Former landfills and contaminated sites are often capped and remediated. These engineering works may also include beneficial reuse of the sites. On-site contaminants and the uneven settlement in the ground above these former waste cells present a number of geotechnical challenges. As such, capping measures generally are selected for their ability to isolate and contain contaminants. Closure measures may also be evaluated on their ability to increase the site’s load bearing capacity for safer reuse.
Capping systems for former waste cells and contaminated sites must be of the highest quality. This is especially true when land reuse is planned (e.g. for playgrounds, public gardens, sport fields). If a more commercial reuse is targeted, such as a parking lot, or if a trafficked route will pass over any part of the land, a higher load capacity is required. Not infrequently, steep slopes must be rebuilt to save space or to properly function within a reuse design.
Geosynthetic capping systems allow for the efficient use of local soils. When considerable land might need to be reformed if external soil sources are required, the ability to use the local site’s soils can provide considerable savings in the construction process, both from a materials acquisition standpoint and in terms of greatly decreased construction timelines. Expensive decontamination measures might be avoided. The reduction or elimination of heavy transport of external material saves not only on cost but on a project’s carbon footprint.
Geomembranes and geosynthetic clay liners encapsulate contaminated areas safely and permanently, mitigating or eliminating pollutant discharge.
These geosynthetic barriers, as rolled goods, can be installed efficiently. Their many product variations, supported by high quality raw materials, allow them to be targeted to site-specific challenges, such as the aggressiveness of the contaminants to be contained, the site topography, precipitation variations and much more. And, compared to traditional sealing solutions (e.g., compacted clay and other in-situ ground improvement measures), geosynthetic systems are significantly thinner yet provide as great or more security. This advantage presents savings in capping costs and enables a site to maximize its storage volume prior to closure.
Geogrid reinforcement is used on these sites as well to enable traffic or construction atop soft soils or to stabilize zones against collapse. Nonwoven geotextiles, including nonwovens embedded within a geogrid, maybe also be used to provide separation and stabilization of soils.
To achieve a better ecological, economical and performance-related GCL for encapsulating contaminated sites a multi-component Bentofix® GCL with an impermeable polyethylene coating can be used. It helps make GCL installations even more effective, safer and longer lasting as two barrier systems are installed in one step. The multi-component Bentofix GCL improves the overall performance and reduces the risks of a single lining system.
Carbofol® HDPE geomembranes encapsulate contaminated areas. They are chemically resistant to contaminated soils. Textured (structured) Carbofol® geomembranes allow strong seals on challenging grades, such as with steep slopes. Smooth Carbofol® is used in slopes up to 1:9 while the homogenously textured varieties are used for steeper installation zones.
Bentofix® geosynthetic clay liners (GCL) are needlepunched and fixed with NAUE’s Thermal Lock process. This firmly bonds the two layers of geotextile and the internal core of high-swelling sodium bentonite powder. The bentonite is encapsulated and protected against piping, as Bentofix® is needlepunched across its entire surface. Bentofix® replaces more expensive, thicker mineral sealing components. These GCLs are resistant to drying and installation damage. The bentonite core’s swelling characteristic gives it a self-healing property. The internal shear strength of Bentofix® also enables its use in steeper slope designs.
Secutex® nonwoven geotextiles protect geomembranes from damage, such as from improperly coarse and angular aggregate layers. Secutex® prevents the mixing of different soil layers and provides filtration of leachate.
Secugrid® and Combigrid® geogrids bridge voids in subsoils and redistribute loads efficiently. They enable space-saving steep slopes and construction atop soft soils.
Combigrid® is a composite reinforcement material, featuring a nonwoven geotextile embedded within a geogrid. This construction provides separation and filtration functions of Secutex® and the high-strength reinforcement of Secugrid® in a single product.
Secudrain® is a powerful, durable drainage material with additional filtering and protection functions.