On a recent visit to a construction Site I could identify clearly why civil works are a pre-requisite for mechanical works.
Look at the picture here: the installation of pipes and steel structure on the concrete pipe-rack cannot proceed before all undergrounds are laid so that the area is backfilled and the cranes have access.
All undergrounds not only means main equipment foundations, but all underground networks, such as drain and sewage pipes with associated pits, pipe support foundations, concrete gutters for cables in paved areas etc.
For that reason, Civil Works Installation drawings (page 88), complete with all underground objects and networks, are required very early, for construction reasons, as completion of civil works is a pre-requisite for mechanical works to proceed.
The irony is that these drawings come last in the Engineering work sequence. Take the example of the drains. This is the last network Process engineer will care about… It will nevertheless be a show stopper for the installation of process lines, which will have been designed much earlier.