Components of water intake facilities that could be infested with zebra mussels include the crib, intake pipe, and screens (McMahon, Ussery, and Clarke 1994). (Figure 10) is a screen clogged with zebra mussels. Live mussels can cause flow reductions; however, the presence of zebra mussel shells (dead organisms) could also be a problem throughout the system. Impellers on trash pumps (which are used to remove flocculent material) can be damaged by shells. Some facilities that have not removed all dead organisms after reactive chemical or mechanical cleaning have been fouled a second time by the dead mussel shells.
Trash racks (Figure 9) and fish protection devices are also likely to be infested with zebra mussels. Designs that are most efficient for protecting fish or collecting trash are the susceptible to heavy infestation. Less efficient designs or those that do not attract zebra mussels may be necessary in infested waters. These fish protection devices will have to be carefully evaluated to determine their vulnerability to zebra mussels.
A zebra mussel control method applicable to the crib is physical cleaning by divers. Chemicals are effective in disinfecting water intakes. If two intake pipes are present, (i.e., a parallel system), one can be shut down, inspected, and cleaned if necessary. Low dissolved oxygen levels in an intake pipe idled for several weeks will kill zebra mussels. Small-diameter pipes have less water exchange than larger diameter pipes and should achieve low dissolved oxygen levels more quickly. Periodic cleaning of screens to remove zebra mussels is recommended. Screens or strainers at the end of a pipe can be cleaned while in place, while some screens or strainers should be removed for additional cleaning. Modifying traveling screens to withstand higher loads of zebra mussels is a consideration. Trash pumps with stainless steel impellers, which are less prone to failure, should be installed if shell accumulation is expected. Antifouling coatings containing copper are effective but must be certified by the EPA as appropriate for a particular use.