From the Washington State Department of Transportation:

We have just posted a new video that describes some of the monitoring involved with the SR99 tunnel project. We hope this would be helpful for your readers/viewers. Feel free to post/link.
https://youtu.be/YewUJ7vjrrs
 
Here is what it shows:
As part of the SR 99 Tunnel Project, WSDOT required its contractor to develop a robust system to monitor the ground, buildings, the Alaskan Way Viaduct and downtown Seattle streets. International firm Soldata was hired to design the monitoring system and review the data 24 hours a day. More than 4,000 different monitoring points near the tunnel alignment take gather measurements and share them with our engineers in real time. This video shows the complexity and scope of the monitoring effort.
 
Here is what it shows:
In addition, we recently posted a video showing how the viaduct has been reinforced and strengthened over the years at the location where the tunneling machine will pass underneath. This too might be timely for your readers/viewers to see given the April 29th start of the Alaskan Way Viaduct closure.
https://www.youtube.com/watch?v=BOpreuHP1oM