Coal Ash Management/Treatment Pond Design

MD&E is currently contracted to design a new coal-combustion byproduct (coal ash) management and treatment pond system for a major Midwestern power utility. The pond system design is to comply with RCRA rules proposed by USEPA in response to a 1 billion gallon release of coal ash slurry from the Kingston Power Plant in eastern Tennessee in 2008. The MD&E design anticipates the retention, settling and treatment of coal ash slurries, stormwater run-off from coal storage piles, boiler blowdown and cooling-tower effluent. Average flow throught the pond system is 3 million gallons per day.

MD&E conducted hydrologic and hydraulic analyses to size a retention pond system consisting of a forebay and flow-through treatment basin. The forebay is designed to facilitate removal of settleable solids. The treatment basin is configured to promote TSS and TDS removal through biological uptake from wetland flora. Effluent from the pond system is directed to a clear-water pond for recycling back to the power plant.

Forebay design includes provisions for access by heavy equipment for periodic removal of accumulated sludges. Routine treatment basin maintenance is proposed to manage excess biomass and minimize the potential for re-mobilization of nutrients and suspended solids. Inlet, outlet and drainage structures have been appropriately sized to maintain normal pool elevations over a broad range of flow conditions.