Page - 615 - in Book of Full Papers - Symposium Hydro Engineering

3. PROPOSED SOLUTION On basis of Client’s requirements, and taking into consideration dam location and characteristics, and usual dredging solutions already experi- mented for similar projects, DRAGFLOW, together with the Contractor THE- TIS COSTRUZIONI decided to propose following technical solution:  Submersible pump located on a pontoon fully equipped, able to cover all the area to be dredged (4,500 m2);  Floating pipeline conveying the slurry from the pontoon to the surface outlet located on the left side of the dam, and from this structure down- stream the dam;  To respect environmental constraints (9 g/l), slurry has been mixed with water discharged by the surface outlet of the dam, managing the gates accordingly;  To check the respect of maximum concentration of sediment in the slurry, three check points have been organized (on the pumping pipeline on the pontoon, just after the confluence of slurry and Ambiesta stream at the toe of the dam itself, and finally at the final confluence between Ambiesta steam and Tagliamento river, 2 km downstream Ambiesta dam;  Service boat to allow the staff involved in the activity to reach the pon- toon and to leave it at the end of the working shift. 3.1. Dredging system Taking into account the characteristics of the sediment to be dredged, and the total dredging time allowed by the Client A2A, average slurry dis- charge has been fixed at 500 m3/hour, and it has been mixed with 4 m3/s clear water, taken form the reservoir, and discharged by the surface outlet of the dam located on the left side of the dam, to meet Client’s requirements (9 g/l). 615