In the parts of the excavation which are not adjacent to existing roads, land containment for basements wall is attained by using double-sided concrete formwork. The poor quality of the material from the excavation meant that it was not suitable as a fill or for compaction of the backfill of the basement wall, so it was necessary to use fill material.

We also noticed that the land characteristics made the slope of the excavation very steep. This fact, along with the depth of the excavation - almost 12 metres -, involved a high risk of entrapment at the bottom of the excavation, in the event that filling and compaction was performed using traditional methods.

To make the filling it was decided to use aggregates that do not require compaction, selecting an aggregate from rubble recycling. This aggregate, composed mostly of ceramic products, provides the soil with a bearing capacity suitable for the pedestrian transit which it was intended.

This solution makes unnecessary for personnel to access to the bottom of the excavation, thus resolving the safety problems raised.

• For backfill of the wall, approximately 9,800 tons of aggregates from recycling were used, with grain size 8/20. The use of recycled aggregates instead of aggregates from a quarry has resulted in a significant reduction in the consumption of natural resources, valuating a material which otherwise would have been destined for a landfill, and making unnecessary to extract natural resources.
• The implementation of this practice at the works demonstrates that using recycled materials, such as recycled aggregates, shows high technical expertise and it has associated clear environmental and financial benefits for the works itself and for Society as a whole.