aldav53
i know of no code ref here , other than that of 'physical damage' that would dictate steel on UG surfacing.
even then, sch 80 goes a long way....
fwiw, there would be more of a focus on the grounding of an isolated sweep, either in burial depth or bonding to it.
there would also be some technicalities feeders/branch circuits vs. service entrance
so you'll need to expand a tad for us
~S~
