One of the most common geomembrane applications is as a pond or dam liner. Pond liners may be used where:
For more information regarding the use of geomembrane applications for pond lining.
Dam Liners Material
The type and thickness of material in dam liners varies. The main determinants of the type of material to be used are:
Liquids that are contained may be drinking water, industrial process waste such as dunder or mine washings, sewerage or molasses.
The subgrade that is to receive the liner requires careful preparation. The subgrade preparation is required to meet the specification of the liner manufacturers. Failure to meet these requirements may result in the invalidation of the any offered guarantees. Typically the embankments are required to be regular and free from sharp or large rocks. Material placed in contact with the liner is required to be less than 10mm in size. Where granular material forms the subgrade it is usual to place a geotextile under layer. The geotextile used is usually a needle punched, non-woven material with a weight of not less than 250gms/m2.
Where ponds are to be constructed in areas where there is vertical gas movement through the subgrade of the pond then it is required to provide a subgrade venting system to prevent gas collecting below the dam liners. Vertical gas movement may be produced by the movement of the water table over a seasonal or diurnal period or by the degrading of vegetation matter at depth. The venting system usually consists of a full geotextile layer underlayed by a herringbone system of slotted pipe or slot drain wrapped in geotextile. The venting system may fulfill a dual roll. The system can double up as a leak detection system and can also be used to monitor the level of the ground water before the level of the contained liquid is reduced to minimum levels.
Lining materials for ponds include HDPE, Polypropylene, Elvaloys and PVC.
The most widely used lining systems are HDPE, which is produced in various thicknesses and textures. HDPE is delivered in 7m rolls weighing approximately 1.6 tonnes. The material is unrolled and welded on site with wedge and extrusion welding equipment.
Lining systems are anchored at the perimeter of the pond by either burying the upper edge or by fixing the perimeter to a concrete anchor beam.