Old River Low Sill Control Structure Dewatering Contract Awarded To McMillen Inc.

The New Orleans Engineer District awarded a $34.2 million contract to McMillen Inc., Boise, Idaho, on August 31 for construction of a steel system to allow dewatering of the Old River Low Sill Control Structure.

The Corps is scheduled to dewater the Old River Low Sill Control Structure in late summer and fall of 2024, when the river is traditionally at low water stages. The purpose is to inspect submerged project features, conduct subsurface investigations of the foundation material and undertake any needed rehabilitation or maintenance work. It will be the first dewatering of the structure since repairs and modifications were undertaken in 1987.

‘Critical Infrastructure’

“By keeping the Mississippi and Atchafalaya rivers on their current courses, the Old River Control Complex infrastructure is critical to both the region and the nation,” said Col. Cullen Jones, commander to the New Orleans District.  “This effort to inspect and repair the Low Sill Structure will help ensure the integrity and successful operation of the complex for years to come.”

The Old River Control Complex, located in Concordia Parish, La., is operated daily to maintain a 70/30 distribution of flows between the Mississippi, Red and Atchafalaya rivers and prevent the Mississippi River from changing course to that of the Atchafalaya River. The Old River Control Complex consists of the Low Sill, Overbank and Auxiliary Control Structures. During the 1973 flood, the Old River Low Sill Control Structure was severely damaged when a large scour hole formed on the upstream approach and beneath the gated portion of the structure. Emergency repairs during the flood prevented the structure from collapsing.