Geosyntec provided comprehensive services to Santee Cooper at the Winyah Generating Station to assist the facility with compliance with the pending implementation of the federal Coal Combustion Residuals (CCR) Rule and Effluent Limitation Guidelines (ELGs).
Wastewater Characterization and Treatment: Geosyntec measured the flow rates and composition of key internal streams, such as the de-water stream. Data collected from the material balance and water balance will allow the utility to identify trends in quality and quantity associated with various generating scenarios. These data will provide an understanding necessary to plan for compliance with the pending Steam Electric Power Generating Effluent Guidelines.
Wet-to-Dry Ash Handling: In preparation of the pending CCR and ELGs, Geosyntec developed plant-wide process flow diagrams of CCR handling systems to identify areas requiring modifications in order to convert to dry handling. In most cases the systems lacked required levels of redundancy. Geosyntec identified options, including the addition of a second fly ash silo, replacement of hydroveyors with vacuum pumps, and installation of cross-connections between hoppers to simultaneously reduce water usage, add operational flexibility, and reduce risk.
Data Management and GIS Clearinghouse: Geosyntec developed a web-based GIS platform and portal to allow project team members instant, secure access to a wide range of site environmental and geotechnical data and project documents. Additionally, data from numerous Cone Penetrometer Test borings were interpolated in 3D and visualized using CTech’s Environmental Visualization Studio, to identify zones in the pond dike that may have a factor of safety around 1.0. This 3D analysis also was used to evaluate geospatial uncertainty in the underlying geotechnical dataset and served as the basis for additional geotechnical testing in the area.
Pond Closure and Landfill Development: Geosyntec’s work to date has included the geotechnical, civil design, and hydrogeological fields. The geotechnical evaluation of the West Ash Pond and Slurry Ponds 3 and 4 was driven by a nationwide review of CCR impoundments by the U.S. Environmental Protection Agency (EPA) after the TVA Kingston Fossil Plant geotechnical failure. Geosyntec 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-foot long perimeter dike impounding CCR materials.
Geosyntec produced a comprehensive report documenting these evaluations for Santee Cooper to respond to the U.S. EPA's review comments. Geosyntec has been tasked to develop closure plans for the ash ponds on site. A cost-based analysis was one of the criteria used to determine whether the ponds would be closed in place or excavated and the materials relocated to a suitable place. A conceptual site model was developed prior to implementing the hydrogeologic investigation to identify and evaluate the mechanisms that control groundwater flow at the site.