L’objet du présent règlement est de définir les mesures particulières prescrites sur le territoire de la communauté d’agglomération en matière de maîtrise des ruissellements, de traitement et de déversement des eaux pluviales dans les réseaux publics enterrés ou à ciel ouvert. Il précise en ce sens le cadre législatif général.
Extrait du règlement
7- General rules
a) It is forbidden to connect rainwater to the sewerage system or to an independent sewerage system.
b) Any increase in runoff caused by new waterproofing (creation or extension of existing buildings or infrastructures) must be compensated for by the installation of rainwater storage systems on the plot (infiltration or retention basins) or other alternative techniques*.
New waterproofing must be compensated for to the extent of 130 litres/m². (minimum) with a maximum leakage rate of 50 l/s per hectare of waterproofing.
If infiltration is not possible (or if the infiltration rate is insufficient) and there is no outlet, diffuse spreading may be considered at a regulated rate of 5 l/s/waterproofed hectare, subject to acceptance by the municipality.
The retention volume to be used in this case is : 170 l/m² of waterproofing.
c) The volume stored must be emptied by infiltration as a priority and not connected to the public network.
d) For building permits involving the demolition of existing buildings, the sizing of the works must take into account all the waterproofed surfaces of the land unit, regardless of the previous degree of waterproofing.
e) In the case of grouped urban development projects (housing estates, ZACs, etc.), storage facilities must be shared by the whole project in order to avoid storage on each plot. Storage facilities created as part of a subdivision permit must be sized for the roadway and for the total waterproofed surfaces likely to be created on each lot.
* Alternative techniques complement or replace conventional sewerage systems. Their main function is to limit peak flows downstream in order to prevent the concentration of water in saturated networks:
- by infiltration when the soil is suitable and outside the catchment protection area,
- par stockage temporaire des eaux de pluie avant leur restitution à débit contrôlé dans le réseau aval (collecteurs, caniveaux, fossé …) si l’infiltration est impossible ou interdite,
- by combining temporary storage and infiltration.
Un catalogue non exhaustif des techniques de stockage à la parcelle est présenté en annexe du règlement : noue, fossé, tranchée drainante, toiture stockante, sols poreux, chaussée réservoir…