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The Chiavàls Tunnel: drilling completed

The drilling of the Chiavàls tunnel, located between Pontebba and Moggio Udinese (in the Udine area) which began last June has just been completed. This achievement, following on from the crossing of the Tagliamento river, is another step forward in the construction of the new DN1200 pipeline for Russian imported gas. The decision to cross by a tunnel this inaccessible area, with its woods representing a natural asset of great value, was dictated by the need to minimise environmental impact.

 

Snam Rete Gas used the innovative T.B.M. technique (Tunnel Boring Machine) for the first time ever in this project, which lines the excavated walls as the boring machine advances. This technology enabled drilling in safe conditions and limited interference with the rock's ground water.

The tunnel, 1,935 m long, was drilled with a full diameter (4.5 m) screened boring machine, clocking up record drilling rates of up to 48 m a day. The photos show the last section of rock detaching. The technique also meant that the route in the Val D'Alba, with surface excavation work, is 300 metres shorter. This area is a site of EU importance (Zuc dal Bor) and has different habitats including black pine forests and pinus mugo and rhododendron woods.

A small part of the site and its vegetation were affected by the works in the area at the end of the Chiavàls tunnel. Different trees and shrubs will be replanted a maquis in the area, in keeping with the natural vegetation at the sides of the tunnel entrance.

 

Special attention was paid to restoring environmental conditions in the storage area in Val di Gleris, used for digging equipment, and in particular to safeguarding the pinus mugo woods and re-establishing the vegetal associations damaged during works. The pinus mugo removed before the start of works to dig the new tunnel were replanted on the upper, sloping part of the storage area and so the pinus mugo woods were restored using material which is genetically and phyto-climatically compatible with the particular environment of the Val di Gleris.

 

The pinus mugo removed using diggers with a bucket to ensure that the roots would be left as intact as possible. The clods of earth around the roots of the pines were protected with jute bags to stop the roots from drying and retain all the soil. The pines were uprooted during the winter dormant season and were temporarily planted close to the worksite. After excavation works were completed and the morphology of the storage area restored, the trees were replanted, digging the right-holes for their size and roots.

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updated
05 August 2016 - 16:35 CEST