Weak rock on Qui-si-Sana peninsula can be problematic for tall buildings - geologist

A protest in Qui-Si-Sana against a number of high-rise projects in the area. Photo: Mark Zammit Cordina

Ivan Martin

Times of Malta 23 June 2016

A geological study submitted as part of the Townsquare high-rise project did not flag a layer of “very weak rock” that could pose problems in supporting tall buildings, an experienced geologist has warned.

“When I say weak, I mean you can practically break the rock with your hands. It’s like chalk. This is a rock that can be problematic if tall buildings are built on it,” Peter Gatt said.

The environment planning statement compiled by environmental consultancy firm ADI as part of the application, says that the only rock types present on the Qui-Si-Sana peninsula were lower globigerina limestone, a strong rock that could support a tall structure – “in fact most of Malta’s towns are built on this rock” – and a layer of phosphate, present across most of the island.

Dr Gatt said that, besides the two layers indicated, the area included a significant amount of middle globigerina limestone, a soft rock. This was the second softest on the island, he pointed out.

You can practically break the rock with your hands. It’s like chalk

The future of the Townsquare project was meant to be decided at a Planning Authority Board hearing scheduled for today. However, the court yesterday upheld a request by residents to suspend any decision until new studies were conducted on a range of issues.

In 2005, Dr Gatt published a scientific paper on the geology of the Qui-Si-Sana area highlighting, among other things, the presence of this much weaker middle globigerina.

“Along the Qui-Si-Sana shore, there is a coastal outcrop where the middle globigerina is clearly visible on top of the phosphate level,” he said.

“What we see in these published test results is a strength of between three and five megapascal below three metres of depth, that is the strength of middle globigerina and not lower globigerina, which would come in at about 15 to 20 megapascal,” he said.The environment planning statement refers to core samples extracted from the area and tested for their tensile strength. Dr Gatt said the results of these tests also “clearly” pointed to the presence of the weaker rock.

Dr Gatt questioned why no geological logs – graphic representations of the core samples taken – had been included in the report.

A scan of the coastal area featured in the report further confounded Dr Gatt, who insisted the middle globigerina was visible at outcrops of the rock face along the Qui-Si-Sana coast.

Architects who spoke to this newspaper warned that the presence of this rock could mean that the developers would have to take a number of precautionary measures, which would include a reassessment of the foundation structures to be laid and of the excavation works to be carried out.

Questions sent to the Environment and Resources Authority yesterday had not been replied to by the time of writing.