Geomorphic Landform Design as an Alternative for Conventional Valley Fill Surface Mine Reclamation: Assessing Conceptual Design, Groundwater Modeling, and Contaminant Desorption

Abstract

This research aimed to evaluate the potential of applying geomorphic landform design (GLD) principles to valley fill reclamation, specifically in southern West Virginia, central Appalachia, USA. When constructing reclaimed landforms, GLD aims to mimic the geomorphology of reference landforms that are stable and in erosive and hydrologic equilibrium. Challenges with the technique have been identified related to use in central Appalachia. Reference landform design values vary by location and need to be quantified at a local scale for site-specific design. Due to the steep slopes of existing valleys, constructing engineered landforms that naturally blend in with the surrounding environment may not ensure stability. Less steep, more stable slopes of geomorphic landforms could create greater stream disturbance to maintain fill volumes. Potential benefits of GLD with respect to groundwater movement and contaminant desorption have also not been quantified. This research presents three major objectives to assess geomorphic landform design in central Appalachia: 1) define the geomorphic characteristics of mature landform reference sites in southern West Virginia; 2) quantify the issues associated with implementing geomorphic reclamation on a field scale at an existing valley fill; and, 3) compare models of groundwater movement and desorption of selenium in reclamation alternatives for a southern WV surface mine. Geomorphic properties of drainage length and drainage density for mature landforms in central Appalachia were 408 ft and 62 ft/ac, respectively. Slopes were steep (>20%), aspects were well distributed in all directions, vegetation was predominately dense core forest, and ephemeral channel heads developed where erosive surface processes created concentrated flow and sediment transport. Potential issues associated with implementing GLD in central Appalachia with respect to landform stability, stable channel mitigation, and mass balance were confirmed. No geomorphic design was able to satisfy all three criteria when the permitted area of impact was maintained. Expanding the area of impact beyond permit boundaries promoted more success in meeting design criteria, but did not comply with reclamation regulations governing excess spoil placement and constructed hillslopes. A quantitative comparison of the groundwater movement and selenium desorption between alternative reclamation designs confirmed potential benefits to geomorphic reclamation. Selenium desorption was reduced by 23-39% in geomorphic fills and was attributed to improved groundwater movement. Geomorphic reclaimed landforms exhibited 23-45% lower infiltration volumes, 12-63% lower groundwater discharge volumes, and approximately 50% shorter groundwater residence times. These findings will be used to provide recommendations to government agencies and the surface mining industry on the practicality of implementing geomorphic reclamation as an alternative to conventional valley fill reclamation in central Appalachia.