Beneficial Use of Mississippi River Navigation Dredged Material

摘要

In August of 2014, Plaquemines Parish Government (PPG), Louisiana entered into an agreement as local sponsor with the United States Army Corps of Engineers (USACE) to beneficially use material dredged from the Lower Mississippi River to restore wetlands and reduce land loss. The agreement is part of the Louisiana Coastal Area (LCA) Program and is for a 10-year period with an average of $10M per year for a total of $100M. The goal is to use dredged material from the federal navigation channel to create marsh and marsh features in the wetlands and bays adjacent to the Mississippi River to help restoration efforts. Planning, engineering, design, hydrodynamic modelling, alternatives assessment, environmental assessment and construction for the first project has been completed in West Bay. The material placement objective was not merely to create wetlands but to develop a feature that would enhance the marsh and submerged aquatic vegetation (SAV) currently being created within the bay and the West Bay Diversion. Several disposal feature geometries were evaluated to optimize placement for enhanced outfall sedimentation of the West Bay Diversion through Delft 3D modelling. Additionally, a cost/benefit analysis of not only direct acreage created, but also acreage anticipated to be created from the diversion enhancement were considered. The second proposed project of the program is the beneficial use of dredged material in the vicinity of Tiger Pass. Alternatives being assessed include bird islands and ridge features to aid in marsh creation and storm protection. These activities represent the first beneficial use projects under the LCA program and aim to extend the beneficial use of navigation dredged material farther into the wetlands to placements areas that not only create marsh from the placement directly but help marsh restoration and retention in the surrounding area.