The key figures in the fight against flooding in Seine-Saint-Denis
- 33 pools departmental retention
- 2 pools of the Interdepartmental Sanitation Union of the Paris Agglomeration (SIAAP) operated by the Department
- 1.5 million cubic meters of total storage capacity
- 1973 : commissioning of the 1st departmental basin, Maurice Audin, in Clichy-sous-Bois (19,000 m3)
3 works to protect the Montreuillois, the Marne and the Seine
The Guernica departmental retention basin and its valve
The new Guernica valve helps limit pollution in Marne. Thanks to it, running rainwater is directed and stored in the Guernica basin. Previously, the excess waste and rainwater was sent to the sewer known as “Bois de Vincennes” then to the Marne.
Guernica Basin
- Storage capacity: 20,000 m3
- Year of commissioning: 2002
- Objective: fight against flooding
Vanne Guernica
- Year of commissioning: 2023
- Objective: limit polluted discharges towards the Marne and the Seine
- Co-financing of the Seine-Normandy Water Agency (AESN)
Photo: aerial view of the Guernica basin during its construction
The retention basin of the Fontaine des Hanots
With its 28 meters height, this pool is the deepest in the Department. Built on land in the commune of Montreuil-sous-Bois, it is the result of a pooling of needs and resources between the Department of Seine-Saint-Denis and the Etablissement Public Territorial Est Ensemble (EPT EE).
Fontaine des Hanots Basin
- Storage capacity: 21,500 m3
- Year of commissioning: 2024
- Objectives: fight against flooding and limit pollution discharged towards the Marne and the Seine
- Co-financing of the Seine-Normandy Water Agency (AESN)
Photo: interior view of the Fontaine des Hanots basin
Experts and technologies to protect residents
For a retention basin to function, a lot of equipment is needed: pumps, valves, instruments for measuring heights and water flows, etc. They are connected to the automated management center of the Water and Water Department. Sanitation (DEA) of the Department, located in Rosny-sous-Bois, which controls them remotely.
The “Central” operators determine the best water management scenarios based on weather forecasts, in order to protect
- the sewers of drowning,
- the residents of the floods,
- waterways from pollution.
On the so-called “unitary” network, that is to say which mixes wastewater with rainwater, as is the case in Montreuil, a retention basin works as follows:
During regular rains, the valves are activated automatically to close the sewer and direct the water towards the basin in order to protect the watercourses.
During heavy rains and storms, the volume of water transported into the sewers increases rapidly. The surplus flows into the basin through a water intake* without having to activate the valve located downstream of the basin. This arrangement makes it possible to limit spillovers onto the roadway or to local residents.
Once the rain stops, the sewers gradually empty. As soon as there is no longer any risk of flooding or discharge into watercourses, the water stored in the basin is pumped and returned via the sewers to the treatment plant for treatment.
When it does not rain, wastewater is transported directly through the sewers to the treatment plant without passing through the basin. The Department's teams can thus maintain it and control its equipment.
Discover how a water intake works
Automated equipment to effectively manage effluent
Pumps
Installed at the bottom of the pool, they allow water to rise up into the sewers. They are put into operation once the risk of flooding has passed so that the storage capacity of the basin is again available for future rainy events.
Eyes
These large water tanks are comparable to large vats. By a tilting movement, they discharge the water they contain to clean the tracks at the bottom of the basin automatically after it has been emptied. This guarantees long-term operation of the basin by maintaining safe access for maintenance workers (absence of gases due to sludge, no risk of slipping).
Valves
Valves are types of doors that are operated to close a sewer and divert the water passing through it to another pipe. They are often installed near a pond supply pipe and thus make it possible to “force” the filling during light rains. This filling thus limits the risk of pollution of waterways.
updated December 26, 2024
