The U. S. Army Corps of Engineers twice widened Upper Hell Gate on the Sasanoa River, which separates Woolwich from Arrowsic. Originally constricted by curves and ledges, which were made even more dangerous by swift currents, the half mile (0.8 kilometer) stretch was widened in 1898 to a minimum of 90 feet (27 meters), then again in 1908 to a minimum of 140 feet (40 meters) and depth of 12 feet (4 meters). The Sasanoa River now permits navigation between Bath and Boothbay Harbor.