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Landslide Response and Repair
Project Impact - Landslides

Sand Point Way NE Retaining Wall Replacement Project

April 22, 2016

Sand Point Way NE re-opened to traffic in the north bound direction on April 22, more than a week before anticipated.

This concludes the detours associated with project.

Thank you all for your ongoing patience during this emergency repair work.

Photos of the construction activity may be viewed HERE.

Project Description

Due to the steep slope and water saturation, soil behind and underneath a retaining wall under the roadway shoulder in the 8500 block of Sandpoint Way NE has been slipping downhill.  As a result SDOT declared an emergency repair necessary and is building a new retaining wall that will be anchored in deeper, more stable soil.

Between February 8 and February 29, Sand Point Way was closed to all traffic at a point somewhat north of the NOAA Center in the Magnuson Park area for this repair which will involve removing part of the roadway, excavating some soil and anchoring fifteen 60 foot long steel I beams, each weighing 6 tons, on end in concrete filled holes to support the soil under Sand Point Way. A new timber retaining wall was then fitted to the piles. (Later on this formed the backside of the new steel reinforced concrete wall.)

Between March 1 and March 15, approximately 220 feet of water main was replaced in the vicinity of the new 90 foot long retaining wall. The new water main (16" in diameter) was installed under the south bound travel lane of Sand Point Way NE. This location, further from the road shoulder, will be more secure in the event of future soil instability.

Between March 15 and March 31 the 12" diameter temporary bypass for the water main was removed, along with the remainder of the paving in the immediate vicinity, after which a new road base was established and the surface repaved. Meanwhile installation of rebar on the face of the retaining wall proceeded.

Between April 4 and April 22 new utility poles were installed and power lines were replaced, concrete was placed to enclose the rebar on the face of the wall and new guard rails were installed. The road shoulders and edge slope were regraded and a final asphalt wearing course was placed and (temporarily) striped.

Project Detour

Sandpoint Way NE was closed in the 8500 block to all traffic (vehicles, bicycles and pedestrians) from February 8 to April 2. This full closure was originally expected to last 4 weeks, but was extended by 4 weeks when it was decided to relocate the water main as well.

Between April 2 and 22, traffic in the northbound direction was detoured during working hours 6:30AM to 3:30PM Monday-Saturday.

The detour route during the project was:

  • n NE 70th Street between Sand Point Way and 35th Avenue NE
  • on 35th Avenue NE between NE 70th Street and NE 95th Street
  • on NE 95th Street between 35th Avenue NE and Sand Point Way NE

Project History


1/27/16 

Relocation of power and water lines begun
Flaggers controlling traffic at times as needed

1/29/16

Electronic message board deployed announcing detour

2/1/16

Project website established

2/3/16

Traffic advisory notice sent to media

2/8/16

Full closure of Sand Point Way NE in the 8500 block went into effect
Detour route is established using NE 70th and 95th Street to 35th Avenue NE

3/1/16

Steel piles for new retaining wall are finished

3/15/16

Installation of water line in western portion of roadway completed

3/31/16 Repaving of roadway completed
4/2/16 Full removal of detour in southbound direction (24/7) and partial removal of northbound detour: detour still in effect during daytime work hours (6:30AM-3:30PM, Monday – Saturday)

4/22/16

Completion of project. Full removal of north bound detour. (24/7)

Questions or Comments?

Please contact:
Art Brochet
Project Communications Lead
art.brochet@seattle.gov
(206) 615-0786

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