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Embankment Remediation Progress
The mission remains the same – safety of the downstream public, safety of our workers, and the quality of the dam repair itself are top priorities.
The cutoff wall remains on schedule to be completed by May 2021. Following completion of the cutoff wall, crest and site restoration will begin and take approximately 12 months. Starting next spring, TVA Dam Safety will control the reservoir fluctuations. The fluctuation plan will be made available this fall at our annual public meeting which is tentatively planned for October. The reservoir is expected to return to normal operations by July 2022.
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Mulching operations took place recently in Grande Harbor.
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Supplemental Vegetation Management
TVA mechanically mulched 650 acres of vegetation that grew on the exposed lakebed in 2019. TVA has mulched more than 550 acres in 2020, with a goal to mechanically treat 900 acres this year. A lesson learned from 2019 is that a combination of both mechanical mulching and the use of EPA-approved herbicides is necessary to properly control previously mulched areas and to further address resident’s safety concerns in difficult-to-access areas.
TVA proposed spraying up to 500 acres of vegetation growing in areas of the reservoir bottom that is not able to be reached by equipment, as well as an additional 100 acres in areas that TVA has previously mulched to address emergent growth.
TVA has prepared a supplemental environmental assessment (EA) to consider environmental impacts associated with using herbicides to treat the 600-acre project area. (Please see letter from Matthew Higdon below.)
Spraying will be conducted by a contractor with experience and qualifications to apply the herbicides. Their work is scheduled to begin soon and should be completed within four months. TVA will notify residents in advance so that they may opt out of mulching or herbicide application on their property.
Areas to be mulched and/or treated with herbicides are available on a map posted on the Boone Dam website along with the supplemental EA.
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Remote control boat used to explore below the water surface and help engineers create models used in dam safety.
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Divers performed manual inspections of Boone Dam in June.
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Tiny Boat Creates Models Used in Boone Dam Safety
TVA uses a variety of methods to perform safety inspections at its dams And at Boone Dam, that includes a swath of more than 200 instruments. At least twice a year it involves manual inspections by divers. Recently a tiny remote control boat was used to perform an inspection of the concrete dam below the water. The boat was used in the tailrace and areas that were too rocky to access with TVA’s sonar boat.
Some may be familiar with above-ground LIDAR data in which laser beams are used to build 3D models. TVA Civil Engineer Eric Edwards says this technology is similar but used under the water.
“It hits points on the river bottom, measuring as it goes, then stitches a model together,” said Edwards, a Civil Inspector in Dam Safety. “It helps us from a dam safety perspective to make sure there is no undermining or scour of the downstream concrete toe.”
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Residents will see a door hanger as part of our communications outreach.
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A Letter to Our Stakeholders
TVA has released a supplemental Environmental Assessment (EA) that addresses the use of herbicides to reduce vegetation growing in portions of the Boone Reservoir drawdown areas. The EA supplements TVA’s 2016 EA relating to seepage remediation at Boone Dam. TVA proposes to use a herbicide mix, including herbicides approved for aquatic settings, on up to 600 acres in the reservoir drawdown area to reduce vegetation growth that may result in safety and hazards once water levels are returned to normal. On June 11, 2020, TVA issued a Finding of No Significant Impact for these activities. For more information, please visit the Boone Dam Seepage Remediation website.
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