Case Study: Seattle SR 520 Floating Bridge Design Coordination Failures (2014)

Project Overview
• Name: SR 520 Evergreen Point Floating Bridge Replacement
• Location: Seattle, Washington
• Year: 2014
• Project Size: $4.4 billion
• Scope: Replacement of a floating highway bridge across Lake Washington
• Lead Agencies/Contractors: Washington State DOT /

Category of the Issue, Problem, or Challenge
• Design
• Structural and Marine Engineering

Summary of the Issue, Problem, or Challenge
During construction, lack of coordinated design changes between structural and marine engineering teams caused misalignment of bridge pontoons, requiring costly on-site modifications and delaying the project.

Root Cause Analysis

• Fragmented design workflows between structural and marine engineering groups.
• Inadequate integration of 3D modeling and BIM tools for clash detection.
• Insufficient communication protocols for design change management.
• Limited early-stage collaboration between disciplines.

Impacts Due to the Issue, Problem, or Challenge
• 7-month project delay due to rework and coordination fixes.
• Additional costs of $25 million for modifications and labor.
• Increased risk of long-term structural issues if left unresolved.

Corrective Actions Taken

1. Implemented integrated BIM-based workflows for real-time coordination.
2. Established formal interdisciplinary design review meetings.
3. Introduced centralized design change tracking and approval systems.
4. Strengthened early-stage collaboration practices across teams.

Lessons Learned

• Cross-disciplinary integration is critical in complex infrastructure projects.
• Digital tools like BIM enable early detection of design conflicts.
• Clear protocols for design change communication reduce risks.
• Early collaboration minimizes costly downstream corrections.

Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation

• Are design disciplines using integrated digital modeling tools?
• Are interdisciplinary reviews regularly scheduled and documented?
• Is there a formalized process for design change approvals?
• Are collaborative practices encouraged from project inception?