CARE-S: computer Aided Rehabilitation of Sewer Networks, EU 5 Framework Program (contract EVK1-CT-2001-00167)

Today many wastewater networks suffer from insufficient capacity, construction failures and pipe deterioration. While the consequences are structural damage and local floods, the rationale behind rehabilitation decisions is often unclear. 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). The project objective 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 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, for example separation of networks, new design of pipelines to meet climate change effects, or computation of the severity of element deterioration, of which parts of the network is the most vulnerable and finally estimation of investment needs. CARE-S can support this by a comprehensive system for Performance Indicators, relying on data from network management system and general statistics. It also contains options for socioeconomic assessment, to find if the network causes over costs for customer. CARE-S is equipped with a tool for analysing and presenting the integrated need for rehabilitation over a long-term planning period. The tactical level deals with situation of each pipeline in network. A careful analysis of condition and probability of performance bottleneck is required, to understand which pipes are prone for upgrading. This may be a structural weakness or insufficient hydraulic capacity. CARE-S enables to import data from visual inspection of the buried pipes in order to analyse the real performance of the system in the current conditions. The topology of the network can be either imported with CCTV files, when the whole network has been inspected, with importing an Hydraulic model, or with importing the GIS-shape files. It is highly recommended to install a hydraulic model for the network. This can be used with data on installation and operation to calculate the hydraulic performance of existing network, when weaknesses due for deterioration are counted. Several structural weakness may occur, and CARE-S offers tools for several situations, being it clogging, roots, impact of leakages etc. The outcome of tactical analysis is a selection and ranking of rehabilitation candidates. The technical level comprises rehabilitation techniques to be applied once a project has been designed. For this purpose a comprehensive database has been developed, containing properties of renovation and repair techniques. Appropriate technology for each rehabilitation project is suggested and the utility’s engineers can choose techniques already applied by the municipality or can try and compute the effect of promoting new and advanced solutions.