Officials Make Step Towards Reducing Flood Risk in Metro East (USA)
Federal and local partners took a significant step towards reducing flood risk to the Metro East.
Representatives from the U.S. Army Corps of Engineers St. Louis District, the Metro East Sanitary District and the Southwestern Illinois Flood Prevention District Council signed a project partnership agreement to address underseepage in the East St. Louis levee system.
The agreement allows the Corps and local sponsors to partner on the construction of levee features that will reduce and control underseepage during floods.
The partnership will also share funding, with the federal government contributing 65 percent of the cost and local sponsors contributing the remaining 35 percent.
“The Corps of Engineers and our partners are committed to preserving and enhancing public safety,” said Col. Chris Hall, St. Louis District commander.
“Critical systems like the East St. Louis levee system need rehabilitation to ensure they are providing the appropriate levels of protection to those that live and work behind them.”
The East St. Louis levee system is located in St. Clair and Madison Counties, Ill., and protects many communities including Edwardsville, Granite City, Pontoon Beach, East St. Louis and Cahokia.
The system is comprised of 28.6 miles of flood protection, including nine miles of levee operated and maintained by the Corps of Engineers along the Chain of Rocks canal.
The system protects more than 86,000 acres of commercial, industrial and residential properties.
The East St. Louis levee is part of the larger Metro East levee system.
Combined, these levees protect approximately 288,000 residents and critical infrastructure valued in excess of 4.8 billion.
The partnership agreement follows reconstruction work that brought together more than $60 million invested by local and federal partners.
The work primarily addressed the system’s above-ground features, including levees and floodwalls, drainage structures, pumping stations, bridges and closure structures.
The work covered by the partnership agreement will combine above and below-ground features to address the greatest risk to the levee, underseepage.
The Metro East levees were built on floodplain soils that consist of clays and silts, typically 10-feet deep.
Below the clays and silts there are about 70 to 100-feet of sand.
That layer of sand in the levee’s foundation allows ground water to flow underneath the levee.
The higher the river level, the more pressure is exerted on the groundwater in the sand. As the pressure builds, it will push water through weaknesses in the clay up to the surface (underseepage).
When the silts and clays travel to the surface in the water, a sandboil forms. As materials are carried to the surface, sandboils make the levee’s foundation unstable.
Press Release, March 11, 2014