THE ANOMALOUS LA ROSSA GROUNDWATER OF THE VAL D'AGRI OIL FIELD, SOUTHERN ITALY

A massive injection of wastewater associated to the production of the Val d'Agri oil field (southern Italy) started since 2 June 2006 in the Costa Molina 2 well, through pumping in the underground of an area subject to an high seismic hazard. In 2011 two anomalous pools of turbid, warm and saline groundwater suddenly appeared on agricultural soils of Contrada La Rossa (Montemurro), at a distance of ~ 2.3 km from the injection well. Site surveys were conducted in order to investigate properties and source of La Rossa murky groundwater, by combining data of previous water analyses with the new ones, field mapping, hydrogeological observations and recently published data on the seismotectonic framework of the area and wastewater induced microseismicity. The results of this investigation: 1) confirm the similarities of La Rossa groundwater with the general properties of oil wastewater from many basins in the world and from Val d’Agri; 2) document the mixing of La Rossa toxic groundwater with meteoric groundwater; 3) indicate that injected wastewater may have reached the surface in Contrada La Rossa after migration for several kilometers in the underground, according to data of Improta et al. (2015), that document the presence of faults with high-permeability fractured zones just below the Costa Molina 2 well and microseismicity induced by wastewater injection; 4) reconstruct the Quaternary tectonic structure of the Costa Molina 2 area, identifying a morphostructure controlled by normal faults oriented NNE-SSW dipping ESE and NNW-SSE dipping WSW, where induced microseismicity appears to be concentrated.