Slides close roads; many areas still vulnerable

It's tough living in a region famous for its rain.

Every year the Seattle area gets pelted with rain that is measured in feet, not inches, and only so much of it can be sucked up by thirsty lawns, gardens and greenbelts. Just ask folks living in West Seattle, Magnolia, South Lake Union, Queen Anne and near Golden Gardens Park what happens to the excess water.

Trees slip, houses slide and — as happened on Monday when several inches of rain fell — the earth moves.

The heavy rainfall that saturated the region spawned numerous slides, closing roads and contributing to a messy Monday. The biggest slide occurred on Golden Gardens Drive, above Golden Gardens Park, when a section of roadway literally slid down the hill. Seattle officials still aren't certain of the cause, but the heavy rain is suspected.

The road will remain closed until spring, said Marybeth Turner, a spokeswoman for the city of Seattle's Emergency Operations Center.

Another slide in the 2400 block of Westlake Avenue North snarled the morning commute and forced residents at the Cascade Condominiums in South Lake Union to briefly evacuate. That slide was caused by a broken drain pipe, according to city officials.

On Monday, slides struck across West Seattle. A section of Beach Drive Southwest near Atlas Place Southwest was closed, but traffic managed to get by after slide debris hit near California Way Southwest and Harbor Avenue Southwest.

The King County Road Services Division reported at least five mudslides outside of Seattle that prompted road closures. The most serious slides were at Northeast 172nd Street at 152nd Place near Woodinville, and at the intersection of Jones Road and 196th Avenue Southeast near Renton.

In the Juanita area, a landslide that occurred on Holmes Point Drive Northeast between Juanita Drive Northeast and 183rd Avenue Northeast prompted King County to close the road.

Sound Transit's Sounder train from Everett to Seattle was shut down Monday morning because of slides along the route. It was unclear when service would resume; Community Transit added buses to its routes from Everett Station to Seattle.

The Golden Gardens slide occurred in an area where there has long been slide activity, said Bill Benzer, who manages the landslide-mitigation program for Seattle Public Utilities. He said they are still investigating what caused the roadway to slip about 200 feet down the hillside. An unoccupied Subaru was swept down the hill along with the road.

Nobody was hurt.

Bill Laprade, senior vice president at Shannon & Wilson in Seattle, said his geotechnical firm was supposed to start examining the bluff above Golden Gardens for instability before Monday's slide. "You have to be willing to take a risk to live there," said Laprade, an engineering geologist.

Laprade said slides often result from a combination of the region's glacial till soils, steep slopes and the high concentration of water that the region receives this time of year.

"Though we only get 34 to 36 inches a year, it's concentrated over November, December and January," he said.

According to the city's Office of Emergency Management, more than 1,326 landslides have occurred in Seattle since 1890. The city even maps areas prone to slides.

The city's history of slides has turned Perkins Lane West into a sort of outdoor classroom. The University of Washington takes civil-engineering students to the street below Magnolia Bluff for firsthand lessons on erosion.

On Monday, Perkins Lane was again closed after crews responded to three small slides.

Alki Point and other scenic points in West Seattle share the same problem: a layer of clay over sand in the middle of the bluff. When groundwater hits the sand and clay layer, it weakens the sand and slides occur, Benzer said.

"It's the geology that was here, and we have to live with it," he said.

Jennifer Sullivan: 206-464-8294 or jensullivan@seattletimes.com

Information from Eastside bureau reporter Amy Roe, Times archives and The Associated Press is included in this report.