Time having elapsed I am left with a problem. Sycamore's three-in-one mentioned KGOO which it is, but it is not Green Valley. Bear correctly identifies Nevada County Airport commonly known locally as Grass Valley because that is where it is. On balance I think I have to go with Bear. Sorry Sycamore, of your guesses only Grass Valley has trees that close to the runway. I had to look Portaville up though as I have never been there.