There are deeper mines than that. The long time the project is taking is also an indicator that it is mostly about repeating a certain set of tasks over and ove

There are deeper mines than that. The long time the project is taking is also an indicator that it is mostly about repeating a certain set of tasks over and over and over again. Certainly there were big challenges, but I imagine they were more of a project planning and management nature than pure engineering problems. It is quite impressive nontheless.