Washington State's DOT does a great job using drones to show off some of its best work. This video captures the ongoing construction of the interior roadways, safety systems and other elements that will carry and safeguard drivers passing beneath downtown Seattle in the new SR 99 tunnel.
The drone enters at the tunnel’s north end, near Seattle Center. Crews are building the tunnel’s interior structures starting from the south, so as the drone advances the tunnel becomes more complete.
The drone flies along the tunnel's upper deck, which is 85% built. At the tunnel’s south end, the drone passes from the bored section of the tunnel (9,270 feet long and dug by Bertha, the tunneling machine) and into the cut-and-cover section, built in the launch pit where Bertha began her tunnel drive.
One big tunnel element not seen in this video is the tunnel’s lower deck. In early November, the tunnel contractor Seattle Tunnel Partners plans to begin delivering large, prefabricated roadway panels to build that deck (the future northbound roadway). You can track progress on that and other tunnel elements on the WSDOT tunnel progress tracker.
There’s much work still to come in building the tunnel’s interior roadway and completing systems like ventilation, sprinklers and traffic cameras. WSDOT will continue to share and document crews’ progress building the tunnel on Twitter.