Project Overview

The transformation of Seattle’s Alaskan Way corridor is one of the most ambitious urban redevelopment projects in the United States. With a total investment exceeding $800 million, the project reimagined a 1.5-mile stretch of prime waterfront real estate that had been dominated for decades by the double-decker Alaskan Way Viaduct. Following the viaduct’s removal in 2019, city leaders seized the opportunity to create a vibrant, people-first public space that connects the downtown core to Elliott Bay.

Completed in phases from 2020 to 2024, the revitalized Alaskan Way now features wide sidewalks, a two-way protected bike path, lush native landscaping, and tree-lined promenades. Over 4,300 Silva Cells were installed throughout the sidewalk and bike path areas, supporting more than 200 new trees. Each tree benefits from approximately 600 cubic feet of soil volume — made even more impressive given the shared tree pit design — providing ideal growing conditions for decades of healthy canopy growth.

Green Space Objectives

The design vision for the new Alaskan Way was led by James Corner Field Operations, with a mandate to enhance Seattle’s urban forest, reconnect people to the water, and improve environmental performance. The waterfront now serves as both a civic space and an ecological corridor, bringing nature into the heart of the city.

Native plantings and shade trees were chosen not only for their aesthetic qualities but also for their environmental functions — cooling public spaces, filtering and slowing stormwater runoff, and creating wildlife-friendly habitat. Along the bike path and sidewalks, Silva Cells are supporting the growth of healthy, mature urban trees with large volumes of lightly compacted soil.

Why Silva Cells Thrive in Streetscapes

Silva Cells are purpose-built for the challenges of dense, high-traffic urban streetscapes like Alaskan Way. In an environment where underground space is contested by utilities, transit infrastructure, and pedestrian needs, the Silva Cell system ensures trees receive uncompromised rooting space without sacrificing loading strength or surface function.

Here, the system was installed in numerous continuous, shared rooting zones, maximizing soil access and allowing trees to benefit from interconnected growing space. This approach promotes stronger, more resilient root systems, translating to healthier, longer-lived trees that can withstand the demands of a bustling urban waterfront.

The Trees

The project’s planting plan features a curated mix of species chosen for their beauty, shade potential, and urban resilience. South to north, the corridor transitions through distinct planting “zones” that each span multiple blocks. Species include:

-Tulip Trees

-London Plane Trees

-Zelkova Trees

-American Elm Trees

-Linden Trees

-Ash Trees

-Sugar Maple Trees

-Swamp White Oak Trees

-Bur Oak Trees

-Green Pillar Oak Trees

-Regal Prince Oak Trees

With Silva Cells providing generous rooting volume and uncompacted, high-quality soil, these trees are set to achieve their full canopy potential, delivering shade, cooling, and — in some cases, like those of the tulip and London plane trees — reaching 50 to 60 feet in height.

What People Are Saying About Alaskan Way

“While the Alaskan Way Viaduct took you through downtown, it didn’t allow you to stop and take it all in. That’s what this new waterfront experience offers.”
— Cale McPherson, WSP Vice President of Project Management

“Removing [the viaduct] provided downtown with a once-in-a-generation opportunity to reconnect with its natural environment thanks to a new 20-acre Waterfront Park.”
— Angela Brady, Director, Office of the Waterfront & Civic Projects

“Waterfront Park is going to be part of the renewal and revitalization — a place that everyone sees themselves in and where memories will be created.”
— Joy Shigaki, CEO, Friends of Waterfront Seattle