December 2006 US Army Corps 

of Engineers 

MISSISSIPPI RIVER GULF OUTLET 

Deep-Draft De-Authorization 

Interim Report to Congress 
i 

EXECUTIVE SUMMARY 

Congressional Direction and Purpose

This interim report to Congress is prepared to aid in identifying a comprehensive plan for 

de-authorizing deep-draft navigation on the Mississippi River-Gulf Outlet (MRGO) from 

the Gulf Intracoastal Waterway (GIWW) to the Gulf of Mexico. The interim report 

offers a general analysis of local conditions, presents options for a plan to de-authorize 

the MRGO channel for deep-draft navigation, and provides a foundation for any required 

additional detailed analysis. This interim report does not contain a final recommendation 

for construction but does evaluate the feasibility of integrating each of the options 

presented under the Louisiana Coastal Protection and Restoration (LACPR) efforts. 

While the December 2007 LACPR report will include a final detailed plan, based on the 

current level of analysis, it appears that full integration into LACPR could be best 

achieved by closing the MRGO to both deep and shallow-draft navigation via an armored 

earthen dam in the vicinity of Hopedale, Louisiana.

Public Law 109-234, the Emergency Supplemental Appropriations Act for Defense, the 

Global War on Terror, and Hurricane Recovery, 2006, reads in part: 

“...the Secretary of the Army, acting through the Chief of Engineers, 

utilizing $3,300,000 of the funds provided herein shall develop a 

comprehensive plan, at full Federal expense, to de-authorize deep-draft 

navigation on the Mississippi River-Gulf Outlet, Louisiana, extending 

from the Gulf of Mexico to the Gulf Intracoastal Waterway: Provided 

further, That, not later than 6 months after the date of enactment of this 

Act, the Secretary shall submit an interim report to Congress comprising 

the plan: Provided further, That the Secretary shall refine the plan, if 

necessary, to be fully consistent, integrated, and included in the final 

report to be issued in December 2007 for the Louisiana Coastal 

Protection and Restoration Plan.” 

A manager’s statement accompanying the legislative language accepted in the 

Congressional Conference Committee report further directs that: 

“The plan shall include recommended modifications to the existing authorized 

current use of the Outlet, including what navigation functions, if any, should be 

maintained and any measures for hurricane and storm protection. The plan shall 

be developed in consultation with St. Bernard Parish, the State of Louisiana, and 

affected Federal Agencies.”
ii 

Background

In 1948, Governor Davis of Louisiana wrote in support of the development of the MRGO 

as follows: 

“Reference is made to the review of reports on the Mississippi River-Gulf and 

Mobile to New Orleans Intracoastal Waterway as proposed by the Chief of 

Engineers, United States Army. I am familiar with the provisions of this proposed 

report and thoroughly concur in the views and recommendations expressed 

therein. The project recommended will be of inestimable benefit to the State of 

Louisiana and to the Nation. A tidewater channel to the sea will permit rapid 

development of sorely needed additional port facilities by the Board of 

Commissioners, Port of New Orleans, and will provide great additional benefits 

to the port. Support of the State of Louisiana for a tidewater canal from New 

Orleans to the Gulf on the eastern side of the Mississippi River is well shown by 

Concurrent Resolution No. 18 of the Louisiana Legislature of 1944, in which it 

was resolved that the Governor of Louisiana be specifically empowered to aid 

and assist the Federal Government in obtaining and completing such a project.”

The MRGO is a Federally-authorized 36-foot deep, 500-foot bottom width waterway 

which allows deep-draft access to New Orleans area port facilities via a shorter route than 

using the Mississippi River. Congress authorized MRGO channel construction in the 

River and Harbor Act of 1956. Public Law 84-445, 70 Stat. 65 states: 

“Be it enacted by the Senate and House of Representatives of the United States of 

America Congress assembled, that the existing project for the Mississippi River, 

Baton Rouge to the Gulf of Mexico, is hereby modified to provide for the 

Mississippi River-Gulf outlet to be constructed under the direction of the 

Secretary of the Army and supervision of the Chief of Engineers, substantially in 

accordance with the recommendation of the Chief of Engineers contained in 

House Document 245, Eighty-Second Congress, at an estimated cost of 

$88,000,000...” 

The MRGO extends from the Inner Harbor Navigation Canal (IHNC) to the 38-foot 

depth contour of the Gulf of Mexico. Construction of the channel began in 1958 and was 

completed in 1968. The channel was built across shallow bays and coastal marshes along 

the southern rim of Lake Borgne and through open water in Breton and Chandeleur 

Sounds. 

In a June 2006 letter to Major General Riley, Director of Civil Works, Governor Blanco 

of Louisiana requested a “plan for closure, restoration of the extensive wetlands lost as a 

direct result of the MRGO, and the integration of this closure into the comprehensive 

hurricane protection plan.” The Governor’s letter was provided during the development 

of the LACPR Preliminary Technical Report but is relevant in stating the position of the 

State of Louisiana regarding planning in this study. 
iii 

Collaborative Planning Approach 

In response to Congressional direction to develop a MRGO de-authorization plan, the 

U.S. Army Corps of Engineers (USACE) established a plan of action for developing this 

interim report. Federal, State and local government parties and other organizations were 

invited to assist in preparation of the report. Invited stakeholder participants included: 

• St. Bernard Parish 

• Governor’s Office of Coastal Activities 

• Louisiana Department of Natural Resources 

• Louisiana Department of Transportation and Development 

• State and Federal Resource Agencies 

• Port of New Orleans 

• Gulf Intracoastal Canal Association 

• Lake Pontchartrain Basin Foundation 

• Coalition to Restore Coastal Louisiana 

• Biloxi Marshlands Corporation 

• Steamship Association of Louisiana 

• Bring New Orleans Back Commission 

• New Orleans Business Council 

• LSU Hurricane Center 

• National Aeronautic and Space Administration 

• Businesses 

• Private citizens 

A series of public stakeholder forums were held to identify various plans and proposals 

for the future of the MRGO. Meetings included technical presentations and open 

discussions on topics including wetlands, navigation, storm protection, and the local 

economy. Each stakeholder group was invited to make detailed presentations on their 

plans. In addition to holding regular stakeholder forums and opening an official public 

comment period for the interim report, an independent team of technical experts was 

chartered to review the report. 

Additional measures to incorporate public input included an internet web page 

(http://www.swg.usace.army.mil/mrgo/) and hosting of a large public meeting. The 

project web page offered interactive capability allowing visitors to submit information 

and opinions via email. A public meeting was held on a weekend and involved an open 

house where stakeholder groups were offered display space to present their points of 

view. The public meeting included a formal presentation of the study process and 

preliminary results from the USACE and an open comment period for public statements 

from citizens, organizations, and elected officials. Over 150 people attended the meeting. 

The collaborative planning effort attempted to identify a consensus plan for deauthorizing the channel but in the end resulted in only identifying common measures or 

features supported by many stakeholders. 
iv 

Development of Options and Opportunities

This report provides a qualitative analysis based on coordination with the State of 

Louisiana, St. Bernard Parish Government, stakeholders, resource agencies and the 

general public. Studies related to navigation, ecosystem restoration and storm damage 

prevention for the area have been conducted by Federal and non-Federal agencies over 

many years. This interim report builds upon past analyses and identifies some of the 

general considerations associated with MRGO deep-draft de-authorization options. For 

this report, the USACE defines deep-draft as vessels requiring depths greater than 14 

feet. Compliance with the National Environmental Policy Act (NEPA) for any deep-draft 

de-authorization option or opportunities selected as a recommended alternative will be 

done through incorporation of that alternative into the Programmatic Environmental 

Impact Statement accompanying the December 2007 LACPR Final Technical Report. 

A USACE technical team evaluated potential modifications to the current uses of the 

navigation channel with the intent of determining if any uses should be maintained. The 

evaluation included information presented in the stakeholder meetings, data gathered 

through a maritime business survey, and government statistics of annual channel 

utilization. Based on the process outlined above, several options were identified for 

development of the MRGO deep-draft de-authorization plan. These include: 

Option 1 – Maintain a shallow-draft MRGO navigation channel. Several variations 

of Option 1 would facilitate integration of the de-authorization plan into LACPR: 

• Option 1a – Maintain a shallow-draft navigation channel without a structure. 

• Option 1b – Construct a salinity control weir at Bayou La Loutre; 

• Option 1c – Construct a salinity control gate at Bayou La Loutre (normally 

closed); 

• Option 1d – Construct a storm protection gate at Bayou La Loutre (normally 

open). 

All of the shallow-draft channel options would include maintenance dredging of a 12 

feet deep by 125 feet wide channel to match the dimensions of the GIWW. 

Option 2 - Close the MRGO channel to deep-draft and shallow-draft vessels. Closure 

of the MRGO to all vessel traffic could be realized by blocking the channel via any of the 

following variations: 

• Option 2a – Construct an armored earthen dam across the MRGO at Bayou La 

Loutre; 

• Option 2b – Restore both banks of Bayou La Loutre across the MRGO at 

Hopedale, Louisiana; or 

• Option 2c – Fill in the entire MRGO channel from the GIWW to the Gulf of 

Mexico. 

Option 3 - Cease all MRGO operations and maintenance activities (dredging, jetty 

repairs, and navigation aids). If Congress chooses to discontinue all activities related 

to maintaining the MRGO, several relic project features would need to be addressed. 

These features include navigation aids such as buoys and lights and the offshore jetties 
v 

located in Breton and Chandeleur Sounds. Development of a complete de-authorization 

plan should include disposal of these relic features. 

Under LACPR and other independent authorities, opportunities for ecosystem restoration 

and hurricane storm surge risk reduction could complement the MRGO de-authorization 

options. These opportunities include: 

• Freshwater diversion into the MRGO and surrounding marshes (possibly in the 

vicinity of Violet Canal); 

• Shoreline protection to prevent wetlands erosion (including maintenance of 

existing projects); 

• Habitat creation through the placement of sediment for rebuilding marshes, 

barrier islands, and ridges; 

• Increase existing levee heights to new hurricane protection levels; and/or 

• New hurricane protection levee alignments or surge protection structures. 

Evaluation of Options and Opportunities

Although the primary purpose of this interim report is to identify measures that could be 

included in a plan to de-authorize deep-draft navigation on the MRGO, the report also 

documents the costs private businesses dependent upon deep-draft navigation might 

incur. All of the businesses that require the deep-draft access previously provided by the 

MRGO are located on the most inland portion of the channel that coincides with the 

GIWW. Businesses along the MRGO currently report experiencing inefficiencies due to 

the lack of deep-draft access to their facilities. 

Preliminary analysis of deep-draft navigation indicates that maintaining the authorized 

dimensions of the MRGO is not cost-effective. Average annual Operations and 

Maintenance (O&M) costs to dredge the MRGO deep-draft channel are $12.5 million. 

However, maintaining the authorized dimensions only produces approximately $6.2 

million per year in transportation efficiencies. 

 

The economic information available indicates that shallow-draft traffic on the MRGO is 

not cost-effective in terms of National Economic Development (NED). The total average 

annual costs for the various shallow-draft alternatives (including construction and 

maintenance dredging) range between approximately $6 million and $9 million. 

Estimated annual benefits associated with maintaining shallow-draft depths are 

approximately $3.7 million. 

This interim report discusses various options for shallow-draft navigation. The MRGO 

serves as an alternate route to the GIWW for inland barge traffic when the IHNC Lock is 

either impassable or congested. The 83-year old lock, which is the oldest in the system 

of locks on the GIWW, is well beyond its original design life of 50 years, increasing the 

likelihood of a catastrophic failure. Since 2001, there have been four lock through 

stoppages of greater than one-day with the longest being during Hurricane Katrina. 

Although construction activities have commenced on the new IHNC Lock, the 

advancement of the lock construction has been delayed, primarily due to funding 
vi 

provisions. A total navigation closure of the GIWW alternate route at MRGO could be of 

national significance due to the effect it would have on industries and national security. 

Without an alternate route, inland navigation would be affected for routine IHNC Lock 

closures as well as by a possible failure of the aging lock. One means of avoiding this 

effect would be a closure or modification sequencing plan for the MRGO. A sequenced 

approach to de-authorizing the MRGO would mitigate the risk to continued navigation on 

the GIWW. 

The relationship between the MRGO and hurricane storm surge has been the topic of 

study and debate before and after Hurricane Katrina. The hypothesized link between the 

channel and surge has received a great deal of media and public attention. A number of 

engineering and hydraulic modeling studies have evaluated these reported connections. 

These studies have reached similar conclusions 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. Studies also demonstrated that the 

most noticeable effect of the MRGO occurs for small surge events where the surrounding 

marsh areas are not completely inundated. These studies have implications for plan 

selection especially in regards to the intended purpose of features or their potential design 

performance during storm events. This reasoning highlights the need to integrate plans 

for the future of the MRGO into long-term plans currently under development in the 

LACPR. 

Linking plans for the de-authorization of the MRGO into the LACPR and other ongoing 

USACE and State of Louisiana work is important. A number of activities in the vicinity 

of the MRGO are pertinent to future plans for the channel. 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. This analysis may be 

especially important in sequencing the design and construction of interrelated projects 

such as levees, navigation features and coastal protection and restoration efforts. 

Interim Report Conclusions

Preliminary analysis indicates that it is not cost effective to maintain shallow-draft 

navigation on the channel between the GIWW and the Gulf of Mexico. Preliminary 

analysis of deep-draft navigation indicates that maintaining the authorized dimensions of 

the MRGO is not cost-effective. Based on this preliminary analysis, closure of the 

MRGO channel to both shallow and deep-draft navigation by an armored earthen dam 

just south of Bayou La Loutre near Hopedale, Louisiana appears to be particularly viable. 

Through incorporation into LACPR, additional measures to provide opportunities for 

hurricane storm surge protection and ecosystem restoration may complement MRGO 

channel closure, including wetland shoreline protection, freshwater diversion, and 

dedicated dredging for coastal habitat creation. These preliminary options will be further 

developed and coordinated for NEPA compliance through the LACPR final planning 

efforts. These measures have been supported by stakeholders and are consistent with 
vii 

most existing Federal and non-Federal plans for ecosystem restoration and hurricane risk 

reduction in the area. 

The LACPR Final Technical Report will provide the design of the closure of the MRGO 

by a structure in the area of the Bayou La Loutre Ridge as well as any other opportunities 

for hurricane storm damage protection and ecosystem restoration. Additionally, several 

major, ongoing efforts (navigable gates to protect the IHNC, emergency supplemental 

erosion protection along the MRGO, and the IHNC Lock replacement project) that 

address key aspects of the project are documented in this interim report. Completing a 

de-authorization plan includes full development and coordination of the MRGO closure 

project through LACPR. 
viii 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY ...........................................................................................................................I

INTRODUCTION AND BACKGROUND ................................................................................................ 1

CONGRESSIONAL DIRECTION...................................................................................................................... 1

BACKGROUND ON THE MRGO ................................................................................................................... 2

VESSEL UTILIZATION OF THE MRGO......................................................................................................... 4

FUTURE OPERATION AND MAINTENANCE OF THE MRGO.......................................................................... 5

RELATIONSHIP BETWEEN THE MRGO AND LEVEES................................................................................... 6

RELATIONSHIP BETWEEN IHNC LOCK AND MRGO .................................................................................. 6

RELATIONSHIP BETWEEN MRGO AND STORM SURGE ............................................................................... 7

PUBLIC VIEWS ON THE MRGO................................................................................................................... 9

RELATED AUTHORITIES AND PLANS........................................................................................................... 9

Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA), 1990.................................. 9

Coast 2050: Toward a Sustainable Coastal Louisiana, 1998............................................................... 9

Continuing Authorities Program ........................................................................................................ 10

Louisiana Coastal Area (LCA) Ecosystem Restoration Study, 2004 .................................................. 10

Louisiana Coastal Protection and Restoration, 2006......................................................................... 10

Emergency Supplemental Appropriations Act for Defense, the Global War on Terror, and Hurricane 

Recovery, 2006.................................................................................................................................... 11

CONDITIONS IN THE PONTCHARTRAIN BASIN............................................................................ 13

Historical Land/Habitat Conditions ................................................................................................... 13

Historical Salinity Conditions............................................................................................................. 14

PRESENT CONDITIONS .............................................................................................................................. 15

Present Navigation Conditions ........................................................................................................... 15

Present Land/Habitat Conditions ....................................................................................................... 16

PLAN FORMULATION ........................................................................................................................... 17

COLLABORATIVE PLANNING APPROACH .................................................................................................. 17

Stakeholder Meetings.......................................................................................................................... 17

State of Louisiana’s Comprehensive Coastal Protection Master Plan ............................................... 20

LOUISIANA COASTAL PROTECTION AND RESTORATION PLANNING.......................................................... 21

OPTIONS DEVELOPED ............................................................................................................................... 22

Additional Opportunities .................................................................................................................... 23

MRGO DEEP-DRAFT DE-AUTHORIZATION OPTIONS ................................................................. 24

OPTION 1A - MAINTAIN A SHALLOW-DRAFT MRGO NAVIGATION CHANNEL WITHOUT A STRUCTURE .. 24

Environmental Considerations ........................................................................................................... 24

Other Considerations.......................................................................................................................... 25

OPTION 1B – CONSTRUCT A SALINITY CONTROL WEIR AT BAYOU LA LOUTRE ....................................... 25

Environmental Considerations ........................................................................................................... 28

Other Considerations.......................................................................................................................... 28

OPTION 1C – CONSTRUCT A SALINITY CONTROL GATE AT BAYOU LA LOUTRE (NORMALLY CLOSED) ... 29

Environmental Considerations ........................................................................................................... 31

Other Considerations.......................................................................................................................... 31

OPTION 1D – CONSTRUCT A STORM PROTECTION GATE AT BAYOU LA LOUTRE (NORMALLY OPEN) ...... 31

Environmental Considerations ........................................................................................................... 32

Other Considerations.......................................................................................................................... 32

OPTION 2A – CONSTRUCT AN ARMORED EARTHEN DAM ACROSS THE MRGO AT BAYOU LA LOUTRE... 33

Environmental Considerations ........................................................................................................... 34

Other Considerations.......................................................................................................................... 34
ix 

OPTION 2B – RESTORE BOTH BANKS OF BAYOU LA LOUTRE ACROSS THE MRGO AT HOPEDALE,

LOUISIANA ............................................................................................................................................... 35

Environmental Considerations ........................................................................................................... 36

Other Considerations.......................................................................................................................... 36

OPTION 2C –FILL IN THE ENTIRE MRGO CHANNEL FROM THE GIWW TO THE GULF OF MEXICO ........... 36

Environmental Considerations ........................................................................................................... 36

Other Considerations.......................................................................................................................... 37

OPTION 3 - CEASE ALL MGRO OPERATIONS AND MAINTENANCE ACTIVITIES ........................................ 37

Environmental Considerations ........................................................................................................... 37

Other Considerations.......................................................................................................................... 37

OPPORTUNITIES FOR ECOSYSTEM RESTORATION AND STORM SURGE REDUCTION .. 38

FRESHWATER DIVERSION INTO MRGO AND SURROUNDING MARSHES ................................................... 38

Environmental Considerations ........................................................................................................... 39

Other Considerations.......................................................................................................................... 40

SHORELINE PROTECTION .......................................................................................................................... 40

Environmental Considerations ........................................................................................................... 41

Other Considerations.......................................................................................................................... 41

HABITAT CREATION BY SEDIMENT PLACEMENT ...................................................................................... 41

Environmental Considerations ........................................................................................................... 42

Other Considerations.......................................................................................................................... 42

INCREASE EXISTING HURRICANE PROTECTION LEVEE HEIGHTS TO NEW PROTECTION LEVELS .............. 42

Environmental Considerations ........................................................................................................... 42

Other Considerations.......................................................................................................................... 43

NEW HURRICANE PROTECTION LEVEE ALIGNMENTS AND SURGE PROTECTION STRUCTURES ................. 43

Environmental Considerations ........................................................................................................... 43

Other Considerations.......................................................................................................................... 43

MRGO AREA SYSTEMS EVALUATION ............................................................................................. 44

COMPARISON OF DEEP-DRAFT DE-AUTHORIZATION OPTIONS ................................................................. 44

ECONOMIC BENEFITS OF DEEP-DRAFT NAVIGATION................................................................................ 44

FINANCIAL ANALYSIS OF DEEP-DRAFT NAVIGATION............................................................................... 46

FINANCIAL ANALYSIS OF SHALLOW-DRAFT NAVIGATION ....................................................................... 47

ANALYSIS OF COMPATIBILITY BETWEEN OPTIONS AND OPPORTUNITIES ................................................. 48

RESULTS AND CONCLUSIONS OF INTERIM REPORT ................................................................. 50

PRELIMINARY COMPREHENSIVE PLAN FOR DE-AUTHORIZING THE MRGO ................... 51

LIST OF ACRONYMS.............................................................................................................................. 52
x 

 

LIST OF TABLES 

Table 1. Federal Investment in the MRGO........................................................................ 4 

Table 2. Transportation Commodities on the MRGO for 2002-2004. .............................. 4 

Table 3. Navigation on the MRGO (includes GIWW traffic). .......................................... 5 

Table 4. IHNC Lock Vessel Delay Periods 2000-2005..................................................... 7 

Table 5. Land Loss in Pontchartrain Basin: 1930s to 2001. ............................................ 13 

Table 6. Comparison of Monthly Summaries of Salinity: 1951-1963 and 1963-1977. .. 15 

Table 7. MRGO Dredging Areas and Estimated Date of First Required Dredging. ....... 24 

Table 8. Comparison of Modeled Salinity....................................................................... 28 

Table 9. Comparison of Deep-Draft De-Authorization Options. .................................... 45 

Table 10. Shallow-Draft Navigation for Different Options............................................. 47 

Table 11. Relationship Between Deep-Draft De-Authorization Options and LACPR. .. 49 

LIST OF FIGURES 

Figure 1. Mississippi River Gulf Outlet De-Authorization Plan Area............................... 2 

Figure 2. Hurricane Protection System for City of New Orleans...................................... 6 

Figure 3. Shoreline Protection Projects Funded by Supplemental Appropriations. ........ 12 

Figure 4. Area in the Vicinity of MRGO......................................................................... 21 

Figure 5. Proposed Construction Location of Option 1b................................................. 26 

Figure 6. Conceptual Plan for Proposed Option 1b. ........................................................ 27 

Figure 7. Conceptual Plan for Proposed Option 1c. ........................................................ 30 

Figure 8. Conceptual Plan for Proposed Option 1d. ........................................................ 32 

Figure 9. Conceptual Plan for Proposed Option 2. .......................................................... 33 

Figure 10. Photo of Violet Diversion Canal. ................................................................... 39 

LIST OF APPENDICES 

Appendix 1 - References 

Appendix 2 - Letter from Governor Blanco 

Appendix 3 - Synopsis of Modeling Reports 

Appendix 4 - Engineering 

Appendix 5 - Economics 
1 

INTRODUCTION AND BACKGROUND 

This report, based on direction from Congress, compares options for a comprehensive 

plan for de-authorization of deep-draft navigation on the Mississippi River-Gulf Outlet 

(MRGO). The report contains information on the economic and environmental 

considerations associated with this de-authorization plan. The report identifies options 

and opportunities that will be further evaluated and integrated under the on-going 

Louisiana Coastal Protection and Restoration Study (LACPR). 

Congressional Direction 

Congress has directed the Secretary of the Army, acting through the Chief of Engineers, 

to plan for de-authorization of deep-draft navigation on the MRGO. Public Law 109-

234, the Emergency Supplemental Appropriations Act for Defense, the Global War on 

Terror, and Hurricane Recovery, 2006, reads in part: 

“...the Secretary of the Army, acting through the Chief of Engineers, 

utilizing $3,300,000 of the funds provided herein shall develop a 

comprehensive plan, at full Federal expense, to de-authorize deep-draft 

navigation on the Mississippi River-Gulf Outlet, Louisiana, extending 

from the Gulf of Mexico to the Gulf Intracoastal Waterway: Provided 

further, That, not later than 6 months after the date of enactment of this 

Act, the Secretary shall submit an interim report to Congress comprising 

the plan: Provided further, That the Secretary shall refine the plan, if 

necessary, to be fully consistent, integrated, and included in the final 

report to be issued in December 2007 for the Louisiana Coastal 

Protection and Restoration Plan.” 

House Report 109-494 provides a Congressional Conference Committee manager’s 

statement accompanying the legislative language further directing that: 

“The plan shall include recommended modifications to the existing authorized 

current use of the Outlet, including what navigation functions, if any, should be 

maintained and any measures for hurricane and storm protection. The plan shall 

be developed in consultation with St. Bernard Parish, the State of Louisiana, and 

affected Federal Agencies.”

Congress has authorized the United States Army Corps of Engineers (USACE) to prepare 

a plan to de-authorize deep-draft navigation on the MRGO channel and has also 

encouraged USACE to identify any measures for hurricane and storm damage reduction. 

Federal and State resource agencies were invited to assist in preparation of the report, 

along with St. Bernard Parish and other local stakeholders. 
2 

Background on the MRGO 

In 1948, Governor Davis of Louisiana wrote in support of the development of the MRGO 

as follows: 

“Reference is made to the review of reports on the Mississippi River-Gulf and 

Mobile to New Orleans Intracoastal Waterway as proposed by the Chief of 

Engineers, United States Army. I am familiar with the provisions of this proposed 

report and thoroughly concur in the views and recommendations expressed 

therein. The project recommended will be of inestimable benefit to the State of 

Louisiana and to the Nation. A tidewater channel to the sea will permit rapid 

development of sorely needed additional port facilities by the Board of 

Commissioners, Port of New Orleans, and will provide great additional benefits 

to the port. Support of the State of Louisiana for a tidewater canal from New 

Orleans to the Gulf on the eastern side of the Mississippi River is well shown by 

Concurrent Resolution No. 18 of the Louisiana Legislature of 1944, in which it 

was resolved that the Governor of Louisiana be specifically empowered to aid 

and assist the Federal Government in obtaining and completing such a project.”

The MRGO is authorized as a 36-foot deep, 500-foot bottom width, waterway which 

allows alternate deep-draft access to the city of New Orleans (Figure 1). Channel 

construction was authorized by the River and Harbor Act of 1956. The MRGO extends 

from the Inner Harbor navigation Canal (IHNC) in New Orleans to the 38-foot depth 

contour in the Gulf of Mexico. Construction of the channel began in 1958 and was 

completed in 1968. The channel was constructed through part of the Gulf of Mexico, 

shallow sounds and coastal wetlands. The MRGO provides a shorter navigation route 

from the Gulf of Mexico to the Port of New Orleans tidewater facilities compared to 

using the Mississippi River to access the ports. 

Figure 1. Mississippi River Gulf Outlet De-Authorization Plan Area. 
3 

The MRGO is approximately 76 miles long. Located south and east of New Orleans it 

begins 9.4 miles out in the Gulf of Mexico where it is authorized to a depth of 38 feet and 

a bottom width of 600 feet. These dimensions extend from mile -9.4 to mile 0 (bar 

channel). The authorized dimensions for the remaining 66 miles of the MRGO are a 

depth of 36 feet and a bottom width of 500 feet. From mile 0 to mile 23, it extends 

through the shallow waters of Breton Sound. This section of the MRGO is often referred 

to as the Sound Reach. From mile 23 to mile 60, the MRGO extends further to the north 

and west, through coastal wetlands. This section of the MRGO is often referred to as the 

Inland Reach. 

At mile 60 the MRGO connects with the Gulf Intracoastal Waterway (GIWW), and the 

two run contiguously westward for six miles to the IHNC, also called the Industrial 

Canal, in New Orleans. This section of the MRGO is often referred to as the GIWW 

Reach. At the direction of Congress, this report considers only de-authorization of the 

MRGO south of its confluence with the GIWW (Inland Reach, Sound Reach, and Bar 

Channel). The Inner Harbor tidewater port area is a complex interconnected system of 

waterways that are authorized at varying depths under different Congressional authorities 

(from the IHNC Lock to the Turning Basin is authorized at 32 feet deep and from the 

Turning Basin to Michoud Canal is authorized at 36 feet deep – the same as most of the 

MRGO). 

Operation and Maintenance (O&M) of the authorized MRGO channel width and depth is 

dependent on Congressional appropriations, which since the mid 1990s have not been 

sufficient to maintain the channel at full authorized dimensions. This funding limitation 

has been compounded by additional needs for emergency dredging of shoaled areas in the 

MRGO following tropical storms or hurricanes and the construction and repair of bankline protection and created wetlands. 

Through discussions with members of the local maritime industry, a consensus was 

reached to start maintaining the channel to narrower widths than authorized without 

affecting safe vessel passage or delaying industry. These pre-Katrina dimensions would 

have provided a single lane of traffic in the MRGO for deep-draft vessels. These 

dimensions were a 36 feet deep by 300 feet wide (minimum) channel from Mile 66 to 

Mile 0 and 38 feet deep by 450 feet wide channel from Mile 0 to Mile -9.4. Advanced 

maintenance and allowable over-depth were included, which increased the depth of 

dredging by six feet between Miles 66 and 23, eight feet across the Sound Reach, and 

four feet through the Bar Channel. No maintenance dredging of MRGO has occurred 

since Hurricane Katrina.

Direct costs of construction, operation, and maintenance of the MRGO have been funded 

by the Federal government. These direct costs have totaled over $578 million since 1958 

as shown in Table 1. 
4 

Table 1. Federal Investment in the MRGO. 

Years Federal Investment 

in MRGO 

1958-1965 $43,304,000

1966-1973 $102,857,000

1974-1981 $73,992,000

1982-1989 $78,886,000

1990-1997 $109,040,000

1998-2005 $170,580,000

Total $578,659,000

Note: Values are in actual dollars. 

Source: USACE Operations Division. 

Appropriations during 1958 to 1968 reflect initial construction costs. Subsequent 

expenditures are for operations and maintenance, primarily dredging activities (LCA, 

2004). The average annual operations and maintenance expenditures for the MRGO is 

$12.5 million (in 2000 dollars). However, following tropical storms and hurricanes 

supplemental expenditures have often been required to return the MRGO to the 

authorized dimensions. Since 1998, the $12.5 million annual O&M appropriation has not 

allowed for dredging of the channel to its full authorized dimensions. 

Vessel Utilization of the MRGO 

Vessels traversing the MRGO carry a wide variety of commodities, including petroleum 

products, chemicals, forest products, manufactured goods, food and farm products, and 

machinery. Waterborne Commerce Statistics Center (WCSC) data for 2002-04 shows 

that the greatest tonnage was for transport of commodities in three categories (Table 2). 

Table 2. Transportation Commodities on the MRGO for 2002-2004. 

 

Tons 

Major Commodity Group 2002 2003 2004 

Chemicals and related products 567,000 590,000 109,000 

Agricultural products 465,000 398,000 292,000 

Soil, sand, gravel, rock, cement, glass 484,000 535,000 317,000 

Historical data from the WCSC also show that use of the MRGO steadily increased, until 

reaching a peak in terms of tonnage carried in 1978, and in terms of the number of 

vessels in 1982. Proportionally, the number of trips has decreased more than the tonnage, 

presumably because ships today are larger and carry greater amounts of cargo. In the last 

20 years for which comparable data are available, use of the MRGO has generally been 

decreasing (Table 3). 
5 

In some cases (1983-1997), these data may represent trips anywhere along the MRGO, 

including that section from Mile 60 to Mile 66, which is contiguous with the GIWW. 

Information in Table 3 for 1998-2005 shows MRGO vessel trips only between Mile 60 to 

Mile -94 (i.e., GIWW to the Gulf of Mexico). The actual number of trips along the 

southernmost part of the MRGO, from Mile 60 into the Gulf of Mexico, has been 

estimated at fewer than two deep-draft vessels per day. 

Table 3. Navigation on the MRGO (includes GIWW traffic). 

Time 

periods 

Average tonnage carried on the 

MRGO 

Average vessel trips on the 

MRGO per year (1983 – 1997); 

Actual vessel trips 1998 -2005 

1983-1987 7,247,000 5,708 

1988-1992 6,304,000 4,437 

1993-1997 5,144,000 5,980 

1998 4,007,000 2,240 

1999 5,369,000 1,886 

2000 5,850,000 2,104 

2001 4,173,000 2,083 

2002 3,290,000 2,445 

2003 2,847,000 3,766 

2004 1,206,000 2,370 

2005 Not available 982 

Source: U.S. Army Corps of Engineers, Waterborne Commerce of the U.S., IWR-WCUS, Part 2.

WCSC data show that from 1970 to 1995, foreign tonnage on the MRGO represented less 

than 75 percent of total tonnage. This includes both inbound and outbound tonnage. Since 

1998, tonnage bound for foreign ports has increased. For example, in 2002 it represented 

85 percent of the total tonnage and 86 percent in 2004. 

The draft of vessels utilizing the MRGO is important when evaluating its value to 

navigation interests. Vessel trips may be grouped into shallow and deep-draft trips. 

WCSC data defines deep-draft trips as vessels reporting over 18 feet in draft. These data 

show, for example, that on the entire length of the MRGO in 2002, approximately 61 

percent of the trips were by shallow-draft vessels, and 39 percent were by deep-draft 

vessels (Note: For this report, the USACE is using the definition of deep-draft vessels 

contained in ER-1105-2-100. This defines deep-draft as vessels requiring greater than 14 

feet). 

Future Operation and Maintenance of the MRGO 

Sections of the MRGO experienced severe shoaling during Hurricane Katrina, leading to 

a current controlling channel depth of approximately 22 feet. The estimated cost to 
6 

return the channel to its authorized dimensions (36 feet deep by 500 feet wide, 38 feet 

deep by 600 feet wide in bar channel) is $130,250,000, which includes advanced 

maintenance dredging and over-depth dredging. For this de-authorization study, although 

no current plans exist to dredge the MRGO, it is important to estimate these costs for 

comparison purposes in evaluating future options for modifying the channel. 

Relationship Between the MRGO and Levees 

The Lake Pontchartrain and Vicinity Hurricane Protection Project generally covers the 

parishes of St. Charles, Jefferson, Orleans and St. Bernard between the Mississippi River 

and Lake Pontchartrain. The project includes levees and floodwalls located on the 

disposal area on the south bank of the MRGO (including the area where it is contiguous 

with the GIWW), along the IHNC and north bank of the GIWW (including the area 

where it is contiguous with the MRGO). Figure 2 shows the general relationship between 

the MRGO and the Lake Pontchartrain and Vicinity hurricane protection system. 

Figure 2. Hurricane Protection System for City of New Orleans. 

Relationship Between IHNC Lock and MRGO 

Completed in 1921, the current IHNC Lock was designed for a working life of 50 years. 

Currently 35 years past its design life, the lock is one of the Nation’s most congested, 

with an average wait of 10 hours, but often as much as 24-36 hours (Table 4). The lock is 
7 

too small to accommodate the volume of existing and projected future traffic. A deepdraft replacement lock was originally authorized in 1956, but legal issues and community 

involvement problems delayed construction until 1998. Since 1998, the new lock has not 

been funded to full construction capability. The lack of a definitive idea about the future 

of the lock has caused uncertainty amongst companies in the study area that use the lock 

and has had significant impacts on their planning. 

Table 4 indicates the number of vessels delayed at the IHNC Lock and the hours of delay. 

Delays were the result of congestion, breakdowns, maintenance work or other factors 

such as Hurricane Katrina in 2005. Most of the delayed vessels are towboats with barges. 

Table 4. IHNC Lock Vessel Delay Periods 2000-2005. 

Year 24 hours - 29 hours 29 hours – 36 hours 36 hours and greater 

2000 228 47 75 

2001 157 13 23 

2002 271 58 16 

2003 195 46 20 

2004 600 186 175 

2005 312 204 206 

An important consideration when discussing options for the MRGO is its use as an 

alternative route for shallow-draft vessels when the IHNC Lock is not functioning or 

when encountering lock through delays. When the lock is not functioning, some vessels 

will take the Mississippi River to Baptiste Collette Bayou and cross Breton Sound to the 

MRGO to by-pass the lock (or vice versa). This route was used following Hurricane 

Katrina (which closed the lock for 16 days) to supply petroleum, coal, and other products 

to locations along the Gulf Coast. Therefore, completion of the deep-draft replacement 

lock between the Mississippi River and the IHNC would help mitigate the economic 

effects of closing the MRGO to deep-draft navigation. The IHNC Lock and its 

authorized replacement are essential components of any discussion about the deauthorization of the MRGO. 

Relationship Between MRGO and Storm Surge 

One much-studied relationship before and after Hurricane Katrina is that of the 

contribution of MRGO to hurricane storm surge. The hypothesized relationship between 

the MRGO and storm surge has received a great deal of media and public attention. 

A 1966 engineering study prepared for USACE (Bretschneider and Collins, 1966) 

examined six different storm scenarios using one-dimensional numerical modeling, and 

concluded that Hurricane Betsy, which occurred in 1965 during the construction of the 

MRGO, would have produced the same storm surge elevations with or without the 

MRGO. 

In 2003, a study was completed using two-dimensional Advanced Circulation (ADCIRC) 

modeling for storm surge (USACE, 2003). The ADCIRC model is used to calculate the 
8 

amount of storm surge under different conditions on ocean shelves, coasts, and estuaries. 

In this study, nine different storm scenarios were modeled, both with and without the 

MRGO (shallow marsh in place of the channel). The nine scenarios were combinations of 

slow, medium, and fast moving storms with weak, moderate, and strong intensity winds, 

and one of these models used the Hurricane Betsy track. The model runs demonstrated 

that the maximum difference in storm surge with and without the MRGO was just over 6 

inches. These models also demonstrated that with the MRGO, drainage of Lake 

Pontchartrain following a surge event was accelerated. 

Following Hurricane Katrina, the Interagency Performance Evaluation Task Force (IPET) 

of USACE studied the New Orleans hurricane protection systems, storm surge, 

performance of flood protection measures, and the consequences of the hurricane. It 

found that the MRGO had little influence on water levels in the IHNC during Katrina, 

because when the marshes are inundated, the water conveyed through the channel is a 

relatively small part of the total surge. The report states that “during Katrina, MRGO was 

far from the ‘hurricane highway’ moniker with which it has been branded.” It found that 

the MRGO levees were overtopped by high surge and high, long-period waves before the 

hurricane made landfall, and that the high velocities of water movement over the levees 

caused scouring and breaching of levees along the MRGO. 

In 2006, USACE analyzed the Southeast Louisiana Hurricane Protection System and 

found that “[t]he southeast trending leg of the Mississippi River Gulf Outlet (MRGO) had 

little influence on the water levels in the IHNC during Katrina” (USACE, 2006b). This 

conclusion was reached after comparing the results of ADCIRC models runs, assuming 

the MRGO channel existed in its pre-Katrina conditions, and then assuming that the 

MRGO did not exist. 

A 2006 study by the Louisiana Department of Natural Resources also evaluated the 

impact of the MRGO on storm surge using ADCIRC modeling. This study considered 

seven different scenarios. These included a 124-knot fast-moving storm, Hurricane Betsy 

conditions, and Hurricane Katrina conditions, both with and without the MRGO, and 

Hurricane Katrina conditions with higher levees. The conclusions were that the MRGO 

does not contribute significantly to peak storm surge during severe storms where the 

wetland system is overwhelmed with water, and that closure will not provide significant, 

direct mitigation of severe hurricane storm surge. However, closure of the MRGO may, 

according to the LDNR study, modestly delay the onset of surge in a few locations and 

“would significantly reduce storm surge scour velocities at some locations” (LDNR, 

2006). Again, this study provided evidence that closure of the MRGO may impede 

drainage of Lake Pontchartrain following a surge event. 

Studies also demonstrated that the most noticeable effect of the MRGO occurs for small 

surge events, where the marsh areas are not completely inundated (USACE, 2006a; 

LDNR, 2006). Further storm surge modeling analyses are underway through LACPR to 

consider scenarios with new structural flood protection features, such as levees and 

floodgates. Solutions to the impact of storm surge that have been posed by the public 

include barrier construction, such as floodgates at some points along the MRGO and 

partially or completely filling in the channel. 
9 

Public Views on the MRGO 

USACE has conducted a number of studies associated with the MRGO from various 

points of view including ecosystem restoration, navigation, and hurricane protection. 

Based upon previous studies, numerous citizen letters, and interactions with local 

governments and the public, the following points have been noted: 

• Construction and use of the MRGO caused the loss of wetlands habitat. 

• Some parties believe that the MRGO exacerbates storm surges in the region. 

• Maintenance dredging costs outweigh the promised economic benefits of the 

MRGO. 

In a letter dated June 2, 2006, Governor Blanco of the State of Louisiana made a request 

for a “plan for closure, restoration of the extensive wetlands lost as a direct result of the 

MRGO, and the integration of this closure into the comprehensive hurricane protection 

plan.” See Appendix 2 for the full text of Governor Blanco’s letter. 

Related Authorities and Plans 

The following sections give a brief background on existing authorities and plans relevant 

to the development of a comprehensive plan for de-authorization of MRGO. 

Coastal Wetlands Planning, Protection and Restoration Act 

(CWPPRA), 1990 

The Coastal Wetlands Planning Protection and Restoration Act (Public Law 101-646) 

provides funding for projects to restore coastal ecosystems in Louisiana and other states. 

In 1993, the CWPPRA Task Force produced the Louisiana Coastal Wetlands Restoration 

Plan. Projects suggested for the Pontchartrain Basin relating to the MRGO included: 

• Close or move the MRGO to prevent erosion and preserve marsh. 

• Stabilize the MRGO banks and create marsh to prevent erosion and preserve 

marsh. 

• Stabilize shorelines, improve hydrology, and manage marshes to preserve the 

landbridges. 

• Introduce and manage freshwater to reduce salinity and preserve marsh and 

swamp throughout the basin. 

Under CWPPRA, individual plans and projects are constructed to preserve and restore 

wetlands. Projects addressing the area surrounding the MRGO include the MRGO 

Disposal Area Marsh Protection (PO-19), Lake Borgne Shore Protection (PO-30), and 

Lake Borgne and MRGO Shoreline Protection (PO-32). Other candidate projects have 

been proposed under the CWPPRA to address coastal erosion problems in the project 

area. 

Coast 2050: Toward a Sustainable Coastal Louisiana, 1998 

The Louisiana Coastal Wetlands Conservation Task Force and the State of Louisiana’s 

Wetlands Conservation & Restoration Authority prepared this plan for the Louisiana 

Department of Natural Resources. It addresses the problem of depletion of coastal land 
10 

across Louisiana, and recommends ecosystem management strategies designed to restore 

wetlands and prevent continued deterioration. 

Among the ecosystem management strategies recommended in the plan are: 

• Close MRGO to deep-draft navigation when adequate container facilities exist on 

the river. 

• Stabilize the entire north bank of the MRGO. 

• Constrict breaches between MRGO and Lake Borgne with created marshes 

• Construct a sill at Seabrook. 

• Wetland sustaining diversion from the Mississippi River near Violet once the 

MRGO is closed. 

• Create marsh in southern lobes of Lake Borgne (by beneficial use of dredged 

material). 

• Dedicated delivery of sediment for marsh building (Eloi Bay and Biloxi Marshes). 

Continuing Authorities Program 

Sections 204 of the Water Resources Development Act (WRDA) 1992, section 206 of 

WRDA 1996, and section 1135 of WRDA 1986 are "continuing authorities" that 

authorize the Secretary of the Army to plan, design, and implement certain ecosystem 

restoration measures, subject to specified cost sharing, without additional project specific 

Congressional authorization. Section 204 authorizes the beneficial use of dredged 

material to restore, protect, and create aquatic and ecologically related habitats, including 

wetlands, in connection with construction or maintenance dredging of an authorized 

navigation project. Additionally, section 206 authorizes certain aquatic ecosystem 

restoration projects that will improve the quality of the environment and that are in the 

public interest. Finally, section 1135 authorizes modification of structures or operations 

at existing USACE projects for the purpose of improving the quality of the environment 

in the public interest. Projects performed under these continuing authorities include the 

placement of dredged material from the MRGO (miles 14 to 12) adjacent to the south 

jetty for wetland creation and the placement of dredged material from mile -2 to -4 on 

Breton Island for island restoration. 

Louisiana Coastal Area (LCA) Ecosystem Restoration Study, 2004 

The USACE and the State of Louisiana prepared a study to identify the most critical 

ecological needs of the coastal area and to describe alternative restoration strategies. The 

MRGO was identified as one of the five specific areas with significant near-term needs, 

and environmental restoration costs for shoreline protection projects in the area are 

estimated at $121,736,000 (2004 dollars). 

The report recommended the construction of rock breakwaters along 23 miles of the 

north bank of the MRGO, and along 15 miles of the southern shore of Lake Borgne. This 

was defined as part of the critical near-term plan for LCA. 

Louisiana Coastal Protection and Restoration, 2006 

Following the severe hurricane season of 2005, Congress directed the USACE to conduct 

an analysis and design on a full range of hurricane risk reduction measures against a 
11 

surge equivalent to “Category 5” storm intensity. The effort spans across all of coastal 

Louisiana and comprehensively integrates the water resource objectives of hurricane 

protection, flood control, and coastal restoration. Working closely with the State of 

Louisiana, a Preliminary Technical Report was prepared by the USACE for the Congress 

in July 2006. In addition to the preliminary analysis and design, the Preliminary 

Technical Report included the following “Prime Points:” 

• Coastal Features and Storm Surge 

• Hurricane Threat to New Orleans 

• Technical Collaboration with the Dutch 

• Strong Houses Resist Storms 

• Coastal Engineering Design Challenges 

The Final LACPR Technical Report will be submitted to Congress in December 2007. 

Emergency Supplemental Appropriations Act for Defense, the Global 

War on Terror, and Hurricane Recovery, 2006 

In addition to providing funding to develop a comprehensive plan to de-authorize deepdraft navigation on the MRGO, this legislation provided nearly $4 billion for levee 

improvements and flood control projects in the New Orleans area. Funds include $1.5 

billion to reinforce or replace floodwalls, $495 million for levee projects, $350 million 

for construction of navigable closures on the IHNC and the GIWW, and $170 million to 

armor critical areas of the levees. Figure 3 details shoreline protection projects on the 

north and south shorelines of the MRGO and on the southeast shore of Lake Borgne 

funded under this appropriation. 

In consideration of construction of navigable closures on the IHNC and GIWW, the 

USACE is evaluating a floodgate at Seabrook that would remain open except under 

severe weather conditions. Gates on the GIWW east of Michoud Canal and on the 

MRGO south of Bayou Bienvenue with a connecting levee is one of the alternatives 

being considered. 
12 

Figure 3. Shoreline Protection Projects Funded by Supplemental Appropriations. 
13 

CONDITIONS IN THE PONTCHARTRAIN BASIN 

The following sections describe the historic and present conditions of the MRGO project 

area and the middle Pontchartrain Basin. 

Historical Land/Habitat Conditions 

The MRGO project area is located within the middle Pontchartrain Basin of the coastal 

Louisiana deltaic plain. The Pontchartrain Basin has been in a destructional phase for 

approximately 1,800 years, during which submergence of the coastal lands has been the 

dominant process (Frazier, 1967; Britsch and Dunbar, 1993; Barras et al., 2003). This 

process is caused by subsidence, sea level rise, and lack of sediment and organic matter 

deposition. For much of coastal Louisiana, including the MRGO area, the amount of 

sediment and organic matter deposition is not sufficient to keep pace with the rate of 

subsidence and sea level rise, causing net submergence of the coastal zone. This is a 

natural part of the deltaic process that has been accelerated by human activity. 

About 700 years ago, the Mississippi River was established in its present channel (Sikora 

and Kjerfve, 1985). Since that time, subsidence has been occurring in the Pontchartrain 

Basin. The construction of Mississippi River levees protects inhabited areas, but prevents 

periodic flooding and sedimentation from replenishing adjacent wetlands. Coastal 

wetlands depend on flooding of the marsh surface and accompanying sediments for 

growth (Cahoon, 1991). Since the leveeing of the river, subsidence has increased due to 

the absence of seasonal river flooding and the influx of sediments (Cahoon et al., 1995). 

Other factors also directly and indirectly influence wetland loss including the 

construction of oil and gas canals and their associated disposal areas (Turner, 1987), 

subsurface faulting (Gagliano, 2005), hydrocarbon extraction (White and Morton, 1997), 

storm events, changes in the relationship between mineral and organic composition in the 

soils (Nyman et al., 1994), and plant dieback associated with phytotoxin accumulation 

(Mendelssohn and McKee, 1988, Webb and Mendelssohn, 1996). 

Britsch and Dunbar have calculated land loss in the basin over various time periods by 

comparing the amount of land in aerial photographs. In the early 1930’s there were 

730,339 acres of land in the basin. Table 5 indicates the changes from land to water in 

the indicated time periods and also shows the percent loss of land. 

Table 5. Land Loss in Pontchartrain Basin: 1930s to 2001. 

Interval Acres Lost % Loss/year 

1930's-58 24,349 0.11%

1958-74 31,751 0.24%

1974-83 12,914 0.18%

1983-1990 7,826 0.14%

1990-2001 13,969 0.17%

(Data compiled from Britsch and Dunbar, 2005.) 
14 

Wetland habitat types occur along the eastern Louisiana coast in bands that roughly 

parallel the shoreline. Salinity and elevation are the principal factors regulating plant 

distribution. Penfound and Hathaway (1938) subdivided the marshes in the MRGO 

project area into four salinity types: saline, brackish, slightly brackish (now commonly 

called intermediate), and fresh. 

 

In 1949 when O’Neil mapped the coastal marshes, he found no fresh marsh in the 

Pontchartrain Basin. He indicated some intermediate marsh in the southern La Branche 

wetlands, eastern New Orleans marshes and the Central Wetlands. Marshes along the 

north and south shores of Lake Pontchartrain were brackish as were the New Orleans 

East and Lake Borgne Land Bridges, most of the Central Wetlands, and the western 

Biloxi Marshes. The eastern Biloxi Marshes were saline. Freshwater areas along the 

shores of Lakes Maurepas and Pontchartrain likely contained cypress-tupelo swamps 

even though O’Neil did not indicate them. In 1998, USGS analyzed 1956 aerial 

photography which indicated 10,200 acres of cypress swamp in the Central Wetlands. 

From 1968 through 2001, fresh and intermediate marshes were found on the western 

shores of Lake Pontchartrain and near the mouth of the Pearl River. The exact locations 

and acreages fluctuated, probably depending on annual rainfall. In 1968, the marshes just 

north of Bayou La Loutre were intermediate. In 1968 and again in 1997 and 2001, there 

were varying amounts of intermediate marsh in the Central Wetlands. Since 1968, 

brackish marsh has been present along the north shore of Lake Pontchartrain, the New 

Orleans East Land Bridge, in the Central Wetlands and in the western Biloxi Marshes. 

The Lake Borgne Land Bridge was all brackish in 1968 and 1978. By 1988, saline marsh 

had encroached up the MRGO to Bayou Dupre. Saline marsh has consistently been 

present in the outer Biloxi Marshes (Chabreck et. al. 1968, 1978, and 1997). 

Construction of the MRGO converted nearly 3,400 acres of intermediate marsh, over 

10,300 acres of brackish marsh, over 4,200 acres of saline marsh and 1,500 acres of 

cypress and levee forest to open water or disposal area (USACE for Environmental 

Subcommittee of the EPA Technical Committee, 1999). Bank erosion on the MRGO has 

been estimated to occur at rates of between 6 and 36 feet per year on the Inland Reach 

(Coastal Environments, 1984). Bank stabilization efforts to prevent erosion and shoaling 

in the channel have included placement of rock dikes and concrete mats along the banks 

of the MRGO in some areas. Material dredged from the channel has been beneficially 

used to restore and nourish over 1,000 acres of wetlands adjacent to the Inland Reach of 

the channel especially between Lake Borgne and the MRGO. 

Historical Salinity Conditions 

Over the past 6,000 to 7,000 years, the salinity of the study area has shifted with the 

major deltaic meandering of the Mississippi River. Modern efforts to control flooding 

and improve navigation included numerous bank stabilization, channel alignment, 

dredging, lock, dam, levee, and spillway projects on the Mississippi River. Such 

alterations to the Mississippi River and surrounding wetlands have increased salinity in 

the study area by altering the flow of freshwater in the region (LCA, 2004). 
15 

Over 80 percent of the annual freshwater inflow to the Pontchartrain Basin is provided by 

precipitation. The flow of water into the lower reaches of the MRGO is predominantly 

driven by tides and winds. While the annual salinity in Lake Pontchartrain increased 

after construction of the MRGO, at least one study found the increase to be statistically 

insignificant (Sikora and Kjerve, 1985). 

A study by Tate et al. (2002) showed that monthly average salinity increased from the 

1951-1963 period to the 1963-1977 period (Table 6). 

Table 6. Comparison of Monthly Summaries of Salinity: 1951-1963 and 1963-1977. 

 Salinity (ppt) 

Location 

1951-

1963 

1963-

1977 Increase

Pass Manchac 1.2 1.6 0.4

North Shore 3.5 4.6 1.1

Little Woods 3.3 5.2 1.9

Chef Menteur 3.8 6.1 2.3

Alluvial City 7.8 12.2 4.4

(Data compiled from Tate et al 2002.) 

According to Tate et al, “Salinity in the region has stabilized, and no significant increase 

in average annual salinity is projected in the foreseeable future for Lake Maurepas and 

Lake Pontchartrain. Salinity is expected to increase in the Lake Borgne region and 

surrounding marshes due to land loss in the area.” 

Present Conditions 

The following sections describe both the navigation and environmental conditions after 

Hurricane Katrina. 

Present Navigation Conditions 

During Hurricane Katrina, approximately five miles of the authorized channel in the 

Breton Sound area was reduced in depth to approximately 22 feet or less. No 

maintenance dredging activities have taken place on the MRGO since Hurricane Katrina. 

The current channel depth has limited the use of the MRGO to vessels with a draft of 22 

feet or less. Current users of the channel are primarily sportsmen, shrimp boats, and 

shallow-draft tows, although some inbound deep-draft vessels are entering the IHNC area 

via the MRGO. 

With the channel too shallow for some deep-draft navigation, businesses that relied upon 

the MRGO for vessels to reach them have found alternative means of operation. Some 

vessels are able to use the Mississippi River and IHNC Lock to reach the MRGO 

tidewater port facilities. Other users are able to dock vessels on the river and 

commodities are transported from facilities on the MRGO to and from these vessels by 
16 

trucks. Some businesses now bring ships into the MRGO unloaded and then transit 

outbound through the IHNC loaded with cargo. Other users have closed or moved their 

facilities to other locations. 

Present Land/Habitat Conditions 

Before Hurricane Katrina, Coast 2050 predicted that between 2000 and 2050, 45,400 

acres of marsh would be lost in the Pontchartrain Basin. It is likely that Hurricane Katrina 

deposited a measurable amount of sediment throughout the Pontchartrain Basin area 

(Turner et. al., 2006). Despite this, between fall 2004 and October 2005, the 

Pontchartrain Basin apparently lost 12,160 acres of wetlands. Habitat analysis indicates 

that over 640 acres each of forested wetlands and fresh marsh was converted to open 

water. About 2,560 acres of intermediate marsh, 3,840 acres of brackish marsh, and 4,480 

acres of saline marsh also became open water (USGS-SWRC-BRPO, 2006). Thus, the 

total amount of marsh lost as a result of Hurricane Katrina was over one third the total 

predicted wetland losses expected by 2050. The storm surge and strong winds from 

Hurricane Katrina also severely damaged the Chandeleur and Breton Islands and adjacent 

seagrass beds according to the USGS. 

 
17 

PLAN FORMULATION 

Public interest in the future of the MRGO is high across academic, environmental, and 

business sectors as well as with citizens and local governments. In conducting this study, 

the USACE emphasized efforts to allow open and broad participation in the planning 

process. The goal of the effort is to carry out a transparent and interactive planning 

initiative. From the beginning the team shared views about the goals, scope, and 

constraints of the study. The following sections detail the planning process and results. 

Collaborative Planning Approach 

In response to Congressional direction to develop a de-authorization plan, the USACE 

established a plan of action for developing this interim report. Federal, State and local 

government parties and other organizations were invited to assist in preparation of the 

report. Invited stakeholder participants included: 

• St. Bernard Parish 

• Governor’s Office of Coastal Activities 

• Louisiana Department of Natural Resources 

• Louisiana Department of Transportation and Development 

• State and Federal Resource Agencies 

• Gulf Intracoastal Canal Association 

• Port of New Orleans 

• Lake Pontchartrain Basin Foundation 

• Coalition to Restore Coastal Louisiana 

• Biloxi Marshlands Corporation 

• Steamship Association of Louisiana 

• Bring New Orleans Back Commission 

• New Orleans Business Council 

• LSU Hurricane Center 

• National Aeronautic and Space Administration 

• Businesses 

• Private citizens 

Stakeholder Meetings 

A series of eight public stakeholder forums were held to identify various plans and 

proposals for the future of the MRGO. Meetings included technical presentations and 

open discussions on topics including wetlands, navigation, storm protection, and the local 

economy. Each stakeholder group was invited to make detailed presentations on their 

plans. In addition to holding regular stakeholder forums and opening an official public 

comment period for the interim report, an independent team of technical experts was 

chartered to review the report. 
18 

The State of Louisiana, environmental organizations, planning groups, businesses, and 

individuals have developed plans for coastal protection and restoration that include 

MRGO related components. In some cases, the plans are specific to the MRGO and in 

others the channel is merely a component of larger proposals. In conducting this study 

the USACE invited stakeholders to present their plans as part of efforts to identify 

common approaches to help achieve consensus. The following non-federal plans and 

studies are highlighted given their relevance to this de-authorization study. 

The features of the St. Bernard Parish Plan in the vicinity of MRGO are summarized 

below and the plan is available on the internet at http://www.sbpg.net/. 

• Construct Five New Floodgates: at Seabrook, on the GIWW, on MRGO near 

Bayou Bienvenue, on Bayou Dupree at Lake Borgne, and on the MRGO near 

Verret. 

• New Bankline Stabilization on the entire shore of Lake Borgne. 

• Breakwaters in Lake Borgne. 

• Restore the Bayou La Loutre Ridge to +8 feet. 

• Total Closure of MRGO by a structure at the Bayou La Loutre Ridge. 

• Rock Dike Closure of MRGO near Lake Athanasio. 

• Total Closure of Alabama Bayou at MRGO. 

• Freshwater Diversion from Mississippi River at Violet and another site. 

The Lake Pontchartrain Basin Foundation has developed a comprehensive habitat 

management plan that includes measures related to the MRGO. Those features are 

highlighted below and the full plan is available on the internet at 

http://www.saveourlake.org/. 

• Constriction of the MRGO channel at the Bayou La Loutre Ridge to 12 feet by 

125 feet. 

• Introduction of freshwater into the system through a diversion off of the 

Mississippi River at the Violet Canal. 

• Armoring of eroding shorelines on the north bank of MRGO and on Lake Borgne 

• Reduction of ship speed on the Inland Reach. 

• Constriction of Bayou Dupre at Lake Borgne. 

• Utilization of previously dredged material for marsh creation. 

• A sill at Seabrook. 

• Discontinuation of advanced maintenance on the MRGO. 

• Utilization of dredged material in a beneficial manner. 

The features of the Bring New Orleans Back Commission recovery plan located in the 

vicinity of MRGO are summarized below and the plan is available on the internet at 

http://www.bringneworleansback.org/. 

• Sector gates Seabrook, GIWW, and MRGO at Bayou Dupre with leaky levee 

between the latter two. 

• Heightening and armoring of existing levees on the MRGO. 

• A new levee on the eastern shore of the MRGO or the placement of surge barriers 

across Lake Borgne. 
19 

• A normally closed deep-draft sector gate in the MRGO with a draft of 

approximately 28 feet. 

• Reintroduction of freshwater. 

• Rebuilding the Bayou La Loutre landbridge. 

• Restoration of the Biloxi Marsh. 

• Armoring the MRGO banks to stop erosion. 

• Aggressive use of dredged material to build land. 

• Vessel speed control. 

A private company, the Biloxi Marshlands Corporation, owns large tracts of wetlands in 

the vicinity of the MRGO and has developed a conservation and management plan for 

their holdings. Features of the company’s plan in the vicinity of MRGO are summarized 

below and the plan is available on the internet at http://www.biloximarshlandscorp.com/. 

• Bayou La Loutre Ridge bank armament on both sides of the bayou. 

• Marsh creation and terracing. 

• Two water control structures in the MRGO. 

• Ridge refurbishment. 

• Vegetative plantings. 

• Massive freshwater diversion. 

• Restore the MRGO to “original” 500-ft width and fill the rest. 

The items noted below represent consensus features either common to all of the nonfederal plans or supported by some of the stakeholder groups. These items were 

developed through a series of independent meetings organized by key stakeholders and 

presented later to the broader audiences attending the USACE-hosted stakeholder 

sessions. The collaborative planning effort attempted to identify a consensus plan for deauthorizing the channel but in the end resulted in only identifying common measures or 

features supported by many stakeholders. De-authorization of deep-draft navigation on 

the MRGO would allow the full incorporation into LACPR some of the stakeholder 

consensus such as: 

• Restore the Bayou La Loutre Ridge. 

• Restoration and protection of the lower Chandeleur Islands. 

• River reintroduction. 

• Shoreline protection on a portion of the shoreline of Lake Borgne. 

• Long distance transport of sediment. 

Additional USACE measures to incorporate public input into the study included an 

internet web page and the hosting of a public meeting. The study web page 

(http://www.swg.usace.army.mil/mrgo/) offers interactive capability allowing visitors to 

submit information and opinions via email and includes a digital library of publications 

related to the history of the channel and maps depicting the area. The information was 

intended to serve as a resource for the study team and interested stakeholders. 

A public meeting was held on October 28, 2006 at the University of New Orleans and 

involved an open house where stakeholder groups were offered display space to present 
20 

their points of view. More than 150 people attended the public meeting, which included 

a formal presentation of the study process and scope from the USACE and an open 

comment period for public statements from citizens, organizations, and elected officials. 

The collaborative planning effort attempted to identify a consensus plan for deauthorizing the channel but in the end resulted in only identifying common measures or 

features supported by many stakeholders. 

State of Louisiana’s Comprehensive Coastal Protection Master Plan 

The Louisiana Coastal Protection and Restoration Authority is developing a Master Plan 

to integrate hurricane protection and coastal restoration. Features of their preliminary 

draft plan in the vicinity of MRGO include: 

• Closure of MRGO at the Bayou La Loutre Ridge, do not fill in the MRGO 

channel. 

• MRGO shoreline stabilization. 

• Maintenance of the MRGO-Lake Borgne Land Bridge, including shoreline 

protection. 

• Restoration of the Bayou La Loutre Ridge. 

• Construction of large Violet Reintroduction to sustain the Biloxi Marshes. 

• Sediment delivery by pipeline into Central Wetlands and establishment of cypress 

swamp through hydrologic management. 

• Sediment delivery by pipeline into Golden Triangle. 

• Accelerate completion of the IHNC Lock. 

• Integration of the MRGO closure plan into the larger hurricane protection plans 

for the area. 

Figure 4 shows the area in the vicinity of MRGO with reference to many of the local 

place names mentioned in this report. 
21 

Figure 4. Area in the Vicinity of MRGO 

Louisiana Coastal Protection and Restoration Planning 

As directed by Congress, the MRGO deep-draft de-authorization plan will be integrated 

into the LACPR plan, which is also being prepared at Congressional direction. As 

required, the Secretary of the Army, through the Chief of Engineers is conducting: 

“a comprehensive hurricane protection analysis and design...to develop and present 

a full range of flood control, coastal restoration, and hurricane protection 

measures...(and) the Secretary shall consider providing protection for a storm surge 

equivalent to a Category 5 hurricane...(and) the analysis shall be conducted in close 

coordination with the State of Louisiana.” 

Compliance with the National Environmental Policy Act (NEPA) for any deep-draft deauthorization option or options selected as a recommended alternative will be done 

through incorporation of that alternative into the Programmatic Environmental Impact 

Statement accompanying the December 2007 LACPR Report. 
22 

Options Developed 

This report provides a qualitative analysis based on coordination with the State of 

Louisiana, St. Bernard Parish Government, stakeholders, resource agencies and the 

general public. Studies related to navigation, ecosystem restoration and storm damage 

prevention for the area have been conducted by Federal and non-Federal agencies over 

many years. This interim report builds upon past analyses and discusses some of the 

general considerations associated with channel de-authorization options. 

A USACE team evaluated potential modifications to the current uses of the navigation 

channel with the intent of determining if any uses should be maintained. The evaluation 

included information presented in the stakeholder meetings, data gathered through 

maritime business surveys, and government statistics of annual channel utilization. 

During the investigation of a plan to de-authorize deep-draft navigation on the MRGO, 

three distinct options were evaluated that limit shallow-draft or close deep-draft 

navigation. The navigation gates and the shoreline protection on the north and south 

shorelines of the MRGO authorized in the 2006 Supplemental Appropriations are part of 

the future project condition and will not be considered part of any option. 

MRGO deep-draft de-authorization options identified for this study are listed below: 

Option 1 – Maintain a shallow-draft MRGO navigation channel. Several variations 

of Option 1 would facilitate integration of the MRGO de-authorization plan into LACPR: 

• Option 1a – Maintain a shallow-draft navigation channel without a structure. 

• Option 1b – Construct a salinity control weir at Bayou La Loutre; 

• Option 1c – Construct a salinity control gate at Bayou La Loutre (normally 

closed); and 

• Option 1d – Construct a storm protection gate at Bayou La Loutre (normally 

open). 

All of the shallow-draft channel options would include maintenance dredging of a 12 feet 

deep by 125 feet wide channel to match the dimensions of the GIWW. 

Option 2 - Close the MRGO channel to deep-draft and shallow-draft vessels. Closure 

of the MRGO to all vessel traffic could be realized by blocking the channel via any of the 

following variations: 

• Option 2a – Construct an armored earthen dam across the MRGO at Bayou La 

Loutre; 

• Option 2b – Restore both banks of Bayou La Loutre across the MRGO at 

Hopedale, Louisiana; or 

• Option 2c – Fill in the entire MRGO channel from the GIWW to the Gulf of 

Mexico. 

Option 3 - Cease all MRGO operations and maintenance activities (dredging, jetty 

repairs, and navigation aids). If Congress chooses to discontinue all activities related 

to maintaining the MRGO, several relic project features would need to be addressed. 

These features include navigation aids such as buoys and lights and the offshore jetties 
23 

located in Breton and Chandeleur Sounds. Development of a complete de-authorization 

plan should include disposal of these relic features. 

Additional Opportunities 

In addition to the navigation options, additional opportunities were identified that are 

components of LACPR and other plans. Under LACPR and other independent 

authorities, opportunities for ecosystem restoration and hurricane storm surge risk 

reduction could complement the MRGO de-authorization options. These opportunities 

include: 

• Freshwater diversion into the MRGO and surrounding marshes (possibly in the 

vicinity of Violet Canal); 

• Shoreline protection to prevent wetlands erosion (including maintenance of 

existing projects); 

• Habitat creation through the placement of sediment for rebuilding marshes, 

barrier islands, and ridges; 

• Increasing existing levee heights to new hurricane protection levels; and/or 

• New hurricane protection levee alignments or surge protection structures. 

These opportunities could be implemented to provide ecosystem restoration and 

hurricane storm protection in the study area. Ecosystem restoration opportunities focus 

on reducing salinity and maintaining or increasing marsh acreage so that the natural 

system can better protect the area during storm events. 

A report prepared for USACE (Tate et. al., 2002) quantified the salinity reductions that 

could be gained in the Lake Pontchartrain estuary from creating a localized channel 

constriction on the MRGO at the Bayou La Loutre Ridge. Using three-dimensional 

hydrodynamic modeling of conditions at different times of the year and with different 

tides and wind effects, the study showed that a constriction to a 125 foot width and 12 

foot depth could achieve salinity reduction but not as much as a total blockage of the 

MRGO. 

Another way to reduce salinity in estuaries is the construction of diversion(s) that would 

move freshwater from the Mississippi River to the MRGO and surrounding wetlands and 

waterways. Coast 2050 recommended diversion of Mississippi River water into the 

wetlands surrounding the MRGO near the Violet siphon. Another recommendation 

presented was to construct a sill near Lake Pontchartrain to limit the influx of saltwater 

carried to the area through the MRGO. The 1997 McAnally and Berger report considered 

diversion of river water through the Bonnet Carre spillway and concluded that peak 

springtime diversions of 10,000 to 30,000 cfs (cubic feet per second) would be required 

to achieve desired salinity levels in the Biloxi Marshes and Mississippi Sound. A 

diversion of this size through Bonnet Carre is not supported by the State of Louisiana. 
24 

MRGO DEEP-DRAFT DE-AUTHORIZATION OPTIONS 

Each of the three deep-draft de-authorization options and their variations were evaluated 

based on environmental and navigation considerations, and their relationships to other 

projects. None of the options provides for a channel allowing deep-draft navigation. The 

level of shallow-draft navigation provided by each option is discussed.

Option 1a - Maintain a Shallow-Draft MRGO Navigation Channel 

Without a Structure 

Under Option 1a, the MRGO would be maintained for commercial and recreational 

shallow-draft navigation only with a maintained depth and width of 12 feet by 125 feet 

for the Inland and Sound Reaches. Sedimentation would be allowed to occur in the 

channel until maintenance dredging would be required. Table 7 shows the different 

channel miles and the projected years when dredging would be necessary. No navigation 

structures would be placed in the MRGO channel. 

Table 7. MRGO Dredging Areas and Estimated Date of First Required Dredging. 

Channel Miles Estimated Year 

Dredging Would Begin 

36 to 27 2045 

27 to 23 2022 

23 to 6 2012 

6 to -8 No dredging required 

-8 to -9 No dredging required 

Environmental Considerations 

In 2000, Tate modeled what effects reducing the channel depth would have on salinity 

within the Lake Pontchartrain Basin. The results of that study showed reducing the 

channel depth without reducing the width would have only a small effect; reducing the 

salinity by 0.5 to 0.8 ppt in the basin. As a result, little or no change in vegetation, land 

loss, or wildlife and fisheries would be expected. 

The implementation of Option 1a would not limit access within the MRGO for fish 

species moving to deeper water depths because a 12 foot channel depth would be 

maintained. There are no available data to indicate that the implementation of this option 

would impact threatened or endangered species. Sea turtles would no longer be impacted 

by hopper dredging in the bar channel. The MRGO is not the preferred habitat of Gulf 

sturgeon, and implementing this option would not have an impact on the species. The 

piping plover might lose future wintering habitat on the remains of Breton Island until 

maintenance dredging resumes (because beneficial use of dredged material would be 

reduced). 
25 

Other Considerations 

Under Option 1a, available sediment for future beneficial uses would be very limited. In 

the future, available sediment for dedicated dredging would be more costly than piggybacking such projects onto maintenance dredging contracts where the cost to mobilize 

and demobilize would be born by the maintenance dredging contract. 

The construction of new bank stabilization along the north and south banks of the 

MRGO, as funded by the 2006 Emergency Supplemental Appropriations, is currently 

underway. Following the completion of the bank stabilization projects, the entire north 

and south banks will be protected to the extent practicable. Option 1a would limit 

benefits of the proposed diversion of freshwater from the Mississippi River at Violet 

because freshwater benefits would not extend past the Central Wetlands. Most of the 

freshwater would be carried up and down MRGO by tides. In addition, MRGO would 

act as a sink for any sediment that might reach it from the diversion. This option would 

be compatible with shoreline protection and habitat creation opportunities. The new 

floodgates on the MRGO to be built under the 2006 Emergency Supplemental 

Appropriations would not be impacted. 

Option 1b – Construct a Salinity Control Weir at Bayou La Loutre 

Under Option 1b, a weir would be constructed just south of Bayou La Loutre to allow 

passage of shallow-draft vessels (Figure 5). This option would not only close the channel 

to deep-draft navigation, but would reduce salinity upchannel of the weir. The MRGO 

would be constricted at the weir to 125-feet wide by 14 feet deep (Note: The weir would 

have to be set at 14 feet to allow safe passage of 12-foot draft vessels—providing a 2-foot 

Keel/Hull clearance over the structure). The weir configuration likely would consist of 

earthen dam sections and pile-supported, reinforced concrete T-wall structures that 

extend from the shorelines and tie into a weir structure (Figure 6). 
26 

Figure 5. Proposed Construction Location of Option 1b. 

The earthen dam, concrete T-wall structures, and weir structure would have steel sheet 

pile, cut-off walls beneath them. It is envisioned that the dam would be constructed in the 

wet by first depositing rock starter dikes underwater to contain fill material. The fill 

material would consist of clay material, ideally dredged by bucket from a nearby 

location, and brought to the site by barge. Because the dam would be built in the wet, 

significant settlement would occur, so the dam would need to be overbuilt to allow for 

expected future settlement. The dam would be rock armored. 
27 

Figure 6. Conceptual Plan for Proposed Option 1b. 

The reinforced concrete T-wall structures would transition from the earthen dam to the 

weir structure, which would be located in the existing channel. Because the weir would 

constrict storm surge waters moving in the MRGO during a storm event, the T-wall 

structures would need to be designed to a level of storm surge caused by waters backing 

up at the weir. 

The weir structure would be a concrete U-frame, or flume, structure consisting of a base 

slab and walls. The clear opening would be 125-feet wide and between 100- and 150-feet 

long. Guide walls and dolphin cells would be needed on both sides of the weir to funnel 

marine traffic through the weir. Design optimization, including possible physical 

modeling, would be required to assess hydraulic performance and ensure safe 

navigability through such a structure. 

The T-walls and U-frame could be constructed either in the wet or pre-cast and floated to 

the site and sunk in place in a controlled manner. Dewatering exacerbates settlement, so 

this would need to be carefully investigated during the design phase of the project, before 

finalizing the method of construction. Settlement concerns may require using a circularcell wall, in lieu of the earthen dam and T-wall, to tie into the weir structure. The 

estimated cost to construct the control structure is between $50 and $60 million, which is 

an average annual cost of $3 million over the 50-year period of analysis. 
28 

 

The remainder of the MRGO would be maintained for shallow-draft navigation 

(minimum channel dimensions of 12 feet depth by 125 feet wide). Sedimentation would 

be allowed to occur in the channel until maintenance dredging is required. Table 6 shows 

the different reaches and year when dredging would first be necessary. Hydraulic and 

geotechnical investigations would be required prior to construction to assure that this is a 

viable option. 

Environmental Considerations 

Using the Tate et al. (2002) model as guidance, Option 1b which reduces channel width 

and depth to 12 feet by 125 feet would result in an average reduction of salinity greater 

than simply reducing the channel depth as in Option 1a. The reductions would not be as 

great as completely closing the channel (see Table 8). By reducing salinity north of the 

gate, stratification in Lake Pontchartrain could be reduced improving benthic habitat. 

Table 8. Comparison of Modeled Salinity. 

April, May, Sept, Oct Average Monthly 

Parts Per Thousand 

Location 

Base 

Salinity

12’ x 125’ 

Salinity 

Change

Closure 

Salinity 

Change 

Pass Manchac 0.6-1.1 -0.1 to -0.3 -0.1 to -0.9 

Frenier 4.6-5.4 - 0.4-1.2 -0.6-1.3 

North Shore 5.4-7.4 -0.8 to -1.0 -0.9 to -1.4 

Little Woods 5.9-8.1 -1.4 to -2.4 -1.6 to -3.1 

Chef Menteur 8.4-11.7 -1.3 to -1.6 -1.7 to -2.2 

Martello Castle 15.4-19.3 -3.9-5.1 -5.4-7.2 

Alluvial City 16.5-20.2 -3.9 to -4.4 -6.0 to -6.6 

Pt aux Marchettes 13.9-17.3 -0.2 to -0.5 -0.5 to – 1.1 

 (Source: Data compiled from Tate 2002) 

Although data are not available to permit quantifying changes in vegetation, it is unlikely 

that the changes in salinity mentioned above would cause large-scale changes in 

vegetation types within the Pontchartrain Basin. Some changes to less saline marsh types 

may occur in marshes along the western shoreline of Lake Borgne and perhaps in the 

Central Wetlands. The land loss impacts and impacts to threatened and endangered 

species are similar to Option 1a. The wildlife and fisheries impacts are also similar to 

Option 1a, but with greater salinity reduction. 

Other Considerations 

Option 1b would be more compatible with the LACPR than Option 1a for the proposed 

freshwater diversion at Violet. It would slightly reduce baseline salinity, but MRGO 

would still act as a sediment sink. However, freshwater would be less likely to be carried 
29 

up and down MRGO with the tide and some would be able to reach the Biloxi Marshes. 

Compatibility with other restoration opportunities is similar to Option 1a. 

Option 1c – Construct a Salinity Control Gate at Bayou La Loutre 

(Normally Closed) 

Under Option 1c, a gated structure would be constructed just downstream of Bayou La 

Loutre (Figure 7) that would allow passage of shallow-draft vessels. The gated structure 

would have a sill depth of 14 feet and a 125-foot wide opening, and would be designed 

for hydraulic loadings proportional to its height. The gate would normally be closed to 

reduce saltwater intrusion, but would be opened for passage of commercial and 

recreational shallow-draft vessels; however, details regarding an operational plan for the 

structure would have to be developed. 

 

The gate would need to be able to operate under both direct and reverse heads; so it is 

envisioned that the gate would either be a sector gate or a barge gate. The sector gate 

option is presented in this report because its use is more widespread throughout south 

Louisiana, but during the feasibility phase of design, the barge gate option would be 

explored. The gate could be operated on-site by a gate master, or remotely with the use of 

video cameras and controls. 

The gate configuration would consist of earthen dam sections and pile-supported, 

reinforced concrete T-wall structures that tie the gate structure into the Bayou La Loutre 

Ridge. The gate structure would be a pile-supported, reinforced concrete monolith 

structure that houses a pair of pie-shaped, space trussed gate leafs called sector gate leafs. 

The gate leafs are operated with a rack and pinion drive system. The monolith also 

houses the gate machinery. 

The earthen dam, concrete T-wall structures, and gate structure would have steel sheet 

pile, cut-off walls beneath them. It is envisioned that the dam would be constructed in the 

wet by first depositing rock starter dikes underwater that would contain fill material. The 

fill material would consist of clay material, ideally dredged by bucket from a nearby 

location. Because the dam would be built in the wet, significant settlement would occur, 

so the dam would need to be overbuilt several feet to allow for expected future 

settlement. The dam would be rock armored. 
30 

Figure 7. Conceptual Plan for Proposed Option 1c. 

The reinforced concrete T-wall structures would transition from the earthen dam to the 

gate structure, which would be located in the existing channel. Because the gate would 

block storm surge waters moving up the MRGO during a storm event, the T-wall 

structures would be need to be designed to a level of storm surge to the top of the 

structures. 

The gate monolith would be a concrete structure with recesses into which the gates would 

retract to create the 125-foot clear opening. Guide walls and dolphin cells would be 

needed on both sides of the weir to funnel marine traffic through the weir. Every 10-20 

years, the structure would need to be dewatered for maintenance and the gates removed 

and refurbished. Routine maintenance would be required as well. 

The T-walls and gate monolith could be constructed using in-the-wet methods or float-in 

methods where a precast unit is floated to the site and sunk in place in a controlled 

manner. Dewatering costs will be a significant portion of the overall construction costs. 

Technically, the principal disadvantage of traditional construction methods is that 

dewatering significantly increases settlement in a marsh environment, so settlement 

would need to be carefully investigated during the design phase of the project. Settlement 

is a particular concern for gate structures because excessive settlement interferes with the 

proper operation of the gates. Potential settlement countermeasures may include using a 
31 

circular-cell tie-in floodwall, in lieu of the earthen dam and T-wall. The estimated cost to 

construct the control structure is estimated to be between $60 and $70 million. In 

addition, personnel would be required to operate the gate for vessel traffic. The average 

annual cost is estimated at $3.6 million over the 50-year period of analysis. 

The remainder of the MRGO would be maintained for shallow-draft navigation 

(minimum dimensions of 12 ft depth by 125 ft width). Sedimentation would be allowed 

to occur in the channel until dredging is required. Hydraulic and geotechnical 

investigations would be required prior to construction to assure that this is a viable 

option. 

Environmental Considerations 

This option was not modeled by Tate for salinity impacts. Since the gate would be closed 

except for passage of vessels, salinity would be closer to that found with the closure in 

Table 8. On the north shore of Lake Pontchartrain, the gate might allow intermediate 

marsh to develop in inland areas during some years. The area east of MRGO could 

convert to brackish marsh and the Central Wetlands could show a change from brackish 

to intermediate marsh with a gate. Land loss, wildlife, threatened and endangered 

species, and fisheries impacts are similar to Option 1b, but with greater salinity reduction. 

Other Considerations 

This option would be the most compatible of the shallow-draft options for freshwater 

diversion opportunities. Compatibility with other restoration opportunities would be 

similar to Option 1a. 

Option 1d – Construct a Storm Protection Gate at Bayou La 

Loutre (Normally Open) 

This option comprises similar structural components and earthwork as Option 1c: a sector 

gate with tie-in T-wall and earthen dam (Figure 8). The difference between this option 

and Option 1c is the gate operating parameters. For Option 1d, the gate would not be 

operated to control salinity, but would only be operated to close the canal for any tropical 

storm event and associated storm surge. Therefore, commercial and recreational shallowdraft vessels could still use the MRGO except during storm events. 

The structure would be constructed to the same elevation as the adjacent Bayou La 

Loutre Ridge and would be effective during weak storm events but would likely be 

overtopped during large storms. Because the gate would be operated infrequently, there 

are some cost savings relative to Option 1c. The most significant cost savings should be 

with respect to the maintenance cost of the gates and the gate monoliths. Since the gates 

would be operated less frequently compared to Option 1c, there should be a longer 

interval between dewaterings of the monolith to perform major maintenance work on the 

gates. Another advantage of Option 1d is that it may be possible to operate the gates 

using a diesel-powered generator instead of having to supply power to the site. However, 

this would likely preclude remote operation of the gates since the generator would need 

to be started on-site to power the gate drive systems. The estimated cost to construct the 
32 

control structure is between $60 million to $70 million. The average annual cost is 

estimated at $3.6 million over the 50-year period of analysis. 

The remainder of the MRGO would be maintained to a controlling depth of 12 feet by 

125 feet wide. Sedimentation would be allowed to occur in the channel until 

maintenance dredging is required. Hydraulic and geotechnical investigations would be 

required prior to construction to assure that this is a viable option. 

Figure 8. Conceptual Plan for Proposed Option 1d. 

Environmental Considerations 

Since this gate would only be closed for strong southerly or easterly winds and/or 

approaching tropical storms, the salinity reduction would be similar to Option 1a (see 

Table 8). Vegetation, land loss, wildlife, threatened and endangered species, and 

fisheries impacts are similar to Option 1a. 

Other Considerations 

Compatibility of Option 1d with restoration opportunities would be similar to Option 1b.
33 

Option 2a – Construct an Armored Earthen Dam Across the 

MRGO at Bayou La Loutre 

Under Option 2a, an armored earthen dam would be constructed just south of Bayou La 

Loutre and would tie in with the southern Bayou La Loutre Ridge (Figure 9) to totally 

block the MRGO channel. The structure would not allow passage of any vessels traveling 

the length of the MRGO. Recreational craft that could use the MRGO to reach Breton 

Sound would have to reach the area via Bayou La Loutre or the Back Levee Canal, a 

longer distance. This option would also mean the loss of a detour route for shallow-draft 

traffic when the IHNC Lock is not operational for long periods of time. 

It is envisioned that the dam would be constructed in the wet, and would be constructed 

of clay fill material dredged nearby, transported by barge, and deposited un-compacted, 

underwater. Rock starter dikes would be constructed first to contain the clay fill material 

subsequently deposited underwater. Average side slopes for the dam could be as shallow 

as 10-foot horizontal:1-foot vertical. As a result, the base of the dam is expected to be 

approximately 960 feet in cross-section at the channel thalweg. Since the dam fill 

material would be un-compacted, a sheet pile cut-off wall would be installed to stop 

seepage below the dam. The dam will be rock armored to prevent erosion. Several feet of 

settlement could be expected both during and after construction, so the dam should be 

overbuilt to allow for this consideration. 

Figure 9. Conceptual Plan for Proposed Option 2. 
34 

The estimated fill volume for the earthen dam is 650,000 cubic yards of clay material. 

There would also need to be approximately 200,000 tons of rock to armor the dam. The 

estimated shoreline protection on the dam is 2,400 feet. The estimated cost to construct 

the earthen dam is $45 to $50 million, which is an average annual cost of $2.7 million 

over the 50-year period of analysis. No costs to maintain channel depth would be 

required, but O&M would be required for the armored dam. 

Sedimentation would be allowed to occur in the remainder of the MRGO. No additional 

activities to maintain channel depth would occur. Hydraulic and geotechnical 

investigations would be required prior to construction to assure that this is a viable design 

option. 

Environmental Considerations 

Using the Tate et al. (2002) model as guidance, damming the MRGO would provide the 

greatest reduction in salinity (Table 8). It would return salinity toward the historical 

conditions throughout the basin. Salinity reduction would reduce stratification and thus 

decrease the low dissolved oxygen zones in Lake Pontchartrain. A dam might help 

reduce salinity spikes at Pass Manchac. Closure might allow intermediate marsh to 

develop in inland areas during some years on the north shore of Lake Pontchartrain. The 

area east of MRGO could be converted from saline to brackish marsh and the Central 

Wetlands could show some conversion to intermediate marsh and possibly cypress 

swamp. Land loss rates, and fisheries and wildlife populations would be similar to 

Option 1b, but with greater salinity reduction. An earthen dam would also potentially 

provide wildlife access to both sides of the MRGO at the Bayou La Loutre Ridge, 

allowing some wildlife species to forage and to breed with populations on both sides of 

the channel. Threatened and endangered species impacts would be similar to Option 1a, 

except that any piping plovers that might use Breton Island would probably not be able to 

since maintenance dredging in the Sound would cease. 

Other Considerations 

Many of the proposed LACPR freshwater diversion projects would benefit from Option 

2a. The Violet freshwater diversion project would become more viable as the primary 

source of freshwater and nutrients to restore the Biloxi marshes. Compatibility with other 

restoration opportunities would be similar to Option 1a. 

Additionally, some user groups are concerned that if the MRGO is not maintained for 

shallow-draft traffic from the GIWW to the Gulf, the inland waterway tows that use the 

MRGO when the IHNC Lock is severely congested or impassable would not have that 

option available. The routine practice is that eastbound shallow-draft tows use the 

GIWW and the IHNC Lock except when the lock and approaches are either impassable 

or congested. During these periods of extreme congestion some tows will travel 

outbound on the Mississippi River to Baptiste Collette where it connects with the MRGO. 

Eastbound tows then travel back inland on the MRGO to the GIWW before continuing 

eastbound to locations in Mississippi, Alabama, and Florida. Westbound tows use the 
35 

reverse route to avoid the IHNC Lock when it is impassable. If the MRGO were closed 

to shallow-draft navigation, this alternative would not be available. The resulting trip 

around the IHNC Lock takes approximately 24 hours. Due to the distance and the 

uncertainty of the weather in Baptiste Collette, few vessels elect to travel along the 

MRGO to by-pass the lock. However, vessels can save time if the lock is down for a 

period of greater than 24 hours and/or there is a long queue. This and the effects of the 

deep-draft de-authorization are discussed in the navigation impacts section of the 

Economics Appendix. 

If the MRGO were not available as an alternative to the IHNC Lock, it has been 

suggested that some tows might divert through the Mississippi River northward to its 

junction with the Ohio River at Cairo, Illinois before connecting back down to the 

GIWW by way of the Tennessee and Tombigbee rivers; however, the time necessary to 

complete this loop currently exceeds even extreme IHNC Lock delay times. The 

Tennessee and Tombigbee route may be advantageous to tows traveling between midand upper points on the Mississippi and Ohio Rivers but not for GIWW east-west 

movements or for Lower Mississippi-GIWW eastward traffic. 

Option 2b – Restore Both Banks of Bayou La Loutre Across the 

MRGO at Hopedale, Louisiana 

Under Option 2b, two earthen dams would be constructed to restore the banks of Bayou 

La Loutre. One dam would connect the ridge on the north side of Bayou La Loutre on 

the Hopedale side with the north ridge on the Biloxi Marsh side. The second dam would 

connect the south ridges across the MRGO. This would totally block the MRGO channel 

with two structures. The structures would not allow passage of any vessels traveling the 

length of the MRGO. Recreational craft traveling from Shell Beach that could use Bayou 

La Loutre or the Back Levee Canal under Option 2a would not be able to use these 

waterways. They would need to exit into Lake Borgne and cross it or launch at Hopedale 

and use the Back Levee Canal. This option would also mean the loss of a detour route for 

shallow draft traffic when the IHNC Lock is not operational for long periods of time. 

It is envisioned that the dams would be constructed in the wet, and would be built with 

clay fill material dredged nearby, transported by barge, and deposited un-compacted, 

underwater. Rock starter dikes would be constructed first to contain the clay fill material. 

Average side slopes for the dams could be as shallow as 10-foot horizontal:1-foot 

vertical. As a result, the base of each dam is expected to be approximately 960 feet in 

cross-section at the channel thalweg. Since the fill material would be un-compacted, sheet 

pile cut-off walls would be installed to stop seepage below the dams. The dams will be 

rock armored to prevent erosion. Several feet of settlement could be expected both during 

and after construction, so the dams should be overbuilt to allow for this settlement. 

The estimated fill volume is 650,000 cubic yards of clay material for each dam. There 

would also need to be approximately 200,000 tons of rock to armor each dam. The 

estimated shoreline protection for the restored banks is 4,800 feet. The estimated cost to 

construct the dams is $90 to $100 million, which is an average annual cost of $5.4 million 
36 

over the 50-year period of analysis. No costs to maintain channel depth would be 

required. 

Sedimentation would be allowed to occur in the remainder of the MRGO. No additional 

activities to maintain channel depth would occur. Hydraulic and geotechnical 

investigations would be required prior to construction to assure that this is a viable 

option. 

Environmental Considerations 

The environmental impacts of Option 2b are the same as Option 2a. 

Other Considerations 

Other considerations for Option 2b are the same as Option 2a. 

Option 2c –Fill in the Entire MRGO Channel from the GIWW to 

the Gulf of Mexico 

Under Option 2c, the entire MRGO would be filled from the intersection of the GIWW to 

Breton Sound. This option has been requested by several stakeholders and was 

frequently noted in public comments. Recreational craft would not be able to use any 

portion of the Inland Reach of the MRGO. This option would also mean the loss of a 

detour route for shallow draft traffic when the IHNC lock is not operational for long 

periods of time. 

Environmental Considerations 

Option 2c could take many years to complete because it would take time to find the well 

over 300 million cubic yards of dredged material needed to fill the channel. The dredged 

material in the disposal area that was removed when the MRGO was built has oxidized so 

it no longer contains sufficient material to refill the channel. In addition, portions of the 

south bank provide the base for a hurricane protection levee. It is uncertain where the 

amount of material needed to fill the channel could be found – especially at a time when 

vast quantities of material are needed to restore hurricane protection levees and create 

wetland habitats throughout coastal Louisiana. In addition, this material could be far 

better used to improve hurricane protection levees in the aftermath of Hurricane Katrina 

or for pressing coastal restoration needs. 

Salinity impacts would be the same as for Option 2a. Assuming that the Inland Reach of 

the MRGO is an average of 1,000 feet wide and the filled area is 39 miles long, about 

4,800 acres of marsh could be created, if the height were controlled carefully. However, 

the cost of creating marsh in a place that is up to 40 feet deep is probably at least eight to 

ten times the cost of creating marsh in an area 5 feet deep. It would take several years to 

find such an amount of fill material since it is likely that hurricane protection projects 

would have a higher priority. Creation of marsh would reduce land loss rates in the lower 

Pontchartrain Basin, benefit wildlife, fisheries and threatened and endangered species, 

but there are likely far less costly ways to receive the same benefit. 
37 

Other Considerations 

To extend the benefits of the freshwater diversion across the filled channel, a new small 

channel would have to be dredged. Marsh creation would be adversely impacted because 

they would be in competition for the limited amount of fill material available. If this 

option is chosen, the navigable flood gates and the shoreline protection under the 

Supplemental Appropriations would not be necessary. 

Option 3 - Cease All MGRO Operations and Maintenance 

Activities 

Under Option 3, no additional Federal funds would be used to maintain a minimum 

channel depth on of the MRGO between the GIWW and the Gulf of Mexico. There 

would be neither construction nor operation and maintenance costs for this option. 

However, the shoreline protection features could be modified as part of LCA or LACPR. 

Relic features, such as jetties and aids to navigation would be considered for removal 

and/or reapplication. Under this option, commercial and recreational shallow-draft 

vessels could still use the MRGO until the MRGO channel filled in to a depth that 

prohibited their navigation. 

Environmental Considerations 

No published literature is currently available to make confident projections on the salinity 

impacts if the USACE ceased dredging of the MRGO. At this stage, it would be assumed 

that salinity would be reduced similar to Option 1a. Impacts to vegetation, land loss, 

wildlife, threatened and endangered species, and fisheries would be similar to Option 1a. 

Other Considerations 

Compatibility with other restoration opportunities would be similar to Option 1a. 

Following completion of the bank stabilization projects under the Supplemental 

Appropriation, the entire north and south banks of the MRGO would be protected. 

However, no maintenance of these features would be done by the Federal government 

unless incorporated into LCA or LACPR plans. 
38 

OPPORTUNITIES FOR ECOSYSTEM RESTORATION AND 

STORM SURGE REDUCTION 

A statement accompanying the legislative language accepted in the Congressional 

Conference Committee requests the identification of “any measures for hurricane and 

storm protection” (House Report 109-494). For this study, measures were identified that 

would prevent or reduce impacts associated with storm surge traveling across the MRGO 

area marshes or potentially overtopping existing levees. The opportunities described 

below are being considered in the development of LACPR plans and may complement 

options in the MRGO Deep-Draft De-authorization plan. 

These opportunities include various levee improvements and coastal restoration measures 

such as: 

• Freshwater diversion 

• Habitat creation by sediment placement 

• Shoreline protection 

• Increasing existing hurricane protection levee heights 

• New hurricane protection levee alignments and surge protection structures 

Freshwater Diversion into MRGO and Surrounding Marshes 

This opportunity involves the diversion of freshwater into the MRGO area via an 

enlarged Violet Canal (Figure 10) or an adjacent site. Diversion of freshwater into the 

area is anticipated to require constructing a pile-supported, sluice-gated, reinforced 

concrete culvert structure with a cut-off wall system in the existing Mississippi River 

levee. The diversion structure would be able to pass up to 15,000 cfs of river water by 

gravity into the canal. The canal would transport the river water approximately 1.5 miles 

to feed the marshes between the Mississippi River and the MRGO. The Mississippi 

River diversion flow rates would be controlled by raising and lowering the sluice gates. 

Portions of the Violet Canal would be widened and lined with either concrete or rock to 

improve the canal’s hydraulics. Diverting 15,000 cfs would require widening the Violet 

Canal from widths of approximately 10 to 25 feet to between 160-feet and 200-feet in 

width at the bank line, depending on whether concrete or rock is used to line the canal. 
39 

Figure 10. Photo of Violet Diversion Canal. 

Widening the Violet Canal also could require the relocations of most of the existing 

facilities located adjacent to the canal. Construction of the freshwater diversion project 

would require the temporary relocation of East St Bernard Highway and possibly the LA 

39 (East Judge Perez Drive) bridge over the Violet Canal. The latter is a high level, fourlane bridge over the canal. Depending on the additional canal width required and the 

location of the bridge abutments, the bridge may have to be relocated. This could be a 

significant potential relocations expense. The preliminary estimated cost of such a 

diversion is $250 million, which is an average annual cost of $12.6 million. 

Environmental Considerations 

A large-scale freshwater diversion project in the vicinity of Violet would greatly increase 

fine sediment transport and deposition into the marshes located between the Mississippi 

River and the MRGO. Although increased fine sediment deposition would create some 

marsh and reduce losses in other marshes in this area, it is unlikely that sediments would 

be transported across the MRGO into Lake Borgne and the Biloxi Marshes because the 

deep water MRGO would trap most of these sediments. 

The introduction of large volumes of freshwater from the Mississippi River would 

substantially lower salinity in the Central Wetlands. Some freshwater from a diversion 

near Violet would likely cross the more dense saline waters of the MRGO and reduce 
40 

salinity in Lake Borgne and the Biloxi Marshes. Coastal marsh vegetation to the east of 

the diversion would greatly benefit from the influence of freshwater, sediment, and 

nutrients; plant productivity would substantially increase. It is likely that much of the 

brackish and intermediate marsh vegetation located in the Central Wetlands would 

convert to intermediate and fresh marsh. In areas immediately adjacent to the diversion 

outfall it is likely that cypress-tupelo swamp could be reestablished if other conditions 

were managed, such as nutria herbivory. 

Some new marsh creation and reduction of future wetlands loss would occur as a result of 

the freshwater diversion. However, the construction of a conveyance channel would 

cause some direct loss of coastal wetlands. Wildlife and threatened and endangered 

species would generally benefit from increased marsh area and plant productivity. Some 

commercial and recreational fisheries in the region would be impacted as saltwaterdependent species were displaced. However, in the long-term, increased wetland area 

would provide additional habitat for juvenile saltwater-dependent fishes. 

Other Considerations 

Because the MRGO would trap most of the sediments and some of the freshwater 

diverted eastward from the Mississippi River, the beneficial effects of freshwater and 

sediment to the estuary would be primarily limited to the Central Wetlands for all of the 

de-authorization options except for the complete closure of the MRGO option (Option 2). 

The complete closure option could provide opportunities to allow for some sediment and 

more freshwater to be transported east of the MRGO into Lake Borgne and the Biloxi 

Marshes. 

A freshwater diversion project near Violet is compatible with all of the proposed 

ecosystem restoration projects and plans. Additionally, the diversion project could 

provide storm surge reduction benefits to compliment proposed hurricane and flood 

protection projects. The additional marsh provided by this option could reduce the 

impacts of small storm surges over the marsh on the adjacent Forty Arpent Levee system 

by preserving the existing marsh that is one of the lines of defense against wave action. 

Some businesses along the Violet Canal, however, could be substantially impacted by 

such a diversion project. As a result, project planning would have to include an 

assessment of potential business relocation requirements. 

Shoreline Protection 

This opportunity includes construction of shoreline protection features such as rock dikes 

at or near the edge of waterways, lakes or bays to prevent the erosion of adjacent 

marshes. Maintenance of existing shoreline protection features has also been identified 

as an opportunity. 

Rock shoreline protection dikes would be designed in shallow offshore waters. Fisheries 

access would be assured by gapping the dikes approximately every 1,000 feet. The 3rd

Emergency Supplemental Appropriation authorized construction of rock shoreline 

protection all along the Inland Reach of the MRGO and on the shoreline of Lake Borgne 
41 

from Doullut’s Canal to Jahnecke’s Ditch. No future maintenance money has been 

appropriated for these projects. There is one project authorized by CWPPRA that 

provides rock on MRGO and Lake Borgne; this project includes maintenance for 20 

years. There are significant opportunities to protect other portions of the Lake Borgne 

shoreline or shorelines in the Biloxi Marshes. Also, if the MRGO is de-authorized, it 

may be possible to move and utilize the jetty rock for shoreline protection. This material 

could be placed to protect the marsh between Fiddler Point and the MRGO created marsh 

on the west or between the MRGO and Deadman Island on the east. 

The maintenance of existing shoreline protection projects on the MRGO and Lake 

Borgne is estimated to cost $250 to 500 per foot (based upon CWPPRA 20-year life 

cycle). Placement of new dikes on lake or bay shorelines is estimated to cost $1,500 per 

foot (also based upon CWPPRA jobs). Site specific evaluation is required to develop 

better cost estimates. 

Environmental Considerations

Shoreline protection that is offshore in shallow water generally allows sedimentation to 

occur between the dike and the shore. As it attained marsh elevation, this area would 

naturally vegetate creating a small amount of marsh. The existing marsh behind the 

shoreline protection would be protected and eroded far more slowly. This would slightly 

reduce land loss in the basin. Shoreline protection would rarely change salinity. Wildlife 

and fisheries would benefit from the marsh that would be saved and created and 

preserved. These wetlands would provide feeding, nesting and resting habitat for 

wildlife. Fisheries access within the estuary would not be affected by the shoreline 

protection projects because of the designed gaps. The rocks and shallow area between 

the rock and shore would provide valuable edge habitat for some fish species. 

Other Considerations 

The three de-authorization options evaluated earlier in this report would not be affected 

by the shoreline protection projects. Shoreline protection is compatible with all other 

flood protection and ecosystem restoration opportunities. The additional marsh preserved 

by this option could help reduce the impacts of small storm surges over the marsh. 

Habitat Creation by Sediment Placement 

Vegetated marsh lands serve as a damper to storm-induced surges and help to reduce 

storm impacts to human structures, such as homes and businesses. Therefore, numerous 

strategies could be utilized to create or restore marsh, barrier islands, and ridges. 

Material could be obtained by mining of sounds, Bayou La Loutre and the Mississippi 

River and the MRGO, or the MRGO spoil bank. It is clear that marsh habitat in the area 

is on the decline due to both natural and man-made factors. It is also clear that marsh 

habitat is important in reducing the potential for damages during a storm event. 

Opportunities should be identified that utilize any or all of these strategies to create or 

restore marsh, barrier island, and ridge habitat in the Middle Pontchartrain Basin to help 

reduce storm damages. Habitat creation or enhancement is anticipated to cost a minimum 

of $10,000/acre, on average. 
42 

Environmental Considerations

Marsh and island creation would rarely change salinity. Restoration of the Bayou La 

Loutre Ridge in conjunction with a dam in the MRGO could reduce salinity in the Biloxi 

Marshes. Created habitat would vegetate with plants similar to those surrounding it at the 

same elevation. All habitat creation projects would reduce land loss rates. These projects 

have substantial direct long-term ecosystem benefits and can have the indirect benefits of 

providing wind and wave erosion protection for nearby wetlands and levees. 

Most wildlife would directly benefit from habitat creation projects such as the restoration 

of marshes and barrier islands. Neotropical migrant birds would benefit from the ridge 

habitat restoration. Shorebirds and waterfowl especially benefit from increased nesting 

sites and foraging areas associated with island creation. Some threatened and endangered 

species, such as sea turtles and piping plovers, could benefit from the creation of 

additional nesting habitat such as beach on Breton, Grand Gosier or Curlew Islands. 

Fisheries access within the estuary would not be affected by the habitat creation projects. 

Most fish and shellfish would benefit from the creation of marsh and island habitat. 

Other Considerations 

The three de-authorization options are not affected by additional habitat creation projects 

such as marsh, ridge, and barrier island creation. The creation of additional marsh, 

barrier island, and ridge habitat is compatible with all other flood protection and 

ecosystem restoration opportunities analyzed. The additional marsh preserved by this 

option could help reduce the impacts of small storm surges over the marsh. 

Increase Existing Hurricane Protection Levee Heights to New 

Protection Levels 

One method of improving hurricane protection for southeast Louisiana is to increase the 

heights of existing levees. Higher levees result in some degree of storm surge risk 

reduction. The advantage of levee raisings over constructing new levee alignments may 

include reduced real estate requirements, fewer construction materials, and smaller 

impacts to wetlands and other coastal habitats. In the MRGO area, some levee raisings 

have been completed along the south bank of the channel as part of Task Force Guardian 

work and additional increases in height to 100-year protection levels are authorized. As 

part of LACPR, teams are evaluating and designing potential levee raisings along 

existing alignments in the vicinity of the MRGO. 

Borrow materials will be required, levee footprints will encroach into adjacent habitats, it 

will be necessary to construct access roads, and there will be associated noise and traffic 

resulting from heavy vehicles and machinery. The levees might include gates or culverts 

to restore hydrology. 

Environmental Considerations

Raising existing levees would generally have no impact on salinity. It is likely that 

wetlands would be destroyed as the levee footprints expanded. Removal of borrow 
43 

material could also turn wetlands to open water. This would increase land loss rates in the 

basin. These impacts would need to be mitigated. Gates or culverts in a levee could 

allow a more natural hydrology. Raising the levees on the MRGO spoil bank would not 

impact wetland vegetation in most cases. Wetlands that were enclosed behind a “leaky” 

levee might have a reduced loss rate due to less edge erosion. Most wildlife and fisheries 

would be adversely impacted by raising levees higher. 

Other Considerations 

Freshwater diversion, habitat creation, and shoreline protection would need to be done 

with consideration of levee raisings, but should not be impacted. The levees would 

provide storm surge protection to people and their homes, personal property and 

businesses. 

New Hurricane Protection Levee Alignments and Surge 

Protection Structures 

Planning and design efforts underway as part of the LACPR are considering new levee 

alignment alternatives for increased hurricane protection in South Louisiana. The 

alternatives under consideration include new levee and flood gate options in the vicinity 

of Lake Borgne and the MRGO. In relation to the MRGO, all of the current proposed 

alternatives for the LACPR include features that would cross the channel at various 

locations. As such, determination of the future authorized depth of the MRGO is a key 

consideration in planning, evaluating, and designing new alignments and surge protection 

structures as part of the LACPR. Design requirements and construction costs are highly 

dependent upon associated navigation needs, if any, that may remain on the MRGO. 

Environmental Considerations 

Impacts to salinity, vegetation, land loss, wildlife, threatened and endangered species and 

fisheries would be significantly more than those described above for options to raise 

existing levees. Since these would be new levees, the levee and borrow footprints would 

impact significantly more wetlands. This impact would mean that mitigation would have 

to be significantly increased over the opportunity for raising levees. 

Other Considerations 

Identifying, designing and building new alignments in the vicinity of MRGO should be 

carefully coordinated with efforts to conserve and restore coastal resources. Planners 

should seek to identify new alignments that minimize direct and indirect impacts to 

wetlands and that are neutral or complimentary with regards to plans for wetlands 

restoration. For example, new alignments should be devised to contribute to the 

distribution of diverted freshwater rather than in locations that would prevent beneficial 

outfall management of freshwater and sediments. If designed in concert, new levee 

protection and coastal restoration features are more likely to support long-term goals of 

both hurricane protection and coastal restoration programs. Such considerations are a 

key guiding factor in ongoing planning efforts for the LACPR. 
44 

MRGO AREA SYSTEMS EVALUATION 

A systems evaluation for the comprehensive plan to de-authorize deep-draft navigation 

on the MRGO should include a direct comparison of deep-draft de-authorization options, 

economic benefits of deep-draft navigation, a financial analysis of deep-draft navigation, 

a financial analysis of shallow-draft navigation, and an analysis of the compatibility 

between the deep-draft de-authorization options and other opportunities for ecosystem 

restoration and storm surge reduction. 

Comparison of Deep-Draft De-authorization Options 

Table 9 on the following page provides comparisons of the economic, social, and 

environmental considerations of each MRGO de-authorization option. These options are 

discussed in detail in earlier sections of the report but the table provides a side-by-side 

comparison of the multiple evaluation factors considered. Although this information is 

preliminary, it is very useful in identifying options and opportunities for inclusion in the 

LACPR evaluations. In particular, at this stage of evaluation Option 2a - an armored 

earthen dam at Bayou La Loutre - appears to offer multiple benefits and opportunities 

with the lowest annual estimated construction costs and operations and maintenance 

costs. 

Economic Benefits of Deep-Draft Navigation 

One benefit of the MRGO is lower shipping costs, as ships require less time and fuel to 

reach their destination when using the MRGO instead of the Mississippi River. This 

benefit is a national economic development (NED) consideration and is used when 

determining cost effectiveness and justification in the Federal water resources 

development planning process. 

Additional benefits provided by the MRGO include the direct jobs created by the 

shipping industry and other industries that rely on vessels utilizing the MRGO, as well as 

the indirect impact of these jobs on the local economy. Prior to Hurricane Katrina, 

businesses located along the MRGO that relied upon the outlet provided approximately 

1,000 direct jobs. The benefits associated with an increased number of jobs are a local or 

regional benefit and not utilized during effectiveness and justification evaluations. 
45 

Table 9. Comparison of Deep-Draft De-Authorization Options. 

DESCRIPTION Option 1a: 

 No Structure 

(maintain for 

shallow-draft) 

Option 1b: 

Salinity Control 

Weir at La Loutre 

Option 1c: 

 Salinity Control 

Gate at La Loutre (normally closed) 

Option 1d: 

Storm Protection Gate 

at La Loutre (normally 

open) 

Option 2a: 

Armored Earthen dam 

at La Loutre Ridge to 

close MRGO 

Economic Considerations 1)Business Reestablishment $13.6M $13.6M $13.6M $13.6M $13.6M 2)Annual Construction $0 $3,071,000 $3,629,000 $3,629,000 $2,652,000  - Annual O&M $6,101,000 $6,101,000 $6,101,000 $6,101,000 $0 3)Impacts to Local Communities 

Some companies along MRGO might choose to relocate, possibly out of state 

Some companies along MRGO might choose to relocate, possibly out of state 

Some companies along MRGO might choose to relocate, possibly out of state 

Some companies along MRGO might choose to relocate, possibly out of state 

Some companies alonMRGO might choose to relocate, possibly out of state 

Social Effects 1) Life, Health, and Safety No impacts No impacts No impacts No impacts No impacts 2) Community Cohesion Potential beneficial 

impacts 

Potential beneficial impacts 

Potential beneficial impacts 

Potential beneficial impacts 

Potential beneficial impacts 

3) Recreation No impacts No impacts No impacts No impacts No impacts 4) Environmental Justice No impacts No impacts No impacts No impacts No impacts 5) Socio-economics No impacts No impacts No impacts No impacts No impacts Environmental Consider. 1) Salinity Small future 

reduction 

Moderate reduction Substantial 

Reduction 

Moderate reduction Substantial Reduction 

2) Vegetation No substantial 

change 

Some possible local changes to less saline marsh 

Possible change to less saline marsh over wider area than 1a 

No substantial change Possible change to les

saline marsh over wider area than 1a 

3) Land Loss No change in basin 

land loss rates 

No change in basin land loss rates 

No change in basin land loss rates 

No change in basin land loss rates 

No change in basin land loss rates 

4) Wildlife No substantial 

change 

No substantial change 

No substantial change 

No substantial change No substantial change 

5) Threatened and Endangered Species 

Coordination if necessary 

Coordination if necessary 

Coordination if necessary 

Coordination if necessary 

Coordination if necessary 

6) Fisheries No substantial 

change 

No substantial change 

No substantial change 

No substantial change No substantial change 

7) Hazardous-ToxicRadioactive Waste No impact Phase 1 ESA will be done Phase 1 ESA will be done Phase 1 ESA will be done Phase 1 ESA will be done 8) Cultural Resources No impacts Surveys needed Surveys needed Surveys needed Surveys needed 
46 

Financial Analysis of Deep-Draft Navigation 

By maintaining navigation at a 12-foot draft, companies whose businesses are dependent 

on deep-draft navigation in the MRGO could be adversely affected. Under all options 

evaluated, up to eight businesses could be impacted by de-authorization of deep-draft 

navigation. Through interviews and a survey, business reestablishment costs were 

determined. The affected firms were asked what depth would have an impact on their 

business and would perhaps prompt them to reestablish facilities elsewhere. Each 

surveyed business estimated its own reestablishment costs. Reestablishment estimates 

provided by these businesses do not reflect depreciation but rather actual purchase for a 

new or used facility with comparable infrastructure and transportation networks. The 

costs presented in this document, in particular those associated with business 

reestablishments, were not prepared using NED procedures. These estimates are not 

based on federal relocation assistance principles. These reported business reestablishment 

costs are not the responsibility of the Federal government. 

Four of the interviewed companies are dependent on the fully authorized dimensions of 

the MRGO to maintain the operation modes they employed prior to Hurricane Katrina. 

These companies estimate that costs to reestablish comparable facilities on the 

Mississippi River or other area waterways would be approximately $244 million or an 

average annual cost of $13.6 million. 

Preliminary analysis of deep-draft navigation suggests that maintaining the authorized 

dimensions of the MRGO is not cost effective. Average annual O&M costs to dredge the 

waterway are $12.5 million while maintaining the authorized dimensions produces 

approximately $6.2 million in transportation efficiencies. 

Two types of inefficiencies were evaluated for this study: transportation inefficiencies 

associated with increased travel time of a vessel and business inefficiencies that involve 

additional steps in these processes. Increased travel time occurs when vessels are unable 

to use the MRGO and are required to use the Mississippi River. These transportation 

inefficiencies for vessels requiring drafts of greater than 12 feet are estimated by the 

effected businesses to be $2.5 million a year. If companies are unable to dock deep-draft 

vessels at their facilities, they often transport their product to an alternative location or 

light-load their vessels. Businesses that remain in the MRGO-serviced area currently 

face transportation inefficiencies of $2.5 million per year associated with modified 

marine operations. The businesses themselves estimated that these business 

inefficiencies are $10 million a year because of modified land operations at their 

facilities, although the USACE has not verified these reported costs. 

It was assumed that business reestablishments would take about four years and during 

this time businesses would have to incur the added costs of light-loading or trucking their 

commodities to/from the river to MRGO facilities. Once the facilities were moved to the 

River these inefficiencies would end but the businesses may incur added costs to travel to 

their new facilities. 
47 

Financial Analysis of Shallow-Draft Navigation 

As part of the analysis, benefits and costs of maintaining a 12-foot channel depth for 

shallow-draft navigation were estimated. If any option of maintaining the channel for 

shallow-draft navigation is selected, the maintenance dredging would occur at different 

times for different sections of the channel. These estimates use the current depths, past 

maintenance dredging requirements and sedimentation rates to determine when dredging 

would first occur in each reach of the channel. Refer back to Table 7 for a list of 

locations along the channel and the estimated time it would take for the channel to fill to 

a point where shallow-draft maintenance dredging would be required. 

The benefits of authorizing the MRGO to 12 feet are the reduction in the transportation 

inefficiencies over the total closure option for the channel. According to the WCSC data, 

an average of 1,407 vessels with depths of 12 feet or less have a one-way passage on the 

Inland and Sound reaches of the MRGO each year. If the MRGO were to be closed, those 

trips would have to be taken by a longer alternate route along the Mississippi River. In 

addition, if the MRGO were to be closed, the MRGO would no longer be available as an 

alternative route to the GIWW for shallow-draft traffic when the IHNC Lock is not 

functioning or is congested. Taking these two issues into account, it is estimated that the 

average annual benefits of authorizing the MRGO to 12 feet is $3.7 million. 

Table 10 is a summary of the shallow-draft options. This preliminary information 

suggests that, with an annual cost of maintenance exceeding $6 million, and annualized 

benefits of approximately $3.7 million, shallow-draft navigation is not cost effective. 

Table 10. Shallow-Draft Navigation for Different Options. 

Option Construction 

Costs 

Average 

Annual 

Costs 1 

Average 

Annual 

Benefits 

Significant 

Ecosystem Restoration

Benefits 

No Structure $0 $6,101,000 $3,674,000 Some long-term reduction 

in salinity and erosion; 

continued BU marsh 

creation 

Salinity Control 

Weir at La Loutre 

$50,000,000 $8,629,000 $3,674,000 Reduction in salinity and 

enhancement of 

freshwater diversions 

Salinity Control 

Gate at La 

Loutre- normally 

closed 

$60,000,000 $9,135,000 $3,674,000 Greater salinity reduction 

and enhancement of 

freshwater diversions 

Storm Protection 

Gate at La 

Loutre- normally 

open 

$60,000,000 $9,135,000 $3,674,000 Reduction in salinity and 

enhancement of 

freshwater diversions 

1 Includes construction and O&M costs. The O&M includes maintenance of existing shoreline protection 

and additional dredging required after tropical storms and hurricanes. 
48 

Analysis of Compatibility Between Options and Opportunities 

All three de-authorization options relate at different levels with the hurricane protection 

and ecosystem restoration opportunities also identified in this report (shoreline 

protection, freshwater diversion, habitat creation, raising existing levees, new levee 

alignments, and storm surge structures) (Table 11). 

For instance, if the MRGO channel is not reduced in width or closed, freshwater and 

sediments diverted from the Mississippi River would have less benefit to the marshes 

located east of the channel. In terms of habitat creation, fresher marsh types would result 

if the channel is restricted or closed
49 

Table 11. Relationship Between Deep-Draft De-Authorization Options and LACPR. 

Option Fresh-water 

Diversion 

Shoreline 

Protection 

Habitat 

Creation 

Increase 

Existing Levee 

Heights 

New Levee 

Alignments or 

Surge 

Reduction 

Structures 

Option 1a -Maintain 12’ navigation 

Not Consistent Consistent Consistent Consistent Consistent 

Option 1b – Weir Some connection 

Mutual goals 

Some connection 

Mutual goals 

Some connection 

Mutual goals 

Consistent Consistent 

Option 1c – Gate mostly closed 

Strong connection 

Mutual goals 

Strong connection 

Mutual goals 

Strong 

connection 

Mutual goals 

Consistent Consistent 

Option 1d – Gate mostly open 

Some connection 

Mutual goals 

Some connection 

Mutual goals 

Some connection 

Mutual goals 

Consistent Consistent 

Option 2a – Earthen Closure 

Strong connection 

Mutual goals 

Strong connection 

Mutual goals 

Strong 

connection 

Mutual goals 

Consistent Consistent 

Option 2b – Double earthen closure 

Strong connection 

Mutual goals 

Strong connection 

Mutual goals 

Strong 

connection 

Mutual goals 

Consistent Consistent 

Option 2c – Fill in channel 

Barely Consistent Consistent Consistent Consistent Consistent 

Option 3 – No Maintenance 

Not Consistent Consistent Consistent Consistent Consistent 
50 

RESULTS AND CONCLUSIONS OF INTERIM REPORT 

For this report, the USACE executed a collaborative planning effort with multiple 

stakeholders. The collaborative planning effort attempted to identify a consensus plan for 

de-authorizing the channel but in the end resulted in only identifying common measures 

or features supported by many stakeholders. 

Implementation of any of the deep-draft de-authorization options presented in this report 

would require additional hydraulic modeling, possible physical modeling, detailed 

engineering design, and completion of environmental compliance evaluations. This 

additional analysis will be conducted as part of the final LACPR Report due to Congress 

in December 2007. Congress directed USACE to “refine the plan, if necessary, to be 

fully consistent, integrated, and included” in the final LACPR plan. 

Preliminary analysis of deep-draft navigation suggests that maintaining the authorized 

dimensions of the MRGO is not cost-effective. Average annual O&M costs to dredge the 

MRGO deep-draft channel are $12.5 million. However, maintaining the authorized 

dimensions only produces approximately $6.2 million per year in transportation 

efficiencies. 

Preliminary economic analysis of the three shallow-draft navigation options in this report 

suggests that maintaining GIWW dimensions is not cost effective due to the irregular use 

of the MRGO by shallow-draft traffic. The average annual costs for construction and 

maintenance dredging range between $6 million and $9 million while estimated benefits 

associated with maintaining shallow-draft depths are approximately $3.7 million. 

Based on the above economic information, this report suggests that constructing an 

armored earthen dam at Bayou La Loutre may present the best option to ensure full 

incorporation into LACPR. Some variation of this option would likely generate the 

greatest benefits by reducing salinity, restoring marshland, and offering some protection 

against minor storm surges. Further analysis should be performed on the location and 

design to ensure the most cost-effective and sound engineering plan. Design 

optimization, including possible physical modeling, would be required to assess hydraulic 

performance. 

Erosion protection options on the banks of the MRGO will be implemented by coastal 

restoration measures directed by emergency supplemental appropriations acts, and any 

remaining erosion protection can be designed as part of the LACPR Report. Freshwater 

diversion can be modeled and designed as part of the LACPR Report. The navigable 

closure on the GIWW will be implemented as directed by the Emergency Supplemental 

Appropriations Act dated June 15, 2006. Habitat creation by the placement of sediment 

can be finalized as part of the LACPR Report, CWPPRA projects, and resumption of the 

LCA study of MRGO features. 
51 

PRELIMINARY COMPREHENSIVE PLAN FOR DEAUTHORIZING THE MRGO 

Preliminary analysis indicates that it may be appropriate to close the MRGO channel to 

both deep-draft and shallow-draft navigation. Maintaining shallow-draft or deep-draft 

navigation is not cost-effective according to current data. Based on this preliminary 

analysis, closure of the MRGO channel to both shallow and deep-draft navigation by an 

armored earthen structure just south of Bayou La Loutre near Hopedale, Louisiana 

appears to be a particularly viable option and may be the best option to support full 

integration into LACPR. 

Through incorporation into LACPR, additional measures to provide opportunities for 

hurricane storm surge protection and ecosystem restoration may complement MRGO 

channel closure. Such opportunities include: 

• Freshwater diversion into the MRGO and surrounding marshes (possibly in the 

vicinity of Violet Canal); 

• Shoreline protection to prevent wetlands erosion (including maintenance of 

existing projects); 

• Habitat creation through the placement of sediment for rebuilding marshes, 

barrier islands, and ridges; 

• Increasing existing levee heights to new hurricane protection levels; and/or 

• New hurricane protection levee alignments or surge protection structures. 

These preliminary options will be further developed and coordinated for NEPA 

compliance through the LACPR efforts. These opportunities have been supported by 

stakeholders and are consistent with many existing Federal and non-Federal plans for 

ecosystem restoration and hurricane protection. 

The LACPR Final Technical Report will provide the design for a comprehensive plan for 

MRGO deep-draft de-authorization as well as any other opportunities for hurricane storm 

damage protection and ecosystem restoration. Additionally, several major, ongoing 

efforts (navigable storm gates to protect the IHNC area, erosion protection along the 

MRGO, and the IHNC Lock replacement project) that address key aspects of the project 

and surrounding system are documented in this interim report. 

Completing a de-authorization plan includes full development and coordination of the 

MRGO de-authorization project with LACPR plans. This report is an important step in 

completing and integrating the MRGO de-authorization into the LACPR because of the 

need to evaluate these plans with other components of the LACPR plans. Evaluation 

steps would include modeling of storm surge interaction with project features, evaluation 

of environmental benefits and impacts, and fully developing initial designs and costs for 

inclusion in a final plan. 
52 

List of Acronyms 

ADCIRC Advanced Circulation Model 

cfs cubic feet per second 

CHL Coastal and Hydraulics Laboratory 

Coast 2050 Plan Coast 2050: Toward a Sustainable Coastal Louisiana Report 

CWPPRA Coastal Wetlands Planning, Protection and Restoration Act 

EPA U.S. Environmental Protection Agency 

ERDC Engineer Research and Development Center 

ESA Environmental Site Assessment 

ft feet 

GIWW Gulf Intracoastal Waterway 

IHNC Inner Harbor Navigation Canal 

IWR Institute for Water Resources 

LCA Louisiana Coastal Area 

LDEQ Louisiana Department of Environmental Quality 

LDNR Louisiana Department of Natural Resources 

MLG Mean Low Gulf 

mph miles per hour 

MRGO Mississippi River-Gulf Outlet 

NED National Economic Development 

NEPA National Environmental Policy Act 

NOAA National Oceanic and Atmospheric Administration 

O & M Operations and Maintenance 

OSA Office of the Secretary of the Army 

PEIS Programmatic Environmental Impact Statement 

ppt parts per thousand 

USACE U.S. Army Corps of Engineers 

USFWS U.S. Fish and Wildlife Service 

WCSC Waterborne Commerce Statistics Center 
Appendix 1 – References 
References 

Barras, J., S. Beville, D. Britsch, S. Hartley, S. Hawes, J. Johnston, P. Kemp, Q. Kinler, 

A. Martucci, J. Porthouse, D. Reed, K. Roy, S. Sapkota, and J. Suhayda. 2003. 

Historical and Projected Coastal Louisiana Land Changes: 1978-2050: USGS 

Open File Report 03-334, 39 p. 

Bretschneider, C. L., and J.I. Collins. 1966. Storm Surge Effects of the Mississippi 

River-Gulf Outlet, Study A. NESCO Report SN-326-A. National Engineering 

Science Company. Pasadena, CA. 

Britsch, L. D. and D. B. Dunbar. 1993. Land Loss Rates Louisiana Coastal Plain. 

Journal of Coastal Research. 9:324-338. 

Cahoon, D. R. 1991. Management implications of sediment dynamics in delta marshes of 

Louisiana. GCSSEPM Foundation Twelfth Annual Research Conference. 

Program and Abstracts, December 5, 1991. 

Cahoon, D. R., D. J. Reed, and J. W. Day, Jr. 1995. Estimating shallow subsidence in 

microtidal salt marshes of the southeastern United States: Kaye and Barghoorn 

revisited. Marine Geology 128:1-9. 

Chabreck, R. H., T. Joanen, and A. W. Palmisano. 1968. Vegetative Type Map of the 

Louisiana Coastal Marshes. Baton Rouge: Louisiana Department of Wildlife and 

Fisheries, Baton Rouge, Louisiana. 

Chabreck, R.H., and G. Linscombe. 1978, 1998 and 1997. Vegetative type map of the 

Louisiana coastal marshes: Louisiana Department of Wildlife and Fisheries, New 

Orleans, Louisiana. 

Coastal Environments, Inc. 1984. Environmental characteristics of the PontchartrainMaurepas Basin and identification of management issues. Coastal Management 

Div., LA Dept. Nat. Res., Baton Rouge. 

Conservation and Restoration Authority. 1998. Coast 2050: Toward a Sustainable Coastal 

Louisiana. Louisiana Department of Natural Resources. Baton Rouge, La. 161 p. 

Frazier, D. E. 1967. Recent Deltaic Deposits of the Mississippi River: Their Development 

and Chronology. Transactions of the Gulf Coast Association of Geological 

Societies V 17, p 287-315. 

Gagliano, S. M. 2005. Effects of natural fault movement on land submergence in coastal 

Louisiana. In: Proceedings of the 14th Biennial Coastal Zone Conference, New 

Orleans, LA. 

LDNR. 2006. The Direct Impact of the MRGO on Hurricane Storm Surge. 81 p. 

Louisiana Coastal Wetlands Conservation and Restoration Task Force and the Wetlands 

Conservation and Restoration Authority. 1998. Coast 2050: Toward a 

Sustainable Coastal Louisiana. Louisiana Department of Natural Resources. 

Baton Rouge, Louisiana. 161 p. 

1
McAnally, W. H. and R. C. Berger. 1997. Salinity Changes in Pontchartrain Basin 

Estuary Resulting from Bonnet Carre Freshwater Diversion: Numerical Model 

Investigation. 90 p. 

Mendelssohn, I. A., and K. L. McKee. 1988. Spartina alterniflora dieback in Louisiana: 

time course investigation of soil and waterlogging effects. Journal of Ecology 

76:509521. 

Nyman, J. A., M. Carloss, R. D. DeLaune, and W. H. Patrick, Jr. 1994. Erosion rather 

than plant dieback as the mechanism of marsh loss in an estuarine marsh. Earth 

Surface Processes and Landforms 19:6984. 

O'Neil, T. 1949. The Muskrat in the Louisiana Coastal Marshes: A Study of the 

Ecological, Geological, Biological, Tidal, and Climatic Factors Governing the 

Production and Management of the Muskrat Industry in Louisiana. Louisiana. 

Department of Wildlife and Fisheries, New Orleans, Louisiana. 152 pp. 

Penfound, W., and E. S. Hathaway. 1938. Plant Communities in the Marshlands of 

Southeastern Louisiana. Ecological Monographs. 8:1-56. 

Sikora, W. B., and B. Kjerfve, 1985. Factors influencing the salinity regime of Lake 

Pontchartrain, Louisiana, a shallow coastal lagoon: analysis of a long-term data 

set. Estuaries, Vol. 8. No. 2A, p. 170-180 June 1985. 

Tate, J.N., A.R. Carrillo, R.C. Berger, and B.J. Thibodeaux, 2002. Salinity changes in 

Pontchartrain Basin Estuary, Louisiana, Resulting from Mississippi River-Gulf 

Outlet partial closure with width reduction, Final Report. USACOE Coastal and 

Hydraulics Laboratory, Vicksburg, MS. 

Turner, R. E. 1987. Relationship between canal and levee density and coastal land loss in 

Louisiana. U.S. Fish and Wildlife Service Biological Report 85(14). 58 p. 

Turner, R.E., J.J. Baustian, E.M. Swenson, and J.S. Spicer. 2006. Wetland Sedimentation 

from Hurricanes Katrina and Rita. Science Express. 21 Sept. 2006. 

USACE for the Environmental Subcommittee of the Technical Committee Convened by 

EPA in Response to St. Bernard Parish Council Resolution 12-98. 1999. Habitat 

impacts of the construction of the MRGO. 83 p. 

USACE. 2003. Numerical Modeling of Storm Surge Effect of MRGO Closure. 19 p. 

USACE, 2004. Louisiana Coastal Area (LCA) Ecosystem Restoration Study – Final, 

Main Report, Volume 1, New Orleans District 

USACE. 2006a. Louisiana Coastal Protection and Restoration. Preliminary Technical 

Report to United States Congress. 62 pp. 

USACE. 2006b. Performance Evaluation of the New Orleans and Southeast Louisiana 

Hurricane Protection System: Draft Final Report of the Interagency Performance 

Evaluation Task Force, Vol. III – The Hurricane Protection System, 

http://ipet.wes.army.mil/. 

U.S. Congress of the United States. House Report 109-494. p. 39. 

2
U. S. Geological Survey (USGS), National Wetlands Research Center, Baton Rouge 

Production Office. 2001. Coastal Louisiana Marsh Vegetation Types. Digital 

Data. 

USGS National Wetlands Research Center –Baton Rouge Project Office. 2006. USGS 

Reports Latest Land-Water Changes. 

Webb, E.C. and I.A. Mendelssohn. 1996. Factors affecting vegetation dieback of an 

oligohaline marsh in coastal Louisiana: Field manipulation of salinity and 

submergence. American Journal of Botany 83(11): 1429-1434. 

White, W.A., and Morton, R.A. 1997. Wetland losses related to fault movement and 

hydrocarbon production, southeastern Texas coast: Journal of Coastal Research. 

v. 13. no. 4. p. 1305–1320. 

3
Appendix 2 – Letter from 

Governor Blanco 


Appendix 3 – Synopsis of 

Modeling Reports 
Hydrology & Hydraulics Synopsis of 

MRGO Modeling Studies 

For Surge, Salinity, Shoreline Stability, and 

Sediment Deposition 

 
Hydrology & Hydraulics Synopsis of 

MRGO Modeling Studies 

For Surge, Salinity, Shoreline Stability, and 

Sediment Deposition 

1. General. - This write-up reviews recent hydraulic modeling reports that document the 

effects of the Mississippi River Gulf Outlet (MRGO) on the following factors: 

• storm surge 

• salinity 

• bank/shoreline stability 

• sediment deposition /dredging 

A brief description of each modeling study is provided including assumptions, 

parameters, and results. The exhibits section at the end of this report includes excerpts of 

the conclusions of each modeling analysis. 

2. Storm surge modeling. – There are three modern modeling studies of the MRGO and 

adjacent tidal system for storm surge effects as follows: 

• Numerical Modeling of Storm Surge Effect of MRGO Closure; MRGO 

Reevaluation Study (EPA Sponsored), Westerink and Luettich Consulting , May 

2004 (pre-Katrina) 

• The Direct Impact of the Mississippi River Gulf Outlet on Hurricane Storm

Surge; URS for Louisiana Department of Natural Resources, Feb 2006 

• Interagency Performance Evaluation Task Force (IPET), Final Draft, Volume IV, 

June 2006 and Appendix E - Westerink, Ebersole, Winer; February 21, 2006 

These studies have all employed the ADCIRC model (ADvanced CIRCulation model) 

developed by Westerink and Luettich. ADCIRC is a two-dimensional depth integrated 

finite element hydrodynamic circulation code for ocean shelves, coasts, and estuaries. 

The computational mesh used for the first two studies was the S08 mesh which includes 

600,331 elements and 314,442 nodes. Node spacing in the S08 mesh varies from 15.5 

miles in distant areas to 330 feet in the New Orleans area. The most recent ADCIRC 

analysis (IPET) used a more detailed mesh identified as TF01. 

The general conclusion of the three ADCIRC modeling studies is that the impact of the 

long, southeast-trending section of the MRGO on storm surge propagation into the New 

Orleans vicinity is very small. Thus, complete filling of the MRGO—or blockage or

partial filling—will not provide significant immediate, direct mitigation of severe storm 

surge. The principal factor given for this result is that the added flow area provided by 

the MRGO is small compared to the expanse of flow area provided by the adjacent 

estuaries and marshes during large surge events. Thus, the most noticeable impact occurs 

for small surge events where propagation over the marsh areas is not a factor. 

1
Finally, additional ADCIRC surge modeling is being conducted for the ongoing FEMA 

map modernization program. This will delineate surge elevations in the study area for 

flood insurance purposes. Excerpts of the conclusions of each of the completed surge 

modeling studies are provided in the Exhibit 1 of this report. 

3. Salinity modeling - The MRGO is known to have had significant salinity impacts to 

Lake Pontchartrain and Lake Borgne starting in 1963 during initial construction through 

completion in 1968 and continuing to the present. TABS-MD modeling studies at ERDC 

have investigated the salinity impacts of the MRGO and various salinity management

schemes such as freshwater diversions and salinity control structures. The models utilize 

a three dimensional code and apply tide, wind, and freshwater inflows representing the 

simulation periods. Three studies were reviewed for this report as follows: 

• Salinity Changes in Pontchartrain Basin Estuary Resulting from Bonnet Carré 

Freshwater Diversion, (ERDC/CHL TR-97-02), William McAnally, R.C. Berger, 

February 1997. 

• Salinity Changes in Pontchartrain Basin Estuary, Louisiana, Resulting from 

Mississippi River-Gulf Outlet Partial Closure Plans with Width Reduction, 

(ERDC/CHL TR-02-12), J. N. Tate, A. R. Carrillo, R. C. Berger, August 2002. 

• Louisiana Coastal Area 3-D Hydrodynamic and Salinity Modeling, Jennifer N. 

Tate, S. Keith Martin, and Tate O. McAlpin, August 2006 Draft. 

The February 1997 salinity modeling study considered the effects of freshwater 

diversions from the Mississippi River to Lake Pontchartrain by way of the Bonnet Carré 

spillway near New Orleans. Four conditions were modeled for April through August of a 

typical year: 

• Base condition with no freshwater diversion 

• Diversions up to 20,000 cfs. 

• Diversions up to 8,500 cfs. 

• No diversions but with the connections between MRGO and Lake Borgne closed. 

Some paraphrased conclusions: 

• The estuary salinity profile responds very slowly to diversions at Bonnet Carré. 

• The MRGO is a significant contributor to salinity via connections to Lake 

Borgne. 

• A Bonnet Carré discharge capacity of 30,000 cfs is required to achieve the desired 

salinity of 6 ppt in the Biloxi Marshes. 

• Diversions to 20,000 cfs reduced salinities up to 4.2 ppt. 

• Diversions up to 8,500 cfs reduced salinities up to 3.4 ppt. 

• Closure of Lake Borgne-MRGO connections reduced salinities by about 2 ppt. 

• It may be possible to approach target salinities by combining control of MRGO 

salinity with freshwater diversions at reduced rates. 

The August 2002 salinity modeling study considered the effects of three different 

combined depth and width reductions on the MRGO at La Loutre ridge as follows: 

• Base condition with no constriction 

2
• Constricted to 20-ft depth and 200-ft width 

• Constricted to 16-ft depth and 160-ft width 

• Constricted to 12-ft depth and 125-ft width 

• Complete closure at La Loutre (from earlier 2001 study) 

The combined depth and width reductions were more successful in reducing salinity than 

depth reductions alone. (Depth reductions were considered in an earlier 2001 study.) 

The narrowest reductions accomplished over half the effects of complete closure. The 

reductions also resulted in higher current velocities at the constriction that could 

negatively impact navigation. Extreme current velocities would occur through the 

constriction for occasional events driven by strong winds 

The final salinity modeling analysis reviewed for this synopsis (Tate, Martin, and 

McAlpin) was only available as a draft report. The modeling characterizes the salinity

regime within the study area for a low, normal and high runoff year from the local 

tributaries. The salinity results for four modeled years – 1983, 1985, 1996, and 2000 are 

described. The provided figures show average monthly salinity contours for each month 

of the four years at the bottom of the water column. 

Excerpts of the conclusions of all three of the salinity modeling studies are provided in 

Exhibit 2 section of this report. Additional salinity modeling will be performed for the

IHNC Floodgates analysis to model the impacts of the three proposed gates being 

considered. The scope for that modeling effort is included in the Exhibit 1. 

4. Bank/shoreline stability - The MRGO is a confined, deep draft navigation channel, so 

its banks can be impacted by vessels moving through the channel. The following study 

analyzing vessel effects was reviewed for this report: 

Mississippi River Gulf Outlet (MRGO) Hydraulic Engineering Study of Channel Bank 

and Shoreline Response to Deep Draft and Container Barge Traffic; Technical 

Memorandum, Vladimir Shepsis, Coast & Harbor Engineering for Louisiana 

Department of Natural Resources, August 26, 2005 

The report presents modeling results of vessel effects on wave generation and bank 

erosion using proprietary models developed by Coast and Harbor Engineering. Model 

alternatives included a base condition of a fully loaded vessel traveling at 10 knots and 

two alternative conditions where the same vessel is light loaded traveling at 10 knots and 

fully loaded traveling at 5 knots. The analysis showed that vessel speed was the 

predominant factor in wave generation and bank erosion. The report recommends that 

limiting velocities be determined for successive reaches along the entire channel as a 

method of reducing bank erosion. 

3
Exhibit 1 

ADvanced CIRCulation (ADCIRC) 

Storm Surge Modeling Studies 

4
1.1 - Numerical Modeling of Storm Surge Effect of MRGO Closure 

for MRGO Re-evaluation Study (EPA Sponsored), Westerink and Luettich Consulting, 

May 2004 

 (Slide Presentation, October 2003)

 

Excerpts: 

Page 1: Summary - An examination of the effect of a closure of the MRGO on storm 

surge elevations was conducted using the ADvanced CIRCulation (ADCIRC) model. 

Nine scenarios consisting of combinations of slow, medium, fast forward speeds with 

weak, moderate, and strong intensities were run twice with identical input parameters 

except for the geometry of the MRGO near the La Loutre ridge where a hypothetical 

closure dike was placed for one set of runs and absent for the other set of runs. Hurricane 

Betsy wind fields were also run twice with the same grids. The difference in maximum 

storm surge elevation between the paired runs for the open MRGO and the MRGO with a 

closure dike at La Loutre Ridge was generally small. The maximum difference between 

the with- and without-closure was 0.54 feet.

Page 37: Conclusions - The ADCIRC model was used to test the influence of the 

MRGO upon storm surge in the areas outside of the federal protection levees. Several 

storm scenarios were run twice with identical runs except for a closed MRGO for one run 

and an open MRGO for the other run. Except for the changed geometry, all other factors 

were the same for the two runs, i.e. same wind forcing, same input files, and same

computer configuration, etc. Of the storm scenarios tested, the largest difference between 

the open and closed MRGO runs was 0.54 feet, which occurred in a small area near the 

hypothetical closure at the LaLoutre ridge. The conclusion of this report has to be that the 

MRGO has a minimal influence upon storm surge propagation 

5
1.2 - The Direct Impact of the Mississippi River Gulf Outlet on Hurricane 

Storm Surge 

URS for Louisiana Department of Natural Resources, Feb 2006, 

Used S08 mesh. Tested closure barrier at Bayou La Loutre ridge and also with entire 

channel filled to +1 MSL. 

Excerpts: 

Page ES-2: Major conclusions of this study are: 

• The MRGO channel does not contribute significantly to peak surge during severe 

storms, when the conveyance of surge is dominated by flow across the entire surface of

the coastal lakes and marsh. Nor does the channel contribute significantly to wave runup. 

• Complete filling of the MRGO—or blockage or partial filling—will not provide 

significant immediate, direct mitigation of severe storm surge. 

• For a few locations outside the Hurricane Protection System closure of the MRGO may 

reduce the peak surge for certain fast-moving, low-to-moderate storms, when the surge is 

not dominated by flow across the open lakes and marsh, and may modestly delay the 

onset of surge. 

6
1.3 - IPET Volume IV and Appendix E

Interagency Performance Evaluation Task Force, Final Draft, Volume IV, June 2006 

also Appendix E - Westerink, Ebersole, Winer; February 21, 2006 

 

Excerpts: 

 Page 7 of Appendix E : The fact that all studies show a larger proportional influence of the 

presence of the MRGO/Reach 2 for low intensity (low peak surge magnitude) events is related to 

the fact that the proportional increase in conveyance due to Reach 2 is greater when the surge is 

small and the water levels in Breton Sound and Lake Borgne are generally low. This also explains 

why we see a more rapid drop in post-storm Lake Pontchartrain levels for large-scale events with 

the MRGO in place. Waters typically withdraw relatively rapidly from Breton Sound and Lake 

Borgne due to the direct connection to open waters. The total combined conveyance of the 

Rigolets, Chef Menteur Pass and the IHNC/GIWW/MRGO system is increased with the MRGO 

in place under the lower post-storm levels on the Mississippi-Alabama shelf. 

7
Exhibit 2 

Salinity Modeling Studies 

8
2.1 Salinity Changes in Pontchartrain Basin Estuary Resulting from Bonnet 

Carré Freshwater Diversion

(ERDC/CHL TR-97-02), William McAnally, R.C. Berger, February 1997 

Excerpt from page viii: 

Numerical model experiments were performed to predict salinity changes that will occur 

in the Lake Pontchartrain basin estuary, Louisiana and Mississippi, as a result of 

proposed Mississippi River freshwater diversions through the Bonnet Carré Spillway near 

New Orleans. One purpose of the diversion is to reduce salinities in the Biloxi Marshes 

by 2 to 8 parts per thousand (ppt) in order to improve oyster productivity. A range of 

monthly salinities has been identified as the desired product of the project. Those 

salinities, called the Chatry salinities in this report, consist of a narrow band of 

“optimum” salinities and a somewhat wider band of “range limits.” 

9
 (CTH = Committee on Tidal Hydraulics) 

10
2.2 Salinity Changes in Pontchartrain Basin Estuary, Louisiana, Resulting 

from Mississippi River-Gulf Outlet Partial Closure Plans with Width 

Reduction 

(ERDC/CHL TR-02-12), J. N. Tate, A. R. Carrillo, R. C. Berger, August 2002 

Excepts from page 6: 

Monthly summaries of salinity for pre- and post-MRGO indicate that salinity has 

increased on the average by the following amounts: 

• 1.1. ppt at Lake Pontchartrain, North Shore. 

• 1.9 ppt at Lake Pontchartrain, Little Woods. 

• 0.4 ppt at Pass Manchac near Pontchatoula. 

• 2.3 ppt at Chef Menteur Pass near Lake Borgne. 

• 4.5 ppt at Bayou LaLoutre, Alluvial City. 

Results and Discussion 

The purpose of this investigation was to determine the effect of the combined depth and width 

closures of MRGO on salinities in Lake Pontchartrain, Lake Borgne, and Biloxi Marsh. The 

results are contained in Plates 1-4. These plates contain the monthly average isohalines for the 

bottom depth for each plan. The isohalines shown for each plan represent the change from the 

base conditions. The base conditions are the month’s average salinity. The plan isohalines are 

then changes from base, where a negative sign (-) indicates the closure reduced the salinity and a 

positive sign (+) indicates an increase in salinity. The averages are given for April, May, 

September, and October. Tables 4-7 give the values for specific station locations (approximate); 

all locations are given on Figure 1. The spring months are representative of the low salinity

period and the autumn months, the high salinity period. The complete closure results from the

prior study are included in this report as well to make comparisons easier. 

11
Excepts from page 20: 

Conclusions: This investigation is concerned with various combinations of depth and 

width reduction of the MRGO channel from the Gulf of Mexico to the city of New 

Orleans. Historical records indicate that when the channel was built, the salinity in Lake 

Pontchartrain and Lake Borgne increased. A previous study concluded that the effects of 

depth reduction alone along the La Loutre Ridge in the MRGO were insignificant in the 

reduction of the salinity in Lake Borgne and Lake Pontchartrain. This numerical model 

study used a sill along the same ridge near the connection of MRGO to the Gulf of 

Mexico with an elevation of -20 ft mlw for a contraction width of 200 ft, -16 ft mlw for a 

160-ft contraction, and -12 ft mlw for a 125-ft contraction. The study is intended to 

investigate the restoration of the historical salinity regime. The study includes the base 

condition of a fully open channel and the completely closed MRGO channel. 

The salinity reduction in Lake Pontchartrain and Lake Borgne with the partial depth and 

width closure was much greater than that for the previous study of depth reduction alone. 

All of the closure plans reduced the salinities in the region and two of the three partial 

closure plans averaged salinity reductions that exceeded half of the complete closure 

reduction. The velocities in the contraction region did increase from the base plan. High 

wind events can cause large velocities in the MRGO contraction. 

12
2.3 Louisiana Coastal Area 3-D Hydrodynamic and Salinity Modeling, 

(Report in draft phase), Cooperative effort between ERDC, MVN, and the CLEAR group 

(LCA) including the University of New Orleans; Draft provide August 2006 

Products – The study goals are to characterize the salinity regime within the study area 

for a low, normal and high runoff year for the local tributaries. In addition the study will 

evaluate the effectiveness of freshwater diversion and control measures at optimizing the 

salinity levels within the critical marshes. The results of the characterizations of the 

salinity regime will be provided to the Coastal Louisiana Ecosystem Assessment and 

Restoration (CLEAR) model for evaluation of ecological response. 

Results 

The salinity results for all four modeled years – 1983, 1985, 1996, and 2000 – are given 

in Plates 1-24. These figures show average monthly salinity contours for each month of 

the four years at the bottom of the water column. The bottom salinity is often greater than 

that at the surface due to the density gradient generated from the higher density salt water 

and stratification when mixing is limited. Therefore, the bottom salinity will give the

maximum values. The contours are scaled at 2 parts per thousand intervals. 

Conclusions 

On average, the low flow years show higher salinities in Lake Pontchartrain than the high 

flow years due to less fresh water entering the system. Most of the monthly averages 

show variations of 6-10 ppt in the salinity in Lake Pontchartrain between the high flow 

year (2-4 ppt) and the low flow year (10-12 ppt). The 32 ppt contour tends to shift 

gulfward as the flow increases. The overall salinity variation when compared to 

freshwater flow into the system is typical in that with less freshwater inflow, the salinity 

of the system increases. 

13
Exhibit 3 

Channel Bank and Shoreline Erosion Modeling Studies 

14
3.1 Mississippi River Gulf Outlet (MRGO) Hydraulic Engineering Study of 

Channel Bank and Shoreline Response to Deep Draft and Container Barge 

Traffic 

Technical Memorandum, Coast & Harbor Engineering for Louisiana Department of 

Natural Resources, August 26, 2005 

Excerpts from executive summary – 

The study was conducted through 

simulation of the hydrodynamic effects 

using the advanced numerical computer 

models VH-LU (2-Dimensional vessel 

hydrodynamic long wave unsteady 

model) and VH-PU (3-Dimensional 

vessel hydrodynamic propwash unsteady 

model). 

Numerical modeling was conducted for 

observed conditions using a deep draft 

container ship with a fully-loaded draft 

of 32 feet and cruising speed of 10 knots. 

Results of the combined pressure field 

and bed erosion modeling showed that by 

reducing vessel draft from 32 feet to 24 

feet, the pressure field erosion is reduced 

approximately 30%. This reduction is insufficient to prevent channel bottom and banks 

from scouring. 

Results of the modeling have demonstrated that by reducing speed of the fully loaded 

deep draft vessel from 10 knots to 5 knots, the pressure field erosion is reduced by more 

than 90%. This reduction results in almost no erosion of the channel banks. 

Based on the results of the numerical modeling, the study has concluded that the most 

promising approach to reduce vessel impacts on the MRGO shoreline and bank erosion 

would be to control vessel speeds in the channel to the level of below impact. This speed 

is preliminarily estimated at 5 knots for deep draft vessels. However, it is likely that 

some areas of the channel may allow a higher vessel speed with no impact on the 

shoreline. 

 

15
Appendix 4 – Engineering 
MRGO Deep-Draft De-authorization 

Engineering Appendix

As part of the MRGO de-authorization plan investigations, a few engineering related 

tasks were investigated; namely, O&M cost determinations and development of 

conceptual level options and opportunities for navigation, ecosystem restoration, and 

hurricane storm protection. The reach of the channel that was studied, as directed by 

Congress, was from the GIWW southeast of the Gulf of Mexico. This analysis does not 

consider the reach of the channel from Mile 60 to 66 which is contiguous with the 

GIWW. While some of the findings of these investigations are reported in the main 

report, this appendix details the procedures and assumptions that were followed to reach 

those findings. This appendix is intended as supporting information and does not include 

fully formulated plans or other information considered during the preliminary phase of 

the study. 

O&M Costs Determinations

Prior to initiating ongoing operations and maintenance, the channel must first be returned 

to the depth at which it will be maintained. For this study we looked at several depths 

and widths: 

 36’ x 500’ (mile 0.0 to 60); 38’ x 600’ (mile -9.4 to 0.0) [authorized 

dimensions]; 

 32’ x 500’ (mile -9.4 to 60); 

 28’ x 500’ (mile -9.4 to 60); 

 24’ x 500’ (mile -9.4 to 60); 

 20’ x 500’ (mile -9.4 to 60); 

 16’ x 500’ (mile -9.4 to 60); 

 14’ x 500’ (mile -9.4 to 60); 

 12’ x 500’ (mile -9.4 to 60); 

 36’ x 300’ (mile -9.4 to 60); 

 32’ x 300’ (mile -9.4 to 60); 

 28’ x 300’ (mile -9.4 to 60); 

 24’ x 300’ (mile -9.4 to 60); 

 20’ x 300’ (mile -9.4 to 60); 

 16’ x 300’ (mile -9.4 to 60); 

 14’ x 300’ (mile -9.4 to 60); 

 12’ x 300’ (mile -9.4 to 60); 

The dimensions above relate to channel bottom dimensions. Side slopes of 1V:2H were 

applied to all the templates emanating from the toe of the channel until it intersects 

natural bay bottom elevation. 

In addition to computing dredge quantities for returning the channel to the above 

dimensions an additional quantity was included to provide for advanced maintenance 

dredging, which is conducted to sustain navigable dimensions between dredging events, 

1 
and allowable over-depth which accounts for the inaccuracies of the dredging process. 

Based upon past dredging practices which in turn are based upon historical shoaling rates, 

the following additional depths were added to the depths above for various reaches of the 

channel. 

 6’ (mile 60 to 23) 

 8’ (mile 23 to 0) 

 4’ (mile 0 to -9.4) 

Figure ENG1 shows the template employed for the 36’x300’ channel between miles 0 

and 23. 

Natural Bay Bottom

2 

1 

 36ft 

Advance 

Maintenance 42ft

Overdepth 44ft 

Fig ENG1: Dredging template for 36x300 channel between mile 0 and 23. 

Channel surveys taken between May and June 2006 were used to create a surface 

indicative of the current elevations within the channel. Any material that is contained 

within the template would be dredged, and thereby forms the quantity reported under the 

initial construction to return the channel to a given operating depth. 

Channel Restoration Costs: 

During an MRGO Stakeholders meeting held at the Corps’ New Orleans District, the 

New Orleans District was requested to determine what the cost would be to restore 

navigation within the channel and enable users to navigate a 30’ channel in the MRGO. 

The New Orleans District, prepared cost estimates for dredging two shoaled areas within 

the channel: Mile 16.4 to 8.0 (cutterhead dredge) and mile -4.6 to -6.8 (hopper dredge). 

Depths considered were -30’, -32’, -34’ and -36’. For each of these depths, dredging cost 

per cubic yard and mobilization and demobilization (mob/demob) costs for both 

cutterhead and hopper dredges were calculated. For the cutter head dredge the 

mob/demob cost was approx $1,100,000 and the dredging cost per cubic yard ranged 

from $1.83 at -36 feet to $4.36 at the -30 feet alternatives. For the hopper dredge, the 

mob/demob cost was approx $250,000 and the dredging costs ranged from $3.61 at -36 

feet to $4.73 at the -30 feet alternatives. 

The unit costs above were utilized in determining costs for returning the channel to an 

operating depth of -36 feet. Prior to using these costs a couple assumptions were made: 

 Disposal operations for this contract represent typical disposal operations 

for the entire channel. In other words, a cutter head dredge is used for 

dredging the channel from mile 60 to 0 and hopper dredge is used for 

dredging of material from 0 to -9.4. Although costs associated with 

2 
cutter head dredging different segments of the channel will vary based 

upon specific disposal plans (i.e. some reaches requiring dikes whereas 

others will be unconfined and within open waters; and variances in 

pumping distances), these differences were not considered under this 

report. This report assumed a variance in costs based solely on quantity. 

 Dredges operate under a minimum cost; thereby, preventing the 

continued reduction in the unit cost to dredge beyond a certain quantity. 

It is assumed this limiting quantity was being approached for both types 

of dredges under the 36 foot cost estimate prepared by MVN. For this 

reason, it was assumed the lowest cost for the cutterhead was $1.80/CY 

and $3.50/CY for the hopper. 

 The unit prices to dredge quantities that fell between those quantities 

determined in the estimates prepared by MVN would be prorated. 

 A time constraint for returning the channel to an operating depth was not 

considered. Therefore, the assumption was made that a single cutter head 

dredge and a single hopper dredge would be utilized. Once time

constraints are set and production rates for various dredges assumed, a 

determination as to the number of dredges required to complete the work

can be determined. 

Table ENG1 and ENG2 show the calculations (quantities and unit costs) that were used 

in determining costs for restoration of the channel to widths of 300’ and 500’ and at 

varying depths. 

3 
Table ENG1: Initial Construction Quantities and Costs for 300ft wide channel. 

Depth Quantity Type Mob/Demob

Unit $ 

per 

Cubic 

Yard Total Cost

300x36: 3,500,000 hopper 250000 3.5 $12,500,000.00

27,100,000 cutter 1000000 1.8 $49,780,000.00

30,600,000 $62,280,000.00

300x32: 1,500,000 hopper 250000 3.5 $5,500,000.00

12,900,000 cutter 1000000 1.8 $24,220,000.00

14,400,000 $29,720,000.00

300x28: 500,000 hopper 250000 4 $2,250,000.00

6,300,000 cutter 1000000 1.8 $12,340,000.00

6,800,000 $14,590,000.00

300x24: 0 hopper 0 -- $0.00

2,400,000 cutter 1000000 2.5 $7,000,000.00

2,400,000 $7,000,000.00

300x20: 0 hopper 0 -- $0.00

400,000 cutter 1000000 5.8 $3,320,000.00

400,000 $3,320,000.00

300x16: 0 hopper 0 -- $0.00

87 cutter 1000000 -- $0.00

87 $0.00

4 
Table ENG2: Initial Construction Quantities and Costs for 500ft wide channel. 

Depth Quantity Type Mob/Demob

Unit $ 

per 

Cubic 

Yard Total Cost

500x36: 10,000,000 hopper 250000 3.5 $35,250,000.00

52,500,000 cutter 1000000 1.8 $95,500,000.00

62,500,000 $130,750,000.00

500x32: 3,400,000 hopper 250000 3.5 $12,150,000.00

29,900,000 cutter 1000000 1.8 $54,820,000.00

33,300,000 $66,970,000.00

500x28: 1,200,000 hopper 250000 4 $5,050,000.00

14,500,000 cutter 1000000 1.8 $27,100,000.00

15,700,000 $32,150,000.00

500x24: 300,000 hopper 250000 5 $1,750,000.00

5,600,000 cutter 1000000 1.8 $11,080,000.00

5,900,000 $12,830,000.00

500x20: 0 hopper 0 -- $0.00

1,200,000 cutter 1000000 4.4 $6,280 , 000.00

1,200,000 $6,280,000.00

500x16: 0 hopper 0 -- $0.00

78,414 cutter 1000000 9 $1,705,726.00

78,414 $1,705,726.00

Ongoing O&M Quantities:

A key component in determining future O&M dredging quantities is deciding on a future 

shoaling rate or rate at which material will be deposited in the channel. This rate can 

sometimes be determined through system modeling which often takes years to perform. 

Given the time constraints imposed on this study, shoaling rates determined by the New 

Orleans District, USACE in 2004 for use in the MRGO re-evaluation Study, and based 

off of historical dredging events, were incorporated into this study. These shoaling rates 

were determined for each mile of the channel for various depths and widths and then 

summarized into reaches. In other words, the rate of shoaling between mile 6 and mile 

23 was approximately the same so an average shoaling rate for this reach of channel was 

assumed. A review of these summaries revealed little differences in the rates amongst 

the different channel configurations. For this reason, this study assumed a constant 

shoaling rate for various reaches that are independent of channel depth and width. These 

reaches and their associated average shoaling rates are shown in Table ENG3. 

5 
Once the shoaling rate is determined, the frequency in which dredging must occur to 

maintain the required depth is calculated. For this, two assumptions were made. First 

each reach would shoal uniformly at the shoaling rate for that reach. Second the entire 

dredging prism (advance maintenance and allowable overdepth) would shoal to project 

depth before dredging occurred. 

Table ENG3: Average shoaling rates and dredging frequencies by mile. 

Mile 

Marker 

Shoaling rate

(ft/yr) 

Prism 

(ft) 

Freq 

(yrs) 

-8 to -9 0.7 4 5.7 

6 to -8 1.7 6 3.5 

23 to 6 2.5 8 3.2 

27 to 23 1.2 6 5 

35 to 27 0.6 6 10 

After determining the shoaling rate, the year at which the first cycle of dredging will 

begin must be determined. This year was determined in two parts. The first part was 

determining how many years shoaling would occur in the channel before deposition filled 

the channel to the bottom of the dredging prism. The second part was applying the time 

frame for the dredging prism to shoal to project grade; in other words, the frequency 

between contracts. 

To determine part one, the centerline elevation of the channel was determined at each 

mile using May/June 2006 survey data. These centerline elevations were then averaged 

to determine an average channel elevation for a given reach. Refer to Table ENG4 

Table ENG4: Average channel depths by reach in June 2006.

Mile Marker 

Avg C/L Elevations 

(MLG) 

 -8 to -9 - 36.5 

6 to -8 -34.8 

23 to 6 -31.2 

27 to 23 -38.7 

35 to 27 -39.3 

These average depths were then compared to the bottom elevation of the dredging prism

for various depths to determine whether immediate dredging of that reach was required 

and if not how many feet the channel needed to shoal before deposition entered the 

dredging prism. If the current elevation was deeper than the bottom elevation of the 

dredging prism, the difference in these two elevations were divided by the shoaling rate 

for that reach to determine how soon before deposition entered the dredging prism. The 

results of this analysis are reported in Table ENG5: 

6 
Table ENG5: No. of years before shoaling starts taking place within the dredging prism. 

Channel Depth

Mile 36 32 28 24 20 16 14 12

-8 to -9 0 0.8 7.5 0 0 0 0 0

6 to -8 0 0 0.7 4.1 7.4 10.8 0 0 

23 to 6 0 0 0 0 1.3 2.9 3.7 4.5

27 to 23 0 0.4 2.8 5.1 7.5 9.8 11.0 12.2

36 to 27 0 1.9 7.6 13.3 19.0 24.7 27.6 30.4

Part two for determining when dredging would be required for any given reach or depth 

is to add together the years shown in Table ENG5 to the frequency of dredging shown in 

Table ENG3. As an example, for a 24 ft deep channel between mile 36 and 27 the first 

dredging contract would be required in year 23.3 [(13.3 + 10) {Table ENG5 + Table 

ENG3)]. For calculation purposes the assumption was made that if Congress directed the 

channel to be dredged as a result of this report, dredging would not commence until 2008. 

Therefore, for those depths that shoaling to the bottom of the dredging prism will take at 

least 2 years, the base year from which the first contract will begin was assumed to be 

2006. For those depths that shoaling to the bottom of the dredging prism will take less 

then 2 years, the base year for from which the first contract will begin is assumed to be 

2008. 

Ongoing O&M dredging costs:

To determine ongoing O&M dredging costs, the same costing information used for the 

initial construction cost was utilized. Due to the overlap of data regarding the dredging 

prism and dredging quantity calculations, a sensitivity analysis of the cost versus 

quantities was undertaken to determine if the hopper dredge and cutter head quantities 

could be combined into a single quantity at a given rate. The result of this analysis 

showed that a combined quantity at $2.00/CY, using the mob/demob cost for a cutter 

head dredge, resulted in a less then 3% difference in the total cost then if the quantities 

are separated using different unit prices per dredge. With the exception of the change in 

the unit price to a constant $2.00/CY all the same assumptions outlined above still apply. 

The cost of each contract per reach per depth was then computed by multiplying the total 

volume within the dredging prism by $2.00/CY and adding the mob/ demob cost. For 

reaches such as mile 26 to 6, at the 12 foot depth, an assumption was made that the entire 

reach would no longer require dredging. In these cases, only half of the dredging prism 

quantity was used in determining the contract cost for that reach. This assumption was 

based upon a review of natural bay bottom elevations within Breton Sound. Differences 

in elevations reported by various resources did not allow for a definitive extent for 

calculating quantities for dredging. However, to capture the effects of deeper water 

across Breton Sound, especially when considering shallow depth plans, a percentage 

approach was adopted. 

The last step in determining yearly contract costs is to recognize that O&M funding 

typically is linear for maintenance dredging of channels such as the MRGO. For this 

7 
reason, high dollar contracts such as would exist for channel mile 23 to 6 at 36 ft 

($16.9M), especially when combined with a contract for mile 6 to -8 ($10.8M) in the 

same year would be broken up into two or three years. 

Options Cost Determinations 

The following sections detail the procedures employed in determining the costs of the 

various options and opportunities investigated. 

Option 1b: Salinity Control Weir at La Loutre:

Under Option 1b, a weir would be constructed near the Bayou La Loutre Ridge to allow 

passage of shallow-draft vessels. The MRGO would be constricted to 125-feet wide by 

14 feet deep. The weir configuration likely would consist of earthen dam sections and 

pile-supported, reinforced concrete T-wall structures that extend from the shoreline and 

tie into a weir structure. The weir would be a pile-supported, reinforced concrete U-frame 

structure with a 125-foot wide clear opening and a sill at Elevation -14.0 NAVD. 

Table ENG6 outlines the items that were considered in estimating the cost of this 

structure. 

8 
Table ENG6: Cost data for Option 1b, Salinity Weir. 

WEIR STRUCTURE (Sill El -14) 

Comparative Quantity and Cost Data Per Sector Gate

 

Item

No. Description Unit Unit Price Quantity Amount

1 Mobilization and Demobilization Lump Sum Lump Sum 1 $1,140,000 

2 Cofferdam-Steel Sheet Piling 70' SF $35 326,000 $11,410,000 

3 Cofferdam-Sand Fill CY $40 12,709 $508,356

3 Cofferdam-Dewatering Lump Sum Lump Sum 1 $760,000 

4 Structure Excavation CY $12 54,889 $658,667

5 Piling-24"diameter steel pipe piles LF $200 20,267 $4,053,333 

6 Pile Test Each $50,000 1 $63,333

7 Tension Connectors Each $250 63 $15,833

8 Sheetpile Cutoffs - Gate Structure SF $30 8,000 $240,000 

9 Stabilization Concrete CY $250 1,100 $275,000

10 Crushed Stone Ton $40 1,600 $64,000 

11 Concrete in Base Slabs CY $650 3,399 $2,209,278 

12 Concrete in Walls CY $900 1,056 $950,000 

13 Crushed Stone Bedding Ton $60 3,589 $215,333 

14 Armor Stone Ton $60 8,867 $532,000

15 Tie-in Floodwall 200 ft ea side for 400 ft total LF $15,200 400 $6,080,000 

16 Structure Backfill CY $15 25,333 $380,000

17 Treated Timber Piling in Guidewalls LF $26 10,556 $274,444 

18 Treated Fender Timbers BF $4 63,333 $228,000

19 Fender System Hardware Lump Sum Lump Sum 1 $29,556 

20 Steel Sheet Pile Dolphins Each $460,000 4 $1,840,000

21 Needle Beams and Needles Lump Sum Lump Sum 1 $211,111 

22 Earthen Dam Fill CY $30 300,000 $9,000,000

 

 

 Construction Cost (incl. 25% contingency) $51,422,800 

 Engineering and Design $2,850,800 

 

 Total Cost $54,273,600 

Option 1c: Salinity Control Gate at La Loutre:

Under Option 1c, a gated structure would be constructed downstream of the La Loutre 

Ridge that would allow passage of shallow-draft vessels. The gated structure would have 

a sill at Elevation -14.0 NAVD and a 125-foot wide opening, and would be designed for 

hydraulic loadings proportional to its height. The gate would normally be closed to 

reduce saltwater intrusion, but would be opened for passage of vessels. The gate would 

need to be able to operate under both direct and reverse heads; so it is envisioned that the 

gate would either be a sector gate or a barge gate. The sector gate option is presented in 

this report because its use is more widespread throughout south Louisiana, but during the 

feasibility phase of design, the barge gate option should be explored. The gate could be 

operated on-site by a gate master, or remotely with the use of video cameras and a PLC 

system configured to operate via the internet. Depending on how often the gate is 

operated, power will need to be supplied to the site. 

9 
Table ENG7 outlines the items that were considered in estimating the cost of this 

structure. 

Option 1d: Storm Protection Gate at La Loutre:

This option comprises the same structural components and earthwork as Option 1c: a 

sector gate with tie-in T-wall and earthen dam. The difference between this option and 

Option 1c is the gate operating parameters. For Option 1d, the gate would not be operated 

to control salinity, but would only be operated to close the canal for a tropical storm

event. Because the gate would be operated infrequently, there are some cost savings 

relative to Option 1c. The most significant cost savings should be with respect to the 

maintenance cost of the gates and the gate monoliths. Since the gates would be operated 

less frequently compared to Option 1c, there should be a longer interval between dewaterings of the monolith to perform major maintenance work on the gates. Another 

advantage of 1d is that it may be possible to operate the gates using a diesel-powered 

generator instead of having to supply power to the site. However, this would likely 

preclude remote operation of the gates since the generator would need to be started onsite to power the gate drive systems. 

With minimal differences between this option and that of Option 1c, at this level of cost 

estimating the construction costs are assumed to be the same as those for Option 1c as 

reflected in Table ENG7. 

10 
Table ENG7: Cost data for Option 1c, Salinity Gate 

SECTOR GATE STRUCTURE (Sill El -14) 

Comparative Quantity and Cost Data Per Sector Gate

 

Item

No. Description Unit Unit Price Quantity Amount

 

1 Mobilization and Demobilization Lump Sum Lump Sum 1 $1,140,000 

2 Cofferdam-Steel Sheet Piling 70' SF $35 326,000 $11,410,000

3 Cofferdam-Sand Fill CY $40 12,709 $508,356

3 Cofferdam-Dewatering Lump Sum Lump Sum 1 $760,000 

4 Structure Excavation CY $12 54,889 $658,667

5 Piling-24"diameter steel pipe piles LF $200 20,267 $4,053,333 

6 Pile Test Each $50,000 1 $63,333

7 Tension Connectors Each $250 63 $15,833

8 Sheetpile Cutoffs - Gate Structure SF $30 8,000 $240,000 

9 Stabilization Concrete CY $250 1,100 $275,000

10 Crushed Stone Ton $40 1,600 $64,000 

11 Concrete in Base Slabs CY $650 10,626 $6,906,900 

12 Concrete in Walls CY $900 2,111 $1,900,000

13 Crushed Stone Bedding Ton $60 3,589 $215,333 

14 Armor Stone Ton $60 8,867 $532,000

15 Tie-in Floodwall 200 ft ea side for 400 ft total LF $15,200 400 $6,080,000 

16 Structure Backfill CY $15 25,333 $380,000

17 Treated Timber Piling in Guidewalls LF $26 25,000 $650,000 

18 Treated Fender Timbers BF $4 150,000 $540,000

19 Fender System Hardware Lump Sum Lump Sum 1 $70,000 

20 Steel Sheet Pile Dolphins Each $460,000 4 $1,840,000

21 Needle Beams and Needles Lump Sum Lump Sum 1 $500,000 

22 Steel Sector Gates Tons $6,000 211 $1,266,667 

23 Mechanical Systems Lump Sum Lump Sum 1 $358,889 

24 Electrical Systems Lump Sum Lump Sum 1 $190,000 

25 Control House Each $50,000 1 $50,000

26 Earthen Dam Fill CY $30 300,000 $9,000,000

 

 

 Construction Cost (incl. 25% contingency) $62,085,400

 Engineering and Design $3,405,800 

 

 Total Cost $65,495,100

Option 2a: Plug channel - Construct closure dam for MRGO:

Under Option 2a, an earthen dam would be constructed near La Loutre Ridge to totally 

block the MRGO channel. The earthen dam would consist of un-compacted clay, a steel 

sheet pile wall to prevent undermining and rock armoring for erosion control. 

The costs for the control structure to close the MRGO at La Loutre Ridge are primarily 

associated with the fill material, the armoring, and the steel sheet pile. 

11 
Clay fill is estimated to cost $30/cy based on recent estimates developed for levee raise 

work in the New Orleans East area. This is clay material delivered by truck and assumes 

that borrow pits are located nearby. The $30/cy is used for this project because while the 

fill material will likely be delivered by barge, which is more cost effective, it will likely 

require longer transport, which will increase the cost. This cost may increase if borrow 

sources become depleted in the New Orleans area and it becomes necessary to transport 

fill material from greater distances. 

Rip rap is estimated to cost $60/ton. This is also based on recent cost estimating being 

done for New Orleans East work. Costs should be about the same because the delivery 

on the New Orleans East projects will likely be by barge as it would be for the MRGO 

project. The distance to the MRGO project may be further from a rip rap source than the 

New Orleans East projects but the value was not modified because the difference cannot 

be quantified. 

Again, based on recent cost estimates for work to be done in the New Orleans East area, 

the cost for sheet pile is $60/ft2

. The unit price for driving sheet pile for New Orleans 

East projects is estimated to be $55/ft

2

. The unit price is increased for work in the 

MRGO due to the fact that the sheet pile will need to be driven from floating plant. 

Clay Fill Material

Volume of fill = 650,000 cubic yards 

Cost of fill = (650,000 cy) x ($30/cy) 

 = $19,500,000 

Rip Rap

Weight of rip rap = 200,000 tons 

Cost of rip rap = (200,000 cy) x ($60/ton) 

 = $12,000,000 

Sheet Pile (PZ-22)

Area of sheet pile = 82,000 ft2

Cost of sheet pile (installed) = (82,000 ft2) x ($60/ft2) 

 = $4,920,000 ≈ $5,000,000 

Contingency (25%) = $9,125,000 

Engineering and Design (6%) = $2,190,000 

Total cost = $19.5M + $12.0M + $5.0M + $9.125M + $2.19M 

 = $47,815,000 

Freshwater diversion pumping station opportunity:

Diversion of freshwater into the MRGO is anticipated to require constructing a pilesupported, sluice-gated, reinforced concrete culvert structure with a cut-off wall system 

that would be built into the existing Mississippi River levee. The diversion structure 

would be able to pass 15,000 cubic feet per second (cfs) of river water by gravity into the 

12 
canal. The canal would transport the river water approximately 1.5 miles to feed the 

marshes between the Mississippi River and the MRGO. The Mississippi River flow rates 

would be controlled by raising and lowering the sluice gates. The canal would be 

widened and lined with either concrete or rock to improve the canal’s hydraulics. 

Recently, the CWPPRA program evaluated a proposal calling for a 4,000-5,000 cfs 

freshwater diversion at Violet. Initial estimates for this proposal were $53-$70 million. 

The Davis Pond Freshwater Diversion structure was completed in 2002 at a cost of 

almost $120 million. The capacity of the Davis Pond structure is 10,650 cfs. Assuming a 

diversion structure at Violet would be designed for flows reaching 15,000 cfs, the 

following computations were used in developing the costs estimate: 

Use the $120 million as the base cost and adjust it by two factors: 

- Factor 1, larger capacity (15,000 cfs vs. 10,650 cfs) 

Factor 1 = 15,000/10,650 = 1.41, use 1.4 

- Factor 2, post-Katrina prices 

Factor 2 = 1.5 (assumed) 

Estimated cost = $120 million x 1.4 x 1.5 

 = $250 million 

These numbers are considered only as a rough estimation of potential Violet freshwater 

diversion costs. Detailed design and cost estimates will be developed if the opportunity 

is pursued. 

There are a couple alternative locations for a diversion channel; however, these locations 

would require the construction of another open water canal from the Mississippi River to 

the MRGO that would need to be maintained. The alignment of this canal could be such 

to utilize the existing storm surge gate at the intersection of the Violet Canal and the 

MRGO; however, a second breach in the 40 Arpent levee may be required. In addition, 

these other locations would prevent the need for relocating businesses impacted by 

widening the Violet Canal. The primary difference in costs between a second channel 

and that of using Violet Canal is the cost of relocating businesses versus the cost of 

digging a second channel. 

13 
Appendix 5 – Economics 
1 

MRGO Deep-Draft De-Authorization 

Economics Appendix 

This appendix presents the Mississippi River Gulf Outlet (MRGO) economic and 

financial de-authorization costs and outlines the methodology used for the cost 

calculations. The economic appendix consists of four components. The first component 

of the analysis is a description of the study area. This component contains a descriptive 

information about the project area, the base condition, and the without and with project 

futures. Discussion of these components is presented to help facilitate understanding of 

the more detailed applications contained in the appendix. The second involves 

identifying the considerations for the businesses located along the MRGO. This was 

accomplished through surveying potentially affected companies and determining what, if 

any, impacts they anticipate. The third component of this analysis involves identifying 

the vessels that use the MRGO for navigational purposes. This component relied on 

analysis of the Waterborne Commerce Statistics Center (WCSC) data to determine vessel 

traffic. The final component discusses the economic impact of flood damage reduction 

that can be attributed to the MRGO. 

Costs and impacts to deep-draft and shallow-draft navigation are presented and, to the 

extent possible, the costs are classified as NED, financial, or other. Where applicable, 

costs are presented in average annual equivalent terms using a 50-year period of analysis 

and the U.S. Army Corps of Engineers vessel operating costs contained in the Economic 

Guidance Memorandums (EGM 05-01, Deep-Draft Cost and EGM 05-06, Shallow-Draft) 

were utilized. 

I. Project Area, Vessel Traffic and Commodity Movements 

The analysis of transportation costs and industry impacts approaches the study by 

comparing the transportation costs for the base condition with discontinuance of 

maintenance of the MRGO federal deep-draft navigation project. In addition to 

discontinuation of MRGO deep-draft, the transportation costs and benefits for alternate 

shallow draft channel depths were evaluated. Alternative transportation mode and 

business reestablishment costs are discussed as well. 

Project Area 

As presented in the main report, the MRGO is approximately 76 miles long. It begins 9.4 

miles into the Gulf of Mexico to the south east of New Orleans where it is authorized to a 

depth of 38 feet and a bottom width of 600 feet. These are designated as miles -9.4 to 

mile 0. The authorized dimensions for the remaining 66 miles of the MRGO are a depth 

of 36 feet and a bottom width of 500 feet. From mile 0 to mile 23 it extends through 

shallow bays of Breton Sound. From mile 23 to mile 60, the MRGO extends further to 

the north and west through coastal wetlands. At mile 60 the MRGO connects with the 

Gulf Intracoastal Waterway (GIWW) and the two run contiguously westward for 6 miles 

to the IHNC, also called the Industrial Canal, in New Orleans. From the westernmost 

point of the MRGO, the IHNC extends north to Lake Pontchartrain and south to the 

IHNC Lock, which connects it with the Mississippi River. The lock between the IHNC 
2 

and the Mississippi River was built in the 1920s and is relatively narrow and shallow. It 

measures 74.5 feet in width, 640 feet in length and 31.5 feet in depth. 

The IHNC Lock presents an obstacle for most of the deep-draft ships using the 

Mississippi River and the IHNC. The alternate route from the Gulf of Mexico to the 

IHNC is the MRGO. The IHNC Lock dimensions are significantly smaller than the 

dimensions of the Panama Canal, and this is mentioned because the Panama Canal and 

“panamax vessels” with their associated width restriction of 106 feet and depth limit of 

36.9 feet, represents a major benchmark in the shipping industry. The panamax vessel 

design is a significant factor in the design of cargo ships, with many ships being built to 

exactly the maximum allowable size. Panamax vessels or anything larger cannot transit 

past mile 60 of the MRGO due to the IHNC Lock restriction. 

Vessel Traffic 

Traffic records from the WCSC show MRGO utilization steadily increasing until 

reaching a peak in terms of tonnage carried in 1978 and in terms vessel trips in 1982. 

Table 1 and Graph 1 display MRGO total domestic and foreign tonnage for the period 

1997-04. The table contains data from 4-year increments from 1970-94 and 1995-04 

continuous records. The graph displays the complete 34-year time line. 

Foreign-flag deep-draft vessel movements consist of self-propelled ocean-going vessels. 

Maximum loaded vessel drafts were approximately 36 feet with vessels taking advantage 

of advance maintenance and tides. For the period 1995-04, approximately 20 percent of 

vessels traveled with loaded drafts over 30 feet. Domestic cargo on the MRGO consists 

of shallow-draft barge traffic and coastwise ocean-going vessels. The maximum loaded 

drafts for the tow vessels are 12 feet or less and domestic coastwise vessels have 

maximum drafts in excess of 30 feet. 

TABLE 1 

Mississippi River-Gulf Outlet, Total Tonnage by Year (1000’s of short tons) 

Year Total Tonnage Foreign Domestic 

1970 4,013 2,522 1,491 

1974 5,308 3,386 1,922 

1978 9,411 5,136 4,275 

1982 5,572 3,878 1,694 

1986 8,145 5,254 2,891 

1990 7,084 4,611 2,473 

1994 4,690 3,347 1,343 

1995 5,701 3,416 2,285 

1996 5,042 3,314 1,728 

1997 5,253 3,552 1,701 

1998 4,007 2,974 1,033 

1999 5,369 4,619 750 

2000 5,850 5,065 785 

2001 4,173 3,634 539 

2002 3,290 2,786 504 

2003 2,847 2,442 406 

2004 1,206 1,045 161 

Source: U.S. Army Corps of Engineers, Waterborne Commerce Statistics Center. 
3 

GRAPH 1

Mississippi River Gulf Outlet

Total Tonnage by Year (1000's)

0

2,000

4,000

6,000

8,000

10,000

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

Domestic Foreign

Comparison of tonnage volumes for the most recent period of record (2002-04) with the 

previous comparable period (1992-94) shows current volumes down by nearly 60 

percent, with drops in both domestic and foreign freight volumes. While total tonnage 

declined, the percentage of foreign freight maintained a larger share of total tonnage than 

domestic freight. The percentage of foreign freight represents 86 percent of 1999-04 total 

tonnage. In spite of distributional changes, the overall trendline illustrates a downturn for 

all traffic, with 2004 volumes representing an historical low before declining further in 

2005 after Hurricane Katrina. While the pre-Katrina declines were driven by a variety of 

factors, the MRGO authorized depth of 36 feet, which is recognizably shallow in 

comparison to other U.S. Gulf Coast deep-draft channels, and the current dimensions of 

the IHNC Lock are contributors. The IHNC Lock dimensions are 640 by 75 by 31.5 

feet. The limitations of the MRGO, in terms of its 36-foot depth and the IHNC likely 

impeded commercial navigation growth during periods of significant increases in the 

sizes of large vessels serving U.S. ports. The lack of funds for operation and 

maintenance dredging during the 1990s, and the need to direct funds for emergency 

dredging during the pre-Katrina years, is also likely to have contributed to declining 

trends. As previously noted, no dredging has occurred since Hurricane Katrina on 

MRGO. 

Annual vessel trip totals are displayed in Table 2 and Graph 2. Table 2 shows that cargo 

vessels have predominated as the primary vessel type. The number of trips decreased 

since peaking in 1982 to a greater extent than has the tonnage, presumably representing a 

move toward larger ships and bigger loads. National trends, as evidenced at other 
4 

TABLE 2: Mississippi River Gulf Outlet 

Number of Trips by Vessel Type (1970-2004) 

Year 

Total 

Trips 

Passenger & Cargo 

Vessels (Dry and Liquid) 

Tow or 

Tugboat 

Barge (Dry and Liquid 

Cargo) 

1970 4,809 1,476 1,220 2,113 

1974 12,941 7,551 1,837 3,553 

1978 17,956 11,828 1,841 4,287 

1982 18,419 15,084 1,190 2,145 

1986 6,212 1,941 1,460 2,811 

1990 4,479 1,486 1,110 1,883 

1994 5,130 3,006 903 1,221 

1995 4,263 2,300 628 1,335 

1996 6,934 5,433 519 982 

1997 5,591 3,797 696 1,098 

1998 2,827 1,700 462 665 

1999 2,368 1,420 296 652 

2000 2,386 1,541 188 657 

2001 2,341 1,550 377 414 

2002 2,590 1,693 488 409 

2003 3,897 1,902 692 1,303 

2004 2,584 1,972 448 164 

Source: U.S. Army Corps of Engineers, Waterborne Commerce Statistics Center. 

GRAPH 2

Mississppi River Gulf Outlet, Number of Trips by Vessel Type

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

Trips

Cargo Vessels Tow and Tug Vessels Barges

Major U.S. ports, towards larger more fully loaded vessels also contribute to the 

downward trend in vessel trips. Declines in annual MRGO vessel trip counts are also, of 

course, directly associated with the declining tonnage volumes as shown in Table 1. 

Since its authorization, the size and draft of vessels using the MRGO tended to increase 
5 

to meet the competitive demand for more efficient movements of bulk commodities. 

Table 3 presents the number of vessel trips by general draft group. The WCSC 

TABLE 3 

Mississippi River Gulf Outlet 

Trips by Vessel Draft (1970-04)

Trips by Vessels Trips by Vessels 

Year Total Less than or equal to 18 ft Greater than 18 ft 

1970 4,809 4,355 91% 454 9%

1980 8,959 7,806 87% 1,153 13%

1990 4,310 3,384 79% 926 21%

1995 3,009 2,132 71% 877 29%

1996 2,563 1,634 64% 929 36%

1997 5,591 4,468 80% 1,123 20%

1998 2,827 1,922 68% 905 32%

1999 2,368 1,327 56% 1,041 44%

2000 2,386 1,193 50% 1,193 50%

2001 2,341 1,447 62% 894 38%

2002 2,590 1,964 76% 626 24%

2003 3,897 3,400 87% 497 13%

2004 2,584 2,278 88% 306 12%

Source: U.S. Army Corps of Engineers, Waterborne Commerce Statistics Center. 

defines shallow-draft trips as trips having loaded drafts of less than or equal to 18 feet, 

while deep-draft trips are defined as trips having loaded drafts over 18 feet. Note: For 

this report, the USACE is using the definition of deep-draft vessels contained in ER1105-2-100. This defines deep-draft as vessels requiring greater than 14 feet. 

Graph 3 displays a comparison of total tonnage by draft class and helps illustrate the 

transition to more fully loaded vessels that occurred and would most likely continue in 

the absence of a shoaled channel and the IHNC Lock restriction. As mentioned, cargo 

vessels are the predominant vessel type. The type of cargo vessel most often found on the 

MRGO is one that carries dry cargo, with very few tanker vessels. Table 4 presents 

distribution of 2000-04 freight tonnage by approximate vessel DWT range, type, and 

beam width. 
6 

GRAPH 3

Mississippi River Gulf Outlet 

Vessel Traffic Trends (Trips and 1000's of Short Tons)

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

1970

1980

1990

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Vessel Drafts Over 18 Feet Total Tonnage (1000's of short tons)

Vessel Drafts <= 18 feet

TABLE 4 

MRGO Approximately Percentage of Foreign Freight by General DWT Range 

Calendar Years 2000, 2002 and 2004 

DWT Range Estimate % of Short tons Beam (ft) Predominant Vessel Type 

<10,000 16% 40-75 Refrigerate red Cargo Vessel 

10,000-19,999 14% 76-106 General Cargo, Containership 

20,000-39,999 29% 89-106 Containership, General Cargo 

40,000-59,999 19% 105-106 Containership, Chemical Carrier 

60,000-75,000 22% 106 Bulk Carrier 

Total 100% 

Source: U.S. Army Corps of Engineers, Waterborne Commerce Statistics Center.

Examination of the 1970-94 historical trendline for ocean-going freight indicates general 

upward movement in volume of cargo per vessel trip. The 1970-04 trendline of the 

average number of short tons, for foreign freight cargo, per self-propelled vessel trip is 

displayed in Graph 4. A general upward trend, with recognizable annual fluctuations, 

was evident until 1988. 
7 

GRAPH 4

Short Tons Per Self-Propelled Vessel Movement 

Ocean-Going Foreign Freight 1000's of short tons, 

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

Short Tons Per Self-Propelled Vessel Movement

In addition to ocean-going freighters, a large number of tugs and towboats use the 

MRGO. Towboats push barges, and the general increase in barge trips relative to tow 

trips suggests transition towards larger volumes per barge and per tow-barge movement. 

Tank barges of 298x54-feet are the most frequent size. The largest tows are generally 4-

barge tow consisting of three 298x54-foot barges and one 150x54-foot barge pushed by 

towboats generally ranging from 1,800 to 3,000 horsepower. A trendline of the average 

number of short tons, for domestic cargo, per barge movement is displayed in Graph 5. 

As with foreign freight, a general upward trend, with recognizable annual fluctuations, 

was evident until 2000. 
8 

GRAPH 5

Domestic Tons Per Barge Movement 

1000's of short tons

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

Short Tons Per Barge Movement

Tables 5 and 6 present detailed information about the type of commodities shipped 

through MRGO. In 2004, the three commodity groups with the greatest number of tons 

transported on the MR-GO are “Manufactured Equipment, Machinery and Products”, 

“Food and Farm Products”, and “Primary Manufactured Goods”. For the three groups, 

foreign commerce represented more than 80% of the total commerce. 

For the purpose of the analysis, it is important to distinguish between two sections of the 

MRGO. The first one is the east-west oriented section that runs between the intersection 

with the GIWW at mile 60 of MRGO and the IHNC, hereafter referred to as GIWW 

Reach. The second one is the section that runs southeast-northwest from mile 60 into the 

Gulf of Mexico, hereafter referred to as Inland Reach. The Sound Reach extends from 

the Gulf of Mexico across Breton Sound. Based upon Congressional direction, this deauthorization study of the MRGO would affect only the portion of the channel that runs 

below the mile 60, that is from the GIWW to the Gulf of Mexico, and therefore only the 

trips that go through that portion of the channel are relevant to the analysis. 
9 

TABLE 5: Mississippi River-Gulf Outlet, Commodities by year (in thousand of short tons) 

1997 1998 1999 2000 2001 2002 

Industry Group 

ton D F ton D F ton D F ton D F ton D F ton D F ton 

Coal 7 0% 100% 48 6% 94% 5 60% 40% 9 22% 78% 3 67% 33% 0 - - 0 Crude Petroleum 13 100% 0% 10 90% 10% 316 2% 98% 54 15% 85% 8 100% 0% 47 100% 0% 63 Petroleum Products (1) 184 58% 42% 166 82% 18% 243 28% 72% 182 27% 73% 180 64% 36% 215 47% 53% 73 Crude Materials (except fuels) (2) 1755 25% 75% 1260 22% 78% 1022 27% 73% 1659 19% 81% 918 14% 86% 928 5% 95% 657 Food and Farm Products (3) 866 30% 70% 658 13% 87% 1766 2% 98% 1458 2% 98% 632 0% 100% 465 0% 100% 405 Primary Manufactured Goods (4) 1091 45% 55% 695 29% 71% 832 19% 81% 1051 12% 88% 810 3% 97% 788 0% 100% 337 Chemicals (5) 798 16% 84% 651 7% 93% 695 5% 95% 738 0% 100% 938 1% 99% 567 0% 100% 590 Manufactured Equipment, Machinery and Products (6) 

531 49% 51% 506 53% 47% 475 36% 64% 659 39% 61% 644 39% 61% 686 44% 56% 674 

All Others 8 0% 100% 14 0% 100% 15 0% 100% 40 0% 100% 40 0% 100% 51 0% 100% 48  TOTAL 5253 32% 68% 4007 26% 74% 5369 14% 86% 5850 13% 87% 4173 13% 87% 3290 15% 85% 2847 

D: domestic participation. F: foreign participation. (1) “Petroleum products” includes gasoline, distillate fuel oil, residual fuel oil, lube & greases, naphtha & solvents, liquid natural gas, amon

(2) “Crude Materials (except fuels)” includes forest products (wood and chips), pulp and waste paper, soil, sand, gravel, rock, stone, iron ore 

ores and scrap, sulphur, clay, salt, slag, among others. 

(3) “Food and Farm Products” includes fish, grain, oilseeds, vegetable products, processed grain and animal feed, among others. (4) “Primary Manufactured Goods” includes paper products, lime, cement, glass, primary iron and steel products, primary non-ferrous prod

products, among others. 

(5) “Chemicals” includes fertilizers and other chemical and related products. (6) “Manufactured Equipment, Machinery and Products” includes textile products, machinery, electrical machinery, vehicles and parts, ship

wood products, rubber and plastic products, among others. 

Source: Waterborne Commerce Statistics Center. 
10 

TABLE 6: Mississippi River-Gulf Outlet, “Dropping off / Picking up” Traffic, Commodities by year (in 

tons) 

1997 1998 1999 2000 2001 2002 

Industry Group 

ton D F ton D F ton D F ton D F ton D F ton D F ton 

Coal 0 - - 3 100% 0% 4 100% 0% 8 25% 75% 2 100% 0% 0 - - 0 Crude Petroleum 0 - - 0 - - 222 0% 100% 46 0% 100% 0 - - 0 - - 0 Petroleum Products (1) 40 100% 0% 67 97% 3% 50 90% 10% 105 43% 57% 96 100% 0% 68 100% 0% 35 Crude Materials (except fuels) (2) 664 62% 38% 804 32% 68% 370 71% 29% 466 68% 32% 209 61% 39% 46 100% 0% 3 Food and Farm Products (3) 0 - - 66 3% 97% 554 0% 100% 800 3% 97% 2 100% 0% 0 - - 108 Primary Manufactured Goods (4) 281 62% 38% 150 59% 41% 332 40% 60% 244 41% 59% 10 100% 0% 0 - - 1 Chemicals (5) 92 75% 25% 112 19% 81% 35 60% 40% 47 0% 100% 8 100% 0% 0 - - 2 1Manufactured Equipment, Machinery and Products (6) 

2 100% 0% 1 100% 0% 1 100% 0% 2 0% 100% 0 - - 2 100% 0% 1 

All Others 0 - - 0 - - 0 - - 2 0% 100% 0 - - 0 - - 0  TOTAL 1079 65% 35% 1203 37% 63% 1568 30% 70% 1720 28% 72% 327 75% 25% 116 100% 0% 150 

D: domestic participation. F: foreign participation. (7) “Petroleum products” includes gasoline, distillate fuel oil, residual fuel oil, lube & greases, naphtha & solvents, liquid natural gas, amon

(8) “Crude Materials (except fuels)” includes forest products (wood and chips), pulp and waste paper, soil, sand, gravel, rock, stone, iron ore 

ores and scrap, sulphur, clay, salt, slag, among others. 

(9) “Food and Farm Products” includes fish, grain, oilseeds, vegetable products, processed grain and animal feed, among others. (10)“Primary Manufactured Goods” includes paper products, lime, cement, glass, primary iron and steel products, primary non-ferrous prod

products, among others. 

(11)“Chemicals” includes fertilizers and other chemical and related products. (12)“Manufactured Equipment, Machinery and Products” includes textile products, machinery, electrical machinery, vehicles and parts, ship

wood products, rubber and plastic products, among others. 

Source: Waterborne Commerce Statistics Center.
11 

Table 7 depicts the actual number of trips along the Inland Reach of MRGO. On average, 

and for the years for which information was available, they represented 89% of total trips 

on the GIWW and Inland Reaches, totalizing an average of 2,254 trips per year. 

TABLE 7: Mississippi River-Gulf Outlet, Number of Trips by Reach 

Year 

Total trips 

(GIWW and 

Inland 

Reaches) 

MRGO below 

mile 60 

(Inland 

Reach) 

Percentage 

2000 2,386 2,088 88% 

2002 2,590 2,357 91% 

2004 2,584 2,318 90% 

Total 7,560 6,763 

Annual Average 2,520 2,254 89% 

Source: Waterborne Commerce Statistics Center.

A traffic forecast was not prepared for this analysis. While the reasons for not preparing 

a forecast primarily relate to practicality, they also relate to the physical impediment of 

the IHNC Lock limited dimensions. As previously noted, “panamax vessels” cannot 

transit the IHNC Lock restriction. Additionally, the limitations of the MRGO, in terms of 

its 36-foot depth likely impeded commercial navigation growth during periods of 

significant increases in the sizes of large vessels serving U.S. ports. The reasons for not 

preparing a forecast also relate to an existing condition where some businesses have 

already chosen to move away from the MRGO. The USACE has been asked to identify 

the reestablishment costs for business that are still located on the MRGO and are 

dependent upon deep-draft navigation. For purposes of the USACE’s economic analysis 

procedures, the reestablishment costs for businesses that have already moved are “sunk 

costs.” Several of the businesses located along the MRGO are involved in the rebuilding 

of New Orleans and are forecasting increasing business. At the base condition depth, the 

businesses located along the IHNC/MRGO would not experience any transportation 

inefficiencies and would not likely choose to relocate. While certain businesses have left 

their facilities along the MRGO since Hurricane Katrina, it is possible that comparable 

businesses may establish operations at those locations. 

MRGO traffic has experienced an overall decline, particularly since calendar year 2000. 

The most recent 3-year average was used as the base condition for the cost calculations. 

II. Business Considerations 

This section presents discussion of the business considerations of the MRGO deauthorization. The first step in determining the business conditions was to identify the 
12 

companies that had the potential to be affected if the MRGO were not maintained at a 

depth of 36 feet. This step was accomplished through analysis of the WCSC data to 

identify where vessels had docked along the MRGO, and a review of past USACE 

reports and studies. A search of published articles on the MRGO was performed to find 

additional companies which may be affected. Aerial photographs were reviewed to 

determine facilities with operations along the MRGO. After an initial list of companies 

was developed, that list was shown to selected stakeholders for input. Using stakeholder 

feedback, a list of affected companies was finalized. The final list included not only the 

large companies with operations along the MRGO, but smaller companies in surrounding 

areas. The nature of the businesses contacted ranged from towing companies to cement 

and construction aggregate yards to scrap facilities. 

The potentially affected companies were contacted by telephone for preliminary 

screening interviews to determine which companies could be potentially impacted by the 

de-authorization. In preparation for those interviews, a copy of the survey was sent out to 

the companies with a letter of introduction. Table 8 lists the companies consulted. 

Interviews were conducted with companies both inside and outside of the study area. The 

interviews outside the study area focused on the towing and other companies that used 

the MRGO and the potential impacts of de-authorization on that aspect of business. 

During the interviews, the companies were asked questions about the nature of their 

operations and their reliance on the MRGO. Interviewers attempted to determine the 

vessels that the companies used for their operations, and the type and quantity of 

commodities each facility was transporting. Incremental analysis was performed to 

determine the impacts of different channel depths on each firm. The full survey is 

attached to this Appendix. 
13 

TABLE 8: Companies Consulted 

All American Crewboats Crosby Tugs Michoud Assembly Facility 

Antill Pipeline Construction Delta Towing New Orleans Cold Storage 

APM Terminals Dupre Brothers Noble Energy 

Bertocci Contracting Dupuy Storage O’Meara Inc 

Biloxi Marsh Lands Ensco Marine Parker Drilling 

Bisso Marine Estis Well Company Pearl River Navigation 

Blanchard Towing International Shipholding 

Corporation 

Peltex 

Boh Brothers Jefferson Marine Ponchatrain Materials 

Corporation 

Bollinger Gulf Repair Joseph Domino Port of New Orleans 

Buzzi Unicem Kearney Companies Settoon Towing 

Caillou Island Towing Lafarge Cement Shell Beach Marina 

Cenac Towing LeBoueff Brothers Towing Southern Scrap 

Central Gulf Towing Lee Marine St. Ann Boat Service 

CG Railways Maersk Tipco 

Corcoran Towing Manson Construction US Gypsum 

Through the industry interviews, it was found that some of the companies currently 

experienced transportation inefficiencies because the MRGO has not been maintained 

since Hurricane Katrina. For those companies, the interviewers attempted to determine 

what the impacts were, and their estimated dollar values. The inefficiencies reported by 

each company, along with a brief description and dollar value are listed as follows: 

• Company 1: Container ships currently are docking at locations along the 

Mississippi River because they cannot access the terminal. Moving a container 

from the river to the terminal costs $185. 

• Company 2: Deep-draft vessels can no longer dock at this company’s facility and 

they have to receive shipments of product via barge. The company estimates that 

there is $7.50-per-ton increase in handling costs from using barges. 

• Company 3: Certain vessels are unable to dock at this company’s facility, and as a 

result, the company has to truck their product to terminals on the Mississippi 

River, resulting in additional labor, overtime, security, and equipment rental costs. 

The company estimates additional costs are $15 per ton. 

• Company 4: Since deep-draft vessels are unable to dock at this company’s 

facility, the company experiences additional costs due to unloading two products 

off ships in midstream. The additional costs are estimated as $13 per ton for one 

product and $15.90 per ton for the other product. These costs include stevedoring, 

demurrage, lost dock revenue, barge rentals, and fuel charges. 

The costs estimated by businesses of moving facilities to another location that are 

presented in this document do not reflect depreciation but rather actual purchase for a 
14 

new or used facility with comparable infrastructure and transportation networks. 

Assessing the reliability of the cost estimates presented by the affected businesses is 

difficult. The wind damages from Hurricane Katrina and the subsequent flooding have 

changed the effective age of structures in the study area. Lack of channel dredging since 

Hurricane Katrina has further compounded the analysis. 

For the remaining structures, a depreciated structure value could be found using the 

Marshall and Swift system of valuation. This value is based on the type of construction, 

effective age of the structure, quality of construction, facility improvements, expected 

useful life of the facility, and area of the state the improvement is in. Along the water 

there were several steel warehouses which were inundated in water and suffered rust 

damage. While some of these warehouses are now used for storage of raw materials and 

spare parts, others are empty. Some of the other facilities are considered “special 

purpose” facilities and the only remaining value of their buildings is scrap. For example, 

while silos on a property are an asset for a cement company, they serve no other purpose 

and may need to be removed for the land to function as a factory. 

III. Navigation Considerations

To calculate the impact of de-authorizing deep-draft navigation of the MRGO on 

transportation costs, the first step was to identify the number of trips going through the 

channel for both deep-draft and shallow-draft vessels. To accomplish this, the vessel 

origin-to-destination routings through the Inland Reach of the MRGO were extracted 

from the Corps detailed vessel records for the years 2000, 2002, and 2004. For purposes 

of analysis, the average of the three periods of detailed routings was held constant 

through the 50-year period of analysis. Based on mileage and industry verification, all 

deep-draft trips diverting from the MRGO would have to use the Mississippi River - 

adding 4 hours per one-way trip to their travel time. The extra time is found by taking the 

additional distance from the Mississippi River to the Gulf of Mexico (37 miles), and 

dividing that by the average vessel operating speed (9.2 miles per hour). An overview of 

annual traffic variation is contained in Table 9. The table displays total MRGO trips by 

vessel draft and boat type for the period after project construction through 2004. While 

ship traffic has declined over the past 34 years, it is difficult to predict the future amounts 

of traffic on the MRGO. Since there is no clear forecast, a conservative practice is to use 

the three-period average. 

Shallow-draft trips were divided into two groups: those that use the MRGO as an 

alternative route when the IHNC Lock is not operable1

, and others that use it on a regular 

basis as an alternative to the Mississippi River. According to the Corps Lock 

Performance Monitoring System (LPMS) data and industry information, there are about 

three major events per year during which shallow-draft vessels use the MRGO as an 

 

1

 The number of trips was estimated assuming that the IHNC lock is closed for more than 24 hours at least 

three times per year (estimated using Lock Performance Monitoring System [LPMS] data for 2000, 2002, 

2004, and 2005). That number was then multiplied by the number of towboats per day that use the IHNC 

lock (also obtained from LPMS data). 
15 

alternative route. Approximately 100 vessels will use the alternative route per year2

. The 

resulting trip around the IHNC Lock takes approximately 24 hours. Due to the distance 

and the uncertainty of the weather in Baptiste Collette, few vessels elect to travel along 

the MRGO to by-pass the lock. However, vessels can save a considerable amount of 

time if the lock is down for a period of greater than 24 hours and/or there is a long queue. 

The additional time lost from not having access to the MRGO is 48 hours3. For the 

second group, it was assumed that the MRGO reduced travel time by four hours. 

TABLE 9. Total Tonnage and Trips by Vessel Draft and Vessel Type

Mississippi River – Gulf Outlet Traffic (1970-2004)

 Total Self-Propelled Vessel Trips 

 Tonnage Loaded Draft Increment (ft) Tows and Barges Total 

Year 1000's 34-36 30-33 21-29 19-20 <=18 Sub-Total Towboats Barges Vessels 

1970 4,013 16 83 275 80 1,017 1,471 1,225 2,113 4,809 

1980 5,541 62 259 744 88 4,951 6,104 1,315 1,540 8,959 

1990 6,960 48 214 559 105 391 1,317 1,110 1,883 4,310 

1995 5,701 18 230 589 40 186 1,063 620 1,326 3,009 

1996 5,042 76 283 503 67 133 1,062 519 982 2,563 

1997 5,253 136 400 520 64 2,677 3,797 696 1,098 5,591 

1998 4,007 98 277 487 42 796 1,700 462 665 2,827 

1999 5,369 117 342 532 48 381 1,420 296 652 2,368 

2000 5,850 193 358 590 49 351 1,541 188 657 2,386 

2001 4,173 117 282 468 25 658 1,550 377 414 2,341 

2002 3,290 83 222 310 10 1,068 1,693 488 409 2,590 

2003 2,847 34 99 346 18 1,405 1,902 692 1,303 3,897 

2004 1,206 8 13 266 13 1,672 1,972 448 164 2,584 

Source: U.S. Army Corps of Engineers, Waterborne Commerce of the U.S., IWR-WCUS, Part 2.

Using the WCSC transit records, the vessels were classified as either “towboats,” 

“barges,” or “self-propelled.” For each of these classifications, the hourly operating costs 

were obtained from USACE Economic Guidance Memorandum (EGM) 05-06 for deepdraft vessels and EGM 05-01 for shallow-draft vessels. In order to determine the 

operating costs for each vessel, information regarding the commodities transported, 

vessel horse power, and dead-weight tonnage (dwt) was used. The costs from the 

Economic Guidance Memorandums and were calculated using the 2004 figures which 

represent conservative estimates. These are not conservative estimates because inflation 

adjustments due to higher fuel costs were not made to the figures in the EGM. Adding 

inflation would increase the cost per trip and the associated transportation inefficiencies. 

Using the average hourly rates and the estimated changes in transportation time, the 

transportation inefficiencies for each passage were calculated. Table 10 shows the vessel 

operating costs used. 

 

2

 These vessels are in addition to the towboat trips presented in the Table 2 of this appendix. As noted in 

the footnote above, the estimate of 100 trips was estimated using LPMS data. 

3

 The 48 hour figure is based on the time spent waiting for the lock to return to operations and was 

estimated at 24 hours plus the additional queue time once the lock is operational. 
16 

TABLE 10: Vessel Operating Costs 

Variable Towboats Barges 

Selfpropelled 

(U.S. Flag) 

Selfpropelled 

(Foreign 

Flag) 

Tanker 

(Foreign 

Flag) 

 

Cost determinant 1800-2000 HP Weighted 

average of 

daily 

operating 

costs by 

commodity 

transported 

Weighted 

average of 

daily operating 

costs by 

commodity 

and tonnage 

transported 

Weighted 

average of 

daily operating 

costs by 

commodity 

and tonnage 

transported 

Dwt 20,000 

 

Total hourly cost $211(US$ 

2004 price 

level) 

$6.7 (US$ 

2004 price 

level) 

$1,124 (US$ 

2002 price 

level) 

$627 (US$ 

2002 price 

level) 

$ 665 (US$ 

2002 price 

level) 

 Additional time using Mississippi River (in hours) 

Additional Hrs. 4 4 4 4 4 

 Additional transit cost per trip 

Additional Cost $847 $28 $4,517 $2,520 $2,673 

U.S. Army Corps of Engineers, Economic Guidance Memorandums (EGM 05-01, Deep-Draft 

Cost and EGM 05-06, Shallow-Draft) 

For the incremental analysis, it was assumed that vessels with a draft of the incremental 

depth or less would continue to use the MRGO. The transportation inefficiencies are 

calculated only for those vessels with a draft greater than the incremental impact. For 

example, with a depth of 32 feet, all vessels with a draft of 32 feet or less will continue to 

use the MRGO, and all vessels with drafts greater than 32 feet will be assumed to divert 

to the Mississippi River. It was assumed that with a draft of 32 feet, there would be 

advanced dredging that would allow adequate underkeel clearance for vessels to pass. It 

was also assumed that those vessels would use an alternative route once the maintenance 

of the channel stops. Table 11 shows the transportation inefficiencies, as represented by 

the net increase in transportation cost associated with using the Mississippi River instead 

of the outlet channel, at each of the incremental depths alternatives. The $2,526,000 

shown in Table 11 is non-inflated impact of transportation cost inefficiencies of not 

having the MRGO available for deep-draft navigation, and it was estimated by the 

businesses themselves. It includes the vessels that use the MRGO as an alternative route 

and also those vessels that use the MRGO as a primary route. If the channel were 

completely closed, average annual transportation inefficiencies would be $6,200,000. 

That figure includes all deep-draft vessels which use the MRGO as a quicker route from 

the Gulf of Mexico and all of the shallow-draft vessels which use the MRGO as an 

alternate route when the IHNC Lock isn’t working. 
17 

TABLE 11. Transportation Inefficiencies for Selected Channel Depths 

(Net Transportation Cost Increase Due to MRGO Depth Reductions) 

Depth Transportation Inefficiencies 

(annual) 

36 feet $0

32 feet $455,000

28 feet $1,102,000

24 feet $1,878,000

20 feet $2,279,000

16 feet $2,413,000

14 feet $2,454,000

12 feet $2,526,000

0 feet (not maintained) * $2,454,000

0 feet (closed) * $6,200,000

* Not maintained indicates that maintenance will cease and the channel will shoal over time. It is 

assumed that the controlling depth of the channel will be 14 feet at the end of the 50-year period of 

analysis. This differs from “closed” which indicates that the channel will be physically blocked 

and/or not accessible by a defined date. 

IV. Economic Considerations of Flood Damage Reduction 

Recent storm surge modeling studies (Appendix 3) suggest that the Inland Reach of the 

MRGO does not significantly influence the development of storm surge in the region for 

large storm events. As a result, complete filling of the MRGO (or blockage or partial 

filling), is not expected to provide a significant reduction in storm surges caused by 

severe events. Because studies show that the Inland and Sound Reaches of MRGO have 

a minor effect on storm surge during severe storm events, closing the MRGO would lead 

to a negligible reduction in storm damages from severe events. For less severe events, it 

is expected that the Hurricane Protection System would offer protection for homes and 

businesses located inside the levee system. Areas outside of the levee system may see 

increased storm surge as a result of the MRGO. 

Homes and businesses in southern St. Bernard located outside of the levees system were 

largely destroyed during Hurricane Katrina. For those wishing to rebuild, the Department 

of Homeland Security’s Federal Emergency Management Agency (FEMA) is providing 

advisory guidelines that can be used as building standards in order to minimize the flood 

impact in areas subject to waves and velocity floodwaters caused by hurricane storm 

surges. For most of these areas outside of the levees, it is recommended that structures be 

built to a minimum elevation of 17 feet. 

It is assumed that the majority of structures that are being rebuilt outside of the levees 

will follow FEMA elevation guidelines. Therefore, any induced storm surge from 

smaller storms resulting from the MRGO would have little impact on structures located 
18 

in the area outside of the levee. A reduction in storm surge resulting from closing the 

MRGO would have a minimal impact on the total amount of storm related damages. 

V. Summary of Economic Analysis 

This section provides a summary of cost estimates to shallow- and deep-draft navigation 

of closing the MRGO to commercial navigation. The annual cost in terms of NED 

annual transportation inefficiencies from not having MRGO available for shallow-draft 

navigation is $3,674,000. The basis for this comparison is a base condition of no 

navigation and assumes that if the MRGO is not available for shallow draft navigation to 

use when the IHNC Lock is not accessible, tows will incur delay costs. The $3,674,000 

value is based on 2000-04 vessel traffic and assumes no traffic growth. A traffic forecast 

was not prepared and 2000-04 traffic levels were assumed to remain relatively constant 

over the 50-year planning period. The $3,674,000 transportation cost inefficiency can be 

viewed a transportation cost benefit and should be compared to the average annual 

MRGO channel maintenance cost ($6 to $9 million annually). The project maintenance 

cost is outlined in the engineering appendix. 

The deep-draft benefit of maintaining the channel at 36 feet versus letting the channel 

shoal to inoperable depths is $5,745,000. This figure based on the difference in 

transportation cost between an authorized depth of 36 feet and an inoperable channel (i.e. 

not accessible to deep- or shallow-draft vessels). This number is contained in Table 12 

and it is the difference between the zero depth transportation inefficiency of $6,200,000 

and the 32-foot transportation inefficiency of $455,000. The transportation inefficiency 

of $5,745,000 can be compared with the channel maintenance costs of $12,500,000 

presented in the Engineering Appendix. 
19 

Addendum to the Economics Appendix: 

MRGO Deep-Draft De-Authorization 

Survey Instrument
20 

United States Army OMB Control Number: 0710-0001 

Corps of Engineers 

SURVEY OF CURRENT AND FORMER USERS 

Mississippi River- Gulf Outlet 

New Orleans, LA 

 Name of Firm: ____________________________________ 

Nature of Business: 

_________________________________________________________

_________________________________________________________

_________________________________________________________ 

 Name of Parent Firm: _______________________________ 

 Mailing Address: ___________________________________ 

 State: ______ Zip _______ 

 Name of Interviewee: _______________________________ 

 Job Title of Interviewee: _____________________________ 

Mailing Address: ____________________________________ 

State: ______ Zip ______________ 

Phone Number: (_____) ___________________ 

FAX Number: (_____) _____________________ 

E-Mail Address: ____________________________________ 
21 

1. Please list the names and addresses of all North American terminals and docks 

owned by this company, their waterway location, and their port-dock codes. 

a. Dock/Terminal Name: ____________________________________ 

Address: _____________________________________________ 

State: ____________________________________ Zip:________ 

Phone Number: ________________________________________ 

Waterway: ____________________________________________ 

River Mile Location: ____________________________________ 

Port/Dock Code: _______________ 

b. Dock/Terminal Name: ________________________________________ 

Address:______________________________________________ 

State: _________________________ Zip:________ 

Phone Number:_________________________________________ 

Waterway:_____________________________________________ 

River Mile Location:______________________________________ 

Port/Dock Code:________________________________________ 
22 

2. Please list the vessels that were used in the past two years for your operations 

using the MR-GO 

Vessel 

Name 

Draft Width Height Type of vessel Frequency of 

use 

 

3. Please give the following information for the primary commodities shipped using 

any method of transportation during the last full calendar year from each terminal 

in the study area: 

Description Code Tons/ Percent by season 

year Spring Summer Fall Winter 

Modes of 

Transport 

Terminals 

used 

 

4. Please give the following information for the primary commodities received using 

any method of transportation during the last full calendar year for each terminal in 

the study area: 

Description Code Tons/ Percent by season 

year Spring Summer Fall Winter 

Modes of 

Transport 

Terminals 

used 

 
23 

 

. 

5. In the left column, please list the major commodities that your firm ships by 

water. Then for each commodity, please list the origin, destination, typical 

annual tonnage, and rate per ton. 

COMMODITY MOST 

FREQUENT 

ORIGIN 

MOST 

FREQUENT 

DESTINATION 

ANNUAL 

TONNAGE 

RATE/TON 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

6. Do you anticipate that these commodities listed in Question 5 will experience a 

growth or a decline in tonnage over the next 5 to 10 years? Please indicate this 

for each commodity listed below. Please provide this information for existing 

commodity movements and for any potential new movements. 

Check 

applicable Commodity Current 

Tonnage Growth Decline

Projected

Cost / 

Ton

Origin Final 

Destination 

 
24 

 

7. What channel depth in the MR-GO is necessary for vessels to move products 

into or out of your plant based on current production / operations? 

____________Feet 

8. Alternative channel depths are being evaluated as part of this study. Please 

indicate your expected annual operations and whether you would relocate 

operations based on the following depths: 

Depth Number of Operations Total Tons shipped Primary Commodity Would Relocate 

36’ 

32’ 

28’ 

24’ 

20’ 

16’ 

14’ 

12’ 

0’ (not maintained) 

0’ (closed) 

9. Below what minimum depth would your operations be adversely impacted? 

How? Below what minimum depth would you be forced to relocate? Why? 

10. If the MR-GO were closed and vessel traffic was prohibited, would your company 

still maintain operations? Yes ____ No ____. 

11. If you answered yes to question 9, how would your plant operations change? 

Please explain. 
25 

12. Would any of your ship traffic use the existing IHNC lock if the MRGO were 

closed to deep-draft traffic? If not why? 

13. Would any of your ship traffic use the new 1200 x 110 x 36 ft IHNC lock, once it 

was built, if the MRGO were closed to deep-draft traffic? If not why? 

14. Is it possible for your operations to be moved to a location along the Mississippi 

River? Yes ____ or No ____. If yes, what would the approximate cost of the 

relocation be? 

 

15. If your firm decides to relocate your business away from the MRGO, would you 

construct new facilities of the same production capacity as your existing facilities 

or would they be built at a larger or smaller scale? If so, how much larger or 

smaller would the new facilities be, percentage wise? 

 

16. If your operations were to relocate, what is the minimum depth for a new facility? 

17. If your operations could not be moved to a location along the Mississippi River 

where would they most likely move and why? What would the approximate cost 

of that relocation be? 

 Land 

Cost 

Equipment 

Cost 

Salvage 

Value of 

Equipment 

Value of Equipment 

Which Could be 

Moved 

Total 

Value 

Location 

In-State 

Out-of-State 

On Mississippi River