CCR Pond Closure Services and Wet-to-Dry Ash Conversion
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Geosyntec's client, a large electric power utility, retained us at the Winyah Generating Station to provide a variety of services related to their disposal of coal combustion residual (CCR).

In general, the project includes four major components: (i) closure of the existing network of CCR ponds containing approximately 12 million cubic yards of CCRs; (ii) permitting and design of landfill capacity for future CCR materials; (iii) wet-to-dry ash conversion; and (iv) wastewater characterization, treatment system design, and permitting.  Their overall goal was to ensure the plant was in compliance with the federal CCR rule and the Effluent Limitation Guideline (ELGs) limits.

Geosyntec's Scope of Services

Geosyntec's geotechnical evaluation of the West Ash Pond and Slurry Pond 3 & 4 was driven by a USEPA's nationwide review of CCR impoundments. We reviewed existing data for the construction of existing impoundments and implemented a rigorous field investigation and laboratory testing program of the dike and subsurface soils along the 10,000-ft long perimeter dike impounding these residual materials.  With much of the pond volume being designed for storage, our approach was to reduce the normal operating pool by nearly 20 feet to maintain adequate short-term storage capacity and residence time for settling. We developed closure plans for the ash ponds and reviewed reports and drawings to evaluate as-built conditions to estimate volumes and the CCR extent, evaluating potential sites for landfilling, including the possibility of constructing a landfill on top of the existing ash ponds.  We completed closure plans for each existing CCR surface impoundment and submitted a solid waste landfill permit application for the landfill development within the footprint of two former surface impoundments. We designed the new landfill to meet the more stringent requirements of either the South Carolina state regulations for a Class Three Landfill or the new Federal CCR rules.

We also designed a preliminary pilot design of a 25 gpm physical/chemical flue-gas desulfurization (FGD) wastewater treatment system to remove solids and metals such as arsenic and mercury. The purpose of the project is to evaluate the systems that most effectively and economically treat FGD wastewater to meet the ELG limits. Currently, FGD wastewater is discharged to a surface impoundment; however, this impoundment will have to be closed under the CCR Rule. We designed the pilot system for maximum operational flexibility and to be operated with a primary clarifier following lime precipitation. Process data are electronically monitored and logged, reducing the need for reliance on manual data gathering and field forms, and improving the ability to monitor and optimize the process in real time.

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Project Summary

  • Location: Georgetown, South Carolina
  • Client: Electric Power Utility
  • Project Practice Areas: Waste Management, Environmental Management
  • Type of Facility: Coal-fired plant
  • Services Provided: USEPA 40 CFR 257, Ash pond closure, Ash excavation and transportation, Hydrogeological studies, CCR geotechnical investigations and testing, Cost estimating and schedule development, CCR landfill design and permitting, Wastewater characterization and treatment design
  • Type of Work: Coal ash pond closure
  • Governing Regulation: Federal regulations