The News Tribune

A state report released Wednesday finds that a catastrophic mudflow from Mount Rainier could cause $13 billion in property destruction to the Puyallup River Valley.

The Washington State Department of Natural Resources says its study is the first to estimate the value of damage that a lahar could cause.

The total value of property at risk from a lahar flowing through six rivers reaches $40 billion and stretches all the way to the Port of Seattle, the study found. But it’s unlikely a lahar would fill all six major drainages that flow from Mount Rainier, said state geologist Dave Norman.

The damage estimate for the Puyallup River Valley includes the value of land, buildings and contents. The projected lahar path goes through Orting, Sumner, Puyallup and Fife to the Port of Tacoma.

“That’s pretty devastating, obviously,” Norman said. “Because Mount Rainier’s such a dangerous volcano, we need to know better what the risk is. That’s what this study does.”

Norman said that because of limited funding, the study did not examine the potential for loss of life.

Puyallup Mayor Rick Hansen said while the study findings are interesting, the ability of people to survive a lahar is the most important thing.

“You’re talking about loss of life that is way more significant to me than the loss of property,” Hansen said, noting that governments need to continue focusing on emergency preparedness.

The report culled property information from the U.S. Census and county assessor-treasurers’ offices. It then used “loss-estimating” software from the Federal Emergency Management Agency.

The damage number for the Puyallup River Valley is hard to fathom. For instance, it is roughly 16 times the total annual budget for Pierce County government.

Sheri Badger, spokeswoman for Pierce County Emergency Management, described the new information as “a point-in-time estimate, and it’s the first one we’ve had.”

Of the projected $13 billion impact, she said: “It’s a huge economic loss. Hopefully, there would be no lives lost as well.”

Her agency and other local public safety departments have worked to minimize potential casualties by setting up lahar early-warning systems.

Pierce County Emergency Management operates 17 outdoor lahar sirens in the Puyallup River Valley that are tested monthly. There are nine other lahar sirens operated by the cities of Puyallup, Fife and Orting, Badger said.

In the event of a lahar, acoustic flow monitors on Mount Rainier would trigger a warning system that includes the 17 sirens and Pierce County Alert, an automated phone notification system. Emergency responders also would be notified, Badger said.

Major lahars occur on Mount Rainier every 500 to 1,000 years. The new damage estimate was based on a lahar similar to the last one to reach the area’s lowlands, the Electron Mudflow, 500 years ago. It was caused by a slope failure on the west flank of Mount Rainier and not by an eruption.

With a consistency of concrete, a lahar would knock buildings off their foundations and, in some cases, inundate them, Norman said.

His agency’s study cost $129,997 and was funded by federal stimulus dollars.

In conjunction with the study, DNR produced an online interactive map to track potential lahar pathways – down to the parcel level. It can be viewed at tinyurl.com/7cpbpak. (Under Interactive Maps, click on Mount Rainier Lahar Hazards.)

Norman said his agency had no idea what the damage estimates would turn out to be. He said he hopes the study will raise awareness of volcanic hazards and help preparation for a lahar.

“It’s almost certain there will be more events,” Norman said. “We just don’t know when.”