Sejerø Bugt Offshore Wind Farm Baseline and Impact Assessment in Relation to Marine Mammals Technical Background Report Rambøll A/S Technical Background Report April 2015 This proposal has been prepared under the DHI Business Management System certified by DNV to comply with ISO 9001 (Quality Management) Sejerø Bugt Offshore Wind Farm Baseline and Impact Assessment in relation to Marine Mammals Technical background report Prepared for Rambøll A/S Represented by Claus Fischer Jensen Project manager Mary S. Wisz Authors Mary S. Wisz, Henriette Schack, Monika Kosecka, Irmina Plichta Quality supervisor Frank Thomsen DHI / Rambøll number 11814614-4 / ROGC-S-RA-000121 Approval date 17 April 2015 Revision 7 Classification Confidential The attached report provides the results from a combined effort with Rambøll and NIRAS being responsible for the acoustic modelling, and NIRAS responsible for the calculations applying the new methodology following the recommendations of the Danish expert group. DHI and NIRAS compiled the impact assessment based on the numbers produced by the NIRAS team. ROGC-S-RA-000121 7 Sejerø Bugt Marine Mammals CONTENTS 1 Executive summary ..................................................................................................... 1 2 Introduction ................................................................................................................. 3 3 Project description ...................................................................................................... 5 4 Background ................................................................................................................. 7 4.1 Baseline methodology .................................................................................................................... 7 4.2 Impact assessment methodology .................................................................................................. 7 4.3 Acoustic monitoring and data analysis .......................................................................................... 8 4.3.1 Acoustic monitoring ........................................................................................................................ 8 4.3.2 Acoustic data analyses ................................................................................................................ 10 4.3.3 Visual observations ...................................................................................................................... 11 5 Baseline conditions, harbour porpoise ................................................................... 13 5.1 Biology ......................................................................................................................................... 13 5.1.1 Hearing ......................................................................................................................................... 15 5.1.2 Protection status .......................................................................................................................... 15 5.1.3 Distribution and abundance in Danish waters ............................................................................. 16 5.1.4 Distribution and abundance at Sejerø ......................................................................................... 25 5.1.5 Importance of Sejerø area for porpoises ..................................................................................... 35 5.2 White-beaked dolphin .................................................................................................................. 35 5.3 Harbour seal ................................................................................................................................. 35 5.3.1 Biology ......................................................................................................................................... 35 5.3.2 Hearing ......................................................................................................................................... 36 5.3.3 Protection status .......................................................................................................................... 36 5.3.4 Distribution and abundance in Danish waters ............................................................................. 37 5.3.5 Distribution and abundance at Sejerø ......................................................................................... 39 5.3.6 Ecological importance of the Sejerø Bugt offshore wind farm area ............................................. 40 5.4 Grey seal ...................................................................................................................................... 40 5.4.1 Biology ......................................................................................................................................... 40 5.4.2 General distribution and abundance in Danish waters ................................................................ 40 5.4.3 Distribution and abundance at Sejerø ......................................................................................... 41 5.4.4 Ecological importance of the Sejerø Bugt offshore wind farm area ............................................. 41 6 Impact assessment during construction, operation and decommissioning phase .......................................................................................................................... 43 6.1 Definitions of zones of impact ...................................................................................................... 43 6.2 Impact assessment during construction ...................................................................................... 45 6.2.1 Likely effects on marine mammals ............................................................................................... 45 6.2.2 Estimation of potential effects on marine mammals .................................................................... 50 6.2.3 Assessment of the significance of impacts during construction .................................................. 55 6.3 Impact assessment during the operation phase .......................................................................... 59 6.3.1 Likely effects on marine mammals ............................................................................................... 59 6.3.2 Estimation of potential effects on marine mammals .................................................................... 63 6.3.3 Assessment of the significance of impacts during operation ....................................................... 65 6.4 Impact assessment during decommissioning .............................................................................. 66 6.4.1 Likely effects on marine mammals ............................................................................................... 66 i 6.4.2 Estimation of potential effects on marine mammals .................................................................... 67 6.4.3 Assessment of the significance of impacts during decommissioning .......................................... 68 7 Cumulative impacts .................................................................................................. 69 7.1 Existing pressures........................................................................................................................ 69 7.1.1 By-catch ....................................................................................................................................... 69 7.1.2 Eutrophication .............................................................................................................................. 69 7.1.3 Contaminants ............................................................................................................................... 69 7.1.4 Shipping ....................................................................................................................................... 70 7.2 Other planned projects ................................................................................................................ 70 8 Natura 2000 ............................................................................................................... 71 8.1 Natura 2000 screening ................................................................................................................ 72 8.1.1 Natura 2000 Sites ........................................................................................................................ 73 9 Mitigation measures ................................................................................................. 75 9.1 Air bubble curtains ....................................................................................................................... 75 10 Monitoring ................................................................................................................. 77 11 Lack of information and uncertainties .................................................................... 79 12 Assessment of strictly protected species .............................................................. 81 13 Conclusion ................................................................................................................ 83 14 References ................................................................................................................ 85 APPENDICES APPENDIX A CPOD deployment and Aerial Surveys FIGURES Figure