River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment 27 March 2020
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River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment 27 March 2020 Mott MacDonald 22 Station Road Cambridge CB1 2JD United Kingdom T +44 (0)1223 463500 mottmac.com River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment 27 March 2020 Mott MacDonald Limited. Registered in England and Wales no. 1243967. Registered office: Mott MacDonald House, 8-10 Sydenham Road, Croydon CR0 2EE, United Kingdom Mott MacDonald | River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment Issue and Revision Record Revision Date Originator Checker Approver Description A 12/10/2018 Brad Morley Celia Figueira Peter Ede First issue Sarah Green B 19/11/2018 Celia Figueira Sarah Green Peter Ede Response to client comments Róisín Ní Mhathúna C 28/02/2020 Philippa Megan Peter Ede and Revised following further Cross and Rogers Stuart Smith comments Emma Lancaster D 27/03/2020 Philippa Megan Peter Ede and Revised to client’s independent Cross and Shelton Stuart Smith review Emma Lancaster Document reference: 399155 | 10 | D The preparation of Rev C and Rev D of this report includes the contribution of Atkins, who worked alongside Mott MacDonald to respond to feedback received on Rev B. 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Under no circumstances m ay this report or any extr act or summary ther eof be used in connection wi th any public or private sec urities offering i ncluding any rel ated mem orandum or prospectus for any securities offering or stock exchange listing or announcement. 399155 | 10 | D | 27 March 2020 Mott MacDonald | River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment Contents Executive summary 1 1 Introduction 3 1.1 Background 3 1.2 Habitats Regulation Assessment Framework 3 1.3 Scope of the Stage 2 Appropriate Assessment 5 1.4 Methodology 5 1.5 Structure of the report 6 2 River Wensum: Costessey boreholes abstraction 7 2.1 Overview of existing abstraction licence 7 2.2 Overview of proposed drought permit 10 2.3 Summary of HRA Stage I Screening Assessment 10 3 River Wensum SAC 12 3.1 Site overview 12 3.2 River Wensum SAC qualifying features 12 3.2.1 Annex I Habitats that are the primary reason for selection of this site 12 3.2.2 Annex II Species that are a primary reason for selection for this site 12 3.2.3 Annex II Species present as a qualifying feature, but not a primary reason for site selection. 13 3.3 River Wensum SAC conservation objectives and improvement plan 13 3.3.1 Site improvement plan 13 3.4 Sensitivities and conservation status of the qualifying features 14 3.4.1 Ranunculion fluitantis and Callitricho-Batrachion vegetation 14 3.4.2 White-clawed crayfish (Austropotamobius pallipes) 14 3.4.3 Desmoulin’s whorl snail (Vertigo moulinsiana) 15 3.4.4 Brook lamprey (Lampetra planeri) 16 3.4.5 Bullhead (Cottus gobio) 17 3.5 Qualifying features within the Zone of Influence 17 4 Impact Assessment 20 4.1 Impact Significance 20 4.1.1 Overview 20 4.1.2 Ranunculion fluitantis and Callitricho-Batrachion vegetation 20 4.1.3 White-clawed crayfish 21 4.1.4 Desmoulin’s whorl snail 21 4.1.5 Bullhead 23 399155 | 10 | D | 27 March 2020 Mott MacDonald | River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment 4.1.6 Brook Lamprey 24 4.2 In-combination effects 24 4.3 Local planning applications 25 4.3.1 Environment Agency drought plans 25 4.3.2 Other Water Company drought plans 25 4.3.3 Water Company Water Resource Management Plans (WRMP) 26 4.3.4 Other plans and projects 26 5 Mitigation and Enhancement Measures 28 6 Conclusions 29 7 References 30 Tables Table 1: Costessey boreholes and Heigham abstraction and transfer licences 10 Table 2: Summary of the hydrological requirements of Desmoulin’s whorl snail 21 Table 3: Summary of the hydrological requirements of brook lamprey 24 Figures Figure 1: Assessment process 4 Figure 2: Location of the River Wensum SAC, SSSI Units 38-39 and 40-44 and Costessey abstraction boreholes 8 Figure 3: 5km buffer defined as the study area for the Appropriate Assessment 9 Figure 4: Range of simulated and observed water levels compared with the requirements of Desmoulin’s whorl snail 22 Figure 5: Piezometer data for land parcel 38/39 23 399155 | 10 | D | 27 March 2020 Mott MacDonald | River Wensum: Costessey Boreholes Permit HRA - Stage 2 Appropriate Assessment Executive summary The River Wensum is a Special Area of Conservation (SAC) from near its source downstream to Hellesdon Mill on the north-western outskirts of Norwich. Anglian Water currently abstract from the river at Heigham to supply Norwich. When required, the boreholes at Costessey are used to supplement water supply, via the Costessey Pits. To maintain security of supply, Anglian Water have proposed a drought action for the Costessey boreholes that would allow a temporary increase in the maximum annual licensed abstraction rate from the boreholes. This increase in groundwater abstraction has the potential to impact groundwater dependent features within the study area as well as flows and river levels within the River Wensum. The Costessey boreholes are adjacent to the SAC which is also a Site of Special Scientific Interest (SSSI). Qualifying features include the following habitats: ● Watercourses of plain to montane levels with the Ranunculion fluitantis and Callitricho- Batrachion vegetation ● White-clawed crayfish (Austropotamobius pallipes) ● Desmoulin’s whorl snail (Vertigo moulinsiana) ● Brook lamprey (Lampetra planneri) ● Bullhead (Cottus gobio) As part of the environmental assessment carried out for this drought permit, a Stage 1 Screening Assessment has been undertaken to assess the environmental effects of the proposed drought permit (Mott MacDonald 2018). The Stage I Screening concluded that there are mechanisms by which potential impacts arising from the proposed drought permit could result in Likely Significant Effects (LSE) on the qualifying features of the River Wensum SAC. This is with the exception of white clawed crayfish (Austropotamobius pallipes). This report details Stage 2 of the Habitats Regulations Assessment (HRA), which is required to provide an assessment of the impacts of the proposed drought permit on the European designated sites within the Zone of Influence (ZoI).