The challenges of dam ownership
From Hammurabi’s Code in Babylon circa 1795 BC to the British House of Lords’ Rule of Rylands and Fletcher in 1868 AD, through to present day safety legislation – dam owners owe a strict duty of care to their adjacent communities and societies overall.
The notion of an ‘Act of God’ has been generally accepted since the 16th century. Liability for dam failure in such cases was measured against the severity of the natural occurrence, reasonable predictability of the event, level of human agency (ability to act) and the reasonableness of precautions taken. This legal development acknowledged that dam owners were not all-seeing and all-knowing, and it reduced the pressure.
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Notwithstanding, in modern times, with our improved ecological knowledge and increased socio-economic awareness, dam ownership is, now more than ever, an incredibly delicate balance of risk and reward. Through the years, the insurance industry has absorbed catastrophic financial losses related to extreme events such as earthquakes and hurricanes. Large dam failures fall into this catastrophic loss category. The reinsurance market currently caps at about $1 billion with deductibles totalling tens of millions of dollars and policy premiums that put significant strain on cash flow and profitability for dam owners. As insurers are becoming more sophisticated, they commonly demand best-practice standards. While this introduces financial pressures on any dam owner’s business plan, one positive effect has been on dam safety through the improved focus on engineering design and operating effectiveness. |
The risks
The three greatest risks to dams are floods, gate failure and internal erosion. Between 1989 and 1998, 76% of all dam failures in the USA were caused by floods, while seepage and piping problems accounted for the next largest segment at 7%. In general, about 44% of large dams fail in floods while 12% of these failures are caused by gates failing to operate.
The biggest flood risks are not from the Maximum Probable Flood but from much more frequent, smaller floods where emergency spillway gates fail to operate on demand. The best spillway designs incorporate free overflow spillways where practicable to mitigate this risk. The higher hazard industry standard for safety gate reliability is often a 1/1000 demand target. This is achieved through sound design, redundancy, frequent testing, maintenance and inspection. Some clues that all may not be well with gate reliability are:
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Internal erosion often manifests itself within the first five years after filling the reservoir. However, it can also occur over a long timeframe as the dam ages and usually provides little warning prior to failure. This is why it is critical to understand your dam’s potential failure modes, how these would develop, how you could detect the problem – and how to build a monitoring and surveillance system with automation and coupling to emergency response systems for risk mitigation.
Terrorist threat is also a new risk for some dams and has created the demand for increased on-site security, in terms of staff as well as electronic surveillance and protection. Investment and expenses rise accordingly for the dam owner.
The future
Dam construction requirements are strongly correlated with population growth. This trend should be expected to continue unless there are dramatic changes in power system structures and/or societal acceptance of alternate energy sources.
Based on the past 100-year historical relationship between dams and population and industrial growth projections, approximately 500 new large hydroelectric dams will be needed in Canada in the next 50 years. Given the length of time needed for the regulatory process, public consultation, land usage and ownership conflicts, and environmental impact assessments – let alone the engineering design and construction activities – this target is clearly beyond reach. As yet, there is no solution.
In moving forward, one litmus test for new dam construction and for sustainable ownership includes five simple, practical questions:
- Will our children be glad to inherit this asset?
- How will it impact our communities?
- Will the decision stand up to evolving societal values?
- Can our company be proud of the project?
- What is the bottom line?
From society’s perspective, we must work harder to generate more stakeholder participation throughout the entire lifecycle of a dam and powerplant. Any impacts should be balanced against the benefits to society, with an overall goal of net zero impact. We must improve our accounting for any risk bearers who are not net beneficiaries of the facility. As we learn from past experiences, push technological boundaries and continually learn about the world around us, it is clear that we must uphold the highest possible standards for personal and environmental safety. The more open, involved and participatory governments, corporations and potential investors can be in the planning stages, the more we can expect public participation from the recreation, environment and commercial perspectives – so that everyone can claim ownership to balanced, sustainable and ‘safe enough’ decisions.
From the engineering perspective, we need to gain a greater understanding of risk analysis and evaluation, improving analytical models that focus on uncertainty. We must create more in-depth knowledge of ‘damage’ versus ‘failure’ and test so-called ’standards’ in a more holistic context of risk management. We must be clear about good knowledge and science – and promote and educate the public in the value of good knowledge versus subjective judgment and traditional unfounded opinion.
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And, finally, since dam safety and hydroelectric generation are not merely points for debate, but real factors in our future, regulators, dam owners, planners, designers and engineers must rise to the challenge of their chosen vocations – for the future benefit of our children. A good design will follow ‘good practice’ and seek efficiencies to minimize costs. But an excellent design will provide for long-term, sustainable assets that will make smart business sense for owners and operators while preventing, controlling and mitigating risks to ‘as low as reasonably practicable’ – while improving the general human condition and enjoyment of our natural resources as we move into the future. |
For further information, please contact:
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Ray Stewart |
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