Coal Combustion Residuals Pond Closures at American Electric Power Plant
American Electric Power (AEP) retired one of its plants in West Virginia, as part of its compliance plan with U.S. Environmental Protection Agency Mercury Air Toxics Standards. The plant is located along the Ohio River and the closure of the coal yard and ash disposal sites is part of the overall disposition of the plant site. AEP retained Tetra Tech to provide engineering, design, and permitting services required to close the fly ash and bottom ash ponds and the coal yard.
The bottom ash pond and coal yard are designed to be clean closures and consisted of a grading plan that prevents impounding water, provides a vegetated surface, and drains toward the Ohio River. The fly ash pond will be closed by capping with soil. Following a geotechnical investigation and evaluation of the dam, a grading plan was designed to prevent ponding. The sequence of planned construction was structured to balance cut and fill between the three closure areas.
Tetra Tech provided services related to the design for removal and closure of the principal spillway, rerouting wastewater pipelines, reducing seepage from the earthen dam, re-grading the existing fly ash materials and dikes, designing a soil cap, and preparing the stormwater pollution prevention plan (SWPP) for the closure and borrow areas. Closure of the fly ash pond also required development and use of two borrow areas to obtain the necessary topsoil for the cap. Tetra Tech investigated and designed the borrow areas and prepared no-rise certifications for work within the Ohio River floodplain for submittal to the county floodplain manager.