The project involved the replacement of the existing DN 500 (20″) San Salvo – Biccari main line for the entire section with an upgrading pipeline (DN 650, 75 bar, 87+875 km) starting at the existing plant in San Salvo (CH) and terminating within the newly constructed plant in Biccari (FG). I.CO.P S.p.A was involved in the construction of two microtunnels and related wells.

Characteristics of the operatio.
The Costa Fracara MT was developed on heterogeneous soils, from cohesive silty and clayey in the central to silty and sandy-gravely at the extremities. Therefore, the following risk mitigation measures were opted for:

• use of a mixed-type tilling head;
• use of an excavation machine equipped with medium-pressure clay nozzles;
• adjustment of drilling mud characteristics to the conditions of the excavated soil, with special attention to lithotype changes.

In the case of the MT Biferno, in order to optimize the movements to supply means and materials at the starting area of the crossing, the departure and arrival locations were reversed from what was planned in the project documentation. As in the Costa Fracara MT, the excavation is developed within two different soil types: therefore, the same technical-constructive precautions were applied.
Also taking into account the hydraulic risk analysis for the starting location, it was planned to:

• realize, along the perimeter of the starting pit, a solid parapet of 1.1m height with respect to the surface of the work surface;
• install “sensitive” equipment in an elevated position above the work surface;
• shape the work surfaces in such a way as to promote the removal of surface runoff water;
• prepare and maintain the work area with a layer of inert material of adequate thickness to ensure the transit and maneuvering of vehicles;
• request communications related to the warning system.