Soil remediation work at the Westdijk in Bunschoten
Project name: Soil remediation wok at Steunberm of the Westdijk in Bunschoten-Spakenburg
Client: Boskalis Nederland
Location: Westdijk, Bunschoten-Spakenburg
In 2017, the Vallei en Veluwe water board reinforced the Westdijk in Bunschoten-Spakenburg as part of the HWBP-2 project, W2063 Eem flood defence and the southern Randmeren. Thermal desorption (TD) soil has been used in the core of the inner berm of the flood defence. The TD soil is covered with a layer of clay. The TD soil was also used to fill the ditch at the foot of the slope. Partly due to settlement on the weak peat substrate, a large part of the TD used is now under the level of the groundwater. As a result, contrary to what was expected beforehand, polluting substances are leaching into the groundwater and thus ending up in the surface water of the adjacent, new ditch at the bottom of the slope. Batch testing showed that the material does not meet the requirements of a large-scale soil application [GBT].
To clean up the pollution, on 4 July 2018 it was decided to excavate the TD soil and completely replace it with clean material. The Thermal Desorption soil was used in a 2.1km-stretch of the supporting berm of the Westdijk. In October 2020, contractor Boskalis started executing the work. The TD soil is expected to have been removed entirely by the autumn of 2021. Any concluding work will continue into the spring of 2022.
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Services performed by SOCOTEC
SOCOTEC was commissioned by Boskalis Nederland to compile a monitoring plan and then implement various control measures in the surrounding area, such as a pre construction survey, vibration measurement, height measurement, noise measurement, measurement of the X-Y-Z coordinates, visual inspection of the sewer and a detailed inspection of the road.