SEMINAR ON WATER SECURITY IN BULGARIA SOFIA, SEPTEMBER 18-19, 2017 DAM SAFETY IN ROMANIA

Transcription

1 SEMINAR ON WATER SECURITY IN BULGARIA SOFIA, SEPTEMBER 18-19, 2017 DAM SAFETY IN ROMANIA

2 Overview Romania has built 2,617 dams out of which 246 are large and medium dams and 1260 are small dams, as per ICOLD classification 75% of all dams have been built between 1965 and dams wait for commissioning as are still in various stages of construction Total storage capacity of large dams commissioned = billion m 3 2

3 Overview (2) Dams ownership is shared mainly by the Romanian Waters Administration (ANAR) and the hydropower company Hidroelectrica, with six dams owned by various industrial plants 61 % of dams have multiple purposes (water supply, hydropower, irrigation and almost all have flood protection purpose) 3

4 Legal and regulatory arrangements for dam safety Water Law #107/1996 is the main regulatory act for dam safety setting the guiding rules for dam safety Complementary implementation regulations and technical norms ICOLD (2012) risk analysis methodology Responsibilities: Dam Manager (local) Dam Owner (central) Line ministry (central) CONSIB (consultative technical body) pivotal role in dam safety system reviews organization of dam monitoring system reviews periodic technical reports on dams safety operation advises upon the operational rules for dams recommends the preparation of technical reviews of hydraulic infrastructure with high failure risk recommends the structural interventions to enhance the safety of infrastructure at risk 4

5 Distribution of roles and responsibilities for dam safety 5

6 Dam accidents and incidents Belci Dam failure (July 1991) Conditions: high flood, technical defections at micro-hydropower plant power supply to action the hydro-mechanical equipment failed because of heavy rainfall Consequences: dam failed, 25 fatalities, 250 households washed away Certej Tailings Dam (October 1971) - the tailings dam failed after a long period of heavy rainfalls, spilling cyanide over the town Consequences: 89 fatalities, four apartment buildings and five households washed away Incidents: Vidraru Dam over discharge of reservoir without early warning alerted the local population Paltinu Dam severe seepage through shoulders required grouting and consolidation 6

7 Belci Dam Paltinu Dam 7

8 Enhancing Safety of Dams at Risk (1) Assessment of safety risk done by ANAR and CONSIB in for most dams 9 large dams found with safety problems and operational restrictions recommended WB technical and financial support requested in 2002 Hazard Risk Mitigation and Emergency Preparedness Project (HRMEP) project dam (Dridu Dam) further damaged by heavy floods in 2005 Initial project cost US$204 Million / Floods and Dam Safety component US$ 101 Million Works costs share: US$ 88.3 M, of which US$ 39 M floods and US$ 49.3 M for dams Project scope: 12 flood protection sites and 13 dams Final project component costs US$ 101 M with US$ 88.5 M for works Works costs share: US$ 35.5 M floods and US$ 53 M dam safety Project scope: 9 flood protection sites and 6 dams mainly because of costs overrun 8

9 Enhancing Safety of Dams at Risk (2) HRMEP Project financed safety interventions for 4 large dams and 2 small dams All dams had restrictions in operations imposed by their deficiencies, mainly with respect to stability and seepage All dams operated at water free board level lower than designed for safety Safety restrictions imposed limitation of services for all users Serious deficiencies of feasibility studies found at engineering design stage! Inaccurate identification of scope of interventions led to substantial increase of costs 89% - the overall cost overrun for dam projects 180% - the cost overrun in the most expensive contract Consequence: 7 dams (including the most unsafe) could not be addressed! 9

10 Enhancing Safety of Dams at Risk (3) Population at Risk - initial Name Population At risk Affected Total Dams in Program 338,085 1,225,000 1,563,085 Dridu 10,435 40,000 50,435 Varsolt 10, , ,800 Berdu 138, , ,000 Poiana Uzului 30,000 80, ,000 Maneciu 42, , ,000 Valea de Pesti 8,000 30,000 38,000 Siriu 85, , ,000 Lesu ,000 35,280 Sanmihaiu 1, , ,060 Taria 5,200 18,000 23,200 Catamarasti ,000 80,950 Buftea 3, , ,500 Pucioasa 2,860 45,000 47,860 Population Protected 79% Name Population At risk Affected Total Completed dams 208, , ,445 Varsolt 10, , ,800 Berdu 138, , ,000 Maneciu 42, , ,000 Taria 5,200 16,000 21,200 Catamarasti ,000 78,950 Dridu 10,435 40,000 50,435 Sanmihaiu 1, , ,060 10

11 Enhancing Safety of Dams at Risk (4) Main deficiencies addressed through the Project: Seepage through the foundation and/or dam body Stability of foundation and dam shoulders Obsolete / nonfunctional hydro-mechanical equipment (bottom outlets, gates, spillway) Obsolete / nonfunctional instrumentation for monitoring, early warning Erosion of side slopes or downstream dam face 11

12 Brief description of Project interventions (1) Varsolt Dam medium size (17 m height, 40 mill. m 3 ) Reservoir: multipurpose water supply, flood protection Operation experience: the reservoir was originally designed as non-permanent and commissioned for permanent use later. A dam foundation sealing was not necessary for a non-permanent used reservoir. Risk assessment: evaluated, category of importance a exceptionally important - high risks. Rehabilitation measures: Sealing of dam body and foundation treatment (concrete cut-off wall 0.6 m thick from the dam crest, 25 m deep). Reshaping of dam body (stability, drainage at the dam toe and downstream channel rehabilitation. Drilling of drains in the new gallery. Rehabilitation of the bottom tunnel and sealing of the old gallery. Construction of new bottom outlet structures on the left bank. Measures for sanitary protection and water quality assurance. Anti-erosion measures upstream of the reservoir. Rehabilitation of the monitoring system and upgrading of the alarm and warning system as well as seismic activities detection system. Estimated costs US$ 7.4 Mill. Actual costs US$ 20.7 Mill. 12

13 Brief description of Project interventions (2) Maneciu Dam Large dam; Earth rock-fill dam with central clay core; H 78 m; W 58 Mm 3 Reservoir: multipurpose water supply, flood control, irrigation and generating electricity. Operation experience: the dam was operated at a restricted water level compared to originally designed parameters. Bottom outlet operation restricted due to too high flow velocities (valves, energy dissipater, no steel lining at concrete structures and damages in downstream areas etc.). Seepage in spillway and damaged concrete. Slope instability occurred on the left downstream bank. Risk assessment: evaluated, category of importance b significant important, - medium risks Earthquake risk assessment: the dam is located in a zone of a very high seismicity (zone A). Rehabilitation measures: Rehabilitation of the bottom outlet: steel lining between valve chamber, dissipater and injections; improvement of other structures, new energy dissipater. Rehabilitation of the spillway channel: sealing of joints in the concrete structures with various methods, improvement of the concrete quality in sections with high flow velocities through usage of highly resistant concrete (20 cm thick). Rehabilitation of the downstream left slope: protection with riprap between elevation 557 and 610 m a. S. L.; Rehabilitation works above 610 m a. S. L.; Additional local measures. Rehabilitation of the monitoring system, alarm and warning system as well as the seismic system. 13

14 Brief description of Project interventions (3) Dridu Dam: Gated weir, main fill dam; Medium dam; H=18 m, W=45 M m 3 Operation experience : severe local erosions of river banks caused by wave actions, seepage through dam body; cavitation problems in spillway section; locally damaged sealing and revetment in channels; damaged hydraulic weir gates; seepage under right side foundation after 2005 flood. Risk assessment: evaluated, category of importance b significant important, medium risks. Earthquake risk assessment: the dam is located in a medium high seismic zone (zone C). Rehabilitation measures: Cut-off wall executed through soil mixing - innovative method in Romania Rehabilitation protection - of the river banks to stop erosion Rehabilitation of the existing dam drainage system: new collecting system and pumping facilities. Rehabilitation of the main dam: drillings and drains from the inspection gallery, construction of a new sealing blanket depth 7 m from dam crest. Rehabilitation of the spillway channel: reconstruction of bottom sills, riprap and reinforced concrete structures Rehabilitation of the hydro-mechanical equipment. Implementing a new information system for the water management, warning and alarm system, etc. 14

15 Deferred intervention - example Siriu Dam: Large, earth-rock-fill dam central clay core; H=122 m; W=155 Mm 3 Reservoir: multipurpose water supply, irrigation, hydropower, flood protection; Operation restricted Operation experience: seepage rates of 15 to 18 l/s were observed in drainage gallery during impounding at an elevation 50 m below normal water board level; problems at hydro-mechanical equipment (bottom outlet, intake gallery, valve chamber etc.); slope instabilities on the left bank downstream; reduced operation capacity of spillway. Risk assessment: evaluated, category of importance A exceptional important - high risks. Earthquake risk assessment: the dam is located in a highly seismic zone (zone b). Proposed repair and rehabilitation measures: Grouting and drainage works in existing galleries plus new, exceeding gallery and piezometers to stabilize the left slope and to decrease seepage. Refurbishment and rehabilitation of hydro-mechanical, electrical equipment and drainage system Bottom outlet, valve chamber Intake gallery, valve chamber Spillway valves and gates Intermediate (semi depth) outlet, gates Water supply system, pipe Rehabilitation of the monitoring system, emergency and alarm system, seismic system etc. Rehabilitation of the dam crest and repair works at the downstream dam slope. 15

16 Lessons Learned Slow adaptation process of technical staff (designers, planners) to technological progress and changed economics of public investment Poor planning capacity at administrative levels (ministry, water authority), unable to do a reasonable prioritization of investment led to The change of generations occurred in early 90s did not enable preservation of the same innovative capacity in staff lacking practical experience in design, planning Insufficient understanding of changes in procurement practice introduced by the harmonization with international principles and rules Reluctance to accept presence of foreign specialists, challenging their capacity to understand the local traditions 16

17 THANK YOU Gabriel Ioniță, Irrigation Engineer 17