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Morganza to the Gulf of Mexico Project

Official Project Name
Morganza to the Gulf of Mexico Project

Location
The proposed work is located in coastal Louisiana approximately 60 miles southwest of New Orleans and includes portions of Terrebonne and Lafourche Parishes. The authorized project area is bounded on the west by Bayou Du Large and State Highway 311 and on the east by Bayou Lafourche with the east and west boundaries forming an apex at Thibodaux, LA. The recommended plan described in the January 2013 Post Authorization Change Report consists of 98 miles of grass-covered earthen levees tying into US 90 near the town of Gibson to the west and Hwy 1 near Lockport, LA to the east. The southern boundary is the Gulf of Mexico.

Purpose
This project aims to protect people and property as well as the remaining fragile marsh from hurricane storm surge in the vicinity of Houma, Louisiana. The area has been affected by an extreme deterioration of coastal marshes as a result of saltwater intrusion, land subsidence and the lack of sediment deposits from the Mississippi River and its tributaries. This deterioration has led to increased hurricane and storm surge inundation. The area is also significantly affected by tides emanating from the Gulf of Mexico.

Status

Morganza to the Gulf of Mexico, Louisiana was authorized in the Water Resources Development Act (WRDA) of 2007, based on a feasibility report submitted in 2002, prior to development and implementation of post-Katrina design criteria. In the interest of public safety, and to be consistent with the design policy established for the Greater New Orleans area, the Corps has now incorporated lessons learned from Hurricanes Katrina and Rita into the designs for Morganza to the Gulf.

The need to incorporate post-Katrina design criteria into the Morganza project has driven project costs more than 20% higher than the cost authorized in WRDA 07, thereby exceeding the Section 902 Limit (WRDA 1986) and triggering the need for reauthorization. A Post Authorization Change (PAC) Report is being developed to seek reauthorization. The PAC report includes feasibility-level designs incorporating the post-Katrina criteria, new project costs and updated economic benefits.

The revised, post-Katrina hydraulic modeling method yields significantly higher storm surge elevations, so higher levees are required to reduce risk. Overall, the levee elevations for the 100-year alternative have increased by an average of 10 feet from the 2002 Feasibility Report to the 2013 PAC report. In accordance with the recommendations of the Interagency Performance Evaluation Task Force (IPET), the robust post-Katrina design criteria requires higher factors of safety, more stringent criteria for levee fill and improved guidelines for soil testing, all contributing to higher project costs.

The draft PAC Report and corresponding Environmental Impact Statement are currently available for public review. The final PAC Report is on schedule to be complete later in 2013.

Interim Features constructed by state and local authorities: Levee Reach J-1, First Lift; Levee Reaches H-2 and H-3, First Lift; Interim Barge Gate on Placid Canal; Interim Barge Gate on Bush Canal

Interim Features under construction by state and local authorities: Interim Barge Gate on Houma Navigation Canal (HNC); Interim Barge Gate on Bayou Grand Caillou; Levee Reach F, First Lift.

Benefit to the Community & Project Features

Benefit to the Community
There is currently no federal hurricane protection in place in this region. This project affects the safety of more than 150,000 people and 1,700 square miles of farmlands, and industrial and residential areas.

Features
The project’s structural features are integrated into the levee alignment in a way that would provide flood protection, drainage, environmental benefits, and navigational passage. The plan includes mitigation efforts for direct environmental impacts.

The recommended plan in the PAC report consists of:
•approximately 98-miles of earthen levee,
•22 floodgates on navigable waterways,
•23 environmental water control structures, and
•a lock complex consisting of a lock in the Houma Navigation Canal measuring 110-ft wide by 800-ft long, an adjoining floodgate measuring 250 feet wide, and a dam closure.
 

Authority

Water Resources Development Act of 2007

Scope

No Information at this time.