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Sewer pipeline from Delfland Water Authority causes a challenge for Acquaint

Pipeline inspection is not always risk-free. That’s why Acquaint is specialised in tackling a large number of these risks. Recently we inspected a pressure pipe from our client Hoogheemraadschap Delfland (Water board).

What Acquaint did not know beforehand was that the inspection would cause the biggest challenge in our history.

Only half-preparation possible

Delfland indicated that it wanted to have the following assessed: ‘It is vital to get a clear picture of the condition of the pipelines. What is the condition, the condition of the material, the degree of degradation and the what is the current wall thickness? Based on this, we hope to determine the remaining lifetime of the pipeline and start planning for maintenance or replacement.’ When setting up a new risk-based asset management system, it came to light that the sewer pipelines from the water board needed to be assessed completely.

Siemen van der Heide, Acquaint Chief Operationing Officer, explains: ‘before an inspection, Acquaint always investigates what is in the pipeline and uses the available drawings to draft a plan.’

Variety in the pipelines

It quickly became clear that this was no simple sewer, but a pipelines with different diameters (from 600 to 750) and different pipe types over its 3.4-kilometre length. The following materials were present: HDPE (high-density polyethylene), cast iron, steel, two types of concrete with sheet steel and AC (asbestos cement). On top of that, the sewer pipeline also exhibited several deviations: Y-piece, including in the wrong direction, so they were not actually piggable, and a check valve in a booster pump for the sewer pipeline (a non-return valve), which required some kind of bypass first to get through.

Modifications reduce workload

Delfland and Acquaint performed various modifications to make the sewer pipeline piggable. A launching trap was built, and at the receipt point at the Nieuwe Waterweg treatment plant, a long discharge pipe was installed leading directly to the primary settling tank. A total bypass of 60 metres was built to conduct the inspection. At the Y-piece at the booster pump a connection was made next to a venting point, to be able to install a potential pump to pump sewage back. All of this was to prevent the risk of getting stuck. Ultimately everything worked out so well that we completed the inspection one day ahead of schedule. Thanks to the experience Acquaint gained during the first run, and the smooth collaboration with the Water board Delfland we were able to conduct two runs the following day.

A satisfied client

Van der Heide beams: ‘The Water board was very happy with the inspection. Delfland was initially positive but critical. The sewer pipeline in question is the main sewer pipeline for the municipality of Westland, making it of critical importance. In the event of a blockage, an overflow would have been unavoidable. Fortunately the entire inspection went smoothly’

Risks and limits

Though it was the highest-risk pipeline that Acquaint had ever dealt with, we wanted the client to be satisfied with the inspection. ‘We will soon carry out a project for Brabant Water. It’s also high-risk, like the one for Water board Delfland. That’s what makes us different. We take on those challenges. Though we do of course need to set limits for ourselves,’ adds Van der Heide.

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