Options offered for closing Mississippi River outlet

In a Congressionally mandated interim report released in mid-December 2006, the U.S. Army Corps of Engineers (USACE) outlined the following three options for de-authorizing deep-draft navigation on the Mississippi River-Gulf Outlet (MRGO) from the Gulf Intracoastal Waterway to the Gulf of Mexico:

• maintain a shallow-draft MRGO navigation channel, 12 feet deep by 125 feet wide;
• close the MRGO to deep- and shallow-draft vessels by constructing an armored earthen dam across the channel near Hopedale, La.; or
• cease all MRGO operations and maintenance activities and remove navigation aids such as buoys, lights, and offshore jetties.

The MRGO is a 36-foot-deep, 500-foot-wide (bottom width) waterway that allows deep-draft access to New Orleans-area port facilities via a route shorter than using the Mississippi River. Construction of the channel began in 1958 and was completed in 1968. The USACE concluded in its interim report that the most viable option is closure of the MRGO to both deep- and shallow-draft navigation. Average annual operations and maintenance costs to dredge the MRGO deep-draft channel are $12.5 million, but the channel only produces an estimated $6.2 million per year in transportation efficiencies.

Additionally, a link has been suggested between the MRGO and Hurricane Katrina’s devastating storm surge. However, the USACE said that engineering and hydraulic modeling studies concluded that "the inland reach of the MRGO does not contribute significantly to peak storm surge during severe storms because the surrounding wetlands are overwhelmed with water. … The most noticeable effect of the MRGO occurs for small surge events where the surrounding marsh areas are not completely inundated."

Nevertheless, the USACE recommends linking plans for de-authorization of the MRGO into Louisiana Coastal Protection and Restoration (LACPR) efforts. "A number of activities in the vicinity of the MRGO are pertinent to future plans for the channel," the USACE says in its interim report. "These activities involve coastal restoration, levee repairs and upgrades, navigation infrastructure maintenance and replacement, and flood control. A systems analysis offers the best evaluation approach for determining the complex interactions of these activities."

Download the USACE’s complete Mississippi River Gulf Outlet Deep-Draft De-authorization Interim Report . The final MRGO de-authorization plan will be included in the final LACPR report in December 2007.