The demolition of City Gate and the shops around Freedom Square, in Valletta is expected to start in July or August when the geological studies being undertaken would have been concluded.

Grand Harbour Regeneration Project CEO Chris Paris said the geological studies served to give architects and engineers more information on the type of rock on site so they could plan how to lay the foundations for the new Parliament building. The studies could not start before the permit was granted.

Architect Konrad Buhagiar, the local representative of Renzo Piano Building Works, the firm entrusted with the design of the City Gate project, explained that three different studies were being carried out on site.

The first was a geothermal study to see whether the initial plans of using boreholes to use less energy to cool the Parliament building in summer and heat it in winter were correct.

He said several boreholes, 150 metres deep, were being drilled so as to ascertain the temperature of the rocks. The investigations had so far proved the assumptions made at design stage, that the holes could be used for the cooling and heating system of the new Parliament because rock is cooler than air in summer and warmer in winter.

About 80 such boreholes will be used on the project. Each hole, four inches in diameter, will have two pipes with water running through. In summer, room temperature water will surface cooler and less electricity would be used in the cooling process.

Mr Buhagiar said other investigations were being carried out inside the shops around Freedom Square. Walls at the back of the now empty shops were being removed to reveal the rock behind so engineers could assess its suitability for new foundations.

He said workers were also uncovering an old trench around the former opera house, where water used to be collected. The trench, known as French drains, is 11 courses deep and is expected to be used to keep humidity out of the new open-air theatre.

When asked, Mr Buhagiar said some parts of Freedom Square underneath the new Parliament building would be dug four metres deep to fit office space. He confirmed that the old railway station and tunnel beneath the square would be preserved.