR TRAPPED AT DETROIT DAM DURING BEACHIE FIRE, TOOK REFUGE IN LOWER LEVEL https://www.www.www.cbbulletin.com/labor-day-wildfires-dam-operator-trapped-at-detroit-dam-during-beachie-fire-took-refuge-in-lower-level/
— CBB, Sept. 24, 2020, LABOR DAY WILDFIRES: EQUIPMENT IN 7 OF 13 BPA TRANSMISSION MAINTENANCE DISTRICTS IMPACTED, ONE LINE DE-ENERGIZED https://www.www.www.cbbulletin.com/labor-day-wildfires-equipment-in-7-of-13-bpa-transmission-maintenance-districts-impacted-one-line-de-energized/
— CBB, Sept. 17, 2020, OREGON FIRES RESULT IN BURNING, EVACUATION OF SEVERAL HATCHERIES, NO LIVES LOST; SOME FISH LOST, TRANSFERRED; 1.6 MILLION RELEASED INTO MCKENZIE RIVER https://www.www.www.cbbulletin.com/oregon-fires-result-in-burning-evacuation-of-several-hatcheries-no-lives-lost-some-fish-lost-transferred-1-6-million-released-into-mckenzie-river/