Reclamation and redevelopment of
contaminated sites

The encapsulation of polluted areas is necessary to prevent the discharge of contaminants. To ensure long-term effectiveness of the liner system, high quality geosynthetic materials should be selected and rigorous construction practices should be followed. This is achieved with the installation of quality assured, 2.0 mm thick Carbofol® high density polyethylene (HDPE) geomembranes. Carbofol® geomembranes are produced to the highest quality standards and have the chemical resistance necessary to contain contaminated soils or liquids. Secutex® (PP) as well as Secudrain® drainage systems act as protection layers for Carbofol® geomembranes. Secugrid® geogrids are used to prevent settlement or deformation of the contaminated subsoil and therefore prevent any stress built-up in the geomembrane. Correctly designed these products prevent damage during the installation process as well as over the operational life of the liner system under subsequent long-term loads.

When the geosynthetic liner system is subjected to high normal loads, the efficiency of a protection or cushioning material is tested in a load plate bearing test (DIN EN 13719). The results of this test determine the minimum mass per unit area that should be used for the protection component. Under lower confining stresses, a minimum mass per unit area for the geosynthetic protection component of no less than 800 g/m is recommended.
Due to the location and topography of many remedial sites, construction on steeper slopes is often necessary. With structured or textured Carbofol® geomembranes, the frictional requirements of demanding steep slope applications can be accommodated. With the proper selection and product specification, the long-term performance and optimum transmission of shear forces is assured. As a replacement to compacted clay liners, Bentofix® is also well suited for the encapsulation of contaminated areas.

To increase the versatility of Bentofix® GCLs, they can be manufactured with either polypropylene (PP) or HDPE geotextiles. When chemically aggressive materials are to be encapsulated, lining products manufactured with HDPE are best to ensure long-term resistance and performance. Regardless of the style of geotextile used, the natural sodium bentonite sealing layer is safely encapsulated between the cover and carrier geotextiles, fully capable of long-term transference of shear forces through the fibre reinforcement. The robust cover and carrier geotextiles used in Bentofix® GCLs are designed to resist the physical stresses of the installation process and prevent damage to the bentonite seal.

Earth Stabilisation
In select cases, a contaminated area may have no bearing strength and conventional construction methods are not possible. In these instances the liner system must be capable of supporting itself as well as overlying soils.

In dredged lagoons for example, the area to be sealed cannot be trafficked nor walked upon due to the lack of bearing strength in the subgrade. By first deploying Secugrid®, a monolithic extruded geogrid, it is possible to traffic over the surface immediately after installation or upon the placement of a mineral levelling layer.

As compacted clay liners are difficult to construct, and can form preferential flowpaths with only small amounts of deformation, Carbofol® geomembranes or Bentofix® geosynthetic clay liners are the materials of choice when lining over soft subgrades.

Decommissioned industrial and mine sites that possess abandoned shafts, underground voids and inhomogeneous areas with low bearing capacity, require an encapsulation system that ensures sufficient load distribution in the event of changing subsoil properties.

Secugrid® geogrids are especially well suited for these applications due to the ability of the grid mesh to interlock with the subsoil. The low initial elongation enables Secugrid® to immediately transfer or distribute stresses between the geogrid and subgrade or cover material.

With complete geosynthetic solutions from NAUE, highly efficient, low profile sealing and drainage systems can be installed that do not require substantial excavation and recompaction or the placement of voluminous mineral layers.

Slope Stability
When remediating areas on steep slopes, Secugrid® geogrids can support the down slope forces in most situations while protecting the sealing elements from potentially harmful stresses as in landfill applications. On steep or long slopes, Secugrid® geogrids can be used to improve the stability of soil veneers or entire lining systems.

Conclusions:
Complete geosynthetic solutions from NAUE are more economical than expensive in-situ treatment or excavation and removal techniques. If the available "airspace" or construction volume is limited, geosynthetic solutions from NAUE offer high performance in a low profile system. Carbofol® geomembranes and Bentofix® geosynthetic clay liners are cost-effective sealing products that are more efficient as well as economical than conventional compacted clay liners. With Secudrain® drainage systems, additional "airspace" can be recouped by effectively replacing mineral drainage layers that are 15 to 30 times thicker!

The high tensile strength of Secugrid® geogrids enables the construction of space saving steep slopes or reduction of settlements. By using Secugrid® with its rigid junctions, even extremely soft subsoils can be built upon.