The object of the contract consists in the demolition of the existing Ventolosa chamber to build in its place a new tank with a total drinking water storage capacity of about 6,000 m3. Of the 6,000 m3 potted in the new tank, about 5,000 m3 have a compensation function and about 1,000 m3 have a reserve function. The compensation volume allows, on the basis of the consumption data indicated in the previous chapter, to guarantee the supply of a peak hourly flow rate equal to Q max = 600 l / s with an average flow rate at the entrance to the tank equal to Q med = 436 l / s.

The new tank, in the event of a temporary stop of the flow rate derived from the springs, guarantees an autonomy of the Algua aqueduct system of about 3 hours with a flow rate of 600 l / s and more than 4 hours with a flow rate of 400 l / s.

The new tank consists of two symmetrical tanks each with a capacity of about 3,000 m3.

The contract works include replacing the current loading tank of the Ventolosa with a new tank with compensation and reserve functions.

Reservoir

The new tank consists of two symmetrical tanks each with a capacity of about 3,000 m3. The two tanks have circulation partitions that prevent water stagnation inside the tank. The perfect circulation of water inside the tank is also guaranteed by the feeding of the two tanks from above and the intake from the bottom. These measures guarantee the perfect quality of the water stored in the tank and avoid the onset of putrefactive phenomena due to stagnation.

By-pass

The tank is equipped with a total by-pass that must be installed before the construction of the tank by microtunnelling and which will guarantee continuity of service during the execution of the work.

Structural layout of the work

The execution of the tank, having to develop below the altitude imposed by the free-flow channel of arrival, requires important excavation works. The excavation fronts are more than 20 m high and, due to lack of space, are almost vertical. For the realization of the provisional works to the excavations are planned Berliners in micropiles with numerous orders of tie rods.

The tie rods have the sole function of supporting the excavation fronts during the initial phase of excavation execution, while the structure of the tank is sized to be able to receive, if there is a loosening of the tie rods over time, the thrust of the ground initially discharged on the Berliner. It is therefore planned, close to the Berlin, a solid reinforced concrete masonry for load distribution, connected, through the reinforced concrete slabs of the walkways, to the inner walls of the tank. The double wall of the tank is therefore structurally collaborating and allows the absorption of the stresses due to the thrust of the ground behind.

Environmental insertion

The harmonization of the tank with the surrounding area is the basic criterion that guided the design of the tank.

For the restoration of the mountain slope, morphologically deeply altered due to the excavations necessary for the realization of the work, a structure surmounting the tank is planned that will allow the restoration of the slope according to a profile as close as possible to the current solution. A series of steps will be made, each to be covered with a limited layer of soil.

To complete the environmental insertion, metal gratings will also be placed on the external facing of the tank. A green roof is provided on the roof.

For a detailed description, please refer to the Special Tender Specifications (hereinafter CSA) and to the technical and graphic documents.