Using historical repair data to create customized predictive failure curves for sewer pipe risk modeling
T. Martin*, D. Johnson** & S. Anschell***
Abstract Seattle Public Utilities (SPU) currently uses predictive failure curves to aid in calculating the risk cost of its sewer pipes. These curves estimate the likelihood of a point failure occurring for a particular pipe and are based on normalized Weibull-based distribution. An analysis was recently undertaken to verify the accuracy of SPU’s existing curves and to possibly replace them with an expected point failure distribution more precisely based on Seattle’s actual sewer pipe failure history. The analysis examined 15 years of point repair data (1989-2004) for vitrified clay and concrete pipe. Study results indicate that both of these pipe materials are incurring point failures at much lower rates than previously predicted by the existing failure curves. This outcome indicates a fairly low and linear, rather than exponential, future expected failure rate for both vitrified clay and concrete pipes. Anecdotal evidence suggests however that the dominant mode of failure for concrete pipes (most likely structural failure due to slow time-based deterioration) has not yet been reached by this fairly young population of pipes. As Seattle’s concrete sewer pipes become older more information may emerge which significantly alters and increases their future expected failure rate. In addition to the results discussed above the analysis also found a statistically significant correlation between certain local conditions (steep slopes, clay soils, and fill soils) and increased potential for pipe failure.
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Performance assessment of hydrants
E.J.M. Blokker*, J.H.G. Vreeburg**, T. Bekhof*** & H.G.P. Blaauwgeers***
Abstract A drinking water network is used for more purposes than only supplying drinking water; also water for fire fighting is being supplied. Depending on the contract between Water Company and fire departments the water company has operational costs and an objective for the level of service with respect to hydrants. This is basically an asset management issue and leads to the interest in the performance (reliability) of hydrants. The Dutch water company Vitens region Overijssel has put a subset of randomly chosen hydrants to an extensive reliability test and statistically examined the hydrants performance between 2004 and 2006. The analytical approach provided insight in failure causes and will also be applicable to determine the performance of valves. With an estimate frequency of use of 6.45% per year and a hydrant failure of 6.8% (2004) to 10.4% (2006) the chance of failure at operation time is 0.44 to 0.67%, or once per 150 to 220 operations. This level of service was acceptable to both Water Company and fire departments in 2004.
Keywords asset management; hydrants; performance measurement
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Preliminary assessment of operational indicators for the sewerage system in Belgrade
I. Milojkovic*, Z. Marjanovic*, B. Obuskovic*, M. Ivetic**, D. Ljubisavljevic** & D. Jaksic***
Abstract For Belgrade Sewerage System started initial design work on the 1880. First building sewerage structures in Belgrade established in 1905. Since 1905, the Belgrade Sewerage System has continued to expand, where it now consists of thirty sewage pumping stations, and a sewer network which is about 1600 km long. 423 operations and maintenance personnel keep the system running on a day-to-day basis.
Operational performance indicators for sewerage systems reflect the current state and condition of operation and maintenance activities in systems. Local institutions have been making efforts to support and promote improvements in these systems. Using IWA’s “Performance Indicators for Wastewater Services” (Matos et al., 2003), a group of experts created a methodology for evaluating the existing sewerage systems in Serbia. The relevant research is being conducted in Belgrade.
Keywords sewerage; urban drainage system; operational performance indicators
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“Making Data Visible”: using geovisualisation to explore and structure problems in an urban water supply system in Uganda
F. Kizito*, H. Mutikanga**, G. Ngirane-Katashaya*** & R. Thunvik****
Abstract This paper describes the application of geovisualisation to facilitate participatory identification and structuring of problems in an urban water supply system in Uganda. The city of Kampala has experienced rapid expansion over the years, with a corresponding increase in the demand for piped water supply. However, this demand was not well matched with expansion of the water supply system, and as a result parts of the city have been facing chronic supply anomalies and insufficiencies. Faced with the task of identifying remedies to the problems in the system, the city water utility company undertook a formal participatory problem structuring and decision analysis process, to try and understand the underlying causes of system failures as well as the temporal and geospatial patterns of these failures. As part of this process, analysis, mapping and geovisualisation of data derived from historical records of water consumption, as well as records of pipe breakages, supply intermittences, and other recorded customer complaints, was done. The data had been collected using custom-made database applications developed in-house and deployed throughout the operational units of the company. The maps so produced were key in bringing the various stakeholders and decision makers to a common understanding of the problem issues, and helped in the formulation of alternative courses of action. Furthermore, with the establishment of a formal discussion forum for problem analysis and decision making, structured participatory decision making was entrenched within the company’s work ethos. It is hoped that in future, the coupling of the geovisualisation tools with the existing operational databases in the company will result in the development of a functional spatial decision support system and a dynamic framework for system performance monitoring and reliability assessment.
Keywords decision support systems; geovisualisation; participatory problem structuring
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Sewer deterioration modelling in HYDROPLAN
E. Ana*, W. Bauwens**, M. Pessemier***, C. Thoeye**** & G. De Gueldre*****
Abstract This paper compares the use and performances of parametric distributions (Herz, Weibull, Gompertz and Log-logistic) and the semi-Markov process in modelling sewer deterioration or ageing. The main aim is to identify the most suitable modelling technique for sewer ageing as part of the efforts to improve the sewer asset management tool Hydroplan, a decision support tool for asset management of sewers developed by the operators of the Flemish wastewater collecting infrastructure, Aquafin NV (Belgium). The models are calibrated and validated using sewer condition data collected by the Leuven (Belgium) municipal utility. Analysis revealed that among the parametric models, Herz and Gompertz capture sewer ageing best. In general, both the parametric and semi-Markov models proved useful in sewer ageing modelling albeit with different data requirements and emphasis.
Keywords ageing; asset management; deterioration modelling; sewer
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Tools for achieving the equilibrium in water supply and waste water sewerage in Slovak Republic
K. Tothova * & S. Stanko*
Abstract The paper describes status of water supply and sewer systems in Slovak Republic. Except quantitative assessment the paper marks the existing framework of water supply and waste water sewerage. In the paper there is presented the impact of Water Company’s transformation in Slovakia on water supply and sewerage system. Responsibility to provide water supply and sewerage switch in the last years from governmental to municipalities who perform their obligations through water companies that are usually private companies. Government lost the control on these companies and only a legislative framework put into a way of these companies by State Regulatory Authority provides a possibility to control them. Coherent changes in asset management implicate positive and negative impact on inhabitants. The transformation makes positive impacts in increasing the investment to water services. Negative impacts concern increase of water and wastewater prices. Moreover the paper describes a role of price regulation, deals with equilibrium of living standard aspects and water services effective. The evaluation results are insufficiency knowledge of price policy and proposals in sustainable growing up of sources.Keywords sustainable development; water price; water supply; waste water sewerage; water companies
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Decision-making aid for rehabilitation of sewer networks: addressing socio‑economic aspects in the CARE‑S project
C. Werey*, J.P. Torterotot */ ****, D. Sousa e Silva**, R. Barbier*, A. König***, A. Pereira**, M. Montginoul* & V. Waechter *
Abstract Rehabilitation of sewer networks has to serve various objectives, both in terms of present general performance, and in terms of long term sustainability. Part of these stakes are external to the sewerage utility operation, such as social impacts of sewer failures, or social impacts of works. These external impacts are to some extend considered in real life decisions, and should therefore also be taken into account in decision support systems. CARE-S project (2003-05), “Computer Aided Rehabilitation of Sewer systems”, has developed a decision support environment and software prototype, including data management procedures, a set of performance indicators, models describing the condition and evolution of sewers, models describing the risks and consequences of failures, a database describing rehabilitation technologies with their characteristics, an assessment of socio-economic criteria, a long term planning tool, multi-criteria decision tools. The objective is to help utility managers to rehabilitate the right pipe, at the right time, with the right technology. The project has been supported by the European Commission under the 5th Framework Program, joining 17 sanitation utilities and 15 research and development teams. Knowledge and assessment of social and economic external costs have been addressed in CARE-S, in order to propose decision making criteria. In addition, public perception and acceptance have been analysed towards critical events : sewer failures and rehabilitation works. Recommendations have been issued for communicating with the public concerning these events. In this paper we will focus on the criteria developed within this project and present the valuation of the impact “loss of trade” on one hand during rehabilitation works, criteria used for the selection of the best technique for rehabilitating the concerned pipe in a multi-criteria decision making procedure, on the other hand during a failure, criteria used for the selection of pipes candidates for rehabilitation.
Keywords asset management; sewer network; rehabilitation; decision making; socio-economics
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Scope of asset management regarding sustainability of water service in urban India
U. Brighu* & R. Franceys**
Abstract The Indian economy has been growing at an average of 9% annually and most economists agree that India has the potential to be an economic super power in the future. However India is a country which has stark contrasts in the income levels and the poor are poor in absolute terms. . In-spite of a booming economy millions do not have access to a regular supply of clean water. The supply of water is considered to be a social service and hence is highly subsidised by the government. The challenges for water utility policy planners and managers are two fold i.e. to provide water service for the constant and rapidly growing population in urban centres and maintaining the service levels for the existing customers with the constraints of inadequate finances and poor water storage (resource) capacity. This paper seeks to briefly study the possible role of asset management practices in assisting the water utility managers to be able to aim for a sustainable water service. The immediate advantage of better asset management would be to improve the levels of service which in turn could justify a hike in prices for the services which would then break the vicious cycle of poor service leading to inadequate revenues. This paper has outlined the various factors which would need to be considered by the water utility managers to implement asset management practices to improve the sustainability of water services in an urban centre in India.
Keywords asset management; developing countries; sustainability; urban centres; water service
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Decision support model for water pipes renewal programming
A. Nafi* & C. Werey**
Abstract Water utilities ensure the delivery of water with the help of networks consisting in long life asset. An integrated asset management policy must be done to improve the performance of assets and ensure the water delivery to the consumers. In order to improve the network in the right way, several criteria must be taken in the decision making process: technical, economical and social ones. The current study, proposes a way to take into account incommensurables criteria for pipe’s renewal with the help of a specific genetic algorithm adapted from NSGA II and coupled with the hydraulic software Epanet 2. The proposed approach allows to select a set of pipes candidates to renewal according to their structural deterioration and hydraulic importance in the operation of the network. The proposed approach was applied on realistic water network in Alsace(France). The detail of case study and main results are presented.
Keywords asset management; genetic algorithms; renewal scheduling; water networks
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Benchmarking enables utilities to identify asset management best practices in North America
T. Brueck* & L. Blankenship**
Abstract North American utilities clearly have much to gain by benchmarking their asset management practices. Benchmarking best practices is part of a comprehensive asset management research program being undertaken by the Water Environment Research Foundation (WERF) (Alexandria, Virginia, USA), with partners including the Global Water Research Coalition (London, England). The benchmarking component will seek to align with a worldwide benchmarking effort on asset management best practices being planned for early 2008 by the Water Services Association of Australia (WSAA, Melbourne, Australia) and the International Water Association (London, England.) North American utilities will compare practices, identify key areas on which to focus and conduct a detailed metric and process benchmarking This consortium-based benchmarking will be used to enrich the Water Environment Research Foundation’s web-based asset management knowledge platform, SIMPLE (Sustainable Infrastructure Management Program Learning Environment). This enrichment with additional practice-based content and tools will reinforce its primary role as a knowledge management platform, around which cost-effective organizational change in asset management can occur and be sustained. The result will be higher levels of practice and diminished levels of difficulty for other utilities to implement strategic asset management.
Keywords analysis; benchmarking; best practices; process benchmarking; tools
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IS4AM: an information system framework for asset management
J. Boudon*, M. Martin**, B. Vanden Bossche***, J. Luçon****, A.P. Darrées***** & E. Brodard******
Abstract The paper presents an overall integrated approach of Information System issues linked to Asset Management. This is the result of a research done by Suez-Envt that is currently used by most water companies of the Group.
The article focuses on 4 original points of the method:
Description of the Target Information System for water companies
This Target Information System has been built using Enterprise Architecture approach (i.e. analysis of business processes, identification of "invariants" of the Water business, etc.). This framework is then usable by all water companies as a template for the evolution of their Information Systems. This is effectively not the specification of an ideal IT system but the principles and the articulations of the water business functions and groups of data. A special focus is made on the technical domains and their backbone, which is composed on three groups of data: the “asset register” (i.e. record of what we "have"), the “events and measurements”, (record of what we "observe") and the “interventions and work” (record of what we "do").
Details of this Target Information System focussed on asset management issues
The second part of the paper gives details of this Target Information System about the data and functionalities necessary to Asset Management, and their integration in the overall IS of a Water company. It describes:
- the tools for business processes of asset management ( = assessment of asset condition and performance, assessment of risks, definition of asset strategies and policies),
- the data needed by asset management processes and the “real life” processes to be controlled to ensure the permanent quality of data.
Method of description of Above Ground Assets, called SAGAD (Shared Above Ground Asset Description)
This method proposes a description of assets which
is common to all the various departments of a water company (designers, asset
managers, operators, schedulers, maintainers, purchasers, accountants, contract
managers, process experts, etc.). SAGAD is therefore the basis of the “Asset
Register”, which is used by all the applications needing a description of the
assets. A special attention is given to the relationships between SAGAD and the
SAGAD is not related to a specific software, and has been successfully used with various technologies, and different levels of integration in the IS.
Principles and rules to control data
The last point of the paper deals with data policy, and more specifically with methods for the selection of data "deserving" to be integrated in the IS. One of these methods is based on the notion of "cost of ignorance".
To conclude, the issue of an "Information System for Asset Management" can be summarised in the following paradox:
- There is no asset management without a robust and reliable Information
- However no Information System is specifically dedicated to asset management.
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Method of annual rehab planning of water distribution networks
L. Tuhovčák* & T. Kucera**
Abstract The paper describes the methodology of annual rehabilitation planning of water distribution networks. This methodology is divided to three basic steps. At the first step, the basic elements of the network (entities) as potential candidates for the rehabilitation are determined. The second basic step of proposed methodology is ranking of estimated entities. The entities are ranked by the values of set of criteria (age of pipes, failure rate, water losses indicators, water quality, pressure condition, reliability index). The recommended rehab technologies are assigning to each entity in the third and last step of this methodology. The case study of this methodology implementation in the real network is the last part of the paper.
Keywords annual rehabilitation planning; water distribution network
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Earthquake countermeasures and appropriate management of pipeline assets in Japan
H. Taniguchi*, S. Ando*, Y. Sato* & K. Takeuchi*
Abstract Improving earthquake resistance of pipelines is a critical issue due to numerous earthquakes in Japan. Success has been achieved in reducing earthquake damage to water facilities through efforts to improve earthquake resistance based on experience of large-scale earthquake (Hyogo, Niigata, and so on). It has also been confirmed that replacing deteriorated pipe to enhance the earthquake resistance of pipeline reduces not only the risk of damage and water supply interruptions due to earthquakes, but also leakage at normal times. Analysis of the pipeline assets based on PIs is very useful to demonstrate the necessity for ensuring the earthquake resistance of pipelines as it is objective and quantitative method.
Keywords aging pipe; earthquake-proof; emergency response manual; performance indicator; seismic damage; assets of the pipeline
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Strategies for condition assessment of sewer systems
Abstract The inspection of sewers can take place whether by means of fixed-intervals in a conventional surface-covering inspection, or by means of need-oriented strategies. Those need-oriented strategies can be differed between a selective inspection, an evaluation of the present sewer condition based on a representative samples and a failure-oriented forecasting strategy.
By setting up and implementing a numerical model it is now possible to carry out a comparison between strategies. Herewith, the potential of success from every single strategy concerning different boundary conditions has been evaluated.
For larger Sewer Systems a failure-oriented forecasting strategy presents a more reasonable alternative than the conventional surface-covering one. The reason is because the holding time from every sewer in a critical condition can be reduced considerably within this kind of oriented-need inspections compared to the conventional ones. Similarly, this method meets the ability to estimate the whole condition of a sewer for a given term in the minimum time, which usually could not be achieved by a conventional inspection. Oriented-need inspection strategies offer even superior advantages when the crop and the ground water pollution regulation controls have been followed from the beginning, in order to reduce holding times within sewers in a critical class-condition.
Keywords condition assessment; maintenance and repair; need-oriented strategy; extrapolation; forecasting
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Cost reduction and hydraulic reliability improvement by pump schedule optimization
C. M. Sousa*, D. I.C. Covas**, H. M. Ramos***, J. T. Valente**** & M. J. Marques*****
Abstract The current paper focuses on the analysis and optimization of operating strategies of water supply systems taking into consideration different points of view related to the technical-hydraulic performance of the system. For this purpose, an integrated software tool has been developed for determining the optimum, or the set of optimal solutions, of pump schedules and tank water levels, that minimize pumping costs (i.e., maximize off-peak electrical energy consumption) and maximize the system hydraulic reliability (i.e., keep as much time as possible storage tanks full). This tool incorporates a ‘hydraulic simulator’ that describes the hydraulic behaviour of the system during 24 hour simulation (EPANET), and an ‘optimization solver’ based on Genetic Algorithms (GA) to determine the optimal solutions without violating system constraints (e.g., minimum and maximum allowable water levels in the storage tank) and ensuring that downstream demands are satisfied. The developed integrated software tool has been applied to two different real life case studies. The first is a water conveyance system - the Póvoa/Vila do Conde system - integrated in the Multimunicipal Water Supply System of Baixo Cávado and Ave. The second is a district metering area of a water distribution network - the Fonte Santa system - part of Amadora Water Supply System. Results have shown that the application of developed performance assessment tool allows the identification of the causes of operating problems in water supply systems, the analysis of alternative operating scenarios and the establishment of investment priorities. The definition of optimal pumping schedules allows the reduction of operation and maintenance costs associated with pumping energy as well as the increase of hydraulic performance of the system.
Keywords optimization; genetic algorithms; hydraulic modelling; pumping costs; reliability; water supply
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O&M of main sewers systems – SANEST example
H. Martins* & C. Gomes**
Abstract SANEST is responsible for providing the collection, transport, treatment and disposal of effluent from the Municipalities located in the Estoril Coast, Amadora, Cascais, Oeiras and Sintra for a period of 20 years, starting in 1996. The Sanitation System comprises one Interceptor with a diameter between 800mm and 2500mm and 25km long, 20 main sewers with diameters between 350mm and 1200mm running along 120km, 1 Wastewater Treatment Plant (WWTP) for 700.000e.p. and 9 Pumping Stations.
In order to optimize the O&M of the sewage system, SANEST contracted in 2005 two outsourcing services for Cleaning, CCTV Inspection, to systematically, record the GIS data update of the main sewers and the cleaning of the reservoirs’ pumping station, in a systematic method over a 3-year planning. A 24 hours pole, including weekends and holidays, to solve obstruction or discharge problems and the production of a monthly report on the results of each of these activities is also included.
According to the specific conditions many SANEST main sewers are fitted, the development of the works is a constant challenge, mainly as for the definition of the solutions to access to the infrastructures to be kept. Some examples of main sewers locations are: stream beds of rivers, slopes with raised gradients, high-density urban zones, a large number of covered manholes, among others. This is still a pioneer contract in Portugal.
Since April 2005 the results achieved have been very good, as we have already cleaned and CCTV Inspected about 62% of the emissaries covered by one of the contracts and 42% of the other ones included in the other contract that started some months later, in September 2005.
As a result of these ongoing maintenance services, supported by occasional construction works to solve the most urgent problems detected, we would like to highlight many benefits such as the annual reduction of the number of obstructions (more than 50%), a complete diagnosis of emissaries (allowing SANEST to plan the amounts to invest in sewage systems’ rehabilitations), accesses’ improvement for future interventions, 24 hours specialized assistance, identification plates in all manholes (about 4.000 units), properties owners identification, complete record update and GIS data and an effective and fast support to our clients in solving sewer discharges.
Keyword CCTV inspection; sewers system; sewer
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Sustainability: doing the right thing for future generations
S. T. Hayashi*, M. S. Mortada** & L. Kell***
Abstract Utilities are faced with increasingly difficult challenges as the world’s population increases and the global climate shifts. At the same time, aging infrastructure and the constraints of human and financial assets present additional challenges. In order to deal with these challenges and provide future generations with a high-quality environment, asset management must become part of a larger sustainable community. By creating a vision, assessing risks, applying sustainable principles, building and maintaining assets for life, using “green” resources, effectively using technology, and realigning practices to incorporate sustainable principles into organizational culture, asset management can become a key strategy for building and maintaining a healthy social, financial, and natural environment. Various utilities have already recognized the need to incorporate goals of sustainable practices into their organization in order to achieve social, environmental, and financial stability.Keywords sustainability; triple bottom line; social; economic; environmental
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Condition assessment of metallic water networks
A. C. Vangdal*, H. E. Larsen** & S. Sægrov***
Abstract A new technology for condition assessment of metallic water pipes based on acoustic resonance technology (ART) has been developed, tested and is now commercially available. ART is developed by Det Norske Veritas (DNV), while the corresponding Pipescanner technology is developed by Breivoll Inspection Technologies. From inside the pipe a Pipescanner collects data showing remaining solid wall thickness, inside corrosion nodules, joints, bends, valves and similar. A method for indication of inside or outside corrosion is also tried out. Findings are shown in 2D colour plots and presented in analysis reports. The analysis report is the product of this technology based service provider. The reports serve as a decision support tool for water network managers and others like consultants, pipe manufacturers, public authorities, investors, insurance companies and financial institutions
Keywords drinking water networks; condition assessment; corrosion; decision support tool
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