The length of the Aduna Tunnel is 4690 m. Nortúnel excavated from the mouth on the Andoain side a mine tunnel with a length of 1479 m, with an excavation section of approximately 120 m², with the tunnel free section of 85 m². A 450 m length gallery is also completed, whose excavation section is approximately 25 m².
It cuts through alternating materials with a sandstone, siltstone, rock and marlaceous origin, going through areas with materials such as earth and rock.
It used perforation, blasting and a backhoe with a hydraulic hammer, excavating according to the NATM, applying support based on projected cement, pins and trusses. A provisional advanced counter arch is to be completed along with a micropile shield when the land is in bad condition (earth type).