Before smartphones and GPS, Ed Wehner was driving to a reservoir for work but got lost a few miles from the dam. So he stopped at a nearby gas station to ask for directions.
“Do you know which way the dam is?” he asked the attendant.
Wehner, now retired, was the chief of dam safety for the U.S. Army Corps of Engineers Pittsburgh District, responsible for operating 16 reservoirs in the region.
“What dam?” the attendant replied.
Wehner eventually found his way, but his experience taught him something. While some communities live just a few miles away from the districts’ dams – these colossal concrete constructions hundreds of feet in height, holding back millions of gallons of water from flooding the region – some of their closest residents don’t know they exist.
The Corps of Engineers has typically built reservoirs tucked behind towns where they can manage the maximum amount of flooding in a watershed. The reservoirs also support environmental stewardship, local wildlife and sustain navigable waterways. Still, these functions are only possible with a dedicated team of engineers who ensure each dam is structurally sound.
Pittsburgh District has a multidisciplinary dam safety team comprised of electrical, mechanical, structural, hydraulic, and geotechnical engineers who conduct periodic inspections at all 16 reservoirs and 23 locks in the district.
“I describe it to people as a doctor's appointment: we're giving our dams and our facilities a checkup to see if anything has changed and could impact dam safety or personnel safety,” said Carolyn Wehner, a civil engineer with the district and Ed Wehner’s daughter.
The team takes detailed notes so district leadership knows of any issues before they become problems in the future.
Talking about dam safety can sound alarming at face value. Of course, a dam failure is a worst-case scenario that could devastate communities, but accurately discussing the topic requires perspective.
When Wehner talks about dam safety, she compares a dam’s failure risk to lightning strikes. The chance of getting struck by lightning is roughly 1 in 1 million, while the possibility of a breach failure at Stonewall Jackson dam is less than 1 in 100 million.
Each dam in the Pittsburgh District is evaluated every five years and rated based on several principles to summarize a Dam Safety Action Class, or DSAC, rating.
The principles include structural, geotechnical, hydraulics, and electrical and mechanical:
- Structural involves the physical components of the dam’s makeup, such as the concrete or steel used to construct it.
- Geotechnical evaluates the geological factors associated with a dam, such as embankments, riverbanks, and upstream and downstream waterway conditions.
- Hydraulics evaluates if a dam’s machinery is causing any undue impacts to a river, such as creating currents.
- Electrical & Mechanical further evaluates a dam’s machinery to verify its mechanical components, such as gates, valves, air compressors, and generators, are functioning correctly.
The team recommends improving a dam’s operations or to minimize possible risks in its reports.
“For instance, if the project loses power, they need a functioning generator on site that's reliable,” said Civil Engineer Morgan Hoge. “We'll identify the risk, so they can kick on and power the dam portion of their project, and still function in water releases, operating gates, and so on.”
The dam safety team also develops and maintains emergency action plans in case any dam fails, regardless of how low its risk may be. In addition, the team works with emergency managers and first responders to ensure communities are safe in any scenario.
One of the most significant undertakings the dam safety team has handled was the East Branch Dam Cutoff Wall Rehabilitation Project in Elk County, Pennsylvania. The seven-year project involved installing a 1,500-foot cutoff wall in the middle of the dam to prevent trace amounts of water from leaking.
“It was kind of like open heart surgery on a dam, and we had to take special measures to prevent it,” said Joe Premozic, the district’s dam safety program manager and the project’s lead safety team engineer."
“During the surgery, we had to make sure we didn’t damage the dam.”
The dam safety team took various steps to ensure the project went smoothly, such as lowering the dam’s water levels as part of interim risk reduction measures, and routinely monitoring hydrologic data.
“We had a 24/7 presence at the dam,” said Premozic. “We also had in the neighborhood of 100 instruments installed that told us the water levels and pressures at various points of the dam in real-time, which enabled us to respond as quickly as possible if we needed to.”
Fortunately, a crisis response never became necessary, and the project concluded in 2020. Premozic says the project was one of the team’s biggest undertakings to date, as well as a major milestone in his 32-year career. Nearly half of his career has been focused solely on dam safety.
Premozic said one of the most critical actions local communities can take to ensure their safety is improving their awareness. For example, a wealth of data about the corps’ dams is available on the National Inventory of Dams website in addition to flood-inundation mapping, which details how flooding could affect an area.
“Most importantly, people should listen to their emergency managers,” Premozic emphasized. “Evacuation notices are not made lightly and they’re not a drill. These notices are made to save your life.”
May is National Dam Safety Month. Throughout May, the corps shines a spotlight on critical infrastructure with a focus on dams’ benefits, risks of failure, and community engagement opportunities. Dam Safety Day culminates on National Dam Safety Awareness Day on May 31, which recognizes the failure of the South Fork Dam in Johnstown on May 31, 1889. The dam’s failure resulted in 3.6 billion gallons of flooding Johnstown, killing 2,209 people, destroying 1,600 homes, and causing more than $17 million in property damage (in 2021 dollars, more than $512 million).