Black Moshannon Creek is in pretty good shape. It receives some mine drainage, but not very much.
The first stretch below the dam gets very warm because of flow from the lake and I think there are very few wild trout there.
But not very far downstream some groundwater comes in and the gradient increases and wild trout appear. By the time you reach the first road bridge below the dam, there are wild trout. And from there to the mouth. A mixture of brookies and browns. Overall, I think more browns than brookies.
It's stocked with hatchery trout and it gets hit hard in the early season. I've seen hordes of people camping along the stream on opening weekend, near the I80 overpass. Tents, trailers, ATVs running around, bonfires, etc.
The fishing for wild trout is "viable", but it's not loaded. I don't know what "Class" the PFBC considers it. You often catch a mix of stockies and wildies. Some stretches are much better than others.
It gets warm in the summer, so that's not the time to fish there.