Senior Geotechnical Engineer
Federal Energy Regulatory Commission
Prevented the collapse of a major dam that threatened the lives and property of thousands of residents and business owners downstream, and could have disrupted New York City’s water supply.
Working in his Washington, D.C. office on a July day in 2015, Joseph Mueller, an engineer with the Federal Energy Regulatory Commission, received an urgent and unsettling phone call.
“Joe, we have a problem," his boss at FERC said, relating news of an impending catastrophe—the possible failure of the 175-foot high Cannonsville Dam in Deposit, New York, about 120 miles northwest of New York City.
A collapse of the dam could have caused flooding downstream in the Delaware River Valley in New York and Pennsylvania, posing a risk to the lives and property of thousands of people, and impacted a major water supply to New York City.
Mueller quickly recognized the gravity of the situation and the difficulty of the technical challenge before him. He gathered information about the dam’s foundation and rushed to the scene to perform a site inspection and determine the threat to the dam’s integrity. At the site, Mueller convened stakeholders, worked through engineering issues and brought the group to consensus on a unique plan that they implemented successfully in less than four weeks.
“If it hadn’t been for Joe’s expertise, I really believe we would have lost this dam,” said William Allerton, director of the Division of Dam Safety and Inspections at FERC, an independent agency whose hydropower program approves dam design and construction plans for private, municipal and state hydroelectric projects. Commission engineers also inspect dams regularly to ensure safety.
Mueller and his colleagues learned that construction workers had drilled holes in the downstream side of the dam to explore the location for a proposed hydroelectric power plant. The borings had tapped into an underground aquifer, releasing murky water under high pressure, and flushing soil from the dam’s foundation.
The combination of water pressure under the dam, a full reservoir of nearly 100 billion gallons of water behind it and uncertainty about how long the aging structure could hold, meant that federal, state and New York City officials had to act fast.
Mueller oversaw a strategy to reduce the looming danger. It involved lowering the reservoir’s water level to reduce pressure on the dam’s foundation; drilling and installing relief wells near the three boreholes to stop the cloudy, uncontrolled flow; and communicating with downstream emergency management agencies to make them aware of the situation in case the condition worsened and evacuations were required.
“Installing relief wells was a counterintuitive but innovative solution suggested by Mueller, which turned out to be the key to solving the problem,” said David Capka, deputy director of FERC’s Division of Dam Safety and Inspection.
He said Mueller also recognized that the initial design and location of the relief wells would not work and convinced the multiagency team to follow his lead on these issues. Mueller oversaw the successful installation of the wells by contractors along with other work to secure the dam that included plugging the original boreholes with cement under high pressure and making sure the areas around them were stabilized.
“This major dam safety incident was resolved safely and efficiently,” Capka said. “This would not have been possible without Joseph Mueller’s leadership and creative problem-solving.”
Ann Miles, director of FERC’s Office of Energy Projects, said the Cannonsville case was “an unusual problem, and it didn’t have a classic solution.”
“We had no idea how much time we had and there was a lot of emotion wondering if this was going to work,” Miles said. “Joseph Mueller took his experience and his knowledge of dams to think through the problem and find a solution that was successful.”
Capka pointed out that Mueller “took a much more active role than [regulators] normally would because the situation was so serious,” and he used his expertise and collaborative skills to achieve success.
Allerton described Mueller as one of the top people in the field of dam safety engineering and someone who has “the ability to explain very complicated engineering situations in a way that anyone can understand.”
Mueller said his 39 years of technical experience, most of it with the Army Corps of Engineers, equipped him to deal with high-stress situations.
“There were times when I wondered if I was doing the right thing,” Mueller said. “But I recognized when others were going in a wrong direction, and I felt confident helping everyone get back on course.”
Thousands of people can now rest assured, he was doing precisely the right thing.