The key component of critical habitat for Northern Redbelly and Smooth Earth Snakes is an Oak-Hickory forest. I think this is because the soil must have been maintained for quite a while if Oak-Hickory is present, so the soil-dwelling snakes could be present.
Another big component is limestone and other rocky outcrops. Here something has made its den along an outcropping.
Permanent water and a fairly dense leaf litter layer is also important. This seepage is probably not permanent, but still adds something to the habitat.
Again, some more pics of rocks and rocky outcropping under a dense Oak-Hickory forest.
A final key ingredient is evidence for food sources. Here's a European earthworm, a primary food-source for these snakes. I also found snails and other soil-inverts at this location.
Random Bonus Picture:
Nothing to do with snakes, just a neat picture of a mushroom.