Geomembranes are commonly used to seal both the bottom and slopes of a pond, basin or deposit.
Though in some cases it will also be necessary to use a watertight floating cover as protection against evaporation, dirt, rain water, and also to prevent the diffusion of gases or odours.
Basic characteristics of a floating cover:
A floating cover consists of a flexible geomembrane of the same dimension as the geomembrane that gives the waterproofing of the pond; it will be fixed at the crest of the slopes. The liquid is then introduced between the two membranes, so that the cover floats on the surface of the liquid.
The level of the surface will vary depending on filling height of the covered liquid. Consequently there will be some remaining material which will be located in the area of the folds and kept in place by lines of ballast and floats. The actual method may vary from site to site.
The geomembrane assures this cover, and floats on the surface of the liquid.
In addition, the geomembrane is fixed in the crest to withstand the wind.
Alternatively, the floating cover may be covered by a layer of water. However, a device must be provided to allow the evacuation of excess rainwater on the cover. Both, pumps and gravity flows are commonly used.
The installation of a gas drainage will enable the evaporation of gases that accumulate under the deck, for example by aeration of the water.
Finally, a trap door will be installed that allows access between the cover and the waterproofing membrane of the basin for subsequent maintenance.