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Safety First – A Shared West Seattle Bridge Safety Management Plan

Just like when a winter storm approaches, we’re implementing a safety checklist to make sure that we’re prepared for the most challenging scenarios a deteriorating West Seattle Bridge could present.  

Earlier this week, we shared the news that traffic likely won’t return to the West Seattle Bridge in 2020 or 2021.  We know that was challenging and frustrating to hear. 

At the same time, we will not shortchange our commitment to consistent communication and transparency, which is why today we are sharing additional updates around how we continue to monitor the bridge daily and prioritize the safety of the community.  

SDOT is focused on six concurrent West Seattle Bridge priorities:

  • Public safety
  • Traffic mitigation to help residents and businesses while the bridge is closed
  • Stabilizing and shoring the West Seattle High-Rise Bridge
  • Closely monitoring and maintaining the low bridge
  • Continuing to assess repair feasibility, timeline, and costs for the West Seattle High-Rise Bridge
  • Clear communication and transparency

As part of the planning, we’re also conducting additional emergency planning in close consultation with the Mayor. The critical steps outlined below will help prepare our response, and we want to be transparent about the planning and engagement that we expect to do in the coming days, weeks and months. 

We’re implementing new, intelligent monitoring systems so we can track the bridge in real time.

Since 2013, we’ve been monitoring cracks in the bridge. While all concrete bridges typically form cracks, we discovered weeks ago these cracks were rapidly accelerating. You can view the West Seattle High-Rise Bridge inspection reports from 2013 through 2020 on our website, which highlights the frequency of inspections to monitor these cracks and the rapid acceleration in recent weeks.

In the days leading up to the March 23 closure of the West Seattle High-Rise Bridge and every day since, we have been inspecting the bridge in person. This is in addition to using gauges that we installed in 2014 over single cracks at eight locations on the bridge. These have helped us track the progression of cracks. There are now multiple cracks at each location, so we need additional information to help monitor and model the deterioration of the bridge so that we can adequately plan for repair.

Out of an abundance of caution and to make sure we understand exactly how the bridge is behaving, we installed additional intelligent monitors. The more data we have the better we will understand the changes in crack and bridge behavior, so we can plan and respond proactively in an informed manner.

We’ve already begun the work to install these monitors and starting next week, new sensors on the driving surface will show us real time movement of the bridge. We’re also installing new instrumentation at Pier 15 and Pier 18 that will measure expansion and contraction of the bridge, and we’re expanding monitoring capabilities to encompass a greater range of crack movement. These components of the intelligent monitoring system will be operational in early May.   

We’re preparing a comprehensive safety management plan in case there is ever an indication of structural failure of the bridge.

Safety is our number one priority. We hope that we don’t have to implement our safety management plan, but if we do, we will be prepared.

To inform our comprehensive safety management plan, we are modeling potential cracking scenarios to thoroughly understand when our plan must be put into action, and which areas may need to be evacuated.

Our safety management plan is a worst case scenario.

The bridge remains stable, and the growth of cracks has slowed since we removed traffic from the bridge on March 23. However, this is an evolving situation. Our safety management plan will help us respond quickly in the event that conditions change. After we engage local stakeholders, we’ll work to finalize an operating plan that outlines actions by SDOT, emergency responders, public, and private property owners, and outlines potential impacts to the general public.

Our recent and upcoming actions to stabilize the bridge decrease the likelihood that such steps will have to be taken, but our plan will fortify our response — and all of our preparedness — if we do.

We’re drafting updated traffic plans in case areas around the High-Rise Bridge become off limits.

We’re prepared to remove traffic from the low bridge and surrounding areas underneath the bridge, for some period of time in the event that the High-Rise Bridge becomes unstable. This would affect everyone traveling on and around our bridges, those who live and work near the structures, and our own teams who work on the bridge itself. We’re creating an emergency traffic plan with our partners that would re-direct transit, freight, and emergency vehicles, as well as personal vehicles, bikes, and pedestrians.

We are acting on phase one of our safety management plan to engage local stakeholders

We’re beginning to engage local stakeholders for feedback on our safety management plan so we can best support community needs as we prioritize safety. This includes the Port, private and public property owners, businesses and marinas.

This contact database would be used for notifying stakeholders of their proximity to the bridge, suggesting worst-case scenario planning for people and property, and sending emergency alerts in the event of risks to public safety.

Sign up to receive West Seattle High-Rise Bridge project update emails.

Visit our West Seattle High-Rise Bridge website to sign up for periodic emails to stay up-to-date on the bridge. On the website you will also be able to see frequently asked questions, view inspection reports, and find links to our West Seattle Bridge blogs.