The San Andrés tunnel is suitable for 653 m, with a 95 m² free section. Completed using conventional measures, via perforation and blasting on lutite and sandstone rocks. The supports are installed using projected cement, pins and metallic trusses, according to the quality of the land. Finally, a final 30 cm waterproofed concrete formwork coating is installed. Between the primary support and the final coating a waterproof sheet and geo-textile is installed.