Last week's discovery of a carp in Lake Calumet has added extra urgency to plans for separating the Great Lakes and Illinois River ecosystems. At the Shedd Aquarium on Friday Senator Dick Durbin announced a bill to be introduced this week that will force the Army Corps of Engineers to study the possibilities of physically separating the Chicago and Calumet rivers from the Illinois River (which would require re-reversing their flow back to Lake Michigan). The costs for such a project will be enormous, as well as the costs of transferring shipping across the barricade. But the danger to the Great Lakes ecosystem is equally great.