Intersection Terrain Model

I'm using Power Geopak V8i SS10. Very new user.

I created the incoming road and the intersection using breaklines. The issue I am running into is that the road coming into the approach has a 6" pavement depth and the intersection has 10" I wanted to model this correctly so I have 2 different terrain models for the 2 separate pavement depths. When I created the first one (incoming road) I just drew in a horizontal geometry line where the pavement depth changes and added that line and the edge of pavement as the boundary and then the centerline geometry as breaklines.

The problem is, when I do it on the intersection portion, I add the edge of pavement as boundary and then add centerline. It triangulates the entire centerline, not just the portion that is in the intersection. So it triangulates all the way back into the incoming road. Is there a way to clip these portions out? I am not sure if this is the best practice but it's what I have right now and need to get it pretty close.

Thanks for the help!