Construction of a Deep Cutoff Wall along the Mississippi River at East Alton, IL

The confluence of the Wood River and the Mississippi River, in East Alton, Illinois, has been plagued with seepage under Lower Wood River Levee to the point that remediation was needed. The Southwestern Illinois Flood Prevention District Council enlisted experts to evaluate, design and construct under-seepage controls. The selected design required the construction of a cement-bentonite cutoff wall, 140 feet deep, excavated through alluvial and outwash soils and embedded in bedrock. The unique aspect of this project was that the cutoff wall was installed using a hydromill cutter under self hardening slurry (SHS), to a depth that had not been reached using this method in past cutoff walls constructed in the United States. The quality control/quality assurance (QC/QA) testing was comprehensive throughout the entire process. This paper will give an overview of the project and a summary of the test results.