SR 520 Bridge Replacement and HOV Program, WA
Image Credit:Tim Rice
AAR Testing and Inspection, a SOCOTEC Company, provided construction materials testing, special inspections, geotechnical sampling, and quality assurance services for the SR 520 Bridge Replacement and HOV Program in Seattle, Washington.
Key Information
Project Name: SR 520 Bridge Replacement and HOV Program
Client: Graham Contracting Ltd.
Owner: Washington State Department of Transportation (WSDOT)
Location: Seattle, WA
Funding: $500+ million
Services Provided: Construction Materials Testing, Special Inspection, QA/QC Oversight
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The Challenge
Delivering Quality for a Landmark Transportation Project
The SR 520 Bridge Replacement and HOV Program represents a major transportation infrastructure investment designed to improve regional mobility while supporting transit, high-occupancy vehicle (HOV), and general-purpose traffic across Lake Washington.
The project included the construction of approximately 6,000 feet of floating bridge, supported by 87 drilled shafts, 139 soldier piles, nearly 400 structural girders, and 21 retaining walls consisting of mechanically stabilized earth (MSE) and cast-in-place systems. Additional work included specialized soil-freeze monitoring for the protection of a 54-inch water main and the successful execution of 52 weekend road closures throughout construction.
The project presented several unique challenges, including:
- A multi-phase Design-Build program integrating a floating bridge, approach structures, and HOV systems
- Over-water construction within high-sensitivity environmental zones
- Complex traffic, marine coordination, and sequencing around active transportation corridors while maintaining uninterrupted operations in an active public environment.
- Long-span structural elements requiring precise tolerances and staged placements
- Structural and geotechnical components extending across Lake Washington
- High public visibility and agency oversight, requiring consistent documentation quality throughout construction
The SOLUTION
Supporting Construction Through Quality Assurance
AAR Testing and Inspection, a SOCOTEC Company, provided comprehensive construction materials testing, special inspections, geotechnical sampling, and quality assurance services throughout the major phases of the project, leveraging extensive experience supporting large-scale infrastructure projects.
Our team supported the contractor and WSDOT by helping verify compliance with project specifications, agency requirements, and applicable standards while maintaining inspection continuity and responsive field coordination.
Services Provided
The Results
Supporting a Major Regional Infrastructure Investment
The SR 520 Bridge Replacement and HOV Program improved regional mobility through a multi-phase Design-Build program integrating a floating bridge, approach structures, and HOV systems across Lake Washington.
Through construction materials testing, special inspections, geotechnical sampling, and quality assurance services, AAR Testing and Inspection, a SOCOTEC Company, supported quality control throughout construction while helping maintain compliance with project requirements in a complex and highly visible infrastructure environment.
This project demonstrates our ability to deliver responsive testing, inspection, and quality assurance services for large-scale transportation infrastructure projects involving structural, geotechnical, civil, and environmental considerations.
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