Premature Failure of Geomembrane Floating Covers in Australia: Causes, Comparisons, and Recommendations

The primary cause of premature failure in geomembrane floating covers in Australia is chemical attack, mainly resulting from chlorine exposure and high surface temperatures. Covers employed in systems with chloramine disinfection have been particularly susceptible to degradation. Furthermore, high-purity water generated by reverse osmosis desalination plants, characterized by negative or very low Langelier Saturation Index, has also posed chemical attack challenges. Accelerating factors such as intense UV exposure and high ambient temperatures have further contributed to the premature failure of RPP covers.

Comparative Performance Analysis: Comparing the performance of RPP and CSPE covers reveals significant differences. The average age of CSPE floating covers at the time of replacement in Australia is 27.25 years, compared to 11.3 years for RPP covers. Notably, several CSPE covers in Australia have exceeded 35 years in service, while the remaining RPP floating covers exhibit serious signs of degradation. CSPE materials offer a proven service life that is 250-300% greater than that of RPP and fPP (formulated Polypropylene).

PVC-EIA Material: While PVC-EIA materials have not been extensively utilized in Australia, their performance has shown relatively short asset life, which appears to be formulation-dependent. Further investigation is warranted to explore the specific factors influencing the performance of PVC-EIA covers and potential solutions to enhance their longevity.

The selection of suitable materials is a crucial factor in ensuring the long-term durability and optimal performance of floating covers. Several challenges and considerations need to be taken into account, as the chosen materials must withstand various environmental factors and stressors, ensuring prolonged service life.

Reinforced Polypropylene (RPP) Covers: RPP covers, although widely used, demonstrate signs of fatigue and premature degradation within 10-15 years of service. Cracks often appear around folds and creases, leading to concerns about the extent of damage to the geomembrane liner material (see photo below). Factors such as prolonged UV exposure, continuous chlorine exposure in potable water disinfection, and stress concentrations at folds due to hydrostatic pressure contribute to the cracking and subsequent material failure.

Chlorosulfonated Polyethylene (CSPE) Covers: CSPE covers have a long-established track record, with over 50 years of proven performance in municipal water containment applications involving chlorine and other disinfectants. CSPE geomembrane material exhibits excellent UV resistance and is backed by a 30-year weathering warranty. Its high flexibility and stress distribution capabilities make it a reliable choice for floating covers.Fortified Geomembranes: Fortified geomembranes are products that undergo extensive dosing with stabilizers, providing enhanced heat resistance, UV stability, and chemical resistance. This fortification significantly improves the durability and longevity of the material, making it suitable for demanding applications like floating covers.

To ensure the selection of suitable materials for floating covers, site-specific conditions must be evaluated, and collaboration with material suppliers is essential. Considering long-term durability factors, such as UV exposure, chemical resistance, and flexibility, aids in making informed decisions regarding material selection. The importance of material selection in floating covers cannot be overstated. RPP covers are prone to premature degradation, while CSPE covers offer superior durability, UV resistance, and flexibility. Choosing fortified geomembranes further enhances the stability and chemical resistance of floating covers. By prioritizing appropriate materials, the longevity and performance of floating covers can be optimized, ensuring reliable and effective protection for various applications.