Digging to China...or something like that

Sammy has developed a fun new habit as well. He has decided to embrace his inner dog and start digging in the backyard. Sammy has only done this two other times. First, when the little neighbor girl had to leave and he was faced with the idea of not having a little slave to pet him all day...which she does. Sammy and Max LOVE this little girl and she will sit for as long as she possibly can with her arms through the fence petting and loving them. So...Sammy frantically started to dig under the fence to go after the little girl. I'm standing at the top of the stairs watching all of this...so he didn't make it very far in his digging expedition. The second time Sammy had a digging party, I was not fortunate enough to catch him....and I only saw him once he was finished and came back up to the door. I was home for Christmas and all the snow had started to melt...leaving a dirty, muddy, slushy MESS in the backyard. Sammy, again, decided to embrace his inner prairie dog and get into the dirt. The result was a DISASTER Seriously, I've never seen a dirtier dog. That picture could win a contest somewhere. Needless to say...he was immediately carried through the house (so he couldn't track his new muddy self all through the house) and thrown into the bath tub. We are still not sure what happened and how he got so dirty. After that, it snowed again...freezing and covering all chances for digging. Now again, he has remembered the art of digging. We have a gate in the backyard to block of an area because it gets REALLY muddy. For some reason, grass just won't grow back there. This also blocks off the gate to the house behind us...with big, mean, barking pitbull dogs who are never on leashes. Max tried to go make friends with them one day...I'll tell that one a different day :) Anyways, Sammy has found a corner of the gate that has sparked his interest. I was sitting on the back steps playing my guitar a few days ago and Sammy sat (in my plain view) and started digging. He did it 3 separate times in the next 10 minutes. And now, everytime I let them out, he goes back and starts digging. I'll open the door to look out, and Sammy sits down right near his newly discovered digging spot, with an innocent look on his face, and looks back at me. ARE YOU KIDDING ME?!? But he manages to sling enough dirt around to come back in the house with dirty feet and little dirty eyebrows. HA! He really looks like an old man now with little dark eyebrows. But, I need to figure out a way to stop his new hobby before my entire house is covered in little muddy sammy prints...any suggestions?