Dam Safety Assessment and Rehabilitation of The Naiman Dam – Kyrgyzstan

Project Name: DAM SAFETY ASSESSMENT AND REHABILITATION OF THE NAIMAN DAM WITHIN THE SCOPE OF CONSULTING SERVICES FOR THE KYRGYZ REPUBLIC WATER MANAGEMENT IMPROVEMENT PROJECT

Country: KYRGYZ REPUBLIC

Finance Source: World Bank

Partners: Mott MacDonald Ltd. (United Kingdom)

Tags: Kyrgyzstan, World Bank, HEPP, Assesment, Supervision

Narrative Description of Project:
Consulting services include investigations, surveys, preparation of designs and tender documents to international standards for 19 irrigation systems (schemes), covering an area of about 85,000 ha, located throughout the country, with the majority of the schemes located in the three southern oblasts. The consulting services also include dam safety assessment of the Naiman Dam, which is situated in Osh Oblast. Naiman Dam has the crest length of 265 m and height of 40.5 m at the maximum section. Freeboard is 2.4 meters plus the wave wall. The dam is earth fill embankment type consist of sand/gravel and pebble size outer shoulders and a wide core of low permeability loamy soil. The upstream and downstream face slopes are varying from 1:2.5 to 1:4 from top to down.
The safety of the dam has been estimated based on site specific seismic risk assessment and findings of the geotechnical investigations performed. Results of the nonlinear seismic analyses indicated that the freeboard is satisfactory for the operating basis earthquake level with a peak ground acceleration (PGA) value of 0.46 g. However, the dam is unsafe under maximum credible earthquake level of 0.70 g for a return period of 5000 years and a catastrophic failure is likely. A comprehensive geotechnical investigation program was planned, tendered and supervised to investigate in-situ strength characteristics of the materials of construction used in different parts of the dam body and foundation soil, the pore pressure distribution within the dam body and seepage that emerges at downstream face at high reservoir levels. Since all of the existing piezometers were out of order, 12 new standpipe piezometers were installed along the dam body and monitored.

The dam was put into operation in 1966 and in general, all the mechanical equipment and their electric supplying units are aged and outworn due to 45 years of operation.

The major remedial works for safe and smooth operation of Naiman Dam are rehabilitation of the draw-off structures; strengthening the water intake and outlet structures, renovating the gate shaft and replacements of the hydro-mechanical equipment with necessary mechanical and electrical auxiliaries.

Description of Actual Services Provided by TEMELSU:
Management, coordination and leading all international and local teams and sub-consultants in:
Topographical surveys and geotechnical investigations, preparation of rehabilitation designs and bidding documents based on World Bank standard bidding documents for off-farm irrigation systems, preparation of river basin management plans for schemes on trans-boundary rivers, reviewing the existing O&M systems on the selected irrigation and dam schemes and propose effective institutional arrangements, carrying out Environmental Assessment studies and preparation of Environmental Monitoring Plans, construction supervision and quality control of all project components and on-the-job training, safety risk assessment of dams, preparation of dam safety plans, and design of remedial works.