We have a local geotech company that has a portable device that can locate and size rebars and WWM to a depth of 12" without degrading the concrete. The testing is expensive (about $700 for a few spot checks) but we have had to utilize their services to verify pours when the contractor did not have the pour inspected prior to the placement of the concrete. The contractor gets to acting really stupid when they get the bill, but it is the only recourse other than digging it all up and starting over.