Basingstoke Water Cycle Study Phase 1 Technical report March 2007 Halcrow Group Limited Basingstoke Water Cycle Study - Phase 1 Technical Report March 2007 Version 1 Revision 6 Contents Amendment Record This report has been issued and amended as follows: Issue Revision Description Date Approved by 1 1 Interim draft report for 3/01/07 EJG comment only 1 2 Draft report for comment 31/01/07 EJG only 1 3 Draft report for comment 04/02/07 EJG only 1 4 Draft final report version 4 16/02/07 EJG 1 5 Draft final report version 5 27/02/07 EJG 1 6 Final report 01/03/07 EJG Contents 1 The Water Cycle 1 2 Proposed Developments and Planning Process 3 3 Water Resources and Water Supply 5 4 Wastewater treatment and disposal 17 4.1 Introduction 17 4.2 Water quality targets and standards 17 4.3 Impact of development on water quality 18 4.4 Headroom for development 18 4.5 Environmental and ecological headroom for development 20 4.6 Compliance with EA RQO 21 4.7 Compliance with chalk river standards 21 4.8 Water framework directive – UKTAG draft environmental standards 23 4.9 Ecological impact of increased orthophosphate 23 4.10 Impact of other discharges in the catchment 24 4.11 Mitigation and alternative options 24 4.12 Novel treatment techniques 25 4.13 Conclusions 26 5 Flood risk assessment 29 5.1 Overview of River Catchments – Test and Loddon 29 5.2 Flood Risk Areas Identified 29 5.3 High Level Assessment of Impact of Flood Risk on Development (and vice versa) 32 5.4 High Level Mitigation Options to Facilitate Development 32 5.5 Conclusions 34 6 Groundwater protection & Sustainable drainage 35 6.1 Groundwater protection 35 6.2 Groundwater flooding 36 6.3 Potential for infiltration SuDS 36 7 Conclusions 41 Appendix 1 - Ecological Appraisal January 2007 1 The Water Cycle Figure 1 below summarises the Water Cycle and shows how water enters, leaves and returns to the river system. Figure 1.1 The Water Cycle 1 2 2 Proposed Developments and Planning Process Phase 1 of the Basingstoke water cycle study is to assess the strategic capacity to accommodate Of this, the majority of the increase in dwellings occurs development at Basingstoke. The specific detail of within the Blackwater and Western Corridor area, and delivering the scale of growth should be considered only a small increase occurs within the Basingstoke & through further technical work to assist the delivery of Deane borough outside of this area. To calculate the the Local Development Framework (LDF). impact of these scenarios on the water cycle, they must be converted into population estimates. This was In accordance with Planning Policy Statement 11 carried out by Hampshire County Council on behalf of (PPS11) the Draft Regional Spatial Strategy (dRSS) Basingstoke & Deane Borough Council using the should indicate the broad scale and location of growth, Chelmer model. but not identify specific locations. This will be for the appropriate LDF to determine. Consequently, the Water Company planning understanding of the Water Cycle Group is that the focus of the Examination in Public (EiP, also known as There are three water companies with a stake in this the Public Examination) Panel will be on the overall water cycle strategy. Thames Water is responsible for capacity of the wider area to accommodate providing sewerage and wastewater treatment for development, not site specifics. This approach lends Basingstoke. South East Water is responsible for itself with regard to waste water treatment and water providing clean water to the east of the Basingstoke & quality, and water resources, but is more difficult when Deane Borough Council area, and Southern Water quantifying river and urban flooding. Whilst clean water responsible for providing clean water to the west of the and sewage can be moved around a network, ensuring area as shown in Figure 3.1. The water companies sufficient lead in time to provide the necessary responsible for providing water supply and wastewater infrastructure, flood risk cannot. collection and treatment, are funded in 5 year planning periods. The money they have available to spend on The water cycle study looked at three different infrastructure is determined by OFWAT in consultation development scenarios to quantify the implications: with government, the Environment Agency and consumer organisations amongst others. The a) Scenario 1 - 740 dwellings/annum – This scenario consultation process is known as the Periodic Review is based on Basingstoke and Deane Borough (PR), and the next review PR09, which will determine Council’s preferred level of development for the how much money they have to spend between 2010 Borough as established in 2006 as the Council’s and 2015 will start in 2008 and conclude in November response to consultation on alternative levels of 2009. The water companies are currently drafting their future growth for inclusion in the RSS. business plans with detailed strategies and costs for b) Scenario 2 - 825 dwellings/annum – This scenario new infrastructure. These business plans will be sent is based on the proposed level of housing provision to the regulator for first submission in June 2008, with in the dRSS. the final submissions following in early 2009. Once c) Scenario 3 - 990 dwellings/annum – This is a funding has been obtained for new or upgraded notional higher growth scenario based on infrastructure, there can be a significant lead in time for increasing the dRSS by 20% planning and construction before the infrastructure can 3 be used (see Table 2.1). Therefore the water Table 2.1 Thames Water estimate of infrastructure companies require detailed information on likely lead in times housing developments up to 2016 well in advance of 2008 if they are to plan and provide the infrastructure Resource Lead in time required to meet those levels of growth. Wastewater treatment 3 – 5 years works upgrade Sewerage network 1 – 3 years upgrades Major resource 8 – 10 + years development (new reservoir, new STW etc) 4 3 Water Resources and Water Supply That part of the Basingstoke & Deane Borough resources in the Basingstoke & Deane Borough Council area within the Western Corridor and Council Area. The WRSE report previously Blackwater Valley sub-region falls within two water mentioned has suggested that an 8% decrease in resource zones (WRZ) as shown in Figure 3.1. per capita consumption can be achieved with a twin These are: track approach and without a change in legislation In the Basingstoke and Deane area this would reduce Hants-Kingclere – Southern Water (SWS) average per capita consumption (pcc) to around Northern Zone – South East Water (SEW) 138litres per head per day (l/hd/d) for new homes, compared to the 120l/hd/d used in the water Southern Water and South East Water have resource scenarios in this study. previously assessed the impact of forecast population and housing growth on water resources The Environment Agency has looked at how water as part of the strategic water resource planning efficiencies of up to 47% can be obtained in new exercise in 2004. For the purposes of this water housing in the May 2006 WRSE report. Therefore cycle we have used the information in these Water the pcc of 120l/hd/d used in this study for new resource plans (WRP04), along with the Water developments, which only represents an efficiency Resources in the South East Group (WRSE) report saving of 20% is an aspirational but entirely (May 2006) on the latest South East Plan housing achievable target although it may need to be provision and distribution received from SEERA, to supported with a change in legislation. The look at the impact of additional forecast growth Environment Agency state that: beyond that assessed by the water companies. “With suitable enabling mechanisms and incentives in place, the achievable range of water efficiency The water cycle study has used the information savings probably lies between 8% and 21% relative presented in the water companyies’ 2004 water to water companies forecast per capita resources plan and updated the population figures consumption. Higher savings should not be ruled out with the latest known population figures obtained but will be more challenging still. To achieve them from the Office of National Statistics and significant regulatory, financial and behavioural Communities and Local Government. The method changes would be required.” used is explained more fully in the Appendix G. • Water resource scenario A The study has looked at three water efficiency and All new properties in Basingstoke and Deane demand management scenarios alongside the three district have per capita consumption rates of 120 population forecast scenarios discussed in chapter 2 litres per person per day, all other developments (Scenarios 1, 2 and 3). The water resource and existing properties have per capita scenarios assessed are aspirational, and may not be consumption rates as stated in the SEW and achieved without a change in regulation and SWS 2004 Water Resource Plans. legislation. These scenarios have been assessed as testing scenarios to look at the limits of what may be achieved and how that would affect water 5 • Water resource scenario B assumed to be the same as used by the water All new properties in Basingstoke and Deane companies in their 2004 water resources plans. district have per capita consumption rates of 120 This target headroom includes the water companies’ litres per person per day, all other metered assessment of total risk and uncertainty in their properties have per capita consumption rates of plans. It does not however include an uncertainty 150 litres per person per day (post 2008). for potential sustainability reductions that may be Unmetered properties have per capita required by the Environment Agency if it is consumption rates as stated in the SEW and determined that a source is causing environmental SWS 2004 Water Resource Plans.