French Open groundskeepers drench the clay courts with water and salt during heat wave

PARIS (AP) — The scorching heat wave that has gripped Paris since the start of the French Open isn’t just pushing the players to their limits. The clay courts risk cracking, too, under the intense sun.

Unseasonably hot weather has seen temperatures soar to at least 32 degrees Celsius (90 Fahrneheit) — far beyond normal for late May in the French capital — on all four days of the tournament so far. And the heat is forecast to continue through the rest of the week.

On Tuesday, the temperature at Roland Garros peaked at 35 C (95 F).

“What we’re experiencing is unprecedented,” said Philippe Vaillant, the head of court maintenance at the French Open. “Even the weather services say it themselves: it’s unprecedented to have temperatures this high for such a long period at this time of year. I had concerns when the weather service announced periods of intense heat.”

When heat waves hit, the clay surface can quickly change in consistency, affecting bounce and player safety.

So, Vaillant and his team of 200 groundskeepers have had to dip into their bag of tricks to protect the venue’s 18 courts, plus 15 additional off-site courts used for practice. There’s extra watering — lots of it — plus the strategic spreading of calcium chloride.

In hot weather, the French Open courts dry out much faster, which leads to quicker, slightly different play on the traditionally slow surface.

Top-ranked Aryna Sabalenka, after her first-round victory over Jessica Bouzas Maneiro, observed: “Now it’s, like, boiling hot and balls are flying, everything is much faster.”

Vaillant’s goal is to preserve clay-court playing conditions as much as possible.

“We’re forced to water the courts a little more, of course,” he said during an interview at Roland Garros on Wednesday.

In the evening, his teams literally soak the courts to recharge the different layers, so that the next day the water rises back up through the limestone base beneath the crushed red brick.

Calcium chloride

Vaillant also has another ally: calcium chloride.

“Which is basically just salt,” he said. “We spread it over the courts in flake form in the morning. It melts on contact with water and helps retain surface moisture. And of course, the court dries out because of player movement.”

During matches, courts are watered between each set — something groundskeepers do not normally do under standard temperature conditions. The watering is kept light so play can resume quickly.

“This light watering reactivates the calcium chloride that remains in the crushed brick layer,” said Vaillant, who started at Roland Garros in 1995. “We only apply it in the morning, roughly one 25-kilogram bag per court.”

Heavy rain earlier this year helped

The heavy rains in May actually helped temper the effects of the current heat wave.

“We were able to let the rain do its job,” Vaillant said. “It recharged all our water-retaining layers, which means that today, after several days of heat-wave conditions, the courts are still in excellent condition and we don’t feel the effects of drought. We allowed some courts to absorb the rain. Once they had absorbed enough water, we covered them. We balanced things so the courts could benefit from the rainfall.”

As a result, the courts are playing a little faster than usual, but not dramatically so.

It’s the limestone that matters

A Roland Garros clay court consists of five layers totaling about 80 centimeters in depth: large stones, gravel, a layer of volcanic-rock residue, limestone, and finally a thin layer of crushed brick that gives the court its ochre color.

“The crushed brick layer is 3 to 5 millimeters thick,” Vaillant said. “The most important part is the limestone layer underneath. That’s the actual playing foundation. The crushed brick is mainly there for color and as a material that provides some sliding ability and an important visual contrast, since the limestone is almost white.

“This limestone layer must remain moist at all times,” he added. “It’s compacted crushed stone maintained through water supply. If we let it dry out too much, the courts could crack. We have to stay vigilant.”

Players’ safety

Since the start of the tournament, players have been putting bags of ice around their necks on changeovers to stay cool — with Frenchman Valentin Royer putting a large ice bag on top of his head during his second-round match against Novak Djokovic on Wednesday.

Heatstroke isn’t the only risk in such conditions. A dry court becomes slippery, which is why watering is important.

“It starts to resemble ‘Holiday on Ice’ (an ice rink),” he said. “It can be dangerous. A player could slip and get injured.”

Saving water

Vaillant and his team needs slightly more than one cubic meter of water per court each day for maintenance.

Throughout the year, rainwater collected in a tank located beneath Court 7 is used to independently irrigate all the green spaces at Roland Garros. For health and safety reasons, however, French regulations currently prevent the courts from being watered with collected rainwater.

“But a decree has just been signed allowing sports surfaces to be watered with rainwater,” Vaillant said. “So we now have projects to collect rainwater in order to water the courts. The construction department is working on the project.”

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