How big is your gully? I think 12-15 tons is ~ one and a half 12 yard dump truck loads.
When I was looking the closest source for oversized rock was in Oklahoma which isn't that far for you.
After much trial and error, this is what I ended up doing. It replaces a 8'-10'-deep gully.
https://i.ibb.co/hKpMXFR/IMG-2346.jpg
