Quote Originally Posted by prh129
Is this an older version of 680? I'm looking at the 2005 version and it states 18" for nonmetallic raceways.
This is true if the breakers are not GFI. That aspect seems to make the difference. If your circuits are all GFI at the breaker box, then 12" is the required depth for nonmetallic raceways. If they are not GFI at the breaker box, then 18" is required.

At least, that is my understanding of the code.