Together with water authority: safe pipelines in dykes
News article
Once every 12 years, the Dutch water authorities assess whether our dykes are still safe. The many gas pipelines present there make this a labour-intensive and costly activity. Marieke Hollebek from the Hollandse Delta water authority and Jan Ribberink from Gasunie are working together on a solution that saves a lot of time and money.
‘A key part of our work is maintaining the sea, river and inner dykes on the islands in the province of Zuid Holland,’ explains Marieke Hollebek, cables and pipelines water safety advisor at the Hollandse Delta water authority (WSHD). ‘We must also check the structures that affect a dyke, like buildings or pipelines. We manage about 365 kilometres of dykes. In them are 1,500 kilometres of cables and pipelines, owned by various parties.’
The core of the partnership
In 2018, all network operators were asked to check the cables and pipelines located in dykes. Is their condition still the same as indicated in the design? And do they still meet the requirements of the NEN 3651 standard, which sets out the ‘safety requirements for pipeline systems on land’? The water authority also asked Gasunie to assess this.
‘We need to prove that we’re within the risk limits,’ explains Jan Ribberink, national route management expert at Gasunie. ‘The core of our partnership with the water authority is the realisation that either party can create a risk for the other. Our whole quality system is aimed at ensuring that our pipelines remain in good condition. We use various systems to keep close track of all the information about possible corrosion, settlement, excavation damage, etc. And we carry out repairs whenever and wherever they are required.’
A new checklist
‘Our pipelines were constructed 50 to 60 years ago,’ explains Ribberink further. ‘A settlement forecast was also performed at the time. Over time a dyke can settle a little in the weak Dutch soil, as a result of which the pipelines settle along with it, causing stress to occur in them. In case of old pipelines or if there are no design calculations, a recalculation will have to be performed based on the latest standards.’
‘Doing all these recalculations soon turned out to be an impossible task,’ explains Hollebek. ‘The Netherlands has 21 water authorities and thousands of pipeline intersections with flood defences. Gasunie therefore came up with another plan: we’ll prepare a checklist and if the pipeline complies with everything on there, it would be deemed OK. We also decided to use a previous strength assessment of the pipeline as a starting point. If we could prove that the safety of the pipeline hadn’t diminished compared to that assessment, the pipeline would have to be approved now as well.’
Better insight into safety
The checklist specifically maps out whether a pipeline has changed significantly over a certain period. ‘Thankfully, the probability of our pipelines no longer complying is very low,’ says Ribberink. ‘Partly thanks to the checklist, the water authorities also know that this risk of failure is low. We investigated this extensively for a few dyke intersections, and everything turned out to comply with the forecasts and standards. Not having to do those calculations for every pipeline intersection will save us a lot of time and money.’
The approach is really starting to take shape, believes Hollebek. ‘But we’re not quite there yet. Since 2017, we’ve been using a failure risk approach for our sea and river dykes based on the risk of flooding. In the next assessment round, we’ll also have to align more with this failure risk approach for the inner dykes. With Gasunie we’re looking into the best way of doing this. But whichever way things go, the checklist does give us better insight into the safety of pipelines in flood defences.’
Partnerships with other water authorities
Hollandse Delta was the first water authority for which Gasunie applied the checklist approach. ‘We have a clear common interest and the collaboration is very positive,’ says Hollebek. ‘We know everything about flood defences and Gasunie knows everything about the safety of gas pipelines. We were the first, after which the other water authorities followed.’
All the water authorities want to know what the exact pressure in every pipeline is and what the tolerances are, says Ribberink. ‘That is the next step: to build up a virtual pipeline dossier in which all the pipelines are described and geographically presented. A jointly compiled, complete dossier with data from both Gasunie and the water authorities. In the future, this will allow us to map out the whole system at the press of a button.’