Fugro’s ground investigation links Dutch subsidence to former peat extraction

Under a contract for the Municipality of Emmen, the Province of Drenthe, and the Vechtstromen Water Authority, Fugro delivered a multidisciplinary programme of geoconsulting, geotechnical investigation and foundation assessment, and analysed the results with DINO-loket data from the TNO Geological Survey of the Netherlands and satellite mapping data from InSAR (Interferometric Synthetic Aperture Radar).

Towards the end of 2019, the Municipality of Emmen received reports of subsidence and damage to pavements, houses and barns from residents in the villages of Nieuw-Amsterdam and Erica. While Fugro found that factors such as vibrations from vehicles are in themselves not the cause of damage, they can intensify the main contributors, which are the presence or absence of peat in the soil and a decrease in groundwater level. Dehydration during dry spells causes the top layer of peat to oxidise, which affects the damage to gardens, underground pipes and pavements, whereas a drop in groundwater level affects the deeper peat layers and can trigger subsidence that damages buildings and other structures. The influence of local abstractions in this process is under investigation by the Water Authority and the damage appears to be greater if different foundation methods are used for the same construction, such as shallow and pile foundations. Heavier structures, such as buildings where dormer windows have been added, also experience more subsidence damage.

Robin Lomulder, senior consultant at Fugro, said: “As the world’s leading Geo-data specialist, Fugro has the knowledge and cutting-edge digital technology to generate a robust understanding of subsurface conditions. With our extensive in-house capability and resources, we were able to work efficiently to deliver the actionable insights sought by our clients and the residents.”