Page - 923 - in Book of Full Papers - Symposium Hydro Engineering

4. DISCUSSIONS There are six large dams located in Izmir Metropolitan Area for providing domestic water. Four of them are located on the turbidities of Kucuk Menderes river while other two were constructed in Gediz basin. The earthquake safety and total risk of these dams are evaluated more detail as given below. Alacatı Kutlu Aktas Dam is a earthfill dam 15.3-m high with a total embankment volume of 280 000 m3. It is located on Hirsiz river in Kucuk Menderes basin. Its construction was finished in 1997. When the reservoir is at operation stage with maximum water level, the facility approximately will impound 16.60 hm3 of water with a reservoir surface area of 2.55 km2. It is mainly designed to provide domestic water with annual capacity of 3.0 hm3. The side slopes of main embankment is 3.0H:1V for upstream and 2.5H:1V for downstream (H=horizontal and V=vertical) (Fig. 2). On the section there is a central impervious zone, which is composed of impervious clay and a transition section of sand, gravel and small- sized crushed rock was designed over rockfill materials (Figure 2). The shell fill in downstream and upstream parts is composed of semi-pervious clayey material. The alluvium on river bed was removed before beginning the construction of the main embankment. The seismic hazard analyses performed throughout this study indicates that this dam is less critical dam within the Izmir Metropolitan Area. It will be subjected to a peak ground acceleration of 0.116 g by an earthquake of 6.1 magnitude and it is only 10.1 km far away from an active fault given in new seismo- tectonic map of Turkey in 2013. Its TRF value is 163.4 and it is identified as risk class of III. The 21-years old embankment is in excellent condition. Balcova dam is a rockfill dam on Ilica River in the Izmir Metropolitan Area. It has a 63.4 m height from river bed. When the reservoir is at maximum capacity, the facility impounds 7.76 hm3 of water with a reservoir surface area of 0.69 km2. Its construction was finished in 1980. It was designed to provide domestic water with annual capacity of 12 hm3. The crest length is 231 m and the side slopes of main embankment is 3.5H:1V for upstream and 3.0H:1V for downstream (H=horizontal and V=vertical) (Fig. 3). 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 river bed, which is composed of different size of river bed material, was removed before beginning the construction of the main embankment According to the seismic hazard analyses of this study, it will be subjected to a peak ground acceleration of 0.288g by an earthquake of 6.1 magnitude and its embankment is only 2.4 km far away from an active fault given in new seismo- tectonic map of Turkey in 2014. Its TRF value is 187.6, and it is identified as risk class of III. This 37-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. 923