Big bump in the airport road

I used WED to add a little area for my plane at KOLM, Olympia, Washington.

However, right in the middle of the ramp, I encounter a huge bump, which when I'm flying the Skymaster causes the loss of the rear engine.

Any idea what could be causing this?

I would guess it's something in the terrain, but Im not sure how to fix it.

I guess I could just move the airport, what being an airport god and all.