From Stantec ERA: Updating and refurbishing our hydropower stations will pay off long-term
July 29, 2020
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It’s critical to develop plans for aging plants around the world
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Over the last decade or so, hydropower refurbishments have become a large part of the world’s energy practice. Many utilities in the United States own hydro fleets built in the post-war period that are now reaching the end of their lifecycle. According to the American Society of Civil Engineers, nearly 2,000 dams in the US were listed as needing repair in 2017. Today, 70% of the dams in the US are more than 50 years old.
Some of these aging plants and dams are modest and the projects are straightforward. Others, however, involve extensive and highly complex repairs to large dams, reservoirs, and powerhouses that haven’t seen significant capital improvements in decades.
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Oroville Dam, California.
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High-hazard dams are of especially concerning. At the time they were built, these dams were designed to withstand extreme weather events. However, as these events have intensified throughout the decades, dams demand more and more maintenance, including upgrades and refurbishments. Taking on a refurbishment project means understanding the risk process during the implementation phase and adhering to current codes and standards, which are ever evolving, to meet our needs.
The incorporation of intermittent energy sources generated from wind and solar has placed additional strain on hydrogenating stations, which must be turned on and off far more frequently to accommodate fluctuating power flows. The evolution of design criteria, as well as new navigation, environment, and water-management regulations, have caused utilities to undertake massive refurbishments to hydropower dams at century-old locations.
" }Grand Coulee Dam Unit G23 Rotor Replacement Time Lapse.
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Understanding aging hydro components are key to refurbishments
Engineering challenges are tough and require a deep, systemic understanding of not just current hydroelectric design standards but the performance and quirks of aging components, like valves, that may have been installed decades ago.
The risks associated with doing nothing are too high. The problem is well understood, but the solutions are expensive and difficult to implement. Examples of aging infrastructure can vary widely. For example, a 50-year-old dam in Eastern Canada was built with concrete with a chemical composition that has expanded steadily, substantially reducing the anticipated lifespan of the spillway.
In another case, we provided planning, project management, and construction management for the complete overhaul of turbines and generators at the almost 80-year-old Grand Coulee Hydropower Plant, a large hydro facility owned by US Bureau of Reclamation on the Columbia River in Washington state. When all upgrades are finished, the entire project is predicted to cost more than $100 million.
" }Hydropower is the nation’s largest renewable electricity resource, providing 7% of our total generation.
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While most of these hydropower refurbishment projects are commissioned by utilities that have realized the need to address long-recognized aging processes, others have come out of left field.
A utility employee in Columbia was driving on the roadway over a looming dam when he noticed a strange kink in the roadbed. When the utility’s engineers came out to inspect the site, they realized that the concrete dam itself had shifted enough to warp the road, a situation that raised alarm bells about the risk of a collapse.
This sort of sudden infrastructure issue can be difficult for clients to absorb. Such refurbishments involve substantial cost and offline time, and, as in the case of the warped dam, may require multi-staged repairs—initially to stabilize the asset and then to develop a sustainable long-term solution.
We perform what amounts to triage, which involves a root-cause analysis and a proposed course of action to mitigate risk. We regard this sort of up-front advisory role as critically important and always make sure we’re bringing the most experienced people on our team to provide insight.
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Mormon Flat Hydroelectric Station, Arizona.
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Reverse-engineering century-old equipment
From my earliest days as a young mechanical engineer working for the Tennessee Valley Authority, I learned that hydroelectric dams must be viewed as highly interconnected systems, not just a set of mechanical and concrete components. The facility, depending on its age, may be highly calibrated to equipment that has long gone out of production.
Not long ago, we were brought in to assess a hydro station where a large valve had been installed as part of an overhaul of the penstock, the intake structures that control water flow. When the utility tested the new equipment, the entire facility began to shake violently.
As we looked more closely at what had been done, it became apparent that the original valve dated back to a design developed in the 1930s by the US Bureau of Reclamation for the Hoover Dam. To properly fix this station, we needed to reverse engineer the original equipment in order to replace it with something that worked in tandem with the rest of the system.
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Hoover Dam. Image courtesy of the US Bureau of Reclamation.
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Responding to aging incidents meet our immediate and long-term needs
These incidents highlight the need for us to invest in the infrastructure behind the energy. Hydropower is the nation’s largest renewable electricity resource, providing 7% of our total generation, and prioritizing its aging infrastructure a no-brainer. When we begin this process with risk-based studies, we can prioritize better budgeting and more sustainable solutions for the future. The actions we take now will help prepare our infrastructure for the next extreme event, while these plants continue to serve us quietly day in and day out.
By studying the structures of the past, and responding to current and future incidents, we are not just meeting our immediate needs but the needs of those to come. We are giving future generations the same opportunity for success.
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