The inflow into aquifers of transition metals leached from muck disposed in quarries is a process that requires a detailed analysis in the framework of the environmental impact studies of dump sites. It is important to thoroughly examine the risks of potential contamination of pre-existing groundwater wells and, more in general, to assess the risk of qualitative deterioration of nearby shallow aquifers. It is necessary to reliably predict the chemical evolution of the meteoric waters interacting with the excavated debris, with particular reference to the concentrations of transition metals, during the percolation in the vadose zone and in the subsequent migration and dispersion in the shallow aquifer. This prediction must include chemical speciation studies of the transition metals, reaction path modelling zones. To apply the proposed method, valid both for natural and backfill materials, it is necessary to carry out on the muck a set of chemical analyses, including the sequential extraction tests. These tests enable to assess the speciation of transition metals that, in turn, allow one to assess the risk of groundwater contamination in a more reliable way compared to the sole application of the single extraction procedures that are usually carried out in compliance with the current legislation. The discussed method is applied to the C.na Pecorara quarry in Tortona (AL), which is the disposal site of the debris produced by tunnel excavation in the framework of the HV/HC “Terzo Valico” project. This study has been carried out to evaluate the possibility that the wells adjacent to the disposal site might be contaminated by Chromium VI, Nickel and Cobalt acquired by meteoric waters percolating through the excavated debris.

The inflow into aquifers of transition metals leached from muck disposed in quarries is a process that requires a detailed analysis in the framework of the environmental impact studies of dump sites. It is important to thoroughly examine the risks of potential contamination of pre-existing groundwater wells and, more in general, to assess the risk of qualitative deterioration of nearby shallow aquifers. It is necessary to reliably predict the chemical evolution of the meteoric waters interacting with the excavated debris, with particular reference to the concentrations of transition metals, during the percolation in the vadose zone and in the subsequent migration and dispersion in the shallow aquifer. This prediction must include chemical speciation studies of the transition metals, reaction path modelling zones. To apply the proposed method, valid both for natural and backfill materials, it is necessary to carry out on the muck a set of chemical analyses, including the sequential extraction tests. These tests enable to assess the speciation of transition metals that, in turn, allow one to assess the risk of groundwater contamination in a more reliable way compared to the sole application of the single extraction procedures that are usually carried out in compliance with the current legislation. The discussed method is applied to the C.na Pecorara quarry in Tortona (AL), which is the disposal site of the debris produced by tunnel excavation in the framework of the HV/HC “Terzo Valico” project. This study has been carried out to evaluate the possibility that the wells adjacent to the disposal site might be contaminated by Chromium VI, Nickel and Cobalt acquired by meteoric waters percolating through the excavated debris.