THE QUARRY WASTE “RAVANETI” IN SICILY: GEOMORPHOLOGIC ASPECT

In Sicily, the activity of extraction and workmanship represents an important productive sector that is substantially concentrated in the two poles; Catania (where the lava stone is worked) and Trapani (in the marble compartment of Custonaci) where over ten types of workable sedimentary and polished rocks are extracted. This area is particularly characterized by the presence of mesozoic carbonatic rocks used as valuable stony materials; "marbles", that are formed in environment of carbonatic and pelagic platforms (seamounts), during an active tectonic regime. They were formed, therefore, in a geologic context which has encouraged their formation with a brecciate texture, of polycyclic origin and with extremely varying colors. In the quarries of the area of Custonaci (75% of the regional production), there are mainly extracted litho types clear ivory colored, variegated with various veins of light brown, distinguished in “Perlato”, “Perlatino of Sicily”, “Avorio Venato”, “Botticino”, according to the more or less heterogeneous and fine grain. To these ones, “Nerello” must be added; a dark grey colored rock with yellow veins. As a consequence of the intense quarrying protracted at the time, the marble basin of Custonaci is now characterized by enormous volumes of discarded deposits coming from cultivation (in some cases they can reach dozens of hectares), called quarry waste (“ravaneti”) which flow into the slopes next to the areas of quarrying. The quarries endanger the Geomorphological integrity of the Custonaci.area. This happens not only in terms of deep and superficial water pollution, or even in terms of atmospheric contamination due to dust dispersion, but, more significantly, intense quarrying and constant removal of rocky materials naturally provoke irreversible alterations of the morphology of the mountain profiles and its plains. In addition, the quarry waste (“ravaneti”), laying right in the quarrying areas,  represents one of the principal sources of hydro geological instability, provoking rock-falls and debris flow. In the past few years, many spots of quarry waste have actually provoked events of landslide in terms of mass transports of detrital deposits. During the accumulation of the quarry waste, the deposits are initially placed according to their own angle of repose, generally elevated with values of up to 40-45° and with granulometric percentages of: rubble 30%, grit 25% and sand 45%. Their disposition, during their accumulation, is a consequence of their surface roughness, irregular shapes and dimensions. The continuous feed from the top naturally leads to the modification of the scarp dimensions and steepness, so the angle of repose is often overcome. What is said involves the partial gravitational mobilization along the slope of quarry waste, with the tendency to have the coarsest elements towards the groin of the slope, as it happens for the strata of the debris cones. These sudden gravitational events are more frequent in the periods of great rainfall and when thinner materials are brought inside of the quarry waste body. There are conditions of insecurity, therefore, for the infrastructures surrounding the areas of mining and a continuous change of the Geomorphology of the places. Such a huge quantity of quarry waste represents a primary resource of good quality loose stony materials. They could be separated and charted according to the following five parameters: typology, granulometry, permeability, activity and drawing areas. Drawing these materials could represent an environmental and Geomorphologic redevelopment of the sites and it represents a partial management of the marble fields. The results of the investigations made on this quarry waste suggested the possibility of exploitation as inert materials for road and railway construction and other infrastructural projects, as also shown by the analytical data of the laboratory experiments. Moreover, "ravaneti" are also suitable to be used as material for the reclamation of disused and abandoned quarries. All of this, represents a favorable result from an environmental point of view as it would get the advantage to reduce the demand of cultivation of new loan quarries and it would be possible to reemploy some quarry waste, avoiding their deposition in areas next to the site of quarrying and modifying the morphological configuration of the territory.