ABSTRACT
The regional framework of Porto area consists of a crystalline fissured basement complex composed of highly deformed and overthrusted Late Proterozoic/Paleozoic metasediments and granitic rocks (Chaminé et al. 2010). For more than six centuries, water was supplied to Porto City through fountains fed by numerous springs. Paranhos and Salgueiros Spring galleries catchworks (3.2 km long) were excavated in the granite substratum of the city to gather the groundwater for public use to Porto inhabitants (Fig. 1). Paranhos is one of the main water galleries excavated in the crystalline bedrock, moderately deformed granitic rocks, randomly crossed by aplitic/pegmatitic veins. Our study is focused in the sector between St. Dinis and Burgães street entrances reaching a total length of 910 m divided in three segments. St. Dinis is the shallower entrance (higher altitude), where overburden is minimum. Ventilation shafts are located in many sectors of the gallery. The tunnel has an internal diameter of 2,20 m and a maximum cover of 21 m and a minimum of 1 m.
