Archived
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Location
Lexington, Kentucky
Start Date
6-5-2026 2:30 PM
End Date
6-5-2026 3:00 PM
Description
Utilities are implementing closure‑by‑removal (CBR) of coal combustion residual (CCR) impoundments as part of corrective action programs to meet groundwater protection standards (GWPSs) and are evaluating closure strategies for Legacy Units. Although CBR and associated decanting and dewatering systems can substantially reduce source mass and improve groundwater quality, lingering “tail” concentrations in the aquifer are often observed after closure because groundwater remediation typically requires extended timeframes. These persistent concentrations may be compounded by secondary source zones beneath the former impoundment, where constituent mass stored in low‑permeability materials or immobile pore spaces is slowly released into the transmissive aquifer after CBR. This presentation focuses on the role of rate‑limited mass transfer in sustaining CCR constituent concentrations following CBR. Using conceptual models of mobile and immobile domains, the discussion will distinguish between relatively fast, near‑equilibrium mass exchange within transmissive layers and slower, rate‑limited mass transfer between transmissive zones and low‑permeability strata. The presentation will also outline how decanting and dewatering strategies can be configured to enhance flushing of the transmissive zone and promote mass transfer from secondary source zones. Numerical modeling case studies will illustrate how secondary sources beneath closed CCR units influence post‑closure groundwater quality even after CCR materials have been removed. The modeling will evaluate the magnitude and duration of concentration rebound, examine sensitivity to mass storage and mass transfer parameters in low‑permeability units, and assess implications for monitored natural attenuation and contingency groundwater treatment. Results will outline strategies to identify and manage concentration rebound and secondary sources and to set realistic expectations for post‑closure groundwater cleanup.
Document Type
Presentation
Archival?
Archival
Included in
Energy Systems Commons, Environmental Indicators and Impact Assessment Commons, Environmental Monitoring Commons, Mining Engineering Commons, Oil, Gas, and Energy Commons, Structural Materials Commons, Sustainability Commons
Methods to Enhance Groundwater Remediation During CBR and Mass Transfer Controls on Post-Closure Groundwater Cleanup at CCR Impoundments
Lexington, Kentucky
Utilities are implementing closure‑by‑removal (CBR) of coal combustion residual (CCR) impoundments as part of corrective action programs to meet groundwater protection standards (GWPSs) and are evaluating closure strategies for Legacy Units. Although CBR and associated decanting and dewatering systems can substantially reduce source mass and improve groundwater quality, lingering “tail” concentrations in the aquifer are often observed after closure because groundwater remediation typically requires extended timeframes. These persistent concentrations may be compounded by secondary source zones beneath the former impoundment, where constituent mass stored in low‑permeability materials or immobile pore spaces is slowly released into the transmissive aquifer after CBR. This presentation focuses on the role of rate‑limited mass transfer in sustaining CCR constituent concentrations following CBR. Using conceptual models of mobile and immobile domains, the discussion will distinguish between relatively fast, near‑equilibrium mass exchange within transmissive layers and slower, rate‑limited mass transfer between transmissive zones and low‑permeability strata. The presentation will also outline how decanting and dewatering strategies can be configured to enhance flushing of the transmissive zone and promote mass transfer from secondary source zones. Numerical modeling case studies will illustrate how secondary sources beneath closed CCR units influence post‑closure groundwater quality even after CCR materials have been removed. The modeling will evaluate the magnitude and duration of concentration rebound, examine sensitivity to mass storage and mass transfer parameters in low‑permeability units, and assess implications for monitored natural attenuation and contingency groundwater treatment. Results will outline strategies to identify and manage concentration rebound and secondary sources and to set realistic expectations for post‑closure groundwater cleanup.
