Simple way to clear out the nest is dump a clip of 9mm into them (back in the days of cheap ammo!)

https://vimeo.com/130597562

That video with the vacuum blew my mind. I could not believe the number of hornets in that hole. Didn’t know they created an underground nest either. Thanks for posting.
I have some hornets in my back yard in a suspended compost container. They got me once. Now I just mow quickly around them. Assuming they will be gone in a couple months. I will definitely be more cautious with the weather turning. They seem to go a bit more crazy.

Que?

Amazing the amount of soil and loose rock they are able to displace.

Polonization I guess.

Yes, they spend a lot of time buzzing around the blooms. Not a lot of bees around here anymore.

Planted a lot of flowers this year and they sure attracted lots of bees. Spent most evenings swatting the carpenter bees. Must have killed at least 100. Those bastards are tearing up my redwood facia.