Background and Campaign Plan

Learn about the case for lids, the goals of the Lid I-5 Steering Committee, and the community’s long term vision.

Lid I-5 Feasibility Study

The primary goal of the campaign is to complete a thorough and technical feasibility study.

The study will evaluate where lids are most reasonable and cost effective along the entire Interstate 5 corridor citywide. Study areas may include Georgetown, the International District, Downtown, Capitol Hill and First Hill, South Lake Union, Eastlake, Wallingford and the University District, Green Lake and Northgate. The extent and quantity of study areas will be contingent upon funding.

Study elements will include structural and transportation engineering, affordable housing opportunities, urban design, land use, social and economic equity, funding options, construction phasing, and best practices. The study will include public outreach and coordination between local government agencies. Based on similar projects this study will cost at least $1.5 million.

Funding Source

We anticipate funding for both projects to be offered by the Washington State Convention Center (WSCC). The WSCC is planning to build new convention facility next to I-5 in Downtown and will offer public benefits to surrounding neighborhoods. Learn more about the community’s proposed public benefits at

How You Can Help

Want to help us secure public benefit funding for the lid study and the Pine-Boren lid park? Join the campaign and stay updated on our advocacy, public events, and volunteer opportunities.


Seattle is growing. People are attracted to our great city by the abundance of jobs, natural beauty, friendly culture, great food, and high quality of living. The Comprehensive Plan anticipates at least another 120,000 people will move to Seattle over the next two decades, and before long we will be a city of one million. Infrastructure of all types – from transportation and schools to public safety and water supplies – will need significant overhaul and reinvestment to keep up with the demand.

The Problems

Seattle’s urban core, and to some extent the rest of the city, face two serious urban design challenges: a lack of public land and neighborhood disconnections caused by Interstate 5.

Scarcity of Land

Seattle’s future depends on public amenities that support growth and economic development. Nowhere is the need for public investment more critical than the Center City. Seattle’s urban core – Downtown, First Hill, Capitol Hill, South Lake Union, and Uptown – has the highest concentration of people and businesses in the Pacific Northwest. It is the heart and soul of Seattle, and indeed the entire state, thanks to its rich variety of finance and technology firms, government offices, restaurants, hotels, art institutions, and night life.

The area is home to 62,000 households (20 percent of the citywide total) and employs 240,000 people. By the year 2035 the area will grow to over 90,000 households and nearly 300,000 employees. New and expanded infrastructure is critical for supporting these new homes and jobs. In our work with local residents we’ve heard a strong desire for at least three critical needs: parks and open space, affordable housing, and civic facilities such as schools and community centers.

However, in the Center City the increasing shortage of redevelopable properties and high land values makes acquiring new sites for public and private uses extremely challenging. This dilemma requires creative solutions.

Neighborhood Disconnections

For over 50 years Interstate 5 has been a physical barrier between many of Seattle’s neighborhoods. Interrupted street grids, noise, pollution, and traffic all have the effect discouraging people from traversing across it or under it on foot. This results in fewer social connections and dampened economic activity. Locations up and down the 20-mile freeway corridor are impacted, including the International District, Yesler Terrace, First Hill, Capitol Hill, Downtown, South Lake Union, Wallingford, the University District, Roosevelt, and Northgate.

The alignment of Interstate 5 overlaid on Seattle's 1924 street grid. (Rand McNally Map, David Rumsey Historical Map Collection)
The alignment of Interstate 5 overlaid on Downtown Seattle’s 1924 street grid. (Rand McNally Map, David Rumsey Historical Map Collection)

The interstate occupies valuable urban land that was once part of these vibrant urban neighborhoods. Until the 1960s, apartments, houses, stores, offices, and light industry blended into a seamless urban fabric. They were places between and part of neighborhoods which weren’t all that different from each other. The street grid offered a variety of travel choices by foot, bike, transit, and car. Where the grade was steep, especially between Capitol Hill and Lake Union, public stairways connected residents to jobs and recreation. Today, most of these spaces and pedestrian routes are gone. Approximately 20 city blocks were demolished between Yesler Way and Denny Way alone.

Citizen activists and local governments have been working to heal the divide. On July 4, 1976, Freeway Park renewed the link between First Hill and Downtown with elegant walkways, grand landscaping, and intricate plazas. In 1988 the Washington State Convention Center opened next to Freeway Park and now hosts over 400,000 visitors a year just above the constant flow of commuters and freight. Since then several studies have looked at continuing this legacy, but the urgency has not returned until now.

Interstate 5 before (left) and after (right) Freeway Park opened in 1976. (University of Washington, College of Built Environments Visual Resources Collection)
Interstate 5 before (left) and after (right) Freeway Park opened in 1976. (University of Washington, College of Built Environments Visual Resources Collection)

Elsewhere, the success of these efforts inspired another lid park over Interstate 90 in Seattle’s Mount Baker neighborhood and plans for two new lids over State Route 520 in Montlake (read more about Seattle’s lids on the History page). The city is also planning a pedestrian and bicycle bridge over I-5 in Northgate to improve access to a future light rail station.

For the past decade Seattle has worked to remove another freeway barrier: the Alaskan Way Viaduct carrying State Route 99. Since 1953 the concrete structure has cut off the city from its public waterfront visually and physically. The Waterfront Seattle project will soon demolish the viaduct, bury SR-99 in a tunnel, and reunite Pioneer Square, Downtown, Pike Place Market, and Belltown with a variety of new public spaces on Elliot Bay. However, the new waterfront will still be difficult to reach on foot for residents east of I-5 and it will not meet all of the need for new park space in the Center City.

Looking south from Olive Way. (Photo: Scot Bonjukian)
Looking south from Olive Way.

Today some of the street grid remains intact in the Downtown area, but the dynamic interactions are largely missing. In many places there is a distinct difference in urban character on the freeway edges, and historically there has not a compelling reason to explore and visit the other side. However, in recent years commercial development like the Starbucks Roastery and Melrose Market, along with residential growth, are drawing more people back and forth across I-5. Multiple mixed-use buildings are planned next to the freeway on what are today parking lots, the last available land in the urban core. This momentum must be built upon to enhance and complete the connections between people and places.

The Solution

Two public challenges – a deficit of developable land and the barrier of an urban freeway – can be addressed with a single solution: lidding more of Interstate 5.

Lids are bridge-type structures made of steel and concrete. They are similar in concept to a typical freeway overpass, but extended parallel along the freeway route. They can range in size from a few thousand square feet to many acres, and can support everything from parking garages and convention centers to parks and residential towers.

Lids convert freeway divisions into urban connections.
Lids convert freeway divisions into urban connections.

Most importantly, lids reclaim valuable land and make more efficient use of limited space. They restitch the urban fabric and encourage more people to connect across the freeway, which enhances social connections and facilitates economic vibrancy.

Public Policy Support

Lid I-5’s objectives are supported by Seattle’s Comprehensive Plan:

Transportation Policy 3.12 – Look for opportunities to reestablish or improve connections across I-5 by creating new crossings, enhancing streets where I-5 crosses overhead, or constructing lids, especially where these can also enhance opportunities for development or open space.

Parks Policy 1.17 – Create innovative opportunities to use existing public land, especially in the right of way, for open space and recreation, including street plazas, pavement to parks, parklets, lidding of reservoirs and highways, and community gardens.

Lids create new land out of thin air without the costly and disruptive process of eminent domain nor a reduction in the local tax base. In the Downtown Seattle core they will also cost less to build than it would to acquire private land.

Based on the average cost of completed and planned lid projects across the U.S., lids built for park space cost about $500 per square foot. Lids which support buildings may cost more. And based on King County Assessor data for the past three years of real estate transactions, purchasing private land – the only alternative to creating new public sites for parks, housing, and other civic functions in Downtown Seattle – would cost at least $1,000 per square foot.

Comparing the average cost of lid parks to the value of land in Downtown Seattle.
Comparing the average cost of lid parks to the value of land in Downtown Seattle.

Other cities around the country face the same challenges Seattle has and have seized the same opportunities. The popularity of freeway lids as an urban design strategy is accelerating; there are are over a dozen lid projects in the concept, design, and construction stages, providing inspirational examples of the that Seattle must build upon. Newer lid projects are mixed use, supporting parks, private development, and civic infrastructure.

See a list of case studies for more information on the many completed and proposed lid projects across the country.

The Lid I-5 campaign is standing on the work of many other organizations which have addressed issues around Interstate 5. See the Melrose Promenade, the First Hill Public Realm Action Plan (PDF), the Pike-Pine Renaissance, and the Blue Ring Strategy (PDF) for just a handful of examples of previous projects which address streets and public spaces in the area.

Community Priorities

At this early stage the Lid I-5 campaign does not call for a specific design. Rather, the campaign promotes a vision of unity and reconnection over I-5 in Downtown and beyond while simultaneously creating new space for parks, housing, schools, and other civic uses. We are building a coalition of local stakeholders to shape and evolve this vision, and we believe the public should have the strongest voice on what future lids are used for.

Seattle’s Center City has a public open space deficit of three acres that will grow to over 20 acres by 2035. With another 55,000 jobs and 28,000 homes expected in the urban core, new park space will be vital for Seattle to remain livable and to attract families and businesses to the urban core. Lidding I-5 will relieve the need for open space and bring a variety of modern park amenities to the Center City. Popular ideas include playgrounds, dog runs, amphitheaters, athletic fields, water features, and a variety of daily programming.

About 100,000 households in Seattle are moderately or severely burdened by housing costs, and increasing land values and population growth is driving the need for greater housing variety and affordability. Lidding I-5 will create new land for public low-income housing where it is needed most: close to the jobs and social services in Downtown and South Lake Union. Building affordable housing near centers of opportunity will empower those most in need and diversify local neighborhoods.

Many of Seattle’s most populous neighborhoods needs have critical shortages of community facilities. Multi-purpose neighborhood centers are key for providing event space and a variety of programs. Downtown and the University District, both recently upzoned, have growing school-age populations and need new elementary and middle schools. Other facilities like art institutions, performance venues, and public safety and utility infrastructure could be more easily implemented if the public land for these uses was available.

Lids over I-5 will support a variety of new pedestrian and bicycle routes, reconnecting neighborhoods that have long been divided by steep grades and narrow sidewalks. Integrating new pathways with park space and retail frontage will be essential to creating lively pedestrian experience, and a string of lids up and down the corridor could facilitate a north-south trail for bicyclists. New walking and biking connections can also be made by reconnecting Seattle’s street grid over I-5.

Lidding I-5 will cut off the noise and fumes of freeway traffic for surrounding homes and businesses, creating a much more attractive and livable urban environment. It will also spur compact redevelopment around the freeway, enabling more people to live within walking distance of urban amenities. Lids could capture and filter automobile pollution, contributing to Seattle’s goal to be carbon neutral by 2050. Other potential environmental benefits are stormwater filtration, renewable energy generation, new wildlife habitat, and reducing the urban heat island.

Local businesses, the lifeblood of our neighborhoods, are essential to a successful lid park and reactivating the gash in Seattle’s urban fabric. Providing opportunities for retail uses on the lid will help rejuvenate and reconnect adjacent neighborhoods. Commercial uses would also attract foot traffic, making nearby public spaces active and safe, and help generate revenue for operating and maintaining the lids. Small scale enterprises like coffee shops, bars and restaurants, theaters, and artist studios could complement outdoor activities like farmer’s markets and concerts.

The Plan

Lidding a freeway doesn’t happen overnight, and we know Seattle has its mind on public issues like homelessness, socioeconomic equality, and finishing the new waterfront parks. But if we start planning for lidding I-5 now the city will be ready when the financial and political forces align to achieve a common vision. We are at the beginning stages of a grassroots effort that will take many years to flourish.

We believe that we can start lidding I-5 one phase at a time starting within the next ten years. Locations between Olive Way and Madison Street are favorable for starting points because of the combination of advantageous topography and a high intensity of urban activities and foot traffic.

Where to start, and how to build it, will depend on the judgement of technical experts like civil engineers and real estate professionals. To that end, our short term goal is fund the creation of a rigorous, multi-disciplinary feasibility study on lidding Interstate 5 citywide.

We anticipate that funding for this study, estimated to cost half a million to a million dollars, may be provided by sources such as the public benefit package of the Washington State Convention Center (WSCC) Addition. The nexus between the WSCC Addition and the request for a lidding feasibility study is the project’s proximity to Interstate 5 and the benefits employees, residents, and visitors would gain from cutting off the sights and sounds of the freeway.

The Seattle Design Commission will make recommendations for the makeup of the public benefit package. Afterwards the Seattle Department of Transportation (SDOT) will negotiate with the developer and the WSCC on the size and scope of the package, and will forward its own recommendation to the Seattle City Council.

Campaign Strategy

Our campaign is based on a four-part strategy.

Coalition Building
We are partnering with a variety of local organizations and institutions who have a stake in the future of Interstate 5 and how Seattle grows. Partners include neighborhood groups, parks advocates, nonprofit organizations public health experts, transportation groups, property owners, and the local business community. Together we have a stronger voice and represent a broad range of community members.

Public Events
The campaign’s first major public event in May 2016 was a resounding success, with nearly 100 people attending a half-day charrette and contributing inspiring ideas for what lidding I-5 could look like. We are planning for the next charrette and will host other events like town halls and panel discussions to spread the word and build public awareness.

For the past 18 months we have been meeting with elected officials and testifying at public hearings. Over the next year we will we accelerate our advocacy campaign to inspire local officials to join us. Key decision makers are the Seattle City Council, the Seattle Mayor, Washington State legislators, and top administrators at the Washington State Department of Transportation.

Public Affairs
We have retained David Yeaworth of Catalyst Strategies to guide our campaign and assist with public affairs. David ran the Waterfront For All campaign and has a decade of experience working for the Seattle City Council, making him a remarkably qualified and valued advisor on setting our vision and garnering the support of key decision-makers. Local media is already providing extensive coverage that we are using to create a city-wide buzz and capture the public’s attention.