Date of Graduation
Statler College of Engineering and Mineral Resources
Civil and Environmental Engineering
The United States has approximately 22% of the world’s coal reserves. Since 1961, the electric power sector has been the major user of coal in the U.S., accounting for 91.9% of the coal consumed in the country in 2021. Sixty-two percent of total U.S. coal production in 2021 was sourced from surface mining, and Wyoming, West Virginia, Pennsylvania, Illinois, and Montana were responsible for 74% of this total production.
Coal-mining activities expose sulfide minerals in rocks that, when in contact with oxidizing conditions, produce sulfate-rich drainage known as acid mine drainage (AMD). AMD treatment typically involves chemical treatments to raise pH and precipitate solubilized metals. This process produces a sludge precipitate known as AMD sludge. The AMD sludge has been commonly disposed of in ponds or underground mine works, in active coal mine refuse areas, and in onsite burial. AMD sludge disposal present management and environmental concerns due to large requirement of area, sludge properties, and the continuous sludge production even after mining activities are ceased. Also, the mined coal often includes impurities and non-coal materials requiring the raw coal to be submitted to a process called coal preparation. The byproduct of this process, named coal slurry, is often disposed of in impoundments. After reaching its capacity, the impoundment is required to be reclaimed, a process that creates regular slopes and channel-based drainage that has increased potential of erosion when compared with the undisturbed terrain.
This study evaluated the use of AMD sludge as a soil amendment as an alternative means of reuse for this material. Six different mixtures containing sludge and topsoil with amounts of sludge of 0%, 10%, 20%, 30%, 40%, and 50% in volume, were analyzed for ground cover, biomass, and stem height during nine weeks of study. The sludge sample used in the study met Resource Conservation and Recovery Act (RCRA) toxicity requirements. Results showed that the addition of AMD sludge up to 50% in volume to topsoil did not reduce ground cover significantly when compared to the only topsoil baseline, suggesting that the sludge may be considered for land application with additional testing at field scale needed.
The second part of the study evaluated the application of geomorphic landform design (GLD) to impoundment reclamation. In contrast with the traditional reclamation, GLD creates slopes and a drainage network that mimic the function of the balanced pre-disturbed landscape. A series of conceptual designs were created. The hydrologic response was evaluated and compared with the traditional reclamation method. The preliminary results showed increased runoff rates and lower time to peak, indicating reduction in infiltration. Slope stability analysis and erosion estimation are necessary to provide basins to long-term advantages of GLD application to impoundment reclamation.
Rodrigues Silva, Amanda, "Evaluating potential soil amendments and geomorphic methods for mine land reclamation" (2022). Graduate Theses, Dissertations, and Problem Reports. 11524.