So thats just the first level, right? How deep was it? And did you cover the boat too?
Heres the one you can dive in:
http://www.underseaadventures.net/silo.htm
Pretty wild setup.
Theres a ton of them all thru WA state, even in the Seattle area (mostly eastside, Redmond, Bothell, Issaquah, etc.). I think most of them have been filled in by now. But some of the outbuildings are still there. Pretty creepy wandering around them.