July 7 project update: A splash of color for the south portal

Posted on Jul 7 2015 8:27 AM
This week, the muted tones of the south portal construction area will welcome an accent of yellow. The infusion of color will come courtesy of four 40-foot-tall, brightly painted steel ventilation stacks that are to be installed at the south portal operations building.
The stacks are central to the tunnel’s ventilation system, which will be capable of removing 1.4 million cubic feet of air per minute should it be necessary. The operations buildings at each end of the tunnel will house operating systems, including safety, lighting and communications. Additionally, they’ll provide space and access for the very thing that inspired the colorful stacks – WSDOT’s yellow maintenance vehicles. Like all aspects of the design, the color palette was developed with guidance from the Seattle Design Commission.
SR 99 tunnel south operations building image
WSDOT and Seattle Tunnel Partners worked with the Seattle Design Commission on the final look and color scheme of the tunnel operations buildings.
Manufactured in Longview, Wash. with American-made steel, the stacks will be delivered by truck to the work zone over the next few days. Crane crews will then hoist them into place before bolting them to the building’s steel frame. If the stacks had their own baseball card, here are some facts that might appear on the back:
  • Height above street level: 102 feet
  • Weight: Approximately 30,000 pounds of steel
  • Diameter: 10 feet
  • Thickness: Three-eighths of an inch
  • Professional debut: July 7 to 8, 2015
  • Position: Vertical
  • Birthplace: The stacks were manufactured in Longview, Wash. by Wayron, a DBE firm based there.
The north portal operations building will also have four yellow ventilation stacks, but their delivery date has yet to be determined. Both buildings were the subject of this post back in April. Crews have made substantial progress on the structures since then, with the ventilation stacks being the most visible markers of that progress to date.
SR 99 tunnel ventilation stack installation
Seattle Tunnel Partners began installing ventilation stacks at the south operations building on July 7.


A one-minute look at the installation of the SR 99 tunnel’s bright yellow ventilation stacks.