Seite - 611 - in Book of Full Papers - Symposium Hydro Engineering

an alert level especially nearby bottom outlet intake, and water intake struc- ture as well. Through the comparison of topographic surveys developed along several years, A2A identified the area where the sediments have to be removed, and the total amount of them. Total area to be dredged (Fig. 4) has a surface of 4,500 m2 and is lo- cated at a water depth variable between 20 and 36 m, according to the water oscillation in the reservoir. Globally 28,000 m3 have to be removed to assure a correct efficiency of the ancillary structures, and the right safety factor. The thickness of the sediment layer to be removed was variable between 6 and 10 m. In the following picture we can appreciate the area to be dredged (green area), which affects dam bottom outlet, located on the left side of the dam (axis indicated with red dotted line), water intake on the right side, through which the water is driven to turbine of Somplago power plant (axis indicated with red dotted line), and the ancient cofferdam, concrete made, built at the beginning of the construction activity, to divert stream water to the dam bottom outlet, to kept dry the area where dam foundations have been built. Fig. 4 Area to be dredged Surface à draguer 611