A statistical approach to guide the management of the anterior part of the sewer system
JAB Post (TU Delft - Sanitary Engineering)
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Abstract
The anterior part of the sewer system consists of a system of gully pots and lateral (house) connections that drain to main sewers. The total length of lateral house connections can be similar to the total length of the sewers they drain to. In addition, there are 7 million gully pots with corresponding lateral connections in the Netherlands alone. Considering the potential consequences of a lateral house connection blockage, proper functioning of these system components is essential. Analysis of literature on main sewer infrastructure strongly related to lateral (house) connections indicate these components to be more susceptible to shared failure mechanisms. Both incorrect use by citizens and the structural condition seem to influence the blockage propensity. Furthermore, recent research has revealed gully pot blockages to make larger contributions to flooding in public spaces than intense storm events and main sewer blockages. Gully pots are equipped with a sand trap to prevent solids from being transported to the downstream water infrastructure. The continuous trapping of solids may eventually impair the hydraulic performance. Lack of knowledge on the condition of the anterior part of a sewer system has led to the prevalence of reactive strategies, where activities are undertaken after the consequences of an operational failure becomes apparent. Next to being more costly, these strategies expose citizens to the consequences of a failure such as tangible damages and health risks. Alternatively, proactive strategies are characterised by activities that are undertaken before a failure occurs. Preserving the functionality of lateral (house) connections and gully pots, given the available resources, calls for knowledge on the effectiveness of proactive strategies and information on blockage prone components to balance proactive and reactive activities. To this end, the general objective of this thesis is to provide a methodology that supports the optimisation of management strategies for the anterior part of the sewer system.