Groundwater Modeling for Closure of the Little Blue Run CCR Disposal Area

Monday, December 4, 2017: 2:30 p.m.
101 C (Music City Center)
Brianne Hastings, P.G. , Environmental, Civil & Environmental Consultants
Thomas Walsh, P.G. , Environmental, Civil & Environmental Consultants, Pittsburgh, PA

The Little Blue Run (LBR) disposal area is a 900+ acre impoundment that has been used since 1975 for the disposal of coal combustion residuals (CCR) from FirstEnergy’s Bruce Mansfield Generating Station. The disposal area consists of a valley fill impoundment supported by an earth and rock fill dam. The CCR materials in LBR consist of calcium sulfite scrubber material, granulated blast furnace slag, lime, and fly ash that are hydraulically placed.

A digital groundwater model was prepared for the facility to compare closure alternatives and to evaluate environmental implications of the facility after closure. The model consisted of nine layers and over 140,000 cells. It was constructed and calibrated to match observed aquifer conditions and groundwater levels within and surrounding LBR. 

As part of the selected long-term closure program, the CCR impoundment will be capped with a geosynthetic liner and soil cover. An anticipated result of closure is a significant drop in the water level and subsequent settlement within the CCR material inside the impoundment. Recognizing that significant settlement could impact the surface drainage and final cover system following closure, the groundwater model was used to predict post closure groundwater levels. A long-term simulation was run to predict the water table draw-down 50 years after the final cover system will be placed. The simulated timeline included disposal, site closure options, and liner placement.

The post-closure water level is predicted to drop more than 100 feet with the maximum amount occurring where the CCR deposits are the thickest. The reduction in water levels appears to be greatly dependent on the areal extent of standing water on top of the impoundment. The majority of water drawdown within the CCR occurs within the first 24 years after closure. This analysis assisted in the selection of the final closure design for LBR.

Slides in PDF
Brianne Hastings, P.G., Environmental, Civil & Environmental Consultants
Ms. Hastings has over eight years of experience as a Hydrogeologist. She is an Assistant Project Manager at Civil & Environmental Consultants, Inc. in the environmental services group where she manages hydrogeologic investigations for the electric power, natural gas, mining, and manufacturing industries. She earned her Masters of Science degree in Hydrogeology from Illinois State University (ISU) in 2011 and her Bachelor of Science degree in Geoscience from Denison University in 2008. She has experience designing and installing groundwater monitoring programs, analyzing groundwater analytical data, performing and analyzing hydrogeologic testing, and preparing digital groundwater models for coal ash impoundments. Ms. Hastings has provided technical support and assistance to geotechnical and hydrogeological investigations, remedial site investigations, engineering feasibility studies, landfill management, remedial construction projects, and soil/groundwater remediation projects. She also has worked in karst terrain focusing on sinkhole identification and treatment.

Thomas Walsh, P.G., Environmental, Civil & Environmental Consultants, Pittsburgh, PA
Mr. Walsh, a Principal at Civil & Environmental Consultants, Inc., has 26 years of experience in conducting and managing large scale environmental projects. These projects have included environmental permitting, environmental assessments, site investigations, remedial designs, and large-scale hydrogeologic assessments, including computer analysis of aquifer test data and digital computer modeling. He is also experienced in the design and installation of monitoring well networks and various types of remediation systems. He has experience conducting and managing environmental assessments at industrial facilities where volatile organic compounds, coal combustion residuals, coatings, resins, electroplating wastes, primary metals manufacturing wastes, PCBs, asbestos, coal tar and wood treating chemicals were manufactured or disposed.

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