The Malta Independent 30 May 2020, Saturday

Water tunnel boring probable cause of vibrations keeping Attard residents awake

Rebekah Cilia Sunday, 3 May 2020, 10:45 Last update: about 26 days ago

A water tunnel that is being excavated between the Pembroke reverse osmosis and a reservoir at Ta’ Qali is probably the cause of the constant vibration being felt by some Attard residents.

Speaking to this newsroom, the residents said that vibrations have been felt throughout the night, keeping them awake for the past week.

This is not the first time people have been deprived of their sleep because of this project. In November 2019, it was reported that politician and university professor Arnold Cassola had written to the Ombudsman voicing his complaint that hundreds of families in the Swieqi and Ibraġġ area were being kept awake because of this tunnel project.

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The Attard residents who spoke to this newsroom first felt the vibrations on the night between Monday and Tuesday of last week. They noted that while noise and vibrations are commonplace in their area due to construction sites and the Central Link project, “it is something you have to live with.” They said, however, that vibrations lasting all throughout the night are not. 

While vibrations were mainly felt from the residences going down to the basements, the noise became much louder. They also confirmed that no one was working on the Central Link project during the night.

The vibrations diminished as the week went by, with the residents suspecting the boring was moving along. They, however, said that it was very insensitive of the Water Services Corporation (WSC) that the same process was being carried out, that of boring at night, despite the previous report to the Ombudsman. 

Cassola had asked the Ombudsman whether the WSC could stop from continuing the works at night, saying that night rest is a fundamental human right.

The Attard residents said the tunnel is an important project, which the country will benefit from, but could not understand why such an inconvenience had to be carried out at night, and if there was no other option, why they were not informed beforehand at least.

A report on the project was also carried out by the Environment Resources Authority (ERA), noting that the construction of the tunnel involves excavation works underneath the localities of Pembroke, Swieqi (I-Ibraġġ), San Ġwann, Iklin, Naxxar, Attard and Ta’ Qali, whereby the entry points will be located at the Ta’ Qali Reservoirs, a quarry at Iklin, a quarry at Tal-Ibraġġ, and the Pembroke RO plant.

The tunnel will have various access nodes, two of which are located in Attard.

ERA noted that given that the tunnel will be excavated by tunnel boring machines, the generation of noise and vibrations is envisaged. Such vibrations could potentially re-radiate within nearby buildings as low-frequency audible noise, and potentially set buildings into mechanical resonance.

It continued to note that as most residential buildings in Malta are mechanically connected to the lower rock strata, such residential structures on the same rock strata as the tunnel, both higher and lower physical heights, are most sensitive to building vibrations and ground-borne noise and could be potentially affected. 

Such impacts are considered of moderate to major significance along the entire tunnel route, whereby the residential areas are envisaged to be predominantly major adversely impacted, ERA said.

The only mitigation measure available, ERA noted, would be the limitation of works to daytime hours, however, this would not reduce the perceived vibration levels. In this instance, the residual impact remains moderate to major significance.

ERA also said that the shafts being built in the Attard area, among others, would have “major” impact due to what they referred to as “sensitive receptors” (including residential areas, schools, old people’s homes and heritage protection sites).
The tunnel connection will allow the pumping of desalinated water to the Ta’ Qali reservoirs for blending with groundwater. Subsequently, the blended water will be distributed to other reservoirs in Malta, including Fiddien, Naxxar, Qrendi and San
Ġwann.

The tunnel will have a total length of 9.8 km, with a varying cross-sectional diameter of 3 to 5m and area of 8.4 m2.

Works on the tunnel started in October 2019 and it is expected that it will take 30 months to complete.

 

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