Monday’s heavy rains have claimed a structural victim on the slopes of Interlaken Park north of Capitol Hill.
Seattle Parks reports that a section of trail in the park has washed away near Boyer Ave E and E Howe above Montlake.
“That part of the trail has been closed and crews are assessing next steps for repair,” the department said Tuesday.
CHS hasn’t made it down to check out the damage yet but the collapse comes in the area where a new $205,000 Interlaken staircase and bike runnel was installed in 2018.
“The steep slopes and geotechnical recommendations required a robust concrete structure with shoring walls and steel pilings to construct the new stair and ramp connection between Interlaken Blvd and Boyer Ave E at E Howe Street,” Seattle Parks announced about the upgrade at the time. “Also included are community requested elements – a bicycle runnel, guard rails and a switchback that connects to the designated crosswalk.”
Remembered this morning that I biked over to Interlaken yesterday morning and locked up at the top of the stairway that collapsed yesterday….there were 4-5 people and 2 dogs using it at the time….Luck. 😬 https://t.co/1LCUOx1dAy
— Kimberly OK Using My Actual Name Kinchen (@SheRidesABike) December 23, 2020
Use of portions of the Interlaken park and greenspace have been shaped by the wet and shifting soils of the slopes of Capitol Hill before. CHS has reported on small slides over the years and concerns about the slopes of northern Capitol Hill and around Interlaken Park. Our nature writer documented the landslide risk of the area in 2014 including the Hill’s geologic past of glacial till and water-pooling clay:
Then we come in. The grade is altered, creating new faults. Hills are denuded of trees, which hold slopes and mitigate flooding. Barriers to natural water flow diverts it toward unforeseen consequences. People understandably want views and build on cliffs, changing the loads on hills. Generally things more even more unstable. West Capitol Hill, Interlaken, North Capitol Hill. Slides every decade going back in our modern record. I won’t tally the slides in Hill history — that would take too long.
A city study of the problem also showed shifting along western Capitol Hill with major slides occuring in 1916. “Four landslides occurred in the 1930s, one in 1961, one in 1974, two in 1986, and seven in 1997,” the study (PDF) reports.
For the most part, recent slides have been mostly limited in damage. Interlaken Drive, which has remained a neighborhood route for drivers even after some areas of roadway in the park were restricted to bicyclists and pedestrians, was closed for months in 2011 after a ten-foot section of the roadway suffered cracking and shifted from water water flowing underneath the pavement. The roadway was reopened after a five-month closure.
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