A few days before the opening of the Paris 2024 Olympic and Paralympic Games, the Seine is finally ready to host the triathlon and marathon swimming competitions. On Friday, July 12, the prefecture of the Île-de-France region, which regularly carries out microbiological analyses of the river water, was able to issue an optimistic bulletin.The quality of the water in the Seine is relatively good over the period observed with more than 80% of analyses conforming to the thresholds of the European directive, and 6 days a week in accordance with the site which will host the Olympic and Paralympic events“, estimated the prefecture in light of the samples taken between July 3 and 9.
Limit discharges into the river in the event of rain
The heavy rainfall in May and June made the forecast uncertain. In the event of rain, rainwater entering the sewage system causes wastewater to be discharged into the Seine. Limiting these discharges was one of the main objectives of the bathing plan launched by the State to clean up the Seine and the Marne, with the primary aim of allowing athletes to enter the Seine without risk to their health.
With an unrivaled scale of 1.4 billion euros, this program brought together several stakeholders, including the City of Paris, the Intercommunal Sanitation Syndicate of the Parisian Agglomeration (SIAAP) and the departments of Val-de-Marne and Seine-Saint-Denis. Several monumental works were completed. Among them, the Austerlitz basin in Paris. With a depth of 30 meters and a diameter of 50 meters, it can store 50,000 cubic meters of wastewater and rainwater from the Parisian combined network. This infrastructure makes it possible to significantly reduce the use of storm overflows intended to evacuate excess water into the Seine to avoid saturation of the sewers.
Siphon under the Marne
For its part, the SIAAP has successfully completed several major projects. The most expensive (315 million euros) allowed the construction of a 9-kilometre long, three-metre diameter collector tunnel between Athis-Mons (Essonne) and the Valenton treatment plant (Val-de-Marne). Its purpose is to retain water upstream of the latter when its capacities are exceeded. The SIAAP has also built a whole range of equipment on the Marne to store and direct water to the Marne Aval treatment plant in Noisy-le-Grand (Seine-Saint-Denis), including a siphon under the river which alone required an investment of 42 million euros. To increase the level of disinfection of treated water, the union has also invested 13 million euros in its two Marne Aval and Valenton treatment plants.
All of the operations should make it possible to reduce to two days, after the last rain, the period during which the events cannot be held, while opening the way for everyone to swim from 2025. This will not be the only legacy of the Olympic Games.The Games had a catalytic effect and allowed for the implementation of works all at the same time, for the same objective. We are building the sanitation system for the next sixty years.“, rejoices Richard Buisset, general director of SIAAP.
Source: www.usinenouvelle.com
