FINAL ENVIRONMENTAL IMPACT STATEMENT DESIGNATION OF THE ATCHAFALAYA RIVER BAR CHANNEL OCEAN DREDGED MATERIAL DISPOSAL SITE PURSUANT TO SECTION 102(c) OF THE MARINE PROTECTION, RESEARCH, AND SANCTUARIES ACT OF 1972 ST. MARY PARISH, LOUISIANA Prepared by: U.S. Environmental Protection Agency Region 6 1445 Ross Avenue Dallas, Texas 75202-2733 In Cooperation with: U.S. Army Corps of Engineers New Orleans District Regional Planning and Environmental Division South 7400 Leake Avenue New Orleans, Louisiana 70118-3651 September 2013 This page intentionally left blank ii Contents Page Contents ..........................................................................................................................................................iii List of Figures..................................................................................................................................................xi List of Tables ..................................................................................................................................................xi Acronyms and Abbreviations .........................................................................................................................xii EXECUTIVE SUMMARY......................................................................................................................... ...1 1.0 INTRODUCTION..…........................................................................................................................18 1.1 PURPOSE AND NEED FOR THE PROPOSED ACTION.….................................................19 1.2 DESCRIPTION OF THE PROPOSED ACTION….................................................................20 1.3 PRIOR REPORTS AND PROJECTS……................................................................................22 1.4 AUTHORITY FOR THE PROPOSED ACTION....….............................................................23 1.5 U.S. ARMY CORPS OF ENGINEERS..…...............................................................................24 1.6 U.S. ENVIRONMENTAL PROTECTION AGENCY..…........................................................24 1.7 COASTAL ZONE MANAGEMENT ACT..….........................................................................25 2.0 ALTERNATIVES…...........................................................................................................................26 2.1 NO-ACTION ALTERNATIVE.................................................................................................28 2.2 SITE ALTERNATIVES.….......................................................................................................29 2.2.1 Beneficial Use …..................................................................................................29 2.2.1.1 Beach Nourishment ….....................................................................31 2.2.1.2 Marsh Creation…….........................................................................32 2.2.1.3 Island Creation – Single Point Unconfined Discharge……..................................................................................33 2.2.1.4 Island Creation – Single Point Confined Discharge …....................33 2.2.2 Screening Process for Ocean Placement Sites.….................................................34 2.3 DEVELOPMENT OF ALTERNATIVE SITES USING THE SCREENING TECHNIQUE – PHASE I ….....................................................................................................35 2.3.1 Ocean Placement Alternative Sites …..................................................................35 2.3.1.1 Nearshore Alternative Site 1 ….......................................................36 2.3.1.2 Nearshore Alternative Site – ODMDS-West…...............................36 2.3.1.3 Mid-Shelf Alternative Site…...........................................................37 2.3.1.4 Deepwater Alternative Site……......................................................38 2.3.2 Zone of Siting Feasibility…..................................................................................39 iii 2.3.2.1 Limits Due to Cost of Transport ……..............................................39 2.3.2.2 Limits Due to Feasibility of Monitoring and Surveillance .....................................................................................40 2.3.2.3 Limits Due to Political Boundaries ….............................................40 2.3.2.4 Conclusion……...............................................................................41 2.3.3 Characterization of Material and Site Sizing …...................................................41 2.3.3.1 Characterization of the Materials Expected to Be Dredged ….......................................................................................41 2.3.3.1.1 Sediment Quality ……......................................................42 2.3.3.1.2 Water Quality ……...........................................................45 2.3.3.2 Characterization of ODMDS-West ….............................................48 2.3.3.3 ODMDS Size Determination……....................................................48 2.3.4 Establishment of Buffer Zones …….....................................................................49 2.3.4.1 Buffer Zone Assignment ….............................................................49 2.3.4.1.1 Biologically Sensitive Areas …........................................49 2.3.4.1.2 Beaches and Recreational Areas ……..............................49 2.3.4.1.3 Navigation Channel…......................................................49 2.3.5 Results of Phase I Evaluation…......................................................................... 49 2.4 EVALUATION OF ELEVEN SPECIFIC CRITERIA – PHASE II…....................................50 2.4.1 40 CFR 228.6(a) (#1) …......................................................................................50 2.4.2 40 CFR 228.6(a) (#2) …......................................................................................51 2.4.3 40 CFR 228.6(a) (#3)….......................................................................................52 2.4.4 40 CFR 228.6(a) (#4) …......................................................................................52 2.4.5 40 CFR 228.6(a) (#5)…...................................................................................... 52 2.4.6 40 CFR 228.6(a) (#6) …..................................................................................... 53 2.4.7 40 CFR 228.6(a) (#7) …......................................................................................54 2.4.8 40 CFR 228.6(a) (#8)……...................................................................................55 2.4.9 40 CFR 228.6(a) (#9) …......................................................................................57 2.4.10 40 CFR 228.6(a) (#10)…….................................................................................58 2.4.11 40 CFR 228.6(a) (#11)…….................................................................................58 2.5 FINAL EVALUATION AND SITE SELECTION — PHASE III ….....................................58 2.5.1 Five General Criteria…........................................................................................59 2.5.1.1 40 CFR 228.5(a) (#1)….................................................................59 2.5.1.2 40 CFR 228.5(b) (#2)….................................................................59 iv 2.5.1.3 40 CFR 228.5(c) (#3)….................................................................60 2.5.1.4 40 CFR 228.5(d) (#4) …................................................................60 2.5.1.5 40 CFR 228.5(e) (#5) …................................................................60 2.6 IDENTIFICATION OF THE PREFERRED ALTERNATIVE …..........................................61 2.6.1 Evaluation of Constraints …................................................................................61 2.6.1.1 Oceanographic Constraints…........................................................61 2.6.1.2 Cultural and/or Historic Constraints ….........................................61 2.6.1.3 Nonliving Resources Constraints …..............................................61 2.6.1.4 Living Resources Constraints …...................................................62 2.6.1.5 Environmental Quality Constraints…...........................................62 2.6.1.6 Recreational Uses Constraints …..................................................62 2.6.2 Preferred Alternative….......................................................................................63 3.0 AFFECTED ENVIRONMENT .…….............................................................................................64 3.1 PHYSICAL ENVIRONMENT................................................................................................64 3.1.1 Climate and Meteorology................................................................................... 64 3.1.2 Air Quality …......................................................................................................64 3.1.3 Oceanography..…................................................................................................66 3.1.3.1 Water Masses …............................................................................66 3.1.3.2 Circulation and Currents..…..........................................................68 3.1.3.3 Waves and Tides.….......................................................................69 3.1.3.4 Bathymetry.....................................................................................70