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New water backbone "Cavern"


Client: Lereti spa
Project: New DN400 water backbone in the municipality of Como
Services: Preliminary, final and executive design and construction management
Location: Como
Status: Built
Year: 2020 - 2021

The assignment concerns the final-executive design, work supervision and testing of the intervention for the construction of an aqueduct line connecting the "Caverna" power plant to the "Breggia" power plant in Via Varese in Como.

The northern area of the Municipality of Como is currently supplied by the flow from the lake, treated in the "Caverna" power plant. The potabilized water is conveyed to the "Breggia" power plant through a DN 400 cast-iron adductor. At Viale Varese, the adductor branches into two parallel lines of different diameters for a distance of about 700 m, and then the first pipeline further splits into two parallel troughs of DN 150 and DN 250.

The state of affairs, thus characterized by a variable-section pipeline, has significant pressure drops at diameter reduction points, and there is also a situation of hydraulic insufficiency, caused by the incapacity of the DN 250 pipeline.

Thus, the planned work is aimed at constructing a suitable feeder for the connection between the "Caverna" power plant and the "Breggia" power plant along Varese Street, which would solve the critical issues present in the existing state.

To ensure adequate continuity of the mains between the "Caverna" power plant and the "Breggia" power plant, a section of DN 400 cast-iron pipeline is planned in the section of Viale Varese subject to criticality, connecting, upstream and downstream, with the existing DN 400 sections. Homogenizing the diameter to the size of the header will guarantee the optimal service between the two power plants by being able to maintain the DN 250 line for distribution to users in the Como "Centro" district. A rapid type cast iron tumbled joint pipeline was chosen, with Zn-Al based coating of 400 micron thickness, considered suitable for laying in the soils in question. Sectioning is envisaged through the installation of the underground type gates, with operating rod and telescopic surface manhole, and the housing of the vent points in prefabricated inspectionable chambers with upper manhole in cast iron class UNI EN 124 D 400, net span Ø 600 mm.

The existing line dedicated to adduction, DN 300, will be taken out of service and used as a possible by-pass in case of maintenance on the planned new adductor, so it is planned to reconnect, at the upstream and downstream ends, the new line to the existing one.