There is a sign at the bridge where Hi-20 crosses the river South of Henry's Lake.
There is a river otter or two that seem to live in the rocks under the bridge. There is a walk on access on the north bound side of Hi-20. You can park on either side of the bridge.
In October I saw fish schooling/breeding. The bead head prince nymph worked well. Let the fly float downstream on the side and then pull it across to the center of the river in a jerking motion.