What are Geomembranes?

What exactly are geomembranes, and why are they useful? 

Polymeric geosynthetic barriers (colloquially “geomembranes”) are, by definition: factory-assembled structures of low-permeability synthetic materials in the form of a sheet, which acts as a barrier to control or mitigate fluid or gas migration into the environment. They are often used in landfills, ponds, coal refuse containment, and other applications to provide a barrier between the soil and possible contaminants (1, 2). 

Geomembranes are known for their durability, flexibility, and resistance to chemicals and temperature changes, making them ideal for many environments. With the ability to prevent soil and groundwater contamination and provide a barrier against harmful vapors, geomembranes play an essential role in protecting the environment and human health.

In this guide, we will explore geomembranes, their properties, applications, and their future.

What are Geomembrane Advantages

Geomembranes are commonly made from raw polymer resins, such as high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). They are processed into sheets of various widths and thicknesses by extrusion (1). 

Geomembranes derive many of their properties from their resin. HDPE and LLDPE resins are often mixed with various additives such as antioxidants, plasticizers, fillers, carbon black, and lubricants to alter their performance under different conditions. For example, carbon black helps improve resistance against ultraviolet radiation (UV), and antioxidants help improve the material’s ability to resist chemical processes that degrade it over time (3-5).    

HDPE geomembrane is one of the cheapest, most widely used geomembranes made from a blend of polyethylene resins and other additives. They are known for their high strength, low cost, and high chemical resistance, making them suitable for use in various landfills and hazardous materials containment.

One of the benefits of HDPE geomembranes is their customizability while possessing sufficient stiffness and strength, enabling them to conform to irregular surfaces and maintain their integrity even when subjected to stress or movement. Due to their high strength and durability, they are suitable for use in applications requiring long-term performance, such as the construction of waste management sites or tailings ponds in the mining industry. Another important fact is that HDPE is “food safe” and PFAS-free, making it the ideal geomembrane for conveying clean water to communities and farms. Finally, HDPE geomembranes are frequently recommended over other types because of their cost efficiency and operational advantages (6).

Geomembranes possess high tensile strength, durability, and chemical resistance, making them an ideal solution for many environmental and geotechnical applications. Additionally, they are lightweight, flexible, and easy to install, which helps reduce construction time and cost.

Table 1. General Geomembranes Properties.

Property	Description
Chemical Resistance	Geomembranes are resistant to most chemicals and acids, making them suitable for use in containment applications.
Weldability	Geomembranes can be easily welded together, which makes it possible to create large, seamless covers and liners.
UV Resistance	Geomembranes can be formulated to withstand UV radiation, which helps them maintain their physical properties and integrity over time.
Permeability	Geomembranes are highly impermeable, which prevents the movement of liquids and gases. This is a critical property for applications where liquids containment, such as landfills, is essential.
Durability	Geomembranes are strong and durable and can withstand the weight of soil and other materials, as well as repeated bending and puncturing.
Thermal Stability and Resistance	Geomembranes have high thermal stability, making them suitable for use in hot environments, such as power plants. Their high operating temperature range also allows them to be used in environments with frequent fluctuations in ambient temperature.
Flexibility	Geomembranes possess good flexibility, which allows them to conform to the contours of the ground and other surfaces, making them easy to install. They also respond well to environmental strains, such as differential settlement.
Lightweight	Geomembranes have lightweight, making them easy to handle and transport.
Ease of Repairing	When a puncture or tear occurs, geomembranes can be simply repaired using welding techniques, minimizing downtime and reducing costs.
Environmentally Friendly	Geomembranes are made of non-toxic materials, making them environmentally friendly and safe for use in sensitive areas.

Cost-Effectiveness and Low Maintenance

Geomembranes come with the economic benefit of being relatively easy to install, lightweight to transport, durable under many conditions, and versatile to support various installation and project conditions. This is in stark contrast with traditional materials such as clay barriers. 

For landfill closures and containment projects, direct and indirect costs should be considered when preparing an HDPE liner cost estimate. Costs include the purchase price and the cost of transporting, installing, and maintaining the liner. Liner monitoring and maintenance is one aspect that is often overlooked but is essential when calculating the liner’s total cost throughout the project’s expected lifetime. Read more about HDPE liner costs here. 

Geomembranes are weldable and easy to maintain. With the right tools, it is straightforward to implement a leak-detection system. Geomembranes can also be manufactured as wider rolls, up to 23 ft (7 m) cores, significantly streamlining the installation process. 

LLDPE geomembranes are similar to HDPE geomembranes but provide different technical benefits. LLDPE is more flexible than HDPE, with increased tensile and elongation properties (6).  

Flexibility

Geomembranes are flexible barriers that support applications such as landfills, containment ponds, and wastewater treatment facilities. They are also thermally stable, making them suitable for use in high-temperature environments, and they retain their properties and remain flexible at low temperatures. Geomembranes are flexible, lightweight, and simple to repair, making them an excellent choice for waste-proofing (6). Moreover, they are made of non-toxic materials and are eco-friendly. 

Finally, geomembranes can be combined with other geosynthetics, such as geotextiles, conductive geomembranes, or textured geomembranes, for more functionality.  

Applications of Geomembranes

Geomembranes have gained widespread use across many industries due to their versatility and ability to provide an effective containment solution. 

Coal Combustion Residuals (CCR)

Coal is still a significant source of electricity in the United States, providing more than 20% of the country’s power—second only to natural gas. Burning coal to heat water that powers steam turbines produces coal combustion residuals (CCR), a byproduct typically disposed of or beneficially used. In 2014, at least 46 million tons of coal ash were beneficially used, accounting for about 40% of all CCR produced. The rest is sent to landfills or specialized ponds for disposal.

Geomembranes can help create safe storage areas for CCR. Today, due to a regulatory amendment by the U.S. Environmental Protection Agency (EPA) in 2015, there are more opportunities to reuse CCR. Visit the CCR application page for more information.

Landfill Closure

Landfill containment is a complicated business. Regulations, leachate and gas production, elevated temperatures, chemical reactions, and liner degradation are considerations that engineers must make when designing a landfill containment system. Add to that the complexity of closure and post-closure care, and it becomes clear why new and better solutions are needed.

One of the most important steps when installing a new landfill or final cover system is selecting a geomembrane manufacturer. The manufacturer must also adhere to best practices or industry norms, which exist after years of trial and error. These practices can ensure your project’s success and impact your bottom line. Geomembranes are used in waste management as liners in landfill containment. They are also used in landfill closures to control odors and gas emissions. Visit the landfill closure application page for more information.

Mining and Ponds

Modern technology depends on extracting valuable elements such as lithium, magnesium, and cobalt from mining. Precious metals such as gold, silver, and copper are equally important. Whether operating an evaporation pond or heap-leaching ore, geomembranes are essential.

Geomembranes and other geosynthetics are utilized throughout many mining operations, serving as the base liner system in tailings storage facilities (TSF), heap leach pads (HLP), ponds, and channels and for HLP, TSF, and waste rock closures (9, 10). Visit the mining application page for more information.

Civil

Civil projects utilize geomembranes, from tunnels and water systems to dams and landfills. Geomembranes in these projects help control costs and speed up installation times while protecting existing structures or the surrounding environment. Geomembranes join the other geosynthetic products to solve a host of project challenges. 

Moreover, geomembranes are utilized in the geotechnics sector to overcome failure load, deformation, and flow issues (9, 11). Visit the civil application page for more information. 

Installation and Maintenance

Geomembrane installation depends on the application. Each installation will have regulations and requirements associated with its installation.

Landfill Installation

For example, when planning the installation of a new municipal solid waste landfill (MSWLF), three important federal requirements must be met: groundwater monitoring, closure and post-closure care, and financial assurance. These requirements are in addition to state regulations under the Resource Conservation and Recovery Act (RCRA). Navigating these regulations can be time-consuming, but it doesn’t have to be complicated. All regulations boil down to one essential function that must be built into all landfills: containment.

The federal requirements for groundwater monitoring highlight the importance of ensuring landfill leachate does not contaminate groundwater sources. Geomembranes are among the best tools engineers can use to help ensure landfill containment. Please review our guidelines for more information about landfill installations. Also, consider our views on the landfill liner thickness.

Pond Installation

Ponds are a common construction type that serves everything from ecological needs to decorative functions. They are also used in water treatment, thermal storage, and farming. One of the most critical considerations in pond design is ensuring containment by adding a geomembrane. 

Because pond site conditions can vary significantly, site preparation is the first step that should be taken when installing geomembranes. Site preparation includes ensuring, when possible, that the site does not experience flooding or high ground water pressure. The bottom of the pond should also be above the water table. Additionally, soil conditions should be inspected to anticipate gas buildup and determine whether a venting system should be installed.

Once the site is considered suitable for pond construction, the area should be cleared and leveled. An essential step is the removal of sharp rocks and other objects, such as vegetation and stubble, from the subgrade. The goal is to ensure intimate contact between the HDPE geomembrane and the subgrade, which helps improve the long-term performance of the pond liner. Read more about installing HDPE pond liners.

Challenges

Geomembranes are ubiquitous outdoor construction materials used as a liner against the encroachment of undesirable elements. But even this synthetic material undergoes significant expansion and contraction throughout the day-night cycle. For this reason, many discussions surround distinctive waves occurring throughout the plane of a laid geomembrane liner due to thermal expansion.

The EPA only recognizes the efficacy of composite liners in “direct and uniform contact” with the underlying compacted soil. There are several ways to deal with thermal expansion and achieve intimate contact. Some strategies adapt to thermal expansion, while others avoid it altogether.

One of the most common adaptive strategies is to push, accumulate, cut, and seam. With this approach, a lift of backfill soil is pushed forward using a bulldozer. The height of the wave grows as the wave is driven. Eventually, the wave of these layers grows so large that the backfilling process cannot continue. At this point, the waves are cut along their crests. The excess material is then folded over and seamed using extrusion fillet welding (12).

Other techniques include using a flat sheet between fixing berms; replacing black geomembrane coatings with a reflective white coating; using a temporary tent over the placement area; and working with nature (12). The last three options are examples of strategies to avoid thermal expansion. Learn more.

The Future of Geomembranes

Geomembranes are constantly evolving, from new design enhancements to improving construction quality control. One example is CleanSeam^®, an integrated geosynthetic release film that mitigates the risk of particle buildup by protecting the geomembrane weld edges from exposure to field conditions.

The negative impacts of dust and debris on geomembrane seams are well understood. When fine particles build up in the geomembrane seaming areas during on-site storage during deployment, it is necessary to clean the area of contaminants before welding. Reducing contamination in applications that include higher concentrations of fine particles, such as coal ash residuals for fine subgrade soils, is challenging. CleanSeam, an integrated geosynthetic release film, mitigates the risk of particle buildup by protecting the geomembrane weld edges from exposure to field conditions. The CleanSeam protective strip is removed directly before seaming, leaving no residue behind, just a clean geomembrane.

Summary

• Geomembranes are synthetic, waterproof barriers used to control fluid or gas migration in the environment, commonly made from high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE) resins.
• They are commonly used in environmental applications, such as the containment of hazardous waste, the separation of contaminated soil and groundwater, the protection of water resources, and reinforcement in retaining walls, slopes, and embankments.
• Geomembranes possess high tensile strength, durability, and chemical resistance, making them an ideal solution for many environmental and geotechnical applications. Additionally, they are lightweight, flexible, and easy to install, which helps reduce construction time and cost.
• The durability of geomembranes refers not only to the physical strength of the material but also to the rate of oxidation, which is influenced by temperature, oxygen concentration, and the chemical composition of the surrounding media.
• Geomembranes are cost-effective and low-maintenance compared to traditional materials such as clay barriers and can be welded and easily maintained with the right tools.