SR 99 tunnel boring machine launch pit site_ April 30-1
Construction is underway just south of Downtown Seattle on the launch pit for the SR 99 tunnel boring machine. The blue cranes are building the underground walls of the launch pit. The walls consist of more than 200 reinforced concrete piles that extend 100 feet below ground level. In summer 2012 crews will start digging the launch pit inside the perimeter of the walls.
Learn more about work underway on the SR 99 tunnel.