louisiana coastal area (lca)

438 Pages·2010·42.62 MB·English

by  Sue Hawes

LOUISIANA COASTAL AREA (LCA)
ECOSYSTEM RESTORATION STUDY

Volume II of VI

Final Integrated Feasibility Study and
Supplemental Environmental Impact Statement

for the

Amite River Diversion Canal Modification
Ascension and Livingston Parishes, Louisiana

October 2010

U.S Army Corps of Engineers Coastal Protection and

New Orleans District Restoration Authority
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LOUISIANA COASTAL AREA (LCA)
ECOSYSTEM RESTORATION STUDY

Volume II of VI

Final Integrated Feasibility Study and
Supplemental Environmental Impact Statement

for the

Amite River Diversion Canal Modification
Ascension and Livingston Parishes, Louisiana

The responsible lead Federal agency for this study is the U. S. Army Corps of
Engineers- Mississippi Valley, New Orleans District (CEMVN). The non-Federal
sponsor for the study is Coastal Protection and Restoration Authority (CPRA).
This report is a combined feasibility report and environmental impact statement
complying with requirements of the U.S. Army Corps of Engineers (USACE) and
the Council of Environmental Quality (CEQ), and is intended to reduce duplication
and paperwork. An asterisk (*) in the table of contents notes paragraphs that are
required for National Environmental Policy Act (NEPA) compliance.

October 2010

U.S Army Corps of Engineers Coastal Protection and

New Orleans District Restoration Authority
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This report contains six volumes.

You are at Volume II which is the element-specific analysis for the
The Louisiana Coastal Area-Amite River Diversion Canal Modification Element.

Volume I: Summary

Volume II: Amite River Diversion Canal Modification

Volume III: Atchafalaya Conveyance to N. Terrebonne Marshes

Volume IV: Convent/Blind River Diversion

Volume V: Terrebonne Basin Barrier Shoreline Restoration

Volume VI: White Ditch Diversion

If you have any questions, or require additional information, please contact:

Mr. Timothy Axtman, Senior Plan Formulator
U.S. Army Corps of Engineers New Orleans District;
P. O. Box 60267, New Orleans, LA 70160-0267

[phone], email: [email protected]
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Final Integrated Feasibility Study and Supplemental
Environmental Impact Statement
for the
LCA Amite River Diversion Canal (ARDC) Modification
Project

LEAD AGENCY: U.S. Army Corps of Engineers (USACE) – Mississippi Valley
Division, New Orleans District

ABSTRACT: The USACE proposes to dredge openings in the existing ARDC
dredged material berm, construct bifurcated conveyance channels, and establish
vegetative plantings in the study area. The natural hydrology in the study area has
been modified by the ARDC and a railroad grade. Sea level changes and geological
subsidence have compounded these effects, leading to poor swamp health and
ecosystem degradation. This project would establish hydrologic connectivity
between the ARDC and the western Maurepas Swamp, allowing the swamp to drain
during seasonal low-flow conditions in the Amite River and promoting the
germination and survival of the seedlings of bald cypress and other trees. This
connectivity would allow nutrients and sediments to be introduced into the swamp
during flood events and localized rainfall events and improve biological productivity.

Without action, the swamp habitat surrounding the ARDC would continue the
conversion from a freshwater swamp to freshwater marsh and open water. Direct
impacts would be the continued impoundment of swamp water within the study
area, decreased hydrologic connectivity, and a transition toward marsh and salinity
tolerant vegetation. Indirect effects would be the decline of wildlife, fishery, and
vegetative resources. Flora and fauna may change as salt-tolerant species replace
fresh water species. Existing habitat would convert to waterbottoms and alter the
benthic community, decreasing available nutrients and detritus. Cumulative
impacts would be the projected conversion of 18,204 acres of swamp to fresh marsh
and open water. The water and air treatment functions of wetlands would subside,
and the integrity of existing resources within the study area would be endangered.

Excluding the No-Action Alternative, the final array of alternatives included seven
options. Alternative 33 was chosen as the recommended plan. It would restore
1,602 acres of swamp habitat, create 679 Average Annual Habitat Units (AAHUs),
5.0 acres of bottomland hardwood habitat, establish hydrologic connectivity, promote
the germination and survival of the seedlings of bald cypress and other trees, and
improve biological productivity. According to the Micro-Computer Aided Cost
Estimating System (MCACES), the total fully funded estimated cost for construction
of this alternative would be $8,540,000.

COMMENTS: Please send comments or questions on this SEIS to the U.S. Army
Corps of Engineers, New Orleans District, Attention: William P. Klein, Jr., P.O. Box
60267, New Orleans, Louisiana 70160-0267. Telephone: [phone]; FAX: (504)
862-2088. The official closing date for receipt of comments will be 30 days from the
date on which the Notice of Availability of the Final SEIS appeared in the Federal
Register.

Table of Contents Volume II – LCA Amite River Diversion Canal Modification

TABLE OF CONTENTS

Volume II – [Louisiana Coastal Area-Amite River Diversion Canal Modification]
Integrated Feasibility Report and Supplemental
Environmental Impact Statement 1

Section Page

Executive Summary ......................................................................................... ES-i

TABLE OF CONTENTS ................................................................................ TOC-i

FIGURES .............................................................................................. TOC-xv
TABLES ............................................................................................. TOC-xix
APPENDICES (VOLUME II) ...................................................................... TOC-xxiii

1.0 STUDY INFORMATION........................................................................... 1-1

1.1 STUDY AUTHORITY ....................................................................... 1-1
1.2 PURPOSE AND SCOPE* ................................................................. 1-3
1.3 STUDY AREA* ................................................................................. 1-5
1.4 HISTORY OF INVESTIGATION ..................................................... 1-8
1.5 PRIOR REPORTS AND EXISTING PROJECTS ............................ 1-8
1.5.1 Federal .............................................................................. 1-10
1.5.2 State .................................................................................. 1-14
1.6 PLANNING PROCESS AND REPORT ORGANIZATION ........... 1-14
1.7 USACE CAMPAIGN PLAN ............................................................ 1-15

2.0 NEED FOR AND OBJECTIVES OF ACTION ...................................... 2-1

2.1 NATIONAL OBJECTIVES ............................................................... 2-1
2.2 PUBLIC CONCERNS ....................................................................... 2-2
2.3 PROBLEMS, NEEDS, AND OPPORTUNITIES* ........................... 2-3
2.3.1 2004 LCA Ecosystem Restoration Report ......................... 2-3
2.3.2 Conceptual Ecological Model ............................................. 2-5
2.3.3 Problems ............................................................................. 2-7
2.3.3.1 Modification of Natural Hydrology ........................ 2-8
2.3.3.2 Subsidence .............................................................. 2-8
2.3.3.3 Sea Level Rise ......................................................... 2-9
2.3.3.4 Tropical Cyclone Events ......................................... 2-9
2.3.4 Effects ............................................................................... 2-10

1 * An asterisk denotes paragraphs that are required for National Environmental Policy Act (NEPA) compliance.

WRDA 2007 Section 7006(e)(3) T O C - i October 2010
Table of Contents Volume II – LCA Amite River Diversion Canal Modification

TABLE OF CONTENTS (cont’d)

Volume II – [Louisiana Coastal Area-Amite River Diversion Canal Modification]
Integrated Feasibility Report and Supplemental
Environmental Impact Statement1

Section Page

2.3.4.1 Impoundment ....................................................... 2-11
2.3.4.2 Decreased Connectivity Resulting in Decreased
Freshwater, Sediment, and Nutrient
Inputs into the Swamps ..................................... 2-14
2.3.4.3 Habitat Changes and Land Loss ......................... 2-15
2.3.4.4 Increased Invasive Species ................................... 2-18
2.3.5 Needs ................................................................................ 2-18
2.3.5.1 Future Without Project Condition ....................... 2-20
2.3.6 Opportunities .................................................................. 2-22
2.4 PLANNING OBJECTIVES ............................................................. 2-23
2.4.1 Goals ................................................................................. 2-23
2.4.2 Objectives ......................................................................... 2-24
2.5 PLANNING CONSTRAINTS ......................................................... 2-25

3.0 ALTERNATIVES* .................................................................................... 3-1

3.1 PLAN FORMULATION RATIONALE ............................................. 3-1
3.1.1 Plan Rationale .................................................................... 3-1
3.1.2 Plan Criteria ....................................................................... 3-2
3.1.2.1 Completeness .......................................................... 3-2
3.1.2.2 Effectiveness ........................................................... 3-2
3.1.2.3 Efficiency ................................................................. 3-2
3.1.2.4 Acceptability ........................................................... 3-2
3.1.3 Environmental Operating Principles ................................ 3-2
3.2 MANAGEMENT MEASURES.......................................................... 3-3
3.2.1 Development of Management Measures ........................... 3-3
3.2.2 Description of Management Measures .............................. 3-4
3.2.3 Screening/Evaluation of Management Measures ............. 3-7
3.2.4 Management Measures Not Carried
Forward for Further Analysis ...................................... 3-12
3.3 PRELIMINARY ALTERNATIVES PLANS ................................... 3-26
3.3.1 Development of Alternative Plans .................................. 3-35
3.3.1.1 Vegetative Plantings ............................................ 3-36
3.3.2 Description of Alternative Plans ..................................... 3-38
3.3.3 Screening/Evaluation of Alternative Plans ..................... 3-38

WRDA 2007 Section 7006(e)(3) T O C - i i October 2010