Bertha, the $80 million tunnel boring machine making a tunnel for cars beneath downtown Seattle, has been humming along without a significant amount of issues since its enormous, two-year repair wrapped up at the end of 2015. But in the final stretch of drilling, it looks like engineers have discovered that the machine may be "several inches off" of alignment with the tunnel route.

Washington State Department of Transportation spokesperson Laura Newborn says that engineers discovered a discrepancy in measurements between two tunnel surveys, and that mining was stopped on Tuesday so engineers could conduct more tests.

The plan is to resume mining next week, and we'll see if that plan holds. The project has been delayed at least four times in the last two years*, and its completion date extended an additional three years after the machine overheated and shut down in December of 2013. In their last schedule update, Seattle Tunnel Partners, the state's tunnel contractors, said that Bertha would reach its disassembly pit this spring.

The machine has just 960 more feet to go to complete its 9,270-foot-long route.

*The machine has been delayed at least four times total.