At each end of the tunnel systems are valves. A valve is opened and closed to allow water to flow freely into and out of the tunnel system. Each valve uses only a 10 hp motor. Recreational watercraft are lucky here at Locks and Dam 15 because we have an auxiliary lock just for them. The auxiliary lock is 360 feet long by 110 feet wide.
Boaters watch the traffic signal to know when to enter the lock.
Once inside they hang onto ropes which keep them somewhat stable during the locking through process. This type of lockage takes about twenty minutes and is free. The operation of a lock is very similar to filling or emptying a bathtub. It is based on the fact that gravity allows water to flow downhill. Valves are located at each end of the lock to fill and empty the lock chamber.