Modeling in Support of Dewatering and Closure Construction of an Upstream Raise CCR Surface Impoundment

Craig Schuettpelz, WSP USA
Tanya Walkenbach, WSP USA
Todd Stong, WSP USA
Shane Stockdill, Rainbow Energy Center

Description

Modeling in Support of Dewatering and Closure Construction of an Upstream Raise CCR Surface Impoundment Authors Mr. Craig Schuettpelz - United States - WSP USA Dr. Tanya Walkenbach - United States - WSP USA Mr. Todd Stong - United States - WSP USA Mr. Shane Stockdill - United States - Rainbow Energy Center Abstract A composite-lined upstream raise coal combustion residual (CCR) surface impoundment at Rainbow Energy Center’s (REC’s) Coal Creek Station ceased receipt of CCR in 2021. During operation, flue gas desulfurization (FGD) material was sluiced into the middle of the facility, which was ringed by drainage and structural layers consisting of bottom ash and fly ash. The unit was able to maintain a smaller environmental footprint by expanding vertically to approximately 100 feet in height. As REC prepares for final cover construction over exposed CCR, the saturated FGD material contained within the core requires dewatering which in turn leads to consolidation and potential movement of contained CCR. Several modeling methods were applied to evaluate these conditions and guide closure construction planning: a “groundwater” model to evaluate how quickly the unit will dewater passively and expedited dewatering via pumping; a consolidation model based on laboratory testing to determine settlement at the surface due to regrading of CCR and construction of an evapotranspiration soil cover; and slope stability reevaluation of the unit to indicate whether the modified closure conditions might affect the expected stability of the facility. The results of these modeling efforts will be discussed briefly in relation to their effects on closure.

 
May 14th, 11:00 AM May 14th, 11:30 AM

Modeling in Support of Dewatering and Closure Construction of an Upstream Raise CCR Surface Impoundment

Grand Rapids, Michigan

Modeling in Support of Dewatering and Closure Construction of an Upstream Raise CCR Surface Impoundment Authors Mr. Craig Schuettpelz - United States - WSP USA Dr. Tanya Walkenbach - United States - WSP USA Mr. Todd Stong - United States - WSP USA Mr. Shane Stockdill - United States - Rainbow Energy Center Abstract A composite-lined upstream raise coal combustion residual (CCR) surface impoundment at Rainbow Energy Center’s (REC’s) Coal Creek Station ceased receipt of CCR in 2021. During operation, flue gas desulfurization (FGD) material was sluiced into the middle of the facility, which was ringed by drainage and structural layers consisting of bottom ash and fly ash. The unit was able to maintain a smaller environmental footprint by expanding vertically to approximately 100 feet in height. As REC prepares for final cover construction over exposed CCR, the saturated FGD material contained within the core requires dewatering which in turn leads to consolidation and potential movement of contained CCR. Several modeling methods were applied to evaluate these conditions and guide closure construction planning: a “groundwater” model to evaluate how quickly the unit will dewater passively and expedited dewatering via pumping; a consolidation model based on laboratory testing to determine settlement at the surface due to regrading of CCR and construction of an evapotranspiration soil cover; and slope stability reevaluation of the unit to indicate whether the modified closure conditions might affect the expected stability of the facility. The results of these modeling efforts will be discussed briefly in relation to their effects on closure.