Decision argumentation of
sewer replacement projects
W. Van Riel *, J. Langeveld *
,**, P. Herder *** and F. Clemens *
,****
* Section Sanitary Engineering, Delft University of Technology, 2600 GA Delft, The Netherlands
(e-mail: w.a.p.vanriel@tudelft.nl)
** Royal HaskoningDHV, 6500 AD, Nijmegen, The Netherlands
*** Section Energy and Industry, Delft University of Technology, 2600 GA, Delft, The Netherlands
**** Deltares, 2600 MH Delft, The Netherlands
Decision-making for sewer asset management is inherently complicated, because of insufficient data and interaction with multiple actors. These constraints cause decision-making to be based on intuition and lacking clear argumentation, hampering decision transparency and reproducibility. Hence, in order to improve current sewer asset management, this study assesses the use of information in decision-making for sewer replacement projects.
Introduction
The research is performed within the Dutch ‘Kennisprogramma Urban Drainage’ (Knowledge Programme Urban Drainage). The involved parties are: ARCADIS, Deltares, Gemeente Almere, Gemeente Breda, Gemeente ’s-Gravenhage, Gemeentewerken Rotterdam, Gemeente Utrecht, GMB Rioleringstechniek, Grontmij, KWR Watercycle Research Institute, Platform Water Vallei en Eem, Royal HaskoningDHV, Stichting RIONED, STOWA, Tauw, vandervalk+degroot, Waterboard De Dommel, Waternet and Witteveen+Bos.
Results & discussion
Conclusions
Sewer replacement projects are initiated by much more information sources than the currently used rational models prescribe. Hence, it is concluded that improved coordination processes between actors seems more promising than (investments in) increased information quality about the sewer system, in order to improve sewer asset management.
Figure 1: Sewer replacement project
The decision argumentation of 166 sewer replacement projects (from 2003 to 2013) at eleven municipalities in the Netherlands was analyzed through semi structured interviews. The interview transcripts were coded (open and axial) in Atlas.ti before the occurrence frequency of every information sources was registered.
Approach
0% 10% 20% 30% 40% 50% 60%
Relative occurrence frequency (n=166) Presence of trees
Planning of road works Citizens' complaints call data
Hydraulic model: Environmental performance
Settlement rate
Separate sewer system instead of combined Hydraulic model: Hydraulic performance
Collapsed sewer pipe Maintenance reports
Groundwater nuisance Managemeable
Planning of urban development
Camera inspection images Pipe age
Information from system
Information from environment
Figure 2: Indicated information sources as decision argumentation with f ≥ 5
30 Information sources were identified, summarized in figure 2, which can be put in two groups, information from system and environment (see figure 3).
42 % of all the mentioned information sources are directly related to the sewer system itself; the other 58 % is information about the environment or obtained via the environment. For several projects no argumentation could be recalled, while other projects were executed, because the decision process was irreversible after evaluating the initial need of the replacement project. Approximately two-thirds of the projects are based on two or more information sources, suggesting an incremental decision process.
Explanation: sewer asset management is a process in a complex socio-technical system, in which decisions are influenced by many variables, often more important than the factual information about the sewer system.
Implication: sewer asset management cannot be observed and analyzed isolated from other values and processes in public space (see figure 4).
Figure 3: Configuration of manager, system and environment
