Page - 925 - in Book of Full Papers - Symposium Hydro Engineering

maximum water level, the facility approximately will impound 158.00 hm3 of water with a reservoir surface area of 5.8 km2. It was mainly designed to provide industrial water for a national chemistry company. The crest width is 10 m and the side slopes of main embankment is 2.5H:1V for upstream and 2.0H:1V for downstream (H=horizontal and V=vertical). On the section there is a central impervious core, which is composed of compacted low-plasticity clay and a transition section of sand, gravel and small-sized crushed rock was designed between the core and rockfill materials for downstream part. The downstream shells are composed of large-sized crushed rocks. The alluvium on river bed, which is composed of mixtures of fine to large size grains, was removed before beginning the construction of the main embankment. The seismic hazard analyses performed throughout this study indicates that Guzelhisar dam is one of the most critical dams within the basin. Detail assessment about its earthquake safety and total risk are introduced by [9]. Tahtalı dam is a rockfill dam on Tahtalı River near Gumuldur County in the Izmir Metropolitan Area. It has a 54.4 m height from river bed. When the reservoir is at maximum capacity, the facility impounds 306.6 hm3 of water in its reservoir. Its construction was finished in 1999. It was designed to provide domestic water with an active volume of 287 hm3. Fig.4 shows a general view from Tahtali dam. On the section there is a central impervious core, which is composed of compacted impervious clay and a transition section of sandy and gravelly aggregates was designed between the core and semi-pervious soils. The alluvium on clay core was removed before beginning the construction of the main embankment. A low- strength concrete wall was constructed for providing impermeability in dense aluvional soil. According to the seismic hazard analyses of this study, it will be subjected to a peak ground acceleration of 0.277g by an earthquake of 5.7 magnitude and its embankment is only 1.9 km far away from an active fault given in the updated seismo-tectonic map of Turkey. Its TRF value is 188.6 and it is identified as risk class of III. It is at second place after Gordes dam when regarding the total capacity of reservoir and one of the most critical dams in Izmır Metropolitan Area. This 19-year old earthfill embankment is in excellent condition, but it cannot meet current seismic design standards. Additionally, it is under near- field motion. Therefore, its seismic upgrade should be provided soon Fig.4. A general view from Tahtali dam 925