Cut and Fill Illustration

I am trying to create this illustration in grasshopper and wanted to prick some else’s brain. It is a cut and fill map for altering topography.
Screenshots show some iterations I have made so far but none have turned out so far.
The goal is to create a surface in the difference of the two sets of curves.

Image found from

To use RegionDifference, I would need closed curves. So I tried that here:

I tried other methods such as loft, edge curves, ruled surface, etc.

It almost works: The “Cut” side/surface works but not the “Cut” side. Also this only works if I isolate one set of Existing + New lines. It goes bonkers if you set multiple curves.

Cut and Fill Illustration.3dm (5.2 MB) CutFill (9.2 KB)

Do you simply want to trim the topography lines within your building outlines and solid hatch the buildings?

No, I am trying to create the red and blue cut and fill areas from the reference photo. Either with a hatch or surface.

Here’s some more screenshots from my rhino model:

Full topo area. The blue lines are building outlines.

Each elevation line has a existing line (dashed) and a new construction line (solid). A set of these are highlighted in this screenshot.

I hadn’t thought of hating before, but I just tried it and still get the same problems.