Seite - 612 - in Book of Full Papers - Symposium Hydro Engineering

As you can imagine, dredging activity has been developed in a quite complicated area from a morphological point of view because of the pres- ence of artificial structures, forcing the submersible pump operator to care- fully proceed between existing structures. In Fig. 5 we can appreciate, through an historical photo taken during construction time, the original mor- phology of the area, with quite big concrete structures (intake screen of the water intake channel) and very steep flanks of the valley. To correctly design dredging system and determine dredging efficiency of the submersible pump, A2A supplied to the tenderers detailed information on the sediments to be dredged, collected through a field campaign devel- oped all along the reservoir (Fig. 6). The information used for the project has been related to the sample taken close to the dam. According to the grain size distribution analysis, the sediment to be dredged showed a granular fraction equal to 5%, meanwhile the cohesive fraction reaches 95% (74% silt and 21% clay). 612