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Charleston Harbor Deepening Project (Post 45) Charleston Harbor

Feb 02, 2017

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    U.S. Army Corps of Engineers

    Charleston District

    Charleston Harbor Deepening Project (Post 45)

    Charleston Harbor, SC

    Appendix P:

    Mitigation Planning and

    Monitoring and Adaptive Management Plan

    April 29, 2015

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    Contents

    1.0 Framework .............................................................................................................................................. 5

    1.1 Minimization and Avoidance Measures.............................................................................................. 5

    2.0 Brackish and Freshwater Wetlands: ....................................................................................................... 8

    2.1 Guidance and Framework ................................................................................................................... 8

    2.2 Wetland Impact Summary .................................................................................................................. 9

    2.3 Mitigation Options for Indirect Wetland Impacts ............................................................................. 10

    2.3.1 Restoration Options ................................................................................................................... 11

    2.3.1.1 NOAA Identified Restoration Opportunities ........................................................................... 11

    2.3.1.2 Tuxbury Horse Trail Restoration ............................................................................................. 13

    2.3.2 Wetland Creation ....................................................................................................................... 14

    2.3.3 Preservation Options ................................................................................................................. 14

    2.3.3.1 US Forest Service Land Acquisition ..................................................................................... 14

    2.3.3.2 Cainhoy Plantation Protection ............................................................................................ 15

    2.3.3.3 West Branch Cooper River Easement Purchase ................................................................. 16

    2.4 Selected Alternative for Mitigation................................................................................................... 17

    2.5 Compliance with the Mitigation Rule ............................................................................................... 25

    2.5.1 Goals and Objectives .................................................................................................................. 25

    2.5.2 Site Selection .............................................................................................................................. 29

    2.5.3 Site Protection............................................................................................................................ 32

    2.5.4 Baseline Conditions .................................................................................................................... 33

    2.5.5 Determination of Credits ........................................................................................................... 40

    2.5.5.1 UMAM Description ............................................................................................................. 41

    2.5.5.2 Functional Analysis Using UMAM ....................................................................................... 42

    2.5.5.3 UMAM Analysis for Preservation Mitigation ...................................................................... 43

    2.5.6 Mitigation Work Plan ................................................................................................................. 45

    2.5.7 Maintenance Plan ...................................................................................................................... 46

    2.5.8 Performance Standards ............................................................................................................. 46

    2.5.9 Monitoring Requirements .......................................................................................................... 47

    2.5.10 Long Term Management Plan .................................................................................................. 47

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    2.5.11 Adaptive Management ............................................................................................................ 48

    2.5.12 Financial Assurances ................................................................................................................ 48

    3.0 Hardbottom Habitat .............................................................................................................................. 49

    3.1 Mitigation Options for Direct Impacts to Hardbottom Habitat ........................................................ 49

    3.1.1 Hardbottom Reef at ODMDS ..................................................................................................... 50

    3.1.2 Depositing limestone rock along outside edge of channel ........................................................ 51

    3.1.3 Barging material from upland sources ....................................................................................... 51

    3.1.4 Barging Cooling Tower debris offshore ...................................................................................... 52

    3.2 Selected Alternative .......................................................................................................................... 52

    4.0 Dissolved Oxygen and the Charleston Harbor Total Maximum Daily Load (TMDL) ............................. 55

    4.1 Mitigation Options for DO Impacts ................................................................................................... 58

    4.1.1 Reallocation of Waste Loads ...................................................................................................... 59

    4.1.2 Submerged Aquatic Vegetation Creation .................................................................................. 59

    4.1.3 Oyster Reef Creation .................................................................................................................. 60

    4.1.4 Flow Deflecting Berms ............................................................................................................... 60

    4.1.5 Oxygen Injection ........................................................................................................................ 60

    4.1.6 Aerating Turbines on the Pinopolis Dam ................................................................................... 61

    4.1.7 Oxygen Injection at the Pinopolis Dam ...................................................................................... 61

    4.1.8 Aerating Weirs in the Cooper and Wando Rivers ...................................................................... 61

    5.0 Monitoring and Adaptive Management: .............................................................................................. 61

    5.1 Hardbottom Habitat .......................................................................................................................... 61

    5.1.1 Guidance and Conceptual Framework ....................................................................................... 61

    5.1.2 Pre-Construction Impact Refinement and Baseline Monitoring ............................................... 62

    5.1.2.1 Direct Impact Area .......................................................................................................... 62

    5.1.2.2 Coordination ................................................................................................................... 62

    5.1.2.3 Success Criteria ................................................................................................................... 62

    5.1.3 Pre-Construction Mitigation Site Refinement............................................................................ 63

    5.1.4 Construction Concurrent Monitoring ........................................................................................ 64

    5.1.4.1 Direct Impact/Footprint .................................................................................................. 64

    5.1.4.2 ODMDS ............................................................................................................................ 64

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    5.1.4.3 Mitigation Sites ............................................................................................................... 64

    5.1.5 Mitigation Monitoring ................................................................................................................ 65

    5.1.5.1 As-builts........................................................................................................................... 65

    5.1.5.2 Recruitment/Mitigation Success. .................................................................................... 65

    5.1.6 Post-Construction Impact Monitoring ....................................................................................... 66

    5.1.6 Reporting .................................................................................................................................... 66

    5.1.6 Adaptive Management .............................................................................................................. 67

    5.2 Wetlands ..........................................