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Cunliffe Road SW Slide Repair Project
Major construction completed in winter 2024
November 2024 – A base gravel layer has been tightly packed down to create a strong, stable foundation for the road before paving. Crews will return to the work site in spring 2025 to complete final paving when the weather is warm and dry.
Status update
December 13, 2024
King County has repaired slide damage on Cunliffe Road SW between the Wingehaven Trail and SW 122nd Place. Work required a seven (7)-week road closure without a detour and was reopened to travelers on December 13, 2024. Crews will return to the road in spring 2025 for final paving when the weather is warm and dry.
Project overview
Over a decade ago, a slide occurred between Wingehaven Park and SW 122nd Place on Cunliffe Road SW. The county performed a temporary repair in 2016, however the slide area is unstable, and a more permanent repair is required now. This work requires crews to close a section of road for up to 6 weeks in fall 2024. The road and hillside need to be stabilized before the soil becomes saturated and heavy with winter rain and snow. We expect the repairs to be complete before the wet season. If it’s not repaired in time, the ground could slide more and continue to worsen.
To stabilize the road and hillside, crews must remove 23 trees and dig down 16 feet where the soil is stable enough. Next, they will build the hillside back up with a rock retaining wall to support the road. The view from the road on the hillside will change after construction.
September 2016 – The county repaired another slide area on a section of Cunliffe Road SW lower down on the road, closer to Puget Sound. Crews removed trees from the slope, dug down to reach stable soil, and then stabilized the hillside with a rock retaining wall. The slide repair work planned for late 2024 will use a similar method.
Location map
This project is located on Cunliffe Road SW near the foot entrance to Wingehaven Park on Vashon Island, WA. View larger image (600KB)
What to expect during construction
- Work hours: We expect workers to be on site Monday through Saturday during daytime hours. Work could begin as early as 7:30 a.m. and last as late as 4 p.m. The road will reopen at night and on Sundays.
- No thru access during work hours: Cunliffe Road SW, between Wingehaven Trail and SW 122nd Place, will be closed to all vehicles, including emergency responders, bicycles, and pedestrians during work hours. The work area will re-open to thru-traffic at least once during the day. There is no detour route. The project team will communicate with residents and first responders about the opening schedule prior to construction. If there is an emergency, crews will be able to open to road, but please give as much advance notice as possible and limit these requests to true emergencies as it will significantly extend the length of the project.
- Please plan ahead: If you know you’ll need routine daytime access during work hours, you may want to arrange to stay elsewhere during the project as the road can only be opened for true emergencies.
- Delivery services: US Mail, deliveries, and garbage/recycling may be restricted or unavailable during construction. Residents may need to arrange to pick up mail at the Post Office. Please have packages delivered outside of project work hours or sent to an alternative location.
- No parking at Wingehaven Park. Access to Wingehaven Park will remain open to the public, however visitors will not be able to park in the small, designated parking area on Cunliffe Road SW, or anywhere near the vicinity of the construction project. Parking may be available on Vashon Highway SW, located .25 miles from the park entrance.
Frequently asked questions
It took our engineers some time to monitor and evaluate the hillside and decide on the best way to repair and restore the road. The steep hillside is made up of many different types of soil and can become easily saturated and the narrow road also posed significant challenges.
The engineers wanted to hold off starting the repair project until it was absolutely necessary. This is because there is only one way for residents to get in and out of the neighborhood, and the work requires a full road closure, which is an inconvenience for neighbors. They monitored the annual rate of soil movement at the slide location and decided that the closure could not be put off any longer. It is important that the project is completed now before the wet and rainy season begins and the hillside and soil become saturated and heavy.
Other complications included coordination with utility companies, property easements with neighbors, and working outside of the bird nesting season.
- Update the project website regularly.
- Provide updates on X/Twitter (@KCroads) and on MyCommute (kingcounty.gov/MyCommute).
- Neighbors can contact abresslour@kingcounty.gov to receive email notifications about this project.
- Have a flyer available to people living near the work area with complete construction timeline and closure details.
Photos
November 2024 – A base gravel layer has been tightly packed down to create a strong, stable foundation for the road before paving. Crews will return to the work site in spring 2025 to complete final paving when the weather is warm and dry.
November 2024 – Both sides of the road are now prepared for a new layer of pavement. To combat water pollution from asphalt grinding and removal, crews lined the ditch with straw bags, called waddles. These waddles act as dams that give dirty water a place to settle, so that cleaner water can continue downstream.
November 2024 – After preparing the uphill side of the road for paving, crews moved on to the downhill side to pull up the existing pavement to prepare it for a fresh asphalt overlay.
November 2024 – Crews prepared the right side of the road for paving first, while leaving the left side for neighbors to pass through when the road reopened each night.
November 2024 – The final stages of excavating the hillside are almost complete. Once the excavator reaches the edge of the hillside, our crews will fill the top of the slope with small rocks.
November 2024 – The rock slope is in the first stages of building. The trench at the bottom of the slope is filled with larger rocks, while the top is filled with smaller ones.
November 2024 – Crews load up rocky material from the local stockpile. Both small and large rocks will be used to create a stable slope along the hillside.
November 2024 – Our crews removed a section of pavement on Cunliffe Rd SW and excavated the hillside to a precise elevation.
January 2016 – This is what the slide area on Cunliffe Road closer to Puget Sound (near house number 12416) looked like before adding the rock retaining wall. Crews anchored a white tarp over the active slide area to control further erosion of the hillside during construction.