I had one maybe a quarter of that size in my yard.
Fortunately I killed them all before I dug up the nest and realized how massive it was!
But ladies and gentlemen, I bought this stuff,
Stryker 54 (ended up getting it on Amazon),
put the nozzle at the entrance and pulled the trigger, and less than a quarter of the can wiped out the entire nest!
I've since used it on ant piles and other hornet nests. Pretty much creates a dense fog that works its way through the nest killing everything on contact. I cannot recommend the product enough.