Recalibration of the Pirot Dam spillway (03)

Located in the TRONCAIS state forest, in the municipality of Isle-et-Bardais in the Allier department, the Pirot Dam is an embankment dam 18 m high, draining a catchment area of 36.5 km². Due to its geometric characteristics (volume of approximately 3.72 hm3 at its normal retention level, RN) and pursuant to the decree of 11 December 2007 (as well as the decree of 12 May 2015), it is classified as a category B dam.

This is a homogeneous embankment structure that was waterproofed using a diaphragm wall in 1998. A hazard study was carried out in 2014. As part of the risk-reduction measures, the hazard study recommended carrying out the studies and then the works deemed essential in the medium term to ensure an adequate level of safety for the structure:

• Installation of a debris boom on the spillway
• Spillway recalibration study
• Spillway recalibration works

Significant considerations were incorporated to frame the execution of the works, including the site's heritage value and its tourism and environmental considerations. The project, for which Hydrostadium was responsible, consisted
therefore in providing full project management services for securing flood evacuation.