West Seattle High-Rise Bridge Safety Program Photo by Life As Art - - PowerPoint PPT Presentation

Department of Transportation

Sound Transit Executive Committee Sam Zimbabwe, Heather Marx June 11, 2020

West Seattle High-Rise Bridge Safety Program

Photo by Life As Art used under CC

Department of Transportation

Presentation overview

• West Seattle High

Bridge Status

• Emergency

contingency planning

• Repair phases and
• ptions
• Upcoming Decisions
• Coordination with

Sound Transit to date

• Managing Traffic

2

Date (xx/xx/xxxx) Department Name Page Number

West Seattle High Bridge Safety Project priorities

• 1. Public safety
• 2. Urgency to return traffic to WSHB
• 3. Traffic mitigation while the bridge is

closed

• 4. Stabilizing and shoring the WSHB
• 5. Closely monitoring and maintaining the

Spokane Street Low Bridge

• 6. Assess repair feasibility, timeline, and

costs for the WSHB

• 7. Clear communication and transparency

3

Department of Transportation

Bridge Background and Details

• Opened in 1984
• Cast-in-place concrete and steel

bridge

• One-of-a-kind, uniquely designed

for topography and geography

• Designed for three lanes in either

direction

• Highest daily traffic volumes among

SDOT roadways

• 84,000 vehicles (2019)
• 17,000 transit riders

This Photo by Unknown Author is licensed under CC BY-SA

4

Department of Transportation

Safety is top priority

• Recent inspections have found cracks

continue to grow, but at slower rate, confirming immediate removal of live load was essential

• Intelligent monitoring equipment

monitors changes to the bridge in real time, with 24/7 alerts

• Potential cracking scenarios modeled

through a Critical Failure Analysis

• Emergency Contingency Plans

developed in the event of failure

6

Department of Transportation

SDOT Three-Phase Approach to WSHB assessment and repairs

• Phase 1: Slow

deterioration, assess problem, immediate repairs

• Phase 2: Shore and stabilize

WSHB and Pier 18

• Phase 3: Repair Bridge and

begin longer term solutions

7

Department of Transportation

Moving Ahead on Multiple Paths

Bridge Activities Since the Closure

• Installed monitoring instrumentation
• Secured a contractor to complete bridge

stabilization

• Continuing to monitor cracking
• Pier 18 repair construction planning
• Issued an RFQ for a design consultant to

consider type, size and location structures in the event of replacement

Department of Transportation

Department of Transportation

Request for Qualifications – issued June 2

• Invites design teams to show their qualifications to design bridge replacement
• Structured to allow maximum flexibility for timing, cost and replacement type

(includes both bridge and tunnel types)

• If repair is possible, then the design team will work on the longer-term replacement
• If repair is not possible, the design team will be already be on board to save time
• Rehabilitation and retrofits design for structures on either side may be included
• Current area to be evaluated is between SR99 and W Admiral Way
• Team expected to be on-board in October

Department of Transportation

WSB Project Milestones

Initial Decision: Repair/Replacement

June July August September October November December January 2021 February March April May June July August September October November December

Bridge Repair/ Replacement Community Task Force & TAP Traffic Mitigation Project Finance Mayor/ Council Actions

Draft Strategies PSRC Planning Grant CIP established Temporary Crack Arrest Pier 18 Release Bridge Demolition Repair Mayor’s 2020- 2021 Budget Council Adoption 2020-2021 Budget Legislative Session Federal BUILD Grant Council Briefing City’s Legislative Agenda Community-Led Prioritization Final Action Plan & Implementation Shoring Replacement Program Council Briefing Council Briefing Council Briefing Council Briefing Council Briefing Council Briefing Council Briefing 10

Demolition (if repl)

5/19/2020 Department of Transportation 11

WSBLE DEIS Duwamish Crossing Alternatives

Insert readable map

DUW-1b DUW-2 DUW-1a

Section of WSHB that needs repair

Department of Transportation

Coordination with Sound Transit To Date

• Joint Sound Transit/SDOT Engineering Work Session on April 30
• Examined whether a combined light rail and vehicle bridge over the Duwamish

could be practical from an engineering design perspective

• Potential next steps:
• in depth study of loading and geometry
• consider if practical from perspectives of environmental review, schedule, construction

coordination, cost, etc.

• set up formal coordination between Sound Transit and West Seattle Bridge capital

project delivery

11

Department of Transportation

Questions / Discussion