The Sizewell C Project 6.3 Volume 2 Main Development Site Chapter 22 Marine Ecology and Fisheries Appendix 22I - Sizewell C Impingement Predictions Based Upon Specific Cooling Water System Design Revision: 1.0 Applicable Regulation: Regulation 5(2)(a) PINS Reference Number: EN010012 May 2020 Planning Act 2008 Infrastructure Planning (Applications: Prescribed Forms and Procedure) Regulations 2009 NOT PROTECTIVELY MARKED SZC-SZ0200-XX-000-REP-100070 Revision 6 Sizewell C – Impingement predictions based upon specific cooling water system design TR406 Impingement predictions NOT PROTECTIVELY MARKED Page 1 of 132 NOT PROTECTIVELY MARKED SZC-SZ0200-XX-000-REP-100070 Revision 6 Sizewell C – Impingement predictions based upon specific cooling water system design TR406 Impingement predictions NOT PROTECTIVELY MARKED Page 2 of 132 NOT PROTECTIVELY MARKED SZC-SZ0200-XX-000-REP-100070 Revision 6 Table of contents Executive summary ................................................................................................................................. 10 1.1 Revisions to impingement assessments ................................................................................... 14 1.1.1 V2 report dated 9/12/2019 ............................................................................................... 14 1.1.2 V3 report dated 17/01/2020 ............................................................................................. 14 1.1.3 V4 report dated 28/01/2020 ............................................................................................. 15 1.1.4 V5 report dated 19/02/2020 ............................................................................................. 15 1.1.5 V6 report dated 27/02/2020 ............................................................................................. 15 2 Background ........................................................................................................................................ 17 2.1 Selection of key taxa for SZC impingement assessment ........................................................... 17 2.1.1 Conservation species impingement data ......................................................................... 18 2.2 Aims of this report .................................................................................................................... 19 3 Selection of impingement mitigation measures for SZC.................................................................. 20 3.1 Biofouling and other blockage risks .......................................................................................... 20 3.2 Impingement Mitigation Optioneering ....................................................................................... 21 3.3 Biota exclusion technology ....................................................................................................... 21 3.3.1 Passive wedge-wire cylinder screens (PWWC screens) .................................................. 22 3.3.2 Bubble curtains ............................................................................................................... 23 3.3.3 Behavioural deterrents – strobe lights .............................................................................. 23 3.3.4 Behavioural deterrents - electric barriers ......................................................................... 23 3.3.5 Behavioural deterrents - Acoustic fish deterrents (AFDs) ................................................. 23 3.3.6 Intake design - LVSE intakes........................................................................................... 24 3.4 Biota Recovery Technology ...................................................................................................... 25 3.4.1 Fish Recovery and Return System .................................................................................. 25 3.5 Conclusions ............................................................................................................................. 26 4 Relevant site features ........................................................................................................................ 26 5 Impingement Assessment Methodology .......................................................................................... 28 5.1 Introduction .............................................................................................................................. 28 5.1.1 Differences in the abundance of fish at the SZB and SZC intake locations ....................... 28 5.1.2 Effect of the proposed SZC intake heads upon the expected impingement rate ............... 29 5.2 SZB impingement data collection and collation ......................................................................... 29 5.3 Estimated annual mean, minimum and maximum losses by the SZB station ............................. 32 5.4 Statistical method used to derive annual impingement estimates at Sizewell ............................ 33 5.5 Predicted annual mean, minimum and maximum losses by the SZC station ............................. 34 5.6 Effect of the intake head design ............................................................................................... 34 5.7 FRR system mortality ............................................................................................................... 34 5.7.1 Trash rack mortality ......................................................................................................... 34 5.7.2 FRR survival ................................................................................................................... 37 5.7.3 Other factors which could potentially affect FRR survival rates ........................................ 37 5.7.4 Values used for FRR survival in the SZC impingement assessment ................................ 39 5.8 EAV conversion factors ............................................................................................................ 40 TR406 Impingement predictions NOT PROTECTIVELY MARKED Page 3 of 132 NOT PROTECTIVELY MARKED SZC-SZ0200-XX-000-REP-100070 Revision 6 5.8.1 Discussion of the Spawner Production Foregone method for calculating EAVs ................ 41 5.8.2 Potential detail change to the EAV calculation methodology in TR383 ............................. 41 5.9 Conversion from EAV numbers to equivalent weight ................................................................. 42 5.10 Evaluating the effect of SZC impingement losses – comparison with ICES stock estimates ...... 43 5.10.1 Are ICES stock units appropriate for assessing the effects of SZC on fish populations? ... 44 5.10.2 Scientific status of the ICES Bass stock unit and the consequent SSB estimate............... 45 5.10.3 Conclusions on the validity of ICES stock units ................................................................ 46 5.10.4 How does ICES deal with non-fishing impacts on stocks?................................................ 47 5.11 Evaluating the effect of SZC impingement losses – Comparison with international landings data 47 5.12 Evaluating the effect of SZC impingement losses – Other comparative data sources ................ 47 6 Assessment of the significance of impingement effects ................................................................. 51 6.1 Screening thresholds for negligible effects in context ................................................................ 51 6.1.1 What is meant by a sustainable fish population? .............................................................. 51 6.1.2 Natural variability of fish stocks ....................................................................................... 52 6.1.3 Comparison with sustainable levels of harvesting rate for data rich stocks ....................... 53 6.1.4 An example of where screening thresholds for fish mortality have been applied for major infrastructure projects ..................................................................................................................... 54 6.1.5 The appropriateness of a 1% SSB screening threshold for impingement effects .............. 54 6.1.6 Appropriateness of a 1% SSB threshold for the endangered European eel ...................... 55 7 Impingement predictions for SZC - finfish ........................................................................................ 56 7.1 Predicted impingement without embedded mitigation measures ............................................... 56 7.2 Predicted SZC impingement with LVSE intake heads fitted....................................................... 56 7.3 Predicted SZC impingement with FRR systems fitted ............................................................... 56 7.4 Predicted SZC impingement with the effect of the LVSE intake heads and FRR systems fitted . 57 7.5 Further consideration of impingement effects on bass and thin-lipped grey mullet ..................... 57 7.6 Consideration of the impingement losses of finfish species of conservation concern ................. 64 7.6.1 Cucumber Smelt ............................................................................................................. 64 7.6.2 River lamprey and sea lamprey ....................................................................................... 65 7.6.3 Twaite shad and allis shad .............................................................................................. 66 7.6.4 European eel .................................................................................................................