River Wensum Restoration Strategy Implementation SSSI Unit 54 Taverham Mill to Hellesdon Mill FEASIBILITY & ENVIRONMENTAL SCOPING ASSESSMENT April 2012 Reference number/code We are The Environment Agency. It's our job to look after your environment and make it a better place - for you, and for future generations. Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier. The Environment Agency. Out there, making your environment a better place. Published by: Environment Agency Anglian Region, Eastern Area Dragonfly House 2 Gilders Way Norwich NR3 1UB Tel: 03708 506 506 Email: [email protected] www.environment-agency.gov.uk © Environment Agency All rights reserved. This document may be reproduced with prior permission of the Environment Agency. River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report River Wensum Restoration Strategy Implementation SSSI Unit 54 Taverham Mill to Hellesdon Mill Feasibility & Environmental Scoping Assessment April 2012 Notice This report was produced by Atkins for the Environment Agency for the specific purpose of assessing the feasibility of restoring favourable condition to the River Wensum SSSI. This report may not be used by any person other than the Environment Agency without Environment Agency express permission. In any event, Atkins accepts no liability for any costs, liabilities or losses arising as a result of the use of or reliance upon the contents of this report by any person other than the Environment Agency. Document History JOB NUMBER: 5078052 DOCUMENT REF: 5078052/60/DG/101 Revision Purpose Description Originated Checked Reviewed Authorised Date v01 Internal Draft Ian Morrissey 18/02/11 v10 Draft for client review Ian Morrissey Kevin Skinner Kevin Skinner Don Ross 16/05/11 v1.0 Final for issue Ian Morrissey Robin Chase Kevin Skinner Don Ross 05/04/2012 Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report Contents Section Page Non Technical Summary 1 1. Introduction 3 1.1 Context 3 1.2 River Wensum Restoration Strategy 7 1.3 Feasibility Assessment aims 9 1.4 Methodology 9 2. Taverham Mill to Hellesdon Mill Overview 12 2.1 Terminology and site location 12 2.2 Previous works within Unit 54 14 2.3 RWRS restoration vision for Unit 54 15 3. Environmental Baseline 17 3.1 Introduction 17 3.2 Common environment features across all reaches 18 3.3 Environmental baseline for each reach within Unit 54 34 4. Consultation 66 4.1 Introduction 66 4.2 Consultation with key stakeholders 66 4.3 Drop-in session September 2009 68 4.4 Future consultation 68 5. Multi-Criteria Analysis Options Appraisal 70 5.1 Introduction 70 5.2 Constructing the MCA tool 70 5.3 Using the MCA Tool 76 6. Developing Conceptual Design 85 6.1 Introduction and approach 85 6.2 Description of River Restoration and Targeted Maintenance options 85 6.3 Reach 01: Hellesdon Reach 92 6.4 Reach 02: Drayton Reach 98 6.5 Reach 03: Costessey Reach 106 7. Cost Estimate 115 7.1 Previous cost estimates 115 7.2 Present cost estimates 116 7.3 Potential cost savings 119 7.4 Delivery 121 7.5 Summary 122 8. Environmental Scoping 124 8.1 Introduction 124 8.2 Method of assessment 126 8.3 Results of scoping 127 9. Consents 135 10. Project Risks 137 Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report 11. Conclusions and Recommendations 139 11.1 Conclusions 139 11.2 Recommendations 140 12. References 141 Appendices 144 Appendix A – Multi-Criteria Analysis technical note Appendix B – Costings Appendix C – Ecology tables Appendix D – Terrestrial SSSI unit links to River Wensum SSSI units List of Figures Figure 1.1- Unit 54 River Wensum location plan 4 Figure 1.2 – Environmental and restoration related investigations and events, showing how this assessment fits within the process of realising restoration on the River Wensum. 6 Figure 1.3 - The approach adopted during feasibility assessment for determining the recommended restoration option on individual reaches and the overall river unit 10 Figure 2.1 - Location of Reaches 01, 02 and 03 within Unit 54 13 Figure 3.1 - Environmental constraints on Unit 54 30 Figure 3.2 - Environmental baseline for Reach 01 (Hellesdon Reach) 37 Figure 3.3 - Environmental baseline for Reach 02 (Drayton Reach) 42 Figure 3.4 - Environmental baseline for Reach 03 (Costessey Reach 47 Figure 6.1 - Conceptual restoration plan for Reach 01 (Hellesdon Reach) 97 Figure 6.2 - Location of sub-reaches within Reach 02 (Drayton Reach) 103 Figure 6.3 - Conceptual restoration plan for Reach 02a (Costessey Mill to Marriott’s Way) 104 Figure 6.4 - Conceptual restoration plan for Reach 02a (Marriott’s Way to Wensum Mount Farm) 105 Figure 6.5 - Location of sub-reaches within Reach 03 (Costessey Reach) 112 Figure 6.6 - Conceptual restoration plan for Reach 03a (Taverham Mill to Place Farm) 113 Figure 6.7 - Conceptual restoration plan for Reach 03b (Place Farm to Costessey Mill) 114 Figure 8.1 - Environmental Scoping within the EIA process 125 List of Tables Table 1.1 - Chapters constituting this report 7 Table 2.1- Summary of previous restoration works consented on Unit 54 14 Table 2.2 - Recommended restoration measures for each reach as provided in the RWRS (JBA, 2007) 15 Table 3.1 - Mill details in Unit 54 (Environment Agency, 2007a) 24 Table 3.2 - WFD quality assessment (Environment Agency, 2010b) 25 Table 3.3 - HDERF Thresholds for SAC/SSSI rivers 26 Table 3.4 - Summary of abstraction impacts relative to naturalised flow and the HDERF in the Q70-95 range27 Table 3.5 - Condition summary of Unit 54 attributes (Natural England, 2010) 29 Table 3.6 - Baseline information common to Unit 54 31 Table 3.7 - Baseline information specific to Reach 01 (Hellesdon Reach) 34 Table 3.8 - Baseline information specific to Reach 02 (Drayton Reach) 38 Table 3.9 - Baseline information specific to Reach 03 (Costessey Reach) 43 Table 4.1 - Consultation undertaken to date 66 Table 5.1 - Overview of the process by which the MCA was constructed and applied 70 Table 5.2 - Restoration measures recommended in previous studies 71 Table 5.3 - Options identified for restoration on the River Wensum 72 Unit 54 Taverham Mill to Hellesdon Mill_final for issue_V1.0.docx River Wensum Restoration Strategy Implementation SSSI Unit 54: Feasibility and Environmental Scoping Report Table 5.4 - Description of river restoration measures as defined under option G5 73 Table 5.5 - Criteria defined for the MCA 75 Table 5.6 - Scoring system defined for the Multi-Criteria Analysis 76 Table 5.7 - Results of MCA for Reach 01 (Hellesdon Reach) 78 Table 5.8 - Results of MCA for Reach 02 (Drayton Reach) 79 Table 5.9 - Results of MCA for Reach 03 (Costessey Reach) 80 Table 5.10 - Summary of favourable options and measures for Unit 54 83 Table 6.1 - Different management classes of restoration activity 86 Table 6.2 - Active and passive river restoration measures 86 Table 6.3 - River restoration measures and their potential ecological benefits 89 Table 6.4 - The effect of river restoration measures according to flow condition 90 Table 6.5 - Significant features and possible measures observed for Reach 01 during site visit (February, 2011) 93 Table 6.6 - Review of strategy objectives and recommendations for Reach 01 94 Table 6.7 - Recommended restoration options for Reach 01 95 Table 6.8 – Key characteristics of Reach 14 sub-reaches 98 Table 6.9 - Significant features and possible measures observed for Reach 02 during site visit (February, 2011) 99 Table 6.10 - Review of strategy objectives and recommendations for Reach 02 100 Table 6.11 - Recommended restoration options for Reach 02 101 Table 6.12 – Restoration measure suitability rating for Reach 02 sub-reaches 101 Table 6.13 – Key characteristics of Reach 14 sub-reaches 106 Table 6.14 - Significant features and possible measures observed for Reach 03 during site visit (February, 2011) 107 Table 6.15 - Review of strategy objectives and recommendations for Reach 03 108 Table 6.16 - Recommended restoration options for Reach 03 109 Table 6.17 – Restoration measure suitability rating for Reach 03 sub-reaches 110 Table 7.1 - RWRS Unit 54 cost estimate (JBA, 2007) 115 Table7.2 - Halcrow PSA Unit 54 cost estimate 116 Table7.3 - Comparison of cost estimates between JBA and Halcrow reports for Unit 54 116 Table 7.4 - Unit 54 cost estimates for various river restoration measures (February 2012) 117 Table 7.5 – Unit 54 cost estimates for each reach / sub-reach 118 Table 7.6 - Measures that typically generate or require spoil 119 Table 7.7 - Gravel substitution using surplus fill 120 Table 7.8 - Recommended phasing of work 121 Table 7.9 Recommended phasing of restoration measures for Unit 54 122 Table 7.10 - Comparison of costs between 2007, 2008 and 2011 studies 123 Table 8.1 - Classifying and evaluating the significance of potential environmental effects in the scoping process (adopted from European Commission, 2001) 126 Table 8.2- Environmental scoping assessment for recommended restoration options 129 Table 8.3 - Issues scoped into the EIA process 133 Table 8.4 - Issues scoped out of the EIA process 134 Table 9.1 - Likely planning consents and permissions 135 Table 10.1 – Key project risks that may delay