Wylfa Newydd Project SignpostingDisposal Site Report Characterisation for the Report Environment Statement (ES) Document Reference Number: ML-OTH-01-DSC DocumentRevision: 1.0 Reference Number: ML-ESX-01-SPR Revision: 1.0 [This page is intentionally blank] Contents 1 Executive Summary ......................................................................................... 1 2 Introduction ...................................................................................................... 2 2.1 Purpose ........................................................................................................... 2 2.2 Wylfa Newydd Project overview....................................................................... 3 Marine Off-Loading Facility .............................................................................. 4 Shore protection .............................................................................................. 4 Cooling Water System ..................................................................................... 5 Breakwaters ..................................................................................................... 6 Temporary access ramp .................................................................................. 6 Temporary barge berth .................................................................................... 6 Disposal of dredged material ........................................................................... 6 Maintenance dredging ..................................................................................... 7 2.3 Background ..................................................................................................... 7 3 Consultation ................................................................................................... 10 4 Regulatory and policy background ................................................................. 15 5 Assessment of the need for characterisation of a disposal site ..................... 21 5.1 Dredging requirements .................................................................................. 21 5.2 Consideration of alternative options to disposal at sea .................................. 21 Prevention ..................................................................................................... 22 Re-use ........................................................................................................... 22 Recycle .......................................................................................................... 24 Recovery ....................................................................................................... 25 Disposal ......................................................................................................... 25 Conclusion ..................................................................................................... 26 5.3 Consideration of potential disposal sites ........................................................ 26 Characteristics of the sites ............................................................................. 34 Summary of disposal site options .................................................................. 38 6 Characteristics of the disposal site ................................................................ 42 6.2 Site description .............................................................................................. 42 6.3 Physical characteristics ................................................................................. 43 Seabed environment ...................................................................................... 43 Water column ................................................................................................ 44 6.4 Biological characteristics ............................................................................... 45 Nature conservation designated sites ............................................................ 45 Phytoplankton and zooplankton ..................................................................... 50 Benthic habitats and species ......................................................................... 53 Fish and shellfish ecology .............................................................................. 70 Marine mammals ........................................................................................... 73 Seabirds ........................................................................................................ 76 6.5 Chemical characteristics ................................................................................ 79 Water Quality ................................................................................................. 79 Sediment Quality ........................................................................................... 82 6.6 Human environment characteristics ............................................................... 84 Page i Fishing ........................................................................................................... 84 Infrastructure ................................................................................................. 86 Recreation ..................................................................................................... 87 Navigation ...................................................................................................... 88 Historic environment ...................................................................................... 90 Seascape character ....................................................................................... 91 7 Characteristics of the material to be disposed ............................................... 93 7.2 Physical properties ........................................................................................ 94 7.3 Chemical contaminant analysis ..................................................................... 94 Radiological analysis ................................................................................................ 99 Dose assessment ........................................................................................ 101 8 Assessment of potential adverse effects ..................................................... 103 8.2 Release of contaminants ............................................................................. 105 Effects on phytoplankton and zooplankton .................................................. 107 Effects on fish and shellfish ......................................................................... 107 Effects on marine mammals ........................................................................ 108 Effects on nature conservation .................................................................... 108 Effects on seabirds ...................................................................................... 108 Effects on benthic ecology ........................................................................... 108 8.3 Increased suspended sediments ................................................................. 109 Effects on phytoplankton and zooplankton .................................................. 110 Effects on fish and shellfish ......................................................................... 110 Effects on marine mammals ........................................................................ 110 Effects on seabirds ...................................................................................... 111 Effects on infrastructure ............................................................................... 111 Effects on fishing ......................................................................................... 111 Effects on nature conservation .................................................................... 112 8.4 Smothering of seabed from sediment disposal ............................................ 112 Effects on benthic habitats and species ....................................................... 113 Effects on fish and shellfish ......................................................................... 115 Effects on infrastructure ............................................................................... 116 Effects on fishing ......................................................................................... 116 Effects on the historic environment .............................................................. 116 8.5 Burial of seabed from rock disposal ............................................................. 116 Effects on benthic habitats and species ....................................................... 117 Effects on fish and shellfish ......................................................................... 118 Effects on nature conservation .................................................................... 118 Effects on infrastructure ............................................................................... 119 Effects on fishing ......................................................................................... 119 Effects on the historic environment .............................................................. 119 8.6 Changes to physical processes ................................................................... 119 Effects on benthic habitats and species ....................................................... 120 Effects on infrastructure ..............................................................................