Geomembranes can be found in landfill engineering, mining heap leach pads, aquaculture ponds, canals, reservoirs, waste water lagoons, biogas digesters, and agricultural irrigation systems. Their main function is to prevent leakage of liquids or gases and keep soils and groundwaters free from contamination.

Even premium specs of HDPE geomembrane and LLDPE geomembrane membranes can be ruined when contractors botch the installation. Flimsy seam welding, insufficient preparation of the subgrade, poor anchoring and similar issues can result in problems of leakages, liner vandalism, expensive future repairs.

This guide covers the total geomembrane installation process step by step, from site preparation through to testing and final inspection.

What Is Geomembrane Installation

Involving the suitable laying, welding together, anchoring and testing of impervious liner materials upon a prepared subgrade surface, to produce a dependable liner.

Common geomembrane materials

• HDPE geomembrane
• LLDPE geomembrane
• Textured geomembrane
• Smooth geomembrane

Installation procedures will vary based on the type of project, the climatic and atmospheric conditions which they have to function within, the gauge of the membranes, and the way in which they are to be applied.

Applications of geomembrane liners

• Landfill liners
• Mining heap leach pads
• Aquaculture ponds
• Canals
• Reservoirs
• Dams
• Waste water lagoons
• Biogas digester covers
• Industrial containment ponds
• Root Barrier Systems

Step 1 — Inspect Project Site

Before the start of any installation works, it is necessary to thoroughly inspect the following:

• Soil
• Ground Conditions
• Drainage
• Conditions on the ground
• Weather
• Slope of Installation
• Access to the Equipment
• Laying Out Liners

A good layout of the area to be covered assists in eliminating excess material

Weld Inspections

Step 2 — Subgrade Preparation

Correct subgrade preparation is one of the most important parts of the geomembrane installation procedure.

The subgrade should be:

• Smooth
• Compacted
• Dry
• Free of protruding sharp stones
• Free of roots and other debris
• Stable and drained

Variances will lead to puncturing the installed geomembrane and there will not be time for re-excavating the problem area and repairing before placing the geomembrane.

Low or “soft” areas of turf can cause the “soft spots” to affect the pleasing appearance of the finished liner.

For landfill and mining jobs and the like, installers often place a geotextile cushion between the subgrade and the geomembrane.

Step 3 — Anchor Trench

Anchor trenches are excavated to “anchor” the geomembrane around the perimeter of the project site.

The size of the trench will vary, and depend upon:

• The angle of the slope
• Expected action of the wind
• Thickness of the liner
• The scope of the job

Installers usually excavate the trench all the way around the edge of the pond, landfill or reservoir before the liner is laid in place.

With the liner placed, workers position the edge of the geomembrane within the trench and backfill it with compacted soil.

Step 4 — Placement

The installers begin to unroll the geomembrane panels in accordance with the approved drawings and layout plan for the project.

Avoid the following:

• Drag the geomembrane across the ground.
• Minimize any equipment interference to prevent the equipment from dragging the liner across rough ground or where plant marks can be made on the geomembrane.
• Minimize use of machinery that will not hold the liner tight in shaping it in place.
• Don’t handle in such a way that the liner is bent over in such a fashion that wrinkles occur.

With accurate thermal “spacings” during placement, it will be simple to snap out adjacent areas.

Maintain all panels running in the same direction to facilitate welding.

Calmer weather conditions make for easier work.

Agitation by heavy wind makes for hard work attempting to control a large sheet of geomembrane.

Step 5 — Panel Alignment and Overlap

Once the geomembrane panels are deployed, workers position adjacent panels next to each other for alignment before welding.

Overlap between panels will only require a typical width of some 100 to 150 mm (4” to 6”).

Keep overlap areas:

• Clean
• Dry
• Free of dust
• Free of moisture

Poor overlap alignment can result in weak weld seams.

Step 6 — Geomembrane Welding

Proper seam welding forms the heart of a geomembrane installation.

The two principal methods of welding are:

• (Hot wedge) welding
• (extrusion) welding

Hot wedge welding is the preferred method of installation for HDPE geomembranes.

The benefits of this method are:

• Strong double-track seams
• High speed of installation
• Cock-up seams and other defects are frequently taken out, resulting in a reduction in seam-making time
• Generally good zips, resulting in a quality weld seam
• Hot wedge welding automatically regulates heat input under differing site conditions
• Speeds up the work
• Speed of work is important since the time-dollar ratio is more heavily weighted towards the person performing the work
• Posts advantages, extrusion welding

Contractors mainly use extrusion welding for:

• Pipe connections
• Repairs
• Corners
• Detail work

An experienced technician should carry out all extrusion welding work.

In order to maintain welding conditions, workers must thoroughly clean surfaces tha4’ become contaminated in the process of work.

The optimum welding temperature, speed and pressure will depend upon:

• The thickness of the geomembrane
• The ambient temperature
• The material being welded
• The condition of the surface to which the geomembrane is welded

Step 7 — Workmanship and Quality Control for Seams

For seams that have been made, tests and inspections should briefly be made by technicians.

Typically tests used in the geomembrane industry include:

Air Pressure Test

This method is employed mainly for double-track weld seams.

Pressure loss indicates a defective seam in most instances.

Vacuum Box Tests

This method is more applicable to an extrusion weld and areas of repair.

Spark Test

On conductive geomembrane systems spark testing is used by technicians.

Destruction Tests

Small samples of the seam area are cut out and the following

Subsequently tested for:

• Peel strength
• Shear strength

Quality plays a vital role on landfill and mining projects as leakage will spoil the work and costs the system as a whole.

Step 8 — Repair Work

If upon testing a failure occurs, the defect should immediately be repaired by; either:

• Extrusion patch welding
• (also “administer a spot repair” and/or)
• Implementing a further layer (cap stripping)

Retesting the areas mentioned prior to tattooing.

Step 9 – Final Inspection

Once the last panel has been installed, inspectors should check the entire geomembrane system for:

• Seam quality
• Anchor trench completion
• Surface damage
• Wrinkles
• Pipe penetrations
• Repair locations

Most projects also require a complete installation report documenting the above.

Weather During the Installation of a Geomembrane

Bad weather can damage geomembrane installations.

Examples of weather conditions to avoid include:

• Heavy rain
• Strong winds
• Sandstorms
• Extreme temperatures

Wet surfaces can weaken the weld seams, while hot weather may create thermal expansion problems while placing geopanels.

Common Geomembrane Installation Mistakes

• Poor earthworks (sharp stones, rubbish, uneven site)
• Poor seam cleaning inside overlaps (dust or moisture)
• Wrong welding settings
• Failing seam tests
• Anchor trenches poorly designed or located, preventing opportunity to seal liner on slopes as it moves subsequently

HDPE Versus LLDPE for Geomembranes Being Installed

Both HDPE and LLDPE have advantages, depending on the application.

Common HDPE Applications Include

• Landfills
• Mines
• Industrial containment facilities

Advantages:

• Very difficult to split
• Strong chemical resistance
• Very good UV resistance

Common LLDPE Applications Include

• Aquaculture ponds
• Decorative ponds
• Agricultural reservoirs

Advantages:

• Good flexibility
• More difficult to welding panels

Installation procedures are similar although welding settings may differ.

Importance of ASTM with the Installation of Geomembranes

Most geomembrane projects within the UKHi and abroad are installed to ASTM specifications.

How do ASTM Standards Help?

ASTM standards improve:

• Quality control
• Weld consistency
• Testing methods
• Long-term performance

A reliable geomembrane manufacturer will be able to tell you if their products are compliant with ASTM standards or if they can pass third-party ASTM testing.

How Long do Properly Installed Geomembranes Last?

If properly installed, HDPE geomembranes can remain in service for decades.

The life expectancy of the sites primarily depends on:

• UV exposure
• Chemical exposure
• Material thickness
• Installation quality
• Maintenance conditions

What is clear is that there are good materials and bad geomembranes, but that the actual process of installation affects long-term service just as much as the quality of the material itself.

Final Thoughts

Geomenbranes have a life beyond laying liner sheeting sheets onto the ground and watching as they do some magic to turn into an impermeable mass; the entire process involves:

• Site preparation
• Sheet deployment
• Welding
• Testing
• Anchoring
• Inspection

Each of the steps in the installation process will affect the long-term performance of the containment system.

Well installed geomembranes will:

• Reduce risk of leakage
• Protect valuable sources of groundwater
• Improve environmental regulatory considerations for newly installed liners
• Extend the liner’s lifecycle
• Reduce maintenance and operating costs

Whether you’re involved in capping landfills or install them on fish ponds, in mining projects or water reservoirs, proper geomembrane installation plays a significant role in the long-term success of the project.

FAQ

Are there, for instance, minimum distance for geomembrane sheets when welding?

Yes. The general recommended overlap is widths of around 100 mm to 150 mm (4 inches to 6 inches), although they will vary.

What is the best kind of weather for the installation of geomembranes?

Kindly aim for dry weather with lowered wind speeds and moderate temperatures.

How does one engage to test the seams of geomembranes?

Common practices are air pressure testing, vacuum testing, and spark testing, along with more intrusive methods like destructive peel tests and shear tests.

Will you install on slopes?

Absolutely. Often geomembranes are installed on the slopes in landfill, mining, and reservoir work. Just be mindful of your anchoring system.

What would be the optimum type of geomembrane for fish-ponds?

Many opt for LLDPE geomembranes for these applications as they tend to provide good flexibility and.

What is the optimum thickness for liners?

The brunt of geomembranes installed are from the 0.5mm – 2.5mm region depending on application.