InSAR in Utilities

Utilities company Stedin saves €80,000 per week on service line maintenance.

Selective repair targets only pipelines at risk and avoids unnecessary digging.

Stedin NV manages over 23,000 kilometers of gas distribution pipelines and 1.9 million connections into homes in The Netherlands. The company uses SkyGeo’s door-by-door subsidence risk estimates to ensure that pipelines with the highest risk are identified and maintained first. With our data Stedin removes the most risk per invested Euro.

The weak link: gas service lines in subsiding cities
Most houses in The Netherlands’ soft soil are built on a foundation so they do not subside. Gas distribution pipelines on the other hand subside with the soil. This creates a hinge point where the gas service pipeline enters the building. These connections are prone to breaking. The severity of subsidence directly correlates with problems in gas delivery service. Therefore subsidence-related maintenance is part of Stedin’s long-term planning.

Previously, Stedin’s knowledge of subsidence effects on risk was based on estimations from 1 soil sample per 10,000 m2 This is not good enough, because ground subsidence in soft-soil areas is a heterogeneous process: within a street, one service line can be okay, and a few doors down, a service line can experience severe strain due to settlements. Real scheduled maintenance planning required more detailed information on subsidence.

Now SkyGeo provides a direct estimate of subsidence effects on distribution lines from door to door, across Stedin’s entire service area.

Actual effects of subsidence on the most vulnerable part of a service line. On the right hand side, a house on foundation; on the left hand side of the photo a flexible service line connection outside of the house, “floating in” subsiding ground.

Subsidence in the Portland area
Just south of the city of Rotterdam, the Portland subdivision was built on four artificial islands. In this area, complaints about the gas delivery service were filed routinely in recent years. Visible signs of rapid subsidence in the roads coincided with high incidence of broken service lines.

Standard maintenance procedure was scheduled and would have dictated replacement of the majority of over 800 pipeline service connections. This scheduled maintenance would have progressed from connections in West Portland first, to the East last. Where no damage is found for several connections in a row, the maintenance is skipped. The operation was budgeted for more than €850,000.

Stedin’s asset manager decided to apply actual subsidence measurements as a proxy for risk in order to prioritize the maintenance activities. SkyGeo‘s satellite-based subsidence measurements started with 30,000 subsidence time series in the 3 km2 area. The data shows 5 years of dynamic subsidence history of streets, buildings and other objects. The measurements were used to create a street-level deformation map. This showed subsidence rates up to 3 cm per year, distributed unpredictably over the area.

Ultimately, only 20% of the service lines in the area were found to be at high risk due to subsidence, including the area where the customer complaints originated. Stedin decided to prioritize maintenance on this 20% of the connections. The other parts of the area are monitored.

As a test, Stedin dug out 5 random pipeline connections selected from the other, low risk 80%. These samples confirmed no damage from subsidence at all as predicted based on our data.

“With SkyGeo’s door-by-door subsidence measurements, Stedin removes the most risk per euro we invest in maintenance.”

Ivo Visser, Risk Analyst, Stedin NV

Based on the results in Portland, Stedin decided to use SkyGeo’s high resolution data to map subsidence risk for the rest of its service area with 1.9 million subscribers. Stedin becomes the first gas distribution company in the world to have this innovative system operational for its network.

Implementing the deformation maps Realizing the importance of accurate and detailed subsidence measurements, Stedin has implemented these maps in their corporate asset management infrastructure. Asset Managers and Network Operations Planners can access the data in a GIS environment, while field personnel can view data on a tablet. Specifically, service lines are identified where likely no subsidence occurs.

Nowadays, before scheduled maintenance gets done by a field crew, the planner assesses the subsidence risk. Since digging up and checking an individual connection costs up to €1,500, Stedin has saved hundreds of thousands of euros in Portland alone while reducing customers’ exposure to construction.

An interpolated risk map detailing subsidence velocity within each street. The outlines of the houses and streets are shown in grey. Stedin could determine the expected subsidence impact per front door. Inset top left: zoom-in of the interpolated street-level subsidence map. Individual homes, garages and streets are outlined in grey. Inset bottom right: zoom-in of the risk map. Service lines going into homes in green (stable) areas are assigned low risk status, service lines in red areas subside rapidly and are assigned high risk.

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