Improvements to the GI-638 highway between Deba and Mutriku requires the building of the de Alkolea tunnel.
Its total length is 106 m, of which the central section is 80 m, built in a gallery, with artificial tunnels in the 16 meter tunnel mouths in the Deba side and 10 m mouth on the Mutriku side.
The gallery tunnel has its mouth at the PK 3+038 and exit mouth at PK 3+118. A single two carriageway pipe in opposite directions.
The average total section of the tunnel excavation is 73 m².
The materials we bought through belong to the Supra Urgonian Complex from the Albian Superior-Cenomanian period. Made up of bands of sandstone flysch and black lutites and by calcareous lutite rocks and black loams.