Concrete surfaces, such as chamber walls, culvert surfaces, bulkhead slots, and similar irregularities, are susceptible to zebra mussel infestations. Infestations of zebra mussels on concrete surfaces as thick as 10 cm have been observed. There is concern about concrete deterioration because of high ammonia levels produced by zebra mussels. However, the major known problems are associated with cleaning and disposing of very large quantities of odorous debris. The high velocities in the filling and emptying system probably preclude major infestation on the culvert boundaries; however, an increase in lock operation time could indicate infestations in these areas. Structural damage, at least in the short term, is expected to be limited to abrasion during cleaning operations. Long-term effects due to chemical actions, for example, have yet to be identified. Early monitoring of observations along the wall just below the waterline during low pool levels is recommended. An accumulation along the slots or sealing surfaces may cause closure problems. However, the expectation is that the weight of bulkheads is adequate to clear the slots and crush any mussel accumulation on the seals. New locks on the Ohio River are designed with low culverts so that air vents are not required. Older locks and high lift locks use air vents for the purpose of preventing cavitation downstream of culvert valves. In the unlikely event of total occlusion, cavitation damage might occur.
Periodic filling and emptying of very low-usage locks will preclude significant attachments within intake manifold, culvert, chamber manifold, and outlet manifold. Cleaning is generally accomplished mechanically. Various mechanical cleaning procedures including scraping, high pressure hosing (possibly barge mounted for near-surface cleaning), and scrubbers (barge mounted for deeper cleaning) are available. Dewatering is probably needed for complete zebra mussel removal. Dewatering during winter months or hot summer months resulting in freezing or desiccation is applicable. Use of an antifouling coating to prevent zebra mussel attachment is probably not cost efficient. For smaller flow passages, the suggested method is physical removal by some type of pigging arrangement. A modified chimney cleaner may be applicable to clean lock air vents if necessary.
Navigation Facility Components at Risk