The Building and Construction Authority (BCA) announced Wednesday that emergency remedial works began on Tuesday at the site of last week's partial collapse at a massive development in Naxxar, after it met affected residents and families to outline the way forward.
In a statement, the BCA said it met residents on Monday, 18 May, together with representatives from Infrastructure Malta, who also addressed road works taking place adjacent to the construction site. During the meeting, residents were informed that emergency works would start following recommendations made by structural engineer and University of Malta professor Alex Torpiano.
Torpiano was appointed by the project's developer, AC Group director Anton Camilleri, known as "tal-Franċiż", to draw up a method statement detailing the works required to eliminate dangers at the site for workers and third parties.
The authority said it imposed several conditions on both the developer and contractor before the works could proceed. These include the obligation to keep the BCA informed of all works being carried out, supported by visual evidence, as well as the requirement for the developer to provide an insurance policy covering the operations.
The BCA also said all expenses related to the emergency works, together with additional costs incurred by the authority, must be borne by the developer. Meanwhile, enforcement officers and officials from the Occupational Health and Safety Authority (OHSA) are carrying out continuous inspections to monitor the intervention works.
The authority pledged to remain in constant contact with residents to safeguard their health, safety and rights.
The emergency intervention follows the publication of a technical report by Prof. Torpiano, which painted a stark picture of the structural instability at the former quarry site, describing conditions there as "very precarious, at various levels".
The report attributes the partial collapse at the foundations of the multi-storey development to a "severe imbalance" between the backfilled material retained within supporting walls and the adjacent excavated void.
According to the report, the collapse was "the result of the construction system adopted and the sequence of backfill material shifting", raising serious questions about the construction methods used on the project.
Torpiano warned that sections of the exposed foundational structure were "clearly unstable", "very dangerous" and liable to fail "without warning". He recommended that the foundations be backfilled again as quickly as possible to stabilise the site.
The report explains that the development sits within a former hardstone quarry that had previously been exhausted and backfilled. The foundations consist of substantial volumes of construction fill reaching heights of up to 12 metres, separated by 23-centimetre-wide radial fin walls supporting a double-curved outer retaining wall.
One of these fin walls appears to have buckled.
According to the report, the outward pressure exerted by the massive volume of fill material was resisted only by the "frictional interface of the toothing ('mursalli')" connecting the fin walls to the outer retaining wall.
However, Torpiano noted that this "toothing" was generally only "one leaf deep", meaning it consisted of a single vertical layer of masonry, while the mortar used was "not likely to have provided any significant bond at the joints".
"It was therefore not surprising that the external wall was pushed out by the pressure," the report concluded.