WaPUG Spring Conference 2012 Paper 1 Elisa Zamora Atkins Principal Consultant [email protected] DAP REVIEW (OFWAT Report) Introduction and background Sewerage planning is largely targeted at resolving and avoiding the adverse consequences of failure of the sewerage system in terms of flooding and pollution. Water and sewerage companies have adapted their approaches to these tasks over time. Variation in responses by companies as part of historic regulatory reporting led Ofwat to seek a more detailed understanding of company practices. Additionally, Ofwat wanted to understand how sewerage planning tools are used by companies, both in planning for the long term and on a business as usual basis. We carried out a high-level review of company practices in August 2011 based on structured interviews with all ten water and sewerage companies in England and Wales. We would like to thank Anglian Water, Dŵr Cymru Welsh Water, Northumbrian Water, Severn Trent Water, Southern Water, South West Water, Thames Water, United Utilities, Wessex Water and Yorkshire Water for their participation. We would also like to thank the Water Services Regulation Authority (Ofwat), the Department for Environment, Food and Rural Affairs (Defra) and the Environment Agency (EA) for contributing their views on current and future practices to support a sustainable drainage industry. Objectives Our objectives included: understanding processes, systems and tools companies have to support robust long term sustainable planning. clearly articulating the approaches and common themes across the industry to a wide range of stakeholders, highlighting good practice. indentifying improvements that could be made to incentivise: Proactive management of the sewerage system to prevent failure occurring Robust decision making to ensure that developments are located in the most sustainable way The greater understanding of drainage systems required if companies are to implement demand reduction rather than increasing capacity. Key observations Companies have differed in their interpretation of the term DAP for historic reporting purposes The majority of companies are no longer commissioning new DAPs for sewerage planning Different systems are being used to deliver the outputs previously delivered by a DAP, although hydraulic analyses of the network are undertaken to understand pollution and flooding issues by all companies All companies are moving towards parallel procedures covering structural, operational and hydraulic analysis of the network with variable degrees of integration When updating hydraulic models, drainage area or sewerage management plans, the most common triggers are o In response to emerging issues o On a risk-based approach o On a rolling programme basis Hydraulic models are maintained rather than rebuilt where appropriate The information obtained through sewerage planning is used by all companies to support their investment planning process The degree to which sewerage planning tools are used to support the development of long term sustainable solutions is variable Generally companies use separate planning tools for sewage treatment and sewer networks, although some companies are evaluating investment needs in an integrated approach. Understanding what processes, systems and tools companies have to support robust long term sustainable planning Companies use drainage area plans (DAPs), drainage area studies (DAS), sewerage management plans (SMPs) or other approaches developed for sewerage planning. When historically reporting “DAP updates”, companies were generally referring to updating of the hydraulic model associated with the DAP, SMP or other. AMP5 approaches to sewerage planning can be grouped into three groups: Group 1 Group 2 Group 3 Hydraulic, structural and Hydraulic issues considered in Hydraulic, structural and operational issues considered specific catchments; structural operational issues considered in on a company wide basis and operational issues defined catchments (traditional considered on a company wide DAP approach) basis Companies have a range of tools for carrying out hydraulic assessments of the network ranging from headroom calculators to verified hydraulic models. Where hydraulic modelling is used, companies undertake this in accordance with the WaPUG Code of Practice (2002), which is the industry standard reference. Coverage of hydraulic systems ranges up to 100%. Companies with less than 100% coverage focus on having cover in larger catchments. Companies with 100% coverage use a risk based approach where more detailed information, such as verified Type II or III models, is available for areas considered high risk and lower risk areas are covered by a more simplified model or headroom calculator. Systems for managing structural and operational failures tend to be regional rather than catchment based. These tend to make use of business as usual data such as CCTV surveys and registers of flooding and pollution incidents. The outputs of the process are used internally for capital and operational maintenance planning and for defining wastewater supply-demand investment. In some cases systems based on current or live data are used for planning operational maintenance activities such as jetting. Company systems for capital maintenance planning, such as sewer rehabilitation, may be integrated with the sewerage planning process or informed by it. Longer term investment planning for wastewater infrastructure supply-demand is generally based on a 25 year horizon. The main issue faced by companies is the uncertainty of planned development. External uses include informing the development process and providing information for surface water management plans (SWMPs). All companies use information on hydraulic capacity to support their planning liaison processes, but the extent to which engagement in planning is a pro-active process varies across companies. Company engagement in the development of SWMPs is predominantly through the provision of hydraulic models. The majority of companies consider the sewerage network and sewage treatment separately although common data on population and flow is generally used for both. Good practice examples Planning on a regional basis: Historically, DAPs considered service failures within a given catchment only. This meant that, where DAP coverage was low, the company would not have full visibility of all the issues. A regional approach enables all issues to be appropriately prioritised, regardless of whether there is a DAP for the area. Use of risk-based approaches to assess hydraulic capacity: Analysis using less complex tools can help to inform where a more detailed model is required and allows companies to effectively target investment in hydraulic tools on a risk basis. Confidence scoring of hydraulic models: A confidence scoring system allows the user to determine whether the model is suitable for the purpose for which it is intended, thereby avoiding costs associated with unnecessary model rebuilds. It also allows targeted model maintenance to address the issue that will make the model fit for purpose. Use live and/or real-time data in the process: This results in live plans which can be used in operational management of the network as well as investment planning, enabling technology such as real-time network control. Also, this means decisions are being made using the most up to date information and remove the need for periodic updates of models or plans. Pro-active engagement in the planning process: This enables companies to make an informed assessment about the scale of future development for their own planning purposes, develop appropriate tools where needed, influence the location of planned development and facilitate the planning process. It supports a risk based assessment of planning. Integrated asset planning: In their move away from DAPs, some companies have developed a very integrated system based approach to identify and prioritise the investment to deliver the business outcomes needed e.g. serviceability. Integrating the business as usual systems with those used for longer term planning is both efficient and effective. Articulation of the approaches and common themes across the industry to a wide range of stakeholders We identified a number of common themes and differences in the approaches to sewerage planning now being taken by companies: Common themes Key differences planning on a regional rather than a catchment basis How the impacts of urban creep and climate change are considered in planning taking a risk based approach to the level of detail in a given integration of non-infrastructure and infrastructure area planning the use of quality assurance procedures for the management The degree to which systems and data can be of hydraulic models considered live the way in which updates to hydraulic models are triggered the use of sustainable techniques and planning for sustainable solutions the use of WaPUG Type II and Type III models how pro-active companies are in planning headroom calculators and /or hydraulic models being used to the scale of charges levied on developers. assess the impacts of development the use of business as usual data and planning on a 25 year horizon Company practices can be summarised in a stylised process: Recommendations for proactive management of the sewerage system to prevent failure occurring Use live / real time data for flow monitoring and operational control to enable headroom to be fully utilised Consistently accounting for