American Society of Civil Engineers

Mitigating Salt-Water Intrusion through Hiram M. Chittenden Locks

by Sherrill Mausshardt, (Grad. Student, Harris Hydr. Lab, Univ. of Washington, Seattle, WA 98195) and Glen Singleton, P.E., (Hydr. Engr., U.S. Army Corps of Engrs., Seattle Dist., Water Mgmt. Sect., Seattle WA 98124)

Journal of Waterway, Port, Coastal and Ocean Engineering, Vol. 121, No. 4, July/August 1995, pp. 224-227, (doi:

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Document type: Technical Note
Abstract: The Seattle metropolitan area surrounds Lake Washington, a large freshwater lake connected to the salt water of Puget Sound by an 8-mi-long ship canal with a lock-and-dam structure at the downstream end of the canal. When raising vessels from Puget Sound to lake level, a strong current of salt water flows from the lock chamber into the freshwater system resulting in two opposing water-management issues at the locks: salt-water intrusion and water conservation. Several physical structures are presented to prevent salt water from propagating upstream with each lake-bound lockage. During heavy use in the summer period, these structures cannot keep up with the amount of seawater entering the freshwater system, and an additional flushing technique is required. Consequently, the U.S. Army Corps of Engineers, which manages the locks, has implemented a “miniflushing” procedure for summer months. Miniflushing is defined as any process that can be temporarily implemented as part of a lockage to minimize salt-water intrusion. Recent field experiments at the locks compare two methods of miniflushing, and a recent improvement in procedure is discussed in this paper.

ASCE Subject Headings:
Civil engineering landmarks
Salt water intrusion
Water management
Fresh water