Much as I hated to do it, the bees had to go. The team fixing my deck refused to complete the job until I had the bee problem "taken care of". I think I mentioned that one of them was stung while they were working on raising the slabs.
So, reluctantly, I called a bee expert to see what could be done. He surmised it was a small colony of bumble bees, not honey bees, which would have been a very different story. Fortuitously, when he arrived no bees were in sight and he opined (optimistically) that they were all out foraging. So he doused the area with a powder which (he said) would discourage them from returning to the nest. We shall see! I didn't ask about any bees still under the deck. Less said the better. My grandson, the environmentalist, was very annoyed with me for not finding a more bee-friendly method of removing them.
You can see he's not getting too close just in case.
A final application to the problem area. I will check for any activity tomorrow and he promised to return to give it another dose if needed.