Blue Ridge Dam Safety Study

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.

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

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.

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.

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.

In addition to the seismic monitoring stations and remote-operated cameras, there is a siren warning system at Blue Ridge Dam. The sirens will activate in the unlikely event of an impending dam failure.

TVA also coordinates closely with the Fannin County Emergency Management Agency to ensure the public is prepared for and notified in the event of any threat.

Some of the communities downstream include McCaysville, Mineral Bluff, Copperhill, and Pleasant Hill.

If the dam were to breach, there could be a variety of impacts to human life, property, essential services, communications, and transportation routes.

TVA works closely with local emergency management agencies who are tasked with keeping residents informed of the risk and evacuating the population in the event of an emergency.

The Blue Ridge Dam was built in 1930 with a technique termed "semi-hydraulic filling". This technique introduces an inherent vulnerability into any dam built with the technique, and it is no longer used in modern dam construction. TVA acquired the dam in 1939.

While TVA did not create the vulnerability which exists at Blue Ridge Dam, we are continuously working to improve the safety of the dam to protect the public.

The life loss associated with a spillway failure is dependent on a variety of factors (as mentioned above in discussion of dam failure), though the threat at the spillway is considerably less than that posed by the dam. TVA estimates several dozen people could lose their lives if the spillway were to fail.

Again, the spillway is judged safe for normal operations in its current condition. However, we are working to reduce the potential risk associated with the spillway's long-term operations.

Blue Ridge Dam has been evaluated against industry standards many times over the past decades, and it has consistently been judged safe to operate.

During the past decade, there have been significant lessons learned in the dam safety industry, as well as significant changes to industry standards and practices. TVA's judgments to increase the safety of the dam and spillway are motivated by an interest in proactively providing appropriate protection for the public and adherence to modern standards in light of these industry changes.

Over the past several years, the dam safety profession has moved toward incorporating greater consideration of downstream consequences within evaluations of dam safety. TVA has been integrating this approach into its dam safety program as part of its ongoing commitment for all TVA dams to conform to modern standards for public protection. This change in industry practices is one factor in TVA's efforts to increase the safety of Blue Ridge Dam.

The most recent evaluations of the spillway at Blue Ridge were also influenced by industry lessons learned from damage to the Oroville Dam spillway in California, as released to the profession in 2018. The Oroville Dam incident demonstrated to the dam safety profession that a particular potential failure mechanism was much more dangerous than previously thought. TVA has judged that the Blue Ridge Dam spillway exhibits some vulnerability to this potential failure mechanism and has chosen to be proactive in addressing the potential issue.

We have initiated a study intended to inform which types of modifications (if any) might be most beneficial for increasing dam safety. This study is scheduled to be completed during calendar year 2026.

In the meantime, we have implemented several activities to ensure ongoing safe operations which include increased in-person monitoring of the dam supplemented by remotely-operated cameras, installation of public warning systems, increased interactions with local emergency management agencies, and placement of emergency response resources at or near the site.

It’s premature to speculate about the impact on the reservoir until we finish the study in 2026.

However, it is a common practice to lower reservoir levels for extended periods during the construction of major dam remediations. This option is one of several which must be considered once TVA has completed the current study and has selected a technique to remediate the dam.

TVA will actively engage the communities nearby and downstream, sharing and seeking comments on any plans to study and select an appropriate approach to increase the safety of the dam and spillway.

Solicitation of public input regarding any proposed actions that may significantly alter a dam is a requirement of the National Environmental Policy Act, and is a vital tool for TVA to maintain and demonstrate its commitment to bettering the quality of life for the citizens we serve.

TVA Dams, including Blue Ridge Dam, have been benefiting the people of the valley region for 90 years. These benefits include flood control, recreation, water supply, environmental stewardship, and the generation of low-cost, clean power.

The waters in and around Blue Ridge are especially known for their value to recreational fishermen, whitewater enthusiasts, and local tourism.

We understand the economic, environmental, and personal value of the dam and its reservoir to those in the nearby community as well as those downstream, and we are committed to ensuring the safe and long-term operations of Blue Ridge Dam for generations to come.

Given the scale of many dam safety remediation projects, concurrent work on both dams is a possibility.

However, we do not yet know how likely it is that projects could be underway simultaneously at these two dams since the studies to define the remediations to be built at each dam have not been completed.

There are no current plans to modify the dam or spillway at Nottely Dam. If later, TVA judges modifications to Nottely Dam are appropriate to protect public safety or if there is an advantage to leveraging TVA resources from projects at Blue Ridge and Chatuge to improve conditions at Nottely Dam, TVA may elect to do so.

A series of studies would need to be conducted prior to developing any plans at Nottely Dam, and no such studies have been initiated.