The construction of Soria great dam (1959) ended in 1972. The dam is a double curvature dome of 132 metres on foundations. A private initiative achieved the construction of the only vaulted dam in the Canary Islands, in a tight where Gran Canaria’s Inter-island Council had previously projected a 90 metres high curved plan gravity dam with foundations (1930) and a hydraulic concrete vaulted dam of a 70 metres high fine wall with foundations (1935).
It was a project by the engineer Saturnino Alonso Vega to build another vaulted dam in Gran Canaria, in a tight of Siberio’s Gully (1968). Its height over the foundations was 78’50 metres, while the top had a length of 190 metres and 5 metres wide. Its reservoir volume was 4.800.000 m³.
In 1972, the thick vault was awarded to the company Dragados y Construcciones, whose representative in the Canary Islands was the engineer Emilio Benítez Pascual, but finally a refurbished project was made in 1973, that defined a rockfill dam solution with asphalt screen in the upper water facing and moved the initial tight some 300 metres lower water. Finished in 1978, its loading occurred suddenly during the extraordinary storm of January, 1979.
The oral tradition collects that Tamadaba’s dry masonry dam was emptied after its first loading. It was immediately repaired. In 1979, happened the same to Siberio’s Dam, after the initial breakage of the plinth due to its scarce sizing and its bad housing. The structure was repaired by means of actions that were carried on until 1984.
Also during the third stage, some concrete dams, such as La Encantadora in La Gomera (gravity) or Ariñez’s dam in Gran Canaria (abutments), although that year the Dam Safety Department put every effort in the design and construction of dams of separate materials. Alonso Franco says that “their opportunity was denied under the belief that the talus of its wet facing minimized to the already meager of its vessels.” We already said that, in the Canary Islands, land is the least of it, what is important is water.
Most of the great dams of separate materials constructed in the Canary Islands are rockfill dams with an upper water screen in the facing. Thus, in La Gomera island the dams of Amalahuigue and Mulagua were constructed, both by the Inter-island Council. But in Gran Canaria, in the mouth of Tirajana’s Crater, a rockfill with central core was constructed. The primitive projects to construct a great dam in the tight of Tirajana’s Gully had been gravity projects.
In the superb article Utilización de materiales pliocuaternarios en presas de materiales sueltos (Use of pliocuaternary materials in dams of separated materials) (1979), the engineers Gómez Laa, Alonso Franco and Romero Hernández highlighted that “Tirajana is a rockfill dam that makes the most the alluvial plan for berms and a cleyey colluvium from basalt, for the impermeabilization.” In one of the books by the engineer José Luis Fernández Casado, the following can be read: “success (there are few comments) observing that the core is central, TIRAJANA.”
In the 21st century, not only must we acknowledge the obvious historical value that Canary Islands’ dams, but to carry out an important revision of the state they are in, specially the masonry dams. In the past, the Dam Safety Department engineers said about the Canary Islands that the civil service should feel concerned. Now, we continue having a civil service, but we do not have a Dam Safety Department.
A personal thought.