Ep 7. Trapped Under Seattle

The episode Trapped Under Seattle of Engineering Disasters season 1 is a gripping tale of the ambitious project that aimed to replace the Alaskan Way Viaduct with a tunnel. The project, titled the Alaskan Way Viaduct Replacement Program, was an ambitious plan by the Washington State Department of Transportation to replace the aging Alaskan Way Viaduct, an elevated freeway that ran along the Seattle waterfront since the 1950s.

As the episode unfolds, the viewers get a glimpse of the complex engineering problems that the project faced, from the challenging geological conditions to the logistical hurdles of building a deep-bore tunnel under an already congested city. The viewers get to hear from the project managers, experts, and officials who worked on the project and gain insights into the planning, design, and execution phases of the project.

The episode starts by introducing the viewers to the Alaskan Way Viaduct and the reasons behind its replacement. The viaduct was built with reinforced concrete, which made it vulnerable to earthquakes. Moreover, it was susceptible to corrosion from the salty air of the Puget Sound that it overlooked. After a devastating earthquake in 2001, the authorities decided that the viaduct needed to be replaced with a safer and more resilient alternative.

The viewers then get to hear about the initial designs for the project, which included a deep-bore tunnel that would run beneath the city, providing an uninterrupted view of the waterfront. However, the idea was not without its challenges. Seattle sits on a seismic zone and had a history of landslides, making it difficult to drill a tunnel deep enough to avoid surface disturbances. Moreover, the path of the tunnel was under the Battery Street neighborhood, which was already congested, with several underground utilities and buildings.

The episode then delves into the engineering challenges that the team faced during the construction of the tunnel. The viewers get to see how the tunneling machine, dubbed Bertha, was assembled and lowered into the ground to begin digging the 2-mile tunnel. However, the viewers soon realize that things did not go as planned. The machine hit a steel pipe, which caused it to malfunction, and it was stuck for over two years. The project faced cost overruns, delays, and technical issues, which made the tunneling experience a nightmare for all involved.

The episode then highlights the efforts made by the engineers to safely extricate Bertha from its location. The team devised a plan to extract the machine piece by piece, which involved drilling a rescue shaft next to it and lifting it out through there. The engineering challenge was immense, as the area was already congested with underground utilities, and any mistake would be disastrous. The viewers get to see the engineers work tirelessly to extract Bertha safely and bring the project back on track.

The episode ends by showing the completed tunnel, which runs from one end of the waterfront to the other. The tunnel is taller, wider, and more robust than its predecessor, and it has the latest safety measures in place to withstand earthquakes and other natural calamities. The viewers get to see some of the beautiful vistas of the city that the tunnel affords and get a sense of how the project will benefit both residents and visitors.

In conclusion, the Trapped Under Seattle episode of Engineering Disasters season 1 is a riveting tale of an ambitious engineering project that faced unforeseen challenges. The episode highlights the risks involved in such endeavors and the importance of proper planning, design, and execution of large infrastructure projects. The episode provides a glimpse into the technical, logistical, and human aspects of the project and showcases the ingenuity and resilience of the engineers involved. The viewers leave with a deeper appreciation of the complex problems that engineers solve every day to keep our society running and safe.