If the dam breaks

It was a beautiful, clear Saturday afternoon in June when the Stillwater Dam gave way.

"Dam" might be an overstatement. In reality, the structure was little more than a boulder-fortified logjam. The breach itself was hardly spectacular; the dam's middle section buckled under the pressure of high water caused by heavy spring rains and melting snowpack.

But after the National Weather Service in Missoula issued a flash-flood warning to downstream residents, the Olney dam took on a certain glamour.

Hundreds of people flocked to the site. The Stillwater Bar, just yards below the dam, kept the spectators crowding its deck supplied with cold bottles of beer.

"That was the biggest public-safety issue, was the bar," said Mark Peck, director of the Flathead County Office of Emergency Services.

Rushing to the scene is a natural reaction. Dams don't break every day. But it's absolutely the wrong response, Peck said.

"'Let's go see' - that's the last thing you want them to do, and it's the first thing they want to do," he said. "It's the looky-lous that are going to be the issue."

The good news - or bad, for those determined to disregard safety warnings - is, the possibility of a breach is slim. A major earthquake could crack concrete, or an asteroid could smash into a dam. But for the most part, authorities are confident the valley's major dams are safe from most natural disasters.

At Hungry Horse Dam, for example, "a more likely scenario is flooding," said John Redding, spokesman for the U.S. Bureau of Reclamation, which operates the dam. "The probability of a worst-case failure like that is not very probable."

Danger from unnatural causes is likewise low, he said.

"Each federal facility, whether it's a dam or an office building, every single federal facility in the United States had to go through a safety program [after Sept. 11, 2001] to find where instances are where there might be a weak spot," he said. "You're not going to get in it or near it without being spotted or stopped."

Redding would not speculate about what might happen if somehow the dam did breach. For security reasons, the Bureau of Reclamation keeps that information, including inundation maps, from the public.

"Since 9/11, a lot of things, a lot of information, has been considered sensitive," he said.

The U.S. Army Corps of Engineers, which operates Libby Dam on the Kootenai River, refused to release information for the same reason.

"We don't discuss specific impacts from scenarios because the dams are part of protected infrastructure for national security," spokeswoman Nola Leyde said. "To protect those dams and people who live below them is not to disclose specifics."

If either dam failed, impacts would be far-reaching. The Kootenai River is the Columbia River's third-largest tributary, and Libby Dam generates enough electricity for the daily needs of 500,000 homes.

A 2006 planning exercise simulating Hungry Horse Dam failing during Memorial Day weekend estimated that 75,000 residents and tourists would need to be evacuated. Portions of Columbia Falls and Kalispell likely would be submerged, and an inland tsunami in Flathead Lake would send water as far as Thompson Falls.

In Polson, water would rise 20 feet, said Stephen Stanley, coordinator of the Lake County Office of Emergency Management. Residents would have plenty of time to prepare, however.

"It's not a wall of water that's going to wipe Polson off the face of the Earth," he said. "It will be hours before it gets to us."

A breach at Kerr Dam on the south end of Flathead Lake would be less disastrous than one at Hungry Horse, Stanley said.

"Kerr for us is kind of a nonevent," he said. "Impacts would be low."

Failure at Pablo Dam would be much worse for Mission Valley residents, said Jolene Jacobson, coordinator of the Confederated Salish and Kootenai Tribes' Office of Emergency Management.

"It would really be catastrophic," she said.

If that dam failed, Stanley said, water would pour out of Pablo Reservoir down U.S. 93. Pablo would be buried under at least 8 feet of water; about a mile south of town, the water would flow southeast, sparing Ronan.

But like the dams farther north, a breach at Pablo Dam is unlikely, he said. All the area's dams are well maintained, he added, and disaster plans are updated regularly.

"It's something we're really active with," he said.

Flathead County is just as serious about dam safety. Authorities have to be, explained Kurt Hafferman, regional officer manager of the Department of Natural Resources and Conservation's Water Resources Division.

However unlikely, the possibility of dam failure always exists.

"All dams have the possibility to breach," he said. "Even small dams can cause large damage."

The worst-case scenario is a clear-weather breach, Hafferman said. Those are the instances that happen without warning and often don't seem dangerous.

"The biggest hazard on these dams is not the knocking-off-the-foundation stuff. It's people trying to drive across inundated roads, not knowing where the edge of the road is, and driving off the road," he said. "It's the smallest thing that causes loss of life."

The state agency maintains several of the county's 80-plus dams, but of those, only two are considered "high hazard." If breached, Smith Lake and Cedar Creek dams potentially could result in fatalities.

About 30 people met in late February to discuss what might happen if Cedar Creek Dam failed. The simulated dam failure stemmed from an Easter-weekend earthquake and resulted in evacuating homes north of Columbia Falls city limits, including Aluminum City.

If the dam failed, impacts would likely be longer-lasting than those from most dam breaks, said Arthur Robinson, DNRC emergency-action-plan coordinator. The railroad embankment would act as a secondary dam, protecting the city of Columbia Falls from the water but creating a sort of quasi-reservoir. Standing water is unusual after a breach, he said.

"Usually it falls into a river and turns into somebody else's problem," he said.

Taking time to go over the dam's action plan was an important step in minimizing potential problems should an emergency occur, Hafferman said.

"If this is an imminent failure, this is not the time you want to find your emergency-action plan needs to be updated," he said. "This is just our proactive stance on dam safety. We try to get out in front of our high-hazard dams."

According to the Montana Dam Safety Act, dams with reservoirs larger than 50 acre-feet - those that impound enough water to cover 50 acres with water 1 foot deep - must get a permit from the state, Hafferman said. Every five years, a licensed professional engineering- and dam-safety expert must inspect the dam.

It's the large, unlicensed dams that may be cause for concern, Peck said. If owners aren't forced to get inspections, they may not regularly check their dams or update emergency-action plans.

"Probably the biggest deal is accountability," he said. "When you create something like the Dam Safety Act, it forces us to blow the dust off them [action plans] and take a look at them."

It forces people "to be proactive rather than reactive," Hafferman agreed.

That is crucial, he said, since there is little people can do to prepare for a breach.

"It's such an unusual occurrence they'll have to rely on us," he said.

Stanley agreed. All people can do, he said, is be aware of what's going on and be ready to leave if necessary.

"It's a pretty self-reliant group in this part of the state," he said. "People are pretty good at taking care of themselves."

Reporter Kristi Albertson may be reached at 758-4438 or by e-mail at kalbertson@dailyinterlake.com.