Paris opens giant water reservoir to clean up Seine for Olympics

July 26, 2024 - August 11, 2024 - A colossal underground reservoir, dug next to Austerlitz station at a cost of $1.5bn, aims to reduce the risk of pollution in the Seine and make the river suitable for bathing again.

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The impressive underground reservoir will hold around 46,000 cubic metres of water, equivalent to the volume of 20 Olympic-sized swimming pools, will collect excess rainwater and prevent bacteria-laden wastewater from entering the Seine.

Once the rainwater is collected there, it will be transported via a tunnel to a treatment plant. When levels of Escherichia coli and intestinal enterococci meet the safety thresholds, it will be passed back into the Seine.

The river water will be regularly tested to determine safety levels for Olympics events

Not only are three Olympic and Paralympic events – triathlon, marathon swimming and Para-triathlon – are scheduled to take place in the Seine in central Paris, but by 2025 three open-air swimming areas will be accessible from the quayside.