OK, here is another one. ( I don't remember if it was asked before,if it was just stop me.)

You have a parking lot being torn up and repaved. You have to run lines across the parking lot before they can pave. They try to dig down the proper 24" depth, but only get 6" then there is all rock in the way. Can you just pour 2" of concrete around the pipe and then pave the parking lot?

What if it is Rigid pipe? Non metallic Rigid?

It's not uncommon to get the AHJ to give you a variance.

This is all case by case.

Harold:
I have came accross two situations where conditions were like you describe. Both were solved with a concrete 'backfill'. I used a'Vermeer Wheel' trencher and rather then consume a lot of time cutting the old concrete and rock, the trench cut wasbackfilled with concrete slurry. I used Sch 80 PVC.

The site PE, and the inspectors had no issues, and no variations were required.

John,

The code says it is OK, but you are only down below the surface, 6"-8" at best with 2" of concrete around the pipe. It still seems a little dicey to me.