Alto Lindoso Dam

The Alto Lindoso Hydroelectrical Development is comprised essentially of:

- The concrete dam of the double curved dome type with a maximum height of 110 metres and a volume of 510,000 m3 extending along the 297m crown and equipped with two depth discharges;

- Two 9 m diameter tunnel overflow discharges with a capacity of 2,770 m3/s and fitted with 6 segment type sluices;

- Two independent water outlets with one for each generator fitted with caterpillar sluices mounted on two concrete towers, 8.7 metres in diameter and 90 metres in height;

- Two chambers and two shafts with total length of the order of 500 metres per generator with an approximate diameter of 5.5 m;

- A spherical valve chamber located at the bottom of two shafts just upstream of the plant where two valves weighing 250 tons each are mounted;

- A subterranean plant measuring 20.85 x 91 m2 with the main floor at an elevation of 27.00, measuring 91 x 21 and at a height of some 40 m;

- Two ´Francis` turbine generators are installed in the plant, each with a potency of 350 MVA and a maximum drop of 281 m;

- A dam shaft linking the plant with the exterior measuring 350 m in height with a diameter of 6.8 m;

- A chamber with butterfly valves downstream of the plant;

- A stand pipe with the following elements; main shaft 65 m in height and a diameter of 21 m;

- A supply chamber 380 m in length and 9,5 m in diameter;

- An expansion chamber 300 m in length and 12 m in diameter;

- The capacity of the main shaft and the respective chambers is of the order of 84,000 m3;

- Return tunnel with a length of 5070 m and a diameter of 8.3 m;

- 18 KV / 400 KV substation.

The return tunnel should also be referred to due to its size and complexity. Said process includes:

- A tunnel 5070 m in length and 8.3 m in diameter as stated above with only two approach chambers corresponding to a section of 53 m2

- The execution of these works represented the pouring of 180,000 m3 of concrete for the shuttered area taking place over 16 months of continuous working;

- A telescopic metal pattern 60 m in length and 8.3 m in diameter equipped with an independent system for movement weighing some 300 tons had to be built for the production of this element;

With said pattern and combining and optimising the means of manufacture, transport and pouring of the concrete, weekly progress was achieved of 115 metres with concrete pouring rates of the order of 35 m3/hour for 24 hours.