Two former landfill sites, containing 461.000 m3 of waste, where completely excavated in order to develop the Vathorst area in Amersfoort.
The two former landfills comprised household waste, industrial waste and sludge. The sites were covered with soil and used for agricultural purposes. With city plans to build a new district called Vathorst in the region, the presence of the two landfills posed challenges for development.
It was decided to completely remove the two landfill sites.The majority of the waste was transported to a sanitary landfill nearby of Smink company in Hoogland (distance less than 5 km). In total, 620.000 m3 material, consisting of 461.000 m3 waste and 160.000 m2 soil was excavated. Smink company landfilled 94% of the waste. The excavated soil (mainly top cover) could be reused almost completely.
Grontmij conducted soil research, and prepared the remediation plan and technical specifications. During the excavation groundwater was lowered by means of pump drainage. The groundwater was pumped into a sedimentation reservoir after which it was discharged to the municipal sewer system. The groundwater beneath the landfills was slightly contaminated. Furthermore, the soil at the bottom of the excavation pit was extensively sampled. After concluding the site was free of any contaminants, the pit was infilled with clean soil, and suitable for further development.
• Municipality of Amersfoort
• Province of Utrecht
• Smink Afvalverwerking BV (contractor)(Now part of Renewi)
• Development company Vathorst C.V.(customer)
Total project fee 18.000.000 euro (this includes landfill tax).
Development company Vathorst C.V. (a public-private partnership) funded the project.
Three person staff from Grontmij were involved in project preparation and remediation supervision. From the contractor over 30 people were involved.
Evidence of success
In summary, the following successes where achieved:
• In total 100% of the waste was excavated;
• The soil top cover was reused almost completely;
• The excavation pit was drained successfully, by which the groundwater contamination was minimized;
• Smart solutions to challenges resulted in remaining within budget.
The following challenges were encountered:
• The amount of (contaminated) groundwater to be discharged to the sewer system;
• The presence of unexpected waste types such as asbestos and series of barrels containing unknown liquids (280 tons in total).
Potential for learning or transfer
A landfill excavation needs extensive in-field supervision to be able to react immediately when unexpected problems (such as unexpected types of waste) arise. This way you make sure that all waste is being treated adequately, and large costs are avoided.
This practice indicates that it is possible to excavate a landfill in order to regain land that can be used as residential area. This is especially helpful in regions with a high land pressure.
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