Feasibility study of underground works of the Aguayo II hydropower plant project

Category: News

E.ON España is planning the extension of the existing pumped-storage plant Aguayo I which is located in northern Spain about 40 km south-south-west of Santander, the capital of Cantabria. It is planned to add a new power plant Aguayo II and connect it to the existing reservoirs of Aguayo I.


Client: E.ON España
Total investment costs: € 600 millions
Project description:
The current proposed overwater intake structure, located in the Mediajo reservoir, would receive and channel water into two penstock tunnels (total length ~1 km) with an excavation diameter of approximately 7 m to power four 250 MW turbines installed within a deep underground cavern complex, consisting of two caverns (power house and transformer cavern), followed by two tailrace tunnels (total length ~3 km) with an excavation diameter of approximately 9 m ending in the Alsa reservoir (underwater intake).
Cantabria’s Triassic is constituted of its three characteristic Germanic facies, principally appears in the extend outcrops of the oriental edge of the Iberian Palaeozoic Asturian massif, in the Escudo de Cabuérniga Sierra and in the Besaya River area (Reinosa area). It lies discordantly over Palaeozoic carbonaceous black slates which would be the underlying formation.
The Mediajo and Alsa reservoir area is included within the Buntsandstein series. Dominant lithology is claystone/ siltstone, followed by sandstones and shales, in similar proportions. Highly altered red shales become greenish clays.
Our services:
The aim of our services is to identify and estimate the feasibility of the underground works of the hydropower plant project Aguayo II concerning the underground works from the technical and economical point of view:
• Identification and compilation of the characteristics of the ground analysing the results of the geotechnical surveys
• Definition of geotechnical rock mass parameters
• Identification and evaluation of the tunnel alignments and cross-sections including possible mining methods with respect to geotechnical matters
• Identification of principal necessary rock consolidation and ground supporting system of the cavern and tunnel construction by means of FEM calculations & wedge analysis
• Analysis & definition of the internal tunnel lining concept of the penstocks & tailrace tunnels
• Time & cost estimation of the underground works