The METRO Tunnel Project
This shows the tunnel as it is descending to go under the Burlington Northern tracks at the south end.
The rail tracks seen here are to carry cars for the removal of dirt as they excavated.
Tracks for commuter trains weren't decided on until later in the project.
It was a highly debated subject whether or not to put rail into the tunnel,
and finally it was decided that they would.
Ironically, the transit agency that evolved to run the rail service decided
to use a different size track, and so the tunnel will be closed for about 3 years --
the same amount of time it took to build the tunnel -- while they install new track.
Photograph by K. L. Slusher