Let me start off by saying that this is my first post

and that I am really enjoying this site and the wealth of knowledge here.
I'm planning to build a SWC (sort of EarthTainer style) out of wood. I've been trying to figure out what to line the inside with to make it hold water and be safe for plants/food.
Firestone makes an EDPM pond liner product called Pondgard. It is advertised as fish safe. Any idea if it would be safe for growing tomatoes? Any better ideas?
Thanks