• Design
• Transportation
• Catastrophic Failure Plan
• Legislation related to SR 520 corridor design

The designs for SR 520 improvements between I-5 and I-405 have undergone many iterations of planning, analysis and stakeholder involvement. This page contains documents that informed the design of the individual projects that make up the SR 520 Bridge Replacement and HOV Program. The documents include community design details, technical analyses, and legislation directing WSDOT to complete these design processes. 

This SR 520 "Rest of the West" webpage contains a listing of key design processes specific to SR 520 reconstruction between Lake Washington and I-5.

Portage Bay Bridge and Roanoke Lid Project design outreach

January 2020 | Summary of 2019 community and stakeholder engagement (PDF 2MB)

January 2020 | Public comment appendices (PDF 3.2MB)

SR 520/I-5 Express Lanes Connection Project

October 2019 |  NEPA/SEPA Environmental Reevaluation: I-5 Design Refinements (PDF 398KB)

2014-2016 West Side Design Refinements

February 2016 | Final concept design report 

• Cover letter (PDF 224KB)
• Chapter 1 - Executive Summary (PDF 6.54MB)
• Chapter 2 - Design Progression Overview (PDF 676KB)
• Chapter 3 - West Side Final Concept Design (PDF 26.3MB)
• Chapter 4 - Next Steps (PDF 368KB)
• Chapter 5 - Glossary (PDF 188KB)
• Chapter 6 - Appendix (PDF 16.3MB)
• Chapter 7 - Public Comment Summary (PDF 14.5MB)

2015 Portage Bay Bridge Area Crime Prevention Through Environmental Design

August 2015  | Portage Bay Bridge CPTED final report (PDF 19MB) 

2011-2012 Seattle Community Design Process

Dec. 20, 2012 | Seattle Community Design Process final report (PDF 31 MB)

Final report broken down in sections

• Cover letter (PDF 50KB)
• Executive summary (PDF 673KB)
• Cover page and table of contents (PDF 265KB)
• Chapter 1 - Executive summary (PDF 672KB)
• Chapter 2 - Process overview (PDF 315KB)
• Chapter 3 - Vision statement and design framework (PDF 574KB)
• Chapter 4 - Nonmotorized and transit connectivity (PDF 19.4MB)
• Chapter 5 - Geographical subareas (PDF 9.7MB)
• Chapter 6 - Next steps (PDF 292KB)
• Chapter 7 - Glossary of terms (PDF 131KB)
• Chapter 8 - Appendix, links and credits (PDF 427KB)

Public comment summaries

• Public comment summary (PDF 2.4MB)
• Individual emails (PDF 3.6MB)
• Organization letters (PDF 2.4MB)
• Survey responses (PDF 2.5MB)
• Reference: Online survey (PDF 784KB)

Sept. 14, 2012 | SCDP draft design report

• Executive summary (PDF 1.7MB)
• Full draft report (PDF 15.1MB)
• Executive summary (PDF 1MB) - 8.5x11 size
• Full draft report (PDF 15.6MB) - 8.5x11 size

Dec. 2011 | SCDP progress update

Seattle Community Design Process - 2011 Progress Update (PDF 1.3MB)

Public comment summaries

• Oct. 1, 2011 (PDF 74KB)
• Nov. 9, 2011 (PDF 73KB)
• Dec. 7, 2011 (PDF 79KB)
• April 12, 2012 (PDF 96KB)
• May 19, 2012 (PDF 79KB)
• June 14, 2012 (PDF 71KB)
• July 16, 2012 (PDF 8.2MB)

2011 Record of Decision

• In August 2011, the Federal Highway Administration published the Record of Decision, which described the project’s course of action and specific mitigation measures. The 2011 Record of Decision can be viewed on the Environmental Documents webpage within the Resource Library.

2011 - Final EIS Preferred Alternative

• In January 2011, we published the final EIS, which evaluated the "Preferred Alternative" design and included a response to comments received on both the draft and supplemental draft EIS documents. The final EIS Preferred Alternative document can be viewed on the Environmental Documents page within the Resource Library.

2010 – ESSB 6392 Workgroup Design Refinements and Transit Connections

Final report (PDF 4MB)

• Appendix A (PDF 4MB): White papers - updated
• Appendix B (PDF 402KB): Participating agency comments
• Appendix C (PDF 3.8MB): Public comments

ESSB 6392 Workgroup Meeting materials

Dec. 13, 2010 - Seattle City Council presentation materials

Dec. 1, 2010 - ESSB 6392 Workgroup meeting

• Meeting agenda (PDF 62KB)
• Meeting presentation (PDF 1MB)

Sept. 13, 2010 - Seattle City Council presentation materials

Sept. 9, 2010 - ESSB 6392 Workgroup meeting #3 materials

• Meeting summary (PDF 84KB)
• Meeting agenda (PDF 67KB)
• Meeting presentation (PDF 1.1MB)

Aug. 19, 2010 - ESSB 6392 Workgroup meeting #2 materials

ESSB 6392 Workgroup meeting #2 materials

• Meeting summary (PDF 102KB)
• Meeting agenda (PDF 62KB)
• Meeting presentatiom (PDF 3.7MB)
• ESSB 6392 Workgroup Implementation (PDF 3.7MB)
• Arboretum Botanical Garden Committee/Technical Coordination Team coordination chart (PDF 60KB)
• Arboretum traffic calming and traffic management (PDF 94KB)
• Bicycle & Pedestrian Route Recommendations (PDF 952KB)
• Bicycle & Pedestrian Route Recommendations - Hamlin and Shelby (PDF 341KB)
• Transit connections: TCT recommended bus stops - Montlake vicinity (PDF 440KB)
• E Lake Washington Boulevard and 24th Avenue E (PDF 335KB)
• SR 520 westbound off-ramp (PDF 360KB)
• Montlake Triangle Charrette design options under consideration (PDF 477KB)

Aug. 3, 2010 - Seattle City Council presentation materials

July 22, 2010 - ESSB 6392 Workgroup meeting #1 materials

• Meeting summary (PDF 241KB)
• Meeting agenda (PDF 56KB)
• Meeting presentation (PDF 884KB)
• ESSB 6392 Workgroup Process fact sheet (PDF 279KB)
• ESSB 6392 Workgroup implementation (PDF 28KB)
• Montlake Triangle Charrette design options under consideration (PDF 405KB)
• Arboretum Botanical Garden Committee/Technical Coordination Team coordination chart (PDF 60KB)
• Technical Coordination Team proposed transit/HOV lane configuration (PDF 9.9MB)
• Montlake area - Potential options for bus stops (PDF 2.5MB)
• SR 520 potential light rail diagrams (PDF 685KB)

July 19, 2010

• Design Refinements and Transit Connections technical coordination team work plan (PDF 57KB)
• Design Refinements and Transit Connections technical coordination team work plan - Public Comment Summary (PDF 679KB)

2008-2011 – Miscellaneous design documents

• SR 520 Memorandum of Understanding with the city of Seattle (PDF 980KB) October 2011
• SR 520 Legislative Workgroup Final Recommendations Report (PDF 2.8MB) December 2009
• Eastside Consolidated Urban Design Report (PDF 24MB) July 2009
• Montlake Cut Tunnel Expert Review Panel Report (PDF 3MB) June 2008

2007-2008 Mediation and ESSB 6099

December 2008 | Westside Project Impact Plan (PDF 6.5MB)

• Option A with suboptions (PDF 8MB)
• Option K with suboptions (PDF 8MB)
• Option L with suboptions (PDF 8MB)

March 2008 | Proposal K - Tunnels at East Montlake and the Arboretum Conceptual Design and Cost Estimate

• Report (PDF 1.3MB)

April 2006 – I-5 to Floating Bridge Tunnel Concept Review

• Full report (PDF 5.6MB)

Transportation reports

• High-Capacity Transit Planning and Financing Findings and Recommendations Report (PDF 2.2MB) December 2010
  • Appendix A: SR 520 Final High-Capacity Transit Plan (PDF 3MB) December 2008
  • Appendix B: Public comment summary (PDF 538KB) December 2010
• Transit Station Usage Study (PDF 1.1MB) August 2005

Catastrophic Failure Plan

• Catastrophic Failure Plan (PDF 576KB) - Executive Summary July 2008

Legislation related to the SR 520 corridor

• Senate Bill 6106 (PDF 1.54MB) March 2018
• Senate Bill 5989 (PDF 50KB) July 2015
• Senate Bill 5988 (PDF 227KB) July 2015
• Senate Bill 5987 (PDF 1.34MB) July 2015
• Senate Bill 6001 (PDF 402KB) April 2014
• House Bill 2814 (PDF 34KB) March 2012
• Senate Bill 5700 (PDF 29KB) May 2011
• Senate Bill 6392 (PDF 62KB) March 2010
• House Bill 2211 (PDF 42KB) May 2009
• House Bill 5352 (PDF 1.37MB) May 2009
• House Bill 1272 (PDF 69KB) May 2009
• House Bill 2878 (PDF 320KB) March 2008
• House Bill 1773 (PDF 80KB) March 2008
• House Bill 3096 (PDF 20KB) March 2008
• Senate Bill 6099 (PDF 24KB) April 2007