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City of Seattle Releases I-5 Lid Feasibility Study

The City of Seattle has released a preliminary technical and financial feasibility study of extending the lid over I-5. The study contemplates options to cover the freeway between Madison Street and Denny Way, including structural analysis, funding models with public and private development, and a framework to maximize public benefits.  

The I-5 Lid Feasibility Study was funded as part of the community benefits package from the Washington State Convention Center expansion project. The $1.5 million for the study was administered by Seattle’s Office of Planning and Community Development (OPCD), which hired a consultant team led by WSP.

OPCD also convened a technical advisory team that included the Washington State Department of Transportation, which owns I-5, to guide the study process and provide input and review during the development of the study. 

The study was funded and launched before the pandemic to explore options for increasing public open space, affordable housing, walking and biking connections, and other amenities, while reducing noise and air pollution associated with I-5. Three lid test cases were evaluated: 

  1. Maximizing open space, improved pedestrian and bike connections, and other public amenities. 
  1. Maximizing private contributions to lid construction with new offices, open space, and improved connections. 
  1. A mix of public amenities, affordable housing, and market-rate development to support lid construction. 

The cost to cover the 0.8-mile stretch of I-5 would range between $966 million to $2.5 billion. Each scenario would require significant public investment, however the lid would bridge a connection between two neighborhoods that were split apart by the construction of I-5 in the 1960s, while creating up to 4,500 new homes and up to ten acres of parks space. 

Currently, portions of I-5 are covered by Freeway Park and the convention center between Seneca Street and Pike Street. Recent successful lid projects in Dallas, Chicago, and Washington, DC have generated new interest in the concept in Seattle. 

“This comprehensive and shelf-stable study will help guide decisions on redevelopment and repair options for I-5 as the State of Washington evaluates the future of the freeway,” said Sam Assefa, Director of the Office of Planning and Community Development. “I-5 is vital – and aging – infrastructure that both benefits and impacts our city. We will continue to work with the state, Downtown neighbors, and other partners as we develop shared near and long-term visions for the freeway and its vicinity.” 

An advisory committee of Downtown stakeholders guided the study. The Department of Neighborhoods also conducted community outreach in surrounding neighborhoods to help prioritize potential public amenities. You may view the study here.