Spillway gates include tainter gates, vertical lift gates, wicket gates, and needles. Wicket type gates remain in a set position for several months and may be an ideal location for zebra mussel development. To maintain pool levels, the wickets are raised to form a dam. When open, the wickets lay on the bottom and, if not properly seated, can swing up and be damaged by prop wash. Other major concerns are encrustations of the eye-bolt, preventing raising, or that the tracks become clogged, causing misoperation. Zebra mussels adding extra weight during raising and causing blockage during closure are a less significant concern.
Detection generally requires that some substrate or structural element be inspected by a diver. These structures are not easily remedied if infestation is severe enough so as to cause problems. For example, two pieces of floating plant are needed to move a wicket. Experience information will be helpful and communications between districts and projects is encouraged.
Navigation Facility Components at Risk