This paper discusses the common environmental issues and requirements project lenders have when financing hydropower dam projects in developing countries. The environmental specialist’s role, as part of the Lender’s Technical Advisor team, is discussed throughout the main phases of project finance (credit approval, financial close, lending/construction and loan repayment/operation). Further, how environmental issues are reviewed and monitored, thereby minimising reputational risks to the lenders are outlined.
Lenders typically consider hydropower dam financing, especially reservoir schemes, as high reputational risk loans. Finance is usually syndicated and although most international lenders are Equator Principles signatories or use the International Financing Corporations (IFC) Performance Standards, some lenders have additional environmental guidelines and requirements to enable financing. These differences are discussed.
Common environmental concerns include loss of habitat of endangered and/or threatened species, changes to river flows, erosion and sediment control during construction, and the minimisation and disposal of project wastes.
These issues are discussed drawing on the author’s experience in monitoring environmental issues of hydropower projects in Asia Pacific and Africa, including both smaller run-of-river schemes and larger storage reservoir projects.
Keywords: Environment, impacts, project financing, concerns, lenders, lenders technical advisor.
Jiri Herza and John Phillips
The design of dams for mining projects requires processes and technology that are unfamiliar to many mine owners and managers. Dam designers rely on ANCOLD assessments of Consequence Category, commonly leading to a High rating for mining dams due to a combination of potential loss of life, impact on environment and damage to assets such as mine voids, process plants, workshops, offices, roads, railways etc.
From this High Consequence Category the relevant annual exceedance probabilities for design parameters and loading conditions such as earthquakes and floods are selected.
Mining companies have sophisticated methods available for assessing risk, yet for their assets they often adopt an order of magnitude lower security for earthquake and floods even though the consequences in terms of lives at risk and impact on project are similar.
The discrepancies in the design standards lead to situations where extreme dam loads are adopted to prevent damage and loss of life in assets that theoretically would have already collapsed under much lower loads.
One difference may be that some mining dams exist in an environment which is controlled by a single entity. Unlike other dams, failure of these mining dams would therefore impact only individuals and assets which fall under the responsibility of the same entity.
This paper discusses the discrepancies between the design of mining dams and the design of other mine infrastructure. The paper considers the impact of discrepancies on the overall risk to the mine and compares the degree of protection offered by a factor of safety and the influence of reliability of design input parameters, alternate load paths and design redundancy.
Keywords: Dams, tailings dams, mining, acceptable risk, factors of safety
P C Blersch, W van Wyk , R Steenkamp
Construction of the partially completed Calueque Dam on the Cunene River in Angola was abandoned in 1976 due to the hostilities in Angola. In 1988 the dam was bombed, causing significant damage to the bridge deck, other structures and equipment. Work to complete and rehabilitate the dam commenced in late 2012 and included major earthworks, extensive concrete repairs and refurbishment and installation of mechanical equipment, including ten spillway radial gates and two outlet gates with lifting equipment, emergency gates and cranes, including electrical and control systems. A number of challenges were encountered in planning and executing the project but were overcome largely as a result of detailed historical project information having been retained well beyond the norm and through the involvement of a key member of the original project team in the current project.
Keywords: Dam rehabilitation, radial gates, zoned earthfill embankment
Kim Robinson, Andrew Pattle and Thomas Shurvell
Rowallan Dam is a 43m high clay core rock fill dam located in Northern Tasmania. The dam impounds 121GL used for hydro power generation and has a High A consequence category.
Over the summer of 2014/15 major reconstruction works were carried out on the dam to repair a piping incident from 1968. The work entailed reconstructing two sections of the dam down to foundation level and the upper 7m of the 568m dam crest. During the work, the dam was temporarily exposed to a significantly increased flood overtopping risk.
A range of measures were taken to manage the overtopping risk; such as increasing the dewatering capacity of the dam, lake draw down, installation of a sheetpile wall, development of emergency backfill procedures and a flood forecasting system.
The focus of this paper is on the flood forecasting system and how this was integrated into the overall management of overtopping risk during construction. The forecast models were run automatically on a 2 hour schedule using the latest BoM forecast, telemetered lake levels and rainfall from 7 gauges surrounding the catchment. The system provided a continuous 7 day lake level forecast which guided the site team on when to release water to manage the storage.
In the event that the lake level forecast reached a predetermined trigger level, the dam safety team would have been automatically notified and various emergency procedures would have been triggered in response to the flood warning.
This paper discusses the measures that were taken to manage the flood risk, how it worked in practice and conclusions which are applicable more generally to managing overtopping risk during dam works.
Keywords: dam construction flood risk, flood forecasting
Richard Herweynen, Tim Griggs, Alan White
The Ministry of Public Utilities, Sarawak, Malaysia used an independent dam safety consultant to advise them on whether the Murum Dam was ready for impoundment. They were looking for a holistic assessment of the dam from a dam safety perspective. As a result, a risk framework was adopted to identify the key issues that needed to be addressed prior to impoundment of the Murum Dam. The process adopted which is presented in this paper, was transparent and defensible; and provided a reasoned approach for which items must be completed prior to the commencement of impoundment. As a result effort was focused on the key activities required prior to impoundment – whether this was the completion of specific works, the availability of key instrumentation to monitor the dams performance, the availability and operation of key dam safety systems, or the appropriate emergency preparedness should a dam safety incident occur during first filling. This systematic process based on a risk based approach, was a useful method of determining the dam’s readiness for impoundment, and provided an excellent way of communicating the importance of activities to the key stakeholders. The authors believe that this method is transferable to other dam projects, for an assessment of a dam’s readiness for impoundment.
Keywords: Dam safety, risk, impoundment, reservoir filling.
Russell Cuerel, Richard Priman, Michel Raymond, Ian Hanks
Following significant flood events across Queensland over the last five years causing significant damage in South East Queensland, Bundaberg Burnett region, St. George in the south west and more recently in Central Queensland in the Callide Valley, there has been renewed interest in finding solutions to flooding issues.
Increasing the available flood storage within a catchment is a well-known method of improving flood mitigation outcomes for developed areas. In many basins/catchments, potential flood storage development options (new storages or augmentations to existing storages) can be identified by reviewing previous water supply investigations and flood studies and by scanning topographic mapping. From such site identification there will often be numerous combinations of possible flood storage development options to consider because of the number of tributaries which may contribute to major flood events.
This paper outlines a methodology to screen, within a relatively short timeframe and at relatively low cost, a large number of identified flood storage development options and combination development scenarios and shortlist for more detailed analysis. The screening process is heavily reliant on hydrologic assessments to rapidly short-list scenarios for assessment and then relies on traditional engineering and economic assessments to do the fine tuning of the analysis.
Keywords: flooding, damages, impacts, flood storage, flood mitigation, dams, benefit-cost ratio.