I'm winging this off the top of my head and will probably get killed for it but there is a FPN somewhere in the Code that conductors under a two inch slab are to be considered OUTSIDE (i.e. exterior) the building.
That would allow you to use # 1 of their local rule.
I need my copy of Ferm's, which is at the office. I'll post again tommorrow.
Alan --an Inspector. CEI-M #138
