Hole in Surface for Retaining Wall

Sometimes quantities overlap and we want to restrict it to a certain area. We can create a boundary around the area we want excluded.

The first step is to extract feature lines from a corridor. This can be done from the Launch Pad and select Create Polyline From Corridor (on the drop down).

Next select the feature lines you want it created from.

Next draw a 3DPolyline to connect the ends of the two feature lines created.

Then go to the Modify Tab on the Ribbon and select the Join Command.

Then add in AutoCAD properties set the 3DPolyline to be closed.

Then add the 3DPolyline as a boudnary to the Datum surface.

This will cause Civil 3D to not calculate quanties where the hole occurs.