Consultant's Report - Minnesota State Legislature

Electrical Deterrents
MINNESOTA DEPARTMENT OF NATURAL RESOURCES
Feasibility Study to Limit the Spread of Zebra Mussels from Ossawinnamakee Lake
While electrical deterrents have been used to limit the dispersal and migration of other aquatic
invasive species, these treatment alternatives appear to only prevent zebra mussel attachment or
settling and may not limit downstream movement of veligers. In the instance that veliger
mortality is achieved, very high frequencies are required. Overall, research suggests that these
technologies might be better served in small-controlled applications such as water intakes or
pipelines. Like acoustic deterrents, electrical barriers or deterrents could be constructed within
the brook or the riverine area of the lake, but with the high flow velocities, effectiveness would
likely be diminished with reduced exposure time. These treatment alternatives would not be
feasible in Muskie Bay due to issues with implementation and overall scale. Aside from low
efficacy and difficult implementation, the capital costs to construct electrical deterrents systems
coupled with the public perception ofthe electrical barrier would likely outweigh any benefits.
Physical Treatments
Physical treatments are generally environmentally friendly and may not require permits;
however, many ofthem are not feasible for lake and brook applications. For treatment in Muskie
Bay, implementation and scale present problems with most of the evaluated physical treatment
alternatives; however, the treatments could be applied in areas downstream of the bay under
controlled scenarios such as a fixed water flow rate. These treatment alternatives could
technically be applied to the brook, but under the high flow conditions, the volume of water
would present significant engineering challenges. For instance, the treatment of the large
continuous volume of water would impact overall effectiveness of strobe lights or UV radiation
by limiting the exposure or contact time. Similarly, the efficiency ofmechanical filtration would
be reduced when treating such a large volume ofwater.
Aside from the previously mentioned alternatives, disposable substrates are a viable treatment
option for specific areas of the lake, but they are not highly efficient in controlling dispersal of
zebra mussel veligers. Mechanical cleaning is not largely applicable to the lake' or the brook, but
could be utilized as a spot treatment in areas that contain hard surfaces infested by juvenile or
adult zebra mussels. Separately, a physical barrier could be implemented near the riverine area
downstream ofMuskie Bay. This alternative will limit navigation and migration, but it would be
highly effective in limiting veligers.
Overall, high capital costs and low efficiencies are disadvantages to many of the evaluated
physical alternatives. It is also believed that many of the difficulties in implementing and
maintaining these alternatives may outweigh the benefits gained by utilizing them. The
permeable barrier, however, is an exception in terms of low efficiencies and limitations with
implementation. If the disadvantage of navigation and migration impacts and high capital costs
can be outweighed, this may be a good alternative for limiting the spread of veligers out of
Muskie Bay.
VI-7 Alternatives Analysis and Recommendations