Both the US Environmental Protection Agency (EPA) and the European Council Directive on the Landfill of Waste describe prescriptive cross sections for hazardous and non-hazardous waste landfill base lining systems. With complete geosynthetic solutions from NAUE, the minimum base lining standards can be easily fulfilled whileperformance can be                  significantly improved.

Sealing

The base lining is designed to prevent the escape of contaminants from landfilled waste into underlying soils. A properly constructed liner system should also allow for the controlled collection and removal of landfill leachate for subsequent treatment.

In regions where local soils are not suitable for the construction of hydraulic barriers, Bentofix® geosynthetic clay liners (GCLs) can be used to protect the hydro-geological resources by providing an effective barrier against potential risks to the environment. Typical compacted clay liners (CCLs) are difficult and expensive to build. In many cases, they are subjected to installation conditions that can cause desiccation cracking and create preferential flow paths. Bentofix® GCLs can replace or augment the typical CCL in most designs to minimise the effects of desiccation. Once covered, Bentofix® GCLs quickly hydrate with existing soil moisture to form a low permeable barrier. The quick and easy installation methods used for Bentofix® yield substantial cost and time savings when compared to expensive construction methods typically required for compacted clay.

When used in combination with Carbofol® HDPE geomembranes, Bentofix® GCLs can achieve superior hydraulic performance with exceptional intimate contact. Also, this

can minimise the lateral flow of leachate in the unlikely event of a puncture. A composite liner system incorporating Carbofol® and Bentofix® as the independent sealing elements is extremely effective when containing both polar and non-polar contaminants.

As Bentofix® geosynthetic clay liners (GCLs) are needle-punched over their entire surface area, they are capable of transmitting shear forces on steep slopes as well as within base lining systems. Bentofix® products produced with needle-punched nonwovens on both outer surfaces (one always scrim reinforced) can be used to achieve higher interface friction angles and shear strengths.

When constructing the base liner system of a municipal or hazardous
waste landfill, Carbofol® HDPE geomembranes can be used to protect and
seal the subsoil from the release of potential contaminants. Carbofol®
smooth-surfaced, 2 mm thick HDPE geomembranes are well suited for the
lining of landfill base seals with slopes up to 9h:1v. Carbofol®
megafriction geomembranes have an embossed structure and are suitable
for more demanding slope conditions.

A project-specific analysis should be performed, including direct
shear testing, to confirm slope stability calculations. During the
manufacturing process, the embossed surface structures are added
directly to the layer of pliable HDPE Carbofol® geomembrane by a molding
process. This step creates a homogeneous structured geomembrane made
from a single material or resin, maximising the product shear strength
characteristics.

Protection

High quality protection geotextiles limit geo membrane damage and
deformation during instal lation as well as during subsequent
operational use.

When properly selected, Secutex® needle-punched polypropylene (PP)
nonwovens are capable of preventing the puncture of Carbofol®
geomembranes under the most demanding conditions.

Depending on the nature of the landfill cover layer, the grain size
and the shape of the drainage layer, various protection systems can be
used (e.g. for fine gravel).

Assuming a well compacted subgrade, a CCL or a Bentofix® GCL, a 2 mm
thick HDPE geomembrane and a 30 – 50 cm thick leachate collection layer
with 8 mm to 32 mm gravel, the following guide can be used to determine
the mass per unit area for the Secutex® rotection layer:

    Design cross sections

 

Height of waste Mass per unit area of Secutex®
15 m 800g/m2
25 m 1,200g/m2
35 m 2,000g/m2
50 m 3,000g/m2

Prior to the utilisation of a nonwoven for puncture protection, puncture tests similar to the cylinder test (EN 13719) are recommended with site-specific materials and the test protocol as specified by the design engineer.

Reinforcement

Long-term slope stability can be obtained with Secugrid® geogrids, when used either alone or in conjunction with other geosynthetic materials. When used with a geomembrane, Secugrid® reinforcement products can support the down-slope forces while protecting the Carbofol® geomembrane from potentially harmful stresses.

The low initial elongation and the interlocking nature of the Secugrid® with mineral drainage layers ensures immediate stress transfer and avoids installation deformation. The relatively thick, flat, monolithic elements of the Secugrid® provide structural security with all normal installation loads.

Conclusion

The repair or remediation of a base liner is technically difficult and expensive. It is for this reason that high-quality products, which can ensure long-term performance, need to be selected during the design phase of a project.

With complete geosynthetic solutions from NAUE, your next lining system will have the latest in geosynthetic innovations and the quality you need to ensure long-term performance.

NAUE can provide the ideal combination of geosynthetics for any project. A wide selection of geosynthetic products and styles allows efficient, project-specific solutions for even the most challenging applications.