All dams incorporate dam wall drain tubes. Mussel veligers/larvae may be able to travel with the normal dam into the drain tubes where they could settle and grow. The occurrence of such infestation is likely to be rare but has been documented at some dam facilities.
Dams incorporate foundation uplift drain pipes. Water in these pipes is generally expected to be ground water and not likely to transport macrofoulers.
Dam structures generally have a rigorous inspection program. In the unlikely event that sufficient mussels should accumulate to restrict the drain flow, the reduced drainage should be picked up during the frequent routine inspections. Sometimes the through the dam drains to a sump. The sumps could become an ideal inspection area to check for the presence of macrofoulers.
All dams have outlet works. Mussel fouling impact on the trashracks and upstream tunnel need to be considered especially as it is usually very difficult to drain these areas. The downstream tunnel may also be at risk of macrofouling but usually this area has greater ease of access for cleaning. Impacts on pressure gates need to be considered as well as any inter-chamber piping and vent lines.
Structures that rely on movable gates to direct or moderate water flow need to consider impact of macrofoulers. Attached mussels can colonize the outside and inside of submersed gates thereby increasing their weight. If the design parameters of the lifting equipment can not cope with much additional weight, the gates could become inoperable. Improper sealing is also a concern if the seals around the doors are colonized. Small drains associated with submersible gates can become clogged as can weep holes in tunnels.