"You've got a MOLE PROBLEM" he said

[charlessenf]

I finally got a roundtoit and took some pictures of the openings - one below, and a few added to the original post (above).

I also have tunnels and what appears to be the excavated soil scattered about as in this image:

 

[dodge man]

Ground squirrels maybe?

 

[Fuddyduddy1952]

You can use a smoke bomb for ground hogs, put it in a hole and run your leaf blower into it.
Any other holes the smoke will come out. Have a shovel & dirt handy to toss dirt into those holes.
There are youtube videos showing technique.