Residual lifetime of plastic sewer pipes

Research objectives

The objective of this project is to provide sufficient knowledge on the current state of plastic sewer pipes and joints in The Netherlands and predict their residual lifetime. The parameters that accelerate the degradation of plastic sewer systems will be investigated and assessed.

Project outline

Introduction
A large part of the sewer system in The Netherlands is occupied by plastic materials (e.g. PVC, PE, GFRP, etc.), which have been used extensively since 1960’s. While the factors which determine the lifespan of plastic pipes and joints have been explored regarding water and gas distribution systems (e.g. Arsénio, 2013, Visser, 2010), the same does not apply for sewer systems in which the environment is totally different and more hostile.

Today, sewer asset management and deterioration models usually depend on visual inspections and have the tendency to connect the age of a pipe to its structural condition. However, pipe age and CCTV inspection data, used as main input in models and in decision making, have proved not to offer a realistic picture of the actual sewer conditions (Stanic, 2012). Thus, more deep approaches have to be implemented in order to have a more comprehensive view.

Approach
Initially, in collaboration with some municipalities, operating pipes of several diameters will be exhumed from the ground and will be tested concerning their structural integrity and their leak tightness. Hence, these experiments will focus on the assessment of the current state of the sewer systems. Additionally, the exploration of available inspection data files has provided indications of possible defects that occur in plastic sewers. Based on the results of the experiments and the inspection data, the research will be directed towards a material science approach, or a pipe-soil interaction approach, or a combination of both.

Scientific relevance

This project aims at understanding and communicating the failure mechanisms that prevail in polymer sewer pipes and how these mechanisms affect the functionality of the system. By conducting experiments and developing models, methods which take into account both the structural and operational conditions in sewers will be established.

Social relevance

In an effort to save capitals, municipalities have become more cautious whether a pipe has to be replaced or not (Rioned, 2016), shifting to a less proactive approach. Reactive replacement, however, could lead to unpredicted costs and working loads, while the release of untreated sewage to the environment, until the damage is noted and fixed, could cause severe consequences. Hence, making a trustful estimation about the period that a pipe is expected to fail is a key issue for sewer asset management, leading to better decision making and more affordable investments.

Research partners

This research project is part of the “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, KWR Watercycle Research Institute, Platform Water Vallei en Eem, Royal HaskoningDHV, Stichting RIONED, STOWA, Sweco Nederland, Tauw, vandervalk+degroot, Waterboard De Dommel, Waternet and Witteveen+Bos.

Literature

Arsénio, A. M. (2013). Lifetime prediction of PVC push-fit joints. doi.org/10.4233/uuid:18a79a31-abd9-4f24-81f5-15935e3523d0

Rioned (2016). Het nut van stedelijk waterbeheer.

Stanić, N., Langeveld, J., & Clemens, F. Identification of the information needs for sewer asset management by assessing failure mechanisms.

Visser, H. a. (2010). Residual lifetime assessment of uPVC gas pipes.