Den repair is part of proper terrier work. Dens, after all, are not just used by groundhogs, but by raccoons, possums, and fox.
This dig was shallow, but a bit of a mess as it was almost in a cave of wood under a fallen tree.
If you just put the dirt back in the hole, you fill the den pipe and leave a big divot where water collects -- a very bad situation for future occupation. I branch over den pipes, as shown, and try to put vegetation, old feed bags, big flat rocks, or bark over the branches to keep the dirt out, with a water-shedding mound of dirt on top.