A friend of mine that runs a hotel had the same problem and used this stuff:
http://www.critter-repellent.com/groundhog/groundhog-removal.php
Said it worked great. They were burrowing under the dirt surrounding 4 steps into the backside of the building.
Hey, thanks and bookmarked. It’s worth a try.
Only problem I noted was it contains the essence of the ground hogs deadliest predator, the fox. LOL. I remember one year visiting Mom and the ground hog family was nesting on one side of the steps, and a family of foxes was on the other. Hope this guy has kept his fear of foxes over the years. He definitely isn’t scared of humans, cats or dogs.