A cave right under the Sliema promenade does not appear to be facing any “immediate” risk of collapse, according to two experts, allaying fears of a potential looming disaster in one of the most popular pedestrian spots.

Concerns about the fissures in the rock eating into the rock under the promenade have been raised in the last years, with the Sliema mayor even saying the promenade could collapse if faced with a heavy storm from the northeast.

Times of Malta visited the site with civil engineers and University of Malta lecturers Adrian Mifsud and Christian Schembri to take a closer look at the cave and others like it to determine just how much of a threat they pose.

But according to Mifsud and Schembri, however, this worst-case scenario is not likely – at least, not anytime soon.

“Even though there does not seem to be any imminent danger, the caves are clearly migrating further inland… There’s no imminent danger, [but] that doesn’t mean there won’t be with time,” engineering geologist Schembri said, upon inspection.

Describing the caves’ expansion as an “ongoing process,” Mifsud stressed that while it did not seem to present an immediate threat, if left unchecked the process could eventually result in collapses like that which befell the Azure Window in 2017.

He thinks that of all the caves, Għar il-Lembi closest to the concrete pier at Chalet merits the most attention because the rock is “very fractured” and the wall above is made from masonry and not concrete like the rest of the promenade.

The pair stressed that while it was important that the caves be studied and taken care of on a regular basis, this was already being done by the Coastal and Storm Water Unit within the Public Works Department.

Such study, they added, “doesn’t mean installing expensive instrumentation. It means taking an educated look at the way the rock is behaving and eroding.”

Pointing to two large caves separated by a pillar-like section of rock under the car park close to Fortizza as an example – a formation called Għar id-Dud – Mifsud said, “although it’s well interlocked [and] I don’t think it will fail tomorrow, in the long term it definitely needs to be monitored”.

Scientists Christian Schembri (left) and Adrian Mifsud.

While the Sliema caves extend under the promenade by several metres, according to the two scientists, they are just the tip of the iceberg, representing several large fissures that extend far into Sliema.

Such fissures, or cracks in the rock, typically run northeast to southwest and occur in many parts of Malta, they explained.

But with these fissures extending further into Sliema, could this pose a problem for some of the large tower blocks springing up further inland?

“If you’ve got a cave 10 metres deep, then the load from buildings 60 metres away is unlikely to create a major problem,” said Mifsud, a geotechnical engineer.

“But if for example, you have a situation like Fort Ricasoli [in Kalkara], where an entire fortification rests on the edge of the cliff, that’s a completely different story. It all depends on the proximity, the amount of load and the properties of the material – there is no clear and direct answer to that question.”

"There’s no imminent danger, [but] that doesn’t mean there won’t be with time,” say UoM lecturers.

The state of the caves gained attention again when Sliema mayor John Pillow took to Facebook to point to the absence of a concrete ledge he said had once stood above the sea near Chalet as evidence the front was eroding.

In a video posted to the social media platform, Pillow warned “we can expect the promenade to collapse if there’s a storm from the northeast.”

But according to the two scientists, while such fears may be premature, they are not completely unfounded.

“Just because there’s no danger right now, it does not mean there’s no danger – it needs to be studied further,” said Schembri.

Adrian Mifsud is a geotechnical engineer and University of Malta lecturer, and Christian Schembri is an engineering geologist and visiting lecturer.