WILCOX — A special event was held Saturday to show the public the progress on cutoff wall construction at the East Branch Dam in Elk County.
Owned and operated by the Pittsburgh District, U.S. Army Corps of Engineers, the dam started to show signs of damage after being impounded in 1952. It was found that a void the size of a school bus had been created due to seepage. It was grouted for the last 60 years and monitored.
With 650 dams under its jurisdiction nationwide, East Branch quickly rose to the top of its list of concerns. In 2008, studies showed an increased risk for internal erosion across the embankment. The pool was lowered and the lengthy process of finding and implementing a solution began.
Years of study and design determined the best way to address the problem was to build a seepage barrier, or “cutoff wall.”
The prep work started in 2011; the contract was awarded in 2014; and construction is set to be completed by early 2020.
In August 2014, the Pittsburgh District awarded the $132.5-million East Branch Dam Cutoff Wall Rehabilitation Project to Layne Christensen Company of Ruther Glen, Virginia. The company’s Bencor Division, of Frisco, Texas – which is performing the dam safety work – was subsequently acquired by The Keller Group LLC. That contract has since risen to approximately $150 million.
“Following the completion of the cutoff wall, the Army Corps will conduct an evaluation of the repair to ensure that it meets the agency’s dam safety standards,” officials said. “Upon verification of the work, the district will implement a water management plan that incrementally raises lake levels while monitoring the performance of the repair. The district’s main objective is to ensure public safety while returning operation of the dam and management of the reservoir to its regular water management plan.”
During Saturday’s tour, hundreds of visitors were shown progress thus far – including the concrete runway that nearly 100 construction workers are functioning on, as well as the large equipment, slurry tanks, backflow ponds, core drill holes, and the cutoff wall route.
The Army Corps has extended the grouting program currently underway to ensure proper treatment of the foundation rock in preparation for installation of a full- depth seepage cutoff wall.
The cutoff wall will consist of a minimum 18-inch-wide continuous vertical concrete cutoff wall approximately 2,300 feet long with an approximate maximum depth of 250 feet through the existing embankment dam into bedrock.
Of the cutoff wall project, Greg Hensley, lead engineer for the Army Corps, said of the cutoff wall that the contractor is basically “building a picket fence one picket at a time.” It laid the first section of cutoff wall last week and continues to slowly work its way across the dam.
Of the concrete runway visitors walked on, Hensley said it will likely be deconstructed following construction, adding, ”We’ve got six acres of job to do on a two acre site.”
“This dam is a really unique anomaly,” said Hensley of the dam, which has been lauded as a key link in a system of flood damage reduction projects for the Allegheny and Upper Ohio rivers.
Hensley explained that dozens of dams across the country are built in similar conditions as East Branch but don’t have the same problems, adding that, “Every once in a while the stars aligned you will have a flaw of such a magnitude that it has to be addressed. There’s just something special about it that makes it go nuts.”
Officials say that despite its issues, since its completion in 1952, the East Branch Clarion River Lake has prevented flood damages estimated to be more than $88 million.
Completion of the cutoff wall and follow up verification of the repair will allow the Corps to operate the dam at full capacity and restore the reservoir to its regular water levels.
Hensley said the filling of the dam to full pool will depend on exactly when work is completed as the first fill is a large and important test of the project’s success.
The Army Corps and the contractor are working to identify and implement efficiencies in sequencing of the work that will reduce the construction schedule.
Following the completion of the cutoff wall, the Army Corps will conduct an evaluation of the repair to ensure that it meets the agency’s dam safety standards.
Upon verification of the work, the district will implement a water management plan that incrementally raises lake levels while monitoring the performance of the repair. The district’s main objective is to ensure public safety while returning operation of the dam and management of the reservoir to its regular water management plan.
For some time, safety has been a question on the minds of residents downstream.
While the dam remains at a reduced pool for safety reasons, Army Corps estimates show that the consequences of flooding from a dam breach at normal high pool runs the risk of endangering approximately 3,300 people; 2,000 structures; and $423 million in land and property.
In September 2016, Elk County officials approved the purchase and implementation of a Swift 911 warning system which will benefit those who could potentially be impacted if the dam were to fail. The system also benefits residents countywide in the event of an emergency.
Elk County Emergency Management Director Mike McAllister was at Saturday’s event with the agency’s mobile command center, explaining to residents how it would answer the call for an emergency and the importance of signing up for mobile alerts at www.elkoes.com/emergency-notifications/.
With many properties without landlines and some areas without cell phone service, McAllister said that receiving emergency warnings is a partnership between OES and individuals.
“You probably have noticed that over the last several months that we have been able to push notifications to people’s cell phones and landlines for emergencies such as the recent tornadoes that occurred,” McAllister explained. “We’re encouraging individuals to sign up for these warnings so they can be alerted to emergencies that occur.”
The agency has done unofficial studies and found that those in the area of the dam will mostly be able to receive the text notifications if an emergency would occur.
“People have to be aware of their surroundings when they’re in it (an emergency),” McAllister said. “That first 48 hours you have to be able to maintain yourself in a disaster because if it’s big enough it’s going to take your resources a while to assist.”