The plan was to leave the IMC in place after driving it and locating the end. I didn't want to have to use the more expensive rigid conduit and leave it in the ground.
Cost comparisons per foot:
Rigid = $2.25
IMC = $1.41
I thought that alternately, I could use SCH40 iron pipe inside larger belled PVC conduit and then pull out the iron pipe after driving it but then I'd have all this left over iron pipe.