Seattle District 1 Councilmember Lisa Herbold shared this update on the West Seattle Bridge and related issues via email to constituents on Friday.

With the length of the bridge closure uncertain, but not short, ensuring good access to fire and EMS services in West Seattle is of vital importance.

My office inquired with Fire Chief Scoggins about Fire and EMS response in West Seattle during the closure of the West Seattle Bridge. Chief Scoggins noted in an update,

The Seattle Fire Department is currently conducting a comprehensive GIS analysis of the impacts on fire and EMS response times due to the closure of the West Seattle Bridge. We expect that analysis to be completed by April 17.

The analysis includes a review of response times before and after the bridge closure, how often and when the lower bridge opens for marine traffic as well as the delays caused by rail traffic.

During the Spokane Street Viaduct construction project another ladder truck was added in West Seattle with funding provided by the Seattle Department of Transportation. This deployment model is just one of several options we will be considering.

In response to the observations of many District 1 residents of inadequate signage at the lower bridge about the restrictions on the use of the bridge and enforcement of those restrictions, SDOT has added new signage to emphasize that access to the bridge is limited to emergency vehicles, transit, and freight. The Seattle Police Department began enforcement earlier this week. I appreciate these steps.

Some restrictions are clearly understandable and necessary. In the days after the closure of the West Seattle Bridge, emergency response vehicles were stuck in traffic.  The upper bridge handled around 100,000 vehicle trips daily, and the estimated capacity of the lower bridge is a maximum of 20,000 trips. So there’s no way all the trips can fit, or even come close to fitting.

That said, I will continue to lift up the voices of West Seattle residents in advocating for traffic management improvements during the bridge closure.  I hope SDOT will re-evaluate the decision they are announcing today that they do not intend to relax restrictions, if the new signage and enforcement result in significantly lesser volumes of people using the bridge, especially during times of day when use is lower, but some people work (e.g. overnight), and for health care workers during the COVID-19 emergency.

That said, there’s a necessary note of caution: once traffic patterns resume normal levels, additional use of the lower bridge will be more difficult. SDOT estimates citywide vehicle traffic is currently 40% of normal, and King County Metro has curtailed service, with reduced ridership 72%.

Two of the buses that are rerouted on to the lower bridge are the C Line and Route 120; both are among Metro’s top 10 routes for ridership; both have some trips cancelled currently.

SDOT Traffic Reports indicate the other east/west access points to the peninsula, Highland Park Way SW, combine for an average of 50,000 daily trips (19,400 for Highland Park, 31,400 for Olson).

Councilmember Pedersen, Chair of the Transportation and Utilities Committee and I have convened biweekly meetings with SDOT to review progress.

SDOT has released inspection reports for the West Seattle Bridge from 2013 to 2020. You can access them at the project webpage or an SDOT blog post.

The Seattle City Council Insight website did a review of the reports, with an explanation of some of the technical terminology.

The March 20, 2020 report is sobering, noting “Since our initial recommendation, our biggest concern has become the extent and rate of cracking near the quarter points of the main span could lead to collapse in the near future if strengthening is not implemented quickly.” The February 21, 2020 report had recommended reducing use of the bridge to two lanes in each direction.

It’s clear the City Council should have been informed about these issues earlier.

One report I’ll be requesting additional information about is the 2014 consultant report, which raised the possibility of a permanent remedy to cracking (based on information known at that time). If you have questions about the reports, please let me know.

The Seattle Times reports that a report on collapse risk should be available in a few weeks.

The Council requested reports on the West Seattle Bridge, regarding congestion management, in both 2015 and 2016.

In 2015 former Councilmember Rasmussen commissioned a West Seattle Bridge/Duwamish Waterway Corridor Whitepaper, and obtained funded for studying the recommendations in the 2016 budget. This led to a May 27, 2016 Progress Report.

Later in 2016 I sponsored  funding in the 2017 budget for studying additional recommendations in the Whitepaper, one of which touches on the challenges at the 5-way intersection underneath the bridge. This led to a March 2017 Congestion Management study.

Neither the 2016 Progress Report nor the 2017 Congestion Management study mention issues related to cracking in the bridge.

To report current conditions on roads and traffic, ask questions, or make recommendations to SDOT, please e-mail 684-ROAD@seattle.gov or call 206-684-ROAD. I’m happy to pass on question and suggestions as well.

At the March 31st City Council Briefing meeting, SDOT indicated an estimate on costs and length of closure was 3-4 weeks away. SDOT has indicated that the bridge must be shored up as a first step, before repairs can proceed, and design for shoring the bridge is currently being worked on.

Below are questions SDOT has sent replies about; the Council hasn’t yet received a report assessing overall condition of bridges in Seattle.

What is the role of the state and federal government as it relates to the WSHB?

Our bridge inspection program is supervised by the WSDOT Local Programs group.  This group is part of the WSDOT Bridge Preservation Office (BPO).  At the federal level, every state DOT is assigned an FHWA Division Bridge Engineer for Washington. At this point their responsibility is to monitor how we handle the situation and comment if they think we need to do something differently.

The reference to pile-driving nearby (Terminal 5 as I recall) as a possible cause or factor in the cracking problem raises the issue of the need for forensic engineering work. I realize the primary engineering task before us is to stabilize and repair the structure. At the same time, it seems that some analysis to figure out what action(s) caused or contributed to the problem would be in order. Is SDOT contemplating or doing such work?

SDOT and the Port of Seattle are confident that impact on the WSHB by pile driving operations at T5 is extremely unlikely.  This is because any vibrations caused by the pile driving activity at T5 attenuate to a negligible amount before reaching the nearest part of the WSHB foundation system which is nearly 1800 feet away.  Moreover, if vibrations from the pile driving at T5 were significant enough to have affected the WSHB, we would have seen significant damage at other building/facilities between T5 and the WSHB.  We are not aware of any such damage.

Questions re: technology used in monitoring

We will be deploying instrumentation on the bridge to measure the distribution of stress throughout the bridge and for movement of specific bridge components. These instrumentation techniques are far more accurate and useful than video instrumentation, since range of visibility from the video instrumentation is limited by comparison.