Is this a manufactured product, or are you planning a DIY project? Since environmental regulations forced changes in treated wood a few years back, things that used to be rated for underground use are no longer rated that way.
Either way, I'd want to investigate and verify that it's still possible to get wood that will survive 20+ underground.
If you're wanting wood, because you think it will be more durable than metail, I'd recommend in you look into high quality plastic ("resin", they often call it) pool walls.
You might want to look at the Above Ground Gallery, too. Unless you want a true deep end, above ground pools offer more bang for the buck, are easier to service, and in a flat area like yours, offer better intrinsic privacy.Above Ground GalleryGood luck!
Above Ground Gallery, cont
Bookmarks