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Stormwater management or how to prevent floods and pollution

Article published on 17.02.12

Stormwater management, a new sanitation challenge
Growing urbanization creates new challenges in storm water management. SUEZ ENVIRONNEMENT and its subsidiaries offer solutions for tackling these challenges through its INFLUX system that establishes a specific dynamic crisis management system to handle floods and by building new storm water facilities. Spotlight on these challenges and solutions.

Growing urbanization and the increasing extent of impermeable surfaces such as streets, pavements and buildings reduce the natural infiltration of rainwater. Currently, only 15% of rain sinks into the ground. This means an increased volume of storm water to be evacuated. And this trend is worsening with the current climate changes that bring recurring heavy rainfalls.

Most stormwater is collected by the wastewater system. However, in a heavy storm, the runoff can overwhelm the normal flow of wastewater and cause floods, saturating treatment plants. This creates a risk that untreated storm water will be discharged directly into the natural environment. It is essential to prevent such discharges because stormwater is loaded with impurities, first from the air (industrial fumes, exhaust gases) then during runoff when it drains away with it residues deposited on roofs and roadways (zinc, sump oil, fuel, heavy metals, etc.). Scientists reckon that storms cause 10 to 15 times more pollution than the outflow from a sewage plant. They also indicate that rainstorms are responsible for 50% of the pollution that flows into rivers and onto beaches in urban areas.

Protecting urban areas and guaranteeing public safety

Growing urbanization presents water-industry players with new challenges and forces them to find stormwater management solutions.

• To protect urban areas and encourage municipalities to get involved in preserving the environment require an improvement in the reuse of storm water by individuals and local authorities. Storm water can actually replace potable water in some cases, thus conserving our water resources. It can be used for domestic purposes (toilets, gardens, washing of clothes, cleaning), industrial purposes (washing industrial vehicles, floors, flushing toilets), or collective purposes (watering of green spaces, street cleaning,etc.).

• Water industry players must guarantee public safety by protecting people and property from floods. They need to help cities to:

• improve the efficiency of infrastructure;
• limit the impact of stormwater by implementing improvement plans (for water quality and energy consumption);
• inform residents in advance in emergency situations;
• prevent future crises.


Optimizing the use of infrastructure

To fulfill these various objectives, Lyonnaise des Eaux provides a whole range of planning, design, construction, operation and network optimization services.

For existing networks, the Group offers an optimization to conduct an inventory of infrastructure to understand how the sanitation system works, the local context, and to define an action plan that is in line with municipality’s objectives.The INFLUX solution deployed in Bordeaux for example, is a relevant response to this need for optimization. Since it was commissioned in 1992 under the name RAMSES it has allowed nearly 300 significant rainfall events to be anticipated or managed effectively.


Anticipating and measuring the impact of rainfall episodes

SUEZ ENVIRONNEMENT also offers anticipation and measurement tools. For example, it has developed tools to measure changes in water quality in receiving areas (in particular, lakes, rivers and fragile ecosystems such as coastal areas). Real-time warning systems that report when a receiving area is being degraded by storm water pollution are currently operating in Biarritz where the M.E.R. system developed by CIRSEE analyzes bathing water quality within an hour as against traditional analyses that take up to 36 hours. In Cannes, SAFEGE and Actimar have put in place the IT-based tool Qualicôte that can predict coastal water quality 48 hours ahead and prevent potential pollution caused by the release of stormwater into the sea.


Designing new infrastructure

Over and above these anticipation and measurement tools, SUEZ ENVIRONNEMENT focuses on designing, building and operating new storm water infrastructures that have a positive impact on the quality of runoff. In Bordeaux, Lyonnaise des Eaux has built new retention ponds. SUEZ ENVIRONNEMENT puts in place treatment plants for the reuse of stormwater. For example, the Toulouse-Blagnac Airport has a plant developed by Lyonnaise des Eaux in partnership with Degrémont Industry (Ondeo IS) and INEO, which allows it to treat part of the stormwater and use the result to spray roads and water green spaces.


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Updated on 21.11.12