The Building Blocks of the SR 99 Tunnel

The tunnel liner that is being placed by the Bertha tunnel boring machine consists of precast concrete segments. This video by the WSDOT shows how they are made at the casting yard, and what Bertha does with them once they get delivered to her where the action is happening. The finished tunnel will consist of over 14,000 of these precast segments! [Source: WSDOT YouTube Channel. Image: YouTube]