Weekend rain causes landslide near West Mercer Way ravine

A mudslide in the 5700 block of West Mercer Way went over a retaining wall and pushed two cars up against a tree, leaving them dangerously close to a ravine edge. - Contributed photo
A mudslide in the 5700 block of West Mercer Way went over a retaining wall and pushed two cars up against a tree, leaving them dangerously close to a ravine edge.
— image credit: Contributed photo

Three homes near a ravine on Holly Lane, off of West Mercer Way, were severely damaged in a landslide that resulted from the weekend’s punishing rainfall.

Emergency preparedness officer Jennifer Franklin, said one home was red-tagged, meaning it had to be vacated. One home was yellow-tagged, which means the homeowners have to avoid certain parts of the house, and a third home was still being assessed as of press time.

It was a busy weekend for firefighters as they responded to a number of water-related calls, said battalion chief Shawn Matheson. He said the department had 22 calls between 7:12 a.m., Sunday, and 5:30 a.m., Monday, all relating to minor flooding, such as plugged storm drains and water in crawl spaces.

Matheson said a landslide at 5700 West Mercer Way pushed two cars together that were parked in a driveway. The vehicles then were pushed into a tree.

“The cars are still teetering on the ravine edge,” said occupant Christine Poli, adding that the cars were crushed. “The property manager is coming and the city already came.”

Poli said the city is waiting to get a report from the geo-technical engineer to see if the home she and her family have lived in for three years will get red-tagged. Poli said the retaining wall has been moving for some time.

“The retaining wall is about to fall over,” Poli said. “We’re from the East Coast; I didn’t know how powerful mudslides can be.”

The fire department also responded to a one-car accident and to a home where a fireplace malfunctioned, Matheson said.

Water created problems for management of wastewater on the Island. Terry Smith, utilities operation manager for Mercer Island, said he got notice at 1:15 a.m., Sunday, that all 18 wastewater stations on the Island were overwhelmed. He said part of the problem is that people illegally hook up roof drains to the sanitary sewer system, intensifying the overload.

Smith said leaks in older pipes create inflow and infiltration, where the effluent from the leaks takes the path of least resistance directly to the city pipes.

“A rain event causes a pump’s run time to increase because of all the water getting into the system that shouldn’t,” Smith said.

He said the rain does help clean the mains, but it also sends other material and debris into the mains, such as twigs and leaves. What is disturbing is the other material they see, such as paper towels and rags.

At one station all three pumps clogged, but they were quickly cleared. The only sewage spill that Smith was aware of was on 97th, where a manhole overflowed, spilling the effluent into the street and subsequently into the lake.

King County reported an overflow at the North Mercer pump station, at 7631 S.E. 22nd St., largely diluted with groundwater and rainwater. The overflow came through a manhole.

“The water came out very rapidly and was spilling into a neighbor’s yard, but response was quick,” said Annie Kolb-Nelson, spokeswoman for King County Dept. of Natural Resources and Parks.

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