Geosynthetic Clay Liners

What is a GCL?

A geosynthetic clay liner (GCL) is comprised of two geotextiles that are needlepunched together, encapsulating a layer of sodium bentonite clay between them. GCLs are known for having consistent, very low permeability. They have the unique ability to seal around penetrations, self-heal punctures, and self-seam at the overlaps.

What makes CETCO GCLs unique?

• Durable needlepunched reinforcement ensure that CETCO GCLs can withstand shear stresses on steep slopes. The high needlepunch density provides higher peak internal shear strengths, without relying on supplemental processing.
• Granular bentonite creates less dust during installation than powdered bentonite and is less likely to shift through the needlepunch reinforcement process resulting in consistent hydraulic performance.
• Supergroove™ technology is a groove in the nonwoven fabric that allows the bentonite to migrate out and self-seam at the overlap. This feature eases the installation process by eliminating the need for supplemental bentonite and the additional labor to apply it.
• Lamination capabilities to provide composite geomembrane-GCL products.

What are the advantages of a GCL over compacted clay?

• Self-healing and self-seaming - Sodium bentonite is a naturally occurring clay with a high affinity for water. When hydrated, sodium bentonite swells up to 15 times its original volume. This provides the ability to seal around penetrations, self-heal punctures, and self-seam at the overlaps.
• Better hydraulic performance - GCLs have a total thickness of less than one inch and provide better hydraulic performance than several feet of compacted clay. A fully hydrated GCL typically has a permeability of 5 x 10^-9 cm/sec, approximately 20 times lower than a typical compacted clay liner permeability.
• Resistant to varying weather conditions - GCLs are less likely to be impacted by freeze-thaw or desiccation-rewetting cycles. Freeze-thaw cycles frequently cause compacted clay liners to crack and lead to increased leakage. A geosynthetic clay liner provides consistent performance and is not subject to performance decreases resulting from varying moisture content, density, or clay content, like compacted clay liners.
• Ease of installation and increased air space - GCLs are an environmentally friendly alternative to clay liners because they require significantly less installation effort than a compacted clay liner. One truckload of GCL is equivalent to 150 truckloads of compacted clay, thereby using up fewer natural resources. When a GCL is used in place of a thicker compacted clay liner it also takes up less air space, which leaves more room for waste.

GCL Selection Process

When designing a GCL, it is imperative that a leachate sample is obtained and submitted for testing as early as possible in the design process to ensure the proper solution is selected.