As part of a capacity enlargement programme for a whole chain of power plants, the storage volume of the Rifa reservoir needed to be increased from 670,000 m³ to 1,100,000m³.

In order to increase the storage volume of the reservoir so dramatically, the existing earth dam needed to be lifted by five metres and the asphalt slopes had to be extended by twelve metres. All WALO’s work had to be undertaken during the normal operation of the power plant, which was achieved by reducing the water level in the reservoir and then working on the slopes above it.

To ensure that the connection between the existing liner and the new extension lining was impermeable and durable, the existing dense asphalt course was milled along its upper edge to form a strong key between the linings. The drainage gravel, the Asphaltic Binder Layer (ABL) and the Dense Asphaltic Concrete (DAC) were installed by paver and the joint between them and the existing asphaltic lining was formed in a conventional manner, ensuring a homogeneous lining system. Further stages of the modernisation included the construction of additional inlet/outlet structures and a further, second extension was created by building a wave-breaker around the crest.