River Great Ouse: Drought Permit for Offord Intake Anglian Water HRA Stage 2 Appropriate Assessment 27 March 2020
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River Great Ouse: Drought Permit for Offord Intake Anglian Water 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 Great Ouse: Drought Permit for Offord Intake Anglian Water 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 Great Ouse: Drought Permit for Offord Intake Anglian Water HRA Stage 2 Appropriate Assessment Issue and Revision Record Revision Date Originator Checker Approver Description A 12/10/2018 Chris McPake Celia Figueira Peter Ede First Issue B 16/11/2018 Chris McPake Celia Figueira Peter Ede Revised following client comments Philippa Cross Peter Ede and C 28/02/2020 Megan Rogers Revised following further comments and Emma Stuart Smith Lancaster Philippa Cross Peter Ede and Revised following client’s D 27/03/2020 Megan Shelton and Emma Stuart Smith independent review Lancaster Document reference: 399155 | 9 | 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 securities offering i ncluding any rel ated mem orandum or prospectus for any securities offering or stock exchange listing or announcement. 399155 | 9 | D | 27 March 2020 Mott MacDonald | River Great Ouse: Drought Permit for Offord Intake Anglian Water HRA Stage 2 Appropriate Assessment Contents Executive summary 1 1 Introduction 2 1.1 Background 2 1.2 Habitats Regulations Assessment framework 2 1.3 Scope of the Stage 2 Appropriate Assessment 3 1.4 Methodology 4 1.5 Structure of the report 5 2 River Great Ouse: Offord Intake 6 2.1 Overview 6 2.2 Proposed drought permit 6 2.3 Summary of HRA Stage I Screening Assessment 7 3 Ouse Washes European designated sites 10 3.1 Site overview 10 3.2 Ouse Washes SAC 10 3.2.1 Overview and qualifying features 10 3.2.2 Conservation objectives 11 3.3 Ouse Washes SPA 11 3.3.1 Overview and qualifying features 11 3.3.2 Conservation objectives 12 3.4 Ouse Washes Ramsar site 12 3.4.1 Overview and qualifying features 12 3.4.2 Conservation objectives 13 3.5 Conservation status of qualifying features, site condition and threats to European sites 13 3.5.1 Conservation status of the main qualifying features 13 3.5.2 Site condition 15 3.5.3 Sensitivities of the qualifying features 15 4 Impact Assessment 17 4.1 Overview 17 4.2 Results of reduction of water quality downstream of Offord intake 18 4.3 Considerations for ecological receptors 21 4.4 Potential impacts on the qualifying features of the Ouse Washes European designated sites 22 4.4.1 Avian qualifying features of Ouse Washes SPA and Ramsar site 22 4.4.2 Spined loach: Qualifying feature of Ouse Washes SAC 23 399155 | 9 | D | 27 March 2020 Mott MacDonald | River Great Ouse: Drought Permit for Offord Intake Anglian Water HRA Stage 2 Appropriate Assessment 4.4.3 Aquatic macrophytes and invertebrates associated with the Ouse Washes Ramsar site 23 4.5 Assessment of significance of effects 24 4.6 In-combination effects 24 4.6.1 Environment Agency drought plans 24 4.6.2 Other water company drought plans 25 4.6.3 Other water company WRMPs 26 4.6.4 Other plans and projects 26 5 Mitigation and Enhancement Measures 28 6 Conclusions 29 7 References 30 Tables Table 1: Current Maximum licensed abstraction quantities at Offord 6 Table 2: Main qualifying features of Ouse Washes SAC/SPA/Ramsar site and conservation status 14 Table 3: Potential impacts of the proposed drought permit for Offord intake 17 Table 4: Baseline water quality WFD EQS assessment for 2005-2012. 20 Table 5: Baseline water quality WFD EQS assessment for 2013-2017 Environment Agency monitoring data. 20 Figures Figure 1: Assessments process 3 Figure 2: Overview of the study area and key environmental features 9 399155 | 9 | D | 27 March 2020 Mott MacDonald | River Great Ouse: Drought Permit for Offord Intake 1 Anglian Water HRA Stage 2 Appropriate Assessment Executive summary Anglian Water Services (Anglian Water) currently abstract from the River Great Ouse at the Offord intake to fill Grafham Water. The current licence permits abstraction of up to 75% of flow in excess of the Minimum Residual Flow (MRF) of 136Ml/d, up to a maximum of 485Ml/d. In support of the 2019 Drought Plan, Anglian Water have proposed drought action to recharge Grafham Water, which will result in an increase in abstraction from the Offord intake. During drought conditions Anglian Water are seeking a drought permit in two stages: ● Stage 1: Maintaining the current MRF of 136Ml/d but increasing abstraction from 75% to 100% of the excess flow, or, ● Stage 2: Reducing the MRF to 68Ml/d and abstracting up to 75% of the excess flow. Anglian Water would only be likely to consider applying for the drought permit in a severe, possibly multi-season drought, if there is a risk of compromising their ability to meet demands on Grafham Water. The implementation of the drought permit has the potential to result in adverse impacts associated with the reduction in flows and water levels, and reduction in water quality downstream of the Offord intake. The Ouse Washes, located approximately 30km downstream of the intake, are designated as the Ouse Washes Special Area of Conservation (SAC), Ouse Washes Special Protection Area (SPA) and Ouse Washes Ramsar site for their international importance to nature conservation. Qualifying features include: ● Spined loach Cobitis taenia; ● Internationally important populations of breeding and over-wintering water birds; ● Internationally important assemblages of over-wintering waterbirds; ● Extensive wetland habitats represented by seasonally-flooding washland; and ● Several nationally scarce aquatic plants and invertebrates. As part of this project, a Stage 1 Screening for the Assessment of Likely Significant Effects (LSE) was undertaken to assess the environmental effects of the proposed drought permit at Offord intake (Mott MacDonald, 2018).