Location: Grey Forest, TX outside San Antonio

Situation: I'm adding a master bathroom where a utility room was located. The home is 1930 built with stone walls, pier & beam thru the main part of the house, and slab on a few later additions. The concrete was poured inside the existing stone walls (stone walls were built, then the concrete poured on top of the dirt to fill the room with concrete). I know the concrete is 5-8" thick on another room, however where they were trenching for the toilet and shower drains, the concrete is about 1/2 inch thick...seriously half a freakin' inch. There is small fill dirt/rock underneath. The inspector will obviously see this when he does his inspection & I want to do this the proper way regardless.

Solution: I have no idea! I cannot fathom any code in the history of ever where this is done properly, but I also don't know how in the world I would correct it. I would really appreciate any wisdom.

What's the solution going to be on something like this?