If you walk or bine along the maintenance trail past park HQ towards Belle Isle, there is a low bridge over a stream. The island on the other side is Sawmill Island and once was home to a water-powered mill. The mill exists in name only and there are few remnants. The existing path over the bridge will lead you through some tough terrain.
JROC has helped maintain this low vehicle bridge and the raised bridge on the east side of Sawmill Island. This project was to help stop the maintenance road from eroding away and hastening rot on the bridge.