Case Study: Seattle Alaskan Way Viaduct Replacement – Design-Build Delivery and Scope Change Challenges (2015)
Project Overview
• Name: Seattle Alaskan Way Viaduct Replacement
• Location: Seattle, Washington
• Year: 2015
• Project Size: $3.3 billion
• Scope: Replacement of the aging Alaskan Way Viaduct with a deep-bore tunnel using Design-Build delivery
• Lead Agencies/Contractors: Washington State Department of Transportation (WSDOT), Design-Build Consortium
Category of the Issue, Problem, or Challenge
• Project Delivery Method
• Design-Build
Summary of the Issue, Problem, or Challenge
During construction, major scope changes related to unforeseen ground conditions and utility conflicts led to design revisions and rework. The Design-Build contract did not adequately address scope change management, leading to disputes and delays.
Root Cause Analysis
- Inadequate geotechnical and subsurface utility investigations pre-construction.
- Contract provisions lacked clear processes for scope changes.
- Limited flexibility in design approvals caused bottlenecks.
- Poor change order documentation and communication.
Impacts Due to the Issue, Problem, or Challenge
• Project delays exceeding 12 months.
• Cost overruns over $150 million.
• Increased stakeholder dissatisfaction and public scrutiny.
Corrective Actions Taken
- Established a formalized scope change management process.
- Increased geotechnical and utility investigation rigor in early phases.
- Streamlined design approval workflows for quicker revisions.
- Improved documentation and transparency on change orders.
Lessons Learned
- Thorough pre-construction investigations reduce scope changes.
- Clear contractual scope change processes are critical.
- Flexible design review workflows facilitate timely adjustments.
- Transparent change order management improves trust.
Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation
- Are subsurface investigations comprehensive before construction?
- Is there a clear contract process for managing scope changes?
- Are design approval procedures flexible and efficient?
- Is change order documentation thorough and communicated?