I recently had a plummer replace 118 ft of iron pipe with pvc which involved tunneling under the slab and removing almost 12 loads of clay. When he finished he had a crew begin to return the clay under the slab. When I returned from work I noticed about 8 loads left over. Is this common? Or should they have workedensure the majority of the clay was returned? I am worried about the integrity of my slab especially living in New Orleans where we loose ground everyday. Also I have noticed that some plummers pump wet sand under the slab after this type of work. Is one more adventageous than the other? I was told by my plummer not to be fooled about pumping sand as being a more viable option. Thank you…Scott.