Installation of a Cutoff Wall Along the Mississippi River

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The East St. Louis Deep Cutoff Wall project rehabilitated a Mississippi River levee protecting approximately 250,000 people and more than $4.5 billion in economic assets. USACE designed a 1,341 m (4,400 ft) seepage barrier through deep alluvial soils, with a maximum depth of 43 m (142 ft) and a minimum 0.6 m (2 ft) key into limestone.<br /><br />The main barrier comprised 610 mm (24 in) thick, single-phase panels excavated under self-hardening slurry. Because two essential utilities could not be moved or taken out of service, the team added cutoff sections around them and installed two-row jet-grout curtains beneath them. The project included a test section and extensive quality control: slurry and grout testing, measurements of panel and column geometry, wet-grab sampling, verification coring, and pump tests.<br /><br />Construction faced difficult ground conditions, including highly permeable gravel, very strong bedrock, and concerns about trench stability. Other complications included restricted access near power lines and at low river levels, the COVID-19 pandemic, and a cutter that became trapped at approximately 43 m depth and took 17 days to recover. Continuous monitoring and emergency planning helped address safety risks.<br /><br />The team installed 265 cutoff-wall panels, along with 167 jet-grout columns. Testing showed the wall and grout curtains met or exceeded specified requirements for strength, permeability, thickness, and continuity. No main-wall panels required remedial work. Pump tests and verification borings confirmed the performance of the utility-crossing barriers. The project’s completion demonstrated how close coordination between USACE and the contractor enabled a technically demanding flood-protection improvement despite substantial construction and logistical challenges.

Keywords

East St. Louis

Deep Cutoff Wall

Mississippi River levee

USACE

seepage barrier

jet grout curtain

flood protection

alluvial soils

quality control

utility crossings