Peer Review of Johnsonville Fossil Plant Dike Stability Improvements

TVA OIG retained Marshall Miller & Associates, Inc. (Marshall Miller) to conduct a peer review of the Stantec Consulting Services, Inc. (Stantec) documents for proposed improvements to the stability of the Northeast Dike of the Ash Disposal Area No. 2 of the Johnsonville Fossil Plant. Based on Marshall Miller's technical review, Stantec used generally accepted methods and practices to design the stability improvements. Based on the Stantec Calculation Package, Stantec also designed a slope configuration that provides acceptable factors of safety for slope stability under long-term, steady-state seepage conditions.Marshall Miller found the plans for construction prepared by Stantec provide suitable guidance for construction, however, they found the details of the graded filter portion of the stabilization berm do not conform closely with current standards of practice and present constructability issues at locations where the installation condition are more challenging.To address this report, TVA management had Stantec review and respond to the findings of this report. Marshall Miller reviewed Stantec's response and concluded that the additional information provided adequately addressed the concerns and recommendations identified in the report.