ᐅ Should the inspection chamber be cast in concrete?

Hello,

My civil engineer is currently installing the inspection shaft (maintenance shaft) for my sewer system.
Instead of using a bottom section that is closed at the base, he placed a ring directly on the ground. He plans to later pour concrete underneath the bottom ring.
I have already read in other forums that this might not be the correct procedure.

I am also looking for a building inspector or construction expert to check this, but it seems difficult to find one in this area.
Additionally, I contacted another civil engineering company and was told that this method is acceptable.

Can anyone give me advice on whether this is an appropriate practice?

Best regards,
Micha

The problem is that although pouring concrete will seal the bottom of the shaft, the load-bearing (the weight of the shaft plus the load from above by cars, trucks, etc.) will still only be transferred through the ring. Since this surface area is smaller than that of a full shaft base, there is a higher risk that the shaft will settle under load. Most likely, the concrete will not form a solid bond with the lower ring and, in the worst case, will retain its concrete height while the ring (and thus the shaft) gradually sinks into the ground.