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Mississippi River Sediment Diversions

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Overview

The impacts of coastal land loss threaten Louisiana’s economy, commerce, infrastructure, and culture. Furthermore, the collapse of coastal Louisiana would negatively impact the entire country – we provide protection for infrastructure that supplies 90% of the nation’s outer continental oil and gas, 20% of the nation’s annual waterborne commerce, 26% (by weight) of the continental U.S. commercial fisheries landings, and winter habitat for five million migratory waterfowl.

The Barataria and Breton Basins are two areas that have experienced significant land loss due to sediment deprivation, hydrologic alteration, subsidence, sea level rise, and salt water intrusion. Since the Mississippi River was leveed in the 1930s, the Barataria and Breton Basins and Mississippi River Delta have lost approximately 700 square miles (or 447,000 acres) of land, representing one of the highest land loss rates in the world.

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The 2012 Coastal Master Plan called for eight sediment diversions along the Mississippi River. Over the past several years, CPRA has conducted in-depth analyses on the Lower Breton  50,000 cfs), Lower Barataria (50,000 cfs), Mid-Breton (35,000 cfs), and Mid-Barataria (50,000 cfs) diversion projects in order to determine which projects should be prioritized for engineering and design and construction. Each project was modeled to predict project effects on variables, such as land building, salinity, sediment transport, nutrients, and water levels. As part of this analysis, the state also considered innovative marsh creation projects that could be implemented in conjunction with sediment diversion projects in order to enhance sediment capture and build more land. This modeling effort helped inform CPRA’s decision in fall 2015 to recommend that the Mid-Breton and Mid-Barataria diversions move forward to preliminary engineering and design. Over the next several years, CPRA will work to optimize operations, formulate the final project design, and apply for appropriate construction permits in order to construct these foundational projects for the coastal master plan. At the same time, planning efforts will continue to evaluate additional diversions.

About Sediment Diversions

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To address the root of the problem, it is important to “reconnect the river” and restore the natural processes that initially built the delta. Controlled sediment diversions offer a unique opportunity to strategically reestablish hydrologic flows, carry land-building sediments, nourish marshes, and sustain land. When utilized along with marsh creation and the full suite of protection and restoration projects, this integrated systems approach can combat the grave land loss that threatens our coast.

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The concept of river diversions is not a new one. We have several other river diversions constructed and operated throughout the state. Caernarvon and Davis Pond were designed and constructed to control salt water intrusion by delivering freshwater into the estuaries. In addition, the Morganza and Bonnet Carre spillways have been built to provide a relief valve to the Mississippi River levees during river flooding events.

While freshwater diversions were not designed to build or maintain land, land growth has occurred at several of these sites. The images below show land growth over time at the outfall areas of Davis Pond and Wax Lake.

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The Mid-Barataria and Mid-Breton diversions will be different. Their primary objective will be to capture and divert sediment from the river and deposit it into the basins to build and maintain land.

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Project Benefits

As outlined in the Coastal Master Plan, CPRA believes our state needs a holistic approach to coastal restoration and protection. In fact, since 2008, CPRA has dredged nearly 30 million cubic yards from Mississippi River borrow sites. This work has created, restored, and nourished nearly 4,000 acres of marsh, barrier island, and ridge habitat utilizing riverine sediment. Additionally, over the next 15 years, CPRA plans to dredge as much as 55-65 million cubic yards.

While dredging provides critically needed short-term benefits, it doesn’t address the root cause or solve our fundamental issue of implementing projects that provide a sustainable and continuous source of new sediment. However, our latest research shows that when implemented together, marsh creation and sediment diversion projects perform better together and for a longer period than they do as individual projects.

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Sediment diversions will complement these restoration projects. The latest estimates show that, on average, the sediment diversion will deliver between 2-3 million cubic yards of sediment a year.

Funding

In early 2013, a U.S. District Court approved two plea agreements resolving certain criminal cases against BP and Transocean which arose from the 2010 Deepwater Horizon explosion and oil spill. The agreements direct a total of $2.544 billion to the National Fish and Wildlife Foundation (NFWF) to fund projects benefiting the natural resources of the Gulf Coast that were impacted by the spill. In Louisiana, this settlement mandated that these funds be dedicated to to “create or restore barrier islands off the coast of Louisiana and/or to implement river diversion projects on the Mississippi and/or Atchafalaya Rivers for the purpose of creating, preserving and restoring coastal habitat”.

Next Steps

Environmental Permitting

The National Environmental Policy Act (NEPA) requires federal agencies to integrate environmental values into their decision-making processes by considering the environmental impacts of their proposed actions and reasonable alternatives to those actions.

An Environmental Impact Statement (EIS) is a detailed analysis that serves to ensure that the policies and goals defined in NEPA are infused into the ongoing programs and actions of the federal agency involved in the project.

The EIS for Mid-Barataria is currently underway. In June 2016 CPRA submitted an updated permit application to the New Orleans District of the U.S. Army Corps of Engineers. In January 2017, CPRA selected Gulf Engineers and Consultants (GEC) as the third-party contractor to lead the EIS. Throughout 2017, GEC will engage the public, other federal agencies, and outside parties to provide input into the preparation of an EIS and comment on the draft EIS when it is completed. The EIS will provide a discussion of significant environmental impacts and reasonable alternatives (including a No Action alternative) which would avoid or minimize adverse impacts or enhance the quality of the human environment.

The EIS process for the Mid-Breton Sediment Diversion project is anticipated to begin in 2018.

Engineering and Design

Over the next several years, CPRA will work to optimize operations, formulate the final project design, and apply for appropriate construction permits in order to construct these foundational projects for the coastal master plan. At the same time, planning efforts will continue to evaluate additional diversions.

In anticipation for the engineering and design solicitation for the Mid-Barataria Sediment Diversion, CPRA is posting all relevant documentation online.  Visit this page to see existing design documents and plans for the future.

Timeline

Both projects will undergo a detailed permitting process and be designed and constructed to high standards with oversight from the Army Corps of Engineers to ensure a safe and dependable facility.

The Mid-Barataria project is several years ahead of the Mid-Breton project. For Mid-Barataria, the current schedule has the project design completed and permitted in 2020. Construction would start soon after and is expected to take between two and four years. The EIS process for Mid-Breton will likely start sometime in 2018 and construction is not anticipated to begin until 2022.

Mid-Barataria Summary Schedule

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Mid-Breton Summary Schedule

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Get Involved

To read more about this program, check out these resources:

CPRA is committed to providing numerous opportunities for public engagement:

  • Attend a Coastal Connections event to visit with CPRA Staff Members and receive relevant program updates. For a schedule of upcoming Coastal Connections, please visit http://coastal.la.gov/calendar/
  • Attend a CPRA Board Meeting to engage with CPRA leadership (schedule can be found at la.gov/calendar)
  • Email us at coastal@la.gov to request a meeting
  • Follow CPRA on Social Media for relevant updates