Local natural resources for the construction of an emergency “green road” on recent volcanic lava in a biosphere reserve territory

Abstract

Building infrastructures in sensitive territories with high environmental protection is a difficult challenge given the need to harmonise the conservation of natural and cultural heritage, the sustainable economic and social development, the use of ecological, recyclable and non-polluting materials ―reducing petroleum-base products, minimising energy consumption and emissions, and reducing impacts on the hydrology. These difficulties are multiplied if the infrastructure is also an emergency work necessary to restore transport links and basic urban services between the villages that were isolated after the recent volcanic eruption on the island of La Palma (Canary Islands), allowing their social, agriculture, tourism and business recovery after the natural disaster. As an added problem, the very recent volcanic lava flows keep temperatures a few metres below the surface that are too high for construction works and for certain materials such as asphalt pavements, and probably maintained beyond the infrastructure lifespan. However, these abundant geomaterials from the volcanic eruption have favourable pozzolanic and binding properties. The recent road (LP-213) on volcanic lava flows at temperatures between 150 and 300 ºC at a depth of 3 m. is an example of building infrastructures in these difficult conditions. Previously, convection temperatures were monitored by means of boreholes, infrared thermal maps and probable subsoil lava channels were drawn up, and topographic survey were prepared using unmanned aerial vehicles (UAS). All the materials come from the volcanic eruption or are locally produced: volcanic ash, aggregates and rockfill; and lime concrete, which is resistant to high temperatures as an alternative to asphalt pavements. All of them are 100% recyclable, thus guaranteeing the sustainability of the resources. The results show that it is possible to build in a sensitive environment in extreme conditions by combining modern surveying techniques with the exclusive use of locally-sourced natural geomaterials, reducing energy consumption and emissions by more than 65%.