Lindsay FlangasThe United States relies on a vast network of dams to power our homes, fill our tubs, and protect our communities from flooding. Many of these dams were built during the infrastructure boom of the ‘50s and ‘60s, or even earlier, and are now in desperate need of modernization or replacement. It’s been estimated that by 2030, as much as 70 percent of the country’s 91,000 dams will be more than 50 years old, with the current average being 57 years. We are facing a dam safety crisis, and we ignore it at our peril.
Aging and poorly maintained dams are, of course, at higher risk for catastrophic failure, but there is a second element at play. Historically the standard engineering approach for dams included planning for “design events.” Engineers looked at the historic record of significant natural events such as heavy rain, flooding and earthquakes to estimate the maximum loads a dam would have to withstand.
Over the past few decades, however, the flaws in this traditional approach have been exposed. Record-breaking weather events are occurring more frequently and the past is no longer an accurate guide to future events. Our improved understanding of seismic risks and how to anticipate them adds an additional vital component to dam design and risk analysis. Today, engineers think about the long-term resilience of their designs in more holistic ways that better capture and accommodate uncertainties. Unfortunately, many of our existing dams may not withstand these forces without significant overhauls. Mitigating the risks of dam failure includes regular maintenance and safety monitoring using appropriate instrumentation, together with strategic investments in dam improvements.
GeoEngineers’ dam safety team has added a performance-based engineering approach to the traditional safety-factor analysis when evaluating dams. This new method is consistent with the dam safety evaluation program started by the US Army Corps of Engineers and endorsed by many regional water management organizations. We model the performance of structures under a variety of real-world loads and conditions. By grounding the analyses in predictive performance data and uncertainties, we can evaluate risk factors over the entire life cycle of a structure. Once dam owners are armed with estimates of annual probability of failure for a given structure, they can make better-informed decisions to mitigate risk and improve resiliency.
On May 31, 1889, the South Fork Dam failed, sending 20 million tons of water into the community of Johnstown, PA, and killing more than 2,200 people. It remains one of the most devastating tragedies in the country’s history.
Adequate safety monitoring is also a core challenge for dam operators. Many rely on manual data collection and processing, which takes time and carries risks of human error. Manual collection also only provides snapshots of varying parameters and may not indicate important trends. Detecting patterns of risk using this method can be difficult, and emergency situations may not be addressed in a timely manner. To address these issues, we deploy wireless sensors and software systems to manage, process and provide real-time visual graphics of dam performance. Action alerts are incorporated in the software which provide 24/7 warnings of potential problems, and can be monitored from a central control room.
The greatest current need is for funding. Most dam operators are very aware of the risks, but simply can’t afford to invest in the necessary improvements. The U.S. Environmental Protection Agency recently announced $6.5 billion in new funding for water infrastructure projects and the U.S. Army Corps of Engineers Water Infrastructure Financing Program (CWIFP) received funding for the first time ever in the Fiscal 2021 Energy and Water Development and Related Agencies Appropriations Act. The initial appropriations for the CWIFP includes $12 million for credit subsidy and $2.2 million for administration of the USACE program. This is a start, but a modest one when compared to the $105 billion investment that the American Society of Civil Engineers estimates will be necessary to update the country’s water infrastructure.
Together we can work to raise awareness about the current state of the US dam network. We can’t simply wait for a disaster to get the public’s attention and generate funding. Let’s talk about what we can do to make our dams safer now, before it’s too late.
