Been trying to get rid of this thing for a while now.  This one cost me $1,200 a few years back because the cut my electric line that runs the well pump.

Saw a large groundhog UP ON THE PORCH!  It ran round the porch and down under the steps.  I immediately got my tools, removed the steps  and alas, there was a huge hole going under the sidewalk cement.  Repeated the same drill as the last den, fill in all but one hole, in goes the flares, then fill in that hole.