Consulting Services for Naryn Cascade Dam Safety Assessment – Kyrgyzstan

Project Name: CONSULTING SERVICES FOR NARYN CASCADE DAM SAFETY ASSESSMENT

Country: KYRGYZ REPUBLIC

Finance Source: Asian Development Bank

Tags: Kyrgyzstan, Asian Development Bank, HEPP, Assessment

Narrative Description of Project:
The objective of assignment is to conduct dam safety assessment that will assess condition of dams and hydropower plants on the Naryn cascade with necessary remedial measures identified.
The Naryn cascade hydropower plants (HPP) are largest hydropower plants in Kyrgyzstan. There are five hydropower plants on the Naryn cascade namely: Toktogul HPP (1200MW), Kurpsai HPP (800MW), Tash-Kumyr HPP (450MW), Shamaldy-Say HPP (240MW), and Uch-Kurgan (180MW).
The dams and hydropower plants shall be evaluated under following subjects:
• Hydrological and hydraulic hazard, ability to safely release large floods
• Geological hazard: Potentially active faults near dam foundation, mass movements into reservoir, mass movements and/or unstable rock masses and appurtenant structures, which may cause overtopping of the dam.
• Change in the elastic modulus rocky foundation long-term exposure of underground flow lines.
• Meteorological hazard: Effect of abnormal inflows due to heavy rainfall or other reason and on sediment transport in tributaries, surface erosion of dams, ageing of concrete, corrosion of the reinforcing steel.
• Water tightness of foundation and tunnels:
• Seismic hazard and reservoir-triggered seismicity (RTS):
• Erosion hazard in the tailrace: Erosion of river banks may threaten appurtenant structures of powerhouse and deposition of sediments near powerhouse and increase of water level under normal operation.
• Technical hazards: Lack of quality of the construction materials; obsolete archiving system.
• Reservoir operation hazards: inadequate or lacking rule curves and instructions for operation of dam cascades under (i) normal operation, (ii) emergency situation, and (iii) severe accident situation.
Access of dam sites in emergency situations: After heavy rain, flood release or strong earthquakes, the dam sites may be inaccessible by road as they will be severely damaged at several locations.

Description of Actual Services Provided by TEMELSU:
Gathering of all pertinent information and review of existing dam safety procedure and documents. Performing an analysis of dams condition measurements and monitoring, preparing prognosis for next periods, submitting an assessment of repair measures carried out in previous period, and making recommendations for following period(s); including proposals of measures for the improvement of the dams safety. Annual Reports for Dam Safety Assessment includes following chapters: Distortion of soil structures or rock structures, Distortion of concrete structures, Monitoring of condition of concrete constructions, Movements of bituminous deformation joints, and sealing condition, Filtration mode in hydro-technical structures and foundations, Measuring facilities and monitoring of condition of structures.

Inspection of the embankment dams and hydraulic-fill dams includes inspection of the wet and dry slopes, fastening and security construction of slopes, top of embankment dam, condition of drainage construction and measuring gauges. Inspection of the concrete dams and structures such as powerhouses and control buildings includes inspection of concrete surfaces and flexible deformation joints. An accurate inspection of water discharge structures together with an assessment of the structure’s concrete addressing possible abrasion or cavitation damages. Inspection of the gates and their driving gears, water level gauges, and other equipment. Structural integral checks to verity the original design of the dams was safe and still safe when using standard practice with state-of-art calculation techniques for recent code loadings and modern design requirements, such as the recommendations in the Bulletins of the International Commission of Large Dams (ICOLD), Euro codes or equal.