ABSTRACT: El Hierro island, 0,2 million years old, is the youngest of the Canary Islands. Since it was recognized UNESCO Biosphere Reserve in 2000, the road infrastructure to be planned has to cause a minimum impact on the landscape of the island. This applies to El Verodal Tunnel to be built in the NW side of the island. Due not only to orography but also to administrative constraints, site studies are scarce. Moreover, the implementation of the existing rock mass classifications for volcanic rocks makes the design of the tunnel harder due to the great variability shown by these materials.

ABSTRACT: The main feature of aquifers in volcanic islands with high rainfall rates and steep topography is that they are on raised, mainly due to the presence of volcanic dikes. Dikes are igneous bodies with very high aspect ratio, which means that their thickness is usually much smaller than the other two dimensions and tend to be vertical or of high dip angle. It can be considered as impermeable and interconnected walls where aquifers, which are recharged by rain, raise the water table between the dikes. This is especially important in volcanic rift zones. The method to obtain water in these volcanic areas involves digging horizontal galleries with explosives. The galleries cross the dikes and drain the water from the water saturated area. The main problem of this type of perforation is to obtain the water continually, without the possibility of water regulation. This question has been solved by means of the reconstruction of several technically viable dikes, to enable the store of water resources through channels in order to regulate the water wealth of the built galleries. Methods, results and viability on the use of the volcanic materials as relevant works of civil engineering highlights on the following paper.

ABSTRACT: El Hierro Hydro-wind Plant is a singular project, as its aim is to make the island energy self-sufficient. It involves constructing two reservoirs—the higher of which began being constructed in September 2009. This article attempts to reflect the peculiarity of the behaviour of the materials at the bottom of this reservoir, which will have to support a significant hydrostatic load, and the difficulty of characterising these in laboratories and design offices in order to assign geotechnical parameters to them which will reflect their geotechnical performance in situ. The studies undertaken to achieve this characterisation are described and the expected settlement of the materials is analysed. Finally, the article describes in detail the ground treatment proposed in order to minimize settlements, whose estimated values are compared with those obtained at the works site.