A twin tunnel was excavated near Bolzano (northeastern Italy), with the crown being located 15 m below the bottom of an old unlined landfill, used until the 60's to dispose of miscellaneous waste, including residues of explosives and pesticides. The paper describes the health and safety plan adopted to protect the workers during construction from leachate infiltration and the techniques proposed for the primary support and the final lining.
Un double tunnel etait perfore, avec des charges d'explosif reduites, pres de Bolzano (au nord-est d'Italie), avec la voûte de l'excavation 15 m au-dessous d'une vieille decharge sans revêtement etanche, utilisee jusqu'à les annèes soixante pour le stockage de dechets melangees avec des substances chimiques, parmi lesquelles residus des explosif et de pesticide. L'article decrits les procedures utilisee pendant l'excavation pour proteger le travailleurs e les modifications adoptee pour Ie revêtement du tunnel.
In der Nahe von Bozen wurde ein Dofppelröhren Tunnel durch abgestuftes Sprengen vorgetrieben. Die Tunnelfirste lagen ca 15 m unterhalb der Basis einer alten, nach unter nicht abgedichteten Abfalldeponie, die diente bis in die 60er Jahre zur Ablagerung von Abfallen unterschiedlischster Art, u.a. Sprengstoffreststoffen und Pestiziden. Die wahrend des Tunnelvortriebs durchgefuehrten Arbeitssicherbeits- und Arbeitsschutzmaβnahmen werden Vorgestellt, sowie die fuer den Zwischen- und Endausbau des Tunnels vorgeschlagenen Maβnahmen.
The Castello Tunnel, a twin tunnel about 780 m long on the motorway between Bolzano and Merano (Alto Adige, northern Italy), passes through a columnar basaltic rock mass near a bend of the River Adige, southwest of Bolzano. Two landfills are located in the area, an "old" landfill (mostly containing industrial waste, With a capacity of 300,000 m3), and a "recent" landfill (mostly containing municipal waste, with a capacity of 2,000,000 m3). A 15 m thick layer of vertically fractured rock separates the tunnel from the overlying old landfill on the Merano side. The recent landfill is upgradient of the tunnel, on the Bolzano side. The ancient Castle Firmiano, which is a historic monument, is located above the tunnel on top of a hill (Figure 1). The old landfill was active from the end of World War II until the 60's. It was first used to dispose of debris from the bombed buildings of Bolzano and perhaps residues of explosives. Landfilling then went on in an uncontrolled manner, because the landfill was open to the public: in addition to municipal waste, it also contains wastes from a pesticide factory, contaminated by lead arsenate. The recent landfill started operations in the 70's and is still active. This landfill contains municipal waste and foundry waste. It is only partly provided with an HDPE base liner. The contamination of the area by the old landfill has been known since at least the 60's, when some agricultural wells had to be closed due to significant impact of heavy metals, arsenic and ammonia. In order to mitigate this impact, the top of the old landfill was levelled off in the 80's and partly covered with a HDPE membrane. The construction of trenches to collect the leachate outcropping from both landfills (and particularly along an old railway track which encompasses the old landfill) in a HOPE lined pond also reduced the amount of impacted water reaching the surrounding area. However, due to the potential for seepage of leachate through the underlying rock mass, various preliminary investigations were carried out in the area prior to starting the construction of the Castello Tunnel under the old landfill in order to assess the existing situation and potential interaction.