Do you mean Canonsburg Lake on Little Chartiers Creek in northern Washington County?
If so, I've fished it before, below the dam. This was probably close to 10 years ago and with spin gear, but I remember catching some smallish Smallmouth and various Sunfish. If that's not where you're talking about, please disregard.
I think the construction work on the dam is done, so you can fish it. I have hit it once or twice before years ago. Certainly not my favorite spot, but you can get into some fish down there.
Hi,
I have not fished below the spillway since I was young, probably forty years ago. The water below the dam is Little Chartiers Creek. It flows for probably less than one-half mile where it enters Chartiers Creek.
On a couple of canoe trips down the Chartiers, I have come across individuals fishing where LCC flows into the main stem.
I bet it's worth trying for bass or trout.