The U.S. Army Corps of Engineers says it will take years and cost a ton of money to re-create the natural barrier that once existed between the Great Lakes and Mississippi River basin. Of course it will. Was anyone expecting it be a quick and cheap solution?

Even if the Army Corps has overestimated the cost, as some critics argue, the project will be expensive, ranging into the billions of dollars. That doesn't make separation not worth doing. Unless there's a proven option that will keep invasive species from moving between the two water systems, separation is still the best answer.

After seven years of study and $25 million, the Army Corps has released a plan with eight options for dealing with invasive species moving from one basin to another. The poster fish for this effort is, of course, the Asian carp, which has been swarming up the Mississippi system for years, wreaking havoc on local habitats and native fish.

The initial short-term plan to keep the large jumping fish out of the Great Lakes relied on an electric barrier in the Chicago Sanitary and Ship Canal. The canal is the connecting link between the systems, built more than a century ago to keep Chicago's wastewater out of Lake Michigan and sending it toward the Mississippi River.

But in addition to fouling the waters south and west of Chicago, the canal threatens to become a highway for species such as the Asian carp, which could do serious damage to the habitats and fisheries in the Great Lakes.


The only sure way -- it appears right now -- to close that highway for the carp is to close the canal to all traffic by building a physical barrier.

In fact, it may be too late to stop the carp; DNA from Asian carp has been found in Lake Michigan, and the Army Corps acknowledged just a few weeks ago that its barrier has serious flaws. Still, sealing off the two systems in a timely way could limit the infestation of the carp and would stop future species from doing further damage.

Creating that barrier could cost between $15.5 billion and $18 billion, the Army Corps says, and could take 25 years to build. Part of the reason for that is the massive amount of work needed to retool Chicago's sanitary and storm water sewer systems.

But maybe that's a good thing for Chicago and those communities that now lie downstream from the city. Forcing the city to properly treat its wastewater and creating a physical barrier to invasive species are both worthy goals. And unless someone finds a better and cheaper way to deal with those issues, closing the canal remains the best answer.

-- The Milwaukee Journal Sentinel