In my backyard (in Oregon), I have a large metal firepit bowl sitting on a few stone tiles (on dirt). I decided to move the whole setup over by a foot, so I picked up one of the tiles. I heard a buzzing noise and saw a bunch of small black ants crawling around on what looked like tiny little white seeds, smaller than rice grains. Then the dirt moved and out popped a big fat bumblebee! Not a honeybee, not a ground wasp, definitely a fuzzy black and yellow bumblebee.
I read up on it and apparently this is a common thing for bumblebees to have ground nests under heavy flat objects. I don't think I can move the nest, as they can be quite deep and big. But I don't want to give up my firepit area for the entire summer, especially since I was planning to host an important event in my backyard. I know bumblebees are beneficial to the environment and that the best thing to do is to leave them be, but I'm afraid that they will sting people hanging out by the firepit. I'm afraid to even start a fire in the fire bowl now.
Any advice? Also, if I do decide to leave the nest alone, then is it better to put the tile back over the hole, or should I just leave it uncovered now? I'm afraid that if I cover it, I'll disturb their ability to access/exit the nest.