Rainwater infiltration ‘might’ have caused Guia landslide

The Municipal Affairs Bureau (IAM) said the cause of the landslide last Friday at the Guia Hill area which led to the fall of the protection wall and interruption of all traffic on Estrada de Cacilhas “might have been caused by the rainwater infiltration in the soil on that area.”

This information came in a reply to the Times, although it was noted that the Civil Engineering Laboratory of Macau has already been commissioned to undertake a further investigation to ascertain the exact causes.

In the meantime, the IAM said that the entity’s responsibility over the issue at the moment is only to collaborate with the Land, Public Works and Transport Bureau (DSSOPT) in the removal of the soil and debris in order to reestablish the circulation of traffic as soon as possible.

According to information also obtained by the Times from the IAM, the “temporary repair work being performed in order to reopen the road to traffic, should take from three days to a week.”

The reopening would ultimately be the decision of the Transport Bureau, when it considers that the safety conditions are sufficient to do so. It is expected that in the first phase, the road will reopen only on one traffic lane that will have to be shared by traffic in both directions.

The full completion of the works in order to reestablish all hillside and regular circulation of Estrada de Cacilhas “is expected to take at least two months, but this will depend on the conditions and the evolution of the works on site,” IAM said.

THE IDES OF MARCH

The IAM said they already knew that the slope in the Guia area had structural problems and, in fact, the works being done at the time of the incident were part of the measures to tackle the issue that had been detected in a late March report from the Slope Safety Information Network task force.

The report indicates that the group, which is a part of the DSSOPT, detected a total of 223 cases of slopes at risk of landslide.

However, in none of the cases was the risk considered high, with 69 of the cases deemed medium risk and 154 low risk.

Within the category of medium risk of landslide, there were 28 cases reported in the Peninsula, 25 in Taipa Island and another 16 in Coloane, allegedly. According to IAM, the Guia case was one of those categorized as medium risk which is why construction works were being held at the site as part of the restoration of that slope.

Meanwhile, preventive measures have been enforced on site in order to guarantee a reinforcement of the part of the wall that did not collapse, making use of large dimension concrete blocks.

Contacted by the Times regarding the case, a local based civil engineer who preferred not to be identified hypothesized that, during the excavation work performed by the IAM, “there might have been vibration transmitted to the wall or even touched [with drillers] in the wall and it eventually fell.” He further noted it is possible to see that there are other areas of the wall that remain in place in which lumps are visible, affirming, “it is not a good omen. They should demolish the rest of the wall, make one in concrete from behind and then place the original stonewall in front of that concrete wall just to decorate.” However, he pointed out that this is only one of the possible solutions.

Regardless of the solution chosen, the engineer said, “They must rush to do this because the Grand Prix is not that far [away],” noting that any of the possible solutions would take some time to finish.

This is a concern that seemed to be endorsed by IAM’s president José Tavares during his comments to the media over the weekend. “We will open a [public] tender and hope to do a total repair within two months. But the restoration project needs to be coordinated with the Cultural Affairs Bureau (IC) because the outer wall is in the area of world heritage sites – we will need to discuss the repair plan with the IC,” he said.