Alrighty. I have a friend who has had a continuous problem over the last 10 years or so with a digging Wasp. ( I saw it myself, but did not get a pic)

It was almost 2 inches long, and though it was definately Wasp-like, it was quite fat for a wasp.

It was digging into the ground (the one I saw went more than 4 inches down into the ground) under her walkway stones. There was a large pile of displaced dirt around the hole.

She has said that they come back every year, but only burrow into a certain part of her yard, sometimes making as many as 10 holes in a 20 sqft area.

The big guy was yellow and black, and made a very loud buzz when it was aggitated, but was not flying, simply buzzing a warning to us.

I love bugs of all types, but if these things have a sting equal to their size (ouch!), I would like to know why they continue to return to her yard. If there is something there that might be attracting them, maybe she can remove it.