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 This page intentionally left blank 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 This page intentionally left blank 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 (504) 862-1921, email: [email protected] This page intentionally left blank 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: (504) 862-2540; 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
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