Crews Monday began work on replacing the roof of the Union Depot in Saranac Lake. The train station, which was built in 1904 by the Delaware and Hudson Railroad, is being renovated so it can be used as a rest stop and visitor center along the 34-mile Adirondack Rail Trail. The 10-mile section of the trail from Saranac Lake to Lake Placid is currently open for walkers, bicyclists and other outdoor enthusiasts.