Hiram Chittenden Locks can be referred to as a complex of two locks that is located on the western end of the Salmon Bay in Washington’s Lake Washington Ship Canal. Locally, they are known as the Ballard Locks. These locks and the associated facilities serve 3 purposes: to prevent sea water from the Puget Sound from mixing with fresh water from other lakes, to move the boats from water level of lakes to Puget Sound water level and vice versa, and finally to maintain the level of fresh water in Lake Union and Lake Washington at 6.1 – 6.7 meters just above sea level.
This complex includes 2 locks; a small 9 by 46 meter lock, and a large 24 by 251 meter lock. This complex includes a 72 meter spillway with 6 gates to aid in water-level control. A fish ladder is also integrated into the locks for the migration of the anadromous fish, especially salmon. On the grounds, there is the visitor’s center and Carl S. English Botanical Gardens. The locks are basically operated and maintained by United States Army of Engineers. They were officially opened on July 4th, 1917. The very first ship passed through here on August 3rd,1916. These locks are named after Army Major Hiram Chittenden.
The Locks Proper
The small lock is used when the lake receives less inflow and therefore the boat traffic is quite low. The 2 locks are important since they allow the draining of one the locks for maintenance without having to interfere with the entire boat traffic. The larger lock can be drained for about 2 weeks, mostly in November, while the small lock is also drained for the same period, mostly in March. These locks are capable of elevating a 230 by 24 meter vessel 7.9 meters above the level of Puget -Sound to the freshwater Salmon Bay level in just 10 to 15 min. The locks can also handle both the pressure boats and the commercial vessels such as the kayaks and cargo ships. Over one million tons of building materials, cargo, fuel and other seafood products pass via the locks every year.
On the southern side of the smaller lock, there is spillway dam with some tainter gates that are used to regulate freshwater levels of lakes and ship canal. These gates release or store the water in order to maintain the water level to just above sea level. The maintenance of the lake level is very necessary for mooring facilities, floating bridges and vessel clearances below the bridges.
Salt Water Barrier
If excess salt water is allowed to enter the Salmon Bay, salt could interfere with the freshwater ecosystem over time. To avoid this, the basin was dredged above the large lock. Heavier salt water then settles in the basin and is later drained via pipe that discharges downstream of locks area. In 1975, the salt water drain was rectified to divert salt water from the basin to the fish ladder. In 1966, more improvements were made when a hinged barrier was placed upstream of the large lock to restrict saltwater intrusion.