While dam safety has improved tremendously since then, the recent evacuation of 200,000 people near Oroville Dam in California reminds us that, while dams are beneficial, they can be dangerous if they fail.
Dam Safety directly impacts TVA’s mission by supporting energy, the environment and economic growth. TVA’s 49 river dams in the Tennessee River system benefit the Valley by providing navigation, flood control, power generation, water supply, recreation and water quality. As a national leader in dam safety, TVA works round the clock to provide these benefits, reduce risks and protect lives and property.
Dam Health Checks
“At TVA, every day is a dam safety awareness day,” says Jennifer Dodd, general manager of Dam Safety. “Every TVA dam is checked regularly to make sure that it is operating as intended.
“Because many of these dams were built in the 1930s, TVA works diligently to make sure that they meet modern safety regulations to stand up to the biggest flood or earthquake that we would ever expect to see in the Tennessee Valley.”
TVA has a long history of safe operations of its dams and ongoing dam safety projects, continuously checking its dams and making improvements. In recent years, visitors to TVA dams have seen large pieces of equipment, barges and cranes nearby as TVA conducts geotechnical evaluations and studies as part of an ongoing “health check” of all 49 dams in the TVA system.
The health checks are part of a continuous improvement campaign to make sure TVA’s dams meet today’s stringent industry safety standards and federal design, operation, maintenance and repair guidelines. With completion this summer of the examination at Beech Dam, TVA will have completed an initial round of health checks at all 49 dams, with further evaluation and assessments to follow.
Extreme Makeovers
Dodd said the health checks also help identify some dams that would benefit from upgrades to make them even better able to withstand extreme events. For example, a 2014 analysis at Pickwick Landing showed that, in a large seismic event, the dam’s south embankment has the potential for damage. TVA’s Dam Safety team took immediate action to mitigate the risks to the public downstream, including installation of a seismic early warning system.
This year TVA conducted exploratory work for a project to help Pickwick Dam withstand a major seismic event. That project will include upgrades to
both the upstream and downstream sides of the dam’s south earthen embankment. Berms will be constructed along the toe of each side of the embankment and areas of extended fill will be placed in select locations. Construction of the upgrades is planned to start this fall, ending in late 2021.
TVA will also conduct further seismic analysis this summer at its Kentucky and Blue Ridge dams on projects to help them withstand extreme seismic events that are unlikely to happen but could have devastating consequences if they did occur.
In other major TVA dam safety activities this year:
- TVA continued progress toward repairing seepage discovered in October 2014 near the base of the earthen embankment at Boone Dam. TVA completed the environmental assessment review and initial grouting test phase (low mobility grouting) in 2016, and the second phase of the grouting program (high mobility grouting) is underway. After continuing monitoring and assessment, TVA refined the repair plan this spring and may move ahead with some project activities, such as construction of a planned rock and sand berm, earlier than initially scheduled. Resequencing planned activities is a normal and expected part of major construction projects, and such changes were anticipated in the Boone Project plan timeline. The project remains on schedule for completion within 5-7 years.
- TVA has completed the initial phase of investigation of seepage identified in April below Little Bear Creek Dam spillway near Russellville, Ala., and is slowly raising the lake level over the spring and summer from its winter pool level of 608’ to 615’, which is about 5 feet below normal summer pool. Inspections and other work around the dam include downstream filter installed to help slow seepage; construction of a sand bag dike to monitor seepage area; ground penetrating radar to better understand the rock and soil composition of the dam; and data collection and analysis.
