A logistics warehouse subject to authorisation (section 1510) suffered flooding. After 4 days of heavy rain, the site’s retention basin, and another basin belonging to the urban community, eventually overflowed. Due to the lack of drainage channels along the nearby county highway road, runoff water worsened the problem. The unloading docks, which form a low point around the entire periphery of the site, acted as a retention basin by protecting the vicinity from flooding.
Losses of utility networks
The electricity networks did not operate during the flooding period from 10 May at 10:45 p.m. to 31 May at 7 p.m. The site’s electrical substation is located on the site’s property line, at a low point in relation to the road. The lift pumps went out after the substation flooded. In order to supply the site with electricity, 3 generators were installed and operated for 25 days to pump stagnant water, and for other purposes. An earlier attempt had been made to pump using agricultural equipment (two 18 m³ tanks) but it proved unsuccessful. The fire brigade was called in to find a better solution.
The site’s telephone service was not affected (the IPBX switch is protected in the computer room by an inverter). The lines used for the remote alarms use the public switched telephone network (PSTN) .
Consequences
The operator reported 36 hours of operational downtime. Trucks waiting to gain access to the site received municipal authorisation to park in 3 streets closed to traffic.
Significant property damage occurred: fence damage, structural collapse and ground movement. Operating losses and property damage were estimated at more than 100 million euros.
Lessons learnt
The ability of the city’s networks to absorb the rainwater proved insufficient during the event. The position of the communal retention basin, located at a high point in relation to the warehouse, as well as the water evacuation capacity in the Lay River were studied. The following work is to be carried out:
- replacement and elevation of the electricity distribution substation to a point 2 m above the natural ground level;
- replacement of the guard station’s power supply cable;
- repair of the fence.
The operator has also expressed concerns regarding the designed discharge flow capacity for its retention basin because even with the pumps in operation, the basin would have overflowed given the heavy rainfall.
