Getting Bertha tunneling under downtown Seattle after a December 2013 stoppage ended up being a roughly two-year endeavor. And not only is the world’s largest tunnel-boring machine again moving forward, but the 57.5-ft-dia machine is now moving again in native Seattle soil.

该机器于2015年12月22日在其维修坑中首次向前移动，但这是穿过120英尺深的维修坑的北墙的破裂，标志着使Bertha重回西雅图的轨道。1月的第一周，伯莎（Bertha）撕破了15英尺厚的混凝土墙，然后在1月7日开采到原始路线计划的本地土壤中。

自12月22日以来，Bertha已向前移动73英尺，允许安装12个混凝土隧道环。本周将发生更多采矿。

Bertha now approaches South Main Street near Pier 48 and is digging well below the area’s notorious fill soil. The top of the machine sits approximately 80 ft below the surface in a mixture of glacially compacted material.

Currently, the joint venture leading the charge, Seattle Tunnel Partners, has two tunneling crews consisting of about 25 members each. Each crew plans to work six, 12-hour shifts per week. Mining progress during each shift may vary, as there is a mix of straightforward mining and planned maintenance needed for Bertha.

According to the most recent schedule of mining put out by STP, Bertha should reach its next expected underground maintenance stop just south of Yesler Way in late January. Once there, crews will spend about three weeks performing final maintenance before the machine tunnels beneath the Alaskan Way Viaduct. Washington State Dept. of Transportation will fully close State Route 99 through downtown for approximately two weeks while the machine passes beneath the viaduct, likely sometime in March.

With Bertha once again moving forward, crews have started disassembling the crane used to repair the cutterhead. All parties hope there will be no need to ever reassemble the crane for another Bertha repair.

Follow Tim Newcomb on Twitter at@tdnewcomb.