The Grave del Pompiere sinkhole (Italy) an example of re-activation of water sink within a high vulnerable karst area

The occurrences of sinkholes are a hazard to many forms of construction and human activity. A number of damages associated with sinkholes can be found throughout the literature. However, while most engineers and geologist have experience of some of the ground engineering hazards created by single cavities, the range of the potential hazards as well as the implication about hydrogeological and geological prevention and protection are not always appreciated. Knowledge of the mechanism of formation of this subtle geohazard is therefore necessary to planners and decision makers for performing the most appropriate and suitable programs of karst land use and development. In Apulia region, due to the widespread presence of carbonate rocks, surface and underground landforms were extensively involved in karst processes. In the last ten years, the region have been repeatedly affected by several sinkhole events, some of which have damages or destroyed roads and buildings. The evolutions of other episodes of land subsidence have threatened some human structures. On 3 January 2005, in the surrounding of Grumo Appula village, a karst sinkhole has occurred. The Nucleo SAF of the Bari Fire Brigade has performed the first exploration being the sinkhole located in the vicinity of a railway. The cavity has called "Grave del Pompiere". Geological and speleological survey have performed. The sinkhole is related to a cave, like dome in shape, arranged along a fault zone. The sedimetological features of the underground deposits, allows us to reconstruct a detailed history of the cavity evolution. On the speleological point of view, the "Grave del Pompiere" can be defined a collapse in fault zone. Taking into account the hydrological features of the Grumo Appulo area, the cavity represent an example of water sink re-activation. The territory appear to be particularly interested by this type of karst forms and the associated environmental evolution. It must be considered as a high vulnerable area. As a consequence, the human activities and constructions can be exposed to subtle natural hazard. A good understanding of the mechanisms of re-activation of the water sinks is therefore very important in the process of risk mitigation.