If the stakes of yesterday were to collect all the waters to keep the health risk away from cities, they have now evolved. Rainwater is seeping less and less as the cities become waterproof and the volumes of rainwater that run off or are collected are increasing.

The consequences are multiple: saturation of sanitation systems, dysfunction of wastewater treatment plants, pollution, flooding… The “all pipe” is no longer the appropriate answer. Let the water penetrate into the soils by using so-called alternative techniques: retention ponds, rain gardens, infiltration vents, draining trenches…

Many municipalities require water retention solutions when issuing building permits. Current techniques make it possible to meet these challenges at a cost that is even more reasonable if it can be treated at the same time as a non-collective sanitation project.