If you have ever zipped between San Francisco and Oakland on BART, you have ridden through one of the Bay Area’s most unusual pieces of infrastructure: the Transbay Tube — a one-of-a-kind underwater tunnel built more like a ship than a subway tunnel.
1) It was not drilled through rock — it was assembled like giant Legos and sunk into a trench
Instead of boring a tunnel deep underground, engineers built the Transbay Tube on land in dozens of massive steel-and-concrete sections, floated them out onto the Bay, then lowered them into a prepared trench on the bottom. The tunnel was constructed in 57 sections, a signature detail that……