My custom ground in X Plane 10?

I have a custom ground made with Sketchup 8 Pro which I made for FSX and Prepar3D.
Can i somehow make this custom ground work in X Plane 10?

Runways that contour with the ground and the taxiways and apron area as well.
I have not found a way to make my 3D custom ground follow the X Plane 10 ground.

Any ideas or knowledge on this?