A new study shows that physically blocking the Chicago Area Water System—the man-made connection between the Mississippi River basin and the Great Lakes—is a feasible solution to prevent Asian carp from infiltrating into Lake Michigan. But a long-term solution is years off and could cost billions. Meanwhile, the invasive species edges ever closer to Lake Michigan.

The $1-million study—commissioned by the Great Lakes Commission and the Great Lakes and St. Lawrence Cities Initiative and conducted by Omaha-based HDR—presented three options for separating the Great Lakes from the Mississippi River via the Chicago Area Waterway System (CAWS). Costs range from $3.3 billion to $9.5 billion. Any of the three options would create a huge civil-works construction project, officials say. But those same officials say the projects would not break ground for at least 10 years and not be complete until 2029.

CAWS, which includes approximately 130 miles of natural and constructed rivers, canals, locks and other structures in Chicago and northwest Indiana, was built in the early 1900s as a response to a public health crisis caused by untreated sewage flowing from the Chicago River into Lake Michigan. Engineers built a system of canals and locks to reverse the river's flow. Water diverted from Lake Michigan created a connection to the Mississippi watershed. There are currently five entry points between the CAWS and Lake Michigan, and the system has become a route for commercial shipping and recreational boating.

What seemed to be a good idea at the time is now proving problematic: Asian carp are steadily migrating up the Mississippi toward Lake Michigan using the CAWS as an entry point. Experts say that if the carp infiltrate the Great Lakes, they would flourish at the expense of other aquatic life. Currently, the fish are being held at bay through a system of electric barriers operated by the U.S. Army Corps of Engineers, but those barriers are at best a temporary fix, officials say.

The three options outlined in the HDR study, released on Jan. 31, vary in terms of cost and complexity. For example, barriers could include sheet piling or impermeable land bridges without cargo or recreational-boat transfer capability or barriers with intermodal cargo transfer facilities and boat lifts. However, the cost of the barriers for each option represents about only 3% of the total cost. Other costs include wastewater treatment plant upgrades and flood-control work as well as alternative routes and options for shipping and recreational boating.

Duane Gapinski, HDR's vice president and federal program director, east, says his firm looked at numerous locations in the water system and finally narrowed down the separation points to the three that "encompassed a wide range of challenges and opportunities." He adds, "The point of the report is not to make a recommendation but just to do some analysis [on] impacts of physical separation."

The so-called Mid-System Alternative—the least costly, with a price tag of between $3.3 billion and $4.3 billion— would construct four barriers but poses fewer challenges in terms of wastewater treatment plant upgrades, flood management and transportation issues than the other options. "Although we have not recommended or identified a preferred alterative, this is the one at this stage of the process that seems the most viable," says David Ullrich, executive director of the Great Lakes and St. Lawrence Cities Initiative.

The Corps is conducting its own study, looking at options beyond physical separation, says Gary O'Keefe, program manager for the "Great Lakes and Mississippi River Interbasin Study." After taking public comments, O'Keefe says, the Corps will evaluate some of the most promising controls. Deciding on the best solution could take years, O'Keefe notes.

A bipartisan group of 31 U.S. lawmakers in a Feb. 3 letter encouraged Jo-Ellen Darcy, assistant secretary of the Army, civil works, to consider incorporating information from the HDR study into the interbasin study "to shorten [the] time frame" for completion.