Semester

Spring

Date of Graduation

2026

Document Type

Dissertation (Campus Access)

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Leslie Hopkinson

Committee Member

John Quaranta

Committee Member

Hema Siriwardane

Committee Member

Nate DePriest

Committee Member

Onur Avci

Abstract

The Appalachian coal fields experienced significant economic downturns with implications of bankruptcies that are expected to affect the legacy of mining permits, which transfers the reclamation responsibilities. The reclamation is required by the Surface Mining Control and Reclamation Act of 1977. Restoration of abandoned mine lands from bond-forfeited mining permits and pre-law sites is ongoing in Appalachia and across the United States. The fist part of this research work presents the results of research investigating geomorphic landform design (GLD) principles for design alternatives for the closure of an abandoned high-hazard water impounding coal refuse facility. The research work applied GLD principles to a coal mine impoundment structure located in Monongalia County, West Virginia, USA. A series of conceptual reclamation designs were created and compared to a conventional plan. The designs were evaluated for stability, hydrologic response, and material requirements. The geomorphic approach to reclaiming the reservoir area generated uniform contour lines that resulted in less backfill material needed for the design compared to the conventional reclamation approach. However, no substantial difference in peak runoff discharge was observed when comparing the hydrologic response of the created designs. Expanding the area of disturbance to the surrounding ridgeline with high elevations required more filling material and tributaries, which may create some slope instability on the hillside. Accordingly, a small disturbance area covering the reservoir was recommended. The final conclusions of the research indicated that overall, complete GLD may not be a viable option as compared to the traditional impoundment closure process. Nevertheless, the option that combined conventional approaches with GLD principles demonstrated some benefits. Coal mining refuse byproducts have been identified as potential sources of rare earth elements (REE). The weathering of stockpiled refuse results in the oxidation of its pyritic shale and, thus, the formation of acid mine drainage (AMD) that is enriched in REE. The second part of this research aimed to determine whether existing surface deposits of coarse coal refuse (CCR) can be managed to provide an economically attractive REE feedstock while controlling CCR’s long-term AMD liability. The study evaluated the mechanics of bench-scale leaching experiments of Appalachian CCR to extract REE. Three coal refuse feedstock types were evaluated: i) “raw” (directly from active coal preparation), ii) “fresh” (unweathered, subsurface, or new pile source), and iii) “weathered” (near surface or older pile source). Unsaturated column leaching tests and saturated jar tests were employed as the most appropriate bench-scale representation of heap leaching in the field. CCR types were tested in their current stockpiled condition without further processing. Results revealed that REE concentrations in AMD increased by 116%-252% and 650%-800% in unsaturated column leaching and saturated jar tests of CCR, respectively. Leaching primarily occurred in the first cycle, leaching the REE compounds made readily available by weathering. Moreover, leaching efficiency increased with increased AMD contact time, and the highest leaching efficiencies were observed in weathered CCR, which was identified as well-graded gravel with sand. Overall, leaching efficiencies were low, and the percentage of REE stored in CCR after leaching remained high. Major elements (e.g., iron and aluminum) were also leached along with REEs, which suggests the exhaustion of the long-term pollutant load from the coal refuse. The third part of the current research project focuses on developing an engineering design for constructing a pilot-scale heap leach pad. The performance of the leach pad was evaluated through 2-D seepage and slope stability analysis that was completed using Plaxis LE, a limit-equilibrium modeling software. Additionally, the suitability of two candidate sites for heap leaching was validated according to some identified criteria using the Analytical Hierarchy Process (AHP). A heap leach circuit was developed based on information from the literature and the column leaching test, and costs were determined. The results showed that the applied solution moved along the expected pathways without encountering any issues. The percentage loss of the applied solution during the first leaching cycle can be reduced to approximately zero by wetting the material prior to leaching. Furthermore, acid-base accounting results showed that all refuse tailings at the site of interest fall into the category of acid-generating samples and indicate a higher potential for continuous acidic drainage production. Therefore, environmental considerations, CCR age, and site size were assigned to have the highest level of importance in the AHP analysis. Cost assessment showed that the most cost-effective heap operation options are those that avoid crushing the material; however, estimating the project's revenue was not possible because further testing is needed to identify the best leaching mechanism.

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