The world's largest storm tank is hidden under a Madrid golf course

A gigantic stomach under the ground.

Below the Madrid Country Club there is a unique underground landscape in the world.

There is not others equal.

Eight kilometers from Puerta del Sol, hidden, almost like a secret from most citizens, it houses a fundamental mission for the city.

Prevent the overflow of the Manzanares River and prevent dirt from the streets from suddenly reaching its channel when storms loom.

A silent, unnoticed, discreet work.

A fundamental mission for the ecosystem.

It is a huge two-story warehouse.

A structure of 85,000 cubic meters of concrete up to 22 meters high.

The equivalent of a cube measuring 57 meters on a side.

Its enormous gray walls store up to eight times the pond of the Retiro Park, as if half of the Bernabéu were flooded.

A 33,000 square meter swimming pool about 12 meters deep.

Welcome to the huge Arroyofresno storm tank.

The roof of this gigantic reservoir is a golf course.

Hundreds of Madrilenians walk and hit the white ball every day with their sticks, alien to the subterranean universe they tread.

The construction of this immense work of engineering is divided into two floors.

The first is a parking lot for employees' cars, like any

in a large shopping center.

The second is the tank itself.

Here it smells like stagnant water.

A fetid smell that penetrates even the best masks on the market.

A pond where natural light does not enter or reluctantly and where the dirt of the streets of the capital is really perceived.

Two workers walk here every day, as if it were a police couple.

They do several kilometers a day.

They keep this miniature swamp complex - accompanied by a large system of pipes and huge pumps - working perfectly.

“We conserve all the elements to avoid critical moments,” says Óscar García, a 44-year-old smiling maintenance technician.

“If we have a rain forecast, we come quickly.

We are always on pre-alert ”, says his colleague Isidoro Gordo, 45, dressed in a blue jumpsuit and a prominent beard.

- They will not waste time on the news ...

- We have six weather applications on our mobile.

They both know whether or not it will rain in five minutes.

They both know the amount.

They both know the exact time.

Two maintenance meteorologists underground.

Little joke.

This storm tank is a recent engineering phenomenon.

There is no week without country visits.

Engineers from the United States, Singapore, Honduras or Mozambique have traveled here.

They want to copy this model.

Even the cinema has set the hook.

It has served to shoot scenes from the series

or films such as

or

All this aquatic store arises from the purification of the waters.

A silent process that takes place alien to human life under the cities.

When it rains, the water carries away tons of litter, cardboard, cigarette butts, oils, wipes, papers, waste: garbage.

Before pouring it into the riverbed or reusing it for irrigation, these storm tanks collect the flow that the sewers collect and, in the case of Madrid, send it to the treatment plants and then, once it is cleaned, to the Manzanares River.

- Is the Madrilenian hygienic at home?

- In recycling, yes;

in the rest we have much to improve.

Manuel Rodríguez is the deputy director of conservation of Canal de Isabel II, the public water company that manages the 15,317 kilometers of pipes in Madrid.

There are so many that if they came together in a straight line they would reach Australia.

Engineer Rodríguez is the voice that manages this great underground stomach.

He says that rain is very dangerous for the first 20 minutes.

That it is at that moment and not later when all the waste is dragged.

If the waterspout is disproportionate, the capacity of the treatment plants would be exceeded and all the remaining flow, loaded with garbage, would go to the rivers with tremendous ecological consequences.

"That's what storm tanks were created for", smiles engineer Rodríguez.

This year alone, the Manzanares has been prevented from being flooded with hundreds of thousands of liters of waste, the equivalent of eight times the Santiago Bernabéu full of water.

In Madrid there are 36 storm tanks;

in the Community, 65 and in Spain, 470. The capacity of the three largest in Madrid is the same as the sum of all the rest.

The Country Club's storm tank was completed in 2009. A team of engineers visited the Netherlands in the late 1990s and fell in love with this aquatic harvesting system.

The City Council opted for this type of construction because the Manzanares is a very shallow river.

Barely covers, one could cross the entire river with the water at the waist.

In the rivers of other large capitals, however, nature takes care of itself to disintegrate the weeds.

In Madrid, no.

It was built in this corner for pure logistics.

It is next to the river and next to one of the treatment plants.

In Madrid it could rain 17 hours straight without stopping and all that water would go to this warehouse.

If it filled up, as it has happened four times - the last one in Easter this year - the technicians would close the hatch.

A huge eight-meter mouth identical to the Metro tunnel.

Once closed, the rest of the water would go to the river, without being treated.

"But it is already much cleaner than before because the first thousands and thousands of liters with garbage remain here," presumes the engineer.

"We have managed to avoid many times what happened on June 24, 1995."

That summer night the gates of hell opened.

An unforeseen waterspout flooded all the streets of Madrid.

All the floodgates of the Manzanares river were ripped out.

There were three unheard-of storms in a row.

Out of nowhere and suddenly.

It had been 25 years since so much water had fallen in the capital of Spain.

First, the rain.

Then the hail.

Millions fell, like chickpeas.

The rain washed away the life of Raquel, a homeless woman who slept in some works in Aravaca.

Hundreds of cars were buried, the Metro, premises, garages, low, first, shops were flooded.

Madrid had waves even at the Bernabéu.

Here the final of the Copa del Rey was played between Deportivo de la Coruña and Valencia.

"It was 22:00 at night and it was surreal," recalls José Luis García Aranda, the match referee by phone.

“It was an impressive thing.

In my life I saw something like it ”.

The game went 1-1 and in minute 79 it looked like an Olympic swimming pool.

Aranda looked at the footballers as if they were swimmers.

"The ball was floating!"

The water was up to the ankles.

He didn't last those last 11 minutes.

He suspended the game.

They all ran towards the dressing room tunnel as if they were in Sanfermines.

80,000 people from A Coruña and Valencia remained in their seats.

King Juan Carlos, in the box, could not believe.

Aranda thought that, being summer, the storm would abate.

He did not want to suspend the game.

It was a decision of tremendous financial proportions.

It was the final of Spanish football.

Thousands of fans from Valencia and A Coruña would have to return to Madrid again.

Around 11:00 pm, Aranda decides to leave the changing room.

Freaked out.

“The water was up to my waist!

I couldn't get on the grass ”.

There are photos in the newspaper library with dozens of electronic gadgets floating around.

A team of firefighters came down to rescue several people from such a water fire.

There were no injuries.

Aranda fled back to her locker room.

He announced the final match.

"People have had to swim out of the cars," reported a Samur member from another point in Madrid.

At one thirty in the morning the emergency services rescued several neighbors who were blocked on the M-30.

A spokesman for the National Meteorological Service, who at no time warned of the possibility of a storm, told EL PAÍS: “We cannot speak to anyone.

I can only tell you that it rains on Madrid ”.

The final resumed days later.

Deportivo won 2-1.

"On the way back, no footballer mentioned the word rain, just in case", remembers the referee Aranda.

"The final was played in two halves, never better said."

The third time came with the opening of the largest storm tank in the world.