Author of article: Luca
Perazzoni (Young Member of SIG)
Authors of paper: M. Comedini,
A. Ferrari, F. Nigro, G. Petito
The new high-speed/high
capacity railroad "Terzo Valico dei Giovi" runs mainly
throughtunnels into rock formations
known as “Ophiolites” that potentially contain asbestos. Duringthe project’s approval
phase, the CIPE (Inter-Ministerial Committee for Economic Planning)
has focused on the Asbestos issue, prescribing the definition of
action execution procedures in the event of the objective proof of
the detection of asbestos.
The Environmental
Observatory has set up a Working Group to draft the Asbestos
Management Plan for Terzo Valico. Based on the geological model, it
defines the “Probability of Occurrence of Asbestos-bearing
Minerals” for each lithological formation with three
asbestos-finding probability classes: Negligible, Medium-Low and
High.
The Asbestos Management
Planestablishes the procedures and frequency of the excavated
material characterization operations. In the case of asbestos
presence, the threshold value that authorises soil management in
terms of by-product is equivalent to 1000 mg/kg.
For conventional tunnelling,
material sampling is carried out directly at the excavation front
from 8 different points of the excavation front.
In figure, a sampling
grid
For tunnels excavated with
Tunnel Boring Machine (also known as TBM), the excavation front is
inaccessible and material is sampled once the rubble is on the
conveyor belt. Special lab analysis, like Scanning Electron
Microscope (SEM) and Phase Contrast Microscopy (PCM), allow to verify
the presence of asbestos in the rock material in 48 hours with an
accuracy of about 100 mg/kg.
Specific monitoring points
have been installed to detect any dispersions of asbestos fibres into
the air, starting from the source of emission, moving out
progressively toward soil deposit sites. Additional monitoring
points detect the emission in sensitive receptors (schools,
buildings, etc).
Government authorities and
supervisory bodies can consult the rock mass and air analyses results
by mean of on purpose databases. Special attention has been
paid to the management and dissemination of the collected data to
the citizens. For this reason, have been develop tools for
communicating this information to the citizens by a web portal. The
experience gained at the “Terzo Valico” sites can be used to
create valid models to be applied, after suitable adjustments, to
other infrastructure projects impacted by similar issues.
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