Opossums do not dig. Somebody else is about when digging is noted.It's not a poor design at all. It's that it was a great digger. Yea I could have dug a 5ft trench and hardware mess along with concrete. But my poor wallet along with my poor design went with 1ft deep mess and 4x4's. don't worry, the possiums didn't go to waste. They are buried in the ground next to my compost so my worms can find a meal too.