By NATALIE MARTIN

In the wake of last month’s deadly landslide in Oso, Vashon’s emergency volunteers are preparing for a significant landslide on Vashon while also attempting to highlight the island’s own risk for slides.

Volunteers with Vashon’s Emergency Operations Center (EOC) team are currently using a fictitious Vashon landslide scenario they created to help plan for such an event. In the detailed scenario — similar to ones the organization has used to help prepare for earthquakes and other emergencies — an 800-meter-wide landslide comes down on a portion of Luana Beach Road. It inundates or moves two dozen homes in the middle of the night and traps an unknown number of people.

For the next few months, EOC volunteers will discuss what Vashon would need to do to respond to such a landslide, hoping to eventually have detailed plans in place and to hold a practice drill.

“We’re going to focus our energies and efforts on preparation for a Vashon event,” said Hank Lipe, chief at Vashon Island Fire and Rescue (VIFR) and commander of the EOC when it is activated. “Hopefully it never occurs, but we want to improve our readiness.”

When Lipe came to VIFR in 2009, he led the creation of a new emergency management plan, a collaboration among the department, VashonBePrepared (VBP) and other organizations. As part of that process, Lipe said he learned that the three greatest risks to the island are earthquakes, severe weather and landslides.

“I’ve never lived in an environment that has the soil conditions we have here in the Puget Sound,” said Lipe, who previously headed a department in New Hampshire. “It was all new to me, and it’s a very dangerous situation.”

Indeed, landslides in the Pacific Northwest happen almost exclusively on coastal bluffs or in river valleys. A King County map shows that much of the coast of Vashon and Maury islands as well as some inland locations on the island are considered at risk for landslides.

“Vashon is largely surrounded by coastal bluffs,” said John Bethel, a geologist with the county Department of Natural Resources and Parks. “It certainly makes sense that the perimeter of Vashon is prone to landsliding.”

Bethel explained that in many parts of Puget Sound, the soil is stratified, and landslides can occur when heavy rains soak the top level of permeable soil and hit the less permeable layer of clay, trapping water in between and compromising the slope’s stability.

“That’s a classic recipe for landsliding at that location. … It certainly is present in many places on Vashon,” he said.

Detailed plans have been drawn in recent years for local emergency response to earthquakes and severe storms, Lipe said, but not for landslides.

After a massive landslide cut off 17 homes and damaged one on Whidbey Island last year, Rick Wallace, a leader with VashonBePrepared and the manager of the EOC, says he got to work on a Vashon landslide scenario. He finished it in collaboration with others after the tragic landslide in Oso last month.

Wallace emphasized that Luana Beach is not necessarily more prone to landslides than any other area identified by the county, but was chosen as the site for the EOC’s exercise because the location presented other challenges that would be helpful in their planning.

He noted that should a major landslide happen, the EOC — a group of dozens of volunteers stationed at the main fire station in an emergency — would be activated long before off-island help could arrive. EOC volunteers are now considering what would be needed during those vital hours, including emergency workers, medical help, equipment and shelter. The response to a landslide is very similar to a response to other emergencies, Wallace noted, and the EOC will ultimately create a guide to be used in the case of an actual landslide event. They will also hold a drill at the fire station using the Luana Beach scenario.

“This isn’t about scaring people,” he said. “It’s about helping people be resilient, people being resilient and coming together as a community.”

Historically, many say, Vashon sees small landslides each rainy season, but larger ones don’t happen as frequently. Dockton Road, for instance, was closed to traffic along Tramp Harbor twice last month after small landslides brought down trees and other debris there.

Some, however, do recall more significant slides on the island. Emma Amiad, a home buyer’s broker on Vashon, says she remembers landslides that have pushed homes into the water in last few decades, and she won’t show homes in some parts of the island that she believes are at risk.

“I realize it may be unfair to the seller. However, I can’t sleep at night thinking about things like that,” she said.

Islanders Bill and LeeAnn Brown know firsthand the threat that landslides pose. Their former home on Bunker Trail, a walk-in neighborhood at the bottom of a steep slope on the north end, was hit by a landslide in 2011 after a winter storm. Thankfully no one was home at the time, LeeAnn said, and the house wasn’t significantly damaged. Dirt and debris buried the front door but didn’t get into the home.

“I would definitely think twice about buying on a hillside again,” she said, noting that a few years earlier a neighbor’s home had been significantly damaged by another slide. However, the county had taken measures to improve drainage on the slope, she said, and the Browns never thought a landslide would happen to them. Their home had been on the spot since the 1930s, she said.

“Because it had been there so long, we didn’t really worry about it,” she said.

The couple was already planning to sell their Bunker Trail home, but had a difficult time doing so after the landslide, which also took about $80,000 off the home’s appraised value, LeeAnn said.

Greg Wessel, an environmental scientist at the county’s Department of Environmental Permitting and Review (DPER) and a Vashon resident, said that while Vashon’s shoreline is prone to landslides, those within the hazard area identified on the county’s map shouldn’t necessarily be alarmed. He called the map very general and said DPER uses more specific data on each parcel to determine landslide risk as part of its construction permitting process. Some areas identified on the map, he said, have greater actual risk than others.

Wessel himself lives in the landslide hazard area, he noted, in a home at the top of a steep slope. He felt comfortable purchasing the house, he said, because it’s set back about 40 feet from the edge.

The county, however, didn’t start assessing landslide risk as part of its permitting process until the 1990s. Homes built before then may not have the same landslide mitigation measures as those built since, Wessel said.

Anyone with concerns about a home can contact DPER for more information on the property, he said. Engineers can also be hired to assess landslide hazards at a location, something Amiad said she recommends to anyone buying a house near the water.

“Does this map suggest there’s a significant hazard everywhere? No, not at all,” Wessel said. “It’s a suggestion that maybe you should ask about it.”

Wessel said a large landslide such as the fictitious Luana Beach one the EOC is using for its planning is not likely to happen on Vashon,  “but it’s something the island might want to think about in terms of emergency planning,” he said.

Lipe said that the EOC hopes to have detailed landslide response plans in place by next winter. He agreed that Vashon residents shouldn’t be alarmed over landslides, but like the risk for a major earthquake, he said, responders want to be prepared for the worst-case scenario.

“When these events happen, we don’t know when they’re coming,” he said. “Preparedness is the key to hopefully saving lives and better outcomes in the long term.”