The usefulness of a pond liner is largely figured in terms of how long it lasts. And while the details may vary between clean-water pond, irrigation reservoir, wastewater lagoon, mining/industrial pit, or other containment application, the basic principles for longevity are similar.
Here are things to consider and provision for to make sure your pond project endures without degrading significantly.
Physical Damage
One threat is often mechanical rather than chemical. Rocks, gravel, roots, construction equipment, animals and even accumulated debris can abrade or puncture a geomembrane. Where the liner is exposed to potentially damaging elements such as these, a protective geotextile or cushioning layer can be installed between the liner and the source of abrasion.
In some applications the liner itself may be covered with soil, sand, concrete, aggregate or another protective layer. The choice has to be appropriate to the particular liner; simply putting rocks on top of a membrane can create a new source of damage.
It’s also important to control what happens around the pond. Vehicles and heavy equipment should not be allowed onto areas where they could contact the liner or degrade the pond banks, and boundaries should be prominently labeled.
Sunlight and UV Exposure
Ultraviolet radiation gradually degrades many synthetic polymers. This is particularly relevant where a liner remains exposed around the shoreline or throughout an uncovered containment facility.
Some geomembranes have excellent UV resistance and can remain exposed, while others benefit substantially from being covered. Some containment pits and ponds are temporary. Selecting a liner designed for the intended exposure is part of the planning equation.
Where practical, covering the membrane can provide additional protection. But the cover material and installation method need to be designed so that they don’t in turn promote punctures, abrasions or excessive load burdens.
Vegetation Control
Roots are an obvious concern when vegetation grows through or beneath a liner. Trees and large shrubs should generally be kept away from lined ponds and containment structures, particularly around slopes, edges and drainage systems.
Vegetation growing above the liner can also become a maintenance problem. A small plant isn’t necessarily going to penetrate a properly installed geomembrane, but extensive root growth, dead vegetation and organic accumulation can create mechanical stresses and make inspection more difficult.
Animal Control
Burrowing animals can be surprisingly destructive. Muskrats, nutria, crayfish and other animals can burrow into banks or beneath liners, while livestock can puncture exposed membranes with hooves.
Animal management therefore becomes part of liner maintenance. Keeping burrowing species under control and preventing livestock from accessing vulnerable liner surfaces can eliminate a source of damage that isn’t related to the liner material itself.
Water Level Management
Large or rapid changes in water level can expose portions of the liner that normally remain underwater, increasing their exposure to UV, temperature fluctuations and mechanical damage.
Conversely, water outside the containment area can produce uplift pressure beneath the liner, whether from migrating groundwater or spillage from the pond. Proper drainage around and beneath the installation is therefore important throughout its service life, not just during construction.
Maintaining appropriate water levels and keeping perimeter drainage functioning can reduce stresses that otherwise accumulate over time.
Chemical Monitoring
For industrial ponds, wastewater lagoons, agricultural applications and other non-potable uses, chemical compatibility is a major consideration.
A liner may be resistant to the fluid or material being stored under normal conditions, but be vulnerable to a particular chemical, concentration, temperature or combination of substances. The same applies to cleaning agents, disinfectants and other chemicals introduced during maintenance.
If the contents of the pond change during the life of the installation, recheck chemical compatibility rather than assuming the original liner remains suitable. Whether clean or toxic contents, pond chemistry will always matter.
Temperature Monitoring
Temperature affects virtually all geomembranes. Heat can increase expansion and contraction, while repeated thermal cycling can contribute to long-term stress.
This is another reason not to install a membrane under excessive tension. Properly designed seams, anchors and allowance for movement give the liner room to accommodate changes in temperature and settlement.
For industrial applications, the operating temperature of the contained material should be considered when selecting the membrane in the first place.
Inspection
A layer of sediment, trash, algae or organic material can hide developing problems. Periodic inspection is therefore one of the simplest forms of preventive maintenance. The important point is to find small problems while they’re still small.
Look for cracks, holes, tears, abrasion, unusual wrinkles, exposed edges, seam separation, bubbling, settlement and changes in the surrounding ground. A change in water level that cannot be explained by evaporation or normal use may also warrant investigation.
Erosion
The perimeter is one of the most vulnerable parts of a lined pond. Rainfall, runoff, wave action and fluctuating water levels can erode soil around the anchor trench or expose the edge of the membrane.
Maintaining drainage channels, slopes, vegetation where appropriate, riprap or other erosion-control measures can prevent the surrounding earthwork from gradually compromising the liner. Don’t neglect the liner after construction—probably the biggest long-term mistake is assuming that a good liner is maintenance-free.
A sensible maintenance program is relatively straightforward: inspect periodically, control vegetation and animals, maintain drainage, keep damaging equipment away, monitor water levels and chemistry, and repair small defects before they become large ones.
For a large or critical containment installation, inspections can become part of a formal asset-management program, with photographs, measurements and records of repairs. More sophisticated installations can also use leak-detection systems or electrical leak-location surveys to identify breaches that aren’t visible from the surface.
The underlying idea is that liner longevity is partly a material-selection issue and partly a protection issue. A high-quality geomembrane installed correctly can have a very long service life, but its environment ultimately determines how long it lasts. Designing the installation so the membrane doesn’t have to withstand unnecessary UV exposure, abrasion, chemical attack, puncture and movement is just as important as choosing the membrane itself.
