TRAVERSE CITY, Mich. -- A federal agency sent Congress a list of alternatives Monday for shielding the Great Lakes from an invasion by Asian carp that could devastate native fish, including construction projects in Chicago waterways that could cost more than $18 billion and take 25 years to complete.
The U.S. Army Corps of Engineers declined to endorse a single plan after studying the matter since 2009, disappointing sponsors of legislation that ordered the agency to move faster. Instead, the Corps analyzed eight possible approaches featuring different mixtures of technology and structures such as locks, sluice gates, physical and electric barriers and water treatment systems.
Battling invasive species is "a shared responsibility" that will require support from Congress and state governments, which would have to choose a strategy and provide the money, said Dave Wethington of the Corps' Chicago district office, project manager for the study.
"We're providing this information to the decision-makers," Wethington said in a phone conference. "We are standing by to move forward to the next step."
The Corps' mission is to prevent invasive species from migrating between the Great Lakes and Mississippi watersheds, which share a boundary nearly 1,500 miles long. But the study focused on a network of rivers and canals in and near Chicago with five direct links between the two giant drainage basins, considered the likeliest route by which Asian carp could reach the lakes.
The Corps said the measures in its report could shut down pathways for 13 potential animal and plant attackers, from the bloody red shrimp to reed sweetgrass and a deadly fish virus. But public and congressional interest is riveted on bighead and silver carp -- voracious Asian fish imported in the early 1970s to gobble algae in Deep South fish ponds and sewage plants.
They escaped during floods and have migrated northward, infesting the Mississippi and Ohio rivers and tributaries in more than two dozen states. Scientists say they can destabilize ecosystems by devouring plankton, a vital link in aquatic food chains.
Prized native species such as perch, walleye and whitefish are vulnerable in the Great Lakes, where a fishing industry valued at $7 billion a year already suffers from pollution and ravages of invasive mussels. Silver carp are notorious for springing from the water when disturbed by motorboats and colliding with their occupants, posing a risk to outdoor recreation.
"The Army Corps must fully develop its proposals and continue working with Congress so that action can be taken to protect the Great Lakes and the hundreds of thousands of jobs that depend on them," said U.S. Sen. Debbie Stabenow, a Michigan Democrat.
Stabenow and Rep. Dave Camp, a Michigan Republican, sponsored a bill that favors placing barriers in the Chicago waterways to physically separate the two watersheds. Four of the options in the Army Corps report would use such structures to cut off some or all of the linkages.
Alternatives that stop short of complete separation propose technologies including installation of electric fish barriers in addition to one located 37 miles south of Lake Michigan. Another device that could be deployed is a new shipping lock system where water would be cleansed of floating invasive species.