CARE_S : Computer Aided Rehabilitation of Sewer Networks - Decision Support Tools for Sustainable Sewer Network Management, EU Fifth Framework Program (contratto EVK1-CT-2001-00167), 2002-2005

The design and condition of sewer and storm water systems in cities worldwide play a crucial role to protect the inhabitants towards pollution and local floods and mitigate damage on constructions. These silent civil servants are these days focused due to political ambitions on cleaner aquatic environment such as the European “Water Framework Directive”. They are also discussed in relationship to tougher future requirements caused by the expected increase of storm intensity and frequency due to the ongoing climate change. Increased runoff caused by urbanization as well as reduced structural capacity because of ageing is also important driver for a necessary upgrade of the wastewater networks. Water and wastewater infrastructure are deteriorating with time. Designing these systems for a particular service life and maintaining them in a safe condition during their entire service life have been recognised as very critical issues. Already to-day many wastewater networks suffer from insufficient capacity, construction failures and pipe deterioration. The consequences are structural damage and local floods leading to inflow of water into basements, traffic disturbances, street and surface erosion, and pollution of local receiving water bodies. European cities spend in the order of 5 billion € per year for wastewater network rehabilitation. This amount is expected to increase significantly over the coming decades. The rationale behind rehabilitation decisions is unclear. Decisions are often made ad hoc and, in the best case, are based on practical experience after failures appear (reactive approach). Some analytical tools to assess the technical or functional state of sewers or the needs for rehabilitation have been available for some time. Usually, though, they do not take into account all aspects of rehabilitation decisions, and they only have been applied for a limited number of wastewater services. This is the background for a project in the 5th Framework Programme in EU, Computer Aided Rehabilitation of Sewers and Storm water networks (CARE-S). It is thought that an integrated planning methodology for wastewater upgrading will improve the societal benefit of investments made in the urban wastewater systems. The project objective therefore was to establish a broad rational framework for sewer network rehabilitation decision-making. The system CARE-S aims to improve the structural and functional reliability of the wastewater networks (risk of in- and exfiltration, collapse and blockage due to pipe deterioration, hydraulic overloading resulting in flooding and/or receiving water pollution), identifying optimal preventive maintenance strategies based on lifetime reliability and life-cycle costs. This is combined with the hydraulic analysis of the network capacity to take care of runoff from rainstorms and snow melt in urban areas, even upgrading the system if necessary. The ultimate product is a Decision Support System (DSS) that enables municipal engineers to establish and maintain effective management of their sewer networks. In other words: Rehabilitate the right sewer at the right time by using the right rehabilitation technique at a minimum total cost, before serious failures occur (pro-active approach). CARE-S supports utilities on planning preventive maintenance which, if it is not done, it will cost more at a later stage to keep the structure in a safe condition The CARE-S system has already been applied for analysis and planning of wastewater network performance and need for improvement in many cities. It is used to support day operation and progress on information systems that daily work rely upon and to analyse rehabilitation need for specific projects. One main experience is that the urban wastewater networks should be managed according to a three-tier approach: strategic, tactic and technologic level. The strategic level deals with long term planning, including long term goals and the adoption of best availab..