You'll need some stealth when searching for this one. Terrain rating may seem moderate to some, but I'm going to err on the high side since it might take a little work to approach GZ. You should not have to get wet.
Update (Nov 10, 2015): The coords are very bouncy in here. I had 4m accuracy when I took the reading, but you are likely to have a tough time with the coords. I will update them when I can. Congrats to carnigrewal and tiggrrr on the FTF!!
Update Oct 9, 2017: Coords were updated. The tree you are interested is the one with its roots exposed just a few steps from the bottom of the stairs. They are big roots, and it's a big tree. But approach the cache from the other side of the stream.