The International Information Center for Geotechnical Engineers

Thursday, 01 February 2018 19:05

Seismic Assessments Using Best Practices for Risk Management of TVA Coal Combustion Residuals Surface Impoundments

In 2015, the Environmental Protection Agency (EPA) issued the “Coal Combustion Residuals (CCR) Rule” to address risks associated with failures of surface impoundments and landfills used to dispose of CCR generated by coal-fired power plants.

The Tennessee Valley Authority (TVA) operates 10 coal-fired power plants in Tennessee, Kentucky, and Alabama. Seismic stability assessments of surface impoundments at these power plants, done by others using simplified and conservative assessments, concluded that six impoundments would not meet the EPA’s CCR Rule requirements. This would necessitate significant stabilizing work which could potentially cost more than $100,000,000 or cause a shutdown of the power plants due to non-compliance to the Fede TVA retained Geocomp to perform a more comprehensive assessment of the six impoundments. Geocomp formulated an approach termed “Best Practices” to more realistically assess the seismic stability of these facilities without the over-conservatism inherent in the previously employed simplified procedures.

Geocomp applied their Best Practice assessments to surface impoundments located at the Allen, Cumberland, Gallatin, Johnsonville, Paradise, and Shawnee Fossil Plants to determine their stability during and after the design earthquake. The Best Practices approach included more comprehensive site investigations, state-of-the-art laboratory testing of high quality samples, and advanced numerical analyses of earthquake shaking effects 

Using Best Practices, Geocomp’s assessments resulted in all six of the potentially non-conforming surface impoundments meeting the Federal EPA CCR Rule requirements for seismic stability by the October 2016 mandated deadline. Therefore, the plants could continue to operate without disruption. Without the results of the Best Practices approach, these plants would have been required to be shut down, or TVA would have had to spend more than $100 million for slope remediation within a short period of time.

 

 This article is part of the latest Q4 2017 Newsletter of Geocomp, you can fin it here.

Source: Geocomp

 

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