Archived
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Location
Lexington, Kentucky
Start Date
5-5-2026 1:00 PM
End Date
5-5-2026 1:30 PM
Description
Rainbow Energy Center’s (REC’s) Coal Creek Station has managed calcium sulfite flue gas desulfurization (FGD) material in composite-lined upstream raise surface impoundments since 2001. The upstream raise surface impoundment utilizes bottom ash (drainage zone) and fly ash (structural zone) produced at Coal Creek Station to contain the FGD placement. FGD material was hydraulically sluiced to the center of the 110-acre Upstream Raise 92 (UR92) coal combustion residual (CCR) unit between 2001 and 2021. The FGD was deposited to a maximum thickness of approximately 100 feet in the center of the unit. Significant consolidation of FGD material occurred with subsequent FGD material deposition and placement of “dry” materials as part of the cap and final cover. Consolidation within UR92 has been notable from 2021 through 2025 and has affected the timeline for closure. During the last four years, in place CCR materials have been regraded and additional soil has been imported to progress toward closure, including a surcharge loading event to expedite consolidation and settlement. Settlement markers installed along the crest of the unit over the thickest areas of FGD material containment and previously installed stand-pipe piezometers allow site engineers to track settlement and pore pressure. This in situ data along with updated consolidation modeling of the unit helps the site move through the closure planning process with the goal of constructing final cover materials in a timeline to minimize future settlement of the cover while allowing for adequate surface water drainage. The results of in situ site settlement data, laboratory testing data, and consolidation modeling efforts will be discussed in relation to their effects and use to manage closure planning.
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
Consolidation Modeling to Support Closure Planning of an Upstream Raise CCR Surface Impoundment Containing FGD Material
Lexington, Kentucky
Rainbow Energy Center’s (REC’s) Coal Creek Station has managed calcium sulfite flue gas desulfurization (FGD) material in composite-lined upstream raise surface impoundments since 2001. The upstream raise surface impoundment utilizes bottom ash (drainage zone) and fly ash (structural zone) produced at Coal Creek Station to contain the FGD placement. FGD material was hydraulically sluiced to the center of the 110-acre Upstream Raise 92 (UR92) coal combustion residual (CCR) unit between 2001 and 2021. The FGD was deposited to a maximum thickness of approximately 100 feet in the center of the unit. Significant consolidation of FGD material occurred with subsequent FGD material deposition and placement of “dry” materials as part of the cap and final cover. Consolidation within UR92 has been notable from 2021 through 2025 and has affected the timeline for closure. During the last four years, in place CCR materials have been regraded and additional soil has been imported to progress toward closure, including a surcharge loading event to expedite consolidation and settlement. Settlement markers installed along the crest of the unit over the thickest areas of FGD material containment and previously installed stand-pipe piezometers allow site engineers to track settlement and pore pressure. This in situ data along with updated consolidation modeling of the unit helps the site move through the closure planning process with the goal of constructing final cover materials in a timeline to minimize future settlement of the cover while allowing for adequate surface water drainage. The results of in situ site settlement data, laboratory testing data, and consolidation modeling efforts will be discussed in relation to their effects and use to manage closure planning.
