To block invasive species such as Asian carp from reaching the Lake Erie basin, the Army Corps of Engineers has proposed a menu of multimillion-dollar projects that could permanently change the face of Eagle Marsh, the natural preserve on Fort Wayne's south side.
The plan rated as the best alternative by the Corps would have the worst impact on the 716-acre wetland. It would erect an “I-wall” averaging 8 feet high across the marsh at the point where the waters of the Mississippi basin and the Great Lakes basin can mingle during floods. It's a costly solution, too, estimated at $12.8 million to build.
The Corps presentation of the alternatives acknowledges the damage this tall wall could do to Eagle Marsh. A report on the alternatives says this plan “is expected to detrimentally alter the wetlands and aquatic habitat within and around Eagle Marsh. The I-wall would further fragment the wetlands into largely unconnected parcels, inhibiting the flow of water and movement of aquatic organisms throughout the local wetland area.”
The Corps report, released for public comment, details nine proposals to make it more difficult for invasive species to move between these vast basins of North American waters. Their construction costs range from a low of $2.4 million to a high of $20.2 million, according to Corps estimates. Their annual maintenance costs are estimated to range from as little as $11,000 a year, in the case of the I-wall plan, to $600,000 per year.
The report notes a major obstacle: No agency beyond the federal government has stepped up to shoulder part of the cost of building the Eagle Marsh barrier. At the same time, the Corps explains how much might be at stake. Already, more than $137 billion a year is spent trying to control invasive species in the United States, according to an estimate cited by the Corps.
The Corps report says that it is not intended to recommend a particular course of action.
Three varieties of Asian carp, five other species of fish, plus a virus and an aquatic parasite that both afflict fish, are rated by the Corps as the most threatening “aquatic nuisance species.”
Eagle Marsh became the focus of the Corps' intense scrutiny and design-brainstorming because a team built from several federal agencies, as well as agencies from several states, identified Eagle Marsh as the most likely pathway for species migration between the basins among 31 potential pathways studied.
Though the rewards of blocking the spread of these nuisance species from one basin to another would be great, the job is daunting, so much so that the Corps admits any effort may be doomed to fail.
“It is important to note that even if one or more of the alternatives identified in this Controls Report are implemented, there is substantial residual likelihood that (nuisance species) could transfer between the basins … using other vectors and pathways outside the scope of this study, (such as) bait buckets, terrestrial transport, commercial food fish, pet trade, recreational boating,” the report said.