Paris bets on giant tank to clean up Seine river in time for Olympics
Construction workers rush to finish underground pool that will collect the capital’s wastewater
Samuel Colin-Canivez, lead engineer for the Paris water system, stood in a 30m-deep concrete cavern as hundreds of construction workers were racing to finish the pharaonic project ahead of next year’s Olympic Games.
Their mission: build a 700-metre tunnel and a large storage tank to clean up the Seine so athletes can compete in it in swimming and triathlon events.
“It’s been a marathon, but we are on the last leg,” Colin-Canivez shouted over the noise of workers banging hammers to install a last section of barbed steel to reinforce the concrete below the tank’s floor. Construction started almost four years ago and is due to complete in spring at a cost of €90mn.
Nestled between a 17th century hospital and the busy Austerlitz station, the underground pool will have a capacity equivalent to 20 Olympic-sized swimming pools, and is designed to capture overflow from the French capital’s antique sewer system during heavy rainfall.
“The goal is to stop untreated water from being dumped in the river,” said Colin-Canivez.
Currently about a dozen times a year the city’s underground sewage tunnels are overwhelmed and to avoid flooding the streets, they release wastewater into the river — including dangerous E Coli bacteria found in toilet discharges.
The new holding tank should help reduce such incidents to only twice a year by holding the water during storms and gradually releasing it afterwards.
It is one of five engineering projects that the Paris region is undertaking to clean up the Seine and Marne rivers to allow residents to swim in them again. Additional new water treatment plants, pipes and pumps have also been built.
Many residents remain sceptical about swimming in the Seine and there are no guarantees that the Olympics-related clean-up will be effective enough to bring bacteria levels down to levels safe enough for athletes to compete.
Paris was forced to cancel several test events this summer when laboratory monitoring tests showed that there was too much E Coli in the Seine. The excessive pollution was caused by a spell of heavy rains — something the new tank should help prevent.
But a second set of test events in late August was also scrapped even though there had been little rain in the days leading up to it, leaving organisers perplexed as to why the water quality was so poor. Investigations later found that a faulty valve had been left open, allowing sewage water to escape, and an automatic monitoring system had failed.
“It was disappointing, but we’re confident we can get it right in time for the games,” said Pierre Rabadan, the deputy mayor of Paris in charge of sports.
If the water quality was not up to standard, Rabadan said, competitions could be delayed by a few days or a week to allow the water quality to improve — but there is no back-up plan for swimming competitions to be held elsewhere.
That has put pressure on Colin-Canivez’s builders toiling underground, as well as others who are working on other parts of the Seine clean-up plan, such as the effort to connect houseboats docked on the Seine to the sewer system.
Another challenge has been convincing homeowners to undertake costly repairs to fix the roughly 20,000 houses and buildings in Paris and surrounding suburbs that are not properly connected to the sewage system.
“Every little thing we can do will help,” said Colin-Canivez.
Swimming in the Seine was banned in 1923 because of pollution, but politicians have long promised to bring it back. Former president Jacques Chirac vowed to get it done when he was Paris mayor in the 1990s, but failed. Heavy rains regularly brought flows of garbage and plastic into the Seine, marring the historic artery of Paris.
Paris mayor Anne Hidalgo has billed the Olympics as a catalyst for the opening of 20 swimming spots by 2025 in the capital, which has become hotter in summer due to global warming. “It would have taken us 20 years to do the clean-up without the extra boost and budget from the Olympics,” said Rabadan.
In addition to swimming events, the Seine will be at the centre of the Paris games in ways that critics have warned may prove overly ambitious and risky.
A plan to hold the opening ceremony on the river has sparked security concerns, with police and military officials raising concerns about securing a parade of some 150 boats carrying 10,000 athletes, as well as crowds of spectators on the quayside.
Organisers dismiss those fears and argue that the unique ceremony will showcase the beauty of the capital’s riverside buildings such as the Eiffel tower, Notre-Dame cathedral and Les Invalides.
Rabadan defended both the parade and the Seine clean-up efforts: “There is no plan B, since pulling off plan A will be complicated enough.”