Shropshire Outline Water Cycle Study Final Report
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Sustaining & Improving the Quality of People’s Lives Shropshire Outline Water Cycle Study Final report Halcrow Group Limited Burderop Park Swindon SN4 0QD June 2010 01793 812479 http://www.halcrow.com/html/our_markets/watercycleplanning.htm Halcrow Group Limited has prepared this report in accordance with the instructions of their client, Shropshire Council, for their sole and specific use. Any other persons who use any information contained herein do so at their own risk. © Halcrow Group Limited 2010 iii Sustaining & Improving the Quality of People’s Lives iv Sustaining & Improving the Quality of People’s Lives Shropshire Outline Water Cycle Study Final report Halcrow Group Limited Burderop Park Swindon SN4 0QD March 2009 01793 812479 http://www.halcrow.com/html/our_markets/watercycleplanning.htm Halcrow Group Limited has prepared this report in accordance with the instructions of their client, Shropshire Council, for their sole and specific use. Any other persons who use any information contained herein do so at their own risk. © Halcrow Group Limited 2010 iii Sustaining & Improving the Quality of People’s Lives Shropshire Outline Water Cycle Study Final report Revision schedule Date Document reference Stage Author Approver 30/11/2009 WUSHWC Draft Ali Cotton Andy McConkey 14/05/2010 WUSHWC Draft Final Ali Cotton Andy McConkey 23/06/2010 WUSHWC Final Ali Cotton / Ali Cotton Emma Smith iv Sustaining & Improving the Quality of People’s Lives TABLE OF CONTENTS 1 Introduction 1 1.1 Background to the water cycle study 1 1.2 Water cycle processes 2 1.3 Objectives of the water cycle study 2 2 Development scenario for WCS 5 2.1 Overview 5 2.2 Shrewsbury and Oswestry 5 2.3 Ironbridge power station 9 2.4 Market towns, local centres and key local centres 9 2.5 Additional dwellings to be accommodated in spatial zones 11 3 Water resources & water supply 13 3.1 Overview 13 3.2 Data and References 13 3.3 Water Company Overview 14 3.4 Environment Agency Water Resource Management 16 3.5 Shropshire Catchment Abstraction Management 18 3.6 Summary of water company overview 22 3.7 Demand Management 24 3.8 Future Demand Scenario Testing 28 3.9 Statement of Response and Variance from the draft WRMP09 34 3.10 Conclusions and Recommendations 35 3.11 Indicative Action Plan 36 4 Wastewater infrastructure assessment 41 4.1 Introduction 41 4.2 Overview of methodology 43 4.3 WwTWs affected by growth 45 4.4 WwTW infrastructure capacity 46 4.5 Wastewater network infrastructure capacity 54 4.6 Ironbridge power station 61 4.7 Conclusions and recommendations 61 5 Water quality 63 v Sustaining & Improving the Quality of People’s Lives 5.1 Introduction 63 5.2 Data and References 64 5.3 Methodology 64 5.4 Water quality assessment 67 5.5 Conclusions and recommendations 85 6 Flood risk management 87 6.1 Introduction 87 6.2 Methodology 88 6.3 Shrewsbury 88 6.4 Oswestry 92 6.5 Ironbridge power station 93 6.6 Market towns, key centres and local centres 96 6.7 Windfall development 100 6.8 Conclusions and recommendations 103 7 Surface water management & mapping 109 7.1 Introduction 109 7.2 Background 109 7.3 Overview of Methodology 110 7.4 Assessment of surface water flooding 112 7.5 Additional surface water flooding evidence 115 7.6 Conclusions and recommendations 116 8 Surface water drainage 119 8.1 Introduction 119 8.2 Data and references 128 8.3 Methodology 129 8.4 County wide mapping 133 8.5 Shrewsbury 135 8.6 Oswestry 137 8.7 Ironbridge power station 139 8.8 Market towns, key centres and local centres 139 8.9 Windfall development 145 8.10 Conclusions and recommendations 145 9 Conclusions and recommendations 148 9.1 Shrewsbury 148 9.2 Oswestry 148 vi Sustaining & Improving the Quality of People’s Lives 9.3 Ironbridge power station 149 9.4 Market towns, key centres and local centres 150 Appendix A. The Water Framework Directive 161 Appendix B. Overview of water company planning 174 Appendix C. Overview of options for demand management 184 Appendix D. Background information on flood risk 196 Appendix E. Flood Risk and Surface Water Drainage 204 Appendix F. Surface Water Vulnerability Mapping 205 vii Sustaining & Improving the Quality of People’s Lives iii Sustaining & Improving the Quality of People’s Lives 1 Introduction 1.1 Background to the water cycle study The Panel Report following the Phase 2 examination of the Regional Spatial Strategy (RSS) for the West Midlands has increased the number of new homes proposed in Shropshire over the next 20 years, from 25,700 to 27,500. The RSS sets out a settlement strategy that identifies the sub regional role of Shrewsbury as a Settlement of Significant Development and Growth Point. Given this role, the RSS proposes that Shrewsbury should accommodate 6,500 dwellings up to 2026 and that development should be of a smaller scale in the market towns and focused on catering for local needs and local regeneration in the villages. Building new homes is not simply a matter of constructing the buildings themselves. To operate effectively as a home, and as part of a wider community, each building is also dependant on a range of services, and the infrastructure necessary to provide these. A critical component of this infrastructure is associated with water; the provision of clean water for drinking and washing; the safe disposal of waste water; and protection from flooding. The addition of a small number of new homes may not represent a significant additional burden on existing water infrastructure. However when large numbers of houses are built, there is a risk that existing infrastructure will be overwhelmed, and both the environment and people's quality of life, will suffer. There is a finite capacity within the environment, and it cannot simply provide more and more water to serve new development. Equally, there is a limit to the amount of waste water that can be safely returned to our rivers and the sea without having a detrimental impact on the environment. Furthermore, we know that extreme rainfall can overwhelm drains and overtop flood defences. Climate change is bringing fresh challenges as patterns of rainfall are predicted to change, with more intense rainfall events. We must also make sure that water infrastructure contributes to the shift to a low carbon economy that is essential if greenhouse gas emissions are to be reduced. Planning for water has to take into account these natural constraints, and factors such as the timing and location imposed by the development itself. Shropshire Council is currently preparing its Core Strategy, as part of the LDF process. LDF documents submitted to the Secretary of State must include an evidence base to support the proposed strategic approach. Shropshire Council commissioned a water cycle study, as part of this evidence base to ensure that development will not have a detrimental impact on the environment and that the necessary water infrastructure can be provided in a timely manner to support growth. 1 Sustaining & Improving the Quality of People’s Lives Halcrow Group Ltd were commissioned to undertake a WCS for Shropshire Council, in partnership with the Environment Agency, Natural England, Severn Trent Water and Welsh Water 1.2 Water cycle processes The water cycle includes the processes and systems that collect, store, or transport water in the environment. Water cycle processes are both above and below ground level, and can be either natural or man-made. In an undeveloped area, the water cycle includes rainfall landing on the ground, where it is either transferred into above ground streams, rivers, wetlands, floodplains, and estuaries to the sea, or is absorbed into the soil, ending up in groundwater storage aquifers. The cycle is completed by evaporation from these systems back into the atmosphere. In a developed area, the natural processes and systems are sometimes adapted for development or public health reasons. For example, water is taken from rivers, treated, and piped via water supply systems into urban areas. Wastewater produced by houses is collected in a below ground sewerage system, where it is transported to a wastewater treatment works before being discharged to the sea, rivers or to groundwater. The natural processes are extremely important for wildlife and ecology, and even man made systems can have biodiversity and wildlife interest. It is important that when building new homes, or even redeveloping existing areas we understand the impact on the natural environment. 1.3 Objectives of the water cycle study As defined in the brief the objectives of the WCS are to: • Undertake a strategic level assessment of infrastructure and environmental capacity in relation to proposed housing and employment development within Shrewsbury, the market towns, key centres and local 2 Sustaining & Improving the Quality of People’s Lives centres, as defined in the Core Strategy Policy Directions document. This assessment should focus on water demand and supply, water quality, and wastewater collection and treatment, flood risk and drainage. • Undertake a detailed assessment of the strategic urban extensions for development in Shrewsbury and Oswestry, to assist understanding of whether there are viable and deliverable options for these settlements and to identify a viable and deliverable infrastructure solution for these locations, identifying likely timescales for provision and the impact this may have on the phasing of development. • Undertake an initial assessment of the Ironbridge Power Station site to provide an understanding of the existing water cycle processes affecting the site and consider strategic water services infrastructure requirements and options. • Provide advice on the effective management of surface water, including setting out design standards for sustainable drainage and providing policy recommendations to ensure the coordinated preparation of Surface Water Management Plans by developers for major site allocations.