The U.S. Army Corps of Engineers (USACE) has awarded an Emergency Sole Source Procurement cutterhead dredge rental contract to Weeks Marine to construct a sill across the bottom of the Mississippi River Ship Channel to block the saltwater wedge to protect the fresh water intakes for the City of New Orleans. The details are limited but the scope of work is expected to include building a sill (think levee on bottom of the channel) at approximately Mile 64 Above Head of Passes. The low water sill was last built in 2012 and is a mitigation feature of deepening the channel originally from 40 feet to 45 feet which in essence carried over to the newly deepened 50 foot channel.
There are limited details available at this time but the sill construction is expected to start with building the sill to an elevation of – 55 feet, meaning there would be 55 feet of water over the top of the sill. The tentative plans expressed building the sill to – 55 feet and then to measure the sill’s impact on the salt water wedge to determine if the sill elevation needs to be built higher. The sill can be built from a -55 feet to a -45 feet, hopefully the sill will not require draft restrictions but they will remain a possibility especially if the sill has to be constructed higher than a -55 feet.
Please accept this update and know that more details are forthcoming, the USACE is working on a lot of projects but the construction of the sill is a true emergency response and needed effort.
The following was shared by the USACE this morning:
*****SALTWATER WEDGE INFORMATION******
- SALTWATER SILL CONTRACT: A Saltwater Sill construction contract was awarded to Weeks Marine on October 3, 2022 through an emergency sole source procurement. The bid opening for Solicitation No. W912P821B0055 has been canceled.
- SALTWATER WEDGE: As of September 30, 2022, the current estimated location of the toe of the saltwater wedge is RM 47.6 AHP.
Saltwater Wedge Information Link: https://www.mvn.usace.army.mil/Missions/Engineering/Stage-and-Hydrologic-Data/SaltwaterWedge/SaltwaterWedgeNow/
The flow in the Mississippi River remains extremely low with the flow today at Red River Landing (Mile AHP) reduced to 147,000 cubic feet per second, additional precipitation across the Mississippi River Basin would be helpful but the long range forecast do not predict a significant rise but are weather-based subject to change. The undersigned will continue to issue updates and request increased(specialized) stage level updates from the National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service (NWS) Lower Mississippi River Forecast Center along with the expected updates from the USACE and Weeks Marine.