Can we equate this large bored hole to a cable tray? Are there any rules on installing cables in cable tray? Would they then apply?
I see in 392.11(A) that multiple cables are allowed to be installed in open cable trays without derating of the conductors, so long as the individual cables do not require derating due to more than three current carrying conductors in one cable.
Using these rules for bored holes in basements is a stretch, I know. But maybe somebody's proposal can borrow some of the verbiage.