Drainage & protection with EnkaDrain, France

Hydropower canal rehabilitation

This canal is located in the Maurienne valley and supplies the Hermillon power station. The part to be restored has been subject to significant settlements ever since its origin, particularly the upstream inlet (diverging), the downstream outlet (converging) and the area around the access ramp.


When operational, this section is subject to a nominal flow rate of 85 m3/s, with a maximum water velocity of 1.8 m/s and a maximum water depth of 7 m. Relining needed to be carried out in those areas where concrete slabs were not given a vinyl bituminous coating upon installation. As a result, multiple cracking, erosion under joints beneath the slabs and runoff in the foundation had become issues.


The installed relining system consists of the following components from top to bottom:
• Reinforced concrete layer (access ramp, bottom of the canal and lower parts of canal side slopes only)
• Drainage geocomposite EnkaDrain in areas with reinforced concrete protection
• 2 mm thick reinforced PVC geomembrane, UV stabilized
• Drainage geocomposite EnkaDrain
• System for detecting and locating potential leaks by means of optical fibre
• Old concrete slabs


• At the bottom side:
Located at the interface of the old slabs and the geomembrane, EnkaDrain protects the geomembrane from damage due to irregularities in the shape of the concrete surface and ensures drainage function in case of a leak in the geomembrane.
• On the top side:
EnkaDrain protects the geomembrane at the interface of the top reinforced concrete layer poured to protect the lining system on the access ramp, the canal bottom and the lower part of the canal side slopes.

The EnkaDrain Wide product range is produced in rolls 5m in width for faster but also more efficient laying thanks to the high flexibility and the absence of shape memory of the geocomposite. The solution implemented in this way prevents the geomembrane from being damaged by high water flow velocities and the carriage phenomenon (the process of sediment moving under the effect of water).

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