We are getting ready to pour our footings the end of this week. After digging the basement, our contractor expressed concern about the loose condition of the floor. We have mostly clay dirt, with lime rock about 2-3 foot down. The rock was solid and we spent $4500.00 blasting 2200+ square feet for the basement and walkout. We blasted prior to excavation in order to use the pressure of the top layers to get a more even and smaller crumbling of the rock. Also for safety of the mobile unit we are currently living in, as it is about 10 feet away from where the new construction will be. However, the basement floor has a lot of "dust" or powdered rock bits now. The concrete workers said we needed to make a decision as to leave it as it is, or to put clean rock in the floor. They said they could not give an opinion, and to contact the building department, who in turn said to call a scientist. Instead of spending the scientist's costly fee for an opinion, we feel we could just go ahead and replace the loose floor with clean rock for about the same money. Do you have any thoughts for us? We feel the foundation is the absolute most important beginning of our new home. We plan to live here for the rest of our lives, and don't want to end up fighting cracks and settling. Any advice would be greatly appreciated.