Going to need some help from the farmers/construction guys, but I am 90% sure that I read about a local track in KC using a machine to de-rock the surface. From what I remember, the machine would take it the top x inches of the surface and sort/mill the dirt for the rocks. The end result was a rock free race track.

When I read it, it all made so much sense that I wondered why all tracks did not do this.

Anyone have experience with this?