TVA is working to ensure that Blue Ridge Dam, constructed in 1930 and later acquired by TVA in 1939,
continues to safely operate for the next 90 plus years benefiting the Blue Ridge community
and those living downstream.
Is the Blue Ridge Dam safe?
The safety of the communities we serve is our top priority. While the dam is safe, TVA always errs on the side of caution. We’re focused on reducing the potential risk associated with the dam’s long-term operations. This focus on safety is important given the dam and reservoir’s potential impact on the safety and livelihood of communities nearby and downstream.
What is wrong with the dam?
The dam was built in a way which makes it vulnerable to a strong earthquake. In the event of an extreme earthquake, the dam could develop significant cracks. If in the rare chance cracks form and there is seepage that continues through the cracks, the cracks could open and lead to an uncontrolled release of the reservoir.
How often do earthquakes occur in the area?
The closest zone of concentrated earthquake activity to Blue Ridge Dam is the East Tennessee Seismic Zone (ETSZ).ETSZ stretches from roughly Middlesboro, Kentucky to Fort Payne, Alabama, and most of the earthquakes within this zone occur 40 miles or more from Blue Ridge Dam.
The ETSZ typically generates only minor earthquakes with a few of these being large enough to be felt each year. Earthquakes large enough to cause damage are rare in the ETSZ and damage from these events has been minor and isolated.
More distant seismic zones are far enough from Blue Ridge Dam that their potential impacts to the dam are minimal.
Despite the rare occurrence of seismic events, the potential consequences of a dam failure are important, as significant losses of human life and extensive property damage could result. TVA’s commitment to protecting the public against a worst-case scenario is the motivation for initiating our study of potential options to remediate the dam.
What is the biggest earthquake that occurred in the area?
Since the Blue Ridge Dam project became operational, the East Tennessee Seismic Zone has generated two earthquakes which had magnitudes of about 4.6- one centered at Alcoa, Tennessee in 1973, and the other centered near Fort Payne, Alabama in 2003. The ground motions in the vicinity of Blue Ridge Dam from these earthquakes were small. Neither quake caused any damage to the dam.
Historically, the largest earthquake within 100 miles of the dam occurred on August 31, 1861, near Hot Springs, North Carolina. This earthquake had an estimated magnitude of 5.6.
Interested citizens can find more information regarding earthquakes in Georgia on the webpage of the Georgia Emergency Management and Homeland Security Agency at gema.georgia.gov/earthquakes
Does TVA have seismic monitoring stations and what do they do?
There are two seismic monitoring stations present at Blue Ridge Dam which measure accelerations of the rock beneath the dam and motions within the dam itself. The monitoring stations provide an automated early warning of any earthquake-generated ground movements at the dam site.
In addition, TVA has positioned two remotely-operated high-resolution cameras trained on the dam and the spillway to provide visuals of these structures at all times.
Finally, TVA has installed dozens of instruments within the dam and its foundation to monitor water pressures and movement of the dam. In addition to regular in-person inspections of the dam and spillway, these instruments provide TVA dam safety professionals with valuable “real-time, 24/7” information which would permit us to respond immediately and appropriately to any seismic event.
What is the probability that the dam will fail?
While all dams carry some inherent risk, the likelihood of a dam failure is very low. We’ve evaluated the dam to be currently safe for normal operations.
However, we are working to reduce the potential risk associated with the dam’s long-term operations.
What is the potential loss of life if the dam fails?
If the dam were to fail, the number of lives which could be lost is dependent upon a variety of factors, such as time of year, time of day, public knowledge and adherence to emergency warnings, number of recreational users on the river, and length of time for a breach to develop. In a worst-case scenario, hundreds of lives could be lost.
Again, the dam is judged safe for normal operations in its current condition. However, we are working to reduce the potential risk associated with the dam’s long-term operations.