Last year a new limestone track for the dairy cows was formed on our farm and it hasn't totally compacted as yet. The wasps know it. There were quite a few digger wasps flying low over the track and the surrounding pasture, some digging test holes, some digging real holes.
The wasp buzzes very noisily whilst in the hole then backs out quickly and deposits the excavated soil a short distance from the hole. This one had several paralysed caterpillars stashed on grass clumps close to the hole, ready to bury when the digging is complete.
Unfortunately I didn't have the time to stay and observe the end of this particular event - we had to pack up to go back to Geelong.