Mastering Geomembrane Selection: Utilizing Standards in 3 Steps for Project Evaluation

For the most part, all geomembranes have a similar broad function: A fluid barrier. When comparing, the confusion lies in the fact that they are manufactured by different methods and constructed differently, which result in varying properties to accomplish the broad fluid barrier function. Plus, the definition of “fluid barrier” is subjective depending on a host of site, application, fluid composition and regulatory factors. Key geomembrane properties are required to support the overall function.

Various testing and industry groups have made efforts to standardize testing of geomembranes, and prepare specifications for groups of geomembranes which have at least some common properties. Organizations which have prepared such materials include those shown below.

Specification standards and test methods circulate in many forms, even with the attempts to establish standards by the organizations listed above. Unfortunately, there are multiple tests for the same properties, even for products considered to be in the same group, which have a common feature of some sort. Often, that common feature is the dominant or differentiating polymer in the composition. But there still usually exist differences in products that make it difficult to establish standards which completely allow an apples-to-apples comparison of test methods. For instance, look at two broad categories by which geomembranes are classified and often described by written standards:

Geomembrane Construction                        Geomembrane Polymer Types

Reinforced                                                      Ethylene Interpolymer Alloy (EIA)

Unreinforced                                                   High-Density Polyethylene (HDPE)

Laminated                                                       Linear Low-Density PE (LLDPE)

Coated                                                             Low Density PE (LDPE)

Extruded Film                                                 Polyvinyl Chloride (PVC)

Blown Film                                                     Chorosulfonated Polyethylene (CSPE)

Co-extruded Film                                           Ethylene Propylene Diene Monomer (EPDM)

Calendered Film                                             Polypropylene (PPE)

                                                                        Blends

                                                                        Multipolymer Layers

Not all, but most, commercially available geomembranes can fall into more than one of the categories in each column. So, a standard that specifies or describes a laminated EIA for instance, cannot be compared to a laminated CSPE or a coated EIA. A standard that specifies an EIA blend cannot be directly compared to a different EIA blend. Some laboratory test methods differ and performance in a number of categories differ. It is necessary to dig deeper into the applicability of a geomembrane standard to make sure it is meaningful.

For all geomembranes, the properties which are essential to longevity center around the broad categories of chemical/environmental resistance and survivability. All products will (or should) provide test values, minimum standards, nominal standards, approximate standards, MARV, etc. in some form to address these items. Where the reported standards fall in that list should be identified to assist in comparison and in design limitations. The essential properties are:

Chemical/Environmental Resistance                                  Survivability

Field and/or Lab test immersions                                        Yield Tensile Strength

UV Resistance                                                                        Seam vs. Sheet strength

Thermal Stability                                                                    Puncture

These properties represent the core of the definition of performance of the geomembrane.

So, how do you use standards to compare geomembranes for a project evaluation?

1. Understand the application. Identify how the geomembrane must perform and what properties provide that performance
2. Consult manufacturers on their products, how they are specifically tested to backup the properties specified.
3. Review published industry-wide standards and specifications as they apply to proprietary specifications. Keep in mind, industry wide standards are created around the lowest common denominator, and they will prescribe minimal levels of performance.

Geomembranes are some of the most cost-effective construction products available for many containment applications. Take a close look before utilizing a standard or specifying a product.

Mammoth Cave Installation

For a more in-depth look at geomembrane specifications and how they compare, visit this series: https://www.xrgeomembranes.com/blog/how-geomembranes-are-specified-part1.