I started a new home constrution project and the contractor poured a footer the same day he discovered there was a cistern, which was removed, right at one of the walls. After pouring, with rebar added and 12" deep, it still sunk significantly in that spot, maybe 3-4" and at least 5' long. His solution is to transit the gap with a lentil (I think concrete block) mortared over the dip. Will this hold? Should I be worried the spot is weak and my wall might sag there? Does the footer need something extra for reinforcement or was this an issue that should be resolved by starting over?
This is my first home project ever and I don't have anyone to advise me on whether to trust this contractor. Any advice much appreciated.