I live in Fairfax, VT, zip is 05454. I'm building a deck, and I'm going to
be pouring concrete into sonotubes. Everything I've read states that the
bottom of the sonotube must be below the frost line. Nowhere does it state
how deep that might be. I assume that the USDA or the department of the
Interior must have a map on this kinda thing, but for the life of me, I
can't find it. Any ideas?