How would you deal with a wasps' nest in the ground, under a huge
lavender bush, in a smallish garden where two dogs want to romp?

My son has this problem and discovered the wasps on return from 2
weeks holiday. He is starting with running the hose into the hole,
but so far to little effect.
Has anyone any experience of dealing with this?
Can anyone recommend a spray or other treatment?
TIA

Pam in Bristol