English: Spillway (second one, and the longest one). This part of the canal bed was George Washington's Patowmack canal (the Little Falls Skirting Canal), before it was repurposed for the Chesapeake and Ohio Canal. Chain Bridge is in the background. This spillway is just before the 4 mile mark, on the 4 mile level (between locks 4 and 5). According to Thomas Hahn, this is the longest spillway on the canal at 354 feet long, and the National Park Service built it in 1936 to relieve canal of excess water.(Hahn, Towpath Guide p. 24)