Recommendations to maintain Dam safety
Based on dam safety concerns and consequences discussed, it is recommended that,
The crest of the bund is reserved for routine maintenance, including replacement of displaced Ralapanawa if necessary, placement of additional boulders if required, and for construction of temporary overtopping protection bund using ‘Sandbags”, as and when required.
The stretch between the Ralapanawa and bitumen road be reserved for the construction of a wave wall to meet the dam safety requirements of future hydrological reviews to be undertaken during the service life of the reservoir and bund.
A safe “Load Capacity” be imposed on the bund top road, and arrangements are made to stop all heavy trucks plying on the bund top road as the bund has not been designed for such traffic loads.
The bund top road is completely closed for all traffic, say from 5:30 am to 7:30 am and then from 6:00 pm to 9:00 pm or as agreed by local authorities, in the preferred 2km long stretch, and then the existing bitumen surfaced bund top road to be used as the walking path (Alternatively, only the upstream-half of the bitumen surfaced bund top road to be used as the walking path while the downstream-half of the bitumen surfaced bund top road to be kept open for one-way light traffic only, subject to nominated maximum speed to ensure the safety of people using the walking path).
An alternative walking path (For example, in the reservoir rim), be investigated which will not compromise the safety of the dam.
The reservation area located immediately downstream of the bund is not used for developments that are been planned by the Urban Development Authority as this area is very sensitive to dam safety issues.
The reservation area located immediately downstream of the bund, which is an integral component of the dam, be a property of the Irrigation Department for inspection and monitoring of critical dam safety features, construction of a toe access road, construction of stabilizing fills if required, stockpiling of construction materials required during dam emergencies, etc.,
A potential failure modes analysis and Risk Assessment be undertaken in accordance with international dam safety standards.
A Design and Safety Review of the dam and appurtenant structures be undertaken in accordance with the international dam safety standards incorporating review of geotechnical parameters of the bund and foundation, hydrology, wave run-up, seismicity, flood handling capacity, reliability of gates and instrumentation, etc.,
Sufficient funds must be allocated to undertake Design and Safety Reviews of all “Extreme” consequence category dams in Sri Lanka.
Sufficient funds must be allocated to routine maintenance of dams (Note: Depending on their nature, some maintenance items, if not addressed in a systematic and timely manner, may eventually become dam safety issues, eventually leading to failure of dams).
Early arrangements must be made to implement the recommendations of the Cabinet Memorandum No. 11-2020 dated October 26, 2020 on the Establishment of a Dam Safety Consultation Centre and a Dam Safety Regulatory Mechanism.