This project concerns the identification of promising, innovative, trenchless rehabilitation and replacement techniques, and the objective assessment of their practical implementation and implications. The Netherlands has almost 120,000 km of buried water mains (excluding connecting pipes), with an overall replacement value of around 20 billion euros. The average age of the distribution network is about 42 years. Over the next decades very large investments will be needed to maintain the network in good condition.
Traditionally, the mains have been replaced almost exclusively by means of excavation. But this costs a lot of money, creates a nuisance in the surrounding area, and brings with it relatively long supply interruptions. Smarter rehabilitation or replacement is possible through the use of trenchless techniques, such as the introduction of constructive liners (CIPP lining), spray lining or close-fit lining. The application of these techniques reduces the nuisance for customers and neighbours and can cut costs.
Trenchless techniques have been available for a few years, but have only been used in a limited way in the Dutch water network. This project is unique because, for the first time, several techniques are simultaneously tested. Also, their feasibility for application in the Netherlands is assessed on the basis of clear criteria concerning both the drinking water sector and the contractors. The results are translated into the application of trenchless rehabilitation and replacement techniques in the Dutch water mains network, with concrete suggestions for the appraisal of individual cases.
The following are the project’s deliverables:
- An evaluation framework based on a Social Cost-Benefit Analysis of the impact of the techniques on relevant elements, such as the installation circumstances, supply interruptions, control, environment, nuisance (impact on the surroundings), costs over the entire life-cycle, and risks.
- A schedule of requirements for the execution of the rehabilitation and replacement techniques in practice (operational tests) on the basis of the evaluation framework.
- An overview of the activities (the process) carried out by drinking water companies and contractors in relation to rehabilitation work, including a risk analysis of the preparatory and execution phases. This risk analysis will cover the probability of delays, cost overruns, technical problems, etc., for the different activities.
- The results of the evaluation of the field trials. The field trials are compared to each other in terms of their relevant corresponding elements.
- A translation of the results of the comparison into the application of innovative rehabilitation or replacement techniques for the management of water mains in the Netherlands.
The project, which started in January 2016, has developed an evaluation method to assess different (trenchless) replacement techniques. The method was developed to provide all the elements relevant to mains’ replacement decision-making in a well-founded and quantitative manner. As a result, it is now possible to evaluate and compare different replacement techniques under a wide range of conditions. This opens the way to a decision-support knowledge database.
The evaluation method has been tested in three fields trials in the project. Two evaluation reports have been produced, and work on the third is currently ongoing. The evaluations’ findings are being used, together with network analyses of the drinking water companies concerned, to produce an overview of the application possibilities of the trenchless techniques evaluated.
The results to-date are published in a conference paper for the 12th Pipeline Technology Conference, to be held on 2-4 May 2017, in Berlin. They will also be presented to the NSTT annual meeting in March 2017. Presentations have also been made at the ‘NSTT No-dig Event, 2015’ and the ‘Drinking Water Innovation Platform’ in 2016.