Ballard Locks have two lock chambers

The Hiram M. Chittenden (Ballard) Locks complex contains two parallel lock chambers-a large main chamber and a smaller auxiliary chamber-that lift and lower vessels between Puget Sound and Seattle’s inland lakes. The lock structures, along with associated spillways and control works, are used to regulate Lake Washington and Lake Union water levels. The U.S. Army Corps of Engineers owns and operates the locks and their water-control facilities at this site.