CCR closure & corrective action management services
Coal ash is the byproduct of burning coal for electricity generation. When coal is burned in power plants, it produces several types of waste materials, including fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) material. These materials are collectively referred to as coal combustion residues (CCRs). The CCRs are typically managed in surface impoundments, waste piles and landfills at or near the site where the residuals are generated. Environmental risks associated with these units are the drivers for RCRA Closure and/or Corrective Action activities required to address any identified risks posed by the CCRs.
Types of CCRs
Fly Ash: A fine, powdery substance that is captured from the flue gases of the combustion process.
Bottom Ash: Larger, heavier particles that fall to the bottom of the combustion chamber.
Boiler Slag: A granular, incombustible byproduct that collects at the bottom of the boiler.
FGD Material: A byproduct of the FGD process, which removes sulfur dioxide from exhaust gases.
CCR surface impoundment closure
Management of environmental risks of CCRs present significant physical challenges because of their geochemical makeup and ability to retain water, especially in CCR surface impoundments. Eliminating or reducing environmental risks related to the on-site or off-site management of CCRs in these units often requires adequate time for dewatering to stabilize and/or solidify the CCRs, ensuring that it can be handled and/or transported safely. ENTACT’s unique skill sets, specialized equipment, and experienced personnel are ideally suited to assist our clients with safe and cost-effective on-site management and/or off-site disposal of the CCRs.
ENTACT is equipped to facilitate the full closure of coal ash surface impoundments (ponds), landfills, or waste piles through either clean closure or a risk-based closure scenario. Clean removal involves dewatering, total excavation, and transportation of all CCR materials off site. At the destination, the coal ash residuals are either placed in landfills or processed further depending on their physical and chemical characteristics and regulatory requirements.
Closure in place allows for the dewatering, excavation, relocation, grading, compaction, and/or capping of coal ash at the designated location onsite. ENTACT also uses our geotechnical construction capabilities such as deep soil mixing and in-situ stabilization to solidify the coal ash.
Management of environmental risks associated with CCRs
Effective management of coal ash involves a combination of techniques designed to handle, process, and dispose of these byproducts responsibly. ENTACT manages coal ash using a variety of techniques including dewatering systems, wet ash conditioning, landfill construction and capping, efficient excavation and transportation practices, and in-situ solidification and stabilization.
Dewatering Systems
Dewatering systems are employed to reduce the moisture content of CCRs, making it easier to excavate, transport, or place, and less likely to create additional environmental hazards. ENTACT uses various techniques to dewater CCRs such as: construction of surface drainage or conveyance channels, use of sumps and pumps, well point dewatering systems for shallow excavations, and deep wells.
Wet Conditioning of CCRs
Wet ash conditioning involves the extraction and stacking of coal ash to allow the material to dry over time. Under certain circumstances, we can add amendments like cement or quick lime to help speed up the drying process. Once dry, coal ash is either placed back in the excavation and capped in place or transported to its off-site destination.
Solidification/Stabilization of CCRs
When coal ash residuals can remain in place, we can solidify and/or stabilize the soils. Solidification and stabilization are enhanced by our comprehensive understanding of crusted ash volume, liquid ash volume, and moisture content, with optimal mix designs completed at our in-house treatability laboratory. ENTACT uses our vast geotechnical construction capabilities to address CCRs left onsite. Our scope can often include in- and ex-situ mixing for berm stability, floating cap construction, and cell stabilization.
Landfill Construction
Landfills are designed to contain coal ash securely, preventing leachate and airborne contaminants from impacting the environment. Key aspects of landfill construction include the placement of liners to prevent leachate, leachate collection systems to prevent groundwater contamination, and capping to prevent water infiltration and gas emissions.
Excavation & Transportation
Excavation and transportation of CCR material can be a critical component of this work. ENTACT uses our solely owned and operated fleet of heavy machinery such as excavators and loaders to remove coal ash from storage areas. The coal ash is then transported to the final destination onsite, or to a designated landfill or recycling facility.
Collected water & treatment
ENTACT is equipped to collect and treat water before it is discharged or leaves the site. We self-perform thorough water treatment processes that include bag, sand, and carbon filtration to remove particulates and solids. When necessary, we also implement specialized metals treatment systems to address any remaining contaminants of concern. This comprehensive approach ensures that all water is treated to the highest standards, preventing any adverse effects on the surrounding environment and upholding our commitment to environmental stewardship. The collected water will be discharged from the site through a general discharge or individual national/state pollutant discharge elimination system permit.
Frequently asked questions
Not all substances present in coal will burn, so the non-combustible material is present in more concentrated amounts in coal ash than coal itself. Commonly found substances in coal ash include arsenic, barium, beryllium, boron, cadmium, nickel, lead, mercury, molybdenum, selenium, thallium and several rare earth minerals. Elevated levels of radioactivity may also be present.
The Environmental Protection Agency (EPA) regulates the disposal of coal combustion residuals, to protect human health and the environment. The key rules and regulations include classification, landfill requirements, surface impoundments, closures, corrective action, post-closure care, beneficial use, monitoring and reporting requirements.
State regulations for the disposal of coal combustion residuals vary. While federal standards set a baseline, states can impose stricter requirements, including more stringent requirements regarding landfill design, surface impoundment management and design, and beneficial use of coal ash residuals. In addition, differences may also arise in permitting processes, enforcement practices, and post-closure care requirements. Some states may also have more stringent monitoring and public involvement procedures, reflecting local environmental priorities and regulatory approaches.
Additives like cement or quick lime can be added under certain conditions to help facilitate the management of coal ash onsite or offsite. If the coal ash is located above the ground water table, it is typically not an issue to introduce a new material as there is little threat of leachate. However, if the coal ash is located below the water table, we take into effect how the additive will affect surrounding groundwater and how it impacts the permitted discharge outfall from the surface impoundment.
Proper management is essential to prevent or minimize the release of contaminants from the CCRs during closure or remediation activities to the surrounding environment.
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WET ASH IMPOUNDMENT CLOSURE
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FLY ASH IMPOUNDMENT CLOSURE AND DAM MODIFICATION
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