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This contribution describes a geodatabase structure designed to manage a large amount of geo-environmental data for the "Gronda di Genova" highway by-pass tunnels in Liguria region (Italy). In particular, an innovative dataset structure founded on an explicit conceptual model was designed to represent the distribution of petrofacies containing Natural Occurring Asbestos (NOA), and their minero-chemical composition. This in order to assess the environmental risk (air dispersion of fibers) due to the tunnel excavation in the asbestos-bearing rocks. Problems related to the GIS (shp) - AutoCAD (layer) conversion have been also considered for delivering the graphic layout of the project and are here discussed.

For a reliable evaluation of the geo-environmental risk due to naturally occurring asbestos (NOA) during rock excavation of large infrastructure projects, a proper procedure is needed. First, it is necessary to provide a detailed geological model tailored to the NOA-related issues that should drive the rock sampling procedures in order to obtain a representative sampling. The sampling procedures should take into account lithological variability and relative spatial distributions of the rock units. The geological model for NOA should be thus constrained by the main NOA petrofacies occurring in a given geotectonic context, which take into consideration both the mineralogical and structural features, and the identification of NOA homogeneous zones in which the NOA petrofacies are distributed. In this paper, some geo-environmental problems faced during the excavation, in meta-ophiolites, of a long highway tunnel are described. The geological model of the complex setting of the tunnel area (northern Italy, Alps-Apennines junction) is described, focusing on how the NOA-related problems were addressed to allow reliable and detailed estimations of NOA contents for each NOA homogeneous zone and the relevant tunnel layout segment.

Naturally-Occurring Asbestos (NOA) may constitute a severe health risk when metamorphic rocks are excavated for large infrastructure projects. For public acceptance, a reliable assessment of the content of NOA is necessary for the design of the construction site, workers' safety, and spoil management. Direct measurements of NOA content can be made by SEM-EDS analyses on an adequate number of samples. Such measurements are sufficiently precise but questions about the representativity of the samples may arise, especially when the rock units are structurally and lithologically complex. Therefore, in order to corroborate the direct assessments, alternative and indirect assessments can be performed by measuring the fracture volumetric porosity, provided that almost all the NOA is deposited as veins in the fractures of the rock mass. Statistical sampling and inference procedures can be applied to derive such an index. In this paper, an indirect assessment of NOA is reported and compared with the assessment obtained by direct measurements. The application is to a metamorphic rock formation through which a tunnel is to be driven as part of the "Gronda di Genova" highway development in Genoa, Italy. Even though significant approximations are made, the indirect assessment is relatively close to the direct measurement.

Realization of large geo-engineering projects in rocks containing naturally occurring asbestos (NOA) must address several crucial geo-environmental issues, including the design of the construction site, the enforcement of health protection measures and the environmentally responsible spoil management. This leads to a compelling need to develop effective and standard procedures to evaluate the distribution and concentration of NOA in rock volumes. NOA petrofacies are here proposed as an innovative tool to evaluate the asbestos distribution and concentration in complex geological settings. NOA petrofacies are fundamental asbestos-bearing rock types, consisting in recurrent lithological and structural features controlling asbestos occurrence. Here we describe and discuss how the NOA petrofacies approach was utilized in a geo-environmental study for the evaluation of asbestos content in a complex meta-ophiolite suite, which will be crossed by the “Gronda di Genova” highway by-pass project (Genoa, NW Italy). NOA petrofacies were used to predict the distribution and relative abundance of NOA in geologically homogeneous zones characterized by the occurrence of specific NOA minerals.

The timing of high-pressure (HP) metamorphism in the internal basement massifs of the Western Alps has been contentious. In the Gran Paradiso massif silvery micaschists, thought to have developed from granitic precursors, contain assemblages indicative of pressures in excess of 18 kbar at 500–550 °C. This paper presents unique geochronological data for the paragenesis of the silvery micaschist HP assemblage. Rb–Sr microsampling of an apatite–phengite pair thought to have remained closed to Rb–Sr exchange since the HP paragenesis formed has yielded an age of 43.0 ± 0.5 Ma. Greenschist retrogression occurred after 36.3 ± 0.4 Ma, probably in the interval 36–34 Ma. The localised disturbance of the Rb–Sr system in phengite, apatite and allanite during retrogression means that only in situ microsampling could obtain meaningful ages from these rocks. The new data indicating a Tertiary age for HP metamorphism in the Gran Paradiso massif agree with recent data for other internal basement massifs in the Western Alps. A model fitting the Gran Paradiso massif into the Western Alpine framework is presented.