Scott, if this is for an underground feeder, skip the UF, and put in a 3/4" PVC conduit instead. If you should ever have to upgrade, or have a failure in one of the conductors, you already have a "hole in the ground." The last well pump I installed using UF, we had to go back and replace the wire. A rock had rubbed against it. If it had been in pipe, it would have only meant replacing the conductors. You can use THHN in pipe buried under ground.