“That event (Oso) moved about 8 million cubic meters of mass,” said Scott Heinze, deputy director of Pierce County’s emergency-management department. “The projection for a Mount Rainier lahar is between 250 to 500 million cubic meters of mass — exponentially greater.”
Pierce County Executive Pat McCarthy pushed for the review, which examined the functionality of the current warning system and also compared it to others around the globe, he said. The sensors, which were installed in the 1990s, monitor fast-moving gushes of mud and debris, or lahars.
Volcanic mudflows — formed by large landslides or suddenly melting snow and ice during eruptions — are considered the mountain’s greatest hazard.
The examination helped Heinze’s department and the U.S. Geological Survey (USGS) make plans to upgrade the detection technology, and now they’re working on a multiyear project to transition from outdated analog equipment to digital.
He said the upgrades aim to increase evacuation time for southeastern Puget Sound residents in potential paths of a massive mudflow, which has the consistency of wet concrete. The changes will also produce more accurate and shareable data for seismologists and volcanologists.
“It’s the difference between having a flip phone and a smartphone,” Heinze said. “We can make phone calls, but we’d like to be able to do more.”
Mount Rainier, which is more than a half-million years old, rumbles with volcanic mudflows every 500 to 1,000 years, Heinze said, adding: “We’re in the window.”
One significant mudflow event — around 5,600 years ago — filled the valleys of the White River some 300 feet deep in the area of present-day Sumner, Enumclaw and Auburn. It shifted watersheds, with sediments flowing off for decades to fill what used to be a part of the Puget Sound, near what is now Federal Way.
A volcanic flow now could destroy entire cities such as Orting, Sumner, Puyallup and Fife, on the mountain’s western side, as well as close a portion of Interstate 5 and the Port of Tacoma.
A computer system at the state emergency-operations center at Camp Murray monitors the lahar-detection sensors, which are in the Carbon and the Puyallup river valleys. If computers detect the rumbling of a lahar, that system alerts 24-hour emergency-monitoring and notification centers, which in turn activate a warning system, according to the USGS.
Television and radio stations, such as NOAA Weather Radio, would broadcast alerts. More than two dozen sirens scattered in cities from Orting to the Port of Tacoma would activate.
Heinze said officials plan to request money from the Legislature this year to double the number of current sirens, costing $1.9 million.
Separately, he said, scientists and emergency managers are in the early stages of planning to increase the number of places with the detection technology to include the White, Nisqually and Cowlitz river valleys, as well as install a volcanic-monitoring network that would offer days, weeks or even months of advance notice of volcanic activity. Mount St. Helens has that technology.
“That for us is the end-all, be-all,” Heinze said. “The technology that’s going into the ground can be utilized in a more predictive way; we just need to have more of it on the ground in the right places.”
The Carbon and the Puyallup river valleys host five lahar-detection sites each, two of which now have the new digital packages. That was Phase One of the long-term upgrade plan. In 2017, project stakeholders hope to have the same setup at all sites, he said.
Also in the upcoming year, local officials plan to continue work with congressional leaders to secure funding for completing the digitization project, at a cost totaling roughly $1?million, Heinze said.
Compared with the Oso landslide — which killed 43 people and destroyed nearly 50 structures when it engulfed the Steelhead Haven neighborhood in Snohomish County on March 22, 2014 — he said scientists consider a lahar in the Puyallup River valley a greater risk. It could travel faster and through a narrower and steeper area, he said.
Heinze said the massive debris flow, moving around 60 mph, would likely lose steam in the Orting Valley as it nears Puyallup, though some prediction models indicate that it would reach the Port of Tacoma. The sediment could also wreak havoc on the region’s main transportation routes.
According to the USGS, people might have between 40 minutes and three hours to reach high ground to escape the concrete-like mud and debris. Officials have developed evacuation plans with marked routes, and they urge preparedness.
“We’re putting the most state-of-the-art equipment in the ground that will tell us a lahar is happening, and we’re trying to get additional sirens,” Heinze said. “But they also need to know what to do when the sirens go off. They have to have a plan. ”
Material from Seattle Times archives was included in this report. Jessica Lee: 206-464-2532 or jlee@seattletimes.com
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