Consultant's Report - Minnesota State Legislature

MINNESOTA DEPARTMENT OF NATURAL RESOURCES
Feasibility Study to Limit the Spread ofZebra Mussels from Ossawinnamakee Lake
implement a vibration system in either the brook or the lake because there are few structures that
can be subjected to vibration.
Overall, acoustic deterrent systems have relatively high capital costs and may be feasible for
certain areas in Ossawinnamakee Lake, but efficiencies ofthese systems have not been proven in
open water settings. In fact, research pertaining to acoustic deterrents for control of zebra
mussels in water intakes was documented as long as thirty years ago primarily for intakes, but
there are no cases to our knowledge of acoustic systems that have been implemented in open
water systems.
Chemical Controls
Chemical treatments have some advantages over the other treatment alternatives because they
have high efficiencies and are relatively easy to implement within open water systems such as
the lake and/or brook. Specifically, Muskie Bay could be utilized as a potential treatment area
and the brook may benefit from residual chemical levels, as exhibited by the current treatment.
Capital costs for chemical treatments are generally reduced due to the limited equipment needed
to implement chemical dosing; however, operational and maintenance costs (i.e., man hours and
chemicals) may be higher than some other treatment alternatives. Overall, the major
disadvantages for chemical treatments include environmental impacts to non-target organisms
and health and safety of the operators that handle the chemicals. With these considerations in
mind, a brief statement is provided (within the subdivided categories) to explain why or why not
each chemical would be advantageous for zebra mussel control in the lake and/or the brook.
Aside from toxicology, chemical treatments are a viable option for implementation in Muskie
Bay or Pelican Brook, although implementation may be more difficult in the brook due to higher
flows.
Oxidizing Agents
The oxidizing chemicals discussed in Section V are generally effective in reducing zebra mussel
populations; however, this class of chemicals is best suited for application within controlled,
closed water systems. The use of oxidizing chemicals in natural, open water systems is limited
due to toxicity and impacts to non-target organisms, potential occupational safety issues, and the
regulatory permitting issues/restrictions. In addition, there could potentially be higher
operational costs (in comparison to non-oxidizing agents) associated with administration of
oxidizing agents because juvenile and adult zebra mussels can detect chemical oxidants and
subsequently close their shells to protect themselves from the harsh environment.
Toxicity is a major disadvantage to several of these chemicals. Chlorine is harmful to the
environment due to release of trihalomethanes and it is toxic to many species other than zebra
mussels. Hydrogen peroxide is not advantageous because it must be utilized at a high
concentration to produce mortality and it is also toxic to native mussels species. Potassium
permanganate is not advantageous because it must be continuously administered in order to
VI-5 Alternatives Analysis and Recommendations