Bertha pushes past halfway mark for SR 99 tunnel

Seattle’s massive tunnel-boring machine, Bertha, is just past the halfway mark as it digs in its journey under the city.

What to know:

  • Bertha at halfway mark of 9,270-foot-tunnel
  • Currently about 200 feet below Pioneer Square
  • Crews about to stop for a month of maintenance
  • Troubled project has been halted several times
  • New tunnel expected to open in early 2019

When the machine tunneled past Pike Place Market on Friday, it pushed beyond the halfway mark of the 9,270-foot-tunnel that will lead to the removal of the Alaskan Way Viaduct.

So far, the drill has excavated 4,635 feet. Much of that progress has happened during the last five months.

Bertha is currently about 190 feet beneath First Avenue between Pike and Pine streets.

Seattle Tunnel Partners said crews will continue mining for a short time before stopping to perform about a month of planned maintenance. It could take more or less time depending on the extent of work needed.  The stop will be used to inspect machine components and replace cutterhead tools.

The finish line for the tunnel is a 90-foot-deep receiving pit near Thomas Street, at the north end of downtown. That pit is mostly complete, according to the Washington State Department of Transportation.

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.

Other work continues, including construction of a double-deck highway within the tunnel.

Tunneling is expected to wrap up in summer 2017. The new SR 99 toll tunnel is expected to open to traffic in early 2019.

According to the contract with STP, the four-lane toll tunnel was originally supposed to open to traffic at the end of 2015.

The project has had major problems. The machine's cutting teeth struck a 119 foot pipe, eight inches in diameter, on December 3, 2013. The machine overheated and came to a halt three days later. It remained mostly inactive for more than two years as crews tried to fix the problem.

In January 2016, Gov. Jay Inslee ordered that the drill stop after a sinkhole formed behind the troubled machine.

>>See new drone footage of Bertha's finish line below.