As required by federal law, the U.S. Army Corps of Engineers (Corps) has provided Congress and the public with its Great Lakes and Mississippi River Interbasin Study (GLMRIS), which provides alternatives and costs to prevent aquatic nuisance species (ANS) from moving between those water systems.

As a result of international commerce, travel, and local practices, ANS have been introduced throughout the Mississippi River and Great Lakes basins. These two basins are connected by man-made channels that, in the past, exhibited poor water quality, which was an impediment to the transfer of organisms between the basins. Now that water quality has improved, these canals allow the transfer of both indigenous and nonindigenous invasive species. ANS can put natural ecosystems and threatened and endangered species at risk and impair commercial and recreational fisheries and recreational uses of the lakes and waterways. 

Chicago area waterway

The GLMRIS focuses on the Chicago Area Waterway System (CAWS), a complex, multiuse waterway that is the primary direct, continuous interbasin connection between the Mississippi River Basin and Lake Michigan.  The report provides eight alternatives to control the transfer of ANS, ranging from continuing current efforts to hydrologic separation using physical barriers.  Each alternative is accompanied by a concept-level design and cost information at the 5 percent design level.  While the GLMRIS Report does not recommend a specific plan, the Corps provides an evaluation matrix of the alternatives to provide decision makers with as much detail as possible. 

Alternatives

The following alternatives are presented in the report:

1. Continuing current efforts (i.e., electric barriers) with no new federal action;
2. Nonstructural control technologies (i.e., education, monitoring, herbicides, ballast water management);
3. A technology concept involving a specialized lock, lock channel, electric barriers, and ANS treatment plants at two mid-system locations in the CAWS;
4. A technology concept (CAWS buffer zone) using the same technologies as number 3, preventing downstream passage from Lake Michigan at five points and preventing upstream passage at a single point at Brandon Road Lock and Dam;
5. Lakefront hydrologic separation with physical barriers separating the basins at four locations along the lakefront of Lake Michigan;
6. Mid-system hydrologic separation with physical barriers separating the basins at two mid-system locations;
7. A hybrid of technology and physical barriers at four mid-system locations, leaving the Cal-Sag channel open; and
8. A hybrid of technology and physical barriers at four mid-system locations, leaving the Chicago Sanitary and Ship Canal open.

Next steps

According to the Corps, several actions need to be completed before the recommendation of any specific alternative for implementation, including further site-specific design analyses, model certification, detailed evaluations of impacts and mitigation requirements, completion of an environmental impact statement under the National Environmental Policy Act, and submission of the report for independent external peer review.

GLMRIS report