Norfolk Vanguard Offshore Wind Farm Chapter 20 Water Resources and Flood Risk Environmental Statement Volume 1
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Norfolk Vanguard Offshore Wind Farm Chapter 20 Water Resources and Flood Risk Environmental Statement Volume 1 Applicant: Norfolk Vanguard Limited Document Reference: 6.1.20 RHDHV Reference: PB4476-005-020 Pursuant to: APFP Regulation 5(2)(a) Date: June 2018 Revision: Version 1 Author: Royal HaskoningDHV Photo: Kentish Flats Offshore Wind Farm Environmental Impact Assessment Environmental Statement Document Reference: PB4476-005-020 June 2018 For and on behalf of Norfolk Vanguard Limited Approved by: Ruari Lean, Rebecca Sherwood Signed: Date: 8th June 2018 For and on behalf of Royal HaskoningDHV Drafted by: Jack Douglas, Natalie James, Ian Dennis Approved by: Jon Allen Signed: Date: 8th June 2018 Environmental Statement Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page i Date Issue Remarks / Reason for Issue Author Checked Approved No. 06/04/18 01D First draft for Norfolk Vanguard Limited JD ID AD review 02/05/18 02D Second draft for Norfolk Vanguard Limited ID CC/ST AH review 08/06/18 01F Final for ES submission ID JA JA June 2018 Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page ii Table of Contents 20 Water Resources and Flood Risk ............................................................................. 1 Introduction ........................................................................................................... 1 Legislation, Guidance and Policy ............................................................................. 1 Consultation ........................................................................................................... 8 Assessment Methodology ..................................................................................... 14 Scope ................................................................................................................... 20 Existing Environment ............................................................................................ 22 Potential Impacts.................................................................................................. 34 Cumulative Impacts .............................................................................................. 80 Inter-relationships ................................................................................................ 91 Interactions .......................................................................................................... 92 Summary .............................................................................................................. 93 References ......................................................................................................... 101 June 2018 Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page iii Tables Table 20.1 NPS assessment requirements 4 Table 20.2 Relevant local planning policies 7 Table 20.3 Consultation response summary 9 Table 20.4 Definitions of sensitivity for water resources and flood risk receptors 15 Table 20.5 Definitions of value levels for water resources and flood risk receptors 17 Table 20.6 Definitions of magnitude of effect for water resources and flood risk receptors 18 Table 20.7 Impact significance matrix 19 Table 20.8 Impact significance definitions 19 Table 20.9 Data sources 21 Table 20.10 Surface water catchments 24 Table 20.11 Geomorphological overview of watercourse crossing locations 26 Table 20.12 Sensitivity and value of surface water resources 30 Table 20.13 Embedded mitigation 35 Table 20.14 Embedded mitigation for water resources and flood risk 37 Table 20.15 Worst case assumptions 39 Table 20.16 Watercourse crossings in surface water catchments 45 Table 20.17 Area of disturbed ground in surface water catchments 55 Table 20.18 Area of permanent infrastructure in surface water catchments 71 Table 20.19 Potential cumulative impacts 80 Table 20.20 Summary of projects considered for the CIA in relation to the water resources and flood risk 82 Table 20.21 Water resources and flood risk inter-relationships 91 Table 20.22 Interactions between impacts 92 Table 20.23 Potential impacts identified for water resources and flood risk 94 Figures (Volume 2) Figure 20.1 Study area Figure 20.2 Main surface water catchments Figure 20.3 Surface water body sub-catchments Figure 20.4 Main Rivers, IDB Drains and other Ordinary Watercourses Figure 20.5 Environment Agency Flood Zone maps Figure 20.6 Groundwater bodies Appendices (Volume 3) Appendix 20.1 Flood Risk Assessment Appendix 20.2 Water Framework Compliance Assessment Appendix 20.3 Geomorphological Walkover Survey Appendix 20.4 Detailed Watercourse Crossing Schedule June 2018 Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page iv Appendix 20.5 Consultation Responses June 2018 Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page v Glossary A/HMWB Artificial or Heavily Modified Water Body AIS Air Insulation Switchgear CoCP Code of Construction Practice CIA Cumulative Impact Assessment CIRIA Construction Industry Research and Information Association CMS Construction Method Statement DCLG Department for Communities and Local Government DCO Development Consent Order Defra Department for Environment, Food & Rural Affairs DMRB Design Manual for Roads and Bridges EA Environment Agency EC European Commission EIA Environmental Impact Assessment ES Environmental Statement ETG Expert Topic Group EU European Union FRA Flood Risk Assessment FWMA Flood and Water Management Act GEP Good Ecological Potential GES Good Ecological Status HDD Horizontal Directional Drilling HDPE High Density Polyethylene HVAC High Voltage Alternating Current HVDC High Voltage Direct Current IDB Internal Drainage Board LNR Local Nature Reserve NPPF National Planning Policy Framework NPPG National Planning Practice Guidance NPS National Policy Statement NV Norfolk Vanguard O&M Operations and Maintenance PDS Project Design Statement PEIR Preliminary Environmental Information Report PPG Planning Practice Guidance RBD River Basin District RBMP River Basin Management Plan RIGS Regionally Important Geological Site SAC Special Area of Conservation SNCI Site of Nature Conservation Interest SPA Special Protection Area SPZ Source Protection Zone SSSI Site of Special Scientific Interest SuDS Sustainable Drainage System WCS Worst Case Scenario WFD Water Framework Directive June 2018 Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page vi Water Management Alliance (comprising a group of 5 Internal Drainage Boards WMA (IDBs) operating in the Anglian Region. WMA members include Broads IDB, East Suffolk IDB, King’s Lynn IDB, Norfolk Rivers IDB and South Holland IDB) Terminology Primarily comprised of an outdoor compound containing reactors (also called inductors, or coils) and switchgear to increase the power transfer capability of Cable Relay Station the cables under the HVAC technology scenario as considered in the PEIR. This is no longer required for the project as the HVDC technology has been selected. Jointing pit Underground structures constructed at regular intervals along the cable route to join sections of cable and facilitate installation of the cables into the buried ducts. Landfall Where the offshore cables come ashore at Happisburgh South. Link boxes Underground chambers or above ground cabinets next to the cable trench housing low voltage electrical earthing links. Areas approx. 100 x 100m used as access points to the running track for duct installation. Required to store equipment and provide welfare facilities. Located Mobilisation area adjacent to the onshore cable route, accessible from local highways network suitable for the delivery of heavy and oversized materials and equipment. Mobilisation zone Area within which the mobilisation area will be located. National Grid overhead line The works to be undertaken to complete the necessary modification to the modifications existing 400kV overhead lines National Grid substation The permanent footprint of the National Grid substation extension. extension National Grid temporary Land adjacent to the Necton National Grid substation which would be works area temporarily required during construction of the National Grid substation extension. Necton National Grid The existing 400kV substation at Necton, which will be the grid connection substation location for Norfolk Vanguard. Buried high-voltage cables linking the onshore project substation to the Necton Onshore 400kV cable route National Grid substation Onshore cable route The 45m easement which will contain the buried export cables as well as the temporary running track, topsoil storage and excavated material during construction. Onshore cables The cables which take the electricity from landfall to the onshore project substation. Onshore project area All onshore electrical infrastructure (landfall; onshore cable route, accesses, trenchless crossing technique (e.g. Horizontal Directional Drilling (HDD)) zones and mobilisation areas; onshore project substation and extension to the Necton National Grid substation and overhead line modification). Onshore project substation A compound containing electrical equipment to enable connection to the National Grid. The substation will convert the exported power from HVDC to HVAC, to 400kV (grid voltage). This also contains equipment to help maintain stable grid voltage. June 2018 Norfolk Vanguard Offshore Wind Farm PB4476-005-020 Page vii The track along the onshore cable route which the construction traffic would Running track use to access workfronts. The Applicant Norfolk Vanguard Limited The project Norfolk Vanguard Offshore Wind Farm,