Residents’ long wait to be rid of floods in Birkirkara, Msida and nearby areas is almost over, with the ambitious project aimed at solving this perennial problem set to be completed by the end of November.

The complex network of underground tunnels stretching 11 kilometres will be able to handle up to 40 millimetres of rain in an hour, which will be channelled into the sea at Ta’ Xbiex. This kind of downpour is normally experienced once every five years.

The tunnel’s outfall in Ta’ Xbiex.

However, some of the excess water will be pumped back to a reservoir in Gżira as part of a plan to replenish the water table.

Project leader Carm Mifsud Borg briefed the Times of Malta on the works left to be done in this major component of the EU-funded National Flood Relief project, which covers 12 localities in all. This part costs €28 million of the €52 million being spent on the whole project.

By the end of this month, Valley Road in Birkirkara and Msida – notorious for torrents of water strong enough to sweep vehicles away – will be connected to the rest of the flood-relief system.

The end of November should see the completion of similar works all the way up to Wied Inċita in Attard and the area near the Lija cemetery.

Apart from these areas, the flood-relief project also has three other independent components. The one in Żebbuġ was completed last July, the Marsascala component is due to be inaugurated soon and that in Qormi has already been operational for a year.

Excavations started in 2012 in Attard and were completed this time last year, when the boring machine broke through the other end of the tunnel at Ta’ Xbiex.

The original plan was to transport the debris by sea but it was eventually scrapped. Instead the excavated material was loaded on to trucks and transported all the way up to Attard via the tunnel itself, to minimise the impact on traffic.

For the past year the project was hampered by the porous Ta’ Xbiex rock, which needed special concrete reinforcement injected from the surface.

Another obstacle was seepage from the sewerage system in Lija.

The project is set to alleviate the heavy flooding at Valley Road in Msida.

“In addition, we obtained new funds to expand the final 1.3 kilometres of the tunnel at Ta’ Xbiex in case the project would need to be further expanded,” Mr Mifsud Borg said.

“This part of the underground complex is similar in size to the St Venera bypass tunnels, with a diameter of 6.5 metres.

“Though it may seem impressive, its full capacity of 30,000 cubic metres is almost insignificant when compared to the deluge which big storms bring about,” he pointed out. Once operational, the system will require regular maintenance to its filtration system, designed to prevent contaminants like oil from being flushed into the sea and possibly into the water table.

“The worst enemy are plastic containers, but the system is designed to cater for any blockage in one of the various gratings spread out along the network,” he said.

Though the final part of the underground water course is seven metres below sea level, the tunnel was designed in such a way as to siphon out its contents into the sea.

The remaining works before the project’s inauguration include the exterior finishing of the outfall and the closure of a nearby temporary access in Ta’ Xbiex. Meanwhile, residents who have for years watched helplessly as their streets became raging rivers are keeping their fingers crossed that no major storms will hit before the project is completed.