How to get arcs to follow irregular path and connect to other form

I’m having some trouble getting my “tunnel” to follow along a path on the ground (drawn out by the bottom tunnel on the ground plane) and connect through to a secondary “tunnel” along the raised curve.
I apologize if the way im describing causes confusion but heres a screen shot of what im trying to describe. I plan on deleting the tunnel that its drawn over so that theres one form doing so instead of two. can anyone give me some advice on how to do this? Im content with the heights of the arcs where they are but if i draw it along the ground plane to have it follow then the individual heights of each arc would change so they match the 45 i have let. Eventually i plan on boolean difference the intersection so it acts as a double height space but thats something ill be able to do myself. the path i intend is drawn in blue in the screen shot.

rhino form file 10.6.3dm (8.3 MB)Rhino form file (19.7 KB)

I’m not sure what you want? The ‘B’ input to SDiff in this model is the one on top. I didn’t touch the other two in the background.

Rhino (25.3 KB)

yes thats pretty close i realized i didn’t explain it well heres another screenshot drawing with a little more detail of what I mean.

I’ve updated the file slightly to simplify it by drawing "form 1 as its own “tunnel” because no changes would need to be made for it. I believe the only change from what you have done would be “form 2” resting on the ground plane with an increase in height of the arches to keep that consistent rise. rhino form file 10.6.3dm (8.4 MB) Rhino form file (24.5 KB)