Seattle sits between the Olympics to the west and the Cascades to the east, and is known for its hilly topography and steep hillsides. These hillsides provide dramatic views, but occasionally pose problems for the infrastructure we’ve built along their sides.
One case in point is alongside Lake Washington, north of Magnuson Park. One small section of the slope here has gradually slipped about 4 feet downhill.
This might happen in any number of spots in the city without attracting much attention, or cause for concern, but this particular section of slope rests both under and behind a City owned retaining wall which supports one shoulder of Sand Point Way NE (a key north-south arterial in NE Seattle), a 16 inch diameter water main and access for the adjoining property.
Replacement work site along Sandpoint Way NE
The slippage here required the city to undertake urgent replacement of the retaining wall at this location. The new wall will be deep enough to reach stable soils and prevent future slippage, but required relocating the overhead utilities (electrical power, fiber optic, phone and cable) and installing a temporary bypass for the vulnerable water main. This work began late in January and required occasional closure of one lane of traffic on Sand Point Way NE.
This past week the replacement work began with a necessary closure of Sand Point Way in the 8500 block to prepare for installation of the 60 foot long steel uprights that will support the wall. Boring holes for these beams, with a crane-supported drill rig, is expected to take most of February. Once the retaining wall is in place a new waterline will be installed, the area behind the wall back filled and the road surface repaved.
While this work is underway (near NE 85th Street) traffic on Sand Point Way NE will be detoured to 35th Avenue NE, via NE 95th Street and NE 70th Street. Traffic signals along the route have been re-timed to help with the additional volumes expected.
Detour Map
It is expected that the southbound lane of Sand Point Way NE will be reopened to traffic past the ongoing construction in early in March, but that the northbound lane isn’t expected to reopen until April.
The Burke-Gilman Trail, higher up this slope, will provide access past the construction zone for pedestrians and bicyclists while the full closure is in place. It will also provide a nice view of the construction work, and wonderful views of the surrounding area, like so many of vantage points offered by Seattle’s steeply sloped terrain. SDOT appreciates the community’s patience while this work is being completed.
Please visit the project page for more information: http://www.seattle.gov/transportation/sandpoint_retainingwall.htm