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“Greenroads” improvements coming to Mercer Street

Greenroads pilot project sign near Fairview Avenue North and Mercer Street

If you’ve been watching the Mercer Corridor Project’s active construction in South Lake Union, you may have recently noticed some new “Greenroads Pilot Project” signs.

Greenroads, a third-party rating system managed by the Greenroads Foundation, is a collection of best practices in roadway design and construction, much like the LEED rating system for buildings. Greenroads independently rated the Mercer Corridor Project and awarded it the highest score of any Greenroads Pilot Project.

So what makes a “green” road?  The Mercer Corridor Project’s innovative design and construction methods include some of the following sustainable solutions – look for these elements as construction continues in South Lake Union:

  • Materials sourced from local suppliers and reuse of on-site fill materials where feasible.

    Conceptual drawing of future “wet median” in the middle of two-way Mercer Street

  • Use of recycled materials as part of new pavement construction.
  • 20-foot “wet median” between eastbound and westbound Mercer Street lanes from Fairview Avenue North to Terry Avenue North.  The wet median will collect stormwater and provide natural drainage, improve safety by separating lanes of oncoming traffic, and add significant visual “green” to the corridor.
  • Rain gardens planted along the east side of Westlake Ave. N adjacent to the new Lake Union Park. Rain gardens naturally store and treat stormwater and these will include native plants and use soil and vegetation as natural stormwater filters.
  • 2.8 acres of landscaping will be installed, including planting approximately 230 trees and more than 20,000 shrubs.
  • New LED streetlights along Mercer St.

    The new Valley Street will include on-street bike lanes and a wide pedestrian promenade

The Mercer Corridor Project’s Greenroads rating also incorporates improvements to the transportation network, such as:

  • Improved pedestrian access, including 21 new curb bulbs and improvements to 32 sidewalk block faces and pedestrian crossings at 12 major intersections.
  • Improved transit access in the corridor.
  • Additional one mile of new bike lanes along Valley Street, Roy Street and 9th Avenue North.
  • An “intelligent transportation system” design including incident management and as well as smart design for transit and truck routes.

Congratulations to the Mercer Corridor Project for this achievement in green design! Find the full Greenroads report at

For updated construction or project information for the Mercer Corridor Project, visit: