In 2002, the U.S. Army Corps of Engineers, working with other federal agencies, constructed an underwater electric fence across the Chicago Sanitary and Ship Canal to prevent aliens — in this case, Asian carp — from making their way into Lake Michigan. Five years later, it appears to be working, at least for now. The Washington Post reports :

The Corps is planning to replace the original barrier with a new, more powerful one capable of lasting at least 20 years, but that project is in limbo because of funding shortfalls and safety concerns.

Half of the new "fence," known as Barrier 2A, is completed, but it cannot be turned on because sparks have been seen jumping between barges that collided in the electrified area; such sparks could trigger an explosion or injure crew members. The Corps, contractors Smith-Root and the U.S. Coast Guard are trying to figure out how to solve that problem. In the meantime, the Coast Guard has barred barges from mooring or passing in the area of the old barrier.

The two halves of the new barrier would each consist of a 130-foot stretch of electrified steel rods running under the canal, with 220 feet in between each half.