Reuse of Surplus Materials from the Excavation of the Albertia Tunnel

The project for reuse of surplus material from excavation of the Albertia tunnel in Guipúzcoa (Spain) entailed the treatment of earth excavated from the 2,090- and 2,080-meter bi-tube tunnel while keeping environmental and landscape impacts to a minimum.

The initial solution included two diversions of the river course, which meant that the river could potentially be polluted with run-off materials; but ultimately the decision was taken to divert the river along the periphery of the filled-in and levelled material. In this way, work to carry out filling of the area was made easier, in addition to other environmental advantages, such as reuse of the surplus materials on site and landscape integration of the new river course and of the deposited material.

The various stages of project development were as follows, all of which had received prior approval from the Environmental Department of the Basque Government:

• Provisional encasing of the river while the new channel was put in place. This made work substantially easier and avoided pollution of the water circulating through the tubes provided.
• Implementation of filling and levelling. Materials used occupy a volume of approximately 640,000 m³.
• Revegetation of filled-in areas. Use of hydroseeding for stabilising the embankments and planting with indigenous tree and shrub species.
• Construction of the new river course using stone and a stepped slope, to facilitate the planting of aquatic vegetation and provision of fish species.

This project fulfils the objective of using the close to 700,000 m³ of material from excavation of the tunnel, whilst taking into consideration landscape integration of the environment and promoting its natural recovery, with particular consideration to biodiversity.