A composite seepage barrier may be built to correct water seepage and erosion at Boone Dam near Gray, Tennessee, US, Tennessee Valley Authority (TVA) has announced.

The repair – which is pending a formal environmental review – was recommended by TVA engineers and other dam safety experts for the earthen embankment portion of the dam.

Involving a multi-stage combination of grout injections and concrete, the project could take five to seven years to complete and is expected to cost between $200 and $300 million.

After seepage under the embankment was discovered in October 2014, a thorough investigation discovered a complex series of underground geological pathways allowing water from both upstream and downstream sources to cause internal erosion. If left uncorrected, the erosion could eventually lead to the failure of the dam.

"The proposed composite seepage barrier should prevent further erosion and we are confident will provide the most robust, long-lasting repair at Boone Dam," said John McCormick, TVA vice president of Safety, River Management and Environment.

Preliminary testing and site preparation work is already underway.