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C z e c h R e n e w a b l e E n e r g y A l l i a n c e
CREA Hydro&Energy, o.s.
Traubova 6 • CZ - 602 00 Brno • e-mail: [email protected]
www.creacz.com
Sulaymania
IRAQIRAQ
INSPECTIONOF THE DERBENDIKHAN DAM
BASIC DAM PARAMETERS
Type: Embankment Dam with Clay Core and Rockfill Shoulders
Upstream &
Downstream Slopes: 1:1.75Maximum Height: 128 mWidth of Crest: 17 mCrest Length: 535 mCrest Level: 495 m a.s.l.Catchment Area: 17,850 km²Reservoir Area
and Volume at El. 485: 113 km² / 3.000 mil.m³
SPILLWAY STRUCTURE
PARAMETERS
Type: Gated Ogee Overflows with Three Radial Gates
Spillway Gate Size: 3 x (15m x 15m)Crest Level at Ogee: El. 470 m a.s.l.Top of Closed Gate: El. 485 m a.s.l.Normal Discharge Capacity at 485 m a.s.l.:
5,700 m3/sMaximum Discharge Capacity at 493.5 m a.s.l.:
11,400 m3/s
HYDRO POWER STATION
PARAMETERS
Type: Surface Power House at Dam Toe
Number of Turbine/
Generator Units: 3 Vertical Francis Turbines
Rated Output: 3 × 83 MW
The subject of the project was to assess thesafety and operational capability of the hy-draulic structure. This concerned an exten-sive inspection of technical and safety super-vision and individual construction parts ofthe hydraulic structure. The inspection itself,tests, measurements and further surveytook place both in the conventional manner,and in the presence of specialized professio-nals (divers, mountaineers, etc.). An integralpart of the entire action was comprehensiveinspections of mechanical technologicalunits. At the end of the project, a report wasprepared, regarding the most serious fin-dings, proposed repairs and recommenda-tions for further operation of the hydraulicstructure.
The Derbendikhan dam lies on the Diyala/Sirwan River approximately 65 km southeastof Sulaymaniyah and 230 km northeast ofBaghdad. It is a multi-purpose hydraulicstructure. The dam is constructed in a nar-row gorge on layers of sedimentary rockssuch as claystone, sandstone, limestone andconglomerate. The construction of the dambegan in 1956 and was completed in 1961.The total volume of the reservoir at the nor-mal operating level 485.00 m a.s.l. is 3,000mil. m3 (about 4 times larger than the volumeof the Orlik reservoir).
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F R I E N D L Y P O W E RCREA Hydro&Energy, o.s.Traubova 6, 602 00 Brno, Czech Republice-mail: [email protected]
INSPECTION OF THE BUILDINGSDuring inspection, a detailed examination and design and technical statussurvey of the inlet structure, tunnels of the bottom outlets and the emergencyspillway structure was carried out. Defects of steel elements and concrete in different sections of the structures were recorded.
INSPECTION OF THE TECHNOLOGICAL UNITSMechanical specialists performed a check of three main hydraulic facilities(Intake gates, bottom outlet with Howell-Bunger valves and spillway radialgates). The gates and valves were checked on the basis of the current con-ditions to a feasible extent and as access permitted. An integral part of thecomprehensive inspections was operation tests of the gates, including a check of the control system.
SPECIAL WORKOne of the other issues of the inspection was surveying the bottom of thereservoir storage to a distance of 1.5 km from the dam with the aim to determine the amount of sediment in this area. The part above the watersurface was surveyed geodetically and the part underwater was measuredusing an echo sounder with a GPS localization system. The surveying resultswere used for creating a digital terrain model. This model was subsequentlycompared with the surveying results obtained before the reservoir had beenfilled.
Professional divers were used for inspections underwater. Diving work wascarried out at depths not exceeding 50 m. For this reason, great attentionwas given to the safety of divers. Special gas mixtures were used for breathing,enriched with helium or a higher content of oxygen (TRIMIX and NITROX).The workplace was equipped with a diving chamber and means for provi-ding first aid. During diving work, the client’s representative was always present, watching the course of surveys on-line on a screen. All work underwater was documented by video recording. The work included an inspection of the intake tower underwater in the reservoir, a check of guiding grooves of the sluice gates, contact surfaces of the gate on the inletto the tunnels, a check of the gates proper and trash racks.
The result of the inspection examination was identifications which were divided into 3 categories in relation to the necessity of their elimination andthe rectification of the situation. These are serious findings, which must beremoved within the shortest possible term, moderate findings, and the lastcategory is minor defects to be removed within a period of 2 years.
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