Bosa - Italia
Sardinia Autonomous Region and Ministry of Public Works
1965-1968 / 1994-2009
Description for Bosa Multi-purpose Project (Italy)
The Monte Crispu arch-gravity dam was realized in the 50s with the aim of controlling the Temo River floods, to protect the city of Bosa, until it became a multi-purpose project including urban water supply and irrigation.
Few engineering firms can claim to have a "family dam". Lamberto Canali, Giorgio Pietrangeli's brother-in-law, countersigned the design for this elegant gravity-arch dam; Liliana Pietrangeli, Giorgio's sister, a mathematical expert, carried out the sophisticated mathematical calculations of the stability of the dam in the early 1960s; Giorgio Pietrangeli designed the auxiliary works, followed the commissioning and for decades was chief engineer during the operation of the dam; finally, Antonio Pietrangeli and his cousin Antonio Brasca followed the rehabilitation of the dam, after almost 50 years of operation.
Bosa multi-purpose project consists in an arch-gravity dam, with a height of approx. 60 m, creating a reservoir with a total storage of 30 Mm3.
The main auxiliary works consist in: an un-gated spillway, positioned on the left abutment; a morning-glory spillway; a middle outlet and a bottom outlet.
The morning-glory and the middle outlet use the same tunnel, positioned on the right side, to discharge the flow downstream dam. Again, on the right side, a second tunnel acts as bottom outlet.
The tunnels of the middle and bottom outlets are equipped with two gates: one upstream for maintenance purposes; another one downstream to regulate the flow.
The morning-glory has been dimensioned to spill a maximum discharge of 150 m3/s, the middle outlet 350 m3/s, finally the bottom outlet 600 m3/s.
In several exceptional flood events the presence of Bosa dam protected the picturesque town of Bosa from suffering damage. The scope of the most recent activities is to combine the main purpose of laminating floods with a secondary purpose to supply drinking water.
- Reservoir ( V = 30 Mm³, LV = 5 Mm³ )
- Arch-gravity dam ( H = 57 m, L_crest = 325 m )
- Bottom outlet ( D = 6 m, L = 280 m, Q = 600 m³/s )
- Middle level outlet ( D = 5 m, L = 360 m )
- Morning glory spillway ( D = 5 m )
Examples of engineering challenges
Over the past few years, the stabilization of the slopes (left and right abutments) has become a necessity to ensure the safety of the foundations of the upper arches of the dam.
The stabilization of the slopes was carried out by expert climbers, scaling the unstable rock wedges, installing anchor bars and rockfall protection nets.
Studio Pietrangeli not only carried out the design, but also supervised the work and was responsible for the safety on site.
In recent years, the bottom outlet has been equipped with gates. In order to minimize the works on the existing works, SP used the same access to the middle outlet for the new submerged gates chamber, where two roller gates have been installed.
The new layout of the plant allows the use of the reservoir not only for flood lamination, but also as a supplementary drinking water supply.
PHASE 1 ( dam construction, 60’s )
- Final design
PHASE 2 ( change of use – from flood control only to flood control, water supply and irrigation )
- Geological studies
- Stability model and dam break analysisPreliminary design
- Final design
Supervision of the works
Installation of regulating gates on the existing unregulated bottom outlet
Dam rehabilitation works (abutments protection and stabilization)
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