- 275 - The licensee indicates that they differ little from the design-basis values. Furthermore, experience feedback from the "Cevenol episodes" (tragic floods in the Hérault and Gard départements) in 2002 and 2003 showed that there was no impact on the premises above water and led to reinforcement of the watertightness of the alleyway in building 500 and the creation of a drain channel in the alleyway. Measures envisaged to reinforce robustness of the facilities to the flood risk For the reasons mentioned above, the licensee does not envisage reinforcing the robustness of the facility to the flood risk. In its opinion, the aggravating elements considered lead to the conclusion that it is pointless reinforcing the robustness of the facility, including with respect to combined earthquake and flooding. The extreme weather conditions (torrential rainfall of higher intensity than that of the design-basis storms events and rising of the water table) were also considered. The licensee recently updated its reference rainfall values referring to the draft flood guide. The new values are currently being appraised by the IRSN. The evaluation must take into account unavailability of the storm water drainage system, local water build-up areas and the location of accesses to buildings containing equipment to be protected. On completion of the review, ASN considers that there is no specific need for the licensee to increase the Mélox facility robustness to the flood risk. FBFC Design of the facility Two rivers, the Joyeuse and the Isère, run along the south side of the industrial site on which the FBFC facility is installed. The site elevation is higher than that of both these rivers. The risk of flooding caused by either of the 2 rivers bursting their banks is nil given the large difference in height between the ground elevation of BNI 98 and the normal water level of each river: +19 metres for the Joyeuse and +24 metres for the Isère. Even in the event of a 100-year flood of one of the rivers, the FBFC site would not be flooded. There are two water tables below the FBFC site: a deep water table dating from the tertiary situated at a depth of 150 to 200 m below the ground elevation. There is absolutely no risk of flooding from this water table; a large-scale surface water table accompanying a watercourse and crossing the FBFC site from east to west over a width of several kilometres. The depth of this water table ranges from 5 to 30 metres in general, and is more precisely at 12 metres under the FBFC site. The water table is below the level of the foundations of the FBFC buildings. Its level is stable even in the event of floods of the Joyeuse or the Isère, which shows that there are no direct exchanges between the water table and the two rivers. The risk of flooding of the FBFC facilities by a rise in this near-surface water table is therefore ruled out. The risk of flooding by rainfall, and notably the 100-year storm events is currently being studied by FBFC. The results should be submitted to ASN in mid-2012 along with the appropriate protection measures where necessary. Measures to protect the facilities against the flood risk The licensee's complementary safety assessment does not provide for measures to protect its facilities against the flood risk. This being said, the results of the above-mentioned study on the flood risk from rainfall could lead it to propose protection measures. Conformity of the facilities with the current frame of reference In the same way as for the seismic risk, conformity of the facility is not guaranteed. Evaluation of the safety margins The licensee's report contains no specific study of the safety margins with respect to the flood risk.
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