Because of their small size and proximity to nutrient-rich, well-oxygenated, flowing waters, measurement systems such as pressure transducers, piezometer lines, gauge wells, float and pulley devices, and mechanical sensors are susceptible to zebra mussel infestations. These small devices provide data (i.e., river stages, status of gates and valves, and lock-chamber water surface elevation) that is used to guide project operators and, for recent designs, to introduce some level of automation into the operation of navigation projects. Infestation of the intake pipe between water source and measurement devices leads to erroneous readings and incorrect conclusions regarding project conditions. No readings lead to non operable automated systems and lack of data for project control. Inaccurate recordings can result from the added weight of zebra mussels on gauge well floats.
Personnel should inspect pressure transducers, piezometer lines, gauge wells, float and pulley devices, and mechanical sensors carefully at least once a year when water temperature is greater then 12 °C. Occlusion of the intake pipe leading from water source to the chamber or still well is of concern. The wells are commonly in the order of 1 m in diameter with a 2- to 3-cm-diameter PVC pipe leading to the river. Consequently, the conditions around the float and pipe make visual inspection nearly impossible.
To minimize infestations within the well and intake piping, chemical treatments can be effective as both preventive and reactive controls. Coordination with local water quality regulators is necessary before any use of chemicals as a treatment strategy. Component surfaces can also be coated with antifoulants to control and prevent zebra mussel infestations. Upon detection of an infestation, zebra mussels can be removed with a wire brush, high-pressure water, scrapers, or other physical means.
Navigation Facility Components at Risk