Considerations for Applying Soil Amendments at Mine Sites

While mining provides essential metals and minerals for humanity, it can also cause environmental contamination, from unstable mining residuals. Management tools are needed to facilitate stabilization of mining residuals using plants (phytostabilization) at both active and abandoned mines to reduce negative environmental impacts. Mining residuals are often acidic, laden with heavy metals, lacking adequate nutrients and physical conditions for plant growth, which are all challenging for establishing plant cover. We have had success using a systematic approach to define site-specific prescriptions using biochar in concert with other soil amendments to improve site conditions facilitating native plant establishment on mine residuals. This framework includes assessing site-specific limitations to plant establishment through laboratory analyses to evaluate pH, heavy metal contamination, nutrient availability, and soil physical attributes (e.g., particle size distribution, bulk density, water-holding capacity), followed by development of site-specific soil amendment prescriptions tailored to ameliorate the limitations present. This presentation describes which site conditions need to be considered when developing a site-specific soil amendment prescription. It will also include our working framework and use case studies to demonstrate the positive and negative aspects of the process.

Impact/Purpose

While mining provides essential metals and minerals for humanity, it can also cause environmental contamination, from unstable mining residuals. This study considers ways to use soil amendments and plants to reduce contaminant availability and create a favorable soil environment to grow plants that stabilize mining wastes. We have developed a framework for assessing site conditions and amending mining residuals and establishing native plants that reduce offsite movement of wastes and reduce environmental exposure to hazardous materials. Across the U.S. there are hundreds of thousands of mine sites that need this kind of intervention and the framework we developed can provide the guidance for successful intervention. This framework provides a path forward for addressing residuals left behind from abandoned and active mines that have sat unremediated for years. The Regions, Tribes and general public will be interested in the remedial opportunities that our approach provides. Now sites that have not been remediated can be improved using locally derived or easily obtained materials such as biochar, biosolids and agricultural lime. This research advances EPA’s goal of cleaning up contaminated sites and protecting human health and the environment.

Citation

Johnson, Mark G, D. Olszyk, M. Bollman, M. Storm, G. King, V. Manning, K. Trippe, K. Spokas, J. Ippolito, D. Watts, T. Ducey, G. Sigua, AND J. Novak. Considerations for Applying Soil Amendments at Mine Sites. EPA Clu-In Webinar, Corvallis, OR, October 16, 2019.