Geomembranes are used for a variety of applications and there are many materials and construction methods designed to suit site-specific needs for each application. We will discuss the proper application, strength, and weakness of each class of geomembrane to help you determine which product class is suitable for your individual project.
Types of Geomembrane:
- Geosynthetic Clay Liner
- Thermoplastic Sheet Liner
- PVC Liner
- EPDM (Rubber Liner)
- Concrete Geocomposite Liner
Geosynthetic Clay Liner (GCL)
GCL products are an exceptionally resilient and easy to install option compared to many other alternative products. A GCL product has the ability to self-seal punctures, burp gasses trapped underneath the liner system, and even heal up to a 2” plug through the system if installed properly. This system does, however, require that the containment area is over excavated by 12” to allow as much sand cover in order to achieve it’s desired properties. This is because a GCL is two geotextiles encapsulating a sodium bentonite (clay) layer that will swell when hydrated. This 12” sand cover is required to maintain pressure in that layer so that any punctures will result in the clay layer seeping out and around the penetrating object.
As a result of that mandatory cover, we will often not recommend a GCL alone if there is a lot of tidal, wave, or channelized flow activity in the containment area as the migration of cover could result in a failure of the system. In these cases, we will often recommend either a different system entirely or the GCL as a form of secondary containment underneath a solid sheet liner that will not be susceptible to scouring.
Thermoplastic Sheet Liner (TPO)
TPO liners are often used in situations where either cost savings is a goal, or there is a risk of exposure to chemicals or pH levels that are not within the stable range of other liner types. There are TPO liners that vary in chemical resistance, and there are even options to incorporate an EVOH barrier to prevent fuel from vaporizing through the liner when the containment is protecting sensitive material such as geofoam.
TPO liners can not self-heal like a GCL, so they often require cushion protection from punctures on one or both sides of the layer. There is a wide range of puncture, tear, and abrasion resistance from very low to extremely high in this product class, and that is reflected in the price when you’re choosing a material. These products can be smooth, textured, and reinforced to custom fit the site-specific need that it’s intended for.
TPO liners can be custom fabricated in our factory, or they can be field-seamed. Fabrication in the field requires the use of special tools with typically range in excess of $10,000.00 and needs a trained operator. Cherokee can provide a connection to a reputable contractor if field installation is required.
PVC Liners are among the most user-friendly products to install and are typically what we recommend on ornamental pond projects as the geomembrane. PVC has a very low puncture resistance, so it is necessary to protect this with a cushion layer (typically a nonwoven geotextile) to offer insurance against abrasion, puncture, and tearing.
PVC liners can be chemically welded at the seam using products supplied with the material, and this makes it an easy choice for many smaller projects and landscape applications where there is going to be plenty of management on the system and DIY repairs may be necessary.
EPDM (Rubber) Liners
EPDM liners are what can be considered the bigger, tougher, more expensive brother of PVC liners. They have a higher puncture resistance than PVC and can be provided with reinforcement so they have a MUCH higher tear and abrasion resistance. Yet they can still be chemically welded at the seams and they are just as flexible and easy to repair as PVC. We typically recommend this product for more critical applications like green roof design, large residential ponds, and waste containment for livestock/aquaculture production.
Concrete Geocomposite Liner
These are a newer product line than many of the others and although their cost is much higher than any alternative product, they are the toughest product out there, especially when used in conjunction with a TPO liner to contain hazardous waste.
There are two construction methods for these. One is a pre-fabricated ready mix fabric that simply needs to be hydrated to cure. And the other is a quilted geotextile that must have liquid grout pumped into it as fill on the site or ships as a prefabricated until after curing off-site. We determine which product is used based on quantities needed, proximity to a ready mix plant, and what the application is. But our normal applications are:
Very high-risk slopes that need to remain stabilized and won’t see a lot of maintenance or inspection, such as a bridge abutment, or high flow channels in a right of way.
Primary containment on large ponds or liquid containment that will be subject to foot traffic, wave action, or high winds.
Please let your local sales rep know your specific site conditions and goals with your geomembrane and we would be glad to provide preliminary design ideas that can help you have a successful and maintenance-free system!