Paving the way to the SR 99 tunnel

Crews working for Seattle Tunnel Partners have reached a concrete milestone at the SR 99 tunnel’s south portal.

As shown in the aerial photo below, crews are building the cut-and-cover section of the tunnel in SODO, just west of Seattle’s stadiums. Earlier this month, they successfully poured the final sections of northbound mainline roadway concrete for this 1,500-foot-long stretch of the future highway. 

Sections of cut-and-cover tunnel at both portals will connect the SR 99 roadway at the surface to the bored section of the tunnel. The northbound lanes of the cut-and-cover section at the south end of downtown will start west of the stadiums near South Royal Brougham Way. As the photo below shows, the lanes will then descend gradually for 1,500 feet before entering the bored section of the tunnel. 

This simulation shows what the south portal will look like when the tunnel opens to traffic. The light blue shading shows the outline of the cut-and-cover section. 

Next steps

With paving complete for this section, crews can now focus on the walls that will support the southbound roadway deck one level above. The newly placed northbound pavement also means construction can start on the southbound roadway deck scaffolding, as shown below.