SEATTLE, WA The State Route 99 tunneling machine Bertha has passed a significant milestone in its journey underneath Seattle, Washington. When the machine tunneled past Pike Place Market, it pushed beyond the halfway mark of a 9,270-foot-tunnel that will lead to the removal of the Alaskan Way Viaduct.

Seattle Tunnel Partners, the Washington State Department of Transportation's contractor for the tunnel project, has now excavated more than 4,635 feet of the SR 99 tunnel. Much of that progress occurred during the past five months, with STP tunneling more than 3,000 feet since leaving a planned maintenance stop on April 29 to begin the push beneath the viaduct.

Bertha is now about 190 feet beneath First Avenue between Pike and Pine streets. According to STP, crews will continue mining for a short time and then stop to perform approximately one month of planned maintenance.

"Bertha has been steadily on the move and made her way to the second half of the tunnel," Gov. Jay Inslee said. "This is good progress and I appreciate everyone's focus on making sure we safely complete this project."

That finish line - a 90-foot-deep receiving pit near Thomas Street, at the north end of downtown - is largely complete, along with many other aspects of the tunnel portals. Although future contractors will make final connections to the highway, several of the ramps and roadways into and out of the tunnel are already in place, along with tunnel operations buildings at each of the portals. New drone footage of Bertha's finish line is now available.

"This program turned a corner earlier this year," said Secretary of Transportation Roger Millar. "We're now closer to the end of the tunnel than we are to the beginning, and everyone on the team is working toward the day when the machine comes out the other side."

Other important work is ongoing, including construction of the double-deck highway within the tunnel.

While STP's crews are making progress, they are also taking time for routine maintenance to help ensure the machine successfully completes the tunnel drive. Like previous maintenance stops, crews will use the upcoming stop to inspect machine components and replace cutterhead tools in hyperbaric conditions. STP expects this round of maintenance to last approximately one month, but it could take more or less time depending on the extent of work needed.

STP's most recent schedule shows that tunneling will wrap up in summer 2017. Work to complete the tunnel's interior structures, along with installing and testing systems should be finished by late 2018. Based on STP's schedule, WSDOT estimates the tunnel would open to traffic in early 2019 when crews finish connecting the tunnel to the existing SR 99 roadways.