EA #511 Construction of Charenton Floodgate U.S. Army Corps of Engineers

December 2020 Regional Planning and Environmental Division South

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ENVIRONMENTAL ASSESSMENT

MISSISSIPPI RIVER AND TRIBUTARIES PROJECT

ATCHAFALAYA BASIN CONSTRUCTION OF CHARENTON 

FLOODGATE

ST. MARY PARISH, LOUISIANA

EA# 511
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Contents

1. Introduction.............................................................................................................................. 4

Proposed Action ............................................................................................................ 4

Authority .......................................................................................................................... 5

Purpose and Need for the Proposed Action.............................................................. 6

Data Gaps and Uncertainties ...................................................................................... 6

Prior National Environmental Policy Act (NEPA) Documents ................................ 9

Public Concerns........................................................................................................... 10

2. Alternatives Including the Proposed Action ..................................................................... 10

2.1 Proposed Action .......................................................................................................... 10

2.2 No-Action Alternative (Future without Project [FWOP]) ........................................ 11

3. Affected Environment............................................................................................................ 13

Description of the Work Area..................................................................................... 13

3.1.1 Description of the Watershed............................................................................. 13

3.1.2 Climate................................................................................................................... 14

3.1.3 Geology.................................................................................................................. 14

Relevant Resources.................................................................................................... 14

3.2.1 Wetlands................................................................................................................ 16

3.2.2 Prime and/or Unique Farmlands........................................................................ 16

3.2.3 Aquatic Resources/Fisheries.............................................................................. 16

3.2.4 Wildlife.................................................................................................................... 17

3.2.5 Threatened and Endangered Species .............................................................. 17

3.2.6 Cultural Resources............................................................................................... 17

3.2.7 Recreational Resources...................................................................................... 19

3.2.8 Visual Resources (Aesthetics)........................................................................... 20

3.2.9 Air Quality .............................................................................................................. 21

3.2.10 Water Quality ....................................................................................................... 21

4. Environmental Consequences............................................................................................. 21

Wetlands ....................................................................................................................... 21

4.2 Prime and Unique Farmlands................................................................................... 22

4.3 Aquatic Resources and Fisheries............................................................................ 22

U.S. Army Corps of Engineers

 Mississippi Valley Division

Regional Planning and Environmental Division South

New Orleans District
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4.4 Wildlife........................................................................................................................... 23

4.5 Threatened and Endangered Species.................................................................... 23

4.6 Cultural Resources...................................................................................................... 24

4.7 Recreational Resources ............................................................................................. 24

4.8 Visual Resources (Aesthetics) .................................................................................. 25

4.9 Air Quality..................................................................................................................... 26

4.10 Water Quality............................................................................................................... 26

4.11 Hazardous, Toxic, and Radioactive Waste ............................................................. 27

4.12 Cumulative Impacts.................................................................................................... 27

5.0 Mitigation............................................................................................................................... 28

6.0 Coordination and Public Involvement............................................................................... 29

7.0 Compliance with Environmental Laws and Regulations ............................................... 29

8.0 Conclusion............................................................................................................................ 30

9.0 Prepared By.......................................................................................................................... 31

10. References ........................................................................................................................... 32

FIGURES

Figure 1: Charenton Floodgate Location Map......................................................................... 7

Figure 2: New Floodgate Plan.................................................................................................... 8

Figure 3: Charenton Floodgate Right-Of-Way Footprint........................................................ 9

Figure 4: Alternative Locations ................................................................................................ 12

TABLES

Table 1: Relevant Resources and Their Institutional, Technical, and Public Importance.

..................................................................................................................................................... 155

Table 2: FY 2017 Fishing/ Hunting Licenses1, Boater Registrations............................... 199

APPENDICES

Appendix A: LDNR Coastal Zone Consistency Coordination Letter

Appendix B: USFWS ESA Consultation 

Appendix C: LDEQ Water Quality Determination Letter

Appendix D: Section 404(b)(1) Evaluation and Public Notice

Appendix E: SHPO Coordination Letter

Appendix F: USDA NRCS Coordination Letter
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ENVIRONMENTAL ASSESSMENT

MISSISSIPPI RIVER AND TRIBUTARIES PROJECT

ATCHAFALAYA BASIN CONSTRUCTION OF CHARENTON 

FLOODGATE

SAINT MARY PARISH, LOUISIANA

EA# 511

1. Introduction

The U.S. Army Corps of Engineers (USACE), Mississippi River Valley Division, 

Regional Planning and Environment Division South (RPEDS), has prepared this 

Environmental Assessment (EA) for New Orleans District (CEMVN) to evaluate 

potential impacts from constructing a new floodgate in front of the existing Charenton 

Floodgate that is located in St. Mary Parish (Figure 1). The Charenton Floodgate is a 

primary feature of the Atchafalaya Basin system and is located on the West Atchafalaya 

Basin Protection Levee. It was built in 1949 to control the flow of freshwater from the 

Atchafalaya Basin into the Charenton Drainage Canal and Bayou Teche. People also 

used the floodgate to navigate their boats through this location in the Atchafalaya levee 

system. This EA has been prepared in accordance with the National Environmental 

Policy Act of 1969 and the Council on Environmental Quality’s Regulations (40 CFR 

1500-1508), as reflected in the USACE Engineering Regulation ER 200-2-2. This EA 

provides sufficient information on the potential adverse and beneficial environmental 

effects to assist the District Commander, U.S. Army Corps of Engineers in making an 

informed decision on the appropriateness of an Environmental Impact Statement (EIS) 

or a Finding of No Significant Impact (FONSI).

 

Proposed Action 

The proposed action consists of constructing a new floodgate structure on the 

Atchafalaya Basin side of the existing Charenton Floodgate structure (Figure 2). The 

proposed project footprint is shown in Figure 3. The floodwalls would extend out a 

couple hundred feet from each side of the new floodgate structure in order to tie-back 

into the existing levee. The existing walls on the monolith would be removed and the 

side slopes would be graded back in order to tie back into the existing levee alignment 

that is already constructed to the project design height. A temporary coffer dam would 

be placed on the Atchafalaya side of the system during construction. The existing 

floodgate structure will remain in place to continue to serve as the line of protection 

during construction until the new floodgates and floodwall are installed. Once the new 

system is in place, the existing steel floodgates will be removed but the concrete 

structure will remain. The bridge across the existing structure will not be impacted 

and will remain open to traffic both during construction and after construction is 

complete. 
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Authority 

The East and West Atchafalaya Basin Protection Levees are part of the Atchafalaya 

Basin project, a prominent feature of the Flood Control, Mississippi River and 

Tributaries (MR&T) project. The Flood Control Act of May 15, 1928, authorized the 

MR&T (PL 7391, 70th Congress), as amended and supplemented. The Atchafalaya 

Basin Floodway extends from the Old River Control Complex near the confluence of 

the Mississippi, Red, and Atchafalaya Rivers in the north, to the Gulf of Mexico in the 

south. The floodway is designed to protect southern Louisiana from MR&T floods by 

diverting up to one-half of the combined flows of the Red and Mississippi Rivers to the 

Gulf. Congress authorized project features to provide environmental protection, public 

access, developmental control, and recreational development within the Atchafalaya 

Floodway with the Supplemental Appropriations Act for Fiscal Year 1985, PL 99-88, 

August 15, 1985 (H.R. 2577, July 2, 1985), and by the Water Resources Development 

Act of 1986 (PL 99-662).

a.) Resolutions of the Committee on Public Works both the U.S. Senate and the 

U.S. House of Representatives authorized the Corps of Engineers to engage in a 

study of certain features of the Atchafalaya Basin Floodway System, Louisiana, 

Feasibility Study as follows:

“RESOLVED BY THE COMMITTEE ON PUBLIC WORKS OF THE UNITED 

STATES SENATE, That the Chief of Engineers of the United States Army, be, 

and is hereby requested to examine and review the project for flood control of the 

Mississippi River in its alluvial valley, and for its improvement from the Head of 

Passes to Cape Girardeau, Missouri as authorized by the Flood Control Act 

approved May 15, 1928, and as amended by subsequent acts of Congress, 

including Public Law 780, Eighty-third Congress, which modified the basic project 

to include a plan of improvement for the control of Old and Atchafalaya Rivers, to 

determine whether, in the light of changed conditions, any modifications, 

extensions, or additions to the existing Old River control system or its operation 

are warranted at this time.” Adopted June 11, 1968.

“RESOLVED BY THE COMMITTEE ON PUBLIC WORKS OF THE UNITED 

STATES SENATE, That the Chief of Engineers of the United States Army, in 

cooperation with other interested Federal and State agencies, such as the 

Environmental Protection Agency, and the Louisiana Stream Control 

Commission, be, and is hereby requested to review and report on the Mississippi 

River and Tributaries Project, published as House Document Numbered 308, 

Eighty-eight Congress, and other pertinent reports, with a view to developing a 

comprehensive plan for the management and preservation of the water and 

related land resources of the Atchafalaya River Basin, Louisiana, which could 

include provisions for reductions of siltation; improvement of water quality; and 

possible improvements of the area for commercial and sport fishing.” Adopted 

March 23, 1972.
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b. Modification of some features of the Atchafalaya Basin, LA project were 

initiated by the Chief of Engineers through his discretionary authority by letter 

dated June 18, 1976, and endorsed by the President of the MRC on June 28, 

1976. This provided for alternate plans to be accomplished within the authorized 

purpose of the Atchafalaya Basin system project as addressed, in specific terms, 

in the 1982 Feasibility Study. The Chief of Engineers has the discretionary 

authority to implement remaining features of the 1982 Feasibility Study as 

outlined by letter dated February 28, 1983, and approved by the President of the 

MRC in a first endorsement to the letter, dated March 11, 1983.

Purpose and Need for the Proposed Action 

The purpose of the proposed action is to construct a new floodgate to meet new design 

height requirements identified in the 2010 Refined Flowline Study Report completed 

for the Atchafalaya Basin. The Charenton Floodgate is currently the lowest spot in this 

line of protection and thus the highest priority on the West Atchafalaya Basin Protection 

Levee. Due to poor condition, the gates have not been operated in over 18 years. The 

levee systems around the perimeter of the Atchafalaya Basin have been raised through 

the years to provide a higher level of protection while the Charenton Floodgate remains

the lowest location along the levee.

Data Gaps and Uncertainties 

Because natural systems are complex and consist of an intricate web of variables that 

influence the existence and condition of other variables within the system, all projects 

(e.g., flood risk management, restoration, etc.) contain inherent uncertainties. The 

effects of tropical storms, increased sea level rise, and climate change on each 

project’s performance are uncertain and are addressed through future projections 

based on existing information. 
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Figure 1. Charenton Floodgate Location Map, St. Mary Parish, Louisiana.
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Figure 2. Proposed New Charenton Floodgate Plan, St. Mary Parish, Louisiana.
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Figure 3. Charenton Floodgate Right-of-Way Footprint

Prior National Environmental Policy Act (NEPA) Documents 

The environmental impacts of constructing the existing Charenton floodgate structure 

were assessed in the January 1982 final Environmental Impact Statement (FEIS), 

entitled "Atchafalaya Basin Floodway System Feasibility Study," which is incorporated 

by reference herein. A Record of Decision (ROD) was signed on December 3, 1986, 

for the 1982 FEIS. EA# 467A, “West Atchafalaya Basin Protection Levee W-86, 2nd 

Lift and Repairs Government Furnished Borrow Sites St. Mary Parish, Louisiana” 
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assessed the impacts of utilizing two government-furnished borrow areas for (Phase 

B) construction of the Levee W-86 project, from B/L Station 4593+00 just north of 

Avoille Cove, to B/L Station 4713+00 at the Charenton Floodgate. The FONSI for EA 

#467A was signed on February 3, 2000. EA #467, "Contractor Furnished Borrow 

Areas, West Atchafalaya Basin Protection Levee, Levee W-86, 2nd Lift and Repairs, 

St. Mary Parish, Louisiana," assessed the impacts of utilizing contractor furnished 

borrow pits for first phase (Phase A) construction of the Levee W-86 project, from 

approximately B/L Stations 4266+00 to 4593+00. The FONSI for EA #467 was signed 

on June 4, 2008. EA #358, "W-85 A&B Levee Enlargement, West Atchafalaya Basin 

Protection Levee, Iberia and St. Mary Parishes, Louisiana," assessed the impacts of 

utilizing three government-furnished borrow areas located near Lake Fausse Pointe for 

the second lift and repairs to Levee W-85. The FONSI for EA #358 was signed on 

October 21, 2002. The borrow areas assessed for the W-85 project are separate from 

the borrow areas proposed for the W-86 Phase B project. The study was guided by the 

premise that the navigation component of the project was no longer needed. The 

navigation authorization was going to be removed through a post-authorization change. 

It was determined in 2010 that removing the navigation function through this structure 

was unacceptable to the local entities. The first is the “Lower Atchafalaya Report” dated 

May 16, 2000. 

Public Concerns 

In October of 2010, a public meeting was organized and hosted by the Chitimacha

Tribe of Louisiana in Charenton, Louisiana. Feedback from the meeting demonstrated 

overwhelming support for the existing Charenton Floodgate to be replaced with a new 

structure and retain the navigation function, continuing to allow regular access into the 

Atchafalaya Basin.

Residents of the lower Atchafalaya Basin are concerned about the floodway's ability to 

pass project floodwaters and to prevent damage to property within and adjacent to the 

floodway system. Residents are concerned about maintaining a structure for safe 

navigation into the Atchafalaya Basin. Widespread public support also exists for the 

protection of environmental resources within the Atchafalaya Basin, with special 

emphasis on preventing further loss or degradation of wetland and woodland habitats. 

The EA#511 will go out for a 30-day public review period allowing agencies and the 

public the opportunity to provide comments on the project.

2. Alternatives Including the Proposed Action

2.1 Proposed Action

Seven alternatives to the proposed action were considered to include five alternative 

locations for the proposed floodgate (Figure 4). These alternatives were: No-action; 

Alternative Location 1, Alternative Location 2A, Alternative Location 2B, Alternative 

Location 3, Alternative Location 4, and Alternative Location 5. Rebuilding the current 

floodgate (Alternative 1) was evaluated and determined to be unacceptable from an 
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engineering standpoint and was eliminated from further consideration. Construction on 

the gulf side of the existing structure (Alternative 3) was also eliminated as

unacceptable because a new bridge with new approaches on each side of it would 

need to be constructed and the roadway is a designated emergency evacuation route

that would be blocked during the construction. Constructing structures offset to the 

existing structure (Alternatives 4 and 5) would require a longer floodgate structure since 

it does not abut into the existing floodgate structure and a new channel to connect the 

Atchafalaya Basin to the Charenton Drainage Canal. These two alternatives were 

eliminated from further consideration because of the additional potential environmental 

impact.

General observations of the construction work required for each location led the 

design team to conclude that Alternative Location 2 would be the most economical 

and least disruptive location to construct the proposed project. Within this selected 

location, two types of tie-back alternatives were developed. Alternative 2-A was 

developed as an earthen levee tie-back system and Alternative 2-B was developed as 

a floodwall tie-back system. Alternative 2-A covers more area because of the new 

earthen levees extending out a couple hundred feet from each side of the new 

floodgate structure in order to tie back into the existing levee alignment that is already 

constructed to the project design height. For this EA the alternatives were renumbered 

and Alternative 1 is now the No Action.

2.2 No-Action Alternative (Future without Project [FWOP])

In the future without project, the proposed action would not be constructed. The 

floodgate elevation would be lower than the adjacent levees. The Charenton Floodgate 

location would continue to be deficient and susceptible to overtopping. 

2.3 Alternative 2-A

Alternative 2-A adds a new floodgate structure to the Atchafalaya Basin side of the 

existing structure. New earthen levees extend out a couple hundred feet from each side 

of the new floodgate structure in order to tie back into the existing levee alignment that 

is already constructed to the project design height. 

Construction work includes relocating the existing freshwater intake pump station. The 

footprint for the new structure and levees would be preloaded with soil and allowed to 

settle for 18 months prior to construction of the main features. Over four feet of 

settlement of the adjacent edge of the existing monolith is estimated. Removal of the 

existing walls on this monolith and side slopes graded back to levee/floodwall/floodgate 

is required for this alternative. The existing monolith foundation is to be left in place 

and allowed to settle. A temporary sheet piling coffer dam will be placed on the 

Atchafalaya side of the system during the construction process.

The existing floodgate structure would remain in place to continue to serve as the line 

of protection throughout construction until the new floodgates and line of protection is 

installed and operational. Once the new system is in place, the existing floodgates and 
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operating equipment are to be removed and scrapped. The existing concrete structure 

will be left in place as it currently exists. The bridge across the existing structure will 

not be impacted by this alternative and is to remain open to traffic during and after 

construction is complete.

Figure 4. Alternative Locations for the Proposed Charenton Floodgate Modification, St. 

Mary Parish, Louisiana.
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3. Affected Environment

Description of the Work Area

The Atchafalaya River Basin is bounded on the east and west by artificial levees that 

were constructed in the 1930s as a direct result of the 1927 flood. The economy within 

this region is largely based on commercial fishing and trapping, outdoor recreation, 

and the extraction of oil and gas. Public access to the project area is via the existing 

Atchafalaya Basin berm road, which parallels the protected side of the levee. The levee 

and berm area are covered by a mixture of turf grasses. The levee crown and access 

ramps are dirt/gravel roadways. Primary habitats within the proposed project are 

forested wetlands and open water.

3.1.1 Description of the Watershed

The Charenton Drainage and Navigation Canal provides a means of accessing Lake 

Fausse Point, Grand Lake, and eventually the Atchafalaya River Main Channel via 

waterway. The Charenton Floodgate is located in the West Atchafalaya Basin Levee at 

the head of the Charenton Drainage Canal, about one mile north of Charenton. It controls 

the amount of fresh water from the Atchafalaya Basin into the Charenton Drainage Canal 

and Bayou Teche and allows for navigation through the levee. It is a part of the watershed 

for the Atchafalaya river system. The Atchafalaya River flows approximately 140 miles 

through southeast Louisiana from Simmesport to Atchafalaya Bay and the Gulf of Mexico, 

with an average headwater discharge of 218,400 cubic feet per second (cfs). In the early 

1500s, the Mississippi River captured the lower Red River and established the 

Atchafalaya River as a distributary. Until the 1950s, the Mississippi River was diverting 

an increasing amount of its discharge into the Atchafalaya, an indication the Mississippi 

was about to shift its course. In the 1960s, the Old River Control Structure was 

completed, in accordance with the Flood Control Act of 1954, to prevent the capture by 

the Atchafalaya River of a large measure of the flow and sediment of the Mississippi 

River. By determinations in the current decision documents, allocation of flowage and 

bedload sediment from the Mississippi River through the Old River Control Complex into 

the Atchafalaya River are controlled in certain percentages. At present, 30 percent of the 

combined flows of the Red River and the Mississippi River are joined to become the 

Atchafalaya River system. Under the current design of the federally authorized MR&T 

Project, the floodways for the MR&T Atchafalaya Basin Flood Control Project are 

designed to pass one half of the project flood for the Mississippi River, or 1.5 million cfs, 

to the Gulf of Mexico. Today the Atchafalaya River is the main distributary of the 

Mississippi.

The Atchafalaya River is the primary source of water to one of the largest wetland 

complexes in the world. The Atchafalaya River Basin is extremely rich in biodiversity and 

productivity and is bounded on the east and west by artificial levees that were constructed 

in the 1930s as a direct result of the flood of 1927 and the authorization of the MR&T 

Project by the Flood Control Act of 1928, as amended. There are primarily three ecoregions in the Atchafalaya Basin: the northern part composed of bottomland hardwood 

forest; the middle, composed of cypress-willow-tupelo swamps; and the lower, which 
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contains freshwater and brackish marsh. The most ecologically important parts of the 

Atchafalaya Basin are 885,000 acres of forested wetlands and 517,000 acres of 

marshland that combine to make this the largest river swamp in North America. 

Atchafalaya Bay was once the delta system for the Mississippi River as it flowed into the 

Gulf of Mexico prior to its re-routing through New Orleans to the east (Walker et al. 2003). 

Therefore, the area received significantly more flow and sediment load and, as a result, 

the bay is very shallow. Historically, this higher flow would have pushed much further into 

Atchafalaya Bay and the mixing zone where river water and seawater met would have 

been much further seaward than its current position. The river discharges into Atchafalaya 

Bay in southern Louisiana through two outlets, Lower Atchafalaya (70 percent of the 

discharge) and Wax Lake (30 percent) (Neill and Allison 2005). 

3.1.2 Climate 

The Atchafalaya River Basin area has a humid, subtropical climate with a strong 

maritime character. Warm, moist southeasterly winds from the Gulf of Mexico are 

present throughout most of the year, with occasional cool, dry fronts occurring as a 

result of northeast high-pressure systems. The influx of cold air occurs less frequently 

in autumn and only rarely in summer. Tropical storms and hurricanes are likely to affect 

the area 3 out of every 10 years, with severe storm damage approximately once every 

2 or 3 decades. The majority of these occur between early June and November. The 

largest recent hurricanes were Katrina and Rita in 2005 which caused damage in the 

proposed work area. Hurricanes Gustav and Ike in 2008, and more recently, Isaac in 

2012, caused additional damage in the proposed work area. Summer thunderstorms 

are common, and tornadoes strike occasionally. Average annual temperature in the 

area is 67° F, with mean monthly temperatures ranging from 82° F in August to 52° F 

in January. Average annual precipitation is 57.0 inches, varying from a monthly 

average of 7.5 inches in July, to an average of 3.5 inches in October 

(http://www.srcc.lsu.edu/).

3.1.3 Geology

The National Resource Conservation Service (2007) classifies the soils within the 

area as and adjacent to the proposed borrow areas as “Schriever clay, frequently 

flooded.” These soils were formed in clayey alluvium laid down over time by sediment 

deposits from the Atchafalaya River. The Schriever series soils have very poor 

drainage and are classified as very slow to impermeable soils, consisting of clayey 

to silty clay loam. This soil association is suitable for growth of bottomland hardwoods

but is generally not well suited for cultivated crops due to frequent flooding. 

Relevant Resources

This section contains a description of relevant resources that could be impacted by the 

project. The relevant resources (Table 1) described in this section are those recognized 

by laws, executive orders, regulations, and other standards of national, state, or 

regional agencies and organizations; technical or scientific agencies, groups, or 
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individuals; and the general public. Important resources found within the proposed 

project area and assessed in this EA are wetlands, water bodies/water quality, wildlife, 

fisheries, threatened and endangered species, cultural resources, recreational 

resources, aesthetics, air quality, and prime and unique farmlands. The floodgate 

project is located in a remote area, so it was determined there would be no direct 

disproportionately high or adverse human health or environmental effects on any 

minority and/or low-income populations as per E.O. 12898, Environmental Justice in 

Minority and Low-Income Populations. Due to the remote location, small size, and short 

duration the project is not expected to produce adverse noise impacts.

Table 1: Relevant Resources and Their Institutional, Technical, and Public 

Importance.

Resource Institutionally Important Technically Important Publicly Important

Wetlands

Clean Water Act of 1977, as amended; 

Executive Order 11990 of 1977, 

Protection of Wetlands; Coastal Zone 

Management Act of 1972, as amended; 

and the Estuary Protection Act of 1968., 

EO 11988, and Fish and Wildlife 

Coordination Act.

They provide necessary habitat for various 

species of plants, fish, and wildlife; they 

serve as ground water recharge areas; they 

provide storage areas for storm and flood 

waters; they serve as natural water filtration 

areas; they provide protection from wave 

action, erosion, and storm damage; and 

they provide various consumptive and nonconsumptive recreational opportunities. 

The high value the public places on the 

functions and values that wetlands 

provide. Environmental organizations and 

the public support the preservation of 

marshes.

Prime and/or 

Unique 

Farmlands

Farmland Protection Policy Act of 1981.

USDA’s NRCS recognizes the importance 

of prime and unique farmlands. Prime 

farmland is available land that has the best 

combination of physical and chemical 

characteristics for producing food, feed, 

forage, fiber, and oilseed crops. Unique 

farmland is land other than prime farmland 

that is used for the production of specific 

high value food and fiber crops, such as 

citrus, tree nuts, olives, and vegetables.

Prime and unique farmland provides

food, feed, forage, fiber, and oilseed crops 

for public consumption.

Aquatic 

Resources/

Fisheries

Fish and Wildlife Coordination Act of 

1958, as amended; Clean Water Act of 

1977, as amended; Coastal Zone 

Management Act of 1972, as amended; 

and the Estuary Protection Act of 1968.

They are a critical element of many 

valuable freshwater and marine habitats; 

they are an indicator of the health of the 

various freshwater and marine habitats; and 

many species are important commercial 

resources.

The high priority that the public places on 

their esthetic, recreational, and 

commercial value.

Wildlife

Fish and Wildlife Coordination Act of 

1958, as amended and the Migratory 

Bird Treaty Act of 1918.

They are a critical element of many 

valuable aquatic and terrestrial habitats; 

they are an indicator of the health of various 

aquatic and terrestrial habitats; and many 

species are important commercial 

resources.

The high priority that the public places on 

their esthetic, recreational, and 

commercial value.

Threatened 

and 

Endangered 

Species

The Endangered Species Act of 1973, 

as amended; the Marine Mammal 

Protection Act of 1972; and the Bald 

Eagle Protection Act of 1940.

USACE, USFWS, NMFS, NRCS, EPA, 

LDWF, and LDNR cooperate to protect 

these species. The status of such species 

provides an indication of the overall health 

of an ecosystem.

The public supports the preservation of 

rare or declining species and their 

habitats.

Cultural 

Resources

National Historic Preservation Act of 

1966, as amended; the Native 

American Graves Protection and 

Repatriation Act of 1990; and the 

Archeological Resources Protection Act 

of 1979.

State and Federal agencies document and 

protect sites. Their association or linkage to 

past events, to historically important 

persons, and to design and construction 

values; and for their ability to yield important 

information about prehistory and history. 

Preservation groups and private 

individuals support protection and 

enhancement of historical resources.

Recreation 

Resources

Federal Water Project Recreation Act of 

1965 as amended and Land and Water 

Conservation Fund Act of 1965 as 

amended.

Provide high economic value of the local, 

state, and national economies.

Public makes high demands on 

recreational areas. There is a high value 

that the public places on fishing, hunting, 

and boating, as measured by the large 

number of fishing and hunting licenses 

sold in Louisiana; and the large per-capita 

number of recreational boat registrations 

in Louisiana.
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Resource Institutionally Important Technically Important Publicly Important

Visual 

Resources 

(Aesthetics)

USACE ER 1105-2-100, and

National Environmental Policy Act of 

1969, the Coastal Barrier Resources 

Act of 1990, Louisiana’s National and 

Scenic Rivers Act of 1988, and the 

National and Local Scenic Byway 

Program.

Visual accessibility to unique combinations 

of geological, botanical, and cultural 

features that may be an asset to a study 

area. State and Federal agencies 

recognize the value of beaches and shore 

dunes.

Environmental organizations and the 

public support the preservation of natural 

pleasing vistas. 

Air Quality Clean Air Act of 1963, Louisiana 

Environmental Quality Act of 1983.

State and Federal agencies recognize the 

status of ambient air quality in relation to 

the NAAQS.

Virtually all citizens express a desire for 

clean air.

Water Quality

Clean Water Act of 1977, Fish and 

Wildlife Coordination Act, Coastal Zone 

Mgt Act of 1972, and Louisiana State & 

Local Coastal Resources Act of 1978.

USACE, USFWS, NMFS, NRCS, EPA, and 

State DNR and wildlife/fishery offices 

recognize value of fisheries and good water 

quality and the national and state standards 

established to assess water quality.

Environmental organizations and the 

public support the preservation of water 

quality and fishery resources and the 

desire for clean drinking water. 

3.2.1 Wetlands

Existing Conditions

Wetlands in the project area provide various habitat opportunities for numerous

wildlife species. A variety of birds utilize forested areas for nesting, breeding, brooding,

and as perches. Wetlands in the project area also provide soft mast (samaras, berries),

which are a valuable nutritional food source for birds, mammals, and other wildlife 

species. The surrounding swamp habitat is dominated by cypress trees other species 

include tupelo, black willow, and hackberry. Ground cover in the project area consists of 

detritus and deadfall from trees within the area, and seedlings of area plant species. 

3.2.2 Prime and/or Unique Farmlands

Existing Conditions

The major agricultural commodity in St. Mary Parish is sugarcane, but other common 

crops grown are soybeans and citrus fruits. Livestock production, which includes cattle, 

horses, rabbits, sheep, goats, and swine are also managed. The Natural Resource 

Conservation Service (NRCS) was consulted because the proposed project would impact 

prime and unique farmland soils. Projects are subject to the Farmland Protection Policy 

Act (FPPA) requirements if they may irreversibly convert farmland to nonagricultural use 

and are completed by a federal agency. Farmland subject to FPPA requirements can be 

forest land, pastureland, cropland, or other land, but not water or urban built-up land.

Coordination with the NRCS was completed on June 11, 2020. The NRCS concluded that 

the proposed construction area will not impact prime farmland and therefore is exempt 

from the rules and regulations of the FPPA—Subtitle I of Title XV, Section 1539-1549.

3.2.3 Aquatic Resources/Fisheries

Existing Conditions

A wide variety of fish species are known to inhabit the area. Important aquatic resources 

expected to occur in the canal include largemouth bass, yellow bass, bluegill, crappie, 

gar, carp, shad, catfish and crawfish.
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3.2.4 Wildlife 

Existing Conditions

Some wildlife species that may inhabit the project area include opossum, gray squirrel, 

swamp rabbit, nutria, raccoon, rats, mice, turtles, snakes, frogs, and toads. Bird species 

known to exist in the area include wading birds, raptors, songbirds, and neo-tropical 

migrants. 

3.2.5 Threatened and Endangered Species 

Existing Conditions

Nine federally threatened, endangered, or candidate species are either known to or may 

possibly occur in St. Mary Parish, Louisiana: Eastern black rail, piping plover (Charadrius 

melodus) (threatened); red knot (Calidris canutus rufa) (threatened); West Indian 

manatee (Trichechus manatus) (endangered); pallid sturgeon (Scaphirhynchus albus) 

(endangered); hawksbill sea turtle (Eretmochelys imbricata) (endangered); leatherback 

sea turtle (Dermochelys coriacea) (endangered); Kemp's ridley sea turtle (Lepidochelys 

kempii) (endangered); loggerhead sea turtle (Caretta caretta) (threatened); Gulf sturgeon 

(Acipenser oxyrhynchus desotoi) (threatened). 

3.2.6 Cultural Resources

Existing Conditions

An evaluation of Charenton Floodgate for eligibility of listing in the National Register of 

Historic Places (NRHP) was conducted in November 2000 by R. Christopher Goodwin 

and Associates, Inc. The results of the evaluation determined that the Charenton 

Floodgate had retained much of the integrity from original construction and continues to 

operate as originally designed. The 2000 evaluation concluded that the floodgate was 

eligible for listing in the NRHP under Criteria A and C.

Under Criterion A, a property must be associated with events important to the broad 

patterns of United States history. As part of the Atchafalaya Floodway, Charenton 

Floodgate relates to the development of flood control for the Mississippi River Valley. The 

floodgate and levees were essential structures in local and national efforts to protect the 

lower Mississippi River Valley from floods. Charenton Floodgate also represents the 

increasing involvement of the USACE in the design and maintenance of flood control 

structures in the Mississippi Valley. The floodgate protects productive resources and 

expanding settlements along the lower Bayou Teche river basin. The Charenton 

Floodgate also frequently opens to allow fresh water to enter Bayou Teche via the 

Charenton Drainage and Navigation Canal. 

To be determined eligible under Criterion C, the property must embody distinctive 

characteristics of a type, period, or method of construction; represent the work of a 

master; possess high artistic value; or represent a significant and distinguishable entity 

whose components may lack individual distinction. Charenton Floodgate represents the 

type of engineering design used during the mid-twentieth century. The floodgate is one 
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of five structures utilizing similar gate technology built along the Atchafalaya Basin 

Floodway between 1941 and 1954. Charenton Floodgate is an excellent representative 

of the engineering construction used by the USACE and of the type and quality of 

materials used.

Charenton Floodgate has undergone few changes over the years. Many of the changes 

include minor alterations or routine maintenance, such as the replacement of the sector 

gates and the replacement of steel handrails with aluminum railings. Although a bridge 

built over the structure was replaced, the overall design of the floodgate is unaltered. 

Charenton Floodgate operates as originally designed. Therefore, the floodgate retains a 

high degree of integrity from its period of significance.

An updated evaluation of the floodgate was completed in 2016 to evaluate changes that 

were made to the structure since the 2000 evaluation, and determine if those changes 

diminished the integrity of the Charenton Floodgate and those qualities that make it 

significant and eligible for listing in the NRHP. The 2016 evaluation concluded that the 

floodgate remained eligible for listing in the NRHP under Criteria A and C.

Consultation with the Louisiana State Historic Preservation Officer (SHPO) and federallyrecognized Tribes was conducted in May and June of 2016 for the proposed undertaking 

and the eligibility of the Charenton Floodgate for listing in the NRHP. In a letter dated 

June 13, 2016, the SHPO concurred that the Charenton Floodgate was eligible for listing 

in the NRHP under Criteria A and C, and that removal of the sector gates and the 

construction of new floodgate structure would cause an adverse effect to the Charenton 

Floodgate. The development of a Memorandum of Agreement (MOA) was recommended 

in order to develop strategies to mitigate for adverse effects to the floodgate. In a letter 

dated January 4, 2017, the Advisory Council on Historic Preservation (ACHP) stated that 

“Based upon the information provided, we have concluded that Appendix A, Criteria for 

Council Involvement in Reviewing Individual Section 106 Cases, of our regulations, 

“Protection of Historic Properties” (36 CFR Part 800), does not apply to this undertaking. 

Accordingly, we do not believe that our participation in the consultation to resolve adverse 

effects is needed.” The Chitimacha Tribe of Louisiana indicated an interest in having the 

floodgate replaced to improve flood protection and improve navigation and requested to 

participate in continued consultation for the development of the MOA.

In September 2020, the USACE reinitiated Section 106 consultation with the LA SHPO, 

the ACHP, and federally-recognized Tribes. On September 21, 2020, the Choctaw Nation 

of Oklahoma submitted written correspondence stating that “St. Mary Parish lies outside 

of our area of historic interest. The Choctaw Nation Historic Preservation Department 

respectfully defers to the other Tribes that have been contacted.” On September 22, 2020, 

the Muscogee (Creek) Nation submitted written correspondence stating that “The project 

area is located outside of our area of interest. We respectfully defer to the other tribes 

who have been contacted for comments.” On October 6, 2020, the USACE received a 

written response from the ACHP stating again that “Based upon the information provided, 

we have concluded that Appendix A, Criteria for Council Involvement in Reviewing 

Individual Section 106 Cases, of our regulations, “Protection of Historic Properties” (36 
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CFR Part 800), does not apply to this undertaking. Accordingly, we do not believe that 

our participation in the consultation to resolve adverse effects is needed.”

3.2.7 Recreational Resources

Existing Conditions

The project is located within the Atchafalaya Basin which is a popular area for bird 

watching, boating, canoeing, fishing, hiking, hunting, photography, camping and wildlife 

viewing. Currently the USACE is preparing a Supplemental Environmental Impact 

Statement (SEIS) for recreation features south of I-10 within Atchafalaya Basin. The SEIS 

analyzes the development of three developed campgrounds, seven primitive 

campgrounds, five new and ten improved boat launches, one visitor center, hiking and 

paddling trails, and wildlife viewing areas.

The Charenton Drainage and Navigation Canal provides a waterway access north to

Lake Fausse Pointe, Grand Lake, and eventually the Atchafalaya River Main Channel. 

These waterways provide opportunities for boating and fishing. Recreational resources 

are publicly important because of the high value that the public places on fishing, hunting, 

and boating, as measured by the large number of fishing and hunting licenses sold in 

Louisiana, and the large per-capita number of recreational boat registrations in Louisiana

(Table 2).

Table 2: FY 2017 Fishing/ Hunting Licenses1, Boater Registrations.

Parish/County

Fishing Licenses Hunting Licenses

ResidentBasicResident–

Saltwater

ResidentBasic

Resident 

Boat2

Registrations

Assumption 2,583 1,581 968 3,607

Iberia 8,013 6,701 2,449 7,655

Iberville 2,798 1,383 1,226 3,320

Pointe Coupee 2,284 955 1,345 2,575

Saint Landry 8,870 4,427 4,666 6,082

Saint Martin 5,432 3,160 2,315 5,119

Saint Mary 6,021 4,789 1,806 7,827

Terrebonne 17,870 17,376 3,991 15,029

Atchafalaya Basin 

Floodway System 

(ABFS) Parishes Total

53,871 40,372 18,766 51,214
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State Totals 376,945 229,436 152,165 320,819

ABFS Percent of State 14.3% 17.6% 12.3% 16%

Source: www.wlf.louisiana.gov/licenses/statistics

1 Number of licenses issued in Parish granting residents fishing or hunting privileges.

2 Resident Boater registration data is for 2011.

Within the vicinity of the project area there are several recreation areas including private 

recreation camps (approx. one mile east of the project); a primitive state campground on 

the south bank of Grand Avoille Cove (approx. 1.5 mile north of the project); a boat launch 

which provides access to Lake Fausse Pointe and Grand Avoille Cove (approx. 2 miles 

north of the project); Millet Point Boat Launch (approx. 4.5 south of the project); Attakapas 

Island WMA (approx. 2 miles east of the project); Lake Fausse Point State Park (approx. 

7 miles north of the project). Also, within the USACE SEIS there is a proposal for a 

primitive campground, Fishers Island, approximately 3 miles north of the project area. 

Currently the Charenton Floodgate is closed; therefore not used by recreational vessels. 

3.2.8 Visual Resources (Aesthetics) 

Existing Conditions

The proposed site currently features the existing Western Atchafalaya River Levee 

(WARL) as a primary structure in the area. The levee is a typical earthen berm, covered 

in turf on both the protected and flood sides. Access roads crest the top of the levee 

and provide vehicular access for maintenance vehicles and visitors alike. There are a 

number of open water areas throughout the area that include the Charenton Drainage 

and Navigation Canal. There are no known state-designated scenic rivers or streams 

near the project area. The vicinity of the project area is characteristic of inland swamps, 

with a variety of vegetation present. The terrain is flat and splotched with low lying 

areas prone to water fill, characteristic of wetland and swamp habitats and a natural 

levee system near banks of nearby rivers and streams. Land use in the area is primarily 

agricultural between the flood gate and the City of Charenton, with a small pocket of 

single-family residential homes.

Other land uses include forested/vacant in the vicinity of the proposed borrow area and 

north of the flood gate in the Atchafalaya Basin. The surrounding habitat is comprised 

of a mixture of deep, wooded areas and the Western Atchafalaya River Levee, which 

acts as the dominant landform feature in the area. Otherwise, the terrain is relatively 

flat with minimal changes in elevation. The landscape is pastoral and serene, 

tremendously adding to the visual quality of the visitor experience. There are no specific 

known or identified protected trees or other plant materials in the immediate project 

area. Public visual and physical access to the project site is limited. There is a local 

street running north from LA Highway 87 that provides a distant view of the project 

area. Otherwise, access is from watercraft only. LA Highway 87 represents a portion 

of the Promised Land Scenic Byway which is a state-recognized scenic bayou.
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3.2.9 Air Quality

Existing Conditions

St. Mary Parish is currently in attainment of all National Ambient Air Quality Standards 

(NAAQS). This classification is the result of area-wide air quality modeling studies, and 

the information is readily available from Louisiana Department of Environmental Quality, 

Office of Environmental Assessment and Environmental Services.

3.2.10 Water Quality

Existing Conditions

The Charenton Drainage and Navigation Canal provides access, northern waterway 

access to Lake Fausse Point, Grand Lake and eventually the Atchafalaya River Main 

Channel. The Charenton floodgate channel is typically non-turbid, due to the limited 

use. As part of its surface water quality monitoring program, the Louisiana Department of 

Environmental Quality (LDEQ) routinely monitors 25 parameters on a monthly or 

bimonthly basis using a fixed station, long-term network (Monitored Assessments) (LDEQ 

1996). Based upon those data and the use of less-continuous information (Evaluated 

Assessments), such as fish tissue contaminants data, complaint investigations, and spill 

reports, the LDEQ has assessed water quality fitness for the following uses: primary 

contact recreation (swimming), secondary contact recreation (boating, fishing), fish and 

wildlife propagation, drinking water supply and shellfish propagation (LDEQ 1996). Based 

upon existing data and more subjective information, water quality is determined to either 

fully, partially, or, not support those uses. A designation of “threatened” is used for waters 

that fully support their designated uses but that may not fully support certain uses in the 

future because of anticipated sources or adverse trends in pollution.

According to the LDEQ Final 2016 Louisiana Water Quality Inventory: Integrated Report 

(305(b)/303(d)), the West Atchafalaya Basin Floodway Charenton Canal from Charenton 

Floodgate to the Intercoastal Waterway; includes Bayou Teche from Charenton to 

Baldwin (subsegment LA060601_00) is “not supporting designated use” for primary 

contact recreation (i.e., swimming); “fully supporting designated use” for secondary 

contact recreation (i.e., boating); is “not supporting designated use” for fish and wildlife 

propagation (i.e., fishing); and is “fully supporting designated use” for drinking water 

supply (LDEQ 2016). 

4. Environmental Consequences

Wetlands

Future Conditions with No Action

Without implementation of the proposed action, no impacts would occur to the 

bottomland hardwood habitat or cypress swamp. The Charenton Floodgate’s elevation 

would continue to be deficient and susceptible to overtopping. 
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Future Conditions with the Proposed Action (Alternative 2B)

With implementation of the proposed action, 14.8 acres (7.2 AHU) of bottomland 

hardwood habitat and 2.2 acres (1.47 AHU) of cypress swamp habitat would be cleared 

and filled for the project to construct a new floodgate. The Wetland Value Assessment 

(WVA) methodology is a quantitative habitat-based assessment methodology developed 

for use in determining wetland benefits or losses. The WVA quantifies changes in wildlife 

habitat quality and quantity that are expected to result from a proposed project. The 

results of the WVA are measured in Annualized Habitat Units (AHUs). The WVA 

methodology provides an estimate of the number of acres benefited or lost due to the 

project’s construction. The WVA model indicates 1.48 AHUs would be lost due to the 

project’s construction. The impacts to the acres of bottomland hardwood and cypress 

swamp are unavoidable because of the foundation needed for the floodgate structure.

Future Conditions with Alternative 2A

With implementation of Alternative 2A, 14.8 acres (7.2 AHU) of bottomland hardwood 

habitat and 2.2 acres (1.47 AHU) of cypress swamp habitat would be cleared and filled 

for the project to construct a new floodgate resulting in unavoidable impact to the 

bottomland hardwood and cypress swamp due to the floodgate structure foundation 

requirements.

4.2 Prime and Unique Farmlands

Future Conditions with No-Action

Without implementation of the proposed action, no direct or indirect impacts to prime 

and unique farmland would occur. 

Future Conditions with the Proposed Action

Farmland Conversion Impact Rating Forms were completed and provided to the NRCS 

(Appendix A). In a letter dated May 05, 2020, the NRCS indicated they had no objection 

to the project. 

4.3 Aquatic Resources and Fisheries

Future Conditions with No Action

Without implementation of the proposed action, the proposed project would not be 

constructed, and impacts to aquatic resources and fisheries resources within the 

proposed project area would not likely change from current conditions.

Future Conditions with the Proposed Action (Alternative 2B)
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With implementation of the proposed action, the temporary cofferdam placed around the 

Atchafalaya side of the project would potentially enclose some fish species. As a result 

of this change, some fish mortality is expected during construction. Fish and aquatic 

organisms outside the cofferdam may be temporarily displaced during construction due 

to increased turbidity. Erosion control methods such as silt fences would be used but 

some runoff is expected along the project. Aquatic and fisheries resources are expected 

to recolonize the area post-construction. Due to the small project scope, cumulative 

impacts would be negligible. The temporary disturbances would not adversely impact the 

fishery population within the region, due to the extensive fish habitat available in the 

vicinity.

Future Conditions with Alternative 2A

With implementation of Alternative 2A, impacts on fisheries would be similar to the 

proposed action.

4.4 Wildlife 

Future Conditions with No Action

Without implementation of the proposed action, the proposed project would not be 

constructed, and impacts to wildlife resources within the proposed project area would 

not likely change from current conditions.

Future Conditions with the Proposed Action (Alternative 2B) 

With implementation of the proposed action, 2.2 acres of wooded wildlife habitat would 

be directly impacted due to its removal during construction. Wildlife would be displaced 

during construction. Indirect impacts such as stress caused by construction equipment 

would occur but would be short term in duration. The loss of habitat and temporary 

disturbance would not adversely impact the general populations of wildlife species 

within the region due to the large amount of comparable habitat available within the 

immediate vicinity of the project area. 

Future Conditions with Alternative 2A

With implementation of Alternative 2A, 3.4 acres of forested wetland habitat would be 

directly impacted due to its removal during construction. The wildlife impacts would be 

similar to those described in the proposed action.

4.5 Threatened and Endangered Species 

Future Conditions with No Action

Without implementation of the proposed action, there would be no direct or indirect 

impacts to threatened and endangered species.
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Future Conditions with the Proposed Action (Alternative 2B)

Federally listed species and/or their designated critical habitat that may occur in St. 

Mary Parish include the piping plover (Charadrius melodus), Eastern black rail, red knot, 

West Indian manatee (Trichechus manatus), sea turtles, Gulf sturgeon (Acipenser 

oxyrhynchus desotoi) and pallid sturgeon (Scaphirhynchus albus). With implementation 

of the proposed action, no threatened or endangered species nor their critical habitats 

are known to occur in areas that would be disturbed by the proposed work. The 

CEMVN has made a determination of “not likely to adversely affect” the 

aforementioned species under the Endangered Species Act. USFWS has concurred 

with this determination on August 06, 2020.

Future Conditions with Alternative 2A

Alternative 2A would have similar results to threatened or endangered species as the 

proposed action.

4.6 Cultural Resources

Future Conditions with No Action

Without implementation of the proposed action, the Charenton Floodgate would 

continue to exist in its current state and condition. The floodgate would not function as 

originally designed, would remain 10 feet deficient in height, and would not provide the 

level of flood protection necessary to meet the new height requirement in accordance 

with the USACE design standards and design criteria. 

Future Conditions with the Proposed Action

With implementation of the proposed action, the sector gates on the Charenton Floodgate 

would be removed and a new floodgate structure would be built in front of the floodgate. 

The main body of the floodgate on either side of the sector gates would remain in place. 

The sector gates on the Charenton Floodgate represent a unique design that allows the 

gates to withstand a head of water from either direction. The sector gates are a significant 

contributing element to the eligibility of the Charenton Floodgate for listing in the NRHP. 

Removal of the sector gates would cause an adverse effect to the Charenton Floodgate 

and would require mitigation to address those adverse effects. The USACE has 

consulted with the Louisiana SHPO, federally-recognized Tribes, and the ACHP to 

develop a MOA and strategies to mitigate for adverse effects associated with the removal 

of the sector gates and construction of the new floodgate structure. The MOA would be 

signed by all consulting parties prior to the signing of the FONSI and the agreed to 

mitigation completed prior to the removal of the sector gates and the commencement of 

any other construction related activities.

4.7 Recreational Resources 

Future Conditions with No Action
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Without implementation of the proposed action, the conditions within the recreational 

environment would continue as they have in the past and would be dictated by the 

natural land use patterns and processes that have dominated the area in the past. 

Future Conditions with the Proposed Action (Alternative 2B)

With implementation of the proposed action, there is the potential that people boating 

and fishing in the adjacent waterway may be temporarily impacted by construction 

activities. When the gate is operational it would be opened upon request. Recreational 

access to the adjacent waterways such as Lake Fausse Pointe, Grand Lake, and the 

Atchafalaya River would be improved with the gate repaired. 

Future Conditions with Alternative 2A

Alternative 2A would have similar impacts as those listed in the Proposed Action. 

4.8 Visual Resources (Aesthetics) 

Future Conditions with No Action

Without implementation of the proposed action, the proposed project would not be 

constructed, and impacts to Visual Resources would not likely change from existing 

conditions.

Future Conditions with the Proposed Action (Alternative 2B)

Given the remote nature of the project area, impacts to Visual Resources would be 

minimal. The project construction site is well out of view of the public. The replacement 

of the gate itself will have minimal impacts due to the fact that it will be similar to what 

was there in the first place. The replacement of the gate will require the removal of 

some forested wetland habitat, but this removal will be on the Atchafalaya Basin side 

of the levee and out of the already minimal to nonexistent public view shed. 

Reconstruction or repair of adjacent levees, concrete work or other necessary 

structures will also have minimal impacts because these structures have already been 

in place prior to construction of the new features. The borrow area will also present 

minimal impacts due to its remote location. The borrow area has minimal access and 

will fit in with existing open water ponds in the area.

Future Conditions with Alternative 2A

Alternative 2A presents similar impacts as those listed in the Proposed Action 

(Alternative 2B). The main difference being that Alternative 2A has a larger 

construction footprint that removes more of the forested wetland habitat on the 

Atchafalaya Basin side of the project area. However; this does not make up for the 

fact that the area is still remote with limit visual access.
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4.9 Air Quality

Future Conditions with No Action

Without implementation of the proposed action, there would be no direct or indirect 

impacts on air quality.

Future Conditions with the Proposed Action (Alternative 2B)

The primary air pollution sources resulting from project implementation would be 

short-term contributions of exhaust from heavy earthmoving machinery utilized in site 

preparation activities combined with potential recreational usage from vehicles and 

boating activities. Project-related contributions of air-born contaminants would be 

anticipated to be site-specific and introduced in small inconsequential volumes 

resulting in no long-term impacts on current or future air quality attainment standards. 

It has been determined that the activities proposed under this project would not exceed 

de minimis levels of direct emissions of a criteria pollutant or its precursors and would 

be exempted by 40 CFR Part 93.153. Overall impacts to air quality would be expected 

to be minimal. With the proposed action, project activities would be expected to 

produce less than 5 tons per year of Volatile Organic Compounds and NOX emissions. 

Thus, the ambient air quality in St. Mary Parish would not noticeably change from 

current conditions, and the status of ambient air quality for the parish would not be 

directly or indirectly altered. 

Future Conditions with Alternative 2A

With implementation of Alternative 2A, impacts on air quality would be similar to the 

proposed action.

4.10 Water Quality

Future Conditions with No Action

Without implementation of the proposed action, there would be no direct or indirect 

impacts on water quality.

Future Conditions with the Proposed Action (Alternative 2B)

With implementation of the proposed action, the temporary cofferdam placed around 

the Atchafalaya side of the project would potentially increase turbidity during 

construction. Erosion control methods such as silt fences would be used but some 

runoff is expected along the project. Water quality impacts are expected to be minor 

and short-term and return to normal post-construction conditions. Due to the small 

project scope, cumulative impacts would be negligible. The temporary disturbances 

would not adversely impact water quality within the region and the water quality

certification for the proposed project was received on June 10, 2020.
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Future Conditions with Alternative 2A

With implementation of Alternative 2A, impacts on water quality would be similar to the 

proposed action.

4.11 Hazardous, Toxic, and Radioactive Waste

The USACE is obligated under Engineer Regulation (ER) 1165-2-132 to assume 

responsibility for the reasonable identification and evaluation of all Hazardous, Toxic, 

and Radioactive Waste (HTRW) contamination within the vicinity of proposed actions. 

ER 1165-2-132 identifies that HTRW policy is to avoid the use of project funds for 

HTRW removal and remediation activities. An ASTM E 1527-13 Phase 1 Environmental 

Site Assessment (ESA) dated May 06, 2020 has been completed for the project area. 

A copy of Phase 1 ESA will be maintained on file at CEMVN. 

Additionally, other HTRW investigations were conducted in the project area and they 

indicate that there is a very low probability that Hazardous, Toxic, and Radioactive 

Waste (HTRW) would be encountered at the project location or the borrow site. No 

further investigation of HTRW is recommended, and the project may proceed without 

further study of HTRW; however, if the project locations or methods change the HTRW 

probability may need to be re-investigated.

4.12 Cumulative Impacts

The Council on Environmental Quality Regulations define cumulative impacts (CI) as “the 

impact on the environment which results from the incremental impact of the action when 

added to other past, present, and reasonably foreseeable future actions, regardless of 

what agency (Federal or non-Federal) or person undertakes such other actions. CI can 

result from individually minor but collectively significant actions taking place over a period 

of time.

Within the last 10 years, no federal levee projects have been constructed within the 

project vicinity. The proposed action would result in minor impacts to the resources 

addressed in this EA and would not be expected to result in significant cumulative 

impacts. The conversion of 14.8 acres of bottomland hardwood and 2.2 acres of cypress 

swamp to uplands is considered relatively minor, due to the large extent of comparable 

habitat in the project vicinity. The Atchafalaya Basin Flood Control Project feature of the 

MR&T project provided for net environmental benefits to the Atchafalaya basin through 

the preservation and enhancement of its economic and natural resources. 

The Atchafalaya Basin Flood Control project’s 1982 FEIS evaluated impacts associated 

with the existing Charenton floodgate feature, as well as with modification of existing 

features required to safely pass the project flood. The project flood translates into river 

flow rates. The Atchafalaya Basin Floodway must be capable of safely passing 1.5 million 

cubic feet per second to the Gulf of Mexico in order to avert floods along the highly 

populated, industrialized corridor of the lower Mississippi River. In addition to flood 
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protection features, the FEIS addressed various environmental features and nonstructural real estate features of various types, including for example, the purchase of 

flowage easements, environmental protection easements and lands in fee as part of the 

project’s recommended plan. The overall positive environmental contribution of the real 

estate feature was designed to offset the direct construction impacts of the flood 

protection features. Together, the environmental and real estate features would 

significantly benefit preservation of the basin’s desired “wet and wild” characteristics. 

Therefore, as previously addressed in the comprehensive plan, project construction 

would not substantially adversely impact the environment on a long-term and/or 

cumulative basis. 

5.0 Mitigation

The Charenton Floodgate is part of the authorized Atchafalaya Basin Floodway System

(ABFS) project. Habitat impacts, both negative and beneficial arising from the ABFS 

Project, were addressed in the 1982 ABFS EIS. The habitat impacts associated with the 

proposed project have been and are compensated by implementation of the ABFS 

Project. The implementation of the Congressionally authorized ABFS Recommended 

Plan described in the 1982 ABFS, Louisiana, Feasibility Study and Final EIS would result 

in over 40,000 annualized habitat units (AHU) of forested wetland habitat (bottomland 

hardwoods and cypress-tupelo), and nearly 3,000 AHU of swamp habitat for the ABFS. 

These cumulative benefits are specifically provided as a result of the acquisition of 

approximately 388,000 acres; 70,000 acres of USACE owned “fee” property to be 

managed for public access and 318,000 acres of developmental control and 

environmental protection easement lands that limit public access and timbering and are 

designed to prevent new structures, hydrological manipulations, and land conversion. 

WRDA 2007 authorized the acquisition of an additional 20,000 acres of fee-interest land 

from willing sellers. Of the authorized 70,000 fee acres, the USACE has purchased about 

47,323 acres on both sides of the Atchafalaya River between U.S. Hwy 190 and I-10. 

Concurrently, the USACE has acquired approximately 94,000 acres of the 318,000 acres 

of developmental control and environmental protection easements over private lands in 

the basin, which will prohibit conversion of forestlands to other uses. 

The Corps minimized wetland impacts to the maximum extent practicable by 

recommending the floodwall tieback alternative instead of an earthen levee option that 

would have impacted 3.4 acres of cypress swamp. Wetland impacts from the proposed 

Charenton Floodgate Modification project would be minor in scope and greatly offset by 

the overall positive contributions of the real estate feature in the ABFS Recommended 

Plan. The proposed Charenton Floodgate Modification project would impact 14.8 acres 

(7.2 AHU) of bottomland hardwood habitat and 2.2 acres (1.47 AHU) of cypress swamp 

habitat; however, these impacts are compensated for by the aforementioned net benefit 

of 40,000 AHU for forested wetland habitats and 3,000 AHU for swamp habitat under the 

Congressionally authorized ABFS Recommended Plan. Direct construction impacts of 

various project measures were designed to be offset by the overall positive contribution 

of environmental and nonstructural real estate features in the ABFS Recommended Plan. 

The loss of 14.8 acres (7.2 AHU) of bottomland hardwood habitat and 2.2 acres (1.47 

AHU) of cypress swamp habitat associated with the proposed Charenton Floodgate 
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Modification project, when taken in context of similar wetland losses addressed by the 

1982 FEIS, are more than adequately compensated for by the aforementioned mitigation 

plan. Therefore, no additional mitigation is necessary. As of the date of this EA, 

approximately 3% of the 40,000 AHU of forested wetland habitat has been utilized and 

approximately 3% of the 3,000 AHU for the swamp habitat has been utilized.

The proposed action is in the overall public interest as it will increase the floodgate height 

and will protect life and property in St. Mary Parish. Upon completion of the work, all 

levee embankments and areas disturbed by the construction activities would be seeded 

with Bermuda grass, fertilized, and mulched. Upon project completion, any disturbed 

areas on the Atchafalaya basin side of the levee that were not filled would be replanted 

with cypress tree saplings. 

6.0 Coordination and Public Involvement

Preparation of this draft EA and draft FONSI is being coordinated with the public, 

appropriate congressional, federal, tribal, state, and local interests, as well as 

environmental groups and other interested parties.

7.0 Compliance with Environmental Laws and Regulations

Environmental compliance for the proposed action will be achieved upon the following: 

• Coordination of this EA and draft FONSI with appropriate agencies, organizations, and 

individuals for their review and comments; 

• Coordination with LDNR confirmed that the proposed action would not impact coastal 

resources and was concluded on May 22, 2020. (Appendix A)

• USFWS concurred with a determination of no effect to any federally-listed threatened or 

endangered species, or their critical habitat, under the jurisdiction of USFWS on August 

05, 2020. (Appendix B) 

• LDEQ determined that the requirements for a Water Quality Certification have been met. 

LDEQ concluded that the deposit of spoil will not violate water quality standards as 

provided for in LAC 33: IX. Chapter 11. Therefore, LDEQ issued U.S. Army Corps of 

Engineers Water Quality Certification for the Atchafalaya Basin Construction, Charenton 

Floodgate Modification. A State Water Quality Certificate was received from the Louisiana 

Department of Environmental Quality on June 10, 2020. (Appendix C)

• Clean Water Act, Section 404(b)(1) Public Notice and Evaluation; (Appendix D)

• In a letter dated June 13, 2016, the LASHPO stated that the sector gates are a significant 

contributing element to the eligibility of the Charenton Floodgate for listing in the NRHP. 

Removal of the sector gates would cause an adverse effect to the Charenton Floodgate 

and would require mitigation to address those adverse effects. In response to the adverse 

effect determination, the USACE proposed to develop a MOA for the undertaking to 

mitigate for adverse effects to the Charenton Floodgate in a letter dated July 8, 2016. In 

a letter dated January 4, 2017, the ACHP stated that “Based upon the information 

provided, we have concluded that Appendix A, Criteria for Council Involvement in 

Reviewing Individual Section 106 Cases, of our regulations, “Protection of Historic 
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Properties” (36 CFR Part 800), does not apply to this undertaking. Accordingly, we do not 

believe that our participation in the consultation to resolve adverse effects is needed.” 

In September 2020, the USACE reinitiated Section 106 consultation with the LA SHPO, 

the ACHP, and federally-recognized Tribes. In September 2020, the USACE reinitiated 

Section 106 consultation with the LA SHPO, the ACHP, and federally-recognized Tribes.

On September 21, 2020, the Choctaw Nation of Oklahoma submitted written 

correspondence stating that “St. Mary Parish lies outside of our area of historic interest. 

The Choctaw Nation Historic Preservation Department respectfully defers to the other 

Tribes that have been contacted.” On September 22, 2020, the Muscogee (Creek) Nation 

submitted written correspondence stating that “The project area is located outside of our 

area of interest. We respectfully defer to the other tribes who have been contacted for 

comments.” On October 6, 2020, the USACE received a written response from the ACHP 

stating again that “Based upon the information provided, we have concluded that 

Appendix A, Criteria for Council Involvement in Reviewing Individual Section 106 Cases, 

of our regulations, “Protection of Historic Properties” (36 CFR Part 800), does not apply 

to this undertaking. Accordingly, we do not believe that our participation in the 

consultation to resolve adverse effects is needed.”

The USACE would fulfill its Section 106 procedures, described in Table1, if the proposed 

action is carried forward by developing a MOA in consultation with the LA SHPO, ACHP, 

and federally-recognized Tribes, and other interested parties that mitigates for adverse 

effects associated with the removal of the sector gates and construction of the new 

floodgate structure. The MOA would be signed by all consulting parties prior to the signing 

of the FONSI and the agreed to mitigation completed prior to the removal of the sector 

gates and the commencement of any other construction related activities. (Appendix E) 

• There would be a low probability of encountering HTRW in the proposed mitigation area 

and borrow area. 

• Coordination with the Natural Resources Conservation Service was completed on May 

5, 2020. NRCS concurred that the proposed actions of this EA will not impact prime 

farmland and therefore is exempt from the rules and regulations of the Farmland 

Protection Policy Act (FPPA)—Subtitle I of Title XV, Section 1539-1549. (Appendix F)

The FONSI will not be signed until the proposed action achieves environmental 

compliance with applicable laws and regulations, as described above.

8.0 Conclusion

This office has assessed the environmental impacts of the proposed action and has 

determined that both individually and cumulatively the proposed action would have no 

adverse impacts on threatened and endangered species or their critical habitats. The 

project would have no significant adverse impact on wetlands, wildlife, fisheries, cultural 

resources, recreation, aesthetics, air quality, or water quality. 
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9.0 Prepared By

Environmental Assessment 511 and the associated Finding of No Significant Impact were 

prepared by Ms. Samantha Martin, Environmental Protection Specialist, with relevant 

sections and contributions prepared by: Mr. Joseph Musso (HTRW); Mrs. Jill Enersen 

(Cultural Resources and Historical Architecture). The address of the preparers is: U.S. 

Army Corps of Engineers, New Orleans District; Regional Planning and Environment 

Division South, CEMVN-PDC-C; 7400 Leake Avenue; New Orleans, Louisiana 70118.
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10. References

Louisiana Department of Environmental Quality (LDEQ). 1996. State of Louisiana Water 

Quality Management Plan, Water Quality Inventory. Appendices A and B. Baton Rouge, 

LA.

Louisiana Department of Environmental Quality (LDEQ). 2018. 2018 Louisiana Water 

Quality Inventory: Integrated Report. Louisiana Department of Environmental Quality, 

Office of Environmental Assessment, Water Quality Assessment Division, Baton Rouge, 

LA. 194 p. + appendices.

Neill, C.F., and M.A. Allison. 2005. Subaqueous deltaic formation on the Atchafalaya 

Shelf, Louisiana. Marine Geology, Vol. 214, Issue 4. pp. 411–430.

Walker, N., Huh, O., Haag, A., Babin, A., Cable, J., Snedden, G., Braudo, D., Wilensky, 

D. and Prasad, K., 2003. A role for remote sensing in managing Mississippi River 

Diversions. Backscatter, Association for Marine Remote Sensin, Vol.14, no.1, 25-28, 

2003.
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APPENDIX A
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APPENDIX B
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APPENDIX C
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APPENDIX D
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APPENDIX F