How can I remove all the 29 Palms ortho?

[Sethos]

So I picked up the 29 Palms airport from X-aviation. Great little strip, good detail.

Problem is, I've started dabbling with building my own ortho and obviously, it doesn't match the stuff used in 29 Palms at all. So I was wondering, how do I remove all the 29 Palm ortho scenery, so I can use my own? Obviously keep the airport and everything else. I tried deleting the two ortho folders but that just gives me an error, then stops loading the entire airport. 

[Sethos]

I got it worked out. Just had to remove the FLATTEN.pol as well.