Some environmental geologic problems at two landfills for municipal solid waste are exposed in the present work. The landfills are situated in Piedmont high terraces zone, one in the municipality of Magliano Alpi in the Cuneo district, the other in the municipality of Grosso Canavese in the Turin district. The plant of Magliano Alpi is located on a high terrace emerging from the eastern part of Cuneo plain the plain of Cuneo, the terrace has formed consequently to the Pleistocene capture of Tanaro River and the successive remounting erosion of the whole river network. The sedimentary sequence observed from the surface downward shows a Holocene complex around ten meters thick, a low permeable Villafranchian Complex (Plio-Pleistocene) and a marine Pliocene Complex constituted by an alternative permeable sands and unproductive clays. The landfill of Grosso Canavese is located on the high terrace that remains as a relict of the ancient alluvial fan of the Stura di Lanzo River around 30 km north-west of Turin. It is realized in the Mindel glaciofluvial deposits (Pleistocene), more than 40 meters thik. For both the sites, a hydrogeological study has been carried out, especially referred to the monitoring wells, in order to characterize the groundwater from both the quantitative and qualitative. Piezometric maps have been realized for visualizing the general direction of the groundwater flow and water samples have been analyzed at the monitoring sessions in order to control the water quality. During these activities, problems relative to a correct sampling from the monitoring wells have been almost always encountered, as well as inconsistencies in the interpolation of water levels. Sometimes the wells were dry, while, in many cases, the regular purging of the wells before the sampling has caused a too slow recovery of the water level. The hydrogeologic study has revealed that in both sites the monitoring wells don’t tap an aquifer, but a saturated but generally low permeable soil. A local permeability may be related to the presence of lenses of permeable soil (sand, silty sand) in a less permeable matrix, and the different modalities of charging and emptying of these lenses could explain in that way the different levels in the monitoring wells. In both experiences, the data recorded by the monitoring wells are probably affected by uncertainties attributable on the well monitoring efficacy. Given their importance for proper hydrological and environmental data acquisition, a correct design as well as a special care in all phases of their realization are fundamental for the monitoring wells. Proposals have been provided for identifying the depth of the underground aquifer below the landfills and properly design the monitoring wells, in order to take samples of water at different depths.
Environmental-geologic problems relative to some landfills located in the Piedmont high terraces (North-western Italy)
BOVE, ANNALISA;DESTEFANIS, Enrico;MASCIOCCO, LUCIANO
2011-01-01
Abstract
Some environmental geologic problems at two landfills for municipal solid waste are exposed in the present work. The landfills are situated in Piedmont high terraces zone, one in the municipality of Magliano Alpi in the Cuneo district, the other in the municipality of Grosso Canavese in the Turin district. The plant of Magliano Alpi is located on a high terrace emerging from the eastern part of Cuneo plain the plain of Cuneo, the terrace has formed consequently to the Pleistocene capture of Tanaro River and the successive remounting erosion of the whole river network. The sedimentary sequence observed from the surface downward shows a Holocene complex around ten meters thick, a low permeable Villafranchian Complex (Plio-Pleistocene) and a marine Pliocene Complex constituted by an alternative permeable sands and unproductive clays. The landfill of Grosso Canavese is located on the high terrace that remains as a relict of the ancient alluvial fan of the Stura di Lanzo River around 30 km north-west of Turin. It is realized in the Mindel glaciofluvial deposits (Pleistocene), more than 40 meters thik. For both the sites, a hydrogeological study has been carried out, especially referred to the monitoring wells, in order to characterize the groundwater from both the quantitative and qualitative. Piezometric maps have been realized for visualizing the general direction of the groundwater flow and water samples have been analyzed at the monitoring sessions in order to control the water quality. During these activities, problems relative to a correct sampling from the monitoring wells have been almost always encountered, as well as inconsistencies in the interpolation of water levels. Sometimes the wells were dry, while, in many cases, the regular purging of the wells before the sampling has caused a too slow recovery of the water level. The hydrogeologic study has revealed that in both sites the monitoring wells don’t tap an aquifer, but a saturated but generally low permeable soil. A local permeability may be related to the presence of lenses of permeable soil (sand, silty sand) in a less permeable matrix, and the different modalities of charging and emptying of these lenses could explain in that way the different levels in the monitoring wells. In both experiences, the data recorded by the monitoring wells are probably affected by uncertainties attributable on the well monitoring efficacy. Given their importance for proper hydrological and environmental data acquisition, a correct design as well as a special care in all phases of their realization are fundamental for the monitoring wells. Proposals have been provided for identifying the depth of the underground aquifer below the landfills and properly design the monitoring wells, in order to take samples of water at different depths.
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