Bumblebee nests

I've been suspecting that I had bumblebees nesting along our path through the woods.  I've heard and seen them flying low and sort of furtively in the area, since last year.Then I learned more about bumblebees and that it's sort of special to find a nest (they burrow in the ground), so I was keeping a more attentive eye out.   Yesterday I happened to be walking out in the morning and caught a medium sized bee in the act of  leaving her burrow, rather clumsily and noisily, bzzzZZzzz, like she hadn't had her coffee yet.  I knew it!I found four little holes in the area, two of which have perfectly clean entrances you can see into before the tunnel curves (so I'm sure those are in use).  What do they do in the rain?  They remind me of bank-dwelling swallows.  They seem to like the clayey soil and the compacted dirt of our path.I must report to bumblebee watch.  It's going to be awfully hard to figure out what kind of bumblebees live there.  It will be a long stakeout, or else I'll have to set up a trail cam, ararar!