To start on this, I made diagrams of where the food facility equipment is in the building. I used some of the old building diagrams as base maps for the newer maps that I am making.
This is my creation of the ground floor (floor zero). I prefer the UK convention for floors, because that makes more sense to me, but I would prefer something even simpler (floor zero, and floors +1 and -1).
This is the ground floor map with the equipment and plumbing schedules. This is the initial draft.
This is me making another section of the ground floor.