On Fri, 03 Dec 2004 17:35:51 GMT, John Moorhead
wrote:
Nope - I'm in Northern California... Well, I *do* want alternate
circuits... The reason for using a single run of 12/3 is that I wouldn't
have to run an additional separate length of wire - everything would be in
the one cable. Sorry if my post didn't make that clear...

John

I'm reasonably certain that's not allowed in the US.

In any case, the lone neutral lacks the capacity for both circuits.
Also if it's in a garage, the GFCI will sense the imbalanced current and
trip.