Boone Dam Seepage Remediation
Update: 2019 Final Supplemental Environmental Assessment
In January 2016, TVA issued a final Environmental Assessment (EA) and Finding of No Significant Impact (FONSI) for the construction activities to remediate seepage at Boone Dam, as well as the associated drawdown of the reservoir water levels. The environmental review of the proposed fix to the dam, located on the border between Sullivan and Washington Counties, Tennessee, helped TVA identify, avoid and mitigate potential environmental effects of the proposed project.
The EA analyzed the effects of our proposal to fix the dam by building a composite seepage barrier from the crest of the dam’s earthen embankment into the foundation soils and bedrock. The barrier proposed by TVA would consist of an injected grout curtain and an excavated and filled concrete diaphragm wall. In addition, TVA would use lands managed by us near the dam for construction support activities and would continue the reservoir drawdown through construction. TVA estimated that the remediation could take up to seven years.
Since the EA was completed, TVA has identified several minor changes to how the final stages of the project would be implemented. On February 22, 2019, TVA issued a final supplemental EA and FONSI for these changes. The proposed changes reviewed in the supplemental EA include changes to:
• The restoration of the dam’s earthen embankment after completion of the seepage barrier: TVA proposes to erect a floodwall on the dam’s crest.
• The disposal of construction spoils generated during the cutoff wall construction: TVA proposes to truck the spoils to nearby disposal facilities.
• The use of nearby lands for construction support activities: TVA would not use the Earl Light Tract for permanent placement of construction spoils, thereby reducing the majority of impacts to the land. Closing a portion of Minga Road would not be necessary and the tract would be reopened for public use earlier than anticipated.
The supplemental EA also provides additional information about how TVA would manage wastewater and stormwater during construction of the cutoff wall.
In October 2014, a sinkhole was discovered near the base of the embankment at Boone Dam, and water and sediment was found seeping from the riverbank below. TVA began assessing the dam’s condition and developing a remediation plan. In October 2015, TVA released a draft EA assessing the environmental impacts of the remediation plan. The draft EA was made available for public review and TVA hosted a public meeting in Johnson City to present its findings and solicit input. TVA considered all comments that were received during the review period. These comments and TVA’s responses are included in an appendix to the final 2016 EA.
TVA also completed a review of how the project complies with the White House Council on Environmental Quality’s policy established in Principles and Requirements for Federal Investments in Water Resources (March 2013). TVA conducted a review of the principles, requirements, and guidelines for water resources investments (PR&G Review) consistent with the Federal Interagency Guidelines issued in June 2015.
More information on this environmental review can be obtained from:
The Boone Dam Project
TVA has found the fix for seepage at Boone Dam: a composite barrier made of non-erodible material. Construction will take five to seven years. Maximum safety measures for area residents and businesses will remain in place throughout the process. Find out more about what happened at Boone Dam, why and how a team of the country’s finest dam engineers and safety experts arrived at the best possible solution. Read more about the Boone Dam Project.