The Val-du-Marne Council is due to begin operations in Fresnes, L'Haÿ-les-Roses and Chevilly-Larue which will see a mass overhaul of the water system.

Starting on September 4 in Fresnes and September 15 in L'Haÿ-les-Roses, plans are in place to demolish and replace 673 metres of the wastewater network.

The same is also due for 580m of the rainwater pipes to get rid of "mixed manholes" which is where the two sets of pipes join and cause the mixture of the two types of water.

The rainwater network is said to be undersized in Val-de-Marne, where an increase in size is said to be essential to avoid its discharge into wastewater.

Private homes in the area are also due to be connected to the networks in an €8.5 million (£7.2 million/$9.2 million) investment over 10 months that is hoped to "limit this nuisance as much as possible".

In L'Haÿ-les-Roses and Chevilly-Larue, which share Paul Hochart Street, €40 million (£34.2 million/$43.4 million) is being invested to improve the compliance of sanitation connections.

The operation is said to be of "great technical complexity", and will require three microtunnel boring machines to work at the same time to make space for the new pipes.

Pollution in the River Seine has caused a headache for Paris 2024 organisers this month as it has led to the cancellation of certain competitions in Games test events. 

Heavy rain in the city was cited for pollution in the river which made it unsafe to swim, leading to the cancellation of the World Aquatics Open Water Swimming World Cup and the swimming segment of a World Triathlon event.

The rainfall causes sewers to overflow and spill out into the rivers.