Klastri, there are many types of trench digging machines, many of them track vehicles that can travel over rough terrain.  The construction industry also uses track and wheel-driven cranes that are capable of traversing rough terrain and they come in many sizes to meet contractors’ need.  Do some research and see for yourself. You must think the people who run the companies that get the contracts are idiots and do not know how to overcome the challenges you mention without having to build interstate highways. I am not suggesting it will be easy, but American ingenuity has always been able to overcome challenges to get the job done.