Case study Bontec Protec + Bontec HF
In Wilp, Attero has a roughly 75-hectare site where waste is processed and stored sustainably. In order to accommodate the anticipated future volume of contaminated sludge, an expansion has been carried out by NTP Infra. To prevent groundwater contamination, a combination sealing is required in accordance with regulations, which entails a double-layered seal.
Read more in our case study: Landfill bottom seal in Wilp.
First, the terrain was leveled and cleared of coarse materials. Subsequently, a layer of sand was applied, in which a controlled drainage system was installed. On top of this layer, the initial sealing layer (10 cm Trisoplast) was applied, which is a waterproof modified clay layer. On this layer, a 2mm thick HDPE sheet was installed and fully welded together. To ensure the quality of the welds, a double weld seam was used, which was then pressurized to 3 bars of air pressure. If the air pressure remains consistently high during this process, it indicates that the applied weld seams are completely sealed. As the client wanted to be certain that the construction would truly be watertight, the independent accredited inspection
organization Enviro Quality Control B.V. individually inspected and documented all weld seams. After such meticulous care, the liner also needed sufficient protection. For this purpose, a high-quality protective non-woven geotextile was installed, designed to have a long lifespan and provide guarantees against damage to the waterproof layer.
As a solution, the Bontec Protec range from BontexGeo was considered. PROTEC combines high tensile strength with significant elongation, allowing the non-woven fabric to wrap around potential objects, thus preventing damage to the liner. These factors, coupled with a high CBR value and excellent performance in cone drop tests, make the Bontec Protec range ideal for long-term protective applications. A lifespan expectancy of 100 years is standard for all Bontec geotextiles.
On top of the liner, the decision was made to apply a layer of Bontec Protec 500. This prevents any sharp materials from coming into contact with the liner. A layer of 1 meter of clean filtered drainage sand was placed on the PROTEC 500 layer. The process of applying this sand layer is performed using tracked excavators, and only afterward are the leachate drainage pipes installed. If the leachate drainage pipes were installed directly before applying the sand layer, there is a risk that they could inadvertently damage the liner. Since excavating trenches for the leachate drainage pipes poses additional risks, and because the leachate drainage pipes are enclosed in a gravel trench, extra protective measures were mandated in these areas. Thus, an 800 grams per square meter nonwoven fabric (Bontec PROTEC 800) was placed on top of the existing PROTEC 500 layer.
Finally, all the collected water needs to be drained, and for this purpose, a ring pipeline has been installed around the entire horizontal area. Drainage gravel has been placed on the ring pipeline. A specially woven filter geotextile, Bontec HF 360, ensures that the drainage gravel maintains its draining function. The Bontec High Flow fabrics combine very high water permeability with very small mesh openings. Due to the combination of materials, the water permeability is on average 2 times higher than that of regular tape fabrics with the same mesh opening. Thanks to the design of the fabric, it will not clog even after extended use, and the HF360 maintains a consistently high water permeability.
The range of woven and non-woven geotextiles from BontexGeo provides a sustainable, long-lasting addition to this project, ensuring prolonged environmental protection. Both for protection and for the filtering layer, the most suitable solutions could be offered.
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